JPH05198214A - Foamed insulation type electric wire and coaxial cable using this - Google Patents

Abstract

PURPOSE:To prevent defects at the time of terminal processing by laser maintaining excellent mechanical characteristics, by longitudinally applying or helically winding the multi-filament of specific plastic in the direction of the length onto the circumference of a foamed insulation layer to cover a copper wire. CONSTITUTION:A foamed insulation layer 2 like a mixture of high-density and low-density polyethylene having an expansion ratio of not less than 60% where the transmission rate of a signal is not lowered is formed on the circumference of a conductor 1. One to six pieces of multi-filaments 3 of polyethylene and the like without aromatic rings in molecular structure causing yellowing and carbonization at the time of laser cutting are longitudinally applied to or helically wound on the circumference of the layer 2 to provide the mechanical strength of such a degree that collapse and break may be prevented at the time of manufacture or processing. An ultraviolet ray curing resin 4 of proper thickness is applied thereto and then hardened by radiating ultraviolet rays thereon for film fixation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a foam insulated wire for signal transmission used in electronic equipment and the like, and a coaxial cable using the same. More specifically, the invention relates to a computer having a short signal propagation delay time and excellent mechanical characteristics. The present invention relates to a foam insulated wire useful as a high-speed signal transmission line and a coaxial cable using it.

[0002]

2. Description of the Related Art Electric wires used for signal transmission lines of general-purpose computers are generally twisted into a stranded conductor by twisting a plurality of strands of a predetermined diameter in order to secure electrical insulation and increase the signal transmission speed. In addition, the outer circumference of the stranded conductor is covered with a resin foam insulating layer. The conductor may be a single wire in addition to the above-mentioned stranded wire conductor.

Further, a drain wire made of, for example, tin-plated or silver-plated annealed copper wire is vertically arranged on the outer periphery of the foam insulation layer of the foamed insulated electric wire, and further, for example, Al foil and polyethylene terephthalate are provided on the outer periphery thereof. A coaxial cable is also used in which a laminating tape composed of a film is wound and then shielded with an insulating material such as polyvinyl chloride.

In these electric wires, the foamed insulating layer of this type has a stretched porous polytetrafluoroethylene tape (hereinafter referred to as EPTFE tape) as disclosed in, for example, Japanese Utility Model Publication No. 2-34735. Is formed by wrapping around the conductor wire. In addition, JP-A-1-173511 and US Pat. No. 4,711,8
As disclosed in No. 11, heat meltable,
Add a blowing agent to tetrafluoroethylene perfluoroalkyl vinyl ether (PFA), tetrafluoroethylene hexafluoropropylene copolymer (FEP), ethylene tetrafluoroethylene copolymer (ETFE), ethylene chlorotrifluoroethylene copolymer, etc. A method of extruding and foaming it on the outer circumference of the conductor is also applied.

This latter method for forming a foamed insulating layer has the advantage of being less expensive than the former method. However, if the expansion ratio during extrusion foaming is increased in order to increase the signal transmission speed, the mechanical strength of the formed foam insulation layer decreases significantly, and this foam insulation layer collapses during the manufacture of the coaxial cable. This may result in deterioration of the electrical characteristics of the cable, and even if the cable is manufactured with extreme care, the foam insulation layer should be removed when removing the jacket or shield layer in the outer periphery when attaching this cable to the connector. The problem arises of rupture and significant collapse.

For this reason, recently, a treatment has also been adopted in which an outer resin layer is further provided on the outer periphery of the foam insulating layer formed by the latter method to reinforce the overall strength. In this case, the resin outer layer is made of thermoplastic polyimide, so as not to affect the signal transmission speed and the characteristic impedance.
Polyether sulfone, polyether ether ketone,
A layer that uses a resin such as polyarylate or polycarbonate and has a dielectric constant of 4 or less, a tensile strength per unit length weight of 500 kgf / g / cm or more, and a thickness of 0.010 to 0.030 mm. Is formed on the outer periphery of the foam insulating layer.

