JPS6197138A - Preparation of optical glass body - Google Patents

Abstract

PURPOSE:To prepare an optical glass body prevented from generation of bubbles by heating and sintering a porous gel having a low bulk density obtd. by hydrolyzing specified >=two kinds of silicon alkoxide. CONSTITUTION:A liquid mixture 1 of starting materials prepd. by mixing 1mol of at least two kinds of silicon alkoxides having different hydrolyzing velocity to each other but consisting of >=2 molar ratio of Si(OCH3)4 and Si(OC2H5)4, etc., with 3-6mol aq. ammonia having 0.01-0.1mol/l NH3 concn., and 3-6mol alcoholic solvent (e.g. ethanol), is charged in a vessel 2. The vessel is closed tightly and the content is allowed to stand to cause gelation to obtain wet gel 4. A porous gel 5 having a low bulk density is obtd. by hydrolyzing the gel 4, which is then vitrified by heating and sintering. Thus, a block body 6 of an oxide of an optical glass body is obtd. The generation of bubbles in the block body is inhibited even if the block body is heated to >=2,000 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION [Background and Objects of the Invention] The present invention provides an I! It is related to the manufacturing method.

Recently, a method of creating a transparent silica glass body by sintering porous gel obtained by hydrolyzing silicon alkoxide (hereinafter referred to as the sol or gel method) has been proposed, and optical fibers can be fabricated using this sol or gel method. The attempt of [j7ect
ronics 1-et-ters 18[12]
, 499 (1982).

The dry silica gel obtained by the above sol/gel method depends on the preparation conditions, but S! When using the raw material of 0CzH5)4, the bulk density of the dry gel is 0.7c+/cm3, and when using the raw material of Si(OCH3)4, a gel with a lower bulk density of 0.6q is produced. It is reported in the above-mentioned literature that a low bulk density of /cm3 can be obtained, and that an optical fiber can be manufactured from this low bulk density dried gel.

Generally, the lower the bulk density of the dry gel, the less foaming the sintered glass body will have at high temperatures. Therefore, in order to produce non-foamed glass, it is required to produce a gel with as low a bulk density as possible. In the conventional gel making method that uses only one type of silicon alkoxide raw material, the limit is a gel with a bulk density of approximately 0.60/C13, and the glass made from this gel does not foam at 1.300°C. But about 2.00
When heated at a high temperature of 0° C., a foaming phenomenon in which air bubbles are generated in a glass body often occurs.

The present invention was made in view of the above-mentioned situation, and an object of the present invention is to provide a method for manufacturing an optical glass body that can prevent the generation of bubbles even when heated at about 2,000°C.

[Summary of the Invention] The method for producing an optical glass body of the present invention provides a method for producing an oxide block of an optical glass body by heating and sintering a porous gel obtained by hydrolyzing a metal alkoxide. In this method, at least two types of silicon alkoxide having different hydrolysis rates are used as raw materials for the alkoxide, and hydrolysis is performed to produce the above-mentioned porous gel having a low bulk density.

〔Example〕

Hereinafter, the method for manufacturing an optical glass body of the present invention will be explained using examples and drawings. The figure is a schematic diagram of the sol/gel process. A raw material mixture 1 obtained by mixing and stirring alcohol and HzO using silicon alkoxide as a raw material is transferred to a suitable glass container 2, the glass container 2 is almost sealed with aluminum foil 3, and left to gel. Wet (wet) containing multiple solvents and water after gelation is completed
) The gel 4 is dried in a drying process to evaporate the solvent alcohol and water to produce a porous dry (Pry) gel 5 for sintering. Next, the dried gel 5 is sintered and vitrified at about 1,300° C. to produce a transparent glass body 6. When producing an optical fiber, the optical fiber is produced from the transparent glass body 6 at about 2,000° C. by a conventional optical fiber rod-in-tube method.

