Optical fiber, optical fiber ribbon, and optical fiber cable

Abstract

This optical fiber comprises: a glass fiber that includes a core and a cladding; and a resin coating layer that covers the glass fiber. The resin coating layer includes: a cured product of a resin composition that contains a photopolymerizable compound and a phosphine oxide photopolymerization initiator; and trimethyl benzoic acid. The phosphine oxide photopolymerization initiator content is 0.001–0.5 mass% of the entire optical fiber, and the trimethyl benzoic acid content is 0.001–0.2 mass% of the entire optical fiber.

Description

Optical Fiber, Optical Fiber Ribbons, and Optical Fiber Cables

[0001] This disclosure relates to optical fibers, optical fiber ribbons, and optical fiber cables. This application claims priority to Japanese Application No. 2024-087493, filed May 29, 2024, and incorporates by reference all of the contents of said Japanese application.

[0002] Generally, optical fibers are provided with a coating resin layer to protect the 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 outside of the primary resin layer. The primary resin layer and the secondary resin layer are each formed from an ultraviolet-curable resin composition containing a photopolymerizable compound and a photopolymerization initiator.

[0003] When connecting optical fibers, it is necessary to remove a part of the coating resin layer from the glass fiber. Patent Document 1 discloses that the removability of the coating resin layer is adjusted by focusing on the adhesion angle of mineral oil to the primary resin layer and the elastic modulus of the secondary resin layer.

[0004] Japanese Patent Application Laid-Open No. 2019-61157

[0005] When an optical fiber is immersed in oil such as mineral oil, the coating resin layer absorbs the oil, which can reduce the adhesion of the coating resin layer to the glass fiber. Optical fibers are required to have a coating resin layer that maintains a certain level of adhesion even when immersed in oil, not just water. On the other hand, when an optical fiber is exposed to light such as fluorescent light, the curing reaction of the coating resin layer progresses over time, which can cause the adhesion of the coating resin layer to the glass fiber to become too high. If the adhesion of the coating resin layer to the glass fiber is too high, the coating removability is reduced, and when the coating resin layer is removed from the glass fiber, part of the coating resin layer may remain on the outer periphery of the glass fiber.

[0006] An object of the present disclosure is to provide an optical fiber, an optical fiber ribbon, and an optical fiber cable that are provided with a coating resin layer that reduces changes over time in adhesion and coating removability.

[0007] (1) An optical fiber according to one aspect of the present disclosure includes a glass fiber including a core and a cladding, and a coating resin layer coating the glass fiber. The coating resin layer includes a cured product of a resin composition containing a photopolymerizable compound and a phosphine oxide-based photopolymerization initiator, and trimethylbenzoic acid, wherein the content of the phosphine oxide-based photopolymerization initiator is 0.001% by mass or more and 0.5% by mass or less, based on the total amount of the optical fiber, and the content of the trimethylbenzoic acid is 0.001% by mass or more and 0.2% by mass or less, based on the total amount of the optical fiber.

[0008] During the optical fiber production process, phosphine oxide-based photopolymerization initiators decompose and participate in the polymerization of photopolymerizable compounds, but some of them may remain undecomposed in the optical fiber. When the optical fiber is exposed to light from a fluorescent lamp or the like, the decomposed phosphine oxide-based photopolymerization initiator may react with molecules containing oxygen or hydrogen atoms, such as water, present in the reaction atmosphere to form trimethylbenzoic acid. When trimethylbenzoic acid is formed, it promotes the reaction between the silane coupling agent contained in the primary resin layer and the glass fiber, making it difficult to remove the coating resin layer from the glass fiber. On the other hand, if the amount of trimethylbenzoic acid in the optical fiber is low, the reaction between the silane coupling agent and the glass fiber may not proceed sufficiently, making it difficult to achieve adequate adhesion between the glass fiber and the coating resin layer.

[0009] In the optical fiber of this embodiment, the content of the phosphine oxide-based photopolymerization initiator is 0.001 mass % or more and 0.5 mass % or less, based on the total amount of the optical fiber, and the content of trimethylbenzoic acid is 0.001 mass % or more and 0.2 mass % or less, based on the total amount of the optical fiber, so that changes over time in adhesion and coating removability can be reduced.

[0010] (2) In the above (1), from the viewpoint of further reducing changes over time in adhesion and coating removability, the phosphine oxide photopolymerization initiator may contain at least one selected from the group consisting of 2,4,6-trimethylbenzoyldiphenylphosphine oxide, 2,4,6-trimethylbenzoylphenylphosphonic acid ethyl ester, phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide, and tri[phenyl(2,4,6-trimethylbenzoyl)phosphinic acid]polyethylene glycol ester.

