KR20000052972A - Dielectric, radiation curable coating compositions and metal conductors coated with such coating - Google Patents

Abstract

PURPOSE: Dielectric radiation-curable coating compositions and metal conductors coated with UV-curable coating compositions which have required properties as insulating materials are provided. CONSTITUTION: Provided is a metal conductor having a cured coating of about 10 to about 500 micrometer thickness which coating has a dielectric dissipation factor(60Hz, 24°C ) of lower than about 0.05 and is a radiation-cured coating formulated from components comprising an acrylate functional urethane oligomer having a hydrocarbon backbone and one or more mono- or polyfunctional diluents and a photoinitiator.

Description

Dielectric-curable coating composition and metal conductor coated with the coating material {DIELECTRIC, RADIATION CURABLE COATING COMPOSITIONS AND METAL CONDUCTORS COATED WITH SUCH COATING}

Metal conductors are generally coated with a dielectric coating to insulate the conductors. The coatings require good insulation under extreme conditions such as transformer coils in various environments and / or distribution transformers. According to US-A-4481258, conventionally, paper was used as the insulating material. Although US-A-4481258 proposed coating as an insulating material, paper is still used in the manufacture of transformer coils. Coatings set forth in US-A-4481258 are certain UV-curing materials including acrylate-ester adducts, acrylate urethane adducts and acrylate functional diluents. The coating requires UV curing and post-cure for 4-17 hours at 130 ° C. The method of manufacturing transformer coils from such coatings is of particular interest because they require post-curing.

Insulating coatings for high power transformer coils generally exhibit several properties.

The metal must be flexible to withstand the bending of the conductor coated with the coating when the coating is wound around the coil so that it can be bent into the required shape after being coated.

As described in US-A-4481258, the coating must be able to withstand oil soak for 28 days at 150 ° C.

-The coating shall maintain adhesion even at the high temperatures encountered under load of the transformer.

-The coating should have a dielectric constant of less than 5% at 60 Hz (24 ° C).

-The coating shall have a dielectric dissipation factor of less than 0.05 at 60 Hz, 24 ° C and less than 0.2 at 60 Hz, 150 ° C before and after exposure to hot oil.

It is an object of the present invention to provide a dielectric radiation curable coating composition and a metal conductor coated with a UV-curable coating composition having the properties required as an insulating material.

Summary of the Invention

The present invention has a dielectric dissipation factor of less than about 0.05 (60 Hz, 24 ° C.), a) an acrylate functional urethane oligomer having a hydrocarbon main chain, b) one or more single- or multivalent diluents, and optionally c) one Or a radiation cured coating material blended from components with more photosensitive radical generating compounds, and having a coating material cured to a thickness of about 10-500 μm.

The present invention also provides a radiation curable coating composition comprising a) an acrylate functional urethane oligomer having a hydrocarbon main chain, b) one or more mono- or multivalent diluents and optionally c) one or more photosensitive radical generating compounds. When the coating is cured with radiation, it has a dielectric dissipation factor of less than about 0.05 at 60 Hz, 24 ° C., has a dissipation factor of less than about 0.2 at 60 Hz, 150 ° C., and a thin coating of 25 μm at 25 ° C. Is elongated by at least about 50%.

The insulating coating layer on the metal conductor has excellent insulating properties at low and high temperatures. The insulating coating layer has a low dielectric constant and good dielectric decomposition value of, for example, less than 5 (at 60 Hz, 24 ° C.). The coating is also flexible so that the metal conductors can be bent.

Preferably the metal conductor is iron, copper, aluminum or silver conductor. Especially aluminum, copper or silver is preferable. The metal conductor may be in the form of a conductor or strip. Coated metal conductors can be used in capacitors, transformers, electric motors, and the like. Coated metal conductors can be used even in hot oil environments due to the excellent properties of the coating. Thus, the present invention is most suitable for coating aluminum or copper strips or conductors used to form distribution transformer coils. The cross section of the strip is generally in the range of about 0.1-1.7 mm thick and 7-60 cm wide. The strip is wound into a coil and then combined with a core to form a transformer.

