Printing method, and printer

Abstract

To suppress bleeding of a transfer image.SOLUTION: A printing method includes an image formation step of performing first processing of discharging color ink from a first inkjet head, and thereby forming an image onto a transfer medium, and a substrate formation step of performing second processing including processing of discharging substrate ink to the transfer medium from a second inkjet head, and thereby superposing the substrate ink on the image, wherein when a region where an adhesive is supplied to the transfer medium at the same timing in an adhesive imparting step is set as a treatment unit region, the substrate formation step delays the second processing until the second processing is completed from the middle of the second processing for the treatment unit region.SELECTED DRAWING: Figure 6

Description

Technical Field

[0001] The present invention relates to a printing method for printing on a transfer medium and a printing apparatus.

Background Art

[0002] As disclosed in Patent Document 1, a printing method for fabric using a transfer sheet as a transfer medium is known. This printing method includes a step of printing first image data on a transfer sheet using black toner and color toner, a step of producing second image data by processing all colors in the printing range of the first image data into black, a step of printing the second image data on the transfer sheet on which the first image data has been printed using white toner instead of black toner, a step of applying an adhesive to the uppermost layer of the printed transfer sheet, a step of pressing the transfer sheet coated with the adhesive against the fabric while heating, and a step of peeling the base material of the transfer sheet.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] When forming an image to be transferred onto a fabric as a transfer medium using an inkjet printer, it is conceivable to attach a powdery hot melt adhesive to the image formed by the ink landing on the transfer sheet and transfer the image onto the fabric. For example, an image of colored ink is formed on a transfer sheet, white ink is overlaid on the image, a powdery hot melt adhesive is attached to the white ink, and the heated hot melt adhesive is attached to the fabric, whereby the image on the transfer sheet can be transferred onto the fabric. When the white ink lands on the image on the transfer sheet, it gradually dries. In the printed area on the transfer sheet, the degree of dryness of the white ink is lower the later the white ink lands. For this reason, when the transfer sheet is tilted for applying a powdered hot melt adhesive or the like, the white ink with a lower degree of dryness may drip downward. When the white ink drips downward, bleeding occurs in the transferred image.

Means for Solving the Problem

[0005] The printing method of the present invention is a printing method for performing printing on the transfer medium, including an adhesive application step of attaching an adhesive to an undercoat ink overlaid on an image formed on the transfer medium, and a transfer step of transferring the image to the transfer medium by attaching the adhesive to the transfer medium. An image forming step of performing a first process of forming the image on the transfer medium by ejecting a colored ink from a first inkjet head; A base forming step of performing a second process including a process of overlaying the undercoat ink on the image by ejecting the undercoat ink from a second inkjet head onto the transfer medium, Taking the area where the adhesive is supplied at the same timing in the adhesive application step with respect to the transfer medium as a processing unit area, The base forming step has an aspect of delaying the second process from the middle of the second process for the processing unit area until the second process is completed.

[0006] Further, the printing apparatus of the present invention is a printing apparatus for performing printing on the transfer medium, including an adhesive application step of attaching an adhesive to an undercoat ink overlaid on an image formed on the transfer medium, and a transfer step of transferring the image to the transfer medium by attaching the adhesive to the transfer medium. A first inkjet head for ejecting a colored ink; A second inkjet head for ejecting the undercoat ink; A driving unit that relatively moves the second inkjet head in a first direction with respect to the transfer medium; A control unit that controls ejection of the colored ink from the first inkjet head, ejection of the base ink from the second inkjet head, and the driving unit, and includes: The control unit: Controls a first process of forming the image on the transfer medium by ejecting the colored ink from the first inkjet head; Controls a second process including a process of overlaying the base ink on the image by ejecting the base ink from the second inkjet head with respect to the transfer medium; Regarding the transfer medium, a region where the adhesive is supplied at the same timing in the adhesive application step is defined as a processing unit region; The control unit has an aspect of performing control to delay the second process from the middle of the second process for the processing unit region until the second process is completed.

Brief Description of Drawings

[0007]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Embodiments for Carrying Out the Invention

[0008] Hereinafter, embodiments of the present invention will be described. Of course, the following embodiments are merely illustrative of the present invention, and not all of the features shown in the embodiments are necessarily essential to the solution means of the invention.

[0009] (1) Outline of Aspects Included in the Present Invention: First, an outline of the aspects included in the present invention will be described with reference to the examples shown in FIGS. 1 to 12. Note that the drawings in the present application are diagrams schematically showing examples, and the scales of each part may be different from the actual ones in order to make each part recognizable, the magnification ratios in each direction shown in these drawings may be different, and the drawings may not be consistent. Of course, each element of this aspect is not limited to the specific examples indicated by the reference numerals. In the "outline of the aspects included in the present invention", the content in parentheses means a supplementary explanation of the immediately preceding word. Also, in the present application, the numerical range "Min~Max" means greater than or equal to the minimum value Min and less than or equal to the maximum value Max.

[0010] [Aspect 1] As exemplified in FIGS. 1, 5, etc., a printing method according to one aspect is a printing method for performing printing on the transfer medium M1, which includes an adhesive application step ST3 of attaching an adhesive 111 to an undercoat ink 36b laminated on an image IM1 formed on the transfer medium M1, and a transfer step ST5 of transferring the image IM1 to the transfer medium M2 by attaching the adhesive 111 to the transfer medium M2. This printing method includes the following steps. An image forming step ST1 of performing a first process of forming the image IM1 on the transfer medium M1 by discharging the colored ink 36a from a first inkjet head (for example, the colored ink head 31). A base forming step ST2 including a process of relatively moving a second inkjet head (for example, the base ink head 32) in a first direction D1 with respect to the transfer medium M1, and a process of overlapping the base ink 36b on the image IM1 by discharging the base ink 36b from the second inkjet head (32). Here, as illustrated in FIGS. 2, 6, etc., a region where the adhesive 111 is supplied at the same timing in the adhesive application step ST3 with respect to the transfer medium M1 is defined as a processing unit region A0. In the base forming step ST2, the second process is delayed from the middle to the completion of the second process with respect to the processing unit region A0.

[0011] By delaying the second process from the middle to the completion of the second process with respect to the processing unit region A0, the drying of the base ink 36b in the portion where the base ink 36b is finally overlapped on the image IM1 in the processing unit region A0 proceeds. Thereby, the flow of the base ink 36b due to the inclination of the transfer medium M1 in the adhesive application step ST3 is suppressed, and the bleeding of the transferred image (the image IM1 to be transferred) due to the base ink 36b dripping downward or the like is suppressed. Therefore, the above aspect can provide a printing method capable of suppressing the bleeding of the transferred image.

[0012] Various examples can be considered in the above-described aspect. For the second inkjet head (32) to move relative to the transfer medium M1 in the first direction D1, it includes the second inkjet head (32) moving in the first direction D1 with the transfer medium M1 not moving, the transfer medium M1 moving in the direction opposite to the first direction D1 with the second inkjet head (32) not moving, and both the transfer medium M1 and the second inkjet head (32) moving along the first direction D1. Further, the second inkjet head (32) may also move relative to the transfer medium M1 in a second direction D2 intersecting the first direction D1. The first inkjet head (31) may move relative to the transfer medium M1 together with the second inkjet head (32), or may move relative to the transfer medium M1 separately from the second inkjet head (32).

[0013] The processing unit region A0 includes the following regions. (Region b1) A region corresponding to one single sheet of the transfer medium when the transfer medium is a single sheet (see, for example, FIG. 8). (Region b2) A region corresponding to one conveyance amount when the transfer medium, which is continuous paper on which lateral printing is performed, is intermittently conveyed (see, for example, FIG. 7). (Region b3) A region corresponding to the conveyance amount for one sub-scan when sub-scanning is performed on the transfer medium on which serial printing is performed. (Region b4) A region corresponding to one cut transfer medium when the transfer medium on which line printing is performed is cut. Printing on single-sheet paper may be performed in any of the lateral method, serial method, and line method. The lateral method is a printing method in which an inkjet head scans in the main scanning direction and the sub-scanning direction intersecting the main scanning direction with respect to the processing unit area of the transfer medium, and ink is ejected from the inkjet head while scanning. The lateral method for continuous paper is a printing method in which ink is ejected from an inkjet head while scanning the inkjet head in the conveyance direction and the direction intersecting the conveyance direction with respect to the region b2 of the transfer medium during conveyance stop, and the continuous paper is intermittently conveyed in the conveyance direction in units corresponding to the region b2. The serial method is a printing method in which an inkjet head reciprocates in the main scanning direction and ink is ejected from the inkjet head while performing sub-scanning between main scans. The line method is a printing method in which ink is ejected from an inkjet head having a length equal to or greater than the width of continuous paper onto the continuous paper being conveyed. The materials of single-sheet paper and continuous paper are not limited to strict paper, and may be resin, metal, etc.

