Surface treatment method, product manufacturing method, surface treatment device, and product

Abstract

The present disclosure relates to a surface treatment method, a product manufacturing method, a surface treatment apparatus, and a product. The product includes a fine periodic structure having a plurality of protrusions extending in parallel with each other in a first direction in each of a first region and a second region adjacent in the first direction on a substrate surface. The fine periodic structure formed in the inside of the first region and the fine periodic structure formed in the inside of the second region are substantially the same periodic structure. End portions of the plurality of protrusions formed in the first region and end portions of the plurality of protrusions formed in the second region are formed in a boundary portion between the first region and the second region.

Description

Technical Field

[0001] This invention relates to a method for forming fine periodic structures on the surface of a product using a laser. Background Technology

[0002] For example, the iridescent colors observed when holding a CD or DVD up to the light originate from interference, diffraction, and refraction caused by periodic structures as small as the wavelength of light, and are known as structural colors. Structural colors can achieve directional gloss that is impossible to achieve in printing, thus serving decorative or anti-counterfeiting purposes.

[0003] It is known that structural colors can be obtained by forming fine periodic structures (diffraction periodic structures) on the surface of a substrate via laser processing. The fine periodic structures formed by laser processing are called laser-induced periodic surface structures (LIPSS).

[0004] International Publication No. 2004 / 035255 discloses a method for irradiating a substrate with a uniaxial laser close to the processing threshold to scan the substrate while its irradiated portions overlap, and forming a fine periodic structure in a manner similar to self-organization by ablating the portion where the incident and scattered light interfere with each other along the substrate surface.

[0005] For example, when structural colors are used for decorative or anti-counterfeiting purposes, there is a high demand for applying structural colors to a large area in order to improve optical effects.

[0006] As is well known, when forming fine periodic structures (LIPSS) using laser processing to impart structural color, the pitch of the periodic structure varies depending on illumination conditions such as the incident angle of the laser beam on the substrate. Since the observed structural color changes when the pitch varies or becomes inconsistent, it is necessary to minimize the variation in the laser's incident angle in the area where the LIPSS is set in order to impart a highly uniform structural color.

[0007] Meanwhile, to perform laser processing at high speed, scanning is typically performed by deflecting the laser beam using an optical scanning mechanism such as a current mirror, rather than mechanically and relatively moving the laser source relative to the workpiece. Increasing the angle at which the optical deflection scan is performed increases the processing range, allowing for high-speed processing, but also increases the variation in the incident angle depending on the position within the processing range.

[0008] Therefore, there is a need for a method to form high-quality structural colors in large areas on the surface of a product with relatively high productivity. Summary of the Invention

[0009] According to a first aspect of the present invention, a surface treatment method for irradiating a substrate surface with a pulsed laser includes: providing a first region and a second region arranged sequentially and adjacent to each other along a first direction on the substrate surface; providing a plurality of scanning paths extending along the first direction and parallel to each other in each of the first region and the second region; and after sequentially scanning each of the plurality of scanning paths provided in the first region by moving the irradiation position of the pulsed laser along the first direction, sequentially scanning each of the plurality of scanning paths provided in the second region by moving the irradiation position of the pulsed laser along the first direction.

[0010] According to a second aspect of the invention, a surface treatment apparatus includes: a deflection unit configured to deflect a laser beam output from a laser source to perform optical scanning of the laser; a moving mechanism configured to mechanically change the positional relationship between the deflection unit and a workpiece; and a controller configured to control the deflection unit and the moving mechanism. Based on a first region and a second region arranged adjacent to each other and sequentially along a first direction on the surface of the workpiece, and a plurality of scanning paths extending parallel to each other along the first direction in each of the first and second regions, the controller performs control to move the deflection unit along the first direction to move the irradiation position of the laser beam to sequentially scan each of the plurality of scanning paths arranged in the first region. Then, the controller performs control to change the positional relationship between the deflection unit and the workpiece in the first direction. Then, the controller performs control to move the deflection unit along the first direction to move the irradiation position of the laser beam to sequentially scan each of the plurality of scanning paths arranged in the second region.

[0011] According to a third aspect of the invention, a product includes a fine periodic structure having a plurality of protrusions extending parallel to each other in a first direction in each of a first region and a second region adjacent to each other in a first direction on a substrate surface. The fine periodic structure formed inside the first region and the fine periodic structure formed inside the second region are substantially the same periodic structure. The ends of the plurality of protrusions formed in the first region and the ends of the plurality of protrusions formed in the second region are formed in a boundary between the first region and the second region. The shape of the protrusions at each end of the plurality of protrusions formed in the first region is different 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 is different from the shape of the protrusions inside the second region.

[0012] Other features of the invention will become clear from the following description of exemplary embodiments with reference to the accompanying drawings. Attached Figure Description

[0013] Figure 1This is a schematic diagram illustrating the laser head portion of a laser processing apparatus according to an embodiment.

[0014] Figure 2 This is a schematic diagram illustrating the configuration of a laser processing apparatus according to an embodiment.

