JPH11183738A - Optical fiber and optical fiber cable - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an optical fiber which is less increased in transmission loss under high-temp. and high-humidity conditions and is excellent in mechanical characteristics by constituting a sheath layer of an ethylene unit and a chlorotrifluoroethylene unit. SOLUTION: The sheath layer of the optical fiber having a core layer and the sheath layer comprises a polymer contg. the ethylene unit and the chlorotrifluoroethylene unit. The optical fiber is exemplified by an optical fiber formed by laminating the sheath layer on the outer periphery of the single or plural core layers, an optical fiber formed by laminating the sheath layer on the outer periphery of the core layer of the refractive index changing continuously or stepwise from the center toward the outer periphery, etc., provided that the refractive index of the outer peripheral part of the core layer is made higher than the refractive index of the sheath layer. While the material constituting the core layer is not particularly limited, MMA polymers, such as polymethyl methacrylate, are preferably used. The material constituting the sheath layer consists of the copolymer contg. the ethylene unit and the chlorotrifluoroethylene unit as copolymn. components.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an optical fiber and an optical fiber cable.

[0002]

2. Description of the Related Art As sheath materials for plastic optical fibers, copolymers comprising tetrafluoroethylene units and vinylidene fluoride units (hereinafter referred to as "TFE / VdF copolymers") and fluoroalkyl methacrylate monomers Copolymers (hereinafter, referred to as "FM / MMA copolymer") composed of units and methyl methacrylate (hereinafter, referred to as "MMA") units are known.

[0003]

The sheath material is TFE / VdF
An optical fiber made of a copolymer is excellent in mechanical properties such as repetition bending resistance, but has a problem that under high-temperature and high-humidity conditions, transmission loss increases due to crystallization and phase separation of a sheath material. On the other hand, an optical fiber whose sheath material is made of an FM / MMA copolymer is excellent in wet heat resistance because the sheath material is amorphous, but mechanical properties because the elongation of the sheath material is insufficient. Was inferior. That is, an optical fiber and an optical fiber cable which have a small increase in transmission loss under high temperature and high humidity conditions and have excellent mechanical properties have not been provided.

[0004]

The gist of the present invention resides in an optical fiber having a core layer and a sheath layer, wherein the sheath layer is made of a polymer containing ethylene units and chlorotrifluoroethylene units. The gist of the present invention resides in an optical fiber cable further having a coating layer on the outer periphery of the optical fiber.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION An optical fiber according to the present invention comprises a single or a plurality of core layers and a sheath layer laminated on the outer periphery, and has a refractive index continuously or stepwise from the center to the outer periphery. Examples include a layer obtained by laminating a sheath layer on the outer periphery of a changing core layer. However, the refractive index of the outer peripheral portion of the core layer is higher than the refractive index of the sheath layer. Hereinafter, for convenience of explanation, an optical fiber in which a sheath layer is laminated on the outer periphery of a single core layer will be described, but the present invention is not limited thereto.

The material constituting the core layer (hereinafter referred to as "core material") is not particularly limited, but an MMA polymer is preferably used. Examples of the MMA polymer include polymethyl methacrylate and a copolymer containing MMA in an amount of 70% by weight or more. As components to be copolymerized with MMA, alkyl methacrylate monomers such as ethyl methacrylate and butyl methacrylate, 2,2,2-trifluoroethyl methacrylate,
Fluoroalkyl methacrylate monomers such as 2,2,3,3-tetrafluoropropyl methacrylate and 2,2,3,3,3-pentafluoropropyl methacrylate, and aromatic ring-containing methacrylate monomers such as phenyl methacrylate and benzyl methacrylate Monomer, other various methacrylate monomers, isopropyl maleimide,
Maleimide monomers such as cyclohexylmaleimide,
Styrene and its derivatives, other polymerizable vinyl monomers and the like are preferably used.

The material constituting the sheath layer (hereinafter referred to as "sheath material") is made of a copolymer containing ethylene units and chlorotrifluoroethylene units as copolymer components. Although the molar content ratio of the ethylene unit and the chlorotrifluoroethylene unit is not particularly limited, it is usually 1: 1. The molecular weight of this copolymer is usually about 100,000 to 150,000. A polymer obtained by copolymerizing one or more types of monomers other than ethylene and chlorotrifluoroethylene may be used as the sheath material. Examples of the monomer to be a copolymerization component include olefin monomers such as propylene, methylpentene, vinyl acetate and vinyl chloride, vinylidene fluoride,
And fluorinated olefin monomers such as tetrafluoroethylene. In order to obtain an optical fiber having excellent heat and moisture resistance and mechanical properties, the total content of ethylene units and chlorotrifluoroethylene units in the sheath is preferably 80% by weight or more. It is also possible to use a blend of such a copolymer and another (co) polymer as the sheath material.

[0008] The optical fiber of the present invention may be an optical fiber cable further provided with a protective layer on its outer periphery. The material constituting the protective layer is not particularly limited, but it is preferable to use a material having a refractive index lower than that of the sheath material by 0.001 or more in order to prevent an increase in transmission loss when the optical fiber is bent. FM / MMA as such material
Preferred examples include fluoroalkyl methacrylate polymers such as copolymers, TFE / VdF copolymers, and copolymers containing ethylene units and vinyl alcohol units. A copolymer containing an ethylene unit and a vinyl alcohol unit is particularly preferable in order to prevent an increase in transmission loss due to oxidation and increase heat resistance. The molar content ratio between ethylene and vinyl alcohol is preferably about 95/5 to 50/50. A copolymer obtained by copolymerizing other monomers such as vinyl acetate, vinyl chloride, propylene, and methylpentene in addition to ethylene and vinyl alcohol can be used as the protective layer. In this case, in order to obtain a sufficient antioxidant effect, the total content of ethylene units and vinyl alcohol units in the protective layer is preferably at least 80% by weight.

