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

Abstract

The resin composition for secondary coating of optical fiber is a resin composition containing a non-reactive carbamate compound with a number average molecular weight of not less than 10,000 and not more than 50,000, a photopolymerizable compound, and a photopolymerization initiator, wherein the content of the non-reactive carbamate compound is not less than 0.05 parts by mass and not more than 5 parts by mass based on the total amount of the resin composition, and the non-reactive carbamate compound is a reaction product of a polyol with a number average molecular weight of not less than 8,000 and not more than 20,000, a diisocyanate, and a compound having active hydrogen.

Description

Technical Field

[0001] The present disclosure relates to a resin composition for secondary coating of an optical fiber, an optical fiber, and a method for producing the optical fiber.

[0002] This patent application claims the priority based on Japanese Patent Application No. 2020-108664 filed on June 24, 2020, and cites all the contents described in the Japanese Patent Application. Background Art

[0003] Generally, an optical fiber is provided with a coating resin layer for protecting a glass fiber as a light transmission body. The coating resin layer is composed of two layers, for example, a primary resin layer in contact with the glass fiber and a secondary resin layer formed on the outer layer of the primary resin layer. The secondary resin layer is required to have a high Young's modulus in order to improve the microbending resistance, and is required to have a smooth surface, damage resistance, and anti-sticking properties in order to improve the handling of the optical fiber.

[0004] For example, Patent Documents 1 and 2 disclose that a resin layer is formed by using a resin composition containing an organic silicon compound to improve surface smoothness. In addition, Patent Documents 3 and 4 disclose that a resin layer is formed by using a resin composition containing a specific urethane (meth) acrylate to improve anti-sticking properties.

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent Application Laid-Open No. 9-278850

[0008] Patent Document 2: Japanese Patent Application Laid-Open No. 9-328632

[0009] Patent Document 3: Japanese Patent Application Publication No. 2006-36989

[0010] Patent Document 4: Japanese Patent Application Publication No. 2005-89586 Summary of the invention

[0011] A resin composition for secondary coating of an optical fiber according to one embodiment of the present disclosure is a resin composition containing a non-reactive carbamate compound having a number average molecular weight of 10,000 to 50,000, a photopolymerizable compound, and a photopolymerization initiator, wherein the content of the non-reactive carbamate compound is 0.05 parts by mass to 5 parts by mass based on the total amount of the resin composition, and the non-reactive carbamate compound is 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. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] [Figure 1 ] Figure 1 This is a schematic cross-sectional view showing an example of the optical fiber according to the present embodiment. DETAILED DESCRIPTION

[0013] [Problems to be Solved by the Present Disclosure]

[0014] In the production line of optical fiber, due to external forces such as contact with guide rollers and screening tests (a test in which a tensile load of several kilograms is applied to the optical fiber to pre-remove the low-strength part), the smoothness of the surface of the coating resin layer gradually deteriorates, and the optical fiber may meander when it is wound on the reel, which may reduce the productivity of the optical fiber. In order to improve the productivity of the optical fiber, the secondary resin layer is required to have excellent surface smoothness and wear resistance. In addition, in order to suppress the deterioration of transmission loss caused by microbending when the optical fiber is densely accommodated in the cable, it is required to increase the Young's modulus of the secondary resin layer. However, the high Young's modulus of the secondary resin layer will lead to a decrease in the toughness of the resin layer, and cracks are easily generated in the secondary resin layer when external force is applied.

[0015] An object of the present disclosure is to provide a resin composition for secondary coating of an optical fiber that can form a resin layer having a high Young's modulus and excellent toughness and excellent surface smoothness and abrasion resistance, and an optical fiber having excellent productivity.

[0016] [Effects of the present disclosure]

[0017] According to the present disclosure, a resin composition for secondary coating of an optical fiber capable of forming a resin layer having a high Young's modulus and excellent toughness and having excellent surface smoothness and abrasion resistance, and an optical fiber having excellent productivity can be provided.

[0018] [Description of Embodiments of the Present Disclosure]

[0019] First, the contents of the embodiments of the present disclosure are listed and described. A resin composition for secondary coating of an optical fiber according to one embodiment of the present disclosure is a resin composition containing a non-reactive carbamate compound having a number average molecular weight of 10,000 to 50,000, a photopolymerizable compound, and a photopolymerization initiator, wherein the content of the non-reactive carbamate compound is 0.05 parts by mass to 5 parts by mass based on the total amount of the resin composition, and the non-reactive carbamate compound is 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.

[0020] Such a resin composition can form a secondary resin layer having a high Young's modulus while maintaining a high elongation at break and having excellent surface smoothness and abrasion resistance when an external force is applied to the optical fiber, thereby improving the productivity of the optical fiber.

