JPH07242856A - Resin composition for coating optical fiber - Google Patents

Abstract

PURPOSE: To provide a resin compsn. for covering optical fibers which contains a specific polyether polyol-based urethane oligomer, etc., and has excellent resistances to weather and heat without detriment to its ultraviolet curing rate.

CONSTITUTION: This compsn. comprises (A) a polyether polyol-based urethane oligomer having ethylenic unsatd. groups and a number average mol.wt. of pref. 3,000-12,000 in an amt. of pref. 16-60 wt.%, (B) a reactive diluent [e.g 2-hydroxyethyl (meth)acrylate] in an amt. of pref. 15-60 wt.%, (C) a compd. of formula I (wherein R¹ to R³ are each a monovalent org. group) in an amt. of pref. 0.5-5.0 wt.%, and (D) a compd. of formula II (wherein R⁴ is a monovalent org. group) in an amt. of pref. 0.05-1.0 wt.%.

COPYRIGHT: (C)1995,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultraviolet-curable resin composition for coating an optical fiber.

[0002]

2. Description of the Related Art Glass fibers used for optical fibers are brittle and easily damaged, and therefore are coated with an ultraviolet (UV) curable resin for protection and reinforcement. From the viewpoint of long-term reliability, it is necessary for this UV-curable resin to have a small change in Young's modulus over time, but for that purpose, the content of uncured substances in the UV-curable resin film is low, etc. Is required. That is, the transmission characteristics of the optical fiber are
Since the physical properties of the coating film made of the UV curable resin, specifically Young's modulus, etc. are strongly influenced, the fact that the content of the uncured resin in the UV curable resin is high is higher than that in the case where the content of the uncured resin is low. Change in physical properties over time. The direct cause of this change in physical properties is post-polymerization of uncured resin,
The bleeding from the UV curable resin of the uncured resin may be mentioned.

Conventionally used UV-curable resin compositions for coating optical fibers have a relatively high curing rate, but increase the drawing rate from a molten glass fiber preform in order to improve the productivity of optical fibers. In the subsequent coating process with the UV curable resin, there is a problem that the UV irradiation amount decreases and the content of the uncured resin in the UV curable resin increases.

Further, the resin for coating an optical fiber is generally easily deteriorated by heat and light, and when it is exposed to light such as outdoors or fluorescent lamps or left for a long time under high heat conditions, yellowing or other discoloration or discoloration occurs. And the so-called weather resistance and heat resistance are poor.

In order to impart weather resistance and heat resistance to these, there is a method of adding an additive such as an ultraviolet absorber to the resin composition for coating an optical fiber. However, there is a problem in that the added ultraviolet absorber absorbs ultraviolet rays necessary for curing, resulting in insufficient curing and lowering of curing speed.

[0006]

DISCLOSURE OF THE INVENTION The present invention solves the problems of the conventional UV-curable resin composition for optical fiber coating, has an excellent UV-curing rate, and has excellent heat resistance and weather resistance. A resin composition for coating an optical fiber is provided.

[0007]

That is, the present invention provides the following components (A) to (D): (A) an ethylenically unsaturated group-containing polyether polyol urethane oligomer (B) a reactive diluent (C). ) A compound represented by the general formula (1)

[0008]

[Chemical 3]

(In the above formula, R ¹ , R ² and R ³ may be the same or different and each represents a monovalent organic group) (D) A compound represented by the general formula (2)

[0010]

[Chemical 4]

The present invention provides a resin composition for coating an optical fiber, containing (wherein R ⁴ represents a monovalent organic group).

As the polyether polyol type urethane oligomer having an ethylenically unsaturated group, which is the component (A) used in the present invention, an ethylenically unsaturated group such as a (meth) acryl group is preferably contained in one molecule, preferably 2 units. There may be mentioned polyether polyol-based urethane oligomers having 5 to 5, particularly preferably 2 to 3. The above polyether polyol-based urethane oligomer having an ethylenically unsaturated group has a polyoxyalkylene structure composed of at least one oxyalkylene group having 2 to 10 carbon atoms (hereinafter, simply referred to as "polyoxyalkylene structure").
It can be obtained by reacting a diol having a group, a compound having an ethylenically unsaturated group, and a diisocyanate.

