JPH11236225A - Method for forming glass element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for forming a glass blank which does not give rise to cracking, clouding and blackening in the resulted glass element by preventing the fusion of a blank and mold surfaces regardless of the component and transition temp. of the blank for glass forming. SOLUTION: This method includes a stage for forming a film consisting of the sulfide or selenide of the one element selected from a group consisting of Mo, W and Nb to a preform and a stage for press forming the preform formed with the film described above by the molds. The film is preferably formed by a sputtering method or vacuum vapor deposition method and the preform consists of the blank for glass forming having the transition temp. >=500 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for molding a glass element, and more particularly, to a precision glass which is capable of preventing fusion of a glass preform and a mold surface in pressure molding of a glass element and free from cracks and blemishes. The present invention relates to a method for forming an element.

[0002]

2. Description of the Related Art A reheat press method has attracted attention as a method for simply molding a precision glass element with high productivity.
In the reheat press method, a preform obtained by melting and solidifying a glass forming material in advance is poured into a forming mold, the inside of the mold is heated, and when the preform is in a moldable state, it is pressed. This is a method in which a molded glass element is cooled in a state held in a mold to obtain a glass element.

However, when a glass element is formed by the reheat press method, the preform and the mold come into contact with each other in a state of being in close contact at a high temperature for a relatively long time. Cracks and clouding occurred on the surface, and a good glass lens could not be obtained.
Furthermore, in the molding of glass molding materials that need to be heated to 500 ° C. or more during pressure molding, particularly in the molding of glass molding materials having a transition temperature of 500 ° C. or more, the above-mentioned fusion occurs violently. I needed to solve this problem.

In order to prevent such fusion, a method of forming a release film on the surface of a preform to reduce the frictional resistance between the surface of the mold and the glass has been widely used. For example, Japanese Patent Publication No. 2-31012 discloses a method in which a carbon coating is previously provided on a surface of a glass lens molding material on which a functional surface is to be formed. However,
The effect of the carbon release film is not enough,
When titanium is contained in the component of the material, there is a problem that the titanium in the component reacts with carbon depending on the conditions at the time of molding, and the surface of the molded glass lens is colored black.

Japanese Patent Publication No. Sho 62-50413 discloses a molding method in which a film capable of forming an anti-reflection film is provided in advance on a surface of a glass lens molding material on which a functional surface is formed prior to pressure molding. Has been proposed. However, in molding a glass material having a high transition temperature which requires heating at 500 ° C. or more during pressure molding, materials usually used for an antireflection film or the like, for example, MgF ₂ , Si
Even if the coating was previously formed with O ₂ , no satisfactory glass element could be formed because of problems such as no effect or generation of more severe cloud.

Japanese Patent Application Laid-Open No. 8-277125 discloses a method of forming a film of yttrium oxide or cerium oxide on a glass surface. According to this method, although a certain effect is observed, fusion or cloud remains, which is not sufficiently satisfactory.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and prevents fusion of a glass molding material to a mold surface irrespective of the composition and transition temperature of the material. It is an object of the present invention to provide a method for forming a glass element which does not cause cracking, clouding or blackening on the glass element to be obtained.

[0008]

SUMMARY OF THE INVENTION The present invention comprises a step of forming a film made of a sulfide or selenide of one element selected from the group consisting of Mo, W and Nb on a preform, and forming the film. The present invention relates to a method for molding a glass element, which comprises a step of pressure-molding a preform obtained by a mold.

The preform used in the present invention may be any glass forming material (hereinafter referred to as a glass material).
It may consist of. Therefore, according to the method of the present invention, when the above-mentioned black discoloration is a problem in the case where titanium is contained in the glass material, or when the above-mentioned fusion or the like is a problem, the transition temperature is 50 ° C.
It is particularly useful when pressure molding a glass material exceeding 0 ° C.

That is, the glass material is not particularly limited, and optical glasses such as borosilicate crown glass, titanium-containing flint glass, lanthanum flint glass, and lanthanum crown glass can be used.

