Printing apparatus, printing method, and printing program

Abstract

To provide a printer, a printing method and a printing program capable of suppressing stickiness of a surface to be printed of a medium to be printed.SOLUTION: The printing apparatus includes a first nozzle configured to discharge a first droplet onto a printing medium based on image data to form an image, a second nozzle configured to discharge a second droplet different from the first droplet and having a smaller amount than the first droplet, a light source configured to emit ultraviolet light for curing the first droplet and the second droplet, and a controller. The controller is configured to execute a first printing process of discharging a first liquid droplet from the first nozzle based on image data, a second printing process of discharging a second liquid droplet smaller than the first liquid droplet from the second nozzle onto the first liquid droplet landed on the medium to be printed after the first printing process, and a curing process of irradiating the first liquid droplet and the second liquid droplet on the medium to be printed with ultraviolet light from the light source.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present disclosure relates to a printing device such as an inkjet printer, a printing method, and a printing program. [Background technology]

[0002] In recent years, a printing technology has become known in which ultraviolet-curable ink droplets are ejected onto a print medium (see Patent Document 1). By irradiating ultraviolet rays onto the ink droplets that have landed on the print medium, the ink droplets are cured and fixed to the print medium. By using ultraviolet-curable ink droplets in this way, it is possible to print on print media other than paper, such as resin or metal, and to obtain a print medium with a glossy print surface. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2019-177601 Summary of the Invention [Problem to be solved by the invention]

[0004] However, with the above-mentioned conventional printing technology, the adhesive force of the ink droplets can cause the printed surface of the print medium to feel sticky (tacky). This stickiness not only makes the surface feel uncomfortable to the touch, but also causes problems such as the print medium sticking to the packaging film during shipping and the adhesion of roll film when the print medium is wrapped around it, resulting in quality degradation.

[0005] Therefore, an object of the present disclosure is to provide a printing device, a printing method, and a printing program that can suppress stickiness on the printing surface of a print medium. [Means for solving the problem]

[0006] The printing device disclosed herein comprises a first nozzle for ejecting ultraviolet-curable first droplets onto a printing medium based on image data to form an image; a second nozzle for ejecting ultraviolet-curable second droplets that are different from the first droplets and are smaller in size than the first droplets; a light source for irradiating ultraviolet light to harden the first droplets and the second droplets; and a control device. The control device executes a first printing process for ejecting the first droplets from the first nozzle based on the image data; a second printing process for ejecting the second droplets, which are smaller in size than the first droplets, from the second nozzle onto the first droplets that have landed on the printing medium after the first printing process; and a hardening process for causing the light source to irradiate the ultraviolet light onto the first droplets and the second droplets on the printing medium, wherein the total area of ​​the second droplets that have landed on the first droplets is smaller than the total area of ​​an image formed by the first droplets that have landed on the printing medium.

[0007] According to the present disclosure, in the second printing process, second droplets smaller in size than the first droplets are ejected from the second nozzles onto the first droplets that have landed on the print medium. The total area of ​​the second droplets that have landed on the first droplets is smaller than the total area of ​​the image formed by the first droplets that have landed on the print medium. This makes it easier to harden the ejected second droplets with ultraviolet light before they wet and spread. This can reduce the contact area of ​​the print surface of the print medium when touched by a person. This can prevent stickiness of the print surface of the print medium. [Effects of the Invention]

[0008] According to the present disclosure, it is possible to provide a printing device, a printing method, and a printing program that can suppress stickiness of the printing surface of a print medium. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a plan view showing the configuration of a printing device according to an embodiment. [Figure 2] FIG. 2 is a diagram showing nozzles in each head in FIG. [Figure 3]FIG. 2 is a block diagram showing the configuration of a control system of the printing apparatus of FIG. 1. [Figure 4] 1 is a diagram showing an image of ink droplets that have landed on a print medium and then spread over time from immediately after landing. [Figure 5] Figure 5A is a diagram showing an image of color ink droplets ejected from the third head onto the printing medium, and Figure 5B is a diagram showing an image of clear ink droplets ejected from the second head onto the color ink droplets on the printing medium. [Figure 6] FIG. 6A is a diagram showing a partial image in a block region of partial image data, and FIG. 6B is a diagram showing an area formed by ink droplets of clear ink ejected onto the partial image of FIG. 6A. [Figure 7] 10A and 10B are diagrams for explaining printing passes onto which ink droplets of clear ink should be ejected during tackiness reduction processing. [Figure 8] FIG. 10 is a diagram illustrating that an area formed in a first printing pass during tack reduction processing does not overlap with an area formed in a second printing pass that follows the first printing pass. [Figure 9] FIG. 9A is a diagram showing a drive waveform for a normal small droplet of clear ink, and FIG. 9B is a diagram showing a drive waveform for a very small droplet of clear ink. [Figure 10] 10 is a flowchart showing a processing flow in the image processing device. [Figure 11] 10 is a flowchart showing a processing flow in the output device. DETAILED DESCRIPTION OF THE INVENTION

[0010] A printing device according to an embodiment of the present disclosure will be described below with reference to the drawings. The printing device described below is merely one embodiment of the present disclosure. Therefore, the present disclosure is not limited to the following embodiment, and additions, deletions, and modifications are possible without departing from the spirit of the present disclosure. Note that, below, identical or corresponding elements will be designated by the same reference numerals throughout the drawings, and duplicated descriptions will be omitted unless otherwise noted.

[0011] FIG. 1 is a plan view showing the configuration of a printing device 100 according to one embodiment. FIG. 2 is a diagram showing the nozzles in each head 20 in FIG. 1. FIG. 3 is a block diagram showing the configuration of a control system for the printing device 100 in FIG. 1. In FIGS. 1 and 2, mutually perpendicular directions are referred to as a first direction Df and a second direction Ds. In this embodiment, for example, the first direction Df is the transport direction of the print medium W, and the second direction Ds is the movement direction of the carriage 41 described below. In the following description, Ds will be referred to as the movement direction, and Df will be referred to as the transport direction. However, the above directions are merely examples and are not limiting.

