JPH0821933A - Optical fiber - Google Patents

Abstract

PURPOSE:To obtain an optical fiber having no pinholes in a coating layer, little transmission loss, excellent physical characteristics against tension or bending of the coating layer, and little transmission loss at a low temp. by forming a coating layer comprising a specified syndiotactic polypropylene. CONSTITUTION:The optical fiber has a coating layer comprising such a syndiotactic polypropylene(s-PP) having >=0.7 fraction of syndiotactic pendants and MFR(melt flow rate) in the range from 0.1 to 20g/10min. If s-PP has <=0.7 fraction of syndiotactic pendants, it has a low melting point and lower flexibility and toughness. If s-PP has >20g/10min MFR, it has too high fluidity at a high temp., and if s-PP has <0.1g/10min MFR, its fluidity is too small to cause problems in the workability. The coating layer is not specified as far as it is formed on an optical fiber, and for example, the layer is a primary layer or a jacket.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical fiber, and more particularly to an optical fiber having a coating layer made of syndiotactic polypropylene and having a low transmission loss, particularly at low temperature.

[0002]

2. Description of the Related Art Optical fibers are used during manufacture, transportation, installation, storage, etc.
Scratches, cracks, dents, etc. are likely to occur due to mechanical external forces such as bending and deformation. In order to protect the optical fiber from this mechanical external force, for example, a jacket made of resin is provided immediately above the cladding layer or via the primary layer or the like. Ultraviolet (UV) curable epoxy acrylate resin and thermosetting silicone resin are known as the primary layer, and polyamide resin is known as the jacket (secondary coating layer). However, in the primary layer, pinholes are likely to occur during curing, and if pinholes are mixed in the primary layer, the tightening force on the optical fiber becomes uneven, and the optical fiber becomes distorted. Therefore, there is a problem that transmission loss increases. Further, the jacket contracts when cooled to a low temperature to bend the optical fiber strand, resulting in an increase in loss, or being rigid and having a physical property against pulling or bending.

The object of the present invention is to solve the above-mentioned problems, to provide a coating layer with no pinholes, to reduce transmission loss, and to provide the coating layer with excellent physical properties against pulling, bending, etc. An object is to provide an optical fiber with low loss.

[0004]

As a result of studies on various polymers suitable for forming the primary layer and the jacket of the above-mentioned optical fiber, the present inventors have found that the specific syndiotactic polypropylene does not require curing when forming the coating layer. The present invention has been completed based on the finding that no pinholes are generated, and that it has both flexibility and toughness, specifically, it has excellent tensile rupture strength and tensile shear strength.

The above object is to achieve the optical fiber of the present invention, namely,
This is achieved by an optical fiber having a coating layer made of syndiotactic polypropylene having a syndiotactic pentad fraction of 0.7 or more and an MFR of 0.1 to 20 g / 10 min.

The s-PP used in the present invention is a concept including not only a homopolymer of polypropylene having a syndiotactic structure but also a copolymer of propylene and other olefins. In the following description, , S-PP including the copolymer. In the present invention, homopolymer s-PP is preferred.

The preferred molecular weight of s-PP used in the present invention is 3,000 to 400,000, more preferably 10,000 to 200,000.

The s-PP used in the present invention needs to have a syndiotactic pentad fraction of 0.7 or more. Here, the syndiotactic pentad fraction is a 1,2,4-trichlorobenzene solution at 135 ° C., and in the 13 C-NMR spectrum measured at 67.8 MHz, it is 2 based on tetramethylsilane.
It refers to the ratio of the peak intensity attributed to all methyl groups of the propylene unit of the peak intensity observed at 0.2 ppm (peak intensity of methyl group attributed to syndiotactic pentad chain). Since s-PP having a syndiotactic pentad fraction of less than 0.7 has a low melting point and lowers flexibility and toughness, the syndiotactic pentad is used in the coating layer of the optical fiber of the present invention. Fraction 0.7
Use the above. The syndiotactic pentad fraction is preferably 0.8 to 8 from the viewpoint of extrusion coatability.
0.95, and more preferably 0.86 to 0.95 in terms of the mechanical strength of the coating layer.

Further, s-PP is ASTM-D-1.
The melt flow rate (MFR) specified by 238 is
It is necessary to have a range of 0.1 to 20 g / 10 minutes. S-PP with MFR over 20 g / 10 min
Fluidity at high temperature becomes too high, and conversely 0.1 g /
S-PP having an MFR of less than 10 minutes has too low a fluidity, and thus any of them has a difficulty in workability when used for forming the coating layer of the optical fiber of the present invention. A preferable range of the MFR is 0.3 to 15 g / 10 minutes from the viewpoint of high temperature fluidity, and a more preferable range is 0.5 to 10 g / 10 minutes from the viewpoint of extrusion processability.

There is no particular limitation on the method for producing s-PP. That is, as the polymerization catalyst used, an organometallic complex catalyst having a symmetrical or asymmetrical molecular structure, for example, a stereospecific polymerization catalyst such as a metallocene compound can be used. Also, the polymerization conditions are not particularly limited, and the polymerization can be performed by a method such as a bulk polymerization method, a gas phase polymerization method, a solution polymerization method using an inert solvent, or the like.

