JP4520364B2 - Amorphous copolymers, optical components and plastic optical fibers - Google Patents

Description

  The present invention belongs to the technical field of optical members, and particularly relates to amorphous copolymers useful as materials for plastic optical fibers, optical waveguides and optical lenses.

 Starting from the discovery of polytetrafluoroethylene (PTFE), various fluorine-containing polymer compounds have been developed to date. Fluorine-containing polymer compounds exhibit excellent chemical resistance, weather resistance, and electrical properties that are not found in conventional polymer materials, and thus have a wide range of uses such as resins, rubbers, paints, and coating materials. However, since conventional fluorine-containing polymer compounds are opaque or milky white translucent due to their crystallinity, they have hardly been used in the optical field where high transparency is required.

 Originally, fluorine-containing polymer compounds have light transmittance in a wide wavelength range due to the heavy atom effect derived from fluorine atoms, and have sufficient potential as a resin for optical applications requiring high transparency. Yes. Furthermore, the fluorine-containing polymer has properties such as low refractive index and low hygroscopicity, and its usefulness is high. Therefore, the transparency of various physical properties of fluorine-containing polymers has been improved in order to develop into optical applications.

For example, Patent Document 1 describes that a copolymer of α-trifluoromethyl acrylate and a vinyl monomer has high transparency (Patent Document 1).
Here, the optical material, in particular, the plastic optical fiber and the polymer waveguide, is required to be compatible with transparency and moisture and heat resistance.
However, although the copolymer shown in Patent Document 1 is amorphous and has transparency, it cannot be said that the heat resistance as a resin is sufficient, and is improved for application to plastic optical fibers and waveguides. is required.

JP 2002-201231 A

 The invention of the present application aims to solve the above-described problems, and provides an amorphous copolymer (fluorine-containing polymer) that has transparency and moist heat resistance and is excellent in elastic modulus, tensile strength, and the like. The issue is to provide. Another object of the present invention is to provide an optical member and a plastic optical fiber having the copolymer.

（一般式（１）中、Ｒ¹及びＲ²は各々独立に、通常の水素原子（¹Ｈ）または重水素原子（²Ｈ）を表す。また、Ｒ³は、通常の水素原子（¹Ｈ）、重水素原子（²Ｈ）、アリール基またはアルキル基である。）
一般式（２）

（一般式（２）中、Ｒ⁴及びＲ⁵は各々独立に、通常の水素原子（¹Ｈ）、重水素原子（²Ｈ）、ハロゲン原子またはアルキル基を表し、またＲ⁶、Ｒ⁷、Ｒ⁸およびＲ⁹は各々独立に、通常の水素原子（¹Ｈ）、重水素原子（²Ｈ）、ハロゲン原子、シアノ基、ニトロ基、アリール基またはアルキル基を表す。また、Ｒ⁶〜Ｒ⁹の中から選ばれる２つが互いに結合して環状構造を形成しても良い。）
（２）前記一般式（２）中、Ｒ⁴〜Ｒ⁹が各々独立に、通常の水素原子（¹Ｈ）または重水素原子（²Ｈ）である（１）に記載の非晶質コポリマー。
（３）（１）または（２）に記載の非晶質コポリマーを含む光学部材。
（４）（１）または（２）に記載の非晶質コポリマーを含むプラスチック光ファイバー。
The present inventors diligently studied in order to solve the above-described problems, and found a novel polymer by the following means to complete the present invention. That is, the means for solving the above problems are as follows.
(1) A repeating unit derived from the monomer (A) represented by the following general formula (1), a repeating unit derived from the monomer (B) represented by the following general formula (2), and a carboxyl group, a hydroxyl group and It consists of a repeating unit derived from vinyl monomer (C) having at least one group selected from the group consisting of epoxy groups, and the molar ratio of monomer (A) to monomer (B) is 1: 9 to 9: 1, An amorphous copolymer in which the repeating units derived from the vinyl monomer (C) occupy 0.01 to 30 mol% of the whole and the weight average molecular weight is 1,000 to 1,000,000 .

(In General Formula (1), R ¹ and R ² each independently represent a normal hydrogen atom ( ¹ H) or a deuterium atom ( ² H). R ³ represents a normal hydrogen atom ( ¹ H). ), A deuterium atom ( ² H), an aryl group or an alkyl group.)
General formula (2)

(In the general formula (2), R ⁴ and R ⁵ each independently represent a normal hydrogen atom ( ¹ H), deuterium atom ( ² H), halogen atom or alkyl group, and R ⁶ , R ⁷ , R ⁸ and R ⁹ each independently represent a normal hydrogen atom ( ¹ H), deuterium atom ( ² H), halogen atom, cyano group, nitro group, aryl group or alkyl group, and R ^{6 to} R Two selected from ⁹ may be bonded to each other to form a cyclic structure.)
(2) The amorphous copolymer according to (1), wherein in the general formula (2), R ^{4 to} R ⁹ are each independently a normal hydrogen atom ( ¹ H) or a deuterium atom ( ² H).
(3) An optical member comprising the amorphous copolymer according to (1) or (2).
(4) A plastic optical fiber comprising the amorphous copolymer according to (1) or (2).

 According to the present invention, it is possible to provide an amorphous copolymer having transparency and wet heat resistance, and having excellent elastic modulus, tensile strength, and the like. Furthermore, the present invention can provide a method for producing the polymer, an optical member comprising the copolymer as a main component, particularly a plastic optical fiber.

Below, the copolymer of this invention, the manufacturing method of this copolymer, and the optical member which has this copolymer as a main component are demonstrated in detail. In the present specification, a numerical range represented by using “to” means a range including numerical values described before and after “to” as a lower limit value and an upper limit value.
In the present invention, “ ¹ H” represents a normal hydrogen atom, and “ ² H” represents a deuterium atom.

First, the monomer (A) represented by the general formula (1) will be described in detail.
General formula (1)

In general formula (1), R ¹ and R ² each independently represent a normal hydrogen atom ( ¹ H) or a deuterium atom ( ² H). R ³ is a normal hydrogen atom ( ¹ H), deuterium atom ( ² H), aryl group or alkyl group.

