JPS6071551A - 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 satd. fatty acid into a material for forming a primer clad layer contg. epoxy resin and a curing agent. CONSTITUTION:A material for forming a primer clad layer for optical glass fiber is obtd. by incorporating 0.01-5wt% satd. fatty acid such as lauric acid basing on the total weight of the compsn. including nonvolatile component into an epoxy resin composition consisting primarily of epoxy resin and curing agent such as phenol resin. After forming a primer clad layer with this 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. By this treatment, the strength of the connected optical fiber 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 This invention relates to a thermosetting material for coating optical glass fins for light transmission.

Optical glass fibers (hereinafter referred to as optical fibers) used for optical transmission are brittle and easily damaged, and have poor flexibility, so they can be easily damaged by even the slightest external force due to such scratches. Destroy. For this reason, 1. It is extremely difficult to use optical fibers as they are for optical transmission.

Therefore, conventionally, an optical fiber is coated with a polymer on its surface immediately after being spun from a glass base material, in order to maintain the initial strength immediately after manufacture and to manufacture an optical fiber that can withstand long-term use. Alternatively, an ultraviolet curable material containing epoxy acrylate oligomer or urethane acrylate oligomer as the main ingredient may be applied to the surface of the optical fiber and cured by light irradiation, or a buffer material such as silicone resin may be used as a base layer for the above material layer. A coating layer having a single layer or multilayer structure is provided by providing a layer or the like.

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, during such a splicing operation, the surface of the optical fiber is easily damaged, which poses a problem of reducing the mechanical strength after splicing.

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 pm or less is first formed, and then the above-mentioned coating is applied on top of this. A layer is provided several tens of μtn thick,
Attempts have been made to prevent a decrease in mechanical strength during connection by removing only the surface side coating layer 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 also the optical fiber surface will be more likely to be damaged when the primer coating layer is peeled off. I couldn't hope for much improvement in 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.

In other words, the present invention provides that a light ≠
0) A material for providing a thin primer coating layer of 1 m or less, in an epoxy resin composition containing an epoxy resin and a curing agent, 0.0 in the total amount of non-volatile content of this composition.
The present invention relates to a coating material for optical fiber, characterized in that it contains a saturated fatty acid in a proportion of 1 to 5% by weight.

As described above, the present invention is characterized in that a specific amount of saturated fatty acid is contained in the material for forming a primer coating layer made of an epoxy resin composition, which prevents the adhesion to the optical fiber surface from being impaired. Since the removal workability of the surface coating layer can be improved without any problem, and there is little 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.

As the epoxy resin in the epoxy resin composition used in the present invention, bisphenol A diglycidyl ether type epoxy resins are particularly preferred, but other types of conventionally known types can be used. Further, the type of curing agent is not particularly limited, and any of various conventionally known curing agents such as phenol resin, urea resin, and melamine resin can be used. The amount of curing agent used is usually 2 out of the total amount of epoxy resin.
It is about 0 to 40% 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 becomes low and the film properties are poor. The upper limit of the number of carbon atoms is not particularly specified as long as it can be dissolved or made compatible with the epoxy resin composition.

Specific examples of the above saturated fatty acids include capric acid, undecylic acid, lauric acid, tridecylic acid, myristic acid,
These include pentadecylic acid, palmitic acid, heptadecylic acid, stearic acid, nonadecanoic acid, arachidic acid, behenic acid, lignoceric acid, cerotic acid, heptacanoic acid, montanic acid, melisic acid, and lafcelic 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 such saturated fatty acids to be used is based on the total amount of non-volatile components of the epoxy resin composition, that is, non-volatile components consisting of the epoxy resin, curing agent, and optional components such as silane coupling agents added as necessary. The proportion of
001 to 5% by weight, preferably 091 to 3% by weight. If the amount is less than 0.001% by weight, the effect of this invention cannot be obtained,
If the amount exceeds 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, causing problems when forming the surface coating layer or under usage conditions after connecting the optical fiber. There is a risk of causing

The coating material of the present invention is produced by combining the above-mentioned epoxy resin curing agent, saturated fatty acid, and various optional components used as necessary with a non-volatile solvent such as selonlube acetate, ethyl cellosolve, diethylene glycol dimethyl ether, toluene, or xylene. is generally 20-5
0% by weight, preferably 20. It is diluted to 40% by weight. Its viscosity is usually set at 500 centipoise or less at 25° C., preferably in the range of 50 to 300 centipoise, so that it can be uniformly applied by a method such as spray painting.

In order to coat an optical fiber with such a coating material, the surface of the optical fiber immediately after spinning is coated with an iopm or less, usually 5 μm or less, particularly preferably 1 to 2 μm, using the coating method described above.
It is sufficient to apply it to about pm and then heat and cure it. In the above application, since the epoxy resin composition can be diluted with a solvent to a low viscosity as described above, this gives good results in adhesion to the optical fiber.

After forming the primer coating layer in this manner, a surface coating layer consisting of a conventionally known single-layer or multilayer polymer coating layer can be provided on this layer. 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 above-mentioned peeling and removing method, 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 1 230 parts of Epicor 1007 (bisphenol A diglycidyl ether epoxy resin manufactured by Shell Chemical Co., Ltd.), urea resin (trade name Beckamine P1 manufactured by Inu Nippon Ink Chemical Co., Ltd.)
38; 170 parts of 6o wt% xylene-butanol solution), 1 part of lauric acid, 300 parts of cellosolve acetate, and 300 parts of toluene were uniformly mixed to obtain a coating material for optical fiber having a viscosity of 90 centipoise at 25°C. .

Example 2 250 parts of Epicote 1007 (mentioned above), 1'IO part of phenol resin (trade name: Super Veracasite 5100I, manufactured by Dainippon Ink Chemical Co., Ltd.), 5 parts of stearic acid, 320 parts of diethylene glycol dimethyl ether, and 320 parts of xylene were uniformly mixed. The viscosity at 25°C is 120
A centipoise coating material for optical fiber 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 lauric 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 stearic acid was not blended.

Using each of the materials of the above Examples and Comparative Examples, this was spray-coated on the surface of a 125-jtm thick optical fiber immediately after spinning so that the thickness after drying and curing would be 1 μm, and then the furnace length was 50 cm, and the furnace temperature was 550 ~ The material was introduced into a heating furnace at 600° C. and cured by heating. Thereafter, a photocurable material containing urethane acrylate oligomer as a main component was further coated on the primer coating layer formed by the above method, and cured by ultraviolet irradiation using an IKW high pressure mercury lamp, and the elastic modulus was 20.
A surface coating layer of b/QrI, thickness 70, and ttm was formed.

When the optical fiber coatings manufactured in this manner were connected by peeling off their surface coating layers and heat fusion, it was found that the peelability of Examples 1 and 2 was good, and the fiber connection part was The tensile strength was 0.8 Kg. However, in Comparative Examples 1 and 2, the peelability was insufficient and the strength of the fiber connection portion varied from 0.3 to 0.8 kg.

Patent applicant: Nitto Electric Industry Co., Ltd.

Claims (1)

[Claims] (1) A material for providing a thin primer coating layer of 1 opm or less between an optical glass fiber and a single-layer or multilayer polymer coating layer covering it, which is an epoxy resin containing an epoxy resin and a curing agent. A coating material for optical glass fibers, characterized in that a resin composition contains a saturated fatty acid in a proportion of 0.01 to 5% by weight based on the total amount of the composition including nonvolatile components.