Optical fiber

Abstract

This optical fiber comprises: a glass fiber that includes a core and a cladding; and a coating resin layer that is in contact with the glass fiber to coat the glass fiber. The coating resin layer has a primary resin layer that 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 resin composition containing: a photopolymerizable compound that contains a urethane (meth)acrylate; a photoinitiator; a silane coupling agent; and an organic base. The contained amount of the organic base is 5-9000 ppm with respect to the total amount of the coating resin layer.

Description

optical fiber

[0001] This application claims priority to Japanese Patent Application No. 2023-074355, filed April 28, 2023, and incorporates by reference all of the contents of said Japanese application.

[0002] In general, optical fibers are provided with a coating resin layer for protecting a glass fiber, which is an optical transmission medium. The coating resin layer includes, for example, a primary resin layer in contact with the glass fiber and a secondary resin layer formed on the outer peripheral surface of the primary resin layer. In order to reduce an increase in transmission loss induced by minute bending that occurs when lateral pressure is applied to the optical fiber, it is required to improve the lateral pressure characteristics of the optical fiber.

[0003] In order to improve the lateral pressure characteristics, it has been considered to reduce the Young's modulus of the primary resin layer or increase the Young's modulus of the secondary resin layer. For example, Patent Document 1 discusses using a resin composition containing a urethane oligomer obtained by reacting a reaction product of an aliphatic polyether diol and a diisocyanate with a monohydric alcohol and a hydroxyl group-containing (meth)acrylate to achieve both flexibility (low Young's modulus) and mechanical strength of the primary resin layer.

[0004] JP 2012-111674 A

[0005] An optical fiber according to one embodiment of the present disclosure comprises a glass fiber including a core and a cladding, and a coating resin layer that contacts the glass fiber and coats the glass fiber, the coating resin layer having a primary resin layer that coats the glass fiber and a secondary resin layer that coats the primary resin layer, the primary resin layer comprising a cured product of a resin composition that contains a photopolymerizable compound including urethane (meth)acrylate, a photopolymerization initiator, a silane coupling agent, and an organic base, and the content of the organic base is 5 ppm or more and 9000 ppm or less based on the total amount of the coating resin layer.

[0006] Fig. 1 is a schematic cross-sectional view showing an example of an optical fiber according to the present embodiment. Fig. 2 is a schematic cross-sectional view showing an example of an optical fiber according to the present embodiment.

[0007] [Problem to be Solved by the Present Disclosure] Optical fibers are required to maintain properties such as strength even when immersed in water for a long period of time. However, optical fibers having a primary resin layer with a low Young's modulus tend to have a low degree of hardening, and when immersed in warm water, the coating resin layer may peel off from the glass fiber, resulting in a decrease in the strength of the optical fiber.

[0008] An object of the present disclosure is to provide an optical fiber that has excellent resistance to hot water and can maintain its strength even when immersed in water for a long period of time.

[0009] Effect of the Present Disclosure According to the present disclosure, it is possible to provide an optical fiber that has excellent resistance to hot water and can maintain its strength even when immersed in water for a long period of time.

[0010] [Description of Embodiments of the Present Disclosure] First, the contents of the embodiments of the present disclosure will be listed and described.

[0011] (1) An optical fiber according to one embodiment of the present disclosure comprises a glass fiber including a core and a cladding, and a coating resin layer that contacts the glass fiber and coats the glass fiber, the coating resin layer having a primary resin layer that coats the glass fiber and a secondary resin layer that coats the primary resin layer, the primary resin layer containing a cured product of a resin composition that contains a photopolymerizable compound including urethane (meth)acrylate, a photopolymerization initiator, a silane coupling agent, and an organic base, and the content of the organic base is 5 ppm or more and 9000 ppm or less based on the total amount of the coating resin layer.

[0012] Such optical fibers have excellent resistance to hot water and can maintain their strength even when immersed in water for a long period of time by incorporating a specific amount of organic base into the primary resin layer that directly coats the glass fiber.

[0013] (2) In the above (1), from the viewpoint of achieving better resistance to warm water, the organic base may be at least one selected from the group consisting of aromatic amines, aliphatic amines having an aromatic ring, heterocyclic amines, and cyclic amides.

[0014] (3) In the above (2), the cyclic amide may be δ-valerolactam or ε-caprolactam, from the viewpoint of further improving the resistance to hot water.

