Coating agent for forming etching resist films

Abstract

Provided is a coating agent for forming an etching resist coating film, with which it is possible to form an etching resist coating film that is excellent in terms of laser removability, resist characteristics, and separability. A coating agent for forming an etching resist coating film according to the present invention contains, in a solvent, 100 parts by mass of an aqueous alkyd resin, 0.10 part by mass or more and 30 parts by mass or less of a melamine resin, 20 parts by mass or more and 200 parts by mass or less of an aluminum-containing oxide, 10 parts by mass or more and 100 parts by mass or less of a titanium-containing oxide, and 0.10 part by mass or more and 5.0 parts by mass or less of carbon black in terms of solid content, and the total amount of the respective solid contents of these components accounts for 80 mass% or more of the total solid content.

Description

Technical Field

[0001] The present invention relates to a coating agent for forming an etching resist film used for forming an etching resist film on the surface of a grain-oriented electrical steel sheet.

Background Art

[0002] Since grain-oriented electrical steel sheets have excellent magnetic properties, they are mainly used as materials for transformer cores. In order to improve the energy use efficiency in transformers, it is required to reduce the iron loss of grain-oriented electrical steel sheets. As one method for reducing the iron loss of grain-oriented electrical steel sheets, a method of introducing linear grooves on the surface of the grain-oriented electrical steel sheet is known. In this method, by forming linear grooves on the surface of the steel sheet, the width of magnetic domains is subdivided and the iron loss is reduced.

[0003] As one method for forming linear grooves on the surface of a steel sheet, a method by an etching process using an etching resist film is known. For example, in Patent Document 1, a coating agent for forming an etching resist film is uniformly applied to the surface of a steel sheet and baked to form an etching resist film. After that, the formed etching resist film is irradiated with a laser to linearly remove the etching resist film, and an etching process is performed to form linear grooves on the surface of the steel sheet.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] As a result of their own investigations, the inventors found that there is room for improvement in the properties of the etching resist film formed on the surface of grain-oriented electrical steel sheets in the above-mentioned prior art. Specifically, when attempting to remove the etching resist film linearly by irradiating it with a laser according to the prior art, the width of the portion where the etching resist film was removed by laser irradiation (hereinafter sometimes referred to as the "film removal portion") varied greatly, or the width of the film removal portion differed greatly from the laser beam diameter. These errors suggest that the etching resist film has poor laser removeability, meaning it is not accurately removed according to the laser irradiation pattern. Poor laser removeability of the etching resist film makes it difficult to accurately form the film removal portion, and as a result, it was sometimes difficult to form linear grooves on the surface of the grain-oriented electrical steel sheet in the designed shape.

[0006] Furthermore, when electrolytic etching was performed using an etching resist film according to the conventional technology, the surface of the etching resist film sometimes discolored, changing its appearance. The change in the color tone of the etching resist film suggests that the resistance of the etching resist film to the electrolytic etching solution (hereinafter sometimes referred to as "resist properties") has decreased. In addition, in the conventional technology, when the etching resist film that was no longer needed after the etching process was completed was peeled off and removed using a strong alkaline aqueous solution, some of the etching resist film sometimes remained on the surface of the grain-oriented electrical steel sheet without being peeled off. The remaining etching resist film suggests that the ease of removal of the etching resist film (hereinafter sometimes referred to as "peelability") is poor.

[0007] This invention has been made in view of the above-mentioned problems of the prior art, and aims to provide an etching resist coating agent that can form an etching resist coating with excellent laser removeability, resist properties, and peelability. [Means for solving the problem]

[0008] The gist of the present invention is as follows:

[0009] [1] In the solvent, in terms of solid content, 100 parts by mass of aqueous alkyd resin, 0.10 parts by mass or more and 30 parts by mass or less of melamine resin, Aluminum-containing oxide, 20 parts by mass or more and 200 parts by mass or less. 10 parts by mass or more and 100 parts by mass or less of titanium-containing oxide, and Carbon black: 0.10 parts by mass or more, and 5.0 parts by mass or less. It contains, A coating agent for forming an etching resist film, wherein the total amount of solids of the aqueous alkyd resin, the melamine resin, the aluminum-containing oxide, the titanium-containing oxide, and the carbon black accounts for 80% by mass or more of the total solids.

[0010] [2] The etching resist film forming coating agent according to [1] above, wherein the aqueous alkyd resin is an aqueous alkyd resin obtained by reacting an alkyd resin with a polymerizable vinyl monomer.

[0011] [3] The etching resist film forming coating agent according to [1] or [2] above, wherein the proportion of the total solid content in the etching resist forming coating agent is 10% by mass or more and 80% by mass or less.

[0012] [4] The etching resist coating agent according to any one of [1] to [3] above, wherein the solvent comprises ethylene glycol mono-n-butyl ether. [Effects of the Invention]

[0013] The etching resist film formed by applying and baking the etching resist film-forming agent according to the present invention onto the surface of a grain-oriented electrical steel sheet exhibits superior laser removeability, resist properties, and peelability compared to conventional techniques. [Modes for carrying out the invention]

[0014] The present invention will be described in detail below.

[0015] <Coating agent for forming etching resist film> In one embodiment, the present invention relates to a coating agent for forming an etching resist film, wherein the solvent contains, in terms of solid content, 100 parts by mass of an aqueous alkyd resin, 0.10 parts by mass or more and 30 parts by mass of melamine resin, 20 parts by mass or more and 200 parts by mass of aluminum-containing oxide, 10 parts by mass or more and 100 parts by mass of titanium-containing oxide, and 0.10 parts by mass or more and 5.0 parts by mass of carbon black, and the total amount of solid content of the aqueous alkyd resin, melamine resin, aluminum-containing oxide, titanium-containing oxide, and carbon black accounts for 80% by mass or more of the total solid content. In the following description of the coating agent for forming an etching resist film, grain-oriented electrical steel sheets, which are finished products obtained by completing all processes up to secondary recrystallization annealing, are used as an example of the target to which the coating agent is applied. However, as will be described later, it should be noted that the target to which the coating agent for forming an etching resist film according to the present invention is applied may also be steel sheets as intermediate products in the process of manufacturing grain-oriented electrical steel sheets.

