JPS6232402A - Production of synthetic resin spherical lens - Google Patents

Abstract

PURPOSE:To form a synthetic resin spherical lens having a refractive index gradient by perfecting the polymn. of transparent spherical gel particles after diffusion which are the base material for a graded index type spherical lens made of a synthetic resin by heating, etc. in a satd. aq. soln. of a monomer. CONSTITUTION:The transparent spherical gel particles after diffusion are perfected in polymn. by heating, etc. not in water but in the satd. aq. soln. of the monomer Mb. The release of the monomer Mb from the gel particles during the heat treatment stage is considerably prevented by such polymn., by which the refractive index gradient in the graded index type spherical lens is steepened and the formation to approximately the square distribution to the periphery or near the periphery of the spherical lens is made possible.

Description

[Detailed Description of the Invention] j-/ Industrial Application Field The present invention relates to a method for manufacturing a synthetic resin ball lens having a refractive index distribution in which the refractive index changes in the normal direction from the center of the sphere to the periphery. .

3-2 Description of the Prior Art As a lens having a refractive index distribution, a transparent rod-shaped body having a refractive index distribution that decreases in the radial direction approximately in proportion to the square of the distance from the central axis is known.

This transparent rod-shaped body has a convex lens effect, and its refractive index distribution is approximated by equation (11).

n (r) -no (/-//jAr2)
In formula (1), n(r) represents a refractive index at a point q distance r from the central axis, nQ represents a refractive index at the central axis, and A represents a positive constant.

A light beam propagates in a meandering manner in such a transparent rod-shaped body, and its periodicity is expressed by equation (2).

L, -2π/'V' The shaped body becomes a light transmission body having a concave lens effect.

n(r)=n□ (1+//2 Br2)
(In formula 31, n(r) and n□ are the same as above, and B is a positive constant.

A method for manufacturing a synthetic resin optical transmitter having such a refractive index distribution is disclosed by Tokkosho! 2-jJj Publication No. 7, Japanese Unexamined Patent Publication No. 1973/-/
Publication No. 639'1, JP-A-Sho! It is described in the It-//9939 publication.

3-3 Problems to be solved by the invention As mentioned above,
A cylindrical Ronde lens with a radial index distribution is attracting attention as a light condensing and imaging element in the field of optoelectronics. However, if the optical axis of the Rondo lens is slightly shifted from the optical axis of the optical system, large aberrations will occur due to skewed rays, which is currently a problem.

However, in the case of a spherical lens, there is no optical axis of the lens, so there is no skewed ray due to axis misalignment. A ball lens whose refractive index decreases from the center point to the outer periphery in an approximately square law distribution is embedded in a medium with an appropriate refractive index, or a ball lens with a uniform refractive index around such a ball lens is used. By using a lens equipped with a rad as a focusing element, it is possible to achieve light focusing with almost no aberration.

However, with conventional techniques, it is extremely difficult to control the refractive index distribution spherically, and such a spherical lens has not yet been obtained. In order to manufacture a synthetic resin ball lens with a refractive index gradient, it is first necessary to obtain the current base material, but if a polymerized base material is used, subsequent monomers with different refractive indexes will be produced. In the process of diffusing the metal, it is extremely difficult to diffuse it to the center of the base material. Therefore, as a base material,
Partially polymerized spherical transparent gel particles are used.

A patent application published in 1973-111 proposed the use of suspension polymerization as a method for producing completely spherical transparent gel particles in large quantities at once.
6211.

When the transparent gel particles thus obtained are subjected to the subsequent diffusion and heat treatment steps, a refractive index distribution in which the refractive index changes in the normal direction from the center to the periphery of the sphere as described above is created. It is possible to mass-produce synthetic resin ball lenses having the following properties at once.

However, in the diffusion step of diffusing the monomer Mb into the transparent gel particles and copolymerizing them, the polymerization is not yet completed and the above-mentioned refractive index distribution is not fixed. Therefore, in the past, in order to separate the transparent gel particles after diffusion from the monomer Mb, they were filtered by suction, and then dispersed in water heated to a predetermined temperature in a container to finally complete the polymerization. Then, heat treatment was performed for a predetermined period of time.

However, as described above, since the gel particles after diffusion are in an incomplete state of polymerization, the monomer Mb that has once diffused in the diffusion step during the heat treatment step is instead released into the water. Therefore, the refractive index gradient formed in the particles becomes gentle, and in the peripheral portion, the monomer Mb is extracted to a large extent, so that the reverse gradient of the refractive index becomes noticeable.

3-G Means for Solving the Problems of the Conventional Method Polymerization of diffused spherical transparent gel particles, which are the base material of a synthetic resin gradient refractive index ball lens, is completed by heating in a saturated aqueous solution of the monomer Mb.

,? -j Effects of the invention The spherical transparent gel particles after diffusion are not in water, but in monomer Mb.
By completing the polymerization by heating etc. in a saturated aqueous solution of Mb, the release of the monomer Mb from the gel particles during the heat treatment process is greatly suppressed. It is possible to form the curve steeply and almost in a square distribution up to the periphery or near the periphery of the spherical lens.

