JP3035154B2 - Enamelled copper wire with enhanced adhesion to copper conductors - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an enameled copper wire.
More specifically, the conductor diameter is 0.05 to 0.08 mm and the thickness of the insulating film is 4.0 to 5.0, which is suitable for use in a flyback transformer (FBT), an ignition coil (IGC), or the like.
The present invention relates to a fine-diameter enameled copper wire having a small diameter of 0 μm, having excellent adhesion between a copper conductor and an insulating film, having no defects even in a thin film, and having good breakdown voltage characteristics.

[0002]

2. Description of the Related Art Conventionally used enameled copper wires are:
A viscous insulating paint in which a synthetic resin such as a polyurethane resin, polyester resin, polyesterimide resin or polyamideimide resin is dissolved in an organic solvent such as cresol or N-methylpyrrolidone is applied and baked a plurality of times on a copper conductor. For example, it is manufactured by applying and baking a polyurethane insulating paint on a copper conductor and repeating it a plurality of times until a prescribed film thickness is obtained. This enameled copper wire is coil-wound and widely used as a component of various electronic devices. The wound coil has a function of mutually converting electric energy and magnetic energy.

In recent years, as various electronic devices have become lighter, thinner and smaller,
The shape of the coil has also been reduced in size, and the space factor of the wire has been improved. Accordingly, the diameter of the enameled copper wire used for the coil is inevitably reduced, the diameter of the copper conductor is reduced, and the thickness of the insulating film is also reduced. Particularly, this tendency is caused by a small coil having a number of turns of several thousand turns, for example, FBT, I
It becomes more remarkable as it becomes GC, and the outer diameter of the coil is also restricted. Therefore, the thickness of the insulating film of the fine-diameter enameled copper wire used for these coils is required to be, for example, 5 μm thick and to have a submicron precision control.

[0004] When a small diameter enameled copper wire is coiled, the enameled copper wire is subjected to strong tension or rubbed by a pulley of a winding machine, so that the insulating film is deteriorated by processing.
As a result, a decrease in various characteristic values, for example, a dielectric breakdown voltage value was inevitable. For this reason, generally, in order to compensate for the decrease in the characteristic value, the thickness of the insulating film is designed and manufactured close to the upper limit of the standard, and as a result, the coil dimensions are restricted on the mounting surface. For this reason, there has been a strong demand from the coil winding industry for the development of a fine-diameter enameled copper wire which has no defects even when the film thickness is small and has excellent winding properties.

[0005]

As described above, an enameled copper wire is formed by, for example, applying and baking a polyurethane insulating paint on a copper conductor a plurality of times. On this occasion,
Crosslinking occurs between the molecular chains of the resin of the paint, and an insulating film having a three-dimensional network structure is formed. However, the bonding between the insulating film baked on the copper conductor and the copper conductor surface by this method is merely mechanical bonding, and strong bonding based on chemical bonding cannot be expected. As a result, if there is a mechanical defect such as pinholes or fine scratches in the insulating film of the fine-diameter enameled copper wire, moisture will penetrate from the defect, and the film will rise from the copper surface, causing one of the causes of film peeling. Had become. Further, when an enameled copper wire is wound around a coil in such a situation, the adhesion of the insulating film at the floating portion is extremely reduced, and a remarkable decrease in electric characteristics is recognized. That is, the first problem is a problem relating to the adhesive interface between the copper conductor and the insulating film, that is, a problem relating to the adhesion between the copper conductor of the enameled copper wire and the insulating film.

[0006] Die scratches during wire drawing remain on the copper conductor surface. In addition, it is impossible to eliminate such scratches.
Die scratches of about m cannot be removed. When the dice scratches are viewed microscopically, the shape of the scratches is concave and forms a linear groove, and occurs along the length direction of the copper conductor.

When an insulating coating is formed by applying and baking an insulating paint on the surface of the copper conductor having the dice scratches, there is a great risk that minute voids (microvoids) are formed at the interface between the conductor surface and the insulating film. . When this microvoid is formed, the electric field in the void is larger than that in the dielectric (insulating film), and the dielectric strength of gas is generally smaller than that of a solid. Therefore, when a high voltage is applied, void discharge occurs. Start.
Then, tan δ of the insulating film increases relatively sharply, and the withstand voltage life decreases. Further, since the corner portion of the die flaw is a place where the electric field is easily concentrated locally, corona discharge starts at this portion, and the insulating film is deteriorated. Therefore, the die scratches cause the breakdown voltage characteristics of the insulating film to deteriorate. That is, the second problem is a problem of the surface of the copper conductor with respect to the breakdown voltage characteristics of the enameled copper wire, that is, a problem that the dice scratch reduces the breakdown voltage characteristics of the insulating film.