[0021] From the viewpoint of easy adjustment of the Young's modulus and elongation at break of the resin layer, the polyol may be a polypropylene polyol. From the viewpoint of imparting appropriate toughness to the secondary resin layer, the compound having active hydrogen may be a monohydric alcohol.

[0022] From the viewpoint of imparting appropriate toughness to the secondary resin layer, the photopolymerizable compound may include 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 to 6000, based on the total amount of the resin composition. The urethane (meth) acrylate may be a reaction product of a polyol having a number average molecular weight of 300 to 2500, a diisocyanate, and a hydroxyl-containing (meth) acrylate.

[0023] From the viewpoint of imparting appropriate toughness to the secondary resin layer, the photopolymerizable compound may contain 30 parts by mass or more and 70 parts by mass or less of a (meth)acrylate containing a bisphenol skeleton based on the total amount of the resin composition.

[0024] An optical fiber according to one embodiment of the present disclosure comprises: a glass fiber including a core and a cladding, a primary resin layer in contact with the glass fiber and coating the glass fiber, and a secondary resin layer coating the primary resin layer, wherein the secondary resin layer comprises a cured product of the above-mentioned resin composition. Such an optical fiber has excellent surface smoothness and abrasion resistance, and can improve the productivity of the optical fiber.

[0025] One embodiment of the present disclosure relates to a method for manufacturing an optical fiber, comprising: a coating step of coating the resin composition on the outer periphery of a glass fiber having a core and a cladding; and a curing step of curing the resin composition by irradiating ultraviolet light after the coating step. Thus, an optical fiber having excellent surface smoothness and abrasion resistance can be manufactured.

[0026] [Details of the embodiments of the present disclosure]

[0027] Specific examples of the resin composition and optical fiber involved in the present embodiment will be described with reference to the accompanying drawings as needed. It should be noted that the present disclosure is not limited to these examples, but is represented by the claims, and is intended to include all changes within the meaning and scope equivalent to the claims. In the following description, the same elements in the description of the drawings are marked with the same symbols, and repeated descriptions are omitted.

[0028] (Resin composition)

[0029] The resin composition according to the present embodiment contains a non-reactive urethane compound, a photopolymerizable compound, and a photopolymerization initiator. In the present specification, "non-reactive" means having no photopolymerizable group.

[0030] The non-reactive carbamate compound involved in the present embodiment includes a non-reactive carbamate compound (hereinafter referred to as "non-reactive carbamate compound (A)") that does not have a photopolymerizable group and has a number average molecular weight (Mn) of 10,000 to 50,000. The Mn of the non-reactive carbamate compound (A) is preferably 12,000 to 45,000, more preferably 14,000 to 44,000, and further preferably 16,000 to 40,000. When the Mn of the non-reactive carbamate compound (A) is less than 10,000, the smoothness and wear resistance of the surface tend to decrease, and when the Mn exceeds 50,000, the resin composition tends to become turbid. In addition, since the non-reactive carbamate compound does not participate in crosslinking, it can bring a plasticizing effect to the coating film, thereby improving the elongation at break. It is believed that the elongation at break can be increased without reducing the Young's modulus of the resin layer through the hydrogen bonding of the carbamate group.

[0031] The non-reactive carbamate compound (A) is a reaction product of a polyol having an Mn of 8000 to 20000, a diisocyanate, and a compound having active hydrogen. The non-reactive carbamate compound (A) has a carbamate structure based on the reaction of a polyol having an Mn of 8000 to 20000 and a diisocyanate, and a non-reactive group based on a compound having active hydrogen bonded to the end of the carbamate structure. The non-reactive group may be an alkyl group.

[0032] 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 improving Young's modulus.

[0033] Examples of the polyol include polyether polyol, polyester polyol, polycaprolactone polyol, polycarbonate polyol, polybutadiene polyol, and bisphenol A-ethylene oxide addition diol. Examples of the polyether polyol include polytetramethylene glycol, polyethylene glycol, and polypropylene polyol. From the viewpoint of easy adjustment of the Young's modulus and elongation at break of the resin layer, polypropylene polyol is preferably used as the polyol. Examples of the polypropylene polyol include polypropylene glycol and polypropylene triol.

[0034] Examples of commercially available polyols having an Mn of 8,000 to 20,000 include PREMINOL S 4013F, PREMINOL S 4318F, PREMINOL S 3011, and PREMINOL 7012 from AGC Corporation.

[0035] The compound having active hydrogen involved in this embodiment is a compound having a group having active hydrogen such as a hydroxyl group, an amino group, or a mercapto group bonded thereto, 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. From the viewpoint of imparting appropriate toughness through the secondary resin layer, the compound having active hydrogen is preferably a monohydric alcohol, more preferably a monohydric alcohol having 5 or less carbon atoms, and further preferably a monohydric alcohol having 3 or less carbon atoms.