Examples of the diol having a polyoxyalkylene structure include polyethylene glycol, polypropylene glycol, polytetramethylene glycol, polyheptamethylene glycol, polyhexamethylene glycol, polydecamethylene glycol, and two or more ion-polymerizable cyclic compounds. Examples thereof include polyether diols obtained by ring-opening copolymerization. Here, examples of the ion-polymerizable cyclic compound include ethylene oxide, propylene oxide, butene-1-oxide, isobutene oxide, 3,3-bischloromethyloxetane, tetrahydrofuran, dioxane, trioxane, tetraoxane, cyclohexene oxide, styrene oxide, epichlorohydrin. Cyclic ethers such as glycidyl methacrylate, glycidyl methacrylate, glycidyl acrylate, allyl glycidyl ether, allyl glycidyl carbonate, butadiene monooxide, isoprene monoxide, vinyl oxetane, vinyl tetrahydrofuran, vinyl cyclohexene oxide, phenyl glycidyl ether, butyl glycidyl ether, and benzoic acid glycidyl ester. Is mentioned.

Further, the above-mentioned ion-polymerizable cyclic compound and a cyclic imine such as ethyleneimine, a cyclic lactone such as γ-propiolactone and glycolic acid lactide, or a cyclic siloxane such as dimethylcyclopolysiloxane are subjected to ring-opening copolymerization. It is also possible to use polymerized polyether diols. Specific combinations of the two or more types of ion-polymerizable cyclic compounds include tetrahydrofuran and propylene oxide, tetrahydrofuran and 2-methyltetrahydrofuran, tetrahydrofuran and 3-methyltetrahydrofuran, tetrahydrofuran and ethylene oxide,
Examples thereof include propylene oxide and ethylene oxide, butene oxide and ethylene oxide, and the like. Also,
The ring-opening copolymer of two or more ion-polymerizable cyclic compounds may be bonded randomly.

Further, the diol having a polyoxyalkylene structure is, for example, PTMG1000 (manufactured by Mitsubishi Kasei Co., Ltd.), PTMG2000 (same), PPG1000 (manufactured by Asahi Ohrin Co., Ltd.), PPG2000 (same), EXCENO.
L2020 (same), EXCENOL1020 (same), P
EG1000 (Nippon Yushi Co., Ltd.), Unisafe DC110
0 (same), Unisafe DC1800 (same), PPTG2
000 (Hodogaya Chemical Co., Ltd.), PPTG1000
(Same), PTG400 (same), PTGL2000
(The same), Z-4441-1 (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), PB
It can also be obtained as a commercial product such as G2000B (the same).

In the present invention, these diols having a polyoxyalkylene structure may be used in combination with diols and / or diamines having no polyoxyalkylene structure. Here, examples of the diol having no polyoxyalkylene structure include polyester diol, polycaprolactone diol, and polycarbonate diol. Examples of the polyester diol include polyhydric alcohols such as ethylene glycol, propylene glycol, tetramethylene glycol, 1,6-hexanediol, neopentyl glycol, 1,4-cyclohexanedimethanol and phthalic acid, isophthalic acid, terephthalic acid, maleic acid. Examples thereof include polyester diols obtained by reacting an acid, a polybasic acid such as fumaric acid, adipic acid, and sebacic acid. Examples of the polycaprolactone diol include ε-caprolactone and, for example, ethylene glycol, tetramethylene glycol, 1,6
-Hexanediol, neopentyl glycol, 1,4
Examples thereof include polycaprolactone diol obtained by reacting a divalent diol such as butanediol, and as the polycarbonate diol, DN-980 (manufactured by Nippon Polyurethane Co.), DN-981 (the same), DN-982.
(Same), DN-983 (Same), PC-8000 (US P.
PG) and the like. Examples of the diamine include ethylenediamine, tetramethylenediamine, hexamethylenediamine, paraphenylenediamine, 4,4′-diaminodiphenylmethane, and other diamines, diamines containing a hetero atom, and polyetherdiamine.