[0015] Figure 3 It is an enlarged photograph of a finely detailed periodic structure in a planar image.

[0016] Figure 4 It is a schematic illustration of a cross-section of a finely periodic structure taken along the Y direction.

[0017] Figure 5A This is a schematic diagram used to describe a scanning method used for reference.

[0018] Figure 5B It is a schematic diagram illustrating the irradiation history of laser pulses using a scanning method for reference.

[0019] Figure 6A This is a schematic diagram used to describe a scanning method according to an embodiment.

[0020] Figure 6B This is a schematic plan view illustrating the irradiation history of laser pulses using the scanning method according to an embodiment.

[0021] Figure 7A It is a schematic plan view used to describe the process of forming a fine periodic structure by setting multiple patches in the first embodiment.

[0022] Figure 7B This is a schematic plan view illustrating the irradiation history of the laser pulses in the first embodiment.

[0023] Figure 8A It is a schematic plan view used to describe the process of forming a fine periodic structure by setting multiple patches in the reference embodiment.

[0024] Figure 8B This is a schematic diagram illustrating the irradiation history of the laser pulses in the reference embodiment.

[0025] Figure 9 yes Figure 7A The enlarged view of the small area shown schematically illustrates how the illumination spots overlap (overlapping pattern).

[0026] Figure 10A This is a schematic plan view used to describe the process of forming a fine periodic structure by setting multiple patches in the second embodiment.

[0027] Figure 10BThis is a schematic plan view illustrating the irradiation history of the laser pulse in the second embodiment.

[0028] Figure 11A This is a diagram illustrating the shape of the patch according to the second embodiment.

[0029] Figure 11B This is a diagram illustrating the shape of another patch according to the second embodiment.

[0030] Figure 11C This is a diagram illustrating the shape of another patch according to the second embodiment.

[0031] Figure 12 This is a schematic diagram illustrating the molded surface of the mold according to the example, presented in a plan view.

[0032] Figure 13 It is a photograph of the molded surface of the mold based on this example.

[0033] Figure 14A This is a diagram illustrating an embodiment in which only triangular patches are arranged.

[0034] Figure 14B This is a diagram illustrating an embodiment in which only hexagonal patches are arranged.

[0035] Figure 15 This is a photograph of the molded resin product on which LIPSS has been transferred, as observed under a microscope.

[0036] Figure 16 This is an enlarged image of the patch that LIPSS has transferred onto the top.

[0037] Figure 17 This is a graph illustrating the result of FFT processing on data obtained from AFM. Detailed Implementation

[0038] The surface treatment method, surface treatment apparatus, etc., as embodiments of the present invention will be described with reference to the accompanying drawings. The embodiments and examples shown below are merely examples, and, for instance, those skilled in the art can appropriately modify the detailed configurations to implement the invention within its scope.

[0039] Please note that in the accompanying drawings referenced in the following description of embodiments and examples, unless otherwise stated, elements indicated by the same reference numerals are assumed to have substantially the same function.

[0040] Additionally, in the following description, for example, the +X direction indicates the same direction as indicated by the X-axis arrow in the illustrated coordinate system, and the -X direction indicates the direction completely opposite to indicated by the X-axis arrow in the illustrated coordinate system. Furthermore, an X-direction without + or - indicates a direction parallel to the X-axis, regardless of whether this direction is the same as indicated by the X-axis arrow in the illustrated coordinate system. This also applies to directions other than the (±)X direction.

[0041] Laser processing equipment

[0042] Figure 1 This is a schematic diagram illustrating a laser head portion included in a laser processing apparatus for forming LIPSS. The laser beam output from the laser oscillator 17 included in the laser head 16 is reflected in a predetermined direction by a current mirror 18, which serves as a deflector, and then passes through a focusing lens 19 to form a beam that irradiates the workpiece 11. At this time, by moving the current mirror 18, the irradiation position of the laser on the workpiece 11 can be changed two-dimensionally for scanning. In the figure, 10 represents the area or range that can be processed by deflecting and scanning the laser beam using an optical scanning component such as the current mirror 18. This area will be referred to as a patch. The size of the patch 10 can be set to match the limitations of the movable range of the current mirror 18. However, in this case, the difference in the incident angle of the laser beam between the central and peripheral portions of the workpiece 11 is too large, and the structural color resulting from the formation of LIPSS may become so uneven as to be aesthetically unacceptable. Therefore, the size of the patch 10 is preferably set to a value that keeps the non-uniformity of the structural color in the patch within an acceptable range, even if this size is smaller than the mechanical movable limit.

[0043] When the area on the workpiece 11 where the LIPSS needs to be formed is too large to be covered by a single patch 10, multiple adjacent patches are used to cover the entire workpiece area. The size of the patch 10 is preferably set such that the difference in the laser incident angle is not too large near the boundary between adjacent patches and the difference in structural color does not exceed the visually permissible range.

