Printing apparatus, print data generation method, and print data generation apparatus

Abstract

To more appropriately transfer an image using a hot-melt resin powder.SOLUTION: A printing method for drawing an image on a transfer medium by transferring an image printed on a transfer medium 50 to the transfer medium, the printing method including a printing step of printing an image on the transfer medium 50 by a printing unit 14 which is a printing device, a hot-melt resin adhering step of adhering hot-melt resin powder to the transfer medium 50, and a transfer step of transferring the image from the transfer medium 50 to the transfer medium, wherein the printing unit 14 includes a color ink head for ejecting color ink and a clear ink head for ejecting clear ink. In the printing stage, clear ink is further ejected from a clear ink head to at least a part of a region where the color ink is ejected from the color ink head on the transfer medium 50.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a printing method, a printing system, and a printing device. [Background technology]

[0002] A transfer printing method using a hot melt layer formed from a resin powder has been known. In this method, for example, an image is printed on a transfer medium (such as a transfer sheet) with a release layer formed on its surface. A hot melt layer is then formed over the entire surface of the transfer medium. The transfer medium and the transfer recipient medium are then stacked and heated and pressurized to transfer the image from the transfer medium to the transfer recipient medium. In this case, for example, a film or the like with a receiving layer formed thereon is used as the transfer medium. An image is printed on the transfer medium using color inks, and a white ink layer is formed on the image using white ink. Hot melt resin powder is then applied to the white ink layer on the transfer medium, and the resulting layer is pressed together using a heat press machine to transfer the image. Other known methods include forming a hot melt layer that matches the image without forming a hot melt layer over the entire surface of the transfer medium (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2019-171840 Summary of the Invention [Problem to be solved by the invention]

[0004] When a white ink layer is formed on an image printed with color inks, the image can be properly expressed on the receiving medium even if the background color of the receiving medium is dark. However, in this case, the white ink layer, which is formed over an area larger than the image, is also transferred to the receiving medium, potentially transferring areas unnecessary for the original image, such as margins, and impairing the design and texture. In contrast, by forming a hot melt layer that matches the image, as in the method disclosed in Patent Document 1, for example, only the areas necessary for the image expression can be transferred from the transfer medium to the receiving medium. Furthermore, in this case, using a light-colored (light-colored) fabric, such as white or beige, as the receiving medium can take advantage of the background color and material of the receiving medium, thereby improving the design and texture.

[0005] However, the method disclosed in Patent Document 1 uses a transfer sheet as the transfer medium that is non-water-repellent but maintains ink impermeability enough to maintain the adhesion of the powder until the image is formed and the powder is sprinkled on it. Furthermore, a specific grade of resin powder with a small particle size is used as the powder. However, in this case, the conditions for the transfer medium and powder that can be used are limited, which may significantly increase printing costs and significantly reduce the flexibility of printing conditions.

[0006] Furthermore, the inventors of the present application conducted various experiments and found that transferring an image without using a white ink layer can sometimes result in a decrease in the quality of the image transferred to the transfer medium. Therefore, there has been a demand for a more appropriate method for transferring an image. Therefore, an object of the present invention is to provide a printing method, a printing system, and a printing device that can solve the above-mentioned problems. [Means for solving the problem]

[0007] The inventors of the present application have conducted extensive research into more appropriate image transfer methods, such as methods for more appropriately transferring images without forming a white ink layer, even when using common color inks and transfer media. Through this research, they discovered that without forming a white ink layer, transferability is reduced in low-gradation areas, which express lighter colors in the image, compared to high-gradation areas, which express darker colors, resulting in unintended transfer unevenness. They also discovered that the reason for this is that the amount of color ink used in low-gradation areas is reduced, resulting in a reduced amount of hot melt resin adhering to those areas, preventing the image from being completely transferred. In this case, the reduced image transferability in those areas results in, for example, scattered uncolored areas on the transfer medium, even in areas that should be colored. This, in turn, results in, for example, transfer unevenness.

[0008] In response to this, the inventors of the present application have devised a method for using a clear ink in addition to the color inks, which does not affect the color of the image. With this configuration, for example, by ejecting additional clear ink onto the transfer medium in the low gradation region of the image, where the amount of color ink used is reduced, it is possible to appropriately prevent the amount of hot melt resin adhered to the transfer medium from being insufficient. This also makes it possible to appropriately prevent, for example, deterioration in the quality of the transferred image due to the occurrence of uneven transfer.

[0009] Furthermore, the inventors of the present application have conducted further intensive research and have found the characteristics necessary to obtain such effects, which have led to the present invention. In order to solve the above-mentioned problems, the present invention provides a printing method for drawing an image on a transfer medium by transferring an image printed on the transfer medium to the transfer receiving medium, the method comprising: a printing step of printing the image on the transfer medium using a printing device that performs printing using an inkjet method; a hot-melt resin application step of applying hot-melt resin powder, which is a powder containing a resin that softens when heated, to the transfer medium on which the image has been printed; and a transfer step of heating the transfer medium to which the hot-melt resin powder has been applied, and applying a hot-melt resin portion, which is a resin portion formed by the hot-melt resin powder being softened by heating, to the transfer receiving medium, thereby transferring the image from the transfer medium to the transfer receiving medium. The printing device comprises a colored ink head, which is an inkjet head that ejects colored ink, which is ink containing coloring materials that exhibit colored colors, and a clear ink head, which is an inkjet head that ejects clear ink, which is colorless and translucent ink, and during the printing step, the clear ink is further ejected from the clear ink head onto at least a portion of an area on the transfer medium onto which the colored ink is ejected from the colored ink head.

[0010] In this configuration, by using clear ink in addition to colored ink when printing on a transfer medium using a printing device, it is possible to appropriately eject inks other than colored ink onto the transfer medium while, for example, appropriately suppressing the influence of the color of the image printed on the transfer medium. Furthermore, by ejecting clear ink at positions where the amount of colored ink ejected is small, the total amount of ink ejected onto the transfer medium can be increased compared to when only colored ink is used. In this case, increasing the total amount of ink can also allow, for example, hot melt resin powder to adhere more appropriately to the transfer medium. Furthermore, this can appropriately prevent, for example, transfer unevenness due to a lack of hot melt resin powder when transferring an image from the transfer medium to a transfer receiving medium. Therefore, with this configuration, it is possible to more appropriately transfer an image using, for example, hot melt resin powder.

[0011] In this configuration, in the printing stage, printing is performed on the transfer medium using colored inks and clear ink, without using white ink, for example. Also, in this configuration, for example, a known transfer film can be suitably used as the transfer medium. For example, a transfer film for transfer using the DTF (Direct to Film) method can be suitably used as the known transfer film. Furthermore, a medium other than film (for example, a paper medium) can also be used as the transfer medium. For example, a cloth medium can be suitably used as the transfer medium. For example, a known color ink (for example, a known ink for textile printing) can be suitably used as the color ink. For example, an ink containing a pigment as a coloring material (for example, an aqueous pigment ink) can be suitably used as the known color ink.

[0012] In the transfer stage, for example, at least a portion of the colorant adhering to the transfer medium is transferred to the transfer medium together with at least a portion of the hot-melt resin portion, thereby transferring the image from the transfer medium to the transfer medium. In this case, using clear ink can be considered to increase the transfer rate of the colorant. More specifically, for example, if the area on the transfer medium onto which colorant ink is ejected from the colorant ink head is defined as the image representation area, the area where the amount of colorant ink ejected per unit area is less than a predetermined reference amount is defined as the low-ink area, and the transfer rate is defined as the proportion of colorant transferred from the transfer medium to the transfer medium during the transfer stage, then in the printing stage, by ejecting clear ink onto at least a portion of the low-ink area of ​​the image representation area using a printing device, the transfer rate of at least a portion of the low-ink area can be considered to be higher than when clear ink is not ejected. This configuration can, for example, appropriately prevent the occurrence of transfer unevenness and ensure proper image transfer. Furthermore, in this case, for example, the low-ink area can be considered to be the area expressing colors in the low-tone range of the image. Furthermore, in this case, focusing on the low-ink-amount region, for example, by ejecting clear ink onto at least a portion of the low-ink-amount region during the printing stage, the amount of hot-melt resin powder that adheres to the location where the clear ink is ejected during the hot-melt resin application stage can be thought of as being greater than when no clear ink is ejected. This configuration, for example, can appropriately increase the transfer rate in the low-ink-amount region. This can also appropriately prevent, for example, the occurrence of transfer unevenness.

[0013] Furthermore, in this configuration, in areas where a sufficient amount of colored ink is ejected, a sufficient amount of hot-melt resin powder can be deposited without using clear ink. Therefore, the amount of clear ink ejected at each position on the transfer medium may be varied, for example, depending on the amount of colored ink ejected at each position. More specifically, for example, if a non-low-ink-volume area is defined as an image representation area where the amount of colored ink ejected per unit area is greater than a predetermined amount greater than the reference amount, and the amount of clear ink ejected per unit area to each position on the transfer medium is defined as the clear ink ejection amount, it is possible to vary the clear ink ejection amount depending on the amount of colored ink ejected per unit area during printing so that the clear ink ejection amount in the low-ink-volume area is greater than the clear ink ejection amount in the non-low-ink-volume area. This configuration, for example, makes it possible to appropriately eject clear ink where necessary while minimizing the amount of clear ink used. Furthermore, in this case, reducing the clear ink ejection amount in the non-low-ink-volume area can prevent the total amount of ink ejected at the same position from becoming excessively large.

[0014] Furthermore, if the total amount of ink ejected to the same position becomes large, problems such as bleeding of colored ink may become more likely to occur. Therefore, it may be possible to set the amount of clear ink ejected to zero in areas where a large amount of colored ink is ejected. More specifically, in this case, for example, clear ink is not ejected in areas where the amount of colored ink ejected per unit area during printing exceeds a preset upper limit. This configuration, for example, can more appropriately prevent the total amount of ink ejected to the same position from becoming excessively large.

[0015] In this configuration, the printing device ejects colored inks and clear inks from the colored ink head and the clear ink head to ejection positions set according to the printing resolution, for example. In this case, it is possible to eject clear ink so that an area including multiple ejection positions is continuously covered with the colored inks and clear inks. More specifically, if an ejection position to which colored inks are ejected from the colored ink head is defined as a colored ejection position and an isolated ejection position is defined as a colored ejection position where no adjacent ejection position is a colored ejection position, the low-ink area can be considered, for example, as an area including the isolated ejection position. Then, during the printing stage, clear ink is ejected from the clear ink head to at least some of the isolated ejection positions in the low-ink area or to ejection positions surrounding the isolated ejection positions, thereby printing on the transfer medium so that an area including multiple ejection positions, including the isolated ejection position, is connected by the colored inks and clear ink, at least in the vicinity of the isolated ejection position. This configuration makes it possible to appropriately increase the total amount of ink ejected near isolated ejection positions in the low-ink-volume region compared to when clear ink is not used, thereby more appropriately adhering hot-melt resin powder to the areas near isolated ejection positions.