Examples of the above diisocyanates include 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, 1,3-xylene diisocyanate, 1,4-xylene diisocyanate, 1,5-naphthalene diisocyanate and p-phenylene diisocyanate. 3,3'-dimethyl-4,4'-diphenylmethane diisocyanate, 4,4'-diphenylmethane diisocyanate, 3,3'-dimethylphenylene diisocyanate, 4,4'-biphenylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, dicyclohexyl Methane diisocyanate, methylenebis (4-cyclohexyl isocyanate), hydrogenated diphenylmethane diisocyanate, 2,
2,4-trimethylhexamethylene diisocyanate,
Examples thereof include bis (2-isocyanatoethyl) fumarate, 6-isopropyl-1,3-phenyl diisocyanate, 4-diphenylpropane diisocyanate, and lysine diisocyanate.

Furthermore, examples of the compound having an ethylenically unsaturated group include (meth) acrylic compounds having a hydroxyl group. Examples of the (meth) acrylic compound having a hydroxyl group include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2-hydroxyoctyl (meth) acrylate, and pentaerythritol tri (meth) acrylate.
Acrylate, glycerin di (meth) acrylate, dipentaerythritol monohydroxypenta (meth) acrylate, 1,4-butanediol mono (meth) acrylate, 4-hydroxycyclohexyl (meth) acrylate, 1,6-hexanediol mono (meth ) Acrylate, neopentyl glycol mono (meth) acrylate, trimethylolpropane di (meth) acrylate, trimethylolethanedi (meth) acrylate, and (meth) acrylate represented by the following structural formula.

[0019]

[Chemical 5]

(In the formula, R ⁵ represents a hydrogen atom or a methyl group, and n represents a number of 1 to 5)

The number average molecular weight of the polyether polyol type urethane oligomer having an ethylenically unsaturated group as the component (A) used in the present invention is preferably from 1000 to 15000, and particularly preferably from 3000 to 12000. When the number average molecular weight of the polyether polyol-based urethane oligomer is less than 1000, the elongation at break of the cured product of the resulting composition is reduced, the toughness is likely to be lowered, and when used as a coating material for an optical fiber, If the number average molecular weight exceeds 15,000, it tends to cause transmission loss of the optical fiber, and the viscosity of the composition becomes high, making it difficult to handle.

In the present invention, as the component (A), in addition to the polyether polyol type urethane oligomer having an ethylenically unsaturated group, a polyester polyol type urethane oligomer having an ethylenically unsaturated group, a polycaprolactone polyol type urethane oligomer and the like may be used. Although they can be used in combination, the proportion of the polyoxyalkylene structure in the component (A) is 50 to 98 even in this case.
It is preferably in the range of 60 to 93% by weight, particularly preferably in the range of 70 to 90% by weight. If the proportion of the polyoxyalkylene structure in the component (A) is less than 50% by weight, the Young's modulus of the cured product on the low temperature side increases, which tends to cause transmission loss of the optical fiber when used as a coating material for the optical fiber. .

Further, in the present invention, the proportion of the ethylenically unsaturated group in the component (A) is usually 0.5 to 10% by weight, preferably 1 to 8% by weight.

The component (A) is preferably a polyether polyol type urethane oligomer having an ethylenically unsaturated group, and the ethylenically unsaturated group is particularly preferably a compound having an acryl group.

The blending ratio of the component (A) in the composition of the present invention is preferably 14 to 70% by weight, particularly preferably 16 to 60% by weight. The ratio of component (A) is 14
If it is less than wt%, the elongation at break of the cured product of the composition obtained will be reduced, and if it exceeds 70 wt%, the viscosity of the composition will increase and the handleability will tend to deteriorate.

In the present invention, the reactive diluent of the component (B) is a liquid diluent at room temperature having at least one ethylenically unsaturated group in the molecule which acts as the reactive diluent of the component (A). As a compound, generally, a (meth) acrylate compound having a (meth) acrylic group as an ethylenically unsaturated group is preferably used. In addition, compounds having an allyl group or a vinyl group as the ethylenically unsaturated group can be used. As these reactive diluents, both monofunctional compounds and polyfunctional compounds are used, and when a cured product having a relatively low elastic modulus is desired, mainly monofunctional compounds are used. It is also possible to adjust the elastic modulus of the cured product by using the polymerizable compound in an appropriate ratio. Next, the reactive diluent will be exemplified.