[0014] In the base formation step ST2, the base ink 36b may be ejected from the second inkjet head (32) that is relatively moving in the first direction D1, or the base ink 36b may be ejected from the second inkjet head (32) that is relatively moving in the second direction D2 without changing the relative position in the first direction D1. The second process may be a combination of a process of overlapping the base ink 36b on the image IM1 while performing main scanning along the second direction D2 and a process of performing sub-scanning in the first direction D1. Further, the second process may be a combination of a process of overlapping the base ink 36b on the image IM1 while performing main scanning along the first direction D1 and a process of performing sub-scanning in the second direction D2. Furthermore, the second process may be a process of overlapping the base ink 36b on the image IM1 while conveying the transfer medium M1 in a direction opposite to the first direction D1. The delay in the second process includes an increase in the number of passes NP, which means the number of main scans accompanied by the ejection of the base ink 36b, performed at the same location on the transfer medium M1, an increase in the processing time of sub-scanning, an increase in the processing time of main scanning, and the like. In the present application, "first", "second",... are terms for identifying each of a plurality of components having similarities, and do not mean an order. Of course, the above remarks are also applicable in the following aspects.

[0015] [Aspect 2] As illustrated in FIG. 6 and the like, the processing unit region A0 may include a first region A1 and a second region A2 where the base ink 36b is overlaid on the image IM1 after the first region A1. The second region A2 may include a portion where the base ink 36b is finally overlaid on the image IM1 in the processing unit region A0. In this printing method, in the base formation step ST2, the second processing for the second region A2 may be delayed. The drying time of the base ink 36b in the second region A2 is shorter than that in the first region A1. By delaying the second processing for the second region A2 instead of the first region A1, the flow of the base ink 36b due to the inclination of the transfer medium M1 in the adhesive application step ST3 is suppressed. Therefore, the above aspect can suppress the bleeding of the transferred image while suppressing the decrease in throughput as much as possible.

[0016] The processing unit region A0 may include a third region A3 where the base ink 36b is overlaid on the image IM1 after the first region A1 and before the second region A2. In this case, in the base formation step ST2, the second processing for the third region A3 may be delayed, and further, the second processing for the second region A2 may be further delayed. The above remarks are also applicable in the following aspects.

[0017] [Aspect 3] As illustrated in FIG. 6 and the like, in the base formation step ST2, in the present printing method, while relatively moving the second inkjet head (32) with respect to the transfer medium M1 along a second direction D2 intersecting the first direction D1, main scanning is performed to eject the base ink 36b. In the sub-scanning between the main scans, the second process may be performed to change the position in the first direction D1 where the base ink 36b is overlaid on the image IM1 by relatively moving the second inkjet head (32) with respect to the transfer medium M1 in the first direction D1. Here, the number of times of the main scanning accompanied by the ejection of the base ink 36b performed at the same location on the transfer medium M1 is defined as the number of passes NP. In the base formation step ST2, the present printing method may perform the second process of making the number of passes NP in the second region A2 larger than the number of passes NP in the first region A1. When the number of passes NP increases in the second region A2, the time of the second process performed on the second region A2 becomes longer. As a result, the second process is delayed from the start time of the second process for the second region A2, and the drying of the base ink 36b proceeds. When the ejection of the base ink 36b is divided into NP times of main scanning, the ejection amount of the base ink 36b per main scan is less for the second region A2 than for the first region A1, and the drying of the base ink 36b proceeds. When the drying of the base ink 36b proceeds, the flow of the base ink 36b due to the inclination of the transfer medium M1 in the adhesive application step ST3 is suppressed. Therefore, the above aspect can suppress the bleeding of the transferred image by a simple method of changing the number of passes for each region.

[0018] [Aspect 4] As illustrated in FIG. 10, the processing unit region A0 may include a continuous region (for example, a first continuous region A11 or a second continuous region A12) that is connected as one in the image IM1. In the base formation step ST2, in the present printing method, when there is a continuous region (A12) exceeding the reference area THS in at least one of the first region A1 and the second region A2, the number of passes NP may be made larger than the number of passes NP when there is no continuous region (A12) exceeding the reference area THS. The larger the continuous area (A11, A12) is, the easier it is for the base ink 36b to flow due to the inclination of the transfer medium M1 in the adhesive application step ST3. When there is a continuous area (A12) with a large area in the first area A1 or the second area A2, the number of passes NP increases compared to the case where there is no continuous area (A12) with a large area, and thus the flow of the base ink 36b due to the inclination of the transfer medium M1 in the adhesive application step ST3 is further suppressed. Therefore, the above aspect can further suppress the bleeding of the transferred image.

[0019] [Aspect 5] As illustrated in FIG. 12, in the present printing method, in the base formation step ST2, when the discharge amount DT of the base ink 36b per unit area exceeds the first discharge amount THD1 in at least one of the first area A1 and the second area A2, the number of passes NP is made larger than the number of passes NP when the discharge amount DT of the base ink 36b per unit area does not exceed the first discharge amount THD1, and the number of passes NP in the second area A2 is made larger than the number of passes NP in the first area A1 when the discharge amount DT of the base ink 36b per unit area remains unchanged. The second process may be performed. The larger the discharge amount DT of the base ink 36b per unit area is, the easier it is for the base ink 36b to flow due to the inclination of the transfer medium M1 in the adhesive application step ST3. Since the drying of the base ink 36b progresses due to an increase in the number of passes NP in the area where the discharge amount DT of the base ink 36b is large, the flow of the base ink 36b due to the inclination of the transfer medium M1 in the adhesive application step ST3 is further suppressed. When the discharge amount DT of the base ink 36b remains unchanged, the second process is delayed from the start time of the second process for the second area A2, and the drying of the base ink 36b progresses because the number of passes NP in the second area A2 is larger than the number of passes NP in the first area A1. Therefore, the above aspect can further suppress the bleeding of the transferred image.

[0020] The discharge amount DT of the undercoat ink 36b per unit area means the ratio (including percentage) of the number of dots formed by the ink droplets 37 for a predetermined number of pixels. When dots of different sizes are formed, it means the ratio when converted to the largest dot (for example, a large dot). A pixel is the smallest element that constitutes an image and to which a color can be independently assigned. For example, when Nd large dots are formed for 100 pixels, the discharge amount DT is Nd%. The above remarks are also applicable in the following aspects.

[0021] [Aspect 6] The undercoat ink 36b may be an ink containing a component that blocks the transmission of light. In this case, since the color of the transfer medium M2 cannot be seen through in the image portion, the image quality of the transferred image can be improved. Here, inks containing a component that blocks the transmission of light include inks containing a component that diffusely reflects light, such as white ink, inks containing a component that absorbs light, such as black ink, inks containing a component that diffusely reflects light and a component that absorbs light, such as gray ink, and the like. This remark is also applicable in the following aspects.

[0022] [Aspect 7] Incidentally, as illustrated in FIGS. 1 and 5, a printing apparatus 1 according to one aspect is a printing apparatus 1 that performs printing on a transfer medium M1, and includes an adhesive application step ST3 of attaching an adhesive 111 to a base ink 36b overlaid on an image IM1 formed on the transfer medium M1, and a transfer step ST5 of transferring the image IM1 to a transfer medium M2 by attaching the adhesive 111 to the transfer medium M2. As illustrated in FIGS. 2 to 4, the present printing apparatus 1 includes a first inkjet head (31) that discharges a colored ink 36a, a second inkjet head (32) that discharges the base ink 36b, a drive unit 50, and a control unit 10. The drive unit 50 relatively moves the second inkjet head (32) in a first direction D1 with respect to the transfer medium M1. The control unit 10 controls the discharge of the colored ink 36a from the first inkjet head (31), the discharge of the base ink 36b from the second inkjet head (32), and the drive unit 50. As illustrated in FIG. 5, the control unit 10 controls a first process of forming the image IM1 on the transfer medium M1 by discharging the colored ink 36a from the first inkjet head (31). The control unit 10 controls a second process including a process of relatively moving the second inkjet head (32) in the first direction D1 with respect to the transfer medium M1, and a process of overlaying the base ink 36b on the image IM1 by discharging the base ink 36b from the second inkjet head (32). Here, a processing unit area A0 is defined as an area where the adhesive 111 is supplied at the same timing in the adhesive application step ST3 with respect to the transfer medium M1. The control unit 10 performs control to delay the second process from the middle of the second process for the processing unit area A0 until the second process is completed.

[0023] The above aspect can provide a printing apparatus capable of suppressing bleeding of a transferred image.

[0024] Furthermore, the above-described embodiments are applicable to a printing system including the above-described printing apparatus, a control method for the above-described printing apparatus, a control method for the above-described printing system, a control program for the above-described printing apparatus, a control program for the above-described printing system, a computer-readable recording medium storing any of the above-described control programs, and the like. Also, the above-described printing apparatus may be composed of a plurality of distributed parts.

[0025] (2) Specific examples of the printing apparatus: FIG. 1 schematically illustrates the configuration of a printing system that forms an image IM1 on a transfer medium M1 and transfers the image IM1 to a transfer target medium M2. The printing system shown in FIG. 1 includes a printing apparatus 1, an adhesive applying apparatus 100, and a thermal transfer apparatus 200. The printing apparatus 1 may be a single printer 2, or may be composed of a printer 2 and a host apparatus HO1 as shown in FIG. 1. The host apparatus HO1 shown in FIG. 1 can generate image data DA1 corresponding to the image IM1 to be transferred, and can transmit the image data DA1 to the printer 2. Hereinafter, the image IM1 to be transferred will also be referred to as the transfer image IM1. The printer 2 includes a printing unit 20 that discharges ink onto the transfer medium M1, and forms an image IM1 corresponding to the image data DA1 on the transfer medium M1. The adhesive applying apparatus 100 includes an adhesive tank 110 that attaches an adhesive 111 to the ink on the transfer medium M1, and a heating unit 120 that heats the transfer medium M1 after the adhesive is applied. The thermal transfer apparatus 200 transfers the image IM1 from the transfer medium M1 to the transfer target medium M2.

[0026] As the transfer medium M1, a transfer film or the like capable of transferring an image by the DTF (Direct to Film) method can be used. As such a transfer film, a resin film such as a PET (polyethylene terephthalate) film can be preferably used. Of course, the material of the transfer medium M1 may include paper, metal, etc. in addition to resin, and the transfer medium M1 may be a metal film or the like. As the adhesive 111, a powdery adhesive such as a powdery hot melt adhesive can be used. The hot melt adhesive is a thermoplastic resin powder, which melts when heated above the melting point and solidifies when cooled. As the hot melt adhesive, an adhesive containing one or more thermoplastic resins selected from polyurethane resins, polyolefin resins, polyamide resins, polyester resins, etc. can be used. As the medium M2 to be transferred, fabrics such as knitted or woven fabrics, non-woven fabrics, etc. can be used, and fabrics processed like T-shirts, etc. may also be used.

[0027] As will be described in detail later, in the printing apparatus 1, an image forming step ST1 and a base forming step ST2 are performed. In the adhesive applying apparatus 100, an adhesive applying step ST3 and a heating step ST4 are performed. In the thermal transfer apparatus 200, a transfer step ST5 is performed.

[0028] FIG. 2 is a plan view schematically illustrating the configuration of a printer 2 including an inkjet head 30. The processing unit region A0 shown in FIG. 2 is a rectangle with a length L0 and a width W0. FIG. 3 is a bottom view schematically illustrating the nozzle surface 30a of the inkjet head 30. FIG. 4 is a block diagram schematically illustrating the configuration of the printing apparatus 1. FIG. 5 schematically illustrates a printing method on the medium M2 to be transferred. FIG. 6 schematically illustrates the division of the processing unit region A0. Printer 2 is an inkjet printer that ejects liquid ink droplets 37. Printer 2 includes a control unit 10, a printing unit 20, a RAM (Random Access Memory) 21 which is a semiconductor memory, a communication I / F (interface) 22, a storage unit 23, an operation panel 24, etc. The control unit 10, RAM 21, communication I / F 22, storage unit 23, and operation panel 24 are connected to a bus and are capable of inputting and outputting information to each other. The printing unit 20 includes an inkjet head 30 and a driving unit 50.

[0029] The control unit 10 includes a CPU (Central Processing Unit) 11 which is a processor, a color conversion unit 12, a halftone processing unit 13, a rasterization processing unit 14, a drive signal transmission unit 15, etc. The control unit 10 can be configured by an SoC (System on a Chip) or the like. Based on the image data DA1 obtained from either the host device HO1, an external memory (not shown), etc., the control unit 10 controls the inkjet head 30 and the driving unit 50 so that an image IM1 of colored ink 36a and a layer of undercoat ink 36b are formed on the transfer medium M1. The image data DA1 can be applied with, for example, RGB data having integer values of, for example, 2 gradations of R (red), G (green), and B (blue) for each pixel. 8 Tonal integer values can be applied.

[0030] The CPU 11 is a device that mainly performs information processing and control in the printer 2. The color conversion unit 12 has, for example, a color conversion LUT (look-up table) in which the correspondence between the gradation values of R, G, and B and the gradation values of C (cyan), M (magenta), Y (yellow), K (black), and W (white) is defined. In the color conversion LUT, the gradation value of W is, for example, the value at which the undercoat ink 36b is used when at least one of the colored inks 36a of C, M, Y, and K is used. For example, when the gradation values of C, M, Y, and K are 0 indicating no use of the colored ink, the gradation value of W may be 0 indicating no use of the undercoat ink, and in the remaining cases, the gradation value of W may be 128 indicating 50% use of the undercoat ink. Thereby, the undercoat ink 36b is overlaid on the position of the image IM1. Of course, the discharge amount of the undercoat ink 36b overlaid on the image IM1 may be less than 50%, more than 50%, or may vary according to the color of the image IM1 within the range where a transfer image IM1 with good image quality can be obtained. The color conversion unit 12 refers to the color conversion LUT and converts the RGB data into ink amount data having, for example, integer gradation values of 2 8 for C, M, Y, and K for each pixel. The ink amount data represents the usage amounts of the inks 36 of C, M, Y, K, and W in units of pixels. Note that the inks 36 shown in FIG. 4 include the colored inks 36a of C, M, Y, and K and the undercoat ink 36b. Also, when the resolution of the RGB data is different from the printing resolution, the color conversion unit 12 converts the resolution of the RGB data into the printing resolution first, or converts the resolution of the ink amount data into the printing resolution.

[0031] The halftone processing unit 13 performs halftone processing on the ink amount data by any of the dither method, error diffusion method, etc., to generate dot data with the number of gradations reduced to, for example, 2 or 4. The dot data is generated for each of C, M, Y, K, and W. The dot data represents the formation state of the dots of the ink 36 in units of pixels. The rasterization processing unit 14 generates raster data by performing rasterization processing to rearrange the dot data in the order in which dots are formed by the driving unit 50.

[0032] The drive signal transmission unit 15 generates a drive signal SG1 corresponding to the voltage signal applied to the drive element 42 of the inkjet head 30 from the raster data and outputs it to the drive circuit 41 of the inkjet head 30. The RAM 21 stores the image data DA1 etc. received from the host device HO1 etc. The communication I / F 22 inputs and outputs information to and from the host device HO1 etc. Examples of the host device HO1 include computers such as personal computers and tablet terminals, mobile phones such as smartphones, etc. The storage unit 23 may be a non-volatile semiconductor memory such as a flash memory, or a magnetic storage device such as a hard disk. The operation panel 24 includes an output unit 25 such as a liquid crystal panel for displaying information, an input unit 26 such as a touch panel for receiving operations on the display screen, etc.

[0033] The drive circuit 41 applies a voltage signal to the drive element 42 according to the drive signal SG1 input from the drive signal transmission unit 15. The drive element 42 may be a piezoelectric element that applies pressure to the ink 36 in the pressure chamber communicating with the nozzle 34, or a drive element that generates bubbles in the pressure chamber by heat to eject ink droplets 37 from the nozzle 34. The ink 36 is supplied from the ink cartridge 35 to the pressure chamber of the inkjet head 30. The ink 36 in the pressure chamber is ejected as ink droplets 37 from the nozzle 34 toward the transfer medium M1 by the drive element 42. When the ink droplets 37 land on the transfer medium M1, dots are formed on the transfer medium M1. When dots of the colored ink 36a are formed on the transfer medium M1, an image IM1 represented by the dot pattern is formed on the transfer medium M1.

[0034] The inkjet head 30 shown in FIG. 3 includes a color ink head 31 that discharges color ink 36a and an undercoat ink head 32 that discharges undercoat ink 36b. The color ink head 31 is an example of a first inkjet head, and the undercoat ink head 32 is an example of a second inkjet head. The color ink 36a is an ink that contains a coloring material such as a pigment as a dispersed substance or a solute in a liquid (for example, water) as a dispersion medium or a solvent. The color ink 36a includes, for example, color inks of C, M, and Y, and an ink of K that is achromatic. The color ink head 31 includes a C ink head 31C that discharges C ink, an M ink head 31M that discharges M ink, a Y ink head 31Y that discharges Y ink, and a K ink head 31K that discharges K ink. The undercoat ink 36b is an ink that contains a component that blocks the transmission of light, and is, for example, a W ink that contains a component that diffusely reflects light. The W ink is an ink that contains a white pigment such as titanium oxide or zinc oxide as a dispersed substance in a liquid such as water as a dispersion medium. By the undercoat ink 36b blocking the transmission of light, the color of the transfer medium M2 that becomes the background of the image IM1 is not affected by the color of the image IM1, and a transfer medium M2 having an image IM1 with good image quality can be obtained. Each ink head (31C, 31M, 31Y, 31K, 32) has a nozzle array direction that intersects the second direction D2 as the scanning direction, for example, a nozzle row in which a plurality of nozzles 34 are arranged in the first direction D1. The plurality of nozzles 34 of each ink head may be arranged in a staggered pattern in the nozzle array direction, in other words, may be arranged in two rows in the nozzle array direction. The nozzle array direction may be shifted from the first direction D1 within a range of less than 90°. Each nozzle 34 of the color ink head 31 discharges the color ink 36a as ink droplets 37, and each nozzle 34 of the undercoat ink head 32 discharges the undercoat ink 36b as ink droplets 37. The inkjet head 30 shown in FIGS. 2 to 4 is mounted on a carriage 33. When the printer 2 performs lateral printing, the carriage 33 is movable along the second direction D2 as the main scanning direction and the first direction D1 as the sub-scanning direction.

