JP2003059346A - Small-diameter wire cord - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wire core having excellent strength and flexibility (node strength) and capable of meeting the demand for high integration, complication, solderability and thinning of a circuit. SOLUTION: This wire cord uses an organic synthetic fiber as a core part, and is composed by forming a conductor by winding a copper wire around the outside of the core part and by coating the circumference of the conductor with a thermoplastic resin. In the small-diameter wire cord, the organic synthetic resin is a polybenzazol fiber having an X-ray meridian half-width factor of 0.3 deg./GPa or less, an elasticity decrease component Er due to molecule orientation variation of 30 GPa or less, a T1C relaxation time of carbon 13 of 2,000 sec or more and a thermal conductivity of 0.23 W/cm K or more.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to automobiles, electronic equipments, audio equipments, telephone cords, and electronic computers typified by supercomputers, personal computers, telephone exchanges, communication equipments, mobile phones, cardiac pacemakers, photographic machines, The present invention relates to an electric wire cord used for precision electronic equipment applications such as hearing aids, video cameras, and micromachines. More specifically, it relates to a small diameter electric wire cord having a small diameter and a high breaking strength.

[0002]

2. Description of the Related Art Although the structure of a wire cord is relatively simple, it is used in a wide variety of fields and is used in various situations. To cope with this, materials for forming a core have been studied conventionally. It was For example, in Japanese Utility Model Laid-Open No. 60-69420, twisted metal is made of polyester or Kevlar (aramid fiber:
A bending-resistant electric wire wound horizontally on a fiber string (such as DuPont's product name), or aramid fiber as a tension member in Japanese Utility Model Laid-Open No. 12113/1990, on which a soft copper wire is concentrically twisted to form a conductor. A small-diameter electric wire is proposed in which the conductor is formed and the conductor is further covered with a synthetic resin insulator. Further, JP-A-63-175303 and JP-A-1-
Japanese Laid-Open Patent Publication No. 107415 proposes a small-diameter electric wire cord using a high-strength polyolefin-based fiber in a core portion to improve soldering workability.

[0003]

In a small-diameter electric wire using an aramid fiber as a core (tension member), the fiber has a high strength, and thus it has not been conventionally possible to use a fine yarn. High-strength small-diameter wire cord can be obtained. However, the aramid fibers generally do not melt by heating, and there is a drawback in that when the wire cord is soldered to the terminals of the equipment, the fiber ends are obstructed and the soldering workability is likely to deteriorate. When heat-meltable polyester fiber is used for the core (tension member), the problem of poor solderability of the wire cord can be avoided, but it is inevitably used to meet the tensile strength standard of the wire cord. It was necessary to increase the fineness of the fiber, and there was a limit to making the wire cord diameter smaller. When a high-strength polyolefin fiber is used in the core, the problems of soldering workability and reduction in diameter of the electric wire cord can be solved due to the excellent heat-melting property and high tensile strength of the fiber. However,
Since the coefficient of static friction resistance between the high-strength polyolefin fiber and the copper wire is low, the copper wire wound around the core made of the fiber is extremely slippery. Therefore, when the electric wire cord receives an extreme external force, the copper wire breaks before the core portion in the electric wire cord breaks, and the electrical continuity is interrupted. The problem to be solved is to increase the coefficient of static frictional resistance between the fiber forming the core and the copper wire. Specifically, the fiber or / and the copper wire forming the core is coated with a resin having a high coefficient of static frictional resistance. It can be resolved to some extent. However, in order to perform the resin coating treatment on the core portion and / or the copper wire, a dedicated coating facility is required and the productivity of the electric wire cord is also reduced. Therefore, of course, the manufacturing cost is increased. In addition, polyolefin fibers have difficulty in adhering to a resin, and when the core is coated with resin, or when the resin is coated as an insulator after forming a conductor by winding a copper wire, that is, interlayer Peeling is likely to be a problem. Furthermore, with the recent trend toward compact and lightweight electronic devices, the complexity and size of electronic circuits have become even more advanced. For this reason,
High flexibility has emerged as a required characteristic for small-diameter wire cords. Therefore, it has been expected to develop a fiber material in which electrical conduction is hard to be interrupted by an external force and the diameter can be reduced.

