JPH01145332A - Production of optical glass - Google Patents

Abstract

PURPOSE:To produce a large-sized lens without polishing, by enclosing a lenticular gel with a sol having low shrinkage in the production of a glass article by sol-gel process and flattening the bottom face of the sol. CONSTITUTION:Fine powder of an alkoxide, salt or oxide of metals constituting a glass is used singly or in combination as a raw material for a glass article in a sol-gel process. The raw material is added with water and, as necessary, a catalyst such as acid or alkali to obtain a sol A. Separately, a sol B having lower shrinkage than the sol A during drying process is prepared. The sol A is poured into a lenticular mold 1 and gelatinized. The sol B is poured into a vessel having flat bottom, the gelatinized sol A is embedded in the sol B, and the sol is gelatinized to obtain a composite gel. A dry gel 4 is prepared by drying the composite gel. The gel of the sol A is spontaneously peeled from the gel of the sol B by the shrinkage difference between the sols. The dry gel is heat-treated and the glass part originated from the sol B is cut off to obtain a lens 7.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for molding an optical lens by a sol-gel method.

[Conventional technology]

Conventional optical lenses were made of glass or plastic. Currently, most lenses are made by polishing glass material into a lens shape, but recently, attempts have been made to manufacture lenses without polishing in order to reduce costs. The optical pickup microlens used can be manufactured without polishing by molding plastic or glass into a lens shape by injection molding or pressing, respectively.

[Problem that the invention seeks to solve]

However, conventional non-polishing techniques such as plastic injection molding and glass press molding into a lens shape have the following problems. First, glass press molding is technically difficult and cannot be used to mold large lenses, and has only been put into practical use for lenses of a few millimeters in diameter at most. Especially when it comes to aspherical lenses, the molding precision is low, making it impossible to make large lenses. on the other hand,
In plastic injection molding, it is impossible to manufacture precise lenses because the plastic material has poor moisture resistance or changes greatly in shape due to temperature changes.

Therefore, the present invention aims to solve these problems.
The objective is to provide a method for molding large-sized optical lenses, which could not be made by press molding, without polishing, using glass, which is a material that is moisture resistant and difficult to change shape.

[Means for solving problems]

The method for manufacturing an optical lens of the present invention is a method for manufacturing a glass body by a sol-gel method using a metal alkoxide or metal salt of a metal constituting the glass, or a fine powder of a metal oxide alone or in combination as a raw material. It is characterized by being molded into a lens shape in the following steps.

a) A process in which metal alkoxides or metal salts of the metals constituting the glass, or fine powders of metal oxides are used as raw materials, either singly or in combination, and water is added, and if necessary, an acid or alkali catalyst is added to form a sol. .

b) A step of injecting the sol into a lens-shaped mold container and gelling it.

c) A step of producing another sol having a composition that has a shrinkage rate smaller than the shrinkage rate in the drying step after gelation of the sol obtained in step a).

d) A step of removing the lens-shaped gel from step b) from the mold and submerging it into the sol from step C) placed in a container with a flat bottom to turn the sol into a gel.

e) A step of shrinking and drying the gel body containing the lens-shaped gel to form a dry gel.

f) A step of heat-treating the dry gel and vitrifying it.

g) A step of removing the outer part of the glass body obtained in step f) and taking out the lens-shaped glass body contained therein.

[For production]

According to the above structure of the present invention, a lens-shaped gel is formed using a sol having a large shrinkage rate during the drying process, and the lens-shaped gel is wrapped around the gel by a sol having a small shrinkage rate. By making the bottom surface flat, the following effects can be achieved. When molding lenses by transferring a mold without polishing, major problems arise such as silica powder, inorganic dust, and scratches caused by various operations during the process that adhere to the surface of the molded product. The best solution to this problem is the method of the present invention, which protects the molded surface of the gel after lens molding by covering it with gel to prevent defects from occurring on the surface. However, if the lens is protected with a gel of the same composition, there is a problem that the lens-shaped gel and the protective gel will fuse together during the process. In order to prevent this phenomenon, by adjusting the shrinkage rate during the gel drying process and making the shrinkage rate of the lens-shaped gel smaller than that of the protective gel, the lens-shaped gel can be separated from the protective gel. , which prevented fusion. Another problem with transfer molding into a lens shape is that the gel is deformed during each step from gelation to sintering. To prevent this, the bottom surface of the protective gel is made flat, and operations during the process are based on the bottom surface.
I decided to process it on a flat board. This allows the deformation to be kept to a level that does not pose a practical problem.

