JP7200951B2 - UV curable resin composition and optical fiber - Google Patents

Description

The present invention relates to an ultraviolet curable resin composition for optical fiber coating and an optical fiber.
This application claims priority based on Japanese Application No. 2018-016700 filed on February 1, 2018, and incorporates all the descriptions described in the Japanese application.

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

In order to improve the microbend characteristics of optical fibers, it is important to reduce the Young's modulus of the primary resin layer. For example, in Patent Document 1, a resin composition containing a urethane oligomer obtained by reacting a reaction product of an aliphatic polyether diol and a diisocyanate with a monohydric alcohol and a hydroxyl group-containing (meth)acrylate is used to prepare a primary resin. A compromise between layer flexibility (low Young's modulus) and mechanical strength is disclosed. Further, in Patent Document 2, curing of a resin composition containing a urethane oligomer obtained by reacting a reaction product of a polyether diol and a diisocyanate with a hydroxyl group-containing (meth)acrylate, a silane compound having a thiol group, and a monohydric alcohol The article is described as having a relatively low Young's modulus and excellent water resistance, making it useful as a primary material.

JP 2012-111674 A JP 2009-197163 A

An ultraviolet curable resin composition for coating an optical fiber according to one aspect of the present invention contains a reaction product of a urethane prepolymer having a hydroxyl group at its end, an isocyanate group-containing (meth)acrylate, and an isocyanate group-containing silane compound. Contains urethane oligomers, monomers and photoinitiators.

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

[Problems to be Solved by the Present Disclosure]
Optical fibers are required to have a high dynamic fatigue coefficient in order to improve their dynamic fatigue characteristics. However, alcohol components such as monohydric alcohol have the effect of corroding glass, so if the alcohol component remains in the primary resin layer, the dynamic fatigue coefficient of the optical fiber may decrease. In addition, since optical fibers are used for several years to several decades after being installed, it is required that the optical fibers do not deteriorate even when used for a long period of time, and their dynamic fatigue coefficients do not decrease.

The present disclosure provides an ultraviolet curable resin composition for coating an optical fiber that can exhibit excellent dynamic fatigue characteristics while having a low Young's modulus, and an optical fiber comprising a coating resin layer formed from the resin composition. intended to provide

[Effect of the present disclosure]
According to the present disclosure, an ultraviolet curable resin composition for coating an optical fiber that can exhibit excellent dynamic fatigue characteristics while having a low Young's modulus, and a coating resin layer formed from the resin composition. It becomes possible to provide an optical fiber.

[Description of the embodiment of the present invention]
First, the contents of the embodiments of the present invention will be listed and explained. An ultraviolet curable resin composition for coating an optical fiber according to one aspect of the present invention (hereinafter also simply referred to as a "resin composition") comprises a urethane prepolymer having hydroxyl groups at its ends and an isocyanate group-containing (meth)acrylate. , a urethane oligomer containing a reactant with an isocyanate group-containing silane compound, a monomer and a photoinitiator.

By using the above specific urethane oligomer, it is possible to obtain a resin composition that has a low Young's modulus and yet exhibits excellent dynamic fatigue properties.

The reactant may have a structure represented by the following formula (1). In formula (1), R ¹ , R ² and R ³ each independently represent an alkyl group having 1 to 3 carbon atoms, and L ¹ represents an alkylene group having 2 to 4 carbon atoms. By using a urethane oligomer having the following structure, it is possible to increase the adhesive strength of the cured product of the resin composition to glass, making it easier to improve the dynamic fatigue characteristics of the optical fiber.

The reactant may have a structure represented by the following formula (2). In formula (2), R ⁴ represents a hydrogen atom or a methyl group, and L ² represents an organic group having 2 to 4 carbon atoms. By using a urethane oligomer having the following structure, the strength of the cured product of the resin composition can be increased, and the dynamic fatigue characteristics of the optical fiber can be easily improved.

An optical fiber according to one aspect of the present invention includes a glass fiber including a core and a clad, a primary resin layer that is in contact with the glass fiber and covers the glass fiber, and a secondary resin layer that covers the primary resin layer. The resin layer is made of a cured product of the ultraviolet curable resin composition. By applying the resin composition according to this embodiment to the primary resin layer, the dynamic fatigue property of the optical fiber can be improved.

[Details of the embodiment of the present invention]
Specific examples of the ultraviolet curable resin composition for coating an optical fiber according to the embodiment of the present invention and an optical fiber to which the composition is applied will be described with reference to the drawings if necessary. The present invention is not limited to these examples, but is indicated by the scope of the claims, and is intended to include all modifications within the scope and meaning equivalent to the scope of the claims. In the following description, the same reference numerals are given to the same elements in the description of the drawings, and overlapping descriptions are omitted.

