Resin composition for coating optical fiber and optical fiber

Abstract

This resin composition for coating an optical fiber contains a photopolymerizable compound and a photopolymerization initiator. The photopolymerization initiator contains a compound represented by formula (1). In formula (1), R1, R2, R3, R4, R5, R6, R7, R8, R9, and R10 are each independently a hydrogen atom or a C1-C10 alkyl group; at least one of R1, R2, R3, R4, and R5 is a C1-C10 alkyl group; and at least one of R6, R7, R8, R9, and R10 is a C1-C10 alkyl group.

Description

Resin composition for optical fiber coating and optical fiber

[0001] This disclosure relates to a resin composition for optical fiber coating and an optical fiber. This application claims priority to Japanese Application No. 2024-089918, filed June 3, 2024, and incorporates by reference all of the contents of said Japanese application.

[0002] Generally, optical fibers are provided with a coating resin layer for protecting 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, and it is known that diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide (hereinafter also referred to as "TPO") is used as the photopolymerization initiator (Patent Documents 1 to 4).

[0003] JP 2009-197163 A JP 2012-111674 A JP 2013-136783 A JP 2014-114208 A

[0004] A resin composition for optical fiber coating according to one embodiment of the present disclosure is a resin composition containing a photopolymerizable compound and a photopolymerization initiator, and the photopolymerization initiator includes a compound represented by the following formula (1): [In formula (1), R １ , R ２ , R ３ , R ４ , R ５ , R ６ , R ７ , R ８ , R ９ , and R １０ each independently represents a hydrogen atom or an alkyl group having 1 to 10 carbon atoms; R １ , R ２ , R ３ , R ４ , and R ５ At least one of R is an alkyl group having 1 to 10 carbon atoms, ６ , R ７ , R ８, R ９ , and R １０ At least one of the groups is an alkyl group having 1 to 10 carbon atoms.

[0005] FIG. 1 is a schematic cross-sectional view showing an example of an optical fiber according to this embodiment.

[0006] [Problem to be Solved by the Present Disclosure] In the light irradiation process for producing an optical fiber, TPO in the resin composition decomposes and the photopolymerizable compound polymerizes to form a coating resin layer, but some TPO may not decompose and remain in the coating resin layer. TPO is designated as a substance of very high concern (SVHC) under the REACH regulation of the European Union (EU).

[0007] The present disclosure aims to provide a resin composition having curability equivalent to that of a conventional resin composition using TPO as a photopolymerization initiator, and an optical fiber having a coating resin layer formed using the resin composition.

[0008] [Effects of the Present Disclosure] According to the present disclosure, it is possible to provide a resin composition having curability equivalent to that of a conventional resin composition using TPO as a photopolymerization initiator, and an optical fiber having a coating resin layer formed using the resin composition.

[0009] [Description of Embodiments of the Present Disclosure] First, the contents of the embodiments of the present disclosure will be listed and described.

[0010] (1) A resin composition for optical fiber coating according to one embodiment of the present disclosure is a resin composition containing a photopolymerizable compound and a photopolymerization initiator, wherein the photopolymerization initiator includes a compound represented by the following formula (1): [In formula (1), R １ , R ２ , R ３ , R ４ , R ５ , R ６ , R ７ , R ８ , R ９ , and R １０ each independently represents a hydrogen atom or an alkyl group having 1 to 10 carbon atoms; R １ , R２ , R ３ , R ４ , and R ５ At least one of R is an alkyl group having 1 to 10 carbon atoms, ６ , R ７ , R ８ , R ９ , and R １０ At least one of the groups is an alkyl group having 1 to 10 carbon atoms.

[0011] Such a resin composition for optical fiber coating has the same curability as conventional resin compositions, even without using TPO as a photopolymerization initiator.

[0012] (2) In the above (1), from the viewpoint of adjusting the Young's modulus of the coating resin layer, the content of the photopolymerization initiator may be 0.1 mass % or more and 10 mass % or less based on the total amount of the resin composition.

[0013] (3) In the above (1) or (2), from the viewpoint of further enhancing the curability of the resin composition, in formula (1), R １ , R ２ , R ４ , R ５ , R ６ , R ７ , R ９ and R １０ is a hydrogen atom, and R ３ and R ８ may be an alkyl group having 1 to 10 carbon atoms.

