JP3223372B2 - Photocurable resin composition and plastic clad optical fiber using the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION TECHNICAL FIELD OF THE INVENTION

The present invention relates to a photocurable resin composition and a plastic clad optical fiber having a cured product thereof as a clad.

[Prior art]

Conventionally, as a cladding material of a plastic clad optical fiber, silicone resin (JP-A-58-30703), polyfluoroalkyl methacrylate copolymer (JP-A-61-66706), vinylidene fluoride / tetrafluoroethylene copolymer have been used. A polymer (JP-B-56-41966) is known. However, these clad materials cannot meet recent advanced requirements such as low loss of the optical fiber and simplification of connector attachment by a crimping method. For example, with a silicone resin, terminal treatment cannot be performed by attaching a crimp-type connector due to insufficient mechanical strength. Vinylidene fluoride / tetrafluoroethylene copolymer is
Poor transparency makes it impossible to reduce the loss of the optical fiber. In addition, polyfluoroalkyl methacrylate copolymer is excellent in transparency, but has a low softening point,
When a crimp-type connector is used, the strength between the fiber connectors is significantly reduced at a high temperature. On the other hand, in recent years, a clad material using an ultraviolet curable resin composition has been proposed as disclosed in Japanese Patent Application Laid-Open No. 62-250047 and U.S. Pat. No. 4,707,076. Since these resin compositions have a crosslinked structure by ultraviolet curing, they have advantages over conventional compositions, such as excellent mechanical strength and improved production speed of optical fibers.

[Problems to be solved by the invention]

However, since these resin compositions contain a compound having only one unsaturated bond in the molecule (such as a monofunctional acrylate), the crosslink density is not sufficient, so that the hardness and heat resistance are low. (Softening temperature) is not yet sufficiently high for practical use, and the mechanical properties of the optical fiber at high temperatures are significantly reduced. Furthermore, since the crosslinking density is insufficient, the softening of the resin due to the swelling of water under high humidity is remarkable. In particular, the holding force between the optical fiber and the connector in the crimping type connector significantly decreases at high temperature or high temperature and high humidity. Furthermore, there is a disadvantage that the core protrudes from the distal end of the connector after being left at a high temperature or high temperature and high humidity or after a heat cycle load. It is thought that such a disadvantage is due in part to the low crosslink density of the resin composition due to the inclusion of the monofunctional unsaturated compound in the composition, and therefore the low softening temperature. In addition, the cured product of this resin composition increases the crosslink density and becomes brittle, so that the effect of improving the mechanical properties due to the increase in the crosslink density cannot be fully utilized and the expected properties have not been achieved. there were.

[Means for Solving the Problems]

Therefore, the present invention provides (i) a compound having at least two unsaturated bonds in a molecule and not containing a urethane bond, and (ii) a compound having at least two unsaturated bonds in a molecule. Containing at least one urethane bond,
formula: A cured product of a photocurable resin composition containing at least one compound represented by the formula (iii) and a photopolymerization initiator and containing no compound having only one unsaturated bond in the molecule. It is intended to solve such a problem by using the above. That is, an object of the present invention is to provide a plastic-clad optical fiber which excels in mechanical strength and which does not reduce mechanical properties, especially the holding force between the crimping connector and the optical fiber even at high temperatures. The present invention seeks to improve the mechanical strength and softening temperature by improving the crosslink density of the composition, and to further reduce the amount of water swelling under high humidity. Since it contains a compound having a urethane bond, the cured composition does not become brittle even if the crosslink density is improved. The photocurable composition of the present invention is superior in mechanical strength to a conventional composition containing no urethane bond, and an optical fiber using a cured product of the composition of the present invention in a clad is a conventional one. The holding force between the fiber and the connector by the crimp-type connector is stronger than that of the connector.