[0035] The driving unit 50 as a lateral system includes a main scanning driving unit 51, a sub-scanning driving unit 52, and a conveying unit 55. The main scanning driving unit 51 shown in FIG. 2 performs main scanning to eject ink 36 from the inkjet head 30 in at least one of the forward direction D11 and the reverse direction D12 while moving the inkjet head 30 along the second direction D2 as the main scanning direction. Focusing on the undercoat ink head 32, it can be said that the main scanning driving unit 51 performs main scanning to eject the undercoat ink 36b while relatively moving the undercoat ink head 32 along the second direction D2 with respect to the transfer medium M1. The sub-scanning driving unit 52 shown in FIG. 2 performs sub-scanning to move the inkjet head 30 along the first direction D1 as the sub-scanning direction during the main scanning intervals. That is, during sub-scanning, the inkjet head 30 moves intermittently along the first direction D1. Focusing on the undercoat ink head 32, it can be said that the sub-scanning driving unit 52 relatively moves the undercoat ink head 32 in the first direction D1 with respect to the transfer medium M1 during the sub-scanning between the main scans. The conveying unit 55 shown in FIGS. 2 and 4 conveys the transfer medium M1, which is a continuous sheet, along the first direction D1 as the conveying direction during the printing intervals of the processing unit area A0. That is, when not printing, the transfer medium M1 moves intermittently along the first direction D1. The conveying unit 55 shown in FIGS. 2 and 4 sends the transfer medium M1 in the first direction D1 along the conveying path 59. The platen 58 is located below the conveying path 59 and supports the transfer medium M1 by contacting the transfer medium M1 in the conveying path 59. The inkjet head 30 controlled by the control unit 10 ejects ink droplets 37 toward the transfer medium M1 supported by the platen 58 to attach the ink 36 to the transfer medium M1. The control unit 10 controls the ejection of the colored ink 36a from the colored ink head 31, the ejection of the undercoat ink 36b from the undercoat ink head 32, and the driving unit 50.

[0036] The undercoat ink head 32 can be arranged in various ways as long as the undercoat ink 36b can be overlaid on the image IM1 with the colored ink 36a. For example, the undercoat ink head 32 may be located at a position facing the forward direction D11 from the C ink head 31C shown in FIG. 3, or may be located at a position facing in the direction opposite to the sub-scanning direction from the colored ink head 31.

[0037] Next, with reference to FIGS. 5, 6, etc., a printing method onto the transfer medium M2 will be described. The printing method shown in FIG. 5 includes the following steps. (c1) An image forming step ST1 of performing an image forming process of forming an image IM1 on the transfer medium M1 by ejecting the colored ink 36a from the colored ink head 31. (c2) An undercoat forming step ST2 of performing an undercoat forming process including a process of relatively moving the undercoat ink head 32 in the first direction D1 with respect to the transfer medium M1, and a process of overlaying the undercoat ink 36b on the image IM1 by ejecting the undercoat ink 36b from the undercoat ink head 32. (c3) An adhesive applying step ST3 of attaching an adhesive 111 to the undercoat ink 36b overlaid on the image IM1 formed on the transfer medium M1. (c4) A heating step ST4 of heating the transfer medium M1 to which the adhesive 111 has been applied. (c5) A transfer step ST5 of transferring the image IM1 to the transfer medium M2 by attaching the adhesive 111 to the transfer medium M2. Note that the image forming process is an example of the first process, and the undercoat forming process is an example of the second process.

[0038] For example, as shown in FIG. 6, assume a scenario where ink 36 is ejected from the inkjet head 30 in units of bands B1 to B6 onto the processing unit area A0. For example, when, for each band, a second main scan in which the base ink 36b lands is performed after the first main scan in which the colored ink 36a lands, the image forming step ST1 is carried out in the first main scan, and the base forming step ST2 is carried out in the second main scan. When the first main scan is a main scan in the forward direction D11, the second main scan may be a main scan in the reverse direction D12 like bidirectional printing, or may be a main scan in the forward direction D11 like unidirectional printing. As long as the base ink 36b does not mix with but overlaps the image IM1 formed by the colored ink 36a, the image forming step ST1 and the base forming step ST2 may be carried out by one main scan in the forward direction D11 by the inkjet head 30 shown in FIG. 3. For each band, the image IM1 may be formed in one pass, the base ink 36b may be overlaid on the image IM1 in one pass, the image IM1 may be formed in multiple passes, or the base ink 36b may be overlaid on the image IM1 in multiple passes.

[0039] In the example shown in FIG. 1, a transfer medium M1 with an undercoat ink 36b laminated thereon is intermittently conveyed from a printer 2 to an adhesive applying device 100 and enters an adhesive tank 110 while being tilted. When the powder adhesive 111 is contained in the adhesive tank 110, the adhesive 111 adheres to the still-un-dried undercoat ink 36b. FIG. 5 shows a state in which an image IM1, the undercoat ink 36b, and the powder adhesive 111 are laminated in this order on the transfer medium M1 in the adhesive applying step ST3. In this way, the adhesive applying step ST3 is carried out. In the example shown in FIG. 1, the transfer medium M1 with the thermoplastic adhesive 111 applied thereto is intermittently conveyed from the adhesive tank 110 to a heating unit 120. During this period, excess adhesive 111 is shaken off due to the transfer medium M1 tilting again or the like. The heating unit 120 heats the transfer medium M1 to which the adhesive 111 has been applied. When the transfer medium M1 is heated to a temperature equal to or higher than the melting temperature of the adhesive 111, the adhesive 111 melts. FIG. 5 shows a state in which an image IM1, the dried undercoat ink 36b, and the melted adhesive 111 are laminated in this order on the transfer medium M1 in the heating step ST4. When the thermal transfer device 200 is capable of heating the transfer medium M1, the heating unit 120 may perform preliminary heating on the transfer medium M1 to a temperature lower than the melting temperature of the adhesive 111. In this way, the heating step ST4 is carried out. In the example shown in FIG. 1, the heated transfer medium M1 is intermittently discharged from the heating unit 120. The discharged transfer medium M1 is cut as necessary, overlapped with a transfer medium M2 with the surface to which the adhesive 111 has been applied facing the transfer medium M2, and carried into the thermal transfer device 200.

[0040] The thermal transfer device 200 presses the transfer medium M1 and the medium to be transferred M2 in a state where the adhesive 111 applied to the transfer medium M1 is in contact with the medium to be transferred M2. When the thermal transfer device 200 includes a heating mechanism, the thermal transfer device 200 heats the transfer medium M1 and the medium to be transferred M2 to a temperature equal to or higher than the melting temperature of the adhesive 111. FIG. 5 shows a state in which the molten adhesive 111, the dried base ink 36b, the image IM1, and the transfer medium M1 are sequentially laminated on the medium to be transferred M2. By pressing the transfer medium M1 and the medium to be transferred M2, the image IM1 adheres to the medium to be transferred M2 via the base ink 36b and the adhesive 111. In this way, a transfer step ST5 for transferring the image IM1 to the medium to be transferred M2 is performed. When the transfer medium M1 is peeled off from the medium to be transferred M2, the image IM1 remains on the medium to be transferred M2, and the medium to be transferred M2 with the image IM1 transferred as shown in FIG. 1 is obtained. Since there is a layer of the base ink 36b between the transferred image IM1 and the medium to be transferred M2, the color of the medium to be transferred M2 is suppressed from affecting the image IM1, and the image quality of the image IM1 is good.

[0041] Although the above-described transfer medium M1 is continuous paper, the transfer medium M1 may be single-sheet paper. In this case, the user may put the printed single-sheet paper into the adhesive tank 110 to attach the powdery adhesive 111 to the base ink 36b. In this operation, the transfer medium M1 tilts.

[0042] When the base ink 36b lands on the image IM1 on the transfer medium M1, it gradually dries. In the processing unit area A0 where the adhesive 111 is supplied at the same timing in the adhesive application step ST3 with respect to the transfer medium M1, the degree of dryness of the base ink 36b is lower as the landing of the base ink 36b is later. For this reason, when the transfer medium M1 tilts for applying the adhesive 111 or the like, the base ink 36b with a low degree of dryness may drip downward. When the base ink 36b drips downward, bleeding occurs in the transferred image IM1, and the image quality of the transferred image IM1 deteriorates.

[0043] The printing apparatus 1 of this specific example solves the above-described problems by delaying the underlayer formation process from the middle to the completion of the underlayer formation process for the processing unit area A0. Note that the delay of the underlayer formation process is performed so as to suppress the decrease in the throughput of the adhesive application step ST3 as much as possible. First, with reference to FIG. 6, an example of the division of the processing unit area A0 and the number of passes NP in each area will be described. Here, the number of passes NP means the number of main scans with ejection of the underlayer ink 36b performed at the same position on the transfer medium M1.