[0007] The tensile strength per unit length and weight referred to herein (Density Normalized Tensile Strengh: DNT)
S, unit: kgf / g / cm) is the value obtained by dividing the tensile strength of a sample with a length of 20 cm by the weight per unit length. The material with a higher DNTS value has a smaller wall thickness. This means that it is possible to form an outer layer having high strength.

[0008]

The DNTS value of the composite layer composed of the foam insulating layer and the resin outer layer is usually 30.
0kgf / g / cm or more and D when using EPTFE tape
Since the NTS value is a large value as compared with about 250 kgf / g / cm, the composite layer has excellent resistance to crushing and the like. Further, as described above, it has an advantage that the cost required for its formation is low. However, on the other hand, since the resin outer layer lacks flexibility, there is a drawback that when the foamed insulated electric wire on which the resin outer layer is formed is bent and wired, the foamed insulating layer is buckled.

Furthermore, when the foam insulating layer and the resin outer layer are cut with a laser during the end processing of the electric wire, the resin outer layer is yellowed or carbonized. Further, when the terminal is processed with the hot blade, the work must be carefully performed, and the work efficiency is poor. Further, Japanese Utility Model Laid-Open No. 2-11016 discloses a foam insulated wire in which a foam insulating layer is provided around a conductor and a skin layer (resin outer layer) is provided on the outer periphery of the conductor, and the skin layer is provided inside the skin layer. There is disclosed a foam insulated electric wire which is arranged along the length direction or reinforced with glass fibers embedded in a skin layer. However, the glass fiber lacks flexibility because it does not extend, and the above foam insulated wire with this fiber arranged on the outer periphery lacks flexibility and cannot cut the coating layer by laser when processing the end of the wire. It has the drawback.

The present invention solves the above-mentioned problems in the foam insulated wire, and has a signal propagation delay time that is substantially equivalent to that of the conventional one, but has a high resistance to crushing, etc.
Foam insulated wire for signal transmission that has excellent mechanical properties that does not cause breakage or crushing of the foam insulation layer even when processing the cable end, and that does not change or carbonize even when processing the terminal with a laser And to provide a coaxial cable using the same.

[0011]

In order to achieve the above-mentioned object, in the present invention, a conductor wire, a foam insulating layer formed on the outer periphery of the conductor wire, and a longitudinal direction of the outer periphery of the foam insulating layer are provided. There is provided a foam insulated electric wire characterized by comprising at least one multifilament of a plastic having no aromatic ring in its molecular structure, which is attached or spirally wound and fixed. There is provided a coaxial cable in which a drain wire is vertically provided on the outer circumference, a conductor foil is further wound on the outer circumference, and a shield layer is formed on the outer side thereof.

In the foam insulated wire of the present invention, the foam insulating layer formed by coating the outer periphery of the conductor is, for example, a mixture of high density polyethylene and low density polyethylene, a mixture of high density polyethylene and medium density polyethylene, Polyolefins such as a mixture of high density polyethylene, medium density polyethylene and low density polyethylene, a mixture of ethylene-propylene copolymer and high density or high molecular weight polyethylene, a mixture of ethylene methyl methacrylate and ethylene-propylene copolymer Polyfluorotrifluoroethylene, tetrafluoroethylene-hexafluoropropylene copolymer, thermoplastic fluororesin such as tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer; and the like.

Of these, a foam of a mixture of high-density polyethylene and low-density polyethylene containing at least 50% by weight of high-density polyethylene, ethylene methyl methacrylate 90 containing 2-10% by weight of methyl methacrylate. -95 wt% and ethylene-propylene copolymer 5-10 wt% mixture foam,
80-90% by weight of ethylene-propylene copolymer having an ethylene component of 5-10% by weight and high-density polyethylene 1
A foam of a mixture composed of 0 to 20% by weight and a foam of a tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer having a melt flow rate of 10 g / 10 minutes or more are preferable.

