JP2009090635A - Liquid ejecting apparatus, and image forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress degradation of an image quality, and also to prevent a width in a first direction of a head unit from being large. <P>SOLUTION: The liquid ejecting apparatus is equipped with (a) the head unit, (b) a moving mechanism, and (c) a control part. The head unit has a plurality of heads in the first direction in which a plurality of nozzles for ejecting a liquid to a medium are arranged in the first direction. The head unit forms a raster line by moving m times relatively to the medium in a second direction that intersects the first direction and ejecting the liquid. The width in the first direction of the head unit is larger than a width in the first direction of the medium. The moving mechanism moves the head unit relatively to the medium alternately in the second direction and the first direction by a plurality of the number of times. The control part forms an image whose resolution is n times of a pitch of the nozzles by relatively moving the head unit by the plurality of the number of times to form a plurality of the raster lines. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a liquid ejection apparatus and an image forming method.

  As one of liquid ejecting apparatuses, an ink jet printer that performs printing by ejecting liquid (ink) onto various media such as paper, cloth, and film is known. This printer includes a head in which a plurality of nozzles that discharge liquid onto a medium are arranged in a first direction (sub-scanning direction), and the head is in a second direction (main scanning direction) that intersects the first direction. The liquid is discharged while moving.

The above-described printer performs, for example, so-called overlap printing or interlace printing from the viewpoint of improving image quality. That is, the printer forms an image by moving the head alternately in the second direction and the first direction a plurality of times to form a plurality of raster lines.
International Publication No. 01/03930 Pamphlet

  Meanwhile, some printers include a head unit having a plurality of the heads along the first direction from the viewpoint of increasing the printing speed. In this case, for example, it is conceivable that the width of the head unit in the first direction is larger than the width of the medium in the first direction so that the liquid is ejected all over the entire width of the medium. However, in such a configuration, when the total movement amount of the head unit in the first direction during printing is large, the liquid is ejected at once over the entire width of the medium during the movement in the second direction. In order to achieve this, it is necessary to increase the width of the head unit in the first direction.

  It is also known that the liquid ejection characteristics differ depending on the individual differences of the heads. For example, one head has a characteristic of easily ejecting liquid, and the other head has a characteristic of hardly ejecting liquid. For this reason, when a plurality of heads constituting the head unit eject liquid, so-called density unevenness or the like occurs due to a difference in ejection characteristics of each head, and as a result, image quality may be deteriorated.

  SUMMARY An advantage of some aspects of the invention is that it suppresses deterioration in image quality and suppresses an increase in the width of the head unit in the first direction.

In order to solve the above problems, the main present invention is:
(A) A plurality of heads in which a plurality of nozzles that discharge liquid to the medium are arranged in the first direction are provided along the first direction, and the second direction intersecting the first direction is directed to the medium. a head unit that forms one raster line by ejecting the liquid by moving relative to m times,
A head unit in which the width in the first direction of the head unit is larger than the width in the first direction of the medium;
(B) a moving mechanism for moving the head unit relative to the medium alternately in the second direction and the first direction a plurality of times;
(C) a controller that forms an image having a resolution n times the pitch of the nozzles by relatively moving the head unit a plurality of times to form a plurality of raster lines;
The total amount of movement of the head unit in the first direction when the head unit is relatively moved a plurality of times is larger than the effective nozzle width of the one head in the first direction × (m × n−1). And smaller than the effective nozzle width × (m × n),
The amount of movement of the head unit in the first direction when the head unit is relatively moved a plurality of times is made larger than the effective nozzle width,
A control unit for forming the image;
A liquid ejecting apparatus comprising (d).

  Other features of the present invention will become apparent from the description of the present specification and the accompanying drawings.

  At least the following will be made clear by the description of the present specification and the accompanying drawings.

(A) A plurality of heads in which a plurality of nozzles that discharge liquid to the medium are arranged in the first direction are arranged along the first direction, and the second direction intersecting the first direction is directed to the medium. a head unit that forms one raster line by ejecting the liquid by moving relative to m times,
A head unit in which the width in the first direction of the head unit is larger than the width in the first direction of the medium;
(B) a moving mechanism for moving the head unit relative to the medium alternately in the second direction and the first direction a plurality of times;
(C) a controller that forms an image having a resolution n times the pitch of the nozzles by relatively moving the head unit a plurality of times to form a plurality of raster lines;
The total amount of movement of the head unit in the first direction when the head unit is relatively moved a plurality of times is larger than the effective nozzle width of the one head in the first direction × (m × n−1). And smaller than the effective nozzle width × (m × n),
Each amount of movement of the head unit in the first direction when the head unit is relatively moved a plurality of times is made larger than the effective nozzle width,
A control unit for forming the image;
A liquid ejection apparatus comprising (d). According to such a liquid ejecting apparatus, it is possible to suppress deterioration in image quality and to suppress an increase in the width of the head unit in the first direction.

In addition, such a liquid ejection device,
n is a natural number of 2 or more,
The controller is
It is preferable that n continuous raster lines are formed by discharging the liquid to the nozzles of the (m × n) heads. In such a case, deterioration of image quality can be effectively suppressed.

In addition, such a liquid ejection device,
The movement amounts of the head unit in the first direction when the head unit is relatively moved a plurality of times are preferably the same. In such a case, deterioration of image quality can be more effectively suppressed.