In the present invention, the glass material is used as a preform preformed into the approximate shape of the glass element to be obtained. The preforming method is not particularly limited as long as it can be formed into the shape, and is conventionally used for preforming a glass material prior to performing pressure forming by a reheat press method. Known methods such as cutting, grinding, polishing, dripping of molten glass, and receiving are performed.

In the method of the present invention, the preform is formed with a film made of a sulfide or selenide of one element selected from the group consisting of Mo, W and Nb. Specifically, molybdenum disulfide, tungsten disulfide, niobium disulfide, molybdenum selenide, tungsten selenide, or niobium selenide, preferably molybdenum disulfide, tungsten disulfide on the contact surface of the preform with the mold Form a coating. These materials are known as solid lubricants, and coatings made of these materials have a layered lattice structure and are easy to slip between layers, so that in the present invention, an effect of preventing fusion or clouding is obtained, and Is considered to be effective in improving the transferability of the shape. Furthermore, these materials have the advantage that the coefficient of friction is very small particularly in a vacuum atmosphere or a clean atmosphere such as an inert gas such as nitrogen or argon required for pressure molding of a high-melting glass material. ("Thin Film Tribology"; Yuji Enomoto and Shojiro Miyake, University of Tokyo Press). Carbon, which has been conventionally used as a coating material, is also used as a good solid lubricant in the atmosphere.However, in a clean atmosphere such as a vacuum atmosphere or a nitrogen atmosphere which is a molding atmosphere, the friction is higher than that of the above materials. It is considered that since the coefficient becomes extremely large, a sufficient effect for preventing fusion and clouding cannot be obtained.

The above-mentioned coating material may be used as a single-component thin film, or another component, for example, silver may be intercalated between layered structures made of any one of the above-mentioned materials. By forming a layer made of another material between layers of a substance having a layered structure, a thin film of a plurality of components may be used. Multi-component thin films are preferred because they have better lubricity than single-component thin films ("Thin Film Triology"; Yuji Enomoto and Shojiro Miyake, University of Tokyo Press).

Such a film can be easily formed on a preform by a conventional general film forming method, for example, a sputtering method, a vacuum deposition method, a CVD method, or the like.
The film forming conditions are not particularly limited as long as the film can be formed, and are set as appropriate. For example, when the film is formed by a sputtering method, specifically, the film is formed under the following conditions. Method: magnetron sputtering, RF power: 400 W, introduced gas: Ar, sputtering time: 15
Min, degree of vacuum: 5 × 10 ⁻³ Torr, substrate heating: no heating.

In the present invention, the coating is formed on the surface of the preform, but the present invention does not limit the formation of the coating on the surface of the mold. However, from the viewpoint of difficulty in forming a film having adhesiveness and heat resistance enough to withstand molding for a long time and repeatedly many times, it is preferable that the coating be formed on the contact surface of the preform with the mold. When a film is formed on the preform side in this way, it is only necessary to form a film that can withstand a single molding.

The preform on which the coating is formed as described above is subjected to pressure molding by a conventionally known reheat press method. Hereinafter, a description will be given using the pressure molding apparatus shown in FIG. This apparatus includes an upper mold 4 (material: silicon carbide) having a mold surface precision mirror-finished in a convex spherical shape and a holding mold 6A (material: silicon carbide) holding the same, and a precision mirror surface in a convex spherical shape. Lower mold 5 having a processed mold surface (material: silicon carbide) and holding mold 6B holding the same (material: silicon carbide)
Is provided. The holding die 6A moves downward integrally with the upper die 4 by the push rod 7 (material: stainless steel), and the lower die 5A.
With the holding die 6B integrated with the holding die 6B. The above-mentioned mold structure is heated by a heating light source 9 installed on the outer periphery of the transparent quartz tube 8, and the temperature is measured and controlled by a thermocouple 10 embedded in a holding mold 6B.

