JP2002114527A - Molding die for optical element and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a molding die for an optical element such that even a processed layer having >=50 μm thickness can be sufficiently used for heat-press molding which can not be realized by a conventional processed layer and that the form of a free curved face is not limited. SOLUTION: The molding die for an optical element has a transfer face to form an optically functional face of the optical element on the molding face of a base body 1. The transfer face has processed layers 2, 3 essentially comprising metals and processed into a desired form by a desired accuracy on the base body 1 and has a surface layer 5 essentially comprising a hard carbon film or a noble metal alloy film on the processed layers. The film in the surface layer sides of the processed layers 2, 3 has higher density than that of the film in the base body sides. Further, an intermediate layer 4 made of carbides, nitrides or carbonitrides is formed between the processed layer 2 and the surface layer 5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical element molding die used for producing optical elements such as lenses and prisms with high precision by press-molding a glass material, and a method for producing the same.

[0002]

2. Description of the Related Art In general, a technique for manufacturing a lens by press-molding a glass material eliminates complicated steps such as polishing required in the conventional manufacturing, and can manufacture a lens simply and inexpensively. Recently, not only lenses but also prisms and other optical elements made of glass have been widely used.

[0003] The properties required of a mold used for press molding of such a glass optical element include excellent hardness, oxidation resistance, heat resistance, mold release properties, mirror workability, and the like. . Conventionally, this type of mold material includes metals, ceramics, and materials coated with them.
Numerous materials have been proposed.

[0004] If some examples, for example, in JP-A-49-51112, 13Cr martensite steel, the JP-A-52-45613, the SiC and Si ₃ N _4, especially JP-A-59-121126 discloses a mixed material of TiC and a metal.
No. 6230 discloses a material obtained by coating a hard metal with a noble metal, and Japanese Unexamined Patent Publication No. 61-183134,
JP-A-61-281030, JP-A-1-3018
Japanese Patent Application Laid-Open No. 64-8352 discloses a diamond thin film or a diamond-like carbon film, respectively.
No. 9 discloses a material coated with a hard carbon film,
Each has been proposed.

[0005]

However, in the conventional mold material as described above, hardness, oxidation resistance, heat resistance,
Release properties and mirror workability cannot all be satisfied.

For example, 13 martensitic steel is liable to be oxidized, and further has the disadvantage that at high temperatures, Fe diffuses into the glass and the glass is colored.

Further, SiC, Si ₃ N ₄ , TiC, a diamond thin film, a diamond-like carbon film, and a hard carbon film
Although the hardness of the material is very high and the mechanical strength is excellent, it is inferior in workability and it is difficult to process it into a highly accurate mold shape. Furthermore, in SiC, Si ₃ N ₄ and TiC,
Oxidation occurs at high temperatures, causing the glass to fuse to the mold.

In a molding die in which a noble metal thin film, a diamond thin film, a diamond-like carbon film, and a hard carbon film are coated on a cemented carbide base material, a diamond grinding wheel is used as a means for processing the cemented carbide. However, it has a disadvantage that it cannot be processed into a spherical surface or a free-form surface having a small curvature. In addition, the free-form surface here is a curved surface including a non-axisymmetric aspherical surface.

As a measure for improvement, it has been proposed to provide a work layer which can be easily and precisely machined on a cemented carbide base material.
No. 230 discloses an electroless Ni-P plating film, and JP-A-7-41326 discloses a ternary alloy containing P (P-N
i, Co, Fe-Si, Ti, Cu, Zr, Nb, M
o, Ru, Rh, Pd, Hf, Ta, W, Re, Os,
Ir), the working layer is subjected to necessary precision machining (cutting) to form a transfer surface, and a noble metal-based alloy thin film is coated on the working layer.
Each has been proposed.

However, since the difference in thermal expansion coefficient between the working layer and the cemented carbide base material is large, if the thickness of the working layer is not less than 30 μm, there is a problem that the working layer is peeled or cracked during hot press molding. there were. Therefore, there is a problem that the shape of a free-form surface or the like that can be formed is limited because the thickness of the processed layer is limited.

