JP2737234B2 - Insulated wire and its manufacturing method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an insulated wire having a low dielectric constant and a small diameter, and a method for producing the same.

[Conventional technology]

As a conventional technique for forming a thin insulating layer on a conductor,
For example, there is a foam extrusion technique as described in JP-B-57-30253. This is generally accomplished by converting a polyolefin resin to a chemical blowing agent such as azodicarbonamide, nitrogen,
It is formed by foaming with an inert gas such as argon, or a gaseous or liquid hydrocarbon or fluorocarbon, or a combination thereof to obtain an insulating layer having a large porosity and a low dielectric constant.

On the other hand, for example, U.S. Pat.
As shown in the 187390 specification, by winding a fluororesin tape having a large porosity by stretching over a conductor,
There is a method of forming an insulating layer. Since this method wraps a tape material with a known dielectric constant on a conductor compared to foam extrusion technology, it can ensure the stability of the dielectric constant of the insulating layer, and realizes a thin film and high porosity insulating layer. be able to.

Further, Japanese Patent Publication Nos. 56-43564 and 57-39006 each disclose a method in which a glass having a particle diameter of several μm to several mm, a hollow sphere or a foamed sphere made of an inorganic material such as alumina is coated with a thermoplastic resin. A melt extrusion method and a method in which a thermoplastic resin such as polyethylene or polyvinyl chloride and inorganic hollow spheres are dissolved in a solvent such as xylene, applied to a conductor, and dried to obtain an insulated wire have been proposed.

[Problems to be solved by the invention]

In recent years, in the medical field, computer measurement field, and other fields, there has been a growing demand for small-diameter, high-density signal transmission lines. The development of electric wires is urgent.

Among the above-mentioned prior arts, the method described in Japanese Patent Publication No. 57-30253 discloses a method for simultaneously melting, foaming, and coating a polyolefin resin on a conductor by a screw extruder. It has a drawback that it is difficult to obtain a degree of foaming and the lower limit of the coating thickness is at most 200 μm. Further, it is not easy to control the degree of foaming by this method.

On the other hand, the methods described in U.S. Pat. Nos. 3,953,566 and 4,187,390 have a problem that, due to the manufacturing method, partial irregularities on the surface of the insulating layer cannot be avoided, and the production line speed is very slow.

The methods described in JP-B-56-43564 and JP-B-57-39006 can easily control the degree of foaming, but have the following disadvantages.

In other words, in the former method of extrusion-coating a hollow sphere foamed sphere coated with a thermoplastic resin, the thermoplastic resin coated on the surface of the hollow sphere is cooled after being melted and applied on a conductor, so that the hollow sphere is joined. When the thickness of the thermoplastic resin layer is reduced for the purpose of obtaining a high porosity, the mechanical strength of the insulating layer formed on the conductor, particularly the elongation, is significantly reduced, while the hollow is used to maintain the mechanical strength of the insulating layer. When the thermoplastic resin layer of the sphere is thickened, the porosity decreases as a result, and the dielectric constant of the electric wire increases. Also, at least in the extruder,
Since a temperature of 150 ° C. or higher and a high pressure are applied, hollow spheres to be used are limited to inorganic materials such as glass and alumina. However, these hollow spheres have a high intrinsic dielectric constant as a material, and a low dielectric constant low loss cable cannot be manufactured.

In the latter method, a thermoplastic resin such as polyethylene or polyvinyl chloride and inorganic hollow spheres are dissolved in a solvent such as xylene and applied, followed by drying, to form an insulated wire. The hollow spheres that can be used are limited, and it is also difficult to produce a low-dielectric-constant low-loss cable.Moreover, since the solvent in the applied liquid composition is evaporated and dried, the production speed is extremely low. ing.

An object of the present invention is to solve the drawbacks of the prior art and to provide an insulated wire capable of realizing a thin coating of 200 μm or less with good electric characteristics and a low dielectric constant, and a method of manufacturing the same.

[Means for solving the problem]

The present inventors have conducted research efforts in accordance with the above-described objects, and have found that a thin-diameter, low-capacitance insulated wire that could not be realized by the prior art can be realized by coating a completely new configuration,
The present invention has been achieved.