[0014] (4) In any of (1) to (3) above, from the viewpoint of suitable use in the primary resin layer of an optical fiber, the resin composition may further contain a silane coupling agent, and the photopolymerizable compound may contain urethane (meth)acrylate.

[0015] (5) In any of (1) to (3) above, from the viewpoint of suitable use in a secondary resin layer of an optical fiber, the photopolymerizable compound may contain at least one selected from the group consisting of urethane (meth)acrylate and epoxy (meth)acrylate.

[0016] (6) 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 that contacts and coats the glass fiber, the coating resin layer containing a cured product of the resin composition according to any one of (1) to (5). Such an optical fiber has properties equivalent to those of conventional optical fibers.

[0017] (7) In the above (6), from the viewpoint of enhancing the curability of the primary resin layer, the coating resin layer may have 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 may contain a cured product of the resin composition described in the above (4).

[0018] (8) In the above (7), from the viewpoint of enhancing the curability of the secondary resin layer, the secondary resin layer may contain a cured product of the resin composition described in the above (5).

[0019] [Details of the Embodiments of the Present Disclosure] Specific examples of resin compositions for optical fiber coatings and optical fibers 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 of the claims. In the following description, the same elements in the drawings will be designated 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.

[0020] (Resin Composition) The resin composition for optical fiber coating according to this embodiment is a resin composition containing a photopolymerizable compound and a photopolymerization initiator, and the photopolymerization initiator contains a compound represented by the following formula (1):

[0021] In formula (1), R １ , R ２ , R ３ , R ４ , R ５ , R ６ , R ７ , R ８ , R ９ , and R１０ each independently represents a hydrogen atom or an alkyl group having 1 to 10 carbon atoms; R １ , R ２ , R ３ , R ４ , and R ５ At least one of R is an alkyl group having 1 to 10 carbon atoms, ６ , R ７ , R ８ , R ９ , and R １０ At least one of the groups is an alkyl group having 1 to 10 carbon atoms.

[0022] The compound represented by the above formula (1) is not designated as an SVHC in the REACH regulation of the EU, and the resin composition according to the present embodiment can form a coating resin layer having physical properties equivalent to those when TPO is used by using the compound represented by formula (1) as a photopolymerization initiator.

[0023] The alkyl group having 1 to 10 carbon atoms in the above formula (1) may be linear or branched. Examples of the alkyl group having 1 to 10 carbon atoms include a methyl group, an ethyl group, a propyl group, an n-butyl group, a t-butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, a nonyl group, and a decyl group.

[0024] The photopolymerization initiator is a compound represented by the formula (1) above, １ , R ２ , R ３ , R ４ , and R ５ At least one of R is an alkyl group having 1 to 5 carbon atoms, ６ , R ７ , R ８ , R ９ , and R １０ and at least one of R is an alkyl group having 1 to 5 carbon atoms. １ , R ２ , R ３ , R ４ , and R ５ At least one of R is an alkyl group having 1 to 3 carbon atoms, ６ , R ７ , R ８ , R９ , and R １０ At least one of the groups may be an alkyl group having 1 to 3 carbon atoms.

[0025] From the viewpoint of further enhancing the curability of the resin composition, the photopolymerization initiator is preferably a compound represented by the formula (1) R １ , R ２ , R ４ , R ５ , R ６ , R ７ , R ９ and R １０ is a hydrogen atom, and R ３ and R ８ is an alkyl group having 1 to 10 carbon atoms, and R １ , R ２ , R ４ , R ５ , R ６ , R ７ , R ９ and R １０ is a hydrogen atom, and R ３ and R ８ is a methyl group.

[0026] Examples of the compound represented by formula (1) include (2,4,6-trimethylbenzoyl)bis(o-tolyl)phosphine oxide, (2,4,6-trimethylbenzoyl)bis(m-tolyl)phosphine oxide, (2,4,6-trimethylbenzoyl)bis(p-tolyl)phosphine oxide, 2,4,6-trimethylbenzoyl)bis(p-ethylphenyl)phosphine oxide, 2,4,6-trimethylbenzoyl)bis(p-butylphenyl)phosphine oxide, and (2,4,6-trimethylbenzoyl)bis(xylyl)phosphine oxide.

[0027] The resin composition according to this embodiment may further contain a photopolymerization initiator (hereinafter referred to as "another photopolymerization initiator") different from the compound represented by formula (1). The other photopolymerization initiator is not particularly limited as long as it is a photopolymerization initiator other than diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide (TPO), and can be appropriately selected from known photopolymerization initiators and used.

