JPH0233296B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a lens body in which a gradient index lens portion is formed in a transparent substrate made of synthetic resin.

In a transparent substrate with parallel planes, there is a refractive index distribution that changes with square approximation in the optical axis direction. A planar lens in which a large number of refractive index gradient lens parts are formed in a line or matrix shape at intervals, and the refractive index distribution gradually changes in a square approximation as it moves away from the optical axis within at least one cross section that includes the optical axis. Are known. In such a flat lens, the lens part may be a lens with the above-mentioned refractive index distribution in all cross sections including the optical axis, that is, a circular lens, or it may be a circular lens with a refractive index distribution as described above in all cross sections including the optical axis. In some cases, the lens has a refractive index distribution that gradually changes, and the refractive index is constant regardless of the distance from the optical axis in a cross section perpendicular to this, so-called a semicylindrical lens.

The above-mentioned plane lenses are used as image transmission elements in various applications such as optical systems of copying machines and facsimile machines, or in optical coupling systems between light sources and optical fibers, or for inserting attenuators or branch circuits between optical fibers. It is useful for peripheral devices for optical communications, such as parallel light conversion elements.

When manufacturing a plane lens as described above using a synthetic resin, as shown in Figure 1, a monomer (monomer mixture) that produces a network polymer (including copolymer) Pa with a refractive index of Na is used. A transparent gel-like substrate 10 is made by partially polymerizing Ma (including Ma), and a mask 12 with openings 11 corresponding to the pattern of the lens portion to be formed is applied to the surface of this substrate 10.
A monomer (including a monomer mixture) Mb that produces a polymer (including a copolymer) Pb having a refractive index Nb different from the above-mentioned refractive index Na is diffused and polymerized into the substrate through the lens portion 13. There are known methods of forming . In this case, if Na>Nb, the lens portion 13 formed in the substrate has a concave lens effect,
If Na<Nb, it will have a convex lens effect.

As another method, as shown in FIG. 2, a transparent gel-like substrate 14 similar to that described above is made, a mask 15 is applied only to the lens portion of the substrate surface, and Na is polymerized with the substrate 14 from the periphery. Different refractive index Nb
There is also a method of diffusing monomers to form polymers.

In this case, the lens portion 16 formed in the substrate exhibits a convex lens effect if Na<Nb,
If Na>Nb, it exhibits a concave lens effect.

However, in the conventional method shown in FIGS. 1 and 2 as described above, masks 12, 15 and gel substrates 10, 1 provided to prevent the diffusion of monomer Mb
Unless the adhesion with 4 is very good, monomeric Mb
enters between the mask and the gel substrate, and monomeric Mb
The problem has often arisen that it is impossible to form a lens body with a refractive index distribution because the lens particles diffuse over the entire surface of the gel substrate.

An object of the present invention is to provide a novel method for manufacturing a synthetic resin flat lens that can solve the above-mentioned conventional problems and avoid the problem of adhesion between a mask and a gel substrate when manufacturing a gradient index flat lens. It is said that

That is, the method for producing a synthetic resin flat lens according to the present invention involves incompletely polymerizing one or more monomers Ma that produces a network polymer Pa having a refractive index of Na to produce a transparent gel-like polymer. A substrate is formed, and one or more monomers Mb that produce a polymer Pb having a refractive index Nb different from that of Na are diffused and permeated into the surface area of the transparent gel substrate. A partial hardening process is applied to the surface area to form a hardened part and an unhardened part in accordance with the pattern of the lens part to be formed, and a hardened part and an unhardened part are formed in the surface area through the surface of the transparent gel substrate on which the hardening process has been performed. Then, the uncured portion and the monomer Mb inside the transparent gel substrate corresponding to the uncured portion are mainly removed. A state is formed in which the monomer Mb remains even in a continuously changing concentration gradient, and in this state, the monomers Ma and
It consists of completing the polymerization of Mb. Note that the term "polymerization" as used in the present invention includes copolymerization.