The foaming rate of these foams is 60% or more, preferably 70% or more. In the case of a low foam having a foaming ratio of less than 60%, the signal transmission speed becomes slow,
This is because high-speed transmission cannot be realized. As a method for forming the foamed insulating layer on the outer periphery of the conductor, the above-mentioned method of extruding and foaming the resin is preferable, but the method may be a conventionally used method and is not particularly limited.

A multifilament made of plastic, which will be described later, is fixed to the outer periphery of the foam insulating layer. The plastic multifilaments used are multifilaments made of plastics having no aromatic ring in the molecular structure, such as polyethylene multifilaments, polytetrafluoroethylene (PTFE) multifilaments, nylon multifilaments, etc. Is preferred, especially
A polyethylene multifilament and a PTFE multifilament are preferable because of their small relative permittivity.

Multifilaments composed of diallyl phthalate, polyarylate, polyetherimide, polyetheretherketone, etc. having an aromatic ring in the molecular structure are not preferred because they cause yellowing or carbonization during laser cutting. The tensile strength of these multifilaments is 1
It is preferably 0 kg / mm ² or more. Tensile strength is 10
This is because multifilaments having a weight of less than kg / mm ² do not sufficiently exert the reinforcing effect of the foam insulating layer.

Further, this multifilament has 5 to 2
It is preferable that four or more 0 denier monofilaments are twisted together. When the monofilaments are twisted with a denier of less than 5 and the number of filaments is less than 4, disconnection is likely to occur in the running line when the filaments are arranged on the outer periphery of the foamed insulating layer, resulting in a significant decrease in work efficiency. Further, if the diameter of the multifilament is thicker than 20 denier, the entire outer diameter of the multifilament becomes 50 μm or more, the roundness of the multifilament is remarkably impaired, and the flexibility is lowered, which is not preferable.

The thickness of the multifilament is 20 to
It is preferably 200 denier. In the case of a multifilament having a thickness of less than 20 denier, the tensile strength is inferior, so that disconnection is likely to occur in the running line, resulting in a marked decrease in productivity. In addition, a multifilament having a thickness of more than 200 denier has a large outer diameter of the obtained foam insulated electric wire, and cannot exhibit the required electric characteristics.

For example, in the case of polyethylene multifilaments, those having a denier of 20 to 100 are preferable,
In the case of PTFE multi-filament, 40-
It is preferably 200 denier. The foam insulated electric wire of the present invention is a multifilament made of the above-mentioned plastic, which is vertically attached in the longitudinal direction of the outer periphery of the foam insulating layer,
Alternatively, the multi-filament is arranged by being wound in a spiral shape, and the multi-filament is fixed to the outer periphery of the foam insulating layer to manufacture.

The number of multifilaments to be used, the pitch thereof in the case of spiral winding, etc. are determined by the mechanical strength of the composite layer composed of the foam insulating layer and the multifilament during the production of the coaxial cable or the end processing of the cable. , Select so that the crushing strength and tensile strength are such that crushing and breaking of the foam insulating layer do not occur. Preferably, the composite layer of DNT
Select so that the S value is 250 kgf / g / cm or more. Usually, 1 to 6 fibers may be fixed to the outer periphery of the foam insulating layer.

The method of fixing the multifilament to the outer periphery of the foamed insulating layer is not particularly limited, but, for example, after arranging the multifilament on the outer periphery of the foamed insulating layer, an appropriate thickness is applied to the multifilament, for example, ultraviolet curing. A method of applying a resin and curing it by irradiating it with ultraviolet rays, a method of applying a polyolefin adhesive and then applying heat to integrate the foam insulating layer and the multifilament, and further polyethylene or polypropylene on the outer periphery. A method of extrusion-coating a material having a low relative permittivity such as with a thickness of 10 to 50 mm can be mentioned.

