JP2001302273A - Optical glass element mold - Google Patents

Abstract

(57) [Problem] To provide a press-molding die capable of forming a high-precision optical glass element having good optical performance by a direct pressing method of optical glass. A metal film is formed as an intermediate layer on a press mold made of a base material having heat resistance and excellent workability,
Furthermore, gold (Au), iridium (Ir), rhenium (Re), osmium (Os), palladium (P
d) containing, as a main component, at least one element selected from the group consisting of rhodium (Rh), ruthenium (Ru), platinum (Pt), tantalum (Ta), tungsten (W), and molybdenum (Mo). A first coating film is formed, and a second coating film containing at least one element selected from the above-mentioned element group as a main component is further formed thereon to obtain a press mold.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an optical glass element, and more particularly to a method for directly press-molding an optical glass element which does not require a polishing step after press molding, and a mold for molding the same.

[0002]

2. Description of the Related Art In recent years, there has been a tendency for optical glass lenses to have an aspherical surface that can simultaneously achieve both simplification of the lens configuration of an optical device and reduction in the weight of the lens portion. In the production of this aspherical lens, the optical polishing method, which is a conventional optical lens production method, is inferior in workability and mass productivity, and the direct press molding method is considered promising.

[0003] The direct press molding method is to heat a mass of optical glass on a non-spherical mold having been finished to a desired surface quality and surface accuracy in advance, or to form a mass of glass that has been heated in advance. This is a method for producing an optical lens which does not require any further polishing or polishing step after press molding.

However, in the above-described method for manufacturing an optical glass lens, after press molding, the image forming quality of the obtained lens must not be impaired. Particularly, in the case of an aspherical lens, it is required that the lens can be molded with high precision. Also,
In consideration of mass productivity, it is required that the mold and the glass at a high temperature have good releasability and can be produced with a short tact.

[0005] Therefore, as a mold material, the chemical action on glass at a high temperature is minimal, the glass press surface of the mold is hardly damaged by abrasion and the like, and the breaking resistance by thermal shock is high. It is necessary that the adhesion between the mold and the glass is low.

[0006] As a mold material which satisfies the conditions necessary for the above press mold for optical glass elements to some extent,
JP-B-63-65613, JP-B-62-2809
As disclosed in Japanese Unexamined Patent Publication No. 3 and Japanese Unexamined Patent Publication No. Sho 62-17029, a mold coated with a thin film mainly composed of a platinum alloy has been proposed.

However, the above-mentioned conventional mold materials do not satisfy all the above-mentioned conditions. For example, the above-mentioned mold material has minimal chemical action on glass at high temperatures, is less likely to be damaged by abrasion or the like on the glass press surface of the mold, and has high resistance to breakage due to thermal shock. When a cemented carbide, SiC, or cermet, which is most commonly used, is used, the adhesion between the platinum alloy and the base material is poor. Ti) An intermediate layer is essential. The metal in the intermediate layer is easily diffused at the molding temperature of the glass, and when the platinum alloy formed thereon does not have sufficient heat resistance at the molding temperature, it diffuses into the platinum alloy layer and emerges at the outermost surface of the mold. May come. When Cr or Ti is present on the outermost surface of the mold, these metals are oxidized even by a trace amount of oxygen, so that the mold and the glass come into firm contact with each other, which is extremely inappropriate as a glass mold. .

[0008] This phenomenon is remarkable in an Au alloy having the lowest surface energy among the noble metal-based alloys and having the lowest adhesion between the mold and the glass. This is considered to be because Au has a much lower melting point and lower heat resistance than other noble metals.

[0009]

SUMMARY OF THE INVENTION Accordingly, in view of the above problems, an object of the present invention is to provide a press forming method for enabling high precision molding of optical glass elements having good optical performance by a direct pressing method of optical glass. It is to provide a mold.

[0010]

Means for Solving the Problems To achieve the above object, a first invention according to the present application is to use a material having heat resistance and excellent workability as a base material of a press molding die, and forming the same into a mold. Work into a stamping die of optical glass element type shape to be formed, further form a metal film as an intermediate layer thereon, and further thereon,
Gold (Au), iridium (Ir), rhenium (Re),
Osmium (Os), palladium (Pd), rhodium (Rh), ruthenium (Ru), platinum (Pt), tantalum (Ta), tungsten (W), and molybdenum (M
o) forming a first coating film containing at least one element selected from the group consisting of: gold (Au), iridium (Ir), and rhenium (R).
e), selected from the group consisting of osmium (Os), palladium (Pd), rhodium (Rh), ruthenium (Ru), platinum (Pt), tantalum (Ta), tungsten (W), and molybdenum (Mo). Using a pair of molds formed with a second coating film containing at least one element as a main component, the glass to be formed is heated to a temperature equal to or higher than its softening temperature in an inert gas atmosphere or vacuum, and then pressure-formed. A method for forming an optical glass element by obtaining an optical glass element.