[0015] (4) In any of the above (1) to (3), the resin composition may contain two or more types of silane coupling agents in order to improve the adhesion of the primary resin layer to the glass fiber.

[0016] (5) In any one of the above (1) to (4), the Young's modulus of the primary resin layer may be 0.6 MPa or less at 23° C. in order to achieve excellent lateral pressure characteristics.

[0017] [Details of the Embodiments of the Present Disclosure] Specific examples of optical fibers and optical fiber ribbons according to embodiments of the present disclosure will be described with reference to the drawings as necessary. The present disclosure is not limited to these examples, but is defined by the claims, and is intended to include all modifications within the meaning and scope equivalent to the claims. In the following description, the same elements in the description of the drawings will be denoted by the same reference numerals, and redundant explanations will be omitted. In the present embodiment, (meth)acrylate means acrylate or the corresponding methacrylate, and the same applies to other similar expressions such as (meth)acrylic acid. In this specification, ppm indicates a mass ratio.

[0018] (Optical Fiber) The optical fiber according to this embodiment includes a glass fiber including a core and a cladding, and a coating resin layer that contacts the glass fiber and coats the glass fiber. The coating resin layer includes a primary resin layer that coats the glass fiber and a secondary resin layer that coats the primary resin layer, and the primary resin layer contains a cured product of a resin composition that includes a photopolymerizable compound containing urethane (meth)acrylate, a photopolymerization initiator, a silane coupling agent, and an organic base. The content of the organic base is 5 ppm or more and 9000 ppm or less based on the total amount of the coating resin layer.

[0019] 1 is a schematic cross-sectional view showing an example of an optical fiber according to the present embodiment. The optical fiber 10 includes a glass fiber 13 including a core 11 and a cladding 12, and a coating resin layer 16 including a primary resin layer 14 and a secondary resin layer 15 provided around the glass fiber 13.

[0020] The cladding 12 surrounds the core 11. The core 11 and the cladding 12 mainly contain glass such as silica glass, and for example, the core 11 can be made of germanium-doped silica glass or pure silica glass, and the cladding 12 can be made of pure silica glass or fluorine-doped silica glass.

[0021] FIG. 2 is a schematic cross-sectional view showing an example of an optical fiber according to this embodiment. In the optical fiber 10A, the cladding 12 may include an inner cladding 121 that surrounds the outer periphery of the core 11 and is in contact with the outer peripheral surface of the core 11, a trench 122 that surrounds the outer periphery of the inner cladding 121 and is in contact with the outer peripheral surface of the inner cladding 121, and an outer cladding 123 that surrounds the outer periphery of the trench 122 and is in contact with the outer peripheral surface of the trench 122. From the viewpoint of hot water resistance, the inner cladding 121 and the outer cladding 123 may be made of silica glass doped with chlorine (Cl). The average chlorine mass concentration is, for example, 500 ppm to 5000 ppm or 500 ppm to 3000 ppm. The trench 122 may be made of silica glass doped with fluorine. The average OH mass concentration of the outer cladding 123 is substantially zero. Here, "substantially zero" specifically means 50 ppm or less.

[0022] 1 and 2 , for example, the outer diameter (D2) of the glass fiber 13 may be 100 μm or more and 125 μm or less, and the diameter (D1) of the core 11 constituting the glass fiber 13 may be 7 μm or more and 15 μm or less. The thickness of the coating resin layer 16 may be, for example, 22 μm or more and 70 μm or less. The thickness of each of the primary resin layer 14 and the secondary resin layer 15 may be 5 μm or more and 50 μm or less.

[0023] The outer diameter (D2) of the glass fiber 13 may be 125 μm or more and 220 μm or less, 150 μm or more and 210 μm or less, or 170 μm or more and 190 μm or less. The outer diameter of the optical fiber 10 may be 200 μm or more and 250 μm or less, 210 μm or more and 240 μm or less, or 220 μm or more and 230 μm or less.

[0024] The primary resin layer 14 can be formed using an ultraviolet-curable resin composition containing a photopolymerizable compound including urethane (meth)acrylate, a photopolymerization initiator, a silane coupling agent, and an organic base.

