WO1990011603A1

WO1990011603A1 - Insulated electric wire

Info

Publication number: WO1990011603A1
Application number: PCT/JP1990/000401
Authority: WO
Inventors: Shinji Inazawa; Kouichi Yamada; Kazuo Sawada
Original assignee: Sumitomo Electric Industries, Ltd.
Priority date: 1989-03-28
Filing date: 1990-03-26
Publication date: 1990-10-04
Also published as: EP0416131A1; HK96795A; JP2890631B2; AU627859B2; EP0416131B1; KR940000845B1; DE69013448T2; CA2029868A1; CA2029868C; DK0416131T3; KR920700456A; JPH0315113A; DE69013448D1; EP0416131A4; AU5273690A

Abstract

An insulated electric wire of this invention is adapted to be used as a wire for wiring or as a wire for winding in a highly vacuum or high-temperature environment such as high-vacuum equipment or high-temperature equipment. This wire comprises a base member (1), a chromium oxide layer (2) and an oxide insulating layer (3). The base member (1) includes a conductor. The chromium oxide layer (2) is formed on the outer surface of the base member (1). The oxide insulating layer (3) is formed on the chromium oxide layer (2) by applying a precursor solution of a metal oxide based on the sol-gel method or an organic acid salt pyrolysis method. The insulated electric wire exhibits excellent flexibility as well as heat resistance and does not provide a source of gas adsorption.

Description

Specification

Title of invention

Insulated wire

Technical field

The present invention relates to an insulated wire, and more particularly to an insulated wire such as a wiring wire and a winding wire used in a high vacuum environment such as a high vacuum device or a device used at a high temperature, or in a high temperature environment. Things.

Background art

Insulated wires may be used for equipment that requires safety at high temperatures, such as heating equipment and fire alarms. Insulated wires are also used in environments where automobiles are heated to high temperatures. Conventionally, as such an insulated wire, an insulated wire in which a conductor is covered with a heat-resistant organic resin such as polyimide-fluorinated resin is used.

When used in applications that require high heat resistance or in environments that require a high degree of vacuum, organic coatings are insufficient in terms of heat resistance and non-gas release. Therefore, the conductor is inserted into an insulated wire in the form of a conductor passed through a ceramic tube, or a tube made of a heat-resistant alloy such as a stainless steel alloy filled with metal oxide fine particles such as magnesium oxide. Ml Cape Inlet (Mineral Insulated Cab 1e) etc. in the form of passing through have been used for such purposes. Further, as an insulated wire that requires flexibility as well as heat resistance, a glass braided insulated wire that uses a fiber woven fabric as an insulating member is exemplified.

For insulated wires coated with organic resins with heat resistance as described above, the highest temperature at which insulation can be maintained is at most

It is about 200 ° C. Therefore, such an organic insulated wire could not be used for applications requiring insulation assurance at temperatures as high as 200 ° C or higher.

Also, insulated wires with improved heat resistance using ceramic tube made of glass have drawbacks such as poor flexibility. Since the MI cable is composed of a heat-resistant alloy tube and a conductor, the outer diameter of the cable increases. As a result, the Ml cable has a relatively large cross section for the amount of power allowed by the conductor passed through the heat-resistant alloy tube. Also, since the outer layer of the MI cable is made of a heat-resistant alloy tube, it has good flexibility. However, in order to use it as a wire for winding wound on a bobbin or the like in a coil shape, it is necessary to bend a pipe made of a heat-resistant alloy at a predetermined curvature. At this time, the bending work performed on the heat-resistant alloy pipe involves difficulty. Also, when the MI cable is wound in a coil shape, it is difficult to improve the winding density because the outer layer pipe is thicker than the conductor.

In addition, when using a glass braided insulated wire that has both heat resistance and flexibility, arrange it in a predetermined shape according to the application. The problem is that glass dust is generated from the glass fiber when the glass fiber is used. This glass dust can be a gas adsorption source. Therefore, if glass-braided insulated wires were used in an environment where a high degree of vacuum was required, it was impossible to maintain a high degree of vacuum due to the gas adsorption source provided by the glass dust. On the other hand, there has been a so-called alumite wire, which is an anodized aluminum or aluminum alloy wire, as an insulated wire with good heat resistance, insulation and heat dissipation. In this alumite electric wire, the base material is limited to aluminum. Further, the inorganic insulating layer formed on the base material is also limited to aluminum oxide. Therefore, there was a problem that a combination of a base material and an inorganic insulating layer suitable for various uses could not be selected.

