Liquid discharge device

Abstract

To provide a liquid discharge device that can suppress deterioration in optical density, in performing printing while discharging extra-large droplets.SOLUTION: A liquid discharge device 1 comprises a discharge head 10, a moving device 18, and a control device 30. The control device 30 generates, on the basis of image data, second printing data in which one impact position of a second droplet and the other impact position of the second droplet which form a continuous dot image B1 are arranged separately from each other in a first direction more than in first image data, when an image printed based on the first printing data includes the continuous dot image B1 in which second dots D2 are continuously arranged in a second direction.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present disclosure relates to a liquid ejection device that ejects liquid. [Background technology]

[0002] Conventionally, there is known a liquid ejection device such as that described in Patent Document 1. This liquid ejection device is described as ejecting droplets that are even larger than normal large droplets (hereinafter referred to as extra-large droplets) using a two-cycle waveform (waveform 5 and waveform 6 in Figure 10 of Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-279998 Summary of the Invention [Problem to be solved by the invention]

[0004] However, these extra-large droplets have a longer shape in the ejection direction during flight compared to large droplets. Furthermore, because the droplets ejected from the head land on the print medium while the head and the print medium move relative to each other, the dots formed on the print medium are longer. When elongated dots on the print medium are aligned in the short direction, perpendicular to the longitudinal direction of the dots, gaps where no droplets are present can form between adjacent elongated dots near the ends of the elongated dots. The presence of such gaps reduces the coverage of the liquid on the print medium and reduces the optical density (OD value).

[0005] Therefore, an object of the present disclosure is to provide a liquid ejection device that can suppress a decrease in optical density when printing by ejecting extra-large droplets. [Means for solving the problem]

[0006] A liquid ejection device according to a first aspect of the present disclosure includes a head having a nozzle surface in which a plurality of nozzles are opened to eject droplets onto a print medium, a moving device that moves the head in a first direction relative to the print medium, and a control device, wherein the control device is configured to cause the second droplets to land on an image on the print medium when printing is performed using first print data including information that specifies at least a predetermined first droplet and a second droplet that has a longer dimension in an ejection direction and a larger volume than the first droplet, and the second droplet is formed as a dot that is elongated in the first direction in an image on the print medium when the image is printed using first print data including information that specifies at least the second droplet as a type of droplet to be ejected from the nozzle. When the image data includes a continuous dot image that is arranged continuously in a second direction that intersects the first direction, the following steps are executed: a generation process for generating second print data based on image data, in which the landing position on the printing medium of one of the second droplets that form the continuous dot image and the landing position on the printing medium of the other second droplet are arranged farther in the first direction than the first print data; and a printing process for ejecting droplets from the nozzles of the head based on the second print data while moving the head and the printing medium relative to each other using the moving device, to form an image on the printing medium. [Effects of the Invention]

[0007] According to the liquid ejection device of the present disclosure, the relative positions of elongated dots aligned in the second direction, which is the short side direction, are shifted in the first direction, which is the long side direction, so that a decrease in optical density near the end portions can be suppressed. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic diagram of a liquid ejection device according to the present disclosure. [Figure 2] FIG. 2 is a schematic cross-sectional view showing the configuration of the ejection head. [Figure 3] FIG. 3 is a block diagram showing the functional configuration of the liquid ejection device. [Figure 4] FIG. 4 is a schematic diagram showing examples of ejection signals input to actuators for ejecting various droplets of ink. [Figure 5]FIG. 5 is a flowchart showing an outline of an example of the operation of the liquid ejection device. [Figure 6] FIG. 6 is a flowchart showing the operation example of FIG. 5 in more detail. [Figure 7] FIG. 7 is a schematic diagram for explaining the operation shown in FIG. 6, showing dots on a print medium when printing is performed using print data generated in each process. [Figure 8] FIG. 8 is a flowchart showing the contents of another operation example. [Figure 9] FIG. 9 is a schematic diagram for explaining the operation shown in FIG. 8, showing dots on a print medium when printing is performed using print data generated in each process. [Figure 10] FIG. 10 is a chart showing the relationship between the rate of increase in image density and the replacement rate in the first data generation process relative to the temperature increase of the ejection head. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, an embodiment of a liquid ejection device according to the present disclosure will be specifically described with reference to the drawings. Note that, in the following, the same or corresponding elements will be designated by the same reference numerals throughout the drawings, and redundant description will be omitted.

