JPS63295452A - Method for preventing fluorescence phenomenon in quartz glass in the ultraviolet region - Google Patents

Abstract

PURPOSE:To prevent fluorescence phenomenon in the range of ultraviolet of quartz glass by heat-treating glass precursor obtd. with alkyl silicate as main raw material and thereafter by steeply rising and lowering temp. of the precursor several times in the region of strain relieving temp. CONSTITUTION:The quartz glass is obtd. by heating and keeping at a temp. for a fixed period the glass precursor synthesized by the sol-gel method using at least alkyl silicate as main raw material. After the heat treatment above- mentioned, the quartz glass given thermal shock by steeply rising and lowering the temp. several times in the region of 200-300 deg.C centering the strain relieving temp. After that, the quartz glass is allowed to cool in a furnace. Thereby, the fluorescence phenomenon in the glass occuring when the glass is irradiated by ultraviolet light of about 254nm is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to the production of quartz glass by the sol-gel process.

[Conventional technology]

Conventionally, in the production of quartz glass, a glass precursor synthesized by the sol-gel method using alkyl silicate as the main raw material is heated and held for a certain period of time. Ta.

[Problem that the invention seeks to solve]

However, for the quartz glass made in this way, 254w
When irradiated with ultraviolet light of m in a dark room, a violet or yellow-green fluorescence phenomenon occurs. The exact cause has not been elucidated, but it is thought to be due to either the internal structure or the presence of impurities.

The present invention is intended to solve these problems, and its purpose is to suppress this phenomenon of glass fluorescence.

(Means for solving the problem) A glass precursor synthesized by a sol-gel method using at least an alkyl silicate as a main raw material is heated and held for a certain period of time in the production of quartz glass. It is characterized by the electric rise and sudden fall several times around the temperature, and then allowed to cool in the furnace.The temperature range of the electric rise and sudden fall near the strain removal temperature is 200°C around the strain removal temperature. ~300
It should be around ℃.

[Effect]

Silica glass is a glass that exhibits excellent properties of heat resistance, chemical resistance, and light transmission, and is also used for IC masks and optical applications. However, it is now known that silica glass exhibits a fluorescence phenomenon in the ultraviolet region whose cause is unknown. It is thought that this is probably due to structural oxygen defects or impurities contained within the glass. This fluorescence phenomenon is thought to cause some adverse effects when used for optical purposes. On the other hand, it was found that by applying several thermal shocks near the strain removal temperature, the fluorescence phenomenon was reduced due to the above-mentioned reduction in oxygen vacancies or structural changes. However, there is a risk that crystallization of the glass will occur if heat treatment is applied in the vicinity of strain removal more than necessary.

〔Example〕

Ethyl silicate5. OJ2 and 0.05N hydrochloric acid aqueous solution, 5. OJ2 was mixed and vigorously stirred to obtain a colorless and transparent homogeneous solution. Ultrafine powdered silica (Aerosil)
DX-50) 1.5 kg was gradually added and thoroughly stirred. 2.4KHz while keeping this sol at 25℃
2 hours of ultrasonic waves, and then 1500G of centrifugal force for 5 hours.
After rinsing for a minute, it was passed through a 40μ filter. The resulting highly homogeneous sol was pH adjusted with 0.1N ammonia solution.
= 4.0, then polyethylene container (300 (關) x 300 (關) x 150H (H))
After pouring 1β into the container and sealing the container, it was left standing for a day and a night. After that, place 7 of the polyethylene container in a constant temperature room at 60℃.
I made a hole with a porosity of 1.0% and put it in for 7 days, and when it dried, the dimensions were 200 x 20.
0 mm x 0, 8 m' (D) A dry gel with a white plate was obtained.

This was placed in a quartz container, placed in an electric furnace, and heated to 300°C.
, 700°C, 900°C, and 1000°C for 5 hours each. The temperature increase rate was 6°C/hour. This was left to cool in the furnace and when taken out, 187 reports x 187 dragons
A 7 m" white sintered gel was obtained.

This was further placed in a graphite heating furnace and held at 1800℃ for 10 minutes, then left to cool inside the furnace, and when taken out, it turned out to be 153w.
A colorless and transparent quartz glass measuring 5×153w×0.8m′ was obtained. After washing this, when it was irradiated with 254 W@ ultraviolet light in a dark room, an ultraviolet fluorescence phenomenon was observed. (
Of these three sheets, one of sample
After heating to 200℃ and holding for 1 hour, 1000℃
After slow cooling to 60°C per hour, the mixture was allowed to cool in the furnace. For yet another sheet (sample ①), the temperature was raised to 1000° C. to 1300° C. for 15 minutes, held at 1300° C. for 10 minutes, and the temperature lowered for 15 minutes, which was repeated three times, and then allowed to cool in the furnace. After taking out the former and the latter, we irradiated a total of 3 sheets, including one that had not been heat-treated (sample ■), with 2540m ultraviolet light in a dark room, and the results were as follows: samples ■, ■, ■. ,
The degree of fluorescence was decreasing. Sample ■ was further heat-treated at 1200℃ for 80 hours, and when it was taken out, the surface of (sample Φ') turned white, and when observed with a lock microscope at 1oOx, β-cristobalite was precipitated. Furthermore, the fluorescence phenomenon did not decrease.

Furthermore, the sample
When sample (■) was taken out after being heat-treated at 00℃ five times, β-
Cristobalite was precipitated on the surface, and the fluorescence phenomenon did not decrease.

(Effects of the Invention) As described above, according to the present invention, in the production of quartz glass, a glass precursor synthesized by a sol-gel method using at least an alkyl silicate as a main raw material is heated and held for a certain period of time. After the treatment, the glass is raised and lowered several times around the strain-removal temperature, and then subjected to a thermal blow.The reason for this is unknown, but the 254 nm ultraviolet light is thought to be caused by structural defects inside the glass. The effect of suppressing the fluorescence phenomenon that occurs in glass when irradiated with light was obtained.

that's all ＼・、－／

Claims (1)

[Claims] In the production of quartz glass, a glass precursor synthesized by a sol-gel method using at least alkyl silicate as the main raw material is heated and held for a certain period of time. A method for preventing fluorescence phenomenon in the ultraviolet region of quartz glass, which is characterized by cooling quartz glass in a furnace after sudden cooling.