JOINED UNIT OF GLASS BASE MEMBERS, AIRTIGHT ENVELOPE, AND METHOD FOR PRODUCING GLASS STRUCTURAL UNIT
A joined unit of glass base members is provided, comprising first and second glass base members and a joining member which extends along opposing surfaces of the first and second glass base members, wherein glass base member is elastically deformed while being depressed in an internal direction of the glass base member in the vicinity of an end portion in a widthwise direction of the joining member, a boundary surface between the elastically deformed glass base member and the joining member and a surface of the elastically deformed glass base member, which are disposed in the vicinity of the end portion in the widthwise direction of the joining member, are positioned on an internal side of the glass base member, and an area, in which a residual stress is a compressive stress, is formed in the vicinity of the end portion in the widthwise direction of the joining member.
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1. Field of the Invention
The present invention relates to a joined unit of glass base members, an airtight envelope, and a method for producing a glass structural unit. The present invention is applicable especially preferably to an envelope of, for example, a display which includes a device therein and a method for producing the same, wherein it is feared for the device that the performance may be deteriorated by the invasion of any gas such as oxygen, water or the like.
2. Description of the Related Art
A technique has been hitherto known, in which opposing glass base members are joined to one another in an airtight manner to form an internal space having the airtightness. This technique is applied to a method for producing an airtight envelope of a flat panel including, for example, the vacuum heat insulating glass, the organic LED display (OLED), the field emission display (FED), and the plasma display panel (PDP). When the airtight envelope as described above is produced, then a joining material is arranged at circumferential edge portions of glass base members, and the glass base members are joined to one another, for example, by means of the heating, provided that a spacing distance defining member, a local adhesive and the like are arranged between the opposing glass base members, if necessary. A method has been suggested as a method for mutually joining the glass base members, wherein an assembly, which is obtained by temporarily assembling the glass base members, is entirely heated (baked) as a whole by means of a heating furnace. Another method has been also suggested, wherein only the circumferential edge portions of the assembly are selectively heated by a local heating means. The local heating is more advantageous than the whole heating in view of the heating and cooling time, the reduction of the energy required for the heating, and the prevention of any thermal deterioration of the functional device contained in the case.
United States Patent Application Publication No. 2008/0171485 discloses an example in which the airtight joining using the laser beam is applied to a method for producing an envelope of OLED by making use of the advantage of the local heating. In this production method, a frit, which is arranged between two glass base members, is firstly heated and melted by a first laser beam to join the glass base members to one another. Subsequently, a second laser beam is radiated onto the joined area to anneal the joined area. Owing to the anneal effect brought about by the second laser beam, the occurrence of any glass breakage, which would be otherwise caused in any inappropriate direction during a cutting step to be performed thereafter, is avoided.
Japanese Patent Application Laid-open No. 2003-286048 discloses a technique in which the breaking strength or fracture strength of a glass base member is enhanced by a laser beam having an extremely short pulse width. In this technique, a heterogeneous phase is formed in the glass base member by radiating the laser beam having the extremely short pulse width onto the glass base member. The heterogeneous phase is a compressive stress layer which is formed in the vicinity of the surface of the glass base member. The strength of the glass base member is enhanced by the formation of the compressive stress layer formed in the vicinity of the surface of the glass base member.
U.S. Pat. No. 5,820,435 discloses a method for producing an envelope of FED. In this production method, a frame member and a joining material (frit) are firstly arranged at circumferential edge portions of a first glass base member and a second glass base member which are arranged oppositely. Subsequently, a laser beam is intermittently radiated along with a direction in which the joining material extends so that the discrete partial joining is obtained. Subsequently, the laser beam is continuously radiated onto the entire circumference of the joining material including the partially joined area so that the continuous airtight joining is obtained.
Japanese Patent Application Laid-open No. 2000-313630 discloses a method for producing fused glass. In this production method, a joining material (frit) is firstly arranged at circumferential edge portions of a first glass base member and a second glass base member which are arranged oppositely. Subsequently, a light source, in which local heating light sources for the pre-heating, the joining, and the gradual cooling are arranged closely to one another in this order, is used to continuously radiate a laser beam onto the entire circumference of the joining material while performing the scanning so that the continuous airtight joining is obtained. The laser radiation is performed in the three stages for the purpose of the pre-heating, the joining, and the gradual cooling. Therefore, the temperature distribution of the radiation objective is gentle, and it is easy to avoid the crack. In the pre-heating stage, the joining material is heated to a temperature which is less than the glass fusion temperature. Therefore, any fusion of glass is not caused.
Japanese Patent Application Laid-open No. 2006-315902 discloses a method for joining two substrates of a display apparatus. In this joining method, a sealing material is firstly arranged at circumferential edge portions of a first glass substrate and a second glass substrate which are arranged oppositely. Subsequently, a first laser beam, which has a wide radiation range and which is capable of simultaneously heating the sealing material and the substrates disposed therearound, is radiated simultaneously with a second laser beam which has a narrow radiation range and which has a high absorptance or absorption factor with respect to the sealing material. The first laser beam has the wider radiation range. Therefore, the sealing material is firstly heated by the first laser beam to such an extent that the sealing material is not melted. After that, the sealing material is heated and melted by the second laser beam.
United States Patent Application Publication No. 2007/0128966 discloses a method for joining two substrates of a display apparatus. In this joining method, a second substrate is arranged so that the second substrate is brought in contact with a joining material (frit) arranged on a first substrate. A laser beam is radiated onto the joining material while performing the scanning at a velocity of 5 mm/s to 300 mm/s. Thus, the two substrates are joined to one another.
SUMMARY OF THE INVENTIONIn a joined unit of glass base members, when the external force acts on a joining member which joins the glass base members to one another, then any crack appears in the joining member, and the strength of the joining member is lowered in some cases. In the case of an airtight envelope which is constructed by the joined unit of glass base members, the decrease in the strength of the joining member results in the long-term decrease in the reliability of the airtightness. When the airtight envelope is used for a display apparatus, any influence is exerted on the stable operation of the display apparatus in some cases.
The external force, which acts on the joined unit of glass base members such as the airtight envelope for the display apparatus or the like, is exemplified by the external force which is caused by the vibration and/or the pressure fluctuation or variation. For example, an airtight envelope, which is produced in a pressure environment of 1 atmosphere, is exposed to a low pressure environment of about 0.2 atmosphere when the airtight envelope is transported by air. The airtight envelope, which is shipped to a region of the high height above sea level, is sometimes used in a low pressure environment of about 0.6 atmosphere. In this way, when the airtight envelope is exposed to the pressure environment of the pressure lower than that of the pressure environment in which the production is performed, then the pressurization, which is exerted on the airtight envelope by the pressure of the external space, is decreased, and the joining member of the airtight envelope undergoes the occurrence of the decrease in the compressive stress and/or the increase in the tensile stress in some cases. In such a situation, any crack tends to appear in the joining member, and the crack, which appears in the joining member, tends to develop in the joining member. For this reason, the decrease in the strength of the joining member and/or the decrease in the airtightness is/are caused with ease.
In view of the above, the present invention provides a technique which makes it possible to suppress the occurrence of any crack in a joining member by the external force in a joined unit of glass base members including a pair of glass base members joined by the joining member.
The present invention is a joined unit of glass base members, comprising:
a first glass base member;
a second glass base member; and
a joining member which joins the first glass base member and the second glass base member, which is capable of providing a viscosity that has a negative temperature coefficient, and which extends at a predetermined width along opposing surfaces of the first glass base member and the second glass base member, wherein:
at least one of the first glass base member and the second glass base member is elastically deformed while being depressed in an internal direction of the glass base member in the vicinity of an end portion in a widthwise direction of the joining member;
a boundary surface between the elastically deformed glass base member and the joining member and a surface of the elastically deformed glass base member, which are disposed in the vicinity of the end portion in the widthwise direction of the joining member, are positioned on an internal side of the glass base member as compared with a boundary surface between the elastically deformed glass base member and the joining member which is disposed in the vicinity of a central portion in the widthwise direction of the joining member; and
an area, in which a residual stress in a thickness direction of the joining member is a compressive stress, is formed in the vicinity of the end portion in the widthwise direction of the joining member.
The present invention is an airtight envelope comprising:
a first glass base member;
a second glass base member; and
a joining member which joins the first glass base member and the second glass base member, which is capable of providing a viscosity that has a negative temperature coefficient, and which extends at a predetermined width along opposing surfaces of the first glass base member and the second glass base member, wherein:
at least one of the first glass base member and the second glass base member is elastically deformed while being depressed in an internal direction of the glass base member in the vicinity of an end portion in a widthwise direction of the joining member;
a boundary surface between the elastically deformed glass base member and the joining member and a surface of the elastically deformed glass base member, which are disposed in the vicinity of the end portion in the widthwise direction of the joining member, are positioned on an internal side of the glass base member as compared with a boundary surface between the elastically deformed glass base member and the joining member which is disposed in the vicinity of a central portion in the widthwise direction of the joining member; and
an area, in which a residual stress in a thickness direction of the joining member is a compressive stress, is formed in the vicinity of the end portion in the widthwise direction of the joining member.
The present invention is a method for producing a glass structural unit, including joining a first glass base member and a second glass base member for forming at least a part of the glass structural unit together with the first glass base member, the method comprising:
a step of arranging a joining member between the first glass base member and the second glass base member so that the joining member is brought in contact with both of the first glass base member and the second glass base member, the joining member being capable of providing a viscosity which has a negative temperature coefficient, and the joining member extending at a predetermined width along opposing surfaces of the first glass base member and the second glass base member;
a step of pressing the joining member in a thickness direction of the joining member; and
a first joining step of radiating a first local heating light beam onto the joining member via the first glass base member so that a radiation position is moved in a direction in which the joining member extends, heating and melting the joining member in an entire region in a widthwise direction, and then cooling the joining member to a temperature of not more than a softening point, wherein:
the following expressions are fulfilled by a velocity of movement v (m/s) of the radiation position brought about by the first local heating light beam and a beam diameter φ (m) of the first local heating light beam provided that d (m) represents a thickness of the first glass base member, a (m2/s) represents a thermal diffusivity of the first glass base, member, and w (m) represents the width of the joining member:
φ/v<(d/8)2/(12a) (Expression 1)
φ>w (Expression 2)
According to the present invention, it is possible to suppress the occurrence of any crack in the joining member by the external force in the joined unit of glass base members including the pair of glass base members joined by the joining member.
Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings.
