JP2017025377A - Method for forming linear groove on the surface of steel sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for forming a linear groove on the surface of a steel sheet utilizing etching, capable of stably forming a linear groove with a uniform shape.SOLUTION: Provided is a method for forming a linear groove on the surface of a steel sheet comprising: a resist application step where a resist is applied to the surface of a steel sheet; an energy beam irradiation step where, while performing scanning on a straight line elongating to a direction crossed with the rolling direction of the steel sheet, by irradiating the surface of the steel sheet with an energy beam, resist removal parts from which the resist has been removed and in which the surface of the steel sheet is exposed are formed on the straight line at intervals; and an etching step where etching is performed to form a linear groove. The energy beam irradiation step is periodically performed in the rolling direction of the steel sheet, the length of the resist removal part is 1 to 10 mm, and the distance between the adjacent resist removal parts is 10 to 300 mm.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a method for forming a linear groove on the surface of a steel sheet, and more particularly to a linear groove forming method capable of stably forming a linear groove having a uniform shape.

  The grain-oriented electrical steel sheet having excellent magnetic properties is mainly used as a material for iron cores of transformers, and in order to improve the energy use efficiency of the transformer, it is required to reduce its iron loss. In addition to methods of reducing the iron loss of grain-oriented electrical steel sheets, the secondary recrystallized grains in the steel sheets are highly aligned in the Goss orientation (sharpening), the film tension is increased, and the steel sheets are made thinner. A method by surface processing of a steel plate is known.

  Iron loss reduction technology by surface processing of steel sheets introduces non-uniform strain to the surface of steel sheets by a physical method and subdivides the width of magnetic domains to reduce iron loss. There is a method in which grooves are formed on the surface of a finish annealed steel sheet using a tooth roll. According to this method, the magnetic domain on the surface of the steel sheet can be subdivided by forming the groove, and the iron loss of the steel sheet can be reduced. Further, it has been found that even when heat treatment such as strain relief annealing is performed after the grooves are formed, the introduced grooves do not disappear, so that the iron loss reduction effect is maintained. However, in this method, since the wear of the tooth-type roll is intense, the groove shape tends to be non-uniform, and in addition, the roll is heated to a high temperature or a lubricant is applied to suppress the wear of the tooth-type roll. There was a problem that the cost increased.

  Therefore, a method has been developed in which a linear groove is formed on the surface of a steel sheet by etching regardless of mechanical means such as a tooth roll. Specifically, after a resist ink is applied in a pattern on the surface of the steel sheet before the forsterite film is formed, a portion where the resist ink is not applied is selectively etched by a method such as electrolytic etching. As a result, a groove is formed on the surface of the steel sheet. In this method, since there is almost no mechanical wear of the apparatus, the maintenance is easier than the method using a tooth roll.

  By the way, it is known that the magnetic properties of a steel sheet in which such linear grooves are formed are greatly influenced by the shape of the linear grooves. It is also known that not only the depth and width of the groove but also the detailed shape such as the curvature of the groove cross section affects the iron loss. For this reason, when the linear groove is formed by the above-described etching method, if the shape of the resist functioning as an etching mask varies, the groove shape varies, and as a result, the magnetic properties of the steel sheet vary. Therefore, in a method of forming a linear groove by etching, a technique has been proposed in which the resist application accuracy is improved and the variation in the magnetic properties of the steel sheet is suppressed.

  For example, Patent Document 1 proposes a technique for forming linear grooves having a uniform shape by controlling the resist ink and the temperature of a steel plate to be constant when applying a resist. By keeping the temperature constant, fluctuations in the viscosity of the resist ink are suppressed, and as a result, variations in groove shape are suppressed.

  Patent Document 2 proposes a technique for controlling conditions such as the viscosity of resist ink to be used and the mesh pattern of a gravure roll within a specific range when applying resist by gravure offset printing. Thereby, generation | occurrence | production of the halftone dot resulting from the gravure cell formed in the surface of the gravure roll can be suppressed, and the precision of a resist pattern can be improved.

  In fields other than electromagnetic steel sheets, techniques for resist patterning using a laser have also been proposed. For example, in Patent Document 3, a resist pattern used as a mask is formed by removing resist ink applied to the material surface with a low-power laser when plating or etching is performed in the production of a printed wiring board, an electrical connector, or the like. The method is shown.

  In Patent Document 4, in the manufacture of a metal / ceramic bonding circuit board, a resist is formed so as to cover the surfaces of the circuit metal plate and the metal base plate of the metal / ceramic bonding board, and this resist is irradiated with a laser. A method for removing an unnecessary portion of the resist has been proposed. After the resist removal by the laser is completed, a circuit pattern is formed by etching the exposed metal.

Japanese Patent Laid-Open No. 11-279646 Japanese Unexamined Patent Publication No. 07-032575 Japanese National Publication No. 04-503718 JP 2013-030523 A

  However, according to the methods proposed in Patent Documents 1 and 2, although there is a certain improvement in the resist shape accuracy, there is still variation in the shape of the linear grooves formed by these methods. The reason is considered as follows.

  In order to form a linear groove on the steel sheet surface by etching, it is necessary to apply an etching resist in a pattern. In principle, various coating methods can be used for the application of the resist, but it is suitable for continuous application to a long substrate and stable even for a hard substrate such as a steel plate. A gravure offset printing method that can be applied is generally used.

  FIG. 11 is a schematic diagram illustrating a general configuration of a gravure offset printing apparatus 100 used for gravure offset printing. In the gravure offset printing, first, the ink 102 is applied to the plate surface of the gravure roll 103 using the pickup roll 101. A gravure cell 104 that is a recess for holding ink is formed on the plate surface of the gravure roll 103, and ink adhering to a portion other than the cell is removed by a doctor blade 105. Next, the coating material is further transferred to the surface of the offset roll 106 and then further transferred to the surface of the substrate 107.

  In order to form a linear groove on the surface of a grain-oriented electrical steel sheet by etching, a resist pattern that functions as an etching mask may be formed using the printing method. An example of the resist pattern is shown in FIG. In this example, a resist 111 is periodically applied to the surface of the steel plate 110 in the rolling direction. Between the portions where the resist is applied, a non-application portion 112 where the resist is not applied is provided, and the surface of the steel plate is exposed at this portion. Therefore, when the steel sheet is etched, the steel sheet surface in the non-coated portion is selectively etched to form a linear groove.

  However, as a result of the study by the present inventors, it is difficult to make a resist pattern formed by a printing method such as gravure offset printing into an ideal shape as shown in FIG. It was found that the shape was as shown in FIG. That is, the boundary between the resist-coated portion and the non-coated portion has a smooth cross section as shown in FIG. 13, and the shape differs depending on the position. As a result, the shape of the non-application part 112 seen from the upper side of the steel sheet was not completely linear as shown in FIG.

