METAL PLATE MANUFACTURING METHOD FOR MANUFACTURING DEPOSITION MASK

Abstract

To provide a method for manufacturing a metal plate capable of accurately forming the component of a vapor deposition mask.SOLUTION: A method for manufacturing a metal plate includes the rolling step of obtaining a metal plate by rolling a base metal. The metal plate 64 having a plurality of hollows 64c positioned on the surface of the metal plate has a hollow correction volume density (V2 (0.2 μm)) of 12000 μm3 / mm2 or less and a hollow correction volume (V2 (0.3 μm)) of 6000 μm3 / mm2 or less, and the hollow correction volume density (V2 (0.2 μm)) is 2.16 times or more and 8.66 times or less of the hollow correction volume density (V2 (0.3 μm)).SELECTED DRAWING: Figure 18

Description

[Technical Field]

[0001] FIELD Embodiments of the present disclosure relate to a metal plate for manufacturing a deposition mask and a method for manufacturing the metal plate. Also, embodiments of the present disclosure relate to a deposition mask and a method for manufacturing the deposition mask. [Background technology]

[0002] In recent years, display devices used in portable devices such as smartphones and tablet PCs are required to have high definition, for example, a pixel density of 500 ppi or more. There is also a growing demand for portable devices to support ultra-high definition (UHD), and in this case, it is preferable that the pixel density of the display device be, for example, 800 ppi or more.

[0003] Among display devices, organic EL display devices have attracted attention due to their excellent responsiveness, low power consumption, and high contrast. A known method for forming pixels in an organic EL display device is to use a deposition mask with through-holes arranged in a desired pattern to form pixels in the desired pattern. Specifically, the deposition mask is first attached to a substrate for the organic EL display device, and then the attached deposition mask and the substrate are placed together in a deposition device to perform a deposition process in which an organic material is deposited on the substrate. This allows pixels containing the organic material to be formed on the substrate in a pattern corresponding to the pattern of the through-holes in the deposition mask.

[0004] A known method for manufacturing a deposition mask involves forming through-holes in a metal plate by etching using photolithography. For example, first, a first resist pattern is formed on a first surface of the metal plate by exposure and development, and a second resist pattern is formed on a second surface of the metal plate by exposure and development. Next, areas of the first surface of the metal plate that are not covered by the first resist pattern are etched to form first recesses on the first surface of the metal plate. Then, areas of the second surface of the metal plate that are not covered by the second resist pattern are etched to form second recesses on the second surface of the metal plate. By performing the etching so that the first recesses and the second recesses communicate with each other, through-holes penetrating the metal plate can be formed. The metal plate used to manufacture the deposition mask is manufactured, for example, by rolling a base material made of an iron alloy containing nickel. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 5382259 Summary of the Invention

[0006] An object of an embodiment of the present disclosure is to provide a metal plate suitable for manufacturing a deposition mask.

[0007] One embodiment of the present disclosure is a method for manufacturing a metal plate for manufacturing a deposition mask, comprising: a rolling step of rolling a base material to obtain the metal plate, the metal plate has a plurality of depressions located on a surface of the metal plate; The surface is 0.1 mm 2 an inspection area having an area of at least one of the plurality of recesses, and a part of the plurality of recesses is located in the inspection area; The metal plate is 12000 μm 3 / mm 2the dent-corrected volumetric density (V2(0.2 μm)) is calculated by dividing the dent-corrected volume by the area of the inspection region, the dent correction volume is a sum of volumes of portions of the part of the plurality of dents located in the inspection region that are 0.2 μm or more away from the surface in a thickness direction of the metal plate, the volume is calculated based on a result of measuring depths of the portions of the plurality of recesses using a laser microscope; The metal plate is 6000 μm 3 / mm 2 The following dent-corrected volume density (V2 (0.3 μm)) is obtained: the dent-corrected volume density (V2 (0.3 μm)) is calculated by dividing the sum of volumes of portions of the part of the plurality of dents located in the inspection area that are 0.3 μm or more away from the surface in the thickness direction of the metal plate by an area of the inspection area; In the method for manufacturing a metal plate, the dent-corrected volume density (V2 (0.2 μm)) is 2.16 times or more and 8.66 times or less the dent-corrected volume density (V2 (0.3 μm)).

[0008] In the method for manufacturing a metal plate according to an embodiment of the present disclosure, the area of the inspection region is 1.5 mm 2 It may be the following:

[0009] In the method for manufacturing a metal plate according to an embodiment of the present disclosure, the dent-corrected volume density (V2 (0.2 μm)) is 996 μm 3 / mm 2 It may be more than that.

[0010] In the method for manufacturing a metal plate according to one embodiment of the present disclosure, the metal plate may be made of an iron alloy containing nickel.

[0011] In the method for manufacturing a metal plate according to an embodiment of the present disclosure, the metal plate may have a thickness of 30 μm or less.

[0012] According to an embodiment of the present disclosure, a metal plate suitable for manufacturing a deposition mask can be efficiently obtained. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a diagram showing a vapor deposition apparatus including a vapor deposition mask device according to an embodiment of the present disclosure. [Figure 2] 2 is a cross-sectional view showing an organic EL display device (an intermediate product of an organic EL display device) manufactured using the vapor deposition mask device shown in FIG. [Figure 3] FIG. 1 is a plan view showing a deposition mask device according to an embodiment of the present disclosure. [Figure 4] FIG. 4 is a partial plan view showing an effective area of the deposition mask shown in FIG. [Figure 5] FIG. 5 is a cross-sectional view taken along line VV in FIG. [Figure 6] FIG. 6 is a cross-sectional view taken along line VI-VI in FIG. [Figure 7] FIG. 7 is a cross-sectional view taken along line VII-VII in FIG. [Figure 8] FIG. 10 is a partial plan view showing a modified example of the effective area of the deposition mask. [Figure 9] FIG. 9 is a cross-sectional view taken along line IX-IX in FIG. 8. [Figure 10] FIG. 2 is an enlarged cross-sectional view showing a through hole and a region in its vicinity. [Figure 11] 1A to 1C are diagrams showing a process of rolling a base material to obtain a metal plate having a desired thickness. [Figure 12] FIG. 1 is a diagram showing a process of annealing a metal plate obtained by rolling. [Figure 13] FIG. 1 is a diagram showing a state in which a plurality of depressions exist on the surface of a metal plate obtained by rolling. [Figure 14] FIG. 2 is a diagram showing an example of a cross section of a metal plate. [Figure 15] 15 is a cross-sectional view showing a step of etching the metal plate shown in FIG. 14 from the first surface side to form a second recess. [Figure 16] 10 is a cross-sectional view showing a step of forming a second recess communicating with the first recess on the second surface side of the metal plate. FIG. [Figure 17] 10A and 10B are diagrams for explaining a state in which the accuracy of the opening dimensions of a through hole decreases due to a depression in a metal plate. [Figure 18] FIG. 10 is a plan view for explaining the metal plate inspection process. [Figure 19] 10A and 10B are cross-sectional views for explaining an inspection process of a metal plate. [Figure 20] 1A to 1C are schematic diagrams for explaining an example of a method for manufacturing a deposition mask overall. [Figure 21] 1A to 1C are diagrams illustrating a process of forming a resist film on a metal plate. [Figure 22] 10A to 10C are diagrams illustrating a process of bringing an exposure mask into close contact with a resist film. [Figure 23] 1A to 1C are diagrams illustrating a process of developing a resist film. [Figure 24] FIG. 10 is a diagram showing a first surface etching step. [Figure 25] FIG. 10 is a diagram showing a step of covering the first recess with resin. [Figure 26] FIG. 10 is a diagram showing a second surface etching step. [Figure 27] FIG. 27 is a diagram showing a second surface etching step subsequent to FIG. 26. [Figure 28] 10A to 10C are diagrams showing steps of removing the resin and the resist pattern from the metal plate. [Figure 29] 10 is a table showing the results of inspecting the state of depressions on the surface of each sample according to the first inspection example. [Figure 30] 4 is a plan view showing an example of a pattern of recesses and ribs formed on each metal plate. FIG. [Figure 31] FIG. 31 is a cross-sectional view of the metal plate shown in FIG. 30. [Figure 32] 10A and 10B are plan views showing other examples of patterns of recesses and ribs formed on each metal plate. [Figure 33] 10 is a scatter diagram showing the correlation between the index obtained by the first inspection example and the dimensional accuracy of the rib portion formed on each sample. FIG. [Figure 34] 10 is a table showing the results of inspecting the state of depressions on the surface of each metal plate sample by the second to fifth inspection examples. [Figure 35] FIG. 10 is a scatter diagram showing the correlation between the index obtained by the second inspection example and the dimensional accuracy of the rib portion formed on each sample. [Figure 36] FIG. 10 is a scatter diagram showing the correlation between the index obtained by the third inspection example and the dimensional accuracy of the rib portion formed on each sample. [Figure 37] FIG. 10 is a scatter diagram showing the correlation between the index obtained by the fourth inspection example and the dimensional accuracy of the rib portion formed on each sample. [Figure 38] FIG. 10 is a scatter diagram showing the correlation between the index obtained by the fifth inspection example and the dimensional accuracy of the rib portion formed on each sample. [Figure 39] FIG. 10 is a diagram showing an example of the distribution of dent-corrected volume density of a plurality of selected metal plates. [Figure 40] FIG. 10 is a diagram showing an example of the distribution of dent-corrected volume density of a plurality of selected metal plates. [Figure 41] FIG. 10 is a diagram showing an example of the distribution of dent-corrected volume density of a plurality of manufactured metal plates. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, an embodiment of the present disclosure will be described with reference to the drawings. In the drawings accompanying this specification, the scale and aspect ratios of the actual objects have been appropriately changed and exaggerated for the sake of ease of illustration and understanding.

[0015] Note that the embodiments of the present disclosure may be combined with other embodiments or variations thereof to the extent that no contradictions arise. Furthermore, other embodiments may be combined with each other, or other embodiments may be combined with variations thereof to the extent that no contradictions arise. Furthermore, variations may be combined with each other to the extent that no contradictions arise.

[0016] Furthermore, in embodiments of the present disclosure, when a plurality of steps are disclosed in a method such as a manufacturing method, other steps that are not disclosed may be performed between the disclosed steps. Furthermore, the order of the disclosed steps may be arbitrary as long as no contradiction occurs.

[0017] Additionally, problems that the embodiments of the present disclosure aim to solve will be described.

[0018] After rolling, depressions such as oil pits may be formed on the surface of a metal plate. The state of the depressions on the surface of the metal plate affects the dimensional accuracy and positional accuracy of the through holes formed in the metal plate. For example, if the depth of the depressions on the surface of the metal plate increases, the dimensions of the through holes formed in the metal plate will be larger than the design values. Therefore, technology to inspect the state of depressions on the surface of metal plates is important.

[0019] A known technique for inspecting undulations such as depressions on the surface of a metal plate involves calculating the arithmetic mean roughness Ra and maximum height Ry of the surface. The arithmetic mean roughness Ra is a value obtained by measuring the position (hereinafter also referred to as the height position) of the surface of the metal plate in the thickness direction of the metal plate at multiple points on a specified straight line and calculating the average. The maximum height Ry is the difference between the maximum and minimum values of the measurement results when the height position of the surface of the metal plate is measured at multiple points on a specified straight line.

[0020] The present inventors conducted extensive research and found that the correlation between the surface roughness index used in conventional techniques, such as the arithmetic mean roughness Ra, and the dimensional accuracy of through holes formed in metal plates is not necessarily high. Therefore, if the quality of a metal plate is judged based on the arithmetic mean roughness Ra, it is necessary to set an unnecessarily strict threshold for pass / fail judgment to prevent erroneous judgment. This results in a decrease in the yield of the metal plate.

[0021] An object of the embodiments of the present disclosure is to provide a metal plate, a method for manufacturing a metal plate, a deposition mask, and a method for manufacturing a deposition mask that can effectively solve such problems.

[0022] 1 to 28 are diagrams illustrating an embodiment of the present disclosure. In the following embodiment and its modified examples, a method for manufacturing a deposition mask used to pattern an organic material in a desired pattern on a substrate when manufacturing an organic EL display device will be described as an example. However, the present disclosure is not limited to such applications, and can be applied to deposition masks used for various purposes.

[0023] In this specification, the terms "plate," "sheet," and "film" are not distinguished from one another solely based on the difference in name. For example, the term "plate" is a concept that includes members that can be called sheets or films.

[0024] Furthermore, the term "plate surface (sheet surface, film surface)" refers to the surface that coincides with the planar direction of the target plate-shaped (sheet-shaped, film-shaped) member when the target plate-shaped (sheet-shaped, film-shaped) member is viewed overall and in a broad perspective. Furthermore, the normal direction used for a plate-shaped (sheet-shaped, film-shaped) member refers to the normal direction to the plate surface (sheet surface, film surface) of the member.

