JPH02308203A - Production of distributed refractive index type synthetic resin rod lens array - Google Patents

Abstract

PURPOSE:To obtain the rod lens array which has less fluctuating optical characteristics and allows the easy formation to small lens diameters by irradiating a transparent gel substrate having a high refractive index with light through a photomask having plural parallel rectilinear patterns to form plural rectilinear parts, then forming a polymer having the refractive index lower than the refractive index of the gel substrate in these rectilinear parts. CONSTITUTION:The gel substrate 1 is produced by partly polymerizing the monomer forming the polymer having the refractive index N1 and thereafter, the photomask 2 having plural pieces of the rectilinear patterns having the same width and inter- pattern distance in parallel is stuck to the gel substrate. The substrate is then irradiat ed with UV rays to form the parts 3 where the polymn. is selectively progressed from the front surface in the gel substrate down to the base. The transparent gel substrate is then immersed for a specified period of time into the monomer 4 forming the polymer having the refractive index N2 lower than N1 and is thereby subjected to the diffusion treatment of the low-refractive index monomer. The distributed index shape is thereafter immobilized by heating or irradiation with light. As a result, the plastic rod lens array 7 having lens bodies 5 of parabolic distributed index shapes 6 in the parts where the polymn. progresses selectively is obtd.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is applicable to optical information processing and optical communication fields such as optical systems for facsimile imaging or optical coupling between optical fibers and semiconductor lasers and light emitting diodes. This article relates to a winning method for a refractive index distribution type synthetic resin rod lens array.

[Conventional technology]

In recent years, with the miniaturization of electronic copying machines, a rondo lens array 12, which is an array of a large number of rondo-shaped gradient index condensing lenses 11, as shown in FIG. 8, is being used as an imaging optical system. . Additionally, in the field of optical fiber communications, a rod lens array as shown in Figure 9 is being considered in order to efficiently couple semiconductor lasers (LDs) or light emitting diodes (LEDs) with multiple optical fibers. It's starting to look like this.

These gradient index rod lens arrays include those that are based on glass and those that are based on synthetic resin. The manufacturing process for lens arrays used as materials is generally complicated, and it takes a long time to form a refractive index distribution. On the other hand, mainly for synthetic resins.

According to a method such as that disclosed in Japanese Patent Application Laid-Open No. 56-37521, - number of refractive index distribution type ronds are first produced, and then a large number of them are assembled to produce a new rod lens array. . Another manufacturing method is to form a large number of holes with the same lens diameter on a transparent plastic substrate, then inject multi-component monomers with different polymerization rates and copolymerization ratios, and heat them. [Applied Optics, 27 (1988) pp. 486-491 (Applied Optics, 27 (1988), pp. 486-491) has been proposed by et al.
7 (1988) pp486-491).

[Problem to be solved by the invention]

The above-mentioned conventional technology requires a complicated process for forming an array of rod lenses, and thus requires a great deal of labor and cost. Furthermore, in the heterogeneous gel copolymerization method of multi-component monomers, it is extremely difficult to stably control the reaction and refractive index distribution. moreover.

For synthetic resins, generally II! ! Since it is difficult to manufacture a rod lens having a diameter of +1 or less in terms of processing accuracy, there is a problem that the range of its use is limited.

An object of the present invention is to provide a method for manufacturing a refractive index gradient synthetic resin rod lens array that is inexpensive, has small variations in optical properties, and can easily form a small lens diameter.

[Means to solve the problem]

The above purpose can be achieved by irradiating light onto a transparent gel substrate with a high refractive index through a photomask having multiple parallel linear patterns! ! After forming a plurality of linear sections that are selectively polymerized, a monomer that forms a polymer with a lower refractive index than the gel substrate is diffused into the gel substrate in the form of a liquid, gas, or #1 drop. This is accomplished by completing the polymerization by heating, light irradiation, etc., forming and fixing a refractive index distribution in a plurality of linear portions where polymerization has proceeded selectively, and forming a lens array.