The present invention solves such a conventional problem, and has a film thickness of 50 μm, which cannot be realized by a conventional processed layer.
m or more, it can be used enough for hot press molding,
Further, an object of the present invention is to provide an optical element molding die in which the shape of a free-form surface is not limited, and a method for manufacturing the same.

[0012]

According to the present invention, there is provided an optical element molding die having a transfer surface for molding an optically functional surface of an optical element on a molding surface of a base material. The transfer surface is formed on the base material, is formed of a metal as a main component, a processed layer processed with a desired shape and accuracy, and a hard carbon film or a noble metal alloy on the processed layer And a surface layer formed of a film as a main component, wherein the film on the surface layer side of the processed layer has a higher density than the base material side.

In this case, as an embodiment of the present invention, it is preferable to form an intermediate layer made of a metal carbide, nitride, or carbonitride between the processed layer and the surface layer. In particular,
Means for making the film on the surface layer side of the processed layer higher in density than the base material side when forming the processed layer include the following configurations.

1) The base material temperature at the end of film formation is controlled to be lower than the base material temperature at the start of film formation.

2) The flow rate of the inert gas at the end of the film formation is controlled to be smaller than the flow rate of the inert gas at the start of the film formation.

3) Control is performed such that only the argon gas is used as the inert gas at the start of film formation, and argon gas and helium gas are used as the inert gas during and after the film formation.

4) The DC bias of the base material at the end of film formation is
It is controlled to be higher than the DC bias at the start of film formation.

Further, it is needless to say that the object of the present invention can be achieved by combining a plurality of these means as required. Further, the base material temperature, the flow rate of the inert gas, the flow rate ratio of the argon gas to the helium gas, and the value of the DC bias are as follows:
It depends on the material and thickness of the processed layer, the material and the shape of the base material, and is not limited to a specific value.

As described above, according to the present invention, since the density of the film on the surface layer side of the processed layer is higher than that of the base material side, the difference in thermal expansion coefficient between the processed layer and the cemented carbide base material is reduced. Even if it is large, it is possible to avoid the problem that the low-density working layer on the base material side peels or cracks during hot press molding because the layer relaxes the stress. Therefore, even if the film thickness is 50 μm or more, a mold for optical element molding which can be sufficiently used for hot press molding and whose shape of the free-form surface is not restricted, which cannot be realized by the conventional processed layer, can be obtained.

[0020]

Embodiments of the present invention will be described below. FIG. 1 is a schematic sectional view of an optical element molding die according to this embodiment. The mold for forming an optical element here has a transfer surface for forming the optically functional surface of the optical element on the forming surface of the base material 1, and the transfer surface is formed on the base material 1. The processed layer 2 having a desired shape and accuracy, containing metal as a main component, and on the processed layer 2,
A surface layer 5 formed mainly of a hard carbon film or a noble metal alloy film;
The density is higher than the base material 1 side. In this embodiment, an intermediate layer 4 is provided between the processing layer 2 and the surface layer 5.

In this embodiment, base material 1 is made of oxide ceramics mainly composed of alumina and zirconia, silicon carbide, silicon nitride, titanium carbide, titanium nitride, and carbide / nitride mainly composed of tungsten carbide. A base ceramic, a cemented carbide mainly containing tungsten carbide, a metal mainly containing molybdenum, tungsten, and tantalum, and preferably a cemented carbide mainly containing tungsten carbide in terms of hardness.

The working layers 2 and 3 are made of one selected from nickel (Ni), cobalt (Co) and iron (Fe); copper (Cu), silicon (Si), titanium (Ti), chromium ( Cr), zirconium (Zr), niobium (Nb), molybdenum (Mo), hafnium (Hf), tantalum (T
a), an alloy with one selected from tungsten (W), or nickel (Ni), cobalt (Co),
One of iron (Fe); and phosphorus (P)
Copper (C), which is an original alloy or one selected from nickel (Ni), cobalt (Co), and iron (Fe);
u), silicon (Si), titanium (Ti), chromium (C
r), zirconium (Zr), niobium (Nb), molybdenum (Mo), hafnium (Hf), tantalum (T
a) and tungsten (W); and a ternary alloy with phosphorus (P). In particular, in terms of cutting workability and diamond tool life with diamond tools,
Preferred are nickel (Ni), cobalt (Co),
One selected from iron (Fe); copper (Cu), silicon (Si), titanium (Ti), chromium (Cr), zirconium (Zr), niobium (Nb), molybdenum (M
o), hafnium (Hf), tantalum (Ta), and tungsten (W); and a ternary alloy of phosphorus (P).

