JP6823263B2 - Insulation coating film - Google Patents

Description

The present invention relates to an insulating coating film used to insulate an electric wire and an ultrafine electric wire using the same.

In recent years, with the development of digital information communication and the expansion of demand, electric wires are widely used for signal transmission of many information and electronic devices.

The electric wires used for the internal wiring of information and electronic equipment are called ultrafine electric wires because the wires are particularly thin among the electric wires, and they are often used together because they have a small diameter and a large number of electric wires are arranged in parallel. Generally, the periphery of the core wire is extruded and coated with a resin for insulation, or a narrow insulator is spirally wound and coated to form a coated electric wire, or as shown in Patent Document 1. Further, there is a structure in which an outer conductor made of a braid or a stranded wire is wound on it, and then an extruded coating or a narrow insulator is spirally wound to form a coating to form an ultrafine coaxial cable. As the narrow insulator, a plastic tape such as polyester is used. Then, when such a plastic tape is repeatedly wound, an adhesive layer is provided so that the wound tape is not unwound, and the overlapped portion of the tape is adhered, and in order to facilitate identification for the purpose of wiring classification, Alternatively, in order to shield the color of the conductor, coloring such as blue, red, yellow, green, and white is usually applied. When coloring a plastic tape, a film is usually coated with a coloring layer containing a pigment or dye of an arbitrary color to obtain a desired color.

Japanese Unexamined Patent Publication No. 2006-32073

Black may be required as the above-mentioned color for identification from the viewpoint of identification or design, but there are the following difficulties in obtaining a black plastic tape.

First, for example, if you try to obtain black by mixing multiple colors, it may be bluish or greenish with respect to the original chromaticity of black, which is insufficient to distinguish it from other colors, or the color is light. There was a problem that the color of the conductor was too transparent and did not play the role of shielding.

Therefore, industrially inexpensive carbon black is often used for black, but when carbon black is used for this purpose, there is a problem that the insulation of the inner core wire or the outer conductor becomes insufficient.

The present invention has been made to provide a film for an insulating coating having a black color having high discriminative property and shielding property and having high insulating property in response to the above problems.

In view of the above problems, the present invention is an insulating coating film used for ultrafine electric wires, which has a total thickness of 0.5 to 15 μm and a chromaticity L ^{* on} at least one surface of 0 to 40. It is an insulating coating film having a transmittance of 0 to 10% and a surface resistivity of 2 × 10 ¹¹ Ω / □ or more on any surface of the film.

According to the insulating coating film of the present invention, a film for insulating coating having a black color having high distinctiveness and shielding property and having high insulating property can be obtained, and by using this, the internal conductor is sufficiently shielded. It is possible to obtain an extra-fine electric wire having a highly designed black color that cannot be seen through. Moreover, since the insulation is high, the reliability is improved, the insulator can be made thinner, and an ultrafine electric wire having a smaller diameter can be obtained.

It is a figure of the film for insulation coating of this invention. As an example of a general electric wire, it is a cross-sectional view of a shielded cable.

The present invention will be described in detail below.

An example of the insulating coating film of the present invention is shown in FIG.

The insulating coating film of the present invention is not particularly limited as a layer structure, but has a structure as exemplified by the following (1) to (5).
(1) Base film / colored layer / adhesive layer (2) Base film / (colored + adhesive layer)
(3) Base film / colored layer (4) Base film / adhesive layer (5) Base film only (“/” means laminating in this order).

The chromaticity of the insulating coating film of the present invention needs to have L ^* of 0 to 40 from the viewpoint of distinctiveness in order to prevent confusion with other colors due to being bluish or greenish. It is preferable that a ^* is 0 or more and 1.0 or less, and b ^* is -10 or more and 0 or less. More preferably, L ^* is 31 or less, and further preferably L ^* is 28 or less, so that a true black color such as jet black is exhibited, and the distinctiveness and designability are remarkably improved.

The transmittance of the insulating coating film of the present invention needs to be in the range of 0 to 10% in order to shield the color of the conductor and obtain distinctiveness. If it exceeds 10%, the color of the conductor may be seen through, which is more preferably in the range of 0 to 8%.

