Optical fiber and method for manufacturing optical fiber

Abstract

An optical fiber comprises: a glass fiber including a core and a cladding, and a coating resin layer in contact with the glass fiber and coating the glass fiber, the coating resin layer comprising a primary resin layer in contact with the glass fiber and coating the glass fiber, and a secondary resin layer coating the primary resin layer, the primary resin layer comprising a cured product of a first resin composition comprising a photopolymerizable compound and a phosphine oxide-based photopolymerization initiator, the secondary resin layer comprising a cured product of a second resin composition comprising a photopolymerizable compound and a phosphine oxide-based photopolymerization initiator, and the amount of unreacted phosphine oxide-based photopolymerization initiator in the coating resin layer is 0.5% by mass or less.

Description

Technical Field

[0001] The present disclosure relates to optical fibers and methods of manufacturing optical fibers.

[0002] This application claims the priority based on Japanese application No. 2020-148903 filed on September 4, 2020, and cites all the contents described in the Japanese application. Background Art

[0003] Generally, an optical fiber includes a coating resin layer for protecting a glass fiber as a light transmission body. The coating resin layer is composed of, for example, two layers: a primary resin layer in contact with the glass fiber and a secondary resin layer formed on the outer layer of the primary resin layer.

[0004] When connecting optical fibers, it is necessary to remove a portion of the coating resin layer from the glass fiber. Patent Document 1 discloses that the removability of the coating resin layer can be adjusted by paying attention to the bonding angle of mineral oil to the primary resin layer and the elastic modulus of the secondary resin layer.

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent Application Publication No. 2019-61157 Summary of the invention

[0008] An optical fiber involved in one embodiment of the present disclosure comprises: a glass fiber including a core and a cladding, and a coating resin layer in contact with the glass fiber and coating the glass fiber, the coating resin layer comprising a primary resin layer in contact with the glass fiber and coating the glass fiber, and a secondary resin layer coating the primary resin layer, the primary resin layer comprising a cured product of a first resin composition comprising a photopolymerizable compound and a phosphine oxide-based photopolymerization initiator, the secondary resin layer comprising a cured product of a second resin composition comprising a photopolymerizable compound and a phosphine oxide-based photopolymerization initiator, and the amount of unreacted phosphine oxide-based photopolymerization initiator in the coating resin layer is 0.5% by mass or less. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] [ Figure 1 ] Figure 1 This is a schematic cross-sectional view showing an example of the optical fiber according to the present embodiment. DETAILED DESCRIPTION

[0010] [Problems to be Solved by the Present Disclosure]

[0011] When the optical fiber is exposed to light such as a fluorescent lamp, the curing reaction of the coating resin layer proceeds over time, and the adhesion of the coating resin layer to the glass fiber may become too high. If the adhesion of the coating resin layer to the glass fiber is too high, when the coating resin layer is removed from the glass fiber, a portion of the coating resin layer may remain on the periphery of the glass fiber.

[0012] An object of the present disclosure is to provide an optical fiber in which the change in coating removability over time is reduced, and a method for producing the optical fiber.

[0013] [Effects of the present disclosure]

[0014] According to the present disclosure, it is possible to provide an optical fiber in which the change in coating removability over time is reduced, and a method for producing the optical fiber.

[0015] [Description of Embodiments of the Present Disclosure]

[0016] First, the contents of the embodiments of the present disclosure are listed and described. An optical fiber involved in one embodiment of the present disclosure comprises: a glass fiber including a core and a cladding, and a coating resin layer in contact with and coating the glass fiber. The coating resin layer comprises a primary resin layer in contact with and coating the glass fiber, and a secondary resin layer coating the primary resin layer. The primary resin layer comprises a cured product of a first resin composition containing a photopolymerizable compound and a phosphine oxide-based photopolymerization initiator, and the secondary resin layer comprises a cured product of a second resin composition containing a photopolymerizable compound and a phosphine oxide-based photopolymerization initiator. The amount of unreacted phosphine oxide-based photopolymerization initiator in the coating resin layer is 0.5% by mass or less.

