Substrate and processing method of substrate

Abstract

To provide a substrate that improves adhesive strength.SOLUTION: A substrate (10) has a main surface (11) to which a specific adhesive is applied. The main surface has a plurality of recesses formed in a grid pattern or along arbitrary directions and a plurality of protrusions formed with irregular shapes and arrangements by laser processing.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a base material to be adhered and a method for processing the adhesion surface of the base material.

Background Art

[0002] Conventionally, as a method for improving the adhesion strength between objects, there is known a method of improving the adhesion strength by roughening the surface of a polyoxymethylene highly oriented body, raising fuzz, and allowing an adhesive to penetrate into a complex interior such as bundled fibers (for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, the method described in Patent Document 1 requires polishing the surface of the polyoxymethylene highly oriented body with sandpaper having a finer mesh than 300 mesh, and there are problems in terms of efficiency and quality.

[0005] One aspect of the present disclosure aims to provide a base material for improving adhesion strength and a method for processing the base material.

Means for Solving the Problems

[0006] In order to solve the above problems, a base material according to one aspect of the present disclosure is a base material to which a predetermined adhesive is applied to a main surface, and a plurality of concave portions formed in a grid shape or along an arbitrary direction on the main surface by laser processing, and protrusions having an irregular shape and arrangement are formed.

[0007] In order to solve the above problems, a method for processing a substrate according to an aspect of the present disclosure is a method for processing a substrate in which a predetermined adhesive is used on a main surface, and includes a step of preparing the substrate and a step of irradiating the main surface of the substrate with a laser. In the step of irradiating the laser, a plurality of concave portions are formed in a grid shape or along an arbitrary direction on the main surface, and protruding portions having an irregular shape and arrangement are formed.

Effects of the Invention

[0008] According to an aspect of the present disclosure, it is possible to improve the adhesive strength.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Modes for Carrying Out the Invention

[0010] Hereinafter, a substrate 10 according to an embodiment of the present disclosure will be described in detail with reference to the drawings. The following embodiments are examples of the embodiments of the present disclosure, and the present disclosure is not construed as being limited to the following embodiments. In the drawings referred to in the present embodiment, the same parts are denoted by the same reference numerals and the description thereof is omitted. Further, the drawings include schematic drawings and may not necessarily reflect the actual object. Further, for the convenience of illustration and understanding, the scale, the aspect ratio of the vertical and horizontal dimensions, etc. may be changed from the actual object and exaggeratedly shown.

[0011] [First Embodiment] (Overview of Substrate 10) The substrate 10 is described here as stainless steel, but the substrate 10 is not limited to stainless steel and may be composed of, for example, metals (such as iron, aluminum, cemented carbide, titanium, etc.). The shape of the substrate 10 is shown as a rectangle having a front surface 11 and a back surface 12 opposite to the front surface 11, but it is not limited thereto. The shape of the substrate 10 may be square, circular, or elliptical. Also, the shape of the substrate 10 is not limited to a plate shape and may be a column shape having a sufficient thickness.

[0012] The X-axis shown in FIG. 1 is an axis extending along the longitudinal direction of the substrate 10, the Y-axis is an axis extending along the short-side direction of the substrate 10, the Z-axis is an axis extending along the height direction of the substrate 10, and is an axis perpendicular to the X-axis and the Y-axis. In the following drawings, the definitions of the X-axis, Y-axis, and Z-axis are the same.

[0013] As an example of the use of the substrate 10, the substrate 10 is used when adhering to an arbitrary object. In the present embodiment, laser light is irradiated from the laser device 20 onto the front surface 11 of the substrate 10 to perform a predetermined laser processing. As the "predetermined laser processing", in the present embodiment, a dimple processing for forming a plurality of dimples 13 (not shown in FIG. 1) as recesses on the front surface 11 is mentioned. After the laser processing is performed, an adhesion operation is performed on the front surface 11 using a predetermined adhesive.

[0014] In the present embodiment, an example of forming the dimples 13 with the front surface 11 of the substrate 10 as the adhesion surface is described, but the dimples 13 may be formed not only on the front surface 11 but also on the back surface 12. In this case, the adhesion surface is formed on both the front surface 11 and the back surface 12. Note that hereinafter, the "front surface 11" may be referred to as the "adhesion surface 11".