The present invention has been made to solve the above-mentioned various problems of the prior art, and is intended to improve the adhesion between a copper conductor of a fine-diameter enameled copper wire and an insulating film and a breakdown voltage characteristic. Considers that the above two major problems must be solved and focuses on the interface between the insulation film and the copper conductor and the dice flaws. An object of the present invention is to provide a fine-diameter enameled copper wire which has excellent adhesion, has no defects even in a thin film thickness, and has good pinhole characteristics and breakdown voltage characteristics.

[0009]

In order to achieve the above object, the present invention provides an aqueous solution of a salt of an alkylimidazole compound, comprising adding a solid polymer electrolyte in which an alkali metal perchlorate is dissolved in a polyolefin oxide. Is applied to the surface of a copper conductor and heated and dried to form a conductive solid intermediate polymer-containing alkylimidazole copper complex film (hereinafter referred to as copper complex film).
An enameled copper wire (hereinafter abbreviated as a strongly adherent enameled copper wire) having an adhesion to a copper conductor provided with an insulating coating by applying and baking an insulating paint on the outer periphery thereof.

[0010] The present invention also relates to the present invention, wherein the alkylimidazole compound is imidazole, 2-methylimidazole,
A strong adhesion enamel, wherein the polyolefin oxide is polyethylene oxide or polypropylene oxide, and the alkali metal perchlorate is lithium perchlorate.-Methylimidazole or 4-methyl-5-hydroxymethylimidazole On the copper wire. It is sufficient that the thickness of the copper complex film is 0.5 to 1.0 μm.

[0011]

The enamelled copper wire of the present invention uses an alkylimidazole which easily forms a chelate compound (complex) with copper, and forms an intermediate layer at the interface between different surfaces of the copper conductor surface and the insulating film. Therefore, the adhesion between the conductor and the insulating film is improved. Further, by adding a polymer solid electrolyte in which an alkali metal perchlorate is dissolved in polyolefin oxide to the intermediate layer of the alkylimidazole, ionic conductivity is imparted to the intermediate layer, so that corona generation is prevented, and the breakdown voltage is reduced. The characteristics are good.

This will be described in more detail. When the alkylimidazole solution of the present invention is applied to the copper conductor surface, the alkylimidazole immediately acts on copper, reacts with cuprous oxide (Cu ₂ O) in the oxide film on the copper conductor surface, and forms an alkyl on the copper conductor surface. An intermediate layer of the imidazole copper complex is formed. The chemical formula is shown below.

[0013]

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When the alkylimidazole copper complex is formed on the copper conductor surface in this manner, the remaining imidazole in the solution is converted into alkylimidazole micelles by van der Waals force specific to long-chain alkyl groups and hydrogen bond specific to imidazole. As a result, the surface of the copper conductor is coated with the micelle, and the "wetting" property of the insulating paint on the conductor surface is greatly improved. Further, when the insulating paint is applied through the micelle formed on the copper conductor, the alkyl group of the alkylimidazole and the alkyl group forming the side chain of the synthetic resin which is a main component of the insulating paint interact with each other. The surface of the copper conductor and the insulating film are firmly adhered to each other due to the van der Waals force unique to the alkyl group.

Further, as described above, the "wetting" of the insulating paint
As a result, the generation of the microvoids is suppressed and the withstand voltage life is improved. Furthermore, since the polymer solid electrolyte is contained in the alkyl imidazole micelle as a conductivity-imparting agent, the intermediate layer acts as an ion-conductive thin film, and is locally formed at the tip of the edge portion of the die scratch on the copper conductor surface. The potential generated when the electric field is easily concentrated on the surface is reduced, and corona discharge is prevented. As a result, the deterioration of the insulating film can be prevented, and the breakdown voltage characteristics are greatly improved.

[0016]

EXAMPLES The contents of the present invention will be described below with reference to examples. Note that the present invention is not limited to the present embodiment.
FIG. 1 is a cross-sectional view showing an embodiment of a strongly-adhesive fine-diameter enameled copper wire according to the present invention, wherein 1 is a copper conductor, 2 is a copper complex film (conductive intermediate layer), and 3 is an insulating film (polyurethane film). Is shown.

