JP2006225190A - Metallic mold for molding optical element and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a metallic mold for molding an optical element free from surface roughness and fusion even if a highly accurate and high-melting optical element is repeatedly press molded. <P>SOLUTION: The metallic mold for molding the optical element has a preform 10 for the metallic mold, an intermediate layer 12 formed at the preform 10 and a protective film 13 formed on the intermediate rayer 12, and the protective film 13 is substantially composed of an amorphous alloy. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a mold for press molding of an optical glass element, in particular, a mold for press molding excellent in heat resistance, oxidation resistance, high temperature strength, and glass resistance resistance, and a method for producing the same.

  In press molding of optical glass elements, the temperature rise and fall cycles between normal temperature and high temperature are repeated for the press mold, so the press mold has excellent heat resistance, oxidation resistance, and high temperature. Strength, abrasion resistance, glass reactivity resistance, etc. are required. In addition, with the miniaturization and high accuracy of optical glass elements, it is also necessary to be able to process with high accuracy.

  Ceramics such as cemented carbide (WC) are used as a base material of a molding die that satisfies these requirements. Cemented carbide has excellent mechanical strength and high oxidation resistance in an inert atmosphere. However, since press molding of the optical glass element is performed at a high temperature, the surface is slightly oxidized by reacting with the optical glass, and the shape accuracy is lowered. Therefore, it is necessary to regrind the surface of the base material, but the cemented carbide, which is the material of the base material, is very hard, so it takes a lot of work to re-polish with high accuracy.

  Accordingly, it has been proposed to form a protective layer of a noble metal alloy on the molding surface of a cemented carbide mold. However, in the protective layer of the noble metal alloy, grain growth occurs at the pressing temperature of the optical glass element, and the surface accuracy of the molding surface deteriorates, so that the number of press molding repetitions is limited. In addition, when a long molding cycle is performed, the base material component (WC) diffuses into the protective layer of the noble metal alloy and forms an oxide on the surface. When the oxide reacts with a component in the optical glass element, the optical glass and the protective layer surface may be fused.

  Under such circumstances, Japanese Patent Application Laid-Open No. 6-144850 (Patent Document 1) discloses rough machining of a molding surface of a base material made of a cemented carbide containing WC as a main component to a shape close to the inverted shape of an optical glass element. An optical glass element molding die is disclosed in which a thin film of an amorphous base alloy such as Ir or Pt is formed on the molding surface by a sputtering method, and the amorphous alloy thin film is cut with high precision. Yes. Although this amorphous alloy thin film does not easily cause grain growth, there is no intermediate layer between the base material and the amorphous base alloy thin film, so that the diffusion of the base material component into the protective film is not sufficiently suppressed. There is.

  JP-A-2004-59368 (Patent Document 2) discloses that after forming an adhesive layer of Ta, Cr or the like on the molding surface of a mold base material by a sputtering method, one or more kinds of noble metal elements are added using Ir as a main material. A glass molding die is disclosed in which a protective film made of an alloy is formed by sputtering and subjected to pressure heat treatment. The adhesion between the base material and the protective film is strengthened by the adhesive layer, and the heat resistance of the mold is improved by the pressure heat treatment. However, when the base material is a cemented carbide, the heat treatment conditions are 650 to 750 ° C. and 14 to 50 hours, so the noble metal alloy in the protective film is considered to be crystallized. Therefore, there is a problem that the diffusion of the base material and the components of the adhesive layer to the protective film is not sufficiently suppressed by repeated press molding.

JP-A-6-144850 JP 2004-59368 A

  Accordingly, an object of the present invention is to provide a mold for molding an optical glass element that does not cause surface roughness or fusion even when a high-precision and high-melting optical glass element is repeatedly press-molded.

  Another object of the present invention is to provide a method for producing such an optical glass element molding die.

  As a result of diligent research in view of the above object, the present inventors formed a protective film made of a substantially amorphous alloy on the base material of the molding die through an intermediate layer, and in an inert gas atmosphere. By heat-treating at a temperature lower than the crystallization temperature of the protective film alloy, the protective film is annealed as a substantially amorphous alloy, and for optical glass element molding excellent in heat resistance, oxidation resistance and glass resistance. It was discovered that a mold can be obtained, and the present invention has been conceived.

