Printing device

Abstract

To provide a printing device that can suppress deterioration in an image quality in a part where colors are printed overlappingly.SOLUTION: A printing device comprises: heads 20 that discharge first liquid and second liquid to a printing medium; energy applying parts 30 that apply energy for curing the first liquid and the second liquid on the printing medium; and a control device 60. The control device has: a first mode in which the first liquid is discharged, then the energy is applied to form a foundation of the first liquid on the printing medium, and the second liquid is discharged, and then the energy is applied to print an image on the foundation; and a second mode in which the second liquid is discharged and then the energy is applied to print an image on the printing medium, without forming the foundation. Discharge quantities of the second liquid at the time of printing the image in the first mode are set to be more than discharge quantities of the second liquid at the time of printing the same image as the above-described image in the second mode.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a printing device. [Background technology]

[0002] Conventionally, an image recording device disclosed in Patent Document 1 is known as an example of a printing device. This image recording device includes a recording head that ejects ink, and a light irradiation device that irradiates light onto the ink that has landed on the recording medium. This image recording device ejects primary color inks and white ink from the recording head onto the recording medium, and records an image on the recording medium by irradiating light onto the ink on the recording medium. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2015-153314 A Summary of the Invention [Problem to be solved by the invention]

[0004] In the image recording device of Patent Document 1, for example, in order to make an image formed by various basic color inks on a transparent recording medium easier to see and to highlight, white ink is discharged onto all pixels of the image recording area of ​​the recording medium or onto pixels not recorded by the basic color inks. In this case, in order to make the amount of ink uniform in the portion of the recording medium on which the image is recorded, the amount of basic ink discharged is smaller in areas where the white ink is discharged in large amounts than in areas where the white ink is not discharged. This can cause color unevenness or banding due to the basic color inks, which can degrade image quality. In view of the above, an object of the present invention is to provide a printing device that can suppress deterioration in image quality in areas where colors are printed in overlapping fashion. [Means for solving the problem]

[0005] A printing device according to one aspect of the present invention includes a head that ejects a first liquid and a second liquid onto a printing medium, an energy application unit that applies energy to harden the first liquid and the second liquid on the printing medium, and a control device, wherein the control device has a first mode in which the first liquid is ejected and then the energy is applied to form a base for the first liquid on the printing medium, and the second liquid is ejected and then the energy is applied to print an image on the base, and a second mode in which the second liquid is ejected and then the energy is applied to print an image on the printing medium without forming the base, and the amount of the second liquid ejected when printing an image in the first mode is greater than the amount of the second liquid ejected when printing the same image in the second mode. Effect of the Invention

[0006] The present invention has an effect of providing a printing device capable of suppressing degradation of image quality in a portion where colors are printed in overlapping fashion.

[0007] The above and other objects, features, and advantages of the present invention will become apparent from the following detailed description of preferred embodiments, taken in conjunction with the accompanying drawings. [Brief description of the drawings]

[0008] [Figure 1] 1 is a perspective view of a printing device equipped with a light irradiation unit with a lid of a housing open; [Diagram 2] 2 is a functional block diagram showing a configuration of the printing device in FIG. 1. [Diagram 3] FIG. 2 is a side view of the head unit in FIG. [Figure 4] 4 is a view of the head unit in FIG. 3 as viewed from below. [Diagram 5] Fig. 5(a) is a diagram showing dots printed in the second mode, Fig. 5(b) is a diagram showing a printing medium A on which an image C is printed in the second mode, and Fig. 5(c) is a cross-sectional view taken along line Vc-Vc in Fig. 5(b). [Figure 6]Fig. 6(a) is a diagram showing dots printed in the first mode, Fig. 6(b) is a diagram showing a printing medium A on which an image C is printed in the first mode, and Fig. 6(c) is a cross-sectional view taken along line VIc-VIc in Fig. 6(b). [Figure 7] 4 is a flowchart showing an example of a control method of the printing device of FIG. [Figure 8] FIG. 8(a) is an image C8a printed by the printing device in the second mode, and FIG. 8(b) is an image C8b printed in the first mode. [Figure 9] FIG. 9(a) is an image C9a printed by the printing device in the second mode, and FIG. 9(b) is an image C9b printed in the first mode. [Figure 10] Image C10 is printed in the first mode by the printing device. [Figure 11] FIG. 11(a) is an image C11a printed by the printing device in the second mode, and FIG. 11(b) is an image C11b printed in the first mode. [Figure 12] FIG. 12(a) is an image C12a printed by the printing device in the second mode, and FIG. 12(b) is an image C12b printed in the first mode. [Figure 13] FIG. 13(a) is an image C13a printed by the printing device in the first mode, and FIG. 13(b) is another image C13b printed in the first mode. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that the same or corresponding elements are denoted by the same reference numerals throughout the drawings.

[0010] (Embodiment 1) <Printing device configuration> 1, the printing device 10 according to the first embodiment is an inkjet printer that ejects liquid from a head 20 onto a printing medium A and applies energy from an energy application unit 30 to the liquid on the printing medium A to perform printing. The printing medium A has a sheet-like shape such as fabric or paper, or a three-dimensional shape such as a ball or a mug, and is made of a material that is impermeable to liquid such as resin or that is more difficult to permeate than paper.

[0011] The printing device 10 includes a head unit 11, a scanning device 40, a conveying device 50, a plurality of tanks 12, and a control device 60 (FIG. 2). The head unit 11 includes a head 20 that ejects the first liquid and the second liquid onto the printing medium A, and an energy applying section 30 that applies energy for curing the first liquid and the second liquid on the printing medium A. The head unit 11 and the control device 60 will be described in detail later.