[0025] Furthermore, terms used in this specification that specify shapes, geometric conditions, physical characteristics, and their degrees, such as "parallel," "orthogonal," "identical," and "equivalent," as well as values of lengths, angles, and physical characteristics, are not to be construed as being bound by strict meanings, but rather as including the range within which similar functions can be expected.

[0026] First, a vapor deposition apparatus 90 for performing a vapor deposition process of depositing a vapor deposition material on a target object will be described with reference to FIG. 1. As shown in FIG. 1, the vapor deposition apparatus 90 may include therein a vapor deposition source (e.g., a crucible 94), a heater 96, and a vapor deposition mask device 10. The vapor deposition apparatus 90 may further include an exhaust means for creating a vacuum atmosphere inside the vapor deposition apparatus 90. The crucible 94 contains a vapor deposition material 98 such as an organic light-emitting material. The heater 96 heats the crucible 94 to evaporate the vapor deposition material 98 under a vacuum atmosphere. The vapor deposition mask device 10 is disposed opposite the crucible 94.

[0027] The deposition mask device 10 will be described below. As shown in FIG. 1, the deposition mask device 10 may include a deposition mask 20 and a frame 15 that supports the deposition mask 20. The frame 15 supports the deposition mask 20 in a state where it is pulled in the direction of its surface to prevent the deposition mask 20 from bending. As shown in FIG. 1, the deposition mask device 10 is placed in a deposition device 90 so that the deposition mask 20 faces a substrate, for example, an organic EL substrate 92, which is an object to which a deposition material 98 is to be attached. In the following description, of the surfaces of the deposition mask 20, the surface facing the organic EL substrate 92 is referred to as a first surface 20a, and the surface opposite the first surface 20a is referred to as a second surface 20b.

[0028] 1, the deposition mask device 10 may include a magnet 93 arranged on the surface of the organic EL substrate 92 opposite to the deposition mask 20. By providing the magnet 93, the deposition mask 20 can be attracted to the magnet 93 by magnetic force, thereby making the deposition mask 20 adhere closely to the organic EL substrate 92.

[0029] 3 is a plan view showing the deposition mask device 10 as viewed from the first surface 20a side of the deposition mask 20. As shown in FIG. 3, the deposition mask device 10 may include a plurality of deposition masks 20. Each deposition mask 20 may include a pair of long sides 26 and a pair of short sides 27. For example, each deposition mask 20 may have a rectangular shape. Each deposition mask 20 may be fixed to the frame 15 at the pair of short sides 27 or at portions in the vicinity thereof by, for example, spot welding.

[0030] The deposition mask 20 may include a metal plate-shaped base material having a plurality of through-holes 25 formed therein. The deposition material 98 that evaporates from the crucible 94 and reaches the deposition mask device 10 passes through the through-holes 25 of the deposition mask 20 and adheres to the organic EL substrate 92. This allows the deposition material 98 to be formed into a film on the surface of the organic EL substrate 92 in a desired pattern corresponding to the positions of the through-holes 25 of the deposition mask 20.

[0031] FIG. 2 is a cross-sectional view showing an organic EL display device 100 manufactured using the vapor deposition apparatus 90 of FIG. 1. The organic EL display device 100 includes at least an organic EL substrate 92 and pixels including a patterned vapor deposition material 98. Although not shown, the organic EL display device 100 further includes electrodes electrically connected to the pixels including the vapor deposition material 98. The electrodes are provided on the organic EL substrate 92 in advance, for example, before the vapor deposition material 98 is attached to the organic EL substrate 92 by a vapor deposition process. The organic EL display device 100 may also include other components, such as a sealing member that seals the space around the pixels including the vapor deposition material 98 from the outside. Therefore, the organic EL display device 100 of FIG. 2 can also be considered an intermediate organic EL display device produced at an intermediate stage in the manufacture of an organic EL display device.

[0032] When a color display using a plurality of colors is desired, vapor deposition devices 90 equipped with vapor deposition masks 20 corresponding to the respective colors are prepared, and the organic EL substrates 92 are sequentially placed in each vapor deposition device 90. This allows, for example, red, green, and blue organic light-emitting materials to be vapor-deposited onto the organic EL substrate 92 in that order.

[0033] Incidentally, the vapor deposition process may be performed inside a vapor deposition apparatus 90, which is in a high-temperature atmosphere. In this case, the vapor deposition mask 20, the frame 15, and the organic EL substrate 92 held inside the vapor deposition apparatus 90 are also heated during the vapor deposition process. At this time, the vapor deposition mask 20, the frame 15, and the organic EL substrate 92 exhibit dimensional change behavior based on their respective thermal expansion coefficients. In this case, if the thermal expansion coefficients of the vapor deposition mask 20 or the frame 15 and the organic EL substrate 92 differ significantly, misalignment occurs due to the difference in dimensional change, resulting in a decrease in the dimensional accuracy and positional accuracy of the vapor deposition material deposited on the organic EL substrate 92.

[0034] To solve this problem, it is preferable that the thermal expansion coefficients of the deposition mask 20 and the frame 15 are equivalent to that of the organic EL substrate 92. For example, when a glass substrate is used as the organic EL substrate 92, an iron alloy containing nickel can be used as the main material of the deposition mask 20 and the frame 15. For example, an iron alloy containing 30% to 54% by mass of nickel can be used as the material of the base material constituting the deposition mask 20. Specific examples of iron alloys containing nickel include Invar material containing 34% to 38% by mass of nickel, Super Invar material containing 30% to 34% by mass of nickel and also cobalt, and low-thermal expansion Fe—Ni-based plating alloys containing 38% to 54% by mass of nickel.

[0035] If the temperatures of the deposition mask 20, the frame 15, and the organic EL substrate 92 do not reach high temperatures during the deposition process, there is no particular need to make the thermal expansion coefficients of the deposition mask 20 and the frame 15 equal to the thermal expansion coefficient of the organic EL substrate 92. In this case, materials other than the iron alloys described above may be used as the material for the deposition mask 20. For example, iron alloys other than the nickel-containing iron alloys described above, such as iron alloys containing chromium, may be used. As the iron alloy containing chromium, for example, iron alloys known as stainless steel may be used. Furthermore, alloys other than iron alloys, such as nickel or nickel-cobalt alloys, may also be used.

[0036] Next, the deposition mask 20 will be described in detail. As shown in Fig. 3, the deposition mask 20 may include a pair of ears (a first ear 17a and a second ear 17b) including a pair of short sides 27 of the deposition mask 20, and a middle portion 18 located between the pair of ears 17a and 17b.

[0037] First, the ears 17a and 17b will be described in detail. The ears 17a and 17b are portions of the deposition mask 20 that are fixed to the frame 15. In the present embodiment, the ears 17a and 17b are integrally formed with the intermediate portion 18. Note that the ears 17a and 17b may be formed of a member separate from the intermediate portion 18. In this case, the ears 17a and 17b are joined to the intermediate portion 18 by, for example, welding.

[0038] Next, the intermediate portion 18 will be described. The intermediate portion 18 may include at least one effective area 22 in which a through-hole 25 extending from the first surface 20a to the second surface 20b is formed, and a peripheral area 23 surrounding the effective area 22. The effective area 22 is an area of the deposition mask 20 that faces the display area of the organic EL substrate 92.

[0039] 3, the intermediate portion 18 includes a plurality of effective areas 22 arranged at predetermined intervals along the long side 26 of the deposition mask 20. One effective area 22 corresponds to the display area of one organic EL display device 100. Therefore, the deposition mask device 10 shown in FIG. 1 enables multi-surface deposition of the organic EL display device 100. Note that one effective area 22 may correspond to a plurality of display areas.

[0040] 3, the effective area 22 may have, for example, a substantially quadrangular shape in a plan view, or more precisely, a substantially rectangular shape in a plan view. Although not shown, each effective area 22 may have a contour of various shapes depending on the shape of the display area of the organic EL substrate 92. For example, each effective area 22 may have a circular contour. Furthermore, each effective area 22 may have a contour that is the same as the outer shape of a display device such as a smartphone.

[0041] The effective area 22 will be described in detail below. FIG. 4 is an enlarged plan view of the effective area 22 from the second surface 20b side of the deposition mask 20. As shown in FIG. 4, in the illustrated example, the plurality of through holes 25 formed in each effective area 22 may be arranged at a predetermined pitch along two directions perpendicular to each other in the effective area 22. An example of the through holes 25 will be described in further detail mainly with reference to FIGS. 5 to 7. FIGS. 5 to 7 are cross-sectional views of the effective area 22 of FIG. 4 taken along the VV direction to the VII-VII direction, respectively.

[0042] As shown in FIGS. 5 to 7 , the plurality of through holes 25 penetrate from a first surface 20a, which is one side of the deposition mask 20 in the normal direction N, to a second surface 20b, which is the other side of the deposition mask 20 in the normal direction N. In the illustrated example, as will be described in detail later, first recesses 30 are formed by etching on the first surface 21a of the metal plate 21, which is one side of the deposition mask 20 in the normal direction N, and second recesses 35 are formed on the second surface 21b of the metal plate 21, which is the other side of the deposition mask 20 in the normal direction N. The first recesses 30 are connected to the second recesses 35, so that the second recesses 35 and the first recesses 30 communicate with each other. The through holes 25 are each composed of the second recesses 35 and the first recesses 30 connected to the second recesses 35.

[0043] 5 to 7 , the opening area of each second recess 35 in a cross section along the plate surface of the deposition mask 20 at each position along the normal direction N of the deposition mask 20 gradually decreases from the second surface 20b side toward the first surface 20a side of the deposition mask 20. Similarly, the opening area of each first recess 30 in a cross section along the plate surface of the deposition mask 20 at each position along the normal direction N of the deposition mask 20 gradually decreases from the first surface 20a side toward the second surface 20b side of the deposition mask 20.

[0044] 5 to 7 , the wall surface 31 of the first recess 30 and the wall surface 36 of the second recess 35 are connected via a circumferential connecting portion 41. The connecting portion 41 is defined by a ridge line of a protruding portion where the wall surface 31 of the first recess 30, which is inclined with respect to the normal direction N of the deposition mask 20, and the wall surface 36 of the second recess 35, which is inclined with respect to the normal direction N of the deposition mask 20, join together. The connecting portion 41 defines a through portion 42 where the opening area of the through hole 25 is minimized in a plan view of the deposition mask 20.

[0045] 5 to 7 , on the other surface of the deposition mask 20 along the normal direction N, i.e., on the first surface 20a of the deposition mask 20, two adjacent through holes 25 are spaced apart from each other along the plate surface of the deposition mask 20. That is, as in the manufacturing method described below, when the first recesses 30 are formed by etching the metal plate 21 from the side of the first surface 21a of the metal plate 21 that corresponds to the first surface 20a of the deposition mask 20, the first surface 21a of the metal plate 21 remains between the two adjacent first recesses 30.

[0046] Similarly, as shown in FIGS. 5 to 7 , on one side of the deposition mask 20 along the normal direction N, i.e., on the side of the second surface 20b of the deposition mask 20, two adjacent second recesses 35 are spaced apart from each other along the plate surface of the deposition mask 20. That is, the second surface 21b of the metal plate 21 remains between two adjacent second recesses 35. In the following description, the portion of the effective area 22 of the second surface 21b of the metal plate 21 that remains unetched is also referred to as a top portion 43. By fabricating the deposition mask 20 so that such a top portion 43 remains, the deposition mask 20 can be provided with sufficient strength. This can prevent the deposition mask 20 from being damaged, for example, during transportation. Note that if the width β of the top portion 43 is too large, a shadow may occur during the deposition process, which may reduce the utilization efficiency of the deposition material 98. Therefore, it is preferable to fabricate the deposition mask 20 so that the width β of the top portion 43 is not excessively large. For example, the width β of the top portion 43 is preferably 2 μm or less. The width β of the top portion 43 generally varies depending on the cutting direction of the deposition mask 20. For example, the widths β of the top portions 43 shown in FIGS. 5 to 7 may differ from one another. In this case, the deposition mask 20 may be configured so that the width β of the top portion 43 is 2 μm or less regardless of the cutting direction of the deposition mask 20. A shadow is a phenomenon in which the second surface 20b or a wall surface of the deposition mask 20 prevents deposition of a deposition material to a region of a deposition target, such as an organic EL substrate 92, that overlaps with a through-hole of the deposition mask 20.