As described above, in the present invention, by using the hardened portion formed on the surface of the transparent gel substrate as a so-called mask when removing monomer Mb, monomer Mb is kept in the above-mentioned state. It will remain inside the board. Since this hardened portion is integrated with the transparent gel substrate, the adhesion between the mask and the transparent gel substrate in the conventional example shown in FIGS. 1 and 2 is not a problem. Therefore, a lens portion with a desired refractive index can be formed within the substrate.

In the present invention, any monomer Ma can be used as long as it forms a transparent network polymer when polymerized, and any monomer Ma that can be cleaved into one molecule to form a crosslink can be used. One or more compounds having two or more bonds may be used. Suitable examples include diallyl phthalate,
diallyl esters such as diallyl isophthalate, diallyl terephthalate, diethylene glycol bisallyl carbonate; triallyl esters such as triallyl trimellidate, triallyl phosphate, triallyl phosphite; allyl methacrylate;
Unsaturated acid allyl esters such as allyl acrylate; divinyl phthalate, divinyl isophthalate,
Mention may be made of vinyl esters such as dibyl terephthalate. Note that the network polymer as used in the present invention
Pa is a homopolymer obtained by polymerizing one of the above-mentioned monomers, a copolymer obtained from two or more of these monomers, and a copolymer obtained from two or more of these monomers.
It contains a copolymer of Ma and monomers such as styrene, methacrylate, vinyl benzoate, etc. Further, it is assumed that this network polymer Pa has a refractive index of Na.

In the present invention, first, the monomer Ma described above is polymerized to produce a transparent gel-like substrate. Polymerization of the monomer is temporarily stopped when the polymer loses its fluidity and becomes a transparent gel, that is, when the polymerization is incomplete. If this polymerization is carried out in a mold or frame having a predetermined shape, the gel substrate can be formed at the same time. Next, a monomer Mb that produces a polymer having a refractive index Nb different from that of Na is diffused and permeated into the obtained gel substrate.

The monomer Mb used in this process may be one that becomes a linear polymer or a network polymer when polymerized, but it may be one that becomes a linear polymer or a network polymer when polymerized. Preferably, those that can be used to produce a transparent copolymer. As such monomer Mb, styrene, methacrylic ester, acrylic ester, vinyl acetate, vinyl chloride, acrylonitrile, butadiene, or a mixture of two or more of these can be suitably used.

Next, on the surface of the transparent gel substrate on which the monomer Mb has been diffused, locally non-uniform polymerization conditions are applied to selectively harden only the surface region. Local heating, light irradiation, electron beam irradiation, etc. can be used as locally non-uniform polymerization conditions, but among these, visible light and/or ultraviolet ray irradiation is the most suitable in terms of method and simplicity. Probably. In addition, if necessary, monomer Ma and/or monomer
A thermal polymerization initiator, a photopolymerization initiator, a photosensitizer, etc. can also be added to Mb. By curing the surface region by applying locally non-uniform polymerization conditions in this manner, a pattern corresponding to the lens portion to be formed is formed by the cured portions and uncured portions.

In other words, the pattern of hardened parts and unhardened parts is
The shape and size of the gradient index lens to be formed,
It is determined depending on the magnitude relationship between Na and Nb.
Furthermore, when a plurality of lenses are provided, their positional relationship also affects the curing pattern.
For example, when forming a circular lens, either a portion corresponding to the circular portion centered on the central optical axis portion is left and the other portions are hardened, or a portion corresponding to the lens portion is hardened into a disk shape. If Na>Nb, the former becomes a convex lens and the latter becomes a concave lens. Na
<Nb, the former becomes a concave lens, and the latter becomes a convex lens. When forming a semicylindrical lens,
Either the lens portion is left in a linear shape and the other portions are hardened, or the portion corresponding to the lens portion is hardened in a linear shape.