[0016] In this configuration, it is possible to use, for example, a medium having an ink-absorbing ink-receiving layer formed thereon as the transfer medium. This configuration can appropriately prevent, for example, bleeding of the colored ink. In this case, it is preferable to have the printing device perform printing in the printing stage so that the colored ink lands at each position on the transfer medium before the clear ink. This configuration can more appropriately prevent, for example, bleeding. In this configuration, it is also possible to use clear ink to reduce, for example, graininess. More specifically, it is possible to use, for example, inks containing a solvent that are fixed to the transfer medium as the solvent evaporates, as the colored ink and the clear ink. Regarding the size of ink dots formed by colored ink spreading on a transfer medium after impact, if the size of the dot formed when both colored ink and clear ink are ejected at the same ejection position is defined as the size when clear ink is used, and the size of the dot formed when only colored ink is ejected at the same ejection position is defined as the size when clear ink is not used, then during the printing stage, for example, clear ink can be ejected at at least some of the ejection positions where colored ink is ejected in the low-ink-volume area so that the size when clear ink is used is larger than the size when clear ink is not used. This configuration, for example, can appropriately increase the size of ink dots formed with colored ink. This can also, for example, appropriately reduce graininess.

[0017] In this configuration, the colored ink can be suitably an ink containing a binder resin, which is a resin that bonds to the transfer medium together with the colorant. In this case, the clear ink can be suitably an ink containing the same resin as the binder resin. This configuration allows for the appropriate use of a clear ink with similar properties to the colored ink. In this case, it can be considered that an ink containing the same resin as the binder resin maintains a state in which hot-melt resin powder is more likely to adhere for a longer period of time than an ink that does not contain the resin. Therefore, by using a clear ink containing the resin, it is possible to more reliably adhere the hot-melt resin powder to the location where the clear ink is ejected. It is also possible to use an ink that does not contain the same resin as the binder resin in the colored ink. Even in this configuration, the use of the clear ink can extend the time it takes for the ink to dry to a state in which the hot-melt resin powder is less likely to adhere to the location where the clear ink is ejected. This also allows for the hot-melt resin powder to be more reliably adhered to the location where the clear ink is ejected, even when a clear ink that does not contain the resin is used.

[0018] Furthermore, it may be preferable for the clear ink dots formed on the transfer medium by ejecting the clear ink onto the transfer medium to be flattened and spread out, for example, to make it easier for the hot melt resin powder to adhere to them. In this case, for example, an adjustment step may be performed to adjust the spread of the clear ink dots formed on the transfer medium during the printing step. This configuration allows, for example, the size of the clear ink dots to be appropriately adjusted. In this case, for example, the adjustment step determines whether the spread of the clear ink dots is insufficient based on the results of printing an image on the transfer medium using a printing device under preset first printing conditions. If it is determined that the spread of the dots is insufficient, for example, second printing conditions, which are different from the first printing conditions and result in a larger spread of the clear ink dots, are selected as printing conditions for the printing device during the printing step. This configuration allows, for example, the hot melt resin powder to adhere more appropriately to the positions where the clear ink is ejected.

[0019] Furthermore, it is also conceivable to use a printing system or printing device having the same features as those described above as a configuration of the present invention. In these cases, for example, the same effects as those described above can be obtained. [Effects of the Invention]

[0020] According to the present invention, for example, image transfer using hot melt resin powder can be more appropriately carried out. [Brief explanation of the drawings]

[0021] [Figure 1] 1A and 1B are diagrams illustrating a printing system 10 according to an embodiment of the present invention. Fig. 1A shows an example of the configuration of the printing system 10. Fig. 1B shows an example of the configuration of a printing unit 14 in the printing system 10. [Figure 2]2(a) to 2(c) are diagrams illustrating in more detail the multiple inkjet heads 202 of the head unit 102. FIGS. [Figure 3] 10 is a flowchart showing an example of an operation executed by the printing system 10 in this example. [Figure 4] 4A and 4B are diagrams explaining the reason for using clear ink in this example. FIG. 4A shows an example of a method for printing on a transfer medium 50 using a conventional method. FIG. 4B shows an example of a method for printing on a transfer medium 50 using a method different from the method shown in FIG. 4A. FIG. 4C shows an example of a method for printing on a transfer medium 50 in this example. [Figure 5] 5A and 5B are diagrams illustrating an image printed on a transfer medium 50. Fig. 5A shows an example of an image printed on a transfer medium 50. Fig. 5B shows an example of the state of color ink dots that make up the image. [Figure 6] 6A to 6C are diagrams showing examples of ejection positions for ejecting color inks and clear ink, and show examples of how to select ejection positions for ejecting clear ink. [Figure 7] 10 is a flowchart showing an example of an operation of generating print data in the print data preparation unit 12. [Figure 8] 8A and 8B are diagrams illustrating an experiment conducted by the inventor of the present application. Fig. 8A shows the composition of the clear ink used in the experiment. Fig. 8B and Fig. 8C show the results of the experiment. DETAILED DESCRIPTION OF THE INVENTION

[0022] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a diagram illustrating a printing system 10 according to an embodiment of the present invention. FIG. 1(a) shows an example of the configuration of the printing system 10. FIG. 1(b) shows an example of the configuration of a printing unit 14 in the printing system 10. Except as described below, the printing system 10 may have the same or similar features as known printing systems 10.

[0023] The printing system 10 is a system for drawing an image on a transfer medium (transfer target) by transferring an image printed on a transfer medium 50 to the transfer medium. The image is transferred from the transfer medium 50 to the transfer medium using a hot-melt resin powder (hot-melt powder), which is a powder containing a resin that softens when heated. In this example, a cloth medium such as fabric (e.g., various fabrics) is used as the transfer medium. The transfer medium may also be a cloth medium processed into a specific product, such as a T-shirt. Furthermore, a known transfer medium used for transferring cloth to a transfer medium can be suitably used as the transfer medium 50. More specifically, a transfer film for transfer using the DTF (Direct to Film) method can be suitably used as the transfer medium 50. Furthermore, PET film, for example, can be used as such a transfer film. Furthermore, a medium other than film (e.g., paper medium) can also be used as the transfer medium 50.

[0024] Furthermore, known resin powders used for transfer printing can be suitably used as the hot melt resin powder. More specifically, known hot melt resin powders used for transferring images onto a cloth receiving medium can be suitably used as the hot melt resin powder. Furthermore, powders containing, for example, urethane, acrylic, polyester, polyamide, or mixtures thereof can be suitably used as such hot melt resin powders. The hot melt resin powder can also be considered, for example, as a thermoplastic resin powder. The hot melt resin powder can also be considered, for example, as a hot melt adhesive powder for transfer printing. The hot melt adhesive powder can also be considered, for example, as a powder of an adhesive that is solid at room temperature and whose main component is a thermoplastic polymer. The hot melt adhesive powder can also be considered, for example, as a powder of a solid adhesive that does not contain water or organic solvents. Such hot melt adhesive powders can include, for example, a multi-component adhesive powder.

[0025] To perform transfer using the above-described transfer medium, transfer medium 50, and hot-melt resin powder, the printing system 10 in this example includes a print data preparation unit 12, a printing unit 14, a powder application unit 16, and a thermal transfer unit 18. The print data preparation unit 12 is configured to prepare print data for controlling the operation of the printing unit 14, and generates print data to be supplied to the printing unit 14 based on image data representing an image to be printed on the transfer medium 50 by the printing unit 14. The print data preparation unit 12 may be, for example, a computer that controls the operation of the printing unit 14 according to a predetermined program. In this example, the print data preparation unit 12 generates print data by performing halftone processing on the image data in accordance with the configuration of the printing unit 14. The print data preparation unit 12 then supplies the print data to the printing unit 14, controlling the operation of the printing unit 14 and causing the printing unit 14 to perform a printing operation. The operation of generating print data in the print data preparation unit 12 will be described in more detail below.

[0026] The printing unit 14 corresponds to the printing device in the printing system 10, and performs inkjet printing on the transfer medium 50 based on the print data supplied from the print data preparation unit 12. In this example, the printing unit 14 is a serial inkjet printer, and performs printing by causing an inkjet head to perform a main scanning operation in which ink is ejected while moving relatively to the printing target in a predetermined main scanning direction (Y direction in the figure). The printing unit 14 also includes a head unit 102, a platen 104, a Y-bar unit 106, a main scanning driver 108, a sub-scanning driver 110, and a controller 120, as shown in FIG. 1(b), for example.

[0027] The head unit 102 includes multiple inkjet heads, which eject ink toward the transfer medium 50. In this example, the head unit 102 includes multiple inkjet heads for color inks that eject different color inks, and a clear ink inkjet head that ejects clear ink. In this case, each color ink is an example of a colored ink, which is an ink containing a colorant. Each of the multiple inkjet heads for color inks is an example of a colored ink head. The clear ink ink head is an example of a clear ink head. In this example, the clear ink can be considered, for example, to be colorless and translucent ink. In this case, the fact that the clear ink is colorless can be considered, for example, to mean that a specific color is not intentionally added. The fact that a specific color is not intentionally added can be considered, for example, to mean that a colorant is not intentionally added. In addition, the fact that the clear ink is colorless and translucent can be considered, for example, to mean that the clear ink is transparent and does not substantially absorb light of a specific color in the visible light range. "Substantially not absorbing light of a specific color" can be understood, for example, as "substantially not absorbing light of a specific color in the visible light region within an acceptable range depending on the quality required for printing." More specifically, the clear ink can be, for example, an ink obtained by removing the colorant from a color ink. In this case, it is possible to further remove substances used in conjunction with the colorant from the color ink in addition to the colorant. For example, if a color ink uses a dispersant (pigment dispersant) to disperse a colorant such as a pigment in the ink solvent, an ink obtained by removing the colorant and dispersant from the color ink can be suitably used as the clear ink. Furthermore, the clear ink can be understood, for example, as a transparent ink that is the same as or similar to the clear ink conventionally used in the technical field of inkjet printing. However, in the field of textile printing, which involves printing on fabric, as in this example, there is usually no reason to use clear ink.Therefore, the clear ink used in this example can be thought of as being used in the field of textile printing, an extension of the use of clear ink used in inkjet printing other than textile printing. The configuration of the head unit 102 will be explained in more detail later.

[0028] The platen 104 is a platform-like member that faces the head unit 102 and supports the transfer medium 50. The Y-bar unit 106 is a member that extends in the main scanning direction at a position facing the platen 104 with the transfer medium 50 sandwiched between them. The Y-bar unit 106 holds the head unit 102 on a surface facing the transfer medium 50 while allowing it to move in the main scanning direction, thereby guiding the movement of the head unit 102 in the main scanning direction during main scanning operation. The main scanning driver 108 is a driver that causes the multiple inkjet heads in the head unit 102 to perform main scanning operation. In this example, the main scanning driver 108 moves the head unit 102 along the Y-bar unit 106 under the control of the control unit 120, causing each inkjet head in the head unit 102 to eject ink. The sub-scanning driver 110 is a driver that causes the multiple inkjet heads in the head unit 102 to perform sub-scanning operation. The sub-scanning operation can be considered, for example, as an operation of moving relative to the transfer medium 50 in a sub-scanning direction (X direction in the figure) perpendicular to the main scanning direction. In this example, the sub-scanning drive unit 110 moves the head unit 102 in the sub-scanning direction relative to the transfer medium 50 between main scanning operations, thereby causing the multiple inkjet heads in the head unit 102 to perform sub-scanning operations. The control unit 120 is a part that includes, for example, the CPU of the printing unit 14, and controls the operation of each part of the printing unit 14 based on the print data supplied from the print data preparation unit 12, thereby controlling the printing operation on the transfer medium 50. Furthermore, as a result, the printing unit 14 prints an image indicated by the image data on the transfer medium 50.

