JP2013071345A - Inkjet printer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To correct deviation of a drawing position caused by change in a drawing cycle while suppressing recognition that a linear graphic extending in the width direction becomes thick.SOLUTION: In this inkjet printer 1, an image is recorded by recording a plurality of lines aligned in the scanning direction on a web 9. To correct the deviation of the drawing position during high speed printing caused by a difference between a first drawing cycle during standard printing and a second drawing cycle during the high speed printing, the lines with respect to each of predetermined numbers of lines are extracted as correction target lines. When no transverse line exists on the correction target line, a correction line similar to the correction target line is recorded adjacent to the correction target line, and when a transverse line exists on the correction target line, recording of the correction line is postponed until a line which does not include a transverse line appears. Thus, while recognition that a transverse line which is a linear graphic extending in the width direction becomes thick is suppressed, the deviation of the drawing position caused by the second drawing cycle can be corrected.

Description

  The present invention relates to an inkjet printer.

  Conventionally, an ink jet printer that records an image on a long sheet of printing paper has been used. As one of such ink jet printers, a plurality of heads that eject ink from a group of ejection openings of a plurality of heads toward a printing sheet that moves only once in a predetermined scanning direction, and extend in a width direction perpendicular to the scanning direction. One-pass type ink jet printers that record lines by sequentially forming lines are known.

  In the one-pass type ink jet printer, in order to increase the resolution in the width direction, a first discharge port array having a plurality of discharge ports in one head and a plurality of discharge ports in the first discharge port array in the width direction A second discharge port array having a plurality of other discharge ports alternately arranged is provided, and the first discharge port array and the second discharge port array are spaced apart from each other in the scanning direction. In such an ink jet printer, a plurality of dots of ink from the first ejection port array are ejected from the ejection ports of the first ejection port array and the second ejection port array at a predetermined drawing cycle, and A plurality of dots of ink from the second ejection port array are alternately arranged in the width direction on the printing paper to form one line. Japanese Patent Application Laid-Open No. 2004-228620 discloses a technique in which a plurality of print heads respectively corresponding to a plurality of colors are shifted by several pixels in the width direction in an inkjet printer.

International Publication No. 97/37854

  By the way, in the one-pass type ink jet printer as described above, the moving speed of the printing paper is doubled, a line formed by a plurality of dots by ink from the first ejection port array, and a line from the second ejection port array It is conceivable to realize high-speed printing while reducing the resolution in the width direction by alternately arranging lines formed by a plurality of dots of ink in the scanning direction. In the case of such high-speed printing, in order to arrange the plurality of lines formed by the second ejection port array in the middle of the plurality of lines formed by the first ejection port array, the drawing cycle at the time of printing at the standard speed A shorter drawing cycle is set. For this reason, the drawing position of the line in the scanning direction is shifted, the resolution in the scanning direction is slightly higher than that at the time of printing at the standard speed, and the length of the image in the scanning direction is shorter than the desired length. Thus, in order to adjust the length of the image in the scanning direction to a desired length, it is conceivable to record the latest line again every time a predetermined number of lines are recorded. However, when the line to be recorded again includes a linear figure (so-called horizontal line) extending in the width direction, the horizontal line becomes thick.

  The present invention has been made in view of the above-described problem, and corrects a drawing position shift caused by a change in a drawing cycle while suppressing a linear figure extending in the width direction from being recognized as being thick. It is aimed.

  The invention according to claim 1 is an ink jet printer, wherein an ejection unit that ejects ink toward a recording medium, and the recording medium is moved relative to the ejection unit only once in a predetermined scanning direction. And a plurality of lines that are parallel to the width direction perpendicular to the scanning direction and are arranged in the scanning direction. A control unit that records an image on the recording medium, and the ejection unit is arranged along an ejection port arrangement direction that intersects the scanning direction, and ejects ink onto the recording medium. A plurality of first discharge ports that form a plurality of first dots, and are arranged along the discharge port arrangement direction and are arranged between the plurality of first discharge ports in the width direction, respectively, on the recording medium In And a plurality of second discharge ports that form a plurality of second dots by discharging the ink, and when the relative movement speed of the recording medium in the scanning direction is the first speed, the plurality of first discharge ports In addition, the plurality of first dots and the plurality of second dots are alternately arranged in the width direction in each of the plurality of lines by ejecting ink from the plurality of second ejection ports in a first drawing cycle. In a case where the relative movement speed of the recording medium is a second speed that is twice the first speed, the plurality of first discharge ports and the plurality of second discharge ports are set to be shorter than the first drawing cycle. Ink is ejected at a second drawing cycle having a high frequency, so that a line that includes a plurality of first dots and does not include a second dot, and a line that includes a plurality of second dots and does not include a first dot Alternately arranged The plurality of lines are recorded, and in the control unit, a) a line for each number of lines determined in advance based on the second drawing period and the first drawing period is caused by the second drawing period. A step of extracting as a correction target line for correcting a shift in drawing position to be performed; and b) whether or not a horizontal line that is a linear figure extending beyond a predetermined length in the width direction exists on the correction target line. C) a correction line similar to the correction target line is recorded adjacent to the correction target line when the horizontal line does not exist on the correction target line, and the correction target line is recorded on the correction target line. When a horizontal line exists, a step of returning to the step b) is performed with the next line of the correction target line as a new correction target line.

