JP3605774B2 - Glass press mold - Google Patents

Description

[0001]
[Industrial applications]
The present invention relates to a glass press-molding die, and particularly to a press die suitably used for press-forming a glass optical element stably with high precision.
[0002]
[Prior art]
In order to stably obtain glass optical elements that require high precision by press molding, the press mold has excellent workability so that the press surface can be processed easily and accurately and smoothly. Is required to have excellent resistance to oxidation or corrosion at high temperatures, mechanical strength, inertness to glass and release properties.
[0003]
However, conventionally, as a press type of a glass optical element, a type using silicon carbide (SiC) or silicon nitrite (Si ₃ N ₄ ) as a mold material is known from Japanese Patent Application Laid-Open No. 52-45613. A press die using such SiC or Si ₃ N ₄ as a mold material has high hardness and excellent mechanical strength, but has a problem that the material has low density and the press surface has poor smoothness. .
[0004]
Japanese Patent Laid-Open Publication No. Sho 59-121126 discloses a mold using a mixed material of titanium carbide (TiC) and a metal as a mold material. A press mold using such a mixed material of TiC and a metal as a mold material easily reacts with glass at a high temperature during press molding, so that the precision and mold releasability of a molded product are reduced, and Since the surface is oxidized and the smoothness of the surface is easily reduced, there is a problem that durability is poor and stable press molding cannot be performed.
[0005]
Further, as a press mold for improving the mold releasability of a glass molded product, there is a press mold in which glass-like carbon (amorphous carbon) is used as a mold material or a diamond-like thin film (diamond-like carbon) is formed on a pressed surface. Japanese Patent Application Laid-Open No. Sho 61-281030 discloses a method in which at least one surface of a glass and a press die is coated with carbon. When the press surface is made of glass-like carbon or diamond-like thin film or carbon-coated surface, the press surface is oxidized due to residual oxygen in the cavity when used for a long time. There is a problem that a change in shape occurs.
[0006]
Japanese Patent Application Laid-Open No. Sho 61-136929 discloses a press die in which an underlayer of a protective layer is provided below a press surface, in which an intermediate layer such as nitride or carbide is provided and a noble metal layer such as platinum is provided as a surface layer. Japanese Patent Application Laid-Open No. 62-132724 discloses a structure in which a silicon carbide film and a nitride film are sequentially laminated on a substrate made of silicon carbide or aluminum nitride. A press die having a surface layer of such a press surface and an underlayer of a protective layer thereunder is likely to cause film peeling and cracks on the surface layer and the protective layer during the press molding is repeated 1000 to 5000 times. There is a problem to say.
[0007]
[Problems to be solved by the invention]
The present invention has been made in order to solve the above-mentioned problems of the conventional press mold of a glass optical element, and has a high temperature resistance to oxidation and corrosion at the time of press molding of glass, mechanical strength, and resistance to glass. It is an object of the present invention to provide a glass press molding die excellent in activity and release properties, and excellent in workability capable of easily and accurately processing a press surface with smoothness.
[0008]
[Means for Solving the Problems]
The present invention relates to a glass press forming die, characterized in that a press surface for press forming glass is a processed surface of a ceramic mainly composed of 50 to 90 wt% of Al ₂ O ₃ and 10 to 50 wt% of SiC. With this configuration, the above object is achieved.
[0009]
[Action]
That is, in the glass press molding die of the present invention, at least a layer having a pressed surface contains 50 to 90 wt%, preferably 80 to 85 wt% of Al ₂ O ₃ and 10 to 50 wt%, preferably 15 to 20 wt% of SiC as main components. Made of ceramics, the denseness of the ceramics enables the basic component alumina to form a pressed surface smoothly, the oxidation resistance or corrosion resistance of the ceramics that enables stable press forming, and inertness to glass It also gives mold release properties, and mechanical strength, and gives the ceramics the ease of grinding and polishing with a diamond tool or diamond grindstone, etc., with the silicon carbide of the auxiliary component lowering the performance given to the above-mentioned alumina ceramics. , Easily and smoothly process the pressed surface of ceramics with high precision Bets can be, to be able to stably keep repeating press forming high-precision optical glass element.
