JPS647018B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to ultraviolet or electron beam curable materials for coating optical glass fibers for light transmission.

Optical glass fibers (hereinafter referred to as optical fibers) used for optical transmission are fragile, easily scratched, and have poor flexibility, so such scratches can easily cause them to break even with the slightest external force. do. For this reason, it is extremely difficult to use the optical fiber as it is for optical transmission.

Therefore, attempts have been made heretofore to coat the surface of an optical fiber with a polymer immediately after spinning it from a glass base material, thereby maintaining the initial strength immediately after manufacture and producing an optical fiber that can withstand long-term use. In other words, the above-mentioned polymer coating refers to applying and curing a solution type or thermosetting type material to the surface of the optical fiber, or coating the surface of the optical fiber with an ultraviolet curable material whose main ingredient is epoxy acrylate oligomer or urethane acrylate oligomer. A coating layer having a single-layer or multi-layer structure is provided by curing the material by irradiating it with light, or by providing a buffer layer such as a silicone resin as a base layer for the material layer.

On the other hand, when using optical fibers coated and protected in this way, it is necessary to connect the optical fibers to each other, but in this case, the coating layer is removed mechanically or with chemicals, and then heated and fused. A method has been adopted to do so. However, the surface of the optical fiber is easily damaged during such connection work, which poses a problem of lowering the mechanical strength after connection.

For this reason, before providing the above-mentioned coating layer on the surface of the optical fiber, that is, on the surface of the optical fiber immediately after spinning from the glass base material, a thin primer coating layer of 10 μm or less is first formed, and then the above-mentioned coating layer is formed on the surface of the optical fiber. Attempts have been made to prevent a decrease in mechanical strength during connection by providing a layer with a thickness of several tens of micrometers and removing only the coating layer on the surface side and fusion splicing with the primer coating layer remaining. ing.

However, since the primer coating layer adheres well to the front side coating layer, the primer coating layer is often peeled off from the optical fiber surface when the front side coating layer is removed. If such simultaneous peeling occurs, not only will the purpose of providing the primer coating layer be lost, but also the optical fiber surface will be more likely to be damaged when the primer coating layer is peeled off. It was not possible to expect much improvement in mechanical strength.

From the above point of view, the inventors have developed a primer coating that adheres well to the optical fiber surface while moderately reducing its adhesion to the surface coating layer, making it difficult for this layer to peel off at the same time. This invention was completed as a result of intensive research to find a material with high practical value that can form a layer.

That is, the present invention provides a material for providing a thin primer coating layer of 10 μm or less between an optical fiber and a single-layer or multilayer polymer coating layer covering the optical fiber, which contains polymerizable carbon-carbon in the molecule. Composing an acrylic acid alkyl ester and/or a methacrylic acid alkyl ester [hereinafter referred to as (meth)acrylic acid alkyl ester] in a composition containing a photopolymerizable compound having two or more double bonds and a photopolymerization initiator. This invention relates to an optical fiber coating material characterized in that the coating material contains 1 to 30% by weight of the entire material.

As described above, the present invention is characterized in that a specific amount of (meth)acrylic acid alkyl ester is contained in the material for forming the primer coating layer. Since the workability of removing the coating layer can be improved and there is less risk that the primer coating layer will peel off at the same time when the surface coating layer is removed, the strength of the optical fiber after splicing can be greatly improved.

The photopolymerizable compound having a polymerizable carbon-carbon double bond in the molecule used in this invention is a compound that is liquid at room temperature and has two or more acryloyl or methacryloyl groups in the molecule as a group containing the double bond. Examples include various oligomers such as urethane (meth)acrylate oligomers, epoxy (meth)acrylate oligomers, ester (meth)acrylate oligomers, and ether (meth)acrylate oligomers. Moreover, it may contain a polymerizable carbon-carbon double bond other than the above-mentioned (meth)acryloyl group, such as liquid polybutadiene.

