JPS59213638A - Preparation of quartz glass - Google Patents

Abstract

PURPOSE:To obtain quartz glass of extremely high purity inexpensively by utilizing a fact that the starting material of the quartz glass in the sol-gel process is in a state of low viscosity in the midway of its prepn., and performing ion exchange treatment during the stage of low vicosity of the soln. CONSTITUTION:A soln. contg. fine SiO2 powder or silica sol obtd. by the hydrolysis of alkyl silicate is treated with an ion exchange resin to remove cations (e.g. Na<+>, K<+>, Al<3+>, etc.) contained as impurities in the soln. The treated soln. is then transferred to an appropriate vessel where it is evaporated and dried to obtain dry gel. Aimed quartz glass of high purity is obtd. by firing the dry gel.

Description

[Detailed Description of the Invention] The present invention relates to a method for manufacturing quartz glass, and more specifically,
(After performing an ion exchange treatment on a solution containing at least silicic acid fine powder or silica sol obtained by hydrolyzing alkyl silicate, the solution is evaporated and dried, and further fired and sintered to vitrify it. Concerning the manufacturing method of quartz glass.

Due to recent technological advances, very strict requirements have been placed on the materials used. For example, there are also demands for high temperature resistant materials and extremely low expansion materials. Quartz glass is well-known as a material that satisfies this requirement.

In addition, quartz glass is used as a substrate for photomasks in recent years, or as a polycrystalline S glass used in the light display section of LCD televisions.
i) It is attracting attention as a basis for transistor arrays.

Because quartz glass has such excellent characteristics, it is used in a variety of fields, and its fields of use are expected to continue to expand in the future.

However, the quartz glass currently in use has the disadvantage that it is very expensive because natural quartz is repeatedly crushed, washed, etc., and then treated at a high temperature of about 2000°C. Synthetic quartz glass also has the disadvantage of being more expensive because it requires a complicated process.

A silica glass manufacturing method called the sol-gel method has recently been proposed, which is cheaper than such conventional methods.

A simple description of this sol-gel method is as follows.

First, a suitable alkyl silicate) (Si(OR)4:
(R represents a suitable organic group) is hydrolyzed in water or aqueous alcohol. A catalyst such as a hydrolysis catalytic acid may also be used. In this way, silica sol is made. In some cases, a bath liquid in which finely powdered silica (Cabosil, manufactured by Cabot Co., Ltd.: Aerosil 2, manufactured by Nippon Aerosil Co., Ltd.; Nivsil 1, manufactured by Nippon Silica Co., Ltd.) may be used, or a bath liquid in which finely powdered silica and the above silica sol are mixed may be used. It's okay.

After the silica sol is produced in this way, it is dried to form a dry gel, which is then further dried and sintered to vitrify it.

The features of this method are as follows.

1. Using quartz as a raw material, it can be produced at a lower temperature than the high-temperature melting method, which is energy-saving.

2.11″1 Manufactured using easy raw materials, high purity glass can be obtained.

3. Highly homogeneous glass can be obtained because the raw material is a low viscosity solution.

When looking at each aspect individually, it has very excellent features. However, in order to obtain quartz glass of very high purity (low alkali content, low cations) using this method, it is necessary to use alkyl silicate that has been purified many times as a raw material, or to use finely powdered silica that has been modified in the process. Therefore, there is a drawback that commercially available raw materials cannot be used. For this reason, the resulting quartz glass may be more expensive than conventional glass.

SUMMARY OF THE INVENTION An object of the present invention is to provide an inexpensive quartz glass that does not have the disadvantage of scorching.

The present invention takes advantage of the above-mentioned sol-gel method to pass through a bath liquid state with low viscosity, which is a feature of the true gel method.
This solution is subjected to ion exchange treatment in this state to remove cations (Na'', which are impurities).

K+, At3+, etc.).
The outline is shown below.

First, a suitable commercially available alkyl silicate, such as ethyl silicate, is added to an aqueous solution containing (or not necessarily containing) alcohol (for example, ethanol) (which may contain hydrochloric acid, ammonia, etc. as a hydrolysis catalyst), and is stirred and mixed. Hydrolysis is carried out. After hydrolysis, a suitable ion exchange resin (SK-IB, produced by Mimari Kasei Co., Ltd.: Amberly; IR-120B, produced by Organo Co., Ltd.) is dispersed in this solution, and the mixture is stirred for an appropriate period of time. (After stirring, remove the resin by filtration. Alternatively, the sol solution may be passed through an ion exchange resin column. Pour the ion exchanged solution in this way into a suitable container and record the evaporation rate history. The dried gel is dried while stirring. By firing the dried gel obtained using an appropriate temperature increase program, the desired high-purity quartz glass can be obtained.

When using Yi powder, the silicic acid fine powder dispersion bath liquid may be subjected to the above ion exchange treatment, and the rest may be carried out in the same manner.

It is also conceivable that after hydrolyzing the alkyl silicate, Kei IW (:□12 powder) is dispersed in the swamp liquid, and then ion exchange treatment is performed, and the rest is carried out in the same manner.

In any case, the key point of the present invention is to perform ion exchange treatment in the solution state before gel solidification, and other operations can be modified in various ways, but are well known to those skilled in the art. .

According to the method using the ion exchange resin of the present invention, when using raw materials with good If such as Cabosil and Aerosil, the conventional method requires careful operation using special equipment to prevent the raw materials from becoming contaminated. , no careful manipulation is required. In addition, the price of hydrated silicic acid fine powder with many impurities such as nibzil is the same as anhydrous silicic acid fine powder (cabosil).

Although it is 1/6 to 1/10 cheaper than Aerosil), it has too many impurities and could not be used in the past, but it can now be used by the method of the present invention.

On the other hand, in order to increase the purity of ethyl silicate, it was necessary to synthesize it using high-purity silicon tetrachloride as a raw material and purify it by distillation several times using a special container (for example, made of quartz glass). According to this, this is no longer necessary.

As stated above, the method for producing quartz glass of the present invention is an excellent method that does not require the aforementioned complex treatments.The quartz glass obtained by the excellent method of the present invention is inexpensive and has high purity. (Base glass for IC photomasks and polycrystalline silicon for LCD TVs, which are expected to develop in the future due to their high quality)
Ranjista.

It can be used as a base for arrays, and it shows great potential as a material for conventionally used mj.

that's all

Claims (1)

[Claims] A method for producing quartz glass in which a solution containing at least silicic acid fine powder or silica sol obtained by hydrolyzing an alkyl silicate is evaporated to dryness to form a dry gel, and the resulting dry gel is fired and sintered to obtain glass. In,
A method for producing quartz glass, characterized in that a solution state before evaporation and drying is treated with at least an ion exchange resin.