[0004]

As described above, there are advantages and disadvantages in using wholly aromatic polyamide fiber, polyester fiber and polyolefin fiber as the core portion of an electric wire cord, and a fiber that satisfies all the above requirements is industrially available. Not produced in. The present invention has been made paying attention to such circumstances. In other words, as a result of diligent study on suitable fiber materials as the core (tension member) of the electric wire cord,
We found that the conventional problems were solved by using a small diameter electric wire cord using polybenzazole fiber with reduced defect sites in the microstructure of the fiber, and we found that it has excellent properties especially for flexibility, Invented.

That is, the present invention has the following configuration. 1. In an electric wire cord in which an organic synthetic fiber is used as a core portion, a copper wire is wound on the outside of the core portion to form a conductor, and the circumference of the conductive wire is covered with a thermoplastic resin, the organic synthetic fiber is an X-ray meridian line. A small-diameter electric wire cord comprising a polybenzazole fiber having a half width factor of 0.3 ° / GPa or less. 2. The polybenzazole fiber has an elastic modulus reduction Er of 30 GPa or less due to a change in molecular orientation. 1
The small-diameter wire cord described in. 3. 2. The small-diameter wire cord according to 1, wherein the polybenzazole fiber has a T1H relaxation time of protons of 5.0 seconds or more. 4. 2. The thin electric wire cord according to 1, wherein the polybenzazole fiber has a T1C relaxation time of carbon 13 of 2000 seconds or more. 5. 2. The small-diameter electric wire cord according to 1, wherein the thermal conductivity of the polybenzazole fiber is 0.23 W / cm K or more. 6. The anisotropy factor of the expansion coefficient of the polybenzazole fiber is -1.
The small-diameter electric wire cord according to 1, which is 4.5 /, 000,000 or less. 7. Fiber elasticity of polybenzazole fiber is 300 GPa
The small-diameter electric wire cord according to 1, which is the above. 8. The thin wire cord according to 1, wherein the void diameter of the polybenzazole fiber is 25.5 Å or more.

The present invention will be described in detail below. The reason why the electric wire cord breaks the electrical continuity due to an external force is that the copper wire breaks before the core portion in the cord breaks. According to JP-A-1-107415, the breakage of the copper wire is caused by the electric wire. It is said that the problem of interruption of electrical conduction can be avoided by setting the coefficient of static friction resistance between the core portion forming the cord and the copper wire to at least 0.20 or more. Polybenzazole fiber is one of the fibers that meet this requirement. If the fiber is used, it is not necessary to coat the fiber and / or the copper wire with a resin having a high coefficient of static friction, and it is possible to work without using the resin. It is advantageous in terms of sex and product price. In addition, polybenzazole fiber has higher adhesiveness than high-strength polyolefin fiber, and the adhesiveness, that is, delamination, in wire cords coated with resin as an insulator is as high as when high-strength polyolefin fiber is used. Does not matter.

The method for producing the fiber necessary for the present invention will be described in detail. Rigid polymers such as so-called ladder polymers have been considered as a means of achieving the ultimate physical properties of small-diameter electric wire cords, but such rigid polymers are not flexible and have flexibility and workability as organic fibers. In order for it to be a linear polymer, it is an essential condition.

SG Wierschke et al.
iety Symposium Proceedings Vol.134, p.313 (1989)
As shown in Fig. 3, the linear polymer having the highest theoretical elastic modulus is cis-type polyparaphenylene benzobisoxazole. This result was also confirmed by Tashiro et al. (Macromolecules vol. 24, p. 3706 (1991)), and among polybenzazoles, cis-type polyparaphenylenebenzobisoxazole has a crystal elastic modulus of 475 GPa (P . Galen et al. Material Research Society Symposium P
roceedings Vol. 134, p.329 (1989)), considered to have the ultimate primary structure. Therefore, in order to obtain the ultimate elastic modulus, the theoretical conclusion is to use polyparaphenylene benzobisoxazole as the polymer material.

Fiberization of the polymer is described in US Pat. No. 5,2961,
No. 85, US Pat. No. 5,385,702, and the heat treatment method is the method proposed in US Pat. No. 5,296,185, but the sound wave propagation velocity of the yarn obtained by such a method is at most 1.3 × 10. It is about ⁶ cm / sec. Therefore, the inventors have keenly felt the need for research on the improvement of these methods, and as a result of earnest research, they have found that the desired physical properties can be easily achieved industrially by the following methods.