Disclosure of the invention

Then, this invention was made in order to solve the said problem, and it aims at providing the insulated wire provided with the following matters.

(a) Have high insulation properties in a high temperature environment.

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(b) Excellent flexibility.

(C) No gas adsorption source.

(d) A combination of a base material and an inorganic insulating layer suitable for various uses can be selected.

The insulated wire according to the present invention comprises a base material and chromium oxide. And an oxide insulating layer. The substrate has an outer surface and includes a conductor. The chromium oxide-containing layer is formed on the outer surface of the substrate. The oxide insulating layer is formed by applying a precursor solution of a metal oxide on the chromium oxide-containing layer by a sol-gel method or an organic acid salt pyrolysis method.

The chromium oxide-containing layer is preferably formed by an electrochemical method. Here, the electrochemical method means an electrolytic plating method or an electroless plating method. Underlayer performing oxide insulating layer in order to function lay favored as a contact脣_{is, C r 0 3 - X (} .. 1 5≤ X≤ 2 5) may be any layer. That is, the layer formed by the electrochemical method has a chromium oxide layer as the outermost layer. The oxide insulating layer preferably contains silicon oxide, aluminum oxide, and zirconium oxide. From the viewpoint of high conductivity and cost, it is preferable that the base material be a copper or copper alloy. In consideration of applications at higher temperatures, the surface layer of the base material preferably contains nickel, chromium, silver, iron or iron alloy, stainless alloy, titanium or titanium alloy.

It is known that a chromium plating layer is formed as a good adhesion layer on a conductor such as a 鋦 or 鋦 alloy. However, insulating oxide ceramics such as silicon oxide obtained by heat treatment of the precursor solution of the metal oxide show little adhesion to the chromium plating layer. This is a book This is based on the knowledge of the inventor.

In addition, in the case of an insulated wire in which a ceramic thin film is formed directly on the surface of a conductor made of copper, the adhesion of the ceramic thin film that functions as an insulating layer to the base material is insufficient. Therefore, in the present invention, a layer having a chromium oxide layer as the outermost layer is formed on the outer surface of the substrate. On this chromium oxide layer, an insulating oxide ceramic adheres as a layer having good adhesion.

The chromium oxide layer is formed by an electrochemical method. When the chromium oxide layer is formed by the electrolytic plating method, an electrolytic solution obtained by adding a small amount of an organic acid to an aqueous solution of chromic acid is used. In general, a surge bath mainly composed of chromic acid and sulfuric acid is known as an electrolytic bath used for performing chromium plating, but differs from this bath in the following points. In other words, the mineral acid mixed in the electrolytic bath has the function of dissolving the chromium oxide generated on the surface of the plating layer during electroplating. Therefore, when a surge bath is used, a glossy metallic chromium layer is plated. In the present invention, it is necessary to preferentially plate chromium oxide. Therefore, a small amount of organic acid is added to the electrolytic bath used in the present invention. When a mineral acid such as sulfuric acid is used, a particularly dilute electrolytic bath must be used. That is, the chromic acid concentration is less than 50 g Z £ and the sulfuric acid concentration is less than 1 g Z IL. In addition, on the outer surface of the layer mainly composed of chromium oxide, The processing of the precursor solution forms a thin film of insulating ceramic, but in order to increase the adhesion of this thin film, the surface of the layer mainly composed of chromium oxide must be rough. I like it.

A chromium oxide-containing layer may be formed by an electrolytic plating method using an electrolytic solution obtained by adding, for example, sodium citrate, sodium carbonate, or the like to an aqueous solution of sodium chromate. At this time, the formed layer is mainly composed of chromium oxide generated by reducing hexavalent chromium in the electrolytic solution to trivalent. In addition, in the case of the electrolytic plating treatment, when 鋦 is used as the base material, the base material surface is oxidized, and a chromium oxide-containing layer is formed outside. However, the oxidation of the chromium oxide-containing layer does not decrease the adhesion of the chromium oxide-containing layer to the substrate due to the oxidation of the substrate surface. The conditions for the electrolytic plating when forming the chromium oxide-containing layer of the present invention are different from the generally used plating in terms of processing current density and the like. In glossy plated, depending on the treatment temperature, the current density is set to 1 0~ 6 O AZdm ^2, in the present invention, the current density is set to 1 0 0~2 0 0 AZdm ² . Under the conditions of the current density, a roughened chromium oxide-containing layer can be formed.