An embodiment of the present invention will be explained below. The joined unit of glass base members and the airtight envelope of the present invention are preferably applicable to an envelope of, for example, FED, OLED, and PDP. The envelope includes, in the internal space, a device which is required to be shut off in an airtight manner from the external atmosphere. The method for producing the glass structural unit of the present invention is applicable to the production of an envelope of, for example, FED, OLED, and PDP. The envelope includes, in the internal space, a device which is required to be shut off in an airtight manner from the external atmosphere. In particular, in the case of the airtight envelope of the envelope for the image display apparatus such as FED or the like, the inside or interior is a pressure-reduced space. Therefore, the airtight envelope receives the load of the atmospheric air on account of the negative pressure of the internal space. Any crack appears in the airtight joined portion due to the load of the atmospheric air in some cases. The crack as described above sometimes deteriorates the long-term reliability of the airtightness of the airtight envelope. According to the method for producing the glass structural unit of the present invention, it is possible to obtain the airtight envelope having the high long-term reliability of the airtightness. It is noted that the method for producing the glass structural unit of the present invention is not limited to the production of the airtight envelope in which the inside is the pressure-reduced space and the production of the airtight envelope in which the circumferential edge portions of the opposing glass base members are joined by the joining member for which the airtightness is required. The method for producing the glass structural unit of the present invention is widely applicable to the production of any general glass structural unit in which glass base members are joined to one another by a joining member. Accordingly, it is possible to obtain the glass structural unit in which any crack hardly appears in the joining member against the external force.
A large number of electron emission elements 27, which emit electrons in accordance with the image signal, are provided on the rear plate 13. Driving matrix wiring lines (X direction wiring lines 28, Y direction wiring lines 29), which are provided to operate the respective electron emission elements 27 in accordance with the image signal, are formed on the rear plate 13. Fluorescent films 34 are provided on the face plate 12 which is positioned oppositely to the rear plate 13. The fluorescent film 34 is composed of a fluorescent substance which emits the light by receiving the radiation of the electrons emitted from the electron emission elements 27 so that an image is displayed. Further, black stripes 35 are provided on the face plate 12. The fluorescent films 34 and the black stripes 35 are provided while being arranged alternately. A metal back 36, which is composed of an Al thin film, is formed on the fluorescent film 34. The metal back 36 has a function as an electrode to attract the electrons, and the electric potential is supplied thereto from a high voltage terminal Hv provided for the envelope 10. A non-evaporable getter 37, which is composed of a Ti thin film, is formed on the metal back 36.
It is appropriate that the face plate 12, the rear plate 13, and the frame member 14 are transparent and light-transmissive. Those usable include, for example, soda-lime glass, high strain point glass, and non-alkali glass or alkali-free glass. It is desirable that these members have the satisfactory wavelength transmissivity at the usable wavelength of the local heating light beam and in the absorptive wavelength range of the joining material as described later on.
Next, the joined unit of glass base members, the airtight envelope, and the method for producing the glass structural unit according to the embodiment of the present invention will be explained with reference to the drawings.
As shown in
In this description, the surface of the glass base member 14, which is disposed in the vicinity of the end portion 91 of the joining member, is designated as “surface 94”. The boundary surface of the portion, at which the joining member 1 and the glass base member 14 are brought in contact with each other in the vicinity of the end portion 91 of the joining member, is designated as “boundary surface 93”. The boundary surface of the portion, at which the joining member 1 and the glass base member 14 are brought in contact with each other in the vicinity of the central portion in the widthwise direction of the joining member 1, is designated as “boundary surface 96”. In this arrangement, the surface 94 and the boundary surface 93 are positioned on the internal side of the glass base member 14 as compared with the boundary surface 96.
The thickness of the joining member, which is provided at the maximum thickness portion 92 of the end portion 91 of the joining member, is designated as “d”. The positions, at which the distance in the widthwise direction of the joining member 1 is d from the maximum thickness portion 92 on the surface of the glass base member 14, are, designated as “positions 141, 142”. A virtual boundary line, which is obtained by connecting the positions 141, 142 with a straight line, is designated as “boundary line 143”. In this arrangement, the boundary surface 93 and the surface 94 are disposed on the internal side of the glass base member of the glass base member 14 as compared with the virtual boundary line 143.
The deformation of the glass base member 14 described above, which is brought about in the vicinity of the end portion 91 of the joining member, is the elastic deformation. The glass base member 14 is depressed or forcibly recessed toward the inside of the base member to cause the elastic deformation in the vicinity of the end portion 91 of the joining member. Accordingly, the compressive stress is generated in the glass base member 14 in the vicinity of the end portion 91 of the joining member. The compressive stress acts as the driving force, and the glass base member 14 presses the end portion 91 of the joining member against the glass base member 13 (rear plate).
Similarly, the compressive stress, which is generated in the glass base member 13 in the vicinity of the end portion 91 of the joining member, acts as the driving force, and the glass base member 13 presses the end portion 91 of the joining member against the glass base member 14.
In this way, the end portion 91 of the joining member is compressed in accordance with the action in which at least one of the opposing glass base members presses the end portion 91 of the joining member against the other glass base member. Therefore, the end portion 91 of the joining member provides the compressive stress area. That is, in the embodiment of the present invention, the compressive stress areas are formed at the both end portions in the widthwise direction of the joining member 1 for joining the glass base members to one another.
The driving force of the action to compress the end portion 91 of the joining member by the glass base member is the compressive stress generated in the glass base member. The driving force is inherent in the glass base member itself for constructing the airtight envelope. Therefore, the action to compress the end portion 91 of the joining member by the glass base member sustainably remains irrelevant to, for example, the pressure fluctuation or variation provided outside the airtight envelope.
Any crack, which is caused by the external force, hardly arises in the joining member 1 owing to the fact that the areas of the compressive stress are formed at the both end portions 91 of the joining member 1. Therefore, the appearance of the crack in the joining member 1 is suppressed irrelevant to, for example, the pressure fluctuation or variation caused during the movement or the transport of the airtight envelope and the difference in the pressure environment between the production and the use. Therefore, the airtight envelope, which has the high long-term reliability of the airtightness, is obtained.
The crack, which is caused by the external force, hardly appears in the joining member when the glass base member is elastically deformed toward the internal side of the glass base member in the vicinity of the end portions disposed on the both sides of the joining member and the areas of the compressive stress are formed at the end portions disposed on the both sides of the joining member in any general joined unit of glass base members without being limited to the airtight envelope. Therefore, the joined unit of glass base members, which is excellent in the strength, is obtained.
As for the glass base member to be used for the airtight envelope in the present invention, it is desirable to use those in which the outgassing is scarcely caused from the glass base member itself. When the airtight envelope of the present invention is used for the display apparatus such as FED, OLED or the like, those preferably usable as the glass base member of the airtight envelope include non-alkali glass or alkali-free glass, borosilicate glass, and high strain point glass, in view of the chemical and thermal stability against, for example, the temperature fluctuation during the operation of the apparatus.
As for the joining material to be used for the airtight envelope of the present invention, it is desirable to use those in which the outgassing is scarcely caused from the joining material itself. When the airtight envelope of the present invention is used for the display apparatus such as FED, OLED or the like, those preferably usable as the joining material include, for example, glass frit, inorganic adhesive, and low melting point glass, in view of the chemical and thermal stability against, for example, the temperature fluctuation during the operation of the apparatus.
Next, an explanation will be made in detail by using
At first, the sample including the joining member 1 is cut out from the airtight envelope. As shown in
Subsequently, the temperature of the prepared sample is adjusted to room temperature or a temperature which is coincident with the assumed environment of use of the airtight envelope. Subsequently, the shape 144 is obtained for the surface of the glass base member and the boundary surface between the joining member 1 and the glass base member on the cutting surface by means of, for example, an optical microscope or a scanning electron microscope. The height of the surface of the glass base member and the height of the boundary surface between the joining member 1 and the glass base member are plotted with respect to the position in the widthwise direction of the joining member 1. Thus, the shape 144 (hereinafter referred to as “boundary shape”) is specified for the surface of the glass base member and the boundary surface between the joining member 1 and the glass base member (
Subsequently, the sample is heated by means of an unillustrated heating apparatus so that the temperature of the sample is not less than the softening point temperature of the joining material. The temperature of the sample is maintained at a temperature of not less than the softening point temperature of the joining material for about 10 minutes, and then the sample is cooled to the temperature (room temperature or the temperature of the assumed environment of the use of the airtight envelope 10) at which the boundary shape 144 has been obtained. A boundary shape 145 of the glass base member is specified in the same manner as in the method for obtaining the boundary shape 144 before the heating (
The obtained boundary shapes 144, 145 of the glass base member are compared with each other. When the boundary shape 145 after the heating, which is provided in the vicinity of the end portion 91 of the joining member, is straighter than the boundary shape 144 before the heating, it is possible to confirm the fact that the glass base member has been elastically deformed in the state before the joining member 1 is softened (
Further, the thickness of the joining member 1, which is provided at the maximum thickness portion 92 of the end portion 91 of the joining member, is designated as “d” in relation to the boundary shape 144 of the glass base member before the heating. The positions, at which the distance in the widthwise direction of the joining member 1 is d from the maximum thickness portion 92 on the surface of the glass base member 14, are designated as “positions 141, 142”. A virtual boundary line, which is obtained by connecting the positions 141, 142 with a straight line, is designated as “boundary line 143”. In this arrangement, when the boundary shape 144 of the glass base member before the heating is disposed on the internal side of the glass base member of the glass base member 14 as compared with the virtual boundary line 143, it is possible to confirm the fact that the glass base member is deformed while being depressed toward the internal side of the glass base member.
In the airtight envelope of the present invention, the compressive stress remains stably in the end portion 91 of the joining member irrelevant to the pressure fluctuation caused at the outside of the airtight envelope. Therefore, it has been successfully confirmed that the crack hardly arises in the joining member in the pressure-reduced environment even when the airtight envelope is placed in a pressure-reduced chamber at 0.1 atmosphere (10 kPa). Further, even when any crack appears in the joining member, it has been successfully confirmed that the crack hardly develops to the end portion 91 of the joining member.
The stress distribution in the widthwise direction of the joining member of the airtight envelope of the present invention can be confirmed by cutting out a sample or specimen including the joining member as shown in
Next, an explanation will be made in detail with reference to
As shown in
The radiating step includes a step of moving the temporary assembly or a light source of the first local heating light beam 41 in the direction in which the joining material 1a extends. The direction, in which the joining material 1a extends, is the direction which is perpendicular to the widthwise direction of the joining material 1a and which is parallel to the glass base members 13, 14 as shown in
In the method for producing the glass structural unit, the glass base members 13, 14 are elastically deformed selectively (locally) in a radiation area 421 during the radiation of the first local heating light beam 41. Accordingly, the method has such a feature that the pressurizing force, which is exerted on the joining material 1a, is increased in the radiation area 421.
The increase in the pressurizing force is caused by the temperature difference (temperature distribution) in the thickness direction of the glass base member (indicated by the arrow y shown in
It is noted that the glass base members 13, 14 themselves have the low energy absorption performance with respect to the wavelength of the first local heating light beam 41. Accordingly, the temperature distribution in the thickness direction of the glass base member is formed in the glass base members 13, 14 such that the temperature is more raised at positions nearer to the joining material 1a in the thickness direction and the temperature is more lowered at positions separated farther from the joining material 1a in the thickness direction (at positions disposed on the more internal side of the glass base member).
