Resin composition, optical fiber, and method for producing optical fiber

Abstract

Provided is a resin composition for a secondary coating of an optical fiber, the resin composition comprising a non-reactive urethane compound having a number-average molecular weight of 10,000-50,000, inclusive, a photopolymerizable compound, and a photopolymerization initiator. The content of the non-reactive urethane compound is 0.05-5 parts by mass, inclusive, based on the total amount of the resin composition, and the non-reactive urethane compound is a reaction product of a polyol having a number-average molecular weight of 8,000-20,000, inclusive, a diisocyanate, and a compound having an active hydrogen.

Description

[Technical field]

[0001] The present disclosure relates to a resin composition for a secondary coating of an optical fiber, an optical fiber, and a method for making an optical fiber. This application claims priority to Japanese Application No. 2020-108664, filed on June 24, 2020, and incorporates by reference all of the contents of said Japanese application. [Background technology]

[0002] Generally, optical fibers are provided with a coating resin layer to protect the glass fiber, which is an optical transmission medium. The coating resin layer is composed of two layers, for example, a primary resin layer that contacts the glass fiber and a secondary resin layer formed on the outer surface of the primary resin layer. The secondary resin layer is required to have a high Young's modulus to enhance microbending resistance, and to have surface slipperiness, scratch resistance, and tack prevention properties to improve the handleability of the optical fiber.

[0003] For example, Patent Documents 1 and 2 disclose that a resin layer is formed using a resin composition containing a silicone compound to improve surface slipperiness. Patent Documents 3 and 4 disclose that a resin layer is formed using a resin composition containing a specific urethane (meth)acrylate to improve tack prevention. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 9-278850 [Patent Document 2] Japanese Patent Application Publication No. 9-328632 [Patent Document 3] JP 2006-36989 A [Patent Document 4] JP 2005-89586 A Summary of the Invention

[0005] A resin composition for a secondary coating of an optical fiber according to one embodiment of the present disclosure is a resin composition containing a non-reactive urethane compound having a number average molecular weight of 10,000 or more and 50,000 or less, a photopolymerizable compound, and a photopolymerization initiator, wherein the content of the non-reactive urethane compound is 0.05 parts by mass or more and 5 parts by mass or less based on the total amount of the resin composition, and the non-reactive urethane compound is a reaction product of a polyol having a number average molecular weight of 8,000 or more and 20,000 or less, a diisocyanate, and a compound having active hydrogen. [Brief description of the drawings]

[0006] [Figure 1] FIG. 1 is a schematic cross-sectional view showing an example of an optical fiber according to the present embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0007] [Problem that this disclosure aims to solve] In optical fiber production lines, the surface slipperiness of the coating resin layer gradually deteriorates due to contact with guide rollers, screening tests (tests in which a tensile load of several kg is applied to an optical fiber to remove low-strength parts in advance), and other external forces, which may cause the optical fiber to meander when wound around a bobbin, resulting in reduced productivity of the optical fiber. In order to improve the productivity of optical fibers, the secondary resin layer is required to have excellent surface slipperiness and abrasion resistance. In addition, in order to suppress the deterioration of transmission loss caused by microbending when optical fibers are densely packed in a cable, it is required to increase the Young's modulus of the secondary resin layer. However, increasing the Young's modulus of the secondary resin layer leads to a decrease in the toughness of the resin layer, making the secondary resin layer more susceptible to cracking when an external force is applied.

[0008] The present disclosure aims to provide a resin composition for secondary coating of an optical fiber, which can form a resin layer having a high Young's modulus and excellent toughness, and has excellent surface slip properties and abrasion resistance, and an optical fiber with excellent productivity.

[0009] [Effects of this disclosure] According to the present disclosure, it is possible to provide a resin composition for a secondary coating of an optical fiber, which can form a resin layer having a high Young's modulus and excellent toughness, and which has excellent surface slip properties and abrasion resistance, and an optical fiber which has excellent productivity.

[0010] [Description of the embodiments of the present disclosure] First, the contents of the embodiments of the present disclosure will be listed and described. A resin composition for a secondary coating of an optical fiber according to one aspect of the present disclosure is a resin composition containing a non-reactive urethane compound having a number average molecular weight of 10,000 to 50,000, a photopolymerizable compound, and a photopolymerization initiator, the content of the non-reactive urethane compound being 0.05 parts by mass to 5 parts by mass based on the total amount of the resin composition, and the non-reactive urethane compound being a reaction product of a polyol having a number average molecular weight of 8,000 to 20,000, a diisocyanate, and a compound having active hydrogen.

[0011] Such a resin composition maintains a high breaking elongation while having a high Young's modulus, and can form a secondary resin layer having excellent surface slip properties and abrasion resistance when an external force is applied to the optical fiber, thereby improving the productivity of the optical fiber.

[0012] The polyol may be a polypropylene polyol since it is easy to adjust the Young's modulus and breaking elongation of the resin layer.The compound having active hydrogen may be a monohydric alcohol since it provides the secondary resin layer with appropriate toughness.

