JPH08187461A - Production of refractive index distribution type microlens - Google Patents

Abstract

PURPOSE: To easily produce a microlens having refractive index distribution high in reproducibility and reliability in optical characteristics such as a refractive index, refractive index difference or dispersion characteristics by precisely controlling the shape of metal distribution in a porous element. CONSTITUTION: In a method for producing a microlens having a refractive index distribution layer wherein a refractive index change region is 1mm or less from a surface by sintering a porous element 6, the surface to which refractive index distribution must be imparted of the porous element 6 is brought into contact with a soln. containing at least one component selected from an org. solvent, water, an acid and alkali or a soln. prepared by further dissolving a metal component in the soln. At this time, a stage 5 is rotated by a motor 3 and the soln. is applied to the porous element 6 on the stage 5 in the thickness half or less that of the refractive index distribution layer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a gradient index microlens of a micro optical system used in a copying machine, a liquid crystal projector, a communication device, a solid-state image pickup device and the like.

[0002]

2. Description of the Related Art In recent years, a new optical area called micro optics has been actively researched and many uses thereof have been studied. However, a lens used in the micro optics area is called a micro lens, and its necessity is It is rising.

In order to manufacture such a microlens, there is a limit to the size and cost that can be processed by polishing which has been performed since ancient times, and therefore a completely new lens manufacturing method has been proposed. As one of them, a method of manufacturing a microlens by the sol-gel method has been studied.
Since the sol-gel method can adjust the chemical composition of the sol in a low-temperature process, multi-component glass having various optical characteristics can be synthesized, and therefore various characteristics (refractive index,
It is expected that microlenses with an Abbe number, color, etc.) will be obtained.

Generally, as a method for producing a microlens by the sol-gel method, a mask is applied on a flat porous body except spots to be distributed by a resist, and then a distribution-imparting solution containing a metal salt is applied. There is a method in which a microlens array having a refractive index distribution on a flat plate is obtained by immersing it to give a distribution and then dissolving the mask.

Further, Japanese Patent Application Laid-Open No. 2-88433 discloses that
The sol is brought into gel while contacting the matrix having the lens pattern, and the resulting wet gel is dried to form a dry gel and then masked, and the dopant is diffused from the center of the lens to increase the refractive index (or lower the refractive index). ), Or a method of obtaining a microlens by performing a step of diffusing a dopant from the end of the lens to increase (or decrease) the refractive index.

On the other hand, a method of increasing the difference in the refractive index between the central portion and the outer peripheral portion of the gradient index optical element is disclosed in JP-A-4-26.
It is disclosed in Japanese Patent No. 0608. In this method, a step of eluting a metal component from a wet gel obtained from a sol containing a silicon alkoxide and a metal alkoxide which is a component for increasing the refractive index is performed a plurality of times, and in the first concentration distribution imparting step, the solution to be immersed is a gel An appropriate time for reaching the center and dissolving the metal component and diffusing the dissolved component out of the gel is defined as the distribution imparting time. After fixing the metal concentration distribution once, in the second and subsequent concentration distribution applying steps, the time for which the solution to be dipped does not reach the center of the gel is adjusted so that the concentration of the metal component in the center of the gel is maintained. It is a method of estimating from the diffusion rate and immersing in a new distribution-imparting solution.

Further, in Japanese Patent Application No. 5-319145, a porous body is intermittently brought into contact with a distribution-imparting solution so that the apparent distribution-imparting time can be easily manipulated to obtain a minute refractive index. A method for precisely controlling the refractive index distribution of a distributed optical element has been proposed.

[0008]

At present, in a micro optical system, as one of high-performance optical elements, a microlens which is small and has various aberrations corrected as in a normal optical system is required. As an example thereof, a microlens array having a refractive index distribution portion having a diameter of 0.1 mm (that is, a depth of 0.05 mm) in FIG.
A microlens array having a 1 mm (that is, a height of 0.05 mm) refractive index distribution portion on a glass plane,
(C) Diameter is 0.1 mm (that is, radius is 0.05 mm)
And a rod-shaped micro-diameter lens. When manufacturing such an optical element, not only the shape of the optical element but also precise control of the refractive index distribution in the porous body, which is the base of the microlens, is indispensable with miniaturization.