The mode of thermal expansion of each of the glass base members 13, 14 differs in the thickness direction on account of the temperature difference in the thickness direction of each of the glass base members 13, 14 as described above. Therefore, as shown in
The phenomenon, in which the difference arises in the thickness direction in relation to the mode of the thermal expansion on account of the temperature distribution in the glass base member and the glass base member is warped, resembles the phenomenon in which the difference arises in the thickness direction in relation to the mode of the thermal expansion on account of the difference in the coefficient of thermal expansion in the thickness direction and the bimetal is warped. The phenomenon, in which the glass base member is warped on account of the temperature distribution in the thickness direction in the method for producing the glass structural unit of the present invention, is hereinafter referred to as “bimetal effect”.
The joining material is melted after the radiation of the first local heating light beam 41, and the temperature difference is increased in the thickness direction of the glass base member. The temperature difference in the thickness direction of the glass base member is gradually relieved in accordance with the action of thermal diffusion after the point in time at which the temperature difference in the thickness direction of the glass base member is maximized. When the radiation condition of the first local heating light beam 41 is appropriately set, then it is possible to regulate the relieving speed of the temperature difference in the thickness direction of the glass base member generated after the radiation of the first local heating light beam 41, and it is possible to regulate the action for increasing the pressurizing force exerted on the joining material.
An explanation will be made in detail with reference to
Therefore, the amount of shrinkage of the joining material 1a is relatively large when the amount of shrinkage of the joining material 1a and the amounts of shrinkage of the glass base members brought about by the cooling are compared with each other. Further, the glass base members are warped in accordance with the bimetal effect in the stages of
The glass base members are elastically deformed by being depressed or forcibly recessed in the internal directions of the glass base members by the end portions 91 of the joining member in the vicinity of the end portions 91 of the joining member. The state, in which the glass base members are elastically deformed in the internal directions of the glass base members at the end portions in the widthwise direction of the joining member 1, is maintained in the pair of glass base members joined by the joining member 1. Therefore, the compressive stress areas are stably formed at the end portions in the widthwise direction of the joining member 1 in the pair of glass base members joined by the joining member 1.
The bimetal effect, which is generated in those stages shown in
Next, an explanation will be made about the requirement to be fulfilled by the method for producing the glass structural unit of the present invention.
In the method for producing the glass structural unit according to the present invention, it is necessary that the bimetal effect, which is in the sense as described above, should be generated in the glass base members at the portions disposed in the vicinity of the irradiation position of the first local heating light beam. Further, it is necessary that the end portions in the widthwise direction of the joining material should be melted and joined in the state in which the glass base members are warped in accordance with the bimetal effect. For this purpose, it is appropriate to join the end portions in the widthwise direction of the joining material in the stage before the heat, which is transferred from the heated and melted joining material having the high temperature to the inside of the glass base members, is diffused in the glass base members to consequently uniformize the temperature distributions in the glass base members. When this requirement is fulfilled in at least one of the pair of glass base members, it is possible to obtain the effect of the present invention such that the compressive stress areas are formed at the end portions in the widthwise direction of the joining member. In view of the above, the following discussion will be made about the first glass base member (rear plate 13) arranged on the incident side of the first local heating light beam.
The heat transfer is caused in the glass base member 13 from the joining material 1a having the high temperature in the stages of
When the joining material 1a having the high temperature is brought in contact with the surface 131 of the glass base member 13 for an extremely short period of time t (s) to heat the glass base member 13, the range (temperature permeation depth) δ (m), in which the temperature is diffused into the interior of the glass base member 13, is expressed as follows provided that the thermal diffusivity of the glass base member 13 is represented by a (m2/s):
δ=(12at)0.5
In the present invention, the heating time t (s) is appropriately regarded as the time of passage of the first local heating light beam. Assuming that the velocity of movement of the radiation position brought about by the first local heating light beam is v (m/s) and the beam diameter in the direction of movement of the first local heating light beam is φ (m), the heating time t (s) is expressed as follows:
t=φ/v
The condition, under which the bimetal effect is generated as described above in the glass base member, is expressed, assuming that the thickness of the glass base member is d (m), as follows: d>>δ. According to the experiments and the investigations performed by the present inventors, the condition, under which the sufficient compressive stress is generated in the vicinity of the end portion 91 (see
d>8×δ
When this expression is replaced with δ and t described above, and the expression is deformed, then the following expression is obtained:
φ/v<(d/8)2/(12a) (Expression 1)
When the thickness d of the first glass base member disposed on the side on which the first local heating light beam is allowed to come and the thermal diffusivity a of the first glass base member are given, it is appropriate that the velocity of movement v and the beam diameter φ in the direction of movement, which fulfill Expression 1 described above, are selected as the radiation condition of the first local heating light beam. Accordingly, the bimetal effect as described above is generated at the radiation position of the first local heating light beam in the glass base member. Further, the area of the sufficient compressive stress is formed at the end portion 91 in the widthwise direction of the joining member to be finally formed.
The thickness d of the glass base member described above can represent the thickness of the glass base member disposed on the incident side as viewed from the joining material preferentially heated by the first local heating light beam. Therefore, when the glass base members disposed on the incident side, which are in the local heating stage, can be grasped as an integrated structure of the two or more glass base members joined before the heating step, the total of the thicknesses of the glass base members capable of being dealt with in the integrated manner is regarded as the thickness d of the glass base members.
In this case, in order to heat the joining material 1a in the entire region in the widthwise direction thereof, it is necessary that the beam diameter φ in the direction of movement of the first local heating light beam should fulfill the following expression provided that the width of the joining material 1a is w:
φ>w (Expression 2)
If the thermal diffusivity a of the glass base member is not clarified directly, the thermal diffusivity a is determined in accordance with Expression 3 described below:
a=λ/Cp/ρ (Expression 3)
In Expression 3, λ represents the thermal conductivity of the glass base member, Cp represents the specific heat capacity of the glass base member, and ρ represents the density of the glass base member.
The joining material, which is applicable to the joined unit of glass base members, the airtight envelope, and the method for producing the glass structural unit according to the present invention, is not specifically limited provided that the material has the softening point lower than the softening point of the glass base member and the viscosity (coefficient of viscosity) has the negative temperature coefficient. The phrase “viscosity has the negative temperature coefficient” means the fact that the viscosity is decreased when the temperature is raised, i.e., the fact that the temperature dependency of the viscosity is negative. These conditions are required in order that the glass base members are elastically deformed in the stage in which the joining material is softened, and the joining material is satisfactorily brought in contact with the pair of glass base members in the stage in which the joining material interposed between the pair of glass base members is melted (see
The glass base member, which is applicable to the joined unit of glass base members, the airtight envelope, and the method for producing the glass structural unit of the present invention, is not specifically limited provided that the glass base member fulfills the foregoing condition that the softening point is higher than the softening point of the joining material. It is preferable to adopt non-alkali glass or alkali-free glass and high strain point glass generally applicable to the display glass, in view of the stability of the dimensional tolerance and the chemical stability against the thermal influence during the production.
The first local heating light beam, which is applicable to the method for producing the glass structural unit and the method for producing the airtight envelope of the present invention, is not specifically limited provided that the light beam has such a wavelength characteristic that the light beam is transmissive through the glass base member and the light beam is absorbable by the joining material. For example, an infrared lamp or the like, which is combined with a convergent optical system, is usable as the first local heating light beam of the present invention. Further, it is preferable to use the semiconductor laser and the gas laser such as the CO2 laser or the like, in view of the fact that the moving radiation is conveniently performed and in view of the fact that the radiation spot is sharp.
The radiation condition of the first local heating light beam, which is applicable to the method for producing the glass structural unit and the method for producing the airtight envelope of the present invention, appropriately fulfills Expressions 1 and 2 described above. In order to localize the area in which the load is concentrated in accordance with the bimetal effect of the glass base members during the radiation and the heating, it is preferable to perform the radiation while the beam diameter φ of the first local heating light beam is decreased within a range in which the beam diameter φ is not less than the width w of the joining material and the velocity of movement v is made higher.
Next, an explanation will be made with reference to the drawings about an embodiment of the method for joining the glass base members in the method for producing the glass structural unit of the present invention. In this embodiment, the glass base members are joined by radiating a second local heating light beam onto the joining material 1a in addition to the first local heating light beam which fulfills the radiation conditions of Expressions 1 and 2 described above. In the embodiment explained herein, the first local heating light beam is radiated, and then the second local heating light beam is radiated to follow the first local heating light beam.
(Step 1)At first, as shown in
Subsequently, as shown in
As shown in
Subsequently, as shown in
With reference to
In this specification, the process of heating and melting the joining material 1a by the radiation of the first local heating light beam 41 and cooling the joining material 1a thereafter is referred to as the first joining step. Further, the process of heating and melting the joining material 1a by the radiation of the second local heating light beam 42 and cooling the joining material 1a thereafter is referred to as the second joining step. In this embodiment, the radiation of the local heating light beam is performed twice approximately simultaneously with a slight difference in time by using the first laser head 61 and the second laser head 62 fixed to the breadboard 60. The first joining step and the second joining step may be performed at mutually distinct timings.
The joining material 1a is successively heated and melted in the direction D in which the joining material 1a extends, by being irradiated with the first local heating light beam 41. After that, the joining material 1a is cooled to a temperature of not more than the softening point. The first local heating light beam 41 is radiated while being moved in the direction in which the joining material 1a arranged on the frame member 14 extends. The joining material 1a is formed to provide a frame-shaped form as a whole on the frame member 14. As shown in
The second local heating light beam 42 is radiated after the joining material 1a, which has been melted by the radiation of the first local heating light beam 41, is cooled to a temperature of not more than the softening point. The second local heating light beam 42 is radiated while following the first local heating light beam 41 while maintaining the spacing distance C between the optical axes with respect to the first local heating light beam 41. Accordingly, a part of the joining material 1a in the widthwise direction, which has been cooled to the temperature of not more than the softening point, is heated and melted again.
The second local heating light beam 42 is radiated to provide such a state that the surrounding of a part of the joining material 1a heated and melted again is surrounded by a part of the joining material 1a having a temperature of not more than the softening point. Specifically, as shown in
It is necessary to fulfill the following requirement in order that the surrounding of the portion heated and melted again by being irradiated with the second local heating light beam 42 is surrounded by the joining material 1a having the temperature of not more than the softening point. That is, it is necessary that the joining material 1a, which has been heated and melted in the entire region in the widthwise direction by being irradiated with the first local heating light beam 41, should be cooled to the temperature of not more than the softening point until the second local heating light beam 42 is radiated. This requirement can be satisfied by adjusting the distance C between the optical axes of the first local heating light beam 41 and the second local heating light beam 42 and the cooling speed of the joining material 1a. In order to secure the side portions 44 which are not melted again on the both sides of the portion which is heated and melted again, it is appropriate that a desired range is heated and melted again by adjusting the radiation condition of the second local heating light beam 42 including, for example, the beam diameter.
When the second local heating light beam 42 is radiated, the joining material 1a is appropriately in such a state that the joining material 1a is cooled to the temperature of not more than the softening point after the joining material 1a is heated and melted in the entire region in the widthwise direction of the joining material 1a.