(Ultraviolet curable resin composition)
The resin composition according to this embodiment contains a urethane oligomer, a monomer and a photopolymerization initiator. The urethane oligomer contains a reaction product of a hydroxyl group-terminated urethane prepolymer (hereinafter also simply referred to as "OH-terminated prepolymer"), an isocyanate group-containing (meth)acrylate, and an isocyanate group-containing silane compound.

Here, (meth)acrylate means acrylate or its corresponding methacrylate. The same applies to other similar expressions such as (meth)acrylic acid.

The urethane oligomer according to the present embodiment is obtained by reacting an OH-terminated prepolymer with an isocyanate group-containing (meth)acrylate and an isocyanate group-containing silane compound.

An OH-terminated prepolymer can be prepared by reacting a polyol compound with a polyisocyanate compound. Obtaining an OH-terminated prepolymer by reacting a polyol compound and a polyisocyanate compound at a ratio (molar ratio) in which the hydroxyl groups (OH) of the polyol compound are excessive relative to the isocyanate groups (NCO) of the polyisocyanate compound. can be done. The OH-terminated prepolymer has a urethane structure based on a reaction between a polyol compound and a polyisocyanate compound, and hydroxyl groups bonded to both ends of the urethane structure.

Examples of polyol compounds include polytetramethylene glycol, polypropylene glycol, polyester polyol, polycaprolactone polyol, polycarbonate diol, polybutadiene polyol, acrylic polyol, and bisphenol A/ethylene oxide added diol. The number average molecular weight (Mn) of the polyol compound is preferably 1000-5000. The Mn of the polyol compound may be 2000-4000.

Examples of polyisocyanate compounds include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, isophorone diisocyanate, dicyclohexylmethane diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, xylylene diisocyanate, hydrogenated xylylene diisocyanate, 1,5-naphthalene diisocyanate, norbornene diisocyanate, 1,5-pentamethylene diisocyanate, tetramethylxylylene diisocyanate and trimethylhexamethylene diisocyanate.

式（３）中、Ｒ^１、Ｒ^２及びＲ^３はそれぞれ独立に炭素数１～３のアルキル基を示し、メチル基、エチル基又はプロピル基であってもよい。Ｒ^１、Ｒ^２及びＲ^３は同一でも異なっていてもよい。Ｌ^１は炭素数２～４のアルキレン基を示し、エチレン基、プロピレン基又はブチレン基であってもよい。The isocyanate group-containing silane compound is not particularly limited as long as it is a compound having an isocyanate group and an alkoxysilyl group. As the isocyanate group-containing silane compound, for example, a compound represented by the following formula (3) can be used.

In formula (3), R ¹ , R ² and R ³ each independently represent an alkyl group having 1 to 3 carbon atoms, and may be a methyl group, an ethyl group or a propyl group. R ¹ , R ² and R ³ may be the same or different. L ¹ represents an alkylene group having 2 to 4 carbon atoms and may be an ethylene group, a propylene group or a butylene group.

By using the compound represented by Formula (3), the structure represented by Formula (1) can be introduced into the urethane oligomer. Since the structure represented by Formula (1) has an alkoxysilyl group, it can function as a silane coupling agent. By using the oligomer having the structure represented by the formula (1) for the primary resin layer, the alkoxysilyl group reacts with the hydroxyl group on the surface of the glass fiber, and the adhesion of the primary resin layer to the glass fiber can be enhanced. It becomes easy to improve the dynamic fatigue property of the fiber.

Examples of compounds represented by formula (3) include 3-isocyanatopropyltrimethoxysilane and 3-isocyanatopropyltriethoxysilane.

式（４）中、Ｒ^４は水素原子又はメチル基を示し、Ｌ^２は炭素数２～４の有機基を示す。Ｌ^２は、炭素数２～４のアルキレン基又はジアルキレンエーテル基であってもよい。The isocyanate group-containing (meth)acrylate is not particularly limited as long as it is a compound having a (meth)acryloyl group and an isocyanate group. As the isocyanate group-containing (meth)acrylate, for example, a compound represented by the following formula (4) can be used.

In formula (4), R ⁴ represents a hydrogen atom or a methyl group, and L ² represents an organic group having 2 to 4 carbon atoms. L ² may be an alkylene group having 2 to 4 carbon atoms or a dialkylene ether group.

By using the compound represented by Formula (4), the structure represented by Formula (2) can be introduced into the urethane oligomer. Since the structure represented by formula (2) has a (meth)acryloyl group that is a photopolymerizable group, the oligomer having the structure represented by formula (2) can be copolymerized with the monomer. can. By using the oligomer having the structure represented by formula (2), a coating resin layer with high strength can be formed, and the dynamic fatigue characteristics of the optical fiber can be easily improved.

Examples of compounds represented by formula (4) include 2-acryloyloxyethyl isocyanate, 2-methacryloyloxyethyl isocyanate and 2-(2-isocyanatoethoxy)ethyl methacrylate.

Organotin compounds are generally used as catalysts for synthesizing urethane oligomers. Organotin compounds include, for example, dibutyltin dilaurate, dibutyltin diacetate, dibutyltin malate, dibutyltin bis(2-ethylhexyl mercaptoacetate), dibutyltin bis(isooctyl mercaptoacetate) and dibutyltin oxide. Dibutyltin dilaurate or dibutyltin diacetate is preferably used as the catalyst in terms of availability and catalytic performance.

The urethane oligomer according to the present embodiment is a reaction product of an OH-terminated prepolymer, an isocyanate group-containing (meth)acrylate, and an isocyanate group-containing silane compound, and has a structure represented by formula (1) at one end. and an oligomer having a structure represented by formula (2) at the other end. Since the oligomer has an alkoxysilyl group and a (meth)acryloyl group in one molecule, it is possible to form a primary resin layer with a low Young's modulus and to increase the adhesion of the primary resin layer to the glass fiber. It is considered that the dynamic fatigue coefficient of the optical fiber can be improved.

The urethane oligomer according to the present embodiment includes a first step of reacting a polyol compound and a polyisocyanate compound to obtain an OH-terminated prepolymer, and an isocyanate group-containing (meth)acrylate and an isocyanate group-containing It can be produced by a second step of reacting a silane compound to obtain a urethane oligomer.

In the first step, the OH of the polyol compound is reacted in a molar ratio in excess of the NCO of the polyisocyanate compound. The molar ratio (OH/NCO) between the OH of the polyol compound and the NCO of the polyisocyanate compound when preparing the OH-terminated prepolymer is preferably more than 1 and 2 or less, and is 1.1 to 2.0. It is more preferable to have On the other hand, when the OH/NCO ratio is less than 1, the ratio of NCO becomes excessive and a urethane prepolymer having an isocyanate group at the end (hereinafter also simply referred to as "NCO-terminated prepolymer") is produced, and the OH/NCO ratio is Above 2, a mixture of OH-terminated prepolymer and unreacted polyol compound is obtained.

It can be confirmed by measuring the amount of residual NCO that an OH-terminated prepolymer was obtained. The residual amount of NCO can be measured by potentiometric titration in accordance with JIS K1603-1. The second step is preferably performed after confirming that the residual amount of NCO is 0.1% by mass or less.

In the second step, the molar ratio (NCO/OH ) is preferably 0.5 to 0.99, more preferably 0.5 to 0.96. When the NCO/OH ratio is 0.5 or more, a urethane oligomer having a (meth)acryloyl group on at least one end can be obtained, and the breaking strength and breaking elongation of the cured product of the resin composition can be increased. When the NCO/OH ratio is 0.99 or less, the isocyanate group-containing silane compound can be further reacted after the OH-terminated prepolymer is reacted with the isocyanate group-containing (meth)acrylate.

The amount of the isocyanate group-containing silane compound added is preferably such that the molar ratio (NCO/OH) of the NCO of the isocyanate group-containing silane compound to the OH groups of the OH-terminated prepolymer is 0.01 to 0.5. It is more preferable to be 01 to 0.4. Thereby, a urethane oligomer having an alkoxysilyl group on at least one end can be obtained. If NCO/OH is 0.01 or more, high adhesion can be obtained, and the dynamic fatigue coefficient can be easily improved. On the other hand, if the adhesion is too high, the removability of the coating will be low, so NCO/OH is preferably 0.5 or less, more preferably 0.4 or less.

The order in which the OH-terminated prepolymer is reacted with the isocyanate group-containing (meth)acrylate and the isocyanate group-containing silane compound is not particularly limited. It is preferred to react a silane compound. This facilitates preparation of a urethane oligomer having a (meth)acryloyl group at one end and an alkoxysilyl group at the other end.

The residual amount of NCO in the urethane oligomer is preferably 0.1% by mass or less. When the residual amount of NCO is 0.1% by mass or less, it becomes easier to suppress changes in physical properties such as an increase in the viscosity of the resin composition over time.

