Printing apparatus and printing method

Abstract

To provide a configuration capable of printing an image that causes various changes depending on a direction in which a medium having irregularities on a surface is viewed.SOLUTION: The control unit controls a first scan while a relative position of a print head capable of discharging ink droplets onto a medium having unevenness on a surface thereof changes in a first scan direction, and a second scan while the relative position of the print head changes in a second scan direction opposite to the first scan direction. The control unit performs a first control of forming an image by causing the print head to eject the ink droplets in the first scanning based on first image data corresponding to a first area, a second control of forming an image by causing the print head to eject the ink droplets in the second scanning based on second image data corresponding to a second area, and a third control of forming an image by causing the print head to eject the ink droplets in both the first scanning and the second scanning based on third image data corresponding to a third area.SELECTED DRAWING: Figure 7

Description

[Technical Field]

[0001] The present invention relates to a printing apparatus that ejects ink droplets onto a medium, and a printing method. [Background technology]

[0002] The printing device disclosed in Patent Document 1 includes a printing device control unit that controls the ejection of droplets by an ejection head mounted on a reciprocating carriage and the scanning of the carriage. The printing device control unit divides the printing area of ​​an image printed on a printing medium having a plurality of irregularities on its surface into a first print image area and a second print image area, and performs different controls on the first print image area and the second print image area. The printing device control unit controls the ejection head to form dots in the first print image area by forward pass ejection control but not by backward pass ejection control, and to form dots in the second print image area by backward pass ejection control but not by forward pass ejection control. When the printed image on the printing medium is viewed from the backward pass side toward the forward pass, the first printed image appears clearer than the second printed image, and when the printed image is viewed from the backward pass side toward the forward pass, the second printed image appears clearer than the first printed image. Therefore, the printed image on the printing medium changes so that a positive image and a negative image are interchanged depending on the direction in which the printing medium is viewed. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2022-80497 Summary of the Invention [Problem to be solved by the invention]

[0004] In order to form a print image on a medium that alternates between a positive and negative image depending on the direction in which the print medium is viewed, control is required to clearly separate the areas of the first print image and the second print image. If the landing positions of ink droplets are misaligned between the forward and backward passes, a visual degradation of image quality, such as a faint slit, may occur at the boundary between the first and second print images. [Means for solving the problem]

[0005] The printing device of the present invention comprises: a print head capable of ejecting ink droplets onto a medium having an uneven surface; a drive unit that changes the relative position of the print head with respect to the medium at least in a first scanning direction and a second scanning direction opposite to the first scanning direction; a control unit that controls a first scan in which the ink droplets are ejected from the print head while the relative position of the print head is changing in the first scan direction, and a second scan in which the ink droplets are ejected from the print head while the relative position of the print head is changing in the second scan direction, a printing area in which an image is formed on the medium includes a first area in which the image is formed in the first scan, a second area in which the image is formed in the second scan, and a third area in which the image is formed in both the first scan and the second scan; The control unit a first control for forming the image in the first area by causing the print head to eject the ink droplets during the first scan based on first image data corresponding to the first area; second control for forming the image in the second area by causing the print head to eject the ink droplets during the second scan based on second image data corresponding to the second area; a third control for forming the image in the third area by causing the print head to eject the ink droplets in both the first scan and the second scan based on third image data corresponding to the third area; and The present invention has an aspect of carrying out the above.

[0006] Furthermore, a printing method of the present invention is a printing method using a print head capable of ejecting ink droplets onto a medium having an uneven surface, the method including changing a relative position of the print head with respect to the medium at least in a first scanning direction and a second scanning direction opposite to the first scanning direction, and performing a first scan in which the ink droplets are ejected from the print head while the relative position of the print head is changing in the first scanning direction, and a second scan in which the ink droplets are ejected from the print head while the relative position of the print head is changing in the second scanning direction, a printing area in which an image is formed on the medium includes a first area in which the image is formed in the first scan, a second area in which the image is formed in the second scan, and a third area in which the image is formed in both the first scan and the second scan; The printing method includes: a first step of forming the image in the first area by ejecting the ink droplets from the print head during the first scan based on first image data corresponding to the first area; a second step of forming the image in the second region by ejecting the ink droplets from the print head during the second scan based on second image data corresponding to the second region; a third step of forming the image in the third area by ejecting the ink droplets from the print head in both the first scan and the second scan based on third image data corresponding to the third area; The present invention has an aspect including the following. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a diagram schematically illustrating an example of the configuration of a printing apparatus. [Figure 2] FIG. 1 is a block diagram illustrating a configuration example of a printing apparatus. [Figure 3] FIG. 2 is a bottom view schematically illustrating an example of a nozzle surface of a print head. [Figure 4]1A and 1B are diagrams showing examples of landing positions of ink droplets on a medium having an uneven surface; [Figure 5] Figure 5A is a diagram showing a schematic example of how the appearance of a first region changes depending on the direction in which the medium on which ink droplets land is viewed during a forward scan, and Figure 5B is a diagram showing a schematic example of how the appearance of a second region changes depending on the direction in which the medium on which ink droplets land is viewed during a backward scan. [Figure 6] 1A and 1B are diagrams schematically showing examples of divisions of print areas and examples of how an image appears depending on the direction in which the medium is viewed. [Figure 7] 7A and 7B are diagrams schematically showing examples of the amount of ink ejected per unit area of ​​each region. [Figure 8] 1A and 1B are diagrams schematically showing examples of divisions of print areas and examples of how an image appears depending on the direction in which the medium is viewed. [Figure 9] 10 is a flowchart illustrating an example of a print control process. [Figure 10] 10 is a flowchart illustrating an example of a print control process. [Figure 11] 10 is a flowchart showing an example of a process for setting Duty3, the amount of ink ejected per unit area; [Figure 12] 10A and 10B are diagrams showing examples of how an image appears depending on the direction in which the medium is viewed when colors are changed depending on the region. DETAILED DESCRIPTION OF THE INVENTION

[0008] The following describes embodiments of the present invention. Of course, the following embodiments are merely examples of the present invention, and not all of the features shown in the embodiments are necessarily essential to the solution of the invention.

[0009] (1) Summary of the aspects included in the present invention: First, an overview of the aspects included in the present invention will be described with reference to the examples shown in Figures 1 to 12. Note that the figures in this application are diagrams showing examples in a schematic manner, and the magnification in each direction shown in these figures may differ, and the figures may not be consistent with each other. Of course, each element of the present aspect is not limited to the specific example indicated by the symbol. In the "Outline of the aspects included in the present invention," the words in parentheses indicate supplementary explanations for the immediately preceding words.

[0010] [Aspect 1] 1 and 2, a printing device 1 according to one embodiment includes a print head 11, a drive unit 20, and a control unit U1. As illustrated in FIG. 4 and other figures, the print head 11 is capable of ejecting ink droplets 17 onto a medium 200 having an asperity 202 on a surface 201. The drive unit 20 changes the relative position of the print head 11 with respect to the medium 200 at least in a first scanning direction D1 and a second scanning direction D2 opposite to the first scanning direction D1. The control unit U1 controls a first scan (e.g., a forward scan S1) in which the ink droplets 17 are ejected from the print head 11 while the relative position of the print head 11 is changing in the first scanning direction D1, and a second scan (e.g., a backward scan S2) in which the ink droplets 17 are ejected from the print head 11 while the relative position of the print head 11 is changing in the second scanning direction D2. Here, the printing area A0 where the image IM0 is formed on the medium 200 includes a first area (e.g., forward ejection area A1) where the image IM0 is formed in the first scan (S1), a second area (e.g., backward ejection area A2) where the image IM0 is formed in the second scan (S2), and a third area (e.g., reciprocating ejection area A3) where the image IM0 is formed in both the first scan (S1) and the second scan (S2), as illustrated in Figure 6 etc. The control unit U110 performs the following control, as illustrated in Figures 9 and 10. (a1) A first control (e.g., a first step ST1) that forms the image IM0 in the first area (A1) by causing the print head 11 to eject the ink droplets 17 in the first scan (S1) based on first image data DA1 corresponding to the first area (A1). (a2) A second control (e.g., a second process ST2) that forms the image IM0 in the second area (A2) by causing the print head 11 to eject the ink droplets 17 in the second scan (S2) based on second image data DA2 corresponding to the second area (A2). (a3) A third control (e.g., a third process ST3) that forms the image IM0 in the third area (A3) by causing the print head 11 to eject the ink droplets 17 in both the first scan (S1) and the second scan (S2) based on third image data DA3 corresponding to the third area (A3).