[0017] When the optical fiber is exposed to light from a fluorescent lamp or the like, the unreacted photopolymerization initiator contained in the coating resin layer may crack, and the coating resin layer may be cured, making it difficult to remove the coating resin layer from the glass fiber. In particular, the reactivity of phosphine oxide-based photopolymerization initiators is high, so it is important to reduce the unreacted amount of phosphine oxide-based photopolymerization initiators in the coating resin layer. The optical fiber involved in this embodiment can reduce the change in coating removability over time.

[0018] From the viewpoint of improving surface curability, the second resin composition may further contain an acetophenone-based photopolymerization initiator. From the viewpoint of reducing the cost of the resin composition, the first resin composition and the second resin composition may not contain a photopolymerization initiator other than the phosphine oxide-based photopolymerization initiator.

[0019] From the viewpoint of further reducing the change in coating removability over time, at least one of the first resin composition or the second resin composition may contain nonylphenol polyethylene glycol acrylate as a photopolymerizable compound, and the amount of unreacted nonylphenol polyethylene glycol acrylate in the coating resin layer may be less than 1.0 mass %.

[0020] The method for manufacturing an optical fiber according to the present embodiment includes: a coating step of coating a first resin composition and a second resin composition on a glass fiber having a temperature of 80° C. or less in a manner that the first resin composition and the second resin composition are sequentially separated from the glass fiber; and a curing step of curing the resin composition by irradiating ultraviolet rays after the coating step. By setting the temperature of the glass fiber immediately before the resin composition is coated on the glass fiber to 80° C. or less, it is easy to reduce the unreacted ratio of the phosphine oxide-based photopolymerization initiator, thereby being able to suppress the coating resin layer from curing over time.

[0021] In the curing step, ultraviolet rays emitted from an ultraviolet light emitting diode (ultraviolet LED) may be irradiated, thereby further reducing the unreacted ratio of the phosphine oxide-based photopolymerization initiator.

[0022] From the viewpoint of curing the inside of the coating resin layer in the curing step, the wavelength of the ultraviolet rays may be within a range of 350 nm to 405 nm.

[0023] [Detailed description of embodiments of the present disclosure]

[0024] Specific examples of the optical fiber and the manufacturing method thereof involved in the present embodiment will be described with reference to the accompanying drawings as needed. It should be noted that the present disclosure is not limited to these examples, but is represented by the claims, and is intended to include all changes within the meaning and scope equivalent to the claims. In the following description, the same elements in the description of the drawings are marked with the same symbols, and repeated descriptions are omitted.

[0025] (optical fiber)

[0026] Figure 1 1 is a cross-sectional view showing the structure of an optical fiber according to one embodiment. Figure 1 , a cross section perpendicular to the central axis direction (optical axis direction) of the optical fiber 1 is shown. Figure 1 As shown, the optical fiber 1 of the present embodiment includes a glass fiber 10 as a light transmission body and a coating resin layer 20 which is in contact with the glass fiber 10 and covers the glass fiber 10 .

[0027] The glass fiber 10 includes: a core 12, and a cladding 14 covering the core 12. The glass fiber 10 is a component made of glass, for example, made of silica (SiO2) glass. The glass fiber 10 transmits light introduced into the optical fiber 1. The core 12 is, for example, arranged in a region including the central axis of the glass fiber 10. The core 12 is, for example, composed of pure SiO2 glass or a substance containing GeO2 and / or fluorine elements in SiO2 glass. The cladding 14 is arranged in a region surrounding the core 12. The cladding 14 has a refractive index lower than that of the core 12. The cladding 14 is, for example, composed of pure SiO2 glass or SiO2 glass to which fluorine elements are added.

[0028] The coating resin layer 20 is an ultraviolet curing resin layer covering the cladding 14. The coating resin layer 20 includes: a primary resin layer 22 covering the outer periphery of the glass fiber 10, and a secondary resin layer 24 covering the outer periphery of the primary resin layer 22. The primary resin layer 22 is in contact with the outer peripheral surface of the cladding 14 and covers the entire cladding 14. The secondary resin layer 24 is in contact with the outer peripheral surface of the primary resin layer 22 and covers the entire primary resin layer 22. The thickness of the primary resin layer 22 is, for example, not less than 10 μm and not more than 50 μm. The thickness of the secondary resin layer 24 is, for example, not less than 10 μm and not more than 40 μm. The coating resin layer 20 may further include a colored resin layer covering the outer periphery of the secondary resin layer 24.

[0029] The primary resin layer 22 includes a cured product of a first resin composition containing a photopolymerizable compound and a phosphine oxide-based photopolymerization initiator. The secondary resin layer 24 includes a cured product of a second resin composition containing a photopolymerizable compound and a phosphine oxide-based photopolymerization initiator. The amount of unreacted phosphine oxide-based photopolymerization initiator in the coating resin layer 20 is 0.5% by mass or less. Thus, the change in the coating removability of the optical fiber over time can be reduced. The amount of unreacted phosphine oxide-based photopolymerization initiator is preferably 0.49% by mass or less, more preferably 0.48% by mass or less, and further preferably 0.45% by mass or less. The lower limit of the amount of unreacted phosphine oxide-based photopolymerization initiator is not particularly limited, and may be 0.01% by mass or more, 0.03% by mass or more, or 0.05% by mass or more.

[0030] Examples of the phosphine oxide-based photopolymerization initiator include 2,4,6-trimethylbenzoyldiphenylphosphine oxide (Omnirad TPO, manufactured by IGM Resins), bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (Omnirad 819, manufactured by IGM Resins), and bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide.

[0031] The first resin composition contains only a phosphine oxide-based photopolymerization initiator as a photopolymerization initiator. From the viewpoint of reducing the cost of the resin composition, the first resin composition and the second resin composition may contain only a phosphine oxide-based photopolymerization initiator as a photopolymerization initiator.

[0032] From the viewpoint of improving surface curability, the second resin composition may further contain an acetophenone-based photopolymerization initiator.

[0033] Examples of the acetophenone-based photopolymerization initiator include 1-hydroxycyclohexyl phenyl ketone (Omnirad 184, manufactured by IGM Resins), 2,2-dimethoxy-2-phenylacetophenone (Omnirad 651, manufactured by IGM Resins), 1-(4-isopropylphenyl)-2-hydroxy-2-methylpropane-1-one, and 2-methyl-1-[4-(methylthio)phenyl]-2-morpholino-propane-1-one (Omnirad 907, manufactured by IGM Resins).

[0034] The photopolymerizable compound according to the present embodiment may include an oligomer and a monomer. Examples of the oligomer include urethane (meth)acrylate and epoxy (meth)acrylate.

[0035] The urethane (meth)acrylate may be a compound obtained by reacting a polyol compound, a polyisocyanate compound, and a hydroxyl group-containing (meth)acrylate compound.

[0036] As the polyol compound, for example, polytetramethylene glycol, polypropylene glycol and bisphenol A-ethylene oxide addition glycol can be listed. From the viewpoint of adjusting the Young's modulus of the coating resin layer, the number average molecular weight (Mn) of the polyol compound can be 300 to 8000. From the viewpoint of reducing the Young's modulus of the primary resin layer, the Mn of the polyol compound constituting the urethane (meth) acrylate contained in the first resin composition can be 1200 to 8000, 2000 to 7000, or 3000 to 6000. From the viewpoint of increasing the Young's modulus of the secondary resin layer, the Mn of the polyol compound constituting the urethane (meth) acrylate contained in the second resin composition can be 300 to less than 1200, 400 to 1100, or 500 to 1000.

[0037] Examples of the polyisocyanate compound include 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, isophorone diisocyanate, and dicyclohexylmethane 4,4'-diisocyanate. Examples of the hydroxyl-containing (meth)acrylate compound include 2-hydroxyethyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 1,6-hexanediol mono(meth)acrylate, pentaerythritol tri(meth)acrylate, 2-hydroxypropyl (meth)acrylate, and tripropylene glycol (meth)acrylate.

[0038] As a catalyst for synthesizing urethane (meth) acrylate, an organic tin compound is generally used. Examples of the organic tin compound include dibutyltin dilaurate, dibutyltin diacetate, dibutyltin maleate, dibutyltin bis(2-ethylhexyl thioglycolate), dibutyltin bis(isooctyl thioglycolate), and dibutyltin oxide. From the perspective of availability or catalyst performance, dibutyltin dilaurate or dibutyltin diacetate is preferably used as the catalyst.