[0044] The above-described areas b1 to b4 are included in the processing unit area A0. FIG. 6 shows an example in which main scanning and sub-scanning are performed in units of bands B1 to B6 for the area b1 for one sheet of single-form paper or the area b2 at the time of lateral printing. The control unit 10 performs control to perform main scanning for ejecting the ink 36 while relatively moving the inkjet head 30 relative to the transfer medium M1 along the second direction D2. The control unit 10 performs control to change the position in the first direction D1 in which the image IM1 is formed on the transfer medium M1 by relatively moving the colored ink head 31 in the first direction D1 relative to the transfer medium M1 in the sub-scanning between main scans. Further, the control unit 10 performs control to change the position in the first direction D1 in which the underlayer ink 36b is overlaid on the image IM1 by relatively moving the underlayer ink head 32 in the first direction D1 relative to the transfer medium M1 in the sub-scanning. The image IM1 is formed on the transfer medium M1 in units of bands B1 to B6 in the order of the first direction D1, and the underlayer ink 36b is overlaid on the image IM1 in units of bands B1 to B6 in the order of the first direction D1. The processing unit area A0 shown in FIG. 6 includes a first area A1 and a second area A2 where the underlayer ink 36b is overlaid on the image IM1 after the first area A1. The second area A2 is an area where the underlayer ink 36b is overlaid on the image IM1 in a main scan after the main scan in which the underlayer ink 36b is overlaid on the image IM1 in the first area A1. FIG. 6 shows various examples C1 to C3 for dividing the bands B1 to B6 into areas.

[0045] In Example C1, bands B1 and B2 are assigned to the first region A1, bands B3 and B4 are assigned to the third region A3, and bands B5 and B6 are assigned to the second region A2. The first region A1 includes the band B1 where the undercoat ink 36b is first overlaid on the image IM1 in the processing unit region A0. The third region A3 is where the undercoat ink 36b is overlaid on the image IM1 after the first region A1 and before the second region A2. The second region A2 includes the band B6 where the undercoat ink 36b is last overlaid on the image IM1 in the processing unit region A0. The control unit 10 delays the undercoat formation process for the third region A3 and further delays the undercoat formation process for the second region A2. In the undercoat formation process shown in FIG. 6, the control unit 10 makes the number of passes NP3 in the third region A3 larger than the number of passes NP1 in the first region A1, and makes the number of passes NP2 in the second region A2 larger than the number of passes NP3 in the third region A3. Therefore, it can be said that the control unit 10 performs control to delay the undercoat formation process from the band B3, which is in the middle of the undercoat formation process for the processing unit region A0, until the undercoat formation process is completed. Also, it can be said that the control unit 10 performs control to further delay the undercoat formation process from the band B5, which is in the middle of the undercoat formation process for the processing unit region A0, until the undercoat formation process is completed.

[0046] By delaying the undercoat formation process from the middle to the completion of the undercoat formation process for the processing unit region A0, the drying of the undercoat ink 36b in the portion of the processing unit region A0 where the undercoat ink 36b is last overlaid on the image IM1 progresses. Thereby, the flow of the undercoat ink 36b due to the tilting of the transfer medium M1 in the adhesive application step ST3 is suppressed. By suppressing the flow of the undercoat ink 36b, bleeding of the transferred image IM1 due to the undercoat ink 36b dripping downward or the like is suppressed, and the image quality of the transferred image IM1 is improved.

[0047] When the number of passes NP increases in the second region A2, the time for the underlayer formation process performed on the second region A2 becomes longer. As a result, the start timing of the underlayer formation process for the second region A2 is delayed, and the drying of the underlayer ink 36b progresses. When the discharge of the underlayer ink 36b is divided into NP main scans, the discharge amount of the underlayer ink 36b per main scan is less for the second region A2 than for the first region A1, and the drying of the underlayer ink 36b progresses. Therefore, the flow of the underlayer ink 36b due to the inclination of the transfer medium M1 in the adhesive application step ST3 is suppressed, and bleeding of the transfer image IM1 is suppressed by a simple method of changing the number of passes NP by region. In addition, since the third region A3 with the number of passes NP3 that is more than the number of passes NP1 and less than the number of passes NP2 is between the first region A1 and the second region A2, the change in the number of passes NP due to the change in region is reduced. As a result, the influence on the image quality of the transfer image IM1 due to the change in the number of passes NP is reduced, and the image quality of the transfer image IM1 is improved.

[0048] In Example C2, the third region A3 is not present in the processing unit region A0, the bands B1 to B4 are assigned to the first region A1, and the bands B5 and B6 are assigned to the second region A2. Even without the third region A3, since the number of passes NP increases in the second region A2, the start timing of the underlayer formation process for the second region A2 is delayed, and the drying of the underlayer ink 36b progresses. Therefore, the flow of the underlayer ink 36b due to the inclination of the transfer medium M1 in the adhesive application step ST3 is suppressed, and bleeding of the transfer image IM1 is suppressed. In Example C3, only the last band B6 is assigned to the second region A2, and the bands B1 to B5 are assigned to the first region A1. Among the processing unit regions A0, the underlayer ink 36b is most likely to flow in the last band B6. Therefore, also in Example C3, the flow of the underlayer ink 36b due to the inclination of the transfer medium M1 in the adhesive application step ST3 is effectively suppressed, and bleeding of the transfer image IM1 is effectively suppressed.

[0049] FIG. 7 schematically illustrates the lateral intermittent conveyance for the continuous paper M11 as the transfer medium M1. The lateral method for the continuous paper M11 is a printing method in which the inkjet head 30 ejects ink 36 while scanning the inkjet head 30 vertically and horizontally with respect to the processing unit area A0 of the continuous paper M11 during conveyance stop, and the continuous paper M11 is fed in the conveyance direction by a conveyance amount L1 corresponding to the processing unit area A0. In the example shown in FIG. 6, the second direction D2 is the main scanning direction, the first direction D1 is the sub-scanning direction and also the conveyance direction. For the continuous paper M11, the adhesive 111 is supplied at the same timing in the adhesive application step ST3 in units of the conveyance amount L1. Therefore, the processing unit area A0 becomes the area b2 corresponding to one conveyance amount L1 when the continuous paper M11 is intermittently conveyed.

[0050] The state SA1 shown in FIG. 7 is a state in which the conveyance of the continuous paper M11 as the transfer medium M1 has stopped and printing is being performed on the processing unit area A01 as the processing unit area A0. When the image IM1 is formed on the processing unit area A01 and the base ink 36b is overlaid on the image IM1, the conveyance unit 55 feeds the continuous paper M11 by a predetermined conveyance amount L1 in the first direction D1. The conveyance amount L1 is the distance obtained by adding a predetermined margin to the length of the processing unit area A0 in the first direction D1. The next state SA2 is a state in which the conveyance of the continuous paper M11 has stopped and printing is being performed on the processing unit area A02 as the processing unit area A0. When the image IM1 is formed on the processing unit area A02 and the base ink 36b is overlaid on the image IM1, the conveyance unit 55 feeds the continuous paper M11 by the conveyance amount L1 in the first direction D1. The next state SA3 is a state in which the conveyance of the continuous paper M11 has stopped and printing is being performed on the processing unit area A03 as the processing unit area A0. As described above, the printer 2 forms the image IM1 on the processing unit area A0 of the continuous paper M11 during conveyance stop, overlays the base ink 36b on the image IM1, and intermittently conveys the continuous paper M11 in the first direction D1 by the conveyance amount L1.

[0051] FIG. 8 schematically illustrates the processing unit area A0 in the single-sheet paper M12. The printing on the single-sheet paper M12 may be any of the lateral method, the serial method, and the line method, but FIG. 8 shows an example of performing the lateral method or the serial method of printing on the single-sheet paper M12. When the transfer medium M1 is a single sheet M12, the adhesive 111 is supplied at the same timing in the adhesive application step ST3 for one single sheet M12. Therefore, the processing unit area A0 becomes the area b1 corresponding to one single sheet.

[0052] In addition, in printing that performs main scanning and sub-scanning, the difference in the landing time of the undercoat ink 36b is larger in the sub-scanning direction than in the main scanning direction. For this reason, by delaying the undercoat formation process from the middle to the completion of the undercoat formation process in the sub-scanning direction rather than in the main scanning direction, bleeding of the transfer image IM1 is preferably suppressed.