[0013] In order to impart appropriate toughness to the secondary resin layer, the photopolymerizable compound may contain 5 parts by mass or more and 40 parts by mass or less of a urethane (meth)acrylate having a number average molecular weight of 500 or more and 6000 or less, based on the total amount of the resin composition, and the urethane (meth)acrylate may be a reaction product of a polyol having a number average molecular weight of 300 or more and 2500 or less, a diisocyanate, and a hydroxyl group-containing (meth)acrylate.

[0014] Since the secondary resin layer imparts appropriate toughness, the photopolymerizable compound may contain 30 parts by mass or more and 70 parts by mass or less of a bisphenol skeleton-containing (meth)acrylate based on the total amount of the resin composition.

[0015] An optical fiber according to one aspect of the present disclosure includes a glass fiber including a core and a cladding, a primary resin layer that contacts the glass fiber and coats the glass fiber, and a secondary resin layer that coats the primary resin layer, the secondary resin layer including a cured product of the resin composition. Such an optical fiber has excellent surface slipperiness and abrasion resistance, and can improve the productivity of the optical fiber.

[0016] The method for producing an optical fiber according to an embodiment of the present disclosure includes a coating step of coating the resin composition on the outer periphery of a glass fiber including a core and a cladding, and a curing step of curing the resin composition by irradiating the resin composition with ultraviolet light after the coating step, thereby making it possible to produce an optical fiber having excellent surface slip properties and abrasion resistance.

[0017] [Details of the embodiment of the present disclosure] Specific examples of the resin composition and optical fiber according to the present embodiment will be described with reference to the drawings as necessary. Note that the present disclosure is not limited to these examples, but is intended to include all modifications within the scope of the claims and meaning equivalent thereto. In the following description, the same elements in the description of the drawings will be given the same reference numerals, and duplicated descriptions will be omitted.

[0018] (Resin composition) The resin composition according to the present embodiment contains a non-reactive urethane compound, a photopolymerizable compound, and a photopolymerization initiator. In this specification, "non-reactive" means that the compound does not have a photopolymerizable group.

[0019] The non-reactive urethane compound according to this embodiment does not have a photopolymerizable group and contains a non-reactive urethane compound having a number average molecular weight (Mn) of 10,000 to 50,000 (hereinafter referred to as "non-reactive urethane compound (A)"). The Mn of the non-reactive urethane compound (A) is preferably 12,000 to 45,000, more preferably 14,000 to 44,000, and even more preferably 16,000 to 40,000. If the Mn of the non-reactive urethane compound (A) is less than 10,000, the surface slippage and abrasion resistance tend to decrease, and if the Mn exceeds 50,000, the resin composition tends to become cloudy. In addition, since the non-reactive urethane compound is not incorporated into the crosslink, it brings about a plasticizing effect on the coating film and can improve the breaking elongation. It is considered that the breaking elongation can be improved without decreasing the Young's modulus of the resin layer due to the hydrogen bond by the urethane group.

[0020] The non-reactive urethane compound (A) is a reaction product of a polyol having an Mn of 8000 or more and 20000 or less, a diisocyanate, and a compound having active hydrogen. The non-reactive urethane compound (A) has a urethane structure based on the reaction between a polyol having an Mn of 8000 or more and 20000 or less and a diisocyanate, and a non-reactive group based on a compound having active hydrogen bonded to the end of the urethane structure. The non-reactive group may be an alkyl group.

[0021] The Mn of the polyol constituting the non-reactive urethane compound (A) may be 8,000 or more, 9,000 or more, or 10,000 or more from the viewpoint of improving toughness, and may be 20,000 or less, 19,000 or less, or 18,000 or less from the viewpoint of increasing Young's modulus.

[0022] Examples of polyols include polyether polyols, polyester polyols, polycaprolactone polyols, polycarbonate polyols, polybutadiene polyols, and bisphenol A-ethylene oxide addition diols. Examples of polyether polyols include polytetramethylene glycol, polyethylene glycol, and polypropylene polyols. It is preferable to use polypropylene polyols as the polyols because it is easy to adjust the Young's modulus and breaking elongation of the resin layer. Examples of polypropylene polyols include polypropylene glycol and polypropylene triol.

[0023] Commercially available polyols having an Mn of 8,000 or more and 20,000 or less include, for example, PREMINOL S 4013F, PREMINOL S 4318F, PREMINOL S 3011, and PREMINOL 7012 manufactured by AGC Corporation.

[0024] The compound having active hydrogen according to the present embodiment is a compound to which a group having active hydrogen, such as a hydroxyl group, an amino group, or a mercapto group, is bonded, and is a compound having no photopolymerizable group, such as a (meth)acryloyl group. Examples of the compound having active hydrogen include alcohol compounds, amine compounds, and thiol compounds. Since the secondary resin layer is provided with appropriate toughness, the compound having active hydrogen is preferably a monohydric alcohol, more preferably a monohydric alcohol having 5 or less carbon atoms, and even more preferably a monohydric alcohol having 3 or less carbon atoms.

[0025] Examples of monohydric 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, and 3-methyl-2-butanol.

[0026] Examples of diisocyanates 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.

