JP5916312B2 - Inkjet printer and printing method thereof - Google Patents

Description

  The present invention relates to a multi-pass inkjet printer that performs printing by a plurality of passes and a printing method thereof.

  2. Description of the Related Art Conventionally, an ink jet printer including a print head having a plurality of nozzles arranged in the main scanning direction is known. One of the image forming methods using such an ink jet printer is an overlap recording method. The overlap recording method is a recording method in which an image on one main scanning line is formed using different nozzles in a plurality of scans in the main scanning direction.

  In addition, the above-described inkjet printer includes a model using a multi-pass method in which an image is formed by repeating scanning in the main scanning direction with nozzles corresponding to a plurality of passes.

  In a multi-pass inkjet printer, the nozzle row of the print head is divided into pass rows corresponding to the respective passes, and the corresponding passes are printed by a plurality of nozzles constituting each pass row. A print region formed by one scan is a band having a bandwidth. As a result, an image is completed at a portion where scanning for the number of passes is completed. For example, when an image is completed by four passes using a print head having four pass rows, the degree of completion of printing increases at a rate of 25% by each scan, and a total of four scans are performed. The image is completed (100%).

  When one scan is completed, the scan position of the print head is moved in the sub-scanning direction (direction orthogonal to the main scanning direction) by the bandwidth by the movement of the print head or the print medium. As a result, printing by the print head proceeds in the sub-scanning direction by a bandwidth for each scan.

  At this time, adjacent bands are printed in duplicate so that no gap is generated between the bands. If there are too many overlapping portions printed in this manner, the density becomes high and becomes conspicuous as band stripes. On the other hand, if the amount is too small, gaps are likely to occur due to variations in paper feed. For this reason, there arises a disadvantage that the printing image quality is not stable.

  As means for solving such inconvenience, Patent Document 1 describes that ink ejection is not performed repeatedly by scanning twice for the same dot in the overlapping portion as described above. Yes.

JP-A-60-107975 (released on June 13, 1985)

  By the way, in an inkjet printer, a composite head that forms a single print head by combining a plurality of print heads (head units) may be used. Such a composite head uses a general-purpose small print head that is easily available as a head unit, so that a long print head can be constructed at a low cost, or a staggered arrangement can be realized for each head. The unit can be offset.

  FIG. 12 shows an example of the configuration of the print head 101 composed of the composite head as described above. FIG. 13 is a plan view showing a printing state when printing is performed using the print head 101.

  As shown in FIG. 12, the print head 101 is configured by linearly joining two head units HU101 having the same configuration. The head unit HU101 has a plurality of nozzles 102 arranged at equal intervals in the sub-scanning direction Y. The nozzle 102 in one head unit HU101 is divided into two first pass rows P101 and second pass rows P102 corresponding to the first pass and the second pass, respectively. The nozzles 102 in the other head unit HU101 are divided into two third pass rows P103 and fourth pass rows P104 corresponding to the third pass and the fourth pass, respectively.

  When printing is performed by the print head 101 configured as described above, 25% printing is performed in the first scanning in the main scanning direction X by the first pass row P101 as shown in FIG. 50% printing is performed in the second scan by the two-pass row P102. Further, 75% printing is performed in the third scan by the third pass row P103 and 100% printing is performed in the fourth scan by the fourth pass row P104 in the same area, thereby completing an image. When each scan ends, the print head 101 or the print medium moves in the sub-scanning direction Y.

  In general, ejection of ink droplets by nozzles at both ends of a print head is not stable. Similarly, in the print head 101 as described above, the ejection of ink droplets by the nozzles 102 at both ends of each head unit HU 101 is not stable. For this reason, ink droplets ejected from the nozzles 102 at the adjacent ends between the second pass row P2 and the third pass row P3 may land on the print medium so as to interfere with each other. In this way, the portion where the ink droplet interferes appears as a band stripe having a higher density than the other portion in the printed image at the position indicated by the two-dot chain line in FIG.

  In order to mitigate such an ink droplet interference phenomenon, it is conceivable to mechanically adjust the mounting position of the print head 101 so as to improve the ink droplet landing accuracy. Examples of such adjustment include adjustment of the position of each head unit HU101 in the main scanning direction X and the sub-scanning direction Y of the print head 101. In this adjustment, the interval between the nozzles at the end of each head unit HU101 is adjusted by adjusting the interval between the head units HU101 constituting the print head 101 in the conveyance direction (sub-scanning direction Y) of the print medium. It is important to. Or as said adjustment, adjustment of the angle of each head unit HU101 of the print head 101 is mentioned. In this adjustment, the distance between the nozzles at the end of each head unit HU101 is adjusted by adjusting the angle so that each head unit HU101 rotates in both directions around a predetermined axis.

  However, if the distance between the nozzle surface of the print head 101 and the print medium is increased to some extent, the ink droplet interference phenomenon cannot be alleviated by the above adjustment, and there is a limit in suppressing the occurrence of band stripes. There is.

  The technique described in Patent Document 1 can be applied to reduce the ink droplet interference phenomenon because the density of the boundary part (overlapping part) between the bands can be adjusted. However, it is difficult to apply the above technique to alleviate the ink droplet interference phenomenon for the following reasons.

  The ink droplet interference phenomenon depends on a characteristic specific to the print head constituting the head unit HU101 (an ink droplet ejection characteristic by the nozzle 102 at the end), and such an interval between the print heads is close. If it happens. For this reason, the technique disclosed in Patent Document 1 that improves the image quality of the boundary portion between the bands cannot cope with the ink droplet interference phenomenon generated by the ink droplet interference between the print heads as described above.

  The present invention has been made in view of the above problems, and an object thereof is to improve the print image quality by suppressing the occurrence of band stripes in printing using a print head composed of a plurality of head units. It is aimed.

An ink jet printer according to the present invention relates to a print head in which a plurality of head units each having a nozzle array including a plurality of nozzles arranged along a sub-scanning direction orthogonal to the main scanning direction are combined, and print data associated with the nozzles. Discharge control means for controlling ink droplets to be ejected and movement for moving the print head in the main scanning direction and moving the print head relative to the print medium in the sub-scanning direction for each scan In order to solve the above problem, in order to solve the above-described problem, the print head is provided only between two adjacent head units. A non-ejection area that does not eject the ink droplets, and the non-ejection area length in the sub-scanning direction of the non-ejection area is two adjacent A band that is longer than the distance between adjacent nozzles between the nozzles, and the width of the nozzle array corresponding to the pass corresponding to the nozzle in the nozzle array of each head unit is formed on the print medium by printing the pass. The image is completed by overlapping the bands by printing all of the passes that are performed in the number of scans that is greater than the number of passes, and the moving unit is configured to pass the pass-corresponding nozzle row for each scan. boundary Gazure, and such that said non-ejection area is shifted between each scan, relatively said printing head width narrower than the width of the path corresponding nozzle rows in the sub-scanning direction with respect to the printing medium The ejection control means moves the data of the first pixel pattern obtained by thinning out the pixels to be printed in the previous scan to a part of both ends of each head unit in the sub-scanning direction. Correspondence to the serial nozzle, in the subsequent scan, is characterized by associating the data of the second pixel pattern that complements the first pixel pattern to the remainder the nozzle of the said end portions.