[0053] When serial printing is performed, the transfer medium M1 is conveyed in the conveyance direction by the conveyance amount for one sub-scan. There is a difference in the landing time of the undercoat ink 36b even during one main scan, and the difference in the landing time of the undercoat ink 36b becomes larger as the distance of the main scan is longer. Therefore, it is also conceivable to divide the processing unit area A0, which is the area corresponding to one conveyance amount in the transfer medium M1, in the main scanning direction. In this case, the processing unit area A0 becomes the area b3 corresponding to the conveyance amount for one sub-scan when sub-scanning is performed on the transfer medium M1 on which serial printing is performed. In order to reduce waste of the transfer medium M1, a plurality of separated images are often arranged on the transfer medium M1 in the main scanning direction. Therefore, a time difference occurs in the landing of the undercoat ink 36b that is overlaid on the images during the same main scan. In such a case, by delaying the undercoat formation process from the middle to the completion of the undercoat formation process during one main scan, the flow of the undercoat ink 36b due to the inclination of the transfer medium M1 in the adhesive application step ST3 is suppressed. For such a delay in the undercoat formation process, for example, it is conceivable to increase the processing time of the main scan in the second area A2.

[0054] When a continuous paper on which an image IM1 with an underlying ink 36b superimposed by line printing is formed is cut, the adhesive 111 is supplied at the same timing in the adhesive application step ST3 for one transfer medium obtained from the continuous paper. Therefore, the processing unit area A0 becomes an area b4 corresponding to one cut transfer medium. In the processing unit area A0, the second area A2 is located closer to the printer 2 than the first area A1. In the second area A2, the underlying ink 36b is superimposed on the image IM1 after the first area A1. In such a case, by delaying the underlying formation process from the middle to the completion of the underlying formation process for the processing unit area A0, the flow of the underlying ink 36b due to the inclination of the transfer medium M1 in the adhesive application step ST3 is suppressed. For such a delay in the underlying formation process, for example, it is conceivable to increase the conveyance time of the transfer medium M1 in the second area A2.

[0055] (3) Specific example of the processing of the printing apparatus: FIG. 9 schematically illustrates a printing control process for controlling the formation of the image IM1 on the transfer medium M1 and superimposing the underlying ink 36b on the image IM1. FIG. 9 also shows an example of the structure of a pass number table T1 for determining the number of passes NP. The printer 2 holds the pass number table T1, and the pass number table T1 may be stored in the storage unit 23. The printing control process shown in FIG. 9 targets lateral printing or serial printing. When the control unit 10 shown in FIG. 4 receives a printing instruction to the transfer medium M1 from the host device HO1 or the operation panel 24, it starts the printing control process. When the printing control process starts, the control unit 10 acquires image data DA1 representing the transfer medium M1 from the host device HO1 or the like (step S102). Hereinafter, the description of "step" may be omitted, and the step number may be indicated in parentheses.

[0056] After acquiring the image data DA1, the control unit 10 converts the gradation value of each pixel into a value representing the usage amounts of the colored ink 36a and the undercoat ink 36b (S104). When the image data DA1 is RGB data and the ink amount data is CMYKW data representing the usage amounts of the inks 36 of C, M, Y, K, and W, the control unit 10 refers to the color conversion LUT and converts each pixel value of R, G, and B into each pixel value of C, M, Y, K, and W. In the color conversion LUT, it is assumed that the gradation value of W is the value at which the undercoat ink 36b is used when at least one of the colored inks 36a of C, M, Y, and K is used. Thereby, the undercoat ink 36b is overlaid on the position of the image IM1. The gradation value of W after color conversion represents the discharge amount of the undercoat ink 36b in the portion overlaid on the image IM1 in the processing unit region A0. Since the discharge amount is represented by 0 to 100%, if the gradation value of W is 0 to 255, the gradation value of W represents the discharge amount by making the gradation values 0 to 255 correspond to the discharge amounts 0 to 100%.

[0057] Next, the control unit 10 performs halftone processing to generate dot data in which the number of gradations of the obtained ink amount data is reduced to, for example, 2 or 4 (S106). The dot data is generated for each of C, M, Y, K, and W. After the halftone processing, the control unit 10 refers to the pass number table T1 and determines the pass number NPi of each region Ai (S108). Here, the region Ai is any one of the first region A1, the second region A2, and the third region A3. The pass number NPi is any one of the pass numbers NP1 to NP3. The pass number table T1 has the pass number NP1 associated with the first region A1, the pass number NP2 associated with the second region A2, and the pass number NP3 associated with the third region A3. FIG. 9 shows that NP1 = 4, NP3 = 8, and NP2 = 12. In this case, the pass number NP1 in the first region A1 is 4, the pass number NP3 in the third region A3 is 8, and the pass number NP2 in the second region A2 is 12. Therefore, the pass number NP3 in the third region A3 is larger than the pass number NP1 in the first region A1, and the pass number NP2 in the second region A2 is larger than the pass number NP3 in the third region A3.

[0058] After determining the number of passes NP, the control unit 10 performs a rasterization process (S110) to generate raster data in which dot data is rearranged so that the undercoat ink 36b is overlaid on the image IM1 in NPi passes of main scanning after the main scanning for forming the image IM1. For example, it is assumed that after one pass of main scanning in which the colored ink 36a lands on each band in the processing unit area A0, NPi passes of main scanning in which the undercoat ink 36b lands are performed. In this case, the control unit 10 generates raster data in which the dot data is rearranged so that the colored ink 36a is ejected in one pass of main scanning to form the image IM1, and then the undercoat ink 36b is ejected in NPi passes of main scanning to be overlaid on the image IM1. Of course, the main scanning in which the colored ink 36a lands on each band may be two or more times, such as NP times.

[0059] Finally, the control unit 10 generates a drive signal SG1 according to the raster data, transmits it to the inkjet head 30, controls the image forming process for forming the image IM1 on the transfer medium M1, and controls the undercoat forming process for overlaying the undercoat ink 36b on the image IM1 in NPi passes of main scanning (S112). The ejection amount of the undercoat ink 36b assigned to each pass of main scanning may be equal, or may be unequal, such as the ejection amount in the NPi-th pass being less than the ejection amounts up to the (NPi - 1)-th pass. The drive unit 50 relatively moves the inkjet head 30 with respect to the transfer medium M1 so that main scanning and sub-scanning are performed according to the control by the control unit 10. The colored ink head 31 ejects the colored ink 36a so that the image IM1 is formed on the transfer medium M1 during main scanning, and the undercoat ink head 32 ejects the undercoat ink 36b so that the undercoat ink 36b is overlaid on the image IM1 during NPi passes of main scanning.

[0060] Here, when the number of passes NP increases in the second region A2 where the base ink 36b is overlaid on the image IM1 after the first region A1 and the third region A3, the time for the base formation process performed on the second region A2 becomes longer. As a result, the start timing of the base formation process for the second region A2 is delayed, and the drying of the base ink 36b proceeds. The discharge amount of the base ink 36b per main scan is smaller for the second region A2 than for the first region A1 and the third region A3, and thus the drying of the base ink 36b proceeds. When the drying of the base ink 36b proceeds, the flow of the base ink 36b due to the inclination of the transfer medium M1 in the adhesive application step ST3 is suppressed. Therefore, bleeding of the transfer image IM1 due to the base ink 36b dripping downward or the like is suppressed, and the image quality of the transfer image IM1 is improved. Further, since the third region A3 having the number of passes NP3 that is more than the number of passes NP1 and less than the number of passes NP2 is between the first region A1 and the second region A2, the influence on the image quality of the transfer image IM1 due to the change in the number of passes NP is reduced, and the image quality of the transfer image IM1 is improved. Note that the delay in the base formation process from the middle may be due to an increase in the time of the sub-scan process included in the base formation process for the second region A2, in addition to the increase in the number of passes NP.

[0061] Incidentally, as illustrated in FIGS. 10 and 11, the control unit 10 may change the number of passes NPi of the region Ai according to the area of the continuous region that is connected as one as the image IM1. FIG. 10 schematically illustrates a sheet for determining the presence or absence of a continuous region exceeding the reference area THS. FIG. 11 schematically shows another example of the print control process together with another structure example of the pass number table. FIG. 10 shows a first continuous region A11 having an area S1 not exceeding the reference area THS and a second continuous region A12 having an area S2 exceeding the reference area THS. The first continuous region A11 is connected as one as the image IM1, and the second continuous region A12 is also connected as one as the image IM1. In FIG. 10, the first region A1 includes a plurality of first continuous regions A11, the second region A2 includes the first continuous region A11 and the second continuous region A12, and the third region A3 includes a plurality of second continuous regions A12.

[0062] The larger the continuous area (A11, A12) is, the easier it is for the base ink 36b to flow due to the inclination of the transfer medium M1 in the adhesive application step ST3. For example, since the first area A1 only includes the first continuous area A11 with a small area, even if the transfer medium M1 inclines in the adhesive application step ST3, the flow of the base ink 36b in the first continuous area A11 included in the first area A1 is small. Although not shown, when there is a second continuous area A12 with a large area in the first area A1, when the transfer medium M1 inclines in the adhesive application step ST3, the flow of the base ink 36b in the second continuous area A12 included in the first area A1 is likely to occur. Therefore, when there is a second continuous area A12 with a large area in the first area A1, the control unit 10 increases the number of passes NP2 compared to the case where the second continuous area A12 does not exist. Thereby, the drying of the base ink 36b existing in the first area A1 proceeds, the flow of the base ink 36b due to the inclination of the transfer medium M1 in the adhesive application step ST3 is further suppressed, and the bleeding of the transfer image IM1 is further suppressed.

