JPH08208278A - Optical fiber core line - Google Patents

Abstract

PURPOSE: To suppress lowering of light-transmitting characteristic over a long period and prevent protruding phenomenon of optical fiber wire by providing a primary coating layer and a specific secondary coating layer on the outer periphery of the optical fiber wire. CONSTITUTION: This optical fiber core line is obtained by providing a primary coating layer composed of an ultraviolet ray curable resin on the outer periphery of an optical fiber wire and providing a secondary coating layer having Young's modulus larger than that of the primary coating layer and obtained by blending 100 pts.wt. crystalline resin with 0.1-5 pts.wt. nucleating agent having melting point higher than that of the crystalline resin on the outer periphery of the optical fiber wire.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical fiber core wire having an improved coating material used for a coating layer.

[0002]

2. Description of the Related Art Conventionally, crystalline resins such as polyamide resins have been widely used as coating layers for optical fiber cores. As such an optical fiber core wire, a protective layer made of a silicone resin or an ultraviolet curable resin is provided on the optical fiber element wire, and an extrusion coating layer made of a crystalline resin such as a polyamide resin is provided thereon. Many things are used.

[0003]

However, since the crystallization of the crystalline resin used for the extrusion coating layer has the property of increasing with time, the crystalline resin undergoes shrinkage immediately after its production, The optical fiber strands are gradually tightened, and microbending generated thereby may deteriorate the optical transmission characteristics, or the optical fiber strands may stick out at the ends of the optical fiber cores. Further, since the crystalline resin has a coefficient of linear expansion larger than that of the optical fiber core wire at a low temperature, there is a possibility that the optical fiber element wire is particularly tightened and the optical transmission characteristic is deteriorated.

Therefore, in order to make up for the drawbacks of the crystalline resin as described above, a copolyamide is used as the polyamide resin to prevent an increase in the tightening force of the covering material (JP-A-55-55).
No. 11231), a lubricant is applied between the optical fiber and the coating layer (Japanese Patent Laid-Open No. 59-51410).

However, when the copolyamide is used as in the former case, the Young's modulus of the coating layer is lowered, and the lateral pressure applied by the external force to the optical fiber strand during use increases the influence on the glass. Is likely to occur, in the latter, in the long term, the lubricant penetrates into the coating layer and the Young's modulus of the coating layer changes,
There is a risk that the light transmission characteristics may be deteriorated or that the lubricant may volatilize (bleed or bloom) and the effect of the lubricant may be reduced.

In view of the above points, the present invention suppresses the tightening of the crystalline resin used for the coating layer to suppress the deterioration of the light transmission characteristics for a long period of time, and the good light transmission characteristics even at low temperatures. It is an object of the present invention to provide an optical fiber core wire and a method for manufacturing the same, in which the protrusion phenomenon of the optical fiber bare wire hardly occurs.

[0007]

In the optical fiber core wire of the present invention, a primary coating layer is provided on the outer periphery of an optical fiber element wire, and a secondary coating layer having a Young's modulus larger than that of the primary coating layer on the outer periphery thereof. In the optical fiber core wire provided with, the gist is that the secondary coating layer is made of a crystalline resin in which a nucleating agent is dispersed, and the melting point of the nucleating agent is higher than the melting point of the crystalline resin.

The optical fiber strand used in the present invention is not particularly limited, but silica glass optical fiber, plastic clad optical fiber, multi-component glass optical fiber and the like can be exemplified.

The primary coating layer provided on the optical fiber strand is coated with a resin having a buffering action against the pressure applied to the optical fiber, such as a silicone resin or an ultraviolet curable resin such as a urethane resin, an acrylic resin or a polyol resin. It is formed by baking or coating and then ultraviolet curing, and the material and the manufacturing method thereof are not particularly limited. However, the primary coating layer has a Young's modulus smaller than that of the secondary coating layer provided on the outer circumference, and has a function of further reducing the influence of the contraction of the secondary coating layer and the lateral pressure applied to the optical fiber strand. .

A feature of the present invention is a secondary coating layer provided on such a primary coating layer. The secondary coating layer is formed of a resin obtained by mixing a crystalline resin with a nucleating agent. The crystalline resin as used herein refers to a resin containing some crystal structure in a polymer, and is roughly classified into a thermoplastic resin and a thermosetting resin. Of these, examples of thermoplastic resins include polyamide 12, polyamide 6, polyamide 66, and polyamide 4.
6, polyamide 10, polyamide 11, polyamide 61
2. Polyamide resin (PA) such as aromatic polyamide
, Low density polyethylene (LDPE), linear low density polyethylene (L-LDPE), medium density polyethylene (M
DPE), ethylene vinyl acetate (EVA), polyethylene resin (PE) such as ethylene ethylene acrylate copolymer (EEA), polypropylene resin (PP) and its derivatives such as homopolymer, copolymer, random copolymer, block copolymer, polyethylene terephthalate (PET), polybutylene terephthalate (PB
T), polycyclopentene terephthalate (PCT),
Crystalline polyphenylene sulfide (PPS), polymethylpentene (TPX), polycellulose acetate,
Examples include polyether ketone (PEEK), polyarylate, and thermoplastic polyimide (TPI). Also,
Examples of thermosetting resins include thermosetting polyimides, phenolic resins, polybenzimidazoles, and the like. In the present invention, it is considered that the thermoplastic resin is preferable to the thermosetting resin in consideration of workability in the manufacturing process. The thermoplastic resin is heated to a predetermined temperature in a usual extruder, extruded onto the already-cured primary coating layer of the optical fiber, and cooled. On the other hand, since the thermosetting resin is difficult to be extrusion-coated, it is baked after being coated on the primary coating layer with a roller, a coating die or the like.

