JPH0551540B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for producing glass.
One aspect of the present invention relates to a method for producing glass by a sol-gel method.

[Conventional technology]

Currently, the methods for producing optical fiber preforms include SiC ₄
The mainstream method is to introduce glass particles into a flame, deposit glass particles on a target, and sinter the resulting glass porous body to obtain a glass lump.
This is an excellent method for obtaining high-purity porous glass at a relatively low cost. However, since this method is a gas phase reaction, it has the disadvantage that the substances that can be used as additives are limited to those that can be gasified.

Therefore, in recent years, Si
A method of obtaining transparent glass by hydrolyzing a metal alkoxide mainly containing silica gel or silica gel containing additive elements, drying the silica gel, and performing a nonporous treatment, etc. is being actively researched.

For example, after a Si alkoxide such as silicon tetramethoxide is thoroughly stirred and mixed with ethanol, water is added and further stirred to hydrolyze it. At this time, it is preferable to add a pH adjuster such as ammonia to the water. Particles begin to precipitate with the start of the hydrolysis reaction, and the reaction solution is transferred to a container coated with silicone on the inside, covered with aluminum foil, etc. to prolong the drying time, and placed in a constant temperature bath at, for example, 60°C. By keeping the sol solution gelled and the gel dried. The gel shrinks as it dries, and drying is usually completed after several days. A method is already known in which the gel thus obtained is taken out and subjected to a porosity treatment such as heating in an oxygen-containing He atmosphere to turn it into transparent glass.

In such a so-called sol-gel method, since alkoxides can be prepared for many metal elements, various substances can be easily added. Another advantage is that glass with extremely high uniformity can be obtained. However, on the other hand, it also has the disadvantage that the gel tends to crack when drying.

In order to prevent such cracking during drying and sintering, the present inventors have already proposed a method in Japanese Patent Application No. 13538/1983, in which particles of a size that cannot be turned into colloids are added to the sol solution. Japanese Patent Application No. 60-96676 describes a product in which a powder containing a glass raw material is mixed with a sol liquid so that the sol liquid contains a thickener and glass raw material particles with a particle size of 1 micron or more. We have proposed a gelling method, and each method is highly effective.

[Problem that the invention seeks to solve]

However, although the gels made by the above two methods are effective in preventing cracking during drying and sintering, the gels made by these methods have large gap diameters and are not uniform on the order of submicrons. This may be undesirable in applications where high performance is required, such as when manufacturing microscopic optical components such as planar waveguides and rod lenses using the sol-gel method. It also becomes difficult to mask with photoresist.

The object of the present invention is to obtain a gel that is hard to crack when drying and has a high degree of uniformity, thereby providing a method for efficiently producing highly uniform glass without foaming during sintering. be.

[Means for solving problems]

The present invention provides a gelatinable sol solution containing silicon alkoxide as at least one of the raw materials.
After mixing particles with a size of 0.005μ or more and 0.5μ or less and small enough to be in a colloidal state, the sol solution is gelled and the resulting gel is dried,
The above object is achieved by a method for manufacturing glass characterized by sintering the dried gel.

The present inventors have already proposed in Japanese Patent Application No. 59-192581 to add about 0.5 to 20 mol % of colloidal particles to the solution during or before hydrolysis of the alkoxide. Further investigation into why the bulk density could be controlled by dispersing colloidal particles in this way revealed that colloidal particles serve as the core of oxides that precipitate due to hydrolysis of alkoxides, resulting in a gel that is difficult to break. I knew I could do it.

In the present invention, the colloid particles may be added after hydrolysis has been completed as long as the sol solution is not gelled, and the amount of colloid particles is preferably approximately 100 mol% or more of the alkoxide. This invention differs from the above invention in this respect. More essentially, in the present invention, colloidal particles exist in the gel regardless of hydrolysis, so that the gap size of the gel can be increased within a range that does not impair uniformity, and it is difficult to crack due to strain during drying. This is what gives you the gel.

If the diameter of the colloid particles added at this time is small,
Since it is less effective in preventing cracking, a particle size of 0.005μ or more is required. If the particle size is large, the gap size will become larger and the effect of preventing cracking will increase, but uniformity will be impaired. In order to obtain a highly uniform gel that is hard to crack during drying, which is the objective of the present invention, the particles are preferably small enough to form a colloid, and have a diameter of 0.5 μm or less. It is also preferable that the particles have an appropriate thickening effect.

