TECHNICAL FIELD

The present invention relates to an optical fiber cable, a harness, and a method of manufacturing an optical fiber cable.

BACKGROUND ART

Optical fibers are used in a wide range of applications, such as communications, sensors, lighting, decorations, displays, and the like. Among optical fibers, a plastic optical fiber having a structure in which an outer periphery of a core made of a highly transparent resin such as polymethyl methacrylate is coated with a resin having a higher transparency and a lower refractive index than the core, has advantages such as lightening of the entire system and excellent workability and flexibility as compared with glass-based optical fibers.

In recent years, plastic optical fibers have been used in mobile communication applications in automobiles, railways, and airplanes, etc., and in OA and sensor applications in factories, because of the improved transmission distance and heat resistance with the improvement of manufacturing technology. In the above applications, it is desired that even if the optical fiber under 105° C. environment is used for a long time, there is no significant increase in the transmission loss of the optical fiber, i.e. an optical fiber having an excellent long-term heat resistance at 105° C. is required.

Usually, an optical fiber is not often used in an optical fiber alone, and in order to impart heat resistance, mechanical properties, flame retardancy, discrimination, etc., the optical fiber is used as an optical fiber cable in which the optical fiber is coated with a thermoplastic resin or the like as a jacketing layer.

An optical fiber cable used in mobile communication applications in automobiles or railways, etc. is provided with a jacketing layer inside the jacketing layer (hereinafter, referred to as an “inner jacketing layer”) for imparting heat resistance, and a jacketing layer on an outer side of the jacketing layer (hereinafter, referred to as an “outer jacketing layer”) for imparting mechanical properties, flame retardancy, discrimination, further heat resistance, and the like.

Furthermore, when an optical fiber cable is disposed in a moving body such as automobiles or railways, it is often laid in the form of a harness bundling two or more kinds of optical fiber cables, or the form of a harness bundling the optical fiber cable and a wire or wire cable.

However, when an optical fiber cable is exposed to a high temperature environment in a state in which the optical fiber cable is bundled with another cable containing vinyl chloride-based resin in the jacketing layer, or in a state in which the optical fiber cable and another cable are bundled with a tape containing vinyl chloride-based resin, there has been problems that the plasticizer in the vinyl chloride-based resin is transferred to the jacketing layer of the optical fiber cable to form cracks in the jacketing layer, and that the plasticizer is transferred to the optical fiber to impair the optical characteristics. That is, there has been a demand for an optical fiber cable having excellent resistance to a plasticizer in a vinyl chloride-based resin. There are many types of plasticizers in vinyl chloride resins, including phthalic acid-based plasticizers, adipic acid-based plasticizers, phosphoric acid-based plasticizers, trimellitic acid-based plasticizers, epoxy-based plasticizers, and aliphatic dibasic acid-based plasticizers. The main examples include di-2-ethylhexylphthalate (DOP), bis(2-ethylhexyl) phthalate (DEHP), and diisononyl phthalate (DINP) as a phthalic acid-based plasticizer, and tris(2-ethylhexyl) trimellitate as a trimellitic acid-based plasticizer.

Further, an optical fiber cable used in a moving body such as automobiles or railways, when connected to the light source of a transmitter or the light receiving element of the receiver, the outer jacketing layer is peeled by the required length, and a plug or ferrule for connection is attached to the surface of the inner jacketing layer by a method such as a laser fusion method or “caulking” method.

As a method of imparting long-term heat resistance under a high temperature environment of 100 to 105° C. to an optical fiber, for example, in Patent Literature 1, a method of manufacturing an optical fiber cable in which a plastic optical fiber is coated using a jacketing material containing an ethylene-vinyl alcohol copolymer at a specific temperature condition has been proposed.

In Patent Literature 2, as a method of imparting long-term heat resistance under a high temperature environment of more than 110° C., an optical fiber cable in which a plastic optical fiber is coated with an oxygen shielding layer made of an ethylene-vinyl alcohol copolymer, and further an outer layer on its outer side is proposed.

Patent Literature 3 discloses an optical fiber cable in which a protective jacketing layer formed of an ethylene-vinyl alcohol copolymer resin and a light blocking jacketing layer formed of nylon 12 are coated on the outer periphery of an optical fiber.

CITATION LIST

Patent Literature

Patent Literature 1: JP2007-47371A

Patent Literature 2: JP2002-055246A

Patent Literature 3: WO2009/157444A1

SUMMARY OF INVENTION

Technical Problem

However, since the optical fiber cable proposed in Patent Literatures 1 to 3 has a jacketing layer formed of an ethylene-vinyl alcohol copolymer resin, although the long-term heat resistance at 105° C. is good, resistance to plasticizers of vinyl chloride-based resins has been insufficient.

