Method for manufacturing articles, articles

Abstract

To provide a method for manufacturing a LIPSS, exhibiting a high quality structural color, over a large area with relatively high productivity.SOLUTION: A surface treatment method in which a first region and a second region arranged in that order along a first direction and adjacent to each other are set on a base-material surface, a plurality of scanning paths parallel to one another extending along the first direction are set in each of the first region and the second region, and a pulse laser is emitted to the base-material surface, is characterized in that, after each of the plurality of scanning paths set in the first region are sequentially scanned while an emitting position of the pulse laser is moved in the first direction, each of the plurality of scanning paths set in the second region is sequentially scanned while the emitting position of the pulse laser is moved in the first direction.SELECTED DRAWING: Figure 7

Description

Technical Field

[0001] The present invention relates to a method for creating a fine periodic structure on the surface of an article using a laser.

Background Art

[0002] For example, the rainbow colors seen when a CD or DVD is held in light are due to interference, diffraction, and refraction by a fine periodic structure on the order of the wavelength of light, and are called structural colors. Structural colors can achieve a directional gloss that cannot be achieved by printing, etc., and are thus used for purposes such as decoration and anti-counterfeiting. It is known that structural colors can be obtained by forming a fine periodic structure (diffraction periodic structure) on the surface of a substrate using laser processing. The fine periodic structure formed by laser processing is called LIPSS (Laser Induced Periodic Surface Structure).

[0003] Patent Document 1 describes a method of irradiating a substrate with a uniaxial laser near the processing threshold and scanning while overlapping the irradiated portions, and self-organizing a fine periodic structure by ablation of the interference portion between the incident light and the scattered light along the substrate surface.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] For example, when using structural colors for purposes such as decoration and anti-counterfeiting, there is often a desire to impart structural colors to a relatively large area in order to enhance the visual effect. When forming a fine periodic structure (LIPSS) by laser processing to impart structural color, it is known that the pitch of the periodic structure changes depending on the irradiation conditions, such as the incident angle when the laser beam is irradiated onto the substrate. Since changes or disturbances in the pitch alter the appearance of the structural color, it is necessary to suppress variations in the incident angle of the laser within the area where the LIPSS is formed in order to impart a highly uniform structural color.

[0006] On the other hand, to perform laser processing at high speed, it is common practice to deflect and scan the laser beam using an optical scanning mechanism such as a galvanometer mirror, rather than mechanically moving the laser light source relative to the workpiece. Increasing the angle of optical deflection allows for a larger processing area, thus enabling high-speed processing, but this results in larger differences in the angle of incidence at different points within the processing area. Therefore, there was a need for a method to manufacture LIPSS exhibiting high structural coloration over a large surface area of ​​an article with relatively high productivity. [Means for solving the problem]

[0007] A first aspect of the present invention is: An article characterized in that, on the surface of a substrate, a periodic structure is provided in each of a first region and a second region adjacent in a first direction, each having a plurality of protrusions extending along the first direction, the boundaries between the first region and the second region are formed with the ends of each of the plurality of protrusions formed in the first region and the ends of each of the plurality of protrusions formed in the second region, the shape of the protrusions at the ends of each of the plurality of protrusions formed in the first region differs from the shape of the protrusions inside the first region, the shape of the protrusions at the ends of each of the plurality of protrusions formed in the second region differs from the shape of the protrusions inside the second region, the substrate is a resin molded product, the plurality of protrusions are formed of a resin material, and the periodic structure exhibits structural color. be. [Effects of the Invention]

[0010] According to the present invention, LIPSS exhibiting high-quality structural color can be manufactured over a large surface area of ​​an article with relatively high productivity. [Brief explanation of the drawing]

[0011] [Figure 1] A schematic diagram showing the laser head portion of a laser processing apparatus according to an embodiment. [Figure 2] A schematic diagram showing the configuration of a laser processing apparatus according to an embodiment. [Figure 3] A magnified photograph of a fine periodic structure taken from a planar view. [Figure 4]A schematic diagram showing a cross-section of a fine periodic structure cut along the Y-direction. [Figure 5] (a) A schematic diagram illustrating a reference scanning method. (b) A plan view schematically showing the history of laser pulse irradiation using the reference scanning method. [Figure 6] (a) A schematic diagram illustrating the scanning method according to the embodiment. (b) A schematic plan view showing the history of laser pulse irradiation by the scanning method according to the embodiment. [Figure 7] (a) A schematic plan view illustrating the procedure for setting up multiple patches to form a fine periodic structure in Embodiment 1. (b) A schematic plan view showing the history of laser pulse irradiation in Embodiment 1. [Figure 8] (a) A schematic plan view illustrating the procedure for forming a fine periodic structure by setting up multiple patches in the reference configuration. (b) A schematic plan view showing the history of laser pulse irradiation in the reference configuration. [Figure 9] This is an enlarged view of the small region 22 shown in Figure 7(a), schematically illustrating the pattern of overlapping irradiation spots. [Figure 10] (a) A schematic plan view illustrating the procedure for setting up multiple patches to form a fine periodic structure in Embodiment 2. (b) A schematic plan view showing the history of laser pulse irradiation in Embodiment 2. [Figure 11] (a) A diagram showing the form of patch 10A according to Embodiment 2. (b) A diagram showing the form of patch 10B according to Embodiment 2. (c) A diagram showing the form of patch 10C according to Embodiment 2. [Figure 12] A schematic diagram showing a plan view of the molding surface of the molding die according to the embodiment. [Figure 13] A photograph showing the molding surface of the molding die according to the example. [Figure 14] (a) A diagram showing an embodiment in which only triangular patches are arranged. (b) A diagram showing an embodiment in which only hexagonal patches are arranged. [Figure 15] A photograph of a resin molded product with LIPSS transferred to the mold surface, observed under a microscope. [Figure 16] Enlarged view of the patch onto which LIPSS was transferred. [Figure 17] Figure showing the result of FFT processing of the data measured by AFM.