[0016] The coating agent for forming an etching resist film according to the present invention contains an aqueous alkyd resin as a main component, and is prepared by dissolving or mixing a melamine resin as a crosslinking agent, an aluminum-containing oxide, a titanium-containing oxide, and carbon black in a solvent. By applying the coating agent for forming an etching resist film according to the present invention onto the surface of a grain-oriented electrical steel sheet and performing baking treatment at a predetermined temperature and for a predetermined time, evaporation of the solvent and a crosslinking reaction occur, and an etching resist film is formed on the surface of the grain-oriented electrical steel sheet. In the present invention, the "coating agent for forming an etching resist film" refers to a liquid coating agent mainly composed of a resin, which is used for forming a film of an etching resist. In the present invention, the "etching resist film" refers to a solid film formed on the surface of a coated material through the above-described steps from the coating agent for forming an etching resist film. The term "etching resist" generally used sometimes means a coating agent for forming an etching resist film, and sometimes means an etching resist film. In this specification, the two terms, the coating agent for forming an etching resist film and the etching resist film, are strictly distinguished.

[0017] As described above, the coating agent for forming an etching resist film is applied while leaving a continuous or discontinuous linear region in a direction intersecting the rolling direction as an uncoated region. In the etching process, in the coated region protected by the etching resist film, contact between the surface of the grain-oriented electrical steel sheet and the etching solution is prevented, and corrosion of the grain-oriented electrical steel sheet does not occur. In the uncoated region, corrosion occurs due to contact between the surface of the grain-oriented electrical steel sheet and the etching solution, and linear grooves are formed. After the etching process is completed, the etching resist film is removed as necessary.

[0018] <Solid content and solid content conversion> Before explaining each component contained in the coating agent for forming an etching resist film according to the present invention, the method of indicating the components will be explained. In this specification, "solid content" refers to the remaining solid components excluding substances lost by evaporation, such as solvents and water, among the components contained in the coating agent for forming an etching resist film. When the coating agent for forming an etching resist film is applied to the surface of a grain-oriented electrical steel sheet and baked, substances such as solvents and water evaporate, and an etching resist film is formed by the remaining solid content.

[0019] In this specification, "in terms of solid content" means that when indicating the content of the components contained in the coating agent for forming an etching resist film, the content is indicated based on the solid content of each component. As will be described later, the coating agent for forming an etching resist film according to the present invention is prepared by mixing an aqueous alkyd resin, a melamine resin, an aluminum-containing oxide, a titanium-containing oxide, and carbon black in a solvent. The aqueous alkyd resin and melamine resin used in the preparation may themselves contain solvents. In addition, the aluminum-containing oxide, titanium-containing oxide, and carbon black may adsorb moisture in the air. Therefore, when indicating the content of each component, it is appropriate to indicate the content in terms of solid content rather than the content of the actually mixed components. Specifically, the mass of the solid content of the aqueous alkyd resin contained in the coating agent for forming an etching resist film is set to 100 parts by mass, and the content is indicated by the mass parts of the solid content of the other components converted based on this.

[0020] The content of each component indicated in terms of solid content does not change before and after the coating and baking processes of the coating agent for forming an etching resist film. Therefore, by quantitatively analyzing the components of the etching resist film after the baking process, the content of each component in terms of solid content contained in the coating agent for forming an etching resist film before the baking process can be known.

[0021] <Components of the coating agent for forming an etching resist film> The following describes each component contained in the coating agent for forming an etching resist film according to the present invention.

[0022] (1) Water-based alkyd resin The coating agent for forming an etching resist film according to the present invention contains 100 parts by mass of an aqueous alkyd resin in terms of solid content in the solvent. As described above, the aqueous alkyd resin is the main component of the coating agent for forming an etching resist film according to the present invention, and is also the main component of the etching resist film after coating and baking treatment. An aqueous resin is a general term for water-dispersible resins in which the resin is uniformly dispersed in water, and water-soluble resins that dissolve easily in water.

[0023] Conventionally known water-based alkyd resins can be used without particular limitation. The alkyd resin used as a raw material for the water-based alkyd resin is obtained by dehydrating and condensing a polybasic acid, a polyhydric alcohol, and an oil or oil-based product, and optionally further reacting it with a monobasic acid. In a preferred embodiment, the coating agent for forming an etching resist film according to the present invention is an water-based alkyd resin obtained by reacting an alkyd resin with a polymerizable vinyl monomer. In this preferred embodiment, by using an water-based alkyd resin obtained by reacting an alkyd resin with a polymerizable vinyl monomer, an etching resist film forming agent capable of forming an etching resist film with excellent resist properties and peelability can be obtained.

[0024] (polybasic acid) Examples of polybasic acids used in the synthesis of alkyd resins include phthalic acid, isophthalic acid, terephthalic acid, trimellitic acid, tetrahydrophthalic acid, succinic acid, maleic acid, adipic acid, sebacic acid, azelaic acid, hymic acid, itaconic acid, methylhexahydrophthalic acid, 1,4-cyclohexanedicarboxylic acid, methylcyclohexentricarboxylic acid, pyromellitic acid, and their anhydrides. These polybasic acids can be used individually or in combination of two or more.

[0025] (Polyhydric alcohol) Examples of polyhydric alcohols used in the synthesis of alkyd resins include ethylene glycol, polyethylene glycol, propylene glycol, polypropylene glycol, butanediol, decanediol, diethylene glycol, pentanediol, neopentyl glycol, butylethylpropanediol, glycerin, trimethylolethane, trimethylolpropane, pentaerythritol, sorbitol, 1,4-cyclohexanedimethanol, and tricyclodecanedimethanol. These polyhydric alcohols can be used individually or in combination of two or more.

[0026] (Oils and fats and processed oil products) Examples of oils and fats used in the synthesis of alkyd resins include tung oil, linseed oil, dehydrated castor oil, safflower oil, soybean oil, castor oil, tall oil, rice bran oil, and their fatty acids, high-diene fatty acids, etc. Furthermore, processed oils and fats obtained using the above-mentioned oils and fats as the main raw material can be used. Examples of such processed oils and fats include modified oils, isomerized oils, polymerized oils, maleated oils, boiled oils, etc., obtained using the above-mentioned oils and fats as the main raw material. These oils and fats and processed oils and fats can be used individually or in combination of two or more types.

[0027] (monobasic acid) Examples of monobasic acids that can be optionally used in the synthesis of alkyd resins include benzoic acid, pt-butylbenzoic acid, methylbenzoic acid, versatic acid, isodecanoic acid, isotridecanoic acid, crotonic acid, and non-drying oil fatty acids. These monobasic acids can be used alone or in combination of two or more.