[0039] When synthesizing urethane (meth)acrylate, a lower alcohol having a carbon number of 5 or less may be used. Examples of the lower alcohol include methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, 2-methyl-2-propanol, 1-pentanol, 2-pentanol, 3-pentanol, 2-methyl-1-butanol, 3-methyl-1-butanol, 2-methyl-2-butanol, 3-methyl-2-butanol, and 2,2-dimethyl-1-propanol.

[0040] As epoxy (meth)acrylate, a compound obtained by reacting a compound having a (meth)acryloyl group with an epoxy resin having two or more glycidyl groups can be used.

[0041] As the monomer, a monofunctional monomer having one polymerizable group and a polyfunctional monomer having two or more polymerizable groups can be used. Two or more monomers can also be used in combination.

[0042] Examples of the monofunctional monomer include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, n-butyl (meth)acrylate, sec-butyl (meth)acrylate, tert-butyl (meth)acrylate, isobutyl (meth)acrylate, n-pentyl (meth)acrylate, isopentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, isopentyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-octyl (meth)acrylate, isooctyl (meth)acrylate, isodecyl (meth)acrylate, lauryl (meth)acrylate, 2-phenoxyethyl (meth)acrylate, 3-phenoxyethyl (meth)acrylate, and 1,2-dimethylformamide. (Meth)acrylate monomers such as benzyl ester, phenoxydiethylene glycol acrylate, phenoxypolyethylene glycol acrylate, 4-tert-butylcyclohexanol acrylate, tetrahydrofurfuryl (meth)acrylate, benzyl (meth)acrylate, dicyclopentenyl (meth)acrylate, dicyclopentenyloxyethyl (meth)acrylate, dicyclopentanyl (meth)acrylate, nonylphenol polyethylene glycol (meth)acrylate, nonylphenol EO modified acrylate, nonylphenoxypolyethylene glycol (meth)acrylate, and isobornyl (meth)acrylate; (meth)acrylic acid, (meth)acrylic acid dimer, carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, ω-carboxyl -Carboxyl-containing monomers such as polycaprolactone (meth)acrylate; heterocyclic (meth)acrylates such as N-acryloylmorpholine, N-vinylpyrrolidone, N-vinylcaprolactam, N-acryloylpiperidine, N-methacryloylpiperidine, N-acryloylpyrrolidine, (meth)acrylate 3-(3-pyridyl)propyl, cyclotrimethylolpropane formal acrylate; maleimide monomers such as maleimide, N-cyclohexylmaleimide, and N-phenylmaleimide; (meth)acrylamide, N,N-dimethyl(meth)acrylamide, N,N-diethyl(meth)acrylamide, N-hexyl(meth)acrylamide, N-methyl(meth)acrylamide N-substituted amide monomers such as acrylamide, N-butyl (meth)acrylamide, N-butyl (meth)acrylamide, N-hydroxymethyl (meth)acrylamide, and N-hydroxymethylpropane (meth)acrylamide; aminoalkyl (meth)acrylate monomers such as aminoethyl (meth)acrylate, aminopropyl (meth)acrylate, N,N-dimethylaminoethyl (meth)acrylate, and tert-butylaminoethyl (meth)acrylate; succinimide monomers such as N-(meth)acryloyloxymethylenesuccinimide, N-(meth)acryloyl-6-oxyhexamethylenesuccinimide, and N-(meth)acryloyl-8-oxyoctamethylenesuccinimide.