Monofunctional compounds: 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, tetrahydrofurfuryl (meth) acrylate, butoxyethyl (meth) acrylate, ethyldiethylene glycol (meth) acrylate, 2-
Ethylhexyl (meth) acrylate, cyclohexyl (meth) acrylate, phenoxyethyl (meth) acrylate, dicyclopentenyl (meth) acrylate,
Polyethylene glycol (meth) acrylate, polypropylene glycol (meth) acrylate, methyltrimethylene glycol (meth) acrylate, diethylaminoethyl (meth) acrylate, 7-amino-3,7
-Dimethyloctyl (meth) acrylate, isobornyl (meth) acrylate, lauryl (meth) acrylate, vinylpyrrolidone, N-vinylcaprolactam, vinylphenol, acrylamide, vinyl acetate, vinyl ether, styrene, "ARONIX M-114"
(Toagosei Co., Ltd.), "ARONIX M-113"
(The same), "TC-110S" (manufactured by Nippon Kayaku Co., Ltd.), and a (meth) acrylic compound represented by the following general formula:

[0028]

[Chemical 6]

(In the formula, R ⁶ represents a hydrogen atom or a methyl group, R ⁷ represents a hydrogen atom or a methyl group, and R ⁸ represents an alkyl group having 1 to ⁸ carbon atoms or an alkyl group having 1 to 12 carbon atoms. Represents an alkylphenyl group having, m is 1 to 12
The number of)

[0030]

[Chemical 7]

(In the formula, R ⁹ represents a hydrogen atom or a methyl group, and p represents a number of 1 to 3.)

Polyfunctional compounds: trimethylolpropane tri (meth) acrylate, ethylene glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate, polyethylene glycol di (meth)
Acrylate, 1,4-butanediol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, trimethylolpropane trioxyethyl (meth)
Acrylate, tricyclodecane dimethanol di (meth) acrylate, dicyclopentadiene di (meth) acrylate, tricyclodecanyl di (meth) acrylate, trimethylolpropane trioxypropyl (meth) acrylate, tris-2-hydroxyethyl isocyanate Nulate tri (meth) acrylate, Tris-2-
Hydroxyethyl isocyanurate di (meth) acrylate, "Biscoat 3700" (Osaka Organic Co., Ltd.).

Among these reactive diluents, especially lauryl (meth) acrylate, N-vinylcaprolactam,
Isobornyl (meth) acrylate, ARONX M-
113 is preferred.

The mixing ratio of these reactive diluents in the composition of the present invention is preferably 10 to 70% by weight, particularly preferably 15 to 60% by weight.

In the present invention, the component (C) is a compound represented by the above general formula (1). The component (C) is a compound that acts as a photopolymerization initiator when the components (A) and (B) are UV-cured.

In the general formula (1), the monovalent organic group represented by R ¹ , R ² and R ³ is, for example, a methyl group, an ethyl group, a propyl group, a butyl group, an amyl group, a hexyl group or a heptyl group. Group, octyl group, ethylhexyl group, isononyl group, dimethylheptyl group, lauryl group,
Stearyl, cyclopropyl, cyclobutyl, cyclopentyl, methylcyclopentyl, cyclohexyl, methylcyclohexyl, norbornadienyl, adamantyl, dimethyloctyl, dimethylnonyl, dimethyldecyl, phenyl, methylphenyl Group, ethylphenyl group, trimethylphenyl group, tertiary butylphenyl group, ethoxyphenyl group, isopropylphenyl group, methoxyphenyl group, dimethoxyphenyl group, isopropoxyphenyl group, thiomethoxyphenyl group, naphthyl group, thiophenyl group, pyridyl group , Dimethylphenyl group, dimethoxyphenyl group, chlorophenyl group, dichlorophenyl group, dibromophenyl group, chloromethoxyphenyl group, chloromethylthiophenyl group, trimethylphenyl , Trimethoxyphenyl group, tetramethylphenyl group, dimethylbutylphenyl group, naphthyl group, dimethylnaphthyl group, dimethoxynaphthyl group, dichloronaphthyl group, dimethoxynaphthyl group, trimethylpyridyl group, dimethoxyfuran group, trimethylthiophene group, -OY A group represented by (wherein Y is a methyl group,
Ethyl group, isopropyl group, n-propyl group, n-butyl group, amyl group, n-hexyl group, cyclopentyl group,
Cyclohexyl group, phenyl group, naphthyl group, chlorophenyl group, dichlorophenyl group, methylphenyl group, ethylphenyl group, isopropylphenyl group, tertiary butylphenyl group, dimethylphenyl group, methoxyphenyl group, ethoxyphenyl group, dimethoxyphenyl group, thiophenyl Group, pyridyl group and the like), an aliphatic hydrocarbon group which may contain an oxygen atom, an aromatic hydrocarbon group which may contain an oxygen atom and the like can be exemplified.