[0011] (3) In (2) above, from the viewpoint of further reducing changes over time in adhesion and coating removability, the phosphine oxide-based photopolymerization initiator may be 2,4,6-trimethylbenzoyldiphenylphosphine oxide, and the content of 2,4,6-trimethylbenzoyldiphenylphosphine oxide may be 0.001 mass % or more and 0.1 mass % or less, based on the total mass of the optical fiber.

[0012] (4) In the above (2), from the viewpoint of further reducing changes over time in adhesion and coating removability, the phosphine oxide-based photopolymerization initiator may be 2,4,6-trimethylbenzoylphenylphosphonic acid ethyl ester, and the content of 2,4,6-trimethylbenzoylphenylphosphonic acid ethyl ester may be 0.001 mass % or more and 0.5 mass % or less based on the total amount of the optical fiber.

[0013] (5) In (2) above, from the viewpoint of further reducing changes over time in adhesion and coating removability, the phosphine oxide-based photopolymerization initiator may be phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide, and the content of phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide may be 0.001 mass % or more and 0.5 mass % or less, based on the total amount of the optical fiber.

[0014] (6) In (2) above, from the viewpoint of further reducing changes over time in adhesion and coating removability, the phosphine oxide-based photopolymerization initiator may be tri[phenyl(2,4,6-trimethylbenzoyl)phosphinic acid]polyethylene glycol ester, and the content of tri[phenyl(2,4,6-trimethylbenzoyl)phosphinic acid]polyethylene glycol ester may be 0.001 mass % or more and 0.5 mass % or less, based on the total amount of the optical fiber.

[0015] (7) An optical fiber ribbon according to one aspect of the present disclosure includes a plurality of parallel-arranged optical fibers according to any one of (1) to (6) above, and a connecting resin layer that coats and connects the plurality of optical fibers. Such an optical fiber ribbon has excellent microbending resistance and low-temperature properties.

[0016] (8) An optical fiber cable according to an aspect of the present disclosure includes the optical fiber ribbon according to (7) housed within the cable. Such an optical fiber ribbon cable has excellent microbending resistance and low-temperature properties.

[0017] (9) An optical fiber cable according to one aspect of the present disclosure includes a plurality of optical fibers according to any one of (1) to (6) housed within the cable. Such an optical fiber ribbon cable has excellent microbending resistance and low-temperature characteristics.

[0018] According to the present disclosure, it is possible to provide an optical fiber, an optical fiber ribbon, and an optical fiber cable that include a coating resin layer that reduces changes over time in adhesion and coating removability.

[0019] 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 optical fiber ribbon according to an embodiment. Fig. 3 is a schematic cross-sectional view showing an optical fiber ribbon according to an embodiment. Fig. 4 is a plan view showing the appearance of an optical fiber ribbon according to an embodiment. Fig. 5 is a schematic cross-sectional view showing an optical fiber cable according to an embodiment. Fig. 6 is a schematic cross-sectional view showing an optical fiber cable according to an embodiment.

[0020] [Details of the Embodiments of the Present Disclosure] Specific examples of optical fibers, optical fiber ribbons, and optical fiber cables 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.

[0021] 1 is a schematic cross-sectional view showing an example of an optical fiber according to an embodiment. The optical fiber 10 includes a glass fiber 13 as an optical transmission body and a coating resin layer 16 that contacts and coats the glass fiber 13.

[0022] The glass fiber 13 includes a core 11 and a cladding 12 that covers the core 11. The glass fiber 13 is a glass member, and is made of, for example, silica (SiO ２ The glass fiber 13 transmits light introduced into the optical fiber 10. The core 11 is provided, for example, in a region including the central axis of the glass fiber 13. The core 11 is made of, for example, pure SiO ２ Glass, GeO ２ The cladding 12 is provided in a region surrounding the core 11. The cladding 12 has a refractive index lower than that of the core 11. The cladding 12 is made of, for example, pure SiO ２ Glass or fluorine-doped SiO ２ Includes glass.

[0023] The coating resin layer 16 is a resin layer that covers the clad 12 and is formed using an ultraviolet-curable resin composition. The coating resin layer 16 has a primary resin layer 14 that covers the outer periphery of the glass fiber 13 and a secondary resin layer 15 that covers the outer periphery of the primary resin layer 14. The primary resin layer 14 is in contact with the outer periphery of the clad 12 and covers the entire clad 12. The secondary resin layer 15 is in contact with the outer periphery of the primary resin layer 14 and covers the entire primary resin layer 14. The thickness of the primary resin layer 14 is, for example, 10 μm or more and 50 μm or less. The thickness of the secondary resin layer 15 is, for example, 10 μm or more and 40 μm or less. The coating resin layer 16 may further include a colored resin layer that covers the outer periphery of the secondary resin layer 15.

