WO2009082221A1

WO2009082221A1 - Radiation-curable resin composition containing dipropyl or dibutyl amine

Info

Publication number: WO2009082221A1
Application number: PCT/NL2008/050831
Authority: WO
Inventors: Hiroyuki Ishii; Hiroshi Miyazawa; Satoshi Kamo; Hirokazu Imai; Takahiko Kurosawa
Original assignee: JSR Corp; DSM IP Assets BV
Current assignee: JSR Corp; DSM IP Assets BV
Priority date: 2007-12-21
Filing date: 2008-12-19
Publication date: 2009-07-02
Anticipated expiration: 2010-06-21
Also published as: JP2009149794A

Abstract

The invention is a liquid curable resin composition comprising: (A) 35-85 mass% urethane (meth) acrylate having a structure derived from polyether polyol, (B) 1-60 mass% ethylenically unsaturated group-containing compound other than (A), (C) 0.01-1 mass% dialkylamine having alkyl groups of 3 or 4 carbons, and (D) 0.01-10 mass% photopolymerization initiator, wherein the total quantity of the composition is 100 mass%. As a result of thorough research while considering this situation, the inventors discovered that, by using dialkylamine having alkyl groups of 3 or 4 carbons, a fast-curing liquid curable resin composition is obtained, by which optical fiber strands having high resistance to hot water immersion are obtained.

Description

Title: RADIATION-CURABLE RESIN COMPOSITION CONTAINING DIPROPYL OR DIBUTYL AMINE

Field of the Invention

The invention relates to a liquid curable resin composition which is fast-curing, by which coated optical fibers, which have excellent resistance to hot water immersion and excellent mechanical strength, are obtained. More specifically, this invention relates to primary coatings for optical fibers, where the primary coating comprises dipropyl or dibutyl amine or a mixture thereof.

Background of the invention

Optical fiber is manufactured by coating glass fiber strands obtained by hot melt drawing of glass with resin for the purpose of protection and strength reinforcement. As this resin coating, a known structure is one in wherein, first, a pliable primary coating layer or "inner primary coating layer" (called "primary coating layer" hereinafter) is provided on the surface of the optical fiber, and on the outside of this, a secondary coating layer also known as a "outer primary coating layer", having high rigidity (called "secondary coating layer" hereinafter) is provided. An optical fiber which has these primary and secondary coating layers is called an optical fiber strand (simply called "optical fiber" hereinafter). Optical fiber ribbon is also well known, wherein a plurality of these optical fiber strands obtained by resin coating are aligned in a row on a flat surface and are bound with a bundling material. The resin composition used for forming the primary coating layer of the optical fiber strand is called the primary material, the resin composition used for forming the secondary coating layer is called the secondary material, and the resin composition used as the bundling material of the ribbon-shaped fiber is called matrix or ribbon material(hereinafter "ribbon material"). As coating methods of these resins, methods by which liquid curable resin composition is coated and then cured by heat or radiation are widely known. Radiation can include many types of light, the preferred light is ultraviolet light, are widely known.

In recent years, excellent storage stability of uncured resin liquid has been sought in such liquid curable resin compositions, and from the viewpoint of optical fiber manufacturing efficiency, fast curing has been sought, and from the viewpoint of optical stability, good resistance to hot water immersion has been sought.

It is known that curing speed can be increased to some extent by selection of the radical-polymerizable monomer or photopolymerization initiator. For example, techniques such as the use of N-vinyl compounds having a ring structure such as N-vinyl caprolactam or N-vinyl pyrrolidone as typical radical-polymerizable monomers which are effective in increasing curing speed, and the concurrent use of a basic compound such as diethylamine as a photosensitizer have been used, see Japanese Unexamined Patent Application Publication No.'s 10-081705, 04-016519 and 02-092911.

However, basic compounds such as diethylamine can cause a reduction in transparency when the optical fiber is immersed in hot water for a long time, which is not necessarily desirable from the viewpoint of long-term stability of transmission characteristics of the optical fiber.