Generally, the metal leads or strips are covered with a straight continuous web, which may be wound for storage or direct use. Therefore, when curing the coating, the surface should be well cured to prevent blocking when the metal conductor is stored. In addition, the coating material of the present invention should be flexible so as not to damage the coating material by winding it for bending and / or storing coils or leads in the manufacture of equipment such as transformers. In addition, the coating is about 25 μm thick and elongates at least about 50%. In particular, the coating has at least one Tg of less than 20 ° C. (measured at the highest point of the tan δ curve by DSM analysis at 1 Hz).

Since coated metal conductors can be used in hot oil environments, it is most preferred that the coating material has a dissipation factor of less than about 0.2 at 60 Hz, 150 ° C. In addition, the coating material preferably has a dissipation factor of less than about 0.05 before and after a high temperature oil aging test at 60 Hz and 24 ° C.

The coating shows insulation even in the form of very thin films. The coating material preferably has a thickness of about 10-500 μm, more preferably between about 10-100 μm.

The first component of the radiation cured coating is an acrylate functional urethane oligomer (a) having a hydrocarbon main chain. The main chain means an oligomer or a polymer having an acrylate urethane group attached thereto. The acrylic rake urethane oligomer is preferably used in an amount of about 20-80 wt.% Based on the total coating composition. More preferably about 30-65 wt.%.

Preferably, the oligomers (a) used in the present invention are (i) hydrocarbon compounds having a group reacting with isocyanates; (ii) polyisocyanates; And (iii) reaction products of hydroxy functional endcapping monomers.

Hydrocarbon compounds (i) having groups which react with isocyanates comprise a plurality of reactive end groups and are provided by linear or branched hydrocarbons which supply a hydrocarbon main chain to the oligomer. The isocyanate reactor can be thiol, amine or hydroxy. In particular, a hydroxyl group is preferable. Because of the amine groups and thiol groups, urethane oligomers may comprise urea groups or thio-urea groups. Preferably, the hydrocarbon moiety has a molecular weight of about 400 to about 4000. In this case, the molecular weight is measured by gel permeation chromatography (GPC), measured on the basis of polystyrene molecular weight, using methylene chloride solvent. The term "hydrocarbon" means a non-aromatic compound comprising a plurality of methylene groups (-CH _2- ), which may include internal unsaturation and / or pendant unsaturation. Fully saturated (ie, hydrogenated) hydrocarbons are preferred because the electrical dissipation factor of the cured coating increases with increasing degree of unsaturation. Suitable hydrocarbon polyols include hydroxy-terminated, fully or partially hydrogenated 1,2-polybutanediene; 1,4- and 1,2-polybutadiene copolymers; 1,2-polybutadiene polyol hydrogenated with an iodine value of 9 to 21; Fully or partially hydrogenated polyisobutylene polyols; Mixtures thereof and the like. Hydrocarbon polyols are preferably substantially fully hydrogenated, with preferred polyols having monomers copolymerized with hydrogenated 1,2-polybutadiene and about 50-80% 1,4-butadiene and 50-20% 1,2-butadiene Hydrogenated 1,4-, 1,2-polybutadiene copolymers. Suitable hydrocarbon polyamines or polythiols include the aforementioned polyols having thiols or amine groups instead of hydroxy groups.

Polyisocyanate component (ii) is aromatic or non-aromatic, with non-aromatic being preferred. Suitable aromatic polyisocyanates are toluene diisocyanates. Non-aromatic polyisocyanates of 4-20 carbon atoms can be used. Suitable saturated aliphatic polyisocyanates include isophorone diisocyanates; Dicyclohexylmethane-4,4'- diisocyanate; 1,4-tetramethylene diisocyanate; 1,5-pentamethylene diisocyanate; 1,7-heptamethylene diisocyanate; 1,8-octamethylene diisocyanate; 1,9-nonamethylene diisocyanate; 1,10-decamethylene diisocyanate; 2,2,4-trimethyl-1,5-pentamethylene diisocyanate; 2,2'-dimethyl-1,5-pentamethylene diisocyanate; 3-methoxy-1,6-hexamethylene diisocyanate; 3-butoxy-1,6-hexamethylene diisocyanate; Omega, omega'-dipropylether diisocyanate; 1,4-cyclohexyl diisocyanate; 1,3-cyclohexyl diisocyanate; Trimethylhexamethylene diisocyanate; And mixtures thereof. Isophorone diisocyanate is a preferred aliphatic polyisocyanate.