The surface resistivity of the insulating coating film of the present invention needs to be 2 × 10 ¹¹ Ω / □ or more on any surface of the film from the viewpoint of insulating properties. It is preferably 4 × 10 ¹¹ Ω / □ or more. Further, in the case of a film composed of a plurality of layers as described in (1) to (4) above, it is preferable that it is 1 × 10 ¹⁰ Ω / □ or more, and more preferably, regardless of which layer is measured. It is 5 × 10 ¹⁰ Ω / □ or more, and more preferably 9 × 10 ¹⁰ Ω / □ or more.

The method for adjusting the chromaticity and transmittance of the insulating coating film of the present invention described above is not particularly limited, and as is generally known, a colored layer or another layer (for example, the configuration of (2) above). Then, a method of kneading a pigment into a coloring + adhesive layer, or a base film in the configuration of (4) or (5) can be mentioned. It is possible to knead and adjust an appropriate amount of the three primary colors, cyanide-based, magenta-based, and yellow-based pigments, but that alone may cause the appearance to be bluish or greenish, resulting in insufficient distinctiveness. It is industrially inexpensive to add carbon black as a pigment, but since carbon black has electrical conductivity, if the amount of carbon black added is large, the surface resistivity will decrease and the insulation will decrease. It ends up.

Therefore, when carbon black is used for the colored layer, the content thereof is preferably in the range of 6 to 40 wt% in the solid content of the colored layer. If it is less than 6 wt%, it is insufficiently distinguished from multiple colors, especially blue, and if it exceeds 40 wt%, the insulating property may be inferior. More preferably, it is in the range of 10 to 30 wt%.

In order to achieve both the above-mentioned chromaticity, transmittance, and surface resistivity, it is preferable to add carbon black after kneading an appropriate amount of the three primary colors, cyanoid, magenta, and yellow pigments. Alternatively, carbon black that has been surface-treated to improve its insulating property may be used.

The base film used in the present invention is not particularly limited, and a generally used polymer film is used. Examples of the polymer film include polyesters such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN), polyolefins such as polypropylene (PP) and polystyrene (PS), polyphenylene sulfide (PPS), polyimide (PI), and polycarbonate. Examples include films such as polyamide, polyvinylidene fluoride, and polyparaxylene. Further, these copolymers, a mixture with other organic polymers, or a laminate may be used. These polymer films may contain known additives such as lubricants and plasticizers. More preferably, it is one selected from polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyphenylene sulfide (PPS), polyimide (PI) and copolymers thereof from the viewpoint of cost and processability. Is preferable, and polyethylene terephthalate (PET) is particularly preferable.

Further, the base film itself may be colored black to have the constitution of (4) or (5) above.

The total thickness of the insulating coating film of the present invention is in the range of 0.5 to 15 μm. If it is less than 0.5 μm, the withstand voltage of the film is low, so that the insulating property is inferior. If the thickness exceeds 15 μm, the rigidity becomes stronger than necessary, and an ultrafine electric wire that can withstand use cannot be manufactured. More preferably, the thickness of the base film is in the range of 1.0 to 10 μm.

The colored layer in the present invention is not particularly limited, and is made of a commonly used coloring material, a binder, fine particles, or the like. As the coloring material, it can be appropriately selected from commonly used pigments and dyes. As the binder, a thermosetting resin or a thermoplastic resin having adhesiveness to the base film can be used. Examples of the thermosetting resin include epoxy resin, phenol resin, xylene resin, urea resin, melanin resin, unsaturated polyester resin, furan resin, acetone formaldehyde resin, and alkyd resin. Examples of the thermoplastic resin include olefin copolymers such as ethylene-vinyl acetate copolymers, polyamide resins, polyester resins, natural rubbers, petrochemical resins, rosin resins, and styrene resins. Examples of the fine particles include organic particles such as melamine resin particles, polyethylene resin particles, and acrylic resin particles, and inorganic particles such as silica, calcium carbonate, magnesium carbonate, aluminum powder, and diatomaceous earth. These particles may be used alone or in combination of two or more.

