Surface modification laser irradiation device, surface modification laser irradiation method, and metal member

Abstract

To provide a surface modification laser irradiation device which prevents large cracking on a surface of a metal member, without using chemicals that are difficult to be treated.SOLUTION: A surface modification laser irradiation device includes a light source device 70 including a laser light source 10 for emitting a laser beam Ld, and an optical system 20 for arranging the laser beam emitted from the laser light source in a previously set optical path toward a target 1 subjected to surface modification and guiding the laser beam, a storage part 50 for storing the target together with a medium 7 which is liquid or gas having thermal conductivity higher than that of air, and a moving mechanism 40 for moving either or both of the target and the laser beam irradiation position, wherein the storage part has a supporting part for supporting the target irradiated with the laser beam through the medium, and laser energy density in which the target in the medium is irradiated with the laser beam from the light source device is equal to or more a bulge start threshold of the target, and is equal to or less than a melting threshold of the target in the medium.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a surface-modifying laser irradiation device and a surface-modifying laser irradiation method used when modifying the surface of a metal component, and to a metal component. [Background technology]

[0002] There is a known technique for modifying a metal surface by chemically treating the metal surface. For example, this technique involves anodizing the surface of an aluminum plate to form minute irregularities, thereby realizing water repellency (see, for example, Non-Patent Document 1). [Prior art documents] [Non-patent literature]

[0003] [Non-Patent Document 1] Surface Technology Vol.65, No9, 2014, pp. 22-27 (426-431) "Super Water- and Oil-Repellent Metal Surfaces Using Anodic Oxidation" Hiroki Habazaki, Graduate School of Engineering, Hokkaido University (8-chome, Kita 13-jo Nishi, Kita-ku, Sapporo, Hokkaido, 060-8628), Takashi Fujii, Advanced Technology Research Laboratories, Technology Development Headquarters, Nippon Steel & Sumitomo Metal Corporation (20-1, Shintomi, Futtsu, Chiba, 293-8511), Katsutoshi Nakayama, Graduate School of Science and Engineering, Hokkaido University (8-chome, Kita 13-jo Nishi, Kita-ku, Sapporo, Hokkaido, 060-8628), Etsuji Tsuji, Graduate School of Engineering, Hokkaido University (8-chome, Kita 13-jo Nishi, Kita-ku, Sapporo, Hokkaido, 060-8628), Yoshinao Aoki, Graduate School of Engineering, Hokkaido University (8-chome, Kita 13-jo Nishi, Kita-ku, Sapporo, Hokkaido, 060-8628) Summary of the Invention [Problem to be solved by the invention]

[0004] In the conventional technology, in order to form a nanodot structure on the surface of a metal member, chemicals are used to modify the surface of the metal member, so that the effect of the nanodot structure can be achieved. However, the current situation is that it takes time and money to dispose of the waste liquid of the chemicals used when modifying the surface of the metal member. In addition, when a laser beam is directly irradiated on a metal member, large cracks are generated.

[0005] Therefore, the present invention has been devised in consideration of the above-mentioned situation, and its objective is to provide a surface modification laser irradiation device, a surface modification laser irradiation method, and a metal component that do not use chemicals that are difficult to process and do not cause large cracks on the surface of the metal component. [Means for solving the problem]

[0006] In order to solve the above problem, the surface modification laser irradiation device of the present invention includes a light source device including a laser light source that irradiates laser light and an optical system that arranges and guides the laser light from the laser light source on a predetermined optical path toward a target to be surface modified, a storage unit that stores the target together with a medium that is a liquid or gas having a higher thermal conductivity than air, and a moving mechanism that moves either the target or the irradiation position of the laser light, or both, and the storage unit has a support unit that supports the target to be irradiated by the laser light through the medium, and the laser energy density at which the laser light from the light source device is irradiated to the target in the medium is equal to or greater than the protuberance start threshold of the target and equal to or less than the melting threshold of the target in the medium.

[0007] In addition, in order to solve the above problem, the surface modification laser irradiation method of the present invention includes the steps of preparing a target to be surface modified by storing it in a storage section filled with a medium that is a liquid or gas having a thermal conductivity higher than that of air, irradiating the target in the prepared storage section with laser light from a laser light source through the medium by an optical system arranged in the light path, and moving one or both of the target and the irradiation position of the laser light via a moving mechanism so that the laser light is irradiated over the entire area of ​​a predetermined irradiation area of ​​the target, and the laser energy density at which the laser light is irradiated to the target in the step of irradiating the laser light is equal to or higher than the protuberance start threshold of the target and equal to or lower than the melting threshold of the target in the medium.

[0008] Further, in order to achieve the above object, the metal member according to the present invention has a surface having a size of 1 / 50 to 1 / 2 of the wavelength of the laser light irradiated thereon, and has 50 particles >1 μm 2 The structure had a periodic dot structure with a density of 100 nm. Effect of the Invention

[0009] The surface modification laser irradiation device and surface modification laser irradiation method of the present invention can form nanometer-sized protrusions on the surface of a metal component at a density equal to or higher than a certain level without using chemicals that are difficult to process, while suppressing cracking of the metal component. [Brief description of the drawings]