Ohta is Polymer Engineering and Science,
As shown in 23, p697 (1983), so-called defect structures such as voids, disordered crystal orientation, and the presence of molecular ends and amorphous portions are present in the fiber. The presence of these defects hinders the transfer of thermal vibrations and sound waves, resulting in a decrease in thermal conductivity. However, since the polybenzazole fiber is produced by removing the solvent from the polymerization solution, generation of voids is unavoidable. For this reason, many methods have been proposed to prevent the deterioration of the physical properties of the fiber by reducing the void diameter in the fiber to 25 Å or less (for example, JP-A-6-240653 and JP-A-6-245).
675 and JP-A-6-234555,
Etc.), it is not easy to produce such a fiber in view of cost and industrial production. However, in order to increase the thermal conductivity of the polybenzazole fiber, it is essential to reduce the defect structure existing in the fiber structure.

A dope composed of polyparaphenylene benzobisoxazole (PBO) and polyphosphoric acid is spun from a spinneret. Thereafter, it is manufactured through coagulation, neutralization, washing with water, drying, and heat treatment under tension. To increase the thermal conductivity,
It is essential to eliminate as much as possible the defective structure such as amorphous that interferes with the thermal vibration propagation of fibers. For this purpose, we succeeded in changing the internal structure of the polybenzazole fiber to the defect structure free even if the void diameter in the fiber is 25.5Å or more, and the polybenzazole fiber having a high propagation speed of sound waves. Was obtained industrially.

In order to bring out the above characteristics, it can be realized by the following production examples. That is, a spun yarn obtained by extruding a polymer dope composed of polyparaphenylene benzobisoxazole into a non-coagulating gas from a spinneret was introduced into a coagulating bath to extract phosphoric acid contained in the dope yarn. After that, neutralization, washing with water, drying, and heat treatment are carried out. At that time, it was found that by heating the fiber at a constant tension of 500 ° C. or higher, polybenzazole having a reduced defect structure inside the fiber was obtained.

The polybenzazole fiber in the present invention means a PBO homopolymer and substantially 85% or more P.
It refers to a random, sequential or block copolymer containing a BO component and polybenzazole (PBZ). Here, the polybenzazole (PBZ) polymer is, for example, “Liquid Crystalline Polymer Com” by Wolf et al.
positions, Process and Products '' U.S. Pat.No. 4703103
Issue (October 27, 1987), "Liquid Crystalline
Polymer Compositions, Process and Products "US Pat. No. 4533692 (August 6, 1985)," Liquid Cr
ystalline Poly (2,6-Benzothiazole) Compositions, Pr
ocess and Products ”US Pat. No. 4,533,724 (1985)
August 6, 2012), "Liquid Crystalline Polymer Composi
tions, Process and Products ”US Pat. No. 4533693 (August 6, 1985), Evers“ Thermooxidative-l
y Stable Articulated p-Benzobisoxazole and p-Benzo
bisoxazole Polymers "US Patent No. 4539567 (1982)
November 16, 2016), "Method for making Hete" by Tsai et al.
rocyclic Block Copolymer "US Pat. No. 4,578,432 (1
March 25, 986), and the like.

The structural unit contained in the PBZ polymer is preferably selected from lyotropic liquid crystal polymers. The monomer units consist of the monomer units described in structural formulas (a) to (h), and more preferably essentially consist of monomer units selected from structural formulas (a) to (d).

[0015]

[Chemical 1]

[0016]

[Chemical 2]

Suitable solvents for forming the dope of the polymer consisting essentially of PBO include cresol and non-oxidizing acids capable of dissolving the polymer. Examples of suitable acid solvents are polyphosphoric acid, methanesulphonic acid and concentrated sulfuric acid or mixtures thereof. Further suitable solvents are polyphosphoric acid and methanesulfonic acid. The most suitable solvent is polyphosphoric acid.

The concentration of polymer in the solvent is preferably at least about 7% by weight, more preferably at least 10%.
% By weight, most preferably 14% by weight. The maximum concentration is
Limited by practical handling properties such as polymer solubility and dope viscosity. Due to these limiting factors, the polymer concentration does not exceed 20% by weight.