On the other hand, a urethane oligomer having a structure different from that of the urethane oligomer according to the present embodiment can be prepared by reacting an NCO-terminated prepolymer with a monohydric alcohol and a hydroxyl group-containing (meth)acrylate. Since such a urethane oligomer has terminal hydroxyl groups derived from a monohydric alcohol, it is possible to lower the crosslink density and lower the Young's modulus of the primary resin layer. However, if unreacted monohydric alcohol remains in the primary resin layer, it may corrode the glass fiber, causing a decrease in the strength of the optical fiber and deterioration in dynamic fatigue characteristics.

In contrast, since no monohydric alcohol is used when preparing the urethane oligomer according to the present embodiment, the dynamic fatigue characteristics of the optical fiber can be improved while maintaining a low Young's modulus.

Hereinafter, the preparation of the urethane oligomer will be described with specific examples. For example, polypropylene glycol is used as the polyol compound, isophorone diisocyanate as the polyisocyanate compound, 2-acryloyloxyethyl isocyanate as the isocyanate group-containing (meth)acrylate, and 3-isocyanatopropyltriethoxysilane as the isocyanate group-containing silane compound.

In the first step, polypropylene glycol and isophorone diisocyanate are reacted to synthesize an OH-terminated prepolymer represented by (a) below. A urethane prepolymer having hydroxyl groups at both ends can be obtained by charging polypropylene glycol in an excess molar ratio relative to isophorone diisocyanate. When the molar ratio (OH/NCO) of OH of polypropylene glycol to NCO of isophorone diisocyanate is more than 1 and 2 or less, OH-terminated prepolymer (a) is mainly produced. On the other hand, when the OH/NCO ratio is less than 1, an NCO-terminated prepolymer is produced, and when the OH/NCO ratio exceeds 2, a mixture of the OH-terminated prepolymer (a) and unreacted polypropylene glycol is formed.
(a) HO-P-(UIUP)n-OH
Here, P represents a residue of polypropylene glycol, I represents a residue of isophorone diisocyanate, U represents a urethane bond, and n represents an integer of 1 or more.

In the second step, the OH-terminated prepolymer (a) is reacted with 2-acryloyloxyethyl isocyanate and 3-isocyanatopropyltriethoxysilane to obtain a mixture of urethane oligomers represented by (b1) to (b5) below. Obtainable.
(b1) AUP-(UIUP)nUA
(b2) AUP-(UIUP)n-OH
(b3) AUP-(UIUP)nS
(b4) SUP-(UIUP)nS
(b5) SUP-(UIUP)n-OH
Here, A represents a residue of 2-acryloyloxyethyl isocyanate and S represents a residue of 3-isocyanatopropyltriethoxysilane.

One hydroxyl group of the OH-terminated prepolymer (a) reacts with 2-acryloyloxyethyl isocyanate, and the other hydroxyl group reacts with 3-isocyanatopropyltriethoxysilane to obtain a urethane oligomer represented by (b3). be done. A urethane oligomer represented by (b1) or (b2) is obtained by reacting the OH-terminated prepolymer with 2-acryloyloxyethyl isocyanate. A urethane oligomer represented by (b4) or (b5) is obtained by reacting the OH-terminated prepolymer with 3-isocyanatopropyltriethoxysilane.

Since the urethane oligomer (b3) has an alkoxysilyl group and a (meth)acryloyl group in one molecule, it can be copolymerized with a monomer and can also react with hydroxyl groups on the glass fiber surface. can. Since the urethane oligomer (b1) is an oligomer having acryloyl groups at both ends, it increases the crosslink density of the cured product. , has the effect of lowering the crosslink density of the cured product, and can reduce the Young's modulus.

Urethane oligomers (b4) and (b5) do not have acryloyl groups and cannot be copolymerized with monomers. In order to suppress the formation of urethane oligomers (b4) and (b5) in the second step, it is desirable to react an isocyanate group-containing silane compound after reacting an OH-terminated prepolymer with an isocyanate group-containing (meth)acrylate. .

A mixture of urethane oligomers (b1) and (b2) is prepared by reacting 2-acryloyloxyethyl isocyanate with the OH-terminated prepolymer (a) at a molar ratio (NCO/OH) of 0.5 to 0.99. can be obtained. Next, the urethane oligomer (b3) can be obtained by reacting the urethane oligomer (b2) with 3-isocyanatopropyltriethoxysilane.

As the monomer, a monofunctional monomer having one ethylenically unsaturated group, which is a polymerizable group, or a polyfunctional monomer having two or more ethylenically unsaturated groups can be used. You may use a monomer in mixture of 2 or more types.