[0028] (Polymerizable vinyl monomer) In a preferred embodiment of the present invention, conventionally known polymerizable vinyl monomers can be used without particular limitation as the polymerizable vinyl monomer to be reacted with the alkyd resin to obtain an aqueous alkyd resin. Examples of polymerizable vinyl monomers used in the reaction with the alkyd resin include (meth)acrylic acid ester monomers such as methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, cyclohexyl (meth)acrylate, methylcyclohexyl (meth)acrylate, ethylcyclohexyl (meth)acrylate, cycloheptyl (meth)acrylate, toluyl (meth)acrylate, and glycidyl (meth)acrylate; aromatic polymerizable unsaturated monomers such as styrene, α-methylstyrene, chlorostyrene, vinyltoluene, vinylnaphthalene, phenyl (meth)acrylate, benzyl (meth)acrylate, and vinyl benzoate; vinyl monomers such as vinyl acetate and vinyl propionate; N-methoxymethyl (meth)acrylamide, N-ethoxymethyl (meth)acrylamide, and N-butoxymethyl N-alkoxy-substituted amide monomers such as (meth)acrylamide; fluorine-containing vinyl monomers such as perfluoroethylene, perfluoropropylene, and vinylidene fluoride; silicon-containing vinyl monomers such as vinyltrimethoxysilane and vinyltriethoxysilane; dialkyl esters such as maleic acid and fumaric acid; alkenes such as ethylene and propylene; conjugated dienes such as butadiene and isoprene; monomers such as vinyl chloride and allyl chloride; (meth)acrylic acid, itaconic acid, monomethyl maleate, monobutyl maleate, monobutyl itaconic acid, sulfonic acid group-containing (meth)acrylate, phosphoric acid group-containing (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate;Lactone adducts to 2-hydroxyethyl (meth)acrylate, ring-opening adducts of ethylene oxide to 2-hydroxyethyl (meth)acrylate or 2-hydroxypropyl (meth)acrylate, ring-opening adducts of propylene oxide to 2-hydroxyethyl (meth)acrylate or 2-hydroxypropyl (meth)acrylate, dimers and trimers of 2-hydroxyethyl (meth)acrylate or 2-hydroxypropyl (meth)acrylate, N,N-dimethylaminoethyl (meth)acrylate, N,N-dimethylaminoethyl (meth)acrylate Examples include ethylaminoethyl (meth)acrylate, N,N-diethylaminoethyl (meth)acrylate, N,N-dipropylaminoethyl (meth)acrylate, N,N-dimethylaminopropyl (meth)acrylate, N,N-methylpropylaminopropyl (meth)acrylate, N,N-diethylaminopropyl (meth)acrylate, N,N-dipropylaminopropyl (meth)acrylate, N,N-dimethylaminopropylacrylamide, and N,N-diethylaminopropylacrylamide. These polymerizable vinyl monomers can be used individually or in combination of two or more.

[0029] Water-based alkyd resin may be commercially available or synthesized from raw materials. When using a commercially available product, it is preferable to use one synthesized from one of the compounds listed above as an example. When synthesizing water-based alkyd resin from raw materials, it is preferable to follow the procedure below. First, a predetermined amount of polybasic acid, polyhydric alcohol, oil or processed oil product, and optionally a monobasic acid are added to a reaction vessel, and the contents are heated while stirring to cause a dehydration condensation reaction. When the acid value of the solids reaches 3 to 30 mg KOH / g, heating is stopped and the mixture is cooled. It is preferable to measure the acid value of the solids in accordance with the Japanese Industrial Standard JIS K 0070. Next, a solvent is added to the resulting reaction mixture to form an alkyd resin solution, and the alkyd resin solution is heated while stirring, and a mixture of polymerizable vinyl monomer and polymerization initiator prepared in advance is added dropwise. After the dropwise addition is complete, the polymerization initiator is further added dropwise to the reaction mixture and stirred to allow the reaction to proceed. Furthermore, a neutralizing agent and solvent are added to the reaction mixture and mixed to obtain a solution containing water-based alkyd resin.

[0030] The aqueous alkyd resin synthesized by the above procedure preferably has an acid value of 30 mg KOH / g or more and 80 mg KOH / g or less, a hydroxyl value of 50 mg KOH / g or more and 150 mg KOH / g or less, a number average molecular weight of 2000 or more and 10000 or less, and a weight average molecular weight of 10000 or more and 50000 or less.

[0031] The solvent used in synthesizing aqueous alkyd resins is not particularly limited. Preferred solvents include, for example, glycol ethers such as ethylene glycol mono-n-butyl ether, diethylene glycol mono-n-butyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol mono-n-butyl ether, propylene glycol mono-t-butyl ether, dipropylene glycol monomethyl ether, methyl cellosolve, ethyl cellosolve, and t-butyl cellosolve; and alcohols such as isopropyl alcohol and butyl alcohol.

[0032] The polymerization initiator used in synthesizing aqueous alkyd resins is not particularly limited. Preferred polymerization initiators include, for example, dibenzoyl peroxide and 2,2'-azobisbutyronitrile.

[0033] The neutralizing agent used in the synthesis of aqueous alkyd resins is not particularly limited. Preferred neutralizing agents include, for example, triethylamine and diethylethanolamine.

[0034] (2) Melamine resin The etching resist forming coating agent according to the present invention contains 0.10 parts by mass or more and 30 parts by mass or less of melamine resin in a solvent, on a solid content basis. The melamine resin is included in the etching resist forming coating agent as a crosslinking agent for crosslinking the aqueous alkyd resin. The inclusion of melamine resin improves the adhesion between the etching resist film and the grain-oriented electrical steel sheet. As the melamine resin, for example, methylated melamine and butylated melamine can be used.

[0035] When the solvent contains 0.10 parts by mass or more of melamine resin per 100 parts by mass of water-based alkyd resin, the adhesion between the formed etching resist film and the grain-oriented electrical steel sheet is enhanced, and the resist properties are improved. On the other hand, when the melamine resin content is 30 parts by mass or less, the crosslinking density does not increase excessively. As a result, the etching resist film maintains appropriate hardness and adhesion, and the peelability of the etching resist film does not deteriorate. Therefore, the melamine resin content per 100 parts by mass of water-based alkyd resin, on a solids basis, is set to 0.10 parts by mass or more and 30 parts by mass or less. The melamine resin content is preferably 1.0 part by mass or more, and more preferably 2.0 parts by mass or more. The melamine resin content is preferably 20 parts by mass or less, and more preferably 15 parts by mass or less.

[0036] (3) Aluminum-containing oxides The etching resist film forming coating agent according to the present invention contains, in terms of solid content, 20 to 200 parts by mass of an aluminum-containing oxide in the solvent. The type of aluminum-containing oxide is not particularly limited and various known ones can be used, for example, alumina, alumina-coated silica, kaolinite, etc. are preferably used. By including an aluminum-containing oxide with a higher thermal conductivity than aqueous alkyd resin, the thermal conductivity of the etching resist film is increased, improving laser removalability. These aluminum-containing oxides can be used alone or in combination of two or more types.