[0027] Examples of the synthesis method of the non-reactive urethane compound (A) include a method of reacting a polyol with a diisocyanate, and then reacting a compound having active hydrogen; a method of reacting a diisocyanate with a compound having active hydrogen, and then reacting a polyol; and a method of simultaneously reacting a polyol, a diisocyanate, and a compound having active hydrogen. When a bifunctional polyol is used, a method of reacting a hydroxyl group (OH) of the polyol with an isocyanate group (NCO) of the diisocyanate, and then reacting a compound having active hydrogen is preferred, and when a trifunctional or higher polyol is used, a method of reacting a diisocyanate with a compound having active hydrogen, and then reacting a polyol is preferred.

[0028] The preparation of the non-reactive urethane compound (A) will be described with a specific example. In the first embodiment, for example, bifunctional polypropylene polyol (polypropylene glycol) is used as the polyol, 2,4-tolylene diisocyanate is used as the diisocyanate, and methanol is used as the compound having active hydrogen. First, polypropylene glycol and 2,4-tolylene diisocyanate are reacted to synthesize an NCO-terminated prepolymer. Next, the NCO-terminated prepolymer is reacted with methanol to synthesize a non-reactive urethane compound. The non-reactive urethane compound (A) can be represented by the following formula (1). M-(UIU-P2)mUM (1) Here, M represents a residue of methanol, U represents a urethane bond, I represents a residue of 2,4-tolylene diisocyanate, P2 represents a residue of polypropylene glycol, and m is an integer of 1 or more. The molar ratio of NCO to OH (NCO / OH) when reacting polypropylene glycol with 2,4-tolylene diisocyanate is preferably 1.5 to 2.5, more preferably 1.8 to 2.2. The molar ratio of methanol to NCO in the NCO-terminated prepolymer is preferably 1.00 to 1.15, more preferably 1.03 to 1.10.

[0029] In the second embodiment, for example, a trifunctional polypropylene polyol (polypropylene triol) is used as the polyol, 2,4-tolylene diisocyanate is used as the diisocyanate, and methanol is used as the compound having active hydrogen. First, 2,4-tolylene diisocyanate is reacted with methanol to obtain an isocyanate with partially blocked NCO. Next, the isocyanate with partially blocked NCO is reacted with polypropylene triol to synthesize a non-reactive urethane compound. The non-reactive urethane compound (A) can be represented by the following formula (2). (HO)t-P3-(UIU)sM (2) Here, M represents a residue of methanol, U represents a urethane bond, I represents a residue of 2,4-tolylene diisocyanate, P3 represents a residue of polypropylene triol, t is 0, 1 or 2, s is an integer of 1 to 3, and t+s is 3. The molar ratio (NCO / OH) of NCO of 2,4-tolylene diisocyanate to methanol is preferably 1.95 to 2.05. The molar ratio (OH / NCO) of OH of polypropylene triol to NCO of partially blocked isocyanate is preferably 1.0 to 1.5, more preferably 1.03 to 1.3.

[0030] From the viewpoint of improving the slipperiness and abrasion resistance of the surface, the content of the non-reactive urethane compound (A) is 0.05 parts by mass or more, preferably 0.1 parts by mass or more, more preferably 0.2 parts by mass or more, and even more preferably 0.3 parts by mass or more, based on the total amount (100 parts by mass) of the resin composition. From the viewpoint of suppressing the decrease in the Young's modulus of the secondary resin layer, the content of the non-reactive urethane compound (A) is 5 parts by mass or less, preferably 4 parts by mass or less, more preferably 3 parts by mass or less, and even more preferably 2 parts by mass or less, based on the total amount of the resin composition.

[0031] From the viewpoint of forming a tough secondary resin layer, the photopolymerizable compound according to this embodiment may contain a urethane (meth)acrylate (hereinafter referred to as "urethane (meth)acrylate (B)") having an Mn of 500 or more and 6000 or less. The Mn of the urethane (meth)acrylate (B) is preferably 600 or more and 5500 or less, more preferably 700 or more and 5000 or less, and even more preferably 1000 or more and 4000 or less. When the Mn of the urethane (meth)acrylate (B) is 500 or more, it becomes easy to form a tough secondary resin layer, and when it is 6000 or less, it becomes easy to increase the Young's modulus of the secondary resin layer.

[0032] Here, (meth)acrylate means acrylate or the corresponding methacrylate. The same applies to other similar expressions such as (meth)acryloyl.

[0033] The content of the urethane (meth)acrylate (B) is preferably 5 parts by mass or more and 40 parts by mass or less, and more preferably 10 parts by mass or more and 35 parts by mass or less, based on the total amount of the resin composition. When it is 5 parts by mass or more, a tough secondary resin layer is easily formed, and when it is 40 parts by mass or less, the Young's modulus of the secondary resin layer is easily increased.

[0034] The urethane (meth)acrylate (B) may be a reaction product of a polyol having an Mn of 300 or more and 2500 or less, a diisocyanate, and a hydroxyl group-containing (meth)acrylate. The urethane (meth)acrylate (B) preferably has a urethane structure based on a reaction between a polyol having an Mn of 300 or more and 2500 or less and a diisocyanate, and a (meth)acryloyl group bonded to an end of the urethane structure.

[0035] Examples of hydroxyl group-containing (meth)acrylates include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, caprolactone (meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, 2-(meth)acryloyloxyethyl-2-hydroxyethyl phthalate, 2-hydroxy-O-phenylphenolpropyl (meth)acrylate, 2-hydroxy-3-methacrylpropyl acrylate, trimethylolpropane di(meth)acrylate, and pentaerythritol tri(meth)acrylate.

