Grain-oriented electrical steel sheet with etching resist coating film and method for producing grain-oriented electrical steel sheet

Abstract

The present invention provides: a method for producing a grain-oriented electrical steel sheet having an etching resist coating film that is excellent in terms of resist characteristics and separability; and a grain-oriented electrical steel sheet with an etching resist coating film, which uses the above-described etching resist coating film. A method for producing a grain-oriented electrical steel sheet according to the present invention comprises: a step for applying a coating agent for forming an etching resist coating film to the surface of a specific steel sheet which is one selected from the group consisting of a hot-rolled steel sheet, a hot-rolled sheet annealed steel sheet, a cold-rolled steel sheet, a primary recrystallization annealed steel sheet, and a secondary recrystallization annealed steel sheet in such a manner that a plurality of non-coated regions, in which the coating agent for forming an etching resist coating film is not applied, are left linearly along a direction that intersects with the rolling direction of the specific steel sheet; a step for subsequently subjecting the specific steel sheet to a baking treatment so as to bake the coating agent for forming an etching resist coating film, thereby forming an etching resist coating film; and a step for subsequently subjecting the specific steel sheet to an etching treatment so as to form a groove in the surface of the specific steel sheet in each of the non-coated regions. The surface insulation resistance coefficient of the etching resist coating film is 20 Ω∙cm2 / sheet or more, and the pencil hardness of the etching resist coating film is H or more and 8H or less.

Description

Grain-oriented electrical steel sheet with etching resist coating and method for manufacturing grain-oriented electrical steel sheet

[0001] The present invention relates to a grain-oriented electrical steel sheet with an etching resist coating and a method for manufacturing the grain-oriented electrical steel sheet.

[0002] Grain-oriented electrical steel sheets have excellent magnetic properties and are primarily used as materials for the iron cores of transformers. To improve the energy efficiency of transformers, it is necessary to reduce the iron loss of grain-oriented electrical steel sheets. One known method for reducing the iron loss of grain-oriented electrical steel sheets is to introduce linear grooves into the surface of the grain-oriented electrical steel sheet. In this method, the width of the magnetic domains is subdivided by forming linear grooves on the surface of the grain-oriented electrical steel sheet, thereby reducing iron loss.

[0003] One known method for forming linear grooves on the surface of a grain-oriented electrical steel sheet is an etching treatment using an etching resist film. For example, Patent Document 1 describes a method for forming linear grooves on the surface of a grain-oriented electrical steel sheet by applying a coating agent for forming an etching resist film to the surface of the grain-oriented electrical steel sheet while leaving continuous or discontinuous linear regions in a direction intersecting the rolling direction as non-coated regions, baking the coating, and then etching the sheet. Patent Document 2 describes a method for forming linear grooves on the surface of a grain-oriented electrical steel sheet by wrapping a cold-rolled sheet, which is not necessarily flat, around a roll surface and applying a coating agent for forming an etching resist film while correcting the shape of the cold-rolled sheet, thereby leaving the non-coated regions correctly and reducing the variation in the shape of the linear grooves formed by the etching treatment.

[0004] JP-A-4-88121 JP-A-6-108300

[0005] As a result of independent investigations, the inventors have 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 conventional techniques. Specifically, when electrolytic etching is performed using an etching resist film according to the conventional technique, a part of the surface of the etching resist film may discolor, causing a change in appearance. The change in color tone of the etching resist film suggests a decrease in the resistance of the etching resist film to the electrolytic etching solution (hereinafter sometimes referred to as "resist properties").

[0006] Furthermore, in the prior art, when an etching resist film that is no longer needed after etching is stripped off using a strong alkaline aqueous solution, there are cases where part of the etching resist film does not peel off and remains on the surface of the grain-oriented electrical steel sheet. The remaining etching resist film suggests that the ease of removal of the etching resist film (hereinafter sometimes referred to as "separability") is poor.

[0007] The present invention has been made in view of the above-mentioned problems associated with the prior art, and aims to provide a method for producing a grain-oriented electrical steel sheet using an etching resist coating that has excellent resist properties and releasability, and a grain-oriented electrical steel sheet with an etching resist coating.

[0008] The gist and configuration of the present invention are as follows.

[0009] [1] A method for producing a grain-oriented electrical steel sheet, comprising the steps of: hot rolling a steel slab to obtain a hot-rolled steel sheet; an optional step of hot-rolling the hot-rolled steel sheet to obtain a hot-rolled annealed steel sheet; cold rolling the hot-rolled steel sheet or the hot-rolled annealed steel sheet once or two or more times with intermediate annealing therebetween to obtain a cold-rolled steel sheet; primary recrystallization annealing the cold-rolled steel sheet to obtain a primary recrystallization annealed steel sheet; and secondary recrystallization annealing the primary recrystallization annealed steel sheet to obtain a secondary recrystallization annealed steel sheet, the specific steel sheet is one selected from the group consisting of the hot-rolled steel sheet, the hot-rolled annealed steel sheet, the cold-rolled steel sheet, the primary recrystallization annealed steel sheet, and the secondary recrystallization annealed steel sheet, and in so doing, leaves a plurality of non-coated regions where the coating agent for forming an etching resist film is not applied linearly along a direction intersecting the rolling direction of the specific steel sheet; thereafter, a baking process is performed on the specific steel sheet to bake the coating agent for forming an etching resist film to form an etching resist film; and thereafter, an etching process is performed on the specific steel sheet to form grooves on the surface of the specific steel sheet in the non-coated regions, and the surface insulation resistance coefficient of the etching resist film is 20 Ω cm ２ / sheet or more, and the pencil hardness of the etching resist film is H or more and 8H or less.

[0010] [2] The method for producing a grain-oriented electrical steel sheet according to the above [1], further comprising the step of removing the etching resist film after the etching treatment.

[0011] [3] A grain-oriented electrical steel sheet, an etching resist film formed on at least one surface of the grain-oriented electrical steel sheet, a plurality of non-coated areas where the etching resist film is not coated and arranged linearly along a direction intersecting the rolling direction of the grain-oriented electrical steel sheet, and grooves formed on the surface of the grain-oriented electrical steel sheet in the non-coated areas, wherein the surface insulation resistance coefficient of the etching resist film is 20 Ω cm ２ / sheet or more, and the pencil hardness of the etching resist film is H or more and 8H or less.

[0012] According to the present invention, it is possible to provide a method for producing a grain-oriented electrical steel sheet using an etching resist film that has excellent resist properties and releasability, and a grain-oriented electrical steel sheet with an etching resist film.

[0013] 1 is a perspective view showing an etching resist coated grain-oriented electrical steel sheet according to the present invention. FIG.

