JPH02283627A - Mold for forming optical glass element - Google Patents

Abstract

PURPOSE:To improve heat and oxidation resistance, wetting resistance and mold releasability from optical glass by press forming a heated and softened optical glass element material in a mold prepared by applying a specific coating thin film to a base metal. CONSTITUTION:Amorphous carbon in which hydrogen is bonded by a high-frequency plasma method, ion beam method, ion plating method, etc., is deposited to provide 0.1-5mum thickness on a base metal 1 subjected to discharge processing, then worked into a desired shape and surface working by grinding to form a coating thin film 2 and provide a top force 4 and a bottom force 3. An optical glass element material 5 ground into a spherical form is then placed on the resultant bottom force 3 and a nonoxidizing gas is subsequently fed from an atmospheric gas feed port 9, simultaneously heated with a heater 7 and softened. The top force 4 is then lowered through a cylinder 8 to press form an element material 5 in a mold cavity formed from the top force 4, the bottom force 3 and a drum mold 6.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a mold for molding an optical glass element by press-molding glass softened by heating.

[Prior art and its problems] Conventionally, optical glass elements have been made by a polishing process, but recently, methods have been developed to soften the optical glass element material by heating and press-form it between an upper mold and a lower mold. Glass molding methods are now being used to manufacture optical glass elements.

In this case, the mold used is a base material that has been processed into the desired curved surface and coated with a thin film. Alloy tungsten carbide (WC), stainless steel,
Ni-based heat-resistant alloys, cermets, silicon carbide (SiC)
, various ceramics such as silicon nitride (SiJ<) are used. In addition, ceramics such as titanium nitride (TiN), platinum (PT), gold (
A mold coated with a noble metal such as Au) or rhodium (Rh) is used.

When an optical glass element is repeatedly molded using such a mold, 1. For example, in the case of a TiN-coated item, the composition of TiN itself is unstable, so if it is in an oxidizing atmosphere, the structural composition of TiN will change. It also affects the properties of the film, such as adhesion with the base material and fa5 with the optical glass element.
It started to get worse. Therefore, care must be taken to ensure that the atmosphere in the molding section is strictly non-oxidizing, and the size of the apparatus cannot be avoided. For example, there are difficulties with shielding methods under high temperatures because non-oxidizing gas is supplied after the inside of the molding section is once evacuated.

Furthermore, when precious metals are used, since the precious metals themselves are soft, they easily cause scratches due to friction with the optical glass element material during molding. There have been some attempts to suppress scratches to some extent by using thin films made of platinum group alloys with nitrides dispersed in them, or by changing the proportions of each noble metal in platinum group alloys, but even these efforts had their limits.

The present invention was made in view of these conventional problems, and it is possible to mold an optical glass element with excellent durability and high precision with good reproducibility without causing scratches on the surface of the mold. The purpose is to provide a mold that can

[Means for Solving the Problems] For the above purpose, the present invention provides a mold for obtaining an optical glass element by heating an optical glass element material, softening it, and press-molding the material, the mold It is characterized in that it is composed of a base material and a thin coating film applied thereon, and the thin coating film is made of amorphous carbon (a-C) to which hydrogen is bonded.

[Function] As a result of various studies and tests, the present inventor has confirmed that amorphous carbon to which hydrogen is bonded has excellent properties as a coating film on the surface of a mold base material.

Amorphous carbon, which does not contain hydrogen, is similar to glassy carbon and is brittle and has low hardness.

On the other hand, amorphous carbon to which hydrogen is bonded has diamond-structured bonds (5p3) or is dispersed in the amorphous material, resulting in a dramatic improvement in hardness.

In the present invention, the mold base material is cemented carbide WC, stainless steel,
After grinding and polishing this base material into a desired shape, amorphous carbon is applied to the surface using one of the high-frequency plasma method, ion beam method, ion blating method, and sputtering method. method, or a combination thereof. At this time, in order to make the film amorphous, the coating conditions are controlled and the amorphous carbon is reduced to 0.
Form 1 to 5 #LII. By using such a mold, it is possible to create a mold that has excellent heat resistance, oxidation resistance, resistance to optical glass elements, mold releasability, high surface hardness, and does not get damaged during molding or handling. or can be obtained.

The mold base materials are cemented carbide WC, stainless steel, and Ni.
Base heat-resistant alloys are preferred.

The reason why we limited the mold base material to the above materials is that these materials are
It is possible to significantly reduce the surface roughness by polishing (R x axmo 1 mouth 2 ≧ no more than 0.000), which increases the adhesion with the coating, and with ceramics etc., fine voids remain and the adhesion becomes difficult. This is because the power also weakens.

