JPH0653578B2 - Optical glass element molding method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for molding an optical glass element formed by pressing a glass material.

2. Description of the Related Art In recent years, optical glass elements such as optical glass lenses have been aspherical in order to achieve simplification of lens configuration of optical devices, weight reduction, and high performance of optical characteristics at the same time. In manufacturing this aspherical glass element, it is difficult to process and mass-produce by a conventional polishing method, and a direct press molding method proposed by Eastman Kodak Company (Japanese Patent Publication No. 54-38126). Gazette) is considered promising.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention In the production of the above glass element, the performance of the optical glass element needs to be superior to that of the optical glass element by the conventional polishing method, and the surface precision and surface roughness are very high. Is required. For example, in the case of a high-precision camera lens, it is required that the surface accuracy is 5 Newton rings, 1 ass or less, and the surface roughness is 0.02 μm or less. Further, it is desired to reduce the size and weight of the optical parts as the size of the optical equipment becomes smaller, and it is extremely difficult to manufacture a large amount of compact optical parts at low cost by the conventional polishing method. Therefore, the direct pressing method has been attracting attention as a method for manufacturing a highly accurate optical glass element. Among the direct pressing methods, the reheat pressing method is suitable for producing a highly accurate optical glass element. The reheat press method is a method in which a glass material having a surface shape close to that of a desired optical glass element is produced, and the glass material is heated, pressed and cooled by a mold and the molded optical glass element is taken out. In this reheat press method, the shape, weight and surface quality of the glass material are important, and these have a great influence on the characteristics of the molded optical glass element. As a method of forming a glass material, a method of grinding a glass material with a curve generator and further polishing it to smooth the surface is generally used. However, although the polishing process can be finished with good surface accuracy, it is difficult to process a glass material having a small radius of curvature with high mass productivity, and the cost also increases. Therefore, the glass material ground by a curve generator is immersed in a hydrofluoric acid aqueous solution, followed by an etching process comprising a step of washing with water and a step of removing water, and then the glass material is pressed. To form an optical glass element. However, on the surface of the optical glass element molded by such a method, fine surface defects during grinding remain without disappearing, so that the optical glass element has a reduced optical characteristic, that is, a reduced transmittance, and an appearance. There is a problem that surface defects are likely to occur and the antireflection film formed on the surface of the glass element after molding has poor adhesion and durability.

In view of the above problems, the present invention is a method for molding an optical glass element having an improved light transmittance and a surface appearance, and further having a surface precision excellent in adhesion and durability of an antireflection film formed on the optical glass element. Is provided.

Means for Solving the Problems The present invention is characterized in that after the glass material is etched, the glass material is subjected to an ion beam treatment.

Action As described above, the direct press method has been attracting attention as a method for manufacturing a highly accurate optical glass element in a large amount at low cost. It is said that the reheat press method is suitable for producing a highly accurate optical glass element.
What is important in the reheat press method is the shape of the glass material,
Control of weight and surface quality, and in particular, surface quality has a great influence on optical characteristics of the optical glass element, that is, light transmittance.

The present invention provides a method of subjecting an as-ground glass material to an etching treatment in advance, and then press-molding the glass material into an optical glass element. As a result, optical characteristics, that is, light transmittance and It improves the appearance of the surface and makes it possible to mold products with excellent adhesion and durability of the antireflection film.

Example A method for forming an optical glass element according to an example of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing a glass material used in Examples,
The glass material is lead glass SF-8. The radius of curvature of the glass material is r ₁ = 2.8 mm and r ₂ = 3.4 mm, and the total length is l =
The diameter of the glass material was 4.3 mm, and the diameter of the glass material was d = 5 mm. This glass material was immersed in 10% hydrofluoric acid at a liquid temperature of 40 ° C. for 10 seconds, washed with distilled water for 3 minutes, and then dried for 15 minutes in a dryer kept at 200 ° C. Ion beam treatment is applied to the glass material obtained by repeating such an immersion process.