For the above reasons, the particles have a particle size of 0.05μ or more, which is small enough to be in a colloidal state, and a particularly preferable particle size is 0.005μ or more and 0.5μ or less.

Also, the amount of particles added depends on the concentration of alkoxide,
Although it varies greatly depending on the particle size, composition, OH group density, and other conditions of the particles to be added, it is generally preferable to add 100 mol% or more of the glass component made of alkoxide as a raw material. Mixing as much powder as possible to prevent further mixing often yields favorable results.

The components of the particles used in the method of the present invention may be any glass raw material. For example, SiO ₂ or SiO ₂
A material obtained by adding an oxide such as Ge, P, A, Ti, Zr, Sn, Pb, or Cs to the material can be used, but the material is not limited thereto.

In the present invention, at least one of the raw materials is a silicon alkoxide, such as silicon methoxide, ethoxide, etc., and this is hydrolyzed to obtain silica gel or silica gel containing additive elements, but the hydrolysis conditions are not particularly limited. For example, add water after mixing with ethanol. Alternatively, a method such as adding water to which ammonia or the like as a PH adjusting agent is added is used. Further, the obtained gel may be dried and sintered using a conventional method.

In the present invention, the above-mentioned raw material containing at least silicon alkoxide may include other alkoxides other than silicon alkoxide, such as Ge, B,
Alkoxides such as P, A, Ti, Zr, Sn, etc. may be added. Further, various dopant elements may be included in the sol liquid in a form other than alkoxide, for example, in the form of an aqueous salt solution.

After the particles are mixed into the sol solution, the sol solution is dried by a conventional method to form a dry gel.

By imparting a dopant distribution to the thus obtained gel and sintering it, various microscopic optical components can be obtained. Examples of micro optical components include optical circuits such as planar waveguides, rod lenses, and the like.

For example, the steps for manufacturing a planar waveguide according to the method of the present invention are as follows. The gel on the flat plate obtained by the method of the present invention described above is impregnated with alcohol, and then immersed in an alcohol solution of Ge alkoxide for several tens of seconds. This creates a layer containing Ge alkoxide on the surface. By soaking this in water diluted with alcohol, the surface Ge
The alkoxide causes hydrolysis, and a layer containing GeO ₂ is formed on the surface of the gel. Let this dry,
A planar waveguide can be obtained by sintering and etching. By creating a pattern on a flat gel using photoresist and performing the above steps, a recessed waveguide can be obtained, eliminating the need for etching.

Further, the steps for manufacturing a rod lens according to the method of the present invention are, for example, as follows. The rod-shaped gel obtained by the method of the present invention is impregnated with a CsNO ₃ aqueous solution. This is soaked in an aqueous solution of H ₃ BO ₃ for several minutes to obtain a gel in which the CsNO ₃ concentration gradually decreases and the H ₃ BO ₃ concentration gradually increases toward the periphery. This is vacuum dried and sintered to dry at low temperatures and in a short time. As a result, a rod lens having a refractive index distribution in the radial direction is obtained.

The gel obtained by the present invention does not easily crack during drying or doping, has high uniformity, and can easily create a precise dopant distribution. Therefore, it is particularly suitable for manufacturing the above-mentioned micro optical components.

The glass produced according to the present invention is not limited to a lump, but may also be in the form of a film or fiber. For example, if the sol obtained according to the present invention is applied onto a glass substrate and then dried, a gel film with a thickness of several microns or more can be obtained. If this is sintered, a glass film with a thickness of several microns or more can be obtained. With a sol solution that uses only alkoxide as a raw material and does not contain powder as in the present invention, it is difficult to create a film of 1μ or more using the same method because the film will break.

〔Example〕

The method of the present invention will be specifically explained below using Examples and Comparative Examples.

Example 1 1/8 mole of Si(OCH ₃ ) ₄ and 1/2 mole of ethanol were mixed using a magnetic stirrer, and 1 mole of 1.9% ammonia water containing 1/50 mole of boric acid was added to the mixture. Mixed. Put this in a mixer
40 g of silica particles (commercial product, trade name Aerosil OX-50) with a particle size of about 0.05 μm were added and stirred vigorously. This was transferred to a beaker, degassed at a pressure of about 60 Torr, and then placed in a pipe with an inner diameter of 10 mmφ.

After gelling at room temperature, it was extruded in water and dried on aluminum foil at room temperature. 500 of this
After calcination in ℃ air and sintering in He at 1450℃,
I was able to get the glass without breaking it.

