JPS62207724A - Production of quartz glass - Google Patents

Abstract

PURPOSE:To obtain quartz glass having high quality effectively and economically by hydrolyzing alkyl silicate with acidic reagent, and adding a salt contg. no metal ion to sol obtd. by mixing superfine particles of silica with the hydrolyzate. CONSTITUTION:Sol is prepd. by mixing a soln. obtd. by the hydrolysis of alkyl silicate using an acidic reagent, with superfine silica powder in a specified proportion. A salt contg. no metal ion is added to the sol. Suitable salt is ammonium salt such as NH4Cl. (NH4)2SO4, etc., and suitable amt. to be added is pref. 0.1-30wt% basing on the weight of the quartz glass after sintering. Then, the sol contg. the salt is dried to dry gel, which is treated in He atmosphere or in vacuum to close the pores in the dry gel. The procedure for closing the pores is executed at a lower temp. by the addn. of the above-described salt, reducing thus loads on the furnace or jigs in the furnace. The glass or precursor of the glass obtd. by this method is held by heating at 1,500-2,200 deg.C to decompose the above described salt. Thus, quartz glass having high quality is obtd.

Description

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

[Summary of the invention]

The present invention is a method for producing quartz glass using a sol-gel method that uses high-temperature treatment.By adding a salt that does not contain metal ions to the sol, the pore-closing temperature of the dry gel is lowered without deteriorating the purity of the quartz glass. [Conventional technology] Dry gel produced using the sol-gel method is closed in a helium atmosphere or under reduced pressure. When a sample made of quartz glass or a glass precursor is heat-treated at 1,500 to 2,200°C, it is possible to produce quartz glass of extremely high optical quality, which is completely free of inclusions. It can now be applied to quartz substrates for IC masks and mother rod nemo for optical communication fibers.

Various methods have been proposed for producing Drive μ, including a solution obtained by hydrolyzing an alkyl silicate with an acidic reagent,
A method using a sol solution obtained by mixing ultrafine silica powder at a predetermined ratio as a raw material is advantageous because it can be produced at low cost and with a high yield.

[Problem that the invention seeks to solve]

The pore closing temperature of the dry gel is determined by the mixing ratio of the alkyl silicate hydrolyzed solution and the ultrafine silica powder. As the mixing ratio of ultrafine silica powder decreases, the pore-closing temperature decreases. However, when the weight of ultrafine silica powder is less than 50% of the weight of silica glass after sintering, the production yield of dry gel is significantly reduced.

When containing 50% or more of ultrafine silica powder, the pore closing temperature is 1
The temperature is 200°C or higher. Considering the purity of the furnace material such as the furnace core tube, quartz glass is preferable, but wear is unavoidable since the temperature exceeds the operating eye temperature.

Sintering at high temperatures also poses a problem in terms of energy savings.

The present invention is intended to solve these problems, and its purpose is to lower the pore-closing temperature of dry gel and efficiently produce high-quality quartz glass.

[Means to solve the problem]

In the present invention, a dry gel prepared using a ZoIv solution obtained by mixing a solution obtained by hydrolyzing an alkyl silicate with an acidic reagent and ultrafine silica powder at a predetermined ratio as a raw material is prepared in a helium atmosphere. The pores become closed under reduced pressure,
The obtained glass or glass precursor was heated to 1500 to 220
In silica glass synthesis, which is heated to 0°C and held for a certain period of time, it is characterized by adding a salt that does not contain metal ions to the sol.

[Effect]

It is known that in the production of glass by the usual melting method, the melting temperature is lowered by adding NarK or the like. In the case of the sol-ge p method, the closing temperature of the dry gel is similarly lowered. As described above, additives having the effect of lowering the closing temperature are noticeable in alkali metals and alkali metals, but this is a phenomenon that is commonly observed in cations such as ammonium ions.

If the component in the closed pores is He or vacuum,
Closed pores disappear by high temperature treatment at 1500 to 2200°C. When pore-closing, it is necessary to sinter in a helium atmosphere or under reduced pressure, and if the pore-closing temperature can be lowered, the burden on the furnace and furnace jig can be significantly reduced.