[0029] In the printing system 10 of this example, the powder application unit 16 applies hot melt resin powder to the transfer medium 50 on which an image has been printed in the printing unit 14. The powder application unit 16 can be considered, for example, as a component for applying hot melt resin powder to the transfer medium 50 on which an image has been printed. In this example, the powder application unit 16 preheats the transfer medium 50 to which the hot melt resin powder has been applied, heating it to a predetermined temperature before transfer. After the hot melt resin powder has been applied to the transfer medium 50, the thermal transfer unit 18 transfers the image from the transfer medium 50 to a transfer recipient medium. In this example, the thermal transfer unit 18 is an example of a transfer unit. The thermal transfer unit 18 can be considered, for example, as a device that transfers an image from the transfer medium 50 to the transfer recipient medium by applying heat and pressure to the transfer medium 50 and the transfer recipient medium while they are stacked together. The operation of applying heat and pressure to the transfer medium 50 and the transfer receiving medium while they are stacked can also be considered, for example, as an operation of placing the transfer medium 50 on the transfer receiving medium and pressing them together. Furthermore, a known heat press or the like can be suitably used as the thermal transfer unit 18. According to this example, for example, an image printed on the transfer medium 50 can be properly transferred to the transfer receiving medium. The image transfer operation performed in the printing system 10 will be described in more detail later.

[0030] In the printing system 10, the print data preparation unit 12, the printing unit 14, the powder application unit 16, and the thermal transfer unit 18 can each be considered a functional component of the printing system 10. In this case, for example, a device including a component that realizes the functions of the printing unit 14 can be considered an example of a printing device. Furthermore, when considering the configuration of the printing system 10 as a device, multiple functional components may be realized by a single device. For example, the print data preparation unit 12 and the printing unit 14 may be realized by a single device. In this configuration, for example, the operation of generating print data from image data and the operation of executing printing can be performed by a single device. Furthermore, the printing unit 14 and the powder application unit 16 may be realized by a single device. In this configuration, for example, operations from printing to preheating can be performed by a single device. Furthermore, it is also possible to configure the entire printing system 10 by a single device. Furthermore, depending on the configuration of the printing system 10, for example, it is also possible to configure any of the functional components shown in FIG. 1(a) by multiple devices. For example, the powder application unit 16 may be configured with a device for applying hot melt resin powder to the transfer medium 50 and a device for preheating. In either configuration, it is preferable that the operation of printing on the transfer medium 50 in the printing unit 14, the operation of applying hot melt resin powder to the transfer medium 50 in the powder application unit 16, and the preheating operation in the powder application unit 16 are performed by a single device. In this case, performing multiple operations by a single device can be thought of as, for example, performing multiple operations consecutively without the user having to carry the transfer medium 50.

[0031] Next, the configuration of the head unit 102 in the printing unit 14 will be described in more detail. FIG. 2 is a diagram illustrating the multiple inkjet heads 202 of the head unit 102 in more detail. FIGS. 2(a) to 2(c) are diagrams showing an example of the configuration of the head unit 102, illustrating an example of how the multiple inkjet heads 202 of the head unit 102 are arranged. As distinguished by the reference numerals 202y, m, c, k, and t in the diagram, the head unit 102 in this example has multiple inkjet heads 202y, m, c, k, and t, each of which ejects ink of a different color. Although not shown, the head unit 102 further has, for example, a carriage that holds these inkjet heads 202.

[0032] Among these inkjet heads 202, the multiple inkjet heads 202y, m, c, k (hereinafter referred to as inkjet heads 202y-k) are inkjet heads that eject color inks, and eject colored inks of different colors. More specifically, inkjet head 202y ejects yellow (Y) ink. Inkjet head 202m ejects magenta (M) ink. Inkjet head 202c ejects cyan (C) ink. Inkjet head 202k ejects black (K) ink. In this case, each of the YMCK color inks is an example of each of the process color inks, which are basic colors used in color expression using the subtractive color mixture method.

[0033] The inks of the YMCK colors ejected from each of the inkjet heads 202y-k may be, for example, known color inks. Examples of known color inks include textile printing inks used for transferring ink onto fabric. Examples of such textile printing inks include inks containing pigments as coloring materials. More specifically, in this example, the inks of the YMCK colors are inks that are fixed to the transfer medium 50 as the solvent evaporates, and include pigments, dispersants, binder resins, and solvents. In this case, the pigment is an example of a coloring material. The dispersant is a substance that disperses the pigment in the solvent. The binder resin is a resin that fixes the pigment to the transfer medium 50. The binder resin can also be considered, for example, as a resin that fixes to the transfer medium 50 together with the coloring materials in the colored inks. The solvent is a liquid that dissolves or disperses other components in the ink. An aqueous solvent such as water is preferably used as the solvent. Furthermore, solvents other than aqueous solvents (organic solvents) may also be used as the ink solvent. More specifically, in this example, the inks of the YMCK colors used in the inkjet heads 202y to 202k are water-based pigment inks for textile printing used for transferring onto a transfer medium such as fabric. In this case, known water-based pigment inks can be suitably used.

[0034] The inkjet head 202t is an inkjet head that ejects clear ink. In this example, the clear ink is colorless and translucent because it does not contain coloring materials such as pigments. More specifically, the clear ink may be, for example, an ink obtained by removing the pigment and dispersant from the inks of the YMCK colors. In this case, the clear ink may also be considered to be, for example, an ink that adheres to the transfer medium 50 as the solvent evaporates. The clear ink may also be considered to contain, for example, the same resin as the binder resin in the inks of the YMCK colors. This configuration allows the appropriate use of clear inks with properties similar to those of the inks of the YMCK colors. Alternatively, the clear ink may be, for example, an ink that does not contain the same resin as the binder resin in the inks of the YMCK colors.

[0035] In the head unit 102, the inkjet heads 202y-k are aligned in the main scanning direction, for example, with their positions aligned in the sub-scanning direction. In this case, the inkjet head 202t may be positioned differently in the sub-scanning direction from the inkjet heads 202y-k, as shown in FIG. 2(a), or may be positioned the same in the sub-scanning direction as the inkjet heads 202y-k, as shown in FIGS. 2(b) and 2(c). More specifically, in the example shown in FIG. 2(a), the inkjet head 202t is disposed on one side of the inkjet heads 202y-k in the sub-scanning direction. In the example shown in FIG. 2(b), the inkjet head 202t is disposed on one side of the inkjet heads 202y-k in the main scanning direction. The head unit 102 may include a plurality of inkjet heads 202t, as shown in FIG. 2(c). 2(c), each of the inkjet heads 202t is disposed on one side of the inkjet heads 202y-k in the main scanning direction. The arrangement of the inkjet heads 202y-k and t in the head unit 102 may be different from that shown in FIGS. 2(a) to 2(c). For example, some of the inkjet heads 202y-k may be positioned differently in the sub-scanning direction from the other inkjet heads 202.

[0036] In this example, the transfer medium may be, for example, a transfer film having an ink-absorbing ink-receiving layer (receiving layer) formed thereon. The ink-receiving layer can be considered to prevent ink bleeding by, for example, absorbing the ink before it spreads excessively on the transfer medium. Using such a transfer medium can appropriately prevent, for example, bleeding of color inks. To more appropriately prevent bleeding of color inks, it is preferable to perform printing in the printing unit 14 (see FIG. 1 ) so that the color inks land at each position on the transfer medium before the clear ink. The color inks landing before the clear ink can be considered to occur when, for example, a color ink and a clear ink are ejected at the same position. As described above, the transfer medium may be a medium other than a film, such as a paper medium. In this case, using a transfer medium having a receiving layer can appropriately prevent, for example, bleeding of ink, allowing printing to be performed appropriately on the transfer medium.

[0037] In this case, in the head unit 102 configured as shown in FIG. 2(a), for example, the inkjet head 202t may be disposed downstream of the inkjet heads 202y-k in the transport direction of the transfer medium. The transport direction of the transfer medium may be considered, for example, as the direction in which the transfer medium moves relative to the head unit 102. In addition, when the head unit 102 configured as shown in FIG. 2(b) is used, for example, the direction of relative movement of the head unit 102 with respect to the transfer medium during main scanning operation may be such that the inkjet head 202t is located behind the inkjet heads 202y-k. In addition, when the head unit 102 configured as shown in FIG. 2(b) is used, for example, the direction of relative movement with respect to the transfer medium during main scanning operation may be bidirectional, in one direction and the other, and clear ink may be ejected from the inkjet head 202t only during main scanning operation in one direction. Furthermore, when using the head unit 102 configured as shown in FIG. 2(c), for example, it is possible to set the direction of relative movement with respect to the transfer medium during main scanning operation to be bidirectional, and eject clear ink from the inkjet head 202t located behind the inkjet heads 202y-k during main scanning operation in each movement direction. Depending on the required printing quality, for example, it is also possible to cause the clear ink to land at each position on the transfer medium before the color inks. In this case, it is also possible to use the head unit 102 configured as shown in FIG. 2(b), set the direction of relative movement with respect to the transfer medium during main scanning operation to be bidirectional, and eject clear ink from the inkjet head 202t during movement in both directions.

[0038] Next, the image transfer operation and the like executed in the printing system 10 will be described in more detail. FIG. 3 is a flowchart showing an example of the operation executed in the printing system 10 in this example. As described above, in the printing system 10 of this example, the printing unit 14 transfers an image printed on a transfer medium to a transfer receiving medium. In this case, the print data preparation unit 12 first generates print data to be supplied to the printing unit 14 based on image data representing the image to be printed on the transfer medium (S102). The operation of generating print data in the print data preparation unit 12 will be described in more detail later. In this case, the printing unit 14 prints an image on the transfer medium based on the print data supplied from the print data preparation unit 12 (S104). In this example, the operation of step S104 is an example of the operation in the printing stage. In step S104, the printing unit 14 ejects color inks from the inkjet heads 202y to 202k in the head unit 102 onto at least a portion of the transfer medium. Then, clear ink is further ejected from inkjet head 202t onto at least a part of the area on the transfer medium onto which color ink is ejected from any of inkjet heads 202y to 202k. The reasons for using clear ink in this example and how the clear ink is ejected will be explained in more detail later.

[0039] After the printing unit 14 prints on the transfer medium, the powder application unit 16 applies hot melt resin powder to the transfer medium on which the image has been printed (S106). In this example, the operation of step S106 is an example of the operation of the hot melt resin application stage. The application of hot melt resin powder to the transfer medium by the powder application unit 16 in step S106 can be performed in the same manner as or similar to the application of hot melt resin powder in known transfer operations using hot melt resin powder. More specifically, the application of hot melt resin powder to the transfer medium can be performed automatically, for example, by an apparatus. In this case, the powder application unit 16 has, for example, a powder ejection unit that ejects hot melt resin powder toward the transfer medium. Alternatively, the application of hot melt resin powder to the transfer medium can be performed manually by a user (operator). In this case, the powder application unit 16 allows the user to apply the hot melt resin powder to the transfer medium by, for example, holding the transfer medium on which the image has been printed in a predetermined state.

[0040] In this example, the hot melt resin powder applied to the transfer medium adheres to the ink on the transfer medium, thereby adhering to the transfer medium. Therefore, the hot melt resin powder adheres only to the positions on the transfer medium where ink was ejected by the printing unit 14 in step S104. In this case, the hot melt resin powder in the positions on the transfer medium where ink was not ejected is removed from the transfer medium using a method identical or similar to known methods, for example, before preheating is performed in the next step. The hot melt resin powder may be removed automatically by a device or manually by a user.