As the coating method, a sputtering method, an ion plating method, an evaporation method or the like is used. Preferably, in the sputtering method, a metal target is used, and an inert gas such as argon is used as an introduced gas. It is desirable to form a film by adhesion from the viewpoint of adhesion to the base material.

The intermediate layer 4 is made of titanium, tantalum, chromium,
Silicon carbide, nitride and carbonitride, preferably titanium nitride (TiN). As the coating method, a sputtering method, an ion plating method, or the like is used. The thickness is preferably 0.1 to 3 μm.

As the surface layer 5, a hard carbon film is desirable in terms of surface hardness, and a high-frequency plasma CVD method, an ion beam evaporation method, a sputtering method, or the like is used as a coating method. Is desirable in terms of adhesion.

The film thickness is preferably from 10 nm to 1 μm. The hard carbon film in the present invention is generally referred to by a researcher as a hydrogenated amorphous carbon film, a diamond-like carbon film (or DLC film: diamond-like).
carbon) or i-C film.

Further, platinum (Pt), palladium (Pd), iridium (Ir), rhodium (R
h), osmium (Os), ruthenium (Ru), rhenium (Re), gold (Au), tungsten (W), and tantalum (Ta). A vacuum evaporation method or the like is used. The thickness is desirably 0.1 to 1 μm in terms of surface hardness.

[0028]

(Example 1) In this example, a mold base material 1 was used.
Is obtained by subjecting a cemented carbide mainly composed of WC to electric discharge machining into a desired approximate shape of a free-form surface.

Next, an Ni-P target and a Cu target were used on the electric discharge machined surface, the flow rate of argon was controlled to be 1 Pa as an introduced gas, and a binary bias was applied to the base material 1 without applying a DC bias. Ni-P
-Form a Cu processing layer 2 of 50 μm. At this time, the temperature of the base material at the start of film formation is set to 550 ° C., and the temperature of the base material at the end of film formation is controlled to 400 ° C. (Film 3)).

Next, this processed layer is cut into a desired free-form surface shape using a diamond tool, and finished by uniform polishing. Next, T
Using an i target and using a nitrogen gas as an introduction gas, an intermediate layer 4 of TiN is formed to 1 μm by reactive sputtering.

Next, a surface layer 5 of a hard carbon film having a thickness of 100 nm is formed on the intermediate layer 4 by an ion beam evaporation method.

Thus, the molding die thus configured was set in a continuous molding machine, and using this, a glass molding (phosphate glass) was performed. A molded product was obtained, and no deterioration of the transfer surface of the molding die was observed.

(Example 2) Here, when forming the above-mentioned processed layer, from the start of film formation until the film thickness becomes 10 μm.
An optical element molding die is manufactured in the same manner as in Example 1 except that the temperature of the base material is set to a constant value of 550 ° C., and the temperature of the base material at the end of film formation is set to a constant value of 400 ° C.

When the molding die was set in a continuous molding machine and glass molding (phosphate-based glass) was performed using the molding die, a good molded product was obtained even after 3000 shot molding. No deterioration of the transfer surface of the mold was observed.

(Comparative Example 1) Here, when forming the processed layer, the temperature of the base material from the start of film formation to the end of film formation was 550.
An optical element molding die is manufactured in the same manner as in Example 1 except that the temperature is kept constant.

When the molding die was set in a continuous molding machine and glass molding (phosphate glass) was performed using the molding die, the shape transferability was deteriorated after 2,000 shot molding, and the molding die was molded. Deterioration of film cracking was also observed on the surface (transfer surface).

(Comparative Example 2) Here, when forming a processed layer, the temperature of the base material from the start of film formation to the end of film formation was set to 400.
An optical element molding die was manufactured in the same manner as in Example 1 except that the temperature was kept constant. However, when a processed layer was formed, film peeling occurred, and a required optical element molding die was obtained. Did not.

