KR19990061687A - Resin Composition for Optical Fiber Inner Coating - Google Patents

Abstract

The present invention relates to a resin composition for coating an optical fiber, and more particularly, to a monofunctional monomer, a silane monomer, and two acyl functional groups having a urethane acrylate oligomer as a main component and including one acrylate functional group. Phosphine oxide-based photopolymerization initiator containing is contained in an appropriate content ratio, while maintaining the tear strength and elongation at break, excellent adhesion to the glass fiber and moisture resistant effect, and induces rapid curing, the resin composition for coating the optical fiber inside will be.

Description

Resin Composition for Optical Fiber Inner Coating

The present invention relates to a resin composition for coating an optical fiber, and more particularly, to a monofunctional monomer, a silane monomer, and two acyl functional groups having a urethane acrylate oligomer as a main component and including one acrylate functional group. Phosphine oxide-based photopolymerization initiator containing is contained in an appropriate content ratio, while maintaining the tear strength and elongation at break, excellent adhesion to the glass fiber and moisture resistant effect, and induces rapid curing, the resin composition for coating the optical fiber inside will be.

With the development of the electronics, information, and telecommunications industries, interest in optical fibers, which is emerging as an important basic material for these industries, is increasing day by day. Since the optical fiber is made of quartz-based glass, it is very weak to external impact. Thus, the optical fiber is coated with a coating agent to minimize deformation or loss of the optical signal during optical signal transmission. However, the coating agent coated on the optical fiber causes defects between the optical fiber and the coating layer due to microbending of the optical fiber as the external temperature is changed, thereby causing a transmission loss. In particular, this phenomenon occurs more severely at low temperatures. In order to solve this problem, the coating layer should have a very low modulus, but another problem that the tear strength of the surface is weakened by imposing a low modulus.

In order to increase the tear strength of the exposed coating layer to prevent the surface damage from the outside by introducing a double coating layer to the outer coating on top of the inner coating layer again.

Therefore, conventionally, the optical fiber is the outer coating of the surface again with a coating agent having another property on the inner coating layer. In the case of the internal coating, since it is in direct contact with the quartz glass, the physical properties of the coating on the optical fiber can be said to be absolute.

In general, the internal coating should have proper adhesion to the quartz-based glass and must be able to overcome the microbanding phenomenon caused by external shock or temperature change by maintaining soft and tough physical properties. In addition, the internal coating should not cause light loss or deterioration of properties due to a decrease in adhesion due to external environmental changes.

Generally, photocurable urethane coating agents are widely known as internal coating agents for optical fibers (US Pat. Nos. 2,948,611 and 3,891,523). U.S. Patent No. 3,437,514 describes a method of reacting a polyol with an excess of diisocyanate and then forming at the end a functional group having a carbon-carbon double bond containing hydroxy. U. S. Patent No. 4,624, 994 describes a composition for coating an optical fiber inside consisting of a urethane acrylate having a polyol as a main component, which has a problem in adhesion to glass.

In general, a resin composition containing urethane acrylate as a main component has a small adhesive force to glass, so that polysiloxene is used as a main component instead of urethane acrylate. However, polysiloxene has a weak tear strength of the cured resin and a low curing rate due to ultraviolet rays, so that when used as an internal coating agent of the optical fiber, there is a problem in high speed curing and stability of the resin. Therefore, there is a need for a composition for coating an optical fiber inside that has a new composition capable of enhancing adhesion to glass while using urethane acrylate rather than containing polysiloxene as a main component.

In the present invention, the urethane acrylate oligomer is blended as a main component to maintain tear strength and elongation at break, and to contain a monofunctional monomer containing one acrylate functional group in an appropriate content ratio so as to provide a low glass transition temperature (T _g). ), A small amount of vinyltrimethoxysilane monomer is added to increase adhesion to glass, prevents moisture, and phosphine oxide-based photopolymerization initiator containing two acyl functional groups The present invention has been completed by facilitating and promoting external hardening to have a strong affinity for glass as well as facilitating the application of an optical fiber outer coating.

Accordingly, an object of the present invention is to provide a urethane acrylate-based composition for coating inside an optical fiber that has excellent adhesion to glass, excellent moisture prevention effect, and induces rapid curing.

30 to 70% by weight of the urethane acrylate oligomer having a number average molecular weight of 6,000 to 20,000; 20 to 60% by weight of a monofunctional monomer containing one acrylate functional group; 0.1 to 10% by weight of silane monomers; And a resin composition for coating the inside of the optical fiber containing 0.1 to 10% by weight of a phosphine oxide-based photopolymerization initiator containing two acyl functional groups.

Referring to the present invention in more detail as follows.

The resin composition according to the present invention contains a polyurethane oligomer as a main component, which is contained within the range of 30 to 70% by weight in the total resin composition. In addition, the physical and chemical properties of the polyurethane oligomer used in the present invention are as follows.

(1) The number average molecular weight distribution is in the range of 6,000 to 20,000, preferably in the range of 8,000 to 15,000 and has a carbon-carbon double bond at the sock end.

(2) One urethane group is contained per molecular weight of 300 to 900 units, preferably 400 to 600 units. That is, a functional group capable of inducing an appropriate amount of tear strength is appropriately disposed in the oligomer chain. As the functional group, the urethane group is excellent, but an amide or urea functional group may be used. The type of functional group is also important, but the amount of distribution in the oligomer chain is also very important.

(3) The polyalkylene functional group having 2 to 6 carbons is contained 40 to 80% by weight, preferably 50 to 75% by weight of the total oligomer weight. The polyalkylene functional group is a polyalkylene polyether, polyalkylene polysulfide or polyalkylene polyester, and the polyalkylene functional group is in the range of 300 to 2,000 molecular weight, preferably 600 to 1,200. The polyalkylene functional group contributes to the improvement of tensile force so that the oligomer absorbs the stress caused by excessive load or extreme temperature change.

In addition to the above-mentioned polyurethane oligomer, it contains a monofunctional monomer and a silane monomer in which one acrylate functional group is contained as a monomer.

The monofunctional monomer containing one acrylate functional group has a carbon-carbon double bond functional group, which enables radical polymerization, and hydrogen crosslinking with glass fibers. In general, the use of a crosslinking agent increases the tensile strength, but drops the tensile force rapidly and hardens at low temperatures and bends at high temperatures. However, the addition of a hydrogen-bondable monofunctional monomer according to the present invention forms a kind of physical crosslink to add a limited tear strength without excessively reducing the tensile force. In addition, the monofunctional monomer of the present invention usually has a glass transition temperature (T _g ) of 10 ° C. or lower, preferably 0 ° C. or lower, and the monomers are cured by lowering the glass transition temperature (T _g ) of the oligomer. Softness is given to physical properties.

Monofunctional monomers that can be applied in the present invention include phenoxyalkyl acrylate, 2-ethylhexyl acrylate, lauryl acrylate, isobornyl acrylate, caprolactone acrylate, vinyl pyrrolidone having 2 to 4 carbons , Diacetone acrylamide, isobutoxymethyl acrylamide, acrylamide, N , N -dimethyl acrylamide, acrylic acid, itaconic acid, dimethyl aminoethyl acrylate, and the like. The monofunctional monomer as described above is included in the range of 20 to 60% by weight, preferably 25 to 45% by weight in the total resin composition according to the present invention.

In addition, in the present invention, as the resin composition for coating the optical fiber using urethane acrylate as a basic oligomer, a silane monomer was used to prevent the adhesion of the cured resin to the quartz-based glass to be significantly reduced with humidity. In general, the adhesion to the glass is hydrogen-bonded to the Si-O bond on the glass surface by the nitrogen of the urethane functional group possessed by the urethane acrylate oligomer, or the reactive monomer containing the nitrogen group (for example, vinyl pyrrolidone) is mixed at a predetermined ratio. To increase the affinity with Si-O. However, as the humidity increases, the Si-O / H / N hydrogen bonds are reduced to SiOH and NH to weaken the adhesion between the coating agent and the glass surface and to weaken the tear strength by weakening the urethane bonds of the oligomer. However, the silane monomer having a substituent used in accordance with the present invention forms a covalent bond (Si-O-Si) with oxygen on the glass surface, thereby fundamentally blocking the influence of humidity. Therefore, the silane monomer not only increases the glass surface adhesion of the coating agent but also fundamentally lowers the moisture absorption rate of the resin composition. The characteristics of the silane-based monomers must have a carbon-carbon double bond capable of bonding with the oligomers used, and must have a substituent such that Si-O on the glass surface can bond with Si of the silane. Such silane monomers include vinyl trimethoxy silane, vinyl tri (methoxyethoxy) silane, γ-methacryl oxypropyltrimethoxy silane, γ- glycid oxypropylmethoxy silane, and the like. Is to use vinyl trimethoxy silane. As such an adhesion increasing agent, the silane monomer is included in the range of 0.1 to 10% by weight in the total composition.

In addition, the phosphine oxide containing two acyl functional groups as a photoinitiator is contained in the range of 0.1-10 weight% in the whole composition. This promotes internal cure and inhibits external cure, resulting in a slight affinity for glass and facilitating application of the optical fiber outer coating.

The resin composition according to the present invention as described above has a glass transition temperature (Tg) of -70 to -60 ° C, and is excellent as an optical fiber internal coating agent because of its excellent adhesion to glass.

When the present invention is described in more detail as follows, the present invention is not limited thereto.

Examples 1-3 and Comparative Examples 1-2

Next, the composition as shown in Table 1 was prepared to prepare a composition for coating the inside of the optical fiber.