[0041] Furthermore, after the powder application unit 16 applies the hot melt resin powder to the transfer medium and removes the unnecessary hot melt resin powder, the transfer medium is preheated (S108). In this case, the transfer medium may be heated to a temperature at which the hot melt resin powder melts. This configuration, for example, allows the hot melt resin powder to be properly fixed to the transfer medium. Fixing the hot melt resin powder to the transfer medium can be considered, for example, as fixing the hot melt resin powder to the transfer medium in a state in which it can be later transferred to a transfer medium. Preheating can also be considered, for example, as heating the transfer medium to a predetermined temperature to make the hot melt resin powder sticky. The preheating performed in step S108 can be performed, for example, using the same or similar method as known in the art. More specifically, in step S108, the transfer medium is heated to a temperature of the hot melt resin powder of about 130°C (e.g., about 120 to 150°C) and maintained in that state for about 5 minutes (e.g., about 1 to 10 minutes).

[0042] After the preheating, the thermal transfer unit 18 transfers (thermal transfers) the image from the transfer medium to the transfer recipient medium (S110). In this example, the operation of step S110 is an example of the operation of the transfer stage. In step S110, the thermal transfer unit 18 applies heat and pressure to the overlapping transfer medium and transfer recipient medium, thereby adhering a hot-melt resin portion, which is a resin portion formed by the hot-melt resin powder softened by the heat, to the transfer recipient medium. The hot-melt resin portion can be considered, for example, to be a resin portion made of hot-melt resin powder that has become sticky by the heat. The hot-melt resin portion may also be, for example, a resin formed by the softened hot-melt resin powder integrating with the hot-melt resin powder. In this example, in step S110, the color material that expresses the color of the image printed on the transfer medium is adhered to the transfer recipient medium along with at least a portion of the hot-melt resin portion, thereby transferring the image from the transfer medium to the transfer recipient medium. This operation can be considered, for example, as transferring an image from the transfer medium to the transfer medium by transferring at least a portion of the colorant adhering to the transfer medium together with at least a portion of the hot-melt resin portion to the transfer medium. The transfer performed in step S110 can be performed in the same manner as or similar to a known method. More specifically, in step S110, the hot-melt resin portion is adhered to the transfer medium by applying pressure while heating at a temperature higher than the preheating temperature in step S108. In this case, the transfer medium and the transfer medium may be heated so that the temperature of the hot-melt resin portion reaches approximately 140°C (e.g., approximately 100 to 180°C). The heating and pressurizing time in step S110 may be shorter than the heating time in the preheating in step S108. For example, the heating and pressurizing time in step S110 may be approximately 5 seconds (e.g., approximately 1 to 30 seconds).

[0043] After the image is transferred from the transfer medium to the transfer receiving medium in step S110, the transfer medium is peeled off from the transfer receiving medium (S112), for example. In this case, the transfer receiving medium onto which the image has been transferred can be considered the output (printed product) of printing in the printing system 10. The peeling of the transfer medium in step S112 can also be performed, for example, in the same or similar manner as a known method. In this example, a transfer medium having a peeling layer formed on its surface can be preferably used. With this configuration, for example, the peeling of the transfer medium in step S112 can be performed easily and appropriately.

[0044] Through the above operations, the printing system 10 can appropriately create a printed product. In this case, by using clear ink in addition to color inks when printing on a transfer medium, it is possible to improve transferability and reduce transfer unevenness and graininess, for example. Therefore, the reasons for using clear ink in this example and how to eject the clear ink will be explained in more detail below.

[0045] FIG. 4 is a diagram explaining the reason for using clear ink in this example, and shows an example of how to print on the transfer medium 50 in this example, compared to how to print on the transfer medium 50 using conventional methods. FIG. 4(a) shows an example of how to print on the transfer medium 50 using the conventional method. FIG. 4(b) shows an example of how to print on the transfer medium 50 using a method different from the method shown in FIG. 4(a). FIG. 4(c) shows an example of how to print on the transfer medium 50 in this example.

[0046] As explained above, in this example, it is considered to use a transfer medium 50 on which an ink-receiving layer 54 is formed. Furthermore, such a transfer medium 50 can also be suitably used in conventional methods. In this case, the transfer medium 50 has a base portion 52 and an ink-receiving layer 54, as shown in each of FIGS. 4(a) to 4(c). The base portion 52 is the base of the transfer medium 50. The ink-receiving layer 54 is a layer for absorbing ink and is formed on the surface of the base portion 52. The ink-receiving layer 54 can also be considered to constitute, for example, a part of the base portion 52. In this case, the base portion 52 can also be considered to constitute the entire transfer medium 50. Furthermore, in this example, the printing unit 14 (see FIG. 1) in the printing system 10 prints on the transfer medium 50 by ejecting ink onto the ink-receiving layer 54 of the transfer medium 50 to form an ink layer on the transfer medium 50. Similarly, in the conventional configuration, printing is performed on the transfer medium 50 by forming an ink layer on the transfer medium 50 using a printing device corresponding to the printing unit 14.

[0047] In a conventional method shown in FIG. 4(a), a printing device with a different configuration from the printing unit 14 of this embodiment, including inkjet heads for color inks and white ink, is used to form a color ink layer 302 and a white ink layer 304 in a printing area 300 on the surface of a transfer medium 50. In this case, the color ink layer 302 is a layer of color inks. The white ink layer 304 is a layer of white ink. The white ink layer 304 can be considered, for example, to conceal the base color of the transfer medium after transfer and function as a background in a subtractive color mixing method. The printing area 300 can be considered, for example, as an area onto which color inks are ejected from an inkjet head. In this case, as shown in the figure, a color ink layer 302 is formed on the transfer medium 50, and then a white ink layer 304 is formed on top of it so as to cover the entire color ink layer 302. The white ink layer 304 is formed, for example, by solidly filling the printing area 300 with a predetermined density.

[0048] In this case, after forming the color ink layer 302 and the white ink layer 304 on the transfer medium 50, as shown in the lower part of FIG. 4( a), a hot-melt resin powder, shown as resin powder 352 in the figure, is adhered to the white ink layer 304. After the resin powder 352 is adhered, the transfer medium 50 and the transfer receiving medium are overlapped, and heat and pressure are applied to transfer the image from the transfer medium 50 to the transfer receiving medium. When printing and transferring in this manner, the formation of the solid white ink layer 304 ensures a sufficient amount of ink at each position in the printing area 300. This allows the resin powder 352 to be appropriately adhered to the printing area 300 on the transfer medium 50. This also allows the resin powder 352 to be appropriately adhered, enabling high-quality image transfer, even when transferring an image including a low-tone range where the amount of ink in the color ink layer 302 is small. In this case, after the image is transferred, the white ink layer 304 becomes a layer below the color ink layer 302 on the transfer medium and functions as a background for the color ink layer 302. Therefore, even when a dark-colored fabric or the like is used as the transfer medium, the image can be properly expressed on the transfer medium.

[0049] However, in this case, the portion corresponding to the white ink layer 304 may be transferred to the transfer medium in addition to the original image, resulting in a loss of design and texture. For example, forming the white ink layer 304 may not be desirable when using a light-colored (pale) material such as white or beige as the transfer medium, or when expressing a design that takes advantage of the color and texture of the material used as the transfer medium (e.g., when using an off-white material). Furthermore, when using a light-colored material such as white as the transfer medium, the base color of the transfer medium after transfer is a light-reflective color, so color expression using the subtractive color mixing method can be performed appropriately without forming the white ink layer 304. In such cases, it is also possible to transfer the image without forming the white ink layer 304, as shown in FIG. 4(b), for example. In this case, a color ink layer 302 is formed in the print area 300 of the transfer medium 50 using a printing device equipped with inkjet heads for color inks. Then, resin powder 352 is deposited directly on the color ink layer 302. After the resin powder 352 has been applied, the transfer medium 50 and the transfer receiving medium are placed on top of each other and heated and pressurized, thereby transferring the image from the transfer medium 50 to the transfer receiving medium. In this case, too, the image can be transferred from the transfer medium 50 to the transfer receiving medium. However, depending on the state of the image drawn on the transfer medium 50, the transfer rate may decrease in part of the image, resulting in unintended uneven transfer.

[0050] More specifically, the color ink layer 302 is formed by ejecting color inks of various colors according to the image to be drawn on the transfer medium 50. In this case, the amount of ink ejected varies depending on the position in the printing area 300. For example, the amount of ink ejected is less in low gradation areas, which express lighter colors in the image, than in high gradation areas, which express darker colors. As a result, the manner in which the resin powder 352 adheres is likely to vary depending on the position in the printing area 300. In this case, for example, in low gradation areas, where the amount of ink is less, the amount of resin powder 352 adhered may decrease, resulting in reduced transferability. This may also result in uneven transfer. Furthermore, the reduced transferability may result in poor expression of low gradations. Regarding this point, for example, in the method shown in FIG. 4( a), a solid white ink layer 304 is formed on the color ink layer 302, so that differences in transferability can be appropriately prevented even if differences in the amount of color ink ejected vary depending on the position. However, in the case of the method shown in FIG. 4(b), the white ink layer 304 is not formed, which makes transfer unevenness more likely to occur, as described above.

[0051] In contrast, in this example, by using clear ink in addition to color ink, the occurrence of transfer unevenness is prevented without forming a white ink layer 304. In this case, as shown in FIG. 4(c), for example, the printing unit 14 uses color ink and clear ink to form an image layer 306, which is an ink layer formed of color ink and clear ink, in the printing area 300 of the transfer medium 50. Then, without forming a white ink layer 304 or the like, resin powder 352 is adhered directly onto the image layer 306. After the resin powder 352 is adhered, the transfer medium 50 and the transfer recipient medium are overlapped and heated and pressurized, thereby transferring the image from the transfer medium 50 to the transfer recipient medium.

[0052] In this example, by using clear ink in addition to color inks when printing on the transfer medium 50 by the printing unit 14, inks other than color inks can be appropriately ejected onto the transfer medium 50 while, for example, appropriately minimizing the effect on the color of the image printed on the transfer medium 50. In this way, for example, even in areas of the printing region 300 where the amount of color ink is small, such as low-gradation areas, clear ink can be ejected, thereby increasing the total amount of ink ejected onto the transfer medium 50 compared to when only color inks are used. Furthermore, by increasing the total amount of ink, for example, the resin powder 352 can be more appropriately attached to the transfer medium 50. This also makes it possible to appropriately prevent, for example, a lack of resin powder 352 from causing poor transferability or uneven transfer during image transfer from the transfer medium 50 to a receiving medium. Therefore, according to this example, for example, image transfer using the resin powder 352 can be more appropriately performed without forming the white ink layer 304. Furthermore, in this case, unlike white ink containing a white pigment, clear ink can be used while minimizing its impact on the design. Furthermore, since the clear ink becomes less noticeable on the transfer medium after transfer, it can be used only in selected areas where it is needed, etc. Therefore, according to this example, it is possible to perform transfer with higher quality while appropriately preventing damage to the design and texture, for example.

[0053] Furthermore, in this example, using clear ink in addition to color inks can reduce graininess after transfer, for example. More specifically, when inkjet printing is performed on a transfer medium 50 having an ink-receiving layer 54, as in this example, it is believed that the ink is less likely to wet and spread on the transfer medium 50 after landing. As a result, it is believed that graininess is more likely to occur, especially in low gradation areas. Furthermore, when transferring an image by adhering resin powder 352, the amount of resin powder 352 that adheres depends on the amount of ink (print volume) ejected at that location. Therefore, for example, when transferring an image using the method shown in FIG. 4(b), the amount of resin powder 352 adhered is reduced in low gradation areas where the print volume is low, and transferability is reduced, resulting in a more noticeable graininess on the transfer medium after transfer.