[0010]
When the ratio of alumina and silicon carbide of the ceramics forming the pressed surface is less than 50 wt% of Al ₂ O _{3 and accordingly} the amount of SiC is more than 50 wt%, the workability of the ceramics is improved. Denseness is reduced, smoothness is reduced when the pressed surface is processed, the press die has poor releasability, gives a glass optical element with reduced accuracy, and has reduced durability due to poor bending strength become. Conversely, when the amount of Al ₂ O ₃ is more than 90 wt%, and therefore the amount of SiC is less than 10 wt%, the denseness of the ceramic is improved, but the hardness is too large, and the workability is significantly reduced. Even if a diamond tool or a diamond grindstone is used, it is very difficult to machine a highly accurate pressed surface.
[0011]
When the ratio of alumina and silicon carbide in the ceramics forming the pressed surface is in a preferable range, Al ₂ O ₃ is in a range of 80 to 85 wt%, and SiC is in a range of 15 to 20 wt%, the press die can easily form the pressed surface. It is possible to obtain a result that the glass optical element can be formed smoothly and accurately and the high precision glass optical element can be press-formed stably, and the durability is extremely high.
[0012]
【Example】
Hereinafter, the present invention will be described with reference to specific examples.
[0013]
Embodiment 1 FIG.
After uniformly mixing 80 wt% of Al ₂ O ₃ powder as a basic component, 19 wt% of SiC powder as an auxiliary component, and about 1 wt% of a lanthanide powder as an additive as a crystal grain growth inhibitor or a sintering aid, 1.5 ton / Pre-baking was performed at 900 ° C. for about 8 hours while applying a pressure of ² cm ² to obtain a chip, and the chip was ground by a diamond tool into a shape and dimensions approximate to a desired press die. The obtained mold was fired at 1500 ° C. for 96 hours to obtain an alumina-based ceramic mold, and the ceramic mold was ground to a substantially final press mold shape with a diamond grindstone. Polishing was performed using the agent to obtain a press die having a smooth press surface with a surface roughness Rmax of 0.06 μm or less.
[0014]
Using the obtained press mold, a step of pressing a SK-based glass (L-BAL35 glass material manufactured by OHARA CORPORATION) heated and softened to 550 ° C. at a mold temperature of about 500 ° C. to form a glass optical element is continuously repeated 6,000 times. Was. As a result, the surface roughness Rmax of the molding surface of the finally obtained glass optical element and the pressing surface of the pressing die were both 0.08 μm or less, and were sufficiently usable.
[0015]
Embodiment 2. FIG.
A ceramic press mold was obtained in the same manner as in Example 1, except that 50 wt% of Al ₂ O ₃ powder as a basic component, 49 wt% of SiC powder as an auxiliary component, and about 1 wt% of Y powder as an additive were used as ceramic raw materials.
[0016]
Using this press mold, a step of pressing a LaK-based glass (L-LAL8 glass material manufactured by Ohara Corporation) heated and softened to 570 ° C. at a mold temperature of about 530 ° C. to form a glass optical element was repeated 6,000 times continuously. As a result, the surface roughness Rmax of the molding surface of the finally obtained glass optical element and the pressed surface of the press mold were both 0.09 μm or less, and were sufficiently usable.
[0017]
In both Examples 1 and 2, an additive was used as a raw material for ceramics. However, almost the same results can be obtained without using an additive, and a composite tantanide or yttrium of a rare earth metal can be obtained. It is not limited to the example. And the glass press molding die of the present invention is not limited to molding of optical elements, and even if the whole is made of ceramics, the part having the pressed surface is made of ceramics, which is made of metal or the like. It may be held by a holder.
[0018]
【The invention's effect】
The glass press forming mold of the present invention is excellent in oxidation resistance and corrosion resistance at high temperature when press forming glass, mechanical strength, inertness to glass and mold releasability, and easily and accurately smoothes the pressed surface. It has a remarkable effect that it can be processed into

Claims (2)

Glass press-molding mold, characterized in that the press surface to press-molding the glass is machined surface of the ceramic mainly containing 50 to 90 wt% of _Al 2 _{O 3} and range of 10 to 50 wt% of SiC. Glass press-molding mold according to claim 1, wherein the ceramic is mainly composed of 80～85Wt% of _Al 2 _{O 3} and 15～20Wt% of SiC.