Of these, a trimethylphenyl group is particularly preferable as R ¹ and a phenyl group is preferable as R ² and R ³ . In the present invention, by using the compound represented by the above general formula (1), which is the component (C), as a photopolymerization initiator, the resin composition for coating an optical fiber can be cured more quickly. Therefore, the productivity of the optical fiber can be improved without affecting the physical properties of the UV curable resin.

In the present invention, a photopolymerizing agent such as benzyl ketal, benzoin ether, benzoin ester or benzophenone may be used in combination as the component (C).

The blending ratio of these components (C) in the composition of the present invention is preferably 0.1 to 10% by weight, particularly preferably 0.5 to 5.0% by weight. If the amount is less than 0.1% by weight, the effect of the present invention cannot be sufficiently exhibited, and 10
Even if it exceeds the weight%, further improvement of the curing speed cannot be expected,
Practically, it is preferably within the above range.

In the present invention, the component (D) is a compound represented by the above general formula (2). This (D) component is
It is a compound that acts as a stabilizer against light and heat of the above-mentioned cured components (A), (B) and (C).

In the above general formula (2), the monovalent organic group represented by R ⁴ is preferably an alkyl group having 1 to 80 carbon atoms, such as a methyl group, an ethyl group, an isopropyl group, an n-propyl group, Examples thereof include n-butyl group, amyl group, n-hexyl group, n-heptyl group, n-octyl group, n-nonyl group, n-decyl group, n-undecyl group and n-dodecyl group. Of these, an n-dodecyl group and an n-octyl group are particularly preferable.

In the present invention, by using the compound represented by the above general formula (2) which is the component (D), the resin for optical fiber coating is weather-resistant, without impairing the curing rate of the resin composition for optical fiber coating, Heat resistance can be imparted.

The blending ratio of the component (D) in the composition of the present invention is preferably 0.05 to 5% by weight, particularly preferably 0.05 to 1.0% by weight. 0.05% by weight
If it is less than the above, the effect of the present invention cannot be sufficiently exerted,
Further, even if it exceeds 5% by weight, the curing rate is lowered, so that it is preferable to be within the above range for practical use.

In the composition of the present invention, other additives such as epoxy resin, polyamide, polyamideimide, polyurethane, polybutadiene, chloroprene, polyether, polyester, pentadiene derivative, SB
SE (styrene / butadiene / styrene block copolymer) and SEBS of the hydrogenated product, SIS (styrene / isoprene / styrene block copolymer), petroleum resin, xylene resin, ketone resin, fluorine-based oligomer, silicone-based oligomer, Polymers or oligomers such as polysulfide-based oligomers can be blended.

Further, various additives other than the above, for example, antioxidants, colorants, ultraviolet absorbers, leveling agents, storage stabilizers, plasticizers, lubricants, solvents, fillers, antioxidants, wettability improvers, coated surfaces. An improving agent and the like can be added as necessary.

The viscosity of the composition of the present invention thus prepared is usually 1000 to 20000 cp / 25 ° C, preferably 2000 to 10000 cp / 25 ° C.

The optical fiber coating resin composition of the present invention can be used for both the primary coating and the secondary coating of an optical fiber, and is particularly preferably used for the primary coating.

[0048]

EXAMPLES The present invention will be further described below with reference to examples. In the following, "parts" means "parts by weight".