Mode for Carrying Out the Invention

[0012] Referring to the drawings, a surface treatment method, a surface treatment apparatus, etc. which are embodiments of the present invention will be described. The following embodiments and examples are illustrative, and for example, regarding the detailed configuration, those skilled in the art can appropriately modify and implement it within the scope not departing from the gist of the present invention. In addition, in the drawings referred to in the following description of the embodiments and examples, unless otherwise specified, elements denoted with the same reference numerals have the same functions. <0,000,091>

[0013] Also, in the following description, for example, when referring to the X plus direction, it refers to the same direction as the arrow of the X axis in the illustrated coordinate system, and when referring to the X minus direction, it refers to the direction opposite to the arrow of the X axis in the illustrated coordinate system by 180 degrees. Also, when simply referring to the X direction, regardless of the difference from the direction of the arrow of the X axis in the illustration, it refers to a direction parallel to the X axis. The same applies to directions other than X.

[0014] (Laser processing apparatus) Figure 1 is a schematic diagram showing the laser head portion of a laser processing device used to form LIPSS. Laser light output from the laser oscillator 17 inside the laser head 16 is reflected in a predetermined direction by the galvanometer mirror 18 (deflection part), then the beam is formed via the focusing lens 19 and irradiated onto the workpiece 11. At this time, by moving the galvanometer mirror 18, the irradiation position of the laser on the workpiece 11 can be changed and scanned in two dimensions. In the figure, 10 indicates the area (range) that can be processed by deflecting and scanning the laser beam with the optical scanning means (galvanometer mirror 18), and this is called a patch. The size of the patch 10 may be set to match the limit of the movable range of the galvanometer mirror 18. However, in that case, the difference in the incident angle of the laser beam between the central and peripheral parts of the workpiece 11 may become too large, which may result in unacceptable non-uniformity in the structural color when LIPSS is formed. Therefore, even if the size of patch 10 is smaller than the mechanical limit of movement, it is best to set it so that the non-uniformity of structural color within the patch remains within an acceptable range.

[0015] If the area on the workpiece 11 where LIPSS should be formed is too large for a single patch 10 to cover, multiple adjacent patches should be set to cover the entire workpiece area. It is best to set the size of the patches 10 so that the difference in the angle of incidence of the laser beam near the boundaries between adjacent patches does not become too large, and the difference in structural color does not exceed a visually acceptable range.

[0016] Furthermore, the mechanism for optically deflecting and scanning the laser beam (the deflection unit) is not limited to this example; for example, a mechanism that performs continuous, high-speed deflection in one direction, such as a polygon mirror, may also be used.

[0017] Figure 2 is a schematic diagram showing the configuration of the laser processing apparatus equipped with the laser head 16 described above. The laser processing apparatus 51 includes a laser head 16 capable of irradiating laser light 52 for processing and a processing stage 55 on which a workpiece 11 can be placed. The laser processing apparatus 51 is also equipped with an X-axis movement mechanism, a Y-axis movement mechanism, and a Z-axis movement mechanism, and is configured to change the relative position between the laser head 16 and the workpiece 11. The laser head 16, the X-axis movement mechanism, the Y-axis movement mechanism, and the Z-axis movement mechanism are controlled by the control unit 100.

[0018] The control unit 100 is a computer that controls the operation of each part of the laser processing apparatus 51, and includes a CPU, memory, I / O control unit, etc. The control unit 100 may also include input devices such as a keyboard and mouse, and output devices such as a display. The memory in the control unit 100 stores control programs for manufacturing periodic structures of fine irregularities (microperiodic structures (nanoperiodic structures)) and information related to the settings of patches and scanning methods. This information may be input by the user through an input device, input from an external computer or storage device via a network through the I / O control unit, or input by attaching a portable memory such as a USB memory.

[0019] Furthermore, although not shown, the laser processing apparatus 51 is equipped with a quarter-wave plate for adjusting the polarization direction of the laser light irradiated onto the workpiece 11. The quarter-wave plate is held between the focusing lens 19 and the workpiece 11 so as to be rotatable around the optical axis. In this embodiment, the angle of rotation of the quarter-wave plate can be adjusted so that the polarization direction of the laser light irradiating the workpiece 11 is perpendicular to the direction of the scanning line SC (X direction), which will be described later. By making such adjustments, it is possible to form a well-shaped LIPSS structure in which the longitudinal direction of each groove is aligned along the direction of the scanning line SC, and it becomes possible to impart a high-quality structural color to the surface of the workpiece 11.

[0020] The laser beam output from the laser head 16 is focused to the irradiation position on the workpiece 11. An optical element (not shown) may be further provided between the laser head 16 and the workpiece 11 for beam shaping and focusing. As one method of controlling the laser irradiation energy density to be near the processing threshold of the workpiece 11, the positional relationship may be adjusted so that irradiation occurs at an off-focus position shifted by a certain distance from the focal point.

[0021] As already mentioned, the laser head 16 incorporates a two-axis galvanometer scanner and an fθ lens, and the irradiation position can be moved at high speed by driving the galvanometer mirror 18. Scanning by the galvanometer mirror 18 can be performed at a higher speed than stage driving by the X-axis movement mechanism and the Y-axis movement mechanism, so scanning within one patch is done using the galvanometer mirror 18, and patch switching is done by moving the stage using the movement mechanism.