Examples of monofunctional monomers include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, n-butyl (meth) acrylate, s-butyl (meth) acrylate, tert-butyl (meth) acrylate, isobutyl (meth)acrylate, n-pentyl (meth)acrylate, isopentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, isoamyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-octyl (meth)acrylate, isooctyl (meth)acrylate, isodecyl (meth)acrylate, lauryl (meth)acrylate, phenoxyethyl (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, benzyl (meth)acrylate, dicyclopentenyl (meth)acrylate Acrylates, dicyclopentenyloxyethyl (meth)acrylate, dicyclopentanyl (meth)acrylate, nonylphenol polyethylene glycol (meth)acrylate (for example, "SR504" manufactured by Sartomer), nonylphenoxypolyethylene glycol (meth)acrylate, isobornyl (Meth)acrylate-based monomers such as (meth)acrylate; (meth)acrylic acid, (meth)acrylic acid dimer, carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, ω-carboxy-polycaprolactone (meth)acrylate Carboxyl group-containing monomers such as; 4-acryloylmorpholine, N-vinylpyrrolidone, N-vinylcaprolactam, N-acryloylpiperidine, N-methacryloylpiperidine, N-acryloylpyrrolidine, 3-(3-pyridinyl)propyl (meth)acrylate, etc. heterocycle-containing monomers; 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, N-methyl (meth)acrylamide, N-butyl (meth)acrylamide, N-butyl (meth)acrylamide, N-methylol (meth)acrylamide, N-methylolpropane (meth)acrylamide, etc. Amide-based monomer; (meth)aminoethyl acrylate, (meth)acrylic acid amino Aminoalkyl (meth)acrylate monomers such as nopropyl, N,N-dimethylaminoethyl (meth)acrylate, and tert-butylaminoethyl (meth)acrylate can be mentioned.

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, Tetraethylene glycol di(meth)acrylate, neopentyl glycol hydroxypivalate di(meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,9-nonane Diol di(meth)acrylate, 1,12-dodecanediol di(meth)acrylate, 1,14-tetradecanediol di(meth)acrylate, 1,16-hexadecanediol di(meth)acrylate, 1,20-eicosandiol Di(meth)acrylate, isopentyldiol di(meth)acrylate, 3-ethyl-1,8-octanediol di(meth)acrylate, EO adduct di(meth)acrylate of bisphenol A (for example, Osaka Organic Chemical Industry Co., Ltd.) Bifunctional monomers such as "Viscoat #700" manufactured by the company), di(meth)acrylate of bisphenol A diglycidyl ether acrylic acid adduct (for example, "Viscoat #540" manufactured by Osaka Organic Chemical Industry Co., Ltd.); trimethylol Propane 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, ditri Methylolpropane tetra(meth)acrylate, dipentaerythritol tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, caprolactone-modified tris[(meth)acryloyloxyethyl]isocyanurate, etc. Trifunctional or higher functional monomers can be mentioned.

The photopolymerization initiator can be appropriately selected from known radical photopolymerization initiators and used. Examples of photopolymerization initiators include 1-hydroxycyclohexylphenyl ketone, 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, 2,4,6- Trimethylbenzoyldiphenylphosphine oxide and bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide.

Two or more kinds of photopolymerization initiators may be mixed and used, but 2,4,6-trimethylbenzoyldiphenylphosphine oxide is preferably included because the resin is excellent in rapid curing.

The resin composition according to this embodiment may further contain a silane coupling agent, a photoacid generator, a leveling agent, an antifoaming agent, an antioxidant, and the like.

The silane coupling agent is not particularly limited as long as it does not interfere with the curing of the resin composition by ultraviolet rays, and any known silane coupling agent can be used. Silane coupling agents such as tetramethylsilicate, tetraethylsilicate, 3-mercaptopropyltrimethoxysilane, vinyltrichlorosilane, vinyltriethoxysilane, vinyltris(β-methoxy-ethoxy)silane, β-(3,4-epoxy) cyclohexyl)-ethyltrimethoxysilane, dimethoxydimethylsilane, diethoxydimethylsilane, 3-acryloxypropyltrimethoxysilane, 3-methacryloxypropyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxy Propylmethyldiethoxysilane, N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane, N-(β-aminoethyl)-γ-aminopropyltrimethyldimethoxysilane, N-phenyl-γ-aminopropyltrimethoxysilane Silane, γ-chloropropyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-aminopropyltrimethoxysilane, bis-[3-(triethoxysilyl)propyl]tetrasulfide, bis-[3-(triethoxysilyl) ) propyl]disulfide, γ-trimethoxysilylpropyldimethylthiocarbamyltetrasulfide and γ-trimethoxysilylpropylbenzothiazyltetrasulfide.