Further, the printing method of the ink jet printer according to the present invention includes a print head in which a plurality of head units each having a nozzle row composed of a plurality of nozzles arranged along the sub-scanning direction orthogonal to the main scanning direction are combined, Control is performed to eject ink droplets in association with print data, the print head is moved in the main scanning direction, and the print head is moved relative to the print medium in the sub-scanning direction for each scan. In order to solve the above-described problem, in the printing method of an inkjet printer that performs printing in a plurality of passes on the printing medium in one scan, the ink droplets are placed only between two adjacent head units. A non-ejection area that does not eject ink, and the non-ejection area length of the non-ejection area in the sub-scanning direction is adjacent between two adjacent nozzles Using the print head configured to be longer than the distance between the nozzles, the width of the nozzle array corresponding to the pass corresponding to the pass in the nozzle array of each head unit is set by the printing of the pass. An image is completed by superimposing the bands by printing all the passes that are performed by scanning a number of times that is greater than the number of passes that matches the width of the band formed on the medium, and the pass-corresponding nozzle for each scan. The print head is moved relative to the print medium with a width narrower than the width of the pass-corresponding nozzle row in the sub-scanning direction with respect to the print medium so that the boundary between the rows is shifted and the non-ejection area is shifted between each scan. The first pixel pattern in which the pixels to be printed are thinned out in the previous scanning is printed by both ends of the head unit in the sub-scanning direction, and the previous scanning is performed in the subsequent scanning. It is characterized in that printing at the second pixel pattern that complements the first pixel pattern.

  According to the above configuration, an image is completed in a band in which printing by all pass sequences is completed by repeatedly performing scanning while moving the print head with respect to the print medium. In the print head, since the non-ejection area is provided only between two adjacent head units, the non-ejection area becomes a buffer zone between the head units, and the nozzles at the end of the head unit Ink droplets ejected from each other do not interfere with each other. Therefore, even when the distance between the print head and the print medium becomes long, it is possible to easily prevent the interference of ink droplets without mechanically adjusting the mounting position of the print head as in the past. .

  Further, since the non-ejection area length is longer than the distance between adjacent nozzles, at least one blank line can be provided. Thus, when scanning is performed in a non-ejection area having a non-ejection area length, a blank row (non-recording area) is formed on the band formed by the previous scanning. Therefore, similarly to the printing method of the conventional inkjet printer, even if the print head is moved in the sub-scanning direction with respect to the print medium in each scan, the end of the band formed in the current scan is It deviates from the edge of the lower band formed by Therefore, since the band boundaries do not overlap, the band boundaries become inconspicuous and banding can be prevented.

  In the ink jet printer configured as described above, since the data of the first pixel pattern is associated with some nozzles at both ends of the head unit, by ejecting ink droplets from the nozzles, Pixels are formed in the thinned state. In addition, since the data of the second pixel pattern is associated with the remaining nozzles at both ends of the head unit, the ink droplets are ejected from the nozzles in the subsequent scanning, so that the previous scanning is interrupted. It is formed so that the drawn pixels are complemented.

  Further, in the printing method as described above, the pixels are formed in the thinned state by performing printing with the first pixel pattern in which the pixels to be printed in the previous scanning are thinned by the both ends of each head unit. Is done. In the subsequent scan, printing is performed with the second pixel pattern by the both end portions, so that the pixels thinned out in the previous scan are complemented.

  As a result, in the portion where the density of the pixels printed in one scan is low, the insufficient pixels are complemented by the subsequent scan. Therefore, the density of the ink droplet does not change suddenly between the bands formed by each head unit, and the occurrence of band stripes due to uneven ink density can be prevented. Therefore, the print quality can be improved.

  Since the ink jet printer according to the present invention is configured as described above, in printing using a print head composed of a plurality of head units, it is possible to improve the print image quality by suppressing the occurrence of band stripes. Play.

It is a top view which shows the structure of the principal part of the inkjet printer which concerns on embodiment of this invention. It is a side view which shows the structure of the principal part of the said inkjet printer. It is a top view which shows the structure of the print head in the said inkjet printer. (A)-(c) is a top view which shows three types of different structures of the junction part of the said print head, and its vicinity. FIG. 3 is a plan view illustrating a specific configuration of the print head according to the first embodiment. (A) is a top view which shows the state by which printing is performed on a printing medium by a multipass system with the said inkjet printer using the print head of Embodiment 1, (b) is sectional drawing which shows the state. FIG. 6 is a plan view illustrating a specific configuration of the print head according to a second embodiment. (A) is a top view which shows the state by which printing is performed on a printing medium by a multipass system with the said inkjet printer using the printing head of Embodiment 2, (b) is sectional drawing which shows the state. FIG. 6 is a plan view illustrating a specific configuration of the print head according to a third embodiment. FIG. 6 is a plan view illustrating a specific configuration of the print head according to a fourth embodiment. FIG. 10 is a plan view illustrating another specific configuration of the print head according to the fourth embodiment. It is a top view which shows the structure of the print head used for the conventional inkjet printer. It is a top view which shows the state by which printing is performed on a print medium by a multipass system using the said conventional print head.

  The embodiment of the present invention will be described with reference to FIGS. 1 to 11 as follows.

[Configuration of inkjet printer]
FIG. 1 is a plan view showing the configuration of the inkjet printer 1, and FIG. 2 is a side view showing the configuration of the inkjet printer 1. FIG. 3 is a plan view showing the configuration of the print head 2. FIG. 4 is a plan view showing the joint portion of the print head 2 and the structure in the vicinity thereof.

  As shown in FIGS. 1 and 2, the inkjet printer 1 includes a print head 2, a guide rail 3, a platen 4, a driving roller 5, a driven roller 6, and a control unit 7. The ink jet printer 1 is a printer that performs recording by a multi-pass method.

[Configuration of print head]
The print head 2 is a print head that ejects ink droplets onto the print medium 11, and is driven in the main scanning direction X along the guide rail 3 during scanning. As shown in FIG. 3, the print head 2 has a plurality of head units HU1, and is configured as a composite head by connecting adjacent head units HU1 to each other.

  The head unit HU1 constituting the print head 2 is not limited to the configuration described here, and various configurations can be employed. The various configurations will be described in each embodiment described later.

  Although not shown, each head unit HU1 may be coupled by fixing its bottom surface to a plate-shaped head coupling member, or coupled by being housed integrally in a case. Further, the head unit HU1 is not limited to these, and is coupled with various coupling structures.

  Each head unit HU1 has a plurality of nozzles 201 arranged in the sub-scanning direction Y, and these nozzles 201 constitute a nozzle row 202. The nozzle 201 opens on the ink ejection surface (nozzle surface) and ejects ink droplets onto the print medium 11. Two adjacent nozzles 201 are formed with a distance d2 between adjacent nozzles. The nozzle row 202 includes at least one pass row P including a plurality of nozzles 201 corresponding to one pass.

  Further, a predetermined number of nozzles 201 at both ends of the head unit HU1 (nozzle row 202) are set as half-discharge nozzles 201a. The discharge of the half discharge nozzle 201a is controlled by the discharge control unit 73 so that the normal nozzle 201 performs printing of 25% in one scan, while performing 12.5% printing in one scan. The Specifically, in the first scan, when a part (half) of the half discharge nozzles 201a discharge ink droplets, the remaining half discharge nozzles 201a do not discharge ink droplets. In the second scan, the half-discharge nozzle 201a that did not discharge ink droplets in the first scan discharges ink droplets, and the remaining half-discharge nozzles 201a do not discharge ink droplets.

  Note that the degree of printing by one scan is not limited to half (12.5%) as described above. For example, 2.5% is printed by one end of the head unit HU1 in the first scan, and 22.5% is printed by the other end of the head unit HU1 in the second scan. May be printed.

  Further, the width printed by the half discharge nozzle 201a at the end of the head unit HU1 is the same at both ends of the head unit HU1.

  A non-ejection area 203 (area shown by hatching in FIG. 3) where ink droplets are not discharged is provided at a portion where adjacent head units HU1 are joined (area shown by hatching in FIG. 3). The non-ejection region 203 is formed between the two nozzles 201 on the joining end side in the two adjacent head units HU1 among the nozzles 201 (ejection nozzles) that eject ink droplets in the nozzle row 202.