The first and second local heating light beams 41, 42 may be radiated from the same side or the first and second local heating light beams 41, 42 may be radiated from the mutually opposite sides with respect to the joining objective provided that the joining material 1a can be irradiated therewith and heated in the predetermined areas respectively (the entire region in the widthwise direction for the first local heating light beam 41 and the central portion in the widthwise direction for the second local heating light beam 42). For example, when the joining material 1a, which is disposed between the frame member 14 and the rear plate 13, is subjected to the radiation, then both of the first and second local heating light beams 41, 42 may be allowed to come from the side of the frame member 14 as shown in
The stress distribution indicates a distribution of the tensile stress and the compressive stress in the Z direction (thickness direction) corresponding to the shearing stress in the plane inclined by 45° with respect to the Y and Z directions provided that X represents the direction in which the joining material 1a extends, Y represents the widthwise direction of the joining material 1a, and Z represents the thickness direction of the joining material 1a.
When the glass base members were joined by heating the joining material 1a as a whole by using a heating furnace as shown in
When the glass base members were joined by radiating only the first local heating light beam 41 as shown in
In this embodiment shown in
Subsequently, as shown in
In the embodiment explained above, the rear plate 13 and the frame member 14 are joined to one another, and the face plate 12 and the frame member 14 are further joined to one another. Accordingly, the envelope 10 is produced, in which the frame member 14 is inserted between the face plate 12 and the rear plate 13. More generally, the present invention provides the method for producing the airtight envelope at least a part of which is composed of the rear plate 13 and the face plate 12. The method for producing the airtight envelope of the present invention is applicable when a glass base member, in which a protruding portion having a shape of the frame member 14 is integrally formed beforehand, is used as one of the rear plate 13 and the face plate 12, and the glass base member is joined to the other plate. Further, the method for producing the airtight envelope of the present invention is applicable when the face plate 12 and the frame member 14 are previously joined to one another, and then the rear plate 13 and the frame member 14 are joined to one another.
The embodiment explained above is such an embodiment that the present invention is applied to the method for producing the airtight envelope to be used for the image display apparatus. More generally, the present invention is applicable when a first glass substrate and a second glass substrate are joined to one another. In this case, both of the first and second local heating light beams may be radiated from the side of the first glass substrate. Alternatively, one of the first and second local heating light beams may be radiated from the side of the first glass substrate, and the other may be radiated from the side of the second glass substrate. Further alternatively, both of the first and second local heating light beams may be radiated from the side of the second glass substrate.
Next, an explanation will be made with reference to the drawings about an embodiment of the method for joining the glass base members in the method for producing the glass structural unit of the present invention. In this embodiment, the glass base members are joined to one another by radiating a second local heating light beam onto a joining material 1a in addition to the first local heating light beam which fulfils the radiation conditions of Expressions 1 and 2 described above. In the embodiment explained herein, the second local heating light beam is radiated prior to the radiation of the first local heating light beam. The first and second local heating light beams are radiated so that the radiation position, which is brought about by the first local heating light beam, follows the radiation position which is brought about by the second local heating light beam.
In the following description, the “first glass base member” is used in the sense of the glass base member on which the joining material is formed, and the “second glass base member” is used in the sense of the glass base member which is arranged oppositely to the first glass base member with the joining material intervening therebetween. Therefore in Steps 1 to 3 described below, the frame member 14, which is the glass base member arranged with the joining material 1a, is the “first glass base member”, and the rear plate 13, which is the glass base member arranged oppositely thereto, is the “second glass base member”. On the other hand, in Step 4, the face plate 12, which is the glass base member arranged with the joining material, is the “first glass base member”, and the frame member 14, which is the glass base member arranged oppositely thereto, is the “second glass base member”.
(Step 1)At first, as shown in
As shown in a right drawing of
Subsequently, as shown in
As shown in
Subsequently, as shown in
With reference to
It is appropriate that the first and second local heating light beams 41, 42 are capable of locally heating the vicinity of the joined area. The semiconductor laser is preferably used as the light source. A processing semiconductor laser, which has a wavelength in the infrared region, is preferred as the light sources of the local heating light beams 41, 42 in view of, for example, the performance to locally heat the joining material 1a and the transmission performance through the glass base member.
The joining material 1a is successively heated and melted in the direction D in which the joining material 1a extends, by being irradiated with the second local heating light beam 42. After that, the joining material 1a is cooled to a temperature of not more than the softening point. The second local heating light beam 42 is radiated while being moved in the direction in which the joining material 1a arranged on the frame member 14 extends. The joining material 1a is formed to provide a frame-shaped form as a whole on the frame member 14. In this situation, at least a part of the joining material 1a in the widthwise direction is melted, followed by being cooled so that the temperature of the joining material 1a is not more than the softening point. Accordingly, partially joined portions, in which the rear plate 13 and the frame member 14 are partially joined to one another, are successively formed in partial areas in the widthwise direction of the joining material 1a in the direction D in which the joining material 1a extends.
As shown in
In order to form the partially joined portion between the frame member 14 and the rear plate 13 by radiating the second local heating light beam 42, it is appropriate that the film thickness of the joining material 1a is allowed to have a distribution in the widthwise direction as described above, and the portion, at which the partially joined portion is intended to be formed, is allowed to have a film thickness larger than film thicknesses of the other portions.
Another method is also available to form the partially joined portion between the frame member 14 and the rear plate 13 by radiating the second local heating light beam 42, wherein the beam intensity of the second local heating light beam 42 may be allowed to have a distribution in the widthwise direction of the joining material 1a. For example, when the joining material 1a, which has the film thickness distribution in the widthwise direction as described above, is replaced with a joining material which has a flat film thickness distribution in the widthwise direction, the beam profile of the second local heating light beam 42 may be changed to such a profile that the beam intensity, which is provided at the portion intended to form the partially joined portion, is stronger than the beam intensities of the other portions. When the second local heating light beam 42, which has such a beam profile that the beam intensity of the portion intended to be formed with the partially joined portion is locally strong, is radiated, the partially joined portion is formed between the frame member 14 and the rear plate 13 in the same manner as in the case in which the film thickness of the joining material 1a is allowed to have the distribution in the widthwise direction. When the beam intensity of the second local heating light beam 42 has the distribution in the widthwise direction of the joining material 1a, a distribution in the widthwise direction arises in the coefficient of expansion of the joining material 1a during the radiation of the second local heating light beam 42. Accordingly, the distribution in the widthwise direction is formed in the film thickness of the joining material 1a during the radiation of the second local heating light beam 42.
As described above, in order to form the partially joined portion, it is also appropriate to utilize the previously prepared film thickness distribution in the joining material 1a. Alternatively, the film thickness distribution in the joining material 1a, which is generated by the distribution of the coefficient of expansion of the joining material 1a during the radiation of the second local heating light beam 42, may be utilized. The distribution of the coefficient of expansion of the joining material 1a during the radiation of the second local heating light beam 42 is the distribution corresponding to the intensity distribution of the second local heating light beam 42. Further, the procedures or techniques as described above may be combined with each other.
It is desirable that the second local heating light beam 42 is radiated so that the partially joined portions 55, 75 are formed within a range of 1% to 90% of the entire width W of the joining material 1a at the respective positions in the direction in which the joining material 1a extends. It is more desirable that the second local heating light beam 42 is radiated so that the partially joined portions 55, 75 are formed within a range of 2% to 50% of the entire width W of the joining material 1a at the respective positions in the direction in which the joining material 1a extends.
As described above, in relation to the joining material 1a, the viscosity (coefficient of viscosity) has the negative temperature coefficient. Therefore, when the joining material 1a is heated and melted, then the viscosity of the joining material 1a is once lowered, and the joining material 1a is fluidized. On the other hand, when the radiation of the local heating light beam is completed, the viscosity of the joining material 1a is restored.
The joining material 1a escapes from the fluidization state when the viscosity is restored to be not less than 106.7 (Pa·sec). The joining material 1a exerts the restraining action to some extent between the rear plate 13 and the frame member 14 on the basis of the viscous property (viscosity or stickiness) thereof. In other words, the second local heating light beam 42 temporarily joins the rear plate 13 and the frame member 14 (
It is appropriate that the partially joined portion is formed at a part of the entire width W of the joining material 1a (joining-scheduled width). The partially joined portion 55 and the unjoined area 54 as the portion formed with no partially joined portion 55 may be disposed at any position in the widthwise direction of the joining material 1a.
The purpose of the second local heating light beam 42 is to temporarily join the rear plate 13 and the frame member 14. Therefore, it is appropriate that the partially joined portions 55 are formed in the direction D while giving the continuity to such an extent that the temporary restraining action is obtained between the rear plate 13 and the frame member 14. In other words, it is appropriate that the partially joined portions 55 are formed continuously without any disconnection in the direction D. Further, it is also allowable that an area, in which the partially joined portion 55 is not formed, partially exists in the direction D. On the other hand, it is preferable that the unjoined area 54 is formed continuously in the direction D, because it is possible to efficiently discharge or exclude the air-gaps (voids) which tend to remain in the joined area.
The first local heating light beam 41 is radiated after the joining material 1a, which has been melted by the radiation of the second local heating light beam 42, has a temperature of not more than the softening point at the respective positions of the joining material 1a. Specifically, the first local heating light beam 41 is radiated when the joining material 1a, which has been melted by the radiation of the second local heating light beam 42, has a viscosity of not less than 106.7 (Pa·sec) at the respective positions of the joining material 1a. The first local heating light beam 41 successively heats and melts the partially joined portions 55, 75 again in the direction D. Further, the first local heating light beam 41 successively heats and melts the unjoined areas 54, 74 in the direction D. Thus, the joining members 56, 76, each of which joins the rear plate 13 and the frame member 14, are formed (
In particular, the timing of radiation of the first local heating light beam 41 is such a timing that the joining material 1a, which has been in the melted state by being irradiated with the second local heating light beam 42, is cooled to provide a state in which the frame member 14 and the rear plate 13 are joined to one another by only the part of the joining material 1a in the widthwise direction. In other words, the state, in which the frame member 14 and the rear plate 13 are joined to one another by only the part in the widthwise direction, is such a state that the joining material 1a restrains the frame member 14 and the rear plate 13. This state is expressed by using the viscosity of the joining material 1a as a state in which the viscosity η (Pa·sec) of the joining material 1a resides in log η≦6.7, wherein the temperature of the joining material 1a is not more than the softening point in this state. The timing, at which the joining material 1a is in this state, is the desirable radiation timing of the first local heating light beam 41.
In order to radiate the first local heating light beam 41 when the temperature of the joining material 1a is in the state of not more than the softening point, it is necessary to ensure the period of time during which the joining material 1a is cooled after the radiation of the second local heating light beam 42. For this purpose, the distance C between the optical axes of the second laser head 62 and the first laser head 61 can be adjusted while considering the cooling speed of the joining material 1a and the scanning velocity (velocity of moving radiation) of the first and second local heating light beams 41, 42.
It is appropriate that the first local heating light beam 41 and the second local heating light beam 42 are capable of heating the desired joining-scheduled areas. Therefore, the first local heating light beam 41 and the second local heating light beam 42 may be positioned on the same side with respect to the joining objective, or they may be positioned on the mutually opposite sides.