[0044] It should be noted that the mechanism (deflection unit) that performs the optical deflection scanning of the laser beam is not limited to this example. For example, a mechanism that performs unidirectional deflection at high speed and continuously, such as a multifaceted mirror, can be used.

[0045] Figure 2This is a schematic diagram illustrating the configuration of a laser processing apparatus including the aforementioned laser head 16. The laser processing apparatus 51 includes a laser head 16 capable of radiating a laser 52 for processing and a processing table 55 for placing a workpiece 11. Furthermore, the laser processing apparatus 51 includes an X-axis movement mechanism, a Y-axis movement mechanism, and a Z-axis movement mechanism, allowing the positional relationship between the laser head 16 and the workpiece 11 to be changed. The laser head 16, the X-axis movement mechanism, the Y-axis movement mechanism, and the Z-axis movement mechanism are controlled by a controller 100.

[0046] The controller 100 is a computer that controls the operation of various parts of the laser processing apparatus 51, and includes a central processing unit (CPU), memory, input / output controller (I / O controller), etc. The controller 100 may also include input devices such as a keyboard or mouse, and output devices such as a display. The memory in the controller 100 stores control programs for forming periodic structures with fine irregularities (fine periodic structures (nano-periodic structures)), as well as information related to the setting of the patch and the scanning method. This information can be input by the user via the input devices, or via the I / O controller from an external computer or storage device through a network, or via a portable memory such as a Universal Serial Bus (USB) memory.

[0047] Additionally, the laser processing apparatus 51 includes a quarter-wave plate (not shown) for adjusting the polarization direction of the laser irradiating the workpiece 11, and this quarter-wave plate is rotatable about the optical axis between the condenser lens 19 and the workpiece 11. In this embodiment, by adjusting the angle of the quarter-wave plate in the rotation direction, the polarization direction of the laser irradiating the workpiece 11 can be adjusted to be perpendicular to the direction (X direction) of the scan line SC, which will be described later. As a result of this adjustment, a well-shaped LIPSS structure can be formed in which the length direction of each groove is aligned along the direction of the scan line SC, thus imparting a high-quality structural color to the surface of the workpiece 11.

[0048] The laser output from the laser head 16 is focused onto the workpiece 11 at the irradiation position. Note that an optical element (not shown) for adjusting the shape and convergence of the beam can be further provided between the laser head 16 and the workpiece 11. As a method for controlling the laser irradiation energy density to be close to the processing threshold of the workpiece 11, the positional relationship can also be adjusted so that the light irradiates the workpiece 11 at an off-focus position a certain distance away from the focal position.

[0049] As described above, the laser head 16 includes a biaxial current scanner and an fθ lens, and the irradiation position can be rapidly moved by driving the current mirror 18. The scanning of the current mirror 18 can be performed at a higher speed than the stage driven by the X-axis and Y-axis moving mechanisms. Therefore, scanning of each patch is performed by using the current mirror 18, and the patch is switched by moving the stage via the moving mechanism.

[0050] As a laser source for laser processing, a pulsed laser that repeatedly emits short pulses of radiation is preferred. Various lasers, such as picosecond and nanosecond pulsed lasers (e.g., CO2 lasers, YAG lasers), can be used; for example, a Ti:sapphire laser is preferred. Ti:sapphire lasers are so-called femtosecond lasers with ultrashort pulses, for example, with output specifications of a pulse width of 120 fs, a center wavelength of 800 nm, a repetition rate of 1 kHz, and an energy per pulse ranging from 0.25 μJ to 400 μJ.

[0051] Laser scanning method in a patch

[0052] Figure 3 An enlarged photograph of the periodic structure (fine periodic structure) according to this embodiment is shown in a plan view. It can be seen that there is a structure in which a large number of fine grooves are arranged at a predetermined pitch parallel to the X direction, which is the first direction, on the surface of the workpiece 11. Figure 4 This is a schematic illustration of a cross-section of a finely periodic structure taken along the Y direction, which is the second direction. Fine grooves or protrusions are arranged along the Y direction at a pitch indicated by 12, and the fine grooves or protrusions have a depth or height indicated by 13. Typically, a LIPSS has a pitch 12 of about 1 μm and a depth (or height) 13 of about 0.5 μm to 0.7 μm.

[0053] To form fine grooves extending along the X-direction in the patch, scanning is performed by moving the pulsed laser along the X-direction, which is a first direction, while irradiating the workpiece 11 with a pulsed laser at a predetermined repetition frequency such that the irradiated areas of the pulses partially overlap. The polarization direction of the laser irradiating the workpiece 11 is adjusted to be perpendicular to the direction of the scan line SC (i.e., the X-direction), which will be described later. The repetition frequency of the pulsed laser, the scanning speed, the irradiation beam diameter, etc., are adjusted to conditions preferred for forming LIPSS, that is, the irradiation energy density on the substrate is adjusted to a value close to the processing threshold. By performing irradiation with an appropriate energy density, the fine periodic structure is formed in a manner similar to self-organization through ablation in the portion where the incident and scattered light interfere with each other along the substrate surface. By irradiating the laser along a scan line, a fine periodic structure consisting of multiple fine grooves or fine protrusions along the scan line can be formed.

