JPS6042239A - Manufacture of glass body having refractive index distribution - Google Patents

Abstract

PURPOSE:To manufacture inexpensively a glass body having a refractive index distribution in the thickness direction under mild conditions by immersing silica gel contg. other added metal in a leaching liq. to leach part of the added metal and by drying and sintering the remaining silica gel. CONSTITUTION:Alcohol and acid are added to Si(OCH3)4 contg. Ge(OCH3)4, and the resulting hydrolyzate is converted into gel in a glass vessel 1 to form wet gel 2. This silica gel 2 is immersed in water 3 as a leaching liq. at room temp. to leach part of the contained Ge. The remaining gel is washed with methanol, dried, and vitrified by sintering in an electric furnace 4. P, B, Ta, Ti, Zr or other element providing a high refractive index to silica may be used in place of Ge as the added element. The leaching liq. is selected in accordance with the kind of the used element. For example, when Ta is used, an aqueous soln. of acid or alkali is suitable for use as the leaching liq.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a method of manufacturing glass having a refractive index distribution in the thickness direction, and is particularly suitable for optical fiber base materials, rod lenses, and other optical components. This invention relates to a glass manufacturing method.

[Background of the invention]

Conventionally, ion exchange methods, CVD methods, and the like are known as methods for providing a refractive index distribution in the thickness direction.

In the ion exchange method, for example, [Applied phys
ics; vow, 19. A7.1113 (19
80) , ], Tt that can be ion exchanged
Borosilicate glass rod containing l and Na+ from 530~
It is treated in a KNOs molten salt at 550C for 50 to 100 hours, and then cut and polished. This method requires holding the glass rod in molten salt for an extended period of time, a process that is extremely harsh. In addition, the materials used are
Since it contained alkali, it was also unreliable in terms of weather resistance.

On the other hand, in the CVD method, reliability was high because a high silica material was used, but it was difficult to create a large refractive index distribution, and there were also problems in terms of manufacturing speed.

[Purpose of the invention]

An object of the present invention is to eliminate the above-mentioned drawbacks of the prior art and to provide a method for manufacturing at a low cost under relatively mild conditions.

[Summary of the invention]

According to the method of the present invention, silica gel to which one or more metals other than silicon are added is immersed in an eluate at least once for a predetermined period of time to elute a portion of the metal components, and then dried and sintered. Glass having a refractive index distribution in the thickness direction is manufactured.

This will be explained in detail below using the implementation column.

[Embodiments of the invention]

Example 1 4.5 mol of alcohol and 4 mol of 1/100N-HC1 aqueous solution were added to 41 mol of 30 mol% (7) Qe (OCHs)4e-containing Si (Oc) (!l) for hydrolysis. As shown in Figure 1, the inner diameter of the cylinder is 8 trag.
The mixture was gelated in a glass container 1 having a diameter of φ to create a wet gel 2. One portion of this gel = approximately 9 in 20 ca of water at room temperature
After immersing in methanol for about 50 minutes and washing, gradually drying at 65C, and using electric furnace 4 at 115C.
When it was sintered and vitrified at 0C, a glass rod with a diameter of 3wnφ and a length of about 10mm was obtained. When this glass rod was cut in a direction perpendicular to the axis and the refractive index distribution in the radial direction was measured, it was found that the refractive index distribution was high at the center and low at the periphery, as shown by curve 5 in Figure 2. Furthermore, when this refractive index distribution is expressed as the refractive index at the position r and a is set as a constant, it has a refractive index distribution close to the following. I found out the second one.

According to the experiments of the present inventors, once the type of added element and the type of eluent are determined, refractive The rate distribution shape can be controlled.

As an additive element, in order to increase the refraction 4f of the central portion and the peripheral portion, an additive element that gives a large refraction 4 to silica, such as Ta and 'pi.

It is necessary to select Zr, Sb, kA, Nb, Snl Pb, Zr, etc.

Furthermore, for example, in the case of Gel P+ B, water is most preferable for the bath, but an acid or alkaline aqueous solution can also be used. Conversely, in the case of Ta, etc., an acid or alkali aqueous solution is preferable. This means that the eluent of the added element -
It is related to the solubility of ＼, and it is necessary to select a diagnostic fluid that has a high solubility depending on the added element used.

In general, the concentration of the acid/alkali used is preferably as high as possible, but from the viewpoint of work, it is preferably about 10N or less.

When the eluate is alkaline, a clap-in portion having a refractive index distribution as shown in curve 1 gland 6 of FIG. 2 is generated around the rod. In this case, this can be accomplished by immersing the material in an alkaline eluent at least once before or after immersing it in water or an acidic eluent. In that case,
The alkaline concentration is approximately 0. IN or higher is preferable.

The amount of eluate needs to be minimal, as long as the gel is immersed in the eluate, but the larger the amount of eluate, the lower the refractive index of the peripheral portion can be. Furthermore, when water is used as the eluent, it is advantageous because the elution can be carried out under running water.

On the other hand, the elution time is determined by the density of the gel, that is, the pore diameter of the porous gel, and the size of the gel. For example, if the pore size is doubled, the elution time will be approximately halved, and
If the size doubles, it will quadruple. For gels with the same density and size, the longer the time, the greater the total elution amount, but the smaller the difference in refractive index between the center and peripheral regions. For example, in the above example, the elution time is 1
When the time was extended to 5 hours, no difference in refractive index was observed. Therefore, it is undesirable to elute for a long time, and there is an upper limit to the elution time depending on the size of the gel.

Although the elution temperature can be set at room temperature, it can be raised to near the boiling point of the eluate if necessary to shorten the elution time.

In the above examples, after the elution treatment, the gel was washed by immersing it in methanol, but this step is not necessarily necessary. However, if the amount of elution is large, the eluate components may adhere to the surface of the porous gel, cause cracks in the gel, or cause crystallization. To prevent this, the gel is washed, and the washing liquid is preferably a liquid with little elution effect, such as methanol or ethanol.

Globanol, butanol and the like are particularly preferred. The lower limit of the washing time and temperature is determined by the density and size of the gel, as well as the elution time and temperature conditions.

In the above examples, a gel obtained by hydrolysis of an alkoxide was used, but in carrying out the present invention, any porous gel to which a second metal oxide is added may be used. Can be used.

Furthermore, it is obvious that similar effects can be expected even if two or more metals are added over time.

Furthermore, although the above examples relate to rod-shaped glass, it is obvious that by using a plate-shaped gel, a plate glass having a refractive index distribution in the thickness direction of the plate can be created.

〔Effect of the invention〕

According to the present invention, the desired refractive index distribution can be achieved at room temperature and in a relatively short period of time (within several hours), making the working environment in the manufacturing process much better than in the past. I can do it. Furthermore, since a silica-based material with a high refractive index can be used, weather resistance can be improved. Furthermore, since the method of the present invention has the feature of being able to process a large amount of samples in a single process, it also has the effect of mass production and cost reduction.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing an example of the process steps of the present invention, and FIG. 2 is a graph showing the refractive index distribution of a glass rod obtained in one example of the present invention.

Claims (1)

[Claims] 1. Silica gel to which at least one metal other than silicon is added is immersed in at least one eluate at least once at a temperature below the boiling point of the eluate to remove the metal components. A method for producing glass having a refractive index distribution in the thickness direction, which comprises eluting a portion of the glass and then drying and sintering the glass. 2. The method for manufacturing a glass body having a refractive index distribution according to claim 1, wherein the one or more eluents include an eluate that is substantially water. 3. The method for manufacturing a glass body having a refractive index distribution according to claim 1, wherein the one or more eluents contain an acidic aqueous solution of 10N or less. 4. The method for manufacturing a glass body having a refractive index distribution according to claim 1, wherein the one or more eluents contain an alkaline aqueous solution of 0.1 to 10 normal. 5. Claim 1, wherein the metal is at least one metal selected from Ge, P, and B.
A method for manufacturing a glass body having the refractive index distribution according to item 2 or 4. 6. The metal is 'l'a, Ti, Zr, 8b, A/1
．． At least one selected from INb, Sn, Pb, and Zn
Claim 1, characterized in that it is metal or metal;
A method for producing a glass body having the refractive index distribution according to item 3 or 4. 7. A method for manufacturing a glass body having a refractive index distribution according to any one of claims 1 to 6, characterized in that the elution temperature is near room temperature. 8. A method for manufacturing a glass body having a refractive index distribution according to any one of claims 1 to 7, which comprises washing the gel after elution and before drying and sintering. . 9. The method for producing a glass body having a refractive index distribution according to claim 8, wherein the cleaning liquid comprises at least one selected from methanol, ethanol, and propanol.