For this reason, a liquid curable resin composition has been proposed, by which optical fiber strands having improved hot water immersion resistance are obtained by controlling the content of the elements zinc and cobalt in the composition to fixed values, see Japanese Unexamined Patent Application Publication No. 2007-119704. However, in this composition as well, there were cases where sufficient hot water immersion resistance was not obtained and muddiness occurred depending on the amine-based sensitizer that was used. Also, there were cases where a Young's modulus sufficient for an optical fiber coating layer was not obtained. It would be desirable to develop a liquid curable resin composition which is fast-curing, by which optical fiber strands which have high resistance to hot water immersion are obtained.

Summary of the invention

In a first aspect the invention is directed to a liquid curable resin composition comprising: (A) 35-85 mass% urethane (meth) acrylate having a structure derived from polyether polyol, (B) 1—60 mass% ethylenically unsaturated group-containing compound other than (A),

(C) 0.01—1 mass% dialkylamine having alkyl groups of 3 or 4 carbons, and

(D) 0.01-10 mass% photopolymerization initiator, wherein the total quantity of the composition is 100 mass%. In a further aspect the invention is directed to an optical fiber coating layer obtained by curing the liquid curable resin composition of the first aspect of the instant claimed invention by irradiation.

In yet a further aspect the invention is directed to an optical fiber having a coating layer according to the second aspect of the instant claimed invention.

Detailed description

The instant claimed invention provides a liquid curable resin composition comprising:

(A) 35—85 mass% urethane (meth) acrylate having a structure derived from polyether polyol,

(B) 1—60 mass% ethylenically unsaturated group-containing compound other than (A), (C) 0.01-1 mass% dialkylamine having alkyl groups of 3 or 4 carbons, and (D) 0.01—10 mass% photopolymerization initiator, wherein the total quantity of the composition is 100 mass%.

As a result of thorough research while considering this situation, the inventors discovered that, by using dialkylamine having alkyl groups of 3 ("propyl") or 4 ("butyl") carbons, a fast-curing liquid curable resin composition is obtained, by which optical fiber strands having high resistance to hot water immersion are obtained, and they thereby achieved the present invention.

The liquid curable resin composition of the instant claimed invention is something by which optical fiber strands having high resistance to hot water immersion are obtained, and which has excellent fast curability. Also, it has good storage stability. It can be used as coating material for optical fibers, particularly as primary material, or as surface coating material of various optical members, or as an optical adhesive and so forth.

The urethane (meth) acrylate of component (A) used in the liquid curable resin composition of the present invention is not particularly restricted as long as it has a structure derived from polyether polyol, but it is obtained, for example, by reacting at least (a) polyether polyol, (b) polyisocyanate and (c) hydroxyl group-containing (meth) acrylate.

