KR20060063667A - Ceramics for a glass mold - Google Patents

Abstract

The present invention relates to the production of glass molding molds using glass molding molds comprising 6 to 50 parts by weight of carbon based on 100 parts by weight of silicon carbide, glass molding molds comprising the ceramics for glass molding molds, and ceramics for glass molding molds. It is about a method. The glass mold can greatly contribute to a reduction in molding cost of a glass hard disk substrate, a glass lens, or the like.

Ceramics for Glass Molding, Glass Lens, Silicon Carbide, Release Property, Wear Resistance

Description

CERAMICS FOR A GLASS MOLD

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to ceramics for glass molding molds which can be used for molding glass hard disk substrates, glass lenses, etc., glass molding molds made of the ceramics, and methods for manufacturing the same.

Glass optical elements such as glass hard disk substrates and glass lenses are fleeted into a desired shape between rows, and further surface-polished into products as necessary.

Because glass optical elements require high precision, in order to obtain glass optical elements stably by press molding, the molding mold is excellent in workability so that the press surface can be processed easily and accurately and smoothly. It is necessary to be inert with respect to glass and to be excellent in releasability at high temperature in oxidation resistance to corrosion resistance.

For example, the technique which focused on the improvement of the releasability until now is disclosed. Japanese Laid-Open Patent Publication No. 62-207726 discloses a glass mold having a carbon film of a specific thickness. Japanese Laid-Open Patent Publication No. 2000-72453 discloses a glass mold molding frame made of a silicon carbide sintered body in which a silicon nitride film is formed on an inner surface of a molding die. In addition, Japanese Laid-Open Patent Publication No. 7-257933 discloses a glass mold made of silicon carbide-based ceramics.

That is, the present invention

[1] The present invention provides ceramics for glass forming molds containing 6 to 50 parts by weight of carbon with respect to 100 parts by weight of silicon carbide,

[2] a glass molding frame comprising the ceramics for the glass molding frame, and

[3] The present invention relates to a method for producing a glass molding mold using the ceramics for glass molding mold.

The present invention relates to a glass molding ceramic, a glass molding frame made of the ceramics, and a manufacturing method of the molding mold, which have excellent high releasability and excellent wear resistance.

According to this invention, it becomes the glass mold which consists of ceramics for glass molding molds which are excellent in mold release property, and also has excellent durability also excellent in abrasion resistance, and ceramics.

The ceramics for glass forming molds of the present invention (hereinafter, sometimes referred to as ceramics) are silicon carbide carbon composite ceramics containing silicon carbide and carbon in a ratio, and have one great feature. It has the characteristics of wear resistance and high durability. In addition, release property here means the release property at the time of using the glass mold for ceramics as a glass mold.

Specifically, the ceramics of the present invention contain 6 to 50 parts by weight, preferably 10 to 40 parts by weight, more preferably 15 to 35 parts by weight of carbon, based on 100 parts by weight of silicon carbide.

According to the ceramics of the present invention, a specific conventional technology for improving releasability, for example, can be specified on the inner surface of a molding frame such as the disclosed technology of JP-A-62-207726 and JP-A-2000-72453. It is different from constituting the release layer of, and if the mold can be obtained simply without constituting such a specific layer, the mold release property of the inner surface of the mold is excellent, and thus the advantage of easily forming and forming the glass mold. Is obtained.

Furthermore, in the present invention, carbon is contained in the silicon carbide-based ceramics, so that the silicon carbide-based ceramics have superior releasability as compared with only silicon carbide-based ceramics such as those disclosed in JP-A-7-257933.

In addition, the material used for the ceramics of this invention can be used individually or in mixture of 2 or more types, respectively.

The silicon carbide used in the ceramics of the present invention may be a matrix of ceramics, and may be either a crystal mold of α or β. The purity is not particularly limited, but is preferably 90% by weight or more and more preferably 95% by weight or more from the viewpoint of sintering with high purity. As a form of silicon carbide, it is preferable that it is powder with an average particle diameter of 5 micrometers or less from a point with favorable sinterability.

The ceramic of the present invention is preferably composed of only silicon carbide and a carbon source having a purity within the range of the above-mentioned family register, but may contain optional components such as carbides other than silicon carbide within the scope of not impairing the effects of the present invention.

In addition, the average particle diameter described in this specification can be measured, for example by the laser diffraction / scattered-light type particle size distribution analyzer (LA720 by Horiba Seisakusho).

