JPH04123004A - Production of lens array - Google Patents

Abstract

PURPOSE:To easily obtain a lens body having excellent molding accuracy by forming a pseudo lens structural body made of a resin by using a mask for special patterning and deforming this resin structural body by heating. CONSTITUTION:An electromagnetic wave reactive resin having thermal deformability is applied on the surface of a transparent substrate and is exposed via a mask for patterning. The transmittance (OD value) of the mask is changed to 4 stages to approximate the lens shape at this time. The resin is subjected to development processing after the exposing, by which the pseudo lens structural body made of the resin changed in the resist thickness to 4 stages is obtd. In succession, this pseudo lens structural body is heat treated. The resin surface is put into a softened and molten state by this treatment and the sectional shape of the pseudo lens structural body is made into a lens-like circular shape. The lens structural body having the smooth surface is thus obtd. The property to control the shape of the lens is improved in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing a lens array in which minute lens bodies are regularly arranged.

[Conventional technology]

Lens arrays, which integrate microlenses with a lens diameter of about 10 to several 100 μm, have been applied to imaging optical systems for facsimiles and electronic copying machines, and recently to condensing optical systems for solid-state image sensors. . Various manufacturing methods for this type of lens array have been developed, among them,
-60756, Applied 0ptics (
A method that utilizes heat deformation of heat deformable resin, as seen in Applied Optics, p. 81 (1988) (hereinafter referred to as
The thermal deformation method) is attracting attention as a highly productive method that utilizes ordinary photolithography techniques.

[Problem to be solved by the invention]

However, since the thermal deformation method described above utilizes the deformation and flow of the resin during heating, there are problems in controlling the lens shape, and in particular, it is difficult to produce long focal length lenses with a large radius of curvature. was. Additionally, when attempting to obtain high fluidity during heat treatment, the pattern width of the resin often changes before and after the heat treatment, resulting in the problem that it is not possible to narrow the distance between individual lenses in the lens array. It had

SUMMARY OF THE INVENTION The present invention is intended to solve the above-mentioned problems, and an object of the present invention is to provide a method for manufacturing a lens array with excellent controllability of lens shapes.

[Means to solve the problem]

In order to solve the above problems, the method for manufacturing a lens array of the present invention involves coating the surface of a transparent substrate with a heat-deformable electromagnetic wave-reactive resin, and then adjusting the transmittance of each lens pattern in accordance with the lens shape. Electromagnetic waves are irradiated through a stepwise patterning mask to form a resin body in which the residual film thickness distribution after development of the reactive resin forms a pseudo-lens shape, and then the resin body is heated and deformed. A lens body is obtained by this.

FIG. 1 shows the flow of a method for manufacturing a lens array according to the present invention.

The film forming step 11 is a step of applying electromagnetic wave-reactive resin onto the lens array substrate so that the film thickness is uniform. As a coating method, a spin code method is suitable, but a dipping method, a roll coating method, etc. can also be used. Furthermore, as the electromagnetic wave-reactive resin, ultraviolet curing resin for microfabrication is easy to use, but depending on the lens characteristics, resins that are sensitive to visible light, infrared light, electron beams, X-rays, etc. can also be used. . In the patterning step 12, through a patterning mask,
This is a process in which electromagnetic waves having a two-dimensional intensity distribution are irradiated to expose the electromagnetic wave-reactive resin. Here, the patterning mask used is one in which the transmittance changes stepwise in the shape of a pseudo lens, as shown in Figure 2, taking into account the desired lens shape and the sensitivity characteristics of the electromagnetic wave-responsive resin used. . The developing step 13 is a step of developing the electromagnetic wave-reactive resin after exposure to obtain a residual film thickness corresponding to the cumulative exposure amount (energy). After this process, the resin body on the lens array substrate has a pseudo lens shape. The heat treatment step 14 is a step in which the resin body forming the pseudo lens shape is heated to a temperature higher than its softening point to form a lens body having an ideal lens shape. Through the above steps, a desired lens body is formed on the lens array substrate.

[Effect]

For electromagnetic wave-reactive resins such as resists, by appropriately setting conditions, a certain relationship can be established between the amount of electromagnetic waves (generally light) irradiation and the residual film thickness of the resist after exposure and development. To establish.

That is, under certain conditions, the remaining film thickness of the resist can be controlled by the amount of electromagnetic wave irradiation. Therefore, by controlling the amount of electromagnetic wave irradiation two-dimensionally according to the lens shape and the characteristics of the electromagnetic wave-reactive resin, the remaining film thickness of the reactive resin after development can be locally changed according to the lens shape. I can do it. In this case, a practical method is to use a patterning mask to control the amount of electromagnetic radiation. In other words, in consideration of the controllability of the OD (optical temperature) value of the mask and the ease of manufacturing, the OD value is changed in a box size of 2 to 10 steps, and the distribution state is made to resemble a pseudo lens.

The pseudo-lens-like resin (resist) structure formed by the patterning mask is heated above the softening point temperature of the resin to soften and melt, and the surface unevenness disappears due to surface tension. becomes a smooth lens body.

Note that it is desirable that the electromagnetic wave-reactive resin used in this case be thermoplastic.

〔Example〕

Hereinafter, the present invention will be described in detail based on Examples.

However, the present invention is not limited to the following examples.