[0012] Further, the transport direction in which the print medium A is transported by the transport device 50 is referred to as the front-rear direction. The scanning direction in which the head unit 11 is moved by the scanning device 40, which is a direction intersecting (for example, perpendicular to) the transport direction, is referred to as the left-right direction. A direction intersecting (for example, perpendicular to) the front-rear direction and the left-right direction is referred to as the up-down direction. However, the arrangement of the printing device 10 is not limited to this.

[0013] The scanning device 40 has a pair of scanning rails 41, a carriage 42, a drive belt 43, and a scanning motor 44, and moves the head unit 11 in the left-right direction. The scanning rails 41 are long members extending in the left-right direction, and are arranged parallel to each other so as to sandwich the head unit 11 between them in the front-rear direction. The carriage 42 carries the head unit 11 and is supported so as to be movable in the left-right direction along the scanning rails 41. The drive belt 43 is stretched across the scanning rails 41 in the left-right direction, and is connected to the scanning motor 44. The scanning motor 44 drives the drive belt 43 to move the carriage 42 back and forth in the left-right direction along the scanning rails 41.

[0014] The transport device 50 has a stage 51, a pair of transport rails 52, a stage support base 53, and a transport motor 54 (FIG. 2), and moves the print medium A in the front-rear direction. The stage 51 is a rectangular flat plate on whose upper surface the print medium A is placed, and defines the distance between the print medium A and the head 20 in the vertical direction. The pair of transport rails 52 extend in the front-rear direction, and support the stage support base 53 so that it can move in the front-rear direction. The stage support base 53, for example, removably supports the stage 51, and is connected to the transport motor 54. The transport motor 54 drives the stage support base 53 to move the stage 51 in the front-rear direction.

[0015] The tank 12 is a container that contains liquid, and is connected to the head 20 to supply the liquid. The liquid is an energy curable liquid that is cured by applied energy. The multiple tanks 12 include five types of tanks 12 for each of the achromatic inks, i.e., white (W) ink and black (K) ink, and chromatic inks, i.e., yellow (Y) ink, magenta (M) ink, and cyan (C) ink.

[0016] <Head unit configuration> 3 and 4, the head unit 11 is disposed on the stage 51 with a gap therebetween so that the lower surface of the head 20 and the lower surface of the energy application unit 30 face the upper surface of the stage 51. The head 20 has a plurality of nozzles 21, a plurality of individual flow paths 22, a plurality of common flow paths 23, a flow path forming body 24, and a plurality of driving elements 25 (FIG. 2), and ejects liquid onto the print medium A. The flow path forming body 24 is, for example, in the shape of a rectangular parallelepiped, and the nozzles 21, the individual flow paths 22, and the common flow path 23 are formed therein. The nozzles 21 open at the lower surface of the flow path forming body 24.

[0017] A plurality of common flow paths 23 are provided in each of, for example, five types of tanks 12 (FIG. 1). The common flow paths 23 are connected to the tanks 12, and liquid is supplied from the tanks 12. The common flow paths 23 extend in the front-rear direction, and a plurality of individual flow paths 22 branch off from the common flow path 23. The upstream ends of the individual flow paths 22 are connected to the common flow path 23, and the downstream ends are connected to the nozzles 21.

[0018] The nozzles 21 are arranged at equal intervals in the front-rear direction to form a nozzle row. The liquid flows from the tank 12 into the common flow path 23, and while flowing through the common flow path 23, it is diverted into the individual flow paths 22 and supplied to the nozzles 21.

[0019] The driving element 25 is a piezoelectric element or the like, which is provided corresponding to the individual flow path 22 and is driven to vary the volume of the individual flow path 22 in response to a driving signal from the control device 60. By driving this driving element 25, pressure is applied to the liquid in the individual flow path 22 corresponding to the driving element 25, and the liquid is ejected from the nozzle 21 connected to the individual flow path 22.

[0020] The energy application unit 30 moves together with the head 20, and is disposed upstream of the head 20 as it moves while ejecting liquid in the direction of movement. For example, in unidirectional printing, the head 20 ejects liquid when it moves to the left, and does not eject liquid when it moves to the right. In this case, the energy application unit 30 is disposed on the right side, which is upstream of the head 20 in the direction of movement to the left during printing. The energy application unit 30 applies energy to the liquid on the printing medium A while moving following the head 20 that ejects liquid onto the printing medium A.

[0021] The energy application unit 30 has a plurality of energy sources 31 and a substrate 32 on which the energy sources 31 are mounted, and applies energy for curing the liquid on the print medium A. The substrate 32 is in the shape of a flat plate, and has the energy sources 31 and an electric circuit to which the control device 60 (FIG. 2) is connected provided on its lower surface. The energy source 31 is, for example, a light source such as an LED, and irradiates light such as ultraviolet light and infrared light.

[0022] <Control device configuration> 2, the control device 60 includes an interface 61, a calculation unit 62, a storage unit 63, and a waveform generation unit 64. The control device 60 may be a single control device performing centralized control, or may be a plurality of control devices performing distributed control.

[0023] The interface 61 is connected to an external device B such as a computer or a network, and the control device 60 receives various data such as print data from the external device B via the interface 61. The print data includes image data such as raster data that indicates an image to be printed on the print medium A. The print data may be stored in advance in the storage unit 63.

[0024] The storage unit 63 is a memory accessible to the calculation unit 62, and is composed of a RAM, a ROM, etc. The RAM temporarily stores various data. Examples of the various data include print data and print data converted by the calculation unit 62. The ROM stores programs for performing various data processing. The programs may be obtained from the external device B, or may be stored in another storage medium.

[0025] The calculation unit 62 is composed of, for example, a processor such as a CPU, and an integrated circuit such as an ASIC. The calculation unit 62 executes a program stored in the ROM to control the driving element 25, the energy source 31, the scanning motor 44, and the transport motor 54, thereby executing the printing process. The details of the printing process will be described later.