As specific methods of manufacturing the urethane (meth) acrylate of component (A), the following methods can be cited, for example: a method in which (a) polyether polyol, (b) polyisocyanate and (c) hydroxyl group-containing (meth) acrylate are added all at once and reacted; a method in which (a) polyether polyol and (b) polyisocyanate are reacted, and then (c) hydroxyl group-containing (meth) acrylate is reacted; a method in which (b) polyisocyanate and (c) hydroxyl group-containing (meth) acrylate are reacted, and then (a) polyether polyol is reacted; and a method in which (b) polyisocyanate and (c) hydroxyl group-containing (meth) acrylate are reacted, and then (a) polyether polyol is reacted, and finally a silane compound having functional groups that can react with isocyanate groups is reacted. As the polyether polyol of component (a) used here, polyether diols obtained by ring-opening polymerization of one type of ion-polymerizable ring compound or polyether diols obtained by ring- opening polymerization of two or more types of ion-polymerizable ring compound, such as polyethylene glycol, polypropylene glycol, polytetramethylene glycol, polyhexamethylene glycol, polyheptamethylene glycol and polydecamethylene glycol, can be cited. As the ion-polymerizable ring compound, ring-type ethers such as ethylene oxide, propylene oxide, butane- 1 -oxide, isobutene oxide, oxetane, 3,3-dimethyloxetane, 3,3-bischloromethyloxetane, tetrahydrofuran, 2-methyltetrahydrofuran, 3-methyltetrahydrofuran, dioxane, trioxane, tetraoxane, cyclohexene oxide, styrene oxide, epichlorhydrin, glycidyl methacrylate, allyl glycidyl ether, allyl glycidyl carbonate, butadiene monoxide, isoprene monoxide, vinyl oxetane, vinyl tetrahydrofuran, vinyl cyclohexene oxide, phenyl glycidyl ether, butyl glycidyl ether, glycidyl ester of benzoic acid and so forth, can be cited. Also, a polyether diol obtained by ring-opening polymerization of the aforementioned ion-polymerizable ring compounds with a ring-type imine such as ethyleneimine, a ring-type lactone acid such as γ-propiolactone or lactide glycolate, or a dimethylcyclopolysiloxane can be used. As specific combinations of the aforementioned two or more types of ion-polymerizable ring compounds, tetrahydrofuran and propylene oxide, tetrahydrofuran and 2-methyltetrahydrofuran, tetrahydrofuran and 3- methyltetrahydrofuran, tetrahydrofuran and ethylene oxide, propylene oxide and ethylene oxide, butane- 1 -oxide and ethylene oxide, and the three-element polymer of tetrahydrofuran, butene-1- oxide and ethylene oxide can be cited. The ring-opening copolymer of these ion-polymerizable ring compounds can be bonded randomly or bonded in block form. From the viewpoint of providing gel resistance and water resistance to the obtained cured material, polypropylene glycol is preferable among these polyether diols, and polypropylene glycol of average molecular weight 1000-7000 as converted to polystyrene by gel permeation chromatography (GPC) is particularly preferable. These polyether diols can be procured as commercial products such as, for example, PTMG 650, PTMG 1000, PTMG 2000 (the above manufactured by Mitsubishi Chemical), Exenol 1020, 2020 and 3020 and Preminol PLM-4002, PML-S-4102 and PML-5005 (the above manufactured by Asahi Glass Urethane), Unisafe DClIOO, DC1800 and DCBlOOO (the above manufactured by Nippon Oils and Fats), PPTG 1000, PPTG 2000, PPTG 4000, PTG 400, PTG 650, PTG 1000, PTG 2000, PTG-LlOOO and PTG-L2000 (the above manufactured by Hodogaya Chemical), Z-3001-4, Z-3001-5 and PBG 2000 (the above manufactured by Daiichi Kogyo Seiyaku), Acclaim 2200, 2220, 3201, 3205, 4200, 4220, 8200 and 12000 (the above manufactured by Sumika Bayer Urethane).

As the polyether polyol of component (a), the aforementioned polyether diols can be used, but in addition, polyester diols, polycarbonate diols, polycaprolactone diols and so forth can also be used. The polymerization mode of these structural units is not particularly restricted, and either random polymerization, block polymerization or graft polymerization is acceptable.

As the polyisocyanate of component (b) used in synthesis of the urethane (meth) acrylate of component (A), aromatic diisocyanate, alicyclic diisocyanate, aliphatic diisocyanate and so forth can be cited. As specific compounds, preferable examples are aromatic diisocyanate and alicyclic diisocyanate, and more preferable examples are 3,4-tolylene diisocyanate and isophorone diisocyanate. These diisocyanates can be used independently or used in a combination of two or more.

As the hydroxyl group-containing (meth) acrylate of component (c) used in synthesis of the urethane (meth) acrylate of component (A), hydroxyl group-containing (meth) acrylates in which hydroxyl groups are bonded to the primary carbon atom (called primary hydroxyl group-containing (meth) acrylates) and hydroxyl group-containing (meth) acrylates in which hydroxyl groups are bonded to the secondary carbon atom (called secondary hydroxyl group-containing (meth) acrylates) are preferable from the viewpoint of reactivity with the isocyanate groups of polyisocyanates. As primary hydroxyl group-containing (meth) acrylates, for example, 2-hydroxyethyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 1,6-hexanediol mono (meth) acrylate, pentaerythritol (meth) acrylate, dipentaerythritol (meth) acrylate, neopentyl glycol mono (meth) acrylate, trimethylolpropane di (meth) acrylate, trimethylolethane di (meth) acrylate and so forth can be cited.

As secondary hydroxyl group-containing (meth) acrylates, for example, 2-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 2-hydroxy-3-phenyloxypropyl (meth) acrylate, 4-hydroxycyclohexyl (meth) acrylate and so forth can be cited. In addition, compounds obtained by addition reaction of (meth) acrylic acid with glycidyl group-containing compounds such as alkylglycidyl ether, allylglycidyl ether and glycidyl (meth) acrylate can be cited.