Suitable polymers, copolymers or dopes are synthesized by known methods. For example, Wolfe et al., U.S. Pat. No. 4533693 (August 6, 1985), Sybert et al., U.S. Pat. No. 4,772,678 (September 20, 1988), Har.
synthesized by the method described in US Pat. No. 4,847,350 of ris (July 11, 1989). Polymers consisting essentially of PBO are described by Gregory et al., US Pat. No. 5,089,591 (1992).
(February 18, 2012), it is possible to achieve a high molecular weight at a high reaction rate in a dehydrating acid solvent under relatively high temperature and high shear conditions.

The dope polymerized in this manner is supplied to the spinning section and is usually discharged from the spinneret at a temperature of 100 ° C. or higher. A plurality of die holes are usually arranged in a circumferential shape or a lattice shape, but other arrangements may be used. The number of spinneret pores is not particularly limited, but it is important that the array of spinneret pores on the surface of the spinneret is maintained at a pore density such that fusion between discharge yarns does not occur.

The spun yarn requires a sufficient draw zone length, as described in US Pat. No. 5,296,185, in order to obtain a sufficient draw ratio (SDR), and at a relatively high temperature (dope It is desirable to uniformly cool with a rectified cooling air having a solidification temperature or higher and a spinning temperature or lower). The length (L) of the draw zone is required to be such that the solidification is completed in the non-solidifying gas, and is roughly determined by the single hole discharge amount (Q). In order to obtain good fiber properties, it is desirable that the draw-out stress in the draw zone is 2 g / d or more in terms of polymer (assuming stress is applied only to the polymer).

The yarn drawn in the draw zone is then introduced into the extraction (coagulation) bath. Since the spinning tension is high, it is not necessary to consider disturbance of the extraction bath and any type of extraction bath may be used. For example, a funnel type, an aquarium type, an aspirator type or a waterfall type can be used. The extract is preferably phosphoric acid aqueous solution or water. Finally, in the extraction bath, the phosphoric acid contained in the yarn is extracted by 99.0% or more, preferably 99.5% or more.
The liquid used as the extraction medium in the present invention is not particularly limited, but preferably water, methanol, ethanol, acetone, ethylene glycol or the like which is substantially incompatible with polybenzazole. Also extraction (coagulation)
It is also possible to separate the bath in multiple stages, dilute the concentration of the phosphoric acid aqueous solution sequentially, and finally wash with water. Further, it is desirable to neutralize the fiber bundle with an aqueous solution of sodium hydroxide and wash it with water. Then, it is dried and heat-treated to produce fibers.

In order to reduce the existence of defects infinitely from the fiber structure (defect-free), the solidification rate should be slowed down,
As a result of diligent study, it was found that it is particularly important to heat-treat the material on which the fiber structure has been carefully formed and then to dry it, and to further heat-treat it. For that purpose, it is important to control the solidification temperature,
The bath temperature is maintained at -20 to 0 degrees Celsius, preferably -15 to -5 degrees Celsius, and more preferably -12 to -8 degrees Celsius. As the coagulant, an aqueous solvent may be used, but an organic solvent compatible with water showed better results. Particularly, a compound having a -OH group having a molecular weight of 400 or less, such as a lower alcohol such as methanol or ethylene glycol, was particularly effective. When the bath temperature is less than -20 ° C, the physical properties of yarn tend to be dramatically reduced, which is not preferable. The drying temperature is a temperature at which the fiber strength is not lowered, specifically, 150 ° C. or higher and 400 ° C. or lower, preferably 200 ° C. or higher and 300 ° C. or lower,
More preferably, the temperature is 220 ° C. or higher and 270 ° C. or lower. Regarding the heat treatment conditions, the temperature is 500 ° C or higher and lower than 700 ° C,
It is preferably carried out at 550 ° C or higher and lower than 650 ° C, more preferably 580 ° C or higher and lower than 630 ° C. The tension applied at this time is 1.5 g / d or more and less than 12 g / d, preferably 3.0 g / d or more 1
It is less than 1 g / d, more preferably 5.0 g / d or more and less than 10.5 g / d. The moisture content of the fiber to be heat treated is 3% or less and 1% or more,
It is preferably adjusted to 2.7% or less and 1.7% or more.

