JPH11292572A - Photocurable composition for coating optical fiber, optical fiber and method for producing the same - Google Patents

Abstract

(57) [PROBLEM] To provide a light having a very low elastic modulus and a high heat resistance using a photocurable composition which is not affected by oxygen even without introducing an inert gas. To provide a fiber and a manufacturing method thereof. A photocurable composition for coating an optical fiber, comprising at least one diallyl phthalate component, pentaerythritol tetra (3-mercaptopropionate), and a photopolymerization initiator, and a photocurable composition comprising the composition. An optical fiber coated and cured on a drawn glass fiber to form a primary coating.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a photocurable composition for coating an optical fiber, an optical fiber, and a method for producing the same.

[0002]

2. Description of the Related Art Fibers for optical communication (hereinafter referred to as optical fibers) have been steadily used since Corning Glass of the United States first commercialized in 1970 as a new high-capacity, high-speed communication medium replacing copper wire cables. Technological innovation is progressing. Currently, over 80% of Japan's intercity communications are conducted through optical fiber. As described above, since the optical fiber is a thin glass fiber having an outer diameter of about 100 to 150 μm, it is extremely weak unless covered, and breaks with a tensile load of only about 100 g. Glass, unlike metal, is a material that exhibits brittle fracture. Therefore, the fiber is generally coated with a resin in order to protect the surface of the fiber, improve the tensile strength and the bending strength, and make the fiber easy to handle. This coating can be broadly divided into a primary coating for reinforcing the fiber, and a secondary coating further covering the primary coating to protect the glass fiber and facilitate handling. As these coating materials, oligomers such as urethane acrylate, polyester acrylate, and silicon acrylate, and acrylic ester-based monomers are used.

The following characteristics are required for the primary coating material. That is, (1) fast curing and good productivity, (2) low water absorption, (3) good adhesion to glass, (4) excellent heat resistance,
(5) It is required to be liquid at room temperature and have an appropriate viscosity. In recent years, a primary coating material having a lower elastic modulus, for example, 0.3 kgf / mm ² or less has been required. This is because, regardless of the structure of the cable, in order to reduce the increase in transmission loss due to the lateral pressure of the optical fiber, it is better to lower the elastic modulus of the primary coating material. However, in the conventional primary coating material, if the crosslinking density is reduced to lower the elastic modulus, the heat resistance during long-term use is deteriorated, and the amount of generated hydrogen is increased. There were problems with reliability.

In order to solve the above-mentioned problems, as disclosed in JP-A-63-74940, a polyurethane containing a structure comprising a copolymer of a (meth) acrylate compound and a diene compound is mainly used. However, heat resistance was not sufficient. Further, JP-A-8-319139 discloses that
Japanese Patent Application Laid-Open No. 9-143233 discloses a reactive oligomer having a polymer of a (meth) acrylate ester as a main chain, a composition comprising a polymer having an ethylenically unsaturated group, and Japanese Patent Application Laid-Open No. 9-151223. There have been proposed compositions containing a urethane (meth) acrylate oligomer as a main component, but none of them has sufficient elastic modulus and heat resistance. Many other proposals have been made in addition to the above.
In most cases, a photopolymerization initiator is added to a mixture of a compound containing an unsaturated bond based on a photocurable monomer. Frequently used monomers are mainly urethane monomers, acrylic monomers, N
-Vinyl amide monomers, vinyl ether monomers and the like. However, in general, it is difficult to satisfy conflicting elastic modulus and heat resistance performance at the same time in a form in which an acrylic monomer and another monomer are mixed. When a urethane-based monomer is used, heat resistance is improved, but it is difficult to reduce the elastic modulus to a desired low level.

Further, the conventional ultraviolet curable resin has a problem that, if oxygen is present at the time of curing, it generally reacts with oxygen and the curing is insufficient. In order to prevent this, Japanese Patent Application Laid-Open No. Hei 6-212545 has adopted a method in which an inert gas is passed through a glass tube to be cured. Also, JP-A-7-165443 and JP-A-7-315886.
Japanese Patent Application Laid-Open Publication No. H11-163873 discloses that measures are taken to prevent the resin from adhering to the glass tube by improving the exhaust hole of the glass tube through which the inert gas flows. In any case, the introduction of an inert gas has conventionally been indispensable to complete the ultraviolet curing. However, if the resin of the coating material can be cured at room temperature in the air without providing these inert gas introduction devices, the facility cost can be greatly reduced, and the cost of the inert gas can be reduced. Can also be saved.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems of the prior art, to prevent oxygen inhibition even without introducing an inert gas, to have a very low elastic modulus, and to provide heat resistance. It is an object of the present invention to provide a photocurable composition for coating an optical fiber capable of forming a film having a high degree of stiffness, an optical fiber having a primary coating formed using the same, and a method for producing the same.