The reaction rate between the hydroxy terminated hydrocarbon and the diisocyanate can be increased by using a catalyst in an amount of 100 to 200 ppm. Suitable catalysts include dibutyl tin dilaurate, dibutyl tin oxide, dibutyl tin di-2-hexanoate, tin oleate, octosan tin, lead octoate, ferrous acetoacetic acid and triethylamine, diethyl Amines such as methylamine, triethylenediamine, dimethyl-ethylamine, morpholine, N-ethyl morpholine, piperazine, N, N-dimethylbenzylamine, N, N-dimethyl laurylamine and mixtures thereof. Preferred catalyst is dibutyl tin dilaurate.

Endcapping monomers (iii) are hydroxy-terminated aliphatic acrylates or methacrylates, preferably alkoxylated (meth) acryl in which 1-10 moles of ethylene, propylene react with acrylic acid or methacrylic acid in butylene oxide Rate.

Suitable hydroxy-terminated monoacrylates used as the end capping monomers include hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate and hydroxypropyl methacrylate. Hydroxyethyl acrylate is preferred because it provides a faster cure rate for polyurethane oligomers. The molar ratio of hydrocarbon compound, diisocyanate and endcapping monomer is preferably about 1: 2: 2.

The second component (b) consists of one or more mono- or multivalent diluents. The diluent is preferably an acrylate or methacrylate functional group. However, small amounts of other forms of monomer may also be used. The amount of component (b) is about 20-80 wt.% Of the total coating composition, more preferably about 20-70 wt.%. Particular preference is given to using about 10-50 wt.% Monofunctional diluent and 5-40 wt.% Multivalent diluent.

The second component (b) of the composition preferably comprises a monofunctional alkyl acrylate or methacrylate diluent relative to the monomer. The alkyl portion of the monomer has 6 to 18, preferably 8 to 15 carbon atoms and exhibits the properties of hydrocarbons. The monomer may be linear, branched or cyclic. The component comprises about 5-50% by weight of the composition based on the total weight of the coating composition. Preferably from about 5% to about 50% by weight of the composition, more preferably from about 10% to about 40% by weight of the composition.

The monomer is selected to be compatible with the oligomers described above. Suitable examples of C ₆ -C ₁₈ alkyl acrylate or methacrylate monomers include hexyl acrylate; Hexyl methacrylate; Cyclohexyl acrylate; Cyclohexyl methacrylate; 2-ethylhexyl acrylate; 2-ethylhexyl methacrylate; Isooctyl acrylate; Isooctyl methacrylate; Octyl acrylate; Octyl methacrylate; Decyl acrylate; Decyl methacrylate; Isodecyl acrylate; Isodecyl methacrylate; Isobornyl acrylate; Isobornyl methacrylate; Lauryl acrylate; Lauryl methacrylate; Stearyl acrylate; Stearyl methacrylate.

The second component also preferably comprises an alkylacrylate multivalent diluent (or monomer) in an amount of about 5-50 wt.%, Preferably 5-40 wt.%. Suitable examples of such polyvalent monomers include C ₄ -C ₁₅ hydrocarbon diol acrylate; C ₄ -C ₁₅ hydrocarbon diol methacrylate; And mixtures thereof. The hydrocarbon includes a cycloalkyl group. Other suitable polyhydric acrylates are (alkoxylated) polyolpolyacrylates. Examples of suitable polyhydric monomers include butanediol dimethacrylate, butanediol diacrylate, propanediol dimethacrylate, propanediol diacrylate, pentanediol dimethacrylate, pentanediol diacrylate, hexanediol dimethacrylate, Hexanediol diacrylate, neopentylglycol dimethacrylate, neopentylglycol diacrylate, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, polypropylene glycol diacrylate, polypropylene glycol dimethacrylate , Cyclohexanedi-methanoldiacrylate or -methacrylate and tricyclodecane dimethanol di (meth) acrylate.