[0010] (Configuration of liquid ejection device) 1 is a schematic diagram of a liquid ejection device 1 according to the present disclosure. The liquid ejection device 1 prints an image on a print medium A using liquid ejected from an ejection head 10 based on image data. An example of such a liquid ejection device 1 applied to an inkjet printer that ejects ink will be described below.

[0011] The liquid ejection device 1 is a serial head type, and alternates between a process of ejecting ink of multiple colors to form an image while the ejection head 10 moves (scans) and a process of transporting the print medium A. Note that, hereinafter, the direction in which the ejection head 10 moves back and forth is referred to as a first direction (or left-right direction), and the direction in which the print medium A is transported, which is perpendicular to the first direction, is referred to as a second direction (or front-back direction). Furthermore, a direction perpendicular to both the first and second directions is referred to as a third direction (or up-down direction). However, the arrangement direction of the liquid ejection device 1 is not limited to this.

[0012] The ejection head 10 is housed in a housing 2 of the liquid ejection device 1. The ejection head 10 has a nozzle surface 12 on which a plurality of nozzles 11 are opened, which eject liquid onto the print medium A based on print data. A more detailed configuration of the ejection head 10 will be described later.

[0013] The liquid ejection device 1 includes a platen 14 disposed opposite the ejection head 10. The platen 14 is positioned below the ejection head 10 at a predetermined distance, and supports the print medium A from below with its flat upper surface.

[0014] The liquid ejection device 1 is equipped with a transport device 15 that transports the print medium A on a platen 14. The transport device 15 has, for example, two transport rollers 16 and a transport motor. The two transport rollers 16 are arranged at a distance from each other in the front and rear with the platen 14 sandwiched between them, and are connected to the rotating shaft of the transport motor via a reducer. Therefore, when the transport motor is driven, the two transport rollers 16 rotate about their axes, transporting the print medium A on the platen 14 in the front-to-rear direction.

[0015] The liquid ejection device 1 is equipped with a moving device 18 that moves the ejection head 10 back and forth in the left and right direction. The moving device 18 has a carriage 19, two guide rails 20, an endless belt 21, and a moving motor. The carriage 19 supports the ejection head 10 and moves back and forth in the left and right direction together with the ejection head 10. The two guide rails 20 extend left and right across the platen 14 and are arranged spaced apart in the front and back with the ejection head 10 sandwiched between them. The two guide rails 20 support the carriage 19 so that it can move (scan) in the left and right direction.

[0016] The endless belt 21 is wound around two pulleys 22 provided near the left and right ends of one of the guide rails 20, and is connected to the carriage 19 at a predetermined location. The movement motor has a rotation shaft connected to either the left or right pulley 22 via a reducer. Therefore, in this movement device 18, when the movement motor is driven to rotate, the endless belt 21 runs, and the carriage 19 supporting the discharge head 10 moves left and right along the guide rail 20.

[0017] The liquid ejection device 1 is provided with a plurality of tanks 24 that store ink of each color to be supplied to the ejection head 10. These tanks 24 are housed inside the housing 2 by opening an openable cover provided on the housing 2. The liquid ejection device 1 of the present disclosure uses ink of four colors, for example, cyan, yellow, magenta, and black, and is provided with four tanks 24 accordingly. One end of a flexible tube 25 is connected to each tank 24, and the other end is connected to an ink supply port of the ejection head 10, and the ink from each tank 24 is sent to the ejection head 10 through the tube 25.

[0018] As described above, the liquid ejection device 1 is exemplified here as a serial head type in which the ejection head 20 moves back and forth, but the present disclosure can also be applied to a line head type that includes a fixedly arranged head (line head) that has a length spanning the entire width of the print medium A. In the case of the line head type, the direction in which the print medium A moves relative to the line head is defined as the first direction.

