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

Abstract

A resin composition comprising: a base resin containing a photopolymerizable compound and a photopolymerization initiator, and surface-modified silica particles having, as a constituent unit of an organosilicon, a T unit having 3 oxygen atoms bonded to a silicon atom, the proportion of a T1 unit included in the T unit being 29 mol% or less.

Description

Technical Field

[0001] This disclosure relates to resin compositions, secondary coating materials for optical fibers, optical fibers, and methods for manufacturing optical fibers.

[0002] This application claims priority based on Japanese Application No. 2020-208202, filed on December 16, 2020, and invokes all the contents set forth in said Japanese application. Background Technology

[0003] Typically, optical fibers have a resin coating layer to protect the glass fibers that act as light transmitters. This resin coating layer may consist of, for example, a primary resin layer and a secondary resin layer.

[0004] To identify optical fibers, a colored layer is sometimes formed on the outermost layer of the fiber. It is known that after temporarily winding up an optical fiber coated with a primary resin layer and a secondary resin layer, the fiber is rewinded and a colored layer is formed on the periphery of the secondary resin layer (for example, see Patent Document 1).

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: International Publication No. 2016 / 080195 Summary of the Invention

[0008] One aspect of the resin composition disclosed herein comprises: a base resin containing a photopolymerizable compound and a photopolymerization initiator, and surface-modified silica particles having T units with three oxygen atoms bonded to silicon atoms as constituent units of the organosilicon, wherein the proportion of T1 units contained in the T units is less than 29 mol%. Attached Figure Description

[0009] [ Figure 1 ] Figure 1 This is a schematic cross-sectional view showing an example of the optical fiber involved in this embodiment. Detailed Implementation

[0010] [The problem this disclosure aims to solve]

[0011] During optical fiber shipment, there are sometimes operations involving rewinding from large spools to small spools. When the surface of the secondary resin layer has low abrasion resistance, damage may occur on the surface of the secondary resin layer during rewinding, causing the resin layer to break down and significantly impairing optical properties. Therefore, the secondary resin layer is required to have excellent resistance to external damage (abrasion resistance).

[0012] The purpose of this disclosure is to provide a resin composition capable of forming a resin layer with excellent resistance to external damage; and an optical fiber having a secondary resin layer formed from the resin composition and capable of preventing damage during roll-up operations.

[0013] [The Effects of This Disclosure]

[0014] According to this disclosure, a resin composition capable of forming a resin layer with excellent resistance to external damage can be provided; and an optical fiber having a secondary resin layer formed from the resin composition and capable of preventing external damage during roll-up operations.

[0015] [Description of embodiments of this disclosure]

[0016] First, embodiments of this disclosure will be listed and described. One aspect of the resin composition disclosed herein includes: a base resin containing a photopolymerizable compound and a photopolymerization initiator, and surface-modified silica particles, wherein the surface-modified silica particles have T units with three oxygen atoms bonded to silicon atoms as constituent units of the organosilicon, and the proportion of T1 units contained in the T units is 29 mol% or less.

[0017] By curing a resin composition containing surface-modified silica particles with specific organosilicon constituent units, a resin layer with excellent resistance to external damage can be formed.

[0018] The surface-modified silica particles may have at least one UV-curable group selected from the group consisting of acryloyl, methacryl, and vinyl groups. This facilitates the formation of a resin layer with a high Young's modulus.

[0019] From the viewpoint of forming a resin layer with a high Young's modulus, the content of surface-modified silica particles can be more than 1% by mass and less than 60% by mass, based on the total amount of the resin composition.

[0020] From the perspective of forming a resin layer with better resistance to external damage, the average primary particle size of surface-modified silica particles can be below 100 nm.

[0021] One aspect of this disclosure relates to an optical fiber whose secondary coating material comprises the aforementioned resin composition. By using the resin composition according to this embodiment as a secondary resin layer, a coating resin layer with excellent resistance to external damage can be formed.

[0022] One aspect of this disclosure relates to an optical fiber comprising: a glass fiber having a core and a cladding; a primary resin layer in contact with and covering the glass fiber; and a secondary resin layer covering the primary resin layer, the secondary resin layer comprising a cured product of the aforementioned resin composition. Therefore, during operations of changing from a large spool to a small spool, damage to the surface of the secondary resin layer that could lead to resin layer destruction can be prevented.