(Step 4)Subsequently, as shown in
In the conventional technique, the laser beam is radiated onto the joining material a plurality of times. However, the joining material is heated and melted by means of the radiation performed once. Even in the case of the technique described in United States Patent Application Publication No. 2008/0171485, the area other than the partially joined area is joined by means of the radiation performed once. When the heating and the melting are performed by means of only the radiation performed once, it is necessary that the thermal energy, which is required to heat and melt the joining material, should be supplied once. Therefore, the quantity of heat, which is applied to the joining objective, is increased, and the local thermal deformation of the glass base member tends to increase at the radiation position. Therefore, the contact between the pair of glass base members to be joined is unstable, and the air-gaps (voids) tend to remain in the joining member. The voids, which remain in the joining member, cause the occurrence of any crack.
On the contrary, in this embodiment, the second local heating light beam 42 is radiated precedingly to form the partially joined portions between the rear plate 13 and the frame member 14, and the components are temporarily joined. Further, the partially joined portions are formed between the face plate 12 and the frame member 14, and the components are temporarily joined. Therefore, the contact between the both glass base members is stabilized during the radiation of the first local heating light beam 41, and the air-gaps (voids) are suppressed from remaining in the joined area. As a result, the airtightness of the joining member is enhanced.
Further, when the first local heating light beam 41 is radiated, as shown in
Next, the proper temperature of the joining material 1a at the partially joined portion, which is provided when the first local heating light beam 41 is radiated, is determined. For this purpose, the radiation timings of the first and second local heating light beams 41, 42 were changed to determine the relationship between the density of cracks generated in the joining member 1 of a test piece and the temperature of the joining material provided immediately before the incidence of the first local heating light beam 41. The temperature of the joining material was normalized with the temperature difference from room temperature (assumed as 25° C.), and a graph shown in
A frit (BAS 115 produced by Asahi Glass Co., Ltd.) having a width of 1 mm and a thickness of 5 μm was used as the joining material. A high strain point glass base member (PD 200 produced by Asahi Glass Co., Ltd.) was used as the glass base member subjected to the joining. The second local heating light beam 42 was radiated under a condition in which the power was 212 W, the wavelength was 808 nm, the beam diameter was 1.2 mmφ, the scanning velocity was 600 to 2000 mm/s, and the laser beam output intensity was 120 W. The first local heating light beam 41 was radiated under a condition in which the wavelength was 808 nm, the beam diameter was 1.2 mmφ, and the scanning velocity was 600 to 2000 mm/s, and the laser beam output intensity was changed within a range of 280 W to 350 W.
As shown in
According to the experimental result shown in
As described above, the first local heating light beam 41 can be radiated in the state in which the temperature of the joining material at the partially joined portion is lowered to room temperature or any temperature of not more than room temperature, and the joining material is cooled and solidified. However, the shrinkage of the glass base member proceeds, and the tensile stress is generated in the cooling process of the joining material at the temperature of not more than the softening point temperature. Therefore, there is such a possibility that the probability of appearance of the crack may be increased in a time-dependent manner in the formed joining member. Therefore, in order to obtain the glass structural unit joined by the joining member having the high long-term reliability, it is empirically preferable that the timing, at which the first local heating light beam 41 is radiated after the radiation of the second local heating light beam 42, is the timing which satisfies the following condition. That is, it is desirable that the first local heating light beam 41 is radiated within a temperature range which satisfies such a condition that the viscosity η of the joining material is not more than 1018 (Pa·sec), i.e., log(η)≦18 is given after the radiation of the second local heating light beam 42. More preferably, it is desirable that the first local heating light beam 41 is radiated within a temperature range which satisfies such a condition that the viscosity η of the joining material is not more than 1013.5 (Pa·sec), i.e., log(η)≦13.5 is given after the radiation of the second local heating light beam 42 in accordance with the same reason. The viscosity, which fulfills the condition of log(η)≦13.5, corresponds to the strain point temperature. Therefore, the latter radiation condition means the fact that the first local heating light beam 41 is radiated when the temperature of the joining material is within a range of not more than the softening point and not less than the strain point temperature after the radiation of the second local heating light beam 42. Accordingly, it is possible to further suppress the occurrence of the crack in the joining member.
In the embodiment explained above, the envelope 10 is produced, in which the rear plate 13 and the frame member 14 are joined to one another, the face plate 12 and the frame member 14 are further joined to one another, and thus the frame member 14 is inserted between the face plate 12 and the rear plate 13. However, more generally, the present invention provides the method for producing the airtight envelope at least a part of which is composed of the rear plate 13 and the face plate 12. Therefore, a glass base member, in which a protruding portion having a shape of the frame member 14 is integrally formed beforehand, can be used as one of the rear plate 13 and the face plate 12, and the glass base member can be joined to the other plate as well. Further, the face plate 12 and the frame member 14 can be previously joined to one another, and then the rear plate 13 and the frame member 14 can be joined to one another as well.
The embodiment explained above resides in the method for producing the airtight envelope to be used for the image display apparatus. More generally, the present invention is applicable when a first glass substrate and a second glass substrate are joined to one another. In this case, both of the first and second local heating light beams may be radiated from the side of the first glass substrate. Alternatively, one of the first and second local heating light beams may be radiated from the side of the first glass substrate, and the other may be radiated from the side of the second glass substrate. Further alternatively, both of the first and second local heating light beams may be radiated from the side of the second glass substrate.
EXAMPLE 1The present invention will be explained in detail below as specifically exemplified by Examples. In Example 1, the production method explained in the foregoing embodiment is applied to join a frame member and a rear plate in an airtight manner. Further, the frame member and a face plate are joined to one another in an airtight manner, and thus a vacuum airtight envelope is produced.
Step 1 (Formation of Joining Material on Frame Member (First Glass Base Member))A frame member 14 was formed as the first glass base member. Specifically, at first, a high strain point glass base member having a thickness of 1.5 mm (PD 200 produced by Asahi Glass Co., Ltd.) was prepared, and the glass base member was cut out into an outer shape of 980 mm×580 mm×1.5 mm. Subsequently, a central area of 970 mm×570 mm×1.5 mm was cut out by means of the cutting processing to form the frame member 14 having a substantially rectangular cross section with a width of 5 mm and a thickness of 1.5 mm. Subsequently, the surface of the frame member 14 was degreased by means of the washing with organic solvent, the rinse with pure water, and the UV-ozone washing.
In Example 1, a glass frit was used as joining materials 1a, 1b. A paste was used as the glass frit, wherein a Bi-based glass frit containing no lead (BAS 115 produced by Asahi Glass Co., Ltd.), which had a coefficient of thermal expansion α=79×10−7/° C., a transition point of 357° C., and a softening point of 420° C., was used as a base material, and an organic substance was dispersed and mixed therewith as a binder. The paste was formed on the frame member 14 to provide a width of 1.5 mm and a thickness of 7 μm along the circumferential length of the frame member 14 by means of the screen printing, followed by being dried at 120° C. Subsequently, in order to burn out the organic substance, the paste was heated and calcinated at 460° C. to form the joining material 1a (
Step 2 (Step of Bringing Frame Member, Electron Source Base Member, and Joining Material in Contact with Other)
A rear plate 13 (electron source base member) was formed as the second glass base member. Specifically, at first, a glass base member having a size of outer shape of 1000 mm×600 mm×1.8 mm (PD 200 produced by Asahi Glass Co., Ltd.) was prepared, and the surface was degreased by means of the washing with organic solvent, the rinse with pure water, and the UV-ozone washing. Subsequently, electron emission elements 27 of the surface electron conduction type and matrix wiring lines 28, 29 were formed in a central area of 960 mm×550 mm of the glass base member obtained as described above. The formed electron emission elements 27 were connected to the matrix wiring lines 28, 29 so that a number of pixels of 1920×3×1080 were successfully driven individually. Subsequently, a non-evaporable getter material composed of Ti was formed as a film having a thickness of 2 μm on the matrix wiring lines 28, 29 by means of the sputtering to form the non-evaporable getter (not shown). The rear plate 13 as the second glass base member was prepared as described above. In order to perform the vacuum evacuation, an opening (not shown) having a diameter of 3 mm to penetrate through the glass base member was previously provided in an area of the rear plate 13 in which the matrix wiring lines 28, 29 were not formed.
Subsequently, the members were temporarily assembled so that the joining material 1a was brought in contact with the surface of the rear plate 13 provided with the electron emission elements 27 while aligning the frame member 14 formed with the joining material 1a with respect to the rear plate 13. After that, in order to uniformize the pressurizing force exerted on the joining material 1a, a glass base member 52 (PD 200 produced by Asahi Glass Co., Ltd.) was auxiliarily arranged to cover the frame member 14. The glass base member 52, which had the same size as that of the rear plate 13, was used. Further, in order to assist the pressurizing force, the rear plate 13, the joining material 1a, and the frame member 14 were pressurized by means of an unillustrated pressurizing apparatus. In this way, the rear plate 13 and the frame member 14 were brought in contact with each other with the joining material 1a intervening therebetween (
Step 3 (First Joining Step of Radiating First Local Heating Light Beam onto Joining Material) and Step 4 (Second Joining Step of Radiating Second Local Heating Light Beam onto Joining Material to Melt Joining Material Again
An explanation will be made in detail with reference to
At first, the first local heating light beam (laser beam) was radiated onto the temporarily assembled structural unit composed of the rear plate 13, the frame member 14, and the joining material 1a manufactured in the step shown in
The radiation condition of the first local heating light beam 41 resided in a wavelength of 980 nm, a laser power of 736 W, and an effective beam diameter of 3.5 mm, and the scanning was performed at a velocity of 600 mm/s in the scanning direction D. The radiation condition of the second local heating light beam 42 resided in a wavelength of 980 nm, a laser power of 73 W, and an effective beam diameter of 0.9 mm. The second local heating light beam 42 was subjected to the scanning while following the first local heating light beam 41 in the same direction and at the same velocity as those of the first local heating light beam 41 while maintaining the spacing distance C between the optical axes of 40 mm with respect to the first local heating light beam 41. As shown in
The steps described above were also performed in the same manner for the three remaining circumferential portions to complete the joining of the rear plate 13 and the frame member 14 (
In the steps of radiating the first and second local heating light beams 41, 42, a radiation thermometer was set in the vicinity of the radiation positions of the first and second local heating light beams to measure the temperature of the joining material 1a. Specifically, the temperature of the joining material 1a was measured at measuring points A1 to A5 (0.1 mmφ) shown in
At first, the temperature of the joining material 1a was measured at the measuring point A1 and the measuring point A2 included in the effective beam of the first local heating light beam 41. The measuring point A2 was disposed at a position separated by 1.5 mm toward the second local heating light beam 42 from the central position of the first local heating light beam 41. The measuring point A1 was disposed at a position separated by 0.6 mm in the direction perpendicular to the scanning direction of the local heating light beam from the measuring point A2. The temperature of the joining material during the radiation of the first local heating light beam 41 was 640° C. to 700° C. at the measuring point A2 and 600° C. to 690° C. at the measuring point A1. Accordingly, it was confirmed that the joining material 1a was melted at the measuring points A1, A2.