[0047] 1 is housed in the deposition mask device 90, the first surface 20a of the deposition mask 20 faces the organic EL substrate 92, and the second surface 20b of the deposition mask 20 faces the crucible 94 holding the deposition material 98, as indicated by the two-dot chain line in FIG. 5. Therefore, the deposition material 98 passes through the second recess 35, the opening area of which gradually decreases, and adheres to the organic EL substrate 92. As indicated by the arrow pointing from the second surface 20b toward the first surface 20a in FIG. 5, the deposition material 98 moves from the crucible 94 toward the organic EL substrate 92 not only along the normal direction N of the organic EL substrate 92 but also in a direction significantly inclined relative to the normal direction N of the organic EL substrate 92. In this case, if the thickness of the deposition mask 20 is large, the deposition material 98 moving obliquely is likely to get caught on the top portion 43, the wall surface 36 of the second recess 35, and the wall surface 31 of the first recess 30. As a result, a large proportion of the deposition material 98 does not pass through the through-holes 25. Therefore, in order to improve the utilization efficiency of the deposition material 98, it is preferable to reduce the thickness t of the deposition mask 20, thereby reducing the height of the wall surface 36 of the second recess 35 and the wall surface 31 of the first recess 30. In other words, it is preferable to use a metal plate 21 having as small a thickness t as possible as long as the strength of the deposition mask 20 can be ensured. In consideration of this, in this embodiment, the thickness t of the deposition mask 20 is, for example, 30 μm or less, preferably 25 μm or less, and more preferably 20 μm or less. The thickness t of the deposition mask 20 may be 18 μm or less, or may be 15 μm or less. On the other hand, if the thickness of the deposition mask 20 is too small, the strength of the deposition mask 20 decreases, and the deposition mask 20 becomes more susceptible to damage or deformation. In consideration of this, the thickness t of the deposition mask 20 may be 5 μm or more, 7 μm or more, 10 μm or more, 13 μm or more, or 15 μm or more. The thickness t is the thickness of the peripheral region 23, i.e., the thickness of the portion of the deposition mask 20 where the first recesses 30 and the second recesses 35 are not formed. Therefore, it can also be said that the thickness t is the thickness of the metal plate 21.

[0048] The range of the thickness t of the deposition mask 20 may be determined by a combination of any one of the above-described multiple upper limit candidate values and any one of the above-described multiple lower limit candidate values. For example, the thickness t of the deposition mask 20 may be 5 μm or more and 30 μm or less, 7 μm or more and 25 μm or less, 10 μm or more and 20 μm or less, or 13 μm or more and 18 μm or less. The range of the thickness t of the deposition mask 20 may be determined by a combination of any two of the above-described multiple upper limit candidate values. For example, the thickness t of the deposition mask 20 may be 25 μm or more and 300 μm or less. The range of the thickness t of the deposition mask 20 may be determined by a combination of any two of the above-described multiple lower limit candidate values. For example, the thickness t of the deposition mask 20 may be 5 μm or more and 7 μm or less.

[0049] 5, the symbol θ1 denotes the minimum angle that a straight line L1, which passes through the connection portion 41, which is the portion of the through-hole 25 with the smallest opening area, and any other position on the wall surface 36 of the second recess 35, forms with respect to the normal direction N of the deposition mask 20. Increasing the angle θ1 is advantageous for allowing the deposition material 98 moving obliquely to reach as far as possible on the organic EL substrate 92 without reaching the wall surface 36. In order to increase the angle θ1, it is effective to reduce the width β of the top portion 43 described above, in addition to reducing the thickness t of the deposition mask 20.

[0050] 7, the symbol α represents the width of the portion of the effective area 22 of the first surface 21a of the metal plate 21 that remains unetched (hereinafter also referred to as the rib portion). The width α of the rib portion and the dimension r2 of the through portion 42 are determined appropriately depending on the dimensions and number of display pixels of the organic EL display device. For example, the width α of the rib portion is 5 μm or more and 40 μm or less, and the dimension r2 of the through portion 42 is 10 μm or more and 60 μm or less.

[0051] The width α of the rib portion may be 10 μm or more, 15 μm or more, or 20 μm or more. The width α of the rib portion may be 35 μm or less, 30 μm or less, or 25 μm or less. The range of the width α of the rib portion may be determined by combining any one of the above-mentioned multiple upper limit candidate values with any one of the above-mentioned multiple lower limit candidate values. For example, the width α of the rib portion may be 10 μm or more and 35 μm or less, 15 μm or more and 30 μm or less, or 20 μm or more and 25 μm or less. The range of the width α of the rib portion may be determined by combining any two of the above-mentioned multiple upper limit candidate values. For example, the width α of the rib portion may be 35 μm or more and 40 μm or less. The range of the width α of the rib portion may be determined by combining any two of the above-mentioned multiple lower limit candidate values. For example, the width α of the rib portion may be 5 μm or more and 10 μm or less.

[0052] The dimension r2 of the through portion 42 may be 15 μm or more, 20 μm or more, 25 μm or more, or 30 μm or more. The lower limit of the dimension r2 of the through portion 42 may be smaller than the above-mentioned 10 μm. For example, the dimension r of the through portion 42 may be 5 μm or more. The dimension r2 of the through portion 42 may be 55 μm or less, 50 μm or less, 45 μm or less, 40 μm or less, or 35 μm or less. The range of the dimension r2 of the through portion 42 may be determined by combining any one of the above-mentioned multiple upper limit candidate values with any one of the above-mentioned multiple lower limit candidate values. For example, the dimension r2 of the through portion 42 may be 15 μm or more and 55 μm or less, 20 μm or more and 50 μm or less, 25 μm or more and 45 μm or less, 30 μm or more and 40 μm or less, or 30 μm or more and 35 μm or less. The range of the dimension r2 of the through portion 42 may be determined by a combination of any two of the above-mentioned multiple upper limit candidate values. For example, the dimension r2 of the through portion 42 may be 55 μm or more and 60 μm or less. The range of the dimension r2 of the through portion 42 may be determined by a combination of any two of the above-mentioned multiple lower limit candidate values. For example, the dimension r2 of the through portion 42 may be 5 μm or more and 10 μm or less.

[0053] 4 to 7 show an example in which the second surface 21b of the metal plate 21 remains between two adjacent second recesses 35, but this is not limiting. As shown in FIG. 8, etching may be performed so that two adjacent second recesses 35 are connected in some locations. That is, there may be a location between two adjacent second recesses 35 where the second surface 21b of the metal plate 21 does not remain. Furthermore, although not shown, etching may be performed so that two adjacent second recesses 35 are connected over the entire area of the second surface 21b. FIG. 9 is a cross-sectional view taken along the IX-IX direction of the effective area 22 of FIG. 8.

[0054] Although not limited thereto, the deposition mask 20 according to the present embodiment is particularly effective when fabricating an organic EL display device with a pixel density of 450 ppi or more. Hereinafter, an example of the dimensions of the deposition mask 20 required for fabricating an organic EL display device with such a high pixel density will be described with reference to Fig. 10. Fig. 10 is an enlarged cross-sectional view showing the through-hole 25 of the deposition mask 20 shown in Fig. 5 and the surrounding area.

[0055] 10, as a parameter related to the shape of the through hole 25, the distance from the first surface 20a of the deposition mask 20 to the connection portion 41 in the direction along the normal direction N of the deposition mask 20, i.e., the height of the wall surface 31 of the first recess 30, is denoted by symbol r1. Furthermore, the dimension of the first recess 30 at the portion where the first recess 30 connects to the second recess 35, i.e., the dimension of the through portion 42, is denoted by symbol r2. Also in FIG. 10, the angle formed by a straight line L2 connecting the connection portion 41 and the tip edge of the first recess 30 on the first surface 21a of the metal plate 21 with the normal direction N of the metal plate 21 is denoted by symbol θ2.

[0056] When an organic EL display device with a pixel density of 450 ppi or more is manufactured, the dimension r2 of the through portion 42 is preferably set to 10 μm or more and 60 μm or less. This makes it possible to provide a deposition mask 20 that can manufacture an organic EL display device with a high pixel density. Preferably, the height r1 of the wall surface 31 of the first recess 30 is set to 6 μm or less.

[0057] Next, the angle θ2 shown in FIG. 10 will be described. The angle θ2 corresponds to the maximum inclination angle of the vapor deposition material 98 that is inclined with respect to the normal direction N of the metal plate 21 and that can reach the organic EL substrate 92 among the vapor deposition material 98 that flies and passes through the through-hole 42 near the connection portion 41. This is because the vapor deposition material 98 that flies through the connection portion 41 at an inclination angle greater than the angle θ2 adheres to the wall surface 31 of the first recess 30 before reaching the organic EL substrate 92. Therefore, by reducing the angle θ2, it is possible to prevent the vapor deposition material 98 that flies at a large inclination angle and passes through the through-hole 42 from adhering to the organic EL substrate 92. This prevents the vapor deposition material 98 from adhering to portions of the organic EL substrate 92 outside the portions that overlap the through-hole 42. In other words, reducing the angle θ2 leads to reduced variations in the area and thickness of the vapor deposition material 98 that adheres to the organic EL substrate 92. From this perspective, for example, the through-hole 25 is formed so that the angle θ2 is 45 degrees or less. 10 shows an example in which the dimension of the first recess 30 in the first surface 21a, i.e., the opening dimension of the through-hole 25 in the first surface 21a, is larger than the dimension r2 of the first recess 30 in the connecting portion 41. That is, an example in which the value of the angle θ2 is a positive value is shown. However, although not shown, the dimension r2 of the first recess 30 in the connecting portion 41 may be larger than the dimension of the first recess 30 in the first surface 21a. That is, the value of the angle θ2 may be a negative value.

[0058] Next, a method for manufacturing the deposition mask 20 will be described.

[0059] First, a method for manufacturing a metal plate used to manufacture a deposition mask will be described. In this embodiment, an example will be described in which the metal plate is made of a rolled material of an iron alloy containing nickel. The rolled material may have a thickness of 30 μm or less. The rolled material may also contain 30 mass % or more and 38 mass % or less of nickel, 0 mass % or more and 6 mass % or less of cobalt, the balance being iron and unavoidable impurities.

[0060] First, iron, nickel, and other raw materials are prepared. For example, the raw materials are prepared so that the iron and nickel ratios relative to the total raw materials are approximately 64% by weight and approximately 36% by weight, respectively. Next, the raw materials are crushed as needed, and then a melting process is carried out in which the raw materials are melted in a melting furnace. For example, the raw materials are melted and mixed using gas discharge such as arc discharge. This process allows the base material for the metal plate to be obtained.

[0061] The melting temperature is set depending on the raw materials, but is, for example, 1500°C or higher. The melting step may include a step of introducing aluminum, manganese, silicon, etc. into the melting furnace for deoxidation, dehydration, denitrification, etc. The melting step may also be carried out under a low-pressure state lower than atmospheric pressure and in an inert gas atmosphere such as argon gas.

[0062] After removing the base material from the melting furnace, a grinding step may be carried out to scrape off the surface of the base material. This allows oxide coatings such as scale to be removed. The specific grinding method is not particularly limited, but may be a so-called grinding method in which the surface of the base material is scraped by rotating a grinding wheel, or a so-called pushing method in which the surface of the base material is scraped by forcing the base material into a cutting tool. The grinding step may be carried out so that the thickness of the base material is uniform.

[0063] Next, as shown in FIG. 11, a rolling process is performed to roll a base material 60 made of an iron alloy containing nickel. For example, the base material 60 is conveyed toward a rolling device 66 including a pair of rolling rolls 66a, 66b (work rolls) while applying a tensile force in the direction indicated by arrow D1. The base material 60 that arrives between the pair of rolling rolls 66a, 66b is rolled by the pair of rolling rolls 66a, 66b. As a result, the thickness of the base material 60 is reduced and the base material 60 is stretched along the conveying direction. This allows a metal plate 64 having a thickness T0 to be obtained. As shown in FIG. 11, the metal plate 64 may be wound around a core 61 to form a wound body 62.

[0064] Note that FIG. 11 merely illustrates an outline of the rolling process, and the specific configuration and procedures for performing the rolling process are not particularly limited. For example, the rolling process may include a hot rolling process in which the base material 60 is processed at a temperature equal to or higher than the temperature at which the crystal orientation of the iron alloy constituting the base material 60 changes, or a cold rolling process in which the base material is processed at a temperature lower than the temperature at which the crystal orientation of the iron alloy changes. Furthermore, the direction in which the base material 60 or the metal plate 64 is passed between the pair of rolling rolls 66a, 66b is not limited to one direction. For example, in FIGS. 11 and 12 , the base material 60 or the metal plate 64 may be gradually rolled by repeatedly passing the base material 60 or the metal plate 64 between the pair of rolling rolls 66a, 66b from left to right and from right to left on the paper.

