JP2014004779A - Inkjet printer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce apparent image degradation even when landing position displacement is caused in droplets discharged from nozzles existing on a conveying direction downstream side.SOLUTION: An inkjet printer 1 includes a plurality of nozzle rows in a printing direction to be a direction for executing printing on a paper sheet P and executes printing by causing the plurality of nozzle rows to discharge ink on the basis of image data while relatively moving the paper sheet P and the plurality of nozzle rows. In the inkjet printer 1, ink is supplied in such a manner that ink with relatively higher brightness is discharged in the nozzle rows provided toward a downstream side of the plurality of nozzle rows.

Description

  The present invention relates to an ink jet printing apparatus that performs printing by relatively moving an ink jet head that ejects ink from nozzles based on image data and a medium.

  In general, an inkjet printing apparatus that performs printing by relatively moving an inkjet head that ejects ink from nozzles and a medium based on image data is well known.

  Among such ink jet printing apparatuses, there is also a line type ink jet printing apparatus provided with a plurality of ink jet heads that eject ink in a direction orthogonal to the transport direction of the printing paper transported on the transport path surface.

  Patent Document 1 proposes a droplet ejection device that controls each head so that the ejection speed of a droplet with a smaller droplet volume is faster when a plurality of types of droplets with different droplet volumes are ejected onto a sheet. Has been.

JP 2010-173178 A

  However, in the droplet discharge device described in Patent Document 1, since the droplets with a smaller droplet amount are controlled for each head so that the discharge speed becomes faster, landing position deviation may occur in the droplets on the downstream side of the head. there were.

  In a line-type inkjet printing apparatus, a total of two rows of nozzles are often provided on the upstream side and the downstream side in the paper transport direction (sub-scanning direction).

  In such a case, an air current is generated by the sheet conveyed directly under the head. When ink is continuously ejected from the nozzle provided on the upstream side in the transport direction, the ink droplets are ejected with a self-air stream, and thus act as a wall that blocks the air stream by transport (hereinafter referred to as this formation). The simulated pseudo wall is called the ink wall). The airflow generated by the conveyance caused by the formation of the ink wall forms a flow that entrains the formed ink wall.

  As described above, when an air flow that entrains the formed ink wall is generated, the landing position shift occurs in the liquid droplets ejected from the nozzles existing on the downstream side in the transport direction, thereby causing image degradation.

  The present invention has been made in view of the above problems, and an ink jet printing apparatus that reduces apparent image deterioration even when a landing position shift occurs in droplets ejected from nozzles existing downstream in the transport direction. The purpose is to provide.

  In order to achieve the above object, a first feature of an ink jet printing apparatus according to the present invention includes an ink jet head comprising a plurality of nozzle rows adjacent to a printing direction, which is a direction in which printing is performed on a recording medium, In an inkjet printing apparatus that performs printing by ejecting ink from the plurality of nozzle rows based on image data while relatively moving a recording medium and the inkjet head, a downstream side of the plurality of nozzle rows Ink is supplied so that ink with relatively high brightness is ejected as the nozzle row.

  A second feature of the inkjet printing apparatus according to the present invention is that a plurality of the inkjet heads are provided in the printing direction, the number of nozzle rows constituting the single inkjet head is a division number, and the lightness of the plurality of inks When the lightness group is a set obtained by dividing the plurality of inks according to the number of divisions, among the plurality of nozzle rows constituting the single inkjet head, the most upstream nozzle row includes the plurality of nozzle rows. Any one color ink belonging to the lightness group having the lowest lightness among the inks is supplied, and any one color ink belonging to the lightness group having the highest lightness is supplied to the most downstream nozzle row. is there.

  According to a third aspect of the inkjet printing apparatus of the present invention, the inkjet printing apparatus includes an inkjet head including a plurality of nozzle rows adjacent to a printing direction, which is a direction in which printing is performed on the recording medium, and the recording medium, the inkjet head, In the inkjet printing apparatus that executes printing by ejecting ink from the plurality of nozzle rows based on the image data while relatively moving the nozzle row, the most upstream nozzle row of the plurality of nozzle rows is the most Ink with low brightness is supplied to the nozzle array on the most downstream side with the highest brightness.

  A fourth feature of the ink jet printing apparatus according to the present invention is that, based on the image data for the upstream nozzle row of the plurality of nozzle rows, the downstream nozzle row existing downstream of the upstream nozzle row. And a control means for controlling the ejection of the droplets so as to increase the propulsive force of the droplets ejected from the ink.

  According to the first feature of the ink jet printing apparatus according to the present invention, since the ink is supplied so that the relatively lighter ink is discharged toward the downstream nozzle row of the plurality of nozzle rows, the printing direction Even when the landing position deviation occurs in the droplets ejected from the nozzles existing on the downstream side, it is possible to reduce the apparent image degradation.

  According to the second feature of the ink jet printing apparatus according to the present invention, a plurality of ink jet heads are provided in the printing direction, and the number of nozzle rows constituting a single ink jet head is defined as the number of divisions, depending on the lightness of the plurality of inks. When a group obtained by dividing a plurality of inks by the number of divisions is a lightness group, the lightness of the plurality of inks from the most upstream nozzle row is the highest among the plurality of nozzle rows constituting a single inkjet head. Printing is performed because any one color ink belonging to the low lightness group is discharged so that any one color ink belonging to the lightness group having the highest lightness is ejected from the most downstream nozzle row. Even when the landing position deviation occurs in the droplets ejected from the nozzles existing on the downstream side in the direction, it is possible to reduce the apparent image degradation.

  According to the third feature of the ink jet printing apparatus according to the present invention, among the plurality of nozzle rows, the ink having the lowest brightness from the nozzle row on the most upstream side and the brightness from the nozzle row on the most downstream side are highest. Since ink is supplied, the apparent image degradation can be reduced most when the landing position deviation occurs in the droplets ejected from the nozzles existing downstream in the printing direction.

  According to the fourth feature of the inkjet printing apparatus of the present invention, the downstream side present downstream of the upstream nozzle row based on the image data for the upstream nozzle row of the plurality of nozzle rows in the printing direction. Since the ejection of droplets is controlled so as to increase the driving force of the droplets ejected from the nozzle rows, the upstream of the printing direction generated from the plurality of nozzle rows and the recording medium relatively moved immediately below them Even when the airflow downstream from the nozzle changes so as to wrap around the ink wall formed by ejecting droplets (ink droplets) from a nozzle row, the landing positions of the droplets due to these airflows Misalignment can be prevented. In particular, it is possible to prevent the landing position deviation of the droplets on the recording medium related to the downstream nozzle row.

