JPH0466907A - Plastic optical fiber - Google Patents

Abstract

PURPOSE:To improve bending and repetitive flexibility by constituting a protective material of all the plastic optical fiber having a fiber-sheath-protective layer structure of a polymer specified in breaking elongation. CONSTITUTION:The generation of flaws in the fiber material layer even in the case of the occurrence of the exertion of an external force to the plastic optical fiber and the adhesion of fats and oils, etc., is more effectively prevented by coating the outer layer of the sheath with a protective layer having the specific breaking strength rather than by improving the resistance of the polymer forming the sheath material layer, by which the optical fiber having the excellent repetitive bending characteristic of the optical fiber is obtd. The protective layer forming material to be provided on the outer side of the sheath of the optical fiber is required to have the sufficient resilience and elongation sufficient for preventing the generation of the flaws to the sheath material layer by the external force exerted to the optical fiber and is required to have >=30% breaking elongation.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application 1] The present invention relates to an all-plastic optical fiber that is excellent in bending and repeated bending properties.

[Prior Art and Problems to be Solved] Demand for plastic optical fibers has recently been increasing for various uses because of their ease of end face processing and good bending resistance and vibration resistance.

All-plastic optical fiber is made of polymethyl methacrylate (hereinafter referred to as PM), which has a high refractive index and good light transmittance.
A core layer is formed of a polymer such as MA) or polycarbonate (hereinafter referred to as PC), and a transparent polymer such as a fluorine-containing polymer with a refractive index lower than that of the core forming polymer is used as a sheath material layer. Its basic structural unit is a core-sheath structure provided on the outer periphery of the core material layer.

Due to its characteristics, all-plastic optical fiber is suitable as a fiber for short-distance communication or as a fiber for sensors, and because of its good workability, it is especially suitable as an optical communication medium in moving bodies, such as optical communication in automobiles. suitable for use as. In addition, because all-plastic optical fibers have good repeated bending characteristics, they are often subjected to repeated bending operations, such as in sensors for robot arms, and their demand for use in vibrating parts is rapidly increasing. However, among conventionally developed all-plastic optical fibers, those that use fluorinated methacrylate polymers as the sheath material have low elongation, so if they are repeatedly used at bent parts, this operation will cause slight cracking in the sheath material layer. The problem is that the optical fiber becomes long and eventually breaks. Vinylidene fluoride polymers also have elongation,
Optical fibers using this as a sheath material are excellent at repeated bending, but when exposed to high temperature environments, the crystallization of polyvinylidene fluoride itself is promoted, causing cloudiness in the sheath material and extremely high transmission loss in the optical fiber. There was a problem.

[Means for Solving the Problems] The present inventors have completed the present invention as a result of studies aimed at solving the above problems, and the gist thereof is to provide a core-sheath protective layer. The basic structure is a plastic optical fiber with a breaking elongation of 30 as a protective material.
% or more of the plastic optical fiber.

That is, the present inventors did not study the weakness of conventionally developed optical fibers against repeated bending, but
It was discovered that the fundamental problems were the occurrence of scratches on the surface of the layered optical fiber due to external force and the occurrence of solvent cracks in the sheath layer due to oil adhesion on the surface of the sheath layer. Therefore, the present inventors discovered that in order to prevent damage to the core material layer even when an external force is applied to the plastic optical fiber or when oil or fat adheres to the plastic optical fiber, the polymer forming the sheath material layer should be We have found that it is more effective to coat the outer layer of the sheath with a protective layer that has a specific elongation at break than to improve its resistance, and that it is possible to obtain an optical fiber that is excellent in repeated bending. be.

The protective layer forming material provided on the outside of the optical fiber sheath is required to have sufficient flexibility and elongation to prevent damage to the sheath material layer due to external force applied to the optical fiber. % or more. A plastic material having a breaking elongation of less than 30% cannot provide the above-mentioned effect to the optical fiber, and even if the thickness of this protective layer is increased, the effect obtained is extremely small.

As the core material of the plastic optical fiber used in carrying out the present invention, a non-grade transparent polymer is suitable, such as a homopolymer or copolymer of methyl methacrylate (70% by weight or more in the copolymer). is preferably composed of methyl methacrylate units, and 30% by weight or less is composed of monomer units copolymerizable with methyl methacrylate.) Examples of the monomer copolymerizable with methyl methacrylate include methyl acrylate, Examples include vinyl heptamers such as ethyl acrylate. In addition, copolymers of methacrylic acid esters such as cyclohexyl methacrylate, t-butyl methacrylate, isobornyl methacrylate, adamantyl methacrylate, benzyl methacrylate, phenyl methacrylate, and naphthyl methacrylate and monomers copolymerizable with these esters , polycarbonate, polystyrene, styrene-methacrylic acid ester copolymers, deuterated polymers in which all or some of the hydrogen atoms of these polymers are substituted with deuterium atoms, and ring structural units represented by the general formula 2 Examples include polymers consisting of 98% by weight or more of monomer units containing methyl methacrylate as a main component.

