Abstract: The invention relates to thermally tempered safety glass comprising an non-abrasive and porous SiO2 layer which is stable during sintering and has a refractive index of between 1.25 and 1.40. The inventive safety glass can be obtained by coating standard soda-lime glass with an aqueous coating solution having a pH value of between 3 and 8 and containing between 0.5 and 5.0 wt. % of [SiOx(OH)y]n particles (0<y<4 and 0<x<2) having a particle size of between 10 and 60 nm, and a surfactant mixture. The coated glass is then dried, thermally hardened at temperatures of at least 600° C. for several minutes, and thermally tempered by a flow of air.

Abstract: An object is to provide a method for producing an optical synthetic quartz glass and an optical synthetic glass, having a birefringence of lower than 0.5 nm/cm and having favorable refractive index distribution, yet without lowering the productivity, as well as to provide an annealing furnace suitably used in practicing said method. In a step of raising the temperature of a columnar optical synthetic quartz glass preform to a temperature of from 800° C. to 1200° C., and after keeping for a definite time, lowering the temperature, the temperature is lowered with a temperature difference of from 1 to 20° C. between the temperature of the light transmitting surface of the optical synthetic quartz glass preform and the temperature of the outer peripheral side surface of the optical synthetic quartz glass preform at temperature-lowering rates of from 2 to 50° C./hour, respectively.

Abstract: A flat glass plate having a low residual stress, suitable for use in preparing a display, can be prepared without an annealing or polishing process by way of controlling the horizontal temperature gradient of a molten glass plate to a specific range during cooling.

Abstract: A system and method for heating, forming, and tempering a glass sheet includes pre-heating the glass sheet to at least a first predetermined temperature. The system and method includes also applying radio-frequency energy to the glass sheet to heat it to at least a second predetermined temperature and cooling at least one outer surface of the glass sheet to at least a third predetermined temperature to temper the glass sheet.

Abstract: The invention provides a method for producing a quartz glass jig for use in semiconductor industries, which enables increasing the surface layer cleanliness simply and surely at low cost; it also provides a quartz glass jig improved in surface layer cleanliness. The inventive means for resolution are a method comprising processing a quartz glass raw material into a desired shape by a treatment inclusive of fire working, annealing for stress removal, and cleaning treatment to obtain the final product, the method is characterized by that it comprises performing gas phase etching step and gas phase purification step on the surface layer of the quartz glass jig after applying the annealing treatment for stress removal but before the cleaning treatment, wherein the gas phase purification step is carried out continuously after the gas phase etching step.

Abstract: A production method of synthetic silica glass according to the present invention comprises a first step of ejecting a silicon compound and a combustion gas containing oxygen and hydrogen from a burner to effect hydrolysis of the silicon compound in oxyhydrogen flame to produce fine particles of silica glass, and thereafter depositing and vitrifying the fine particles of silica glass on a target opposed to the burner to obtain a synthetic silica glass ingot; a second step of heating the synthetic silica glass ingot or the like obtained in the first step up to a first retention temperature of not less than 900° C., retaining the ingot or the like at the first retention temperature, and cooling the ingot or the like at a temperature decrease rate of not more than 10° C./h down to a temperature of not more than 500° C.; and a third step of heating the synthetic silica glass ingot or the like obtained in the second step up to a second retention temperature of not less than 500° C.

Abstract: A silica glass member for use with a light having a specific wavelength of 250 nm or shorter, in which the difference in the maximum and the minimum values of hydroxyl group concentration as measured in a plurality of points within a plane vertical to an optical axis whose center is the crossing point of its optical axis with the optical axis of the silica glass member is 50 ppm or lower; and in which the plurality of signed birefringence values obtained based on the birefringence values measured on several points within a plane vertical to an optical axis whose center is the crossing point of its optical axis with the optical axis of the silica glass member and the direction of the fast axis fall within a range of from −2.0 to +2.0 nm/cm. Thus, a silica glass member having high optical transmittance and a high resistance against ultraviolet radiations is provided.