  The non-ejection area 203 has a non-ejection area length d1 in the sub-scanning direction Y. This non-ejection region length d1 is longer than the distance d2 between adjacent nozzles, which is the distance between two adjacent nozzles 201. The non-ejection area length d1 is such that at least ink droplets ejected from the nozzle 201 at the end of the head unit HU1 do not interfere with ink droplets ejected from the nozzle 201 at the end of the adjacent head unit HU1. Set to distance.

  Here, the non-ejection region 203 is configured as follows.

(1) Configuration in which a gap is provided between the head units As shown in FIG. 4A, the non-ejection region 203 is formed by joining two adjacent head units HU1 with a gap therebetween. The interval between the head units HU1 is set by the arrangement position of the head unit HU1 on the joining member 204 that joins the head unit HU1.

  In this configuration, the non-ejection area length d1 is determined by the interval between the head units HU1. Therefore, by appropriately setting the arrangement position of the head unit HU1, the non-ejection area length d1 can be easily set without changing the configuration of the head unit HU1 itself.

(2) Configuration for Setting Non-Ejecting Nozzles As shown in FIG. 4B, the non-ejecting region 203 has a predetermined number of nozzles 201 in the vicinity of the joining end portions of two adjacent head units HU1 joined without a gap. Is set as a non-ejection nozzle 201b that does not eject ink droplets. The number of non-ejection nozzles 201b at the joint end of one head unit HU1 is not particularly limited, but is determined according to the length of the non-ejection region length d1. The example shown in FIG. 4B shows a configuration in which one non-ejection nozzle 201b is provided at the joining end of one head unit HU1.

  The non-ejection nozzle 201b does not eject ink droplets even if it has a function of ejecting ink droplets because the ejection control unit 73 associates blank row data. Therefore, by appropriately changing the non-ejection nozzles 201b associated with the blank line data, different non-ejection regions 203 can be provided in the print head 2 having the nozzle row 202 having the same configuration according to the printing conditions. .

(3) Configuration in which non-ejection nozzles are set and an interval is provided between the head units This configuration is a combination of the configuration shown in FIG. 4B and the configuration shown in FIG. In such a configuration, for example, the non-ejection region 203 is provided by setting the non-ejection nozzle 201b, and the interval between the head units HU1 is adjusted. As a result, it is possible to finely adjust the non-ejection area tension d1 that cannot be dealt with by increasing the number of non-ejection nozzles 201b.

(4) Configuration without nozzles As shown in FIG. 4C, the non-ejection region 203 is formed by not providing the nozzles 201 in the two adjacent head units HU1 joined without a gap. This corresponds to not providing the non-ejection nozzle 201b in the configuration shown in FIG.

  In this configuration, the blank rows that can be formed by the non-ejection region 203 are fixed, but there is no need to associate the blank row data with the non-ejection nozzles 201b by the ejection control unit 73 as in the configuration shown in FIG. The control of the control unit 7 can be simplified. Also, by setting the non-ejection nozzle 201b in combination with the configuration shown in FIG. 4B, a blank line can be added according to the printing conditions.

[Configuration of support and drive mechanism]
The platen 4 is a support base provided at a position facing the guide rail along which the print head 2 moves. The platen 4 defines a position of the print medium 11 and has a mechanism for fixing the print medium 11 by suction or the like.

The driving roller 5 (moving means) is a roller that is rotated by being applied with a driving force via a driving shaft, and two rollers are arranged at a predetermined interval in the main scanning direction. The driven roller (moving means) 6 is a roller that rotates in a direction opposite to the driving roller 5 by coming into contact with the driving roller 5, and two rollers are arranged at positions facing the driving roller 5. The drive roller 5 and the driven roller 6 sandwich the print medium 11 therebetween, thereby causing the print medium 11 to move in a direction opposite to the sub-scanning direction Y perpendicular to the main scanning direction X according to the rotation of the driving roller 5. It conveys at the pitch. This pitch is shorter than the length of the path string P. Further, although the pitch is set equal in each scan, it may be set unequal in each scan.

(Configuration of control unit)
The control unit 7 includes a main scanning control unit 71, a sub scanning control unit 72, and a discharge control unit 73.

  The main scanning control unit 71 controls the operation of a motor or the like that drives the print head 2 in order to move the print head 2 in the main scanning direction X. The main scanning control unit 71 outputs a scanning start signal before the start of scanning and outputs a scanning end signal after the end of scanning in order to perform a line feed for each scanning.

  The sub-scanning control unit 72 (moving unit) controls the operation of a motor that drives the driving roller 5 in order to transport the print medium 11 in the direction opposite to the sub-scanning direction Y. The sub-scan control unit 72 controls the rotation of the motor so that the print medium 11 is transported by the transport amount of the above pitch every time each scan is finished.

  The ejection control unit 73 (ejection control means) performs ejection control based on the print data so that ink droplets are ejected from the nozzles 201 of each pass row P as the print head 2 moves in the main scanning direction X. . In addition, the ejection control unit 73 performs ejection control by switching the pass sequence P for ejecting ink to the next pass sequence P based on the scanning start signal output from the main scanning control unit 71.

  The ejection control unit 73 controls the half ejection nozzle 201a to eject only the scan of ejecting ink droplets in two scans. Specifically, the ejection control unit 73 converts print data of a pixel pattern (first pixel pattern) that prints a part (half) of pixels (dots) in the previous one scan into the pixel pattern. Corresponding to the corresponding half-discharge nozzle 201a. In addition, the discharge control unit 73 corresponds to the half discharge nozzle corresponding to the print data of the pixel pattern (second pixel pattern) for performing printing that complements the remaining (half) pixels thinned out in the previous scan in the subsequent scan. Correspond to 201a.

  When using the print head 2 having the above-described non-ejection region 203 shown in FIG. 4B, the ejection control unit 73 performs ejection control different from normal ejection control. Specifically, the ejection control unit 73 associates blank line data with the non-ejection nozzle 201b, and does not associate blank line data with the nozzle 201 that ejects ink droplets.

[Realization of control unit by software]
Each block of the control unit 7, in particular, the main scanning control unit 71, the sub-scanning control unit 72, and the ejection control unit 73 shown in FIG. 2 may be configured by hardware logic, or software using a CPU as follows. It may be realized by.

  That is, the control unit 7 includes a CPU (Central Processing Unit) that executes instructions of a control program that implements the functions of the main scanning control unit 71, the sub-scanning control unit 72, and the ejection control unit 73, and a ROM ( A read only memory (RAM), a RAM (Random Access Memory) for developing a control program, and a storage device (print medium) such as a memory for storing the control program and various data are provided. Then, an object of the present invention is to supply a print medium in which a program code (execution format program, intermediate code program, source program) of software that realizes the above-described functions is recorded so as to be readable by a computer, to the inkjet printer 1, Can also be achieved by reading and executing the program code recorded on the print medium.

  Examples of the print medium include a tape system such as a magnetic tape and a cassette tape, a magnetic disk such as a floppy (registered trademark) disk / hard disk, and an optical disk such as a CD-ROM / MO / MD / BD / DVD / CD-R. Can be used, such as a disk system including IC, a card system such as an IC card (including a memory card) / optical card, or a semiconductor memory system such as mask ROM / EPROM / EEPROM / flash ROM.

  In addition, the inkjet printer 1 may be configured to be connectable to a communication network, and the program code may be supplied via the communication network. The communication network is not particularly limited. For example, the Internet, intranet, extranet, LAN, ISDN, VAN, CATV communication network, virtual private network, telephone line network, mobile communication network, satellite communication. A net or the like is available. Further, the transmission medium constituting the communication network is not particularly limited. For example, even in the case of wired such as IEEE 1394, USB, power line carrier, cable TV line, telephone line, ADSL line, etc., infrared rays such as IrDA and remote control, Bluetooth ( (Registered trademark), 802.11 wireless, HDR, mobile phone network, satellite line, terrestrial digital network, and the like can also be used. The present invention can also be realized in the form of a computer data signal embedded in a carrier wave in which the program code is embodied by electronic transmission.

