JPS6360403A - Production of optical transmission body made of synthetic resin - Google Patents

Abstract

PURPOSE:To obtain a stable optical transmission body having the optical transmission characteristics which do not change with every production lot by dividing a stage for diffusing and impregnating a polymerizable monomer to >=2 stages, varying the diffusion rate of the monomers to be diffused and impregnated in each stage and diffusing and impregnating the monomers in order of the higher diffusion speeds. CONSTITUTION:The optical transmission body made of the synthetic resin having the refractive index distribution continuous from the center toward the surface is produced by diffusing and impregnating the polymerizable monomer (B) forming the polymer having the refractive index different from the refractive index of a crosslinked polymer (A) having a required network density to said polymer to apply the concn. distribution continuous from the center toward the surface to the polymer, then polymerizing the unreacted monomer. The stage for diffusing and impregnating the polymerizable monomer (B) is divided to >=2 stages and the monomers to be diffused and impregnated in the respective stages are varied. The monomers are diffused and impregnated in order of the higher diffusion rates. The disturbance in the refractive index distribution in the surface layer is thereby obviated and the change in the optical transmission characteristics with every production lot is prevented.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention is applicable to various types of optical fibers such as plastic transmission bodies having a continuous refractive index distribution from the surface to the inside, such as light-concentrating plastic optical fibers and Rondo lenses. The present invention relates to a method of manufacturing a transmission body.

[Conventional technology]

A conventional method for forming a refractive index distribution of an optical transmission body is, for example, disclosed in Japanese Unexamined Patent Publication No. 4
As described in No. 9-65840 and JP-A-57-177101, a rod is made of a monomer that becomes a high refractive index polymer.
This is carried out by forming a high refractive index polymer (paste polymer rod) having a shape of a shape, and then diffusing and impregnating it with a monomer that will become a low refractive index polymer. In this method, a cross-linked semi-polymer (reticular polymer containing 2 to 80% by weight of solvent-soluble components) consisting of monomers having two or more polymerizable functional groups in the molecule is used as Pace Polymer Loft. or (1) a monomer having one polymerizable functional group in the molecule (functional monomer) and a monomer having two or more polymerizable functional groups in the molecule as the base polymer loft; There is a method using a cross-linked polymer made of monomers (polyfunctional monomers).

[Problem that the invention seeks to solve]

In order to form a continuous attribute rate distribution using these methods, important points are the relationship between the impregnating property of the monomer to be diffused and impregnated and the refractive index distribution, and the relationship between the impregnating property and the cross-linking density of the base polymer rod. becomes.

Furthermore, the conditions during polymerization for polymerizing the polymer after diffusion impregnation are also an important point.

In the case of method (2), that is, when obtaining a pace polymer rod using only a polyfunctional monomer, if the polymerization reaction is allowed to proceed until the polymerization is completed, the cross-link density (wire mesh) of the cross-linked polymer (network structure) will increase. Due to the densification, it becomes difficult to diffuse the polymerizable monomer in the process of diffusing the polymerizable monomer to form a polymer having a refractive index different from that of the paste polymer rod. For this reason, in the case of method It is necessary to stably obtain a "reticular polymer containing up to 80% by weight." However, at present, it is difficult to stop the reaction at a certain polymerization time, and it is necessary to find a method to accurately detect the polymerization rate and a method to efficiently stop the polymerization reaction during the polymerization process. The polymerization reaction involved involves troublesome and practically difficult problems.

Therefore, method (2) has undesirable problems as a product in that the content of unpolymerized components and mesh density tend to vary from manufacturing loft to manufacturing loft, and the optical transmission characteristics of the manufactured optical transmitter also tend to change from manufacturing loft to manufacturing loft. be.

Method (2) is an improvement of (2) and is a method in which the network density of the base polymer loft is controlled to a predetermined degree by a combination of monomers. Specifically, in the production of the base polymer loft, -functionality This is a polymerization method using a mixed monomer consisting of a monomer and a polyfunctional monomer, and the network density is determined by the amount of polyfunctional monomer (component that forms the network structure).
It is determined by the blending ratio of That is, by changing the blending ratio of -functional and polyfunctional monomers, the diffusion rate and amount of unpolymerized components can be arbitrarily controlled. Therefore, the variation in mesh density is extremely small, and the variation from manufacturing loft to manufacturing loft can be reduced.