Abstract: A method for forming plural waveguide structures in an optical substrate, such as lithium niobate, employs multiple stages of annealed proton exchange. In each stage, the substrate is masked to define a region corresponding to at least one waveguide structure. The mask-defined region is exposed to a proton exchange agent for a predetermined time and at a predetermined temperature, and the substrate is then annealed at predetermined time/temperature conditions. By selecting appropriate process parameters for each APE stage, each of the resultant waveguide structures may be optimized for desired physical and optical characteristics. The method may be utilized, for example, to fabricate sub-Rayleigh range couplers having high coupling efficiencies.

Abstract: The invention relates to a method for relaxing stress in glass, especially at the base of the neck of a television funnel, comprising at least the following steps: the glass which is to be relaxed is heated from an initial temperature T1 to a holding temperature T2; said glass is maintained at the holding temperature T2 for a period of time t2 until the glass has relaxed; the glass is cooled to a temperature T3 which is always less than T1; the temperature T2 is maintained, and the heating and cooling processes are carried out by means of a regulating circuit comprising at least one temperature sensor for detecting the temperature and one heating unit as a control element. The invention is characterised in that the heating unit comprises infrared beam emitters for heating the glass which is to be relaxed, said beams having a thermal delay time of less than 10 s, especially less than 5 s.

Abstract: The invention relates to the loading of quartz glass objects with hydrogen in an annealing process in a furnace for improving the homogeneity of the refractive index and the laser resistance while, at the same time, maintaining a specified stress birefringence of each of the glass objects. Initially, the distribution of the refractive index, the stress birefringence, the distribution of the hydrogen and the differences in refractive index, which are to the equalized, are determined in the respective glass object, after which the hydrogen change, which is necessary for equalizing the refractive index, is determined. Furthermore, the annealing temperature and its holding time, as well as the hydrogen concentration and the hydrogen pressure in the furnace are adjusted to achieve a sufficiently equalized distribution of refractive index.

Abstract: In a process for producing an air-quench-toughened glass plate, defective glass plates containing nickel sulfide (NiS) are removed by compulsory breaking the glass plates. Such compulsory breakage is carried out in the course of a batch-manner soaking process carried out after a toughening step; in the course of a toughening step carried out after generation of cracks in an annealing step; in the course of a toughening step carried out after generation of cracks in a pretreatment step; or in the course of a continuous annealing step carried out after a toughening step. Through the method, NiS-free toughened glass plates of high quality can be produced.

Abstract: A film forming device in a substrate manufacturing apparatus a stage section on which a cassette storing a plurality of glass substrates is mounted. A treatment section for subjecting the substrate to a predetermined treatment is arranged to oppose the stage section. A washing section for washing the substrate is arranged near the stage section and the treatment section and deviated from a space between the stage section and the treatment section in a second direction crossing a first direction passing through the stage section and the treatment section. A transfer robot is arranged between the stage section and the treatment section. The transfer robot transfers the substrate between the stage section, treatment section, and washing section and loads the substrate, washed in the washing section, directly into the treatment section.

Abstract: Disclosed is an optical glass comprising, expressed as weight percentages, greater than or equal to 18 percent and less than 30 percent of SiO2, greater than or equal to 12 percent and less than 23 percent of BaO, 22 to 37 percent TiO2, greater than or equal to 7 percent and less than 16 percent Nb2O5, 5 to 20 percent of Na2O, 0 to 6 percent of K2O, 0 to 5 percent of CaO, 0 to 5 percent of SrO, 0 to 4 percent of ZrO2, 0 to 3 percent of Ta2O5, 0 to 1 percent of Sb2O5, and greater than or equal to 0 percent and less than 0.5 percent of P2O5, and by essentially not comprising PbO, As2O3, and F. The optical glass exhibits a refractive index (nd) greater than or equal to 1.80 and an Abbé number (vd) less than or equal to 30. A method of manufacturing a glass material for press molding is disclosed.

