JP2000028876A - Plastic optical fiber cord - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a plastic optical fiber cord which does not give rise to trouble at the time of connecting a terminal part to various appliances by using a ferrule and lessens optical transmission loss at the time of use. SOLUTION: This plastic optical fiber cord is constituted by forming a primary coating 2 consisting of a polyamide resin and a secondary coating 3 consisting of a polyvinyl chloride(PVC) resin substantially not contg. an easy- migration plasticizer on the outer periphery of the plastic optical fiber cord 1 and further, forming a ternary coating 7 consisting of the PVC resin substantially not contg. the migratory plasticizer on the outer peripheral side thereof.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plastic optical fiber cord used for various kinds of information transmission in automobiles, trains, ships, aircrafts, and the like, and in particular, the cord itself has a small diameter and its end is used for various devices. The present invention relates to a plastic optical fiber cord which does not cause any trouble at the time of connection and further reduces optical transmission loss during use as much as possible.

[0002]

2. Description of the Related Art A conventional plastic optical fiber has a structure in which a plastic material having excellent light transmission characteristics, such as a methyl methacrylate polymer, is used as a core material, and its outer periphery is covered with a cladding material having a smaller refractive index than the core material. And
When the optical fiber 1 is put into practical use, the optical fiber 1 is protected as shown in the cross-sectional view of FIG.
A primary protective layer 2 made of a fluororesin or fluorinated polyethylene or the like is formed on the outer peripheral side, and a secondary protective layer 3 made of a vinyl chloride resin is formed on the outer peripheral side. Further, protection is reinforced by passing through a protective tube 4 made of a vinyl chloride resin or the like. At this time, it is also known that a further reinforcement is achieved by inserting a reinforcing fiber 5 such as an aramid fiber between the primary coating 2 and the secondary coating 3.

On the other hand, the most widely used vinyl chloride resin as a material for the secondary coating contains a plasticizer (DOP: dioctyl phthalate, etc.) in order to provide moldability and flexibility. Molecular plasticizers are liable to migrate due to bleeding, and if a vinyl chloride resin containing this is used as a material for the secondary coating, the plasticizer with easy migration migrates toward the optical fiber 1 through the primary coating,
Cracks are generated in the optical fiber, leading to a reduction in mechanical strength and an increase in transmission loss, which poses a serious problem in practical use.

Therefore, in order to suppress an increase in transmission loss due to the transfer of the plasticizer, for example, Japanese Patent Application Laid-Open No. 63-1135
No. 11 proposes providing a functional protective layer without migration of a plasticizer.

[0005] When used as a plastic optical fiber cord, for example, FIG.
As shown in FIG. 2, a metal ferrule 6 is attached to both ends of a cord using a fluororesin as the primary coating 2 and a vinyl chloride resin as the secondary coating 3, and the tip of the metal ferrule 6 is fused and polished to obtain light. A method of increasing the transmittance is adopted. However, in such a tip structure, when the optical fiber cord is exposed to a high temperature of, for example, 80 ° C. or more for a long time, the fluorine resin constituting the primary coating 2 and the secondary coating 3
Due to the difference in shrinkage from the vinyl chloride resin constituting the optical fiber, the optical fiber 1 jumps out of the metal ferrule 6, which may cause a problem that connection with the connector cannot be made (see FIG. 3). .

An optical fiber cord using a polyethylene resin as the primary coating and a vinyl chloride resin as the secondary coating is also known. In this case, the shrinkage ratio between the optical fiber and the polyethylene resin is reduced. Due to the difference, the primary coating made of the polyethylene resin is greatly pulled. At this time, in the case where the reinforcing fibers (such as aramid fibers) as described above are disposed between the primary coating and the secondary coating, the reinforcing fibers meander so as to be pulled by the primary coating,
The lateral pressure acts on the optical fiber, causing an increase in optical transmission loss.

Further, Japanese Patent Application Laid-Open No. 63-11351 mentioned above is disclosed.
As described in JP-A No. 1 (Kokai) No. 1 (1993), even if the resin is improved so as to prevent the transfer of the plasticizer, the terminal processing as shown in FIG. When exposed to a high temperature of about 90 ° C. or more in this state, the plasticizer contained in the secondary coating jumps out and enters from the end face of the optical fiber, so that an increase in optical transmission loss is inevitable.