[0043] Examples of the polyfunctional monomer include ethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, di(meth)acrylate of an alkylene oxide adduct of bisphenol A, tetraethylene glycol di(meth)acrylate, hydroxypivalic acid neopentyl glycol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, 1,12-dodecanediol di(meth)acrylate, 1,14-tetradecanediol di(meth)acrylate, 1,16-hexadecanediol di(meth)acrylate, 1,20-eicosandiol di(meth)acrylate, isoprene glycol di(meth)acrylate, and 3-ethyl-1,8-octanediol di(meth)acrylate. (Meth)acrylate, EO adduct di(meth)acrylate of bisphenol A, trimethylolpropane tri(meth)acrylate, trimethyloloctane tri(meth)acrylate, trimethylolpropane polyethoxy tri(meth)acrylate, trimethylolpropane polypropoxy tri(meth)acrylate, trimethylolpropane polyethoxy polypropoxy tri(meth)acrylate, tri[(meth)acryloyloxyethyl]isocyanurate, pentaerythritol tri(meth)acrylate, pentaerythritol polyethoxy tetra(meth)acrylate, pentaerythritol polypropoxy tetra(meth)acrylate, pentaerythritol tetra(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate, dipentaerythritol tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, and caprolactone-modified tri[(meth)acryloyloxyethyl]isocyanurate.

[0044] From the viewpoint of improving the coating property on glass fiber by adjusting the viscosity of the resin composition or optimizing the Young's modulus of the cured product, at least one of the first resin composition or the second resin composition may contain nonylphenol polyethylene glycol acrylate as a monofunctional monomer, and preferably, the first resin composition contains nonylphenol polyethylene glycol acrylate. Examples of nonylphenol polyethylene glycol acrylate include nonylphenol ethylene oxide modified (8 mol adduct) acrylate, nonylphenol ethylene oxide modified (1 mol adduct) acrylate, and nonylphenol ethylene oxide modified (4 mol adduct) acrylate.

[0045] From the viewpoint of suppressing the change of coating removability over time, the amount of unreacted nonylphenol polyethylene glycol acrylate in the coating resin layer may be less than 1.0 mass %, preferably 0.95 mass % or less, more preferably 0.93 mass % or less, and further preferably 0.90 mass % or less. The lower limit of the amount of unreacted nonylphenol polyethylene glycol acrylate is not particularly limited, and may be 0.1 mass % or more, 0.3 mass % or more, or 0.5 mass % or more.

[0046] The resin composition may further contain a silane coupling agent, a leveling agent, a defoaming agent, an antioxidant, a sensitizer, and the like.

[0047] The silane coupling agent is not particularly limited as long as it does not hinder the curing of the resin composition. Examples of the silane coupling agent include tetramethyl silicate, tetraethyl silicate, mercaptopropyl trimethoxysilane, vinyl trichlorosilane, vinyl triethoxysilane, vinyl tri(β-methoxy-ethoxy)silane, β-(3,4-epoxycyclohexyl)-ethyl trimethoxysilane, dimethoxydimethylsilane, diethoxydimethylsilane, 3-acryloxypropyl trimethoxysilane, γ-glycidoxypropyl trimethoxysilane, γ-glycidoxypropyl methyl diethoxysilane, γ-methacryloxypropyl trimethoxysilane, N-(β-aminoethyl)silane, and the like.

[0047] The invention also includes bis-[3-(triethoxysilyl)propyl]tetrasulfide, bis-[3-(triethoxysilyl)propyl]disulfide, γ-trimethoxysilylpropyldimethylthiocarbamoyl tetrasulfide, and γ-trimethoxysilylpropylbenzothiazolyl tetrasulfide.

[0048] (Method for manufacturing optical fiber)

[0049] The optical fiber manufacturing method according to the present embodiment includes: a coating step of coating the first resin composition and the second resin composition on the outer circumference of a glass fiber at a temperature of 80° C. or less; and a curing step of curing the resin composition by irradiating ultraviolet rays after the coating step.

[0050] In the coating step, the first resin composition is coated on the surface of the glass fiber 10 to form a first resin layer (a layer corresponding to the primary resin layer 22 after curing) composed of the first resin composition on the surface of the glass fiber 10, and the second resin composition is coated on the surface of the first resin layer to form a second resin layer (a layer corresponding to the secondary resin layer 24 after curing) composed of the second resin composition on the surface of the first resin layer. That is, in the coating step, the first resin composition and the second resin composition are coated on the glass fiber 10 at a temperature of 80° C. or less in a manner of being sequentially away from the glass fiber 10.

