JP2787771B2 - Core-sheath plastic optical fiber - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a plastic optical fiber, and more particularly to a plastic optical fiber having excellent processing characteristics. [Prior art] An optical fiber whose core is made of plastic is inferior in light transmission loss and heat resistance as compared with inorganic glass-based ones, but has a large diameter, a large numerical aperture, a light weight, and is extremely flexible. Are better. Among them, optical fibers using a polymethyl methacrylate-based resin as a core component have begun to be used for short-distance optical communication applications. In an optical fiber having a core-sheath structure, it is important to select a sheath component that makes use of the characteristics of these core components. Japanese Patent Publication No. 53-21660 describes an optical fiber whose sheath is made of a copolymer of vinylidene fluoride and tetrafluoroethylene. The vinylidene fluoride copolymer has good adhesion to the core material and is essentially a crystalline polymer,
It is easily crystallized by heating or cooling to grow spherulites. As a result, the light passing through the core material is scattered by the crystallization state of its sheath, which has a disadvantage that the light transmission performance is reduced. On the other hand, for example, a polymer mainly containing an alkyl fluoride methacrylate as shown in JP-B-56-8321 is essentially an amorphous polymer, and has a good property when used as a sheath material of an optical fiber. While maintaining transparency, there is a drawback that adhesion and flexibility with the core material are poor, and workability is also poor. [Problems to be Solved by the Invention] The plastic optical fiber that has been conventionally developed has no problem when used in a substantially linear shape, but it is bent like a data link or an optical fiber for connecting OA equipment. When used in applications that require considerable bending during joining, there is a disadvantage that the optical transmission characteristics are rapidly reduced and the recoverability is poor. [Means for Solving the Problems] Accordingly, the present inventors have studied the purpose of developing a plastic optical fiber which does not have the above-mentioned difficulties, and as a result, have completed the present invention. The core is a polymethyl methacrylate-based resin, the sheath is a core-sheath type plastic optical fiber composed of the following polymer, the average diameter of which is 1000 μm, parallel light having a wavelength of 650 nm is incident from one end thereof, The transmitted light amount of light when emitted from the other end is I ₀ , the wound transmitted light amount Ia when the transmitted light amount is measured in the same manner with the optical fiber wound 100 times around a 10 mm diameter mandrel, Unwrapping light recovery when measuring the amount of transmitted light in the same way
A core-sheath type plastic optical fiber characterized in that when Ib, I ₀ , Ia, and Ib satisfy the relations of the following formulas [I] and [II]. [Polymer for forming sheath] General formula (A) (Wherein n represents an integer of 5 to 11).
Weight%, general formula (b) (Wherein X represents a hydrogen atom or a fluorine atom, and m represents an integer of 1 to 4).
Consisting essentially of a copolymer of 0% to 38% by weight and other copolymerizable monomers and having a diameter of 5 kg at 230 ° C. under a load of 5 kg.
A copolymer having a melt flow index value of 30 or less indicating the amount of the polymer discharged from a nozzle having a length of 2 mm and a length of 8 mm in 10 minutes. The optical fiber sheath material polymer preferably used in the present invention has good transparency and heat resistance, which are characteristics of a fluoroalkyl methacrylate polymer which is a conventionally used sheath polymer. Good flexibility and processability lacking in the fluoromethacrylate polymer are provided. As the long-chain fluoroalkyl methacrylate used to make the sheath polymer, 1,1,2,2-tetrahydroperfluorooctyl methacrylate, 1,1,2,2-
Tetrahydroperfluorodecanyl methacrylate,
Examples thereof include 1,1,2,2-tetrahydroperfluorododecanyl methacrylate and 1,1,2,2-tetrahydroperfluorotetradecanyl methacrylate. These compounds may be used alone or as a mixture of two or more. 10 to 48% by weight of long-chain fluoroalkyl methacrylate
Preferably, it is used in the range of 10 to 29.95% by weight. If this amount is less than 10% by weight, a polymer having sufficient mechanical properties cannot be obtained. On the other hand, if it exceeds 48% by weight, the glass transition temperature of the polymer becomes low and sufficient heat resistance cannot be obtained. As the short-chain fluoroalkyl methacrylate, trifluoroethyl methacrylate, 2,2,3,3-tetrafluoropropyl methacrylate, 2,2,3,3,3-pentafluoropropyl methacrylate, 2,2,3,3,4 , 4,5,5-octafluoropentyl methacrylate and the like are preferred. These compounds may be used alone or as a mixture of two or more. 52 to 90% by weight of short-chain fluoroalkyl methacrylate
Used in the range. When this amount is lower than 52% by weight, the proportion of long-chain fluoroalkyl methacrylate in the polymer increases, the glass transition temperature decreases, and sufficient heat resistance cannot be obtained, or the proportion of the monomer of the third component decreases. Increase
The refractive index may increase. As other copolymerizable monomers, chain alkyl (meth) acrylates, methacrylates having a cyclic hydrocarbon group, and vinyl monomers capable of forming a hydrophilic homopolymer are used. Examples of the chain alkyl (meth) acrylate include methyl (meth) acrylate, ethyl (meth) acrylate,
N-propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate,
Secondary butyl (meth) acrylate and the like can be mentioned. Methyl methacrylate is preferred. Examples of the methacrylate having a cyclic hydrocarbon group include phenyl methacrylate,
Cyclohexyl methacrylate, adamantyl methacrylate, (iso) bornyl methacrylate, tricyclo [5.2.1.0 ^2.6 ] -dec-8-yl methacrylate and the like are used. Vinyl monomers capable of forming a hydrophilic homopolymer include (meth) acrylic acid, glycidyl methacrylate, methyl glycidyl methacrylate, acrylamide, 2-hydroxyethyl (meth) acrylate,
Hydroxypropyl (meth) acrylate and the like can be mentioned. Methacrylic acid is preferred. These copolymerizable monomers are used in the range of 0 to 38% by weight, preferably 0 to 20% by weight. If this amount exceeds 38% by weight, the refractive index of the polymer may increase. The sheath component polymer used in the present invention can be produced by a known method such as a suspension polymerization method or a bulk polymerization method. As the radical polymerization initiator used for the polymerization, for example, 2,2 '
-Azobis (isobutyronitrile), 1,1'-azobis (cyclohexanecarbonitrile), 2,2'-azobis (2,4-dimethylpareronitrile), azobisisobutanol diacetateazo-tertiary butane, etc. And organic peroxides such as ditertiary butyl peroxide, dicumyl peroxide, ditertiary butyl perphthalate, ditertiary butylperacetate, and ditertiary amylperoxide. The proportion of the polymerization initiator to be added is preferably 0.001 to 1 mol% with respect to the monomer. It is necessary that the sheath polymer used in the present invention has a melt flow index value of 30 or less. When the melt flow index value exceeds 30, the flexibility and workability are significantly reduced. Polymers having a melt flow index value of 3 to 25 have excellent formability. The melt flow index value was represented by the number of grams discharged from a nozzle having a diameter of 2 mm and a length of 8 mm in 10 minutes when the polymer was subjected to a force of 5 kg at 230 ° C. A polymer having a melt flow index value of 30 or less can be obtained by adjusting the addition ratio of a polymerization initiator and / or a chain transfer agent and the polymerization reaction temperature. As the chain transfer agent, for example, n-butyl mercaptan, tertiary butyl mercaptan, n-octyl mercaptan, n-dodecyl mercaptan and the like are used, and it is preferable to add them at a ratio of about 1 mol% or less based on the monomer. The sheath polymer used in the present invention preferably has an intrinsic viscosity (in methyl ethyl ketone at 25 ° C.) of 0.4 dl / g or more. Further, the glass transition temperature (Tg) determined from the peak of E ″ in viscoelasticity measurement is preferably 75 ° C. or more. When producing the optical fiber of the present invention, polymethyl having excellent optical transmission performance is used as a core component. As the polymethyl methacrylate resin, polymethyl methacrylate, a copolymer containing methyl methacrylate units as a main component, preferably containing at least 70% by weight, or a deuterated resin thereof is used. Examples of the copolymerizable component with methyl methacrylate include methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, 2-
Acrylic acid esters such as ethylhexyl acrylate,
Cyclohexyl methacrylate, benzyl methacrylate, ethyl methacrylate, propyl methacrylate,
And methacrylic acid esters such as butyl methacrylate. As the polymethyl methacrylate-based resin, for example, a resin produced by a continuous bulk polymerization method as disclosed in JP-B-53-42260 is preferably used. In addition, the general formula (Wherein R represents an aliphatic or alicyclic hydrocarbon group) a polymer comprising 2% by weight or more of a ring structural unit represented by the following formula and 98% by weight of a monomer unit mainly composed of methyl methacrylate. It can also be a component. The polymer for an optical fiber sheath material of the present invention is obtained by dissolving in a solvent such as ethyl acetate, dimethylformamide, or dimethylacetamide and coating the surface of the fiber of the core component made of an organic polymer, or a core-sheath composite spinning method. Accordingly, a core-sheath type plastic optical fiber can be obtained. The core-sheath plastic optical fiber made as described above must have the following characteristics. That is, the average diameter is 1000 μm, and the wavelength is 650 n
When the parallel light of m is incident from one end and emitted from the other end, the transmitted light amount is I ₀ , and the light transmission is measured in the same manner with this optical fiber wound 100 times around a 10 mm diameter mandrel. When the amount of transmitted light is measured in the same manner as in the case of unwinding the light amount _Ia , the conditions of the formulas [I] and [II] are satisfied. If the value of I _b / I ₀ × 100 is less than 80%, the flexibility of the plastic optical fiber is not good, and such an optical fiber cannot be a plastic optical fiber having good processing characteristics. In addition, when I _a / I ₀ × 100 is less than 20%, it indicates that the light transmittance is remarkably reduced at the time of bending, and from this point, an optical fiber having good handleability is required. Can not. [Effect] The sheath-core type plastic optical fiber of the present invention has excellent bending resistance and workability as described above, and its reliability and light transmission characteristics are extremely good. Hereinafter, the present invention will be described in more detail by way of examples. Example 1 63% by weight of 2,2,2-trifluoroethyl methacrylate, 20% by weight of 1,1,2,2-tetrahydroperfluorodecyl methacrylate and 17% by weight of methyl methacrylate,
Further, n-octyl mercaptan is used for these monomers.
A monomer mixture containing 0.05% and 0.1% of 2,2'-azobisisobutyronitrile was prepared in the absence of oxygen, polymerized in a reactor maintained at 70 ° C for 8 hours, and then heated at 120 ° C. The polymerization was carried out for 2 hours. The obtained polymer had a refractive index of 1.4195, a diameter of 2 mm, and a length of 8 mm. The amount of polymer discharged at 230 ° C. under a load of 5 kg for 10 minutes (melt flow index value) was 5.4. The intrinsic viscosity at 25 ° C. was 0.68. Also E ″ of vibron measurement
The glass transition temperature (Tg) determined from the peak was 95.4 ° C. An optical fiber having a core diameter of 980 μm and a sheath thickness of 10 μm was obtained by a composite melt spinning machine having this polymer as a sheath, a core of polymethyl methacrylate, and a core-sheath spinneret. The optical transmission loss of this optical fiber is 92 dB /
It was 154 dB / km at km and 650 nm. The optical transmission loss after standing in air at 85 ° C for 100 hours was 95 dB / km at 590 nm and 159 dB / km at 650 nm. In addition, in order to examine the flexibility, the winding light amount retention rate when a 15 m optical fiber was repeatedly wound around a 10 mm diameter mandrel was evaluated. As a result, the light intensity retention after winding 100 times was 31.4%. The light recovery rate after unwrapping was 89.1%. Examples 2-5 and Comparative Examples 1-3 The monomer composition of the sheath component was changed, and the amounts of the polymerization initiator and the chain transfer agent added and the polymerization reaction temperature were adjusted.
An optical fiber was obtained in the same manner as described above. The same characteristic evaluation as in Example 1 was performed using this optical fiber. The results are shown in the table below. The symbols in the table mean the following compounds.

   ────────────────────────────────────────────────── ─── Continuation of front page    (72) Inventor Yoshihiro Uozu               Mitsubishi Ray, 20-1, Miyukicho, Otake City, Hiroshima Prefecture               Yeon Co., Ltd.                (56) References JP-A-62-265606 (JP, A)

Claims (1)

(57) [Claims] The core is a polymethyl methacrylate-based resin, the sheath is a core-sheath type plastic optical fiber composed of the following polymer, the average diameter of which is 1000 μm, a parallel light beam having a wavelength of 650 nm is incident from one end, and the other end. I ₀ the transmitted amount of light when allowed emitted from the winding amount of transmitted light Ia when the quantity of transmitted light was measured in the same manner in the state of the optical fiber wound 100 times diameter mandrel 10 mm, the winding Unwrapping light recovery amount Ib when measuring the amount of transmitted light in the same way as unwinding
Wherein I ₀ , Ia, and Ib satisfy the following formulas [I] and [II]. [Polymer for forming sheath] General formula (A) (Wherein n represents an integer of 5 to 11).
Weight%, general formula (b) (Wherein X represents a hydrogen atom or a fluorine atom, and m represents an integer of 1 to 4).
Consisting essentially of a copolymer of 0% to 38% by weight and other copolymerizable monomers and having a diameter of 5 kg at 230 ° C. under a load of 5 kg.
A copolymer having a melt flow index value of 30 or less indicating the amount of the polymer discharged from a nozzle having a length of 2 mm and a length of 8 mm in 10 minutes.