[0007]

SUMMARY OF THE INVENTION The present invention provides at least one
An object of the present invention is to provide a photocurable composition for coating an optical fiber, comprising: a kind of diallyl phthalate component, pentaerythritol tetra (3-mercaptopropionate) and a photopolymerization initiator. The present invention further provides an optical fiber having a primary coating comprising the above-described photocurable composition on a drawn glass fiber. The optical fiber of the present invention can be manufactured by applying the above-described photocurable composition on a drawn glass fiber and curing the composition to form a primary coating.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The diallyl phthalate component used in the composition of the present invention includes diallyl orthophthalate,
There are three isomers, diallyl isophthalate and diallyl terephthalate. In the present invention, at least one of them may be used. The difference between the isomers is
As can be seen from the thermal properties after curing, it is preferable that all or the main component of the diallyl phthalate component be diallyl ortho phthalate in consideration of compatibility between high heat resistance and low elastic modulus.

In the composition of the present invention, at least one
Of various diallyl phthalate components and pentaerythritol tetra (3-mercaptopropionate)
It is preferable to use an equivalent ratio of 1: 3. If both components are blended at a ratio outside this equivalence ratio range, it will not be polymerized and will not serve as a coating material. 1.5: 1 equivalent ratio
The ratio is more preferably from 1: 1.5 in terms of uniformity of the cured product and polymerizability.

[0010] The composition of the present invention further contains a photopolymerization initiator. This photopolymerization initiator is contained in the composition in an amount of 0.005 to 0.005.
Preferably, it is contained in a proportion of from 10 to 10% by weight. When the addition amount of the photopolymerization initiator is less than 0.005% by weight, a sufficient reaction for curing does not occur, unreacted materials remain, and desired performance cannot be obtained. After the addition of the photopolymerization initiator, the reaction occurs rapidly, and the stability as a solution is impaired.

As the photopolymerization initiator that can be used in the present invention, any known photopolymerization initiator may be used as long as it generates a radical by light and reacts with the radical polymerizable unsaturated group. Examples of such photopolymerization initiators include, for example, benzoin, benzoin ethyl ether, benzoin propyl ether, benzoin isopropyl ether, benzoin isobutyl ether, benzyl dimethyl ketal, acetophenone diethyl ketal, 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy -2-methyl-1-phenylpropan-1-one, 2,
4,6-trimethylbenzoyldiphenylphosphine oxide, 1- (4-isopropylphenyl) -2-hydroxy-2-methylpropan-1-one, 2-methyl-
1- [4- (methylthio) phenyl] -2-morpholino-propan-1-one, 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butane-1-
ON, anthraquinone, 2-methylanthraquinone, 2
-Ethylanthraquinone, 2,2-dimethoxy-2-phenylacetophenone, 3-methylacetophenone,
N, N-dimethylaminoacetophenone, benzophenone, 4-phenylbenzophenone, 4,4'-dimethoxybenzophenone, 4,4'-diaminobenzophenone, 4,4'-bis (dimethylamino) benzophenone, 4,4'-bis ( Diethylamino) benzophenone, 3,3′-dimethyl-4-methoxybenzophenone, 4-chlorobenzophenone, isophthalophenone,
4-benzoyl-4′-methyl-diphenyl sulfide, xanthone, fluorenone, benzaldehyde, fluorene, thioxanthone, 2,4-diethylthioxanthone, 2-isopropylthioxanthone, 2-chlorothioxanthone, triphenylamine, carbazole,
Michler's ketone, benzoin propyl ether, 2,
4,6-trimethylbenzoyldiphenylphosphine oxide, bis (2,6-dimethoxybenzoyl)-
Examples thereof include 2,4,4-trimethylpentylphosphine oxide, and these can be used alone or in combination of two or more.

