JPH0822749B2 - Glass manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of use] The present invention relates to an optimum production method for obtaining a large size and high quality glass by a sol-gel method.

[Conventional technology]

Heretofore, some examples of a method for producing quartz glass by the sol-gel method have been reported. ((1) Nogami, Nakatani et al. Journal
of Non-Crystalline Solids, 37, 191 (1980)
(2) Ravi-Novich et al., Journal of Non-Crystallin
e Solids, 47, 435 (1982) (3) Toki et al.
-237577) Among them, the method of Toki et al. Is a porous material prepared by uniformly dispersing ultrafine silica powder in a hydrolyzing solution of a metal alkoxide, and using a sol prepared by adjusting the pH value of the dispersion liquid to 3 to 6. Since it has a process of sintering a dry gel, it is possible to produce a large-scale quartz glass (for example, 15 × 15 × 0.5 cm) that is difficult to produce with the other two examples with good yield. It can be said that this is the best manufacturing method.

[Problems to be solved by the invention]

However, in the conventional manufacturing method of Toki et al., The silica glass obtained after sintering is liable to contain impurities such as metal ions, crystals, bubbles, and foreign matters of indefinite shape. There is a problem in quality when it is used for applications requiring particularly high quality, such as a photomask substrate for use.

Therefore, the present invention is to solve such a conventional quality problem, and its object is to remove impurities such as metal ions,
It is an object of the present invention to provide a method for producing a homogeneous and high-quality glass free from crystals, bubbles, and irregular shaped foreign matter.

[Means for solving problems]

The present invention is a sol containing an alkyl silicate as a main raw material.
In the method for producing glass by the gel method, (1) a first solution in which a first silica component obtained by hydrolyzing an alkyl silicate with a basic catalyst is dispersed,
A first step of preparing a wet gel by gelating a sol prepared by mixing a second solution having a second silica component obtained by hydrolyzing an alkyl silicate with an acidic catalyst to prepare a wet gel; The method has a second step of drying the wet gel to produce a dry gel, and a third step of sintering the dry gel to produce a transparent glass body, and the first step satisfies all of the following conditions: It is characterized by

a) The concentration of the first silica component in the first solution is 0.05.
Must be g / ml or higher.

b) Mixing the first solution and the second solution in a ratio of silicon in each solution in the range of 20:80 to 95: 5.

c) The effective silica component in the sol must be 0.10 g / ml or more.

d) Gelation after adjusting the PH value of the sol to a predetermined value of 3 or more.

e) Purifying the raw materials of the first solution and the second solution by distillation.

f) The sol is filtered at least once with a filter having a pore size of 100 μm or less.

g) Perform the preparation of the first solution, the preparation of the second solution, and the adjustment of the sol in an atmosphere of cleanliness class 100 or less.

h) Subjecting the sol to a centrifugal force of 50 to 10,000 G and using the supernatant thereof, or subjecting the sol to a reduced pressure treatment at least once during the step before gelation.

(2) The second step in (1) above is characterized in that at least one of the following conditions is satisfied.

a) Perform in a container with a porosity of 10% or less.

b) To reduce the porosity of the drying container at the beginning of the rate-decreasing drying period or at the end of the constant-rate drying period. c) The contact surface of the drying container with the sol is made of a hydrophobic material or the surface tension of the sol. Use a material with a small critical surface tension.

d) The contact surface of the drying container with the sol is smooth.

e) Heating from room temperature to a temperature in the range of 40-160 ° C at a heating rate of 120 ° C / hr or less.

(3) At least part of the second step in (2) above is 40-
It is characterized by being kept at a constant temperature in the range of 160 ° C.

(4) After maintaining at a constant temperature in the second step in (2) above, lower the temperature by 3 to 30 ° C. at the beginning of the rate-decreasing drying period or at the beginning of the constant-rate drying period, and then maintain at the above-mentioned constant temperature. Is characterized by.

[Action]

According to the present invention, since a high-purity liquid raw material can be selected as a raw material, essentially high-quality glass can be produced without impurities such as metal ions, dust, dust, and other foreign substances. More specifically, the means for solving the problems, b to g and the second to fourth items, are the wet gel preparation of the composition which is hard to break in the drying step, and the composition which is hard to break in the sintering step. The wet gel preparation, the porous dry gel preparation which is hard to break in the sintering step, the aging and drying method for preparing the dry gel with a good yield, and the like are the conditions such that a large-sized glass can be produced economically with a good yield. In addition, by means of a, hp described in the first aspect of the means for solving the problems, impurities such as metal ions, crystals, bubbles, and foreign matters having an irregular shape are extremely less than those of the conventional ones. For example, it is possible to easily produce high-quality glass that can be used for applications requiring particularly high quality, such as photomask substrates for ICs. Therefore, by combining the conditions of the first and second means for solving these problems, extremely high quality glass can be manufactured more stably and with high yield.

