JPS6253457B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for manufacturing optical glass fiber coatings using ultraviolet or electron beam curable coating materials. When transmitting light using an optical glass fiber (hereinafter referred to as an optical fiber), when mechanical side pressure is applied to the optical fiber, the transmitted light is significantly weakened, causing transmission loss. For this reason, normal optical fiber cables have an outer coating layer on the surface of the optical fiber made of a highly rigid material that protects it from lateral pressure, and an inner layer made of a low-rigidity material that absorbs and reduces minute internal strains by a buffering effect. A covering inner layer is provided. A typical example of such an optical fiber cable is an optical fiber that has been coated with resin to prevent breakage due to minute scratches on the surface of the optical fiber, and a low-rigidity inner layer made of silicone resin is placed on top of the optical fiber. Further, it is known that a highly rigid outer layer made of polyamide such as nylon is coated by extrusion. However, in the conventional cable described above, there was a problem that air bubbles were mixed into the interface between the inner and outer layers during the formation of the outer layer, which caused lateral pressure and increased optical transmission loss. In addition, since the molding methods for the inner layer forming process and the outer layer forming process are completely different, a batch system is required, which complicates the entire coating process.Nylon resin is crystalline, so extrusion speed is limited, and the inner layer The silicone resin used as the forming material is expensive, which poses problems in terms of coating work and in terms of lowering the price of optical fiber cables. The present invention aims to provide an industrially useful method for manufacturing an optical fiber coating that avoids all of the above problems. - For forming an inner layer with a tensile modulus of 1000 Kg/cm ² or less after curing, comprising a high viscosity liquid or solid main material having carbon double bonds and a monoacrylate or monomethacrylate as a reactive diluent. After applying the material, a hardened inner layer is formed by irradiation with ultraviolet rays or electron beams, and then a main material of the same type as the main material of the above-mentioned inner layer forming material and a polyfunctionality as a reactive diluent thereof are applied. The tensile modulus after curing of a material containing acrylate or methacrylate is
The present invention relates to a method for producing an optical fiber coating, which comprises applying an outer layer forming material having a weight of 3000 kg/cm ² or more and then irradiating it with ultraviolet rays or electron beams to form a hardened outer layer. According to the manufacturing method of the present invention, the above-mentioned inner layer forming material is first applied to the surface of the optical fiber, and then a hardened inner layer is formed by irradiation with ultraviolet rays or electron beams, and then the above-mentioned outer layer forming material is applied thereon. The coating objective can be achieved by applying the material and then irradiating it with UV or electron beams to form a hardened outer layer. In this case, since the materials forming the inner and outer layers are of the same type using the same type of main material, the material for forming the outer layer is partially impregnated into the ultraviolet-cured inner layer during the formation of the outer layer, and the interface between them is integrated. As shown by the solid line in the drawing, a coating layer is formed in which the tensile modulus continuously increases from the low-rigidity inner layer to the high-rigidity outer layer. Therefore, unlike the conventional coating layer that has a complete two-layer structure consisting of a low-rigidity inner layer and a high-rigidity outer layer, as shown by the dotted line in the figure, there is less air bubbles mixed into the interface between the inner and outer layers. Furthermore, even if air bubbles are mixed in, a continuous layer of relatively high rigidity is formed by impregnation and hardening inside the bubbles, so that the adverse effects of air bubbles on the optical fiber are reduced. Furthermore, according to the manufacturing method of the present invention, as described above, the same type of material using the same type of main material is used as the material for forming the inner and outer layers, and the coating on the optical fiber and curing with ultraviolet rays or electron beams are repeated. Since the purpose of coating can be achieved with
Furthermore, since each material does not require very expensive components, it is very advantageous in terms of coating work and cost reduction of optical fiber cables. In this invention, the main material used for the material for forming the inner and outer layers is a high viscosity liquid or solid compound having a polymerizable carbon-carbon double bond in the molecule,
Here, the viscosity in the case of high viscosity liquid is 25℃.
It is more than 10 poise. Typical such main materials include polyether (meth)acrylate, polyester (meth)acrylate, urethane (meth)acrylate, epoxy (meth)acrylate, and polybutadiene (meth)acrylate.
(meth)acrylates such as acrylate,
Other examples include unsaturated polyester resins and allyl compounds. The reactive diluent used in combination with the main material is for reducing or dissolving the viscosity of the main material, and also polymerizes and hardens together with the main material to become a component of the cured product. Therefore, like the main material, a low viscosity liquid compound having a polymerizable carbon-carbon double bond in the molecule is used, and in particular, a (meth)acrylate compound is selected and used as an effective compound. The amount of this reactive diluent used is 10 to 70% by weight based on the total amount of the main material,
It is preferably used in a proportion of 30 to 50% by weight. As a component of the material for forming the inner and outer layers, a photopolymerization initiator for assisting ultraviolet curing is usually used. Specific examples of the photopolymerization initiator include benzoin alkyl ethers such as benzoin isobutyl ether, benzophenone, acetophenone, and thioxanthone. The amount used is about 1 to 5 parts by weight per 100 parts by weight of the main material and reactive diluent. In addition, in the case of electron beam curing, such a photopolymerization initiator is not necessary. The inner layer-forming material and the outer layer-forming material, which are made of the above constituent components and optionally add other optional components, must have the same type of main material, and by using the same type of main material, , the impregnation of the material for forming the outer layer into the inner layer is improved,