In addition, (a) a plurality of heads in which a plurality of nozzles that discharge liquid to the medium are arranged in the first direction are arranged in the first direction, and the medium is arranged in the second direction intersecting the first direction. A head unit that forms a single raster line by moving relative to m times and ejecting the liquid, wherein the width of the head unit in the first direction is greater than the width of the medium in the first direction. A large head unit
An image having a resolution n times the pitch of the nozzles is formed by alternately moving the medium relative to the medium in the second direction and the first direction a plurality of times to form the plurality of raster lines. An image forming method comprising:
(B) The total amount of movement of the head unit in the first direction when the head unit is relatively moved a plurality of times is the effective nozzle width of the one head in the first direction × (m × n−1). Larger than the effective nozzle width x (m x n),
The amount of movement of the head unit in the first direction when the head unit is relatively moved a plurality of times is made larger than the effective nozzle width,
An image forming method comprising forming the image. According to such an image forming method, it is possible to suppress deterioration in image quality and to prevent the width of the head unit in the first direction from increasing.

== Configuration example of inkjet printer ==
An ink jet printer (hereinafter referred to as “printer 1”), which is an example of a liquid ejection device, is attached to a strip-shaped printing tape T, which is an example of a medium, on a unit image to be cut out later, for example, a wrap film of fresh food. A seal-like printed matter is printed by an inkjet method. Here, the printing tape T is roll paper (continuous paper) with release paper, and images to be printed are continuously printed in a direction in which the printing tape T continues.

<< Configuration of Printer 1 >>
FIG. 1 is a block diagram of the overall configuration of the printer 1. FIG. 2A is a schematic sectional view of the printer 1, and FIG. 2B is a schematic top view of the printer 1. FIG. 3 shows the nozzle arrangement on the lower surface of the head unit 40.

  When the printer 1 receives the print data, the controller 10 which is an example of a control unit controls each unit (conveyance unit 20, drive unit 30, and head unit 40) to form an image on the print tape T. The state in the printer 1 is monitored by the detector group 50, and the controller 10 controls each unit based on the detection result.

  The transport unit 20 transports the print tape T from the upstream side to the downstream side in the direction in which the print tape T continues (hereinafter referred to as the transport direction). The transport unit 20 includes a feed roller 21, a feed roller 22, a suction table 23, and the like. The feed roller 21 feeds the roll-shaped printing tape T before printing to the suction table 23 which is a printing area. The suction table 23 vacuums the printing tape T from below and holds the printing tape T. The delivery roller 22 delivers the printed printing tape T from the printing area. The printing tape T sent out from the printing area is wound up in a roll shape by a winding mechanism.

  The drive unit 30 is a moving mechanism that freely moves the head unit 40 in a main scanning direction corresponding to the transport direction and a sub-scanning direction corresponding to the width direction of the printing tape T. The drive unit 30 includes, for example, an X movement table that moves the head unit 40 in the main scanning direction, a Y movement table that moves the X movement table holding the head unit 40 in the sub scanning direction, and a motor that moves them. (Not shown).

  The head unit 40 forms a dot row (raster line) on the printing tape T by ejecting ink while moving in the main scanning direction. Since the collection of dot rows forms an image, the image is printed by forming the dot rows. The head unit 40 has ten heads 41, and the ten heads 41 are arranged in a staggered manner in the width direction (sub-scanning direction). The head unit 40 can be ejected over the entire width of the printing tape T by one movement in the main scanning direction, that is, the width of the head unit 40 in the sub-scanning direction is larger than the width of the printing tape T. Ten heads are arranged to be larger.

  Further, on the lower surface of each head 41, a nozzle row Y for discharging yellow ink, a nozzle row M for discharging magenta ink, a nozzle row C for discharging cyan ink, and a nozzle row K for discharging black ink are formed. Has been. In each nozzle row, 360 nozzles are arranged at a constant interval (360 dpi) in the width direction. Of the two heads adjacent to each other in the width direction (here, the head 41 (1) and the head 41 (2) will be described as examples) The two nozzles # 359 and # 360 and the innermost nozzles # 1 and # 2 of the front head 41 (2) are located on the same line (that is, the nozzles overlap). In this embodiment, the sub-scanning direction corresponds to the first direction, and the main scanning direction corresponds to the second direction.

<< Moving Mode of Head Unit 40 During Printing >>
FIG. 4A to FIG. 4I are schematic diagrams for explaining the movement mode of the head unit 40 during printing. The printer 1 forms each dot row (raster line) by moving the head unit 40 four times in the main scanning direction. At the time of printing, the printing tape T is held on the suction table 23 without being conveyed.

  The head unit 40 before printing stands by at the home position (position shown in FIG. 4A). At the time of printing, first, the head unit 40 is moved from the downstream side to the upstream side in the main scanning direction by the drive unit 30 (FIG. 4B). During this movement (pass 1), ink is ejected from each nozzle of the head unit 40 over the entire width of the print tape T, and a dot row of pass 1 is formed on the print tape T. The head unit 40 moved in the main scanning direction is moved from the back side to the front side in the sub scanning direction by the drive unit 30 (FIG. 4C), and then the head unit 40 is again moved from the upstream side to the downstream side in the main scanning direction. While moving (pass 2) (FIG. 4D), ink is ejected from the nozzles over the entire width of the print tape T, and a dot row of pass 2 is formed. Here, “pass” means that the head unit 40 moves once in the main scanning direction, and the number after the pass indicates the order in which the pass is performed.

  As described above, the head unit 40 moves in the main scanning direction of the head unit 40 for dot formation (FIGS. 4B, 4D, 4F, and 4H) and moves in the sub-scanning direction of the head unit 40 (FIG. 4C). 4E and 4G) are alternately performed. Thereby, a plurality of dot rows (raster line groups) are formed over the entire width of the printing tape T. Then, after the fourth movement in the main scanning direction (pass 4, FIG. 4H) is completed, the head unit 40 moves to the back side in the sub-scanning direction (FIG. 4I) and is positioned at the home position shown in FIG. 4A. . This completes a series of movements of the head unit 40 during printing.