[0063] In FIG. 10, since the second area A2 includes the second continuous area A12 with a large area, when the transfer medium M1 inclines in the adhesive application step ST3, the flow of the base ink 36b in the second continuous area A12 included in the second area A2 is likely to occur. In particular, in the second area A2 including the portion where the base ink 36b is finally overlaid on the image IM1 in the processing unit area A0, the flow of the base ink 36b is likely to occur. Although not shown, when there is only the first continuous area A11 with a small area in the second area A2, even if the transfer medium M1 inclines in the adhesive application step ST3, the flow of the base ink 36b in the first continuous area A11 included in the second area A2 is small. Therefore, when there is a second continuous area A12 with a large area in the second area A2, the control unit 10 increases the number of passes NP2 compared to the case where the second continuous area A12 does not exist. Thereby, the drying of the base ink 36b existing in the second area A2 proceeds, the flow of the base ink 36b due to the inclination of the transfer medium M1 in the adhesive application step ST3 is further suppressed, and the bleeding of the transfer image IM1 is further suppressed.

[0064] Still, while changing the number of passes NP2 according to the area of the continuous area in the second area A2, the number of passes NP1 may be fixed in the first area A1, or while changing the number of passes NP1 according to the area of the continuous area in the first area A1, the number of passes NP2 may be fixed in the second area A2. Also for the third area A3, the control unit 10 may make the number of passes NP3 when the large second continuous area A12 exists larger than the number of passes NP3 when the second continuous area A12 does not exist.

[0065] The pass number table T2 shown in FIG. 11 also has the number of passes NP1 associated with the first area A1, the number of passes NP2 associated with the second area A2, and the number of passes NP3 associated with the third area A3. However, the number of passes NPi changes according to the area of the continuous area. In FIG. 11, when the second continuous area A12 exceeding the reference area THS does not exist in the area Ai, NP1 = 4, NP3 = 8, and NP2 = 12, and when the second continuous area A12 exists in the area Ai, NP1 = 6, NP3 = 10, and NP2 = 14. Therefore, in any of the areas Ai, the number of passes NPi when including the second continuous area A12 is larger than the number of passes NPi when not including the second continuous area A12. Still, the number of passes NPi within the same area may be switched in three or more steps.

[0066] The printing control process shown in FIG. 11, compared with the printing control process shown in FIG. 9, has the pass number table T1 replaced by the pass number table T2, and the process of S202 is added between S106 and S108. When dot data for C, M, Y, K, and W are generated through the processes of S102 to S106, the control unit 10 extracts continuous regions included in the region Ai and obtains the area of each continuous region (S202). For example, the control unit 10 extracts the continuous regions included in the first region A1, the continuous regions included in the second region A2, and the continuous regions included in the third region A3 based on the image data DA1, RGB data, ink amount data, or dot data, and calculates the area of each continuous region. The area of the continuous region can be obtained, for example, by counting the number of pixels included in the continuous region. Next, the control unit 10 refers to the pass number table T2 and determines the pass number NPi for each region Ai (S108). The control unit 10 determines that the continuous region is the second continuous region A12 when the area of the continuous region exceeds the reference area THS, and determines that the continuous region is the first continuous region A11 when the area of the continuous region does not exceed the reference area THS. Moreover, for each region Ai, the control unit 10 determines the pass number NPi of "large area continuous region exists" when the second continuous region A12 exists, and determines the pass number NPi of "large area continuous region does not exist" when the second continuous region A12 does not exist.

[0067] For example, as shown in FIG. 10, assume that the first continuous region A11 and the second continuous region A12 are arranged in the processing unit region A0. Since the second continuous region A12 does not exist in the first region A1, the control unit 10 determines the pass number NP1 to be 4. Since the second continuous region A12 exists in the third region A3, the control unit 10 determines the pass number NP3 to be 10. Since the second continuous region A12 exists in the second region A2, the control unit 10 determines the pass number NP2 to be 14.

[0068] After determining the number of passes NP, the control unit 10 performs a rasterization process (S110) of generating raster data in which dot data is rearranged so that the undercoat ink 36b is overlaid on the image IM1 NPi times after the main scanning for forming the image IM1. Finally, the control unit 10 generates a drive signal SG1 according to the raster data, transmits it to the inkjet head 30, controls an image forming process of forming the image IM1 on the transfer medium M1, and controls an undercoat forming process of overlaying the undercoat ink 36b on the image IM1 in NPi main scans (S112). When there is a second continuous region A12 with a large area in the region Ai, the number of passes NPi is larger than when the second continuous region A12 does not exist, so that the flow of the undercoat ink 36b due to the inclination of the transfer medium M1 in the adhesive application step ST3 is further suppressed. Therefore, bleeding of the transferred image IM1 is further suppressed.

[0069] Also, as illustrated in FIG. 12, the control unit 10 may change the number of passes NPi of the region Ai according to the discharge amount DT of the undercoat ink 36b per unit area for each region Ai. Note that the discharge amount DT of the undercoat ink 36b is also referred to as the undercoat ink discharge amount DT. The "discharge amount DT of W" shown in FIG. 12 means the discharge amount DT of the undercoat ink per unit area. FIG. 12 schematically shows an example of changing the number of passes NPi according to the discharge amount DT of the undercoat ink per unit area. FIG. 12 also shows a structural example of a pass number table T3 for determining the number of passes NPi according to the discharge amount DT of the undercoat ink.

[0070] The pass number table T3 shown in FIG. 12 also has a pass number NP1 associated with the first region A1, a pass number NP2 associated with the second region A2, and a pass number NP3 associated with the third region A3. However, the pass number NPi changes according to the base ink discharge amount DT in the region Ai. In FIG. 12, the threshold values of the base ink discharge amount DT per unit area are a first discharge amount THD1 and a second discharge amount THD2 greater than the first discharge amount THD1. When the base ink discharge amount DT of the region Ai does not exceed the first discharge amount THD1, NP1 = 2, NP3 = 3, and NP2 = 4. When the base ink discharge amount DT of the region Ai exceeds the first discharge amount THD1 but does not exceed the second discharge amount THD2, NP1 = 4, NP3 = 6, and NP2 = 8. When the base ink discharge amount DT of the region Ai exceeds the second discharge amount THD2, NP1 = 8, NP3 = 12, and NP2 = 16. Therefore, it can be said that the pass number table T3 has information that makes the pass number NPi of the region Ai be NP1 < NP3 < NP2 if the base ink discharge amount DT does not change. For each region Ai, the pass number NPi when the base ink discharge amount DT per unit area exceeds the first discharge amount THD1 is larger than the pass number NPi when the base ink discharge amount DT per unit area does not exceed the first discharge amount THD1. For each region Ai, the pass number NPi when the base ink discharge amount DT per unit area exceeds the second discharge amount THD2 is larger than the pass number NPi when the base ink discharge amount DT per unit area does not exceed the second discharge amount THD2. Therefore, it is also possible to read "the second discharge amount THD2" as "the first discharge amount THD1".

[0071] In addition, while making the pass number NP2 when DT > THD1 in the second region A2 larger than the pass number NP2 when DT ≤ THD1, the pass number NP1 in the first region A1 may be constant regardless of the base ink discharge amount DT. Also, while making the pass number NP1 when DT > THD1 in the first region A1 larger than the pass number NP1 when DT ≤ THD1, the pass number NP2 in the second region A2 may be constant regardless of the base ink discharge amount DT. The same can be said for the third region A3.

[0072] The printing control process that refers to the pass number table T3 can be performed according to the printing control process shown in FIG. 9. For example, in S108, the control unit 10 may calculate the average value of the discharge amount of the undercoat ink 36b of the portion overlaid on the image IM1 for each region Ai as the undercoat ink discharge amount DT based on the W data included in the CMYKW data. Thereafter, the control unit 10 may refer to the pass number table T3 and select the pass number NPi of the section including the undercoat ink discharge amount DT for each region Ai.

[0073] As shown in FIG. 12, in the first region A1, when the undercoat ink discharge amount DT1 exceeds the second discharge amount THD2, the control unit 10 determines the pass number NP1 to be 8 corresponding to "large" in the "first region A1" of the pass number table T3. In the third region A3, when the undercoat ink discharge amount DT3 exceeds the second discharge amount THD2, the control unit 10 determines the pass number NP3 to be 12 corresponding to "large" in the "third region A3" of the pass number table T3. In the second region A2, when the undercoat ink discharge amount DT2 does not exceed the first discharge amount THD1, the control unit 10 determines the pass number NP2 to be 4 corresponding to "small" in the "second region A2" of the pass number table T3.

[0074] The larger the undercoat ink discharge amount DT per unit area, the easier it is for the undercoat ink 36b to flow due to the inclination of the transfer medium M1 in the adhesive application step ST3. Since the drying of the undercoat ink 36b progresses as the pass number NP increases in the region where the undercoat ink discharge amount DT is large, the flow of the undercoat ink 36b due to the inclination of the transfer medium M1 in the adhesive application step ST3 is further suppressed, and the bleeding of the transferred image IM1 is suppressed.