Here, the first coating film may be a film composed of the above-mentioned element alone or an alloy film composed of a combination of the above-mentioned elements. Also, the second coating film may be a film composed of the above-mentioned element alone or an alloy film composed of a combination of the above-mentioned elements.

In the above construction, since a material having heat resistance and excellent workability is used as the base material for the press molding die, the performance required for the base material is sufficient, and further, a precious metal based material is further added. Since the metal film is coated twice, diffusion of the metal intermediate layer between the base material and the coating film can be prevented. Therefore, the intermediate layer metal does not diffuse to the surface, and the mold and the glass do not adhere firmly. Further, the noble metal film on the outermost surface is sufficiently hard, has sufficient scratch resistance, and has no reactivity with glass. Therefore, it is important in optical glass element molding method, excellent in oxidation resistance, inert to glass, excellent in mechanical strength that does not lose shape accuracy when pressed, and excellent in workability, precision processing Completely fulfill the condition that it must be easy to do.

The thickness of the first coating film is 1
5 nm to 5000 nm is preferable, and more preferably 3 nm to 5000 nm.
It is 0 nm to 300 nm. If the thickness is too thin, there is no effect of preventing the diffusion of the intermediate layer metal. If the thickness is too thick, it is not only economically wasteful but also causes peeling of the film and deterioration of the film strength. The thickness of the second coating film is 50 nm to
10 μm is preferred, and more preferably 100 nm to 10
00 nm. If it is too thin, there is no mold and glass release effect, and if it is too thick, it is economically wasteful,
This is because it causes film peeling and film strength deterioration.

The intermediate metal film is usually made of chromium (Cr) or titanium (Ti).
Nitride films such as N, Si ₃ N ₄ , AlN, BN, etc., TaC,
A carbide film such as SiC, WC, Cr ₃ C ₂ or the like may be used. Further, it is conceivable that there is no intermediate metal film, but in this case, the adhesion between the first coating film and the base material is deteriorated, so that applicable combinations are limited. In this case, the first
The coating film functions as a diffusion prevention film for the components of the base material.

A second invention according to the present application is to use a material having heat resistance and excellent workability as a base material of a press molding die,
This is processed into a mold having the shape of an optical glass element to be molded, a metal film is formed thereon as an intermediate layer, and gold (Au), iridium (Ir), rhenium (Re), Osmium (Os), palladium (Pd),
Rhodium (Rh), ruthenium (Ru), platinum (P
t), at least one selected from the group consisting of tantalum (Ta), tungsten (W), and molybdenum (Mo)
Forming a first coating film containing a seed element as a main component, and further forming gold (Au) and iridium (I
r), rhenium (Re), osmium (Os), palladium (Pd), rhodium (Rh), ruthenium (R
u), forming a second coating film containing at least one element selected from the group consisting of platinum (Pt), tantalum (Ta), tungsten (W), and molybdenum (Mo) as a main component. This is a mold for molding optical glass elements.

Here, the first coating film may be a film composed of the above-mentioned element alone or an alloy film composed of a combination of the above-mentioned elements. Also, the second coating film may be a film composed of the above-mentioned element alone or an alloy film composed of a combination of the above-mentioned elements.

In the above structure, since the material having heat resistance and excellent workability is used as the base material for the press molding die, the performance required for the base material is sufficient. Since the film is coated twice, diffusion of the metal intermediate layer between the base material and the coating film can be prevented. Therefore, the interlayer metal diffuses to the surface,
The mold and glass do not stick firmly. Further, the noble metal film on the outermost surface is sufficiently hard, has sufficient scratch resistance, and has no reactivity with glass. Therefore, it is excellent in oxidation resistance required for optical glass element molding dies, is inert to glass, has excellent mechanical strength that does not lose shape accuracy when pressed, and has excellent workability, precision processing Completely satisfy the condition that it must be able to be done easily.

The third invention according to the present invention is directed to a method of manufacturing the first coating film, wherein the element or the alloy forming the first coating film has a melting point Tm.
The optical glass element molding die according to the second invention, wherein 0.33 times [K] is higher than the molding temperature of the glass to be molded.