A conventional method of masking and Japanese Patent Laid-Open No. 2-88
Even if an attempt is made to manufacture a minute microlens by the method described in Japanese Laid-Open Patent Publication No. 433 or JP-A-4-260608,
Since the diffusion of metal ion species in the porous body is fast, the distribution application time is very short, and slight variations in manufacturing conditions such as solution temperature, solution concentration, and distribution application time are It has a drawback that the reproducibility and reliability are poor in the optical characteristics such as the refractive index, refractive index difference, dispersion characteristics, etc. of the microlenses having a fired refractive index distribution, which vary the distribution shape of the composition of the metal species. It was

Further, even if an attempt is made to manufacture a microlens as shown in FIG. 2 by the method described in Japanese Patent Application No. 5-319145, the surface of the gel is smaller than the surface area of the gel because the porous body is very small. Since a relatively large amount of the distribution-imparting solution adhered, it was not possible to accurately manufacture a glass body having a desired refractive index distribution.

The present invention has been made in view of the above conventional problems, and in a method for producing a microlens having a portion having a refractive index distribution of 1 mm or less in diameter, particularly 0.5 mm or less, for obtaining a porous body, A method for easily manufacturing a microlens having a highly reproducible and reliable refractive index distribution in optical characteristics such as refractive index, refractive index difference, and dispersion characteristic by precisely controlling the shape of metal distribution in a porous body. The purpose is to provide.

[0012]

In order to solve the above-mentioned problems, the invention according to claim 1 has a refractive index distribution in which the portion where the refractive index changes is 1 mm or less from the surface by sintering a porous body. In a method for producing a microlens having a layer, a porous body is provided with a refractive index distribution to a solution containing at least one selected from an organic solvent, water, an acid and an alkali, or a solution in which a metal component is dissolved in the solution. The step of bringing the surfaces to be in contact with each other and applying the solution to a thickness of half or less of the refractive index distribution layer is adopted.

The invention according to claim 2 is a method for producing a microlens having a refractive index distribution portion whose refractive index change portion is 1 mm or less from the surface by sintering the porous body, The body has a substantially cylindrical shape, and the solution and the curved side surface of the substantially cylindrical porous body are brought into contact with each other, and the solution has a thickness equal to or less than the radius of the curved side surface of the substantially cylindrical porous body. It was decided to have a step of applying to give a refractive index distribution in the radial direction.

The invention according to claim 3 is a method for producing a microlens having a refractive index distribution portion in which the portion where the refractive index changes is 1 mm or less from the surface by sintering the porous body, The body is a flat plate, and after forming a resist on the surface of the porous body having a substantially circular hole in a part thereof, the solution and the substantially circular hole of the porous body are brought into contact with each other to form the substantially circular shape. In the step of producing a substantially hemispherical refractive index distribution portion centered on the hole of, having a step of applying the solution to the substantially circular hole to a thickness not greater than the radius of the hemispherical refractive index distribution portion, did.

[0015]

The gel, which is a porous body, is dipped in a solution for imparting distribution, and the metal component in the porous body is dissolved to form a metal concentration distribution. In general, a solution of an organic solvent, water, an acid, an alkali, or a mixed solution thereof, or a solution obtained by dissolving these solutions and a metal component (especially a metal salt) is used as the solution for the metal species of the porous body. A solution having a solubility that dissolves is used. On the other hand, in order to maintain the metal concentration distribution imparted to the porous body, a solution having a solubility that precipitates the metal species is used.

Hereinafter, the drawbacks of the conventional method will be clarified from the viewpoint of its operation, and then the operation of the present invention for solving the above-mentioned drawbacks will be described.

In the conventional method, the gel, which is a porous body, is completely immersed, and the liquid phase is exchanged until the distribution-imparting solution reaches the center of the porous body. Here, when the diameter of the gel is very small, the distribution-imparting solution adheres to the gel in an excessive amount,
The desired refractive index distribution could not be obtained because the distribution was too advanced. Even in the distribution fixing step, the desired distribution of the refractive index cannot be obtained because the excessive distribution fixing solution dissolves a part of the metal concentration distribution component formed in the porous body and disturbs the shape with feces. It was In other words, when the diameter of the gel is very small, the amount of solution of the distribution-imparting solution or the distribution-fixing solution is the distribution shape of the metal species of the gradient index optical element, and thus the optical properties such as the refractive index, refractive index difference, and dispersion characteristics It is an important parameter that controls the characteristics. Therefore, if the amount of the distribution-imparting solution or the amount of the distribution-fixing solution can be controlled so as to be brought into contact with the porous body, the distribution shape of the metal species of the gradient index optical element in the microlens can be precisely controlled. It will be possible.

