JPS63295447A - Production of optical glass element - Google Patents

Abstract

PURPOSE:To obtain a transcription face having high transcription coefficient and to stably produce a high-precision optical glass element by using a stock wherein the relation of both the difference between diameter of the required optical glass element and diameter of the glass stock for molding, and the moving rate of a molding die is specified and press-molding it. CONSTITUTION:An optical glass element 5 is produced by charging a glass stock 1 for molding into a molding die 4, heating and molding it under pressure. In this case, when the difference between diameter of the required optical glass element 5 and diameter of the glass stock 1 for molding is defined as Y and the moving rate of the molding die 4 is defined as X, the glass stock 1 wherein the following relation is satisfied is used. 0.02X<Y<0.8X. Thereby the shape of the glass stock for molding can be properly decided and the pressure of pressing is firstly exerted to a transcription face and then exerted to the part of diameter of a lens and thereby such possibilities that transcription is made insufficient are reduced. The transcription face having high transcription coefficient is obtained because the diameter of the lens is formed after the pressure of pressing is sufficiently exerted to the transcription face.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method of manufacturing an optical glass element, which is mainly used in reheat press molding of a high-precision optical glass element (for example, a lens, a prism, etc.).

BACKGROUND OF THE INVENTION In recent years, optical glass elements have been trending toward aspheric surfaces that can simultaneously simplify the lens structure of optical equipment and reduce the weight of the lens portion. In order to manufacture this aspherical lens at low cost and in large quantities, a direct press molding method (Special Publication Publication No. 54-3
No. 8126 has been studied, and among them, the reheat press method is considered to be promising.

(Japanese Unexamined Patent Publication No. 60-81032) Problems to be Solved by the Invention In the production of the above-mentioned optical glass element, the optical performance of the optical glass element must be superior to that of the optical glass element produced by the conventional polishing method. Therefore, extremely high surface accuracy and surface roughness are required. For example, in the case of a high-precision camera lens, the surface accuracy is required to be within 5 Newton rings and 1 candy, and the surface roughness to be within 0.03 μm. As a method for manufacturing such a highly precise optical glass element, the reheat press method is effective. The reheat press method is a method of manufacturing optical glass elements by heating and pressing an optical glass material that has been processed in advance into a shape close to the desired optical glass element. The surface quality and shape accuracy of the glass material can be reduced to 0.1μ by surface treatment.
For example, when a molding glass material with a surface roughness of about 0.5 μm is molded, the transmittance decreases due to the poor surface condition, and the optical performance of such an optical glass element decreases. Although it is insufficient, it is possible to obtain an optical glass element with high transmittance by molding a glass material for molding whose surface roughness has been reduced to 0.1 μm or less by surface treatment. However, unless the difference between the diameter of the desired optical glass element and the diameter of the glass material for molding is processed to a length corresponding to the amount of movement of the pair of molds, it is not possible to stably obtain a highly accurate optical glass element. When press-molding a molding glass material with a small amount of movement of the mold, if the difference between the diameter of the desired optical glass element and the diameter of the molding glass material is zero, the press pressure will be divided to the left and right, making it difficult to achieve high precision. When molding a glass material for molding where the surface of the mold cannot be transferred to the glass or the mold moves a lot, if the difference between the diameter of the desired optical glass element and the diameter of the glass material for molding becomes too large, the lens causes eccentricity.

In other words, the shape of the optical glass material has a very large influence on lens performance.

Means for Solving the Problems In order to solve the above-mentioned problems, the present invention aims to change the shape of the glass used when manufacturing high-precision optical glass elements by the reheat press method to the desired diameter and molding of the optical glass element. An optical glass element in which a glass material for molding is press-molded into a shape according to the relational expression 0.02X < Y < 0.8X, where Y is the difference in diameter of the glass material for use and X is the amount of movement of the mold. The present invention provides a method for manufacturing.

What is most important in the reheat press method is the method of deforming the glass material for molding. The general conditions for starting deformation are molding start temperature and press pressure. However, since the heating method differs depending on the shape of the glass material, the forming start temperature differs even for forming glass materials having the same glass composition. Therefore, the press pressure during molding differs, making it difficult to stably obtain a highly accurate transfer surface. Such problems can be solved by carrying out the method of manufacturing an optical glass element of the present invention.

That is, with the glass material for molding of the present invention, an appropriate shape of the glass material for molding can be determined based on the desired lens diameter and the amount of movement of the mold. There is less chance of press pressure being applied to the lens diameter part before the transfer surface, resulting in insufficient transfer, and the lens diameter is formed after sufficient press pressure is applied to the transfer surface, resulting in an extremely high transfer rate. It is possible to obtain However, it may be possible to reduce the diameter of the glass material for molding in order to increase the press pressure on the transfer surface, but this needs to be taken into consideration as it may cause eccentricity.

