JPS6218509A - Fiber for optical transmission - Google Patents

Abstract

PURPOSE:To suppress the foaming from UV resin coating layers of a fiber for optical transmission by forming the UV resin coating layers into multi- layered structure and setting the moisture absorption rate of the outermost layer at <=0.6%. CONSTITUTION:The soft UV resin layer (about 90mum film thickness) 2 and the hard UV resin layer (50mum film thickness) 3 on the outermost layer are coated on the optical fiber 1 consisting of quartz and the moisture absorption rate (measured after resting for 24hr in 23 deg.C and 50% RH as standard measuring conditions) of the UV resin constituting the hard UV resin layer 3 of the outermost layer is set at <=0.6%. The generation of the foam from the coating layers and the remaining of the foam in the juncture are thereby obviated and the low-temp. characteristic assisted by the protective covering is maintained. The reliability is thus improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Summary of the Invention] The present invention eliminates the generation of bubbles from the coating layer of an ultraviolet curable resin-coated optical fiber and uses an ultraviolet curable resin layer as a protective coating that maintains low-temperature properties. It has a multi-layer structure, and the moisture absorption of the ultraviolet curable resin for the outermost protective coating is 0.6%.
The following is an ultraviolet curable resin-coated optical fiber having a Young's modulus in the range of 30 to 100 Ky/m.

[Industrial application field]

The present invention uses an ultraviolet curable resin (
Hereinafter, it will be referred to as UV resin. ) fiber optics for optical transmission;
It is related to

[Conventional technology]

In recent years, the core and cladding are made of silica glass.

Optical transmission fibers using UV resin as a protective coating material for so-called silica-based optical fibers have been developed and are already in practical use. UV resin has a faster curing speed than the conventionally used thermosetting silicone resin, and is expected to increase the manufacturing speed of original transmission fibers.It is also expected to be cheaper in the future, so it is recommended to use UV resin. Optical transmission fibers have been shown to be promising in practical use from an economic standpoint.

This UV resin-coated optical fiber can have various dimensions depending on its usage, but in order to maintain the required transmission characteristics, it basically has a soft UV resin layer on the inside. It is common to have a multilayer structure with a hard UV resin hard layer on the outside. Also, depending on the application,
Furthermore, a thermoplastic resin such as Ml-12 may be coated thereon as a protective coating layer.

[Problems to be Solved by the Invention] As a result of various studies on UV resin-coated optical transmission fibers, it was found that there were two major problems during production.T
L straw, # on the outer peripheral surface of the UV resin coated optical transmission fiber.
When coating with thermoplastic resin extrusion such as Y-12,
It was found that bubbles were generated from the coating layer of the UV resin light transmission fiber due to the heat of the molten resin, making it impossible to uniformly coat the thermoplastic resin coating layer.

Furthermore, when connecting UV resin-coated optical transmission fibers to each other, if a swallow shrink sleeve using hot-melt adhesive is applied, air bubbles may be generated from the coating layer of the UV resin-coated optical transmission fibers, causing This results in air bubbles remaining in the film, resulting in concerns about reliability.

As a result of examining the above-mentioned phenomenon, the cause of the bubbles that occur is U.
It was found that this was due to the moisture C2 contained in the V resin coating layer C2. Moreover, this water was hardly contained in the UV resin raw material during the production of the UV resin-coated optical transmission fiber, and the UV resin-coated optical transmission fiber is mainly absorbed by absorbing moisture in the air after the production of the UV resin-coated optical transmission fiber. This is due to a number of things.

The UV resins that cause this hygroscopicity include phrethane acrylate, epoxy acrylate, butadiene acrylate, polyester acrylate, and silicone acrylate, which contain many polar groups such as carbonyl groups, ester groups, ether groups, and urethane groups. The main component of these UV resins is whether to suppress the eCC wettability of these UV resins or not, which is considered to be a problem related to suppressing the foaming phenomenon described above.

[Failure to solve the problem]

In the present invention, the UV resin coating layer of the UV resin coated optical transmission fiber is made to have a multilayer structure, and the moisture absorption amount of the outermost layer is 0. 6% or less, and the outermost r
The Young's modulus Y of m is in the range of 50 to 100 Ky/mm2. This will be explained below with reference to the drawings.