It is a top view of the inkjet head unit with which the inkjet printing apparatus which is Example 1 of this invention is provided. It is the figure which showed typically the droplet discharged from the nozzle of the inkjet head 110 with which the inkjet printing apparatus 1 which is Example 1 of this invention is provided, and the produced | generated airflow. (A) is the figure seen from the conveyance direction upstream of the paper, (b) is a perspective view. (A) is the figure which showed arrangement | positioning of the nozzle of the inkjet head with which the inkjet printing apparatus 1 which is Example 1 of this invention is provided, (b) is the nozzle of the upstream of the inkjet head shown to (a). FIG. 4C is a diagram illustrating the position of ink ejected from the row, and FIG. 5C is a diagram illustrating the position of ink ejected from a nozzle row on the downstream side of the inkjet head. It is the figure explaining landing position shift by the ink jet printer which is Example 1 of the present invention. (A) is the figure which showed arrangement | positioning of the nozzle of an inkjet head, (b) is the nozzle arrange | positioned in the both ends and the center part among the nozzle rows of the upstream head shown to Fig.4 (a), It is the figure which showed the shift | offset | difference of the landing in the main scanning direction discharged from the nozzle arrange | positioned in the both ends and center part among the nozzle rows of a downstream head, (c) is the nozzle of the upstream head shown to (a). The figure which showed the shift | offset | difference of the landing in the sub-scanning direction discharged from the nozzle arrange | positioned at both ends and a center part among nozzles, and the nozzle arrange | positioned at a both ends and center part among nozzle rows of a downstream head It is. It is a top view of the inkjet head unit with which the inkjet printing apparatus which is Example 2 of this invention is provided. It is a functional block diagram which shows the function structure of the inkjet printing apparatus which is Example 3 of this invention. It is the flowchart which showed the process sequence by the inkjet printing apparatus which is Example 3 of this invention. It is the figure which showed an example of the drive waveform of the drive voltage applied to the inkjet head with which the inkjet printing apparatus which is Example 3 of this invention is provided. (A) shows a drive waveform when discharging from the inkjet head at a low discharge speed, and (b) shows a drive waveform when discharging from the inkjet head at a medium discharge speed. c) shows a driving waveform when ejecting from the inkjet head at a high ejection speed. It is the figure explaining conversion of the image data in the inkjet printing apparatus which is Example 4 of this invention. (A) shows an example of image data read by the image reading unit, and (b) and (c) show an example of converted image data. It is the figure which showed an example of the nozzle of the inkjet head with which the inkjet printing apparatus which is a modification of Example 4 of this invention is provided.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the following, description will be given using a line-type inkjet printing apparatus having a plurality of inkjet heads in the conveyance direction (sub-scanning direction) of the printing paper. In this case, the printing direction described in the claims of the present application is: This is synonymous with the conveyance direction (sub-scanning direction) of the printing paper.

  In Embodiment 1 of the present invention, a plurality of staggered patterns are arranged in the direction (sub-scanning direction) and the direction perpendicular to the printing paper (sub-scanning direction), and ink is arranged in two rows upstream and downstream in the conveyance direction. An ink-jet head provided with nozzles (nozzle rows) for ejecting ink, and printing images, characters, and the like by ejecting ink from the upstream and downstream nozzles of the ink-jet head toward the paper based on image data The ink jet printing apparatus 1 will be described as an example.

<Configuration of Inkjet Printing Apparatus 1>
FIG. 1 is a plan view of an inkjet head unit provided in an inkjet printing apparatus 1 that is Embodiment 1 of the present invention.

  The inkjet unit 11 includes a plurality of line-type inkjet heads 110 to 116 arranged in a plurality of lines in the main scanning direction, that is, a direction orthogonal to the conveyance direction of the paper P.

  The sheet P is printed by ejecting ink from the plurality of inkjet heads 110 to 116 while being conveyed in the sub-scanning direction directly below the inkjet unit 11. Here, the sub-scanning direction corresponds to the printing direction of the present application.

  The inkjet unit 11 includes inkjet heads of cyan (C), black (K), magenta (M), and yellow (Y). Specifically, the inkjet unit 11 includes inkjet heads 110a to 110f that store cyan (C) ink, and inkjet heads 112a to 112f and 114a to 114f that store black (K) and yellow (Y) ink. And inkjet heads 116a to 116f storing magenta (M) ink.

  The inkjet heads 110a, 110c, and 110e and the inkjet heads 110b, 110d, and 110f are staggered in the sub-scanning direction so that cyan (C) ink can be ejected without a gap in the main scanning direction of the conveyed paper P. They are arranged in two rows so as to form a lattice.

  As will be described later, the inkjet heads 110a to 110f are provided with nozzle rows in two rows, one on the upstream side and one on the downstream side in the transport direction of the paper P. The ink jet heads 110a to 110f are provided with an ink reservoir chamber for containing cyan (C) ink, and a piezo element is disposed in the ink reservoir chamber. Then, when a drive voltage is applied to the piezo element with a predetermined drive waveform, cyan (C) ink is ejected from the nozzle row communicating with the ink reservoir.

  Similarly, the inkjet heads 112, 114, and 116 are arranged in two rows in a staggered pattern in the sub-scanning direction without any gap in the main-scanning direction of the conveyed paper P, and each of the black (K) , Magenta (M), yellow (Y), one or two colors of ink are ejected.

  FIG. 2 is a diagram schematically illustrating droplets discharged from the nozzles of the inkjet head 112 included in the inkjet printing apparatus 1 according to the first embodiment of the present invention and the generated airflow. (A) is the figure seen from the conveyance direction (printing direction) upstream of the paper P, (b) is a perspective view.

  As shown in FIGS. 2A and 2B, it is assumed that droplets D are continuously ejected from three upstream nozzles at the center of the inkjet head 112 in the main scanning direction. At this time, ink droplets are formed in a pseudo manner by continuously ejecting the droplets D.

  When the paper P is conveyed in the sub-scanning direction, airflows F1 to F6 are generated. Of these, the airflows F3 and F4 flowing through the central portion in the main scanning direction flow around the formed ink wall. Form. On the other hand, the airflows F1, F2, F5, and F6 form a linear flow in the sub-scanning direction without being affected by the ink wall.

  In addition, the inkjet heads 112a to 112f are provided with nozzles for ejecting ink at lower portions on the upstream side and the downstream side in the transport direction of the paper P.

  FIG. 3A is a diagram showing the arrangement of nozzles of the inkjet head 112a, and FIG. 3B shows the position of ink ejected from the upstream nozzle row of the inkjet head 112a shown in FIG. (C) is a diagram showing the position of the ink ejected from the nozzle row on the downstream side of the inkjet head 112a. The nozzles of the inkjet heads 110, 112, 114, and 116 all have the same physical structure.

  As shown in FIG. 3A, the inkjet head 112a includes an upstream head 112aa provided with a nozzle on the upstream side in the transport direction of the paper P, and a downstream head 112ab provided with a nozzle on the downstream side in the transport direction of the paper P. It has. The upstream head 112aa and the downstream head 112ab are heads having the same configuration, and the upstream head 112aa and the downstream head 112ab are configured so that ink can be ejected without a gap in the main scanning direction of the conveyed paper P. It is provided at a position shifted in the scanning direction.

  In the upstream head 112aa, nozzle rows 112a1 are arranged in one row in the main scanning direction, and in the downstream head 112ab, nozzle rows 112a2 are arranged in one row in the main scanning direction.

  Then, ink is ejected from the nozzle row 112a1 and the nozzle row 112a2 while the paper P is transported in the transport direction (sub-scanning direction), so that print dots (pixels) are printed on the paper P.