Negative effects caused by air bubbles can be eliminated. In addition, the inner layer forming material has a tensile modulus of 1000 Kg/cm 2 or less (usually 5 Kg/cm ² or less) after curing with ultraviolet rays or electron beams.
cm ² ), the material for forming the outer layer must have a tensile modulus of 3000 Kg/cm ² or higher (usually up to 50000 Kg/cm ² ), and if it does not satisfy the above range, it cannot be used as a buffer as an inner layer. Both the effect and the lateral pressure protection effect as an outer layer cannot be sufficiently exhibited. In order to make the materials for forming the inner and outer layers have the tensile modulus as described above, since the main ingredients of both materials are the same as mentioned above, the type and, if necessary, the amount of the reactive diluent in both materials must be adjusted. In particular, as the type of reactive diluent, monoacrylates or monomethacrylates are used as the material for forming the inner layer, and polyfunctional acrylates or methacrylates are used as the material for forming the outer layer. Both tensile moduli after curing can be easily adjusted within the above range. Examples of the monoacrylates or monomethacrylates used as the inner layer forming material include polyethylene glycol mono(meth)acrylate, ethylene glycol mono(meth)acrylate, polypropylene glycol mono(meth)acrylate, and 1,6-hexanediol mono(meth)acrylate. Examples thereof include meth)acrylate, 1,4-butanediol mono(meth)acrylate, tetrahydrofurfuryl(meth)acrylate, phenoxyethyl(meth)acrylate, and 2-hydroxy-3-phenoxy(meth)acrylate. In addition, the polyfunctional acrylate or methacrylate as the material for forming the outer layer is as follows:
For example, ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate
Acrylate, butylene glycol di(meth)acrylate, neopentyl glycol di(meth)
Acrylate, 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, pentaerythritol tri(meth)acrylate, trimethylolpropane tri(meth)acrylate, and the like. The material for forming inner and outer layers consisting of the above components is
It is generally handled as a solvent-free type, but its viscosity is usually around 1000 to 7000 centipoise at 25°C. If the viscosity is too low or too high, the coating workability for optical fibers will be lost, which is not preferable. In the method of manufacturing the optical fiber coating of the present invention, the above-mentioned inner layer forming material is first applied to the surface of the optical fiber and then cured by irradiation with ultraviolet rays or electron beams. It is usually about 10 to 50 μm. Further, the thickness of the entire cured film after coating the above-mentioned outer layer forming material on this inner layer and curing it by irradiating it again with ultraviolet rays or electron beams is generally about 20 to 200 μm. As detailed above, according to the manufacturing method of the present invention, a specific inner layer forming material is coated on the surface of the optical fiber, cured by irradiation with ultraviolet rays or electron beams, and then a specific outer layer forming material is coated on the surface of the optical fiber. Since the optical fiber coating can be obtained through a continuous process of coating the material and curing it by irradiating it with ultraviolet rays or electron beams, it is possible to greatly improve the coating workability, and it is possible to improve the coating workability. It is possible to suppress an increase in optical transmission loss due to the inclusion of air bubbles at the interface, and further to reduce material costs. EXAMPLES Below, examples of the present invention will be described in more detail. In addition, in the following, parts mean parts by weight. Example 1 1,4-polybutadiene urethane acrylate
30 parts, 70 parts of polyethylene glycol monoacrylate with an average molecular weight (w) of 1200, and 3 parts of benzoin isobutyl ether.
1780 centipoise inner layer forming material and 1,4-
An optical fiber coating material according to the present invention was prepared, comprising an outer layer-forming material having a viscosity of 4050 centipoise at 25°C and consisting of 60 parts of polybutadiene urethane acrylate, 40 parts of neopentyl glycol diacrylate, and 3 parts of benzoin isobutyl ether. The above-mentioned inner layer forming material and outer layer forming material were applied separately on a release plate and completely cured by ultraviolet irradiation, and the tensile modulus of each cured film was measured. The inner layer forming material was 18 kg. /cm ² , and the outer layer forming material was 3800Kg/cm ² . In addition, the above-mentioned drawings show the relationship between the thickness direction and tensile modulus of the cured material when the above-mentioned inner and outer layer forming materials are sequentially applied on a release plate and cured by ultraviolet rays, in contrast to conventional materials. This is what is shown. Next, using the above-mentioned coating material, an inner layer forming material was first applied to the surface of the optical fiber made from the fiber base material produced by the VAD method, and then ultraviolet rays were applied at a speed of 50 m/min using a 2KW high-pressure mercury lamp. was irradiated and cured to form an inner layer with a thickness of 40 μm. Next, an outer layer forming material was applied onto this inner layer, and then cured by irradiation with ultraviolet rays under the same conditions as above to form a cured coating layer having an overall thickness of 140 μm. The optical fiber sheath manufactured in this way effectively suppresses the increase in transmission loss due to lateral pressure by the inner sheathing layer with a low rigidity and the outer sheathing layer with a high rigidity, and also prevents air bubbles between the inner and outer layers. Therefore, the increase in transmission loss was small. Examples 2 to 5 Inner layer forming materials and outer layer forming materials having the compositions shown in the following table were prepared using the four materials according to the present invention.
It was used as a coating material for optical fibers. The viscosity (25° C.) of each material for forming the inner and outer layers and the tensile modulus of the cured product measured in the same manner as in Example 1 were as shown in the same table.