The various properties of quartz glass lie in its high purity, and in particular, metal ions can have an adverse effect even in extremely negative amounts. Salts that do not contain metal ions, such as ammonium salts, have almost no effect on the properties of quartz glass even if most of them are decomposed and removed during the firing process and remain in the glass.

〔Example〕

Example 1゜Ethyl silicate 44ON and 0.05N hydrochloric acid aqueous solution 3
60M was stirred vigorously to obtain a colorless and transparent homogeneous solution. Ultrafine powder silica (AerosilOX-50) 15
0.17 was added gradually and stirred thoroughly. This sol was irradiated with 28KHz ultrasonic waves for 2 hours while being kept at 20°C, and then centrifugal force of 1500G was applied for 10 minutes.
passed through the filter. There, the speed ratio ammonium powder 13.5.9 (NH4CI/S i O2-5%)
was added and stirred for 10 minutes. Furthermore, CL1 normal ammonia water was added dropwise to adjust L/5PI (4.2).

700a was poured into a polypropylene container with inner dimensions of 30 crIL x 50 cIrL x 10 crtLH, and kept at 60°C for 3 days in a sealed state. When it was dried at 60° C. for 7 days with a lid having an aperture ratio of 1%, a plate-shaped drive μ was produced.

The dry gel was placed in a gas exchange furnace with a quartz glass core tube, and heated at a rate of 60°C/hr for 80°C while flowing dry air.
The temperature was raised to 0°C. 11 pure helium gas from 800℃
It started flowing into the reactor core tube at a flow rate of 50 min.
The temperature was raised to 1150°C at a rate of °C/hr and held at 1150°C for 5 hours. Vitrification has been completed and the specific gravity is 2.
The size that was 20 is 15crnX15cWLxQ
, 4c7rL. Ink p-johns and β-cristobalite type crystals with a diameter of about 10 μm were detected.

The quartz glass plate was placed in a graphite heating furnace, and after the furnace was purged with nitrogen gas, the temperature was raised to 1800° C. over 2 hours and held for 10 minutes. The temperature is lowered to 1200°C at a rate of 1600°C/hr,
Thereafter, the temperature was lowered to room temperature at a rate of 100°C/hr.

It was mirror-polished to a thickness of 2M, and a condensing lamp was applied to it in a dark room at an illuminance of 5G, 000Aux, but no light spot could be detected. The crystals had completely disappeared, there was no distortion, and the optical quality was extremely high. No alkali metals or alkaline earth metals were detected in chemical analysis. Still, the transmittance in the ultraviolet region was maintained at 90% or more up to 250u.

Comparative example 1゜Example 1. The sol was prepared in the same manner as described above, and drive μ was prepared without adding ammonium chloride. The dry gel was placed in a gas exchange furnace with a quartz glass core tube, and Example 1. Although it was heated in the same manner as above, it remained white and opaque, and its specific gravity was 2.15.

Transferred to a graphite heating furnace, the same procedure as that of Example 1 was carried out. When heated to 1800° C. in the same manner as above, many bubbles were observed with the naked eye.

Comparative Example 2 Example 1. Drive μ was prepared using the same sol preparation without adding ammonium chloride. Drive P was placed in a gas exchange furnace with a quartz glass core tube, and heated to 60℃/
The temperature was raised to 800°C at a rate of hr. Pure helium gas begins to flow into the reactor core tube from 800°C at a flow rate of 11/min, and is heated to 1200°C at a rate of 50°C/hr.
It was held at 200°C for 5 hours. remains white and opaque;
Specific gravity was 2.18.

Transferred to a graphite heating furnace, Example 1. 180 in the same way as
When heated to 0°C, bubbles could be observed with the naked eye.