That is, the present invention relates to an insulated wire having a coating layer of an energy ray-curable resin composition in which hollow spheres made of a thermoplastic resin are mixed on the outer periphery of a conductor, wherein the outer diameter of the hollow spheres in the insulating layer is smaller than that of the conductor. A thin-walled insulated wire characterized in that it has a maximum value in the vicinity and gradually decreases toward the outer periphery of the coating layer. There is little change in electric capacity,
This is a very excellent insulated wire having a smooth coating layer and capable of high-speed production.

The present invention also provides a method for producing an insulated wire in which an energy-ray-curable resin composition containing a mixture of hollow spheres is applied to the outer periphery of a conductor and then cured to form an insulating coating layer. The outer diameter of the hollow sphere in the coating layer is the largest in the vicinity of the conductor by applying the energy ray-curable resin composition while using the sphere, and the conductor is preheated, and gradually toward the outer periphery of the coating It is intended to provide a method of manufacturing a thin-walled insulated wire, characterized in that it is made smaller.

FIG. 1 is a sectional view of an example of the insulated wire of the present invention,
Reference numeral 1 denotes a conductor, and 2 denotes an insulating layer coated with an energy ray-curable resin 22 mixed with hollow spheres 21. As shown in the figure, the outer diameter of the hollow sphere 21 in the insulating layer 2 increases as it approaches the conductor 1 side, and gradually decreases toward the outer periphery of the insulating layer 2.

The method for manufacturing the insulated wire of the present invention having such an inclined outer diameter distribution that the outer diameter of the hollow sphere is larger toward the conductor in the insulating coating layer will be described with reference to a specific example of the present invention shown in FIG. Conductor 1 extended from supply device 3 in FIG.
After being preheated by the heating device 6, the resin enters a resin coating device 4 where a coating resin component obtained by mixing the hollow spheres 2 with the energy ray-curable resin is applied to the outer periphery thereof. The preheating temperature is preferably, for example, about 100 to 300 ° C. The applied resin composition for coating is cured by irradiation with energy rays such as heat, ultraviolet rays or electron beams in a resin curing device 5,
The coating 2 is formed on the conductor 1. At this time, since the conductor 1 is preheated, the hollow sphere expands significantly toward the conductor. The resin coating device 4 is preferably a device capable of uniformly coating a relatively high-viscosity coating resin composition containing hollow spheres therein. For example, a known technique such as coating with a pressure die and dipping with an open die may be used. Can be.

The hollow sphere referred to in the present invention is a hollow body containing therein a low-boiling liquid, a chemical foaming agent that generates a gas by thermal decomposition, or at least one gas such as air, nitrogen, argon, and isobutane. The outer shell is vinylidene chloride,
Made of thermoplastic resin such as polyethylene, fluorine resin, etc.
It expands when heated at 50 ° C to 200 ° C.

This hollow sphere has a sphere diameter of 1 to 50 μm and a shell thickness of 0.5 μm in order to realize a thin and low capacitance coating layer of 200 μm or less.
The following is preferable, which does not impair the smoothness of the coating layer,
The reason is that the porosity is increased by mixing hollow spheres.

As the energy ray-curable resin composition according to the present invention, for example, a thermosetting resin, an ultraviolet ray-curable resin, an electron beam-curable resin, and the like can be mentioned, but in terms of forming a coating at a high speed, the curing speed is high. UV-curable resins are preferred. As such an energy ray-curable resin layer, for example, silicone resin, epoxy resin, urethane resin, polyester resin, epoxy acrylate, urethane acrylate, fluorinated acrylate, silicone acrylate, polyester acrylate and the like can be used. In order to reduce the capacitance, the dielectric constant of the energy ray-curable resin composition itself is preferably low, and the dielectric constant of the energy ray-curable resin is preferably 4.0 or less, more preferably 3.0 or less. In order to further lower the dielectric constant of the energy ray-curable resin, it is particularly preferable to select silicon resin, fluorinated acrylate, silicon acrylate and the like. Also, foaming agents generally added to this kind of resin for covering insulated wires,
The addition of additives such as antioxidants, light stabilizers, resin coupling agents, surface treatment agents, particle dispersants, etc., enhances the low capacitance and the stability, mechanical properties, functionality, etc. of the coating resin. It is effective for.