【table】

[Table] A coating layer consisting of a hardened inner layer and a hardened outer layer was formed on the surface of an optical fiber in the same manner as in Example 1 using each of the above-mentioned coating materials. As in the case of Example 1, each of the obtained optical fiber coatings effectively suppressed the increase in transmission loss due to pressure measurement by the inner coating layer with a low rigidity and the outer coating layer with a high rigidity. Furthermore, there was little increase in transmission loss due to air bubbles between the inner and outer layers.

[Brief explanation of the drawing]

The drawing is a characteristic diagram for explaining the properties of a cured product of the coating material for optical glass fiber.

Claims (1)

[Claims] 1 After curing, the surface of the optical glass fiber contains a highly viscous liquid or solid main material having a polymerizable carbon-carbon double bond in its molecules and a monoacrylate or monomethacrylate as a reactive diluent thereof. After applying an inner layer forming material with a tensile modulus of 1000 Kg/cm ² or less, a hardened inner layer is formed by irradiation with ultraviolet rays or electron beams, and then a material of the same kind as the main material of the above inner layer forming material is applied on top of this. After applying an outer layer forming material containing a main material and a polyfunctional acrylate or methacrylate as a reactive diluent and having a tensile modulus of 3000 Kg/cm ² or more after curing, irradiation with ultraviolet rays or electron beams is performed. 1. A method for producing an optical glass fiber coating, comprising: forming a hardened outer layer.