[0025] The resin composition may contain trace amounts of acid components, such as acrylic acid, derived from the photopolymerizable compound. The acid components may hydrolyze and deactivate the silane coupling agent, causing the resin composition to change over time. In contrast, the resin composition according to this embodiment contains an organic base, which neutralizes the acid components and prevents the deactivation of the silane coupling agent. This makes it possible to produce an optical fiber that exhibits excellent hot water resistance even after a certain period of time has passed since the resin was produced. This effect is particularly pronounced when the primary resin layer has a low Young's modulus.

[0026] The organic base may be an amine compound or an amide compound. Examples of the amine compound include aromatic amines such as aniline, aliphatic amines having an aromatic ring such as benzylamine, and heterocyclic amines such as pyrrolidine, piperidine, and pyridine. Examples of the amide compound include cyclic amides such as δ-valerolactam and ε-caprolactam.

[0027] Basic components are generally known to corrode glass. If the molecular structure of the basic component is large, the steric hindrance makes it difficult for glass corrosion reactions to occur, and therefore the organic base may be an aromatic amine, an aliphatic amine having an aromatic ring, a heterocyclic amine, or a cyclic amide. From the viewpoint of further suppressing deactivation of the silane coupling agent, a heterocyclic amine or a cyclic amide may be used as the organic base. From the viewpoint of further improving hot water resistance, δ-valerolactam or ε-caprolactam may be used as the organic base.

[0028] The content of the organic base is 5 ppm or more and 9000 ppm or less based on the total amount of the coating resin layer from the viewpoint of improving hot water resistance.The content of the organic base may be 8 ppm or more, 10 ppm or more, 100 ppm or more, 500 ppm or more, 800 ppm or more, or 1000 ppm or more based on the total amount of the coating resin layer from the viewpoint of suppressing deactivation of the silane coupling agent, and may be 8500 ppm or less, 8000 ppm or less, 7000 ppm or less, 6000 ppm or less, or 5000 ppm or less from the viewpoint of suppressing corrosion of glass.

[0029] The photopolymerizable compound includes a urethane (meth)acrylate. For example, a urethane (meth)acrylate obtained by reacting a polyol compound, a polyisocyanate compound, and a hydroxyl group-containing (meth)acrylate compound can be used. The urethane (meth)acrylate may be used alone or in combination of two or more.

[0030] Examples of polyol compounds include polytetramethylene glycol, polypropylene glycol, and bisphenol A-ethylene oxide addition diol. Examples of polyisocyanate compounds include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, isophorone diisocyanate, and dicyclohexylmethane 4,4'-diisocyanate. Examples of hydroxyl group-containing (meth)acrylate compounds 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 mono(meth)acrylate.

[0031] From the viewpoint of adjusting the Young's modulus of the primary resin layer, the number average molecular weight (Mn) of the polyol compound may be 1,000 or more and 10,000 or less, 1,500 or more and 9,000 or less, 2,000 or more and 8,000 or less, or 3,000 or more and 6,000 or less.

[0032] Organotin compounds are generally used as catalysts for synthesizing urethane (meth)acrylates. Examples of organotin compounds include dibutyltin dilaurate, dibutyltin diacetate, dibutyltin maleate, dibutyltin bis(2-ethylhexyl mercaptoacetate), dibutyltin bis(isooctyl mercaptoacetate), and dibutyltin oxide. In terms of easy availability or catalytic performance, dibutyltin dilaurate or dibutyltin diacetate may be used as the catalyst.

[0033] A lower alcohol having 5 or less carbon atoms may be used during synthesis of the urethane (meth)acrylate. Examples of lower alcohols 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.

[0034] From the viewpoint of adjusting the Young's modulus of the primary resin layer, the content of the urethane (meth)acrylate may be 15 parts by mass or more and 80 parts by mass or less, 20 parts by mass or more and 70 parts by mass or less, or 30 parts by mass or more and 60 parts by mass or less, relative to 100 parts by mass of the total amount of the resin composition.

[0035] The photopolymerizable compound according to this embodiment may further include a photopolymerizable compound (hereinafter referred to as a "monomer") other than urethane (meth)acrylate.

[0036] The monomer may be a monofunctional monomer having one polymerizable group or a polyfunctional monomer having two or more polymerizable groups. Two or more types of monomers may be used in combination.

