JPS63277525A - Production of optical glass - Google Patents

Abstract

PURPOSE:To contrive to improve refractive index distribution characteristics, by immersing sol obtained from a Si alkoxide in an organic solvent and optionally carrying out pretreatment of soaking a gelatinous porous material in a solution of a water-soluble salt of a metallic ion. CONSTITUTION:First a solution comprising a Si alkoxide as a main component is hydrolyzed to form sol and a gelatinous porous material is obtained from a solution containing a water-soluble salt of a metallic ion. Before the gelatinous porous material is dried and heated to form a glass material, the gelatinous porous material is immersed in an organic solvent which has low solubility of the water-soluble salt and is miscible with water. In the operation, water in the pores is replaced with the organic solvent, the metallic salt is precipitated to promote solidification of the metallic ion. Further optionally pretreatment of soaking the gelatinous porous material in a solution of a water-soluble salt of a different metallic ion is carried out to give a desired refractive index distribution. Promotion of the solidification of the metallic ion improves refractive index distribution characteristics.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention involves adding a metal salt aqueous solution to a sol obtained by hydrolyzing a metal alkoxide to form a gel-like porous body.
The present invention relates to improvements in the method of manufacturing a glass body by heating this gel body, and particularly relates to a technique for precisely controlling the concentration distribution of metal ions in the gel body.

[Prior Art] A method known as the so-called sol-gel method is to obtain a sol by hydrolyzing a solution containing Si alkoxide as a main component, gelatinize the sol, and then heat the gel body to obtain a transparent glass body. It has recently attracted particular attention because it has many advantages, such as being able to form glass at much lower working temperatures than the melting method. One way to obtain a multicomponent glass body using such a sol-gel method is to introduce all of the metal oxides that make up the glass in the form of their metal alkoxides, but the hydrolysis rate of each metal alkoxide is different. Therefore, it is difficult to obtain a homogeneous gel body and even a homogeneous glass body, and the glass compositions to which this method can be applied are limited. In addition, an acid catalyst is required to carry out hydrolysis without using alcohol as a solvent, which causes cracks, and heat is generated due to hydrolysis. On the other hand, main components such as Si are introduced in the form of alkoxide and formed into a sol by hydrolysis, and other glass constituent metal oxides are added to the above sol in the form of their water-soluble metal salts. An improved method for forming gel-like porous bodies from mixtures has been proposed.

According to the above-mentioned improved method, there are fewer restrictions on the type of metal element to be added (it can be applied to a variety of glass compositions. Also, if it is a water-soluble salt, there is less heat generated by the hydrolysis reaction.

Furthermore, in the above improved method, a specific metal salt of another type is brought into contact with the gel-like porous material and permeated into the interior through the pores in the porous material, thereby creating a concentration gradient from the surface to the center. It is also possible to fabricate a glass body whose refractive index gradually changes from the center to the surface (J, Nc
n-Cr)'st, 5olids, s5, 1986,
P244).

[Problems to be Solved by the Invention] In the conventional improvement method described above, most of the metal ions introduced in the form of water-soluble salts do not contribute to the formation of the skeleton of the gel body, but rather close the pores of the gel body. It often remains in the liquid phase it fills. For this reason, a phenomenon occurs in which these metal ions move to the surface of the gel body together with water when the gel body dries, resulting in redistribution of metal ions.

If such movement of metal ions occurs, the refractive index distribution in the resulting glass body will not be uniform, resulting in unexpected disturbances in the refractive index distribution.

The same applies when a glass body having a refractive index gradient of a predetermined shape (for example, parabolic shape) is produced by diffusing other water-soluble salts into the gel-like porous body to give a 7 seismic intensity gradient. As a result of the movement of metal ions when the gel body dries, the refractive index distribution in the final glass body may become thicker (deviate from the originally intended distribution shape, or the distribution gradient may change). There is a problem in that the refractive index changes in the direction of smoothing, making it impossible to obtain a sufficient refractive index difference.

