Resin composition, secondary coating material for optical fiber, optical fiber, and method for manufacturing optical fiber

Abstract

The resin composition includes a base resin containing a photopolymerizable compound and a photopolymerization initiator and surface-modified silica particles. The surface-modified silica particles have a T unit in which three oxygen atoms are bonded to a silicon atom as a structural unit of silicone, and the proportion of T1 units included in the T unit is 29 mol% or less.

Description

Technical Field

[0001] The present disclosure relates to a resin composition, a secondary coating material for an optical fiber, an optical fiber, and a method for manufacturing an optical fiber. This application claims priority based on Japanese Application No. 2020-208202 filed on December 16, 2020, and incorporates all the descriptions described in the above Japanese application.

Background Art

[0002] Generally, an optical fiber has a coating resin layer for protecting a glass fiber that is an optical transmission body. The coating resin layer is composed of, for example, a primary resin layer and a secondary resin layer.

[0003] In order to identify an optical fiber, a coloring layer may be formed on the outermost layer of the optical fiber. It is known that the coloring layer is formed on the outer periphery of the secondary resin layer after the optical fiber coated with the primary resin layer and the secondary resin layer is once wound up and then the optical fiber is fed out again (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

[0005] The resin composition according to one aspect of the present disclosure includes a base resin containing a photopolymerizable compound and a photoinitiator, and surface-modified silica particles. The surface-modified silica particles have a T unit in which three oxygen atoms are bonded to a silicon atom as a constitutional unit of silicone, and the ratio of the T1 unit contained in the T unit is 29 mol% or less.

Brief Description of the Drawings

[0006] [Figure 1]Figure 1 is a schematic cross-sectional view showing an example of an optical fiber according to this embodiment. [Modes for carrying out the invention]

[0007] [Issues this disclosure aims to address] During the shipment of optical fibers, rewinding from large bobbins to smaller bobbins is sometimes necessary. If the surface of the secondary resin layer has low scratch resistance, scratches may occur on the surface of the secondary resin layer during rewinding, potentially damaging the resin layer and severely impairing its optical properties. Therefore, the secondary resin layer is required to have excellent scratch resistance (abrasion resistance).

[0008] This disclosure aims to provide a resin composition capable of forming a resin layer with excellent resistance to trauma, and an optical fiber comprising a secondary resin layer formed from the resin composition, which can prevent damage during rewinding.

[0009] [Effects of this disclosure] According to this disclosure, it is possible to provide a resin composition that can form a resin layer with excellent resistance to trauma, and an optical fiber that has a secondary resin layer formed from the resin composition and can prevent damage during rewinding.

[0010] [Description of Embodiments in this Disclosure] First, the contents of the embodiments of this disclosure will be listed and explained. A resin composition according to one aspect of this disclosure comprises a base resin containing a photopolymerizable compound and a photopolymerization initiator, and surface-modified silica particles, wherein the surface-modified silica particles have a T unit in which three oxygen atoms are bonded to a silicon atom as a constituent unit of silicone, and the proportion of T1 units contained in the T unit is 29 mol% or less.

[0011] By curing a resin composition containing surface-modified silica particles having specific silicone structural units, a resin layer with excellent scratch resistance can be formed.

[0012] The surface-modified silica particles may have at least one UV-curable group selected from the group consisting of acryloyl groups, methacryloyl groups, and vinyl groups. This facilitates the formation of a resin layer with a high Young's modulus.

[0013] From the viewpoint of forming a resin layer with a high Young's modulus, the content of surface-modified silica particles may be 1% by mass or more and 60% by mass or less based on the total amount of the resin composition.

[0014] From the viewpoint of forming a resin layer with superior scratch resistance, the average primary particle size of the surface-modified silica particles may be 100 nm or less.

[0015] A secondary coating material for an optical fiber according to one aspect of this disclosure includes the above-mentioned resin composition. By using the resin composition according to this embodiment as a secondary resin layer, a coating resin layer with excellent resistance to trauma can be formed.