[0012] The printing device 100 includes an output device 101 and an image processing device 102. The output device 101 and the image processing device 102 are connected to each other so that they can communicate with each other wirelessly or via a wired connection such as a network. The image processing device 102 generates print data from image data of a print image, which is an image to be printed on a print medium W by the output device 101, and transmits the generated print data to the output device 101 wirelessly or via a wired connection. The output device 101 prints the print image on the print medium W based on the print data received from the image processing device 102. Examples of the print medium W include fabric, resin material, metal material, and sheet-fed film.

[0013] The output device 101 is, for example, a serial head type inkjet printer. Based on print data, the output device 101 alternately repeats a pass process in which an inkjet head (hereinafter referred to as a head) 20 is moved in a movement direction Ds to eject ink droplets, and a transport process in which the print medium W is transported in a transport direction Df. This causes a predetermined image to be printed on the print medium W. In FIG. 1, the print medium W is transported in the transport direction Df, from the bottom to the top of the page.

[0014] The output device 101 includes a head unit HU having a plurality of heads 20 , a platen 11 , a plurality of tanks 12 , a moving device 30 , a transport device 40 , and a light source 80 .

[0015] The head 20 prints an image on the print medium W using predetermined ink droplets based on print data. Examples of the multiple heads 20 included in the head unit HU include a first inkjet head (hereinafter referred to as the first head) 21, a second inkjet head (hereinafter referred to as the second head) 22, and a third inkjet head (hereinafter referred to as the third head) 23. These heads are arranged side by side in the order of the first head 21, the second head 22, and the third head 23 from one side in the transport direction Df. As a result, the second head 22 is located downstream of the third head 23 in the transport direction Df of the print medium W. Furthermore, the first head 21 is located downstream of the second head 22 in the transport direction Df of the print medium W. Note that, hereinafter, when the term "head 20" is used, the head 20 is meant to include the first head 21, the second head 22, and the third head 23.

[0016] In this embodiment, for example, the first head 21 prints on the print medium W using UV-curable white ink, the second head 22 prints on the print medium W using UV-curable clear ink, and the third head 23 prints on the print medium W using UV-curable color ink. In this embodiment, the third head 23 corresponds to the first head, and the second head 22 corresponds to the second head. However, the above colors of ink ejected by each head 20 are merely examples and can be changed as appropriate. A head that ejects special color ink may also be provided.

[0017] The platen 11 has a flat upper surface and defines the distance between the print medium W placed on that upper surface and the nozzle surface of the head 20 provided opposite it. The platen 11 moves back and forth in the transport direction Df. As a result, the print medium W supported by the platen 11 moves back and forth in the transport direction Df.

[0018] Ink is stored in each tank 12. The tanks 12 are connected to the head 20 via a flow path described below to supply ink to the head 20. The tanks 12 are containers that store ink. The number of tanks 12 is equal to or greater than the number of types of ink. For example, the tanks 12 include four first tanks 12a that store four types of color ink, one or more second tanks 12b that store white ink, and one or more third tanks 12c that store clear ink. Examples of color inks include cyan ink, magenta ink, yellow ink, and black ink.

[0019] The first tank 12a is connected to the third head 23 via a first flow path 13a. Color ink is supplied from the first tank 12a to the third head 23 via the first flow path 13a. The second tank 12b is connected to the first head 21 via a second flow path 13b. White ink is supplied from the second tank 12b to the first head 21 via the second flow path 13b. The third tank 12c is connected to the second head 22 via a third flow path 13c. Clear ink is supplied from the third tank 12c to the second head 22 via the third flow path 13c.

[0020] The transport device 40 has a drive unit including, for example, a ball screw or rack and pinion (not shown), and a transport motor 46. The drive unit is connected to the transport motor 46. The rotation of the transport motor 46 moves the platen 11 in the transport direction Df, transporting the print medium W in the transport direction Df.

[0021] The movement device 30 includes a carriage 41, two guide rails 42, a movement motor 34, and an endless belt 44. The two guide rails 42 extend above the platen 11 in the movement direction Ds, sandwiching the carriage 41 between them in the transport direction Df. The carriage 41 supports the first head 21, the second head 22, and the third head 23. The carriage 41 is supported by the two guide rails 42 so as to be movable in the movement direction Ds. The endless belt 44 extends in the movement direction Ds and is attached to the carriage 41 and to the movement motor 34 via a pulley 45. The endless belt 44 operates when the movement motor 34 rotates. As a result, the carriage 41 reciprocates in the movement direction Ds along the guide rails 42 while supporting the first head 21, the second head 22, and the third head 23. As a result, the first head 21, the second head 22, and the third head 23 are reciprocated in the movement direction Ds by the carriage 41.

[0022] A light source 80 is provided for each head 20. The light source 80 is provided to the side of each head 20 in the movement direction Ds. The light source 80 corresponding to the first head 21 emits ultraviolet light that hardens the white ink droplets ejected from the first head 21. The light source 80 corresponding to the second head 22 emits ultraviolet light that hardens the clear ink droplets ejected from the second head 22. The light source 80 corresponding to the third head 23 emits ultraviolet light that hardens the color ink droplets ejected from the third head 23.

[0023] Next, as shown in FIG. 2, the first head 21, the second head 22, and the third head 23 have the same configuration. The first head 21 has a plurality of nozzles 121. The first head 21 has a plurality of nozzle rows NL, each of which is configured by arranging a plurality of nozzles 121 in a predetermined nozzle row direction Dn at a predetermined interval. Each nozzle row NL extends in the nozzle row direction Dn. The nozzle row direction Dn is, for example, parallel to the transport direction Df. The nozzle rows NL are arranged at a predetermined interval in the movement direction Ds. The arrangement of the nozzle rows NL in the second head 22 and the third head 23 is the same as the arrangement of the nozzle rows NL in the first head 21. Also, in FIG. 2, the nozzles constituting the nozzle row NL in the second head 22 are designated 221, and the nozzles constituting the nozzle row NL in the third head 23 are designated 321. The second head 22 has a plurality of nozzles 221. The third head 23 has a plurality of nozzles 321.

