JPH01158402A - Plastic clad optical fiber and clad material - Google Patents

Abstract

PURPOSE:To obtain a plastic clad optical fiber which has a high serviceable temp. and sufficient strength by consisting said fiber of a specific compsn. for curing. CONSTITUTION:This optical fiber is constituted of the compsn. for curing which consists essentially of a copolymer obtd. by copolymerizing a fluoroalkyl acrylate or methacrylate monomer and one of an epoxy group-contg. vinyl compd. and epoxy reactive vinyl compd. and the other of the epoxy group-contg. vinyl compd. and the epoxy reactive vinyl compd. Namely, the fiber is eventually formed of the cured matter obtd. by curing the clad material and the clad having the refractive index lower than the refractive index of the core is obtd. The plastic clad optical fiber having the high serviceable temp. and the sufficient strength is thereby obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a cladding material for a plastic-clad optical fiber and a plastic-clad optical fiber having a cladding formed from the cladding material.

[Prior Art] Optical fibers can be roughly divided into the following three types of optical fibers: (1) Glass optical fiber (AGF), in which both the core and cladding are made of glass, (2) Plus deck, in which both the core and cladding are made of plastic. (3) Plastic clad optical fiber (PCF) whose core is glass and cladding is plastic.

AGF is used for long-distance communications because of its low transmission loss, but since it is made entirely of glass, it is particularly vulnerable to bending, and a large diameter core cannot be obtained. For this reason, strength is maintained by providing several coating layers as protective layers on the outside of the cladding layer. In addition, since APF is made entirely of plastic deck, it is strong against bending, and large diameter cores can be manufactured, but transmission loss is high and the usable temperature range is limited to the softening temperature of plastic. has been done. For example, A with methyl methacrylate (M M A ) polymer as the core
In PF, the usable temperature range is limited to about 80°C, which is the heat distortion temperature of the MMA polymer. In order to improve this, copolymerization with monomers such as maleic anhydride that increases the heat distortion temperature is being considered.
It has the disadvantage that the temperature at which it can be used is not sufficient.

On the other hand, PCF has the low transmission loss of a glass core and can be used at high temperatures, and the high flexibility of a plus deck cladding, so it can be expected to be an optical fiber with a large diameter and excellent long-distance transmission performance. . For example, silicone resins and fluoroalkyl acrylates are currently used as cladding materials. However, the refractive index difference between the cladding made of silicone resin and the core is not sufficient, and the strength of the cladding is low, so when processing connectors using the crimping method, transmission loss increases due to crimping. However, there are problems such as a small pulling force, and it has the disadvantage that it is not possible to actually process a connector.

Furthermore, although a cladding made of fluoroalkyl acrylate is a material with a low refractive index and high strength, it has a drawback in that the pull-out force of the canome type connector is significantly reduced at high temperatures due to its low heat deformation temperature.

[Object of the Invention] An object of the present invention is to provide a plastic clad optical fiber that can be used at a high temperature and has sufficient strength.

[Structure of the Invention] The object of the present invention is to provide (a) a copolymer obtained by copolymerizing a fluoro[J alkyl acrylate or methacrylate monomer and one of an epoxy group-containing vinyl compound and an epoxy-reactive vinyl compound; (b) A cladding material for a plastic clad optical fiber characterized by comprising a curing composition containing the other of an epoxy group-containing vinyl compound and an epoxy-reactive vinyl compound as a main component, or (a) a fluoroalkyl acrylate or methacrylate monomer. , a vinyl group-containing fluoroalkyl acrylate polymer obtained by separately reacting an epoxy group-containing vinyl compound and an epoxy-reactive vinyl compound, and (b) a curing composition containing the fluoroalkyl vinyl compound as a main component. This is achieved by a cladding material for a plastic clad optical fiber, which is characterized in that it consists of a plastic cladding material.

According to the present invention, it is possible to obtain a plastic clad optical fiber which is formed from a cured product obtained by curing the above cladding material and has a cladding having a lower refractive index than the core.

In the copolymerization of a fluoroalkyl acrylate or methacrylate monomer and an epoxy group-containing vinyl compound or an epoxy-reactive vinyl compound, other copolymerizable monomers, such as styrene, maleic acid, maleic anhydride, etc., may be present in the copolymerization. good. The amount of other copolymerizable monomers used is preferably 10 mol% or less of the monomer mixture.