[0036] Examples of the monohydric alcohol include methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, 2-methyl-2-propanol, 1-pentanol, 2-pentanol, 3-pentanol, 2-methyl-1-butanol, 3-methyl-1-butanol, 2-methyl-2-butanol, and 3-methyl-2-butanol.

[0037] Examples of the diisocyanate include 2,4-toluene diisocyanate, 2,6-toluene 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.

[0038] As a method for synthesizing the non-reactive urethane compound (A), for example, there can be mentioned a method of reacting a polyol with a diisocyanate and then reacting with a compound having active hydrogen; a method of reacting a diisocyanate with a compound having active hydrogen and then reacting with a polyol; and a method of reacting a polyol with a diisocyanate and a compound having active hydrogen simultaneously. When a bifunctional polyol is used, it is preferred to use a method of reacting a hydroxyl group (OH) of a polyol with an isocyanate group (NCO) of a diisocyanate and then reacting with a compound having active hydrogen, and when a trifunctional or higher polyol is used, it is preferred to use a method of reacting a diisocyanate with a compound having active hydrogen and then reacting with a polyol.

[0039] Regarding the preparation of the non-reactive carbamate compound (A), specific examples are listed and explained. As a first method, for example, a bifunctional polypropylene polyol (polypropylene glycol) is used as a polyol, 2,4-toluene diisocyanate is used as a diisocyanate, and methanol is used as a compound having active hydrogen. First, polypropylene glycol is reacted with 2,4-toluene diisocyanate to synthesize an NCO-terminated prepolymer. Then, the NCO-terminated prepolymer is reacted with methanol to synthesize a non-reactive carbamate compound. The non-reactive carbamate compound (A) can be represented by the following formula (1).

[0040] M-(UIU-P2)mUM (1)

[0041] Here, M represents a residue of methanol, U represents a urethane bond, I represents a residue of 2,4-toluene diisocyanate, P2 represents a residue of polypropylene glycol, and m is an integer greater than 1. The molar ratio of NCO to OH (NCO / OH) when polypropylene glycol and 2,4-toluene diisocyanate are reacted is preferably 1.5 to 2.5, more preferably 1.8 to 2.2. The molar ratio of methanol to NCO of the NCO-terminated prepolymer is preferably 1.00 to 1.15, more preferably 1.03 to 1.10.

[0042] As a second method, for example, a trifunctional polypropylene polyol (polypropylene triol) is used as a polyol, 2,4-toluene diisocyanate is used as a diisocyanate, and methanol is used as a compound having active hydrogen. First, 2,4-toluene diisocyanate is reacted with methanol to obtain an isocyanate in which NCO is partially blocked. Next, the isocyanate in which NCO is partially blocked is reacted with polypropylene triol to synthesize a non-reactive carbamate compound. The non-reactive carbamate compound (A) can be represented by the following formula (2).

[0043] (HO)t-P3-(UIU)sM (2)

[0044] Here, M represents a residue of methanol, U represents a urethane bond, I represents a residue of 2,4-toluene 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-toluene 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, and more preferably 1.03 to 1.3.

[0045] From the viewpoint of improving the smoothness and wear 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 further 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 further preferably 2 parts by mass or less, based on the total amount of the resin composition.

[0046] From the viewpoint of forming a strong secondary resin layer, the photopolymerizable compound according to the present embodiment may include a urethane (meth) acrylate having an Mn of 500 to 6000 (hereinafter referred to as "urethane (meth) acrylate (B)"). The Mn of the urethane (meth) acrylate (B) is preferably 600 to 5500, more preferably 700 to 5000, and further preferably 1000 to 4000. When the Mn of the urethane (meth) acrylate (B) is 500 or more, a strong secondary resin layer is easily formed, and when it is 6000 or less, the Young's modulus of the secondary resin layer is easily increased.

[0047] Here, (meth)acrylate refers to acrylate or its corresponding methacrylate. The same applies to other similar expressions such as (meth)acryloyl.

[0048] The content of 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 strong 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.

[0049] Urethane (meth)acrylate (B) may be a reaction product of a polyol having an Mn of 300 to 2500, a diisocyanate, and a hydroxyl-containing (meth)acrylate. Urethane (meth)acrylate (B) preferably has a urethane structure formed by a reaction of a polyol having an Mn of 300 to 2500 and a diisocyanate, and a (meth)acryloyl group bonded to a terminal of the urethane structure.

[0050] Examples of the hydroxyl-containing (meth)acrylate 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-phenylphenol propyl (meth)acrylate, 2-hydroxy-3-methacryloylpropyl acrylate, trimethylolpropane di(meth)acrylate, and pentaerythritol tri(meth)acrylate.