BEST MODE FOR CARRYING OUT THE INVENTION

The unsaturated bond in the present invention means a carbon-carbon double bond, and examples thereof include a vinyl group, an allyl group, an acryl group and a methacryl group having excellent reactivity. In addition, in order for the cured product of the composition to function as a clad, the refractive index must be equal to or less than the refractive index of the core material. For this purpose, the compound of the present composition can contain a fluorine atom. The composition according to the present invention is uniformly applied to the core glass, and is applied to a thin wall of 1 to 100 μm.
Desirably, it is ~ 10000cps. For this reason, it is desirable to use a polymer having an appropriate degree of polymerization for the compound having a urethane bond of the present invention. As a compound having such a urethane bond, polyurethane (meth) acrylate can be given. This polyurethane (meth) acrylate can contain either or both of polyester and polyether in the molecule. It can also include polycarbonate. This polymer may contain a fluorine atom so that the cured product of the composition has an appropriate refractive index. Next, as a compound having two or more unsaturated bonds in a molecule and not containing a urethane bond, the following compounds having two or more (meth) acryloyl groups in a molecule can be mentioned: 4-butanediol di (meth) acrylate, ethylene glycol di (meth) acrylate, glycerol dimethacrylate, tetraethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, 1,3-butylene glycol di (meth) acrylate, Neopentyl glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, triglycerol diacrylate, 1,6-hexanediol di (meth) acrylate, tripropylene glycol diacrylate, manufactured by Nippon Kayaku Co., Ltd .: Trade name Kayalad MANDA, Kaya Head R-604, trimethylolpropane tri (meth) acrylate, pentaerythritol triacrylate, pentaerythritol tetra (meth) acrylate, ditrimethylolpropane tetraacrylate, dipentaerythritol hexaacrylate. Next, having at least two unsaturated bonds in the molecule,
The compound containing a fluorine atom has a general formula: [Wherein, R ¹ represents hydrogen or a methyl group, and Rf represents a fluorine-containing organic group. n is a number of 2 or more, preferably 2 to 5. ], And preferably a compound represented by the following formula: [In the formula, R ¹ and R ² represent hydrogen or a methyl group, x represents 1 or 2, and y represents an integer of 2 to 6. ] The compound shown by these is mentioned. The kinds of these compounds constituting the composition and the composition ratio thereof can be selected so as to give necessary cured physical properties. Preferably, the viscosity before curing 100～10000Cps, breaking strength after curing 1.0 kg / mm ² or more, a Young's modulus 10 kg / mm ² or more, elongation at break of 10% or more and less refractive index of 1.44, and a wavelength It is desirable that the transmittance at 850 nm be 90% or more (0.1 mm thick). Next, as the photopolymerization initiator, a compound which easily generates a radical upon irradiation with ultraviolet rays is desirable, and the following compounds can be mentioned. The preferred addition amount is 0.01 to 10% by weight. Benzophenone, acetophenone, benzyl, benzoin, benzoin methyl ether, benzoin isobutyl ether, benzyl dimethyl ketal, α, α'-azobisisobutyronitrile, benzoyl peroxide, 1-hydroxycyclohexyl phenyl ketone, 2,
2-dimethoxy-2-phenylacetophenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one. In particular, when used as a cladding material for an ultraviolet light guiding fiber, 1-hydroxycyclohexyl phenyl ketone or 2-hydroxy-2-methyl-1-phenylpropan-1-one is preferred. Further, a coupling agent for improving adhesion to the core glass can be included as at least one of the compounds constituting the composition of the present invention. As a coupling agent,
Those which have high compatibility with the composition of the present invention, are colorless and transparent, and preferably have the same refractive index as the composition of the present invention are desirable. Addition of the coupling agent improves the fiber strength, improves the holding power between the crimp-type connector and the optical fiber under high temperature and high temperature and high humidity, and improves the holding strength after leaving at high temperature, high temperature and high humidity, and after heat cycle load. The amount of core protrusion from the connector tip can be reduced. Preferred coupling agents include monomers such as diethoxydivinylsilane and dimethoxydivinylsilane, and these monomers and (meth) acrylates having an unsaturated bond in an ester side chain as shown in the following formula (III). Can be mentioned. [Wherein, R ¹ is hydrogen or a methyl group, Rf is a fluoroalkyl group, Rx is a hydrocarbon group having an unsaturated bond, R is hydrogen, a methyl group, an ethyl group or a propyl group, Z is a single bond, or Represents an organic group consisting of carbon, hydrogen and oxygen. As the group Z consisting of carbon, hydrogen and oxygen,-(CH
_{2) n} - or _{- (CH 2) n - (} CF 2) m -, or -COO
— (CH ₂ ) _n —. (M and n are integers from 1 to 10) When the composition of the present invention is used as a cladding of a plastic clad optical fiber, the composition is coated on a core made of quartz or optical glass by a die coating method or a spray coating method. May be applied and cured by irradiation with active light such as ultraviolet rays. The irradiation dose can be appropriately determined according to the type and amount of the compound contained in the composition. Next, an example is shown and the present invention is explained concretely.

