TWI888721B - Insulated wire and production method thereof, coil and electronic device - Google Patents

Abstract

An insulated wire, a production method of the insulated wire, and a coil and an electronic device using the insulated wire are provided. The insulated wire has a long voltage application life and excellent flexibility. The insulated wire includes a conductor and an insulating layer laminated on the outer peripheral side of the conductor. The insulating layer includes a liquid crystal polyester, and the film thickness uniformity D calculated by the following formula (A) of the insulating layer is 5% or less. D=(D _max-D _min)×100%/(D _avg×2) formula (A) In formula (A), D _maxrepresents the maximum thickness of the insulating layer, D _minrepresents the minimum thickness of the insulating layer, and D _avgrepresents the average thickness of the insulating layer.

Description

Insulated wire and manufacturing method thereof, coil and electronic device

The present invention relates to an insulated wire, and in particular to an insulated wire with a long voltage application life, a manufacturing method thereof, a coil and an electronic device.

In inverter-related devices (e.g., coils for electronic devices such as high-speed switching devices, inverter motors, and transformers), an insulated wire (e.g., enameled wire) with a coating layer (insulating film) of an insulating resin formed around the conductor is used as a magnetic conductor.

In recent years, with the popularization of hybrid cars and electric cars, there is a need to improve motor efficiency, and to operate motors and control converters at high voltages. When insulating wires are used at such high voltages, local discharge (corona discharge) occurs on the surface of the insulating film, causing degradation of the insulating film. In order to suppress this local discharge, resins with low dielectric constants are used as the constituent materials of the insulating film.

As mentioned above, insulated wires need to have high insulation resistance in high voltage environments to extend their voltage application life. In addition, the demand for miniaturization and high output of rotary motors such as automotive motors is increasing, which requires winding insulated wires on small-sized bobbins, increasing the winding density of insulated wires, or placing as many bent insulated wires as possible into limited spaces such as stator slots (status lot). Therefore, such insulated wires are required to have not only high insulation resistance but also high flexibility.

In view of this, an object of the present invention is to provide an insulated wire with a long voltage application life and excellent flexibility, a method for manufacturing the insulated wire, and a coil and an electronic device using the insulated wire.

The present invention provides an insulated wire, comprising: a conductor, and an insulating layer laminated on the outer peripheral side of the conductor. The insulating layer comprises liquid crystal polyester, and the film thickness uniformity D of the insulating layer is less than 5% calculated by the following formula (A): D=(D _max -D _min )×100%/(D _avg ×2) Formula (A) In formula (A), D _max represents the maximum thickness of the insulating layer, D _min represents the minimum thickness of the insulating layer, and D _avg represents the average thickness of the insulating layer.

In one embodiment of the present invention, the liquid crystal polyester comprises structural units from the following (A), (B), and (C), (A) aromatic hydroxy carboxylic acid (B) aromatic dicarboxylic acid (C) a compound selected from at least one of aromatic diols, aromatic diamines, and aromatic amines having a phenolic hydroxyl group.

In one embodiment of the present invention, the liquid crystal polyester comprises structural units from the following (A'), (B'), (C'), (A')-O-Ar ¹ -CO- (B')-CO-Ar ² -CO- (C')-X-Ar ³ -Y- wherein Ar ¹ represents a phenyl group, a naphthyl group or a biphenyl group, Ar ² represents a phenyl group, a naphthyl group, a biphenyl group or a group formed by condensation of multiple aromatic groups, Ar ³ represents a phenyl group or a group formed by condensation of multiple aromatic groups, and X and Y represent -O- or -NH-, respectively.

In one embodiment of the present invention, the above-mentioned liquid crystal polyester includes structural units derived from the following (A'), (B'), and (C''): (A')-O-Ar ¹ -CO- (B')-CO-Ar ² -CO- (C'')-NH-Ar ³ -Y- wherein Ar ¹ represents a phenyl group, a naphthyl group, or a biphenyl group, Ar ² represents a phenyl group, a naphthyl group, a biphenyl group, or a group formed by condensation of multiple aromatic groups, Ar ³ represents a phenyl group or a group formed by condensation of multiple aromatic groups, and Y represents -O- or -NH-.

In one embodiment of the present invention, the monomers constituting the above-mentioned (C'') include aromatic hydroxylamine and aromatic hydroxylamide.

In one embodiment of the present invention, based on the total amount of monomers constituting the above-mentioned (C'') being 100 mol%, the amount of aromatic hydroxylamine used is 30-90 mol%, and the amount of aromatic hydroxylamide used is 10-70 mol%.

In one embodiment of the present invention, the film thickness uniformity D of the above-mentioned insulating layer is less than 3%.

In one embodiment of the present invention, the film thickness uniformity D of the above-mentioned insulating layer is less than 1%.

In one embodiment of the present invention, the thickness of the insulating layer is greater than or equal to 2 μm and less than or equal to 50 μm.

The present invention further provides a method for manufacturing an insulating wire, and the manufacturing method of the insulating wire as described above includes the following steps: A coating step, coating a liquid composition including a liquid crystal polyester and an aprotic solvent on the outer periphery of the conductor, and A heating step, heating the conductor coated with the liquid composition.

The present invention further provides a coil including the above-mentioned insulated wire.

The present invention further provides an electronic machine, comprising the coil as described above.

Based on the above, since the insulating layer in the insulated wire of the present invention has a specific uniformity of film thickness, an insulated wire with a long voltage application life and excellent flexibility can be obtained.

[Insulating wire] Figure 1 is a cross-sectional view of an insulating wire of an embodiment of the present invention. As shown in Figure 1, the insulating wire 1 of the present invention includes: a conductor 11, and an insulating layer 12 laminated on the outer peripheral side of the conductor 11. The insulating layer 12 includes liquid crystal polyester, and the film thickness uniformity D of the insulating layer 12 is less than 5%. The following specifically describes each component in the insulating wire.

[Conductor] As the conductor in the insulated wire, any conductor conventionally used for insulated wires can be used without particular limitation. For example, metal conductors such as copper wires and aluminum wires can be cited.

As a preferred example of the conductor in the insulated wire of the present invention, a conductor 11 having a rectangular cross section (flat shape) can be used as shown in FIG. 1 , or a conductor having a square, circular or elliptical cross section can be used.

Among the flat conductors, as shown in FIG1 , in consideration of suppressing partial discharge at the corners, it is preferred that the flat conductor 11 has chamfers 13 at four corners. The radius of curvature of the chamfer 13 is preferably 0.6 mm or less, and more preferably 0.2 mm to 0.4 mm.

There is no particular restriction on the size of the conductor. If it is a flat conductor, the width (long side) of its rectangular cross section is preferably 1.0 mm to 5.0 mm, more preferably 1.4 mm to 4.0 mm; the thickness (short side) is preferably 0.4 mm to 3.0 mm, more preferably 0.5 mm to 2.5 mm. The ratio of thickness to width (short side: long side) is preferably 1:1 to 1:4. If it is a circular cross-section conductor, the cross-sectional diameter is preferably 0.3 mm to 3.0 mm, more preferably 0.4 mm to 2.7 mm.