[0022] For laser processing, pulsed lasers that repeatedly emit short pulses can be suitably used as the laser light source. Various types of lasers can be used, such as picosecond and nanosecond pulsed lasers like CO2 lasers and YAG lasers, and for example, titanium-sapphire lasers can be suitably used. Titanium-sapphire lasers are so-called femtosecond lasers that emit ultrashort pulses, and have output specifications such as a pulse width of 120 fs, a center wavelength of 800 nm, a repetition frequency of 1 kHz, and an energy of 0.25 μJ to 400 μJ per pulse.

[0023] (Laser scanning method within one patch) Figure 3 shows a magnified photograph of the periodic structure (microperiodic structure) according to this embodiment, taken from a plan view. It can be seen that when the surface of the workpiece 11 is viewed from the plan, there is a structure in which a large number of microgrooves are arranged in parallel along the X direction (first direction) at a predetermined pitch. Figure 4 is a schematic diagram showing a cross-section of the microperiodic structure cut along the Y direction (second direction), where the microgrooves (or micro-protrusions) are arranged in the Y direction at a pitch indicated by 12, and the microgrooves (or micro-protrusions) have a depth (or height) indicated by 13. In a typical LIPSS, the pitch 12 is 1 μm, and the depth (or height) 13 is about 0.5 μm to 0.7 μm.

[0024] To form micro-grooves extending in the X direction within a patch, a pulsed laser is irradiated onto the workpiece 11 at a predetermined repetition frequency, and the pulsed laser is scanned in the X direction (first direction) so that the irradiation areas of each pulse partially overlap, thereby forming micro-grooves. The polarization direction of the laser light irradiating the workpiece 11 is adjusted to be perpendicular to the direction of the scanning line SC (X direction), which will be described later. The repetition frequency, scanning speed, irradiation beam diameter, etc., of the pulsed laser are adjusted to conditions suitable for forming LIPSS, that is, so that the irradiation energy density on the substrate is near the processing threshold. By irradiating with an appropriate energy density, a fine periodic structure is formed self-organically by ablation of the interference portion of the incident light and the scattered light along the substrate surface. By irradiating with a laser along a single scanning line, a fine periodic structure consisting of multiple micro-grooves (or micro-protrusions) can be formed along that scanning line. To align fine grooves extending in the X direction in the Y direction over a certain width, it is necessary to scan the laser multiple times in the X direction. There are two methods for scanning the laser in the X direction: moving the irradiation position in the X-positive direction over time, and moving it in the X-minus direction over time.

[0025] Figures 5(a) and 6(a) are schematic diagrams illustrating two methods for scanning a laser. For simplicity, these diagrams assume that nine scanning lines are set on patch 10 to form numerous fine grooves. In a plan view of patch 10, the scanning order of the nine scanning lines SC (scanning paths) that scan the laser beam is indicated by circled numbers 1 to 9, and the direction in which the irradiation position is moved for each scanning line SC is indicated by an arrow.

[0026] Furthermore, Figures 5(b) and 6(b) are schematic plan views showing the irradiation history when laser pulses are irradiated according to the scanning methods in Figures 5(a) and 6(a), respectively. The shape of the pulsed laser irradiation spot LS is typically shown as a circle, but in chronological order, newer irradiation spots are superimposed on older irradiation spots. Therefore, in areas where old and new pulses irradiate the same area, the irradiation shape of the old pulse is obscured by the irradiation shape of the new pulse.

[0027] As shown in Figure 5(a), if a so-called raster scan is employed, in which the scan lines are scanned in the order of circled numbers 1 to 9 while alternately switching the beam movement between the X-plus and X-minus directions, it is not necessary to return the galvanometer scanner to the same starting point in the X direction for each scan line. Therefore, the processing time is reduced. On the other hand, as shown in Figure 6(a), if all the scan lines indicated by circled numbers 1 to 9 are irradiated while moving the beam in the X-plus direction, the irradiation position must be returned to the starting point in the X direction each time the scan line (scanning path) is switched, so the processing time is longer than in Figure 5(a).

[0028] Looking at the pulse irradiation history, as is clear from comparing Figure 5(b) and Figure 6(b), the pattern of overlap of the irradiation spots LS is not uniform within patch 10 in the former case, while it is more uniform in the latter. As mentioned above, LIPSS works by irradiating with a laser at an intensity near the processing threshold, scanning while overlapping the irradiated areas, and forming a fine periodic structure self-organizing through the ablation of the interference portion of the incident light and scattered light along the substrate surface. Therefore, if the overlap of the irradiation spots LS is non-uniform, it is not possible to substantially uniformly impart a structural color with excellent appearance quality within patch 10.

[0029] Therefore, in the embodiment of the present invention, as shown in Figure 6(a), within a single patch, the laser is scanned such that the direction in which the irradiation spot moves is the same for all scanning lines.

[0030] Furthermore, when setting up multiple patches and forming fine periodic structures in each patch, the scanning line direction is set to be parallel to the other patches to ensure that the structural colors of the patches do not differ. In addition, the scanning direction of the illumination spot is the same for every scan line in every patch. This ensures that substantially the same structural color is assigned within every patch. The following describes a procedure for creating a fine periodic structure by setting up multiple patches in order to impart structural color to a relatively large area on the outer surface of a workpiece.

[0031] [Embodiment 1] Figure 7(a) is a schematic plan view illustrating the procedure for forming a fine periodic structure to impart structural color to a relatively large area on the outer surface of a workpiece. In this embodiment, structural color is applied to an area 21 on the outer surface of the workpiece 11. Since the area 21 is too large to be covered by a single patch, in this embodiment nine square patches 10 are set up and arranged adjacently in a 3x3 matrix. Note that the shape of the patches 10 may be a rectangle with sides of unequal lengths, rather than a square.

[0032] In each patch 10, as explained with reference to Figure 6(a), the laser beam scan line SC (not shown) is set parallel to the X direction, and in each scan line SC, the laser beam is scanned such that the direction in which the irradiation spot moves is the X-plus direction (first direction).