Next, the unpolymerized monomer Mb diffused in the uncured portion and inside the substrate is removed through the patterned surface of the transparent gel substrate. Various methods can be used for removal, such as immersion in a solvent capable of dissolving monomer Mb, vaporization under reduced pressure, and performing the latter after the former. When monomer Mb is removed from the transparent gel substrate using this method, it is difficult for the monomer Mb inside to escape through the part that was hardened in the previous stage of this process. The unhardened part and the monomer Mb inside it mainly escape through the unhardened part. Due to this phenomenon, a concentration distribution of the monomer Mb is generated in the transparent gel substrate near the cured portion. After forming the concentration distribution of monomer Mb in the transparent gel substrate in this way, the polymerization of monomer Ma and remaining monomer Mb is completed, and the monomer
By fixing the distribution of Mb, it is possible to form a gradient index lens portion as described above in a plastic substrate.

Next, the present invention will be described in detail based on embodiments shown in the drawings.

First, as shown in FIG. 3A, a transparent gel substrate 17 is prepared by polymerizing a monomer Ma forming a network polymer Pa having a refractive index Na in molds 18 and 19. Next, a polymer with a refractive index of Nb is coated on the surface of this transparent gel substrate 17.
The monomer Mb that generates Pb is brought into contact with it in a liquid phase or a gas phase, and the monomer Mb is diffused from the entire surface of the transparent gel substrate 17, as shown in FIG. 3A. monomer
The higher the temperature when diffusing Mb, the more monomeric Mb
Although the diffusion rate is high, it should not be so high that monomer Mb polymerizes alone or copolymerizes with monomer Ma. Next, as shown in Figure 3B,
A circular light shielding mask 20 for shielding light is placed on the surface of a transparent gel substrate 17 on which monomer Mb is diffused, and light is irradiated. The diameter R1 of the mask 20 is the third
It is equal to the diameter R2 of the circular hole (uncured part) 21 in the hardened part as shown in Figure C, which is much smaller than the diameter R3 of the lens part 22 shown in Figure 3 D. It's better to be there. The light to be irradiated is preferably ultraviolet rays used for ordinary photocurable resins. By light irradiation, a hardened portion 23 is formed as shown in FIG. 3C. The thickness of the hardened portion 23 must be thick enough that the monomer Mb does not easily pass through it, but as long as this condition is satisfied, it is preferably thinner. In the next step, monomer Mb is removed from the hole 21 with diameter R2 in the hardened portion 23, but if R2 becomes sufficiently smaller than the diameter R3 of the lens to be formed, the isoconcentration curve of monomer Mb will be hole 2
The portion 1 is parallel to the surface of the transparent gel substrate 17, and the cross section does not have a concentric spherical shape. monomer
To remove Mb, if monomeric Mb is much more volatile than monomeric Ma, it is sufficient to reduce the pressure; if the volatilities are similar, the solubility may be reduced. Methods of immersion in different solvents may be used. Monomer Ma and monomer
If Mb is removed in approximately equal amounts, the monomer
Since the concentration distribution of Mb has already been formed in the substrate, if the transparent gel substrate 17 is kept in contact with the monomer Ma when completing the polymerization, the shortage of the monomer Ma caused by the removal of the monomer Ma can be compensated for. Shrinkage during polymerization can be alleviated. By removing the monomer Mb through the hole 21, the polymerization is completed to fix the concentration distribution of the monomer Mb formed, and then the surface is polished, as shown in FIG. 3D. A synthetic resin flat lens 24 having a spherical lens portion 22 having a cross section is completed. The diameter R3 of the lens portion 22 is determined by the diameter R2 of the hole in the cured portion 23 (=diameter R1 of the light shielding mask), the crosslinking density of the transparent gel substrate 17,
It is affected by monomeric Mb removal conditions, etc. The lens portion 22 becomes a convex lens when Na>Nb, and becomes a concave lens when Na<Nb.

FIG. 4 shows another embodiment of the invention.