The fiber according to the present invention has an X-ray meridional diffraction half-width factor of 0.3 ° / GPa or less, preferably 0.25 ° / GPa or less, more preferably 0.2 ° / GPa or less, and most preferably 0.15. Degrees below ° / GPa. More preferably, the elastic modulus decrement Er due to molecular orientation change is 30 GPa or less, preferably 25 GPa or less, more preferably 20 GPa or less, T1H relaxation time of proton is 5.0 seconds or more, preferably 6.5 seconds or more, and further preferably 8 T of carbon 13 indicating seconds or more
1C relaxation time is 2000 seconds or more, preferably 2300 seconds or more, more preferably 2700 seconds or more, thermal conductivity is 0.23W / cm K or more, preferably 0.3W / cmK or more, more preferably 0.36W / cmK or more, void diameter is 25 5 Å or more, preferably 30 Å or more, 150 Å
Less, more preferably 35 Å or more and less than 90 Å.

An analysis method for proving the realization of a defect-free structure will be described below. Since polybenzazole fiber has a very rigid structure as an organic fiber,
It is not easy to make ultrathin sections and observe them with an electron microscope. Crystals have structural asymmetry called axial shift and do not form a firm and complete crystal. Therefore, sufficient information cannot be obtained even by analysis using static wide-angle X-ray diffraction or small-angle X-ray scattering method. It was Therefore, measuring the X-ray diffraction while applying stimulation (stress) to the fiber,
Structural analysis was performed by evaluating the relaxation time using MR.

(Measurement method of X-ray full width at half maximum factor) An apparatus for applying tension to a fiber was prepared, and a goniometer (Ru-
200 X-ray generator, RAD-rA system), and the stress dependence of the (00 10) diffraction line width was measured. It was operated at an output of 40 kV x 100 mA, and CuKα rays were generated from a copper rotating target. The diffraction intensity was recorded on a Fujifilm Imaging Plate (Fujifilm FDL UR-V). Diffraction intensity is read out by JEOL's digital microluminography (PIX
sysTEM) was used. In order to evaluate the full width at half maximum of the obtained peak profile with high accuracy, curve fitting was performed using the synthesis of Gaussian function and Lorentz function. The results obtained were plotted against the stress applied to the fiber. The data points are arranged in a straight line, and the half-width factor (Hws) was evaluated from the slope.

(Measurement Method of Orientation Change Factor) The above-mentioned device for applying stress to the fiber was attached to a small angle X-ray scattering device manufactured by Rigaku, and the spread of the peak in the azimuth direction of the (200) diffraction point was measured, The elastic modulus Er due to the orientation change was measured.

The orientation change <sin ² φ> was calculated from the azimuth profile I (φ) of (200) diffraction intensity using the following formula.

[Formula 1] The origin of the azimuth was φ = 0 on the meridian.

The theory proposed by Nosalt (Polymer 21, p
According to 1199 (1980)), the strain (ε) of the whole fiber can be described as a synthesis of crystal elongation (εc) and rotation contribution (εr). ε = εc + εr εc is the crystal modulus Ec and stress σ, and εr is
Using the result of measuring in ² φ> as a function of σ, ε
Can be rewritten as the following formula to calculate. ε = σ / Ec + (<cosφ> / <cosφ ₀ > -1) Here, φ ₀ represents the orientation angle when the stress is 0, and φ represents the orientation angle when the stress is σ.

The elastic modulus decrement Er caused by the orientation change is defined by the following equation.

[Formula 2] Here, the inside of the bracket in the second term on the right side of the above equation is the slope of the tangent line of ε at σ = 0.