[0019] (Configuration of ejection head) Fig. 2 is a schematic cross-sectional view showing the configuration of the ejection head 20. As shown in Fig. 2, the ejection head 20 has a flow path section 50 in which a plurality of plates made of metal such as stainless steel are stacked. A portion of each plate is fully or half-etched to form a supply manifold 51 and individual channels 52 that communicate with the nozzles 11 within the flow path section 50. The individual channels 52 also include a supply throttle path 53, a pressure chamber 54, a descender 55, and a nozzle hole 56, and the lower end opening of the nozzle hole 56 forms the nozzle 11.

[0020] A driving unit 60 is laminated on the flow path unit 50. The driving unit 60 is configured, for example, by laminating a piezoelectric ceramic layer 61, a common electrode 62, and a piezoelectric ceramic layer 63 so as to cover almost the entire area of ​​the upper surface of the ejection head 20, and further by arranging a plurality of individual electrodes 64 corresponding to each pressure chamber 53. The piezoelectric ceramic layer 61, the common electrode 62, and the portion of the piezoelectric ceramic layer 63 that corresponds to each pressure chamber 53, together with the corresponding individual electrode 64, constitute an actuator 65 corresponding to one individual channel 52.

[0021] In such an ejection head 20, ink is supplied from a tank 24 to a supply manifold 51, and further supplied from the supply manifold 51 to each individual channel 52. An ejection pressure is applied to the ink in the pressure chamber 53 of the individual channel 52 by driving (displacing) the actuator 65 corresponding to that individual channel 52. When the ejection pressure is applied, the ink in that individual channel 52 moves toward the nozzle hole 56 and is ejected from the nozzle 11 as droplets.

[0022] The above-described configuration of the ejection head 20 is merely an example, and the configuration of the ejection head 20 according to the present disclosure is not limited to this. For example, the ejection head 20 may have a return manifold in addition to the supply manifold 51, and may further include a return flow path that passes ink from the downstream end of the descender 55 to the return manifold.

[0023] (Hardware functional configuration) Fig. 3 is a block diagram showing the functional configuration of the liquid ejection device 1. As shown in Fig. 3, the liquid ejection device 1 has a functional configuration mainly made up of hardware, including a control device 30, a storage device 31 connected to the control device 30, an interface 32, a head driving device 33, and a temperature sensor 34. The control device 30 is also connected to the transport device 15 and the moving device 18 described above.

[0024] The control device 30 is, for example, a computer, and includes a processor such as an MPU, or an integrated circuit such as an ASIC. The storage device 31 is a memory accessible from the control device 30, and includes, for example, RAM and ROM. The RAM temporarily stores image data included in the print job, first print data and second print data generated from this image data, and various data used during calculations by the control device 30. The ROM stores computer programs and data for various data processing operations. Therefore, the control device 30 controls the operation of each part of the liquid ejection device 1 by executing computer programs while referencing the data stored in the storage device 31.

[0025] The interface 32 is a connection device that connects the control device 30 to external devices of the liquid ejection device 1. Examples of external devices include other computers, communication networks, recording media, displays, and other liquid ejection devices. The liquid ejection device 1 obtains a print job including image data and print setting information from an external device, such as a computer, via this interface 32.

[0026] The head driver 33 has a head driver circuit electrically connected to each actuator 65 of the ejection head 10, and controls the operation of each actuator 65 based on instructions from the control device 30. That is, the control device 30 outputs a control signal for driving the actuator 65 to the head driver circuit, and the head driver circuit generates an ejection signal based on the input control signal and outputs this ejection signal to each actuator 65. As a result, each actuator 65 is driven based on the corresponding ejection signal. Therefore, the ejection timing and size of the ink ejected from each nozzle 11 (volume of ink droplet) can be controlled.

[0027] (About ejection signals and droplets) 4 is a schematic diagram showing examples of ejection signals input to the actuator 65 to eject various droplets of ink. In this diagram, in order from smallest to largest volume, an ejection signal WS1 for a small droplet, an ejection signal WS2 for a medium droplet, an ejection signal WS3 for a large droplet (first droplet), and an ejection signal WS4 for an extra-large droplet (second droplet) are shown.

