Printing apparatus

Abstract

In a printing device equipped with a serial-type inkjet head, this prevents nozzle ejection failures and deterioration of image quality. [Solution] The printing apparatus (1) comprises a serial inkjet head 30 that reciprocates in a movement direction D2 perpendicular to the transport direction D1 of the medium M and prints by ejecting ink from nozzles 31a to 35a, and a control unit (91) that reciprocates the inkjet head 30 in the movement direction D2. The control unit (91) controls the inkjet head 30 to print an image P by dividing it into a forward printing range A1 that prints during the forward movement and a return printing range A2 that prints during the return movement, depending on the position in the movement direction D2.

Description

Technical Field

[0001] The present invention relates to a printing apparatus including a serial inkjet head.

Background Art

[0002] Conventionally, serial inkjet heads are known that perform printing only during forward movement (or only during reverse movement), or that perform printing at the same position in the moving direction of the inkjet head both during forward movement and during reverse movement (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, when the inkjet head performs printing only in one direction during forward movement or reverse movement, ink is not ejected when moving in the reverse direction, so the ink in the nozzles dries, and ejection failure (non-ejection) occurs. In particular, when the medium is heated to accelerate drying of the ink landing on the medium, or when wind is blowing on the medium to prevent the evaporation component of the ink from evaporating and the vapor of the air on the medium from becoming saturated, ejection failure is likely to occur.

[0005] Also, when the inkjet head performs printing at the same position both during forward movement and during reverse movement, the ink landing on the medium does not dry sufficiently before the ink lands in the next pass printing, and the image quality deteriorates.

[0006] An object of the present invention is to provide a printing apparatus including a serial inkjet head that can prevent nozzle ejection failure and deterioration of image quality. [Means for solving the problem]

[0007] In one embodiment, the printing apparatus includes a serial inkjet head that reciprocates in a direction perpendicular to the transport direction of the medium and prints by ejecting ink from a nozzle, and a control unit that reciprocates the inkjet head in the direction of movement, and the control unit controls the inkjet head to print an image divided into a forward printing range that is printed during the forward movement and a return printing range that is printed during the return movement, depending on the position in the direction of movement. [Effects of the Invention]

[0008] According to the above embodiment, in a printing apparatus equipped with a serial inkjet head, nozzle ejection failures and deterioration of image quality can be prevented. [Brief explanation of the drawing]

[0009] [Figure 1] This is a perspective view showing a printing apparatus according to one embodiment. [Figure 2] This is a cross-sectional view showing a printing apparatus according to one embodiment. [Figure 3] This is a right side view showing an inkjet head and the like in one embodiment. [Figure 4] This is a block diagram showing the main control configuration of a printing apparatus according to one embodiment. [Figure 5] This is an explanatory diagram (part 1) illustrating the forward printing range and return printing range in one embodiment. [Figure 6] This is an explanatory diagram (part 2) illustrating the forward printing range and return printing range in one embodiment. [Figure 7] This is an explanatory diagram (part 3) illustrating the forward printing range and return printing range in one embodiment. [Figure 8] This is an explanatory diagram illustrating the forward and return printing ranges in a comparative example. [Modes for carrying out the invention]

[0010] A printing apparatus 1 according to one embodiment of the present invention will be described below with reference to the drawings.

[0011] Figures 1 and 2 are perspective and cross-sectional views of the printing apparatus 1.

[0012] Figure 3 is a right side view showing the inkjet head 30, etc.

[0013] Figure 4 is a block diagram showing the main control configuration of the printing apparatus 1.

[0014] Note that the front-to-back, up-and-down, and left-to-right directions shown in Figures 1 to 3 and Figures 5 to 8 (described later) are examples where the transport direction D1 of the medium M is the front direction and the movement direction D2 of the inkjet head 30 is the left-to-right direction. For example, the front-to-back and left-to-right directions are horizontal directions, and the up-and-down direction is vertical directions.