[0054] To create a fine groove extending in the X direction within a region of a certain width along the Y direction, multiple laser scans along the X direction are required. To perform laser scans along the X direction, there are methods for moving the irradiation position along the +X direction in a time sequence, and methods for moving the irradiation position along the -X direction in a time sequence.

[0055] Figure 5A and Figure 6A This is a schematic diagram illustrating two methods of laser scanning. For simplicity, it is assumed here that nine scan lines are set in patch 10 to form a large number of fine grooves. Patch 10 is shown in a plan view. The nine scan lines SC, which are the scan paths being scanned by the laser, are represented by 1 to 9 according to the scanning order, and the direction of movement of the irradiation position for each scan line SC is indicated by an arrow.

[0056] in addition, Figure 5B and Figure 6B These are schematic examples of passing through Figure 5A and Figure 6A The scanning method executes a planar diagram of the irradiation history of the laser pulses. The shape of the irradiation spot LS of the pulsed laser is usually illustrated as a circle, but in the time series, newer irradiation spots are repeatedly drawn over older irradiation spots. Therefore, in the portion irradiated by older and newer pulses in an overlapping manner, from the view, the irradiation shape of the older pulse is covered by the irradiation shape of the newer pulse.

[0057] like Figure 5A As shown, if so-called raster scanning is used, where scanning is performed sequentially along scan lines 1 to 9 while alternately switching the beam movement direction between the +X and -X directions, the current scanner does not need to return to the same starting point in the X direction for each scan line. Therefore, the processing time can be shortened. Conversely, in situations such as... Figure 6A As shown, when scanning is performed by moving the beam along the +X direction in all scan lines 1 to 9, the irradiation position needs to be returned to the starting point in the X direction each time the scan line used as the scan path is switched. Therefore, the processing time required is longer than that of traditional methods. Figure 5A The length of the middle.

[0058] Here, by viewing the pulse irradiation history, it can be seen that, according to Figure 5B and Figure 6BA comparison clearly shows that in the former case, the overlapping pattern of the irradiated spot LS is non-uniform in patch 10, while in the latter case, the overlapping pattern of the irradiated spot LS is more uniform in patch 10. As described above, LIPSS ablates the portions along the substrate surface where incident and scattered light interfere with each other by irradiating a laser at an intensity close to the processing threshold to perform scanning simultaneously on the overlapping irradiated portions, forming a fine periodic structure in a manner similar to self-organization. Therefore, if the overlapping pattern of the irradiated spot LS is non-uniform, a structural color with high-quality appearance cannot be substantially uniformly imparted to patch 10.

[0059] Therefore, in this embodiment, laser scanning is performed such that the direction of the illumination spot movement is the same for all scan lines in each patch, such as... Figure 6A As shown.

[0060] Furthermore, when multiple patches are set and a fine periodic structure is formed in each patch, the direction of the scan lines is set to be parallel among the multiple patches, so that the structural color is consistent across the patches. Additionally, scanning is performed such that the direction of the illumination spot movement is the same in all scan lines across all patches, and all patches are assigned substantially the same structural color.

[0061] The process of setting up multiple patches and forming a fine periodic structure to apply structural color to a large area on the outer surface of the workpiece will be described below.

[0062] First Embodiment

[0063] Figure 7A This is a schematic plan view illustrating the process of forming a fine periodic structure to impart structural color to a large area on the outer surface of a workpiece. In this embodiment, structural color is imparted to area 21 on the outer surface of the workpiece 11. Area 21 has dimensions that cannot be covered by a single patch; therefore, in this embodiment, nine square patches 10 are arranged adjacent to each other in a 3×3 matrix shape. Note that the patch 10 can be rectangular with unequal side lengths instead of square.

[0064] In any patch 10, the laser scan line SC (not shown) is set to be parallel to the X direction, as shown in reference Figure 6A The process involves scanning the laser, causing the irradiated spot to move along the +X direction, which is the first direction, in each scan line SC.

[0065] Then, in this embodiment, nine patches are selected sequentially and irradiated with a laser to proceed according to... Figure 7AThe order of the numbers shown in the patch forms the LIPSS. When patches arranged horizontally (X direction) in a matrix arrangement are called rows and patches arranged vertically (Y direction) are called columns, patches arranged in a row are processed sequentially, and then patches in the next row adjacent to the previous row are processed sequentially.

[0066] like Figure 6A As shown, the order in which scan lines are selected in each patch follows the Y direction. The direction of change of the selected patch rows in the patch matrix arrangement is the Y direction, which is the same as the direction of change of the selected scan lines in each patch.