(Measurement Method of Solid State NMR) Solid 13C-N
MR measurement is made by Varian XL-300 spectroscope (1H measurement 300MHZ, 13C measurement 75MHz), TH
AMWAY solid state amplifier A55-8801, A55
-6801MR, using a solid probe made by DOTY. The measurement was carried out by CP-MAS with 1H nucleus and 13
The longitudinal relaxation time of C nucleus was measured. The measurement is performed at room temperature, sample rotation speed 4 KHz, 1H 90 degree pulse 4.5 microseconds,
The rocking magnetic field strength was 55.5 KHz, the decoupler strength was 55.5 KHz, the contact time was 3 milliseconds, and the pulse waiting time was 40 seconds. 1H nuclear relaxation time (T1H) is C
Peak intensity I (t) with retention time (t) of the peak appearing at 128 ppm, measured by P-MAS inversion recovery method
Was determined by curve fitting according to the formula I (t) = A · exp (-t / T1H). Vertical relaxation time of 13C nucleus (T1
C) has a retention time of 0, 0.
001,1.56,3.12,6.24,12.5,2
5.0, 50.0, 100, 150, 200, 300,
It was measured as 400, 500, 600, 700, 800 seconds. The attenuation of the peak intensity I (t) with the retention time (t) of the peak appearing at 128 ppm is I (t) = Ao · e
xp (-t / 0.1) + Aa · exp (-t / T1Ca)
+ Ab ・ exp (-t / T1Cb) + Ac ・ exp (-t
/ T1Cc) was calculated by curve fitting. here,
Let T1Cc (T1Ca≤T1Cb≤T1Cc) be the relaxation time T1C of the 13C carbon nucleus.

(Measurement of Thermal Conductivity) The thermal conductivity was measured by Fu
Method of jishiro et al. (Jpn. J. Appl. Vol. 36 (1997) p563
Measurement was carried out at a temperature of 100 K according to 3).

<Measurement Method of Small Angle X-Ray Scattering> The void diameter was evaluated by the following method using the small angle X-ray scattering method. The X-rays used for measurement are rotor flex RU-3 manufactured by Rigaku Corporation.
It was generated using 00. A copper anticathode was used as a target, and the operation was performed at a fine focus of 30 kV x 30 mA. The optical system was a point-focusing camera manufactured by Rigaku Corporation, and the X-rays were monochromatic using a nickel filter. The detector is
Fuji Photo Film Co., Ltd. Imaging Plate (FDLUR
-V) was used. Distance between sample and detector is 200mm to 350mm
Any suitable distance between can be used. A helium gas was filled between the sample and the detector in order to suppress interfering background scattering from air and the like. The exposure time was 2 hours to 24 hours. Digital micrography (FDL5000) manufactured by Fuji Photo Film Co., Ltd. was used to read the scattering intensity signal recorded on the imaging plate. For the obtained data, a Guinier plot (the natural logarithm ln (I) of the scatter intensity after the background correction is squared to the scatter vector to the scatter intensity I in the equatorial direction after the background correction is performed.
plotting against k ² ) was made. Here, the scattering vector k is k = (4π / λ) sin θ, λ is the X-ray wavelength 0.1458 nm, θ
Is half the scattering angle 2θ.

Next, the single yarn fineness, which is an important requirement of the present invention, will be described. Conventionally, an electric wire cord formed by winding a copper wire on the core part with a non-heat-melting fiber as the core part has difficulty in quick workability and soundness of the soldered part when soldering to a device side terminal. It has been said that there is. One of the means for solving this problem is the use of heat-meltable organic synthetic fibers.
However, the present inventors have found that even in the case of an electric wire cord having a non-thermofusible fiber as the core, if the single yarn fineness of the fiber constituting the core is made as thin as possible and the amount of fiber used is reduced, I have found that it does not cause any problems. That is, one of the important constitutional requirements of the present invention is to dispose the polybenzazole fiber having a single yarn fineness of 1.0 denier or less as a tension member in the core portion of the electric wire cord. Single yarn fineness is 1.0
When the denier is exceeded, the flexibility of the fiber bundle protruding from the central position of the cord upon soldering the cord to the terminal on the device side is lowered, and therefore the soldering workability and the contact failure of the soldering portion cannot be improved. There is no lower limit to the single yarn fineness of the fibers used for the core, and it is preferable that the fineness is as thin as possible. However, it may be appropriately set in consideration of the difficulty of the spinning technique and the spinning production.