In the vinyl group-containing fluoroalkyl acrylate polymer, either the fluoroalkyl acrylate or methacrylate monomer and either the epoxy group-containing vinyl compound or the epoxy-reactive vinyl compound are copolymerized.

Examples of the fluoroalkyl acrylate monomer include I I-1, l I-(-1-lifluoroethyl acrylate, l H, 11-1, 3H-tetrafluoropropyl acrylate, 21-1-hexafluoroisopropyl acrylate, l H, l H, 51-I-octafluoropentyl acrylate, nonafluoro-t
-Butyl acrylate, III, IH, 2H, 2H-heptadecafluorodecyl acrylate, and other alcohol acrylic esters in which a linear or branched aliphatic alkyl group is fluorinated.

Examples of the fluoroalkyl methacrylate monomer include I H,I l-1-trifluoroethyl methacrylate, l H, l I-1, 3l-1-tetrafluoropropyl methacrylate, 211-hexafluoroisopropyl methacrylate, I H,I tl, 5
11-octafluoropentyl methacrylate, nonafluoro-t-butyl methacrylate, I H, I I-
(.

Examples include methacrylic esters of alcohols in which linear or branched aliphatic alkyl groups are fluorinated, such as 2 H, 21-1-hebutadecafluorodecyl methacrylate. These acrylate monomers and methacrylate monomers may be used alone or in combination of two or more.

Examples of the epoxy group-containing vinyl compound include glycidyl acrylate and glycidyl methacrylate. The epoxy group-containing vinyl compounds may be used alone or in combination of two or more.

Epoxy-reactive vinyl compounds have at least two functional groups that can react with epoxy groups. Examples of functional groups that can react with epoxy groups include carboxylic acid groups (-COOH) and amino groups (-NHx). As a compound having a carboxylic acid group, for example, acrylic acid, methacrylic acid, dicarboxylic acid HOOC(CHt)ncOOH (here, n
= 1 to 8), compounds having a carboxylic anhydride group, such as maleic anhydride, compounds having an amino group, such as 2-aminoethyl acrylate, 2-aminoethyl methacrylate, 1(zN(CHt)nNH*) (Here, n=1 to 8) etc. Epoxy-reactive vinyl compounds may be used alone or in a mixture of 62 or more types.

To produce the cladding material of the present invention, first a fluoroalkyl acrylate or methacrylate monomer, an epoxy group-containing vinyl compound or an epoxy-reactive vinyl compound, and other copolymerizable compounds which may or may not be present are used. A monomer mixture consisting of monomers is preferably copolymerized at 80°C to 140°C using a radical initiator. As the polymerization method, any of bulk polymerization, solution polymerization, emulsion polymerization, and suspension polymerization may be used.
Bulk polymerization with less contamination of impurities is preferred.

The radical initiator is preferably a compound that generates radicals at 80 to 140°C, but is not particularly limited, and examples include di-t-butyl peroxide, t-butyl hydroperoxide, and dicumyl peroxide. , cumene hydroperoxide, azobisisobutyronitrile, and the like. The amount of polymerization initiator is 10% of the monomer mixture.
The amount is preferably 1 part by weight or less relative to 0 parts by weight, and more preferably 0.5 parts by weight or less in order to reduce the influence of decomposition residues on transmission loss. Further, after copolymerization, it is preferable to remove residual monomer components under reduced pressure.

When copolymerizing a monomer mixture containing an epoxy group-containing vinyl compound, the amount of the epoxy group-containing vinyl compound is preferably 1 to 20 mol% of the monomer mixture. If the amount of the epoxy group-containing vinyl compound is too small, a sufficient crosslinked network will not be formed, and if the temperature increases, the cladding will have low strength and will even flow.

On the other hand, if the amount of the epoxy group-containing vinyl compound is greater than this, the cladding not only becomes extremely brittle but also has a high refractive index, making it unusable.

On the other hand, when copolymerizing a monomer mixture containing an epoxy-reactive vinyl compound, the epoxy-reactive vinyl compound preferably accounts for 10 mol% of the monomer mixture.

Two types of curing compositions (hereinafter referred to as "first curing composition" and "second curing composition") prepared from the copolymer thus obtained are used as cladding materials. The cladding of the plastic clad optical fiber is formed by applying the cladding material onto the core by casting or dipping and then curing it. Preferably, the core consists of quartz glass or multicomponent glass.