Example 2 A dry gel was obtained in the same manner as in Example 1, except that 40 g of the powder attached to Matsufuru during VAD soot application was used as colloidal particles, no boric acid was added to the raw materials, and aqueous ammonia was reduced to 0.3%. This gel
After calcining at 900°C, the gel was impregnated with a 10% boric acid aqueous solution and dried again. Calcining at 900°C was performed to prevent cracking when impregnated with boric acid aqueous solution.
The thus obtained gel was calcined in air at a temperature of 500°C and then sintered in He at 1450°C to obtain glass without cracking.

Example 3 15 g of silica particles (commercially available under the trade name Aerosil) with a particle size of approximately 0.012μ as colloid particles
10 mm in the same manner as in Example 1 except that the amount of boric acid was 1/100 mol and the aqueous ammonia was 1%.
A gel in a φ pipe was obtained.

This gel was extruded in water, half was placed in a 20 mm diameter pipe to slowly dry it, and the other half was placed on aluminum foil and both were dried at room temperature. The former dried without cracking, was calcined in air at 500°C, and then sintered in He at 1450°C to obtain glass. The latter cracked during drying, but the pieces were relatively large, measuring about 4 to 5 mm.

Comparative Example 1 Example 3 except that no silica particles were added
I did the same thing. The material dried in a 20mmφ pipe contained cracks and foamed when sintering was attempted. When dried on aluminum foil, the pieces were small, about 1 to 2 mm in size.

Example 4 A plate of fluorine-containing quartz glass (refractive index 1.453) was immersed in the sol solution obtained in the same manner as in Example 1, pulled up, placed in a shear dish, covered with a lid, and slowly dried. After calcining this in air at a temperature of 500℃,
The material was sintered in He at 1450°C, and the resulting material was sintered in an oxyhydrogen flame to obtain a transparent glass film. This film thickness is
The thickness was about 50μ, and it could be used for applications such as planar waveguides.

Comparative Example 2 A fluorine-containing quartz glass plate was immersed in the sol solution obtained in the same manner as in Comparative Example 1, pulled up, placed in a shear dish, covered with a lid, and slowly dried. The resulting gel film had a thickness of about 0.3μ. When the gel film was soaked in a sol solution and dried twice to increase the film thickness, the gel film was cracked.

Example 5 The gel obtained in Example 2 was polished into a plate shape and then heated to 900°C.
It was calcined in After impregnating it with ethanol, it was immersed in a 3% ethanol solution of Ge(OC ₂ H ₅ ) ₄ for 30 seconds, and then immediately immersed in ethanol for 1 second. Furthermore, add 13% ammonia water to 20g of 50% aqueous solution of ethanol.
I added the drops and left it for 60 minutes. After taking it out and drying it, it was impregnated with a 10% boric acid aqueous solution and dried again. After calcining this in air at 500℃
A planar waveguide base material with a high refractive index layer on the surface was obtained by sintering in He at 1450℃.

Example 6 The calcined gel obtained in the same manner as in Example 5 was masked with a photoresist, a groove with a width of about 30 μm was cut, and then ethanol was impregnated. Example 5 below
A channel-type planar waveguide was obtained in the same manner.

Comparative Example 7 Silica particles were granulated by mixing 120 g of silica particles with a particle size of about 0.012 μm and 300 g of water using a mixer, and then drying the mixture using a drier.

Mix 1/8 mol of Si(OCH ₃ ) ₄ and 1/2 mol of ethanol in a magnetic stirrer, and add 0.3%
After adding 1 mol of ammonia water and further mixing, this was placed in a mixer. 25g of granulated silica particles were added to it and stirred vigorously. This was transferred to a beaker, degassed at a pressure of about 60 Torr, gelled in a pipe with an inner diameter of 10 mm at room temperature, extruded in water, and dried on aluminum foil. An attempt was made to polish this gel into a plate shape and mask it with photoresist, but the gap was so large that the photoresist soaked into the gel and could not be masked.

(Effects of the Invention) The method of the present invention makes it possible to obtain a gel that is difficult to crack during drying, difficult to foam during sintering, and has high uniformity, thereby making it possible to efficiently manufacture highly uniform glass. Has excellent effects.

Claims (1)

[Claims] 1. Particles having a particle size of 0.005μ or more and 0.5μ or less and small enough to be in a colloidal state are mixed into a gelatable sol solution in which at least one of the raw materials is silicon alkoxide, and then the sol solution is gelled. A method for producing glass, which comprises: drying the resulting gel; and sintering the dried gel.