If necessary, a photosensitizer or a hydrogen donor can be used together with these photopolymerization initiators. Examples of photosensitizers and hydrogen donors include triethylamine, diethylamine, ethanolamine, methyldiethanolamine, triethanolamine, dimethylaminoethanol, diethylaminoethyl (meth) acrylate, p-dimethylaminoacetophenone,
Dimethylaminobenzoic acid, methyl 4-dimethylaminobenzoate, ethyl 4-dimethylaminobenzoate, isoamyl 4-dimethylaminobenzoate, ethyl 4-diethylaminobenzoate, N, N-dimethylbenzylamine, triphenylphosphine, p- Thioglycol and the like. These photosensitizers and hydrogen donors may be used alone or in combination of two or more.

[0013] In addition to the above essential components, the photocurable composition for coating an optical fiber of the present invention contains various additives such as a thermal polymerization inhibitor, an antioxidant, a light stabilizer, a plasticizer, and a surfactant. , Silane coupling agent, chain transfer agent, anti-aging agent,
Leveling agents, storage stabilizers, solvents, fillers and the like can be added. These additives must be used within a range that does not impair the effects of the present invention.

The photocurable composition for coating an optical fiber of the present invention has a very low elastic modulus and a high heat resistance, and is therefore suitable for use as a primary coating for optical fibers. The primary coating is
The photocurable composition can be formed by applying the photocurable composition to glass fibers and curing the composition. For curing, X-ray,
Although ionizing radiation such as an electron beam can be used, it is preferable to use actinic rays such as ultraviolet rays. The photocurable composition cures quickly even with a small amount of irradiation of actinic rays such as ultraviolet rays and exhibits high curability, and is therefore useful for improving the productivity of a coating material. Moreover, the cured product cured by light irradiation is excellent in flexibility (low elastic modulus) and resistant to expansion and contraction, so that it is particularly useful as a material for protecting an optical fiber. When used as a coating material for optical fibers, transmission loss due to microbending and lateral pressure is suppressed,
There is an advantage that it can be used for a long time.

Next, the present invention will be described in more detail with reference to the drawings. FIG. 1 is a sectional view of the optical fiber of the present invention. The optical fiber of the present invention has a primary coating 2 and a secondary coating 3 formed on a glass fiber 1 using the above-described photocurable composition. In the optical fiber of the present invention, the primary coating preferably has a thickness of 10 to 200 μm. When the thickness of the primary coating is less than 10 μm, sufficient elasticity cannot be obtained, and when the thickness exceeds 200 μm,
It is difficult to process to a uniform thickness.

The coating material for the secondary coating is not particularly limited. Generally, a coating material having a higher elastic modulus and mechanical strength than the primary coating is used, and conventionally known materials which require the introduction of an inert gas during the curing reaction are used. Can be used.
The thickness of the secondary coating is preferably between 5 and 100 μm. If the thickness of the secondary coating is less than 5 μm, sufficient mechanical strength cannot be obtained, and if it exceeds 100 μm, it becomes difficult to work to a uniform thickness.

FIG. 2 is a schematic system diagram of an apparatus for implementing the method of manufacturing an optical fiber according to the present invention. The preform is heated and melted in a drawing furnace (only a resistance heating furnace is shown in FIG. 2) including a preform feeding device and a resistance heating furnace, and spun into a glass fiber. Preform 10
It is heated and melted in a resistance heating furnace 11, spun, and adjusted to a predetermined outer diameter by a fiber outer diameter measuring device 12. A coating applicator 1 is applied to the glass fiber thus drawn.
The above-mentioned photocurable composition is applied in 3 and the coating layer is cured by irradiating ultraviolet rays with an ultraviolet irradiating device 15 while collating the positions of the fibers with a positioning mirror 14, and is wound via a capstan roller 16. The optical fiber is wound by 17.

The coating applicator 13 used at this time has a structure as shown in FIG. 3, and has a structure in which a small hole is formed at the tip of a cone-shaped metal container having a taper so as to penetrate the fiber. That is, the coating applicator 13 is provided with the supply port 1 for the photocurable composition.
8 and glass fiber through-holes 19 and 20. A coating layer having a predetermined thickness is obtained by adjusting the diameter, the taper angle, and the viscosity of the photocurable composition of the glass fiber through-hole. When coated with the photocurable composition used in the present invention, it is not necessary to introduce an inert gas or the like into the curing device (the ultraviolet irradiation device 15 in FIG. 2).