As described above, the purpose of the first coating film is to prevent diffusion of the underlying metal. In order to prevent metal diffusion, it is required that the first coating film has a somewhat high heat resistance at the glass forming temperature. Generally, a numerical value called the Tamman temperature is used as a measure of the heat resistance of a metal. The term “Tamman temperature” refers to a temperature at which self-diffusion (the same type of molecules or atoms exchange positions with each other by thermal motion) in various solids starts. The following approximate relationship holds between the temperature T (K) and the melting point Tm of the solid. For metals, T ~
0.33 Tm. ["Chemical Dictionary 4", p267
(1963 Kyoritsu Shuppan), “Chemical Dictionary”, p.829 (19
94, Tokyo Kagaku Dojin)] The present inventor conducted an experiment using this Tamman temperature as a guide. As a result, if 0.33 times the melting point of the first coating film is higher than the glass forming temperature, the surface of the underlying metal is determined. Has been found to be able to prevent diffusion to

Therefore, with the above configuration, the intermediate layer metal does not diffuse to the surface, and the mold and the glass do not stick firmly. Further, the noble metal film on the outermost surface is sufficiently hard, has sufficient scratch resistance, and has no reactivity with glass. Therefore, it is excellent in oxidation resistance required for optical glass element molding dies, is inert to glass, has excellent mechanical strength that does not lose shape accuracy when pressed, and has excellent workability, precision processing Completely satisfy the condition that it must be able to be done easily.

According to a fourth aspect of the present invention, there is provided a superstructure having a cutting layer made of a cemented carbide containing tungsten carbide (WC) as a main component and a free-cutting ceramic on a molding surface as a press molding die base material. A mold for forming an optical glass element according to a second invention, wherein a hard alloy or boron nitride-containing silicon nitride is used.

In the above construction, the cemented carbide is not only capable of electric discharge machining, but also in the case of performing general grinding, compared to silicon carbide and silicon nitride conventionally used as molds for molding glass lenses. In addition, there is a feature that a high-precision mold shape can be easily processed. In addition, since free-cutting ceramics and boron nitride-containing silicon nitride have sufficient strength and hardness, they can be cut, so that precision processing can be easily performed. Furthermore, no special equipment is required for processing. Processing time is also short. Therefore, the mold cost can be extremely reduced. Furthermore, it has become possible to produce surfaces that can only be made by cutting. Also, as compared with a method of forming a plating layer and cutting the layer, this base material is excellent in heat resistance, so that it can be used for forming a high melting point glass, and there is no difference from plating.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings.

A cemented carbide having a diameter of 16 mm is prepared by using a radius of curvature of 1
A pair of optical glass lenses having upper and lower dies having a concave pressing surface of 0 mm was processed into a press-molding die shape.

The press surfaces of these molds were polished to a mirror surface using diamond particles of 0.1 μm. Next, coating films shown in Tables 1 to 3 were formed on the mirror surface by sputtering. FIG. 1 shows the configuration of the mold.

Next, the optical element was molded using the mold shown in the above table.

The glass is borosilicate glass SK12 (nd)
= 1.58313, vd = 59.4, transition point Tg = 55
0 ° C., yield point At = 588 ° C.) and low acid softening point glass PSK50 (nd = 1.59380, νd = 61.
4, transition point Tg = 381 ° C., yield point At = 403 ° C.),
High refractive index lanthanum glass LaSF016 (nd = 1.
77250, νd = 49.6, transition point Tg = 686 ° C.,
Using the yield point At = 706 ° C.), a ball lens was formed.

FIG. 2 schematically shows the apparatus used for the molding test. In FIG. 2, 24 is a chamber, 25 is an upper shaft, 26
Is a lower shaft, 27 is a block with a built-in heater (heater block), 28 is a heater block, 29 is an upper mold,
0 is a lower mold, 31 is glass, and 32 is a hydraulic cylinder.

