JPS6173911A - Optical fiber core - Google Patents

Abstract

PURPOSE:To obtain excellent bendability without an increase in transmission loss owing to a change in service temp. by using a thermoplastic resin mixed and synthesized with a specific oxazoline compd. under melting of liquid crystalline polyester forming an anisotropic melt for a secondary coating layer. CONSTITUTION:The liquid crystalline polyester forming the anisotropic melt is used and the secondary coating layer of the thermoplastic resin formed by adding the phenylene bisoxazoline expressed by the formula (R1-8 are H or methyl) thereto and mixing and synthesizing the same under melting of said polyester is provided. The liquid crystalline polyester which has at least 0.3 intrinsic viscosity, contains the groups of the formulas II and III at an equal ratio within an about 18-38mol% and contains 64-24mol% the group of the formula IV is used. The resulted product obtd. by mixing and reaction of the above-mentioned oxazoline compd. as the chain extender of the liquid crystalline polyester under melting of said polyester has the excellent ultimate elongation. Such resulted product is used as the secondary coating material for an optical fiber, by which the good bendability is obtd. without the increase in the transmission loss owing to the change in the service temp. for a long length.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to a cored optical fiber coated with a thermoplastic resin having a low coefficient of linear expansion.

``Prior Art'' As is well known, Hikari 7-IPA is a fragile material with a diameter of 150 μm or less, so scratches tend to occur on its surface during manufacturing or cable-making processes, which can become a source of stress concentration. However, it has the disadvantage that it easily breaks when stress is applied from the outside. Ninth, for the purpose of protecting the optical fiber surface and maintaining its initial strength, the bare surface of the optical fiber is coated with plastic immediately after spinning.

This plastic coating generally consists of a 1v< coating layer and a secondary coating layer. The primary coating layer is made of a low Young's modulus material and is intended to maintain the initial strength of the optical fiber and to prevent increased fiber microbending costs due to non-uniformity of the secondary coating.

On the other hand, the secondary coating layer is made of a tough thermoplastic resin such as polyamide, and is intended to be used as a container for handling in making cables, etc.

Conventionally, the following two types of optical fiber core wires have been proposed as the above-mentioned optical fiber core wires. One is a tight-engineered deaf core wire, in which a primary coating layer made of thermosetting or ultraviolet curable resin such as silicone resin and a secondary coating layer made of thermoplastic resin such as polyamide resin are tightly adhered to each other. The structure is The other type is a loose tube type core wire, in which the primary coating layer is made of a thermosetting resin such as acrylic resin or an ultraviolet a-curing resin, and the protective plastic tube is made of a thermoplastic resin such as polyethylene terephthalate or polypropylene. It has a structure in which it is held loosely within the secondary coating layer.

"Problems to be Solved and Eliminated by the Invention" The above-mentioned tight g-shaped core fiber is designed to prevent the increase in microbending loss of fibers with uneven coating by modifying the primary coating layer. It has the advantage of not requiring high coating uniformity in the coating process. however,
The coefficient of linear expansion GK of conventional secondary coating materials is on the order of 10 °C, and this value is much larger than the coefficient of linear expansion of 7-IPA itself, on the order of 10 °C. Due to the expansion and contraction of ei+-, bending occurs in the eli fiber, resulting in an increase in microbending loss. on the other hand.

The loose tube type core wire has the advantage that the increase in microbending loss due to expansion and contraction of the protective plastic, which is the secondary coating, can be alleviated by appropriately setting the extra length of the 7-eyeper in the loose tube. There is. However, since the difference in linear expansion coefficient between the secondary coating layer and the fiber itself is large, an increase in microbending loss due to expansion and contraction of the secondary coating layer still occurs.

On the other hand, in order to prevent the increase in microbending loss due to the difference in linear expansion coefficient between the secondary coating layer and the fiber, the present inventors have developed a low linear expansion coefficient on the order of 10-'C-' using the current extrusion molding method. We proposed an optical fiber core using liquid crystalline polyester as a secondary coating material. However, although this liquid crystalline polyester has a low coefficient of linear expansion and a high modulus of elasticity, its ultimate elongation is extremely low, and therefore, a core wire coated with this material has the disadvantage that it easily breaks during bending. are doing.

