JPH06239621A - Production of refractive index distribution type multicomponent-based glass - Google Patents

Abstract

PURPOSE:To readily produce a refractive index distribution type multicomponent-based glass having optically wide uses by more approaching a refractive index distribution, conventionally found in the case of a radial type refractive index distribution type optical element and tending to jumping up from a parabola to the parabolic shape. CONSTITUTION:This refractive index distribution type multicomponent-based glass is produced by a sol-gel method. In the process, a wet gel is dried while covering the surface of the wet gel in the direction at right angles from the direction of concentration distribution in the wet gel with a mask after a step for imparting the concentration distribution of a component contributing to the refractive index into the wet gel. Thereby, the moving direction of a solvent during the drying is controlled.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a lump glass body by a sol-gel method, and more particularly to a method for producing a multi-component glass having a refractive index distribution in the radial direction.

[0002]

2. Description of the Related Art There are two methods for producing a gradient index bulk multi-component glass by the sol-gel method, which are roughly classified according to the starting materials of the components that impart a refractive index distribution. One is a method using a metal alkoxide as the starting material (JP-A-61-183136, USP 4,7).
97, 376), and another method using a metal salt as a starting material (JP-A-63-2775).
No. 25, etc.).

The former is a method in which a silicon alkoxide is partially hydrolyzed using a catalyst such as hydrochloric acid, and the liquid contains a metal alkoxide as a component for increasing the refractive index of titanium or the like, water for hydrolysis, a solvent alcohol or the like. To prepare a sol, and after gelling and aging, immersing the gel in hydrochloric acid etc. to elute a part of the components for increasing the refractive index, and further subject the gel to treatment such as washing. After applying, it is a method of drying to obtain a dry gel, and finally baking to obtain a gradient index optical element.

On the other hand, the latter is sol by partially hydrolyzing silicon alkoxide or the like using a catalyst such as hydrochloric acid and adding a metal salt solution of a component such as lead acetate for increasing the refractive index to the solution. Was prepared, and after gelation and aging, the gel was sequentially immersed in a sparingly soluble solution of a metal salt such as alcohol to deposit and fix fine crystals of the metal salt in the gel pores, and then the gel Is immersed in a potassium acetate solution to exchange lead in the gel with potassium in the solution at an appropriate time, and then again immersed in a sparingly soluble solution of a metal salt such as alcohol to fix the metal salt. Is performed, then dried to obtain a dry gel, and finally baked to obtain a gradient index optical element.

In the latter method, unlike the former method (method using a metal alkoxide as a starting material), since the component for increasing the refractive index is supplied by the metal salt, the metal salt and the gel skeleton structure are provided. Since there is no binding relationship between and, it requires a step of fixing the introduced component in the gel. This fixing step is performed by immersing the gel in the solution to replace the solvent in the gel with a solvent in which the metal salt component is poorly soluble, and by precipitating fine crystals of the metal salt component in the gel, gel pores It is to be fixed in the sediment.

Comparing these two methods, the metal alkoxides that can be used in the former method are limited to alkoxides such as Si, B, Ti, Ge, Nb, Ta, P and Al which are liquids at room temperature. Since the types of elements that can be used for glass synthesis are extremely small, the former method is more limited in the composition system that can be produced than the latter method. Therefore, the latter method is suitable for producing a lump glass or a gradient index optical element with various composition systems.

[0007]

The optimum refractive index distribution of the gradient index optical element differs depending on the optical system to which it is applied, but the radial type gradient index optical element generally has a parabolic (quadratic curve) distribution. A close distribution shape is desirable for aberration correction.

However, the refractive index profile obtained when the gradient index optical glass is actually manufactured by the latter method described in the prior art is greatly deviated from the parabolic shape as shown in FIG. The refractive index distribution curve tends to jump at the outer peripheral portion of, and there is a drawback that an inflection point exists in the middle of the radial distribution curve.