[0026] The waveform generating unit 64 generates a waveform signal that defines the waveform of the drive signal output to the drive element 25. The waveform generating unit 64 may be a dedicated circuit, or may be configured with a calculation unit 62 and a storage unit 63. The waveform signal is, for example, a pulse signal, which is a signal for driving the drive element 25 to eject liquid from the head 20, and includes multiple types of waveform signals that eject different amounts of liquid.

[0027] The calculation unit 62 generates waveform selection data by, for example, selecting one type of waveform signal from multiple types of waveform signals for each nozzle 21 and for each drive cycle of the drive element 25 corresponding to the nozzle 21 in accordance with the amount of liquid ejected for each droplet based on the print data. Here, the calculation unit 62 generates the waveform selection data such that the higher the density of the image to be printed, the greater the ejection waveform signal that ejects a larger amount of liquid based on the print data.

[0028] The control device 60 is connected to the driving element 25 via a head driving circuit 65. The control device 60 outputs a waveform signal and waveform selection data to the head driving circuit 65 as control data. The head driving circuit 65 generates a driving signal corresponding to the waveform signal selected by the waveform selection data and outputs it to the driving element 25. The driving element 25 drives in response to the driving signal of the ejection waveform signal. As a result, the volume of the individual flow paths 22 is changed, and pressure is applied to the liquid in the individual flow paths 22, causing the liquid to be ejected from the nozzle 21.

[0029] The control device 60 is also connected to the energy source 31 via an energy source drive circuit 66, and outputs control data for the energy source 31 based on the print data to the energy source drive circuit 66. In this way, the control device 60 controls the switching of the energy source 31 between on and off.

[0030] Furthermore, the control device 60 is connected to the scanning motor 44 via a scan drive circuit 67, and outputs control data for the scanning motor 44 to the scan drive circuit 67 based on the print data. The control device 60 is also connected to the carry motor 54 via a transport drive circuit 68, and outputs control data for the carry motor 54 to the transport drive circuit 68 based on the print data. In this way, the control device 60 controls the drive timing, rotation speed, rotation amount, etc. of the scanning motor 44 and the carry motor 54.

[0031] <Printing process> In the printing process, the control device 60 controls the driving element 25 to execute a discharge operation for discharging liquid from the head 20. The control device 60 also controls the energy source 31 to execute an application operation for applying energy from the energy application unit 30. Furthermore, the control device 60 controls the scanning motor 44 to execute a movement operation for moving the head unit 11 in the left-right direction. The control device 60 controls the transport motor 54 to execute a transport operation for transporting the printing medium A forward.

[0032] In this pass including the ejection action, the application action, and the movement action, the head 20 ejects liquid from the nozzles 21 while moving to the left. As a result, the liquid lands on the printing medium A facing the underside of the head 20, and the liquid forms dots on the printing medium A, with multiple dots lined up in the left-right direction. Then, the energy application unit 30 applies energy from the energy source 31 while moving to the left following the head 20. As a result, energy is applied to the printing medium A facing the energy source 31, and the liquid on the printing medium A is cured by the energy and fixed to the printing medium A.

[0033] Then, by performing a transport operation after the pass, the print medium A moves forward relative to the head 20. Furthermore, by performing a pass after the transport operation, multiple dots are lined up in the front-to-back direction. In this way, as the control device 60 alternately repeats passes and transport operations and proceeds with printing, an image is printed on the print medium A by multiple dots being lined up in both the left-right direction and the front-to-back direction.

[0034] <Print mode> The printing process has a first mode and a second mode depending on whether or not a base is formed. In the first mode, the control device 60 ejects the first liquid and then applies energy to form a base of the first liquid on the printing medium A, and ejects the second liquid and then applies energy to print an image on the base. In the second mode, the control device 60 ejects the second liquid and then applies energy to print an image on the printing medium A without forming a base. The control device 60 makes the ejection amount of the second liquid when printing an image in the first mode greater than the ejection amount of the second liquid when printing the same image as the image in the second mode.

[0035] Specifically, the liquid includes a first liquid and a second liquid. The first liquid is a liquid used to form a base, and the second liquid is a liquid used to form an image on the base. For this reason, the first liquid is determined by the user or determined in advance according to the color of the image, and is, for example, a color different from the color used in the image, a color different from the color most frequently used in the image, or a color different from the color used in the outline of the image, for example, white ink. The second liquid is determined based on image data and is a color used to form the image, and is, for example, black ink and chromatic ink, and may or may not include white ink.

[0036] The mode switching between the first mode and the second mode may be performed by a user operation. In this case, for example, the printing device 10 is provided with an input device, and the user operates the input device to input mode data. As a result, the control device 60 determines the first mode or the second mode based on the mode data, and executes the printing process according to the determined mode. Note that the mode switching may be performed based on the print data. In this case, the print data includes, in addition to the image data, mode data indicating the first mode or the second mode.

[0037] <Second mode> In the second mode, the control device 60 divides the image to be printed based on the image data into a matrix of pixels, which are multiple regions, and acquires pixel data for each pixel. The pixel data indicates the density of each pixel color, and has, for example, an RGB value. The RGB value represents 256 gradations for each color of R (red), G (green), and B (blue), and the gradation represents the degree of darkness or lightness.

[0038] The control device 60 performs color conversion processing to convert the colors represented in the image into the colors of the liquids provided in the printing device 10, and converts the colors of the pixel data into the colors of the drawing data based on a predetermined correspondence. This predetermined correspondence is a conversion table showing the correspondence between the colors of the pixel data and the colors of the drawing data, which is determined in advance and stored in the storage unit 63. For example, the colors of the pixel data are the three colors of RGB, and the colors of the drawing data are the five colors of the liquids provided in the printing device 10, CMYKW.