The s-PP may include, if necessary, an antioxidant or stabilizer such as a hindered phenol type, an amine type or a thioether type, a copper damage inhibitor such as an amide or a hydrazide type, a benzophenone type or a benzoin type. Additives that are usually used for plastics may be added, such as an anti-UV agent such as a system, a lubricant such as a higher fatty acid or a metal salt thereof, a processing aid, and a filler such as silica or clay.

The s-PP used in the present invention has excellent fluidity in a wide range of temperatures, so that it can be extruded, injection molded,
Alternatively, it is excellent in moldability by other methods. Furthermore, since it has a high melting point and is excellent in flexibility and toughness,
It can be suitably used for forming a coating layer of an optical fiber.

In the optical fiber of the present invention, the coating layer is not particularly limited as long as it is formed on the optical fiber,
Examples include primary layers and jackets. When the coating layer is the primary layer, the thickness is usually 0.03 to 0.6.
mm, preferably about 0.05 to 0.4 mm. The jacket formed on the primary layer is not particularly limited, and examples thereof include those made of the above-mentioned s-PP and known polyamide resins, and among these, the above-mentioned jacket made of s-PP is preferable.

On the other hand, when the coating layer is a jacket, the thickness is usually 0.03 to 0.5 mm, preferably 0.06 to
It is formed to about 0.3 mm. The primary layer formed under the jacket is not particularly limited, and examples thereof include those made of the above s-PP, known ultraviolet (UV) curable epoxy acrylate resin, thermosetting silicone resin, and the like. However, the primary layer made of s-PP is preferable.

In the optical fiber of the present invention, one layer of s-PP in which the above-mentioned primary layer and jacket are integrated.
It may have a coating layer made of. At this time, the coating layer usually has a thickness of 0.06 to 1.0 mm, preferably
It is formed to about 0.08 to 0.8 mm.

A general method can be used for forming the coating layer, for example, a method of extrusion coating an optical fiber with s-PP, a method of coating an s-PP solution dissolved in a solvent, and drying. .

Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited to these examples.

[0018]

【Example】

Examples 1-8 Syndiotactic pentad fraction 0.80-0.9
5, various syndiotactic polypropylene shown in Table 1 was extruded at 180 ° C. using an extruder.
A coating layer having a thickness of 0.15 mm was formed on the outer peripheral surface of the optical fiber. With respect to each of the obtained optical fibers, a pinhole in the coating layer was confirmed, and a transmission loss test at -30 ° C was performed, and the results are shown in Table 1. The pinholes can be confirmed by observing the surface of the coating layer of each optical fiber using an optical microscope with a magnification of 200 and checking whether there is a pinhole having a diameter of 10 μm or more per 1 cm of the fiber along the entire circumference. Was evaluated as the number of

Comparative Example 1 An optical fiber was produced in the same manner as in the above-mentioned example except that s-PP having a syndiotactic pentad fraction of 0.6 was used as the coating layer forming resin.

Comparative Example 2 In the above example, a solventless silicone UV curable resin (trade name X-62-7003 was used instead of s-PP.
80 consisting of 60 μm UV curable resin layer (primary layer) made of Shin-Etsu Chemical Co., Ltd. and modified acrylate-based UV curable resin (trade name 3001 made by ThreeBond Co., Ltd.)
A coating layer consisting of a UV curable resin layer (secondary coating layer) of μm was formed. The coating layer is formed by coating the optical fiber with the primary layer by DIP, heating and drying, and then UV.
It was cured, and then the secondary coating layer was DIP coated, dried by heating, and then UV-cured. Comparative Examples 1-2
The optical fiber obtained in 1. was confirmed for pinholes in the coating layer and a transmission loss test was performed at -30.degree. C. in the same manner as in the above example, and the results are shown in Table 1.

[0021]

[Table 1]

As shown in Table 1, the optical fibers of the examples have no pinholes in the coating layer and show excellent transmission loss test results at low temperatures.

[0023]

The optical fiber of the present invention has a coating layer made of a specific syndiotactic polypropylene. Since this coating layer does not require a curing treatment at the time of film formation, it is possible to eliminate the conventional curing treatment by ultraviolet rays or heat, and suppress the generation of pinholes in the coating layer. Therefore, according to this coating layer, the tightening force for the optical fiber becomes uniform, the optical fiber is not distorted, and the optical fiber exhibits excellent transmission efficiency. Further, since no curing treatment is required, the manufacturing efficiency of the optical fiber can be improved and the production cost can be reduced. The coating layer made of a specific syndiotactic polypropylene has both flexibility and toughness. Therefore, according to this coating layer,
The optical fiber can be given high resistance to pulling and bending, contraction is suppressed when cooled to a low temperature, and transmission loss at a low temperature can be significantly reduced. Further, since the coating layer exhibits sufficient physical properties even if it is a single layer, it is not necessary to form a jacket with the primary layer unlike the coating layer of the conventional optical fiber, and the primary layer and the jacket are not necessary. Can be integrated.

Claims (3)

[Claims] 1. A syndiotactic pentad fraction of 0.7 or more and an MFR of 0.1 to 20 g / 10.
An optical fiber having a coating layer made of syndiotactic polypropylene in the range of minutes. 2. The optical fiber according to claim 1, wherein the coating layer is a primary layer. 3. The optical fiber according to claim 1, wherein the coating layer is a jacket.