Carbon in the ceramics of the present invention is a single substance of carbon and consists of a crystal phase and / or an amorphous phase. Specifically, amorphous carbon, graphite, etc. are mentioned as a single body of carbon. Crystal phase of these groups are 1580cm in the spectrum obtained by measurement with the laser Raman spectroscopy ^- has a peak of over 1450 ~ 1700cm ^-1 which is centered around the vicinity of ^1, as the crystal structure, e.g., a graphite mold flat hexagonal structure, Although a rhombic structure etc. are mentioned, There is no limitation in particular. In addition, the amorphous phase has a peak of over 1300 ~ 1450cm ^-1 which is centered around the vicinity of 1360cm ^-1.

In the ceramics of the present invention, excellent releasability which has not been conventionally achieved is achieved by making the content of carbon 6 parts by weight or more with respect to 100 parts by weight of silicon carbide as compared with the conventional ceramics used for the glass mold. Moreover, favorable wear resistance is achieved by setting it as 50 weight part or less with respect to 100 weight part of silicon carbides.

In view of securing both high strength and high fracture toughness, the ceramic of the present invention preferably has a peak area ratio (constant / non-crystalline phase) of the laser Raman spectral intensity between the carbon crystal phase and the amorphous phase, preferably from 1 to 10, more Preferably it is 1-5. It is considered that the peak area ratio corresponds to the graphitization degree of carbon. When this value is within the range of the family register, good strength and fracture toughness can be achieved. In the measurement of the spectrum, for example, an argon laser Raman spectrometer manufactured by NEC Corporation is used.

The ceramics of the present invention are excellent in releasability by including the specific amount of carbon described above, and have sufficient mechanical strength (strength, hardness, fracture toughness, coefficient of friction, Wear resistance). This property contributes to the development of the durability of the ceramics of the present invention.

Such ceramics of the present invention, in addition to being able to easily form a glass mold, depending on its properties, generally required properties of the glass mold, for example, chemical stability against high temperature glass (oxidation resistance, Corrosion resistance, inertness to glass), abrasion resistance, release to glass, surface smoothness, and the like contributes greatly to the provision of the glass mold.

In the manufacturing method of the glass shaping | molding die of this invention, the ceramics of this invention are used. In the method for producing a glass mold, for example, the raw material mixture of the ceramic of the present invention is calcined, molded into a desired mold, and then fired, and the mold is made of a ceramic sintered body (silicon carbide carbon composite ceramics). The method of manufacturing by grinding | polishing the inner surface of is mentioned.

In the production of the glass forming mold of the present invention, it is preferable that the single carbon in the ceramics be produced from a suitable carbon source during the manufacturing process. That is, the said silicon carbide, the carbon source mentioned later, and additives normally used as desired (for example, well-known sintering aids, such as a boron compound, a titanium compound, an aluminum compound, an yttria compound, etc.) are wet-mixed and calcined. . By this plasticization process, the carbon source is converted into carbon alone. What is necessary is just to adjust the mixing ratio of each raw material at the time of wet mixing so that the composition of the ceramics obtained may be as mentioned above.

The wet mixing may be performed using a ball mill, a vibration mill, a planetary mill, or the like. Moreover, as a solvent to be used, organic solvents, for example, aromatic solvents such as benzene, toluene and xylene, alcohol solvents such as methanol and ethanol, ketone solvents such as methyl ethyl ketone and the like are preferable. As the other solvent, water, a mixed solvent of water and the organic solvent can also be used.

Although the calcination of the mixture after wet mixing may be carried out according to a known method, it is preferable under the inert atmosphere (for example, from the viewpoint of sufficiently converting the carbon source to be used for carbon alone, preventing free sintering of particles and maintaining good dispersibility). For example, heat treatment is performed at 150 to 800 degrees under an atmosphere such as nitrogen gas or argon gas.

The carbon source is not particularly limited as long as it is soluble or dispersible in the organic solvent used for wet mixing, and is converted to carbon under the plasticizing conditions. As a carbon source, for example, in the case of a solid powder, a material having an average particle diameter of about 0.1 to 100 µm is preferably used. As the carbon source, aromatic hydrocarbons are preferable since the conversion to carbon after calcination is high, and examples thereof include furan resin, phenol resin, coal tar pitch, and the like. Among them, phenol resin, Coal tar pitch is more suitably used.