Preferred alkyl acrylate monomers include isobornyl acrylate, 2-ethylhexyl acrylate, isooctyl acrylate, cyclohexyl acrylate, hexanediol diacrylate, tricyclodecane dimethanol diacrylate.

Other diluents may preferably be used in amounts of less than about 10 wt.%. Examples of such diluents include N-vinyl functional groups or vinyl ether functional compounds having a molecular weight of less than 500. Examples of the diluent include N-vinyl caprolactam, butyl-vinyl ether, triethylene glycol divinyl ether, butanediol-divinyl ether, and the like.

The viscosity of the entire coating composition at 25 ° C. is adjusted to less than about 2000 mPa · s, preferably less than about 800 mPa · s at 25 ° C. as measured using a Kuet apparatus (cup-and-bob viscometer with a frequency of 100 rpm). Sufficient diluent is used so as to be sufficient.

Preferably the coating composition of the present invention does not comprise a large amount of monomers having relatively strong dipole moments such as N-vinylpyrrolidone, phenoxyethyl acrylate, polyoxyalkyllanalkylphenol acrylate and the like. In addition, the coating composition does not contain a large amount of a monomer easily containing a dipole, such as an acrylate containing an aromatic group, such as phenyl acrylate. One of ordinary skill in the art can readily determine the amount allowed in the composition by measuring the dissipation factor.

The coating is radiation cured and can be cured with electron beam irradiation or light with a wavelength of about 200-700 mm. In the latter case, the composition comprises a photosensitive radical generating compound or a mixture of compounds as photoinitiator.

The photoinitiator, which is used in small but effective amounts to promote radiation cure, should provide a suitable cure rate at which no premature gelation of the composition occurs.

Suitable photoinitiators include: hydroxycyclohexylphenyl ketone; Hydroxymethylphenylpropanone; Dimethoxyphenyl-acetophenone; 2-methyl-1, [4- (methyl thio) phenyl] -2-morpholino-propanone-1; 1- (4-isopropylphenyl) -2-hydroxy-2-methylpropan-1-one; 1- (4-dodecylphenyl) -2-hydroxy-2-methylpropan-1-one; 4- (2-hydroxyethoxy) phenyl- (2-hydroxy-2-propyl) ketone; Diethoxyacetophenone; 2,2-di-sec-butoxyacetophenone; Diethoxy-phenyl acetophenone; And mixtures thereof.

If photoinitiators are used, it is preferred to include from about 1.0 to about 10.0 weight percent of the composition relative to the total composition. The amount of photoinitiator is preferably about 2.0 to about 7.0% by weight. When the amount of photoinitiator is used, the photoinitiator should be selected to have a curing rate of less than about 2.0 J / cm 2, preferably less than 1.0 J / cm 2, as measured by the dose versus modulus curve.

In addition, the composition preferably includes an adhesion promoter. The adhesion promoter is preferably a compound having groups involved in the radical curing reaction and groups attached to the metal conductor.

The group participating in the curing reaction may preferably be vinyl, (meth) acrylate or thiol. The group attached to the metal conductor is preferably hydroxy, acid, zirconate, titanate or silane. The acid can be for example carboxylic acid, phosphoric acid or sulfonic acid. Most preferred are (meth) acrylate functional carboxylic acids or phosphoric acid. Some examples of suitable adhesion promoters include, but are not limited to, hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, di- or trialkoxy zirconate or titanate, vinyl trimethoxysilane, mercapto Propyltrimethoxysilane, acrylic acid, methacrylic acid, β-carboxyethylacrylate, Ebecryl 170 and Eversil 169. The Eversil product is an acrylate ester derivative commercially available from Radcure Specialties in Atlanta, Georgia, and is a phosphate adhesion promoter.

