JPH0610692B2 - Plastic fiber optic fiber - Google Patents

Description

TECHNICAL FIELD The present invention relates to a plastic optical fiber having good resistance to moisture and heat.

Conventional technology and its drawbacks Plastic optical fiber (hereinafter referred to as POF)
Is usually a polymer whose main component is polymethylmethacrylate, and the cladding is vinylidene fluoride.
It is composed of a polymer containing a tetrafluoroethylene copolymer or a fluoroalkyl methacrylate as a main component. In such a POF, the polymethylmethacrylate forming the core is naturally easily broken, and therefore, in order to make it difficult to break, the POF is stretched in its length direction. For this reason, this kind of POF has the property that when it is heated to 100 to 120 ° C., it shrinks and the length thereof shrinks to about 50%. Also, this POF is, for example, 7
When it is placed under high temperature and high humidity such as 0 to 80 ° C. and 80 to 100% RH, it shrinks, resulting in an increase in transmission loss.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a POF that does not deteriorate in transmission characteristics even when placed under high temperature and high humidity.

Structure of the Invention In the POF of the present invention, one or more coating layers are formed on the POF element wire, and the outermost layer of these coating layers is ethylene.
It is composed of an ethyl acrylate copolymer.

Specific Structure of the Invention and Its Action FIG. 1 shows an example of the POF of the present invention. In the figure, reference numeral 1 is a POF strand. This POF strand 1 is the core 1
It is composed of a and a cladding 1b and is stretched at the time of manufacturing the wire. A coating layer 2 is provided on the POF element wire 1. The coating layer 2 is made of an ethylene / ethyl acrylate copolymer and has a film thickness of 0.1 to
It is about 1 mm. The ethylene / ethyl acrylate copolymer used here preferably has a content of ethyl acrylate as a copolymer component in the range of 9 to 22 wt%. The content of ethyl acrylate is 9w
When it is less than t%, the adhesion between the coating layer 2 and the cladding 1b of the POF strand 1 is low, the shrinkage of the strand 1 cannot be suppressed sufficiently, and the melting temperature of the ethylene / ethyl acrylate copolymer is high. In addition, since the POF element wire 1 is placed in a high temperature state during the formation of the coating layer 1, shrinkage occurs and the core 1
A slight bend occurs at the interface between a and the cladding 1b, which increases transmission loss and causes inconvenience. In addition, the content rate is 22 wt%
If it exceeds, the effect of improving the resistance to moist heat can be obtained, but the thermal softening point of the ethylene / ethyl acrylate copolymer becomes too low and it cannot be put to practical use. Furthermore, when the film thickness of the coating layer 2 is less than 0.1 mm, the film thickness is too thin to counter the contraction force of the POF element wire 1, and the moist-heat resistance cannot be obtained. The increase in the effect reaches the ceiling and is uneconomical.

The coating layer 2 is formed by an extruder equipped with a crosshead die. The extrusion temperature is about 120 to 150 ° C. In order to prevent the strand 1 from shrinking due to heat during extrusion coating, the POF take-up speed after extrusion coating should be higher than the delivery speed of the POF strand 1 so that a tensile force is constantly applied to the strand 1. It is also preferable to take measures such as water cooling the mandrel portion of the die through which the wire 1 passes in order to prevent minute bending of the core cladding interface of the wire 1.

In such a POF, the adhesion between the cladding 1b of the POF element wire 1 and the ethylene / ethyl acrylate copolymer of the coating layer 2 is good, and the linear expansion coefficient of the ethylene / ethyl acrylate copolymer itself is 1.7. Since it is as high as ~ 2.6 × 10 ^-4 / ° C, when this POF is placed under moist heat conditions,
Although the F strand 1 tries to shrink, the coating layer 2 made of an ethylene / ethyl acrylate copolymer is in close contact with the strand 1, so that the force to shrink the strand 1 is equal to the ethylene / ethyl acrylate copolymer weight. It is canceled by the thermal expansion force of the united body, the contraction of the POF element wire 1 is effectively suppressed, and thus the increase of transmission loss can be prevented. Further, since the strand 1 is prevented from contracting, fluctuations at the interface between the core 1a and the cladding 1b do not occur, and an increase in transmission loss due to this fluctuation is also prevented. Furthermore, since the coating layer 2 can be formed by the extrusion coating method, this POF can be efficiently obtained at low cost.