The cladding material made of the first curing composition comprises (1) a copolymer obtained by copolymerizing a fluoroalkyl acrylate monomer and an epoxy group-containing vinyl compound, and an epoxy-reactive vinyl compound, or (2) Fluoroalkyl acrylate is obtained by copolymerizing a methacrylate monomer and an epoxy-reactive vinyl compound (obtained by mixing a polymer and an epoxy group-containing vinyl compound, optionally using a solvent. Examples include ketone solvents such as acetone, methyl ethyl ketone, and medyl isobutyl ketone, aliphatic ether solvents such as diethyl ether and ethyl methyl ether, and aliphatic halogen solvents such as chloroform, dichloro[!ethane, and chlorofluorocarbons]. It is a solvent.

In mixing, the epoxy-reactive functional groups are mixed in equal amounts with the epoxy groups. An inorganic acid such as phosphoric acid may be added as a catalyst. When there are few epoxy-reactive functional groups, sufficient bulk curing cannot be expected. Also, the use of a large excess of epoxy-reactive functional groups should be avoided as this will make the material brittle.

The cladding material made of the first curing composition is usually cured by heating.
Preferably, the reaction is carried out at °C.

Furthermore, a compound that reacts with an epoxy group or an epoxy-reactive group (for example, a carboxyl group) may be used as a component other than the above to contribute to ripe hardening without casting. Examples of compounds that react with epoxy groups include intermolecular anhydrides such as acetic anhydride (for example, (Cl[2')nc
o) 20 (where n is 1 to 5)), intramolecular anhydrides such as maleic anhydride, and aliphatic diamines. Examples of compounds that react with carboxyl molecules include:
These include aliphatic diamines.

The cladding material consisting of the 21i1'-forming composition is obtained by mixing a vinyl group-containing fluoroalkyl acrylate polymer and a fluoroalkyl vinyl compound, using a solvent such as methyl ethyl ketone if necessary.

Vinyl group-containing fluoroalkyl acrylate polymers can be produced by reacting a copolymer obtained by copolymerizing a fluoroalkyl acrylate or methacrylate monomer with an epoxy group-containing vinyl compound, or by reacting a copolymer obtained by copolymerizing a fluoroalkyl acrylate or methacrylate monomer with an epoxy-reactive vinyl compound. It is a polymer obtained by reacting a copolymer obtained by copolymerizing an acrylate or methacrylate monomer and an epoxy-reactive vinyl compound with an epoxy group-containing vinyl compound.

The amount of the epoxy-reactive vinyl compound to be reacted after copolymerization is such that the epoxy-reactive method yields 1 to 5 moles per mole of epoxy groups in the copolymer. - On the other hand, the amount of the epoxy group-containing vinyl compound to be reacted after copolymerization is
Preferably, the amount of epoxy groups is 1 to 10 times the mole of epoxy reactive groups in the copolymer. Considering optical properties, about 1 to 3 times the molar amount is more preferable.

Examples of the fluoroalkyl vinyl compound include the same compounds as the above-mentioned fluoroalkyl acrylate and methacrylate monomers.

The cladding material made of the second curing composition can be cured by light irradiation, radiation irradiation, or heating, but it is particularly preferable to carry out by light or electron beam irradiation. During curing of the cladding material, photoinitiators, e.g. benzophenone, acetophene, etc., generally have an effective initiation wavelength between 200 and 350 nm, and compounds which contain at least two vinyl groups, e.g. trimethylolpropane triacrylate, trimethylene Preference is given to adding a-propane trimethacrylate.

[Effect of the invention] The cladding layer formed from the cladding material of the invention is ff
In the plastic-clad optical fiber, the cladding is sufficiently crosslinked, so that thermal deformation of the cladding does not occur. In addition, the adhesion between the crat and the core has been improved, allowing the crimping method to be used in connector processing without any inconvenience. Furthermore, it has improved heat resistance.

According to the present invention, not only the fields where conventional PCP is used, but also the fields where AGF or APF are used! +!
It is possible to use PCF in F. For example, it can be conveniently used in optical communication, energy transport, short-distance LAN, etc., and is easy to connect.

[Example] Examples and comparative examples are shown below.