Examples of the aryl group are preferably those having 8 or less carbon atoms, and more preferably substituted or unsubstituted phenyl groups. As the substituent, a halogen atom (a chlorine atom, a fluorine atom, etc.) is preferable. Examples of the aryl group include a phenyl group, a methylphenyl group, a pentafluorophenyl group, a tribromophenyl group, a pentabromophenyl group, and a p-methoxyphenyl group.
The alkyl group may be linear, branched or cyclic, preferably linear or branched, and more preferably linear. The alkyl group preferably has 10 or less carbon atoms, more preferably 5 or less. The alkyl group may have a substituent, and the substituent is preferably a halogen atom (chlorine atom, fluorine atom, etc.). Examples of the alkyl group include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, tert-butyl group, trifluoromethyl group, trifluoroethyl group, pentafluoropropyl group, tetrafluoropropyl group. Group, octafluoropentyl group, hexafluoroisopropyl group and the like.

Specific examples of the monomer represented by the general formula (1) are listed below, but the monomer represented by the general formula (1) that can be used in the present invention is not limited to these specific examples. Absent. H of the C—H bond contained in the following monomer may be ¹ H or ² H.

（一般式（２）中、Ｒ⁴及びＲ⁵は各々独立に、通常の水素原子（¹Ｈ）、重水素原子（²Ｈ）、ハロゲン原子またはアルキル基を表し、またＲ⁶、Ｒ⁷、Ｒ⁸およびＲ⁹は各々独立に、通常の水素原子（¹Ｈ）、重水素原子（²Ｈ）、ハロゲン原子、シアノ基、ニトロ基、アリール基またはアルキル基を表す。また、Ｒ⁶〜Ｒ⁹の中から選ばれる２つが互いに結合して環状構造を形成しても良い。） Next, the monomer (B) represented by the general formula (2) will be described in detail.
General formula (2)

(In the general formula (2), R ⁴ and R ⁵ each independently represent a normal hydrogen atom ( ¹ H), deuterium atom ( ² H), halogen atom or alkyl group, and R ⁶ , R ⁷ , R ⁸ and R ⁹ each independently represent a normal hydrogen atom ( ¹ H), deuterium atom ( ² H), halogen atom, cyano group, nitro group, aryl group or alkyl group, and R ^{6 to} R Two selected from ⁹ may be bonded to each other to form a cyclic structure.)

Examples of the aryl group are preferably those having 8 or less carbon atoms, and examples thereof include a phenyl group, a methylphenyl group, a pentafluorophenyl group, a tribromophenyl group, a pentabromophenyl group, and a p-methoxyphenyl group.
The alkyl group may be linear, branched or cyclic, preferably linear or branched, and more preferably linear. The alkyl group preferably has 10 or less carbon atoms, more preferably 5 or less, and still more preferably 3 or less. The alkyl group may have a substituent, and the substituent is preferably a halogen atom (chlorine atom, fluorine atom, etc.). Examples of the alkyl group include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, tert-butyl group, trifluoromethyl group, trifluoroethyl group, pentafluoropropyl group, tetrafluoropropyl group. Group, octafluoropentyl group, hexafluoroisopropyl group and the like.
Moreover, two selected from R ^{4 to} R ⁹ may be bonded to form a cyclic structure. In this case, the size of the ring is preferably a 5-membered ring or a 6-membered ring.

H of the C—H bond contained in R ^{4 to} R ⁹ may be ¹ H or ² H. R ^{4 to} R ⁹ preferably do not contain a polymerizable group.

Specific examples of the monomer represented by the general formula (2) are given below, but the monomer represented by the general formula (2) that can be used in the present invention is not limited to these specific examples. Absent. H of the C—H bond contained in the following monomer may be ¹ H or ² H.

 Next, the vinyl monomer (C) having at least one group (functional group) selected from the group consisting of a carboxyl group, a hydroxyl group and an epoxy group at the terminal will be described.

 The vinyl monomer (C) can be broadly classified into the same electron-withdrawing monomers as the monomer (A) and the same electron-donating monomers as the monomer (B). The monomer (A) and the monomer (B) Either of them may be used as long as it can be copolymerized with.

 Common electron donating monomers include vinyl ethers such as methyl vinyl ether, ethyl vinyl ether, cyclohexyl vinyl ether, isobutyl vinyl ether, carboxylic acid vinyl esters such as vinyl acetate and vinyl pivalate, N-vinylformamide, N-vinylcarbazole, and the like. And compounds having an unsaturated double bond in the nitrogen atom, styrene derivatives such as α-methylstyrene, p-methylstyrene, and tert-butylstyrene, and olefins such as ethylene, propylene, and 1-hexene. Among them, vinyl ethers and carboxylic acid vinyl esters are particularly preferred as the structure of the monomer (C1) having a functional group at the terminal.

Specific examples of the electron donating vinyl monomer (C1) having at least one group selected from a carboxyl group, a hydroxyl group, and an epoxy group at the terminal are given below. Monomers that can be used in the present invention are specific examples thereof. It is not limited to. Further, H of the C—H bond contained in the following monomer may be ¹ H or ² H.

 Common electron-withdrawing monomers include (meth) acrylic acid and its esters, α-trifluoromethylacrylic acid and its esters, α-cyanoacrylic acid and its esters, unsaturated dicarboxylic acid and its esters , Nitrile compounds such as acrylonitrile and crotonnitrile, and halogenated olefin compounds such as vinylidene chloride. Among them, the monomer (C2) structure having a functional group at the terminal is preferably α-trifluoromethylacrylic acid and esters thereof, α-cyanoacrylic acid and esters thereof, unsaturated dicarboxylic acid and esters thereof, α-Trifluoromethylacrylic acid and its esters, unsaturated dicarboxylic acid and its esters are particularly preferred. Moreover, unsaturated dicarboxylic acids may form an acid anhydride.

Specific examples of the electron-withdrawing vinyl monomer (C2) having at least one group selected from a carboxyl group, a hydroxyl group, and an epoxy group at the terminal are given below. Monomers that can be used in the present invention are specific examples thereof. It is not limited to. Further, H of the C—H bond contained in the following monomer may be ¹ H or ² H.