Another Specific Example of the Invention FIG. 2 shows another example of the POF of the present invention. In the POF of this example, a first coating layer 3 made of an ultraviolet curable resin is formed on the POF strand 1, and the first coating layer 3 is formed.
A second coating layer 4 made of an ethylene / ethyl acrylate copolymer is provided on the top. First coating layer 3
The ultraviolet curable resin forming the is a resin obtained by applying an ultraviolet curable resin liquid containing an unsaturated resin, a vinyl compound and a photopolymerization initiator as the main components to the strand 1 and irradiating it with ultraviolet rays to cure it. The unsaturated resin, a resin having a radically polymerizable double bond in the main chain or side chain of the resin molecule,
Examples thereof include unsaturated polyester type, epoxy acrylate type, urethane acrylate type, polyester acrylate type, polyether acrylate type, acrylic type, oil / fatty acid type, unsaturated polybutadiene type, melamine acrylate type and long side chain vinyl compounds. The vinyl compound is used as a crosslinking agent and a diluent for the unsaturated resin, and a vinyl monomer such as a styrene monomer having 1 to 4 unsaturated groups is used. Further, the photopolymerization initiator is usually in the near ultraviolet region (300 to 45).
It is preferable to generate a radical by being excited at 0 nm), and benzoin compounds, azo compounds, diphenyl sulfide compounds, organic peroxide compounds, organic dye compounds, iron / phthalocyanine compounds, etc. are used. As the ultraviolet ray source for curing, a fluorescent chemical lamp, a high pressure mercury lamp, or the like is used. Specifically, a plurality of mercury lamps are arranged on the circumference, and the POF element wire 1 coated with a predetermined amount of the above-mentioned ultraviolet curable resin is made to run at a predetermined linear velocity and irradiated and cured within a few seconds. The film thickness of the first coating layer 3 is in the range of 5 to 200 μm.

In the POF of this example, since the ultraviolet curable resin forming the first coating layer 3 maintains appropriate hardness and strength and is in close contact with the POF strand 1, the first coating layer 3 is kept when it is placed under moist heat. Acts like a tension member, and the contraction of the wire 1 is suppressed. Further, since the third coating layer 3 made of the ultraviolet curing resin strongly adheres to the second coating layer 4 made of the ethylene / ethyl acrylate copolymer, the heat shrinkage force of the ethylene / ethyl acrylate copolymer is reduced by the ultraviolet curing resin. It acts on the strand 1 through the wire and similarly functions to suppress the shrinkage of the strand 1. Therefore, the POF of this example is extremely rich in wet heat resistance.

3 (a) to 3 (d) show application examples of the POF of the present invention. The example shown in FIG. 3 (a) is 7 POs.
It is a cable in which the F strands 1 ... Are twisted together, and a coating layer 5 made of an ethylene / ethyl acrylate copolymer is provided so as to cover the entire strands. Further, in the example shown in FIG. 3 (b), three POF element wires 1 are arranged in parallel, and a coating layer 5 made of an ethylene / ethyl acrylate copolymer is provided so as to cover the parallel three cores. It is a code.
In the example of FIG. 3 (c), six strands 1 ... Are twisted around a tension member 6 such as a steel stranded wire or an FRP cord, and a coating layer made of an ethylene / ethyl acrylate copolymer is formed on the strand. 5 is formed into a cable. further,
In the example of FIG. 3 (d), one POF element wire 1 and one POF element wire 1 are provided in parallel on both sides of the tension member 6, and a coating layer 5 made of an ethylene / ethyl acrylate copolymer is provided on them. Is.

