JPS6071549A - Cladding material for optical glass fiber - Google Patents

Abstract

PURPOSE:To improve workability for removing a clad layer of optical glass fiber without spoiling the adhesivity to the surface of the optical fiber by incorporating a specified amt. of alkyl (meth)acrylate in a material for forming a primer clad layer contg. photopolymerizable compds. and photopolymn. initiator. CONSTITUTION:A material for forming a primer clad layer for optical glass fiber is obtd. by incorporating 1-30wt% alkyl (meth)acrylate into a compsn. consisting primarily of a photopolymerizable compd. having >=2 polymerizable C=C double bond in a molecule and a photopolymn. initiator. After forming a primer clad layer with the above-described material, a single or multilayered surface clad layer is formed. When the optical fiber is to be connected, the surface clad layer is peeled and removed leaving the primer clad layer, and the fiber is bonded by fusing. In this treatment, the strength of the optical fiber after connection is improved because the primer clad layer is not removed simultaneously with the removal of the surface clad layer.

Description

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

Optical glass fibers (hereinafter referred to as optical fibers) used for optical transmission are brittle, easily damaged, and have poor flexibility, so they are easily destroyed not only by such scratches but also by external force. . For this reason, it is extremely difficult to use optical fibers as they are 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 production 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 by removing only the coating layer on the surface side and performing fusion splicing with the primer coating layer remaining. .

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 the surface of the optical fiber will be more likely to be damaged when the primer coating layer is peeled off. There was no hope of improving 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 structure in which a single layer is formed between the optical fiber and the monolayer or multilayer polymer coating layer covering the fiber.
A material for providing a thin primer coating layer of 0 μm or less, which contains acrylic acid in a composition containing a photopolymerizable compound having two or more polymerizable carbon-carbon double bonds in the molecule and a photopolymerization initiator. An optical fiber comprising an alkyl ester and/or a methacrylic acid 7/l/4/l/x stellate (hereinafter referred to as (meth)acrylic acid alkyl ester) in an amount of 1 to 80% by weight of the entire composition. This relates to coating materials.

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. The workability of removing the coating layer can be improved, and the strength of the optical fiber after splicing can be greatly improved since there is little fear that the primer coating layer will peel off at the same time when the surface coating layer is removed.

The photopolymerizable compound having a polymerizable carbon-carbon double bond in the molecule used in this invention has two or more acryloyl groups or methacryloyl groups in the molecule as a group containing the double bond, and is liquid at room temperature. 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 poly-butadiene.

In this invention, together with the oligomeric photopolymerizable compound, it usually serves as a diluent and contains (meth) in the molecule.
It is preferable to use together a low viscosity liquid photopolymerizable compound as a monomer having two or more acryloyl groups. A specific example of this is, for example, ethylene glycol
Acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate,
Polypropylene glycol di(meth)acrylate, butylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,6-hexanethiol di(meth)acrylate, penta Examples include (meth)acrylic acid polyesters such as erythritol 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, the layer strength can be increased by increasing the crosslinking density using the above monomer. The proportion of these monomers used is preferably 20 to 80% by weight based on the total amount with the oligomer.

As the photopolymerization initiator used in this invention, any conventionally known ones 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-jetoxyacetophenone, benzyl dimethyl ketal, 1, 1-dichloroacetophenone,
Examples include thioxanthone-based initiators such as 2-methylthioxanthone and chlorothioxanthone. The amount of these photopolymerization initiators to be used is the total amount of the photopolymerizable compound and the (meth)acrylic acid alkyl ester described below.
The amount may be generally 0.1 to 10 parts by weight, preferably 1 to 5 parts by weight, per 1 part by weight of 0.00 weight.

The (meth)acrylic acid alkyl ester used in this invention preferably has an alkyl group with carbon atoms of 5 or more, particularly preferably 10 or more. To prevent simultaneous peeling. 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. As mentioned above, these (meth)acrylic acid alkyl esters give good results in the removal workability of the surface coating layer, but at the same time they also act as diluents for the photopolymerizable compounds, and they also act as a diluent for the photopolymerizable compounds. The primer coating layer is polymerized and cured together with the above compounds to modify the properties of the primer coating layer.