[0024] The coating resin layer 16 includes a cured product of a resin composition containing a photopolymerizable compound and a phosphine oxide-based photopolymerization initiator, and trimethylbenzoic acid, the content of the phosphine oxide-based photopolymerization initiator being 0.001% by mass or more and 0.5% by mass or less, based on the total amount of the optical fiber, and the content of the trimethylbenzoic acid being 0.001% by mass or more and 0.2% by mass or less, based on the total amount of the optical fiber. This makes it possible to obtain an optical fiber with reduced changes over time in adhesion and coating removability.

[0025] The contents of the phosphine oxide-based photopolymerization initiator and trimethylbenzoic acid in the optical fiber can be adjusted by changing the amount of the phosphine oxide-based photopolymerization initiator blended in the resin composition used to form the coating resin layer, the production speed when producing the optical fiber, the time until additional irradiation with ultraviolet light after production of the optical fiber, and the like.

[0026] Examples of phosphine oxide photopolymerization initiators include 2,4,6-trimethylbenzoyldiphenylphosphine oxide (Omnirad TPO-N, manufactured by IGM Resins B.V.), 2,4,6-trimethylbenzoylphenylphosphonic acid ethyl ester (Omnirad TPO-L, manufactured by IGM Resins B.V.), phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide (Omnirad 819, manufactured by IGM Resins B.V.), tri[phenyl(2,4,6-trimethylbenzoyl)phosphinic acid]polyethylene glycol ester (Omnipol TP, manufactured by IGM Resins B.V.), and bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide.

[0027] Omnipol TP has a structure represented by the following formula (1): In formula (1), a, b, and c each independently represent an integer of 0 or greater, and a+b+c is 3 or greater.

[0028] From the viewpoint of further reducing changes over time in adhesion and coating removability, the phosphine oxide photopolymerization initiator may include, for example, at least one selected from the group consisting of 2,4,6-trimethylbenzoyldiphenylphosphine oxide, 2,4,6-trimethylbenzoylphenylphosphonic acid ethyl ester, phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide, and tri[phenyl(2,4,6-trimethylbenzoyl)phosphinic acid]polyethylene glycol ester.

[0029] From the viewpoint of further reducing changes over time in adhesion and coating removability, the phosphine oxide-based photopolymerization initiator may be 2,4,6-trimethylbenzoyldiphenylphosphine oxide, and the content of 2,4,6-trimethylbenzoyldiphenylphosphine oxide may be 0.001 mass % or more and 0.1 mass % or less, 0.001 mass % or more and 0.09 mass % or less, or 0.001 mass % or more and 0.08 mass % or less, based on the total amount of the optical fiber.

[0030] From the viewpoint of further reducing changes over time in adhesion and coating removability, the phosphine oxide-based photopolymerization initiator may be 2,4,6-trimethylbenzoylphenylphosphonic acid ethyl ester, and the content of 2,4,6-trimethylbenzoylphenylphosphonic acid ethyl ester may be 0.001 mass % or more and 0.5 mass % or less, based on the total amount of the optical fiber.

[0031] From the viewpoint of further reducing changes over time in adhesion and coating removability, the phosphine oxide-based photopolymerization initiator may be phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide, and the content of phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide may be 0.001 mass % or more and 0.5 mass % or less, based on the total amount of the optical fiber.

[0032] From the viewpoint of further reducing changes over time in adhesion and coating removability, the phosphine oxide-based photopolymerization initiator may be tri[phenyl(2,4,6-trimethylbenzoyl)phosphinic acid]polyethylene glycol ester, and the content of tri[phenyl(2,4,6-trimethylbenzoyl)phosphinic acid]polyethylene glycol ester may be 0.001 mass % or more and 0.5 mass % or less, based on the total amount of the optical fiber.

[0033] The resin composition according to this embodiment may further contain a photopolymerization initiator other than the phosphine oxide-based photopolymerization initiator, such as 1-hydroxycyclohexyl phenyl ketone, 2,2-dimethoxy-2-phenylacetophenone, 1-(4-isopropylphenyl)-2-hydroxy-2-methylpropan-1-one, and 2-methyl-1-[4-(methylthio)phenyl]-2-morpholino-propan-1-one.

[0034] The photopolymerizable compound may contain urethane (meth)acrylate from the viewpoint of adjusting the Young's modulus of the coating resin layer. As the urethane (meth)acrylate, for example, a reaction product of 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.

[0035] 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.

[0036] 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, or 2,000 or more and 8,000 or less. From the viewpoint of adjusting the Young's modulus of the secondary resin layer, the Mn of the polyol compound may be 300 or more and 3,000 or less, 400 or more and 2,500 or less, or 500 or more and 2,000 or less.