[0028] The ejection signal WS1 for small droplets has a periodic waveform, with one period T consisting of the period from the slight vibration pulse Pa to the stabilization pulse Pb. FIG. 4 illustrates two periods of the ejection signal. The ejection signal WS1 includes an ejection pulse P1 between the slight vibration pulse Pa and the stabilization pulse Pb during one period T. The slight vibration pulse Pa is a pulse signal that vibrates the ink meniscus in the nozzle 11, improving the stability of subsequent droplet ejection and increasing the droplet ejection speed. The ejection pulse P1 is a pulse signal that ejects droplets from the nozzle 11, and has a duration close to an integer multiple of the natural period of the ejection head 20, for example. The stabilization pulse Pb is a pulse signal that is applied after droplets are ejected, and is, for example, a pulse with an opposite phase to the ejection pulse P1, stabilizing the meniscus in the nozzle 11.

[0029] Like the ejection signal WS1, the ejection signal WS2 for medium droplets also has an ejection pulse P2 during one cycle T from the slight movement pulse Pa to the stabilization pulse Pb, and the ejection signal WS3 for large droplets also has an ejection pulse P3 during one cycle T from the slight movement pulse Pa to the stabilization pulse Pb. The pulse widths of the ejection pulses P1, P2, and P3 increase in this order. The volume of the ejected droplets varies depending on the pulse widths of the ejection pulses P1, P2, and P3, and the larger the pulse width, the larger the droplet volume.

[0030] Incidentally, in the above-mentioned ejection at the period T, if one attempts to further increase the volume of ejected droplets and achieve a higher duty cycle, it is necessary to input multiple ejection pulses (for example, two) in one period T, or to input an ejection pulse with a larger pulse width. However, when multiple ejection pulses are input, the pulse width of each ejection pulse becomes smaller, making it impossible to increase the volume. Furthermore, when an ejection pulse with a larger pulse width is input, it becomes impossible to input a stabilization pulse Pb in one period T.

[0031] Therefore, in this disclosure, a normal two-cycle (2T) signal is used, with a slight movement pulse Pa and a stabilization pulse Pb inserted at the beginning and end of the signal, and multiple ejection pulses P4 (three in FIG. 4) with relatively wide pulse widths inserted between these pulses Pa and Pb to form the ejection signal WS4 for the extra-large droplet (second droplet). In other words, the large droplet (first droplet) is a single droplet formed by a waveform of one cycle (T), and the extra-large droplet (second droplet) is a single droplet formed by a waveform of two cycles (2T). This results in the second droplet having a larger volume and a longer ejection dimension than the first droplet.

[0032] In this way, the liquid ejection device 1 of the present disclosure can selectively eject droplets of various volumes, including small droplets, medium droplets, large droplets, and extra-large droplets, from the nozzle 11. Note that in the above description, an ejection signal having one period that is substantially two normal periods T has been exemplified as the ejection signal WS4 for extra-large droplets, but this is not limited to this. For example, an ejection signal having one period that is three or more normal periods T may also be used.

[0033] 3, the transport device 15 has a transport drive circuit electrically connected to the transport motor described above, and the operation of the transport motor is controlled by the control device 30 via the transport drive circuit. This allows the transport device 15 to transport the print medium A on the platen 14 intermittently or continuously in the forward / backward direction, which is the second direction, and to stop and hold the print medium A at a predetermined position on the platen 14.

[0034] The movement device 18 has a movement drive circuit electrically connected to the movement motor described above, and the operation of the movement motor is controlled by the control device 30 via the movement drive circuit. This allows the movement device 18 to move the carriage 19 supporting the ejection head 10 in the left and right direction, which is the first direction, at different speeds, and to stop the carriage 19 at any position within its movable range. Therefore, the ejection head 10 mounted on the carriage 19 is moved back and forth in the left and right direction relative to the print medium A by the movement device 18.

[0035] The liquid ejection device 1 forms an image on the print medium A in each pass by ejecting ink while moving the ejection head 10 using the movement device 18. That is, the liquid ejection device 1 transports the print medium A using the transport device 15 and stops it at a predetermined position on the platen 14. Next, the liquid ejection device 1 moves the ejection head 10 left and right using the movement device 18 to eject ink onto the print medium A. In this way, a partial image for one pass is formed on the stopped print medium A by the ink ejected while the ejection head 10 moves left and right. Then, after the partial image for one pass is formed, the print medium A is transported a predetermined distance again by the transport device 15 and stopped, and the next partial image for one pass is formed by ejecting ink. The liquid ejection device 1 alternately repeats this process of transporting the print medium A and ejecting ink, thereby printing an entire image consisting of one or more partial images on the print medium A.