The present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is to provide a cored optical fiber that does not increase transmission loss due to changes in operating temperature over a long length and has excellent flexibility. .

It is well known that when certain crystalline polymers are heated, the anisotropy of the crystals and the fluidity of the liquid change before melting and becoming a liquid. It is possible to go through a state of having . This state f: A liquid crystalline material called liquid crystal is a liquid crystalline polyester resin. The present inventors have already studied the extrusion coating of Hikari 7 AiPa wire using this liquid crystalline polyester resin.

As a result, the resin described in Japanese Patent Application No. 58-80797, which was extruded at a high shear rate of 10"8@+!-"μ, had a low coefficient of linear expansion on the order of 10°C. I found out that it shows. In particular, the liquid crystalline polyester resin is 3=2 (volume ratio) of phenol and tetoxchloroethane.
At a concentration of 9.5 P/d in a mixed solution, the intrinsic viscosity measured at 30°C is 0.3 or more, and it is composed of the following three divalent groups, among which group (5) In the case of polyester/terephthalate-P-hydroxybenzoic acid copolymer (CPET/FOB copolymer) containing equal amounts within the range of 18 to 38 mol% and containing 1clt-64 to 24 mol% of groups, + 102sec-' or more shear alignment, low linear expansion coefficient of I x 10 = °C-1 or less and 4G
+a of Pa or more -0-CH2-CH2-0- However, the ultimate elongation of the above liquid crystalline polyester resin, which has a low coefficient of linear expansion and a high modulus of elasticity due to shear orientation, is 1%.
Optical 7-IPA core wire coated with this material has the disadvantage that the two-wavelength &l- easily breaks when bent.

Akira Motomoto et al.
In order to improve the ultimate elongation of the OB copolymer, we conducted intensive studies and found that phenylenebisoxazoline, which is known as a chain extender for polyester resin, was added to the melted liquid crystalline tl polyester at a rate of 0.1 ~
It has been discovered that the ultimate elongation of the final product can be improved by adding and mixing 4% by weight and allowing the reaction to occur, leading to the present invention.

Phenylenebisoxacyl/ used in the present invention is a compound represented by the following general formula (wherein R8 to R8 represent a hydrogen atom or a methyl group), and ¥! From the point of view of fK liquid crystal forming ability (for the benzene ring), this complex compound is preferably a p-substituted compound or an m-substituted compound, and all of R□ to R8 are hydrogen atoms. As a specific example, 2.2
'-p-phenylenebis(2-oxazoline)-2+
2 m-phenylenebis(2-oxazoline), 2t
i-p-phenylenebis(4-methyl-2-oxazoline).

2.2'-p-phenylenebis(4,4-dimethyl-2
-oxazoline)-2,2'-m-phenylenebis(4
-methyl-2-oxazoline), 2,2'-m-phenylenebis<4,4'-dimethyl-2-oxazoline), etc. Phenylenebisoxazoline may be added to the melted liquid crystalline polyester and mixed.
It is also possible to mix it with the liquid crystalline polyester in a solid state and then melt it and heat it. However, since the viscosity increases significantly after warping, it is recommended that this process be carried out in a reactor that has extrusion capacity (dispensing capacity). preferable. For example, an excellent method is to prepare a master chip by melt-mixing liquid crystalline polyester and phenylenebisoxazoline t-S using a twin-screw extruder with high mixing capacity. The master chip manufactured in this way can be extrusion coated onto an optical fiber using a conventional (single-screw) extruder.

The added brass of phenylene and suoquinazoline is 0.1 weight compared to liquid crystalline polyester! IkX~41 is a loss%. This means that when 0.1 weight tX is less than 0.1%, no improvement in the ultimate elongation of the final product is observed, and when it exceeds 4λ elongation, anisotropy occurs! This is because the ability to form 8-products is lost and the linear expansion coefficient becomes 1O-5°C-1 or more even at a shear rate of 10 seconds or more. More preferably, it is added in a range of 0.3 to 25% by weight.

Below, the single-shot I3IIJ will be explained in more detail. It should be noted that the two views are not limited to the following examples.