[0016] An optical fiber according to one aspect of the present disclosure comprises a glass fiber including a core and cladding, a primary resin layer in contact with and covering the glass fiber, and a secondary resin layer covering the primary resin layer, wherein the secondary resin layer includes a cured product of the resin composition. This prevents scratches from occurring on the surface of the secondary resin layer and the resulting damage to the resin layer when rewinding from a large bobbin to a small bobbin.

[0017] A method for manufacturing an optical fiber according to one aspect of the present disclosure comprises a coating step of applying the resin composition to the outer circumference of a glass fiber composed of a core and a cladding, and a curing step of curing the resin composition by irradiating it with ultraviolet light after the coating step. This makes it possible to produce an optical fiber that can be prevented from being damaged during rewinding work.

[0018] [Details of the embodiments of this disclosure] Specific examples of the resin composition and the optical fiber according to the embodiments of the present disclosure will be described while referring to the drawings as necessary. Note that the present disclosure is not limited to these examples, and is shown 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 are denoted by the same reference numerals, and redundant descriptions are omitted. As used herein, "(meth)acrylate" means acrylate or the corresponding methacrylate. The same applies to other similar expressions such as "(meth)acryloyl".

[0019] <Resin composition> The resin composition according to the present embodiment is an ultraviolet curable resin composition containing a base resin containing a photopolymerizable compound and a photopolymerization initiator, and surface-modified silica particles.

[0020] (Surface-modified silica particles) The structural units of silicone in the silicone compound are generally classified into M units (units in which one oxygen atom is bonded to a silicon atom), D units (units in which two oxygen atoms are bonded to a silicon atom), T units (units in which three oxygen atoms are bonded to a silicon atom), and Q units (units in which four oxygen atoms are bonded to a silicon atom). The structures of M units, D units, T units, and Q units can be represented by the following formulas. In the formulas, R represents a monovalent organic group.

[0021]

Chemical formula

[0022] The T unit is a structure derived from a silane compound represented by R-Si-(OR')3. R represents a monovalent organic group. Examples of the monovalent organic group include an alkyl group, a phenyl group, a (meth)acryloxyalkyl group, an alkenyl group, a styryl group, and a vinyl group. R' represents an alkyl group such as a methyl group or an ethyl group.

[0023] The T unit includes T1 units, in which one oxygen atom is bonded to other silicon atoms, T2 units, in which two oxygen atoms are bonded to other silicon atoms, and T3 units, in which three oxygen atoms are bonded to other silicon atoms, depending on the degree of condensation of the silane compound. The structures of T1, T2, and T3 units can be represented by the following formulas.

[0024] [ka]

[0025] The proportion of each constituent unit is that of the solid silicone compound. 29 It can be calculated by measuring the Si-NMR spectrum (for example, 29 Structural analysis of silicon-containing materials by Si NMR method, Asahi Glass Research Report 66 (2016), pp. 32-36.

[0026] Unmodified silica particles are mainly composed of Q units. The surface-modified silica particles according to this embodiment have Q units based on the siloxane structure of the silica particles before surface modification, and T units based on the siloxane structure introduced by surface modification. (Solid) 29 In the Si-NMR spectrum, the Q-unit chemical shift is observed in the range of -90 ppm to -120 ppm, and the T-unit chemical shift is observed in the range of -35 ppm to -75 ppm. In the T-unit spectrum, the T1 unit has a peak top around 50 ppm, the T2 unit around 60 ppm, and the T3 unit around 70 ppm. Therefore, by integrating the T-unit signal of the surface-modified silica particles, the proportion of each unit (T1, T2, and T3) can be calculated from the signal area.

[0027] In this embodiment, T units are introduced into the surface-modified silica particles by treating the surface of the silica particles with a silane compound. From the viewpoint of forming a resin layer with excellent scratch resistance, the proportion of T1 units contained in the T units of the surface-modified silica particles is 29 mol% or less, preferably 28 mol% or less, and more preferably 26 mol% or less. The lower limit of the proportion of T1 units may be 1 mol% or more, 5 mol% or more, or 8 mol% or more.