In FIG. 2, both upper and lower molds have a convex spherical shape, and are intended to manufacture a biconcave spherical lens. However, the upper and lower molds are independently a concave spherical shape, a concave aspherical shape, and a convex type. It may have any shape, such as an aspherical shape or a planar shape, depending on the shape of the glass element to be obtained. Further, in the present invention, a glass element having high surface accuracy can be formed without problems such as fusion by mirror-finishing the contact surface with the upper and lower mold preforms to a desired surface accuracy. Further, the method of the present invention uses an upper mold and / or a lower mold in which a pattern such as a V-shape, a saw-tooth shape, a hemispherical array or the like is precisely machined on a molding surface (see an upper mold 14 in FIG. 3). Can be easily provided without any problem such as fusion.

When actually performing pressure molding, the preform 3 on which the coating is formed is placed in the upper and lower molds, and the preform 3 is moved together with the upper and lower molds 4 and 5 and the holding molds 6A and 6B by a heating light source 9. In a heated state, the push rod 7 is lowered, and a load is applied to the upper die 4 and the holding die 6A for holding the upper die 4 to perform pressure molding. When a material having a high transition temperature such as a lanthanum glass or a titanium-containing glass is used as the glass material, the pressure molding is performed in a vacuum, a nitrogen atmosphere, or an atmosphere such as an inert gas. Is preferred. During molding, these glass materials are heated to the transition temperature or higher, so that the surface of the mold is oxidized, and even if the above-mentioned coating is formed on the preform in the present invention, fusion is likely to occur.

After the pressure molding, the pressure of the push rod 7 is removed,
Cooling is performed while surrounding the press-formed product in the mold (4, 5, 6A, 6B) to obtain a glass element. In the glass element thus obtained, no fusion occurred between the obtained molding surface and the mold surface, and no cracks, blemishes, blackening, etc. occurred on the surface.

A coating is usually left on the molding surface of the glass element thus obtained. However, the glass element is rubbed lightly with a cloth containing an abrasive, or acid-treated with a strongly acidic solution such as diluted aqua regia. The remaining film can be easily removed by, for example, treating with a commercially available vapor-deposited film remover.

In this specification, the description is given of the case where the above-mentioned film material is formed into a thin film on a preform by pressure molding, but the present invention is not limited to this. That is, a particle diameter of 0.5 μm or less, preferably 0.1 μm or less made of the above material is applied to the preform and laminated on the preform molding surface,
The effect of the present invention can be obtained even by press molding. However, when applying as fine particles, it is difficult to laminate uniformly to a predetermined thickness, and there is a limit in reducing the particle size of the fine particles. Therefore, when transferring a highly accurate mirror surface or a fine pattern shape, It is preferable to form a thin film on the preform.

The method of the present invention can be used for manufacturing a wide range of precision glass elements such as optical elements such as spherical or aspherical lenses, as well as high-precision positioning substrates such as optical fibers. The molding method of the glass element of the present invention,
Further, a specific description will be given based on the following examples.

[0023]

EXAMPLE 1 An SiO ₂ —B ₂ O ₃ —La ₂ O ₃ glass (transition temperature: 623 ° C.) was used as a glass material, and this was used as a cylindrical preform 1 (diameter: 20 mm, thickness: As shown in FIG. 1, a tungsten disulfide thin film 2 (thickness: 5 mm) was formed on the upper and lower surfaces of this cylindrical preform 1 by sputtering.
00)).

Next, using the preform on which the tungsten disulfide film 2 was formed, a spherical glass lens was formed by a reheat press method using a pressure forming apparatus shown in FIG. This apparatus has an upper mold 4 (material: silicon carbide, surface roughness Rmax 0.02 μm) having a mold surface precision mirror-finished into a convex spherical shape.
m) and holding mold 6A for holding it (material: silicon carbide)
Similarly, a lower mold 5 (material: silicon carbide, Rmax 0.02 μm) having a mold surface precision mirror-finished to a convex spherical shape and a holding mold 6B (material: silicon carbide) holding the same are provided. . Holding die 6 by push rod 7 (material: stainless steel)
A moves downward integrally with the upper die 4 and engages with the holding die 6B integrated with the lower die 5. The above-mentioned mold structure is heated by a heating light source 9 installed on the outer periphery of the transparent quartz tube 8, and the temperature is measured and controlled by a thermocouple 10 embedded in a holding mold 6B.