[0067] For example, in the bottom row, patches are processed in the order of numbers 1, 2, and 3 as shown in the figure. Then, processing shifts to the row adjacent to it in the +Y direction, and patches are processed in the order of numbers 4, 5, and 6. In this embodiment, as shown in the figure, the configuration in which adjacent patches are processed in each row of the matrix in the order of the +X direction as the first direction is utilized. That is, the direction of the patch processing order (i.e., the +X direction) is consistent with the direction of the movement of the illumination spot in each scan line that serves as the scan path (i.e., the +X direction).

[0068] Please note that, in relation to the claims, for example, Figure 7A The patch with a scan order of 1 can be called the first region, the patch with a scan order of 2 can be called the second region, and the patch with a scan order of 4 can be called the third region. Then, in the first region, which is parallel to the X-direction, the side that contacts the third region can be called the first side, and in the third region, which is parallel to the X-direction, the side that contacts the first region can be called the second side.

[0069] Here, for comparison, we will refer to Figure 8A A reference embodiment is described in which the processing order of the patch is set using a method different from that of the previous embodiment. Figure 8A In the illustrated reference embodiment, nine square patches 10 are arranged adjacent to each other in a 3×3 matrix shape, similar to the embodiment. The nine patches are selected sequentially and irradiated with a laser according to the order of their indicated numbers to form a LIPSS. In this reference embodiment, as shown, a configuration is utilized in which adjacent patches are processed in a -X direction order within each row. That is, the processing order of the patches (i.e., the -X direction) is opposite to the direction in which the irradiation spot moves within each scan line (i.e., the +X direction).

[0070] Figure 7B This is an illustrative example based on... Figure 7A A plan view of the laser pulse irradiation history of the scanning method of the illustrated embodiment. Figure 8B This is an illustrative example based on... Figure 8AA plan view of the laser pulse irradiation history of the scanning method of the reference embodiment shown. Similar to what has already been described. Figure 5B and Figure 6B In the time series, the newer illumination spot is repeatedly drawn over the older illumination spot. Therefore, in the portion irradiated by the older and newer pulses in an overlapping manner, the illumination shape of the older pulse is covered by the illumination shape of the newer pulse when viewed from the perspective of the view.

[0071] according to Figure 7B and Figure 8B A comparison clearly shows that at the boundaries between patches, i.e., at the ends of the scan lines, the overlapping pattern of the illumination spots LS is more irregular in the latter case than in the former. LIPSS is a fine, periodic structure formed in a manner similar to self-organization by irradiating a laser at an intensity close to the processing threshold to perform scanning simultaneously on the overlapping irradiated portions, ablating the portions along the substrate surface where incident and scattered light interfere with each other. Therefore, if there are portions where the regularity of how the illumination spots LS overlap differs from their surroundings, then the fine structure therein is substantially different from its surroundings, and thus the structural color appears different from its surroundings. That is, a structural color with excellent quality in appearance cannot be uniformly formed in region 21.

[0072] Specifically, in Figure 8B In the case of the illustrated reference embodiment, it can be seen that the regularity of how the illumination spots overlap differs significantly from its surroundings at the boundaries between patches arranged along the X direction and between patches arranged along the Y direction. Therefore, when visually recognizing the region 21 forming the LIPSS, the horizontal and vertical lines corresponding to the boundaries between patches can be seen in a grid pattern within the rainbow structural colors.

[0073] On the contrary, Figure 7B In the illustrated embodiment, at the boundary between patches arranged along the Y direction (the second direction), i.e., at the boundary parallel to the X direction (the first direction), the regularity of how the illumination spots overlap is not disturbed. Furthermore, at the boundary between patches arranged along the X direction, i.e., at the boundary parallel to the Y direction, although the regularity of how the illumination spots overlap differs slightly from its surroundings, the disturbance to the regularity is less than in the reference embodiment. Figure 9 yes Figure 7A The enlarged view of small region 22 shown schematically illustrates the pattern of overlapping illumination spots. The illumination spot shapes schematically represented by LSA are regularly arranged in most areas of the individual patches, while the illumination spot shapes represented by LSB and LSC are illustrated at the boundaries between patches arranged along the X direction, i.e., at the ends of the patches along the X direction. Note that the ends of the patches along the X direction correspond to the start and end points of laser illumination along the scan line.

[0074] LSB and LSC are slightly different patterns from LSA, but the disturbance of how the illumination spots overlap at the boundaries between patches is less. Figure 8B The reference embodiment shown is as follows: Essentially identical periodic structures are formed in the portions schematically represented by the overlapping LSAs, while portions represented by the LSBs and LSCs contain slightly different shapes, but the differences between them are minor.

[0075] As can be seen from the above, in the reference embodiment, the grid-like lines are obvious in the area where the structural color is presented. However, according to this embodiment, the boundaries between patches arranged along the Y direction are almost visually indistinguishable, and the boundaries between patches arranged along the X direction are not prominent. Therefore, when a large area is given structural color by setting multiple patches and forming LIPSS, the vertical lines in the boundaries between patches are almost indistinct, and a highly uniform structural color can be given to the entire area.

[0076] In the first embodiment, LIPSS is formed based on the following conditions (1) to (5).