[Other configurations of inkjet printer]
In order to move the printing area on the printing medium 11 in the sub-scanning direction Y, the inkjet printer 1 transports the printing medium 11 in the direction opposite to the sub-scanning direction Y and moves the print head 2 in the sub-scanning direction Y. A configuration that does not allow it to be used. However, the present invention is not limited to the above configuration as long as the print head 2 can move relative to the print medium 11.

  For example, the inkjet printer 1 is configured to move the print head 2 relative to the print medium 11 by fixing the print medium 11 without conveying it and moving the print head 2 in the sub-scanning direction Y. May be adopted. In this configuration, the driving roller 5 and the driven roller 6 are unnecessary, and a mechanism for driving the print head 2 in the sub-scanning direction Y is required. An example of such a mechanism is a mechanism that drives the print head 2 together with the guide rail 3 in the sub-scanning direction Y. Further, the sub-scanning control unit 72 controls the operation of the above mechanism in place of the control of the driving roller 5.

[Color of ink droplets ejected in each scan]
The ejection color of the ejection nozzle assigned to each pass row P, that is, the color of the ink droplet for each pass row P ejected by the nozzle 201 (hereinafter referred to as “pass row ejection color”) may be single (identical). May be different. Alternatively, a single ejection color is ejected from the nozzle 201 for each head unit HU1, and in the case of multicolor printing, all of the heads HU1 corresponding to the number of colors are scanned when printing is performed. You may comprise so that the ink drop of a color may be discharged.

  When preparing the head unit HU1 for each color and performing multicolor printing, from the viewpoint of printing speed, it is preferable to scan the head unit HU1 at a time to eject ink droplets of all colors. However, from the viewpoint of improving the image quality, it is preferable to eject ink droplets of a single color in a single scan (ie, a single pass row discharge color or a single discharge color for each head unit HU1).

  Since the pass row discharge color or the discharge color for each head unit HU1 is single in one scan, each pass row P or all the pass rows P of the print head 2 are discharged on the print medium 11 during one scan. The colors of the ink droplets that land are the same. As a result, the ink droplets of a plurality of colors do not ooze at the time of landing, and the color of the printed image is improved. Further, since the order of the colors of the ink droplets to be landed is the same between the bands of the same layer, it is possible to prevent a change in color between the bands due to the difference in the landing order.

  For example, when printing is performed using cyan and magenta ink, if the discharge color of the first scan is cyan, cyan ink droplets land on the print medium 11, so that the first layer of cyan is formed. It is formed. If the ejection color of the second scan is magenta, the second layer of magenta is formed by further landing the magenta ink droplets on the print medium 11. The same applies to the case where there is a single pass row ejection color in one scan.

  As a result, the ink droplets ejected from each pass line P do not bleed within the band upon landing, and the color of the printed image is improved. In addition, since the degree of bleeding of the ink droplets landed on the lower band does not differ between the bands of the same layer, the color does not change between the bands.

  On the other hand, when the pass-line ejection color is not single, the following inconvenience occurs. First, ink droplets ejected from each pass row P are blurred when landing. Secondly, different ink droplets land between the bands in the same layer in a different order. For this reason, since the degree of bleeding of the ink droplets landed on the lower band differs between the bands of the same layer, the color changes between the bands. Therefore, it is preferable that the pass row ejection color or the ejection color for each head unit HU1 is single in one scan so as not to damage the printed image.

[Embodiment 1]
Details of the above-described print head 2 will be described with reference to FIGS.

[Configuration of print head]
FIG. 5 is a plan view showing the configuration of the print head 21.

  The aforementioned print head 2 is configured as a print head 21 as shown in FIG. The print head 21 has two head units HU21, and is configured by connecting the head units HU21 to each other.

  The head unit HU21 has a plurality of nozzles 201 arranged in a row, like the head unit HU1 described above, and a nozzle row 202 is configured by these nozzles 201. In addition, a predetermined number of nozzles 201 on both ends of the nozzle row 202 are set as half-discharge nozzles 201a.

  In the nozzle row 202, two adjacent nozzles 201 are arranged at an interval of an adjacent nozzle distance d2. Further, the non-ejection region 203 is provided at the joint between the adjacent head units HU21 as described above as shown in any of FIGS. The non-ejection area length d1 of the non-ejection area 203 is longer than the distance d2 between adjacent nozzles.

  In the head unit HU21 arranged on one end side of the print head 21, the nozzle row 202 is divided into a first pass row P1 and a second pass row P2. The first path row P1 is disposed on the end side of the head unit HU21, and the second path row P2 is disposed on the adjacent head unit HU21 side.

  On the other hand, in the head unit HU21 arranged on the other end side of the print head 21, the nozzle row 202 is divided into a third pass row P3 and a fourth pass row P4. The third path row P3 is disposed on the adjacent head unit HU21 side in the head unit HU21, and the fourth path row P4 is disposed on the end side of the head unit HU21.

  The number of nozzles (ratio of the number of nozzles) in the first pass row P1 and the second pass row P2 is set according to the printing conditions and the like. Similarly, the number of nozzles of the third pass row P3 and the fourth pass row P4 is also set according to the printing conditions and the like. Therefore, the number of nozzles in the first pass row P1 and the second pass row P2 may not be the same, and the number of nozzles in the third pass row P3 and the fourth pass row P4 may not be the same.

  Further, the head unit HU21 has two path rows P, but may have three or more path rows P.

  Furthermore, although the print head 21 is configured by combining the same type of head units HU21, the print head 21 is not limited thereto, and may be configured by combining different types of head units.

[Printing operation by inkjet printer]
A multi-pass printing operation of the inkjet printer 1 using the print head 21 configured as described above will be described. Here, FIG. 6A shows a printing state of the inkjet printer 1 in a plan view, and FIG. 6B shows a side view of the printing medium 11 as viewed from the main scanning direction X. ).

  6A shows the position of the print head 21 for each scan in a state shifted in the main scanning direction X so that the relative movement state of the print head 21 with respect to the print medium 11 can be easily understood. Yes.

  In the following description, when common reference is made to the first pass sequence P1 to the fourth pass sequence P4, it is simply referred to as “pass sequence P”.

  In the print head 21 in FIG. 6A, the hatched portion is an area where the half-discharge nozzle 201a is provided. In FIG. 6B, the hatched portion is a portion where ink droplets are ejected by the half ejection nozzle 201a, and “1” to “5” are formed by the first scan to the fifth scan, respectively. It is shown that it is the part which was done.

<First scan>
As shown in FIGS. 6A and 6B, first, in the first scan, a part of the first pass row P1 is scanned from the origin of the image, so that the ink is placed on the print medium 11. A band is formed with the width of the nozzle 201 from which the droplet has been discharged. In this band, the region where ink droplets are ejected by the normal nozzle 201 has a printing degree of 25%, and the region where ink droplets are ejected by the half-discharging nozzle 201a has a printing degree of 12.5%.

  When the ink droplets are ejected from the half ejection nozzle 201a, the ejection control unit 73 performs ejection control based on the print data of the first pixel pattern, so that ink is ejected from half the half ejection nozzles 201a at the end of the head unit HU21. Drops are ejected. Thus, printing is performed in a state where half of the pixels are thinned out, and a band with a printing degree of 12.5% is formed.

<Second scan>
In the second scanning, by the print medium 11 is conveyed only the short predetermined pitch from path array P in the sub-scanning direction Y opposite direction, the pitch in the sub-scanning direction Y with respect to the print head 21 the print media 11 Just move. In this state, scanning from a part of the second pass row P2 and the first pass row P1 is performed from the origin of the image. At this time, scanning by the half discharge nozzle 201a on one end side in the second pass row P2 is not performed.