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

[0015] <Grain-oriented electrical steel sheet with etching resist film> In one embodiment, the present invention provides a grain-oriented electrical steel sheet, an etching resist film formed on at least one surface of the grain-oriented electrical steel sheet, a plurality of non-coated regions where the etching resist film is not applied and which are provided linearly along a direction intersecting the rolling direction of the grain-oriented electrical steel sheet, and grooves formed on the surface of the grain-oriented electrical steel sheet in the non-coated regions, wherein the surface insulation resistance coefficient of the etching resist film is 20 Ω cm ２ The present invention relates to a grain-oriented electrical steel sheet with an etching resist film, wherein the number of sheets is at least one and the pencil hardness of the etching resist film is from H to 8H.

[0016] FIG. 1 is a perspective view showing a grain-oriented electrical steel sheet with an etching resist film according to this embodiment. As shown in FIG. 1 , the grain-oriented electrical steel sheet with an etching resist film 1 according to this embodiment includes a grain-oriented electrical steel sheet 2 and an etching resist film 3 formed on at least one surface of the grain-oriented electrical steel sheet 2. In this embodiment, the "etching resist film" refers to a solid film formed on the surface of the grain-oriented electrical steel sheet by applying a coating agent for forming an etching resist film to the surface of the grain-oriented electrical steel sheet and baking the coated surface at a predetermined temperature for a predetermined time to evaporate the solvent and cause a cross-linking reaction. As will be described later, in the etching process, the area protected by the etching resist film 3 prevents contact between the surface of the grain-oriented electrical steel sheet 2 and the etching solution, preventing corrosion of the grain-oriented electrical steel sheet 2. Note that, although the etching resist film 3 is formed on one surface of the grain-oriented electrical steel sheet 2 in FIG. 1 , the etching resist film 3 may be formed on both surfaces of the grain-oriented electrical steel sheet 2.

[0017] As shown in FIG. 1 , the grain-oriented electrical steel sheet 1 with an etching resist coating according to this embodiment has a plurality of linear non-coated regions 4 that are not coated with the etching resist coating and that are arranged in a direction intersecting the rolling direction of the grain-oriented electrical steel sheet 2. In this embodiment, the linear non-coated regions 4 are arranged not parallel to the rolling direction but intersecting each other. In FIG. 1 , the rolling direction of the grain-oriented electrical steel sheet 2 is the left-right direction in the figure. The angle between the rolling direction and the direction in which the linear non-coated regions 4 are arranged is preferably 50° or more, more preferably 60° or more, and most preferably 90°, as shown in FIG. 1 . When the angle between the two is 90°, the effect of subdividing the magnetic domain width and the effect of reducing iron loss due to the formation of grooves are maximized. The non-coated regions 4 may be arranged linearly and continuously as shown in FIG. 1 , or may be arranged discontinuously. The spacing between the non-coated regions 4 may be equal to or not equal to the spacing shown in FIG. 1 .

[0018] As shown in Figure 1, the grain-oriented electrical steel sheet 1 with an etching resist coating according to this embodiment has grooves 2a formed on the surface of the grain-oriented electrical steel sheet 2 in the non-coated regions 4. By immersing the grain-oriented electrical steel sheet 1 with an etching resist coating in an etching treatment liquid and bringing the etching treatment liquid into contact with the surface of the grain-oriented electrical steel sheet 2 exposed in the non-coated regions 4, the surface of the grain-oriented electrical steel sheet 2 is corroded into the shape of the non-coated regions 4, and the grooves 2a are formed. When the etching resist coating 3 and the non-coated regions 4 are provided on both sides of the grain-oriented electrical steel sheet 2, the grooves 2a are also formed on both sides of the grain-oriented electrical steel sheet 2. The cross-sectional size of the grooves 2a in the grain-oriented electrical steel sheet 1 with an etching resist coating according to this embodiment can be, for example, 0.20 mm in width and 20 µm in depth.

[0019] (Surface Insulation Resistance Coefficient) In the grain-oriented electrical steel sheet 1 with an etching resist film according to this embodiment, the surface insulation resistance coefficient of the etching resist film 3 is 20 Ω·cm ２ / sheet or more. In this specification, the "surface insulation resistance coefficient" refers to the value obtained by measuring the electrical resistance between a contact electrode in contact with the surface of the etching resist film 3 on one surface of the etching-resist-coated grain-oriented electrical steel sheet 1 and an earth electrode electrically connected to the etching-resist-coated grain-oriented electrical steel sheet 1, which is the substrate, and dividing the measured electrical resistance value by the contact area of ​​the contact electrode. The surface insulation resistance coefficient calculated in this way is equal to the electrical resistance per unit area of ​​the etching resist film 3.

[0020] The surface insulation resistance coefficient is preferably measured in accordance with Japanese Industrial Standard JIS C 2550-4 or a similar standard established by the International Electrotechnical Commission, IEC 60404-11. The presence or absence of grooves 2a does not significantly affect the value of the surface insulation resistance coefficient. Therefore, the surface insulation resistance coefficient may be measured using either an etched resist-coated grain-oriented electrical steel sheet 1 with grooves 2a formed therein, or an etched resist-coated grain-oriented electrical steel sheet 1 before the grooves 2a are formed. When calculating the contact area of ​​the contact electrode in measuring the surface insulation resistance coefficient, it is advisable to ignore the area of ​​the uncoated region 4 of the contact area where the etched resist film 3 is not applied.

[0021] When the etching process for forming the grooves 2a is performed by electrolytic etching, the surface insulation resistance coefficient of the etching resist film 3 is a good indicator of the resistance of the etching resist film 3 to the electrolytic etching solution, i.e., the resist characteristics. ２ An etching resist film 3 having a surface insulation resistance coefficient of 50 Ω cm or more has high resist properties. When electrolytic etching is performed using such an etching resist film 3, the etching resist film 3 does not deteriorate during the electrolytic etching. Therefore, the current value during electrolytic etching is stable, and grooves 2a having a shape that faithfully reflects the contour shape of the non-coated region 4 can be formed. The surface insulation resistance coefficient of the etching resist film 3 is 50 Ω cm ２ The upper limit of the surface insulation resistance coefficient is not particularly limited, but is preferably 200 Ω cm ２ / sheet or less.