Further, as shown in FIG. 1, in the structure in which the protective tube is inserted into the protective tube for protection of the outermost layer, the operation of inserting the cord into the tube is not only complicated and time-consuming, but also requires a long time. Since the gap between the cords is indispensable, the cords themselves and others have a large diameter. In addition, the gap between the secondary coating and the protective tube causes lateral pressure characteristics to change in the longitudinal direction when a local external pressure acts on the cord, which also leads to an increase in optical transmission loss.

[0009]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems pointed out in the prior art, and has as its object to process both ends using a metal ferrule or the like. Even in the case, under the conditions of high temperature use, there is no occurrence of the protrusion of the tip portion, the meandering of the reinforcing fiber, the increase in light transmission loss due to the migration of the plasticizer, and the like, and furthermore, the use of the protective tube is omitted, and there is no gap. An object of the present invention is to provide a small-diameter optical fiber cord.

[0010]

The plastic optical fiber cord according to the present invention, which has solved the above-mentioned problems, comprises a primary coating made of a polyamide resin on the outer periphery of the plastic optical fiber, and a plasticizer with easy migration. A secondary coating made of a vinyl chloride resin containing no vinyl chloride resin is formed, and a tertiary coating made of a vinyl chloride resin containing substantially no easy-to-migrate plasticizer is further formed on the outer peripheral side thereof. Has a gist.

As the vinyl chloride resin substantially free of the migratory plasticizer used as the secondary coating or the tertiary coating, a plasticized modified vinyl chloride copolymer resin or a vinyl chloride resin having a high migration resistance is used. Those plasticized by a molecular plasticizer are used. Also, in the present invention, a reinforcing material formed by forming a reinforcing fiber layer between the primary coating and the secondary coating is recommended as a preferred embodiment. In addition, the tertiary coating formed in close contact with the secondary coating by extrusion molding or the like can reduce the diameter of the entire optical fiber cord, and can also suppress optical transmission loss due to deterioration of lateral pressure characteristics. preferable.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, a plastic optical fiber (element wire) is used, for example, as shown in FIG.
In order to protect 1, a primary coating 2 made of a polyamide resin and a secondary coating 3 made of a vinyl chloride resin substantially containing no easy-to-migrate plasticizer are formed. A tertiary coating 7 made of a vinyl chloride resin substantially free of a migration plasticizer is formed. In the figure, 5 represents a reinforcing fiber layer.

The reason why the polyamide resin is selected as a constituent material of the primary coating 2 is that the polyamide resin has excellent strength and that the heat shrinkage of the optical fiber (element wire) ) It is relatively close to the heat shrinkage of the methacrylate polymer used as 1 and the vinyl chloride resin which is a constituent material of the secondary and tertiary coatings, and the protrusion from the ferrule due to the difference in heat shrinkage as described above. This does not cause the problem described above, or the problem of meandering of the reinforcing fibers.

Therefore, in selecting the type of the polyamide resin specifically, a resin whose heat shrinkage is close to the heat shrinkage of the methacrylic acid ester polymer is used as a selection criterion. Nylon 6
6, nylon 11, nylon 12, and the like are preferred, and these may be a blend of two or more if necessary. These polyamide resins have a heat shrinkage at 90 ° C. of 0.5 to 1.2.
%, More preferably in the range of 0 to 0.6%.

Next, in the present invention, a vinyl chloride resin is used as a constituent material for both the secondary coating and the tertiary coating. An important point is that a plasticizer which can easily migrate is used as the vinyl chloride resin. An object of the present invention is to eliminate the problem of plasticizer migration by using a material substantially free of the plasticizer.

Here, the vinyl chloride resin substantially free of the migratory plasticizer is a vinyl chloride copolymer resin obtained by copolymerizing a monomer component having a plasticity improving effect, or another polymer having a high plasticity. Blend-type vinyl chloride resin in which the plasticity of the resin itself is increased by blending, or a vinyl chloride-based resin plasticized with a plasticizer that is difficult to migrate even under high temperature conditions.