Abstract: A method of manufacturing an integrated optic device having at least one waveguide formed in a surfaced thereof is described. The waveguide is formed utilizing a two-step proton exchange process in which the substrate is bathed in a strong acid and then subjected to a plurality of annealing cycles.

Abstract: The invention concerns a quartz glass body for an optical component for the transmission of UV radiation with a wavelength of 250 nm and less, especially for a wavelength of 157 nm, as well as a process for the manufacture of the quartz glass body where fine quartz glass particles are formed by flame hydrolysis of a silicon compound, deposited and vitrified. Suitability of a quartz glass as represented by high base transmission and radiation resistance depends on structural properties caused by local stoichiometric deviations, and on the chemical composition. The quartz glass body according to the inventions is distinguished by a uniform base transmission (relative change of base transmission ≦1%) in the wavelength range from 155 nm to 250 nm (radiation penetration depth of 10 mm) of at least 80%, a low OH content (less than 10 ppm by weight) and a glass structure substantially free from oxygen defect centers.

Abstract: A method for heat treating a synthetic quartz glass for optical use in a heating furnace, that comprises covering the surroundings of a synthetic quartz glass body with a SiO2 powder having a mean dissolved hydrogen molecule concentration of 1×1019 molecules/cm3 or higher, and then heat treating the body.

Abstract: The present invention relates to a laser annealing system which reduces damages and contamination to a chamber window by adding a buffer window between the chamber window and a silicon film being annealed by a laser beam. The laser annealing system includes a chamber window for passing a laser beam therethrough, a chamber wall constituting an outer frame of the chamber, wherein the chamber wall and the chamber window form a sealed inner space, a process chamber in which a laser annealing takes place by annealing the substrate with a laser, and a buffer layer formed between the chamber window and the substrate to reduce any contaminants from the annealing process from being deposited directly on the chamber window. The buffer layer may be equipped with a predetermined pattern to selectively block the laser beam in accordance with the pattern in order to selectively anneal the silicon film formed on the substrate.

Abstract: A method of thermally treating a glass or glass-like material, preferably a glass sheet, without the use of conventional tunnel-type furnaces, to effect rapid heating of glass and glass-like materials from any initial temperature to any required temperature so that the glass sheet can be processed by shaping, bending, tempering, annealing, coating and floating of the glass sheet without cracking of the glass sheet is described. In the inventive method a microwave radiation with appropriate uniformity, frequency and power density is chosen so as to accomplish glass heating from any initial temperature to any required (e.g., softened) temperature in a selected short time while ensuring that the temperature distribution on the external surfaces and in the interior of the glass sheet that arises from microwave exposure is uniform enough to prevent the exposed glass sheet's internal thermal stress from exceeding its modulus of rupture, thereby avoiding glass breakage.

Abstract: A method is provided for manufacturing a synthetic silica glass. The method includes the steps of maintaining a silica glass member, which is formed using a flame hydrolysis method and having an OH group concentration of about 500 ppm to about 1300 ppm, at a predetermined holding temperature for a predetermined period of time so as to substantially relax the structure of the silica glass member. The method further includes the step of subsequently cooling the silica glass member to a first predetermined temperature at a cooling rate of about 10 K/hour or less, and thereafter, cooling the silica glass member to a second predetermined temperature at a cooling rate of about 1 K/hour or less. The method further includes the step of further cooling the silica glass member to a third predetermined temperature at a cooling rate of about 10 K/hour or less.