The method for forming the colored layer in the present invention is not particularly limited, but the material of the colored layer can be dissolved and dispersed in an organic solvent, coated and dried on the base film, and provided. As a coating method, for example, a gravure coater, a reverse roll coater, a wire bar coater, an air doctor coat, or the like can be used for the coating. Of these, a colored layer formed by using a gravure coating is preferable.

The thickness of the colored layer in the present invention is not particularly limited, but is preferably in the range of 100 to 3000 nm. If it is less than 100 nm, it may be too thin to produce hue, and if it is thicker than 3000 nm, ink powder may fall off when spirally wound around the outer circumference of the shield conductor after microslit. The range is more preferably 500 to 2000 nm from the viewpoint that ink powder does not fall off while ensuring a hue sufficient to shield the base.

The adhesive layer in the present invention is preferably a thermosetting adhesive, and the type is not particularly limited, and examples thereof include unsaturated polyester resin, melamine resin, epoxy resin, and phenol resin. Unsaturated polyester resins are preferably used because they are easy to handle, have good workability, and have good mechanical properties.

The thickness of the adhesive layer in the present invention is not particularly limited, but is preferably in the range of 100 to 3000 nm. If it is less than 100 nm, it may be too thin to adhere, and if it is thicker than 3000 nm, the processability of the coating deteriorates, and it is more preferably in the range of 500 to 2000 nm.

Further, the insulating coating film in the present invention is suitably used for ultrafine electric wires.

A cross-sectional view of a shielded cable is shown in FIG. 2 as an example of an electric wire produced by using the insulating coating film of the present invention.

The shielded cable is composed of two parallel cores. A pair of two core wires whose center conductor (core wire) is insulated with an insulator is covered with a shield conductor, and a drain wire is provided between the shield conductor and the two core wires so as to be in contact with the conductive surface of the shield conductor. Are vertically attached to ensure mutual conduction and electromagnetic wave shielding. Further, an insulating coating film having a heat-bonding function is wound and adhered as an outer cover so that the shield conductor is not unwound. The insulating coating film of the present invention is suitably used as this jacket. The coating method is not particularly limited, and may be spiral winding or cigarette winding.
[Measurement method of physical properties and evaluation method of effect]
(1) Total Thickness Using a Digimatic Standard Outside Micrometer (model number "MDC-25SX") manufactured by Mitutoyo Co., Ltd., 10 films were stacked and measured to determine the total thickness (μm).

(2) Saturation Using a spectrophotometer (model number "CM-2500d") manufactured by Konica Minolta Co., Ltd., the measurement field is set to 2 °, and L ^* a ^* b ^* L ^* a specified by the color system. ^* B ^* was measured to determine the chromaticity.

The measurement surface was the surface opposite to the surface on which the base film was exposed.

(3) Transmittance The transmittance was measured using a portable black-and-white transmission densitometer (model number "Ihac-T5") manufactured by Ihara Electronics Co., Ltd., and the transmittance (%) was determined. The measurement surface was the surface opposite to the surface on which the base film was exposed.

(4) Surface resistivity Measured according to the method of JIS C2151: 2006 (Annex 2). Electrodes having the above-defined shape are formed by vapor-depositing aluminum on both sides of the film, and a super-insulation meter SM-8220 manufactured by Hioki E.E. , Surface resistivity was measured. The measurement surface was the surface opposite to the surface on which the base film was exposed.

(5) Insulation test of electric wire After cutting the dielectric breakdown film to a predetermined width and winding it around a shield conductor in a spiral shape to cover it, a 1 KV DC voltage is braided using a Zumbach spark tester as a measuring device. Was applied with the (+) pole and the outermost circumference of the electric wire as the (-) pole = ground, and the entire length was continuously inspected at 5 m / min, and the number of dielectric breakdowns was counted. Those in which 0 to 1 dielectric breakdown occurred at 10 m were evaluated as good "◯", and those in which 2 or more dielectric breakdown occurred at 10 m were evaluated as "x".

(6) Concealment of core wire color When the insulating coating film is cut to a predetermined width and wound around a shield conductor in a spiral shape, the conductor color that can be shielded is good "○", the conductor color. Those that could not be shielded were marked as defective "x".

Hereinafter, the present invention will be specifically described based on Examples, but the present invention is not limited to these Examples.

