JP4842212B2 - Mold for glass hard disk substrate - Google Patents

Description

  The present invention relates to a glass hard disk substrate mold, and more particularly to a glass hard disk substrate mold containing silicon carbide-carbon composite ceramics and a method for manufacturing a glass hard disk substrate using the same.

  The glass hard disk substrate is a magnetic recording medium substrate that is preferably used in an information recording apparatus. This glass hard disk substrate usually has a glass raw material placed between an upper mold and a lower mold of a mold, molded into a desired shape by hot pressing, and further, the surface is polished if necessary. It is commercialized by.

  As a material of a mold for forming such a glass hard disk substrate, various ceramics are used because of excellent thermal stability (Patent Document 1).

On the other hand, in Patent Document 2, a ceramic material (such as silicon carbide) having a specific particle diameter and carbon having a specific particle diameter are blended at a specific ratio as a raw material for a mold when forming ceramics, glass, metal, or the like. A ceramic composite sintered body is disclosed.
JP 2002-230747 A JP 2004-67432 A

  However, in the production of a glass hard disk substrate, the molding material as described in Patent Document 1 tends to wear due to the speeding up and the frequency of molding, and the glass component has a high temperature and the mold surface. There is a problem in that the surface accuracy of the molded glass is lowered by reacting with. Further, in the ceramic composite sintered body described in Patent Document 2, since the particle size of the carbon particles contained is very small, the glass component adheres strongly to the surface of the mold and is difficult to peel from the mold. There was a problem that continuous molding was difficult.

  Accordingly, the present invention provides a glass hard disk substrate mold having low reactivity with glass, high wear resistance and durability, and good releasability from the surface of the molded glass. A method for manufacturing a glass hard disk substrate is provided.

  The present invention is a mold containing silicon carbide-carbon composite ceramics, wherein the silicon carbide-carbon composite ceramics contains 15 to 50 parts by weight of carbon particles with respect to 100 parts by weight of silicon carbide, The present invention relates to a glass hard disk substrate mold having an average particle diameter in the range of 0.3 to 100 μm (hereinafter also referred to as “mold of the present invention”).

  The present invention is a method for producing a glass hard disk substrate, comprising a step of placing a glass raw material in a mold and press-molding the glass raw material, wherein the mold is the glass hard disk substrate mold according to the present invention. This relates to a method for manufacturing a glass hard disk substrate.

  According to the glass hard disk substrate mold of the present invention, the glass hard disk has low reactivity with glass, high wear resistance and durability, and good releasability from the surface of the molded glass. A substrate mold and a glass hard disk substrate manufacturing method using the same can be provided.

(Molding mold for glass hard disk substrate)
As described above, the mold of the present invention contains 15 to 50 parts by weight of carbon particles with respect to 100 parts by weight of silicon carbide, and the average particle diameter of the carbon particles is in the range of 0.3 to 100 μm. -Carbon composite ceramics (hereinafter also referred to as “composite ceramics”) are included.

  Thus, in the mold according to the present invention, the composite ceramic material contains 15 to 50 parts by weight of carbon particles with respect to 100 parts by weight of silicon carbide. The amount of carbon is larger than the amount of carbon used as a sintering aid in the production of one silicon carbide composite ceramic. By setting it as such content, the reactivity with the glass at the time of glass shaping | molding is suppressed, and it becomes a shaping | molding die which shows high abrasion resistance and durability. Further, as in Patent Document 2, sufficient durability that cannot be achieved with ceramics having a very high carbon content can be ensured.

  Further, in the mold according to the present invention, the average particle size of the carbon particles contained in the composite ceramic is 0.3 to 100 μm, and this average particle size is much higher than the carbon particles in the ceramic of Patent Document 2. The particle size is very large. By using carbon particles having such a large particle diameter, the adhesion between the molded glass and the mold surface can be reduced, and good mold release can be achieved.