FIG. 2 is a schematic view of a vacuum apparatus used for the ion beam processing. 20 is a vacuum chamber, 21 is a glass material after etching, 22 is a substrate supporting dome, 23 is an ion beam gun, 24 is an ion beam, and 25 is an ion beam. It is a gas exhaust port.

First, the vacuum chamber 20 is evacuated to 1 × 10 ⁻⁵ Torr,
The temperature of the glass material 21 after the etching treatment on the substrate supporting dome 22 is heated to about 300 ° C., and argon (Ar) gas is introduced into the ion beam gun 23 so as to be about 4 × 10 ⁻⁵ Torr in the vacuum chamber. Then, a voltage of 1 KV is applied to the electrode of the ion beam to generate the ion beam, and the glass material 21 after the etching process is irradiated with the ion beam.

FIG. 3 shows an assembly diagram of the mold used for molding and the glass material.

First, the glass material 30 that has been subjected to the above treatment, one side is 3.
4 mm, the other is supplied between a pair of mirror-finished molds 31 and 32 having a radius of curvature of 6.08 mm, and after being heated to a temperature near the glass softening point by an appropriate method, a pressing mechanism (not shown) Thus, pressure is applied to the molds 31 and 32 to perform pressure molding. Reference numeral 33 is a barrel type for controlling the tilt / decenter, center thickness and the like of the optical glass element. In the cooling process after the completion of deformation, pressurization is maintained below the glass strain point,
Pressurization is stopped when the temperature reaches a preset value,
Perform accurate transfer molding.

Comparative Example The optical transmittance at the center wavelength of 780 nm between the optical glass element of the above-mentioned example of the present invention and the optical glass element molded without performing the ion beam irradiation treatment was 82 without the ion beam irradiation treatment. %, But the average was 88% or more according to the present invention. (Measurement number: 20 times) A decrease in the number of appearance surface defects of the optical glass element was also observed.

Further, in order to compare the adhesion and durability of the antireflection film formed on the surface of the optical glass element of the present invention, an adhesive tape peeling test (temperature: 80 ° C., relative temperature: 90%, left in high temperature / high humidity atmosphere for 300 hours) After that, the adhesive tape was adhered to the surface of the optical glass element and peeled off. As a result, peeling occurred in the conventional example, but there was no abnormality in the case of the present invention.

As described above, it is apparent that the optical element according to the present invention is superior to the conventional example in optical characteristics, that is, the transmittance and the adhesion and durability of the antireflection film.

EFFECTS OF THE INVENTION As is clear from the above description, the optical glass element molding method of the present invention is a method of molding an optical glass element by pressing a glass material that has been subjected to an etching treatment in advance. It is characterized in that it is subjected to a treatment of irradiating with an ion beam, and it is possible to improve the optical characteristics, that is, the transmittance and the surface appearance, and to obtain the surface accuracy with excellent adhesion and durability of the antireflection film. You can
Its practical value is enormous.

[Brief description of drawings]

FIG. 1 is a diagram of a glass material that has been ground into a biconvex shape used in one embodiment of the present invention, and FIG. 2 is a schematic view of a vacuum device used in the ion beam treatment of one embodiment of the present invention. The figure is an assembly drawing of the mold and glass material during molding. 20 ... Vacuum tank, 21 ... Glass material (etched), 22 ... Substrate support dome, 23 ... Ion beam gun, 24 ... Ion beam, 25 ... Gas exhaust port, 3
0 …… Glass material (etched, ion beam treated), 31, 32 …… Mold, 33 …… Cylinder mold.

Claims (3)

[Claims] 1. A method of molding an optical glass element by pressing a glass material that has been subjected to etching treatment in advance, wherein an ion beam is applied to the surface of the optical glass material that has been subjected to the etching treatment before pressing. A method for molding an optical glass element, characterized by improving the surface accuracy of the optical glass material by irradiation. 2. The method for molding an optical glass element according to claim 1, wherein the etching treatment comprises a step of immersing the glass material in a hydrofluoric acid aqueous solution, a step of washing with water and a step of removing water. . 3. The ion beam treatment is 1 × 10 ⁻⁴ Torr.
The method for molding an optical glass element according to claim 1, wherein the method is performed in a vacuum below.