JPS63303834A - Production of optical element - Google Patents

Abstract

PURPOSE:To prevent unnecessary ion exchange and loss of a transparent dielectric material and to efficiently obtain an optical element by utilizing the fine pore of a porous material having communicated pore to hold fused salt in the case of bringing the fused salt into contact with the transparent dielectric and producing the optical element with an ion exchanging method. CONSTITUTION:A porous material 2 (e.g. porous glass) in which many fine pore having fine diameter are communicated with fine communicated pore is immersed into fused salt (e.g. sodium nitrate) contg. exchangeable cations to hold the fused salt in the fine pore of the porous material 2. Then the aimed optical element is obtained by bringing this porous material 2 into contact with a transparent dielectric 1 (e.g. glass) and ion-exchanging the cations incorporated in the transparent dielectric 1 with the cations contained in the fused salt via a contact part by an ion exchanging method. Further as the ion exchanging method, a thermal diffusion method and an electric field migration method, etc., are used.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method for manufacturing an optical element using an ion exchange method.

More specifically, the present invention relates to a method of utilizing the pores of a porous body having communicating pores to retain the molten salt in an ion exchange method carried out by contacting a transparent dielectric with a molten salt.

[Conventional technology]

In recent years, with the development of micro-optics, optical elements with various functions have become necessary. Among these, graded index optical elements allow light rays to meander through a transparent dielectric material, allowing the image formation position of an object to be selected arbitrarily, and are often used as parts for optical communication and copying machines. It is becoming.

Many manufacturing methods have been proposed to date for manufacturing this gradient index optical element, but among them, the ion exchange method has been researched the longest and is currently in practical use. In this method, monovalent cations in a transparent dielectric and monovalent cations in a molten salt in contact with the dielectric are exchanged using heat or heat (heat + electric field).

Generally, in the case of thermal ion exchange (thermal diffusion method), a method is known in which a transparent dielectric is completely immersed in a container filled with molten salt. In addition, when producing a flat microlens as shown in FIG. 2, in order to convert only a part of the transparent dielectric 3 into a lens by thermal diffusion, a mask 4 having an opening 5 is formed by vapor-depositing a metal such as Ti. ion exchange with the molten salt 6 through this opening. However, this method has the drawback that when immersing in molten salt for a relatively long time as in the thermal diffusion method, diffusion tends to occur from other than the predetermined openings due to deterioration of the mask due to heat.

Next, ion exchange (electric field transfer method) using (heat + electric field) has been attracting considerable attention in recent years as a method for producing flat microlenses (Appl, 0p).
t0. ■、411. (1983). This method aims to speed up the thermal diffusion of ions by using an electric field. For this reason, although the problem of mask deterioration in the thermal diffusion method is considerably improved, the following new problems have arisen.

(2) In order to bring both sides of the transparent dielectric substrate into contact with the molten salt, a container is required to contain the molten salt, and it is usually necessary to process the dielectric substrate into a box-shaped structure to hold the molten salt. Therefore, there is a lot of loss of dielectric material, and processing time is also required.

■Instead of the box-shaped structure, a method of applying a conductive paste made of clay and molten salt was also used, but since the molten salt could not be replenished, it was difficult to apply an electric field for a long time, and It is difficult to mix the molten salt uniformly.

(Problems to be Solved by the Invention) The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a highly efficient method of manufacturing an optical element that does not have the above-mentioned problems.

[Means for solving problems]

That is, the present invention relates to a method for manufacturing an optical element by an ion exchange method in which a molten salt and a transparent dielectric are brought into contact with each other, and the optical element is characterized in that the molten salt is held in a porous body having communicating holes. This is a manufacturing method.

As the molten salt used in the present invention, sodium nitrate, potassium nitrate, etc. containing exchangeable cations are generally used. Various materials such as glass and crystal can be used as the material for the transparent dielectric, but glass is generally preferably used. Materials for the porous body include metals, ceramics, glass, etc., and glass, which is easily available, is preferably used.

The porous body having communicating pores of the present invention refers to a porous body in which a large number of pores of minute diameter forming the porous body are connected through minute pores. For example, in the case of porous glass, several dozen ~Several thousand pores exist in the glass skeleton mainly composed of 5i02 and are connected to each other at random without directionality. Therefore, by appropriately selecting a porous glass having different pore sizes depending on the viscosity of the liquid, it is possible to impregnate and retain various liquid molten salts.

A fiber assembly obtained by bundling a large number of alumina fibers, quartz fibers, etc. and polishing the bundle in two planes perpendicular to the fiber rows can also be used as the porous body.

The present invention will be explained below using figures.

FIG. 1 shows the basic configuration of the present invention. In the figure, 1 is a transparent dielectric material, and 2 is a porous material in which molten salt is impregnated and held in its pores. The monovalent cation in the transparent dielectric material contacts the molten salt in the porous material through an ion exchange reaction, whereby only one cation is exchanged. The exchange rate is determined by the processing temperature, the type of molten salt, the composition of the transparent dielectric, etc.