Example 1 Production of a strongly-adhesive fine-diameter enameled copper wire (1) Preparation of polymer solid electrolyte Lithium perchlorate was added so that lithium content was 10% in 100 g of polyethylene oxide (molecular weight 1700).
64 g was added, and the mixture was stirred at room temperature for 30 minutes and dissolved to prepare a solid polymer electrolyte as an ion-conductive conductivity imparting agent. (2) Preparation of alkyl imidazole solution (conductive intermediate layer forming agent) 50 g of polymer solid electrolyte prepared in the above (1) in 1000 ml of Glyquat-L (trade name of Shikoku Chemicals), which is an aqueous solution of higher alkyl imidazole salt Was added and stirred at room temperature for 30 minutes to prepare an alkylimidazole solution. (3) Production of 0.05 mm Polyurethane Copper Wire Production of 0.05 mm polyurethane copper wire having strong adhesion will be described with reference to FIG. 1. The alkylimidazole solution prepared in the above (2) was applied on a copper conductor 1 having a diameter of 0.05 mm using a felt, followed by a furnace length of 1.4 m and a furnace inlet temperature of 40 m.
Using a drying and baking oven at 0 ° C. and a furnace outlet temperature of 450 ° C., drying at a linear velocity of 180 m / min.
Was provided. Next, on this intermediate layer 2, a polyurethane paint T
The operation of applying PU-20 (trade name of Totoku Paint Co., Ltd.) using a felt and then baking at the same temperature and the same linear speed using the above furnace was repeated 5 times to provide a polyurethane film 3 and finish. A polyurethane copper wire having an outer diameter of 0.058 mm was produced. The degree of drying of the intermediate layer 2 was evaluated based on the degree of discoloration of the copper conductor surface.

Comparative Example Production of Fine Diameter Enamelled Copper Wire Production of a polyurethane copper wire of 0.05 mm will be described with reference to FIG. The same polyurethane coating TPU-20 as used in the first embodiment was applied on the copper conductor 1 having a diameter of 0.05 mm in the same baking furnace as in the first embodiment under the same conditions and at the same linear speed. Then, a polyurethane film 3 was provided to produce a polyurethane copper wire having a finish outer diameter of 0.058 mm.

Characteristics Tests The small-diameter enameled copper wires produced in Example 1 and Comparative Example were tested in accordance with JIS C3003 “Testing methods for enameled copper wires and enameled aluminum copper wires”. The results are shown in Table 1 below.

[0020]

[Table 1]

As is clear from Table 1 above, it can be seen that the thin enameled copper wire of the present invention has various properties superior to those of the comparative example. That is, it can be seen that the occurrence of pinholes in the water is small, so that the adhesion to the copper conductor is excellent, and that the breakdown voltage and the corona generation voltage are high, so that the breakdown voltage characteristics are excellent.

[0022]

The first effect of the small-diameter enameled copper wire of the present invention is to form an alkylimidazole copper complex on the copper conductor surface,
In addition, since the intermediate layer having ion conductivity is formed, the adhesion of the insulating film baked through the intermediate layer to the copper conductor surface is greatly improved. The second effect is that ionic conductivity is imparted by the ionic carrier of the polymer solid electrolyte as a component of the intermediate layer, and the phenomenon that the electric field is locally concentrated due to the edge effect of fine scratches such as dice scratches is reduced. Is done. Therefore, corona discharge generated from the edge portion is prevented, the corona generation voltage is increased, and the breakdown voltage characteristics are improved. From the effects 1 and 2 described above, it has become possible to improve the reliability of the coil, so that it can be widely used in transformers for high-voltage generating parts such as flyback transformers and ignition coils, and the effect contributing to industry is extremely large. Is big.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing one embodiment of a small-diameter enameled copper wire having enhanced adhesion to a copper conductor according to the present invention.

FIG. 2 is a cross-sectional view showing a conventional small-diameter enameled copper wire.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Copper conductor 2 Polymer solid electrolyte containing alkyl imidazole copper complex film (conductive intermediate layer) 3 Insulation film (polyurethane film)

Claims (4)

(57) [Claims] An alkylimidazole solution obtained by adding a polymer solid electrolyte obtained by dissolving an alkali metal perchlorate in polyolefin oxide to an aqueous solution of a salt of an alkylimidazole compound, is applied to the surface of a copper conductor, and heated and dried. Then, an alkyl imidazole copper complex film containing a polymer solid electrolyte as a conductive intermediate layer is provided, and an insulating paint is applied to the outer periphery of the film and baked to provide an insulating film. Strengthened enameled copper wire 2. The enameled copper wire according to claim 1, wherein said alkylimidazole compound is imidazole, 2-methylimidazole, 4-methylimidazole or 4-methyl-5-hydroxymethylimidazole. 3. The enameled copper wire with enhanced adhesion to a copper conductor according to claim 1, wherein the polyolefin oxide is polyethylene oxide or polypropylene oxide. 4. The enameled copper wire with enhanced adhesion to a copper conductor according to claim 1, wherein the alkali metal perchlorate is lithium perchlorate.