[0015] The adhesive used for the bonding surface 11 subjected to laser processing is not particularly limited in properties as long as it can be fluidized during bonding. For example, it may be liquid at room temperature, or it may be one that softens by heating, such as a hot melt resin or a brazing material. As long as it has such properties, the material is not particularly limited. Such an adhesive may be applied to the bonding surface 11 or may be disposed on the bonding surface 11.

[0016] (Details of the dimples 13) Next, with reference to FIGS. 2 to 3, the details of the main surface properties formed on the bonding surface 11 of the adherend by laser processing will be described. FIG. 2 is an enlarged view of a part of the bonding surface 11 on which a plurality of dimples 13 are formed by laser processing. FIG. 3 is a simulation screen schematically showing the dimples 13 and the protrusions 14 formed between the dimples 13 adjacent in the diagonal direction. In FIG. 3, the bonding surface 11 is shown as a flat surface for convenience, but it is not limited thereto. The bonding surface 11 may be a curved surface, or may have polygonal inclined surfaces (for example, concave portions such as V-shaped or quadrangular pyramid-shaped).

[0017] As shown in FIG. 2, a plurality of dimples 13 are formed on the bonding surface 11 of the base material 10 by laser processing. The plurality of dimples 13 are continuously formed adjacent to each other in a grid pattern along the X-axis direction and the Y-axis direction. Between the dimples 13, fine protrusions 14 protruding in the Z-axis direction from the bonding surface 11, that is, upward in the vertical direction, are formed (see FIG. 3). Note that the reference signs are omitted in FIG. 3. As shown in FIGS. 2 and 3, the protrusions 14 are formed between the dimples 13 adjacent in the diagonal direction, not in the X-axis direction and the Y-axis direction. Also, note that the protrusions 14 shown in FIG. 3 are schematically shown using a predetermined simulation software and have a different shape from the actual protrusions 14.

[0018] In FIG. 2, the adjacent dimples 13 have the same intervals in both the X-axis direction and the Y-axis direction, but these intervals may be different. In this case, for example, a group of dimples formed as a column in the X-axis direction and a group of dimples (a column in the X-axis direction) adjacent to the group of dimples in the Y-axis direction are formed separately. Alternatively, a group of dimples may be formed in one column in the X-axis direction or the Y-axis direction. Further, the plurality of dimples 13 may be formed in only one row along an oblique direction, rather than along the X-axis direction or the Y-axis direction of the bonding surface 11, that is, rather than along the horizontal direction or the vertical direction, and may be formed in two or more rows along the oblique direction. When the plurality of dimples 13 are formed in two or more rows along the oblique direction, each row may be formed separately without contacting each other. Furthermore, the intervals between the adjacent dimples 13 may be irregular.

[0019] (Details of the protrusions 14 formed between the dimples) Next, with reference to FIG. 4, the details of the protrusions 14 formed between the dimples 13 and the dimples 13 will be described. FIG. 4 is a cross-sectional view taken along line A-A of FIG. 2. In FIG. 4, for the sake of convenience of explanation, in order to distinguish each of the plurality of dimples 13, they are referred to as dimple 13A, dimple 13B, ···. Also, in order to distinguish each of the plurality of protrusions 14, they are referred to as protrusion 14A, protrusion 14B, ···.

[0020] As shown in FIG. 4, a protrusion 14A is formed between the dimple 13A and the dimple 13B on the bonding surface 11. Also, a protrusion 14B is formed between the dimple 13B and the dimple 13C on the bonding surface 11. Also, a protrusion 14C is formed between the dimple 13C and the dimple 13D on the bonding surface 11. Also, a protrusion 14D is formed between the dimple 13D and the dimple 13E on the bonding surface 11. Also, a protrusion 14E is formed between the dimple 13E and the dimple 13F on the bonding surface 11. Also, a protrusion 14F is formed between the dimple 13F and the dimple 13G on the bonding surface 11. Also, a protrusion 14G is formed between the dimple 13G and the dimple 13H on the bonding surface 11.

[0021] Although any of the protrusions 14A to 14G protrudes upward in the Z-axis direction, that is, upward in the vertical direction, from the bonding surface 11, the shapes and sizes of the protrusions 14A to 14G are different from each other. Specifically, the shape of the protrusion 14A is rod-shaped and protrudes so as to incline in the obliquely upper right direction, and there is no special change in the overall size.

