JPH0573699B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a method for manufacturing an optical glass element by press-molding a high-precision optical glass element that does not require a polishing step after press-molding. Prior Art In order to directly mold a high-precision glass element by pressing, it is required that the quality of image formation be good. For this reason, the mold material must be chemically inert to glass at high temperatures, the glass pressing surface of the mold must be sufficiently hard and resistant to damage such as scratches, and it must also be suitable for pressing at high temperatures. The mold must not undergo plastic deformation, have excellent heat resistance and thermal shock resistance, and must also have good workability and be capable of ultra-precision machining. As a manufacturing method using a mold that relatively satisfies these properties, for example, tungsten carbide (WC), cermet, or zirconia (ZrO ₂ ) is used as the base material, and a platinum-based alloy film is formed on these base materials. Press-molding molds for optical glass elements made of silicon carbide (SiC) or silicon nitride (Si ₃
A method for manufacturing an optical glass element using a press molding mold using N ₄ ) has been proposed (Japanese Unexamined Patent Publication No. 45613/1983). Problems to be Solved by the Invention In the case of conventional mold materials such as silicon carbide and silicon nitride, their hardness is extremely high, so it is difficult to process the glass press surface into a spherical or aspherical shape with high precision. was extremely difficult. Moreover, since these materials are all sintered types, they contain a third component as a sintering aid to improve their sintering properties, so they are relatively weak compared to glass containing lead or alkali elements. It easily reacts, and when press molding is repeated, the mold and glass react, causing the glass to adhere to the mold, making it impossible to mold a highly accurate optical glass element with good image formation quality. In addition, in the case of molds made of tungsten carbide, cermet, or zirconia base material with a platinum alloy film formed on these base materials, protrusions may occur if the glass is pressed at a high temperature exceeding 550°C. I got irritated because of this. For this reason, high softening point glass such as BK-7 could not be press-molded using a mold formed with the platinum-based alloy film. Means for Solving the Problems In order to solve the above-mentioned problems, the present invention selects materials that are easy to precisely process and have heat resistance and thermal shock resistance, such as tungsten carbide and cermet, as the base material of the mold. A mold for press forming is made by forming a heat-resistant Ru-Ir alloy film, Ru-Re alloy film, or Ru-Os alloy film on the base material by sputtering, which has poor reactivity with optical glass and is heat resistant. Configured. By using a mold with the above-mentioned configuration, we attempted to provide a high-temperature glass press mold that does not cause surface roughness even at high temperatures of 550°C or higher. This is an attempt to manufacture an optical glass element by press molding. Effects In the present invention, the Ru-Ir alloy film, Ru-Re alloy film, and Ru-Os alloy film have poor reactivity with optical glass, and protrusions are generated even at high temperatures of 550°C or higher. The alloy film was formed on a base material such as WC or cermet by a sputtering method to form a press molding mold. By using the mold produced as described above, it is possible to press-form a high softening point glass such as BK-7 into an optical glass element with good image formation quality. Example Hereinafter, an example of the method for manufacturing an optical glass element of the present invention will be described with reference to the drawings. Tungsten carbide and cermet with a diameter of 20 mm and a thickness of 6 mm were respectively processed into a pair of press-molding molds for optical glass elements, each consisting of a concave upper mold with a radius of curvature of 46 mm and a concave lower mold with a radius of curvature of 200 mm. After mirror-polishing the press surfaces of these molds using ultrafine diamond abrasive grains, a Ru-Ir alloy film, Ru-Re alloy film, or Ru-Os alloy film is applied to a thickness of 2 to 3 μm using a sputtering method. An alloy film was formed. The figure shows the upper and lower molds produced in this manner set in a press machine. 1 is an upper mold, 2 is a lower mold, 3 is a heater for the upper mold, 4 is a heater for the lower mold, 5 is a piston cylinder for the upper mold, 6
1 is a piston cylinder for the lower mold, 7 is a supply glass lump, 8 is a jig for supplying the glass lump, 9 is an outlet for the press-molded optical glass element, 10 is a preheating furnace for the supply glass lump, and 11 is a canopy. be. After heating a lump 7 made of BK-7 optical glass containing approximately 68% SiO ₂ , B ₂ O ₃ , Na ₂ O, K ₂ O and trace components into a spherical shape with a radius of 10 mm in a preheating furnace 10 . , upper and lower molds 1 and 2 held at 730℃
Place it on the lower mold ² of
The temperature of the upper and lower molds is then cooled to 300° C. to produce an optical glass element press-molded with convex surfaces on both sides, and taken out from the outlet 9 to complete the press-molding process of the optical glass element. After repeating the above process 500 times, the upper and lower molds 1 and 2 used were removed from the press machine, and the surface condition of the molds and the pressed surface of the pressed optical glass element were examined using a scanning electron microscope for surface roughness. It was evaluated using a meter. Tables 1 to 3 show the results of press experiments when the composition of the sputtered film was changed.