[0051] Urethane (meth)acrylate (B) can be obtained by reacting a polyol having an Mn of 300 to 2500 with a diisocyanate in a manner such that NCO / OH is 1.5 to 6, and then reacting with a hydroxyl-containing (meth)acrylate. When NCO / OH is within the above range, a strong secondary resin layer is easily formed.

[0052] For the preparation of carbamate (meth) acrylate (B), specific examples are listed and described. For example, polypropylene glycol is used as a polyol, 2,4-toluene diisocyanate is used as a diisocyanate, and 2-hydroxyethyl acrylate is used as a hydroxyl-containing (meth) acrylate. First, polypropylene glycol is reacted with 2,4-toluene diisocyanate to synthesize an NCO-terminated prepolymer. Then, the NCO-terminated prepolymer is reacted with 2-hydroxyethyl acrylate to synthesize carbamate acrylate. Carbamate acrylate (B) can be represented by the following formula (3).

[0053] A-(UIUP)nUA (3)

[0054] Here, A represents a residue of 2-hydroxyethyl acrylate, U represents a urethane bond, I represents a residue of 2,4-toluene diisocyanate, P represents a residue of polypropylene glycol, and n is an integer greater than 1. n can change the ratio of urethane bonds in urethane acrylate by changing NCO / OH. The smaller the NCO / OH, the larger n becomes, and the larger the NCO / OH, the smaller n becomes.

[0055] From the viewpoint of improving the toughness of the secondary resin layer, the Mn of the polyol constituting the urethane (meth)acrylate (B) is more preferably 350 to 2200, further preferably 400 to 2000, and still further preferably 500 to 1500.

[0056] As a catalyst for synthesizing the non-reactive carbamate compound (A) and the carbamate (meth) acrylate (B), an organic tin compound or an amine compound can be used. Examples of the organic tin compound include dibutyltin dilaurate, dibutyltin diacetate, dibutyltin maleate, dibutyltin bis(2-ethylhexyl thioglycolate), dibutyltin bis(isooctyl thioglycolate), and dibutyltin oxide. From the perspective of availability or catalytic performance, dibutyltin dilaurate or dibutyltin diacetate is preferably used as the catalyst.

[0057] From the viewpoint of imparting appropriate toughness to the secondary resin layer, the photopolymerizable compound involved in the present embodiment may also include a (meth)acrylate containing a bisphenol skeleton. As a (meth)acrylate compound having a bisphenol skeleton, for example, bisphenol A epoxy di(meth)acrylate, bisphenol F epoxy di(meth)acrylate, bisphenol A EO adduct di(meth)acrylate, bisphenol F EO adduct di(meth)acrylate, bisphenol A PO adduct di(meth)acrylate, and bisphenol F PO adduct di(meth)acrylate can be cited. Epoxy di(meth)acrylate is a compound obtained by reacting a compound having a (meth)acryloyl group such as (meth)acrylic acid with an epoxy compound having two or more glycidyl groups. From the viewpoint of easily obtaining a strong physical property with a good balance of high Young's modulus and elongation at break, the (meth)acrylate containing a bisphenol skeleton preferably includes bisphenol A epoxy di(meth)acrylate or bisphenol A EO adduct di(meth)acrylate.

[0058] The content of the (meth)acrylate containing a bisphenol skeleton may be 30 parts by mass or more, 35 parts by mass or more, or 40 parts by mass or more, and may be 70 parts by mass or less, 65 parts by mass or less, or 60 parts by mass or less, based on the total amount of the resin composition.

[0059] The photopolymerizable compound involved in this embodiment may further include photopolymerizable compounds (hereinafter referred to as "monomers") other than urethane (meth) acrylate and (meth) acrylate containing a bisphenol skeleton. As monomers, monofunctional monomers having one photopolymerizable ethylenically unsaturated group and polyfunctional monomers having two or more ethylenically unsaturated groups may be used. Monomers may also be used in combination of two or more.