An insulating oxide layer is formed on the chromium oxide-containing layer by applying a precursor solution of a metal oxide. As used herein, the term “metal oxide precursor solution” refers to a solution prepared from a metal organic compound, and is prepared by a sol-gel method or It is roughly classified according to the organic acid salt pyrolysis method, and includes the following two types of evenings.

The first type of precursor solution is a solution formed by subjecting a compound containing a hydrolyzable metal-oxygen-organic group bond such as a metal alkoxide and metal acetate to a hydrolysis reaction and a dehydration condensation reaction. is there. This solution may contain an organic solvent such as alcohol, a starting compound such as a metal alkoxide, water and a catalyst necessary for the hydrolysis reaction. Also, unlike hydroxide sols generated from inorganic salts, they often contain organic residues such as alkoxides.

The second type of precursor solution is a solution in which a metal organic compound such as an organic acid salt of a metal is dissolved in a suitable organic solvent. In the method using a precursor solution of this type, a metal oxide is generated by heating and thermally decomposing after coating. For this reason, the decomposition temperature of the metal organic compound used needs to be lower than its boiling point or sublimation point.

The metal-organic compound referred to in this specification is, for example, "metal — organicco mpounds" described in journal of Materials Science 12 (1977) pp. 1203 to 128. It is the same concept as.

In addition, the coating must be left above room temperature to volatilize organic solvents and remove residual organic matter. However, the temperature of this neglected atmosphere constitutes the substrate The temperature must not be higher than the melting point of the metal used.

By applying a metal oxide precursor solution, almost all metal oxide-based ceramic coatings can be formed. As an example of a metal oxide formed by this method include S i 0 ₂ AI ₂ 〇 3, Z r 0 T i 0 2, M g O , and the like. Examples of the metal alkoxide used in the first type of precursor solution include ethoxide, propoxide, butoxide and the like. As the organic acid salt used in the second type of precursor solution, a metal salt such as naphthenic acid, caprylic acid, stearic acid, and octylic acid is preferable.

An oxide insulating layer formed from a precursor solution of a metal oxide by a sol-gel method or an organic acid salt pyrolysis method is a completely metal oxide oxide. This oxide is preferably formed by a heat treatment in an atmosphere of an oxygen stream. The decomposition of the compound contained in the solution applied on the chromium oxide-containing layer is usually completed completely at a temperature of about 500 ° C. However, if the heat treatment is performed at a higher temperature, the reaction between the elements constituting the chromium oxide-containing layer and the metal or metalloid contained in the applied solution is accelerated, so that the chromium oxide-containing layer is accelerated. The adhesion between the metal and the oxide layer is improved.

Thus, the ceramic oxide insulating layer exhibits excellent heat resistance even at a high temperature of 500 ° C. or more. Further, the chromium oxide-containing layer has excellent adhesion to the conductor constituting the base material. Therefore, compared with the case where the oxide insulating layer is formed directly on the outer surface of the conductor by heat treatment of the precursor solution of the metal oxide, the adhesive force between the oxide insulating layer and the outer surface of the base material is higher. Is improved. Therefore, the insulated electric wire provided by the present invention has heat resistance and good flexibility.

Further, the oxide insulating layer formed on the chromium oxide-containing layer has a smooth outer surface. Therefore, it is possible to obtain a high breakdown voltage in proportion to the film thickness and to reduce the number of gas adsorption sources.

In the present invention, a chromium oxide-containing layer is formed between the substrate and the oxide insulating layer. Therefore, a combination with an inorganic insulating layer suitable for various uses can be selected via the chromium oxide-containing layer.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a cross-sectional view showing a cross section of an insulated wire according to the present invention, corresponding to the first embodiment.

FIG. 2 is a cross-sectional view showing a cross section of an insulated wire according to the present invention corresponding to the second embodiment.

FIG. 3 is a cross-sectional view showing a cross section of an insulated wire according to the present invention in accordance with a third embodiment.

FIG. 4 is a cross-sectional view showing a cross section of an insulated wire according to the present invention corresponding to the fourth embodiment. FIG. 5 is a graph showing the measurement results of the surface roughness of the chromium oxide-containing layer formed according to Examples 3 and 4. FIG. 6 is a graph showing the measurement results of the surface roughness of the chromium plating layer formed according to the comparative example.