〔Example〕

Example 1. (Quartz glass lens) Add 180 g of water to 208 g (1 mol) of nylon silicate.
g (10 mol) and 20 ml of 1N hydrochloric acid were added thereto, and the mixture was thoroughly stirred for hydrolysis. Add 90g (1.5g) of silica fine powder to this.
Add mole) (stir and disperse. Clumps and dust were removed by centrifugation, ultrasonic waves, filtration, etc. to make a homogeneous sol. This sol is called A sol.

A B sol, which shrinks less during the drying process than the A sol, is prepared as follows. In other words, 208g (1 mole) of ethyl silicate
180g (10mol) of water, 1N hydrochloric acid 20a+
L was added and stirred thoroughly for hydrolysis. 138 g (2.3 mol) of silica fine powder was added to this and stirred to remove lumps and dust to form a homogeneous sol.

Next, as shown in FIG. 1, the A sol was injected into a lens-shaped mold at a pH value of 4.5 and gelled.

Sol B was added to a container with a flat bottom after its pH value was adjusted to 4.5, and the gel body of Sol A was submerged in the sol to form a gel. In other words, the gel body of the B sol is for protection, and has a structure in which a lens-shaped gel exists in the center. This composite gel was dried at 60° C. for 10 days to obtain a dry gel.

At this time, the gel of sol A and the gel of sol B were separated due to the difference in shrinkage rate. 130% of this dry gel
It was heat-treated to 0°C to produce transparent quartz glass.

Next, the glass portion formed by B sol was cut and removed to obtain a lens body. This surface had the same level of surface precision as polishing.

Example 2. (Multi-component glass) 12 g of boric acid was added to each of the A sol and B sol of Example 1.
10 g of sodium methoxide was added. By performing the subsequent operations in exactly the same manner as in Example 1, a borosilicate glass lens could be formed.

By the above method, barium borosilicate glass lens bodies can be manufactured by adding barium sulfate to the sol, and lead glass lens bodies can be manufactured by adding lead alkoxide. In other words, the composition of the glass can be arbitrarily adjusted by adding the necessary metal compound.

〔Effect of the invention〕

As described above, according to the invention, the glass manufacturing method uses the sol-gel method, and by gelation in the mold, protection with gels with different shrinkage rates, flattening the bottom surface, and operation with a level, the lens shape is achieved. It has become possible to form 2. improve the surface accuracy to that of a polished surface, and 3. minimize deformation. The above will make it possible to lower the price of lenses and will make a major contribution to the field of video equipment.

[Brief explanation of the drawing]

1a) to 1f) are process diagrams showing the steps of the present invention. Above Figure 1

Claims (1)

[Claims] (1) In a method for manufacturing a glass body by a sol-gel method using metal alkoxides or metal salts of the metals constituting the glass, or fine powders of metal oxides alone or in combination as raw materials, the lens shape is formed in the following steps. A method for manufacturing an optical lens, characterized by molding. a) A process in which metal alkoxides or metal salts of the metals constituting the glass, or fine powders of metal oxides are used as raw materials, either singly or in combination, and water is added, and if necessary, an acid or alkali catalyst is added to form a sol. . b) A step of injecting the sol into a lens-shaped mold container and gelling it. c) A step of producing another sol having a composition that has a shrinkage rate smaller than the shrinkage rate in the drying step after gelation of the sol obtained in step a). d) A step of removing the lens-shaped gel from step b) from the mold and submerging it in the sol from step c) placed in a flat-bottomed container to turn the sol into a gel. e) A step of shrinking and drying the gel body containing the lens-shaped gel to form a dry gel. f) A step of heat-treating the dry gel and vitrifying it. g) Step of removing the outer part of the glass body obtained in f) and taking out the lens-shaped glass body contained therein.