The outer diameter of the electric wire cord is regulated and a breaking strength of a certain level or more is required. For example, in the field of application such as earphones, if the wire cord diameter is 1 mm or less, 3500
A tensile strength of g or more is required, and assuming that the strength utilization factor of the fiber of the core in the cord is 0.87, the tensile strength (TS) of the fibrils constituting the core and the total fineness of the fiber (D
en), the relationship of the following Expression 1 is established. TS x Den ≧ 4000 g (Formula 1)

As is clear from this relational expression, the tensile strength and the total fineness of the fibers forming the core should be set so that the tensile strength of the electric wire cord is 4000 g or more. This means that if the tensile strength is high, the total fineness can be lowered, which in turn leads to a reduction in the diameter of the cord. From this point of view, the tensile strength of the fiber used as the tension member is one of the important constituent features of the present invention. That is, in the present invention, it is important to use polybenzazole fiber having a tensile strength of at least 4.0 GPa or more from the viewpoint of reducing the diameter of the electric wire cord. When the tensile strength is less than 4.0 GPa, the fineness of the fiber for obtaining the strength required for the conductive wire (for example, the tensile strength of the earphone cord is 3500 g) is inevitably increased as described later, and the electric wire which is the object of the present invention. It is difficult to reduce the cord diameter. The wire cord diameter is 1 mm
In the following cases, when the tensile strength of the fiber is less than 4000 g, the tensile strength of the earphone cord becomes 3500 g, and the standard cannot be achieved. It is natural that the tensile strength of the fiber forming the core of the electric wire cord is not limited to 4000 g or more and the higher the tensile strength, the better.

As described above, the outer diameter of the electric wire cord is regulated, and for example, as a product standard of earphones, the cord diameter is required to be 1.0 mm or less. For example, when the wire cord diameter is 1.0 mm, the standard thermoplastic resin coating layer thickness is 300 μm, and the standard copper wire winding layer thickness is 6 μm.
The thickness (diameter) of the tension member fiber bundle as 0 μm
Is calculated to be 280 μm. When this apparent fiber bundle diameter is converted into the fineness of the polybenzazole fiber, it corresponds to 850 denier. If a polybenzazole fiber having a fineness of less than this fineness and a tensile strength of more than a certain level (for example, 4000 g or more) is used, it is possible to obtain an electric wire cord having a diameter of 1.0 mm or less.

[0038]

EXAMPLES The present invention will be described below with reference to examples, but of course the present invention is not limited thereto. Each scale used in the evaluation of the present invention was obtained by the following procedure.

<Fiber fineness> The single yarn fineness is 50 m when using Denicon [search Co., Ltd.] for a sample adjusted for 24 hours in an atmosphere of a temperature of 20 ° C. and a humidity of 65 RH%.
m and the number of 20 were measured, and the arithmetic mean value was calculated. The total fineness of the sample adjusted under the above conditions is 10m on the lap reel.
It was wound up, the weight was measured, and this was converted into a weight of 9000 m to obtain.

<Tensile Properties of Fiber Bundle and Cord> JI
In accordance with SL-1013, using Tensilon manufactured by Orientec Co., Ltd., a gripping interval of 20 cm and a pulling speed of 10
The measurement was performed at 0% / min, n = 10, and the tensile properties were determined by a personal computer process.

<Measurement Method of Knot Strength> A knot strength was evaluated by measuring in accordance with the above-mentioned tensile strength test method in the state where one Z-twisted main knot was made at the center of the gripping interval of the sample.