[0037] Examples of catalysts that may be used in synthesizing urethane (meth)acrylate include dibutyltin dilaurate, dibutyltin diacetate, dibutyltin maleate, dibutyltin bis(2-ethylhexyl mercaptoacetate), dibutyltin bis(isooctyl mercaptoacetate), copper naphthenate, cobalt naphthenate, zinc naphthenate, triethylamine, 1,4-diazabicyclo[2.2.2]octane, 2,6,7-trimethyl-1,4-diazabicyclo[2.2.2]octane, bismuth octylate, bismuth 2-ethylhexanoate, bismuth neodecanoate, bismuth acetate, zirconium tetraacetylacetonate, normal propyl zirconate, normal butyl zirconate, and zirconium monoacetylacetonate. In terms of availability or catalytic performance, dibutyltin dilaurate or dibutyltin diacetate may also be used as the catalyst.

[0038] When synthesizing the urethane (meth)acrylate, a lower alcohol having 5 or less carbon atoms 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.

[0039] The photopolymerizable compound may contain epoxy (meth)acrylate from the viewpoint of imparting appropriate toughness to the coating resin layer. As the epoxy (meth)acrylate, a reaction product of a diglycidyl ether compound having a bisphenol skeleton and a compound having a (meth)acryloyl group, such as (meth)acrylic acid, may be used. The epoxy (meth)acrylate may be used alone or in combination of two or more.

[0040] Examples of epoxy (meth)acrylates include (meth)acrylic acid adducts of bisphenol A diglycidyl ether, (meth)acrylic acid adducts of bisphenol AF diglycidyl ether, and (meth)acrylic acid adducts of bisphenol F diglycidyl ether.

[0041] The photopolymerizable compound may contain at least one of urethane (meth)acrylate and epoxy (meth)acrylate from the viewpoint of adjusting the Young's modulus of the secondary resin layer.

[0042] The photopolymerizable compound may further include a photopolymerizable compound (hereinafter referred to as a "monomer") other than urethane (meth)acrylate and epoxy (meth)acrylate.

[0043] Examples of the monomer include a monofunctional monomer having one polymerizable group and a polyfunctional monomer having two or more polymerizable groups. The monomer may be used alone or in combination of two or more.

[0044] 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, and 2-ethylhexyl (meth)acrylate. (Meth)acrylate monomers such as acrylate, n-octyl (meth)acrylate, isooctyl (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, dicyclopentanyl (meth)acrylate, nonylphenol polyethylene glycol (meth)acrylate, nonylphenoxypolyethylene glycol (meth)acrylate, and isobornyl (meth)acrylate; (meth)acrylic acid, (meth)acrylic acid dimer, carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, ω-carboxymethyl (meth)acrylate, Carboxy group-containing monomers such as carboxy-polycaprolactone (meth)acrylate; heterocycle-containing monomers such as N-(meth)acryloylmorpholine, N-vinylpyrrolidone, N-vinylcaprolactam, 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.

[0045] Examples of polyfunctional monomers 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, propylene oxide modified neopentyl glycol di(meth)acrylate, and polytetraethylene 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-eicosanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, isopentyl diol di(meth)acrylate p) acrylate, 3-ethyl-1,8-octanediol di(meth)acrylate, tricyclodecyl 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.

[0046] The photopolymerizable compound may contain an alkylene oxide-modified polyfunctional monomer in order to adjust the Young's modulus of the primary 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. Examples of alkylene oxide-modified polyfunctional monomers include alkylene oxide-modified di(meth)acrylates and alkylene oxide-modified tri(meth)acrylates.

[0047] 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.

[0048] Examples of alkylene oxide-modified tri(meth)acrylates include 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, and pentaerythritol tri(meth)acrylate.

[0049] The resin composition according to this embodiment may further contain a silane coupling agent from the viewpoint of being suitably applied to the primary resin layer.

[0050] 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 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-trimethoxysilylpropyldimethylthiocarbamoyltetrasulfide, and γ-trimethoxysilylpropylbenzothiazyltetrasulfide.

[0051] The resin composition according to this embodiment may further contain a leveling agent, an antifoaming agent, an antioxidant, a sensitizer, and the like.

[0052] The viscosity at 25°C of the resin composition according to this embodiment may be 1000 mPa·s or more, 1500 mPa·s or more, or 2000 mPa·s or more from the viewpoint of storage stability, and may be less than 10000 mPa·s, 8000 mPa·s or less, or 6000 mPa·s or less from the viewpoint of coatability.

[0053] The primary resin layer 14 can be formed by curing a resin composition containing a photopolymerizable compound including urethane (meth)acrylate, a phosphine oxide-based photopolymerization initiator, and a silane coupling agent.