[0022] (Pencil Hardness) In the etching-resist coated grain-oriented electrical steel sheet 1 according to this embodiment, the pencil hardness of the etching-resist coating 3 is H or more and 8H or less. In this specification, "pencil hardness" refers to the hardness of the hardest pencil that did not produce any scratches when a test was conducted in which a pencil of known hardness was pressed against the etching-resist coating 3 and moved, and the resulting scratches were observed. The pencil hardness is preferably measured in accordance with Japanese Industrial Standard JIS K 5600-5-4 or ISO 15184, an ISO standard established by the International Organization for Standardization (ISO). Specifically, pencils with hardnesses ranging from H to 9H are prepared, and the cores of the pencils are pressed against the etching-resist coating 3 of the etching-resist coated grain-oriented electrical steel sheet 1 at an angle of 45° with a load of 750 g, scanning three times over a distance of 7 mm or more. The pencil scanning direction is preferably parallel to the direction of the linear non-coated regions 4. After the test, the surface of the etching resist film 3 is visually inspected, and the test is repeated with increasing hardness until at least two scratches of 3 mm or more appear. The hardness of the hardest pencil that did not cause scratches is then defined as the pencil hardness of the etching resist film 3. If scratches appear with a pencil with a hardness of H, the pencil hardness is defined as "less than H."

[0023] The pencil hardness of the etching resist film 3 is a good indicator of the scratch resistance of the etching resist film 3. If the pencil hardness of the etching resist film 3 is H or higher, it is possible to prevent scratches from being formed in the etching resist film 3 during the process from forming the etching resist film 3 on the surface of the grain-oriented electrical steel sheet 2 until the grain-oriented electrical steel sheet 1 with the etching resist film is subjected to an etching treatment. This prevents deterioration of the etching resist film 3 caused by scratches during the electrolytic etching process, thereby improving the resist characteristics. The pencil hardness of the etching resist film 3 is preferably 3H or higher. If the pencil hardness of the etching resist film 3 is 8H or lower, the adhesion of the etching resist film 3 to the grain-oriented electrical steel sheet 2 is improved.

[0024] <Method for manufacturing grain-oriented electrical steel sheet> In another embodiment, the present invention is a method for manufacturing grain-oriented electrical steel sheet, including a step of hot-rolling a steel slab to obtain a hot-rolled steel sheet, an optional step of hot-rolled annealing the hot-rolled steel sheet to obtain a hot-rolled annealed steel sheet, a step of cold-rolling the hot-rolled steel sheet or the hot-rolled annealed steel sheet once or two or more times with intermediate annealing therebetween to obtain a cold-rolled steel sheet, a step of primary recrystallization annealing the cold-rolled steel sheet to obtain a primary recrystallization annealed steel sheet, and a step of secondary recrystallization annealing the primary recrystallization annealed steel sheet to obtain a secondary recrystallization annealed steel sheet, a step of applying a coating agent for forming an etching resist film to the surface of a specific steel sheet selected from the group consisting of: a step of applying a coating agent for forming an etching resist film to the surface of the specific steel sheet, the coating agent being one selected from the group consisting of: a step of applying a coating agent for forming an etching resist film to the surface of the specific steel sheet, the coating agent being not applied in a linear manner along a direction intersecting with the rolling direction of the specific steel sheet, the step of leaving a plurality of non-coated regions in which the coating agent for forming an etching resist film is not applied; a step of subsequently baking the specific steel sheet to bake the coating agent for forming an etching resist film to form an etching resist film; and a step of subsequently etching the specific steel sheet to form grooves on the surface of the specific steel sheet in the non-coated regions, ２ The present invention relates to a method for producing a grain-oriented electrical steel sheet, wherein the number of sheets is at least one and the pencil hardness of the etching resist film is H or more and 8H or less.

[0025] (1) Specific Steel Sheet In the manufacturing method of a grain-oriented electrical steel sheet according to this embodiment, first, a steel sheet to which a coating agent for forming an etching resist film is applied is prepared. The steel sheet to which the coating agent for forming an etching resist film is applied is any steel sheet that will ultimately become a grain-oriented electrical steel sheet and has been hot-rolled. Grain-oriented electrical steel sheets are generally manufactured through the following steps: a step of hot-rolling a steel slab to obtain a hot-rolled steel sheet; an optional step of hot-rolling the hot-rolled steel sheet to obtain a hot-rolled annealed steel sheet; a step of cold-rolling the hot-rolled steel sheet or the hot-rolled annealed steel sheet once or twice or more times with intermediate annealing between them to obtain a cold-rolled steel sheet; a step of primary recrystallization annealing the cold-rolled steel sheet to obtain a primary recrystallization annealed steel sheet; and a step of secondary recrystallization annealing the primary recrystallization annealed steel sheet to obtain a secondary recrystallization annealed steel sheet.

[0026] When a grain-oriented electrical steel sheet is manufactured using a steel sheet 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. While thinner steel sheets reduce iron loss, excessively thin steel sheets not only deteriorate shape stability but also increase the manufacturing costs of the steel sheet. Therefore, the thickness of the grain-oriented electrical steel sheet is preferably 50 μm or more. Furthermore, as the sheet thickness increases, iron loss also increases. Therefore, the thickness of the grain-oriented electrical steel sheet is preferably 0.50 mm or less, and more preferably 0.30 mm or less.

[0027] In this embodiment, there are two types of steel sheets to which the coating agent for forming an etching resist film is applied. One is a secondary recrystallization annealed steel sheet obtained by completing all processes up to the secondary recrystallization annealing described above. The other is a steel sheet as an intermediate product in the manufacturing process of a grain-oriented electrical steel sheet. Specific examples of the latter include a hot-rolled steel sheet, a hot-rolled annealed steel sheet, a cold-rolled steel sheet, and a primary recrystallization annealed steel sheet. The hot-rolled steel sheet and the hot-rolled annealed steel sheet may include a steel sheet before or after intermediate annealing in the case where cold rolling is performed two or more times with intermediate annealing in between, but in which all cold rolling has not been completed.

[0028] In this embodiment, the target to be etched by applying the coating agent for forming an etching resist film is a specific steel sheet selected from the group consisting of a hot-rolled steel sheet, a hot-rolled annealed steel sheet, a cold-rolled steel sheet, a primary recrystallization annealed steel sheet, and a secondary recrystallization annealed steel sheet. However, if an intermediate product is etched to form grooves on the steel sheet surface and then further rolled, the grooves formed by the etching may disappear. For this reason, when an intermediate product other than a secondary recrystallization annealed steel sheet is selected as the specific steel sheet, it is preferable to select a cold-rolled steel sheet after all cold rolling has been completed (hereinafter sometimes referred to as a "final cold-rolled steel sheet") or a primary recrystallized steel sheet.