[0011] As illustrated in FIG. 4, when the medium 200 has irregularities 202 on its surface 201, ink droplets 17 ejected from the print head 11, whose relative position has changed in the first scanning direction D1, tend to land on the protruding portions 203 on the surface 201 upstream in the first scanning direction D1 (e.g., the upstream side 204 in the first scanning direction). Therefore, when the medium 200 on which the image IM0 has been formed is viewed from the upstream side in the first scanning direction D1, the first region (A1) appears darker than the second region (A2), as illustrated in FIG. 6 and other figures. Furthermore, ink droplets 17 ejected from the print head 11, whose relative position has changed in the second scanning direction D2, tend to land on the protruding portions 203 on the surface 201 upstream in the second scanning direction D2 (e.g., the upstream side 205 in the second scanning direction). Therefore, when the medium 200 is viewed from the upstream side in the second scanning direction D2, the second region (A2) appears darker than the first region (A1), as illustrated in FIG. 6 and other figures. Here, the third area (A3) where ink droplets 17 land in both the first scan (S1) and the second scan (S2) has little change in appearance depending on the viewing direction. This results in diverse changes in the image IM0 depending on the viewing direction of the medium 200. Therefore, the above embodiment can provide a printing device that can print images that produce diverse changes depending on the viewing direction of a medium with an uneven surface.

[0012] There are various examples of the above-described aspects. Examples of media having an uneven surface include fabric made of many fibers, embossed paper with an uneven surface, etc. For example, fabric has an uneven surface due to the combination of fibers. Changes in the relative position of the print head with respect to the media include movement of the print head without movement of the media, movement of the media without movement of the print head, and movement of both the media and the print head. The first scanning direction may be the forward direction of main scanning in a printing device that repeats main scanning and sub-scanning, or the direction in which a medium is fed, etc. The second scanning direction may be the backward direction of main scanning in a printing device that repeats main scanning and sub-scanning, or the direction in which a medium moves when the medium is fed back, etc. In this application, the terms "first," "second," etc. are terms for distinguishing between elements among a plurality of elements having similarities, and do not necessarily imply an order. Of course, the above remarks also apply to the following aspects.

[0013] [Aspect 2] The ink 16 that becomes the ink droplets 17 may be a pigment ink that contains a pigment. When the pigment ink lands on the medium 200, the pigment particles tend to remain on the surface 201 of the medium 200, making it possible to more clearly see the changes in the image IM0 depending on the direction in which the medium 200 is viewed. Therefore, the above embodiment can more clearly see the various changes in the image depending on the direction in which the medium is viewed. Although not included in the above-mentioned embodiment 2, the case where the ink 16 that becomes the ink droplets 17 is a dye ink containing a dye is also included in the disclosure of the present application.

[0014] [Aspect 3] As illustrated in Figure 6, the control unit U1 may divide the printing area A0 into the first area (A1), the second area (A2), and the third area (A3) so that the third area (A3) is adjacent to both the first area (A1) and the second area (A2). The presence of the third region (A3) between the first region (A1), which appears dark when viewed from the upstream side in the first scanning direction D1, and the second region (A2), which appears dark when viewed from the upstream side in the second scanning direction D2, allows the appearance to change smoothly when the viewing direction of the medium 200 changes. Therefore, the above embodiment can improve the quality of an image that changes depending on the viewing direction of the medium. Although not included in the above-mentioned embodiment 3, the case where the third region (A3) is not adjacent to the first region (A1) or the case where the third region (A3) is not adjacent to the second region (A2) is also included in the disclosure of the present application.

[0015] [Aspect 4] As illustrated in Figure 7B, the amount of ink 16 per unit area required to form the image IM0 in the third region (A3) (e.g., Duty3, the amount of ink ejected per unit area) may be greater than the amount of ink 16 per unit area required to form the image IM0 in the first region (A1) and the second region (A2) (e.g., Duty1, Duty2, the amount of ink ejected per unit area). As a result of the tests, it was found that when the amount of ink ejected per unit area (amount of ink 16 per unit area) is the same across the entire image IM0, as illustrated in Figures 6 and 7A, when the medium 200 is viewed from upstream in the first scanning direction D1, the third region (A3) appears lighter than the second region (A2), which is thinner than the first region (A1), and when the medium 200 is viewed from upstream in the second scanning direction D2, the third region (A3) appears lighter than the first region (A1), which is thinner than the second region (A2). 7B and 8, by making the amount of ink ejected per unit area (Duty3) in the third region (A3) greater than the amounts of ink ejected per unit area (Duty1, Duty2) in the first region (A1) and the second region (A2), it is possible to reduce the difference in density between the third region (A3) and the second region (A2) when the medium 200 is viewed from the upstream side in the first scanning direction D1, and it is possible to reduce the difference in density between the third region (A3) and the first region (A1) when the medium 200 is viewed from the upstream side in the second scanning direction D2. Therefore, the above embodiment can improve the quality of an image that changes depending on the direction in which the medium is viewed. Although not included in the above-mentioned aspect 4, the case where the amount of ink ejected per unit area of ​​the third region (A3) is equal to or less than the amount of ink ejected per unit area of ​​the first region (A1) and the second region (A2) is also included in the disclosure of the present application.

[0016] [Aspect 5] 7B, the amount of ink 16 per unit area ejected as the ink droplets 17 from the print head 11 in the first region (A1) is defined as Duty 1, and the amount of ink 16 per unit area ejected as the ink droplets 17 from the print head 11 in the second region (A2) is defined as Duty 2. The amount of ink 16 per unit area ejected as the ink droplets 17 from the print head 11 in the third region (A3) during the first scan (S1) (for example, 0.5×Duty 3) may be greater than 0.5×Duty 1, less than Duty 1, greater than 0.5×Duty 2, and less than Duty 2. The amount of ink 16 per unit area (e.g., 0.5 x Duty3) ejected as ink droplets 17 from the print head 11 during the second scan (S2) in the third region (A3) may be greater than 0.5 x Duty1, less than Duty1, greater than 0.5 x Duty2, and less than Duty2. In the third region (A3), the amount of ink ejected per unit area (0.5 × Duty3) during the first scan (S1) is greater than 0.5 × Duty1, less than Duty1, greater than 0.5 × Duty2, and less than Duty2, thereby reducing the difference in density between the third region (A3) and the second region (A2) when the medium 200 is viewed from the upstream side in the first scanning direction D1. In the third region (A3), the amount of ink ejected per unit area (0.5 × Duty3) during the second scan (S2) is greater than 0.5 × Duty1, less than Duty1, greater than 0.5 × Duty2, and less than Duty2, thereby reducing the difference in density between the third region (A3) and the first region (A1) when the medium 200 is viewed from the upstream side in the second scanning direction D2. Therefore, the above aspect can improve the quality of images that change depending on the direction in which the medium is viewed.

[0017] [Aspect 6] 11, the printing device 1 may further include a receiving unit U2 that receives a setting of a Duty3 ink ejection amount per unit area, which is the amount of ink 16 per unit area required to form the image IM0 in the third region (A3). The control unit U1 may perform the third control to form the image IM0 in the third region (A3) by causing the print head 11 to eject the ink droplets 17 based on the third image data DA3, so that the amount of ink 16 per unit area required to form the image IM0 in the third region (A3) is the Duty3 ink ejection amount per unit area. In the above cases, the density of the third area compared to the first and second areas can be adjusted depending on the type of medium, etc.

[0018] [Aspect 7] The first image data DA1, the second image data DA2, and the third image data DA3 may be data representing a plain image of the same color. Tests have shown that when the first area (A1), the second area (A2), and the third area (A3) are solid images of the same color, there is a clear change in the shade depending on the viewing direction of the medium 200. Therefore, the above embodiment can provide a suitable example of producing a variety of changes in the image depending on the viewing direction of the medium.

[0019] [Aspect 8] As shown in Fig. 12, the first image data DA1 may be data representing a plain image of a first color (cyan in the example of Fig. 12). The second image data DA2 may be data representing a plain image of a second color (magenta in the example of Fig. 12) different from the first color. The third image data DA3 may be data representing a plain image of a mixture of the first color and the second color. When the medium 200 on which the image IM0 is formed is viewed from the upstream side in the first scanning direction D1, the first region (A1) of the first color appears darker than the second region (A2) of the second color, and a third region (A3) of a mixed color of the first and second colors is also visible. When the medium 200 is viewed from the upstream side in the second scanning direction D2, the second region (A2) of the second color appears darker than the first region (A1) of the first color, and a third region (A3) of a mixed color of the first and second colors is also visible. Because color changes appear depending on the direction from which the medium 200 is viewed, the above embodiment can produce color changes in the image depending on the direction from which the medium is viewed.