[Effect]

In the present invention, by irradiating a transparent gel substrate with light through a photomask, the irradiated area is compared with the unirradiated area.
This is the location where polymerization has selectively progressed. These differences in polymerization progress result in differences in the density of each part forming the gel substrate, so when a monomer with a low refractive index is internally diffused into the gel substrate, the diffusion rate in both parts increases. It will be different.

In other words, the diffusion rate is relatively slower in the irradiated area than in the unirradiated area, so this difference is compensated for by impregnation.

By adjusting the conditions of diffusion and fixation of the refractive index distribution, it is possible to form a refractive index distribution in the light irradiated portion of the gel substrate. Here, if a light irradiation part having only one straight line is formed in the gel substrate, a uniform gradient index rod lens can be formed in this part. In the present invention, after forming a light irradiation part consisting of a plurality of straight lines in a gel substrate, internal diffusion of a low refractive index monomer and fixing treatment of the refractive index distribution shape are performed, thereby forming a refractive index distribution type rod. It is characterized by producing a lens array. Further, in the present invention, since the lens diameter can be defined by light irradiation, it becomes easy to form a micro rod lens array with a diameter of 1 or less.

In the present invention, since this light irradiation part corresponds to the rod lens part, it needs a width and thickness ranging from several μm to several meters depending on the lens diameter. Therefore, when producing a large-diameter lens array, the portions that are selectively polymerized by light irradiation are uniformly formed not only on the surface of the gel substrate but also inside the gel substrate.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below with reference to the drawings from FIG.

First, as shown in the cross-sectional view of FIG.
Gel substrate 1 was prepared by partially polymerizing at 00°C (
After a), a photomask 2 having a plurality of parallel straight patterns with the same width and distance between patterns is attached to the gel substrate and irradiated with light, preferably ultraviolet rays in consideration of ease of handling and economical efficiency. , forming a portion 3 in which polymerization is selectively progressed from the top surface to the bottom surface of the gel substrate (b)
. This polymerization progressing portion corresponds to the ultraviolet irradiation portion. In this case, in order to prevent adhesion or adhesion between the photomask 2 and the gel substrate, a non-adhesive or non-adhesive transparent film may be interposed between the two.

Next, the transparent gel substrate is immersed in monomer 4 forming a polymer with a lower refractive index Nz than N1 for a certain period of time at room temperature to 100°C to perform a diffusion treatment of the low refractive index monomer. conduct(
C). Thereafter, the refractive index distribution shape is fixed by heating or light irradiation (d). At this time, in order to prevent volatilization of the low refractive index monomer, other plastic films or plastic plates may be brought into close contact with both surfaces of the substrate and heated or irradiated with light. Diffusion of low refractive index monomers is slow in the UV irradiated areas and faster in the non-irradiated areas.
Lens bodies 5 having a parabolic refractive index distribution shape 6 as shown in FIG. 2 are formed in an array in the irradiated part, that is, the part where polymerization has progressed selectively, to form a refractive index distribution type plastic rod lens array. You can get 7.

The diameter of this rod lens array largely depends on the thickness of the gel substrate, the width of each linear pattern on the photomask 2, and the distance between the patterns, but in general, the diameter of the formed lens tends to be slightly larger than the pattern width. . Therefore, for example, when producing a lens with a diameter of around 1 m, the thickness of the gel substrate should be 1 to 2 III, and the linear pattern width should be 0 to 3.
~1, Orrn, distance between patterns 0.3~1.0m
If we do this, we can obtain a nearly circular lens array with a diameter of 1 m. In addition, in order to obtain an elliptical lens that can be used as a gradient index anamorphic lens, it can be easily manufactured by using a thin gel substrate and using one having the same pattern width and distance between patterns.

Further, the refractive index distribution shape 6 is determined by impregnation, diffusion, and refractive index distribution fixing processing conditions, but a distribution shape having a parabolic curve has the best lens performance.