Abstract: A method of thermally treating a glass or glass-like material, preferably a glass sheet, without the use of conventional tunnel-type furnaces, to effect rapid heating of glass and glass-like materials from any initial temperature to any required temperature so that the glass sheet can be processed by shaping, bending, tempering, annealing, coating and floating of the glass sheet without cracking of the glass sheet is described. In the inventive method a microwave radiation with appropriate uniformity, frequency and power density is chosen so as to accomplish glass heating from any initial temperature to any required (e.g., softened) temperature in a selected short time while ensuring that the temperature distribution on the external surfaces and in the interior of the glass sheet that arises from microwave exposure is uniform enough to prevent the exposed glass sheet's internal thermal stress from exceeding its modulus of rupture, thereby avoiding glass breakage.

Abstract: A method for processing a glass fiber material, wherein the glass fiber material has been heat treated at a temperature less than or equal to the annealing temperature of the glass for a length of time effective to prevent separation and fraying of the edges of the material upon cutting.

Abstract: A simple and economical method is described for compacting or shrinking flat glass panes. The method ensures high temperature homogeneity in the glass. First, the glass panes are cleaned and then a stack of glass panes to be treated is assembled without applying a release agent to any of the glass panes. Then the stack of glass panes is placed between ceramic panels made of silicon-infiltrated silicon carbide and this stack together with the ceramic panels is subjected to a heat treatment in a radiation furnace at temperatures ranging from 300° C. to 900° C. The ceramic panels have a thermal conductivity, which, in the region of the heat treatment temperature, is at least 5 times as large as that of the glass panes. The ratio of the total thickness of the ceramic panels to the height of the glass stack should be at least 1/&lgr;/40W/(mK), wherein &lgr; is the thermal conductivity of the ceramic panel at the temperatures of the heat treatment.

Abstract: Glass or glass ceramic plates with elevated thermal resistance and process for their production. After cooling, the glass or glass ceramic plates are subjected to zone annealing, whereby the plates are divided into two zones in which annealing is done at respectively different temperatures, and whereby the zones with the elevated temperature correspond, during annealing, to the sub-areas of the finished glass or glass ceramic plates in which compression stress builds up after uneven heating corresponding to the respective specific application of the glass or glass ceramic plates. The glass or glass ceramic plates that are obtained are thus characterized in that they are divided into two sub-areas, whereby one sub-area exhibits structural compression and the other sub-area exhibits compression stress. Glass or glass ceramic plates that are resistant to breakage that is caused by uneven heating result.

Abstract: A sintered dense glass, alumina-doped optical fiber preform is stretched and is then heated to a temperature of 1490-1495° C. to remove bubbles without causing crystallization. Thereafter, the stretched glass body is either drawn directly into an optical fiber or overclad and then drawn into a fiber.

Abstract: The invention is a method of making silicate based glass compositions with phosphorus compounds included in the composition as spectral modifiers to impart desirable color and improved energy absorbance properties. The phosphorus compound is generally a metal phosphide which is added to the batch glass composition in amounts greater than 0.05 weight percent prior to melting. The composition and method result in a finished glass suitable for use in architectural and automotive glazings.

Abstract: A process for greatly improving the DC drift problem associated with LiNbO3 and LiTaO3 substrates. The process immerses the substrates in a heat bath comprised of a strong acid and then subjects the substrates to cyclical annealing.

Abstract: A laser surface method involves applying a laser beam treatment in one or several steps to a series of generally similar surfaces of given depth. Properties of the laser treatment are selected so as to change the physical state of each surface. Ellipsometry measurements are made in a region of the first surface before application of the laser beam treatment to the second surface, so as to obtain a physico-chemical characterization of the first surface. Both the laser beam application and the ellipsometry measurement are conducted under generally similar working conditions, so that the change of the physical state of each surface produced by the laser treatment can be controlled in a real time, in-situ, rapidly and nondestructively.

Abstract: A method of manufacturing an array substrate of a liquid crystal display device where the array substrate comprises a glass substrate and a thin film transistor formed on the glass substrate, the method comprising the steps of, heat-treating the glass substrate at a temperature ranging from (Ts-200.degree. C.) to Ts (Ts: a strain point of glass constituting the glass substrate), and quenching the glass substrate by quenching means which is capable of promoting a cooling of the glass substrate and controlling the cooling rate of the glass substrate.