From the above, it can be seen that the method (2) is a method capable of reducing the reproducibility of the monomer impregnation diffusivity of the pace polymer rod, that is, the variation in the diffusion impregnation property between manufacturing lofts.

However, it has been found that this method does not solve all the problems encountered in producing an optical transmission body having a continuous refractive index distribution from the center to the outer periphery, and has the following drawbacks.

By the above method (2), a monomer forming a polymer having a refractive index different from that of the base rod is impregnated and diffused to form a concentration distribution, and then the monomer is polymerized to form an optical transmission body having a refractive index distribution. When a monomer with a small molecular weight is used as an impregnating monomer, it is convenient to impregnate the base rod by diffusion, but the monomer evaporates from the surface when it is then heated for polymerization. Consecutive losses occur and the refractive index distribution becomes undesirable.

Therefore, usually the base rod is impregnated with an impregnating monomer to form an attribute distribution, and then the surface of the base rod is wrapped with a film of polyethylene or polyethylene terephthalate, etc. to prevent the volatilization of the monomer while heating polymerization. I do.

However, depending on the sealed state at the time of winding, variations occur in the refractive index distribution state of the final product. Furthermore, there are various difficulties in practical application, such as there being a limit to the length of the optical transmission body that can be produced.

The purpose of the present invention is to provide a stable optical transmitter whose optical transmission characteristics do not change from manufacturing loft to manufacturing loft in the production of a synthetic resin optical transmitter having a continuous attribute rate distribution, and to develop a method suitable for mass production. By providing the above, it is an object of the present invention to put synthetic resin optical transmission bodies into practical use.

[Means for solving problems]

In order to achieve the above object, the present inventors investigated various methods, and as a result, they arrived at the present invention.

The method for manufacturing a synthetic resin light transmitting body according to the present invention includes adding a polymerizable monomer (B
) is diffused and impregnated to give a continuous concentration distribution from the center to the surface, and then unreacted monomers are polymerized to obtain a synthetic resin optical transmitter with a continuous refractive index distribution. The process of diffusing and impregnating the monomer (B) is divided into two or more stages, and the monomers to be diffused and impregnated in each stage have different diffusion speeds, and the diffusion impregnation is performed in order from the one with the fastest diffusion speed. Features.

The cross-linked polymer (2) forming the base polymer rod may have the required network density so that it can be diffused and impregnated with the polymerizable monomer (B) forming a polymer having a different refractive index. Often, for example, a cross-linked polymer obtained by polymerizing a mixture of a polyfunctional JJiffi compound such as ethylene glycol dimethacrylate or trimethylolpropane trimecacrylate and a monofunctional monomer such as benzyl methacrylate or phenyl methacrylate is used. It is preferable because there is little variation in mesh density and there is little variation from manufacturing loft to manufacturing loft.

Monomers with different molecular weights are used as monomers with different diffusion rates to be diffused and impregnated into the pace polymer rod. In the polymerizable monomers shown, different monomers of R2 are used. Diffusion impregnation in the first stage
As the lfi form, methyl methacrylate and ethyl methacrylate are preferable, and as the monomer to be diffused and impregnated in the second stage, hexyl methacrylate, n-dodecyl methacrylate, and 2-ethylhexyl methacrylate are preferable.

In order to use two of these monomers and diffusely impregnate them into the base polymer loft in two stages, in the first stage,
A single monomer or a mixture of monomers in which R2 is H or a relatively small alkyl group having 1 to 4 carbon atoms in the above formula (1) is diffused and impregnated to form a refractive index distribution. Next, as the second stage, R2 in 2 (1) is diffused and impregnated with a single monomer or a mixture of monomers in which R2 is a relatively large alkyl group with 4 to 12 carbon atoms, and the surface is impregnated with the second stage. Replace with monomer.