[0077] (1) Set up and arrange multiple square or rectangular patches in a matrix shape.

[0078] (2) In each patch, multiple scan lines are set to be parallel to the X direction.

[0079] (3) Perform laser scanning such that the direction of the laser spot movement in each scan line is the +X direction. Set the direction of the order of the scan lines selected for laser irradiation in each patch to the +Y direction.

[0080] (4) When the patches arranged horizontally (X-direction) in the matrix are called rows and the patches arranged vertically (Y-direction) are called columns, the patches arranged in a row are processed sequentially, and then the patches in the other row are processed sequentially (processing is based on row order). When laser processing changes from one row to another, a change occurs in the +Y direction from one row to the adjacent row. That is, the direction of the selection order of the scan lines irradiated by the laser in each patch is set to the same direction as the processing order of the patch rows in the matrix (i.e., the +Y direction).

[0081] (5) In each row, process adjacent patches in the order of the +X direction. That is, set the direction of patch processing in each row to the same direction as the direction of movement of the illumination spot in each scan line (i.e., the +X direction).

[0082] According to this embodiment, it is possible to form fine structures (LIPSS) exhibiting high-quality structural colors over a large area with relatively high productivity. That is, a method and manufacturing apparatus for producing products with excellent structural colors can be provided.

[0083] The method for forming LIPSS according to this embodiment can be implemented in an embodiment where the surface of a product is directly laser-processed (surface treatment) to impart a structural color to the product. Alternatively, the method can be implemented in an embodiment where the surface treatment involves laser processing of the molding surface of a mold used to manufacture the product, rather than directly laser-processing the product. That is, the method can also be implemented in an embodiment where a fine periodic structure for imparting a structural color to the product is formed on the molding surface of the mold by laser processing. In the fine periodic structure of the molding surface, the unevenness is the opposite of the fine periodic structure formed on the product. If the shape of the molding surface of the mold is transferred to a molding material such as a resin material using a surface-treated mold, a high-quality structural color can be imparted to a molded product such as a molded resin product, wherein the boundaries of the patches for forming LIPSS on the molding surface are not prominent.

[0084] The LIPSS according to this embodiment can be formed on various products such as anti-counterfeiting stickers and various printer components (e.g., printer ink cartridges, printer drum covers, and printer external parts). That is, high-quality structural colors can be applied to the substrate surface of these products.

[0085] Second Embodiment

[0086] As a second embodiment, a method for performing laser processing during LIPSS formation by setting a patch of a different shape than that in the first embodiment will be described. Note that in the description of the second embodiment, elements identical to those described in the first embodiment will be simplified or omitted.

[0087] In the first embodiment, LIPSS is formed according to conditions (1) to (5) above. In the second embodiment, condition (1) is different from that in the first embodiment, and conditions (2) to (5) are substantially the same as those in the first embodiment.

[0088] Figure 10A This is a schematic plan view illustrating the process in the second embodiment of setting up multiple patches and forming a fine periodic structure in each patch when a structural color is applied to a large area on the outer surface of the workpiece. In this embodiment, a structural color is applied to area 21 on the outer surface of the workpiece 11. In this embodiment, patches 10A, 10B, and 10C of three shapes are provided and arranged adjacent to each other in a 4×3 matrix shape to cover area 21. Figures 11A to 11C These are schematic plan views used to describe patches 10A, 10B, and 10C.

[0089] like Figures 11A to 11C As shown, in each patch, the laser scanning line SC is set parallel to the X direction, as described in condition (2). Furthermore, in each scanning line SC, laser scanning is performed such that the direction of movement of the irradiated spot is the +X direction. Additionally, compared to the first embodiment... Figure 6A Similarly, the order of the scan lines illuminated by the laser in each patch follows the +Y direction.

[0090] In addition, Figures 11A to 11C In the middle, as Figure 10A In the X-direction of the row direction, the side where adjacent patches touch each other is indicated by a thick line as edge CS. In the first embodiment, the side where adjacent patches touch each other in the X-direction is perpendicular to the X-direction. In contrast, in this embodiment, edge CS is not perpendicular to the X-direction, but intersects it obliquely (at an angle other than 90°). The acute angle at the intersection, i.e., the smaller angle, is denoted by α in the figure.

[0091] Figure 10B yes Figure 10A The enlarged view of small region 32 shown schematically illustrates the pattern of overlapping illumination spots. The illumination spot shapes schematically represented by LSA are regularly arranged in most areas of the individual patches, while the illumination spot shapes represented by LSB and LSC are illustrated at the boundaries between patches arranged along the X-direction, i.e., at the ends of the patches along the X-direction. Note that the ends of the patches along the X-direction correspond to the start and end points of laser illumination along the scan line.

[0092] The LSB and LSC are slightly different patterns from the LSA, and it can be seen that in this embodiment, the LSB and LSC are arranged obliquely along the edge CS, with a lower arrangement density than the LSA. Figure 9 The arrangement density of the first embodiment shown is low. That is, because the overlapping pattern of the irradiated spot is disturbed in the portion at the boundary between the patches, the boundary between the patches arranged along the X direction becomes less obvious when observing the structural color assigned to region 21 than in the first embodiment.

