JPS61186226A - Production of quartz glass - Google Patents

Abstract

PURPOSE:In sol-gel method using a metallic alkoxide and fine powder silica, to obtain high-quality quartz glass suitable as a parent material for optical fiber, etc. easily in improved economic efficiency, by adding a doping material to the fine powder silica. CONSTITUTION:Fine powder silica is previously blended with a doping material by a method to disperse the fine powder silica into ethyl alcohol, etc. and to blend the dispersion with the doping agent (e.g., germanium oxide powder) uniformly, etc. The fine powdery silica blended with the doping agent and a metallic alkoxide (e.g., ethyl silicate) as main raw materials are processed by sol-gel method, to produce quartz glass. Consequently, since the doping agent added is used as fine powder particles but not a metallic alkoxide, a uniform and high-purity sol solution can be easily prepared, so high-quality glass can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for manufacturing quartz fiber glass using finely powdered silica mixed with a dopant.

[Conventional technology]

As one of the manufacturing methods of quartz glass,
237577), a sol-gel method using finely powdered silica and metal alkoxide is known. Generally, in this manufacturing method, a sol solution obtained by mixing a hydrolyzed solution of a metal alkoxide and finely powdered silica prepared by various methods is subjected to a polycondensation reaction to prepare a gel that becomes a precursor of sintered glass. Next, this gel body is sufficiently dried and then sintered at a predetermined temperature to obtain a transparent glass body. Conventionally, in the sol-gel method using fine powder silica, fine powder particles were It is possible to easily obtain a high-quality, large-area, large-volume glass body, which has been difficult to achieve using the sol-gel method that does not use the method or other methods that involve melting.

[Problems that the invention attempts to solve]

In the conventional sol-gel method using finely powdered silica, a dopant in the form of a metal alkoxide is used to impart various characteristics to the resulting quartz-based glass. However, this method has the advantage that it is easy to mix the raw materials because the metal alkoxide used as the dopant is a liquid.
The following problems are pointed out.

(1) Many of the metal alkoxides used as doping materials are highly reactive, react quickly with minute amounts of moisture in the atmosphere, and easily decompose into oxides and the like. Therefore, it is difficult to handle.

(2) Because of its high reactivity, local reactions tend to proceed, and a homogeneous sol may not always be obtained.

(3) Since the doping material is a highly reactive metal alkoxide, the number of steps is large and complicated in order to suppress local heterogeneous reactions.

(4) Although there are some exceptions, metal alkoxides used as dopants are generally very expensive, so
In the sol-gel method, which tends to increase the cost of the product, the quality of the sintered glass body is the quality of the sol, that is,
It is extremely important to obtain a high-quality sol, as it greatly depends on the homogeneity, purity, and dispersibility of the particles. The present invention is intended to solve these problems, and its purpose is to use the doping material in the form of fine powder particles rather than in the form of metal alkoxide, thereby achieving higher quality than before. The aim is to easily prepare a sol solution and produce a sintered glass body with excellent functionality.

[Means to solve the problem]

In order to solve the above problems, the method for manufacturing silica-based glass of the present invention is characterized in that a dopant is mixed into finely powdered silica in a sol-gel method using metal alkoxide and finely powdered silica as main raw materials. do. Furthermore, at this time, one or more kinds of fine powders are physically mixed with the fine powder silica, or chemically dissolved in solid solution, or both are equally used as a doping material.

This manufacturing method can be applied to any type of glass that uses the sol-gel method using fine powder particles and metal alkoxide as raw materials, and is not limited to ordinary flat glass.
It is also very effective when manufacturing glass having a multilayer structure such as glass for optical fibers. Of course, it is clear that it can be applied to the production of all types of glasses, including not only quartz-based glasses but also other germanium-based, fluorine-based, chalcogenide-based, and nitride-based glasses.

〔Example〕

The present invention will be explained in detail below using the production of quartz glass as an example.

[Example 1] Purified commercially available ethyl silicate (trade name Nicol: +-
) 28, :ffruco-)K,ni,) 520.8
A hydrolysis solution (hereinafter referred to as solution A) was prepared by mixing and stirring f and a 0.02N hydrochloric acid solution iso, or, in about 1 hour.

Next, ultrafine silica particles (product name: Aerosil 0x50.
Nippon Aerosil Co., Ltd.) 150 f' was gradually added to 99.5% ethyl alcohol (Kanto Kagaku, Ni,) 300 i, 1 m, and after thorough stirring, ultrasonic waves were irradiated for 3 hours to uniformly disperse the silica ultrafine particles. Ta. Furthermore, in order to remove large particle size silica and foreign substances, centrifugation was performed under a centrifugal force of 500G.
A silica ultrafine particle solution (hereinafter referred to as solution B) was prepared by performing the following steps.