[0024] Nozzle 321 is for ejecting ink droplets of color ink as ultraviolet-curable first droplets onto a print medium W based on image data to form an image. Nozzle 221 is for ejecting ink droplets of clear ink as ultraviolet-curable second droplets different from the color ink droplets, which are smaller in amount than the color ink droplets. Nozzle 121 is for ejecting ink droplets of ultraviolet-curable white ink onto a print medium W based on image data to form an image, etc. In this embodiment, nozzles 121, 221, and 321 are capable of ejecting large, medium, and small ink droplets. In this embodiment, nozzles 121, 221, and 321 eject large ink droplets, except for the second printing process described below. Nozzle 321 corresponds to the first nozzle, and nozzle 221 corresponds to the second nozzle.

[0025] 3, the first head 21 is provided with a first drive element 27 arranged for each nozzle 121. The second head 22 is provided with a second drive element 28 arranged for each nozzle 221. The third head 23 is provided with a third drive element 29 arranged for each nozzle 321. The first drive element 27, the second drive element 28, and the third drive element 29 are piezoelectric elements, heat generating elements, electrostatic actuators, or the like. Each drive element 27, 28, 29 applies pressure to the ink to eject ink droplets from the corresponding nozzle 121, 221, 321.

[0026] The output device 101 in the printing device 100 includes a second control device 50. The output device 101 also includes a second storage device 51, a second communication interface 52, a first head drive circuit 53, a second head drive circuit 54, a third head drive circuit 57, a movement drive circuit 55, a transport drive circuit 56, and a light source control circuit 58, all of which are connected to the second control device 50.

[0027] The second storage device 51 is a memory accessible from the second control device 50, and includes, for example, RAM and ROM. The RAM temporarily stores print data and various data used during calculations by the second control device 50. The ROM stores print programs and various data for various data processing operations.

[0028] The second control device 50 is configured as a computer and includes a processor such as a CPU. The second control device 50 controls the operation of each part of the output device 101 by executing a print program while referring to data stored in the second storage device 51. The second control device 50 may be configured as a single device, or may be configured so that multiple independently arranged devices work together to perform the operation of the output device 101. The second control device 50 also receives various data such as print data from the image processing device 102 via the second communication interface 52.

[0029] The first head drive circuit 53 includes a multiplexer and controls the operation of the first drive element 27 based on instructions from the second control device 50. In this case, the second control device 50 outputs a control signal for driving the first drive element 27 to the first head drive circuit 53, and the first head drive circuit 53 generates a drive signal based on the control signal and outputs this drive signal to the first drive element 27. The first drive element 27 imparts a predetermined ejection energy to the white ink in the first head 21 at a predetermined timing based on the drive signal. This causes white ink to be ejected from the nozzle 121. The second head drive circuit 54, like the first head drive circuit 53, includes a multiplexer and controls the operation of the second drive element 28 based on instructions from the second control device 50. This causes clear ink to be ejected from the nozzle 221. The third head drive circuit 57, like the first head drive circuit 53 and the second head drive circuit 54, also includes a multiplexer and controls the operation of the third drive element 29 based on instructions from the second control device 50. This causes the color ink to be ejected from the nozzle 321.

[0030] The movement drive circuit 55 controls the operation of the movement motor 34 of the movement device 30 based on instructions from the second control device 50. This causes the carriage 31 to move back and forth in the movement direction Ds. Therefore, the first head 21, the second head 22, and the third head 23 move back and forth in the movement direction Ds.

[0031] The transport drive circuit 56 controls the operation of the transport motor 46 of the transport device 40 based on instructions from the second control device 50. As a result, the platen 11 transports the print medium W intermittently or continuously along the transport direction Df, and stops the print medium W at a predetermined position.

[0032] The light source control circuit 58 causes the light source 80 to emit ultraviolet light based on instructions from the second control device 50. As a result, the ink droplets ejected onto the print medium W are cured by the ultraviolet light.

[0033] The image processing device 102 in the printing device 100 is a device that processes print images to be printed by the output device 101, and is configured, for example, by a personal computer, a tablet, or a smartphone. The image processing device 102 includes a first control device 61, and a first storage device 62, a first communication interface 63, a reading device 64, and a display device 65 that are connected to the first control device 61.

[0034] The first storage device 62 is a memory accessible from the first control device 61, and includes, for example, RAM and ROM. The RAM temporarily stores image data and various data used in calculations by the first control device 61. The ROM stores printing programs and various data for various data processing. Examples of the image data include raster data that indicates the image to be printed on the print medium W.

[0035] The first control device 61 is configured as a computer and includes a processor such as a CPU. The first control device 61 controls the operations of the output device 101 and the display device 65 by executing a printing program while referencing data stored in the first storage device 62. The first control device 61 may be configured as a single device, or may be configured such that multiple independently arranged devices cooperate to perform the operations of the image processing device 102. The first control device 61 transmits various data such as print data to the output device 101 via the first communication interface 63. In this embodiment, the first control device 61 cooperates with the second control device 50 of the output device 101 to configure the control device 70 of the printing device 100.

[0036] The reading device 64 reads a printing program stored in a storage medium KB, such as a CD-ROM or a USB flash memory. The read printing program is stored in the first storage device 62. Alternatively, the printing program may be downloaded via a predetermined communication network and stored in the first storage device 62. The display device 65 is, for example, a touch panel display, and outputs operation information by the user to the first control device 61. The display device 65 also displays a print image to be printed by the output device 101 based on image data.

[0037] Next, FIG. 4 is a diagram showing an image of ink droplets that have landed on the print medium W wetting and spreading over time immediately after landing.

[0038] As shown in FIG. 4, ink droplets ejected from the head 20 and landing on the print medium W tend to wet and spread over the print medium W as time passes after landing. Therefore, when ink droplets are cured by ultraviolet light while wet and spread on the print medium W, the surface area of ​​the cured ink droplets (aggregates of ink droplets), in other words, the contact area that can be touched by a person, increases. Therefore, due to the adhesive force of ultraviolet-curable ink droplets, the printed surface of the print medium W may become sticky (tacky) when touched by a person. Therefore, the printing device 100 of this embodiment executes a process to reduce tackiness (hereinafter referred to as tackiness reduction process).

[0039] Figure 5A is a diagram showing an image of color ink droplets ejected from the third head 23 onto the printing medium, and Figure 5B is a diagram showing an image of clear ink droplets ejected from the second head 22 onto the color ink droplets on the printing medium.