[0065] In the rolling process, the surface roughness of the metal plate 64 can be adjusted by adjusting the diameter of the rolling rolls 66a and 66b that come into contact with the base material 60. For example, by reducing the diameter of the rolling rolls 66a and 66b, the volume of depressions (described later) present on the surface of the metal plate 64 can be reduced. This allows, for example, the volume density (corrected for depressions) (described later) to be reduced to 15,000 μm 3 / mm 2 It can be the following:

[0066] The diameter of the rolling roll is preferably 28 mm or more. The diameter of the rolling roll may be 40 mm or more, or may be 50 mm or more. The diameter of the rolling roll is preferably 150 mm or less. The diameter of the rolling roll may be 120 mm or less, 100 mm or less, or 80 mm or less. The range of the diameter of the mill roll may be determined by a combination of any one of a plurality of upper limit candidate values and any one of a plurality of lower limit candidate values. For example, the diameter of the mill roll may be 28 mm or more and 150 mm or less, or 40 mm or more and 120 mm or less. The range of the diameter of the mill roll may also be determined by a combination of any two of a plurality of upper limit candidate values. For example, the diameter of the mill roll may be 120 mm or more and 150 mm or less. The range of the diameter of the mill roll may also be determined by a combination of any two of a plurality of lower limit candidate values. For example, the diameter of the mill roll may be 28 mm or more and 40 mm or less. The diameter of the mill roll is preferably 28 mm or more and 150 mm or less, more preferably 40 mm or more and 120 mm or less, more preferably 50 mm or more and 100 mm or less, and more preferably 50 mm or more and 80 mm or less.

[0067] In the rolling process, the pressure of the rolling actuator may be adjusted to adjust the shape of the metal sheet 64. In addition to the rolling rolls (work rolls) 66a, 66b, the shape of the backup rolls may be adjusted as appropriate, and the position of the backup rolls may be adjusted as appropriate in the sheet width direction.

[0068] Furthermore, in the rolling process, the rolling speed, i.e., the conveying speed of the base material, may be adjusted. It is preferable to slow the rolling speed in order to further reduce the dent-corrected volume density. By slowing the rolling speed, the amount of coolant, such as rolling oil, that gets caught between the base material 60 and the rolling rolls 66a, 66b can be reduced. This reduces the number and area of oil pits formed on the surface of the metal plate 64.

[0069] The rolling speed is preferably 30 m / min or more. The rolling speed may be 50 m / min or more, 70 m / min or more, or 100 m / min or more. The rolling speed is preferably 200 m / min or less. The rolling speed may be 150 m / min or less, 100 m / min or less, or 80 m / min or less. The rolling speed may be determined by a combination of any one of a plurality of upper limit candidate values and any one of a plurality of lower limit candidate values. For example, the rolling speed may be 30 m / min or more and 200 m / min or less, or 50 m / min or more and 150 m / min or less. The rolling speed range may also be determined by a combination of any two of the plurality of upper limit candidate values. For example, the rolling speed may be 150 m / min or more and 200 m / min or less, or 100 m / min or more and 150 m / min or less. The rolling speed range may also be determined by a combination of any two of the plurality of lower limit candidate values. For example, the rolling speed range may be 30 m / min or more and 50 m / min or less, or 50 m / min or more and 70 m / min or less. The rolling speed is preferably 30 m / min or more and 200 m / min or less, more preferably 30 m / min or more and 150 m / min or less, more preferably 30 m / min or more and 100 m / min or less, and more preferably 30 m / min or more and 80 m / min or less.

[0070] In the cold rolling process, a coolant such as kerosene or neat oil may be supplied between the base material 60 and the rolling rolls 66a, 66b. This allows the temperature of the base material to be controlled. From the viewpoint of further reducing the dent-corrected volume density, it is preferable to reduce the amount of coolant supplied.

[0071] Furthermore, by appropriately selecting the coolant, the number and area of oil pits and rolling streaks formed on the surface of the metal sheet 64 can be adjusted. For example, neat oil can be used as the coolant. Neat oil has the characteristic of being less likely to increase in viscosity during rolling. Therefore, by using neat oil as the coolant, the amount of coolant caught between the base material 60 and the rolling rolls 66a, 66b can be reduced. This makes it possible to suppress the formation of oil pits on the surface of the metal sheet 64.

[0072] In addition, the number and area of oil pits and rolling streaks formed on the surface of the metal sheet 64 can be adjusted by appropriately selecting the surface roughness of the rolling roll. For example, by reducing the surface roughness Ra of the rolling roll, it is possible to suppress the formation of rolling streaks on the surface of the metal sheet 64. The surface roughness Ra of the rolling roll is preferably 0.2 μm or less. The surface roughness Ra of the rolling roll may be 0.15 μm or less, 0.1 μm or less, or 0.05 μm or less. The surface roughness Rz of the rolling roll is preferably 2.0 μm or less. The surface roughness Rx of the rolling roll may be 1.5 μm or less, 1.0 μm or less, or 0.5 μm or less. In addition, the surface roughness Rz of the rolling roll is preferably 2.0 μm or less. The surface roughness Rz of the rolling roll may be 1.5 μm or less, 1.0 μm or less, or 0.5 μm or less. The surface roughness Ra and Rz are measured based on JIS B 0601:2013.

[0073] An analysis step for analyzing the quality and characteristics of the base material 60 or the metal plate 64 may be performed before, after, or during the rolling step. For example, the base material 60 or the metal plate 64 may be irradiated with fluorescent X-rays to analyze the composition. Furthermore, the amount of thermal expansion of the base material 60 or the metal plate 64 may be measured by thermomechanical analysis (TMA).

[0074] Thereafter, in order to remove residual stress accumulated in the metal sheet 64 due to rolling, an annealing process may be performed using an annealing device 67, as shown in FIG. 12. The annealing process may be performed while pulling the metal sheet 64 in the conveying direction (longitudinal direction), as shown in FIG. 12. That is, the annealing process may be performed as continuous annealing while conveying, rather than so-called batch annealing. In this case, it is preferable to set the temperature and conveying speed so as to prevent deformation such as buckling of the metal sheet 64. By performing the annealing process, it is possible to obtain a metal sheet 64 from which residual strain has been removed to a certain extent. Note that FIG. 12 shows an example in which the metal sheet 64 is conveyed horizontally during the annealing process, but this is not limited thereto, and the metal sheet 64 may be conveyed in other directions, such as vertically, during the annealing process.

[0075] The conditions for the annealing step are appropriately set depending on the thickness and reduction rate of the metal plate 64, but for example, the annealing step is performed within a range of 500°C to 600°C for 30 to 90 seconds. Note that the number of seconds above represents the time required for the metal plate 64 to pass through a space adjusted to a predetermined temperature in the annealing device 67. The temperature for the annealing step may be set so as not to soften the metal plate 64.

[0076] The lower limit of the temperature for the annealing step may be lower than the aforementioned 500°C. For example, the temperature for the annealing step may be equal to or higher than 400°C or equal to or higher than 450°C. The upper limit of the temperature for the annealing step may be higher than the aforementioned 600°C. For example, the temperature for the annealing step may be equal to or lower than 700°C or equal to or lower than 650°C. The temperature range for the annealing step may be determined by a combination of any one of the aforementioned multiple upper limit candidate values and any one of the aforementioned multiple lower limit candidate values. For example, the temperature for the annealing step may be equal to or higher than 400°C and equal to or lower than 700°C, or equal to or higher than 450°C and equal to or lower than 650°C. The temperature range for the annealing step may be determined by a combination of any two of the aforementioned multiple upper limit candidate values. For example, the temperature for the annealing step may be equal to or higher than 650°C and equal to or lower than 700°C. The temperature range for the annealing step may be determined by a combination of any two of the aforementioned multiple lower limit candidate values. For example, the temperature for the annealing step may be equal to or higher than 400°C and equal to or lower than 450°C.

[0077] The annealing time may be 40 seconds or more, or 50 seconds or more. The lower limit of the annealing time may be shorter than the aforementioned 30 seconds. For example, the annealing time may be 10 seconds or more, or 20 seconds or more. The annealing time may be 80 seconds or less, 70 seconds or less, or 60 seconds or less. The upper limit of the annealing time may be longer than the aforementioned 90 seconds. For example, the annealing time may be 100 seconds or less. The annealing time range may be determined by combining any one of the above-mentioned multiple upper limit candidate values with any one of the above-mentioned multiple lower limit candidate values. For example, the annealing time may be 10 seconds or more and 100 seconds or less, 20 seconds or more and 90 seconds or less, 30 seconds or more and 80 seconds or less, 40 seconds or more and 70 seconds or less, or 50 seconds or more and 60 seconds or less. The annealing time range may be determined by combining any two of the above-mentioned multiple upper limit candidate values. For example, the annealing time may be 90 seconds or more and 100 seconds or less. The range of the annealing time may also be determined by a combination of any two of the above-mentioned multiple lower limit candidate values. For example, the annealing time may be 10 seconds or more and 20 seconds or less.

[0078] Preferably, the annealing step is performed in a non-reducing atmosphere or an inert gas atmosphere. Here, a non-reducing atmosphere refers to an atmosphere that does not contain a reducing gas such as hydrogen. "Does not contain a reducing gas" means that the concentration of a reducing gas such as hydrogen is 10% or less. In the annealing step, the concentration of the reducing gas may be 8% or less, 6% or less, 4% or less, 2% or less, or 1% or less. Furthermore, an inert gas atmosphere refers to an atmosphere in which the concentration of an inert gas such as argon gas, helium gas, or nitrogen gas is 90% or more. In the annealing step, the concentration of the inert gas may be 92% or more, 94% or more, 96% or more, 98% or more, or 99% or more. Performing the annealing step in a non-reducing atmosphere or an inert gas atmosphere can prevent nickel compounds such as nickel hydroxide from being formed on the surface layer of the metal plate 64. The annealing device 67 may have a mechanism for monitoring the inert gas concentration or a mechanism for adjusting the inert gas concentration.

[0079] Before the annealing step, a cleaning step may be performed to clean the metal plate 64. This makes it possible to prevent foreign matter from adhering to the surface of the metal plate 64 during the annealing step. As a cleaning liquid for cleaning, for example, a hydrocarbon-based liquid can be used.

[0080] 12 shows an example in which the annealing step is performed while the metal sheet 64 is being pulled in the longitudinal direction, but the present invention is not limited to this. The annealing step may be performed while the metal sheet 64 is wound around the core 61. In other words, batch annealing may be performed. When the annealing step is performed while the metal sheet 64 is wound around the core 61, the metal sheet 64 may develop a tendency to warp in accordance with the winding diameter of the wound body 62. Therefore, depending on the winding diameter of the wound body 62 and the material constituting the base material 60, it may be advantageous to perform the annealing step while the metal sheet 64 is being pulled in the longitudinal direction.

[0081] Thereafter, a slitting process may be carried out in which both ends of the metal plate 64 obtained by the rolling process are cut off over a predetermined range in the width direction so that the width of the metal plate 64 falls within a predetermined range. This slitting process is carried out to remove cracks that may occur at both ends of the metal plate 64 due to rolling. By carrying out such a slitting process, it is possible to prevent the phenomenon in which the metal plate 64 breaks, or so-called plate cuts, from occurring from cracks.

[0082] The width of the portion cut off in the slitting step may be adjusted so that the shape of the metal plate 64 after the slitting step is symmetrical in the width direction. The slitting step may also be performed before the above-mentioned annealing step.

[0083] Note that the long metal plate 64 having a predetermined thickness may be manufactured by repeating at least two of the above-described rolling, annealing, and slitting steps multiple times.

[0084] Furthermore, after the rolling step or the annealing step, a visual inspection step may be performed to inspect the appearance of the metal plate 64. The visual inspection step may include a step of inspecting the appearance of the metal plate 64 using an automatic inspection machine. The visual inspection step may also include a step of visually inspecting the appearance of the metal plate 64.

[0085] Furthermore, after the rolling process or the annealing process, a shape inspection process may be performed to inspect the shape of the metal plate 64. For example, a three-dimensional measuring device may be used to measure the position of the surface of the metal plate 64 in the thickness direction within a predetermined region of the metal plate 64.

[0086] Meanwhile, the present inventors have conducted extensive research and found that many dents exist on the surface of a metal sheet 64 after rolling. FIG. 13 is a diagram showing the state in which a plurality of dents 64c exist on the surface of a metal sheet 64 obtained by rolling, for example, on the first surface 64a. The dents 64c are, for example, oil pits 64e and rolling streaks 64f. The oil pits 64e are depressions formed on the surface of the metal sheet 64 due to oil present between the base material 60 and the rolling rolls 66a and 66b. In this embodiment, the dents 64c refer to depressions, such as the oil pits 64e, that exist on the surface of the metal sheet 64 and have a depth of 0.2 μm or more. The density of the dents 64c present on the surface of the metal sheet 64 is, for example, 3 dents / mm 2 More than 500 pieces / mm 2 The value of 0.2 μm is a preferable value for the correction distance dC, which will be described later. The dimension of the recess 64c in the surface direction of the metal plate 64 is, for example, 1 μm or more and 60 μm or less.

[0087] A known technique for inspecting undulations such as dents 64c on the surface of a metal plate 64 involves calculating the arithmetic mean roughness Ra and maximum height Ry of the surface. In both the arithmetic mean roughness Ra and maximum height Ry, the position of the surface of the metal plate 64 in the thickness direction is measured at multiple points on a predetermined line, such as line R1 or line R2, as shown in FIG. 13. However, as shown in FIG. 13, the density of dents 64c may vary depending on the location. As a result, as shown in FIG. 13, the density of dents 64c located on line R2 may be significantly lower than the density of dents 64c located on line R1. Thus, techniques such as the arithmetic mean roughness Ra and maximum height Ry may result in relatively large variations in inspection results.

[0088] Furthermore, it is believed that techniques such as arithmetic mean roughness Ra and maximum height Ry cannot provide sufficient information regarding the shape and volume of the depressions 64c. These issues with arithmetic mean roughness Ra and maximum height Ry will be described with reference to Fig. 14. Fig. 14 is a diagram showing an example of a cross section of a metal plate 64.

[0089] FIG. 14 shows three types of depressions. The depression 64c_1 located on the left side and the depression 64c_2 located in the center have the same opening diameter A. The wall surface of the depression 64c_1 has a shape that convex toward the metal plate. On the other hand, the wall surface of the depression 64c_2 has a shape that convex outward, opposite to the shape of the depression 64c_1. The two depressions 64c_3 located on the right side have an opening diameter A / 2. In other words, the sum of the opening diameters of the two depressions 64c_3 is the same as the opening diameter of the depression 64c_1 and the opening diameter of the depression 64c_2. The depths of the three types of depressions 64c_1, 64c_2, and 64c_3 are all B. When the surface roughness caused by the three types of depressions 64c_1, 64c_2, and 64c_3 is measured with a measuring instrument, the arithmetic mean roughness Ra is expressed by the following formula. Ra=∫A×B / 2dx Therefore, the three types of depressions 64c_1, 64c_2, and 64c_3 have the same influence on the measured value of the arithmetic mean roughness Ra. On the other hand, as shown in FIGS. 15 to 17, the dimensions of the through holes 25, the first recesses 30, the second recesses 35, the top portions 43, the ribs, and the like formed by etching the metal plate 64 are affected not only by the depth of the recesses 64c but also by the volume of the recesses 64c. As will be described later, in this embodiment, the surface roughness is evaluated based on the volume of the recesses. In this case, the three types of recesses 64c_1, 64c_2, and 64c_3 have different influences on the recess-corrected volumetric density (described later). Specifically, the influence of recess 64c_1 on the recess-corrected volumetric density is greatest. Furthermore, the influence of one recess 64c_2 on the recess-corrected volumetric density is smaller than the influence of two recesses 64c_3 on the recess-corrected volumetric density.

[0090] 15 is a cross-sectional view showing a process of forming first recesses 30 by etching the metal plate 64 shown in FIG. 14 from the first surface 64a side using the first resist pattern 65a as a mask. The volume of the left recess 64c_1 is larger than the volume of the right recess 64c_2. Therefore, in the area where the left recess 64c_1 was located, etching progresses in the thickness direction and the surface direction of the metal plate 64 faster than in the area where the right recess 64c_2 was located. Therefore, the dimensions of the first recess 30_1 formed in the area where the left recess 64c_1 was located are larger than the dimensions of the first recess 30_2 formed in the area where the right recess 64c_2 was located.

[0091] 16 is a cross-sectional view showing a step of etching the metal plate 64 shown in FIG. 15 from the second surface 64b side using the second resist pattern 65b as a mask to form second recesses 35 communicating with the first recesses 30_1, 30_2 on the second surface 64b side of the metal plate 64. Since the dimension of the first recess 30_1 on the left side is larger than the dimension of the first recess 30_2 on the right side, the dimension of the outline of the connection portion 41 connecting the first recess 30_1 on the left side and the second recess 35 also becomes larger than the dimension of the outline of the connection portion 41 connecting the first recess 30_2 on the right side and the second recess 35.

[0092] FIG. 17 is a diagram illustrating a state in which the accuracy of the opening dimensions of the through hole 25 on the first surface 20a side is reduced due to a depression 64c in the metal plate 64. In the area where the large-volume depression 64c was present, the etching solution can penetrate into the depression 64c at the start of the etching process. Therefore, etching can proceed faster in the thickness direction and the surface direction of the metal plate 64 in the area where the large-volume depression 64c was present than in other areas. Therefore, for example, if the large-volume depression 64c is present in the metal plate 64 near the edge of the opening of the first resist pattern 65a or near the edge of the opening of the second resist pattern 65b, the dimension of the through hole 25 in the surface direction of the metal plate 64 may be large in the area where the depression 64c was present. As a result, as indicated by reference numeral 30_1 in FIG. 17 , the dimension r3 of the first recess 30 constituting the through hole 25 on the first surface 20a may vary in the area where the large-volume depression 64c was present. Furthermore, there may be variations in the dimension r2 of the through portion 42 formed by the connection portion 41 connecting the first recess 30 and the second recess 35. As a result, it is considered that the dimensional accuracy and positional accuracy of the deposition material adhered to the organic EL substrate 92 may decrease. Note that such variations in the opening dimension may also occur in the second recess 35 on the second surface 20b side.

[0093] As described above, whether the through holes 25 can be precisely formed in the metal plate 64 depends not only on the depth of the depressions 64c formed in the surface of the metal plate 64 but also largely on the volume of the depressions 64c. Meanwhile, conventional techniques based on the arithmetic mean roughness Ra or the like cannot appropriately acquire information about the volume of the depressions 64c. For this reason, when inspecting the metal plate 64 using the arithmetic mean roughness Ra, it is necessary to set an unnecessarily strict threshold for pass / fail judgment to prevent metal plates 64 that are unsuitable for manufacturing deposition masks 20 from passing the inspection. As a result, it is thought that the yield of the metal plates 64 will decrease.

[0094] In order to solve such problems, in this embodiment, it is proposed to inspect the metal plate 64 while taking into consideration the volume of the recess 64c. This makes it possible to more accurately predict the degree of deterioration in the dimensional accuracy of the through hole 25 of the deposition mask 20 caused by the recess 64c. Therefore, it is possible to inspect the metal plate 64 without setting an unnecessarily strict threshold for pass / fail judgment, thereby increasing the yield of the metal plate 64. Hereinafter, an example of an inspection process taking into consideration the volume of the recess 64c will be described with reference to FIGS. 18 and 19.

[0095] Figure 18 is an enlarged plan view showing a portion of the first surface 64a of the metal plate 64. A plurality of recesses 64c are formed on the first surface 64a. In Figure 19, the symbol D1 indicates the conveyance direction of the metal plate 64 during the rolling process (hereinafter also referred to as the first direction). The symbol D2 indicates the direction perpendicular to the first direction D1 (hereinafter also referred to as the second direction).

[0096] In the inspection process, the quality of the metal plate 64 is judged based on the volume of a plurality of recesses 64c located in an inspection area 711 on the first surface 64a shown in Figure 18. The area U1 of the inspection area 711 is, for example, 0.1 mm 2 More than 1.5mm 2 The area U1 of the inspection area 711 is set to 0.1 mm 2 By doing so, it is possible to suppress variations in the inspection results based on the position of the inspection area 711. In addition, when the area U1 of the inspection area 711 is set to 1.5 mm 2 By doing the following, it is possible to prevent the time required for the inspection from becoming excessive.

[0097] The inspection process includes a calculation step S1 and a determination step S2. In the calculation step S1, a dent-corrected volume density is calculated. As will be explained in the examples below, the dent-corrected volume density is an index that has a high correlation with the dimensional accuracy of the components of the deposition mask 20. In the determination step, the metal plate 64 is determined to be good when the dent-corrected volume density is equal to or less than a predetermined threshold value.

[0098] First, the calculation step S1 will be described. The calculation step S1 includes a measurement step S11 and a processing step S12. In the measurement step S11, first, as shown in FIG. 18, an image is taken of each of a plurality of unit areas 712, and the depth of the depression 64c is measured from the obtained image. As shown in FIG. 18, for example, the unit area 712 is a rectangular area having sides of length W1 and length W2. The unit area 712 corresponds to the range of an image that can be acquired in one image capture. In the example shown in FIG. 18, the side of length W1 is parallel to the first direction D1, and the side of length W2 is parallel to the second direction D2. For example, W1 is 270 μm, and W2 is 202 μm. Note that the side of length W1 being parallel to the first direction D1 means that the angle formed between the side of length W1 and the first direction D1 is within the range of -10° to +10°. Similarly, the side of length W2 being parallel to the second direction D2 means that the angle formed between the side of length W2 and the second direction D2 is within the range of −10° to +10°.

[0099] As shown in FIG. 18 , multiple images are captured so that two adjacent unit areas 712 partially overlap in the first direction D1 and so that two adjacent unit areas 712 partially overlap in the second direction D2. The multiple images obtained in this manner are stitched together using image stitching software or the like to obtain an image of an area larger than one unit area 712. Then, from the image obtained by stitching, for example, an area indicated by reference numeral 711 in FIG. 18 is extracted as an inspection area. For example, the inspection area 711 is defined so as to surround one central unit area 712 of the nine unit areas 712 shown in FIG. 18 and partially include each of the eight surrounding unit areas 712. The length of the inspection area 711 in the first direction D1 is, for example, 700 μm, and the length of the inspection area 711 in the second direction D2 is, for example, 500 μm.

[0100] In FIG. 18, reference numeral 713 indicates pixels corresponding to the resolution of the inspection device. One pixel 713 corresponds to, for example, one spot of a laser that the inspection device irradiates onto the metal plate 64. The lengths W3 and W4 of the pixel 713 in the first direction D1 and the second direction D2 are preferably 0.1 μm or more and 0.4 μm or less. The area U2 of the pixel 713 is preferably 0.01 μm 2 More than 0.2μm 2 If the area of the unit region 712 is 270 μm×202 μm and the resolution of the unit region 712 in the first direction D1 and the second direction D2 is 1024×768, the length W3 and the length W4 of the pixel 713 in the first direction D1 and the second direction D2 are both 0.263 μm. Also, the area U2 of the pixel 713 is 0.069 μm. 2 becomes.

[0101] Fig. 19 is a cross-sectional view showing a metal plate 64 in which a recess 64c is formed, cut parallel to the first direction D1. In Fig. 19, the symbol d(k) represents the distance from the first surface 64a to the bottom surface of the recess 64c at a pixel 713 located at a coordinate x(k) in the first direction D1. k is an integer, and the range that k can take is determined by the resolution of the image.

[0102] Note that, in addition to the clear depressions 64c as shown in FIG. 19, minute irregularities and undulations may exist on the first surface 64a of the metal plate 64. Therefore, when measuring the depth of the depressions 64c using the first surface 64a as a reference, variations in the measurement results of the depth of the depressions 64c may occur due to the state of the first surface 64a around the depressions 64c. In consideration of this issue, in the measurement step S11 and the processing step S12, the position of a reference plane RP, which is a virtual plane, may be used as the position of the first surface 64a in the thickness direction of the metal plate 64. The reference plane RP will be described below.

[0103] The reference plane RP of the first surface 64a is a plane estimated by, for example, the least squares method. Specifically, first, the position of the inspection area 711 in the thickness direction of the surface of the first surface 64a of the metal plate 64 is measured using a laser microscope, which will be described later. Next, a predetermined plane is provisionally set as the reference plane RP, and the square of the distance from the surface position of the first surface 64a to the reference plane RP is calculated for each pixel 713. In this case, the plane that minimizes the sum of the squares of the distances can be used as the reference plane RP.

[0104] 19, in the measurement step S11, the depth d(k) of the recess 64c is measured for each pixel 713 in the inspection area 711. The measured depth value is the distance from the measured value of the position in the thickness direction of the surface of the first surface 64a of the metal plate 64 to the reference plane RP estimated by the least squares method.

[0105] The inspection device used in the measurement step S11 may be, for example, a laser microscope. In measurement using a laser microscope, first, laser light is irradiated onto an inspection area 711 on the first surface 64a of the metal plate 64. Next, the laser light reflected by the inspection area 711 is captured as a two-dimensional reflection image of the inspection area 711 using an image sensor such as a CCD or CMOS. The two-dimensional reflection image is then analyzed based on the principles of a confocal microscope to measure the position of each pixel 713 of the inspection area 711 in the thickness direction of the surface of the first surface 64a of the metal plate 64. As the laser microscope, for example, a VK-X200 series laser microscope manufactured by Keyence Corporation may be used.

[0106] In process step S12, information about the volume of the depression 64c in the inspection area 711 is calculated based on the depth of the depression 64c measured at each pixel 713 in the inspection area 711.

[0107] In this embodiment, first, as shown in Fig. 19, a correction plane CP is set that is located a predetermined correction distance dC toward the second surface 64b from the reference plane RP in the thickness direction of the metal plate 64. Next, the sum of the volumes of the portions of the depressions 64c located in the inspection region 711 that are located closer to the second surface 64b than the correction distance dC in the thickness direction of the metal plate 64 is calculated. For example, for portions of the depressions 64c located in the inspection region 711 that have a depth greater than the correction distance dC, a value d(k)-dC is calculated by subtracting the correction distance dC from the depth d(k). Next, the value d(k)-dC is multiplied by the area U2 of the pixel 713. As a result, for each pixel 713, the volume V(k) (= {(d(k)-dC)×U2}) of the portion of the dent 64c located on the second surface 64b side of the correction plane CP is calculated. Next, each volume V(k) is integrated over the entire inspection region 711. As a result, the total volume V1 (hereinafter also referred to as dent correction volume) of the portion of the dent 64c located in the inspection region 711 located on the second surface 64b side of the correction plane CP can be calculated.

[0108] Next, the dent-corrected volume V1 is divided by the area U1 of the inspection region 711. This makes it possible to calculate the dent-corrected volume per unit area (hereinafter also referred to as the dent-corrected volume density) V2.

[0109] The above-mentioned correction distance dC is preferably 0.1 μm or more and 0.5 μm or less, for example, 0.2 μm. By calculating the dent-corrected volume density V2 by appropriately setting the correction distance dC, it is possible to improve the correlation between the dent-corrected volume density V2 and the dimensional accuracy of the components of the deposition mask 20, as will be supported by examples described later. In the following description, the dent-corrected volume V1 and the dent-corrected volume density V2 obtained when the correction distance dC is set to z μm may be referred to as the dent-corrected volume V1 (z μm) and the dent-corrected volume density V2 (z μm), respectively. For example, when the correction distance dC is 0.2 μm, the notations dent-corrected volume V1 (0.2 μm) and the dent-corrected volume density V2 (0.2 μm) may be adopted.

[0110] Subsequently, a determination step S2 is performed in which the metal plate 64 is determined to be good when the dent-corrected volume density V2 is equal to or less than a predetermined threshold TH1. This makes it possible to select the metal plate 64 capable of accurately forming components of the deposition mask 20, such as the through-holes 25.

[0111] The threshold value TH1 is appropriately determined based on the dimensional accuracy required for the components of the deposition mask 20, the setting of the correction distance dC, etc. For example, when the error in the opening dimensions of the through-holes 25 of the deposition mask 20, such as the dimension r3 of the first recess 30 and the dimension r2 of the through-hole 42, is required to be ±1.0 μm or less and the correction distance dC is 0.2 μm, the threshold value TH1 is set to 15000 μm. 3 / mm 2 The threshold value TH1 can be set to 12000 μm. 3 / mm 2 may be 10,000 μm 3 / mm 2 may be 9000 μm 3 / mm 2 may be 6000 μm 3 / mm 2 may be 5000 μm 3 / mm 2 may be 3000 μm 3 / mm 2 may be 1000 μm 3 / mm 2 may be.

[0112] The determination step S2 may determine that the metal plate 64 is good when the dent-corrected volume density V2 is equal to or greater than the threshold value TH2 and equal to or less than the threshold value TH1. That is, the determination step S2 may use a threshold value TH2 that defines a lower limit of the dent-corrected volume density V2 in addition to the threshold value TH1 that defines an upper limit of the dent-corrected volume density V2. When the metal plate 64 has a dent-corrected volume density V2 that is equal to or greater than the threshold value TH2, the adhesion of the resist film to the surface of the metal plate 64 can be improved. The upper limit threshold value TH1 may be referred to as a first threshold value, and the lower limit threshold value TH2 may be referred to as a second threshold value. The threshold value TH2 is set to 10 μm 3 / mm 2 may be 100 μm3 / mm 2 may be 500 μm 3 / mm 2 may be 1000 μm 3 / mm 2 may be 3000 μm 3 / mm 2 may be 4000 μm 3 / mm 2 may be 5000 μm 3 / mm 2 may be.

[0113] The range of the dent-corrected volume density V2 of the metal plate 64 determined to be good in the determination step S2 may be determined by a combination of any one of the above-mentioned multiple candidates for the upper threshold value TH1 and any one of the above-mentioned multiple candidates for the lower threshold value TH2. For example, the dent-corrected volume density V2 of the metal plate 64 determined to be good, i.e., the selected metal plate 64, may be determined to be good in the range of 10 μm 3 / mm 2 More than 15000μm 3 / mm 2 May be less than 100 μm 3 / mm 2 More than 12000μm 3 / mm 2 May be less than 500 μm 3 / mm 2 More than 10000μm 3 / mm 2 May be less than 1000 μm 3 / mm 2 More than 9000μm 3 / mm 2 May be less than 3000 μm 3 / mm 2 More than 6000μm 3 / mm 2 May be less than 4000 μm 3 / mm 2 More than 6000μm 3 / mm 2The range of the dent-corrected volume density V2 of the selected metal plate 64 may be determined by a combination of any two of the above-mentioned multiple candidates for the upper threshold value TH1. For example, the dent-corrected volume density V2 of the selected metal plate 64 may be 12000 μm or less. 3 / mm 2 More than 15000μm 3 / mm 2 The range of the dent-corrected volume density V2 of the selected metal plate 64 may be determined by a combination of any two of the above-mentioned multiple candidates for the lower limit threshold value TH2. For example, the dent-corrected volume density V2 of the selected metal plate 64 may be set to 10 μm or less. 3 / mm 2 More than 100μm 3 / mm 2 It may be the following:

[0114] Fig. 39 is a diagram showing an example of the distribution of dent-corrected volume density V2 of a plurality of metal plates 64 selected based on the judgment condition that judges a metal plate having a dent-corrected volume density V2 equal to or less than a threshold value TH1 as a non-defective product. In Fig. 39, the horizontal axis represents the value of the dent-corrected volume density V2 calculated for each metal plate 64. The vertical axis represents the number of metal plates 64 having a dent-corrected volume density V2 within the range shown on the horizontal axis. For example, among the plurality of selected metal plates 64, 3 / mm 2 More than 9000μm 3 / mm 2 The number of metal plates 64 having a dent-corrected volume density V2 less than 17 is 17.

[0115] In the example of FIG. 39, the threshold value TH1 is 15000 μm 3 / mm 2 In this case, most of the metal plates 64 judged as non-defective, for example, 95% or more, are 15000 μm 3 / mm 2 As shown in FIG. 39, due to measurement errors or the like, some of the selected metal plates 64 have a dent-corrected volume density V2 of 15,000 μm. 3 / mm 2In some cases, the cavity-corrected volumetric density V2 may be greater than

[0116] Fig. 40 is a diagram showing an example of the distribution of dent-corrected volume density V2 of a plurality of metal plates 64 selected based on the judgment condition that judges a metal plate having a dent-corrected volume density V2 equal to or greater than a threshold value TH2 and equal to or less than a threshold value TH1 as a non-defective product. The horizontal and vertical axes shown in Fig. 40 have the same meanings as those in Fig. 39. In the example of Fig. 40, the threshold value TH2 is 3000 µm 3 / mm 2 and the threshold value TH1 is 15000 μm 3 / mm 2 As described above, in the example of Fig. 40, the range of metal plates 64 that are selected as non-defective is narrower than in the example of Fig. 39. In this case, performing the selection shown in Fig. 40 also results in performing the selection shown in Fig. 39.

[0117] In the above description, an example has been shown in which the inspection process of inspecting the metal plate 64 based on the dent-corrected volume density V2 is used to determine whether the metal plate 64 is good or bad, i.e., to sort the metal plates 64. That is, an example has been shown in which the inspection process functions as a sorting process of sorting the metal plates 64 in the manufacturing method of the metal plate 64. However, the inspection process may be used for purposes other than sorting the metal plates 64 in the manufacturing method of the metal plate 64.

[0118] The selection conditions in the selection process are arbitrary. For example, the selection process may select metal plates 64 having a dent-corrected volumetric density V2 that falls within a range defined by a combination of any one of the above-mentioned multiple candidates for the upper threshold value TH1 and any one of the above-mentioned multiple candidates for the lower threshold value TH2. The selection process may also select metal plates 64 having a dent-corrected volumetric density V2 that falls within a range defined by a combination of any two of the above-mentioned multiple candidates for the upper threshold value TH1. The selection process may also select metal plates 64 having a dent-corrected volumetric density V2 that falls within a range defined by a combination of any two of the above-mentioned multiple candidates for the lower threshold value TH2.

[0119] An example will be described in which the inspection process is used for purposes other than sorting the metal plates 64 in the manufacturing method of the metal plates 64. For example, the inspection process may be used to optimize the conditions for manufacturing the metal plates 64, such as the rolling ratio and the amount of oil used. Specifically, the inspection process may be used to manufacture metal plates 64 using various rolling ratios and amounts of oil used, calculate the dent-corrected volume density V2 of each of the obtained metal plates 64, and set appropriate manufacturing conditions that can reduce the dent-corrected volume density V2. In this case, in the manufacturing process of the metal plates 64, it is not necessary to perform the sorting based on the inspection process on all the metal plates 64. For example, the inspection process may be performed on only some of the metal plates 64. Alternatively, once the manufacturing conditions are set, the inspection process may not be performed at all.

[0120] Fig. 41 is a diagram showing an example of the distribution of dent-corrected volume density V2 of a plurality of metal plates 64 manufactured under manufacturing conditions found using a judgment condition for judging a metal plate having a dent-corrected volume density V2 equal to or less than a threshold value TH1 as a non-defective product. The horizontal and vertical axes shown in Fig. 41 have the same meanings as those in Fig. 39. In the example of Fig. 41, the threshold value TH1 is 15000 µm 3 / mm 2 In the example of FIG. 41, even if the selection step is not performed, the manufactured metal plates 64 have a diameter of 15,000 μm. 3 / mm 2 It has a cavity-corrected volume density V2 of:

[0121] According to the method for manufacturing a metal plate according to this embodiment, it is possible to obtain a metal plate 64 having a dent-corrected volume density V2 that satisfies the above-mentioned criteria. 3 / mm 2 It is possible to obtain the metal plate 64 having the following recess-corrected volume density V2. This makes it possible to prevent the dimensional accuracy of the through-holes 25 of the deposition mask 20 from being reduced due to the recesses 64c. This makes it possible to improve the dimensional accuracy and positional accuracy of the deposition material that passes through the through-holes 25 and adheres to the organic EL substrate 92.

[0122] Next, a method for manufacturing a deposition mask 20 using a metal plate 64 that has passed the above-described inspection process will be described mainly with reference to FIGS. 20 to 28. FIG. 20 is a diagram showing a manufacturing apparatus 70 for manufacturing a deposition mask 20 using a metal plate 64. First, a wound body 62 is prepared by winding the metal plate 64 around a core 61. Then, the core 61 is rotated to unwind the wound body 62, thereby supplying a band-like metal plate 64 as shown in FIG.

[0123] The supplied metal plate 64 is transported by transport rollers 75 to a processing device 72 and a separating device 73 in this order. The processing device 72 performs a processing step in which the metal plate 64 that has passed the inspection step is processed to form through holes 25 in the metal plate 64. In the present embodiment, a large number of through holes 25 corresponding to a plurality of deposition masks 20 are formed in the metal plate 64. In other words, a plurality of deposition masks 20 are allocated to the metal plate 64. The separating device 73 performs a separation step in which a portion of the metal plate 64 in which a plurality of through holes 25 corresponding to one deposition mask 20 has been formed is separated from the metal plate 64. In this manner, a sheet of deposition mask 20 can be obtained.

[0124] 20 to 28, the processing steps will be described. The processing steps include a step of etching a long metal plate 64 using photolithography to form a first recess 30 in the metal plate 64 from the first surface 64a side, and a step of etching the metal plate 64 using photolithography to form a second recess 35 in the metal plate 64 from the second surface 64b side. The first recess 30 and the second recess 35 formed in the metal plate 64 communicate with each other, thereby forming a through hole 25 in the metal plate 64. In the example described below, the step of forming the first recess 30 is performed before the step of forming the second recess 35, and a step of sealing the formed first recess 30 is performed between the step of forming the first recess 30 and the step of forming the second recess 35. Each step will be described in detail below.

[0125] First, as shown in FIG. 21 , resist films 65c and 65d containing a negative photosensitive resist material are formed on the first and second surfaces 64a and 64b of the metal plate 64. For example, a coating liquid containing a photosensitive resist material such as casein is applied to the first and second surfaces 64a and 64b of the metal plate 64, and then the coating liquid is dried to form the resist films 65c and 65d. Alternatively, the resist films 65c and 65d may be formed by attaching a dry film to the first and second surfaces 64a and 64b of the metal plate 64. The dry film contains, for example, an acrylic photocurable resin.

[0126] Next, exposure masks 68a and 68b are prepared, each of which blocks light from passing through the regions of the resist films 65c and 65d that are to be removed. The exposure masks 68a and 68b are then placed on the resist films 65c and 65d, respectively, as shown in FIG. 22. An alignment step may be performed to adjust the relative positional relationship between the exposure mask 68a on the first surface 64a and the exposure mask 68b on the second surface 64b. The exposure masks 68a and 68b are, for example, glass dry plates that block light from passing through the regions of the resist films 65c and 65d that are to be removed. The exposure masks 68a and 68b are then tightly attached to the resist films 65c and 65d by vacuum contact. A positive photosensitive resist material may be used, in which case an exposure mask is used that allows light to pass through the area of the resist film that is to be removed.

[0127] Thereafter, the resist films 65c, 65d are exposed to light through exposure masks 68a, 68b (exposure step). Furthermore, the resist films 65c, 65d are developed to form an image on the exposed resist films 65c, 65d (development step). In this manner, as shown in FIG. 23, a first resist pattern 65a can be formed on the first surface 64a of the metal plate 64, and a second resist pattern 65b can be formed on the second surface 64b of the metal plate 64. The development step may include a resist heat treatment step to increase the hardness of the resist films 65c, 65d or to more firmly adhere the resist films 65c, 65d to the metal plate 64. The resist heat treatment step may be performed, for example, at a temperature above room temperature and below 400°C.

[0128] Next, as shown in FIG. 24 , a first-surface etching process is performed in which regions of the first surface 64a of the metal plate 64 that are not covered by the first resist pattern 65a are etched using a first etching solution. For example, the first etching solution is sprayed toward the first surface 64a of the metal plate 64 through the first resist pattern 65a from a nozzle disposed on the side facing the first surface 64a of the transported metal plate 64. As a result, as shown in FIG. 24 , the first etching solution progresses in the regions of the metal plate 64 that are not covered by the first resist pattern 65a. This forms a large number of first recesses 30 on the first surface 64a of the metal plate 64. As the first etching solution, for example, one containing a ferric chloride solution and hydrochloric acid is used.

[0129] 25, the first recess 30 is covered with a resin 69 that is resistant to a second etching liquid used in a subsequent second-surface etching step. That is, the first recess 30 is sealed with the resin 69 that is resistant to the second etching liquid. In the example shown in FIG. 25, the film of the resin 69 is formed so as to cover not only the formed first recess 30 but also the first surface 64a (first resist pattern 65a).

[0130] 26, a second-surface etching step is performed in which regions of the second surface 64b of the metal plate 64 that are not covered by the second resist pattern 65b are etched to form second recesses 35 in the second surface 64b. The second-surface etching step is performed until the first recesses 30 and the second recesses 35 communicate with each other, thereby forming through holes 25. As with the first etching solution described above, a second etching solution containing, for example, a ferric chloride solution and hydrochloric acid is used.

[0131] The corrosion by the second etching liquid occurs in the portion of the metal plate 64 that is in contact with the second etching liquid. Therefore, the corrosion progresses not only in the normal direction N (thickness direction) of the metal plate 64 but also in a direction along the plate surface of the metal plate 64. Preferably, the second-surface etching step is completed before the two second recesses 35 formed at positions facing the two adjacent holes 67b in the second resist pattern 65b join together on the back side of the bridge portion 67a located between the two holes 67b. This allows the top portion 43 to remain on the second surface 64b of the metal plate 64, as shown in FIG. 27.

[0132] Thereafter, as shown in Fig. 28, resin 69 is removed from metal plate 64. Resin 69 can be removed by using, for example, an alkaline remover. When an alkaline remover is used, resist patterns 65a and 65b are also removed at the same time as resin 69, as shown in Fig. 28. After resin 69 is removed, resist patterns 65a and 65b may be removed separately from resin 69 using a remover different from the remover used to remove resin 69.

[0133] Thereafter, the portion of the metal plate 64 in which the plurality of through holes 25 corresponding to one deposition mask 20 are formed is separated from the metal plate 64, thereby obtaining the deposition mask 20.

[0134] Next, a method for manufacturing the deposition mask device 10 by combining the deposition mask 20 and the frame 15 will be described. First, the frame 15 is prepared. Then, the second surface 20b of the deposition mask 20 is fixed to the frame 15 by welding or the like. For example, first, with the frame 15 and the deposition mask 20 overlapping each other, an image of the deposition mask 20 is taken from the first surface 20a side using a camera or the like. At this time, tension may be applied to the deposition mask 20. Next, the position of the deposition mask 20 with respect to the frame 15 is detected based on the image obtained by the image capture. For example, the position of the outline of the deposition mask 20 in the longitudinal direction D1 is detected. Next, the position of the deposition mask 20 is adjusted so that the deposition mask 20 is at a predetermined position with respect to the frame 15.

[0135] Next, a deposition method for depositing a deposition material 98 onto a substrate such as an organic EL substrate 92 using a deposition mask 20 will be described. First, the deposition mask device 10 is positioned so that the deposition mask 20 faces the organic EL substrate 92. Then, a magnet 93 is used to bring the deposition mask 20 into close contact with the organic EL substrate 92. In this state, the deposition material 98 is evaporated and caused to fly to the organic EL substrate 92 through the deposition mask 20, thereby allowing the deposition material 98 to adhere to the organic EL substrate 92 in a pattern corresponding to the through-holes 25 of the deposition mask 20.

[0136] In the method for manufacturing the deposition mask 20 according to the present embodiment, the deposition mask 20 is manufactured using a metal plate 64 that has passed an inspection step that is performed based on the total volume of the depressions 64c formed in the surface of the metal plate 64. This makes it possible to prevent the depressions 64c from causing a decrease in the dimensional accuracy of the through holes 25 in the deposition mask 20. This makes it possible to improve the dimensional accuracy and positional accuracy of the deposition material that passes through the through holes 25 and adheres to the organic EL substrate 92.

[0137] It should be noted that various modifications can be made to the above-described embodiment. Below, modifications will be described with reference to the drawings as necessary. In the following description and the drawings used in the following description, parts that can be configured similarly to the above-described embodiment will be designated by the same reference numerals as those used for the corresponding parts in the above-described embodiment, and duplicated explanations will be omitted. Furthermore, if it is clear that the effects obtained in the above-described embodiment can also be obtained in the modified embodiment, the explanations thereof may be omitted.

[0138] In the above-described embodiment, an example has been shown in which the first surface 64a of the surface of the metal plate 64 on which the first recess 30 is formed is the object of inspection in the inspection process. However, this is not limited to this, and the second surface 64b of the surface of the metal plate 64 on which the second recess 35 is formed may also be the object of inspection in the inspection process. Furthermore, both the first surface 64a and the second surface 64b of the metal plate 64 may also be the object of inspection.

[0139] In the above-described embodiment, an example has been described in which the inspection step of the metal plate 64 is performed in equipment separate from equipment that performs the manufacturing method of the deposition mask 20, such as the processing step and the separation step. In other words, an example has been described in which the inspection step of the metal plate 64 is one step in the manufacturing method of the metal plate 64. However, this is not limited to this, and the inspection step of the metal plate 64 may be performed in equipment that performs the manufacturing method of the deposition mask 20. In other words, the inspection step of the metal plate 64 may be one step in the manufacturing method of the deposition mask 20.

[0140] In the above-described embodiment, the dent-corrected volume density on the surface of the metal plate 64 before the through-holes 25 are formed is 15000 μm 3 / mm 2 In the metal plate 64 after the through-holes 25 are formed, that is, in the metal plate 21 of the deposition mask 20, the dent-corrected volume density on the surface is 15000 μm 3 / mm 2As described above, during the etching process, the portions of the metal plate 64 where the through holes 25 are not formed are covered with the resist pattern. For this reason, the portions of the metal plate 21 of the deposition mask 20 located at the ears 17a, 17b and the peripheral region 23 may have depressions 64c equivalent to those of the metal plate 64 before the through holes 25 are formed. Therefore, by setting the ears 17a, 17b and a part of the peripheral region 23 on the surface of the metal plate 21 of the deposition mask 20 as the inspection region and performing the inspection process described above taking the volume of the depressions 64c into consideration, the depression-corrected volume density on the surface of the metal plate 21 of the deposition mask 20 can be calculated.

[0141] Other aspects of the present disclosure will now be described.

[0142] One embodiment of the present disclosure is a method for manufacturing a metal plate for manufacturing a deposition mask, the metal plate having a plurality of depressions located on a surface of the metal plate, and the manufacturing method includes an inspection process for determining whether the metal plate is good or bad based on the sum of the volumes of the plurality of depressions located on a portion of the surface.

[0143] In the method for manufacturing a metal plate according to an embodiment of the present disclosure, the inspection step may include a calculation step of calculating a dent-corrected volume density by dividing a sum of volumes of portions of the plurality of dents that are at least a correction distance away from the surface in a thickness direction of the metal plate by an area of the portion of the surface, and a determination step of determining the metal plate as good if the dent-corrected volume density is equal to or less than a first threshold. In this case, the determination step may determine the metal plate as good if the dent-corrected volume density is equal to or greater than a second threshold and equal to or less than a first threshold.

[0144] In the method for manufacturing a metal plate according to an embodiment of the present disclosure, the inspection step may include a calculation step of calculating a dent-corrected volume density by dividing a sum of volumes of portions of the plurality of dents that are at least a correction distance away from the surface in a thickness direction of the metal plate by an area of the portion of the surface, and a selection step of selecting the metal plates whose dent-corrected volume density is equal to or less than a first threshold. In this case, the selection step may select the metal plates whose dent-corrected volume density is equal to or greater than a second threshold and equal to or less than the first threshold.

[0145] In the method for manufacturing a metal plate according to an embodiment of the present disclosure, the correction distance may be 0.2 μm.

[0146] In the method for manufacturing a metal plate according to an embodiment of the present disclosure, the first threshold value is 15000 μm 3 / mm 2 The second threshold may be 10 μm. 3 / mm 2 may be.

[0147] In the method for manufacturing a metal plate according to an embodiment of the present disclosure, the calculation step may include a measurement step of measuring the depth of the depression at each position of the portion of the surface.

[0148] In the method for manufacturing a metal plate according to an embodiment of the present disclosure, the measuring step may measure the depth of the depression using a laser microscope.

[0149] In the method for manufacturing a metal plate according to an embodiment of the present disclosure, the area of the part of the surface is 0.1 mm 2 It may be more than that.

[0150] One embodiment of the present disclosure is a metal plate for manufacturing a deposition mask, the metal plate having a plurality of dents located on a surface of the metal plate, and when a sum of volumes of portions of the plurality of dents located on a part of the surface that are 0.2 μm or more away from the surface in a thickness direction of the metal plate is referred to as a dent-corrected volume, the dent-corrected volume density calculated by dividing the dent-corrected volume by an area of the part of the surface is 15000 μm 3 / mm 2 the dent correction volume is calculated based on the results of measuring the depth of the dent at each position of the portion of the surface using a laser microscope, and the area of the portion of the surface is 0.1 mm or less. 2 That's it, a metal plate.

[0151] In the metal plate according to one embodiment of the present disclosure, the dent-corrected volume density is 10 μm 3 / mm 2 It may be more than that.

[0152] In the metal plate according to one embodiment of the present disclosure, the metal plate may be made of an iron alloy containing nickel.

[0153] One embodiment of the present disclosure is a method for manufacturing a vapor deposition mask having a plurality of through holes formed therein, the method comprising: a step of preparing a metal plate manufactured by the above-described metal plate manufacturing method, or the above-described metal plate; and a processing step of etching the metal plate to form the through holes in the metal plate.

[0154] One embodiment of the present disclosure is a deposition mask comprising: a metal plate having a plurality of dents located on a surface; and a plurality of through holes formed in the metal plate; wherein, when a sum of volumes of portions of the plurality of dents located on a portion of the surface that are 0.2 μm or more away from the surface in a thickness direction of the metal plate is referred to as a dent-corrected volume, the dent-corrected volume density calculated by dividing the dent-corrected volume by an area of the portion of the surface is 15000 μm or more. 3 / mm 2the dent correction volume is calculated based on the results of measuring the depth of the dent at each position of the portion of the surface using a laser microscope, and the area of the portion of the surface is 0.1 mm or less. 2 That's it for the deposition mask.

[0155] In the deposition mask according to the embodiment of the present disclosure, the recess correction volume density is 10 μm 3 / mm 2 It may be more than that. [Example]

[0156] Next, the embodiments of the present disclosure will be described more specifically with reference to examples. However, the embodiments of the present disclosure are not limited to the descriptions of the following examples as long as they do not depart from the gist of the present disclosure.

[0157] (First test example) First, a base material was prepared, which was an iron alloy containing 36% by mass of nickel and the remainder being iron and unavoidable impurities. Next, the base material was subjected to the rolling, slitting, and annealing processes described above to produce two types of wound bodies (hereinafter referred to as Sample 1 and Sample 2) each having a 15 μm thick long metal plate wound thereon. Similarly, seven types of wound bodies (hereinafter referred to as Samples 3 to 10) each having a 20 μm thick long metal plate wound thereon were produced.

[0158] Next, the above-mentioned inspection process was carried out to inspect the undulations of the surface of each sample. First, each sample was cut out from the center in the width direction to prepare a square test piece with a side length of 5 cm. Next, a measurement process was carried out to measure the surface position of each pixel 713 in the test piece inspection area 711 using a laser microscope. The laser microscope used was a VK-X200 series laser microscope manufactured by Keyence Corporation.

[0159] The settings of the laser microscope when measuring the surface position of the test piece were as follows. Laser light: Blue (wavelength 408nm) Objective lens: 50x Optical zoom: 1.0x Measurement mode: Surface profile Measurement size: Standard (1024 x 768) ·Measurement quality: high speed RPD: Yes -How to fix the test piece: Place it on the KOKUYO magnetic sheet RPD stands for Real Peak Detection. "With RPD" means that the test piece surface position is measured by detecting the peak of reflected laser light.

[0160] The area of the inspection area 711 will now be described. For the first to fourth samples and the seventh to tenth samples, nine areas (images) measured under the above-mentioned "standard (1024 x 768)" setting were joined to form the inspection area 711. In this case, the area U1 of the inspection area 711 is 0.35 mm 2 For the fifth and sixth samples, the four areas (images) measured under the above-mentioned "standard (1024 x 768)" setting were joined to form the inspection area 711. In this case, the area U1 of the inspection area 711 was 0.175 mm 2 It was.

[0161] Next, a processing step was carried out to calculate the dent-corrected volume V1 and dent-corrected volume density V2 on the surface of the test piece based on the measurement results. First, the above-mentioned reference plane RP was calculated based on the least squares method using the [reference plane setting] function of the laser microscope. At this time, no region was specified and the entire area was the target. Other settings of the laser microscope were as follows: [Surface shape correction] Yes Correction method: Waviness removal, Correction strength: 5 [Smoothing] Size: 3x3, Type: Simple average [Height cut level] Medium

[0162] Next, based on the measurement results of the surface position of the test piece obtained from the sample and the calculation results of the reference plane RP, the dent-corrected volume V1 and dent-corrected volume density V2 of each test piece were calculated. At this time, the correction distance dC between the reference plane RP and the correction plane CP was set to 0.2 μm. The calculation results of the dent-corrected volume density V2 are shown in Figure 29.

[0163] Next, a sheet of metal plate 21 cut out from each of the above-described samples was etched to form a pattern of recesses and rib portions on each metal plate 21, and the dimensional accuracy of the pattern was evaluated. FIG. 30 is a plan view showing an example of a pattern of recesses 81 and rib portions 82 formed on each metal plate 21. FIG. 31 is a cross-sectional view of the metal plate 21 shown in FIG. 30. In the example shown in FIGS. 30 and 31, the metal plate 21 was etched to form recesses 81 so that rib portions 82 extending along the first direction D1 remained on the metal plate 21. The design values of the dimension Z1 of the recesses 81 and the dimension Z2 of the rib portions 82 in a direction (here, width direction D2) perpendicular to the direction in which the rib portions 82 extend (here, rolling direction D1) were each 30 μm.

[0164] Next, the width of the rib portion 82 formed on each metal plate 21 was measured using a laser microscope. Specifically, the width of the rib portion 82 was measured at a total of 25 locations at intervals of 2 μm along the direction in which the rib portion 82 extends (here, the first direction D1). In addition, the standard deviation of the measurement results of the width of the rib portion 82 at the 25 locations was tripled (hereinafter also referred to as 3σ(D1)) to calculate the value. The 3σ(D1) values for the metal plates 21 cut out from each sample are also shown in FIG. 29 mentioned above.

[0165] The laser microscope used was a laser microscope equipped with a measurement unit and a control unit manufactured by Keyence Corporation. The model number of the measurement unit was VK-X160, and the model number of the control unit was VK-X150.

[0166] When the width of the rib portion 82 was measured, the laser microscope settings were as follows. Brightness: 7140 Measurement mode: Surface profile Measurement size: High resolution (2048 x 1536) ·Measurement quality: High precision APERTURE SHUTTER: Open ·LASER SUTTER:Open Objective lens: 100x Optical zoom: 1.0x Measurement: Reflection measurement Width measurement repeatability: 3σ=0.03μm

[0167] Next, a sheet of metal plate 21 cut from each of the above-described samples was etched in a pattern different from that shown in FIG. 30 to form a pattern of recesses 81 and rib portions 82 on each metal plate 21. Specifically, as shown in FIG. 32, the metal plate 21 was etched to form recesses 81 so that rib portions 82 extending along the second direction D2 remained on the metal plate 21. Next, the width of the rib portions 82 formed on each metal plate 21 was measured using a laser microscope. Specifically, the width of the rib portions 82 was measured at a total of 25 locations at intervals of 2 μm along the direction in which the rib portions 82 extended (here, the second direction D2). In addition, a value obtained by tripling the standard deviation of the measurement results of the width of the rib portions 82 at the 25 locations (hereinafter, also referred to as 3σ(D2)) was calculated. The value of 3σ(D2) for the metal plate 21 cut from each sample is also shown in FIG. 29.

[0168] Furthermore, the average value 3σ(ave) of the above-mentioned 3σ(D1) and 3σ(D2) was calculated for the metal plate 21 cut out from each sample. The 3σ(ave) values for the metal plate 21 cut out from each sample are also shown in the above-mentioned FIG.

[0169] Next, the correlation coefficient R between the dent-corrected volume density V2 (0.2 μm) and the 3σ (ave) of the width of the rib portion 82 calculated for each sample 2 As a result, the correlation coefficient R 2 33 is a scatter plot showing the correlation between the dent-corrected volume density V2 (0.2 μm) and the 3σ (ave) of the width of the rib portion 82.

[0170] (2nd test example to 5th test example) The surface undulations of the first to tenth samples were inspected based on the dent-corrected volume density V2 in the same manner as in the first inspection example, except that the correction distance dC between the reference plane RP and the correction plane CP was changed. Specifically, in the second inspection example, the correction distance dC was set to 0.1 μm to calculate the dent-corrected volume density V2 (0.1 μm). In the third inspection example, the correction distance dC was set to 0.3 μm to calculate the dent-corrected volume density V2 (0.3 μm). In the fourth inspection example, the correction distance dC was set to 0.4 μm to calculate the dent-corrected volume density V2 (0.4 μm). In the fifth inspection example, the correction distance dC was set to 0.5 μm to calculate the dent-corrected volume density V2 (0.5 μm). The calculation results of the dent-corrected volume densities V2 (0.1 μm), V2 (0.3 μm), V2 (0.4 μm), and V2 (0.5 μm) for each sample are shown in FIG. 34 together with the above-mentioned dent-corrected volume density V2 (0.2 μm).

[0171] Next, the correlation coefficient R between the dent-corrected volume density V2 (0.1 μm) and the 3σ (ave) of the width of the rib portion 82 calculated for each sample 2 As a result, the correlation coefficient R 2 35 is a scatter diagram showing the correlation between the dent-corrected volume density V2 (0.1 μm) and the 3σ (ave) of the width of the rib portion 82.

[0172] In addition, the correlation coefficient R between the dent-corrected volume density V2 (0.3 μm) and the 3σ (ave) of the width of the rib portion 82 calculated for each sample 2 As a result, the correlation coefficient R 2 36 is a scatter plot showing the correlation between the dent-corrected volume density V2 (0.3 μm) and the 3σ (ave) of the width of the rib portion 82.

[0173] In addition, the correlation coefficient R between the dent-corrected volume density V2 (0.4 μm) and the 3σ (ave) of the width of the rib portion 82 calculated for each sample 2 As a result, the correlation coefficient R 237 is a scatter diagram showing the correlation between the dent-corrected volume density V2 (0.4 μm) and the 3σ (ave) of the width of the rib portion 82.

[0174] In addition, the correlation coefficient R between the dent-corrected volume density V2 (0.5 μm) and the 3σ (ave) of the width of the rib portion 82 calculated for each sample 2 As a result, the correlation coefficient R 2 38 is a scatter plot showing the correlation between the dent-corrected volume density V2 (0.5 μm) and the 3σ (ave) of the width of the rib portion 82.

[0175] According to the first inspection example, by inspecting the undulations on the surface of the metal plate based on the volume of the depressions, it was possible to obtain an index that has a high correlation with the dimensional accuracy of the rib portion 82 formed by etching.

[0176] Furthermore, as can be seen from a comparison between the above-mentioned first inspection example and the second to fifth inspection examples, according to the first inspection example, by setting the correction distance dC between the reference surface RP and the correction surface CP to 0.2 μm, an index having a high correlation with the dimensional accuracy of the rib portion 82 formed by etching could be obtained.

[0177] In the second inspection example, in which the correction distance dC was set to 0.1 μm, the correction distance dC was too small, so not only specific dents that have a significant impact on the dimensional accuracy of the rib portion 82 were detected, but also dents that have almost no impact on the dimensional accuracy of the rib portion 82, which is thought to have resulted in a low correlation coefficient.In the third to fifth inspection examples, in which the correction distance dC was set to 0.3 μm or more, the correction distance dC was too large, so when evaluating a relatively smooth metal plate with a low dent density, differences in dent density and size were not properly reflected in the dent-corrected volume density V2, which is thought to have resulted in a low correlation coefficient. [Explanation of symbols]

[0178] 10. Deposition mask device 15 frames 20 Deposition mask 21 Metal plate 22 Effective Area 23 Surrounding Area 25 through holes 30 First recess 31 Wall 35 Second recess 36 Wall 41 Connection 41a Missing part 43 Top section 50 Intermediate products 64 Long metal plate 64c depression 65a First resist pattern 65b Second resist pattern 65c First resist film 65d Second resist film 711 Inspection Area 712 unit area 713 pixels 72 Processing equipment 73 Separation device 80 samples 81 Recess 82 Rib section 90 Vapor deposition equipment 92 Organic EL board 98 Evaporation Materials

Claims

1. A method for evaluating a metal plate for manufacturing a deposition mask, comprising: a step of calculating a correlation coefficient between a plurality of recess-corrected volume densities calculated based on a plurality of correction distances and a standard deviation of the width of the rib portion, the rib portion is a portion of the surface of the metal plate that is located between a plurality of recesses formed by etching the metal plate and remains unetched; the metal plate has a plurality of depressions located on a surface of the metal plate; The surface is 0.1 mm ２ an inspection area having an area of at least one of the plurality of recesses, and a part of the plurality of recesses is located in the inspection area; the plurality of dent-corrected volume densities are calculated by dividing dent-corrected volumes corresponding to the plurality of corrected distances by an area of the inspection region; the dent correction volume is a sum of volumes of portions of the part of the plurality of dents located in the inspection area that are at least the correction distance away from the surface in the thickness direction of the metal plate, The evaluation method, wherein the volume is calculated based on a result of measuring the depth of the part of the plurality of depressions using a laser microscope.

2. The evaluation method according to claim 1 , wherein the plurality of correction distances include a first correction distance, a second correction distance that is greater than the first correction distance, and a third correction distance that is greater than the second correction distance.

3. 3. The evaluation method described in claim 2, wherein the correlation coefficient between the multiple dent-corrected volume densities calculated based on the second corrected distance and the standard deviation is higher than the correlation coefficient between the multiple dent-corrected volume densities calculated based on the first corrected distance and the standard deviation, and is also higher than the correlation coefficient between the multiple dent-corrected volume densities calculated based on the third corrected distance and the standard deviation.

4. 4. The evaluation method according to claim 3, wherein the first corrected distance is 0.1 μm, the second corrected distance is 0.2 μm, and the third corrected distance is 0.3 μm.

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