The above-mentioned preform 3 is placed in the upper and lower molds,
Under a nitrogen atmosphere, the upper and lower dies 4, 5
And the preform 3 together with the holding dies 6A and 6B
The push rod 7 was lowered while being heated to ℃, and a load was applied to the upper mold 4 and the holding mold 6A for holding the upper mold 4 to perform pressure molding.
(Pressure: 500 kg / cm ² , pressurization time: 30 seconds). Next, the pressure of the push rod 7 was removed, and the press-formed product was cooled while surrounding the press-formed product in the mold (4, 5, 6A, 6B), and then the press-formed product was taken out.

When the pressed product was visually observed,
No fusion occurred between the obtained molding surface and the mold surface, and the concave spherical shapes corresponding to the convex spherical shapes of the upper and lower dies 4 and 5 were transferred as they were and a good surface precision was obtained. A quality biconcave spherical lens was obtained. In the obtained biconcave spherical lens, the molding surface of the upper mold has a surface roughness Rmax of 0.03 μm, and the molding surface of the lower mold has a surface roughness of Rmax0.
03 μm.

Example 2 A P ₂ O ₅ —TiO ₂ —Nb ₂ O ₅ system glass (transition temperature: 598 ° C.) was used as a glass material, and this was used as a cylindrical preform 1 (diameter: 25 mm, thickness: 3 mm). ), And a thin film 2 (thickness: 300 °) of molybdenum disulfide was formed on the upper and lower surfaces of the preform 1 by a sputtering method as shown in FIG.

Next, using the preform 13 on which the molybdenum disulfide film was formed, a V-shaped patterned glass substrate was formed by a reheat press method using a pressure forming apparatus shown in FIG. This device uses a V-shaped pattern (depth 0.
Upper mold 14 (material: cemented carbide) having a precision-machined mold surface and holding mold 16A (material:
And a lower mold 15 (material: cemented carbide) having a surface ground mold surface and a holding mold 16B (material: high density carbon) holding the same. Push rod 1
7 (material: stainless steel), the holding mold 16A becomes the upper mold 14
And moves downward together with the holding die 16B integrated with the lower die 15. The above-mentioned mold structure is heated by an induction heating source 19 having a high-frequency coil installed on the outer peripheral portion of the ceramic tube 18, and the temperature is measured and controlled by a thermocouple 20 embedded in the holding mold 16 </ b> B. .

The above-mentioned preform 13 is connected to the upper and lower dies 14, 1
5, the preform 13 was heated to 650 ° C. together with the upper and lower dies 14, 15 and the holding dies 16A and 16B by the induction heating source 19, and the push rod 17 was lowered. A load was applied to the holding mold 16A for holding it and molded (pressure: 50 kg / cm ² ,
Pressurization time: 40 seconds). Next, the pressure of the push bar 17 was removed, and the press-formed product was cooled while surrounding the press-formed product in the mold (14, 15, 16A, 16B), and then the press-formed product was taken out.

When the pressed product was visually observed,
No fusion was observed between the obtained molding surface and the mold surface, and the desired fine pattern shape was well transferred.

Example 3 An SiO ₂ -B ₂ O ₃ -La ₂ O ₃ system glass (transition temperature: 623 ° C.) was used as a glass material, and this was used as a cylindrical preform 1 (diameter: 30 mm, thickness: 4 mm). ), And as shown in FIG. 1, a niobium disulfide thin film 2 (thickness: 400) is formed on the upper and lower surfaces of the cylindrical preform 1 by sputtering.
Å) formed.

