JPH0223842B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a plastic optical fiber that can be used as an optical fiber core, an optical fiber cord, an optical fiber cable, or the like. [Prior Art] Inorganic glass optical fibers, which have excellent optical transmission properties over a wide range of wavelengths, have been known as optical fibers for optical transmission, but they have poor workability and are susceptible to bending stress. Plastic optical fibers based on synthetic resin have been developed because they are relatively expensive. Synthetic resin optical fibers have a core-sheath structure, with a core made of a polymer with a high refractive index and good light transmittance, and a sheath made of a transparent polymer with a lower refractive index. obtained by doing. The polymer useful as a core component with high light transparency is preferably an amorphous material, and polymethyl methacrylate or polystyrene is generally used. Among these, polymethyl methacrylate has excellent transparency, mechanical properties, weather resistance, etc., and is used industrially as a core material for high-performance plastic optical fibers. However, the glass transition temperature (Tg) of polymethyl methacrylate is 100°C, and the plastic light transmitting fiber with polymethyl methacrylate as its core cannot be used at all if the operating environment exceeds 100°C. Limitations in heat resistance limit the use of plastic optical fibers. For this reason, for example, in Japanese Patent Application Laid-Open No. 58-18608, for example, polycarbonate,
It has been proposed that the mechanical properties of the optical fiber improve the heat resistance by creating a structure with three or more layers using heat-resistant and high-strength engineering plastics such as polyamide and polyacetal. Even if new materials are used, the selection of material usage characteristics and the optimization of material combinations are insufficient, and heat resistance is not improved to the desired degree, resulting in deterioration of optical transmission loss at high temperatures. This has significantly delayed its use as an optical communication means or optical sensor means installed in high-temperature areas such as rooms. [Problems to be Solved by the Invention] The present invention solves the problems of heat resistance and optical transmission loss associated with the conventional plastic optical fibers mentioned above, and provides a plastic optical fiber with excellent heat resistance and low optical transmission loss. This is what we provide. [Means for Solving the Problems] That is, the plastic optical fiber of the present invention, which was discovered as a means for solving the above problems, has an intrinsic viscosity (in methylene chloride at 20°C) of 0.3 to 0.6 dl/g. It is characterized in that its basic structural units are a core material layer made of polycarbonate, a sheath material layer made of fluorine-containing polymer, and a protective layer made of polycarbonate with a heat distortion temperature of 125° C. or higher. [Embodiment] FIGS. 1 to 3 are cross-sectional views for explaining an example of the structure of the plastic optical fiber of the present invention. The example shown in FIG. 1 is an optical fiber core wire having a three-layer structure of a core material layer (core) 1, a sheath material layer (cladding) 2, and a protective layer 3. Hereinafter, the same elements as in Fig. 1 will be represented by the same symbols. The example in Fig. 2 is composed of a core 1, a cladding 2, a protective layer 3 made of an organic polymer, and a jacket material made of an organic polymer. This optical fiber cable has a four-layer structure including a coating layer 4. In the example shown in FIG. 3, a plurality of optical fiber cores 5 having a three-layer structure consisting of a core 1, a cladding 2, and a protective layer 3 made of an organic polymer are coated with a coating layer 4 of a jacket material made of an organic polymer. It is a multi-core optical fiber cord. The structure of the plastic optical fiber of the present invention is not limited to the examples shown in FIGS. 1 to 4, but it is sufficient that at least the basic structural unit is composed of the core and cladding used in the present invention. Furthermore, a fiber structure can be adopted, for example, a tension member made of steel or FRP or a metal coating is incorporated into the optical fiber, or a structure in which the coating is further layered by a desired number of layers is also possible. . A suitable polycarbonate for forming the core 1 has the general formula

[Formula], where R ₁ is

【formula】

【formula】 Alicyclic polycarbonate represented by

【formula】

【formula】

【formula】

【formula】

Examples include aromatic polycarbonates represented by the formula: Copolymers of these and dioxy compounds such as 4,4'-dioxydiphenyl ether, ethylene glycol, p-xysolene glycol, and 1,6-hexanediol can also be used. The intrinsic viscosity (in methylene chloride, 20°C) of the polycarbonate constituting the core 1 must be in the range of 0.3 to 0.6 dl/g. If the intrinsic viscosity is less than 0.3 dl/g, the polycarbonate will crystallize in the spinning machine, resulting in poor loss of the resulting optical fiber, which is not preferred. If the intrinsic viscosity exceeds 0.6 dl/g, it becomes very difficult to control yarn diameter unevenness, which is not preferable. Melt flow rate [MFR] of the core polycarbonate corresponding to the intrinsic viscosity in the above range ₁ (Japanese Industrial Standard JIS K7210-1976, method A (manual cutting method),
Test temperature 230℃, test load 5Kg, die length 8.000
±0.025mm, inner diameter 2.095±0.005mm, sample filling amount 5
Desirable values for molecular weight [MW] ₁ are in the following ranges: 3g/10min ≦[MFR] ₁ ≦30g/10min 1.3×10 ⁴ ≦[MW] ₁ ≦2.8×10 ^4To adjust the intrinsic viscosity to such [MFR] ₁ and [MW] ₁ , for example, According to conventionally known methods, the degree of polymerization is adjusted during the preparation of the polycarbonate constituting the core by polymerization. In the present invention, the intrinsic viscosity (in methylene chloride, 20°C) of the polycarbonate constituting the core 1 is more preferably 0.35 to 0.45 dl/g. As the base material of the cladding 12, a substantially transparent polymer having a refractive index lower by 0.01 or more than that of the base material of the core 11 is used, but in the present invention, a fluorine-containing polymer with a refractive index of 1.48 or less Select and use. Examples of such fluorine-containing polymers include:
Special Publication No. 1978-8978, Special Publication No. 56-8321, Special Publication No. 1973
-8322, Japanese Patent Publication No. 1983-8323, and Japanese Patent Publication No. 1983-
It is possible to use polymerized esters of methacrylic acid and fluorinated alcohols as disclosed in No. 60243 and the like. Further, when polycarbonate or polystyrene is used as the core, for example, polymethyl methacrylate can be used as the cladding. Further, other specific examples of the clad include vinylidene fluoride polymers as described in Japanese Patent Publication No. 43-8978 or Japanese Patent Publication No. 53-42260, and other vinylidene fluoride-hexafluoride polymers. Propylene copolymers, methacrylic acid ester polymers other than the polymethyl methacrylate, and methylpentene polymers can also be used as the cladding. Furthermore, polymerized or copolymerized esters of α-fluoroacrylic acid and fluorinated alkyl alcohol or alkyl alcohol can also be used. Examples of such homopolymers or copolymers of α-fluoroacrylic acid esters include polymers containing at least one repeating unit of the following general formula []. General formula []

[Formula] (In the formula, R is an alkyl group having 1 to 5 carbon atoms, 1 carbon number
-5 fluorinated alkyl group or a cycloalkyl group having 3 to 6 carbon atoms. ) In the repeating unit of the general formula [], the alkyl group having 1 to 5 carbon atoms represented by R is:
For example, methyl group, ethyl group, n-propyl group,
iso-propyl group, n-butyl group, i-butyl group,
Examples include sec-butyl group and tert-butyl group. Examples of the fluorinated alkyl group having 1 to 5 carbon atoms represented by R include _-CH2F , _{-CH2CF3 ,} -
CH ₂ CF ₂ CF ₃ , −CH ₂ CF ₂ CF ₂ H,

【formula】

[Formula] -C (CF ₃ ) ₃ , -CH ₂ CH ₂ CF ₂ CF ₂ CF ₃ , -
CH ₂ CF ₂ CF ₂ CF ₂ CF ₂ H, -CH ₂ CF ₂ CF ₂ CF ₂ CF ₃ , etc. Examples of the cycloalkyl group having 3 to 6 carbon atoms represented by R include a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, and a cyclohexyl group. One or more of the hydrogen atoms constituting these alkyl groups, fluorinated alkyl groups, and cycloalkyl groups are, for example, halogen atoms,
It may be substituted with a monovalent organic group or the like. In the repeating unit of general formula [], R is more preferably an alkyl group having 1 to 3 carbon atoms or a fluorinated alkyl group having 1 to 3 carbon atoms. Further, the structure of the sheath material layer polymer may be composed of only one or two or more types of repeating units of the above general formula [], or one or two types of repeating units of the above general formula []. In addition to the above,
Other repeating units or functional groups may be introduced, and in this case, it is desirable to contain 10 mol% or more of one or more repeating units of the general formula []. Furthermore, when two or more types of repeating units of the general formula [] with different R are used, these repeating units can be used in any ratio. For example, a repeating unit in which R is an alkyl group having 1 to 3 carbon atoms and a repeating unit in which R is a fluorinated alkyl group having 1 to 3 carbon atoms may be combined in any blending ratio. Suitable polycarbonates constituting the protective layer 3 include those shown in the description of the core 1 above.
General formula:

[Fiber characteristics evaluation method]

(1) Optical transmission loss Measured by the method disclosed in Japanese Patent Application Laid-open No. 7602/1983. The measurement light wavelength was 770 nm, and the numerical aperture of the fiber incident light was 0.6. The unit is dB/
Km. (2) Heat resistance Increase in optical transmission loss (dB/Km) after heating the fiber at 125℃ for 3000 hours. Measurement wavelength of 770nm. Examples 2-3, Comparative Examples 1-2 The same plastic optical fibers as in Example 1 were obtained, except that the core and protective layer components used were changed as shown in Table 1. The properties of these fibers were evaluated in the same manner as in Example 1, and the results are shown in Table 1.

〔Effect of the invention〕

The plastic optical fiber of the present invention can be used for a variety of purposes as a fiber for optical transmission, and has excellent heat resistance so that it can be used even under harsh conditions such as in the engine rooms of automobiles and ships. Moreover, it has a low optical transmission loss even though it has a polycarbonate core.

[Brief explanation of drawings]

1 to 3 are cross-sectional views for explaining an example of the structure of the plastic optical fiber of the present invention. More specifically, FIG. 1 is an example of the structure of the optical fiber, and FIG. Configuration Example of Optical Fiber Cable FIG. 3 is a cross-sectional view for explaining a configuration example of a multi-core optical fiber cord. 1... Core material layer (core), 2... Sheath material layer (cladding), 3... Protective layer, 4... Covering layer.

Claims (1)

[Claims] 1 Intrinsic viscosity (in methylene chloride, 20℃) is 0.3~
Core material layer made of 0.6dl/g polycarbonate,
A plastic optical fiber characterized in that its basic constituent units are a sheath material layer made of a fluorine-containing polymer and a protective layer made of polycarbonate having a heat deformation temperature of 125°C or higher.