(Example 1)
Using a 4.0 μm-thick polyethylene terephthalate film (Toray Co., Ltd. “Lumilar (registered trademark)” type name CX40) as a base material, cyan, magenta, and yellow pigments are kneaded on one side of the film. Using an ink prepared to be black by kneading so that the ratio of carbon black in the solid content of the colored layer after drying is 8 wt%, a colored layer is formed so that the thickness after drying is 1000 nm, and further. As an adhesive layer, a polyester resin PK-21 manufactured by Totoku Paint Co., Ltd. was applied together with a curing agent so that the thickness after drying would be 1000 nm.

At this time, the surface resistivity of the polyethylene terephthalate film was 9 × 10 ¹¹ Ω / □, and the surface resistivity in the state where the colored layer was formed on the polyethylene terephthalate film was 2 × 10 ¹² Ω / □. Similarly, the surface resistivity in the state where the adhesive layer was formed on the polyethylene terephthalate film was 5 × 10 ¹¹ Ω / □.

The insulating coating film thus produced is cut to a width of 2.5 mm, wound around a shield conductor in a spiral shape, and heat-bonded to produce a black shielded cable, and the surface resistivity of the coated surface and the electric wire The insulation test and the color shielding property of the conductor were evaluated.

The surface resistivity of the coated surface was 6 × 10 ¹¹ Ω / □, the insulation test of the electric wire was as good as 0, and the shielding property of the conductor was as good as ◯.

(Example 2)
The same procedure as in Example 1 was carried out except that the proportion of carbon black in the colored layer was 35 wt%. The surface resistivity of the coated surface was 4 × 10 ¹¹ Ω / □, the insulation test of the electric wire was as good as one, and the shielding property of the conductor was as good as ◯.

(Comparative Example 1)
The same procedure as in Example 1 was carried out except that the proportion of carbon black in the colored layer was 42 wt%. The surface resistivity of the coated surface was 3 × 10 ¹⁰ Ω / □, the insulation test of the electric wire was poor with 5 pieces, and the shielding property of the conductor was good with ○.

(Comparative Example 2)
This was carried out in the same manner as in Example 1 except that the colored layer did not contain carbon black. The surface resistivity of the coated surface was 7 × 10 ¹¹ Ω / □, the insulation test of the electric wire was good with 0 pieces, and the shielding property of the conductor was poor with ×.

(Comparative Example 3)
The same procedure as in Example 1 was carried out except that the colored layer did not contain carbon black and the colored layer was formed by kneading only cyanide-based and magenta-based pigments. The surface resistivity of the coated surface was 8 × 10 ¹¹ Ω / □, the insulation test of the electric wire was good with 0 pieces, and the shielding property of the conductor was poor with ×.

(Comparative Example 4)
The same procedure as in Example 1 was carried out except that a polyethylene terephthalate film having a thickness of 20.0 μm was used as a base material. The surface resistivity of the coated surface was 7 × 10 ¹¹ Ω / □, but it was too thick to wind well in a spiral shape, and a shielded cable could not be manufactured.

1. 1. Insulation coating film 1a. Base film 1b. Colored layer 1c. Adhesive layer 2. General shielded cable 3. Center conductor (core wire)
4. Insulator 5. Drain wire 6. Shield conductor 6a. Metal layer 6b. Base film 7. Cover (film for insulation coating)
7a. Base film 7b. Colored layer 7c. Adhesive layer

Claims (4)

An insulating coating film used for ultrafine electric wires, having a total thickness of 0.5 to 15 μm, a chromaticity L ^{* on} at least one surface of 0 to 40, and a transmittance of 0 to 10%. An insulating coating film having a surface resistivity of 2 × 10 ¹¹ Ω / □ or more on any surface of the film. The insulating coating film according to claim 1, which has an adhesive layer having thermal adhesiveness on at least one surface. The layer structure is a base film / colored layer / adhesive layer, or a base film / (colored and adhesive layer), or a base film / colored layer, or a base film / adhesive layer, or a base film. The insulating coating film according to claim 1, which is any of the above. The insulating coating film according to claim 3, wherein the colored layer contains carbon black, and the content of carbon black is 6 to 40 wt%.

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