In this invention, in addition to the above-mentioned oligomeric photopolymerizable compound, a low-viscosity liquid photopolymerizable compound that serves as a diluent and is a monomer having two or more (meth)acryloyl groups in the molecule is used in combination. It is preferable to do so. Specific examples include 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, and butylene glycol di(meth)acrylate. (meth)acrylate, neopentyl glycol di(meth)acrylate, 1,4-butanediol di(meth)
Examples include (meth)acrylic acid polyesters such as acrylate, 1,6-hexanediol di(meth)acrylate, pentaerythritol tri(meth)acrylate, and trimethylolpropane tri(meth)acrylate.

These monomeric photopolymerizable compounds are extremely useful for making the primer coating layer hard and strong. That is, since the primer coating layer is made to be a thin layer of 10 μm or less, sufficient layer strength may not be maintained depending on the type of oligomer. Therefore, layer strength can be increased by increasing the crosslinking density using the above monomer. The proportion of these monomers used is preferably such that the total amount with the oligomer is 20 to 80% by weight.

As the photopolymerization initiator used in this invention, any conventionally known initiator can be used, such as benzoin ether initiators such as benzoin ethyl ether and benzoin isobutyl ether, methyl 0-benzoylbenzoate, 4,4'- Benzophenone initiators such as bisdimethylaminobenzophenone, acetophenone initiators such as 2,2-diethoxyacetophenone, benzylmethyl ketal, 1,1-dichloroacetophenone, 2-methylthioxanthone, chlorothioxanthone, etc. Examples include thioxanthone-based initiators. The amount of these photopolymerization initiators used is as follows:
The amount may be generally 0.1 to 10 parts by weight, preferably 1 to 5 parts by weight, based on 100 parts by weight of the total amount of the photopolymerizable compound and the (meth)acrylic acid alkyl ester described below.

The (meth)acrylic acid alkyl ester used in this invention preferably has an alkyl group with 5 or more carbon atoms, particularly preferably 10 or more carbon atoms. At the same time, it becomes difficult to prevent the peeling off. The upper limit of the number of carbon atoms may be appropriately determined based on solubility with the photopolymerizable compound.

Specific examples of typical (meth)acrylic acid alkyl esters include stearyl (meth)acrylate, lauryl (meth)acrylate, and tridecyl (meth)acrylate. In addition, these (meth)acrylic acid alkyl esters are
As mentioned above, it gives good results in the removal workability of the surface coating layer, but at the same time, it also acts as a diluent for the photopolymerizable compound and polymerizes and cures with the above compound by light irradiation to form the primer coating layer. Modify the properties of.

The amount of the (meth)acrylic acid alkyl ester to be used is determined based on its proportion in the entire composition, that is, the photopolymerizable compound, the photopolymerization initiator, and other optional components such as a silane coupling agent added as necessary. and further the above (meth) in the total amount of the above (meth)acrylic acid alkyl ester.
The proportion of acrylic acid alkyl ester is 1 to 30% by weight, preferably 5 to 20% by weight. If it is less than 1% by weight, the effect of this invention cannot be obtained, and if it is less than 30% by weight.
If the amount increases, the adhesion or adhesion with the optical fiber may be impaired, and the adhesion or adhesion with the surface coating layer may become too poor, causing problems during the formation of the surface coating layer or under the usage conditions after connecting the optical fiber. There is. Moreover, excessive use is undesirable because it reduces the strength of the primer coating layer itself.

The coating material of the present invention is made by uniformly mixing the above-mentioned photopolymerizable compound, photopolymerization initiator, alkyl (meth)acrylate, and various optional components used as necessary. The viscosity is usually set at 1000 centipoise or less at 25°C, preferably in the range of 50 to 800 centipoise, so that it can be applied uniformly by a method such as spray painting.

In order to coat an optical fiber with such a coating material, it is applied to the surface of the optical fiber immediately after spinning using the above-mentioned coating method to a thickness of 10 μm or less, usually 5 μm or less, and particularly preferably about 1 to 2 μm. The polymer may be cured by irradiation with ultraviolet rays or electron beams as the case may be.

The above-mentioned curing means is advantageous in that the coating operation can be carried out more quickly than a method of drying or curing by heating using an organic solvent solution type coating material or a thermosetting coating material. Good results can also be obtained in terms of equipment costs for curing.