[Insulating layer] As an insulating layer in an insulated wire, as shown in FIG1 , a single insulating layer 12 may be stacked on a conductor 11, or the insulating layer 12 may be multiple layers. The thickness of the insulating layer is 2 μm to 50 μm, preferably 10 μm to 50 μm, and more preferably 20 μm to 40 μm. When the insulating layer is a multiple-layer structure, the thickness of the insulating layer is calculated based on the total thickness of the multiple insulating layers. When the thickness of the insulating layer is less than 2 μm, sufficient strength cannot be obtained; and when the thickness of the insulating layer is greater than 50 μm, sufficient flexibility cannot be obtained, and thus the performance is poor.

[Thickness uniformity D of insulating layer] The thickness uniformity D of the insulating layer in the insulating wire is 5% or less as calculated by the following formula (A): D = (D _max -D _min ) × 100% / (D _avg × 2) Formula (A) In formula (A), D _max represents the maximum thickness of the insulating layer, D _min represents the minimum thickness of the insulating layer, and _Davg represents the average thickness of the insulating layer.

The film thickness uniformity D is preferably 3% or less, and more preferably 1% or less. If the film thickness uniformity D of the insulating layer is not within the above range, the voltage application life of the obtained insulating wire is poor.

[Liquid crystal polyester] Liquid crystal polyester is included as an insulating layer in an insulated wire. The liquid crystal polyester in the present invention is a polyester called a thermotropic liquid crystal polymer, which is a melt that shows optical anisotropy at a temperature of 450°C or less.

The liquid crystal polyester of the present invention includes structural units from the following (A), (B), and (C): (A) aromatic hydroxy carboxylic acid (B) aromatic dicarboxylic acid (C) a compound selected from at least one of aromatic diols, aromatic diamines, and aromatic amines having a phenolic hydroxyl group.

More specifically, the liquid crystal polyester of the present invention preferably includes structural units derived from the following (A'), (B'), and (C'): (A')-O-Ar ¹ -CO- (B')-CO-Ar ² -CO- (C')-X-Ar ³ -Y- wherein Ar ¹ represents a phenyl group, a naphthyl group, or a biphenyl group, Ar ² represents a phenyl group, a naphthyl group, a biphenyl group, or a group formed by condensation of multiple aromatic groups, Ar ³ represents a phenyl group or a group formed by condensation of multiple aromatic groups, and X and Y represent -O- or -NH-, respectively.

More specifically, the liquid crystal polyester in the present invention preferably includes structural units derived from the following (A'), (B'), and (C''), and the content of the structural units derived from (C'') is 10~35 mol% relative to all the structural units. (A')-O-Ar ¹ -CO- (B')-CO-Ar ² -CO- (C'')-NH-Ar ³ -Y- wherein Ar ¹ represents a phenyl group, a naphthyl group or a biphenyl group, Ar ² represents a phenyl group, a naphthyl group, a biphenyl group or a group formed by condensation of multiple aromatic groups, Ar ³ represents a phenyl group or a group formed by condensation of multiple aromatic groups, and Y represents -O- or -NH-.

It should be noted here that the above-mentioned "structural unit from (A')" corresponds to the above-mentioned "structural unit from (A)". The above-mentioned "structural unit from (B')" corresponds to the above-mentioned "structural unit from (B)". The above-mentioned "structural unit from (C')" and "structural unit from (C'')" correspond to the above-mentioned "structural unit from (C)". The following specifically describes the structural units included in the liquid crystal polyester.

(A) Aromatic Hydroxycarboxylic Acid The structural unit derived from (A) aromatic hydroxycarboxylic acid can be exemplified by the structural units represented by the following formulae (A-1) to (A-5), wherein the aromatic ring may be substituted by a halogen atom, an alkyl group or an aromatic group. Formula (A-1) Formula (A-2) Formula (A-3) Formula (A-4) Formula (A-5)

Among them, the alkyl group as a substituent in the aromatic ring is usually an alkyl group having 1 to 10 carbon atoms, preferably methyl, ethyl, n-propyl, and n-butyl. The aromatic group as a substituent in the aromatic ring is usually an aromatic group having 6 to 20 carbon atoms, preferably phenyl.

Specific examples of the (A) aromatic hydroxycarboxylic acid include p-hydroxybenzoic acid, m-hydroxybenzoic acid, 6-hydroxy-2-naphthoic acid, 3-hydroxy-2-naphthoic acid, 4-hydroxy-1-naphthoic acid, 4-(4-hydroxyphenyl)benzoic acid, and the like.

(B) Aromatic dicarboxylic acid The structural unit derived from (B) aromatic dicarboxylic acid can be listed as the structural unit shown in the following formula (B-1) to formula (B-10), wherein the aromatic ring can be substituted by a halogen atom, an alkyl group or an aromatic group. The specific substituents are the same as the substituents listed for the above-mentioned (A) aromatic hydroxycarboxylic acid, and will not be repeated here. Formula (B-1) Formula (B-2) Formula (B-3) Formula (B-4) Formula (B-5) Formula (B-6) Formula (B-7) Formula (B-8) Formula (B-9) Formula (B-10)

Specific examples of (B) aromatic dicarboxylic acids include terephthalic acid, isophthalic acid, 2,6-naphthalene dicarboxylic acid, 1,5-naphthalene dicarboxylic acid, biphenyl-4,4'-dicarboxylic acid, diphenyl ether-4,4'-dicarboxylic acid, diphenyl sulfide-4,4'-dicarboxylic acid, diphenyl sulfide-4,4'-dicarboxylic acid, and benzophenone-4,4'-dicarboxylic acid.

(C) a compound selected from at least one of aromatic diols, aromatic diamines and aromatic amines having a phenolic hydroxyl group

The structural units of aromatic diols can be listed as the structural units shown in the following formulas (C-1-1) to (C-1-10), wherein the aromatic ring can be substituted by a halogen atom, an alkyl group or an aromatic group. The specific substituents are the same as the substituents listed for the aromatic hydroxycarboxylic acid (A) above, and will not be described in detail here. Formula (C-1-1) Formula (C-1-2) Formula (C-1-3) Formula (C-1-4) Formula (C-1-5) Formula (C-1-6) Formula (C-1-7) Formula (C-1-8) Formula (C-1-9) Formula (C-1-10)

Specific examples of the aromatic diol include hydroquinone, resorcinol, 2,6-naphthalene diol, 1,5-naphthalene diol, biphenyl-4,4'-diol, biphenyl-2,5-diol, 2,2-bis(4-hydroxyphenyl)propane, 2,2-bis(4-hydroxy-3,5-dimethylphenyl)propane, bis(4-hydroxyphenyl)ether, bis-(4-hydroxyphenyl)ketone, bis-(4-hydroxyphenyl)sulfone, and the like.