Example 1 Polyparaphenylene benzobisoxazole 14.0 (by weight) having an intrinsic viscosity of 24.4 dL / g measured with a methanesulfonic acid solution at 30 ° C., obtained by the method disclosed in US Pat. No. 4,536,933. %, And a spinning dope composed of polyphosphoric acid having a phosphorus pentoxide content of 83.17% was used for spinning. The dope was passed through a metal mesh filter material, then kneaded and defoamed with a biaxial kneading device, and then the pressure was raised to maintain the polymer solution temperature at 170 ° C and from a spinneret having 166 holes. After spinning at 170 ° C and cooling the discharged yarn using cooling air at a temperature of 60 ° C, it is further cooled naturally by 40
The discharged yarn was cooled to 0 ° C and then introduced into a coagulation bath. Fibers were prepared using a phosphoric acid aqueous solution having a concentration of 25% and a temperature of -15 ° C as a coagulating liquid. Next, the fiber was wound around a gozette roll, the yarn was washed with ion-exchanged water in a second extraction bath at a constant speed, and then the fiber was immersed in a 0.1 N sodium hydroxide solution for neutralization. After further washing with water in a washing bath, it was wound up, dried in a drying oven at 80 ° C., and allowed to stand until the moisture content in the fiber became 2% or less. Further tension 5.0 g /
d, heat treatment was performed at a temperature of 600 ° C. for 2.4 seconds. The fiber thus obtained was used as a raw yarn for producing a composite yarn. The X-ray meridian half-width factor of this fiber was measured to be 0.24 ° /
GPa and Er are 24 GPa, T1H relaxation time of proton is 6.5 seconds, T1C relaxation time of carbon 13 is 2370 seconds,
Thermal conductivity 0.28 W / cm K, expansion factor anisotropy factor -100
7 / 10,000, fiber strength 6.2 GPa, fiber elastic modulus 34
It was 5 GPa, the void diameter was 32Å, and the fineness was 249 denier. Next, the polybenzoxazole fiber (PBO fiber) produced in this manner is used as the core (tension member).
Oxygen-free copper wire bundle 1 used for
Four wires were wound to form a composite conductive wire. Then, a vinyl chloride resin (PVC) coating was applied to the composite conductor to prepare an earphone cord. The earphone cords thus obtained were evaluated for solderability, cord diameter and the like. Table 1 shows the evaluation results
It was shown to.

[0043]

[Table 1]

(Comparative Example 1) X-ray meridian half-width factor was measured to be 0.35 ° / GPa, Er was 34 GPa,
T1H relaxation time is 4.2 seconds, T1C relaxation time of carbon 13 is 189
0 seconds, thermal conductivity 0.19 W / cm K, expansion coefficient anisotropy factor -4 million, fiber strength 5.9 GPa, fiber elastic modulus 260 GPa, void diameter 22Å, fineness 252 denier The same code as in Example 1 was prepared and evaluated except that a certain polybenzoxazole fiber (PBO fiber) was used. The results are shown in Table 1.

Comparative Example 2 The same code as in Example 1 was prepared and evaluated except that Kevlar 29 having a fineness of 250 denier was used. The results are summarized in Table 1.

Example 2 A core obtained by separating monofilaments from the yarn prepared in Example 1 was taken out,
A urethane resin was sprayed on a wire wound with a silver wire having a diameter of 5 μm to prepare a small diameter cord. The results are summarized in Table 1.

Comparative Example 3 Under the same conditions as in Example 1 except that polybenzazole fiber was used instead of the Kevlar 29 used in Comparative Example 2 and the monofilament was taken out. Created a small diameter cord.
The results are summarized in Table 1.

[0048]

According to the present invention, it is possible to obtain an electric wire cord having excellent strength and flexibility (knot strength), and it is possible to meet the demands for higher integration, complexity, solderability and diameter reduction of circuits. .

Claims (8)

[Claims] 1. An electric wire cord comprising an organic synthetic fiber as a core portion, a copper wire wound around the core portion to form a conductor, and the periphery of the conductive wire being coated with a thermoplastic resin. Is the X-ray meridian diffraction half-width factor of 0.3 ° / GP
A small-diameter electric wire cord comprising a polybenzazole fiber of a or less. 2. The thin electric wire cord according to claim 1, wherein the polybenzazole fiber has an elastic modulus reduction Er of 30 GPa or less due to a change in molecular orientation. 3. Polybenzazole fiber is a proton T1H.
The small-diameter electric wire cord according to claim 1, wherein the relaxation time is 5.0 seconds or more. 4. The small-diameter electric wire cord according to claim 1, wherein the polybenzazole fiber has a T1C relaxation time of carbon 13 of 2000 seconds or more. 5. The thermal conductivity of polybenzazole fiber is 0.23 W /
The small-diameter electric wire cord according to claim 1, which has a cm K or more. 6. The small-diameter electric wire cord according to claim 1, wherein the anisotropy factor of expansion coefficient of the polybenzazole fiber is 4.5 / million or less. 7. The fiber elastic modulus of the polybenzazole fiber is 30.
It is 0 GPa or more, The small diameter electric wire cord of Claim 1 characterized by the above-mentioned. 8. The void diameter of the polybenzazole fiber is 25.
The small-diameter electric wire cord according to claim 1, which is 5 Å or more.