[0028] The proportion of T2 units and T3 units contained in a T unit is not particularly limited. The proportion of T2 units may be, for example, 10 mol% or more, 15 mol% or more, or 20 mol% or more, or 70 mol% or less, 68 mol% or less, or 66 mol% or less. The proportion of T3 units may be, for example, 1 mol% or more, 4 mol% or more, or 6 mol% or more, or 70 mol% or less, 64 mol% or less, or 62 mol% or less.

[0029] The silane compound may be a silane compound having an ultraviolet-curable group. When a silane compound having an ultraviolet-curable group is used, examples of R in the T unit and T1 unit include (meth)acryloxyalkyl groups, alkenyl groups, styryl groups, and vinyl groups, and examples of R' include methyl groups and ethyl groups. By having acryloyl groups, methacryloyl groups, or vinyl groups in the surface-modified silica particles, a resin layer with even better scratch resistance can be formed.

[0030] Examples of silane compounds having UV-curable groups include 3-methacryloxypropyltrimethoxysilane, 3-acryloxypropyltrimethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-acryloxypropyltriethoxysilane, 8-methacryloxyoctyltrimethoxysilane, 8-acryloxyoctyltrimethoxysilane, 7-octenyltrimethoxysilane, p-styryltrimethoxysilane, vinyltrimethoxysilane, and vinyltriethoxysilane.

[0031] In this embodiment, the surface-modified silica particles are dispersed in a dispersion medium. By using surface-modified silica particles dispersed in a dispersion medium, the surface-modified silica particles can be uniformly dispersed in the resin composition, thereby improving the storage stability of the resin composition. The dispersion medium is not particularly limited as long as it does not inhibit the curing of the resin composition. The dispersion medium may be reactive or non-reactive.

[0032] As a reactive dispersion medium, monomers such as (meth)acryloyl compounds and epoxy compounds may be used. Examples of (meth)acryloyl compounds include 1,6-hexanediol di(meth)acrylate, EO-modified bisphenol A di(meth)acrylate, polyethylene glycol di(meth)acrylate, PO-modified bisphenol A di(meth)acrylate, polypropylene glycol di(meth)acrylate, polytetramethylene glycol di(meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, (meth)acrylic acid adducts of propylene glycol diglycidyl ether, (meth)acrylic acid adducts of tripropylene glycol diglycidyl ether, and (meth)acrylic acid adducts of glycerin diglycidyl ether. As (meth)acryloyl compounds, compounds exemplified by the monomers described later may be used.

[0033] As a non-reactive dispersion medium, a ketone solvent such as methyl ethyl ketone (MEK), an alcohol solvent such as methanol (MeOH) or propylene glycol monomethyl ether (PGME), or an ester solvent such as propylene glycol monomethyl ether acetate (PGMEA) may be used. In the case of a non-reactive dispersion medium, the resin composition may be prepared by mixing the base resin with the surface-modified silica particles dispersed in the dispersion medium, and then removing a portion of the dispersion medium.

[0034] From the viewpoint of reducing the proportion of T1 units, surface-modified silica particles are preferably dispersed in an alcohol-based solvent, and more preferably dispersed in MeOH.

[0035] From the viewpoint of further improving the scratch resistance of the resin layer, the average primary particle size of the surface-modified silica particles is preferably 100 nm or less, and may be 90 nm or less or 80 nm or less. From the viewpoint of increasing the strength of the secondary resin layer, the average primary particle size of the surface-modified silica particles may be 1 nm or more, 2 nm or more, or 5 nm or more. The average primary particle size can be measured, for example, by image analysis of electron microscope images, light scattering method, BET method, etc. The average primary particle size can be measured in accordance with the method described in any of JIS Z 8827-1, JIS Z 8827-2, JIS Z 8828, or JIS Z 8830. When the primary particle size of the silica particles is small, the dispersion medium appears transparent to the naked eye. When the primary particle size is relatively large (40 nm or more), the dispersion medium in which the primary particles are dispersed appears cloudy, but no precipitates are observed.