[0033] In this embodiment, nine patches are selected sequentially according to the numbered order shown within the patch in Figure 7(a), and laser light is irradiated to form LIPSS. If the horizontal direction (X direction) of the patch matrix arrangement is considered rows and the vertical direction (Y direction) is considered columns, then the patches in one row are processed sequentially, and then the patches in another row adjacent to that row are processed sequentially.

[0034] The order in which scan lines are selected within each patch follows the Y direction, as shown in Figure 6(a). The direction in which the order in which patch rows are selected within the patch matrix array is the Y direction, which is the same direction as the order in which scan lines are selected within each patch. For example, looking at the bottom row, the patches are processed in the order of numbers 1, 2, and 3 shown in the figure, and then the process moves to the adjacent row in the Y-plus direction, where the patches are processed in the order of numbers 4, 5, and 6. In this embodiment, as shown in the figure, in any row of the matrix, adjacent patches are processed in an order along the X-plus direction (first direction). That is, the direction in which the patch processing order is arranged (X-plus direction) coincides with the direction in which the irradiation spot moves in each scan line (scan path) (X-plus direction).

[0035] Furthermore, in relation to the description in the claims, for example, in Figure 7(a), the patch with scanning order 1 may be called the first region, the patch with scanning order 2 may be called the second region, and the patch with scanning order 4 may be called the third region. In this case, of the two sides of the first region that are parallel to the X direction, the side that abuts the third region may be called the first side, and of the two sides of the third region that are parallel to the X direction, the side that abuts the first region may be called the second side.

[0036] For comparison, a reference configuration in which the patch processing order is set in a different way from the embodiment will be described with reference to Figure 8(a). In the reference configuration shown in Figure 8(a), similar to the embodiment, nine square patches 10 are placed adjacent to each other and arranged in a 3x3 matrix, and nine patches are selected in order according to the illustrated number order within the patch and irradiated with a laser to form LIPSS. In this reference configuration, as shown in the figure, adjacent patches in each row are processed in an order along the X-minus direction. That is, the direction in which the patch processing order is arranged (X-minus direction) is opposite to the direction in which the irradiation spot moves in each scan line (X-plus direction).

[0037] Figure 7(b) is a schematic plan view showing the history of laser pulse irradiation corresponding to the scanning method of the embodiment shown in Figure 7(a). Figure 8(b) is a schematic plan view showing the history of laser pulse irradiation corresponding to the scanning method of the reference embodiment shown in Figure 8(a). Similar to Figures 5(b) and 6(b) already described, new irradiation spots are shown overlaid on older irradiation spots in chronological order. That is, in areas where old and new pulses overlap, the irradiation shape of the old pulse is hidden and not visible by the irradiation shape of the new pulse.

[0038] As is clear from comparing Figure 7(b) and Figure 8(b), the pattern of overlap of the irradiation spots LS at the boundaries between patches (ends of the scan lines) is more irregular in the latter than in the former. LIPSS works by irradiating with a laser at an intensity near the processing threshold, scanning while overlapping the irradiated areas, and forming a fine periodic structure self-organized by ablation of the interference areas between the incident light and the scattered light along the substrate surface. Therefore, if there are areas where the regularity of the overlap of the irradiation spots LS differs from the surrounding areas, the microstructure will be substantially different from the surroundings, resulting in a different appearance from the surrounding structural color. In other words, it becomes impossible to uniformly form a structural color with excellent appearance quality within region 21.

[0039] Specifically, in the reference configuration shown in Figure 8(b), it can be seen that the regularity of the overlapping of the irradiated spots at the boundaries between patches aligned in the X direction and between patches aligned in the Y direction is significantly different from that of the surrounding areas. As a result, when the region 21 where LIPSS is formed is observed visually, vertical and horizontal lines corresponding to the patch boundaries appear in a grid pattern within the iridescent structural color.

[0040] In contrast, in the embodiment shown in Figure 7(b), there is no disorder in the regularity of the overlapping irradiation spots at the boundaries between patches aligned in the Y direction (second direction), i.e., the boundary lines parallel to the X axis (first direction). Also, at the boundaries between patches aligned in the X direction, i.e., the boundary lines parallel to the Y axis, the regularity of the overlapping irradiation spots differs slightly from the surrounding areas, but the disorder in regularity is smaller than in the reference embodiment. Figure 9 is an enlarged view schematically showing the manner (pattern) of the overlapping irradiation spots by enlarging the small region 22 shown in Figure 7(a). In most areas within each patch, the irradiation spot shape schematically shown as LSA is regularly arranged, but at the boundaries between patches aligned in the X direction (the X-direction ends of the patches), the irradiation spot shapes shown as LSB and LSC are shown. Note that the X-direction ends of the patches correspond to the starting point or ending point when irradiating with a laser along the scan line.

[0041] While LSB and LSC have slightly different patterns from LSA, the disruption in the overlap of irradiation spots at the patch boundaries is smaller compared to the reference configuration shown in Figure 8(b). In other words, substantially the same periodic structure is formed in the areas schematically represented by the overlap of LSA, and although there are areas with slightly different shapes in the areas represented by LSB and LSC, the differences are minor.

[0042] As is clear from the above, in the reference form, grid-like lines are conspicuous in the areas exhibiting structural color, whereas in this embodiment, the boundaries between patches aligned in the Y direction are hardly visible, and the boundaries between patches aligned in the X direction are also not conspicuous. Therefore, when setting multiple patches to form LIPSS over a large area and apply structural color, the vertical lines at the patch boundaries are hardly noticeable, and a highly uniform structural color can be applied to the entire area.