[0051] By controlling the temperature of the glass fiber in the coating process, it is easy to reduce the unreacted ratio of the phosphine oxide-based photopolymerization initiator. The temperature of the glass fiber is preferably 75° C. or less, more preferably 70° C. or less. The lower limit of the temperature of the glass fiber is not particularly limited, and may be 30° C. or more, 40° C. or more, or 45° C. or more.

[0052] In the curing step, the first resin layer and the second resin layer are cured by irradiating ultraviolet rays, so that the primary resin layer 22 is formed from the first resin layer and the secondary resin layer 24 is formed from the second resin layer.

[0053] As the ultraviolet light source, for example, ultraviolet LEDs and ultraviolet lamps can be cited. The wavelength of ultraviolet light emitted by ultraviolet LEDs is, for example, in the range of 300nm to 450nm, and the wavelength of ultraviolet light emitted by ultraviolet lamps is, for example, in the range of 200nm to 450nm. Ultraviolet LEDs are preferably used because they have high illumination and can reduce power consumption, and ultraviolet LEDs having ultraviolet wavelengths in the range of 350nm to 405nm are more preferably used. The time for irradiating ultraviolet light using ultraviolet LEDs is, for example, 4×10 -3 For example, ultraviolet rays are irradiated in an inert gas atmosphere such as a nitrogen atmosphere.

[0054] Example

[0055] Hereinafter, the present disclosure will be described in more detail by showing the evaluation test results using the examples and comparative examples related to the present disclosure. It should be noted that the present disclosure is not limited to these examples.

[0056] [First resin composition]

[0057] (Resin composition P1)

[0058] As an oligomer, urethane acrylate a obtained by reacting polypropylene glycol having a molecular weight of 4000, 2,4-toluene diisocyanate, and hydroxyethyl acrylate was prepared. 78 parts by mass of urethane acrylate a, 9 parts by mass of nonylphenol polyethylene glycol acrylate (trade name "SR504" manufactured by Sartomer), 7 parts by mass of N-vinyl caprolactam, 5 parts by mass of 1,6-hexanediol diacrylate, and 1 part by mass of 2,4,6-trimethylbenzoyldiphenylphosphine oxide (Omnirad TPO) were mixed to prepare resin composition P1.

[0059] [Second resin composition]

[0060] (Resin composition S1)

[0061] As an oligomer, urethane acrylate b obtained by reacting polypropylene glycol having a molecular weight of 600, 2,4-toluene diisocyanate, and hydroxyethyl acrylate was prepared. 27 parts by mass of urethane acrylate b, 30 parts by mass of tripropylene glycol diacrylate (trade name "TPGDA" of "Dicel Olex Co., Ltd."), 40 parts by mass of 2-phenoxyethyl acrylate (trade name "Lite Acrylate PO-A" of "Kyoei Chemical Co., Ltd."), 1 part by mass of TPO, and 2 parts by mass of 1-hydroxycyclohexyl phenyl ketone (Omnirad 184) were mixed to prepare resin composition S1.

[0062] (Resin composition S2)

[0063] Resin composition S2 was prepared by mixing 29 parts by mass of urethane acrylate b, 30 parts by mass of TPGDA, 40 parts by mass of PO-A, and 1 part by mass of TPO.

[0064] [Production of optical fiber]

[0065] (Example 1)

[0066] In the coating step, the resin composition P1 was used to form a first resin layer with a thickness of 32.5 μm on the periphery of a glass fiber with a diameter of 125 μm at a temperature of 80°C, and the resin composition S1 was used to form a second resin layer with a thickness of 27.5 μm on the periphery.

[0067] In the curing process, an ultraviolet LED (emission wavelength λ = 385 nm) was used with an irradiation dose (illuminance × irradiation time) of 29 mW / cm 2 The first layer and the second layer were cured by irradiating with ultraviolet light under the condition of 100 ℃ and 200 ℃ for 10 seconds, thereby producing an optical fiber having a coating resin layer composed of a primary resin layer and a secondary resin layer.

[0068] (Example 2-5 and Comparative Example 1-2)

[0069] An optical fiber was produced in the same manner as in Example 1 except that the temperature of the glass fiber and the ultraviolet irradiation conditions were changed to the values ​​shown in Table 1.