  The invention according to claim 2 is the ink jet printer according to claim 1, wherein in the image data, each pixel corresponds to a dot drawing position, and the horizontal line represents each pixel value in the image data. Is a set of a plurality of pixels in which the recording density corresponding to is equal to or greater than a predetermined threshold, and the first number in the width direction continues for the first number or more and the number in the scanning direction is equal to or less than the second number.

  A third aspect of the present invention is the ink jet printer according to the first or second aspect, wherein the discharge section includes a head provided with the plurality of first discharge ports and the plurality of second discharge ports. The discharge port arrangement direction is slightly inclined with respect to the width direction, and the first discharge ports and the corresponding second discharge ports are arranged in a direction perpendicular to the discharge port arrangement direction.

  In the present invention, it is possible to correct a shift in the drawing position due to a change in the drawing cycle while suppressing that the linear figure extending in the width direction is recognized as being thick.

1 is a perspective view showing an external appearance of an ink jet printer according to an embodiment. It is a bottom view of a discharge part. It is a figure which shows a discharge outlet group. It is a figure which shows the dot on a web. It is a figure for demonstrating the arrangement | sequence of the dot drawn on a web. It is a figure which simplifies and draws a part of head. It is a figure which simplifies and shows the formation process of the dot with respect to a web. It is a figure which simplifies and shows the formation process of the dot with respect to a web. It is a figure which simplifies and shows the formation process of the dot with respect to a web. It is a figure which simplifies and shows the formation process of the dot with respect to a web. It is a figure which simplifies and shows the formation process of the dot with respect to a web. It is a figure which simplifies and shows the formation process of the dot with respect to a web. It is a figure which simplifies and shows the formation process of the dot with respect to a web. It is a figure which simplifies and shows the formation process of the dot with respect to a web. It is a figure which simplifies and shows the formation process of the dot with respect to a web. It is a figure which shows the flow of the image recording in an inkjet printer.

  FIG. 1 is a perspective view showing an appearance of an inkjet printer 1 according to an embodiment of the present invention. The ink jet printer 1 is an image recording apparatus that discharges micro droplets of ink onto a long sheet-like web 9 as a recording medium and records an image on the web 9 (that is, prints an image). In the present embodiment, a color image is recorded on the web 9 that is a printing sheet.

  An ink jet printer 1 shown in FIG. 1 includes a moving mechanism 2, a discharge unit 3, and a control unit 7 that controls these configurations. The moving mechanism 2 moves the web 9 in the Y direction in FIG. 1 (that is, the longitudinal direction of the web 9 and hereinafter referred to as “scanning direction”). The ejection unit 3 is fixed to a frame 25 provided on the base 20 so as to straddle the movement mechanism 2 above the movement mechanism 2 (that is, (+ Z) side), and ejects ink toward the web 9. .

  In the inkjet printer 1, the web 9 is moved relative to the ejection unit 3 only once in the scanning direction by the moving mechanism 2, and the ejection of ink from the ejection unit 3 is controlled by the control unit 7 based on the image data. Then, micro droplets of ink are ejected onto the moving web 9. Thereby, lines in which a plurality of dots of ink are arranged in the width direction (that is, lines extending in parallel with the width direction) are sequentially formed on the web 9 in the scanning direction, and the plurality of lines are arranged in the scanning direction. As a result, an image is recorded on the web 9.

  In the moving mechanism 2, a plurality of rollers 21 each long in the X direction in FIG. 1 are arranged in the Y direction. The X direction is a direction that is horizontal and perpendicular to the Y direction, and is also the width direction of the web 9. A supply unit 22 for holding a roll-shaped web 9 (supply roll) is provided on the (+ Y) side of the plurality of rollers 21, and a roll-shaped web 9 (winding-up) is provided on the (−Y) side of the plurality of rollers 21. A winding unit 23 for holding a roll is provided. The web 9 is rolled in each of the supply unit 22 and the winding unit 23. In the following description, the web 9 simply means the web 9 being conveyed (that is, the web 9 on the plurality of rollers 21).

  One roller 21 a of the moving mechanism 2 is provided with an encoder 29 that detects the moving speed of the web 9 in the scanning direction, and the control unit 7 controls the rotation of the motor of the winding unit 23 based on the output of the encoder 29. Thus, the web 9 is conveyed at a constant speed in the (−Y) direction. When the web 9 is conveyed, a load (tension) in the direction opposite to the scanning direction (that is, (+ Y) direction) is applied to the web 9 by the motor of the supply unit 22, so The web 9 moves smoothly without undulations.

  FIG. 2 is a bottom view showing the configuration of the ejection unit 3, and shows the scanning direction of the ejection unit 3 with respect to the web 9 (that is, the Y direction) in the vertical direction. The ejection unit 3 is a head unit that is an aggregate of a plurality of heads 5. The ejection unit 3 has four long attachment members 32 that extend to substantially the same length as the width of the web 9 in the width direction, and the four attachment members 32 are arranged and fixed on the head unit body 31 in the scanning direction. Is done. A plurality of heads 5 are arranged and attached to each attachment member 32 in the width direction, and one head is arranged in the width direction by the plurality of heads 5 attached to one attachment member 32 by substantially the same length as the width of the web 9. A column is constructed. A plurality of relatively short attachment members 32 may be arranged in the width direction, and one head row may be configured by the heads 5 attached to the plurality of attachment members 32 arranged in the width direction.

  Each head 5 has a plurality of ejection port groups 60 (in FIG. 2, one ejection port group 60 is illustrated by a double line), and each ejection port group 60 intersects the scanning direction. It is a set of a plurality of discharge ports arranged along the discharge port arrangement direction. Each of the plurality of heads 5 included in the (+ Y) side head row 51a includes an ejection port group 61K that ejects K (black) ink and an ejection port group 61C that ejects C (cyan) ink. Are provided in order from the (+ Y) side (toward the (-Y) side). Each of the plurality of heads 5 included in the head row 52a adjacent to the (−Y) side of the head row 51a includes a discharge port group 64C that discharges C ink and a discharge port group 64K that discharges K ink. A discharge port group 63 </ b> C that discharges ink and a discharge port group 63 </ b> K that discharges K ink are sequentially provided from the (+ Y) side.

  Each of the plurality of heads 5 included in the head row 51b adjacent to the (−Y) side of the head row 52a is a discharge port group 61M that discharges M (magenta) ink, and discharge that discharges Y (yellow) ink. A plurality of outlet groups 61Y, 62M for ejecting M ink and an outlet group 62Y for ejecting Y ink in order from the (+ Y) side, and included in the (−Y) side head row 52b. Each of the heads 5 includes a discharge port group 64Y that discharges Y ink, a discharge port group 64M that discharges M ink, a discharge port group 63Y that discharges Y ink, and a discharge port that discharges M ink. It has group 63M in order from the (+ Y) side.

  The heads 5 included in the head arrays 51a and 51b (hereinafter referred to as “head array 51” when referring to one of the head arrays) are tilted by a predetermined minute rotation angle about an axis parallel to the Z axis. The discharge port group 60 of each head 5 is similarly inclined. In addition, the head 5 of the head rows 52a and 52b (hereinafter referred to as “head row 52” when referring to any one of the head rows) is the head 5 of the head row 51 centered on an axis parallel to the Z axis. The opposite side is tilted and fixed by the same rotation angle, and the ejection port group 60 of each head 5 is similarly tilted. In other words, in each head 5, the ejection port array direction is slightly inclined with respect to the width direction.

  Thus, each head 5 of the head array 51 ejects two ejection port groups 60 that eject ink of one color, and two ejection port groups 60 that eject ink of other colors arranged in the same manner as these. Each head 5 of the head row 52 corresponding to this head row 51 also discharges two ejection port groups 60 that eject one color ink, and other color inks arranged in the same manner as these. In each head 5, the ejection port group 60 that ejects ink of one color and the ejection port group 60 that ejects ink of another color are alternately arranged in the scanning direction. The

  FIG. 3 is a diagram showing the ejection port group of one head 5, and FIG. 3 shows only the ejection port group that ejects the same color of the heads 5 of the head row 51. Hereinafter, the discharge port group that precedes the relative traveling direction ((+ Y) direction) of the discharge unit 3 with respect to the web 9 is referred to as a “first discharge port group 61” and is separated from the first discharge port group 61 in the scanning direction. The succeeding ((−Y) side) discharge port group is referred to as a “second discharge port group 62”. In the following description, only the discharge port group that discharges one of the four colors of CMYK will be described. However, the discharge port group that discharges other colors of ink has the same configuration. And placement.

  As shown in FIG. 3, the first discharge port group 61 includes a first front discharge port array 611 having a plurality of first discharge ports 610 and a first rear discharge port array having a plurality of first discharge ports 610. 612. Each of the first front outlet row 611 and the first rear outlet row 612 is inclined by a predetermined minute angle from the width direction (X direction) in a plane parallel to the web 9 (a plane parallel to the XY plane). A plurality of first discharge ports 610 are arranged at a constant pitch in parallel with the discharge port arrangement direction. In the first discharge port group 61, any one first discharge port 610 of the first rear discharge port row 612 is intermediate between two adjacent first discharge ports 610 of the first front discharge port row 611 in the width direction. A plurality of first discharge ports 610 are arranged in a zigzag manner so that is positioned. Similarly to the first discharge port group 61, the second discharge port group 62 includes a plurality of second discharge ports 620 in two rows in a staggered manner along the discharge port arrangement direction (that is, the second front discharge port row 621 and Arranged as a second rear outlet row 622).

  Further, in the first discharge port group 61 and the second discharge port group 62, when attention is paid only to the width direction, one first discharge port 610 of the first front discharge port array 611 and the first discharge port 610 are concerned. One second discharge port 620 of the second discharge port group 62 is located between the first discharge ports 610 of the first rear discharge port array 612 adjacent to each other in the width direction. That is, the discharge port arrangement direction (that is, the rotation angle of the head 5) is determined so that the plurality of second discharge ports 620 are respectively disposed between the plurality of first discharge ports 610 in the width direction. In other words, the minute angle with respect to the width direction of the discharge port arrangement direction is such that any one of the second discharge port groups 62 is located between two first discharge ports 610 adjacent to each other in the first discharge port group 61 with respect to the width direction. The angle at which the second discharge port 620 interpolates is set. Thereby, in the head 5 of FIG. 3, the plurality of first discharge ports 610 and the second discharge ports 620 of the first discharge port group 61 and the second discharge port group 62 are densely continuous in the width direction. On the other hand, in the direction perpendicular to the discharge port arrangement direction, the first discharge ports 610 and the second discharge ports 620 corresponding to the first discharge ports 610 are arranged.

  In the present embodiment, when attention is focused only on the width direction, a plurality of first discharge ports 610 are arranged at a pitch corresponding to 180 dpi in each of the first front discharge port array 611 and the first rear discharge port array 612. When viewed as the entire first discharge port group 61, the plurality of first discharge ports 610 are arranged at a pitch corresponding to 360 dpi. Further, in each of the second front discharge port array 621 and the second rear discharge port array 622, a plurality of second discharge ports 620 are arranged at a pitch corresponding to 180 dpi, and the second discharge port group 62 as a whole is viewed. The plurality of second discharge ports 620 are arranged at a pitch corresponding to 360 dpi. Further, when the first discharge port group 61 and the second discharge port group 62 are viewed together, a plurality of discharge ports (that is, the first discharge port 610 and the second discharge port 620) are arranged at a pitch corresponding to 720 dpi. Is done.

  In the ejection unit 3 illustrated in FIG. 2, in the head row 52 as well, as in the head row 51, a plurality of ejection ports that eject ink of one color in each head 5 are arranged at a pitch corresponding to 720 dpi. . Further, the plurality of heads 5 in the head row 52 are arranged between two adjacent heads 5 in the head row 51 when attention is paid only to the width direction. When attention is paid only to the ejection port for ejecting ink of one color, the ejection port located at the end of the head 5 of the head row 51 and the end of the head 5 adjacent to the head 5 in the width direction in the head row 52 The distance in the width direction between the discharge ports located in the section, that is, the distance between the two discharge ports closest in the width direction in the two heads 5 is equal to the pitch corresponding to 720 dpi. Therefore, in the entire discharge unit 3, the discharge ports continue in the width direction at a pitch corresponding to a predetermined resolution (720 dpi) for one color.