〔Example〕

Various conditions relating to the production of large-sized high-quality glass were confirmed in the following examples.

Preparation of First Liquid Table 1 shows the distilled and purified ethyl silicate, distilled and purified ethanol, distilled and purified water, and the highest grade 29% aqueous ammonia for commercial electronics filtered by a membrane filter having a pore size of 0.2 μm. The mixture was mixed with the composition, vigorously stirred for 4 hours, and then left standing overnight in a cool dark place to grow silica fine particles. After concentrating the silica fine particle dispersion, the pH value was adjusted for stabilization, and the solution was filtered through a membrane filter having a pore size of 10 μm to prepare a first liquid.

The average particle diameters of the silica fine particles in the obtained first liquids A, B, and C were 0.15 μm, 0.25 μm, and 0.40 μm, respectively, as measured by a light transmission type centrifugal sedimentation particle size analyzer. It was

Preparation of the second liquid Distilled and purified ethyl silicate 18.9 and pore size 0.2 μm
0.02N hydrochloric acid filtered by a membrane filter
6.15 and 6.15 were mixed and vigorously stirred to carry out hydrolysis reaction to obtain a second liquid. The second liquid was prepared in a total of 3 batches in the same manner.

Preparation of sol Mix 1 batch of 1st liquid A and 2nd liquid, then pore size
A sol A was prepared by filtering with a 8 μm membrane filter.

In the same manner, 1 batch of the first liquid B and 1 batch of the second liquid were mixed and then filtered with a membrane filter having a pore size of 2.0 μm to prepare sol B.

Similarly, one batch of the first liquid C and one batch of the second liquid were mixed, and then filtered with a membrane filter having a pore size of 30 μm to prepare sol C.

The pH values and liquid temperatures of the above-mentioned Sols A, B, and C were almost the same, and were 4.5 and 20 ° C., respectively.

In addition, was performed in a clean room of cleanliness class 100. Further, by applying a centrifugal force of 50 to 10,000 G to the sol and using the supernatant thereof, or to subject the sol to a reduced pressure treatment at least once during the step before gelation, it is necessary to perform the treatment in the quartz glass. It is effective in reducing air bubbles, foreign substances, etc., and contributes to improving the quality of quartz glass.

Gelation-Drying Next, 900 ml each of the sol A is poured into 50 polypropylene containers (internal dimensions: 300 × 300 × 100 mm), and the lid is closed to gel to form 50 wet gels. did.

In the same manner, 50 wet gels were prepared from each of the sol B and the sol C.

The 150 wet gels obtained were then aged in a sealed state at 30 ° C for 3 days, then replaced with a lid having a 0.4% open area ratio and the temperature was raised from room temperature to 65 ° C. When it was held and dried, a stable dry gel which was not broken even when left in the air was obtained in the yield shown in Table 2 in 10 to 14 days. The porosity of the drying container may be reduced at the beginning of the rate-decreasing drying period or at the end of the constant-rate drying period. It is more preferable that the contact surface of the drying container with the sol is smooth.
Furthermore, regarding the heating rate, from room temperature to 120 ° C / hr or less
It is preferable to raise the temperature to a temperature in the range of 40 to 160 ° C.
Further, when the temperature is raised, it may be maintained at a constant temperature in the range of 40 to 160 ° C. After holding at a constant temperature, lower the temperature by 3 to 30 ° C at the beginning of the rate-decreasing drying period or the beginning of the constant-rate drying period.
After that, the temperature may be kept constant again.

Sintering The above three kinds of dry gel were put into a sintering furnace and the temperature rising rate was 30
The mixture was heated from 30 ° C to 200 ° C at a rate of ° C / hr and kept at this temperature for 5 hours, then heated to 300 ° C and kept for 5 hours for desorption water treatment. Then, from 300 ℃ to 700 at a heating rate of 30 ℃ / hr
After heating to ℃ and holding at this temperature for 20 hours, heating rate
Heat from 700 ℃ to 900 ℃ at 30 ℃ / hr, 10 at this temperature
The temperature was maintained, and the temperature was raised from 900 ° C to 1000 ° C at a heating rate of 30 ° C / hr, and the temperature was maintained for 10 hours to perform decarbonization, deammonium chloride treatment, and dehydration condensation reaction acceleration treatment.

After this, heating rate is 30 ℃ / hr while flowing He gas into the furnace.
It was heated up to 1250 ° C. and kept at this temperature for 2 hours to carry out a pore closing treatment.