  By this scanning, the first layer band is formed on the print medium 11 adjacent to the first layer band formed by the first scanning in the same manner as described above, and the first layer formed by the first scanning is formed. A band is also formed on one band (the bands overlap). On the band formed by the first scanning and having a printing degree of 12.5%, the band is formed by the scanning of the nozzle 201 so that the printing degree is 37.5%. On the other hand, on the band having a printing degree of 25% formed by the first scanning, a band is formed by the scanning of the nozzle 201 so that the printing degree becomes 50%.

  Thus, by transporting the print medium 11 at a predetermined pitch shorter than the pass line P, the overlapping portion of the band is printed with a reduced printing degree, and an image is completed by a plurality of scans.

<Third scan>
Also in the third scan, the print head 21 moves in the sub-scanning direction Y with respect to the print medium 11 in the same manner as described above. In this state, scanning is performed from the image origin by the half-discharge nozzle 201a, the non-discharge region 203, the second pass row P2, and the first pass row P1 on one end side in the third pass row P3.

  By this scanning, a band of the first layer is formed on the print medium 11 in the same manner as described above adjacent to the band of the first layer formed by the second scanning. In addition, a band is formed on the band having a printing degree of 12.5% formed by the second scanning so that the printing degree is 37.5% by the scanning of the nozzle 201. Further, a band is formed on the band having a printing degree of 25% formed by the second scanning so that the printing degree becomes 50% by the scanning of the nozzle 201. Further, a band is formed on the band formed by the second scanning and having a printing degree of 37.5% so that the printing degree is 50% by the scanning of the half-discharge nozzle 201a.

  When the ink droplets are ejected from the half ejection nozzle 201a, the ejection control unit 73 performs ejection control based on the print data of the second pixel pattern, whereby the remaining half of the half ejection nozzles 201a at the end of the head unit HU21. Ink droplets are ejected from. Thus, 12.5% of the pixels thinned out in the first scan are complemented on the band in which half the pixels are formed in the first scan through the band formed in the second scan. A band with a printing degree is formed.

  In this way, the ink droplets are ejected by the half ejection nozzle 201a over two scans, thereby completing 25% printing performed in one scan by the normal nozzle 201.

  Furthermore, on the band formed by the second scan and having a printing degree of 50%, a portion where no band is formed by the scanning of the non-ejection region 203 and a printing degree of 62.5% by the scanning of the semi-ejection nozzle 201a. There is a part where a band is formed.

<4th scan>
Even in the fourth scan, the print head 21 moves in the same manner as described above. In this state, scanning by a part of the fourth pass row P4, the third pass row P3, the non-ejection region 203, the second pass row P2, and the first pass row P1 is performed from the origin of the image.

  By this scanning, a band of the first layer is formed on the print medium 11 in the same manner as described above adjacent to the band of the first layer formed by the third scanning. In addition, a band is formed on the band having a printing degree of 12.5% formed by the third scanning so that the printing degree is 37.5% by the scanning of the nozzle 201. In addition, a band is formed on the band having a printing degree of 25% formed by the third scanning so that the printing degree is 50% by the scanning of the nozzle 201. Furthermore, a band is formed on the band formed by the third scanning and having a printing degree of 37.5% so that the printing degree is 50% by the scanning of the half discharge nozzle 201a.

  On the band formed by the third scan and having a printing degree of 50%, a portion where no band is formed by the scanning of the non-ejection region 203 and a printing degree of 62.5% by the scanning of the semi-ejection nozzle 201a. There is a portion where a band is formed. A band is formed on the band formed by the second scan and the third scan having a print degree of 50% so that the print degree becomes 75% by the scan of the nozzle 201. Furthermore, a band is formed on the band formed by the third scan with a print degree of 62.5% so that the print degree is 87.5% by the scan of the nozzle 201.

<5th scan>
Even in the fifth scan, the print head 21 moves in the same manner as described above. In this state, scanning by the fourth pass row P4, the third pass row P3, the non-ejection region 203, the second pass row P2, and the first pass row P1 is performed from the origin of the image.

  By this scanning, the first layer band is formed on the printing medium 11 in the same manner as described above adjacent to the first layer band formed by the fourth scanning. In addition, a band is formed on the band having a printing degree of 12.5% formed by the fourth scanning so that the printing degree is 37.5% by the scanning of the nozzle 201. Further, a band is formed on the band having a printing degree of 25% formed by the fourth scanning so that the printing degree becomes 50% by the scanning of the nozzle 201. Further, a band is formed on the band formed by the fourth scanning and having a printing degree of 37.5% so that the printing degree is 50% by the scanning of the half-discharge nozzle 201a.

  On the band formed by the fourth scan with a printing degree of 50%, the portion where the band is not formed by the scanning of the non-ejection region 203 and the printing degree of 62.5% by the scanning of the semi-ejection nozzle 201a. There is a portion where a band is formed. In addition, on the band having a printing degree of 50% formed by the third scanning and the fourth scanning, the band is formed by the scanning of the nozzle 201 so that the printing degree becomes 75%.

  On the band having a printing degree of 62.5% formed by the fourth scanning, a band is formed by the scanning of the nozzle 201 so that the printing degree becomes 87.5%. In addition, a band is formed on the band having a printing degree of 75% formed by the fourth scanning so that the printing degree becomes 100% by the scanning of the nozzle 201. Furthermore, a band is formed on the band formed by the fourth scanning and having a printing degree of 87.5% so that the printing degree becomes 100% by the scanning of the half discharge nozzle 201a.

[Summary of Embodiment]
<Non-ejection area>
The print head 21 of the present embodiment is configured by joining two head units HU21, and a non-ejection area 203 that does not eject ink droplets is provided at the joint of the head unit HU21.

  Thereby, the non-ejection area 203 becomes a buffer zone between the head units HU21, and ink droplets ejected from the nozzles 201 at the end of the head unit HU21 do not interfere with each other. Therefore, even when the distance between the nozzle surface of the print head 21 and the print medium 11 is increased, the interference of ink droplets can be easily performed without mechanically adjusting the mounting position of the print head 21 as in the prior art. Can be prevented.

<Non-ejection area length>
Since the non-ejection area length d1 is longer than the distance d2 between adjacent nozzles, at least one blank line can be provided. Accordingly, when scanning is performed in the non-ejection area 203 having the non-ejection area length d1 longer than the distance d2 between adjacent nozzles, a blank row (non-recording area) is formed on the band formed in the previous scanning. The Therefore, similarly to the printing method of the conventional inkjet printer, even if the print head 21 is moved by a predetermined pitch width with respect to the print medium 11 in each scan, the end portion of the band formed in this scan is , It deviates from the end of the lower band formed in the previous scan.

  For example, as in the third scan to the fifth scan shown in FIGS. 6A and 6B, the boundaries of the first pass row P1 to the fourth pass row P4 are sequentially shifted, and thus formed as a result. The band boundary also shifts from the lower band boundary. As a result, the band boundaries do not overlap, so the band boundaries are not noticeable, and banding can be prevented.

<Semi-discharge nozzle>
The print head 21 has half-discharge nozzles 201a at both ends of the head unit HU21. As a result, in the portion where the density of the pixels printed by the scanning by the half discharge nozzle 201a is low, the insufficient pixels are complemented by the subsequent scanning. Therefore, the density of the ink droplets does not change suddenly between the bands formed by each head unit HU21, and band stripes due to uneven ink density can be prevented.

  If the half-discharge nozzle 201a is provided at each end of each of the first pass row P1 to the fourth pass row P4, the above-described effect can be further enhanced, but the number of overlapping prints increases, and the printing speed decreases. On the other hand, by providing the semi-discharge nozzles 201a at both ends of the head unit HU21, it is possible to improve the print quality while minimizing the number of overlapping prints and minimizing the decrease in print speed. .

[Embodiment 2]
Details of the above-described print head 2 will be described with reference to FIGS.