[0036] The urethane (meth)acrylate (B) can be obtained by reacting a polyol having an Mn of 300 or more and 2500 or less with a diisocyanate at an NCO / OH ratio of 1.5 or more and 6 or less, and then reacting the resulting mixture with a hydroxyl group-containing (meth)acrylate. When the NCO / OH ratio is within the above range, a tough secondary resin layer can be easily formed.

[0037] The preparation of the urethane (meth)acrylate (B) will be described with a specific example. For example, polypropylene glycol is used as the polyol, 2,4-tolylene diisocyanate is used as the diisocyanate, and 2-hydroxyethyl acrylate is used as the hydroxyl group-containing (meth)acrylate. First, polypropylene glycol and 2,4-tolylene diisocyanate are reacted to synthesize an NCO-terminated prepolymer. Next, the NCO-terminated prepolymer and 2-hydroxyethyl acrylate are reacted to synthesize a urethane acrylate. The urethane acrylate (B) can be represented by the following formula (3). A-(UIUP)nUA (3) Here, A represents a residue of 2-hydroxyethyl acrylate, U represents a urethane bond, I represents a residue of 2,4-tolylene diisocyanate, P represents a residue of polypropylene glycol, and n is an integer of 1 or more. By changing n, the ratio of urethane bonds in the urethane acrylate can be changed. The smaller the NCO / OH, the larger n becomes, and the larger the NCO / OH, the smaller n becomes.

[0038] From the viewpoint of improving the toughness of the secondary resin layer, Mn of the polyol constituting the urethane (meth)acrylate (B) is more preferably 350 or more and 2200 or less, further preferably 400 or more and 2000 or less, and even more preferably 500 or more and 1500 or less.

[0039] An organic tin compound or an amine compound is used as a catalyst when synthesizing the non-reactive urethane compound (A) and the urethane (meth)acrylate (B). Examples of organic tin compounds include dibutyltin dilaurate, dibutyltin diacetate, dibutyltin maleate, dibutyltin bis(2-ethylhexyl mercaptoacetate), dibutyltin bis(isooctyl mercaptoacetate), and dibutyltin oxide. In terms of easy availability or catalytic performance, it is preferable to use dibutyltin dilaurate or dibutyltin diacetate as a catalyst.

[0040] Since the photopolymerizable compound according to the present embodiment provides the secondary resin layer with appropriate toughness, it may contain a bisphenol skeleton-containing (meth)acrylate. Examples of the (meth)acrylate compound having a bisphenol skeleton include bisphenol A epoxy di(meth)acrylate, bisphenol F epoxy di(meth)acrylate, EO adduct di(meth)acrylate of bisphenol A, EO adduct di(meth)acrylate of bisphenol F, PO adduct di(meth)acrylate of bisphenol A, and PO adduct di(meth)acrylate of bisphenol F. The epoxy di(meth)acrylate is a compound obtained by reacting an epoxy compound having two or more glycidyl groups with a compound having a (meth)acryloyl group such as (meth)acrylic acid. Since it is easy to obtain tough physical properties with a good balance between high Young's modulus and breaking elongation, it is preferable that the bisphenol skeleton-containing (meth)acrylate contains bisphenol A epoxy di(meth)acrylate or EO adduct di(meth)acrylate of bisphenol A.

[0041] The content of the bisphenol skeleton-containing (meth)acrylate may be 30 parts by mass or more, 35 parts by mass or more, or 40 parts by mass or more, based on the total amount of the resin composition, and may be 70 parts by mass or less, 65 parts by mass or less, or 60 parts by mass or less.

[0042] The photopolymerizable compound according to the present embodiment may further include a photopolymerizable compound (hereinafter referred to as "monomer") other than urethane (meth)acrylate and bisphenol skeleton-containing (meth)acrylate. As the monomer, a monofunctional monomer having one photopolymerizable ethylenically unsaturated group, or a polyfunctional monomer having two or more ethylenically unsaturated groups may be used. Two or more types of monomers may be mixed and used.

[0043] Examples of monofunctional monomers include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, n-butyl (meth)acrylate, s-butyl (meth)acrylate, t-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, dicyclopentenyloxyethyl (meth)acrylate, dicyclopentanyl (meth)acrylate, (Meth)acrylate monomers such as acrylate, nonylphenol polyethylene glycol (meth)acrylate (for example, trade name "SR504" manufactured by Sartomer), nonylphenoxy polyethylene glycol (meth)acrylate, isobornyl (meth)acrylate, 3-phenoxybenzyl (meth)acrylate, methylphenoxyethyl (meth)acrylate, phenoxydiethylene glycol (meth)acrylate, phenoxypolyethylene glycol (meth)acrylate, m-phenoxybenzyl (meth)acrylate, 2-(2-ethoxyethoxy)ethyl (meth)acrylate, and 2-hydroxy-3-phenoxypropyl acrylate; carboxy group-containing monomers such as (meth)acrylic acid, (meth)acrylic acid dimer, carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, and ω-carboxy-polycaprolactone (meth)acrylate;N-Acryloylmorpholine, N-Vinylpyrrolidone, N-Vinylcaprolactam, 3-(3-pyridinyl)propyl (meth)acrylate, N,N-Dimethylacrylamide, N-Hydroxyethylacrylamide, N,N-Diethylacrylamide, N-Isopropylacrylamide, N,N-Dimethylaminopropylacrylamide, N,N-Dimethylaminopropylacrylamide·Methyl chloride salt, Diacetoneacrylamide, N-Acryloylpiperidine, N-Methacryloylpiperidine, N-Acryloylpyrrolidine, Maleimide, Nitrogen-containing monomers such as N-cyclohexylmaleimide, N-phenylmaleimide, (meth)acrylamide, N,N-dimethyl(meth)acrylamide, N-hexyl(meth)acrylamide, N-methyl(meth)acrylamide, N-butyl(meth)acrylamide, N-methylol(meth)acrylamide, N-methylolpropane(meth)acrylamide, aminoethyl(meth)acrylate, aminopropyl(meth)acrylate, N,N-dimethylaminoethyl(meth)acrylate, and t-butylaminoethyl(meth)acrylate are included.

