JPS61178428A - Production of optical glass - Google Patents

Abstract

PURPOSE:To suppress the diffusion of dopant and obtain formed glass article, by increasing the molecular weight of the dopant in producing optical glass having the distribution of the dopant by the sol-gel method. CONSTITUTION:Two kinds of solution consisting essentially of a metal alcoholate consisting essentially of a silicon alcoholate, water and an alcohol, and having different compositions of the metal alcoholate are prepared. The first solution is them cast into a mold, hydrolyzed and gelatinized to lose fluid ity. At this time, the second solution is brought into contact with the gelatinized material of the first solution, cast and gelatinized. The gelatinized material is then taken out of the above-mentioned mold, and the formed material of the gel is dried and heated to give the aimed optical glass product having the distribution of the dopant. The alcoholate of the material to be the dopant in the second solution is previously hydrolyzed and polycondensed to increase the molecular weight before contact with the gelatinized material of the first solution.

Description

[Detailed Description of the Invention] 11 YupB Yuko! In the present invention, by hydrolyzing a metal alkoxide mainly composed of silicon and sintering the resulting porous gel,
The present invention relates to a method of manufacturing silica-based glass having a refractive index and dopant distribution.

BACKGROUND OF THE INVENTION Conventionally, a so-called sol-gel method has been proposed and used to produce highly pure ceramics by hydrolyzing a metal alkoxide and drying and sintering the resulting gel. That is, silicon alcoholate solution,
Direct hydrolysis in a container with a predetermined shape, and drying and sintering the resulting gel in that shape to make it non-porous and create a transparent glass body in the desired shape. There is.

Since this method of directly obtaining a molded product in the desired shape from a metal alcoholate solution involves molding a liquid,
Compared to the conventional method of compressing powder and then sintering it,
This method is excellent in terms of uniformity, simplicity of process, and low sintering temperature. Furthermore, compared to conventional glass melting methods, it can be said that this method is superior in terms of lower sintering temperatures and improved controllability of composition.

By the way, in recent years, it has been proposed to use the above-mentioned sol-gel method to fabricate optical fiber base materials and optical waveguides having a refractive index distribution (Japanese Patent Laid-Open No. 58-99134 and the 31st Applied Physics Association Proceedings of the joint conference, p10
829P-ni-1). That is, after preparing a gel corresponding to a low refractive index portion and before drying it, a sol solution containing a dopant that forms a high refractive index portion is applied to the surface of the gel, and
The purpose is to produce a glass molded article with a refractive index distribution by gelling the coating liquid, drying it, and sintering it.

This method is based on the conventional refractive index distribution forming method (for example, VA
Compared to the D method and the CVD thin film formation method, this method has advantages in that the process is simple and economical, and the refractive index distribution can be easily patterned.

However, because dopants diffuse very easily in gels produced by the sol-gel method and in porous glass, it is difficult to produce glass molded products with a step-like refractive index distribution using the above method. there were.

Problems to be Solved by the Invention As mentioned above, the application of the sol-gel method to the production of glass molded products with a refractive index distribution is more difficult than the conventionally common VAD method, CVD method, etc. This is extremely advantageous. However, as mentioned above, there were problems such as dopant diffusion, and this was still insufficient for practical and industrial use.

Therefore, improving such a method and promoting its practical use is of great significance in reducing the manufacturing cost of glass products having a refractive index distribution and further improving their quality.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a method for manufacturing glass molded products, especially optical glass, which suppresses the diffusion of dopants and has a nearly step-like refractive index distribution. One of the objectives is to provide glass molded products.

Means for Solving the Problems The present inventors have proposed that in the diffusion of dopants into gels,
As a result of detailed studies and repeated experiments on the effects of the dopant state, we found that normal molecules and ions diffuse easily in the gel before drying, and we have developed methods to suppress this diffusion. found that it is effective to increase the molecular weight of the dopant. The present invention was completed based on this knowledge.

That is, the method for producing optical glass of the present invention involves preparing two types of solutions containing a metal alcoholate mainly composed of silicon alcoholate, water and alcohol, and having different compositions of the metal alcoholate, The first solution was poured into the mold and hydrolyzed, and when the fluidity disappeared due to gelation, the second solution was poured into contact with the gelled product of the first solution to gel it. After that, when the gel molded body is removed from the mold and dried and heated to produce an optical glass product having a dopant distribution, the alcoholate of the substance to be the dopant in the second solution is added to the second solution. 1
This special feature is characterized in that the molecular weight of the alcoholate as a dopant is increased by hydrolytic polycondensation in advance before contacting with the gelled product of the solution. It can be carried out according to the method. In the first method, the second solution itself is
The second method is to perform hydrolytic polycondensation to the extent that gelation does not occur.The second method is to prepare a third solution containing a substance to be a dopant, hydrolyze and polycondensate the solution to the extent that gelation does not occur, and then add the necessary and the like components to obtain a solution corresponding to the second solution. Equivalent effects can be expected with either of these two methods.