Example 1 S with slow hydrolysis rate! (0, Cz Hs) a
and S i (OCH3 → 4), which has a high hydrolysis rate, while adding ethanol as a solvent and stirring it.
．． 05 mole/1 NH 38 degree aqueous ammonia was added to make a homogeneous mixed solution. And 5i(QCzHa)a and S
A mixed solution was quickly prepared to have a composition of 4 moles of ethanol and 4 moles of aqueous ammonia per 1 mole of f (OCH3)4 in total. Also, S i (OCz Hs )
/S i (OCH3)4 molar ratio is O/1. O,
0,210,8,0,410,6,0,610,4,0
, 810, 2, and prepared mixed liquids with five different compositions.

In this way, the obtained homogeneous mixed liquid was
The mixture was placed in a glass container 2 having a length of 200 mm, the upper end of which was almost sealed with aluminum foil 3, and then left at room temperature for about 1 day to gel. Next, several pinholes were made in the aluminum foil 3 covering the glass container 2, and the gel was kept in a constant temperature bath at 70°C (not shown) for 10 days and in a constant fan at 120°C for 1 day. The remaining water and ethanol were evaporated and dried. The bulk densities of the five types of dry gels obtained as described above are calculated by plotting the bulk density of the gel on the vertical axis and Si (OC2Ha )4 /S t (OCH
3) as shown in curve A of FIG. 2, which is shown by taking the molar ratio of 4. That is, Si(OCH3) has a high hydrolysis rate.
When 4 is used alone, the bulk density is 0.600/
cm3, and S t (O
When C2HIS)a was used alone, the time required for gelation was extremely long, and the gel could not be formed well.

On the other hand, S i (OC2Ha )a /S i
With a composition in which the molar ratio of (QCH3)4 was 0.810.2, a gel with a minimum low bulk density of 0.400/ca+3 was obtained.

Glass obtained by sintering the five types of gels mentioned above under the same conditions had no bubbles, but when heated at a high temperature of about 2,000°C, the smaller the bulk density, the less foaming the glass had, and P = 0.
The glass made from the 4g/c+a3 gel had no foaming and was a clean, non-porous, transparent glass body. A comparison of the foaming of glasses made with the above five compositions is shown in Figure 2 by the amount of black coating on the O stamp pad.The larger the black coating amount, the more foaming occurs. Those without foam indicate no foaming. The above-mentioned non-foamed silica glass rond was preformed using a known technique and then made into a fiber to create an optical fiber. Although the drawing temperature of the fiber was approximately 1.900° C., there was no foaming, and it was confirmed that the glass could be used for optical fibers.

As described above, according to the method for manufacturing an optical glass body of this example, two types of silicon alkoxides, which are the same element but have different hydrolysis rates, are used as raw materials for the oxide, and are hydrolyzed to create a gel (hereinafter referred to as It is clear that by using the cumulative hydrolysis rate method (referred to as the cumulative hydrolysis rate method), it is possible to create a gel with a lower bulk density than the conventional gel creation method, and it is possible to prevent the high-temperature foaming phenomenon that often occurs with glasses produced by the sol and gel methods. It became. That is, generation of bubbles can be prevented even when heated at about 2,000°C. The reason why the gel made using the different hydrolysis rate method of this example has a lower roughness density than the gel made by the conventional method using only one type of metal alkoxide for one raw material element is because of the hydrolysis rate. This is thought to be due to the gel strengthening effect of the slow alkoxide raw material. Alkoxide raw materials with a fast hydrolysis rate react first and form a gel network structure, while those with a slow hydrolysis rate react later and deposit on the surface of the already formed network structure, destroying the entire gel structure. This is expected to result in the strengthening of Therefore, the stronger the gel, the smaller the shrinkage of the gel with respect to the shrinkage force caused by the surface tension of the same solvent, and as a result, a gel with a lower bulk density can be realized.

In this example, St (OCH3)a and 5i (OCZ
Although we have explained the case of two types of silicon alkoxides in H6), it is of course possible to apply this heterohydrolysis rate method to the case of a mixture of three or more types of St (OR) a (R: alkyl group). It will be done.

[Effects of the Invention] As described above, the method for manufacturing an optical glass body of the present invention has the effect of preventing the generation of bubbles even when heated at a high temperature of about 2,000°C.