The present invention has been made in view of the above. As a result of earnest research, the present inventor has found that FIG.
In the case of a microlens array having a minute diameter as shown in (B), the desired distribution depth has a large relationship with the amount of the distribution-imparting solution, as shown in the sectional view of FIG. 3 (A). Found. In FIG. 3 (A), the part powder indicated by 1 is the refractive index distribution portion, and in FIG. 3 (B), the raised protrusion is the refractive index distribution portion. Further, in the case of the cylindrical lens as shown in FIG. 2C, the radial depth has a large relationship with the liquid amount of the distribution-imparting solution as shown in the sectional view of FIG. 3B. Found. In FIG. 3B, 2
The powder indicated by is the refractive index distribution site.

That is, by applying the distribution-imparting solution to a thickness of half or less of the desired refractive index distribution phase of the porous body,
It has been found that it is possible to precisely control the distribution shape of the metal species of the gradient index optical element with a minute lens.
This is because the relationship between the amount of the distribution-imparting solution and the depth at which the distribution should be imparted to the porous body is
It means that it can be determined only by the surface area to which the distribution is given rather than the volume.

In the distribution imparting step, the distribution can be imparted by diffusing the applied distribution imparting solution, but since a new excess amount of the distribution imparting solution is not supplied from the surface phase, it is introduced onto the porous body. Since only the applied liquid layer is diffused and the distribution imparting speed is reduced, fine distribution control is possible even with an extremely small diameter.

After the distribution is imparted, the distribution-imparting solution may be naturally evaporated or the porous body may be immersed in a large amount of the distribution-fixing solution to wash away the distribution-imparting solution. It is preferable to remove the distribution-imparting solution, since organic substances, acids, etc. may remain or the distribution shape formed in the porous body may collapse. For this method,
As in the case of giving the distribution, an appropriate amount of the distribution fixing solution may be applied to the porous body, or the gas may be blown to blow off the distribution giving solution, or a combination thereof may be used.

The case where the present invention is used in the distribution imparting step has been described above.
It is effective as described below. As mentioned earlier,
A solution having a low solubility of metal species is used as the distribution fixing solution for fixing the metal concentration in the porous body. However, when trying to manufacture the minute optical system lens by the conventional method,
Since the amount of the distribution fixing solution with which the porous body comes into contact is very large, many metal salts are dissolved or re-diffused, and the metal concentration distribution formed in the distribution providing step is destroyed. On the other hand, when the present invention is used, since the distribution fixing solution contacting the porous body is small, the metal species can be dissolved or the metal component distribution can be fixed without re-diffusion,
It is possible to obtain a desired distribution shape without breaking the metal component distribution of the porous body.

The so-called spin coating method is suitable for the step of applying the distribution-imparting solution or the distribution-fixing solution to the porous body. FIG. 1 shows a spin coating apparatus. A disc-shaped stage 5 that rotates around an axis in a horizontal plane is connected to a motor 3 via a gear mechanism 4. The porous body 6 is placed on the stage 5. A solution dropping port 7 for the distribution-imparting solution or the distribution-fixing solution is arranged above the porous body 6.

For example, when giving distribution to a microlens array of a porous body as shown in FIG. 2A, the porous body 6 is rotated at a high speed by using the device as shown in FIG. An appropriate amount of solution is dropped from the solution dropping port 7 to the center of the porous body 6. Then, the solution uniformly spreads toward the outer peripheral portion of the porous body 6 due to the shearing force. In many cases, such as when the porous body 6 has a flat surface or gentle irregularities, it is possible to drop the solution at one point and spread it evenly. You may drop it at several points.

The solution coating method is optimal because the spin coating method can be applied to any case.
This is achieved by changing the rotation speed of the stage 5 on which the porous body 6 is placed in the apparatus as shown in FIG.
This is because a solution having any viscosity can be applied to a uniform thickness. Further, as another application method, a method of applying the solution with a brush, a so-called dip coating method of passing the porous body through the solution for a moment, or the like may be used.

The porous material is a so-called gel obtained by gelling a sol obtained by hydrolyzing silicon alkoxide or the like, or a soot produced by the CVD method or the VAD method,
Porous glass produced by a phase separation method or the like is used. The thickness of the solution to be applied needs to be appropriately changed depending on the amount and shape of pores present in the porous body (pore volume, specific surface area, pore diameter), but is generally prepared by the sol-gel method or the like. Any porous body having a density of about 0.3 to 1.8 g / cm ³ may be used.

Acids and their metal salts and alkalis include organic acid salts such as acetic acid, lactic acid, citric acid, malic acid, maleic acid and oxalic acid, inorganic acids such as hydrochloric acid, nitric acid and nitrous acid and salts thereof, and water. Oxides, alkalis such as ammonium and bases thereof can be used.