[0037] Examples of monofunctional monomers include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, n-butyl (meth)acrylate, s-butyl (meth)acrylate, tert-butyl (meth)acrylate, isobutyl (meth)acrylate, n-pentyl (meth)acrylate, isopentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, isoamyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-octyl (meth)acrylate, and isobutyl (meth)acrylate. Octyl (meth)acrylate, isodecyl (meth)acrylate, lauryl (meth)acrylate, 2-phenoxyethyl (meth)acrylate, 3-phenoxybenzyl acrylate, phenoxydiethylene glycol acrylate, phenoxypolyethylene glycol acrylate, 4-tert-butylcyclohexanol acrylate, tetrahydrofurfuryl (meth)acrylate, benzyl (meth)acrylate, dicyclopentenyl (meth)acrylate, dicyclopentenyloxyethyl (meth)acrylate, dicyclopenta (Meth)acrylate monomers such as nonyl (meth)acrylate, nonylphenol polyethylene glycol (meth)acrylate, nonylphenoxy polyethylene glycol (meth)acrylate, 2-hydroxyethyl (meth)acrylate, nonylphenol ethylene oxide-modified (meth)acrylate, tricyclodecanyl (meth)acrylate, polypropylene glycol mono(meth)acrylate, and isobornyl (meth)acrylate; (meth)acrylic acid, (meth)acrylic acid dimer, and carboxyethyl (meth)acrylate; Carboxy group-containing monomers such as carboxypentyl (meth)acrylate and ω-carboxy-polycaprolactone (meth)acrylate; heterocycle-containing monomers such as N-vinylpyrrolidone, N-vinylcaprolactam, N-(meth)acryloylmorpholine, N-(meth)acryloylpiperidine, N-(meth)acryloylpyrrolidine, 3-(3-pyridine)propyl (meth)acrylate and cyclic trimethylolpropane formal acrylate; maleimide-based monomers such as maleimide, N-cyclohexylmaleimide and N-phenylmaleimide;Amide-based monomers such as (meth)acrylamide, N,N-dimethyl(meth)acrylamide, N,N-diethyl(meth)acrylamide, N-hexyl(meth)acrylamide, N-methyl(meth)acrylamide, N-ethyl(meth)acrylamide, N-butyl(meth)acrylamide, N-methylol(meth)acrylamide, and N-methylolpropane(meth)acrylamide; aminoalkyl (meth)acrylate-based monomers such as aminoethyl (meth)acrylate, aminopropyl (meth)acrylate, N,N-dimethylaminoethyl (meth)acrylate, and tert-butylaminoethyl (meth)acrylate; and succinimide-based monomers such as N-(meth)acryloyloxymethylene succinimide, N-(meth)acryloyl-6-oxyhexamethylene succinimide, and N-(meth)acryloyl-8-oxyoctamethylene succinimide.

[0038] From the viewpoint of excellent copolymerizability with other monomers and improving the curing rate, an N-vinyl monomer having a cyclic structure may be used as the monofunctional monomer. The content of the N-vinyl monomer may be 1 part by mass or more and 15 parts by mass or less, or 2 parts by mass or more and 10 parts by mass or less, relative to 100 parts by mass of the total amount of the resin composition.

[0039] Examples of polyfunctional monomers include polyethylene glycol di(meth)acrylate, tricyclodecanediyldimethylene di(meth)acrylate, isocyanuric acid ethylene oxide modified di(meth)acrylate, ethylene oxide modified bisphenol F di(meth)acrylate, ethylene oxide modified bisphenol A di(meth)acrylate, polypropylene glycol di(meth)acrylate, propylene oxide modified bisphenol A di(meth)acrylate, and propylene oxide modified neopentyl glycol di(meth)acrylate. , polytetraethylene glycol di(meth)acrylate, neopentyl glycol hydroxypivalate 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-eicosanediol di(meth)acrylate, neopentyl glycol di (Meth)acrylate, isopentyldiol di(meth)acrylate, 3-ethyl-1,8-octanediol di(meth)acrylate; trimethylolpropane tri(meth)acrylate, trimethyloloctane tri(meth)acrylate, trimethylolpropane polyethoxy tri(meth)acrylate, trimethylolpropane polypropoxy tri(meth)acrylate, trimethylolpropane polyethoxypolypropoxy tri(meth)acrylate, tris[(meth)acryloyloxyethyl]isocyanurate, pentaerythritol tri(meth)acrylate, pentaerythritol polyethoxytetra(meth)acrylate, pentaerythritol polypropoxytetra(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 tris[(meth)acryloyloxyethyl]isocyanurate.

