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

Abstract

This resin composition for primary covering of an optical fiber contains: a photopolymerizable compound containing urethane (meth)acrylamide; and a photopolymerization initiator, wherein the urethane (meth)acrylamide has a (meth)acrylamide group at at least one terminal of a urethane bond.

Description

Technical Field

[0001] The present disclosure relates to a resin composition for primary coating of an optical fiber, an optical fiber, and a method for manufacturing an optical fiber. This application claims priority based on Japanese Application No. 2020-168494 and Japanese Application No. 2020-168496 filed on October 5, 2020, and incorporates all the descriptions described in the above Japanese applications.

Background Art

[0002] Generally, an optical fiber includes a coating resin layer for protecting a glass fiber that is an optical transmission body. The coating resin layer is composed of, for example, a primary resin layer in contact with the glass fiber and a secondary resin layer formed on the outer layer of the primary resin layer. For the resin composition for primary coating of an optical fiber, it is known to use urethane (meth) acrylate, which is a reaction product of a polyol, a diisocyanate, and a hydroxyl group-containing (meth) acrylate. For example, Patent Documents 1 to 5 describe resin compositions for primary coating containing urethane (meth) acrylate as an oligomer.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Summary of the Invention

[0004] The resin composition for primary coating of an optical fiber according to one aspect of the present disclosure contains a photopolymerizable compound containing urethane (meth) acrylamide and a photoinitiator, and the urethane (meth) acrylamide has a (meth) acrylamide group at at least one end of the urethane bond.

Brief Description of Drawings

[0005]

Figure 1

Embodiments for Carrying Out the Invention

[0006] [Problems to be Solved by the Present Disclosure] The resin composition for primary coating tends to have a slower curing rate compared to the resin composition for secondary coating. In order to improve the productivity of optical fibers, it is required to improve the curing rate of the resin composition for primary coating. If the curing of the primary resin layer is insufficient, defects (voids) may occur in the primary resin layer, or peeling may occur between the glass fiber and the primary resin layer, which is likely to cause an increase in transmission loss.

[0007] An object of the present disclosure is to provide a resin composition capable of forming a resin layer suitable for primary coating of an optical fiber with a high curing rate, and an optical fiber having excellent productivity.

[0008] [Effects of the Present Disclosure] According to the present disclosure, it is possible to provide a resin composition capable of forming a resin layer suitable for primary coating of an optical fiber with a high curing rate, and an optical fiber having excellent productivity.

[0009] [Description of Embodiments of the Present Disclosure] First, the contents of the embodiments of the present disclosure will be listed and described. The resin composition for primary coating of an optical fiber according to one aspect of the present disclosure contains a photopolymerizable compound containing urethane (meth) acrylamide and a photoinitiator, and the urethane (meth) acrylamide has a (meth) acrylamide group at at least one end of the urethane bond.

[0010] Such a resin composition has a high curing rate and does not cause defects in the primary resin layer and delamination between the glass fiber and the primary resin layer. Therefore, a resin layer suitable for primary coating of an optical fiber can be formed, and the productivity of the optical fiber can be improved.

[0011] From the viewpoint of increasing the curing rate of the primary resin layer, the urethane (meth) acrylamide may include a urethane oligomer having a (meth) acrylamide group at one end of the urethane bond, a urethane oligomer having (meth) acrylamide groups at both ends of the urethane bond, or a mixture thereof.

[0012] From the viewpoint of further increasing the curing rate of the primary resin layer, the urethane oligomer having a (meth) acrylamide group at one end of the urethane bond may include a urethane oligomer having a (meth) acrylamide group at one end of the urethane bond and a (meth) acryloyloxy group at the other end.

[0013] The urethane (meth) acrylamide may include a urethane oligomer having (meth) acrylamide groups at both ends of the urethane bond and a urethane oligomer having a (meth) acrylamide group at one end of the urethane bond and a group based on at least one compound selected from a monohydric alcohol and an active hydrogen-containing silane compound at the other end. This makes it easier to adjust the balance between the curing rate of the resin composition and the Young's modulus of the primary resin layer.

[0014] From the viewpoint of enhancing the photocurability of the resin composition, the content of urethane (meth) acrylamide may be 10 parts by mass or more and 90 parts by mass or less based on 100 parts by mass of the total amount of the resin composition.

[0015] From the viewpoint of lowering the Young's modulus of the resin composition, the number average molecular weight of urethane (meth) acrylamide may be 10,000 or more and 37,000 or less.

[0016] In order to adjust the Young's modulus of the primary resin layer, the photopolymerizable compound may further contain (meth) acrylate ester.

[0017] In order to further improve the curing rate of the resin composition, the photopolymerizable compound may further contain an N-vinyl compound and may further contain a (meth) acrylamide compound.

[0018] The 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, and the primary resin layer includes a cured product of the above resin composition. Such an optical fiber is excellent in productivity without causing defects in the primary resin layer or peeling between the glass fiber and the primary resin layer.

[0019] The method for manufacturing an optical fiber according to one aspect of the present disclosure includes a coating step of coating the above 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 ultraviolet rays after the coating step. Thereby, an optical fiber excellent in productivity can be produced.

[0020] [Details of Embodiments of the Present Disclosure] Specific examples of the resin composition and the optical fiber according to the present embodiment will be described with reference to the drawings as necessary. It should be noted that the present disclosure is not limited to these examples, and is shown by the claims, and is intended to include all modifications within the meaning and scope equivalent to the claims. In the following description, the same reference numerals are given to the same elements in the description of the drawings, and duplicate descriptions are omitted. As used herein, "(meth)acrylamide" means acrylamide or the corresponding methacrylamide. The same applies to other similar expressions such as "(meth)acryloyloxy" and "(meth)acrylate".

[0021] (Resin composition) The resin composition according to the present embodiment contains a photopolymerizable compound containing urethane (meth)acrylamide and a photopolymerization initiator. Urethane (meth)acrylamide is a urethane oligomer having a (meth)acrylamide group at at least one end of a urethane bond. Since the (meth)acrylamide group is more photopolymerizable than the (meth)acryloyloxy group, urethane (meth)acrylamide has a faster curing rate than urethane (meth)acrylate having no (meth)acrylamide group, and can improve the productivity of optical fibers.

[0022] Urethane (meth)acrylamide may be a urethane oligomer having a (meth)acrylamide group at one end of a urethane bond, or a urethane oligomer having (meth)acrylamide groups at both ends of a urethane bond. That is, the urethane (meth)acrylamide according to the present embodiment can include a urethane oligomer having a (meth)acrylamide group at one end of a urethane bond, a urethane oligomer having (meth)acrylamide groups at both ends of a urethane bond, or a mixture thereof.

[0023] The urethane (meth) acrylamide according to this embodiment can include a urethane oligomer having (meth) acrylamide groups at both ends of the urethane bond from the viewpoint of further increasing the curing rate of the resin composition. The urethane oligomer having (meth) acrylamide groups at both ends of the urethane bond may be a reaction product of a polyol, a diisocyanate, and N-hydroxyalkyl (meth) acrylamide.