The average particle size of the carbon particles contained in the composite ceramic is preferably 0.5 μm or more, more preferably 0.7 μm or more, and even more preferably 1 μm or more in order to ensure better releasability. It is. Similarly, it is preferably 25 μm or less and more preferably 5 μm or less in order to ensure better release properties. Specifically, the average particle diameter of the carbon particles is preferably 0.5 to 25 μm, more preferably 0.7 μm to 5 μm, and still more preferably 1 to 5 μm. The average particle size of the carbon particles is a volume average particle size D ₅₀ measured by a laser diffraction / scattered light type particle size distribution measuring device (trade name LA720, manufactured by Horiba, Ltd.) (hereinafter the same).

  The mold of the present invention is a mold used for manufacturing a glass hard disk substrate, but the glass hard disk substrate may be a crystallized glass (glass ceramic) even if it is a substrate made of amorphous glass (amorphous glass). It may be a substrate made of glass and is not particularly limited as long as it is a glass substrate.

  The content of the carbon particles contained in the composite ceramic is preferably 15 to 45 parts by weight with respect to 100 parts by weight of silicon carbide, more preferably 15 parts, from the viewpoint of ensuring higher wear resistance and durability. -30 parts by weight.

  The silicon carbide raw material may be either α or β crystal type. Further, the purity of the silicon carbide raw material is not particularly limited, but is preferably 90% by weight or more, more preferably 95% by weight, from the viewpoint of sintering at higher density and further improving wear resistance and durability. That's it. The average particle diameter of the silicon carbide raw material (particles) is not particularly limited. However, since the sinterability is better, the raw material is preferably a powder of 0.1 to 10 μm.

The carbon particles contained in the composite ceramic are preferably a simple substance of carbon, and are composed of a crystalline phase, an amorphous phase, or a mixed phase of a crystalline phase and an amorphous phase. These single crystal phases preferably have a crystal phase peak from 1450 to 1700 cm ⁻¹ centered around 1580 cm ⁻¹ in a measurement spectrum obtained by laser Raman spectroscopy. The crystal structure is not particularly limited, but preferred examples include a graphite-type planar hexagonal structure and a rhombohedral structure. Also, amorphous phase, in the measurement spectrum obtained by laser Raman spectroscopy, it is preferable to have a peak of the crystal phase toward 1300～1450Cm ^-1 centered around 1360 cm ^-1.

  The carbon particles contained in the composite ceramic have a laser Raman spectral intensity of a crystalline phase and an amorphous phase from the viewpoint of ensuring higher wear resistance and durability, and further achieving higher strength and fracture toughness. The peak area ratio (crystalline phase / amorphous phase) is preferably 1 to 10, more preferably 1 to 5. Since the peak area ratio is generally considered to correspond to the degree of graphitization of carbon, if this value is within the above range, better strength and fracture toughness can be achieved. For the measurement of the spectrum, an argon laser Raman spectrometer (manufactured by NEC) can be used. In order to obtain such a peak area ratio, preferably, as a carbon source, an alkyl-modified phenol resin or coal tar pitch having a residual carbon ratio of 30 to 95% by weight, more preferably a residual carbon ratio of 40 to 90% by weight is selected. Good. In addition, a residual carbon rate means the weight% of fixed carbon in the carbon source measured based on JISK2425.

  The average particle size of silicon carbide contained in the composite ceramic is preferably 0.3 μm or more from the viewpoint of ensuring higher wear resistance and durability. Similarly, from the viewpoint of ensuring higher wear resistance and durability, it is preferably 100 μm or less, more preferably 50 μm or less, and further preferably 4 μm or less. Specifically, the average particle diameter of silicon carbide is preferably 0.3 to 100 μm, more preferably 0.3 to 50 μm, and still more preferably 0.3 to 4 μm. In addition, the average particle diameter of silicon carbide can be measured by the same method as the average particle diameter of the carbon particles. Silicon carbide serves as a matrix in the composite ceramic, and the crystal type thereof may be either α or β.

  The composite ceramic is preferably composed of silicon carbide and carbon, but may further contain an optional component such as a carbide other than silicon carbide as long as the effects of the present invention are not impaired.