The above metal salt used as a distribution-imparting solution,
By appropriately changing the solution containing at least one component selected from an acid, an organic solvent, an alkali, and water, the concentration distribution shape of the metal species in the porous body can be changed. For example, the porous body is made to contain a metal component to be distributed in advance, and the metal component is eluted from the porous body by contacting with a solution for eluting the metal component containing acid, water, organic solvent, alkali and the like. Thereby, distribution can be given to the porous body.

When it is desired to impart a concentration distribution to a plurality of metals, the first metal species is contained in the porous body,
The distribution can be imparted to the first and second metal components by bringing them into contact with the distribution imparting solution in which the component for dissolving the metal component and the second metal component are mixed.

The amount of the distribution-imparting solution is determined in consideration of the diffusion rate of the metal species to be distributed, the solution composition and concentration, the liquid temperature, the contact time, the composition and pore diameter of the porous body, and the diameter of the porous body. It is necessary to appropriately change parameters such as the time to be applied to the distribution-imparting solution, but by controlling these parameters, it becomes possible to control the distribution shape in the porous body with high accuracy.

By fixing the distribution of the porous material obtained by these operations, drying and firing, a refractive index distribution with high reproducibility and reliability is obtained in optical characteristics such as refractive index, refractive index difference and dispersion characteristics. The microlens can be easily manufactured.

Further, the present invention can be applied to a flat plate microlens in which lenses are arranged in a flat plate shape at regular intervals, a rod shape such as a cylinder, a prism or an elliptic cylinder, or a spherical or elliptical shape, or a waveguide. . Further, it is particularly effective when the diffusion distance of the metal species from the surface of the porous body is short. That is, in the case of a rod shape or the like, it is effective when it is extremely small. It is also particularly effective for a flat plate microlens. It is particularly effective when the diffusion rate of the metal species contained in the porous body is high.

[0033]

【Example】

 [Embodiment 1] FIG. 4 shows a conceptual diagram of the whole process of this embodiment.
You. 41.8 g of Si (OCH₃) _Four70ml of eta
Add the nol and add 9.6 ml of 2N hydrochloric acid to add water.
Dissolve this solution, and add 1 mol / l lead acetate aqueous solution to 80 m
1 and 32 ml of 17N acetic acid were added to prepare a sol. This
The sol is a square glass substrate with a side of 1 cm and a thickness of 5 mm.
The plate 8 was coated and gelled. The thickness of 9 layers of gel
It was 2 mm. With a diameter of 0.005 mm on the surface of the gel
With the mask member 11 in which 25 circular patterns 10 are formed
Masked, matrix-shaped circular exposed areas
Was formed.

Distribution was given by the apparatus shown in FIG. That is, the masked substrate 10 is placed on the stage 5, and the stage 5 is moved by the motor 3.
It is rotated at a speed of 0 rpm, and 1 mol / l potassium acetate of H
0.5 ml of the distribution-imparting solution 12 of ₂ O: methanol = 5: 5 (vol ratio) was dropped to a thickness of 0.2 mm, K ⁺ and Pb 2 ⁺ were exchanged, and the mask was not masked. Distribution was given to the part. After that, the mask member 11 is removed, and drying and baking are performed to form a refractive index distribution portion 14 having a radius of 0.05 mm in the gel 9 layer, and a microlens array having a desired parabolic refractive index distribution shape is obtained. Was given.

[Comparative Example 1] A porous substrate prepared in the same manner as in Example 1 was immersed in 20 ml of a distribution-imparting solution, and then 20
Treated twice with ml acetone. After that, drying and sintering were performed in the same manner as in Example 1, but the distribution shape collapsed, and a microlens array having a desired refractive index distribution shape could not be obtained.

Example 2 The sol produced in the same manner as in Example 1 was coated on a glass substrate having a mask formed of an organic photoresist. This is to form a hemispherical pattern by utilizing the water repellent effect of the organic photoresist. After gelling this sol, the mask was removed to form a convex gel lens pattern having a diameter of 0.5 mm. This gel lens plate is turned upside down, that is, with the convex portion facing downward, the surface of the distribution-imparting solution similar to that in Example 1 is contacted with a diameter of about 0.1 mm from the center of the convex shape, and after the distribution is imparted, the distribution-fixing treatment Then, the obtained substrate was heat-treated to obtain a light-collecting element having a matrix-like convex shape and having a refractive index distribution formed by the tops of the surfaces of the lens pattern.