[0036] The liquid ejection device 1 further includes a temperature sensor 34. A known sensor such as a thermocouple or a thermistor can be used as the temperature sensor 34, which detects the temperature of the ejection head 20 and transmits the detected value to the control device 30. In addition to the above, the liquid ejection device 1 may also include, as functional hardware components, output devices such as a display and a speaker that output various types of information to the outside, and input devices such as a touch panel and a physical switch that accept input of information from the outside.

[0037] (Software functional configuration) Meanwhile, the liquid ejection device 1 has a functional configuration mainly composed of software, which includes a generation processing unit 40 including a halftone processing unit 41, a first data generation processing unit 42, a determination processing unit 43, and a second data generation processing unit 44. The liquid ejection device 1 further includes a first substitution processing unit 45, a second substitution processing unit 46, and a print processing unit 47. Each of these processing units 40 to 47 functions when the control device 30 executes a computer program stored in the storage device 31.

[0038] The halftone processing unit 41 generates halftone data by halftone processing image data including RGB values ​​included in the print job. This halftone data is print data that includes information specifying any or all of small droplets, medium droplets, and large droplets (first droplets), excluding extra-large droplets (second droplets), as the types of droplets to be ejected from the nozzles 11. The generated halftone data is stored in the storage device 31, for example, until the print job is completed, and is then erased.

[0039] The first data generation processor 42 executes a first data generation process to generate first print data based on halftone data that includes a designation for large droplets. This first print data is print data in which at least some of the designations for large droplets (first droplets) in the halftone data have been replaced with designations for extra-large droplets (second droplets). This first data generation process is performed when certain conditions are met, such as when part of the image data in a print job includes a high-duty image that is equal to or greater than a predetermined value. The generated first print data is stored in the storage device 31 until the print job is completed, and is then erased.

[0040] The determination processing unit 43 executes a process for determining whether a continuous dot image is included in an image formed on a print medium when printed using the first print data. That is, the first print data includes a designation for extra-large droplets, and when extra-large droplets of ink are ejected while the ejection head 20 and the print medium A are moved relatively in the first direction, dots (hereinafter referred to as "second dots D2") that are longer in the first direction are formed on the print medium A. These dots are longer in the first direction than dots (hereinafter referred to as "first dots D1") that are formed on the print medium A by ejecting large droplets of ink. Such second dots D2 arranged consecutively in a second direction intersecting the first direction constitute a continuous dot image B1, and the determination process determines whether this continuous dot image B1 is included.

[0041] The second data generation processing unit 44 is a process that generates second print data based on the first print data. This second print data is print data in which the landing positions on the print medium A of one extra-large droplet that forms the continuous dot image B1 and the landing positions on the print medium A of the other extra-large droplet are positioned further away in the first direction than in the first print data. The generated second print data is stored in the storage device 31, for example, until the print job is completed, and is then erased.

[0042] The generation processing unit 40 of the present disclosure includes the functions of the above-described processing units 41 to 44. However, the generation processing unit 40 only needs to generate the second print data when the first print data ultimately includes a continuous dot image. Therefore, when generating the second print data, it is not necessary to actually generate halftone data and the first print data.

[0043] When an extra-large droplet is located at the edge of an image on the print medium A in the first direction when printed using the first print data, the first replacement processor 45 executes a first replacement process to replace the extra-large droplet with multiple large droplets in the first print data. When an extra-large droplet is ejected, tiny droplets (satellite droplets) may be generated immediately thereafter, and if these satellite droplets adhere to the print medium A, image quality will deteriorate. Therefore, by executing the first replacement process, it is possible to prevent satellite droplets from adhering to the margins of the print medium A and suppress deterioration in image quality.