[0060] Examples of the monofunctional monomer include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, n-butyl (meth)acrylate, sec-butyl (meth)acrylate, tert-butyl (meth)acrylate, isobutyl (meth)acrylate, n-pentyl (meth)acrylate, isopentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, isopentyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-octyl (meth)acrylate, isooctyl (meth)acrylate, isodecyl (meth)acrylate, lauryl (meth)acrylate, phenoxyethyl (meth)acrylate, tetrahydrocannaphthalene (meth)acrylate, and the like. furfuryl, benzyl (meth)acrylate, dicyclopentenyl (meth)acrylate, dicyclopentenyloxyethyl (meth)acrylate, dicyclopentyl (meth)acrylate, nonylphenol polyethylene glycol (meth)acrylate (e.g., 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, (Meth)acrylate monomers such as 2-hydroxy-3-phenoxypropyl acrylate; (meth)acrylic acid, (meth)acrylic acid dimer, carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, ω-carboxy-polycaprolactone (meth)acrylate and other carboxyl-containing monomers; N-acryloylmorpholine, N-vinylpyrrolidone, N-vinylcaprolactam, 3-(3-pyridyl)propyl (meth)acrylate, N,N-dimethylacrylamide, N-hydroxyethylacrylamide, N,N-diethylacrylamide, N-isopropylacrylamide, N,N-dimethylaminopropylacrylamide, N,N-dimethylaminopropylacrylamide / methyl chloride salt, diacetone acrylamide, N-acryloylpiperidine, N-methacryloylpiperidine, N-acryloylpyrrolidine, maleimide, N-cyclohexylmaleimide, N-phenylmaleimide, (meth)acrylamide, N,N-dimethyl(meth)acrylamide, N-hexyl(meth)acrylamide, N-methyl(meth)acrylamide, N-butyl(meth)acrylamide, N-hydroxymethyl(meth)acrylamide, N-methylolpropane(meth)acrylamide, aminoethyl(meth)acrylate, aminopropyl(meth)acrylate, N,N-dimethylaminoethyl(meth)acrylate, tert-butylaminoethyl(meth)acrylate and the like nitrogen-containing monomers.

[0061] Examples of the polyfunctional monomer 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-butanediol di(meth)acrylate, and 1,3-butylene glycol di(meth)acrylate. meth)acrylate, 1,4-butanediol di(meth)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-eicosandiol di(meth)acrylate, isoprene glycol di(meth)acrylate, 3-ethyl- 1,8-octanediol di(meth)acrylate, tricyclodecanol di(meth)acrylate, 9,9-bis[4-(2-hydroxyethoxy)phenyl]fluorene di(meth)acrylate and other bifunctional monomers; trimethylolpropane tri(meth)acrylate, trimethyloloctane tri(meth)acrylate, trimethylolpropane polyethoxy tri(meth)acrylate, trimethylolpropane polypropoxy tri(meth)acrylate, trimethylolpropane polyethoxy polypropoxy tri(meth)acrylate, tri[(meth)propylene [(meth)acryloyloxyethyl] isocyanurate, pentaerythritol tri(meth)acrylate, pentaerythritol polyethoxy tetra(meth)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 tri[(meth)acryloyloxyethyl] isocyanurate and other trifunctional or higher monomers.

[0062] As the photopolymerization initiator, one may be appropriately selected from known radical photopolymerization initiators and used. 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), (2,4,6-trimethylbenzoyl)-phenylphosphonic acid ethyl ester (Omnirad TPO-L, manufactured by IGM Resins), 2-benzoyl-2-dimethylamino-4'-morpholinobutylphenone (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 1-(4-morpholin-4-yl-phenyl)-2-(4-methyl-phenyl)-1-(4-morpholin-4-yl-phenyl)-butane-1-one. Resins Co., Ltd.), bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (Omnirad 819, IGM Resins Co., Ltd.), and 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one (Omnirad 907, IGM Resins Co., Ltd.).

[0063] The photopolymerization initiator may be used in combination of two or more. From the viewpoint of excellent rapid curability of the resin composition, the photopolymerization initiator preferably contains 2,4,6-trimethylbenzoyldiphenylphosphine oxide.

[0064] The content of the photopolymerization initiator is preferably 0.2 to 5 parts by mass, more preferably 0.3 to 4 parts by mass, and even more preferably 0.4 to 3 parts by mass, based on the total amount of the resin composition.

[0065] The resin composition according to the present embodiment may further contain a photoacid generator, a leveling agent, a defoaming agent, an antioxidant, and the like.

[0066] As the photoacid generator, a + B - As the photoacid generator, for example, sulfonium salts such as CPI-100P, 110P (manufactured by San-Apro Co., Ltd.), Omnicat 270, 290 (manufactured by IGM Resins Co., Ltd.); iodonium salts such as Omnicat 250 (manufactured by IGM Resins Co., Ltd.), WPI-113, 116, 124, 169, 170 (manufactured by FUJIFILM Wako Pure Chemical Corporation) can be listed.

[0067] From the viewpoint of coating properties, the viscosity of the resin composition according to the present embodiment at 25° C. is preferably 0.5 Pa·s to 10 Pa·s, and more preferably 1 Pa·s to 9 Pa·s.

[0068] (optical fiber)

[0069] Figure 1 The optical fiber 10 includes a glass fiber 13 including a core 11 and a cladding 12 , and a coating resin layer 16 provided on the periphery of the glass fiber 13 and including a primary resin layer 14 and a secondary resin layer 15 .

