JPS58167436A - Production of optical glass - Google Patents

Abstract

PURPOSE:After a porous gel resulting from hydrolysis of a metal alkoxide is deaerated, the product is sintered by heating, processed at elevated temperatures to give a clear optical glass free from bubbling even when processed or treated at elevated temperatures. CONSTITUTION:For example, Si(OCH3)4 is combined with a prescribed amount of Ge(OCH3)4 and mixed with methanol, further with aqueous ammonium hydroxide solution to prepare a sol by stirring. Then, a vessel 2 containing the above sol 3 is placed in the vacuum vessel 1 of a deaeration system consisting of vacuum gauge 4, vacuum valve 5, leak valve 6 and vacuum pump 7. Then, the vessel 1 is adjusted in vacuum to less than 10<-1>torr, before the sol 3 changes into gel to effect deaeration, thus removing the air dissolving in the sol 3. Further, deaeration is continued until the sol loses its flowability at all into a gel. Then, the resultant gel is dried, sintered by heating to give the objective clear glass. During the sintering, there is no bubbling caused by the air.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of manufacturing a transparent glass body by heating and sintering a porous gel obtained by a hydrolysis reaction of a metal alkoxide, and particularly relates to a method for manufacturing a transparent glass body for optical devices such as optical fibers. The present invention relates to a method for manufacturing optical glass.

Conventionally, as one method for producing glass using a hydrolysis reaction, an alkoxysilane or an alkoxysilane to which an elemental alkoxide has been added is hydrolyzed to obtain silica gel or a silica gel containing an added oxide, and then 1000 There is a known method for obtaining a dense glass by gradually heating it to a temperature above ℃ in an oxidizing atmosphere to perform processes such as removing adsorbed water, removing residual organic matter, and making it non-porous (for example, , Japanese Patent Application Publication No. 51-34219;
Journal of Materials Science, Vol. 14 (1979), pp. 607-611).

However, when heat treatment is performed using the above method, cracks may occur or foaming may occur during the heat treatment process. Particularly when processing at high temperatures, e.g. 1300°C or higher,
It often foamed.

Therefore, its use had to be extremely limited.

On the other hand, as a method for effectively removing residual moisture from porous phosphor glass, it is necessary to expose it to a chlorine-containing atmosphere at a temperature of 600 to 1000°C (de-zero treatment) and then
A method of making the material non-porous at 00 to 1300°C is known (Japanese Patent Publication No. 42-23036).

According to the experimental studies conducted by the present inventors, it was found that when this method is applied to the 01-1 removal treatment of Noriyoku gel containing additives, foaming can be significantly reduced, but it cannot be completely suppressed. . In other words, it has been found that foaming at high temperatures is not simply caused by the evaporation of water remaining in the glass body, but is also caused by glass caused by people other than humans.

The purpose of the present invention is to solve the above-mentioned problems of the prior art, based on the experimental studies of the present inventors, and to produce a transparent optical glass that does not foam even when processed and treated at high temperatures. Our goal is to provide the following.

The present inventors carefully observed the foaming phenomenon that occurs at a high temperature of 1000 to 2000° C., and conducted a component analysis of the foaming gas of a glass body containing a small amount of OIl (1000 ppm or less). As a result, the components of the foaming gas are mostly air components (nitrogen, oxygen, argon, etc.);
And, by sufficiently removing the air dissolved in the sol immediately after preparing the mixed liquid, that is, in the sol state where gelation has not yet occurred, almost no foaming occurs even when heated at high temperatures. We have come to discover the fact that this is possible.

Therefore, the feature of the method for manufacturing optical glass of the present invention is that a metal alkoxide is made into a sol solution based on a hydrolysis reaction, and after that is gelled, it is heated and sintered to vitrify it. The purpose of this process is to perform a process to remove gas, mainly air, dissolved in the sol before it becomes a gel.

According to the present invention, it is possible to easily and reliably produce optical glass that does not foam even during high-temperature processing.

Below, the present invention will be explained more specifically and in detail with reference to test examples.

Test Example 1 10 mol of Ge(OCH3)4 was added to 4'+ mol of Si(OCi-13), and further 6.5 mol of Cl was added.
After adding l30I and mixing, the concentration was 5 x 10 mol/
4.8 mol of NH4OH aqueous solution was added and mixed well with a magnetic stirrer.

Next, a vacuum pressure gauge 4 and a vacuum valve 5 as shown in FIG.
A sol liquid container 2 containing the mixed liquid (sol) 3 prepared as described above is placed in a vacuum container 1 of a vacuum degassing device equipped with a leak valve 6 and a vacuum pump 7, and the mixed liquid is in a sol state. While the sol has not yet gelatinized, adjust the degree of vacuum in the vacuum container 1 in the vacuum device to 10' Torr or less and perform deaeration treatment by reducing pressure for 15 minutes to remove air dissolved in the sol solution. did.

The sol subjected to vacuum degassing treatment as described above was prepared with an inner diameter of 1[
] mmφ, length 20 [A 1 mm silicon-coated cylindrical glass container for gel preparation is filled to about 80%, and placed again in the vacuum container 1 of the vacuum device described above, and the sol liquid is Deaeration treatment was performed until the fluidity completely disappeared to form a gel.

The deaeration treatment time in this test was approximately 30 minutes.