In addition to silicon alkoxide, for example, Ge (OR) a, T 1 (OR
)s, Ta(OR)s, etc. It is thought that the effect of the differential hydrolysis rate method can be expected as in the case of the above-mentioned 5i(OR)a.

[Brief explanation of the drawing]

Figure 1 is a schematic diagram of the process for carrying out the method of manufacturing a glass body of the present invention, and Figure 2 is a diagram showing the molar ratio of silicon alkoxide with a fast hydrolysis rate and silicon alkoxide with a slow rate of hydrolysis and the dry gel ratio when carrying out the method of the present invention. This is a bluff showing the relationship with density. 1... Mixed liquid, 4... Wet gel, 5... Dry gel. 6...Transparent glass body. 1st eye 2nd eye SL('CzHd, 15b(""a)4 (mol b51
Display of the case 1982 Patent No. M 216773 2 Name of the invention Method for manufacturing optical glass bodies 3 Name of the person making the amendment (512) Representative of Hitachi Cable Co., Ltd.
rl Luo li 5, Column 6 of the scope of patent claims of the subject of the amendment, Contents of the amendment as shown in the attached sheet 7, Attachment with a list of attached documents (Claims l!ll) 1 or more copies Claims (1) A method for producing an oxide block body of an optical glass body by heating and sintering a porous gel obtained by hydrolyzing a metal alkoxide, the raw material for the metal alkoxide comprising:
A method for producing an optical glass body, characterized in that the above-mentioned porous gel having a bottom bulk density is produced by hydrolysis using at least two types of silicon alkoxides having different hydrolysis rates. (2) The above two types of alkoxides having different hydrolysis rates are silicon alkoxides S i (OCHa )4 and S i (OCz Ha )4, and claim 1 for manufacturing the above-mentioned optical glass body of silica glass. The method for producing an optical glass body described in Section 3. (3) The above silicon alkoxide S f (OCZ H6
)&/Above silicon alkoxide S i (OCH3)
3. The method for producing an optical glass body according to claim 2, wherein the molar ratio of 4 to 4 is 2 or more. The above silicon alkoxide S i (OCz Hs )
4 and the above silicon alkoxide S i (C)CH3
2. The method for producing an optical glass body according to claim 1, wherein the amount of water and alcohol solvent used is 3 to 6 mol each per 1 mol of the raw materials. (5) The method for producing an optical glass body according to claim 4, wherein the alcohol solvent is ethanol. (6) The water used for the above hydrolysis is 0.01 to 0.1
The method for producing an optical glass body according to claim 1, wherein the ammonia water has an ammonia concentration of mol/1. that's all

Claims (1)

[Scope of Claims] (1) In a method for producing an oxide block body of an optical glass body by heating and sintering a porous gel obtained by hydrolyzing a metal alkoxide, the raw material for the metal alkoxide includes:
A method for producing an optical glass body, characterized in that the porous gel having a low bulk density is produced by hydrolysis using at least two types of silicon alkoxides having different hydrolysis rates. (2) The above two types of alkoxides having different hydrolysis rates are silicon alkoxides Si(OCH_3)4 and Si(OC_2H_5)_4, and the above-mentioned optical glass body of silica glass is manufactured according to claim 1. A method for manufacturing an optical glass body. (3) The above silicon alkoxide Si (OC_2H_5
)_4/Silicon alkoxide Si (OCH_3)
The method for producing an optical glass body according to claim 2, wherein the molar ratio of _4 is 2 or more. The above silicon alkoxide Si (OC_2H_5)_4
and the above silicon alkoxide Si (OCH_3)_4
2. The method for producing an optical glass body according to claim 1, wherein the amount of water and alcohol solvent used is 3 to 6 mol each per 1 mol of the raw materials in total. (5) The method for producing an optical glass body according to claim 4, wherein the alcohol solvent is ethanol. (6) The water used for the above hydrolysis is 0.01 to 0.0
The method for producing an optical glass body according to claim 1, wherein the ammonia water has an ammonia concentration of 1 mol/l.