3-6 Examples Hereinafter, the method for manufacturing a synthetic resin ball lens according to the present invention will be explained based on examples.

First, a reticular polymer (including copolymer) with a refractive index of Na, Pa
The monomers (including monomer mixtures) forming Ma together with an initiator or these at a predetermined temperature To and time t.

The prepolymerized sol is added dropwise or dropwise into a predetermined container containing a solvent and a dispersant at a predetermined temperature T1°C1 time t1 and rotation speed rl (r
Suspension polymerization is carried out at pm) and partially polymerized to produce large spherical transparent gel particles at once. At this time, the gel particles contain 20 to 90% of the solvent-insoluble component (reticular polymer).
It is left in an uncompleted state containing % by weight of polymer.

Since the spherical transparent gel particles produced as described above are dispersed in the polymerization system in a predetermined container, the polymerization system is suction-filtered to separate the transparent gel particles.

Next, the separated particles are treated with a refractive index N different from that of the Na.
A monomer (including a monomer mixture) forming a polymer (including a copolymer) having b Pb is added to a container containing Hb, and at a predetermined temperature TiC for 1 hour t2, from the surface of the sphere. Diffusing monomer Mb toward the center and polymerizing it,
A refractive index distribution in which the refractive index changes continuously in the normal direction from the center to the periphery of the sphere is formed in the transparent gel particles.

Thereafter, in order to separate the transparent gel particles after diffusion from the monomer Mb, suction filtration is performed again. Then, in order to finally complete the polymerization, the temperature is set to T3 in a predetermined container.
The monomer Mb is dispersed in a saturated aqueous solution heated to .degree. C., and heat-treated for a predetermined time t3 and under stirring at rotation Wir3(rl)m).

All synthetic resin ball lenses obtained in large quantities in this way have a refractive index distribution that changes continuously in the normal direction from the center to the periphery; Compared to the case of heat treatment in water, it is formed steeply and to the periphery or near the periphery.

Compared to a normal spherical lens with a uniform refractive index, a Cor lens corrects not only spherical aberration but also coma aberration.

The monomer Ma to be the raw material of the transparent gel object as the lens base material in the above embodiments is a monomer having two or more types of groups among allyl group, acrylic acid group, methacrylic acid group, or vinyl group. You can use your body. Next, specific examples of monomer Ma will be given.

(1) Allyl compound 7 Diallyl esters such as diallyl talate, diallyl isophthalate, diallyl terephthalate, diethylene glycol bisallyl carbonate, triallyl trimellidate,
Triallyl esters such as triallyl phosphate and triallyl phosphite; Unsaturated allyl esters such as allyl methacrylate and allyl acrylate.

(Compound represented by 21RIR2-R3 A compound in which R1 and R3 are both a vinyl group, an acrylic group, a vinyl ester group, or a methacryl group; either one of R1 and R3 is a vinyl group, an acrylic group, a methacryl group, or a vinyl group) A compound in which the ester group is one of two groups and the other is one of the remaining three groups, where R2 is Oa-CH3 which can be selected from the covalent groups shown below. -((H2CH20)m -CH2CH2-(m-o-
,zc+)-(CH2)p
(p sw 3~/j) (GHz) iH -CH2-CCH2 (i, j-/~3) (GHz) jH (3) A mixture of the monomers of (1) and (2) above, or a monovinyl compound , a mixture of at least seven of the five types of vinyl esters, acrylic esters, and methacrylic esters and the monomer (1) or (2) (or a mixture thereof).

Furthermore, examples of the monomer Mb include the following. X (4) A compound represented by CH2-C-C00Y, where X is a hydrogen atom or a methyl group, -CCH2)j
HC1-/~l), i-propyl group, i\butyl group, S
-butyl group, t-butyl group, (h-0~2) and -(C
H2CH20)p CH2CH3(p-/~6), or -(CF2)a-F (
a-/ ~6), -0H2(CF2)bH(b-/
-f), -0H2CH20・(J[20F:s, -(
(J2CH20)cCF20F2H(C-/ ~If
), -CH2CH20・CH2(CF2)aF(a
-/~6), -CH2(CFg)dO(CF2MF
(d −/ ~, 2.1 −/−4) and −3i (OC2
H5) represents a group selected from the group consisting of 3.

(5) CH2-CHoC-R4 compound where R4 is -(CH2)f-CH5(f-0-
2), represents a group selected from ◇ (6) (Mixture monomer M of monomers of 41 and (5)
(1) to (3) above as a, (4) as monomer Mb
Any of (6) to (6) can be combined.

In addition, in order to adjust the gelation state of the transparent gel object, (
As mentioned in section 3), 7 unsaturated groups are added to the crosslinkable monomer Ma.
Method of adding monomers having gBr4, CG
A method of adding a chain transfer agent such as 14 t-mercaptans or a method of using both together is effective.

Next, test examples of the present invention will be explained.