[0029] In this embodiment, the etching resist film formed on the surface of the specified steel sheet may be burned or altered at high temperatures during heat treatment of the specified steel sheet. Therefore, when the above-mentioned intermediate product is used as the specified steel sheet to which the coating agent for forming an etching resist film is applied, it is preferable to apply the coating agent for forming an etching resist film, followed by baking and etching treatments in succession, and then carry out the subsequent heat treatment steps. Note that the number of times this series of steps for forming grooves on the surface of the specified steel sheet is carried out may be one or more.

[0030] (2) Application of Coating Agent for Forming an Etching Resist Film In the method for producing a grain-oriented electrical steel sheet according to this embodiment, the coating agent for forming an etching resist film is applied to the surface of the specific steel sheet, leaving a plurality of non-coated regions where the coating agent for forming an etching resist film is not applied, which are linearly arranged along a direction intersecting the rolling direction of the specific steel sheet. The surface to which the coating agent for forming an etching resist film is applied may be one surface of the specific steel sheet or both surfaces of the specific steel sheet.

[0031] In this specification, the term "coating agent for forming an etching resist film" refers to a liquid coating agent containing a resin as a main component, which is used to form an etching resist film. Preferred components of the coating agent for forming an etching resist film used in this embodiment will be described later. The method for applying the coating agent for forming an etching resist film is not particularly limited. When gravure printing is used as a method for applying the coating agent for forming an etching resist film, as shown in FIG. 1, a coated region where an etching resist film 3 is formed and a non-coated region 4 where no etching resist film is applied can be formed simultaneously.

[0032] As described above, in this embodiment, the direction in which the linear non-coated regions 4 are provided is a direction intersecting the rolling direction, and the angle formed between the rolling direction and the direction in which the linear non-coated regions 4 are provided is preferably 50° or more, more preferably 60° or more, and most preferably 90° as shown in FIG. 1 . The non-coated regions 4 may be provided in a continuous linear manner as shown in FIG. 1 , or may be provided discontinuously. The intervals at which the non-coated regions 4 are provided may be equal intervals as shown in FIG. 1 , or may not be equal intervals. The width of the non-coated regions 4 may be, for example, 0.20 mm.

[0033] (3) Baking Treatment of Coating Agent for Forming Etching Resist Film In the method for producing a grain-oriented electrical steel sheet according to this embodiment, the specific steel sheet coated with the coating agent for forming an etching resist film is baked. The method for performing the baking treatment is not particularly limited, and commonly used baking treatments such as hot air, infrared heating, and induction heating can be applied.

[0034] In the manufacturing method of grain-oriented electrical steel sheet according to this embodiment, the baking temperature can be a temperature commonly used. The baking temperature is preferably a maximum steel sheet temperature of 120°C or higher and 350°C or lower. In this specification, the "maximum steel sheet temperature" refers to the temperature measured on the surface of the specific steel sheet and the maximum temperature reached in the heat treatment process. If the maximum steel sheet temperature is 120°C or higher, the curing of the coating agent for forming an etching resist film proceeds sufficiently. The maximum steel sheet temperature is more preferably 150°C or higher, and even more preferably 170°C or higher. If the maximum steel sheet temperature is 350°C or lower, thermal decomposition of the etching resist film can be prevented. The maximum steel sheet temperature is more preferably 300°C or lower, and even more preferably 260°C or lower. The baking time in the baking process, i.e., the time from the start of heating until the maximum steel sheet temperature is reached, is not particularly limited.

[0035] In the method for producing a grain-oriented electrical steel sheet according to this embodiment, the amount of etching resist film deposited on one side is 0.50 g / m ２The adhesion amount of the etching resist film is preferably 0.50 g / m or more. ２ By setting the above, it is possible to provide a specific steel sheet with an etching resist film having particularly excellent resist properties. ２ It is more preferable that the amount of the etching resist film deposited on one side is 20 g / m or more. ２ The deposition amount of the etching resist film is preferably 20 g / m or less. ２ The amount of etching resist film deposited on one side can be determined by dissolving and removing only the etching resist film from the specific steel sheet with the etching resist film after baking treatment using a hot alkali or the like, and measuring the change in weight of the specific steel sheet before and after removal.

[0036] (4) Etching Treatment In the method for producing a grain-oriented electrical steel sheet according to this embodiment, the special steel sheet on which the etching resist film has been formed is etched to form grooves on the surface of the special steel sheet in the non-coated areas. The etching method is not particularly limited, but may be, for example, electrolytic etching. When electrolytic etching is performed, the electrolyte may be NaCl, KCl, CaCl ２ , NaNO ３ It is preferable to use a current density of 5 to 50 A / dm ２ The electrolysis time is preferably about 5 to 20 seconds. The conditions of the etching process are preferably adjusted so that, in a cross section perpendicular to the extension direction of the groove formed by the etching process, the angle between the sidewall of the groove and the plate thickness direction is 60 degrees or less, and the height of the convex portion 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.

[0037] In the method for manufacturing a grain-oriented electrical steel sheet according to this embodiment, after the etching treatment, the remaining treatments required to convert the specific steel sheet into a grain-oriented electrical steel sheet are appropriately carried out depending on the treatment stage of the specific steel sheet in the manufacturing process of the grain-oriented electrical steel sheet described above, thereby making it possible to manufacture a grain-oriented electrical steel sheet with reduced iron loss.

[0038] In the method for producing a grain-oriented electrical steel sheet according to this embodiment, after grooves have been formed by etching, the etching resist film remains on the specific steel sheet coated with the etching resist film. This etching resist film may or may not be peeled off after the etching process. If the etching resist film is not peeled off, it can also function as an insulating tension film. When the etching resist film is to be removed, the method for the removal process is not particularly limited, and any known method can be used. For example, the etching resist film can be removed by immersing the specific steel sheet coated with the etching resist film in an alkaline solution such as an aqueous NaOH solution to soften the etching resist film, and then rinsing and removing the etching resist film with a brush.

[0039] (5) Surface Insulation Resistance Coefficient and Pencil Hardness In the method for producing a grain-oriented electrical steel sheet according to this embodiment, the surface insulation resistance coefficient of the etching resist film is 20 Ω cm ２ / sheet or more, and the pencil hardness of the etching resist film is H or more and 8H or less. The method for measuring the surface insulation resistance coefficient and pencil hardness of the etching resist film and the effects of controlling these values ​​within the ranges specified in the present invention have already been explained, so explanation will be omitted here. In order to control the surface insulation resistance coefficient and pencil hardness of the etching resist film within the above ranges, it is effective to control the adhesion amount of the etching resist film within the above ranges, as well as to adjust the components of the coating agent for forming the etching resist film used to form the etching resist film.