  This variation is unavoidable in resist pattern formation by gravure offset printing because it cannot be completely eliminated even if the temperature control of the resist ink and steel plate described in Patent Document 1 is performed. It is thought that. That is, the transfer of the resist ink from the gravure roll to the steel plate surface in the gravure offset printing is performed via the offset roll as described above. At that time, the shape of the resist ink transferred to the surface of the offset roll is a convex bowl shape facing the outside of the roll as shown in FIG. As a result, the end surface of the resist pattern formed by transferring the resist ink onto the steel plate surface becomes smooth as described with reference to FIG. Furthermore, the shape of the resist ink is affected by variations in the gravure cell shape, and thus varies depending on the location.

  Therefore, in order to avoid the problems in the gravure offset printing as described above, it is conceivable to form a resist pattern using an energy beam such as a laser as described in Patent Documents 3 and 4. In other words, instead of directly forming a resist pattern by printing using a gravure roll, the resist is instantly evaporated by irradiating an energy beam to a portion that does not require application after applying the resist uniformly over the entire surface of the steel sheet. Alternatively, the resist is sublimated to selectively remove the irradiated portion of the resist. With such a method, the shape of the portion from which the resist is removed is not affected by variations in gravure cells, and it is expected that a linear groove having a uniform shape can be formed.

However, when the resist is removed by the energy beam, there is a problem that the removed resist adheres to the optical system of the energy beam irradiation apparatus and the beam property is deteriorated. For example, the size of the resist to be removed by the energy beam is set to 1000 mm length × width 0.1 mm × thickness 0.003 mm per beam scanning, and removal is performed 444 times per hour (resist removal unit). Equivalent to a case where the distance in the rolling direction is 3 mm and the line speed is 80 mpm), as many as 133 mm ^{3 of} resist per hour are vaporized. When a part of the vaporized resist adheres to the optical system or the like of the beam irradiation apparatus, the beam is shielded, so that the beam property changes with time as the resist adhesion amount increases. When the beam property changes with time, the shape of the resist pattern changes accordingly, and the magnetic properties of the finally obtained electrical steel sheet vary.

  As a method for preventing the influence of such a vaporized resist, a method is conceivable in which an air stream is generated in the energy beam irradiation portion and fumes generated by the vaporization of the resist are collected. However, if the wind speed is increased in order to reliably collect a large amount of fumes, the steel plate vibrates and a focus shift occurs. When the energy beam is out of focus, the amount of resist removed varies, so that a uniform resist pattern cannot be formed despite the use of the energy beam. On the other hand, if the wind speed is reduced to prevent the vibration of the steel sheet, the fume recovery efficiency is reduced, the beam property cannot be sufficiently suppressed over time, and frequent maintenance of the equipment is required. There arises a problem that the beam is shielded by the fumes floating on the surface.

  Thus, even when trying to use resist removal with an energy beam to form a resist pattern for simply forming a linear groove on the surface of a steel sheet, it is not possible to stably obtain a linear groove with a uniform shape. was there.

  The present invention has been made in view of the above circumstances, and is a method of forming a linear groove on a steel sheet surface by using etching, which can stably form a linear groove having a uniform shape. It aims to provide a possible method.

As a result of further investigation on resist removal in the method of forming linear grooves by etching, the present inventors have obtained the following knowledge.
(1) By irradiating the resist with an energy beam, the resist can be altered, and the adhesion between the steel sheet and the resist can be reduced.
(2) When there is a deteriorated resist around the portion where the resist is removed and the steel plate is exposed, an etchant enters between the resist and the steel plate during etching and is covered with the resist. Part of the steel plate is also etched.
(3) If the phenomena (1) and (2) are used, the linear grooves can be formed by etching without removing all the resists for forming the linear grooves with an energy beam.

  Based on the above knowledge, the present inventors have completed the present invention by conducting a detailed study on the resist pattern formation conditions.

That is, the gist configuration of the present invention is as follows.
1. A method of forming linear grooves on a steel sheet surface,
A resist coating step of coating a resist on the steel sheet surface;
By irradiating the surface of the steel sheet with an energy beam while scanning a straight line extending in a direction crossing the rolling direction of the steel sheet, the resist removal portion where the resist is removed and the surface of the steel sheet is exposed An energy beam irradiation process that forms an interval on a straight line; and
Etching to form a linear groove in the region irradiated with the energy beam,
The energy beam irradiation step is periodically performed in the rolling direction of the steel plate,
The resist removal portion has a length in the scanning direction of the energy beam of 1 mm or more and 10 mm or less,
The method of forming a linear groove | channel on the steel plate surface whose distance between the said resist removal parts adjacent on the said straight line is 10 mm or more and 300 mm or less.

2. The energy beam is a laser;
In the resist coating step, a thick film portion having a resist coating thickness of 2.0 μm or more and a thin film portion having a resist coating thickness of 1.0 μm or less are formed,
The method for forming linear grooves on a steel sheet surface according to claim 1, wherein in the energy beam irradiation step, the thin film portion becomes the resist removal portion.

3. Application of the resist in the resist application process is performed by gravure printing using a gravure roll,
The said gravure roll has the following pattern A for forming the said thick film part in the surface, and the following pattern B for forming the said thin film part, The linear groove | channel on the steel plate surface of Claim 2 How to form.
Pattern A: A pattern in which gravure cells with a mesh length L are arranged at equal intervals of 2 L or less Pattern B: A pattern without cells, or a cell whose volume is 1/2 or less of the cells in pattern A, etc. Patterns arranged at intervals

4). The irradiation of the laser in the energy beam irradiation step,
Laser diameter in a direction perpendicular to the laser scanning direction on the steel sheet surface: 0.4 mm or less,
Output: 1500 W or less, and irradiation energy per unit scanning length: 5 J / m or more and 60 J / m or less,
The method of forming a linear groove | channel on the steel plate surface of Claim 2 or 3 performed on condition of this.

5. The energy beam is an electron beam having an acceleration voltage of 40 kV or more;
In the resist coating step, the resist coating thickness is 2.0 μm or less,
In the energy beam irradiation step, the resist removal portion is formed by controlling the scanning speed of the electron beam and irradiating the electron beam until the resist is removed and the surface of the steel sheet is exposed. A method of forming a linear groove on the surface of the steel sheet.

6). 6. The steel plate surface according to claim 5, wherein in the energy beam irradiation step, an electron beam scanning speed V _{1 at} a position where the resist removal portion is formed is less than an electron beam scanning speed V _{2 at} other positions. A method of forming a linear groove.

  According to the method of forming linear grooves on the steel sheet surface of the present invention, in the method of forming linear grooves on the steel sheet surface using etching, adhesion of the resist to the energy beam irradiation apparatus is suppressed, and therefore uniform. A linear groove having a simple shape can be formed stably. In addition, since the frequency of maintenance for removing the resist adhering to the apparatus can be reduced, a steel sheet with linear grooves can be efficiently manufactured at low cost.