By using a silane coupling agent, it is possible to adjust the adhesion between the glass fiber and the primary resin layer, and to further improve the dynamic fatigue characteristics. The content of the silane coupling agent is preferably 0.1 to 3% by mass, more preferably 0.3 to 2% by mass, based on the total amount of the resin composition.

An onium salt having a structure of A ⁺ B ⁻ may be used as the photoacid generator. Examples of photoacid generators include sulfonium salts such as CPI-100P, CPI-101A, CPI-200K, CPI-210S, CPI-310B, and CPI-400PG (manufactured by San-Apro Co., Ltd.), WPI-113, and WPI-116. , WPI-169, WPI-170, WPI-124 (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), (4-methylphenyl) [4-(2-methylpropyl) phenyl] iodonium salts such as iodonium hexafluorophosphate mentioned.

The characteristics after curing of the resin composition according to the present embodiment are obtained by using a resin film (cured product of the resin composition) obtained by curing under conditions of 1000 mJ/cm ² and 1000 mW/cm ² (UVA) with a metal halide lamp. can be evaluated as

The 2.5% secant Young's modulus of the resin film according to the present embodiment is preferably 0.1 to 1.5 MPa at 23° C.±2° C., more preferably 0.1 MPa or more and less than 0.8 MPa. . When the 2.5% secant Young's modulus is 0.1 MPa or more, the resin composition according to the present embodiment can be used to form a primary resin layer having an appropriate toughness. It is easy to reduce the increase in loss. When the 2.5% secant Young's modulus is 1.5 MPa or less, it is easy to improve the microbend characteristics of the optical fiber.

The breaking strength of the resin film according to the present embodiment is preferably 1.0 MPa or more at 23° C.±2° C., more preferably 3 MPa or more. When the breaking strength is 1.0 MPa or more, it is easy to suppress the generation of voids in the primary resin layer.

(optical fiber)
FIG. 1 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 including a core 11 and a clad 12 , and a coating resin layer 16 including a primary resin layer 14 and a secondary resin layer 15 provided around the glass fiber 13 .

Cladding 12 surrounds core 11 . The core 11 and the clad 12 mainly contain glass such as quartz glass. For example, germanium-doped quartz can be used for the core 11, and pure quartz or fluorine-doped quartz is used for the clad 12. be able to.

In FIG. 1, for example, the outer diameter (D2) of the glass fiber 13 is approximately 125 μm. The diameter (D1) of the core 11 forming the glass fiber 13 is approximately 7 to 15 μm. The coating resin layer 16 has a structure of at least two layers including the primary resin layer 14 and the secondary resin layer 15 . The total thickness of the coating resin layer 16 is usually about 60 μm, and the thicknesses of the primary resin layer 14 and the secondary resin layer 15 are substantially the same, ranging from 20 to 40 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. When a large number of optical fibers are assembled to form a cable, it is preferable that the coating diameter of the optical fibers is small. In that case, the total thickness of the coating resin layer 16 is preferably 30 to 40 μm. The thickness of the primary resin layer and the secondary resin layer can each be 10 to 30 μm.

The resin composition according to this embodiment can be applied to the primary resin layer. That is, the primary resin layer is a resin containing a urethane oligomer containing a reaction product of a hydroxyl group-terminated urethane prepolymer, an isocyanate group-containing (meth)acrylate, and an isocyanate group-containing silane compound, a monomer, and a photopolymerization initiator. The composition can be cured to form. Thereby, the dynamic fatigue property of the optical fiber can be improved.

From the viewpoint of reducing transmission loss due to microbending, the Young's modulus of the primary resin layer is preferably 0.1 to 1.5 MPa at 23.degree.

The Young's modulus of the secondary resin layer may be 500-2000 MPa at 23°C. When the Young's modulus of the secondary resin layer is 500 MPa or more, the microbending property is easily improved, and when it is 2000 MPa or less, the secondary resin layer can be given appropriate toughness, so cracks are less likely to occur.

The Young's modulus of the secondary resin layer can be measured 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 pulled out in a cylindrical shape. At this time, the primary resin layer and the secondary resin layer are integrated, but since the Young's modulus of the primary resin layer is 1/1000 to 1/10000 of that of the secondary resin layer, the Young's modulus of the primary resin layer is can be ignored. Next, after the solvent is removed from the coating resin layer by vacuum drying, a tensile test is performed at 23° C. (at a tensile speed of 1 mm/min), and the Young's modulus can be obtained by the secant formula of 2.5% strain.