In this example, as well as the method described above, first the formwork 2 is
A transparent gel substrate 25 is formed by partially polymerizing a monomer Ma that forms a network polymer Pa having a refractive index Na within 6 and 27.
A monomer Mb that forms a polymer Pb having a refractive index Nb is brought into contact with the polymer Pb and diffused from the entire surface as shown in FIG. 4A. The temperature at this time is set to be lower than that at which Mb polymerizes. Next, as shown in FIG. 4B, a light-shielding mask 28 with a circular hole corresponding to the lens portion to be formed is placed on the transparent gel substrate 25 in which the monomer Mb is diffused, and ultraviolet rays are irradiated. . The diameter R4 of the hole in the light-shielding mask 28 is equal to the diameter R5 of the hardened portion 29 shown in FIG.
This is approximately the diameter of the lens portion 31 shown in FIG.
will be equal to R6. By irradiating the ultraviolet rays, a disk-shaped hardened portion 29 is formed as shown in FIG. 4C.
It is desirable that this thickness be as thin as possible as long as monomer Mb does not pass through. Next, monomer Mb is removed from the transparent gel substrate 25. The monomer is removed from the uncured portion 30 on the surface of the transparent gel substrate 25.
When Mb escapes, a concentration gradient is generated, and monomer Mb moves there from below the hardened portion 29 and from the deep part of the transparent gel substrate 25, and a new concentration gradient is generated. After forming the concentration distribution of the monomer Mb with a concentric circular cross section in this way, the polymerization is completed to fix it, and then the surface is polished.
Spherical lens portion 31 having a cross section as shown in Figure D
The synthetic resin flat lens 32 having the above formed thereon is completed. The diameter R6 of the lens portion 31 is approximately determined by the diameter R5 of the hardened portion 29 (=the diameter R4 of the hole in the light shielding mask). The lens portion 31 becomes a concave lens when Na>Nb, and becomes a convex lens when Na<Nb.

By curing the substrate surface leaving a large number of uncured circular parts as described above, or by forming a large number of island-like circular hardened parts on the substrate surface, a gradient index spherical lens can be obtained. A synthetic resin flat lens is obtained, which is composed of an array of . Furthermore, if the light-shielding mask has a linear pattern, it is also possible to manufacture a gradient index flat lens equivalent to a semicylindrical lens or a lenticular lens in which light rays are focused in a line.

Specific Example 1 This specific example 1 follows the method shown in Figure 3. First, 3% by weight of benzoyl peroxide and benzophenone were dissolved in diethylene glycol bisallyl carbonate (CR-39) and poured into a mold. 20mm x 20mm x 5
A transparent gel substrate of mm size was prepared. 2, 2, 2 this
- immersed in trifluoroethyl methacrylate (3FMA) to diffuse into the gel body from the surface. Next, a brass disk with a diameter of 2 mm was placed in the center, and the area around the area corresponding to the brass disk was hardened by irradiating ultraviolet light from an ultra-high pressure mercury lamp. Next, this was placed in a desiccator, and a vacuum pump was connected to reduce the pressure, and 3FMA was vaporized and removed from the uncured portion with a diameter of 2 mm. This was held at 80°C for 15 hours to complete polymerization, and the surface was polished. The center of this CR-39/3FMA copolymer block was a convex lens with a focal length of 30 mm.

Specific Example 2 This specific example 2 follows the method shown in FIG. 3. First, benzoyl peroxide and benzophenone are dissolved in diallylisophthalate (DAIP) in an amount of 3% by weight, and poured into a mold. at °C
Heating was performed for 180 minutes to produce a transparent gel substrate measuring 20 mm x 20 mm x 5 mm. This was immersed in methyl methacrylate (MMA) and diffused from the surface into the gel substrate. Next, a brass disk with a diameter of 2 mm was placed in the center, and the area around the area corresponding to the brass disk was hardened by irradiating ultraviolet light from an ultra-high pressure mercury lamp. Next, this was placed in a desiccator, a vacuum pump was connected to reduce the pressure, and the MMA was extracted from the uncured part with a diameter of 2 mm. This was held at 80°C for 15 hours to complete polymerization, and the surface was polished. The center of this DAIP/MMA copolymer block was a convex lens with a focal length of 30 mm.