[0015] As shown in Figures 1 and 2, the printing device 1 comprises a housing 10 and a base 20. As shown in Figure 3, the printing device 1 also comprises an inkjet head 30 (see Figures 2 and 3), a platen 40, a suction fan 50, a drive roller 61, and a nip roller 62. As shown in Figure 4, the printing device 1 also comprises a heating unit 81, a winding drive unit 82, a roller drive unit 83, a control unit 91, a storage unit 92, a display unit 93, an input unit 94, and an interface unit 95. Furthermore, as shown in Figure 5, which will be described later, the printing device 1 also comprises a guide 70.

[0016] As shown in Figure 1, the housing 10 has a cylindrical shape extending in the direction D2 of movement of the inkjet head 30, which is parallel to the width direction of the medium M, and houses the inkjet head 30 and the like, as shown in Figure 2. The housing 10 is provided with a front opening 11 as an exit for the medium M and a rear opening 12 as an inlet for the medium M. The medium M is, for example, roll paper.

[0017] As shown in FIGS. 1 and 2, the base 20 has a right leg portion 21 (see FIG. 1), a left leg portion 22, a winding holding portion 23, and a feeding holding portion 24 (see FIG. 2).

[0018] As shown in FIG. 1, the right leg portion 21 supports the lower right portion of the housing 10, and the left leg portion 22 supports the lower left portion of the housing 10. The right leg portion 21 and the left leg portion 22 face each other.

[0019] The winding holding portion 23 is supported by the front portions of the right leg portion 21 and the left leg portion 22. As shown in FIG. 2, the winding holding portion 23 has a winding shaft 23a for winding the medium M. This winding shaft 23a is a drive shaft that rotates counterclockwise in FIG. 2 by the drive of a winding drive portion 82 (see FIG. 4) described later, thereby winding up the slack of the medium M conveyed by the drive roller 61.

[0020] The feeding holding portion 24 is supported by the rear portions of the right leg portion 21 and the left leg portion 22. The feeding holding portion 24 has a feeding shaft 24a for feeding the medium M. Note that the feeding shaft 24a can be called a driven shaft because the medium M is fed by the conveying force of the drive roller 61 described later.

[0021] As shown in FIG. 5, the inkjet head 30 is a carriage having head units 31 to 35. In FIG. 5, since the head units 31 to 35 are arranged inside the inkjet head 30, the head units 31 to 35 are illustrated by broken lines (hidden lines).

[0022] Head units 31-35 are arranged in the main scanning direction (movement direction D2) at the same position in the sub-scanning direction (transport direction D1). Head units 31-35 are arranged, for example, according to the color of ink to be ejected, and have nozzles 31a, 32a, 33a, 34a, and 35a arranged in the sub-scanning direction (transport direction D1). In other words, head units 31-35 (inkjet heads 30) have multiple nozzle rows that eject ink of different colors. The inks are, for example, water-based inks, solvent inks, or base inks used for underprinting.

[0023] Head units 31-35 print by moving back and forth in the movement direction D2 each time the medium M is transported in the transport direction D1 by one-quarter of the length of the print area. In the example in Figure 5, the image P has four parts (first part Pa, second part Pb, third part Pc, and fourth part Pd) consisting of identical white letters "D" (only partially shown) (non-printing areas). In the example in Figure 5, the first to fourth parts Pa to Pd are in a state where the downstream quarter in the transport direction D1 is printed four times (shown with the darkest halftone pattern), the next downstream quarter is printed three times (shown with the next darkest halftone pattern), the next downstream quarter is printed twice (shown with the next darkest halftone pattern), and the upstream quarter is printed once (shown with the lightest halftone pattern). In other words, head units 31-35 perform printing in four passes. Furthermore, the image P may be the same image repeatedly printed in the transport direction D1 of the medium M, or it may be different images repeatedly printed (variable printing) in the transport direction D1 of the medium M.

[0024] As shown in Figure 3, the platen 40 is located below the inkjet head 30. The platen 40 attracts the medium M with air (indicated by arrows) drawn in by the suction fan 50. The platen 40 is made of, for example, aluminum and is heated by a heating unit 81 (see Figure 4), which will be described later. This heats the medium M and dries the ink that has landed on the medium M. Note that the platen 40 and suction fan 50 are not shown in Figure 2.