[Example 1] A first example of the present invention will be described by taking as an example a case where a positive UV curing resist is used as the electromagnetic wave-reactive resin.

On a transparent glass substrate, a film thickness of approximately 2.4 μm was applied using a spin-coding method to coat a Fe-norvolac positive resist.
The film was formed so that After drying at about 90° C. for 20 minutes, it was exposed to light through a patterning mask.

FIG. 2 shows the transmittance distribution of the patterning mask during exposure. The shape drawn by the dotted line in the figure is the desired lens shape, and the lens shape was approximated by changing the transmittance (OD value) of the mask in four stages. FIG. 3 shows the relationship between the cumulative exposure amount and the remaining film thickness of the positive resist used here. Third
The transmittance of the mask was determined by considering the characteristics shown in the figure.

After exposure, development was performed under predetermined conditions to obtain a resin pseudo-lens structure in which the resist thickness varied in four stages. Next, this pseudo lens structure was heated at 210°C for 3
Heat treatment was performed for 0 minutes. Through this treatment, the resin surface became softened and molten, and the discontinuous uneven shape of the resin surface changed to a continuous and smooth state due to the action of surface tension in the molten state.

The cross-sectional shape of the resin structure after heat treatment is shown in FIG. 4, and it can be seen that a lens body having an ideal circular shape was obtained by the heat treatment. The specifications of the manufactured convex lens were a lens diameter of 45 μm, a lens center thickness of 2.5 μm, and a focal ratio H of 171 μm, and could be manufactured with an error within 4% (with respect to focal length) with respect to the design value. Furthermore, the specifications of the lens array are: array size 10 mm x 10
mm, and the inter-lens pitch was 50 μm, and the variation in lens characteristics within the lens array was generally within 5%, which was good.

[Example 2] As in Example 1, a phenol novolac positive type resist was formed on a transparent glass substrate by the spin code method to a film thickness of about 2.4 μm. After prebaking under appropriate conditions, exposure was performed through a patterning mask of the same type as used in Example 1, followed by development to obtain a pseudo lens structure. After that, using the same light source used during patterning, the glass substrate was exposed for about 5 minutes (irradiation exposure amount was about 1200 mJ/c).
m2) and the remaining resin (resist) layer was modified. Thereafter, heat treatment was performed at 170° C. for 30 minutes in the same manner as in Example 1, whereby the cross-sectional shape of the pseudo lens structure was made into a lens-like circular shape, and a lens structure having a smooth surface was obtained. The reason why the heat treatment temperature in this example is lower than that in Example 1 is because the resin (resist) layer is modified, and the wavelength of the irradiated light is adjusted to match the characteristics of the photosensitive resin. If selected appropriately, it is also possible to control the viscosity, heat resistance, etc. of the resin to some extent. By utilizing this property, it is possible to produce a lens with a large radius of curvature and a long focal length.

The specifications of the manufactured convex lens were a lens diameter of 55 μm, a lens center thickness of 2.5 μm, and a focal length of 250 μm, and the lens could be manufactured with an error within 5% (with respect to the focal length) with respect to the design value. Further, the specifications of the lens array were as follows: array size: 10 mm + xlO mm; inter-lens pitch: 60 μm; variation in lens characteristics within the lens array was generally within 5%, which was good.

In each of the above examples, convex circular lenses were manufactured, but
It is clear that by changing the shape of the lens pattern of the patterning mask used and the transmittance distribution of electromagnetic waves, it is possible to produce various lenses other than circular, such as elliptical, blade-shaped, lenticular, etc., as well as concave lenses.

〔Effect of the invention〕

As explained above, in the method for manufacturing a lens array of the present invention, first, the remaining film thickness distribution of the electromagnetic wave-reactive resin is shaped into a pseudo lens shape using a patterning mask in which the electromagnetic wave transmittance changes stepwise. By performing a two-step process of creating a resin structure having a shape and then heating and deforming the resin structure, a lens body with excellent molding accuracy can be easily manufactured. In the conventional method of obtaining a lens body by thermally fluidizing a single-stage rectangular pattern, the resin was required to have great thermal fluidity, and therefore the distance between individual lenses could not be made very narrow.However, the method of the present invention Since the resin does not require much fluidity compared to conventional methods, it is possible to reduce the distance between individual lenses. Further, the manufacturing method of the present invention has features such that a lens body with a large radius of curvature can be easily manufactured and a resin material with excellent heat resistance can be used as the lens material.

[Brief explanation of the drawing]

FIG. 1 is a flowchart conceptually showing a method for manufacturing a lens array according to the present invention. FIG. 2 is a diagram showing the transmittance distribution of the patterning mask used in the example. FIG. 3 is a sensitivity curve diagram of the positive resist used in Examples. FIG. 4 is a diagram showing the cross-sectional shape of the lens body produced in Example 1 after heat treatment. 11...Film forming process 12...Patterning process 13...Developing process Heat treatment process and above

Claims (1)

[Claims] After applying heat-deformable electromagnetic wave-reactive resin to the surface of a transparent substrate, electromagnetic waves are irradiated through a patterning mask in which the transmittance of each lens pattern changes stepwise in accordance with the lens shape. A method for manufacturing a lens array, comprising: molding a resin body whose residual film thickness distribution after development of the reactive resin forms a pseudo-lens shape, and then obtaining a lens body by heating and deforming the resin body.