[0054] In contrast, in this example, by using clear ink in addition to color ink, the color ink can be made to wet and spread more easily on the transfer medium 50 than when only color ink is used. This can also increase the size of the ink dots formed on the transfer medium 50 by the color ink, making it less likely to produce a grainy appearance. In this case, as described above, the use of clear ink can also appropriately prevent a decrease in transferability in the low gradation range. Therefore, for example, it is possible to more appropriately prevent a grainy appearance from becoming more noticeable on the transfer medium after transfer. In this case, it is preferable that the printing unit 14 ejects the color ink and clear ink at each position on the transfer medium 50 where the color ink is ejected so that the clear ink lands before the color ink completely dries. This configuration, for example, can more appropriately achieve a state in which the color ink wets and spreads more easily on the transfer medium 50.

[0055] Furthermore, as can be understood from the above explanation, in this example, it is preferable to eject clear ink particularly onto positions in the low gradation range of the image. Therefore, an example of how clear ink is ejected will be explained in more detail below. Figures 5 and 6 are diagrams illustrating an example of how clear ink is ejected in this example. Figure 5 is a diagram illustrating an image printed on transfer medium 50. Figure 5(a) shows an example of an image printed on transfer medium 50. Figure 5(b) shows an example of the state of color ink dots that make up the image.

[0056] When printing (color printing) using multiple color inks by the printing unit 14 (see FIG. 1) as in this example, the amount of ink of each color ejected at each position on the transfer medium 50 varies depending on the color to be expressed at that position. In this case, it can be considered that the gradation varies depending on the position of the image. The printing unit 14 prints an image having, for example, a high gradation portion 312, a medium gradation portion 314, and a low gradation portion 316 on the transfer medium 50. More specifically, FIG. 5(a) shows an example of an image to be printed when printing is performed on multiple printing areas 300a-c by the printing unit 14. In this case, the printing area 300a is a printing area including the high gradation portion 312, the medium gradation portion 314, and the low gradation portion 316. The printing area 300b is a printing area consisting only of the low gradation portion 316. The printing area 300c is a printing area consisting only of the high gradation portion 312. In this example, each of the print areas 300a to 300c is an example of an image representation area on the transfer medium 50 onto which color ink is ejected from one of the inkjet heads 202y to 202k (see FIG. 2).

[0057] In this case, the high gradation portion 312 can be considered, for example, as a portion of the image that expresses colors with gradations higher than a predetermined first reference. In this case, the gradation of the image being higher than the first reference can be considered, for example, as the gradation of a color corresponding to one of the color inks (one of the YMCK colors) being higher than the first reference. The medium gradation portion 314 can be considered, for example, as a portion of the image other than the high gradation portion 312 and the low gradation portion 316. The low gradation portion 316 can be considered, for example, as a portion of the image that expresses colors with gradations lower than a predetermined second reference that is lower than the first reference. In this case, the gradation of the image being higher than the second reference can be considered, for example, as the gradations of all the colors of the color ink (all the YMCK colors) being lower than the second reference. The high gradation portion 312 can be considered, for example, as a portion that expresses colors in a predetermined high gradation range. The high gradation portion 312 can also be considered, for example, as an area of ​​the image that expresses deep or dark colors. The low gradation portion 316 can also be considered, for example, as an area that expresses a color in a predetermined low gradation range. The low gradation portion 316 can also be considered, for example, as a portion that expresses a light color or a bright color in an image.

[0058] Furthermore, when printing using an inkjet method, such as the printing unit 14 of this example, gradation is expressed by varying the density of ink dots formed per unit area. In this case, in the high gradation area 312, many dots 402 are formed densely, as shown, for example, on the left side of FIG. 5(b). In the low gradation area 316, fewer dots 402 are formed sparsely compared to the high gradation area 312, as shown, for example, on the right side of FIG. 5(b). In FIG. 5(b), the intersections of the vertical and horizontal dashed lines indicate ink ejection positions set according to the printing resolution. In this case, each of the high gradation area 312, the medium gradation area 314, and the low gradation area 316 in the image can also be considered in relation to the amount of color ink ejected per unit area. More specifically, in this case, the high gradation area 312 can be considered, for example, as an area where a larger amount of color ink is ejected per unit area. The low gradation portion 316 can be considered, for example, as an area where the amount of color ink ejected per unit area is reduced.

[0059] In this example, the low gradation area 316 is an example of a low-ink area, which is an area where the amount of color ink ejected per unit area is less than a predetermined reference amount. The high gradation area 312 is an example of a non-low-ink area, which is at least a portion of an area that does not fall under the low-ink area category. A non-low-ink area can be considered, for example, as an area in each of the printing areas 300a-c where the amount of color ink ejected per unit area is greater than a predetermined amount. In this example, this predetermined amount can be considered to be greater than the reference amount for the low-ink area. Depending on the configuration of the printing unit 14, for example, the combined high gradation area 312 and medium gradation area 314 can also be considered an example of a non-low-ink area. In this case, the predetermined amount for the non-low-ink area can be considered, for example, to be the same as the reference amount for the low-ink area.

[0060] As explained above, in this example, the printing unit 14 uses clear ink in addition to color ink to print on the transfer medium 50. In this case, clear ink is ejected onto at least a portion of the low gradation portion 316 of the image. In this case, it is also possible to eject color ink and clear ink onto ejection positions set on the transfer medium 50 according to the printing resolution, as shown in FIG. 6, for example.

[0061] FIG. 6 shows examples of ejection positions for ejecting color ink and clear ink, focusing on a portion of multiple ejection positions in the low gradation area 316 (see FIG. 5). FIGS. 6(a) to 6(c) are diagrams showing examples of how to select ejection positions for ejecting clear ink, showing various examples of how clear ink is ejected onto positions in the low gradation area 316 where color ink dots 402 are discretely formed. Positions where color ink dots 402 are discretely formed can be considered to be positions where multiple color ink dots 402 are formed with spaces between them, as shown in the upper left corners of each of FIGS. 6(a) to 6(c). In this case, the multiple dots 402 can be considered to be spread out to a size where they do not touch each other. In this case, if clear ink were not used, the amount of ink per unit area would be reduced, potentially resulting in poor transferability.

[0062] In contrast, in this example, as described above, the amount of ink per unit area is increased by additionally using clear ink. Regarding the method of discharging clear ink, if we consider increasing the total amount of ink discharged near each discharge position, the simplest approach would be to discharge a predetermined amount of clear ink at all discharge positions, as shown in the lower left of FIG. 6( a). In this case, the lower left diagram shows an arrangement of ink dots 404 formed by clear ink at the same positions as the multiple discharge positions shown in the upper left diagram. In addition, in the case shown in FIG. 6( a), the clear ink dots 404 are formed at all discharge positions spaced at intervals according to the printing resolution. In this case, when the color ink dots 402 and the clear ink dots 404 are combined, as shown on the right side of the figure, clear ink dots 404 are formed both at positions where color ink dots 402 are present and at positions where color ink dots 402 are not present. With this configuration, for example, in low gradation areas where the amount of color ink is reduced, clear ink is added to compensate for the ink volume. Therefore, with this configuration, for example, it is possible to appropriately increase the total amount of ink ejected near each ejection position.

[0063] However, depending on the quality required for printing, it may be preferable to eject clear ink only at some of the ejection positions rather than at all of the ejection positions. More specifically, for example, if ejecting clear ink at all of the ejection positions results in an excessive amount of ink per unit area, it may be possible to reduce the number of positions onto which clear ink is ejected in accordance with the preferred upper limit amount of ink. In this case, clear ink dots 404 may be formed only at some of the ejection positions, as shown in Figures 6(b) and 6(c).

[0064] More specifically, in the example shown in FIG. 6(b), as shown in the lower left of the figure, only ejection positions where color ink dots 402 are not formed are selected, and clear ink dots 404 are formed. In this case, when the color ink dots 402 and the clear ink dots 404 are combined, either color ink dots 402 or clear ink dots 404 are formed at each ejection position, as shown on the right side of the figure. Even with this configuration, for example, in low gradation areas where the amount of color ink is small, clear ink is added to compensate for the ink volume. Therefore, even with this configuration, for example, the total amount of ink ejected near each ejection position can be appropriately increased.

[0065] Furthermore, the ejection positions for ejecting the clear ink do not necessarily need to be precisely aligned with the ejection positions for ejecting the color inks. More specifically, when printing using an inkjet method, the ejection positions for ejecting the color inks are determined, for example, by halftone processing. In this case, even if the gradation to be expressed is the same, the ejection positions for the color inks are not necessarily the same. Furthermore, in this example, when clear ink is ejected only at some of the ejection positions, the ejection positions for ejecting the clear ink can also be determined by a predetermined process, such as halftone processing. In this case, the ejection positions for ejecting the clear ink are also determined by the results of the process. In such a case, the relationship between the ejection positions for ejecting the color inks and the ejection positions for ejecting the clear ink is not strictly determined according to a predetermined relationship, but can be determined, for example, based on the relationship between the gradation of the image before halftone processing or the relationship between the amount of ink ejected per unit area. In this case, as shown in FIG. 6(c), for example, among the ejection positions where color ink dots 402 are formed, color ink dots 402 and clear ink dots 404 are formed at some of the ejection positions, while clear ink dots 404 are not formed at other ejection positions, resulting in only color ink dots 402 being formed. Furthermore, among the ejection positions where color ink dots 402 are not formed, clear ink dots 404 are formed only at some of the ejection positions. Even with this configuration, it can be thought of as, for example, compensating for the amount of ink by adding clear ink to low gradation regions where the amount of color ink is reduced. Therefore, even with this configuration, it is possible to appropriately increase, for example, the total amount of ink ejected near each ejection position.

[0066] Furthermore, the method of selecting the ejection positions for ejecting the clear ink is not limited to the method described above, and other methods may be used. For example, the ejection positions where the color ink dots 402 are formed may be confirmed based on the results of the halftone process, and the ejection positions where the dots 404 are formed may be determined based on those ejection positions. In this case, it is possible to form the clear ink dots 404 at the ejection positions where the color ink dots 402 are formed, such as ejection positions adjacent to the ejection positions where the color ink dots 402 are formed. In this case, the clear ink dots 404 may also be formed at the ejection positions where the color ink dots 402 are formed.

[0067] As can be understood from the above explanation, in this example, clear ink is ejected to areas of the printing area on the transfer medium 50 where the amount of color ink ejected is small, thereby improving the adhesion of the hot melt resin powder. In this case, it is possible to adhere a sufficient amount of hot melt resin powder to areas where a sufficient amount of color ink is ejected, without using clear ink. Furthermore, for example, if the total amount of ink ejected per unit area, including color ink and clear ink, becomes too large, problems such as bleeding of the color ink may become more likely to occur. Therefore, the amount of clear ink ejected at each position on the transfer medium 50 may be varied depending on, for example, the amount of color ink ejected at each position.

[0068] More specifically, if the amount of clear ink ejected per unit area onto each position on the transfer medium 50 is defined as the amount of clear ink ejected, it is conceivable to differentiate the amount of clear ink ejected between the high gradation area 312 (see FIG. 5 ), where a greater amount of color ink is ejected per unit area, and the low gradation area 316, where a smaller amount of color ink is ejected per unit area, in the printing region. In this case, for example, it is conceivable to differentiate the amount of clear ink ejected depending on the amount of color ink ejected per unit area, so that the amount of clear ink ejected in the low gradation area 316 is greater than the amount of clear ink ejected in the high gradation area 312. This configuration, for example, makes it possible to appropriately eject clear ink where necessary while minimizing the amount of clear ink used. Furthermore, reducing the amount of clear ink ejected in the high gradation area 312 can, for example, prevent the total amount of ink ejected onto the same position from becoming excessively large.