BEST MODE FOR CARRYING OUT THE INVENTION

Example 1

(a) Formation of chromium oxide-containing layer

Electrolytic plating was applied to the outer surface of a copper wire with a wire diameter of 2 mm ø. At this time, as the electrolyte, a solution having a concentration of 40 gZ £ of chromic anhydride and 0.45 gZ £ of sulfuric acid was used. The bathing condition was 50 bath temperature. C, the current density was 140 AZ dm ² , and the processing time was 2 minutes. Thus, a chromium oxide-containing layer was formed on the outer surface of the copper wire with a thickness of about 1 m.

(b) Preparation of coating solution used for sol-gel method

Tetrabutyl orthosilicate: water: isopropyl alcohol = 8: 32: 60 A nitric acid was added to a solution mixed at a molar ratio of 3/100 with respect to tetrabutyl orthosilicate. They were added in molar proportions. Thereafter, the solution was heated and stirred at a temperature of 80 ° C. for 2 hours. As a result, a coating solution used for the sol-gel method was synthesized.

(c) Coating

The wire rod obtained by (a) is coated with the coating solution of (b). (ID

The wire coated with the coating solution on the outer surface in this manner was immersed in the solution _{9 and} subjected to heating for 10 minutes at a temperature of 400 ° C. 10 times. Finally, the wire was heated in a stream of oxygen at a temperature of 500 ° C. for 10 minutes.

FIG. 1 shows the insulated wire obtained as described above. FIG. 1 is a cross-sectional view showing a cross section of the insulating wire obtained in Example 1. Referring to FIG. 1, a chromium oxide-containing layer 2 is formed on the outer surface of copper wire 1. On this chromium oxide-containing layer 2, a silicon oxide layer 3 is formed as an oxide insulating layer by a sol-gel method. The thickness of the insulating layer formed by the oxide containing layer 2 and the silicon oxide layer 3 was about 4.0 m.

The breakdown voltage was measured to evaluate the insulation properties of the insulated wires obtained. At room temperature, the breakdown voltage was 800 V, and at 800, it was 600 V. Even when this insulated wire was wound on the outer peripheral surface of a cylinder having a diameter of 10 cm, no crack was generated in the insulating layer.

Example 2

(a) Formation of chromium oxide containing layer

A copper wire having a wire diameter of 2 mm0 was degreased with steam using perchlorethylene. Then, the copper wire was immersed in a solution mixed at a volume ratio of 85% phosphoric acid: 70% nitric acid: water = 15: 2: 3 to roughen the surface.

Next, the copper wire was used as the cathode and the stainless steel plate was used as the anode. Electrolytic plating was performed by passing a DC current of 0.5 A / dm ² . At this time, about 1 solution of 30 g each of sodium chromate, sodium citrate and sodium carbonate dissolved in water was used as the electrolyte.

Thus, a copper oxide layer having a thickness of about 1 m is formed on the outer surface of the copper wire, and a chromium oxide-containing layer is formed to a thickness of about 0.1 zm outside the copper oxide layer. Was done.

(b) Preparation of coating solution used for sol-gel method

Te Torapuchiruoru DOO Jirukone preparative _{_{[(C 4 H 9 0)}} 4 Z r]: Water: .eta.-butyl alcohol = 5: 1 5: 8 2 0 mixed solution Monore ratio at a temperature of 1 2 0 ° C The mixture was heated and stirred for an hour. As a result, a coating solution used for the sol-gel method was synthesized.

(C) Coating

The wire obtained in (a) was immersed in the coating solution in (b). The wire coated with the coating solution on the outer surface in this manner was heated 10 times at a temperature of 400 ° C. for 10 minutes.

The insulated wire obtained as described above is shown in FIG. FIG. 2 is a cross-sectional view showing a cross section of the insulated wire obtained in Example 2. Referring to FIG. 2, a copper oxide layer 12 is formed on the outer surface of copper wire 11. A chromium oxide containing layer 13 is formed outside the copper oxide layer 12. Has been established. A zirconium oxide layer 14 is formed on the chromium oxide-containing layer 13 as an oxide insulating layer by a sol-gel method. The thickness of the insulating layer formed by the copper oxide layer 12, the chromium oxide-containing layer 13 and the zirconium oxide layer 14 was about 3. O Azm.