[0039] The control device 60 performs halftone processing to convert the gradation represented by the image into a gradation that can be formed by the printing device 10, and converts the gradation of the pixel data into the gradation of the drawing data based on a predetermined correspondence relationship. This predetermined correspondence relationship is a conversion table that indicates the correspondence relationship between the gradation of the pixel data and the gradation of the drawing data, and is determined in advance and stored in the storage unit 63.

[0040] The gradation of the drawing data is set, for example, according to the presence or absence of dots formed by the liquid ejected from the nozzles 21. In this case, the gradation is data indicating two gradations, namely, no dots, where no liquid is ejected, and dots, where a predetermined amount of liquid is ejected. This halftone process converts the pixel data indicating 256 gradations into drawing data indicating two gradations, with dots and without dots. This generates the drawing data for the image.

[0041] The control device 60 performs rasterization processing, arranges the drawing data for the image arranged in a matrix according to the ejection order of liquid from the nozzles 21 in the ejection operation (the order of dot formation), and allocates it to each nozzle 21 and each drive cycle of the drive element 25 corresponding to the nozzle 21. The control device 60 generates a waveform signal and waveform selection data for each nozzle 21 and each drive cycle based on the drawing data for the image, and outputs them to the head drive circuit 65 as control data to drive the drive element 25. The colors of the drawing data for the image correspond in advance to the nozzles 21, and the gradations of the drawing data correspond in advance to the waveform selection data.

[0042] As a result, in the second mode, the second liquid of a color corresponding to the color of the image is ejected from the head 20 as shown in FIG. 5(a). For example, dots of the second liquid, such as dots Dk of black ink, dots Dy of yellow ink, dots Dm of magenta ink, and dots Dc of cyan ink, are formed on the printing medium A. Then, light energy is applied from the energy application unit 30 to the second liquid on the printing medium A, and the dots are fixed on the printing medium A. By repeating this, an image C made up of a plurality of dots is printed directly on the printing medium A as shown in FIG. 5(b) and FIG. 5(c).

[0043] <First mode> In the first mode, the control device 60 acquires the area of ​​the background. This area of ​​the background may be a predetermined area, or may be set according to the size of the print medium A or the size of the image. For example, the area of ​​the background may be set so that the outer edge of the print medium A and the outer edge of the background coincide with each other so as to cover the entire print medium A. Alternatively, the area of ​​the background may be set so that the outer edge of the background is located a predetermined distance inside the outer edge of the print medium A so as to cover a part of the print medium A. Alternatively, the area of ​​the background may be set so that the image is placed on the background, with an area where the gradation of the pixel data is equal to or higher being the image area, and the outer edge of the background is located a predetermined distance outside the outer edge of the image area.

[0044] The control device 60 generates drawing data in which the base color is the color of the first liquid, the base area of ​​the printable area has dots, and the area other than the base area has no dots. The control device 60 performs a rasterization process on this base drawing data, divides the base control data for each pass, and outputs the result to the head drive circuit 65.

[0045] Similarly to the second mode, the control device 60 acquires a plurality of pixel data based on the image data of the print data, performs color conversion processing and halftone processing, and generates drawing data for the image from the pixel data. The control device 60 then performs a correction processing on the drawing data so that the ejection amount of the second liquid when printing an image in the first mode is greater than the ejection amount of the second liquid when printing the same image as the image in the second mode. For example, in the correction processing, the control device 60 increases the ejection amount of the chromatic ink when printing an image in the first mode compared to the ejection amount of the chromatic ink when printing the same image as the image in the second mode.

[0046] Specifically, since black is produced by evenly mixing chromatic colors, in the correction process, the control device 60 performs correction to replace some or all of the black dots with three chromatic color dots based on a predetermined correspondence. This predetermined correspondence is a conversion table showing the correspondence between the gradation of black and the gradation of chromatic colors, which is determined in advance and stored in the storage unit 63. Here, the arrangement of the three chromatic color dots of C, Y, and M that replace one black dot is corrected so that they are dispersed or overlapped to appear black.

[0047] As a result, the black dot Dk formed with the black ink shown in Fig. 5(a) is replaced with the chromatic color dots Dc, Dy, and Dm formed with the three chromatic color inks of C, Y, and M shown in Fig. 6(a). The total amount of the three chromatic color inks of the chromatic color dots Dc, Dy, and Dm replaced from one black dot Dk is greater than the amount of black ink for this one black dot Dk. Therefore, the ejection amount of the second liquid for forming an image in the first mode is greater than the ejection amount of the second liquid for forming an image in the second mode.

[0048] Then, the control device 60 performs a rasterization process on the corrected drawing data for the image, generates control data for the image, divides it for each pass, and outputs it to the head driving circuit 65. In such a first mode, the passes of the printing process include a base pass and an image pass. Therefore, in the printing process, after the base pass is performed according to the base control data, a transport operation is not performed, but the image pass is performed according to the image control data and then the transport operation is performed.

[0049] 6(b) and 6(c), when the head 20 moves to the left in the base pass and ejects the first liquid based on the base control data, dots of the first liquid are formed on the printing medium A. When the energy application unit 30 moves to the left following the head 20 and applies energy to the first liquid on the printing medium A, the dots of the first liquid are fixed on the printing medium A. As a result, a base E consisting of a plurality of dots is printed directly on the printing medium A.

[0050] When the base pass is completed, the control device 60 moves the head 20 and the energy application unit 30 to the right without transporting the printing medium A forward, and then starts the image pass. In this image pass, the head 20 moves to the left and ejects the second liquid based on the image control data, so that dots of the second liquid are formed on the base E. The energy application unit 30 moves to the left following the head 20 and applies energy to the second liquid on the base E, so that the dots of the second liquid are fixed on the base. As a result, an image C made up of a plurality of dots is printed on the base E.

[0051] After the base pass and image pass in the current pass are completed, the print medium A is transported forward and the next pass is executed. In this manner, the base pass, image pass, and transport operation are alternately repeated to print the entire image C.