Next, using the preform on which the niobium disulfide film 2 was formed, a spherical glass lens was formed by a reheat press method using a pressure forming apparatus shown in FIG. This apparatus has an upper mold 4 (material: silicon carbide, surface roughness Rmax 0.02 μm) having a mold surface precision mirror-finished into a convex spherical shape, and a holding mold 6A (material: silicon carbide) holding the same. And a lower mold 5 (material: silicon carbide, surface roughness Rmax 0.02 μm) having a mold surface precision mirror-finished in a convex spherical shape and a holding mold 6B (material: silicon carbide) holding the same. . Holding die 6 by push rod 7 (material: stainless steel)
A moves downward integrally with the upper die 4 and engages with the holding die 6B integrated with the lower die 5. The above-mentioned mold structure is heated by a heating light source 9 installed on the outer periphery of the transparent quartz tube 8, and the temperature is measured and controlled by a thermocouple 10 embedded in a holding mold 6B.

The above-mentioned preform 3 is placed in the upper and lower molds,
Under a nitrogen atmosphere, the upper and lower dies 4, 5
And the preform 3 together with the holding dies 6A and 6B
The push rod 7 was lowered while being heated to ℃, and a load was applied to the upper mold 4 and the holding mold 6A for holding the upper mold 4 to perform pressure molding.
(Pressure: 500 kg / cm ² , pressurization time: 30 seconds). Next, the pressure of the push rod 7 was removed, and the press-formed product was cooled while surrounding the press-formed product in the mold (4, 5, 6A, 6B), and then the press-formed product was taken out.

When the pressed product was visually observed,
No fusion occurred between the obtained molding surface and the mold surface, and the concave spherical shapes corresponding to the convex spherical shapes of the upper and lower dies 4 and 5 were transferred as they were and a good surface precision was obtained. A quality biconcave spherical lens was obtained. In the obtained biconcave spherical lens, the molding surface of the upper mold has a surface roughness Rmax of 0.03 μm, and the molding surface of the lower mold has a surface roughness of Rmax0.
03 μm.

[0035] except for the use of carbon as a comparative example 1 film materials, in the same manner as in Example _{2, P 2 O 5 -TiO 2} -Nb 2 O 5 -based glass (transition temperature: 598 ° C.) preform film A carbon thin film having a thickness of 500 ° was formed. The preform on which the above film was formed was used in Example 2.
In the same manner as in the above, pressure molding was performed by the pressure molding apparatus.

As a result, the obtained glass lens was evaluated in the same manner as in Example 2. As a result, fine fusion, cracking and fogging were observed, and the glass surface was colored black. Regarding the pattern shape, chipping due to fusion occurred. It is considered that the black coloring is caused by the reaction of carbon in the thin film with titanium in the glass material for molding. According to this comparative example, it is clear that the carbon film is not sufficient as a release film material.

[0037]

According to the glass element forming method of the present invention,
Without being limited by the components of the glass molding material and the transition temperature, fusion between the material and the mold surface can be prevented, and a good glass element free from cracks, blemishes and blackening can be easily molded. Further, in the method of the present invention, a glass element on which a pattern is precisely transferred can be easily provided by using a mold having a pattern.

[Brief description of the drawings]

FIG. 1 shows a schematic cross-sectional configuration diagram of an example of a preform on which a coating is formed.

FIG. 2 shows a schematic cross-sectional configuration diagram of an example of a pressure molding apparatus employing a reheat press method.

FIG. 3 is a schematic cross-sectional view showing an example of a pressure molding apparatus employing a reheat press method.

[Explanation of symbols]

1: preform, 2: coating, 3: coated preform, 4: upper die, 5: lower die, 6A, 6B: holding die, 7: push rod, 8: ceramic tube, 9: heating light source,
10: thermocouple, 13: preform on which a coating was formed,
14: upper mold, 15: lower mold, 16A, 16B: holding mold, 1
7: push rod, 18: ceramic tube, 19: induction heating source,
20: thermocouple.

Claims (3)

[Claims] 1. A step of forming a coating made of a sulfide or selenide of one element selected from the group consisting of Mo, W and Nb on a preform, and forming the coating on the preform by a mold. A method for forming a glass element, comprising a step of performing pressure forming. 2. The method according to claim 1, wherein the coating is formed by a sputtering method or a vacuum evaporation method. 3. The preform is made of a glass molding material having a transition temperature of 500 ° C. or higher.
Or a method for forming a glass element according to item 2.