[0054] From the viewpoint of improving the microbending resistance of the optical fiber, the Young's modulus of the primary resin layer 14 may be 0.80 MPa or less, 0.70 MPa or less, 0.60 MPa or less, or 0.55 MPa or less at 23°C ± 2°C. If the Young's modulus of the primary resin layer is 0.80 MPa or less, external forces are less likely to be transmitted to the glass fiber, and an increase in transmission loss due to microbending tends to be more easily suppressed. From the viewpoint of further improving the low-temperature properties of the optical fiber, the Young's modulus of the primary resin layer may be 0.10 MPa or more, 0.15 MPa or more, 0.20 MPa or more, or 0.35 MPa or more at 23°C ± 2°C.

[0055] The Young's modulus of the primary resin layer 14 can be measured by the Pullout Modulus (POM) method at 23°C. Two locations of the optical fiber are 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 is removed. Next, one chuck device is fixed, and the other chuck device is 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 chuck movement 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 can be calculated using the following formula: Young's modulus (MPa) = ((1 + n)W / πLZ) × ln(Dp / Df)

[0056] The secondary resin layer 15 can be formed by curing a resin composition containing a photopolymerizable compound including at least one of urethane (meth)acrylate and epoxy (meth)acrylate, and a phosphine oxide-based photopolymerization initiator.

[0057] From the viewpoint of improving the microbending resistance of the optical fiber, the Young's modulus of the secondary resin layer 15 may be 750 MPa or more, 800 MPa or more, 900 MPa or more, or 1000 MPa or more at 23° C.±2° C. The upper limit of the Young's modulus of the secondary resin layer is not particularly limited, but from the viewpoint of imparting appropriate toughness to the secondary resin layer, it may be 2000 MPa or less, 1800 MPa or less, or 1500 MPa or less at 23° C.±2° C.

[0058] The Young's modulus of the secondary resin layer 15 can be measured, for example, by the following method. First, the optical fiber is immersed in a mixed solvent of acetone and ethanol, and only the coating resin layer is extracted in a cylindrical shape. At this time, the primary resin layer and the secondary resin layer are integrated, but the Young's modulus of the primary resin layer is 1 / 10,000 to 1 / 1,000 of that of the secondary resin layer, so the Young's modulus of the primary resin layer can be ignored. Next, the solvent is removed from the coating resin layer by vacuum drying, and then a tensile test (tensile speed: 1 mm / min) is performed at 23°C, and the Young's modulus can be determined using the secant equation with 2.5% strain.

[0059] The method for manufacturing the optical fiber may include a coating step of coating a resin composition used to form a coating resin layer on the outer periphery of a glass fiber including a core and a cladding, and a curing step of curing the resin composition by irradiating it with ultraviolet light after the coating step.

[0060] (Optical fiber ribbon) An optical fiber ribbon can be produced using the optical fibers according to this embodiment. The optical fiber ribbon according to this embodiment includes the optical fiber and a connecting resin layer that coats and connects a plurality of the optical fibers. By using the optical fiber, the optical fiber ribbon according to this embodiment has excellent microbending resistance and low-temperature characteristics.

[0061] 2 is a schematic cross-sectional view showing an optical fiber ribbon according to one embodiment. The optical fiber ribbon 100 includes a plurality of optical fibers 10 and a connecting resin layer 40 in which the optical fibers 10 are (integrally) coated with a ribbon resin and connected. While FIG. 2 shows four optical fibers 10 as an example, the number is not particularly limited.

[0062] The optical fibers 10 may be integrated in a state where they are in contact with each other and arranged in parallel, or some or all of the optical fibers 10 may be integrated in a state where they are arranged in parallel with a fixed interval between them. The center-to-center distance F between adjacent optical fibers 10 may be 220 μm or more and 280 μm or less. When the center-to-center distance is 220 μm or more and 280 μm or less, the optical fibers can be easily placed in existing V-grooves, and an optical fiber ribbon with excellent bulk fusion splicing properties can be obtained. The thickness T of the optical fiber ribbon 100 may be 164 μm or more and 285 μm or less, depending on the outer diameter of the optical fibers 10.

[0063] 3 is a schematic cross-sectional view showing an example of an optical fiber ribbon in which optical fibers are integrated in a state in which they are arranged in parallel at a fixed interval. The optical fiber ribbon 100A shown in FIG. 3 is formed by connecting 12 optical fibers 10, each of which has two optical fibers 10, at a fixed interval with a ribbon resin. The ribbon resin forms a connecting resin layer 40.

[0064] The ribbon resin may be a resin material generally known as a ribbon material. From the viewpoint of preventing damage to the optical fiber 10 and facilitating its severability, the ribbon resin may contain a thermosetting resin such as a silicone resin, an epoxy resin, or a urethane resin, or an ultraviolet-curing resin such as an epoxy acrylate, a urethane acrylate, or a polyester acrylate.