  At this time, as the paper P is transported, an air flow is generated in the transport direction (sub-scanning direction). When the ink wall formed by the continuous discharge of ink from the upstream head 112aa is generated by the air flow generated by the conveyance, the path is blocked by the ink wall. For this reason, the airflow caused by the conveyance immediately below the ink wall changes to an airflow that flows around from the left and right sides (both sides in the main scanning direction) of the ink wall.

  As a result, the liquid droplets ejected from the nozzle row 112a2 of the downstream head 112ab receive an airflow that is pushed in the X1 direction and the X2 direction.

  Therefore, as shown in FIG. 3B, the droplets ejected from the upstream nozzle regularly land, but on the other hand, as shown in FIG. 3C, the airflow flowing in the X1 direction and the X2 direction Due to the influence, the liquid droplets ejected from the nozzle 110a2 of the downstream head 110ab land at positions shifted in the X1 direction and the X2 direction. Therefore, unevenness and fading can be produced in the finish, and the print image is deteriorated.

  FIG. 4 is a diagram for explaining landing position deviation by the ink jet printing apparatus 1 that is Embodiment 1 of the present invention.

  4A is a diagram showing the arrangement of the nozzles of the inkjet head 112a, and FIG. 4B is a diagram illustrating both ends and the center of the nozzle row 112a1 of the upstream head 112aa shown in FIG. 4A. Nozzle 112a1a, nozzle 112a1b, nozzle 112a1c, and nozzle array 112a2 of downstream head 112ab, and nozzle 112a2a, nozzle 112a2b, and nozzle 112a2c arranged at both ends and in the central portion. FIG. 4C is a diagram showing landing deviation, and FIG. 4C shows the nozzles 112a1a, 112a1b, and nozzles arranged at both ends and the center of the nozzle row 112a1 of the upstream head 112aa shown in FIG. 112a1c and both ends of the nozzle row 112a2 of the downstream head 112ab and the middle Parts in arranged nozzles 112A2a, nozzle 112A2b, a diagram showing the deviation of landing in the sub scanning direction discharged from the nozzle 112A2c.

  As shown in FIG. 4B, the landing positions of the droplets ejected from the nozzles 112a2a and 112a2c arranged at both ends of the nozzle row 112a2 of the downstream head 112ab are shifted in the main scanning direction. .

  On the other hand, as shown in FIG. 4C, in the sub-scanning direction, there is a significant positional deviation with respect to the landing positions of the droplets ejected from either the nozzle row 112a1 of the upstream head 112aa or the nozzle row 112a2 of the downstream head 112ab. Cannot be confirmed.

  Therefore, as described above, it is estimated that the liquid droplets ejected from the nozzle row 112a2 of the downstream head 112ab have landed at positions shifted in the X1 direction and the X2 direction due to the influence of the airflow flowing in the X1 direction and the X2 direction. it can.

  Therefore, in the inkjet printing apparatus 1 that is Embodiment 1 of the present invention, the droplets discharged from the nozzle row 112a2 of the downstream head 112ab are displaced in the X1 direction and the X2 direction due to the influence of the airflow flowing in the X1 direction and the X2 direction. In order to make unevenness and faintness inconspicuous even when landed at a different position, the nozzle of the upstream head is configured to be supplied with ink having relatively low lightness. Specifically, black (K) ink having the lowest lightness among cyan (C), black (K), magenta (M), and yellow (Y) is ejected from the nozzle row 112a1 of the upstream head 112aa. Ink is supplied so that yellow (Y) ink having the highest brightness is ejected from the nozzle row 112a2 of the downstream head 112ab. Further, the ink is ejected from the nozzle 114a1 of the upstream head 114aa so that black (K) ink having the lowest lightness among cyan (C), black (K), magenta (M), and yellow (Y) is ejected. Ink is supplied so that yellow (Y) ink having the highest brightness is ejected from the nozzle 114a2 of the downstream head 114ab.

  The inkjet head 110 is supplied with cyan (C) ink, and the inkjet head 116 is supplied with magenta (M) ink. Therefore, for the inkjet heads 110 and 116, the ink ejected from the nozzles of the upstream head and the ink ejected from the downstream head have the same color.

  As described above, the inkjet printing apparatus 1 according to the first embodiment of the present invention is configured such that yellow (Y) ink having relatively high brightness is supplied to the nozzles of the downstream head. Since this yellow (Y) ink has high brightness, even when the liquid droplets discharged from the nozzle row of the downstream head land on the position shifted in the X1 direction and the X2 direction due to the influence of the air current, it is difficult to stand out. . Therefore, unevenness and fading are not noticeable in the finish, and apparent print image deterioration can be prevented.

  In the first embodiment of the present invention, the nozzle row of the upstream heads of the inkjet heads 112 and 114 has black (B) with the lowest brightness among cyan (C), black (K), magenta (M), and yellow (Y). K) ink is supplied, yellow (Y) ink having the highest brightness is supplied to the nozzle row of the downstream head, cyan (C) ink is supplied to the inkjet head 110, and inkjet head 116 is supplied to the inkjet head 116. The magenta (M) ink is supplied. However, the present invention is not limited to this, and it is only necessary to supply ink having relatively high brightness to the nozzles of the downstream head. For example, as shown in the following modification, ink is supplied. You may do it.

<Modification of Example 1>

  As in Modification 1 shown in Table 1, the black (K) ink having the lowest brightness and the cyan (C) ink having the higher brightness are adjacent to each other in a single inkjet head. While supplying to one nozzle row, you may make it discharge from a some inkjet head. This is because the landing position deviation of cyan (C) ink is more difficult to recognize than the landing position deviation of black (K) ink, and it is possible to prevent the appearance of the printed image from deteriorating.

  As in Modification 2, the black (K) ink having the lowest lightness and the yellow (Y) ink having the highest lightness are supplied to two adjacent nozzle rows in a single inkjet head. The ink is discharged from a plurality of inkjet heads, and other magenta (M) ink and cyan (C) ink are supplied to two adjacent nozzle rows in a single inkjet head, You may make it discharge from an inkjet head.

  Further, as in the second and third modifications, cyan (C) ink and magenta (M) ink may be supplied to either the upstream or downstream nozzle row. This is because there is no significant difference in brightness, and whether or not landing deviation is noticeable differs depending on the image data and the person observing.

  In the first embodiment of the present invention, ink having relatively low brightness is supplied to the upstream nozzle row of the two nozzle rows, and ink having relatively high brightness is supplied to the downstream nozzle row. However, the present invention is not limited to this.

  The number of nozzle rows is not limited to two, and the upstream nozzle row of the plurality of nozzle rows may be configured to be supplied with ink having a lower lightness. For example, when the inkjet head is composed of four nozzle rows and black (K), cyan (C), magenta (M), and yellow (Y) ink is supplied, the printing direction is upstream to downstream. Ink is supplied to each nozzle row so that ink with high brightness is supplied in the order of black (K), cyan (C), magenta (M), and yellow (Y).

  As described above, even in this case, inks other than the most upstream and downstream nozzle rows, that is, cyan (C) and magenta (M) inks may be supplied in the order of magenta (M) and cyan (C). .

