JPH03247523A - Manufacture of silica glass and silica glass - Google Patents

Abstract

PURPOSE:To reduce the structural defects in silica glass, in the method for converting a porous glass base metal constituted of glass fine particles into a transparent one, by shrinking the base metal under heating at a specified temp. and thereafter converting it into a transparent one in an atmosphere with specified pressure or O2 partial pressure and temp. CONSTITUTION:A porous glass base metal 13 obtd. by depositing glass fine particles synthesized by a burner for synthesizing from SiCl4 is shrunken in an electric furnace 14 at a temp. lower than the one at which it is converted into transparent glass, i.e., 1200 to 1350 deg.C and is discharged as a shrunken base metal 12. Next, the obtd. shrunken base metal 12 is mounted on a stand 23 made of carbon in a carbon electric furnace 21 having a carbon heater 22, a rotary pump 25 and a vacuum pump 26. Then, the shrunken base metal 12 is converted into transparent glass in the furnace 21 in an atmosphere under <=30Torr pressure or <=1% O2 partial pressure at >=1350 deg.C. By this method, the silica glass having few structural defects and hardly emitting fluorescence even if irradiated with ultraviolet rays having short wave length can be obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for producing quartz glass and quartz glass, particularly quartz glass with few structural defects and a method for producing the same.

[Prior Art] Conventionally, as a typical manufacturing method for quartz glass, glass fine particles are synthesized by a chemical vapor phase method using an oxyhydrogen burner, and the glass fine particles are deposited on a starting member to form a porous glass base material. A method of forming a porous glass base material into transparent glass is known.

Figure 4 shows an example of a conventional method for producing quartz glass. 1 is a quartz glass seed rod which is a starting member, 2 is a transparent vitrified portion of a porous glass base material, and 3 is a porous glass. A base material, 4 is an electric furnace, 5 is a synthesis burner, and 6 is a glass raw material binding thread.

Normally, the porous glass base material 3 is heated under normal pressure or slightly positive pressure to make it transparent vitrified, but this is often done in a helium atmosphere in order to speed up the vitrification rate. However, it is difficult to maintain a perfect seal in the electric furnace for transparentization, and vitrification is performed in an oxygen-containing atmosphere, which can avoid the inclusion of oxygen in the atmosphere.
As a result, there is a drawback that structural defects occur in the glass.

[Problems to be Solved by the Invention] An object of the present invention is to solve the problem of structural defects occurring in quartz glass, which the prior art had.

[Means for Solving the Problems] In contrast, the present invention supplies silicon chloride for glass raw materials, hydrogen gas, oxygen gas, and inert gas to a burner, generates glass fine particles by a flame hydrolysis reaction, In a method for producing quartz glass in which a porous glass base material is formed by depositing this on a starting member and transparent quartz glass is produced from the porous glass base material, the porous glass base material is heated to a transparent vitrification temperature. Quartz is heated and shrunk at a lower temperature in the range of 1200-1350°C, and then becomes transparent vitrified at a temperature of 1350°C or higher in an atmosphere with a pressure of 30 Torr or less or an oxygen partial pressure of 1% or less, and has few structural defects. The present invention provides a method for manufacturing quartz glass, which is characterized by manufacturing glass.

The present invention also provides a quartz glass characterized in that the intensity of fluorescence emitted by ultraviolet irradiation is extremely low.

First, the basic concept of the present invention will be explained.

FIG. 3 shows the ratio of fluorescence intensity caused by structural defects in the glass to the oxygen partial pressure in the atmosphere during transparent vitrification of the porous glass base material (the horizontal axis is on a logarithmic scale). This shows the fluorescence intensity of a sample cut from a porous glass base material and made into transparent glass by changing the oxygen partial pressure in the atmosphere.
The fluorescence intensity of the sample vitrified in an air atmosphere is shown as 100. Here, the wavelength of ultraviolet rays that irradiate the sample is 254 nm, and the wavelength of fluorescence is approximately 650 nm.

As can be seen from Figure 3, lowering the oxygen partial pressure lowers the fluorescence intensity.

In the present invention, it is desirable that the oxygen partial pressure at the time of vitrification be 1% or less, preferably 0.1% or less, for the above reasons, but for this reason, it is preferable to vitrify the atmosphere at 30 Torr or less, preferably 3 Torr or less. preferable.