Abstract: A coating for a clear (flint) glass container that can be readily formulated to provide a wide range of colors and finishes and protect the contents from natural and ultraviolet light. When applied and cured the coating will provide increased abrasion and impact resistance and process through all container filling operations.

Abstract: A glass substrate manufacturing method advantageously applicable to magnetic recording disk glass substrates, LCD glass substrates, photomasks glass substrates, or optical memory glass substrates. The method includes the steps of forming a film of a solution on at least a principal surface of a sheet glass formed using a down-drawing method, the solution containing a water soluble inorganic material and a surface-active agent; sandwiching both sides of a single sheet glass on which the film is formed or of a laminated structure of two or more sheet glasses with a densified sheet with a high flatness to pressure the single glass or laminated structure; and heating and annealing the single sheet glass or laminated structure to flatten the same. The end side of the flatten glass substrate is treated with a treating solution containing a hydrofluosilicic acid.

Abstract: A silica glass has a structure determination temperature of 1200K or lower and a hydrogen molecule concentration of 1.times.10.sup.17 molecules/cm.sup.3 or more. The silica glass is used together with light in a wavelength region of 400 nm or shorter. The silica glass is produced by heating a silica glass ingot having a hydrogen molecule concentration of 1.times.10.sup.17 molecules/cm.sup.3 or more to a temperature of 1200-1350K, retaining the ingot at that temperature for a given period of time, and then, cooling the ingot to a temperature of 1000K or lower at a temperature-lowering rate of 50K/hr or less to anneal the ingot.

Abstract: A mesh belt is stretched in an annealing lehr and a plurality of fine mesh elements, which constitute a fine mesh having gas-permeability and elasticity, formed by weaving a heat-resistant wire, are fixed onto the mesh belt so as to be arranged along the moving direction of the mesh belt with predetermined spaces in the direction of the width of the mesh belt whereby a flaw which may be produced in a glass product to be annealed when it is placed on the mesh belt in the annealing lehr, is prevented.

Abstract: A method and an apparatus for coating a hot glass substrate with a mist of fine droplets from a solution of a chemical precursor or mixture of precursors in a solvent, by nebulizing a solution with ultrasonic vibration to form a mist of fine droplets; conducting the mist to the hot glass substrate; and depositing the mist on the hot glass substrate to pirolize it and form the desired coating on the glass substrate. The nebulization is carried out by applying vibration of ultrasonic frequency to the solution obtaining the mist of fine droplets and conducting the fine droplets by a stream of a carrier gas, to be deposited on a surface of the hot glass substrate, particularly on a continuous glass ribbon during production in the float glass manufacturing process mainly at the beginning of the annealing chamber where the temperature of glass ribbon is 580.degree. C.-610.degree. C.

Abstract: In each of the second and subsequent heat treatments, in a case where a glass substrate shrinks by heat treatment at the same average cooling rate as the average cooling rate in the immediately preceding heat treatment, the average cooling rate is set to be larger than that in the immediately preceding heat treatment, and inversely, in a case where the glass substrate extends, the average cooling rate is set to be smaller than that in the immediately preceding heat treatment.

Abstract: A composition useful as a restorative material includes a curable matrix with whiskers which preferably have a silicon dioxide containing coating thereon that are then silanized and may also include optional particulate filler of the type which may release fluorides. The polymeric matrix bonds more tightly to the whiskers due to the coating of silicon dioxide on the surface of the whiskers and the coaction between said silicon dioxide and the silane compound. Particles adhered to the whisker also enhance the mechanical properties by virtue of the whisker's surface being thereby roughened. A method of manufacture is also disclosed.

Abstract: Air is blowed before an annealing step to corner portions in an inner face portion of a glass panel which has been press-formed in a mold to cool that portions to be stronger than the other portion whereby a temperature difference between the corner portions and the other portion is reduced.

Abstract: A glass substrate is positioned between a chamber with a reduced pressure and a chamber filled with a heated helium, and the glass substrate is forcibly bent by the pressure difference and the heated helium gas into a uniform shape. The irradiation of laser light is carried out in this state to compensate the difference of annealing effects due to fine difference of deformation of the respective glass substrates.

Abstract: A glass substrate manufacturing method advantageously applicable to magnetic recording disk glass substrates, LCD glass substrates, photomask glass substrates, or optical memory glass substrates. The glass substrate is formed by chemically strengthening a glass substrate by immersing the glass substrate in a chemical reinforcement solution heated and then ion exchanging ions on the surface layer of the glass substrate with ions in the chemical reinforcement solution; removing the substrate from the chemical reinforcement solution and then annealing it to a temperature higher than the crystallization temperature of a molten salt; rapidly cooling the glass substrate at a rate at which the crystallization of the molten salt deposited on the surface of the glass substrate is prevented; and then cleaning the surface of the glass substrate.

Abstract: A method and apparatus for annealing glass sheets, in which glass sheets are retained within a frame having edge retaining members. The edge retaining members retain the edges of the glass sheet during the annealing operation, thereby hindering warpage and surface damage of the glass sheet during the annealing process.

Abstract: A method of heat-treating a glass substrate where the substrate is thermally treated (such as the formation of films, growth of films, and oxidation) around or above its strain point. After thermally treating the substrate around or above its strain point the glass substrate may be slowly cooled at a rate of 0.01.degree. to 0.5.degree. C./min to achieve maximum shrinkage of the substrate. Following further thermal treatments the substrate may be quickly cooled at a rate of 10.degree. C./min to 300.degree. C./sec to suppress shrinkage of the glass substrate. The substrate can have films such as aluminum nitrate films, silicon oxide films, silicon films, insulating films, semiconductor films, etc. Film formation can occur either before or after thermal treatment of the substrate around or above its strain point and before further thermal treatments.

Abstract: A furnace is provided for the heating of glass sheets to be bent, whereby precise control of the temperature profile across a sheet may be achieved, resulting in improved control over the shape to which the sheet is bent. The furnace has at least one differential heating zone provided with a plurality of main heating elements, and at least one shield for directing heat radiated by said heating elements whereby a controlled differential heating of the glass sheet may be achieved. Transport means, e.g. wheeled boxes, are provided to advance the sheet through the furnace and bending means, e.g. gravity bending ring moulds, may bend the sheet either during, or subsequent to, the heating step.

Abstract: Silica tubes and sleeves are used to protect fusion splices between the ends of the fiber coil and polarizing fibers. Use of silica for most of the subassembly components matches the coefficients of thermal expansion of the subassembly to that of the fiber coil, and also allows the coil to be annealed at extremely high temperatures. Annealing yields fiber coils of lowered birefringence, particularly when used with spun fibers. Ferrules are used to adjust the angular orientation of the fibers with respect to their planes of polarization.

Abstract: The invention is a method for improving the flatness of nonmetallic substrates and preferably glass disks. The method comprises the steps of mounting the glass disk on a support. The support preferably comprises a refractory metal having a cooling rate substantially similar to the disk. The disk is then subjected to heating to a temperature in the anneal region for the given material for a period ranging from about 0.5 hours to 12 hours or longer, and then the disk is controllably cooled. The glass disk is preferably cooled at a rate of about 0.25.degree. C./minute to 1.5.degree. C./minute to room temperature. The invention also comprises a hard disk glass memory element and a data storage and retrieval device comprising this element.

Abstract: Sheet glass (2) is rendered fire resistant such that it will not shatter under a build-up of heat to 900.degree. C., by providing a thin coating (1) on one or both its surfaces, the coating being stable and adherent to the glass at up to 900.degree. C., the coating preferably comprising an oxide, nitride, oxynitride or fluoride of a metal or of silicon, or a metal silicide, the sheet having been toughened by tempering before or after coating and having its edges (3) ground and polished before the tempering step to remove all imperfections therefrom.

Abstract: Optical waveguide paths are formed under the surface of a glass substrate by a method comprising (a) forming by ion-exchange a dopant ion path on a first substrate surface, (b) applying an electrode to the second surface, (c) contacting the first surface with a molten salt bath, and (d) applying an electrical field across the substrate to drive the dopant ions deeper into the substrate. The current resulting from high fields can overheat the substrate, thereby causing substrate warping and burying of paths to uneven depths. One aspect of the invention involves cooling the substrate by flowing the molten salt along the first surface of the substrate at a sufficient rate of flow to adequately decrease its temperature and by rapidly flowing the furnace atmosphere over the surface of the substrate. A further aspect of the invention involves initially applying a voltage V.sub.i across the substrate, allowing the current to increase to a predetermined level I.sub.

Abstract: A method for annealing a deposited material on a substrate structure, where the annealing temperature of the deposited material is greater than the melting temperature of the substrate structure, including the step of inserting the substrate structure into an oven preheated to a temperature above the annealing temperature. The substrate structure is kept in the oven for a time interval wherein the mean temperature of the deposited material is above the annealing temperature and the mean temperature of the substrate structure is below its melting temperature. The substrate structure may be actively cooled while in the oven, thus increasing the time interval the mean temperature of the deposited material can be maintained above the annealing temperature.

Abstract: A glass vacuum flask coating method comprising a step to put a metal material in the gap between an inner flask and an outer flask before said inner and outer flasks being formed into a blank for a glass vacuum flask, after the process of exhausting and tipping-off said metal material being heated by a magnetic field generated from an inductance coil into a metal vapor inside said gap, permitting said metal vapor to be adhered to the glass surface inside said gap, forming into a metal reflecting film thereon.

Abstract: A process for producing a low-loss embedded waveguide is disclosed, which comprises: a first ion exchange step in which a glass substrate containing a monovalent ion and capable of undergoing ion exchange is subjected to thermal ion exchange through an ion exchange-control film provided on the substrate and having a predetermined waveguide pattern formed therein, by immersing the substrate in a first molten salt containing a first monovalent ion capable of changing the refractive index of the substrate; an etching step in which the ion exchange-control film is removed form the substrate by etching; an electric field-applying annealing step in which an electric field is applied to the substrate at substantially right angles to the substrate at a temperature near the temperature at which the first ion exchange step was conducted, provided that the side of the substrate which had the ion exchange-control film is used as a positive potential side; and a second ion exchange step in which the resulting glass substr

Abstract: The invention relates to heat treatment of a glass plate for strengthening only a peripheral region of the glass plate while annealing the major region. The glass plate is heated to a temperature of 550.degree.-650.degree. C. and placed on a ring-like holder which is maintained at a temperature lower than the temperature of the glass plate by 100.degree. to 600.degree. C. such that the peripheral region of the glass plate makes contact with a ring-like upper surface of the holder. Then glass palte on the ring-like holder is kept in an annealing chamber maintained at a temperature in the range from 50.degree. to 500.degree. C. and not higher than the initial temperature of the ring-like holder. After that the glass plate is allowed to cool down to room temperature. This method is applicable to either flat glass plates or curved glass plates and very suitable for treating glass plates ranging from 1.5 to 3.0 mm in thickness.

Abstract: The present invention is directed to a four-step process for molding glass articles of high precision and excellent surface figure. A glass preform having an overall geometry closely approximating that of the desired final product is placed into a mold, the mold and preform are brought to a temperature at which the glass exhibits a viscosity between 10.sup.8 -10.sup.12 poises, a load is applied to shape the glass into conformity with the mold, and thereafter the resulting glass article is removed from the mold at a temperature above the transformation range of the glass. The glass article is then annealed.