JPS647019B2 - - 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. A coating material for optical fiber, characterized in that a composition containing a photopolymerizable compound having two or more double bonds and a photopolymerization initiator contains 0.01 to 5% by weight of a saturated fatty acid based on the total composition. This is related.

As described above, the present invention is characterized in that a specific amount of saturated fatty acid is contained in the material for forming the primer coating layer, so that the surface coating layer can be removed without impairing its adhesion to the optical fiber surface. The primer coating layer is less likely to peel off at the same time as 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. Further, it may also 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 o-benzoylbenzoate, 4,4'- Benzophenone initiators such as bisdimethylaminobenzophenone, acetophenone initiators such as 2,2-diethoxyacetophenone, benzyldimethyl ketal, 1,1-dichloroacetophenone, 2-methylthioxanthone, chlorothioxanthone, etc. Examples include thioxanthone-based initiators. The amount of these photopolymerization initiators used is as follows:
Usually 0.1 to 100 parts by weight of the photopolymerizable compound
The amount may be 10 parts by weight, preferably 1 to 5 parts by weight.

The saturated fatty acids used in this invention are preferably straight chain fatty acids, but branched fatty acids can also be used depending on the case. The number of carbon atoms is preferably 10 or more, and those with a small number of carbon atoms are not preferred because the melting point will be low and the film properties will be poor. There is no particular upper limit to the number of carbon atoms, as long as it can be dissolved or made compatible with the photopolymerizable compound.

Specific examples of the above saturated fatty acids include capric acid, undecylic acid, lauric acid, tridecylic acid,
myristic acid, pentadecyl acid, palmitic acid,
heptadecylic acid, stearic acid, nonadecanoic acid,
These include arachic acid, behenic acid, lignoceric acid, cerotic acid, heptacanoic acid, montanic acid, melisic acid, and lactacic acid. These fatty acids may be synthetic fatty acids or natural fatty acids, and may be high-purity single fatty acids or mixed fatty acids.

The amount of the saturated fatty acid to be used is determined based on the proportion of the saturated fatty acid in the entire composition, that is, the photopolymerizable compound, the photopolymerization initiator, optional components such as a silane coupling agent added as necessary, and the saturated fatty acid. The proportion of the above-mentioned saturated fatty acids in the total amount is 0.01 to 5% by weight, preferably 0.05 to 3% by weight. If it is less than 0.01% by weight, the effect of this invention cannot be obtained, and if it is more than 5% by weight, the adhesion or adhesion with the optical fiber will be impaired, and the adhesion or adhesion with the surface coating layer will be too poor, and the surface coating layer Problems may occur during the formation of the optical fiber or under the usage conditions after the optical fiber is connected.

The coating material of the present invention is made by uniformly mixing the above-mentioned photopolymerizable compound, photopolymerization initiator, saturated fatty acid, and various optional components used as necessary, and has a viscosity that is comparable to spray coating. Usually at 25℃, it can be applied evenly using methods such as
It is set to 1000 centipoise or less, preferably in the range of 50 to 500 centipoise.

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 1 350 parts of diacrylate of bisphenol A diglycidyl ether, 650 parts of neopentyl glycol diacrylate, 1 part of stearic acid, and 30 parts of benzyl methyl ketal were uniformly mixed and exposed to light having a viscosity of 110 centipoise at 25°C. A fiber coating material was obtained.

Example 2 300 parts of diacrylate of bisphenol A diglycidyl ether, 700 parts of tripropylene glycol diacrylate, 3 parts of lauric acid, and 30 parts of benzyl methyl ketal were uniformly mixed and exposed to light having a viscosity of 120 centipoise at 25°C. A fiber coating material was obtained.

Comparative Example 1 An optical fiber coating material was obtained in the same manner as in Example 1, except that 1 part of stearic acid was not blended.

Comparative Example 2 An optical fiber coating material was obtained in the same manner as in Example 2, except that 3 parts of lauric acid was not blended.

Using each material of the above examples and comparative examples, it was applied to the surface of a 125 μm thick optical fiber immediately after spinning.
After spray painting to a thickness of 2 μm, it was polymerized and cured by irradiation with ultraviolet light using a 1KW high-pressure mercury lamp. 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 give an elastic modulus of 20 Kg/cm ² and a thickness of 70 μm.
A surface coating layer was formed.

When the optical fiber coatings produced in this way were connected by heat fusion after peeling off their respective surface coating layers, it was found that the peelability of Examples 1 and 2 was good, and the fiber connection area was The tensile strength was 0.8Kg. However, in Comparative Examples 1 and 2, the peelability was insufficient, and the strength of the fiber connection portion varied from 0.5 to 0.8 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 polymerizable carbon-carbon double bonds in the molecule. 2
In a composition containing a photopolymerizable compound and a photopolymerization initiator, 0.01 to 10% of the total amount of saturated fatty acid is added to the composition.
A coating material for optical glass fiber, characterized in that it contains 5% by weight.