The present invention has been made in view of the above conventional problems, and prevents the refractive index distribution from jumping up in the vicinity of the surface portion (outer peripheral portion in the radial type, end face portion in the axial type), and particularly the radial type. In the case of gradient index optical elements, it is possible to easily manufacture a refractive index profile multi-component glass with a wide range of optical uses, which has a refractive index profile that tends to jump from a parabola, which has been observed in the past, closer to a parabolic shape. The purpose is to provide a method of doing.

[0010]

In order to solve the above problems, the present invention provides a method for producing a gradient index optical element by a sol-gel method, wherein the concentration distribution of the components contributing to the refractive index in the wet gel is After the step of applying, the wet gel surface perpendicular to the concentration distribution direction in the wet gel was covered with a mask and dried.

The reason why the refractive index distribution curve jumps up only when a metal salt is used as a raw material is as follows.
It was found that the direct cause of the jump of the refractive index was the jump of the lead component distribution curve. Therefore, as a result of further studying the cause of the lead component jumping up, when a metal salt was used as a raw material, the solvent in the gel was replaced with a solvent in which the metal salt component was poorly soluble, and fine crystals of the metal salt component were precipitated in the gel. By doing so, the precipitate is fixed in the gel pores, but the solubility of the lead component (specifically lead acetate) in the sparingly soluble solvent is slight but not zero, so the lead component when the solvent dries It was also concluded that the direct cause of this problem is that it moves simultaneously with the solvent toward the gel surface in the state of being dissolved in the solvent.

For example, acetone, which is used as a poorly soluble solvent for fixing the lead component, progresses during the solvent exchange such as the solvent such as IPA used in the previous step of acetone substitution, the solvent originally contained in the gel, and the solvent exchange. It also contains water and alcohol produced by the reaction in the gel, and actually dissolves lead acetate more than the solubility of acetone. Therefore, even if a clean parabolic concentration distribution is formed, the solvent containing lead moves to the outer periphery of the gel in the solvent drying step, only the solvent evaporates and dries on the gel surface, and the lead component is concentrated inside the gel. Result. Due to this phenomenon, the lead concentration distribution collapses from the parabolic shape, and as a result, a jump is formed on the outer periphery of the gel.

From the above, if the movement direction of the solvent during the drying can be controlled so that the lead component does not move due to the drying of the solvent in the direction in which a clean concentration distribution shape is desired to be maintained, the above-mentioned problems occur. It can be solved. Therefore, the present inventors have succeeded in realizing a refractive index profile without jumping by providing a mask on the surface of the gel and controlling the moving direction of the solvent during drying.

Here, the case where the gel is masked will be specifically described. In the radial type gradient index optical element, since the distribution in the radial direction is particularly important in terms of optical characteristics, in order to prevent the solvent from moving in the radial direction, the surface perpendicular to the radial direction having the concentration distribution, that is, the cylindrical surface of the gel rod is Mask and dry. By doing so, the solvent in the gel does not move in the direction of the cylindrical surface of the gel, but moves only in the axial direction toward the end surface portion of the gel without the mask, and the drying progresses. Therefore, since the solvent does not move in the radial direction of the gel, the lead component concentration distribution does not jump up and the refractive index distribution shape does not collapse. However, since the gel shrinks slightly as it dries, the material of the mask provided on the cylindrical surface of the gel has chemical resistance to organic solvents present in the wet gel and also causes gel shrinkage. Natural rubber (polyisoprene), butyl rubber, or the like is desirable if the solvent present in the wet gel before drying is acetone, which has elasticity to follow.

On the other hand, in the axial type gradient index optical element, since the distribution in the optical axis direction is particularly important in terms of optical characteristics,
The same effect can be obtained by masking and drying the plate surface of the plate-like gel, which is important in the optical axis direction having the concentration distribution, so as not to move the solvent in the optical axis direction. In the case of the axial type, since the masking surface is a flat surface, a plate-shaped mask may be made of a solvent-resistant material instead of a rubber-based elastic material.