Since the composite ceramic in the present invention contains carbon particles having a relatively large particle diameter and preferably silicon carbide having a relatively large particle diameter, the void diameter is preferably small in order to ensure the strength of the composite ceramic. The maximum void diameter is preferably 300 μm or less, more preferably 0 to 100 μm, still more preferably 50 μm or less, and even more preferably 25 μm or less. The maximum void diameter can be measured as follows. That is, the voids on the surface of the composite ceramic can be obtained by obtaining an image (photograph) of the voids with a VH-8000 type manufactured by Keyence Corporation, and analyzing the obtained image. In the image analysis, the major axis diameter (mm) and minor axis diameter (mm) of the randomly oriented void holes are measured to obtain (major axis diameter + minor axis diameter) / 2, and the VH− The maximum value of the obtained values for the voids in the field of view when the magnification of the 8000 type is 100 times is the maximum void diameter. The major axis diameter and the minor axis diameter are respectively defined as follows. When the gap hole is sandwiched between two parallel lines, the width of the gap hole that minimizes the distance between the two parallel lines is called the minor axis diameter. On the other hand, two parallel lines in a direction perpendicular to the parallel line When the gap hole is sandwiched between the two parallel lines, it is called the major axis diameter. In addition, when forming at a pressure of 0.5 to ⁵ t / cm ² in mold forming, CIP (COLD ISOSTATIC PRESS), HIP (HOT ISOSTATIC PRESS), etc., the maximum void diameter of the composite ceramic can be reduced to 300 μm or less. .

  Since the mold according to the present invention has high mold releasability, it is preferable that at least a part of the surface that comes into contact with the glass during glass molding is composed of the composite ceramics. Is preferably composed of the composite ceramic. Moreover, the whole said shaping | molding die may be comprised from the said composite ceramics. As a specific example, when the molding die of the present invention includes a die and a punch, either or both of the die and the punch may be made of the composite ceramic. Further, for either one or both of the die and the punch, a part or the whole of the contact surface with the glass may be composed of the composite ceramic.

  Examples of the shape of the mold of the present invention include the same shapes as those of conventionally known molds. The mold according to the present invention is characterized by including the composite ceramic as described above. As described above, if at least a part of the surface in contact with the glass includes the composite ceramic, the mold releasability with respect to the glass is improved. Therefore, the shape itself is not limited at all.

  When producing a glass hard disk substrate using the mold of the present invention, the shape of the contact surface with the glass in the mold is transferred to the molded glass surface, so that the contact surface is as smooth as possible. It is preferable. Specifically, from the viewpoint of substrate polishing efficiency after molding and the smoothness of the contact surface, the centerline average roughness Ra of the contact surface is preferably 0.001 to 10 μm, more preferably 0.01. It is -9.5 micrometers, More preferably, it is 0.02-9 micrometers. The centerline average roughness Ra can be determined according to JIS B0651. Since the center line average roughness Ra can be set within the above range by increasing the density of the sintered body, a calcined powder (composite ceramic) as described later may be used.

(Production method of composite ceramics)
The composite ceramic in the glass hard disk substrate mold of the present invention can be prepared as follows.

  The composite ceramics can be manufactured by calcining a raw material mixture containing silicon carbide and a carbon source, if necessary, and then shaping the mixture into a desired shape and firing it. As will be described later, when the entire mold of the present invention is composed of this composite ceramic, it may be formed into a desired mold shape, and a part of the mold of the present invention is composed of this composite ceramic. In such a case, it may be formed into a desired shape as a part of the mold.

  As described above, the composite ceramic preferably contains a simple substance of carbon, but this simple substance of carbon is preferably generated from a suitable carbon source during the production. Specifically, silicon carbide, a carbon source, which will be described later, and, if desired, a conventionally known additive may be wet mixed and calcined. In this calcination step, carbon as a carbon source is usually converted into a simple substance. What is necessary is just to set the mixing rate of each said raw material suitably so that the composite ceramics obtained may contain 15-50 weight part carbon particles with respect to 100 weight part of silicon carbide.