== Density unevenness due to difference in ejection characteristics of each head 41 ==
It is known that ink ejection characteristics vary depending on individual differences of the heads 41. For example, while ink is likely to be ejected from the nozzle of one head 41, it may be difficult to eject ink from the nozzle of another head 41. For this reason, when printing is performed by the head unit 40 having ten heads 41 having individual differences, so-called density unevenness may occur due to the difference in ejection characteristics of the heads 41.

  Here, among the ten heads 41, the head 41 (3), the head 41 (4), and the head 41 (5) will be described as an example. Temporarily, the head 41 (3) has a characteristic that it is difficult to eject ink (the amount of ink ejected is less than the proper amount), and the head 41 (4) ejects ink normally (the amount of ink ejected is appropriate). The head 41 (5) has a characteristic that it is easy to eject ink (the amount of ink ejected is larger than an appropriate amount). For this reason, if it is necessary to form a dot with an appropriate discharge amount (hereinafter referred to as a medium dot), the head 41 (3) has a dot (hereinafter referred to as a small dot) with a smaller discharge amount than the appropriate amount. The head 41 (4) forms a medium dot, and the head 41 (5) forms a dot whose discharge amount is larger than an appropriate amount (hereinafter referred to as a large dot). It should be noted that most of the other heads 41 out of the ten heads 41 form medium dots in the same manner as the head 41 (4).

  5A and 5B are diagrams for explaining density unevenness due to a difference in ejection characteristics of the heads 41. FIG. The dot rows shown in FIGS. 5A and 5B are formed in two passes, FIG. 5A shows the dot row after pass 1, and FIG. 5B shows the dot row after pass 2.

  In the first dot row of the five dot rows, pass 1 and pass 2 are formed by the head 41 (3). Therefore, only small dots are arranged in the first dot row. In the second dot row, pass 1 is formed by the head 41 (3), and pass 2 is formed by the head 41 (4). For this reason, in the second dot row, small dots and medium dots are alternately arranged. In the third dot row, pass 1 and pass 2 are formed by the head 41 (4), and only medium dots are arranged. In the fourth dot row, pass 1 is formed by the head 41 (4) and pass 2 is formed by the head 41 (5), and medium dots and large dots are alternately arranged. The fifth dot row is formed by the head 41 (5) in pass 1 and pass 2, and only large dots are arranged.

  In such a case, the first dot row is formed with only small dots, and appears lighter than a dot row formed with medium dots (dots with an appropriate discharge amount). That is, it is recognized as density unevenness. Similarly, the fifth dot row is formed of only large dots and looks darker than a dot row formed of medium dots. That is, it is recognized as density unevenness. When the number of the first dot row and the fifth dot row increases, the density unevenness becomes conspicuous and the image quality further deteriorates.

  On the other hand, since the third dot row is formed with only medium dots, it has an appropriate density. Further, since the second and fourth dot rows occupy half of the medium dots, even if small dots and large dots are included, the density is neutralized as a whole and is difficult to be recognized as density unevenness.

  As described above, in a configuration in which a dot row is formed using a plurality of heads 41 having different ink ejection characteristics, the dot row is formed by only one head 41 (the head 41 (3) and the head 41 (5) described above). When it is formed, there may be a problem that the density unevenness becomes remarkable.

== Relationship between total sub-scanning amount of head unit and width of head unit during printing ==
The printer 1 according to the present embodiment is configured such that ink is ejected over the entire width of the printing tape T during four movements in the main scanning direction (pass 1 to pass 4). This is because the resolution of the image (for example, the resolution in the sub-scanning direction is 720 dpi) is finer than the nozzle pitch (360 dpi), and the head unit 40 is moved in the sub-scanning direction in units of 720 dpi. This is to form dot rows with fine spacing.

  On the other hand, the head unit 40 moves three times in the sub-scanning direction during four passes of pass 1 to pass 4 (FIGS. 4C, 4E, and 4G). In order to cause ink to be ejected over the entire width of the printing tape T in pass 1 to pass 4, depending on the total movement amount of the three movements (hereinafter also referred to as total sub-scanning amount). The width of the head unit 40 in the sub-scanning direction is different. This point will be described with reference to FIGS. 6A and 6B.

  FIG. 6A shows the width of the head unit 40 when the total sub-scanning amount is increased. FIG. 6B shows the width of the head unit 40 when the total sub-scanning amount is reduced. 6A and 6B is in the state immediately before the first movement in the main scanning direction (pass 1), and the right head unit 40 shown by the solid line is the fourth head unit 40. It is in a state immediately before the movement in the scanning direction (pass 4). Therefore, the amount of deviation in the sub-scanning direction between the dotted head unit 40 and the solid head unit 40 is the total sub-scanning amount of the head unit 40.

  As can be seen from FIGS. 6A and 6B, the larger the total sub-scanning amount, the larger the width in the sub-scanning direction of the head unit 40 so that ink is ejected over the entire width of the printing tape T. That is, the number of heads 41 constituting the head unit 40 increases. When the width of the head unit 40 is increased, the printer 1 may be increased in size in order to secure an installation space for the head unit 40.

== Print processing according to the present embodiment ==
In order to suppress the above-described problem, that is, the density unevenness and the width of the head unit 40 in the sub-scanning direction are suppressed, the printer 1 executes a printing process described below.

  In this printing process, so-called overlap printing is performed, and the head unit 40 moves twice (m times) in the main scanning direction to form one dot row (raster line). Further, the resolution of an image which is a set of raster lines is 720 dpi in both the main scanning direction and the sub-scanning direction, and the resolution in the sub-scanning direction of the image is twice (n times) the nozzle pitch (360 dpi). . In this printing process, (1) the total movement amount (total sub-scanning amount) of the head unit 40 when the head unit 40 moves three times in the sub-scanning direction is the effective amount of the single head 41 in the sub-scanning direction. Nozzle width (described later) × (m × n−1) is larger than the effective nozzle width × (m × n), and (2) the head unit when the head unit 40 is moved three times. A feature is that each of the 40 movement amounts in the sub-scanning direction (sub-scanning amount) is made larger than the effective nozzle width of one head 41 to form an image.

  Various operations of the printer 1 when the printing process is executed are mainly realized by the controller 10. In particular, this embodiment is realized by the CPU 12 processing a program stored in the memory 13. And this program is comprised from the code | cord | chord for performing the various operation | movement demonstrated below.

  FIG. 7 is a flowchart for explaining the printing process. The flowchart shown in FIG. 7 starts when the controller 10 receives print data from the computer 90 (FIG. 1) via the interface 11.

In this printing process, first, the controller 10 sends the printing tape T to the printing area by the transport unit 20 (step S2). That is, the feed roller 21 feeds the printing tape T before printing to the suction table 23 that is a printing area.
Next, the controller 10 causes the drive unit 30 to eject the ink from the nozzles while moving the head unit 40 in the main scanning direction (FIG. 4B) (step S4). That is, the controller 10 forms a dot row of pass 1 on the printing tape T held on the suction table 23. Since the image (printed material) is formed by four passes, when the dot row of pass 1 is formed, the controller 10 moves the head unit 40 to the drive unit 30 by a certain amount of sub-scanning in the sub-scanning direction (FIG. 4C (Step S6: No, Step S8).
Then, the controller 10 forms a dot row with the movement of the head unit 40 in the main scanning direction (FIGS. 4D, 4F, and 4H) and moves the head unit 40 in the sub-scanning direction until the dot formation process is completed. (FIGS. 4E and 4G) are alternately performed (steps S4 to S8).

  Here, the overlap printing according to the present embodiment will be described. Overlap printing is a printing method in which one dot row (raster line) is formed by two or more nozzles. Specifically, one nozzle intermittently forms a dot row every several dots in the main scanning direction. Then, dot rows are formed so as to complement the intermittent dot rows already formed by other nozzles.

  8 and 9 are diagrams for explaining overlap printing according to the present embodiment. However, for simplicity of explanation, only the nozzle row C of the four nozzle rows (nozzle row Y, nozzle row M, nozzle row C, nozzle row K) of each head 41 is shown, and the number of nozzles of each head 41 is also shown. Reduced to 16. For this reason, FIG. 8 shows the positions in the pass 1 to pass 4 of the nozzle row C of the heads in the sub-scanning direction (head 41 (1), head 41 (2), etc.) among the ten heads 41. FIG. 9 shows the state of dot formation, and FIG. 9 shows the positions in pass 1 to pass 4 of nozzle row C of the head (head (10), head 41 (9), etc.) on the front side in the sub-scanning direction. The state of dot formation is shown. 8 and 9, dots formed by the nozzles of the head 41 (1) and the head 41 (7) are indicated by white circles (◯), and the nozzles of the head 41 (2) and the head 41 (8) are formed. The dots to be formed are indicated by black circles (●), the dots formed by the nozzles of the head 41 (3) and the head 41 (9) are indicated by white triangles (Δ), and the nozzles of the head 41 (4) and the head 41 (10) are Dots to be formed are indicated by black triangles (▲), dots formed by the nozzles of the head 41 (5) are indicated by white rhombuses (）), and dots formed by the head 41 (6) are indicated by black rhombuses (♦).

  In pass 1 to pass 4, dots are formed in the pixels in the print area by the nozzles in the nozzle row C. Here, the “pixel” refers to a grid on a grid virtually defined on the printing tape T in order to regulate the positions where dots are formed. Further, in order to specify and describe the pixels, the pixels arranged in the main scanning direction are represented by “rows”, and the pixels arranged in the sub scanning direction are represented by “columns”. Note that the pixels shown in FIGS. 8 and 9 are arranged at an interval of 720 dpi in both the main scanning direction and the sub-scanning direction.

  First, in pass 1, ink is ejected from the nozzles of each head 41. Then, dot rows are formed in the pixels of the odd rows (R1, R3, R5,...) And the odd rows (1, 3, 5,...) Shown in FIG. For example, ink is ejected from the nozzle # 1 of the head 41 (3), and dots are formed in odd-numbered pixels in the R3 row. Similarly, ink is ejected from the nozzle # 2 of the head 41 (3), and dots are formed on the pixels in the odd columns of the R5th row. In this way, each nozzle forms a dot every other pixel in the main scanning direction in each row corresponding to each position.

  Note that the ink ejection method of the overlapping nozzles of two heads adjacent to each other in the width direction (here, the head 41 (3) and the head 41 (4) will be described as an example) is a non-overlapping nozzle (for example, This is different from the method of ejecting ink from the nozzle # 3) of the head 41 (3). That is, in pass 1, the nozzle # 15 and the nozzle # 16 of the head 41 (3) on the back side in the width direction form a dot row on the 3 × 7 • 11... Nozzle # 1 and nozzle # 2 of the head 41 (4) on the near side form a dot row on the 1 × 5 × 9. In this manner, the nozzles of the two adjacent heads 41 alternately discharge ink to form dot rows in odd-numbered pixels.

  After the end of pass 1, the head unit 40 performs a predetermined sub-scanning amount F (specifically, 35/720 dpi) from the back side to the front side in the sub-scanning direction as the first movement in the sub-scanning direction during printing. Just move.

  In pass 2 after the movement of the head unit 40, dot rows are formed in pixels in even-numbered rows (R2, R4, R6,...) And even-numbered columns (2, 4, 6,...). For example, ink is ejected from the nozzle # 1 of the head 41 (3), and dots are formed in the even-numbered pixels of the R38th row. Similarly, ink is ejected from the nozzle # 2 of the head 41 (3), and dots are formed at even-numbered pixels in the R40th row. In the second pass, the nozzle # 15 and the nozzle # 16 of the head 41 (3) on the back side in the width direction among the adjacent heads form a dot row in pixels of 4, 8, 12,. Nozzle # 1 and nozzle # 2 of the head 41 (4) on the near side form a dot row in the pixels of 2, 6, 10. That is, as in the first pass, the nozzles of two adjacent heads 41 alternately discharge ink to form dots in even-numbered pixels (the same applies to the third pass and the fourth pass described later). is there).

  After the end of pass 2, the head unit 40 moves by a predetermined sub-scanning amount F (35/720 dpi) as the second movement in the sub-scanning direction.

  Similarly, in pass 3, dot rows are formed in pixels in even rows and in even rows. As a result, for example, the R53 (odd number) dot row is completed by pass 1 and pass 3.

  After the end of pass 3, the head unit 40 moves by a sub-scanning amount F (35/720 dpi) having the same magnitude as the first and second sub-scanning amounts as the third movement in the sub-scanning direction. Thus, each movement amount F of the three movements of the head unit 40 in the sub-scanning direction has the same magnitude. Then, each movement amount F and the total of the three sub-scanning amounts of the head unit 40 (total sub-scanning amount 3F) are set so as to satisfy a predetermined relationship with the effective nozzle width of one head 41 described below. Has been.

  First, the effective nozzle will be described. About an effective nozzle, a view differs according to the presence or absence of the overlap nozzle (above-mentioned) between the adjacent heads 41. FIG. When there is no overlap nozzle, the effective nozzles of each head 41 are all the nozzles in the nozzle row (see FIG. 11). On the other hand, when there are overlap nozzles, the effective nozzles of each head 41 are determined in consideration of the overlap nozzles. Specifically, the effective nozzles of the head 41 include nozzles that do not overlap the nozzle row of the head 41 and nozzles that distribute the overlap nozzles of the head 41 evenly in relation to the other heads 41. .

  Here, how the overlap nozzles are evenly distributed will be described. For example, in FIG. 8, nozzle # 15 and nozzle # 16 of the head 41 (3) overlap with nozzle # 1 and nozzle # 2 of the head 41 (4). In such a case, nozzle # 15 of nozzle # 15 and nozzle # 16 is included in the effective nozzle of head 41 (3), and nozzle # 2 of nozzle # 1 and nozzle # 2 is the head. The overlap nozzles are evenly distributed so as to be included in 41 (4) effective nozzles. Thus, half of the overlapping nozzles of the head 41 are distributed to the head 41 so as to be included in the effective nozzles.

  The ten heads 41 of the present embodiment each have an overlap nozzle, and the effective nozzles of each head 41 are as follows. The effective nozzles of the head 41 (1) are the nozzles # 1 to # 14, the nozzle # 1 of the head 41 (2), the nozzle # 15 that overlaps the nozzle # 2, and the nozzle # 15 of the nozzle # 16. 15 nozzles. On the other hand, the effective nozzles of the head 41 (2) are the nozzle # 15 of the head 41 (1), the nozzle # 1 overlapping the nozzle # 16, the nozzle # 2 of the nozzle # 2, and the nozzle # 3 to the nozzle # 3. 14 nozzles # 1 of the head 41 (3), nozzle # 15 overlapping nozzle # 2 and nozzle # 15 of nozzle # 16. The effective nozzles of the head 41 (3) to the head 41 (9) are the nozzle # 2 to the nozzle # 15, similarly to the head 41 (2). On the other hand, the effective nozzles of the head 41 (10) are fifteen nozzles # 1 and # 2 of the nozzle # 1 and nozzle # 2 that overlap the nozzle of the head 41 (9), and nozzles # 3 to # 16. Nozzle.

  Next, the effective nozzle width determined from the above-described effective nozzle will be described. The effective nozzle width is a width of effective nozzles in the sub-scanning direction (the effective nozzles are arranged at intervals of 2/720 dpi in the sub-scanning direction). In this embodiment, the effective nozzle width of the head 41 (1) and the head 41 (10) is 30/720 dpi because there are 15 effective nozzles. On the other hand, the effective nozzle width of the head 41 (2) to the head 41 (9) is 28/720 dpi because there are 14 effective nozzles. In the printer 1, each moving amount F (35/720 dpi) of the head unit 40 in the sub-scanning direction is larger than the smaller effective nozzle width (28/720 dpi) of the two effective nozzle widths. Is set.

  The relationship between the total sub-scanning amount 3F and the effective nozzle width (28/720 dpi) is set as follows. As described above, one raster line is formed by moving the head unit 40 m times (twice) in the main scanning direction, and the image resolution (720 dpi) is n times (twice) the nozzle pitch (360 dpi). ). At this time, in the printer 1, the total sub-scanning amount 3F (105/720 dpi) at the time of printing by the head unit 40 is larger than the effective nozzle width (28/720 dpi) × (m × n−1), and The effective nozzle width is set to be smaller than (28/720 dpi) × (m × n). In this embodiment, since m and n are each 2, the total sub-scanning amount 3F (105/720 dpi) is larger than (28/720 dpi) × 3 (= 84/720 dpi) and (28 / 720 dpi) × 4 (= 112/720 dpi).

  Continue explaining overlap printing. In pass 4, dot rows are formed in pixels in even rows and odd rows. As a result, for example, the R52 (even) row dot row is completed by pass 2 and pass 4. As described above, in the overlap printing of this embodiment, one dot row is formed by two different nozzles.

  Here, the nozzles of which heads 41 form the dot rows (raster lines) in the print area will be considered. Here, the dot row in the print area refers to a dot row completed like the dot row of the R52th row, and in the present embodiment, refers to the dot rows from the R52 row to the Rn row (FIG. 9).

  As shown in FIGS. 8 and 9, all the dot rows in the print area are formed by nozzles of two different (or three) heads 41. That is, the odd-numbered (R53, etc.) dot columns are formed by nozzles of different heads 41 in pass 1 and pass 3, and the even-numbered (R52, etc.) dot columns are different heads in pass 2 and pass 4. It is formed by 41 nozzles. Thus, the reason why each dot row is formed by the nozzles of two (or three) different heads 41 is that the sub-scanning amount F of the head unit 40 is equal to the effective nozzle width of one head 41 (28/720 dpi). This is because it is larger than.

  Here, the dot rows formed by the nozzles of two different heads 41 are nozzles that do not overlap (nozzle # 5 of head 41 (1) and nozzle # 12 of head 41 (3), as in the R60th row. ) Only. On the other hand, the dot rows formed by the nozzles of the three different heads 41 are overlap nozzles (nozzle # 15 of the head 41 (4) and nozzle # 1 of the head 41 (5)) as in the R59th row. This is a dot row formed by nozzles that do not overlap (nozzle # 8 of the head 41 (2)).

  In addition, when two adjacent dot rows in the print area are viewed, the nozzles forming the two dot rows are nozzles of four different heads 41 (or five different heads 41). For example, the nozzles that form the dot rows of the R52 and R53 rows are four heads with different heads 41 (1), 41 (2), 41 (3), and 41 (4). Nozzle. That is, the head 41 (1) and the head 41 (3) form the R52th dot row, and the head 41 (2) and the head 41 (4) form the R54th dot row. Further, the nozzles forming the R59th and R60th dot columns are the head 41 (1), the head 41 (2), the head 41 (3), the head 41 (4), and the head 41 (5). The nozzles of the five heads are different. That is, the head 41 (1) and the head 41 (3) form the dot row of the R60th row, and the head 41 (2), the head 41 (4), and the head 41 (5) form the dot row of the R59th row. To do. Thus, one head 41 does not form a continuous dot row.

The overlap printing according to the present embodiment has been described above. Returning to the flowchart shown in FIG. 7, the description of the print processing will be continued. When the dot formation process is completed by forming the dot row of pass 4 (step S6: Yes), in other words, when a printed matter (image) is printed on the printing tape T, the controller 10 causes the drive unit 30 to the head unit 40. Is moved in the sub-scanning direction (FIG. 4I) and is positioned at the home position (step S10).
Next, the controller 10 sends out the printing tape T on which dots are formed (printed printing tape T) from the printing area by the transport unit 20 (step S12). That is, the delivery roller 22 delivers the printed printing tape T from the printing area.
If there is further print data to be printed (step S14: Yes), the controller 10 repeats the above-described operation (steps S2 to S12) to print on the print tape T. On the other hand, when there is no print data (step S14: No), the controller 10 ends the print processing.

<< Effectiveness of this printing process >>
In the printing process described above, the controller 10 forms an image by setting each sub-scanning amount F (35/720 dpi) in the sub-scanning direction of the head unit 40 to be larger than the effective nozzle width (28/720 dpi). , Degradation of image quality can be suppressed.

  That is, as described above, the raster line formed by only the nozzles of one head 41 (the head 41 (3) having a small discharge amount and the head 41 (5) having a large discharge amount as described in FIG. 5). As the number increases, density unevenness tends to become more prominent (see FIG. 5). Therefore, by making the single sub-scanning amount F of the head unit 40 larger than the effective nozzle width, each dot row (raster line) in the printing area is formed by nozzles of two or three different heads 41. (FIGS. 8 and 9). Accordingly, since there is no raster line formed by only one head 41, it is possible to suppress the density unevenness from being noticeable, and as a result, it is possible to suppress deterioration in image quality.

  In addition, by making the sub-scanning amount F larger than the effective nozzle width, it is possible to suppress the density unevenness due to the joint between the adjacent heads 41 from becoming significant. That is, since the head unit 40 is formed by connecting ten heads 41 in the sub-scanning direction, it is known that density unevenness occurs due to the low positional accuracy of the joints. When an image is formed by a plurality of passes, for example, if the joint in pass 1 and the joint in pass 2 match in the sub-scanning direction, density unevenness caused by the joint becomes noticeable. On the other hand, when the sub-scanning amount F is made larger than the effective nozzle width as in the main printing process, the head joints in pass 1 to pass 4 are dispersed as shown in FIGS. Therefore, it is possible to suppress the density unevenness from becoming remarkable.

  Further, the controller 10 determines that the head unit 40 has a total sub-scanning amount 3F (105/720 dpi) in the sub-scanning direction larger than the effective nozzle width of one head 41 in the sub-scanning direction × (m × n−1), In addition, by forming the image by making it smaller than the effective nozzle width × (m × n), it is possible to suppress an increase in the width of the head unit 40 in the sub-scanning direction.

  That is, as described above, the larger the total sub-scanning amount of the head unit 40, the larger the width of the head unit 40 in the sub-scanning direction (see FIG. 6). Therefore, when m and n are 2, the total sub-scanning amount 3F is set to be larger than the effective nozzle width × 3 and smaller than the effective nozzle width × 4, whereby each raster line in the print area is set. The total sub-scanning amount of the head unit 40 can be reduced while forming the nozzles with the nozzles of two or three different heads 41 (FIGS. 8 and 9). As a result, even when ink is ejected over the entire width of the printing tape T in each pass of overlap printing, it is possible to suppress an increase in the width of the head unit 40 (the number of heads 41 increases).

Therefore, according to the above-described printing process, it is possible to suppress deterioration in image quality and to increase the width of the head unit 40 in the sub-scanning direction.
Further, in the above printing process, the controller 10 forms n (2) continuous raster lines by ejecting ink to the nozzles of m × n (= 4) heads 41, so that n Density unevenness can be more effectively suppressed in each continuous raster line.
Further, in the printing process described above, the controller 10 sets the movement amounts (sub-scanning amounts F) to the same size (35/720 dpi) when the head unit 40 moves three times in the sub-scanning direction. For this reason, dot rows are periodically formed, density unevenness occurrence positions are regularly dispersed, and it is possible to effectively suppress density unevenness.

== Printing Process According to Second Embodiment ==
In the printing process according to the above-described embodiment (first embodiment), overlap printing is performed as shown in FIGS. In the second embodiment, interlaced printing is performed without performing overlap printing (in the first embodiment, interlaced printing is also performed). Here, interlaced printing means a printing method in which raster lines that are not formed are sandwiched between raster lines that are formed in one pass. That is, a raster line that is not formed in one pass is complemented with another pass to form a continuous raster line.

  The resolution of the image according to the second embodiment is 720 dpi in the main scanning direction and 1440 dpi in the sub-scanning direction. The resolution 1440 dpi in the sub-scanning direction is four times (n = 4) the nozzle pitch (360 dpi). In addition, since the head unit 40 forms one raster line by one movement, m = 1. Further, also in the second embodiment, the head unit 40 alternately performs four movements in the main scanning direction and three movements in the main scanning direction as shown in FIG.

  In the printing process according to the second embodiment, the controller 10 also determines (1) the total amount of movement of the head unit 40 when the head unit 40 has moved three times in the sub-scanning direction. The effective nozzle width in the direction × (m × n−1) and smaller than the effective nozzle width × (m × n), and (2) the head unit when the head unit 40 has moved three times. Each of the 40 movement amounts in the sub-scanning direction is made larger than the effective nozzle width to form an image.

  FIG. 10 is a diagram for explaining interlaced printing according to the second embodiment. In FIG. 10, as in FIG. 8, only the nozzle row C is shown, and dots formed by the nozzles of the head 41 (1) are indicated by white circles (◯), and the nozzles of the head 41 (2) are formed. The dots are indicated by black circles (●), the dots formed by the nozzles of the head 41 (3) are indicated by white triangles (Δ), the dots formed by the nozzles of the head 41 (4) are indicated by black triangles (▲), and the head The dots formed by the nozzle 41 (5) are indicated by white rhombuses (◇), and the dots formed by the head 41 (6) are indicated by black rhombuses (♦).

  A single sub-scanning amount F of the head unit 40 during printing is 71/1440 dpi, which is larger than the effective nozzle width {28/720 dpi (= 56/1440 dpi)} of one head 41. Here, a dot row in a printing area formed by the head unit 40 that moves with such a sub-scanning amount will be considered.

  The dot rows in the print area are formed based on a certain regularity. That is, four consecutive raster lines (these raster lines are formed by different heads 41) are repeatedly formed as a lump. That is, La (four consecutive raster lines) shown in FIG. 10 is repeatedly formed, and the raster lines before and after La are also repeatedly formed for every four raster lines. In this way, since the sub-scanning amount F is larger than the effective nozzle width, continuous raster lines are not formed by the same head 41, so even if a raster line that causes density unevenness is formed by a certain head 41, The raster lines are formed in a dispersed manner without being continuous. As a result, it is possible to suppress the density unevenness from becoming prominent, and as a result, it is possible to suppress deterioration in image quality.

  The total sub-scanning amount F3 of the head unit 40 is 213/1440 dpi. The total sub-scanning amount F3 is larger than the effective nozzle width × (m × n−1), that is, 56/1440 dpi × 3 (= 168/1440 dpi), and the effective nozzle width × (m × n). That is, it is smaller than 56/1440 dpi × 4 (= 224/1440 dpi). As a result, as in the first embodiment, the width of the head unit 40 is increased (the number of heads 41 is increased) even when ink is ejected over the entire width of the printing tape T in each pass of interlaced printing. Can be suppressed.

  In the second embodiment, the resolution in the sub-scanning direction is 1440 dpi, which is four times the nozzle pitch (360 dpi) (n = 4). However, the present invention is not limited to this. For example, the resolution in the sub-scanning direction may be 720 dpi and twice the nozzle pitch (n = 2). That is, if interlaced printing can be realized, n may be a natural number of 2 or more.

== Other Embodiments ==
The liquid ejection device and the like according to the present invention have been described above based on the above embodiment. However, the above-described embodiment is intended to facilitate understanding of the present invention and is intended to limit the present invention. is not. The present invention can be changed and improved without departing from the gist thereof, and the present invention includes the equivalents thereof.

  In the above embodiment, the liquid ejection device is embodied as an ink jet printer. However, the present invention is not limited to this, and other liquids (for example, a liquid material in which particles of functional material are dispersed, a flow such as a gel, etc.) are used. The present invention can also be embodied in a liquid discharge device that discharges (injects) a shape. For example, a liquid material ejecting apparatus that ejects a liquid material in the form of dispersed or dissolved materials such as electrode materials and color materials used in the manufacture of liquid crystal displays, color filters, EL (electroluminescence) displays, and surface emitting displays, It may be a liquid ejecting apparatus for ejecting a bio-organic material used for biochip manufacturing, or a liquid ejecting apparatus for ejecting a liquid as a sample used as a precision pipette. In addition, a transparent resin liquid such as UV curable resin is used to form a liquid ejection device that ejects lubricating oil pinpoint to precision machines such as watches and cameras, and micro hemispherical lenses (optical lenses) used in optical communication elements. A liquid discharge device that discharges a liquid onto the substrate, a liquid discharge device that discharges an etching solution such as acid or alkali to etch the substrate, and a fluid discharge device that discharges gel. The present invention can be applied to any one of these discharge devices.

  In the above embodiment, the raster line is formed by moving the head unit 40 four times in the main scanning direction and three times in the sub-scanning direction while the printing tape T is stopped (see FIGS. 8 and 8). 9) However, the present invention is not limited to this. For example, the raster line may be formed by moving the head unit 41 only in the main scanning direction and the printing tape T moving in the sub-scanning direction. Also, the head unit 41 does not move and the printing tape T is not moved. A raster line may be formed by moving in the main scanning direction and the sub-scanning direction. That is, the raster line may be formed by the head unit 40 moving relative to the printing tape T in the main scanning direction and the sub-scanning direction.