[0028] Other photopolymerization initiators include, for example, 2,4,6-trimethylbenzoylphenylphosphonic acid ethyl ester (Omnirad TPO-L, manufactured by IGM Resins), 1-hydroxycyclohexyl phenyl ketone (Omnirad 184, manufactured by IGM Resins), 2-benzoyl-2-dimethylamino-4'-morpholinobutyrophenone (Omnirad 369, manufactured by IGM Resins), 2-dimethylamino-2-(4-methyl-benzyl)-1-(4-morpholin-4-yl-phenyl)-butan-1-one (Omnirad 379, manufactured by IGM Resins), and 2,2-dimethoxy-2-phenylacetophenone (Omnirad 651, manufactured by IGM Resins). Examples of suitable methyl benzoyl esters include bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (Omnirad 819, IGM Resins), tri[phenyl(2,4,6-trimethylbenzoyl)phosphinic acid] polyethylene glycol ester (Omnipol TP, IGM Resins), and 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one (Omnirad 907, IGM Resins).

[0029] Omnipol TP has a structure represented by the following formula (2): In formula (2), a, b, and c each independently represent an integer of 0 or greater, and a+b+c is 3 or greater.

[0030] From the viewpoint of increasing the curability of the resin composition and adjusting the Young's modulus of the coating resin layer, the content of the photopolymerization initiator may be 0.1 mass % or more and 10 mass % or less, 0.3 mass % or more and 7 mass % or less, 0.5 mass % or more and 5 mass % or less, or 0.8 mass % or more and 3 mass % or less, based on the total amount of the resin composition.

[0031] The content of the photopolymerization initiator may be 0.1 parts by mass or more and 10 parts by mass or less, 0.3 parts by mass or more and 7 parts by mass or less, 0.5 parts by mass or more and 5 parts by mass or less, or 1 part by mass or more and 3 parts by mass or less, relative to 100 parts by mass of the total amount of the photopolymerizable compounds.

[0032] The photopolymerizable compound may contain at least one compound selected from the group consisting of urethane (meth)acrylates and epoxy (meth)acrylates, from the viewpoint of adjusting the Young's modulus of the coating resin layer.

[0033] The urethane (meth)acrylate may be, for example, a reaction product of a polyol compound, a polyisocyanate compound, and a hydroxyl group-containing (meth)acrylate compound. The urethane (meth)acrylate may be used alone or in combination of two or more.

[0034] 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.

[0035] 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. 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, 500 or more and 2,000 or less, or 600 or more and 1,500 or less.

[0036] 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.

[0037] 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.

[0038] The photopolymerizable compound may contain epoxy(meth)acrylate from the viewpoint of adjusting the Young's modulus of the coating resin layer and increasing the strength of the secondary resin layer. The epoxy(meth)acrylate may be 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. The epoxy(meth)acrylate may be used alone or in combination of two or more.

[0039] 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.

[0040] From the viewpoint of further increasing the strength of the secondary resin layer, the content of the epoxy (meth)acrylate may be 30 parts by mass or more, 35 parts by mass or more, 40 parts by mass or more, or 45 parts by mass or more, relative to 100 parts by mass of the total amount of the photopolymerizable compound, and may be 70 parts by mass or less, 65 parts by mass or less, 60 parts by mass or less, or 50 parts by mass or less.

[0041] The photopolymerizable compound may further include a photopolymerizable compound (hereinafter referred to as a "monomer") other than epoxy (meth)acrylate and urethane (meth)acrylate.

[0042] 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.

[0043] 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.

[0044] 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.

[0045] 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.

[0046] 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.

[0047] 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.

[0048] From the viewpoint of being suitably applied to the primary resin layer, the resin composition according to this embodiment may further contain a silane coupling agent, and the photopolymerizable compound may contain urethane (meth)acrylate.

[0049] 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.

[0050] The resin composition according to this embodiment may further contain a leveling agent, an antifoaming agent, an antioxidant, a sensitizer, and the like.

[0051] 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 coatability, and may be less than 10000 mPa·s, 8000 mPa·s or less, or 6000 mPa·s or less from the viewpoint of coatability.

[0052] The resin composition according to the present embodiment is an ultraviolet-curable resin composition and can be suitably used as a material for forming a coating resin layer of an optical fiber. By forming a coating resin layer using the resin composition according to the present embodiment, it is possible to form a coating resin layer having physical properties equivalent to those obtained when TPO, which is commonly used as a photopolymerization initiator, is used.