[0044] When a first arrangement B2 exists in which two consecutive large droplets and one extra-large droplet are positioned adjacent to each other along the first direction of an image on the print medium A when printed using the first print data, the second replacement processor 46 replaces the first arrangement B2 with a second arrangement B3 in which one extra-large droplet is positioned between two consecutive large droplets. Images formed by ejecting large droplets in succession, such as the first arrangement B2, have a lower density than images formed with extra-large droplets. Therefore, by replacing the first arrangement B2 with the second arrangement B3 as described above, the density of the image can be increased.

[0045] The printing processing unit 47 performs a printing process in which droplets are ejected from the nozzles 11 of the ejection head 20 based on one of the halftone data, the first printing data, and the second printing data, while moving the ejection head 20 and the printing medium A relative to each other using the moving device 18, to form an image on the printing medium A.

[0046] (Example 1 of operation of liquid ejection device) Next, the operation of the liquid ejection device 1 as described above will be described. Figure 5 is a flowchart showing an outline of an operation example 1 of the liquid ejection device 1. As shown in this flowchart, the liquid ejection device 1 determines whether or not a print job has been received (step S1). If not (S1: NO), the operation of step S1 is repeated. On the other hand, if a print job has been received (S1: YES), the generation processing unit 40 executes a generation process to generate second print data (step S2), and then executes a print process using this second print data (step S3).

[0047] FIG. 6 is a flowchart showing Operation Example 1 in more detail. Operation Example 1 will be further described with reference to FIG. 6. The liquid ejection device 1 determines whether or not a print job has been received, for example, via the interface 32 (step S10). If no print job has been received (S10: NO), the operation of step S10 is repeated. On the other hand, if a print job has been received (S10: YES), halftone processing is executed (step S11), and halftone data is generated from the image data and stored in the storage device 31.

[0048] The liquid ejection device 1 determines whether a specific condition is met, such as whether the image data contains a high-duty image of a predetermined value or more (step S12). If the specific condition is not met (S12: NO), the halftone data generated in step S11 is determined to be the print data (step S19), and printing processing is executed (step S18). On the other hand, if the specific condition is met (S12: NO), the first data generation processing unit 42 executes first data generation processing (step S13).

[0049] FIG. 7 is a schematic diagram for explaining Operation Example 1, showing dots on a print medium A when printing is performed using print data generated by each process in Operation Example 1. Note that a row of dots along a first direction is referred to as a dot row, and the Nth row of dots arranged in a second direction is referred to as row N, and the N+1th row of dots arranged in a second direction is referred to as row N+1. As shown in the first step of FIG. 7, the halftone data does not include a designation of extra-large droplets, and an image printed using the halftone data is composed of first dots D1 in both row N and row N+1. Note that while FIG. 7 describes halftone data that includes only a designation of large droplets, it may also include designations of small and medium droplets.

[0050] The second step in Figure 7 shows a printed image based on the first print data generated by performing the first data generation process on this halftone data. Comparing the first and second steps, it can be seen that two consecutive first dots D1 in the first direction in the printed image based on the halftone data have been replaced with one second dot D2. That is, the designation of two consecutive large drops in the first direction in the halftone data has been replaced with a designation of a single extra-large drop in the first print data. In the first data generation process (S13) in Figure 6, the designation of these two large drops is replaced with a designation of a single extra-large drop, and the first print data is generated.

[0051] Next, the determination processing unit 43 executes a determination process based on the first print data (step S14). That is, it determines whether or not the print image based on the first print data includes the continuous dot image B1 (step S15). If the continuous dot image B1 is not included (S15: NO), the first print data generated in step S13 is determined to be the print data (step S20), and the print process is executed (step S18).

[0052] On the other hand, if the continuous dot image B1 is included (S15: YES), the second data generation processing unit 44 executes the second data generation process (step S16). In the example of Fig. 7, the continuous dot image B1 in which extra-large droplets are arranged continuously in the second direction exists as surrounded by the dashed line in the printed image shown in the second step (three in Fig. 7). Therefore, the second data generation process (S16) is executed.