The structural units of aromatic diamines can be listed as the structural units shown in the following formulas (C-2-1) to (C-2-10), wherein the aromatic ring can be substituted by a halogen atom, an alkyl group or an aromatic group. The specific substituents are the same as the substituents listed for the above-mentioned (A) aromatic hydroxycarboxylic acid, and will not be described in detail here. Formula (C-2-1) Formula (C-2-2) Formula (C-2-3) Formula (C-2-4) Formula (C-2-5) Formula (C-2-6) Formula (C-2-7) Formula (C-2-8) Formula (C-2-9) Formula (C-2-10)

Specific examples of the aromatic diamine include p-phenylenediamine, m-phenylenediamine, biphenyl-4,4'-diamine, bis(4-aminophenyl)methane, bis(4-aminophenyl)ether, bis-(4-aminophenyl)ketone, bis-(4-aminophenyl)sulfonium, and the like.

The structural units of the aromatic amines having phenolic hydroxyl groups derived from the aromatic amines having phenolic hydroxyl groups can be listed as the structural units shown in the following formulas (C-3-1) to (C-3-6), wherein the aromatic rings can be substituted by halogen atoms, alkyl groups or aromatic groups. The specific substituents are the same as the substituents listed for the aromatic hydroxycarboxylic acids (A) above, and will not be described in detail here. Formula (C-3-1) Formula (C-3-2) Formula (C-1-3) Formula (C-3-4) Formula (C-3-5) Formula (C-3-6)

As specific examples of aromatic amines having a phenolic hydroxyl group, aromatic hydroxylamines and aromatic hydroxyamides can be cited. Examples of aromatic hydroxylamines include 3-aminophenol, 4-aminophenol, 4-amino-4'-hydroxybiphenyl, etc. Examples of aromatic hydroxyamides include 3-hydroxyacetaniline, 4-hydroxyacetaniline, etc. If the monomers constituting (C'') include aromatic hydroxylamines and aromatic hydroxyamides, the voltage application life of the resulting insulating wire is better.

Furthermore, as the structural units constituting the above-mentioned (A), (B), and (C), not only the above-mentioned monomers but also ester derivatives or amide derivatives of the above-mentioned monomers may be used.

Examples of the ester derivatives or amide derivatives of carboxylic acids include highly reactive derivatives such as acyl chloride compounds or anhydride compounds generated by subjecting a carboxylic acid group to a polyester formation reaction or a polyamide formation reaction; and derivatives of esters or amides formed by reacting a carboxylic acid group with alcohols, glycols or amines of polyesters or polyamides generated by an ester exchange reaction or an amide exchange reaction.

As an example of an ester derivative of a phenolic hydroxyl group, a phenolic hydroxyl group is reacted with a carboxylic acid group through an ester exchange reaction to form a polyester, thereby forming an ester derivative.

As the amide derivative of the amino group, for example, an amine group is reacted with a carboxylic acid group through an amide exchange reaction to form a polyamide, thereby forming an amide derivative.

[Content of each structural unit of liquid crystal polyester] The lower limit of the content of the structural unit derived from (A) is preferably 10 mol% relative to all structural units. The upper limit of the content of the structural unit derived from (A) is preferably 70 mol%, more preferably 60 mol%, and even more preferably 50 mol% relative to all structural units.

The lower limit of the content of the structural unit derived from (B) is preferably 15 mol %, more preferably 20 mol %, and further preferably 25 mol % relative to the total structural units. The upper limit of the content of the structural unit derived from (B) is preferably 45 mol % relative to the total structural units.

The lower limit of the content of the structural unit derived from (C) is preferably 15 mol %, more preferably 20 mol %, and further preferably 25 mol % relative to the total structural units. The upper limit of the content of the structural unit derived from (C) is preferably 45 mol % relative to the total structural units.

The lower limit of the ratio of the content of the structural unit derived from (B) to the content of the structural unit derived from (C) (B/C) is preferably 0.9, more preferably 1, and further preferably 1.2, and the upper limit is preferably 2, more preferably 1.5, and further preferably 1.3.

In addition, the liquid crystal polyester may contain only one type of structural unit from (A), (B), and (C), or two or more types. In addition, the liquid crystal polyester may also contain other structural units other than (A), (B), and (C). The content of other structural units is preferably 10 mol% or less, and more preferably 5 mol% or less, relative to all structural units.

Among them, when the monomers constituting the structural unit derived from (C'') include aromatic hydroxylamine and aromatic hydroxylamide, the voltage application life of the prepared insulating wire is better.

Based on the total amount of monomers constituting the structural unit derived from (C'') being 100 mol%, the amount of aromatic hydroxylamine used is preferably 30-90 mol%, and the amount of aromatic hydroxylamide used is preferably 10-70 mol%. When the amount of aromatic hydroxylamine and aromatic hydroxylamide used falls within the above range, the voltage application life of the obtained insulating wire is better.

The liquid crystal polyester of the present invention has a weight average molecular weight of 10,000 to 100,000, preferably 13,000 to 95,000, and more preferably 15,000 to 90,000, as measured by gel permeation chromatography (GPC) and converted to polystyrene.

[Method for producing liquid crystal polyester] The method for producing the liquid crystal polyester of the present invention is not particularly limited. For example, the following method can be cited: Acetylation of (A) aromatic hydroxycarboxylic acid and (C) at least one compound selected from aromatic diols, aromatic diamines and aromatic amines having phenolic hydroxyl groups with excess fatty acid anhydride to obtain an acylate. Thereafter, the acylate is polymerized with (A) aromatic hydroxycarboxylic acid and/or (B) aromatic dicarboxylic acid through an ester exchange/amide exchange reaction to obtain the obtained product.

In the acylation reaction, the amount of fatty acid anhydride added is preferably 1.0 to 1.2 equivalents, more preferably 1.05 to 1.1 equivalents, relative to the total amount of phenolic hydroxyl groups and amine groups. If the amount of fatty acid anhydride added is too small, there is a tendency for the reaction device to be blocked due to the sublimation of acylated products or other reactants during polymerization reactions such as transesterification or transamide exchange; if the amount of fatty acid anhydride added is too large, there is a problem that the obtained liquid crystal polyester is easily colored.

The acylation reaction is preferably carried out at 130° C. to 180° C. for 5 minutes to 10 hours, more preferably at 140° C. to 160° C. for 10 minutes to 3 hours.

In the acylation reaction, the fatty acid anhydride is not particularly limited, and examples thereof include acetic anhydride, propionic anhydride, butyric anhydride, isobutyric anhydride, valeric anhydride, pivalic anhydride, 2-ethylhexanoic anhydride, dichloroacetic anhydride, trichloroacetic anhydride, monobromoacetic anhydride, dibromoacetic anhydride, tribromoacetic anhydride, monofluoroacetic anhydride, difluoroacetic anhydride, trifluoroacetic anhydride, glutaric anhydride, maleic anhydride, succinic anhydride, β-bromopropionic anhydride, and the like. The fatty acid anhydride may be used alone or in combination of two or more. From the viewpoint of price and operability, acetic anhydride, propionic anhydride, butyric anhydride, or isobutyric anhydride is preferred, and acetic anhydride is more preferred.