[0036] The content of surface-modified silica particles is preferably 1% by mass or more and 60% by mass or less based on the total amount of the resin composition (total amount of base resin and surface-modified silica particles), but may also be 3% by mass or more and 50% by mass or less, 5% by mass or more and 40% by mass or less, or 10% by mass or more and 35% by mass or less. When the content of surface-modified silica particles is 1% by mass or more, it becomes easier to form a resin layer with a high Young's modulus. When the content of surface-modified silica particles is 60% by mass or less, it becomes easier to improve the coatability of the resin composition and it is possible to form a resin layer with excellent toughness.

[0037] (Base resin) The base resin according to this embodiment contains a photopolymerizable compound and a photopolymerization initiator. The photopolymerizable compound according to this embodiment may include urethane (meth)acrylate from the viewpoint of adjusting the Young's modulus. Note that the photopolymerizable compound according to this embodiment does not contain surface-modified silica particles having UV-curable groups.

[0038] As the urethane (meth)acrylate, urethane oligomers obtained by reacting polyol compounds, polyisocyanate compounds, and hydroxyl group-containing (meth)acrylate compounds can be used. Two or more types of urethane (meth)acrylate may be used in mixture form.

[0039] 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.

[0040] From the viewpoint of adjusting the Young's modulus of the resin layer, the number-average molecular weight (Mn) of the polyol compound may be 300 to 3000, 400 to 3000, or 500 to 2500.

[0041] Organotin compounds are generally used as catalysts when 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. From the viewpoint of readily available materials or catalytic performance, it is preferable to use dibutyltin dilaurate or dibutyltin diacetate as a catalyst.

[0042] Lower alcohols with 5 or fewer carbon atoms may be used when synthesizing urethane (meth)acrylates. 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.

[0043] The photopolymerizable compound according to this embodiment may contain epoxy (meth)acrylate from the viewpoint of adjusting the Young's modulus. Examples of epoxy (meth)acrylate include aliphatic epoxy (meth)acrylate and aromatic epoxy (meth)acrylate. Aliphatic epoxy (meth)acrylate means epoxy (meth)acrylate without an aromatic ring, and aromatic epoxy (meth)acrylate means epoxy (meth)acrylate having an aromatic ring.

[0044] As the aliphatic epoxy (meth)acrylate, a reaction product of an aliphatic epoxy compound having two or more glycidyl groups and a compound having a (meth)acryloyl group, such as (meth)acrylic acid, can be used.

[0045] From the viewpoint of increasing the toughness of the resin layer, it is preferable that the aliphatic epoxy (meth)acrylate has an ethylene oxide group or a propylene oxide group. Examples of aliphatic epoxy (meth)acrylates include (meth)acrylic acid adducts of propylene glycol diglycidyl ether, (meth)acrylic acid adducts of polypropylene glycol diglycidyl ether, (meth)acrylic acid adducts of ethylene glycol diglycidyl ether, and (meth)acrylic acid adducts of polyethylene glycol diglycidyl ether.

[0046] Examples of commercially available aliphatic epoxy (meth)acrylates include the product names "Epoxy Ester 40EM," "Epoxy Ester 70PA," "Epoxy Ester 200PA," and "Epoxy Ester 80MFA" manufactured by Kyoeisha Chemical Co., Ltd.

[0047] As aromatic epoxy (meth)acrylates, reaction products of aromatic epoxy compounds having two or more glycidyl groups and compounds having (meth)acryloyl groups, such as (meth)acrylic acid, can be used. Examples of aromatic epoxy (meth)acrylates include (meth)acrylic acid adducts of bisphenol A diglycidyl ether.

[0048] From the viewpoint of increasing the strength of the resin layer, the epoxy (meth)acrylate content may be 10% to 70% by mass, 20% to 60% by mass, or 30% to 50% by mass, based on the total amount of photopolymerizable compounds.

