JPH0223843B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to optical fibers, optical fiber cores,
The present invention relates to a plastic optical fiber that can be used as an optical fiber cord or optical fiber cable. [Prior Art] Conventionally, inorganic glass optical fibers have been known as optical fibers for optical transmission, which have excellent optical transmission properties over a wide range of wavelengths, but they not only have poor workability and are susceptible to bending stress. Because of their high cost, plastic optical fibers based on synthetic resins have been developed. 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 to improve the mechanical properties and heat resistance of optical fibers by creating a structure with three or more layers using heat-resistant and high-strength engineering plastics such as polyamide and polyacetal. Even if materials are used, they do not have sufficient heat resistance and optical transmission loss deteriorates at high temperatures, making them unsuitable for use as optical communication means or optical sensor means installed in high-temperature areas such as the engine rooms of automobiles and ships. was significantly delayed. Furthermore, if an attempt is made to increase heat resistance using this type of material, other properties desired in the optical fiber may be impaired, resulting in problems such as increased loss due to repeated bending. . In addition, there is a manufacturing problem when forming the three layers (core, sheath, and protective layer) together by melt composite spinning, unless the fluidity of the material constituting each layer is optimized, thread spots may occur on the formed fiber. This has resulted in problems such as structural defects, adversely affecting optical transmission characteristics, and interfering with fiber connections. [Problems to be Solved by the Invention] The present invention mainly aims to solve the problems of heat resistance, deterioration of mechanical properties, and manufacturing problems associated with the conventional plastic optical fibers described above. By optimizing the selection and combination of fiber constituent materials, it is possible to provide a plastic optical fiber that is free from structural defects, has excellent heat resistance, has excellent resistance to repeated bending operations, and has low optical transmission loss. [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 a core material layer made of a polymer containing methyl methacrylate as a main component, The basic constituent units are a sheath material layer made of a polymer containing at least one of the repeating units represented by the formula [] and a protective layer made of polycarbonate, and each was measured under the conditions of a test temperature of 230°C and a test load of 5 kg. The melt flow rate [MFR] ₁ of the core material layer polymer, the melt flow rate [MFR] ₂ of the sheath material layer polymer, and the melt flow rate [MFR] ₃ of the protective layer polycarbonate are such that [MFR] ₁ ≦ [MFR] ] ₂ ≦ [MFR] ₃ ≦ 40 g/10 minutes. [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. . In the present invention, the melt flow rate [MFR] ₁ and [MFR] ₂ are, for example, in accordance with the Japanese Industrial Standards.
JIS K7210−1976, American Materials Testing Standard ASTM
D1238-82, a melt flow rate that can be measured in accordance with the international standard ISO 1133. For example, when complying with JIS K7210-1976, method A (manual cutting method) is used, the test temperature is 230 ° C, and the test load is It is measured at 5Kg. In addition, as other test conditions, the die length was 8.000±0.025mm;
The inner diameter is determined to be 2.095±0.005mm. The sample filling amount is 5 g, and in the case of method A, the sample collection time is about 30 seconds. Also, when measuring in accordance with ASTM D1238-82 and ISO1133, these test conditions and measurement conditions are adopted. Furthermore, the equipment and tools used for measurement, as well as the measurement procedure, can be determined within the range specified by each standard. As the base material for the cores 1 and 1', an amorphous transparent polymer is suitable, such as a homopolymer or copolymer of methyl methacrylate, of which 70 to 100% by weight of the starting monomer is methacrylate. methyl acid,
Preferably, 30 to 0% by weight is a monomer copolymerizable with methyl methacrylate. Examples of monomers that can be copolymerized with methyl methacrylate include vinyl monomers such as methyl acrylate and ethyl acrylate. Also usable are deuterated polymers in which all or some of the hydrogen atoms of these polymers containing methyl methacrylate as a main component are replaced with deuterium atoms. In the repeating unit of the general formula [] constituting the sheath material layer polymer used in the present invention, examples of the alkyl group having 1 to 5 carbon atoms represented by R include a methyl group, an ethyl group, an n-propyl group, iso-propyl group, n-butyl group, i-butyl group, sec-
There are butyl groups, tert-butyl groups, etc. Examples of _the fluorinated alkyl group having 1 to 5 carbon atoms represented by R include _-CH2F , _{-CH2CF3 , -CH2CF2CF3 ,}
−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, -
There are 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,
For example, it may be substituted with a halogen atom, 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,
As described below as a manufacturing method, other repeating units and functional groups may be introduced.
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. The polymer constituting the sheath material layer has the above general formula []
α-fluoroacrylic acid alkyl ester, which is the monomer that forms the basis of the repeating unit represented by
One or more monomers selected from fluorinated alkyl ester of α-fluoroacrylate and cycloalkylesteryl α-fluoroacrylate, and one or two other copolymerizable monomers as necessary. [The copolymerizable monomers include, for example, methacrylic acid, methacrylic acid alkyl esters such as methyl methacrylate, methacrylic acid fluorinated alkyl esters such as 2,2,3,3,3-pentafluoropropyl methacrylate, Examples include vinylidene fluoride. ] using
By polymerizing according to conventionally known polymerization methods,
Obtainable. [MFR] ₂ of the sheath material layer polymer needs to be as follows: [MFR] ₁ ≦ [MFR] ₂ ≦ [MFR] ₃ ≦ 40 g/10 minutes. If [MFR] ₂ is less than the value of [MFR] ₁ , the flow of the polymer in the nozzle is likely to be disturbed and optical transmission loss due to interface asymmetry between the core and sheath, that is, structural asymmetry increases, which is not preferable. [MFR] ₂ exceeding 40 g/10 minutes is not preferable because the coating of the sheath becomes large and the degree of polymerization of the sheath material becomes too low, resulting in poor bending characteristics of the optical fiber. A more preferable range of [MFR] ₂ is: [MFR] ₁ ≦[MFR] ₂ ≦30 g/10 minutes, and an even more preferable range is: 5 g/10 minutes≦[MFR] ₂ ≦20 g/10 minutes. As a suitable polycarbonate constituting the protective layer 3, the general formula

