JPS62244005A - Fiber for optical transmission - Google Patents

Abstract

PURPOSE:To improve the reliability of glass strength by forming a protective coating of a material having <=30g/<2>.mm.24hr coefft. of moisture permeation. CONSTITUTION:The protective coating of an optical fiber constituted by forming the protective coating consisting of an acrylate resin curable by radiation to the outside periphery of a glass fiber consisting of quartz glass consists of the material having <=30g/m<2>.mm.24hr coefft. of moisture permeation. The total coefft. of moisture permeation of the coating layer is 30g/m<2>.mm.24hr and the innermost protective coating in contact with the glass fiber consists of the material having <=0.6% moisture absorption rate, if the protective coating consists of plural layers. The deterioration of the strength of the glass under moisture and heat is thereby suppressed and the glass is improved.

Description

[Detailed Description of the Invention] [Summary of the Invention] A protective coating made of a radiation-curable acrylate resin applied to the outer periphery of a quartz-based glass fiber has a moisture permeability coefficient of 30 g/-.
・If the material is made of tuts・24hr or less and the protective coating has two or more layers, the total moisture permeability coefficient of the protective coating is
, /flL1・mm・24hr or less, and the innermost protective coating in contact with the glass fiber is made of a material with a moisture absorption of 0.6- or less, thereby suppressing the decrease in glass fiber strength under moist heat and water immersion. Fiber for use.

[Industrial application field]

The present invention uses urethane acrylate cured by radiation such as ultraviolet rays in a fiber made of quartz glass.

This invention relates to a 7-eyeper for optical transmission that is coated with a protective coating made of acrylate resin such as epoxy acrylate.

[Conventional technology]

Conventionally, this type of optical transmission fiber has used acrylate resins such as urethane acrylate and epoxy acrylate, which can be cured by radiation such as ultraviolet rays, in addition to thermosetting silicone resin as a protective coating applied to the outer periphery of the glass fiber. Optical fiber has been introduced. The reason is,
Because it uses a light-curing reaction, it is a faster optical fiber manufacturing technology than before, and it uses a smaller beak curing furnace compared to conventional thermosetting furnaces, which simplifies the equipment. In addition, the material of the ultraviolet curable acrylate resin itself is economically effective due to its low price due to its raw material composition.

[Problem that the invention seeks to solve]

As a result of the inventors' investigation of optical fibers using ultraviolet-curable acrylate resin from the viewpoint of transmission characteristics and reliability of glass strength, it was found that the following problems existed in terms of reliability of glass strength. .

When we evaluated the tensile strength of optical fibers coated with UV-curable acrylate resin with various coating structures in moist heat or water immersion tests, we found that the strength of some optical fibers decreased significantly. This phenomenon of strength reduction has not been observed in conventional thermosetting silicone resin coated fibers. When the cause of this was investigated, it was found that it was caused by the moisture permeability coefficient of the protective coating material, and especially the amount of moisture absorbed by the coating material in contact with the glass.

[Means for solving problems]

In order to solve the conventional problems, the present invention provides an optical fiber in which a protective coating made of radiation-curable acrylate-based resin is applied to the outer periphery of a glass fiber made of quartz glass. The coating has a moisture permeability coefficient of 50 g
The second invention is characterized in that it is made of a material with a temperature of 7m", normal temperature, and 24h. When the protective coating has multiple layers, the total moisture permeability coefficient of the coating layer is 50y/m", twn, and 24h. , the amount of moisture absorbed by the innermost protective coating in contact with the glass fiber is 0.
．． It is characterized by being made of a material with a hardness of 6 or less. Examples will be described below along with the progress that led to the present invention.

〔Example〕

The structure of an ultraviolet curable acrylate resin will be described as a general structure of a radiation curable acrylate resin that is cured by radiation irradiation as a protective covering material according to the present invention.

The composition of UV-curable acrylate resin is as follows:
It mainly consists of the following three things. They are: oligomer (prepolymer), monomer (reactive diluent, 2 reactive crosslinker) and photoinitiator. As an oligomer,
2 acryloyl groups (CH, =CHCOO-') at the end
It must have a molecular weight M of 1,000 to 10,000, and its name is determined depending on its main chain structure.

Typical examples include urethane acrylate, epoxy acrylate, polyester acrylate, silicone acrylate, and mixtures thereof. In addition, for those with a urethane skeleton, polybutadiene is used depending on the internal main chain structure.

Polyethers, polyesters, mixed polyethers, polyethers, and other names are added in front of urethane acrylate to distinguish them.

Examples of monomers include acrylic monomers with one or more 7-acryloyl groups at the end, and tz-nyl groups CCH, =CH-
'), including ethylhexyl acrylate, isobornyl acrylate, tetrahydrofurfuryl alcohol-modified acrylate, insifneuric acid triacrylate, and trimethylolpropane triacrylate.

There are various types such as N-vinyl-2-pyrrolidone.

Examples of photoinitiators include benzophenone, penzyl dimedyl ketal, 2-hydroxy-2-methylpropiophenone, and 1-hydroxycyclohexylphenyl ketone. In addition to these main ingredients, various additives such as plasticizers and stabilizers may be added. The compounding ratio of these is \30 to 70 weight percent of oligomer, 1 to 70 weight percent of oligomer, 1 to 10 weight percent of photoinitiator.
The weight percentage can be determined according to the required characteristics.