The secondary resin layer 15 can be formed, for example, by curing an ultraviolet curable resin composition containing a urethane oligomer, a monomer and a photopolymerization initiator. A conventionally known technique can be used for the resin composition for the secondary resin layer. The urethane oligomer, monomer and photopolymerization initiator may be appropriately selected from the compounds exemplified for the above resin composition. However, the resin composition forming the secondary resin layer has a different composition from the resin composition forming the primary resin layer.

Hereinafter, the results of evaluation tests using examples and comparative examples according to the present invention will be shown, and the present invention will be described in more detail. However, the present invention is not limited to these examples.

[Urethane oligomer]
(Synthesis example 1)
An OH-terminated prepolymer is prepared by reacting polypropylene glycol of Mn 4000 with isophorone diisocyanate at an OH to NCO molar ratio (OH/NCO) of 1.1. As a catalyst, 200 ppm of dibutyltin dilaurate is added to the final total charge. After confirming that the residual amount of NCO was 0.1 mass% or less, 2-Acryloyloxyethyl isocyanate is added to the solution and reacted for 1 hour. Next, 3-isocyanatopropyltriethoxysilane is added so that the molar ratio of NCO of 3-isocyanatopropyltriethoxysilane to OH of the OH-terminated prepolymer (NCO/OH) is 0.3, and further reaction is carried out. After confirming that the residual amount of NCO is 0.1% by mass or less, the reaction is terminated to obtain a urethane oligomer (U-1).

(Synthesis example 2)
Prepare an OH-terminated prepolymer with an OH/NCO of 1.5, add 2-acryloyloxyethyl isocyanate to an NCO/OH of 0.6, and add an NCO/OH of 0.2. A urethane oligomer (U-2) is obtained in the same manner as in Synthesis Example 1, except that 3-isocyanatopropyltriethoxysilane is added.

(Synthesis Example 3)
Prepare an OH-terminated prepolymer with an OH/NCO of 1.5, add 2-acryloyloxyethyl isocyanate to an NCO/OH of 0.7, A urethane oligomer (U-3) is obtained in the same manner as in Synthesis Example 1, except that 3-isocyanatopropyltriethoxysilane is added.

(Synthesis Example 4)
Prepare an OH-terminated prepolymer with an OH/NCO of 1.5, add 2-acryloyloxyethyl isocyanate to an NCO/OH of 0.9, A urethane oligomer (U-4) is obtained in the same manner as in Synthesis Example 1, except that 3-isocyanatopropyltriethoxysilane is added.

(Synthesis Example 5)
Prepare an OH-terminated prepolymer with an OH/NCO of 1.5, add 2-acryloyloxyethyl isocyanate to an NCO/OH of 0.96, and add an NCO/OH of 0.01. A urethane oligomer (U-5) is obtained in the same manner as in Synthesis Example 1 except that 3-isocyanatopropyltriethoxysilane is added.

(Synthesis Example 6)
Prepare an OH-terminated prepolymer with an OH/NCO of 2.0, add 2-acryloyloxyethyl isocyanate to an NCO/OH of 0.8, and add an NCO/OH of 0.2. A urethane oligomer (U-6) is obtained in the same manner as in Synthesis Example 1, except that 3-isocyanatopropyltriethoxysilane is added.

(Synthesis Example 7)
An NCO-terminated prepolymer is prepared by reacting polypropylene glycol of Mn 4000 with isophorone diisocyanate at an NCO/OH of 1.5. 200 ppm of dibutyltin dilaurate is added to the final total charge. Next, 0.3 mol of methanol and 0.7 mol of 2-hydroxyethyl acrylate are added to 1 mol of NCO in the NCO-terminated prepolymer to carry out a reaction to obtain a urethane oligomer (U-7).

(Synthesis Example 8)
An NCO-terminated prepolymer is prepared by reacting polypropylene glycol of Mn 600 with isophorone diisocyanate at an NCO/OH of 1.5. 200 ppm of dibutyltin dilaurate is added to the final total charge. Next, 2-hydroxyethyl acrylate was added so that the OH molar ratio of 2-hydroxyethyl acrylate to NCO in the NCO-terminated prepolymer (OH/NCO) was 1.05, and the reaction was carried out at 80° C. for 1 hour. , to obtain a urethane oligomer (U-8).

[Resin composition for primary resin layer]
Urethane acrylate oligomer, N-vinylcaprolactam, isobornyl acrylate, nonylphenol polyethylene glycol acrylate (“SR504” manufactured by Sartomer), and 2,4,6-trimethylbenzoyldiphenylphosphine at the blending amounts (parts by mass) shown in Table 1. The oxide and 3-acryloxypropyltrimethoxysilane were mixed to prepare a resin composition for the primary resin layer of each example and comparative example.

