JP2011194800A - Inkjet printer and image recording method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To restrain a banding irregularity from being caused in an image recorded on a recording surface.SOLUTION: Heads 31 and 32 discharging color ink and white ink, respectively are arranged in a row in a main scanning direction in a head unit and each of the heads has a plurality of discharge openings arranged in a subsidiary scanning direction. In recording an image, every time the main scanning of the head unit completes, the head unit relatively moves by a step movement distance d in the subsidiary scanning direction. In the head unit, a working range A1, a resting range B1, and a working range A2 continuing in the subsidiary scanning direction are sequentially set and each range has a width which is an integral multiple of the step movement distance. In parallel with the main scanning, the discharge of ink to a group 31A of working discharge openings within the working range A1 of the head 31 and a group 32A of working discharge openings within the working range A2 of an additional head 32 is controlled, and the discharge of ink from other discharge openings is stopped. As a result, the banding irregularity is restrained from being caused in an image to be recorded.

Description

  The present invention relates to an inkjet printer that discharges a plurality of types of ink, and an image recording method that is executed in the inkjet printer.

  Conventionally, a multilayer in which a layer of a uniform image (so-called solid image) with white ink and an image of a color ink of a color other than white (hereinafter referred to as “color ink image”) are overlaid. Printing is in progress. For example, when recording a color image with a white background color on a transparent object, a white ink layer is first formed on the recording surface of the object, and then the color ink is formed on the white ink layer. A so-called surface printing is performed to record an image, or a color ink image is first recorded on the recording surface, and then a white ink layer is formed on the color ink image layer.

  In Japanese Patent Application Laid-Open No. 2004-260688, an inkjet printer that moves a plurality of heads in a main scanning direction with respect to a recording medium and intermittently moves the recording medium in a sub-scanning direction perpendicular to the main scanning direction, A method in which heads that discharge white ink are arranged on both sides in the main scanning direction or both sides in the sub-scanning direction of the head that discharges ink, and white ink is discharged from one of the heads to perform front or back printing Is disclosed.

  In the ink jet recording apparatus of Patent Document 2, an image recording nozzle array in which a plurality of nozzles are arranged in the sub-scanning direction and an auxiliary recording nozzle array in which a plurality of nozzles are arranged in the sub-scanning direction are in the main scanning direction. Are lined up. At the time of front printing, the area on the subsequent half of the sub-scan in the image recording nozzle array that discharges color ink is selected as the ink discharge area, and the preceding half in the auxiliary recording nozzle array that discharges white ink. This area is selected as the ink ejection area. In addition, at the time of back printing, the area on the preceding half of the sub-scan in the image recording nozzle array is selected as the ink ejection area, and the area on the subsequent half in the auxiliary recording nozzle array is selected as the ink ejection area. Is done. In the apparatus of Patent Document 2, there is no need to dispose heads that discharge white ink on both sides in the main scanning direction or both sides in the sub-scanning direction of the head that discharges color ink unlike the apparatus of Patent Document 1. The head unit can be downsized. Note that Patent Document 3 discloses a method of performing three-layer printing by the same method as Patent Document 2.

JP 2003-285427 A International Publication No. 2005/105452 Pamphlet US Patent Application Publication No. 2006/158473

  By the way, in the methods of Patent Documents 2 and 3, as described above, the area on the subsequent side or the front side half of the sub-scan of the head that discharges color ink is selected as the ink ejection area in accordance with the front printing or the back printing. The area on the leading or trailing half of the head that ejects white ink is selected as the ink ejection area. Therefore, the area on the recording surface to which the color ink is applied in one main scan comes into contact with the area on the recording surface to which the white ink is applied, and the color ink and the area near the boundary between these areas are in contact with each other. Bleeding with white ink is likely to occur. Such bleeding becomes banding unevenness (also simply called banding), and the quality of the recorded image is deteriorated.

  SUMMARY An advantage of some aspects of the invention is that it suppresses occurrence of banding unevenness in an image recorded on a recording surface by an ink jet printer.

  The invention according to claim 1 is an ink jet printer, the first head having a plurality of ejection openings arranged in the sub-scanning direction and ejecting the first type of ink toward the recording surface of the object. A second head that is arranged in the sub-scanning direction and has a plurality of ejection ports that eject the second type of ink toward the recording surface, and is perpendicular to the sub-scanning direction and parallel to the recording surface A head unit provided side by side in the main scanning direction, and main scanning for moving the head unit relative to the object in the main scanning direction, and each time the main scanning is completed a predetermined number of times, the head A moving mechanism for performing sub-scanning in which the unit is moved relative to the object by a step moving distance shorter than the width of the head unit in the sub-scanning direction in the sub-scanning direction; A control unit that controls ejection of ink from the first head and the second head in parallel with the main scanning of the main unit, and in the head unit, a first operating range that is continuous in the sub-scanning direction, A pause range and a second motion range are set in order, and the width of the first motion range, the pause range and the second motion range in the sub-scanning direction is an integral multiple of the step movement distance, respectively, and the control unit Accordingly, in parallel with the main scanning of the head unit, ink ejection is controlled to the first operation ejection port group included in the first operation range among the plurality of ejection ports of the first head. The ejection of ink from the suspension ejection port group included in the pause range and the second operation range is paused, and the first operation range and the plurality of ejection ports of the second head are stopped. Ejection of ink from sleep outlet group included in stop range is paused, the ejection of ink is controlled to the second operating outlet group included in the second operating range.