These hydroxyl group-containing (meth) acrylates can be used as one type independently, or as a combination of two or more types.

The used proportions of (a) polyether diol, (b) polyisocyanate and (c) hydroxyl group-containing (meth) acrylate used in synthesis of the urethane (meth) acrylate of component (A) are 1.1—2 equivalents of isocyanate contained in polyisocyanate, and 0.1-1 equivalents of hydroxyl group in hydroxyl group- containing (meth) acrylate, with respect to 1 equivalent of hydroxyl group contained in polyether polyol.

Also, in synthesis of the urethane (meth) acrylate of component (A), polyether polyol and diamine can be used together. As this diamine, diamines such as ethylene diamine, tetramethylene diamine, hexamethylene diamine, paraphenylene diamine and 4,4'-diaminodiphenylmethane, or diamines that contain hetero atoms, or polyether diamines and so forth can be cited.

A portion of the hydroxyl group-containing (meth) acrylate can be substituted with an alcohol. As the alcohol, for example, methanol, isopropyl alcohol, n-butyl alcohol, t-butyl alcohol and so forth can be cited. By using these compounds, the Young's modulus of the resin can be adjusted. In synthesis of the urethane (meth) acrylate of component (A), urethane catalysts such as copper naphthenate, cobalt naphthenate, zinc naphthenate, dibutyl tin dilaurate, dioctyl tin dilaurate, tetrabutoxy titanium, zirconium tetraacetylacetate, bismuth octenate, bismuth neodecanate, triethylamine, l,4-diazabicyclo[2.2.2]octane and

2,6,7-trimethyl-l,4-diazabicyclo[2.2.2]octane can be used in the proportion of 0.01—1 mass% with respect to the total quantity of reactant. Also, the reaction temperature is preferably 5-90⁰C, more preferably 10-80⁰C.

From the viewpoint of obtaining good breaking elongation of the cured material and appropriate viscosity of the liquid curable resin composition, the preferred molecular weight of the urethane (meth) acrylate of component (A) is normally 500-40,000, more preferably 700-30,000, by average molecular weight as converted to polystyrene by GPC.

Also, as the urethane (meth) acrylate of component (A), urethane (meth) acrylate having a structure derived from polypropylene glycol is preferable.

From the viewpoint of obtaining good mechanical characteristics such as Young's modulus and breaking elongation of the cured material as well as appropriate viscosity of the liquid curable resin composition, the urethane (meth) acrylate of component (A) is compounded in the liquid curable resin composition of the present invention in a quantity of preferably 35—85 mass%, more preferably 55-85 mass%, even more preferably 70-85 mass%. If the quantity exceeds 85 mass%, it is not good as a resin for optical fiber coating because the Young's modulus exceeds 2.0 MPa, and workability decreases and water resistance is poor because the viscosity of the liquid curable resin composition exceeds 6.0 Pa-s. If it is less than 35 mass%, fracture strength is poor.

The component (B) used in the liquid curable resin composition of the present invention is an ethylenically unsaturated group-containing compound other than component (A), and is typically a reactive diluent. As component (B), for example, (Bl) compounds having one ethylenically unsaturated group (called "polymerizable monofunctional compound" hereinafter), and (B2) compounds having two or more ethylenically unsaturated groups (called "polymerizable polyfunctional compounds" hereinafter) can be cited.

As polymerizable monofunctional compounds of component (Bl), N-vinyl compounds such as N-vinyl pyrrolidone and N-vinyl caprolactone; alicyclic structure-containing (meth) acrylates such as isobornyl (meth) acrylate, bornyl (meth) acrylate, tricyclodecanyl (meth) acrylate and dicyclopentanyl (meth) acrylate; benzyl (meth) acrylate, 4-butylcyclohexyl