  The additive is not particularly limited, and examples thereof include known sintering aids such as boron compounds, titanium compounds, aluminum, and yttria compounds.

  The wet mixing can be performed using a ball mill, a vibration mill, a planetary mill or the like. The solvent used for the wet mixing is not particularly limited, but is preferably an aromatic solvent such as benzene, toluene or xylene; an alcohol solvent such as methanol or ethanol; or an organic solvent such as a ketone solvent such as methyl ethyl ketone. As other solvents, water, a mixed solvent of water and the organic solvent, or the like can be used.

  The calcination of the wet-mixed mixture is not particularly limited and can be performed by a conventionally known method, but from the viewpoint of maintaining good dispersibility while more sufficiently converting the carbon source to be used to carbon simple substance, It is preferable to carry out heat treatment at 150 to 800 ° C. in an inert atmosphere (in an atmosphere such as nitrogen gas or argon gas).

  The carbon source is not particularly limited, and a carbon source that is soluble or dispersible in the organic solvent used for wet mixing and that is converted to carbon under the calcination conditions can be used. When the carbon source is a solid powder, a material having an average particle size of about 0.1 to 100 μm is preferable from the viewpoint of dispersibility. The carbon source is preferably an aromatic hydrocarbon because of its high conversion rate to carbon after calcination, and specifically includes furan resins, phenol resins, coal tar pitch, etc. Coal tar pitch is more preferred. These calcined materials can also be used as a carbon source.

As described above, the silicon carbide raw material (particles) may be either α or β crystal type. Further, the purity of the silicon carbide raw material is not particularly limited, but is preferably 90% by weight or more, more preferably 95% by weight from the viewpoint of sintering at a higher density and further improving wear resistance and durability. % Or more. The average particle diameter of the silicon carbide raw material (particles) is not particularly limited, but is preferably a powder of 0.1 to 10 μm because the sinterability is better. The average particle size of the silicon carbide raw material (particles) is a volume average particle size D ₅₀ measured by a laser diffraction / scattered light type particle size distribution measuring device (trade name LA720, manufactured by HORIBA, Ltd.) The same).

  Next, the calcined mixture is granulated as desired, and then formed into a desired shape. The molding method is not particularly limited, and a block is formed by a mold molding method, an injection method, a CIP (COLD ISOSTATIC PRESS) method, and the block is machined as necessary to produce a molded body having a desired shape. do it.

  Subsequently, the obtained molded body is subjected to a firing step. The firing method is not particularly limited and may be a conventionally known method, but it is preferable to perform the treatment at 1800 to 2300 ° C. in an inert atmosphere or under vacuum. By treating at such a firing temperature, the mechanical properties such as density, strength and hardness of the sintered body can be improved. As the firing method, it is preferable to employ a hot press, a HIP (HOT ISOSTATIC PRESS) method or the like in order to achieve higher density.

  In addition to being easy to process and mold, this composite ceramic is one of the problems to be solved by the present invention depending on its properties. Greatly contributes to the characteristics of glass hard disk substrate molds, such as chemical stability (oxidation resistance, corrosion resistance, inertness to glass) and abrasion resistance, releasability from glass, and surface smoothness. To do.

  In order not to make the average particle size of carbon particles and silicon carbide in the composite ceramics excessively fine, the residual carbon ratio and particle size of the carbon raw material are adjusted to the preferred ranges, the calcining conditions are adjusted, and the raw material It is preferable not to dissolve excessively. Moreover, about silicon carbide, it is preferable to adjust a baking condition, to improve crystallinity, and to make a particle grow moderately.

(Method for producing mold of the present invention)
Next, although the suitable manufacturing method of the shaping | molding die of this invention is demonstrated, the manufacturing method of the shaping | molding die of this invention is not limited to these. When the entire mold according to the present invention is composed of the composite ceramic, the calcined mixture may be formed into a desired mold and fired in the above-described composite ceramic manufacturing process. Further, when a part of the molding die of the present invention is composed of the composite ceramic, as described above, a part made of the composite ceramic is produced and incorporated as a part of the molding die. Molds can be manufactured.