[0024] Examples of the polyol include polyether polyol, polyester polyol, polycaprolactone polyol, polycarbonate polyol, polybutadiene polyol, and bisphenol A-ethylene oxide adduct diol. Examples of the polyether polyol include polytetramethylene ether glycol, polyethylene glycol, and polypropylene glycol. From the viewpoint of easily adjusting the Young's modulus and elongation at break of the resin layer, it is preferable to use polypropylene glycol, polytetramethylene ether glycol, or polycarbonate polyol as the polyol.

[0025] From the viewpoint of obtaining a Young's modulus suitable for the primary resin layer, the number average molecular weight (Mn) of the polyol is preferably 2000 or more and 20000 or less, more preferably 2400 or more and 19000 or less, and still more preferably 2800 or more and 18000 or less.

[0026] Examples of the diisocyanate 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 N-hydroxyalkyl (meth) acrylamide include N-hydroxymethyl (meth) acrylamide, N-hydroxyethyl (meth) acrylamide, and N,N-dimethylol (meth) acrylamide. It is preferable to use N-hydroxyethyl acrylamide as the N-hydroxyalkyl (meth) acrylamide.

[0028] From the viewpoint of adjusting the Young's modulus of the primary resin layer, the urethane (meth) acrylamide may further have a group based on at least one compound selected from monohydric alcohols and active hydrogen-containing silane compounds. Such a urethane (meth) acrylamide may be a reaction product of a polyol, a diisocyanate, an N-hydroxyalkyl (meth) acrylamide, and at least one compound selected from monohydric alcohols and active hydrogen-containing silane compounds.

[0029] From the viewpoint of adjusting the balance between the curing rate of the resin composition and the Young's modulus of the primary resin layer, the urethane (meth) acrylamide may further contain a urethane oligomer having a (meth) acrylamide group at one end of the urethane bond and a group based on at least one compound selected from monohydric alcohols and active hydrogen-containing silane compounds at the other end.

[0030] By introducing a group based on a monohydric alcohol into the urethane (meth) acrylamide, the proportion of the (meth) acrylamide group, which is a photopolymerizable group, can be reduced, and the Young's modulus of the primary resin layer can be reduced.

[0031] The resin composition according to this embodiment contains a urethane oligomer having a (meth) acrylamide group at one end of the urethane bond and a group based on a monohydric alcohol at the other end, whereby the proportion of the photopolymerizable group is reduced, and it becomes easier to reduce the Young's modulus of the primary resin layer. The urethane oligomer having a (meth) acrylamide group and a group based on a monohydric alcohol is a reaction product of a polyol, a diisocyanate, an N-hydroxyalkyl (meth) acrylamide, and a monohydric alcohol.

[0032] 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.

[0033] By introducing a group based on an active hydrogen-containing silane compound into urethane (meth)acrylamide, the proportion of the (meth)acrylamide group, which is a photopolymerizable group, can be reduced, the Young's modulus of the primary resin layer can be reduced, and the adhesion to glass fiber can be improved.

[0034] The resin composition according to this embodiment contains a urethane oligomer having a (meth)acrylamide group at one end of the urethane bond and a group based on an active hydrogen-containing silane compound at the other end, whereby the Young's modulus of the primary resin layer can be reduced and the adhesion to glass fiber can be improved. The urethane oligomer having a (meth)acrylamide group and a group based on an active hydrogen-containing silane compound is a reaction product of a polyol, a diisocyanate, an N-hydroxyalkyl (meth)acrylamide, and an active hydrogen-containing silane compound.

[0035] Examples of the active hydrogen-containing silane compound include N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-triethoxysilyl-N-(1,3-dimethyl-butylidene)propylamine, N-phenyl-3-aminopropyltrimethoxysilane, 3-mercaptopropylmethyldimethoxysilane, and 3-mercaptopropyltrimethoxysilane.

[0036] Examples of the method for synthesizing urethane (meth) acrylamide include, for example, a method in which a polyol and a diisocyanate are reacted and then N-hydroxyalkyl (meth) acrylamide (optionally, a monohydric alcohol or an active hydrogen-containing silane compound) is reacted; a method in which a diisocyanate and N-hydroxyalkyl (meth) acrylamide (optionally, a monohydric alcohol or an active hydrogen-containing silane compound) are reacted and then a polyol is reacted; and a method in which a polyol, a diisocyanate, and N-hydroxyalkyl (meth) acrylamide (optionally, a monohydric alcohol or an active hydrogen-containing compound) are reacted simultaneously.

[0037] When using a bifunctional polyol, a method in which the hydroxyl group (OH) of the polyol and the isocyanate group (NCO) of the diisocyanate are reacted and then N-hydroxyalkyl (meth) acrylamide (optionally, a monohydric alcohol or an active hydrogen-containing silane compound) is reacted is preferred. When using a polyol having a functionality of 3 or more, a method in which a diisocyanate and N-hydroxyalkyl (meth) acrylamide (optionally, a monohydric alcohol or an active hydrogen-containing silane compound) are reacted and then a polyol is reacted is preferred.

[0038] Hereinafter, the preparation of urethane (meth) acrylamide will be described with specific examples. For example, bifunctional polypropylene polyol (polypropylene glycol) is used as the polyol, 2,4-tolylene diisocyanate is used as the diisocyanate, N-hydroxyethyl acrylamide is used as N-hydroxyalkyl (meth) acrylamide, methanol is used as the monohydric alcohol, and 3-mercaptopropyltrimethoxysilane is used as the active hydrogen-containing compound.

[0039] First, polypropylene glycol and 2,4-tolylene diisocyanate are reacted to synthesize an NCO-terminated prepolymer. Next, the NCO-terminated prepolymer is reacted with N-hydroxyethyl acrylamide, methanol, and 3-mercaptopropyltrimethoxysilane to synthesize urethane acrylamide. Urethane acrylamide can be represented as a mixture of the following (1) to (3). Am-(U-I-U-P)n-U-I-U-Am (1) Am-(U-I-U-P)n-U-I-U―M (2) Am-(U-I-U-P)n-U-I-U-SC (3)

[0040] Here, Am represents the residue of N-hydroxyethyl acrylamide, M represents the residue of methanol, SC represents the residue of 3-mercaptopropyltrimethoxysilane, U represents a (thio)urethane bond, I represents the residue of 2,4-tolylene diisocyanate, P represents the residue of polypropylene glycol, and n is an integer of 1 or more.