[0020] [Aspect 9] 3, the printing apparatus 1 may further include a treatment liquid deposition unit (e.g., a treatment liquid head 11P) that can deposit, onto the medium 200, a treatment liquid containing an aggregating agent that aggregates the pigment contained in the ink droplets 17. As illustrated in FIGS. 9 and 10, the control unit U1 may cause the print head 11 to eject the ink droplets 17 after the treatment liquid deposition unit (11P) deposits the treatment liquid onto the medium 200. When the pigment ink lands on the medium 200, the pigment aggregates due to the aggregating agent, making it more likely to remain on the surface 201 of the medium 200, and changes in the image IM0 depending on the direction in which the medium 200 is viewed become even more apparent. Therefore, the above embodiment can make the various changes in the image depending on the direction in which the medium is viewed even more apparent. In particular, since precision in the position where the pigment remains is required to intentionally separate the print area A0 between the first scan (S1) and the second scan (S2) and cause various changes in the image IM0 depending on the direction in which the medium 200 is viewed, it is preferable that an aggregating agent be applied to the medium 200 before the pigment ink lands. The treatment liquid application unit is not limited to the treatment liquid head 11P, but may be a roll coater-type liquid application device that applies treatment liquid to a rotating roll to coat the entire surface of the medium. Furthermore, although not included in the above-mentioned embodiment 9, if the pigment contained in the ink droplets 17 is fixed to the surface of the medium, the printing device may not have a treatment liquid application unit.

[0021] [Aspect 10] As illustrated in FIGS. 9 and 10, a printing method according to one aspect is a printing method for performing the first scan (S1) and the second scan (S2), and includes the following steps. (b1) A first process ST1 of forming the image IM0 in the first area (A1) by ejecting the ink droplets 17 from the print head 11 during the first scan (S1) based on first image data DA1 corresponding to the first area (A1). (b2) A second process ST2 in which the image IM0 in the second area (A2) is formed by ejecting ink droplets 17 from the print head 11 in the second scan (S2) based on second image data DA2 corresponding to the second area (A2). (b3) A third process ST3 of forming the image IM0 in the third area (A3) by ejecting the ink droplets 17 from the print head 11 in both the first scan (S1) and the second scan (S2) based on third image data DA3 corresponding to the third area (A3). The above aspect can provide a printing method capable of printing an image that produces various changes depending on the viewing direction of a medium having an uneven surface.

[0022] Furthermore, the above-described aspects are applicable to a printing system including the above-described printing device, a printing method for the printing system, a control program for the above-described printing device, a control program for the above-described printing system, a computer-readable non-transitory medium on which any of the above-described control programs is recorded, etc. The above-described printing device may be composed of multiple distributed parts.

[0023] (2) Specific examples of printer configuration: 1 and 2 show a schematic configuration of a printing device 1 including a host device 100 and a printing unit 2. Fig. 3 shows a schematic illustration of a nozzle surface 11a of a print head 11. Fig. 4 shows a schematic illustration of landing positions of ink droplets 17 on a medium 200 having an asperity 202 on its surface 201. 1 and 2 show a serial inkjet printer as an example of the printing unit 2. The Y-axis direction in FIG. 1 indicates the feed direction D3, which is the direction in which the medium 200 is transported. The X-axis direction in FIG. 1 indicates the first scanning direction D1 shown in FIG. 3 and also indicates the width direction of the medium 200 that intersects with the feed direction D3. The X-axis and Y-axis directions may be horizontal as shown in FIG. 1, or may be a direction other than the horizontal direction, such as up and down. In this specific example, the Y-axis and X-axis directions are assumed to be perpendicular to each other, but the Y-axis and X-axis directions may intersect at an angle other than 90°. The Z-axis direction in FIG. 1 indicates the vertical direction that intersects with the X-axis and Y-axis directions, and in this specific example, is assumed to be perpendicular to the X-axis and Y-axis directions. The Z-axis direction may be a direction other than the vertical direction, such as a horizontal direction.

[0024] 1 and 4 is a medium having irregularities 202 on a surface 201, such as a fabric made up of many fibers, and is a long, printable material supplied in a rolled state. The printing unit 2 shown in FIGS. 1 and 2 includes a drive unit 20 equipped with a head unit 10, a print control unit 30 that controls the operation of the printing unit 2, and the like. Upon receiving print data from the host device 100, the printing unit 2 controls the head unit 10 and drive unit 20 using the print control unit 30 in accordance with the print data, and prints an image IM0 on the medium 200.

[0025] The head unit 10 shown in FIG. 2 includes a print head 11, which is an inkjet head, and a head control unit 10c that controls the print head 11. As shown in FIGS. 1 and 3, the head unit 10 is mounted on a carriage 41 that is movable in a first scanning direction D1 and a second scanning direction D2 opposite to the first scanning direction D1, and moves back and forth along with the carriage 41. A drive unit 20 changes the relative position of the print head 11 with respect to the medium 200 in at least the first scanning direction D1 and the second scanning direction D2. Under the control of a print control unit 30, the head unit 10 moves in the first scanning direction D1 or the second scanning direction D2 while ejecting ink droplets 17 from each nozzle 14 of the nozzle array NL onto the medium 200 that is stopped on a platen 55, thereby forming a dot pattern of ink droplets 17 on the medium 200. The print control unit 30 and the host device 100 are examples of a control unit U1 that controls the forward scan S1 and the backward scan S2 shown in FIG. 4.

[0026] The print head 11 shown in FIGS. 2 and 3 includes color ink heads (11C, 11M, 11Y, and 11K) capable of ejecting color inks as the ink 16, and a treatment liquid head 11P capable of ejecting treatment liquid as the ink 16. Color inks are inks that contain a colorant such as a pigment as a dispersoid or solute in a liquid (e.g., water) that serves as a dispersion medium or solvent. The color ink heads shown in FIG. 3 include a C ink head 11C capable of ejecting C (cyan) ink, an M ink head 11M capable of ejecting M (magenta) ink, a Y ink head 11Y capable of ejecting Y (yellow) ink, and a K ink head 11K capable of ejecting K (black) ink. The color inks in this example are pigment inks containing pigments. The treatment liquid contains an aggregating agent that aggregates the pigments contained in the ink droplets 17. The treatment liquid can be, for example, a liquid containing a solvent such as water, a cationic compound serving as an aggregating agent, a surfactant, or the like. The cationic compound acts to aggregate the pigment and fix it to the surface 201 of the medium 200. Examples of the cationic compound that can be used include polyvalent metal salts, organic acids, cationic resins, and cationic surfactants. The treatment liquid head 11P is an example of a treatment liquid application unit that can apply a treatment liquid to the medium 200.

[0027] Each individual head (11C, 11M, 11Y, 11K, 11P) has a nozzle row NL in which multiple nozzles 14 are arranged in a nozzle arrangement direction intersecting the first scanning direction D1, for example, in the feed direction D3, and is equipped with a drive circuit 12, drive elements 13, etc. The multiple nozzles 14 included in each nozzle row NL may be arranged in a direction shifted from the feed direction D3 or may be arranged in a staggered pattern. Each nozzle 14 of the color ink head is capable of ejecting colored ink as ink droplets 17, and each nozzle 14 of the treatment liquid head 11P is capable of ejecting treatment liquid as droplets. The drive circuit 12 applies a voltage signal to the drive elements 13 in accordance with a drive signal input from the print control unit 30. The drive elements 13 may be piezoelectric elements that apply pressure to ink 16 in pressure chambers connected to the nozzles 14, or drive elements that use heat to generate bubbles in the pressure chambers to eject droplets such as ink droplets 17 from the nozzles 14. Of course, the droplet ejection method is not limited to these. For example, a method may be used in which ink is continuously ejected in droplet form from the nozzle using a strong electric field between the nozzle and an acceleration electrode located in front of the nozzle, and printing information signals are applied from a deflection electrode while the droplets are flying, thereby performing printing. The droplet ejection method may also be an electrostatic attraction method, a mechanical vibration method, or the like. The electrostatic attraction method is a method in which droplets are ejected in response to a print information signal without being deflected. The mechanical vibration method is a method in which pressure is applied to the ink using a small pump and the nozzle is mechanically vibrated using a quartz oscillator or the like, thereby forcibly ejecting droplets.

[0028] Ink 16 is supplied to the pressure chambers of the print head 11 by an ink supply unit 19. The ink supply unit 19 includes an ink tank, an ink supply path that supplies ink from the ink tank to the print head 11, and the like. The ink tank, ink supply path, and ink supply path to the nozzles 14 that eject ink of the same color are provided independently for each color. The ink 16 in the pressure chambers is ejected as droplets such as ink droplets 17 from the nozzles 14 toward the medium 200 by the drive elements 13, and dots of the droplets are formed on the medium 200. A print image IM0 consisting of a plurality of dots is formed on the medium 200.