FIGS. 3 and 4 show conceptual diagrams of microlens production by the thermal diffusion method and ion exchange method according to the present invention. In FIG. 3, the protrusion 9 is provided by processing a part of the porous body 8 that impregnates and retains molten salt, or by using another porous body together, and ion exchange is performed through this contact portion. .

The molten salt in the porous body 8 is continuously replenished to the 9 parts by the capillary action of the pores to continue ion exchange. According to this method, there is no need for a container for holding the molten salt, and since the transparent dielectric material 7 and the porous material 8 do not come into contact with each other except in necessary areas, unnecessary ion exchange does not occur. Furthermore, a mask 11 provided with an opening 12 as shown in FIG. 4 can be used. The mask 11 is usually formed by Ti vapor deposition, etc., and the size of the opening 12 is minute, with a diameter of several tens of microns to several liters and a thickness of several hundred to tens of thousands. 12
Since the molten salt container as shown in FIG. 2 is not required, the positions of the transparent dielectric IO and the porous body 13 can be reversed by utilizing the molten salt holding ability of the porous body 13. It is possible. Figure 3.4 shows an example in which a transparent dielectric and a molten salt contact each other at one point to perform ion exchange to produce one microlens, but by providing multiple contact areas to perform ion exchange, multiple microlenses can be fabricated. It is also possible to obtain a microphone lens at the same time. It is also possible to simultaneously obtain a plurality of lenses of the same or different types by impregnating and retaining molten salts of the same or different types in a plurality of porous bodies and bringing them into contact with the transparent dielectric at a plurality of locations to perform ion exchange.

FIG. 5 is an example of manufacturing a microlens by the electric field transfer method according to the present invention. 14 is a glass substrate which is a transparent dielectric;
15 is a mask, 16 is an opening in the mask, 17 and 18
This is a porous glass material whose pores are each impregnated with a molten salt. 19 and 20 are electrodes, and 21 is a DC power source. A voltage is applied between the electrodes 19 and 20 that are in contact with the porous glass holding the molten salt, and the monovalent cations in the molten salt held on the porous glass 18 are opened by the electric field effect. Inject into the glass substrate through the tube. If the mask 15 deteriorates, the opening 16 may be made of porous glass without using a mask. In this electric field transfer method, molten salts are spaced apart on both sides of a glass substrate, and both molten salts are held in the porous glass.

FIG. 6 is a diagram showing an example in which the shape of porous glass is changed. As shown in the figure, by processing the porous glasses 22 and 23 to provide molten salt supply parts a and b, replenishment can be easily performed. According to this method, compared to the case of using a base that was conventionally difficult to replenish, or the method of processing a glass substrate into a box shape each time, it can be used repeatedly, replenishment is easy, and efficiency is significantly improved.

〔Example〕

Examples according to the present invention will be described below.

(Example 1) FIG. 7 shows an example in which a plurality of types of gradient index lenses are manufactured by a thermal diffusion method.

Optical glass block containing a total of 18 mol% of Na and Ni (
A sample 27 was prepared in which the entire surface of a cube measuring 10 mm x 10 mm x 10 mm was polished. Porous glass protrusions 32, 33.34 with a diameter of
．． Porous glass (5x5X3mm
, pore diameter 400) 28.29, 30°31 were brought into close contact. Note that the porous glasses 28, 29, 30 and 31 were each preliminarily treated with T12 So, 30 mol%, and Z at 520°C.
nSo470 mol%; T12 So440 mol%, Z
nSo460 mol%; T12 So450 mol%, Z
nSo450 mol%; T12 So, 60 mol%,
The specimens were immersed in four types of molten salts containing 40 mol % of ZnSo for 1 hour. After completing the above preparations, heat the sample to 500℃.
Heat treatment was performed for 100 hours. In the obtained glass block, a refractive index distribution is formed in the regions shown in 36.37 and 38.39, and the diffusion depth is 1.47°1, respectively.
．． Although there was not much difference between 50, 1.55, and 1.59 mm,
The refractive index difference is 0.116. O,132,0,14
Four types of lenses with considerable differences of 5, 0, and 162 were obtained at the same time.

(Example 2) FIG. 8 shows an example of manufacturing a plurality of gradient index lenses with the same performance by the electric field transfer method.

Optical glass substrate containing a total of 18 mol% of Na and Ni (30
A sample 40 of 30×30-1 (2 mm x 30 x 5 mm) was prepared in which two surfaces were polished to parallel planes. A mask 41 having a large number of openings with a diameter of 0.5 m + 2 at intervals of 1.0 m was formed on one side of this polished surface by Ti evaporation. At the same time, porous glass with a pore diameter of about 400 people (30x 30x
Prepare two sheets of 3 mm) and heat them at 520℃T12So,
The porous glass was immersed in a molten salt containing 60 mol %, Zn5O, and 40 mol % for 1 hour to uniformly impregnate and maintain the molten salt in the porous glass. Next, place the two pieces of porous glass 43.
The 30X 30mm surfaces of the two were completely brought into close contact. Furthermore, electrodes 45 and 46 made of platinum plates were attached to opposite sides of the contact surface between the porous glass and the glass substrate, and connected to a power source 47 so that the Ti mask side became the positive electrode. After completing the above preparations, the sample was placed in an electric furnace maintained at 500° C., and current was applied for 4 hours under constant current control of 0.2 A to transfer an electric field. When the surface of the obtained sample on the Ti mask side was polished, the diameter was 2.2 mm.
A large number of mm hemispherical lenses were formed, and lenses with the same performance at the periphery of the block as at the center were obtained.