[0041] The reactants for synthesizing urethane acrylamide may contain the following (4) to (6) as by-products. (4) to (6) are called adducts and function as a kind of monomer. Am-U-I-U-I-U―Am (4) Am-U-I-U-I-U-M (5) Am-U-I-U-I-U-SC (6)

[0042] The reactants for synthesizing urethane acrylamide may also contain the following (7) to (12) as by-products. Since (7) to (12) do not have a photopolymerizable group, it is desirable that they are not generated. M-(U-I-U-P)n-U-I-U-M (7) Sc-(U-I-U-P)n-U-I-U-SC (8) M-(U-I-U-P)n-U-I-U-SC (9) M-U-I-U-M (10) M-U-I-U-SC (11) SC-U-I-U-SC (12)

[0043] When preparing urethane (meth) acrylamide, the addition of methanol and 3-mercaptopropyltrimethoxysilane is optional. When methanol and 3-mercaptopropyltrimethoxysilane are not added, (1) is generated as the main component and (4) is generated as a by-product.

[0044] When reacting a polyol and a diisocyanate, the molar ratio of NCO to OH (NCO / OH) is preferably 1.1 or more and 4.0 or less, more preferably 1.2 or more and 3.5 or less, and still more preferably 1.4 or more and 3.0 or less. The total molar ratio of N-hydroxyalkyl (meth) acrylamide, monohydric alcohol, and active hydrogen-containing silane compound to NCO of the NCO-terminated prepolymer is preferably 1.00 or more and 1.15 or less, and more preferably 1.03 or more and 1.10 or less. The total molar ratio of monohydric alcohol and active hydrogen-containing silane compound to NCO of the NCO-terminated prepolymer is preferably 0 or more and 0.5 or less.

[0045] From the viewpoint of adjusting the balance between the curing rate of the resin composition and the Young's modulus of the resin layer, urethane (meth) acrylamide may include a urethane oligomer having (meth) acrylamide groups at both ends of the urethane bond, and a urethane oligomer having a (meth) acrylamide group at one end of the urethane bond and a group based on at least one selected from monohydric alcohol and active hydrogen-containing silane compound at the other end.

[0046] From the viewpoint of enhancing the photocurability of the resin composition, the content of urethane (meth) acrylamide is preferably 10 parts by mass or more and 90 parts by mass or less, more preferably 20 parts by mass or more and 80 parts by mass or less, and still more preferably 30 parts by mass or more and 75 parts by mass or less based on 100 parts by mass of the total amount of the resin composition.

[0047] The urethane oligomer having a (meth)acrylamide group at one end of the urethane bond may include a urethane oligomer having a (meth)acrylamide group at one end of the urethane bond and a (meth)acryloyloxy group at the other end. As a photopolymerizable group, the urethane oligomer having a (meth)acrylamide group and a (meth)acryloyloxy group has a faster curing rate than the urethane oligomer having only a (meth)acryloyloxy group, and can improve the productivity of the optical fiber.

[0048] The urethane oligomer having a (meth)acrylamide group and a (meth)acryloyloxy group is a reaction product of a polyol, a diisocyanate, an N-hydroxyalkyl (meth)acrylamide, and a hydroxyl group-containing (meth)acrylate.

[0049] Examples of the hydroxyl group-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-phenylphenolpropyl (meth)acrylate, 2-hydroxy-3-methacryloylpropyl acrylate, trimethylolpropane di(meth)acrylate, and pentaerythritol tri(meth)acrylate. As the hydroxyl group-containing (meth)acrylate, it is preferable to use 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, or 2-hydroxybutyl (meth)acrylate.

[0050] As another method for synthesizing urethane (meth)acrylamide when using a hydroxyl group-containing (meth)acrylate as an essential component, for example, after reacting a polyol and a diisocyanate, N-hydroxyalkyl (meth)acrylamide and a hydroxyl group-containing (meth)acrylate (optionally, a monohydric alcohol or an active hydrogen-containing silane compound) are reacted; a method in which a diisocyanate, N-hydroxyalkyl (meth)acrylamide and a hydroxyl group-containing (meth)acrylate (optionally, a monohydric alcohol or an active hydrogen-containing silane compound) are reacted and then a polyol is reacted; a method in which a polyol, a diisocyanate, N-hydroxyalkyl (meth)acrylamide, and a hydroxyl group-containing (meth)acrylate (optionally, a monohydric alcohol or an active hydrogen-containing silane compound) are reacted simultaneously can be mentioned.

[0051] When using a bifunctional polyol, a method in which the hydroxyl group (OH) of the polyol and the isocyanate group (NCO) of the diisocyanate are reacted and then N-hydroxyalkyl (meth)acrylamide and a hydroxyl group-containing (meth)acrylate (optionally, a monohydric alcohol or an active hydrogen-containing silane compound) are reacted is preferred. When using a polyol having three or more functional groups, a method in which a diisocyanate, N-hydroxyalkyl (meth)acrylamide and a hydroxyl group-containing (meth)acrylate (optionally, a monohydric alcohol or an active hydrogen-containing silane compound) are reacted and then a polyol is reacted is preferred.

[0052] Hereinafter, the preparation of a urethane oligomer having a (meth)acrylamide group and a (meth)acryloyloxy group will be described with specific examples. For example, bifunctional polypropylene polyol (polypropylene glycol) is used as the polyol, 2,4-tolylene diisocyanate is used as the diisocyanate, N-hydroxyethyl acrylamide is used as the N-hydroxyalkyl (meth)acrylamide, 2-hydroxyethyl acrylate is used as the hydroxyl group-containing (meth)acrylate, methanol is used as the monohydric alcohol, and 3-mercaptopropyltrimethoxysilane is used as the active hydrogen-containing silane compound.

[0053] First, polypropylene glycol and 2,4-tolylene diisocyanate are reacted to synthesize an NCO-terminated prepolymer. Next, an NCO-terminated prepolymer is reacted with N-hydroxyethyl acrylamide, 2-hydroxyethyl acrylate, methanol, and 3-mercaptopropyltrimethoxysilane to synthesize a urethane oligomer. The urethane oligomer can be represented as a mixture of the following formulas (21) to (27). Am-(U-I-U-P)n-U-I-U-Ac (21) Am-(U-I-U-P)n-U-I-U-Am (22) Ac-(U-I-U-P)n-U-I-U-Ac (23) Am-(U-I-U-P)n-U-I-U-M (24) Am-(U-I-U-P)n-U-I-U-SC (25) Ac-(U-I-U-P)n-U-I-U-M (26) Ac-(U-I-U-P)n-U-I-U-SC (27)

[0054] Here, Am represents the residue of N-hydroxyethyl acrylamide, Ac represents the residue of 2-hydroxyethyl acrylate, M represents the residue of methanol, SC represents the residue of 3-mercaptopropyltrimethoxysilane, U represents a (thio)urethane bond, I represents the residue of 2,4-tolylene diisocyanate, P represents the residue of polypropylene glycol, and n is an integer of 1 or more.