[0049] The photopolymerizable compound according to this embodiment may include photopolymerizable compounds other than urethane (meth)acrylate and epoxy (meth)acrylate (hereinafter referred to as "monomers").

[0050] Monofunctional monomers having one polymerizable group and polyfunctional monomers having two or more polymerizable groups can be used as monomers. Two or more monomers may also be used in mixture form.

[0051] 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 (meth)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, isobornyl (meth)acrylate, etc.; (meth)acrylic acid, (meth)acrylic acid dimer, carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, ω-carb Carboxyl group-containing monomers such as xy-polycaprolactone (meth)acrylate; heterocyclic 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 monomers such as maleimide, N-cyclohexylmaleimide, and N-phenylmaleimide;Examples include amide 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 monomers such as aminoethyl (meth)acrylate, aminopropyl (meth)acrylate, N,N-dimethylaminoethyl (meth)acrylate, and tert-butylaminoethyl (meth)acrylate; and succinimide monomers such as N-(meth)acryloyloxymethylenesuccinimide, N-(meth)acryloyl-6-oxyhexamethylenesuccinimide, and N-(meth)acryloyl-8-oxyoctamethylenesuccinimide.

[0052] Examples of polyfunctional monomers include ethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, di(meth)acrylate of alkylene oxide adducts of bisphenol A, tetraethylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate of hydroxypivalate, 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, Isopentyldiol di(meth)acrylate, 3-Ethyl-1,8-Octanediol di(meth)acrylate, Bisphene EO adducts of Nol A di(meth)acrylate, trimethylolpropane tri(meth)acrylate, trimethyloloctan tri(meth)acrylate, trimethylolpropane polyethoxytri(meth)acrylate, trimethylolpropane polypropoxytri(meth)acrylate, trimethylolpropane polyethoxypolypropoxytri(meth)acrylate, tris[(meth)acryloyloxyethyl]isocyanurate, pentaerythritol tri(meth)acrylate, pentaery Examples include thritol polyethoxytetra(meth)acrylate, pentaerythritol polypropoxytetra(meth)acrylate, pentaerythritol tetra(meth)acrylate, ditrimethylolpropanetetra(meth)acrylate, dipentaerythritol tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, and caprolactone-modified tris[(meth)acryloyloxyethyl]isocyanurate.

[0053] As a photopolymerization initiator, one can be appropriately selected and used from known radical photopolymerization initiators. Examples of photopolymerization initiators include 1-hydroxycyclohexylphenyl ketone (Omnirad 184, 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, IGM Resins), 2,4,6-trimethylbenzoyldiphenylphosphine oxide (Omnirad TPO, IGM Resins), and bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (Omnirad 819, IGM Resins).

[0054] The content of the photopolymerization initiator may be 0.2% by mass or more and 6.0% by mass or less, 0.4% by mass or more and 3.0% by mass or less, or 0.6% by mass or more and 2.0% by mass or less, based on the total amount of the photopolymerizable compound.

[0055] The resin composition may further contain a silane coupling agent, a leveling agent, an antifoaming agent, an antioxidant, a sensitizer, and the like.

[0056] The silane coupling agent is not particularly limited as long as it does not interfere with the curing of the resin composition. Examples of silane coupling agents 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, and N-(β-aminoethyl)-γ Examples include 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.

[0057] The resin composition according to this embodiment can be suitably used as a secondary coating material for optical fibers. By using the resin composition according to this embodiment as a secondary resin layer, a coating resin layer with excellent scratch resistance can be formed.

[0058] <Optical fiber> Figure 1 is a schematic cross-sectional view showing an example of an optical fiber according to this embodiment. The optical fiber 10 comprises 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 on the outer circumference of the glass fiber 13.

[0059] The cladding 12 surrounds the core 11. The core 11 and cladding 12 mainly contain glass such as quartz glass. For example, germanium-doped quartz glass can be used for the core 11, and pure quartz glass or fluorine-doped quartz glass can be used for the cladding 12.