[0070] The cladding 12 surrounds the core 11. The core 11 and the cladding 12 mainly include glass such as quartz glass. For example, the core 11 can use quartz glass doped with germanium or pure quartz glass, and the cladding 12 can use pure quartz glass or quartz glass doped with fluorine.

[0071] exist Figure 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 generally about 22 μm to 70 μm. The thickness of each layer of the primary resin layer 14 and the secondary resin layer 15 can be about 5 μm to 50 μm.

[0072] 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 can be about 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 about 245 μm to 265 μm.

[0073] 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 can be about 8 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 about 173 μm to 221 μm.

[0074] 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 can be about 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 about 144 μm to 174 μm.

[0075] By using the resin composition according to this embodiment for the secondary resin layer, an optical fiber with excellent productivity can be produced.

[0076] The method for producing an optical fiber according to the present embodiment includes: a coating step of coating the resin composition on the outer circumference of a glass fiber including a core and a cladding; and a curing step of curing the resin composition by irradiating ultraviolet rays after the coating step.

[0077] 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 further 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.

[0078] 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 become one, but since the Young's modulus of the primary resin layer is more than 1 / 1000 and less than 1 / 10000 of the Young's modulus 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 is performed at 23°C (tensile speed is 1 mm / min), and the Young's modulus can be calculated by the secant formula of 2.5% strain.

[0079] 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 70° C. or higher, more preferably 75° C. or higher. From the viewpoint of suppressing an increase in transmission loss of the optical fiber at low temperatures, the Tg of the secondary resin layer is preferably 105° C. or lower, more preferably 95° C. or lower.

[0080] 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 pulled out in a cylindrical shape. Next, the solvent is removed from the coating resin layer by vacuum drying, and then the dynamic viscoelasticity is measured using the "RSA-G2" manufactured by TA Instruments under the conditions of tensile mode (distance between marking lines: 25 mm), frequency 11 Hz, heating rate 5°C / min, and temperature range 25°C to 150°C, and the peak temperature of tanδ is calculated as Tg. Usually, the Tg of the primary resin layer is below 0°C, so the Tg of the primary resin layer can be ignored.

[0081] The primary resin layer 14 can be formed, for example, by curing a resin composition containing urethane (meth)acrylate, a monomer, a photopolymerization initiator, etc. The resin composition forming the primary resin layer has a composition different from that of the resin composition for the secondary coating. The resin composition for the primary coating can be prepared using a conventionally known technique.

[0082] The Young's modulus of the primary resin layer is preferably 0.5 MPa or less. When the Young's modulus of the primary resin layer exceeds 0.5 MPa, external force is easily transmitted to the glass fiber, and the increase in transmission loss due to microbending may become large.

[0083] Sometimes, multiple optical fibers are arranged side by side and integrated with a tape resin to form an optical fiber tape. The resin composition disclosed herein can also be used as a tape resin. Thus, similar to optical fibers, the smoothness and wear resistance of the surface of the optical fiber tape when an external force is applied can be improved.

[0084] Example

[0085] Hereinafter, the present disclosure will be described in more detail by showing the evaluation test results using the examples and comparative examples related to the present disclosure. It should be noted that the present disclosure is not limited to these examples.

[0086] [Synthesis of non-reactive carbamate compounds]

[0087] (A-1)

[0088] A polypropylene glycol (AGC Corporation, PREMINOL S4013F) having an Mn of 12,000 was reacted with 2,4-toluene diisocyanate (TDI) at 60°C for 1 hour in a molar ratio of NCO to OH (NCO / OH) = 2.0 to prepare an NCO-terminated prepolymer. As a catalyst, 200 ppm of dibutyltin dilaurate was added relative to the final total amount added. Then, methanol was added in a molar ratio of OH of methanol to NCO of the NCO-terminated prepolymer of 1.05, and the mixture was reacted at 60°C for 1 hour to obtain a non-reactive urethane compound (A-1) having an Mn of 25,600.

[0089] (A-2)

[0090] A non-reactive urethane compound (A-2) having an Mn of 43,300 was obtained in the same manner as in the synthesis of (A-1) except that a polypropylene glycol having an Mn of 18,000 (manufactured by AGC Corporation, PREMINOL S4318F) was reacted with TDI so that NCO / OH=2.0 to prepare an NCO-terminated prepolymer.