[0016]

Example 1 Tetramethyl silicate 30 ml, tetraethyl silicate 30 ml, triethyl borate 12.
4 ml are mixed, and 1 / 100N hydrochloric acid 25 ml is mixed with this.
Was added and stirred at room temperature for 1 hour to carry out a partial hydrolysis reaction. Here, a 1.25 mol / l lead acetate aqueous solution 10
A mixture of 7.63 ml and 15.35 ml acetic acid was added. After further stirring this for 3 minutes at room temperature,
The mixture was allowed to stand for 2 minutes, dispensed in a polypropylene container of φ35 mm, and gelled at room temperature. The obtained gel is 5 at 30 ° C.
Aging is carried out for one day, and further immersion in a 0.61 mol / l solution of lead acetate using a mixed solvent of IPA (isopropyl alcohol): water = 8: 2 at 60 ° C. is carried out to remove acetic acid and age the gel. It was This gel was labeled with IPA, IPA:
By dipping acetone in the order of 8: 2, 5: 5, and acetone for 2 days each, fine crystals of lead acetate were deposited and fixed in the gel pores.

The obtained homogeneous gel was treated with 0.305 mol / l.
Solution of potassium acetate in ethanol, and 0.15
After dipping in 150 ml of a solution adjusted to be an ethanol solution of acetic acid of 3 mol / l for 16 hours to impart distribution, IPA: acetone = 5: 5, acetone, and then by immersing in acetone for 2 days each, Fine crystals of lead acetate and potassium acetate were deposited and fixed in the gel pores.

A cylindrical natural rubber mask having a diameter of 18 mm was covered on the cylindrical surface of this gel and dried at 30 ° C. for 5 days to obtain a dry gel. During the drying, the gel shrank from φ32 mm to φ22 mm, but the tubular mask shrank as the gel shrank and did not separate from the cylindrical surface, and the drying was completed successfully. Remove the mask from the resulting dry gel 570
By heating up to ℃ and sintering, a colorless transparent glass body without cracks was obtained. When the refractive index distribution of the glass body was examined, the refractive index distribution was close to a parabolic distribution with no jumping to the outer peripheral portion as shown in FIG.

[0019]

Example 2 A sol prepared in the same manner as in Example 1 was used as φ8.
It was poured into a 0 mm polypropylene container to a height of 30 mm and gelled at room temperature. After aging the obtained gel, acetic acid was further removed and aged. IP this gel
By immersing A, IPA: acetone = 8: 2, 5: 5, and acetone in this order, lead acetate microcrystals were deposited and fixed in the gel pores.

The obtained homogeneous gel was immersed in an ethanol solution of sodium acetate for 1 hour to give a distribution, and then IP
Lead acetate and sodium acetate were fixed in the gel pores by immersing A: acetone = 5: 5, acetone, and acetone in this order. The wet gel thus obtained was sandwiched between Teflon plates, dried, and then sintered to obtain a colorless and transparent glass plate. When the refractive index distribution in the axial direction of this glass plate was examined, a monotonic increase in the refractive index was observed from the surface of the glass to a depth of about 3 mm, and the refractive index did not collapse at the glass surface portion.

[0021]

As described above, according to the manufacturing method of the present invention, it is possible to prevent the refractive index distribution from jumping up in the vicinity of the surface portion, and to easily provide a refractive index distribution type multi-component glass which is optically versatile. It becomes possible to manufacture.

[Brief description of drawings]

FIG. 1 is a graph showing a refractive index distribution of a radial-direction gradient index optical element manufactured according to Example 1 of the present invention.

FIG. 2 is a graph showing a refractive index distribution of a radial direction gradient index optical element manufactured by a conventional manufacturing method.

Claims (1)

[Claims] 1. A method of manufacturing a gradient index optical element by a sol-gel method, after the step of imparting a concentration distribution of a component that contributes to the refractive index to the wet gel, with respect to the concentration distribution direction in the wet gel. A method for producing a gradient index multi-component glass, which comprises drying a vertical wet gel surface with a mask.