Next, a copolymer having the monomer (A), the monomer (B) and the monomer (C) as essential components will be described.
The copolymer of the present invention is formed, for example, by alternating copolymerization of an electron-withdrawing monomer and an electron-donating monomer. Polymerization, the molar ratio of the monomer represented by the monomers represented by one general formula (1) (A) (electron-withdrawing monomer) 1 and the general formula (2) (B) (electron donating monomer) A : B is 1: 9 to 9: 1, more preferably 3: 7 to 7: 3, more preferably 4: 6 to 6: intends row copolymerization in a ratio of 4. In particular, when copolymerization is performed using the monomer (A) and the monomer (B) and the monomer (C), when the monomer (C) is an electron-withdrawing monomer, the total amount of the electron-withdrawing monomer (A + C) The monomer (C) has an electron donating property so that the number of moles is approximately equal to the number of moles of the electron donating monomer (B) (for example, (A + C) :( B) = 40-60 mol%: 60-40 mol%). In the case of a monomer, the number of moles of the electron-withdrawing monomer (A) is approximately equal to the number of moles of the total amount (B + C) of the electron-donating monomer (for example, (A) :( B + C) = 40 to 60 mol%: 60 to 40 mol%), it is particularly preferable to carry out copolymerization. Here, the unreacted rate can be further increased by reducing the ratio of the electron-withdrawing monomer to the electron-donating monomer. The proportion of the monomer to carry out the remaining copolymer (C), accounting for 0.01 to 30 mol% of the total, preferably 0.1 to 20 mol%.

 When the copolymer is used in an optical member, particularly in an optical fiber, the hydrogen atom of the monomer (A), monomer (B), or monomer (C) used is preferably deuterium.

As a method for producing the polymer, a known polymerization method can be used. Examples thereof include a bulk polymerization method, a solution polymerization method, an emulsion polymerization method in water or in an emulsion, or a suspension polymerization method. The polymerization method is appropriately selected depending on the required performance of the target optical member. For example, a bulk polymerization method is preferable for an optical waveguide typified by a core material of a plastic optical fiber, and a clad polymerization method is appropriately selected from a bulk polymerization method, a solution polymerization method, an emulsion polymerization method, and a suspension polymerization method for the fiber cladding material. The
For example, when the bulk optical polymerization method is employed for the purpose of plastic optical fibers, it is possible to suppress the mixing of dust that causes Rayleigh scattering and to achieve an advantage that a low transmission loss can be achieved.

 Solvents generally used for solution polymerization include ester solvents such as ethyl acetate, methyl acetate or butyl acetate, ketone solvents such as acetone, methyl ethyl ketone and methyl isobutyl ketone, and aromatic solvents such as toluene, xylene and benzene. be able to.

As a polymerization initiator, it can select suitably according to the kind and polymerization method of a monomer to be used, but benzoyl peroxide (BPO), tert-butylperoxy-2-ethylhexanate (PBO), di-tert- Peroxide compounds such as butyl peroxide (PBD), tert-butyl peroxyisopropyl carbonate (PBI), n-butyl 4,4, bis (tert-butylperoxy) valerate (PHV), or 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 Examples include azo compounds such as (2-methylpropionate), di-tert-butyl-2,2′-azobis (2-methylpropionate), and 4,4-azobis (4-cyanopentanoic acid). Two or more kinds of polymerization initiators may be used in combination.
In the case of processes carried out in an aqueous medium, further inorganic free radical generators such as persulfates or “redox” compounds can be used.

 Moreover, you may use a chain transfer agent suitably for molecular weight adjustment. The chain transfer agent is mainly used for adjusting the molecular weight of the polymer. About the said chain transfer agent, according to the kind of polymeric monomer, a kind and addition amount can be selected suitably. The chain transfer constant of the chain transfer agent for each monomer can be referred to, for example, Polymer Handbook 3rd edition (edited by J. BRANDRUP and EH IMMERGUT, published by JOHN WILEY & SON). The chain transfer constant can also be obtained by experiment with reference to Takayuki Otsu and Masaaki Kinoshita "Experimental Method for Polymer Synthesis", Kagaku Dojin, published in 1972.

As chain transfer agents, alkyl mercaptans (n-butyl mercaptan, n-pentyl mercaptan, n-octyl mercaptan, n-lauryl mercaptan, tert-dodecyl mercaptan, etc.), thiophenols (thiophenol, m-bromothiophenol, p-bromothiophenol, m-toluenethiol, p-toluenethiol, etc.) are preferred, and among them, alkyl mercaptans such as n-octyl mercaptan, n-lauryl mercaptan, and tert-dodecyl mercaptan are more preferred. A chain transfer agent in which a hydrogen atom of a C—H bond is substituted with a deuterium atom or a fluorine atom can also be used.
Two or more chain transfer agents may be used in combination.

 In general, the polymerization temperature depends on the decomposition rate of the selected initiator system and is preferably 0-200 ° C, more preferably 40-120 ° C. The polymerization time is preferably 24 to 72 hours.

The copolymer of the present invention obtained as described above is preferably transparent (ultraviolet to near infrared region) and soluble in common solvents (particularly tetrahydrofuran (THF), ethyl acetate, acetone). The molecular weight of the copolymers of the present invention, the weight average molecular weight, 1 a 000～1,000,000 (weight average molecular weight of styrene conversion measured by gel permeation chromatography), preferably 2,000～900 3,000, more preferably 3,000 to 800,000. The glass transition temperature (Tg) of the copolymer is preferably 60 to 180 ° C, more preferably 70 to 180 ° C, and still more preferably 80 to 180 ° C. The glass transition temperature (Tg) of the copolymer of the present invention is preferably 60 to 180 ° C, more preferably 80 to 160 ° C. This glass transition temperature is mainly related to the amount of repeating units derived from monomer (B) present in the copolymer. The transparency of the obtained copolymer also depends on the content of the repeating unit derived from the monomer (B).
Furthermore, the elastic modulus of the copolymer of the present invention is preferably 500 to 3000 MPa. Moreover, it is preferable that the refractive index of the copolymer of this invention is 1.2-3.0. In addition, the tensile strength of the copolymer of the present invention is preferably 20 to 200 MPa.

Specific examples of the copolymer of the present invention are given below, but the copolymer of the present invention is not limited to these specific examples. In addition, the numerical value described in structural formula represents the composition ratio (molar ratio).