Mono or diesters or phosphoric acids having the structure of Formula 1 are also suitable as adhesion promoters:

(In Formula 1, m + 1 + p = 3, R = H or CH ₃ , A = C _n H _{2 n} , and 2≤n≤6, R '= C ₁ to C ₁₄ alkyl, aryl, alkaryl or Alkyleneoxy)

Representative examples of various kinds of organophosphate esters having the general formula (I) having the general formula (1) above include:

(1) methylmethacryloyloxyethyl phosphate, wherein

(R = CH ₃ ; A = -C ₂ H _4- ; R '= CH ₃ , m = 1 and p = 1);

(2) ethyl methacryloyloxyethyl phosphate, wherein

(R = CH ₃ ; A = -C ₂ H _4- ; R '= C ₂ H ₅ , m = 1 and p = 1);

(3) propylacryloyloxyethyl phosphate, wherein

(R = H; A = -C ₂ H _4- ; R '= C ₃ H ₇ , m = 1 and p = 1);

(4) methylacryloyloxyethyl phosphate, wherein

(R = H; A = -C ₂ H _4- ; R '= CH ₃ , m = 1 and p = 1);

(5) ethylacryloyloxyethyl phosphate, wherein

(R = H; A = -C ₂ H _4- ; m = 1 and p = 1; R '= C ₂ H ₅ );

(6) propylmethacryloyloxyethyl phosphate, wherein

(R = CH ₃ ; A = -C ₂ H _4- ; R '= C ₃ H ₇ ; m = 1 and p = 1);

(7) bis (methacryloxyethyl) phosphate, wherein

(R = CH ₃ ; A = -C ₂ H _4- ; m = 2, l = 0; p = 1); And

(8) bis (acryloxyethyl) phosphate, wherein

(R = H; A = -C ₂ H _4- ; m = 2; l = 0; p = 1).

The adhesion promoter helps to attach the coating composition to the metal conductor. The adhesion promoter may be used in the range of about 0.2 to 5 wt.% Of the composition. The quantification of adhesion promoters is too large and must be treated so that the insulation is not reduced below acceptable levels. It is an unexpected advantage of the coating composition of the present invention that adhesion promoters are used in effective amounts and good insulation is obtained.

In addition to the components, the composition may also include other components known to those of ordinary skill in the art, including stabilizers, surfactants, plasticizers, chain transfer agents, and the like.

In addition, a small amount of a dye or dye may be usefully used to color the coating material. The coated metal conductor can be simply visually adjusted. This is particularly useful when the metal conductor is partially covered. Suitable dyes or dyes are, for example, copper phthalocyanine blue, crystal violet lactone (blue), crystal maleite green, sheet ed rubin (red). If a pigment is used the quantitation will be about 0.2-5 wt.% Relative to the coating composition.

The coating can be applied onto the metal conductor using known coating methods such as spraying, vacuum coating dipping and doctoring. The coating can be used under a nitrogen atmosphere to prevent oxygen inhibition, but this is not necessary. For example, if a relatively large amount of photoinitiator is used, curing of the film surface is also suitable.

The invention will be further illustrated by the following non-limiting examples.

Preparation of Acrylate Functional Oligomer A

Isophorone diisocyanate (IPDI 429 g) is dissolved in lauryl acrylate with 1 g of BHT (butylate hydroxy toluene), 0.7 g of phenolthiazine and 2 g of dibutyltin dilaurate. 224 g of hydroxyethyl acrylate (HEA) is slowly added to the mixture and the temperature is maintained below 35 ° C. 2318 g of hydrocarbon diol are added to the acrylate isocyanate adduct (Nisso PB 2000) and reacted. About 105 g of lauryl acrylate is added and the final NCO content is determined to be less than 0.1%. The oligomer A has a theoretical molecular weight of 3089 and is a clear solution of 85% oligomer in 15% laurylacrylate.

Preparation of Acrylate Functional Oligomer B

In a similar manner to the preparation of oligomer A, oligomers are prepared from 400 g of IPDI, 139 g of HEA, 2876 g of Nisso PB 2000 and 380 g of lauryl acrylate. Theoretical molecular weight of the oligomer is 5733.