[0055] When synthesizing the urethane oligomer, the reactants may contain the following (28) to (34) as by-products. (28) to (34) are called adducts and function as a kind of monomer. Am-U-I-U-Ac (28) Am-U-I-U-Am (29) Ac-U-I-U-Ac (30) Am-U-I-U-M (31) Am-U-I-U-SC (32) Ac-U-I-U-M (33) Ac-U-I-U-SC (34)

[0056] When synthesizing the urethane oligomer, the reactants may contain the following (35) to (40) as by-products. Since (35) to (40) do not have a photopolymerizable group, it is desirable that they are not generated. M-(U-I-U-P)n-U-I-U-M (35) SC-(U-I-U-P)n-U―I-U-SC (36) M-(U-I-U-P)n-U-I-U-SC (37) M-U-I-U-M (38) M-U-I-U-SC (39) SC-U-I-U-SC (40)

[0057] When preparing the urethane oligomer, the addition of methanol and 3-mercaptopropyltrimethoxysilane is optional. When methanol and 3-mercaptopropyltrimethoxysilane are not added, a mixture of (21) to (23) and (28) to (30) is generated.

[0058] When reacting a polyol with a diisocyanate, the molar ratio of NCO to OH (NCO / OH) is preferably 1.1 or more and 4.0 or less, more preferably 1.2 or more and 3.5 or less, and still more preferably 1.4 or more and 3.0 or less. The molar ratio of N-hydroxyalkyl (meth)acrylamide to NCO of the NCO-terminated prepolymer is preferably 0.1 or more and 0.95 or less, more preferably 0.2 or more and 0.8 or less. The molar ratio of the hydroxyl group-containing (meth)acrylate to NCO of the NCO-terminated prepolymer is preferably 0.1 or more and 0.95 or less, more preferably 0.2 or more and 0.9 or less. The total molar ratio of N-hydroxyalkyl (meth)acrylamide, hydroxyl group-containing (meth)acrylate, monohydric alcohol, and active hydrogen-containing silane compound to NCO of the NCO-terminated prepolymer is preferably 1.00 or more and 1.15 or less, more preferably 1.03 or more and 1.10 or less. The total molar ratio of monohydric alcohol and active hydrogen-containing silane compound to NCO of the NCO-terminated prepolymer is preferably 0 or more and 0.5 or less.

[0059] (From the viewpoint of enhancing the photocurability of the resin composition, the content of urethane (meth)acrylamide containing a urethane oligomer having a (meth)acrylamide group and a (meth)acryloyloxy group is preferably 30 parts by mass or more and 90 parts by mass or less, more preferably 40 parts by mass or more and 80 parts by mass or less, and still more preferably 45 parts by mass or more and 75 parts by mass or less based on 100 parts by mass of the total amount of the resin composition.)

[0060] (From the viewpoint of obtaining a Young's modulus suitable for the primary resin layer, the number average molecular weight (Mn) of urethane (meth)acrylamide is preferably 6000 or more and 40000 or less, more preferably 8000 or more and 38000 or less, and still more preferably 10000 or more and 37000 or less.)

[0061] The photopolymerizable compound according to this embodiment may further contain urethane (meth)acrylate. Urethane (meth)acrylate is a urethane oligomer having a (meth)acryloyloxy group and not having a (meth)acrylamide group. Urethane (meth)acrylate can be obtained by reacting a polyol, a diisocyanate, and a hydroxyl group-containing (meth)acrylate by a conventional method.

[0062] The polyol and diisocyanate used for the synthesis of urethane (meth)acrylate are not particularly limited, and may be selected from the compounds exemplified in the synthesis of the above-mentioned urethane (meth)acrylamide.

[0063] Examples of the hydroxyl group-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-phenylphenolpropyl (meth)acrylate, 2-hydroxy-3-methacryloylpropyl acrylate, trimethylolpropane di(meth)acrylate, and pentaerythritol tri(meth)acrylate.

[0064] The Mn of the urethane (meth)acrylate may be 5000 or more and 30000 or less, 6000 or more and 20000 or less, or 8000 or more and 15000 or less from the viewpoint of obtaining a Young's modulus suitable for the primary resin layer.

[0065] The total content of urethane (meth)acrylamide and urethane (meth)acrylate may be 40 parts by mass or more and 90 parts by mass or less based on the total amount of the resin composition.

[0066] When synthesizing urethane (meth) acrylamide and urethane (meth) acrylate, an organotin compound or an amine compound is used as a catalyst. Examples of the organotin compound include dibutyltin dilaurate, dibutyltin diacetate, dibutyltin maleate, dibutyltin bis(2-ethylhexyl mercaptoacetate), dibutyltin bis(isooctyl mercaptoacetate), and dibutyltin oxide. From the viewpoints of easy availability and catalytic performance, it is preferable to use dibutyltin dilaurate or dibutyltin diacetate as the catalyst.

[0067] The photopolymerizable compound according to this embodiment may further contain a photopolymerizable compound having no urethane bond (hereinafter referred to as "monomer"). Examples of the monomer include (meth)acrylate esters, N-vinyl compounds, and (meth)acrylamide compounds. The monomer may be a monofunctional monomer having one photopolymerizable ethylenically unsaturated group, or a polyfunctional monomer having two or more ethylenically unsaturated groups.

[0068] Examples of monofunctional (meth)acrylic acid esters 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, dicyclopentenyl oxyethyl (meth)acrylate, dicyclopentanyl (meth)acrylate, nonylphenol polyethylene glycol (meth)acrylate, 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, 2-hydroxy-3-phenoxypropyl acrylate, carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, and ω-carboxy-polycaprolactone (meth)acrylate.

[0069] Examples of polyfunctional (meth)acrylic acid esters include bifunctional monomers such as 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, cyclohexane dimethanol di(meth)acrylate, dipropylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, neopentyl glycol hydroxypivalate di(meth)acrylate, 1,3-butylene glycol di(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-eicosanediol di(meth)acrylate, isopentyldiol 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, bisphenol A epoxy di(meth)acrylate, bisphenol F epoxy di(meth)acrylate, EO adduct of bisphenol A di(meth)acrylate, EO adduct of bisphenol F di(meth)acrylate, PO adduct of bisphenol A di(meth)acrylate, and PO adduct of bisphenol F di(meth)acrylate;Trimethylolpropane tri(meth)acrylate, trimethylol octane tri(meth)acrylate, trimethylolpropane polyethoxytri(meth)acrylate, trimethylolpropane polypropoxytri(meth)acrylate, trimethylolpropane polyethoxypolypropoxytri(meth)acrylate, tris[(meth)acryloyloxyethyl] isocyanurate, pentaerythritol tri(meth)acrylate, pentaerythritol polyethoxytetra(meth)acrylate, pentaerythritol polypropoxytetra(meth)acrylate, pentaerythritol tetra(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate, dipentaerythritol tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, caprolactone-modified tris[(meth)acryloyloxyethyl] isocyanurate and other monomers having a functionality of 3 or more are exemplified.;

[0070] By including a (meth)acrylate in the photopolymerizable compound, the Young's modulus of the resin layer can be adjusted. The content of the (meth)acrylate may be 1 part by mass or more and 60 parts by mass or less, 5 parts by mass or more and 50 parts by mass or less, or 10 parts by mass or more and 40 parts by mass or less based on 100 parts by mass of the total amount of the resin composition.