Embodiment 3 Here, when forming a processed layer, the flow rate of Ar gas at the start of film formation is set to be 4 Pa, and the flow rate of Ar gas at the end of film formation is 0.5 Pa.
, And a mold for forming an optical element is manufactured in the same manner as in Example 1 except that the base material temperature is set to a constant value of 550 ° C.

The molding die was set in a continuous molding machine, and a glass molding (phosphate glass) was performed using the molding die. As a result, a good molded product was obtained even after 3000 shot molding. No deterioration of the molding surface (transfer surface) of the mold was observed.

Example 4 Here, when forming a processed layer, the flow rate of Ar gas at the start of film formation was set to be 4 Pa, and the flow rate of Ar gas at the end of film formation was 0.5 Pa.
Except that control is performed so that
Manufacture mold for optical element molding.

When the molding die was set in a continuous molding machine and glass molding (phosphate-based glass) was performed using the molding die, a good molded product was obtained even after 3000 shot molding. No deterioration of the molding surface (transfer surface) of the mold was observed.

(Comparative Example 3) Here, when forming the processing layer, the Ar gas flow rate from the start of the film formation to the end of the film formation was set to a pressure of 4
An optical element molding die is manufactured in the same manner as in Example 3, except that Pa is kept constant.

This molding die was set in a continuous molding machine, and glass molding (phosphate glass) was performed using the molding die. After 1800 shots, the shape transferability deteriorated, and the molding die was molded. Deterioration of film cracking was also observed on the surface (transfer surface).

(Comparative Example 4) Here, when forming a processed layer, the same procedure as in Example 3 was carried out except that the flow rate of Ar gas from the start of film formation to the end of film formation was kept constant at a pressure of 0.5 Pa. Although a mold for forming an optical element was manufactured, when a processed layer was formed, film cracks occurred, and a required mold for forming an optical element could not be obtained.

(Embodiment 5) Here, when forming the processing layer, the ratio of the He gas flow rate / Ar gas flow rate at the start of film formation was 0/0.
1 and the He gas flow rate at the end of film formation / A
An optical element molding die is manufactured in the same manner as in Example 1 except that the r gas flow ratio is controlled to be 1/20, and the base material temperature is set to be constant at 550 ° C.

The molding die was set in a continuous molding machine, and using this, a glass molding (phosphate glass) was performed. As a result, a good molded product was obtained even after 3000 shot molding. No deterioration of the molding surface (transfer surface) of the mold was observed.

(Embodiment 6) Here, when forming the processed layer, the ratio of the He gas flow rate / Ar gas flow rate at the start of film formation was 0/0.
1 and the He gas flow rate at the end of film formation / A
Except for controlling the r gas flow ratio to be 1/20,
In the same manner as in Example 1, an optical element molding die is manufactured.

The molding die was set in a continuous molding machine, and glass molding (phosphate-based glass) was performed using the molding die. As a result, a good molded product was obtained even after 3000 shot molding. No deterioration of the molding surface (transfer surface) of the mold was observed.

(Embodiment 7) Here, when forming a processed layer, a DC bias at the start of film formation is not applied, and a DC bias at the end of film formation is controlled to be 500 V, and the base material temperature is set to 550. An optical element molding die is manufactured in the same manner as in Example 1 except that the temperature is set to be constant.

The molding die was set in a continuous molding machine, and glass molding (phosphate glass) was performed using the molding die. A good molded product was obtained even after 3000 shot molding. No deterioration of the molding surface (transfer surface) of the mold was observed.

(Embodiment 8) Here, when forming a processed layer, a DC bias was not applied at the start of film formation, and the DC bias at the end of film formation was controlled to be 500 V.
In the same manner as in Example 1, an optical element molding die is manufactured.

When the molding die was set in a continuous molding machine and glass molding (phosphate glass) was performed using the molding die, a good molded product was obtained even after 3000 shot molding. No deterioration of the molding surface (transfer surface) of the mold was observed.

(Embodiment 9) Here, when forming a processed layer, instead of using Ni-P as a target, Ni, C
o, instead of a binary alloy of the combination of Fe-P and Cu (Cu, Si, Ti, Cr, Zr, Nb, Mo, H
f, Ta, W), except that one type of target is used, a mold for molding an optical element is manufactured in the same manner as in Example 1.