[0037] Alumina, also known as alumina sol, is not particularly limited in shape and may be granular or fibrous, for example. Regarding size, in the case of granular alumina, an average particle size of 5.0 nm or more and 100 nm or less is preferable, and in the case of fibrous alumina, a length of 50 nm or more and 200 nm or less is preferable from the viewpoint of the mixability of the coating agent and the appearance of the coating film. By setting the size of the alumina within the above range, it becomes easier to uniformly mix the alumina into the coating agent for forming etching resist films, and the stability of the coating agent can be improved. Here, "stability of the coating agent" specifically refers to the stability as a coating agent, such as the fact that aluminum-containing oxides do not precipitate and the quality does not deteriorate when used as a coating agent for forming etching resist films.

[0038] Kaolinite, also known as kaolin, is a hydrated aluminum silicate containing alumina and silica. From the viewpoint of the stability of the coating agent, the particle size of kaolinite is preferably between 1.0 μm and 30 μm.

[0039] Alumina-coated silica is a mixture of alumina and silica. Alumina-coated silica is preferable from the viewpoint of coating stability because the alumina is unevenly distributed on the silica surface. The particle size of alumina-coated silica is preferably between 1.0 μm and 30 μm from the viewpoint of coating stability.

[0040] When the solvent contains 20 parts by mass or more of aluminum-containing oxide per 100 parts by mass of the solids content of the aqueous alkyd resin, the laser removeability and resist properties are improved. On the other hand, when the aluminum-containing oxide is contained at 200 parts by mass or less, the adhesion of the etching resist film is improved. Therefore, the content of aluminum-containing oxide per 100 parts by mass of aqueous alkyd resin, on a solids basis, should be between 20 parts by mass and 200 parts by mass. Preferably, the content of aluminum-containing oxide is 30 parts by mass or more. Preferably, the content of aluminum-containing oxide is 150 parts by mass or less.

[0041] (4) Titanium-containing oxides The etching resist film forming coating agent according to the present invention contains, in terms of solid content, 10 to 100 parts by mass of titanium-containing oxide in the solvent. The type of titanium-containing oxide is not particularly limited and various known types can be used, for example, titania (rutile type) and titania (anatase type) are preferably used. By including a titanium-containing oxide with a higher thermal conductivity than aqueous alkyd resin, the thermal conductivity of the etching resist film is increased, improving laser removalability. These titanium-containing oxides can be used alone or in combination of two or more types.

[0042] When the solvent contains 10 parts by mass or more of titanium-containing oxide per 100 parts by mass of solids of the aqueous alkyd resin, the laser removeability and resist properties are improved. On the other hand, when the titanium-containing oxide is contained at 100 parts by mass or less, it becomes easier to uniformly mix the titanium-containing oxide into the coating agent, improving adhesion. Therefore, the content of titanium-containing oxide per 100 parts by mass of aqueous alkyd resin, on a solids basis, should be between 10 parts by mass and 100 parts by mass. Preferably, the content of titanium-containing oxide is 15 parts by mass or more. Preferably, the content of titanium-containing oxide is 80 parts by mass or less.

[0043] (5) Carbon Black The coating agent for forming an etching resist film according to the present invention contains 0.10 parts by mass or more and 5.0 parts by mass or less of carbon black in the solvent, on a solid content basis. The inclusion of an appropriate amount of carbon black improves laser removability. That is, the carbon black in the present invention is not included as a pigment for coloring the etching resist film, but rather, like aluminum-containing oxides and titanium-containing oxides, is included for the purpose of improving the laser removability of the etching resist film. The type of carbon black is not particularly limited, and various known types can be used.

[0044] When the solvent contains 0.10 parts by mass or more of carbon black per 100 parts by mass of the solids content of the water-based alkyd resin, the laser removal performance is improved. On the other hand, when the carbon black content is 5.0 parts by mass or less, it becomes easier to uniformly mix the carbon black into the coating agent, improving the stability of the coating agent and improving the laser removal performance. Therefore, the carbon black content per 100 parts by mass of water-based alkyd resin, on a solids basis, should be between 0.10 parts by mass and 5.0 parts by mass. Preferably, the carbon black content is 1.0 part by mass or more. Preferably, the carbon black content is 3.0 parts by mass or less.

[0045] The exact reason why the laser removeability of the etching resist coating agent according to the present invention is further improved when carbon black is included in addition to aluminum-containing oxide and titanium-containing oxide is not fully understood, but the inventors believe the following: As mentioned above, the inclusion of aluminum-containing oxide and titanium-containing oxide in the solvent increases the thermal conductivity of the etching resist coating. In contrast, although the thermal conductivity of graphite, which constitutes carbon black, is higher than that of aqueous alkyd resin, the amount of carbon black in the solvent in this invention is less than the amount of aluminum-containing oxide and titanium-containing oxide. Furthermore, the particle size of carbon black is very fine. Therefore, the improvement in the thermal conductivity of the etching resist coating due to the inclusion of carbon black is not significant.

[0046] On the other hand, the emissivity of carbon black is greater than that of aluminum-containing oxides and titanium-containing oxides. Furthermore, as mentioned above, when carbon black is contained in an amount of 5.0 parts by mass or less, it can be uniformly mixed into the coating agent. Therefore, when a laser is irradiated onto the surface of an etching resist film containing a predetermined amount of carbon black, the carbon black particles uniformly dispersed on the surface radiate heat only within the area irradiated by the laser. As a result, the property of the etching resist film to be precisely removed according to the laser irradiation pattern, i.e., the laser removeability, is thought to be further improved compared to cases where carbon black is not contained.

[0047] As will be shown in the examples described later, the inventors' studies have shown that the above-mentioned unique effect of carbon black is achieved when the solvent contains 0.10 parts by mass or more of carbon black per 100 parts by mass of aqueous alkyd resin. This is because even with a trace amount, the carbon black is uniformly dispersed on the surface of the etching resist film, thereby achieving the above-mentioned effect due to heat radiation. On the other hand, if the solvent contains more than 5.0 parts by mass of carbon black per 100 parts by mass of aqueous alkyd resin, the laser removal performance actually decreases. This is because, as mentioned above, it becomes difficult to uniformly mix the carbon black into the coating agent. Thus, the preferred range of carbon black content in the present invention is significantly different from the preferred range of content when carbon black is simply added as a pigment for coloring.

[0048] As described above, in the etching resist forming coating agent according to the present invention, aluminum-containing oxide, titanium-containing oxide, and carbon black are all components that contribute to improving laser removability. However, the mechanism of contribution to laser removability and the preferred range of content differ significantly between aluminum-containing oxide and titanium-containing oxide, which are metal oxides, and carbon black, which is a nonmetal element. In the present invention, by including optimal amounts of metal oxides and carbon black with different properties, it is possible to achieve better laser removability compared to when only one of them is included.