[0040] The first control device 61 executes a process for generating first print data for ejecting ink droplets of color ink from the nozzles 321 onto the print medium W based on the image data. The first control device 61 also executes a process for generating second print data for ejecting ink droplets of clear ink from the nozzles 221 onto the ink droplets of color ink that have landed on the print medium based on the image data. This second print data is generated for a block region BR (FIG. 6) where the printing rate is equal to or greater than a predetermined value. Details will be described later. The first control device 61 transmits the first print data and second print data to the second control device 50 via the first communication interface 63.

[0041] 5A, the second control device 50 executes a first printing process that causes the nozzles 321 to eject ink droplets of color ink based on first print data that is based on image data. That is, the second control device 50 causes the third head 23 to execute the first printing process. As a result, a predetermined image is formed on the print medium W using ink droplets of color ink.

[0042] The second control device 50 executes a curing process in which the light source 80 irradiates ultraviolet light onto the color ink droplets that have landed on the print medium. In this case, according to an embodiment in which the light source 80 is disposed upstream of the third head 23 in the movement direction Ds during execution of a printing pass, ultraviolet light is irradiated from the light source 80 immediately after the color ink droplets are ejected from the third head 23. This allows the color ink droplets to be cured immediately after being ejected.

[0043] Next, as shown in FIG. 5B , after the first printing process and the curing process, the second control device 50 executes a second printing process in which droplets of clear ink are ejected from the nozzles 221 onto the droplets of color ink that have landed on the print medium W in a smaller amount than the droplets of color ink. That is, the second control device 50 executes the second printing process on the second head 22. As a result, droplets of clear ink are ejected onto the droplets of color ink that have spread and hardened on the print medium W. In this case, the second control device 50 uses small droplets of the large, medium, and small droplets that can be ejected from the nozzles 221 as clear ink droplets in the second printing process. As a result, small droplets of clear ink are ejected onto the large droplets of color ink that have landed on the print medium W, and therefore the amount of clear ink droplets ejected is smaller than the amount of color ink droplets ejected.

[0044] Here, the total area of ​​the clear ink droplets that land on the color ink droplets is smaller than the total area of ​​the image made up of the color ink droplets that land on the print medium W. Specifically, for example, the area per pass of the clear ink droplets that land on the color ink droplets is smaller than the area per pass of the image made up of the color ink droplets that land on the print medium W. Even more specifically, for example, the area per unit area (e.g., per pixel) per pass of the clear ink droplets that land on the color ink droplets is smaller than the area per unit area (e.g., per pixel) per pass of the image made up of the color ink droplets that land on the print medium W.

[0045] The second control device 50 executes a curing process in which the light source 80 irradiates ultraviolet light onto the clear ink droplets that have landed on the color ink droplets on the print medium. In this case, if the light source 80 is positioned upstream of the second head 22 in the movement direction Ds during execution of a printing pass, ultraviolet light is irradiated from the light source 80 immediately after the clear ink droplets are ejected from the second head 22. This allows the clear ink droplets to be cured immediately after being ejected. The first printing process, second printing process, and curing process described above are performed for each partial image data PD (FIG. 6), which will be described later.

[0046] The second control device 50 may move the carriage 41 in the movement direction Ds at a first speed when ejecting color ink droplets from the nozzles 321 of the third head 23 in the first printing process. As a result, the nozzles 321 eject color ink droplets onto the print medium W while moving in the movement direction Ds at the first speed. Furthermore, the second control device 50 may move the carriage 41 in the movement direction Ds at a second speed faster than the first speed when ejecting clear ink droplets from the nozzles 221 of the second head 22 in the second printing process. As a result, the nozzles 221 eject clear ink droplets onto the print medium W while moving in the movement direction Ds at the second speed. Note that the second printing process is performed in a printing pass different from the printing pass of the first printing process. Alternatively, the second head 22 and the third head 23 may be configured to be supported by different carriages. In this case, when ink droplets of color ink are ejected from the nozzles 321 of the third head 23 supported by one carriage in the first printing process, the one carriage is moved in the movement direction Ds at a first speed. Also, when ink droplets of clear ink are ejected from the nozzles 221 of the second head 22 supported by the other carriage in the second printing process, the other carriage is moved in the movement direction Ds at a second speed.

[0047] The tackiness reduction process in this embodiment will be described in detail below. Fig. 6A is a diagram showing a partial image PG in a block region BR of partial image data PD, and Fig. 6B is a diagram showing a region CG formed by ink droplets of clear ink ejected onto the partial image PG in Fig. 6A.

[0048] After acquiring image data, the first control device 61 of the image processing device 102 executes a process of acquiring a plurality of partial image data PD that partially constitute the image data, as shown in FIG. 6A. This divides the image data into a plurality of partial image data PD. In FIGS. 6A and 6B, partial image data PD1, partial image data PD2, and partial image data PD3 are shown as three partial image data PD. The area corresponding to the partial image data PD may be, for example, an area equivalent to one printing pass of the second head 22 and the third head 23.

[0049] Next, the first control device 61 executes a process of dividing the area corresponding to each partial image data PD into a plurality of block areas BR. For example, the area corresponding to the partial image data PD may be divided into 12 block areas BR each consisting of 3 rows and 4 columns. Note that in Figures 6A and 6B, 40 block areas BR each consisting of 10 rows and 4 columns are shown as an example in the entire image data. In the following description, row and column numbers will be used to identify each of the 40 block areas BR.

[0050] The first control device 61 then acquires the printing rate (duty) for each of the divided block regions BR as described above. For example, for the partial image data PD1 in FIG. 6A, the first control device 61 acquires the printing rate for that block region BR based on the data of the portion of the partial image data PD1 that corresponds to the block region BR to be acquired. This allows the printing rate for the block region BR to be acquired for each block region BR. The same applies to each block region BR in the partial image data PD2 and each block region BR in the partial image data PD3.

[0051] The first control device 61 then determines for each block region BR whether the printing rate in that block region BR is equal to or greater than a predetermined value (e.g., 50%). For example, for the partial image data PD1 in FIG. 6A, the partial image PG1 exists across the block region BR in the first row, first column, the block region BR in the first row, second column, the block region BR in the second row, first column, the block region BR in the second row, second column, the block region BR in the third row, first column, and the block region BR in the third row, second column. The first control device 61 determines that the printing rate of each of the block region BR in the first row, first column, the block region BR in the first row, second column, the block region BR in the second row, first column, the block region BR in the second row, first column, and the block region BR in the third row, second column is equal to or greater than a predetermined value. Note that the predetermined value of the printing rate can be changed as appropriate.