【table】

[Table] ☆: Comparative example

【table】

[Table] ☆: Comparative example

【table】

[Table] ☆: Comparative example As is clear from the table, lenses with good image forming quality could be press-molded with the Ru-Ir binary alloy without surface roughness on the pressed surface over the entire composition range. Also Ru−Ir2
Good results were also obtained with a type in which at least 10 wt% or less of at least one metal element selected from the group consisting of Ta, Rh, and Cr was added to the base alloy. Ru−Re2
For the original alloy, good results were obtained with an alloy film with a Re content of 0 to 80 wt%. In addition, the alloy composition includes Ta,
Good press test results were also obtained with a mold in which 10 wt% or less of at least one metal element selected from the group consisting of Rh and Cr was added. The results for the Ru-Os alloy film were similar to those for the Ru-Re alloy film. Next, even when cermets with TiN as the main component were selected as the base material and sputtered films of various compositions were formed to form press molding molds, there was no effect of changing the base material, and when WC was used as the base material. The same results as the experimental results were obtained. As mentioned above, TiC is a material whose base material has excellent workability and does not undergo warp deformation at high temperatures or cracks due to thermal shock.
Cermets containing Cr ₃ C ₂ or A ₂ O ₃ as a main component are also considered to be suitable materials as the base material. Furthermore, although a concave press molding mold was used to explain the present invention, the shape of the mold surface is not limited to the shape shown in this example, and is also suitable for the shape of optical glass elements such as prisms. Needless to say, it is something that can be done. Effects of the Invention As described above, the present invention selects a material with excellent processing precision, heat resistance, and thermal shock resistance, such as tungsten carbide or cermet, as a base material, and coats the base material with a material that is reactive with optical glass. Ru-Ir alloy film with no heat resistance and excellent heat resistance, Ru
- A high-precision high-melting optical glass element with good image forming quality is produced by press-molding high-melting point optical glass using a press-molding mold made by forming a Re-based alloy film or a Ru-Os-based alloy film. This is an extremely useful invention for mass-producing high-precision, high-melting-point optical elements at low cost.

[Brief explanation of the drawing]

The figure is a configuration diagram of a press machine incorporating a mold for direct press molding of an optical glass element of the present invention. DESCRIPTION OF SYMBOLS 1... Upper mold, 2... Lower mold, 3... Heater for upper mold, 4... Heater for lower mold, 5... Piston cylinder for upper mold, 6... Piston cylinder for lower mold, 7... ...Supplied glass lumps, 8...Glass supply jig, 9...Press-molded optical glass element outlet, 10...Preheating furnace for supplied glass lumps, 11...Shell.

Claims (1)

[Scope of Claims] 1. A material having heat resistance and excellent processing accuracy is used as a base material, and a Ru-Ir alloy film with an Ir content of less than 40 wt% or more than 95 wt%, Ru- 1. A method of manufacturing an optical glass element, which comprises press-molding an optical glass element using a press-molding mold formed with a Re-based alloy film or a Ru-Os-based alloy film. 2 The composition of the Ru-Ir alloy film is 90wt of Ru and Ir.
% or more, and the balance is at least 10 wt % of at least one metal element selected from the group consisting of Rh, Ta, and Cr, according to claim 1. A method for manufacturing an optical glass element. 3 A Ru-Re binary alloy in which the composition of the Ru-Re alloy film contains 20 wt% or more of Ru, and at least one selected from the group consisting of the above-mentioned binary alloy composition as a main component and the remainder being Rh, Ta, and Cr. 2. The method for manufacturing an optical glass element according to claim 1, wherein the alloy composition comprises 10 wt% or less of at least one type of metal element. 4 A Ru-Os binary alloy in which the composition of the Ru-Os alloy film contains 20 wt% or more of Ru, and at least one selected from the group consisting of the above-mentioned binary alloy composition as the main component, with the remainder being Rh, Ta, and Cr. 2. The method for manufacturing an optical glass element according to claim 1, wherein the alloy composition comprises 10 wt% or less of at least one type of metal element. 5 The base material is a cemented carbide whose main component is WC, a cermet whose main component is TiN, a cermet whose main component is TiC, a _cermet whose main component is _Cr3C2 , or a _cermet whose main component is _Al2O3 . 2. The method of manufacturing an optical glass element according to claim 1, wherein the optical glass element is made of cermet.