[0025] The drive roller 61 rotates counterclockwise in Figure 3 by the drive of the roller drive unit 83 (see Figure 4), which will be described later, thereby conveying the medium M in the conveying direction D1. The nip roller 62 is positioned above the drive roller 61 and conveys the medium M by nipping it together with the drive roller 61. The nip roller 62 is a driven roller that is biased toward the drive roller 61.

[0026] The guide 70 shown in Figure 5 is a rail, shaft, etc., that extends in the direction of movement D2. The inkjet head 30 moves in the direction of movement D2 along the guide 70. Therefore, the inkjet head 30 has an actuator (head drive unit), such as a motor, to move the inkjet head 30 in the direction of movement D2.

[0027] The heating unit 81 shown in Figure 4 is, for example, a heater located at the bottom of the platen 40, which heats the platen 40, thereby heating the medium M being conveyed on the platen 40.

[0028] The winding drive unit 82 is an actuator such as a motor that drives the winding shaft 23a of the winding holding unit 23.

[0029] The roller drive unit 83 is an actuator such as a motor that drives the drive roller 61.

[0030] The control unit 91 has a processor (e.g., CPU: Central Processing Unit) that functions as an arithmetic processing unit that controls the operation of the printing device 1, and controls the operation of each part of the printing device 1, such as moving the inkjet head 30 back and forth in the movement direction D2. As will be described in more detail later, the control unit 91 controls the inkjet head 30 to print the image P by dividing it into a forward printing range A1, which is printed when moving forward (forward movement direction D2a), and a return printing range A2, which is printed when moving back (return movement direction D2b), depending on the position in the movement direction D2.

[0031] The memory unit 92 may include, for example, a ROM (Read Only Memory), which is a read-only semiconductor memory in which a predetermined control program is pre-recorded, or a RAM (Random Access Memory), which is a semiconductor memory that can be written to and read at any time and used as a working memory area as needed when the processor executes various control programs, or a hard disk drive.

[0032] The display unit 93 includes a display, lamps, etc., that show various types of information.

[0033] The input unit 94 is an operation key, touch panel, or the like that accepts user input information. A single operation panel may function as both the display unit 93 and the input unit 94.

[0034] The interface unit 95 exchanges various types of information with external devices such as user terminals that transmit print data to the printing device 1.

[0035] Next, we will explain how to determine the forward printing range A1 and the return printing range A2 shown in Figure 5.

[0036] The control unit 91 controls the inkjet head 30 to print the image P in two separate areas, a forward printing area A1 where printing is performed during forward movement and a return printing area A2 where printing is performed during return movement, depending on the position in the movement direction D2. The forward printing area A1 is the area where the inkjet head 30 prints while moving in the forward movement direction D2a, and the return printing area A2 is the area where the inkjet head 30 prints while moving in the return movement direction D2b. The control unit 91 may determine the forward printing area A1 and the return printing area A2 for each head unit 31 to 35, that is, for each nozzle row (nozzles 31a to 35a) that ejects ink of different colors.

[0037] In the example in Figure 5, the image P consists of four parts separated from each other in the direction of movement D2 (first part Pa, second part Pb, third part Pc, and fourth part Pd). The control unit 91 should determine the forward printing range A1 and the return printing range A2 such that the boundary between the forward printing range A1 and the return printing range A2 is a position where the number of ink ejecting nozzles 31a to 35a is relatively small. In the example in Figure 5, the control unit 91 determines the first part Pa and the third part Pc as the forward printing range A1, and the second part Pb and the fourth part Pd as the return printing range A2, because there are no ink ejecting nozzles 31a to 35a in the gaps between the first part Pa and the second part Pb, the gap between the second part Pb and the third part Pc, and the gap between the third part Pc and the fourth part Pd.

[0038] As a result, as shown by the thick arrows in Figure 5, the range in which the inkjet head 30 does not eject ink when moving in the forward direction D2a is upstream of the first part Pa in the forward direction D2a (non-ejection time t1), between the first part Pa and the third part Pc (non-ejection time t2), and downstream of the third part Pc in the forward direction D2a (non-ejection time t3). Similarly, the range in which the inkjet head 30 does not eject ink when moving in the return direction D2b is upstream of the fourth part Pd in ​​the return direction D2b (non-ejection time t4), between the fourth part Pd and the second part Pb (non-ejection time t5), and downstream of the second part Pb in the return direction D2b (non-ejection time t6).