Regarding the film thickness, if it is less than 0.1 mm, the oxidation of the base material surface cannot be suppressed by the film alone at high temperatures, and the surface will gradually deteriorate, and if it is more than 5 mm, the surface precision will deteriorate. Since there is a risk of destroying the surface shape, it is set to Ojμs to 51Ls.

Embodiments of the present invention will be described below with reference to the drawings.

[Example] Fig. 1 is a schematic diagram of an optical glass element molding apparatus using the mold of the present invention. 3 in Fig. 0 is a lower flat.

4 is an upper mold, and the upper mold 4 can be raised and lowered by a cylinder 8. Further, 12 is a shield box, 9 is an atmospheric gas supply port, and 7 is a heater lO for heating the optical glass element material 5, which is a thermocouple.

FIG. 3 is an enlarged view of the mold used here. In this example, cemented carbide WC was used as the base material 1, and amorphous carbon to which hydrogen was bonded was coated on the surface using a high-frequency plasma method.

To manufacture the mold, first, it was subjected to electrical discharge machining, then processed into the desired shape using an ultra-precision lathe, and polished with a diamond abrasive to give a surface roughness of 0.0IJLII. Using methane gas (C1,) as a raw material, amorphous carbon was deposited on this base material under high-frequency glow discharge at 2.3 MHz while keeping the gas pressure at 10 Pa to form a coating 2 with a thickness of 1.0 IL-. . The Vickers hardness of the coating 2 at this time was 4000 kg/-2.

As for the molding method, first, an optical glass element material F2 (manufactured by Ohara Optical Glass) 5 polished into a spherical shape is placed on the lower mold 3.
Heater 7 was used to heat up to 480°C. Here, the mold temperature was measured by a thermocouple IO. Also, during heating, the atmosphere gas supply port 9 is
Nitrogen gas, which is more non-oxidizing, was introduced.

After reaching the predetermined temperature, the cylinder 8
was lowered, and the optical glass element material 5 was press-molded between the upper mold 4, the lower mold 3, and the body mold 6 at a pressure of about 100 kg/cm''.

Thereafter, it is cooled, and when the temperature of the molded part falls below the transition point of the optical glass material (430°C), the pressure is released, and the cylinder 8 is raised to form the optical glass element 11 (fourth
(see figure) was taken out.

The above experiment was repeated, and it was possible to mold two high-precision optical glass elements with good reproducibility without causing any scratches on the surface of the mold.

11 As in the first embodiment, the mold 3 used was a mold in which cemented carbide WC was used as the base material 1, and 1.0 .mu.m of amorphous carbon bonded with hydrogen was coated thereon. In addition, 5O3420 is used as the base material for the upper mold 4, and after grinding and polishing,
A mold coated with amorphous carbon to a thickness of 2.0% by ion beam sputtering was used.

At this time, the gas pressure was 10-'Pa and the coating was applied under a voltage of 700V.The molding method was the same as in the first example, and LF5 (manufactured by Ohara Optical Glass Co., Ltd.) was used as the optical glass material, and the coating was heated at 540°C.
It was molded in. After molding, it was cooled to 430° C., and then the pressure was released, and the optical glass element 11, which was a molded product, was taken out.

As a result, it was possible to mold a highly accurate optical glass element with good reproducibility without causing any scratches on the surface of the mold.

[Effects of the Invention] As described above, according to the mold of the present invention, a coachib coating of amorphous carbon to which hydrogen is bonded is formed on the surface of the molding base material, and preferably cemented carbide w is used as the base material.
By using C, stainless steel, and Ni-based heat-resistant alloys, it not only has excellent heat resistance, oxidation resistance, wettability with optical glass elements, and mold releasability, but also has high surface hardness that makes it easy to mold. The effect is that the life of the mold is extended without causing any scratches on the surface.

[Brief explanation of drawings]

FIG. 1 is a schematic cross-sectional view of an optical glass element molding apparatus using the mold of the present invention, FIG. An enlarged view of the mold, FIG. 4, is a schematic diagram of the molded optical glass element. In the figure, 1 is a mold base material, 2 is a coating film, 3 is a lower mold, 4 is an upper mold, 5 is an optical glass element material, 6 is a body mold, 7
is the heater, 8 is the cylinder 9 is the atmospheric gas supply 0.10
is a thermocouple, and 11 is a molded optical glass element. Patent applicant: Asahi Optical Industry Co., Ltd. Application agent: Patent attorney Shigemi Nishino

Claims (1)

[Claims] A mold for obtaining an optical glass element by heating and softening an optical glass element material and press-molding the material, the mold comprising a base material and a thin coating film applied thereon, A mold for forming an optical glass element, characterized in that it is made of amorphous carbon to which hydrogen is bonded.