 The copolymer of the present invention is useful as a material for optical members. As an optical member containing the copolymer of the present invention, for example, optical elements (including in-vehicle use), optical elements such as optical waveguides, still cameras, video cameras, telescopes, glasses, plastic contact lenses, solar collectors Examples thereof include lenses for light, concave mirrors, mirrors such as polygons, and prisms such as pentaprisms. Since a copolymer having a very low birefringence can be obtained by selecting a monomer, it can be used for a substrate such as a scattering plate or an optical disk, and an optical switch. Among these, it is preferably used for optical elements, lenses, and mirrors, and more preferably used for optical fibers, optical waveguides, and lenses. In this specification, although the optical fiber which is a particularly preferable embodiment will be described in detail, the copolymer of the present invention can be preferably applied to other optical members.

Hereinafter, an embodiment of a method for producing an optical member using the copolymer of the present invention will be described. In the embodiment described below, the copolymer of the present invention is applied to the formation of a plastic optical member having a core portion and a cladding portion. Using the solution or solid of the copolymer, for example, a plastic optical fiber preform is produced by the following method ((1) is described in JP-A-11-109144 (page 7, embodiment of the invention)). can do. However, the present invention is not limited to these.
(1) A thermoplastic resin is melted, a melt of the copolymer of the present invention is injected into the central portion thereof, and a refractive index adjusting agent or a copolymer containing the refractive index adjusting agent is injected into the central portion of the thermoplastic resin. A method of manufacturing a preform by thermally diffusing the material.
(2) Using a rotating glass tube or the like, a tube made of a hollow thermoplastic resin is formed in the outermost layer, and the solution of the copolymer of the present invention and a refractive index adjusting agent are injected into this hollow portion to rotate. A method for producing a preform by gradually increasing the amount of addition of the refractive index adjusting agent while volatilizing an organic solvent to form a layer by reducing pressure or heating.
(3) A method for producing a preform without including a refractive index adjusting agent in the production method according to (1) and (2).
(4) Using a rotating glass tube or the like, a tube made of a hollow thermoplastic resin is formed in the outermost layer, and the copolymer of the present invention (a copolymer having a refractive index different from that of the thermoplastic resin) is formed in the hollow portion. The refractive index is preferably higher than that of the thermoplastic resin, and the difference in refractive index is preferably 0.001 or more, more preferably 0.005 or more, and still more preferably 0.01 or more. A hollow preform (PF) by injecting a polymerizable composition (a composition containing a monomer, a polymerization initiator, a chain transfer agent if necessary, and a refractive index adjusting agent if necessary) and polymerizing with heat or light.
(5) In (4), when the polymerizable composition is polymerized stepwise to produce a hollow PF of a plurality of concentric rotating polymers, a plurality of types of monomers having different refractive indexes are used. A method of manufacturing a preform while gradually increasing its refractive index toward the center. In this case, the outermost thermoplastic resin is not essential.

  The thermoplastic resin used in the above method may be any thermoplastic resin that provides sufficiently high mechanical strength at the operating temperature of the plastic optical fiber, but preferably has a tensile elastic modulus at room temperature of 2000 MPa or more. Among these, particularly representative ones include polymethacrylate resins, polycarbonate resins, linear polyester resins, polyamide resins, acrylonitrile / styrene copolymer resins (AS resins), acrylonitrile / butadiene / styrene copolymers. Examples thereof include polymer resins (ABS resins), polyacetal resins, cyclic polyolefin resins, polystyrene resins, tetrafluoroethylene copolymer resins, chlorotrifluoroethylene copolymer resins, and the like. In addition, it was confirmed that the copolymer of the present invention usually has no problem in the adhesion with the thermoplastic resin.

The refractive index modifier is also called a dopant, and is a compound different from the refractive index of the polymer or polymerizable monomer used in combination. The refractive index difference is preferably 0.005 or more. The dopant has the property that the polymer containing it has a higher refractive index than the additive-free polymer. These have a difference in solubility parameter of 7 (cal / cm in comparison with a polymer produced by synthesis of monomers as described in Japanese Patent No. 3333292 and JP-A-5-173026. ³ ) Within ^1/2 , the difference in refractive index is 0.001 or more, and the polymer containing this has the property that the refractive index changes compared to the additive-free polymer. Any of those that can be stably coexistent with each other and that are stable under the polymerization conditions (polymerization conditions such as heating and pressurization) of the polymerizable monomer that is the above-described raw material can be used.

  In addition, the dopant may be a polymerizable compound, and when a dopant of the polymerizable compound is used, a copolymer containing this as a copolymerization component has an increased refractive index as compared with a polymer not containing this. It is preferable to use those having the property of Further, a dopant having the above-mentioned properties, which can stably coexist with a polymer, and is stable under the polymerization conditions (polymerization conditions such as heating and pressurization) of the polymerizable monomer as the raw material described above is used as a dopant. Can be used. In the present invention, the refractive index distribution type core portion may be formed by selecting a plurality of types of monomers having different refractive indexes and gradually changing the composition ratio. By forming a gradient index core using a dopant, the resulting optical member can be a gradient index plastic optical fiber having a wide transmission band that has been stretched into a filament, or a plug adjusted to a desired diameter. The reform is sliced to form a flat lens (GRIN (GRreaded Index) lens).

  Examples of the dopant include benzyl benzoate (BEN), diphenyl sulfide (DPS), triphenyl phosphate (TPP), and phthalic acid as described in Japanese Patent No. 3333292 and JP-A-11-142657. Benzyl n-butyl (BBP), diphenyl phthalate (DPP), biphenyl (DP), diphenylmethane (DPM), tricresyl phosphate (TCP), diphenyl sulfoxide (DPSO), diphenyl sulfide, bis (trimethylphenyl) sulfide, diphenyl sulfide Derivatives, dithian derivatives, 1,2-dibromotetrafluorobenzene, 1,3-dibromotetrafluorobenzene, 1,4-dibromotetrafluorobenzene, 2-bromotetrafluorobenzotrifluoride, chloropentafluorobenze , Bromopentafluorobenzene, iodo pentafluorobenzene, deca fluoro benzophenone, perfluoro acetophenone, perfluoro biphenyl, chloro-heptafluoro-naphthalene, and the like bromo heptafluoro naphthalene. The sulfurized diphenyl derivative and dithiane derivative are appropriately selected from the compounds specifically shown below. Among them, BEN, DPS, TPP, DPSO, sulfurized diphenyl derivatives, and dithian derivatives are preferable. In addition, compounds obtained by substituting hydrogen atoms present in these compounds with deuterium atoms can also be used for the purpose of improving transparency in a wide wavelength region. Examples of the polymerizable compound include tribromophenyl methacrylate. When a polymerizable compound is used as the refractive index adjusting component, it is more difficult to control various properties (particularly optical properties) because the polymerizable monomer and the polymerizable refractive index adjusting component are copolymerized when forming the matrix. However, it may be advantageous in terms of heat resistance.