[0040] <Solid Content and Solid Content Equivalent> Before describing each component contained in the coating agent for forming an etching resist film used in this embodiment, we will explain how to label the components. In this specification, "solid content" refers to the remaining solid components contained in the coating agent for forming an etching resist film, excluding substances that are lost by evaporation, such as solvents and water. When the coating agent for forming an etching resist film is applied to the surface of a specific steel plate and baked, substances such as solvents and water evaporate, and an etching resist film is formed by the remaining solid content.

[0041] As used herein, the term "solids content equivalent" refers to the content of each component in a coating agent for forming an etching resist film being expressed based on the solid content of the component. As described below, the coating agent for forming an etching resist film used in this embodiment is synthesized by mixing an aqueous alkyd resin, a melamine resin, and an extender pigment in a solvent. The aqueous alkyd resin and melamine resin used in the synthesis may themselves contain a solvent. Furthermore, the volume pigment may adsorb moisture from the air. Therefore, when expressing the content of each component, it is appropriate to express the content in terms of solids content, rather than the mass ratio of the components actually mixed. Specifically, the mass of the solid content of the aqueous alkyd resin contained in the coating agent for forming an etching resist film is defined as 100 parts by mass, and the content is expressed in parts by mass of the solid content of the other components converted based on this.

[0042] The content of each component expressed in terms of solid content remains unchanged before and after application and baking of the coating agent for forming an etching resist film. Therefore, by quantitatively analyzing the components of the etching resist film after baking, the content of each component, calculated as solid content, contained in the coating agent for forming an etching resist film before baking can be determined.

[0043] <Components of Coating Agent for Forming Etching Resist Film> Next, the components contained in the coating agent for forming an etching resist film used in this embodiment will be described. (1) Water-based Alkyd Resin The coating agent for forming an etching resist film used in this embodiment preferably contains 100 parts by mass of water-based alkyd resin in terms of solid content in a solvent. As described above, the water-based alkyd resin is the main component of the coating agent for forming an etching resist film used in this embodiment, and also serves as the main component of the etching resist film after application and baking. Water-based resin is a general term for both water-dispersible resins in which the resin is uniformly dispersed in water, and water-soluble resins that are easily soluble in water.

[0044] As the aqueous alkyd resin, conventionally known ones can be used without any particular limitation. Alkyd resins, which are the raw materials for aqueous alkyd resins, can be obtained by subjecting a polybasic acid, a polyhydric alcohol, and a fat or oil or processed fat product to a dehydration condensation reaction, and optionally further reacting with a monobasic acid. In a preferred embodiment, the coating agent for forming an etching resist film is an aqueous alkyd resin obtained by reacting an alkyd resin with a polymerizable vinyl monomer. In this preferred embodiment, by using an aqueous alkyd resin obtained by reacting an alkyd resin with a polymerizable vinyl monomer, a coating agent for forming an etching resist film can be obtained that can form an etching resist film with excellent resist properties and removability.

[0045] (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, himic acid, itaconic acid, methylhexahydrophthalic acid, 1,4-cyclohexanedicarboxylic acid, methylcyclohexenetricarboxylic acid, pyromellitic acid, and anhydrides thereof. These polybasic acids can be used alone or in combination of two or more.

[0046] (Polyhydric Alcohols) 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, tricyclodecanedimethanol, etc. These polyhydric alcohols can be used alone or in combination of two or more.

[0047] (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, hygienic fatty acids, etc. Furthermore, processed oil products can be obtained using the above-mentioned oils and fats as the main raw material. Examples of such processed oil products include modified oils, isomerized oils, polymerized oils, maleated oils, boiled oils, etc., which are obtained using the above-mentioned oils and fats as the main raw material. These oils and fats and processed oil products can be used alone or in combination of two or more.

[0048] (Monobasic Acid) Examples of monobasic acids optionally used in the synthesis of alkyd resins include benzoic acid, p-t-butylbenzoic acid, methylbenzoic acid, versatic acid, isodecanoic acid, isotridecanoic acid, crotonic acid, non-drying oil fatty acids, etc. These monobasic acids can be used alone or in combination of two or more.

[0049] (Polymerizable vinyl monomer) In a preferred embodiment, as the polymerizable vinyl monomer to be reacted with the alkyd resin to obtain the aqueous alkyd resin, any conventionally known polymerizable vinyl monomer can be used without any particular limitation. 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 (meth)acrylate. N-alkoxy-substituted amide monomers such as diethyl(meth)acrylamide; fluorine-containing vinyl monomers such as perfluoroethylene, perfluoropropylene, and vinylidene fluoride; silicon-containing vinyl monomers such as vinyltrimethoxysilane and vinyltriethoxysilane; dialkyl esters of 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, maleic acid monomethyl ester, maleic acid monobutyl ester, itaconic acid monobutyl ester, sulfonic acid group-containing (meth)acrylates, phosphoric acid group-containing (meth)acrylates, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate;Lactone adducts of 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 ... Examples of the polymerizable vinyl monomer include N,N-methylethylaminoethyl (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-dimethylaminopropyl acrylamide, and N,N-diethylaminopropyl acrylamide. These polymerizable vinyl monomers can be used alone or in combination of two or more.

[0050] The aqueous alkyd resin may be commercially available or synthesized from raw materials. When using a commercially available product, it is preferable to use one synthesized using one of the compounds listed above as raw materials. When synthesizing an aqueous alkyd resin from raw materials, the following procedure is preferably used. First, a predetermined amount of polybasic acid, polyhydric alcohol, oil or fat or processed oil product, and optionally a monobasic acid are charged into 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 mgKOH / g, heating is stopped and the mixture is cooled. The acid value of the solids is preferably measured in accordance with Japanese Industrial Standard JIS K 0070. Next, a solvent is added to the resulting reaction mixture to form an alkyd resin solution. The alkyd resin solution is heated with stirring, and a previously prepared mixture of polymerizable vinyl monomer and polymerization initiator is added dropwise. After the dropwise addition is complete, the polymerization initiator is further added dropwise to the reaction mixture, and the mixture is stirred and allowed to react. Furthermore, a neutralizing agent and a solvent are added to the reaction mixture and mixed to obtain a solution containing a water-based alkyd resin.

[0051] The aqueous alkyd resin synthesized by the above procedure preferably has an acid value of 30 mgKOH / g or more and 80 mgKOH / g or less, a hydroxyl value of 50 mgKOH / g or more and 150 mgKOH / g or less, a number average molecular weight of 2,000 or more and 10,000 or less, and a weight average molecular weight of 10,000 or more and 50,000 or less.

[0052] The solvent used in synthesizing the water-based alkyd resin is not particularly limited. Preferred solvents include 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.

[0053] The polymerization initiator used in synthesizing the water-based alkyd resin is not particularly limited, but preferred examples of the polymerization initiator include dibenzoyl peroxide and 2,2'-azobisbutyronitrile.

[0054] The neutralizing agent used in synthesizing the water-based alkyd resin is not particularly limited, but preferred neutralizing agents include, for example, triethylamine and diethylethanolamine.

[0055] (2) Melamine Resin The coating agent for forming an etching resist used in this embodiment preferably contains 0.10 parts by mass or more and 30 parts by mass or less of a melamine resin in a solvent, calculated as solid content. The melamine resin is contained in the coating agent for forming an etching resist as a crosslinking agent that crosslinks the aqueous alkyd resin. The inclusion of the melamine resin improves adhesion between the etching resist film and the specified steel sheet. Examples of the melamine resin that can be used include methylated melamine and butylated melamine.

[0056] When the solvent contains 0.10 parts by mass or more of melamine resin per 100 parts by mass of the aqueous alkyd resin, calculated as solid content, the adhesion between the formed etching resist film and the specific steel plate is enhanced, and the resist properties and pencil hardness are improved. On the other hand, when the melamine resin is contained in an amount of 30 parts by mass or less, the crosslink 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 content of the melamine resin is set to 0.10 parts by mass or more and 30 parts by mass or less per 100 parts by mass of the aqueous alkyd resin, calculated as solid content. The content of the melamine resin is preferably 1.0 part by mass or more, and more preferably 2.0 parts by mass or more. The content of the melamine resin is preferably 20 parts by mass or less, and more preferably 15 parts by mass or less.

[0057] (3) Extender Pigment The coating agent for forming an etching resist film used in this embodiment preferably contains an extender pigment in an amount of 5.0 parts by mass or more and 100 parts by mass or less, calculated as solids, in the solvent. The extender pigment is contained in the coating agent for forming an etching resist film as a coating extender. Extender pigments are generally inexpensive and chemically stable, and therefore can be suitably used as an extender for an etching resist film. The type of extender pigment is not particularly limited, and various known extender pigments can be used. Preferred examples of extender pigments include calcium carbonate, barium sulfate, and aluminum hydroxide. These extender pigments can be used alone or in combination of two or more types.

[0058] When the solvent contains 5.0 parts by mass or more of the extender pigment per 100 parts by mass of the solids content of the aqueous alkyd resin, the thickness of the etching resist film can be easily ensured, and the resist properties are improved. On the other hand, when the extender pigment is contained in an amount of 100 parts by mass or less, the extender pigment concentration does not become excessive, and adhesion and resist properties do not deteriorate. Therefore, the content of the extender pigment is set to 5.0 parts by mass or more and 100 parts by mass or less per 100 parts by mass of the aqueous alkyd resin, calculated as solids content. The content of the extender pigment is preferably 6.0 parts by mass or more, and more preferably 10 parts by mass or more. The content of the extender pigment is preferably 80 parts by mass or less, and more preferably 50 parts by mass or less.

[0059] Since extender pigments are generally insulators, the higher the ratio of extender pigments contained in the etching resist film, the higher the surface insulation resistance coefficient, and the better the resist characteristics. In particular, when the adhesion amount of the etching resist film is small, by increasing the ratio of extender pigments contained in the etching resist film, the surface insulation resistance coefficient can be increased to 20 Ω cm. ２ Conversely, when the adhesion amount of the etching resist film is large, electrical resistance can be ensured by components other than the extender pigment, so that the surface insulation resistance coefficient can be controlled to 20 Ω cm or more without increasing the ratio of the extender pigment so much. ２ On the other hand, in relation to the pencil hardness, it is desirable not to make the ratio of the extender pigment contained in the etching resist film too high. This is because the higher the ratio of the extender pigment, the relatively lower the ratio of the water-based alkyd resin that binds the extender pigment, resulting in a decrease in pencil hardness.

[0060] (4) Total Solids Content In the coating agent for forming an etching resist film used in this embodiment, the total solid content of the aqueous alkyd resin, the melamine resin, and the extender pigment preferably accounts for 80% by mass or more of the total solids content. In this specification, "total solids content" refers to the total solid content of all components contained in the coating agent for forming an etching resist film. If the total solid content of the aqueous alkyd resin, the melamine resin, and the extender pigment accounts for 80% by mass or more, the components of the etching resist film formed by the coating agent for forming an etching resist film are not significantly diluted by other components described below. Therefore, the effects of the present invention exhibited by the etching resist film are not impaired. There is no particular upper limit on the total solid content of the aqueous alkyd resin, the melamine resin, and the extender pigment, and this total content may be 100% by mass or less.

[0061] (5) Solvent The coating agent for forming an etching resist film used in this embodiment preferably contains a water-based alkyd resin, a melamine resin, and an extender pigment in a solvent. The solvent functions to uniformly dissolve the resin and uniformly mix the pigment, and also facilitates application of the coating agent for forming an etching resist film. In addition, from the viewpoint of affinity with water, the solvent more preferably contains ethylene glycol mono-n-butyl ether.

[0062] The solvent can be used by mixing with a hydrophilic solvent. Specific examples of hydrophilic solvents include glycol ethers such as 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, as well as alcohols such as isopropyl alcohol and butyl alcohol. These solvents can be used alone or in combination of two or more.

[0063] The solvent may be mixed with a hydrophobic solvent such as toluene, xylene, etc. These hydrophobic solvents may be used alone or in combination of two or more.

[0064] The proportion of the solvent in the coating agent for forming an etching resist film is not particularly limited, but is preferably 20% by mass or more and 90% by mass or less. In other words, the proportion of the total solids in the coating agent for forming an etching resist film is preferably 10% by mass or more and 80% by mass or less. When the amounts of the solvent and total solids in the coating agent for forming an etching resist film are within the above ranges, the storage stability of the coating agent for forming an etching resist film and the workability when applying it to a specific steel sheet are good.

[0065] (6) Other Components The coating agent for forming an etching resist film used in a preferred embodiment further contains one or more selected from surfactants, rust inhibitors, lubricants, leveling agents, neutralizing agents, antifoaming agents, antioxidants, and coloring pigments in a solvent. These components are added to further improve the performance and uniform application of the etching resist film. These other components can be used alone or in combination of two or more. If the total amount of the solid content of these other components is 20 mass% or less of the total solid content, the performance of the etching resist can be sufficiently maintained.

[0066] <Method for Producing a Coating Agent for Forming an Etching Resist Film> The method for producing a coating agent for forming an etching resist film is not particularly limited, but preferably follows the procedure below. First, a portion of a solution containing an aqueous alkyd resin is placed in a reaction vessel equipped with a stirrer, thermometer, reflux condenser, etc., and an extender pigment and, if necessary, a hydrophilic solvent are added to uniformly disperse the resulting mixture. Next, the remainder of the solution containing the aqueous alkyd resin and a melamine resin are added and dispersed to obtain a dispersion. If necessary, a leveling agent, a neutralizing agent, an antifoaming agent, and water are added to the resulting dispersion to obtain a coating agent for forming an etching resist film.

[0067] The effects of the present invention will be specifically explained below based on examples, but the present invention is not limited to these examples.

[0068] (1) Production of a coating agent for forming an etching resist film As starting materials, the water-based alkyd resin, melamine resin, extender pigment, and other components shown in Table 1 were prepared. Of the starting materials shown in Table 1, the water-based alkyd resin was produced by the method described below. The other starting materials used were those of the manufacturers and trade names shown in Table 1.

[0069]

[0070] The waterborne alkyd resins shown in Table 1 were produced by the following method. 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 placed in a reaction vessel equipped with a stirrer, thermometer, reflux condenser, dehydrator, and nitrogen gas inlet tube. The mixture was stirred and heated under a nitrogen atmosphere until the temperature reached 220°C. The reaction was continued until the acid value of the solid content of the mixture reached 8 mgKOH / g, and then the mixture was cooled. The acid value of the solid content 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 as a solvent to the obtained reaction mixture and mixed to obtain an alkyd resin solution having 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 3,200, and a weight average molecular weight of 19,500.

[0071] Next, 150 parts by mass of the obtained alkyd resin solution was charged into a reaction vessel equipped with a stirrer, thermometer, reflux condenser, etc., and stirred while heating. Once the temperature of the solution 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 a dehydration condensation reaction. After completion of the dropwise addition, 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 further added dropwise over 3 hours, and the reaction was continued with stirring at 110°C for 2 hours, followed by cooling. Next, 14 parts by mass of triethylamine was added to the obtained reaction mixture and stirred, and then 5 parts by mass of ethylene glycol mono-n-butyl ether was added and mixed to obtain a solution containing an aqueous alkyd resin having 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 3,200, and a weight average molecular weight of 25,700.

[0072] Next, the starting materials listed in Table 1 were mixed according to the following procedure to prepare a coating agent for forming an etching resist film having the components and solids content shown in Table 2. First, a portion of the solution containing the aqueous alkyd resin was placed in a disperser, and the extender pigment, the organic pigment among the other components, and ethylene glycol mono-n-butyl ether (5% by mass of the total) as a solvent were added and uniformly dispersed. A particle gauge was used to confirm that the particle size of the extender pigment was 10 μm or less. Next, the remaining resin and melamine resin were added and dispersed to obtain a dispersion. Furthermore, to improve film-forming properties, a surfactant among the other components was added to the resulting dispersion in an amount of 0.5% by mass. Furthermore, triethylamine was added as a neutralizing agent and ethylene glycol mono-n-butyl ether was added as a solvent to adjust the pH of the coating agent for forming an etching resist film to 9.0 and the solids content to 60% by mass.

[0073] The components and solid content of the resulting etching resist-forming coating agents No. 1 to 22, which have different component compositions, are shown in Table 2. The content of each component shown in Table 2, expressed in mass %, is the proportion of the solid content of each component to the total solid content, i.e., the total amount of solid content of all components contained in the etching resist-forming coating agent. Furthermore, the content expressed in parts by mass is the mass part of the other component based on 100 parts by mass of the aqueous alkyd resin.

[0074]

[0075] (2) Production of Grain-Oriented Electrical Steel Sheet with Etching Resist Coating In the production process of grain-orientated electrical steel sheet, steel sheets with a width of 150 mm and a length of 300 mm were cut out from the final cold-rolled steel sheet with a thickness of 0.23 mm after all cold rolling was completed, the primary recrystallized steel sheet after primary recrystallization annealing, and the secondary recrystallization annealed steel sheet after secondary recrystallization annealing, and used as specific steel sheets. The coating agent for forming an etching resist film produced by the above method was uniformly applied to the entire surface of one side of this specific steel sheet using a roll coater. In this example, the coating agent for forming an etching resist film was uniformly applied to the specific steel sheet for the purpose of evaluating the etching resist film. However, as described above, when gravure printing is used as a method for applying the forming coating agent, coated and uncoated areas can be formed simultaneously.

[0076] The specific steel sheets coated with the coating agent for forming an etching resist film were then baked in a hot air baking oven at the maximum steel sheet temperature and for the drying time shown in Table 3, and then allowed to cool to room temperature. Next, grain-oriented electrical steel sheets with etching resist films were obtained by carrying out the unperformed manufacturing steps of the grain-oriented electrical steel sheets for the specific steel sheets No. 19 to 22, which used final cold-rolled steel sheets or primary recrystallization annealed steel sheets as the specific steel sheets.

[0077] Next, the properties of the grain-oriented electrical steel sheets with etching resist films Nos. 1 to 22 manufactured by the above method were evaluated by the following methods. The evaluation results are shown in Table 3.

[0078]

[0079] <Adhesion weight> The adhesion weight of the etching resist film after baking treatment was measured by gravimetric method. Specifically, using a heated potassium hydroxide solution, only the etching resist film was dissolved and removed from the specific steel plate with the etching resist film, and the weight change of the specific steel plate before and after dissolution and removal was measured. The adhesion weight was calculated by dividing the measured weight change by the area of ​​one side of the specific steel plate.

[0080] <Surface Insulation Resistance Coefficient> The surface insulation resistance coefficient of the grain-oriented electrical steel sheet with the etching resist coating was measured by the method specified in Japanese Industrial Standard JIS C 2550-4. The voltage between the contact electrodes was set to 0.5 V, and the pressure of the contact electrodes was set to 2 N / mm. ２ The surface insulation resistance coefficient was evaluated according to the following evaluation criteria. A rating of A or B was considered to be pass, and F was considered to be fail. (Evaluation criteria) A: 50 Ω·cm ２ / piece or more B: 20Ω・cm ２ / sheet or more, 50Ω・cm ２ / sheet or less F: 20 Ω cm ２ / less than

[0081] <Pencil Hardness> The pencil hardness of the etching resist film of the grain-oriented electrical steel sheet with an etching resist film was measured by the method specified in Japanese Industrial Standard JIS K 5600-5-4. Pencils (Uni, manufactured by Mitsubishi Pencil Co., Ltd.) with hardnesses ranging from H to 9H were prepared, and the pencil cores were pressed against the etching resist film 3 of the grain-oriented electrical steel sheet 1 with an etching resist film at an angle of 45° and a load of 750 g, scanning three times over a distance of 7 mm or more. After the test, the surface of the etching resist film 3 was visually inspected, and the test was repeated with increasing hardness until at least two scratches of 3 mm or more were formed. The hardness of the hardest pencil that did not cause any scratches was recorded as the pencil hardness of the etching resist film 3. When scratches were formed with a pencil with a hardness of H, the pencil hardness was recorded as "less than H."