[0075] If the undercoat ink discharge amount DT does not change, the control unit 10 makes the number of passes NP3 in the third region A3 larger than the number of passes NP1 in the first region A1, and makes the number of passes NP2 in the second region A2 larger than the number of passes NP3 in the third region A3. Therefore, it can be said that the control unit 10 performs control to delay the undercoat formation process from the middle of the undercoat formation process for the processing unit region A0 until the undercoat formation process is completed. As a result, the drying of the undercoat ink 36b in the portion of the processing unit region A0 where the undercoat ink 36b is finally overlapped with the image IM1 progresses, and the flow of the undercoat ink 36b due to the inclination of the transfer medium M1 in the adhesive application step ST3 is suppressed. Since the pass number table T3 shown in FIG. 12 takes into account both the pass number NP related to the bleeding of the transfer image IM1 and the undercoat ink discharge amount DT, the bleeding of the transfer image IM1 is preferably suppressed.

[0076] Although not shown, the pass number NPi of each section of the pass number table T3 shown in FIG. 12 may be changed according to the area of the continuous region. For example, in the second region A2, when DT ≦ THD1, if there is a second continuous region A12 exceeding the reference area THS, NP2 = 6 may be set, and if there is no second continuous region A12, NP2 = 4 may be set. In the second region A2, when THD1 < DT ≦ THD2, if there is a second continuous region A12 exceeding the reference area THS, NP2 = 10 may be set, and if there is no second continuous region A12, NP2 = 8 may be set. In the first region A1, when DT ≦ THD1, if there is a second continuous region A12 exceeding the reference area THS, NP1 = 4 may be set, and if there is no second continuous region A12, NP1 = 2 may be set. In the first region A1, when THD1 < DT ≦ THD2, if there is a second continuous region A12 exceeding the reference area THS, NP1 = 6 may be set, and if there is no second continuous region A12, NP1 = 4 may be set.

[0077] (4) Modification example: Various modification examples of the present invention can be considered. For example, the entity performing the above-described processing is not limited to the CPU, and may be an electronic component other than the CPU, such as an ASIC (Application Specific Integrated Circuit). Of course, a plurality of CPUs may cooperate to perform the above-described processing, or the CPU and other electronic components (for example, ASIC) may cooperate to perform the above-described processing. A part of the print control processing shown in FIGS. 9 and 11 may be performed by the host device HO1. In this case, the control unit of the printing apparatus 1 is a combination of the control unit 10 in the narrow sense and the host device HO1. The combination of the colors of the colored inks 36a is not limited to C, M, Y, and K, and may include orange, green, light cyan with a lower concentration than C, light magenta with a lower concentration than M, dark yellow with a higher concentration than Y, light black with a lower concentration than K, and the like. Of course, even when the colored inks 36a do not include some of the inks of C, M, Y, and K, the aspects of the present application are applicable.

[0078] The undercoat ink 36b is not limited to the W ink, and may be a K ink containing a light-absorbing component, a gray ink containing a light-scattering component and a light-absorbing component, or the like. Further, even when the color of the transfer medium M2 serving as the background of the image IM1 is transmissive, a clear ink through which light is transmissive can also be used as the undercoat ink 36b.

[0079] (5) Conclusion: As described above, according to the present invention, various aspects can provide a configuration capable of suppressing bleeding of the transferred image. Of course, even in an aspect consisting only of the constituent elements according to the independent claims, the above-described basic operations and effects can be obtained. In addition, configurations in which the respective configurations disclosed in the above-described examples are mutually replaced or the combinations are changed, known techniques, and configurations in which the respective configurations disclosed in the above-described examples are mutually replaced or the combinations are changed, etc. are also feasible. The present invention includes these configurations and the like.

Description of Reference Numerals

[0080] 1…Printing device, 2…Printer, 10…Control unit, 20…Printing unit, 30…Inkjet head, 30a…Nozzle surface, 31…Colored ink head, 32…Undercoat ink head, 33…Carriage, 34…Nozzle, 36…Ink, 36a…Colored ink, 36b…Undercoat ink, 37…Ink droplet, 50…Drive unit, 51…Main scanning drive unit, 52…Sub-scanning drive unit, 55…Conveyor unit, 100…Adhesive application device, 110…Adhesive tank, 111…Adhesive, 120…Heating unit, 200…Thermal transfer device, A0, A01, A02, A03…Processing unit area, A1…First area, A2…Second area, A3…Third area, A11…First continuous area, A12…Second continuous area, D1…First direction, D2…Second direction, D11…Forward direction, D12…Return direction, DA1…Image data, DT…Discharge amount, IM1…Image, L1…Conveyor amount, M1…Transfer medium, M2…Medium to be transferred, M11…Continuous paper, M12…Single sheet paper, NP…Number of passes, ST1…Image forming process, ST2…Undercoat forming process, ST3…Adhesive application process, ST4…Heating process, ST5…Transfer process, T1~T3…Number of passes table, THD1…First discharge amount, THD2…Second discharge amount, THS…Reference area.

Claims

1. A printing method for printing on the transfer medium, which includes an adhesive application step of applying an adhesive to an undercoat ink overlapped on an image formed on the transfer medium, and a transfer step of transferring the image to the transfer medium by attaching the adhesive to the transfer medium, an image forming step of performing a first process of forming the image on the transfer medium by ejecting a colored ink from a first inkjet head, and an undercoat forming step of performing a second process including a process of overlapping the undercoat ink on the image by ejecting the undercoat ink from a second inkjet head onto the transfer medium, wherein a region where the adhesive is supplied at the same timing in the adhesive application step with respect to the transfer medium is defined as a processing unit region, and in the undercoat forming step, the second process is delayed from the middle to the completion of the second process for the processing unit region.

2. The processing unit region includes a first region and a second region where the undercoat ink is overlapped on the image after the first region, the second region includes a portion where the undercoat ink is finally overlapped on the image in the processing unit region, and in the undercoat forming step, the second process for the second region is delayed. The printing method according to claim 1.

3. In the undercoat forming step, main scanning is performed to eject the undercoat ink while relatively moving the second inkjet head along a second direction with respect to the transfer medium, and in the sub-scanning between the main scans, the second inkjet head is relatively moved with respect to the transfer medium in a first direction intersecting the second direction to change the position in the first direction where the undercoat ink is overlapped on the image, thereby performing the second process, wherein the number of times of the main scanning accompanied by the ejection of the undercoat ink performed at the same location on the transfer medium is defined as the number of passes, and in the undercoat forming step, the second process is performed to make the number of passes in the second region larger than the number of passes in the first region. The printing method according to claim 2.

4. The processing unit region includes a continuous region that is connected as one as the image. The printing method according to claim 3, wherein in the underlayer forming step, when there is a continuous area exceeding a reference area in at least one of the first area and the second area, the number of passes is made larger than the number of passes when there is no continuous area exceeding the reference area.

5. In the underlayer forming step, main scanning is performed to discharge the underlayer ink while relatively moving the second inkjet head with respect to the transfer medium along a second direction intersecting the first direction, and in the sub-scanning between the main scans, the second inkjet head is relatively moved in the first direction with respect to the transfer medium to perform a second process of changing the position in the first direction where the underlayer ink is overlaid on the image. Regarding the transfer medium, the number of times of the main scanning accompanied by the discharge of the underlayer ink at the same position is defined as the number of passes. The printing method according to claim 2, wherein in the underlayer forming step, in at least one of the first area and the second area, when the discharge amount of the underlayer ink per unit area exceeds a first discharge amount, the number of passes is made larger than the number of passes when the discharge amount of the underlayer ink per unit area does not exceed the first discharge amount, and when the discharge amount of the underlayer ink per unit area does not change, a second process is performed in which the number of passes in the second area is made larger than the number of passes in the first area.

6. The printing method according to claim 1 or claim 2, wherein the underlayer ink is an ink containing a component that blocks the transmission of light.

7. A printing apparatus that performs printing on a transfer medium in order to carry out an adhesive application step of attaching an adhesive to an underlayer ink overlaid on an image formed on the transfer medium, and a transfer step of transferring the image to a transfer target medium by attaching the adhesive to the transfer target medium, the printing apparatus including: a first inkjet head that discharges a colored ink; a second inkjet head that discharges the underlayer ink; a drive unit that relatively moves the second inkjet head in a first direction with respect to the transfer medium; a control unit that controls the discharge of the colored ink from the first inkjet head, the discharge of the underlayer ink from the second inkjet head, and the drive unit; The control unit: controls a first process of forming the image on the transfer medium by discharging the colored ink from the first inkjet head. Controlling a second process including a process of overlapping the base ink on the image by discharging the base ink from the second inkjet head onto the transfer medium; Using, as a processing unit area, an area where the adhesive is supplied at the same timing in the adhesive application step with respect to the transfer medium; A printing apparatus, wherein the control unit performs control to delay the second process from a midway through the second process to completion of the second process with respect to the processing unit area.

Images