[0023] One aspect of this disclosure relates to a method for manufacturing optical fibers, comprising: a coating step of coating the aforementioned resin composition onto the outer periphery of a glass fiber consisting of a core and a cladding; and a curing step of curing the resin composition by irradiation with ultraviolet light after the coating step. This enables the production of optical fibers that can prevent damage during rewinding operations.

[0024] [Details of the embodiments disclosed herein]

[0025] Specific examples of resin compositions and optical fibers related to embodiments of this disclosure will be described with reference to the accompanying drawings as needed. It should be noted that this disclosure is not limited to these examples, but is defined by the claims and is intended to include all variations within the same meaning and scope as the claims. In the following description, the same symbols are used to denote the same elements in the description of the drawings, and repeated descriptions are omitted. (Meth)acrylate in this specification refers to acrylate or its corresponding methacrylate. The same applies to other similar expressions such as (meth)acryloyl.

[0026] <Resin Composition>

[0027] The resin composition involved in this embodiment is an ultraviolet-curable resin composition comprising a base resin containing a photopolymerizable compound and a photopolymerization initiator, and surface-modified silica particles.

[0028] (Surface-modified silica particles)

[0029] The organosilicon building blocks of organosilicon compounds are generally classified into: M units (units with one oxygen atom bonded to a silicon atom), D units (units with two oxygen atoms bonded to a silicon atom), T units (units with three oxygen atoms bonded to a silicon atom), and Q units (units with four oxygen atoms bonded to a silicon atom). The structures of the M, D, T, and Q units can be represented by the following formula. In the formula, R represents a monovalent organic group.

[0030] [Chemical Formula 1]

[0031]

[0032] The T unit comes from the structure of silane compounds represented by R-Si-(OR')3. R represents a monovalent organic group. Examples of monovalent organic groups include alkyl, phenyl, (meth)acryloyloxyalkyl, alkenyl, styryl, and vinyl groups. R' represents alkyl groups such as methyl and ethyl.

[0033] Based on the degree of condensation of silane compounds, the T unit comprises: a T1 unit with one oxygen atom bonded to another silicon atom, a T2 unit with two oxygen atoms bonded to another silicon atom, and a T3 unit with three oxygen atoms bonded to another silicon atom. The structures of the T1, T2, and T3 units can be represented by the following formula.

[0034] [Chemical Formula 2]

[0035]

[0036] The proportions of each constituent unit can be determined by measuring the solid content of organosilicon compounds. 29 Calculations can be made using Si-NMR spectra (e.g., refer to "Utilizing..."). 29 "Structural Analysis of Silicon-Containing Materials by Si NMR", Asahi Glass Research Report 66 (2016), pp. 32-36.

[0037] Unmodified silica particles are primarily composed of Q units. The surface-modified silica particles involved in this embodiment have Q units based on the siloxane structure of the unmodified silica particles, and T units based on the siloxane structure introduced through surface modification. In solid... 29 In the Si-NMR spectrum, the chemical shifts of the Q units were observed in the range of -90 ppm to -120 ppm, and the chemical shifts of the T units were observed in the range of -35 ppm to -75 ppm. Within the T units, the T1 unit has peaks around 50 ppm, the T2 unit around 60 ppm, and the T3 unit around 70 ppm. Therefore, by integrating the signal of the T units possessed by the surface-modified silica particles, the proportions of each T1, T2, and T3 unit can be calculated based on the signal area.

[0038] In the surface-modified silica particles of this embodiment, T-units are introduced by treating the surface of the silica particles with a silane compound. From the viewpoint of forming a resin layer with excellent resistance to external damage, the proportion of T1 units included 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 value of the proportion of T1 units can be 1 mol% or more, 5 mol% or more, or 8 mol% or more.

[0039] There is no particular limitation on the ratio of T2 units and T3 units contained in a T unit. The ratio of T2 units can 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 ratio of T3 units can 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.

[0040] The silane compound can be a silane compound having UV-curable groups. When using a silane compound with UV-curable groups, examples of R in the T and T1 units include (meth)acryloyloxyalkyl, alkenyl, styryl, and vinyl groups, and examples of R' include methyl and ethyl groups. By having the surface-modified silica particles have acryloyl, methacryloyl, or vinyl groups, a resin layer with further improved resistance to external damage can be formed.