[Embodiment 3] FIG. 9 shows an example of processing porous glass and replenishing molten salt using the electric field transfer method.

In the configuration shown in Example 2, porous glasses 43 and 44 were replaced with 51 and 52. The porous glass 51 was prepared by plane-grinding a plate-shaped glass (40 x 30 x 5 mm) with a pore diameter of approximately 400 mm from one end of a 40 x 30 mm surface until the thickness of the portion corresponding to 30 x 30 mm was 3 mm. Similarly, the porous glass 52 has the above-mentioned plate shape (40x
30 x 5 mm) was prepared by surface grinding a portion corresponding to tox 30 mm from one end of a 40 x 30 Ql11 surface until the thickness was 3 mm.

Next, four glass substrates on which the Ti masks shown in Example 2 were formed were prepared, and one of them was preheated at 520°C with a T12
It was sandwiched between porous glass 51.52 which was immersed in a molten salt containing 50,460 mol % and ZnSo 440 mol % for 1 hour and then taken out. Next, platinum plate electrodes 53 and 54 were attached to opposite surfaces of the contact surfaces between the porous glasses 51 and 52 and the glass substrate 48, and connected to a power source so that the Ti mask 49 side became the positive electrode. After completing the above preparations, the sample was placed in an electric furnace maintained at 500° C., and current was applied under constant current control of 0.2 A for 4 hours to transfer an electric field. However, at this time, Figure 9c,
The molten salt was replenished to part d at a rate of 1-1 hourly.

After 4 hours, the sample was taken out, another glass substrate was attached, and electric field transfer was continued, and this process was repeated to process four glass substrates.

When the surface on the Ti mask side of each of the four obtained samples was polished, many hemispherical lenses with a diameter of 2.2m+o were formed, and lenses with the same performance as the central part were formed in the peripheral part of the glass substrate. Obtained. Furthermore, there was almost no variation among the four samples, and this method made it possible to fabricate microlenses almost continuously for a long time.

〔Effect of the invention〕

According to the present invention, unnecessary ion exchange and loss of transparent dielectric material are prevented by using a porous body having communicating holes as a holder for molten salt in the ion exchange method, and molten salt can be easily replenished for a long time. It is now possible to manipulate time. Furthermore, it has become possible to simultaneously bring different types of molten salt into contact with multiple parts of the transparent dielectric, making it possible to create a new integrated optical element that has multiple types of refractive index distributions. Furthermore, even in cases where the mask is severely deteriorated, by substituting a suitable porous material, ion exchange can be performed without the need for a mask, which has great industrial value as a method for manufacturing optical elements.

[Brief explanation of drawings]

FIG. 1 is a vertical cross-sectional view showing the basic concept of the present invention, FIG. 2 is a vertical cross-sectional view showing an example of a conventional thermal diffusion method, and FIGS. 3 and 4 are examples of a thermal diffusion method according to the present invention. A vertical cross-sectional view showing
Fig. 5 is a longitudinal cross-sectional view showing a configuration in which the present invention is applied to the electric field transfer method, Fig. 6 is a longitudinal cross-sectional view showing an example in which the shape of porous glass is changed, and Fig. 7 is a longitudinal cross-sectional view showing a configuration in which the present invention is applied to the thermal diffusion method. A horizontal sectional view showing an applied embodiment, and FIGS. 8 and 9 are vertical sectional views showing an embodiment in which the present invention is applied to an electric field transfer method. 1, :l, 7, 10.14, 24, 27.40.48・
---Transparent dielectric material, 4.11, 15, 25.41.4
9------Mask, 5. +2.16, 26, 42.
50---Mask opening, 6 ・---・---------
−−−−−−−−−−−−=molten salt, 9.32,33
．． 34.35------Protrusion, 19.45.5
3= −−−−−−−−−−−−− Negative electrode, 20.46
．． 54---------------Positive electrode, 21
．． 47.55-----------DC power supply.

Claims (1)

[Claims] 1. A method for manufacturing an optical element by an ion exchange method in which a molten salt and a transparent dielectric are brought into contact, characterized in that the molten salt is held in a porous body having communicating holes. A method for manufacturing an optical element. 2. The method for manufacturing an optical element according to claim 1, wherein the transparent dielectric material and a porous body having a plurality of communicating holes that hold the same or different kind of molten salt are brought into contact at a plurality of locations. 3. The method for manufacturing an optical element according to claim 1 or 2, wherein the ion exchange method is an electric field transfer method.