The amount of the (meth)acrylic acid alkyl ester to be used is determined based on the proportion of the total composition, that is, the amount of the photopolymerizable compound, the photopolymerization initiator, and the silane coupling agent added as necessary. Ingredients and further above (
The proportion of the above (meth)acrylic acid alkyl ester in the total amount of the meth)acrylic acid alkyl ester is
1 to 80% 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 more than 30% 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. 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 1 at 25°C, which can be applied evenly by methods such as spray painting.
000 centivoise or less, preferably in the range of 50 to 800 centivoise.

In order to coat an optical fiber with such a coating material, the surface of the optical fiber immediately after spinning is coated with the above-mentioned coating method to coat the surface with a thickness of 10 μm or less, usually 5 μm or less, and particularly preferably 1 to 2 μm.
After coating to a thickness of about .mu.m, it may be polymerized and cured by irradiation with ultraviolet rays or, if necessary, electron beams.

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 that are still being cured.

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 described in "2" 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 above-mentioned peeling and removing method, and other known methods may be used.

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, 4 parts of 1,6-hexanediol diacrylate
0 parts of lauryl acrylate, 10 parts of lauryl acrylate, and 3 parts of benzoin isobutyl ether were uniformly mixed to obtain an optical fiber coating material having a viscosity of 580 centipoise at 25°C.

Comparative Example 1 50 parts of diacrylate of bisphenol A diglycidyl ether, 5 parts of l.6-hexanediol diacrylate
0 parts of benzoin isobutyl ether and 3 parts of benzoin isobutyl ether were uniformly mixed to obtain an optical fiber coating material having a viscosity of 550 centivoids at 25°C.

Using each of the materials of Example 1 and Comparative Example 1, 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 rays using an IKW high-pressure mercury lamp to polymerize. hardened. Thereafter, a photocurable material containing urethane acrylate oligomer as a main component is 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 of 9/cd and a thickness of 70 μm. did.

When we peeled off the surface coating layers of the optical fiber coatings produced in this way and connected them by heat fusion, it was found that the peelability of Example 1 was good, and the tensile strength of the fiber connection part was was 0.8 kg. However, in Comparative Example 1, the peelability was insufficient and the strength of the fiber connection portion 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
1 part, stearyl methacrylate 5 parts, and benzyl dimethyl ketal 3 parts were uniformly mixed to give a viscosity of 5 parts at 25°C.
A 50 centipoise coating material for optical fiber was obtained.

Comparative Example 2 50 parts of diacrylate of bisphenol A diglycidyl ether, 50 parts of neopentyl glycol diacrylate
1 part and 8 parts of benzyl dimethyl ketal were uniformly mixed.
An optical fiber coating material having a viscosity of 530 centivoids at 25°C was 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 rays using an IKW high-pressure mercury lamp and polymerized. hardened. Thereafter, a photocurable material containing urethane acrylate oligomer as a main component is 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 9/Cd of 140 and a thickness of 70 μm. did.

The surface coating layers of the optical fiber coatings manufactured in this manner were peeled off and then connected by heat fusion.The peelability of Example 2 was good, and the tensile strength of the fiber connection part was The strength was 0.8 kg. However, in Comparative Example 2, the peelability was insufficient and the strength of the fiber connection portion varied by 0.3/-0.6 kg. −Patent applicant Nitto Electric Industry Co., Ltd.

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 multi-layer polymer coating layer covering it, which has polymerizable carbon-carbon double bonds in its molecules. A composition containing a photopolymerizable compound having two or more of the above and a photopolymerization initiator is characterized by containing an acrylic acid alkyl ester and/or a methacrylic acid alkyl ester in an amount of 1 to 80% by weight of the entire composition. Coating material for optical glass fiber.