[0065] When the optical fibers 10 are arranged in parallel at regular intervals, i.e., when adjacent optical fibers 10 are joined via ribbon resin without touching each other, the thickness of the connecting portion at the center of the optical fibers 10 may be 150 μm or more and 220 μm or less. Because the optical fiber ribbon is prone to deformation when being stored in a cable, the optical fiber ribbon may have a recess at the connecting portion of the optical fibers. The recess may be formed in a triangular shape with a narrowing angle on one side of the connecting portion.

[0066] The optical fiber ribbon according to this embodiment may have connecting portions and non-connecting portions intermittently in the longitudinal and width directions. FIG. 4 is a plan view showing the appearance of an optical fiber ribbon according to one embodiment. The optical fiber ribbon 100B has a plurality of optical fibers, a plurality of connecting portions 20, and non-connecting portions (separated portions) 21. The non-connecting portions 21 are formed intermittently in the longitudinal direction of the optical fiber ribbon. The optical fiber ribbon 100B is an intermittently connected optical fiber ribbon in which connecting portions 20 and non-connecting portions 21 are provided intermittently in the longitudinal direction for every two optical fibers 10A. A "connecting portion" refers to a portion where adjacent optical fibers are integrated via a connecting resin layer, and a "non-connecting portion" refers to a portion where adjacent optical fibers are not integrated via a connecting resin layer and there is a gap between the optical fibers.

[0067] In the optical fiber ribbon having the above configuration, the non-connecting portions 21 are intermittently provided at the connecting portions 20 provided every two fibers, making the optical fiber ribbon easily deformable. Therefore, when mounting the optical fiber ribbon in an optical fiber cable, the optical fiber ribbon can be easily rolled up and mounted, making it suitable for high-density mounting. Furthermore, the connecting portions 20 can be easily torn starting from the non-connecting portions 21, making it easy to separate the optical fibers 10 from the optical fiber ribbon into individual fibers.

[0068] (Optical fiber cable) In the optical fiber cable according to the present embodiment, the optical fiber ribbon is housed within the cable. In the optical fiber cable according to an embodiment of the present disclosure, the optical fiber ribbon is housed within the cable. The optical fiber cable according to the present embodiment may be configured such that the plurality of optical fibers are housed within the cable without being coated with a ribbon resin, and in another embodiment of the optical fiber cable according to the present disclosure, a plurality of the optical fibers are housed within the cable. By using the optical fiber or the optical fiber ribbon, the optical fiber cable according to the present embodiment has excellent microbending resistance and low-temperature properties.

[0069] An example of an optical fiber cable is a slotted optical fiber cable having a plurality of slots (grooves). The optical fiber ribbons can be mounted in the slots so that the mounting density in each slot is approximately 25% to 65%. The mounting density refers to the ratio of the cross-sectional area of ​​the optical fiber ribbons mounted in the slot to the cross-sectional area of ​​the slot.

[0070] An example of an optical fiber cable according to this embodiment will be described with reference to Figures 5 and 6. In Figures 5 and 6, an intermittently connected optical fiber ribbon is housed, but a bundle of optical fibers that are not coated with a ribbon resin may also be housed.

[0071] FIG. 5 is a schematic cross-sectional view of a slotless optical fiber cable 60 using the intermittently connected optical fiber ribbons 100B described above. The optical fiber cable 60 includes a cylindrical tube 61 and multiple optical fiber ribbons 100B. The multiple optical fiber ribbons 100B may be bundled together using fillers 62 such as aramid fibers. Each of the multiple optical fiber ribbons 100B may have different markings. The optical fiber cable 60 is formed by twisting multiple bundled optical fiber ribbons 100B together, extruding a resin to form a tube 61 around the bundle, and then covering the tube with a tension member 63 and an outer jacket 64. If waterproofing is required, a water-absorbing yarn may be inserted inside the tube 61. The tube 61 may be formed using a resin such as polybutylene terephthalate or high-density polyethylene. A tear cord 65 may be provided on the outside of the tube 61.

[0072] FIG. 6 is a schematic cross-sectional view of a slotted optical fiber cable 70 using the intermittently connected optical fiber ribbons 100B described above. The optical fiber cable 70 includes a slotted rod 72 having a plurality of slots 71 and a plurality of optical fiber ribbons 100B. The optical fiber cable 70 is configured such that a plurality of slots 71 are radially formed in a slotted rod 72 having a central tension member 73. The plurality of slots 71 may be twisted in a spiral or SZ shape along the longitudinal direction of the optical fiber cable 70. Each slot 71 accommodates a plurality of optical fiber ribbons 100B that have been unwound from a parallel state and placed in a dense state. Each optical fiber ribbon 100B may be bundled with an identification bundling material. A pressure winding tape 74 is wound around the slotted rod 72, and an outer jacket 75 is formed around the pressure winding tape 74.