[0044] 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, triethylene glycol di(meth)acrylate, cyclohexanedimethanol di(meth)acrylate, dipropylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, hydroxypivalic acid neopentyl glycol di(meth)acrylate, 1,3-butylene glycol di(meth)acrylate, and 1,4-butanediol di(meth)acrylate. difunctional monomers such as ethyl acrylate, diethylene glycol 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, tricyclodecanol di(meth)acrylate, and 9,9-bis[4-(2-hydroxyethoxy)phenyl]fluorene di(meth)acrylate;Trimethylolpropane tri(meth)acrylate, trimethylol octane tri(meth)acrylate, trimethylolpropane polyethoxy tri(meth)acrylate, trimethylolpropane polypropoxy tri(meth)acrylate, trimethylolpropane polyethoxy polypropoxy tri(meth)acrylate, tris[(meth)acryloyloxyethyl]isocyanurate, pentaerythritol tri(meth)acrylate, pentaerythritol polyethoxy tetra(meth)acrylate ) acrylate, pentaerythritol polypropoxy tetra(meth)acrylate, pentaerythritol tetra(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate, dipentaerythritol tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, caprolactone-modified tris[(meth)acryloyloxyethyl]isocyanurate, and other trifunctional or higher monomers;

[0045] The photopolymerization initiator can be appropriately selected from known radical photopolymerization initiators. Examples of the photopolymerization initiator include 1-hydroxycyclohexyl phenyl ketone (Omnirad 184, manufactured by IGM Resins), 2,2-dimethoxy-2-phenylacetophenone (Omnirad 651, manufactured by IGM Resins), 2,4,6-trimethylbenzoyldiphenylphosphine oxide (Omnirad TPO, manufactured by IGM Resins), ethyl (2,4,6-trimethylbenzoyl)-phenylphosphinate (Omnirad TPO-L, manufactured by IGM Resins), 2-benzoyl-2-dimethylamino-4'-morpholinobutyrophenone (Omnirad TPO369, manufactured by IGM Resins), 2-dimethylamino-2-(4-methyl-benzyl)-1-(4-morpholin-4-yl-phenyl)-butan-1-one (Omnirad TPO379, manufactured by IGM Resins), and 2-dimethylamino-2-(4-methyl-benzyl)-1-(4-morpholin-4-yl-phenyl)-butan-1-one (Omnirad TPO379, manufactured by IGM Resins). Examples of suitable amines include bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (Omnirad 819, IGM Resins), bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (Omnirad 819, IGM Resins), and 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one (Omnirad 907, IGM Resins).

[0046] Two or more kinds of photopolymerization initiators may be mixed for use. The photopolymerization initiator preferably contains 2,4,6-trimethylbenzoyldiphenylphosphine oxide, since this has excellent rapid curing properties for the resin composition.

[0047] The content of the photopolymerization initiator is preferably 0.2 parts by mass or more and 5 parts by mass or less, more preferably 0.3 parts by mass or more and 4 parts by mass or less, and even more preferably 0.4 parts by mass or more and 3 parts by mass or less, based on the total amount of the resin composition.

[0048] The resin composition according to this embodiment may further contain a photoacid generator, a leveling agent, an antifoaming agent, an antioxidant, and the like.

[0049] The photoacid generator is A + B -Examples of the photoacid generator include sulfonium salts such as CPI-100P and 110P (manufactured by San-Apro Co., Ltd.), Omnicat 270 and 290 (manufactured by IGM Resins), and iodonium salts such as Omnicat 250 (manufactured by IGM Resins), WPI-113, 116, 124, 169 and 170 (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.).

[0050] From the viewpoint of coatability, the viscosity of the resin composition according to this embodiment at 25° C. is preferably from 0.5 Pa·s to 10 Pa·s, and more preferably from 1 Pa·s to 9 Pa·s.

[0051] (Optical Fiber) 1 is a schematic cross-sectional view showing an example of an optical fiber according to the present embodiment. The optical fiber 10 includes a glass fiber 13 including a core 11 and a cladding 12, and a coating resin layer 16 including a primary resin layer 14 and a secondary resin layer 15 provided on the outer periphery of the glass fiber 13.