That is, the present invention is achieved by the following means.
(1) A mold base material, an intermediate layer formed on the base material, and a protective film formed on the intermediate layer, wherein the protective film is made of a substantially amorphous alloy. An optical glass element molding die characterized by the above.
(2) In the optical glass element molding die described in (1) above, the intermediate layer is made of Ti, V, Cr, Ni, Nb, Mo, Rh, Ta, W, Re, Ir, and alloys thereof. An optical glass element molding die comprising at least one selected from the group.
(3) The optical glass element molding die according to (2), wherein the intermediate layer is made of Mo.
(4) In the optical glass element molding die according to any one of (1) to (3), the protective film is at least one selected from the group consisting of Pt, Ru, Rh, Pd, Re, and Os. An optical glass element molding die, which is an Ir-based alloy containing
(5) A method for producing a mold for optical glass element molding according to any one of (1) to (4) above, wherein an intermediate layer is formed on a mold base material, and the intermediate layer is protected. A method comprising forming an amorphous alloy thin film as a film, and performing a heat treatment at a temperature lower than a crystallization temperature of the alloy and in an inert gas atmosphere.
(6) The method for producing a mold for molding an optical glass element according to the above (5), wherein the heat treatment temperature is 500 to 600 ° C.

  The optical glass element molding die of the present invention has a protective film on the molding surface of the base material through an intermediate layer and is annealed while the protective film is substantially amorphous. The growth is suppressed, and the diffusion of the base material and intermediate layer components into the protective film is sufficiently suppressed, so that press molding can be repeated many times without surface roughness or fusion.

(1) Optical Glass Element Molding Mold As shown in FIG. 1, a base material 10 constituting the molding mold of the present invention has a molding surface 11 having a reverse shape of a desired optical glass element. A protective film 13 is formed through the intermediate layer 12. Since the molding surface 11 of the base material 10 is polished with high precision, the molding surface 14 of the protective film 13 also has a highly precise inverted shape.

In order to be used for press molding of optical glass, the base material 10 is made of a material having high mechanical strength under high temperature and pressure. Such materials include cemented carbide, which is a sintered body of WC particles and Co metal binder, cemented carbide obtained by sintering WC particles, ceramics such as SiC, ZrO ₂ and TiC, and ceramics other than WC (Cr ₂ O ₃ , Al ₂ O ₃ etc.) and a cermet which is a sintered body of a binder such as Ni metal is preferred.

  The intermediate layer 12 is a single layer or multiple layers. In the case of multiple layers, the composition of each layer may be the same or different. By providing the intermediate layer 12, the adhesion between the base material 10 and the protective film 13 is improved. The material of the intermediate layer 12 is preferably a pure metal or alloy having a melting temperature equal to or higher than the molding temperature of the optical glass element. Specific examples include Ti, V, Cr, Ni, Nb, Mo, Rh, Ta, W, Re, Ir, and alloys thereof. Among these, Mo that is chemically stable from a low temperature to a high temperature is particularly preferable.

  The protective film 13 is made of a substantially amorphous alloy. Since the protective film 13 is made of an amorphous alloy, it is possible to suppress the diffusion of the components of the base material 10 and the intermediate layer 12 into the protective film 13, and repeat press forming many times without surface roughness or fusion. Can do. The material of the protective film 13 is preferably a metal such as Pt, Ru, Rh, Pd, Re, Os, Ir, and particularly contains at least one selected from the group consisting of Pt, Ru, Rh, Pd, Re, and Os. Ir-based alloys are preferred. Since the Ir alloy has high hardness, it is preferable because the molding surface 14 of the protective film 13 is hardly scratched even if press molding is repeated.

(2) Manufacturing method of mold for molding optical glass element High precision molding by grinding one surface of base material 10 sintered to near net shape of inverted shape of optical glass element and then polishing with diamond abrasive Surface 11 is formed.

  The intermediate layer 12 may be formed by a known method, but for example, sputtering, vacuum deposition, ion plating, plasma CVD, etc. are preferable, and sputtering is particularly preferable. When the intermediate layer 12 is made of an alloy, the intermediate layer 12 having a desired composition can be formed by changing the area ratio of each metal if the target is constituted by blocks of the respective constituent metals.

  As a method for forming the protective film 13, for example, a sputtering method, a vacuum deposition method, an ion plating method, plasma CVD, or the like is preferable, and a sputtering method is particularly preferable. As in the case of the intermediate layer 12, the target for the protective film 13 can be composed of blocks of constituent metals.