After forming the primer coating layer in this way, an optical fiber coating with excellent light transmission properties can be obtained by providing a surface coating layer consisting of a conventionally known single-layer or multilayer polymer coating layer on this layer. It will be done. In order to connect these coatings to each other, the surface coating layer may be peeled off mechanically or manually, and the primer coating layer may be heat-fused with the primer coating layer remaining. Here, since the primer coating layer is unlikely to be peeled off at the same time during the peeling and removal, the strength of the optical fiber after connection is increased. Note that the means for removing the surface coating layer is not limited to the peeling and removing method described above, and may be any other known removing means.

Examples of this invention will be described below. In the following, parts mean parts by weight.

Example 1 50 parts of diacrylate of bisphenol A diglycidyl ether, 40 parts of 1,6-hexanediol diacrylate, 10 parts of lauryl acrylate, and 3 parts of benzoin isobutyl ether were uniformly mixed until the viscosity at 25°C was 580. A centipoise coating material for optical fiber was obtained.

Comparative Example 1 50 parts of bisphenol A diglycidyl ether diacrylate, 50 parts of 1,6-hexanediol diacrylate, and 3 parts of benzoin isobutyl ether were uniformly mixed to prepare an optical fiber with a viscosity of 550 centipoise at 25°C. A coating material was obtained.

Using each of the materials of Example 1 and Comparative Example 1 above, this was coated to a thickness of 5 μm on the surface of a 125 μm thick optical fiber immediately after spinning, and then irradiated with ultraviolet rays using a 1KW high-pressure mercury lamp to polymerize. hardened. Thereafter, a photocurable material containing urethane acrylate oligomer as a main component was further applied onto the primer coating layer formed by the above method and cured by ultraviolet irradiation to form a surface coating layer with an elastic modulus of 20 Kg/cm ² and a thickness of 70 μm. Formed.

When the optical fiber coatings produced in this way were connected by heating and fusing after peeling off their surface coating layers, it was found that the peelability of Example 1 was good, and the tensile strength of the fiber connection was good. The weight was 0.8Kg. However, in Comparative Example 1, the peelability was insufficient and the strength of the fiber connection was poor.
It varied between 0.3 and 0.6 kg.

Example 2 50 parts of diacrylate of bisphenol A diglycidyl ether, 45 parts of neopentyl glycol diacrylate, 5 parts of stearyl methacrylate,
Three parts of benzyl dimethyl ketal were uniformly mixed to obtain an optical fiber coating material having a viscosity of 550 centipoise at 25°C.

Comparative Example 2 50 parts of diacrylate of bisphenol A diglycidyl ether, 50 parts of neopentyl glycol diacrylate, and 3 parts of benzyl dimethyl ketal were uniformly mixed to produce a coating material for optical fiber having a viscosity of 530 centipoise at 25°C. Obtained.

Using each of the materials of Example 2 and Comparative Example 2 above, this was coated to a thickness of 5 μm on the surface of a 125 μm thick optical fiber immediately after spinning, and then it was irradiated with ultraviolet light using a 1KW high-pressure mercury lamp and polymerized. hardened. Thereafter, a photocurable material containing urethane acrylate oligomer as a main component was further applied onto the primer coating layer formed by the above method and cured by ultraviolet irradiation to form a surface coating layer with an elastic modulus of 140 Kg/cm ² and a thickness of 70 μm. Formed.

When the optical fiber coatings produced in this manner were connected by heat fusion after peeling off their surface coating layers, it was found that the peelability of Example 2 was good, and the tensile strength of the fiber connection was good. The weight was 0.8Kg. However, in Comparative Example 2, the peelability was insufficient, and the strength of the fiber connection was poor.
It varied between 0.3 and 0.6 kg.

Claims (1)

[Claims] 1 A material for providing a thin primer coating layer of 10 μm or less between an optical glass fiber and a single-layer or multilayer polymer coating layer covering it, which contains a polymerizable carbon-carbon double bond in the molecule. 2
Optical glass characterized in that a composition containing a photopolymerizable compound and a photopolymerization initiator contains an acrylic acid alkyl ester and/or a methacrylic acid alkyl ester in an amount of 1 to 30% by weight of the entire composition. Coating material for fiber.