When the gradient index rod lens array 7 obtained as described above is used for imaging optics or a light coupling system, the lens array can be cut to a predetermined pitch and then the end faces are optically polished.

Figures 3 and 4 are cross-sectional views of another manufacturing method according to the present invention. 6 Figure 3 shows that the selectively polymerized portion 3 formed by ultraviolet irradiation is directed inward from the surface of the gel substrate. This is a method of manufacturing a lens array in which only a portion of a certain distance is formed. Furthermore, according to this method, as shown in FIG. 4, two parallel rows of refractive index gradient lens arrays can be formed by simultaneously irradiating ultraviolet rays from both sides of the substrate. As for the method of arranging the lens array, by changing the position of the photomask, it is possible to produce an arrangement 8 in which the center axes of each lens body are coincident in both rows, and an arrangement 9 in which the center axes of the lens bodies are different from each other. In addition, in the manufacturing method shown in FIG. 4, a light-shielding plastic, metal, or ceramic film is provided approximately in the center of the gel substrate.

Alternatively, by interposing a thin plate, the light irradiation on both sides of the gel substrate can be prevented from interfering with each other.

Figure 5 shows that after impregnating the gel substrate with a low refractive index monomer, the transparent
Alternatively, if the opaque plastic thin plate 10 is closely attached to both sides of the gel substrate to prevent the low refractive index monomer from volatilizing during heating and to fix the refractive index distribution shape, a cross-sectional view of the rod lens array according to another manufacturing method is shown. be. If the plastic thin plate is directly adhered to the gel substrate, it can be used as a reinforcing plate during lens cutting and polishing, and as a protective material for the lens itself.

FIG. 6 is a sectional view of a lens array obtained by stacking two rod lens arrays obtained by the method shown in FIG. This can be produced by bonding two lens arrays obtained in the step (d) of FIG. 1 with an adhesive or the like. Alternatively, it can be produced by stacking two impregnated gel substrates obtained in (c) and then fixing the refractive index distribution shape by heating or light irradiation. Figure 7 shows the fifth
After overlapping two gel substrates after impregnation obtained in (c) of the figure, a transparent or opaque thin plastic plate is brought into close contact with their upper and lower surfaces, and the refractive index is determined by heating or light irradiation. FIG. 3 is a cross-sectional view of a rod array obtained by fixing the distribution shape. As described above, the method according to the present invention makes it possible to manufacture a two-dimensional gradient index rod lens array by sequentially overlapping a plurality of a-rad lens arrays.

In the present invention, the monomer forming the gel substrate may be a monomer forming a transparent polymer or a monomer mixture, but impregnation of a low refractive index monomer into the gel substrate is sufficient. It is preferable that the process be carried out smoothly. For this reason, using a monomer that causes the gel substrate to partially form a crosslinked structure can reduce dissolution and deformation of the gel substrate after impregnation.

It is suitable because it has the advantage that transparency is not impaired even when copolymerized with a low refractive index monomer. These monomers are compounds with multiple types of polymerizable double bonds such as vinyl groups, acrylic groups, methacrylic groups, and allyl groups, and reactive groups such as epoxy groups, hydroxyl groups, carboxyl groups, and isocyanate groups. It will be done. In addition, in addition to these covalent bonds, for example, monomers that form a crosslinked structure due to metal ion bonds can also be used.To give three examples,
Vinyl acrylate, vinyl methacrylate, vinyl phthalate, divinyl phthalate, divinyl isophthalate, divinylbenzene, divinylnaphthalene, ethylene glycol divinyl ether, α-vinyl naphthoate, β-vinyl naphthoate, diallyl phthalate, diallyl isophthalate , allyl acrylate, allyl methacrylate, β-methacrylate, diethylene glycol bisallyl ether, diethylene glycol bisallyl carbonate,
tera-ethylene glycol dimethacrylate, bisphenol A dimethacrylate, allyl trimellitate,
Triallyl phosphate, triallyl phosphite, diphenyldiallylsilane, diphenyldivinylsilane, triallyl isocyanate.

These include triallylcyanate, glycidyl methacrylate, hydroxyethyl methacrylate, hydroxyethyl acrylate, and a monomer composition containing a heavy metal and an aromatic ring as disclosed in JP-A-60-181107. These monomers may be used alone or in combination. It is also possible to use it in combination with common monofunctional monomers such as styrene and its derivatives, methacrylic esters, and acrylic esters.

The gel substrate is made by combining these monomers with a thermal polymerization initiator such as benzoyl peroxide, lauroyl peroxide, disilysyl peroxydicarbonate, azobisisobutane, azobisisobutyronitrile, and benzoin ethyl ether, benzoin methyl. After adding a photopolymerization initiator such as ether, it is poured into a mold with a gasket interposed between two glass plates or resin plates, and partially polymerized at room temperature to 100°C. The amount of the thermal polymerization initiator or photopolymerization initiator can be selected in the range of 0.01 to 5 parts by weight depending on the reactivity of the monomer, but may not be added if the reaction is fast.

Furthermore, the polymerization rate can be adjusted by adding a solvent or a chain transfer agent such as a mercaptan to a monomer having a high polymerization rate.

In the present invention, the refractive index distribution of the Rondo lens is determined not only by the refractive index Nl when the gel substrate becomes a polymer, but also by the type of impregnating monomer that forms the polymer having a lower refractive index N2. It is also influenced by.

That is, the larger the difference between Nz and N2, the easier it becomes to form a distribution with a larger difference in refractive index.

Therefore, the diffusion monomer that can be used in the present invention has one or two polymerizable double bonds such as vizyl, acrylic, methacrylic, and allyl groups, or reactive groups such as epoxy, carboxyl, and hydroxyl groups. Compounds that have more than one species and have a low refractive index are preferred. Examples of these are methyl methacrylate, ethyl methacrylate, trifluoroethyl methacrylate, trihydroperchloropropyl methacrylate, methyl acrylate, ethyl acrylate.

These monomers include trichloroethyl acrylate, glycidyl methacrylate, hydroxyethyl methacrylate, hydroxyethyl acrylate, methacrylic acid, acrylic acid, allyl glycidyl ether, and these monomers can be used alone or in combination of two or more. . A thermal polymerization initiator or a photopolymerization initiator is added to these monomers in advance before the impregnation step. Further, in the present invention, when manufacturing a rod lens array for an imaging optical system, the lens is required to have small chromatic aberration. Therefore, it is more preferable to select a combination of monomers for producing a gel substrate and monomers for diffusion that have similar Atbe numbers (indicating the wavelength dependence of the refractive index) of the respective polymers. be.

In the present invention, the monomer having a low refractive index can be diffused into the gel substrate by immersing the gel substrate in the monomer and diffusing it in a liquid state, or by adding the monomer for diffusion. After heating it to steam, a gel substrate is placed in the steam atmosphere to create a gaseous state.

Alternatively, there is a method of dispersing it in the form of mist droplets. Of the two methods, the former is preferred because it can simplify the installation of the diffusion treatment and reduce the loss of the diffusion monomer compared to the latter.

〔Example〕

Hereinafter, the present invention will be explained in further detail using Examples.

<Example 1> As shown in FIG. 1, in this example, 90 parts by weight (hereinafter abbreviated as parts) of diethylene glycol bisallyl carbonate, 10 parts of methyl acrylate, 2 parts of benzoyl peroxide, and benzoin ethyl ether were prepared. A mixed solution of 0.5 parts was poured into a mold consisting of a 120 x 120 mm glass plate treated with silicone mold release and a tube gasket of vinylidene fluoride and trifluoroethylene copolymer with an outer diameter of about 211 nm, and heated at 70°C. Cured by heating for hours, thickness 1.7
A transparent gel substrate of 100 m x 100 m was obtained (a).