After the chamber 24 is evacuated by a vacuum pump (not shown), N ₂ gas is introduced,
After the inside of the heater block 4 is set to the N ₂ atmosphere, the heater blocks 27 and 2
8, the upper mold 29 and the lower mold 30 are heated, and the viscosity (SK1) corresponding to the viscosity of the glass to be formed corresponds to 10 ⁻⁹ d · Pa · s.
2: 630 ° C, PSK50: 420 ° C, LaSF01
6: 740 ° C.), the upper shaft 25 was pulled up by the hydraulic cylinder 32, and the molding material (ball lens) was placed on the lower die 30 by an unillustrated automatic hand. After maintaining the mold temperature as it is for 2 minutes, the upper shaft 25 was lowered by the hydraulic cylinder 32, and the ball lens was pressed by the upper mold 29 and the lower mold 30 with a force of 3,000 N for 3 minutes.
Thereafter, cooling is performed at 70 ° C./min, and the upper and lower mold temperatures are set to desired temperatures (SK12: 540 ° C., PSK 50: 340 ° C., L
aSF016: 620 ° C.), the upper mold 29 is raised, and the molded product 3 on the lower mold 30 is moved by an automatic hand (not shown).
Then, the molded product 31 was taken out of the chamber 24 through a replacement device (not shown). The upper and lower molds are heated again, and the above operation is repeated until 5,000 shots (sh
ot) Molding was performed.

As shown in the above table, if the melting point of the first coating film is 0.33 times higher than the glass forming temperature, good moldability is obtained, as shown in the above table. If the temperature is lower than the molding temperature of the glass, heating to the molding temperature only requires the underlying Cr or Ti
Diffused on the surface and the color of the mold changed, resulting in deterioration of the releasability, peeling of the film, and fusion of the glass and the mold.

Further, the melting point of the second coating film is set at 0.1.
When 33 times is higher than the glass forming temperature, the C
Although r and Ti do not diffuse to the outermost surface, good moldability can be obtained if 0.33 times the melting point of the first coating film is higher than the glass forming temperature, but lower than the glass forming temperature. In this case, the underlying Cr or Ti is first.
And a stress was generated between the first coating film and the second coating film. As a result, the adhesion between the two was deteriorated, and the film was peeled off.

In this embodiment, the thickness of the intermediate layer film is set to 5
0 nm, the thickness of the first coating film is 50 nm,
Although the film thickness of the coating film was 250 nm, the film thickness of each layer is not limited to this, and it is possible to suitably mold as long as the film thickness is as described above.

Further, after a stepped mold having a shape that cannot be ground and polished as shown in FIG. 3 was machined by cutting with a carbide tool, the pressed surface was finished with extremely high precision by cutting with a diamond tool. The mold base material used at this time was not a cemented carbide but a material that could be cut (for example, a free-cutting ceramic provided on a cemented carbide base material, BN-containing silicon nitride, or the like).

The same test as described above was carried out for this mold, but exactly the same results were obtained. This molded product is a kind of diffraction grating, and is an example of a so-called fine optical element.

The shapes that cannot be processed by grinding and polishing here include elements having a free-form surface (so-called free-form surface elements), elements having a fine pattern (so-called fine optical elements), and various shapes (spherical and aspherical surfaces). (A flat surface or the like) are combined to form a mold having a complicated shape that cannot be produced by polishing or a complicated shape to be bonded, and a combination of these shapes.

[0036]

[Table 1]

[0037]

[Table 2]

[0038]

[Table 3]

[0039]

According to the present invention, it is possible to obtain a mold which satisfies all the above-mentioned necessary conditions which cannot be realized by the conventional mold material by the above-mentioned structure. Can be directly pressed and molded.

That is, according to the first invention, a material having heat resistance and excellent workability is used as a base material for a press molding die, which is processed into a press die having an optical glass element type shape to be molded. Forming a metal film thereon as an intermediate layer,
Furthermore, gold (Au), iridium (Ir), rhenium (Re), osmium (Os), palladium (P
d) containing, as a main component, at least one element selected from the group consisting of rhodium (Rh), ruthenium (Ru), platinum (Pt), tantalum (Ta), tungsten (W), and molybdenum (Mo). A first coating film is formed, and gold (Au) and iridium (I
r), rhenium (Re), osmium (Os), palladium (Pd), rhodium (Rh), ruthenium (R
u), platinum (Pt), tantalum (Ta), tungsten (W), and molybdenum (Mo) are formed with a second coating film containing as a main component at least one element selected from the group consisting of: Using a pair of molds, the glass to be molded in an inert gas atmosphere or under vacuum is heated above its softening temperature and then pressure molded to obtain an optical glass element, which is an ideal method for molding glass optical elements. .