The following methods (I) and (II) are preferable as a method for producing a core portion having a graded-index (GI) type refractive index profile using the dopant and the copolymer of the present invention. However, it is not limited to these methods.
(I) A cylindrical shaped product a made of a fluorine-containing copolymer and a cylindrical shaped product b made of the copolymer of the present invention containing a dopant are produced by melt extrusion molding. By inserting the molded body b into the molded body a and heating it, the dopant in the molded body b is melted and diffused to form a GI-type refractive index distribution. This method is an embodiment of the method (1).
(II) A solution of a fluorinated copolymer is poured into a cylindrical molded body, and the pressure is reduced while rotating to remove the solvent, and a layer made of the fluorinated copolymer is formed on the inner surface. Next, a solution of the copolymer containing the dopant is injected, the pressure is reduced while rotating, and the solvent is removed to form a copolymer layer containing the dopant on the inner surface of the fluorine-containing copolymer layer. While increasing the addition amount of the dopant, the same operation is repeated to form a plurality of layers, thereby giving a GI-type refractive index distribution. This method is an embodiment of the method (2).

  In addition, other additives can be added as long as the optical transmission performance is not deteriorated. For example, a stabilizer can be added for the purpose of improving weather resistance and durability. Further, for the purpose of improving optical transmission performance, a stimulated emission functional compound for optical signal amplification can be added. By adding the compound, the attenuated signal light can be amplified by the excitation light, and the transmission distance can be improved. For example, it can be used as a fiber amplifier in a part of the optical transmission link. These additives can also be added by polymerization after adding to the raw material monomer.

  A plastic optical fiber can be produced by melt-drawing a preform. For stretching, for example, it is preferable that the preform is heated and melted by passing through the inside of a heating furnace (for example, a cylindrical heating furnace) and then continuously stretched and spun. Although heating temperature can be suitably determined according to the material etc. of preform, generally 180-250 degreeC is preferable. The stretching conditions (stretching temperature and the like) can be appropriately determined in consideration of the diameter of the obtained preform, the diameter of the desired plastic optical fiber, the material used, and the like. In particular, since the refractive index distribution type optical fiber has a structure in which the refractive index changes from the center direction of the cross section toward the circumference, it is necessary to uniformly heat and stretch and spin so as not to destroy this distribution. Therefore, it is preferable to use a cylindrical heating furnace or the like that can uniformly heat the preform in the cross-sectional direction for heating the preform. The heating furnace preferably has a temperature distribution in the direction of the drawing axis. A narrow melted portion is preferable because the shape of the refractive index profile is less likely to be distorted and the yield is increased. Specifically, preheating and gradual cooling are preferably performed before and after the melting region so that the region of the melting portion becomes narrow. Furthermore, the heat source used for the melting region is more preferably one that can supply high output energy even to a narrow region such as a laser.

  As described above, a hollow preform may be obtained depending on the preform manufacturing method. When stretching a preform having such a shape, stretching is preferably performed under reduced pressure.

  In order to maintain the linearity and its roundness, the drawing is preferably performed using a drawing spinning apparatus having an alignment mechanism that keeps the center position constant. By selecting the drawing conditions, the orientation of the polymer of the fiber can be controlled, and the mechanical properties such as the bending performance of the fiber obtained by drawing and the heat shrinkage can also be controlled. Further, the tension during drawing can be set to 10 g or more in order to orient the molten plastic as described in JP-A-7-234322, or described in JP-A-7-234324. As described above, the amount is preferably 100 g or less so as not to leave a strain after melt stretching. Furthermore, as described in JP-A-8-106015, a method of performing a preheating step at the time of stretching may be employed. Regarding the fiber obtained by the above method, the bending and lateral pressure characteristics of the fiber can be improved by defining the breaking elongation and hardness of the obtained wire as described in JP-A-7-244220. Further, as in JP-A-8-54521, a transmission layer can be further improved by providing a low refractive index layer on the outer periphery to function as a reflective layer.

  The plastic optical fiber manufactured by the above-described method can be used for various purposes as it is. In addition, for the purpose of protection and reinforcement, the present invention can be used for various applications in the form having a coating layer on the outside, the form having a fiber layer, and / or a state where a plurality of fibers are bundled. The coating process is performed, for example, by passing the fiber strands through opposed dies having holes through which the fiber strands pass, filling the molten coating resin between the opposed dies, and moving the fiber strands between the dies. Fiber can be obtained. In order to protect the coating layer from stress on the internal fiber when it is flexible, it is desirable that the coating layer is not fused with the fiber strand. Further, at this time, since the fiber strand is thermally damaged by being in contact with the molten resin, it is desirable to select a resin that can be melted at a moving speed or low temperature so as to suppress damage as much as possible. At this time, the thickness of the coating layer depends on the melting temperature of the coating material, the wire drawing speed, and the cooling temperature of the coating layer. In addition, a method of polymerizing a monomer applied to the optical member, a method of winding a sheet, a method of passing the optical member through an extruded hollow tube, and the like are known.

  By covering the strands, it is possible to manufacture a plastic optical fiber cable. At that time, as the form of the coating, a close-contact type coating in which the interface between the coating material and the plastic optical fiber is in contact with the entire circumference, and a loose type coating having a gap at the interface between the coating material and the plastic optical fiber There is. In the loose type coating, for example, when the coating layer is peeled off at the connection portion with the connector or the like, moisture may enter from the gaps at the end face and diffuse in the longitudinal direction. However, in the case of a loose-type coating, since the coating and the strand are not in close contact, most of the damage such as stress and heat applied to the cable can be mitigated by the coating layer, and the damage to the strand can be reduced. Since it can be reduced, it can be preferably used depending on the purpose of use. As for the propagation of moisture, by filling the voids with fluid semi-solid or powdery particles, moisture propagation from the end face can be prevented, and heat and A coating with higher performance can be formed by having functions different from moisture propagation prevention such as improvement of mechanical functions. In order to produce a loose type coating, the void layer can be formed by adjusting the position of the extrusion nipple of the crosshead die and adjusting the pressure reducing device. The thickness of the gap layer can be adjusted by pressurizing / depressurizing the nipple thickness and the gap layer.

