JP2003277074A - Method for removing film of die for forming and die for forming - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To remove a film deteriorated by forming of a glass optical element without damaging the shape of the surface of a die base material. <P>SOLUTION: The film deposited on the forming surface of the die for forming the glass optical element is removed. The film lower in the rate of polishing per unit time as compared with the film on the front layer which is the forming surface abutted by the glass optical element is arranged as the lower layer than the front layer and the film on the front surface deteriorated by the forming is removed by the polishing. At this time, the film is polished until the film lower in the rate of polishing arranged as the lower layer appears over the entire front surface. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for removing a film formed on a molding surface of a molding die for molding a glass optical element such as a lens or a prism, and a molding die.

[0002]

2. Description of the Related Art In a method of manufacturing a glass optical element such as a lens or a prism by molding, a base material that precisely creates a shape of a molding surface and has little thermal deformation (for example, tungsten carbide, a tungsten carbide type alloy, various ceramics, etc.). A film is formed on the molding surface of (1) for the purpose of preventing surface roughness due to high temperature of the molding surface and preventing adhesion, fusion, and chemical reaction with glass. As the material of the film, diamond-like hard carbon-based or noble metal-based materials are used.

These films are deteriorated by various problems such as precipitation of glass material components, scratches, film peeling, and the like, as the number of molding times increases. When it deteriorates, it can be regenerated by polishing the extreme surface layer with ultrafine diamond abrasive grains, but the shape accuracy may deteriorate due to the polishing operation. When the shape accuracy deteriorates in this way, it becomes necessary to perform shape creation and polishing of the surface of the base material by mechanical processing such as grinding. However, since each of the base materials as described above is a material having a high mechanical strength, it is not easy to correct and process it into a desired shape by machining and polishing, which causes a cost problem in molding the glass optical element. Has become.

As a method of removing the film other than the above-mentioned polishing, a method of removing the carbon-based film by reactive low pressure plasma etching (Japanese Patent No. 2783749) or a method of removing the carbon-based film by oxygen plasma ashing (special Japanese Patent Publication No. 7-55840) has been proposed. Further, after removing the film by these methods, polishing is performed as necessary to re-form a film to obtain a molding die.

[0005]

The method for polishing a deteriorated surface layer using the diamond abrasive grains as described above is very useful as a method for regeneration, but the shape accuracy is deteriorated by repeating the operation. When the above occurs, the base material itself may be processed, resulting in a problem that it is necessary to finish the shape of the base material surface with high accuracy by mechanical processing such as grinding and polishing processing.

On the other hand, when low-pressure plasma etching or oxygen plasma ashing is performed, the material of the film that can be removed is limited, and the residue after performing these treatments is removed by polishing or acid treatment. Therefore, there is a problem that the number of steps increases.

The present invention has been made in consideration of the above problems of the prior art, and the film formed on the surface of the mold disturbs the shape of the surface of the substrate even with an extremely simple operation. It is an object of the present invention to provide a method for removing a film of a molding die, which can be removed without any treatment. Another object of the present invention is to provide a molding die obtained by regenerating the die removed by this method.

[0008]

According to the present invention, when a film is removed by a polishing process, the polishing process is stopped by a film having a smaller processing amount per unit time than the film to be removed from the surface layer. The surface film is removed while maintaining the shape of the surface of the die base material. Further, a molding die is obtained by re-forming the removed film on the surface from which the film has been removed.

From the above, the method of removing the film of the molding die of the invention of claim 1 is a method of removing the film formed on the molding surface of the molding die of the glass optical element. When a film with a lower polishing rate per unit time than the surface film that is the molding surface that the element contacts is placed below the surface film, and the surface film deteriorated by molding is removed by polishing. It is characterized in that polishing is performed until a film having a low polishing rate arranged in the lower layer appears on the entire surface.

According to a second aspect of the present invention, there is provided a method of removing a film of a molding die according to the first aspect, wherein a film having a low polishing rate has a polishing amount per unit time with respect to a surface layer film. 1 /
It is characterized by being 5.

The molding die of the invention of claim 3 is the same as that of claim 1.
Alternatively, the film of the surface layer is removed by removing the film described in the item 2, and then the film of the same material as the surface layer is formed again.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (Embodiment 1) FIGS. 1 and 2
1 shows Embodiment 1 of the present invention, FIG. 1 is a sectional view of a mold for molding a glass optical element, and FIG. 2 is a front view of a polishing machine.