Since the nucleating agent added to the crystalline resin in the present invention needs to be the starting point of crystallization when the crystalline resin is solidified from the molten state, the melting point of the nucleating agent is the melting point of the crystalline resin. Higher is desired. Therefore, the suitable nucleating agent depends on the crystalline resin. Further, the processing temperature (extrusion temperature) of the crystalline resin (for example, about 12 for polyamide 12)
A nucleating agent that melts at 0 to 250 ° C. is more preferable because it has good dispersibility at the processing temperature. here,
Polyamide 12 (melting point about 158 ° C, decomposition temperature about 400
C.) for example, suitable nucleating agents are, for example, lithium stearate (melting point about 220 ° C.), barium stearate (melting point about 220 ° C.), barium hydroxystearate (melting point about 220 ° C.), lauric acid. Metal soap such as barium (melting point about 240 ° C) and bisphosphate (4
-T-butylphenyl) sodium (melting point of about 250 ° C or higher), methylenebis (2,4-di-t-butylphenol) acid phosphate sodium salt (melting point of about 400)
℃ or more) such as phosphate compounds, 1-3,2-
4, dibenzylidene sorbitol (melting point about 205-21
0 ° C.), bis (p-ethylbenzylidene) sorbitol (melting point: about 210 to 230 ° C.) and other sorbitol compounds, and fumed silica and nylon 66 powder. As these nucleating agents, those having a structure having a lipophilic group and a hydrophilic group and forming micelles in the resin are desirable from the viewpoints of dispersibility in the resin and easy starting point during crystallization.

Further, regarding the nucleating agent, in addition to the nucleating agent materials described so far, it is also effective to define the addition amount as follows. In the present invention, the nucleating agent is crystalline resin 100.
It is preferable to add 0.1 to 5 parts by weight of a nucleating agent to parts by weight. The reason is that if the blending amount is less than 0.1 part by weight, the blending amount is small to be the starting point of crystallization, and it is difficult to make the crystal grain size of the entire secondary coating layer uniform.
This is because even if the nucleating agent is blended in an amount of more than 5 parts by weight, the improvement of the effect beyond a certain level is hardly seen. A more preferable addition amount is 0.
1 to 1.0 parts by weight.

[0013]

The progress of crystallization of the crystalline resin is greatly influenced by the amount of the starting material and the ambient temperature. Therefore, by adding a nucleating agent as a starting point of crystallization, the progress of crystallization is accelerated, and the crystallinity and the crystal grain size can be reduced. Therefore, the change in the secondary coating layer and the linear expansion coefficient due to the progress of crystallization over a long period of time can be suppressed to be small.

[0014]

EXAMPLE An example of the present invention will be described below. Examples 1 to 11 Inner layer made of silicone resin as primary coating layer (tensile strength 0.2 MPa, coating thickness 200 μ)
m) and outer layer (tensile strength 3.0 MPa, coating thickness 400)
μm) is provided on a silica-based multimode optical fiber strand (GI type 50/125) having a diameter of 0.4 mm, and a crystalline resin as shown in Table 1 is mixed with a nucleating agent having a melting point higher than that of the crystalline resin. An extruder with a diameter of 40 mm (L /
D = 30) and melt coated to a thickness of 0.25 mm,
An optical fiber core wire having a diameter of 0.9 mm is manufactured, and
It was set to 11.

[Comparative Examples 1 and 2] As a secondary coating layer for optical fiber cores similar to those in Examples, a resin obtained by mixing a crystalline resin as shown in Table 1 with a nucleating agent having a melting point lower than that of the crystalline resin is used. Comparative Examples 1 and 2 were prepared by using.

Comparative Example 3 Comparative Example 3 was prepared by using a crystalline resin (no nucleating agent was mixed) as shown in Table 1 as a secondary coating layer for the same optical fiber core wire as that of the example.

The properties of Examples 1 to 11 and Comparative Examples 1 to 3 immediately after production were examined according to the following test methods.