When the glass moldability of this molding die was measured, it was equal to that of Example 1 as shown in Table 1.

[0055]

[Table 1] (Embodiment 10) Here, an optical system was manufactured in the same manner as in Embodiment 2, except that a carbide, nitride, or carbonitride of titanium, tantalum, chromium, or silicon was formed instead of forming the TiN film of the intermediate layer. Manufactures an element molding die.

When the glass moldability of this mold was measured, it was the same as that of Example 1 as shown in Table 2.

[0057]

[Table 2] (Embodiment 11) Here, instead of forming the hard carbon film of the surface layer, Pt, Pd, Ir, Rh, Os, Ru, R
An optical element molding die is manufactured in the same manner as in Example 2 except that a binary alloy of e, Au, W, and Ta is formed to a thickness of 0.5 μm.

The Vickers hardness and the glass moldability of this mold were measured.
Was equivalent to

[0059]

[Table 3] Further, in the above embodiments, the respective components of the processed layer, the intermediate layer, and the surface layer were changed. However, it is needless to say that the same effect was obtained by combining these components.

Example 12 Here, a mold for molding an optical element is manufactured in the same manner as in Example 1 except that the intermediate layer is not formed.

When the molding die was set in a continuous molding machine and glass molding (phosphate-based glass) was performed using the molding die, a good molded product was obtained even after 2,000 shot molding. In the shot, deterioration of transfer accuracy was observed.

(Example 13) In this example, when forming the intermediate layer, the metal Ti was heated and evaporated with an electron gun and ion-plated in nitrogen plasma to form TiN. Similarly, an optical element molding die is manufactured.

The molding die was set in a continuous molding machine, and glass molding (phosphate glass) was performed using the molding die. As a result, a good molded product was obtained even after 3000 shot molding. No surface degradation was observed.

[0064]

As described above, the present invention relates to an optical element molding die having a transfer surface for forming an optically functional surface of an optical element on a molding surface of a base material. Is formed on the base material, mainly composed of metal, a processed layer processed with a desired shape and accuracy, on the processed layer,
A surface layer formed of a hard carbon film or a noble metal alloy film as a main component, wherein the film on the surface layer side of the processed layer has a higher density than the base material side.

Therefore, even if the film thickness is 50 μm or more, a mold for optical element molding which can be sufficiently used for hot press molding and whose shape of a free-form surface is not restricted, which cannot be realized by the conventional processed layer, can be obtained. Can be provided.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of an optical element molding die according to an embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Mold base material 2 Working layer (low density) 3 Working layer (high density) 4 Intermediate layer 5 Surface layer

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) C23C 14/14 C23C 14/14 D 14/16 14/16 B 14/32 14/32 F 14/34 14/34 A S (72) Inventor Keiji Hirabayashi 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (72) Inventor Nobuyuki 3-30-2 Shimomaruko 3-chome, Ota-ku, Tokyo F-term within Canon Inc. Reference) 4K029 AA02 BA21 BA22 BA24 BA25 BA26 BA34 BA54 BA55 BA58 BA60 BB02 BD03 CA03 CA05 DC03 DC04 DD01 FA01

Claims (9)