  In the above embodiment, interlaced printing was performed (n = 2 or n = 4) as shown in FIGS. 8 to 10, but interlaced printing was not performed (that is, n = 1). Alternatively, only overlap printing may be performed. For example, overlap printing with n = 1 and m = 2 may be performed (m may be a natural number larger than 2).

  In the above embodiment, the overlapping nozzles of adjacent heads 41 (for example, nozzle # 15 of head 41 (3) and nozzle # 1 of head 41 (4)) alternately eject ink. Although one raster line is formed (that is, both of the two overlapping nozzles eject ink), the present invention is not limited to this.

  For example, only one of the overlapping nozzles of the adjacent heads 41 may eject ink. Specifically, for the head 41 (3), ink is ejected from the nozzles # 1 and # 2 of the overlap nozzles (nozzles # 1, # 2, # 15, and # 16), and the nozzles # 15 and # 2 are ejected. No ink may be ejected from 16. Similarly, with respect to the head 41 (4), ink is ejected from the nozzles # 1 and # 2 of the overlapping nozzles (nozzles # 1, # 2, # 15, and # 16) and from the nozzles # 15 and # 16. The ink may not be ejected. In such a case, the number of effective nozzles (14) of each head 41 is equal.

  In the above case, since the nozzles (mainly overlap nozzles) at the joints between adjacent heads 41 are used in the same manner, raster lines corresponding to the joints between the heads 41 are also formed at equal intervals. (That is, regularly formed) can suppress density unevenness caused by the joint.

  In the above embodiment, the head unit 40 has the overlap nozzle (for example, the nozzle # 15 of the head 41 (1)) as shown in FIG. 4, but the present invention is not limited to this. Absent. For example, as shown in FIG. 11, the head unit 40 may not have an overlap nozzle. Effective nozzles in such a case are all the nozzles (nozzle # 1 to nozzle # 360) of the nozzle row of each head 41. The effective nozzle width is the width of all nozzles in the nozzle row. FIG. 11 is a diagram illustrating a head unit 40 according to another embodiment.

1 is an overall configuration block diagram of a printer 1. FIG. FIG. 2A is a schematic sectional view of the printer 1, and FIG. 2B is a schematic top view of the printer 1. The nozzle arrangement on the lower surface of the head unit 40 is shown. FIG. 4A to FIG. 4I are schematic diagrams for explaining the movement mode of the head unit 40 during printing. 5A and 5B are diagrams for explaining density unevenness due to a difference in ejection characteristics of the heads 41. FIG. FIG. 6A shows the head unit 40 when the total sub-scanning amount is increased. FIG. 6B shows the head unit 40 when the total sub-scanning amount is reduced. 6 is a flowchart for explaining the printing process. It is a figure for demonstrating the overlap printing concerning a present Example. It is a figure for demonstrating the overlap printing concerning a present Example. It is a figure for demonstrating the interlaced printing which concerns on 2nd embodiment. It is the figure which showed the head unit 40 which concerns on other embodiment.

Explanation of symbols

1 printer,
10 controller, 11 interface, 12 CPU, 13 memory,
14 unit control circuit, 20 transport unit, 21 feed roller,
22 delivery roller, 23 suction table, 30 drive unit,
40 head units, 41 heads, 50 detector groups,
90 computers

Claims (4)

(A) A plurality of heads in which a plurality of nozzles that discharge liquid to the medium are arranged in the first direction are provided along the first direction, and the second direction intersecting the first direction is directed to the medium. a head unit that forms one raster line by ejecting the liquid by moving relative to m times,
A head unit in which the width in the first direction of the head unit is larger than the width in the first direction of the medium;
(B) a moving mechanism for moving the head unit relative to the medium alternately in the second direction and the first direction a plurality of times;
(C) a controller that forms an image having a resolution n times the pitch of the nozzles by relatively moving the head unit a plurality of times to form a plurality of raster lines;
The total amount of movement of the head unit in the first direction when the head unit is relatively moved a plurality of times is larger than the effective nozzle width of the one head in the first direction × (m × n−1). And smaller than the effective nozzle width × (m × n),
The amount of movement of the head unit in the first direction when the head unit is relatively moved a plurality of times is made larger than the effective nozzle width,
A control unit for forming the image;
A liquid ejection apparatus comprising (d). The liquid ejection device according to claim 1,
n is a natural number of 2 or more,
The controller is
The liquid ejecting apparatus, wherein the n consecutive raster lines are formed by ejecting the liquid to the nozzles of the (m × n) heads. The liquid ejection device according to claim 1 or 2, wherein
The liquid ejecting apparatus according to claim 1, wherein the movement amounts of the head unit in the first direction when the head unit relatively moves a plurality of times are the same. (A) A plurality of heads in which a plurality of nozzles that discharge liquid to the medium are arranged in the first direction are provided along the first direction, and the second direction intersecting the first direction is directed to the medium. A head unit that forms one raster line by ejecting the liquid by moving relative to m times, wherein the width of the head unit in the first direction is larger than the width of the medium in the first direction Unit
An image having a resolution n times the pitch of the nozzles is formed by alternately moving the medium relative to the medium in the second direction and the first direction a plurality of times to form the plurality of raster lines. An image forming method comprising:
(B) The total amount of movement of the head unit in the first direction when the head unit is relatively moved a plurality of times is the effective nozzle width of the one head in the first direction × (m × n−1). Larger than the effective nozzle width x (m x n),
The amount of movement of the head unit in the first direction when the head unit is relatively moved a plurality of times is made larger than the effective nozzle width,
An image forming method comprising forming the image.

Images