The main object of the present invention is to solve the above-mentioned conventional problems, and to make it possible to precisely control the distribution of metal ions in the gel body at a stage before drying the gel-like porous body and heat-treating it for vitrification. It is an object of the present invention to provide a method that can reliably immobilize in a distributed state.

[Means for Solving the Problems] In the first invention of the present application, an aqueous solution containing a water-soluble salt of a specific metal ion is added to a sol obtained by hydrolyzing a solution mainly composed of silicon alkoxide to form a gel. In the method of obtaining a glass body by drying and heating the gel-like porous body after obtaining the gel-like porous body, before performing the drying and heating vitrification treatment,
The gel-like body is immersed in an organic solvent that has low solubility in the metal salt and is miscible with water.

Further, in the second invention of the present application, in producing a glass body having a refractive index gradient, a gel-like porous body is immersed in an aqueous solution of a metal salt different from the raw material metal salt of the gel-like porous body, A treatment that provides a metal ion concentration distribution that changes from the surface to the inside of the gel-like porous body, and a process that immerses the gel-like porous body in an organic solvent that has low solubility for both types of metal salts and is miscible with water. Do this.

In the method of the present invention, alkoxysilanes such as tetramethoxysilane and tetraethoxysilane can be used as the silicon source for producing the sol, and these silicon alkoxides act as catalysts for hydrolysis and polycondensation reactions. Add a small amount of hydrochloric acid, etc.

Before this sol gels, Pb forms a metal oxide other than silicon, which forms the basic composition of the glass.

Tit Cst Rbt Bat Sr, Ta+ Nb
+ An aqueous solution or an alcoholic aqueous solution containing a water-soluble salt of a metal ion such as La is added to the above sol. When this mixture is allowed to stand still under appropriate conditions, the polycondensation reaction progresses to form a gel, and the gel body contracts.

The gel-like porous material thus obtained is mainly 5i-
It consists of a skeleton made of 0-3t bonds and pores surrounded by the skeleton, and the pores are occupied by liquid phase substances such as alcohol and water.

Next, desirably, the porous gel material is slightly dried to partially volatilize the solvent contained in the gel-like porous material, and then immersed in the metal salt solution again.

That is, the above-mentioned former volatilization treatment removes a portion of the liquid contained in the porous body in order to improve the shape retention of the gel-like porous body, and the communicating pores in the porous body disappear due to contraction. It is preferably dried until the diameter is reduced to about 70%. Since ion movement occurs during this process, in order to once again distribute the ions uniformly, this gel-like porous body is immersed in the same metal salt solution as that added to the sol of Si+jcon alkoxide.

Next, the gel-like porous body is immersed in an organic solvent that has low solubility in the metal salt and is miscible with water.

The organic solvent used in the present invention is not particularly limited, and should be appropriately selected depending on the water-soluble metal salt used.

For example, nitrates, acetates, carbonates, etc. can generally be used as water-soluble salts for Pbs Tit Cs, etc., and organic solvents for these include alcohols such as ethyl alcohol, propyl alcohol, sec-butyl alcohol, tertiary-butyl alcohol, etc. Ketones such as acetone, ethers such as dimethyl ether, etc. can be used.

If a glass body having a uniform refractive index is to be manufactured, the gel-like porous body that has been subjected to the above-described treatment is subjected to a drying treatment and then subjected to a transparent sintering treatment to form a glass body. In addition, when molding a glass body with a refractive index gradient within the cross section, such as a base material for a gradient index lens, the gel-like porous body should be Perform the secondary processing described in . For example, if you want to create a glass body with a distribution in which the refractive index is maximum in the center and gradually decreases in a parabolic manner toward the periphery, ions that increase the refractive index in the glass, such as Pbs, Tl, and Cs, are added to the gel by the primary treatment described above. After that, it is immersed in an aqueous solution of a water-soluble metal salt of an ion such as KsNa or Zn, which has a relatively small contribution to the refractive index in the glass, or an aqueous alcohol solution. This step causes interdiffusion of a metal salt of a high refractive index component such as PB and a metal salt of a low refractive index component such as K through the liquid phase in the pores of the gel body. After a predetermined diffusion treatment time, that is, when a metal ion concentration distribution that gradually changes from the center to the surface is generated, the gel-like porous body is taken out from the solution, and a high refractive index component salt and a low refractive index component salt are added. It is immersed in an organic solvent that has low solubility for both and is miscible with water. This organic solvent immersion achieves fixation of the metal ions interdiffused between the metal salts into the pores.