[0052] The cladding 12 surrounds the core 11. The core 11 and the cladding 12 mainly contain glass such as silica glass, and for example, the core 11 can be made of silica glass doped with germanium or pure silica glass, and the cladding 12 can be made of pure silica glass or silica glass doped with fluorine.

[0053] 1, for example, the outer diameter (D2) of the glass fiber 13 is about 100 μm to 125 μm, and the diameter (D1) of the core 11 constituting the glass fiber 13 is about 7 μm to 15 μm. The thickness of the coating resin layer 16 is usually about 22 μm to 70 μm. The thickness of each of the primary resin layer 14 and the secondary resin layer 15 may be about 5 μm to 50 μm.

[0054] When the outer diameter of the glass fiber 13 is about 125 μm and the thickness of the coating resin layer 16 is 60 μm to 70 μm, the thickness of each of the primary resin layer 14 and the secondary resin layer 15 may be about 10 μm to 50 μm, for example, the thickness of the primary resin layer 14 may be 35 μm and the thickness of the secondary resin layer 15 may be 25 μm. The outer diameter of the optical fiber 10 may be about 245 μm to 265 μm.

[0055] When the outer diameter of the glass fiber 13 is about 125 μm and the thickness of the coating resin layer 16 is 24 μm to 48 μm, the thickness of each of the primary resin layer 14 and the secondary resin layer 15 may be about 8 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 about 173 μm to 221 μm.

[0056] When the outer diameter of the glass fiber 13 is about 100 μm and the thickness of the coating resin layer 16 is 22 μm to 37 μm, the thickness of each of the primary resin layer 14 and the secondary resin layer 15 may be about 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 about 144 μm to 174 μm.

[0057] By applying the resin composition according to this embodiment to the secondary resin layer, an optical fiber with excellent productivity can be produced.

[0058] The method for manufacturing an optical fiber according to this embodiment includes a coating step of coating the above-mentioned resin composition onto the outer periphery of a glass fiber including a core and a cladding, and a curing step of curing the resin composition by irradiating it with ultraviolet light after the coating step.

[0059] From the viewpoint of improving the microbending resistance of the optical fiber, the Young's modulus of the secondary resin layer is preferably 800 MPa or more, more preferably 1000 MPa or more, and even more preferably 1200 MPa or more at 23° C.±2° C. The Young's modulus of the secondary resin layer is not particularly limited, but from the viewpoint of imparting appropriate toughness to the secondary resin layer, it may be 3000 MPa or less, 2500 MPa or less, or 2000 MPa or less at 23° C.±2° C.

[0060] 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 extracted into 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 can be ignored. Next, the solvent is removed from the coating resin layer by vacuum drying, and then a tensile test (tensile speed 1 mm / min) is performed at 23°C, and the Young's modulus can be obtained by the secant equation with 2.5% strain.

[0061] From the viewpoint of improving the heat resistance of the secondary resin layer, the glass transition temperature (Tg) of the secondary resin layer is preferably not less than 70° C., and more preferably not less than 75° C. From the viewpoint of suppressing an increase in the transmission loss of the optical fiber at low temperatures, the Tg of the secondary resin layer is preferably not more than 105° C., and more preferably not more than 95° C.

[0062] The Tg 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 extracted into a cylindrical shape. Next, the solvent is removed from the coating resin layer by vacuum drying, and then the dynamic viscoelasticity is measured using a TA Instruments "RSA-G2" under the conditions of a tensile mode (gauge length: 25 mm), a frequency of 11 Hz, a heating rate of 5°C / min, and a temperature range of 25°C to 150°C, and the peak top temperature of tan δ can be obtained as the Tg. Since the Tg of the primary resin layer is usually below 0°C, the Tg of the primary resin layer can be ignored.

[0063] The primary resin layer 14 can be formed by curing a resin composition containing, for example, urethane (meth)acrylate, a monomer, a photopolymerization initiator, and the like. The resin composition forming the primary resin layer has a different composition from the resin composition for the secondary coating. The resin composition for the primary coating can be prepared using a conventionally known technique.

[0064] The Young's modulus of the primary resin layer is preferably 0.5 MPa or less. If the Young's modulus of the primary resin layer exceeds 0.5 MPa, external forces are easily transmitted to the glass fiber, and the increase in transmission loss due to microbending may become significant.

[0065] In some cases, optical fibers are arranged in parallel and integrated with a ribbon resin to form an optical fiber ribbon. The resin composition according to the present disclosure can also be used as a ribbon resin. This can improve the surface slipperiness and abrasion resistance when an external force is applied to the optical fiber ribbon, just like with optical fibers. EXAMPLES

[0066] The present disclosure will be described in more detail below by showing the results of evaluation tests using examples and comparative examples according to the present disclosure. Note that the present disclosure is not limited to these examples.

[0067] [Synthesis of non-reactive urethane compounds] (A-1) Polypropylene glycol (AGC Corporation, PREMINOL S4013F) with Mn 12000 and 2,4-tolylene diisocyanate (TDI) were reacted at 60°C for 1 hour with a molar ratio of NCO to OH (NCO / OH) = 2.0 to prepare an NCO-terminated prepolymer. As a catalyst, dibutyltin dilaurate was added at 200 ppm relative to the final total amount charged. Next, methanol was added so that the molar ratio of OH of methanol to NCO of the NCO-terminated prepolymer was 1.05, and the mixture was reacted at 60°C for 1 hour to obtain a non-reactive urethane compound (A-1) with Mn 25600.