[0019]

Next, the present invention will be described in more detail with reference to Examples, but the present invention is not limited thereto.

Example 1 96.6 parts by weight of diallyl orthophthalate, pentaerythritol tetra (3-mercaptopropionate) 1
33.4 parts by weight, 2-hydroxy- as a photopolymerization initiator
2-methyl-1-phenylpropan-1-one (Ciba.
Manufactured by Specialty Chemicals Co., Ltd., trade name, Darocur 1173) 1.0 part by weight and 2-methyl-1-
1.0 parts by weight of [4- (methylthio) phenyl] -2-morpholino-propan-1-one (trade name, Irgacure 907, manufactured by Ciba Specialty Chemicals Co., Ltd.) is mixed in a dark place to form a photocurable composition. I got something. The following evaluation was performed about the obtained photocurable composition. The results are shown in Table 1.

[Evaluation Method] Elastic Modulus The photocurable composition was coated on a glass plate with a dry coating thickness of 150 ±
After coating so as to have a thickness of 30 μm, the irradiation intensity is 1000 mJ / c using a 100 W / cm metal halide lamp.
and cured at m ^2. The elastic modulus of this cured film was measured according to JIS K7113-1981 at 23 ° C. and 50% relative humidity. Heat resistance The photocurable composition is applied on a glass plate with a dry coating thickness of 150 ±
After coating so as to have a thickness of 30 μm, the irradiation intensity is 1000 mJ / c using a 100 W / cm metal halide lamp.
and cured at m ^2. The cured film was immersed in a thermostat at 120 ° C. for 10, 20, 40 and 80 days, and then the elastic modulus was measured in the same manner as described above. This measured value was divided by the initial value (the value before immersion), and the degree of deterioration due to heat was examined. The number indicates that the heat resistance is better as the number is closer to “1”.

Example 2 The photopolymerization initiator was 2-benzyl-2-dimethylamino-1
-(4-morpholinophenyl) -butan-1-one (trade name, manufactured by Ciba Specialty Chemicals Co., Ltd.)
(Irgacure 907) The test was performed in the same manner as in Example 1 except that the weight was changed to 2.0 parts by weight. Table 1 shows the results.

Example 3 96.6 parts by weight of diallyl isophthalate, pentaerythritol tetra (3-mercaptopropionate) 10
3.4 parts by weight, 2-hydroxy-2 as a photopolymerization initiator
1.0 part by weight of -methyl-1-phenylpropan-1-one (trade name, Darocure 1173, manufactured by Ciba Specialty Chemicals Co., Ltd.) and 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) 1.0 part by weight of butan-1-one (trade name, Irgacure 369, manufactured by Ciba Specialty Chemicals Co., Ltd.) was mixed in a dark place, and the obtained photocurable composition was treated in the same manner as in Example 1. The test was performed and evaluated in the same manner. Table 1 shows the results.

Example 4 A test was conducted in the same manner as in Example 2 except that 96.6 parts by weight of diallyl terephthalate was used instead of diallyl orthophthalate, and the results are shown in Table 1.

Comparative Example 1 1 mol of a copolymer of 1,2-butylene oxide and tetrahydrofuran (number-average molecular weight 3000), 2 mol of 2,4-tolylene diisocyanate, and a trace amount of dibutyltin dilaurate as a catalyst were stirred under nitrogen gas reflux under stirring. At 70 ° C. for 2 hours in a vessel with a reaction. Next, 2 mol of 2-hydroxypropyl acrylate, a trace amount of t-butylhydroquinone and a trace amount of dibutyltin dilaurate as a polymerization inhibitor were added, and the mixture was further reacted at 70 ° C. until almost no isocyanate groups were present. 50 parts by weight of nonylphenoxypolypropylene glycol monoacrylate and 2 parts by weight of 2,4,6-trimethylbenzoyldiphenylphosphine oxide were mixed and stirred at 60 ° C. for 2 hours with 50 parts by weight of the thus obtained oligomer to obtain a photocurable composition. Was. Table 1 shows the results of the evaluation of the photocurable composition obtained above.