[0052] Similarly, for the partial image data PD2 in FIG. 6A , the partial image PG2 exists across the block region BR at row 4, column 3, the block region BR at row 4, column 4, the block region BR at row 5, column 3, the block region BR at row 5, column 4, the block region BR at row 6, column 3, and the block region BR at row 6, column 4. On the other hand, for the partial image data PD2, a portion of the partial image PG1 exists in the block region BR at row 4, column 1 and the block region BR at row 4, column 2. In this example, the print rates of the block region BR at row 4, column 1, the block region BR at row 4, column 2, the block region BR at row 4, column 3, and the block region BR at row 4, column 4 are all less than a predetermined value. Therefore, the first control device 61 determines that the print rates of the block region BR at row 5, column 3, the block region BR at row 5, column 4, the block region BR at row 6, column 3, and the block region BR at row 6, column 4 are equal to or greater than the predetermined value.

[0053] Similarly, for partial image data PD3 in Figure 6A, part of partial image PG2 exists in block region BR at row 7, column 3 and block region BR at row 7, column 4. In this example, the printing rates of block region BR at row 7, column 3 and block region BR at row 7, column 4 are set to be less than a predetermined value. Therefore, the first control device 61 determines that for partial image data PD3 in Figure 6A, there is no block region BR whose printing rate is equal to or greater than the predetermined value.

[0054] If the printing rate is equal to or greater than a predetermined value, the first control device 61 generates second print data for the partial image data PD that includes a block region BR whose printing rate is equal to or greater than the predetermined value. In this case, the first control device 61 may generate second print data for each piece of partial image data PD. For example, for the partial image data PD1, the first control device 61 generates second print data for ejecting clear ink droplets onto a total of six block regions BR whose printing rate is equal to or greater than the predetermined value: the block region BR in the first row and first column, the block region BR in the first row and second column, the block region BR in the second row and first column, the block region BR in the second row and second column, the block region BR in the third row and first column, and the block region BR in the third row and second column. In other words, the first control device 61 generates second print data for each block region BR whose printing rate is equal to or greater than the predetermined value. In the example of FIG. 6B , second print data is generated for ejecting clear ink droplets onto a region CG1 that includes the six block regions BR, as the region CG formed by clear ink droplets. However, the above-mentioned area CG1 may be in the same position and have the same area as the partial image PG1 in the block area BR at row 1, column 1, the block area BR at row 1, column 2, the block area BR at row 2, column 1, the block area BR at row 2, column 2, the block area BR at row 3, column 1, and the block area BR at row 3, column 2.

[0055] Similarly, for partial image data PD2, the first control device 61 generates second print data for ejecting clear ink droplets onto a total of four block regions BR, each having a print rate equal to or greater than a predetermined value: the block region BR at row 5, column 3; the block region BR at row 5, column 4; the block region BR at row 6, column 3; and the block region BR at row 6, column 4. In the example of FIG. 6B , the second print data is generated for ejecting clear ink droplets onto region CG2, which includes the four block regions BR, as the region CG formed by clear ink droplets. However, region CG2 may be in the same position and have the same area as partial image PG2 in the block region BR at row 5, column 3; the block region BR at row 5, column 4; the block region BR at row 6, column 3; and the block region BR at row 6, column 4.

[0056] Fig. 7 is a diagram illustrating the printing passes into which clear ink droplets should be ejected during tackiness reduction processing, and Fig. 8 is a diagram illustrating that region Rc1 formed in the first printing pass during tackiness reduction processing does not overlap with region Rc2 formed in the second printing pass following the first printing pass.

[0057] In the second printing process, the second control device 50 causes the nozzles 221 to eject clear ink droplets in the printing pass in which the printing range of the second head 22 is largest. In this case, the second control device 50 identifies the printing pass in which the printing range is largest based on the position of the region CG in which the clear ink droplets are to be ejected, as described in FIG. 6B, and the transport amount in the transport direction Df of the print medium W. In the example of FIG. 7, in the first pass (first printing pass), the range in which clear ink droplets can be ejected in the region Rc1 in which color ink droplets have been ejected by the third head 23 is only a portion of the region Rc1 in the transport direction Df. Also, in the third pass (third printing pass), the range in which clear ink droplets can be ejected in the region Rc1 in which color ink droplets have been ejected by the third head 23 is larger than in the first pass, but in this case too, it is only a portion of the region Rc1 in the transport direction Df. In contrast, in the second pass (second printing pass), the range in which clear ink droplets can be ejected onto region Rc1 onto which color ink droplets have been ejected by the third head 23 includes the entire region Rc1. Therefore, by ejecting clear ink droplets from the nozzles 221 in the printing pass in which the printing range of the second head 22 is largest, it is possible to eject clear ink droplets onto the color ink droplets in region Rc1 in a single printing pass. In this case, the second control device 50 turns on the light source 80 only when ejecting clear ink droplets in the above printing pass. The second control device 50 turns off the light source 80 in printing passes other than the printing pass in which the clear ink droplets are ejected.

[0058] 8, the second control device 50 executes the second printing process so that a first region Rr1 onto which clear ink droplets are ejected by the nozzles 221 in the first printing pass and a second region Rr2 onto which clear ink droplets are ejected in a second printing pass subsequent to the first printing pass do not overlap. In the example of FIG. 8, the second head 22 ejects clear ink droplets onto the first region Rr1 corresponding to the region Rc1 onto which color ink droplets are ejected by the third head 23 in the first printing pass. Then, the transport amount of the print medium W is controlled so that a second region Rr2 corresponding to the region Rc2 onto which color ink droplets are ejected by the third head 23 in the second printing pass does not overlap with the first region Rr1. As a result, the second head 22 ejects clear ink droplets onto the second region Rr2 that no longer overlaps with the first region Rr1.

[0059] While the above description has been given of ejecting small droplets from the nozzles 221 of the second head 22, it is also possible to eject extremely small droplets from the nozzles 221 as follows: Fig. 9A is a diagram showing a drive waveform Wd1 for normal small droplets of clear ink, and Fig. 9B is a diagram showing a drive waveform Wd2 for extremely small droplets of clear ink.