[0029] The drive unit 20 includes a main scanning unit 40, a transport unit 50, and other components, and moves the head unit 10 and the medium 200 relative to one another under the control of the print control unit 30. In this example, the main scanning unit 40 includes a carriage 41, a guide shaft 42, a carriage motor (not shown), and other components, and moves the head unit 10 in the first scanning direction D1 and the second scanning direction D2 under the control of the print control unit 30. The medium 200 does not move in either the first scanning direction D1 or the second scanning direction D2. The guide shaft 42 is arranged with its longitudinal direction facing the first scanning direction D1 and supports the carriage 41 so that it can move in the first scanning direction D1 and the second scanning direction D2. The carriage motor (not shown) moves the carriage 41 back and forth along the guide shaft 42. Therefore, the main scanning unit 40 moves the print head 11 in the first scanning direction D1 and the second scanning direction D2 under the control of the print control unit 30. The transport unit 50 of this example includes a medium supply unit 51, a medium storage unit 52, multiple transport rollers 53, a platen 55, etc., and moves the medium 200 in the feed direction D3 under the control of the print control unit 30. The print head 11 does not move in the feed direction D3. The supply unit 51 rotatably supports a reel around which the medium 200 is wound in a roll, and sends the medium 200 out to the transport path. The storage unit 52 rotatably supports a reel that takes up the medium 200, and takes up the medium 200 from the transport path after printing is complete. The multiple transport rollers 53 include a drive roller that moves the medium 200 in the feed direction D3, a driven roller that rotates as the medium 200 moves, etc. The medium 200 supplied from the supply unit 51 to the transport path passes through the printing area on the platen 55 and is then taken up by the storage unit 52. When the printing unit 2 performs lateral printing, the carriage 41 carrying the print head 11 may move in the feed direction D3 and in the sub-scanning direction opposite thereto.

[0030] The print control unit 30 includes a communication I / F (interface) 31, a processor (CPU) 32 (Central Processing Unit), memory 33, a drive control unit 34, and the like, and controls the operation of the print unit 2. The communication I / F 31, CPU 32, memory 33, and drive control unit 34 are electrically connected, allowing information to be input and output to one another. The memory 33 includes, for example, a semiconductor memory called ROM (Read Only Memory), a semiconductor memory called RAM (Random Access Memory), and an NVM (Non-Volatile Memory). The NVM can be a non-volatile semiconductor memory such as a flash memory, a magnetic storage device such as a hard disk, or the like. The memory 33 is a storage medium that secures an area for storing programs run by the CPU 32, a working area for the programs, and the like. The print control unit 30 may be configured by a SoC (System on a Chip) or the like, and may include an ASIC (Application Specific Integrated Circuit).

[0031] The communication I / F 31 is connected to a communication I / F 117 of the host device 100. The communication I / Fs 31 and 117 perform bidirectional data communication. The CPU 32 executes a program stored in the memory 33 to control the head unit 10 and the drive unit 20 via the drive control unit 34. The drive control unit 34 includes a movement control signal generation circuit 35, an ejection control signal generation circuit 36, and a drive signal generation circuit 37, and controls the operation of the head unit 10 and the drive unit 20 under the control of the CPU 32. The movement control signal generation circuit 35 generates movement control signals that control the main scanning unit 40 and the transport unit 50 in accordance with instructions from the CPU 32, and outputs these signals to the drive unit 20. The ejection control signal generation circuit 36 ​​generates head control signals based on print data to select nozzles that eject ink 16, select the ejection amount, control the ejection timing, etc. in accordance with instructions from the CPU 32, and outputs these signals to the head control unit 10c of the head unit 10. The drive signal generation circuit 37 generates drive signals that drive the drive elements 13 of the print head 11 and outputs these signals to the drive circuit 12. The drive control unit 34 drives the drive elements 13 that correspond to each nozzle 14 based on the head control signal and the drive signal.

[0032] As described above, the print control unit 30 controls the main scan in which the head unit 10 moves in the first scanning direction D1 and the second scanning direction D2 while ejecting droplets such as ink droplets 17, and the sub-scan in which the medium 200 is fed a predetermined amount in the feed direction D3 between the main scans.

[0033] The host device 100 shown in FIGS. 1 and 2 includes a CPU 111, a ROM 112, a RAM 113, a storage device 114, a display device 115, an input device 116, a communication I / F 117, and the like. These elements 111 to 117 are electrically connected to each other, allowing them to input and output information to and from each other. The CPU 111, ROM 112, and RAM 113 are included in a host-side control unit 110. Examples of the host device 100 include computers such as personal computers (including tablet terminals), mobile phones such as smartphones, digital still cameras, and the like. The host device 100 may include the elements 111 to 117 in a single housing, or may be composed of multiple devices separated so as to be able to communicate with each other. The host device 100 and the printing unit 2 may be present in a common housing.

[0034] The storage device 114 stores an operating system, various driver programs including the print control program PR0, application programs, setting information, and the like. The CPU 111 loads information stored in the storage device 114 into the RAM 113 as needed and executes the loaded programs to perform various processes. The storage device 114 may be a nonvolatile semiconductor memory such as a flash memory, a magnetic storage device such as a hard disk, or the like. The computer-readable medium storing the print control program PR0 is not limited to a storage device internal to the host device 100, but may also be a recording medium RD external to the host device 100. The display device 115 is a human interface for displaying information and may be, for example, an LCD panel. The input device 116 is a human interface for inputting information and may be, for example, a pointing device, hard keys including a keyboard, a touch panel attached to the surface of a display panel, or the like. The host device 100 including the input device 116 is an example of the reception unit U2.

[0035] 4 shows a schematic diagram of an image IM0 being formed by bidirectional printing in four passes P1 to P4 on a medium 200 having an uneven surface 202. For clarity, ink droplets 17 that land on the upstream side 205 in the second scanning direction are hatched. In the first pass P1 and the third pass P3, a forward scan S1 is performed as a first scan, and ink droplets 17 are ejected while the print head 11 moves in the first scanning direction D1. It can also be said that the print head 11 ejects ink droplets 17 while the relative position of the print head 11 is changing in the first scanning direction D1. Because the ink droplets 17 ejected from the print head 11 have a component that moves in the first scanning direction D1, they tend to land on the upstream side 204 of the convex portions 203 on the surface 201 of the medium 200 in the first scanning direction. Note that if the medium 200 moves in the second scanning direction D2 without moving the print head 11, it can also be said that the relative position of the print head 11 changes in the first scanning direction D1. In this case, too, the ink droplets 17 ejected from the print head 11 tend to land on the upstream side 204 of the first scanning direction. Meanwhile, in the second pass P2 and the fourth pass P4, a backward scan S2 is performed as a second scan, and ink droplets 17 are ejected while the print head 11 is moving in the second scanning direction D2. It can also be said that the print head 11 ejects ink droplets 17 while the relative position of the print head 11 is changing in the second scanning direction D2. Because the ink droplets 17 ejected from the print head 11 contain a component that moves in the second scanning direction D2, they tend to land on the upstream side 205 of the convex portions 203 on the surface 201 of the medium 200 in the second scanning direction. Note that when the medium 200 moves in the first scanning direction D1 without moving the print head 11, it can also be said that the relative position of the print head 11 changes in the second scanning direction D2. In this case, too, the ink droplets 17 ejected from the print head 11 tend to land on the upstream side 205 of the second scanning direction.

[0036] Furthermore, if the coloring material of the ink droplets 17 penetrates into the medium 200, it becomes difficult to see the changes in the image IM0 depending on the direction in which the medium 200 is viewed. Therefore, it is preferable that the ink 16 that becomes the ink droplets 17 is a pigment ink that contains a pigment. This is because when the pigment ink lands on the medium 200, the pigment particles tend to remain on the surface 201 of the medium 200, making the changes in the image IM0 depending on the direction in which the medium 200 is viewed even more apparent.

[0037] Furthermore, if the affinity between the medium 200 and the ink droplets 17 is low, the ink droplets 17 that land on the protrusions 203 will be fixed at a position closer to the bottom 206 of the asperities 202 than their actual landing position. For example, if the dispersion medium of the ink 16 is water and the medium 200 is made of hydrophobic fibers such as polyester-based synthetic fibers or polyamide-based synthetic fibers, the affinity between the medium 200 and the ink droplets 17 can be said to be low. Therefore, it is preferable that a treatment liquid containing a flocculant be ejected from the treatment liquid head 11P onto the medium 200 before the pigment-containing ink droplets 17 are ejected from the print head 11. If the treatment liquid is present on the surface 201 of the medium 200, the pigment will be flocculated by the flocculant when the pigment ink lands on the medium 200, making it more likely to remain on the surface 201 of the medium 200. This makes the change in the image IM0 depending on the direction in which the medium 200 is viewed more clearly.

[0038] If the print head 11 does not eject ink droplets 17 during the backward scan S2 but ejects them during the forward scan S1, the ink droplets 17 tend to land unevenly on the upstream side 204 of the convex portion 203 in the first scanning direction, as shown in FIG. 5A. The area where the ink droplets 17 land as shown in FIG. 5A will be referred to as the forward ejection area A1 as an example of a first area. Conversely, if the print head 11 does not eject ink droplets 17 during the forward scan S1 but ejects them during the backward scan S2, the ink droplets 17 tend to land unevenly on the upstream side 205 of the convex portion 203 in the second scanning direction, as shown in FIG. 5B. The area where the ink droplets 17 land as shown in FIG. 5B will be referred to as the backward ejection area A2 as an example of a second area.

[0039] FIG. 5A shows a schematic example of how the appearance of the outward ejection region A1 changes depending on the direction in which the medium 200 onto which the ink droplets 17 land during the outward scan S1 is viewed. When an observer views the forward discharge region A1 from the upstream side in the first scanning direction D1, the color material of the ink droplets 17 that have landed on the upstream side 204 in the first scanning direction is easily visible, and therefore the image IM0 formed in the forward discharge region A1 appears dark. On the other hand, when an observer views the forward discharge region A1 from the downstream side in the first scanning direction D1, i.e., the upstream side in the second scanning direction D2, the color material of the ink droplets 17 that have landed on the upstream side 204 in the first scanning direction is difficult to see, and therefore the image IM0 formed in the forward discharge region A1 appears light. Therefore, the appearance changes depending on the direction from which the forward discharge region A1 is viewed in the first scanning direction D1.

[0040] FIG. 5B shows a schematic example of how the appearance of the backward discharge area A2 changes depending on the direction in which the medium 200 onto which the ink droplets 17 land during the backward scan S2 is viewed. When an observer views the backward discharge region A2 from the upstream side in the second scanning direction D2, the color material of the ink droplets 17 that have landed on the upstream side 205 in the second scanning direction is easily visible, so the image IM0 formed in the backward discharge region A2 appears dark. On the other hand, when an observer views the backward discharge region A2 from the downstream side in the second scanning direction D2, i.e., the upstream side in the first scanning direction D1, the color material of the ink droplets 17 that have landed on the upstream side 205 in the second scanning direction is difficult to see, so the image IM0 formed in the backward discharge region A2 appears light. Therefore, the appearance changes depending on the direction from which the backward discharge region A2 is viewed in the second scanning direction D2, i.e., the first scanning direction D1.

[0041] Here, it is assumed that the printing area where image IM0 is formed on medium 200 is divided into two areas: an outward path discharge area A1 and a backward path discharge area A2. In this case, when an observer views medium 200 from the upstream side in first scanning direction D1, outward path discharge area A1 appears dark and backward path discharge area A2 appears light. On the other hand, when an observer views medium 200 from the upstream side in second scanning direction D2, outward path discharge area A1 appears light and backward path discharge area A2 appears dark. Therefore, printed image IM0 on medium 200 changes so that a positive image and a negative image are interchanged depending on the direction from which medium 200 is viewed. However, if the positive and negative images are simply swapped, the phenomenon may be difficult to discern depending on the image, such as the image remaining the same regardless of the viewing direction. Furthermore, to print an image IM0 on the medium 200 in which the positive and negative images swap depending on the viewing direction of the medium 200, control is required to clearly separate the outgoing path discharge area A1 and the returning path discharge area A2. If the landing positions of the ink droplets 17 deviate between the outgoing path and the returning path, a noticeable degradation in image quality, such as a faint slit, such as a white slit, may occur at the boundary between the outgoing path discharge area A1 and the returning path discharge area A2.

[0042] 6 and 8, the print area A0 where image IM0 is formed on medium 200 is divided into an outward discharge area A1, a backward discharge area A2, and a reciprocating discharge area A3 to reduce the above-mentioned possibility. The reciprocating discharge area A3 is an example of a third area where image IM0 is formed during both the outward scan S1 and the backward scan S2.

[0043] FIG. 6 is a diagram showing an example of division of the print area A0 and a first example of how the image IM0 appears depending on the direction in which the medium 200 is viewed. As shown in FIG. 6, the printing area A0 includes an outgoing path discharge area A1, a backward path discharge area A2, and a reciprocating path discharge area A3. The outgoing path discharge area A1 is an area where ink droplets 17 do not land during the backward scan S2 and where image IM0 is formed during the outgoing scan S1. The backward path discharge area A2 is an area where ink droplets 17 do not land during the outgoing scan S1 and where image IM0 is formed during the backward scan S2. The reciprocating path discharge area A3 is an area where image IM0 is formed during both the outgoing scan S1 and the backward scan S2. In this specific example, the control unit U1 divides the printing area A0 into the outgoing path discharge area A1, the backward path discharge area A2, and the reciprocating path discharge area A3 so that the reciprocating path discharge area A3 is adjacent to both the outgoing path discharge area A1 and the backward path discharge area A2. In other words, the control unit U1 divides the printing area A0 so that the outgoing path discharge area A1 and the backward path discharge area A2 are not adjacent to each other.

[0044] To achieve printing of the three regions (A1 to A3), the control unit U1 divides the image data representing the input image into first image data DA1, second image data DA2, and third image data DA3 (see FIG. 9). When changes in the appearance of the print image IM0 are expressed by shading, the input image may be a plain image. For example, if the input image is a plain image of 100% K, the image data representing the input image will be data indicating a 100% amount of K ink per unit area. If the size of the ink droplets 17 ejected from the print head 11 is constant, image data representing an input image of 100% K can be said to be data in which K ink droplets 17 are ejected to all pixels. The amount of ink ejected per unit area of ​​the input image (referred to as Duty (%)) may be less than 100%. The amount of ink ejected per unit area (Duty (%)) corresponds to the number of ink droplets 17 ejected per 100 pixels. When the size of the ink droplets 17 ejected from the print head 11 varies, the ink ejection duty per unit area corresponds to the number of ink droplets 17 ejected per 100 pixels converted into the maximum size. Of course, the color of the solid input image may be C, M, or Y, or may be a mixture of two or more colors. When the input image is a solid image, the first image data DA1, second image data DA2, and third image data DA3 are data representing a solid image of the same color.

[0045] FIG. 7A shows an example of the amount of ink ejected per unit area for each pass when image data representing a 100% monochrome input image is allocated to three areas (A1 to A3). 7A, the amount of ink ejected per unit area of ​​the forward ejection region A1 is 50% during the forward scan S1 of the first pass and 50% during the forward scan S1 of the third pass, totaling 100%. The amount of ink ejected per unit area of ​​the backward ejection region A2 is 50% during the backward scan S2 of the second pass and 50% during the backward scan S2 of the fourth pass, totaling 100%. The amount of ink ejected per unit area of ​​the reciprocating ejection region A3 is 25% during the forward scan S1 of the first pass, 25% during the backward scan S2 of the second pass, 25% during the forward scan S1 of the third pass, and 25% during the backward scan S2 of the fourth pass, totaling 100%.

[0046] The bottom part of Figure 6 shows a schematic diagram of how image IM0 appears when printed on medium 200 using the amount of ink ejected per unit area of ​​Figure 7A when the dispersion medium of ink droplets 17 is water and medium 200 is a hydrophobic fabric. When an observer views the printing area A0 in Figure 6 from the upstream side in the first scanning direction D1, the outgoing path discharged area A1 appears dark, the backward path discharged area A2 appears light, and the reciprocating path discharged area A3 appears lighter than the backward path discharged area A2. When an observer views the printing area A0 in Figure 6 from the upstream side in the second scanning direction D2, the backward path discharged area A2 appears dark, the outgoing path discharged area A1 appears light, and the reciprocating path discharged area A3 appears lighter than the outgoing path discharged area A1. In any case, the appearance of the reciprocating path discharged area A3 changes little depending on the viewing direction, and various changes appear in the image IM0 depending on the viewing direction of the medium 200.

[0047] Although the amount of ink ejected per unit area of ​​the three regions (A1 to A3) is the same, the reason why the reciprocating ejection region A3 appears to be the thinnest is unclear, but it is presumed as follows. As shown in FIG. 4 , ink droplets 17 that land on the convex portions 203 of the medium 200 are fixed at positions closer to the bottoms 206 of the convex portions 202 than the actual landing positions. Here, the number of ink droplets 17 that land on the upstream sides 204 of the convex portions 203 in the first scanning direction in the reciprocating discharge region A3 is half the number of ink droplets 17 that land on the upstream sides 204 of the convex portions 203 in the first scanning direction in the forward discharge region A1. Furthermore, the number of ink droplets 17 that land on the upstream sides 205 of the convex portions 203 in the second scanning direction in the reciprocating discharge region A3 is half the number of ink droplets 17 that land on the upstream sides 205 of the convex portions 203 in the second scanning direction in the backward discharge region A2. From these facts, it is presumed that a relatively small number of ink droplets 17 that land on the upstream sides 204 and 205 in the first scanning direction in the reciprocating discharge region A3 are hidden by the bottoms 206, and that the reciprocating discharge region A3 is the thinnest.