[0070] (Example 6)

[0071] In the coating step, the resin composition P1 was used to form a first resin layer with a thickness of 32.5 μm on the periphery of a glass fiber with a diameter of 125 μm at a temperature of 60°C, and the resin composition S2 was further used to form a second resin layer with a thickness of 27.5 μm on the periphery.

[0072] In the curing process, ultraviolet LED is used with an irradiation of 21mW / cm 2 The first layer and the second layer were cured by irradiating with ultraviolet light having an emission wavelength of 385 nm under the condition of 100 ℃ and 200 ℃ for 10 seconds, thereby producing an optical fiber having a coating resin layer consisting of a primary resin layer and a secondary resin layer.

[0073] (Examples 7-9 and Comparative Example 3)

[0074] An optical fiber was produced in the same manner as in Example 6 except that the temperature of the glass fiber and the ultraviolet irradiation conditions were changed to the values ​​shown in Table 2.

[0075] (Determination of unreacted amount)

[0076] After immersing 1 g of the optical fiber in acetone, the unreacted TPO and nonylphenol polyethylene glycol acrylate extracted from the acetone were measured by GC-FPD analysis. "Flontea Lab UA-1" was used as a chromatography column.

[0077] (Coating removable)

[0078] The optical fiber plate was placed at a distance of 30 cm from a 30 W fluorescent lamp and allowed to stand at room temperature for 14 days. The coating resin layer was then removed from the optical fiber at 23°C using a "Jacket Remover JR-6" manufactured by Sumitomo Electric Industries, Ltd. The coating residue of the resin layer remaining on the glass fiber was wiped off using a "Kimwipe" (manufactured by Nippon Paper Corporation) moistened with ethanol. The case where the coating residue was wiped off once was evaluated as "A"; the case where it was wiped off 2 to 3 times was evaluated as "B"; the case where it was wiped off 4 or more times or the coating residue could not be wiped off was evaluated as "C".

[0079] [Table 1]

[0080]

[0081] [Table 2]

[0082]

[0083] Explanation of symbols

[0084] 1. Fiber Optic

[0085] 10. Fiberglass

[0086] 20 Coating resin layer

[0087] 22 Primary resin layer

[0088] 24 Secondary resin layer

Claims

1. An optical fiber having: A glass fiber comprising a core and a cladding, and a coating resin layer in contact with and coating the glass fiber, wherein: The coating resin layer includes a primary resin layer that contacts the glass fiber and coats the glass fiber, and a secondary resin layer that coats the primary resin layer. The primary resin layer includes a cured product of a first resin composition containing a photopolymerizable compound and a phosphine oxide-based photopolymerization initiator. The secondary resin layer comprises a cured product of a second resin composition containing a photopolymerizable compound and a phosphine oxide-based photopolymerization initiator. The amount of the unreacted phosphine oxide-based photopolymerization initiator in the coating resin layer is 0.5% by mass or less, At least one of the first resin composition or the second resin composition contains nonylphenol polyethylene glycol acrylate as the photopolymerizable compound. The amount of unreacted nonylphenol polyethylene glycol acrylate in the coating resin layer is less than 1.0% by mass.

2. The optical fiber according to claim 1, wherein The second resin composition further contains an acetophenone-based photopolymerization initiator.

3. The optical fiber according to claim 1, wherein The first resin composition and the second resin composition do not contain a photopolymerization initiator other than the phosphine oxide-based photopolymerization initiator.

4. A method for manufacturing an optical fiber, which is the method for manufacturing an optical fiber according to any one of claims 1 to 3, comprising: A coating step of coating the first resin composition and the second resin composition on glass fibers at a temperature of 80° C. or less in a manner that they are sequentially spaced away from the glass fibers; and After the coating step, a curing step is performed to cure the resin composition by irradiating ultraviolet rays.

5. The method for manufacturing an optical fiber according to claim 4, wherein: In the curing step, ultraviolet rays emitted from an ultraviolet light emitting diode are irradiated.

6. The method for manufacturing an optical fiber according to claim 5, wherein: The wavelength of the ultraviolet rays is within the range of 350 nm to 405 nm.

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