(meth) acrylate, acryloylmorpholine, vinylimidazole, vinylpyridine and so forth can be cited. In addition, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, isopropyl (meth) acrylate, butyl (meth) acrylate, amyl (meth) acrylate, isobutyl (meth) acrylate, t-butyl (meth) acrylate, pentyl (meth) acrylate, isoamyl (meth) acrylate, hexyl (meth) acrylate, heptyl (meth) acrylate, octyl (meth) acrylate, isooctyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, nonyl (meth) acrylate, decyl (meth) acrylate, isodecyl (meth) acrylate, undecyl (meth) acrylate, dodecyl (meth) acrylate, lauryl (meth) acrylate, stearyl (meth) acrylate, isostearyl (meth) acrylate, tetrahydrofurfuryl (meth) acrylate, butoxyethyl (meth) acrylate, ethoxydiethylene glycol (meth) acrylate, benzyl (meth) acrylate, phenoxyethyl (meth) acrylate, polyethylene glycol mono (meth) acrylate, polypropylene glycol mono (meth) acrylate, methoxyethylene glycol (meth) acrylate, ethoxyethyl (meth) acrylate, methoxypolyethylene glycol (meth) acrylate, methoxypolypropylene glycol (meth) acrylate, diacetone (meth) acrylamide, isobutoxymethyl (meth) acrylamide, N,N-dimethyl (meth) acrylamide, t-octyl (meth) acrylamide, dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, 7-amino-3,7-dimethylactyl (meth) acrylate, N.N-diethyl (meth) acrylamide, N,N-dimethylaminopropyl (meth) acrylamide, hydroxybutyl vinyl ether, lauryl vinyl ether, cetyl vinyl ether, 2-ethylhexyl vinyl ether, 2-hydroxy-3-phenoxypropyl acrylate, nonylphenolethylene oxide modified (meth) acrylate, and the compounds represented by the following general formula can be cited.

Formula 1

In the formula, R¹ is a hydrogen atom or a methyl group. R² and R³ are, each independently, a hydrogen atom, a phenyl group or an alkyl group of 1—10 carbons, n is 0—10.

Among these polymerizable monofunctional compounds of component (Bl), N-vinyl compounds such as N-vinyl pyrrolidone and N-vinyl caprolactone, and monofunctional (meth) acrylates having aliphatic hydrocarbon groups of 10 or more carbons are preferable. Here, as aliphatic hydrocarbon groups of 10 or more carbons, those of 10—24 carbons that contain a straight chain, branched chain or alicyclic form are preferable. Among these, isobornyl (meth) acrylate, isodecyl (meth) acrylate or lauryl (meth) acrylate is preferable, and isobornyl (meth) acrylate and/or isodecyl (meth) acrylate are particularly preferable. As commercial products of these polymerizable monofunctional compounds of component (Bl), IBXA (manufactured by Osaka Organic Chemical Industry), Aronix M-110, M-Hl, M-113, M-114, M-117 and TO- 1210 (the above manufactured by Toa Gosei), epoxy ester M-600A (manufactured by Koeisha Chemical) and so forth can be used.

The polymerizable polyfunctional compound of (B2) is not particularly restricted as long as it can be used as a resin composition for optical fiber, but as preferred examples, polyethylene glycol acrylate, tricyclodecane diyl dimethylene di (meth) acrylate, di (meth) acrylate of bisphenol A to which ethylene oxide was added, tris (2-hydroxyethyl) iocyanurate tri (meth) acrylate, hexane diol diacrylate (HDDA) and so forth can be cited. As commercial products of these polymerizable multifunctional compounds of component (B2), for example, Light-Acrylate 9EG-A and 4EG-A (the above manufactured by Koeisha Chemical), Yupima UV and SA1002 (the above manufactured by Mitsubishi Chemical), Aronix M-215, M-315 and M- 325 (the above manufactured by Toa Gosei) and so forth can be cited.

These polymerizable monofunctional compounds of component (Bl) and polymerizable polyfunctional compounds of component (B2) can also be used together.

This component (B) is compounded in the liquid curable resin composition of the present invention in a proportion of preferably 1—60 mass%, more preferably 2-45 mass%. If it is less than 1 mass%, curability may be lost. If it exceeds 60 mass%, this causes changes in the shape of the coating and the coating process is not stable due to low viscosity.

As the dialkylamine which is component (C) of the present invention, dipropylamine, dibutylamine and so forth can be cited, and dibutylamine is particularly preferable.