[0009] A coating layer made of polyethylene, polyvinyl chloride or the like can be further provided on the outer periphery of the optical fiber of the present invention. It is also possible to coat a reinforcing material such as Kevlar together.

[0010] The optical fiber of the present invention can be manufactured by a known method. For example, an optical fiber can be obtained by supplying a polymer used as a core material and a sheath material to a two-layer composite spinning nozzle and spinning. By using a three-layer composite spinning nozzle instead of the two-layer composite spinning nozzle, an optical fiber having a protective layer can be obtained. The optical fiber is preferably further stretched after spinning to impart strength. The formation of the coating layer can be performed by a known method.

[0011]

The present invention will be described in detail with reference to the following examples. Example 1 MMA was used as a monomer, di-t-butyl peroxide was used as a polymerization initiator, and n-octyl mercaptan was used as a chain transfer agent. PMMA obtained by volatilization and removal was used as a core material, and a copolymer composed of ethylene units and chlorotrifluoroethylene units and having a copolymer composition ratio (molar ratio) of 1: 1 was used as a sheath material.

The core material and the sheath material were supplied to a two-layer composite spinning nozzle, melt-spun at 230 ° C., and stretched to obtain an optical fiber having a diameter of 1 mm. The outer periphery of the optical fiber was coated with polyethylene to obtain an optical fiber cable having a diameter of 2.2 mm.

With respect to this optical fiber cable, repeated bending resistance, resistance to moist heat, bending loss, and heat resistance were measured. The results are shown in Table 1.

The repetitive bending resistance is such that, in a state where an optical fiber cable is sandwiched between two cylinders having a radius of curvature of 15 mm, 90 degrees are provided on each cylinder side with one end of the optical fiber cable (total 180 degrees). ) The number of bends when it is determined that the cable is substantially broken due to a sudden increase in transmission loss when repeatedly bent. A load of 500 g is applied to the other end of the optical fiber cable. The moist heat resistance is represented by the transmission loss that increases when the optical fiber cable is left for 1000 hours at a temperature of 75 ° C. and a relative humidity of 95%. Bending loss has a radius of 25.4
It is represented by an increased transmission loss when the optical fiber cable is wound 15 times around a rod-shaped object having a length of 15 mm. The heat resistance is represented by an increased transmission loss when the optical fiber cable is left at a temperature of 95 degrees for 1000 hours.

Example 2 MMA as a monomer and azobis (2,2) as a polymerization initiator
4,4-trimethylpentane), n- as a chain transfer agent
Using butyl mercaptan, the degree of polymerization is 50% at 135 degrees.
After polymerizing to a low boiling point compound, PMMA obtained by devolatilization and removal was used as a core material, and TF was used as a material for the protective layer.
An optical fiber cable was obtained in the same manner as in Example 1 except that the E / VdF copolymer was further used and spinning was performed at 220 ° C. using a three-layer composite spinning nozzle. The characteristics of this optical fiber cable were measured in the same manner as in Example 1, and the results are shown in Table 1.

Example 3 The monomers, polymerization initiator and chain transfer agent used in the production of the core material of Example 2 were dissolved in butyl acetate as a solvent and polymerized at 135 ° to a polymerization rate of 98%. Devolatilizes low-boiling compounds,
The PMMA obtained by the removal is used as a core material, and a copolymer composed of ethylene units and vinyl alcohol units and having a copolymer composition ratio (molar ratio) of 75/25 is used as a material for the protective layer. An optical fiber cable was obtained in the same manner as in Example 2 except that the temperature was changed to ° C. The characteristics of this optical fiber cable were measured in the same manner as in Example 1, and the results are shown in Table 1.

COMPARATIVE EXAMPLE 1 A copolymer comprising MMA units, 2,2,2-trifluoroethyl methacrylate units and 1,1,2,2-tetrahydroxyperfluorodecyl methacrylate units was used as a sheath material. In the same manner as in Example 1, an optical fiber cable was obtained. The characteristics of this optical fiber cable were measured in the same manner as in Example 1, and the results are shown in Table 1.

Comparative Example 2 An optical fiber cable was obtained in the same manner as in Example 1 except that a TFE / VdF copolymer was used as a sheath material. The characteristics of this optical fiber cable were measured in the same manner as in Example 1, and the results are shown in Table 1.

[0019]

[Table 1]

[0020]

The optical fiber and the optical fiber cable of the present invention have a small increase in transmission loss under high temperature and high humidity conditions and have excellent mechanical properties.

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Kikue Irie 20-1, Miyukicho, Otake City, Hiroshima Prefecture Inside Mitsubishi Rayon Co., Ltd. Central Research Laboratory

Claims (5)

[Claims] 1. An optical fiber having a core layer and a sheath layer, wherein the sheath layer is made of a polymer containing ethylene units and chlorotrifluoroethylene units. 2. A polymer constituting a sheath layer comprises ethylene units and chlorotrifluoroethylene units in a total amount of 80% by weight.
The optical fiber according to claim 1, which contains the above. 3. The optical fiber according to claim 1, wherein the core layer comprises a methyl methacrylate polymer. 4. An optical fiber according to claim 1, further comprising a protective layer on the outer periphery of the optical fiber, wherein the protective layer is made of a polymer containing ethylene units and vinyl alcohol units. 5. An optical fiber cable further comprising a coating layer on the outer periphery of the optical fiber according to claim 1.