Example 1 IH, IH-octafluoropentyl methacrylate (
90 mol%) and glycidyl methacrylate (10 mol%
) was heated at 120°C for 20 hours using 1g of di-t-butyl peroxide O as a radical polymerization initiator.
Time copolymerized. After polymerization, drying was performed under reduced pressure at 120°C to remove unreacted monomers. methyl edyl ketone loo
Using mQ as a solvent, it was mixed with 3 g of adipic acid and 1 g of phosphoric acid having 1/2 times the mole of glycidyl groups of carboxylic acid groups.

This mixed solution was applied to a quartz core (outer diameter 2
PCF' strands (outer diameter 230 μm) were obtained by coating the PCF' wires (outer diameter 230 μm) and heating them at 300° C.

Depending on the connector, the pull-out force is 1kg when evaluating the caulking property.
The transmission loss increase was 0.5 dB/km.

The cured cladding material had a glass transition temperature of 50°C, but showed no flow or tack when heated to higher temperatures.

Comparative Example I 100 g of I H,l H-octafluoropentyl methacrylate was polymerized at 120° C. for 20 hours using 091 g of di-butyl peroxide as a radical polymerization initiator. After the reaction, drying was performed under reduced pressure at 120° C. for 1 hour to remove unreacted monomers.

Methyl edyl ketone 100j! Using Q as a solvent, this mixed solution was applied to a quartz core (outer diameter 200
A PCF wire (outer diameter: 230 μm) was obtained by coating the film on a substrate (outer diameter: 230 μm) and heating and drying at 300° C.

The glass transition temperature of the cured cladding material is 35°C, and at temperatures above this it exhibits not only fluidity but also tackiness.
It was not suitable as a cladding for optical fibers.

Patent applicant Sumitomo Electric Industries, Ltd.

Claims (1)

[Scope of Claims] 1. (a) A copolymer obtained by copolymerizing a fluoroalkyl acrylate or methacrylate monomer with either an epoxy group-containing vinyl compound or an epoxy-reactive vinyl compound, and (b) an epoxy group. A cladding material for a plastic clad optical fiber, comprising a curing composition containing the other of a containing vinyl compound and an epoxy-reactive vinyl compound as a main component. 2. The cladding material for a plastic clad optical fiber according to claim 1, wherein the group reactive with the epoxy group of the epoxy-reactive vinyl compound is a carboxylic acid group, a carboxylic anhydride group, or an amino group. 3, (a) a vinyl group-containing fluoroalkyl acrylate polymer obtained by separately reacting a fluoroalkyl acrylate or methacrylate monomer with an epoxy group-containing vinyl compound and an epoxy-reactive vinyl compound, and (b) a fluoro A cladding material for plastic clad optical fibers, characterized by comprising a curing composition containing an alkyl vinyl compound as a main component. 4. The cladding material for a plastic clad optical fiber according to claim 3, wherein the group reactive with the epoxy group of the epoxy-reactive vinyl compound is a carboxylic acid group, a carboxylic anhydride group, or an amino group. 5. In a plastic clad optical fiber in which the core is glass and the cladding is plastic, (a) fluoroalkyl acrylate is obtained by copolymerizing a methacrylate monomer and one of an epoxy group-containing vinyl compound and an epoxy-reactive vinyl compound. It is characterized by having a cladding made of a cured product obtained by curing a copolymer and (b) a curing composition containing the other of an epoxy group-containing vinyl compound and an epoxy-reactive vinyl compound as main components. plastic clad optical fiber. 6. A plastic clad optical fiber according to claim 5, wherein the core is made of quartz glass or multicomponent glass. 7. The plastic clad optical fiber according to claim 5, wherein the curing is performed by heating. 8. A plastic clad optical fiber in which the core is glass and the cladding is plastic, obtained by separately reacting (a) a fluoroalkyl acrylate or methacrylate monomer with an epoxy group-containing vinyl compound and an epoxy-reactive vinyl compound. It is characterized by having a cladding made of a cured product obtained by curing a vinyl group-containing fluoroalkyl acrylate polymer and (b) a curing composition containing a fluoroalkyl vinyl compound as a main component. plastic clad optical fiber. 9. A plastic clad optical fiber according to claim 8, wherein the core is made of quartz glass or multicomponent glass. 10. The plastic clad optical fiber according to claim 8, wherein the curing is carried out after the photoinitiator and the compound having at least two vinyl groups are mixed. 11. The plastic clad optical fiber according to claim 8, wherein the curing is performed by light or electron beam irradiation.