【Example】

Polymer (I) is used as a polymer having two or more unsaturated bonds and urethane bonds in the molecule, and
The compounds shown in the table were mixed at a predetermined ratio to prepare a clad material composition. The numerical values in Table 1 are parts by weight. Immediately after the quartz rod is drawn to an outer diameter of 200 μm, these resin compositions are applied and UV-cured under a nitrogen atmosphere.
An optical fiber of 230 μm was obtained. Furthermore, after extruding and coating an ethylene tetrafluoroethylene copolymer with an outer diameter of 500 μm on these optical fibers, Kevlar ™ (K
EVLAR) was applied vertically to the periphery, and polyvinyl chloride was further extruded and coated in a loose shape to an outer diameter of 2.2 mm to obtain an optical fiber cord. The physical properties when the crimping type optical connector was attached to these optical fibers and optical fiber cords were as shown in Table 2. Comparative Examples 1 to 3 Polymers (II) to (IV) having two or more unsaturated bonds in the molecule and no urethane bond were used, and a resin composition having the composition shown in Table 1 below was used. Prepared.

[Table 1] Using these compositions, an optical fiber was manufactured in the same manner as in the example, and an optical fiber cord having the same structure as the example was carefully manufactured under the same conditions. The physical properties when the crimping type optical connector was attached to these optical fibers and optical fiber cords were as shown in Table 2.

[Table 2]

【The invention's effect】

As described above, the optical fiber using the photocurable composition according to the present invention for the clad has excellent mechanical properties, and in particular, there is little decrease in physical properties at high temperatures. That is, the holding force between the crimp-type connector and the optical fiber is large even at high temperatures (85 ° C. or higher), and the amount of core protrusion from the connector tip after standing at high temperature or high temperature and high humidity or after a heat cycle load is small. . Therefore, for example, it is effective as an optical fiber for a short-distance optical communication system while it is used under high temperature and high humidity with a crimp type connector attached.

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 ──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Hiroaki Nishimoto 1-3-1, Shimaya, Konohana-ku, Osaka-shi, Osaka Sumitomo Electric Industries, Ltd. Osaka Works (56) References JP-A-2-255711 (JP, A )

Claims (2)

(57) [Claims] 1. An optical fiber having a silica-based or optical glass core as a core and a plastic having a lower refractive index than the core as a clad, wherein the clad material has (i) at least two unsaturated bonds in a molecule; At least one compound containing no urethane bond, and (ii) a compound having at least two unsaturated bonds in the molecule and containing at least one urethane bond: And (iii) a photopolymerization initiator, and a cured product of a photocurable resin composition containing no compound having only one unsaturated bond in the molecule. A plastic-clad optical fiber, characterized in that: 2. A compound (i) having at least two unsaturated bonds in a molecule contained in the photocurable resin composition and containing no urethane bond, has a general formula: [In the formula, R ¹ is a hydrogen or methyl group, Rf is a fluorine-containing organic group, and n represents a number of 2 or more. The plastic clad optical fiber according to claim 1, which is a compound represented by the following formula: