JP2010105343A - Liquid discharge apparatus and liquid discharge method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent an image quality from being degraded as a result of gap of a formation position of dots (strike position of ink) between a first nozzle array and a second nozzle array if a medium size changes because there is a risk that the medium size changes due to, for example, drying or the like before printing is carried out by the second nozzle array after printing is carried out by the first nozzle array. <P>SOLUTION: The liquid discharge apparatus has the first nozzle array in which a plurality of the nozzles for discharging the liquid are arranged in a predetermined direction, the second nozzle array in which a plurality of the nozzles for discharging the liquid are arranged in the predetermined direction, and a controller which corrects discharge of the liquid from at least one of the first nozzle array and the second nozzle array according to a position on the medium in case of printing to the medium by the second nozzle array after printing to the medium by the first nozzle array. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

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

For example, a nozzle row in which nozzles are arranged in the paper width direction (hereinafter referred to as a first nozzle row), a nozzle row in which nozzles are arranged in the paper width direction on the downstream side of the first nozzle row in the transport direction (hereinafter referred to as a second nozzle row), and And a liquid ejecting apparatus that prints an image using these two nozzle rows (see, for example, Patent Document 1). In such a liquid ejecting apparatus, for example, the printing resolution can be increased by forming dots by the second nozzle row between the dots formed by the first nozzle row.
JP 2008-149624 A

  However, the size of the medium may change due to, for example, drying after printing with the first nozzle row and before printing with the second nozzle. When the size of the medium changes, the dot formation position (ink landing position) by the first nozzle array and the second nozzle array shifts, and the image quality deteriorates.

  Accordingly, an object of the present invention is to prevent deterioration in image quality.

  A main invention for achieving the above object is a first nozzle row in which a plurality of nozzles for discharging liquid are arranged in a predetermined direction, a second nozzle row in which a plurality of nozzles for discharging liquid are arranged in the predetermined direction, After printing on the medium with the first nozzle row and then printing on the medium with the second nozzle row, at least one of the first nozzle row and the second nozzle row according to the position on the medium And a controller for correcting the discharge of the liquid from the liquid discharge device.

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

=== Summary of disclosure ===
At least the following matters will become clear from the description of the present specification and the accompanying drawings.

A first nozzle row in which a plurality of nozzles that discharge liquid are arranged in a predetermined direction, a second nozzle row in which a plurality of nozzles that discharge liquid are arranged in the predetermined direction, and the first nozzle row are printed on the medium. And a controller that corrects ejection of liquid from at least one of the first nozzle row and the second nozzle row in accordance with a position on the medium when printing on the medium with the second nozzle row. Thus, a liquid ejection device having the above is clarified.
According to such a liquid ejecting apparatus, it is possible to prevent deterioration in image quality of an image formed by the first nozzle row and the second nozzle row.

In this liquid ejection apparatus, it is preferable that a drying mechanism that accelerates drying of the medium printed by the first nozzle row is provided between the first nozzle row and the second nozzle row.
According to such a liquid ejecting apparatus, the printing time can be shortened.

In the liquid ejecting apparatus, it is preferable that the correction is performed according to the position on the medium when a ruled line is printed by the first nozzle row and the second nozzle row.
According to such a liquid ejecting apparatus, the ruled line can be corrected so as not to be divided, which is effective in printing the ruled line.

In this liquid ejection apparatus, it is preferable that the controller determines whether or not to perform the correction according to the direction of the ruled line and the number of dots in the width direction of the ruled line.
According to such a liquid ejecting apparatus, it is possible to correct the ruled line more accurately.

In this liquid ejection apparatus, each nozzle of the first nozzle row and each nozzle of the second nozzle row are alternately arranged in the predetermined direction, and the ruled line is a ruled line in the predetermined direction. When the ruled line is formed with one dot in the width direction of the ruled line using each nozzle of the first nozzle row and each nozzle of the second nozzle row, the controller It is desirable to perform the correction by adjusting the liquid ejection timing from the second nozzle row in accordance with the position of the nozzle.
According to such a liquid ejecting apparatus, it is possible to correct the 1-dot ruled line in the same direction (predetermined direction) as the direction of each nozzle row so as not to break up.

In this liquid ejection apparatus, each nozzle of the first nozzle row and each nozzle of the second nozzle row are alternately arranged in the predetermined direction, and the ruled line is in a direction intersecting the predetermined direction. When the ruled line is a ruled line formed by using a certain nozzle in the first nozzle row and a certain nozzle in the second nozzle row to form two dots in the width direction of the ruled line, The controller preferably performs the correction by changing the nozzle of the second nozzle row used for forming the ruled line according to the position on the medium.
According to such a liquid ejecting apparatus, it is possible to correct the two-dot ruled line in the direction intersecting with the direction of each nozzle row so as not to be divided.

In the liquid ejecting apparatus, a plurality of the ruled lines having different numbers of dots in the width direction are printed in a plurality of regions on the medium. The ruled line patterns are respectively formed in the predetermined direction and in a direction intersecting the predetermined direction. The position on the medium where the correction is performed is preferably determined based on the printing result of each ruled line pattern.
According to such a liquid ejecting apparatus, it is possible to more accurately correct the landing position of the liquid ejected from the second nozzle according to the position on the medium body.

  Also, a liquid ejection method using a liquid ejection apparatus, comprising: a first nozzle row in which a plurality of nozzles that eject liquid are arranged in a predetermined direction; and a second nozzle row in which a plurality of nozzles that eject liquid are arranged in the predetermined direction. When the first nozzle row prints on the medium and then the second nozzle row prints on the medium, the first nozzle row and the second nozzle according to the position on the medium. A liquid ejection method for correcting the ejection of liquid from at least one of the columns becomes clear.

  Hereinafter, an embodiment of the present invention will be described using a printer 1 (line head printer) which is one of liquid ejecting apparatuses.

=== Configuration of Printer ===
FIG. 1 is a block diagram of the overall configuration of the printer 1. FIG. 2A is a cross-sectional view of the printer 1. FIG. 2B is a diagram illustrating a state in which the printer 1 transports the paper S (medium).

  The printer 1 includes a controller 60, a transport unit 20, a head unit 30, a heater unit 40, and a detector group 50. The printer 1 that has received the print data from the computer 110 that is an external device prints an image on the paper S by controlling each unit (conveyance unit 20, head unit 30, heater unit 40) with the controller 60. Further, the detector group 50 monitors the situation in the printer 1, and the controller 60 controls each unit based on the detection result.

  The controller 60 is a control unit for controlling the printer 1. The interface unit 61 is for transmitting and receiving data between the computer 110 which is an external device and the printer 1. The CPU 62 is an arithmetic processing unit for controlling the entire printer 1. The memory 63 is for securing an area for storing a program of the CPU 62, a work area, and the like. The CPU 62 controls each unit by a unit control circuit 64 according to a program stored in the memory 63.

  The transport unit 20 feeds the paper S to a printable position, and transports the paper S at a predetermined transport speed in the transport direction during printing. The paper feed roller 23 is a roller for automatically feeding the paper S inserted into the paper insertion opening onto the transport belt 22 in the printer 1. Then, the annular transport belt 22 is rotated by the transport rollers 21A and 21B, and the paper S on the transport belt 22 is transported in the transport direction. The paper S is electrostatically adsorbed or vacuum adsorbed to the transport belt 22 (not shown).

  The head unit 30 is for ejecting ink onto the paper S, and has a plurality of heads. In the present embodiment, the head unit 30 has two heads (a first head 31 and a second head 32). Each of these heads is a first head from the upstream side to the downstream side in the transport direction. 31 and the second head 32 are arranged in this order. A plurality of nozzles for ejecting ink are provided on the lower surface of each head. The relationship between each head and the nozzle will be described later.

  The heater unit 40 has a drying mechanism 41. The drying mechanism 41 is provided between the first head 31 and the second head 32. The drying mechanism 41 promotes drying of the paper S printed by the first head 31 by heating the paper S to, for example, 40 to 50 degrees before printing the paper S by the second head 32. .

  The detector group 50 is for monitoring the situation in the printer 1. For example, the detector group 50 is attached to the transport roller 21 </ b> A and used for control such as transport of paper, and the presence or absence of transported paper S. There are paper detection sensors to detect.

<About the head>
FIG. 3 is a diagram illustrating the nozzle arrangement of the first head 31 and the second head 32. In the figure, the nozzle arrangement as viewed from the top of the printer is shown. Originally, each nozzle present on the lower surface of the head is blocked by other elements and cannot be viewed from the top of the printer. However, for ease of explanation, the positions where the nozzles are present are shown transparently when viewed from the top of the printer.

  The first head 31 and the second head 32 are a full-line type in which the nozzles of each nozzle row are continuously arranged from one end to the other end in the width direction of the paper (hereinafter also referred to as the paper width direction). Head. Note that the first head 31 and the second head 32 of the reference example shown here are shown to be shorter than actual in the paper width direction due to space limitations. The first head 31 and the second head 32 can eject ink droplets over the entire width of the paper.

  In the figure, a first head 31 is disposed on the upstream side in the sheet conveyance direction, and a second head 32 is disposed on the downstream side in the conveyance direction. Both the first head 31 and the second head 32 have the same nozzle arrangement.

  The first head 31 includes eight nozzle rows from nozzle row a to nozzle row h. Each nozzle row of the first head corresponds to the first nozzle row. The nozzle row a and the nozzle row b are a black ink nozzle group that discharges black K ink droplets. The nozzle row c and the nozzle row d are a cyan ink nozzle group for ejecting cyan C ink droplets. The nozzle row e and the nozzle row f are a magenta ink nozzle group for ejecting magenta M ink droplets. The nozzle row g and the nozzle row h are a yellow ink nozzle group for ejecting yellow Y ink droplets. Thus, each nozzle group includes two nozzle rows.

  In each of the nozzle arrays a to h, nozzles are formed at a pitch of 180 dpi. The two nozzle rows in each nozzle group are formed by shifting 360 dpi in the paper width direction. As a result, for example, the nozzles of the nozzle row b are arranged between the nozzles of the nozzle row a in the paper width direction.

  Similarly, the nozzles of the nozzle row d are shifted by 360 dpi in the paper width direction and are arranged between the nozzles of the nozzle row c. Further, the nozzles in the nozzle row f are shifted by 360 dpi in the paper width direction and are arranged between the nozzles in the nozzle row e. The nozzles in the nozzle row h are shifted between the nozzles in the nozzle row g by being shifted by 360 dpi in the paper width direction.

  The second head 32 also includes eight nozzle rows from nozzle row a to nozzle row h. Each nozzle row of the second head corresponds to the second nozzle row. As described above, the nozzle arrangement of the second head 32 is the same nozzle arrangement as that of the first head 31. However, the second head 32 is fixed to the printer 1 so as to be shifted by 720 dpi in the paper width row direction (direction intersecting the paper transport direction) with respect to the first head 31.

  By doing so, the nozzles of the black ink nozzle group of the second head 32 are positioned between the nozzles of the black ink nozzle group of the first head 31 in the paper width direction. As a result, ink droplets can be landed on the paper with a resolution of 720 dpi in the paper width direction.

  Similarly, the nozzles of the cyan ink nozzle group of the second head 32 are positioned between the nozzles of the cyan ink nozzle group of the first head 31. Further, the nozzles of the magenta ink nozzle group of the second head 32 are positioned between the nozzles of the magenta ink nozzle group of the first head 31. Further, the nozzles of the yellow ink nozzle group of the second head 32 are positioned between the nozzles of the yellow ink nozzle group of the first head 31. For each ink color, ink droplets can be landed on the paper with a resolution of 720 dpi in the paper width direction.

  Although only the first head 31 and the second head 32 are shown in FIG. 3, the first head 31 and the second head 32 have a distance D0 with the drying mechanism 41 interposed therebetween as shown in FIGS. 2A and 2B. Is fixed to the printer 1.

  When the paper S is transported in the transport direction and ink droplets are ejected from the nozzles, the ink droplets land along the transport direction. At that time, each nozzle of the first head nozzle row a, nozzle row c, nozzle row e, and nozzle row g is arranged in an overlapping position when viewed from the transport direction, so that ink droplets are ejected onto the same raster line. Will do. The same can be said for the nozzle row b, the nozzle row d, the nozzle row f, and the nozzle row h. The same is true for each nozzle of the second head 32.

  By ejecting ink droplets of each ink color on the same raster line, the ink colors land on the paper so as to overlap.

  FIG. 4A is a diagram illustrating a state where ink droplets from the first head 31 have landed on a sheet. FIG. 4B is a diagram illustrating a state in which ink droplets from the first head 31 and the second head 32 have landed on the paper. In this figure, the horizontal direction of the paper S is the paper width direction of each head described above. In the figure, a state in which ink droplets are stacked in the order of landing on the paper S is shown. Here, as shown in the figure, it is shown that ink droplets land in the order of black K, cyan C, magenta M, and yellow Y.

  In the figure, the number shown after the code indicating the ink color is the number of the ejected head. For example, “K1” indicates black ink K ejected from the first head 31, and “C2” indicates cyan ink C ejected from the second head 32.

  The nozzle interval in the paper width direction for each ink color of the first head 31 was 360 dpi. Further, in the first head 31, the positions of the nozzles of the respective ink colors are the same in the paper width direction (arranged so that the nozzles of the respective colors overlap each other when viewed from the transport direction). Therefore, when ink droplets are ejected from all the nozzles of the first head 31, each ink droplet lands at a resolution of 360 dpi in the paper width direction. For example, “K1” at the right end of FIG. 4A is a dot formed by the nozzles in the a row of the first head 31, and “K1” on the left side is formed by the nozzles in the b row of the first head 31. Dot. From FIG. 3, the interval between the dots formed by the nozzles in the a row and the dots formed by the b row is 360 dpi.

  In addition, while the paper S is being transported in the transport direction, ink droplets are ejected onto each pixel of the paper S in the order of black K, cyan C, magenta M, and yellow Y. Therefore, as shown in FIG. 4A, ink droplets land on the paper S in the order of black K, cyan C, magenta M, and yellow Y.

  Further, the second head 32 is arranged 720 dpi away from the nozzle of the first head 31 in the paper width direction. For this reason, as shown in FIG. 4B, the ink droplets from the second head 32 land with a deviation of 720 dpi in the paper width direction from the landing position of the ink droplets from the first head 31. That is, dots are formed by the second head 32 between the dots formed by the first head 31. For example, in the figure, for example, the second “K2” from the right end is a dot formed by the nozzles in the a row of the second head 32, and the “K2” next to the two left is the b row of the second head 32. This is a dot formed by the nozzle. Similar to the first head 31, in the second head 32, the dot interval between the dots formed by the nozzles in the a row and the dots formed by the nozzles in the b row is 360 dpi. Thus, since dots are formed by the second head 32 between the dots formed by the first head 31, the dot interval in the paper width direction is 720 dpi.

  As can be seen from the figure, raster lines are alternately printed by the first head 31 and the second head 32 in the paper width direction. In the present embodiment, the first head 31 forms an odd number of raster lines, and the second head 32 forms an even number of raster lines.

  In the following embodiments, one of the four color nozzle groups of each head will be described using (for example, a black ink nozzle group).

<Printing procedure>
When receiving a print command and print data from the computer 110, the controller 60 analyzes the contents of various commands included in the print data and performs the following processing using each unit.
First, the controller 60 rotates the paper feed roller 23 to feed the paper S to be printed onto the transport belt 22. Then, the controller 60 rotates the transport belt 22 by the transport rollers 21A and 21B. As the transport belt 22 rotates, the fed paper S is transported on the transport belt 22 without stopping at a constant speed, and sequentially passes under the first head 31, the drying mechanism 41, and the second head 32. . During this time (while the paper S passes under each head), ink is intermittently ejected from the nozzles of each head according to instructions from the controller 60. As a result, a dot row composed of a plurality of dots is formed on the paper S along the transport direction and the paper width direction. Finally, the controller 60 discharges the paper S on which image printing has been completed.

=== First Embodiment ===
As described above, in the printer 1, the printing resolution is increased by forming dots with the nozzle rows of the second head 32 between the dots formed with the nozzle rows of the first head 31.
When printing is performed using two heads (first head 31 and second head 32) as described above, printing is performed by the first head 31 when printing is performed using the second head 32 at the subsequent stage (downstream in the transport direction). The dried paper S is preferably dried from the viewpoint of preventing bleeding between dots. Therefore, in the present embodiment, a drying mechanism 41 is provided between the first head 31 and the second head 32, and the drying of the paper S is promoted by the drying mechanism 41. By doing so, the distance D0 between the first head 31 and the second head 32 can be set short, and the printing time can be shortened.
However, when the paper S is dried, the paper S may shrink due to evaporation of moisture or the like. When the paper S shrinks, the dot formation positions (ink landing positions) of the first nozzle array and the second nozzle array are shifted, and the image quality deteriorates. This problem is particularly noticeable when printing a fine ruled line. For example, when printing one ruled line, there is a possibility that two ruled lines are formed.

<Relationship between ruled line thickness and displacement>
First, the relationship between the thickness and displacement of a ruled line when printing ruled lines using two heads (nozzle rows) will be described with reference to the drawings. The dot diameter of the dots used in this embodiment is 70 μm, and the resolution is 720 dpi in the paper width direction and 1440 dpi in the transport direction. Further, in the following drawings, the displacement of the ink landing position by the second head 32 is zero (no deviation), 50 μm (plus side and minus side), and 75 μm (plus side and minus side) with the first head 31 as a reference. ) Is shown. Regarding the deviation in the transport direction, the downstream side in the transport direction is the plus side, and the upstream side is the minus side. Further, regarding the shift in the paper width direction, the direction in which the shift of the second head 32 with respect to the first head 31 in FIG. 3 is further increased (left side in FIG. 3) is the plus side, and the opposite direction is the minus side. Further, in the following description, a ruled line with one dot in the ruled line width direction is called a one-dot ruled line, a ruled line with two dots in the ruled line width direction is called a two-dot ruled line, and the number of dots in the ruled line width direction is three. The ruled line is called a three-dot ruled line.

<For 1-dot ruled lines>
FIG. 5 is an explanatory diagram of the influence of deviation in a one-dot ruled line.
In each figure, preceding dots (dots formed by the nozzles of the first head 31) are indicated by black circles, and succeeding dots (dots formed by the nozzles of the second head 32) are indicated by white circles. .

  The upper part of the figure shows a case where a ruled line in the paper width direction is printed, and the deviation amount in the transport direction is zero, 50 μm, and 75 μm in order from the left side of the figure. In each case, the subsequent dot formation position (ink landing position) is shifted to the plus side and the minus side in the transport direction.

  Further, the lower part of the figure shows a case where a ruled line in the transport direction is printed, and the deviation amount in the paper width direction is zero, 50 μm, and 75 μm in order from the left side of the figure. In each case, the subsequent dot formation position (ink landing position) is shifted to the plus side and minus side in the paper width direction.

  Further, on the left side of each figure, the position of the nozzle of each head corresponding to each dot is shown. For example, in the case of a ruled line in the paper width direction, the uppermost dot in the figure is formed by the nozzles in the a row of the first head 31. Further, the dots below that are formed by the nozzles in the a row of the second head 32. Further, the dots below that are formed by the nozzles in the b row of the first head 31.

As shown in the figure, when printing a one-dot ruled line in the paper width direction, one ruled line is formed up to a deviation of 50 μm, but the ruled line is split into two when the deviation is 75 μm.
On the other hand, when printing a one-dot ruled line in the transport direction, only one nozzle of one head (in the figure, the nozzles in row a of the first head 31) is used. Therefore, it is one ruled line regardless of the deviation of the ink landing positions of the two heads.

  As described above, in the case of a one-dot ruled line, the degree of image quality deterioration varies depending on the direction of the ruled line. Specifically, when printing a 1-dot ruled line in the paper width direction, the image quality may deteriorate. On the other hand, when printing a 1-dot ruled line in the transport direction, the image quality does not deteriorate.

<For 2-dot ruled lines>
FIG. 6 is an explanatory diagram of the influence of deviation in a 2-dot ruled line.
The upper part of the figure shows a case where a ruled line in the paper width direction is printed, and the deviation amount in the transport direction is zero, 50 μm, and 75 μm in order from the left side of the figure. In this case as well, as in the case of the one-dot ruled line, the subsequent dot formation position (ink landing position) is shifted to the plus side and the minus side in the transport direction.

Further, the middle stage and the lower stage in the figure show a case where a ruled line in the transport direction is printed.
The middle part of the figure shows a case where the leading dot is formed on the upper side and the trailing dot is formed on the lower side. That is, the dot formed by the first head 31 is the upper two dots, and the dot formed by the second head 32 is the lower two dot ruled lines. For example, when there is no deviation in the figure, the upper dot (black) is formed first by the nozzles in the a row of the first head 31, and the lower dot (white) is moved by the nozzles in the a row of the second head 32. Formed from.

  In the lower part of the figure, the upper and lower positions of the preceding dot and the succeeding dot are reversed. That is, the dot formed by the first head 31 is on the lower side, and the dot formed by the second head 32 is the upper two-dot ruled line. For example, in the figure, when there is no deviation, the lower dot (black) is formed first by the b-row nozzles of the first head 31, and the upper dot (white) is moved backward by the a-row nozzles of the second head 32. Formed from.

In each figure, the shift amount in the paper width direction is zero, 50 μm, and 75 μm in order from the left side of the figure. Here, as in the case of the 1-dot ruled line, the formation position of the succeeding dots (ink landing position) is shifted to the plus side and minus side in the paper width direction. Is printed, one ruled line is formed even when the deviation in the transport direction is 75 μm. That is, when printing a 2-dot ruled line in the paper width direction, it can be said that it is not easily affected by a shift in the transport direction.

Also, in the ruled line in the transport direction where the preceding dot is higher than the succeeding dot (middle stage in the figure), if the deviation in the paper width direction is in the minus direction (the positions of the dots formed by each head are reversed). Is a ruled line. However, when the shift amount is in the plus direction (50 μm and 75 μm), the ruled line is split into two.
Also, in the ruled line in the transport direction (the lower part of the figure) where the preceding dot is lower than the succeeding dot, if the deviation in the paper width direction is positive, the positions of the dots formed by each head are reversed. It is a ruled line. However, when the deviation is in the negative direction (50 μm and 75 μm), the ruled line is split into two.

As described above, in the case of a two-dot ruled line, the degree of image quality deterioration varies depending on the direction of the ruled line and the direction of the shift. Specifically, when the ruled line in the transport direction prints the ruled line on the upper side, the image quality may be deteriorated due to the subsequent dot being shifted in the plus direction in the paper width direction. Further, when the ruled line in the transport direction prints the ruled line on the lower side, the image quality may deteriorate due to the subsequent dot being shifted in the minus direction in the paper width direction.
On the other hand, when printing a ruled line in the paper width direction, the ruled line is not split into two even if the succeeding dots are displaced by 75 μm respectively on the plasma side and the minus side in the transport direction. It can be said that the image quality is hardly deteriorated.

<For 3-dot ruled lines>
FIG. 7 is an explanatory diagram of the influence of deviation in a three-dot ruled line.
Note that the notation in the figure is the same as in the case of the 1-dot ruled line and the 2-dot ruled line described above, and a description thereof will be omitted.
In the three-dot ruled line, both the transport direction and the paper width direction are one ruled line without being divided even if they are shifted by 75 μm. This is considered because the influence of the shift amount on the thickness of the ruled line is reduced. Therefore, when the number of dots in the ruled line width direction is larger than that of the three-dot ruled line (in the case of a thick ruled line), even if a deviation occurs, the ruled line is only thickened and the ruled line is difficult to be divided.

<Effects on image quality due to division of ruled lines>
As described above, it is a thin ruled line that breaks the ruled line due to the deviation of the ink landing positions by the nozzle arrays of the two heads. In the present embodiment, the ruled line is divided into two ruled lines in the case of a 1-dot ruled line and a 2-dot ruled line. In the case of a 1-dot ruled line, the ruled line is split if a deviation in the transport direction occurs when printing a ruled line in the paper width direction. In the case of a 2-dot ruled line, when printing a ruled line in the transport direction, The ruled line split when the side shift occurred. When the ruled lines are split in this way, it is possible to visually confirm the deterioration of the image quality.

8A and 8B are diagrams illustrating sample images when a shift in the paper width direction occurs when printing with two heads. 8A is a diagram in the case where the deviation in the paper width direction is 50 μm in the minus direction, and FIG. 8B is a diagram in the case where the deviation in the paper width method is 50 μm in the plus direction.
In FIG. 8A and FIG. 8B, the horizontal line of the lowercase letter e and the horizontal line of the numeral 4 are printed as 2-dot ruled lines.
Comparing FIG. 8A and FIG. 8B, in FIG. 8A (deviation amount is minus 50 μm), the horizontal line e is one line, whereas in FIG. 8B (deviation amount is plus 50 μm), it is split into two. Yes. In FIG. 8A, the horizontal line 4 is a single line, whereas in FIG. 8B, it is split into two. Thus, the image quality deteriorates due to the division of the ruled lines.

<About shrinkage of paper S>
As described above, the ruled lines are divided by the deviation of the landing positions of the inks ejected from the nozzles of the two heads in the case of thin ruled lines (1 dot ruled lines and 2 dot ruled lines in this embodiment). In the case of a 1-dot ruled line, the ruled line is likely to be divided due to a shift in the transport direction when forming a ruled line in the paper width direction. In the case of a 2-dot ruled line, a shift in the paper width direction when forming a ruled line in the transport direction. Ruled lines are likely to break up. Therefore, in the present embodiment, the position of the succeeding dot (dot formed by the second head 32) is corrected when a thin ruled line is printed.
Here, when the paper S shrinks due to drying or the like, the shrinking direction differs depending on the position of the paper S.

  FIG. 9 is a schematic diagram showing the orientation when the paper S shrinks. When the paper S shrinks as shown in FIG. 9, the paper S generally shrinks toward the center of the paper S. For this reason, the amount of shrinkage is small at the central portion of the paper S, and the amount of shrinkage increases as the edge of the paper S is reached. In the paper width direction, the upper half of the paper S shrinks to the plus side (downward in the figure), and the lower half shrinks to the minus side (upward in the figure). In addition, the transport direction is contracted to the plus side (right direction in the figure) on the upstream side from the center, and is contracted to the minus side (left direction in the figure) on the downstream side from the center. As described above, the shrinking direction (shift direction) differs depending on the position of the paper S. For this reason, in the present embodiment, in consideration of the shrinkage of the paper S, the landing position of the ink ejected from the nozzle row of the second head 32 is corrected according to the position of the paper S.

  In the case of a 2-dot ruled line in the transport direction, as shown in FIG. 6, there are two types: a ruled line with the preceding dot on the upper side and the succeeding dot on the lower side, and a ruled line with the preceding dot on the lower side and the succeeding dot on the upper side. There is. For this reason, when printing a two-dot ruled line in the transport direction, the necessity for correction differs depending on the direction in which the paper S shrinks (position on the paper S) and which of the two types of ruled lines to be printed.

FIG. 10 is an explanatory diagram of the deviation between the position of the paper S and the 2-dot ruled line in the transport direction.
The upper part of the figure shows an example of raster lines (L1 to L5) in the case of printing a two-dot ruled line in the transport direction on the upper side of the paper S (area A in the figure). An example of raster lines (L6 to L10) in the case of printing a 2-dot ruled line in the transport direction on the lower side (area B in the figure) is shown. In FIG. 10, dots formed by the first head 31 are indicated by black circles, and dots formed by the second head 32 are indicated by white circles. In the paper S in the figure, areas indicated by A and B are areas in which the amount of change from printing by the first head 31 to printing by the second head 32 is a predetermined value (for example, 50 μm) or more.

Assuming that there is no change in the paper S, when the same a row of the first head 31 and the second head 32 is used, the dots formed by the second head 32 are the first head as in L1 and L6 in the figure. It is formed below the dots formed at 31. In other words, the raster line formed later becomes a 2-dot ruled line below the raster line formed first.
On the other hand, when different rows (a row and b row) of the first head 31 and the second head 32 are used, dots formed by the second head 32 are formed by the first head 31 as in L2 and L7 in the figure. Formed above the dots. In other words, the raster line formed later becomes a two-dot ruled line above the raster line formed first.

  Here, it is assumed that the paper S contracts in the direction of the arrow in the drawing after printing by the first head 31 until printing by the second head 32. As described above, in the case of the upper side of the paper S (for example, the area A in the drawing), the paper S shrinks in the downward direction (plus direction). For this reason, in the region A, the landing position of the ink ejected by the second head 32 is shifted upward. For example, when the paper S is shrunk when the L2 ruled line is printed in the area A, the raster line formed by the second head 32 is formed above the target position. It splits into two like L4. On the other hand, when the L1 ruled line is printed in the area A, the raster line formed by the second head 32 is formed above the target position, and the ruled line becomes, for example, L3 in the figure. Specifically, although the vertical relationship of dots (raster lines) is reversed, it is a ruled line without division.

  In this way, on the upper side of the paper S, there is a high possibility that the ruled lines are split when different rows of the two heads are used. That is, there is a possibility that the ruled line is split when the raster line formed later is above the raster line formed earlier (opposite to the shrinking direction).

  In this case, the data in the a row of the second head 32 may be moved to the b row of the second head 32 immediately below it. In other words, the ruled line data for two raster lines in the transport direction may be shifted by one raster line to the lower side (plus side) in the paper width direction in the figure. By doing so, the landing position of the ink ejected from the second head 32 is corrected in the same direction as the shrinking direction of the paper S as indicated by L5 in the figure, so that the ruled lines are less likely to be split. Therefore, deterioration of image quality can be prevented.

  Further, in the case of the lower side of the paper S (for example, the region B in the figure), the paper S shrinks upward (minus direction). For this reason, in the region B, the landing position of the ink ejected by the second head 32 is shifted downward. For example, when the paper S is shrunk when the L6 ruled line is printed in the region B, the raster line formed by the second head 32 is formed below the target position. It will split into two like L8. On the other hand, when the L1 ruled line is printed in the area B, the raster line formed by the second head 32 is formed below the target position, so that, for example, L9 is obtained. Specifically, although the vertical relationship of dots (raster lines) is reversed, it is a ruled line without division.

  Thus, on the lower side of the paper S, there is a high possibility that the ruled line is split when the same row of the two heads is used. That is, there is a possibility that the ruled line is split when the raster line formed later is lower than the raster line formed earlier (opposite to the shrinking direction).

  In this case, the data in the a row of the second head 32 may be transferred to the b row of the second head 32 one level above. In other words, the ruled line data for two raster lines in the transport direction may be shifted by one raster line to the upper side (minus side) in the paper width direction in the figure. By doing so, as indicated by L10 in the figure, the ink landing position by the second head is corrected in the same direction as the shrinking direction of the paper S, so that the ruled lines are less likely to be split. Therefore, deterioration of image quality can be prevented.

<About print processing>
FIG. 11 is a flowchart of the printing process according to the present embodiment.
First, the controller 60 repeatedly determines whether there is a print instruction from the computer 110 (S101). If it is determined that there is a print instruction (YES in S101), the controller 60 acquires print target data (S102) and analyzes the print target data (S103). Specifically, it is analyzed whether the area to be printed is text, graphic, or photograph, and it is determined whether or not there is a text area in the area to be printed (S104).

If it is determined that there is a text area in the print target data (YES in S104), the controller 60 performs a text correction process (S105) and generates print data (S106). Details of the text correction process will be described later.
On the other hand, if it is determined in step S104 that there is no text area in the print target data (NO in S104), print data is generated based on the print target data. Then, the generated printing data is output to each unit (S107), and printing is executed (S108).

<About text correction processing>
When it is determined that there is a text area in the above-described print processing flow, the controller 60 executes text correction processing. In this text correction process, it is scanned whether dots are formed for each pixel of the print target data. Then, when dots are continuously formed with a certain width (for example, 1 dot) and a predetermined length or more (for example, 10 dots or more), and dots are not formed on the surrounding pixels, it is determined as a ruled line.
FIG. 12 is a flowchart of text correction processing according to the first embodiment. The text correction process will be described with reference to FIG. In the following description, FIG. 9 and FIG. 10 are also referred to.

  First, the controller 60 determines whether there is a ruled line of 2 dots or less by scanning the print target data (S201). That is, it is determined whether there is a ruled line having a ruled line width of 2 dots or 1 dot. If it is determined that there is no ruled line of 2 dots or less (NO in S201), the text correction process is terminated. If it is determined that there is a ruled line of 2 dots or less (YES in S201), it is determined whether the ruled line is a 2-dot ruled line (S202).

  When the controller 60 determines that the line is a 2-dot ruled line (YES in S202), the controller 60 executes the 2-dot ruled line text correction process shown in steps S203 to S210 and determines that the line is not a 2-dot ruled line. (NO in S202), the text correction process for 1-dot ruled lines shown in steps S211 to S215 is executed. First, the text correction procedure for a 2-dot ruled line will be described.

  If the controller 60 determines that it is a 2-dot ruled line (YES in S202), it determines whether the 2-dot ruled line is a ruled line in the transport direction (S203). If it is determined that the two-dot ruled line is a ruled line in the transport direction (YES in S203), the correction processing on the upper side of the paper S shown in steps S204 to S206, or steps S208 to S208, depending on the ruled line printing position. Correction processing on the lower side of the paper S shown in S210 is performed.

If the controller 60 determines that the printing position of the 2-dot ruled line on the paper S is within a predetermined range from the upper end (area A in FIG. 10) (YES in S204), then the controller 60 uses it to print the ruled line. It is determined whether the rows of the first head 31 and the second head 32 are different (S205). That is, it is determined whether the subsequent dot is the upper ruled line. As described above, when the succeeding dot on the upper side of the paper S is an upper ruled line, it is likely to be divided due to the shift. Therefore, when the first head 31 and the second head 32 are in the same column (YES in S205), the succeeding dot ( The landing position of the dots formed by the second head 32 is corrected. For example, when the ruled line L2 in FIG. 10 is printed, the ruled line data is changed so that the nozzles of the second head 32 to be used are the nozzles in the b-row that are one position lower than the a-row. In other words, the ruled line data for two raster lines is shifted by one raster line to the plus side in the paper width direction. By doing so, the positions of the dots formed by the second head 32 are corrected in the direction in which the paper shrinks (plus direction). As a result, the ruled lines are less likely to break up, and image quality deterioration can be prevented.
Thereafter, the controller 60 determines whether there is another ruled line of 2 dots or less (S207).

If the controller 60 determines in step S204 that the printing position of the 2-dot ruled line on the paper S is not within the predetermined range from the upper end (area A in FIG. 10) (NO in S204), the printing position is the lower end of the paper S. Is determined within a predetermined range (region B in FIG. 10) (S208). If it is determined that the printing position of the 2-dot ruled line is within a predetermined range from the lower end of the paper S (for example, area B in FIG. 10) (YES in S208), the first head 31 used for printing the ruled line It is determined whether the rows of the second heads 32 are the same (S209). That is, it is determined whether the subsequent dot is a lower ruled line. As described above, when the succeeding dot is the lower ruled line on the lower side of the paper S, it is likely to be divided due to the shift. Therefore, when the first head 31 and the second head 32 are in the same row (YES in S209), the landing position of the succeeding dot (dot formed by the second head 32) is corrected. For example, when the ruled line of L6 in FIG. 10 is printed, the ruled line data is changed so that the nozzles of the second head 32 to be used are the nozzles in the b row that is one position higher than the a row. In other words, the ruled line data for two raster lines is shifted by one raster line to the minus side in the paper width direction (S210). By doing so, as indicated by L10 in FIG. 10, the positions of the dots formed by the second head 32 are corrected in the direction in which the paper shrinks (minus direction). As a result, the ruled lines are less likely to break up, and image quality deterioration can be prevented.
Thereafter, the controller 60 executes step S207 for determining whether there is another ruled line of 2 dots or less.

  If it is determined in step S203 that it is not a ruled line in the transport direction (NO in S203), it is a ruled line in the paper width direction. As described above, since there is no need to correct the 2-dot ruled line in the paper width direction, step S207 is executed to determine whether there is another ruled line of 2 dots or less. Also, as shown in FIG. 10, when printing on the upper side (for example, area A) of the paper S, the ruled lines are less likely to be split when the head rows used are the same. Therefore, if it is determined in step S205 that the first and second head columns are the same (NO in S205), step S207 is performed to determine whether there is another ruled line of 2 dots or less without performing correction. Execute. Also, as shown in FIG. 10, in the case of printing on the lower side of the paper S (for example, the region B), the ruled lines are less likely to be split when the head rows used are different. Therefore, if it is determined in step S209 that the first head and the second head are different (NO in S209), step S207 is performed to determine whether there is another ruled line of 2 dots or less without performing correction. To do. If it is determined in step S208 that the print position is not within the predetermined range from the lower end (NO in S208), the ruled line print position is not included in the A area or the B area. Accordingly, the ruled line is printed in an area where the change in the size of the paper S is small (an area where the deviation is small). Therefore, step S207 for determining whether there is another ruled line of 2 dots or less without performing correction. Execute.

Next, the text correction process for 1-dot ruled lines shown in steps S211 to S215 will be described. If it is determined in step S202 that the ruled line is not a two-dot ruled line (NO in S202), the ruled line is a one-dot ruled line. Therefore, the controller 60 first determines whether the direction of the ruled line is the paper width direction (S211). As described above, when forming a one-dot ruled line in the transport direction, only one head (one nozzle) is used, so that it is not affected by the deviation of the ink landing position due to the change in the paper S. . Therefore, if it is determined in step S211 that the direction of the ruled line is not the paper width direction (NO in S211), that is, if it is a one-dot ruled line in the transport direction, is there any other ruled line of two dots or less? Step S207 for determining is executed.
In step S211, when it is determined that the direction of the ruled line is the paper width direction (NO in S211), the content of correction is changed according to the printing position on the paper S.

  First, the controller 60 determines whether the printing position on the paper S is within a predetermined range from the upstream end in the transport direction (S212). When the printing position on the paper S is at the upper end side in the transport direction, the paper S changes toward the downstream side (plus side) in the transport direction as shown in FIG. That is, the formation position of the preceding dot formed by the first head 31 moves to the plus side. In other words, the dot formation position by the second head 32 is shifted to the minus side. Accordingly, when it is determined that the printing position of the 1-dot ruled line on the paper S is within a predetermined range from the upstream end in the transport direction (YES in S212), the controller 60 discharges from each nozzle row of the second head 32. The head unit 30 is controlled so as to advance the timing. For example, the drive waveform of the drive signal is changed. By doing this, the ink landing position by the second head 32 moves to the downstream side in the transport direction (plus direction), so that the ruled line is less likely to be disrupted, and deterioration of the image quality of the one-dot ruled line can be prevented. And step S207 which discriminate | determines whether there exists other ruled lines of 2 dots or less is performed.

  On the other hand, when it is determined that the printing position of the 1-dot ruled line on the paper S is not within the predetermined range from the upstream end in the transport direction (NO in S212), the controller 60 determines that the printing position of the 1-dot ruled line on the paper S is It is determined whether it is within a predetermined range from the downstream end in the transport direction (S212). When the printing position on the paper S is downstream in the transport direction, the paper S changes toward the upstream side (minus side) in the transport direction as shown in FIG. That is, the formation position of the preceding dot formed by the first head 31 moves to the minus side. In other words, the dot formation position by the second head 32 is shifted to the plus side. Accordingly, when it is determined that the printing position on the paper S is within a predetermined range from the downstream end in the transport direction (YES in S214), the controller 60 delays the ejection timing from each nozzle row of the second head 32. The head unit 30 is controlled. For example, the drive waveform of the drive signal is changed. By doing so, the ink landing position by the second head 32 moves to the upstream side (minus direction) in the transport direction, so that the ruled line is less likely to be disrupted, and deterioration of the image quality of the one-dot ruled line can be prevented.

  If NO in step S214, the printing position of the 1-dot ruled line on the paper S is an area excluding a predetermined range at both ends in the transport direction. Here, since the change amount of the paper S is small, the shift amount is also small. Therefore, in this case, step S207 is executed to determine whether there is another ruled line of 2 dots or less without performing the text correction process.

If it is determined in step S207 that there is another ruled line of 2 dots or less (YES in S207), the process returns to step S202, and the above-described processing is performed again for the ruled line.
On the other hand, when it is determined that there is no other ruled line of 2 dots or less (NO in S207), the text correction process is terminated.

Thus, in this embodiment, the landing position of the ink ejected from the nozzles of the second head 32 is corrected according to the position of the paper S and the type of ruled line. Thereby, even if the paper S shrinks after printing by the first head 31, it is possible to make it difficult to break the ruled lines, and to prevent deterioration of image quality.
In the present embodiment, the ink landing position by the second head 32 is corrected. However, the ink landing position by the first head 31 may be corrected.

  For example, when printing a ruled line of L2 (a preceding dot is a two-dot ruled line on the lower side) in the area A of the paper S in FIG. You may make it change to the nozzle of a row of a position. That is, the ruled line data for two raster lines may be shifted by one raster line to the minus side in the paper width direction. In this case, the position of the dots formed by the first head 31 is corrected in the direction opposite to the direction in which the paper S contracts (the same direction as the direction in which the dots formed by the second head 32 are shifted). As in the case of shifting one raster line to the plus side in the direction (L5 in FIG. 10), the ruled line is less likely to be split.

  Similarly, when the L6 ruled line (the preceding dot is the upper two-dot ruled line) is printed in the area B of the paper S in FIG. 10, the nozzles in the row a of the first head 31 to be used are positioned one position below. You may make it change to the nozzle of b row. That is, the ruled line data for two raster lines may be shifted by one raster line to the plus side in the paper width direction. Also in this case, since the dots formed by the first head 31 are formed in the direction opposite to the direction in which the paper S shrinks (the same direction as the direction in which the dots formed by the second head deviate), minus the paper width direction. As in the case of shifting to the side (L10 in FIG. 10), the ruled lines are less likely to be split.

  In addition, although the ejection timing of the nozzle row of the second head 32 is advanced in step S213 of FIG. 12, the ejection timing of the nozzle row of the first head 31 may be delayed. Similarly, in step S215, the discharge timing of the nozzle row of the second head 32 is delayed, but the discharge timing of the nozzle row of the first head 31 may be advanced. By doing so, the landing position of the ink ejected from the first head 31 can be corrected in the direction opposite to the direction in which the paper S contracts (the same direction as the direction in which the dots formed by the second head 32 are shifted). Therefore, the ruled lines are less likely to break up.

=== Second Embodiment ===
In the second embodiment, the correction method is different from that of the first embodiment.
FIG. 13 is a flowchart of text correction processing according to the second embodiment. FIG. 14 is an explanatory diagram for correcting a 2-dot ruled line, and FIG. 15 is an explanatory diagram for correcting a 1-dot ruled line. 14 and 15, black circles indicate dots (preceding dots) formed by the first head 31, and white circles indicate dots (following dots) formed by the second head 32. Yes.

First, the controller 60 determines whether there is a ruled line of 2 dots or less by scanning the print target data (S301). That is, it is determined whether there is a ruled line having a ruled line width of 2 dots or 1 dot. If it is determined that there is no ruled line having a line width of 2 dots or less (NO in S301), the text correction process is terminated. If it is determined that there is a ruled line having a line width of 2 dots or less (YES in S301), the controller 60 determines whether the ruled line is a 2-dot ruled line (S302). When it is determined that the line is a 2-dot ruled line, a text correction process for 2-dot ruled line is executed. When it is determined that the line is not a 2-dot ruled line, a text correction process for 1-dot ruled line is executed. First, the text correction procedure for a 2-dot ruled line will be described.
If it is determined that the line is a 2-dot ruled line (YES in S302), the controller 60 determines whether the direction of the ruled line (hereinafter referred to as the ruled line direction) is the transport direction (S303).
If it is determined that it is a 2-dot ruled line in the transport direction, it is determined whether the printing position of the ruled line is within a predetermined range from the upper end or the lower end of the paper S (S304).

  As described with reference to FIG. 6, in the case of a two-dot ruled line in the transport direction, the preceding dot row (raster line) is formed by a certain nozzle of the first head 31, and the subsequent dot row (raster line) is the second. It is formed by a certain nozzle of the head 32 (left side in FIG. 14). For this reason, in the region where the deviation of the landing position of the ink ejected from each nozzle in the paper width direction is large, for example, as shown in the middle of FIG. 14, the ruled line is split into two.

  Therefore, when it is determined that the printing position of the 2-dot ruled line in the transport direction is within a predetermined range from the upper end or the lower end of the paper S (YES in S304), the controller 60 forms the preceding dot (formed by the first head 31). The print data is changed so that the dot size is increased and the subsequent dots (dots formed by the second head 32) are not formed (S305). In other words, a ruled line is printed using only preceding dots. In this way, as shown on the right side of FIG. 14, the ruled line in the transport direction can be printed with a line width thicker than the one-dot ruled line (line width close to the two-dot ruled line) so as not to be divided. Deterioration can be prevented.

  Thereafter, the controller 60 determines whether there is another ruled line of 2 dots or less (S306). When it is determined in step S303 that the 2-dot ruled line is not a ruled line in the transport direction (NO in S203), the ruled line is a ruled line in the paper width direction. As shown in FIG. 6, in the 2-dot ruled line in the paper width direction, there is a low possibility of splitting due to the deviation of the ink landing position by each head. In this case, the controller 60 executes step S305 without performing correction. If it is determined in step S304 that the printing position is not within the predetermined range from the upper end or the lower end of the paper S (NO in S304), the deviation of the landing position of the ink ejected from each nozzle is small. Step S306 is executed to determine whether there is another 2-dot ruled line.

  On the other hand, if it is determined in step S302 that the ruled line is not a two-dot ruled line (NO in S302), that is, if it is determined that the ruled line is a one-dot ruled line, the controller 60 determines whether the ruled line direction is the paper width direction. Judgment is made (S307). When it is determined that it is a one-dot ruled line in the paper width direction (YES in S307), it is determined whether the printing position of the ruled line is within a predetermined range from the upstream end or the downstream end in the transport direction of the paper S (S308). .

  As described with reference to FIG. 5, in the case of a one-dot ruled line in the paper width direction, one ruled line is formed by alternately arranging preceding dots and succeeding dots (left side in FIG. 15). For this reason, in the region where the deviation of the landing position in the transport direction of the ink ejected from each nozzle is large, the ruled line is split into two as shown in the middle of FIG. 15, for example.

  Therefore, when it is determined that the ruled line printing position is within a predetermined range from the upstream end or the downstream end in the transport direction of the paper S (YES in S308), the controller 60 forms the preceding dot (formed by the first head 31). The print data is changed so that the dot size is increased and the subsequent dots (dots formed by the second head 32) are not formed (S305). In other words, the print data is changed so as to thin out subsequent dots. By doing so, a one-dot ruled line in the paper width direction is printed only by the nozzles of the first head 31 as shown on the right side of FIG. Therefore, it is possible to perform printing without breaking the ruled line (one-dot ruled line) in the paper width direction, and it is possible to prevent image quality deterioration.

  If it is determined in step S307 that the 2-dot ruled line is not a ruled line in the paper width direction (NO in S307), the ruled line is a ruled line in the transport direction. As shown in FIG. 5, the 1-dot ruled line in the transport direction is formed by only one head, and is not affected by the deviation of the ink landing position by each head. Therefore, in this case, the controller 60 executes step S306 without performing correction. If it is determined in step S308 that the ruled line printing position is not within the predetermined range from the upstream end or the downstream end in the transport direction of the paper S (NO in S308), the print direction of the ink ejected from each nozzle is determined in the transport direction. The deviation of the landing position is small. Therefore, in this case, step S306 for determining whether there is another 2-dot ruled line is performed without performing correction.

  If it is determined in step S306 that there is another ruled line of 2 dots or less (YES in S306), the process returns to step S302 to determine whether the ruled line is a 2-dot ruled line. On the other hand, if it is determined in step S306 that there is no other ruled line of 2 dots or less (NO in S306), the text correction process is terminated.

  Thus, in the second embodiment, when printing ruled lines, the ejection of ink from each head is adjusted in accordance with the printing position of the ruled lines so that the preceding dots are enlarged and the subsequent dots are not formed. . By doing so, the ruled lines can be printed so as not to be divided reliably, and the image quality of the ruled lines can be prevented from being deteriorated. It should be noted that the succeeding dots may be formed large and correction may be made so as not to form the preceding dots. In this case as well, the ruled lines can be printed so as not to be divided.

=== Third Embodiment ===
In the above-described embodiment, an area for text correction on the paper S is set in advance. However, in the third embodiment, a ruled line pattern having a plurality of ruled lines having different line widths in the paper width direction and the conveyance direction is provided on the paper S. Printing is performed in a plurality of areas, and an area for text correction is determined based on the printing result.

  16A and 16B are examples of ruled line patterns. FIG. 16A shows a ruled line pattern in the paper width direction, and FIG. 16B shows a ruled line pattern in the transport direction.

Each pattern is formed with a plurality of ruled lines having different line widths. For example, in the ruled line in the paper width direction shown in FIG. 16A, the rightmost ruled line is a one-dot ruled line, the left neighbor is a two-dot ruled line, and the left neighbor is a three-dot ruled line in that order. The number increases and the ruled lines become thicker.
In FIG. 16B, the topmost ruled line is a 1-dot ruled line, and the ruled line below it is a 2-dot ruled line. Note that the 1-dot ruled line in the transport direction is formed using only the first head 31 (or the second head 32) as shown in FIG. Also. In the case of a 2-dot ruled line in the transport direction, the two types of ruled lines shown in FIG. 6 are printed. Specifically, for example, in the upper two-dot ruled line in FIG. 16B, an upper (paper width direction minus side) raster line is formed by the first head 31, and a lower (paper width direction plus side) raster line is formed by the second head. 32 is a ruled line. The lower two-dot ruled line in the figure is a ruled line in which the upper raster line is formed by the second head 32 and the lower raster line is formed by the first head 31.
The number of dots in the ruled line width direction increases and the ruled line becomes thicker toward the lower side of the figure.

  In FIG. 16B, there are two 2-dot ruled lines in the transport direction, but in FIG. 16A there is one 2-dot ruled line in the paper width direction. This is because, when forming a two-dot ruled line in the paper width direction, dots formed by the first head 31 and dots formed by the second head 32 are alternately formed on each raster line in the paper width direction. In this case, if the shift amount is the same with respect to the shift in the plus direction and the minus direction in the transport direction, the degree of image quality deterioration is the same (see FIG. 6). That is, in the case of a two-dot ruled line in the paper width direction, the deviation in the transport direction (plus and minus direction deviation) can be evaluated with one ruled line. The same can be said for other ruled lines in the paper width direction (for example, one-dot ruled lines).

  FIG. 17 is a diagram illustrating an example of an evaluation pattern in which the ruled line pattern of FIGS. 16A and 16B is printed on the paper S. As described above, the ruled line patterns shown in FIGS. 16A and 16B are printed on a plurality of locations on the paper S by the first head 31 and the second head 32. In this embodiment, the paper S is divided into four equal parts in the vertical direction and the horizontal direction to divide the paper S into 16 areas (D1 to D16), and the ruled line patterns shown in FIGS. 16A and 16B are printed in the respective areas. . Thereby, the presence or absence of the division | segmentation of the ruled line of each ruled line pattern can be confirmed for every area | region and every ruled line.

  For example, when the paper S shrinks and a paper width direction shift occurs, the two-dot ruled line in the transport direction is likely to be split as described above. Since the paper S shrinks toward the center, the position of the dot (following dot) formed by the second head 32 is shifted to the minus side in the paper width direction above the center of the paper S in the paper width direction. Therefore, referring to FIG. 6, on the upper side of the paper S, the ruled line (the lower two-dot ruled line on the lower side of FIG. 16B) in which the preceding dot is formed on the lower side of the two 2-dot ruled lines in FIG. It's easy to do. Therefore, on the upper side of the paper S, the printing result of the lower two-dot ruled line of the two two-dot ruled lines may be viewed. Then, based on the print result of the test pattern, an area where the two-dot ruled line is split may be specified, and it may be determined to apply the correction in that area.

  For example, if the lower two-dot ruled line in FIG. 16B is split in the evaluation pattern areas D1 to D4, the printing position on the paper S is in the range of the areas D1 to D4 in step S204 of FIG. It may be determined whether or not.

  On the other hand, below the center of the paper S in the paper width direction, the positions of dots (following dots) formed by the second head 32 are shifted to the plus side in the paper width direction. Therefore, referring to FIG. 6, on the lower side of the paper S, the ruled line in which the preceding dot is formed on the upper side (the two-dot ruled line on the upper side in FIG. 16B) of the two 2-dot ruled lines in FIG. Cheap. Therefore, on the lower side of the paper S, the printing result of the upper two-dot ruled line of the two two-dot ruled lines may be viewed. Then, based on this printing result, an area where the 2-dot ruled line is split may be specified, and it may be determined to apply correction in that area.

  For example, if the upper two-dot ruled line in FIG. 16B is split in the evaluation pattern areas D13 to D16, is the print position on the paper S in the range of the areas D13 to D16 in step S208 of FIG. It may be determined whether or not.

  Further, as described above, the one-dot ruled line in the paper width direction is likely to be broken due to the shift in the transport direction due to the shrinking of the paper S. Since the paper S shrinks toward the center, the position of the dot (following dot) formed by the second head 32 is on the upstream side in the transport direction on the left side (upstream side) of the center of the paper S in the transport direction. (Minus side) Therefore, when the 1-dot ruled line in the paper width direction is split on the left side of the center in the transport direction of the paper S, the left side of the split ruled line is formed by the second head 32, and the right side is the first head. 31 (see the shift in the negative direction in FIG. 5).

  On the other hand, the position of dots (following dots) formed by the second head 32 is shifted to the downstream side (plus side) in the transport direction on the right side (downstream side) from the center in the transport direction of the paper S. Therefore, when the 1-dot ruled line in the paper width direction is split on the right side of the center in the transport direction of the paper S, the left side of the split ruled line is formed by the first head 31 and the right side is the second head. 32 (see the shift in the plus direction in FIG. 5).

  For example, if the one-dot ruled line in FIG. 16A is split in the evaluation pattern areas D4, D8, D12, and D16, the printing position on the paper S is changed to the areas D4, D8, D12, and D12 in step S212 in FIG. What is necessary is just to judge whether it is the range of D16. If the one-dot ruled line in FIG. 16A is split in the areas D1, D5, D9, and D13, the printing position on the paper S is in the range of the areas D1, D5, D9, and D13 in step S212 in FIG. It may be determined whether or not.

Thus, in the third embodiment, whether or not correction is necessary is determined for each position on the paper S and each type of ruled line, based on the printed result of the ruled line pattern. By doing so, the correction for each ruled line according to the position on the paper S can be performed more accurately.

=== Other Embodiments ===
Each of the above embodiments is intended to facilitate understanding of the present invention and is not intended to limit the present invention. The present invention can be changed and improved without departing from the gist thereof, and it is needless to say that the present invention includes equivalents thereof. In particular, the embodiments described below are also included in the present invention.

<About Printer 1>
In the above embodiment, an ink jet printer that discharges ink, which is an example of a liquid, has been described. However, the present invention is not limited to this, and the present invention can also be applied to a liquid discharge apparatus that discharges liquid other than ink. For example, textile printing devices for patterning fabrics, color filter manufacturing devices, display manufacturing devices such as organic EL displays, DNA chip manufacturing devices that manufacture DNA chips by applying DNA-dissolved solutions to chips, circuit board manufacturing It may be a device or the like. In addition, as an ink ejection method for ejecting ink from the nozzles of the printer 1, a piezo method in which an ink chamber is expanded or contracted by driving a piezo element, or bubbles are generated in the nozzle using a heating element. Alternatively, a thermal method in which ink is discharged and ink is ejected by the bubbles may be used.

  In the embodiment of FIG. 3, the nozzles of the first head 31 and the nozzles of the second head 32 have the same nozzle pitch, the nozzle pitch of the nozzles of the first head 31, or the nozzles of the second head 32. However, the nozzles of the first head 31 and the nozzles of the second head 32 may be aligned in the paper width direction. In this case, for example, K nozzles (nozzles in the nozzle row a and nozzle row b) of the first head 31 are used every other nozzle in the paper width direction, and the K nozzles of the nozzles in the second head 32 are similarly paper width. Use every other nozzle in the direction, and the nozzle used by the K nozzle of the first head 31 and the nozzle used by the K nozzle of the second head 32 may be different nozzles in the paper width direction, or The nozzles used by the K nozzles of the first head 31 and the nozzles used by the K nozzles of the second head 32 may be nozzles at different positions in the paper width direction.

<About drying mechanism>
The drying mechanism 41 may be any device that can dry the medium. For example, the drying mechanism 41 may be a device that applies active energy rays such as warm air, infrared rays, UV, and microwaves to the medium.
Note that the paper S may be naturally dried after printing by the first head 31 until printing by the second head 32 without providing the drying mechanism 41. In this case, since the drying mechanism 41 is not used, the printing cost can be reduced.

<About correction target>
In the present embodiment, the case of a ruled line as the correction target has been described, but the same correction may be performed on an image printed using the first head 31 and the second head 32. In this case, if the landing position of the ink ejected from the second head is corrected according to the position of the paper S for the thin pattern of the image, the deterioration of the image quality can be prevented as in the case of the ruled line. .

1 is an overall configuration block diagram of a printer according to an embodiment. FIG. 2A is a cross-sectional view of the printer, and FIG. 2B is a diagram illustrating how the printer transports paper. FIG. 3 is a diagram illustrating a nozzle arrangement of a first head 31 and a second head 32. FIG. 4A is a diagram illustrating a state where ink droplets from the first head 31 have landed on a sheet. FIG. 4B is a diagram illustrating a state in which ink droplets from the first head 31 and the second head 32 have landed on the paper. It is explanatory drawing of the influence of the shift | offset | difference in a 1 dot ruled line. It is explanatory drawing of the influence of the shift | offset | difference in a 2 dot ruled line. It is explanatory drawing of the influence of the shift | offset | difference in a 3 dot ruled line. 8A and 8B are diagrams illustrating sample images when a shift in the paper width direction occurs when printing with two heads. 8A is a diagram in the case where the deviation in the paper width direction is 50 μm in the minus direction, and FIG. 8B is a diagram in the case where the deviation in the paper width method is 50 μm in the plus direction. It is a schematic diagram which shows direction when the paper S shrinks. FIG. 5 is an explanatory diagram of a deviation between the position of the paper S and the 2-dot ruled line in the transport direction. It is a flowchart of a printing process. It is a flowchart of the text correction process of 1st Embodiment. It is a flowchart of the text correction process of 2nd Embodiment. It is explanatory drawing of correction | amendment of 2 dot ruled line. It is explanatory drawing of 1 dot ruled line | wire correction | amendment. 16A and 16B are examples of ruled line patterns. FIG. 16A shows a ruled line pattern in the paper width direction, and FIG. 16B shows a ruled line pattern in the transport direction. It is a figure which shows an example of an evaluation pattern.

Explanation of symbols

1 printer,
20 transport unit, 21A, 21B transport roller, 22 transport belt,
23 paper feed roller, 30 head unit, 31 first head, 32 second head,
40 heater units, 41 drying mechanisms, 50 detector groups,
60 controller, 61 interface unit, 62 CPU,
63 memory, 64 unit control circuit,
110 computers

Claims (8)

A first nozzle row in which a plurality of nozzles for discharging liquid are arranged in a predetermined direction;
A second nozzle row in which a plurality of nozzles for discharging liquid are arranged in the predetermined direction;
After printing on the medium with the first nozzle row and then printing on the medium with the second nozzle row, at least one of the first nozzle row and the second nozzle row according to the position on the medium A controller for correcting the discharge of liquid from
A liquid ejection apparatus having The liquid ejection device according to claim 1,
A liquid ejection apparatus having a drying mechanism that promotes drying of the medium printed by the first nozzle array between the first nozzle array and the second nozzle array. The liquid ejection device according to claim 1 or 2,
A liquid ejection apparatus that performs the correction according to a position on the medium when a ruled line is printed by the first nozzle row and the second nozzle row. The liquid ejection device according to claim 3,
The liquid ejection device, wherein the controller determines whether or not to perform the correction according to the direction of the ruled line and the number of dots in the width direction of the ruled line. The liquid ejection device according to claim 4,
Each nozzle of the first nozzle row and each nozzle of the second nozzle row are alternately arranged in the predetermined direction,
The ruled line is a ruled line in the predetermined direction, and the ruled line is formed with one dot in the width direction of the ruled line using each nozzle of the first nozzle row and each nozzle of the second nozzle row. In this case, the controller performs the correction by adjusting the liquid discharge timing from the second nozzle row in accordance with the position on the medium. The liquid ejection device according to claim 4,
Each nozzle of the first nozzle row and each nozzle of the second nozzle row are alternately arranged in the predetermined direction,
The ruled line is a ruled line in a direction intersecting the predetermined direction, and the number of dots in the width direction of the ruled line is 2 using a certain nozzle in the first nozzle row and a certain nozzle in the second nozzle row. The controller performs the correction by changing the nozzle of the second nozzle row used for forming the ruled line according to the position on the medium. apparatus. The liquid ejection device according to any one of claims 3 to 6,
A plurality of the ruled lines having different numbers of dots in the width direction are printed in a plurality of regions on the medium, respectively, with a ruled line pattern formed in the predetermined direction and a direction intersecting the predetermined direction,
A liquid ejecting apparatus, wherein a position on the medium for performing the correction is determined based on a printing result of each ruled line pattern. A first nozzle row in which a plurality of nozzles for discharging liquid are arranged in a predetermined direction;
A second nozzle row in which a plurality of nozzles for discharging liquid are arranged in the predetermined direction;
A liquid discharge method by a liquid discharge apparatus having
After printing on the medium with the first nozzle row and then printing on the medium with the second nozzle row, at least one of the first nozzle row and the second nozzle row according to the position on the medium A liquid ejection method for correcting the ejection of liquid from the liquid.