[0060] In the second printing process, the second control device 50 switches from the drive waveform Wd1 of FIG. 9A, which ejects ejectable small droplets from the nozzles 221, to the drive waveform Wd2 of FIG. 9B, which divides the volume of the small droplet into multiple extremely small droplets and ejects them. In the drive waveform Wd1 of FIG. 9A, the pulse TP1 indicating the ejection timing is high, and the pulse Tw1 indicating the non-ejection timing is low. The width of the pulse Tw1 of FIG. 9B is narrower than the width of the pulse Tw1 of FIG. 9A. When the second control device 50 controls the ejection of the third head 23 and the second head 22 using the drive waveform Wd1, the relatively long width of the pulse Tw1 increases the speed of the tails of the ejected ink droplets, which promotes the coalescence of the ink droplets and extends the tails of the ink droplets. Therefore, the ink droplets ejected from the third head 23 and the second head 22 are small droplets. On the other hand, when the second control device 50 controls the ejection of the second head 22 using the drive waveform Wd2, the width of the pulse Tw1 is relatively short, which reduces the speed of the tail of the ejected ink droplet, making it difficult for the ink droplets to merge. As a result, the ink droplets ejected from the third head 23 and the second head 22 are extremely small.

[0061] In this embodiment, the second control device 50 transmits predetermined drive waveforms to the third head 23 and the second head 22. The second control device 50 also transmits data indicating ink droplet sizes represented by signals of "11" (large droplets), "10" (medium droplets), and "01" (small droplets) to the third head 23 and the second head 22 separately from the drive waveforms. The data received by the third head 23 and the second head 22 is collated by each multiplexer.

[0062] When the third head 23 and the second head 22 move at the first speed, the second control device 50 transmits to the third head 23 and the second head 22 a drive waveform Wd1 for ejecting small droplets (a drive waveform that is not divided into multiple tiny droplets). On the other hand, when the third head 23 and the second head 22 move at the second speed, the second control device 50 transmits to the third head 23 and the second head 22 a drive waveform Wd2 for splitting the volume of a small droplet into multiple tiny droplets and ejecting them, instead of the drive waveform Wd1. In this case, when the third head 23 and the second head 22 are moved at the first speed, ink droplets are ejected only from the third head 23, and no ink droplets are ejected from the second head 22, so tiny droplets are not ejected from the second head 22. On the other hand, when the third head 23 and the second head 22 are moved at the second speed, ink droplets are ejected only from the second head 22, and no ink droplets are ejected from the third head 23, so that minute droplets are not ejected from the third head 23. As a result, even with the same "01" signal, the small droplets ejected from the third head 23 are not split into minute droplets, and only the small droplets ejected from the second head 22 are split into minute droplets.

[0063] Alternatively, the following configuration may be adopted. In the second printing process, the second control device 50 uses a drive waveform Wd2 for dividing the volume of a small droplet into multiple extremely small droplets and ejecting them, instead of the drive waveform Wd1 for ejecting a small droplet that can be ejected from the second head 22. In this case, the second control device 50 transmits the drive waveform Wd1 to the third head 23 and the drive waveform Wd2 to the second head 22. The second control device 50 also transmits data indicated by signals for ink droplet sizes of "11" (large droplet), "10" (medium droplet), and "01" (small droplet) to the third head 23 and the second head 22 separately from the drive waveforms. The data received by the third head 23 and the second head 22 is collated by each multiplexer.

[0064] The second control device 50 transmits to the third head 23 a drive waveform Wd1 for ejecting small droplets (a drive waveform that is not divided into multiple tiny droplets). On the other hand, the second head 22 receives a drive waveform Wd2 for splitting the volume of a small droplet into multiple tiny droplets and ejecting them, instead of the drive waveform Wd1 for ejecting small droplets. Even in this embodiment, as a result, even with the same "01" signal, the small droplets ejected from the third head 23 are not divided into tiny droplets, and only the small droplets ejected from the second head 22 are divided into tiny droplets.

[0065] Alternatively, the following aspect may be adopted. The second control device 50 supplies a drive voltage higher than the drive voltage of the third head 23 to the second head 22 via the second head drive circuit 54. The second control device 50 then uses a drive waveform in the second head 22 that indicates a drive voltage higher than the drive voltage of the drive waveform for ejecting small droplets as color ink droplets in the third head 23, causing the nozzles 221 to divide the volume of small droplets into multiple microdroplets and eject them as clear ink droplets. In this way, in this aspect, the drive waveform used in the third head 23 and the drive waveform used in the second head 22 have similar shapes (but are not completely identical). That is, the drive waveform used in the third head 23 and the drive waveform used in the second head 22 have the same pulse widths and timings for the high pulses and low pulses, while the voltage of the high pulse (ejection voltage) in the drive waveform used in the second head 22 is higher than that of the drive waveform used in the third head 23.

[0066] Next, a series of processing flows in the printing device 100 of this embodiment will be described using flowcharts. Fig. 10 is a flowchart showing the processing flow in the image processing device 102. Fig. 11 is a flowchart showing the processing flow in the output device 101.

[0067] 10, first, the first control device 61 of the image processing device 102 acquires image data (step S1). Next, the first control device 61 executes a process of acquiring a plurality of partial image data PD that partially configure the image data (step S2).

[0068] Next, the first control device 61 divides the area corresponding to each partial image data PD into a plurality of block areas BR (step S3). Then, the first control device 61 acquires the printing rate of each divided block area BR (step S4). After that, the first control device 61 determines whether the printing rate of each block area BR is equal to or greater than a predetermined value (e.g., 50%) for each block area BR (step S5). If the printing rate of each block area BR is equal to or greater than the predetermined value (Yes in step S5), the first control device 61 generates second print data (tackiness-reduced data) for the partial image data PD including the block area BR whose printing rate is equal to or greater than the predetermined value (step S6).

[0069] If the printing rate in the block region BR is not equal to or greater than the predetermined value (No in step S5), and after the processing of step S6, the first control device 61 determines whether or not second print data (tackiness-reduced data) has been generated for all of the partial image data PD (step S7). If second print data has been generated for all of the partial image data PD (Yes in step S7), the first control device 61 transmits the partial image data PD and the second print data, or only the partial image data PD, to the second control device 50 of the output device 101 (step S8). On the other hand, if second print data has not been generated for all of the partial image data PD (No in step S7), the first control device 61 returns to the processing of step S2 and repeats the subsequent processing.