[0068] (A-2) A non-reactive urethane compound (A-2) with Mn 43300 was obtained in the same manner as in the synthesis of (A-1), except that polypropylene glycol with Mn 18000 (AGC Corporation, PREMINOL S4318F) was reacted with TDI at NCO / OH=2.0 to prepare an NCO-terminated prepolymer.

[0069] (A-3) Isophorone diisocyanate (IPDI) and methanol were reacted at 60°C for 1 hour at NCO / OH=2.0 to prepare a partially blocked isocyanate. As a catalyst, dibutyltin dilaurate was added at 200 ppm relative to the final total amount charged. Next, polypropylene triol (AGC Corporation, PREMINOL S 3011) with Mn10000 was added to the partially blocked isocyanate so that OH / NCO=1.05 was obtained, and the mixture was reacted at 60°C for 1 hour to obtain a non-reactive urethane compound (A-3) with Mn16600.

[0070] (Y-1) A non-reactive urethane compound (Y-1) with Mn 7300 was obtained in the same manner as in the synthesis of (A-1), except that polypropylene glycol with Mn 3000 and TDI were reacted at NCO / OH=2.0 to prepare an NCO-terminated prepolymer.

[0071] (Y-2) A non-reactive urethane compound (Y-2) with Mn 9700 was obtained in the same manner as in the synthesis of (A-1), except that polypropylene glycol with Mn 4000 and TDI were reacted at NCO / OH=2.0 to prepare an NCO-terminated prepolymer.

[0072] (Y-3) A non-reactive urethane compound (Y-3) with Mn 63200 was obtained in the same manner as in the synthesis of (A-1), except that polypropylene glycol with Mn 18000 was reacted with TDI at NCO / OH=1.5 to prepare an NCO-terminated prepolymer.

[0073] [Synthesis of urethane acrylate] (B-1) Polypropylene glycol with Mn 400 and IPDI were reacted at 60°C for 1 hour with NCO / OH = 1.5 to prepare an NCO-terminated prepolymer. As a catalyst, dibutyltin dilaurate was added at 200 ppm relative to the final total amount charged. Next, 2-hydroxyethyl acrylate (HEA) was added so that the molar ratio of OH of HEA to NCO of the NCO-terminated prepolymer was 1.05, and the reaction was continued at 60°C for 1 hour to obtain urethane acrylate (B-1) with Mn 1900.

[0074] (B-2) A urethane acrylate (B-2) with Mn 2200 was obtained in the same manner as in the synthesis of (B-1), except that a polypropylene glycol with Mn 600 and TDI were reacted at NCO / OH=2.0 to prepare an NCO-terminated prepolymer.

[0075] (B-3) A urethane acrylate (B-3) with Mn 760 was obtained in the same manner as in the synthesis of (B-1), except that polypropylene glycol with Mn 600 and TDI were reacted at NCO / OH=6.0 to prepare an NCO-terminated prepolymer.

[0076] (B-4) A urethane acrylate (B-4) with Mn of 2900 was obtained in the same manner as in the synthesis of (B-1), except that a polypropylene glycol with Mn of 1000 and TDI were reacted at NCO / OH=2.0 to prepare an NCO-terminated prepolymer.

[0077] (B-5) A urethane acrylate (B-5) with Mn of 5400 was obtained in the same manner as in the synthesis of (B-1), except that polypropylene glycol with Mn of 2000 was reacted with TDI at NCO / OH=2.0 to prepare an NCO-terminated prepolymer.

[0078] (Z-1) A urethane acrylate (Z-1) with Mn of 11,400 was obtained in the same manner as in the synthesis of (B-1), except that polypropylene glycol with Mn of 3,000 and IPDI were reacted at NCO / OH=1.5 at 60°C for 1 hour to prepare an NCO-terminated prepolymer.

[0079] The Mn of the polyol is the value listed in the catalog of each product. The Mn of the non-reactive urethane compound and the urethane acrylate were measured using a Waters ACQUITY APC RI system under the following conditions: sample concentration: 0.2 mass% THF solution, injection volume: 20 μL, sample temperature: 15°C, mobile phase: THF, XT column for organic solvents: particle size 2.5 μm, pore size 450 Å, column inner diameter 4.6 × column length 150 mm + particle size 2.5 μm, pore size 125 Å, column inner diameter 4.6 × column length 150 mm + particle size 1.7 μm, pore size 45 Å, column inner diameter 4.6 × column length 150 mm, column temperature: 40°C, flow rate: 0.8 mL / min.

[0080] [Resin composition for secondary coating] As diacrylates containing a bisphenol skeleton, bisphenol A epoxy di(meth)acrylate (Viscoat #540) and EO adduct diacrylate of bisphenol A (Viscoat #700) were prepared. As monomers, tripropylene glycol diacrylate (TPGDA) and 2-phenoxyethyl acrylate (POA) were prepared. As photopolymerization initiators, 2,4,6-trimethylbenzoyldiphenylphosphine oxide (Omnirad TPO) and 1-hydroxycyclohexyl phenyl ketone (Omnirad 184) were prepared.