[0071] Examples of the N-vinyl compound include N-vinylpyrrolidone, N-vinylcaprolactam, N-vinylmethyl oxazolidinone, N-vinylimidazole, and N-vinyl-N-methylacetamide.

[0072] By including an N-vinyl compound in the photopolymerizable compound, the curing rate of the resin composition can be further improved. The content of the N-vinyl compound may be 1 part by mass or more and 30 parts by mass or less, 2 parts by mass or more and 20 parts by mass or less, or 5 parts by mass or more and 15 parts by mass or less based on 100 parts by mass of the total amount of the resin composition.

[0073] Examples of the (meth)acrylamide compound include dimethyl(meth)acrylamide, diethyl(meth)acrylamide, (meth)acryloylmorpholine, hydroxymethyl(meth)acrylamide, hydroxyethyl(meth)acrylamide, isopropyl(meth)acrylamide, dimethylaminopropyl(meth)acrylamide, dimethylaminopropylacrylamide·methyl chloride salt, diacetoneacrylamide, (meth)acryloylpiperidine, (meth)acryloylpyrrolidine, (meth)acrylamide, N-hexyl(meth)acrylamide, N-methyl(meth)acrylamide, N-butyl(meth)acrylamide, N-methylol(meth)acrylamide, and N-methylolpropane(meth)acrylamide.

[0074] By including the (meth)acrylamide compound in the photopolymerizable compound, the curing rate of the resin composition can be further improved. The content of the (meth)acrylamide compound may be 1 part by mass or more and 30 parts by mass or less, 2 parts by mass or more and 20 parts by mass or less, or 5 parts by mass or more and 15 parts by mass or less based on 100 parts by mass of the total amount of the resin composition.

[0075] The photoinitiator can be appropriately selected and used from known radical photoinitiators. Examples of the photoinitiator 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-trimethylbenzoyl diphenylphosphine oxide (Omnirad TPO, manufactured by IGM Resins), ethyl (2,4,6-trimethylbenzoyl)-phenylphosphinate (Omnirad TPO-L, manufactured by IGM Resins), 2-benzyl-2-dimethylamino-4'-morpholinobutyrophenone (Omnirad 369, manufactured by IGM Resins), 2-dimethylamino-2-(4-methyl-benzyl)-1-(4-morpholin-4-yl-phenyl)-butan-1-one (Omnirad 379, manufactured by IGM Resins), bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (Omnirad 819, manufactured by IGM Resins), and 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one (Omnirad 907, manufactured by IGM Resins).

[0076] Two or more photoinitiators may be mixed and used. Since the resin composition is excellent in rapid curability, it is preferable that the photoinitiator contains 2,4,6-trimethylbenzoyl diphenylphosphine oxide.

[0077] The content of the photoinitiator 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 still 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.

[0078] The resin composition according to this embodiment may further contain a photoacid generator, a silane coupling agent, a leveling agent, an antifoaming agent, an antioxidant, an ultraviolet absorber, etc.

[0079] Examples of the photoacid generator include A + B -An onium salt having the structure may also be used. Examples of the photoacid generator include sulfonium salts such as CPI-100P and 110P (manufactured by San-Apro 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 Corporation).

[0080] Examples of the silane coupling agent include tetramethyl silicate, tetraethyl silicate, mercaptopropyltrimethoxysilane, vinyltrichlorosilane, vinyltriethoxysilane, vinyltris(β-methoxy-ethoxy)silane, β-(3,4-epoxycyclohexyl)-ethyltrimethoxysilane, dimethoxydimethylsilane, diethoxydimethylsilane, 3-acryloxypropyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, γ-methacryloxypropyltrimethoxysilane, N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane, N-(β-aminoethyl)-γ-aminopropyltrimethyldimethoxysilane, N-phenyl-γ-aminopropyltrimethoxysilane, γ-chloropropyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-aminopropyltrimethoxysilane, bis-[3-(triethoxysilyl)propyl]tetrasulfide, bis-[3-(triethoxysilyl)propyl]disulfide, γ-trimethoxysilylpropyldimethylthiocarbamyltetrasulfide, and γ-trimethoxysilylpropylbenzothiazyltetrasulfide.

[0081] The viscosity of the resin composition according to this embodiment at 25°C is preferably 0.5 Pa·s or more and 10 Pa·s or less, more preferably 0.8 Pa·s or more and 9 Pa·s or less, and even more preferably 1 Pa·s or more and 8 Pa·s or less from the viewpoint of coatability. The viscosity of the resin composition at 25°C can be measured using a B-type viscometer (Digital Viscometer DV-II manufactured by Brookfield) under the conditions of spindle: No. 18 and rotation speed 10 rpm.

[0082] (Optical fiber) FIG. 1 is a schematic cross-sectional view showing an example of an optical fiber according to this embodiment. The optical fiber 10 includes a glass fiber 13 including a core 11 and a clad 12, and a coating resin layer 16 including a primary resin layer 14 and a secondary resin layer 15 provided on the outer periphery of the glass fiber 13.

[0083] The clad 12 surrounds the core 11. The core 11 and the clad 12 mainly contain glass such as quartz glass. For example, quartz glass added with germanium or pure quartz glass can be used for the core 11, and pure quartz glass or quartz glass added with fluorine can be used for the clad 12.

[0084] In FIG. 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.

[0085] 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 or more and 70 μm or less, 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.

[0086] 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 or more and 48 μm or less, 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.

[0087] 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 or more and 37 μm or less, 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.

[0088] By applying the resin composition according to the present embodiment to the primary resin layer, an optical fiber excellent in productivity can be produced.

[0089] The manufacturing method of the optical fiber according to the present embodiment includes a coating step of applying the resin composition to the outer periphery 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.

[0090] From the viewpoint of improving the microbend resistance characteristics of the optical fiber, the Young's modulus of the primary resin layer is preferably 0.8 MPa or less, more preferably 0.5 MPa or less, at 23°C ± 2°C. When the Young's modulus of the primary resin layer exceeds 0.8 MPa, an external force is likely to be transmitted to the glass fiber, and the increase in transmission loss due to microbending may be large.

[0091] The Young's modulus of the primary resin layer can be measured by the Pullout Modulus (POM) method at 23°C. Fix two locations of the optical fiber with two chuck devices, remove the coating resin layer (primary resin layer and secondary resin layer) portion between the two chuck devices, then fix one chuck device and gently move the other chuck device in the opposite direction of the fixed chuck device. When the length of the portion of the optical fiber clamped by the moving chuck device is L, the moving amount of the chuck is Z, the outer diameter of the primary resin layer is Dp, the outer diameter of the glass fiber is Df, the Poisson's ratio of the primary resin layer is n, and the load during the movement of the chuck device is W, the Young's modulus of the primary resin layer can be obtained from the following formula. Young's modulus (MPa) = ((1 + n)W / πLZ) × ln(Dp / Df)

[0092] The secondary resin layer 15 can be formed, for example, by curing a resin composition containing a photopolymerizable compound containing urethane (meth)acrylate, a photoinitiator, etc. The resin composition forming the secondary resin layer has a composition different from that of the resin composition for primary coating. The resin composition for secondary coating can be prepared using a conventionally known technique. The resin composition for secondary coating may contain urethane (meth)acrylamide, may contain urethane (meth)acrylate, or may contain urethane (meth)acrylamide and urethane (meth)acrylate.