[0039] In the example shown in Figure 6, image P consists of the letters "ABCDEF" located in the center of the movement direction D2, and straight lines located above and below these letters (upstream and downstream in the transport direction D1) that extend across the entire movement direction D2. In this case, if one of the "ABCDEF" letter portion and the other non-letter portion were determined to be the forward printing range A1 and the other the return printing range A2, the usage ratio of nozzles 31a to 35a would differ between the forward printing range A1 and the return printing range A2. Therefore, in the example shown in Figure 6, the control unit 91 divides the letter portion into the forward printing range A1 and the return printing range A2, and also divides the non-letter portion into the forward printing range A1 and the return printing range A2, in order to make the usage ratio of nozzles 31a to 35a as close to the same as possible. The usage ratio of nozzles 31a to 35a is, for example, the ratio of nozzles 31a to 35a used during forward printing or return printing to the total number of nozzles 31a to 35a used (for example, 50:50 or 40:60). The control unit 91 should select forward printing range A1 and return printing range A2 with a usage ratio of 40:60 rather than forward printing range A1 and return printing range A2 with a usage ratio of 30:70, so that the usage ratio of nozzles 31a to 35a in the forward printing range A1 and return printing range A2 approaches the same.

[0040] As a result, as shown by the thick arrows in Figure 6, the range in which the inkjet head 30 does not eject ink when moving in the forward direction D2a is upstream of the textless portion upstream of the forward direction D2a (forward printing range A1) (non-ejection time t11), in the text portion of the return printing range A2 (non-ejection time t12), and downstream of the text portion of the text portion of the forward direction D2a (non-ejection time t13). Similarly, the range in which the inkjet head 30 does not eject ink when moving in the return direction D2b is upstream of the textless portion upstream of the return direction D2b (forward printing range A1) (non-ejection time t14), downstream of the text portion of the return printing range A1 (non-ejection time t15), and downstream of the text portion of the return printing range A2 (non-ejection time t16).

[0041] Incidentally, the longer the ink non-ejection time of the inkjet head 30, the more likely the ink in nozzles 31a to 35a is to dry out. Therefore, for example, if the sum of non-ejection time t13 and non-ejection time t14 (and the stop time after forward movement and before return movement) or the sum of non-ejection time t16 and non-ejection time t11 (and the stop time after return movement and before forward movement) in the example of Figure 6 above exceeds a specified upper limit, the control unit 91 should further subdivide the areas without text and determine the forward printing range A1 and the return printing range A2 so as not to exceed the upper limit.

[0042] In the example shown in Figure 7, image P is identical to image P shown in Figure 6, and consists of the letters "ABCDEF" located in the center of the movement direction D2, and straight lines located above and below these letters (upstream and downstream in the transport direction D1) that extend across the entire movement direction D2. In the example shown in Figure 7, the control unit 91 divides the letter portion into a forward printing range A1 and a return printing range A2, and divides the upstream and downstream letterless portions in the forward movement direction D2a into forward printing range A1 and return printing range A2, respectively.

[0043] As a result, as shown by the thick arrows in Figure 7, the range in which ink is not ejected when the inkjet head 30 moves in the forward direction D2a is upstream of the textless portion upstream of the forward direction D2a (forward printing range A1) (non-ejection time t21), in the return printing range A2 in the textless portion upstream of the forward direction D2a (non-ejection time t22), in the return printing range A2 in the text portion (non-ejection time t23), and downstream of the textless portion downstream of the forward direction D2a (non-ejection time t24) compared to the forward printing range A1. Furthermore, the range in which ink is not ejected when the inkjet head 30 moves in the return direction D2b is upstream of the textless portion (return printing range A2) upstream of the return direction D2b (non-ejection time t25), in the textless portion upstream of the return direction D2b, in the forward printing range A1 (non-ejection time t26), in the text portion, in the forward printing range A1 (non-ejection time t27), and downstream of the textless portion downstream of the return direction D2b, beyond the return printing range A2 (non-ejection time t28).