[0069] The amount of clear ink ejection may be different between the medium gradation section 314 and the low gradation section 316, for example. In this case, it is possible to vary the amount of clear ink ejection depending on the amount of color ink ejected per unit area, so that the amount of clear ink ejection in the low gradation section 316 is greater than the amount of clear ink ejection in the medium gradation section 314. The amount of clear ink ejection may also be different between the high gradation section 312 and the medium gradation section 314. In this case, it is possible to vary the amount of clear ink ejection depending on the amount of color ink ejected per unit area, so that the amount of clear ink ejection in the medium gradation section 314 is greater than the amount of clear ink ejection in the high gradation section 312. It is also possible to set the amount of clear ink ejection to zero in areas where a large amount of color ink is ejected, such as the high gradation section 312. In this case, for example, clear ink is not ejected in positions where the amount of color ink ejected per unit area is greater than a preset upper limit. With this configuration, for example, it is possible to more appropriately prevent the total amount of ink ejected to the same position from becoming excessively large.

[0070] As described above, in this example, the use of clear ink increases the adhesion of hot melt resin powder, for example, in the low gradation area 316. In this case, the use of clear ink can be considered to increase the transfer rate of, for example, the pigment colorant. In this case, if the transfer rate is defined as the proportion of colorant that moves from the transfer medium 50 to the transfer receiving medium during transfer, then ejecting clear ink onto at least a portion of the low gradation area 316 during printing by the printing unit 14 can be considered to increase the transfer rate in at least a portion of the low gradation area 316 compared to when clear ink is not ejected. Focusing on the low gradation area 316, for example, ejecting clear ink onto at least a portion of the low gradation area 316 by the printing unit 14 can be considered to increase the amount of hot melt resin powder that adheres to the positions where the clear ink is ejected in the powder application unit 16 (see FIG. 1 ) compared to when clear ink is not ejected.

[0071] As explained above, when printing is performed using the inkjet method, the ejection positions of the color inks are determined, for example, by halftone processing. In the printing system 10 of this example, the print data preparation unit 12 (see FIG. 1) performs halftone processing on the image data to generate print data. In this case, the position of the clear ink to be ejected may also be determined during the series of operations performed by the print data preparation unit 12 to generate the print data. In this case, the print data preparation unit 12 generates the print data by, for example, the operations shown in FIG. 7.

[0072] FIG. 7 is a flowchart showing an example of the operation of generating print data in the print data preparation unit 12. As described above, in this example, the print data preparation unit 12 generates print data to be supplied to the printing unit 14 based on image data representing an image to be printed on the transfer medium 50 in the printing unit 14. In this operation, image data is first input to the print data preparation unit 12 (S202). As the image data, for example, commonly known color image data representing a color image can be used. As such image data, for example, an RGB image representing a color image using red (R), green (G), and blue (B) as primary colors can be suitably used. The image data can be input to the print data preparation unit 12 from outside the print data preparation unit 12 via a network, a storage medium, or the like. As the color image represented by the image data, an image representing each of the basic colors (primary colors) of color expression in three or more gradations can be used. More specifically, as a color image represented by image data, for example, an image in which each of the basic RGB colors is expressed with 8-bit or more gradation can be suitably used.

[0073] After the image data is input, the print data preparation unit 12 performs preprocessing on the image data to match the halftone processing to be performed later (S204). Examples of preprocessing include resolution conversion, color conversion, and color separation. In this case, resolution processing refers to, for example, changing the resolution of an image to match the printing resolution of the printing unit 14. Color conversion refers to, for example, converting the color of an image to match the color of the ink used in the printing unit 14. The color conversion process may involve converting an image represented by the print data into an image that expresses colors in the YMCK color system to match the YMCK inks used for printing. Color separation may be, for example, dividing the image to be processed into images for each color of ink used in the printing unit 14. The print data preparation unit 12 performs color separation on the image after the resolution change and color conversion processes to generate multiple grayscale images, each corresponding to a YMCK color. In this case, the grayscale image corresponding to each color of YMCK can be thought of as indicating, for example, the amount of ink of that color to be ejected at each position on the image. As the grayscale image corresponding to each color of YMCK, it is conceivable to generate a grayscale image with gradation of 8 bits or more.

[0074] Furthermore, in this example, after performing the preprocessing, the print data preparation unit 12 generates a clear ink image, which is an image used to determine the ejection positions of the clear ink (S206). In this case, the clear ink image can be considered, for example, as an image for which the ejection positions of the clear ink are determined by subsequent halftone processing. For example, a grayscale image can be generated as the clear ink image. In this case, the clear ink image can be considered, for example, as indicating the amount of clear ink to be ejected at each position of the image. For example, the clear ink image can be generated as an image with the same number of gradations as the grayscale images corresponding to the YMCK colors generated by the color separation process. More specifically, in this example, the print data preparation unit 12 calculates the total amount of color ink to be ejected at each position of the image based on the grayscale images corresponding to the YMCK colors generated by the color separation process. Then, the value (gradation) of each pixel of the clear ink image is determined based on this total amount. With this configuration, for example, the amount of clear ink ejected can be appropriately changed depending on the amount of color ink ejected at each position of the image during printing by the printing unit 14.

[0075] After generating the clear ink image, the print data preparation unit 12 performs halftone processing on the grayscale images corresponding to the YMCK colors and the clear ink image (S208). Halftone processing can be considered, for example, as processing for reducing the number of gradations of an image to match the configuration of the printing unit 14. Halftone processing can also be considered, for example, as processing for generating a raster image (RIP processing) that specifies the ejection positions of ink of a corresponding color from the grayscale image. In this example, the print data preparation unit 12 performs halftone processing on the grayscale images corresponding to the YMCK colors to generate a raster image that specifies the ejection positions of ink of that color. The print data preparation unit 12 also performs halftone processing on the clear ink image to generate a raster image that specifies the ejection positions of clear ink. The print data preparation unit 12 supplies data including these raster images to the printing unit 14 as print data. This configuration allows, for example, print data specifying the ejection positions of each color ink and clear ink to be appropriately supplied to the printing unit 14.

[0076] Here, the operation of the print data preparation unit 12 can be performed in the same manner as or similar to known operations for generating print data, except for the points described above. Furthermore, among the operations of the print data preparation unit 12 described above, operations other than those related to the clear ink image can be performed in the same manner as known operations for generating print data, for example. Furthermore, in this example, as described above, the print data preparation unit 12 performs color separation processing based on image data input to the print data preparation unit 12 to generate grayscale images corresponding to each color of YMCK. Then, a clear ink image is generated based on the grayscale images corresponding to each color of YMCK generated by the color separation processing. In this case, the clear ink image can also be considered to be generated based on, for example, the image data input to the print data preparation unit 12. Furthermore, in this case, the operation of the print data preparation unit 12 can be considered to automatically determine the ejection position of the clear ink based on image data that does not directly specify the ejection position of the clear ink. Furthermore, the operation of the print data preparation unit 12 can also be considered to determine the amount of clear ink to be ejected at each position of the image according to the gradation of the image indicated by the image data. Furthermore, in a modified example of the operation of the print data preparation unit 12, instead of generating a clear ink image in the print data preparation unit 12, data indicating the clear ink image may be supplied to the print data preparation unit 12 together with the image data. In this case, it is also possible to supply data directly indicating the ejection position of the clear ink to the print data preparation unit 12, rather than the clear ink image.

[0077] Next, an experiment conducted by the inventor of the present application in relation to the configuration described above will be described. As described above, when printing is performed on a transfer medium using only color inks, it is conceivable that the transferability from the transfer medium to the transfer-receiving medium will be reduced in the low gradation range (low gradation part). In this case, it is conceivable that the graininess will be more noticeable in the low gradation range in the image transferred to the transfer-receiving medium. In response to this, in this example, clear ink is used to compensate for the total amount (liquid amount) of ink, thereby improving the transferability of the image and reducing (improving) the graininess. Furthermore, the inventor of the present application conducted actual experiments and confirmed that the use of clear ink reduces the graininess.

[0078] FIG. 8 is a diagram illustrating an experiment conducted by the inventor of the present application. FIG. 8(a) shows the composition of the clear ink used in the experiment. FIGS. 8(b) and 8(c) show the results of the experiment. In this experiment, known aqueous pigment inks were used as the color inks. For the sake of convenience, only black ink, which has the most noticeable graininess, was used as the color ink. Two types of clear ink, shown in the figure as ink A and ink B, were used. In this case, ink A can be considered, for example, as an ink obtained by removing the pigment, which is a coloring material, from the color inks. Ink B can be considered, for example, as an ink obtained by removing the pigment, which is a coloring material, and the resin (resin emulsion) corresponding to the binder resin, from the color inks. In this case, ink A and ink B can be considered to be substantially transparent inks. Ink A can be considered, for example, as an ink that is transparent and contains a resin.

[0079] In this experiment, as shown in FIG. 8(b), the amount of color ink and clear ink ejected per unit area was varied to confirm the graininess on the transfer medium after transfer. The observed graininess was then quantified by referring to a limit sample. In the table shown in FIG. 8(b), the upper table shows the results of the experiment using ink A. The lower table shows the results of the experiment using ink B. In the table, the numbers 0 to 200 associated with ink A or ink B indicate the amount of clear ink (ink A or ink B) ejected per unit area (print volume). The numbers 0 to 200 associated with color ink (black) indicate the amount of color ink ejected per unit area. Furthermore, 0 indicates that the corresponding ink is not ejected. The amount of ink ejected per unit area increases in proportion to the number. Furthermore, the graininess was evaluated using a five-point scale (1 to 5). In this case, the most noticeable graininess corresponds to number 1, and the least noticeable graininess corresponds to number 5.

[0080] As can be seen from the table in the figure, when no clear ink is ejected, the graininess becomes more noticeable when the ejection volume of color ink is small. Furthermore, when the ejection volume of color ink is small, the graininess can be reduced by increasing the ejection volume of clear ink. Furthermore, when using either ink A or ink B as the clear ink, the graininess can be reduced. Furthermore, when comparing ink A and ink B, ink B reduces the graininess with a smaller ejection volume. This is likely due in part to the fact that ink A does not contain resin, which makes it dry more easily than ink B. More specifically, hot-melt resin powder, for example, is likely to adhere more easily to inks containing liquid components before it is completely dried. Therefore, when using ink B, which dries easily, it is likely necessary to eject a larger volume than ink A. Furthermore, with ink B, the resin is likely to maintain its adhesiveness even when it has dried to a certain extent. Therefore, in this respect, it is also likely that ink B can be used with a smaller amount to reduce the graininess.

[0081] Furthermore, the results shown in Figure 8(b) show that, whether ink A or ink B is used, graininess can be sufficiently reduced when the total ink ejection volume, combining the amount of color ink and the amount of clear ink, exceeds a certain amount. This also shows that, for example, in areas where the amount of color ink ejected is sufficiently large, graininess does not occur even if clear ink is not ejected. Therefore, the results of this experiment also show that it is preferable to change the amount of clear ink ejected depending on the amount of color ink ejected.