[Effect] In the present invention, although the effect of oxygen during vitrification is not necessarily clear, since the fluorescence intensity is reduced by the production method of the present invention, defects of non-bridging oxygen radicals or peroxide radicals are reduced. is possible.

[Example] FIG. 1 shows a production system for the porous quartz glass base material used in this example. 11 is a quartz glass seed rod, 12 is a contracted base material, 13 is a porous glass base material, 14 is an electric furnace, 15
1 is a synthesis burner, and 16 is a glass raw material combination system.

A porous glass base material 13 made by depositing glass fine particles synthesized from 5iC1 in a synthesis burner is heated at 1300°C.
The material was shrunk in an electric furnace maintained at a temperature of 100 m and was taken out as a shrunk base material 12.

Next, in the production system shown in FIG. 2, 21 is a carbon electric furnace, 22 is a contracted base material, 23 is a carbon stand, 24 is a carbon heater, 25 is a rotary pump, and 26 is a vacuum pump.

The porous glass base material 13 is heated and shrunk using the production system shown in FIG.
The atmosphere of the carbon electric furnace 21 is set to I Torr from 1200°C to 150°C.
The temperature was raised to 0° C. at a rate of 30° C./hr and then cooled to obtain a transparent quartz glass body.

The outer diameter of the deposited porous glass preform 13 was 200 mm, the outer diameter of the contracted preform 12.22 was 115 mm, and the outer diameter of the obtained transparent glass was 85 mm. Further, when the fluorescence intensity of the quartz glass obtained from the transparent vitrified base material by the ultraviolet irradiation was measured, it was 0.5, and a synthetic quartz glass with almost no fluorescence was obtained.

[Effects of the Invention] As described above, according to the present invention, in the method of converting a porous glass base material on which glass fine particles are deposited into transparent vitrification,
By reducing the structural defects in quartz glass, it has the excellent effect of emitting almost no fluorescence even when irradiated with short wavelength ultraviolet rays, and in particular, it reduces transmission loss caused by structural defects in optical fibers that transmit light energy. The effect of making it possible to minimize the amount of damage is also recognized.

In addition, by enlarging the vacuum furnace for transparent vitrification, it is possible to convert multiple porous glass base materials into transparent vitrification at once, and by not using expensive helium gas, synthetic quartz can be produced. This has the effect of contributing to reducing the cost of glass.

[Brief explanation of drawings]

Figures 1 and 2 are explanatory diagrams of an embodiment of the method of the present invention, and Figure 3 is an illustration of an embodiment of the method of the present invention.
The figure is a graph showing the relationship between oxygen partial pressure and fluorescence intensity, and FIG. 4 is an explanatory diagram of the conventional method. 1 , 11・ 2 ・ ・ ・ ・ 3, 13・ 4, 14・ 5, 15・ 6, 16・ 12, 22・ 21 ・ ・ 23・ ・ 24・ ・ ・ 25・ ・ ・ 26・ ・ ・ ・- Quartz glass seed rod - Transparent vitrified portion of porous glass base material - Porous glass base material - Electric furnace for transparent vitrification - Burner for synthesis - Glass raw material supply system - Shrink base material - Carbon electric furnace・Carbon stand, carbon heater, rotary pump, vacuum pump! Zutsu? Figure Figure Figure O7l 0 Ozzude & (%) City Map

Claims (3)

[Claims] (1) Silicon chloride for glass raw materials, hydrogen gas, oxygen gas, and inert gas are supplied to a burner, glass particles are generated by flame hydrolysis reaction, and the particles are deposited on the starting member to form a porous glass base material. In the quartz glass manufacturing method of forming transparent quartz glass from the porous glass base material, the porous glass base material is heated at a temperature in the range of 1200 to 1350°C lower than the transparent vitrification temperature to shrink. After that, the pressure is 30 Torr.
1350℃ or less in an atmosphere with an oxygen partial pressure of 1% or less
A method for producing quartz glass, which is characterized by producing quartz glass that becomes transparent at a temperature above and has few structural defects. (2) Quartz glass characterized by extremely low intensity of fluorescence emitted by ultraviolet irradiation. (3) Claim 2 characterized in that the wavelength of the irradiated ultraviolet rays is 254 nm and the wavelength of the fluorescence is about 650 nm.
Quartz glass as described.