Next, a glass container for gel preparation was removed from the vacuum container, and the top of the glass container for gel preparation was covered with aluminum foil to prevent evaporation of the sol. This sample is referred to as sample m1.

Separately, as a comparative sample, a mixed solution (sol) prepared under exactly the same conditions and with the same composition as in Sample Part 1 above was filled into a glass container as it was without degassing, and then The head was covered with aluminum foil and allowed to gel at room temperature. This sample is referred to as sample Na2.

The gels in samples N11 and Flies 2 above both contain large amounts of water and alcohol, so in order to gradually evaporate water and alcohol from inside the gels, the gels were sealed in an aluminum upper part. 1mm diameter on foil lid
Drill several pinholes (same number as mi and N112), 7
After being maintained at a temperature of 0° C. for one week, it was dried at 120° C. for one day and night to obtain a dry gel having a bulk density of about 0.6 g/crt+3.

For both samples N[Ll and l@2, the dried gels prepared in this way were taken out of the container, placed in an electric furnace, and heated to 800°C at a heating rate of 200°C/hr in an oxygen atmosphere. , and then heated and sintered to 1200° C. in a He atmosphere at a heating rate of 20° C./hr to obtain transparent glass bodies in each case. These transparent glass bodies were further heated and deformed to 1400° C. or higher (a temperature at which drawing can be performed in the case of optical fiber production).

As a result of the above, the sample height 2 which was not degassed in the sol state had air bubbles in the glass body, whereas the
In sample-1, which was subjected to deaeration treatment in a sol state, no bubbles were found in the glass body. The effect of the present invention was confirmed in comparison with sample height 2.

In the above, in order to degas the gas dissolved in the sol liquid, the liquid prepared as a sol liquid was degassed under reduced pressure, but the gas dissolved in the sol liquid was degassed. In addition to the above method, before preparing the sol liquid, each metal alkoxide raw material liquid, alcohol, water, etc. are separately degassed under reduced pressure, and then mixed in a vacuum or in a He atmosphere to prepare the sol liquid. It is okay to do so. This method is particularly effective when the gelation time is extremely short, within several minutes.

Test Example 2 Under the same conditions and method as Test Example 1, 5r (QC) 13
)Gc (OCI-13)4. Mepnor, NH
A mixed solution (sol) was prepared using a 4OH aqueous solution.

Similar to the degassing treatment for sample mi in Test Example 1, this sol was removed from the sol state to a vacuum degree of 1.
The sol was placed in a vacuum container of Q'Torr or less, and degassed under reduced pressure for about 10 minutes to remove air dissolved in the sol.

The sol after vacuum degassing treatment has an inner diameter of 10 mmφ and a length of 200 m.
A cylindrical gel preparation glass container coated with silicone was filled to about 80% of the volume, and gelatinized in air at room temperature. The time from filling the sol to gelation was about 10 minutes.

This gel was heated at 70°C for 1 week and then at 120°C for 1 week.
It was dried day and night to produce a dried gel with a bulk density of about 0.6 g/cm3.

This sample is designated as sample l1a3.

Sample height 6 of this dry gel was sintered under the same conditions as in Test Example 1, the resulting glass body was heated at an even higher temperature, and the foaming behavior was compared with sample height 1 and Na2 of Test Example 1. As a result, the following results were obtained.

(1) Foaming was less than that of undegassed sample Nα2.

(2) However, the amount of foaming was slightly larger than that of the sample height 1 which was gelled in vacuum.

From the above results, it seems that degassing the sol alone has the effect of reducing foaming, but when it is gelled in the air, air re-dissolves in the degassed sol, which causes foaming. Conceivable. Therefore, for a sol with a long gelation time, it is gelled in a He atmosphere, but as in sample height 1 of Test Example 1, the degassing treatment must be continued until the sol solution gels. , gelation in vacuum was found to be desirable.

In addition, in the above test example, a method of degassing treatment by reduced pressure was described, but other methods such as (a) a method of distilling the sol in a desired gas atmosphere, such as Ice; (1)) a method of distilling the sol in the sol; Bubble by introducing the desired gas into the
There is a method of replacing air with this gas and degassing it.

In the above test example, a binary glass of GeO2 and Si02 was described, but it goes without saying that the method of the present invention can also be applied to the production of glass by hydrolysis of -component, metal alkoxide of two or more components. There is no such thing.

As described above, the method for manufacturing optical glass of the present invention has a remarkable effect in processing and molding an optical glass body at high temperatures without foaming.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of a degassing device for a sol liquid using reduced pressure in the sol-gel method. 1... Vacuum container 2... Sol liquid container 6...
Sol liquid 4...Vacuum pressure gauge 5...Vacuum valve 6...Leak valve 7...Vacuum pump attorney Junnosuke Nakamura Continuation of page 1 Hitachi, Ltd. Central Research Laboratory No. 2

Claims (4)

[Claims] (1) A method in which a metal alkoxide is made into a sol liquid through a hydrolysis reaction, which is then gelled and then vitrified by heating and sintering, in which the gas dissolved in the sol liquid is degassed. A method for manufacturing optical glass, characterized by: (2) Claim 1, wherein the gas is air.
A method for producing optical glass as described in Section 1. (3) The above degassing treatment is performed continuously in a bowl where the sol solution gels.
A method for producing optical glass as described in Section 1. (4) The method for manufacturing optical glass according to any one of claims 1 to 6, wherein the degassing treatment is performed in a clean atmosphere of 10' Torr or less.