[0044] In the embodiment described above, the printing apparatus 1 includes a serial inkjet head 30 that reciprocates in a movement direction D2 perpendicular to the transport direction D1 of the medium M and performs printing by ejecting ink from nozzles 31a to 35a, and a control unit 91 that reciprocates the inkjet head 30 in the movement direction D2. The control unit 91 also controls the inkjet head 30 to print an image P by dividing it into a forward printing range A1, which prints during the forward movement, and a return printing range A2, which prints during the return movement, depending on the position in the movement direction D2.

[0045] By the way, as shown in the comparative example in Figure 8, if the same image P (first to fourth parts Pa to Pd) as shown in Figure 5 is all within the forward printing range A1, then, as indicated by the thick arrows in Figure 8, the area in which ink is not ejected when the inkjet head 30 moves in the forward movement direction D2a is all except the first to fourth parts Pa to Pd (non-ejection time t31 to t35), and the area in which ink is not ejected when the inkjet head 30 moves in the return movement direction D2b is the entire movement (non-ejection time t36). In this way, if the non-ejection time of ink becomes long, such as during the non-ejection time t36, the ink in nozzles 31a to 35a dries out, causing ejection problems (such as non-ejection). In contrast, in this embodiment, the inkjet head 30 prints the image P by dividing it into a forward printing range A1, which is printed during the forward movement, and a return printing range A2, which is printed during the return movement. This shortens the non-ejection time and suppresses the drying of the ink in nozzles 31a to 35a, thereby preventing ejection defects. Furthermore, compared to an embodiment in which the inkjet head 30 prints at the same position (for example, the first to fourth sections Pa to Pd) during both the forward and return movements, the ink that has landed on the medium M is allowed to dry sufficiently before the ink lands in the next pass, preventing deterioration of image quality. Therefore, according to this embodiment, in a printing apparatus 1 equipped with a serial-type inkjet head 30, ejection defects of nozzles 31a to 35a and deterioration of image quality can be prevented.

[0046] Furthermore, in this embodiment, the control unit 91 determines the forward printing range A1 and the return printing range A2 such that the boundary between the forward printing range A1 and the return printing range A2 is at a position where the number of ink ejecting nozzles 31a to 35a is relatively small.

[0047] This makes it possible to reduce the visibility of image unevenness caused by misalignment of the bullet points at the boundary between the forward printing area A1 and the return printing area A2. Therefore, it is possible to further prevent deterioration of image quality.

[0048] In this embodiment, the inkjet head 30 has multiple nozzle rows (rows of nozzles 31a to 35a in each of the head units 31 to 35) that eject ink of different colors from each other, and the control unit 91 determines the forward printing range A1 and the return printing range A2 for each nozzle row (nozzles 31a to 35a).

[0049] This makes it possible to reduce the visibility of image unevenness caused by misalignment of the bullet points at the boundary between the forward printing area A1 and the return printing area A2. Therefore, it is possible to further prevent deterioration of image quality.

[0050] Furthermore, in this embodiment, the control unit 91 determines the forward printing range A1 and the return printing range A2 such that the usage ratio of nozzles 31a to 35a in the forward printing range A1 and the return printing range A2 approaches the same.

[0051] In this way, by making the total number of nozzles 31a to 35a used in the forward printing area A1 and the return printing area A2 similar, the ink non-ejection time is extended, which suppresses the drying of the ink in nozzles 31a to 35a, while making it easier for the ink that has landed on the medium M to dry. Therefore, it is possible to further prevent ejection failures of nozzles 31a to 35a and deterioration of image quality.

[0052] In this embodiment, the control unit 91 determines the forward printing range A1 and the return printing range A2 so that the ink non-ejection time of the inkjet head 30 does not exceed a specified upper limit.

[0053] Therefore, the ink non-discharge time is extended, which suppresses the drying of ink in nozzles 31a to 35a. Consequently, it is possible to further prevent discharge failures in nozzles 31a to 35a.

