JPH0140964B2 - - Google Patents

Description

[Detailed description of the invention] (a) Technical field The present invention relates to a method of coating a glass fiber for optical transmission (hereinafter referred to as an optical fiber).
In particular, the present invention provides a method for extrusion coating of fluororesin that does not cause deterioration of optical fiber properties.

(b) Background technology The coating structure for optical fibers is disclosed in Japanese Patent Application Laid-Open No. 1986-
As proposed in Japanese Patent No. 125754, the most common is a so-called double coating structure consisting of a relatively thin coated and baked layer and an extruded coating layer. On the other hand, as the coating material, silicone resin, epoxy resin, urethane resin, nylon, polyethylene, etc. have been proposed for each of the coated and baked layer and the extruded coating layer. Among these coating materials, the thermoplastic resins used for the extruded coating layer have a low melting point and are subject to significant oxidative deterioration at high temperatures, and fluororesin is one that can withstand long-term use at high temperatures of 150°C or higher. This is used as an extrusion coating layer for so-called heat-resistant coated optical fibers.

However, according to studies by the present inventors, optical fibers using fluororesin as an extruded coating layer have significantly lower mechanical strength than optical fibers using nylon, polyethylene, etc. as an extruded coating layer.
It was not something that could be put to practical use. For example, an optical fiber with a glass fiber outer diameter of 125 μm and a silicone resin coated and baked layer coating thickness of approximately 150 μm is coated with nylon-12.
The average strength of the extrusion coated with a thickness of 250μm is
6.2Kg, while the same optical fiber
The average strength of the extrusion coated with ETFE (ethylene-tetrafluoroethylene copolymer) to a thickness of 250 μm was 3.6 kg.

(C) Disclosure of the Invention As a result of detailed study on the phenomenon of decrease in mechanical strength of glass fiber during extrusion coating with fluororesin, the present inventors have found that the decrease in strength occurs during melt extrusion of fluororesin. It was discovered that this was due to the influence of fluorine gas or fluoric acid, and based on this knowledge, the present invention was achieved.

In other words, it is thought that the generated hydrofluoric acid passes through the coated baking layer and reaches the glass fiber surface, corroding the glass surface or destroying the chemical bond between the glass surface and the coating baking layer, resulting in the above-mentioned decrease in strength. . Furthermore, when a core fiber using fluorine resin as an extrusion coating material is irradiated with an electron beam, etc., a decrease in the mechanical strength of the optical fiber is observed before and after irradiation. Or it may be due to the influence of hydrofluoric acid.

According to the studies of the present inventors, in order to prevent or reduce the generation of fluorine gas or fluoric acid during melt extrusion of a fluororesin, it is necessary to lower the extrusion temperature of the fluororesin to near the melting point of the fluororesin. In this case, the resin viscosity increases during extrusion,
It was found that large residual strain remained after molding. This residual strain causes the coating material to shrink over time,
This causes an increase in transmission loss due to so-called microbending.

As a result of further study by the present inventors, it was found that fluorine gas and fluoric acid generated during melt extrusion of fluororesin are adsorbed to glass fibers when adsorbent powder solids such as titanium oxide and calcium carbonate are present. It has been found that there is no reduction in the mechanical strength of the optical fiber without reaching the surface.

The present invention was completed based on the above knowledge, and consists of a first coating layer consisting of a coated and cured layer of a resin composition on a glass fiber wire for optical transmission, and a second coating layer consisting of an extruded fluororesin coating layer thereon. In a coated light transmission glass fiber with a coating layer, the first coating layer is
The present invention relates to a coated optical transmission glass fiber characterized in that an adsorbent powder solid is added in a range of 0.05 to 20% by weight.

The adsorbent powder solids used in the present invention include metal oxides such as zinc oxide, aluminum oxide, titanium oxide, magnesium oxide, calcium oxide, silicon oxide, and iron oxide, carbonates such as calcium carbonate, carbon powder, and activated carbon. Examples include powders having a melting point and decomposition temperature of 350°C or higher, and these can be used alone or in combination of one or more types. Many of these adsorbent powder solids are used as inorganic pigments, and they may also function as pigments.

The amount of adsorbent powder solids needs to be 0.05% by weight or more in terms of adsorption effect, and needs to be 20% by weight or less from the viewpoint of not causing deterioration of the physical properties of the resin composition.

Examples of the fluororesin used in the second coating layer of the present invention include tetrafluoroethylene, tetrafluoroethylene-hexafluoropropylene copolymer,
Examples include ethylene-tetrafluoroethylene copolymer, chlorotrifluoroethylene, and vinylidene fluoride.

The material for the first coating layer below the fluororesin extrusion coating layer of the present invention is not particularly limited, and silicone resins, epoxy resins, urethane resins, polyesters, polybutadiene, and modified products thereof can be used. This first coating layer does not need to be a single layer, but may have a multilayer structure consisting of an inner layer that does not contain adsorbent powder solids and an outer layer that contains adsorptive powder solids.

Example 1 After drawing an optical fiber mainly composed of quartz glass with an outer diameter of 125 μm, before contacting other solid materials, 55% of silicon dioxide powder was added to a two-component room temperature curing silicone resin.
The resin composition containing % by weight was applied to a thickness of 150 μm and cured.

The resulting silicone resin fiber was coated with an ethylene-tetrafluoroethylene copolymer by extrusion to an outer diameter of 0.9 mm.

Example 2 After drawing an optical fiber mainly composed of quartz glass with an outer diameter of 125 μm, before it comes into contact with other solid materials, a 50 μm thick two-component room-temperature curing silicone resin containing no silicon dioxide powder is applied. Apply with water, cure,
Furthermore, a two-component room temperature curing type silicone resin containing 5% by weight of silicon dioxide powder was applied thereon to a thickness of 100 μm and cured. The resulting silicon-coated fiber was coated with a tetrafluoroethylene-hexafluoropropylene copolymer by extrusion to an outer diameter of 0.9 mm.

Comparative Example 1 After drawing an optical fiber mainly composed of quartz glass with an outer diameter of 125 μm, a two-component room temperature curing silicone resin without silicon dioxide powder added was applied to a thickness of 150 μm before it came into contact with other solid materials. and cured. The resulting silicon-coated optical fiber was coated with an ethylene-tetrafluoroethylene copolymer by extrusion to an outer diameter of 0.9 mm.

The mechanical strength of the fluororesin-coated optical fibers obtained in Example 1, Example 2, and Comparative Example 1 was determined when the sample length was 20 m;
As a result of the tensile test with η=20, Example 1 weighed 6.2Kg, Example 2 weighed 6.1Kg, while Comparative Example 1 weighed 3.4Kg.
This clearly shows the adsorption effect of fluorine gas and fluoric acid by the adsorbent powder solid of the present invention.

Claims (1)

[Claims] 1. In a coated glass fiber for light transmission, in which a first coating layer made of a coated and cured layer of a resin composition is provided on a bare wire of a glass fiber for light transmission, and a second coating layer made of an extruded fluororesin coating layer is provided thereon. , a coated glass fiber for optical transmission, characterized in that an adsorbent powder solid is added to the first coating layer in a range of 0.05 to 20% by weight.