4 of Solution A and 4 of Solution B were mixed and stirred to become homogeneous, and then the hydrogen ion concentration (hereinafter referred to as PH value) of the mixed solution was adjusted to 5.6 using 02N ammonia water. A predetermined amount of this cladding solution was poured into a rotating cylindrical container made of vinyl chloride (inner diameter 40 ml, length 250 mm, inner surface silicated), and the cylindrical container was rotated at a speed of 1200 revolutions per minute using the apparatus shown in Figure 1. A cylindrical clad gel having a hollow portion in the direction of the rotation axis was obtained. Gelation time was approximately 55 minutes.

Next, 3.14 f/ of amorphous high-purity germanium dioxide powder (average particle size 0.13 μm) was added to solution B 115 for removal, stirred until it became sufficiently homogeneous, and then irradiated with ultrasonic waves for about 1 hour. The dispersibility of germanium oxide particles was improved. Thereafter, this solution and Solution A 115 were mixed and sufficiently stirred, and then the pH value of the solution was adjusted to 4.8 using 0.2N aqueous ammonia.

This core solution was poured into the cylindrical hollow part created during the production of the Talarad gel, and was applied at a rate of 2 min.
The gel was formed while rotating the cylindrical container at a speed of 0.00 rpm to obtain a cladding and core integrated gel. Gel time is approximately 28
It was a minute.

This clad/core integrated gel is packed in a polypropylene container (
600 x 250 x 150), and the aperture ratio is 0.
The top lid was covered with a number of holes with a diameter of 2%, and the gel was placed in a constant temperature dryer at 55°C for about 14 days to obtain a dried solid gel. This dried gel was heated to 850°C in an electric furnace with a silicon carbide heating element in an air atmosphere at a heating rate of 1°C/M, and at that temperature, chlorine gas was introduced using helium gas as a carrier, followed by oxygen gas. Water molecules, hydroxyl groups, organic molecules, etc. present in the dried gel were sufficiently removed. Thereafter, the gel body was made non-porous by heating again to 1650°C at a temperature increase rate of 1°C/- to obtain a transparent sintered body.

When the quality of the obtained transparent sintered body was examined, it was found that 1
The number of amorphous foreign particles of μm or larger and bubbles is less than one each per 0.1 al, and light scattering is extremely small, so it is believed that sufficient optical properties can be obtained when used as a base material for optical fibers. It was expected.

The optical fiber base material obtained by this method had the same high quality as the optical fiber base material obtained by the conventional manufacturing method (Organization N [L19205) using the dope material as a metal alkoxide. . Furthermore, since fewer steps are required compared to conventional manufacturing methods, yields can be further improved, and the raw materials used are inexpensive.
It was possible to easily obtain a low-cost, high-quality optical fiber base material.

[Example 2] Purified commercially available ethyl silicate (trade name! Covco)
2B, = + Leco) K, to) 1041.5r and 0.
02N hydrochloric acid solution was mixed and stirred to prepare a colorless and transparent homogeneous solution. Next, silicon tetrachloride and titanium tetrachloride were used as starting materials, and amorphous titanium dioxide was dissolved at a molar ratio of 4% using a vapor phase synthesis method to form an amorphous high-grade material with an average particle size of 0.13 μm. Pure silica particles were synthesized. The silica fine particles 304,5F were gradually added to the ethyl silicate hydrolysis solution, stirred for about 2 hours, and then irradiated with ultrasonic waves for about 4 hours to uniformly disperse the silica particles in the solution. Further, in order to remove large-sized silica fine particles that were not uniformly dispersed but agglomerated, centrifugal filtration was performed under a centrifugal force of 500 G to prepare an ultrafine silica particle solution (hereinafter referred to as a sol solution). The hydrogen ion concentration of this sol solution was 0.
Adjust the pH to 5.1 using 2N ammonia water,
Polypropylene container (150mm x 150++o
++X 70 mm) to a depth of about 10 degrees (approximately 220 mm), and after sealing the container to prevent liquid leakage, it was mounted on the rotating device shown in FIG. 3. Move the rotating device to 500G (G=980crn/B2
) The sol solution was gelled under centrifugal force to obtain a flat gel body having the shape shown in FIG. The time until gelation was approximately 95 minutes. This gel body was placed in another polypropylene container (300mm x 250mn x 150m).
), the gel was placed in a constant-temperature dryer at 55° C. with a lid on which a number of holes with a diameter of 1 W were made so that the opening ratio was 2%, and a dried gel was obtained in about 14 days. This dried gel was heated to 800° C. at a heating rate of 1° C./jth in an electric furnace with a silicon carbide heating element in an air atmosphere, and maintained at that temperature for 4 hours. Furthermore, chlorine gas using helium gas as a carrier,
Furthermore, water molecules remaining in the dried gel by flowing oxygen gas,
hydroxyl group.