Next, the mixture after calcination is molded into a mold after granulation as desired. Molding may be performed, for example, by forming a block by a die molding method, an injection method, or a cold isostatic press method, and then machining the block as desired to produce a molded body of a molding die. Moreover, the glass mold of this invention also includes the thing in which all or one part of the glass contact surface of a glass mold is a molded object using the ceramic particle of this invention. For example, any one of the dies or punches of the glass molding die consisting of a die and a punch may be a molded body using the ceramic particles of the present invention. In this way, all or part of the glass mold of the present invention or all of the glass contact surfaces is made of the ceramic for glass mold of the present invention.

Then, the obtained molded object is provided to a baking process. Although baking may be performed in accordance with a well-known method, it is preferable to carry out at 1800-2300 degree | times under inert atmosphere or under vacuum. When the firing temperature is within this range, mechanical properties such as the density of the sintered body, the machine such as hardness, and the like can be improved. As the firing method, for example, a hot press, a hot isostatic press (HIP) method or the like may be used to increase the density.

If desired, the surface (surface in contact with glass) corresponding to the inner surface of the molding die made of the silicon carbide carbon composite ceramics thus obtained is polished as desired, the final glass molding die is obtained. Although the method of grinding | polishing is not specifically limited, Since the said ceramics is a high hardness material, since grinding | polishing by grinding wheel particles other than diamond takes a long time, it is preferable to grind with diamond grinding wheel particles. From the viewpoint of securing the surface smoothness of the surface in contact with the glass of the glass forming mold so that a ready-to-use glass product can be obtained without forming, the average particle diameter of the diamond grindstone particles to be used is preferably 2 µm or less.

The desired glass shaping | molding die is obtained by the above. The silicon carbide carbon composite ceramics constituting the mold are obtained as a very high density sintered compact when fired by, for example, the HIP method. Although it is preferable that the relative density of a glass shaping | molding die is high from a viewpoint of providing favorable smoothness to a glass surface, It is specifically 95% or more, More preferably, it is 98% or more. In addition, the relative density can be obtained by subtracting the bulk density from the theoretical density. In addition, a bulk density is measured by JIS R1634. In addition, when ceramics consist of multiple components, the theoretical density of each component x content (weight%) ÷ 100 of each component is computed, and let the sum total of the value for each component obtained in this way be the theoretical density of the said whole ceramics. .

In addition, it is preferable that the glass hard disk substrate or glass lens manufactured using the molding die of the present invention can be used directly without polishing after molding. For this purpose, the surface of the surface in contact with the glass of the surface in contact with the glass of the molding die is preferred. Surface roughness is preferably as smooth as possible. Specifically as centerline average roughness Ra of the said surface of a shaping | molding die, Preferably it is 1-200 nm, More preferably, it is 1-50 nm, More preferably, it is 3-20 nm. In addition, center line average roughness Ra can be calculated | required by JIS B0651.

The glass mold of the present invention is excellent in wear resistance, and very little reactivity with glass. In addition, it is excellent in releasability with glass, and the glass after shaping | molding has the surface smoothness to the extent that post-polishing is substantially unnecessary. Furthermore, even after repeated use for a long time, the surface of the mold is not roughened and mold release defects are exhibited, and high durability is exhibited. Therefore, according to the glass shaping | molding die of this invention, shaping | molding cost of a glass hard disk board, a glass lens, etc. can be reduced.

<Example>

Examples 1-6 and Comparative Examples 1-3

As a carbon source, β- silicon carbide (purity of 98% by weight), and a sintering aid of an average particle size 0.5㎛ shown in Table 1 B ₄ C 2% of mixed wet vibration mill ethanol by weight, plasticizer argon gas atmosphere for 1.5 hours at 600 It was. Blocks were formed from the mixture after calcining by the CIP method, and the obtained blocks were processed with an NC machine to form a glass mold for glass lenses, and fired at 2200 degrees for 4 hours under an argon gas atmosphere. The surface which contact | connected the glass of the shaping | molding die after baking was grind | polished with the diamond grindstone particle of an average particle diameter of 0.5 micrometer, and the final glass shaping | molding die was obtained. In addition, in Table 1, a phenol resin is a novolak-type thing, a thing with a residual ash rate of 49 weight%, and a coal tar pitch is a thing with a residual carbon rate 53 weight%. In addition, carbon content shows content of carbon with respect to 100 weight part of silicon carbides.