[0082] As explained above, the use of clear ink in this example also makes it possible to prevent transfer unevenness. Similarly to the graininess described above, transfer unevenness was also able to be appropriately prevented when either ink A or ink B was used as the clear ink. More specifically, when ink A was used, the evaluation results for transfer unevenness were as shown in the table in FIG. 8(c). In the table in FIG. 8(c), the amounts of color ink and clear ink are shown as the ejection amount (print amount) per unit area. Each square in the table shows the total ink ejection amount, which is the sum of the amount of color ink and the amount of clear ink, as the total print amount per unit area. In this table, the area surrounded by a thick solid line indicates the area where no problematic transfer unevenness occurred. This area can also be considered, for example, as the area where transfer unevenness is eliminated by ejecting clear ink. Additionally, the area bounded by the dashed lines on the upper and left sides and the thick solid lines on the lower and right sides in the upper left corner of the area bounded by the thick solid line represents an area where only minor transfer unevenness occurred. This area can also be considered, for example, as an area where transfer unevenness is significantly reduced by ejecting clear ink. The results shown in Figure 8(c) confirm that when ink A is used, the use of clear ink in addition to color inks improves transferability. Furthermore, in this case, it can be confirmed that the use of clear ink can prevent transfer unevenness, particularly in the low gradation range where transfer unevenness occurs without the use of clear ink.

[0083] In the above experiments, the color inks and clear ink (Ink A or Ink B) were ejected in such a way that the color inks were ejected at each position on the transfer medium, and then the clear ink was ejected at the same position before the color ink at that position completely dried. In this case, the color inks and clear ink were ejected simultaneously onto the transfer medium. Although not shown, an experiment corresponding to the table in Figure 8(c) was also conducted for Ink B. This experiment also confirmed that the transferability of Ink B was improved by using clear ink in addition to the color inks, and that the use of clear ink prevented transfer unevenness in the low gradation range where transfer unevenness would occur if clear ink was not used.

[0084] Next, supplementary explanations will be given regarding the configuration described above. As explained above, in this example, a textile printing ink (textile pigment ink) containing a pigment as a coloring material can be suitably used as the color ink. In this case, an ink having a composition in which the coloring material (pigment) and dispersant are removed from the color ink can be suitably used as the clear ink. In this regard, if the ink characteristics (liquid properties) of the color ink and clear ink used simultaneously in the printing unit 14 differ significantly, differences in the ink aggregation and separation on the transfer medium may occur, potentially resulting in a deterioration in print quality (poor image quality). In contrast, using the above-described clear ink can appropriately prevent significant differences in the characteristics between the color ink and the clear ink. This also enables, for example, more appropriate high-quality printing.

[0085] As described above, it is also possible to use color inks containing a binder resin and clear inks containing the same resin as the binder resin in the color inks. In this case, it is believed that the inclusion of the same resin as the binder resin in the clear ink allows the hot-melt resin powder to adhere more easily to the clear ink for a longer period of time than, for example, a clear ink containing no resin. Therefore, by using clear ink containing a resin, it is possible to more reliably adhere, for example, hot-melt resin powder to the positions where the clear ink is ejected. Furthermore, as can be seen from the experimental results described above with reference to FIG. 8 , it is also possible to use inks that do not contain a resin as the clear ink. In this case, too, the use of clear ink can extend the time it takes for the ink to dry to a state where hot-melt resin powder is less likely to adhere to the positions where the clear ink is ejected. This also allows the hot-melt resin powder to be properly adhered to the positions where the clear ink is ejected, even when using clear inks that do not contain a resin. Regarding the differences in composition between color inks and clear inks, the reduction in the amount of clear ink caused by removing some components (such as colorants) from the color ink can be adjusted by appropriately changing the amount of solvent. It is also possible to use a resin that is different from the binder resin in the color ink as the resin contained in the clear ink.

[0086] As described above, in this example, by using clear ink in addition to color ink, for example, the color ink dots can be made to wet and spread more easily, thereby increasing the size of the dots. In this regard, the wetting and spreading of color inks due to the ejection of clear ink can also be considered to be, for example, bleeding between the clear ink and the color inks. Furthermore, this bleeding can be considered to be bleeding that does not reduce print quality, unlike inter-color bleeding that occurs between color inks of different colors. Furthermore, bleeding between the clear ink and the color ink can also be considered to be, for example, reducing the color density and increasing the dot diameter compared to when color inks are used alone, thereby reducing the graininess in low gradation areas.

[0087] One might think that using so-called light-colored inks would be sufficient to reduce the graininess. In this case, for example, light-colored inks with reduced pigment concentrations could be used in addition to the YMCK inks with normal color saturation. However, when printing for the same purpose as this example, if light-colored inks are used to reduce the graininess, it would be necessary to use light-colored inks for at least the three MCK colors. This would require adding at least three inkjet heads to the head unit 102 (see FIG. 1 ) in the printing unit 14, which would result in problems such as constricting the ink slots and increasing the size of the head unit 102. Furthermore, even if light-colored inks were used, the hot-melt resin powder would be less likely to adhere in the extremely low gradation range, where the gradation of the image is particularly low, potentially resulting in uneven transfer. In contrast, this example uses a colorless, uncolored clear ink instead of light-colored inks corresponding to specific ink colors, thereby reducing the graininess while minimizing the number of inkjet heads. In this case, it is also possible to eject the required amount of ink even in the extremely low gradation range, thereby making it possible to appropriately prevent the occurrence of transfer unevenness and the like.

[0088] Furthermore, in this example, the reduction of graininess through the use of clear ink can be considered to be related to, for example, the fact that the size of color ink dots can be increased when clear ink is used compared to the size of color ink dots when clear ink is not used, as described above. In this regard, in this example, both color ink and clear ink can be considered to be ejected at least some of the ejection positions. In this case, with regard to the size of color ink dots formed by the spread of color ink on the transfer medium after impact, if the size of a dot formed when both color ink and clear ink are ejected at the same ejection position is defined as the size when clear ink is used, and the size of a dot formed when only color ink is ejected at the ejection position is defined as the size when clear ink is not used, then the printing unit 14 can be considered to eject clear ink at least some of the ejection positions where color ink is ejected, for example, in low-tone areas of the image, so that the size when clear ink is used is larger than the size when clear ink is not used. This configuration can, for example, appropriately increase the size of ink dots formed with color ink. This can also, for example, appropriately reduce graininess.

[0089] As described above, in this example, the use of clear ink in low-tone areas of the image allows the hot-melt resin powder to adhere more appropriately. In this regard, if color inks are used instead of clear ink, it is considered that the hot-melt resin powder is particularly unlikely to adhere to isolated ink dots that are not surrounded by other ink dots. Therefore, in this example, it is preferable to eject clear ink at the ejection position of the isolated color ink dot or at a neighboring ejection position to increase the total amount of ink near the ejection position of the isolated color ink dot. More specifically, in this example, the printing unit 14 ejects color ink and clear ink from inkjet heads for color ink and clear ink at ejection positions set according to the printing resolution. In this case, it is considered that the printing unit 14 ejects clear ink so that an area including multiple ejection positions is continuously covered with color ink and clear ink. The continuous coverage of an area including multiple ejection positions with color ink and clear ink can be thought of, for example, as an arrangement of multiple ink dots that come into contact with each other on the transfer medium being formed in an area including multiple ejection positions.

[0090] Furthermore, in this case, if a color ink ejection position from an inkjet head for color ink is defined as a colored ejection position, and a color ink ejection position where no adjacent ejection positions are colored ejection positions is defined as an isolated ejection position, the low gradation portion of the image can be considered, for example, as a region including the isolated ejection position. In this case, the operation of the printing unit 14 can be considered, for example, as ejecting clear ink from an inkjet head for clear ink to at least some of the isolated ejection positions in the low gradation portion or to ejection positions surrounding the isolated ejection positions. By ejecting clear ink in this manner, the printing unit 14 prints on the transfer medium so that, for example, an area including multiple ejection positions including the isolated ejection position is connected by color ink and clear ink, at least in the vicinity of the isolated ejection position. This configuration, for example, can appropriately increase the total amount of ink ejected near the isolated ejection position in the low gradation portion compared to when clear ink is not used. This also allows, for example, hot melt resin powder to be more appropriately applied to the vicinity of the isolated ejection position. In this case, the operation of ejecting clear ink from the inkjet head for clear ink to ejection positions surrounding the isolated ejection positions in the printing unit 14 can be considered to be, for example, an operation of ejecting clear ink from the inkjet head for clear ink to at least some of the ejection positions to which color ink is not ejected. In this case, for example, ejecting clear ink to ejection positions between different isolated ejection positions can be considered to connect the multiple color ink dots at the different isolated ejection positions with dots of clear ink. This configuration allows, for example, the hot melt resin powder to be more appropriately adhered to the vicinity of the isolated ejection positions.

[0091] As explained above, when transferring an image using a hot-melt resin powder, it is conventional to use a white ink in addition to the color inks. However, the application and usage of the clear ink in this example differ in various respects from the application and usage of the white ink in conventional configurations. More specifically, when color printing is performed using an inkjet method, if a white ink layer is formed on top of a color ink layer, the white ink layer functions as a light-reflecting background in color expression (color reproduction) using a subtractive color mixing method. Furthermore, when transferring an image using a hot-melt resin powder, the white ink layer also plays a major role as a concealing layer that conceals the background color (base color) of the transfer medium to which the image is transferred. Furthermore, due to these characteristics of the white ink layer, the white ink layer is usually formed in an area that includes the entire image drawn with the color inks.

[0092] In contrast, the clear ink used in this example is a translucent ink, and therefore, even if a clear ink layer is formed, it does not normally function as a background layer that reflects light or as a layer that conceals the base color of the transfer medium. Furthermore, as can be understood from the above explanation, in this example, the purpose of using the clear ink can be achieved even if the clear ink is ejected only on a portion of an image drawn with color inks. Furthermore, unlike forming a white ink layer that functions as a concealing layer, when using clear ink as in this example, inks other than the color ink do not become excessively noticeable on the transfer medium. Therefore, as explained above, this example allows for appropriate high-quality printing that makes use of the texture, etc., of the transfer medium, for example, when using white or light-colored (pale-colored) fabric as the transfer medium. Furthermore, in this case, at least in these respects, the use and manner of use of the clear ink in this example differ from the use and manner of use of white ink in conventional configurations.

[0093] As explained above, in this example, the amount of clear ink ejected at each position on the transfer medium may be varied depending on, for example, the amount of color ink ejected at each position. In this case, if the amount of color ink ejected (print volume) in an area on the transfer medium containing each pixel is less than a predetermined amount (X%), clear ink may be ejected in that area to compensate for (replenish) the insufficient amount of ink (liquid volume). Furthermore, if the amount of ink landing per unit area exceeds the predetermined print volume (liquid volume), bleeding may occur, or excessive hot-melt resin powder may adhere, leaving traces of hot-melt resin powder on the transfer medium. Therefore, the total amount of color ink and clear ink ejected (print volume) in an area on the transfer medium containing each pixel may be set to a value not exceeding another predetermined amount (Y%, Y>X). In contrast, when using white ink, for example, if the amount of white ink ejected at each position on the transfer medium is varied as described above, it is possible that the white ink will land dotted among the color inks. As a result, it is possible that the colors of some areas of the printed image will appear blurred. In particular, if white ink is further ejected onto low-tone areas in the image, some of the color ink dots will be covered with white ink, making the colors in the light-colored low-tone areas even lighter, making it impossible to print in the intended color. Therefore, in this respect, too, it can be said that the use and manner of use of the clear ink in this example differ from the use and manner of use of white ink in conventional configurations.