[0049] (6) Total solid content The etching resist film forming coating agent according to the present invention has a total solid content of 80% by mass or more of the total solid content of the aqueous alkyd resin, melamine resin, aluminum-containing oxide, titanium-containing oxide, and carbon black. In this specification, "total solid content" refers to the total solid content of all components contained in the etching resist film forming coating agent. If the ratio of the total solid content of the aqueous alkyd resin, melamine resin, aluminum-containing oxide, titanium-containing oxide, and carbon black to the total solid content is 80% by mass or more, the components of the etching resist film formed by the etching resist film forming coating agent will not be greatly diluted by the other components described later. Therefore, the effects of the present invention exhibited by the etching resist film will not be impaired. There is no particular upper limit to the ratio of the total solid content of the aqueous alkyd resin, melamine resin, aluminum-containing oxide, titanium-containing oxide, and carbon black to the total solid content, and the ratio of the total amount may be 100% by mass or less.

[0050] (7) Solvent The etching resist film forming coating agent according to the present invention contains an aqueous alkyd resin, a melamine resin, an aluminum-containing oxide, a titanium-containing oxide, and carbon black in a solvent. The solvent functions to uniformly dissolve the resin and uniformly mix the pigment, and also facilitates the application of the etching resist film forming coating agent. Furthermore, from the viewpoint of affinity with the aqueous alkyd resin, it is preferable that the solvent contains ethylene glycol mono-n-butyl ether.

[0051] Hydrophilic solvents can be used in combination with the solvent. Specific examples of hydrophilic solvents include glycol ethers such as diethylene glycol mono-n-butyl ether, propylene glycol mono-methyl ether, propylene glycol mono-ethyl ether, propylene glycol mono-n-butyl ether, propylene glycol mono-t-butyl ether, dipropylene glycol mono-methyl ether, methyl cellosolve, ethyl cellosolve, and t-butyl cellosolve, as well as alcohols such as isopropyl alcohol and butyl alcohol. These solvents can be used individually or in combination of two or more.

[0052] The solvent may be a mixture of hydrophobic solvents such as toluene and xylene. These hydrophobic solvents can be used individually or in combination of two or more.

[0053] The proportion of solvent in the etching resist film-forming coating agent is not particularly limited, but is preferably 20% by mass or more and 90% by mass or less. In other words, the proportion of total solids in the etching resist film-forming coating agent is preferably 10% by mass or more and 80% by mass or less. If the amounts of solvent and total solids in the etching resist film-forming coating agent are within the above ranges, the storage stability of the etching resist film-forming coating agent and the workability when applying it to grain-oriented electrical steel sheets are good.

[0054] (8) Other ingredients In a preferred embodiment, the etching resist film forming coating agent according to the present invention further contains one or more selected from surfactants, rust inhibitors, lubricants, leveling agents, neutralizing agents, defoaming agents, antioxidants, and coloring pigments in a solvent. These components are added to further improve the performance and uniformity of the etching resist film. These other components can be used alone or in combination of two or more. The performance of the etching resist film can be sufficiently maintained if the total amount of solids of these other components is 20% by mass or less of the total solids.

[0055] <Method for manufacturing a coating agent for forming an etching resist film> Next, a method for producing an etching resist film-forming coating agent according to the present invention will be described. The method for producing an etching resist film-forming coating agent is not particularly limited, but the following procedure is preferred. First, a portion of the solution containing an aqueous alkyd resin is added to a reaction vessel equipped with a stirrer, thermometer, reflux condenser, etc., and aluminum-containing oxide, titanium-containing oxide, carbon black, and, if necessary, a hydrophilic solvent are added and uniformly dispersed. Next, the remaining portion of the solution containing the aqueous alkyd resin and melamine resin are added and dispersed to obtain a dispersion. A leveling agent, neutralizing agent, defoaming agent, and solvent or water are added to the obtained dispersion as necessary to obtain an etching resist film-forming coating agent.

[0056] <Method for manufacturing steel sheets with etching resist coating> Next, a preferred manufacturing method for producing an etching resist-coated steel sheet using the etching resist-forming coating agent according to the present invention will be described. However, the manufacturing method for an etching resist-coated steel sheet using the etching resist-forming coating agent according to the present invention is not limited to the manufacturing method described herein.

[0057] (1) Steel plate First, a steel sheet is prepared to which the etching resist coating agent is to be applied. The steel sheet to which the etching resist coating agent is to be applied is a steel sheet that will ultimately become a grain-oriented electrical steel sheet, and is one of the steel sheets that has been hot-rolled. Grain-oriented electrical steel sheets are generally manufactured in the following way: a steel slab is hot-rolled to make a hot-rolled steel sheet, then the hot-rolled steel sheet, or a hot-rolled annealed sheet obtained by hot-rolling the hot-rolled steel sheet, is cold-rolled once or two or more times with an intermediate annealing in between to make a cold-rolled steel sheet, then the cold-rolled steel sheet is subjected to primary recrystallization annealing to make a primary recrystallized sheet, and then the primary recrystallized sheet is subjected to secondary recrystallization annealing to obtain a secondary recrystallized sheet.

[0058] When manufacturing grain-oriented electrical steel sheets using steel sheets with an etching resist coating, the components and composition of the final grain-oriented electrical steel sheet are not particularly limited. The thickness of the grain-oriented electrical steel sheet is also not particularly limited. Thinning the steel sheet reduces iron loss, but if it is too thin, the shape stability deteriorates and the manufacturing cost of the steel sheet increases. Therefore, it is preferable that the thickness of the grain-oriented electrical steel sheet be 50 μm or more. Furthermore, as the sheet thickness increases, iron loss increases accordingly. Therefore, it is preferable that the thickness of the grain-oriented electrical steel sheet be 0.50 mm or less, and more preferably 0.30 mm or less.

[0059] In the present invention, there are two types of steel sheets to which the etching resist film-forming coating agent is applied. One is a grain-oriented electrical steel sheet, which is a finished product obtained by completing all the processes up to the secondary recrystallization annealing described above. The other is a steel sheet that is an intermediate product in the process of manufacturing grain-oriented electrical steel sheets. Specific examples of the latter include hot-rolled steel sheets after hot rolling, hot-rolled annealed steel sheets obtained by hot-rolling steel sheets, cold-rolled steel sheets after cold rolling when cold rolling is performed once, cold-rolled steel sheets before or after intermediate annealing or cold-rolled steel sheets after intermediate annealing when cold rolling is performed two or more times with intermediate annealing in between, primary recrystallized steel sheets after primary recrystallization annealing, etc. In the present invention, the steel sheets to which the etching resist film-forming coating agent is applied are collectively referred to as "steel sheets," regardless of whether they are the finished products or intermediate products described above.