[For production]

According to the method of the present invention, the monomer that is first impregnated into the pace polymer rod and forms a continuous refractive index profile has a fast diffusion rate, so that the time required for diffusion impregnation is short. Next, this is impregnated with a monomer with a slow diffusion rate, that is, a monomer with a large molecular weight, and in order to form a layer of a high-boiling point monomer with a large molecular weight on the surface, the following polymerization step (polymerization temperature of 60 to 7
The volatilization of the monomer due to heating at 0°) can be suppressed.

As described above, according to the present invention, it is possible to prevent the monomer impregnated into the pace polymer rod from volatilizing in the subsequent heating polymerization step and disrupting the refractive index distribution. Furthermore, when the monomer represented by the general formula (1) is used as the monomer for diffusion impregnation, and a monomer in which R2 is an alkyl group having 4 to 12 carbon atoms is used in the second stage, the surface layer The monomer has a high boiling point and at the same time has low solubility in water, so the thermal polymerization can also be carried out in an aqueous phase.

〔Example〕

The present invention will be explained below using examples.

Example 1 (1) Production process of pace polymer rod (high refractive index loft) [Blend composition] Benzyl methacrylate 100 g (-functional monomer) Tertiary dodecyl mercaptan 15 g (molecular weight regulator) Monofunctional monomer, A monomer mixture containing two polyfunctional monomers, a molecular weight regulator and a thermal polymerization initiator as described above was placed in a Teflon tube with an inner diameter of 4 W and a length of 300 mm, and immersed in a water tank at 70°C. Polymerization was carried out in this state for 3 hours to produce a flexible transparent cross-linked polymer, which was taken out from the Teflon tube to obtain a base polymer rod.

(2) Diffusion impregnation process of low refractive index polymer-forming monomer (2) A monomer mixture (Bl) consisting of 100 g of methyl methacrylate and 3.0 g of lauroyl peroxide, a monomer mixture (Bl) consisting of 100 g of hexyl methacrylate, and 3.0 g of lauroyl peroxide. Each of the polymer mixtures (B2) was placed in a glass tube with an inner diameter of 20φ. Next, the paste polymer rod 7 is immersed in the above monomer (B) kept at 20° C. to diffuse and impregnate the monomer (B1) into the base polymer rod. When the monomer (B,) reaches the center of the base polymer loft (soaked for 3 hours), the monomer (Bl)
Then, the sample was taken out and immersed in monomer (B2) for 30 minutes.

As a result, the monomer diffused and impregnated into the surface layer of the pace polymer loft contains more (B2) than (Bl).

(3) Monomer polymerization process Once the monomer diffusion impregnation in (2) above has been completed and a refractive index distribution has been formed, the temperature is controlled at 70°C, and the air is replaced with N2.
A so-called GI type optical transmission body in which the refractive index continuously changes from the center to the surface was produced by heating and polymerizing in an open atmosphere substituted with 100° C. for 5 hours and then at 100° C. for 10 hours. Measuring the refractive index distribution of this Gl type optical transmission body,
Shown in Figure 1 (al).

(4) Confirmation of the refractive index distribution state The rod on which the refractive index distribution was formed was cut (sliced into rings) with a thickness of 1 mm, and the refractive index distribution was measured by differential interferometry using an interference microscope (Interfaco).

Comparative Example 1 The pace polymer rod prepared in Example 1 was immersed in monomer (B1) for 3 hours and 30 minutes in the diffusion impregnation step (2) to form a refractive index distribution, and then The same heating polymerization as in 3) was carried out. As a result, during the heating polymerization, the monomer (81) impregnated into the pace polymer rod volatilizes from the surface of the loft, increasing the refractive index of the rod surface, as shown in Figure 1 (bl
The refractive index distribution was as shown in .

Example 2 Monomer mixture (Bl) consisting of 100 g of methyl methacrylate and 3.0 g of lauroyl peroxide, n-
A monomer mixture (BO) consisting of 100 g of dodecyl methacrylate and 3.0 g of lauroyl peroxide was prepared and placed in each glass tube with an inner diameter of 20φ. Next, the pace polymer rod produced in Example 1 (B1
) for 2 hours (B, has not reached the center of the rod) (
B2) for 2 hours (at this point, B reached the center of the loft) to form a refractive index distribution.