That is, the vinyl chloride homopolymer is hard and poor in plasticity and cannot be used as a coating in which flexibility is indispensable as in the present invention. However, polyvinyl chloride has a plasticizing effect such as ethylene-vinyl acetate, for example. If the copolymerizable component is modified by graph polymerization or the like, the polymer itself can be given flexibility without using a plasticizer.

As the hard-to-migrate plasticizer, for example, a polyester-based plasticizer represented by TOTM (trioctyl trimellitate) or the like, or another high-molecular plasticizer is used. That is, the optical fiber cord of the present invention is mainly used for connecting internal devices such as automobiles, and the required heat resistance in these applications is 80 to 9%.
Since about 0 ° C. is sufficient, a polymer plasticizer as described above does not substantially cause a plasticizer migration problem,
Sufficient plasticity can be imparted to the vinyl chloride resin. By the way, DOP (such as dioctyl phthalate), which is widely used as a plasticizer for vinyl chloride resins
When low molecular weight plasticizers (usually, plasticizers having a molecular weight of about 390 or less) are used, they may migrate toward the optical fiber under high temperature conditions during use, causing the above-described light transmission loss. Become.

As described above, in the present invention, a polyamide-based resin is used as a constituent material of the primary coating, and a vinyl chloride-based material substantially free of an easily migrating plasticizer is used as a constituent material of the secondary coating and the tertiary coating. It has a feature in the use of resin, and various changes can be made in other configurations as long as these requirements are satisfied.

For example, as is already known, it is extremely effective to arrange a reinforcing fiber 4 such as an aramid fiber or a polyamide fiber between the primary coating and the secondary coating so as to reinforce the tension applied during use. is there.

The primary coating and the secondary coating are formed on the outer peripheral side of the optical fiber by extrusion according to a conventional method. This is preferable because it can suppress the decrease in the lateral pressure characteristics due to the gap as previously pointed out with the tube insertion type cord, and can further reduce the diameter of the cord as a whole.

In the illustrated example, a code having a structure in which a single optical fiber is coated is shown. However, a plurality of optical fibers may be inserted in the primary coating so that a plurality of signals can be simultaneously transmitted and received. Of course it doesn't matter.

[0023]

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples, and may be appropriately changed within a range that can conform to the spirit of the preceding and following examples. Of course, it is also possible to implement
All of them are included in the technical scope of the present invention.

Example An optical fiber cord having the structure shown in Table 1 was experimentally manufactured, and a lateral pressure characteristic test and a load resistance test were performed by the following methods. The following materials were used for the primary coating, the secondary coating, and the tertiary coating, respectively.

(Constituent material) Core material: polymethyl methacrylate (PMMA) for both examples and comparative examples Cladding material: fluororesin for both examples and comparative examples Primary coating: polyamide resin (nylon 12) for both examples 1 and 2 Example: Vinylidene fluoride polymer Secondary coating: Example 1 Ethylene-vinyl acetate graft-modified vinyl chloride resin (EVA-grafted PVC) Example 2 Vinyl chloride resin with 40% TOTM Comparative Example DOP 40% added vinyl chloride resin Tertiary coating: Example 1 ... Ethylene-vinyl acetate graft modified vinyl chloride resin (EVA graft PVC) Example 2 ... TOTM 40% added vinyl chloride resin Comparative example: None Uses vinyl resin tube)

(Side pressure characteristic test method) As shown in FIG. 5, a load was applied to a substantially central portion of a 5 m sample cord by a press plate having a diameter of 50 mm, and the load and the optical loss when transmitting optical information having a wavelength of 690 nm were measured. Examine the relationship.

(Load resistance test method)
The winding is performed five times with a winding diameter of 00 mm or 200 mm, and the relationship between the load and the amount of light loss when a load is applied thereto as shown in FIG. 6 is examined.

(Heat aging property test method)
C. in a thermostat at 0 ° C. for 0 to 1000 hours.
Each sample code was taken out every time and wound five times with the diameter in the above load resistance test method being 100 mm in diameter, and the amount of light loss when a load was applied to this as shown in FIG. Investigate the tendency of light loss due to migration.