In the transesterification/amide exchange reaction, the acyl group content of the acylated product is preferably 0.8 to 1.2 times the equivalent relative to the carboxyl group content. The reaction temperature of the transesterification/amide exchange reaction is preferably 400°C or less, more preferably 350°C or less. In addition, the heating rate of the reaction is preferably 0.1 to 50°C/min, more preferably 0.3 to 5°C/min. In addition, in order to shift the equilibrium between the reactants and the products, it is preferred to dilute the by-product fatty acid or the unreacted fatty acid anhydride from the reaction system by evaporation or the like during the reaction.

In addition, the acylation reaction and the transesterification/amidation reaction can be carried out in the presence of a catalyst. As the catalyst, substances that are known as catalysts for polyester polymerization can be used, such as metal salts such as magnesium acetate, stannous acetate, tetrabutyl titanium, lead acetate, sodium acetate, potassium acetate, antimony trioxide, and organic compounds such as N,N-dimethylaminopyridine and N-methylimidazole. The catalyst is usually present during the acylation reaction, and it is not necessary to remove the catalyst even after the acylation reaction. If the catalyst is not removed, the next step of treatment can be carried out directly. In addition, the above catalyst can be further added when the next treatment is carried out.

The polymerization reaction of the ester exchange/amide exchange reaction is usually carried out by melt polymerization, but melt polymerization and solid phase polymerization can also be used together. Solid phase polymerization can be carried out by known solid phase polymerization methods after extracting the polymer from the melt polymerization step, solidifying it, and crushing it into powder or flakes. Specifically, it can be listed as a method of heat treatment in a solid phase state at 20°C~350°C for 1 hour to 30 hours in a nitrogen environment. Solid phase polymerization can be carried out under stirring or in a static state without stirring. In addition, as long as an appropriate stirring mechanism is provided, the melt polymerization tank and the solid phase polymerization tank can be the same reaction tank. After solid phase polymerization, the obtained liquid crystal polyester can be granulated by a known method.

Among them, the liquid crystal polyester of the present invention includes at least one method prepared in the following manner, and specific examples of the method include adding monomers in batches during the acylation reaction, changing the reaction temperature during the acylation reaction, or stepwise changing the reaction temperature during the ester exchange/amide exchange reaction.

[Manufacturing method of insulating wire] As a manufacturing method of insulating wire, the following steps can be listed: (1) a coating step of coating a liquid composition including a liquid crystal polyester and an aprotic solvent on the outer periphery of a conductor, and (2) a heating step of heating the conductor coated with the liquid composition. Each step is described in detail below.

(1) Coating step In the coating step, a liquid composition including the liquid crystal polyester of the present invention and an aprotic solvent is coated on the outer periphery of the conductor directly or through another layer. Here, the conductor may have another base coating layer formed on the surface by a known method before the coating step.

As aprotic solvents, preferably: 1-chlorobutane, chlorobenzene, 1,1-dichloroethane, 1,2-dichloroethane, chloroform, 1,1,2,2-tetrachloroethane and other halogen solvents; ether solvents such as ether, tetrahydrofuran, 1,4-dioxane and other ketone solvents; ester solvents such as ethyl acetate and other ester solvents; lactone solvents such as γ-butyrolactone; ethyl carbonate, propyl carbonate, etc. Carbonate solvents; amine solvents such as triethylamine and pyridine; nitrile solvents such as acetonitrile and succinonitrile; amide solvents such as N,N'-dimethylformamide, N,N'-dimethylacetamide, tetramethylurea, N-methyl-2-pyrrolidone; nitro solvents such as nitromethane and nitrobenzene; sulfide solvents such as dimethyl sulfoxide and cyclobutane sulfone; and phosphoric acid solvents such as hexamethylphosphamide and tri-n-butyl phosphate.

These solvents can be used alone or in combination of two or more. From the perspective of environmental impact, it is preferred to use a solvent that does not contain halogen atoms, and from the perspective of solubility, it is preferred to use a solvent with a dipole moment of 3 or more and 5 or less. Specifically, it is preferred to use amide solvents such as N,N'-dimethylformamide, N,N'-dimethylacetamide, tetramethylurea, and N-methyl-2-pyrrolidone; and lactone solvents such as γ-butyrolactone. It is more preferred to use solvents such as N,N'-dimethylformamide, N,N'-dimethylacetamide, and N-methyl-2-pyrrolidone.

The concentration of the liquid crystal polyester in the liquid composition can be appropriately selected according to the application, preferably 0.5 mass% to 50 mass%, and more preferably 5 mass% to 30 mass%. When the concentration of the liquid crystal polyester is less than 0.5 mass%, it may be difficult to apply uniformly due to the low viscosity of the solution, and more heat needs to be supplied to dry the solvent, resulting in increased costs; and when the concentration of the liquid crystal polyester exceeds 50 mass%, it may be difficult to apply uniformly due to the high viscosity of the solution, and the liquid composition itself is also easy to colloidal, which is not good.

In addition, a liquid composition obtained by dissolving a liquid crystal polyester in a solvent may be used as a coating liquid as it is, but it is preferably passed through a filter or the like to remove minute foreign matter contained in the solution.

In addition, the liquid composition may include other resins, other solvents, other fillers or additives in addition to the above-mentioned liquid crystal polyester and aprotic solvent.

As a method of applying the liquid composition to the outer periphery of the conductor, for example, a method using a coating device having a liquid composition tank for storing the liquid composition and a coating mold can be cited. According to the coating device, when the conductor is inserted into the liquid composition tank, the liquid composition adheres to the outer periphery of the conductor and then passes through the coating mold, so that the liquid composition has a substantially uniform thickness.

(2) Heating step In the heating step, the liquid composition coated on the linear body of the conductor or the base coating layer formed by the coating step is heated to form an insulating layer. By the above heating, the solvent in the liquid composition evaporates, forming an insulating layer with excellent electrical properties, mechanical properties, and thermal properties.

The device used in the heating step is not particularly limited, and an example thereof may be a cylindrical baking furnace that is relatively long in the direction of travel of the conductor. The heating method is not particularly limited, and an example thereof may be a conventionally known method such as hot air heating, infrared heating, and high frequency heating.