  In the first embodiment of the present invention, the inkjet printing apparatus 1 that discharges four colors of cyan (C), black (K), magenta (M), and yellow (Y) has been described as an example. However, the present invention is not limited thereto.

  In Embodiment 2 of the present invention, an inkjet printing apparatus that discharges six colors of light magenta (LM) and light cyan (LC) in addition to cyan (C), black (K), magenta (M), and yellow (Y) is provided. An example will be described.

  FIG. 5 is a plan view of an inkjet head unit 11A provided in the inkjet printing apparatus 1 according to the second embodiment of the present invention.

  The ink jet unit 11 </ b> A includes a plurality of line type ink jet heads 110 to 120 arranged in a plurality of lines in the main scanning direction, that is, a direction orthogonal to the transport direction of the paper P.

  The sheet P is printed by ejecting ink from the plurality of inkjet heads 110 to 120 while being conveyed in the sub-scanning direction immediately below the inkjet unit 11A.

  The ink jet unit 11A has six color ink jet heads of cyan (C), black (K), magenta (M), yellow (Y), light magenta (LM), and light cyan (LC). Specifically, the inkjet unit 11A includes inkjet heads 110a to 110f and 112a to 112f that store cyan (C) and light cyan (LC) ink, and an inkjet that stores black (K) and yellow (Y) ink. Heads 114a to 114f, 116a to 116f, and inkjet heads 118a to 119f and 120a to 120f storing magenta (M) and light magenta (LM) inks are provided.

  The inkjet heads 110a to 110f are provided with nozzle rows in two rows, one on the upstream side and one on the downstream side in the transport direction of the paper P.

  Similarly, the inkjet heads 112, 114, 116, 118, and 120 are arranged in two rows in a staggered pattern in the sub-scanning direction without any gap in the main-scanning direction of the conveyed paper P, respectively. As described above, one or two inks of cyan (C), black (K), magenta (M), yellow (Y), light magenta (LM), and light cyan (LC) are ejected.

  In the inkjet printing apparatus 1 according to the second embodiment of the present invention, the most common of cyan (C), black (K), magenta (M), and yellow (Y) from the nozzle row 114a1 of the upstream head 114aa of the inkjet head 114. Ink is supplied so that black (K) ink with low lightness is discharged, and black (K) ink with the lowest lightness is discharged from the nozzle row 116a1 of the upstream head 116aa of the inkjet head 116. Supply ink.

  Also, yellow (Y) ink having the highest lightness among cyan (C), black (K), magenta (M), and yellow (Y) is ejected from the nozzle row 114a2 of the downstream head 114ab of the inkjet head 114. Ink is supplied so that yellow (Y) ink having the highest brightness is discharged to the nozzle row 116a2 of the downstream head 116ab of the inkjet head 116.

  Further, among the six colors of ink, the remaining cyan (C), magenta (M), light magenta (LM), and light cyan (LC) are supplied with relatively high lightness to the nozzle row of the downstream head. Configure as follows. Specifically, light magenta (LM) and light cyan (LC) inks are ejected from the nozzle array of the downstream head so that cyan (C) and magenta (M) inks are ejected from the nozzle array of the upstream head. Ink is supplied.

  For example, ink is supplied from the nozzle row 110 a 1 of the upstream head 110 aa of the inkjet head 110 and the nozzle row 112 a 1 of the upstream head 112 aa of the inkjet head 112 so that cyan (C) ink is ejected, and downstream of the inkjet head 110. Ink is supplied from the nozzle row 110a2 of the head 110ab and the nozzle row 112a2 of the downstream head 112ab of the inkjet head 112 so that light cyan (LC) ink is ejected.

  Further, ink is supplied from the nozzle row 118 a 1 of the upstream head 118 aa of the inkjet head 118 and the nozzle row 120 a 1 of the upstream head 120 aa of the inkjet head 120 so that magenta (M) ink is ejected, and downstream of the inkjet head 118. Ink is supplied from the nozzle row 118a2 of the head 118ab and the nozzle row 112a2 of the downstream head 112ab of the inkjet head 120 so that light magenta (LM) ink is ejected.

  As described above, according to the inkjet printing apparatus 1 that is Embodiment 2 of the present invention, in addition to cyan (C), black (K), magenta (M), and yellow (Y), light magenta (LM), light cyan The inkjet printing apparatus 1 that discharges six colors (LC) is also configured so that ink having a relatively high brightness is supplied to the nozzle array of the downstream head. Even when the liquid droplets discharged from the liquid droplets land at positions shifted in the X1 direction and the X2 direction, it is possible to obtain a printed matter in which landing deviation is not noticeable. Therefore, unevenness and fading are not noticeable in the finish, and apparent print image deterioration can be prevented.

<Modification of Example 2>
Further, as a modification of the second embodiment of the present invention, a set in which the number of nozzle rows constituting a single inkjet head is a division number and a plurality of inks are divided by the division number according to the lightness of the plurality of inks. When a lightness group is selected, one of the plurality of nozzle rows constituting a single ink jet head from the most upstream nozzle row has any one color ink belonging to the lightness group having the lowest lightness among the plurality of inks. The ink may be supplied so that any one color ink belonging to the lightness group having the highest lightness is ejected from the most downstream nozzle row.

  Specifically, in addition to cyan (C), black (K), magenta (M), and yellow (Y), light magenta (LM) and light cyan (LC) are ordered in the order of lightness, and this lightness order. Is divided into the same number of groups as the number of nozzle rows constituting a single inkjet head.

  In Embodiment 2 of the present invention, since one inkjet head is composed of two nozzle rows, the K, C, and M lightness groups with low lightness and the lightness groups with high lightness Y, LM, and LC are used. Divided into two brightness groups.

  In one inkjet head, one nozzle selected from K, C, and M is applied to the nozzle row upstream in the printing direction, and Y, LM, and LC are selected from the nozzle row downstream in the printing direction. One ink is applied, and these inks are supplied for each nozzle row of each inkjet head. In this case, if the ink supplied to each nozzle row of one inkjet head is represented by (upstream side, downstream side), (K, LC), (K, LM), (K, Y), (C, LC) ), (C, LM), (C, Y), (M, LC), (M, LM), and (M, Y).

  As a result, the inkjet printing apparatus 1 that discharges six colors of light magenta (LM) and light cyan (LC) in addition to cyan (C), black (K), magenta (M), and yellow (Y) is also finished. Unevenness and faintness are not noticeable, and apparent print image deterioration can be prevented.

  In the first embodiment of the present invention, the configuration is such that ink having a relatively high brightness is supplied to the nozzle row of the downstream head, so that the liquid droplets discharged from the nozzle row of the downstream head are affected by the air current. The inkjet printing apparatus 1 that obtains a printed matter in which landing deviation is not noticeable even when landing at positions shifted in the X1 direction and the X2 direction has been described as an example.