  Next, an image recording operation of the inkjet printer 1 shown in FIG. 1 will be described. In the following description, the description will be given focusing on the ink of one color, but the same operation is performed in the printing of the ink of other colors. In the inkjet printer 1, the web 9 is moved in the scanning direction by the moving mechanism 2, and the ink discharge unit 3 controlled by the control unit 7 synchronizes with a predetermined dot clock (that is, at a predetermined drawing cycle). Minute droplets are ejected. Specifically, first, the movement of the web 9 is started, and one head having the first discharge port group 61 and the second discharge port group 62 shown in FIG. 3 based on image data prepared in advance by the control unit 7. 5 and a plurality of other heads 5 arranged in the same head row as the head 5, ink ejection is turned on to the first ejection ports 610 of the first ejection ports 610 of the first ejection port group 61. / OFF is controlled simultaneously, and dots are formed (ie, drawn) on the web 9.

  4 is a diagram showing dots formed on the web 9 by the head 5 shown in FIG. 3. In FIG. 4, dots are virtually formed even when ink is not ejected in accordance with image data. It is supposed to be done. As indicated by solid circles in FIG. 4, ink is ejected onto the web 9 by the first ejection ports 610 of the first front ejection port array 611, whereby a plurality of first dots 811 are formed in the width direction. They are simultaneously formed at a constant pitch with respect to (X direction).

  When the first dot 811 is formed, the first rear discharge port array 612 located on the (−Y) side of the first front discharge port array 611 immediately reaches the upper side of the first dot 811 on the web 9. The discharge control for the first discharge ports 610 of the first rear discharge port array 612 is simultaneously performed. A plurality of first dots 812 are formed so as to interpolate between two adjacent first dots 811 in FIG. Accordingly, the first front discharge port array 611 and the first rear discharge port array 612 of the first discharge port group 61 cause the plurality of first dots 811 and 812 to be on the virtual line segment 83 along the discharge port array direction. Formed.

  When the web 9 further moves and the second discharge port group 62 reaches above the first dots 811 and 812 on the web 9, the discharge control for the second discharge ports 620 of the second front discharge port array 621 is performed. , And the discharge control for the second discharge ports 620 of the first rear discharge port array 612 is sequentially performed simultaneously. A plurality of second dots 821 and 822 (indicated by broken-line circles in FIG. 4) are formed by ejecting ink from the second ejection ports 620 onto the web 9. At this time, each of the second dots 821 and 822 is formed between the two first dots 811 and 812 adjacent to each other on the line segment 83 (however, the second dot 822 on the (+ X) side is excluded). . That is, the first dots 811 and 812 drawn by the first discharge port group 61 are interpolated in the width direction by the second dots 821 and 822 drawn by the second discharge port group 62. In this way, under the control of the control unit 7, in the head 5 included in the head row 51, the discharge control is simultaneously performed for each of the discharge port rows 611, 612, 621, 622, and drawing is performed on the line segment 83 on the web 9. Is called.

  As the web 9 further moves and the same positions as the dots 811, 812, 821, and 822 on the web 9 with respect to the scanning direction pass under the head row 52, as shown in FIG. A plurality of dots are formed on a plurality of line segments 84 that are continuous with each other and are inclined in the opposite direction to the line segment 83. In FIG. 5, the length in the scanning direction is exaggerated, but in reality, the inclination of the line segments 83 and 84 is very small compared to the length in the X direction. Is hardly recognized by the human eye, and a plurality of line segments 83 and 84 that are continuously folded are recognized as lines 85 that are parallel to the width direction. In each color of CMYK, dots are formed on a plurality of lines 85 arranged at predetermined intervals in the scanning direction, whereby color printing with four colors of CMYK is realized on the web 9.

  Next, standard printing and high-speed printing in the inkjet printer 1 will be described. In the following, in order to simplify the description, one color dot drawing by a part of the ejection ports shown in FIG. 6 of one head 5 will be described. In order to facilitate understanding of the figure, in FIG. 6, the first front outlet row 611 and the first rear outlet row 612 of the first outlet group 61 and the second front side of the second outlet group 62 are shown. The partial discharge port array 621 and the second rear discharge port array 622 are drawn in parallel to the horizontal direction of the paper surface. FIG. A thru | or FIG. C, FIG. A thru | or FIG. C and FIG. A through FIG. In C, the dots formed by the ink from each of the ejection port arrays 611, 612, 621, and 622 are drawn in parallel to the horizontal direction of the paper surface. In addition, each discharge port and each dot are drawn in a rectangle, and in fact, adjacent dots that partially overlap each other are drawn so as not to overlap. Further, “a” and “b” are drawn in the first discharge port 610 and in the first dots 811 and 812 formed by the first front discharge port array 611 and the first rear discharge port array 612, respectively. Symbols “e” and “f” are drawn in the second discharge ports 620 and in the second dots 821 and 822 formed by the second front discharge port array 621 and the second rear discharge port array 622, respectively.