[0093] From the viewpoint of improving the microbend resistance characteristics 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 still more preferably 1200 MPa or more at 23°C ± 2°C. The upper limit value of 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.

[0094] 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 in a cylindrical shape. At this time, although the primary resin layer and the secondary resin layer are integrated, since the Young's modulus of the primary resin layer is 1 / 1000 or more and 1 / 10000 or less of the Young's modulus of the secondary resin layer, the Young's modulus of the primary resin layer can be ignored. Next, after removing the solvent from the coating resin layer by vacuum drying, a tensile test (tensile speed is 1 mm / min) is performed at 23°C, and the Young's modulus can be obtained by the secant method of 2.5% strain.

[0095] From the viewpoint of improving the heat resistance of the secondary resin layer, the Tg of the secondary resin layer is preferably 70°C or higher, more preferably 75°C or higher. From the viewpoint of suppressing the increase in transmission loss at low temperatures of the optical fiber, it is preferably 105°C or lower, more preferably 95°C or lower.

[0096] By using the resin composition according to this embodiment as the resin composition for primary coating, the manufacturing method of the optical fiber according to this embodiment can manufacture an optical fiber with excellent productivity.

Examples

[0097] Hereinafter, the results of evaluation tests using examples and comparative examples according to the present disclosure will be shown to explain the present disclosure in more detail. Note that the present invention is not limited to these examples.

[0098] [Synthesis of urethane acrylamide] (A-1) Polypropylene glycol of Mn3000 (trade name "Sunnex PP-3000" manufactured by Sanyo Chemical Industries, Ltd.) and 2,4-tolylene diisocyanate (TDI) were reacted at 60 °C for 1 hour with a molar ratio of NCO to OH (NCO / OH) of 1.5 to prepare an NCO-terminated prepolymer. As a catalyst, dibutyltin dilaurate was added at 200 ppm based on the final total charge amount. Next, N-hydroxyethyl acrylamide (HEAA) was added so that the molar ratio of OH of HEAA to NCO of the NCO-terminated prepolymer was 1.05, and the reaction was carried out at 60 °C for 1 hour to obtain urethane acrylamide (A-1) with Mn11400.

[0099] (A-2) PP-3000 and TDI were reacted at 60 °C for 1 hour with NCO / OH of 1.5 to prepare an NCO-terminated prepolymer. Dibutyltin dilaurate was added at 200 ppm based on the final total charge amount. Next, methanol was added so that the molar ratio of OH was 0.4 to NCO of the NCO-terminated prepolymer, and HEAA was added so that the molar ratio of OH was 0.65, and the reaction was carried out at 60 °C for 1 hour to obtain urethane acrylamide (A-2) with Mn11300.

[0100] (A-3) PP-3000 and TDI were reacted at 60 °C for 1 hour with NCO / OH of 1.5 to prepare an NCO-terminated prepolymer. Dibutyltin dilaurate was added at 200 ppm based on the final total charge amount. Next, 3-mercaptopropyltrimethoxysilane (MPTS) was added so that the molar ratio of SH was 0.1 to NCO of the NCO-terminated prepolymer, and HEAA was added so that the molar ratio of OH was 0.95, and the reaction was carried out at 60 °C for 1 hour to obtain urethane acrylamide (A-3) with Mn11400.

[0101] (A-4) Polypropylene glycol of Mn4000 (trade name "PP-4000" manufactured by Sanyo Chemical Industries, Ltd.) and TDI were reacted at 60 °C for 1 hour with an NCO / OH ratio of 1.5 to prepare an NCO-terminated prepolymer. Dibutyltin dilaurate was added at 200 ppm based on the final total charge. Next, MPTS was added so that the molar ratio of SH to NCO of the NCO-terminated prepolymer was 0.05, methanol was added so that the molar ratio of OH was 0.2, and HEAA was added so that the molar ratio of OH was 0.8, followed by reaction at 60 °C for 1 hour to obtain urethane acrylamide (A-4) with Mn15900.

[0102] (A-5) Polycarbonate diol of Mn3000 (trade name "ETERNACOLL PH-300" manufactured by Ube Industries, Ltd.) and TDI were reacted at 60 °C for 1 hour with an NCO / OH ratio of 1.5 to prepare an NCO-terminated prepolymer. Dibutyltin dilaurate was added at 200 ppm based on the final total charge. Next, methanol was added so that the molar ratio of OH to NCO of the NCO-terminated prepolymer was 0.4, and HEAA was added so that the molar ratio of OH was 0.65, followed by reaction at 60 °C for 1 hour to obtain urethane acrylamide (A-5) with Mn11600.

[0103] (A-6) Polytetramethylene glycol of Mn3000 (trade name "PTG-L" manufactured by Hodogaya Chemical Co., Ltd.) and TDI were reacted at 60 °C for 1 hour with an NCO / OH ratio of 1.5 to prepare an NCO-terminated prepolymer. Dibutyltin dilaurate was added at 200 ppm based on the final total charge. Next, methanol was added so that the molar ratio of OH to NCO of the NCO-terminated prepolymer was 0.4, and HEAA was added so that the molar ratio of OH was 0.65, followed by reaction at 60 °C for 1 hour to obtain urethane acrylamide (A-6) with Mn11500.

[0104] (A-7) Polypropylene glycol of Mn12000 (trade name "PREMINOL S4013F" manufactured by AGC Inc.) and TDI were reacted at 60 °C for 1 hour with an NCO / OH ratio of 2.0 to prepare an NCO-terminated prepolymer. Dibutyltin dilaurate was added at 200 ppm based on the final total charge amount. Next, 3-mercaptopropyltrimethoxysilane (MPTS) was added so that the molar ratio of SH to NCO of the NCO-terminated prepolymer was 0.05, methanol was added so that the molar ratio of OH was 0.2, and 2-hydroxyethyl acrylamide (HEAA) was added so that the molar ratio of OH was 0.8, and the reaction was carried out at 60 °C for 1 hour to obtain urethane acrylamide (A-7) of Mn23400.

[0105] (A-8) Polypropylene glycol of Mn18000 (trade name "PREMINOL S4318F" manufactured by AGC Inc.) and TDI were reacted at 60 °C for 1 hour with an NCO / OH ratio of 2.0 to prepare an NCO-terminated prepolymer. Dibutyltin dilaurate was added at 200 ppm based on the final total charge amount. Next, 2-hydroxyethyl acrylamide (HEAA) was added so that the molar ratio of OH to NCO of the NCO-terminated prepolymer was 1.05, and the reaction was carried out at 60 °C for 1 hour to obtain urethane acrylamide (A-8) of Mn36500.