  In the inkjet printing apparatus 1 that is Embodiment 3 of the present invention, the upstream head of the inkjet head 110 is configured to increase the propulsive force of the droplets discharged from the nozzle 110a2 downstream of the upstream nozzle 110a1 of the inkjet head 110. An example of the ink jet printing apparatus 1 in which droplets discharged from both the upstream and downstream nozzles regularly land regardless of the airflow flowing in the X1 direction and the X2 direction by independently controlling the 110aa and the downstream head 110ab, respectively. Will be described. In addition, about the inkjet head unit with which the inkjet printing apparatus 1 which is Example 3 of this invention is provided, since it is the same as the inkjet head unit with which the inkjet printing apparatus 1 which is Example 1 of this invention shown in FIG. Description is omitted.

  In the inkjet printing apparatus 1 according to the third embodiment of the present invention, the propulsive force of the droplets ejected from the downstream nozzle (row) is based on the image data corresponding to the upstream nozzle (row) of the inkjet head 110. The ejection of ink droplets (droplets) from these nozzle rows is controlled so as to increase more than the upstream nozzles (rows). More specifically, the ink ejected from the upstream nozzles (rows) is independently controlled by independently controlling the ejection of ink droplets from the upstream nozzles (rows) and the downstream nozzles (rows) of the inkjet head 110. When an ink wall is generated by a droplet, the downstream side generated by the influence of the airflow is increased by increasing the propulsive force of the ink droplet ejected from the downstream nozzle (row) affected by the landing position by the ink wall. Misalignment of the droplets ejected from the nozzles is prevented.

<Functional Configuration of Inkjet Printing Apparatus 1>
FIG. 6 is a functional configuration diagram illustrating a functional configuration of the inkjet printing apparatus 1 that is Embodiment 3 of the present invention.

  As shown in FIG. 6, the inkjet printing apparatus 1 includes an image reading unit 2, a paper feeding unit 3, a printing unit 4, a paper discharge unit 5, an operation panel unit 6, a control unit 7, a RAM 71, and a ROM 72. And.

  The image reading unit 2 is provided on the upper part of the ink jet printing apparatus 1, photoelectrically reads image data from a document as a copy object by a device such as a scanner, and supplies the image data to the control unit 7. Note that the image data is also supplied from a terminal connected to the image forming apparatus.

  The paper feed unit 3 picks up and conveys sheets (recording media) P stacked on a paper feed table (not shown) one by one, corrects skew feeding, and supplies the paper to the printing unit 4 at a predetermined timing.

  The printing unit 4 includes the above-described inkjet unit 11 and a conveyance unit (not shown) that conveys the paper P supplied from the paper supply unit 3 to the inkjet unit 11. The inkjet unit 11 prints an image by ejecting ink and adhering it to the paper P based on the image data supplied from the control unit 7.

  The paper discharge unit 5 stores the paper P on which an image is printed by the inkjet unit 11.

  The operation panel unit 6 is provided on the upper part of the ink jet printing apparatus 1 and inputs a display / input panel 61, a start key for starting printing, a stop key for stopping printing, the number of prints, and the like. And various operation keys such as a numeric keypad (none of which are shown), and supply operation signals based on user operations to the control unit 7.

  The display / input panel 61 of the operation panel unit 6 includes a pressure-sensitive or electrostatic transparent touch panel disposed on the front surface and a liquid crystal display panel (none of which is shown) disposed on the back surface of the touch panel. doing. The user can perform various setting input operations by directly touching the surface of the touch panel with a finger or the like while viewing the display screen of the liquid crystal display panel.

  The RAM 71 is composed of a volatile semiconductor or the like, and stores data necessary for the control unit 7 to execute various processes.

  The ROM 72 is composed of a nonvolatile semiconductor or the like and stores various control programs executed by the control unit 7.

  The control unit 7 includes a determination unit 75, a device control unit 76, and an image processing unit 77 in terms of its functions.

  The determination unit 75 determines whether or not the impact of ink droplets ejected from the downstream nozzles is affected by the ejection of ink from the upstream nozzles of the inkjet head 110. More specifically, whether or not an ink wall is formed by ink droplets ejected from the nozzles on the upstream side of the inkjet head 110 is determined from the image data relating to the print job.

  Based on the determination result by the determination unit 75, the image processing unit 77 increases the number of droplets of the image data corresponding to the nozzles on the downstream side of the inkjet head 110 for pixels with a small number of droplets to be ejected. Convert.

  When the determination unit 75 determines that an ink wall is formed, the device control unit 76 increases the propulsive force of the droplets ejected from the nozzles on the downstream side of the nozzles on the upstream side of the inkjet head 110. The nozzles on the upstream side and the nozzles on the downstream side of the inkjet head 110 are independently controlled.

  For example, the device control unit 76 increases the upstream head 110aa and the downstream head 110ab so as to increase the propulsive force of the droplets discharged from the nozzle 110a2 on the downstream side of the nozzle 110a1 on the upstream side of the cyan (C) inkjet head 110. And are controlled independently. Specifically, the device control unit 76 individually controls each nozzle of the upstream head 110aa and individually controls each nozzle of the downstream head 110ab.

  In addition, the device control unit 76 generates a propulsive force of yellow (Y) droplets discharged from the downstream nozzle 112a2 from the black (K) droplets discharged from the upstream nozzle 112a1 of the inkjet head 112. The upstream head 110aa and the downstream head 110ab are independently controlled so as to increase.

  Similarly, the device controller 76 propels the yellow (Y) droplets ejected from the downstream nozzle 114a2 from the black (K) droplets ejected from the upstream nozzle 114a1 of the inkjet head 114. So that the upstream head 114aa and the downstream head 114ab are independently controlled.

  Further, the device control unit 76 increases the propulsive force of the droplets ejected from the nozzle 116b2 on the downstream side of the nozzle 116b1 on the upstream side of the magenta (M) inkjet head 116, and the upstream head 116ba and the downstream head 116bb. And are controlled independently.

  In order to simplify the control, it is possible not to perform the above-described control for the yellow (Y) inkjet head. This is because yellow (Y) is difficult to visually recognize, and even if the landing position is deviated, it is not noticeable and often does not cause a problem in print quality.

<Operation of Inkjet Printing Apparatus 1>
Next, the operation of the inkjet printing apparatus 1 that is Embodiment 3 of the present invention will be described.

  FIG. 7 is a flowchart showing a processing procedure performed by the inkjet printing apparatus 1 according to the third embodiment of the present invention. Note that the inkjet heads 110 to 116 perform the same control, and thus the inkjet head 110 will be described as an example.

  As shown in FIG. 7, the control unit 7 determines whether printing is requested (step S101). Specifically, the control unit 7 determines whether or not an operation signal requesting print processing is supplied from the operation panel unit 6 by a user operation.

  If it is determined in step S101 that printing is requested (in the case of YES), the determination unit 75 of the control unit 7 determines that 60 nozzles adjacent to the upstream head (upstream head) are simultaneously based on the supplied image data. It is determined whether or not to discharge (step S103).

  If it is determined in step S103 that the 60 nozzles adjacent to the upstream head do not discharge simultaneously (in the case of NO), the device control unit 76 of the control unit 7 sets normal printing conditions (step S105). Specifically, the device control unit 76 performs the inkjet operation so that the propulsive force of the droplets ejected from the upstream nozzle and the downstream nozzle of the inkjet head 110 is the same (without intentionally changing). The ejection of ink droplets from the upstream nozzle and the downstream nozzle of the head 110 is controlled.