Test example/ First, DAI (diallyl isophthalate) (polymer refractive index Na-/, j4) as the monomer Ma, BPO (over-brewed benzene yb) o, osri, DBP0 as an initiator
(Ditert-butyl peroxide) O, OS
was added, and then polymerized at a temperature of -90° C. to -56 molecules for 1 hour to produce a sol having fluidity prior to gelation. This sol consisted of 10% by weight ffi of a methanol-insoluble component (linear polymer).

Next, 200 g of water as a solvent and PVA (polyvinyl alcohol)/J9 as a dispersant were added together with this sol into a flask equipped with a stirring device, and the temperature was raised to Tl-9.
0°C 1 rotation speed 14-j 0 (rpm) for time t
Suspension polymerization was carried out for 1 m4i hours, and partially polymerized spherical transparent gel particles were produced at once. The transparent gel particles consist of 75% by weight of methanol-insoluble components (reticular polymer portion and linear polymer portion) and 25% by weight of methanol-soluble components (monomer and low molecular weight prepolymer portion). Ta.

Next, the transparent gel particles produced above were filtered by suction to separate them from the polymerization system, and then the separated particles were heated to a temperature of T2-70''C.
A (2,2,2-trifluoroethyl methacrylate)
(Polymer refractive index Nb -/, 112 IO) was added to the solution for 20 hours and held for t2-/ hours to diffuse JFMA into the particles and polymerize at the same time.

Thereafter, the particles are filtered again by suction in order to separate them from the JFMA particles after diffusion. Finally, a saturated aqueous solution of JFMA in a container heated to a temperature of T3-qO″C
In addition during q, rotation 'f&r3-33Orpm, time t3
The polymerization was completed in -, -# hours, and the refractive index changed continuously in the normal direction from the center of the sphere to the periphery.

When the refractive index distribution formed in the obtained synthetic resin gradient index ball lens was measured using an interference microscope, it was as shown in FIG. In FIG. 1, the horizontal axis represents the ratio of the distance r to the radius Rp of the sphere, and the vertical axis represents the refractive index at the same point. The difference in refractive index was about three times larger than that in the case of heat treatment in water, and a nearly square distribution was formed up to the vicinity of the periphery.

Test Example λ First, DAI was used as the monomer Ma, and BP was used as the initiator.
After adding OO,03 and 0.059 of dicumyl peroxide, the molecules were combined at a temperature of -90°C for a time of -57 minutes to obtain a sol. This sol contained methanol-insoluble components ( It consisted of % linear polymer)/double polymer.

Next, in a flask with a stirrer containing 200 g of water as a solvent and PVA (polyvinyl alcohol) as a dispersant, the temperature was 1-90° C.
Partially polymerized spherical transparent gel particles were prepared in large batches by suspending at l-torpm for tlsJ hours. These transparent gel particles contain components that are insoluble in methanol (
It consisted of 75% by weight (reticular polymer portion and linear polymer portion) and 25% by weight of methanol-soluble components (monomer and low molecular weight prepolymer portion).

Next, the transparent gel particles produced above were filtered by suction to separate them from the polymerization system, and then the separated particles were added to JFMA in a container heated to a temperature of T2-70''C. Hold for a minute to allow 3FMA to diffuse into the particles and simultaneously polymerize.

Thereafter, the particles are suction-filtered again to separate them from the JFMA. And finally the temperature T3-Q″C
jF containing PvAIO9 in a container heated to
Added to MA saturated aqueous solution 2009, rotation speed r3-Jj
Polymerization was completed after a waiting time of Orpm time t3-is, and a synthetic resin ball lens whose refractive index changed continuously in the normal direction from the center to the periphery of the ball was obtained.

All of the obtained spherical lenses have a desired diameter within a range of ±0.02 mm from 5°, and the particle size can be considered to be constant.

When the refractive index distribution formed in the obtained synthetic resin gradient index ball lens was measured using an interference microscope, it was as shown in FIG. In FIG. 2, the vertical axis indicates the difference between the refractive index n at a distance of r/R1) from the center and the refractive index no at the center point. The difference in refractive index was approximately one times larger than that in the case of heat treatment in water, and a nearly square distribution was formed up to the vicinity of the periphery.

[Brief explanation of drawings]

FIG. 1 is a graph showing an example of the cross-sectional circular refractive index distribution of a spherical lens obtained by the method of the present invention, and FIG. 2 is a graph showing another example of the refractive index distribution.

Claims (3)

[Claims] (1) Network polymer (including copolymer) with refractive index Na, Pa
A step of forming spherical transparent gel particles by partially polymerizing a sol obtained by prepolymerizing monomers (including monomer mixtures) Ma or monomers Ma to form , by suspension polymerization. (2) A polymer (
The spherical transparent gel particles are added to a monomer (including a monomer mixture) Mb that forms Pb (including a copolymer), and the monomer Mb is diffused from the surface of the sphere toward the center and polymerized. , forming in the transparent gel particles a refractive index distribution in which the refractive index continuously changes from the center of the sphere to the periphery; (3) A method for manufacturing a synthetic resin gradient index sphere lens, which includes the step of adding the transparent gel particles to a saturated aqueous solution of the monomer Mb and fixing the refractive index distribution by completing polymerization by heating or the like. .