[0106] (B-1) Polypropylene glycol of Mn3000 (trade name "Sunnex PP-3000" manufactured by Sanyo Chemical Industries, Ltd.) and 2,4-tolylene diisocyanate (TDI) were reacted at 60 °C for 1 hour with a molar ratio of NCO to OH (NCO / OH) of 1.5 to prepare an NCO-terminated prepolymer. As a catalyst, dibutyltin dilaurate was added at 200 ppm based on the final total charge amount. Next, N-hydroxyethyl acrylamide (HEAA) was added so that the molar ratio of OH to NCO of the NCO-terminated prepolymer was 0.9, and 2-hydroxyethyl acrylate (HEA) was added so that the molar ratio of OH was 0.15, and the reaction was carried out at 60 °C for 1 hour to obtain urethane acrylamide (B-1) of Mn11400.

[0107] (B-2) PP-3000 and TDI were reacted at 60 °C for 1 hour with an NCO / OH ratio of 1.5 to prepare an NCO-terminated prepolymer. As a catalyst, dibutyltin dilaurate was added at 200 ppm based on the final total charge amount. Next, HEAA was added so that the molar ratio of OH to the NCO of the NCO-terminated prepolymer was 0.3, and HEA was added so that the molar ratio of OH was 0.75, and the reaction was carried out at 60 °C for 1 hour to obtain a urethane acrylamide (B-2) with Mn 11400.

[0108] (B-3) PP-3000 and TDI were reacted at 60 °C for 1 hour with an NCO / OH ratio of 1.5 to prepare an NCO-terminated prepolymer. As a catalyst, dibutyltin dilaurate was added at 200 ppm based on the final total charge amount. Next, HEAA was added so that the molar ratio of OH to the NCO of the NCO-terminated prepolymer was 0.5, HEA was added so that the molar ratio of OH was 0.15, and methanol was added so that the molar ratio of OH was 0.4, and the reaction was carried out at 60 °C for 1 hour to obtain a urethane acrylamide (B-3) with Mn 11300.

[0109] (B-4) Polypropylene glycol with Mn 4000 (trade name "Sun Nix PP-4000" manufactured by Sanyo Chemical Industries, Ltd.) and TDI were reacted at 60 °C for 1 hour with an NCO / OH ratio of 1.5 to prepare an NCO-terminated prepolymer. As a catalyst, dibutyltin dilaurate was added at 200 ppm based on the final total charge amount. Next, HEAA was added so that the molar ratio of OH to the NCO of the NCO-terminated prepolymer was 0.6, HEA was added so that the molar ratio of OH was 0.2, methanol was added so that the molar ratio of OH was 0.2, and 3-mercaptopropyltrimethoxysilane (MPTS) was added so that the molar ratio of SH was 0.05, and the reaction was carried out at 60 °C for 1 hour to obtain a urethane acrylamide B-4) with Mn 15900.

[0110] (B-5) The polycarbonate diol of Mn3000 (trade name "ETERCOLL PH-300" manufactured by Ube Industries, Ltd.) and TDI were reacted at 60 °C for 1 hour with an NCO / OH of 1.5 to prepare an NCO-terminated prepolymer. As a catalyst, dibutyltin dilaurate was added at 200 ppm based on the final total charge amount. Next, HEAA was added so that the molar ratio of OH to NCO of the NCO-terminated prepolymer was 0.5, HEA was added so that the molar ratio of OH was 0.15, and methanol was added so that the molar ratio of OH was 0.4, and the reaction was carried out at 60 °C for 1 hour to obtain a urethane acrylamide (B-5) with Mn11500.

[0111] (B-6) The polytetramethylene glycol of Mn3000 (trade name "PTG-L" manufactured by Hodogaya Chemical Co., Ltd.) and TDI were reacted at 60 °C for 1 hour with an NCO / OH of 1.5 to prepare an NCO-terminated prepolymer. As a catalyst, dibutyltin dilaurate was added at 200 ppm based on the final total charge amount. Next, HEAA was added so that the molar ratio of OH to NCO of the NCO-terminated prepolymer was 0.5, HEA was added so that the molar ratio of OH was 0.15, and methanol was added so that the molar ratio of OH was 0.4, and the reaction was carried out at 60 °C for 1 hour to obtain a urethane acrylamide (B-6) with Mn11500.

[0112] (B-7) The polypropylene glycol of Mn12000 (trade name "PREMINOL S4013F" manufactured by AGC Inc.) and TDI were reacted at 60 °C for 1 hour with an NCO / OH of 2.0 to prepare an NCO-terminated prepolymer. As a catalyst, dibutyltin dilaurate was added at 200 ppm based on the final total charge amount. Next, HEAA was added so that the molar ratio of OH to NCO of the NCO-terminated prepolymer was 0.6, HEA was added so that the molar ratio of OH was 0.2, methanol was added so that the molar ratio of OH was 0.2, and 3-mercaptopropyltrimethoxysilane was added so that the molar ratio of SH was 0.05, and the reaction was carried out at 60 °C for 1 hour to obtain a urethane acrylamide (B-7) with Mn23300.

[0113] (B-8) Polypropylene glycol of Mn18000 (trade name "PREMINOL S4318F" manufactured by AGC Inc.) and TDI were reacted at 60 °C for 1 hour with an NCO / OH of 2.0 to prepare an NCO-terminated prepolymer. As a catalyst, 200 ppm of dibutyltin dilaurate was added based on the final total charge amount. Next, HEAA was added so that the molar ratio of OH to NCO of the NCO-terminated prepolymer was 0.6, HEA was added so that the molar ratio of OH was 0.2, and 3-mercaptopropyltrimethoxysilane was added so that the molar ratio of SH was 0.25, and the reaction was carried out at 60 °C for 1 hour to obtain a urethane acrylamide (B-8) of Mn36600.

[0114] [Synthesis of urethane acrylate] (Y-1) PP-3000 and TDI were reacted at 60 °C for 1 hour with an NCO / OH of 1.5 to prepare an NCO-terminated prepolymer. 200 ppm of dibutyltin dilaurate was added based on the final total charge amount. Next, HEA was added so that the molar ratio of OH to NCO of the NCO-terminated prepolymer was 1.05, and the reaction was carried out at 60 °C for 1 hour to obtain a urethane acrylate (Y-1) of Mn11300.

[0115] (Y-2) PP-3000 and TDI were reacted at 60 °C for 1 hour with an NCO / OH of 1.5 to prepare an NCO-terminated prepolymer. 200 ppm of dibutyltin dilaurate was added based on the final total charge amount. Next, methanol was added so that the molar ratio of OH to NCO of the NCO-terminated prepolymer was 0.4, and HEA was added so that the molar ratio of OH was 0.65, and the reaction was carried out at 60 °C for 1 hour to obtain a urethane acrylate (Y-2) of Mn11200.