[0048] Here, when the difference in density between the backward discharged region A2 and the forward discharged region A3 is reduced when viewed from the upstream side in the first scanning direction D1, and when the difference in density between the forward discharged region A1 and the forward discharged region A3 is reduced when viewed from the upstream side in the second scanning direction D2, the quality of the printed image IM0 improves. An example of the amount of ink discharged per unit area for this purpose is shown in Figure 7B.

[0049] In Fig. 7B, the ink ejection amount per unit area of ​​the forward ejection region A1 and the backward ejection region A2 is the same as that shown in Fig. 7A. On the other hand, the ink ejection amount per unit area of ​​the reciprocating ejection region A3 is 30% in the forward scan S1 of the first pass, 30% in the backward scan S2 of the second pass, 30% in the forward scan S1 of the third pass, and 30% in the backward scan S2 of the fourth pass, for a total of 120%. Here, the amount of ink 16 per unit area ejected as ink droplets 17 from the print head 11 in the forward ejection region A1 is defined as Duty 1. The amount of ink 16 per unit area ejected as ink droplets 17 from the print head 11 in the backward ejection region A2 is defined as Duty 2. The amount of ink 16 per unit area ejected as ink droplets 17 from the print head 11 in the reciprocating ejection region A3 is defined as Duty 3. Duty 3 is the amount of ink ejected per unit area from the reciprocating ejection region A3, and is greater than Duty 1 and Duty 2, the amounts of ink ejected per unit area from the forward ejection region A1 and the backward ejection region A2, respectively.

[0050] Furthermore, the amount of ink 16 per unit area ejected as ink droplets 17 from the print head 11 during forward scan S1 in reciprocating discharge region A3 is 30 + 30 = 60%, which is greater than 0.5 × Duty 1, less than Duty 1, greater than 0.5 × Duty 2, and less than Duty 2. The amount of ink 16 per unit area ejected as ink droplets 17 from the print head 11 during backward scan S2 in reciprocating discharge region A3 is 30 + 30 = 60%, which is greater than 0.5 × Duty 1, less than Duty 1, greater than 0.5 × Duty 2, and less than Duty 2.

[0051] Figure 8 shows a schematic example of the division of the print area A0 and a second example of how the image IM0 appears depending on the viewing direction of the medium 200. The bottom part of Figure 8 shows a schematic diagram of how the image IM0 appears when printed on the medium 200 with the amount of ink ejected per unit area of ​​Figure 7B when the dispersion medium of the ink droplets 17 is water and the medium 200 is a hydrophobic fabric. When an observer views the printed area A0 in Figure 8 from the upstream side in the first scanning direction D1, the outgoing path discharged area A1 appears dark and the backward path discharged area A2 appears light, the difference in density between the reciprocating path discharged area A3 and the backward path discharged area A2 is small, and the backward path discharged area A2 blends in with the reciprocating path discharged area A3. When an observer views the printed area A0 in Figure 8 from the upstream side in the second scanning direction D2, the backward path discharged area A2 appears dark and the outgoing path discharged area A1 appears light, the difference in density between the reciprocating path discharged area A3 and the outgoing path discharged area A1 is small, and the forward path discharged area A1 blends in with the reciprocating path discharged area A3.

[0052] 7B and 8, completely different patterns appear depending on the viewing direction of the medium 200. Therefore, by setting Duty3 > Duty1 and Duty3 > Duty2, the difference in density between the outward path discharge area A1 or the return path discharge area A2, whichever appears lighter, and the reciprocating discharge area A3 is reduced, improving the quality of image IM0, which changes depending on the viewing direction of the medium 200. In the reciprocating discharge area A3, by setting the amount of ink discharged per unit area during the forward scan to be greater than 0.5 x Duty1, less than Duty1, greater than 0.5 x Duty2, and less than Duty2, and by setting the amount of ink discharged per unit area during the backward scan to be greater than 0.5 x Duty1, less than Duty1, greater than 0.5 x Duty2, and less than Duty2, the difference in density between the forward discharge area A1 or the backward discharge area A2, whichever appears lighter, and the reciprocating discharge area A3 is reduced, improving the quality of the image IM0, which changes depending on the direction in which the medium 200 is viewed.

[0053] (3) Specific examples of printing device processing: 9 and 10 schematically illustrate a print control process for controlling printing of the image IM0 shown in FIG. 8 on the medium 200. The host device 100, which serves as the control unit U1 shown in FIGS. 1 and 2, starts the print control process upon receiving an instruction to print on the medium 200. In the example shown in FIGS. 9 and 10, the host device 100 performs steps S102 to S106, and the printing unit 2 performs steps S108 to S122. Here, steps S104 and S118 correspond to the first process ST1, steps S106 and S120 correspond to the second process ST2, and steps S104, S106, S118, and S120 correspond to the third process ST3. Hereinafter, the word "step" may be omitted, and the step symbol may be shown in parentheses.

[0054] When the print control process starts, the host device 100 performs a process of dividing the input image corresponding to the print area A0 into three areas (A1 to A3) (S102). For example, the host device 100 displays the input image on the display device 115 and receives an operation to divide the image into three areas (A1 to A3) via the input device 116. The host device 100 may divide the input image into three areas (A1 to A3) so that the reciprocating discharge area A3 is adjacent to both the forward discharge area A1 and the backward discharge area A2. Here, of the image data representing the input image, data corresponding to the forward discharge area A1 is defined as first image data DA1, data corresponding to the backward discharge area A2 is defined as second image data DA2, and data corresponding to the reciprocating discharge area A3 is defined as third image data DA3. The process of S102 can also be said to be a process of dividing the image data representing the input image into first image data DA1, second image data DA2, and third image data DA3.

[0055] Next, the host device 100 allocates 100% of the first image data DA1 corresponding to the outgoing path discharge area A1 and 60% of the third image data DA3 corresponding to the reciprocating path discharge area A3 to the outgoing path data in the print data (S104). In the example shown in Fig. 7B, 50% of the ink ejection volume per unit area of ​​the first image data DA1 and 30% of the ink ejection volume per unit area of ​​the third image data DA3 are allocated to the outgoing path data of the first pass, and 50% of the ink ejection volume per unit area of ​​the first image data DA1 and 30% of the ink ejection volume per unit area of ​​the third image data DA3 are allocated to the outgoing path data of the third pass. The host device 100 also allocates 100% of the second image data DA2 corresponding to the return pass discharge area A2 and 60% of the third image data DA3 corresponding to the reciprocating discharge area A3 to the return pass data in the print data (S106). In the example shown in Fig. 7B, 50% of the ink ejection volume per unit area of ​​the second image data DA2 and 30% of the ink ejection volume per unit area of ​​the third image data DA3 are allocated to the return pass data for the second pass, and 50% of the ink ejection volume per unit area of ​​the second image data DA2 and 30% of the ink ejection volume per unit area of ​​the third image data DA3 are allocated to the return pass data for the fourth pass.

[0056] After processing S106, the host device 100 generates print data by adding treatment liquid application data for applying treatment liquid to the medium 200 before the forward pass data and backward pass data described above, and sends this print data to the printing unit 2. The treatment liquid application data is data that instructs the treatment liquid head 11P to eject treatment liquid on the forward pass and backward pass before passes P1 to P4, which cause the color ink heads (11C, 11M, 11Y, 11K) to eject ink droplets 17. When the printing unit 2 receives the print data from the host device 100, the print control unit 30 takes charge of the processes from S108 onwards in accordance with the print data.

[0057] In S108, the printing unit 2 uniformly ejects treatment liquid from the treatment liquid head 11P while the print head 11 is moving in the first scanning direction D1 in accordance with the treatment liquid deposition data, so that the amount of ink ejected per unit area is, for example, 50%. After the processing of S108, the printing unit 2 uniformly ejects treatment liquid from the treatment liquid head 11P while the print head 11 is moving in the second scanning direction D2 (S110), so that the amount of ink ejected per unit area is, for example, 50%. The reason why treatment liquid is ejected from the treatment liquid head 11P on the forward pass in S108 and the return pass in S110 is to apply the same amount of treatment liquid to both the upstream side 204 in the first scanning direction and the upstream side 205 in the second scanning direction of the convex portion 203 shown in FIG. In this manner, the control unit U1 causes the print head 11 to eject ink droplets 17 after the treatment liquid has been applied to the medium 200 by the treatment liquid head 11P.

