JPH03141123A - Production of refractive index profile type optical element - Google Patents

Abstract

PURPOSE:To enable production of an element having a large caliber in a short time by treating a wet gel containing a refractive index imparting metal component according to a specific method in producing a refractive index profile type optical element using a sol-gel method. CONSTITUTION:A metal component, e.g. titanium tetrabutoxide, for imparting a refractive index profile is added to a solution of a silicon alkoxide in an alcohol to carry out hydrolysis and form a sol, which is subsequently injected into a suitable cylindrical forming container and then allowed to stand to prepare a rodlike wet gel 1 having a shorter length (B) in the axial direction than that of the diameter (A). Masks 2 such as glass plates are then contact bonded to both end faces of the wet gel 1. In this state, the resultant assembly is immersed in a solution 3, e.g. hydrochloric acid, for dissolving and diffusing the metal component to impart a desired refractive index profile in the radial direction. The masks 2 are subsequently removed to dry and sinter the rodlike wet gel. Thereby, a refractive index profile type optical element is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for manufacturing a gradient index optical element by a sol-gel method, which is applied to manufacturing optical lenses and the like.

[Conventional technology]

Conventionally, a method for manufacturing a refractive index distribution type optical element in which a refractive index distribution is imparted in the radial direction of a rod-shaped glass body is a sol-type optical element.
A gel method is used.

In this method, a sol containing a metal component for imparting a refractive index distribution is prepared, the sol is placed in a cylindrical container to prepare a rod-shaped wet gel, and then the rod-shaped wet gel is dissolved in the metal component. A rod-shaped glass body (bulk body) is obtained by immersing it in a diffusible solution to give a desired composition distribution, that is, a refractive index distribution, and then drying it to form a dry gel and firing it, and then a vaginal rod-shaped glass body. This was a method of manufacturing a gradient index optical element by cutting and polishing the material to a desired length.

[Problem to be solved by the invention]

However, the production of bulk bodies (rod-shaped glass bodies) using the sol-gel method has the disadvantage of requiring extremely slow drying because it is necessary to shrink and dry the gel without destroying it. ing. Therefore, when attempting to fabricate a gradient index optical element with a large diameter, the diameter of the rod-shaped wet kel must be increased, which poses the problem that the larger the diameter, the longer the drying time. Was.

In view of the above-mentioned problems, the present invention aims to provide a method for manufacturing a gradient index optical element, which can produce a large diameter gradient index optical element used as a normal optical lens in a short period of time. There is.

[Means and effects for solving the problems] A method for manufacturing a gradient index optical element according to the present invention is a method for producing a gradient index optical element by a sol-gel method, in which a metal component for imparting a gradient index is used. A rod-shaped wet gel having an axial length shorter than the diameter is immersed in a solution for dissolving and diffusing metal components with both end faces covered with a mask to impart a desired refractive index distribution in the radial direction, After that, the mask is removed and then the rod-shaped wet gel is dried and sintered, thereby allowing the solution to enter only in the radial direction of the rod-shaped wet gel, while drying the wet gel in the axial direction. It was designed to be carried out mainly from the beginning.

These points will be explained in detail below.

The drying time of a wet gel depends on the distance traveled by the solvent in the wet gel to be released outside the gel, so for a long rod-shaped wet gel as shown in Figure 2 (A), the drying time is will depend on the gel diameter.

However, if a rod-shaped wet gel with an axial length shorter than the diameter as shown in Figure 1 (A) is used, the drying time will be the shortest axial length, regardless of the radius of the gel. The shorter the length in the axial direction, the shorter the drying time becomes possible.

However, when a wet gel with a short axial length is immersed in a solution for melting and diffusing metal components to impart a refractive index distribution, the solution enters from the end face of the wet gel, and the metal components elute and diffuse. As a result, a phenomenon occurs in which the desired radial refractive index distribution cannot be obtained.

The present invention has been developed in consideration of the above points, and when producing a wet gel using the sol-gel method, a rod-shaped wet gel with an axial length shorter than the diameter is formed, and then a metal component is melted to impart a refractive index distribution.・Before immersing the wet gel in the diffusion solution, use a mask such as a plate that has good adhesion with the wet gel, has good dissociation properties after immersion, and is chemically stable against the wet gel and the immersion solution. After covering both end faces of the mask and immersing it in that state, the mask is removed during drying to enable drying from the axial direction and shorten the drying time.

The shorter the axial length of the rod-shaped wet gel, the shorter the drying time, so productivity can be maximized by setting it to the minimum length calculated from the shape of the desired optical element. becomes.

The reason for using a plate-like material as a mask for wet gel is that wet gel is extremely porous and is always filled with liquid, so it easily cracks when exposed to the atmosphere from the liquid. Because it is a substance, it is necessary to mask it, and the wet gel must be able to withstand the harsh conditions of being immersed in a strong acid solution to impart a refractive index distribution. This is because it is considered to be the most suitable material that satisfies the two conditions. This method is simple and most effective for wet gels that cannot be treated with conventional methods such as coating or vapor deposition of masking agents.

〔Example〕

Hereinafter, the present invention will be explained in detail based on the illustrated embodiments.