The following characteristics were evaluated about the obtained glass molding die. The evaluation results are shown in Table 1 together.

(1) laser Ramanbi

The laser Raman ratio, that is, the peak area ratio (crystal phase / non-crystalline phase) of the laser Raman spectral intensity between the crystalline phase and the non-phase carbon was determined by an argon laser Raman spectrometer manufactured by NEC.

(2) relative density

The relative density was calculated by obtaining the bulk density from JIS R1634 and subtracting it from the theoretical density.

(3) surface roughness

Surface roughness, ie, the centerline roughness Ra of the surface in contact with the glass, was measured according to JIS using a roughness machine manufactured by Kosakagiken.

(4) release

The glass lens was produced using the glass mold, and the release property in the glass mold of a glass lens was evaluated as follows. That is, under the heat of 700 degrees, the lens glass cullets were molded at an impression load of 300 kg / cm ² , and evaluated according to the following evaluation criteria in mold release during 100 continuous moldings.

[Evaluation standard]

(Double-circle): All 100 times show favorable mold release.

○: One out of 100 causes mold release defect

△: causes mold release defect 2 to 4 times out of 100

×: 5 or more times out of 100 causes mold release defects

(5) durability

Durability was evaluated according to the following evaluation criteria by visual observation and surface roughness of the molding die after the test of said (4).

[Evaluation standard]

◎: No change in roughness without blur on the surface

○: slight change in roughness is observed without blur on the surface

△: slight blurring and roughness change on the surface

×: blur and roughness change is recognized on the entire surface

Carbon source Carbon content (parts by weight) Ramanbi Laser Relative density (%) Roughness (nm) Dysplasia durability Example 1 Phenolic Resin 10 1.2 99 7 ○ ◎ Example 2 Coal tar pitch 15 1.5 98 9 ○ ◎ Example 3 Phenolic Resin 20 1.3 97 8 ◎ ○ Example 4 Coal tar pitch 20 2.5 96 11 ◎ ○ Example 5 Coal tar pitch 30 2.1 96 10 ◎ ○ Example 6 Coal tar pitch 40 3.5 95 13 ○ ○ Comparative Example 1 Phenolic Resin 2 Inability to measure 99 6 × △ Comparative Example 2 Phenolic Resin 5 0.6 98 9 △ △ Comparative Example 3 Coal tar pitch 60 2.9 89 29 × ×

In Table 1, the glass forming molds of Examples 1 to 6 made of ceramics of the present invention containing a specific amount of carbon relative to silicon carbide were formed of Comparative Examples 1 to 3 made of ceramics whose carbon content was outside the scope of the present invention. It can be seen that it is excellent in releasability and durability compared to the frame.

According to the present invention, ceramics for glass molds, molds made of the ceramics, and methods for producing the molds are provided which are excellent in mold release properties and further have high durability excellent in wear resistance. The glass shaping die of the present invention can greatly contribute to the reduction of molding cost of a glass hard disk substrate, a glass lens, or the like.

Claims (11)

6-50 weight part of carbon is contained with respect to 100 weight part of silicon carbide, The ceramics for glass shaping dies characterized by the above-mentioned. The ceramic mold for glass forming mold according to claim 1, wherein the peak area ratio (crystal phase / amorphous phase) of laser Raman spectral intensities of a crystal phase and an amorphous phase of carbon is 1 to 10. The glass molding die which consists of ceramics for glass molding dies of Claim 1 characterized by the above-mentioned. The glass forming mold according to claim 3, wherein all or part of the glass forming mold is made of ceramics. The glass molding mold which consists of ceramics for glass molding molds of Claim 2 characterized by the above-mentioned. The glass molding mold according to claim 5, wherein all or part of all or the glass contact surfaces are made of ceramics for glass molding mold. The glass forming mold according to claim 3, wherein the relative density is 95% or more. 6. The glass forming mold according to claim 5, wherein the relative density is 95% or more. The glass forming mold according to claim 3, wherein the center line average roughness Ra of the surface in contact with the glass is 1 to 200 nm. The manufacturing method of the glass molding die characterized by using the ceramic for glass molding die of Claim 1. Use as a glass forming mold of ceramics, characterized by containing 6 to 50 parts by weight of carbon with respect to 100 parts by weight of silicon carbide.