JPS6283337A - Production of microlens array - Google Patents

Abstract

PURPOSE:To easily produce the titled plate microlens array wherein lenses having large numerical aperture and diameter are arranged by forming a columnar protrusion on the surface of photosensitive glass by etching, welding low m.p. glass thereon and softening the glass. CONSTITUTION:A photomask 1 wherein many circular shielding parts 2 are arranged on the surface of the photosensitive glass and UV rays are irradiated. Then the photomask 1 is removed, only the irradiated part is crystallized by heat treatment, the material is dipped in a weakly acidic soln. to etch only the crystallized part 5 and the unexposed part is formed as a columnar protrusion on the glass sheet. Then the powder of low m.p. glass 6 having a lower softening point than the photosensitive glass 3 is coated and heated to soften the low m.p. glass. The glass on the columnar protrusion is deformed into a spherical shape by surface tension and the shape of a convex lens is formed. Consequently, the microlens array wherein lenses with reduced aberration and having large numerical aperture and diameter are arranged is easily formed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] 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 1] Microlenses have recently attracted attention as constituent materials for various optical components for optical communication, and microlens arrays in which a large number of these lenses are arranged are particularly popular as transfer lenses in optical systems for copiers and mini-fax machines. This contributes to the miniaturization of devices.

The conventional method for creating a microlens array is a diameter of 1111 m.
The robin-shaped lenses after eruption are arranged in 2 to 3 rows of plain wood,
The common method was to form an array, but recently the 11th
As shown in the figure, a metal film 11 is formed on a single flat glass 10L.
After thermally bonding the metal film and arranging a large number of holes 12 in this metal film using photo-phosphorography technology, this
The molten cylinder containing high refractive ions is immersed at high temperature to diffuse the ions through the pores of the metal film, and as shown in FIG.
Flat microlenses made by arranging three 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 also uses the same F7+ trinography technology used in the integrated circuit manufacturing process to process them 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 small aberrations, for example, it is necessary to strictly control the shape of the ion diffusion part and the ion concentration distribution, and sometimes the electric current is It is also necessary to forcefully diffuse and import ions by applying L1.

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 too large, the shape of the diffusion part will not be semicircular. It has to be controlled, and it is not necessarily a good method in terms of productivity.

The present invention improves the problems of the conventional flat microlens 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 arranges cylindrical protrusions on the surface of a photosensitive glass plate by etching, and then melts low-melting glass on this surface and softens it. With,
Only the surface of the cylindrical projection is deformed into a spherical shape by the surface tension of the glass to form a convex lens. Hereinafter, the features of the present invention will be explained using specific examples along with the drawings.

[Example] As shown in FIGS. 1 and 2, a photomask 1 having a large number of circular light shielding portions 2 arranged on the surface of a photosensitive glass 3 is placed. Here, photosensitive glass refers to raw materials such as Aa and CeO.
Ag metal colloid is formed as a nucleus only in the part irradiated with ultraviolet rays, and by heat treatment it is made of lithium silicate glass containing lithium metasilicate (LizO.5i).
02) Because microcrystals are precipitated, this is a unique glass in which only the ultraviolet irradiated area can be etched much faster than the base glass. A typical composition is U.S. Patent No. 2,684,911.
(1954). Further, as a photomask, as shown in FIG. 3, a large number of metal thin film 4 which does not transmit ultraviolet rays may be vapor-deposited on the surface of the photosensitive glass in a circular shape through a photomask having a large number of aberrations arranged.

Next, when ultraviolet rays are irradiated through a photomask having a circular shielding part 2 as shown in FIG. 2, a latent image 3a consisting of AQ that has captured photoelectrons is formed in the irradiated part.

At this point, the photomask 1 is removed or the evaporated metal film 4 is removed.
If used as a shield, after removing it,
Heat treatment is performed at 00°C to 530°C to generate metal colloid in the irradiated area, and R-heated to a temperature of 550 to 600°C.
As shown in FIG. 4, the mixture is held for an appropriate time to form a portion 5 in which lithium metasilicate crystals are precipitated. In this case, since no nuclei are formed in the unexposed portion of the photosensitive raw glass 3, no crystals are precipitated during this heat treatment and the original transparent glass state is maintained.

Next, this glass plate is immersed in a 2-6% diluted hydrofluoric acid aqueous solution) 6. Since the crystallized portion 5 is etched approximately 30 times faster than the unexposed glass portion, by etching it for a desired time. As shown in FIGS. 5 and 6, the unexposed glass portion can be formed as a cylindrical projection portion 3b on the glass plate. Next, as shown in FIG. 7, a powder of low-melting glass 6 having a softening point lower than that of photosensitive glass is coated in a controlled thickness by using substantially the same means as when fusing glass for passivation.

At this time, it is necessary to match the expansion coefficients of the low melting point glass 6 and the photosensitive glass 3 as much as possible. For example, there is a method of powdering glass whose expansion coefficient matches that of photosensitive glass, dissolving it in a mixed solution of amyl acetate and cellulose nitrate, or a zero-organic solvent such as acetone, and applying the powder. Alternatively, there is a method in which the low melting point glass 7 is polished in advance into a sheet shape and the photosensitivity is set on the glass as shown in FIG.

According to this method, the thickness can be easily controlled, and the amount of glass that rests on the cylindrical part when softened later can be easily adjusted. When the temperature is raised by -L in the state shown in Figure 7 or Figure 8 to soften the low melting point glass, the glass 8 resting on the cylindrical protrusion is deformed into a spherical shape due to surface tension, as shown in Figure 9. It can be made into a convex lens shape. An example of a case where a large number of such lenses are arranged is shown in FIG. Here, since the crystallized portion 6 other than the lens is opaque, no matter how the low melting point glass is fused, it not only does not affect the characteristics of the lens, but also has the effect of preventing stray light coming out of the lens. .

[Effects of the Invention] According to the present invention, a flat microlens with small aberrations and arranged with lenses having a large numerical aperture and a large diameter can be easily manufactured.

[Brief explanation of drawings]

Figure 1 is a cross-sectional view of the process of arranging a photomask on the surface of a glass plate 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 process of Figure 1. Figure 4 is a cross-sectional view of a state in which crystals have been precipitated in the ultraviolet irradiated area by heat treatment, and Figure 5 is a state in which an unexposed glass part is protruded in a cylindrical shape. , and FIG. 6 is a perspective view as well.
Figure 7 is a cross-sectional view of a state in which low-melting glass powder is applied to the top surface of the glass shown in Figure 5, Figure 8 is a cross-sectional view of a state in which a low-melting glass sheet is applied instead of the glass powder in Figure 5, and Figure 9
The figure is a cross-sectional view of glass placed on a cylindrical protrusion and deformed into a spherical shape, FIG. 10 is a perspective view of a flat microlens produced by the method of the present invention, and FIG. 11 is a cross-sectional view showing a conventional manufacturing method. FIG. 12 is a sectional view of the microlens array according to FIG. 11. DESCRIPTION OF SYMBOLS 1... Photomask, 2... Circular light shielding part in photomask, 3... Photosensitive glass substrate, 3a... Latent image exposed to ultraviolet rays, 4... Metal vapor deposited film, 5... ...Crystallized part, 6...Low melting point glass powder, 7...Low melting point glass sheet, 8... Lens part. Applicant Hoya Co., Ltd. Agent Masayuki Asakura Figure 1 Light irradiation Figure 4 Figure 6 Figure 7

Claims (1)

[Claims] A photomask pattern with a circular light shielding part is placed on the surface of a photosensitive glass plate, and the photosensitive glass is irradiated with ultraviolet rays through this mask, and the photosensitive glass is heated to a high temperature to crystallize only the irradiated part. Then, a process of etching only the crystallized parts with a weak acid solution and arranging the unexposed parts as cylindrical protrusions on the glass, and then fusing low melting point glass to the glass surface and softening it. A method for manufacturing a microlens array, comprising the step of deforming only the low melting point glass in contact with a cylindrical protrusion into a spherical shape by the surface tension of the glass to form a convex lens shape.