As the heating condition of the heating step, it is preferred to heat at 300°C or more for 10 seconds or more and less than 3 hours, more preferably to heat at 300°C or more for 10 seconds or more and less than 15 minutes, and even more preferably to heat at 300°C or more for 10 seconds or more and less than 30 seconds. By heating at a high temperature for a short time, the thermal conductivity in the thickness direction of the insulating layer can be further improved. If the heating time is less than 10 seconds, the evaporation of the solvent and the formation of the insulating layer are insufficient, and the appearance, electrical properties, mechanical properties, and thermal properties of the insulating wire may be deteriorated. In principle, even if the heating time is shortened by increasing the heating temperature to a higher temperature, the amount of heat applied to the insulating layer can be made equal, but excessively rapid heating will cause blistering of the insulating layer and deterioration of mechanical properties. There is no particular upper limit to the heating temperature, but due to considerations such as deterioration of the properties of the insulating wire, productivity, and cost, the upper limit is, for example, 400°C. On the other hand, if the heating time exceeds 3 hours, not only will the thermal conductivity of the insulating layer in the thickness direction be reduced, but the properties of the insulating wire will also be reduced, which is not good in terms of productivity and cost.

In addition, the insulating wire formed by the heating step can be further heated as needed. The electrical, mechanical and thermal properties of the insulating wire can be improved by further heating. There is no particular limitation on the heating device, and for example, batch heating can be performed after the insulating wire is manufactured using the above-mentioned heating device. There is no particular limitation on the heating method, and it can be performed by a conventionally known method such as hot air heating, infrared heating, and high-frequency heating.

The coating step and the heating step are usually repeated several times. By repeating the coating step and the heating step, the thickness of the insulating layer can be increased. At this time, the aperture of the coating mold should be appropriately adjusted according to the number of repetitions.

[Coil and electronic device] The insulated wire of the present invention can be used as a coil in various electronic devices and other fields that require electrical characteristics (voltage resistance). For example, the insulated wire of the present invention can be used in motors, transformers, etc. to form high-performance electronic devices. It is particularly suitable for use as a winding of a drive motor of a hybrid vehicle (HV) or an electric vehicle (EV). As described above, according to the present invention, an electronic device such as an HV and EV drive motor using the insulated wire of the present invention as a coil can be provided.

The coil of the present invention may have a shape suitable for various electronic devices, for example, a coil shape formed by winding the insulating wire of the present invention, or a shape formed by bending the insulating wire of the present invention and then electrically connecting specific parts.

There is no particular limitation on the coil formed by winding the insulating wire of the present invention, and an example thereof is a coil formed by winding a long insulating wire into a spiral shape. In such a coil, there is no particular limitation on the number of windings of the insulating wire. Usually, an iron core or the like is used when winding the insulating wire. [Example] [Synthesis example of liquid crystal polyester]

Synthesis Example 1 After introducing nitrogen into a reaction vessel equipped with a nitrogen inlet, a stirrer, a heater, a condenser and a thermometer, 138.1 g (1.0 mol) of p-hydroxybenzoic acid (hereinafter referred to as a1), 747.6 g (4.5 mol) of terephthalic acid (hereinafter referred to as b1), 453.5 g (3.0 mol) of 3-hydroxyacetaniline (hereinafter referred to as c2-1) and 816.7 g (8.0 mol) of acetic anhydride were added. Then, the above components were slowly stirred under a nitrogen flow to raise the temperature of the solution to 150°C, and at this temperature, a total of 163.7 g (1.5 mol) of 3-aminophenol (hereinafter referred to as c1-1) was added three times (each time at an interval of 1 hour), and then the reaction was maintained at the above temperature for 1 hour. Then, the by-product acetic acid and unreacted acetic anhydride are distilled off from the reaction system, and the solution is heated to 300°C at a heating rate of 1.0°C/min, and then decompressed at 300°C. After reacting at 300°C for 1 hour, the product is taken out of the reaction vessel and cooled to room temperature. The cooled product is crushed with a pulverizer to obtain a powdered liquid crystal polyester (A-1) of Synthesis Example 1. 8 g of the powdered liquid crystal polyester (A-1) is added to 92 g of N-methyl-2-pyrrolidone and heated to 140°C to completely dissolve it to obtain a brown transparent solution.

Synthesis Example 2 After introducing nitrogen into a reaction vessel equipped with a nitrogen inlet, a stirrer, a heater, a condenser and a thermometer, 276.2 g (2.0 mol) of m-hydroxybenzoic acid (hereinafter referred to as a2), 664.6 g (4.0 mol) of isophthalic acid (hereinafter referred to as b2), 302.3 g (2.0 mol) of 4-hydroxyacetoaniline (hereinafter referred to as c2-2) and 918.8 g (9.0 mol) of acetic anhydride were added. Then, the above components were slowly stirred under a nitrogen flow to raise the temperature of the solution to 150°C, and at this temperature, a total of 218.3 g (2.0 mol) of 4-aminophenol (hereinafter referred to as c1-2) was added three times (each time at an interval of 1 hour), and then the reaction was maintained at the above temperature for 1 hour. Then, the by-product acetic acid and unreacted acetic anhydride are distilled off from the reaction system, and the solution is heated to 300°C at a heating rate of 1.0°C/min, and then decompressed at 300°C. After reacting at 300°C for 1 hour, the product is taken out of the reaction vessel and cooled to room temperature. The cooled product is crushed with a pulverizer to obtain a powdered liquid crystal polyester (A-2) of Synthesis Example 2. 8 g of the powdered liquid crystal polyester (A-2) is added to 92 g of N-methyl-2-pyrrolidone and heated to 140°C to completely dissolve it to obtain a brown transparent solution.

Synthesis Example 3 After introducing nitrogen into a reaction vessel equipped with a nitrogen inlet, a stirrer, a heater, a condenser and a thermometer, 564.5 g (3.0 mol) of 6-hydroxy-2-naphthoic acid (hereinafter referred to as a3), 756.7 g (3.5 mol) of 2,6-naphthalenedicarboxylic acid (hereinafter referred to as b3) and 1123.0 g (11.0 mol) of acetic anhydride were added. Then, the above components were slowly stirred under a nitrogen flow to raise the temperature of the solution to 150°C, and at this temperature, a total of 648.3 g (3.5 mol) of 4-amino-4'-hydroxybiphenyl (hereinafter referred to as c1-3) was added three times (each time at an interval of 1 hour), and then the reaction was maintained at the above temperature for 1 hour. Then, the by-product acetic acid and unreacted acetic anhydride are distilled off from the reaction system, and the solution is heated to 300°C at a heating rate of 1.0°C/min, and then decompressed at 300°C. After reacting at 300°C for 1 hour, the product is taken out of the reaction vessel and cooled to room temperature. The cooled product is crushed with a pulverizer to obtain a powdered liquid crystal polyester (A-3) of Synthesis Example 3. 8 g of the powdered liquid crystal polyester (A-3) is added to 92 g of N-methyl-2-pyrrolidone and heated to 140°C to completely dissolve it to obtain a brown transparent solution.