[0091] (A-3)

[0092] Isophorone diisocyanate (IPDI) and methanol were reacted at 60°C for 1 hour so that NCO / OH=2.0 to prepare a partially blocked isocyanate. As a catalyst, 200 ppm of dibutyltin dilaurate was added relative to the final total amount. Next, polypropylene triol (AGC Corporation, PREMINOL S 3011) with an Mn of 10,000 was added to the partially blocked isocyanate so that OH / NCO=1.05, and the mixture was reacted at 60°C for 1 hour to obtain a non-reactive urethane compound (A-3) with an Mn of 16,600.

[0093] (Y-1)

[0094] A non-reactive urethane compound (Y-1) having an Mn of 7300 was obtained in the same manner as in the synthesis of (A-1) except that a polypropylene glycol having an Mn of 3000 was reacted with TDI at NCO / OH=2.0 to prepare an NCO-terminated prepolymer.

[0095] (Y-2)

[0096] A non-reactive urethane compound (Y-2) having an Mn of 9700 was obtained in the same manner as in the synthesis of (A-1) except that a polypropylene glycol having an Mn of 4000 was reacted with TDI at NCO / OH=2.0 to prepare an NCO-terminated prepolymer.

[0097] (Y-3)

[0098] A non-reactive urethane compound (Y-3) having an Mn of 63200 was obtained in the same manner as in the synthesis of (A-1) except that a polypropylene glycol having an Mn of 18000 was reacted with TDI at NCO / OH=1.5 to prepare an NCO-terminated prepolymer.

[0099] [Synthesis of urethane acrylate]

[0100] (B-1)

[0101] Polypropylene glycol having an Mn of 400 was reacted with IPDI at 60°C for 1 hour in a manner of NCO / OH=1.5 to prepare an NCO-terminated prepolymer. As a catalyst, 200 ppm of dibutyltin dilaurate was added relative to the final total amount. Next, 2-hydroxyethyl acrylate (HEA) was added in a manner such that the molar ratio of OH of HEA to NCO of the NCO-terminated prepolymer was 1.05, and the mixture was reacted at 60°C for 1 hour to obtain a urethane acrylate (B-1) having an Mn of 1900.

[0102] (B-2)

[0103] Urethane acrylate (B-2) having an Mn of 2200 was obtained in the same manner as in the synthesis of (B-1) except that a polypropylene glycol having an Mn of 600 was reacted with TDI so as to have NCO / OH=2.0 to prepare an NCO-terminated prepolymer.

[0104] (B-3)

[0105] Urethane acrylate (B-3) having an Mn of 760 was obtained in the same manner as in the synthesis of (B-1) except that a polypropylene glycol having an Mn of 600 was reacted with TDI so as to have NCO / OH=6.0 to prepare an NCO-terminated prepolymer.

[0106] (B-4)

[0107] Urethane acrylate (B-4) having an Mn of 2900 was obtained in the same manner as in the synthesis of (B-1) except that a polypropylene glycol having an Mn of 1000 was reacted with TDI at NCO / OH=2.0 to prepare an NCO-terminated prepolymer.

[0108] (B-5)

[0109] Urethane acrylate (B-5) having an Mn of 5400 was obtained in the same manner as in the synthesis of (B-1) except that a polypropylene glycol having an Mn of 2000 was reacted with TDI so as to have NCO / OH=2.0 to prepare an NCO-terminated prepolymer.

[0110] (Z-1)

[0111] Urethane acrylate (Z-1) having an Mn of 11400 was obtained in the same manner as in the synthesis of (B-1) except that polypropylene glycol having an Mn of 3000 was reacted with IPDI at 60°C for 1 hour so that NCO / OH=1.5 to prepare an NCO-terminated prepolymer.

[0112] The Mn of the polyol is the value listed in the catalog of each product. The Mn of the non-reactive urethane compound and urethane acrylate was measured using an ACQUITY APC RI system manufactured by Waters 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 solvent: particle size 2.5 μm, pore size Column inner diameter 4.6 × column length 150mm + particle size 2.5μm, pore size Column inner diameter 4.6 × column length 150mm + particle size 1.7μm, pore size Column inner diameter: 4.6×column length: 150 mm, column temperature: 40° C., flow rate: 0.8 mL / min.

[0113] [Resin composition for secondary coating]

[0114] As diacrylates containing a bisphenol skeleton, bisphenol A epoxy di(meth)acrylate (Viscoat#540) and bisphenol A EO adduct diacrylate (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.

[0115] A non-reactive urethane compound, urethane acrylate, diacrylate containing a bisphenol skeleton, a monomer, and a photopolymerization initiator were mixed in the amounts (parts by mass) shown in Table 1 or Table 2 to prepare a resin composition for secondary coating of each Example and Comparative Example.

[0116] (Appearance of the resin composition for secondary coating)

[0117] The resin composition was visually observed, and was rated as “OK” if transparent, and rated as “NG” if turbid. The resin composition of Comparative Example 4 was not used for the preparation of an optical fiber because it was turbid.