  Furthermore, you may provide a coating layer (secondary coating layer) further in the outer periphery of a coating layer (primary coating layer) as needed. Flame retardants, UV absorbers, antioxidants, radical scavengers, photosensitizers, lubricants, etc. may be introduced into the secondary coating layer, and as long as moisture permeation resistance is satisfied, Introduction is possible. Some flame retardants contain halogen-containing resins such as bromine, additives, and phosphorus, but metal hydroxides are added as flame retardants from the standpoint of safety such as reduction of toxic gases. It is becoming mainstream. Since the metal hydroxide has moisture as crystal water inside, and the attached water cannot be completely removed during the manufacturing process, the flame retardant coating by the metal hydroxide is the moisture-permeable coating of the present invention. It is desirable to provide as an outer layer coating (secondary coating layer) of (primary coating layer). Moreover, in order to provide a plurality of functions, coatings having various functions may be laminated. For example, in addition to flame retardancy as in the present invention, a barrier layer for suppressing moisture absorption of the wire and a moisture absorbing material for removing moisture, such as a moisture absorbing tape or moisture absorbing gel, are provided in the coating layer or between the coating layers. In addition, a flexible material layer for relaxing stress at the time of flexibility, a cushioning material such as a foam layer, a reinforcing layer for increasing rigidity, and the like can be selected and provided depending on the application. In addition to the resin, if the thermoplastic resin contains a fiber having a high elastic modulus (so-called tensile fiber) and / or a highly rigid metal wire, the mechanical strength of the resulting cable can be reinforced. It is preferable because it is possible. Examples of the tensile strength fiber include aramid fiber, polyester fiber, and polyamide fiber. Examples of the metal wire include stainless steel wire, zinc alloy wire, copper wire and the like. None of these are limited to those described above. In addition, a metal tube exterior for protection, an aerial support line, and a mechanism for improving workability during wiring can be incorporated.

  In addition, depending on the type of use, the cable shape is a collective cable in which the strands are concentrically arranged, an aspect called a tape core wire arranged in a row, and a collective cable in which they are gathered together with a presser roll or wrap sheath The form can be selected according to the situation.

  In addition, the cable using the optical fiber of the present invention has a higher tolerance than the conventional optical fiber with respect to the axis deviation, so it can be used for joining by butt, but it is connected using an optical connector for connection at the end. It is preferable to securely fix the portion. As the connector, it is possible to use various commercially available connectors such as PN type, SMA type, SMI type, F05 type, MU type, FC type, and SC type that are generally known.

  The optical fiber and the optical signal transmission system using the optical fiber cable of the present invention include optical signal processing including optical components such as various light emitting elements and light receiving elements, optical switches, optical isolators, optical integrated circuits, and optical transceiver modules. It consists of devices. Moreover, you may combine with another optical fiber etc. as needed. Any known technique can be applied as a technique related to them. For example, the basic and actual of plastic optical fiber (published by NTS Corporation), Nikkei Electronics 2001.1.2.3, pp. 110-127 “Printed Wiring You can refer to "This time, optical components are mounted on the board." Combined with various technologies described in the above documents, internal wiring in computers and various digital devices, internal wiring in vehicles and ships, optical terminals and digital devices, optical links between digital devices, general households and housing complexes・ Suitable for optical transmission systems suitable for short distances such as high-speed, large-capacity data communications and control applications that are not affected by electromagnetic waves, including optical LANs in factories, offices, hospitals, schools, etc. Can be used.

  Further, IEICE TRANS. ELECTRON. , VOL. E84-C, No. 3, MARCH 2001, p. 339-344 “High-Uniformity Star Coupler Using Diffused Light Transmission”, Journal of Japan Institute of Electronics Packaging, Vol. 3, No. 6,2000, pages 476 to 480, and those described in "Interconnection with Optical Sheet Bus Technology", and Japanese Patent Laid-Open Nos. 10-123350, 2002-90571, 2001-290055, etc. Optical buses described: Japanese Patent Laid-Open Nos. 2001-74971, 2000-329962, 2001-74966, 2001-74968, 2001-318263, 2001-31840, etc. Optical star couplers described in JP 2000-241655 A, etc .; JP 2002-624457, JP 2002-101044, JP 2001-305395 A, etc. Optical signal transmission apparatus and optical data bus system; optical signal processing described in JP-A-2002-23011, etc. Apparatus: Optical signal cross-connect system described in Japanese Patent Application Laid-Open No. 2001-86537, etc .; Optical transmission system described in Japanese Patent Application Laid-Open No. 2002-26815, etc .; Japanese Patent Application Laid-Open No. 2001-339554, Japanese Patent Application Laid-Open No. 2001-339555, etc. Multi-function system described in the official gazette; and various optical waveguides, optical splitters, optical couplers, optical multiplexers, optical demultiplexers, etc., combined with transmission / reception that is multiplexed, etc. A system can be constructed. In addition to the above optical transmission applications, it can also be used in the fields of illumination, energy transmission, illumination, and sensors.

 EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples. However, materials, reagents, substance amounts and ratios, operations, and the like shown in the following examples can be appropriately changed without departing from the spirit of the present invention. Therefore, the scope of the present invention is not limited to the following specific examples. In the following, all parts and% are based on mass unless otherwise specified.

Average molecular weight The average molecular weight of the copolymer was measured by gel permeation chromatography (GPC) by dissolving a part of the obtained copolymer in tetrahydrofuran (THF). The average molecular weight of the copolymer in the present invention is a value using polystyrene as a standard substance.

Glass transition temperature The glass transition temperature was measured by raising the temperature at 10 ° C./min using a differential scanning calorimeter (product number: DSC6200, manufactured by Seiko Denshi).

Tensile test First, a polymer film having a thickness of 200 μm was prepared from a powdered polymer after reprecipitation purification using a high-temperature press, and a 100 mm × 500 mm film was cut out therefrom to obtain a test piece.
Using this test piece, the elastic modulus and tensile breaking strength were measured with a Tensilon universal testing machine (product number: RTC-1210A, manufactured by ORIENTEC) at a tensile speed of 3 mm / min and a measurement temperature of 25 ° C.

Refractive index Using a refractometer (DR-M2, manufactured by ATAGO), the refractive index of the film specimen prepared above was measured at an observation wavelength of 589 nm and a measurement temperature of 25 ° C.

[Example 1] Synthesis example of copolymer 1 2-trifluoroethyl-α-trifluoromethyl acrylate (TFETFMA) (A3) / 1,4-dioxene (B1) / α-trifluoromethylacrylic acid (TFMAA) (C2 -1).
That is, in a test tube having a capacity of 10 ml, 4.44 parts (20 mmol) of TFETFMA (manufactured by Tosoh Corporation), 1.72 parts (20 mmol) of 1,4-dioxene (manufactured by Tokyo Chemical Industry), 0.056 parts of TFMAA (manufactured by Tosoh Corporation) ( 0.4 mmol), dimethyl 2,2'-azobis (2-methylpropionate) (manufactured by Wako Pure Chemical Industries, Ltd.), 0.00092 parts (0.004 mmol), purged with argon, and sealed with a silicon stopper. Polymerization was carried out at 50 ° C. for 24 hours. The obtained rod-shaped polymer was dissolved in THF, poured into hexane, and subjected to reprecipitation purification twice to obtain 4.6 g of a copolymer having a Tg = 158 ° C. and a weight average molecular weight (Mw) = 365,000. . The copolymer was dissolved in ethyl acetate, THF, acetone and the like. The copolymer was dissolved in THF, coated on a glass slide, and the solvent (THF) was distilled off. The resulting film was completely transparent. As a result of measuring the strength with Tensilon, the elastic modulus of the copolymer was 1730 MPa, and the tensile strength was 26 MPa. The refractive index of the copolymer was 1.41.

Example 2 Synthesis Example of Copolymer 2 The copolymer 2 was synthesized using TFET FMA (A3) / 1,4-dioxene (B1) / maleic anhydride (C2-15).
That is, 1.72-part (20 mmol) of 1,4-dioxene (manufactured by Tokyo Chemical Industry), 4.44 parts (20 mmol) of TFET FMA (manufactured by Tosoh Corp.), 0.4% (20 mmol) of maleic anhydride (manufactured by Wako Pure Chemical Industries) 039 parts (0.4 mmol), dimethyl 2,2′-azobis (2-methylpropionate) (manufactured by Wako Pure Chemical Industries, Ltd.), 0.00092 parts (0.004 mmol) were charged, purged with argon, and sealed with a silicon stopper And polymerized at 50 ° C. for 24 hours. The obtained rod-shaped polymer was dissolved in THF, poured into hexane, and subjected to reprecipitation purification twice to obtain 4.4 g of a copolymer having a Tg = 158 ° C. and a weight average molecular weight (Mw) = 328,000. It was. The copolymer was dissolved in ethyl acetate, THF, acetone and the like. The polymer was dissolved in THF, coated on a glass slide, and the solvent (THF) was distilled off. The resulting film was completely transparent. As a result of measuring the strength with Tensilon, the elastic modulus of the copolymer was 1850 MPa, and the tensile strength was 30 MPa. The refractive index of the copolymer was 1.41.

Example 3 Synthesis Example of Copolymer 3 Using 1H, 1H, 3H-tetrafluoropropyl-α-trifluoromethyl acrylate (TFPTTFMA) (A4) / 1,4-dioxene (B1) / TFMAA (C2-1) And synthesized.
That is, 1,4-dioxene (manufactured by Tokyo Chemical Industry) 1.72 parts (20 mmol), TFPTFMA 5.08 parts (20 mmol), TFMAA (manufactured by Tosoh) 0.056 parts (0.4 mmol), Dimethyl 2,2′-azobis (2-methylpropionate) (manufactured by Wako Pure Chemical Industries, Ltd.) 0.00194 (0.01 mmol) was charged, purged with argon, sealed with a silicon stopper, and sealed at 50 ° C. for 24 hours. Polymerization was performed. The obtained rod-shaped polymer was dissolved in THF, poured into hexane, and subjected to reprecipitation purification twice to obtain 5.1 g of a copolymer having Tg = 145 ° C. and a weight average molecular weight (Mw) = 148000. The copolymer was dissolved in ethyl acetate, THF, acetone and the like. The copolymer was dissolved in THF, coated on a glass slide, and the solvent (THF) was distilled off. The resulting film was completely transparent. As a result of measuring the strength with Tensilon, the elastic modulus of the copolymer was 1550 MPa, and the tensile strength was 27 MPa. The refractive index of the copolymer was 1.41.

Example 4 Synthesis Example of Copolymer 4 The copolymer 4 was synthesized using TFPTFMA (A4) / 1,4-dioxene (B1) / maleic anhydride (C2-15).
In a 50 ml eggplant flask, 1.72-part (20 mmol) of 1,4-dioxene (manufactured by Tokyo Chemical Industry), 5.08 parts (20 mmol) of TFPTFMA (manufactured by Tosoh Corporation), 0.039 parts of maleic anhydride (manufactured by Wako Pure Chemical Industries, Ltd.) (0.4 mmol), dimethyl 2,2′-azobis (2-methylpropionate) (manufactured by Wako Pure Chemical Industries, Ltd.), 0.00194 parts (0.01 mmol), were added, and 6.8 parts of methyl ethyl ketone was added thereto. After replacing with argon, the tube was sealed with a silicon stopper, and solution polymerization was performed at 50 ° C. for 24 hours. The obtained polymer solution was poured into hexane as it was, and reprecipitation purification was performed twice to obtain 4.9 g of a copolymer having a Tg = 145 ° C. and a weight average molecular weight (Mw) = 185000. The polymer was dissolved in ethyl acetate, THF, acetone and the like. The polymer was dissolved in THF, coated on a glass slide, and the solvent (THF) was distilled off. The resulting film was completely transparent. As a result of measuring the strength with Tensilon, the elastic modulus of the copolymer was 1610 MPa, and the tensile strength was 15 MPa. The refractive index of the copolymer was 1.41.