[0041] 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.

[0042] The surface-modified silica particles involved in this embodiment 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 hinder the curing of the resin composition. The dispersion medium can be reactive or non-reactive.

[0043] As a reactive dispersion medium, monomers such as (meth)acryloyl compounds and epoxy compounds can 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 methacrylate, (meth)acrylate adduct of propylene glycol diglycidyl ether, (meth)acrylate adduct of tripropylene glycol diglycidyl ether, and (meth)acrylate adduct of glycerol diglycidyl ether. Compounds exemplified among the monomers described later can also be used as (meth)acryloyl compounds.

[0044] As a non-reactive dispersion medium, ketone solvents such as methyl ethyl ketone (MEK); alcohol solvents such as methanol (MeOH) and propylene glycol monomethyl ether (PGME); or ester solvents such as propylene glycol monomethyl ether acetate (PGMEA) can be used. When using a non-reactive dispersion medium, a resin composition can be prepared by mixing the base resin and surface-modified silica particles dispersed in the dispersion medium, and then removing a portion of the dispersion medium.

[0045] From the viewpoint of reducing the proportion of T1 units, surface-modified silica particles are preferably dispersed in alcohol solvents, and more preferably dispersed in MeOH.

[0046] From the viewpoint of further improving the resistance of the resin layer to external damage, the average primary particle size of the surface-modified silica particles is preferably 100 nm or less, or may be 90 nm or less, or 80 nm or less. From the viewpoint of improving 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 determined, for example, by image analysis of electron micrographs, light scattering method, BET method, etc. The average primary particle size can be determined according to the method described in any one of JIS Z 8827-1, JIS Z 8827-2, JIS Z 8828, or JIS Z 8830. When the primary particle size is small, the dispersion medium containing the silica particles appears transparent to the naked eye. When the primary particle size is relatively large (40 nm or more), the dispersion medium containing the primary particles appears cloudy, but no precipitates are observed.

[0047] Based on the total amount of the resin composition (the total amount of base resin and surface-modified silica particles), the content of surface-modified silica particles is preferably 1% by mass or more and 60% by mass or less, or it can be 3% by mass or more and 50% by mass or less, 5% by mass or more and 40% by mass or more, 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 is easy 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 is easy to improve the coatability of the resin composition and form a resin layer with excellent toughness.

[0048] (Base resin)

[0049] The base resin involved in this embodiment contains a photopolymerizable compound and a photopolymerization initiator. From the viewpoint of adjusting Young's modulus, the photopolymerizable compound involved in this embodiment may contain urethane (meth)acrylate. It should be noted that the photopolymerizable compound involved in this embodiment does not contain surface-modified silica particles with UV-curable groups.

[0050] As urethane (meth)acrylates, urethane oligomers obtained by reacting polyol compounds, polyisocyanate compounds, and hydroxyl-containing (meth)acrylate compounds can be used. Two or more urethane (meth)acrylates can also be used in combination.

[0051] Examples of polyol compounds include: polytetramethylene glycol, polypropylene glycol, and bisphenol A-ethylene oxide addition glycol. Examples of polyisocyanate compounds include: 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, isophorone diisocyanate, and dicyclohexylmethane 4,4'-diisocyanate. Examples of hydroxyl-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.

[0052] From the perspective of adjusting the Young's modulus of the resin layer, the number average molecular weight (Mn) of the polyol compound can be above 300 and below 3000, above 400 and below 3000, or above 500 and below 2500.

[0053] Organotin compounds are commonly used as catalysts in the synthesis of urethane (meth)acrylates. Examples of organotin compounds include dibutyltin dilaurate, dibutyltin diacetate, dibutyltin maleate, bis(2-ethylhexyl mercaptoacetate) dibutyltin, bis(isooctyl mercaptoacetate) dibutyltin, and dibutyltin oxide. From the perspective of availability or catalyst performance, dibutyltin dilaurate or dibutyltin diacetate is preferred as the catalyst.

[0054] In the synthesis of urethane (meth)acrylates, lower alcohols with 5 or fewer carbon atoms can also be used. 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.

