JPS59146950A - Manufacture of quartz glass - Google Patents

Abstract

PURPOSE:To manufacture quartz glass of high quality free from defects such as bubbles by a sol-gel method by adding finely powdered silica to an alkyl silicate soln. while applying ultrasonic waves to the soln. and by mixing them. CONSTITUTION:Water or alcohol and hydrochloric acid are added to ethyl silicate, and they are mixed by stirring to carry out hydrolysis. Finely powdered silica is gradually added to the resulting soln. while applying ultrasonic waves to the soln. At this time, the finely powdered silica is easily dispersed by stirring the soln. Ultrasonic waves are applied for a while after adding the silica so as to increase the uniformity of formed silica sol. The silica sol is separated by filtration and converted into gel. The pH of the separated silica sol may be increased by dropping an aqueous ammonia soln. so as to shorten the gelling time. The dry gel is put in a furnace and sintered to obtain quartz glass.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing quartz glass, and more particularly, a method for producing quartz glass at a low temperature by a sol-gel method using an alkyl silicate and finely powdered silica as main raw materials. , alkyl silicate, water, 9 hydrochloric acid, etc. The process is carried out while applying ultrasonic waves to form a sol, which is then gelled into a transparent and homogeneous silica glass.

First, to talk about the usefulness of quartz glass, in recent years quartz glass (with impurity concentrations such as copper and boron of 0.1
PPM or higher purity products began to be produced and used in crucibles, boards, diffusion furnaces, etc. in the production of germanium, silicon, and other semiconductors. ! In addition, beakers for physics and chemistry, cells for optical measurements, and cells for optical measurements have also been developed, and those with fewer hydroxyl groups and those with good optical uniformity have been developed, and are used for each optical purpose, especially for optical measurements. Silica glass fiber for communications has recently been attracting attention. However, as shown in the above example, the raw material cost of quartz glass, which is no longer necessary, is only 1% higher with the current manufacturing method. Due to the increased demand for processing at higher temperatures and higher temperatures, it has become extremely difficult to process.

Therefore, the possibility of producing quartz glass at low cost is highly anticipated, and recently, the method of producing quartz glass at low temperatures using the sol-gel method has been attracting particular attention.

A brief explanation of the silica glass manufacturing method using the sol-gel method is as follows.

i A common alkyl silicate 5i (OR)4 (R is an argyl group having 1 to 10 carbon atoms), a common alcohol solution (
water) and finely powdered silica to form a silica sol.
The solvent is concentrated into silica gel by heating or other treatment. The bulk silica gel obtained here is placed in a furnace and sintered according to a predetermined program to form quartz glass.

The above is the method for manufacturing quartz glass using the sol-gel method.The advantages of this manufacturing method are 1) It can be manufactured at a lower temperature than the high-temperature melting method using quartz as a raw material, which saves energy.2) Raw materials Because it is easy to purify, high-purity glass can be obtained.3) Since a low-viscosity solution is used as a raw material, highly uniform glass can be obtained. The production of quartz glass using this method has been extensively researched.

However, according to the materials published in 1, there are various problems, and the current situation is that it has not been put into commercial use.

One of these problems is that when adding finely powdered silica to a raw material solution, the viscosity of the solution increases rapidly if it exceeds the viscous level.9 Mechanical stirring is quite difficult. . As a result, it is very difficult to obtain a uniform silica sol and it takes a long time. Therefore, when this sol is gelatinized and the resulting dry gel is completely sintered to form quartz glass, it has the disadvantage that bubbles are generated in the glass, and it is easy to cause inappropriate VC'fX and scratches. As a countermeasure for this, the stirring time after addition of fine powdered silica is set at the entire time.

Despite all treatments such as ultrasonic waves and filtration, including the addition of gold, the problem was still opaque, and the problem could not be resolved due to the difficulty of adding fine powder silica.

Therefore, an object of the present invention is to provide a method for producing transparent and homogeneous quartz glass by adding finely powdered silica to a raw material solution to a silica sol with a high level of efficiency, gelling and sintering. It is.

As a method of manufacturing quartz glass that satisfies the above conditions,
The following method was devised.

In other words, after stirring and mixing ethyl silicate, water, alcohol (with or without), and hydrochloric acid and performing a hydrolysis reaction, while applying ultrasonic waves to this solution, fine powder silica (for example, (trade name) )Aeresll(Diguss
Company a), (Franeil (Franeol Hanto, Ca
b-o-8il (Cabot 3. DO8ilica (
Dow Oorning Co.) and Arc 5ilic
a (PP0 company) e, t, c) f Gradually add. If stirring is added at this time, dispersion into the fine powder silica solution becomes easier. Then, in order to further increase the uniformity of this silica sol, ultrasonic waves are applied for a while (1 to s)lr). After this, filtration is performed, and in some cases, operations such as adding all the drops of ammonia water to increase the pH value and shortening the gelation time are added to gelatinize, and the resulting dry gel is then placed in a furnace and sintered. 1 is made of quartz glass. Using the method of this invention, ultrasonic imaging makes it very easy to disperse fine silica powder into a solution, and it takes only a short time, and a sol with higher uniformity can be obtained compared to adding by stirring. Silica glass also has no defects such as bubbles and can be manufactured with high quality.

