JPH05232330A - Production of plastic optical fiber - Google Patents

Abstract

PURPOSE:To intensify the adhesive strength between a core and a clad and to lessen an increase in transmission loss by subjecting the surface of a core material after drawing to a plasma treatment. CONSTITUTION:After the core material 1 is drawn, the surface of the core material 1 is subjected to the plasma treatment and thereafter, the clad material is applied and stuck thereto. Transmittable plastics, such as PMMA(polymethyl methacrylate), polycarbonate and polystyrene, are used for the core material and silicone resins and fluororesins having the refractive index smaller than the refractive index of the core material 1 are used for the clad material in order to impart flexibility to the plastic optical fiber in such a case. Since the objective is the treatment of the surface of the core material 1, the generation of plasma in a microregion is simply necessitated and, therefore, the atm. plasma treatment which uses He for a carrier gas and generates the plasma by the glow discharge generated by an electrode 2 under an atm. pressure is suitable. Even more, this atm. plasma treatment does not require the pressure reduction in a chamber and is, therefore, convenient.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention is for example a few meters in a factory.
An optical fiber used as an optical signal transmission line for transmitting an optical signal over a short distance of about 30 m, specifically, in the field of FA (Factory Automation), particularly, it is repeatedly bent like a joint part of an arm of a robot. The present invention relates to a method for manufacturing an optical fiber which is laid and used in a part or a part in a factory where heat history is applied.

[0002]

2. Description of the Related Art In the FA field, control of machine robots and the like is progressing at higher speed and more precisely, and accordingly, in the field, higher speed and large capacity signals are handled. However, there is a problem that the electromagnetic noise causes the work robot and the like to malfunction.

If an optical fiber is used for the signal transmission line, the influence of electromagnetic noise from the transmission line can be avoided. For this reason, plastic optical fibers that are not broken like silica optical fibers have been used for short-distance signal transmission.

[0004]

Plastic optical fibers (step index type multi-mode plastic optical fibers) are manufactured by a lot drawing method, a coating method,
Although it is manufactured by a melt composite spinning method or the like, the plastic optical fiber manufactured by these methods is not sufficiently strong in adhesion strength between the core material and the clad material as it is,
When the fiber is repeatedly bent or subjected to heat history, the core and the clad are separated from each other to form a gap therebetween, and the interface between the core and the clad becomes irregular. Therefore, there is a problem that the mode of the propagating light beam in the fiber is disturbed at this irregular portion, which causes an increase in transmission loss of the fiber.

Generally, in a plastic optical fiber, when PMMA (polymethylmethacrylate), polycarbonate or the like is used for the core material, silicon resin, fluororesin or the like is used for the clad material, and the core diameter is It accounts for about 90% or more of the fiber diameter, and the clad layer is only thinly attached to the surface of the core layer, so the adhesion strength between the core material and the clad material is insufficient, and the fiber may be repeatedly bent or heated. As described above, when a history is applied, the core and the clad are separated from each other to form a gap between the two, and the interface between the core and the clad becomes irregular. Is disturbed and the transmission loss of the fiber increases.

Further, when the plastic optical fiber is pulled or contracted, a refractive index distribution is formed in the core, which changes the propagation mode of the fiber, which also increases the transmission loss of the fiber. There was a problem.

For this reason, if a commercially available plastic optical fiber is used in a portion which is repeatedly bent like a joint of an arm of a work robot or a portion to which a thermal history is applied, transmission loss increases and signal transmission becomes impossible. There was a problem that it would end up.

An object of the present invention is to improve the adhesion strength between the core material and the clad material to prevent the occurrence of irregularities in the interface between the core and the clad, which occur when the fiber is bent and when a thermal history is applied. Another object of the present invention is to provide a method of manufacturing a plastic optical fiber that can be used, can suppress an increase in transmission loss, and can be used even in a bent portion.

[0009]

According to the method for producing a plastic optical fiber of the present invention, after drawing a core material as shown in FIGS. 1 and 2, the surface of the core material 1 is subjected to plasma treatment, and then the clad material. Is applied and adhered.

In the present invention, in order to make the plastic optical fiber flexible, a transparent plastic such as PMMA (polymethyl methyl methacrylate), polycarbonate or polystyrene is used as the core material, and the clad material is used. For this, silicon resin or fluororesin having a smaller refractive index than the core material is used.

The core material 1 after being drawn through the plasma has a wire diameter of about 1 to 2 mm or less. After the plasma treatment, the surface is coated with the clad material of about several hundreds of micrometers or less.

As a plasma processing method, microwave or R is used.
F plasma or the like is generated, and the generated plasma is passed through at a speed of several meters per minute. The plasma conditions are a microwave, an RF or the like, the carrier - gas A _r, using an inert gas or active gas such as O _2, such as H _e (may be plasma is generated).