[0029]

[Table 1]

The results are as shown in FIGS. 7 to 10. First, from FIGS. 7 to 9, the optical fiber cords of Examples 1 and 2 were compared with those of the conventional material in both the results of the lateral pressure test and the withstand load test. It can be seen that the amount of optical loss is smaller than the optical fiber cord of the example, and the optical transmission loss can be greatly reduced. As is clear from FIG. 10, in Examples 1 and 2, the decrease in the amount of light loss due to holding at a high temperature for a long time is smaller than that in the comparative example, and in the example, the decrease in the amount of light loss due to the transfer of the plasticizer is suppressed. It is clear that

[0031]

The present invention is constituted as described above, and is used as a coating for protecting a plastic optical fiber.
While using the primary coating made of polyamide resin,
The following advantages can be obtained by using a vinyl chloride resin substantially free of a migratory plasticizer as the secondary coating and the tertiary coating formed on the outer periphery thereof.

Since the thermal contraction rates of the optical fiber and the coating are close to each other, even when both ends are processed using a metal ferrule or the like, the optical fiber protrudes from the ferrule end under high temperature use conditions. The problem of poor connection to the connector or the light transmission loss due to meandering of the reinforcing fiber can be suppressed.

Since the vinyl chloride resin which does not cause migration of the plasticizer is used as a constituent material of the secondary coating and the tertiary coating, the optical fiber does not deteriorate due to the migration of the plasticizer, and the light transmission loss is suppressed.

By forming the tertiary coating in close contact with the outer peripheral side of the secondary coating by extrusion molding, the lateral pressure characteristic does not decrease as pointed out in the prior art using a protective tube, and the cord has a small diameter. Can be.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a conventional optical fiber cord.

FIG. 2 is a schematic explanatory view showing an example of processing a terminal of an optical fiber cord.

FIG. 3 is a schematic cross-sectional view of a main part for describing a problem that occurs when a conventional optical fiber cord is used.

FIG. 4 is a schematic cross-sectional view illustrating the optical fiber cord of the present invention.

FIG. 5 is an explanatory view showing a lateral pressure characteristic test method adopted in an example.

FIG. 6 is an explanatory view showing a load-bearing load test method adopted in Examples.

FIG. 7 is a graph showing a result of a lateral pressure characteristic test.

FIG. 8 is a graph showing the results of a load-bearing characteristic test when the winding diameter is 100 mm.

FIG. 9 is a graph showing the results of a load-bearing characteristic test when the winding diameter is 200 mm.

FIG. 10 is a graph showing the results of a heat aging property test obtained in Examples.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Optical fiber (element wire) 2 Primary coating 3 Secondary coating 4 Protective tube 5 Reinforcing fiber layer 6 Metal ferrule 7 Tertiary coating

Continued on the front page F term (reference) 2H001 KK03 KK17 KK22 2H050 AB43X AB47Y BB03Q BB09R BB09S BB10R BB10S BB17R BB17S

Claims (5)

[Claims] 1. A primary coating made of a polyamide-based resin and a secondary coating made of a vinyl chloride-based resin substantially free of an easy-to-migrate plasticizer are formed on the outer periphery of a plastic optical fiber, and further on the outer periphery side. A plastic optical fiber cord characterized in that a tertiary coating made of a vinyl chloride resin substantially free of an easy-to-migrate plasticizer is formed thereon. 2. The vinyl chloride resin substantially free of a migratory plasticizer used as the secondary coating or the tertiary coating is a plasticized modified vinyl chloride copolymer resin. Plastic optical fiber cord. 3. The plasticizer according to claim 1, wherein the vinyl chloride resin substantially free of a migratory plasticizer used as the secondary coating or the tertiary coating is plasticized by a polymeric plasticizer. Plastic optical fiber cord. 4. The plastic optical fiber cord according to claim 1, wherein a reinforcing fiber layer is formed between the primary coating and the secondary coating. 5. The plastic optical fiber cord according to claim 1, wherein the secondary coating and the tertiary coating are in close contact with each other.