Hereinafter, each aspect of the present invention will be explained in more detail according to Examples.

Example 1 Purified commercially available ethyl silicate (lEi (Offlt
) 4) 44 mt 5.4 mt of ethanol (without adding, 66 m, t of hydrochloric acid solution and 56 m, t of water were mixed to perform a hydrolysis reaction. After applying ultrasonic waves to this solution, finely powdered silica ((product name) Cab-o-8i, 1(Ca
bar, company))1! M"'i was added gradually, and after the addition, ultrasonic waves were applied for 2 hours to uniformly distribute the molten silica. Stirring was not performed when all the fine powder silica was added. Next, this It was filtered through a whole glass filter.Here, aqueous ammonia was added dropwise to this filtrate, and the pH value was adjusted to f5.5.
Although it is known that the gelation time can be considerably shortened by adjusting it to about -5.0, it is considered that this is not a direct influence for the purpose of this experiment. (As a result of conducting this test in the event of a disaster, no differences were observed in the quartz glass after sintering.) This solution't [50y measurement υ After gelatinization, place in a constant temperature bath with a lid with a hole that allows the evaporation rate to be adjusted, and dry for 8 days at 60°C for 4 days and 80°C for 2 days.
Diameter 6.2 crn.

A dried gel with a thickness of 0.3 strokes was obtained. When this dried gel was placed in a spreading furnace and heated and sintered at a heating rate of 180°C/hr, it became transparent in diameter at 1150°C! A 5.0 cm piece of quartz glass was obtained. The analysis results of various physical properties of this quartz glass, including Vickers hardness of 800 kg/- specific gravity of 2.2, infrared absorption spectrum, near-infrared absorption spectrum, and refractive index, all agree with those of fused silica glass, which is superior to its older brother. It turned out to be made of quartz glass.

Lid, V in quartz glass previously obtained by the sol-gel method
There were no large bubbles of about 50 μm observed, and 1
There were also almost no small bubbles of 0 μm or less.

Example 2 A hydrolysis reaction was carried out using the same amount of raw materials as in Example 1.

After the reaction, ultrasonic waves are applied to the solution while stirring, and fine powder silica ((trade name) Cab-o-8il (Cabot)
) 15 ff was gradually added, and after excitation, stirring and ultrasonication were continued for 1.5 hours to improve uniformity. Next, this was filtered with a glass filter, and the filtrate'(i-[diameter 10o
5 in a petri dish made of DEFRON (DuPont's registered open collar).
02 measurement, after gelation, put in a thermostatic bath with a lid with a hole that allows the evaporation rate to be adjusted, and dry in the same manner as in Example 1 to form a 6.2 cm diameter, 0.3 crtr. A dry gel was obtained. This dry gel was heated in the same manner as in Example 1.
8, and a transparent quartz glass with a diameter of 5.0 (:rn).The physical properties of this quartz glass were exactly the same as those of fused silica glass, and it was found to be a perfect silica glass. Very well, almost no bubbles were observed.

Example row 6 In example rows 1 and 2, representative examples were failed, but
This is only a small part; other raw materials include fine powder silica ((trade name) Cab-o-8il (Oabo
Company T)) Children k 2-50? In this case, seven tests were carried out, for each case, when addition was carried out using only ultrasonic waves, and when both stirring and ultrasonic waves were used in combination. The effect of increasing the uniformity of the silica sol was further increased when both stirring and ultrasonic waves were used together. The sintered silica glass was extremely homogeneous and its physical properties matched those of fused silica glass.

As shown above, the full implementation failed? , when adding powdered silica, shake #J by applying ultrasonic waves.
The uniform pouring of the /8 liquid is greatly improved, and therefore the quartz glass obtained by sintering this gel is also very easy to use.
(It's obvious that it will be an A-grade one.)

As a result, the quartz glass obtained by the present invention has the advantage that it can be produced at a considerably lower cost than the quartz glass produced by the conventional method (melting method). I am using it in the field of science and chemistry (5. ION)
Not only can it be used in photomasks during the fabrication process, boards for reactor core stands, etc., but it is also of good quality, so it is thought that its applications will expand to a wider range of areas.

that's all -2shi

Claims (1)

[Claims] A method for producing quartz glass using a sol-gel method using alkyl silicate and finely powdered silica as main raw materials, and adding finely powdered millica to all the raw materials while applying ultrasonic waves.