After that, the rod with the refractive index distribution formed therein was immersed in distilled water controlled at 70°C, and the underwater heating polymerization was carried out for 55 minutes.
I did it for an hour. As a result, the obtained rod became slightly cloudy. However, after this, it was taken out of the water and heated to 100℃ for 10 minutes.
It became transparent and radish by heating for a certain period of time. When the refractive index distribution of the obtained product was measured, it showed a refractive index distribution as shown in FIG. From this, it is thought that the reason for the slight cloudiness during polymerization in distilled water was simply water absorption into the rod. It is considered that this moisture was dried during the subsequent heating polymerization at 100° C. and returned to transparency.

In addition, since the refractive index distribution of the surface layer of the rod was hardly disturbed, it is considered that even when polymerized in water, monomer (B2) was insoluble in water, so it was directly polymerized and turned into a polymer.

Example 3 (1) Manufacturing process of pace polymer rod (high refractive index) [Blend composition] Phenyl methacrylate 100 g Lauroyl peroxide 0.5 g The above monomer mixture was heated at 80°C for 2 hours in the same manner as in Example 1. A paste polymer rod was produced by heating and polymerizing.

(2) Diffusion impregnation process of low refractive index polymer forming monomer 50 g of methyl methacrylate, 150 g of ethyl methacrylate,
Monomer mixture (Bl) consisting of 3.0 g of lauroyl peroxide (2-ethylhexyl methacrylate)
50g, n-dodecyl methacrylate 50g.

A monomer mixture (B2) consisting of 0.3 g of lauroyl peroxide was prepared. The base bolima rod of (1) above was heated at 20°C for three times each in the order of (B+) and (th).
time.

Diffusion impregnation was performed for 40 minutes to form a refractive index distribution.

(3) Monomer polymerization step After completing the monomer diffusion impregnation in (2) above and forming a refractive index distribution, the product was heated at 70°C for 5 hours and at 100°C for 10 hours in a Nt-substituted oven. We have fabricated an optical transmitter whose refractive index changes continuously from the center to the surface in response to time. This refractive index distribution was measured and shown in FIG.

〔effect〕

As described above, according to the present invention, in manufacturing a synthetic resin optical transmission body having a continuous refractive index distribution, there is no disturbance in the refractive index distribution of the surface layer, and the optical transmission characteristics do not change from manufacturing loft to manufacturing loft. This is a highly practical method that can produce stable optical transmission bodies and is suitable for mass production.

[Brief explanation of drawings]

Figures 1(a), 2, and 3 show the measurement results of the refractive index distribution state using the loft interfaco obtained in Examples 1 and 2.3, and the first opening) shows the results of measuring the refractive index distribution state using the loft interfaco obtained in Comparative Example 1. FIG.

Claims (1)

[Claims] 1. A cross-linked polymer (A) having a required network density,
After diffusing and impregnating the polymerizable monomer (B) that forms a polymer having a refractive index different from that of the polymer (A) to give a continuous concentration distribution from the center to the surface, unreacted monomers are In a method for manufacturing a synthetic resin optical transmission body having a continuous refractive index distribution from the center to the surface by polymerizing the bodies, the step of diffusing and impregnating the polymerizable monomer (B) is divided into two or more stages. , and a method for producing a synthetic resin optical transmission body, characterized in that the monomers to be diffused and impregnated have different diffusion rates in each step, and the diffusion impregnation is carried out in order from the one with the highest diffusion rate. 2. The cross-linked polymer (A) having the required network density has a monomer having one polymerizable functional group in the molecule and 2 in the molecule.
2. The method for producing a synthetic resin optical transmitter according to claim 1, which is obtained by polymerizing a mixture with a monomer having at least one polymerizable functional group. 3. The polymerizable monomer (B) to be diffused and impregnated has the general formula R_
1; represents H or CH_3; R_2; represents H or an alkyl group having 1 to 12 carbon atoms; In the first impregnation step, a monomer in which R_2 in formula (1) is H or an alkyl group having 1 to 4 carbon atoms is used, and in the second impregnation step, R_
3. The method for producing a synthetic resin optical transmitter according to claim 1 or 2, using a monomer in which 2 is an alkyl group having 4 to 12 carbon atoms.