JPS6289901A - Production of distributed index type plastic lens - Google Patents

Abstract

PURPOSE:To quickly form a distributed index type plastic lens having an excellent light focusing characteristic by immersing a circular cylindrical transparent polymer contg. an epoxy group into a soln. mixture composed of a specific lower molecular compd. then drying the same. CONSTITUTION:The circular cylindrical transparent polymer contg. the epoxy group is immersed into the soln. mixture composed of a swellable liquid and the lower molecular compd. which has reactivity with the epoxy group and forms a polymer having the refractive index lower than the refractive index of said polymer by reacting therewith to disperse the lower molecular compd. into the polymer and to effect the reaction therebetween, then the polymer is dried. The transparent polymer contg. the epoxy group is most preferably a polymer essentially consisting of a beta-methyl glycidyl methacrylate and the liquid to be used for swelling is exemplified by a solvent mixture composed of methanol, etc., and ehtyl ether, etc. The lower molecular compd. is exemplified by a fluorinated carboxylic acid, etc. The formation of the refractive index distribution exhibiting the high light focusing characteristic is thereby relatively easily executed.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to an improved graded refractive index plastic protective lens array, an optical fiber coupling element, an optical demultiplexer, a rod lens used in a line sensor, etc. A wide range of applications are expected.

[Prior art] As a gradient index lens,
No. 16 proposes a glass fiber body whose refractive index gradually decreases from the central axis toward the surface.

Regarding plastic gradient index lenses,
For example, [1] Special Publication No. 47-2fi913, (2) Special Publication No. 47-28059, (3) Special Publication No. 54-3 ('1
No. 301, (4) Special Publication No. 52-5857 and (5)
Various preparation methods have been proposed in Japanese Patent Publication No. 58-212078 and the like. Among these, (1) to (4)
) method is difficult to manufacture an optical transmission body with high light focusing properties, it is extremely difficult to select manufacturing conditions to improve light focusing properties, or even if conditions with high light focusing properties are found by chance. Each has its own problems as an industrial technology, such as not necessarily being able to achieve reproducibility. Compared to these methods (1) to 14), method (5) has the advantage that it has a wider selection range of conditions for forming the refractive index distribution and can obtain products with good relative softness reproducibility. .

However, (5) (1) under the described production conditions, i.e., after the reactive transparent polymer is immersed in the swelling liquid and swelled to a predetermined volume, the reactive transparent polymer is reactive with the polymer;
In addition, the method of diffusing and reacting a low-molecular compound that reacts to produce a polymer with a refractive index lower than that of the polymer into the interior of the polymer, and then drying it, separates the swelling process and the diffusion process, so the refractive index Distributed lenses have problems in that they take a long time to manufacture and it is difficult to precisely control the refractive index distribution.

[Problem that the invention seeks to solve]

In order to solve this problem, after repeated studies, we found that by applying the method shown below, we were able to obtain a polymer with the desired refractive index distribution in a relatively short period of time, and also under appropriate conditions. It has been found that by selecting , it is possible to obtain a refractive index distribution closer to the target refractive index distribution than in the conventional method.

[Means for solving problems]

The gist of the present invention is to combine a cylindrical transparent polymer containing an epoxy group with a swelling liquid to form a polymer that is reactive with the epoxy group and has a refractive index lower than that of the polymer. The polymer is immersed in a mixed solution with a low molecular compound to be produced, and this low molecular compound is diffused and reacted inside the polymer.
The present invention provides a method for manufacturing a gradient index lens, which is then dried. By using a liquid mixture of a swelling liquid and a low-molecular-weight compound in this way, it has become possible to easily form a refractive index distribution exhibiting high light focusing properties and in a relatively short time. Furthermore, when these steps are performed continuously, a gradient index optical transmission body and fiber can be obtained.