Example 2 44011 Ll of ethyl silicate and 590 ytl of a 0.05 N hydrochloric acid aqueous solution were gently stirred to obtain a colorless and transparent homogeneous solution. There, ultrafine powdered silica (AerosilOX)
-50) 220g was gradually added and stirred thoroughly. While keeping this ρ at 20℃, apply 28K) iz ultrasonic waves to the
After irradiation for a period of time and further applying a centrifugal force of 1500 G for 10 minutes, the sample was passed through a 1 μm filter. There, ammonium chloride powder 6811 (NH4C1/S i Oz −
20%) and stirred for 10 minutes. Furthermore, α1 normal ammonia water was added dropwise to adjust the pH to 4.2.

Inner size 30c! The mixture was poured into a polypropylene container of rL x 30 crrL x 10 crItH for 700 d, and kept at 30°C for 3 days in a sealed state. A plate-shaped drive p was produced by covering with a lid having an aperture ratio of 1% and drying it at 60° C. for 7 days.

The dry gel was placed in a gas exchange furnace with a quartz glass core tube, and heated at 60°C/hr for 8 hours while dry air was flowing in.
The temperature was raised to 00°C. M helium gas from 800℃ to I
A? It begins to flow into the reactor core tube at a flow rate of /min, and the temperature reaches 15℃.
The temperature was raised to 1150°C at a rate of
Holds time. Although it was translucent, its specific gravity was 2.20.

The size was 15crILX 15cmX 0.4611.

The quartz glass precursor was placed in a graphite heat-generating furnace, and after the furnace was replaced with nitrogen gas, the temperature was raised to 1850° C. in 2 hours and held for 5 minutes. The temperature was lowered to 1200°C at a rate of 10 OC/br, and thereafter the temperature was lowered to room temperature at a rate of 100°C/hr.

Thickness 21! Mirror polished to IE, 50. OO0
4! A condensing lamp was applied to achieve the illumination intensity of ux, but no light spot could be detected. The crystals have completely disappeared,
There was no distortion and the optical quality was extremely high.

No alkali metals or alkaline metals were detected in chemical analysis. In addition, the transmittance in the ultraviolet region is 25011K.
It held more than 90% until now.

Example 3 440ml of ethyl silicate and α05 normal hydrochloric acid water bath solution 3
The mixture was stirred thoroughly for 60 minutes to obtain a colorless and transparent homogeneous solution. Ultrafine powder silica (Aerosil0X-50) 15
0.9 was gradually added and stirred thoroughly. This sol 2
Irradiated with 28KHz ultrasonic waves for 2 hours while keeping the temperature at 0℃,
After further applying a centrifugal force of 1500 G for 10 minutes, the mixture was passed through a 1 μm filter. There, 2.7 g of ammonium sulfate powder ((NH4) 2 So 4/S i O2 =
1%) and stirred for 10 minutes. Furthermore, 0.1N ammonia water was added dropwise to adjust the pH to 4.2.

700M was poured into a polypropylene container with inner dimensions of 30cWL x 30cIIL x 10c1rLH and kept at 30°C for 3 days in a sealed state. Close the lid with an opening ratio of 1% and heat at 60℃ for 7 days.
After drying for several days, a plate-shaped Draigle was produced.

Drive P was placed in a vacuum furnace with a Mufito tube as the core tube and lined with a quartz glass tube, and was heated while dry air was flowing in.
The temperature was raised to 800°C at a rate of 0°C/hr. 800
℃ to 1150° C. using a rotary pump at a rate of 30° C./hr while maintaining the paper pressure below ITo, rr, and held at 1000° C. for 5 hours. It was translucent, but the specific gravity was 2. ．． It was 2 degrees. The size is 15cr
rL×15cIrLXO14cr! It was L.

The quartz glass precursor was placed in a graphite heat-generating furnace, and after replacing the furnace with nitrogen gas, the temperature was raised to 1750° C. over 2 hours and held for 30 minutes. The temperature was lowered to 1200°C at a rate of 1000°C/hr, and thereafter the temperature was lowered to room temperature at a rate of 100°C/hr.