[0040] The photopolymerizable compound according to this embodiment may contain an alkylene oxide-modified polyfunctional monomer in order to adjust the Young's modulus of the resin layer. The alkylene oxide-modified polyfunctional monomer may have at least one selected from the group consisting of an ethylene oxide (EO) chain and a propylene oxide (PO) chain. The ethylene oxide chain can be represented as "(EO)n" and the propylene oxide chain can be represented as "(PO)n". n is an integer of 1 or greater, and may be 2 or greater or 3 or greater, or may be 30 or less, 25 or less, or 20 or less.

[0041] Examples of alkylene oxide-modified di(meth)acrylates include polyethylene glycol di(meth)acrylate, isocyanuric acid ethylene oxide-modified di(meth)acrylate, ethylene oxide-modified bisphenol F di(meth)acrylate, ethylene oxide-modified bisphenol A di(meth)acrylate polypropylene glycol di(meth)acrylate, propylene oxide-modified bisphenol A di(meth)acrylate, and propylene oxide-modified neopentyl glycol di(meth)acrylate.

[0042] The photopolymerization initiator can be appropriately selected from known radical photopolymerization initiators. Examples of the photopolymerization initiator include 1-hydroxycyclohexylphenyl ketone (Omnirad 184, manufactured by IGM Resins), 2,2-dimethoxy-2-phenylacetophenone, 1-(4-isopropylphenyl)-2-hydroxy-2-methylpropan-1-one, bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide, 2-methyl-1-[4-(methylthio)phenyl]-2-morpholino-propan-1-one (Omnirad 907, manufactured by IGM Resins), 2,4,6-trimethylbenzoyldiphenylphosphine oxide (Omnirad TPO, manufactured by IGM Resins), and bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (Omnirad 819, manufactured by IGM Resins).

[0043] The content of the photopolymerization initiator may be 1 part by mass or more and 10 parts by mass or less, 2 parts by mass or more and 8 parts by mass or less, or 3 parts by mass or more and 7 parts by mass or less, relative to 100 parts by mass of the total amount of the photopolymerizable compounds. The content of the photopolymerization initiator may be 0.2 parts by mass or more, 0.4 parts by mass or more, or 0.6 parts by mass or more, relative to 100 parts by mass of the total amount of the photopolymerizable compounds, and may be 6 parts by mass or less, 5 parts by mass or less, or 4 parts by mass or less.

[0044] The silane coupling agent is not particularly limited as long as it does not interfere with the curing of the resin composition. Examples of the silane coupling agent include tetramethyl silicate, tetraethyl silicate, mercaptopropyltrimethoxysilane, vinyltrichlorosilane, vinyltriethoxysilane, vinyltris(β-methoxyethoxy)silane, β-(3,4-epoxycyclohexyl)-ethyltrimethoxysilane, dimethoxydimethylsilane, diethoxydimethylsilane, 3-acryloxypropyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, γ-methacryloxypropyltrimethoxysilane, N-(β-aminoethyl)-γ Examples of silane coupling agents include N-aminopropyltrimethoxysilane, N-(β-aminoethyl)-γ-aminopropyltrimethyldimethoxysilane, N-phenyl-γ-aminopropyltrimethoxysilane, γ-chloropropyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-aminopropyltrimethoxysilane, bis-[3-(triethoxysilyl)propyl]tetrasulfide, bis-[3-(triethoxysilyl)propyl]disulfide, γ-trimethoxysilylpropyldimethylthiocarbamyltetrasulfide, and γ-trimethoxysilylpropylbenzothiazyltetrasulfide. The resin composition according to this embodiment may contain two or more types of silane coupling agents from the viewpoint of improving the adhesion of the primary resin layer to the glass fiber.

[0045] The content of the silane coupling agent may be 0.1 parts by mass or more and 5.0 parts by mass or less, 0.2 parts by mass or more and 4.0 parts by mass or less, or 0.3 parts by mass or more and 3.0 parts by mass or less, relative to 100 parts by mass of the total amount of the resin composition.