[Claims] An optical element molding die having a transfer surface for forming an optically functional surface of an optical element on a molding surface of a base material, wherein the transfer surface is formed on the base material. Comprising a metal as a main component, a processed layer processed with a desired shape and accuracy, and a surface layer formed on the processed layer with a hard carbon film or a noble metal-based alloy film as a main component, Of the working layer,
An optical element molding die, wherein the film on the surface layer side has a higher density than the base material side. 2. Using a cemented carbide mainly containing tungsten carbide as a base material of a molding die, and sputtering a metal target with an inert gas on the molding surface of the molding die, thereby forming When forming a processing layer, so that the film on the surface layer side of the processing layer has a higher density than the base material side,
The base material temperature at the end of film formation is controlled to be lower than the base material temperature at the start of film formation, and the processing layer thus formed is cut into a desired shape and uniformly polished,
A method for manufacturing an optical element molding die, characterized in that a hard carbon film is subjected to ion beam deposition on the processed layer, and a noble metal based alloy thin film is formed with a surface layer by sputtering. 3. Using a cemented carbide mainly composed of tungsten carbide as a base material of a molding die, and sputtering a metal target with an inert gas on a molding surface of the molding die, thereby forming a material on the base material. When forming a processing layer, so that the film on the surface layer side of the processing layer has a higher density than the base material side,
The inert gas flow rate at the end of film formation is controlled so as to be smaller than the inert gas flow rate at the start of film formation, and the processed layer thus formed is cut into a desired shape and uniformly polished. A method for producing an optical element molding die, characterized in that a hard carbon film is subjected to ion beam evaporation on the processed layer, and a noble metal based alloy thin film is formed with a surface layer by sputtering. 4. Using a cemented carbide mainly composed of tungsten carbide as a base material of a molding die, a metal target is sputtered with an inert gas on a molding surface of the molding die to form the base material. When forming a processing layer thereon, the inert gas at the start of film formation is only argon gas so that the film on the surface layer side of the processing layer has a higher density than the base material side. After the completion of the process, the inert gas at the time of termination is controlled to be an argon gas and a helium gas, and the processed layer thus formed is cut into a desired shape and evenly polished. A method for producing an optical element molding die, characterized in that ion beam deposition is performed for a film, and a surface layer is formed by sputtering for a noble metal based alloy thin film. 5. The method according to claim 5, wherein a metal target is sputtered with an inert gas on a molding surface of the molding die using a cemented carbide mainly containing tungsten carbide as a base material of the molding die. When forming a processing layer thereon, the DC bias of the base material at the end of film formation is set such that the DC bias at the start of film formation is such that the film on the surface layer side of the processing layer has a higher density than the base material side. Controlled to be higher, the processed layer thus formed, after cutting and uniform polishing into a desired shape, on the processed layer, in the case of a hard carbon film, ion beam evaporation, And a method of manufacturing a mold for molding an optical element, wherein a surface layer is formed by sputtering in the case of a noble metal-based alloy thin film. 6. An optical element molding die according to claim 1, wherein an intermediate layer made of a metal carbide, nitride, or carbonitride is formed between the processed layer and the surface layer. . 7. A carbide, between the processing layer and the surface layer,
The method for manufacturing an optical element molding die according to any one of claims 2 to 5, wherein the intermediate layer is formed by sputtering or ion plating nitride or carbonitride. 8. The base material is a cemented carbide containing tungsten carbide as a main component, and the working layer is one selected from nickel (Ni), cobalt (Co), and iron (Fe), and copper (Fe). Cu), silicon (Si), titanium (Ti), chromium (Cr), zirconium (Zr), niobium (Nb), molybdenum (Mo), hafnium (Hf), tantalum (T
a) a ternary alloy of one selected from tungsten (W) and phosphorus (P), and the intermediate layer is a carbide, nitride, or carbonitride of titanium, tantalum, chromium, or silicon; The layer is a hard carbon film or platinum (Pt), palladium (Pd), iridium (Ir), rhodium (R
h), one or more alloy thin films selected from osmium (Os), ruthenium (Ru), rhenium (Re), gold (Au), tungsten (W), and tantalum (Ta). 7. The optical element molding die according to 6. 9. The base material is a cemented carbide containing tungsten carbide as a main component, and the processed layer is one selected from nickel (Ni), cobalt (Co), and iron (Fe), and copper ( Cu), silicon (Si), titanium (Ti), chromium (Cr), zirconium (Zr), niobium (Nb), molybdenum (Mo), hafnium (Hf), tantalum (T
a) a ternary alloy of one selected from tungsten (W) and phosphorus (P), and the intermediate layer is a carbide, nitride, or carbonitride of titanium, tantalum, chromium, or silicon; The layer is a hard carbon film or platinum (Pt), palladium (Pd), iridium (Ir), rhodium (R
h), one or more alloy thin films selected from osmium (Os), ruthenium (Ru), rhenium (Re), gold (Au), tungsten (W), and tantalum (Ta). 8. The method for producing an optical element molding die according to 7.