[Comparative Example 1]
It was synthesized by bulk polymerization using TFET FMA / styrene (St).
In a test tube with a capacity of 10 ml, 2.4 parts (23.2 mmol) of St (manufactured by Wako Pure Chemical Industries), 5.15 parts (23.2 mmol) of TFET FMA (manufactured by Tosoh), dimethyl 2,2′-azobis (2-methylpro) Pionate) (manufactured by Wako Pure Chemical Industries, Ltd.) was charged in 0.038 parts (0.23 mmol), purged with argon, sealed with a silicon stopper, and polymerized at 50 ° C. for 24 hours. Polymerization was fired and a rod-shaped polymer could not be obtained. The polymer was dissolved in THF, poured into hexane, and subjected to reprecipitation purification twice to obtain 6.9 g of a copolymer having Tg = 85 ° C. and weight average molecular weight (Mw) = 398000. The copolymer was dissolved in ethyl acetate, THF, acetone and the like. The copolymer was dissolved in THF, coated on a glass slide, and the solvent (THF) was distilled off. The resulting film was completely transparent. As a result of measuring the strength with Tensilon, the elastic modulus of the copolymer was 1670 MPa, and the tensile strength was 34 MPa. The refractive index of the copolymer was 1.465.

[Comparative Example 2]
It was synthesized by solution polymerization using TFET FMA / styrene (St).
In a 50 ml eggplant flask, 4.8 parts (46.4 mmol) of St (manufactured by Wako Pure Chemical Industries), 10.3 parts (20 mmol) of TFET FMA (manufactured by Tosoh), dimethyl 2,2′-azobis (2-methylpropionate) ) (Manufactured by Wako Pure Chemical Industries, Ltd.) was charged with 0.076 parts (0.463 mmol), and 20 parts of toluene was added thereto, followed by substitution with argon, followed by solution polymerization at 65 ° C. for 24 hours. The obtained polymer solution was poured into hexane as it was, and reprecipitation purification was performed twice to obtain 13.4 g of a copolymer having a Tg = 85 ° C. and a weight average molecular weight (Mw) = 78000. The polymer was dissolved in ethyl acetate, THF, acetone and the like. The polymer was dissolved in THF, coated on a glass slide, and the solvent (THF) was distilled off. The resulting film was completely transparent. As a result of measuring the strength with Tensilon, the elastic modulus of the copolymer was 1440 MPa, and the tensile strength was 9.5 MPa. The refractive index of the copolymer was 1.465.

Tables 1 and 2 describe the measurement results for the polymers synthesized in Examples 1 to 5 and Comparative Example 1.

[Example 5] Example of production of step index type optical fiber using copolymer 1 TFET FMA (A3) in a hollow pipe of tetrafluoroethylene / vinylidene fluoride copolymer (refractive index 1.36) produced by melt extrusion molding (Manufactured by Tosoh) 66.6 parts (0.3 mol), 1,4-dioxene (B1) (manufactured by Tokyo Kasei) 25.8 parts (0.3 mol), TFMAA (C2-1) (0.84 parts by Tosoh) (0.006 mol), 0.0138 part (0.0006 mol) of dimethyl 2,2′-azobis (2-methylpropionate) (manufactured by Wako Pure Chemical Industries, Ltd.), purged with argon, and then at 50 ° C. for 24 hours. The polymerization was further carried out for 48 hours at 90 ° C. The preform obtained was dried under reduced pressure at 50 ° C. for 24 hours, and then melt-stretched at 230 to 270 ° C. to obtain a step index. Transmission loss at .650nm got the type of optical fiber was 150 dB / miles.

[Example 6] Example of production of step index type optical fiber using copolymer 3 TFPTFMA (manufactured by Tosoh Corporation) in a hollow pipe of tetrafluoroethylene / vinylidene fluoride copolymer (refractive index 1.36) produced by melt extrusion molding ) 76.2 (0.3 mol) (A4), 1,4-dioxene (B1) (manufactured by Tokyo Chemical Industry) 25.8 parts (0.3 mol), TFMAA (C2-1) (0.84 parts by Tosoh ( 0.006 mol), dimethyl 2,2′-azobis (2-methylpropionate) (manufactured by Wako Pure Chemical Industries, Ltd.), 0.0345 parts (0.0035 mol), and after purging with argon, at 50 ° C. for 24 hours, The polymerization was carried out for 48 hours at 90 ° C. The obtained preform was dried under reduced pressure at 50 ° C. for 24 hours, and then melt stretched at 230 to 270 ° C. Transmission loss of the optical fiber at .650nm got in was 160 dB / miles.

[Comparative Example 3]
In a hollow pipe of tetrafluoroethylene / vinylidene fluoride copolymer (refractive index 1.36) produced by melt extrusion molding, 87.2 parts (0.3 mol) of TFET FMA (manufactured by Tosoh), 30 parts of isobutyl vinyl ether (0 .3 mol), dimethyl 2,2′-azobis (2-methylpropionate) (manufactured by Wako Pure Chemical Industries, Ltd.), 0.0345 parts (0.0035 mol) parts were charged, and after substitution with argon, polymerization started. It suddenly boiled and did not lead to a preform.

Claims (4)

From the repeating unit derived from the monomer (A) represented by the following general formula (1), the repeating unit derived from the monomer (B) represented by the following general formula (2), and a carboxyl group, a hydroxyl group and an epoxy group at the terminal A vinyl monomer (C) -containing repeating unit having at least one group selected from the group consisting of a monomer (A) and a monomer (B) in a molar ratio of 1: 9 to 9: 1; C) Amorphous copolymer having repeating units derived from 0.01 to 30 mol% of the whole and having a weight average molecular weight of 1,000 to 1,000,000 .

(In General Formula (1), R ¹ and R ² each independently represent a normal hydrogen atom ( ¹ H) or a deuterium atom ( ² H). R ³ represents a normal hydrogen atom ( ¹ H). ), A deuterium atom ( ² H), an aryl group or an alkyl group.)
General formula (2)

(In the general formula (2), R ⁴ and R ⁵ each independently represent a normal hydrogen atom ( ¹ H), deuterium atom ( ² H), halogen atom or alkyl group, and R ⁶ , R ⁷ , R ⁸ and R ⁹ each independently represent a normal hydrogen atom ( ¹ H), deuterium atom ( ² H), halogen atom, cyano group, nitro group, aryl group or alkyl group, and R ^{6 to} R Two selected from ⁹ may be bonded to each other to form a cyclic structure.) 2. The amorphous copolymer according to claim 1, wherein in the general formula (2), R ^{4 to} R ⁹ are each independently a normal hydrogen atom ( ¹ H) or a deuterium atom ( ² H). An optical member comprising the amorphous copolymer according to claim 1. A plastic optical fiber comprising the amorphous copolymer according to claim 1.