[0046] From the viewpoint of improving the glass strength of the optical fiber, the Young's modulus of the primary resin layer may be 0.6 MPa or less, 0.55 MPa or less, 0.5 MPa or less, or 0.4 MPa or less at 23°C. The lower limit of the Young's modulus of the primary resin layer is not particularly limited, but may be 0.05 MPa or more, 0.1 MPa or more, or 0.2 MPa or more. The Young's modulus of the primary resin layer can be measured by the Pullout Modulus (POM) method at 23°C. The Young's modulus of the primary resin layer can be adjusted by the type of urethane (meth)acrylate, the molecular weight of the urethane (meth)acrylate, the type of monomer, the amount of monomer blended, etc.

[0047] The secondary resin layer 15 may be formed using a conventionally known resin composition for secondary resin layers, for example, by curing a resin composition containing urethane (meth)acrylate, a monomer, and a photopolymerization initiator.

[0048] The Young's modulus of the secondary resin layer 15 may be 800 MPa or more, 1000 MPa or more, or 1200 MPa or more at 23°C from the viewpoint of further improving the hot water resistance of the optical fiber. The Young's modulus of the secondary resin layer 15 may be 2000 MPa or less, 1800 MPa or less, or 1500 MPa or less at 23°C from the viewpoint of forming a resin layer with excellent toughness. The Young's modulus of the secondary resin layer can be measured by a tensile test of the coating resin layer. The Young's modulus of the secondary resin layer can be adjusted by the type of urethane (meth)acrylate, the molecular weight of the urethane (meth)acrylate, the type of monomer, the amount of monomer blended, etc.

[0049] The present disclosure will be described in more detail below by showing the results of evaluation tests using examples and comparative examples according to the present disclosure, but the present disclosure is not limited to these examples.

[0050] [Resin Composition for Primary Resin Layer] (Photopolymerizable Compound) As photopolymerizable compounds, urethane acrylate obtained by reacting polypropylene glycol with a molecular weight of 4000, isophorone diisocyanate, and hydroxyethyl acrylate, nonylphenylol EO-modified acrylate (EO-NPA), 1,6-hexanediol diacrylate (1,6-HAD), isobornyl acrylate, and trimethylolpropane triacrylate were prepared. (Photopolymerization Initiator) As a photopolymerization initiator, 2,4,6-trimethylbenzoyldiphenylphosphine oxide (TPO) was prepared. (Silane Coupling Agent) As silane coupling agents, 3-mercaptopropyltrimethoxysilane (MPTS) and tetraethoxysilane (TEOS) were prepared. (Organic Base) As organic bases, δ-valerolactam, ε-caprolactam, pyridine, aniline, and benzylamine were prepared.

[0051] A photopolymerizable compound, a photopolymerization initiator, and a silane coupling agent were mixed in the amounts (parts by mass) shown in Table 1 or Table 2, and then an organic base was added so that the content in the coating resin layer was the content (ppm) shown in Table 1 or Table 2, to prepare a resin composition for the primary resin layer of each test example.

[0052] [Resin composition for secondary resin layer] A urethane (meth)acrylate obtained by reacting polypropylene glycol having a molecular weight of 1000, isophorone diisocyanate, and 2-hydroxyethyl acrylate was prepared. 60 parts by mass of this urethane (meth)acrylate, 19 parts by mass of isobornyl acrylate, 20 parts by mass of trimethylolpropane triacrylate, and 1 part by mass of 2,4,6-trimethylbenzoyldiphenylphosphine oxide were mixed together to prepare resin composition S for the secondary resin layer.

[0053] [Fabrication of Optical Fiber] Optical fibers were fabricated by forming a primary resin layer of 17.5 μm thick on the outer periphery of a glass fiber having a diameter of 125 μm and composed of a core and a cladding using the resin compositions of Test Examples 1 to 11, and further forming a secondary resin layer of 15 μm thick on the outer periphery of the primary resin layer using Resin Composition S. Test Examples 1 to 9 correspond to Examples, and Test Examples 10 and 11 correspond to Comparative Examples.