In addition, in the following Table 1, the urethane acrylate oligomer was polymerized by the method disclosed in US Pat. No. 4,624,994 and has a number average molecular weight of 15,000. Isobonyl acrylate, lauryl acrylate, and caprolactone acrylate (Sartomer SR495) were used as the monofunctional monomer. The photoinitiators used Irgacure 184 and Irgacure 819 from Sivagai Company, Switzerland.

division Example (% by weight) Comparative Example (% by weight) One 2 3 One 2 Urethane acrylate oligomer 59 58 56.5 59.5 59.5 Isobonyl Acrylate 18 18 18 18 18 Lauryl acrylate 10.5 10.5 10.5 10.5 10.5 Caprolactone acrylate 18 18 18 18 18 Vinyltrimethoxysilane 0.5 1.5 3 0 1.5 Irgacure 184 2 2 2 2 4 Irgacure 819 2 2 2 2 0

Experimental Example

(1) Water Sensitivity Measurement

Hygroscopicity is calculated as the weight difference after immersion of the cured resin in water and before immersion. Specimens of the respective resin compositions prepared in Examples 1 to 3 and Comparative Examples 1 to 2 were prepared in a size of 2.54 cm wide, 7.6 cm long, and 250 μm thick. The weight (A) of the produced specimen was measured. The specimen was immersed in water at 23 ° C. for 24 hours, then taken out, dried with a paper towel, and weighed (B). After standing at room temperature for 48 hours, the weight (C) was measured again. And the moisture absorption rate was computed by following formula (1) and formula (2). The results are shown in Table 2 below.

In the above equation: A is the initial weight, B is the weight after soaking in water for 24 hours, C is the weight after drying.

Adhesion to Glass Measurement

The adhesion of the cured resin was measured after leaving the coating on a glass plate for 1 week at 50% humidity, and after 24 hours at 95% humidity. The surface of the specimen was applied with a polyethylene powder-water slurry prior to removal from the humidifier to prevent evaporation of moisture. The specimens were cut into films with a width of 2.54 cm and a thickness of 75 μm, and the other one was attached to the glass plate. The cut side was hooked on the top of the Instron tester and the glass plate was hooked on the bottom to be 180 ° to measure the adhesion. The results are shown in Table 2 below.

division Example Comparative Example One 2 3 One 2 Hygroscopicity (%) Weight change 3.2 2.1 0.9 4.5 4.0 Extraction weight 1.8 1.2 0.5 3.0 2.5 Adhesion to glass (N × 10 ^-2 ) Relative Humidity (50%) 57 68 70 45 51 Relative Humidity (95%) 54 66 69 41 47 Modulus (MPa) 1.34 1.29 1.32 1.32 1.30 Breaking strength (MPa) 1.13 1.15 1.12 1.14 1.15 Elongation at Break (%) 135 134 131 132 134

Except for the moisture absorption rate in Table 2, the physical values are cured to a thickness of 75㎛ on the quartz glass plate.

As described above, the resin composition according to the present invention contains a urethane acrylate oligomer as a main component, and has excellent tear strength and elongation at break, but also has high adhesion to glass fibers, excellent moisture resistance, and induces rapid curing. Useful as an internal coating.

Claims (4)

30 to 70% by weight of a urethane acrylate oligomer having a number average molecular weight of 6,000 to 20,000; 20 to 60% by weight of a monofunctional monomer containing one acrylate functional group; 0.1 to 10% by weight of silane monomers; And 0.1 to 10% by weight of a phosphine oxide-based photopolymerization initiator containing two acyl functional groups. According to claim 1, wherein the urethane acrylate oligomer contains one urethane group per molecular weight of 300 to 900 units, the polyalkylene functional group having 2 to 6 carbon units is contained in the oligomer 40 to 80% by weight Resin composition for coating the optical fiber inside. The monofunctional monomer according to claim 1, wherein the monofunctional monomer containing one acrylate functional group is phenoxyalkyl acrylate having 2 to 4 carbons, 2-ethylhexyl acrylate, lauryl acrylate, isobornyl acrylate, and capro. One or two selected from lactone acrylate, vinyl pyrrolidone, diacetone acrylamide, isobutoxymethyl acrylamide, acrylamide, N , N -dimethyl acrylamide, acrylic acid, itaconic acid, and dimethyl aminoethyl acrylate Resin composition for coating the optical fiber inside, characterized in that the mixture of the above. The method of claim 1, wherein the silane monomer is selected from vinyl trimethoxy silane, vinyl tri (methoxyethoxy) silane, γ-methacryl oxypropyltrimethoxy silane, and γ-glycidoxy oxypropylmethoxy silane. A resin composition for coating the optical fiber, characterized in that the species or a mixture of two or more kinds.