  In the present embodiment, components having the same functions as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted as appropriate.

[Configuration of print head]
FIG. 7 is a plan view showing the configuration of the print head 22.

  The aforementioned print head 2 is configured as a print head 22 as shown in FIG. The print head 22 has four head units HU22, and is configured by connecting the head units HU22 to each other.

  The head unit HU22 has a plurality of nozzles 201 arranged in a row, like the head unit HU1 described above, and a nozzle row 202 is configured by these nozzles 201. In addition, a predetermined number of nozzles 201 on both ends of the nozzle row 202 are set as half-discharge nozzles 201a.

  In the nozzle row 202, two adjacent nozzles 201 are arranged at an interval of an adjacent nozzle distance d2. Further, the non-ejection region 203 is provided at the joint portion between the adjacent head units HU22 with the above-described configuration as shown in any one of FIGS. The non-ejection area length d1 of the non-ejection area 203 is longer than the distance d2 between adjacent nozzles.

  Of the four head units HU22, the nozzle row 202 of the head unit HU22 arranged at one end of the print head 22 corresponds to the first pass row P1, and the nozzle row of the head unit HU22 adjacent to the head unit HU22. 202 corresponds to the second pass sequence P2. The nozzle row 202 of the head unit HU22 arranged at the other end of the print head 22 corresponds to the fourth pass row P4, and the nozzle row 202 of the head unit HU22 adjacent to the head unit HU22 is the third pass row. Corresponds to P3.

  The head unit HU22 has one path row P, but may have two or more path rows P.

  The print head 22 is configured by combining the same type of head units HU22. However, the print head 22 is not limited thereto, and may be configured by combining different types of head units.

[Printing operation by inkjet printer]
The multi-pass printing operation of the inkjet printer 1 using the print head 22 configured as described above will be described. Here, FIG. 8A shows a printing state of the inkjet printer 1 in a plan view, and FIG. 8B shows a side view of the printing medium 11 as viewed from the main scanning direction X. ).

  In FIG. 8A, the position of the print head 2 in each scan is shown in a state shifted in the main scanning direction X so that the relative movement state of the print head 2 with respect to the print medium 11 can be easily understood. Yes.

  In the following description, when common reference is made to the first pass sequence P1 to the fourth pass sequence P4, it is simply referred to as “pass sequence P”.

  In the print head 22 of FIG. 8A, the hatched portion is an area where the half-discharge nozzle 201a is provided. In FIG. 8B, the hatched portions are portions where ink droplets are ejected by the half ejection nozzle 201a, and “1” to “5” are formed by the first scan to the fifth scan, respectively. It is shown that it is the part which was done.

<First scan>
As shown in FIGS. 8A and 8B, first, in the first scanning, scanning is performed by a part of the first pass row P1 from the origin of the image. At this time, scanning by the half discharge nozzle 201a on one end side in the first pass row P1 is not performed.

  By this scanning, a band is formed on the print medium 11 with the width of the nozzle 201 from which the ink droplets are ejected. In this band, the region where ink droplets are ejected by the normal nozzle 201 has a printing degree of 25%, and the region where ink droplets are ejected by the half-discharging nozzle 201a has a printing degree of 12.5%.

  When the ink droplets are ejected from the half ejection nozzle 201a, the ejection control unit 73 performs ejection control based on the print data of the first pixel pattern, so that ink is ejected from the half of the half ejection nozzles 201a at the end of the head unit HU22. Drops are ejected. Thus, printing is performed in a state where half of the pixels are thinned out, and a band with a printing degree of 12.5% is formed.

<Second scan>
In the second scan, the print medium 21 is conveyed by a predetermined pitch (band width) shorter than the pass train P in the direction opposite to the sub-scanning direction Y, so that the print head 21 is moved with respect to the print medium 11 in the sub-scanning direction Y. Move by the bandwidth. In this state, scanning is performed from the origin of the image by a part of the second pass row P2, the non-ejection region 203, and the first pass row P1.

  By this scanning, a band of the first layer is formed on the print medium 11 in the same manner as described above adjacent to the band of the first layer formed by the first scanning.

  On the band formed by the first scanning and having a printing degree of 12.5%, the band is formed by the scanning by the half discharge nozzle 201a so as to obtain a printing degree of 25%. On the other hand, on the band having a printing degree of 25% formed by the first scanning, a band is formed by the scanning by the nozzle 201 so that the printing degree becomes 50%.

  When the ink droplets are ejected from the half ejection nozzle 201a, the ejection control unit 73 performs ejection control based on the print data of the second pixel pattern, whereby the remaining half of the half ejection nozzles 201a at the end of the head unit HU22. Ink droplets are ejected from. As a result, a band having a printing degree of 12.5% is formed on the band in which half the pixels are formed in the first scan so as to complement the pixels thinned out in the first scan.

<Third scan>
Also in the third scan, the print head 21 moves in the sub-scanning direction Y with respect to the print medium 11 in the same manner as described above. In this state, scanning by the non-ejection region 203, the second pass row P2, and the first pass row P1 is performed from the origin of the image.

  By this scanning, a band of the first layer is formed on the print medium 11 in the same manner as described above adjacent to the band of the first layer formed by the second scanning.

  On the band formed by the second scanning and having a printing degree of 12.5%, the band is formed by the scanning of the half discharge nozzle 201a so that the printing degree becomes 25%. In addition, on the band having a printing degree of 50% formed by the first scanning and the second scanning, the printing degree of 37.5% and 50% are obtained by the scanning of the semi-discharge nozzle 201a and the nozzle 201, respectively. A band is formed. Further, a band is formed on the band formed by the second scanning and having a printing degree of 37.5% so that the printing degree is 50% by the scanning of the half discharge nozzle 201a.

<4th scan>
Even in the fourth scan, the print head 21 moves in the same manner as described above. In this state, scanning from a part of the third pass row P3, the non-ejection region 203, the second pass row P2, the non-ejection region 203, and the first pass row P1 is performed from the origin of the image. At this time, scanning by the half discharge nozzle 201a on one end side in the third pass row P3 is not performed.

  By this scanning, a band of the first layer is formed on the print medium 11 in the same manner as described above adjacent to the band of the first layer formed by the third scanning.

  On the band formed by the third scanning and having a printing degree of 12.5%, the band is formed by the scanning of the half discharge nozzle 201a so that the printing degree becomes 25%. Further, on the band with the printing degree of 50% formed by the second scanning and the third scanning, the printing degree of 37.5% and 50% is obtained by the scanning of the half discharge nozzle 201a and the nozzle 201, respectively. A band is formed. Further, a band is formed on the band formed by the third scanning and having a printing degree of 37.5% so that the printing degree is 50% by the scanning of the half-discharge nozzle 201a. Further, on the band formed by the second scanning and the third scanning and having a printing degree of 50%, the printing degree of 62.5% and 75% is obtained by the scanning of the half discharge nozzle 201a and the nozzle 201, respectively. A band is formed.

<5th scan>
Even in the fifth scan, the print head 21 moves in the same manner as described above. In this state, a part of the fourth pass row P4, the non-ejection region 203, the third pass row P3, the non-ejection region 203, the second pass row P2, the non-ejection region 203 and the first pass row P1 from the origin of the image. Scanning is performed.

  By this scanning, the first layer band is formed on the printing medium 11 in the same manner as described above adjacent to the first layer band formed by the fourth scanning.