Subsequently, the temperature of the joining material 1a was measured at the measuring point A5 included in the effective beam of the second local heating light beam 42 and the measuring points A3, A4 positioned outside the effective beam of the second local heating light beam 42. The measuring point A5 was disposed at a position separated by 0.3 mm in the direction opposite to the first local heating light beam 41 from the central position of the second local heating light beam 42. The measuring point A3 was disposed at a position separated by 1.0 mm toward the first local heating light beam 41 from the central position of the second local heating light beam 42. The measuring point A4 was disposed at a position separated by 0.6 mm in the direction perpendicular to the scanning direction of the laser beam from the measuring point A5. The temperature of the joining material during the radiation of the second local heating light beam 42 was 670° C. to 710° C. at the measuring point A5. On the other hand, the temperature was 110° C. to 180° C. at the measuring point A3, and the temperature was 230° C. to 330° C. at the measuring point A4.
According to the measurement results obtained as described above, it was confirmed that the joining material 1a was melted by the radiation of the first local heating light beam 41, the joining material 1a was thereafter once cooled to the temperature of not more than the softening point, and the joining material 1a was subsequently melted again by the radiation of the second local heating light beam 42. Additionally, it was confirmed that the joining material 1a was retained at the temperature of not more than the softening point at the positions disposed around the radiation position of the second local heating light beam 42 including those disposed in the direction (widthwise direction) perpendicular to the scanning direction as well. In Example 1, the temperature of the joining material was confirmed by observing the indication of the radiation thermometer while radiating the laser beam. However, the temperature may be measured by bringing a thermocouple in contact with the joining material.
Step 5 (Step of Preparing Frame Member, Joining Material, and Face Plate)Subsequently, PD 200 produced by Asahi Glass Co., Ltd. having the same size of outer shape as that of the rear plate was used as the glass base member in the same manner as the rear plate 13 to manufacture a face plate 12 provided with fluorescent films 34 and the like.
Step 6 (Step of Bringing Frame Member, Joining Material, and Face Plate in Contact with Each Other), Step 7 (First Joining Step of Radiating First Local Heating Light Beam onto Joining Material), and Step 8 (Second Joining Step of Radiating Second Local Heating Light Beam onto Joining Material to Melt Joining Material Again)
The face plate 12 and the frame member 14 were joined to one another by using the first and second local heating light beams 41, 42 in the same manner as in Steps 1 to 4 to complete the airtight envelope. The glass base member 52 was not used in Steps 6 to 8. The radiation condition of the laser beam and the scanning method resided in the same conditions as those of Steps 3 and 4. The positional relationship between the laser heads 61, 62 and the radiation objective was as shown in
The FED apparatus was manufactured as described above. When the apparatus was operated, the electron emission performance and the image display performance were stably maintained for a long period of time. It was confirmed that the joining member secured the stable airtightness and the strength of such an extent that the strength is applicable to FED.
In relation to the first local heating light beam 41 and the frame member 14, there are provided in the step 3 under the condition of Example 1:
φ=3.5 mm
w=1.5 mm
v=600 mm/s
d=1.5 mm
a=4.5×10−1 mm2/s
from which the following expressions are provided:
φ/v=5.8×10−3
(d/8)2/12a=6.5×10−3
wherein it has been confirmed that the radiation of the first local heating light beam 41 fulfills Expressions 1 and 2.
Similarly, in relation to the first local heating light beam 41 and the face plate 12, there are provided in the step 7 under the condition of Example 1:
φ=3.5 mm
w=1.5 mm
v=600 mm/s
d=1.8 mm
a=4.5×10−1 mm2/s
from which the following expressions are provided:
φ/v=5.8×10−3
(d/8)2/12a=9.4×10−3
wherein it has been confirmed that the radiation of the first local heating light beam 41 fulfills Expressions 1 and 2.
The vacuum airtight envelope manufactured in Example 1 was arranged in a pressure-reduced chamber of 10 kPa for 100 hours. It was confirmed that the development of any crack to arrive at the end portion of the joining member and the decrease in the degree of vacuum were not caused. A cross-sectional sample or specimen, which included the end portions of the joining member for joining the rear plate 13 and the frame member 14 and the joining member for joining the face plate 12 and the frame member 14, was investigated to confirm the elastic deformation in the directions directed to the inside of the base members, of the glass base members in the vicinity of the end portions of the joining members. The stress distribution was evaluated, and it was confirmed that the compressive stress areas 71 as shown in
In Example 2, as shown in
As for the joining member for joining the face plate 12 and the frame member 14, the compressive stress area was formed at the central portion in the widthwise direction of the joining member, and the tensile stress areas were formed on the both sides to interpose the compressive stress area therebetween. Therefore, even when any crack appears from the end portion in the widthwise direction of the joining member by the external force allowed to act on the joining member, the airtightness is maintained for a long period of time, because the development of the crack is prohibited in the compressive stress area disposed at the central portion. As for the joining member for joining the rear plate 13 and the frame member 14, the compressive stress areas were formed at the central portion in the widthwise direction and the end portions in the widthwise direction of the joining member, and the tensile stress areas were formed to be interposed therebetween, in the same manner as in Example 1. Therefore, the crack hardly develops, in addition to which it is possible to preferably suppress the occurrence of the crack itself in the joining member by the external force. Therefore, the airtightness can be maintained more stably for a long period of time.
The FED apparatus was manufactured as described above. When the apparatus was operated, the electron emission performance and the image display performance were stably maintained for a long period of time. It was confirmed that the joining member secured the stable airtightness and the strength of such an extent that the strength is applicable to FED.
In relation to the first local heating light beam 41 and the integrated unit of the face plate 12, the frame member 14, and the joining material 1a, there are provided in the step of
φ=3.5 mm
w=1.5 mm
v=600 mm/s
d=3.3 mm
a=4.5×10−1 mm2/s
from which the following expressions are provided:
φ/v=5.8×10−3
(d/8)2/12a=3.2×10−2
wherein it has been confirmed that the radiation of the first local heating light beam 41 fulfills Expressions 1 and 2.
The vacuum airtight envelope manufactured in Example 2 was arranged in a pressure-reduced chamber of 10 kPa for 100 hours. It was confirmed that the development of any crack to arrive at the end portion of the joining member and the decrease in the degree of vacuum were not caused. A cross-sectional sample or specimen, which included the end portions of the joining member for joining the rear plate 13 and the frame member 14, was investigated to confirm the elastic deformation in the directions directed to the inside of the base members, of the glass base members in the vicinity of the end portions of the joining members. It was confirmed that the compressive stress areas 71 as shown in
The airtight joining was performed for a frame member and a rear plate by applying the embodiment described above, and the airtight joining was further performed for the frame member and a face plate to produce a vacuum airtight envelope.
(Step 1)At first, a frame member 14 was formed. Specifically, a high strain point glass base member having a thickness of 1.5 mm (PD 200) was cut out into an outer shape of 980 mm×580 mm×1.5 mm. Subsequently, a central area of 970 mm×560 mm×1.5 mm was cut out by means of the cutting processing to form the frame member 14 having a substantially rectangular cross section with a width of 5 mm and a thickness of 1.5 mm. Subsequently, the surface of the frame member 14 was degreased by means of the washing with organic solvent, the rinse with pure water, and the UV-ozone washing.
Subsequently, a joining material 1a was formed on the frame member 14. In Example 3, a glass frit was used as the joining material 1a (equivalently as a joining material 1b as well). The glass frit, which was used, was a paste wherein a Bi-based glass frit containing no lead (BAS 115), which had a coefficient of thermal expansion α=79×10−7/° C., a transition point of 357° C., and a softening point of 420° C., was used as a base material, and an organic substance was dispersed and mixed therewith as a binder. Subsequently, the joining material 1a, which had a width of 1 mm and a thickness of 7 μm, was formed along the circumferential length on the frame member 14 by means of the screen printing, followed by being dried at 120° C. Further, in order to burn out the organic substance, the heating and the calcination were performed at 460° C. to form the joining material 1a (
Subsequently, an electron emission element substrate (board) was prepared as a rear plate 13, wherein electron emission elements 27 and driving matrix wiring lines 28, 29 were previously formed on a glass base member composed of a high strain point glass base member (PD 200) having an size of outer shape of 1000 mm×600 mm×1.8 mm. Subsequently, the frame member 14 formed with the joining material 1a and the rear plate 13 were arranged oppositely so that they are brought in contact with each other with the joining material 1a intervening therebetween. Specifically, the frame member 14 and the rear plate 13 were opposed to one another and they were brought in contact with each other while performing the alignment so that the surface of the frame member 14, on which the joining material 1a was formed, was opposed to the surface of the rear plate 13 (surface disposed on the inner surface side of the airtight envelope) on which the electron emission elements 27 were formed. In order to uniformize the pressing force exerted on the joining material 1a, a third glass base member 52, which was composed of the high strain point glass base member (PD 200) and which had the same size as that of the rear plate 13, was placed on the frame member 14. Further, the third glass base member 52 was pressed by an unillustrated pressurizing apparatus in order to assist the pressing force. The rear plate 13 and the frame member 14 were brought in contact with each other with the joining material 1a intervening therebetween as described above (
Subsequently, the laser beams were radiated onto the temporarily assembled structural unit composed of the rear plate 13, the frame member 14, the joining material 1a, and the third glass base member 52. Two processing semiconductor laser apparatuses were prepared as laser light sources. Laser heads 61, 62 were fixed to a breadboard 60 at a distance between optical axes of 50 mm. Any one of the laser heads 61, 62 was set so that the optical axis of each of the first and second local heating light beams 41, 42 is perpendicular to the third glass base member 52. Each of the laser heads 61, 62 was arranged so that the distance between the laser emission port and the third glass base member 52 was 10 cm (
The second local heating light beam 42 was a laser beam having a wavelength of 980 nm, a laser power of 212 W, and an effective diameter of 2 mm, and the second local heating light beam 42 was subjected to the scanning at a velocity of 1000 mm/s in the direction D (
In order to confirm the states of the joining member before and after the radiation of the first and second local heating light beams 41, 42, the joined state was confirmed by means of an unillustrated radiation thermometer and an unillustrated high speed camera in which the observing range was set in the vicinity of the radiation positions of the laser heads. The left drawing of
The joined state between the rear plate 13 and the frame member 14 was confirmed by means of an optical microscope. As a result, it was confirmed that the satisfactory joining involving no air-gap (void) was obtained over the substantially entire width W of the joining material 1a.
(Step 4)Subsequently, a face plate 12, which was formed with fluorescent films and other components and which had the same size of outer shape as that of the rear plate 13, was prepared. The face plate 12 and the frame member 14 were joined to one another in accordance with the same or equivalent procedures as those in Steps 1 to 3 described above. In Step 4, the third glass base member 52 for the pressing was not used, and the laser beams were directly radiated from the positions disposed over or above the face plate 12. The joining material 1b was formed on the face plate 12, and the radiation condition of the laser beam (for example, the arrangement condition and the specification of the laser head) was the same as that in Step 3 (
The airtight envelope was manufactured as described above, and the FED apparatus was completed in accordance with the ordinary method. When the completed FED was operated, it was confirmed that the electron emission and the image display were successfully performed stably for a long period of time, and the stable airtightness, which was to such an extent that the airtightness was applicable to FED, was secured.