[0060] In the present invention, the steel sheet to which the etching resist film-forming coating agent is applied and the etching process is performed may be either the finished product or the intermediate product as described above. However, if the intermediate product is subjected to etching to form grooves on the surface of the steel sheet and then further rolling is performed, the grooves formed by the etching process may disappear. For this reason, when using an intermediate product, it is preferable to use a cold-rolled steel sheet or a primary recrystallized sheet after all cold rolling has been completed.

[0061] In the present invention, the etching resist film formed on the surface of the steel sheet may burn out or deteriorate under the high temperatures during heat treatment of the steel sheet. Therefore, when the above-mentioned intermediate product is used as the steel sheet to which the etching resist film forming agent is applied, it is preferable to perform the application of the etching resist film forming agent, followed by the baking treatment, laser irradiation treatment, and etching treatment in succession, and then carry out the subsequent heat treatment processes. The number of times these series of processes for forming grooves on the surface of the steel sheet are performed may be once or two or more times.

[0062] (2) Application of coating agent for forming etching resist film Next, the etching resist film-forming coating agent according to the present invention is uniformly applied to the surface of the steel plate. The method of applying the etching resist film-forming coating agent is not particularly limited, but it can be applied by methods such as roll coating, flow coating, knife coating, or spray coating. The surface to which the etching resist film-forming coating agent is applied may be one surface of the steel material or both surfaces of the steel material.

[0063] (3) Baking treatment of coating agent for etching resist film formation Next, the steel plate coated with the etching resist film-forming agent is subjected to a baking treatment. The method of baking treatment is not particularly limited, and baking treatments using commonly practiced methods such as hot air, infrared heating, and induction heating can be applied.

[0064] The temperature during the baking process of a steel sheet coated with the etching resist film-forming coating agent according to the present invention is preferably 120°C or higher and 350°C or lower at its maximum achievable steel sheet temperature. In this specification, "maximum achievable steel sheet temperature" refers to the temperature measured on the surface of the steel sheet and is the highest temperature reached during the heat treatment process. If the maximum achievable steel sheet temperature is 120°C or higher, the hardening of the etching resist film-forming coating agent proceeds sufficiently. The maximum achievable steel sheet temperature is more preferably 150°C or higher, and even more preferably 170°C or higher. If the maximum achievable steel sheet temperature is 350°C or lower, thermal decomposition of the etching resist film can be prevented. The maximum achievable steel sheet temperature is more preferably 300°C or lower, and even more preferably 260°C or lower.

[0065] The baking time in the baking process, that is, the time from the start of heating until the maximum steel sheet temperature is reached, is not particularly limited. However, from the viewpoint of sufficiently volatilizing the solvent component in the coating agent for forming the etching resist film and forming the film, it is preferable that the baking time be 3 seconds or more. On the other hand, when the baking process is performed by induction heating, it is preferable to set the baking time to 30 seconds or less from the viewpoint of suppressing the occurrence of cell-shaped film component unevenness called Bénard cells. Furthermore, when the baking process is performed by a method other than induction heating, it is preferable to set the baking time to 60 seconds or less from the viewpoint of productivity.

[0066] The amount of etching resist coating applied per side is 0.50 g / m². 2 The above is preferable. The amount of etching resist film attached is 0.50 g / m². 2 By doing so, it is possible to provide a steel sheet with an etching resist coating that has particularly excellent resist properties. The amount of etching resist coating attached to one side is 3.0 g / m². 2 It is more preferable to have the above. Also, the amount of etching resist film attached to one side should be 20 g / m². 2 The following is preferable: The amount of etching resist film to be attached is 20 g / m². 2By doing the following, deterioration of the coating's adhesion and increased costs can be prevented. The amount of etching resist coating attached to each side can be determined by dissolving and removing only the etching resist coating from the steel sheet with the etching resist coating after baking using a hot alkali, and measuring the change in the weight of the steel sheet before and after removal.

[0067] (4) Laser irradiation Next, the laser is scanned in a direction intersecting the rolling direction of the steel sheet, and the surface of the steel sheet coated with the etching resist film is irradiated with the laser. This laser irradiation locally heats and removes the etching resist film in the irradiated area, resulting in the formation of a coating removal area where the surface of the steel sheet is exposed. The coating removal area is selectively etched in the etching process described later, forming linear grooves on the surface of the steel sheet. The arrangement and dimensions of the linear grooves formed by etching affect the final magnetic properties of the grain-oriented electrical steel sheet. Therefore, the pattern of the etching resist film, i.e., the arrangement and dimensions of the coating removal area, should be determined considering the magnetic properties of the grain-oriented electrical steel sheet.

[0068] The linear coating removal section is provided in a direction intersecting the rolling direction, and the angle between the rolling direction and the direction in which the linear coating removal section is provided is preferably 50° or more, more preferably 60° or more, and most preferably 90°. The coating removal section may be provided linearly and continuously, or it may be provided discontinuously. The spacing between the coating removal section may be equal or not. The width of the coating removal section can be, for example, 0.20 mm.

[0069] In the laser irradiation process, laser scanning is preferably performed periodically in the rolling direction of the steel sheet. In this case, the spacing between the linear coating removal sections in the rolling direction of the steel sheet is preferably 1.0 mm or more and 30 mm or less. Any laser can be used as the laser light source, as long as it is capable of removing the etching resist coating, but from the viewpoint of output, it is preferable to use a solid-state laser such as a fiber laser or a CO2 laser. The laser output, irradiation energy per unit scanning length, scanning speed, beam diameter, and beam length-short axis ratio should be determined considering the shape of the coating removal section, productivity, and cost.

[0070] (5) Etching process Next, the steel plate with the etching resist coating after laser irradiation is etched to form grooves on the surface of the steel plate in the areas where the coating has been removed. By forming etched grooves on the surface of the steel plate, the width of the magnetic domains is narrowed, and iron loss is reduced. The etching method is not particularly limited, but for example, electrolytic etching can be used. When electrolytic etching is performed, it is preferable to use NaCl, KCl, CaCl2, NaNO3, etc. as the electrolyte, and the current density is 5 to 50 A / dm 2 The degree of electrolysis and the electrolysis time are preferably set to about 5 to 20 seconds. The conditions for the etching process described above are preferably adjusted so that, in a cross section perpendicular to the direction of extension of the groove formed by the etching process, the angle between the side wall of the groove and the plate thickness direction is 60 degrees or less, and the height of the protrusion formed at the bottom of the groove is 1 / 2 or less of the maximum depth of the groove. By adjusting the shape of the groove in this way, the effect of reducing iron loss is increased. The depth of the groove can be, for example, 20 μm.