[0093] When the intersection angle α is small, the LSBs and LSCs are more dispersed along the X direction, thus tending to make the boundaries between patches arranged along the X direction less distinct. Therefore, α is preferably equal to or less than 45°. However, with a small α, the area of ​​each patch that can be optically scanned within the limited light deflection range of the laser processing apparatus is smaller. The size of α is preferably set with consideration of the balance between the effect of making the boundaries between patches less distinct in the area imparting structural color and the increase in manufacturing time, and is preferably suitably set in the range of 20° to 70°.

[0094] According to this embodiment, fine structures (LIPSS) exhibiting high-quality structural colors can be formed over a large area with relatively high productivity. Furthermore, similar to the first embodiment, this embodiment can be implemented not only in embodiments where the surface of a product is directly laser-processed to impart structural colors, but also in embodiments where the molding surface of a mold used to manufacture the product is surface-treated by laser processing. If the shape of the molded surface of the mold is transferred to a molding material such as resin by using a surface-treated mold, a structural color can be imparted to the molded resin product, making the boundaries between patches used when performing laser processing on the molded surface of the mold indistinct.

[0095] Example

[0096] An example will be described of forming LIPSS shapes by laser processing on the surface of a mold to give decorative effects to molded resin products. Figure 12 This is a schematic diagram illustrating the molding surface of the mold, which is the object of processing 11, in a plan view. In this example, the LIPSS is formed in a ring-shaped region 21 with a circular outer edge and an elongated circular inner edge. The figure also illustrates lines indicating the shape of the patch set by applying the idea of ​​the second embodiment.

[0097] STAVAX was used as the mold material. An LP400U manufactured by GF Machining Solutions was used as the laser processing equipment. An ultrashort pulse laser oscillator manufactured by AMPLITUDE SYSTEMS was used as the laser source, with a wavelength of 1030 nm. A pulsed laser with a pulse energy of 7.5 μJ per pulse and a lens focal length of approximately 170 mm was used, and the laser spot diameter was set to 40 μm by adjusting the distance between the lens and the molded surface of the model. A current mirror was used as the laser scanning method, with a scanning speed of 500 mm / s, a scanning pitch of 5 μm, and a short pulse laser irradiation frequency of 101 kHz. The area irradiated by the laser through optical scanning using the current mirror was set to a 40 mm × 40 mm square, and the shape of each patch was set to be contained within this square area.

[0098] Laser scanning is performed using the scanning method described in the second embodiment, thus forming a LIPSS in the annular region 21. The formed LIPSS has the following characteristics: Figure 4 The schematically shown cross-section has a periodic structure, with the pitch 12 of fine grooves or fine protrusions being approximately 1 μm, and the depth or height 13 of the fine grooves or fine protrusions being in the range of 0.3 μm to 0.5 μm.

[0099] Figure 13 This is a photograph of the molded surface of the mold on which the LIPSS is formed. Although it is difficult to see in the photograph, the annular region 21 exhibits high-quality structural color as observed by the human eye, and in region 21, the boundaries between patches are almost visually indistinguishable.

[0100] Molded resin products are manufactured using injection molding with molds. The molded resin products with LIPSS transferred onto the molded surface exhibit high-quality structural colors, and the boundaries between patches set by laser processing of the mold are almost imperceptible to the human eye.

[0101] Figure 15 An example photograph of a LIPSS molded resin product with a molded surface transferred with the mold, as observed under a microscope. Although the boundaries between patches created by laser processing of the mold are almost invisible to the human eye, the boundaries between the patches of the transferred LIPSS can be observed as black when viewed under a microscope.

[0102] Figure 16 It is a transfer printed with LIPSS Figure 15 The image shown is an enlarged view of the patch, specifically an enlarged view of region A and its boundary portion. Region A includes a first region and a second region adjacent to each other in a first direction, and the boundary portion is the end of the first region or the end of the second region. Figure 17 Atomic force microscopy (AFM) observations of regions B and C are shown. Region B is part of the boundary portion of either the end of the first region or the end of the second region, while region C is part of the interior of the first region. Both the first and second regions contain finely periodic structures comprising multiple mutually parallel protrusions extending along a first direction. In regions B and C, AFM measurements were performed at 16 locations (a total of 128 locations) in the direction intersecting the first direction, arranged in eight rows with a pitch of 0.078125 μm along the first direction.

