JPS6283334A - Production of microlens array - Google Patents

Abstract

PURPOSE:To easily produce the titled microlens array wherein many convex lenses are arranged by arranging a photomask on photosensitive glass, irradiating UV rays, then heat treating, etching only the irradiated part, and softening and deforming only the unirradiated part by reheat treatment. CONSTITUTION:The photomask 1 wherein many circular shield parts 2 are arranged is provided on the surface of the photosensitive glass 3 and UV rays are irradiated. Then the photomask 1 is removed and only irradiated part is crystallized by heat treatment. The glass sheet 3 is then dipped in a weakly acidic soln., hence the crystallized part 5 is etched and the unexposed part of the glass is formed on the glass sheet as a columnar projecting part 3b. By utilizing the fact that the softening temp. of the crystallized part 5 of the irradiated part is higher than that of the columnar projecting part 4 of the unirradiated part, the material is heated to soften only the unirradiated part 4 into a spherical shape and a convex lens 3c is formed. The microlens array wherein many minute convex lenses 3c are arranged on the flat glass sheet can be easily formed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing a microlens array in which a large number of minute convex lenses are arranged on a flat glass.

[Prior Art] Microlenses have recently attracted attention as constituent materials for various optical components for optical communication, and in particular, microlens arrays, which are made up of a large number of these lenses, are used as transfer lenses in optical systems for copiers and mini-fax machines. This contributes to the miniaturization of equipment.

The conventional method for creating a microlens array was to arrange several rondo-shaped lenses with a diameter of about 1 m in two or three rows in an array. First, a metal film 11 is vapor-deposited on a sheet of flat glass 10, and a large number of holes 12 are arranged in this metal film 11 using photophosphorography technology. A flat plate made by immersing it in a molten salt containing gold at high temperature to diffuse ions through the holes 12 of the gold B film, and arranging microlenses consisting of semicircular spherical high refractive ion diffusion parts 13 on the glass flat plate. Microlenses are attracting attention. This method not only does not require complicated processes such as arranging, gluing, and fixing a large number of rod lenses, but it also uses the same photolithography technology used in the integrated circuit manufacturing process to process rod lenses all at once with high precision. Lenses can be arranged into an array.

[Problems to be Solved by the Invention] However, in order to create a lens with little aberration, for example, it is necessary to strictly control the shape of the ion diffusion part and the ion concentration distribution. It is also necessary to forcefully diffuse and import ions by applying a voltage.

In addition, when creating a large lens, if the hole in the mask is small, it will take a considerable amount of time to create it, and if the hole in the mask is made larger, the shape of the diffusion part will no longer be semicircular. This method must be controlled, and it is not necessarily a good method in terms of productivity.

The present invention improves the problems of the conventional flat microphone lens array manufacturing method as described above, and provides a microlens array in which lenses with large numerical apertures and diameters are arranged.

[Means for Solving the Problems] Therefore, the present invention utilizes photosensitive glass in which the ultraviolet irradiation portion has a property of being easily crystallized by heat treatment, and arranges a photomask in which a large number of circles are arranged on the photosensitive glass. Then, after irradiating with ultraviolet rays, heat treatment is performed to crystallize only the irradiated area, and then only the irradiated area is etched in a weak acid solution to arrange the unirradiated area as cylindrical protrusions, softening the crystallization of the irradiated area. Taking advantage of the fact that the temperature is higher than that of the cylindrical protrusion in the unirradiated part, this is heated to soften only the unirradiated part and deform it into a spherical shape, which is called a convex lens. Hereinafter, the features of the present invention will be explained using specific examples along with the drawings.