[0055] From the viewpoint of adjusting Young's modulus, the photopolymerizable compound involved in this embodiment may also include epoxy (meth)acrylates. Examples of epoxy (meth)acrylates include aliphatic epoxy (meth)acrylates and aromatic epoxy (meth)acrylates. Aliphatic epoxy (meth)acrylates refer to epoxy (meth)acrylates that do not have an aromatic ring, while aromatic epoxy (meth)acrylates refer to epoxy (meth)acrylates that do have an aromatic ring.

[0056] As an aliphatic epoxy (meth)acrylate, the reaction product of aliphatic epoxy compounds having two or more glycidyl groups and compounds having (meth)acryloyl groups, such as (meth)acrylic acid, can be used.

[0057] From the viewpoint of improving the toughness of the resin layer, aliphatic epoxy (meth)acrylates preferably have ethylene oxide or propylene oxide. Examples of aliphatic epoxy (meth)acrylates include: (meth)acrylate adducts of propylene glycol diglycidyl ether, (meth)acrylate adducts of polypropylene glycol diglycidyl ether, (meth)acrylate adducts of ethylene glycol diglycidyl ether, and (meth)acrylate adducts of polyethylene glycol diglycidyl ether.

[0058] Commercially available aliphatic epoxy (meth)acrylate products include, for example, those manufactured by Kyoei Chemical Co., Ltd. under the trade names "Epoxy Ester 40EM", "Epoxy Ester 70PA", "Epoxy Ester 200PA" and "Epoxy Ester 80MFA".

[0059] 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.

[0060] From the perspective of improving the strength of the resin layer, based on the total amount of photopolymerizable compounds, the content of epoxy (meth)acrylate can be 10% to 70% by mass, 20% to 60% by mass, or 30% to 50% by mass.

[0061] The photopolymerizable compounds involved in this embodiment may include photopolymerizable compounds other than urethane (meth)acrylates and epoxy (meth)acrylates (hereinafter referred to as "monomers").

[0062] As monomers, monofunctional monomers having one polymerizable group or polyfunctional monomers having two or more polymerizable groups can be used. Two or more monomers can also be used in combination.

[0063] Examples of monofunctional monomers include: methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, sec-butyl methacrylate, tert-butyl methacrylate, isobutyl methacrylate, n-pentyl methacrylate, isopentyl methacrylate, hexyl methacrylate, heptyl methacrylate, isopentyl methacrylate, 2-ethylhexyl methacrylate, n-octyl methacrylate, isooctyl methacrylate, isodecanyl methacrylate, lauryl methacrylate, 2-phenoxyethyl methacrylate, and propylene. 3-Phenoxybenzyl acrylate, phenoxy diethylene glycol acrylate, phenoxy polyethylene glycol acrylate, 4-tert-butylcyclohexanol acrylate, tetrahydrofurfuryl acrylate, benzyl acrylate, dicyclopentenyl acrylate, dicyclopentenoxyethyl acrylate, dicyclopentyl acrylate, nonylphenol polyethylene glycol (meth)acrylate, nonylphenoxy polyethylene glycol (meth)acrylate, isobornyl acrylate, and other (meth)acrylate monomers; (meth)acrylic acid, (meth)acrylate dimer, carboxyethyl acrylate, carboxypentyl acrylate, ω-carboxyl-polycaprolactone Monomers containing carboxyl groups, such as methacrylates; monomers containing heterocycles, such as N-(meth)acryloylmorpholine, N-vinylpyrrolidone, N-vinylcaprolactam, N-(meth)acryloylpiperidine, N-(meth)acryloylpyrrolidine, 3-(3-pyridyl)propyl (meth)acrylate, and cyclotrimethylolpropane methyl acetal acrylate; maleimide-based monomers, such as maleimide, N-cyclohexylmaleimide, and N-phenylmaleimide; (meth)acrylamide, N,N-dimethyl (meth)acrylamide, N,N-diethyl (meth)acrylamide, N-hexyl (meth)acrylamide, and N-methyl (meth)acrylamide. Amide monomers such as amide, N-ethyl(meth)acrylamide, N-butyl(meth)acrylamide, N-hydroxymethyl(meth)acrylamide, and N-hydroxymethylpropane(meth)acrylamide; aminoalkyl ester 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.