[0022] The shape of the protrusion 14B is rod-shaped and protrudes so as to incline in the obliquely upper left direction, and there is no special change in the overall size.

[0023] Unlike the protrusions 14A and 14B, the protrusion 14C protrudes straight upward, and further, a flange portion 141 protruding leftward is formed at its tip. Thus, the protrusion 14C is formed such that its width (diameter) increases upward in the vertical direction.

[0024] Unlike the protrusions 14A and 14B, the protrusion 14D protrudes straight upward, and further, its size gradually decreases and it is formed to be sharpened.

[0025] Unlike the protrusions 14A and 14B, the protrusion 14E protrudes straight upward, and further, a flange portion 142 protruding leftward and a flange portion 143 protruding rightward are formed at its tip. Thus, the protrusion 14E is formed such that its width (diameter) increases upward in the vertical direction. Incidentally, as another expression, it may be paraphrased that the protrusion 14E has flange portions 142 and 143 that expand in a mushroom shape from the tip.

[0026] The shape of the protrusion 14F is trapezoidal in reverse, and is formed such that its size gradually increases upward in the vertical direction.

[0027] Unlike the protrusions 14A and 14B, the protrusion 14G protrudes upward, and a cap portion 144 protruding rightward is formed at its tip. Thus, the protrusion 14G is formed such that its width (diameter) increases upward in the vertical direction.

[0028] As described above, the protrusions 14A to 14G have no regularity in their respective shapes, nor is there any regularity in their arrangement.

[0029] Here, an example of the mechanism for forming the protrusions 14A to 14G will be described. Generally, it is known that ablation occurs when laser light having a predetermined pulse width is irradiated. Ablation is a phenomenon in which when laser light is irradiated on the surface of a solid, the constituent substances of the solid surface explosively evaporate with the generation of plasma. Due to the explosive evaporation caused by ablation, high-temperature evaporated substances may deposit around. The substances deposited around are called so-called debris. The protrusions 14A to 14G are formed by the rapid cooling and solidification of high-temperature evaporated substances before they become debris. Since they are formed in this way, the shapes and sizes of the protrusions 14A to 14G are different from each other. There are the protrusion 14C having the cap portion 141, the protrusion 14E having the cap portions 142 and 143, and the protrusion 14G having the cap portion 144. On the other hand, there are also the protrusions 14A, 14B, 14D, and 14F that do not have such cap portions. According to the inventors, it has been found that by appropriately adjusting the material of the base material 10, the amount of heat applied by the laser light, the irradiation time, etc., it is possible to form a mixture of protrusions with cap portions and protrusions without cap portions.

[0030] In addition, in FIG. 4, the shapes of the dimples 13A to 13H are shown as dimple shapes, but are not limited thereto. The shapes of the dimples 13A to 13H may be any shape as long as they are shapes formed according to the type of laser processing.

[0031] Further, the pitch distance indicating the interval between the dimples 13A and 13B is not particularly limited. For example, any length may be sufficient as long as the protrusions 14A to 14G are formed to have a strength such that they do not easily chip off.

[0032] [Second Embodiment] Next, with reference to FIGS. 5 to 6, a second embodiment of the present disclosure will be described. In the following description, the differences from the first embodiment will be mainly described.

[0033] FIG. 5 is an enlarged view of a part of the bonding surface 11 in which the groove portion 16 is formed by laser processing. FIG. 6 is a cross-sectional view taken along line B-B of FIG. 5.

[0034] The similarities and differences between FIGS. 5 and 2 will be described. First, the similarities will be described. Similar to FIG. 2, in FIG. 5, a plurality of recesses are formed on the bonding surface 11 of the base material 10 by laser processing. Further, the base material 10 has a plurality of protrusions 17 having irregular shapes and arrangements.