[0052] <Printing device control method> The control method for the printing device 10 is executed by the control device 60, for example, in accordance with the flowchart of Fig. 7. First, the control device 60 acquires print data (step S1). The control device 60 performs color conversion processing and halftone processing on the image data of the print data to generate drawing data for an image (step S2). The control device 60 also acquires mode data from an input device or the like (step S3), and determines whether or not the printing process is to be executed in the first mode based on the mode data (step S4).

[0053] If the mode data is the first mode (step S4: YES), the control device 60 generates drawing data for the base (step S5). In addition, the control device 60 corrects the ejection amount of the second liquid when printing an image in the first mode for the drawing data for the image generated in step S2 so that the ejection amount of the second liquid is greater than the ejection amount of the second liquid when printing the same image as the image in the second mode (step S6).

[0054] The control device 60 executes a base pass based on the base drawing data generated in step S5, and prints the base E on the printing medium A (step S7). Next, the control device 60 executes an image pass based on the image drawing data corrected in step S6, and prints the image C on the base E (step S8). Then, the control device 60 executes a transport operation and transports the printing medium A forward (step S9). If all passes in the print data have not been completed (step S10: NO), the control device 60 returns to step S7 and executes the next pass. On the other hand, if all passes in the print data have been completed (step S10: YES), the control device 60 ends the printing process.

[0055] Furthermore, if the mode data is the second mode (step S4: NO), the control device 60 executes a pass based on the drawing data for the image generated in step S2, and prints the image C on the print medium A (step S11). Then, the control device 60 executes a transport operation, and transports the print medium A forward (step S12). If all passes in the print data have not been completed (step S13: NO), the control device 60 returns to step S11 and executes the next pass. On the other hand, if all passes in the print data have been completed (step S13: YES), the control device 60 ends the print process.

[0056] In this way, in the printing device 10, the amount of the second liquid ejected when printing an image in the first mode is made greater than the amount of the second liquid ejected when printing the same image in the second mode. Therefore, even if the second liquid does not easily spread on the base, color unevenness and banding caused by the second liquid are reduced, and deterioration of image quality in areas where colors are printed in overlapping fashion can be suppressed.

[0057] In addition, the amount of chromatic ink ejected when printing an image in the first mode is made greater than the amount of chromatic ink ejected when printing the same image in the second mode. For example, one black ink dot Dk is replaced with three chromatic ink dots Dc, Dy, and Dm. As a result, the area of ​​the chromatic ink dots Dc, Dy, and Dm is larger than the dot Dk, and it is possible to suppress degradation of image quality in areas where colors are printed in overlapping fashion.

[0058] (Embodiment 2) In the printing device 10 of embodiment 2, the control device 60 controls the amount of ejection of the second liquid so that the size of target dots, which are at least a portion of the dots that make up an image in the first mode, is larger than the size of dots that correspond to the target dots among the dots that make up the same image in the second mode.

[0059] 7, the control device 60 sets the gradation of the drawing data according to the size of the dots formed by the liquid ejected from the nozzles 21. The gradation is data indicating four gradations, for example, no dots where no liquid is ejected from the nozzles 21, small dots formed with less than a predetermined amount of liquid, medium dots formed with a predetermined amount of liquid, and large dots formed with more than a predetermined amount of liquid. The control device 60 converts the pixel data indicating 256 gradations into drawing data of four gradations by halftone processing, and generates drawing data for an image.

[0060] In the second mode, image C is printed based on the drawing data for the image in step S11 of Fig. 7. Here, the control device 60 generates waveform selection data so that a smaller amount of liquid than a predetermined amount is ejected for a small dot, generates waveform selection data so that a predetermined amount of liquid is ejected for a medium dot, and generates waveform selection data so that a larger amount of liquid is ejected for a large dot. The control device 60 drives the drive element 25 in accordance with this waveform selection data, so that an amount of liquid according to the dot size is ejected from the head 20 corresponding to the drive element 25.

[0061] 8(a), small dots D1, medium dots D2, and large dots D3 made of the second liquid based on the drawing data for the image are formed on the printing medium A. The second liquid then spreads on the printing medium A. Then, light energy is applied from the energy application unit 30 to the second liquid on the printing medium A, and the dots are fixed to the printing medium A. By repeating this process, an image C8a made up of a plurality of dots is printed directly on the printing medium A.

[0062] In contrast, in the first mode, in step S6 of Fig. 7, the control device 60 corrects the drawing data for the image. In this correction process, the control device 60 corrects the gradation of the drawing data for the image, with small dots and medium dots as target dots, so as to increase the size of the target dots. As a result, all small dots in the image are corrected to medium dots, and all medium dots in the image are corrected to large dots. Note that some small dots and medium dots in the image may be corrected to be target dots and increased in size. Also, small dots may be corrected to large dots larger than medium dots.

[0063] As a result, in step S8 of Fig. 7, the control device 60 executes an image pass based on the corrected drawing data for the image. As shown in Fig. 8(b), the second liquid in an amount according to the drawing data is ejected from the head 20, dots D2 and D3 of the second liquid are formed on the base E, and an image C8b composed of a plurality of dots is printed on the base E.

[0064] In this way, for target dots arranged at the same position in the images C8a and C8b, small dots D1 are printed in the second mode, whereas medium dots D2 are printed in the first mode. Also, for other target dots arranged at the same position in the images C8a and C8b, medium dots D2 are printed in the second mode, whereas D3 are printed in the first mode. Therefore, the ratio of large dots D2 and D3 among the multiple dots constituting the images C8a and C8b is higher in the first mode than in the second mode. As a result, even if the second liquid is difficult to spread on the base E, the ejection amount of the second liquid for forming the image C8b is large, so that deterioration of image quality in the portion where colors are printed in overlapping can be suppressed.