In the coating resin composition obtained by mixing the expandable hollow sphere and the energy ray-curable resin, the mixing ratio of the expandable hollow sphere to the energy ray-curable resin is such that the expansion of the hollow sphere and the curing of the energy ray-curable resin are performed. In order to make the porosity of the coating formed by 40% or more, 5% by volume or more, so that the coating resin composition can be applied continuously,
That is, it can be arbitrarily set in order to obtain a target porosity within a range of 50% by volume or less for use as a viscous fluid that can be continuously applied.

It is practically preferable that the viscosity of the coating resin composition after mixing the hollow spheres and the energy ray-curable resin is in the range of 100 to 100,000 cps. In particular, in order to easily apply the coating process, it is desirable that the viscosity is in the range of 1000 to 10,000 cps,
Among the energy ray-curable resins, an ultraviolet-curable resin whose viscosity can be freely selected is suitable for obtaining a coating resin composition of 1,000 to 10,000 cps.

The coating thickness is not particularly limited, but is preferably 500 μm or less in order to sufficiently cure the energy ray-curable resin.

The conductor according to the present invention is not particularly limited, and a conventionally known electric conductor, for example, copper, aluminum, an alloy thereof, or a material obtained by plating the surface thereof can be used.

[Action]

The reason why the present invention can realize a small-diameter low-capacitance insulated wire that cannot be realized by the prior art is as follows.

Here, in describing the operation of the present invention, the relationship between the porosity and the dielectric constant will be described. The porosity V of the present invention is measured by a density method and calculated by the following equation (1).

(Ρ ₀ −ρ) / ρ ₀ × 100 (%) (1) where ρ ₀ is the density of the base resin, and ρ is the density of the resin containing hollow spheres.

The dielectric constant ε of the resin composition containing the hollow spheres is determined by the dielectric constant ε ₁ of the base resin itself, the dielectric constant ε ₂ of the gas in the hollow spheres, and the porosity V that can be formed by containing the hollow spheres. Is determined and expressed by the following equation (2):
Already known.

Therefore, by selecting the material forming the hollow spheres and its porosity, the content of the hollow spheres in the resin composition, and the material of the resin composition, it is possible to stably form the desired voids in the coating layer, An insulating layer having a desired dielectric constant can be formed.

Then, ε is a low dielectric constant aimed at by the present invention, that is,
To 1.60 selects epsilon ₁ of the base resin, the porosity is required to be greater than 40%.

As shown in FIG. 1, the insulated wire of the present invention has an advantage that the outer diameter of the hollow sphere is larger on the conductor side, so that the dielectric constant near the conductor is low and the insulation is good.

In the present invention, the conductor is preheated to about 100 to 300 ° C. in advance, and the coating resin composition mixed with the hollow spheres is applied thereto. Although the agent or gas expands remarkably, the outer peripheral portion of the coating layer hardly expands because the influence of the temperature of the conductor is no longer exerted. In this state, it enters the coating curing device in the next step, and in the case of thermal curing, there is a slight expansion of the hollow sphere at the outer periphery, but an insulating layer is formed so that the outer diameter gradually decreases from inside to outside. it can.

In addition, in the base resin to which high heat is applied for curing, there is a risk that the gas in the resin hollow sphere expands and contracts, or the hollow sphere itself is deformed and the porosity cannot be maintained. When an ultraviolet-curable resin is used as the mold resin, in addition to the above-mentioned preferable in terms of the inclination of the outer diameter distribution of the hollow sphere, heat is not applied at the time of curing, a resin hollow sphere having a low dielectric constant can be used. Further, by selecting a resin having a low intrinsic dielectric constant as the energy ray-curable resin, it is possible to realize a coating having a very low dielectric constant.

The expanded hollow sphere has an average particle size of about 1 to 100 μm.
Since it has a thin shell thickness of 0.5 μm or less, voids can be reliably formed even when coated with a thin film.
Even with an insulating layer of 0 μm or less, it is possible to manufacture an insulated wire capable of high-speed transmission with a capacitance of 1.60 or less.

In addition, the present invention applies an energy ray-curable resin composition mixed with hollow spheres, and then cures the resin composition by irradiation of energy rays such as heat, ultraviolet rays or electron beams. And the production speed can be greatly improved as compared with the case of tape winding.