Furthermore, since the solubility of metal salts and the extraction rate of water differ depending on the type of organic solvent, it is possible to control the distribution of metal ions formed within the gel body by adjusting the composition of the organic solvent and treatment time. .

The gel-like porous body subjected to the above-described treatment is then subjected to a drying treatment and then converted into a glass body by a normal transparent sintering treatment.

That is, by gradually heating the glass composition to a temperature slightly higher than the glass transition temperature, the water, alcohol, and organic solvent in the gel body are scattered, and the pores of the gel body are further closed to form a transparent body. becomes. In the high temperature range of this heating process, transparency can be promoted by using a helium gas atmosphere.

[Function] A water-soluble metal salt is used as one of the raw materials for producing a gel-like porous body, and by soaking the formed gel-like porous body in a organic solvent that has low solubility for the metal salt, the pores of the gel body are dissolved. The water present in the organic solvent is replaced by the child solvent, and the salt has low solubility in this organic solvent, causing precipitation of the metal salt in the pores, promoting the fixation of metal ions in the pores. Ru. Therefore, in the drying process, the phenomenon that occurs when the liquid phase in the pores moves to the surface of the gel body with the metal ions described above is suppressed.

As a result, the desired refractive index distribution shape is realized in the glass body obtained after the transparent sintering process.

That is, according to the method of the present invention, controllability of distribution formation is improved. The present invention will be described in detail below with reference to specific examples.

Example] Example 1 5 ml of tetramethoxysilane and 5 ml of tetraethoxysilane
1, 10 ml of 0.8 mol/l boric acid aqueous solution and 0.8 mol/l boric acid aqueous solution.
After adding 0.025 ml of concentrated hydrochloric acid and stirring, the mixture was left to stand until the liquid temperature cooled to room temperature.

0.25 mol/1 lead acetate 30 in 15 ml of the resulting solution
A mixed solution of 5 ml of lead nitrate of m1 and 0.5 mm, I+//l was poured into a polypropylene container with an inner diameter of 24+ mm.

By sealing this container and leaving it as it is, it gels, contracts, and separates from the container wall. Next, remove the gel body from the container,
By leaving it in the atmosphere at 30℃ for a day and night, the diameter of
A gel-like porous material of 5+am was obtained.

This gel-like porous material was mixed with 80m1 of Improper Tool and 2
Immerse it in a solution of 50g of lead acetate in 0ml of water.
It was held at 60°C for 2 days.

Thereafter, the gel-like porous body was immersed in an impropat tool at 30°C, held for 2 days, and then dried at 60°C in the air. After drying, it was heated in a tubular electric furnace where the atmosphere could be controlled.

The heating conditions were a heating rate of 30°C/hour from room temperature to 460°C, and a heating rate of 1 hour at 240°C and 460°C.
Hold for 2 hours, raise the temperature from 460℃ at a rate of 15℃/hour, hold at 600℃ for 16 hours, and then raise the temperature to room temperature for 10 hours.
It was cooled at a rate of 0°C/hour. Oxygen gas was flowed at 501/min until the temperature was slightly higher than 460° C., and then helium gas was flowed instead of oxygen until cooling started.

By the above heat treatment, a transparent, bubble-free glass body with a diameter of 7 mm and a length of 9 mm was obtained. FIG. 1 shows the results of measuring the radial lead concentration distribution in the cross section of the obtained cylindrical glass body using an X-ray microanalyzer. Further, as a comparative example, a glass sample was prepared in the same manner as in the above-mentioned example except that the process of immersing the gel-like porous body in a 30° C. impropat tool was omitted. The results of measuring the lead concentration distribution in the same sample are shown in FIG. 1 as a "comparative example".