Further, the dopant may be any element as long as it can change the refractive index of silica glass, for example, selected from the group consisting of Group Ⅰ, Group Ⅰ and the lanthanum series of the periodic table of elements. It can be at least one element.

In the method of the present invention, first, the first solution is heated and gelled while being rotated in a container of a predetermined size, which can be rotated about the long axis, for example, in a tubular shape, and then the dopant is preliminarily added in accordance with either of the above two methods. Inject the second solution which has undergone hydrolysis and polycondensation to have a high molecular weight, and perform the same operation to add the first solution.
By gelling the solution on the gelling layer, taking it out from the container, drying and sintering according to a conventional method, the dopant distribution becomes clear, and a glass molded article having a refractive index distribution can be easily formed.

Thus, according to the method of the present invention, little or no diffusion of the dopant during the formation of the compact can be prevented and a refractive index profile can be formed. In this case, the condition of the second solution must be adjusted when the first layer of gel and the second solution containing the dopant are brought into contact with each other.

That is, when producing an optical waveguide or a fiber base material having a refractive index distribution using the second solution containing the dopant according to the present invention, the first method is to first add an alcohol solution of an alcoholate such as Ge5At. Add some water,
The hydrolytic polycondensation of the alcoholate is proceeding, and a certain amount of silicon alcoholate and water are added to the alcoholate solution before it is brought into contact with the gel of the first solution. After the second solution gels, it is dried and sintered. Of course, Ge, A
It is also possible to add a certain amount of silicon alcoholate to the alcoholate solution of No. 1 in advance.

In addition, when fabricating a waveguide laser, the same process can be used by adding an alcoholate of a laser emitting substance such as NCF (for fabricating a Faraday rotating glass waveguide, lead, titanium, bismuth, Of course, it is possible to use the same process by adding alcoholates of group I, group V and lanthanum elements such as antimony, cerium, etc.Also, by changing the pH of the alcoholate solution,
It is also possible to add other additives within the scope of the present invention, in which the alcoholate of the dopant is previously subjected to hydrolytic polycondensation to increase its molecular weight within a range where the solution does not gel.

EXAMPLES Hereinafter, the method of the present invention will be explained in more detail according to Examples, but the scope of the present invention is not limited in any way by the Examples below.

Example 1 Tetrabutoxygermanium, methanol, tert-
Butanol and water in a molar ratio of 1:20:10:0.
3 and aged at 45°C to proceed with hydrolysis.

After aging the solution for two days, tetramethoxysilane in a molar ratio of 9 times that of tetrabutoxygermanium and water in a molar ratio of 4 times that of tetrabutoxygermanium were added. This was applied to a dry gel having a thickness of 6IIID to a thickness of about 130 μm, and after gelling, drying and sintering was performed to fabricate an optical waveguide. The undried gel was obtained by gelatinizing a liquid containing tetramethoxysilane, methanol, and water at a molar ratio of 1:4:4 at 65°C. Sintering was performed by heating to 1100°C in vacuum. FIG. 1 shows the results of XMA analysis of the distribution of Ge in the film thickness direction of the leading wave film thus produced. It can be seen that a small amount of 6e is diffused from the applied part to the base, but it can be seen that Ge is distributed almost in a step-like manner. Corresponding to this 6e distribution, the refractive index also became step-like, making it possible to fabricate a waveguide structure.

For comparison, when an optical waveguide film was prepared using the same method as described above without hydrolyzing and polycondensing tetrabutoxygermanium in advance, the Ge film thickness in the optical waveguide film prepared in the same manner was The results of an XMA analysis of the direction distribution are shown in FIG. Ge mixed into the application area
was found to be mostly diffused at the base, making it impossible to fabricate a waveguide structure.