[0054] In the above explanation, an example was given in which multiple forward printing ranges A1 and return printing ranges A2 are set in the movement direction D2 of the inkjet head 30. However, it is sufficient to set one or more forward printing ranges A1 and return printing ranges A2. However, if many forward printing ranges A1 and return printing ranges A2 are set, the number of boundaries where image unevenness is likely to occur due to misalignment of ink droplets increases. Therefore, it is preferable to set the number of forward printing ranges A1 and return printing ranges A2 to be less than or equal to a specified number, depending on how easily the ink dries. In addition, the control unit 91 may pre-determine the forward printing ranges A1 and return printing ranges A2 regardless of the content of the image P in order to simplify control.

[0055] Furthermore, the above explanation described examples where the forward printing area A1 and the return printing area A2 are located separately (see Figure 5) and examples where they are located side by side without any gaps (see Figures 6 and 7). However, in order to make the image unevenness caused by the misalignment of the projectiles at the boundary between the forward printing area A1 and the return printing area A2 less noticeable, the forward printing area A1 and the return printing area A2 may partially overlap at the boundary.

[0056] Furthermore, the above description described examples of determining the forward printing range A1 and return printing range A2, which are common to the entire inkjet head 30, as well as examples of determining the forward printing range A1 and return printing range A2 for each head unit 31-35 (a row of nozzles ejecting inks of different colors). However, the forward printing range A1 and return printing range A2 may also be determined for each nozzle 31a-35a, or for each group of multiple nozzles 31a-35a. For example, the boundary between the forward printing range A1 and the return printing range A2 may be shifted by the number of print dots for each single nozzle 31a-35a, or the forward printing range A1 and return printing range A2 may be determined for each single nozzle 31a-35a so that the negative ejection time does not exceed a specified upper limit, or the forward printing range A1 and return printing range A2 may be determined for the upstream half and the downstream half of the inkjet head 30 in the transport direction D1. In addition, the inkjet head 30 may eject ink of a single color.

[0057] Furthermore, in the above explanation, the control unit 91 explained, as a criterion for determining the forward printing range A1 and the return printing range A2, that the boundary between the forward printing range A1 and the return printing range A2 is a position where the number of ink-ejecting nozzles 31a to 35a is relatively small, that the usage ratio of nozzles 31a to 35a in the forward printing range A1 and the return printing range A2 approaches the same, and that the ink non-ejection time of the inkjet head 30 does not exceed a specified upper limit. However, other criteria such as the upper limit of the forward printing range A1 and the return printing range A2, and the ink ejection amount of nozzles 31a to 35a may be adopted. Moreover, it is desirable that at least one of the above criteria be adopted, and it is even more desirable that multiple criteria be adopted.

[0058] Examples of using multiple criteria include tentatively determining the forward print range A1 and return print range A2 using one criterion and then modifying and finalizing them using other criteria, or determining the forward print range A1 and return print range A2 by considering multiple criteria simultaneously. An example of modifying the forward printing range A1 and return printing range A2, which were tentatively determined based on one criterion, using another criterion is to tentatively determine multiple boundaries between the forward printing range A1 and return printing range A2 based on the fact that the boundary between the forward printing range A1 and return printing range A2 is a position where the number of ink-ejecting nozzles 31a to 35a is relatively small (an example of one criterion). From the multiple boundaries tentatively determined, a combination of boundaries that brings the usage ratio closest to the same is selected based on the fact that the usage ratio of nozzles 31a to 35a in the forward printing range A1 and return printing range A2 approaches the same (an example of another criterion), and the position of the boundary (i.e., the forward printing range A1 and return printing range A2) is determined. Another example of determining the forward printing range A1 and return printing range A2 by considering multiple criteria simultaneously is to select a position where the number of criteria that are satisfied is large for each arbitrary position in the direction of movement D2, and then determine the position of the boundary (i.e., the forward printing range A1 and return printing range A2).

[0059] Furthermore, in the above description, the medium M is a roll of paper that is transported by unwinding and winding, and this roll of paper can be said to be a medium M with a wide width in the movement direction D2 of the inkjet head 30. In this embodiment, even if the travel distance in the movement direction D2 is long, the forward printing range A1 and the return printing range A2 can be determined, thereby effectively preventing ejection failures of the nozzles 31a to 35a. Therefore, this embodiment is particularly suitable when roll paper is used as the medium M. However, the medium M may be a single sheet of paper, or it may be made of a material other than paper, such as a plastic material. Also, in the above description, the ink that has landed on the medium M is forcibly dried by heating by a heating unit 81, etc., but the drying of the ink that has landed on the medium M may be done by natural drying.