  FIG. A thru | or FIG. C is a diagram sequentially illustrating dot formation when the moving speed of the web 9 in the scanning direction by the moving mechanism 2 (that is, the relative moving speed with respect to the ejection unit 3) is the standard speed that is the first speed. In standard printing in which the web 9 moves at a standard speed, ink is ejected from the first ejection ports 610 (see FIG. 6) of the first ejection port group 61 in the first drawing cycle, so that FIG. As shown in A, a plurality of first dots 811 and 812 are formed on each line 85 indicated by a two-dot chain line. The distance between each of the two first dots 811 and 812 adjacent in the scanning direction, that is, the distance between the two lines 85 adjacent in the scanning direction is determined by the moving speed of the web 9 and the first drawing cycle. In the present embodiment, the distance corresponds to 360 dpi. Further, the distance between each of the two first dots 811 and 812 adjacent in the width direction is determined by the arrangement of the first discharge ports 610 in the first discharge port group 61, and in the present embodiment, as described above. The distance corresponds to 360 dpi.

  Subsequently, ink discharge is also started from the second discharge ports 620 (see FIG. 6) of the second discharge port group 62, and the plurality of first discharge ports 610 and the plurality of second discharge ports 620 are in the first drawing cycle. As a result of the ink being discharged, FIG. B and FIG. As shown in C, in each of the plurality of lines 85, a plurality of first dots 811 and 812 and a plurality of second dots 821 and 822 are alternately arranged in the width direction. The distance in the width direction between each two adjacent dots on each line 85 is a distance corresponding to 720 dpi. Further, the distance between dots in the scanning direction is a distance corresponding to 360 dpi as described above.

  FIG. A thru | or FIG. C and FIG. A through FIG. C is a diagram sequentially illustrating dot formation when the moving speed of the web 9 in the scanning direction by the moving mechanism 2 is a second speed that is twice the first speed. FIG. A thru | or FIG. When the web 9 moves at the second speed, the first drawing is temporarily performed from the first discharge port 610 of the first discharge port group 61 and the second discharge port 620 of the second discharge port group 62. A dot formed when ink is ejected in a cycle is shown. Assuming that such printing is performed, FIG. B and FIG. As shown in C, in each of the plurality of lines 85, a plurality of first dots 811 and 812 and a plurality of second dots 821 and 822 are alternately arranged in the width direction, and each two adjacent two lines 85 are adjacent to each other. The distance in the width direction between the dots is a distance corresponding to 720 dpi. On the other hand, the distance between two adjacent dots in the scanning direction (that is, the distance in the scanning direction of the two adjacent lines 85) is a distance corresponding to 180 dpi because the moving speed of the web 9 is doubled. Become. Therefore, the distance in the scanning direction and the distance in the width direction between adjacent dots are greatly different.

  Therefore, in the inkjet printer 1, in the high-speed printing in which the web 9 is moved at the second speed, the frequency is slightly higher than the first drawing period from the plurality of first discharge ports 610 and the plurality of second discharge ports 620. By discharging ink in the second drawing cycle, FIG. A through FIG. As shown in C, the line 85 includes a plurality of first dots 811 and 812 and does not include the second dots 821 and 822, and includes a plurality of second dots 821 and 822 and does not include the first dots 811 and 812. A plurality of lines 85 in which the lines 85 are alternately arranged in the scanning direction are recorded.

  The line 85 including the second dots 821 and 822 is disposed approximately at the center in the scanning direction of two adjacent lines 85 including the first dots 811 and 812. The distance in the width direction between each two adjacent dots on each line 85 is a distance corresponding to 360 dpi. Further, the distance between two first dots 811 and 812 adjacent in the scanning direction (the same applies to the distance between two second dots 821 and 822 adjacent in the scanning direction) means that the ink is discharged in the second drawing cycle. , The distance D1 is slightly shorter than the distance corresponding to 180 dpi, and the distance between the adjacent lines 85 in the scanning direction is a distance D2 slightly shorter than the distance corresponding to 360 dpi.