This component (C) is compounded in the liquid curable resin composition of the present invention in a proportion of preferably 0.01—10 mass%, more preferably 0.05-5 mass%. If it is less than 0.01 mass%, curing speed may be reduced. If it exceeds 1 mass%, the mechanical strength of the optical fiber may be reduced.

Component (D) of the present invention is a photopolymerization initiator. As the photopolymerization initiator of component (D), for example, 1-hydroxycyclohexyl phenylketone, 2,2-dimethoxy-2-phenylacetophenone, xanthone, fluorenone, benzaldehyde, fluorine, anthraquinone, triphenylamine, carbazole, 3-methylacetophenone, 4-chlorobenzophenone, 4,4'-dimethoxybenzophenone, 4,4'-diaminobenzophenone, Michler's ketone, benzoin propyl ether, benzoin ethyl ether, benzyl methyl ketal, l-(4-isopropylphenyl)-2-hydroxy-2-methylpropane-l-on, 2-hydroxy-2-methyl-l-phenylpropane-l-on, thioxanthone, diethylthioxanthone, 2-isopropylthioxanthone, 2-chlorothioxanthone, 2- methyl- 1 - [4- (methylthio)phenyl] - 2- morpholino- propane- 1 - on, 2,4,6-trimethylbenzoyl diphenylphosphine oxide, bis-(2,6-dimethoxybenzoyl)-2,4,4- trimethylpentylphosphine oxide and so forth can be cited. As commercial products of the above, Irgacure 184, 369, 651, 500, 907, 819, Irgacure 1700, Irgacure 1850, CGI1870, CG2461, Darocure 1116 and 1173 (the above manufactured by Ciba Specialty Chemicals), Lucirin TPO (manufactured by BASF), Ubecryl P36 (manufactured by UCB) and so forth can be cited. The polymerization initiator of component (D) is compounded in the liquid curable resin composition of the present invention in a proportion of preferably 0.01—10 mass%, more preferably 0.05—5 mass%.

Also, various additives other than the above components may be compounded in the liquid curable resin composition of the present invention. For example, dyes, silane coupling agents, oxidation inhibitors, thermal polymerization inhibitors, leveling agents, surfactants, storage stabilizers, plasticizers, lubricants, solvents, fillers, aging inhibitors, wetting improvement agents, coated surface improvement agents and so forth can be compounded as necessary. As silane coupling agents, for example, γ-aminopropyltriethoxy silane, γ-mercaptopropyltrimethoxysilane and γ-methacryloxypropyltrimethoxysilane can be cited, and as commercial products, SH6062 and SZ6030 (the above manufactured by Toray Dow Corning Silicone), KBE903, 603 and 403 (the above manufactured by Shin-Etsu Chemical) and so forth can be cited. As oxidation inhibitors, for example, Sumilizer GA-80 (manufactured by Sumitomo Chemical), Irganox 1010 and Irganox 1035 (the above manufactured by Ciba Specialty Chemicals) and so forth can be cited.

The viscosity of the liquid curable resin composition of the present invention at 25°C is preferably 1.0—6.0 Pa-s. Also, when used as an optical fiber primary layer, the Young's modulus of the cured material is preferably 0.5—2.0 MPa (ultraviolet irradiation condition: 1 J/cm²).

The liquid curable resin composition of the present invention is cured by irradiation. Here, the irradiation is preferably by infrared rays, visible light rays, ultraviolet rays, X rays, α rays, β rays, γ rays, electron beam and so forth, but ultraviolet rays are particularly preferable.

As another embodiment of the present invention, the liquid curable resin composition described above is an optical fiber coating layer obtained by being coated on glass fiber strands or on another optical fiber coating layer and being cured by irradiation. When ultraviolet rays are used for irradiation, the preferable irradiation condition is 50—300 J/cm². The optical fiber coating layer of the present invention can form any portion of or all optical fiber coating layers, but preferably it forms the primary coating layer of optical fiber.