In order to evaluate the insulation properties of the obtained insulated wires, the insulation breakdown voltage was measured. At room temperature, the breakdown voltage was 700 V, and at 700 ° C, it was 500 V. Further, even when this insulated wire was wound on the outer peripheral surface of a cylinder having a diameter of 10 cm, no crack was generated in the insulating layer.

Example 3

(a) Formation of chromium oxide-containing layer

Electrolytic treatment was applied to the outer surface of a nickel-plated copper wire with a wire diameter of 1.8 mm0. At this time, as the electrolytic solution, those having a concentration of chromic anhydride of 200 £, ammonium metavanadate of 20 gZ £, and acetic acid of 6.5 g ZL were used. The plating conditions were such that the base material was used as a cathode, the bath temperature was 50 ° C., the current density was 150 A / dm ² , and the treatment time was 2 minutes. Thus, a chromium oxide-containing layer having a thickness of about 1 m was formed on the outer surface of the nickel-plated copper wire.

The surface condition of the chromium oxide-containing layer is determined by the surface roughness of IS0468-19882, medium and line average roughness Ra is 0.15 m and maximum height Ry is 0.87. m. Surface roughness measurements are made by S loan company of America The measurement was carried out using a DEKTAK 3030 surface profiler under the conditions of a stylus diameter of 0,5 τη ^, a stylus pressure of 10 mg, a standard length of 50 m, and no cutoff filter. The measurement results are shown in FIG.

(b) Preparation of coating solution used for organic acid salt pyrolysis method

A coating solution was prepared by dissolving 20 g of 2-ethylhexanoic silicate in 10 OmJL of dibutyl ether.

(c) Coating

The wire obtained in (a) was immersed in the coating solution in (b). The wire coated with the coating solution on the outer surface in this manner was subjected to 10 heating steps of 500 ° C. for 10 minutes.

FIG. 3 shows the insulated wire obtained as described above. FIG. 3 is a cross-sectional view showing a cross section of the insulated wire obtained in Example 3. Referring to FIG. 3, a Nigger-plated copper wire having a Nigel plating layer 22 formed on the outer surface of copper wire 21 is used as a base material. A chromium oxide-containing layer 23 is formed on the outer surface of the nickel-plated copper wire. On the chromium oxide containing layer 23, a silicon oxide layer 24 is formed as an oxide insulating layer by an organic acid salt pyrolysis method. The thickness of the insulating layer composed of the chromium oxide containing layer 23 and the silicon oxide layer 24 was about 5 m. In order to evaluate the insulation properties of the obtained insulated wires, the insulation breakdown voltage was measured. At room temperature, the dielectric breakdown voltage was 500 V, at 800 ° C, it was 300 V, and on the outer peripheral surface of a 5 cm diameter cylinder, No cracks were generated in the insulating layer even when it was wound.

Example 4

(a) Formation of chromium oxide-containing layer

A so-called stainless clad II wire with a wire diameter of 1.8 mm0, in which a stainless alloy (SUS304) was fitted on the outer surface of the copper wire, was used as the base material. Electrolytic plating was applied to the outer surface of the stainless steel clad copper wire. At this time, the electrolyte used had a concentration of chromic anhydride of 208 g and ammonium metavanadate of 20 g ZJ acetic acid of 6.5 g / i. The plating conditions were as follows: the base material was used as the cathode, and the bath temperature was 50. C, current density was 150 AZ dm ² , and processing time was 2 minutes. In this way, a chromium oxide-containing layer having a thickness of about 1 m was formed on the outer surface of the stainless steel clad copper wire.

The surface condition is determined by the Sur R ace Roughness of IS 0 4 6 8-1 9 8 2, the center line average roughness Ra is 0.15 ^ m and the maximum height Ry is 0.87 m Met. The measurement was performed using a surface shape measuring instrument DEKTAK 300 manufactured by Sloan of America, with a stylus diameter of 0.5 m, a stylus pressure of 10 mg, a reference length of 50 πι, and a cut-off filter. Conditions not used Made below. As a result of this measurement, the one shown in FIG. 5 was obtained as in Example 3.

(b) Preparation of coating solution used for organic acid salt pyrolysis method

25 g of aluminum butler i-butoxide was dissolved in 1-ethylene glycol monomethyl ether 1 O Om Jl, and then heated and stirred at 150 ° C for 1 hour. After allowing this solution to cool to room temperature, 3 g of alumina particles having a nominal particle size of 0.03 jam were mixed to prepare a coating solution.