Example 1 Copolymerization diol of butene oxide and ethylene oxide having a number average molecular weight of 4000 (PBG20 manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.)
00B) 2 parts, 3 parts of tolylene diisocyanate and 2 parts of 2-hydroxyethyl acrylate were reacted at a ratio of 50 parts of polyether polyol urethane acrylate, 20 parts of isobornyl acrylate as a reactive diluent, and N- 6 parts vinylcaprolactam and Aronix M-113 (Toagosei Co., Ltd.) 21.2
5 parts, and 2,4,6-trimethylbenzoyldiphenylphosphine oxide 1.5 parts, Irganox
1035 (Ciba Geigy) 1.0 part, diethylamine 0.1 part, 2-hydroxy-4-n-dodecyloxy-
Benzophenone (made by Shiraishi Calcium Co., SEESORB
0.15 parts of 103) were blended to obtain a composition A.

Comparative Example 1 A composition B was obtained in the same manner as in Example 1 except that 2-hydroxy-4-n-dodecyloxy-benzophenone was omitted.

Test Example Using the liquid compositions obtained in Example 1 and Comparative Example 1, a test piece was prepared as described below, and its Young's modulus, gel fraction, heat resistance and weather resistance were evaluated. The results are shown in Table 1.

(1) Preparation of test piece: A liquid material was applied onto a glass plate using an applicator bar having a thickness of 150 μm, and 25 mJ / cm ² , 100 mJ / cm ² or 500 m was applied thereto.
A cured film was obtained by irradiating with UV of J / cm ² . Then, peel the cured film from the glass plate, 23 ℃,
A test piece was prepared by adjusting the condition for 24 hours at a relative humidity of 50%. (2) Measurement of Young's modulus (based on JIS K7113):
Using a tensile tester, Young's modulus of the test piece was measured under the conditions of 23 ° C., a pulling speed of 1 mm / min, and a marked line distance of 25 mm.

(3) Gel Fraction: The initial weight of the cured film obtained by irradiating with ultraviolet rays of 500 mJ / cm ² was weighed (the initial weight is W ₀ ), and this was measured using a Soxhlet extractor. Was extracted as a solvent for 12 hours. Then, the film is dried in a vacuum dryer at 50 ° C.
After being dried for 12 hours and then left at room temperature for 1 hour, the weight was weighed (the dry weight is W ₁ ). The gel fraction was calculated from the following formula.

[0054]

[Equation 1]

(4) Heat resistance test: The cured film obtained by irradiating ultraviolet rays of 100 mJ / cm ² was left in a constant temperature bath at 120 ° C. for 7 days and then taken out, and the color difference ΔE of the film was measured. (5) Weather resistance test: A cured film obtained by irradiating with ultraviolet rays of 100 mJ / cm ² was subjected to QU using a UVB-313 lamp.
The film was put in a V-accelerated weathering tester (made by Q-PANEL) for 3 days and then taken out, and the color difference ΔE of the film was measured.

[0056]

[Table 1]

[0057]

EFFECT OF THE INVENTION By using the optical fiber coating resin composition of the present invention, the UV curing rate is not impaired,
It is possible to obtain a resin for coating an optical fiber, which has excellent weather resistance and heat resistance.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Norihiko Saito 2-11-24 Tsukiji, Chuo-ku, Tokyo Japan Synthetic Rubber Co., Ltd. (72) Inventor Mitsufumi Suwa 2-11-24 Tsukiji, Chuo-ku, Tokyo Japan Synthetic Rubber Co., Ltd. (72) Inventor Toru Otaka 2-11-24 Tsukiji, Chuo-ku, Tokyo Japan Synthetic Rubber Co., Ltd. (72) Inventor Takashi Ukaji 2-11, Tsukiji, Chuo-ku, Tokyo No. 24 within Japan Synthetic Rubber Co., Ltd.

Claims (1)

[Claims] 1. The following components (A) to (D): (A) a polyether polyol-based urethane oligomer having an ethylenically unsaturated group (B) a reactive diluent (C) represented by the general formula (1). Compound embedded image (In the formula, R ¹ , R ² and R ³ may be the same or different and each represents a monovalent organic group.) (D) A compound represented by the general formula (2) (In the formula, R ⁴ represents a monovalent organic group), and a resin composition for coating an optical fiber.