  On the band formed by the third scan and the fourth scan and having a printing degree of 50%, the band is set so that the printing degree is 37.5% and 50% by the scanning of the half discharge nozzle 201a and the nozzle 201, respectively. Is formed. In addition, on the band formed by the fourth scan and having a printing degree of 37.5%, a band is formed by the scanning of the half discharge nozzle 201a so that the printing degree is 50%. In addition, on the band formed by the third scan and the fourth scan and having a printing degree of 50%, the band is printed at a printing degree of 62.5% and 75% by the scanning of the half discharge nozzle 201a and the nozzle 201, respectively. It is formed. Further, a band is formed on the band having a printing degree of 6.25% formed by the fourth scanning so as to have a printing degree of 75% by the scanning of the half discharge nozzle 201a. Further, on the band having a printing degree of 75% formed by the fourth scanning, the bands are formed by the scanning of the half discharge nozzle 201a and the nozzle 201 so that the printing degree is 87.5% and 100%, respectively. Is done.

[Summary of Embodiment]
<Non-ejection area>
The print head 22 of the present embodiment is configured by joining four head units HU22, and a non-ejection area 203 that does not eject ink droplets is provided at the joint of the head unit HU22.

  As a result, similarly to the print head 21, the non-ejection area 203 becomes a buffer zone between the head units HU 22, and ink droplets ejected from the nozzles 201 at the end of the head unit HU 22 do not interfere with each other. Therefore, even when the distance between the nozzle surface of the print head 22 and the print medium 11 is increased, the interference of ink droplets can be easily performed without mechanically adjusting the mounting position of the print head 22 as in the past. Can be prevented.

<Non-ejection area length>
Since the non-ejection region length d1 is longer than the distance d2 between adjacent nozzles, the end of the band formed by the current scan is more similar to the end of the lower band formed by the previous scan, as in the print head 21. Misaligned. Accordingly, since the end portions of the bands of the respective layers do not become the same line during printing, the boundaries between the bands become inconspicuous and banding can be eliminated.

<Semi-discharge nozzle>
The print head 22 has half-discharge nozzles 201a at both ends of the head unit HU22. As a result, as in the print head 21, in the portion where the pixel density is low in the scanning by the half-discharge nozzle 201a, the insufficient pixel is complemented by the subsequent scanning. Therefore, the density of the ink droplets does not change suddenly between the bands formed by each head unit HU21, and band stripes due to uneven ink density can be prevented.

  Since the print head 22 is provided with the half-discharge nozzles 201a at both ends of the first pass row P1 to the fourth pass row P4, the print quality can be improved as compared with the print head 22, but it is redundant. As a result, the printing speed decreases because of the increase in the number of places to print. Therefore, the print head 22 can be suitably used when the print quality is more important than the print speed.

[Embodiment 3]
Details of the above-described print head 2 will be described with reference to FIG.

  In the present embodiment, components having the same functions as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted as appropriate.

  FIG. 9 is a plan view showing the configuration of the print head 23.

  The aforementioned print head 2 is configured as a print head 23 as shown in FIG. The print head 23 has two head units HU 21 as in the case of the print head 21 described above, and is configured by connecting the head units HU 21 together.

  Unlike the print head 21, the print head 23 is coupled so that the head units HU 21 are arranged offset in a direction orthogonal to the sub-scanning direction Y. Further, although both head units HU21 are in contact with each other, they may be separated in the main scanning direction X and / or the sub-scanning direction Y.

  Although not shown, both head units HU21 may be arranged in a positional relationship opposite to that of the head unit HU21 shown in FIG.

  Even when multi-pass printing is performed by the inkjet printer 1 using the print head 23 configured as described above, printing is performed as shown in FIGS. 6 (a) and 6 (b). As a result, as in the case of using the print head 21, it is possible to easily prevent interference of ink droplets, to eliminate banding, and to prevent generation of band stripes due to uneven ink density.

[Embodiment 4]
Details of the above-described print head 2 will be described with reference to FIGS. 10 and 11.

  In the present embodiment, components having the same functions as the components in the above-described second embodiment are denoted by the same reference numerals and description thereof is omitted as appropriate.

  FIG. 10 is a plan view showing the configuration of the print head 24. FIG. 11 is a plan view showing the configuration of the print head 25.

  The aforementioned print head 2 is configured as a print head 24 as shown in FIG. The print head 24 has four head units HU 22 as in the case of the print head 22 described above, and is configured by coupling the head units HU 22 together.

  Unlike the print head 22, the print heads 24 are coupled so as to be arranged in a so-called staggered arrangement (staggered arrangement) that is alternately offset in the direction orthogonal to the sub-scanning direction Y. Further, the head units HU22 are partially in contact with each other, but may be separated in the main scanning direction X and / or the sub-scanning direction Y.

  Although not shown, each head unit HU22 may be disposed in the opposite positional relationship to the head unit HU22 shown in FIG.

  On the other hand, the aforementioned print head 2 is configured as a print head 25 as shown in FIG. The print head 25 has four head units HU22 as in the above-described print head 22, and is configured by coupling the head units HU22 to each other.

  Unlike the print head 22, the print head 25 is coupled so as to be arranged in a so-called laminar arrangement that is sequentially offset in the same direction orthogonal to the sub-scanning direction Y. Further, the head units HU22 are partially in contact with each other, but may be separated in the main scanning direction X and / or the sub-scanning direction Y.

  Although not shown, each head unit HU22 may be disposed in the opposite positional relationship to the head unit HU22 shown in FIG.

  Even when multi-pass printing is performed by the inkjet printer 1 using the print heads 24 and 25 configured as described above, printing is performed as shown in FIGS. As a result, as in the case where the print head 22 is used, it is possible to easily prevent interference of ink droplets, to eliminate banding, and to prevent occurrence of band stripes due to uneven ink density.

[Additional Notes]
The ink jet printer 1 includes print heads 2, 21 to 25 in which a plurality of head units HU1, HU21, and HU22 having a nozzle row 202 composed of a plurality of nozzles 201 arranged along a sub-scanning direction Y orthogonal to the main scanning direction X are combined. And an ejection control unit 73 for controlling the nozzle 201 to eject ink droplets in association with print data, and the print heads 2, 21 to 25 are moved in the main scanning direction X, and the print head 2 is scanned for each scan. , 21 to 25 are provided with a driving roller 5, a driven roller 6 and a sub-scanning control unit 72 that move the sub-scanning direction Y relative to the print medium 11, and a plurality of passes through the print medium 11 in one scan. Print. In the inkjet printer 1, the print heads 2, 21 to 25 have a non-ejection area 203 that does not eject ink droplets only between two adjacent head units HU1, HU21, and HU22. The non-ejection region length d1 in the sub-scanning direction Y is longer than the inter-adjacent nozzle distance d2 between the two adjacent nozzles 201, and the nozzle 201 corresponding to the pass in the nozzle row 202 of each head unit HU1, HU21, HU22. The width of the nozzle array corresponding to pass is equal to the width of the band formed on the print medium 11 by the pass printing, and the bands are overlapped by printing all the passes performed by the number of scans larger than the number of passes. in to complete the image, the driving roller 5, driven roller 6 and the sub-scanning control unit 72, the path for each scanning corresponding nozzle array boundary Gazure and As non-ejection area 203 is shifted between each scan, it is relatively moved in narrower than the width of the path corresponding nozzle rows in the sub-scanning direction Y relative to the print medium 11 to print head 2,21～25, discharge In the previous scan, the control unit 73 converts the first pixel pattern data obtained by thinning out the pixels to be printed into a part of the nozzles 201 (half-discharge nozzles) at both ends in the sub-scanning direction Y of each head unit HU1, HU21, HU22. 201a), and in the subsequent scan, the second pixel pattern data that complements the first pixel pattern is associated with the remaining nozzles 201 (half-discharge nozzles 201a) at both ends.