[0081] The non-reactive urethane compound, urethane acrylate, bisphenol skeleton-containing diacrylate, monomer, and photopolymerization initiator were mixed in the amounts (parts by mass) shown in Table 1 or Table 2 to prepare resin compositions for the secondary coating of each Example and Comparative Example.

[0082] (Appearance of the resin composition for secondary coating) The resin composition was visually observed, and if it was transparent, it was rated “OK”, and if it was cloudy, it was rated “NG”. The resin composition of Comparative Example 4 was cloudy, and therefore was not used for producing an optical fiber.

[0083] (Resin composition for primary coating) A resin composition for primary coating was obtained by mixing 70 parts by weight of urethane acrylate (Z-1), 19 parts by weight of nonylphenol polyethylene glycol acrylate (manufactured by Sartomer, product name "SR504"), 5 parts by weight of N-vinyl caprolactam, 5 parts by weight of isobornyl acrylate, and 1 part by weight of Omnirad TPO.

[0084] [Fabrication of optical fiber] A primary coating resin composition and a secondary coating resin composition were applied to the outer peripheral surface of a glass fiber 13 having a diameter of 125 μm. Next, each resin composition was cured by irradiating with ultraviolet light to form a coating resin layer 16 including a primary resin layer 14 and a secondary resin layer 15, thereby producing an optical fiber 10. The thickness of the primary resin layer 14 was 35 μm, and the thickness of the secondary resin layer 15 was 25 μm.

[0085] (Young's modulus of secondary resin layer) The optical fiber was immersed in a mixed solvent of acetone and ethanol, and only the coating resin layer was extracted into a cylindrical shape. Next, the solvent was removed from the coating resin layer by vacuum drying, after which a tensile test was performed at 23°C (tensile speed 1mm / min) and Young's modulus was calculated using the secant formula with 2.5% strain. Young's modulus of 1200MPa or more was rated as "A", Young's modulus of 800MPa or more but less than 1200MPa was rated as "B", and Young's modulus of less than 800MPa was rated as "C".

[0086] (Secondary resin layer break elongation) The optical fiber was immersed in a mixed solvent of acetone and ethanol, and only the coating resin layer was extracted into a cylindrical shape. Next, the solvent was removed from the coating resin layer by vacuum drying, and then a tensile test (tensile speed 50 mm / min) was performed at 23°C to determine the breaking elongation. A breaking elongation of 10% or more was rated as "A," a breaking elongation of 5% to less than 10% was rated as "B," and a breaking elongation of less than 5% was rated as "C."

[0087] (Frequency of optical fiber winding abnormalities) To evaluate the productivity of optical fiber, the frequency of winding defects was measured. At a linear speed of 1000 m / min, the optical fiber was rewound for 500 km (50 km x 10 bobbins), and the longitudinal transmission loss of each bobbin was evaluated using an OTDR (optical pulse tester). The measurement wavelength was 1550 nm. Points where point discontinuities exceeded 0.05 dB (winding defect frequency) were rated as "A" if there were 2 points or less / 500 km, "B" if there were 3 to 5 points / 500 km, and "C" if there were 6 points or more / 500 km.

[0088] [Table 1]

[0089] [Table 2] [Explanation of symbols]

[0090] 10 Optical Fiber 11 cores 12 Clad 13 Glass Fiber 14 Primary resin layer 15 Secondary resin layer 16 Coating resin layer

Claims

1. A resin composition comprising a non-reactive urethane compound having a number average molecular weight of 10,000 or more and 50,000 or less, a photopolymerizable compound, and a photopolymerization initiator, The content of the non-reactive urethane compound is 0.05 parts by mass or more and 5 parts by mass or less based on the total amount of the resin composition, The resin composition for a secondary coating of an optical fiber, wherein the non-reactive urethane compound is a reaction product of a polyol having a number average molecular weight of 8,000 or more and 20,000 or less, a diisocyanate, and a compound having active hydrogen.

2. The resin composition according to claim 1 , wherein the polyol is a polypropylene polyol.

3. The resin composition according to claim 1 or 2, wherein the compound having an active hydrogen is a monohydric alcohol.

4. the photopolymerizable compound contains 5 parts by mass or more and 40 parts by mass or less of a urethane (meth)acrylate having a number average molecular weight of 500 or more and 6000 or less, based on the total amount of the resin composition; The resin composition according to any one of claims 1 to 3, wherein the urethane (meth)acrylate is a reaction product of a polyol having a number average molecular weight of 300 to 2500, a diisocyanate, and a hydroxyl group-containing (meth)acrylate.

5. The resin composition according to claim 1 , wherein the photopolymerizable compound contains a bisphenol skeleton-containing (meth)acrylate in an amount of 30 parts by mass or more and 70 parts by mass or less based on the total amount of the resin composition.

6. a glass fiber including a core and a cladding; a primary resin layer that is in contact with and covers the glass fiber; A secondary resin layer that covers the primary resin layer, An optical fiber, wherein the secondary resin layer comprises a cured product of the resin composition according to claim 1 .

7. A coating step of coating an outer periphery of a glass fiber including a core and a clad with the resin composition according to any one of claims 1 to 5; a curing step of curing the resin composition by irradiating the resin composition with ultraviolet light after the coating step; A method for manufacturing an optical fiber, comprising:

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