Preparation of Acrylate Functional Oligomer C

In a similar manner to the preparation of oligomer A, oligomer C is prepared from 81 g of IPDI, 42 g of HEA, 430 g of Nisso PB 2000 and 140 g of isobornylacrylate. The theoretical molecular weight of the oligomer is 3093.

Example 1-7

The coating material is made of this oligomer together with the additional diluents and photoinitiators set forth in Table 1 below in mixture A-C at 15% dilution. The coating material is added to an aluminum plate and cured with 2J / cm 2 light of the molten D bulb. To measure the dissipation factor, a 150 μm thick film was cast on a glass plate and cured at 2 J / cm; The dissipation factor was measured at 24 ° C. and 150 ° C. at 60 Hz with a standard device with stainless steel electrodes. The results are also disclosed in Table 1 below.

ingredient One 2 3 4 5 6 7 Oligomer A 51.8 57 57 Oligomer B 51.8 57 57 Oligomer C 57 Lauryl acrylate 36.4 36.4 Isobonylacrylate 30 30 30 30 30 Photomer 3016 ¹⁾ 9.1 9.1 SA 1002 ²⁾ 10 10 10 10 SR 349 ³⁾ 10 Irgacure 500 2.7 2.7 3 3 3 3 3 Dissipation Factor at 24 ℃, 60Hz 0.028 0.038 0.030 0.033 0.033 0.015 0.027 Dissipation Factor at 150 ℃, 60Hz 0.098 0.106 0.021 0.023 0.023 0.010 0.028 Dielectric constant <3.0 <3.0 <3.0 <3.0 <3.0 <3.0 <3.0

1) Photomer 3016 is bisphenol-A-diacrylate.

2) SA 1002 is tricyclododecanedimethanol diacrylate.

3) SR 349 is ethoxylate bis phenol-A-diacrylate.

Example 8-18

In a similar manner, additional coating compositions are prepared and tested. The oligomer C is used in this example.

Compositions and results are summarized in Tables 2 and 3. The coating is spin coated on an aluminum panel, cured at 1 J / cm to form a 12.5 μm film, and the coating is cast on a glass plate and cured at 2 J / cm 2.

ingredient 8 9 10 11 12 13 Oligomer C 50 50 50 54 48.5 53.8 Isobonylacrylate 24 10.8 10.8 SA 1002 20 24 20 23.3 Hexanediol diacrylate 24 25.9 25.8 Cyclohexyl acrylate 20 Isooctylacrylate 19.4 Tarocure 1173 3 3 3 6 6 5.9 Evercrill 170 3 3 3 3.2 2.9 3.2 Phthalocyanine blue 0.5 Viscosity (25 ℃) 700 500 785 730 450 730 % Dissipation at 25 ° C 0.20 0.029 0.019 0.024 -0.02 0.025 Dissipation rate at 150 ℃ 0.83 0.032 0.060 0.082 -0.05 0.053 Stability at 150 ° C immersion Pass Pass A slight flaw Pass Pass Pass Blocking of Coatings at 60 ° C nd nd nd Pass Pass Pass Dielectric Constant at 24 ℃ 60Hz <2.7 <2.7 <2.7 <2.7 <2.7 <2.7 % Elongation Tg (℃) -17 -11 90% bending test Pass Pass Pass Pass Pass Pass

14 15 16 17 18 ingredient Oligomer C 50 60 50 50 50 Isobonylacrylate 14 14 20 24 Tricyclodecane dimethanol diacrylate 30 24 20 20 Hexanediol diacrylate 20 24 Tarocure 1173 3.0 3.0 3.3 3.0 3.0 Evercrill 170 3.0 3.0 3.3 3.0 3.0 Viscosity (mPa.s) 1910 785 700 1240 1090 Dissipation Factor at 25 ℃, 60Hz 0.020 0.029 0.019 0.024 -0.02 Dissipation Factor at 150 ℃, 60Hz 0.083 0.032 0.060 0.082 -0.08 Stability at 150 ° C immersion Pass Pass A slight flaw Pass Pass 180。 bending test Pass Pass Pass Pass Pass

