JPS5921542A - Coating material for optical glass fiber - Google Patents

Abstract

PURPOSE:To obtain the titled material having low viscosity, superior adhesive strength to an optical fiber and a high curring rate and giving a flexible resin coat, by blending a specified epoxy resin with a salt of Lewis acid. CONSTITUTION:A coating material obtd. by blending an epoxy resin contg. >=4C aliphatic epoxy resin having two or more epoxy groups in the moelcule such as long-chain aliphatic diglycidyl ether of 1,4-butanediol or diglycidyl ether of polyether polyol having >=200 average mol.wt. as the principal component with a salt of Lewis acid such as the diazonium salt of Lewis acid is used as a material for forming an intermediate layer which is more flexible than a surface layer between an optical glass fiber and the surface layer covering the fiber and having superior wear resistance such as a polyethylene or polyamide resin layer. The coating materil has low viscosity, superior adhesive strength to the optical fiber and a high curing rate, and the resulting resin coat is flexible.

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates to materials for coating optical glass fibers for light transmission.

Optical glass fibers (hereinafter simply referred to as optical fibers) used for optical transmission are fragile, easily damaged, and have poor flexibility. destroy it. Therefore, conventionally, an optical fiber is coated with a resin on its surface immediately after being manufactured from a glass rod or the like.

One such resin coating is to provide a surface layer such as polyamide resin or polyethylene, which has excellent abrasion resistance, on the surface of the optical fiber, and an intermediate layer that is more flexible than the above layer between this layer and the optical fiber. It is known that there is a The intermediate layer may be used as a primer layer to increase the initial strength of the optical fiber, or as a buffer layer to reduce the effect on the optical fiber when the hard surface layer is thickened, or as a combination of the primer layer and buffer layer. It functions as a double layer.

Conventionally, thermosetting materials such as urethane resins and general epoxy resins have been used to form such intermediate layers, but they require a long time to cure, resulting in poor productivity and poor curing. Due to this, the adhesion with the optical fiber was not sufficient, and there were also problems in terms of flexibility, and as a result, the transmission characteristics were significantly deteriorated due to lateral pressure, resulting in a lack of long-term reliability.

Furthermore, as an alternative to the above-mentioned materials, ultraviolet curing type materials such as epoxy acrylate have been proposed, but the polymerization and curing reaction of these types of materials is easily inhibited by oxygen in the air, and the volume at the time of curing is Due to the large shrinkage rate, productivity and adhesion to optical fibers were poor, and flexibility was still insufficient.

The present invention was made to solve the above problems, and in particular, the coating for optical fiber has a low viscosity, excellent adhesion to the optical fiber, a fast curing speed, and a flexible resin coating. The purpose is to provide materials.

That is, the present invention provides a material for forming the intermediate layer in a covering structure in which an intermediate layer, which is more flexible than the above layer, is provided between an optical fiber and a surrounding surface layer having excellent abrasion resistance. A photocurable coating for optical fiber, characterized in that a Lewis acid salt is blended into an epoxy resin mainly composed of an aliphatic epoxy resin having 4 or more carbon atoms and having 2 or more epoxy groups in the molecule. It is related to materials.

The coating material of the present invention can be adjusted to a suitable viscosity for optical fibers, and can be quickly applied to optical fibers and then irradiated with light such as ultraviolet rays without causing polymerization inhibition due to oxygen in the air. The curing speed is significantly faster than that of conventional heat curing types and ultraviolet curing types. In addition, the volumetric shrinkage rate during curing is small, and there is no concern that internal distortion will occur due to curing shrinkage.

As described above, according to the coating material of the present invention, the productivity of the optical fiber coating can be greatly improved, and the adhesion between the optical fiber and the intermediate layer can be improved. Moreover, the intermediate layer formed in this manner has excellent flexibility, and this and the above-mentioned good adhesion give very good results to the transmission characteristics of the optical fiber.

The epoxy resin used in this invention is mainly an aliphatic epoxy resin having 4 or more carbon atoms and having 2 or more epoxy groups in the molecule, and by using such an epoxy resin, the flexibility of the resin coating can be improved. Good results in sex. The above-mentioned aliphatic epoxy resin may be linear or branched, and includes various types such as ether type and ester type. Specifically, long-chain aliphatic diglycidyl ethers with 1,4-butanediol, 1,5-heptanediol, and 1,6-hexanediol, and diglycidyl ethers of polyether polyols with an average molecular weight of 200 or more are listed. It will be done.

Along with such aliphatic epoxy resins, the strength of the intermediate layer (
Aromatic epoxy resin,
Other epoxy resins such as alicyclic epoxy resins and heterocyclic epoxy resins may also be used in combination. However, in order not to impair the characteristics of the aliphatic epoxy resin, it is desirable that the proportion thereof be less than 50% by weight, preferably 40% by weight or less.

In this invention, the Lewis acid salt blended into the above-mentioned epoxy resin acts as a photopolymerization initiator, and specifically, it has the following general formula; (wherein R is hydrogen, chlorine, bromine, or methyl group) , a methoxy group, a hydroxyl group, or a monovalent group such as N(CH3)2).

The blending amount is usually 0.00 parts by weight per 100 parts by weight of the epoxy resin.
It is about 1 to 10 parts by weight.