(Production of resin film)
After applying the resin composition onto a polyethylene terephthalate (PET) substrate using a spin coater, an electrodeless UV lamp system "F600V-10 (D bulb)" manufactured by Heraeus was used to apply 1000±100 mJ/cm ² . and 1000±100 mW/cm ² to form a resin layer having a thickness of 200±20 μm on the PET substrate. The resin layer was peeled off from the PET substrate to obtain a resin film for evaluation.

(Young's modulus)
The resin film is punched into a dumbbell shape of JIS K 7127 type 5, and under the conditions of 23 ± 2 ° C. and 50 ± 10% RH, using a tensile tester at a tensile speed of 1 mm / min and a gauge line distance of 25 mm Tensile and stress-strain curves were obtained. Young's modulus was determined by the 2.5% secant line. A Young's modulus of 0.1 MPa or more and less than 0.8 MPa was evaluated as A, 0.8 MPa or more and 1.5 MPa or less as B, and over 1.5 MPa as C. A sample with a Young's modulus of 0.1 to 1.5 MPa was regarded as acceptable.

(Breaking strength)
The resin film is punched into a dumbbell shape of JIS K 7127 Type 5, and under the conditions of 23 ± 2 ° C. and 50 ± 10% RH, using a tensile tester at a tensile speed of 50 mm / min and a gauge line distance of 25 mm. Tensile and stress-strain curves were obtained. Breaking strength was determined from the stress at break. Breaking strength was evaluated as A when 3 MPa or more, B when 1 MPa or more and less than 3 MPa, and C when less than 1 MPa. A case where the breaking strength was 1 MPa or more was regarded as acceptable.

(Resin composition for secondary resin)
50 parts by mass of urethane acrylate oligomer (U-8), 20 parts by mass of isobornyl acrylate, 15 parts by mass of bisphenol A acrylic acid adduct, 14 parts by mass of trimethylolpropane triacrylate and 2,4,6- 1 part by mass of trimethylbenzoyldiphenylphosphine oxide was mixed to obtain a resin composition for a secondary resin.

[Fabrication of optical fiber 10]
The outer peripheral surface of the glass fiber 13 is coated with the mold resin composition for the primary resin layer and the resin composition for the secondary resin layer, respectively, to form the coating resin layer 16 having the primary resin layer 14 and the secondary resin layer 15. Then, an optical fiber 10 was produced. The thickness of the primary resin layer 14 was set to 35 μm, and the thickness of the secondary resin layer 15 was set to 25 μm.

(Dynamic fatigue characteristics)
According to the test method of IEC60793-1-33, the produced optical fiber was subjected to a tensile test 15 times under three conditions of tensile speed of 5 mm/min, 50 mm/min, and 500 mm/min, and the dynamic fatigue coefficient (Nd) was obtained. rice field. Nd was evaluated as A when 22 or more, B when 20 or more and less than 22, and C when less than 20. When Nd was 20 or more, the dynamic fatigue characteristics were judged to be good.

DESCRIPTION OF SYMBOLS 10... Optical fiber, 11... Core, 12... Clad, 13... Glass fiber, 14... Primary resin layer, 15... Secondary resin layer, 16... Coating resin layer.

Claims (4)

A urethane oligomer containing a reaction product of a hydroxyl-terminated urethane prepolymer, an isocyanate group-containing (meth)acrylate, and an isocyanate group-containing silane compound, a monomer, and a photopolymerization initiator,
The urethane prepolymer having hydroxyl groups at its ends has a urethane structure and hydroxyl groups bonded to both ends of the urethane structure,
The isocyanate group-containing (meth)acrylate is a compound represented by the following formula (4),
An ultraviolet curable resin composition for coating an optical fiber, wherein the reactant has a structure represented by the following formula (2).

(In the formula, R ⁴ represents a hydrogen atom or a methyl group, and L ² represents an alkylene group having 2 to 4 carbon atoms or a dialkylene ether group .) The ultraviolet curable resin composition according to claim 1, wherein the reactant has a structure represented by the following formula (1).

(In the formula, R ¹ , R ² and R ³ each independently represent an alkyl group having 1 to 3 carbon atoms, and L ¹ represents an alkylene group having 2 to 4 carbon atoms.) The urethane oligomer contains, as the reactant, an oligomer having a structure represented by the formula (1) at one end and a structure represented by the formula (2) at the other end. 3. The UV-curable resin composition according to item 2. a glass fiber comprising a core and a cladding;
a primary resin layer covering the glass fiber in contact with the glass fiber;
and a secondary resin layer covering the primary resin layer,
An optical fiber, wherein the primary resin layer comprises a cured product of the ultraviolet curable resin composition according to any one of claims 1 to 3.

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