  On the other hand, if it is determined in step S103 that 60 nozzles adjacent to the upstream head are to be ejected simultaneously (in the case of YES), the determination unit 75 of the control unit 7 reads the supplied image data (for example, read by the image reading unit 2). It is determined whether or not the printing rate of the received image data is 80 (%) or more (step S107).

  If it is determined in step S107 that the printing rate of the supplied image data is 80 (%) or more, the determination unit 75 of the control unit 7 discharges more than the pixel corresponding to 10 mm in the transport direction (printing direction). It is determined whether or not to perform (step S109).

  Specifically, when the processing conditions of steps S103, S107, and S109 are satisfied, an ink wall is formed with the ink ejected immediately below the inkjet head 110.

  As described above, when the paper P is transported by a transport unit (not shown), an air flow is generated in the transport direction (printing direction), and this air flow is formed by continuously ejecting ink from the upstream head 110aa. The path is blocked by the ink wall. Therefore, the airflow caused by the conveyance immediately below the ink wall changes into an airflow that wraps around from the left and right sides (both sides in the main scanning direction) of the ink wall.

  Therefore, the liquid droplets discharged from the nozzle 110a2 of the downstream head 110ab receive an airflow that is pushed in the X1 direction and the X2 direction.

  Therefore, in the first embodiment of the present invention, when the processing conditions of steps S103, S107, and S109 are not satisfied, an ink wall is not generated, and the impact on the landing position deviation of the ink droplet from the downstream head 110ab is relatively small. And the process of step S105 is executed.

  On the other hand, in step S109, when it is determined that more than the pixel corresponding to 10 mm is ejected in the sub-scanning direction (in the case of YES), the device control unit 76 of the control unit 7 sets the printing condition for the propulsive force improvement control ( Step S111). Specifically, the device control unit 76 of the control unit 7 generates a drive waveform of a drive voltage applied to the inkjet head 110 in order to eject ink from the nozzle 110a2 of the downstream head 110ab, and ink from the nozzle 110a1 of the upstream head 110aa. Control is performed to increase the driving force of the ejected droplets from the driving waveform of the driving voltage applied to the inkjet head 110 for ejection.

  FIG. 8 is a diagram illustrating an example of a drive waveform of a drive voltage applied to the inkjet head 110. FIG. 8A shows a drive waveform when discharging from the inkjet head 110 at a low discharge speed, and FIG. 8B shows a drive waveform when discharging from the inkjet head 110 at a medium discharge speed. FIG. 8C shows a drive waveform when ejecting from the inkjet head 110 at a high ejection speed.

  As shown in FIG. 8A, when discharging from the inkjet head 110 at a low discharge speed, the device control unit 76 of the control unit 7 generates a positive voltage pulse V1 for contracting the ink chamber from the time t2 to the time t5. Apply for a while.

  Further, as shown in FIG. 8B, when ejecting from the inkjet head 110 at a medium ejection speed, the device control unit 76 of the control unit 7 expands the ink chamber in order to urge ejection for one drop. The negative voltage pulse V2 to be applied is applied from the time t1 to the time t2, and then the positive voltage pulse V1 for contracting the ink chamber is applied from the time t4 to the time t5.

  Furthermore, as shown in FIG. 8C, when ejecting from the inkjet head 110 at a high ejection speed, the device control unit 76 of the control unit 7 expands the ink chamber to urge ejection for one drop. After applying the negative voltage pulse V2 from the time t1 to the time t2, the positive voltage pulse V1 for contracting the ink chamber is applied from the time t3 to the time t5, which is earlier than the time t4.

  In this way, the device control unit 76 of the control unit 7 changes the drive waveform so that the speed of the liquid droplets ejected from the nozzle 110a2 of the downstream head 110ab becomes the liquid droplets ejected from the nozzle 110a1 of the upstream head 110aa. The drive waveform of the drive voltage applied to the inkjet head 110 can be controlled so as to be faster than this speed.

  For example, the device control unit 76 of the control unit 7 shows the drive waveform of the drive voltage applied to the inkjet head 110 in order to discharge ink from the nozzle 110a2 of the downstream head 110ab, as shown in FIG. 8B. The printing condition is set as the driving waveform of the driving voltage applied to the inkjet head 110 to eject ink from the nozzle 110a1 of the upstream head 110aa as the low-speed driving waveform shown in FIG. .

  Note that the device control unit 76 generates a medium-speed driving waveform shown in FIG. 8B for a part of the nozzle 110a2 of the downstream head 110ab that affects the landing position due to the ink wall generated by the ejection of the upstream head 110ab. Printing conditions may be set, and the printing conditions may be set as the low-speed driving waveform shown in FIG. 8A for the remaining nozzles including the upstream head 110aa. That is, it may be determined whether or not each nozzle is affected by the ink wall, and the ejection of ink droplets may be controlled independently for each independent nozzle.

  In this way, the device control unit 76 of the control unit 7 generates the drive waveform of the drive voltage applied to the inkjet head 110 in order to eject the ink from the nozzle 110a2 of the downstream head 110ab, and the ink from the nozzle 110a1 of the upstream head 110aa. The ejection waveform is set so as to increase the driving force of the ejected droplet from the drive waveform of the drive voltage applied to the inkjet head 110 for ejection, and the ejection of the ink droplet is controlled.

  Returning to FIG. 7, the device control unit 76 of the control unit 7 executes the printing process in step S105 or S111 based on the set printing condition (step S113).

  Thereby, according to the inkjet printing apparatus 1 which is Example 3 of this invention, the speed of the droplet discharged from the nozzle 110a2 of the downstream head 110ab is higher than the speed of the droplet discharged from the nozzle 110a1 of the upstream head 110aa. Since the speed is increased, the influence of the air flow that is blocked by the ink wall formed by the continuous ejection of ink from the upstream head 110aa and changes around the ink wall from the left and right (main scanning direction) can be reduced. In addition, the liquid droplets ejected from any of the nozzles on the downstream side can be landed at an appropriate position on the paper P, and a good printed matter with no printing unevenness or fading can be generated.

  Furthermore, even when the liquid droplets ejected from the nozzle array of the downstream head land at positions shifted in the X1 direction and the X2 direction due to the reduced airflow, the inkjet printing apparatus according to the third embodiment of the present invention. According to No. 1, since it is configured such that yellow (Y) ink having relatively high brightness is supplied to the nozzles of the downstream head, deviation in landing is not noticeable, and unevenness and fading are not noticeable in the finish. It is possible to prevent the appearance of the printed image from deteriorating.

  In the third embodiment of the present invention, the drive waveform of the drive voltage applied to the inkjet head 110 for ejecting ink from the nozzle 110a2 of the downstream head 110ab is set to the inkjet waveform for discharging the ink from the nozzle 110a1 of the upstream head 110aa. The inkjet printing apparatus 1 that controls the driving waveform to increase the propulsive force of the ejected droplets from the driving waveform of the driving voltage applied to the head 110 has been described as an example. However, the present invention is not limited to this.

  Droplets ejected from the drive voltage applied to the inkjet head 110 to eject ink from the nozzle 110a2 of the downstream head 110ab and from the drive voltage applied to the inkjet head 110 to eject ink from the nozzle 110a1 of the upstream head 110aa The driving voltage may be controlled to increase the driving force.