[0060] In Figure 1, for example, the outer diameter (D2) of the glass fiber 13 is approximately 100 μm to 125 μm, and the diameter (D1) of the core 11 constituting the glass fiber 13 is approximately 7 μm to 15 μm. The thickness of the coating resin layer 16 is typically approximately 22 μm to 70 μm. The thickness of each layer of the primary resin layer 14 and the secondary resin layer 15 may be approximately 5 μm to 50 μm.

[0061] When the outer diameter (D2) of the glass fiber 13 is approximately 125 μm and the thickness of the coating resin layer 16 is 60 μm or more and 70 μm or less, the thickness of each layer of the primary resin layer 14 and the secondary resin layer 15 may be approximately 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 approximately 245 μm to 265 μm.

[0062] When the outer diameter (D2) of the glass fiber 13 is approximately 125 μm and the thickness of the coating resin layer 16 is between 27 μm and 48 μm, the thickness of each layer 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 179 μm to 221 μm.

[0063] When the outer diameter (D2) of the glass fiber 13 is approximately 100 μm and the thickness of the coating resin layer 16 is between 22 μm and 37 μm, the thickness of each layer of the primary resin layer 14 and the secondary resin layer 15 may be approximately 5 μm to 32 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 144 μm to 174 μm.

[0064] The resin composition according to this embodiment can be applied to a secondary resin layer. The secondary resin layer can be formed by curing a resin composition containing the surface-modified silica particles and a base resin. By including the cured resin composition according to this embodiment in the secondary resin layer 15, it is possible to prevent scratches from occurring on the surface of the secondary resin layer and the resin layer from being destroyed when rewinding from a large bobbin to a small bobbin. Furthermore, the anti-blocking effect suppresses sticking between fibers, allowing the optical fiber to be wound onto the small bobbin without winding abnormalities such as skipping.

[0065] The method for manufacturing an optical fiber according to this embodiment comprises a coating step of applying the resin composition to the outer circumference of a glass fiber composed of a core and cladding, and a curing step of curing the resin composition by irradiating it with ultraviolet light after the coating step. By coating the glass fiber with the resin composition according to this embodiment, an optical fiber that can prevent damage during rewinding work can be manufactured. In this embodiment, the resin composition is not applied directly to the glass fiber, but rather the resin composition for primary coating is applied directly to the glass fiber. That is, in the coating step, a primary coating that comes into contact with the glass fiber and a secondary coating that does not come into contact with the glass fiber are formed by the resin composition according to this embodiment.

[0066] The Young's modulus of the secondary resin layer is preferably 1300 MPa to 3600 MPa at 23°C, more preferably 1400 MPa to 3000 MPa, and even more preferably 1600 MPa to 2800 MPa. When the Young's modulus of the secondary resin layer is 1300 MPa or higher, the lateral pressure characteristics are easily improved, and when it is 3500 MPa or lower, appropriate toughness can be imparted to the secondary resin layer, making it less likely for cracks to occur in the secondary resin layer.

[0067] The primary resin layer 14 can be formed, for example, by curing a resin composition containing urethane (meth)acrylate, monomer, photopolymerization initiator, and silane coupling agent. Conventional known techniques can be used for the resin composition for the primary resin layer. The urethane (meth)acrylate, monomer, photopolymerization initiator, and silane coupling agent may be appropriately selected from the compounds exemplified in the base resin above. However, the resin composition forming the primary resin layer has a different composition from the base resin forming the secondary resin layer.

[0068] In some cases, multiple optical fibers are arranged in parallel and integrated with a ribbon resin to form an optical fiber ribbon. The resin composition according to this disclosure can also be used as a ribbon resin. This improves the trauma resistance and lateral pressure characteristics of the optical fiber ribbon. [Examples]

[0069] The results of evaluation tests using the test examples described herein are shown below, and the disclosure will be explained in more detail. However, the present invention is not limited to these test examples.