[0103] Figure 17The Fast Fourier Transform (FFT) results of the measurement data are illustrated. The value of the portion with the maximum height in the FFT results of the data measured by atomic force microscopy (AFM) is set as the height of the protrusion. It can be seen that the height of the protrusion is 0.3 μm or more inside the first region and the second region, while the height of the protrusion at the boundary is 0.25 μm or less. That is, it was found that at the boundary, the periodic structure of the protrusion is disturbed, thus reducing its height, so that the boundary is visually perceived as black when observed under a microscope. It was found that the boundary is visually recognizable by the human eye when the center line of the boundary that is visually perceived as black, i.e., the line connecting the center of the portion of the protrusion with a height of 0.25 μm or less in the first direction, extends in a direction perpendicular to the first direction. That is, preferably, the center line of the boundary is tilted such that the angle between the center line of the boundary and the first direction is 20° to 70°. As a result, the boundary is almost unrecognizable by the human eye. The shape of the patch (e.g., the first region) on which the LIPSS is transferred can be triangular or quadrilateral. Alternatively, the shape can be hexagonal or polygonal. Furthermore, the shape does not have to be a polygon consisting only of straight lines; it can also include curves.

[0104] Please note that the present invention is not limited to the above embodiments and examples, and can be modified in various ways within the technical concept of the present invention.

[0105] For example, to cover the entire area to be processed, the first embodiment uses multiple rectangular patches, while the second embodiment uses triangular and parallelogram patches. However, the shape and layout of the patches are not limited to these examples. For instance, they can be utilized as... Figure 14A The configuration shown only involves arranging triangular patches, or it can be achieved using, for example... Figure 14B The example shown uses a hexagonal patch. However, polygonal patches with different shapes can be arranged in the area to be processed. Furthermore, the patch shape does not have to be a polygon composed only of straight lines; it can also utilize shapes that include curves intersecting the scanning direction of the laser.

[0106] Other embodiments

[0107] While the invention has been described with reference to exemplary embodiments, it should be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the appended claims should be given the broadest interpretation to cover all such modifications and equivalent structures and functions.

Claims

1. A product comprising: A periodic structure is disposed in each of a first region and a second region adjacent to each other in a first direction on the surface of a substrate, and each of the periodic structures has a plurality of protrusions extending along the first direction. The ends of the plurality of protrusions formed in the first region and the ends of the plurality of protrusions formed in the second region are formed in the boundary between the first region and the second region. The shape of each protrusion at the 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 each protrusion at the end 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 molded resin product, with multiple protrusions formed from resin material and a periodic structure exhibiting a structural color.

2. The product according to claim 1, wherein, The height of the protrusion inside the first region and the height of the protrusion inside the second region are 0.3 μm to 0.5 μm or 0.5 μm to 0.7 μm.

3. The product according to claim 1, wherein, The height of the protrusions in the boundary portion is less than 0.25 μm, and Among them, the multiple protrusions formed in the first region are higher than the protrusions in the boundary region.

4. The product according to claim 1, wherein, The angle between the centerline of the boundary and the first direction is more than 20° and less than 70°.

5. The product according to claim 1, wherein, The periodic structures formed within the first region and the periodic structures formed within the second region are essentially the same periodic structures.

6. The product according to claim 1, wherein, At least one of the first and second regions has a triangular or hexagonal shape.

7. The product according to claim 1, in, The first region includes a first side extending along a first direction. The second region includes a second side extending along the first direction, and The first side and the second side are in contact with each other.

8. The product according to any one of claims 1-7, wherein, The substrate is the substrate for the sticker.

9. The product according to any one of claims 1-7, wherein, The substrate is the base plate of the printer components.

10. The product according to claim 9, wherein, Printer components are any of the ink cartridge, drum cover, and external components.

11. A method for manufacturing a product according to any one of claims 1-10, the method comprising: The shape of the molded surface is transferred onto the molding material to give the surface of the molding material a structural color.

12. The manufacturing method according to claim 11, wherein the molded surface exhibits a structural color.

13. The manufacturing method according to claim 11, comprising: A first processing area and a second processing area are arranged adjacent to each other along the X direction on the molding surface of the mold. In each of the first and second processing areas, multiple scanning paths extending along the X direction and parallel to each other are set. While moving the irradiation position of the pulsed laser along the X direction, the scanning paths in the multiple scanning paths set in the first processing area are scanned sequentially. Then, while moving the irradiation position of the pulsed laser along the X direction, the scanning paths in the multiple scanning paths set in the second processing area are scanned sequentially. as well as The surface to be machined or molded.

14. The manufacturing method according to claim 13, comprising: A third processing area is provided on the molding surface, which is adjacent to the first processing area along the Y direction intersecting the X direction; Multiple scanning paths that extend along the X direction and are parallel to each other are set in the third processing area; While moving the irradiation position of the pulsed laser along the X direction, scanning is performed on each of the multiple scanning paths set in the first processing area, and the scanning path is selected according to the arrangement order of the scanning paths along the Y direction; and After scanning all the scanning paths in the first processing area, a scanning path is selected from the multiple scanning paths set in the third processing area according to the arrangement order of the scanning paths along the Y direction, and the selected scanning path is scanned while moving the irradiation position of the pulsed laser along the X direction, thereby scanning all the scanning paths in the third processing area.

15. The manufacturing method according to claim 13, wherein, The polarization direction of the pulsed laser irradiating the molded surface is perpendicular to the X-direction.

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