[0060] Furthermore, although the inkjet head 30 performs printing in four passes as described above, the number of times the inkjet head 30 reciprocates at each position on the medium M may be any number of passes or more.

[0061] It should be noted that the present invention is not limited to the embodiments described above, and the components can be modified and implemented in practice without departing from the spirit of the invention. Furthermore, various inventions can be formed by appropriately combining the multiple components disclosed in the embodiments described above. For example, all the components shown in the embodiments may be combined as appropriate. It goes without saying that various modifications and applications are possible without departing from the spirit of the invention. The invention described in the specification and drawings of this application is listed below.

[0062] [Note 1] A serial inkjet head performs printing by reciprocating in a direction perpendicular to the media transport direction and ejecting ink from nozzles, The system includes a control unit that moves the inkjet head back and forth in the direction of movement, The control unit controls the inkjet head to print the image in two separate areas, depending on its position in the direction of movement: a forward printing area for printing during forward movement and a return printing area for printing during return movement. A printing apparatus characterized by the following features.

[0063] [Note 2] The control unit determines the forward printing range and the return printing range such that the boundary between the forward printing range and the return printing range is at a position where the number of nozzles ejecting ink is relatively small. The printing apparatus described in Appendix 1, characterized by the features described herein.

[0064] [Note 3] The inkjet head has multiple rows of nozzles that eject inks of different colors from each other. The control unit determines the forward printing range and the return printing range for each nozzle row. A printing apparatus as described in Appendix 1 or 2, characterized by the above.

[0065] [Note 4] The control unit determines the forward printing range and the return printing range such that the nozzle usage ratio in the forward printing range and the return printing range approaches the same. A printing apparatus characterized by any one of the appendices 1 to 3.

[0066] [Note 5] The control unit determines the forward printing range and the return printing range so that the ink non-ejection time of the inkjet head does not exceed a specified upper limit. A printing apparatus characterized by any one of the appendices 1 to 4. [Explanation of Symbols]

[0067] 1 Printing device 10 cabinets 11 Front opening 12 Rear opening 20 base 21 Right leg 22 Left leg 23 Winding and holding section 23a Winding shaft 24 Unwinding and holding section 24a Unwinding shaft 30 inkjet heads 31-35 Head Unit 31a~35a Nozzles 40 Platen 50 Suction Fan 61 Drive roller 62 Nipple Roller 70 Guide 81 Heating section 82 Winding drive unit 83 Roller drive unit 91 Control Unit 92 Memory section 93 Display section 94 Input section 95 Interface section A1 Outbound print range A2 return print range D1 Conveying direction D2 Movement direction D2a Outbound direction of travel D2b Return journey direction M medium P Image Pa Part 1 Pb 2nd part Pc 3rd part Pd 4th part

Claims

1. A serial inkjet head performs printing by reciprocating in a direction perpendicular to the media transport direction and ejecting ink from nozzles, The system includes a control unit that moves the inkjet head back and forth in the direction of movement, The control unit controls the inkjet head to print the image in two separate areas, depending on its position in the direction of movement: a forward printing area for printing during forward movement and a return printing area for printing during return movement. A printing apparatus characterized by the following features.

2. The control unit determines the forward printing range and the return printing range such that the boundary between the forward printing range and the return printing range is at a position where the number of nozzles ejecting ink is relatively small. The printing apparatus according to claim 1, characterized in that it is a printing apparatus.

3. The inkjet head has multiple rows of nozzles that eject inks of different colors from each other. The control unit determines the forward printing range and the return printing range for each nozzle row. The printing apparatus according to claim 1, characterized in that it is a printing apparatus.

4. The control unit determines the forward printing range and the return printing range such that the nozzle usage ratio in the forward printing range and the return printing range approaches the same. The printing apparatus according to claim 1, characterized in that it is a printing apparatus.

5. The control unit determines the forward printing range and the return printing range so that the ink non-ejection time of the inkjet head does not exceed a specified upper limit. The printing apparatus according to claim 1, characterized in that it is a printing apparatus.

Images