[0073] 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. Note that the present disclosure is not limited to these examples.

[0074] [Resin Composition for Primary Resin Layer] (Photopolymerizable Compound) As photopolymerizable compounds, urethane acrylate a obtained by reacting polypropylene glycol having a molecular weight of 4000, isophorone diisocyanate, and hydroxyethyl acrylate, nonylphenol EO-modified acrylate (EO-NPA, manufactured by Toagosei Co., Ltd., trade name "Aronix M-113"), N-vinyl caprolactam, and neopentyl glycol diacrylate were prepared. (Photopolymerization Initiator) As phosphine oxide-based photopolymerization initiators, 2,4,6-trimethylbenzoyldiphenylphosphine oxide (manufactured by IGM Resins B.V., trade name "Omnirad TPO-N"), phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide (manufactured by IGM Resins B.V., trade name "Omnirad 819"), 2,4,6-trimethylbenzoylphenylphosphonic acid ethyl ester (manufactured by IGM Resins B.V., trade name "Omnirad TPO-L"), and tri[phenyl(2,4,6-trimethylbenzoyl)phosphinic acid]polyethylene glycol ester (manufactured by IGM Resins B.V., trade name "Omnipol TP") were prepared. (Silane Coupling Agent) 3-mercaptopropyltrimethoxysilane (MPTS) was prepared as a silane coupling agent.

[0075] A photopolymerizable compound, a photopolymerization initiator, and a silane coupling agent were mixed in the amounts (parts by mass) shown in Table 1 to prepare a resin composition for the primary resin layer.

[0076]

[0077] [Resin Composition for Secondary Resin Layer] (Photopolymerizable Compound) As photopolymerizable compounds, urethane acrylate b obtained by reacting polypropylene glycol having a molecular weight of 1000, isophorone diisocyanate, and 2-hydroxyethyl acrylate, urethane acrylate c obtained by reacting polypropylene glycol having a molecular weight of 600, isophorone diisocyanate, and 2-hydroxyethyl acrylate, epoxy acrylate (acrylic acid adduct of bisphenol A diglycidyl ether, manufactured by Osaka Organic Chemical Industry Ltd., trade name "Viscoat #540"), isobornyl acrylate, trimethylolpropane polyethoxy triacrylate (manufactured by Miwon Specialty Chemical Co., Ltd., trade name "Miramer M3150"), and trimethylolpropane triacrylate were prepared. (Photopolymerization initiator) 1-hydroxycyclohexyl phenyl ketone (manufactured by IGM Resins B.V., trade name "Omnirad 184") was prepared as an alkylphenone-based photopolymerization initiator, and Omnirad TPO-N, Omnirad TPO-L, Omnirad 819, and Omnipol TP were prepared as phosphine oxide-based photopolymerization initiators.

[0078] The photopolymerizable compound and the photopolymerization initiator were mixed in the amounts (parts by mass) shown in Table 2 to prepare resin compositions for the secondary resin layer.

[0079]

[0080] [Fabrication of Optical Fiber] A resin composition for the primary coating and a resin composition for the secondary coating were each applied to the outer peripheral surface of a glass fiber with a diameter of 125 μm. Next, each resin composition was cured by irradiating with ultraviolet light to form a primary coating layer and a secondary coating layer, thereby fabricating an optical fiber. The primary coating layer was 32 μm thick, the secondary coating layer was 28 μm thick, and an optical fiber with an outer diameter of 245 μm was fabricated. The optical fiber was fabricated at a manufacturing speed of 3000 m / min. After fabrication of the optical fiber, additional ultraviolet irradiation was performed on the optical fiber as needed. Test Examples 1 to 14 correspond to working examples, and Test Examples 15 to 18 correspond to comparative examples.

[0081] [Evaluation] The optical fiber of each test example was evaluated as follows. The results are shown in Tables 3, 4 and 5.

[0082] (Phosphine oxide initiator and trimethylbenzoic acid content) 0.5 g of optical fiber was placed in a vial, 20 mL of acetone was added, and extraction was performed for 60 minutes using an ultrasonic cleaner. The extract was measured using a gas chromatograph (GC) to determine the content (mass%) of the phosphine oxide initiator and trimethylbenzoic acid in the optical fiber. The measurement device used was a "GC2030" manufactured by Shimadzu Corporation, and the column used was a "UA-1" manufactured by Frontier Labs (non-polar, inner diameter 0.25 mm x length 30 m, film thickness 0.25 μm). The measurement temperature was raised from 100 ° C to 160 ° C at a rate of 20 ° C / min, then raised to 230 ° C at a rate of 5 ° C / min, and then raised to 350 ° C at a rate of 60 ° C / min, and held at 350 ° C for 15 minutes.