Synthesis Example 4 After introducing nitrogen into a reaction vessel equipped with a nitrogen inlet, a stirrer, a heater, a condenser and a thermometer, 552.5 g (4.0 mol) of a1, 774.7 g (3.0 mol) of diphenyl ether-4,4'-dicarboxylic acid (hereinafter referred to as b4) and 816.7 g (8.0 mol) of acetic anhydride were added. Then, the above components were slowly stirred under a nitrogen flow to raise the temperature of the solution to 150°C, and at this temperature, a total of 453.5 g (3.0 mol) of c2-1 was added three times (each time with an interval of 1 hour), and then the reaction was maintained at the above temperature for 1 hour. Then, the by-product acetic acid and unreacted acetic anhydride are distilled off from the reaction system, and the solution is heated to 300°C at a heating rate of 1.0°C/min, and then decompressed at 300°C. After reacting at 300°C for 1 hour, the product is taken out of the reaction vessel and cooled to room temperature. The cooled product is crushed with a pulverizer to obtain a powdered liquid crystal polyester (A-4) of Synthesis Example 4. 8 g of the powdered liquid crystal polyester (A-4) is added to 92 g of N-methyl-2-pyrrolidone and heated to 140°C to completely dissolve it to obtain a brown transparent solution.

Synthesis Example 5 After introducing nitrogen into a reaction vessel equipped with a nitrogen inlet, a stirrer, a heater, a condenser and a thermometer, 690.6 g (5.0 mol) of a2, 675.6 g (2.5 mol) of benzophenone-4,4'-dicarboxylic acid (hereinafter referred to as b5), 277.8 g (1.5 mol) of c1-3, 151.2 g (1.0 mol) of c2-2 and 1020.9 g (10.0 mol) of acetic anhydride were added. Then, the above components were slowly stirred under a nitrogen flow to raise the temperature of the solution to 140°C, reacted at this temperature for 1 hour, then raised to 150°C and reacted for 1 hour, and finally raised to 160°C and reacted for 1 hour. Then, the by-product acetic acid and unreacted acetic anhydride are distilled off from the reaction system, and the solution is heated to 300°C at a heating rate of 1.0°C/min, and then decompressed at 300°C. After reacting at 300°C for 1 hour, the product is taken out of the reaction vessel and cooled to room temperature. The cooled product is crushed with a pulverizer to obtain a powdered liquid crystal polyester (A-5) of Synthesis Example 5. 8 g of the powdered liquid crystal polyester (A-5) is added to 92 g of N-methyl-2-pyrrolidone and heated to 140°C to completely dissolve it to obtain a brown transparent solution.

Synthesis Examples 6 to 8 The synthesis methods of the liquid crystal polyesters in Synthesis Examples 6 to 8 are the same as those in Synthesis Example 5. The difference is that the amount of each monomer and acetic anhydride used is changed. The formulas are shown in Tables 1 and 2.

Synthesis Example 9 After introducing nitrogen into a reaction vessel equipped with a nitrogen inlet, a stirrer, a heater, a condenser and a thermometer, 376.36 g (2.0 mol) of a3, 1032.9 g (4.0 mol) of b4, 222.3 g (1.2 mol) of c1-3, 423.2 g (2.8 mol) of c2-1 and 816.7 g (8.0 mol) of acetic anhydride were added. Then, the above components were slowly stirred under a nitrogen flow to raise the temperature of the solution to 140°C, and reacted at this temperature for 3 hours. Then, the by-product acetic acid and unreacted acetic anhydride were distilled off from the reaction system, and the solution was heated to 280°C at a heating rate of 1.0°C/min, and then decompressed at 280°C. After reacting at 280°C for 20 minutes, the temperature was then raised to 300°C and the reaction was continued for 20 minutes, and finally the temperature was raised to 320°C and the reaction was continued for 20 minutes. Afterwards, the product was taken out of the reaction vessel and cooled to room temperature. The cooled product was crushed with a pulverizer to obtain a powdered liquid crystal polyester (A-9) of Synthesis Example 9. 8 g of the powdered liquid crystal polyester (A-9) was added to 92 g of N-methyl-2-pyrrolidone and heated to 140°C to completely dissolve it, so as to obtain a brown transparent solution.

Synthesis Examples 10 to 12 The synthesis methods of the liquid crystal polyesters in Synthesis Examples 10 to 12 are the same as those in Synthesis Example 9. The difference is that the amount of each monomer and acetic anhydride used is changed. The formulas are shown in Tables 1 and 2.

Synthesis Example 13 After introducing nitrogen into a reaction vessel equipped with a nitrogen inlet, a stirrer, a heater, a condenser and a thermometer, 69.1 g (0.5 mol) of a2, 1035.0 g (5.5 mol) of a3, 432.4 g (2.0 mol) of b3 and 1123 g (11.0 mol) of acetic anhydride were added. Then, the above components were slowly stirred under a nitrogen flow to raise the temperature of the solution to 150°C, and at this temperature, a total of 218.3 g (2.0 mol) of c1-1 was added three times (each time with an interval of 1 hour), and then the reaction was maintained at the above temperature for 1 hour. Then, the by-product acetic acid and unreacted acetic anhydride are distilled off from the reaction system, and the solution is heated to 310°C at a heating rate of 1.0°C/min, and then decompressed at 310°C. After heating at 310°C for 30 minutes, the product is taken out of the reaction vessel and cooled to room temperature. The cooled product is crushed with a pulverizer to obtain a powdered prepolymer. The flow temperature of the above prepolymer is 181°C. Thereafter, the above prepolymer is heated from room temperature to 250°C within 6 hours under a nitrogen flow, and heated at 250°C for 10 hours to perform solid phase polymerization. Then, the product was cooled to room temperature and crushed, and then the product was heated from room temperature to 255°C within 6 hours under nitrogen flow, and then solid phase polymerization was performed again for 3 hours. After solid phase polymerization, the product was taken out from the reaction vessel and cooled to room temperature. After the cooled product was crushed with a crusher, a powdered liquid crystal polyester (A-13) of Synthesis Example 13 was obtained, and its flow temperature was 310°C. 8 g of the powdered liquid crystal polyester (A-13) was added to 92 g of N-methyl-2-pyrrolidone and heated to 140°C to completely dissolve it to obtain a brown transparent solution.

Synthesis Example 14 In a reaction vessel equipped with a nitrogen inlet, a stirrer, a heater, a condenser and a thermometer, after introducing nitrogen, 1317.3 g (7.0 mol) of a3, 387.3 g (1.5 mol) of b4, 163.7 g (1.5 mol) of c1-2 and 1123 g (11.0 mol) of acetic anhydride were added. Then, the above components were slowly stirred under a nitrogen flow to raise the temperature of the solution to 140°C, and reacted at this temperature for 1 hour, then raised to 150°C and reacted for 1 hour, and finally raised to 160°C and reacted for 1 hour. Then, the by-product acetic acid and unreacted acetic anhydride are distilled off from the reaction system, and the solution is heated to 290°C at a heating rate of 1.0°C/min, and then decompressed at 290°C. After heating at 300°C for 30 minutes, the product is taken out of the reaction vessel and cooled to room temperature. The cooled product is crushed with a pulverizer to obtain a powdered prepolymer. The flow temperature of the above prepolymer is 181°C. Thereafter, the above prepolymer is heated from room temperature to 250°C within 6 hours under a nitrogen flow, and heated at 250°C for 10 hours to perform solid phase polymerization. Then, the product was cooled to room temperature and crushed, and then the product was heated from room temperature to 255°C within 6 hours under a nitrogen flow, and then solid phase polymerization was performed again for 3 hours. After solid phase polymerization, the product was taken out of the reaction vessel and cooled to room temperature. After the cooled product was crushed with a crusher, a powdered liquid crystal polyester (A-14) of Synthesis Example 14 was obtained, and its flow temperature was 310°C. 8 g of the powdered liquid crystal polyester (A-14) was added to 92 g of N-methyl-2-pyrrolidone and heated to 140°C to completely dissolve it to obtain a brown transparent solution.