Next, on the glass substrate, 1
A photomask, in which 40 blanks were left at equal intervals of m, and the rest were all chromium-deposited, was placed tightly on the gel substrate, and exposed using a high-pressure mercury lamp with an irradiation intensity of 6 mW/al.
UV exposure was performed for a minute (b). Thereafter, the exposed gel substrate was immersed in 2.2.2-trifluoroethyl methacrylate containing 0.5 parts of benzoyl peroxide at 40° C. for 2 hours (C), and the substrate was diluted to a thickness of 2IIM. ! It was sandwiched between two silicone-released glass plates with a silicone resin gasket interposed in between and heated at 70°C for 5 hours at 90°C with the whole covered with a polyethylene terephthalate film.
Cure was carried out after 5 hours. After the obtained transparent substrate was released from the glass plate, the cross section of the substrate was cut to a thickness of approximately 1 nn.

After polishing, the cross section was immersed in matching oil and interference fringes were observed using an interference microscope. As a result, the rod lens array obtained was arranged in the shape shown in FIG. 1(d). Each - rod lens body has a radius of approximately 0.
．． It has a nearly circular cross section with 7 strokes, and the maximum refractive index difference is 0.0.
It was 38.

Further, the distance between the rod lenses from the center was about 2 m. The refractive index distribution shape showed a parabolic curve as shown in 6 in FIG. 2, which was close to an ideal state.

<Example 2> 33 parts of acrylic acid and 37 parts of cinnamic acid were dissolved in benzene, and barium hydroxide monohydrate (Ba(○H)Z・H) was dissolved at room temperature.
30 parts of z○) were gradually added to carry out the reaction. Water and benzene contained in this solution were removed under reduced pressure to obtain a monomer composition. 50 parts of this monomer composition, 50 parts of chlorstyrene
A mixed solution consisting of 1 part, 0.2 parts of cimilistyl peroxydicarbonate, and 0.5 parts of benzoin ethyl ether was poured into the same mold as in Example 1, and heated and cured at 60°C for 1 hour. Thickness 1.7 mm, 1 as shown in a)
A transparent gel substrate measuring 0.00 x 100 mm was obtained.

Next, using the same photomask and conditions as in Example 1,
Ultraviolet light exposure was performed for 5 minutes using a high-pressure mercury lamp (b).

Then 20 parts of methacrylic acid containing 0.3 parts of similystyl peroxydicarbonate.

After immersing the exposed gel substrate in an immersion solution containing 44 parts of allyl glycidyl ether and 36 parts of glycidyl methacrylate at 25°C for 2 hours (C), the substrate was heated to a thickness of 2 Iffi+.
Two transparent epoxy resin plates (1
, 5t) and heated to 40°C.

Post-curing was performed at 70° C. for 1 hour and 10 hours. The obtained transparent substrate had a sandwich-structured rod lens array as shown in FIG. 5(d).

This substrate was cut and polished to a thickness of approximately 1++n, the cross section was immersed in matting oil, and interference fringes were observed using an interference microscope. As a result, each rod lens body had a substantially circular cross section with a radius of about 0.8 mm, the maximum refractive index difference was 0.034, and the refractive index distribution shape showed a parabolic curve.

<Example 3> 26 parts of acrylic acid and 45 parts of cinnamic acid were dissolved in benzene, and 29 parts of barium hydroxide monohydrate was gradually added at room temperature to carry out the reaction. Water and benzene contained in this solution were removed under reduced pressure to obtain a monomer composition. This monomer composition 4
0 parts, 40 parts of chlorstyrene, 10 parts of lead methacrylate,
Then, a mixed solution consisting of 0.2 parts of similistilperoxydicarbonate and 0.5 parts of benzoin ethyl ether was poured into the same mold as in Example 1, and cured at 60°C for 30 minutes to form a mold with a thickness of 1.7 mm and a 100% A transparent gel substrate with a size of 100 mm was obtained. Next, using the same photomask conditions as in Example 1, UV exposure was performed for 5 minutes using a high-pressure mercury lamp. Thereafter, the exposed gel substrate was placed in an immersion solution consisting of 20 parts of methacrylic acid containing 0.3 parts of similisyl peroxydicarbonate, 44 parts of allyl glycidyl ether, and 36 parts of 2,2.2-trifluoromethacrylic acid. 25
It was immersed at 0°C for two hours. After dipping, the two gel substrates were stacked and sandwiched between two transparent epoxy resin plates (1.5 tons) with a 41 m thick gasket interposed, and post-cured at 40°C for 1 hour and at 70°C for 10 hours. .