[0064] Examples of multifunctional monomers include: ethylene glycol dimethacrylate, polyethylene glycol dimethacrylate, polypropylene glycol dimethacrylate, neopentyl glycol dimethacrylate, tripropylene glycol dimethacrylate, dimethacrylate of bisphenol A epoxide adduct, tetraethylene glycol dimethacrylate, neopentyl glycol dimethacrylate of hydroxypentanoic acid, 1,4-butanediol dimethacrylate, 1,6-hexanediol dimethacrylate, 1,9-nonanediol dimethacrylate, 1,12-dodecanediol dimethacrylate, 1,14-tetradecanediol dimethacrylate, 1,16-hexadecanediol dimethacrylate, 1,20-eicosenediol dimethacrylate, isopentyl glycol dimethacrylate, and 3-ethyl-1,8-octanediol. Di(meth)acrylate, bisphenol A EO adduct di(meth)acrylate, trimethylolpropane tri(meth)acrylate, trimethyloloctane tri(meth)acrylate, trimethylolpropane polyethoxytri(meth)acrylate, trimethylolpropane polypropoxytri(meth)acrylate, trimethylolpropane polyethoxypolypropoxytri(meth)acrylate, tri[(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 tri[(meth)acryloyloxyethyl]isocyanurate.

[0065] As photopolymerization initiators, a suitable selection can be made from known free radical photopolymerization initiators. Examples of photopolymerization initiators include: 1-hydroxycyclohexylphenyl ketone (Omnirad 184, manufactured by IGM Resins), 2,2-dimethoxy-2-phenylacetophenone, 1-(4-isopropylphenyl)-2-hydroxy-2-methylpropane-1-one, bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide, 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinyl-propane-1-one (Omnirad 907, manufactured by IGM Resins), 2,4,6-trimethylbenzoyl diphenylphosphine oxide (Omnirad TPO, manufactured by IGM Resins), and bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (Omnirad 819, manufactured by IGM Resins).

[0066] Based on the total amount of photopolymerizable compounds, the content of photopolymerization initiator can be 0.2% by mass or more but less than 6.0% by mass, 0.4% by mass or more but less than 3.0% by mass, or 0.6% by mass or more but less than 2.0% by mass.

[0067] The resin composition may further contain silane coupling agents, leveling agents, defoamers, antioxidants, sensitizers, etc.

[0068] As a silane coupling agent, there are no particular limitations as long as it does not hinder the curing of the resin composition. Examples of silane coupling agents include: tetramethyl silicate, tetraethyl silicate, mercaptopropyltrimethoxysilane, vinyltrichlorosilane, vinyltriethoxysilane, vinyltri(β-methoxy-ethoxy)silane, β-(3,4-epoxycyclohexyl)-ethyltrimethoxysilane, dimethoxydimethylsilane, diethoxydimethylsilane, 3-acryloyloxypropyltrimethoxysilane, γ-epoxypropoxypropyltrimethoxysilane, γ-epoxypropoxypropylmethyldiethoxysilane, γ-methacryloyloxypropyltrimethoxysilane, N-(β-aminoethyl)silane, etc. N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane, N-phenyl-γ-aminopropyltrimethoxysilane, γ-chloropropyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-aminopropyltrimethoxysilane, bis-[3-(triethoxysilyl)propyl]tetrasulfide, bis-[3-(triethoxysilyl)propyl]disulfide, γ-trimethoxysilylpropyldimethylthiocarbamoyltetrasulfide, and γ-trimethoxysilylpropylbenzothiazolyltetrasulfide.

[0069] The resin composition described in this embodiment can be applied to the secondary coating material of optical fibers. By using the resin composition described in this embodiment as a secondary resin layer, a coating resin layer with excellent resistance to external damage can be formed.

[0070] (optical fiber)

[0071] Figure 1 This is a schematic cross-sectional view showing an example of an optical fiber according to this embodiment. The optical fiber 10 includes: a glass fiber 13 containing a core 11 and a cladding 12, and a coating resin layer 16 disposed on the outer periphery of the glass fiber 13 and containing a primary resin layer 14 and a secondary resin layer 15.

[0072] The cladding 12 surrounds the core 11. The core 11 and the cladding 12 are mainly composed of glass such as quartz glass. For example, the core 11 can be made of quartz glass with added germanium, and the cladding 12 can be made of pure quartz glass or quartz glass with added fluorine.

[0073] exist Figure 1For 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 can be approximately 5 μm to 50 μm.