In addition to the above-mentioned components, this optical fiber coating material also contains various modifying resins such as acrylic resin, polyamide resin, polyether, polyurethane, polyamideimide, silicone resin, and phenol resin, as well as a curing accelerator. , an organosilicon compound, a surfactant, and other various additives may be added.

In order to actually coat an optical fiber with the optical fiber coating material of the present invention, it may be carried out according to a conventionally known method, and generally, the coating material of the present invention is coated on the surface of the optical fiber in a process subsequent to the spinning process. After coating, it is polymerized and cured by irradiation with light such as ultraviolet rays. The thickness at this time is thin in the case of a primer layer and relatively thick in the case of a buffer layer, but is generally appropriately selected from a range of about 20 to 150 .mu.m. After forming the intermediate layer in this way, the desired optical fiber coating can be obtained by further providing a hard surface layer of polyethylene, polyamide resin, or the like with excellent abrasion resistance on the surface of the intermediate layer.

As detailed above, the optical fiber coating material of the present invention has a structure in which an intermediate layer that is more flexible than the above layer is provided between the optical fiber and the surrounding surface layer that has excellent wear resistance. The productivity of the optical fiber coating, the flexibility of the intermediate layer, and the adhesion to the optical fiber can all be improved.

EXAMPLES Below, examples of the present invention will be described in more detail. In addition, in the following, parts shall mean parts by weight.

Example 1 3 parts of 4-methylphenyldiazonium salt of boron tetrafluoride was dissolved in 70 parts of polypropylene glycol diglycidyl ether with an average molecular weight of 300 and 30 parts of Epon 1004 (bisphenol A type epoxy resin manufactured by Shell Oil Co.) Thus, the optical fiber coating material of the present invention was obtained.

Example 2 3 parts of iodonium salt of boron tetrafluoride was dissolved in 50 parts of Epon 871 (dimer acid glycidyl ester manufactured by Shell Oil Co., Ltd.; aliphatic epoxy resin) and 50 parts of 1,4-butanediol diglycidyl ether. , the optical fiber coating material of the present invention.

Example 3 3 parts of a sulfonium salt of boron tetrafluoride was dissolved in 70 parts of polypropylene glycol diglycidyl ether having an average molecular weight of 600 and 30 parts of Epon 828 (bisphenol A type epoxy resin manufactured by Shell Oil Co., Ltd.). It was used as a coating material for optical fibers.

Comparative Example 30 parts of bisphenol A diglycidyl ether diacrylate and polyethylene glycol (average molecular weight 400)
An optical fiber coating material was prepared by dissolving 3 parts of benzoin isobutyl ether in 70 parts of diacrylate.

When the characteristics of each material of Examples 1 to 3 and Comparative Example were investigated, they were as shown in the following table.

1) After coating on a glass plate with a thickness of 50μ, 80W/c
Curing speed when photocuring with a high-pressure mercury lamp of m x 2 lamps.

2) 0.3 mm thick sheets were produced at a conveyor speed of 10 m/min, and 10 sheets were stacked and measured.

3) Apply it on a glass plate with an applicator to a thickness of 50μ,
It was cured at a conveyor speed of 10 m/min, and a cross-cut tape peeling test was conducted.

In the numerical values in the table, the denominator is the number of samples and the numerator is the number of samples that were not peeled off.

Next, the materials of Example 1 and Comparative Example were actually subjected to an optical fiber coating test to evaluate their performance. The results were as shown below. In this test, for simplicity, only a coating corresponding to the intermediate layer was applied. This is because the performance when a surface layer such as polyethylene is further provided on the intermediate layer can be sufficiently predicted from the above test results.

Test Example 1 In a step subsequent to the spinning process, the coating material shown in Example 1 was applied to the surface of an optical fiber with a diameter of 125 μm spun at a speed of 50 m/min, and then ultraviolet rays (two lamps with an output of 2 KW) were irradiated. and cured. The outer diameter after coating was approximately 200 μm, and the surface was uniform. Moreover, the breaking strength was 5.0 kg, and no increase in transmission loss was observed up to -40°C.

Test Example 2 In a step subsequent to the spinning process, the coating material shown in the comparative example was applied to the surface of an optical fiber with a diameter of 125 μm spun at a speed of 50 m/min, and then cured in the same manner as in Test Example 1. Ta. The outer diameter after coating was approximately 200 μm, and the surface remained sticky. Also, the strength is 3-5K
g, and a rapid increase in transmission loss was observed below -20°C.

As mentioned above, the optical fiber coating material of the present invention has a fast curing speed, so it can be coated quickly and with good adhesion in the process subsequent to the optical fiber spinning process, and it is highly flexible after curing, so it has the following advantages: By further providing a surface layer with excellent abrasion resistance, there is an advantage that an optical fiber coating with excellent transmission characteristics can be obtained.

Patent applicant: Nitto Electric Industry Co., Ltd. Agent Patent Attorney Moto Kunio Negi

Claims (1)

[Claims] (1) A material for forming the intermediate layer in a corrugated body having a structure in which an intermediate layer that is more flexible than the above layer is provided between the optical glass fiber and the surrounding surface layer that has excellent wear resistance. A photocurable coating for optical glass fiber, characterized in that a Lewis acid salt is blended into an epoxy resin mainly consisting of an aliphatic epoxy resin having 4 or more carbon atoms and having 2 or more epoxy groups in the molecule. material.