Abstract: The present invention provides a polishing composition which can polish an object to be polished at a high polishing speed and with fewer scratches (defects). The present invention is a polishing composition containing silica of which a maximum peak height in a weight change rate distribution curve obtained by thermogravimetric measurement in a range of 25° C. or higher and 250° C. or lower is ?0.011 or more and less than 0, a pH at 25° C. of the polishing composition being less than 6.0.

Abstract: The present invention relates to a method of manufacturing a formed article comprising forming an upper surface of a glass material that has been positioned on a forming surface of a mold to obtain the formed article by heating the glass material to a temperature permitting deformation to bring a lower surface of the glass material into tight contact with the forming surface. Glass having upper and lower surfaces being spherical in shape is employed as the glass material, a mold having a forming surface being a free-form surface other than a spherical surface is employed as the mold, the upper surface of the glass material is formed into a roughly offset surface relative to the forming surface of the mold. The present invention permits the manufacturing of formed articles of desired shape with high precision by hot sag molding method. The present invention also permits the easy and simple determination of the surface shapes of molds and glass materials employed in hot sag molding method.

Abstract: When mirror polishing is performed on a glass substrate by bringing a polishing pad into contact with the surface of the glass substrate while supplying a polishing liquid containing polishing grains to the substrate surface, the pH of the polishing liquid is maintained within a certain range or the agglomeration degree or dispersion degree of the polishing liquid is controlled. Consequently, an adequate mirror polishing rate can be maintained and there can be obtained a glass substrate having a good end shape.

Abstract: A fiber optic connector fiber stub remover and method for automated fiber stub removal. The device has a top plate with a platen opening, and a platen with a well that carries a polishing film over the well. An air pocket is formed between the polishing film and the well. The platen is positioned with a top surface of the polishing film accessible via the platen opening. A fixture holds connector ends of fiber optic cables with fiber stubs extending therefrom, and a weight biases the fiber stubs into contact with the polishing film. A motor is controlled by a motor control unit to control a ramp up time and final speed of movement of the platen over a timespan. Each connector ends moves independently relative to the polishing film. The air pocket provides shock absorption of the polishing film so that an ideal pressure is exerted on each fiber stub during stub removal.

Abstract: A glass for a magnetic recording medium substrate permitting the realization of a magnetic recording medium substrate affording good chemical durability and having an extremely flat surface, a magnetic recording medium substrate comprised of this glass, a magnetic recording medium equipped with this substrate, and methods of manufacturing the same. The glass is an oxide glass not including As or F.

Abstract: Provided is a laminate (1) obtained by integrally laminating glass sheets (4) on both surfaces of a resin sheet (2). The glass sheets (4) have a thickness of 300 ?m or less and end surfaces (4a) of the glass sheets (4) are chamfered.

Abstract: The present invention provides a glass substrate for magnetic disk in which surface irregularity of a principal surface is suppressed and a method for efficiently manufacturing a glass substrate for magnetic disk. The method includes the steps of: forming a sheet glass material by performing press forming to molten glass, a principal surface of the sheet glass material having target flatness for the glass substrate for magnetic disk, the sheet glass material having a surface shape to be ground using a grinding abrasive grain; grinding the sheet glass material using a fixed abrasive grain; and polishing the sheet glass material using a loose abrasive grain, the sheet glass material having surface irregularity of the principal surface ground using the fixed abrasive grain.

Abstract: There are provided, a method for efficiently manufacturing a glass substrate for magnetic disk in which the degree of surface irregularity of the principal surface is suppressed, and the glass substrate for magnetic disk. When manufacturing a glass substrate for magnetic disk including a pair of principal surfaces, a glass blank is formed by pressing molten glass or softened glass with planar press forming surfaces of dies in such a way that the molten glass or the softened glass is sandwiched from the both sides. Temperature condition is equalized around the pair of principal surfaces of the glass blank during the pressing.

Abstract: Disclosed is a method of producing a glass substrate for an information recording medium including a rough polishing step of performing a rough polishing on a glass material containing 0.01 to 2 mass % of cerium oxide; a washing step of washing the glass material after the rough polishing step, so that the cerium content of the glass material surface becomes 0.125 ng/cm2 or less; and a precision polishing step of performing precision polishing on the glass material after the washing step by cyclically using a polishing material containing colloidal silica.

Abstract: A manufacturing method of a glass substrate for magnetic disk including a pair of principal surfaces is disclosed The method includes the steps of: dropping process for dropping a lump in vertically downward direction, the lump made by cutting molten glass; pressing process for forming a sheet glass material by sandwiching substantially simultaneously the lump from both sides of the dropping path of the lump with surfaces of the pair of dies at the timing when at least a cut mark of the lump protrudes from a pair of dies facing together, and performing press forming to the lump; and removing process for removing the glass material protruding from the pair of dies.

Abstract: Provided are a pressure-sensitive adhesive tape, a polishing pad, a method of manufacturing the same, a polishing device and a method of manufacturing a glass substrate. The illustrative pressure-sensitive adhesive tape may be a pressure-sensitive adhesive tape for a polishing material. The pressure-sensitive adhesive tape may be effectively fixed to a surface plate without bubbles, and have excellent resistance to water and a polishing solution and shear strength applied in a polishing process. In addition, the pressure-sensitive adhesive tape may be easily removed from a carrier or surface plate for a polishing pad without residues after polishing.

Abstract: To produce a meniscus lens from synthetic quartz glass for use in a microlithography apparatus, which lens has a first optical surface (7) and a second optical surface (8) with the same direction of curvature as the first optical surface (7), SiO2 particles are formed by oxidation or flame hydrolysis of a silicon-containing starting compound and deposited layer by layer on a substrate to form a cylindrical SiO2 blank which contains layers with a surface normal extending in the direction of growth. To allow such layers, which have however the least possible adverse effect on optical or mechanical properties, it is proposed according to the invention that the blank is plastically worked in a hot forming process under the effect of a deforming force to form a preform (6), which has at least the first curved surface (7) and in which the layers are curved in the direction of curvature, and that the meniscus lens is obtained from the preform.

Abstract: A method for processing a coated glass substrate may include a high-temperature activation process.

Abstract: An aspect of the present invention relates to an optical glass, which comprises, denoted as weight percent, 2 to 37 percent of SiO2, 0 to 25 percent of B2O3, 0 to 10 percent of GeO2, 18 to 55 percent of a combined content of Li2O, Na2O, K2O, CaO, SrO, and BaO, and 27 to 55 percent of a combined content of TiO2, Nb2O5, and WO3, wherein the weight ratio of SiO2 content relative to a combined content of SiO2 and B2O3 ranges from 0.1 to 1, a weight ratio of the Li2O content to a combined content of Li2O, Na2O, K2O, CaO, SrO, and BaO ranges from 0 to 0.4, and a weight ratio of TiO2 content relative to a combined content of TiO2, Nb2O5, and WO3 ranges from 0.35 to 1, with a refractive index nd of 1.860 to 1.990 and an Abbé number ?d of 21 to 29.

Abstract: Method of manufacturing cover glass plate includes drop step, press step and processing step. In the drop step, molten glass is dropped onto lower mold. In the press step, the molten glass on the lower mold is pressed with upper mold having concave portion so as to fill the concave portion of the upper mold with the molten glass and furthermore, the concave portion is overlapped to area between the upper mold and the lower mold so as to form preform formed with molded main body having first surface to which the shape of the concave portion of the upper mold is transferred and overlap portion having second surface which is portion other than the molded main body and to which the shape of the lower mold is transferred. In the processing step, all the overlap portion is removed from the preform.

Abstract: This disclosure features use of a paper or polymer film that includes a slip agent that can transfer to its surfaces. Once the paper or film is pressed against a glass sheet, this will leave a thin surface roughness of slip agent that can prevent or reduce glass surface scratches from other surfaces or particles during shipping or finishing (e.g., cutting to size, conveyance of glass), thereby improving the yield of glass shipments between glass forming plants and customers. The thin discontinuous layer of slip agent remaining on the glass surface can be washed off easily in subsequent washing processes. The paper or film can have the slip agent imbibed within the paper or coated on it as a surface member.

Abstract: The method for polishing glass products, comprises the following steps: specifying a contour or form or shape of the glass product; detecting the location or position of the glass product; calculating a path for a laser beam on the basis of the contour of the glass product and the location of the glass product; and scanning the path with the laser beam for polishing the glass product in order to fuse mold joints together or smoothen/polish them.

Abstract: When mirror polishing is performed on a glass substrate by bringing a polishing pad into contact with the surface of the glass substrate while supplying a polishing liquid containing polishing grains to the substrate surface, the pH of the polishing liquid is maintained within a certain range or the agglomeration degree or dispersion degree of the polishing liquid is controlled. Consequently, an adequate mirror polishing rate can be maintained and there can be obtained a glass substrate having a good end shape.

Abstract: A method of making a 3D glass article includes forming at least one marker on an edge of a 2D glass piece. The 2D glass piece is thermally reformed into a 3D glass article, where the at least one marker formed on the edge of the 2D glass piece is carried over to an edge of the 3D glass article. The 3D glass article is aligned on a support using the at least one marker on the edge of the 3D glass article. Then, the edge of the 3D glass article is finished to a final shape and dimension.

Abstract: An optical glass in the form of an oxide glass, characterized by comprising, denoted as cation percentages: P5+ 14 to 36%; Bi3+ 12 to 34%; Nb5+ 12 to 34%; Ti4+ 5 to 20%; and W6+ 0 to 22%; wherein the total content of Bi3+, Nb5+, Ti4+, and W6+ is equal to or greater than 50%; and in that the Knoop hardness is equal to or higher than 370, the refractive index nd is equal to or higher than 2.02, and the Abbé number vd is equal to or lower than 19.0. A glass material for press molding and an optical element comprised of this optical glass. A method for manufacturing a glass material for press molding comprising the step of mechanically processing this optical glass.

Abstract: An aspect of the present invention relates to an optical glass, which comprises, denoted as weight percent, 2 to 37 percent of SiO2, 0 to 25 percent of B2O3, 0 to 10 percent of GeO2, 18 to 55 percent of a combined content of Li2O, Na2O, K2O, CaO, SrO, and BaO, and 27 to 55 percent of a combined content of TiO2, Nb2O5, and WO3, wherein the weight ratio of SiO2 content relative to a combined content of SiO2 and B2O3 ranges from 0.1 to 1, a weight ratio of the Li2O content to a combined content of Li2O, Na2O, K2O, CaO, SrO, and BaO ranges from 0 to 0.4, and a weight ratio of TiO2 content relative to a combined content of TiO2, Nb2O5, and WO3 ranges from 0.35 to 1, with a refractive index nd of 1.860 to 1.990 and an Abbé number ?d of 21 to 29.

Abstract: A method for manufacturing a glass blank for magnetic disk and a method for manufacturing a glass substrate for magnetic disk are provided which are capable of producing a glass blank for magnetic disk having a good surface waviness by press forming. The method includes a forming process of press-forming a lump of molten glass using a pair of dies, wherein in the forming process, press forming is performed using thermally equalizing means for reducing a difference in temperature in the press forming surface of the die during pressing of the molten glass.

Abstract: The present invention provides a single-crystal silicon pulling silica container including an outer layer made of opaque silica glass containing gaseous bubbles and an inner layer made of transparent silica glass that does not substantially contain the gaseous bubbles; the container also including: a bottom portion, a curved portion, and a straight body portion, wherein continuous grooves are formed on a surface of the inner layer from at least part of the bottom portion to at least part of the straight body portion through the curved portion. As a result, there are provided the single-crystal silicon pulling silica container that can reduce defects called voids or pinholes in the pulled single-crystal silicon and a method for manufacturing such a silica container.

Abstract: Methods for separating glass articles from glass substrate sheets are described herein. In one embodiment, a method includes focusing a laser beam on at least one surface of the glass substrate sheet such that the laser beam has an asymmetrical intensity distribution at the at least one surface of the glass substrate sheet. The method further includes translating the laser beam on the at least one surface of the glass substrate sheet along a desired groove line to form at least one groove on the at least one surface of the glass substrate sheet. The at least one groove extends partially through a thickness of the glass substrate sheet along the desired groove line and has bevelled or chamfered walls. The glass article may be separated from the glass substrate sheet along the at least one groove.

Abstract: Methods for separating strengthened glass articles from glass substrate sheets and strengthened glass substrate sheets are described herein. In one embodiment, a method of separating a glass article from a glass substrate sheet includes forming at least one groove on at least one surface of the glass substrate sheet. The at least one groove continuously extends around a perimeter of the glass article and extends partially through a thickness of the glass substrate sheet. The method further includes strengthening the glass substrate sheet by a strengthening process and separating the glass article from the glass substrate sheet along the at least one groove such that one or more edges of the glass article are under compressive stress. In another embodiment, a strengthened glass substrate sheet includes an ion exchanged glass having one or more grooves in one or more strengthened surface layers, the one or more grooves defining glass articles.

Abstract: Methods for separating glass articles from strengthened glass substrate sheets and strengthened glass substrate sheets are provided. In one embodiment, a method includes forming at least one groove on at least one surface of the glass substrate sheet and strengthening the glass substrate sheet by a strengthening process. The groove defines the glass article and partially extends through a thickness of the glass substrate sheet. The method further includes generating an initiation defect on the groove at an initiation location to cause a through crack to self-propagate through the glass substrate sheet along the groove, thereby separating the glass article from the glass substrate sheet. In another embodiment, a strengthened glass substrate sheet includes a strengthened glass having a glass article groove and an initiation groove on a surface, the glass article groove defining a glass article.

Abstract: To provide a method for manufacturing a glass blank for magnetic disk and a method for manufacturing a glass substrate for magnetic disk, which are capable of producing a glass blank for magnetic disk having a good surface waviness by press forming, and a method for manufacturing a glass substrate for magnetic disk. A method for manufacturing a glass blank for magnetic disk, which includes a forming process of press-forming a lump of molten glass using a pair of dies, wherein in the forming process, press forming is performed using thermally equalizing means for reducing a difference in temperature in the press forming surface of the die during pressing of the molten glass.

Abstract: According to the process for producing a glass substrate for an information-recording medium of the present invention, a glass plate 10 is roughly polished by a polishing machine 1 using a polishing liquid 7 containing a polishing agent containing cerium oxide as a main component in the rough polishing step, followed by cleaning so as to adjust the amount of cerium oxide on the surface of the glass plate to be 0.125 ng/cm2 or less. The glass plate after rough polishing is thereafter finely polished with a polishing agent containing colloidal silica in the fine polishing step.

Abstract: The present invention relates to a tempered glass sheet for a touch panel, and to a method for manufacturing the tempered glass sheet for a touch panel. The method for manufacturing the tempered glass sheet for a touch panel consisting of tempered glass includes: a first step in which mother glass, including cell glass for a plurality of touch panels, is tempered; a second step in which a process for forming a substrate is performed, which includes forming a transparent electrode by the mother glass unit; and a third step in which, after the substrate-forming process and a half-etching process are completed, the mother glass is cut for the mother glass unit and the cut surface is ground after cutting.

Abstract: A high-refractivity low-dispersion optical glass that can be stably supplied and has excellent glass stability and that has coloring reduced, composed of in mass %, 5 to 32% of total of SiO2 and B2O2, 45 to 65% of total of La2O2, Gd2O2 and Y2O2, 0.5 to 10% of ZnO, 1 to 20% of total of TiO2 and Nb2O5, and optionally other components. The optical glass has a refractive index nd of 1.89 to 2.0, an Abbe's number ?d of 32 to 38 and a coloring degree ?70 of 430 nm or less.

Abstract: A manufacturing method of a glass substrate for magnetic disk including a pair of principal surfaces is disclosed The method includes the steps of: dropping process for dropping a lump of molten glass; pressing process for forming a sheet glass material by sandwiching simultaneously the lump from both sides of the dropping path of the lump with surfaces of the pair of dies facing together, and performing press forming to the lump; and machining process for machining the sheet glass material, wherein the press forming sandwiches the lump while moving the pair of dies in the direction of drop of the lump so that relative speed of the lump to that of the pair of dies approaches zero.

Abstract: An optical glass comprising, by mass %, 12 to 40% of SiO2, 15% or more but less than 42% of Nb2O5, 2% or more but less than 18% of TiO2, (provided that Nb2O5/TiO2 is over 0.6), 0.1 to 20% of Li2O, 0.1 to 15% of Na2O, and 0.1 to 25% of K2O, and having an Abbe's number ?d of 20 to 30, a ?Pg,F of 0.016 or less and a liquidus temperature of 1,200° C. or lower.

Abstract: A glass wafer is provided that is made of a copper ions containing phosphate or fluorophosphate glass. The glass wafer has a diameter greater than 15 centimeters and a thickness of less than 0.4 millimeters. The glass wafer has two plane-parallel surfaces at least one of which is polished.

Abstract: The disclosure is directed to a cutting process involving: (a) creating a starter crack using a scribe wheel, (b) application of laser or electrothermal heating, and (c) subsequent cooling from a gas or an aerosol jet, as the laser beam and cooling jet move along the desired cutting line. The cutting process can be implemented for cutting a glass panel or other substrate into a plurality of smaller panels. The starter crack may be created on any of the smaller panels within about 10 mm to about 20 mm from the corner of the smaller panel.

Abstract: Apparatus, systems and methods for forming complex edges on a glass member through the use of a glass slumping process are disclosed. According to one aspect of the invention, a method of forming a complex edge in a glass forming process includes grinding an edge of a glass member and polishing the edge of the glass member. Grinding the edge of the glass member causes the edge of the glass member to have a first level of complexity. The method also includes performing a slumping process on the glass member. Performing the slumping process causes the edge of the glass member to have a second level of complexity that is more complex than the first level of complexity.

Abstract: Disclosed is a method or process for forming a glass wiring board substrate for integrated circuit wiring boards, including providing a first molding surface (20) positioned on a first mold (22) having truncated conical pins (24) protruding therefrom, the pins (24) having a diameter at the top end (26) thereof of 150 micrometers or less, and a minimum pitch (28) of 400 micrometers or less, providing a glass sheet (30) having first and second surfaces (32,34) on opposite major sides thereof, pressing the first surface (32) of the glass sheet against the molding surface (20), heating the glass sheet (30) and the first molding surface (20) together to a temperature sufficient to soften a glass of which the glass sheet (30) is comprised, such that the pattern of the first molding (20) surface is replicated in the first surface (32) of the glass sheet (30), thereby producing a formed glass sheet (30?) having an array of holes (40) therein, cooling the formed glass sheet (30?) and the molding surface (20) together

Abstract: Methods and apparatus for separating substrates are disclosed, as are articles formed from the separated substrates. A method of separating a substrate having first and second surfaces includes directing a beam of laser light to pass through the first surface and, thereafter, to pass through the second surface. The beam of laser light has a beam waist located at a surface of the substrate or outside the substrate. Relative motion between the beam of laser light and the substrate is caused to scan a spot on a surface of the substrate to be scanned along a guide path. Portions of the substrate illuminated within the spot absorb light within the beam of laser light so that the substrate can be separated along the guide path.

Abstract: Methods and apparatus for machining substrates are disclosed, as are articles formed from the separated substrates. A method of machining a substrate having a first surface and a second surface opposite the first surface can include forming a first recess in the substrate extending from the first surface toward the second surface, forming a second recess in the substrate extending from the second surface toward the first surface, and removing a portion of the substrate extending from the first recess to the second recess to form an opening in the substrate.

Abstract: The present invention relates to a method for producing an optical member base material for EUVL, comprising performing the following in this order to obtain an optical member base material for EUVL: a preliminary-polishing step of preliminarily polishing a film forming surface and a back surface of the film forming surface of a glass substrate; a measuring step of measuring a total thickness distribution and a flatness of the glass substrate; and a corrective-polishing step of locally polishing only the back surface of the glass substrate depending on the measurement result of the measuring step.

Abstract: A method is provided for manufacturing a high-precision mold whereby a feature matching a desired feature design is carved into a hard mold material (41) using, for example, a diamond grinding wheel and/or a diamond turning point. Inherent imprecision and errors (49) introduced by the use of the grinding wheel/turning point are measured to determine deviations from the desired feature design. An ultrafast shortpulse laser is then activated to desirably ablate the deviations, thereby correcting the errors and conforming the feature to the desired shape. Furthermore, a thin film (1602) may be formed over the feature either prior to or after the laser ablation process, where the error measurement and laser ablation processes detects and ablates errors on the surface of the thin film, respectively. Additionally, the laser ablation process may be applied directly to, for example, an optical lens (1400) formed from an imprecise mold to remove any errors and imperfections thereon.

Abstract: An optical glass that is an oxide glass having a very high refractive index in spite of its low-dispersion property, having excellent glass stability and having less susceptibility to coloring.

Abstract: A method and system for preparing polysilicon slim rods, the method and system including: placing a piece of polysilicon on a fixture; applying a predetermined laser beam or abrasive jet to the piece of polysilicon; and separating a polysilicon slim rod from the piece of polysilicon. The laser beam may be used for either cutting or for cracking depending on the operating parameters chosen. There may also be various combinations of cutting and cracking used in order to separate the slim rod from the piece of polysilicon. For example, the laser cut may be a scribing and/or partial cut and the separation may be completed by cracking the remaining silicon. In this case, the cracking may be accomplished by, for example, mechanical bending or laser cracking. Generally speaking, a laser beam used for cracking may be different from and have differing operating parameters from a laser beam used for cutting.