Since the purpose of the present invention is to treat the surface of the core material 1, it is sufficient that plasma is generated in a minute area. Therefore, the carrier - using H _e a gas, glow at atmospheric pressure -
Atmospheric pressure plasma treatment in which plasma is generated by electric discharge is suitable. Moreover, this atmospheric pressure plasma treatment is convenient because there is no need to reduce the pressure inside the chamber.

If the plasma output is too high, the core material 1 passing through the plasma will be heated to a high temperature and the drawn core material 1 will be softened, causing problems such as uneven wire diameters. The output is set to about several tens W or less so that the core material 1 does not reach a high temperature.

[0015]

In the method for producing a plastic optical fiber of the present invention, the surface of the core material 1 after drawing is plasma-treated, so that the adhesion strength between the core and the clad is increased, and the core is not bent even if it is bent or subjected to heat history. And the clad are less likely to come off, and a gap is less likely to be created between the core and the clad,
The increase in transmission loss is suppressed.

[0016]

EXAMPLE 1 Polycarbonate was used as the core material, and the cladding was coated to prepare an optical fiber. Specifically, after a core base material having a diameter of about 3 cm is prepared with a polycarbonate, the base material is drawn to a diameter of about 0.8 mm, and the drawn core material 1 is plasma-treated by the apparatus shown in FIG. After that, a fluorocarbon resin was coated on the outer periphery as a clad material.
A fiber was produced by tailing. The plasma treatment conditions in Fig. 1 under reduced pressure, the carrier - the A _r gas flow as a gas - and to generate a plasma in the microwave output 30W
And the plasma treatment was performed on the surface of the core material 1 through the core material 1 at a speed of 5 m / min.

When the manufactured fiber was subjected to a 180 ° repeated bending test using a mandrel having a diameter of 20 mm, the transmission loss after being repeatedly bent 10,000 times was about 2 dB / 1.
It was about 0 m increase.

A heat cycle test was conducted under conditions of a low temperature of 0 ° C., a high temperature of 130 ° C., a moving time of 4 hours and a holding time of 2 hours. When the transmission loss was measured at the end of 50 cycles, only a slight increase of about 0.5 dB / 10 m was observed.

[0019]

[Example 2] Example 1 using polystyrene as the core material
An optical fiber was manufactured by coating the clad in the same manner as in. In this case, a fiber was produced by adding a plasma treatment step to the step before coating the clad material.

When the manufactured fiber was subjected to a 90 ° repeated bending test, the transmission loss after being repeatedly bent 10,000 times was about 1.6 dB / 10 m increase.

Further, as in Example 1, a heat cycle test was conducted under the conditions of a low temperature of 0 ° C., a high temperature of 120 ° C., a moving time of 4 hours and a holding time of 2 hours. When the transmission loss was measured at the end of 50 cycles, a slight increase of about 0.3 dB / 10 m was observed.

[0022]

[Example 3] Polycarbonate was used as a core material, plasma treatment was performed by glow discharge at atmospheric pressure, and then a clad material was applied. Specifically, as in Example 1, a base material having a diameter of about 3 cm was prepared with a polycarbonate, and the base material was drawn to have a diameter of about 0.8 mm. After performing plasma treatment with an atmospheric pressure plasma device, fluorocarbon resin as the clad material is used as the core material 1
Was applied to the surface of the to prepare a fiber. The H _e gas flow as the gas - - carrier 2 and, RF in to generate plasma, and the output 30 W, the plasma treatment of the surface through the core material 1 is drawn through the first at a speed of 5 m / min I did.

The produced fiber was subjected to a 180 ° repeated bending test using a mandrel having a diameter of 20 mm as in Example 1, and the transmission loss after repeatedly bending 10,000 times was about 1.7 dB / 10 m. Was about the increase.

Further, as in Example 1, a heat cycle test was conducted under the conditions of a low temperature of 0 ° C., a high temperature of 130 ° C., a moving time of 4 hours and a holding time of 2 hours. When the transmission loss was measured at the end of 50 cycles, only a slight increase of about 0.5 dB / 10 m was observed.

[0025]

In the optical fiber manufactured by the method for manufacturing a plastic optical fiber of the present invention, since the adhesion strength between the core and the clad becomes strong, it occurs when the fiber is bent and when a thermal history is applied. There is no irregularity in the interface between the core and the clad, and the increase in transmission loss is small. Therefore, it is suitable to be used as an optical transmission line for countermeasures against electromagnetic noise in a repeatedly bent portion such as a joint portion of a robot or a portion to which a thermal history is applied.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a method for manufacturing a plastic optical fiber according to a first embodiment of the present invention.

FIG. 2 is an explanatory diagram of a method for manufacturing a plastic optical fiber according to a third embodiment of the present invention.

[Explanation of symbols]

 1 core material

Claims (1)

[Claims] 1. A method for producing a plastic optical fiber, which comprises drawing a core material, subjecting the surface of the core material 1 to plasma treatment, and then applying and adhering a clad material thereto.