[0083] (Coating Stripping Force) An optical fiber was immersed in jelly (trade name "LT-410", manufactured by SHANGHAI HONGHUI OPTICS COMMUNICATION TECH. CO., LTD.) at 85°C for 120 days. In accordance with JIS C 6821, the coating stripping force (N) of the optical fiber was measured before and after immersion, and the average value of the coating stripping force of the optical fiber was calculated in accordance with the international standard (IEC 60793-1-2). The average value of the coating stripping force in the international standard is 1.0 N or more and 5.0 N or less.

[0084] (Pullout Force) An optical fiber was placed 60 cm away from a 40 W white fluorescent lamp and irradiated with 1000 lux light at room temperature for 7 days. The pullout force per 10 mm when pulling the coating resin layer from the glass fiber was measured for the optical fiber before and after irradiation with 1000 lux light, based on the method described in JP 2001-194565 A and the like. The rate of change in pullout force was calculated using the following formula: Rate of change (%) = (pullout force after irradiation - pullout force before irradiation) / pullout force before irradiation × 100

[0085]

[0086]

[0087]

[0088] 10, 10A... Optical fiber 11... Core 12... Cladding 13... Glass fiber 14... Primary resin layer 15... Secondary resin layer 16... Coating resin layer 20... Connecting portion 21... Non-connecting portion 40... Connecting resin layer 60, 70... Optical fiber cable 61... Cylindrical tube 62... Interposer 63, 73... Tension member 64, 75... Outer jacket 65... Tear cord 71... Slot 72... Slot rod 74... Holding winding tape 100, 100A, 100B... Optical fiber ribbon D1... Core diameter D2... Outer diameter of cladding F... Center-to-center distance T... Thickness

Claims

1. An optical fiber comprising a glass fiber including a core and a cladding, and a coating resin layer coating the glass fiber, wherein the coating resin layer contains a cured product of a resin composition containing a photopolymerizable compound and a phosphine oxide-based photopolymerization initiator, and trimethylbenzoic acid, the content of the phosphine oxide-based photopolymerization initiator being 0.001% by mass or more and 0.5% by mass or less, based on the total amount of the optical fiber, and the content of the trimethylbenzoic acid being 0.001% by mass or more and 0.2% by mass or less, based on the total amount of the optical fiber.

2. The optical fiber according to claim 1, wherein the phosphine oxide photopolymerization initiator comprises at least one selected from the group consisting of 2,4,6-trimethylbenzoyldiphenylphosphine oxide, 2,4,6-trimethylbenzoylphenylphosphonic acid ethyl ester, phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide, and tri[phenyl(2,4,6-trimethylbenzoyl)phosphinic acid]polyethylene glycol ester.

3. The optical fiber according to claim 2, wherein the phosphine oxide photopolymerization initiator is 2,4,6-trimethylbenzoyldiphenylphosphine oxide, and the content of the 2,4,6-trimethylbenzoyldiphenylphosphine oxide is 0.001 mass % or more and 0.1 mass % or less, based on the total amount of the optical fiber.

4. The optical fiber according to claim 2, wherein the phosphine oxide photopolymerization initiator is 2,4,6-trimethylbenzoylphenylphosphonic acid ethyl ester, and the content of the 2,4,6-trimethylbenzoylphenylphosphonic acid ethyl ester is 0.001 mass % or more and 0.5 mass % or less, based on the total mass of the optical fiber.

5. The optical fiber according to claim 2, wherein the phosphine oxide photopolymerization initiator is phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide, and the content of the phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide is 0.001 mass % or more and 0.5 mass % or less, based on the total mass of the optical fiber.

6. The optical fiber according to claim 2, wherein the phosphine oxide photopolymerization initiator is tri[phenyl(2,4,6-trimethylbenzoyl)phosphinic acid]polyethylene glycol ester, and the content of the tri[phenyl(2,4,6-trimethylbenzoyl)phosphinic acid]polyethylene glycol ester is 0.001% by mass or more and 0.5% by mass or less, based on the total mass of the optical fiber.

7. An optical fiber ribbon comprising a plurality of optical fibers according to any one of claims 1 to 6 arranged in parallel, and a connecting resin layer that coats and connects the plurality of optical fibers.

8. An optical fiber cable in which the optical fiber ribbon according to claim 7 is housed.

9. An optical fiber cable in which a plurality of optical fibers according to any one of claims 1 to 6 are housed within the cable.

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