A methanol solution of Nran tetramethoxide containing titanium tetral butoxide as a metal component for imparting a refractive index distribution was prepared as a sol, and the above sol was poured into a cylindrical polypropylene container with an inner diameter of 50 mm to a height of 50 mm. After that, a wet gel 1 was prepared as shown in FIG. 1(A), in which the axial length B was longer than the diameter A.

Next, take out the obtained wet gel l from the container and
As shown in Figure (B), a diameter of 5 mm is attached to both end surfaces of the wet gel l.
A mask 2 made of a 0 mm glass plate was pressure-bonded and, while maintaining that state, was immersed in hydrochloric acid 3 to impart a titanium concentration distribution by elution of titanium. After the immersion was completed, the glass plate 2 that had been crimped was removed and dried at 60°C for 7 days to obtain a dry gel. After that, it is fired to a diameter of 20.6mm.
A rod-shaped glass body (bulk body) 4 was obtained. The refractive index distribution in the radial direction of the rod-shaped glass body 4 was controlled in the same way both at the end face and inside the rod-shaped glass body 4, as shown in FIG. 1(C).

As a comparative example, when producing a rod-shaped wet gel, the inner diameter was 50 mm.
Pour the sol into a mm container to a depth of 100 mm and prepare as shown in Figure 2 (
As shown in A), a wet gel 1' whose axial length B' is longer than the diameter A' was prepared, and the mask 2 was immersed in hydrochloric acid 3 without pressure bonding to both end faces, and then dried. From what I saw, the drying time to become a dry gel was 2.
It took a long time, 0 days, and the refractive index distribution after manufacturing the glass body 4' was disturbed at the end face as shown in FIG. 2(C).

As shown above, it has been confirmed that by using the mask 2, accurate control of the refractive index distribution becomes possible, and by making the wet gel 1 thinner, the drying time can be significantly shortened.

Star 2'i[g! A mask 2 made of film-like Teflon (registered trademark) was crimped onto both end surfaces of a rod-shaped wet gel l having a diameter of 60 mm and an axial length of 50 mm, which was prepared in the same manner as in the first embodiment. While holding the sample, it was immersed in hydrochloric acid 3 to impart a titanium concentration distribution. Thereafter, after drying at 60° C. for 7 days, the dry gel was fired to obtain a rod-shaped glass body 4 having a diameter of 20.4 mm.

In this case, the radial refractive index distribution of the glass body 4 was controlled in the same way both at the end face and inside.

In each of the above embodiments, a glass plate or a Teflon film is used as the mask 2, but it is a material that is chemically stable against hydrochloric acid 3 and wet gel 1 and has good contact with the end surface of wet gel 1. Anything is fine as long as it is good,
For example, Saran Wrap (registered trademark), polypropylene plate,
nickel plate.

Hastelloy plates can also be used as masks.

A convex lens-shaped wet gel 5 as shown in FIG. 3(A) was prepared by pouring a sol prepared in the same manner as in Example 1 into a suitable container.

Next, a mask 2' made of Teflon block processed into a shape that tightly adheres to the biconvex curved surface of the obtained wet gel 5 is brought into close contact with the biconvex curved surface, and while maintaining that state, hydrochloric acid 3 The titanium was immersed in the liquid to give it a titanium concentration distribution.

After the immersion, the mask 2' was removed from the wet gel 5 and dried at 60°C for 7 days to obtain a dry gel. Thereafter, it was fired to obtain a biconvex glass body 6 with a diameter of 20.8 mm. The radial refractive index distribution of the glass body 6 is shown in FIG.
It was as shown in B).

In this example, an example was shown in which a wet gel 5 having a biconvex curved surface was used, but by using wet gels having various shapes including a concave surface and an aspheric surface,
It is also possible to provide a special three-dimensional refractive index distribution.

It goes without saying that in each of the above embodiments, it is also possible to provide a refractive index distribution by eluting one portion of gold or a metallic component.

〔Effect of the invention〕

The method for manufacturing a gradient index optical element according to the present invention has an important practical advantage in that the manufacturing time for an optical element with a large diameter can be significantly reduced by shortening the drying time.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the first and second embodiments of the method for manufacturing a gradient index optical element according to the present invention and the refractive index distribution of the optical element manufactured using the method, and FIG. 2 is a diagram showing a comparative example and the refractive index distribution of the optical element manufactured using the method. A diagram showing the refractive index distribution of the optical element,
FIG. 3 is a diagram showing the refractive index distribution of the third example and the optical element manufactured thereby. ■... Rod-shaped wet gel, 2, 2'... Mask, 3... Hydrochloric acid, 4... Rod-shaped glass body, 5...
Convex lens-shaped wet gel, 6...biconvex glass body. , IP2 area (A) (B) (C) (A) (B) Age 3 figure (A) (B)

Claims (1)

[Claims] In a method for manufacturing a gradient index optical element using a sol-gel method, a rod-shaped wet gel containing a metal component for imparting a refractive index distribution and having an axial length shorter than the diameter is covered with a mask on both end surfaces. It is immersed in a solution for dissolving and diffusing metal components to impart a desired refractive index distribution in the radial direction.
A method for manufacturing a gradient index optical element, characterized in that the mask is then removed, and then the rod-shaped wet gel is dried and sintered.