Abstract: A method of improving strength of a chemically-strengthened glass article comprises exposing a target surface of the glass article to an ion-exchange strengthening process, the ion-exchange strengthening process generating a chemically-induced compressive layer in the glass article. Thereafter, dynamic interfacing of the target surface of the glass article with a sheared magnetorheological fluid is performed to remove at least a portion of the chemically-induced compressive layer from the glass article, wherein the parameters of the dynamic interfacing of the glass article with the sheared magnetorheological fluid are such that a thickness of the removed portion of the chemically-induced compressive layer is less than approximately 20% of the chemically-induced compressive layer.

Abstract: A glass manufacturing device includes a main body defining a working space, a fixing device and a grit blower in communication with the working space. The fixing device includes a first fixing assembly, a second fixing assembly, and a locking assembly. The first and second fixing assemblies are rotatably connected with each other and used for clamping a glass substrate. The first fixing assembly includes a number of shielding elements spaced from each other. The locking assembly is used for locking the first and second fixing assemblies. The grit blower is disposed opposite to the first fixing assembly and used for blasting grit on the glass substrate, and thus the portions of the glass substrate which are not shielded by the shielding elements are cut off during the process of grit-blasting. Remaining portions of the glass substrate shielded by the shielding elements are the desired product.

Abstract: A method for manufacturing obscured glass includes providing a glass substrate including a pre-obscured surface; applying a first harden process to the glass substrate to form a strength layer inward the pre-substrate surface; and applying a blasting process to the pre-obscured surface of the glass substrate to form an obscured layer inward the pre-obscured surface, wherein a thickness of the obscured layer is less than that of the strength layer.

Abstract: An optical glass comprising, by mol %, 0.1 to 40% of SiO2, 10 to 50% of B2O3, 0 to 10% of total of Li2O, Na2O and K2O, 0 to 10% of total of MgO, CaO, SrO and BaO, 0.5 to 22% of ZnO, 5 to 50% of La2O3, 0.1 to 25% of Gd2O3, 0.1 to 20% of Y2O3, 0 to 20% of Yb2O3, 0 to 25% of ZrO2, 0 to 25% of TiO2, 0 to 20% of Nb2O5, 0 to 10% of Ta2O5, over 0.1% but not more than 20% of WO3, 0 to less than 3% of GeO2, 0 to 10% of Bi2O3, and 0 to 10% of Al2O3, the mass ratio of the content of SiO2 to the content of B2O3, SiO2/B2O3, being 1 or less, the optical glass having a refractive index nd of 1.86 to 1.95 and an Abbe's number ?d of (2.36?nd)/0.014 or more but less than 38.

Abstract: A manufacturing method of a sheet glass material for magnetic disk, the method includes, dropping process for dropping a lump of molten glass; pressing process for sandwiching simultaneously the lump from both sides of the dropping path of the lump with surfaces of a pair of dies facing together, and performing press forming to the lump to obtain a sheet glass material, wherein at least one of the pair of dies has a concave shape with respect to the dropping path of the lump.

Abstract: A glass manufacturing device includes a main body defining a working space, a fixing device and a grit blower in communication with the working space. The fixing device includes a first fixing assembly, a second fixing assembly, and a locking assembly. The first and second fixing assemblies are rotatably connected with each other and used for clamping a glass substrate. The first fixing assembly includes a number of shielding elements spaced from each other. The locking assembly is used for locking the first and second fixing assemblies. The grit blower is disposed opposite to the first fixing assembly and used for blasting grit on the glass substrate, and thus the portions of the glass substrate which are not shielded by the shielding elements are cut off during the process of grit-blasting. Remaining portions of the glass substrate shielded by the shielding elements are the desired product.

Abstract: A manufacturing method of a sheet glass material for magnetic disk, the method includes, dropping process for dropping a lump of molten glass; pressing process for sandwiching simultaneously the lump from both sides of the dropping path of the lump with surfaces of a pair of dies facing together, and performing press forming to the lump to obtain a sheet glass material, wherein at least one of the pair of dies has a convex shape with respect to the dropping path of the lump.

Abstract: A manufacturing method of a glass blank for magnetic disk including a pair of principal surfaces, the method including: dropping process for dropping a lump of molten glass; pressing process for forming a sheet glass material by sandwiching simultaneously the lump from both sides of the dropping path of the lump with surfaces of the pair of dies facing together, and performing press forming to the lump; and temperature adjusting process for adjusting temperature of the lump before the pressing process such that viscosity variation of the lump is reduced with respect to positions over the entirety of the lump in the pressing process.