[0010] [Figure 1] 1 is a block diagram showing a surface modification laser irradiation device according to the present invention; [Diagram 2] 2 is a perspective view showing a schematic irradiation state of laser light irradiated from a cylindrical lens onto a target in the surface modification laser irradiation device of FIG. 1. FIG. [Figure 3A] 3 is a front view showing a schematic enlarged view of a part of a target irradiated with laser light in FIG. 2. [Figure 3B]3 is a front view showing a schematic view of the irradiation position of the laser light in FIG. 2 on a part of the target. [Figure 4A] 1 is a plan view showing a state in which protrusions are formed on the surface of a titanium plate, which is a metal member according to the present invention. FIG. [Figure 4B] 4B is an enlarged perspective view showing a protrusion in FIG. 4A. [Diagram 5] 2 is a flowchart showing a surface modification laser irradiation method according to the present invention. [Figure 6A] FIG. 2 is a block diagram showing a first modified example of the surface modification laser irradiation device according to the present invention. [Figure 6B] FIG. 11 is a block diagram showing a second modified example of the surface modification laser irradiation device according to the present invention. [Figure 6C] 1 is a schematic diagram showing the configuration of a first application example of a surface-modifying laser irradiation device according to the present invention; FIG. [Figure 6D] FIG. 2 is a schematic diagram showing the configuration of a second application example of the surface modification laser irradiation device according to the present invention. [Figure 7A] FIG. 1 is a graph showing the relationship between crater diameter [μm] and laser energy density (Laser fluence) [J / cm2] when a titanium plate is irradiated with laser light in the atmosphere. [Figure 7B] FIG. 1 is a graph showing the relationship between crater diameter [μm] and laser energy density (Laser fluence) [J / cm2] when a titanium plate is irradiated with laser light in water. [Figure 8A] This is an FE-SEM photograph at 20,000 times magnification showing a portion of a titanium plate in which protrusions were formed by irradiating the titanium plate with laser light in air at a laser energy density of 0.22 J / cm2, N=100, and 100 pulses. [Figure 8B] This is an FE-SEM photograph at 20,000 times magnification showing a portion of a titanium plate in which protrusions were formed by irradiating the titanium plate with laser light in air at a laser energy density of 0.22 J / cm2, N=100, and 100 pulses. [Figure 8C]This is an FE-SEM photograph at 20,000 times magnification showing a portion of a titanium plate in which protrusions were formed by irradiating the titanium plate with laser light in air at a laser energy density of 0.22 J / cm2, N=100, and 100 pulses. [Figure 8D] This is an FE-SEM photograph at 20,000 times magnification showing a portion of a titanium plate in which protrusions were formed by irradiating the titanium plate with laser light in air at a laser energy density of 0.22 J / cm2, N=100, and 100 pulses. [Figure 9A] This is an FE-SEM photograph at 20,000 times magnification of a portion of a titanium plate in which protrusions were formed by irradiating laser light with 100 pulses, N=100, at a laser energy density of 0.22 J / cm2 in water. [Figure 9B] This is an FE-SEM photograph at 20,000 times magnification of a portion of a titanium plate in which protrusions were formed by irradiating laser light with 100 pulses, N=100, at a laser energy density of 0.22 J / cm2 in water. [Figure 9C] This is an FE-SEM photograph at 20,000 times magnification of a portion of a titanium plate in which protrusions were formed by irradiating laser light with 100 pulses, N=100, at a laser energy density of 0.22 J / cm2 in water. [Figure 9D] This is an FE-SEM photograph at 20,000 times magnification of a portion of a titanium plate in which protrusions were formed by irradiating laser light with 100 pulses, N=100, at a laser energy density of 0.22 J / cm2 in water. [Figure 10A] This is an FE-SEM photograph showing the surface state of the titanium plate before being irradiated with laser light at 20,000 times magnification. [Figure 10B] This is an FE-SEM photograph at 20,000 times magnification showing the surface state of a titanium plate irradiated with 100 pulses of laser light at a laser energy density of 0.50 J / cm2 in air. [Figure 10C] This is an FE-SEM photograph at 20,000 times magnification showing the surface state of a titanium plate irradiated with 100 pulses of laser light at a laser energy density of 0.50 J / cm2 in water. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, an example of an embodiment of the present invention will be described with reference to the drawings. Note that the present invention is not limited to the embodiment described below. 1, the surface modification laser irradiation device 100 includes a light source device 70, a storage section 50, and a moving mechanism 40, and stores a metal member (hereinafter referred to as a target) 1 in the storage section 50, and performs surface modification of the target 1 by irradiating the target 1 with laser light Ld through a medium 7, which is a liquid or gas having a higher thermal conductivity than air and is placed inside the storage section 50. Note that the metal member serving as the target 1 will be described as being made of a titanium plate as an example.

[0012] As shown in FIG. 1, the surface modification laser irradiation device 100 includes, as an example, a light source device 70 having a laser light source 10 and an optical system 20 arranged on a preset optical path to guide the laser light Ld from the laser light source 10 to the target 1, a storage unit 50 for storing the target 1 to be irradiated with the laser light Ld via the optical system 20 of the light source device 70, and a moving mechanism 40 for moving the target 1 so that the laser light Ld is irradiated to the entire area of ​​the preset irradiation area of ​​the target 1. In addition, the surface modification laser irradiation device 100 further includes a visible light laser light source 30 for confirming that the laser light Ld from the laser light source 10 is appropriately irradiated to the target 1, a CMOS camera 60 as an imaging camera used when adjusting the laser light Ld, and a photodetector 28 for detecting the intensity of the laser light Ld irradiated to the target 1, and can be used for optical adjustment before irradiation of the target. In addition, the camera and the photodetector are retracted during processing.

[0013] The surface modification laser irradiation device 100 includes a first optical path P1 along which the laser light Ld travels from the laser light source 10 to the target 1, and a second optical path P2 along which the visible laser light Ls travels from the visible light laser light source 30 to the target 1. The first optical path P1 and the second optical path P2 are configured to share a part of the optical path including the cylindrical lens 27 serving as an objective lens toward the target 1.

[0014] As an example, the first optical path P1 includes a first reflecting mirror 21a1 that reflects the laser light Ld from the laser light source 10, a half-wave plate 23a that rotates the polarization direction of the laser light Ld from the first reflecting mirror 21a1, a polarizing prism 24a that arbitrarily varies the transmission intensity of the s-polarized light that passes through the half-wave plate 23a and travels straight ahead according to the polarization direction, a second reflecting mirror 21a2 to a fourth reflecting mirror 21a4 that reflect the s-polarized laser light Ld from the polarizing prism 24a, a mirror 22 that reflects the laser light Ld from the fourth reflecting mirror 21a4, a fifth reflecting mirror 21a5 that reflects the laser light Ld from the mirror 22, and a cylindrical lens 27 that is an objective lens that collects the laser light Ld from the fifth reflecting mirror. The mirror 22 is a wavelength selection mirror that reflects the wavelength of the laser light Ld and transmits visible laser light Ls, which will be described later.

[0015] Furthermore, in the first optical path P1, a first ND filter 26a1 is disposed in an optical path between the polarizing prism 24a and the second reflecting mirror so as to be freely installable and retractable, and a second ND filter 26a2 is disposed in an optical path between the fourth reflecting mirror 21a4 and the mirror 22 so as to be freely installable and retractable. These first ND filter 26a1 and second ND filter 26a2 are used at the time of setting before performing the surface modification processing of the target 1, and are intended to attenuate the light intensity of the laser light Ld. In addition, in the first optical path P1, a first shutter 25a is disposed between the third reflecting mirror 21a3 and the fourth reflecting mirror 21a4. The first shutter 25a is used to control the passage and blocking of the laser light Ld, for example, at the time of setting the laser light Ld before performing the surface modification processing, or when ensuring safety.