[0070] [Preparation of resin composition] (Urethane acrylate) As urethane acrylates, we prepared two types: urethane acrylate (UA-1) obtained by reacting Mn600 polypropylene glycol, 2,4-tolylene diisocyanate, and 2-hydroxyethyl acrylate, and urethane acrylate (UA-2) obtained by reacting Mn12000 polypropylene glycol, 2,4-tolylene diisocyanate, and 2-hydroxyethyl acrylate.

[0071] (Epoxy acrylate) As the epoxy acrylate (EA), we prepared a (meth)acrylic acid adduct of bisphenol A diglycidyl ether (manufactured by Osaka Organic Chemical Industry Co., Ltd., trade name "Viscote 540").

[0072] (monomer) As monomers, we prepared isobornyl acrylate (trade name "IBXA", manufactured by Osaka Organic Chemical Industry Co., Ltd.), 2-phenoxyethyl acrylate (trade name "Light Acrylate PO-A", manufactured by Kyoeisha Chemical Co., Ltd.), and tripropylene glycol diacrylate (trade name "TPGDA", manufactured by Daicel Ornex Co., Ltd.).

[0073] (Photopolymerization initiator) As a photopolymerization initiator, 2,4,6-trimethylbenzoyldiphenylphosphine oxide (Omnirad TPO) was prepared.

[0074] (Surface-modified silica particles) As surface-modified silica particles, a silica sol containing silica particles surface-treated with 3-methacryloxypropyltrimethoxysilane, as shown in Table 1, was prepared. The proportion of each constituent unit in the surface-modified silica particles was determined using the following procedure in solid form. 29 The calculation was performed by measuring the Si-NMR spectrum.

[0075] Four milliliters of each silica sol were collected, the dispersion medium was evaporated in the air, and then the surface-modified silica particles were isolated by drying in an 80°C constant temperature bath for 24 hours. 200 mg of the surface-modified silica particles were added to an acetone solution containing 13.7 mg of chromium(III) acetylacetonate (Cr(acac)3) as a relaxation reagent, and the mixture was sonicated for 30 minutes to obtain a mixed solution. The amount of Cr(acac)3 added was 1% by mass relative to Si (based on Cr). The mixed solution was dried in a 90°C constant temperature bath for 24 hours to prepare a sample for NMR measurement.

[0076] Solid sample 29 Si-NMR spectra were measured using the DD-MAS method under the following conditions, and the proportions of T1 units, T2 units, and T3 units in the T units of the surface-modified silica particles were calculated. Measurement device: Ascend500 + AVANCE III HD (Bruker Japan Co., Ltd.) Probe: 4mmφ MAS VTN probe MAS rotation speed: 8kHz Cumulative count: 2048

[0077] [Table 1]

[0078] (Resin composition) A base resin was prepared by mixing a photopolymerizable compound and a photopolymerization initiator in the amounts (parts by mass) shown in Table 2 with 1 part by mass of Omnirad TPO. After mixing the base resin with the silica sol, most of the dispersion medium was removed to prepare the resin composition for each test example so that the content of surface-modified silica particles in the resin composition was 30% by mass. Test Examples 1 to 6 correspond to examples, and Test Example 7 corresponds to a comparative example.

[0079] The following evaluations were performed using the resin compositions obtained in the test examples. The results are shown in Table 2.

[0080] (Young's modulus) After coating a polyethylene terephthalate (PET) film with a spin coater, UV light was applied using an electrodeless UV lamp system (D-bulb) (Heraeus) at a rate of 1000 ± 100 mJ / cm². 2 The resin was cured under the specified conditions to form a resin layer with a thickness of 200 ± 20 μm on the PET film. The resin layer was peeled off the PET film to obtain a resin film.