Comparative Synthesis Example 1 After introducing nitrogen into a reaction vessel equipped with a nitrogen inlet, a stirrer, a heater, a condenser and a thermometer, 138.1 g (1.0 mol) of a1, 747.6 g (4.5 mol) of b1, 163.7 g (1.5 mol) of c1-1, 453.5 g (3.0 mol) of c2-1 and 816.7 g (8.0 mol) of acetic anhydride were added. Then, the above ingredients were slowly stirred under a nitrogen flow to raise the temperature of the solution to 150°C, and reacted at this temperature for 3 hours. Then, the by-product acetic acid and unreacted acetic anhydride are distilled off from the reaction system, and the solution is heated to 300°C at a heating rate of 1.0°C/min, and then decompressed at 300°C. After reacting at 300°C for 1 hour, the product is taken out of the reaction vessel and cooled to room temperature. The cooled product is crushed with a pulverizer to obtain a powdered liquid crystal polyester (A'-1) of Comparative Synthesis Example 1. 8 g of the powdered liquid crystal polyester (A'-1) is added to 92 g of N-methyl-2-pyrrolidone and heated to 140°C to completely dissolve it to obtain a brown transparent solution.

Comparative Synthesis Example 2 to Comparative Synthesis Example 3 The synthesis methods of the liquid crystal polyesters of Comparative Synthesis Example 2 to Comparative Synthesis Example 3 are the same as those of Comparative Synthesis Example 1. The difference lies in that the amount of each monomer and acetic anhydride used is changed, and the formula is shown in Table 1 and Table 2.

Comparative Synthesis Example 4 After introducing nitrogen into a reaction vessel equipped with a nitrogen inlet, a stirrer, a heater, a calcium chloride filling tube, a condenser and a thermometer, 835.88 g of N-methyl-2-pyrrolidone was added. Then, 78.55 g of bis(4-aminophenyl)ether was added while slowly stirring under a nitrogen flow to completely dissolve it. After that, 85.57 g of pyromellitic dianhydride was added dropwise over 5 hours while slowly stirring. Then, the reaction was carried out at 80°C for 12 hours. Finally, the solution was cooled to room temperature to obtain the polyimide precursor (A'-4) of Comparative Synthesis Example 4.

In addition, the compounds corresponding to the abbreviations in Table 1 and Table 2 are shown below. Abbreviation Chinese name a1 4-Hydroxybenzoic acid a2 m-Hydroxybenzoic acid a3 6-Hydroxy-2-naphthoic acid b1 Terephthalic acid b2 Isophthalic acid b3 2,6-Naphthalene dicarboxylic acid b4 Diphenyl ether-4,4'-dicarboxylic acid b5 Benzophenone-4,4'-dicarboxylic acid c1-1 3-Aminophenol c1-2 4-Aminophenol c1-3 4-Amino-4'-hydroxybiphenyl c2-1 3-Hydroxyacetaniline c2-2 4-Hydroxyacetaniline c3-1 p-phenylenediamine c3-2 Biphenyl-4,4'-diamine

[Table 1] Ingredients (unit: mole%) Synthesis example A-1 A-2 A-3 A-4 A-5 A-6 A-7 A-8 Structural unit (A) Aromatic hydroxycarboxylic acid a1 10 - - 40 - 10 - - a2 - 20 - - 50 - - 10 a3 - - 30 - - 50 70 - Structural unit (B) Aromatic dicarboxylic acids b1 45 - - - - 20 - - b2 - 40 - - - - 15 - b3 - - 35 - - - - 45 b4 - - - 30 - - - - b5 - - - - 25 - - - Structural unit (C) Aromatic Hydroxylamines c1-1 15 - - - - 18 - - c1-2 - 20 - - - - - 40 c1-3 - - 35 - 15 - - - Aromatic Hydroxylamide c2-1 30 - - 30 - 2 - - c2-2 - 20 - - 10 - 10 - Aromatic diamines c3-1 - - - - - - - 5 c3-2 - - - - - - 5 - Acetic anhydride (unit: mole) 80 90 110 80 100 100 90 80

[Table 2] Ingredients (unit: mole%) Synthesis example Comparative synthesis example A-9 A-10 A-11 A-12 A-13 A-14 A'-1 A'-2 A'-3 Structural unit (A) Aromatic hydroxycarboxylic acid a1 - 30 - 20 - - 10 - - a2 - - 40 - 5 - - 50 - a3 20 - - 30 55 70 - - 20 Structural unit (B) Aromatic dicarboxylic acids b1 - - 30 - - - 45 - - b2 - - - 25 - - - - - b3 - - - - 20 - - - - b4 40 - - - - 15 - - 40 b5 - 35 - - - - - 25 - Structural unit (C) Aromatic Hydroxylamines c1-1 - 15 - - 20 - 15 - - c1-2 - - - - - 15 - - - c1-3 12 - - - - - - 15 12 Aromatic Hydroxylamide c2-1 28 - 30 - - - 30 - 28 c2-2 - 20 - 25 - - - 10 - Aromatic diamines c3-1 - - - - - - - - - c3-2 - - - - - - - - - Acetic anhydride (unit: mole) 80 90 80 80 110 110 110 110 80 [Example of Insulated Wire]

Example 1 After stirring and defoaming the solution of the liquid crystal polyester (A-1) of Synthesis Example 1, a liquid composition is obtained. Then, the liquid composition is directly applied to the outer periphery of a copper conductor with a diameter of 1.0 mm by a mold, and the copper conductor is heated at a certain linear speed through a cylindrical baking furnace to form an insulating layer on the outer periphery of the copper conductor. In the baking furnace, the copper conductor is heated for 15 seconds in an environment of more than 300°C. The above steps are repeated to form an insulating layer with a thickness of 30 μm on the outer periphery of the copper conductor.

Examples 2 to 14 and Comparative Examples 1 to 4 Examples 2 to 12 and Comparative Examples 1 to 4 use the same manufacturing method as the insulating wire of Example 1, but the difference is that the type of liquid crystal polyester and the film thickness of the insulating layer are changed. The evaluation results are shown in Table 3.