Another embodiment of the present invention is an optical fiber having the aforementioned optical fiber coating layer. The optical fiber of the present invention is not restricted by which layer the aforementioned coating layer forms as long as it has the aforementioned optical fiber coating layer, but preferably, optical fiber or optical fiber ribbon in which multiple optical fibers are bundled as a ribbon, in which the aforementioned optical fiber coating layer is the primary coating layer and which has also a secondary coating layer, can be cited. The optical fiber of the present invention is obtained by coating glass fiber obtained by melting quartz parent material with a primary coating material and curing it by irradiation, then coating it with a secondary coating material and curing it by irradiation. The optical fiber of the present invention has high resistance to hot water immersion. The following examples further illustrate the invention but, of course, should not be construed as in any way limiting its scope.

Examples

Synthesis Example 1 (synthesis of urethane (meth) acrylate) 50.968 parts of polypropylene glycol of average molecular weight 2000 containing 6-8 ppm of zinc and cobalt compound, 7.920 parts of isophorone diisocyanate, 0.015 parts of 2,6-di-t-butyl-p-cresol and 0.005 parts of phenothiazine were put in a reaction vessel equipped with a stirrer, and it was cooled to a liquid temperature of 15 ⁰C while stirring. Then, 0.49 parts of dibutyl tin dilaurate was added, after which the liquid temperature was gradually raised to 35 ⁰C over the course of 1 hour while stirring. After that, the liquid temperature was raised to 50 ⁰C and it was reacted. After the remaining isocyanate group concentration was less than 1.45 mass% (proportion with respect to added quantity), 2.365 parts of 2-hydroxyethyl acrylate was added, and this was stirred at a liquid temperature of approximately 60 ⁰C and reacted. The reaction was considered complete when the remaining isocyanate group concentration was less than 0.1 mass%. The obtained urethane acrylate oligomer was used as oligomer A.

Synthesis Example 2 (preparation of secondary coating material)

15.4 parts of isophorone diisocyanate, 0.013 parts of

2,6-di-t-butyl-p-cresol and 0.047 parts of dibutyl tin dilaurate were put in a reaction vessel equipped with a stirrer, and it was cooled to a liquid temperature of 10 ⁰C while stirring. Then, 11.32 g of hydroxyethyl acrylate was dripped in while controlling the liquid temperature to 20 ⁰C or less, after which it was stirred for an additional 1 hour and reacted. Then, 25.4 g of polytetramethylene glycol of average molecular weight 1000 and 9.36 g of alkylene oxide addition diol of bisphenol A of average molecular weight 400 were added, and stirring was continued for 3 hours at liquid temperature 70-75 ⁰C. The reaction was considered complete when the remaining isocyanate was less than 0.1 mass%. It was cooled to 50-60⁰C, and then 9.7 g of isobornyl acrylate, 14.55 g of SA-1002 (manufactured by Mitsubishi Chemical), 9.7 g of N-vinyl caprolactam, 2.91 g of Irgacure 184 (manufactured by Ciba Specialty Chemicals) and 0.3 g of Sumilizer GA-80 (manufactured by Sumitomo Chemical) were added, this was stirred until uniform, and a liquid curable resin composition was obtained.

Implementation Examples 1-2, Comparative Examples 1-3 (preparation of primary coating material)

The compounds shown in Table 1 were put in a reaction vessel equipped with a stirrer in the proportions (parts by mass) shown in Table 1, and they were stirred at a liquid temperature of 50 ⁰C until the solution became uniform, and liquid curable resin compositions of implementation examples and comparative examples were obtained.

Manufacturing Example 1 (manufacture of optical fibers strands)

Using optical fiber drawing equipment (manufactured by Yoshida Industries), the compositions of the implementation examples and comparative examples were coated and cured as the primary coating material on quartz glass fiber, after which secondary coating material was coated and cured. The manufacturing conditions of the optical fiber were as follows.

As for the diameter of the optical fiber, the diameter of the glass fiber was 125 μm, but when the primary coating material obtained in the implementation examples or comparative examples was coated and cured, the diameter was 200 μm. In addition, the secondary coating material obtained in synthesis example 3 was coated on top of the formed primary coating layer, and when it was cured, it resulted in a diameter of 245 μm. A UV lamp (SMX 3.5 kw) manufactured by ORC was used as the ultraviolet irradiation equipment. The drawing speed of the optical fiber was 200 m/minute. Test Example 1

The liquid curable resin compositions obtained by the aforementioned Examples and Comparative Examples were cured and test specimens were prepared by the methods below, and the following evaluations were performed. Results are shown in Table 1.