[0035] Next, the differences will be described. In FIG. 5, unlike FIG. 2, the plurality of recesses are groove portions 16 formed along the X-axis and the Y-axis. By forming the groove portions 16 in a grid pattern, a plurality of column-shaped island portions 15 are formed so as to be surrounded by the groove portions 16. Similar to the groove portions 16, the island portions 15 are also formed continuously adjacent to each other along the X-axis and the Y-axis. Further, protrusions 17 are formed on the inner surfaces of the groove portions 16. Note that since the intervals between the adjacent groove portions 16 in FIG. 5 are substantially the same for the groove portions 16 in the X-axis direction and the groove portions 16 in the Y-axis direction, the planar shape of the formed island portions 15 is substantially square and substantially the same shape. However, by making the intervals of the respective groove portions 16 in the X-axis direction and the Y-axis direction different, the shape of the island portions 15 may be rectangular, or the shapes of the respective island portions 15 may be different. Further, by arbitrarily setting the angle between the two intersecting groove portions 16, it may be a polygon such as a triangle or a pentagon. Note that the area of the island portions 15 may be increased by increasing the interval between the adjacent groove portions 16.

[0036] (Details of the island portion 15, groove portion 16, and protrusion portion 17) In FIG. 6, for the sake of convenience in explanation, in order to distinguish each of the plurality of island portions 15, they are referred to as island portion 15A, island portion 15B, and so on. Also, in order to distinguish each of the plurality of groove portions 16, they are referred to as groove portion 16A, groove portion 16B, and so on. Further, in order to distinguish each of the plurality of protrusion portions 17, they are referred to as protrusion portion 17A, protrusion portion 17B, and so on.

[0037] As shown in FIG. 6, an island portion 15A is formed between the groove portion 16A and the "left-end groove portion" omitted in FIG. 6. Also, an island portion 15B is formed between the groove portion 16A and the groove portion 16B. Also, an island portion 15C is formed between the groove portion 16B and the groove portion 16C. Also, an island portion 15D is formed between the groove portion 16C and the groove portion 16D. Also, an island portion 15E is formed between the groove portion 16D and the "right-end groove portion" omitted in FIG. 6.

[0038] The longitudinal cross-sectional shapes of the island portions 15A to 15E are shown as trapezoidal shapes, but this is just an example and is not limited to trapezoidal shapes. For example, they may be rectangular or square. As long as the shapes of the island portions 15A to 15E are columnar shapes, they may be shapes other than frustum-of-a-square-pyramid shapes. For example, they may be cuboids or cubes, or may also be frustum-of-a-pyramid shapes or prism shapes with a polygonal planar shape.

[0039] A protrusion portion 17A is formed on the bottom surface of the groove portion 16A between the island portion 15A and the island portion 15B. Also, a protrusion portion 17B is formed on the bottom surface of the groove portion 16B between the island portion 15B and the island portion 15C. Also, a protrusion portion 17C is formed on the bottom surface of the groove portion 16C between the island portion 15C and the island portion 15D. Also, a protrusion portion 17D is formed on the bottom surface of the groove portion 16D between the island portion 15D and the island portion 15E.

[0040] The protrusion portions 17A to 17D protrude upward in the vertical direction, similar to the protrusion portions 14A to 14G shown in FIG. 4, and the shapes and sizes of the protrusion portions 17A to 17D are different from each other.

[0041] Unlike the protrusion 17B and the protrusion 17C, the protrusion 17A protrudes upward, and further, a cap portion 171 protruding leftward and a cap portion 172 protruding rightward are formed at its tip. Thus, the protrusion 17A is formed such that its width (diameter) increases upward in the vertical direction. As another expression, it may be paraphrased that the protrusion 17A has cap portions 171 and 172 that expand mushroom-like from the tip.

[0042] The shape of the protrusion 17B is rod-shaped and protrudes obliquely upward to the upper right, and there is no special change in the overall size.

[0043] The shape of the protrusion 17C is rod-shaped and protrudes obliquely upward to the upper left, and there is no special change in the overall size.

[0044] Unlike the protrusion 17B and the protrusion 17C, the protrusion 17D protrudes upward, and further, a cap portion 173 protruding rightward is formed at its tip. Thus, the protrusion 17D is formed such that its width (diameter) increases upward in the vertical direction.

[0045] Although the mechanism by which the protrusions 17A to 17D are formed has not been identified, it is presumed to be the same as the mechanism by which the protrusions 14A to 14G are formed. Therefore, the description is omitted.

[0046] In addition, in FIG. 6, the protrusions 17A to 17D are shown as being formed on the bottom surface among the inner surfaces of the groove portions 16A to 16D, but it is not limited to this. For example, the protrusions 17A to 17D may also be formed on the side surfaces of the groove portions 16A to 17D.

[0047] (Function and effect) As described above, according to the base material 10 according to the present embodiment, the following function and effect can be obtained.

[0048] The base material 10 to which a predetermined adhesive is used at least on the adhesive surface 11 has a plurality of recesses formed in a grid shape or in an arbitrary direction by laser processing, and a plurality of protrusions having irregular shapes and arrangements. The "arbitrary direction" mentioned here means, for example, an arbitrary direction in which laser light is irradiated. An example thereof is the X-axis direction or the Y-axis direction shown in FIG. 1, but the coordinate axes can be set arbitrarily.

[0049] According to the above configuration, when the adhesive is applied to the adhesive surface 11 of the base material 10, the adhesive enters the recesses, thereby improving the adhesive force in the thrust direction. Further, the adhesive penetrates so as to be entangled with the plurality of protrusions having irregular shapes and arrangements, thereby improving the adhesive force in the radial direction. As a result, it becomes possible to improve the adhesive strength. When a plurality of fine protrusions such as fluff are formed on the adhesive surface 11 of the base material 10, when the adhesive is applied to the adhesive surface 11 of the base material 10, the adhesive penetrates to the inside so as to be entangled with the fine protrusions. As a result, it becomes possible to improve the adhesive strength. As described above, the prior art has to be polished with sandpaper, which has a problem in terms of efficiency. By using laser processing as in the present embodiment, the adhesive surface 11 of the base material 10 can be processed efficiently. In addition, there is a possibility that the quality may vary with sandpaper, but by using laser processing as in the present embodiment, processing for improving the adhesive force can be applied to the entire adhesive surface, so that a high-quality base material 10 can be provided.

[0050] As shown in FIG. 4, the recesses are grid-shaped dimples 13, and the protrusions 14 are formed between the diagonally adjacent dimples 13.

[0051] According to the above configuration, a plurality of fine protrusions 14 like fuzz are formed on the adhesive surface 11. When an adhesive is applied to the adhesive surface 11 of the base material 10, the adhesive penetrates into the interior so as to be entangled with the fine protrusions 14. Since the adhesive cures in that state, an anchor effect mainly occurs in the radial direction. Furthermore, since the shape of the protrusions 14 is irregular and the arrangement is also irregular, the adhesive force becomes higher. Also, since the recesses are dimples 13, an anchor effect with respect to the thrust direction can be obtained. Thereby, it becomes possible to improve the adhesive strength.

[0052] As shown in FIG. 6, it has columnar island portions 15 formed by groove portions 16 which are a plurality of recesses formed along an arbitrary direction, and a plurality of protrusions 17 having irregular shapes and arrangements are formed on at least the inner surface of the groove portions 16.

[0053] With the above configuration, since the plurality of recesses are groove portions 16, the fluidity of the adhesive is high. Also, since the groove portions 16 are formed so as to form columnar island portions 15, the adhesiveness with respect to the thrust direction becomes higher. Also, when an adhesive is applied to the adhesive surface 11 of the base material 10, a plurality of fine protrusions 17 like fuzz are formed on the inner surface of the groove portions 16, and the adhesive penetrates into the interior so as to be entangled with the fine protrusions 17. Since the adhesive cures in that state, an anchor effect occurs. Furthermore, since the shape of the protrusions 17 is irregular and the arrangement is also irregular, the adhesive force becomes higher. Also, columnar island portions 15A to 15E can be formed on the adhesive surface 11 of the base material 10, and the shape of the adhesive surface 11 can have variations. Thereby, it becomes possible to use the base material 10 for adhesion between various objects.

[0054] Also, as shown in FIGS. 4 and 6, among the plurality of protrusions 14A to 14G and 17A to 17D, at least one protrusion (for example, protrusions 14C, 17D) may have a cap portion (for example, cap portions 141, 173) that protrudes in at least one direction from the tip. The "one direction" mentioned here is an arbitrary direction not particularly limited, but for example, it may be the X-axis direction shown in FIG. 4. Also, the "at least one protrusion" may be protrusion 14G. In this case, the cap portion that protrudes in at least one direction from the tip means cap portion 144.

[0055] According to the above configuration, when an adhesive is applied to the adhesive surface 11 of the base material 10, the adhesive enters the gaps formed by the cap portions 141 and 173, and the hardening of the adhesive there causes the return of the hook to bite in, so that it is possible to improve the adhesive strength in the thrust direction and the radial direction by the so-called anchor effect.

[0056] Also, as shown in FIGS. 4 and 6, among the plurality of protrusions 14A to 14G and 17A to 17D, at least one protrusion (for example, protrusions 14E, 17A) may have a cap portion (for example, cap portions 142, 143, 171, 172) that expands mushroom-like from the tip.

[0057] According to the above configuration, when an adhesive is applied to the adhesive surface 11 of the base material 10, the adhesive enters the gaps formed by the mushroom-like expanding cap portions 142 and 143, and the hardening of the adhesive there is expected to further improve the above-described anchor effect, making it possible to further improve the adhesive strength in the thrust direction and the radial direction.

[0058] The present disclosure is not limited to the above-described embodiments, and various modifications are possible within the scope shown in the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present disclosure.

[0059] 〔Supplementary Notes〕 Also, the present disclosure can also be expressed as follows.

[0060] The substrate according to Embodiment 1 of the present disclosure is a substrate in which a predetermined adhesive is used on the main surface, and a plurality of recesses formed in a grid shape or along an arbitrary direction on the main surface by laser processing, and a plurality of protrusions having irregular shapes and arrangements are formed.

[0061] The substrate according to Embodiment 2 of the present disclosure is, in Embodiment 1 above, the recesses are in a grid shape, and the protrusions may be formed between adjacent recesses.

[0062] The substrate according to Embodiment 3 of the present disclosure is, in Embodiment 1 above, has column-shaped island portions formed by the plurality of recesses formed along the arbitrary direction, and the plurality of protrusions having irregular shapes and arrangements may be formed in the plurality of recesses.

[0063] The substrate according to Embodiment 4 of the present disclosure is, in Embodiment 2 or 3 above, at least one of the plurality of protrusions may have a cap portion protruding in at least one direction from the tip.

[0064] The substrate according to Embodiment 5 of the present disclosure is, in any of Embodiments 1 to 4 above, at least one of the plurality of protrusions may have a cap portion spreading in a mushroom shape from the tip.

[0065] The processing method of the substrate according to Embodiment 6 of the present disclosure is a processing method of a substrate in which a predetermined adhesive is used on the main surface, and includes a step of preparing the substrate and a step of irradiating the main surface of the substrate with a laser. In the step of irradiating the laser, a plurality of recesses are formed in a grid shape or along an arbitrary direction on the main surface, and a plurality of protrusions having irregular shapes and arrangements are formed.

Explanation of Reference Numerals

[0066] 10 Substrate, 11 Main surface (adhesive surface), 12 Back surface, 13 Dimple, 14, 17 Protrusion, 15 Island portion, 16 Groove portion, 20 Laser device, 141 to 144, 171 to 173 Cap portion

Claims

1. A substrate having a major surface to which a specific adhesive is applied, A plurality of recesses formed in a grid pattern or along any direction on the main surface by laser processing; and a plurality of protrusions having irregular shapes and arrangements. Base material.

2. The recesses are in a grid shape, and the protrusions are formed between adjacent recesses. The substrate of claim 1.

3. a columnar island portion formed by a plurality of the recesses formed along the arbitrary direction, The plurality of protrusions having the irregular shape and arrangement are formed in the plurality of recesses. The substrate of claim 1.

4. At least one of the plurality of protrusions has a cap portion protruding in at least one direction from a tip thereof. The substrate according to claim 2 or 3.

5. At least one of the plurality of protrusions has a cap portion extending from a tip thereof in a mushroom shape. The substrate according to any one of claims 1 to 3.

6. A method for processing a substrate having a major surface to which a predetermined adhesive is applied, comprising the steps of: Providing the substrate; irradiating the main surface of the substrate with a laser; having In the step of irradiating the laser, a plurality of recesses are formed on the main surface in a grid pattern or along an arbitrary direction, and a plurality of protrusions having an irregular shape and arrangement are formed. Method of processing the substrate.

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