[Formula], where R ₁ is

【formula】

【formula】 Alicyclic polycarbonate represented by

【formula】

【formula】

【formula】

【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 650 nm, and the fiber incident light had a numerical aperture of 0.6. The unit is dB/
Km. (2) Repeated bendability The light intensity retention rate is 50% when the fiber is repeatedly bent 180° on a mandrel with a diameter 5 times the fiber diameter.
The number of bends was read. (3) Heat resistance Increase in optical transmission loss (dB/Km) after heating the fiber at 115℃ for 3000 hours. (4) Thread unevenness Thread unevenness was measured over a length of 500 m using a laser line diameter measuring device. Examples 2-4, Comparative Examples 1-3 Plastic optical fibers were obtained as in Example 1, except that the spinning temperature or the composition of the sheath components 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.

[Table] Examples 9 to 11, Comparative Examples 12 to 13 Optical fibers were obtained as in Example 1, except that the spinning temperatures were 230°C, 240°C, 210°C, and 250°C.
Similarly, thread spotting (loss) was evaluated and the results are shown in Table 2.

〔Effect of the invention〕

The plastic optical fiber produced according to 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 the engine compartment of automobiles and ships. It also has good resistance to repeated bending operations, has no structural defects, and has low optical transmission loss.

[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)

[Scope of Claims] 1. A core material layer made of a polymer containing methyl methacrylate as a main component, a sheath material layer made of a polymer containing at least one repeating unit represented by the following general formula [], and The melt flow rate [MFR] ₁ of the core material layer polymer and the melt flow rate of the sheath material layer polymer were measured under the conditions of a test temperature of 230°C and a test load of 5 kg using a protective layer made of polycarbonate as the basic structural unit. [MFR] ₂ and the melt flow rate [MFR] ₃ of the protective layer polycarbonate take values that satisfy the relationship [MFR] ₁ ≦ [MFR] ₂ ≦ [MFR] ₃ ≦ 40 g/10 min. optical fiber. [Note] 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. 2. The plastic optical fiber according to claim 1, wherein the protective layer has a thickness of 10 to 250 μm. 3. The plastic optical fiber according to claim 1 or 2, wherein the spinning temperature is 215 to 245°C.