By selecting the content of the hollow spheres in the resin composition and the material of the resin composition as described above, the dielectric layer is coated with a predetermined resin composition to form an insulating layer. The fluctuation of the capacitance due to the above instability can be avoided. Therefore, an insulated wire of stable quality can be easily manufactured.

Furthermore, the present invention is that the fine hollow spheres having a particle diameter of 1 to 100 μm have a larger diameter on the conductor side and a smaller diameter on the outer peripheral portion, and the ratio of the base resin is larger on the outer peripheral portion,
Since the insulating layer surface can be made smooth, the mechanical strength of the coating can be improved.

〔Example〕

Example 1 An ultraviolet-curable resin mainly composed of silicone acrylate having a viscosity of 700 cps (dielectric constant after curing is 2.95), containing an isobutane gas foaming agent, has an average particle size of 5 to 10 μm, and a shell thickness of 0.5.
20 μm by volume of a hollow sphere made of a vinylidene chloride polymer shell having a thickness of μm was added to the ultraviolet-curable resin, followed by stirring and dispersion to prepare a coating resin composition having a viscosity of 5000 cps.

According to the production line shown in FIG. 2, a silver-plated copper wire having an outer diameter of 150 μm was preliminarily heated in an infrared furnace at 200 ° C., and then the above-mentioned resin composition for coating was applied to a thickness of 40 μm with a pressure die to obtain mercury. The expansion of the hollow sphere and the curing of the ultraviolet-curable resin were simultaneously performed through an ultraviolet-infrared irradiation device comprising a lamp to obtain an insulated wire of the present invention having an outer diameter of 400 μmφ.

Observation of the coating cross section of the insulated wire revealed that the size of the hollow sphere was 40-50 μmφ at the portion closest to the center conductor, 20-30 μmφ at the center of the coating cross section, and 10-20 μmφ at the outermost coating.
The distribution was such that the degree of expansion was larger as the conductor was closer to the preheated conductor. The porosity of the covering of the insulated wire (by the density method)
Was 70% and the dielectric constant was 1.46 (f = 1 MHz), which was a low dielectric constant.

〔The invention's effect〕

As described above, the insulated wire of the present invention contains a hollow sphere made of a thermoplastic resin in the insulating layer, which has a portion expanded by heat, so that the closer to the conductor, the larger the porosity and the lower the dielectric constant. it can. Also, since the degree of expansion of the hollow sphere is smaller as it is closer to the coating jacket, the coating surface is formed as a richer and smoother coating of the base resin while having a large porosity, and the mechanical strength of the coating is improved. Is advantageous.

The production method of the present invention has an effect that a distribution in which the outer diameter of the hollow sphere is inclined can be realized. The thin insulated wire of the present invention is suitable for use as a high-speed transmission insulated wire such as a medical measuring instrument and a computer measuring instrument.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of one example of the insulated wire of the present invention, and FIG. 2 is a schematic explanatory view showing one example of the method of manufacturing the insulated wire of the present invention. In the figure, 1 is a conductor, 2 is a hollow sphere-containing coating layer, 21 is a hollow sphere,
22 is a resin, 3 is a supply device, 4 is a coating device, 5 is an energy beam irradiation device, 6 is a preheating furnace, and 7 is a winding machine.

Continuation of front page (56) References JP-A-57-13610 (JP, A) JP-A-58-64713 (JP, A) JP-A-59-227933 (JP, A) JP-A-63-181208 (JP, A) , A) JP-A-63-211515 (JP, A) J.P.

Claims (2)

(57) [Claims] 1. An insulated wire having a coating layer of an energy ray-curable resin composition in which hollow spheres made of a thermoplastic resin are mixed on the outer periphery of a conductor, wherein the outer diameter of the hollow spheres in the insulating layer is equal to that of the conductor. A thin-walled insulated wire having a maximum value in the vicinity and gradually decreasing toward the outer periphery of the coating layer. 2. A method for producing an insulated wire in which an energy ray-curable resin composition containing a mixture of hollow spheres is applied to the outer periphery of a conductor and then cured to form an insulating coating layer. The outer diameter of the hollow sphere in the coating layer is largest near the conductor by applying the energy ray-curable resin composition while using the hollow sphere and preheating the conductor, and toward the outer periphery of the coating. A method for manufacturing a thin-walled insulated wire, characterized in that the wire is gradually reduced in size.