Claims (17)

The coating material has a dielectric dissipation factor (60HZ, 24 ° C.) of less than about 0.05, and (a) an acrylate functional urethane oligomer having a hydrocarbon backbone; (b) one or more mono- or multivalent diluents and optionally; And (c) a radiation cured coating material formulated with a component comprised of a photoinitiator. The method of claim 1, And said metal is iron, copper, aluminum or silver. The method of claim 2, And the metal is aluminum, copper or silver. The method according to any one of claims 1 to 3, Wherein said cured coating material is a thin coating of 25 μm and has an elongation of at least about 50% at 25 ° C. 17. The method according to any one of claims 1 to 4, And wherein the cured coating material has a dissipation factor of less than about 0.2 at 60 Hz, 150 ° C. The method according to any one of claims 1 to 5, And the coating material is additionally formulated with a component consisting of an adhesion promoter. The method according to any one of claims 1 to 6, The cured coating includes (a) about 20 to about 80 wt.% Acrylate functional urethane oligomer having a hydrocarbon backbone; (b) about 20 to about 80% of one or more mono- or polyacrylate functional monomers and optionally; (c) about 1 to about 10 wt.% of one or more photosensitive radical generating compounds; And (d) a radiation cured coating material optionally formulated with a component consisting of about 0.2-5 wt.% Of an adhesion promoter. The method according to any one of claims 1 to 7, Wherein the cured coating is a cured coating by irradiating light with a wavelength of about 200-700 μm, component (c) is present at about 1-10 wt.% Of the total coating composition. Metal conductors. The method according to any one of claims 1 to 8, The cured coating material comprises (a) about 30-65 wt.% Acrylate functional urethane oligomer having a hydrocarbon backbone; (b) about 20-70 wt.% of at least two acrylate functional diluents, one is monoacrylate and one is a polyacrylate functional compound; (c) about 1-10 wt.% of one or more photosensitive radical generating compounds; (d) a metal conductor having a cured coating material, characterized in that the coating material is formulated with a component consisting of about 0.2-5 wt.% acid functional adhesion promoter. The method according to any one of claims 6 to 9, And said adhesion promoter is an acid functional compound. The method according to any one of claims 1 to 10, Wherein said coating material is formulated from components, wherein one of said components is a colorant or dye about 0.2-5 wt.%. The method according to any one of claims 1 to 11, And the coating material has a thickness of about 10-100 μm. The method according to any one of claims 1 to 12, And the coating material has a dielectric constant of less than about 5 metal conductors with cured coatings. The method according to any one of claims 1 to 13, And the coating material has a dielectric dissipation factor (60 Hz, 24 ° C.) of less than about 0.05 after exposure to high temperature oil (150 ° C.). The method according to any one of claims 1 to 14, The coating consists essentially of (a) about 30-65 wt.% Acrylate functional urethane oligomer with hydrocarbon backbone, (b1) about 10-50 wt.% Mono-acrylate functional diluent, (b2) about 5-40 wt. .% Poly-acrylate functional diluent, (c) about 2-7 wt.% Of at least one photoinitiator, (d) about 0.2-4 wt.% Adhesion promoter, (e) about 0.2-2 wt.% Of pigment A metal conductor having a cured coating, characterized in that it is formulated from the constituents. (a) an acrylate functional urethane oligomer having a hydrocarbon main chain; (b) one or more mono- or multivalent diluents and optionally; And (c) at least one photosensitive radical generating compound, comprising: The coating cured by irradiation has a dielectric dissipation factor of less than about 0.05 at 60 Hz and 24 ° C., has a dissipation factor of less than about 0.2 at 60 Hz and 150 ° C., and a thin coating of 25 μm at 25 ° C. is at least about 50%. Radiation-curing coating composition, characterized in that it has an elongation. The method of claim 16, And the urethane oligomer is a reaction product of a hydrocarbon polyol, a polyisocyanate and a hydroxyfunctional endcapping monomer.