[0043] In Embodiment 1, LIPSS was formed based on the following conditions (1) to (5). (1) Multiple square or rectangular patches were set and arranged in a matrix. (2) In each patch, multiple scan lines were set parallel to the X direction within the patch. (3) In each scan line, the laser beam was scanned so that the direction in which the irradiation spot moved was in the X-plus direction. Within a single patch, the order in which the scan lines to which the laser beam was irradiated was in the order along the Y-plus direction. (4) If the horizontal direction (X direction) of the patch matrix arrangement is defined as rows and the vertical direction (Y direction) as columns, then the patches in one row are laser-processed sequentially, and then the patches in the next row are laser-processed sequentially (row-by-row processing). When laser processing moves from one row to another, it is set to move to the next row adjacent in the Y-plus direction relative to the row in question. In other words, the direction in which the scanning lines for irradiating with laser light within a single patch are selected and the direction in which the processing order of the patch rows in the matrix is ​​arranged are the same (Y-plus direction). (5) In each row, adjacent patches were processed in an order along the X-plus direction. That is, the direction in which the processing order of the patches in a row was aligned with the direction in which the illumination spot moved in each scan line was the same (X-plus direction).

[0044] According to this embodiment, high-quality structural color microstructures (LIPSS) can be manufactured over a large area with relatively high productivity. In other words, a method and apparatus for manufacturing articles having excellent structural color can be provided.

[0045] The method for forming LIPSS according to this embodiment can be carried out by directly laser processing (surface treatment) the surface of an article to impart structural color to the article. Furthermore, instead of directly laser processing the article, the method can also be carried out by surface treating the molding surface of the mold used to manufacture the article with laser processing. That is, the method can also be carried out by laser processing to form a fine periodic structure (with the concave and convex orientations reversed from the fine periodic structure formed on the article) on the molding surface of the mold to impart structural color to the article. By using a molding die that has undergone such surface treatment and transferring the shape of the molding surface of the mold to a molding material (e.g., a resin material), the boundaries of the patches formed when LIPSS is formed on the molding surface will not be noticeable, and a high-quality structural color can be imparted to the molded product (e.g., a resin molded product).

[0046] The LIPSS according to this embodiment can be formed on various articles, such as anti-counterfeiting seals and various printer parts (e.g., printer cartridges, printer drum covers, printer exterior parts). In other words, it can impart a high-quality structural color to the substrate surface of these articles.

[0047] [Embodiment 2] As Embodiment 2, a method of laser processing in which a patch with a different shape than that of Embodiment 1 is set when forming LIPSS will be described. In the description of Embodiment 2, matters that are common to the description of Embodiment 1 will be simplified or omitted. In Embodiment 1, LIPSS was formed based on the conditions (1) to (5) described above, but in Embodiment 2, condition (1) is different from Embodiment 1, while conditions (2) to (5) are the same as in Embodiment 1.

[0048] Figure 10(a) is a schematic plan view illustrating the procedure for applying structural color to a relatively large area on the outer surface of a workpiece in Embodiment 2, by setting up multiple patches and forming a fine periodic structure for each patch. In this embodiment, structural color is applied to an area 21 on the outer surface of the workpiece 11. In this embodiment, three types of patches 10A, 10B, and 10C are set up and arranged adjacently in a 4x3 matrix to cover the area 21. Figure 11(a) is a schematic plan view illustrating patch 10A, Figure 11(b) is a schematic plan view illustrating patch 10B, and Figure 11(c) is a schematic plan view illustrating patch 10C.

[0049] As shown in Figures 11(a) to 11(c), in each patch, the laser beam scan line SC is set parallel to the X direction, as described in condition (2). Furthermore, in each scan line SC, the laser beam is scanned so that the direction in which the irradiation spot moves is in the X-plus direction. Also, within a single patch, the order in which the scan lines irradiating the laser beam are selected is the same as in Figure 6(a) of Embodiment 1, following the Y-plus direction.

[0050] Furthermore, in Figures 11(a) to 11(c), the edges where adjacent patches in the X direction (row direction) meet in Figure 10(a) are shown as edges CS with thick lines. In Embodiment 1, the edges where adjacent patches in the X direction (row direction) meet were perpendicular to the X direction (row direction), but in this embodiment, edges CS do not intersect the X direction (row direction) perpendicularly, but rather diagonally (at an angle other than 90 degrees). The acute angle (the smaller angle) of the intersection is shown as α.

[0051] Figure 10(b) is a schematic enlarged view showing the overlapping pattern of the irradiation spots, obtained by enlarging the small region 32 shown in Figure 10(a). In most areas within each patch, irradiation spot shapes schematically indicated as LSA are arranged regularly, but at the boundaries between patches aligned in the X direction (the X-direction ends of the patches), irradiation spot shapes indicated as LSB and LSC are shown. Note that the X-direction ends of the patches correspond to the starting or ending points when irradiating with the laser along the scan line.

[0052] Although LSB and LSC have slightly different patterns from LSA, in this embodiment, LSB and LSC are arranged diagonally along edge CS, and it can be seen that the arrangement density is smaller compared to Embodiment 1 shown in Figure 9. In other words, because the arrangement density of areas where the overlapping of irradiation spots is disordered at the patch boundaries is small, when looking at the structural color applied to region 21, the boundaries between patches aligned in the X direction are even less noticeable than in Embodiment 1.

[0053] The smaller the intersection angle α, the more the LSB and LSC are dispersed in the X direction, and the more inconspicuous the boundaries between patches aligned in the X direction tend to become. Therefore, it is best to set α to, for example, 45 degrees or less. However, the smaller α is, the smaller the area of ​​a single patch that can be optically scanned within the limited optical deflection range of the laser processing machine becomes. It is desirable to set the size of α in consideration of the balance between the effect of making the boundaries between patches less noticeable within the region where structural color is applied and the increase in the time required for manufacturing, and it is preferable to set it appropriately within the range of 20 degrees or more and 70 degrees or less.