  In the mold of the present invention, it is preferable that the surface in contact with the glass in the production of the glass hard disk substrate is smooth as described above. For this reason, it is preferable to grind the contact surface with the said glass as needed. The polishing method is not particularly limited, but when the composite ceramic is a high-hardness material, polishing with abrasive grains other than diamond requires a long time, and therefore it is preferable to polish with diamond abrasive grains. From the viewpoint of sufficiently ensuring the surface smoothness of the contact surface with the glass in the mold of the present invention, the average grain size of the diamond abrasive grains used is preferably 2 μm or less.

  The composite ceramic constituting the mold of the present invention is obtained as a very high density sintered body when fired by the HIP method. It is preferable that the relative density of the mold is high because good smoothness can be imparted to the surface of the glass to be molded. Specifically, the relative density of the mold is preferably 95% or more, more preferably 98% or more. This relative density can be calculated by dividing the bulk density by the theoretical density (true specific gravity), and the bulk density can be measured based on JIS R1634. When the ceramic is composed of a plurality of components, the theoretical density of each component × the content (% by weight) of each component ÷ 100 is calculated, and the sum of the calculated values for each component obtained is calculated as the ceramics. The overall theoretical density.

(Manufacturing method of glass hard disk substrate)
As described above, the method for producing a glass hard disk substrate of the present invention includes a step of placing a glass raw material in a mold and press-molding the glass raw material under heating conditions as necessary. It is a manufacturing method of a board | substrate, Comprising: The said shaping | molding die is a shaping | molding die for glass hard disk substrates of this invention. Thus, in the manufacturing method of the present invention, the molding die of the present invention may be used as the molding die, and the other steps, processing conditions, etc. are not limited at all.

  Although an example of the manufacturing method of the glass hard disk board | substrate of this invention is demonstrated using FIG. 1, this invention is not restrict | limited to this.

  FIG. 1 is a cross-sectional view showing an example of a glass hard disk substrate mold of the present invention. As shown in the figure, the mold includes an upper mold 10a and a lower mold 10b facing each other, and an outer peripheral portion 12 that connects the upper mold 10a and the lower mold 10b so as to be movable up and down. 101b is a processed surface (contact surface with glass) in the lower mold 10b. In the molding die, at least the processing surface 101a of the upper mold 10a and the processing surface 101b of the lower mold 10b are made of the composite ceramic described above. Note that the mold does not have to include an outer peripheral portion.

  First, the glass material 11 is disposed between the upper mold 10a and the lower mold 10b of the mold (for example, disposed on the processing surface 101b of the lower mold 10b). And the glass material 11 is pressed by moving the upper mold | type 10a and the lower mold | type 10b, and a glass hard disk board | substrate is shape | molded by cooling this after that. Then, the molded glass hard disk substrate is released from the mold, and a glass hard disk substrate is obtained. The method for producing a glass hard disk substrate mold of the present invention is characterized by the use of the mold of the present invention, and the conditions of temperature and load are not limited at all and as conventionally known. Can be set.

  The glass material 11 may be an unheated glass raw material (about room temperature) disposed between the upper mold 10a and the lower mold 10b, and may be pressed while being heated, or the glass raw material 11 is set to a predetermined temperature in advance. It may be heated to form molten glass, and this may be caused to flow from the molten glass tank through the outflow pipe to the processing surface of the lower mold 10b. The temperature of the heat treatment is not particularly limited, but is preferably 200 to 1500 ° C from the viewpoint of moldability, more preferably 400 to 1500 ° C, still more preferably 500 to 1400 ° C, and still more preferably 600 to 1400 ° C. The temperature of the molten glass is not particularly limited as long as the glass raw material is melted, but is preferably 200 to 1500 ° C, more preferably 400 to 1500 ° C, and further preferably 500 to 500 ° C from the viewpoint of moldability. It is 1400 degreeC, More preferably, it is 600-1400 degreeC.