[0053] (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 cured product of the resin composition for optical fiber coating described above. According to the optical fiber according to this embodiment, an optical fiber can be obtained that includes a coating resin layer that has physical properties equivalent to those of a conventional coating resin layer that uses a TPO.

[0054] 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 that contacts and coats the glass fiber 13. The coating resin layer 16 has a primary resin layer 14 that coats the glass fiber 13 and a secondary resin layer 15 that coats the primary resin layer 14.

[0055] 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 silica glass doped with germanium or pure silica glass, and the cladding 12 can be made of pure silica glass or silica glass doped with fluorine.

[0056] 1 , for example, the outer diameter (D2) of the glass fiber 13 may be approximately 80 μm to 125 μm, and the diameter (D1) of the core 11 constituting the glass fiber 13 may be approximately 7 μm to 15 μm. The thickness of the coating resin layer 16 may be, for example, 20 μm to 70 μm. The thickness of each of the primary resin layer 14 and the secondary resin layer 15 may be approximately 10 μm to 50 μm.

[0057] When the outer diameter of the glass fiber 13 is about 125 μm and the thickness of the coating resin layer 16 is 60 μm to 70 μm, the thickness of each of the primary resin layer 14 and the secondary resin layer 15 may be about 10 μm to 50 μm, for example, the thickness of the primary resin layer 14 may be 35 μm and the thickness of the secondary resin layer 15 may be 25 μm. The outer diameter of the optical fiber 10 may be about 245 μm to 265 μm.

[0058] The thickness of the coating resin layer 16 may be approximately 27 μm to 48 μm. In this case, the thickness of each of the primary resin layer 14 and the secondary resin layer 15 may be approximately 10 μm to 38 μm, for example, the thickness of the primary resin layer 14 may be 25 μm and the thickness of the secondary resin layer 15 may be 10 μm. The outer diameter of the optical fiber 10 may be approximately 180 μm to 220 μm.

[0059] The primary resin layer 14 can be formed by curing a resin composition containing a photopolymerizable compound containing urethane (meth)acrylate, a photopolymerization initiator containing the compound represented by formula (1), and a silane coupling agent. That is, the primary resin layer 14 may include a cured product of the resin composition according to this embodiment.

[0060] 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.

[0061] 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)

[0062] The secondary resin layer 15 can be formed by curing a resin composition containing a photopolymerizable compound including at least one compound selected from the group consisting of urethane (meth)acrylate and epoxy (meth)acrylate, and a photopolymerization initiator including the compound represented by the above formula (1). That is, the secondary resin layer 15 may include a cured product of the resin composition according to this embodiment.

[0063] 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.

[0064] 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.

[0065] The method for manufacturing the optical fiber may include a coating step of coating the resin composition according to the present embodiment onto 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.

[0066] 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, although the present disclosure is not limited to these examples.

[0067] (Photopolymerizable Compound) As the urethane (meth)acrylate, urethane acrylate a obtained by reacting polypropylene glycol having a molecular weight of 4000, isophorone diisocyanate, and 2-hydroxyethyl acrylate, urethane acrylate b obtained by reacting polypropylene glycol having a molecular weight of 1000, isophorone diisocyanate, and 2-hydroxyethyl acrylate, and urethane acrylate c obtained by reacting polypropylene glycol having a molecular weight of 600, isophorone diisocyanate, and 2-hydroxyethyl acrylate were prepared. As the epoxy (meth)acrylate, epoxy acrylate (trade name "Viscoat #540", manufactured by Osaka Organic Chemical Industry Co., Ltd.), which is an acrylic acid adduct of bisphenol A diglycidyl ether, was prepared. As monomers, nonylphenylol EO-modified acrylate (EO-NPA, manufactured by Toagosei Co., Ltd., trade name "Aronix M-113"), N-vinylcaprolactam, neopentyl glycol diacrylate, tripropylene glycol diacrylate, polypropylene glycol diacrylate (manufactured by Shin-Nakamura Chemical Co., Ltd., trade name "APG-400"), EO-modified bisphenol A diacrylate (manufactured by Miwon Specialty Chemical Co., Ltd., trade name "Miramer M2300"), and trimethylolpropane polyethoxy triacrylate (manufactured by Miwon Specialty Chemical Co., Ltd., trade name "Miramer M3150") were prepared.