When a glass material for molding that satisfies these conditions is subjected to heating and pressure molding, it is possible to stably obtain a highly accurate transfer surface.

EXAMPLE An example of the present invention will be described below with reference to the drawings.

FIG. 1 shows a method for manufacturing an optical glass element according to a first embodiment of the present invention. In FIG. 1, the glass material 1 has the same spherical shape as the glass material 1 shown in FIG. Reference numeral 4 indicates upper and lower molds for manufacturing an optical glass element, and the optical glass element 5 molded by this pair of molds is shown below the dotted line.

The method for manufacturing a meniscus lens will be described below with reference to FIGS. 1 and 3. The mold 4 used was made of carbide, with the upper mold having a concave surface and the lower mold having a convex surface. The diameter of the mold, which is the diameter of the optical glass element, was 8.2M. As a glass material for molding, it is polished to have a surface roughness of 0.
．． A spherical material having a diameter of 0.05 μm or less and indicated by 1 in FIG. 3 was used.

This shape is a φ5.6 crane. The molding method used was to place a molding glass material into a mold, heat it, and pressurize it. The molding conditions were a mold temperature of 510° C., a press pressure of 20 kg/cd, a holding time of 30 seconds, and a nitrogen atmosphere. The wavefront aberration of the optical glass element after press molding is RM
It was possible to obtain an optical glass element having a highly accurate transfer surface with S = 0.024λ. In this case, the lens thickness is 2.3fi, and the molding glass material is φ5.6m.
Since it is set to m, it is calculated that X=3.3 fl. Therefore, since yl+y2=Y, Y=2.6m in this case
satisfies the conditional expression of the present invention, and a highly accurate optical glass element can be manufactured.

A second embodiment of the present invention will be described below with reference to the drawings. FIG. 2 is a diagram showing a method for manufacturing an optical glass element of the present invention. In the figure, 3 is the same glass material as shown in FIG. 3, and was ground into a biconvex shape with a radius of curvature of 3.5 mm, a center wall thickness of 6.2 mm, and an edge diameter of 4 mm. 6
is a mold, and both the upper and lower molds have a concave shape. The regulating die 7 is for regulating the amount of movement of the upper molding die, and has an inner diameter of 5+.
It was set as n.

A glass material was held between the mold and the regulating mold configured as described above, and press molding was performed. The molding conditions are as described above.
An optical glass element having a lens thickness of 4.3 mm was obtained under the same conditions as in the example. In this case, the amount of movement X of the mold is 1
．． 9m, and yl+y2- as a glass material for molding.
Since Y satisfies the conditions, a highly accurate optical glass element can be manufactured.

Effects of the Invention As is clear from the above explanation, the method for manufacturing an optical glass element of the present invention is based on the method in which the difference between the diameter of the desired optical glass element and the diameter of the glass material for molding is Y, and the amount of movement of the mold is X. In this case, press molding is performed using a molding glass material that has the relational expression of 0.02X < y < 0.8 The shape of the glass material can be determined. Therefore, there is less possibility that pressure is applied to the lens diameter part before the transfer surface, resulting in insufficient transfer, and the lens diameter is formed after press pressure is sufficiently applied to the transfer surface, resulting in an extremely high transfer rate. It is possible to obtain a transfer surface. It goes without saying that the shape of the glass material for molding is not limited to that shown in FIG. 3 shown in the embodiment, and may be of any shape as long as it satisfies the relational expression between X and Y.

The method for manufacturing an optical glass element of the present invention makes it possible to stably obtain an optical glass element with very high precision.
The industrial value of the present invention is extremely large.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a mold and a glass material for molding in an embodiment of the present invention, FIG. 2 is a sectional view of a mold and a glass material for molding in a second embodiment of the invention, and FIG. 3 is a sectional view of a mold and a glass material for molding in a second embodiment of the invention. It is a perspective view showing the shape of the glass material for use. 1.2.3...Glass material for molding, 4.6...
... Molding mold, 5... Optical glass element, 7.
...Restricted type. Name of agent: Patent attorney Toshio Nakao 1 person/---garasu se 4--→payF; -Weisho 3I

Claims (3)

[Claims] (1) If Y is the difference between the diameter of the desired optical glass element and the diameter of the glass material for molding, and X is the amount of movement of the mold, 0.0
A method for manufacturing an optical glass element, characterized in that press molding is performed using a molding glass material having a relational expression of 2X<Y<0.8X. (2) The amount of movement X of the molds is defined as the press distance from when the pair of molds contacts the molding glass material to when the desired lens shape is formed. 1) A method for manufacturing an optical glass element according to item 1). (3) Manufacturing an optical glass element according to claim (1), wherein the difference Y between the diameter of the optical glass element and the diameter of the glass material for molding is not larger than the diameter of the glass material for molding. Method.