Mirror-polished to a thickness of 2 mlK and OO0lu to 5 in a dark room.
A condensing lamp was applied so that the illuminance was x, but no light spot could be detected. The crystals had completely disappeared, there was no distortion, and the optical quality was extremely high.

No alkali metals or alkaline metals were detected in chemical analysis. In addition, the transmittance in the ultraviolet region is 250 x m
It held more than 90% until now.

Example 4 (Ethyl silica) 880 d and 1180 ml of O, OSS normal hydrochloric acid aqueous solution were mixed and stirred thoroughly to obtain a colorless and transparent homogeneous solution. There, ultrafine powdered silica (Cob-0-8il L
-90) 440.9 was gradually added and stirred thoroughly.

This sol was irradiated with ultrasonic waves at 28K) for 2 hours while being kept at 20°C, and then subjected to centrifugal force of 1500G for 10 minutes, and then passed through a 1 μm filter.

There, ammonium chloride powder 54.9 (NH4C1/
5iO2-5%) and stirred for 10 minutes. Furthermore α1
Standard ammonia water was added dropwise to adjust the pH to 4.8.

15 in a Teflon container with an inner diameter of 6 (1 m% and a length of 60 crIL)
00- Injected and capped tightly. Mounted on a rotating device with the center axis of the cylinder as the rotation axis, and rotated at 100 Or-p and 2 m.
Rotated time. Transfer the gel to a constant temperature bath at 30°C, leave it for 4 days, and then transfer the gel, which has linearly shrunk by about 5%, to a polypropylene container (inner size: 2 ocm x 70 cIIL x 15cIIL).
H) and covered with a lid with an aperture ratio of 1%. After drying at 60° C. for 10 days, a tube-shaped Draigle was produced.

The drive was placed in a gas exchange furnace with a quartz glass core tube, and dry air was introduced into the furnace at a rate of 21/m1nO. The temperature was raised to 700°C at a rate of 60°C/hr and held for 5 hours. Switch the inflow gas to a mixed gas of helium (t81/m1n) and chlorine (Q, 21/fnin), and
External heating was performed to 1000°C at a rate of 0°C/hr. Switch the inflow gas to oxygen (217 m in) and heat to 1000°C and 1
Each sample was held at 050°C for 5 hours.

Finally, the inflow gas was switched to helium (2ilm1n), and the temperature was maintained at 1050°C, 11100°C, and 1150°C for 5 hours each.

Although it was translucent, its specific gravity was about #1 and 2.20. Size: Outer diameter 311m% Inner diameter 1cIrL1 Length 75
It was crrL.

The obtained quartz glass precursor was heated with graphite as a heating element for about 2 hours.
The sample was moved at a speed of 20 f/min in a ring heater at 000°C. Next, put it in an electric furnace and heat it at 1200℃ for 1
After holding for a period of time, the temperature was lowered at a rate of 100° C./hr to remove strain.

When irradiated with a laser beam having a wavelength CL of 655 μm, no scattering was observed at all. Further, when the moisture content was determined by absorption at 2.72 μm, it was found to be 1 ppm or less.

Example 5 440 ml of ethyl silica and 360 ml of a 0.05N aqueous hydrochloric acid solution were vigorously stirred to obtain a colorless and transparent homogeneous solution. There, ultrafine powdered silica (AerosilOX-50
) 150g was gradually added and thoroughly stirred. This sol was irradiated with 28 KHz ultrasound for 2 hours while being kept at 20°C, and then subjected to a centrifugal force of 1500 G for 10 minutes.
It was passed through a 1 μm filter. Add 155g of hydrazinium chloride powder (NzHsCJ?/5ioz=5
%) and stirred for 10 minutes. 01 normal ammonia water was added dropwise to the rainbow to adjust the PI to 44.2.

Pour 700 ml of ylX 3 oax j D (yH) into a polypropylene container with an inner dimension of 30, and keep it closed at 30°C for 5 days. Cover with a lid with a 1% open area and dry at 60°C for 7 days. As a result, we were able to fabricate a plate-shaped drive μ.