[0058] 10, the printing unit 2 prints on the forward path discharge area A1 and the reciprocating discharge area A3 according to the forward path data, and prints on the reverse path discharge area A2 and the reciprocating discharge area A3 according to the reverse path data. First, in S112, the printing unit 2 assigns 1 to a variable n, which indicates the number of the pass. In S114, the printing unit 2 determines whether the variable n indicates that the final pass has been passed. In the example shown in FIG. 7B, the number of passes is 4, so if the variable n is greater than 4, the condition is met, and in this case, the printing unit 2 ends the print control process. If the variable n indicates that the final pass is not yet reached, the printing unit 2 determines whether the variable n indicates an odd-numbered pass (S116). In the example shown in FIG. 7B, the condition is met if the variable n is 1 or 3, and in this case, the printing unit 2 ejects colored ink droplets 17 into the forward pass discharge area A1 and the reciprocating discharge area A3 according to the forward pass data (S118). As a result, in the forward scan S1 of the first and third passes, ink droplets 17 ejected from the print head 11 based on 100% of the first image data DA1 land on the forward pass discharge area A1, and ink droplets 17 ejected from the print head 11 based on 60% of the third image data DA3 land on the reciprocating discharge area A3. 7B, the condition is met when the variable n is 2 or 4, in which case the printing unit 2 ejects colored ink droplets 17 to the backward ejection area A2 and the reciprocating ejection area A3 in accordance with the backward data (S120). As a result, in the forward scan S1 of the second and fourth passes, the ink droplets 17 ejected from the print head 11 based on 100% of the second image data DA2 land on the backward ejection area A2, and the ink droplets 17 ejected from the print head 11 based on 60% of the third image data DA3 land on the reciprocating ejection area A3.

[0059] After the process of S118 or S120, the printing unit 2 adds 1 to the variable n (S122) and returns the process to S114. As described above, the control unit U1 performs first control (S104, S118) to form an image IM0 in the forward discharge area A1 by causing the print head 11 to discharge ink droplets 17 during the forward scan S1 based on the first image data DA1. The control unit U1 also performs second control (S106, S120) to form an image IM0 in the backward discharge area A2 by causing the print head 11 to discharge ink droplets 17 during the backward scan S2 based on the second image data DA2. The control unit U1 also performs third control (S104, S106, S118, S120) to form an image IM0 in the reciprocating discharge area A3 by causing the print head 11 to discharge ink droplets 17 during both the forward scan S1 and the backward scan S2 based on the third image data DA3.

[0060] As described above, the print area A0 includes the forward discharge area A1, the backward discharge area A2, and the reciprocating discharge area A3, which has little change in appearance depending on the viewing direction, so that the image IM0 changes in a variety of ways depending on the viewing direction of the medium 200. Therefore, this specific example can print an image IM0 that changes in a variety of ways depending on the viewing direction of the medium 200, which has the irregularities 202 on the surface 201. Furthermore, because the reciprocating discharge area A3 is located between the outgoing discharge area A1, which appears dark when viewed from the upstream side in the first scanning direction D1, and the returning discharge area A2, which appears dark when viewed from the upstream side in the second scanning direction D2, the appearance changes smoothly when the direction in which the medium 200 is viewed changes. Therefore, the image IM0, which changes depending on the direction in which the medium 200 is viewed, is of high quality. In tests, when the outward path discharge area A1, the backward path discharge area A2, and the reciprocating discharge area A3 were all solid images of the same color, a clear change in density was observed depending on the direction in which the medium 200 was viewed. Here, by setting Duty 3 > Duty 1 and Duty 3 > Duty 2 as shown in Figures 7B and 8, the difference in density between the outward path discharge area A1 or the backward path discharge area A2, whichever appeared lighter, and the reciprocating discharge area A3, was reduced, and a high-quality image IM0 was obtained that changed depending on the direction in which the medium 200 was viewed. More specifically, in the reciprocating discharge area A3, the amount of ink discharged per unit area during the forward scan was set to be greater than 0.5 x Duty1, less than Duty1, greater than 0.5 x Duty2, and less than Duty2, and the amount of ink discharged per unit area during the return scan was set to be greater than 0.5 x Duty1, less than Duty1, greater than 0.5 x Duty2, and less than Duty2, thereby obtaining a high-quality image IM0 that changes depending on the direction in which the medium 200 is viewed.

[0061] (4) Variation: The present invention can be embodied in various modifications. For example, the printing unit 2 may be a line-type inkjet printer equipped with a print head having a nozzle row across the entire width of the medium 200. In this case, the first scanning direction D1 may be the normal transport direction of the medium 200, and the second scanning direction D2 may be the movement direction of the medium 200 when the medium 200 is fed back. The number of passes for forming the image IM0 is not limited to four passes, but may be two passes, or six passes or more. The medium is not limited to a long medium, but may be cut medium. The medium is also not limited to fabric, but may be embossed paper or the like having a textured surface. Although a fabric made of many fibers has been shown as an example of a medium having projections and recesses, a woven fabric in which warp and weft threads intersect at predetermined intervals may also be used. In a woven fabric, the warp or weft threads that function as projections appear on the surface at predetermined intervals, so the effects of the present invention can be stably achieved regardless of the printing position on the medium. The colors of the ink droplets 17 are not limited to C, M, Y, and K, but may also be orange, green, light cyan with a lower density than C, light magenta with a lower density than M, dark yellow with a higher density than Y, light black with a lower density than K, etc. Of course, the present invention is also applicable to cases where the colors of the ink droplets 17 do not include some of C, M, Y, and K. The images in each of the three areas (A1 to A3) are not limited to plain images, but may also be images with patterns. The entity that performs the above-described processing is not limited to a CPU, but may be an electronic component other than a CPU, such as an ASIC (Application Specific Integrated Circuit), etc. Of course, multiple CPUs may work together to perform the above-described processing, or a CPU and another electronic component (for example, an ASIC) may work together to perform the above-described processing. The above-described processes can be changed as needed, such as by changing the order of the processes, etc. For example, in the print control process of FIGS.

[0062] In the example shown in Fig. 7B, Duty3 of the ink ejection amount per unit area of ​​the reciprocating ejection region A3 is set to 120%, that is, 60% for the forward movement and 60% for the return movement, but the optimal Duty3 of the ink ejection amount per unit area may vary depending on the combination of the ink 16 and the medium 200. Therefore, a process for setting Duty3 of the ink ejection amount per unit area may be performed, as shown in Fig. 11. Fig. 11 shows a schematic example of the process for setting Duty 3, the amount of ink ejected per unit area. Fig. 11 also shows an example of a UI (user interface) screen 500 displayed on the display device 115 shown in Figs. 1 and 2. When the host device 100 shown in Figs. 1 and 2 receives an instruction to set Duty 3, the amount of ink ejected per unit area, it starts the setting process shown in Fig. 11.

[0063] When the setting process starts, the host device 100 displays a UI screen 500 on the display device 115 (S202). The UI screen 500 shown in FIG. 11 includes Duty1, the amount of ink ejected per unit area during a forward scan in the forward ejection region A1, Duty2, the amount of ink ejected per unit area during a backward scan in the backward ejection region A2, and an input field 501. The input field 501 allows an operation to input, via the input device 116, at least one of the amount of ink ejected per unit area during a forward scan in the reciprocating ejection region A3 and the amount of ink ejected per unit area during a backward scan in the reciprocating ejection region A3. The Duty3, the amount of ink ejected per unit area, is the sum of the amounts of ink ejected per unit area during a forward scan and a backward scan. The host device 100 may accept an input to the input field 501 via the input device 116 so that the amount of ink ejected per unit area during a forward scan and a backward scan is the same. 11, the ink ejection amount per unit area Duty3 of the reciprocating ejection area A3 is set to 110%, that is, 55% for the forward path and 55% for the return path. The host device 100 including the input device 116 is an example of a receiving unit U2 that receives the setting of the ink ejection amount per unit area Duty3, which is the amount of ink 16 per unit area required to form the image IM0 in the reciprocating ejection area A3.

[0064] When the host device 100 receives input of the ink ejection amount per unit area in the input field 501, it sets the received ink ejection amount per unit area as the ink ejection amount per unit area of ​​the reciprocating ejection area A3 (S204), and ends the setting process. Thereafter, the host device 100 applies the ink ejection amount per unit area Duty3 to the reciprocating ejection area A3 in the print control process shown in Figures 9 and 10, thereby causing the printing unit 2 to print the image IM0. The print control process that is performed after the setting process shown in Figure 11 is performed will be described below with reference to Figures 9 and 10.