[0053] Specifically, second print data is generated in which the landing positions on the print medium A of one of the extra-large droplets forming continuous dot image B1 and the landing positions on the print medium A of the other extra-large droplet are positioned further apart in the first direction than in the first print data. The third step in Figure 7 shows a printed image based on the second print data generated by the second data generation process. In the case of Figure 7, as can be seen by comparing the second and third steps, the second print data is generated by shifting the extra-large droplets in N rows in the first direction by the dimension of one large droplet. Once the second print data is generated in step S16 in this manner, the second print data is determined as the print data (step S17), and printing is performed (step S18).

[0054] Note that shifting the positions of the extra-large droplets in step S16 may result in the edge positions of the image being shifted relative to the edge positions in the original image data. In such cases, the shift in edge positions can be suppressed by changing the droplets that define the image edges to droplets of a different size.

[0055] As described above, the liquid ejection device 1 of the present disclosure uses extra-large droplets (second droplets) that have a larger volume than large droplets and form elongated dots (second dots D2) in the first direction on the recording medium A, thereby improving the optical density (OD value) of the image. Furthermore, when a continuous dot image in which second dots D2 are aligned in the second direction is included, printing is performed using second print data in which one second dot D2 and the other second dot D2 are spaced apart in the first direction. This makes it possible to suppress a decrease in the OD value of the second dots D2 near the ends in the first direction.

[0056] In this operation example 1, between receiving a print job (S10) and executing print processing (S18), halftone data is generated (S11), first print data is generated (S13), and second print data is generated (S16), and each generated data is stored in storage device 31. Therefore, for example, even after generating the first print data, there is no need to regenerate the halftone data if desired to use it, which reduces the load on control device 30. Similarly, even after generating the second print data, there is no need to regenerate the halftone data or first print data if desired to use it, which reduces the load on control device 30.

[0057] (Example 2 of operation of liquid ejection device) Next, an explanation will be given of Operation Example 2, which is another operation of the liquid ejection device 1. FIG. 8 is a flowchart showing Operation Example 2. FIG. 9 is a schematic diagram for explaining Operation Example 2, showing dots on the print medium A when printing is performed using print data generated in each process of Operation Example 2. Note that the flowchart in FIG. 8 differs from the flowchart in FIG. 6 in that steps S13A and S13B have been added. The first and second steps in the schematic diagram in FIG. 9 are the same as the first and second steps in the schematic diagram in FIG. 7. Therefore, the explanation of the same parts of FIGS. 8 and 9 as those in FIGS. 6 and 7 will be omitted here.

[0058] As shown in Fig. 8, in operation example 2, after the first data generation process (S13) is performed, the first replacement process is performed (step S13A). For example, as shown in the second step of Fig. 9, if a second dot D2 formed by an extra-large droplet is located at an end in the first direction of the printed image produced by the first print data, this extra-large droplet is replaced with a plurality of large droplets in the first print data. As a result, as shown in the third step of Fig. 9, the second dot D2 formed by an extra-large droplet is replaced with a first dot D1 formed by a large droplet at each end of the Nth and N+1th columns in the printed image.

[0059] Furthermore, in the second operational example shown in FIG. 8, after the first replacement process (S13A) is performed, the second replacement process (step S13B) is performed. For example, as shown in the third step in FIG. 9, the printed image based on the first print data after the first replacement process includes a first arrangement B2 in which two consecutive large droplets and one extra-large droplet are positioned adjacent to each other along the first direction. In this case, this first arrangement B2 is replaced with a second arrangement B3 in which one extra-large droplet is positioned between two consecutive large droplets. As a result, the dot arrangement of extra-large droplet, large droplet, large droplet is replaced with a dot arrangement of large droplet, extra-large droplet, large droplet.

[0060] After the first replacement process (S13A) and the second replacement process (S13B) are executed in this manner, the operations from step S14 onwards are executed in the same manner as described in Fig. 6. As a result, when the second data generation process (S16) is executed, for example, second print data is generated in which the landing positions of one extra-large droplet and the landing positions of the other extra-large droplet that form the continuous dot image B1 are positioned further apart in the first direction than in the first print data, as shown by the transition from step 4 to step 5 in Fig. 9.