[0068] (Photopolymerization Initiator) As photopolymerization initiators, (2,4,6-trimethylbenzoyl)bis(p-tolyl)phosphine oxide (TMO, CAS number: 270586-78-2, compound represented by formula (1)), 2,4,6-trimethylbenzoyldiphenylphosphine oxide (Omnirad TPO-N), and 1-hydroxycyclohexylphenyl ketone (Omnirad 184) were prepared.

[0069] (Silane Coupling Agent) 3-mercaptopropyltrimethoxysilane (MPTS) was prepared as a silane coupling agent.

[0070] [Resin Composition for Primary Resin Layer] 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 resin compositions for the primary resin layer of Test Examples 1 to 3. Test Examples 1 and 2 correspond to Examples, and Test Example 3 corresponds to a Comparative Example.

[0071]

[0072] [Resin composition for secondary resin layer] A photopolymerizable compound and a photopolymerization initiator were mixed in the amounts (parts by mass) shown in Table 2 to prepare resin compositions for the secondary resin layer of Test Examples 4 to 12. Test Examples 4 to 9 correspond to Examples, and Test Examples 10 to 12 correspond to Comparative Examples.

[0073]

[0074] [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 it 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. Test Examples 13 to 20 correspond to working examples, and Test Examples 21 to 27 correspond to comparative examples.

[0075] [Evaluation] The optical fibers of Test Examples 13 to 27 were evaluated as follows, and the results are shown in Tables 3 and 4.

[0076] (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.

[0077] (Young's modulus of secondary resin layer) The Young's modulus of the secondary resin layer was determined by immersing an optical fiber in a solvent (ethanol:acetone=3:7) and removing the glass fiber to obtain a pipe-shaped coating resin layer (length: 50 mm or more), leaving the layer at rest for one day or more under conditions of 23±2°C and 50±10% RH, and then performing a tensile test to determine the Young's modulus from the 2.5% secant value.

[0078] (TPO 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 TPO content (mass%) in the optical fiber. A "GC2030" manufactured by Shimadzu Corporation was used as the measuring device, and a "UA-1" manufactured by Frontier Labs (non-polar, 0.25 mm inner diameter x 30 m length, 0.25 μm film thickness) was used as the column. 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.

[0079]

[0080]

[0081] REFERENCE SIGNS LIST 10... Optical fiber 11... Core 12... Cladding 13... Glass fiber 14... Primary resin layer 15... Secondary resin layer 16... Coating resin layer D1... Diameter D2... Outer diameter

Claims

1. A resin composition for optical fiber coating, comprising a photopolymerizable compound and a photopolymerization initiator, wherein the photopolymerization initiator comprises a compound represented by the following formula (1): [In formula (1), R １ , R ２ , R ３ , R ４ , R ５ , R ６ , R ７ , R ８ , R ９ , and R １０ each independently represents a hydrogen atom or an alkyl group having 1 to 10 carbon atoms; R １ , R ２ , R ３ , R ４ , and R ５ At least one of R is an alkyl group having 1 to 10 carbon atoms, ６ , R ７ , R ８ , R ９ , and R １０ At least one of the groups is an alkyl group having 1 to 10 carbon atoms.

2. The resin composition according to claim 1, wherein the content of the photopolymerization initiator is 0.1 mass % or more and 10 mass % or less, based on the total amount of the resin composition.

3. In the formula (1), R １ , R ２ , R ４ , R ５ , R ６ , R ７ , R ９ and R １０ is a hydrogen atom, and R ３ and R ８ The resin composition according to claim 1 or claim 2, wherein is an alkyl group having 1 to 10 carbon atoms.

4. The resin composition according to any one of claims 1 to 3, further comprising a silane coupling agent, and the photopolymerizable compound includes a urethane (meth)acrylate.

5. A resin composition according to any one of claims 1 to 3, wherein the photopolymerizable compound comprises at least one selected from the group consisting of urethane (meth)acrylate and epoxy (meth)acrylate.

6. An optical fiber comprising a glass fiber including a core and a cladding, and a coating resin layer that contacts and coats the glass fiber, wherein the coating resin layer comprises a cured product of the resin composition according to any one of claims 1 to 5.

7. The optical fiber according to claim 6, wherein the coating resin layer comprises 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 the resin composition according to claim 4.

8. The optical fiber according to claim 7, wherein the secondary resin layer comprises a cured product of the resin composition according to claim 5.

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