Table 1

In Table 1,

SR306H: Tripropylene glycol diacrylate (manufactured by Sartomer) Lucirin TPO: 2,4,6-trimethylbenzoyldiphenylphosphine oxide (manufactured by BASF)

SH6062: γ-mercaptoxypropyltrimethoxysilane (manufactured by Toray Dow Corning) 1. Young's Modulus:

Liquid curable resin composition was coated on a glass sheet using an applicator bar 250 μm thick, and this was cured by irradiation with ultraviolet rays at 1 J/cm² or 20 mJ/cm² in nitrogen, and film for Young's modulus measurement was obtained. Long narrow samples were created from this film such that the elongated part was 6 mm wide and 25 mm long, and these underwent tensile testing at temperature 23 ⁰C, humidity 50%. At a pulling rate of 1 mm/minute, Young's modulus was determined from the tensile strength at strain of 2.5%.

2. Curing Speed:

Curing speed was taken as the Young's modulus for the case where ultraviolet irradiation was at 20 mJ/cm² divided by the Young's modulus for the case where ultraviolet irradiation was at 1 J/cm². However, it was rounded to two decimal places.

3. Resistance to Hot Water Immersion:

A hot water immersion test was performed on the liquid curable resin compositions obtained in the implementation examples and comparative examples. The secondary coating material prepared in synthesis example 2 was coated on a glass sheet using an applicator bar 70 μm thick, and this was cured by irradiation with ultraviolet rays at 100 mJ/cm² in air. Then, the primary coating material prepared in the implementation examples and comparative examples was coated on the prepared cured film using an applicator bar 130 μm thick, and this was cured by irradiation with ultraviolet rays at 500 mJ/cm² in nitrogen. In addition, the secondary coating material prepared in synthesis example 2 was coated on a glass sheet using an applicator bar 200 μm thick, and this was cured by irradiation with ultraviolet rays at 500 mJ/cm² in nitrogen, and test film was obtained. Long narrow samples were created from this cured film such that they were 10 mm wide and 30 mm long. These long narrow samples were immersed in 60 ⁰C hot water, and they were observed by optical microscope. After immersion in hot water for 720 hours, the samples were evaluated as "O" if no bubbles of 10 μm or more was seen, or as "X" if bubbles of 10 μm or more was seen.

All references, including publications, patent applications, and patents, cited herein are hereby incorporated by reference to the same extent as if each reference were individually and specifically indicated to be incorporated by reference and were set forth in its entirety herein. The use of the terms "a" and "an" and "the" and similar referents in the context of describing the invention (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The terms "comprising," "having," "including," and "containing" are to be construed as open-ended terms (i.e., meaning "including, but not limited to,") unless otherwise noted. Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., "such as") provided herein, is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention unless otherwise claimed. No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the invention.

Preferred embodiments of this invention are described herein, including the best mode known to the inventors for carrying out the invention. Variations of those preferred embodiments may become apparent to those of ordinary skill in the art upon reading the foregoing description. The inventors expect skilled artisans to employ such variations as appropriate, and the inventors intend for the invention to be practiced otherwise than as specifically described herein. Accordingly, this invention includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Moreover, any combination of the above-described elements in all possible variations thereof is encompassed by the invention unless otherwise indicated herein or otherwise clearly contradicted by context.

Claims

1. A liquid curable resin composition comprising:

(B) 1—60 mass% ethylenically unsaturated group-containing compound other than (A),

(C) 0.01-1 mass% dialkylamine having alkyl groups of 3 or 4 carbons, and

(D) 0.01—10 mass% photopolymerization initiator, wherein the total quantity of the composition is 100 mass%.

2. The liquid curable resin composition according to claim 1, wherein component (C) is dibutylamine.

3. The liquid curable resin composition according to claim 1 or 2, wherein component (A) is urethane (meth) acrylate having a structure derived from polypropylene glycol.

4. An optical fiber coating layer obtained by curing the liquid curable resin composition according to any one of claims 1—3 by irradiation.

5. An optical fiber having a coating layer according to claim 4.