[0071] In the method for manufacturing grain-oriented electrical steel sheets, after etching, the remaining processing necessary to convert the steel sheet into grain-oriented electrical steel sheets is appropriately performed according to the processing stage of the steel sheet in the grain-oriented electrical steel sheet manufacturing process described above, thereby enabling the production of grain-oriented electrical steel sheets with reduced iron loss.

[0072] In a method for manufacturing grain-oriented electrical steel sheets, the etching resist coating remains on the steel sheet after grooves have been formed by etching. This etching resist coating may or may not be removed after etching. If the etching resist coating is not removed, it can also function as an insulating tension coating. When removing the etching resist coating, the method of removal is not particularly limited and any well-known method can be used. As a method for removing the etching resist coating, for example, one can employ a method in which the steel sheet is immersed in an alkaline solution such as an aqueous NaOH solution to soften the etching resist coating, and then the etching resist coating is washed away using a brush. [Examples]

[0073] The effects of the present invention will be described in detail below based on examples, but the present invention is not limited to these examples.

[0074] Example 1 (1) Manufacturing of coatings for forming etching resist films As starting materials, the resins, melamine resin, aluminum-containing oxides, titanium-containing oxides, carbon black, and other components shown in Table 1 were prepared. Of the starting materials shown in Table 1, the aqueous alkyd resin indicated by symbol a1 was manufactured by the method described later. For the other starting materials, those from the manufacturers and trade names shown in Table 1 were used.

[0075] [Table 1]

[0076] The aqueous alkyd resin indicated by symbol a1 in Table 1 was produced by the method described below. First, 75 parts by mass of linseed oil, 16 parts by mass of glycerin, 40 parts by mass of phthalic anhydride, 1 part by mass of maleic anhydride, 20 parts by mass of pentaerythritol, and 5 parts by mass of xylene were added to a reaction vessel equipped with a stirrer, thermometer, reflux condenser, dehydration device, and nitrogen gas inlet pipe. The mixture was heated and stirred under a nitrogen atmosphere until the temperature reached 220°C, and the reaction was carried out until the acid value of the solids in the mixture reached 8 mg KOH / g, after which it was cooled. The acid value of the solids was measured in accordance with Japanese Industrial Standard JIS K 0070. Next, 72 parts by mass of ethylene glycol mono-n-butyl ether was added to the resulting reaction mixture as a solvent and mixed to obtain a solution of alkyd resin with an oil length of 55%, an acid value of 8 mgKOH / g, a hydroxyl value of 120 mgKOH / g, a heating residue of 65%, a number average molecular weight of 3200, and a weight average molecular weight of 19500.

[0077] Next, 150 parts by mass of the obtained alkyd resin solution was placed in a reaction vessel equipped with a stirrer, thermometer, reflux condenser, etc., and stirred while heating. Once the solution temperature reached 110°C, a mixture obtained by pre-mixing 16 parts by mass of styrene, 16 parts by mass of methyl methacrylate, 4 parts by mass of acrylic acid, and 1 part by mass of dibenzoyl peroxide as a polymerization initiator was added dropwise over 4 hours to carry out the dehydration condensation reaction. After the dropwise addition was complete, while maintaining the reaction mixture at 110°C, a mixture of 0.5 parts by mass of dibenzoyl peroxide and 5 parts by mass of ethylene glycol mono-n-butyl ether as a polymerization initiator was added dropwise over 3 hours, and the reaction was continued by stirring at 110°C for 2 hours, after which it was cooled. Next, 14 parts by mass of triethylamine was added to the resulting reaction mixture and stirred. Then, 5 parts by mass of ethylene glycol mono-n-butyl ether was added and mixed to obtain a solution (symbol a1 in Table 1) containing an aqueous alkyd resin with an oil length of 38, an acid value of 56 mgKOH / g, a hydroxyl value of 84 mgKOH / g, a heating residue of 65%, a number average molecular weight of 3200, and a weight average molecular weight of 25700.

[0078] Next, the starting materials shown in Table 1 were mixed according to the following procedure to prepare an etching resist film-forming coating agent having the components and solid content shown in Table 2. First, a portion of the resin-containing solution was placed in a disperser, and aluminum-containing oxide, titanium-containing oxide, carbon black, an organic pigment (f1 or f2) from among the other components, and ethylene glycol mono-n-butyl ether as a solvent in an amount of 10% by mass of the total were added and uniformly dispersed. The particle size of components other than the resin or solvent was confirmed to be 10 μm or less using a particle gauge. Next, the remaining resin and melamine resin were added and dispersed to obtain a dispersion. Furthermore, in order to improve film-forming properties, a surfactant (f3 or f4) from among the other components was added in an amount of 0.5% by mass of the total to the obtained dispersion. Furthermore, triethylamine was added as a neutralizing agent and ethylene glycol mono-n-butyl ether as a solvent to adjust the pH of the etching resist film-forming coating agent to 9.0 and the proportion of total solids in the etching resist film-forming coating agent to 63.0% by mass.

[0079] Table 2 shows the components and solid content of etching resist forming coatings No. 1 to 33, each with a different component composition. In Table 2, the mass percentages indicate the proportion of each component's solid content to the total solid content. The parts by mass percentages indicate the proportion of other components relative to 100 parts by mass of the resin (symbol a1, a2, or a3). Note that for comparative example No. 33 among the etching resist forming coatings shown in Table 2, a water-based epoxy resin (symbol a3) is used instead of a water-based alkyd resin.

[0080] [Table 2]

[0081] (2) Manufacturing of steel sheets with etching resist coating A steel sheet measuring 150 mm in width and 300 mm in length was cut from a grain-oriented electrical steel sheet with a thickness of 0.23 mm and used as the test material. The etching resist coating agent, manufactured by the method described above, was uniformly applied to the entire surface of one side of this test material using a roll coater. Next, the test material coated with the etching resist coating agent was baked in a hot air furnace at the maximum steel sheet temperature and drying time shown in Table 3, and then allowed to cool to room temperature to obtain a steel sheet with an etching resist coating.

[0082] Next, the etching resist coated steel sheets No. 1 to 33, manufactured by the above method, were evaluated for their properties using the following method. The evaluation results are shown in Table 3.

[0083] [Table 3]

[0084] <Amount of adhesion> The amount of etching resist film deposited after baking was measured by gravimetric method. Specifically, the etching resist film was dissolved and removed from the test material using a heated potassium hydroxide solution, and the weight change of the steel plate before and after dissolution and removal was measured. The amount of deposited film was determined by dividing the measured weight change by the area of ​​one side of the test material.

