JPS61232231A - Silica glass manufacturing method - Google Patents

Abstract

PURPOSE:To obtain a high-quality quartz glass free of contaminant, by passing a sol solution used as a raw material for sol-gel process twice or more through a final filter having a specific mesh size. CONSTITUTION:Sol solution composed mainly of an alkyl silicate and ultrafine silica powder is passed or circulated twice or more through a final filter having mesh size of <=5mum. Aggregated coarse particles and foreign material such as dust can be removed by this process to afford a high-quality quartz glass free of contaminant.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for producing quartz glass by a sol-gel method.

[Summary of the invention]

The present invention provides a method for producing quartz glass using the sol-gel method, in which the final filter is removed during the sol preparation process.
If it passes more than once, it can be circulated.
This improves the filtration accuracy of the prepared sol and makes it possible to completely remove foreign substances (coarse particles, dust, etc.) from the glass after sintering.

[Conventional technology]

In the production of quartz glass by the conventional sol-gel method using alkyl silicate and ultrafine silica as the main raw materials, a filtration process is used to remove foreign substances such as coarse silica particles and dust present in the prepared sol. The final filter was passed through only once.

[Problems and Objectives to be Solved by the Invention] However, in the above-mentioned conventional technology, since the final filter is simply passed through once, depending on the shape of foreign matter such as dust and coarse particles, particles with a size smaller than the pore diameter may be generated. Since these particles pass through to some extent, they remain in the glass after sintering, causing defects and making it difficult to manufacture high-quality glass.

The present invention is intended to solve these problems, and its purpose is to provide a method for manufacturing high-quality quartz glass using the Schiflugel method, which improves f overaccuracy by improving the conventional technology. There is a place K.

[Means for solving problems]

The method for producing quartz glass of the present invention includes, in addition to the conventional technique, a plurality of final filter passes during the sol preparation pass-through process in the production of quartz glass by the sol-gel method using alkyl silicate and ultrafine silica as main raw materials. It is characterized by rotating.

[Effect]

According to the invention, the prefilter remaining in the prepared sol
When the sol is passed through the sol by cycling the foreign substances such as insufficiently dispersed and agglomerated coarse particles and dust that were not removed by the sol, the K decreases. It can be shown that f overaccuracy can be completely eliminated by improving the accuracy.

[Example] (1) Commercially available ethyl silica) 28 (Si (Ow
let) 4) 152t, Ilo 1 HTiOl
1084 and ultrafine particle silica (trade name Aerosil oxso (Degussa)) 45Kl were mixed at the same time, and stirred for 4 hours using a Dissilver (stirring and dispersing device).
A sol in which ethyl silicate is hydrolyzed and ultrafine silica is dispersed to some extent is prepared, and then the sol is irradiated with ultrasonic waves (combined with stirring) to further improve dispersibility.
This was carried out for 5 hours. At this time, the sol temperature was kept constant using a cooling device in order to prevent the sol temperature from increasing due to ultrasonic irradiation.

As the next step, the sol is subjected to centrifugation treatment (3000rpH1,5Q wk
) was added.

The subsequent filtration process was performed with the following configuration.

Pore diameter 10μm, 7μm, 5μm, 3μm 1μm
In the conventional method, the sample was passed through each filter in order, but after this, the sample was further passed through a filter with a pore size of 1 μm.

J) The pH value of the passed sol was adjusted to 3 to 6 by dropwise addition of a weak base such as aqueous ammonia, and recentrifugation treatment was performed to remove the gel-like substance generated at this time. After this, conventionally, the final filter was passed through a filter with a pore size of 1 μm only once, but here, two
Pass through 4, 10, and 20° times, size 36X
60 each in a 24 x 12 [α] polypropylene container
0g.

40[Pour it into one container and let it gel in a sealed state, then
When shrinkage begins, change the lid of the container to one with holes of a specified porosity to adjust the drying rate, place it in a dryer, and heat it from room temperature to 60-80°C at a heating rate of 5'C/r. Heat it to a temperature of 10~
A dried gel with a size of 25.3XIL8Xα5 was obtained in 15 days. These dried gels were put into a sintering furnace, and heated and sintered using a predetermined heating method to obtain a transparent glass body at 1300 to 1450°C. The size of this glass is 1 & 8
X 11.5XQ, 35 (m) Te weight was around 180g.
When the glass was observed using a condensing lamp, the amount of foreign matter in the glass was significantly reduced compared to before. Moreover,
The number of times the sample was passed through the final filtration filter before being put into the container was small, and in the cases where it was passed more than 10 times, no foreign matter could be observed. In addition, the results of physical property analysis of Tora's glass are Vickers hardness,
The specific gravity, coefficient of thermal expansion, infrared absorption spectrum, near-infrared absorption spectrum, refractive index, and other values matched those of fused silica glass.

(2) After subjecting the sol prepared in the same manner as in Example 1 to centrifugation, passing, pH value adjustment, and re-centrifugation, the sol was equally divided into five batches each containing SOZ. ,
The final filter is O, (15,1°2.3 hours, flow rate 3
It was circulated at ~5t/-. After this, in the same manner as Example 1,
80 pieces of each batch were put into containers to obtain quartz glass.

The longer the circulation time of the final filter, the fewer foreign substances in the quartz glass obtained here were observed, and they were hardly observed after 1 hour or more. In addition, the results of physical property analysis regarding these glasses include Vickers hardness, specific gravity, coefficient of thermal expansion,
Infrared absorption spectrum.

The near-infrared absorption spectrum and refractive index matched those of fused silica glass.

〔Effect of the invention〕

In this way, the silica glass produced according to the present invention can be manufactured by using the above-described filtration method to remove coarse particles, dust, etc. in the sol that cause foreign matter in the silica glass after sintering. It is a very high quality quartz glass as it can be almost completely removed.

In this way, quartz glass has been used until now because it has the advantage of being lower cost than conventional methods such as the fusion method, and it is also easy to produce very high quality quartz glass. We believe that its application will expand to a variety of fields, including photomask substrates for engineering C, base materials for optical fibers, etc.

Claims (1)

[Claims] (1) A method for producing quartz glass, which includes the following treatment method during the sol preparation filtration process in producing quartz glass by a sol-gel method using alkyl silicate and ultrafine silica as main raw materials. a) Pass through the final filter (pore size 5 μm or less) twice or more b) Circulate the filter described in a) for a predetermined period of time