[0070] 11, the second control device 50 of the output device 101 determines whether or not a print job has been received from the first control device 61 of the image processing device 102 (step S11). If data related to the print job has been received (Yes in step S11), the second control device 50 executes printing processing based on the received data (step S12). On the other hand, if data related to the print job has not been received (No in step S11), the second control device 50 waits until a print job is sent from the first control device 61.

[0071] As described above, according to the printing device 100, in the second printing process, droplets of clear ink are ejected from the nozzles 221 onto the droplets of color ink that have landed on the print medium W in a smaller amount than the droplets of color ink. The total area of ​​the clear ink droplets that have landed on the droplets of color ink is smaller than the total area of ​​the image formed by the droplets of color ink that have landed on the print medium W. This makes it easier to harden the ejected clear ink droplets with ultraviolet light before they wet and spread. This can reduce the contact area with the print surface of the print medium W when touched by a person. This can prevent the print surface of the print medium W from becoming sticky.

[0072] Furthermore, in this embodiment, the first control device 61 generates first print data based on image data for ejecting color ink droplets from the nozzles 321 onto the print medium W. The first control device 61 also generates second print data based on the image data for ejecting clear ink droplets from the nozzles 221 onto the color ink droplets that have landed on the print medium W. Because the first print data and the second print data are based on the same image data, it is easy to determine positions other than those at which color ink droplets should be ejected and at which clear ink droplets do not need to be ejected. This prevents clear ink droplets from being ejected more than necessary, thereby conserving the clear ink.

[0073] Furthermore, in this embodiment, when ejecting clear ink droplets from the nozzles 221 of the second head 22 in the second printing process, the second control device 50 moves the carriage 41 in the movement direction Ds at a second speed that is faster than the first speed. This allows the clear ink droplets to be cured by ultraviolet light before they wet and spread over the color ink droplets.

[0074] Furthermore, in this embodiment, the second control device 50 uses small droplets of the large, medium, and small droplets that can be ejected from the nozzles 221 as clear ink droplets in the second printing process. In this case, small clear ink droplets are ejected onto large color ink droplets that have landed on the print medium W. This makes it easier to eject smaller amounts of clear ink droplets than color ink droplets. It also makes it easier to harden the clear ink droplets with ultraviolet light before they wet and spread on the color ink droplets. This makes it easier to reduce the contact area with the print surface of the print medium W when touched by a person.

[0075] 9A for ejecting ejectable small droplets from the nozzles 221, to the drive waveform Wd2 of FIG. 9B for dividing the volume of the small droplets into multiple tiny droplets and ejecting them. This causes tiny clear ink droplets to be ejected onto the color ink droplets, making it possible to make the volume of the clear ink droplets smaller than the volume of the color ink droplets.

[0076] Furthermore, in this embodiment, in the second printing process, the second control device 50 may use a drive waveform Wd2 for dividing the volume of a small droplet into multiple extremely small droplets and ejecting them, instead of the drive waveform Wd1 for ejecting ejectable small droplets from the second head 22. In this case, the drive waveform Wd1 is sent to the third head 23, and the drive waveform Wd2 is sent to the second head 22. Even in this case, extremely small clear ink droplets are ejected on top of the color ink droplets, and the volume of the clear ink droplets can be made smaller than the volume of the color ink droplets.

[0077] Furthermore, in this embodiment, the second control device 50 uses a drive waveform in the second head 22 that indicates a drive voltage higher than the drive voltage of the drive waveform for ejecting small droplets as color ink droplets in the third head 23, and causes the nozzles 221 to split the volume of small droplets into multiple tiny droplets and eject them as clear ink droplets. This also makes it possible to eject tiny clear ink droplets on top of the color ink droplets.

[0078] Furthermore, in this embodiment, in the second printing process, the second control device 50 causes the nozzles 221 to eject ink droplets of clear ink in the printing pass that maximizes the printing range of the second head 22. This makes it possible to eject ink droplets of clear ink onto the area where the ink droplets of clear ink should be ejected in one pass, thereby improving the efficiency of the process.

[0079] Furthermore, in this embodiment, the second control device 50 executes the second printing process so that the first region Rr1 onto which the clear ink droplets are ejected by the nozzles 221 in the first printing pass and the second region Rr2 onto which the clear ink droplets are ejected in the second printing pass that follows the first printing pass do not overlap. In this case, it is possible to avoid unnecessary consumption of the clear ink that would result from the clear ink droplets being ejected overlappingly into the first region Rr1 and the second region Rr2.

[0080] In this embodiment, the first printing process, the second printing process, and the curing process are performed for each partial image data PD. In this case, because each process is performed for each partial image data PD, the time from the first printing process and the second printing process to the start of the curing process can be shortened compared to when each process is performed for the entire image data. This makes it easier to quickly cure the clear ink droplets with ultraviolet light before they wet and spread over the color ink droplets.

[0081] In this embodiment, the first control device 61 determines for each block area BR whether the printing rate in that block area BR is equal to or greater than a predetermined value, and if the printing rate is equal to or greater than the predetermined value, generates second print data for the partial image data PD that includes the block area BR whose printing rate is equal to or greater than the predetermined value. In this case, generation of second print data for areas of the printing surface of the print medium W that do not become sticky is avoided.

[0082] Furthermore, in this embodiment, the first control device 61 generates second print data for each block area BR whose print rate is equal to or greater than a predetermined value. In this case, the processing load on the first control device 61 can be reduced.

[0083] The present disclosure is not limited to the above-described embodiment, and modifications can be made without departing from the spirit of the present disclosure. For example, the following modifications are possible.

[0084] In the above embodiment, the light sources 80 may be provided on both sides in the movement direction Ds of each head 20. In this case, the first printing process, the second printing process, and the curing process can be performed on the outward and return paths in the movement direction Ds.

[0085] In the above embodiment, the second head 22 and the third head 23 may be supported by separate carriages.

[0086] Furthermore, in the above embodiment, each head 20 is a serial head type, but this is not limiting, and each head 20 may be a line head type.