[0065] First, the host device 100 performs a process of dividing the input image into three regions (A1 to A3) (S102). Next, the host device 100 allocates 100% of the first image data DA1 corresponding to the forward path discharge region A1 and a duty factor 3 / 2 (%) of the third image data DA3 corresponding to the reciprocating discharge region A3 to the forward path data in the print data (S104). Furthermore, the host device 100 allocates 100% of the second image data DA2 corresponding to the reverse path discharge region A2 and a duty factor 3 / 2 (%) of the third image data DA3 corresponding to the reciprocating discharge region A3 to the reverse path data in the print data (S106). After processing S106, the host device 100 adds treatment liquid application data before the forward path data and the reverse path data to generate print data, and sends the print data to the printing unit 2.

[0066] When the printing unit 2 receives the print data, it ejects treatment liquid on the forward pass (S108) and on the backward pass (S110). Thereafter, the printing unit 2 forms image IM0 in the forward pass discharge area A1 during the forward scan S1, forms image IM0 in the backward pass discharge area A2 during the backward scan S2, and forms image IM0 in the reciprocating discharge area A3 during both the forward scan S1 and the backward scan S2 (S112 to S122 in FIG. 10). The print control unit 30 causes the print head 11 to eject ink droplets 17 based on the third image data DA3 so that the amount of ink 16 per unit area required to form image IM0 in the reciprocating discharge area A3 is Duty3. As a result, image IM0 corresponding to Duty3 is formed in the reciprocating discharge area A3. In the example shown in FIG. 11, the density of the reciprocating discharge area A3 compared to the outgoing path discharge area A1 and the returning path discharge area A2 can be adjusted depending on the type of medium 200, etc.

[0067] As illustrated in Fig. 12, the print image IM0 may be formed by changing the color according to the regions (A1 to A3). Fig. 12 schematically illustrates how the image IM0 appears depending on the direction from which the medium 200 is viewed when the color is changed according to the regions (A1 to A3). The image IM0 shown in FIG. 12 can be formed by dividing the input image so that the color changes according to the regions (A1 to A3) in the division process of S102 shown in FIG. 9. In S102, the host device 100 displays, for example, a color input image on the display device 115 and receives an operation to divide the image into three regions (A1 to A3) according to color via the input device 116. As an example, assume that the color of the forward discharge region A1 is C, the color of the backward discharge region A2 is M, and the color of the reciprocating discharge region A3 is a mixture of C and M. In this case, the first image data DA1 is data representing a solid image in C as a first color, and the second image data DA2 is data representing a solid image in M ​​as a second color different from the first color. The third image data DA3 is data representing a solid image in C and M as a mixture of C and M.

[0068] 9 and 10 is performed, a printed image IM0 such as that shown in the lower part of Fig. 12 is formed. When the medium 200 having the image IM0 is viewed from the upstream side in the first scanning direction D1, the outward discharged region A1 of C appears darker than the backward discharged region A2 of M, and the reciprocating discharged region A3 of a mixed color of C and M is also visible. When the medium 200 is viewed from the upstream side in the second scanning direction D2, the backward discharged region A2 of M appears darker than the outward discharged region A1 of C, and the reciprocating discharged region A3 of a mixed color of C and M is also visible. In the example shown in Fig. 12, a color change appears depending on the direction in which the medium 200 is viewed, and therefore, a color change depending on the direction in which the medium 200 is viewed can be produced in the image IM0.

[0069] (5) Conclusion: As explained above, according to the present invention, it is possible to provide a configuration in which an image that produces various changes depending on the viewing direction on a medium having an uneven surface can be printed by various aspects. Of course, even in an aspect consisting only of the elements according to the independent claims, the basic functions and effects described above can be obtained. Furthermore, it is possible to implement configurations in which the components disclosed in the above examples are substituted with each other or the combination is changed, or configurations in which the components disclosed in the publicly known techniques and the above examples are substituted with each other or the combination is changed, etc. The present invention also includes these configurations. [Explanation of symbols]

[0070] 1...printing device, 2...printing section, 10...head unit, 11...print head, 11P...treatment liquid head, 14...nozzle, 16...ink, 17...ink droplet, 20...drive section, 30...print control section, 40...main scanning section, 41...carriage, 50...convex section, 100...host device, 110...host side control section, 115...display device, 116...input device, 200...medium, 201...surface, 202...unevenness, 203...convex section, 204...upstream side in first scanning direction, 205...second Upstream side of scanning direction, 206...bottom, 500...UI screen, 501...input field, A0...printing area, A1...forward ejection area, A2...return ejection area, A3...reciprocating ejection area, D1...first scanning direction, D2...second scanning direction, D3...feed direction, DA1...first image data, DA2...second image data, DA3...third image data, IM0...image, S1...forward scanning, S2...return scanning, ST1...first process, ST2...second process, ST3...third process, U1...control unit, U2...reception unit.

Claims

1. a print head capable of ejecting ink droplets onto a medium having an uneven surface; a drive unit that changes the relative position of the print head with respect to the medium at least in a first scanning direction and a second scanning direction opposite to the first scanning direction; a control unit that controls a first scan in which the ink droplets are ejected from the print head while the relative position of the print head is changing in the first scan direction, and a second scan in which the ink droplets are ejected from the print head while the relative position of the print head is changing in the second scan direction, a printing area in which an image is formed on the medium includes a first area in which the image is formed in the first scan, a second area in which the image is formed in the second scan, and a third area in which the image is formed in both the first scan and the second scan; The control unit a first control for forming the image in the first area by causing the print head to eject the ink droplets during the first scan based on first image data corresponding to the first area; second control for forming the image in the second area by causing the print head to eject the ink droplets during the second scan based on second image data corresponding to the second area; a third control for forming the image in the third area by causing the print head to eject the ink droplets in both the first scan and the second scan based on third image data corresponding to the third area; and A printing device that performs the above.

2. 2. The printing apparatus according to claim 1, wherein the ink that forms the ink droplets is a pigment ink that contains a pigment.

3. 3. The printing device according to claim 1, wherein the control unit divides the printing area into the first area, the second area, and the third area so that the third area is adjacent to both the first area and the second area.

4. 2. The printing device according to claim 1, wherein the amount of ink per unit area required to form the image in the third region is greater than the amount of ink per unit area required to form the image in the first region and the second region.

5. If the amount of ink ejected per unit area as ink droplets from the print head in the first region is defined as Duty 1, and the amount of ink ejected per unit area as ink droplets from the print head in the second region is defined as Duty 2, then: the amount of ink per unit area ejected as ink droplets from the print head during the first scan in the third region is greater than 0.5×Duty1, less than Duty1, greater than 0.5×Duty2, and less than Duty2; 2. The printing device according to claim 1, wherein the amount of ink per unit area ejected as ink droplets from the print head during the second scan in the third region is greater than 0.5 x Duty 1, less than Duty 1, greater than 0.5 x Duty 2, and less than Duty 2.

6. a receiving unit configured to receive a setting of a Duty3 amount of ink ejected per unit area, which is an amount of ink required per unit area to form the image in the third region; The printing device described in claim 4 or claim 5, wherein the control unit performs the third control to form the image in the third area by causing the print head to eject the ink droplets based on the third image data so that the amount of ink required per unit area to form the image in the third area is the ink ejection amount per unit area Duty 3.

7. 3. The printing device according to claim 1, wherein the first image data, the second image data, and the third image data are data representing solid images of the same color.

8. A printing device as described in claim 1 or claim 2, wherein the first image data is data representing a solid image of a first color, the second image data is data representing a solid image of a second color different from the first color, and the third image data is data representing a solid image of a mixed color of the first color and the second color.

9. the ink that becomes the ink droplets is a pigment ink containing a pigment, the printing device further includes a treatment liquid application unit that applies a treatment liquid containing an aggregating agent that aggregates the pigment contained in the ink droplets to the medium; The printing device according to claim 1 , wherein the control unit causes the print head to eject the ink droplets after the treatment liquid has been applied to the medium by the treatment liquid application unit.

10. A printing method for a print head capable of ejecting ink droplets onto a medium having an uneven surface, the method comprising: changing a relative position of the print head with respect to the medium at least in a first scanning direction and a second scanning direction opposite to the first scanning direction; and performing a first scan in which the ink droplets are ejected from the print head while the relative position of the print head is changing in the first scanning direction; and a second scan in which the ink droplets are ejected from the print head while the relative position of the print head is changing in the second scanning direction, a printing area in which an image is formed on the medium includes a first area in which the image is formed in the first scan, a second area in which the image is formed in the second scan, and a third area in which the image is formed in both the first scan and the second scan; The printing method includes: a first step of forming the image in the first area by ejecting the ink droplets from the print head during the first scan based on first image data corresponding to the first area; a second step of forming the image in the second region by ejecting the ink droplets from the print head during the second scan based on second image data corresponding to the second region; a third step of forming the image in the third area by ejecting the ink droplets from the print head in both the first scan and the second scan based on third image data corresponding to the third area; A printing method including:

Images