  After the protective film 13 is formed, the protective film 13 is annealed while being substantially amorphous by performing heat treatment in an inert gas atmosphere such as argon or nitrogen and at a temperature lower than the crystallization temperature. The heat treatment temperature is preferably 500 to 600 ° C.

  The present invention will be described in more detail with reference to the following examples, but the present invention is not limited thereto.

Example 1
The base material 10 is formed by sintering WC so as to have a molding surface having a shape substantially equal to the inverted shape of the optical glass element, and after grinding to increase the accuracy of the molding surface, a diamond abrasive is used. Polishing was performed so that the surface roughness was 0.02 μm or less. An intermediate layer 12 made of Mo and having a thickness of 1 μm was formed on the obtained molding surface 11 by sputtering. Further, a noble metal alloy amorphous film composed of 80% by mass of Ir, 10% by mass of Re, and 10% by mass of Rh was formed as a protective film 13 on the surface of the intermediate layer 12 to a thickness of 1 μm by sputtering. The temperature of the base material 10 during sputtering was about 300 ° C. The obtained mold was annealed while keeping the protective film 13 substantially amorphous by heat-treating the base material 10 at 580 ° C. for 5 hours in an inert gas (argon) atmosphere.

  Components of the base material 10 and the intermediate layer 12 were not detected from the molding surface 14 of the mold thus obtained. Further, the surface roughness of the molding surface 14 did not change before and after the heat treatment.

  An optical glass element was actually press-molded using this molding die. As the optical glass, L-BAL35 glass [manufactured by OHARA INC.] Was used. The temperature of the optical glass during press molding was 580 ° C., and the temperature of the optical glass when taken out from the molding die after press molding was 230 ° C. The press molding cycle was repeated 5000 times, but no change in the surface roughness of the protective film 13 was observed. Further, no fusion with the optical glass occurred.

Comparative Example 1
After forming the intermediate layer 12 of Mo having a thickness of 1 μm by sputtering on the molding surface 11 of the base material 10 made of WC produced in the same manner as in Example 1, 80% Ir, 10% by mass as the protective film 13 An amorphous film of a noble metal alloy composed of Re and 10% by mass of Rh was formed to a thickness of 1 μm by sputtering. The temperature of the base material 10 during sputtering was about 300 ° C. The protective film 13 was polycrystallized by heat treatment at 700 ° C. for 5 hours in an inert gas atmosphere.

  Components of the base material 10 and the intermediate layer 12 were detected from the molding surface 14 of the mold thus obtained. Moreover, the molding surface 14 had spiders. From this, it can be seen that the molding surface 14 is rough.

  When press molding was performed under the same conditions as in Example 1 using this molding die, the protective film 13 and the optical glass were fused at about the 30th time, and a part of the protective film 13 was the intermediate layer 12. Peeled off.

It is sectional drawing which shows schematically the optical glass element shaping die by one Example of this invention.

Explanation of symbols

10 ... base material
11 ... Molded surface
12 ... Middle layer
13 ... Protective film
14 ... Molded surface

Claims (6)

A mold base material, an intermediate layer formed on the base material, and a protective film formed on the intermediate layer, wherein the protective film is made of a substantially amorphous alloy. A mold for forming an optical glass element. The optical glass element molding die according to claim 1, wherein the intermediate layer is selected from the group consisting of Ti, V, Cr, Ni, Nb, Mo, Rh, Ta, W, Re, Ir, and alloys thereof. An optical glass element molding die comprising at least one kind. 3. The optical glass element molding die according to claim 2, wherein the intermediate layer is made of Mo. The optical glass element molding die according to any one of claims 1 to 3, wherein the protective film contains at least one selected from the group consisting of Pt, Ru, Rh, Pd, Re, and Os. An optical glass element molding die characterized by the above. A method for producing a mold for forming an optical glass element according to any one of claims 1 to 4, wherein an intermediate layer is formed on a base material for the mold, and an amorphous alloy is formed as a protective film on the intermediate layer. A method comprising forming a thin film and performing a heat treatment at a temperature lower than the crystallization temperature of the alloy and in an inert gas atmosphere. The method for producing an optical glass element molding die according to claim 5, wherein the heat treatment temperature is 500 to 600 ° C.