(1) Optical transmission characteristics The optical fiber core wire of each embodiment is at room temperature and -30.
The optical transmission loss in an atmosphere of ° C was measured at a wavelength of 1.31 µm using a dummy optical fiber and OTDR. (2) Crystallinity The secondary coating layer of the optical fiber core is stripped off, and about 0.1 g of the stripped coating is placed in a scanning differential thermal analyzer (DSC), -1
After raising the temperature between 0 ° C and 260 ° C at 10 ° C / min, 1
The temperature was lowered at 0 ° C / min. At that time, 150 ° C when heating
The crystallinity was calculated by the following formula, with the area of the exothermic peak appearing near the crystallization peak area as the area of the exothermic peak appearing near 175 ° C. when the temperature was lowered. Crystallinity (%) = 1- (crystallization peak area / recrystallization peak area) (3) Crystal grain size (laser small angle scattering) Strip the secondary coating layer of the optical fiber core wire
It was cut to a thickness of 0 μm and analyzed by a scattering pattern of transmitted light obtained by irradiating with red laser light. (4) Coefficient of linear expansion (thermo-mechanical analysis, TMA) An optical fiber element wire is pulled out from an optical fiber core wire, cut into a length of about 2 mm, and heated at a temperature of -30 ° C to 60 ° C at a speed of 2 ° C / min. Then, the elongation was measured with a weight of 0.1 g applied. (5) Amount of protrusion The amount of protrusion from the end face of the optical fiber element wire was measured after performing four heat cycles at a temperature of −30 ° C. and 60 ° C. for a holding time of 2 hours and a transition time of 2 hours.

The melting points of the crystalline resins and nucleating agents used in the examples and comparative examples of the present invention shown in Table 1 are as follows. Crystalline resin: Polyamide 12 (melting point: about 178 ° C.) PBT (polybutylene terephthalate) (melting point: about 224)
Nucleating agent: Barium stearate (melting point: about 220 ° C) Methylenebis (2,4-di-t-butylphenol) acid phosphate sodium salt (melting point: 400 ° C or higher) Bis (p-ethylbenzylidene) sorbitol (melting point: about 210 to 230) C) 1,2-hydroxystearate calcium (melting point approx. 1
20 ° C)

[0020]

[Table 1]

From these results, in the examples of the present invention, the crystallinity was over 90% in all cases, the crystal grain size was smaller than in the comparative examples, and there was little room for crystallization to increase with time. Recognize. The light transmission characteristics are improved in comparison with Comparative Example 3 in which no nucleating agent is added. It can be seen that the linear expansion coefficient of the example is lower than that of the comparative example.
In addition, in FIGS. 1 to 3, the addition amount of the nucleating agent is displayed in logarithm on the horizontal axis,
The vertical axis shows a graph in which the optical transmission characteristics at room temperature and −30 ° C. and the protrusion amount of the optical fiber strand are taken. Although it has been described above that the light transmission characteristics are improved by adding the nucleating agent, it can be seen from FIGS. 1 and 2 that a more remarkable effect can be obtained when the amount of the nucleating agent added is 0.1 parts by weight or more. . From FIG. 3, which shows the relationship between the amount of nucleating agent added and the amount of protrusion, it can be seen that the amount of protrusion significantly decreases when the amount of nucleating agent added is 0.1 parts by weight or more. Furthermore, the amount of nucleating agent added is 5
Even if the amount is more than 100 parts by weight, almost no improvement is seen in the properties, and a problem such as blooming of the nucleating agent occurs.

[0022]

INDUSTRIAL APPLICABILITY According to the present invention, by adding a nucleating agent having a melting point higher than that of the crystalline resin to the crystalline resin, the crystal grain size is reduced, the crystallinity is increased, the linear expansion coefficient is lowered, and Sex is stable. Therefore, the optical transmission characteristics at room temperature and low temperature are improved.

[Brief description of drawings]

FIG. 1 is a diagram showing optical transmission characteristics at room temperature of an optical fiber according to the present invention.

FIG. 2 is a diagram showing an optical transmission characteristic of the optical fiber according to the present invention at −30 ° C.

FIG. 3 is a diagram showing the amount of protrusion of an optical fiber according to the present invention.

(72) Inventor Mitsuo Ito 2-1-1 Oda Sakae, Kawasaki-ku, Kawasaki-shi, Kanagawa Prefecture Showa Electric Wire & Cable Co., Ltd. (72) Inventor Takeo Shiono 2-chome Oda, Kawasaki-ku, Kawasaki-shi, Kanagawa No. 1 Showa Electric Cable Co., Ltd.

Claims (3)

[Claims] 1. An optical fiber core in which a primary coating layer is provided on the outer periphery of an optical fiber element wire, and a secondary coating layer having a Young's modulus larger than that of the primary coating layer is provided on the outer periphery of the primary coating layer. In the optical fiber core wire, the secondary coating layer is made of a crystalline resin in which a nucleating agent is dispersed, and the melting point of the nucleating agent is higher than the melting point of the crystalline resin. 2. The optical fiber core wire according to claim 1, wherein the crystalline resin is a thermoplastic resin. 3. A nucleating agent of 0.
The optical fiber core wire according to claim 1 or 2, wherein 1 to 5 parts by weight is mixed.