In relation to the first local heating light beam 41 and the frame member 14, there are provided in the step 3 under the condition of Example 3:
φ=2 mm
w=1 mm
v=1000 mm/s
d=1.5 mm
a=4.6×10−1 mm2/s
from which the following expressions are provided:
φ/v=2×10−3
(d/8)2/12a=6.4×10−3
wherein it has been confirmed that the radiation of the first local heating light beam 41 fulfills Expressions 1 and 2.
Similarly, in relation to the first local heating light beam 41 and the face plate 12, there are provided in the step 4 under the condition of Example 3:
φ=2 mm
w=1 mm
v=1000 mm/s
d=1.8 mm
a=4.6×10−1 mm2/s
from which the following expressions are provided:
φ/v=2×10−3
(d/8)2/12a=9.2×10−3
wherein it has been confirmed that the radiation of the first local heating light beam 41 fulfills Expressions 1 and 2.
The vacuum airtight envelope manufactured in Example 3 was arranged in a pressure-reduced chamber of 10 kPa for 100 hours. It was confirmed that the development of any crack to arrive at the end portion of the joining member and the decrease in the degree of vacuum were not caused. A cross-sectional sample or specimen, which included the end portions of the joining member for joining the rear plate 13 and the frame member 14 and the joining member for joining the face plate 12 and the frame member 14, was investigated to confirm the elastic deformation in the directions directed to the inside of the base members, of the glass base members in the vicinity of the end portions of the joining members. The stress distribution was evaluated, and it was confirmed that the compressive stress areas 71 as shown in
Example 4 is the same as or equivalent to Example 3 except that a central portion in the direction of the width W of the joining material 1a was formed to be higher than the surroundings thereof by 1.3 μm as shown in
The joined state between the rear plate 13 and the frame member 14 was confirmed by means of an optical microscope. As a result, it was confirmed that the satisfactory joining involving no air-gap (void) was obtained over the substantially entire width W of the joining material 1a.
The airtight envelope was manufactured as described above, and the FED apparatus was completed in accordance with the ordinary method. When the completed FED was operated, it was confirmed that the electron emission and the image display were successfully performed stably for a long period of time, and the stable airtightness, which was to such an extent that the airtightness was applicable to FED, was secured.
In relation to the first local heating light beam 41 and the frame member 14, there are provided in the step 3 under the condition of Example 4:
φ=2 mm
w=1 mm
v=1000 mm/s
d=1.5 mm
a=4.6×10−1 mm2/s
from which the following expressions are provided:
φ/v=2×10−3
(d/8)2/12a=6.4×10−3
wherein it has been confirmed that the radiation of the first local heating light beam 41 fulfills Expressions 1 and 2.
Similarly, in relation to the first local heating light beam 41 and the face plate 12, there are provided in the step 4 under the condition of Example 4:
φ=2 mm
w=1 mm
v=1000 mm/s
d=1.8 mm
a=4.6×10−1 mm2/s
from which the following expressions are provided:
φ/v=2×10−3
(d/8)2/12a=9.2×10−3
wherein it has been confirmed that the radiation of the first local heating light beam 41 fulfills Expressions 1 and 2.
The vacuum airtight envelope manufactured in Example 4 was arranged in a pressure-reduced chamber of 10 kPa for 100 hours. It was confirmed that the development of any crack to arrive at the end portion of the joining member and the decrease in the degree of vacuum were not caused. A cross-sectional sample or specimen, which included the end portions of the joining member for joining the rear plate 13 and the frame member 14 and the joining member for joining the face plate 12 and the frame member 14, was investigated to confirm the elastic deformation in the directions directed to the inside of the base members, of the glass base members in the vicinity of the end portions of the joining members. The stress distribution was evaluated, and it was confirmed that the compressive stress areas 71 as shown in
Example 5 was the same as or equivalent to Example 3 except that the joining material 1a was formed on the rear plate 13 which was the base member disposed on the distal side as viewed from the laser head as shown in
The airtight envelope was manufactured as described above, and the FED apparatus was completed in accordance with the ordinary method. When the completed FED was operated, it was confirmed that the electron emission and the image display were successfully performed stably for a long period of time, and the stable airtightness, which was to such an extent that the airtightness was applicable to FED, was secured.
The joining material 1b is formed on the frame member 14 in Example 5. However, the joining material 1b can be formed on the face plate 12 as well.
In relation to the first local heating light beam 41 and the frame member 14, there are provided in the step of
φ=2 mm
w=1 mm
v=1000 mm/s
d=1.5 mm
a=4.6×10−1 mm2/s
from which the following expressions are provided:
φ/v=2×10−3
(d/8)2/12a=6.4×10−3
wherein it has been confirmed that the radiation of the first local heating light beam 41 fulfills Expressions 1 and 2.
Similarly, in relation to the first local heating light beam 41 and the face plate 12, there are provided in the step of
φ=2 mm
w=1 mm
v=1000 mm/s
d=1.8 mm
a=4.6×10−1 mm2/s
from which the following expressions are provided:
φ/v=2×10−3
(d/8)2/12a=9.2×10−3
wherein it has been confirmed that the radiation of the first local heating light beam 41 fulfills Expressions 1 and 2.
The vacuum airtight envelope manufactured in Example 5 was arranged in a pressure-reduced chamber of 10 kPa for 100 hours. It was confirmed that the development of any crack to arrive at the end portion of the joining member and the decrease in the degree of vacuum were not caused. A cross-sectional sample or specimen, which included the end portions of the joining member for joining the rear plate 13 and the frame member 14 and the joining member for joining the face plate 12 and the frame member 14, was investigated to confirm the elastic deformation in the directions directed to the inside of the base members, of the glass base members in the vicinity of the end portions of the joining members. The stress distribution was evaluated, and it was confirmed that the compressive stress areas 71 as shown in
In Example 6, the face plate 12 and the frame member 14 were joined to one another by means of the whole heating, and then the rear plate 13 and the frame member 14 were laser-joined to one another in the same manner as in Example 3. The temperature of the joining material 1a, which was obtained immediately before the radiation of the first local heating light beam 41, was 260 to 290° C. as indicated by the measured value of the radiation thermometer, which was not more than the softening point of the joining materials 1a.
The airtight envelope was manufactured as described above, and the FED apparatus was completed in accordance with the ordinary method. When the completed FED was operated, it was confirmed that the electron emission and the image display were successfully performed stably for a long period of time, and the stable airtightness, which was to such an extent that the airtightness was applicable to FED, was secured.
Any member, which tends to be affected by the heat, is not installed on the face plate 12 unlike the rear plate 13. Therefore, it is possible to adopt the production method as described above.
In relation to the first local heating light beam 41 and the integrated unit of the face plate 12, the frame member 14, and the joining material 1a, there are provided in the step 4 of
φ=2 mm
w=1 mm
v=1000 mm/s
d=3.3 mm
a=4.6×10−1 mm2/s
from which the following expressions are provided:
φ/v=2×10−3
(d/8)2/12a=3.1×10−2
wherein it has been confirmed that the radiation of the first local heating light beam 41 fulfills Expressions 1 and 2.
The vacuum airtight envelope manufactured in Example 6 was arranged in a pressure-reduced chamber of 10 kPa for 100 hours. It was confirmed that the development of any crack to arrive at the end portion of the joining member and the decrease in the degree of vacuum were not caused. A cross-sectional sample or specimen, which included the end portions of the joining member for joining the rear plate 13 and the frame member 14, was investigated to confirm the elastic deformation in the directions directed to the inside of the base members, of the glass base members in the vicinity of the end portions of the joining members. The stress distribution was evaluated, and it was confirmed that the compressive stress areas 71 as shown in
Example 7 was the same as or equivalent to Example 3 except that the distance (50 mm) between the optical axes of the first local heating light beam 41 and the second local heating light beam 42 in Example 3 was changed to 200 mm. The temperature of the joining material 1a, which was obtained immediately before the radiation of the first local heating light beam 41, was 150 to 190° C. as indicated by the measured value of the radiation thermometer, which was not more than the softening points of the joining materials 1a, 1b. It was confirmed that only parts of the joining materials 1a, 1b in the widthwise direction were subjected to the joining, and a temporary fixed state was obtained.
The airtight envelope was manufactured as described above, and the FED apparatus was completed in accordance with the ordinary method. When the completed FED was operated, it was confirmed that the electron emission and the image display were successfully performed stably for a long period of time, and the stable airtightness, which was to such an extent that the airtightness was applicable to FED, was secured.
In relation to the first local heating light beam 41 and the frame member 14, there are provided in the step 3 of
φ=2 mm
w=1 mm
v=1000 mm/s
d=1.5 mm
a=4.6×10−1 mm2/s
from which the following expressions are provided:
φ/v=2×10−3
(d/8)2/12a=6.4×10−3
wherein it has been confirmed that the radiation of the first local heating light beam 41 fulfills Expressions 1 and 2.
Similarly, in relation to the first local heating light beam 41 and the face plate 12, there are provided in the step 4 of
φ=2 mm
w=1 mm
v=1000 mm/s
d=1.8 mm
a=4.6×10−1 mm2/s
from which the following expressions are provided:
φ/v=2×10−3
(d/8)2/12a=9.2×10−3
wherein it has been confirmed that the radiation of the first local heating light beam 41 fulfills Expressions 1 and 2.
The vacuum airtight envelope manufactured in Example 7 was arranged in a pressure-reduced chamber of 10 kPa for 100 hours. It was confirmed that the development of any crack to arrive at the end portion of the joining member and the decrease in the degree of vacuum were not caused. A cross-sectional sample or specimen, which included the end portions of the joining member for joining the rear plate 13 and the frame member 14 and the joining member for joining the face plate 12 and the frame member 14, was investigated to confirm the elastic deformation in the directions directed to the inside of the base members, of the glass base members in the vicinity of the end portions of the joining members. The stress distribution was evaluated, and it was confirmed that the compressive stress areas 71 as shown in
Example 8 was the same as or equivalent to Example 3 except that only the first local heating light beam 41 was radiated without performing the radiation of the second local heating light beam 42.
In relation to the first local heating light beam 41 and the frame member 14, there are provided in the step 3 of
φ=2 mm
w=1 mm
v=1000 mm/s
d=1.5 mm
a=4.6×10−1 mm2/s
from which the following expressions are provided:
φ/v=2×10−3
(d/8)2/12a=6.4×10−3
wherein it has been confirmed that the radiation of the first local heating light beam 41 fulfills Expressions 1 and 2.
Similarly, in relation to the first local heating light beam 41 and the face plate 12, there are provided in the step 4 of
φ=2 mm
w=1 mm
v=1000 mm/s
d=1.8 mm
a=4.6×10−1 mm2/s
from which the following expressions are provided:
φ/v=2×10−3
(d/8)2/12a=9.2×10−3
wherein it has been confirmed that the radiation of the first local heating light beam 41 fulfills Expressions 1 and 2.