[0087] Furthermore, in the above embodiment, the image processing device 102 and the output device 101 are configured separately and independently, and the concept encompassing these is the printing device (or printing system) 100, but this is not limited to this. A processing unit capable of executing the same processing as that by the image processing device 102 and a processing unit capable of executing the same processing as that by the output device 101 may be provided in a single printing device. [Explanation of symbols]

[0088] 21 First Head 22 Second Head 23 Third Head 41 Carriage 50 Second control device 61 First control device 70 Control device 80 light source 100 Printing device 101 Output Device 102 Image processing device 221,321 nozzles BR Block Area Df Conveying direction Ds moving direction PD Partial image data Rr1 1st area Rr2 2nd area W Printing medium Wd1, Wd2 drive waveform

Claims

1. a first nozzle for ejecting ultraviolet curable first droplets onto a print medium based on image data to form an image; a second nozzle for ejecting second droplets of an ultraviolet curable type different from the first droplets, the second droplets being smaller in amount than the first droplets; a light source that irradiates ultraviolet light to harden the first droplets and the second droplets; a control device; The control device a first printing process for ejecting the first droplets from the first nozzles based on the image data; a second printing process in which, after the first printing process, second droplets smaller in size than the first droplets are ejected from the second nozzles onto the first droplets that have landed on the printing medium; a curing process in which the light source irradiates the ultraviolet light onto the first droplets and the second droplets on the printing medium; A printing device, wherein a total area of ​​the second droplets that land on the first droplets is smaller than a total area of ​​an image formed by the first droplets that land on the print medium.

2. The control device a process of generating first print data for ejecting the first droplets from the first nozzles onto the print medium based on the image data; 2. The printing device according to claim 1, further comprising: a process for generating second print data for ejecting the second droplets from the second nozzles onto the first droplets that have landed on the printing medium based on the image data.

3. a first head having the first nozzle; a second head having the second nozzle; a carriage that moves in a predetermined movement direction while supporting the first head and the second head, 2. The printing device according to claim 1, wherein the control device moves the carriage in the movement direction at a first speed when ejecting the first droplet from the first nozzle in the first printing process, and moves the carriage in the movement direction at a second speed faster than the first speed when ejecting the second droplet from the second nozzle in the second printing process.

4. The printing device according to claim 1 , wherein the control device uses, as the second droplets, the small droplets of the large droplets and the small droplets that can be ejected from the second nozzles in the second printing process.

5. 2. The printing device according to claim 1, wherein, in the second printing process, the control device switches from a drive waveform for ejecting a small droplet that can be ejected from the second nozzle to a drive waveform for dividing the volume of the small droplet into multiple extremely small droplets and ejecting them.

6. a first head having the first nozzle; a second head having the second nozzle, The control device causing the first head to execute the first printing process; causing the second head to execute the second printing process; 2. The printing device according to claim 1, wherein in the second printing process, instead of a drive waveform for ejecting a small droplet that can be ejected from the second nozzle, a drive waveform for dividing the volume of the small droplet into a plurality of extremely small droplets and ejecting them is used.

7. a first head having the first nozzle; a second head having the second nozzle, a drive voltage higher than a drive voltage of the first head is supplied to the second head; 2. The printing device according to claim 1, wherein the control device uses a drive waveform in the second head that indicates a drive voltage higher than a drive voltage of a drive waveform for ejecting a small droplet as the first droplet in the first head, and causes the second nozzle to divide the volume of the small droplet into a plurality of the tiny droplets and eject them as the second droplet.

8. the second head is provided downstream of the first head in a transport direction of the print medium, The printing device according to claim 3 , wherein the control device causes the second nozzles to eject the second droplets in a pass in which the printing range of the second head is maximized in the second printing process.

9. 9. The printing device according to claim 8, wherein the control device executes the second printing process so that a first area onto which the second droplets are ejected by the second nozzles in a first pass and a second area onto which the second droplets are ejected by a second pass subsequent to the first pass do not overlap.

10. the control device executes a process of acquiring partial image data that partially constitutes the image data; The printing device according to claim 2 , wherein the first printing process, the second printing process, and the curing process are performed for each of the partial image data.

11. The control device Dividing an area corresponding to the partial image data into a plurality of block areas; determining whether the printing rate in each block area is equal to or greater than a predetermined value; The printing device according to claim 10 , wherein, when the printing rate is equal to or greater than a predetermined value, the second print data is generated for the partial image data including the block area whose printing rate is equal to or greater than the predetermined value.

12. The printing device according to claim 11 , wherein the control device generates the second print data for each of the block areas in which the printing rate is equal to or greater than a predetermined value.

13. A printing method using a printing device including: a first nozzle for ejecting ultraviolet-curable first droplets onto a printing medium based on image data to form an image; a second nozzle for ejecting ultraviolet-curable second droplets different from the first droplets, the second droplets being smaller in size than the first droplets; and a light source for irradiating ultraviolet light to cure the first droplets and the second droplets, Discharging the first droplet from the first nozzle based on the image data; After the first droplet is ejected, the second droplet is ejected from the second nozzle onto the first droplet that has landed on the print medium, the second droplet being smaller in size than the first droplet; causing the light source to irradiate the ultraviolet light onto the first droplets and the second droplets on the printing medium; A printing method, wherein a total area of ​​the second droplets that land on the first droplets is smaller than a total area of ​​an image formed by the first droplets that land on the print medium.

14. A printing program to be executed by a computer in a printing device including: a first nozzle for ejecting ultraviolet-curable first droplets onto a printing medium based on image data to form an image; a second nozzle for ejecting ultraviolet-curable second droplets different from the first droplets, the second droplets being smaller in size than the first droplets; and a light source for irradiating ultraviolet light to cure the first droplets and the second droplets, The computer a first ejection execution means for causing the first nozzle to eject the first droplet based on the image data; a second ejection execution means for ejecting, from the second nozzle, a second droplet of liquid smaller in size than the first droplet onto the first droplet that has landed on the print medium after the first droplet has been ejected; and the light source functions as an irradiation execution unit that irradiates the first droplets and the second droplets on the printing medium with the ultraviolet light; A printing program, wherein a total area of ​​the second droplets that land on the first droplets is smaller than a total area of ​​an image formed by the first droplets that land on the print medium.

Images