[0054] According to this embodiment, a high-quality structural color microstructure (LIPSS) exhibiting a high structural color on the surface of an article can be manufactured over a large area with relatively high productivity. Furthermore, similar to Embodiment 1, this can be implemented not only by directly laser processing the surface of an article to impart structural color to the article, but also by forming the molding surface of the mold used to manufacture the article by laser processing. By using a molding die manufactured in this manner to transfer the molding surface shape to a molding material (e.g., a resin material), structural color can be imparted to a resin molded product in a way that makes the boundaries of the patches created when the molding surface of the mold is laser processed less noticeable. [Examples]

[0055] This example shows how to create a LIPSS shape by laser processing the surface of a molding die, with the aim of adding decorative properties to a resin molded product. Figure 12 is a schematic diagram of the molding surface of the molded die, which is the workpiece 11, in a plan view, and shows an example in which a LIPSS shape is formed in a ring-shaped region 21 with a circular outer edge and an oval inner edge. The figure also shows lines indicating the shape of the patch set by applying the concept of Embodiment 2.

[0056] STAVAX was used as the material for the molding die. An LP400U (manufactured by GF Machining Solutions) was used as the laser processing machine. An ultrashort pulse laser oscillator manufactured by AMPLITUDE SYSTEMS was used as the laser light source. The wavelength was 1030 nm. A pulse energy of 7.5 μJ per pulse and a lens with a focal length of approximately 170 mm were used, and the laser irradiation spot diameter was set to 40 μm by adjusting the distance between the lens and the molding surface of the molding die. For the laser scanning method, a galvanometer mirror was used, with a scanning speed of 500 mm / s, a scanning interval of 5 μm, and a short-pulse laser irradiation frequency of 101 kHz. The area that could be irradiated with the laser by optical scanning with a galvanometer mirror was defined as a square with sides of 40 mm, and the shape of each patch was to be contained within this square area.

[0057] In Embodiment 2, a laser was scanned using the scanning method described above to form a LIPSS in the ring-shaped region 21. The formed LIPSS had a periodic structure, as schematically shown in Figure 4, with a pitch 12 of microgrooves (or microprotrusions) of approximately 1 μm and a depth (or height) 13 of 0.3 to 0.5 μm.

[0058] Figure 13 is a photograph of the molded surface of the mold on which LIPSS was formed. Although difficult to discern in the photograph, the ring-shaped region 21 exhibited high-quality structural coloration to the naked eye, and the patch boundaries were hardly visible within region 21.

[0059] When resin molded products were produced by injection molding using the mold in question, the resin molded products onto which LIPSS was transferred exhibited high-quality structural color, and the boundary lines of the patches created when the mold was laser-processed were barely visible to the naked eye.

[0060] Figure 15 shows a photograph of a resin molded product with LIPSS transferred to the mold surface, observed under a microscope. The boundaries of the patches created when the mold was laser-processed were barely visible to the naked eye, but when observed under a microscope, the boundaries of the LIPSS-transferred patches appear black.

[0061] Figure 16 is a magnified view of the patch onto which LIPSS was transferred, as shown in Figure 15. It is a magnified view of region A, which includes the first and second regions adjacent in the first direction, and the boundary portion that is the edge of the first region or the edge of the second region. Figure 17 shows the results of AFM observations of region B, which is a part of the boundary portion that is the edge of the first region or the edge of the second region, and region C, which is a part of the interior of the first region. Both the first and second regions have a fine periodic structure with multiple parallel protrusions extending along the first direction. In regions B and C, AFM measurements were taken at 16 locations with a pitch of 0.078125 μm in a direction intersecting the first direction, and at 128 locations in 8 rows with a pitch of 0.078125 μm in the first direction.

[0062] Figure 17 shows the results of processing the measured data with an FFT (Fast Fourier Transform). In the FFT (Fast Fourier Transform) results of the data measured by AFM, the value of the highest part is defined as the height of the convexity. It can be seen that the height of the convexity in the interior of the first region and the interior of the second region is 0.3 μm or more, and the height of the convexity at the boundary is 0.25 μm or less. In other words, at the boundary, the periodic structure of the convexity is broken down and the height becomes lower, so it is visible as black when observed with a microscope. It was found that if the center line of this black-visible boundary (the line connecting the centers in the first direction of the part where the height of the convexity is 0.25 μm or less) extends perpendicular to the first direction, the boundary will be visible to the naked eye. In other words, it is preferable to tilt the boundary so that the angle between the center line of the boundary and the first direction is between 20° and 70°. As a result, the boundary becomes almost invisible to the naked eye. The shape of the patch onto which LIPSS is transferred (e.g., the first region) may be a triangle, a quadrilateral, a hexagon, or a polygon. Furthermore, it does not have to be a polygon composed solely of straight lines; it may also include curves.

[0063] [Other embodiments] Furthermore, the present invention is not limited to the embodiments and examples described above, and many modifications are possible within the technical concept of the present invention.

[0064] For example, in Embodiment 1, multiple rectangular patches are set up to cover the entire area to be processed, and in Embodiment 2, triangular and parallelogram patches are set up and arranged. However, the shape and arrangement of the patches are not limited to these examples. For example, as shown in Figure 14(a), only triangular patches may be arranged, or as shown in Figure 14(b), hexagonal patches may be used. Furthermore, polygonal patches of different shapes than those exemplified may be placed within the area to be processed. Moreover, the shape of the patches does not have to be a polygon composed only of straight lines; it may also include curves that intersect with the scanning direction of the laser beam.