The vacuum airtight envelope manufactured in Example 8 was arranged in a pressure-reduced chamber of 10 kPa for 100 hours. It was confirmed that the development of any crack to arrive at the end portion of the joining member and the decrease in the degree of vacuum were not caused. A cross-sectional sample or specimen, which included the end portions of the joining member for joining the rear plate 13 and the frame member 14 and the joining member for joining the face plate 12 and the frame member 14, was investigated to confirm the elastic deformation in the directions directed to the inside of the base members, of the glass base members in the vicinity of the end portions of the joining members. The stress distribution was evaluated, and it was confirmed that the compressive stress areas 71 as shown in
Example 9 was the same as or equivalent to Example 3 except that the distance (50 mm) between the optical axes of the first local heating light beam 41 and the second local heating light beam 42 in Example 3 was changed to 2 mm.
In relation to the first local heating light beam 41 and the frame member 14, there are provided in the step 3 of
φ=2 mm
w=1 mm
v=1000 mm/s
d=1.5 mm
a=4.6×10−1 mm2/s
from which the following expressions are provided:
φ/v=2×10−3
(d/8)2/12a=6.4×10−3
wherein it has been confirmed that the radiation of the first local heating light beam 41 fulfills Expressions 1 and 2.
Similarly, in relation to the first local heating light beam 41 and the face plate 12, there are provided in the step 4 of
φ=2 mm
w=1 mm
v=1000 mm/s
d=1.8 mm
a=4.6×10−1 mm2/s
from which the following expressions are provided:
φ/v=2×10−3
(d/8)2/12a=9.2×10−3
wherein it has been confirmed that the radiation of the first local heating light beam 41 fulfills Expressions 1 and 2.
The vacuum airtight envelope manufactured in Example 9 was arranged in a pressure-reduced chamber of 10 kPa for 100 hours. It was confirmed that the development of any crack to arrive at the end portion of the joining member and the decrease in the degree of vacuum were not caused. A cross-sectional sample or specimen, which included the end portions of the joining member for joining the rear plate 13 and the frame member 14 and the joining member for joining the face plate 12 and the frame member 14, was investigated to confirm the elastic deformation in the directions directed to the inside of the base members, of the glass base members in the vicinity of the end portions of the joining members. The stress distribution was evaluated, and it was confirmed that the compressive stress areas 71 as shown in
As exemplified by Examples 8 and 9, the compressive stress areas 71 are formed at least at the end portions in the widthwise direction of the joining member by performing the radiation of the first local heating light beam at the beam diameter φ and the velocity of movement v which satisfy Expressions 1 and 2 with respect to the thickness d of the glass base member, the thermal diffusivity a of the glass base member, and the width w of the joining material. Therefore, it is possible to obtain the joined unit of glass base members, the airtight envelope, or the glass structural unit subjected to the joining with the joining member capable of preferably suppressing the appearance of any crack by the external force.
In Examples 1 to 7, the auxiliary radiation of the second local heating light beam is performed in addition to the main radiation performed with the first local heating light beam to fulfill the radiation condition represented by Expressions 1 and 2. Accordingly, the joined unit of glass base members, the airtight envelope, or the glass structural unit, which is subjected to the joining with the joining member capable of further suppressing the appearance and the development of the crack, is obtained.
As exemplified by Examples 1 and 2, the compressive stress area 71 is also formed at the central portion in the widthwise direction of the joining member by performing the auxiliary radiation of the second local heating light beam for heating and melting only the central portion in the widthwise direction of the joining material while following the main radiation with the first local heating light beam. Therefore, it is possible to suppress the development of the crack more reliably.
As exemplified by Examples 3 to 7, the pair of glass base members can be temporarily fixed when the main radiation is performed, by performing the auxiliary radiation of the second local heating light beam for heating and melting only the part of the joining material in the widthwise direction prior to the main radiation with the first local heating light beam. Accordingly, it is possible to more stably perform the joining effected by the main radiation, it is possible to preferably suppress the remaining of air-gaps (voids) at the inside of the joining member, and it is possible to suppress the appearance of the crack from the inside of the joining member.
While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.
This application claims the benefit of Japanese Patent Application No. 2009-250277, filed on Oct. 30, 2009, Japanese Patent Application No. 2010-059377, filed on Mar. 16, 2010, Japanese Patent Application No. 2010-200173, filed on Sep. 7, 2010, which are hereby incorporated by reference herein in their entirety.
Claims
1. A joined unit of glass base members, comprising:
- a first glass base member;
- a second glass base member; and
- a joining member which joins the first glass base member and the second glass base member, which is capable of providing a viscosity that has a negative temperature coefficient, and which extends at a predetermined width along opposing surfaces of the first glass base member and the second glass base member, wherein:
- at least one of the first glass base member and the second glass base member is elastically deformed while being depressed in an internal direction of the glass base member in the vicinity of an end portion in a widthwise direction of the joining member;
- a boundary surface between the elastically deformed glass base member and the joining member and a surface of the elastically deformed glass base member, which are disposed in the vicinity of the end portion in the widthwise direction of the joining member, are positioned on an internal side of the glass base member as compared with a boundary surface between the elastically deformed glass base member and the joining member which is disposed in the vicinity of a central portion in the widthwise direction of the joining member; and
- an area, in which a residual stress in a thickness direction of the joining member is a compressive stress, is formed in the vicinity of the end portion in the widthwise direction of the joining member.
2. The joined unit of glass base members according to claim 1, wherein:
- an area, in which a residual stress in the thickness direction of the joining member is a compressive stress, is formed at the central portion in the widthwise direction of the joining member; and
- an area, in which a residual stress in the thickness direction of the joining member is a tensile stress, is formed adjacently to the area which is formed at the central portion in the widthwise direction of the joining member to provide the compressive stress and the area which is formed at the end portion in the widthwise direction of the joining member to provide the compressive stress.
3. An airtight envelope comprising:
- a first glass base member;
- a second glass base member; and
- a joining member which joins the first glass base member and the second glass base member, which is capable of providing a viscosity that has a negative temperature coefficient, and which extends at a predetermined width along opposing surfaces of the first glass base member and the second glass base member, wherein:
- at least one of the first glass base member and the second glass base member is elastically deformed while being depressed in an internal direction of the glass base member in the vicinity of an end portion in a widthwise direction of the joining member;
- a boundary surface between the elastically deformed glass base member and the joining member and a surface of the elastically deformed glass base member, which are disposed in the vicinity of the end portion in the widthwise direction of the joining member, are positioned on an internal side of the glass base member as compared with a boundary surface between the elastically deformed glass base member and the joining member which is disposed in the vicinity of a central portion in the widthwise direction of the joining member; and
- an area, in which a residual stress in a thickness direction of the joining member is a compressive stress, is formed in the vicinity of the end portion in the widthwise direction of the joining member.
4. The airtight envelope according to claim 3, wherein:
- an area, in which a residual stress in the thickness direction of the joining member is a compressive stress, is formed at the central portion in the widthwise direction of the joining member; and
- an area, in which a residual stress in the thickness direction of the joining member is a tensile stress, is formed adjacently to the area which is formed at the central portion in the widthwise direction of the joining member to provide the compressive stress and the area which is formed at the end portion in the widthwise direction of the joining member to provide the compressive stress.
5. A method for producing a glass structural unit, including joining a first glass base member and a second glass base member for forming at least a part of the glass structural unit together with the first glass base member, the method comprising:
- a step of arranging a joining member between the first glass base member and the second glass base member so that the joining member is brought in contact with both of the first glass base member and the second glass base member, the joining member being capable of providing a viscosity which has a negative temperature coefficient, and the joining member extending at a predetermined width along opposing surfaces of the first glass base member and the second glass base member;
- a step of pressing the joining member in a thickness direction of the joining member; and
- a first joining step of radiating a first local heating light beam onto the joining member via the first glass base member so that a radiation position is moved in a direction in which the joining member extends, heating and melting the joining member in an entire region in a widthwise direction, and then cooling the joining member to a temperature of not more than a softening point, wherein:
- the following expressions are fulfilled by a velocity of movement v (m/s) of the radiation position brought about by the first local heating light beam and a beam diameter φ (m) of the first local heating light beam provided that d (m) represents a thickness of the first glass base member, a (m2/s) represents a thermal diffusivity of the first glass base member, and w (m) represents the width of the joining member: φ/v<(d/8)2/(12a) (Expression 1) φ>w (Expression 2)
6. The method for producing the glass structural unit according to claim 5, further comprising:
- a second joining step of radiating a second local heating light beam onto the joining member cooled to the temperature of not more than the softening point in the first joining step so that a radiation position is moved in the direction in which the joining member extends, heating and melting only a central portion of the joining member interposed between both side portions in the widthwise direction of the joining member so that the both side portions are not softened, and then cooling the heated and melted central portion of the joining member to a temperature of not more than the softening point.
7. The method for producing the glass structural unit according to claim 6, wherein the second local heating light beam is radiated so that the radiation position, which is brought about by the second local heating light beam, follows the radiation position which is brought about by the first local heating light beam.
8. The method for producing the glass structural unit according to claim 5, further comprising:
- a second joining step of radiating a second local heating light beam onto the joining member prior to the radiation of the first local heating light beam in the first joining step so that a radiation position is moved in the direction in which the joining member extends, successively heating and melting parts in the widthwise direction of the joining member in the direction in which the joining member extends, thereafter cooling the heated and melted parts of the joining member to a temperature of not more than the softening point, and successively forming partially joined portions in partial areas in the widthwise direction of the joining member in the direction in which the joining member extends, wherein:
- the second local heating light beam is radiated so that the radiation position, which is brought about by the first local heating light beam, follows the radiation position which is brought about by the second local heating light beam.
9. The method for producing the glass structural unit according to claim 8, wherein the second local heating light beam is radiated so that the partially joined portions are formed continuously in the direction in which the joining member extends.
10. The method for producing the glass structural unit according to claim 8, wherein the first local heating light beam is radiated during a period in which a temperature of the joining member fulfills a range of −0.1≦(T2−25)/(Tsf−25)≦1 at each of positions of the joining member provided that T2 represents the temperature of the joining member and Tsf represents the softening point of the joining member.
11. The method for producing the glass structural unit according to claim 8, wherein the first local heating light beam is radiated during a period in which the viscosity of the joining member is not more than 1018 (Pa·sec) at each of positions of the joining member.
12. The method for producing the glass structural unit according to claim 8, wherein the first local heating light beam is radiated during a period in which the viscosity of the joining member is not more than 1013.5 (Pa·sec) at each of positions of the joining member.
Type: Application
Filed: Oct 25, 2010
Publication Date: May 5, 2011
Applicant: CANON KABUSHIKI KAISHA (Tokyo)
Inventors: Mamo Matsumoto (Hiratsuka-shi), Tomohiro Saito (Kouza-gun), Matsutaka Maeda (Kawasaki-shi), Nobuhiro Ito (Yamato-shi), Toshitami Hara (Tokyo)
Application Number: 12/911,183
International Classification: H05K 5/06 (20060101); C03B 23/203 (20060101);