[0016] As an example, the second optical path P2 includes a first visible light reflecting mirror 21b1 that reflects the visible laser light Ls from the visible light laser source 30, a second visible light reflecting mirror 21b2 that reflects the visible laser light Ls from the first visible light reflecting mirror 21b1, a half-wave plate 23b that rotates the polarization direction of the visible laser light Ls from the second visible light reflecting mirror 21b2, a polarizing prism 24b that treats the visible laser light Ls transmitted through the half-wave plate 23b as s-polarized light and arbitrarily varies the transmission intensity, a third visible light reflecting mirror 21b3 that reflects the visible laser light Ls transmitted through the polarizing prism 24b, a mirror 22 that transmits light from the third visible light reflecting mirror 21b3, a fifth reflecting mirror 21a5 that reflects the visible laser light Ls from the mirror 22, and a cylindrical lens 27 that collects the visible laser light Ls from the fifth reflecting mirror 21a5 and irradiates the visible laser light Ls onto the target 1.

[0017] In the second optical path P2, a second shutter 25b is disposed in the optical path between the polarizing prism 24b and the third visible light reflecting mirror 21b3 to control the blocking of the passage of the visible laser light Ls. In the surface modification laser irradiation device 100, the first optical path P1 and the second optical path P2 share a part of the optical path. As an example, the first optical path P1 and the second optical path P2 share the optical path from the mirror 22 to the objective lens. Further, in order to measure the light intensity of the laser light Ld on the first optical path P1, a photodetector 28 is provided between the cylindrical lens 27 and the target 1 so as to be freely installed and retracted. As an example, the photodetector 28 detects the light intensity of the laser light Ld and adjusts it so that it falls within a preset threshold range.

[0018] The laser light source 10 may be, for example, a CO2 laser, a fiber laser, a titanium sapphire laser, an excimer laser, or a YAG laser, and a YAG laser is used here. The laser light source 10 used here can output wavelengths such as a fundamental wavelength of 1064 nm, a second harmonic of 532 nm, and a third harmonic of 355 nm, and as an example, a laser light Ld of a second harmonic of 532 nm is used. This laser light source 10 irradiates the laser light Ld for surface modification of the target 1. The laser light source 10 operates so that the laser light Ld has a predetermined pulse number. As an example, the laser light source 10 operates so that the laser light Ld is irradiated to the target 1 in a range of 50 to 600 pulses. The wavelength band of the laser light Ld is preferably in the range of 266 nm to 10.6 μm.

[0019] Furthermore, the laser energy density F irradiated from the laser light source 10 is equal to or higher than the protrusion start threshold of the protrusion 2 and equal to or lower than the melting threshold, that is, F=0.22 to 0.43 J / cm 2 The laser energy density F is in the range of 0.22 J / cm 2 If the laser energy density F is less than 0.43 J / cm 2 , the protrusions 2 cannot be formed. 2 If it exceeds this value, the protrusion 2 will melt and cracks will easily occur on the metal surface. Note that the laser energy density F is measured between the storage portion 50 and the cylindrical lens 27 as an example here.

[0020] For example, a He-Ne laser can be used as the visible light laser light source 30. The visible light laser light source 30 uses red visible laser light Ls, which is visible light that does not modify the surface of the target 1. By using this visible laser light, the operator can visually confirm the position where the visible laser light Ls is irradiated, and can confirm the irradiation position of the laser light Ld that modifies the surface of the target 1.

[0021] The optical system 20 disposed on the first optical path P1 includes, for example, a first reflecting mirror 21a1 to a fifth reflecting mirror 21a5, a mirror 22, a half-wave plate 23a, a polarizing prism 24a, and a cylindrical lens 27 serving as an objective lens. Note that, here, the ND filters 26 (first ND filter 26a1, second ND filter 26a2) are disposed on the optical path in preparation for adjusting the laser light Ld, and are removed from the optical path when surface modification is performed.

[0022] The reflecting mirror 21a arranged on the first optical path P1 reflects the laser light Ld in the direction of a preset optical path. The reflecting mirror 21a includes a first reflecting mirror 21a1 to a fifth reflecting mirror 21a5, each of which reflects the laser light Ld in a predetermined angular direction and guides it to the target 1. The reflecting mirror 21a is configured to reflect the laser light Ld of a preset wavelength and pass light of other wavelengths. The visible light reflecting mirror arranged in the second optical path P2 reflects the visible laser light Ls in the direction of a preset optical path. The visible light reflecting mirrors are made up of the first visible light reflecting mirror 21b1 to the third visible light reflecting mirror 21b3, and are configured to reflect light of a preset wavelength and pass light of other wavelengths. Therefore, the fifth reflecting mirror 21a5 is configured to reflect the laser light Ld and the visible laser light Ls.

[0023] The half-wave plate 23a in the first optical path P1 is rotated to arbitrarily rotate the polarization direction of the laser light Ld irradiated from the laser light source 10 and reflected from the first reflecting mirror 21a1. The half-wave plate 23a in the first optical path P1 rotates the laser light Ld, and the polarization prism 24a changes the transmission intensity of the s-polarized light so that the s-polarized light is used as the laser light Ld for surface modification. As an example, a damper 29 that absorbs light that is not allowed to pass is disposed next to the polarization prism 24a at a position perpendicular to the laser light Ld passing through it.

[0024] The half-wave plate 23b of the second optical path P2 arbitrarily rotates the polarization direction of the visible laser light Ls irradiated from the visible laser light source 30 and reflected from the first visible light reflector 21b1. The half-wave plate 23a of the second optical path P2 rotates the visible laser light Ls, and the polarizing prism 24b changes the transmission intensity of the s-polarized light so that the s-polarized visible laser light Ls is irradiated onto the target 1 as a mark for surface modification. As an example, the visible laser light Ls uses a red wavelength, and the wavelength band is not limited as long as it is visible light that can be viewed with the light intensity of light that does not modify the surface.

[0025] The mirror 22 shared by the first optical path P1 and the second optical path P2 is set to reflect the laser light Ld on the first optical path P1 and transmit the visible laser light Ls on the second optical path P2. This mirror 22 is the starting point of the optical path shared by the first optical path P1 and the second optical path P2. The cylindrical lens 27 focuses the laser light Ld from the first optical path P1 or the visible laser light Ls from the second optical path P2 and irradiates the target 1. The cylindrical lens 27 focuses the laser light Ld so that the vertical width is small without changing the horizontal width, and irradiates the surface of the target 1 with light so that the focus is constant (see LA in FIG. 2). For example, a cylindrical lens 27 having a focal length f=300 mm is used. This cylindrical lens 27 is preferably arranged so as to be movable in the optical path direction, and the focus can be adjusted according to the position of the target 1. It is preferable that the cylindrical lens 27 is used in combination with an fθ lens, for example. By using an fθ lens together with the cylindrical lens, it becomes possible to irradiate the laser light Ld with a focus always kept constant with respect to the irradiation area, even if the target 1 or the laser light Ld moves.

[0026] As an example, the light source device 70 accommodates the laser light source 10, the optical system 20, and the visible light laser light source 30 in a housing, and the cylindrical lens 27 is disposed so as to face the opening of the housing. The laser light Ld irradiated from the cylindrical lens 27 forms a horizontally elongated irradiation area LA as shown in Fig. 2 and Fig. 3A. This irradiation area LA is irradiated onto the surface of the target 1 with a vertical interval Hd, with a height indicated by WT and a width indicated by WD.

[0027] The storage unit 50 used in the surface modification laser irradiation device 100 stores the medium 7, which is a liquid or gas having a higher thermal conductivity than air, together with the target 1. The target 1 is placed in the storage unit 50 in which the medium 7 is placed. The target 1 is stored in the storage unit 50 via, for example, a support part 53 installed inside the storage unit 50 so that the position of the target 1 is fixed in the storage unit 50. The storage unit 50 has a light incidence surface 51 on which the laser light Ld is incident and a back surface 52 opposite the light incidence surface 51, which are formed of a material that transmits at least the laser light Ld. Note that, in this embodiment, the storage unit 50 has a surface formed of a material that transmits light in the direction in which the laser light Ld is incident, but the upper surface of the stored medium 7 may be the light incidence surface.

[0028] In addition, it is preferable that the opening of the storage unit 50 is closed so that the medium 7 in the storage unit 50 does not spill out when the target 1 is stored and moved by the lid through the moving mechanism 40. In the figure, the storage unit 50 is shown as an example in which the target 1 is processed as a single-wafer type such as a titanium plate. In addition, when the lid side is the light incident surface, it is preferable that the bottom surface facing the lid is formed of a material that transmits light. When the storage unit 50 has a housing shape, all the surfaces of the housing may be formed of a material that transmits laser light. The surface of the storage unit 50 facing the placed target 1 or the entire surface is formed of a material such as glass that transmits laser light Ld and visible laser light Ls.

[0029] For example, when the target 1 is in the shape of a plate, the support portion 53 includes linear guides 53a, 53a arranged in parallel so as to pass through both ends of the plate and slide the same. The linear guide 53a is installed on one storage surface side of the storage unit 50 and supports a portion of both ends of the target 1. A horizontal guide that supports a portion of the target may be installed together with the linear guides 53a, 53a. By installing the horizontal guide, a portion of the lower end of the target 1 is supported, so that the target 1 can be supported more stably. The support unit 53 supports the target 1 by sliding the target 1 from above to below on the linear guide 53a, and supports the target 1 in a fixed state within the medium 7. The support unit 53 is not particularly limited as long as it is configured so that the target 1 is fixed at a preset position within the medium 7 and does not cover the irradiation area.

[0030] The medium 7 stored in the storage section 50 is a liquid having a higher thermal conductivity than air, such as water, methanol, ethanol, acetone, or oil, or a gas such as helium or hydrogen. Here, as an example, water (tap water or filtered water) is used as the medium 7, and it is more preferable to use pure water or ultrapure water. By using the medium 7, heat can be released from the target 1 when the target 1 is irradiated with the laser light Ld, and the surface of the target 1 can be appropriately modified. Here, the target 1 is a metal member, a titanium plate, so that the desired convex portion 2 can be formed without causing large cracks compared to when the target 1 is irradiated with the laser light Ld in the atmosphere.

[0031] When pure water or ultrapure water is used in the storage unit 50, it is preferable to provide a configuration that prevents impurities from remaining mixed in the medium 7 stored in the storage unit 50. That is, it is more preferable that the storage unit 50 is configured to have a filter and a circulation device installed at a position that does not interfere with the irradiation of the laser light Ld, and to circulate the medium 7 through the filter by the circulation device to remove dirt from the medium 7. It is preferable to operate the circulation device when the target 1 is replaced with a new one.

[0032] In addition, the storage unit 50 is connected to a moving mechanism 40 so that the stored target 1 can be irradiated with the laser light Ld over the entire area of ​​a preset irradiation area. As shown in FIG. 2, the moving mechanism 40 is detachably connected to the storage unit 50 via an attachment unit 43, and the target 1 can be moved up, down, left, and right by moving the storage unit 50. As an example, the moving mechanism 40 includes a vertical guide mechanism 41 that moves the storage unit 50 in the vertical direction, and a horizontal guide mechanism 42 that supports the vertical guide mechanism 41 and moves the storage unit 50 together with the vertical guide mechanism 41 in the horizontal direction. The storage unit 50 is configured to move in the horizontal direction along the horizontal guide mechanism 42 and move in the vertical direction by the vertical guide mechanism 41, so that the laser light Ld can be irradiated over the entire area of ​​the irradiation area of ​​the target 1.

[0033] In addition, in the rear of the storage unit 50, which is opposite to the surface irradiated with the laser light Ld, a CMOS camera 60, which is an imaging camera, is arranged so as to be freely installed and removed when adjusting the laser light Ld. The CMOS camera 60 is arranged so as to be able to observe, for example, the state of the laser beam diameter of the laser light Ld using the first ND filter 26a1 and the second ND filter 26a2 arranged in the first optical path P1. The CMOS camera 60 is arranged so as to be able to move in the optical axis direction, and is used when adjusting the state of the laser beam diameter of the laser light Ld. The CMOS camera 60 is removed when performing surface modification of the target 1.

[0034] Further, the photodetector 28 is configured to be detachably disposed on the optical path between the fifth reflecting mirror 21a5 and the storage section 50. The photodetector 28 is used when measuring the amount of the laser light Ld before performing surface modification. As an example, the above-mentioned laser energy density uses a value detected via the photodetector 28 between the storage section 50 and the cylindrical lens 27. After being used in the preparation process, the photodetector 28 is removed from the optical path.

[0035] The target 1 is a metal member, for example a titanium plate. The titanium plate is used, for example, as the body of a vehicle such as an airplane or a car. When the titanium plate is irradiated with the laser beam Ld in the medium 7, a convex portion 2 having a convex shape, for example as shown in FIG. 4B, is formed on the flat metal surface. In this case, the convex portion 2 has a unit area (1 μm 2 ) Approximately 50 pieces / μm 2 It is preferable that the above-mentioned conditions are satisfied (see FIG. 9B). Furthermore, in the case of the target 1, which is a metal member on which the protrusions 2 are formed by laser irradiation, no large cracks are generated on the metal surface compared to the case of laser irradiation in the atmosphere (see FIG. 10B and FIG. 10C). When the protrusions 2 are formed on the metal member, which is the target 1, by additional processing in which the target 1 in the medium 7 is irradiated with the laser light Ld, it is possible to improve water repellency and sound deadening without generating large cracks. In addition, biocompatibility is improved and the surface can be roughened for joining different types of materials, which contributes to a multi-material society.

[0036] As shown in Fig. 4A and Fig. 4B, the protrusions 2 are formed in a short cylindrical shape with a base side having a larger area than the tip side. 2 In other words, the protrusions 2 are formed in a periodic dot structure with a density of 1 μm 2 The protrusions 2 are formed so that there are more than 50 protrusions per unit area (1 μm). The protrusions 2 are formed on the metal surface in nano-order sizes by irradiation with laser light Ld from the light source device 70. The intervals between the protrusions 2 are determined according to the wavelength of the laser light LD used. For example, when a 532 nm laser light Ld is used, the protrusions 2 are formed in nano-order sizes on the metal surface. 2 ) is an interval at which more than 50 protrusions 2 are formed.

[0037] The protrusions 2 may be 100 nm or more and 266 nm or less, or even 30 nm or less. 2 ) Approximately 50 pieces / μm 2It is preferable that the protrusions 2 are formed so that the number of protrusions exceeds 10. It is to be noted that if the protrusions 2 have different sizes, the wavelength band in which the sound deadening effect is achieved can be widened. In practice, the density of the protrusions 2 is more preferably more than 50, and even more preferably 55 or more. The protrusions 2 are formed at intervals related to the wavelength of the laser light Ld irradiated from the light source device 70. For this reason, in this example, the wavelength of the laser light Ld irradiated from the light source device 70 is in the range of 266 nm to 10.6 μm, but the intervals may be increased by 1 μm depending on the wavelength. 2 The number of protrusions formed per unit area varies. When forming the protrusions 2, the laser energy density F of the laser light Ld is equal to or higher than the protrusion start threshold and equal to or lower than the melting threshold, F=0.22 J / cm 2 More than 0.43J / cm 2 Irradiation is performed in the following ranges:

[0038] As described above, the surface modification laser irradiation device 100 can perform surface modification of the target 1 by irradiating the target 1 with laser light Ld from the laser light source 10 through the medium 7 stored in the storage section 50, thereby forming a convex portion 2 on the metal surface of the target 1. For example, when the target 1 is a titanium plate, the surface is modified to form the protrusions 2 into a unit area (1 μm 2 By providing a predetermined number or more of protrusions 2 per unit area, a water repellent effect and a sound deadening effect can be generated on the surface of the titanium plate. Note that it is preferable that the protrusions 2 are formed at intervals of more than 50 per unit area.

[0039] Next, an example of a surface modification laser irradiation method will be described with reference to Fig. 5. Note that the same reference numerals are used for the configurations already described, and the description may be omitted as appropriate. Here, a case where the surface modification laser irradiation device 100 shown in Fig. 1 is used will be described. The surface modification laser irradiation method S10 includes the steps of: preparing a metal member to be surface modified by storing it in a storage section filled with a liquid or gas medium having a higher thermal conductivity than air; irradiating the metal member in the prepared storage section with laser light from a laser light source via an optical system arranged in the light path; and moving one or both of the metal member and the irradiation position of the laser light via a moving mechanism so that the laser light is irradiated over the entire predetermined irradiation area of ​​the metal member.

[0040] In the preparation step S11, a metal member as a target 1 to be surface modified is stored in a storage section 50 filled with a medium 7 to prepare it. In the preparation step S11, when pure water is used as the medium 7, the target 1 is supported on the support section 53 of the storage section 50 in a state where the storage section 50 is filled with pure water, or the storage section 50 is filled with pure water as the medium 7 in a state where the target 1 is supported on the support section 53. The storage section 50 is supported by the moving mechanism 40 and the focus of the laser light Ld is adjusted. As an example, the focus of the laser light Ld is adjusted as follows. In the surface modification laser irradiation device 100, the cylindrical lens 27 is once removed from the optical path, and further, a metal mesh is supported on the support section 53 of the storage section 50 instead of the target 1.

[0041] Then, with the first ND filter 26a1 and the second ND filter 26a2 placed on the first optical path P1, the laser light source 10 irradiates the laser light Ld, and the position of the storage section 50 is adjusted so that the CMOS camera 60 focuses on the metal mesh. Furthermore, the photodetector 28 is placed just before the target and the light intensity is adjusted. Thereafter, the photodetector 28 is removed. Next, a cylindrical lens is placed on the optical path, and the cylindrical lens 27 is adjusted via the CMOS camera 60 to a position where the laser light Ld is focused. Furthermore, after adjustment of the laser light Ld from the laser light source 10 is completed, the metal mesh is removed, the target 1 is supported by the support portion 53, and the visible laser light Ls from the visible light laser light source 30 is irradiated through the second optical path P2 to check whether the visible laser light Ls is irradiated onto the irradiation area of ​​the target 1. After performing the adjustment process in this manner, the next process is performed.

[0042] In the step S12 of irradiating the laser light, the laser light Ld is irradiated from the laser light source 10 via the optical system 20 to the target 1 supported by the support part 53 in water, which is the medium 7 stored in the storage part 50 (see LA in FIG. 2). In this step S12 of irradiating the laser light, the laser light Ld is irradiated in a state in which the first ND filter 26a1 and the second ND filter 26a2 are removed from the first optical path P1. When irradiating the laser light Ld, the laser light Ld is irradiated to the irradiation area of ​​the target 1 by setting the range of 50 pulses to 600 pulses. When irradiating the target 1 with the laser light Ld, the laser energy density F is set to 0.22 J / cm, which is equal to or higher than the protrusion start threshold and equal to or lower than the melting threshold of the projections 2, in the wavelength range of 266 nm to 10.6 μm. 2 More than 0.43J / cm 2 The range is as follows. In the step S12 of irradiating the laser light, the s-polarized laser light Ld is used. The laser light Ld may be circularly polarized.

[0043] The laser light Ld is irradiated to the target 1, which is a metal member, at a temperature equal to or higher than the swelling threshold and equal to or lower than the melting threshold in the water, which is the medium 7. Here, the laser energy density F of the laser light Ld is set to 0.22 J / cm 2 The above limit is 0.22 J / cm 2 This is because the protrusions 2 cannot be formed on the surface of the metal member unless the laser energy density is equal to or higher than this. The laser energy density at which the protrusions 2 can start to protrude and form is defined as the damage threshold (protrusion start threshold). In addition, when the laser energy density of the laser light Ld is 0.43 J / cm 2If the melting threshold is exceeded, the protrusions 2 will melt even in the medium 7, and furthermore, cracks will be more likely to occur in the metal surface. When the target 1 is irradiated with the laser light Ld in the medium 7, the tip side of the protrusions 2 is formed on the metal surface without melting, and no large cracks will occur. The protrusions 2 are formed to a size (height) that is between 1 / 50 and 1 / 2 of the wavelength of the laser light Ld, 532 nm. A plurality of protrusions 2 with sizes (heights) of 10 nm to 30 nm and sizes (heights) of 100 nm to 266 nm are formed, and the size (height) of the protrusions 2 is determined based on the unit area (1 μm 2 ) 50 pieces > 1μm 2 The above is formed.

[0044] When the medium 7 is water (pure water, ultrapure water), the refractive index is 1 / 1.33 (1 / n) [n is the refractive index] compared to the refractive index n=1 in air, and the intervals between the protrusions 2 formed on the metal surface are closer than in air. The protrusions 2 are formed at intervals close to the wavelength of the irradiated laser light Ld, so for example, for a 532 nm laser light Ld, taking into account the refractive index in water, the intervals are in the range of 532 / 1.33=400 nm±10, and the intervals are between 1 / 50 and 1 / 2 of 400 nm. The laser energy density in water is 0.22 J / cm 2 If the laser energy density is less than 0.22 J / cm, the protrusions 2 are not formed on the metal surface. In other words, the range of the laser energy density is 0.22 J / cm, which is equal to or higher than the protrusion start threshold at which the protrusions 2 begin to be formed and equal to or lower than the melting threshold. 2 More than 0.43J / cm 2 As already described, the measurement position of the laser energy density is between the storage unit 50 and the cylindrical lens, for example, a position equivalent to the light entrance surface 51 immediately before the storage unit 50.

[0045] In contrast, when protrusions are formed on a metal surface in the atmosphere, the number of protrusions 2 formed by irradiation with the laser beam Ld is small, and the number of protrusions per unit area (1 μm 2 ) is less than 50 per 1000 μm. In addition, when the laser energy density of the laser light Ld is increased and irradiated onto the metal surface in the atmosphere (see FIG. 10B), cracks are generated.

[0046] Next, in the surface modification laser irradiation method S10, a step S13 of moving the target or the laser light irradiation position is performed. This step S13 is a step of moving one or both of the target 1 and the laser light irradiation position via a moving mechanism. In this step S13, as an example, the target 1 stored in the storage unit 50 is moved by moving the storage unit 50. When moving the target 1, for example, a moving mechanism configured to move the storage unit 50 as shown in FIG. 2 is used. When moving the laser light irradiation position, for example, a mechanism configured like a galvano mirror 22B (see FIG. 6B) is used.

[0047] In this step S13, the moving mechanism 40 is set in advance, and the horizontal guide mechanism 42 moves the target 1 in the horizontal direction (see M1) so that the target 1 can be irradiated with the laser light Ld from the upper left to the upper right as shown in FIG. 3B (see LA in FIG. 3B). Then, the target is moved up one level (see M2) by the vertical guide mechanism 41. At this time, the irradiation area LA of the laser light Ld moves horizontally from the right end to the left end with, for example, an irradiation width WD and an irradiation height WT, with an up-down movement interval Hd. By repeating such movements, the entire irradiation area of ​​the target 1 is irradiated with the laser light Ld. In this step S13, it is preferable to set in advance so that, when the laser light Ld moves to irradiate the entire irradiation area, the power supply of the laser light source 10 is temporarily cut off or the optical path is blocked by the first shutter 25a. Then, the target 1 after the irradiation of the entire irradiation area with the laser light Ld is removed from the storage section 50, and a new target 1 is supported by the support section 53 of the storage section 50, and the same process is repeated.

[0048] By carrying out the surface modification laser irradiation method S10, the titanium plate, which is an example of a metal member that is the target 1, can be surface modified. Note that the target 1 may be another metal such as stainless steel as long as it is a metal member. The target 1 is, for example, a panel that is a sheet, but it may be in the form of a metal sheet or metal foil as described later. Furthermore, by forming the protrusions 2 on the target 1, the water repellency of the surface of the target 1 is improved.

[0049] The surface modification laser irradiation device 100 may be, for example, surface modification laser irradiation devices 100A and 100B having the configurations shown in Figures 6A and 6B. In addition, the surface modification laser irradiation method may use surface modification laser irradiation devices 100A to 100D shown in Figures 6A to 6D. In Figures 6A and 6B, the configurations already described will be omitted and different configurations will be mainly described below. As shown in FIG. 6A, the surface modification laser irradiation device 100A uses circularly polarized laser light Ld, unlike the s-polarized light in FIG. 1. To obtain circularly polarized laser light Ld, a quarter-wave plate 23c is placed after the polarizing prism 24a to convert linearly polarized light into circularly polarized light. In addition, in order to set the same polarization conditions for the visible laser light Ls from the visible light laser source 30, a quarter-wave plate may be placed after the polarizing prism 24b. Therefore, the surface modification laser irradiation device 100A irradiates the target 1 with circularly polarized laser light Ld.

[0050] As shown in FIG. 6B, the surface modification laser irradiation device 100B is configured to change the irradiation position of the laser light Ld as a moving mechanism. Note that, although FIG. 6B shows the configuration of an optical system using the circularly polarized laser light Ld, the optical system may be an optical system using the s-polarized laser light Ld. In the surface modification laser irradiation device 100B, a galvano mirror 22B is disposed as a moving mechanism at the position of the fifth reflecting mirror 21a5, and a light emission unit 27B including an fθ lens 27b1 and a diffractive optical element 27b2 is provided to input the laser light Ld from the galvano mirror 22B and emit it to the irradiation area of ​​the target 1.

[0051] The galvano mirror 22B reflects the laser light Ld at a different angle so that the laser light Ld is irradiated over the entire irradiation area of ​​the target 1. The light emitting unit 27B, which includes an fθ lens 27b1 and a diffractive optical element 27b2, scans the laser light Ld from the galvano mirror 22B at a constant speed on the focal plane. The storage unit 50 is supported by the moving mechanism 40B here, but when the laser light Ld is irradiated onto the target 1, the moving mechanism 40B may support the storage unit 50 at a predetermined position, or may move the storage unit 50 in conjunction with the galvano mirror 22B to move the target 1 together.

[0052] Also, the surface modification laser irradiation apparatus 100C, 100D may be configured as shown in FIG. 6C and FIG. 6D. In FIG. 6C, when the target 1C has a roll-to-roll configuration, the surface modification laser irradiation apparatus 100C further includes a conveying means 200. That is, the surface modification laser irradiation apparatus 100C includes a light source device 70A, a storage section 50C, and a moving mechanism 40C, and here, the moving mechanism 40C includes a conveying means 200 and a moving means 140. The target 1C is sheet-shaped, and irradiation regions are formed at regular intervals. The conveying means 200 includes a conveying roller arranged in a conveying section 201, a plurality of conveying rollers 202 that convey the target 1C into the storage section 50C, and a plurality of conveying rollers 203 arranged in a conveying section 204 that conveys the target 1C from the storage section 50C.

[0053] The storage unit 50C is disposed directly below the light source device 70A with water (pure water) stored therein as the medium 7C. The storage unit 50C is provided with a support roller as a support unit 53C for supporting the irradiation area of ​​the target 1. The light source device 70A has the configuration already described, and irradiates the irradiation area of ​​the target 1 with the laser light Ld output from the cylindrical lens 27 serving as an objective lens. The moving means 140 moves the irradiation area of ​​the target 1C to a preset position in conjunction with the conveying means 200. When the irradiation of the irradiation area of ​​the target 1C with the laser light Ld is completed, the conveying means 200 moves the target 1C so that the next irradiation area is conveyed to the position of the support unit 53A. By repeating such an operation, the irradiation area of ​​the target 1C is irradiated with the laser light Ld. Note that the light source device 70B, which changes the irradiation position of the laser light Ld, may be used instead of the light source device 70A.

[0054] 6D, the surface modification laser irradiation device 100D includes the light source device 70B, the conveying means 300, and the storage unit 50D, and is configured to move the irradiation position of the laser light Ld to the light source device 70B side. The conveying means 300 includes a conveying belt 301 that conveys the target 1D into the storage unit 50D, a conveying support belt 302 that conveys the irradiation area of ​​the target 1 to the irradiation position of the laser light Ld and also functions as the support unit 53D, and an unloading belt 303 that receives the target 1D conveyed from the conveying support belt 302 and conveys it out of the storage unit 50D. The conveying means 300 moves the target 1D by rotating the endless belts arranged on both sides. Furthermore, the storage unit 50D stores therein a gas having a higher thermal conductivity than air as the medium 7D, such as helium, and is provided with opening / closing shutters 54D, 54D at the loading and unloading points of the target 1D in the storage unit 50D, and closing the loading and unloading points with the opening / closing shutters 54D, 54D minimizes the outflow of the medium 7D in the storage unit 50D.

[0055] In addition, the position of the storage section 50D facing the light emission section 27B of the light source device 70B is formed of a light-transmitting member that transmits the laser light Ld. Furthermore, a positioning mechanism 53D1 is disposed between the transport support belts 302. The positioning mechanism 53D1 has a contact portion that contacts the end face of the target 1D and is installed so as to be freely stretchable, and is equipped with a moving portion that moves the contact portion so as to contact and separate from the end face of the target 1. Therefore, when the target 1D is transported to a predetermined position in the storage section 50D by the transport support belts 302, the contact portion of the positioning mechanism 53D1 extends, and the contact portion presses the end face of the target 1 by the moving portion, thereby positioning the target 1D at the irradiation position of the laser light Ld. Note that, when the positioning of the target 1D is completed, the positioning mechanism 53D1 lowers the contact portion to the same height as the target so as not to interfere with the transport of the target 1D, and stores the target 1D in preparation for the positioning work of the next target 1D.

[0056] In the surface modification laser irradiation device 100D, when the target 1D is placed on the carry-in belt 301, the opening / closing shutter 54D of the carry-in section opens, and the target 1D is transferred from the carry-in belt 301 to the transport support belt 302. The opening / closing shutter 54D of the carry-in section is closed, and the transport support belt 302 that has received the target 1D transports the target 1D to a preset position and stops it. Then, the contact portion of the positioning mechanism 53D1 is extended to push and move the end face of the target 1D, thereby moving the target 1D to the irradiation position of the laser light Ld.

[0057] The positioning mechanism 53D1 stores the contact portion and returns to its original position. When the positioning of the target 1D is completed, the laser light Ld is irradiated from the light source device 70B, and the laser light Ld reflected at a different angle by the galvano mirror 22B (see FIG. 5B) is irradiated onto the irradiation area of ​​the target 1D, thereby modifying the surface of the target 1D. When the irradiation of the laser light Ld is completed, the opening / closing shutter 54D of the carry-out section is opened, and the target 1D is carried out to the carry-out belt 303 by the transport support belt 302. When the target 1D is handed over to the carry-out belt 303, the opening / closing shutter 54D of the carry-out section is closed, thereby completing the surface modification of one target 1D. By repeating the above operations, the surface modification of the next target 1D can be performed. The surface modification laser irradiation apparatuses 100A to 100D can achieve the same effects as those described for the surface modification laser irradiation apparatus 100.

[0058] Next, an embodiment of the present invention will be described below. The surface modification laser irradiation device used was that shown in FIG. 1. In a configuration according to the prior art, the target 1 was supported by the support portion 53 so that the target 1 was in the atmosphere without water (pure water) serving as the medium 7 being placed in the storage portion 50, and the laser light Ld was irradiated in that state. On the other hand, in a configuration according to an embodiment of the present invention, the target 1, a titanium plate, was irradiated with the laser light Ld while the titanium plate was supported by the support portion 53 and water (pure water) serving as the medium 7 was placed in the storage portion 50. The laser light source 10 used was a YAG laser 532 (nm), with a pulse width of 10 ns, a repetition rate of 10 Hz, and a laser spot size (FWe -1 M) is X=8.8mm, Y=19μm, and the laser energy density (Laser fluence) is 0.10J / cm 2 from 3.3 J / cm 2 The number of pulses was 200 pulses, and the movement interval was X=16 μm.

[0059] A condenser lens with f=300 mm was used as the objective lens. The size of the target 1 was a titanium plate with a length and width of 10 mm to 15 mm × 10 mm to 15 mm. In the following, the laser energy density is expressed as F=J / cm. 2 The storage unit 50 used here is, as an example, a bottomed rectangular cylindrical container made of quartz glass. The size of the container as the storage unit 50 is 30 mm wide, 30 mm deep, and 50 mm high, and quartz with a thickness of 2 mm and surface accuracy of λ / 4 is used. The medium stored in the storage unit 50 is water (pure water). The target 1 is fixed to the quartz glass surface that is one side of the container, and the laser light Ld is irradiated onto the surface of the target 1 after passing through 2 mm of quartz glass and approximately 27 mm of water.

[0060] As shown in Fig. 10A, the metal surface of the titanium plate as the target 1 before being irradiated with the laser beam Ld is in a flat state. Then, as shown in Figs. 8A to 8D and Figs. 9A to 9D, the target 1 is irradiated with F=0.22 J / cm 2 The laser beam Ld was irradiated under the condition of N = 100. In addition, Figures 8A to 8D and Figures 9A to 9D show FE-SEM photographs of the metal surface of four arbitrary points of the titanium plate irradiated with the laser beam Ld, magnified at 20,000 times.

[0061] 7A and 7B show the relationship between the laser energy density and the size of the protrusion (dot diameter). As shown in FIG. 7B, in water, which is the medium 7, the protrusion start threshold value is 0.22 J / cm 2 This is the melting threshold of 0.43 J / cm 2 It can be seen that the protrusion 2 is formed as follows. As shown in FIGS. 8A to 8D, when the laser beam Ld was irradiated in the atmosphere, the number of the protrusions 2 was 47 / 1 μm in each of FIGS. 8A to 8D. 2 , 48 pieces / 1μm 2 , 49 pieces / 1μm 2 , 44 pieces / 1μm 2 , and the average number is 47 / 1μm2 There were 100 pieces.

[0062] On the other hand, as shown in FIGS. 9A to 9D, when the laser beam Ld was irradiated underwater, the number of protrusions 2 was 63 / μm in each of FIGS. 9A to 9D. 2 , 44 pieces / 1μm 2 , 71 pieces / 1μm 2 , 58 pieces / 1μm 2 , and the average number is 59 / 1μm 2 It was confirmed that it was an individual. In this way, unit area (1 μm 2 The water repellency effect can be further improved by arranging a large number of protrusions per 100 mm, i.e., 50 or more protrusions at intervals between the protrusions. Also, in terms of sound deadening and other effects, a higher density of the protrusions 2 (narrower intervals between the protrusions 2) leads to a further improvement in the effect.

[0063] That is, in the surface modification laser irradiation device and method according to the present invention, the laser light Ld is irradiated through the medium 7 at a laser energy density that is equal to or higher than the protrusion start threshold of the protrusions 2 and equal to or lower than the melting threshold, for example, 0.22 J / cm 2 More than 0.43J / cm 2 The irradiation of the laser light Ld is preferably performed with 50 to 600 pulses in the wavelength range of 266 nm to 10.6 μm. The protuberance threshold and the melting threshold differ depending on the type and configuration of the target 1 and the medium 7, and are preferably within the above-mentioned range of 0.22 J / cm. 2 More than 0.43J / cm 2 The values ​​shown below are merely examples and are not limiting.

[0064] Although the titanium plate is described as an example of a metal member as a target, it may be, for example, stainless steel or other metal members. In addition, even if it is a bulk-shaped metal member other than a plate-shaped metal member, a convex portion can be formed in the same way as a metal plate. Furthermore, it is also applicable to an insulating material and a resin material. [Explanation of symbols]

[0065] 1 Target (metallic material: titanium plate) 2 Convex 7 Medium (water, pure water, ultrapure water) 10 Laser light source 20 Optical system 21 Reflector 22. Mirror 23 Half-wave plate 24 Polarizing Prism 25 Shutter 26 ND Filters 27 Cylindrical lens (objective lens) 30 Visible light laser source 40 Moving mechanism 50 Storage section 53 Support part 60 CMOS camera (imaging camera) 70 Light source device 100, 100A-100D Surface modification laser irradiation equipment S10 Surface modification laser irradiation method S11 Preparation process S12 A step of irradiating the medium with laser light. S13 Moving process

Claims

1. A light source device including a laser light source that irradiates laser light and an optical system that guides the laser light from the laser light source along a preset optical path toward a target to be surface modified; a storage section for storing the target together with a medium, which is a liquid or gas having a thermal conductivity higher than that of air; a moving mechanism for moving either the target or the irradiation position of the laser light, or both of the target and the laser light; the storage unit has a support unit that supports the target to be irradiated by the laser light through the medium, A surface modification laser irradiation device, wherein the laser energy density at which the laser light from the light source device is irradiated onto the target in the medium is equal to or higher than a threshold at which the target starts to rise and is equal to or lower than a threshold at which the target in the medium starts to melt.

2. 2. The surface modification laser irradiation device according to claim 1, wherein the medium is any one of a liquid such as water, methanol, ethanol, acetone, and oil, or a gas such as helium and hydrogen.

3. A step of preparing a target to be surface modified by storing it in a storage unit filled with a medium that is a liquid or gas having a thermal conductivity higher than that of air; a step of irradiating a laser beam from a laser light source onto a target in a prepared storage section through the medium by an optical system arranged in a light path; and moving one or both of the target and the irradiation position of the laser light via a moving mechanism so that the laser light is irradiated over the entire area of ​​a preset irradiation area of ​​the target, A surface modification laser irradiation method, wherein in the step of irradiating the laser light, the laser energy density at which the laser light is irradiated onto the target is equal to or higher than a threshold at which the target starts to rise and is equal to or lower than a threshold at which the target melts in the medium.

4. 4. The surface modification laser irradiation method according to claim 3, wherein the laser light has a wavelength in the range of 266 nm to 10.6 μm and has a pulse length of 50 to 600 pulses.

5. 4. The surface modification laser irradiation method according to claim 3, wherein the target is a metal member.

6. The surface is irradiated with laser light with a size of 1 / 50 or more and 1 / 2 or less, and 50 particles > 1 μm 2 A metal member having protrusions spaced at intervals such that the density of the protrusions is equal to or greater than the density of the metal member.

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