As is clear from Figure 1, by immersing the gel-like porous material in the Improper Tool, the movement of lead ions in the subsequent drying process is suppressed, and the distribution of lead becomes uniform in the radial direction. Become.

Although the lead concentration at the edge of the glass body surface was not measured in the measurements shown in Figure 1, the lead concentration distribution in the comparative example suggests that lead ions are also transported to the surface along with the moisture that moves to the surface during the drying process. It is thought that it is concentrated at the edges of the cracked surface.

Examples 2 and 3 A gel-like porous body with a diameter of 15 mm was manufactured in exactly the same manner as in Example 1.

Next, this gel-like porous material was immersed in a 5 mol/l aqueous solution of potassium nitrate at 30°C for 2 hours, and then
It was immersed in 0°C Improper Tools, and in Example 3, 30°C acetone for 2 hours. After that, it was made into a whole (diameter 7■■, length 9mm by applying the same drying and heating transparency treatment as in Example 1).
A cylindrical glass body was obtained. The concentration distribution of lead ions in the half-body direction of this glass sample was measured from the transmitted intensity of X-rays, and the results are shown in FIG.

As shown in FIG. 2, both Examples 2 and 3 have lead concentration distributions that are high in the center and gradually decrease toward the periphery, and at the same time, the distribution slopes are clearly different between the two.
It can be seen that the effect of suppressing the movement of lead ions differs depending on the type of organic solvent in which the gel-like porous material is immersed. In other words, this shows that it is possible to precisely control the shape of the concentration distribution of lead ions by selecting the type of organic solvent, treatment time, etc.

Figure 3 shows the glass body obtained in Example 3 with a thickness of 0.5+
The graph shows the results of cutting out an am disk and measuring the refractive index distribution using a Matsuhatsu Ender interferometer.The distribution is parabolic in the range from the center to 3III, and the refractive index difference between the periphery and the center is 0. It was 037.

On the other hand, the refractive index difference obtained by the conventional method without immersion in an organic solvent is o, oie (J, Non-
Cryst, 5olids+ 85*1986, P2
44) According to the method of the present invention, the movement of metal ions in the gel-like porous material during drying is suppressed, and as a result, the concentration distribution based on metal salt interdiffusion is maintained, and the concentration distribution between the center and the periphery after vitrification is maintained. It was confirmed that a large difference in refractive index could be obtained between the parts.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the lead concentration distribution in the glass produced by the first invention method and the lead concentration distribution in the glass produced by the conventional method. FIG. 3 is a diagram showing a comparison of the lead concentration distribution in the produced glasses, and is a diagram showing the results of measuring the refractive index distribution in the cross section of the glass of Example 3 in FIG. 2. Patent applicant: Nippon Sheet Glass Co., Ltd. LCT21'Iryo Figure 1 Figure 2 Figure 3

Claims (3)

[Claims] (1) A gel-like porous body is obtained by adding a solution containing a water-soluble salt of a specific metal ion to a sol obtained by hydrolyzing a solution mainly composed of silicon alkoxide, and then the gel-like porous body is A method for obtaining a glass body by drying and heating, wherein the gel-like porous body is immersed in an organic solvent that has low solubility in the salt and is miscible with water before the vitrification treatment. Method. (2) In claim 1, after partially volatilizing the solvent contained in the gel-like porous material prior to the immersion treatment in the organic solvent, the gel-like porous material contains the same water-soluble salt as the salt. A method for manufacturing optical glass that involves immersing it in a solution. (3) A gel-like porous body is obtained by adding a solution containing a water-soluble salt of a specific metal ion to a sol obtained by hydrolyzing a solution mainly composed of silicon alkoxide, and then the gel-like porous body is In a method of obtaining a glass body by drying and heating, a gel-like porous body is immersed in a solution containing a water-soluble salt of a metal ion different from the above-mentioned ions, and the gel-like porous body is immersed in a solution from the surface of the gel-like porous body to the inside. A step of providing a gradually changing concentration distribution of metal ions, and a step of immersing the gel-like porous body in an organic solvent that has low solubility for both types of water-soluble salts and is miscible with water. A method for producing optical glass having a refractive index gradient characterized by: