JP5559710B2 - Optical fiber - Google Patents

Description

  The present invention relates to an optical fiber, and more particularly to an optical fiber having a high glass transition temperature and high transparency and mainly composed of methyl methacrylate, which is a general-purpose monomer.

Conventionally, an optical fiber having a methacrylic resin such as polymethyl methacrylate (hereinafter sometimes abbreviated as PMMA) as a core is known. Such plastic optical fibers have various advantages such as good flexibility, light weight, good workability, and easy to manufacture at a low cost as a fiber having a large aperture.
However, since the glass transition temperature of PMMA (hereinafter sometimes abbreviated as Tg) is about 105 ° C., high heat resistance, which is considered to be required to be about 120 ° C., such as in an automobile engine room, is required. It cannot be used in the environment.
In addition, in the case of a refractive index distribution type (GI type) optical fiber to which a high-refractive-index low-molecular compound called a dopant is added for the purpose of imparting high-speed communication performance, Tg further decreases. Therefore, it cannot be applied to various sensors that require a Tg of about 100 ° C., link use in home appliances, and the like.

  Therefore, from the viewpoint of heat resistance, the PMMA-based GI optical fiber can be used as a residential high-speed network application, but the long-life light source wavelength is limited to about 660 to 680 nm. In these wavelength regions, the transmission loss is about 200 to 330 dB (see Patent Document 1), which is a range in which the loss increases sharply as the wavelength increases, and is required for home use in consideration of loss deterioration due to PMMA moisture absorption. If the communication distance is 30 m or more, especially 50 m or more, it cannot be used.

On the other hand, copolymerization with monomers that make up high Tg polymers, and monomers that make up highly transparent polymers, such as monomers with hydrogen atoms in the molecule replaced by fluorine or deuterium, are proposed. Has been.
For example, an optical fiber having a core member made of a copolymer of N-substituted isopropylmaleimide (hereinafter abbreviated as iPrMID) and methyl methacrylate (hereinafter sometimes abbreviated as MMA) has a transparency of not more than 300 dB / km at 660 nm. In addition, it has been reported that even when exposed to an atmosphere of 125 ° C. for 1000 hours, a decrease in the amount of transmitted light is hardly observed (see Non-Patent Document 1).
However, in the case of a dopant-added GI type optical fiber containing PMMA as a main component and several tens of percent by weight of N-substituted isopropylmaleimide, Tg is expected to be 100 ° C. or lower.

Further, it has been reported that an optical fiber using a copolymer of a fluorine-containing styrene derivative and an alkyl methacrylate derivative as a core material can obtain a low loss of 50 to 100 dB / km in a wavelength region of 650 to 660 nm (Patent Document 2). reference).
However, there is no specific description regarding the hydrogen atom substitution ratio and copolymer composition ratio of both monomers, and from the loss value, the fluorine-containing styrene derivative is the main component, or the hydrogen atom of the alkyl methacrylate derivative is substituted with deuterium or fluorine. It is easily guessed that the ratio of being used is high.

Further, a polymer of a styrene derivative having a structure substituted with a halogen atom or a trifluoromethyl group (hereinafter abbreviated as CF ₃ group) and a copolymer containing such a styrene derivative have a Tg higher than that of PMMA. It has been reported (Patent Document 3).
However, in order to increase scattering loss due to composition fluctuation, it is necessary to include 60 mol% or more (in terms of conversion, about 72 wt% or more) of this styrene derivative. For example, a styrene derivative having only one CF ₃ group is used alone. There were problems such as difficulty in polymerization.

  Under such circumstances, a material for optical fibers mainly composed of PMMA having high Tg and high transparency is expected.

Japanese Patent No. 3333292 JP 62-111111 A JP 60-147703 A

S. Taneichi, et al., POF'94 Conference Proceedings, 106 (1994)

  The present invention has been made in view of the above problems, and an object thereof is to provide an optical fiber having high Tg and high transparency and mainly composed of methyl methacrylate which is a general-purpose monomer.

The optical fiber of the present invention is an optical fiber comprising a core part and a clad part disposed on the outer periphery of the core part,
(A) An optical fiber comprising a core part and a clad part disposed on the outer periphery of the core part, wherein the core part is 75 to 98% by weight of methyl methacrylate and 2,3,4,5,6-pentafluorostyrene A copolymer derived from 2 to 25% by weight is the main constituent, and the cladding part is made of a polymer having a refractive index equal to or lower than the refractive index of the core part,
(B) The core part is composed mainly of a copolymer derived from 75 to 95% by weight of methyl methacrylate and 5 to 25% by weight of 4-trifluoromethyl 2,3,5,6, and tetrafluorostyrene, Whether the cladding part is made of a polymer having a refractive index equal to or lower than the refractive index of the core part,
(C) The core part mainly comprises a copolymer derived from 50 to 80% by weight of methyl methacrylate and 20 to 50% by weight of 2-trifluoromethylstyrene, and the cladding part has a refractive index of the core part. It is characterized by comprising a polymer having the following refractive index.
Of these optical fibers, those containing a dopant in the core and having a refractive index distribution are preferable.

  According to the present invention, it is possible to obtain an optical fiber having high Tg and high transparency and having methyl methacrylate as a main component as a main component.

The optical fiber of the present invention includes a core part and a clad part disposed on the outer periphery of the core part. However, in this specification, it may be called an optical fiber including the coating layer which coat | covers the outer periphery of a clad part.
In the optical fiber of the present invention, the core part and the clad part are not the optical core and clad (that is, the presence or absence of the dopant) in the optical fiber, but are the main components constituting the core. A layer constituted by the coalescence is referred to as a core portion, and a layer constituted by a polymer that is a main component constituting the cladding is referred to as a cladding portion.

Optical fibers are usually classified into multimode optical fibers and single mode optical fibers, but the optical fibers of the present invention are particularly advantageous for multimode optical fibers.
Furthermore, although the multimode optical fiber is classified into a step index (SI) type and a graded index (GI) type having a refractive index distribution, the optical fiber of the present invention is preferably a GI type. Here, the refractive index distribution means that the refractive index changes in a stepwise manner with a constant curve or a curve close to a parabola in the radial direction from the center of the fiber. Among these, those having a refractive index that decreases in the radial direction from the center are preferable. By providing such a refractive index distribution, the communication speed can be improved.

  Further, the refractive index may once decrease in a curvilinear or stepwise manner from the center of the fiber in the radial direction, and then increase in a curvilinear or stepwise manner. In this case, the core part and the outermost layer of the cladding part preferably have a higher refractive index, but the outermost layer of the cladding part may have a higher refractive index than the core part.

In the optical fiber of the present invention, the polymer constituting the core portion is
(A) a polymer mainly comprising a copolymer derived from methyl methacrylate and 2,3,4,5,6-pentafluorostyrene (hereinafter sometimes abbreviated as 5FSt),
(B) a polymer mainly comprising a copolymer derived from methyl methacrylate and 4-trifluoromethyl 2,3,5,6, tetrafluorostyrene (hereinafter sometimes abbreviated as TTFS), or (c ) A polymer having a copolymer derived from methyl methacrylate and 2-trifluoromethylstyrene (hereinafter sometimes abbreviated as 2TFMS) as a constituent component (preferably, a main constituent component).
Here, the main constituent component means a component contained at the highest content (weight) among the components constituting the core portion.
In particular, (a ′) a polymer mainly comprising a copolymer derived from 75 to 98% by weight of methyl methacrylate and 2 to 25% by weight of 5FSt,
(B ′) a polymer mainly comprising a copolymer derived from 75 to 95% by weight of methyl methacrylate and 5 to 25% by weight of TTFS,
(C ′) A polymer mainly comprising a copolymer derived from 50 to 80% by weight of methyl methacrylate and 20 to 50% by weight of 2TFMS is preferred. Since the copolymer tends to become brittle as the amount of 2TFMS increases, the main component is a copolymer derived from more than 50% by weight of methyl methacrylate and 80% by weight or less and 20% by weight or more and less than 50% by weight of 2TFMS. More preferred is a polymer.

Moreover, the polymer which comprises a clad part will not be specifically limited if it is a polymer which has a refractive index used as a core part or less, However, The thing which is transparent and excellent in adhesiveness with a core part is preferable.
For example, vinylidene fluoride-tetrafluoroethylene copolymer, vinylidene fluoride-tetrafluoroethylene-hexafluoropropylene terpolymer, fluoroalkyl methacrylate polymer, copolymer of two kinds of fluoroalkyl methacrylate having different alkyl groups Examples thereof include a copolymer, a copolymer of fluoroalkyl methacrylate and fluoroalkyl acrylate, and a mixture of vinylidene fluoride-tetrafluoroethylene copolymer and fluoroalkyl methacrylate polymer or fluoroalkyl acrylate polymer.

  The core part preferably comprises a dopant. By containing the dopant, the refractive index of the core part in the optical fiber can be changed to give a refractive index distribution. Among these, those having a refractive index that decreases in the radial direction from the center are preferable. By providing such a refractive index distribution, the communication speed can be improved. In particular, in order to impart a refractive index distribution, it is effective to adjust the dopant concentration distribution in the core portion. The clad part may contain a dopant.

  The dopant is suitably a compound that is compatible with the polymer of the monomer constituting the core portion and has a refractive index higher than the refractive index of these polymers. By using a compound having good compatibility, the core portion is not turbid, scattering loss is minimized, and the communication distance can be increased.

  Candidate dopants include low molecular weight compounds or compounds in which hydrogen atoms present in these compounds are substituted with deuterium atoms. Examples of the low molecular weight compounds include diphenyl sulfone and diphenyl sulfone derivatives (for example, diphenyl sulfone such as 4,4′-dichlorodiphenyl sulfone and 3,3 ′, 4,4′-tetrachlorodiphenyl sulfone), diphenyl sulfide, and diphenyl sulfoxide. , Dibenzothiophene, sulfur compounds such as dithian derivatives; phosphate compounds such as triphenyl phosphate (TPP), tris-2-ethylhexyl phosphate (TOP), triethyl phosphate (TEP), tricresyl phosphate; benzyl benzoate; phthalic acid Benzyl n-butyl; diphenyl phthalate; biphenyl; diphenylmethane and the like. These may be used alone or in combination of two or more.

  The amount of dopant in the core part can be appropriately adjusted depending on the composition of the polymer constituting the core part, the intended refractive index, the composition of the polymer constituting the clad part used, the type of dopant used, etc. The refractive index of the core portion can be adjusted to a suitable value by setting the amount to about 0.1 to 25 parts by weight with respect to 100 parts by weight of the polymer constituting the.

The polymer constituting the core part and the clad part of the optical fiber of the present invention can be produced by a method known in the art.
For example, the method of attaching | subjecting the mixture of the monomer which comprises a polymer to solution polymerization, block polymerization, emulsion polymerization, suspension polymerization, etc. are mentioned. Of these, the bulk polymerization method is preferred from the viewpoint of preventing the introduction of foreign substances and impurities.
The polymerization temperature at this time is not particularly limited, and for example, about 80 to 150 ° C. is suitable. The reaction time can be appropriately adjusted according to the amount and type of monomer, the amount of polymerization initiator and chain transfer agent described later, the reaction temperature, and the like, and about 20 to 60 hours is suitable.
These polymers may be produced simultaneously or successively when molding the core part and / or the clad part described later.

The polymer constituting the core part preferably does not use any other monomer component other than the above-mentioned copolymer of MMA and 5FSt, the copolymer of MMA and TTFS, or the copolymer of MMA and 2TFMS. However, it may further contain a polymerizable monomer or the like as long as the properties of the obtained optical fiber are not impaired.
For example, as a (meth) acrylic acid ester compound, ethyl methacrylate, n-propyl methacrylate, n-butyl methacrylate, ethyl acrylate, n-propyl acrylate, n-butyl acrylate, etc .; Styrene, α-methylstyrene, chlorostyrene, bromostyrene, etc .; vinyl esters, vinyl acetate, vinyl benzoate, vinyl phenyl acetate, vinyl chloroacetate, etc .; maleimides, Nn-butylmaleimide, N-tert-butyl Examples thereof include deuterium substitutions of these monomers such as maleimide, N-isopropylmaleimide, N-cyclohexylmaleimide and the like.

In producing the polymer, it is preferable to use a polymerization initiator and / or a chain transfer agent.
Examples of the polymerization initiator include ordinary radical initiators. For example, benzoyl peroxide, t-butyl peroxy-2-ethyl hexanate, di-t-butyl peroxide, t-butyl peroxyisopropyl carbonate, n-butyl 4,4, bis (t-butyl peroxy) valerate Peroxide compounds such as 2,2′-azobisisobutyronitrile, 2,2′-azobis (2-methylbutyronitrile), 1,1′-azobis (cyclohexane-1-carbonitrile), 2 , 2′-azobis (2-methylpropane), 2,2′-azobis (2-methylbutane), 2,2′-azobis (2-methylpentane), 2,2′-azobis (2,3-dimethylbutane) ), 2,2′-azobis (2-methylhexane), 2
, 2′-azobis (2,4-dimethylpentane), 2,2′-azobis (2,3,3-trimethylbutane), 2,2′-azobis (2,4,4-trimethylpentane), 3, 3'-azobis (3-methylpentane), 3,3'-azobis (3-methylhexane), 3,3'-azobis (3,4-dimethylpentane), 3,3'-azobis (3-ethylpentane) ),
Dimethyl-2,2′-azobis (2-methylpropionate), diethyl-2,2′-azobis (2-methylpropionate), di-t-butyl-2,2′-azobis (2-methyl) And azo compounds such as propionate). These may be used alone or in combination of two or more.
The polymerization initiator is suitably used at about 0.01 to 2% by weight based on the total monomers.

  The chain transfer agent is not particularly limited, and known ones can be used. For example, alkyl mercaptans (n-butyl mercaptan, n-pentyl mercaptan, n-octyl mercaptan, n-lauryl mercaptan, t-dodecyl mercaptan, etc.), thiophenols (thiophenol, m-bromothiophenol, p-bromothio) Phenol, m-toluenethiol, p-toluenethiol, etc.). Of these, alkyl mercaptans such as n-butyl mercaptan, n-octyl mercaptan, n-lauryl mercaptan, t-dodecyl mercaptan are preferably used. Moreover, you may use the chain transfer agent by which the hydrogen atom of C-H bond was substituted by the deuterium atom or the fluorine atom. These may be used alone or in combination of two or more.

  Chain transfer agents are usually used to adjust the molecular weight to an appropriate molecular weight in terms of molding and physical properties. The chain transfer constants of chain transfer agents for each monomer are, for example, Polymer Handbook 3rd edition (edited by J. BRANDRUP and EHIMMERGUT, published by JOHN WILEY & SON) “Experimental Methods for Polymer Synthesis” (Co-authored by Takayuki Otsu and Masami Kinoshita, Chemical) It can be obtained by experiment with reference to the same person, published in 1972. Therefore, in consideration of the chain transfer constant, it is preferable to appropriately adjust the type and addition amount according to the type of monomer. For example, about 0.1-4 weight part is mentioned with respect to 100 weight part of all the monomer components.

  The polymer constituting the core part and / or the clad part has a weight average molecular weight in the range of about 5 to 300,000, preferably about 1 to 250,000. This is to ensure appropriate flexibility and transparency. The core portion and the clad portion may have different molecular weights, for example, for viscosity adjustment. A weight average molecular weight refers to the value of polystyrene conversion measured by GPC (gel permeation chromatography), for example.

  In the polymer constituting the optical fiber of the present invention, a compounding agent, for example, a heat stabilization aid, a processing aid, a heat resistance, is added to the polymer as long as it does not impair the performance of the optical fiber such as transparency and heat resistance. You may mix | blend an improver, antioxidant, a light stabilizer, etc. Each of these can be used alone or in combination of two or more. Examples of the method of mixing these blends with the monomer or polymer include a hot blend method, a cold blend method, and a solution mixing method. It is done.

  As a method for producing the optical fiber of the present invention, a method known in the art can be used. For example, interfacial gel polymerization, rotational polymerization, melt extrusion dopant diffusion, composite melt spinning, and rod-in-tube to form one or two or more cladding portions on the outer periphery of one or more core portions Laws can be used. Further, a preform may be formed in advance, and drawing, drawing, and the like may be performed. However, a fiber may be directly formed by the method described above.

Specifically, there is a method in which a hollow clad part is produced and a core part is produced in the hollow part of the clad part.
In this case, the monomer constituting the core part is introduced into the hollow part of the cladding part, and the polymer is polymerized while rotating the cladding part to form a core part having a higher refractive index than the cladding part. This operation may be performed only once to form a single-layer core portion, or a multi-layer core portion may be formed by repeating this operation.

The polymerization vessel used can be a glass, plastic, or metallic cylindrical tube-shaped vessel (tube) having mechanical strength that can withstand external force such as centrifugal force caused by rotation and heat resistance during heat polymerization.
The rotation speed of the polymerization vessel at the time of polymerization is exemplified by about 500 to 3000 rpm.
Usually, the monomer is filtered through a filter to remove dust contained in the monomer.

Therefore, it is preferably introduced into the polymerization vessel.

Furthermore, the method of forming a core part and a clad part using two or more melt extruders, two or more multilayer dies, and a multilayer spinning nozzle may be used.
That is, the polymer and the like constituting the core part and the clad part are respectively heated and melted and injected from the individual flow paths to the multilayer die and the multilayer spinning nozzle. A core or a preform can be formed by extruding one or two or more concentric clad portions on the outer periphery of the core and extruding and integrating them with the die and nozzle.

In order to give a GI-type refractive index distribution in an optical fiber, for example, as described in WO 93/08488, the monomer composition ratio is made constant, a dopant is added, and the monomer is bulk polymerized at the interface of the polymer. The interfacial gel polymerization that imparts a dopant concentration distribution by the reaction or the rotational gel polymerization method in which the reaction mechanism of the interfacial gel polymerization is performed by the rotational polymerization method and the monomer charge composition ratios with different refractive indexes are gradually changed, that is, , By controlling the polymerization rate of the previous layer (lowering the polymerization rate), polymerizing the next layer having a higher refractive index, so that the refractive index distribution gradually increases from the interface with the cladding to the center. Examples of the method include rotational polymerization.
In addition, after forming the core part and the clad part using two or more melt extruders, two or more layers of multi-layer dies and a multi-layer spinning nozzle, the dopant is introduced into the peripheral part or the center in the heat treatment zone provided subsequently. A melt-extrusion dopant diffusion method that diffuses toward the part and imparts a dopant concentration distribution, and introduces a polymer or the like having a different amount of dopant into two or more melt-extruders to form a core part and / or a multilayer structure. A method of extruding the clad part is exemplified.

When an SI type refractive index distribution is provided, it is suitable to perform rotational polymerization or the like with the monomer composition ratio and / or the amount of dopant added constant from the beginning to the end.
In the case of providing a multi-step type refractive index distribution, it is preferable to polymerize the next layer having a higher refractive index by controlling the polymerization rate of the previous layer (increasing the polymerization rate) in rotational polymerization or the like.

When an optical fiber preform is formed by the above-described method or the like, a plastic optical fiber can be produced by melt-drawing the preform. For example, the stretching is exemplified by a method in which the preform is heated by passing through an interior of a heating furnace or the like, melted, and then stretched and spun. The heating temperature can be appropriately determined according to the material of the preform and the like, for example, about 180 to 250 ° C. is exemplified. The stretching conditions (stretching temperature and the like) can be appropriately adjusted in consideration of the diameter of the obtained preform, the diameter of the desired optical fiber, the material used, and the like.
In addition, when the core part is produced by a rotational gel polymerization method or a rotational polymerization method, since the center part is hollow, it is preferable to stretch the preform while decompressing from the top during stretching.