Example 2 Tetrabutoxygermanium, ethanol, water, and tributoxyneodymium in a molar ratio of 1:15:0.3:
After mixing at a ratio of 0.15 and aging at 20°C to advance hydrolysis, a molar ratio of 9 to tetrabutoxygermanium was mixed.
Add 2 times the amount of tetramethoxysilane and 40 times the amount of water to the solution, and before gelling,
00mm, 150μ on the surface of a undried gel with a thickness of 6mIII
A waveguide glass laser was produced by coating the film in a thickness of m and gelling it, followed by drying and sintering. The undried gel contains tetramethoxysilane, methanol, n-butanol, and water in a molar ratio of 1:
They were mixed at a ratio of 2:1:4 and gelled at 45°C. Sintering was carried out in vacuum up to 1150°C.

After attaching a mirror to the end face of the waveguide, the fabricated waveguide glass radar was heated to 1.06 μm by xenon flash excitation.
The laser oscillated.

Example 3 Triisopropoxyaluminum, tetramethoxysilane, isopropanol, and water were mixed in a molar ratio of 1i2:2:0.
After aging a solution in which a small amount of triisopropoxyantimony was added to a mixed solution at a ratio of 2 to 2 at 15°C for 2 days, tetramethoxysilane with a molar ratio of 7 to triisopropoxyaluminum and 35 times the amount of water were added. Before adding to the solution and gelling, a diameter of 100 mm prepared in advance,
A 100 μm layer of the solution was applied onto the surface of a undried gel with a thickness of 5 mm, and after gelation, drying and sintering were performed to produce a waveguide Faraday rotating glass.

The undried gel was prepared by mixing tetramethoxysilane and isopropane water in a molar ratio of 1:1.5:4 and heating at 50°C.
It is made into a gel. Sintering was performed by heating to 1150° C. in vacuum.

The Verdet constant of the fabricated waveguide Faraday rotating glass was measured and was found to be 0.08 min/Oe-cm (
6,328 people).

DETAILED DESCRIPTION OF THE INVENTION As described above, according to the present invention, a glass molded article having a localized portion of a dopant can be produced by simply using a simple process of gelling a metal alcoholate solution. Depending on the selection, optical waveguides, laser glasses, and Faraday rotation glasses can be easily produced. In addition, a molding process is used during gelation,
This has the advantage that a concavo-convex pattern can be formed and the distribution shape of the dopant can be controlled three-dimensionally.

Therefore, according to the present invention, it is possible to easily produce not only optical waveguides but also glass molded products having a three-dimensional distribution of dopants, and by refining the raw materials, optical waveguides with extremely low loss, glass lasers with high excitation efficiency, and Not only can Faraday rotary glass with excellent uniformity be manufactured, but the distribution shape of the dopant can be controlled three-dimensionally, and high-performance optical circuit components such as optical splitters, couplers, waveguide lasers, and isolators can be manufactured at low cost. can.

[Brief explanation of drawings]

FIG. 1 shows the results of XMA measurement of the distribution of Ge, which is a dopant, in the film thickness direction in a leading waveguide fabricated according to the present invention. FIG. 2 shows the results of similarly measuring the distribution of 6e, which is a dopant, in the film thickness direction in a leading waveguide fabricated by the conventional sol-gel method using XMA. Patent Applicant Nippon Telegraph and Telephone Public Corporation Agent Patent Attorney Masahiko Arai Depth μm) Figure 2 Depth μm) Procedural Amendment (Voluntary) June 4, 1985

Claims (3)

[Claims] (1) Prepare two types of solutions containing a metal alcoholate mainly composed of silicon alcoholate, water and alcohol, and having different compositions of the metal alcoholate, and
Pour the solution into the mold, hydrolyze it, and when it loses its fluidity due to gelation, pour the second solution into contact with the gelled product of the first solution to gel it. ,
In the method of manufacturing optical glass having a dopant distribution by removing from the mold, drying, and heating, an alcoholate of a substance to be a dopant in the second solution,
The method for producing optical glass as described above, characterized in that the glass is hydrolyzed and polycondensed in advance to increase its molecular weight before contacting with the gelled product of the first solution. (2) The molecular weight of the metal alcoholate serving as the dopant is increased by performing hydrolytic polycondensation in advance to the extent that the second solution itself does not gel. the method of. (3) In order to increase the molecular weight of the metal alcoholate that will become the dopant, first prepare a solution of the third metal alcoholate that will become the dopant, perform hydrolytic polycondensation to the extent that the solution does not gel, and then Claim 1, characterized in that the method is carried out by adding at least a metal alcoholate corresponding to the host oxide and water to prepare a solution corresponding to the second solution. Method.