JPS6158818A - Silica glass manufacturing method - 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 quartz glass by a sol-gel method.

[Conventional technology]

In the conventional quartz glass production using the sol-gel method using alkyl silicate and finely powdered silica as the main raw materials, there is no centrifugation treatment during the process, or even if it is included, there is no centrifugation treatment during the process. No particular consideration was given to the state of the sol at that time.

[Problem that the invention seeks to solve]

However, in the above-mentioned conventional technology, if there is no centrifugation treatment during the sol preparation process, large particles with insufficient dispersion and agglomeration and large particles with high impurity content remain in the sol, and these particles remain after sintering. may cause foreign matter (crystals, bubbles, etc.) in the glass. Furthermore, even if centrifugation is used, the sol state during centrifugation is not taken into consideration, resulting in problems such as poor separation efficiency and uneven sol state after treatment, making it difficult to determine the sintering conditions for the post-process. has.

Therefore, the present invention aims to solve these problems.
The purpose of this is to more effectively remove agglomerated particles that cause foreign matter in the glass after sintering and large particles that are highly toxic to anastomoses from the prepared sol, and to improve the sol state after treatment. The object of the present invention is to provide a centrifugal separation method that keeps the amount constant.

[Means to solve problems]

The centrifugation step of the present invention limits the state of the sol before and during the centrifugation step. ・Centrifugation of the sol is carried out while maintaining the sol temperature at 1.r3 to 501.
■ When the sol temperature is maintained at 10 to 50°C, the viscosity of the sol is 10°C or less, ■ There is no particle force of 1 μm or more in the sol before the centrifugation process. Effect: The particle diameter that can be separated by centrifugation is determined by the rotation speed, radius of rotation, sedimentation distance, particle density, dispersion medium density, dispersion medium viscosity, and time. Among these factors, the viscosity of the dispersion medium, that is, the viscosity of the sol, varies depending on the temperature and the degree of aggregation of 5t(oH)+ in the hydrolyzed solution of ethyl silicate. Viscosity alone is difficult to limit because it is affected by temperature and degree of polymerization. Therefore, in the present invention, by setting the temperature range, the degree of polymerization and the viscosity of the dispersion medium are kept constant.However, by the dispersion process before centrifugation, a dispersed state is created in which no particles larger than 1 μm are present. This is to keep the concentration of fine powdered silica in the sol constant.

〔Example〕

Commercially available ethyl silicate (Si (OKg),) 330t
When nfL and 0.02NH01155mK were mixed and stirred vigorously, a homogeneous and transparent solution was formed within 30 minutes due to a hydrolysis reaction. Further, when H, o i 5smA was added to the solution, the solution initially became cloudy, but became uniformly transparent after stirring for about 20 minutes. 112.5f of finely powdered silica (trade name: Aerosil 0X5QCDaqq%j4 Company) was added to the solution.
Added, stirred for 2 to 3 hours, and irradiated with ultrasonic waves (combined with stirring) 2
After 5 hours, the appearance became a uniform white sol. The ultrasonic irradiation was carried out for 2 to 5 hours until there were no particles larger than 1 μm in the sol. A particle size distribution measuring device was used. Alternatively, a similar white sol could be prepared by mixing the above raw materials at the same time and performing the same dispersion treatment.

The temperature of the sol prepared as described above was adjusted as shown in the table below, and the next step of centrifugation was carried out. As can be seen from the table above, the temperature dependence of the viscosity of the sol is not significant.

This is because the degree of progress of the hydrocondensation reaction of 81(OH)4 in the sol has a large effect on the viscosity of the sol.
The degree of polymerization varies depending on the sol preparation time and thermal history up to the centrifugation step. Therefore, even if the sol temperatures are the same, there will be a large difference in viscosity. The centrifugation conditions were 500 rpm and 20 minutes. After centrifugation, 0.1N ammonia water was added dropwise to each sol while stirring, and the pH value was adjusted to 3 to 5. Each of these sols was put into a polypropylene container 6001 having a size of 36 x 2 ax 12 cc + n), and the container was covered with a lid to form a gel in an airtight state. After gelation of each sol, at the point when it starts to shrink, the container is changed to one with holes of a predetermined porosity in order to adjust the drying speed, and placed in a dryer at a heating rate of 5°C / hr to 60°C to 80°0, then shrink and dry at this temperature for 7 to 10 days, depending on the conditions during centrifugation, but the size will increase to 24.5 to 25.5.
)X (18,5~20.0)X (0,35~o
, s s ) [Cm':L dry gels were obtained. These dried gels were put into a sintering furnace, heated and sintered using a prescribed heating method, and heated to 1300°C (5 to 120 minutes) to form a transparent gel. Size 1a, o ~ 19o) x (14, o ~ 1s, o) x
(o, so ~0.~50) [cm] A glass body with a weight of around 1757 was obtained. The following table shows the sintering time (
(holding time at 1300°C until it becomes transparent) and defects inside the glass (crystals, dust, bubbles). As can be seen from this table, it can be seen that there are quite large differences depending on the centrifugal processing conditions, but under the processing conditions of the present invention, the sintering time is constant and glass of the same level of high quality can be obtained. It was done. The results of various physical property analyzes regarding these glasses were consistent with fused silica glass, including Vickers hardness of 800 S/2, specific gravity of 2.2, infrared absorption spectrum, near-infrared absorption spectrum of 1, and refractive index for all sub-pulls.

〔Effect of the invention〕

In this way, by limiting the sol state during centrifugation during the sol preparation process, the quartz glass produced according to the present invention can be prevented from causing foreign matter in the prepared sol and in the glass after sintering. Large agglomerated particles and large particles with a high impurity content can be efficiently removed, and the sol state after treatment remains almost constant, resulting in a glass of stable quality and of a high standard.

Additionally, it has the great advantage of being able to be manufactured at considerably lower cost than the melting method. Therefore, not only in fields where quartz glass has been used up until now, but also in terms of quality, as quartz glass with high purity and few defects can be easily manufactured, photomask substrates for process 0, We believe that its application will expand to a variety of fields, including as base materials for optical fibers.

Claims (3)

[Claims] (1) In the production of quartz glass by the sol-gel method using alkyl silicate and finely powdered silica as the main raw materials, centrifugation of the sol is performed while maintaining the sol temperature at 10 to 50°C during the sol preparation process. A method for producing quartz glass characterized by: (2) The method for producing quartz glass according to claim 1, wherein the viscosity of the sol is 100 centipoise or less when the sol temperature is maintained at 10 to 50°C. (3) The method for producing quartz glass according to claim 2, wherein the sol before centrifugation contains no particles of 1 μm or more.