[0085] <Adhesion> The test material was cut to a size of 30 mm in width and 50 mm in length. A cellophane adhesive tape measuring 24 mm in width and 50 mm in length was applied to the surface of the cut test material where the etching resist film was formed (the test surface). Next, with the test surface as the compression side, the test material was bent 180° using a 5 mm diameter round bar. After that, the cellophane adhesive tape was peeled off, and the area ratio of the etching resist film that adhered to and peeled off the cellophane adhesive tape was calculated. The adhesion was evaluated according to the following criteria. An evaluation of A or B was considered a pass, and an F was considered a fail. (Evaluation Criteria) A: The area ratio is 5.0% or less. B: The area ratio is greater than 5.0% and less than or equal to 10%. F: Area ratio is greater than 10%

[0086] <Scratch resistance> Two pieces each of the test material were prepared, cut to a size of 100 mm in width and 200 mm in length. For each of the two test materials, the test surfaces on which the etching resist film was formed were placed together, and a pressure of 196 kPa (2 kgf / cm²) was applied in the direction normal to the test surface. 2 While applying pressure, the surface was slid in the longitudinal direction at a relative speed of 2 cm / s for 10 seconds. Next, the surface defects on the test surface were visually observed, and the defect area ratio was calculated. Scratch resistance was then evaluated according to the following criteria. An evaluation of A, B, or C was considered a pass, and an F was considered a fail. (Evaluation Criteria) A: Almost no defects were observed. B: Slight scuff marks are visible. C: Clear signs of abrasion are visible. F: Damage is present to the extent that the base metal is exposed.

[0087] <Laser Removability> The laser removal capability of etching resist coatings was evaluated as follows. First, a steel plate with an etching resist coating was irradiated with a laser. The output of the light source used for irradiation was 2.0 kW, the beam diameter was 50 μm, and the beam's long-short axis ratio was 1.02. The scanning speed was 10 m / s. These laser irradiation conditions were set with the goal of achieving a coating removal width of approximately 40 μm. Next, the width of the coating removal area after laser irradiation was measured using an optical microscope and evaluated according to the following criteria. An evaluation of A or B was considered a pass, and an F was considered a fail. (Evaluation Criteria) A: The width of the coating removal area is in the range of 30 μm or more and 50 μm or less. B: The width of the coating removal area is in the range of 20 μm or more and 60 μm or less. F: The width of the coating removal area fluctuates beyond the range of 20 μm or more and 60 μm or less.

[0088] <Resistance Characteristics> The test material was cut to a size of 30 mm in width and 250 mm in length, and subjected to electrolytic etching. The resist properties were evaluated by visually observing the surface appearance of the etching resist film after electrolytic etching and calculating the area percentage of the discolored portion. A 20% NaCl aqueous solution was used as the electrolyte for electrolytic etching. The electrolytic etching conditions were an electrolyte temperature of 25°C and a current density of 8 A / dm². 2 The energizing time was set to 3 minutes. The resist characteristics were evaluated according to the following criteria. An evaluation of A or B was considered a pass, and an F was considered a fail. (Evaluation Criteria) A: The area percentage of the discolored portion is 0.0% or less. B: The area percentage of the discolored portion is greater than 0.0% and less than or equal to 5.0%. F: The area percentage of discolored areas is greater than 5.0%

[0089] <Removability> The etching resist coating was removed from the test material whose resist properties had been evaluated as described above by immersing it in a 15% sodium hydroxide aqueous solution at 50°C for 10 seconds, then removing it and washing it with water. The peelability was evaluated by visually observing the test surface of the test material after the etching resist coating had been removed and calculating the area percentage of the portion where the etching resist coating had been removed. The peelability was evaluated according to the following criteria. An evaluation of A or B was considered a pass, and an F was considered a fail. (Evaluation Criteria) A: The area ratio of the peeled portion is 100%. B: The area ratio of the peeled portion is 90% or more but less than 100%. F: The area ratio of the delaminate portion is less than 90%.

[0090] According to the evaluation results shown in Table 3, the etching resist film formed using the etching resist film forming coating agent according to the present invention passed the characteristic evaluation results for all evaluation items. On the other hand, test materials No. 24 to 32, in which the content of the etching resist film forming coating agent on a solid content basis did not meet the numerical range of content specified in the present invention, and test material No. 33, which used a water-based epoxy resin, failed the characteristic evaluation results for at least one evaluation item.

[0091] Example 2 Using the same method as in Example 1, the starting materials shown in Table 1 were mixed to prepare an etching resist film-forming coating agent having the components and solid content shown in Table 4. Similar to Example 1, the proportion of total solids in the etching resist film-forming coating agent was adjusted to 63.0% by mass at all levels. However, unlike in Example 1, the proportions of water-based alkyd resin and melamine resin in the etching resist film-forming coating agent were not fixed but adjusted to the proportions shown in Table 4. Table 4 shows the components and solid content of etching resist-forming coating agents No. 34 to 59 with different component compositions.

[0092] [Table 4]

[0093] Next, etching resist coated steel sheets were manufactured using the same method as in Example 1, and the characteristics of the manufactured etching resist coated steel sheets No. 34 to 59 were evaluated using the same method as in Example 1. However, a hot air furnace or induction heating furnace was used for the baking process. The evaluation results are shown in Table 5.

[0094] [Table 5]

[0095] According to the evaluation results shown in Table 5, the etching resist film formed using the etching resist film forming agent according to the present invention passed the characteristic evaluation results for all evaluation items.

Claims

1. In the solvent, in terms of solid content, 100 parts by mass of aqueous alkyd resin, 0.10 parts by mass or more and 30 parts by mass or less of melamine resin, Aluminum-containing oxide, 20 parts by mass or more and 200 parts by mass or less. 10 parts by mass or more and 100 parts by mass or less of titanium-containing oxide, and Carbon black: 0.10 parts by mass or more, and 5.0 parts by mass or less It contains, A coating agent for forming an etching resist film, wherein the total amount of solids of the aqueous alkyd resin, the melamine resin, the aluminum-containing oxide, the titanium-containing oxide, and the carbon black accounts for 80% by mass or more of the total solids.

2. The coating agent for forming an etching resist film according to claim 1, wherein the aqueous alkyd resin is an aqueous alkyd resin obtained by reacting an alkyd resin with a polymerizable vinyl monomer.

3. The etching resist film forming coating agent according to claim 1 or 2, wherein the proportion of the total solid content in the etching resist film forming coating agent is 10% by mass or more and 80% by mass or less.

4. The etching resist coating agent according to claim 1 or 2, wherein the solvent comprises ethylene glycol mono-n-butyl ether.

5. The coating agent for forming an etching resist film according to claim 3, wherein the solvent comprises ethylene glycol mono-n-butyl ether.

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