[0061] As described above, Operation Example 2 of the liquid ejection device 1 of the present disclosure achieves the same effects as Operation Example 1. Furthermore, by performing the first replacement process (S13A) in Operation Example 2, it is possible to suppress degradation of image quality caused by satellite droplets landing on the margins when extra-large droplets are ejected at the edge of an image. Furthermore, by performing the second replacement process (S13B) in Operation Example 2, it is possible to suppress degradation of image density and achieve an image with higher density.

[0062] (Variation) The liquid ejection device 1 described with reference to Figure 3 is equipped with a temperature sensor 34. When the liquid ejection device 1 performs continuous printing, the temperature of the ejection head 10 increases over time from the start of printing due to heat generated by the actuator 65. When the temperature of the ejection head 10 increases, the viscosity of the ink decreases, even if the ejection signal waveform input to the actuator 65 is the same, and the volume of ink ejected from the nozzle 11 increases.

[0063] Therefore, in order to avoid unnecessarily increasing the density of the image, the substitution rate at which two large droplets are replaced with one extra-large droplet may be changed in accordance with the temperature of the ejection head 10 in the first data generation process (S13).

[0064] Fig. 10 is a chart showing the relationship between the rate of increase in image density and the replacement rate in the first data generation process relative to the temperature rise of the ejection head 10. As shown in Fig. 10, the rate of increase in image density increases as the temperature of the ejection head 10 rises, so the replacement rate is set to gradually decrease. By replacing large droplets with extra-large droplets in accordance with this setting in the first data generation process, it is possible to maintain the density before the temperature rise, even if the temperature of the ejection head 10 rises. [Industrial Applicability]

[0065] The present disclosure can be applied to a liquid ejection device. [Explanation of symbols]

[0066] 1 Liquid discharge device 10 Discharge head 11 nozzles 30 Control device 34 Temperature Sensor 40 Generation Process 41 Halftone processing section 42 First data generation processing unit 45 First replacement processing unit 46 Second replacement processing unit 47 Print processing unit 52 individual channels 65 Actuator

Claims

1. a head having a nozzle surface in which a plurality of nozzles that eject droplets onto a print medium are opened; a moving device that moves the head in a first direction relative to the print medium; a control device; The control device a generation process for generating, based on image data, second print data in which the landing positions on the print medium of one of the second droplets forming the continuous dot image and the landing positions on the print medium of the other second droplet are positioned farther apart in the first direction than in the first print data, when an image on the print medium formed when printed using first print data including information specifying at least the second droplets out of a predetermined first droplet and a second droplet having a longer dimension in the ejection direction and a larger volume than the first droplet as the type of droplet to be ejected from the nozzle includes a continuous dot image in which dots elongated in the first direction formed by the landing of the second droplets are continuously arranged in a second direction intersecting the first direction; a printing process in which droplets are ejected from the nozzles of the head based on the second print data while the head and the print medium are moved relative to each other by the moving device, thereby forming an image on the print medium; A liquid ejection device that performs the above.

2. the head has an individual channel communicating with the nozzle, and an actuator that is driven by a periodic waveform ejection signal to apply pressure to the liquid in the individual channel for ejecting it from the nozzle; the first droplet is one droplet formed by one cycle of the waveform of the ejection signal, the second droplet is a single droplet formed by a waveform of the ejection signal for two or more cycles; The liquid ejection device according to claim 1 .

3. The control device a first replacement process for replacing the second droplet with a plurality of the first droplets when the second droplet is located at an end of the image in the first direction in the first print data; The liquid ejection device according to claim 1 .

4. The control device if there is a first arrangement in the first print data in which two consecutive first droplets and one second droplet are positioned adjacent to each other along the first direction of the image, a second replacement process is performed to replace the first arrangement with a second arrangement in which one second droplet is positioned between two consecutive first droplets; The liquid ejection device according to claim 1 .

5. The generation process includes: a halftone process for generating halftone data based on the image data, the halftone data including a designation of the first droplet but not including a designation of the second droplet; a first data generation process for generating the first print data by replacing at least some of the first droplet designations with the second droplet designations based on the halftone data; Including, The liquid ejection device according to claim 1 .

6. a temperature sensor for detecting the temperature of the head; The control device In the first data generation process, a replacement rate from the designation of the first droplet to the designation of the second droplet is changed in accordance with the temperature of the head. The liquid ejection device according to claim 5 .

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