As the polymer for forming the sheath material of the plastic optical fiber used in carrying out the present invention, a substantially transparent polymer having a refractive index that is 0.01 or more lower than the refractive index of the polymer for forming the core component may be used. Usually, the difference in refractive index with the polymer for forming the core component is 0. It is preferable to select from those in the range of O1 to 0.15. As the polymer constituting the sheath material layer, conventionally known polymers can be used. For example, when a broom is made of a homopolymer or copolymer of methyl methacrylate as the core material, the polymer described in Japanese Patent Publication No. 43 -8978
No., Special Publication No. 56-8321, Special Publication No. 56-8322, Special Publication No. 56-8323, and Japanese Patent Publication No. 1983-60243
It is preferable to use a fluorinated alkyl methacrylate polymer as disclosed in No. Furthermore, when polycarbonate or polystyrene is used as the core material, for example, polymethyl methacrylate can be used as the polymer for forming the sheath material. Other shaft-forming polymers include Japanese Patent Publication No. 43-8978 or Japanese Patent Publication No. 53-42.
Vinylidene fluoride polymers, vinylidene fluoride-hexafluoropropylene copolymers, and vinylidene fluoride-tetrafluoroethylene copolymers as described in No. 260.
Hexafluoropropylene copolymer, fluorinated alkyl-
In addition to α-fluoroacrylate polymers, JP-A-63-
Perfluoropolymers having a ring structure as exemplified in JP 261204 or USP 4754009 can also be used.

The polymer for forming the protective material used in making the plastic optical fiber of the present invention must have an elongation at break of 30% or more. For example, vinyl chloride resin, polyvinylidene chloride resin, vinyl butyral resin,
Vinyl alcohol resin, acrylic ester resin, polyethylene, polyolefin resin represented by polypropylene, polysulfone, polycarbonate, nylon, polyacetal, polyethylene terephthalate, polychlorotrifluoroethylene, polyvinylidene fluoride,
Examples include fluororesins such as tetrafluoroethylene, but these may be either homopolymers or copolymers. Even if a polymer with a breaking elongation of 30% or less is formed as a protective layer on the outside of the sheath material layer of an optical fiber, the sheath material layer of this type of optical fiber may be damaged due to repeated bending, or may be damaged by oils and fats. As a result, the sheath material layer is subjected to solvent cracking, causing scratches, resulting in destruction of the core material layer. On the other hand, the optical fiber of the present invention, in which the protective layer is formed of a polymer with a breaking elongation of 30% or more, does not have such disadvantages, has high reliability, and has good handling properties. ing.

The present invention will be specifically explained below using Examples.

Example 1 Polymethyl methacrylate silica with a polymerization rate of 45-t% obtained by continuous bulk polymerization as a core material forming polymer was devolatilized and melted using a vented devolatilizing extruder with a barrel temperature of 230°C, and the resin temperature was 234°C was fed to a 215°C three-layer composite spinning head.

Trifluorinated ethyl methacrylate/methyl methacrylate/methacrylic acid = 80/19/1 (trifluorinated ethyl methacrylate/methyl methacrylate/methacrylic acid = 80/19/1 (
wt%) of the copolymer was melted using an extruder with a barrel temperature of 210°C and fed to a 3-layer composite spinning head at 215′C with a resin temperature of 222°C.

Ethylene-ethyl acrylate copolymer (product name EEA manufactured by Nippon Unicar Co., Ltd.) (700% elongation at break) as a polymer for forming the protective material was melted using an extruder with a barrel temperature of 210°C, and the resin temperature was 208°C. The mixture was fed to a three-layer composite spinning head at 215°C.

The core, sheath, and protection materials were each metered using a metering gear pump set at 215°C, fed to a three-layer composite spinning nozzle, and discharged as a concentric three-layer optical fiber.

The obtained optical fiber had an outer diameter of 1000 m, a sheath thickness of 5-1 and a protection thickness of 5-1, and the optical transmission loss when transmitting 650 nm light was extremely good at 128 dB/Km. In addition, in a bending test in which this optical fiber was sandwiched between bars of 10 mm diameter and repeatedly bent at 180 degrees under a load of 500 g, the fiber could be bent repeatedly up to 20,000 times without breaking.

Examples 2 to 4, Comparative Examples 1 to 3 Optical fibers were made in the same manner as in Example 1 except that the sheath material and protective material were changed as shown in Table 1, and the optical transmission loss and repeated bending were evaluated. The number of times was measured. The results obtained are shown in Table 1.

P in the table? IMA: Polymethyl methacrylate 3FM
:) Lifluoroethyl methacrylate 17FM: 3.3,4,4,5,5,6,6.
7.7,8,8,9,9.1010,10 Pentadecafromdecyl methacrylate MMA: Methyl methacrylate MAA: Methacrylic acid Example 5 Bisphenol A type polycarbonate with a viscosity average molecular weight of 20,000 was used as the core material, and the barrel temperature 260°C
The resin temperature is 2.
It was fed at 46°C to a 250°C three-layer composite spinning head.

Perfluoro(2,2-dimethyl-1,3 dioxole) and tetrafluoroethylene 50150mo as sheath material
It was melted using an extruder with a barrel temperature of 230°C using 1% copolymerization and fed to a 3-layer composite spinning head at 250°C with a resin temperature of 235''C.

Ethylene-ethyl acrylate copolymer (
EEA: Breaking elongation 700%) at barrel temperature 210”
Melt using an extruder C, and melt at a resin temperature of 208°C.
A three-layer composite spinning head was fed at 50°C.

The core, sheath, and protection materials were each metered using a metering gear pump set at 250°C, fed to a three-layer composite spinning nozzle, and discharged as a concentric three-layer optical fiber.

The obtained optical fiber had an outer diameter of 11000a and a sheath thickness of 5-1
The protection thickness was 10 ttm, and the transmission loss at 770 nn+ was extremely excellent at 720 dB/-.

The number of repeated bending is 100. The results were extremely good with no breakage up to '000 cycles.

Patent applicant: Mitsubishi Rayon Co., Ltd.

Claims (1)

[Claims] 1. A plastic optical fiber which is an all-plastic optical fiber having a core-sheath-protective layer structure, characterized in that the protective material is made of a polymer having a breaking elongation of 30% or more.