Further, the printing method of the inkjet printer 1 is a print head in which a plurality of head units HU1, HU21, and HU22 having a nozzle row 202 composed of a plurality of nozzles 201 arranged in the sub-scanning direction Y orthogonal to the main scanning direction X are combined. 2, 21 to 25, and controls the nozzle 201 to correspond to the print data to eject ink droplets, move the print heads 2, 21 to 25 in the main scanning direction X, and print heads for each scan 2 is a printing method for an inkjet printer in which a plurality of passes are printed on the print medium 11 by one scan by moving 2, 21 to 25 relative to the print medium 11 in the sub-scanning direction Y. This printing method has a non-ejection area 203 that does not eject ink droplets only between two adjacent head units HU1, HU21, and HU22, and the non-ejection area length in the sub-scanning direction Y of the non-ejection area 203. Using the print heads 2, 21 to 25 configured so that d1 is longer than the distance d2 between adjacent nozzles between two adjacent nozzles 201, the pass in the nozzle row 202 of each head unit HU1, HU21, HU22 The width of the pass-corresponding nozzle row composed of the nozzles 201 corresponding to the same as the width of the band formed on the printing medium 11 by the printing of the pass, and printing of all passes performed by scanning more times than the number of passes. the image is completed by overlapping the band by the path for each scanning corresponding nozzle array boundary Gazure and mark as non-ejection area 203 is shifted between each scan The heads 2, 21 to 25 are moved relative to the print medium 11 in the sub-scanning direction Y with a width narrower than the width of the pass-corresponding nozzle row, and both end portions of the head units HU 1, HU 21, HU 22 in the sub-scanning direction Y Thus, in the previous scan, printing is performed with a first pixel pattern obtained by thinning out the pixels to be printed, and in subsequent scans, printing is performed with a second pixel pattern that complements the first pixel pattern. The scanning position of the non-ejection area is shifted.

  According to the above configuration, scanning is repeatedly performed while moving the print heads 2, 21 to 25 with respect to the print medium 11, whereby an image is completed in a band where printing by all the pass rows P is completed. In the print heads 2, 21 to 25, the non-ejection area 203 is provided only between the two adjacent head units HU 1, HU 21, HU 22. The ejection region 203 becomes a buffer zone, and ink droplets ejected from the nozzles 201 at the ends of the head units HU1, HU21, and HU22 do not interfere with each other. Therefore, even when the distance between the print heads 2, 21 to 25 and the print medium becomes long, it is easy without mechanically adjusting the mounting positions of the print heads 2, 21 to 25 as in the past. Ink droplet interference can be prevented.

  Further, since the non-ejection area length d1 is longer than the distance d2 between adjacent nozzles, at least one blank line can be provided. Thus, when scanning is performed in the non-ejection area 203 having the non-ejection area length d1, a blank line (non-recording area) is formed on the band formed by the previous scanning. Therefore, similarly to the printing method of the conventional inkjet printer, even if the print heads 2, 21 to 25 are moved in the sub-scanning direction with respect to the print medium 11 in each scan, the end of the band formed in this scan The part is shifted from the end of the lower band formed by the previous scan. Therefore, since the band boundaries do not overlap, the band boundaries become inconspicuous and banding can be prevented.

  In the inkjet printer 1 configured as described above, the data of the first pixel pattern is associated with some of the nozzles 201 (half-discharge nozzle 201a) at both ends of the head units HU1, HU21, and HU22. By discharging ink droplets from the nozzle 201, pixels are formed in a thinned state. In addition, since the data of the second pixel pattern is associated with the remaining nozzles at both ends of the head unit, the ink droplets are ejected from the nozzles 201 in the subsequent scanning, so that the previous scanning is performed. It is formed so that the thinned pixels are complemented.

  Further, in the printing method as described above, thinning is performed by printing with the first pixel pattern in which the pixels to be printed in the previous scanning are thinned out by the both ends of each head unit HU1, HU21, HU22. Pixels are formed in the state. In the subsequent scan, printing is performed with the second pixel pattern by the both end portions, so that the pixels thinned out in the previous scan are complemented.

  As a result, in the portion where the density of the pixels printed in one scan is low, the insufficient pixels are complemented by the subsequent scan. Therefore, the density of the ink droplet does not change suddenly between the bands formed by each head unit, and the occurrence of band stripes due to uneven ink density can be prevented. Therefore, the print quality can be improved.

  Since the present invention prevents the occurrence of band fringes between bands in an inkjet printer that employs a multi-pass method, it can be suitably used for applications that require high print quality.

DESCRIPTION OF SYMBOLS 1 Inkjet printer 2 Print head 3 Guide rail 4 Platen 5 Drive roller (moving means)
6 Followed roller (moving means)
7 control unit 11 print medium 21 print head 22 print head 23 print head 24 print head 25 print head 71 main scanning control unit 72 sub-scanning control unit (moving means)
73 Discharge Control Unit (Discharge Control Unit)
201 Nozzle 201a Semi-discharge nozzle 201b Non-discharge nozzle 202 Nozzle row 203 Non-discharge region d1 Non-discharge region length d2 Distance between adjacent nozzles HU1 Head unit HU21 Head unit HU22 Head unit P Pass row P1 First pass row P2 Second pass row P3 Third pass row P4 Fourth pass row X Main scanning direction Y Sub scanning direction

Claims (2)

A print head in which a plurality of head units each having a nozzle row composed of a plurality of nozzles arranged in the sub-scanning direction orthogonal to the main scanning direction are combined, and control is performed so that ink droplets are ejected in association with the print data. An ejection control unit that moves the print head in the main scanning direction, and a moving unit that moves the print head relative to the print medium in the sub-scanning direction for each scan. In an inkjet printer that prints multiple passes in a single scan,
The print head has a non-ejection area that does not eject ink droplets only between two adjacent head units, and the non-ejection area length in the sub-scanning direction of the non-ejection area is adjacent. Longer than the distance between adjacent nozzles between the two nozzles,
The width of the pass-corresponding nozzle row consisting of the nozzles corresponding to the pass in the nozzle row of each head unit matches the width of the band formed on the print medium by printing of the pass,
Complete the image by overlaying the bands by printing all the passes performed in a number of scans greater than the number of passes,
The moving means moves the print head in the sub-scanning direction with respect to the print medium so that a boundary of the pass-corresponding nozzle row is shifted for each scan and the non-ejection area is shifted between each scan. Move it relatively narrower than the width of the pass-capable nozzle row,
In the previous scan, the ejection control unit associates the data of the first pixel pattern obtained by thinning out the pixels to be printed with some of the nozzles at both ends in the sub-scanning direction of each head unit, and in the subsequent scan An ink jet printer characterized in that data of a second pixel pattern that complements the first pixel pattern is associated with the remaining nozzles at both ends. A print head including a plurality of head units each having a nozzle row composed of a plurality of nozzles arranged along a sub-scanning direction orthogonal to the main scanning direction is provided, and ink droplets are ejected in association with print data to the nozzles Controlling, moving the print head in the main scanning direction, and moving the print head relative to the print medium in the sub-scanning direction for each scan, so that a plurality of scans are performed on the print medium in one scan. In a printing method of an inkjet printer that performs printing of a pass of
There is a non-ejection area that does not eject ink droplets only between two adjacent head units, and the non-ejection area length of the non-ejection area in the sub-scanning direction is between two adjacent nozzles. Using the print head configured to be longer than the distance between adjacent nozzles,
In the nozzle row of each head unit, the width of the pass-corresponding nozzle row composed of the nozzles corresponding to the pass matches the width of the band formed on the print medium by printing of the pass,
Complete the image by overlaying the bands by printing all the passes performed in a number of scans greater than the number of passes,
The width of the pass-corresponding nozzle row in the sub-scanning direction with respect to the print medium so that the boundary of the pass-corresponding nozzle row is shifted every scan , and the non-ejection area is shifted between each scan. Move it relatively narrower,
The first pixel pattern obtained by thinning out the pixels to be printed in the previous scan is printed by both ends of the head unit in the sub-scanning direction, and the second pixel that complements the first pixel pattern in the subsequent scan A printing method of an ink jet printer, wherein printing is performed with a pixel pattern.

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