[0065] <Variation 1> In the printing device 10 of variant example 1, in embodiment 2, the control device 60 controls the amount of ejection of the second liquid when printing a character image in the first mode so that the dots among the target dots that are located at the edges of the image are not made larger than the size of the dots corresponding to the target dots in the second mode, and so that the dots that are located other than at the edges of the image are made larger than the size of the dots corresponding to the target dots in the second mode.

[0066] For example, as shown in FIG. 9(a), an image C9a of a character composed of a plurality of medium dots D2 is printed based on print data in the second mode. When printing the image C9a in the first mode based on this print data, the control device 60 corrects the drawing data for the image in step S6 of FIG. 7. In this correction process, for example, the control device 60 sets all medium dots D2 constituting the image C9a as target dots. Then, the control device 60 determines, among the target dots, a dot that has a pixel without a dot among the eight pixels surrounding it as a dot De located at the edge of the image C9a. In this way, the dot De located at the edge of the image C9a is not adjacent to a dot in any direction, including the front-back direction, the left-right direction, and the diagonal direction.

[0067] 9B, the control device 60 corrects the gradation of the drawing data for the image so that the dot size of the dots Di other than the dots De located at the edge of the image C9b among the target dots is increased. Also, the control device 60 does not correct the gradation of the dots De located at the edge of the image C9b among the target dots. As a result, the size of the dots De is maintained at medium dots D2, and the dots Di inside the edge dots De in the image C9b are increased in size from medium dots D2 to large dots D3.

[0068] 7, the control device 60 executes an image pass based on the corrected drawing data for the image. As a result, as shown in FIG 9(b), dots D2 and D3 are formed of the second liquid on the base E, and an image C9b composed of the multiple dots D2 and D3 is printed on the base E.

[0069] In this way, the inner dots Di in the image C9b are printed larger. As a result, even if the second liquid does not easily spread on the base E, the amount of the second liquid ejected to form the image C9b is large, so it is possible to suppress deterioration in image quality in areas where colors are printed in overlapping fashion. In contrast, the size of the dots De at the edges of the image C9b is not significantly corrected, so it is possible to prevent the size of the image C9b from becoming larger.

[0070] The control device 60 may correct the gradation of the image drawing data so that the size of the dots De located at the edge of the image C9b among the target dots is reduced. As a result, the size of the dots De at the edge of the image C9b is reduced from medium dots D2 to small dots D1. Therefore, the size of the dots De at the edge of the image C9b is corrected to be smaller, so that the increase in the size of the image C9b can be reduced.

[0071] (Embodiment 3) In the printing device 10 of embodiment 3, the control device 60 controls the amount of the second liquid ejected so that the size of the largest dot among the multiple dots that make up an image in the first mode is larger than the size of the largest dot among the multiple dots that make up the same image in the second mode.

[0072] 7, the control device 60 sets the gradation of the drawing data according to the size of the dots formed by the liquid ejected from the nozzles 21. The gradation is data indicating four gradations, for example, no dot, small dot, medium dot, and large dot. However, the control device 60 converts pixel data indicating 256 gradations into drawing data of four gradations by halftone processing to generate drawing data for an image.

[0073] The second liquid is ejected from the head 20 based on the drawing data for the step S1 image in Fig. 7. As a result, when an image is printed in the second mode in 1, small dots D1, medium dots D2, and large dots D3 made of the second liquid are formed on the printing medium A, as shown in Fig. 8(a), and an image C8a made of these dots is printed on the printing medium A.

[0074] In contrast, in the first mode, in step S6 of Fig. 7, the control device 60 corrects the drawing data for this image. In the correction process, the control device 60 sets the large dot, which is the largest of the small dots, medium dots, and large dots that make up the image, as the target dot in the gradation of the drawing data for the image. The control device 60 then increases the ejection amount of the second liquid for forming the target dot to an amount greater than the ejection amount of the second liquid for forming the large dot D3, but equal to or less than the maximum amount that the head 20 can eject. As a result, the gradation is corrected so that the size of the large dot D3 becomes an extra-large dot D4, which is larger than the large dot D3.

[0075] 7, the control device 60 executes an image pass based on the corrected drawing data for the image. Here, the second liquid is ejected from the head 20 in an amount greater than the amount of the large dots D3, and as shown in FIG 10, extra-large dots D4 made of the second liquid are formed on the base E, and an image C10 composed of a plurality of dots including the extra-large dots D4 is printed on the base E.

[0076] In this way, for target dots that are located at the same position in images C8a and C10, they are printed with large dots D3 in the second mode, whereas they are printed with extra-large dots D4 that are larger than the large dots in the first mode. As a result, even if it is difficult for the second liquid to spread on the base E, the ejection volume of the second liquid for forming image C10 is large, so that deterioration in image quality in areas where colors are printed in overlapping fashion can be suppressed.

[0077] <Variation 2> In the printing device 10 relating to variant example 2, in embodiment 3, the control device 60 controls the amount of ejection of the second liquid when printing a character image in the first mode so that the size of the largest dot among the multiple dots constituting the image, which is located at the edge of the image, is not made larger than the size of the largest dot in the second mode, and the size of the largest dot located other than the edge of the image is made larger than the size of the largest dot in the second mode.

[0078] For example, as shown in FIG. 11(a), an image C11a composed of a plurality of large dots D3 is printed based on print data in the second mode. When printing an image in the first mode based on this print data, the control device 60, in step S6 of FIG. 7, corrects the drawing data for the image by taking the largest large dot D3 of all dots constituting the image C11b as the target dot as shown in FIG. 11(b). At this time, the control device 60 determines, based on the drawing data, that among the target dots, a dot having no dot among the eight pixels surrounding it is a dot De arranged at the edge of the image C11b. In this way, the dot De arranged at the edge of the image C11b is not adjacent to any dot in any direction, including the front-back direction, the left-right direction, or the diagonal direction.