  For example, if the drive voltage applied to the inkjet head 110 to eject ink from the nozzle 110a1 of the upstream head 110aa is V1 (V), it is applied to the inkjet head 110 to eject ink from the nozzle 110a2 of the downstream head 110ab. The printing condition is set with the driving voltage set to 1.2V1 (V).

  Thereby, the propulsive force of the droplets discharged from the nozzle 110a2 of the downstream head 110ab is increased, that is, the velocity of the droplets discharged from the nozzle 110a2 of the downstream head 110ab is discharged from the nozzle 110a1 of the upstream head 110aa. Therefore, the influence of the air flow that changes by moving around the ink wall from the left and right (main scanning direction) is blocked by the ink wall formed by the continuous ejection of ink from the upstream head 110aa. Since it can be reduced, the liquid droplets ejected from both the upstream and downstream nozzles can be landed at appropriate positions on the paper P, and a good printed matter free from printing unevenness and blurring can be generated.

  As described above, when the speed of the liquid droplets discharged from the nozzle 110a2 of the downstream head 110ab is made higher than the speed of the liquid droplets discharged from the nozzle 110a1 of the upstream head 110aa, the device control unit 76 sets the nozzle of the downstream head 110ab. The ink ejection timing is controlled in accordance with the ejection speed of the ink ejected from 110a2. Specifically, the device control unit 76 delays the timing of ejecting the ink droplets by an amount corresponding to the increased velocity of the droplets ejected from the nozzle 110a2 so that the ink droplets land at an appropriate position. Control.

  Thereby, even if the speed of the droplet discharged from the nozzle 110a2 of the downstream head 110ab is different from the speed of the droplet discharged from the nozzle 110a1 of the upstream head 110aa, the droplet can be landed at an appropriate position. it can.

  Moreover, in the inkjet printing apparatus 1 which is Example 1 of this invention, the speed of the droplet discharged from the nozzle 110a2 which is a nozzle row of the downstream head 110ab is discharged from the nozzle 110a1 which is the nozzle row of the upstream head 110aa. Although the control is performed so as to be faster than the droplet speed, the unit to be controlled is not limited to the nozzle unit. You may make it control independently about every nozzle in a nozzle row.

  Furthermore, the device control unit 76 may determine the ejection timing based on the head gap that is the distance from the ejection surface of the inkjet head 110 to the paper P (the front surface). Specifically, the longer the head gap, the longer it takes to land, so the discharge timing may be controlled earlier.

  In the third embodiment of the present invention, the drive waveform of the drive voltage applied to the inkjet head 110 to eject ink from the nozzle 110a2 of the downstream head 110ab, and the inkjet head 110 to eject ink from the nozzle 110a1 of the upstream head 110aa. The inkjet printing apparatus 1 that controls the drive waveform to increase the propulsive force of the ejected droplets from the drive waveform of the drive voltage applied to the above has been described as an example, but is not limited thereto.

  In the fourth embodiment of the present invention, based on the determination result of the determination unit 75, the image data corresponding to the nozzle 110a2 of the downstream head 110ab is increased so that the number of droplets is increased for pixels with a small number of droplets to be discharged. The inkjet printing apparatus 1 that converts and independently controls the upstream side and the downstream side of the inkjet head 110 based on the converted image data will be described as an example. Since the inkjet heads 110 to 116 perform the same control, the inkjet head 110 will be described as an example.

  FIG. 9 is a diagram for explaining conversion of image data in the inkjet printing apparatus 1 according to the fourth embodiment of the present invention. (A) shows an example of image data read by the image reading unit 2, and (b) and (c) show an example of converted image data. The configuration of the inkjet head unit shown in FIG. 1 and the functional configuration shown in FIG.

  As shown in FIG. 9A, the image data read by the image reading unit 2 is, for example, multi-value drop data (drop values [0 to 5]) in a unit area portion of 3 pixels × 3 pixels. Expressed.

  Here, 1 drop data is generated at 5 locations in a unit area portion of 3 pixels × 3 pixels, and the density is 5 drops as a whole.

  Here, when the drop value is 1 or 2, since the ejected ink droplets are sparse, they are easily affected by the air flow, and naturally the ink wall formed by continuously ejecting ink from the upstream head 110aa It is also easily affected by airflow that changes from the left and right (main scanning direction).

  Therefore, in the ink jet printing apparatus 1 that is the fourth embodiment of the present invention, the ink wall is generated by the ejection from the upstream head 110aa, and the drop value of the image data ejected from the downstream head 110ab is 1 or 2. The image data is converted so that the drop value is increased to 3 or more, for example, while ensuring the density in the unit area portion.

  For example, as shown in FIG. 9B, the image processing unit 77 of the control unit 7 positions 5 drop data in the unit area portion of the central portion, and the drop data is set to 0 for the other unit area portions. As a whole, the pixel pattern is replaced with a pixel pattern having a density of 5 drops.

  In addition, the image processing unit 77 compares the threshold value with each pixel in the right direction in order from the upper left pixel, for example, as in the error diffusion method, and compares the error generated in the previous pixel. As shown in FIG. 9C, the 5 drop data may be positioned at a pixel in which 5 drops are accumulated.

  Then, the device control unit 76 of the control unit 7 independently controls the upstream nozzle and the downstream nozzle of the inkjet head 110 based on the image data converted by the image processing unit 77.

  As described above, according to the inkjet printing apparatus 1 that is Embodiment 4 of the present invention, image data corresponding to the nozzle 110a2 of the downstream head 110ab of the inkjet head 110 is liquidated for pixels with a small number of droplets to be ejected. Since the number of droplets is converted to increase and the upstream head 110aa and the downstream head 110ab of the inkjet head are independently controlled based on the converted image data, the droplets discharged from the nozzle 110a2 of the downstream head 110ab Is converted into droplets with a large drop value, and the droplets are densely packed. Therefore, the air flow changes so as to go around the ink wall formed by continuous ejection of ink from the upstream head 110aa from the left and right (main scanning direction). Can be reduced.

  As a result, the liquid droplets ejected from both the upstream and downstream nozzles can be landed at appropriate positions on the paper P, and a good printed matter free from printing unevenness and fading can be generated.

  Further, according to the inkjet printing apparatus 1 that is Embodiment 4 of the present invention, the upstream head 110aa and the downstream head 110ab of the inkjet head are independently controlled without changing the drive voltage and the drive waveform, so that energy consumption is reduced. Can be reduced.

  Note that the larger the drop value, the more densely ejected ink droplets become, and the more difficult it is to decelerate. Therefore, the speed of the ejected droplets is relatively faster than that with a small number of drops. Therefore, the device controller 76 controls the ink ejection timing according to the ejection speed based on the number of droplets ejected from the nozzle 110a2 of the downstream head 110ab. Specifically, the device controller 76 delays the discharge timing by an amount corresponding to an increase in the speed of the droplet discharged from the nozzle 110a2 (by an amount corresponding to an increase in the number of drops) so as to land at an appropriate position. Control to do.