  FIG. A through FIG. In the high-speed printing shown in C, high-speed printing is realized while maintaining the resolution in the scanning direction while reducing the resolution in the width direction as compared with the standard printing. In high-speed printing, the resolution in the scanning direction is slightly higher than the resolution in the scanning direction at the time of standard printing as described above. Therefore, when the same number of lines 85 are drawn, the length of the image in the scanning direction is standard. Slightly shorter than when printing.

  In order to correct such a shift in the length of the image in the scanning direction, that is, a positional shift of each line 85 in the scanning direction, the last recorded line 85 is recorded every time a predetermined number of lines 85 are drawn. It may be possible to draw again. However, when a horizontal line that is a linear figure extending in the width direction exists on the latest line 85, when the latest line 85 is drawn again, the horizontal width of the horizontal line in the scanning direction is drawn wider than the actual width. May be recognized by the observer. Therefore, in the ink jet printer 1, the drawing position shift caused by the second drawing cycle is corrected by the following method.

  As shown in FIG. 10, in the inkjet printer 1, first, the correction cycle of the line 85 (that is, the number of lines 85 recorded until the correction of the line 85 is performed) is the second drawing cycle and the first drawing cycle. Is determined in advance as a predetermined number of lines and stored in the control unit 7 (step S11). In the present embodiment, the number of correction period lines is determined to be 300.

  Subsequently, ink is ejected from the ejection unit 3 in the second drawing period based on the image data, and a plurality of lines 85 are sequentially recorded in the scanning direction. At this time, it is confirmed whether or not the line 85 scheduled to be recorded next (hereinafter referred to as “drawing line”) is a line equal to an integral multiple of the correction cycle (initially, the 300th line 85). (Step S12). When the drawing schedule line is a line different from an integral multiple of the correction cycle, the drawing schedule line is recorded on the web 9 (step S13), and the process returns to step S12. Actually, the recording of the line to be drawn is performed with a delay of a plurality of lines from the confirmation in step S12. On the other hand, when the drawing line is a line equal to an integral multiple of the correction cycle, the drawing line is extracted as a correction target line for correcting a drawing position shift caused by the second drawing cycle (step S14). .

  Next, it is confirmed whether or not a horizontal line extending beyond a predetermined length in the width direction exists on the correction target line (step S15). The horizontal line is confirmed in the image data immediately before shading (that is, the image data after being converted into CMYK) in which each pixel corresponds to the dot drawing position on the web 9. In the inkjet printer 1, the horizontal line in the image data has a recording density that is a density of CYMK corresponding to each pixel value equal to or higher than a predetermined threshold value, and continues for a first number or more in the width direction and is also in the scanning direction. Is defined as a set of a plurality of pixels whose consecutive number is equal to or less than the second number. The second number is “3”, for example.

  As a specific horizontal line confirmation method, for example, in the above-described step S12, the control unit 7 confirms the data of the line to be drawn, the recording density is equal to or higher than the threshold value, and the first number in the width direction. If a continuous pixel row exists in the drawing schedule line, 1 is added to the horizontal line detection variable whose initial value is 0. When the horizontal line detection variable is 1 or more, it is confirmed whether or not there is a pixel column similar to the above in the same position in the width direction as the pixel column of the line to be drawn. If it exists, 1 is set in the horizontal line detection variable. If it does not exist, the horizontal line detection variable is returned to the initial value of 0.

  In step S15, when the horizontal line detection variable is greater than 0 and equal to or less than the second number, it is determined that a horizontal line exists on the correction target line. When the horizontal line detection variable is 0, or when the horizontal line detection variable is larger than the second number, it is assumed that there is no horizontal line on the correction target line. When the horizontal line detection variable is larger than the second number, the pixel row on the correction target line is a part of a pattern extending in the scanning direction, so that the correction target line is redrawn as described later. However, it is difficult to recognize that the length of the pattern in the scanning direction has increased. The horizontal line on the correction target line may be detected by various other methods.

  When there is no horizontal line on the correction target line, the correction target line is recorded on the web 9, and further, a correction line similar to the correction target line is recorded adjacent to the rear side in the scanning direction of the correction target line. (Step S16). On the other hand, if there is a horizontal line on the correction target line, after the correction target line is recorded (step S17), the next drawing-scheduled line is set as the correction target line (step S18). Then, returning to step S15, steps S15, S17, and S18 are repeated until the presence or absence of a horizontal line on the correction target line is confirmed and the correction line is recorded. Actually, the recording of the correction target line and the correction line is delayed by a plurality of lines from the confirmation in step S15. In the inkjet printer 1, steps S12 to S18 are repeated until there are no more drawing lines, whereby an image corresponding to the image data is recorded on the web 9 (step S19).