[0054] (Young's Modulus of Primary Resin Layer) The Young's modulus of the primary resin layer was measured by the POM method at 23°C. Two locations of the optical fiber were fixed with two chuck devices, and the portion of the coating resin layer (primary resin layer and secondary resin layer) between the two chuck devices was removed. Next, one of the chuck devices was fixed, and the other chuck device was slowly moved in the opposite direction of the fixed chuck device. When the length of the portion of the optical fiber sandwiched between the moving chuck devices is L, the amount of movement of the chuck device is Z, the outer diameter of the primary resin layer is Dp, the outer diameter of the glass fiber is Df, the Poisson's ratio of the primary resin layer is n, and the load during movement of the chuck device is W, the Young's modulus of the primary resin layer was calculated using the following formula: Young's modulus (MPa) = ((1 + n)W / πLZ) × ln(Dp / Df)

[0055] (Young's modulus of secondary resin layer) The Young's modulus of the secondary resin layer was determined from the 2.5% secant value by performing a tensile test (gauge length: 25 mm) at 23°C using a pipe-shaped coating resin layer (length: 50 mm or more) obtained by removing the glass portion from the optical fiber. The Young's modulus of the secondary resin layer was 1000 MPa.

[0056] (Organic Base Content) The content of the organic base contained in the coating resin layer was determined using a gas chromatography apparatus (manufactured by Shimadzu Corporation under the trade name "GC-2010") according to the following procedure. First, a calibration curve was created using an ethanol standard solution of each organic base. Next, 0.5 g of optical fiber was placed in a container, 5 mL of ethanol was added, the container was capped, and ultrasonic waves were applied for 60 minutes to obtain an extract. The measurement was performed using a UA-1 column (film thickness: 0.25 μm, inner diameter: 0.25 mm, length: 30 m) manufactured by Frontier Labs Co., Ltd., at column temperatures of 100 ° C. (20 ° C. / min) → 160 ° C. (5 ° C. / min) → 230 ° C. (60 ° C. / min) → 350 ° C. (held for 15 minutes). An FID was used as a detector, and the amount of organic base contained in the extract was quantified to calculate the content of the organic base contained in the coating resin layer.

[0057] (Hot Water Test) The transmission loss of the optical fiber at a wavelength of 1.55 μm was measured by an OTDR (Optical Time Domain Reflectometer) method. Next, the optical fiber was immersed in hot water at 60° C. for 60 days, and then the transmission loss of the optical fiber at a wavelength of 1.55 μm was measured. If the difference between the transmission loss before immersion in hot water and the transmission loss after immersion in hot water for 60 days was 0.05 dB / km or less, the optical fiber was evaluated as "A," and if it exceeded 0.05 dB / km, the optical fiber was evaluated as "B."

[0058] (Glass Strength) An optical fiber bundle was immersed in 85°C warm water for 60 days, and the glass strength was evaluated before and after immersion. The glass strength was judged to be good or bad by measuring the 50% strength. The 50% strength is the strength at which half of the optical fibers under test break in a tensile test of the optical fiber. In this test example, the tensile test was performed on each optical fiber under test at a pulling speed of 25 mm / min. When the 50% strength value of the glass strength after immersion was less than 80% of the 50% strength value of the glass strength before immersion, it was evaluated as "C", when it was 80 to 90%, it was evaluated as "B", and when it was more than 90% it was evaluated as "A".

[0059]

[0060]

[0061] 10, 10A... Optical fiber 11... Core 12... Cladding 13... Glass fiber 14... Primary resin layer 15... Secondary resin layer 16... Coating resin layer 121... Inner cladding 122... Trench 123... Outer cladding

Claims

1. a glass fiber including a core and a clad; and a coating resin layer that is in contact with the glass fiber and coats the glass fiber; the coating resin layer includes a primary resin layer that coats the glass fiber and a secondary resin layer that coats the primary resin layer, the primary resin layer comprises a cured product of a resin composition containing a photopolymerizable compound including urethane (meth)acrylate, a photopolymerization initiator, a silane coupling agent, and an organic base; An optical fiber, wherein the content of the organic base is 5 ppm or more and 9000 ppm or less based on the total amount of the coating resin layer.

2. 2. The optical fiber according to claim 1, wherein the organic base is at least one selected from the group consisting of aromatic amines, aliphatic amines having an aromatic ring, heterocyclic amines, and cyclic amides.

3. 3. The optical fiber of claim 2, wherein the cyclic amide is δ-valerolactam or ε-caprolactam.

4. The optical fiber according to claim 1 , wherein the resin composition contains two or more types of the silane coupling agent.

5. 4. The optical fiber according to claim 1, wherein the primary resin layer has a Young's modulus of 0.6 MPa or less at 23°C.