  Thereby, even if the speed of the droplet discharged from the nozzle 110a2 of the downstream head 110ab and the speed of the droplet discharged from the nozzle 110a1 of the upstream head 110aa are relatively different due to the difference in the number of drops, it is appropriate. A droplet can be landed at a position.

  In the third and fourth embodiments of the present invention, when the processing conditions of steps S103, S107, and S109 are satisfied, this is blocked by the ink wall formed by the continuous ejection of ink from the upstream head 110aa. Although it is determined that the influence of the airflow that changes around the ink wall from the left and right (main scanning direction) has a large influence on the landing position deviation, the printing condition for the propulsive force improvement control is set, but this is not restrictive. Even when the processing conditions of steps S103, S107, and S109 are not satisfied, the printing conditions for the propulsive force improvement control may be set.

  In the first to fourth embodiments of the present invention, nozzles on the upstream side in the transport direction of the paper P are provided, the upstream head in which the nozzles are arranged in a line in the main scanning direction, and the nozzles on the downstream side in the transport direction of the paper P As an example, the inkjet printing apparatus 1 is arranged in two rows so that the combination with the downstream head in which the nozzles are arranged in one row in the main scanning direction is arranged in a staggered pattern in the sub scanning direction. Although explained, it is not limited to this.

  FIG. 10 is a diagram illustrating an example of nozzles of the inkjet head 110 provided in the inkjet printing apparatus 1 that is a modification of the fourth embodiment of the present invention.

  As shown in FIG. 10A, two rows of nozzles may be arranged in the printing direction on one ink jet head instead of the combination of the upstream head and the downstream head. Further, two or more nozzle rows may be arranged.

  In addition, as shown in FIG. 10B, each color is not arranged in two rows so as to form a staggered pattern in the sub-scanning direction, but from one end to the other end in the main scanning direction. Until then, they may be arranged in one row per color in the sub-scanning direction.

  Even in such a case, according to the inkjet printing apparatus 1 that is Embodiment 4 of the present invention, the propulsive force of the droplets discharged from the nozzle 110a2 on the downstream side of the nozzle 110a1 on the upstream side of the inkjet head 110 is increased. As described above, the upstream side nozzle 110a1 and the downstream side nozzle 110a2 of the inkjet head 110 are independently controlled. As a result, the propulsive force of the droplets ejected from the nozzle 110a2 of the downstream head 110ab is increased more than the propulsive force of the droplets ejected from the nozzle 110a1 of the upstream head 110aa, so that the air current that flows around the formed ink wall Regardless, droplets ejected from both the upstream and downstream nozzles can be landed at appropriate positions, and a good printed matter with no printing unevenness or fading can be generated.

  In addition, the inkjet head 110 described in FIG. 10A and FIG. 10B is applicable not only to the modified example of the fourth embodiment but also to all the above-described embodiments and modified examples. 10A and 10B corresponds to the drawing for explaining a case where the plurality of nozzle rows constituting the inkjet head described in the claims of the present application are two rows.

  In the first to fourth embodiments of the present invention, the control unit 7 determines that printing is requested when an operation signal for requesting printing processing is supplied from the operation panel unit 6 by a user operation. For example, the present invention is not limited thereto, and it may be determined that printing is requested when a print job is received from a terminal connected via a network.

  In the first to fourth embodiments of the present invention, a plurality of inkjet heads are arranged in a staggered manner in the main scanning direction (a direction perpendicular to the transport direction), and the line head is configured. The present invention can be similarly applied to a configuration in which a line head is constituted by a single scale-like inkjet head.

  In the first to fourth embodiments of the present invention, the line-type inkjet printing apparatus 1 including a plurality of inkjet heads 110 that eject ink in a direction orthogonal to the conveyance direction of the sheet P conveyed on the conveyance path surface is provided. Although described as an example, the present invention is not limited to this, and is of course applicable to a serial-type inkjet printing apparatus that prints on the paper P that is intermittently conveyed in the sub-scanning direction while the inkjet head 110 moves in the main-scanning direction. it can. Even in the case of a serial type ink jet printing apparatus, the air flow generated by moving the ink jet head 110 changes to an air flow that circulates around the ink wall ejected from the upstream nozzle row in the printing direction. This is because it affects the landing position of the ink droplets ejected from the nozzle array on the side. In the case of a serial type inkjet printing apparatus, the direction in which the inkjet head 110 moves, that is, the main scanning direction corresponds to the printing direction of the present application.

  As described above, any inkjet printing apparatus that includes a plurality of nozzle arrays that eject ink in the printing direction and that prints on a medium based on image data while relatively moving the plurality of nozzle arrays and the recording medium. The technique according to the present invention can also be applied to an inkjet printing apparatus.

DESCRIPTION OF SYMBOLS 1 ... Inkjet printer 2 ... Image reading part 3 ... Paper feed part 4 ... Printing part 5 ... Paper discharge part 6 ... Operation panel part 7 ... Control part 11 ... Inkjet unit 61 ... Display / input panel 71 ... RAM
72 ... ROM
75: Determination unit 76 ... Device control unit 77 ... Image processing unit 110a to 110f ... Inkjet head 110a1 ... Nozzle 110a2 ... Nozzle 110aa ... Upstream head 110ab ... Downstream head 110b1 ... Nozzle 110b2 ... Nozzle 110ba ... Upstream head 110bb ... Downstream head 112a- 112f, 114a-114f, 116a-116f, 118a-118f, 120a-120f ... Inkjet head

Claims (4)

An inkjet head comprising a plurality of nozzle rows adjacent to a printing direction, which is a direction in which printing is performed on a recording medium, while moving the recording medium and the inkjet head relatively, based on image data, In an inkjet printing apparatus that performs printing by discharging ink from a plurality of nozzle rows,
Ink jet printing apparatus, wherein ink is supplied such that ink having a relatively high brightness is ejected toward a downstream nozzle row of the plurality of nozzle rows. A plurality of the inkjet heads are provided in the printing direction,
When the number of nozzle rows constituting the single inkjet head is a division number, and a set obtained by dividing the plurality of inks by the division number according to the lightness of the plurality of inks is a lightness group, Among the plurality of nozzle rows constituting the ink jet head, the most upstream nozzle row has any one color ink belonging to the lightness group having the lowest lightness among the plurality of inks arranged on the most downstream nozzle row. The inkjet printing apparatus according to claim 1, wherein any one color ink belonging to the lightness group having the highest lightness is supplied. An inkjet head comprising a plurality of nozzle rows adjacent to a printing direction, which is a direction in which printing is performed on a recording medium, while moving the recording medium and the inkjet head relatively, based on image data, In an inkjet printing apparatus that performs printing by discharging ink from a plurality of nozzle rows,
Among the plurality of nozzle arrays, an ink having the lowest brightness is supplied to the nozzle array on the most upstream side, and an ink having the highest brightness is supplied to the nozzle array on the most downstream side. Based on the image data for the upstream nozzle row of the plurality of nozzle rows, the propulsive force of the droplets by the ink ejected from the downstream nozzle row existing downstream of the upstream nozzle row is increased. Control means for controlling the ejection of droplets,
The inkjet printing apparatus according to any one of claims 1 to 3, further comprising:

Images