  As described above, in the inkjet printer 1, when there is no horizontal line on the correction target line, a correction line similar to the correction target line is recorded adjacent to the correction target line, and the horizontal line is displayed on the correction target line. If present, the recording of the correction line is postponed until a line that does not include a horizontal line appears. Accordingly, it is possible to correct the drawing position shift caused by the second drawing cycle while suppressing that the horizontal line, which is a linear figure extending in the width direction, is recognized as thickened. Such a configuration of the ink jet printer 1 is particularly suitable for an ink jet printer in which the ejection ports 60 of each head 5 are similarly tilted by the head 5 being tilted and fixed by a minute rotation angle.

  As mentioned above, although embodiment of this invention has been described, this invention is not limited to the said embodiment, A various change is possible.

  For example, each ejection port group 60 of the head 5 may have only one ejection port array. In the inkjet printer 1, as long as the web 9 can be moved relative to the ejection unit 3, for example, a moving mechanism that moves the ejection unit 3 in the scanning direction may be provided. In addition, the configuration of the inkjet printer 1 may be applied to a sheet-fed inkjet printer that sequentially prints on a plurality of fixed-size printing paper such as A4.

  In the inkjet printer 1, an image may be recorded on a recording medium other than printing paper, such as a plastic film. When an image is recorded on a plastic film or the like, for example, an ultraviolet curable ink is used as the ink ejected from the ejection unit 3.

  The configurations in the above-described embodiments and modifications may be combined as appropriate as long as they do not contradict each other.

DESCRIPTION OF SYMBOLS 1 Inkjet printer 2 Movement mechanism 3 Discharge part 5 Head 7 Control part 9 Web 85 Line 610 1st discharge port 620 2nd discharge port 811,812 1st dot 821,822 2nd dot S11-S19 Step

Claims (3)

An inkjet printer,
An ejection unit that ejects ink toward the recording medium;
A moving mechanism for moving the recording medium relative to the ejection unit only once in a predetermined scanning direction;
By controlling the ejection of ink from the ejection unit based on image data, and forming a plurality of lines each parallel to the width direction perpendicular to the scanning direction and arranged in the scanning direction, A controller for recording on the recording medium;
With
The discharge part is
A plurality of first discharge ports arranged along a discharge port arrangement direction intersecting with the scanning direction, and forming a plurality of first dots by discharging ink onto the recording medium;
A plurality of nozzles arranged along the discharge port arrangement direction and arranged between the plurality of first discharge ports in the width direction, and ejecting ink onto the recording medium to form a plurality of second dots. A second outlet,
With
When the relative movement speed of the recording medium in the scanning direction is the first speed, ink is ejected from the plurality of first ejection ports and the plurality of second ejection ports at a first drawing period. In each of the plurality of lines, a plurality of first dots and a plurality of second dots are alternately arranged in the width direction,
When the relative movement speed of the recording medium is a second speed that is twice the first speed, the frequency from the plurality of first discharge ports and the plurality of second discharge ports is higher than the first drawing period. By ejecting ink at a high second rendering cycle, lines that include a plurality of first dots and do not include the second dots and lines that include a plurality of second dots and do not include the first dots alternate. In the control unit, the plurality of lines arranged in a line are recorded.
a) A line for each number of lines determined in advance based on the second drawing cycle and the first drawing cycle is extracted as a correction target line for correcting a drawing position shift caused by the second drawing cycle. And a process of
b) confirming whether or not there is a horizontal line that is a linear figure extending beyond the predetermined length in the width direction on the correction target line;
c) When the horizontal line does not exist on the correction target line, a correction line similar to the correction target line is recorded adjacent to the correction target line, and when the horizontal line exists on the correction target line A step of returning to the step b) as a new correction target line after the correction target line;
An ink jet printer, wherein: The inkjet printer according to claim 1,
In the image data, each pixel corresponds to a dot drawing position,
In the image data, the horizontal line has a recording density corresponding to each pixel value equal to or higher than a predetermined threshold value, and continues for a first number or more in the width direction and has a second number in the scanning direction. An inkjet printer characterized by being a set of a plurality of pixels equal to or less than the number. The inkjet printer according to claim 1 or 2,
The discharge unit includes a head provided with the plurality of first discharge ports and the plurality of second discharge ports;
The discharge port array direction is slightly inclined with respect to the width direction,
An inkjet printer, wherein each first ejection port and a corresponding second ejection port are arranged in a direction perpendicular to the ejection port array direction.

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