  Further, heat treatment may be performed at an arbitrary stage. This heat treatment allows the dopant to diffuse toward the periphery or center of the optical fiber or preform. The conditions (for example, temperature, time, pressure, atmosphere composition, etc.) at this time are preferably adjusted arbitrarily.

The optical fiber of the present invention can be applied as it is. In addition, as described above, by coating the outer periphery with a coating material such as one or a plurality of resin layers, fiber layers, metal wires, and / or bundling a plurality of fibers, various uses such as optical fiber cables. Can be applied to.
The resin for coating the optical fiber is not particularly limited, but it is preferable to select a resin that satisfies the strength, flame retardancy, flexibility, chemical resistance, heat resistance, and the like necessary for the optical fiber cable and the like. For example, vinyl chloride resin, chlorinated vinyl chloride resin, chlorinated polyethylene resin, polyethylene resin, acrylic resin, fluorine resin, polycarbonate resin, nylon resin, polyester resin, ethylene-vinyl acetate copolymer, ethylene-vinyl acetate copolymer , Vinyl chloride-ethylene-vinyl acetate copolymer, vinyl acetate-vinyl chloride copolymer and the like as main components. Moreover, what used the composition which added the additive mentioned above to these resin may be used.
Examples of the fibers include aramid fibers, polyester fibers, and polyamide fibers.
Examples of the metal wire include stainless steel wire, zinc alloy wire, copper wire and the like.

The method of coating the resin on the outer periphery of the optical fiber is not particularly limited, and examples thereof include a method of coating and extruding the surface layer after forming the optical fiber.
Moreover, it is preferable that the cable using the optical fiber is securely fixed to the jack portion by using a connecting optical plug at the end portion. As a connector constituted by a plug and a jack, various commercially available connectors such as PN type, SMA type, SMI type, F05 type, MU type, FC type, and SC type can be used. In addition, a plug for connection is not used at the end of the cable using an optical fiber, but a plugless connector such as OptoLock (trade name, manufactured by Firecoms) is attached to the connection device side such as a media converter, and the disconnected cable is inserted and connected. It is also possible to do.
Hereinafter, embodiments of the optical fiber of the present invention will be described in detail, but the present invention is not limited to the following examples.

Example 1
MMA 95% by weight, 5FSt 5% by weight, di-t-butyl peroxide as a polymerization initiator and n-lauryl mercaptan as a chain transfer agent are each 0.01 parts by weight and 0.05 parts by weight per 100 parts by weight of the total monomer components. Further, 5 parts by weight of diphenyl sulfide was added as a dopant and mixed with stirring. The mixed solution is filtered using a membrane filter having a pore size of 0.1 μm, the filtered solution is put into a polymerization vessel, and the polymerization is performed for about 40 hours while maintaining the temperature of the polymerization vessel at 110 ° C. I got a rod.

  80% by weight of MMA, 20% by weight of tetrafluoroethyl methacrylate, di-t-butyl peroxide as a polymerization initiator and n-lauryl mercaptan as a chain transfer agent were each added in an amount of 0. It added so that it might become 01 weight part and 0.22 weight part, and it stirred and mixed. This mixed solution is filtered using a membrane filter having a pore size of 0.1 μm, and the filtrate is put into a polymerization vessel, and the polymerization vessel is polymerized over about 40 hours while maintaining the temperature of the polymerization vessel at 110 ° C. to obtain a clad member rod. It was.

The core member and the clad member were formed into a multilayered structure of the core part and the clad part using separate extruders and a two-layer mold connected to them. By passing this laminate through the heating channel for a certain period of time, the dopant contained in the core portion was diffused into the cladding portion.
Furthermore, XYLEX X7300CL [product name, manufactured by SABIC Innovative Plastics, polyester composite polycarbonate (Vicat softening temperature: 108 ° C.)] (hereinafter also referred to as PC)] (hereinafter also referred to as PC) was melted by another extruder. Using a layer mold, the outermost periphery was covered by joining the flow path through which the melt of the core part and the clad part passes. The molten resin discharged from the mold outlet was taken to obtain a GI POF having a core part diameter, a cladding part diameter, and a fiber outer diameter of 200 μm, 280 μm, and 750 μm, respectively. The following (1) and (2) were evaluated for the obtained optical fiber sample.

(1) Transmission loss: The transmission loss at 665 nm was measured using the cutback method.
(2) Glass transition temperature measurement: A sample was sampled from the core member rod, and measured by a DSC method in a nitrogen atmosphere at a heating rate of 10 ° C./min.

Examples 2 and 3 and Comparative Examples 1 and 2
As shown in Table 1, each optical fiber sample was prepared in the same manner as in Example 1 except that the ratio of the monomer component in the core portion was changed, and transmission loss and Tg measurement were similarly performed on the sample.

Example 4
MMA 90% by weight, TTFS 10% by weight, di-t-butyl peroxide as a polymerization initiator and n-lauryl mercaptan as a chain transfer agent are each 0.01 parts by weight and 0.05 parts by weight per 100 parts by weight of the total monomer components. In addition, 5 parts by weight of diphenyl sulfide was added as a dopant and mixed with stirring. The mixed solution is filtered using a membrane filter having a pore size of 0.1 μm, the filtered solution is put into a polymerization vessel, and the polymerization is performed for about 40 hours while maintaining the temperature of the polymerization vessel at 110 ° C. I got a rod.
Other than that, an optical fiber was prepared in the same manner as in Example 1, and the transmission loss and Tg were measured in the same manner for the sample.

Example 5 and Comparative Example 3
As shown in Table 1, each optical fiber sample was prepared in the same manner as in Example 4 except that the ratio of the monomer component in the core portion was changed, and transmission loss and Tg measurement were similarly performed on the sample.

Example 6
MMA 75% by weight, 2TFMS 25% by weight, di-t-butyl peroxide as a polymerization initiator and n-lauryl mercaptan as a chain transfer agent are each 0.01 parts by weight and 0.05 parts by weight per 100 parts by weight of the total monomer components. In addition, 5 parts by weight of diphenyl sulfide was added as a dopant and mixed with stirring. The mixed solution is filtered using a membrane filter having a pore size of 0.1 μm, the filtered solution is put into a polymerization vessel, and the polymerization is performed for about 40 hours while maintaining the temperature of the polymerization vessel at 110 ° C. I got a rod.
Other than that, an optical fiber was prepared in the same manner as in Example 1, and the transmission loss and Tg were measured in the same manner for the sample.

Example 7 and Comparative Example 4
As shown in Table 1, each optical fiber sample was prepared in the same manner as in Example 6 except that the ratio of the monomer component in the core portion was changed, and transmission loss and Tg measurement were similarly performed on the sample. These results are shown in Table 1.

  The present invention is useful as a component of an optical fiber or optical fiber cable intended for high-speed communication, and further, by changing the shape, optical elements such as an optical waveguide, for still cameras, for video cameras, for telescopes, The present invention can be applied to optical members such as lenses for spectacles, plastic contact lenses, sunlight condensing lenses, concave mirrors, mirrors such as polygons, and prisms such as pentaprisms.

Claims (3)

An optical fiber comprising a core part and a clad part arranged on the outer periphery of the core part,
The core part is mainly composed of a copolymer derived from 75 to 95% by weight of methyl methacrylate and 5 to 25% by weight of 4-trifluoromethyl 2,3,5,6-tetrafluorostyrene,
The optical fiber, wherein the clad part is made of a polymer having a refractive index equal to or lower than the refractive index of the core part. An optical fiber comprising a core part and a clad part arranged on the outer periphery of the core part,
The core part is mainly composed of a copolymer derived from 50 to 80% by weight of methyl methacrylate and 20 to 50% by weight of 2-trifluoromethylstyrene,
The optical fiber, wherein the clad part is made of a polymer having a refractive index equal to or lower than the refractive index of the core part. Includes a dopant in the core portion, the optical fiber according to claim 1 or 2 having a refractive index distribution.