As shown in FIG. 1, a molding die 10 for removing a film is provided with a base material 1 made of tungsten carbide (binderless cemented carbide).
A 200 Å chromium film 2 is formed, and a 2000 Å-thick Pt-Ir-based noble metal film 3 is formed on the chromium film 2 to form the molding surface 3a. These films were formed using the ion beam sputtering method.

The substrate 1 is formed into a concave aspherical shape by grinding and polishing, and its surface accuracy is 0.085 μm.
The mPV and the surface roughness are 0.041 μmRy. The surface accuracy of the molding surface 3a after forming the chromium film 2 and the noble metal film 3 on this surface is 0.094 μm, and the surface roughness is 0.0
It is 32 μm Ry. The surface precision and the surface roughness were measured with a stylus type measuring machine (trade name "Form Talysurf", manufactured by Taylor Hobson Co., Ltd.).

In this embodiment, the noble metal film 3 is removed. As shown in FIG. 2, the polishing machine 20 has an upper shaft portion 30 and a lower shaft portion 40. The lower shaft portion 40 includes a motor 41 and a rotating shaft 42 connected to the motor 41, and the mold 10 is fixed to the upper portion of the rotating shaft 42.

In the upper shaft portion 30, a rotating shaft 32 is attached to a swinging mechanism 31 at an inclination angle of 45 degrees, the rotating shaft 32 is connected to a motor 33, and a polisher 34 is attached to the lower portion of the rotating shaft 32. The polisher 34 is a spherical member made of felt bob. The upper shaft portion 30 can be pressed downward by a pressing mechanism (not shown).
The processing is performed by pressing the polisher 34 against the surface of the mold 10 by the pressure of the pressure mechanism, interposing the liquid in which the abrasive particles are dispersed at the interface, and then rotating the lower shaft portion 40 by the motor 41 and the upper portion by the motor 33. Rotation of the shaft 30 and further swinging mechanism 3
It is carried out by the left and right reciprocating motion by 1.

In this embodiment, the abrasive grain size is 1.
0 μm diamond abrasive grains were used, and the diamond abrasive grains were dispersed in oil and used for polishing. The speed of the reciprocating motion of the polisher 34 is set so that the film should be removed more toward the outer periphery of the mold 10, and thus the speed becomes slower toward the outer periphery, but the speed is set depending on the shape to be processed. Not not.

Table 1 shows the surface precision and surface roughness before and after the removal of the noble metal film 3 and during the polishing process when the polishing process is performed according to this embodiment. As shown in Table 1, the surface accuracy decreases while the noble metal film 3 is being removed in the middle of the process, while the surface accuracy is not processed before the processing when the chromium film 2 appears on the entire surface. It is almost the same as the state of. This is because the polishing amount per unit time when processing the noble metal film 3 and the chromium film 2 under the same polishing conditions is 0.13 for the chromium film when the noble metal film is 1. This is because the shape irregularity that had occurred during the processing of the noble metal film appeared on the surface of the chromium film, and the progress of polishing was almost stopped at the surface layer of the chromium film, and the irregularity of the shape that had occurred up to that point was almost cancelled. . The elemental analysis of the polished surface was conducted by ESCA, and it was confirmed that no precious metal component remained at the end of polishing.

[0019]

[Table 1]

As described above, in this embodiment, by utilizing the difference in the polishing amount of the noble metal film 3 and the chromium film 2 per unit time, the noble metal film can be removed without destroying the surface shape before processing. Is possible. Moreover, there is no problem in surface roughness.

Next, in this embodiment, with respect to the surface of the mold 10 on which the chromium film 2 appears on the surface layer as described above,
The chrome film is formed by ion beam sputtering to 70
A noble metal film having a thickness of 0Å and a thickness of 2,000Å was formed. By this film formation, it became possible to obtain a mold for molding a glass optical element having the same performance as in the initial stage.

(Embodiment 2) FIGS. 3 and 4 show Embodiment 2 of the present invention. FIG. 3 is a sectional view of a molding die for molding a glass optical element, and FIG. A comparison is shown.