[0079] The control device 60 then corrects the gradation of the drawing data for the image so that the amount of the second liquid ejected to form the dots Di other than the dots De located at the edge of the image C11b is increased among the target dots. The control device 60 also does not correct the gradation of the dots De located at the edge of the image C11b among the target dots. As a result, the dots De at the edge of the image C11b are maintained in size as large dots D3, and the dots Di inside the edge dots De in the image are increased in size from large dots D3 to extra-large dots D4.

[0080] 7, the control device 60 executes an image pass based on the corrected drawing data for the image. As a result, as shown in FIG 11(b), dots are formed with the second liquid on the base E, and an image C11b composed of a plurality of dots is printed on the base E.

[0081] In this way, the inner dots Di in the image C11b are printed larger. As a result, even if the second liquid does not easily spread on the base E, the amount of the second liquid ejected to form the image C11b is large, so it is possible to suppress deterioration in image quality in areas where colors are printed in overlapping fashion. In contrast, the size of the dots De at the edges of the image C11b is not significantly corrected, so it is possible to prevent the size of the image C11b from becoming larger.

[0082] The control device 60 may correct the gradation of the image drawing data so that the size of the dots De located at the edge of the image C11b among the target dots is reduced. As a result, the size of the dots De at the edge of the image C11b is reduced from large dots to medium dots or small dots. Therefore, the size of the dots De at the edge of the image C11b is corrected to be smaller, so that the increase in the size of the image C11b can be reduced.

[0083] (Embodiment 4) In the printing device 10 of embodiment 4, the control device 60 controls the head 20 so that the number of ejections of the second liquid when printing an image in the first mode is greater than the number of ejections of the second liquid when printing the same image in the second mode.

[0084] Specifically, in step S2 of Fig. 7, the control device 60 sets the gradation of the drawing data depending on the presence or absence of dots. This gradation is, for example, data showing two gradations, that is, without dots and with dots. The control device 60 converts the pixel data showing 256 gradations into drawing data with two gradations by halftone processing, and generates drawing data for the image.

[0085] When an image is printed in the second mode in step S11 of Fig. 7, the second liquid is ejected from the head 20 based on the drawing data for the image, and dots of the second liquid are formed on the printing medium A, as shown in Fig. 12(a). Then, light energy is applied from the energy application unit 30 to the second liquid on the printing medium A, and the dots are fixed to the printing medium A. By repeating this process, an image C12a made up of a plurality of dots is printed directly on the printing medium A.

[0086] In contrast, in the first mode, in step S6 of Fig. 7, the control device 60 corrects the drawing data for this image. In this correction process, the control device 60 corrects the gradation so that pixels without dots become pixels with dots so that the number of dots constituting the image in the drawing data for the image increases. For example, the control device 60 corrects the gradation of the drawing data so that a pixel F between a pixel without dot and a pixel with dot in the left-right direction and between a pixel without dot and a pixel with dot in the front-rear direction is replaced with a pixel without dot.

[0087] As a result, in step S8 of Fig. 7, the control device 60 executes an image pass based on the corrected drawing data for the image. Here, by ejecting the second liquid from the head 20 at pixels F that change from no dots to dots, dots D are formed of the second liquid on the base E as shown in Fig. 12(b), and an image C12b composed of a plurality of dots D is printed on the base E. In this way, even if the second liquid is difficult to spread on the base E due to the increase in the number of dots D that compose the image C12b, the ejection amount of the second liquid for forming the image C12b is large, and therefore degradation of image quality in the portion where colors are printed in overlapping can be suppressed.

[0088] (Embodiment 5) The printing device 10 according to the fifth embodiment includes a carriage 42 that carries a head 20 and moves in a scanning direction. The control device 60 controls the carriage 42 and the head 20 so that the control for printing an image on the printing medium A includes ejection control for ejecting at least the second liquid from the head 20 while moving the carriage 42 in the scanning direction, and controls the carriage 42 and the head 20 so that the total number of ejection controls when printing an image on the printing medium A with the second liquid in the first mode is greater than the total number of ejection controls when printing the same image as the image with the second liquid in the second mode.

[0089] Specifically, for example, as shown in FIG. 9(a), an image C9a of a character composed of a plurality of medium dots D2 is printed based on print data in the second mode. When printing the image C9a based on this print data in the first mode, the control device 60 corrects the drawing data for the image in step S6 of FIG. 7. In this correction process, the control device 60 corrects the drawing data so that the image pass has a plurality of discharge controls including a discharge operation and a movement operation, and the number of discharge controls is greater in the first mode than in the second mode. For example, interlaced printing is performed so that all or part of the images formed by the plurality of discharge controls overlap each other. In this case, the control device 60 performs a rasterization process on the drawing data for the image to divide it for each pass, and corrects the drawing data for each pass to be assigned to each of the plurality of discharge controls.

[0090] Then, in step S8 of Fig. 7, the control device 60 generates control data for the image based on the drawing data and outputs it to the head driving circuit 65. As a result, the control device 60 performs a plurality of ejection controls in the image pass based on the drawing data of that pass, and then performs the application operation. Therefore, the control device 60 ejects the second liquid from the head 20 moving to the left in accordance with the drawing data of the pass. As a result, dots D2 are formed from the second liquid, and an image C13a is formed on the base E, as shown in Fig. 13(a).

[0091] Then, the control device 60 moves the head 20 to the right without applying energy from the energy application unit 30, and ejects the second liquid from the head 20 moving to the left in accordance with the drawing data of the same path in accordance with the drawing data of the path. As a result, dots D2 made of the second liquid overlap dots D2 formed by the previous drawing control. In this way, after performing drawing control multiple times, the control device 60 applies energy from the energy source 31 while the energy application unit 30 moves to the left. As a result, the second liquid hardens and is fixed on the base E.