The obtained transparent substrate had a rod lens array having a structure as shown in FIG. Interference fringes on the cross section of this substrate were observed in the same manner as in Example 1. As a result, each rod lens body has a circular cross section with a radius of approximately 0.8 parts m, and the maximum refractive index difference is 0.039 mm. The refractive index distribution shape showed a parabolic curve.

〔Effect of the invention〕

According to the present invention, since the refractive index distribution type synthetic resin rod lens array can be manufactured in an integrated manner, the process of forming rod lenses into an array is unnecessary, and a lens array that is inexpensive and has small variations in optical properties can be obtained. It will be done. Furthermore, since the diameter of each rod lens can be defined with high accuracy by irradiating light through a photomask, it becomes easy to form small lenses with a diameter that is difficult to achieve with a single synthetic resin.

[Brief explanation of drawings]

FIG. 1 is a process diagram showing a method of manufacturing a refractive index distribution type synthetic resin rod lens array according to an embodiment of the present invention. FIG. 2 is a perspective view and a refractive index distribution shape diagram of a rod lens array obtained by the present invention, and FIG. 3 is a sectional view showing another example of the method for manufacturing a refractive index distribution type synthetic resin rod lens array according to the present invention. FIG. 4 is a cross-sectional view showing an example of a method for manufacturing a refractive index distribution type synthetic resin rod lens array formed on both sides of a substrate according to the present invention, and FIG. 5 is a refractive index distribution with substrates provided on both sides according to the present invention FIGS. 6 and 7 are cross-sectional views of a two-layer superimposed refractive index gradient type synthetic resin rod lens array obtained by the present invention, and FIG. FIG. 9 is a perspective view of a gradient index rod lens array, and is a perspective view showing an example of a method for optically coupling a semiconductor laser or a light emitting diode, and an optical fiber to a gradient index rod lens array. DESCRIPTION OF SYMBOLS 1... Gel substrate, 2... Photomask, 3... Selectively polymerized portion, 4... Low refractive index monomer, 5
...Lens body, 6...Refractive index distribution, 7,8.9...
・Rod lens array, 10...plastic thin plate,
11...Gradient refractive index condenser lens, 12...Rod lens array, 13...Semiconductor laser or light emitting diode, total 1 person 6 figures (b) Mouth ■ I ■■ Next 1 figure High 9 figure

Claims (1)

[Claims] 1. (a) A step of forming a transparent gel substrate by partially polymerizing a monomer forming a polymer with a refractive index of N_1; (b) A photoform having a plurality of parallel linear patterns. irradiating the transparent gel substrate with light through a mask to form a plurality of linear portions in which selective polymerization has proceeded in the transparent gel substrate; (c) a step of irradiating the transparent gel substrate with light through a mask; (d) diffusing the monomers forming the coalescence into the transparent gel substrate in a liquid, gas, or atomized state, and forming a refractive index distribution in the selectively polymerized portions of the transparent gel substrate; A method for manufacturing a refractive index distribution type synthetic resin rod lens array, comprising a step of fixing the refractive index distribution by completing polymerization by heating, light irradiation, or the like. 2. In the step of irradiating the transparent gel substrate with light through a photomask to form a plurality of linear portions that are selectively polymerized in the transparent gel substrate, the portions that are selectively polymerized are the same as those of the transparent gel substrate. 2. The method of manufacturing a gradient index synthetic resin rod lens array according to claim 1, wherein the lens array is formed uniformly from the surface to the inside.