Specific examples of the transparent polymer containing an epoxy group used in the present invention include glycidyl acrylate, glycidyl methacrylate, β-methylglycidyl acrylate,
At least one monomer of β-methylglycidyl methacrylate and other monomers, such as methyl methacrylate, ethyl methacrylate, propyl methacrylate, cyclohexyl methacrylate, hensyl methacrylate, phenyl medacrylate, ethylene, α-methyl methacrylate, etc. copolymers with trifluoroethyl methacrylate, hexafluoroisopropyl methacrylate, pentafluoropropyl methacrylate, ethylene glycol dimethacrylate, pentaerythritol diacrylate, trimethylolpropane triacrylate, or glycidyl methacrylate, β-methylglycidyl methacrylate Examples include homopolymers of

Among these, polymers whose main component is β-methylglycidyl methacrylate have relatively good thermal stability of the epoxy group, high transparency, and a relatively high second-order transition point (approximately 75°C). For this reason, it is the most preferable.

The cylindrical transparent polymer containing an epoxy group used in the present invention can be produced by, for example, extruding a mixture of a partially polymerized product and a photopolymerization initiator through a nozzle, and forming it into a cylindrical door shape using a photopolymerization method. It is carried out by the method of A nozzle hole diameter of about 1 mm to 5 mm is suitable for the cylindrical transparent polymer used in the present invention. As the photopolymerization initiator, conventionally known ones can be used, such as benzoin alkyl ether.

Specific examples of the liquid used for swelling the epoxy group-containing polymer used in the present invention include methanol, ethanol, propatool, ethylene glycol and these alcohols, methyl acetate, ethyl acetate, methyl ethyl ketone, methitool, and anisole. Examples include, but are not limited to, mixed solvents of ethylene glycol dimethyl ether, etc., and ethyl ether, isopropyl ether, butyl ether, etc.

Specific examples of low-molecular compounds that are reactive with epoxy groups and have a refractive index lower than that of the polymer used in the present invention include fluorinated carboxylic acids represented by the following general formulas (11 to decoy), Examples include fluorinated carboxylic anhydrides represented by the general formula (-) and fluorinated alcohols represented by the ~ side of the general formula.

CnF2n, C0OH(I) CnF2n+ICH2COOH(1) H(CF2C'F21mC'00H(IN) H(CF
2CF2)mCH2COOH(■)CnF2n+ICO
/H(CF2CF2)mCH2Co/CnFzn+t
CHzOH(IX: )H(CF2CF2)mCH20
H(X)H(CF2CF2)mCH2COOH(yJ
)CnF21+lCH2CH20H(■) (in the formula, n is 1
An integer of ~12, m represents an integer of 1-6. ) Using a mixture of these low molecular weight compounds and the swelling agent mentioned above,
A refractive index distribution is given to a cylindrical transparent polymer containing an epoxy group, but in order to give the polymer high-precision light focusing performance, it is necessary to make the refractive index distribution as shown by the following theoretical formula (1) as much as possible. It is necessary to carry out a diffusion reaction of low molecular weight compounds to achieve a match.

n(r) =n(o) 5ech (gr+ +
1) Distance from r-rod center to surface direction To this end, it is necessary to use a mixed solution with an appropriately adjusted ratio of low molecular weight compound and swelling agent, and in some cases, 2
It is necessary to use a combination of two or more types of low molecular weight compounds or two or more types of swelling agents.

Further, the mixed liquid, reaction time (immersion time), and reaction temperature must be appropriately selected and determined so as to match the refractive index distribution of the theoretical formula (1) as much as possible.

After the low-molecular-weight compound that is reactive with epoxy groups is arranged with a continuous gradient concentration from the surface of the cylindrical polymer toward the center, when the polymer is taken out from the reaction tank and dried, mixing is required. A two-stage drying method in which pre-drying is performed under conditions that do not exceed the boiling point of the swelling agent in the liquid plus 10°C, followed by drying at a temperature in the range of 120 to 150°C until almost no swelling agent remains in the polymer. is preferred. The reason for this is that air bubbles may be generated in the polymer due to rapid heating at high @ρ.

〔Example〕

Hereinafter, the present invention will be explained in more detail with reference to Examples.

In addition, production of transparent polymers and evaluation of lens performance in Examples were performed as follows.