As shown in FIG. 3, the mold 17 for removing the film has a base material 11 made of a silicon carbide sintered body.
Then, the chrome film 1 having a thickness of 1000 Å is formed on the surface of the base material 11.
2 is formed, a chromium nitride film 13 having a thickness of 500Å is formed on the chromium film 12, and a thickness of 3 is formed on the chromium nitride film 13.
The molding surface 14a is formed by depositing the 000Å Pt-Ir-based noble metal film 14. These films were formed using the ion beam sputtering method.

The surface of the base material 11 is formed into a planar shape by grinding and polishing. The accuracy of the surface of the base material 11 is 0.030 μmPV, and the surface roughness is 0.028 μmRy.
Has become. Forming surface 1 after forming chromium film 12, chromium nitride film 13 and noble metal film 14 on this surface
The surface accuracy of 4a is 0.033 μm, and the surface roughness is 0.026 μm.
It is Ry.

In this embodiment, the noble metal film 14 and the chromium nitride film 13 are removed, and the method and apparatus for removing the film are the same as in the first embodiment. Figure 4
Surface precision PV and surface roughness Ry before and after and during the removal of the noble metal film 14 and the chromium nitride film 13 by polishing.
Indicates. The surface accuracy was measured with an interferometer, and the surface roughness was measured with a foam Talysurf.

The state in the middle of processing is a state in which both the noble metal film 14 and the chromium nitride film 13 are exposed on the surface. Although the surface precision is lowered in this state, the area degree is almost the same as the state before the processing when the processing in which the chromium film 12 appears on the entire surface of the surface is completed. This is because the polishing amount per unit time when polishing the noble metal film 14, the chromium nitride film 13, and the chromium film 12 under the same polishing condition is 0.71 for the chromium nitride film when the noble metal film is 1. The chrome film has a thickness of 0.13, which is due to the fact that the processing amount of the chrome film 12 per unit time is sufficiently smaller than that of other films.
For the same reason as in the first embodiment, the disturbance of the shape that occurs during polishing is canceled.

As described above, in this embodiment, by utilizing the difference in the polishing amount of the noble metal film 14, the chromium nitride film 13, and the chromium film 12 per unit time, the surface shape before processing is not destroyed. Noble metal film 14 and chromium nitride film 1
It is possible to remove 3. Moreover, there is no problem in surface roughness.

In this embodiment, a chromium film having a thickness of 50 is formed by ion beam sputtering on the surface of the mold 17 on which the chromium film 12 has appeared on the surface as described above.
0Å, chromium nitride film is 500Å, precious metal film is 3
A film was formed at 000Å. This makes it possible to obtain a mold for molding a glass optical element having the same performance as in the initial stage.

What is important in the present invention according to the above-mentioned embodiment is how much the material (film / base material) constituting the mold is polished under a predetermined polishing processing condition per unit time. In order to remove the desired film while maintaining the surface shape, it is desirable that the difference in the polishing amount per unit time between the film to be removed and the film to stop polishing is about 5 times or more.

[0030]

According to the inventions of claims 1 and 2, the film formed on the surface of the molding die can be removed by a simple operation without disturbing the shape of the substrate surface.

According to the third aspect of the present invention, the molding die can be remanufactured in a state where the shape of the original surface is maintained, and the remanufacturing can be easily performed.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a molding die used in a first embodiment of the present invention.

FIG. 2 is a front view of a polishing machine.

FIG. 3 is a sectional view of a molding die used in a second embodiment.

4 (a) to (c) are front views of a molding surface changed by polishing in the second embodiment.

[Explanation of symbols]

10,17 Mold for molding 1,11 Base material 2,12 chrome film 3,14 precious metal film 13 Chromium nitride film

Claims (3)

[Claims] 1. A method for removing a film formed on a molding surface of a molding die for a glass optical element, which comprises polishing per unit time as compared with a surface layer film which is a molding surface with which the glass optical element contacts. A film with a low processing speed is placed below the surface film, and when the surface film that has deteriorated due to molding is removed by polishing, polishing is performed until the film with a low polishing speed is placed on the lower surface and appears on the entire surface. A method for removing a film of a molding die, comprising: 2. The removal of the film of the molding die according to claim 1, wherein the film having a low polishing rate has a polishing amount per unit time of about 1/5 with respect to the surface film. Method. 3. A molding die, wherein after removing the film of the surface layer by removing the film according to claim 1 or 2, the film of the same material as that of the surface layer is re-deposited.