Organic molecules etc. were removed. Thereafter, it was heated again to 1350° C. at a temperature increase rate of 1° C./cm to obtain a flat plate-shaped transparent sintered body.

Part of the sample surface crystallized due to external contamination during sintering, but most of the sample was a transparent glass body. When examining the quality of the obtained transparent glass body, it was found that there were amorphous foreign substances and crystals of 1 μm or more.

The number of microbubbles is 2 and 2 per 1 ct/1, respectively.
Individual.

It was of high quality with less than 0 pieces. The silica glass produced here containing several mol% of titanium dioxide is known as an extremely low expansion glass and hardly expands in the temperature range of 200 to -100℃ (it has even lower expansion than quartz glass, which is known for its low expansion). ). However, this type of glass has traditionally been produced using a melting method.
However, since it is very difficult to obtain large and uniform glass, the manufacturing cost is high, and therefore it has been used only in extremely limited fields. but,
By using the manufacturing method of the present invention, high-quality, large-area silica-titania glass can be manufactured at low cost, so it is highly anticipated that it will be used in fields such as the space industry, where future development is highly anticipated. .

As shown in the above examples, the method for producing quartz glass by the sol-gel method using dopants as fine particles is as follows:
Compared to the conventional case of adding dopants in the form of metal alkoxides, glass of the same or higher quality can be easily obtained with fewer steps. Here, examples have been shown using quartz glass as an example, but if the sol-gel method using metal alkoxide and fine particles is applied, it is not limited to quartz fiber glass, but can also be applied to germanium-based and fluorine-based glass.

This method can be applied to a wide range of glass manufacturing methods, including chalcogenide and nitride glasses.

〔Effect of the invention〕

As explained above, in the present invention, a homogeneous and highly pure sol solution can be easily prepared by using the dopant to be added as fine powder particles instead of as a metal alkoxide.

In the sol-gel method, the quality of the sol used greatly influences the quality of the final glass body, so the above-mentioned method, which facilitates the production of high-quality sol, is particularly effective in producing quartz glass. In addition, it is possible to reduce the amount of metal alkoxides used, which are generally expensive, and at the same time shorten the number of steps.
It is also very effective economically. Due to its high quality, silica-based glass synthesized by the above method can be widely applied to various optical materials, such as base materials for optical fibers, optical components, glass plates for photomasks, etc., and as various electronic materials. be.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a rotating device in which the rotating shaft is parallel to the longitudinal direction of the container. 1... Center line of rotation 2... Bearing 3... Cylindrical container for rotation 4... Holder for fixing the container 5... Motor for rotation 6...Support stand FIG. 2 is a diagram showing a rotating device in which a rotating shaft exists in the normal direction of the rotating shaft in FIG. 1. 1...Rotary table 2...Rotating cylindrical container 3...Holder for fixing the container 4...Rotation center line 5...Rotation axis 6...Bearing 7...Rotation motor 8...Support stand FIG. 3 is a diagram showing a rotation device used in manufacturing flat glass. 1... Raw material injection container 2... Sealing lid 5... Raw material solution, gel body 4... Rotating container 5... Rotating Motor No. 4FA is a schematic diagram of a flat gel body obtained using the rotating device of FIG. 3. Figure 1 Figure 4

Claims (5)

[Claims] (1) A method for producing quartz glass by a sol-gel method using metal alkoxide and finely powdered silica as main raw materials, which is characterized in that finely powdered silica mixed with a dopant is used. (2) The method for producing quartz-based glass according to claim 1, characterized in that finely powdered silica is used which is physically mixed with one or more types of dopants. (3) Claim 1, characterized in that finely powdered silica in which one or more types of doping materials are chemically dissolved is used.
or 2. The method for producing quartz-based glass according to item 2. (4) In the method for manufacturing silica-based glass as set forth in claim 1, the quartz-based glass is a base material for an optical fiber. A method for producing quartz glass. (5) In the method for producing quartz-based glass according to claim 1, the silica-based glass is plate glass, optical glass, or electronic material glass. A method for producing quartz-based glass according to items 1 to 3.