(c) Coating

The insulated wire obtained as described above is shown in FIG. FIG. 4 is a cross-sectional view showing a cross section of the insulated wire obtained in Example 4. Referring to FIG. 4, a stainless steel clad copper wire having a stainless alloy layer 32 on the outer surface of copper wire 31 is used as a base material. A chromium oxide-containing layer 33 is formed on the outer surface of the stainless steel copper wire. On this chromium oxide-containing layer 33, an aluminum oxide layer 34 is formed as an oxide insulating layer by an organic acid salt pyrolysis method. This aluminum oxide layer 34 is made of aluminum that is originally mixed in the coating solution. It is composed of an aluminum oxide mixed layer containing fine particles. The film thickness of the insulating layer composed of the chromium oxide containing layer 33 and the aluminum oxide layer 34 was about 12 m.

The breakdown voltage was measured to evaluate the insulation properties of the insulated wires obtained. At room temperature, the breakdown voltage was 900 V, and at 800 ° C, it was 700 V. In addition, no cracks occurred in the insulating layer even when this insulated wire was wrapped around the outer circumference of a 15 cm diameter cylinder.

Comparative example

(a) Formation of metal chrome plating layer

Electrolytic plating was applied to the outer surface of a nickel-plated copper wire with a wire diameter of 1.8 mm. At this time, the electrolyte used had a concentration of 250 g / p of chromic anhydride and 2.5 gZJl of sulfuric acid. The plating conditions were such that the substrate was used as a cathode, the bath temperature was 50 ° C., the current density was 40 A / dm ² , and the treatment time was 2 minutes. Thus, a chromium-containing layer having a thickness of about 1 m was formed on the outer surface of the nickel-plated copper wire.

According to the surface roughness of IS04668-19982, the average surface roughness Ra was 0.06; / m, and the maximum height Ry was 0.51 m. Was. The measurement was performed using a surface profiler DE KT AK300, manufactured by Sloan of America, with a stylus diameter of 0.5 ^ m, a stylus pressure of 10 mg, a reference length of 50 μm, and a Conditions without using a filter Made below. The results of this measurement are shown in FIG. Glossy chrome metal layer formed on the outer surface of nickel-plated copper wire o

(b) Preparation of coating solution used for organic acid salt pyrolysis method

A coating solution was prepared by dissolving 20 g of 2-ethylhexane silicate silicate in 10 O mA of dimethyl ether.

(c) Coating

The wire obtained in (a) was immersed in the coating solution in (b). The wire coated with the coating solution on the outer surface in this way was subjected to a heating step at a temperature of 500 ° C. for 10 minutes.After the heating, the formed insulating layer was peeled into a film. And showed no adhesion.

Industrial applicability

As described above, the insulated wire according to the present invention can be used as a wiring wire, a winding wire, or the like used in a high vacuum environment such as a high vacuum device or a high-temperature device, or in a high temperature environment. Are suitable.

Claims

The scope of the claims

1. a substrate (1) having an outer surface and including a conductor;

A chromium oxide-containing layer (2) formed on the outer surface of the substrate,

An oxide insulating layer (3) formed by applying a precursor solution of a metal oxide on the chromium oxide-containing layer.

2. The insulated wire according to claim 1, wherein the chromium oxide-containing layer (2) is formed by an electrolytic plating method.

3. The insulated wire according to claim 1, wherein the oxide insulating layer (3) includes any of silicon oxide, aluminum oxide, and zirconium oxide.

4. The insulated wire according to claim 1, wherein the base material (1) contains any of copper and a copper alloy.

5. The substrate according to claim 1, wherein the base material includes any one of nickel, chromium, and stainless steel in its surface layer (22).

Insulated wire according to item 4.

6. The insulated wire according to claim 1, wherein said oxide insulating layer (3) includes ceramic fine particles dispersed therein.

7. a substrate (1) having an outer surface and including a conductor;

Chromium oxide-containing layer formed on outer surface of base material (2) Formed on chromium oxide-containing layer by sol-gel method An insulated wire, comprising: a coated oxide insulating layer (3).

8. A substrate (21) having an outer surface and including a conductor, and a chromium oxide-containing layer (2) formed on the outer surface of the substrate.

3) and

An insulated wire comprising: an oxide insulating layer (24) formed on the chromium oxide-containing layer by an organic acid salt pyrolysis method.