It is an optical microscope photograph of the steel plate surface after energy beam irradiation (a) and after etching (b). It is a schematic diagram of the steel plate cross section in the position where the energy beam was irradiated and the resist removal part was formed in one Embodiment of this invention. It is a schematic diagram of the steel plate surface after energy beam irradiation and the resist removal part were formed in one Embodiment of this invention. It is a figure which shows typically the resist removal part after energy beam irradiation in one Embodiment of this invention. It is a figure which shows the relationship between the output of a laser, and a resist removal rate. It is a figure which shows the relationship between the diameter of a laser, and the width | variety of a resist removal part. It is the schematic diagram which showed arrangement | positioning of the gravure cell for apply | coating a resist uniformly on the whole surface. It is the schematic diagram which showed arrangement | positioning of the gravure cell in one Embodiment of this invention. It is the schematic diagram which showed arrangement | positioning of the gravure cell in one Embodiment of this invention. FIG. 8 is an enlarged view of a part of the gravure cell pattern shown in FIG. 7. It is the schematic showing the general structure of the apparatus used for gravure offset printing. It is a schematic diagram showing the shape of an ideal resist pattern. It is a schematic diagram showing the shape of an actual resist pattern. It is a schematic diagram showing the ink shape in gravure offset printing.

  First, resist alteration due to energy beam irradiation will be described. FIG. 1 (a) shows the surface of a steel sheet observed with an optical microscope after the resist is uniformly applied to the surface of the steel sheet and the surface is irradiated with a laser while linearly scanning. The laser irradiation conditions were adjusted so that the resist was not completely removed and the steel plate surface was not exposed. The slightly white vertical line seen in the center of the figure corresponds to the laser-irradiated part and is not shown in the photograph, but the length of this vertical line is 100 mm and there is an unformed resist area at both ends. . In this white portion, the resist remains and the surface of the steel sheet is not exposed, but it is presumed that the resist is heated and changed in quality by the laser.

  When electrolytic etching was performed on the steel plate after the laser irradiation, a clear white line was observed in the portion irradiated with the laser as shown in FIG. In this portion, the resist is removed and the steel plate surface is exposed. As described above, the reason why the resist remaining in the portion irradiated with the laser is removed in the etching process is not necessarily clear, but the resist is altered by the laser irradiation, and the resist with the steel plate or the non-irradiated portion of the resist is changed. As a result of the loss of the bonding force, it is considered that the etching solution enters between the resist and the steel plate from the unformed region of the resist during etching, and the resist in the portion is detached from the steel plate surface.

  As described above, if etching can be performed without completely removing the resist by irradiation with an energy beam, the amount of resist to be vaporized can be reduced, so that the resist adheres to an energy beam irradiation apparatus such as an optical system. It is considered that the fluctuation of the beam property caused by it can be suppressed. However, in order to remove the resist in the portion irradiated with the laser, an entrance for the etching solution to enter between the steel plate and the resist is necessary. When applying a resist by a printing method such as gravure offset printing, the resist is not applied to the end surface of the steel plate, so the interface between the resist and the steel plate is exposed at the end surface. It can function as an inflow port. However, when the plate width is wide, it takes time for the etchant entering from the end to reach the center of the plate width, so the time for etching the steel plate is greatly different between the center and end of the steel plate. As a result, the groove shape varies.

  Therefore, in addition to altering the resist by irradiating while scanning with an energy beam, the present inventors further removed the resist in the portion irradiated with the energy beam and exposed the surface of the steel plate. It has been found that if the removal portions are formed at appropriate intervals, the entire portion irradiated with the energy beam can be etched with sufficient uniformity.

  FIG. 2 is a schematic view of a cross section of a steel plate at a position where an energy beam is irradiated and a resist removal portion is formed. In the resist 20 applied to the surface of the steel plate 10, resist removal portions 21 where the resist 20 is removed and the surface of the steel plate 10 is exposed are formed at regular intervals. When the steel plate 10 in such a state is immersed in an etching solution for etching, etching is performed from the portion where the interface between the steel plate 10 and the resist 20 is exposed, that is, the portion shown as the etchant intrusion portion 22 in FIG. The liquid penetrates and the etching of the steel sheet proceeds.

  Next, a method for carrying out the present invention will be specifically described. The following description shows a preferred embodiment of the present invention, and the present invention is not limited to the following description.

In the method of the present invention, the following steps (1) to (3) are sequentially performed on the steel sheet.
(1) resist coating process,
(2) Energy beam irradiation step, and (3) Etching step.
Optionally, a resist drying step can be provided between (1) the resist coating step and (2) the energy beam irradiation step.

[steel sheet]
In the present invention, a steel plate is used as the base material. The kind of steel plate is not particularly limited, and any steel plate can be used regardless of whether it is a hot rolled steel plate or a cold rolled steel plate. As the steel sheet, it is preferable to use a grain-oriented electrical steel sheet or a steel sheet for the grain-oriented electrical steel sheet (middle stage of the grain-oriented electrical steel sheet manufacturing process). The steel sheet preferably contains Si in a range of 2.0 to 8.0% by mass from the viewpoint of reducing iron loss, and in addition, Si is 2.5 to 4.5% by mass from the viewpoint of sheet passability. It is more preferable to contain in the range.

  If a coating is formed on the surface of the steel sheet, etching may be hindered depending on the type of the coating. Therefore, it is preferable that a coating that is insoluble or hardly soluble in the etching solution (electrolytic solution) is not formed on the surface of the steel plate, and a resist described later is directly applied to the surface of the steel plate. When a grain-oriented electrical steel sheet is used as the steel sheet, a film such as a forsterite film or a tension imparting film is not formed on the surface of the grain-oriented electrical steel sheet, and a resist is formed on the surface of the grain-oriented electrical steel sheet. It is preferably formed directly.

[Resist application process]
Prior to the energy beam irradiation, a resist is applied to the surface of the steel plate. The resist functions as an etching resist for preventing the steel sheet from being etched in an etching process described later. As the resist, any material can be used as long as it can prevent the etching of the steel sheet, but a thermosetting resin mainly containing any one of alkyd resin, epoxy resin, and melamine resin is used. It is preferable to use it. UV curability and electron beam curability as used in the semiconductor field are not necessarily required. Further, in terms of suppressing ink sag, the resin should have a high viscosity, and the resist is preferably applied at a constant temperature of 40 ° C. or lower in order to obtain a high viscosity.

  Application of the resist to the steel sheet surface is not particularly limited and can be performed by any method, but is preferably performed by roll application. Among these, it is preferable to use a gravure printing method using a gravure roll, and it is more preferable to use a gravure offset printing method using an offset roll. In the present invention, the gravure printing method refers to all printing methods using a gravure roll, and includes a gravure offset printing method.

  The resist coating pattern in the present invention is not particularly limited, and can be any pattern as long as a desired linear groove can be finally formed, but the resist is coated on the entire surface of the steel sheet. It is preferable. The film thickness of the resist is not particularly limited, but if it is excessively thick, the amount of resist to be removed by energy beam irradiation increases. Therefore, the resist film thickness is preferably 20 μm or less, more preferably 15 μm or less. preferable. On the other hand, if the resist is too thin, the function as an etching resist is lowered, so the resist film thickness is preferably 0.1 μm or more, and more preferably 0.5 μm or more. Here, the resist film thickness is the thickness immediately before etching.

[Resist drying process]
After applying the resist, it is preferable to dry the resist prior to the next energy beam irradiation step. The drying method is not particularly limited, and for example, hot air drying or vacuum drying can be used. In the case of hot air drying, the drying temperature is preferably 180 to 300 ° C. In the case of vacuum drying, the pressure is preferably 10 Pa or less, and the drying time is preferably 5 seconds or more.

[Energy beam irradiation process]
Next, the surface of the steel plate coated with the resist is irradiated with an energy beam while scanning a straight line extending in a direction crossing the rolling direction of the steel plate. By this energy beam irradiation, a resist removal portion in which the resist is removed and the surface of the steel sheet is exposed is formed on a straight line irradiated with the beam at an interval. The resist removing portion functions as an intrusion portion in which an etching solution (electrolytic solution) enters between the resist and the steel plate in an etching process described later. Further, it is considered that, in the portion other than the portion where the resist removal portion is formed among the portions irradiated with the energy beam, the resist is altered by the irradiation of the beam, and the adhesion to the steel plate is lowered.

  FIG. 3 is a schematic view showing an example of the steel sheet surface after the energy beam is irradiated and the resist removal portion is formed. In this example, the energy beam irradiation while scanning in the plate width direction is repeated at a certain interval in the rolling direction to partially remove the resist 20 applied to the surface of the steel plate, and to remove the resist removing portion 21. Forming.

In the present invention, the length d ₁ of the resist removing portion 21 in the scanning direction of the energy beam is 1 mm or more and 10 mm or less. This is because if d ₁ is less than ₁ mm, the etching solution cannot sufficiently enter during etching, resulting in poor etching. On the other hand, if d ₁ is larger than 10 mm, the amount of resist removed by the energy beam increases, and the amount of generated fumes increases, resulting in an increase in the number of maintenance of the apparatus. Incidentally, d ₁ is preferably set to 2mm or 5mm or less.

Further, the distance d ₂ between the resist removal portions 21 adjacent on the straight line scanned with the energy beam is set to 10 mm or more and 300 mm or less. If d ₂ exceeds 300 mm, the time required for the etching solution to enter the inside increases, and as a result, the uniformity of the etching amount in the scanning direction of the energy beam decreases. Therefore, it is preferable to reduce d ₂ in terms of the uniformity of the etching amount. However, if d ₂ is excessively reduced, the number of resist removal portions formed per unit length increases. As a result, the energy beam Since the amount of resist removed by this increases, d ₂ is set to 10 mm or more. D ₂ is preferably 20 mm or more and 100 mm or less.

The energy beam is preferably scanned over the full width of the steel plate. As shown in FIG. 3, the resist may remain at the width direction end portion of the steel plate, or a resist removal portion may be formed. As shown in FIG. 3, when the resist remains at the end in the plate width direction, for the same reason as d ₂ above, the distance from the end of the steel plate on the straight line scanned with the energy beam to the resist removing portion 21 d ₃ is preferably 300 mm or less, and more preferably 100 mm or less.

The width d ₄ of the resist removing portion 21 in the direction perpendicular to the energy beam scanning direction is not particularly limited and can be an arbitrary value. By varying the d _4, it is possible to change the width of the finally obtained linear grooves may be set to d ₄ as linear grooves having a desired width can be obtained. When a grain-oriented electrical steel sheet is used as the steel sheet, the width of the linear groove is preferably 200 μm or less from the viewpoint of improving magnetic properties. Under general etching conditions, the width of the linear groove is equal to or greater than the width d ₄ of the resist removal portion. Therefore, in order to reduce the width of the linear groove to 200 μm or less, d ₄ is preferably set to 200 μm or less. . The value of d ₄ can generally be adjusted by controlling the energy beam diameter. For example, in order to set d ₄ to 200 μm or less, the diameter of the energy beam in the direction orthogonal to the scanning direction may be set to 0.4 mm or less. Here, the diameter of the energy beam is a diameter at a position where the intensity is 1 / e of the maximum intensity in the intensity profile. In the following description, “width of linear groove”, “width of resist removal portion”, and “diameter of energy beam” are values in a direction perpendicular to the scanning direction of the energy beam unless otherwise specified. .

The energy beam irradiation is repeatedly performed at different positions in the rolling direction of the steel sheet. The position where the energy beam is scanned in the rolling direction is not particularly limited and may be any position. However, it is preferable that the energy beam is equally spaced as in the example shown in FIG. The distance d ₅ between the resist removal portions 21 in the rolling direction is:
When a grain-oriented electrical steel sheet is used as the steel sheet, d ₅ is preferably 2 mm or more and 10 mm or less from the viewpoint of improving magnetic properties.

  In the example shown in FIG. 3, the energy beam is irradiated while scanning in the direction orthogonal to the rolling direction of the steel sheet, that is, in the sheet width direction. However, if the scanning direction of the energy beam is a direction crossing the rolling direction, Good. Moreover, when using a grain-oriented electrical steel sheet as a steel plate, it is preferable to make the angle of the energy beam scanning direction with respect to the width direction of the steel plate 40 ° or less from the viewpoint of enhancing the effect of reducing iron loss.

  The irradiation with the energy beam can be performed using one energy beam source, but a plurality of energy beam sources can also be used. When multiple energy beam sources are used, the beam emitted from each energy beam source does not need to be scanned across the entire width of the steel sheet, and the sum of the scanning range of each energy beam source covers the full width of the steel sheet. It ’s fine.

[Etching process]
After completion of the energy beam irradiation process, etching is performed to form linear grooves on the steel sheet surface. In the etching, an etching solution enters from the resist removal portion formed in the energy beam irradiation process, and penetrates between the resist and the steel plate that have been altered by the energy beam irradiation, whereby the energy beam is scanned in a linear shape. Etching proceeds over the entire area. In this way, since it is not necessary to remove the resist over the entire area where the linear groove is formed, the amount of resist that volatilizes and contaminates the apparatus can be minimized, and the linear groove can be formed stably. Become.

As the method used for etching, any method can be used as long as it can etch a steel sheet, but it is preferable to use at least one of chemical etching and electrolytic etching, and electrolytic etching is used from the viewpoint of controlling the etching amount. It is more preferable. In the case of chemical etching, an aqueous solution such as FeCl ₃ , HNO ₃ , HCl, H ₂ SO ₄ can be used as an etching solution. In the case of electrolytic etching, an aqueous solution of NaCl, KCl, CaCl ₂ , NaNO ₃ or the like can be used as an etching solution (electrolytic solution). The pH of the etching solution is preferably 2 to 11, and the temperature of the etching solution is preferably controlled to be constant within a range of 20 to 70 ° C.

  Further, when etching is performed, it is preferable to stir the etching solution. By stirring the etching solution, temperature and concentration unevenness in the etching tank can be eliminated and etching can be performed uniformly. Further, the etching efficiency can be improved by increasing the flow rate of the plating solution in the tank. The method for performing the stirring is not particularly limited. For example, mechanical stirring, stirring by circulating an etching solution, or the like can be used. When performing mechanical stirring, it is preferable to use a resin stirring member in consideration of resistance to the etching solution. In the case of performing agitation by circulation, for example, an etching solution ejection port is provided in the etching tank, and the etching solution can be ejected from the ejection port using a pump or the like.

When the etching is performed by electrolytic etching, the steel sheet can be energized by any method. For example, using a radial cell or horizontal cell etching tank, direct energization or indirect energization can be performed. It can be carried out. Electrolysis conditions, a steel sheet or the processed may be appropriately adjusted depending on the electrolytic solution or the like to be used, for example, can be adjusted within the range of current density of 1~100A / dm ^2.

  Next, the case where a laser is used as the energy beam (first embodiment) and the case where an electron beam is used (second embodiment) will be described more specifically.

(First embodiment)
First, the case where a laser is used as the energy beam will be described.
Any laser can be used as long as it can alter and remove the resist, but a solid laser such as a fiber laser, a CO ₂ laser, or the like is preferably used. The laser scanning is preferably performed by rotational driving of a polygon mirror from the viewpoint of speeding up. Although any number of irradiation devices can be used for the laser irradiation, it is preferable to use one to three irradiation devices. If there are more than three irradiation devices, the time required for maintenance will increase and productivity will be reduced. In addition, the irradiation area per device will become shorter, the line speed will increase excessively, and the etching process will be sufficient. The groove cannot be formed. In addition, since many steel plates generally used have a plate width of about 1 m, it is difficult to irradiate a laser uniformly over the entire plate width when the number of irradiation devices is one, and the beam properties are made uniform. Therefore, it is necessary to increase the beam diameter. Therefore, it is more preferable that the number of laser irradiation devices is two or three. Further, in order to further suppress contamination of the apparatus by the resist vaporized by laser irradiation, it is preferable to collect the resist in a dust collector by blowing or sucking. However, in order to prevent the steel plate from vibrating and defocusing, it is preferable that the air volume at the time of blowing or sucking is 100 m ³ / min or less.

-Resist coating thickness When a laser is used as the energy beam, in the resist coating process, a thick film portion with a resist coating thickness of 2.0 μm or more and a thin film portion with a resist coating thickness of 1.0 μm or less Preferably formed. In this way, by forming the resist thick part and thin part at the stage of applying the resist, it is only necessary to scan the laser while keeping the conditions such as the output and the scanning speed constant. The resist is left, and the resist removal portion in which the steel sheet surface is exposed by completely removing the resist in the thin film portion can be formed.

The reason why the coating thickness of the resist in the thick film portion and the thin film portion is limited as described above is as follows.
Table 1 shows the results of testing whether or not the resist is removed when a plurality of test pieces having different resist coating thicknesses are irradiated with a laser under the same conditions. When the resist was removed by laser irradiation and the steel plate surface was exposed, the resist removal was “possible”, and when the steel plate surface was not exposed, the resist removal was “impossible”. As a result of the test, in the test piece having a resist coating thickness of 1.0 μm, the resist irradiated with the laser was completely removed, but in the test piece having a coating thickness of 2.0 μm or more, the resist remained in the laser irradiation portion. did.

  From this result, a laser is scanned under a certain condition by forming a thick film portion having a resist coating thickness of 2.0 μm or more and a thin film portion having a resist coating thickness of 1.0 μm or less. It can be seen that the resist removal portion can be selectively formed only in the thin film portion. The above test was carried out under the conditions of a laser scanning speed of 5 m / sec, a beam diameter of 0.4 mm, and an output of 250 W, but almost the same tendency was observed under general laser irradiation conditions. . Under conditions where the laser output and energy are extremely high, the steel plate surface may be partially exposed even if the resist coating thickness is 2.0 μm or more. In that case, the laser output is reduced. Alternatively, it is preferable to increase the laser scanning speed to lower the irradiation energy per unit scanning length. In order to ensure that the resist remains in the portion irradiated with the laser where the linear groove is not formed even after the laser irradiation, the thickness of the resist applied to the thick film portion should be 3.0 μm or more. Preferably, it is more preferably 5.0 μm or more. On the other hand, the coating thickness of the resist in the region not irradiated with the laser, that is, the region between the straight lines scanned with the laser is not particularly limited, but is preferably 0.3 μm or more, and more preferably 0.5 μm or more. It is more preferable.

Irradiation energy per unit scanning length The resist is more easily removed as the irradiation energy per unit scanning length of the laser (= output / scanning speed of the laser beam on the steel plate, hereinafter also referred to simply as irradiation energy) increases. Table 2 shows the results of irradiating the test pieces having the same resist coating thickness with lasers with different irradiation energies. As shown in FIG. 4, the “resist removal rate by irradiation” in Table 2 indicates the maximum width of the resist removal portion in the range of a predetermined length (observation length): x after the laser irradiation. (Rolling direction): d, area of resist removal portion: A, A / (d × x) × 100. Here, x was 3 mm. For "resist removal by etching", electrolytic etching is performed after laser irradiation, the resist is removed from the part irradiated with the laser and the steel plate surface is exposed, "Yes", the steel plate surface is not exposed Was “impossible”. The laser output was 800 W, the resist film thickness was 8 μm, and the conditions for electrolytic etching were 20 ° C. in 20% NaCl solution, current density: 10 A / dm ² , and energization time: 3 min.

  As a result of the above test, it was found that when the irradiation energy was 80 J / m, the resist was completely removed by laser irradiation even though the laser output was about 800 W. On the other hand, when the irradiation energy was 60 J / m, 40 J / m, 10 J / m, and 5 J / m, the resist was not removed even when the laser irradiation was performed. It was possible to remove the resist. On the other hand, when the irradiation energy was 3 J / m, the resist in the laser irradiated portion could not be removed even if etching was performed after laser irradiation. This is probably because the irradiation energy was too low to alter the resist and reduce the adhesive strength with the steel sheet. Based on the above results, the irradiation energy per unit scanning length of the laser is 5 J / m or more and 60 J in order to make the resist not removed by laser irradiation alone but removed by subsequent etching. / M or less is preferable. The irradiation energy is more preferably 10 J / m or more and 30 J / m or less.

Output The irradiation energy (J / m) per unit scanning length of the laser described above is a value obtained by dividing the laser output (W = J / sec) by the laser scanning speed (m / sec). Therefore, the irradiation energy can be controlled by adjusting the laser output and the scanning speed. However, even with the same irradiation energy, the former is easier to remove the resist under the conditions of high output and high scanning speed and low output and low scanning speed.

  FIG. 5 is a diagram showing the relationship between the laser output and the resist removal rate by laser irradiation when the laser scanning speed is constant (100 m / sec). The resist film thickness was 7 μm. According to the experimental results shown in FIG. 5, it can be seen that when the output is 1500 W or more, the resist is removed by laser irradiation. Therefore, in order to prevent unintended portions of the resist from being removed, the laser output is preferably set to 1500 W or less.

-Scanning speed The scanning speed of the laser is not particularly limited, but a higher one is advantageous in terms of productivity. For example, when a linear groove is formed at a rolling direction interval s (mm): 3 mm with respect to a steel plate having a width of 1200 mm, the line speed (feeding speed) is set to 50 mpm (meter per minute). In order to achieve this, it is necessary to set the laser scanning speed to 111 m / sec or more. From the viewpoint of productivity, the scanning speed is preferably set to 333 / s (m / sec) or more. On the other hand, if the scanning speed is excessively increased, the line speed increases accordingly. Therefore, when the etching process is performed on the same line, the etching time is shortened and a groove having a desired size cannot be formed. Therefore, the scanning speed is preferably 400 m / sec or less.

-Laser diameter The width of the resist removal portion depends on the diameter of the irradiated laser. FIG. 6 is a diagram showing the relationship between the diameter of the laser and the width of the resist removal portion formed by the laser irradiation when the laser irradiation is performed so that the resist removal rate becomes 100%. As is clear from this result, the width of the resist removal portion is approximately proportional to the diameter of the laser used. And the width of the linear groove finally formed by etching depends on the etching conditions, but it is narrower than the width of the resist removal portion which is an opening provided in the resist functioning as an etching mask. Absent. Therefore, the diameter of the laser to be used is selected so that a linear groove having a desired width is finally obtained. When a grain-oriented electrical steel sheet is used as the steel sheet, the width of the linear groove is preferably 200 μm or less from the viewpoint of improving magnetic properties. Therefore, from the relationship shown in FIG. 6, the laser diameter is preferably 0.4 mm or less.

-Application of resist by gravure printing When a laser is used as an energy beam, as described above, in the resist application process, a thick film portion having a resist application thickness of 2.0 μm or more and a resist application thickness of 1. It is preferable to form a thin film portion having a thickness of 0 μm or less. In order to apply the resist in a state having such a film thickness distribution, it is preferable to use a gravure printing method. In the present invention, the gravure printing method refers to all printing methods using a gravure roll, and includes a gravure offset printing method.

  Gravure cells (recesses) for holding ink are periodically arranged on the plate surface of a gravure roll used in the gravure printing method. FIG. 7 is a schematic view showing the arrangement of gravure cells 30 for uniformly applying a resist over the entire surface. Thus, if the gravure roll in which the gravure cells are arranged in a uniform pattern as a whole is used, the resist can be uniformly applied to the entire surface of the steel sheet.

  On the other hand, when a resist is applied so as to have a thick film portion and a thin film portion, a gravure cell pattern (hereinafter referred to as pattern A) for forming the thick film portion and a thin film portion are formed. A gravure roll provided with a gravure cell pattern (hereinafter referred to as a pattern B) may be used. FIG. 8 and FIG. 9 are schematic views showing examples of cell arrangement of gravure rolls provided with the pattern A and the pattern B described above. Patterns as shown in FIGS. 8 and 9 are repeatedly formed on the plate surface of an actual gravure roll in the axial direction and the circumferential direction of the roll, respectively. In the examples shown in FIGS. 8 and 9, the cell pattern is formed in parallel to the circumferential direction of the gravure roll, but when forming a linear groove having an angle with respect to the plate width direction of the steel plate. The cell pattern may be arranged to be inclined with respect to the circumferential direction of the gravure roll.

Gravure cell pattern (1)
In the example shown in FIG. 8, cells are formed at equal intervals in the pattern A portion, but there are no cells in the pattern B portion. When a gravure roll having such a pattern is used, a resist is applied as usual to a portion corresponding to the pattern A on the surface of the steel sheet. On the other hand, since there is no cell in the pattern B portion, the resist ink is only supplied from the cell of the adjacent pattern A portion to the portion corresponding to the pattern B on the surface of the steel sheet, and as a result, the resist is thinly applied. Will be. In printing using such a gravure roll, the axial direction of the gravure roll corresponds to the plate width direction of the steel plate, and the circumferential direction of the gravure roll corresponds to the rolling direction (passing plate direction).

When the gravure cell pattern is used, the cell size and interval in the pattern A may be adjusted so that an appropriate resist coating thickness can be obtained. FIG. 10 is an enlarged view of a part of the gravure cell pattern shown in FIG. The pattern A portion, gravure cells of the mesh length L are arranged at equal intervals in the axial direction and circumferential direction of the gravure roll at intervals d _m. If d _m is too large, by the resist ink amount is reduced to be applied to the portion between the cell and the cell, there are cases where uneven coating occurs. Therefore, d _m is preferably less 2L. Here, d _m is the distance between the centers of the cells. The mesh length L is not particularly limited, but is preferably 30 to 500 μm.

The pattern A and the pattern B correspond to the thick film portion and the thin film portion, respectively, and after laser irradiation, the resist remains in the portion corresponding to the pattern A on the steel plate surface, while the surface of the steel plate surface A resist removal portion is formed in a portion corresponding to the pattern B. Therefore, in order to make the length of the resist removal portion 1 mm or more and 10 mm or less and the distance between the resist removal portions 10 mm or more and 300 mm or less, the length d _A of the pattern A portion in the gravure roll circumferential direction is 10 mm or more. and 300mm or less, the pattern portion B in the gravure roll circumferential length d _B may be set to 1mm or 10mm or less.

  In addition, although the resist removal part actually formed by the resist irradiation process is formed at regular intervals in the rolling direction of the steel plate as shown in FIG. 3, the pattern B for forming the resist removal part is formed. It is not necessary to arrange the gravure roll at a certain interval on the plate surface, and it may be formed continuously in the circumferential direction of the roll. When the pattern B is continuously formed in the circumferential direction of the gravure roll, a thin film portion is formed in the resist applied to the steel plate surface so as to continuously extend in the rolling direction (through plate direction) of the steel plate. However, in the thin film portion, only the portion irradiated with the laser becomes the resist removal portion, and the resist remains in the portion not irradiated with the laser.

However, in the case where cells are not provided in the pattern B portion as described above, if the area where the cells do not exist becomes too wide, the resist ink is not applied to the area. As a result, at the end of the resist coating process, in the portion corresponding to the pattern B on the steel sheet surface, that is, in the linear region continuously extending in the rolling direction, the steel sheet surface is exposed, and the etching process continues in that part. It will be etched. Therefore, d _B is more preferably at most 2L.

Gravure cell pattern (2)
Next, in the example shown in FIG. 9, gravure cells having a mesh length L are formed at equal intervals in the pattern A portion as in the examples shown in FIGS. However, a gravure cell having a smaller volume than the gravure cell of the pattern A portion is formed in the pattern B portion. Since the volume of the gravure cell is small, the amount of resist ink applied to the region corresponding to the pattern B portion on the steel sheet surface is reduced, and as a result, a thin film portion is formed. In order to stably form the thin film portion, it is preferable that the volume of the gravure cell in the pattern B portion is ½ or less of the volume of the cell formed in the pattern A portion. The other points are preferably the same as the gravure cell pattern (1) described above.

In addition, when using a laser as an energy beam, it is preferable to use the looper for making plate feeding speed constant. When processing a steel plate continuously, generally, a process is continuously performed without interrupting by welding and passing coils. In the case of the welding or the like, as a result of the plate passing speed being reduced at a part of the line, the plate passing speed in the laser irradiation unit may be reduced. Then, the laser scanning speed v decreases according to the equation v = L _L / s × v _L , and the irradiation energy increases, which may change the quality of the resist (where L _L : Processing length per laser, s: beam interval in rolling direction, v _L : plate feed speed). In order to prevent this, it is preferable to install a looper in the line so that the plate passing speed in the laser irradiation unit is always constant.

(Second embodiment)
Next, the case where an electron beam is used as the energy beam will be described.
In the first embodiment using a laser, the resist removal portion is formed by applying a resist in advance while scanning the laser under a certain condition. On the other hand, when an electron beam is used as the energy beam, it is preferable that the resist removal portion is formed by keeping the coating thickness of the resist constant and controlling the scanning speed of the electron beam. This is because, unlike a laser that performs scanning by mechanical control, scanning of an electron beam is performed by electrical control, and thus has a high degree of freedom in varying the scanning speed. Electron beam irradiation is electrically scanned, so that irradiation conditions such as scanning speed can be accurately controlled even when scanning is performed at high speed. Therefore, the resist removal portion can be formed with sufficient accuracy by controlling the scanning speed.

Specifically, the electron beam scanning speed V _{1 at} the position where the resist removal portion on the steel plate surface is formed is lower than the electron beam scanning speed V _{2 at} other positions while controlling the scanning speed. It is preferable to irradiate a beam. In regions where the scanning speed is slow, the irradiation energy per unit scanning length increases, so the resist is removed. On the other hand, in regions where the scanning speed is high, the irradiation energy per unit scanning length decreases, so the resist only changes in quality. It remains without being removed.

  At that time, the acceleration voltage of the irradiated electron beam is preferably constant, and more preferably 40 kV or more. This is because if the acceleration voltage is too low, the transmission of the electron beam to the resist is lowered. If the electron beam permeability is low, alteration such as thermosetting occurs only on the surface layer of the resist, and the adhesion between the steel plate and the resist cannot be sufficiently lowered. It becomes difficult to remove. The acceleration voltage of the electron beam is more preferably 60 kV or higher. When electrons with high acceleration voltage are irradiated, the electrons lose energy mainly in the iron core, and the temperature rises. For this reason, since the resist is thermally cured through the base iron, the resist is easily peeled off at the surface of the base iron. On the other hand, if the acceleration voltage is excessively increased, the entire apparatus becomes excessively large in order to shield X-rays generated with the irradiation of the electron beam, so that the acceleration voltage is preferably 150 kV or less.

As described above, the scanning of the electron beam alternates between scanning at the speed V ₁ and scanning at the speed V ₂ on a straight line extending in a direction crossing the rolling direction of the steel sheet under the condition of V ₁ <V _2. It is preferable to repeat the steps. Since the portion scanned at the speed V ₁ corresponds to the resist removal portion, the length of the portion in the electron beam scanning direction is preferably 1 mm or more and 10 mm or less. Further, the portion scanned at the speed V ₂ is a portion where the resist remains even after the electron beam irradiation, and the length of the portion in the electron beam scanning direction is preferably 10 mm or more and 300 mm or less. Here, the scanning speed of the electron beam is a value obtained by (predetermined scanning length) / (time required to move the scanning length). V ₂ is preferably high from the viewpoint of production, and is preferably 100 m / sec or more. On the other hand, if V ₂ is excessively increased, it is necessary to increase the beam current value in order to sufficiently obtain the effect of electron beam irradiation, and as a result, the beam diameter increases. Therefore, V ₂ is preferably 500 m / sec or less. V ₁ was, may be appropriately adjusted so that the resist removal portion can be formed, but preferably set to 1 / 2V ₂ or less, and more preferably to 1 / 3V ₂ or less.

  When using an electron beam, the resist coating thickness is preferably 2 μm or less over the entire surface of the steel sheet. If the coating thickness exceeds 2 μm, the amount of resist that needs to be removed by electron beam irradiation increases, and the maintenance cycle of the apparatus is shortened. When applying the resist by gravure printing, as shown in FIG. 7, a gravure roll in which gravure cells are uniformly formed on the plate surface can be used.

  When using an electron beam, it is possible to measure the line speed and control the timing of beam irradiation so that the irradiation interval in the rolling direction is constant based on the measurement result even when the plate is passed at high speed. Is possible. Therefore, it is not always necessary to install a large looper facility for keeping the irradiation plate passing speed constant. The conditions other than those described in the second embodiment can be the conditions described in the first embodiment.

  Next, the present invention will be specifically described based on examples. The following examples show preferred examples of the present invention, and the present invention is not limited to the examples. Embodiments of the present invention can be modified as appropriate within the scope of the gist of the present invention, and any of them can be included in the technical scope of the present invention.

<Example 1>
Linear grooves were formed on the surface of the steel sheet by a method using a laser as an energy beam. As the steel sheet, a grain-oriented electrical steel sheet containing 3.4% Si having a thickness of 0.22 mm was used. First, after rolling according to a conventional method to obtain the grain-oriented electrical steel sheet, an etching resist was applied to the surface of the steel sheet by a gravure offset printing method. The gravure cell patterns of the gravure roll used are the following three types.

[Gravure cell pattern]
Type 1: A pattern in which cells A having a mesh length of 120 μm are arranged at regular intervals at intervals of 135 μm and a pattern B in which no cells exist are alternately formed in the gravure roll axial direction (shown in FIG. 8) Type).
Type 2: Pattern A in which cells having a mesh length of 100 μm are arranged at regular intervals at intervals of 115 μm, and patterns in which cells having a quarter volume of the cells of pattern A are arranged at regular intervals at intervals of 115 μm B is a pattern formed alternately in the axial direction of the gravure roll (type shown in FIG. 9).
Type 3: A pattern in which cells having a mesh length of 90 μm are formed at equal intervals on the entire surface at intervals of 105 μm (type shown in FIG. 7).

  Table 3 shows the type of gravure cell pattern used and the film thickness and length of each of the thick film portion and thin film portion of the resist formed. In addition, No. of a present Example. In 1-6, the thin film part was formed in parallel with the rolling direction of the steel plate. The lengths of the thick film portion and the thin film portion shown in Table 3 are the lengths in the width direction of the steel sheet, and are equal to the lengths in the roll axis direction of the pattern A portion and the pattern B portion, respectively.

After applying the resist ink under the above conditions, the resist was dried at 220 ° C. for 60 seconds. Next, the laser was irradiated under the conditions shown in Table 3 while scanning linearly in the width direction of the steel sheet. The diameter of the laser was 0.2 to 0.4 mm, and irradiation was periodically performed at intervals of 3.5 mm in the rolling direction. The length of the resist removal portion formed by this laser irradiation in the laser scanning direction is equal to the length of the thin film portion in Table 3. The distance between adjacent resist removal portions is equal to the length of the thick film portion in Table 3.

  The surface of the steel plate after the laser irradiation was observed, and the formation of the resist removal portion and the resist removal state in the thick film portion were evaluated. Regarding the item of “resist removal portion”, “○” was given for those in which a resist removal portion having a length in the laser scanning direction of 1 mm or more and 10 mm or less was formed. In addition, regarding the item of “thick film part resist removal”, the part where the resist has been completely removed in the part of the thick film part irradiated with the laser is “Yes”, and the resist is partially removed. The part that had been removed was “partially”, and the part in which the resist was not removed was designated “none”. The evaluation results are as shown in Table 3.

Subsequently, electrolytic etching was performed. The electrolyte was NaCl, and the current density was adjusted so that a desired cleaning groove was formed in advance. The electrolysis conditions were a 20% NaCl aqueous solution at 25 ° C., a current density of 8 A / dm ² , and an energization time of 3 min. The surface of the steel sheet after the etching was observed, and the resist was completely removed from the thick film part where the laser was irradiated. The thing was made into "x". After the etching, the resist remaining on the front and back surfaces of the steel plate was removed with an aqueous NaOH solution. The temperature of the NaOH aqueous solution was maintained at 50 to 70 ° C. Thereafter, water washing and surface washing were performed.

  As a result of the above test, the length and interval of the resist removal portion satisfy the conditions of the present invention. In 1 to 4, linear grooves could be formed by etching. Of these, No. In Nos. 1 and 2, since the laser output or irradiation energy is large, the thick film resist was partially removed by laser irradiation. In Nos. 3 and 4, the resist in the thick film portion was not removed by laser irradiation, and the linear groove could be formed with high accuracy. Further, in these embodiments, it is not necessary to remove all the resist existing in the portions where the linear grooves are formed, and it is only necessary to form the resist removal portions discretely, so that the amount of resist to be vaporized can be minimized. We were able to. As a result, the linear grooves could be stably formed without frequent maintenance of the apparatus.

  On the other hand, no. 5, although the length of the resist removal portion satisfied the conditions of the present invention, the distance between adjacent resist removal portions is as large as 600 mm. It could not be removed over the entire direction. As a result, a linear groove having an appropriate shape was not formed. No. 3 using a type 3 gravure cell pattern. In No. 6, the resist was uniformly applied to the entire surface of the steel plate with a thickness of 1 μm. As a result, the resist was removed in the entire region irradiated with the laser, and a large amount of fumes was generated. As described above, in the method of removing the resist with the laser over the entire width of the plate, the component of the volatilized resist adheres to the apparatus, so that uniform beam quality cannot be obtained over a long time, and the groove shape varies.

<Example 2>
A linear groove was formed on the surface of the steel sheet by a method using an electron beam as an energy beam. A directional electrical steel sheet similar to that used in Example 1 was used as the base material, and a resist was uniformly applied to the surface by gravure offset printing so as to have a film thickness of 1 μm. After drying at 200 ° C. for 30 seconds, an electron beam was irradiated while scanning in parallel with the plate width direction at an interval of 3.5 mm in the rolling direction. Table 4 shows the electron beam irradiation conditions.

  Subsequently, electrolytic etching and subsequent cleaning were performed in the same manner as in Example 1. At the end of etching, the surface of the steel plate was observed to evaluate “irradiation portion resist removal”. In the evaluation, “◯” indicates that the resist was removed in the portion irradiated with the electron beam, and “×” indicates that the resist remained. The evaluation results are as shown in Table 4.

No. In Example 7, electron beam irradiation was performed while alternately repeating a low speed scan at a speed V _{1 of} 140 m / sec and a high speed scan at a speed V _{2 of} 280 m / sec. The scanning length of the low-speed scanning unit was 3 mm, and the scanning length of the high-speed scanning unit was 30 mm. At the time after the electron beam irradiation, in the low-speed scanning portion, the resist was removed by the electron beam irradiation to form a resist removal portion, but the resist was not removed in the high-speed scanning portion. And the resist of the high-speed scanning part was fully removed by the subsequent etching, and the formation of the linear groove on the steel plate surface was appropriately performed.

  In contrast, no. In No. 8, the electron beam was scanned at a constant speed (280 m / sec), and no low-speed scanning unit was provided. As a result, the resist removal portion could not be formed properly, and the resist in the portion irradiated with the electron beam was not completely removed even by etching. Further, the width and depth of the grooves formed on the steel sheet surface after etching were not uniform.

DESCRIPTION OF SYMBOLS 10 Steel plate 20 Resist 21 Resist removal part 22 Etching liquid penetration part 30 Gravure cell 100 Gravure offset printing apparatus 101 Pickup roll 102 Ink 103 Gravure roll 104 Gravure cell 105 Doctor blade 106 Offset roll 107 Printed material 110 Steel plate 111 Resist 112 Non-application part

Claims (6)

A method of forming linear grooves on a steel sheet surface,
A resist coating step of coating a resist on the steel sheet surface;
By irradiating the surface of the steel sheet with an energy beam while scanning a straight line extending in a direction crossing the rolling direction of the steel sheet, the resist removal portion where the resist is removed and the surface of the steel sheet is exposed An energy beam irradiation process that forms an interval on a straight line; and
Etching to form a linear groove in the region irradiated with the energy beam,
The energy beam irradiation step is periodically performed in the rolling direction of the steel plate,
The resist removal portion has a length in the scanning direction of the energy beam of 1 mm or more and 10 mm or less,
The method of forming a linear groove | channel on the steel plate surface whose distance between the said resist removal parts adjacent on the said straight line is 10 mm or more and 300 mm or less. The energy beam is a laser;
In the resist coating step, a thick film portion having a resist coating thickness of 2.0 μm or more and a thin film portion having a resist coating thickness of 1.0 μm or less are formed,
The method for forming linear grooves on a steel sheet surface according to claim 1, wherein in the energy beam irradiation step, the thin film portion becomes the resist removal portion. Application of the resist in the resist application process is performed by gravure printing using a gravure roll,
The said gravure roll has the following pattern A for forming the said thick film part in the surface, and the following pattern B for forming the said thin film part, The linear groove | channel on the steel plate surface of Claim 2 How to form.
Pattern A: A pattern in which gravure cells with a mesh length L are arranged at equal intervals of 2 L or less Pattern B: A pattern without cells, or a cell whose volume is 1/2 or less of the cells in pattern A, etc. Patterns arranged at intervals The irradiation of the laser in the energy beam irradiation step,
Laser diameter in a direction perpendicular to the laser scanning direction on the steel sheet surface: 0.4 mm or less,
Output: 1500 W or less, and irradiation energy per unit scanning length: 5 J / m or more and 60 J / m or less,
The method of forming a linear groove | channel on the steel plate surface of Claim 2 or 3 performed on condition of this. The energy beam is an electron beam having an acceleration voltage of 40 kV or more;
In the resist coating step, the resist coating thickness is 2.0 μm or less,
In the energy beam irradiation step, the resist removal portion is formed by controlling the scanning speed of the electron beam and irradiating the electron beam until the resist is removed and the surface of the steel sheet is exposed. A method of forming a linear groove on the surface of the steel sheet. 6. The steel plate surface according to claim 5, wherein in the energy beam irradiation step, an electron beam scanning speed V _{1 at} a position where the resist removal portion is formed is less than an electron beam scanning speed V _{2 at} other positions. A method of forming a linear groove.