[Table 3] Insulation layer composition Evaluation items Resin type Film thickness(μm) Film thickness uniformity D (%) Voltage application life Embodiment 1 A-1 30 1.1 ◎ 2 A-2 20 1.5 ◎ 3 A-3 30 3.2 ○ 4 A-4 25 4.5 ○ 5 A-5 20 1.1 ◎ 6 A-6 50 0.7 ◎ 7 A-7 30 4.9 ○ 8 A-8 30 3.3 ○ 9 A-9 50 1 ◎ 10 A-10 10 0.9 ◎ 11 A-11 30 3.2 ○ 12 A-12 30 2.9 ○ 13 A-13 30 4.5 ○ 14 A-14 30 5 ○ Comparative example 1 A'-1 30 10.5 X 2 A'-2 20 9.8 X 3 A'-3 50 11.7 X 4 A'-4 30 16.5 X [Evaluation method]

Film thickness uniformity First, use a laser diameter measuring machine to measure the outer diameter of the insulating wire produced in each embodiment and comparative example. Subtract the diameter of the copper conductor itself from the measured outer diameter value to obtain the thickness of the insulating layer itself. Then, calculate the film thickness uniformity D of the insulating layer using the following formula (A): D=(D _max -D _min )×100%/(D _avg ×2) Formula (A) In formula (A), D _max represents the maximum thickness of the insulating layer, D _min represents the minimum thickness of the insulating layer, and D _avg represents the average thickness of the insulating layer.

Partial discharge initiation voltage Two insulated wires prepared in each embodiment and comparative example were twisted together to form a spiral test piece. A 50Hz sinusoidal AC voltage was applied between the conductors, and the voltage (effective value) when the discharge amount was 10pC was measured while continuously increasing the voltage. The voltage at this time was set as the partial discharge initiation voltage. The measurement temperature was set to room temperature (20°C). The partial discharge initiation voltage was measured using a partial discharge tester (KPD2050 manufactured by Kikuchi Electric Chemical Industry Co., Ltd.).

Voltage application life Two insulated wires prepared in each embodiment and comparative example were twisted together to form a spiral test piece. Then, a voltage of 110% of the above-mentioned partial discharge initiation voltage was applied between each conductor. Specifically, if the partial discharge initiation voltage is 600 V, the applied voltage is 660 V. The time required for the insulation to be destroyed by applying the above-mentioned voltage value in an environment of 20°C was measured. The voltage application life evaluation standards are as follows: ◎: voltage application time ≥ 5000 minutes ○: 5000 minutes > voltage application time ≥ 4000 minutes △: 4000 minutes > voltage application time ≥ 3000 minutes ╳: voltage application time < 3000 minutes

[Evaluation results] As shown in Table 3, the voltage application life evaluation of the insulating wires of Comparative Examples 1 to 4 having an insulating layer with a film thickness uniformity D exceeding 5% was poor compared to the insulating wires (Examples 1 to 14) having an insulating layer with a film thickness uniformity D of 5% or less.

In addition, when the monomers constituting the structural units derived from (C'') in the insulating layer include aromatic hydroxylamine and aromatic hydroxylamide (Examples 1, 2, 5, 6, 9, 10), the voltage application life of the manufactured insulating wire can be further increased.

In summary, the insulated wire of the present invention has an insulating layer with a film thickness uniformity D of 5% or less, and therefore, the insulated wire has a long voltage application life and excellent flexibility.

In addition, when the monomers constituting the structural unit derived from (C'') in the insulating layer include aromatic hydroxylamine and aromatic hydroxylamide, the voltage application life of the manufactured insulating wire can be further increased.

Although the present invention has been disclosed as above by the embodiments, they are not intended to limit the present invention. Any person with ordinary knowledge in the relevant technical field can make some changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention shall be defined by the scope of the attached patent application.

1: Insulation wire 11: Conductor 12: Insulation layer 13: Chamfer

FIG. 1 is a cross-sectional view of an insulated wire according to an embodiment of the present invention.

1: Insulated wire

11: Conductor

12: Insulation layer

13: Chamfer

Claims (10)

An insulating wire comprises: a conductor; and an insulating layer laminated on the outer peripheral side of the conductor, the insulating layer comprises liquid crystal polyester, the thickness of the insulating layer is greater than or equal to 2 μm and less than or equal to 50 μm, and the film thickness uniformity D of the insulating layer is less than or equal to 5% calculated by the following formula (A): D=(D _max -D _min )×100%/(D _avg ×2) Formula (A) In formula (A), D _max represents the maximum thickness of the insulating layer, D _min represents the minimum thickness of the insulating layer, and D _avg represents the average thickness of the insulating layer, and the liquid crystal polyester comprises structural units from the following (A), (B), and (C), (A) Aromatic hydroxycarboxylic acid (B) Aromatic dicarboxylic acid (C) At least one compound selected from aromatic diols, aromatic diamines, and aromatic amines having a phenolic hydroxyl group. An insulating wire as described in claim 1, wherein the liquid crystal polyester includes structural units from the following (A'), (B'), and (C'), (A')-O-Ar ¹ -CO- (B')-CO-Ar ² -CO- (C')-X-Ar ³ -Y- wherein Ar ¹ represents a phenyl group, a naphthyl group, or a biphenyl group, Ar ² represents a phenyl group, a naphthyl group, a biphenyl group, or a group formed by condensation of multiple aromatic groups, Ar ³ represents a phenyl group or a group formed by condensation of multiple aromatic groups, and X and Y represent -O- or -NH-, respectively. An insulating wire as described in claim 2, wherein the liquid crystal polyester includes structural units from the following (A'), (B'), and (C''), (A')-O-Ar ¹ -CO- (B')-CO-Ar ² -CO- (C'')-NH-Ar ³ -Y- wherein Ar ¹ represents a phenyl group, a naphthyl group, or a biphenyl group, Ar ² represents a phenyl group, a naphthyl group, a biphenyl group, or a group formed by condensation of multiple aromatic groups, Ar ³ represents a phenyl group or a group formed by condensation of multiple aromatic groups, and Y represents -O- or -NH-. The insulated wire as described in claim 3, wherein the monomers constituting the (C'') include aromatic hydroxylamine and aromatic hydroxylamide. The insulated wire as described in claim 4, wherein based on the total amount of monomers constituting the (C'') being 100 mol%, the amount of the aromatic hydroxylamine used is 30-90 mol%, and the amount of the aromatic hydroxylamide used is 10-70 mol%. An insulated wire as described in claim 1, wherein the film thickness uniformity D of the insulating layer is less than 3%. An insulated wire as described in claim 1, wherein the film thickness uniformity D of the insulating layer is less than 1%. A method for manufacturing an insulated wire, manufacturing the insulated wire as described in any one of claims 1 to 7, the method for manufacturing the insulated wire comprising: a coating step, coating a liquid composition on the outer periphery of the conductor, the liquid composition comprising a liquid crystal polyester and an aprotic solvent; and a heating step, heating the conductor coated with the liquid composition. A coil comprising the insulated wire as described in any one of claims 1 to 7. An electronic machine comprises the coil as described in claim 9.

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