Then, it was heated to 1400 ° C. at a temperature rising rate of 60 ° C./hr and kept at this temperature for 1 hour to make it non-porous, and a transparent glass body was obtained with a yield of 100%.

The results of physical property analysis of this glass body were all in agreement with those of quartz glass.

Polished both sides of the quartz glass obtained here 150 × 150 ×
A quartz glass plate of 2 [mm] was used.

The quartz glass plate produced in this example was of extremely high quality with no foreign matters such as bubbles. In addition, the spectral characteristics in the ultraviolet and visible regions were flat, which was a quality that could be used as a photomask substrate used in IC manufacturing.

〔The invention's effect〕

Thus, the glass produced according to the present invention comprises a solution in which fine silica particles, which are a hydrolysis reaction product of an alkyl silicate under a basic catalyst, are dispersed and a hydrolysis reaction solution of an alkyl silicate with an acidic catalyst, which are predetermined. In order to prepare a wet gel by gelating a high-purity sol prepared by mixing in a ratio and drying the wet gel to form a porous dry gel and then sintering the transparent glass, impurities such as metal ions, High quality glass with extremely few crystals, bubbles, and irregular shaped foreign matter can be produced.By using a means to prevent mixing of dust, foreign matter, etc., and a means to remove them, it is possible to stabilize the extremely high quality glass described above. Can be manufactured with high yield. Also Al, Ti, Ge, Na, Ca, Mg,
By adding various elements such as Li and Te at the time of sol preparation, it is easy to manufacture high-quality glass in a multi-component system with various compositions. That is, according to the present invention, 1) high purity, 2) no internal crystals, 3) no bubbles inside the glass, 4) no irregular foreign matter, and 5) large size. It has the effect of making it possible to provide high-quality glass that satisfies the requirements.

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Hirohito Kitabayashi Hirohito Kitabayashi 3-5 Yamato, Suwa City, Nagano Seiko Epson Corporation (56) References JP-A-60-215532 (JP, A) JP-A-59 -213638 (JP, A) JP 61-58818 (JP, A) JP 60-86037 (JP, A) JP 61-26521 (JP, A) JP 60-264335 (JP, A) ) JP-A 61-40825 (JP, A) JP-A 60-46933 (JP, A) JP-A 60-90834 (JP, A)

Claims (4)

[Claims] 1. A sol containing an alkyl silicate as a main raw material.
In the method for producing glass by the gel method, a first solution in which a first silica component obtained by hydrolyzing an alkyl silicate with a basic catalyst is dispersed, and a second silica component obtained by hydrolyzing an alkyl silicate with an acidic catalyst And a second solution having a predetermined ratio are mixed together to form a wet gel by gelling a sol, and a second step of drying the wet gel to form a dry gel
A third step of sintering the dry gel to produce a transparent glass body
And a step, wherein the first step satisfies all of the following conditions. a) The first silica component in the first solution should be 0.05 g / ml or more. b) Mixing the first solution and the second solution in a ratio of silicon in each solution in the range of 20:80 to 95: 5. c) The effective silica component in the sol must be 0.10 g / ml or more. d) Gelation after adjusting the PH value of the sol to a predetermined value of 3 or more. e) Purifying the raw materials of the first solution and the second solution by distillation. f) The sol is filtered at least once with a filter having a pore size of 100 μm or less. g) Perform the preparation of the first solution, the preparation of the second solution, and the adjustment of the sol in an atmosphere of cleanliness class 100 or less. h) A centrifugal force of 50 to 10,000 G is applied to the sol and the supernatant is used, or the sol is subjected to a reduced pressure treatment at least once during the step before gelation. 2. The method for producing glass according to claim 1, wherein in the second step, at least one of the following conditions is satisfied. a) Perform in a container with a porosity of 10% or less. b) To reduce the porosity of the drying container at the beginning of the rate-decreasing drying period or at the end of the constant-rate drying period. c) The contact surface of the drying container with the sol is made of a hydrophobic material or the surface tension of the sol. Use a material with a small critical surface tension. d) The contact surface of the drying container with the sol is smooth. e) Heating from room temperature to a temperature in the range of 40-160 ° C at a heating rate of 120 ° C / hr or less. 3. At least part of the second step is 40-160.
The glass manufacturing method according to claim 1, wherein the glass is maintained at a constant temperature in the range of ° C. 4. In the second step, the temperature is maintained at a constant temperature, and then 3 at the beginning of the rate-decreasing drying period or the beginning of the constant-rate drying period.
The method for producing glass according to claim 3, wherein the temperature is lowered to -30 ° C and then kept at a constant temperature.