[0022]

Examples of the invention

Example 1 As shown in FIG. 1, a conductive wire 1 having a wire diameter of 0.2 mm contains fluorocarbon as a foaming agent and 1% by weight of polon nitride as a nucleating agent, and has a melt flow rate of 20.
GFA of 10 minutes was extruded and foamed to form a foamed insulating layer 2 having a foaming rate of 65% and a thickness of 0.3 mm.

Then, on the outer periphery of the foamed PFA layer, PT
FE multifilament (TOYOFRON 100-15-
100, manufactured by Showa Industry Co., Ltd., tensile strength 18.9 kg / mm ² ,
Six pieces (thickness 200 denier) 3 were vertically provided, and a polypropylene layer (outer resin layer) 4 having a thickness of 30 to 50 μm was coated thereon to manufacture a foam insulated electric wire. Then, as shown in FIG. 2, a laminate consisting of an Al tape with a thickness of 9 μm and a polyethylene terephthalate tape with a thickness of 4 μm, with a drain wire 5 having a diameter of 0.2 mm being vertically attached to the outer periphery of the obtained foam insulated wire. After winding the tape 6, a polyvinyl chloride sheath 7 having a thickness of 0.5 mm was further placed on the outer side of the tape 6 to manufacture a coaxial cable.

The signal propagation delay time of this coaxial cable (n
s / m) is TDR (Time Domain Reflectometry, IE-0120 TDK SYSTEM of Iwatsu Electronics Co., Ltd.)
It was measured at. In addition, conductor 1 from the foam insulated wire shown in FIG.
Of a composite layer consisting of expanded PFA layer 2, PTFE multifilament 3 and polypropylene layer 4
The TS value was measured.

Further, the foam insulated wire was wound around a mandrel having a curvature of 20 times its outer diameter, and the presence or absence of buckling of the composite layer was observed to examine the buckling property. Furthermore, the composite layer was completely cut by irradiating a laser from above the electric wire, and at that time, the presence or absence of yellowing or carbonization was observed to examine the laser processability. Further, at a position 50 mm away from the end of the above coaxial cable, the polyvinyl chloride sheath and the shield tape were peeled off at once by using a stripper manufactured by Carpenter, Inc. of America, and the presence or absence of breakage in the foamed PTA layer 2 at that time And the terminal processability was investigated.

The above results are collectively shown in Table 1. Example 2 Seven strands having a wire diameter of 0.1 mm are twisted together to form a stranded conductor,
Along with the outer periphery thereof, a foaming agent-containing polyolefin containing ethylene methyl methacrylate as a main component and containing polypropylene in an amount of 2 to 10% by weight is extruded to obtain a foaming ratio of 70%.
Then, a foamed insulating layer having an outer diameter of 0.9 to 0.93 mm and a thickness of 0.30 to 0.32 mm was formed.

Next, three polyethylene multi-filaments (Techmilon NA2) were formed on the outer periphery of the foam insulating layer.
10, Mitsui Petrochemical Industry Co., Ltd., tensile strength 150kg / m
m ² and thickness 100 denier) were evenly arranged vertically, and fixed with PPET1303S (trade name, a polyolefin adhesive manufactured by Toagosei Chemical Industry Co., Ltd.). A coaxial cable was manufactured from the obtained foam insulated wire in the same manner as in Example 1, and its signal propagation delay time and DN of the composite layer were measured.
The TS value, buckling, laser processability, and terminal processability were investigated. The results are shown in Table 1.

Example 3 A foam insulated wire was produced in the same manner as in Example 1 except that the number of PTEF multifilaments arranged was 2, and the foam insulated wire was prepared in the same manner as in Example 1. Then, a coaxial cable was manufactured. The signal propagation delay time of this coaxial cable, the DNTS value of the composite layer, the buckling property, the laser processability, and the terminal processability were examined. The results are shown in Table 1.