Accordingly, a first object of the present invention is to provide an optical fiber cable excellent in resistance to plasticizers of vinyl chloride-based resins and long-term heat resistance at 105° C., and a harness containing the same.

Incidentally, plasticizers of vinyl chloride-based resins targeted by the present invention includes di-2-ethylhexyl phthalate (DOP), bis (2-ethylhexyl) phthalate (DEHP), diisononyl phthalate (DINP), adipic acid-based polyester, and tris (2-ethylhexyl) trimellitate (hereinafter, abbreviated as “plasticizer of vinyl chloride-based resin”)

Furthermore, the present inventors have found, as an embodiment of an optical fiber cable to solve the above problems in the present invention, an optical fiber cable in which a jacketing layer is formed such that a jacketing inner layer, a jacketing intermediate layer and a jacketing outer layer are formed in this order concentrically on the outer periphery of an optical fiber. However, it was found from the study of the present inventors that when simply by coating the jacketing inner layer, and then forming the jacketing intermediate layer for obtaining a peripheral portion of an optical fiber cable, the adhesion between the jacketing inner layer and the jacketing intermediate layer becomes insufficient, and accordingly when peeling the jacketing outer layer of the optical fiber cable in order to attach a plug or ferrule for connection, the jacketing intermediate layer is peeled off, and hence the connecting plug or the like cannot be attached.

Accordingly, a second object of the present invention is to provide a method of manufacturing an optical fiber cable in which a jacketing layer is formed such that a jacketing inner layer, a jacketing intermediate layer and a jacketing outer layer are formed in this order concentrically on the outer periphery of an optical fiber, and the adhesion between the jacketing inner layer and the jacketing intermediate layer is excellent.

Solution to Problem

As a result of repeated studies made by the present inventors to solve the above problems, this invention is completed.

That is, according to a first aspect of the present invention, there is provided an optical fiber cable comprising an optical fiber and a jacketing layer formed on the outer periphery of the optical fiber, wherein the jacketing layer comprises at least two or more layers of a jacketing inner layer and a jacketing outer layer formed in this order concentrically; a material constituting the jacketing inner layer is composed of a resin material having an oxygen permeability of 2.0 cc·20 μm/(m2·day·atm) or less; a material constituting the jacketing outer layer comprises at least one selected from a polyolefin-based resin, a polybutylene terephthalate-based resin, and a fluorine-based resin containing no chlorine atom in its structure; and the following general formula (i) and (ii) are satisfied when an outer diameter of the optical fiber is denoted by A (μm), an outer diameter of the optical fiber cable is denoted by B (μm), and a thickness of the jacketing outer layer is denoted by c (μm):
900≤A≤1100  (i)
0.40≤2×c/(B−A)≤0.70  (ii).

According to a second aspect of the present invention, there is provided a harness obtained by bundling the optical fiber cable (C1), and a cable (C2) including a jacketing layer composed of a material containing a vinyl chloride-based resin.

According to a third aspect of the present invention, there is provided a method of manufacturing an optical fiber cable comprising an optical fiber and a jacketing layer formed on the outer periphery of the optical fiber, the jacketing layer being obtained by forming a jacketing inner layer, a jacketing intermediate layer and a jacketing outer layer in this order concentrically, wherein a material constituting the jacketing inner layer is an ethylene-vinyl alcohol-based resin; a material constituting the jacketing intermediate layer comprises a polyamide-based resin (N); a material constituting the jacketing outer layer comprises at least one selected from a polyolefin-based resin, a polybutylene terephthalate-based resin, and a fluorine-based resin containing no chlorine atom in its structure; and, the method comprises coating the jacketing inner layer and the jacketing intermediate layer simultaneously on the outer periphery of the optical fiber by supplying the material constituting the jacketing inner layer and the material constituting the jacketing intermediate layer into a co-extrusion coating apparatus with a compression type two-layer collective coating cross head.

Advantageous Effect of Invention

According to an embodiment of the present invention, it is possible to provide an optical fiber cable having excellent resistance to a plasticizer of a vinyl chloride-based resin (hereinafter, referred to as “plasticizer resistance of optical fiber cable”) and long-term heat resistance at 105° C. (hereinafter, referred to as “105° C. long-term heat resistance”), and a harness containing the same.

According to another embodiment of the present invention, in an optical fiber cable in which a jacketing layer is formed such that a jacketing inner layer, a jacketing intermediate layer and a jacketing outer layer are formed in this order concentrically on the outer periphery of an optical fiber, it is possible to provide a method of stably manufacturing an optical fiber cable having excellent adhesion between the jacketing inner layer composed of a material containing a EVOH resin and a jacketing intermediate layer composed of a material containing a nylon-based resin (polyamide-based resin).

According to the manufacturing method of the present invention, it is possible to produce an optical fiber cable having excellent workability when attaching a plug or ferrule to an end portion of the optical fiber cable.