According to the second aspect of the present invention, a material having heat resistance and excellent workability is used as a base material of a press molding die, which is processed into a press die having an optical glass element shape to be molded. A metal film is formed thereon as an intermediate layer, and further, gold (Au), iridium (Ir), and rhenium (R
e), selected from the group consisting of osmium (Os), palladium (Pd), rhodium (Rh), ruthenium (Ru), platinum (Pt), tantalum (Ta), tungsten (W), and molybdenum (Mo). A first coating film containing at least one element as a main component is formed, and further, gold (Au), iridium (Ir), rhenium (Re), osmium (Os), palladium (Pd),
Rhodium (Rh), ruthenium (Ru), platinum (P
t), at least one selected from the group consisting of tantalum (Ta), tungsten (W), and molybdenum (Mo)
By forming a second coating film containing the seed element as a main component, a press-molding mold for optical glass that satisfies all of the above-mentioned requirements for the mold material for optical glass is provided. This is extremely effective for mass-producing an accurate optical glass element with an extremely short tact.

According to the third invention, the melting point Tm [K] of the element alone or the alloy forming the first coating film is used.
0.33 times higher than the forming temperature of the glass to be formed, the base component is blocked by the first coating film, and the metal intermediate layer component between the base material and the surface layer diffuses and emerges on the surface. It provides a press mold for optical glass that can exhibit the original performance of the surface layer, and satisfies all the requirements for the mold material for optical glass described above. This is extremely effective for mass-producing elements with extremely short tact.

According to the fourth aspect of the present invention, a cemented carbide having tungsten carbide (WC) as a main component, a cemented carbide having a cutting layer made of free-cutting ceramics on a molding surface is used as a base material for a press molding die. In addition, since silicon nitride containing boron nitride is used, the time and cost required for processing the mold can be significantly reduced.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing an embodiment of the present invention.

FIG. 2 is a schematic sectional view of a press forming apparatus for an optical element.

FIG. 3 is a schematic sectional view of a press mold for an optical element.

[Explanation of symbols]

 Reference Signs List 1 mold base material 2 metal film (Cr or Ti) 3 first coating film 4 second coating film 5 diffraction grating molding die 24 chamber 25 upper shaft 26 lower shaft 27 heater block 28 heater block 29 upper die 30 lower die 31 glass 32 hydraulic cylinder

Claims (4)

[Claims] 1. A material having heat resistance and excellent workability is used as a base material for a press molding die, which is processed into a press die having the shape of an optical glass element to be molded, and further as an intermediate layer thereon. A metal film is formed, and gold (Au), iridium (Ir), rhenium (Re), osmium (O
s), palladium (Pd), rhodium (Rh), ruthenium (Ru), platinum (Pt), tantalum (Ta), tungsten (W), and at least one element selected from the group consisting of molybdenum (Mo) Is formed as a main component, and a gold (A) is further formed thereon.
u), iridium (Ir), rhenium (Re), osmium (Os), palladium (Pd), rhodium (R
h), ruthenium (Ru), platinum (Pt), tantalum (Ta), tungsten (W), and molybdenum (M
o) softening the glass to be formed in an inert gas atmosphere or under vacuum using a pair of molds formed with a second coating film containing at least one element selected from the group consisting of: A method for forming an optical glass element, wherein the optical glass element is obtained by heating to a temperature equal to or higher than a temperature and then performing pressure molding. 2. A material having heat resistance and excellent workability is used as a base material of a press molding die, which is processed into a press die having the shape of an optical glass element to be molded, and further as an intermediate layer thereon. A metal film is formed, and gold (Au), iridium (Ir), rhenium (Re), osmium (O
s), at least one element selected from the group consisting of palladium (Pd), rhodium (Rh), ruthenium (Ru), platinum (Pt), tantalum (Ta), tungsten (W), and molybdenum (Mo) Is formed as a main component, and a gold (A) is further formed thereon.
u), iridium (Ir), rhenium (Re), osmium (Os), palladium (Pd), rhodium (R
h), ruthenium (Ru), platinum (Pt), tantalum (Ta), tungsten (W), and molybdenum (M
An optical glass element molding die, wherein a second coating film containing at least one element selected from the group consisting of o) as a main component is formed. 3. The forming temperature of the glass to be formed, wherein 0.33 times the melting point Tm [K] of the element alone or the alloy forming the first coating film is higher than the forming temperature of the glass to be formed. Mold for molding optical glass elements. 4. A press-working mold base material includes a cemented carbide mainly composed of tungsten carbide (WC), a cemented carbide having a cutting layer made of free-cutting ceramic on a molding surface, or a nitride containing boron nitride. The mold for molding an optical glass element according to claim 2, wherein silicon is used.