JPH0755839B2 - Molding glass material - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a glass material for molding which is used for ultra-precision glass molding of high precision optical glass elements such as lenses and prisms used in optical equipment.

2. Description of the Related Art In recent years, as a method of manufacturing a high-precision optical lens, in particular, an aspherical glass lens or the like, many attempts have been made and realized by one-shot molding without using an optical polishing method and without a polishing step. As one of the forming methods, there is a method in which the glass material is heated to a deformable temperature, for example, a temperature near the softening point, and is formed using a means such as press forming. (For example, Japanese Unexamined Patent Publication No. 51-60208) Problems to be Solved by the Invention In the method for producing an optical glass element by the reheat press method, a glass material for molding which is previously processed into a shape close to a desired optical glass element is heated. An optical glass element is manufactured by pressure molding. An important point in the reheat pressing method is the control of surface quality, shape and weight of the glass material for molding. By satisfying these conditions, the accuracy required for the lens can be achieved. FIG. 3 shows the transmittance of an optical glass element obtained by press molding glass forming materials having different surface roughness by conventional polishing. The horizontal axis represents the surface roughness of the glass material for molding, and the vertical axis represents the transmittance of the molded optical glass element. Magnesium fluoride is vapor-deposited as an antireflection film on the surface of the optical glass element. The transmittance required for the lens is 98%. As can be seen from FIG. 3, if the surface roughness of the glass material for molding formed by polishing is 0.1 μm or more, the optical glass element press-molded has low transmittance and insufficient optical performance. This is because the surface of the glass material for molding has cracks as shown in FIG. 4, and therefore cracks remain on the surface of the optical glass element even after press molding. That is, when the glass material for molding is finished by polishing, the performance of the optical glass element is not satisfied unless the surface roughness is 0.1 μm or less, and the surface roughness must be finished with high accuracy. Further, it is difficult to control the shape and weight of the material as described above, and at the same time, it takes a long time to adjust. As a result, the cost of the glass material for molding becomes high, which causes a problem of high cost of the optical glass element.

Means for Solving the Problems In view of the above problems in the present invention, the surface of the glass material ground to a shape similar to the desired optical glass element used when manufacturing a highly accurate optical glass element by the reheat press method The glass material for molding is obtained by using a means for smoothing the etching process.

Effect In the present invention, by using the above-mentioned means, cracks on the surface of the glass material ground and processed can be eliminated, and the optical performance of the press-molded optical glass element can be sufficiently satisfied even if the surface roughness is poor.

Example Hereinafter, an experimental result of an example of the present invention will be described with reference to the drawings.

The glass material used is lead glass SF-6, and the shape of the glass material processed for optical glass element molding has a radius of curvature of 2.
9 mm, center thickness 5.2 mm, edge thickness 5.0 mm, biconvex shape, surface roughness 1.0 μm. Etching treatment was performed so that the unevenness on the surface of the glass material subjected to the grinding process had no cracks as shown in FIG. FIG. 2 shows a sectional view of a part of the surface of the glass material for molding after the etching treatment. Hydrofluoric acid was used as the etching treatment liquid, the treatment time and other conditions were changed, and the treatment was performed, followed by washing with isopropyl alcohol and drying to obtain a glass material for molding having a surface roughness as shown in Table 1. Created.

The etching process takes a very short time, from 3 seconds to 60
It is about a second. This glass material for molding was press-molded. Molding conditions are mold temperature 510 ℃, press pressure 20kg / cm
^2. Pressing time was 10 seconds, and the operation was performed in a nitrogen atmosphere. Magnesium fluoride was vapor-deposited as an antireflection film on the surface of the molded optical glass element. FIG. 1 shows the transmittance of the optical glass element obtained by press-molding the glass material for molding obtained by the above-mentioned method. The horizontal axis shows the surface roughness of the glass material for molding, and the vertical axis shows the transmittance. The theoretical value of transmittance is 98%. As is clear from FIG. 1, in the case of a glass material for molding treated to eliminate cracks on the surface irregularities, the optical glass element formed by press molding as a lens has a surface roughness of 1 μm. It can be seen that the optical performance is satisfied.

EFFECTS OF THE INVENTION As described above, in the present invention, it is confirmed that the optical performance of the press-molded lens is sufficiently obtained if the surface roughness is 1 μm or less by eliminating the unevenness cracks on the surface of the glass material for molding by the etching treatment. did.

Compared with the glass material for polishing, the glass material for molding has a looser surface roughness specification and the processing time is significantly shortened, so that the cost of the optical glass element can be reduced.

[Brief description of drawings]

FIG. 1 is a graph showing the transmittance of an optical glass element produced by press-molding a molding glass material in one embodiment of the present invention, and FIG. 2 is a partial cross-section of the surface of the molding glass material of the present invention. Fig. 3 is a graph showing the transmittance of an optical glass element made by press-molding a glass material for molding made by polishing, and Fig. 4 is a part of the surface of the glass material for molding made by polishing. FIG.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Masaaki Sunohara 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (56) References JP-A-61-251526 (JP, A)

Claims (1)

[Claims] 1. A glass material for molding produced through a grinding process, which is supplied into a cavity composed of an upper mold and a lower mold and is heated and pressed, and is a glass material in the grinding and grinding process. A glass material for molding, characterized in that the surface roughness of the surface is made to be 1 μm or less by removing cracks on the surface of the glass by etching treatment.