[0082] <Adhesion> A grain-oriented electrical steel sheet with an etching resist film was cut into a size of 30 mm wide and 50 mm long, and a cellophane adhesive tape with a width of 24 mm and a length of 50 mm was attached to the surface (test surface) on which the etching resist film had been formed after cutting. Next, with the test surface as the compression side, the grain-oriented electrical steel sheet with the etching resist film was bent 180° using a round rod with a diameter of 5 mm, and then the cellophane adhesive tape was peeled off. The area ratio of the etching resist film that had adhered to the cellophane adhesive tape and peeled off was calculated, and the adhesion was evaluated according to the following criteria. A rating of A or B was considered pass, and F was considered fail. (Evaluation Criteria) A: Area ratio is 5.0% or less B: Area ratio is more than 5.0% and 10% or less F: Area ratio is more than 10%

[0083] <Scratch Resistance> Two pieces of each type of grain-oriented electrical steel sheet with an etching resist film were prepared by cutting into a size of 100 mm in width and 200 mm in length. For each of the two grain-oriented electrical steel sheets with an etching resist film, the test surfaces on which the etching resist film was formed were placed together, and a pressure of 196 kPa (2 kgf / cm) was applied in the direction normal to the test surfaces. ２ ) while applying a pressure of 1000 kJ / s, the specimen was slid lengthwise at a relative speed of 2 cm / s for 10 seconds. Next, scratches on the surface of the test surface were visually observed to calculate the scratch occurrence area ratio, and scratch resistance was evaluated according to the following criteria. A rating of A, B, or C was considered to be pass, and F was considered to be fail. (Evaluation criteria) A: Almost no scratches were observed B: Only a few scratches were observed C: Clear scratches were observed F: Scratches were observed to the extent that the base steel was exposed

[0084] <Resist Properties> The grain-oriented electrical steel sheet with the etching resist film was cut into a size of 30 mm in width and 250 mm in length and subjected to electrolytic etching. The appearance of the etching resist film after electrolytic etching was visually observed, and the resist properties were determined by calculating the area ratio of the part where discoloration was observed. A 20% aqueous NaCl solution was used as the electrolyte for electrolytic etching. The conditions for electrolytic etching were an electrolyte temperature of 25°C, a current density of 8 A / dm２ The current was applied for 3 minutes. The resist characteristics were evaluated according to the following criteria. A rating of A or B was considered to be pass, and F was considered to be fail. (Evaluation criteria) A: The area ratio of the area where discoloration was observed was 0.0% or less. B: The area ratio of the area where discoloration was observed was greater than 0.0% and less than 5.0%. F: The area ratio of the area where discoloration was observed was greater than 5.0%.

[0085] <Removability> The grain-oriented electrical steel sheet with the etching resist film, which had been evaluated for the resist properties as described above, was immersed in a 25% aqueous sodium hydroxide solution at 50°C for 10 seconds, then removed and washed with water to remove the etching resist film. The test surface of the grain-oriented electrical steel sheet after the etching resist film had been removed was visually observed, and the area ratio of the peeled portion of the etching resist film was calculated to evaluate the removability. The removability was evaluated according to the following criteria. A rating of A or B was considered to be pass, and F was considered to be fail. (Evaluation criteria) A: The area ratio of the peeled portion was 100% B: The area ratio of the peeled portion was 90% or more but less than 100% F: The area ratio of the peeled portion was less than 90%

[0086] According to the evaluation results shown in Table 3, the etching resist films of the grain-oriented electrical steel sheets with etching resist films Nos. 1 to 12 and Nos. 19 to 22 according to the present invention passed the property evaluation results in all evaluation items. On the other hand, the etching resist films of the grain-oriented electrical steel sheets with etching resist films Nos. 13 to 18, which did not satisfy the properties specified in the present invention in terms of surface insulation resistance coefficient or pencil hardness, failed the property evaluation results in any of the evaluation items.

[0087] 1 Grain-oriented electrical steel sheet with etching resist coating 2 Grain-oriented electrical steel sheet 2a Groove 3 Etching resist coating 4 Non-coated area

Claims

1. A method for producing a grain-oriented electrical steel sheet, comprising the steps of: hot rolling a steel slab to obtain a hot-rolled steel sheet; an optional step of hot-rolling the hot-rolled steel sheet to obtain a hot-rolled annealed steel sheet; cold rolling the hot-rolled steel sheet or the hot-rolled annealed steel sheet once or at least twice with intermediate annealing therebetween to obtain a cold-rolled steel sheet; primary recrystallization annealing the cold-rolled steel sheet to obtain a primary recrystallization annealed steel sheet; and secondary recrystallization annealing the primary recrystallization annealed steel sheet to obtain a secondary recrystallization annealed steel sheet, the specific steel sheet is one selected from the group consisting of the hot-rolled steel sheet, the hot-rolled annealed steel sheet, the cold-rolled steel sheet, the primary recrystallization annealed steel sheet, and the secondary recrystallization annealed steel sheet, and in so doing, leaves a plurality of non-coated regions where the coating agent for forming an etching resist film is not applied linearly along a direction intersecting the rolling direction of the specific steel sheet; thereafter, a baking process is performed on the specific steel sheet to bake the coating agent for forming an etching resist film to form an etching resist film; and thereafter, an etching process is performed on the specific steel sheet to form grooves on the surface of the specific steel sheet in the non-coated regions, and the surface insulation resistance coefficient of the etching resist film is 20 Ω cm ２ / sheet or more, and the pencil hardness of the etching resist film is H or more and 8H or less.

2. The method for producing a grain-oriented electrical steel sheet according to claim 1, further comprising the step of removing the etching resist film after the etching treatment.

3. A grain-oriented electrical steel sheet comprising: an etching resist film formed on at least one surface of the grain-oriented electrical steel sheet; a plurality of non-coated areas where the etching resist film is not coated, the non-coated areas being linearly arranged along a direction intersecting the rolling direction of the grain-oriented electrical steel sheet; and grooves formed on the surface of the grain-oriented electrical steel sheet in the non-coated areas, wherein the surface insulation resistance coefficient of the etching resist film is 20 Ω cm ２ / sheet or more, and the pencil hardness of the etching resist film is H or more and 8H or less.

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