  The pressure to be applied at the time of pressing is not particularly limited, but is preferably 0.2 to 50 MPa, more preferably 0.3 to 40 MPa, and further preferably 0.4 to 30 MPa because the pressing time can be further shortened. . The pressing may be performed by moving both the upper mold 10a and the lower mold 10b, or may be performed by applying pressure to the upper mold 10a as indicated by an arrow in FIG.

  The kind of the glass raw material is not limited at all, and the form after molding may be a raw material that becomes amorphous glass or a raw material that becomes crystallized glass (glass ceramic).

(Information recording medium)
According to the present invention, an information recording medium provided with the glass hard disk substrate described above can also be provided. In this case, a glass hard disk substrate produced by the above-described method may be used, and other configurations of the information recording medium are not limited at all.

Wet mixing of carbon source shown in Table 1 below, β-silicon carbide particles having an average particle size of 0.5 μm (purity 98 wt%), and sintering aid B ₄ C (2 wt%) with ethanol in a vibration mill After drying, it was calcined at 500 ° C. for 2 hours, and this calcined product was wet pulverized with ethanol to form a slurry. This slurry was granulated with a spray dryer to obtain granules. These granules are used to form blocks by the CIP method, and the resulting blocks are processed with an NC (Numerical Control) processing machine to form a glass mold, and further fired at 2200 ° C. for 4 hours in an argon gas atmosphere. did. In addition, the silicon carbide-carbon composite ceramic in this invention is formed by this baking. About the shaping | molding die after baking, the surface which contacts glass was grind | polished with the diamond abrasive grain of average particle diameter of 2 micrometers, and the shaping | molding die for glass hard disk substrates was finally obtained. In Table 1 below, the carbon content indicates the carbon content after firing with respect to 100 parts by weight of silicon carbide.

  About the obtained shaping | molding die, each characteristic was evaluated with the following measuring methods. These results are also shown in Table 1 below.

(1) Laser Raman ratio The laser Raman ratio is the peak area ratio (crystalline phase / amorphous phase) of the laser Raman spectral intensity between the crystalline phase and the amorphous phase of carbon particles. Argon laser Raman spectrometer (NEC Corporation) Manufactured).

(2) Surface roughness About the said shaping | molding die, centerline average roughness Ra of the surface which contacts glass was measured based on JISB0651 using the roughness meter (made by Kosaka Giken).

(3) Releasability A hard disk substrate was produced using the produced mold under the following conditions, and the releasability of the hard disk substrate from the hard disk substrate mold was evaluated as follows. That is, a glass Gob lump (viscosity log η: 1 to 4) as a raw material was put into the mold and a pressure of 20 MPa was applied to produce a glass hard disk substrate. Further, 1000 glass hard disk substrates were continuously manufactured using the same mold, and the releasability of each glass hard disk substrate was evaluated based on the following evaluation criteria.

(Hard disk substrate manufacturing conditions)
Glass _{components: SiO 2, Li 2 O,} AL 2 O 3, B 2 O 3, Na 2 O, K 2 O
Glass temperature immediately before pressing: 1200 to 1400 ° C. (measured with a radiation thermometer)
Pressing method: The temperature of the molten glass having a predetermined weight is lowered to the forming temperature region (log η = 7 to 10) by the direct pressing method, and the glass lump is press-formed by the forming die.
Cooling condition: The heat of the pressed product is absorbed by the heat exchange fluid (water) during pressing. Thereby, a high-quality and efficient glass molded product is made by cooling a press surface.

(Evaluation criteria)
◎: 1000 pieces showed good mold release ○: 1 out of 1000 caused mold release failure Δ: 2-4 pieces out of 1000 caused mold release failure ×: 5 or more out of 1000 pieces However, good mold separation means that there is no movement of the press product when the upper mold of the mold is separated from the press product. Improper mold release is immediately after pressing. When the upper mold of the mold is separated from the press product, the press product moves or the press product sticks to the upper mold.

(4) Durability Durability of the mold is determined by visually observing the appearance and roughness of the surface and measuring the centerline average roughness Ra for the mold after the releasability test of (3). And evaluated based on the following evaluation criteria. The center line average roughness Ra was determined by measuring one point at each of the center portion and the outer peripheral portion of the contact surface (press surface) with the glass of the forming die (upper die) and obtaining the difference between the two measured values. FIG. 2 schematically shows the upper mold of the mold. 2A is a sectional view of the upper mold of the mold, and FIG. 2B is a plan view of the upper mold of the mold. As shown in FIG. 2 (B), about the center part, 2 mm (arrow X in the figure) is measured around the center point of the pressing surface of the mold (upper mold), and the outer periphery part is the outer periphery. The inner 2 mm (arrow Y in the figure) 10 mm on the inner side from the inner solid line in FIG. In the following evaluation criteria, “roughness change” means the difference in roughness in the difference between the central portion and the outer peripheral portion, that is, the amount of change generated before and after the releasability test for the difference between the central portion and the outer peripheral portion. Means. In addition, when the durability of the mold is highly evaluated, it can be said that the wear resistance is also good.

(Evaluation criteria)
◎: No change in roughness ◯: Some change in roughness is observed Ra Δ10% or less △: Change in roughness is observed Ra Δ20% or less ×: Large change in roughness is recognized Ra Ra Δ30% or less

  According to the glass mold for a hard disk substrate of the present invention, the reactivity with glass is low, the wear resistance and durability are excellent, and the mold release from the mold surface is good. Become. For this reason, even if the mold of the present invention is used continuously and for a long period of time, it is possible to suppress the roughening of the processed surface of the mold and the mold release failure, and it is possible to manufacture a glass hard disk substrate at a high frequency. Become. In addition, the yield of the obtained glass hard disk substrate is improved, and it is possible to realize surface smoothness to the extent that polishing after molding is substantially unnecessary. Therefore, according to the molding die of the present invention, the molding cost of the glass hard disk substrate can be reduced.

FIG. 1 is a cross-sectional view showing an example of a glass hard disk substrate mold of the present invention. FIG. 2 is a drawing showing an upper die of a glass hard disk substrate mold in an embodiment of the present invention, A is a cross-sectional view of the upper die, and B is a plan view of the upper die.

Explanation of symbols

10a Upper mold 10b Lower mold 11 Glass material 12 Outer periphery 101a Processing surface 101b Processing surface

Claims (6)

A glass mold for hard disk substrate containing silicon carbide-carbon composite ceramics,
The silicon carbide-carbon composite ceramic contains 15 to 50 parts by weight of carbon particles with respect to 100 parts by weight of silicon carbide , and the average particle size of the carbon particles in the silicon carbide-carbon composite ceramics is 0.3 to 100 μm. range der of is, the silicon carbide - range average particle diameter of the silicon carbide is 0.2~100μm carbon composite ceramics, mold for glass hard disk substrate. The glass hard disk substrate mold according to claim 1, wherein a peak area ratio (crystalline phase / amorphous phase) of laser Raman spectral intensity between the crystalline phase and the amorphous phase of the carbon particles is 1 to 10. 3. The glass hard disk substrate mold according to claim 1 , wherein the composite ceramic has a maximum void diameter of 300 μm or less. 4. The glass hard disk according to claim 1 , wherein a center line average roughness Ra of the surface of the mold that contacts the glass at the time of molding the glass hard disk substrate is 0.001 μm or more and 10 μm or less. 5. Mold for substrate. A method for producing a glass hard disk substrate comprising a glass forming step of placing a glass raw material in a mold and press-molding the glass raw material,
The said shaping | molding die is a manufacturing method of the glass hard disk substrate which is a shaping | molding die for glass hard disk substrates as described in any one of Claim 1 to 4 . 6. The glass hard disk substrate according to claim 5 , wherein in the glass forming step, the glass raw material is formed by applying a pressure of 0.2 to 50 MPa to the glass raw material while being heated to 200 ° C. to 1500 ° C. 6. Manufacturing method.

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