[0092] In this way, by performing ejection control multiple times in the imaging pass, the number of dots D2 forming the image C13a increases as shown in Fig. 13(a). Therefore, even if the second liquid does not easily spread on the base E, the ejection amount of the second liquid for forming the image C13a is large, so that deterioration of image quality in the portion where colors are printed in overlapping fashion can be suppressed.

[0093] In the second mode, similarly to the first mode, the control device 60 may perform a plurality of ejection controls in an imaging pass based on drawing data for the same pass. Also, in an imaging pass, the application operation may be performed after each of the plurality of ejection controls.

[0094] Furthermore, the multiple ejection controls may be performed so that the positions of the dots D2 in Fig. 13(b) are shifted from one another. In this case, the dots may be shifted so that they partially overlap by transporting the print medium A a distance shorter than the interval between adjacent nozzles 21 in the rear direction between successively executed ejection controls. This increases the resolution of the image C13b in the front-rear direction compared to the resolution based on the interval between the nozzles 21. Note that at least one of the nozzles 21 that eject the second liquid and the ejection timing of the second liquid may be changed so that the positions of the dots are shifted from one another in the left-right direction.

[0095] <Other Modifications> In all the above-described embodiments and modifications, a light source that generates light energy is used as the energy source 31 of the energy application unit 30, but this is not limiting. For example, the energy source 31 may be a radio wave generator that generates thermal energy and energy by radio waves such as microwaves. In this case, a liquid that is hardened by radio waves is used as the liquid.

[0096] A heater that applies heat may be used as the energy source 31 of the energy application unit 30. Examples of this heater include a radiation heater, a hot air heater, and a contact heater. In this case, the liquid used is a liquid that hardens when heated, such as latex ink.

[0097] In all of the above-described embodiments and modified examples, the printing device 10 uses a serial head system in which the head 20 is moved in the left-right direction by the carriage 42. However, the printing device 10 may not be provided with a carriage 42 and may use a line head system in which the head 20 is fixed.

[0098] In all of the above-described embodiments and modified examples, a piezoelectric element is used for the driving element 25, but this is not limiting. For example, a thermal actuator such as a heating resistor that generates bubbles, or an electrostatic actuator such as an electrode that generates an electrostatic force may be used for the driving element 25.

[0099] In all the above embodiments and modified examples, the printing device 10 performs unidirectional printing, but bidirectional printing may also be performed. In this case, the printing device 10 has a pair of energy application units 30 arranged to sandwich the head 20 in the left-right direction. The right energy application unit 30 of the pair of energy application units 30 applies energy to the liquid on the printing medium A while moving leftward following the head 20 that moves leftward and ejects liquid onto the printing medium A. The left energy application unit 30 of the pair of energy application units 30 applies energy to the liquid on the printing medium A while moving rightward following the head 20 that moves rightward and ejects liquid onto the printing medium A.

[0100] It should be noted that all the above-mentioned embodiments may be combined with each other as long as they do not exclude each other. Also, many improvements and other embodiments of the present invention will be apparent to those skilled in the art from the above description. Therefore, the above description should be construed as merely illustrative and is provided for the purpose of teaching those skilled in the art the best mode for carrying out the present invention. Details of the structure and / or function of the present invention may be substantially modified without departing from the spirit of the present invention. [Industrial Applicability]

[0101] The printing apparatus of the present invention is useful as a printing apparatus capable of suppressing deterioration in image quality in areas where colors are printed in overlapping fashion. [Explanation of symbols]

[0102] 10:Printing device 20: Head 30: Energy application section 42: Carriage 60: Control device

Claims

1. a head that ejects the first liquid and the second liquid onto a printing medium; an energy applying unit that applies energy for hardening the first liquid and the second liquid on the printing medium; A control device having a storage unit that stores a conversion table indicating a correspondence relationship between a gradation of black and a gradation of a chromatic color, the second liquid includes black ink and three chromatic color inks, The control device includes: a first mode in which the first liquid is ejected and then the energy is applied to form a base of the first liquid on the printing medium, and the second liquid is ejected and then the energy is applied to print an image on the base; and a second mode in which the second liquid is ejected without forming the base, and then the energy is applied to print an image on the printing medium; a printing device which, when printing an image in the first mode, replaces some or all of the black dots formed with the black ink in the second mode among the multiple dots constituting the image with dots formed with the three chromatic color inks based on the correspondence between the black gradation and the chromatic color gradation shown in the conversion table, thereby making the amount of the second liquid ejected when printing an image in the first mode greater than the amount of the second liquid ejected when printing the same image in the second mode.

2. The printing apparatus of claim 1 , wherein the first liquid is a white ink.

3. The printing apparatus according to claim 1 , wherein the energy applying unit applies energy for hardening the first liquid and the second liquid on the printing medium.

4. A system comprising: a head which ejects a first liquid and a second liquid onto a printing medium; an energy imparting unit which imparts energy for hardening the first liquid and the second liquid on the printing medium; a memory unit which stores a conversion table showing the correspondence between gradations of black and chromatic colors; a control device; and an external device which transmits various data to the control device, the second liquid includes black ink and three chromatic color inks, The control device includes: a first mode in which the first liquid is ejected and then the energy is applied to form a base of the first liquid on the printing medium, and the second liquid is ejected and then the energy is applied to print an image on the base; and a second mode in which the second liquid is ejected without forming the base, and then the energy is applied to print an image on the printing medium; When printing an image in the first mode, the system replaces some or all of the black dots formed with the black ink in the second mode among the multiple dots constituting the image with dots formed with the three chromatic color inks based on the correspondence between the black gradation and the chromatic color gradation shown in the conversion table, thereby making the amount of the second liquid ejected when printing an image in the first mode greater than the amount of the second liquid ejected when printing the same image in the second mode.

Images