[0081] A resin film was punched into a dumbbell shape according to JIS K 7127 Type 5. Under conditions of 23±2℃ and 50±10%RH, it was subjected to tensile testing using a tensile testing machine at a tensile speed of 1 mm / min and a gauge length of 25 mm to obtain a stress-strain curve. The Young's modulus of the resin film was determined by the tangent curve.

[0082] [Fabrication of optical fibers] A urethane acrylate (UA-3) was prepared by reacting polypropylene glycol with a molecular weight of 4000, isophorone diisocyanate, hydroxyethyl acrylate, and methanol. A resin composition for the primary resin layer was prepared by mixing 75 parts by mass of UA-3, 12 parts by mass of nonylphenol EO-modified acrylate, 6 parts by mass of N-vinylcaprolactam, 2 parts by mass of 1,6-hexanediol diacrylate, 1 part by mass of 2,4,6-trimethylbenzoyldiphenylphosphine oxide, and 1 part by mass of 3-mercaptopropyltrimethoxysilane.

[0083] A glass fiber with a diameter of 125 μm, consisting of a core and cladding, was coated with a resin composition for the primary resin layer and the resin composition of the test example for the secondary resin layer. The resin compositions were then cured by irradiation with ultraviolet light, forming a primary resin layer with a thickness of 35 μm and a secondary resin layer with a thickness of 25 μm on its outer periphery, thereby fabricating an optical fiber. The linear velocity was set to 1500 m / min.

[0084] (Lateral pressure characteristics) The transmission loss of 1550nm wavelength light when an optical fiber was wound in a single layer on a 280mm diameter bobbin covered with sandpaper was measured using the OTDR (Optical Time Domain Reflectometer) method. The transmission loss of 1550nm wavelength light when an optical fiber was wound in a single layer on a 280mm diameter bobbin without sandpaper was also measured using the OTDR method. The difference in the measured transmission losses was calculated, and a difference of 0.6dB / km or less was rated "A," while a difference greater than 0.6dB / km was rated "B."

[0085] (Rewind rate) When optical fiber was rewinded from a large bobbin to a small bobbin, the increase in transmission loss was defined as the rewinding rate. A rewinding rate of 0% was rated as "A", a rewinding rate greater than 0% but less than 30% was rated as "B", and a rewinding rate of 30% or more was rated as "C".

[0086] [Table 2] [Explanation of symbols]

[0087] 10 Optical Fibers 11 cores 12 clad 13. Glass fiber 14 Primary resin layer 15. Secondary resin layer 16. Coating resin layer

Claims

1. The resin composition comprises a base resin mixed with a photopolymerizable compound and a photopolymerization initiator, and surface-modified silica particles. The surface-modified silica particles have a T unit as a constituent unit of silicone, in which three oxygen atoms are bonded to a silicon atom, and the proportion of T1 units contained in the T unit is 29 mol% or less. A secondary coating material for optical fibers, wherein the surface-modified silica particles have at least one UV-curable group selected from the group consisting of acryloyl groups, methacryloyl groups, and vinyl groups.

2. The secondary coating material according to claim 1, wherein the content of the surface-modified silica particles is 1% by mass or more and 60% by mass or less based on the total amount of the resin composition.

3. The secondary coating material according to claim 1 or claim 2, wherein the average primary particle size of the surface-modified silica particles is 100 nm or less.

4. The secondary coating material according to claim 3, wherein the average primary particle size of the surface-modified silica particles is 1 nm or more.

5. The secondary coating material according to any one of claims 1 to 4, wherein the proportion of T1 units contained in the T units is 5 mol% or more.

6. Glass fiber including core and cladding, A primary resin layer that is in contact with and covers the glass fiber, The system comprises a secondary resin layer covering the primary resin layer, An optical fiber wherein the secondary resin layer comprises a cured product of the secondary coating material according to any one of claims 1 to 5.

7. A coating step of applying a secondary coating material according to any one of claims 1 to 5 to the outer circumference of a glass fiber composed of a core and a cladding, A method for manufacturing optical fibers, comprising a curing step of curing the secondary coating material by irradiating it with ultraviolet light after the coating step.

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