[Example 3] Using silicon tetrachloride and lead chloride as raw materials, 20 soot of SiO ₂ -PbO having a diameter of 1 mm were prepared by the VAD method. Prepare a solution in which potassium chloride is dissolved in a mixed solution of water and ethanol, rotate the soot at a speed of 100 rpm by using a device as shown in FIG. 5, and brush each soot surface 0.5 mm.
This solution was applied so that it touched. Since the brush used a soft bristle material, it was in the direction of rotation with the soot, and it was considered that the brush actually touched only an area smaller than 0.5 mm. After that, a strong wind was blown to the soot by a fan to remove the solution, and then dried. By firing these soots up to 570 ° C., it was possible to obtain a glass body having a so-called convex distribution in which the refractive index is high at the center of the glass body and low at the edges. An analysis of the refractive index distributions of these rods revealed that all the glass had a diameter of 0.3 mm and had the same refractive index distribution.

Example 4 As a substrate glass, the composition ratio (mol%) was 63SiO ₂ -10Na ₂ O-5ZnO.
Using a porous glass consisting -2ZrO ₂ -20B ₂ O _3. A diameter of 0.
A 02 mm predetermined pattern was formed and masked.

Distribution was given by the apparatus shown in FIG. That is, the substrate is placed on the stage, the stage is rotated at a speed of 200 rpm by a motor, and 0.01 ml of a 1 mol / l thallium nitrate nitric acid aqueous solution is dropped onto the substrate from the distribution imparting solution dropping port 7.
After exchanging K ⁺ and Tl ^{+ for} a minute and drying the substrate with a fan, a nitric acid aqueous solution of 1 mol / l thallium nitrate was made to have a thickness of 0.5 ml and dropped 0.2 mm onto the substrate again to give a distribution for 10 minutes. I went. Then, the mixture was treated twice with 0.7 ml of acetone to fix the distribution.

By removing the mask and performing drying and baking, a 0.6 cm square microlens having a desired refractive index profile with a diameter of 0.6 mm was obtained. When this microlens was used as a light-collecting element of a solid-state image sensor, a compact size and high sensitivity were realized.

[0041]

As described above, by using the present invention, the shape of the metal distribution in the porous body can be precisely controlled, and the reproducibility and the optical characteristics such as the refractive index, the refractive index difference, and the dispersion characteristic can be obtained.
A highly reliable microlens can be easily manufactured.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an apparatus for applying a distribution to a microlens array by a spin coating method in a distribution applying step in the present invention.

FIG. 2 is a schematic diagram of an example of a microlens array and a microlens to which the present invention is applied.

FIG. 3 is a schematic cross-sectional view of an example of a microlens array and a microlens to which the present invention is applied.

FIG. 4 is a conceptual diagram showing a manufacturing process of Example 1.

5 is a schematic configuration diagram of an apparatus used in Example 3. FIG.

[Explanation of symbols]

 1,2,14 Refractive index distribution site 6 Porous body 7 Solution drop port 8 Substrate 9 Gel 11 Mask member 12 Distribution imparting solution 13 Distribution fixing solution 17 Soot 18 Brush

Claims (3)

[Claims] 1. A method for producing a microlens having a refractive index distribution layer in which the portion of the refractive index change is 1 mm or less from the surface by sintering the porous body, wherein the porous body is made of organic solvent, water, or water. The surface containing the refractive index distribution is brought into contact with a solution containing at least one selected from acids and alkalis or a solution in which a metal component is dissolved in the solution, and the solution has a thickness of half or less of that of the refractive index distribution layer. A method of manufacturing a graded-index microlens, which comprises a step of coating. 2. A method for producing a microlens having a refractive index distribution portion in which the refractive index change portion is 1 mm or less from the surface by sintering the porous body, wherein the porous body has a substantially columnar shape. It has a shape, and the solution and the curved side surface of the substantially cylindrical porous body are brought into contact with each other, and the solution is applied to the curved side surface of the substantially cylindrical porous body to a radius of less than or equal to the radial direction. A method of manufacturing a gradient index microlens, comprising the step of imparting a gradient index distribution. 3. A method for producing a microlens having a refractive index distribution portion in which the refractive index change portion is 1 mm or less from the surface by sintering the porous body, wherein the porous body is a flat plate, After preparing a resist having a substantially circular hole in a part thereof on the surface of the porous body, the solution and the substantially circular hole of the porous body are brought into contact with each other, and the substantially circular hole is used as a center to form a substantially circular hole. In the step of producing a hemispherical refractive index distribution site, the solution has a step of applying the solution to the substantially circular hole to a thickness not greater than the radius of the hemispherical refractive index distribution site. Of manufacturing a micro-lens.