[0074] When the outer diameter (D2) of the glass fiber 13 is approximately 125 μm and the thickness of the coated resin layer 16 is between 60 μm and 70 μm, the thickness of each layer of the primary resin layer 14 and the secondary resin layer 15 can be approximately 10 μm to 50 μm. For example, the thickness of the primary resin layer 14 can be 35 μm, and the thickness of the secondary resin layer 15 can be 25 μm. The outer diameter of the optical fiber 10 can be approximately 245 μm to 265 μm.

[0075] When the outer diameter (D2) of the glass fiber 13 is approximately 125 μm and the thickness of the coated 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 can be approximately 10 μm to 38 μm. For example, the thickness of the primary resin layer 14 can be 25 μm, and the thickness of the secondary resin layer 15 can be 10 μm. The outer diameter of the optical fiber 10 can be approximately 179 μm to 221 μm.

[0076] When the outer diameter (D2) of the glass fiber 13 is approximately 100 μm and the thickness of the coated 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 can be approximately 5 μm to 32 μm. For example, the thickness of the primary resin layer 14 can be 25 μm, and the thickness of the secondary resin layer 15 can be 10 μm. The outer diameter of the optical fiber 10 can be approximately 144 μm to 174 μm.

[0077] The resin composition described in this embodiment can be applied to a secondary resin layer. The secondary resin layer can be formed by curing a resin composition comprising the aforementioned surface-modified silica particles and a base resin. By including the cured product of the resin composition described in this embodiment in the secondary resin layer 15, damage to the surface of the secondary resin layer, preventing destruction of the resin layer, can be prevented during operations from changing from a large spool to a small spool. Furthermore, the anti-blocking effect inhibits fibers from sticking together, allowing optical fibers to be wound onto the small spool without winding abnormalities such as skipping.

[0078] The optical fiber manufacturing method according to this embodiment includes: a coating step of coating the above-described resin composition onto the outer periphery of a glass fiber consisting of a core and a cladding; and a curing step of curing the resin composition by irradiation with ultraviolet light after the coating step. By using the resin composition of this embodiment to coat the glass fiber, an optical fiber capable of preventing damage during rewinding operations can be manufactured. It should be noted that the resin composition of this embodiment is not directly coated onto the glass fiber, but rather the resin composition for primary coating is directly coated onto the glass fiber. That is, in the coating step, a primary coating that contacts the glass fiber and a secondary coating that utilizes the resin composition of this embodiment but does not contact the glass fiber are formed.

[0079] The Young's modulus of the secondary resin layer at 23°C is preferably 1300 MPa or more and 3600 MPa or less, more preferably 1400 MPa or more and 3000 MPa or less, and even more preferably 1600 MPa or more and 2800 MPa or less. When the Young's modulus of the secondary resin layer is 1300 MPa or more, it is easy to improve the lateral pressure characteristics. When it is 3500 MPa or less, it can impart appropriate toughness to the secondary resin layer, so the secondary resin layer is less likely to crack.

[0080] The primary resin layer 14 can be formed, for example, by curing a resin composition comprising urethane (meth)acrylate, monomers, a photopolymerization initiator, and a silane coupling agent. The resin composition used for the primary resin layer can utilize existing known techniques. The urethane (meth)acrylate, monomers, photopolymerization initiator, and silane coupling agent can be suitably selected from compounds shown in the examples of the aforementioned base resin. However, the resin composition forming the primary resin layer has a different composition from the base resin forming the secondary resin layer.

[0081] Sometimes multiple optical fibers are arranged side-by-side and integrated with a ribbon resin to form an optical fiber ribbon. The resin composition disclosed herein can also be used as a ribbon resin. This improves the fiber ribbon's resistance to external damage and lateral pressure characteristics.

[0082] Example

[0083] The following describes the evaluation test results using the test examples involved in this disclosure and provides a more detailed explanation of this disclosure. It should be noted that this invention is not limited to these test examples.

[0084] [Preparation of the resin composition]

[0085] (Carbamate acrylates)

[0086] As urethane acrylates, urethane acrylate (UA-1) obtained by reacting polypropylene glycol, 2,4-toluene diisocyanate and 2-hydroxyethyl acrylate with Mn of 600; and urethane acrylate (UA-2) obtained by reacting polypropylene glycol, 2,4-toluene diisocyanate and 2-hydroxyethyl acrylate with Mn of 12000.