[0026]

[Table 1]

Example 5 96.6 parts by weight of diallyl orthophthalate, pentaerythritol tetra (3-mercaptopropionate) 1
33.4 parts by weight, 2-hydroxy- as a photopolymerization initiator
2-methyl-1-phenylpropan-1-one (Ciba.
Manufactured by Specialty Chemicals Co., Ltd., trade name, Darocur 1173) 1.0 part by weight and 2-methyl-1-
1.0 part by weight of [4- (methylthio) phenyl] -2-morpholino-propan-1-one (trade name, Irgacure 907, manufactured by Ciba Specialty Chemicals Co., Ltd.) was mixed in a dark place to form a photocurable composition. I got something. Glass fibers were manufactured by a drawing method using the apparatus shown in FIG. In the step of primary coating, the photocurable composition prepared above was applied to a thickness of 70 μm while being drawn on the outer periphery of a glass fiber having an outer diameter of 125 μm at a drawing speed of 200 m / min, and cured by irradiating ultraviolet rays. Further, in a separate step, the primary-coated fiber was coated with a composition mainly composed of an epoxy acrylate-based photocurable resin to form a secondary coating, thereby obtaining an optical fiber having an outer diameter of 465 μm. When the obtained optical fiber was squeezed with a wire having a diameter of 1 mm and the interface between the glass fiber and the coating material was observed for peeling, no peeling was observed.

Example 6 As a photopolymerization initiator, 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butan-1-one (trade name, Irgacure 369, manufactured by Ciba Specialty Chemicals Co., Ltd.) ) An optical fiber was obtained in the same manner as in Example 5, except that 2.0 parts by weight was used. When the obtained optical fiber was evaluated in the same manner as in Example 5, no peeling was observed.

Comparative Example 2 The procedure of Example 5 was repeated except that a liquid UV-curable composition containing urethane acrylate as a main component and an acetophenone-based photopolymerization initiator were used as a coating material for the glass fiber. The operation produced the optical fiber. However, the curable composition was not completely cured due to oxygen inhibition during ultraviolet curing, and the coating material of the obtained optical fiber was easily peeled from the glass.

Comparative Example 3 An optical fiber was manufactured under the same conditions as in Comparative Example 2 by changing the drawing speed to 50 m / min. As a result, the coating material was easily peeled off the glass because of oxygen inhibition. This comparative example shows that curing is not performed due to the influence of oxygen even when the drawing speed is reduced so that the photocurable composition is sufficiently irradiated with ultraviolet rays.

[0031]

The photocurable composition of the present invention is cured by irradiation with actinic rays at room temperature in the air, and is not hindered by oxygen during the curing. It is possible to form a primary coating having high adhesion, very low elastic modulus, and high heat resistance. Therefore, according to the method for manufacturing an optical fiber of the present invention, the manufacturing equipment can be greatly reduced, the cost for the inert gas can be saved, and a high-speed, efficient and highly reliable optical fiber can be manufactured. can do. The optical fiber of the present invention has extremely small transmission loss due to microbending and lateral pressure, and maintains high reliability even when used for a long period of time.

[Brief description of the drawings]

FIG. 1 is a sectional view of an optical fiber of the present invention.

FIG. 2 is a schematic system diagram of an optical fiber manufacturing apparatus.

FIG. 3 is a cross-sectional view of a coating applicator in the optical fiber manufacturing apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Glass fiber 2 Primary coating 3 Secondary coating 10 Base material 11 Resistance heating furnace 12 Fiber outer diameter measuring device 13 Coating applicator 14 Alignment mirror 15 Ultraviolet irradiation device 16 Capstan roller 17 Winding machine 18 Photocurable composition Supply port of 19 Glass fiber through hole 20 Glass fiber through hole

Claims (4)

[Claims] 1. A photocurable composition for coating an optical fiber, comprising at least one diallyl phthalate component, pentaerythritol tetra (3-mercaptopropionate) and a photopolymerization initiator. 2. The photocurable composition for coating an optical fiber according to claim 1, comprising a diallyl phthalate component and pentaerythritol tetra (3-mercaptopropionate) in an equivalent ratio of 3: 1 to 1: 3. 3. An optical fiber having a primary coating comprising the photocurable coating composition according to claim 1 on a drawn glass fiber. 4. A method for producing an optical fiber, comprising applying the photocurable coating composition according to claim 1 onto a drawn glass fiber and curing the composition to form a primary coating.