JPS6086038A - Production of quartz glass - Google Patents

Abstract

PURPOSE:To obtain a transparent and high-quality quartz glass, in the production of quartz glass by a sol-gel process, by applying ultrasonic radiation to a silicate solution under agitation prior to the adjustment of the pH, and using the obtained sol as a raw material. CONSTITUTION:An alkyl silicate (e.g. ethyl silicate) is mixed with an aqueous solution of hydrochloric acid, the obtained uniform solution is added with a specific amount of silica fine powder, and ultrasonic radiation is applied to the obtained mixture under vigorous agitation of the liquid with e.g. a stirrer to effect the uniform dispersion of the silica powder. The pH of the mixture is adjusted to 3-6 with an alkali, and the product is put into a definite vessel, gelatinized, and dried. The obtained dry gel is sintered to form the objective quartz glass.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention uses alkyl silicate and finely powdered silica as raw materials in a low-temperature synthesis method of quartz glass using a sol-gel method in which the pny is adjusted to 3 to 6. The present invention relates to a method for producing transparent, high-quality quartz glass.

Quartz glass has come to be used in many parts such as Ruho, boards, and diffusion furnaces during the IC manufacturing process, and its usefulness has been recognized, and products with fewer hydroxyl groups and better optical uniformity have been developed. Therefore, quartz glass fibers for use in various optical applications, particularly for optical communications, have recently attracted attention.

As described above, quartz glass is used in various fields, and the scope of its use is expanding. However, the manufacturing cost of quartz glass is high, and the problem is that it is expensive. The sol-gel method has been attempted as a method for manufacturing inexpensive, high-quality quartz glass.

As a method for obtaining large-sized quartz glass with good yield using the sol-gel method, ultrafine powder silica is added to a sol obtained by hydrolyzing alkyl silicate, and further [after adjusting PR to 3 to 6, There is a method of drying and sintering at 90°C.

This method simultaneously solved the problem of cracks during dry gel production and the problems of cracks and cracks during sintering, and it became possible to manufacture fairly large quartz glass (41 nchφ or more) at low cost.

However, the quality is still poor, and this seems to be due to a problem with the state of dispersion of the ultrafine silica powder in the sol.

Ultrafine powdered silica tends to form lumps, which causes sintering residue and foaming. As a method for breaking up lumps, it is very effective to perform ultrasonic vibration before adjusting the pH. The average particle size of silica in the sol has been significantly reduced, making it possible to obtain high-quality quartz glass.

However, since ultrasonic waves travel in a straight line and attenuate with distance, they have the disadvantage that a uniform ultrasonic vibration effect cannot be obtained over the entire sol. Such non-uniformity cannot be solved simply by lengthening the ultrasonic time, which wastes a lot of energy. Particularly when processing a large amount of sol, local differences in the ultrasonic vibration effect become significant, and there may be places where the ultrasonic waves do not reach at all.

As described above, it is difficult to obtain an effective dispersion effect by simply irradiating ultrasonic waves, making it difficult to improve quality.

Some kind of solution is essential. The object of the present invention is to produce transparent, high-quality quartz glass by applying ultrasonic vibration uniformly and effectively.

The outline of the present invention is to move a sol within a container using a stirring motor, stirrer, shaker, etc., and irradiate the sol with ultrasonic waves. By introducing this method,
A decrease in viscosity and a decrease in average particle size occurred within a very short period of time, making the dispersion very effective. It would have been even better if the sol was cooled during irradiation with ultrasonic waves to control the heat generation of the sol.

When the sol prepared by the above procedure was dried to form a dry gel and further heated to form quartz glass, the quality was extremely poor, containing almost no air bubbles.

Hereinafter, the present invention will be explained in detail based on Examples.

Example 1 Ethyl silicate 440- and 0.1N hydrochloric acid aqueous solution 36
0- was vigorously stirred to obtain a colorless and transparent homogeneous solution. Fine silica powder (Aerosil OX-50) 3
50 t was gradually added and stirred thoroughly. The AniNZ was irradiated with ultrasound for 1 hour while stirring was continued.

Due to ultrasonic vibration, the viscosity changes from 50L:P (25℃) to 3(
l CP decreased. The average particle size also ranges from 0.22μm to 0.22μm.
18 μmK decrease, no particles larger than 0.4 μm exist,
It was shown that the dispersion was carried out uniformly and effectively.

0.1N ammonia water was added dropwise to this sol, and the pH was set to 4.
5 and then transferred to a polypropylene container. After gelation, the pinhole was removed and dried at ω°C. The obtained dry gel was heated to 3200°C at a heating rate of 180°C/hr to produce colorless and transparent quartz glass.

This quartz glass contains almost no air bubbles and has a water content of 0.
It was as low as 15 ut% and showed good optical properties.

Example 2 Ethyl silicate 22 and 0.1N hydrochloric acid aqueous solution 18!
The mixture was stirred vigorously to obtain a colorless and transparent homogeneous solution.

There, fine silica powder (Aerosil LIX-50
) 7.5 UP was gradually added and stirred thoroughly. A cooling tube was placed in the sol, and while the temperature of the sol was maintained at 20° C., ultrasonic waves of 4 KHg were irradiated for 2 hours.

Viscosity changes from 50CP (25℃) to 25℃ due to ultrasonic vibration.
It dropped to CP. The average particle size also varies from 22μ to 0. ]6μ
m, and no particles larger than 0.4 μηi were present.

Even from the sol treated in large quantities in this manner, extremely high quality quartz glass could be produced by the same heat treatment as in Example 1.

As shown in the embodiments above, the present invention is an indispensable manufacturing method for manufacturing high quality quartz glass with a good yield. The sol-gel method has the advantage of being able to produce quartz glass at low cost, but it has been considered difficult to produce high-quality glass. The present invention can also be expected to be applied to optical applications.

that's all Applicant: Macashiki Company Tamuwa Seikosha Agent Patent attorney senior management

Claims (1)

[Claims] Using at least alkyl silicate b and ultrafine powder silica as raw materials, the sol is uniformly dispersed by ultrasonic vibration, and then the PH
A method for producing quartz glass, which is characterized by irradiating the sol with ultrasonic waves while stirring, using a low-temperature synthesis method of quartz glass using a sol-gel method in which the sol-gel method adjusts the sol to 3 to 6.