〔Example〕

FIG. 1 shows a cross-sectional structure of a first embodiment of an optical transmission fiber according to the present invention. Quartz-based optical fiber 11' knee U
V Resin Soft II (film thickness approx. 90 prn) 2 N
The outermost layer is coated with a UV resin hard layer (film thickness 50 μm) 5, and the moisture absorption amount of the UV resin in the outermost UV resin hard layer 3 is measured (standard measurement conditions: 23°C, 50% RH).
We made prototypes with various levels of N9-12 coating (measured after being left for 24 hours inside), and applied N9-12 coating to the outer periphery.
The occurrence of bubbles in the -12 coating was observed.

The results are shown in Table 1.

Table 1 The Young's modulus in Table 1 indicates the secant Young's modulus at 2.5% elongation at a sheet thickness of 250 μm and a tensile speed of 11/min.

From the results in Table 1, it is clear that if the UV resin has physical properties with a moisture absorption of 0.6% or less under the standard measurement conditions, there will be no adverse effect on both the exterior and interior appearance of the coating, and the Ny- It was confirmed that an original transmission fiber coated with N, Y-12 could be obtained without adversely affecting the transmission loss after extrusion. Note that the outer diameter of the #y-12 coating can vary from thin to thick, but from the viewpoint of heat capacity, the thicker the wall, the more susceptible it is to the amount of moisture absorption.

FIG. 2 is a cross-sectional structure of a second embodiment of the optical transmission fiber according to the present invention 1. A quartz-based optical fiber secondary coating hard layer 4 was coated with a film thickness of 250 μm. We prototyped a UV resin-coated optical transmission fiber in which the outermost layer was coated with UV resin with varying moisture absorption amounts of the UV resin in the outermost UV resin secondary coating hard layer under the same standard measurement conditions as in Example 1. Then, these optical transmission fiber cores were connected to each other using a connection method using heat-shrinkable tubes, and the state of the connections was observed. The results are shown in Table 2.

Table 2 From the results in Table 2, if the moisture absorption amount of the UV resin in the outermost UV resin secondary coating hard layer 4 exceeds 0.6%, air bubbles will be generated due to the heat of the hot melt adhesive during connection. , it is confirmed that air bubbles remain in the connection area.

FIG. 3 shows a third embodiment of the present invention, and the first and second embodiments are examples of a single fiber wire containing one optical fiber in the form of a UV resin-coated optical transmission fiber. As for the third factor, for example, in the case of a tape core wire containing five optical fibers in parallel, the present invention (UV resin with physical properties of moisture absorption according to the outermost layer of UV resin 2 coated hard II51) By doing so, the same effect as in the case of a single optical fiber can be obtained.

Note that the optical transmission fiber of the present invention (in which the outermost layer U
It is desirable that the Young's modulus of the V-resin be larger from the point of view of protective coating, but from the point of view of five-temperature characteristics, it is better to keep the Young's modulus below a certain level. From the first and second examples, it is clear that in the case of the present invention, the Young's modulus is in the range of 30 to 100/'
It was confirmed that a distance of 71 m” is desirable.

〔Effect of the invention〕

As described above, the optical transmission fiber of the present invention has UV
The resin coating layer has a multilayer structure, and the moisture absorption amount of the UV resin in the outermost UV resin hard layer is 0.6% or less, and the Young's modulus is in the range of 30 to 100 Kg/mm''. The generation of air bubbles from

It is highly effective because it removes residual air bubbles at the connection part (=) and improves reliability by maintaining low-temperature characteristics in conjunction with the protective coating.

Embodiment 2 of the present invention has a cross-sectional structure, and FIG. 3 shows a cross-sectional structure of Embodiment B of the present invention.

1... Optical fiber, 2... UV resin soft layer, 3...
...UV resin hard layer, 4, 5...UV resin secondary coating) 1-hard layer

Claims (2)

[Claims] (1) In an optical transmission fiber in which a quartz-based optical fiber whose core and cladding are made of quartz-based glass is protectively coated with an ultraviolet curable resin layer, the ultraviolet curable resin layer has a multilayer structure, and the multilayer structure is ultraviolet curable. 1. An optical transmission fiber characterized in that an ultraviolet curable resin for a protective coating on the outermost layer of a shaped resin layer has a moisture absorption of 0.6% or less. (2) The ultraviolet curable resin for the protective coating of the outermost layer is:
The optical transmission fiber according to claim 1, characterized in that the Young's modulus is in the range of 30 to 100 kg/mm^2.