[0065] The present invention can also be realized by supplying a program that implements one or more of the functions of the embodiments to a system or device via a network or storage medium, and by having one or more processors in the computer of that system or device read and execute the program. It can also be realized by a circuit (e.g., an ASIC) that implements one or more functions.

[0066] The embodiments described above include the disclosures of the following items. [Disclosure 1] On the substrate surface, a first region and a second region are set, arranged adjacent to each other in this order along a first direction. In each of the first and second regions, a plurality of parallel scanning paths extending along the first direction are set, In a surface treatment method in which a pulsed laser is irradiated onto the surface of a substrate, After sequentially scanning each of the plurality of scanning paths set in the first region while moving the irradiation position of the pulsed laser in the first direction, Each of the plurality of scanning paths set in the second region is scanned sequentially while moving the irradiation position of the pulsed laser in the first direction. A surface treatment method characterized by the following features. [Disclosure 2] In the surface treatment method described in Disclosure 1, A third region is set on the surface of the substrate, adjacent to the first region, along a second direction intersecting the first direction. In the third region, a plurality of parallel scanning paths extending along the first direction are set, When scanning each of the plurality of scanning paths set in the first region while moving the irradiation position of the pulsed laser in the first direction, the scanning paths are selected in the order they are arranged along the second direction, and after scanning all of the scanning paths in the first region, From the plurality of scanning paths set in the third region, scan paths are selected in the order they are arranged in the second direction, and the irradiation position of the pulsed laser is moved in the first direction while scanning, thereby scanning all of the scan paths in the third region. A surface treatment method characterized by the following features. [Disclosure 3] In the surface treatment method described in Disclosure 1 or 2, At least one of the first region and the second region is a parallelogram, a polygon, or a shape having curved sides. A surface treatment method characterized by the following features. [Disclosure 4] In the surface treatment method described in Disclosure 2, The first region has a first edge parallel to the first direction, The third region has a second side parallel to the first direction, The first side and the second side are in contact. A surface treatment method characterized by the following features. [Disclosure 5] In the surface treatment method described in any one of disclosures 1 to 4, The polarization direction of the pulsed laser irradiated onto the substrate surface is perpendicular to the first direction. A surface treatment method characterized by the following features. [Disclosure 6] By the surface treatment method described in any one of disclosures 1 to 5, A structural color is applied to the surface of the substrate. A surface treatment method characterized by the following features. [Disclosure 7] In the surface treatment method described in any one of disclosures 1 to 6, The aforementioned substrate surface is the molding surface of the molding die. A surface treatment method characterized by the following features. [Disclosure 8] A periodic structure is formed on the molded surface by the surface treatment method described in Disclosure 7, the shape of the molded surface is transferred to the molding material, and a structural color is imparted to the surface of the molding material. A method for manufacturing an article characterized by the following: [Disclosure 9] The device comprises a deflection unit that optically deflects and scans the laser light output from a laser light source, a moving mechanism that mechanically changes the relative position between the deflection unit and the workpiece, and a control unit that controls the deflection unit and the moving mechanism. The control unit, based on a first region and a second region set on the surface of the workpiece, which are adjacent to each other in a first direction, and a plurality of parallel scanning paths set in each of the first region and the second region, extending along the first direction, The deflection unit moves the irradiation position of the laser beam in the first direction and sequentially scans each of the plurality of scanning paths set in the first region, The moving mechanism changes the relative position of the deflection part and the workpiece in the first direction, Furthermore, the deflection unit is controlled to sequentially scan each of the plurality of scanning paths set in the second region while moving the irradiation position of the laser light in the first direction. A surface treatment apparatus characterized by the following: [Disclosure 10] In the surface treatment apparatus described in Disclosure 9, The control unit, based on a third region set on the surface of the workpiece, adjacent to the first region along a second direction intersecting the first direction, and a plurality of parallel scanning paths extending along the first direction in the third region, The deflection unit selects scanning paths from the plurality of scanning paths set in the first region in the order they are arranged along the second direction, scans while moving the irradiation position of the laser beam in the first direction, and after scanning all of the scanning paths in the first region, The moving mechanism changes the relative position of the deflection part and the workpiece in the second direction, Furthermore, the deflection unit is controlled to select scanning paths from among the plurality of scanning paths set in the third region in the order they are arranged in the second direction, and to scan while moving the irradiation position of the laser beam in the first direction, thereby scanning all of the scanning paths in the third region. A surface treatment apparatus characterized by the following: [Disclosure 11] In the surface treatment apparatus described in disclosure 9 or 10, At least one of the first region and the second region is a parallelogram, a polygon, or a shape having curved sides. A surface treatment apparatus characterized by the following: [Disclosure 12] In the surface treatment apparatus described in Disclosure 10, The first region has a first edge parallel to the first direction, The third region has a second side parallel to the first direction, The first side and the second side are in contact. A surface treatment apparatus characterized by the following: [Disclosure 13] In the surface treatment apparatus described in any one of disclosures 9 to 12, The system includes a mechanism for adjusting the polarization direction of the laser light, and the polarization direction of the laser light irradiated onto the surface of the workpiece can be adjusted to be perpendicular to the first direction. A surface treatment apparatus characterized by the following: [Disclosure 14] In the surface treatment apparatus described in any one of disclosures 9 to 13, The laser light forms a structure exhibiting structural color on the surface of the workpiece. A surface treatment apparatus characterized by the following: [Disclosure 15] On the surface of the substrate, a periodic structure is provided in each of the first and second regions adjacent in the first direction, having a plurality of mutually parallel protrusions extending along the first direction. The periodic structure formed inside the first region and the periodic structure formed inside the second region are substantially the same periodic structure. At the boundary between the first region and the second region, the ends of each of the plurality of protrusions formed in the first region and the ends of each of the plurality of protrusions formed in the second region are formed. The shape of the protrusions at each end of the plurality of protrusions formed in the first region differs from the shape of the protrusions inside the first region, and the shape of the protrusions at each end of the plurality of protrusions formed in the second region differs from the shape of the protrusions inside the second region. An article characterized by the following: [Disclosure 16] In the articles described in Disclosure 15, The article is characterized in that the height of the protrusions at the boundary is 0.25 μm or less, and the plurality of protrusions formed in the first region are higher than the protrusions at the boundary. [Disclosure 17] In the articles described in disclosure 15 or 16, An article characterized in that the angle between the center line of the boundary portion and the first direction is 20° or more and 70° or less. [Disclosure 18] In the articles described in any one of disclosures 15 to 17, At least one of the first region and the second region is a parallelogram, a polygon, or a shape having curved sides. An article characterized by the following: [Disclosure 19] In the articles described in any one of disclosures 15 to 18, The article is characterized in that the base material is a base material for an anti-counterfeiting seal. [Disclosure 20] In the articles described in any one of disclosures 15 to 18, The article is characterized in that the aforementioned substrate is a substrate for printer components. [Disclosure 21] In the articles described in any one of disclosures 15 to 18, The surface of the substrate is characterized in that it is the molding surface of a mold. [Explanation of Symbols]