[0118] (Resin composition for primary coating)

[0119] 70 parts by mass of urethane acrylate (Z-1), 19 parts by mass of nonylphenol polyethylene glycol acrylate (manufactured by Sartomer, trade name "SR504"), 5 parts by mass of N-vinyl caprolactam, 5 parts by mass of isobornyl acrylate, and 1 part by mass of Omnirad TPO were mixed to obtain a resin composition for primary coating.

[0120] [Fabrication of optical fiber]

[0121] The resin composition for primary coating and the resin composition for secondary coating were applied to the outer peripheral surface of the glass fiber 13 having a diameter of 125 μm, respectively. Then, each resin composition was cured by irradiating ultraviolet rays to form a coating resin layer 16 having a primary resin layer 14 and a secondary resin layer 15, thereby manufacturing the optical fiber 10. 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.

[0122] (Young's modulus of secondary resin layer)

[0123] The optical fiber was immersed in a mixed solvent of acetone and ethanol, and only the coating resin layer was pulled out in a cylindrical shape. Next, the solvent was removed from the coating resin layer by vacuum drying, and then a tensile test was performed at 23°C (tensile speed was 1 mm / min), and the Young's modulus was calculated using the secant formula of 2.5% strain. The case where the Young's modulus was 1200MPa or more was evaluated as "A", the case where the Young's modulus was 800MPa or more and less than 1200MPa was evaluated as "B", and the case where the Young's modulus was less than 800MPa was evaluated as "C".

[0124] (Elongation at break of secondary resin layer)

[0125] The optical fiber was immersed in a mixed solvent of acetone and ethanol, and only the coating resin layer was pulled out in a cylindrical shape. Next, the solvent was removed from the coating resin layer by vacuum drying, and then a tensile test was performed at 23°C (tensile speed was 50 mm / min) to obtain the elongation at break. The case where the elongation at break was 10% or more was evaluated as "A", the case where the elongation at break was 5% or more and less than 10% was evaluated as "B", and the case where the elongation at break was less than 5% was evaluated as "C".

[0126] (Fiber winding abnormal frequency)

[0127] In order to evaluate the productivity of the optical fiber, the winding abnormality frequency was measured. 500km of optical fiber (50km×10 spools) was rewound at a line speed of 1000m / min, and the longitudinal transmission loss of each spool was evaluated using an OTDR (optical pulse tester). The measurement wavelength was set to 1550nm. The situation where the Point Discontinuities exceeded 0.05dB (winding abnormality frequency) was evaluated as "A" for less than 2 / 500km; 3 to 5 / 500km was evaluated as "B"; and 6 or more / 500km was evaluated as "C".

[0128] [Table 1]

[0129]

[0130] [Table 2]

[0131]

[0132] Explanation of symbols

[0133] 10. Fiber Optics

[0134] 11 Core

[0135] 12 Cladding

[0136] 13 Fiberglass

[0137] 14 Primary resin layer

[0138] 15 Secondary resin layer

[0139] 16 Coating resin layer

Claims

1. A resin composition for secondary coating of an optical fiber, comprising a non-reactive urethane compound having a number average molecular weight of 10,000 to 50,000, a photopolymerizable compound, and a photopolymerization initiator, wherein the non-reactive compound has no photopolymerizable group. 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 100 parts by mass of the total amount of the resin composition. The non-reactive urethane compound is 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. The photopolymerizable compound includes 5 parts by mass or more and 40 parts by mass or less of urethane (meth)acrylate having a number average molecular weight of 500 to 6000, based on 100 parts by mass of the total amount of the resin composition. 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-containing (meth)acrylate. The (meth)acrylate in the urethane (meth)acrylate and the hydroxyl-containing (meth)acrylate refers to acrylate or the corresponding methacrylate.

2. The resin composition according to claim 1, wherein The polyol constituting the non-reactive urethane compound is a polypropylene polyol.

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

4. The resin composition according to claim 1 or 2, wherein The photopolymerizable compound includes 30 parts by mass or more and 70 parts by mass or less of a (meth)acrylate containing a bisphenol skeleton based on 100 parts by mass of the total amount of the resin composition. The (meth)acrylate in the (meth)acrylate containing a bisphenol skeleton refers to acrylate or its corresponding methacrylate.

5. An optical fiber having: Glass fiber with core and 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 comprises a cured product of the resin composition according to any one of claims 1 to 4 .

6. A method for manufacturing an optical fiber, comprising: A coating step of coating the resin composition according to any one of claims 1 to 4 on the periphery of a glass fiber having a core and a cladding; as well as After the coating step, a curing step is performed to cure the resin composition by irradiating ultraviolet rays.

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