Next, as an optical fiber coated with these ultraviolet curable acrylate resins, the following structure is generally being considered. That is, in the case of a glass diameter of 125 μm, there is a coating with an outer diameter of 250 μm to 500 IprrLφ, and from the viewpoint of transmission characteristics and mechanical properties, the inner layer has a Young's modulus of 0.05 to 0.5 Kgfi. Soft resin with 5 to 100 Kg/ms on the outer layer
There are those with a structure of at least two or more layers of hard resin with a Young's modulus of structure is common. Regarding these physical properties, various resin designs can be considered for UV-curable acrylate resins based on the composition design described above, but as a result, the curing properties (curing speed), temperature dependence of Young's modulus, hygroscopicity, moisture absorption, etc. There are differences in rate (or water absorption rate), durability, etc. From the viewpoint of long-term reliability, optical fibers obtained from coating materials and combinations thereof that satisfy manufacturability, transmission characteristics, and durability of coating materials are selected from among these resin design factors.
Regarding strength deterioration, under high temperature.

Tested in moisture-proof compound and in moist heat (or warm water). As a result, it was found that there were large differences in strength changes depending on the type of coating material. In view of this fact, we investigated the physical properties of the UV-curable acrylate resin that is the coating material, and found that regardless of the composition of the UV-curable acrylate resin, the moisture permeability coefficient and moisture absorption of the cured coating (1) (
It was found that the amount of water absorbed greatly depends on the amount of water absorbed. Therefore, we fabricated prototype optical fibers with coating structures with various levels of physical properties, and investigated their strength deterioration under moist heat. Specific examples will be described below.

Example 1: A Gl type (refractive index difference = 1) glass fiber 1 with a core diameter of 50 μmφ and a cladding diameter of 125 μmφ whose cross-sectional structure is illustrated in FIG. A protective coating 2 made of acrylate resin was coated with an outer diameter of 250#φ, and the coating was heated for 50°C under moist heat (60°C x 95-RH).
Changes in tensile strength when left in the sun were investigated. The moisture permeability coefficient shown here was measured in accordance with JIS Z20B at 4℃ and 90SRH using the moisture permeable cup method, using a sample with a groove thickness of approximately 250μ, and was converted to per song. It is something. In addition, Young's modulus was determined according to JISK71)3, and was 250. It is expressed as the secant modulus when stretched to 2.5 inches at a tensile speed ν=1 fIwlL/min with a JIS No. 2 dumbbell sheet shape of #thickness. The tensile strength test of the coated fiber was conducted at a gauge distance of 300 mm and a tensile speed of 100 fntI.
From the results shown in Table 1, the moisture permeability coefficient was approximately 30 rt/-・Jairai・24h.
It can be seen that materials with materials No. 2, 3, 4, and 5 below r have little strength loss under moist heat. However, Young's modulus is 2
Materials with 0 KP or higher N1) Due to transmission characteristics, for materials of 5, 4.5, low temperature (-20 to -401):
), it is preferable that the Young's modulus is 20 Kp or less.

Example 2: A sample of a two-layer coated fiber having an inner protective coating 21 made of soft resin and an outer protective coating 22 made of hard resin, the cross-sectional structure of which is illustrated in FIG. 2 of the general configuration according to the present invention, was carried out. The same evaluation as in Example 1 was performed. 1 indicates a glass fiber.

The coating diameter is an inner layer diameter of 300 μmφ and an outer layer diameter of 400 μmφ.

The results are shown in Table 2. In Table 2, the amount of moisture absorption is 23℃
The saturated water content at 50% KH was evaluated using the Karl Fischer method.

From the results shown in Table 2, in the case of a two-layer coating structure, the total moisture permeability coefficient is considered to be the geometric average of each of the two layer coatings, and if the moisture permeability coefficient is 30g□2・twn・24hde or less, the inner protective layer Sample No. whose moisture absorption value of soft resin is less than about 0.6
, 2, 4, and 6 are found to be effective in suppressing the decrease in fiber tensile strength.

In each of the above embodiments, the structure of the optical 7-eyeper is based on the basic structure shown in FIG.
For example, the two-layer coating structure illustrated in FIG. 2 has been described, but the present invention is an optical fiber element having an inner layer and an outer protective layer 21 and 22 applied to the glass fiber 1, the cross-sectional structure of which is illustrated in FIG. 3. Arrange multiple books in parallel and further '
*A tape core K having a structure of being covered all at once with a secondary coating 3 made of external radiation curing type acrylate resin can also be applied and is an embodiment of the present invention.

〔Effect of the invention〕

As described above, the optical transmission fiber having the moisture permeability coefficient of the protective coating and the moisture absorption amount of the innermost layer coating in the case of a multilayer coating structure according to the present invention suppresses and improves the decrease in glass strength under moist heat. It can be done, and the effect is remarkable.

[Brief explanation of drawings]

1 and 2 are cross-sectional structures of an optical transmission fiber and an embodiment of the present invention, respectively, and FIG. 3 is a cross-sectional structure of a ribbon core according to another embodiment. 1... Glass fiber 2... Protective coating 21... Inner layer protection, [1) 22... Outer layer protective coating 5... Secondary coating

Claims (2)

[Claims] (1) On the outer periphery of the glass fiber made of quartz glass,
An optical transmission fiber provided with a protective coating made of radiation-curable acrylate resin, characterized in that the protective coating is made of a material with a moisture permeability coefficient of 30 g/m^2・mm・24 hr or less. Transmission fiber. (2) On the outer periphery of the glass fiber made of quartz glass,
In an optical transmission fiber provided with a protective coating made of radiation-curable acrylate resin, the protective coating has a multilayer structure of two or more layers, and the moisture permeability coefficient of the protective coating is 30 g/m^2.mm.・24
hr or less, wherein the innermost protective coating in contact with the glass fiber of the multilayer structure is made of a material with a moisture absorption of 0.6% or less.