[0067] 10, 10A, 10B, 10C... Patch / 11... Workpiece / 12... Pitch / 13... Depth (or Height) / 16... Laser Head / 17... Laser Oscillator / 18... Galvano Mirror / 19... Focusing Lens / 21... Area / 22... Small Area / 32... Small Area / 51... Laser Processing Equipment / 52... Laser Light / 55... Processing Stage / 100... Control Unit / CS... Side / LS... Irradiation Spot / LSA, LSB, LSC... Irradiation Spot Shape / SC... Scan Line / α... Intersection Angle of Side CS and X Direction

Claims

1. On the surface of the substrate, a periodic structure is provided in each of the first and second regions adjacent in the first direction, each having a plurality of protrusions extending along the first direction. At the boundary between the first region and the second region, the ends of each of the plurality of protrusions formed in the first region and the ends of each of the plurality of protrusions formed in the second region are formed. The shape of the protrusions at each end of the plurality of protrusions formed in the first region differs from the shape of the protrusions inside the first region, and the shape of the protrusions at each end of the plurality of protrusions formed in the second region differs from the shape of the protrusions inside the second region. The aforementioned base material is a resin molded product, and the plurality of protrusions are formed from a resin material. The aforementioned periodic structure exhibits structural color. An article characterized by the following:

2. In the article described in claim 1, The height of the protrusion within the first region and the height of the protrusion within the second region are 0.3 to 0.5 μm or 0.5 to 0.7 μm. An article characterized by the following:

3. In the article described in claim 1, The height of the protrusions at the boundary is 0.25 μm or less, and the plurality of protrusions formed in the first region are higher than the protrusions at the boundary. An article characterized by the following:

4. In the article described in claim 1, The angle between the center line of the boundary portion and the first direction is 20° or more and 70° or less. An article characterized by the following:

5. In the article described in claim 1, The periodic structure formed within the first region and the periodic structure formed within the second region are substantially the same periodic structure. An article characterized by the following:

6. In the article described in claim 1, The shape of at least one of the first region and the second region is either a triangle or a hexagon. An article characterized by the following:

7. In the article described in claim 1, The first region comprises a first edge along the first direction, The second region comprises a second edge along the first direction, The first and second sides are in contact with each other. An article characterized by the following:

8. In the article according to any one of claims 1 to 7, The aforementioned substrate is a seal substrate. An article characterized by the following:

9. In the article according to any one of claims 1 to 7, The aforementioned substrate is a substrate for printer components. An article characterized by the following:

10. In the article described in claim 9, The aforementioned printer component is one of the following: a cartridge, a drum cover, or an outer casing. An article characterized by the following:

11. In a method for manufacturing an article that produces an article according to any one of claims 1 to 7, The shape of the molding surface of the molding die is transferred to the molding material, and the structural color is applied to the surface of the molding material. A manufacturing method characterized by the following features.

12. In the manufacturing method described in claim 11, The molded surface exhibits structural coloration. A manufacturing method characterized by the following features.

13. In the manufacturing method described in claim 11, On the molding surface of the aforementioned molding die, a first processing area and a second processing area are set, arranged adjacent to each other in this order along the X direction. In each of the first and second processing regions, a plurality of parallel scanning paths extending along the X direction are set, After sequentially scanning each of the plurality of scanning paths set in the first processing area while moving the irradiation position of the pulsed laser in the X direction, Each of the plurality of scanning paths set in the second processing area is scanned sequentially while moving the irradiation position of the pulsed laser in the X direction, and the surface of the molded surface is processed. A manufacturing method characterized by the following features.

14. In the manufacturing method described in claim 13, A third processing region is set on the molding surface, adjacent to the first processing region along the Y direction intersecting the X direction, In the third processing area, a plurality of parallel scanning paths extending along the X direction are set, When scanning each of the plurality of scanning paths set in the first processing area while moving the irradiation position of the pulsed laser in the X direction, the scanning paths are selected in the order they are arranged along the Y direction, and after scanning all of the scanning paths in the first processing area, From the plurality of scanning paths set in the third processing area, scan paths are selected in the order they are arranged in the Y direction, and the irradiation position of the pulsed laser is moved in the X direction while scanning, thereby scanning all of the scan paths in the third processing area. A manufacturing method characterized by the following features.

15. In the manufacturing method described in claim 13, The polarization direction of the pulsed laser irradiated onto the molding surface is perpendicular to the X direction. A manufacturing method characterized by the following features.

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