Specific Example 3 This specific example 3 follows the method shown in Figure 4. First, benzoyl peroxide and benzophenone were dissolved in diethylene glycol bisallyl carbonate (CR-39) in an amount of 3% by weight each, and then poured into a mold. Heat it at 80℃ for 90 minutes, and make 50mm x 50mm x 5
A transparent gel substrate of mm size was prepared. This was immersed in vinyl benzoate (VB) in which benzoyl peroxide and benzophenone were each dissolved in an amount of 3% by weight, and diffused from the surface into the gel substrate. Next, the diameter is 3mm
A black light-shielding mask with 25 circular light-transmitting parts arranged in a 5 x 5 matrix was placed on top of the gel substrate, and ultraviolet light from an ultra-high pressure mercury lamp was irradiated onto the surface of the gel substrate in the form of a disk with a diameter of 3 mm. 25 hardened parts were formed in the form of islands. This was immersed in acetone to dissolve the monomer from the uncured portion, and the acetone was removed under reduced pressure. Next, bring CR-39 into contact with this surface and heat it at 80°C.
for 15 hours to complete the polymerization and remove the CR-
The 39 homopolymer was polished off and smoothed.
On the surface of this CR-39/VB copolymer block,
Lenses with a focal length of approximately 30 mm were formed in a 5 x 5 matrix.

Specific Example 4 In this specific example 4, a line pattern was used as the light-shielding mask in the method shown in FIG. Dissolve in weight percent, pour into a mold and heat at 80℃ for 90 minutes to form a 50mm x 50mm x 5mm
A transparent gel substrate was prepared. This is 1, 1, 3
- immersed in trihydroperfluoropropyl methacrylate (4FMA) and diffused from the surface. A glass plate with 40 black lines of 200 μm width arranged at 1 mm intervals was placed on top of this, and after irradiating it with ultraviolet rays from an ultra-high pressure mercury lamp, the glass plate was removed and the pressure was reduced.
4FMA was volatilized from the uncured surface. This is 80℃
The mixture was held for 15 hours to complete polymerization, and the surface was polished. When parallel light passes through this CR-39/
Forty bright lines were observed on the plate placed at a distance of 30 mm from the 4FMA copolymer block.

[Brief explanation of drawings]

FIG. 1 and FIG. 2 are cross-sectional views showing a conventional example of a method for manufacturing a synthetic resin flat lens, respectively.
FIG. 4 is a cross-sectional view showing an embodiment of the method for manufacturing a synthetic resin flat lens according to the present invention. In addition, in the codes used in the drawings, 17, 25
...transparent gel substrate, 20,28...light-shielding mask,
21, 30... Uncured part, 23, 29... Cured part, 22, 31... Lens part, 24, 32...
It is a synthetic resin flat lens.

Claims (1)

[Claims] 1. A refractive index distribution that gradually changes in the optical axis direction in a transparent substrate made of synthetic resin, and a refractive index distribution that gradually changes as the distance from the optical axis increases within at least one cross section that includes the optical axis. In a method for manufacturing a synthetic resin flat lens in which a single or a plurality of gradient index lens parts are formed, the method includes: (a) one type of synthetic resin that produces a reticular polymer Pa having a refractive index of Na; A step of incompletely polymerizing two or more types of monomers Ma to form a transparent gel-like substrate; (b) producing a polymer Pb having a refractive index Nb different from that of Na in this transparent gel substrate; (c) applying a partial hardening treatment to the surface area of the substrate to form a hardened portion and an uncured portion in accordance with the pattern of the lens portion to be formed; forming a hardened part in the surface region; (d) mainly removing the unhardened part and the monomer Mb inside thereof through the hardening-treated surface of the transparent gel substrate; , thereby forming a state in which the monomer Mb remains in the transparent gel substrate in the vicinity of the cured portion with a concentration gradient that continuously changes; (e) the monomer A method for manufacturing a synthetic resin flat lens, comprising the step of completing polymerization of the monomers Ma and Mb in the residual state of Mb.