[0094] Furthermore, it may be preferable for the clear ink dots formed on the transfer medium by ejecting the clear ink onto the transfer medium in the printing unit 14 to be flattened and spread out, for example, to make it easier for the hot melt resin powder to adhere. In this case, it may be possible to adjust the spread of the clear ink dots during the operations performed in the printing system 10. This configuration, for example, allows the size of the clear ink dots to be appropriately adjusted. In this case, the operation of adjusting the spread of the clear ink dots may be considered, for example, as an adjustment stage operation that adjusts the spread of the clear ink dots formed on the transfer medium by the printing unit 14. The adjustment stage may be considered, for example, as a stage of adjusting the flattening of the ink dots (leveling adjustment). The adjustment stage operation may be considered, for example, as a leveling stage operation for flattening the ink dots. The adjustment stage adjustment may be performed, for example, before the printing stage (printing stage) in the printing unit 14 prints on the transfer medium. Furthermore, the adjustment stage operation may be performed, as needed, after the printing unit 14 prints on the transfer medium.

[0095] Furthermore, when performing the adjustment stage operation to adjust the ink dot spread, for example, the printing unit 14 prints an image on a transfer medium under preset first printing conditions. Then, based on the printing results, it is determined, for example, whether the clear ink dot spread (dot gain) is insufficient. If it is determined, for example, that the dot spread is insufficient, second printing conditions different from the first printing conditions are selected as printing conditions for the printing unit 14 to perform printing in the printing stage. In this case, for example, conditions that increase the spread of the clear ink dots are selected as the second conditions. This configuration makes it possible, for example, to appropriately determine whether the printing conditions need to be changed to further flatten the ink dots, and appropriately change the printing conditions as necessary. This also makes it possible, for example, to more appropriately flatten the clear ink dots in a subsequent printing operation on a transfer medium performed by the printing unit 14. Furthermore, for example, in a subsequent operation, it is possible to more appropriately adhere hot melt resin powder to the positions where the clear ink was ejected.

[0096] In this case, during the adjustment stage, the second printing conditions may be, for example, printing conditions that slow the printing speed compared to the first printing conditions. Furthermore, printing conditions that slow the printing speed may be, for example, conditions that increase the number of printing passes. In this case, the number of passes may be considered, for example, the number of main scanning operations performed on the same position on the printing target. Furthermore, when the number of passes is increased, the relative movement amount of the inkjet head in one sub-scanning operation may be reduced, resulting in a slower medium transport speed. Furthermore, in this case, the printing speed under the first printing conditions may be, for example, the normal printing speed (standard printing speed) of the printing unit 14. Furthermore, in this case, the printing speed under the second printing conditions may be, for example, a printing speed slower than the normal printing speed. Furthermore, selecting the second printing conditions during the adjustment stage may be considered, for example, to select a printing speed slower than a specific printing speed corresponding to the printing speed under the first printing conditions.

[0097] In order to increase the spread of the clear ink dots, it is possible to adjust the specific surface area by increasing the size of the droplets (ink droplets) ejected from the inkjet head. It is also possible to adjust the spread of the dots by changing the waveform (drive waveform) of the drive signal that drives the inkjet head to eject droplets. Therefore, the second printing conditions may be different from the first printing conditions, for example, in terms of these factors.

[0098] Furthermore, for example, when using a printing unit 14 configured to use a heater for heating during printing, the printing conditions may be changed by changing the heater's heating temperature. For example, when using a clear ink that fixes to the transfer medium by evaporating its solvent, a heater that heats the transfer medium may be used. In this case, for example, by lowering the heater's heating temperature under the second printing condition compared to the heating temperature under the first printing condition, the ink drying speed can be slowed and the clear ink dots can be made to spread more widely. In this case, for example, when using a printing unit 14 configured to print while transporting the medium, the heating temperature of an after-heater, which is a heater disposed downstream of the inkjet head in the transport direction, may be adjusted as described above. Furthermore, when an after-heater is used in the printing unit 14, for example, the after-heater may be divided into multiple regions (e.g., two or three regions) and the temperature may be adjusted. In this case, the multiple regions may be divided into a region closer to the inkjet head in the transport direction and a region farther from the inkjet head. In this case, it is also possible to change the heating temperature of the afterheater individually for each region. This configuration allows, for example, more detailed adjustment of the spread of ink dots. Furthermore, it is also possible to use, for example, a heater that heats an inkjet head as the heater in the printing unit 14. In this case, by changing the heating temperature of this heater, it is possible to change, for example, the viscosity of the ink before ejection. Furthermore, by increasing the heating temperature under the second printing conditions compared to the heating temperature under the first printing conditions, it is possible to reduce the viscosity of the ejected ink, making it easier for the ink to spread on the transfer medium. [Industrial Applicability]

[0099] The present invention can be suitably used in, for example, a printing method. [Explanation of symbols]

[0100] 10 Printing system, 102 Head unit, 104 Platen, 106 Y-bar unit, 108 Main scanning drive unit, 110 Sub-scanning drive unit, 12 Print data preparation unit, 120 Control unit, 14 Printing unit, 16 Powder application unit, 18 Thermal transfer unit, 202 Inkjet head, 300 Printing area, 302 Color ink layer, 304 White ink layer, 306 Image layer, 312 High gradation area, 314 Medium gradation area, 316 Low gradation area, 352 Resin powder, 402 Dots, 404 Dots, 50 Transfer medium, 52 Base unit, 54 Ink receiving layer

Claims

1. A printing method for drawing an image on a transfer medium by transferring an image printed on a transfer medium to the transfer medium, comprising: a printing step of printing the image onto the transfer medium using a printing device that performs printing using an inkjet method; a hot melt resin applying step of applying a hot melt resin powder, which is a powder containing a resin that softens when heated, to the transfer medium on which the image is printed; a transfer step of heating the transfer medium to which the hot melt resin powder is attached, and attaching a hot melt resin portion, which is a resin portion formed by softening the hot melt resin powder by heating, to the transfer medium, thereby transferring the image from the transfer medium to the transfer medium; Equipped with The printing device a color ink head that is an inkjet head that ejects color ink that is ink containing a coloring material that exhibits a color; a clear ink head, which is an inkjet head that ejects clear ink, which is colorless and translucent ink; Equipped with a printing method comprising the step of: in the printing step, further discharging the clear ink from the clear ink head onto at least a part of an area of ​​the transfer medium onto which the colored inks are discharged from the colored ink heads;

2. In the transferring step, at least a part of the color material adhering to the transfer medium is moved to the transfer-receiving medium together with at least a part of the hot-melt resin portion, thereby transferring the image from the transfer medium to the transfer-receiving medium; an area on the transfer medium onto which the color inks are ejected from the color ink head is defined as an image expression area; A region in which the amount of colored ink ejected per unit area is less than a predetermined reference amount is defined as a small-ink region, When the ratio of the color material that moves from the transfer medium to the transfer receiving medium in the transfer step is defined as a transfer rate, In the printing step, the clear ink is ejected by the printing device onto at least a part of the small amount of ink area of ​​the image representation area, The printing method according to claim 1 , wherein the transfer rate in at least a portion of the small amount of ink region is increased compared to a case where the clear ink is not ejected.

3. The printing method according to claim 2, characterized in that by ejecting the clear ink onto at least a portion of the small amount of ink area during the printing stage, the amount of hot melt resin powder that adheres to the position where the clear ink is ejected during the hot melt resin deposition stage is made greater than in the case where the clear ink is not ejected.

4. a non-low-ink-amount region is defined as a region of the image representation region where the amount of colored ink ejected per unit area is greater than a predetermined amount that is greater than the reference amount; When the amount of the clear ink ejected per unit area onto each position on the transfer medium is defined as the clear ink ejection amount, A printing method as described in claim 2 or 3, characterized in that, in the printing stage, the clear ink ejection amount in the small amount of ink area is made larger than the clear ink ejection amount in the non-small amount of ink area, and the clear ink ejection amount is varied depending on the amount of colored ink ejected per unit area.

5. 5. The printing method according to claim 4, wherein in the printing step, the clear ink is not ejected onto positions where the amount of the colored ink ejected per unit area is greater than a preset upper limit amount.

6. the printing device ejects the colored inks and the clear ink from the colored ink heads and the clear ink heads to ejection positions that are set according to a printing resolution; When the ejection position where the colored ink is ejected from the colored ink head is defined as a colored ejection position, and the colored ejection position where the adjacent ejection position is not the colored ejection position is defined as an isolated ejection position, the small amount of ink region is a region including the isolated ejection position, A printing method according to any one of claims 2 to 5, characterized in that, in the printing stage, the clear ink is ejected from the clear ink head onto at least some of the isolated ejection positions in the small amount of ink region, or onto the ejection positions surrounding the isolated ejection positions, so that, at least in the vicinity of the isolated ejection positions, a range including the isolated ejection positions is connected by the colored ink and the clear ink, and printing is performed on the transfer medium.

7. 7. The printing method according to claim 1, further comprising an adjusting step of adjusting how the dots of the clear ink formed on the transfer medium in the printing step spread.

8. 8. The printing method according to claim 7, wherein, in the adjustment stage, it is determined whether the spread of the clear ink dots is insufficient based on the result of printing the image on the transfer medium by the printing device under preset first printing conditions, and if it is determined that the spread of the dots is insufficient, second printing conditions that are different from the first printing conditions and that result in greater spread of the clear ink dots are selected as printing conditions under which the printing device will print in the printing stage.

9. A printing system for drawing an image on a transfer medium by transferring an image printed on a transfer medium to the transfer medium, a printing device that prints on the transfer medium using an inkjet method; a transfer unit that transfers an image from the transfer medium to the transfer receiving medium; Equipped with the transfer unit heats the transfer medium to which the hot melt resin powder is attached, the hot melt resin powder being a powder containing a resin that softens when heated, in a state where the hot melt resin powder is attached to the transfer medium on which the image is printed, and attaches a hot melt resin portion, which is a resin portion formed by the hot melt resin powder being softened by heating, to the transfer medium, thereby transferring the image from the transfer medium to the transfer medium; The printing device a color ink head that is an inkjet head that ejects color ink that is ink containing a coloring material that exhibits a color; a clear ink head, which is an inkjet head that ejects clear ink, which is colorless and translucent ink; and A printing system comprising: a clear ink head that further ejects the clear ink onto at least a portion of an area of ​​the transfer medium onto which the colored inks are ejected from the colored ink heads.

10. A printing device that prints on a transfer medium by an inkjet method in a printing system that draws an image on a transfer medium by transferring an image printed on the transfer medium to the transfer medium, a color ink head that is an inkjet head that ejects color ink that is ink containing a coloring material that exhibits a color; a clear ink head, which is an inkjet head that ejects clear ink, which is colorless and translucent ink; Equipped with The image is transferred from the transfer medium to the transfer-receiving medium by adhering hot-melt resin powder, which is a powder containing a resin that softens when heated, to the transfer medium on which the image is printed, heating the transfer medium to which the hot-melt resin powder is adhered, and adhering a hot-melt resin portion, which is a resin portion formed by the hot-melt resin powder softening when heated, to the transfer-receiving medium, thereby transferring the image from the transfer medium to the transfer-receiving medium; Further, the clear ink is ejected from the clear ink head onto at least a part of the area of ​​the transfer medium onto which the colored inks are ejected from the colored ink head; The printing device is characterized in that the clear ink ejection amount, which is the amount per unit area of ​​the clear ink ejected to each position on the transfer medium, is varied depending on the amount of the colored ink ejected per unit area.

Images