[0087] (Epoxy acrylate)

[0088] As an epoxy acrylate (EA), a (meth)acrylic acid adduct of bisphenol A diglycidyl ether (manufactured by Osaka Organic Chemical Industry Co., Ltd., trade name "Viscoat540") was prepared.

[0089] (monomer)

[0090] As monomers, isobornyl acrylate (trade name "IBXA", manufactured by Osaka Organic Chemical Industry Co., Ltd.), 2-phenoxyethyl acrylate (trade name "Light Acrylate PO-A", manufactured by Kyoei Chemical Co., Ltd.), and tripropylene glycol diacrylate (trade name "TPGDA", manufactured by DAICL-ALLNEX Co., Ltd.) were prepared.

[0091] (Photopolymerization initiator)

[0092] 2,4,6-trimethylbenzoyl diphenylphosphine oxide (Omnirad TPO) was prepared as a photopolymerization initiator.

[0093] (Surface-modified silica particles)

[0094] As surface-modified silica particles, silica sols containing silica particles surface-treated with 3-methacryloyloxypropyltrimethoxysilane, as shown in Table 1, were prepared. The proportions of each constituent unit of the surface-modified silica particles were determined by following the steps outlined below. 29 Calculations were performed using Si-NMR spectra.

[0095] Four mL of each silica sol was taken, and after the dispersion medium was evaporated in the atmosphere, it was dried in a constant temperature bath at 80 °C for 24 hours to separate the surface-modified silica particles. 200 mg of the surface-treated silica particles were added to an acetone solution containing 13.7 mg of chromium acetylacetone (Cr(acac)3) as a moderating agent, followed by ultrasonic treatment for 30 minutes to obtain a mixture. Cr(acac)3 was added at 1% by mass relative to Si (assuming Cr content). The mixture was dried in a constant temperature bath at 90 °C for 24 hours to prepare the sample for NMR determination.

[0096] The solid content of the sample was determined using the DD-MAS method under the following conditions. 29 Si-NMR spectra were used to calculate the proportions of T1, T2, and T3 units in the T units of surface-modified silica particles.

[0097] Measuring device: Ascend500+AVANCE III HD (Bruker Japan Co., Ltd.)

[0098] Probe: 4mm φ MAS VTN probe

[0099] MAS rotation speed: 8kHz

[0100] Total number of times: 2048

[0101] [Table 1]

[0102] Silica sol Si-1 Si-2 Si-3 Si-4 Si-5 Si-6 Si-7 Dispersion medium MeOH MeOH MeOH MeOH MeOH MeOH MEK Average primary particle size (nm) 5～10 10～15 10～15 15～20 20～25 40～70 10～15 T1(％) 25 20 10 10 10 10 30 T2(％) 65 60 50 50 40 30 45 T3(％) 10 20 40 40 50 60 25

[0103] (Resin Composition)

[0104] A base resin was prepared by mixing a photopolymerizable compound and a photopolymerization initiator with 1 part by mass of Omnirad TPO in the proportions shown in Table 2. Resin compositions for each test example were prepared by mixing the base resin and silica sol, removing most of the dispersion medium, such that the content of surface-modified silica particles in the resin composition was 30% by mass. Test Examples 1-6 correspond to the Examples, and Test Example 7 corresponds to the Comparative Example.

[0105] The resin compositions obtained in the experimental examples were evaluated as follows. The results are shown in Table 2.

[0106] (Young's modulus)

[0107] The resin composition was coated onto a polyethylene terephthalate (PET) film using a spin coater, and then subjected to UV light at 1000 ± 100 mJ / cm² using an electrodeless UV lamp system (D-bulb) (Heraeus). 2 The resin layer was cured under certain conditions to form a resin layer with a thickness of 200±20μm on the PET film. The resin layer was then peeled off from the PET film to obtain the resin film.

[0108] The resin film was punched into a dumbbell shape according to JIS K 7127 Type 5. It was then stretched using a tensile testing machine at a tensile speed of 1 mm / min and a mark spacing of 25 mm under conditions of 23±2℃ and 50±10%RH to obtain the stress-strain curve. The Young's modulus of the resin film was determined based on the tangent.