[0116] (Z-1) A urethane acrylate (Z-1) with Mn 2200 was obtained in the same manner as the synthesis of (Y-1), except that polypropylene glycol of Mn600 (trade name "PP-600" manufactured by Sanyo Chemical Industries, Ltd.) and TDI were reacted at an NCO / OH ratio of 2.0 to prepare an NCO-terminated prepolymer.

[0117] The Mn of the polyol is the value described in the catalog of each product. The Mn of the urethane acrylamide and urethane acrylate was measured using an ACQUITY APC RI system manufactured by Waters under the conditions of 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, and flow rate: 0.8 mL / min.

[0118] As the photopolymerizable compounds, nonylphenol polyethylene glycol acrylate (trade name "Aronix M-113" manufactured by Toagosei Co., Ltd.), 2-(2-ethoxyethoxy)ethyl acrylate (EOEOEA), trimethylolpropane triacrylate (TMPTA), N-vinylcaprolactam (NVCL), acryloylmorpholine (ACMO), bisphenol A epoxy di(meth)acrylate (trade name "Biscoat #540" manufactured by Osaka Organic Chemical Industry Co., Ltd.), and tripropylene glycol diacrylate (TPGDA) were prepared. As the photoinitiators, 2,4,6-trimethylbenzoyl diphenylphosphine oxide (Omnirad TPO) and 1-hydroxycyclohexyl phenyl ketone (Omnirad 184) were prepared. As the silane coupling agent, 3-acryloxypropyltrimethoxysilane (APTMS) was prepared.

[0119] [Resin Composition for Primary Coating] The resin compositions for primary coating of each Example and Comparative Example were prepared by mixing a photopolymerizable compound, a photoinitiator, and a silane coupling agent in the blending amounts (parts by mass) shown in Table 1, Table 2, or Table 3.

[0120] [Resin Composition for Secondary Coating] 25 parts by mass of urethane acrylate (Z-1), 36 parts by mass of TPGTA, 37 parts by mass of biscoat #540, 1 part by mass of Omnirad TPO, and 1 part by mass of Omnirad 184 were mixed to obtain a resin composition for secondary coating.

[0121] [Production of Optical Fiber] The resin composition for primary coating and the resin composition for secondary coating were respectively applied to the outer peripheral surface of a glass fiber 13 with a diameter of 125 μm. Then, each resin composition was cured by irradiating ultraviolet rays to form a coated resin layer 16 including a primary resin layer 14 and a secondary resin layer 15, and an optical fiber 10 was produced. The thickness of the primary resin layer 14 was set to 35 μm, and the thickness of the secondary resin layer 15 was set to 25 μm. The production of the optical fiber was respectively carried out by changing the line speed to 2500 m / min, 3000 m / min, and 3500 m / min.

[0122] (Young's Modulus of Primary Resin Layer) The Young's modulus of the primary resin layer was measured by the Pullout Modulus (POM) method at 23°C.

[0123] (Gel Fraction) The optical fiber was immersed in methyl ethyl ketone at 60°C for 12 hours to extract the uncured components in the coated resin layer. After taking out the optical fiber, methyl ethyl ketone was removed by a vacuum dryer, and the gel fraction was determined by the following formula. Gel fraction [%] = (mass of optical fiber after extraction - mass of glass fiber) / (mass of optical fiber before extraction - mass of glass fiber) × 100 The uncured components in the primary resin layer and the secondary resin layer are extracted. Since the same resin composition is used for the secondary resin layer, the curability of the primary resin layer can be compared. When the gel fraction is more than 80%, it is evaluated as "A"; when the gel fraction is 70% or more and 80% or less, it is evaluated as "B"; when the gel fraction is less than 70%, it is evaluated as "C".

[0124] (Low-temperature characteristics) The optical fiber was wound around a glass bobbin in a single layer with a tension of 50 g. The transmission characteristics of the signal light with a wavelength of 1550 nm were measured under the temperature conditions of 23°C and -40°C respectively, and the transmission losses at 23°C and -40°C were obtained. When the transmission loss difference obtained by subtracting the transmission loss at 23°C from the transmission loss at -40°C is less than 0 dB, it is evaluated as "A"; when it is 0 dB or more and 0.01 dB / km or less, it is evaluated as "B"; when it is more than 0.01 dB / km, it is evaluated as "C".

[0125] [Table 1]

[0126] [Table 2]

[0127] [Table 3] [Explanation of symbols]

[0128] 10 Optical fiber 11 Core 12 Cladding 13 Glass fiber 14 Primary resin layer 15 Secondary resin layer 16 Coating resin layer

Claims

1. A resin composition for primary coating of an optical fiber, containing a photopolymerizable compound containing urethane (meth) acrylamide and a photoinitiator, wherein the urethane (meth) acrylamide has a (meth) acrylamide group at at least one end of a urethane bond.

2. The resin composition according to claim 1, wherein the urethane (meth) acrylamide contains a urethane oligomer having a (meth) acrylamide group at one end of a urethane bond, a urethane oligomer having (meth) acrylamide groups at both ends of a urethane bond, or a mixture thereof.

3. The resin composition according to claim 2, wherein the urethane oligomer having a (meth) acrylamide group at one end of the urethane bond contains a urethane oligomer having a (meth) acrylamide group at one end of the urethane bond and a (meth) acryloyloxy group at the other end.

4. The resin composition according to any one of claims 1 to 3, wherein the urethane (meth) acrylamide contains a urethane oligomer having (meth) acrylamide groups at both ends of a urethane bond and a urethane oligomer having a (meth) acrylamide group at one end of the urethane bond and a group based on at least one compound selected from a monohydric alcohol and an active hydrogen-containing silane compound at the other end.

5. The resin composition according to any one of claims 1 to 4, wherein the content of the urethane (meth) acrylamide is 10 parts by mass or more and 90 parts by mass or less based on 100 parts by mass of the total amount of the resin composition.

6. The resin composition according to any one of claims 1 to 5, wherein the number average molecular weight of the urethane (meth) acrylamide is 10,000 or more and 37,000 or less.

7. The resin composition according to any one of claims 1 to 6, wherein the photopolymerizable compound further contains a (meth) acrylate ester.

8. The resin composition according to any one of claims 1 to 7, wherein the photopolymerizable compound further contains an N-vinyl compound.

9. The resin composition according to any one of claims 1 to 8, wherein the photopolymerizable compound further contains a (meth) acrylamide compound.

10. An optical fiber including a core and a cladding, and a primary resin layer in contact with the optical fiber and coating the optical fiber. A secondary resin layer that covers the primary resin layer, and An optical fiber in which the primary resin layer contains a cured product of the resin composition according to any one of claims 1 to 9. **Claim 11** An application step of applying the resin composition according to any one of claims 1 to 9 to the outer periphery of a glass fiber including a core and a cladding; A curing step of curing the resin composition by irradiating ultraviolet rays after the application step; A method for manufacturing an optical fiber, including.

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