Example 4 Except that the material used for forming the foamed insulation layer was a mixture of 50% by weight of high density polyethylene and 50% by weight of low density polyethylene (melt flow rate 0.35 g / 10 minutes). In the same manner as in Example 2, a foam insulated wire and a coaxial cable were manufactured.

The signal propagation delay time of this coaxial cable, the DNTS value of the composite layer, the buckling property, the laser processability, and the terminal processability were examined. The results are shown in Table 1. Example 5 The material used for forming the foamed insulation layer was a mixture of 15% by weight of high-density polyethylene and 85% by weight of ethylene-propylene copolymer having an ethylene content of 7% by weight (melt flow rate 2.7 g / 10 Minutes), and a foam insulated wire and a coaxial cable were produced in the same manner as in Example 2.

The signal propagation delay time of this coaxial cable, the DNTS value of the composite layer, the buckling property, the laser processability, and the terminal processability were examined. The results are shown in Table 1. Comparative Example 1 An electric wire in which only the foamed PFA layer of Example 1 is formed, a coaxial cable is manufactured using the electric wire, and its signal propagation delay time, DNTS value, buckling property, laser processability,
The terminal processability was investigated. The results are shown in Table 1.

COMPARATIVE EXAMPLE 2 PFA (PF) was formed on the outer periphery of the foamed PFA layer of the electric wire of Comparative Example 1.
A340J, manufactured by Mitsui DuPont Fluorochemical Co., Ltd.) was extrusion-coated to form a resin outer layer having a thickness of 40 to 50 μm.
The signal propagation delay time, DNTS value, buckling property, laser processability, and terminal processability of the obtained electric wire were investigated. The results are shown in Table 1.

Comparative Example 3 The resin used for the resin outer layer was polyarylate (U-800).
An electric wire was manufactured in the same manner as in Comparative Example 2 except that the electric wire was No. 0, manufactured by Unitika Ltd. The signal propagation delay time, DNTS value, buckling property, laser processability, and terminal processability of the obtained electric wire were investigated. The results are shown in Table 1.

[0034]

[Table 1]

[0035]

As is apparent from the above description, the foamed insulated wire of the present invention and the coaxial cable using the same have substantially the same signal propagation delay time as the conventional one, and
DNTS value is very high. This high DNTS value is an effect brought about by fixing the multifilament made of plastic on the outer periphery of the foam insulating layer. Further, at the time of fixing, since the resin outer layer is not formed by extrusion coating under high temperature unlike the conventional case, heat damage to the foam insulating layer is prevented.

Further, since the flexibility is good and the buckling does not occur, the wiring work becomes easy. Furthermore, since the foamed insulating layer and the multifilament are formed of a fluororesin such as polyethylene or PTFE, yellowing or carbonization does not occur during laser processing, and the terminal processability thereof is excellent.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an example of a foam insulated wire of the present invention.

FIG. 2 is a sectional view showing an example of a coaxial cable of the present invention.

[Explanation of symbols]

 1 conductor 2 foam insulation layer 3 multifilament made of plastic 4 polypropylene resin layer (adhesive layer) 5 drain wire 6 laminate tape (conductor foil) 7 sheath

Claims (2)

[Claims] 1. A molecular structure comprising a conductor, a foam insulating layer formed on the outer periphery of the conductor, and at least one wire fixed longitudinally or spirally wound around the outer periphery of the foam insulating layer. A foam insulated electric wire comprising a multifilament of plastic having no aromatic ring. 2. A conductor, a foam insulating layer formed on the outer circumference of the conductor, and at least one molecular structure vertically or spirally fixed along the outer circumference of the foam insulating layer in a molecular structure. A foam insulated wire made of a plastic multi-filament having no aromatic ring, a drain wire vertically arranged outside the foam insulated wire, and a conductor wound around the drain wire and the foam insulated wire. A coaxial cable comprising a foil and a shield layer covering the conductor foil.