JPH03187935A - Manufacturing method of quartz glass body - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for producing a quartz-based glass body having a refractive index distribution.

[Prior Art] A sol-gel method using a metal alkoxide is known as a method for producing quartz glass having a refractive index distribution that is conventionally used for rod lenses and the like.

This method first uses silicon alkoxide, which is the quartz component that is the main component of glass, and a metal alkoxide other than silicon, which is the component for forming the refractive index distribution.
Water is added to an alcohol solution of these metal alkoxides to perform a sol-gel reaction by hydrolysis and condensation of the alkoxides, thereby creating a jelly-like wet gel that is porous and contains water and alcohol inside.

Next, when the wet gel is immersed in an aqueous solution of an acid such as hydrochloric acid, a part of the metal component forming the refractive index distribution is eluted out of the gel based on a diffusion mechanism, and a concentration gradient is formed within the wet gel. . By drying the wet gel to obtain a dry gel and sintering this at 1200° C. or higher, a doped quartz glass having a refractive index distribution can be obtained.

[Problems to be Solved by the Invention] The above-mentioned conventional technology has the problems that cracks are likely to occur during gel drying and sintering, and that fine bubbles are bombarded with each other in the glass after sintering. Ta.

In recent years, the demand for glass with good optical properties has increased, and the demand for glass that is free of cracks and bubbles has become stronger.
Preventing the occurrence of such cracks and bubbles has become extremely important.

The occurrence of the cracks and bubbles described above is considered to be due to the non-uniformity of the microstructure of the gel, which is a porous body.

An object of the present invention is to provide a method for producing a quartz-based glass body having a refractive index distribution free from the above-mentioned cracks and bubbles.

[Means for Solving the Problems] The present invention has been made to achieve the above object, and the gist thereof is as follows.

A gel produced by a sol-gel reaction is treated with an acid using a solution containing silicon alkoxide and a metal alkoxide other than silicon to partially elute the metal alkoxide other than the silicon alkoxide, and the resulting gel is dried. A method for producing a quartz-based glass body including a sintering step, wherein the water used in the step is ultrapure water with a specific resistance of 16 MΩam or more.

In the present invention, the specific resistance of the water used is 16 MΩcm.
If it is lower than this, it is not preferable because it contains a large amount of inorganic or organic impurities and the fine structure of the gel formed by the sol-gel reaction becomes non-uniform, making cracks and bubbles more likely to occur during drying and sintering.

[Operation] The occurrence of cracks and bubbles in quartz glass by the above-mentioned sol-gel method is thought to be due to the non-uniformity of the microstructure of the gel, which is a porous body.

According to the study results of the present inventors, it is considered that inorganic or organic impurities in the pure water used in the manufacturing process affect the non-uniformity of the microstructure of the gel. In the present invention, the amount of impurities is regulated by the value of specific resistance,
The object of the present invention can be achieved by using water having the above specific resistance.

3- [Example] The present invention will be specifically explained with reference to Examples.

Ti(0-n-C,H,)4: 5i(QC)(, ),
:H,O: n-C3H7011 ratio is 0.0 in molar ratio.
A silica sol dispersion is prepared by mixing 2=0.8:4:4.

Next, the silica sol dispersion was put into a glass tube with an inner diameter of 15 mm, and the tube was sealed and left at room temperature for 3 days to obtain a gel body.

The above gel body is metal alkoxide S i (OCH,)4
It is an incomplete structure with a glass network produced by insufficient hydrolysis and condensation reaction of and T i (0-n-C4IL)4, and contains water and n-C3H70H.

The gel body is taken out from the glass tube and immersed in a 5% hydrochloric acid aqueous solution for 20 hours to elute metal components other than Si, that is, part of the Ti component, from the incomplete network structure consisting of Si components and Ti components. Provide a concentration gradient to the Ti component inside the gel body 9 Next, the gel body is immersed in water to be washed to remove the hydrochloric acid component.

The gel body obtained above was dried and sintered at 1200° C. or higher to produce a transparent glass body with a diameter of 5 mmφ and a length of 800 mm.

In all of the above steps, ultrapure water with a specific resistance of 16 MΩcm was used as the silica sol dispersion, 5% aqueous hydrochloric acid solution, dehydrochloric acid removal, washing, etc.

For comparison, the case where the ultrapure water was used and the specific resistance of 8 M
1 for each case using pure water of Q cm
0 transparent glass bodies were prepared in the same manner, and the occurrence of cranks and bubbles was examined.

As a result, when ultrapure water with a specific resistance of 16 MΩcm was used, no cracks were observed and only one bubble was observed. On the other hand, resistivity 8M
When using Ωem pure water, 3 had cracks and 8 had bubbles, and only 1 had neither cracks nor bubbles. there were.

Note that the refractive index distribution in the radial direction of the transparent glass body is not affected by the above-mentioned difference in resistivity of water, and in graph 1, the distance from the outside to the center is plotted on the horizontal axis, and the refractive index of each part is plotted on the vertical axis. When plotted, it showed a linear concentration distribution.

In this example, a case was shown in which methoxide was used as the metal alkoxide, but metal alkoxides such as ethoxy, propoxy, butoxy, etc. can also be used.

Further, as metal alkoxides other than alkoxysilane, metal alkoxides such as germanium, zirconium, tantalum, etc. may be used in addition to titanium.

Furthermore, as the eluting acid aqueous solution for forming a refractive index distribution in the sintered glass body, an aqueous solution of sulfuric acid, nitric acid, hydrofluoric acid, etc. can be used in addition to hydrochloric acid.

[Effects of the Invention] According to the method of the present invention for manufacturing a quartz-based glass body by a metal alkoxide sol-gel method using ultrapure water with a specific resistance of 16 MΩcm or more, a glass body without cracks or bubbles caused by drying and sintering can be produced. Therefore, it is possible to provide a quartz-based glass body with excellent optical properties.

Claims (1)

[Claims] 1. Partial elution of metal alkoxides other than silicon alkoxides by acid-treating a gel produced by a sol-gel reaction using a solution containing silicon alkoxides and metal alkoxides other than silicon alkoxides. , a method for producing a quartz-based glass body including a step of drying and sintering the obtained gel, wherein the water used in the step is ultrapure water with a specific resistance of 16 MΩcm or more. manufacturing method.