The dry gel was placed in a gas replacement furnace using quartz glass as the furnace/B tube, and the temperature was raised to 800°C at a rate of 60°C/hr while flowing dry air. Pure helium gas at 800℃ begins to flow into the reactor core tube at a flow rate of 11/min, and the temperature reaches 30℃.
Raise the temperature to 1150℃ at a rate of 1150℃ / hr.
It was held for 5 hours. Vitrification has been completed and the specific gravity is 2
．． It was 20 years old. Size is 15CrrL x 15cW
It was LXQ, 4crrL. Inclusion crystals and β-cristobalite type crystals with a diameter of about 10 μm were detected.

The quartz glass plate was placed in a graphite heat-generating furnace, and after purging with nitrogen gas, the temperature was externally raised to 1800° C. over 2 hours and held for 10 minutes. The temperature is lowered to 1200°C at a rate of 1000°C/hr,
Thereafter, the temperature was lowered to room rM at a rate of 100°C/hr.

Thickness Z tax K m heavy polishing, 50,000 yen in dark room
A condensing lamp was applied so that the illuminance was 0 Aux, but no light spot could be detected. The crystals have completely disappeared,
There was no distortion, and the material was optically of madder quality. No alkali metals or alkaline earth metals were detected in the chemical analysis. In addition, the transmittance in the ultraviolet region was maintained at 90% or more up to 250 m (Comparative Example 440 points) and 360 Tnl of a 0.05N hydrochloric acid aqueous solution were vigorously stirred to form a colorless and transparent homogeneous solution. I got it. There, ultrafine powdered silica (AerosilOX-
50) 1501! was gradually added and thoroughly stirred. 28KHz while keeping this sol at 20℃
Ultrasonic waves were applied for 2 hours, and centrifugal force of 1500G was applied for 1 hour.
After 0 minutes, it was passed through a 1 μm filter. There, 118g of ammonium chloride powder (NH4C1/5
t02-40%) was added and stirred for 10 minutes. 0 more
．． 1N ammonia water was added dropwise to adjust the pH to 4.2.

7001rL13 was poured into a polypropylene container with inner dimensions of 50cIIL x 30cr and x 10cIrLH, and kept at 50°C for 3 days in a sealed state. Close the lid with an opening ratio of 1%, and
It was dried at 0°C for 7 days. A large amount of ammonium chloride was precipitated on the surface of the dry gel.

Example 1. When sintered in the same manner as above, many cracks occurred and a dense glass state was not obtained.0 [Effects of the Invention] As described above, according to the present invention, alkyl silicate is hydrolyzed with an acidic reagent. The glass or glass precursor obtained by closing the pores of Drive μ, which is prepared from a sol solution obtained by mixing the solution obtained by In silica glass synthesis, in which silica glass is heated to 1500-2200℃ and held for a certain period of time, by adding salt that does not contain metal ions to the sol, the pore-closing temperature of the dry gel can be lowered without degrading the purity of the silica glass. High quality quartz glass can be manufactured efficiently.

According to the present invention, even quartz glass produced by the sol-gel method can be used to produce quartz substrates for thin film transistors, quartz substrates for IC masks,
Furthermore, it has become possible to apply it to port chains for optical communication fibers, etc.

that's all

Claims (1)

[Claims] (1) A dry gel prepared using a sol solution obtained by mixing a solution obtained by hydrolyzing an alkyl silicate with an acidic reagent and ultrafine silica powder at a predetermined ratio as a raw material, In silica glass synthesis, in which the pores are closed in an atmosphere or under reduced pressure, the resulting glass or glass precursor is heated to 1500 to 2200°C, and held for a certain period of time, a salt that does not contain metal ions is added to the sol. A method for producing quartz glass. (2) The salts added to the sol are NH_4Cl, (NH_
4) The method for producing quartz glass according to claim 1, wherein the quartz glass is an ammonium salt such as _2SO_4. (6) The amount of salt added is 0 to the weight of quartz glass after sintering.
．． The method for producing quartz glass according to claim 1 or 2, wherein the content is 1 to 30%.