(1) Preparation of a cylindrical transparent polymer containing an epoxy group A cylindrical transparent polymer having a surface diameter of 1 mm was prepared by extruding it from a tube, irradiating it with ultraviolet rays from around it, and taking it off with a nip roller.

Table 1 (11) Evaluation of lens performance (a) Evaluation device Lens performance was evaluated using an evaluation device as shown in the drawings. In the drawing, (1) is an optical bench, (2) is a tungsten lamp for a light source, (3) is a condensing lens, (4) is an aperture, and (5) is a chromium-plated glass for a photomask. A glass plate precision-processed into a square pattern of 1 rrm, (6) a sample stand, (7) a Polaroid camera, and (8) a sample for evaluation.

(Preparation of sample) Cut the prototype gradient index lens to a length 1) that is approximately 1/2 of the period (λ) of the light beam determined from the undulation of the passing He-Ne laser beam. The sample was polished so that both end surfaces became parallel planes perpendicular to the long axis, and used as an evaluation sample.

9 Evaluation method As shown in the drawing, the prototype sample (8) is set on the sample stage (6), and the aperture (4) is adjusted so that the light from the light source (1) is focused on the condensing lens ( 3) After passing through the diaphragm (4) and the processed glass plate (5), the light enters the entire end face of the sample, and then the sample (8) and Polaroid camera (7) are focused on the Polaroid film. Adjust as follows.
A square grid image was taken and the distortion of the grid was observed.

Example 1 Cylindrical transparent polymer A was immersed in a reaction solution consisting of 50 parts by weight of ethylene glycol dimethyl ether, 50 parts by weight of isopropyl ether, and 4 parts by weight of octafluoropentanoic acid, reacted for 7 hours, and then heated at 75°C. It was dried in a vacuum dryer for 12 hours and then at 140° C. for 4 hours to produce a gradient index lens. As a result of evaluating the lens performance of this sample, it was found to be very good with no distortion.

Example 2 Cylindrical transparent polymer B was immersed in a reaction solution consisting of 100 parts by weight of ethanol at 70°C and 1 part by weight of octafluoropentanoic acid, reacted for 5 hours, and then dried in a vacuum dryer at 80°C for 12 hours. It was further dried under reduced pressure at 140° C. for 4 hours to produce a gradient index lens. As a result of evaluating the lens performance of this sample, it was found to be very good with no distortion.

Example 3-8 and Comparative Examples 1 to 3 Gradient index lenses were prepared using the cylindrical transparent polymers shown in Table 1 and using the reaction solutions and reaction conditions shown in Table 2. Drying at this time was carried out under the same conditions as in Example 2. Second
The table shows the obtained 5A MeOHl
o(13FAA1 50X20 p8
B MeOHloo 7FBA 1
60X7 pGDM: Ethylene glycol dimethyl ether IPE: Isopropyl ether MeOH: Methanol 8 FPA: 5H-octafluoropropentanoic acid 7
FBA: Heptafluoroic acid 12'F'HA: 7H-dodecafluorohbutanoic acid 15FOA: Heptadecafluorooctanoic acid 3F
AA: ) Rifluoroacetic acid [Effects of the Invention] According to the present invention, a gradient index plastic lens with excellent light focusing ability can be manufactured in a short time.

[Brief explanation of drawings]

The drawings show the gradient index plastic obtained by the present invention 1. FIG. 2 is an explanatory diagram of a device for evaluating the performance of lenses. In the drawing, (1) is the optical bench, (2) is the tungsten lamp for the light source, (3) is the condensing lens, (4) is the aperture, and (5) is the chrome coating of the chrome-plated glass for the photomask. A glass plate precision-processed into a 1.1 m square grid pattern, (7) a Polaroid camera, and (a) 8) a sample for evaluation.

Claims (1)

[Claims] Mixing a cylindrical transparent polymer containing an epoxy group with a swelling liquid and a low molecular compound that is reactive with the epoxy group and reacts to produce a polymer having a lower refractive index than this polymer. 1. A method for producing a gradient index plastic lens, which comprises immersing the polymer in a liquid to diffuse and react the low-molecular-weight compound inside the polymer, and then drying the polymer.