"Real #A1F111" PETlPOB copolymer with 50 mol% PUB-containing residue (
-viscosity 0.65) and 2.2'-m- of zoMLy%
The reaction product (intrinsic viscosity 1.29) obtained by adding phenylenebis(2-oxazoline) to the melt was prepared using a die with a diameter of 11.3 mm, a diameter of 0.9 mm, and a die-mouth land. Extrude at 240°C using an extruder with a 10-length extrusion section (dice Kawaguchi I!i).

I
A core wire with an outer diameter of 1.0 [(drawdown ratio LO)] was prepared by extruding it onto a bare optical fiber of 0 Am (7 eye diameter: 125 μm). The secondary coating layer (PET
/POB copolymer layer) Young's modulus, coefficient of linear expansion, and ultimate elongation are 9.4 GPa, 5×10 °C, and 5.2%, respectively.
The permissible bending radius of the core wire was 1.5 -, and the transmission loss at 20°C in the strand stage was Z at a wavelength of 0.85 μm.
45d~1 The loss of the core H according to the present invention is at a wavelength of 0.85μ
m, 144 dB/te at 20°C, -60°C
No increase in loss was observed from 60°C to 60°C.

“Example 2” PET/POB copolymer with a POB content of 50 mol% (
2.2'-m- with an intrinsic viscosity of 0.65) and 1.5%
Mix phenylene bis(2-oxazoline) powder,
Reactant (intrinsic viscosity 1.22) gold heated to 90C and passed through a ratio twin-screw extruder seven times, die diameter 1.3mm, nipple diameter α9IIIm, land length at die exit 10
Using an extruder with a layered extrudate, at an extrusion temperature (die exit temperature) of 280°C and a shear rate of I x 10 sec, the outer diameter was 400 μm (7-eyeper outer diameter 125 μm).
A core wire with an outer diameter of 1.0 m (drawdown ratio 1.0) was prepared by extruding it onto the Aipa bare wire. Polymer weight, a expansion rate, and ultimate elongation are &6GPa, 7X10, respectively.
℃.

5.6%, and the allowable bending radius of the core wire was 1.5 degrees. In addition, the transmission loss at 20°C in the strand stage is at wavelength 0.
．． The loss of the core wire according to the present invention is 246 dB/b at a wavelength of 0.85 μm and 20°C.
-, and no increase in loss was observed from -60°C to 60°C.

"Comparative Example" PET/PoB copolymer with a POB content of 50 mol% (
A core wire with an outer diameter of LQmO was produced by extruding the material with an intrinsic viscosity of α65) under the same extrusion conditions as in Example f111.

The Young's modulus, coefficient of linear expansion, and ultimate elongation of the secondary coating layer (PET/POB copolymer real NA) of the core wire produced in this way are each I
L3GPa, 2X1G"°C-', 1.8%, and the allowable bending radius of the core wire was 4 degrees.

"Effects of the Invention" As explained above and compared, the Hikari 7 Eyepa core wire of the present invention uses a molten liquid crystalline thermoplastic resin exhibiting large ultimate elongation and low coefficient of linear expansion as the secondary α material of the Hikari 7 Eyer. There is no increase in transmission loss due to changes in wind speed over a long length, and it has excellent flexibility.

■ Enter Japan II story public corporation

Claims (2)

[Claims] (1) A liquid crystalline polyester that forms an anisotropic melt;
0.1% to 4% by weight based on this liquid crystalline polyester
Phenylenebisoxazoline represented by the following general formula ▲ There are mathematical formulas, chemical formulas, tables, etc. An optical fiber core having a secondary coating layer made of a thermoplastic resin synthesized by (2) The liquid crystalline polyester has an intrinsic viscosity of at least 0.3 and has the following formulas (A) and (B) (A) ▲ Numerical formulas, chemical formulas, tables, etc. ▼ (B) -O-CH_2-CH_2-O - groups (A) and (B) represented by 18 to 38 mol%
Equal amounts of each are included within the range of and at the same time, the following formula (C) (
C) The optical fiber core according to claim 1, characterized in that it is a polyester containing 64 to 24 mol% of the group (C) represented by ▼ (numerical formula, chemical formula, table, etc.).