Since these POFs also have the coating layer 5 made of an ethylene / ethyl acrylate copolymer, the POF strands 1 ... Can be effectively prevented from shrinking even when placed under moist heat, resulting in an increase in transmission loss. Never come

Experimental Example Hereinafter, an example will be shown to clarify the action hardening of the POF of the present invention.

[Experimental Example 1] As a POF strand, the core is made of polymethylmethacrylate polymer and the cladding is made of fluorinated alkylmethacrylate polymer, and the transmission loss at a wavelength of 0.66 μm is 265 dB / km. A 0.0 mm wire (manufactured by Mitsubishi Rayon, Eska Extra EK-40) was prepared. A coating layer made of five kinds of ethylene / ethyl acrylate copolymers having different contents of ethyl acrylate was formed on this strand by an extrusion coating method. Extrusion temperature is 14
The temperature was 0 ° C, the die diameter of the extruder was 2.0 mm, and the thickness of the coating layer was 0.6 mm.

After measuring the transmission loss of the obtained POF at the same wavelength, 8
Wet heat treatment was performed at 0 ° C. and 95% RH for 60 days. Then, the change in transmission loss and the shrinkage rate due to the wet heat treatment were obtained.

For comparison, the wires and ethylene
The same wet heat treatment was performed on the product having a coating layer formed of a vinyl acetate copolymer, a polyester elastomer, and low density polyethylene, and the same measurement was performed. The results are also shown in Table 1.

As is clear from the results shown in Table 1, the coating layer formed of the ethylene / ethyl acrylate copolymer having an ethyl acrylate content of 9 to 22 wt% has an increase in transmission loss of 10 dB / It is about km and the shrinkage rate is about 3.5%, which is lower than that of the case where the coating layer made of EVA, LDPE and polyester elastomer is formed, and it can be seen that the wet heat resistance is excellent. When the content of ethyl acrylate is, for example, 25%, the increase in transmission loss can be sufficiently suppressed but the thermal softening point is 40.
It becomes as low as ℃, and it is not suitable to use this POF above this temperature. Also, with 7%, the thermal softening point is as high as 70 ° C, the heat resistance is sufficient, and the transmission loss increase amount is a little larger at 22 dB / km. It is only increased by 8 to 9%, and can be sufficiently used depending on the application.

[Experimental Example 2] The POF element wire used in Experimental Example 1 was formed with a first coating layer having a film thickness of 20 μm and made of three kinds of ultraviolet curable resins, and then ethylene / ethyl acrylate copolymerization with an ethyl acrylate content of 18 wt% was performed. A second coating layer having a coating thickness of 0.6 mm made of a united body was formed and the same moist heat resistance was examined. The results are shown in Table 2.

As is clear from the results shown in Table 2, it is understood that the one formed by additionally forming the first coating layer made of the ultraviolet curable resin has extremely high resistance to moist heat.

EFFECTS OF THE INVENTION The POF of the present invention has the outermost layer of the ethylene / ethyl acrylate copolymer among the coating layers formed on the POF strands, and thus the POF strands can be formed under high temperature and high humidity. The shrinkage is surely suppressed, the transmission loss does not increase, and the wet heat resistance is good.

[Brief description of drawings]

1 and 2 are schematic cross-sectional views showing examples of the plastic optical fiber of the present invention, and FIGS. 3 (a) to 3 (d) are schematic diagrams showing application examples of the plastic optical fiber of the present invention. FIG. 4 is a schematic perspective view showing a sample piece used in the experimental example. 1 ... POF element wire, 2 ... coating layer, 4 ... second coating layer,
5 ... coating layer.

Claims (1)

[Claims] 1. A plastic optical fiber, wherein one or more coating layers are formed on a stretched plastic optical fiber strand, and the outermost layer of the coating layers is made of an ethylene / ethyl acrylate copolymer. Fiber.