[Example] First, as shown in FIGS. 1 and 2, a photomask 1 having a large number of circular shielding portions 2 arranged on the surface of a photosensitive lath 3 is placed. Here, photosensitive glass refers to Shorin's 80 or Ce.
Made of lithium silicate glass containing 0z, AQ metal colloid is generated as a nucleus only in the part irradiated with ultraviolet rays, and lithium metasilicate (L i ?○) is formed by heat treatment.
・SiO2) It is a unique glass that precipitates microcrystals and can be etched only in the ultraviolet irradiated area much faster than the base glass. Typical composition is U.S. Patent No. 2
, 684, 911 (1954). Further, as a photomask, as shown in FIG. 3, a circular metal evaporation g! It would be nice to have a C with many 4s arranged.

Next, when ultraviolet rays are irradiated through the photomask 1 having a circular shielding section 2 as shown in FIG. 2, a latent image 3a (FIG. 3) made of AQ that has captured photoelectrons is formed in the irradiated section. At this point, the photomask 1 is removed, or if the vapor-deposited metal film 4 is used as a shielding part, after removing it, heat treatment is performed at 400°C to 530°C to generate metal colloid in the irradiated part and make it rough. The temperature is then raised to 550-600 DEG C. and maintained for an appropriate period of time as shown in FIG. 4 to form a portion 5 in which lithium metasilicate crystals are precipitated. In this case, since no nuclei are formed in the unexposed area, crystals do not precipitate during this heat treatment and the original transparent glass state is maintained.

Next, when this glass plate is immersed in a 2-6% dilute hydrofluoric acid aqueous solution, the crystallized portion 5 will be etched approximately 30 times faster than the unexposed glass portion. As shown in FIGS. 5 and 6, the unexposed glass portion can be formed as a cylindrical protruding portion 3b on a glass machine.

The softening temperature of the unexposed glass portion is around 500°C, which is much lower than the softening temperature of the exposed crystallized portion 5, which is 800°C or higher.
It is much higher than the softening temperature of the glass part, and the crystallized part 5
By reheating at a temperature lower than the softening temperature of
As shown in FIG. 9, the cylindrical protrusion portion 3b made of glass is softened, and the surface tension creates a spherical shape (as shown in FIG. 10).
It can be transformed into a spherical lens body 3c) to have a lens shape.

Here, a mask 1 with a circular shielding part 2 on the right side is simply arranged on the photosensitive glass as shown in FIG. It is also conceivable to crystallize the crystallized portion, squeeze out the unexposed glass portion by shrinking the crystallized portion, and form a spherical protrusion on the glass substrate due to surface tension with the help of softening.

That is, it is possible to form a spherical protrusion already at the stage shown in Fig. 4, but in this case, it would be difficult to make a lens with a large diameter of 1 m to 2 cm, and the numerical aperture would have to be increased. It's also difficult. Compared to this method, the present invention is characterized in that it is possible to form not only a large-diameter lens but also a high-aperture lens because a glass portion is formed in advance as a protrusion in a portion that is to become a spherical lens by etching. In addition, without using photosensitive glass, etching is simply performed using photophosphorography technology using an optical glass substrate, a cylindrical protrusion is provided on the optical glass plate, and this is heated at a temperature higher than the softening temperature of the glass. There is also an idea to soften the protrusions and make a spherical lens body, but in this case, the text and the substrate glass have the same softening point, and there is a risk that the substrate itself will soften. Even if it were possible to heat only the protrusions, the process would be expected to be complicated. According to the present invention, the softening point of the substrate portion is approximately 300° C. or more higher than that of the protrusion, so there is no possibility that the substrate portion will soften.

Furthermore, another specific example of the present invention will be shown. As shown in FIG. 7, a photoresist 6 is applied to the surface of the photosensitive glass 3, a photomask 1 having a circular shielding part 2 is placed on top of the photoresist 6, and ultraviolet rays are irradiated to form a latent image 3a. . After removing the photomask 1 and roughly etching the exposed areas of the photoresist, the glass plate is etched with a dilute hydrofluoric acid aqueous solution, and the exposed areas are eroded, leaving a circle ↑ on the glass plate, as shown in Figure 8. A shaped protrusion 3b is formed. Next, the photoresist is removed, heat treated at 400-530°C to generate metal colloid in the irradiated area, and further heated at 550-600°C.
The temperature is raised to 0° C. and held for a long time to precipitate rhidium metasilicate crystals 5 in the exposed area and soften the cylindrical protrusions as shown in FIGS. 9 and 10 to form a spherical lens body 3C. do. According to this method, in the etching process for forming the cylindrical protrusions, the surface of the unexposed area that will later become the lens is etched by 7.
Since it is covered with Otoresist, the surface will not be roughened.
It has the advantage of being able to be etched. Furthermore, since the parts other than the lens are crystallized, they are opaque and can prevent stray light.

[Effect of the invention 1 As described above, according to the present invention, a photosensitive raw glass having a property that the ultraviolet ray irradiated part is easily crystallized by heat treatment is used, a photomask is placed on this photosensitive raw glass, L, and the ultraviolet rays are irradiated. By irradiating only the irradiated area and softening only the unirradiated area, it is possible to easily produce a microlens array in which a large number of small high-aperture convex lenses are deformed into a spherical shape and arranged.

[Brief explanation of drawings]

Figure 1 is a cross-sectional view of the process of arranging a photomask on the surface of photosensitive raw glass and irradiating it with ultraviolet rays in the method for manufacturing a microlens array of the present invention, Figure 2 is a perspective view of the same, and Figure 3 is the same as Figure 1. Figure 4 is a cross-sectional view of the case where a metal vapor deposited film is used in the step of 1. Figure 4 is a cross-sectional view of a state in which crystals are precipitated in the ultraviolet irradiated area by heat treatment, and Figure 5 is a cross-sectional view of the state in which the unexposed glass part is made to protrude in a cylindrical shape. Figure 6 is a perspective view, Figure 7 is a cross-sectional view of photoresist coated on the surface of photosensitive raw glass, a photomask is placed and ultraviolet rays are irradiated, Figure 8 is etching. 9 is a cross-sectional view at a stage where the cylindrical protrusion is softened by heat treatment to form a spherical lens body; FIG. 10 is a perspective view of a flat microlens array according to the method of the present invention; FIG. 11 12 is a sectional view showing a conventional manufacturing method, and FIG. 12 is a sectional view of a flat microlens array produced by the method shown in FIG. DESCRIPTION OF SYMBOLS 1... Photomask, 2... Circular light shielding part in photomask, 3... Photosensitive glass, 3a... Latent image by ultraviolet irradiation, 3b... Cylindrical protrusion, 3c... - Spherical lens body, 4... Metal vapor deposited film, 5... Crystallized portion, 6... Photoresist. Applicant Hoya Co., Ltd. Agent Masayuki Asakura Figure 1 Figure 6 Figure 4 Figure 7 Figure 8 Figure 9 r Figure 10 Figure 11 Figure 12

Claims (1)

[Claims] 1. A step of arranging an array of circular photomask patterns on the surface of a photosensitive glass plate, a step of irradiating the photosensitive glass with ultraviolet rays through this mask, and a step of heating the photosensitive glass at a high temperature. After the heat treatment, only the crystallized parts are etched with a weak acid solution at room temperature so that the unirradiated parts are arranged as cylindrical protrusions, and the cylindrical protrusions are formed by reheating. A method for manufacturing a microlens array, comprising the step of softening and deforming a portion into a spherical shape to form a convex lens. 2. The circular photomask pattern is a metal vapor deposited film formed on the surface of a photosensitive raw glass plate.
2. Method for manufacturing a microlens array as described in Section 1. 3. In the process of arranging an array of circular photomask patterns, photoresist is applied to the surface of the photosensitive glass plate in advance, the photomask pattern is arranged, and after UV irradiation, the irradiated areas are etched using the photoresist. , a patent claim characterized in that after arranging an array of cylindrical protrusions in the unirradiated area, the steps of crystallizing the irradiated area and softening and deforming the cylindrical protrusions in the unirradiated area into a spherical shape by heating are performed simultaneously. A method for manufacturing a microlens array according to item 1.