[0109] [Fiber Optic Fabrication]

[0110] A urethane acrylate (UA-3) was prepared by reacting polypropylene glycol (molecular weight 4000), isophorone diisocyanate, hydroxyethyl acrylate, and methanol. A resin composition for a primary resin layer was prepared by mixing 75 parts by weight of UA-3, 12 parts by weight of nonylphenol EO-modified acrylate, 6 parts by weight of N-vinylcaprolactam, 2 parts by weight of 1,6-hexanediol diacrylate, 1 part by weight of 2,4,6-trimethylbenzoyl diphenylphosphine oxide, and 1 part by weight of 3-mercaptopropyltrimethoxysilane.

[0111] A resin composition for a primary resin layer and a resin composition used as a test example for a secondary resin layer were coated onto the outer periphery of a 125 μm diameter glass fiber consisting of a core and a cladding. The resin composition was then cured by irradiation with ultraviolet light, forming a 35 μm thick primary resin layer and a 25 μm thick secondary resin layer on its outer periphery, thus fabricating an optical fiber. The line speed was set to 1500 m / min.

[0112] (lateral pressure characteristics)

[0113] Optical fiber was wound in a single layer onto a 280 mm diameter spool covered with sandpaper. The transmission loss of light at a wavelength of 1550 nm was measured using an OTDR (Optical Time Domain Reflectometer). Conversely, optical fiber was wound in a single layer onto a 280 mm diameter spool without sandpaper, and the transmission loss of light at a wavelength of 1550 nm was measured using the OTDR method. The difference between the measured transmission losses was calculated. Cases with a transmission loss difference of less than 0.6 dB / km were rated "A", and cases with a transmission loss difference exceeding 0.6 dB / km were rated "B".

[0114] (Resubmission rate)

[0115] When rewinding optical fiber from a large spool to a small spool, the percentage increase in transmission loss is used as the rewinding rate. A rewinding rate of 0% is rated as "A", a rewinding rate of more than 0% but less than 30% is rated as "B", and a rewinding rate of more than 30% is rated as "C".

[0116] Test case 1 2 3 4 5 6 7 Silica sol Si-1 Si-2 Si-3 Si-4 Si-5 Si-6 Si-7 UA-1 20 20 20 20 20 20 20 UA-2 1 1 1 - 1 1 1 EA 40 40 40 40 40 40 40 IBXA 15 15 15 15 15 15 15 POA 20 20 20 20 20 20 20 TPGDA 4 4 4 5 4 4 4 Young's modulus (MPa) 2600 2500 2500 2400 2300 2200 2200 Lateral pressure characteristics A A A A A A A Re-roll rate A A A A A A B

[0117] Explanation of symbols

[0118] 10 optical fibers

[0119] 11 cores

[0120] 12 cladding layers

[0121] 13. Glass fiber

[0122] 14 Primary resin layer

[0123] 15 secondary resin layers

[0124] 16 Coated resin layer

Claims

1. A resin composition comprising: a base resin containing a photopolymerizable compound and a photopolymerization initiator, and a surface-modified silica particle, the surface-modified silica particle has a T unit having 3 oxygen atoms bonded to a silicon atom as a constituent unit of an organosilicon, a proportion of a Tl unit included in the T unit, 1 oxygen atom of which is bonded to another silicon atom, is 29 mol% or less, the surface-modified silica particle has at least one ultraviolet-curable group selected from the group consisting of an acryloyl group, a methacryloyl group, and a vinyl group.

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

3. The resin composition according to claim 1 or claim 2, wherein, an average primary particle diameter of the surface-modified silica particle is 100 nm or less.

4. The resin composition according to claim 3, wherein, an average primary particle diameter of the surface-modified silica particle is 1 nm or more.

5. The resin composition according to claim 1 or claim 2, wherein, a proportion of the Tl unit included in the T unit is 5 mol% or more.

6. A secondary coating material for an optical fiber, comprising the resin composition according to any one of claims 1 to 5.

7. An optical fiber comprising: a glass fiber including a core and a cladding, a primary resin layer in contact with the glass fiber and covering the glass fiber, and a secondary resin layer covering the primary resin layer, the secondary resin layer contains a cured product of the resin composition according to any one of claims 1 to 5.

8. A method for manufacturing an optical fiber, comprising: a coating step of coating the resin composition according to any one of claims 1 to 5 on an outer circumference of a glass fiber composed of a core and a cladding; and a curing step of curing the resin composition by irradiating ultraviolet rays after the coating step.

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