  A second aspect of the present invention is the ink jet printer according to the first aspect, wherein the first operation discharge port group and the second operation are performed in a forward path and a return path of the relative movement of the head unit in the main scanning direction. The ejection of ink from the ejection port group is controlled, and the moving mechanism performs the sub-scanning every time a predetermined number of relative reciprocating movements of the head unit are completed.

  A third aspect of the present invention is the ink jet printer according to the first or second aspect, wherein the width of the pause range in the sub-scanning direction is equal to the step moving distance.

  A fourth aspect of the present invention is the ink jet printer according to any one of the first to third aspects, wherein in the head unit, the first operating range, the pause range, and the first continuous in the sub-scanning direction. 2 operating ranges, another resting range, and a third operating range are set in order, and the widths of the other resting range and the third operating range in the sub-scanning direction are each an integral multiple of the step moving distance. In parallel with the main scanning of the head unit, the controller discharges ink from a pause ejection port group included in the other pause range among the plurality of ejection ports of the first head. The ejection is stopped and the ejection of ink is controlled to the third operation ejection port group included in the third operation range, and the other pause range among the plurality of ejection ports of the second head. Ejection of ink from sleep outlet group contained in the preliminary third operating range is paused.

  A fifth aspect of the present invention is the ink jet printer according to any one of the first to fourth aspects, wherein one of the first head and the second head ejects color ink, and the other is white ink or clear. Ink is ejected.

  A sixth aspect of the present invention is the ink jet printer according to any one of the first to fifth aspects, wherein the head unit ejects ink from the first head and the second head onto the recording surface. The first type of ink and the second type of ink are radiation curable.

  A seventh aspect of the present invention is the ink jet printer according to any one of the first to sixth aspects, wherein the sub scanning of the first operation range, the pause range, and the second operation range is performed by the control unit. The direction width can be changed.

  The invention according to claim 8 is the ink jet printer according to claim 1, wherein the head unit includes a plurality of heads arranged in the main scanning direction, and each of the plurality of heads is A plurality of ejection openings arranged in the sub-scanning direction and ejecting ink toward the recording surface, and in the head unit, the operation range and the pause are continuously within the range of the width in the sub-scanning direction. The ranges are alternately set, the number of the operation ranges is N, the width of each operation range is an integral multiple of the step movement distance, the width of each pause range is equal to the step movement distance, In FIG. 5, N-layer images are stacked on the recording surface by performing discharge control on the discharge port of any one of the heads.

  The invention according to claim 9 is an image recording method executed in an inkjet printer, wherein the inkjet printer is arranged in the sub-scanning direction and applies the first type of ink toward the recording surface of the object. A first head having a plurality of ejection openings for ejecting, and a second head arranged in the sub-scanning direction and having a plurality of ejection openings for ejecting a second type of ink toward the recording surface, A head unit arranged in a main scanning direction perpendicular to the sub-scanning direction and parallel to the recording surface, the image recording method comprising: a) moving the head unit relative to the object in the main scanning direction Each time the main scanning is completed a predetermined number of times, the head unit is moved in the sub-scanning direction to be smaller than the width of the head unit in the sub-scanning direction. A step of performing sub-scanning that moves relative to the object by a long step movement distance; and b) discharging ink from the first head and the second head in parallel with the main scanning of the head unit. And c) prior to the step a), the head unit includes a step of sequentially setting a first operating range, a pause range, and a second operating range in the sub-scanning direction, The widths in the sub-scanning direction of the first operating range, the pause range, and the second operating range are each an integral multiple of the step moving distance, and in the step b), in parallel with the main scanning of the head unit. The ejection of ink is controlled to the first operation ejection port group included in the first operation range among the plurality of ejection ports of the first head, and the pause range and the second operation range are controlled. Ink ejection from the included pause ejection port group is paused, and among the plurality of ejection ports of the second head, ink ejection from the pause operation port group included in the first operation range and the pause range is performed. The ink ejection is controlled with respect to the second operation ejection port group that is stopped and included in the second operation range.

  A tenth aspect of the present invention is the image recording method according to the ninth aspect, wherein in the step b), the first operation discharge is performed in a forward path and a return path of the relative movement of the head unit in the main scanning direction. Ink ejection from the outlet group and the second operation ejection port group is controlled, and the sub-scanning is performed every time the head unit completes a predetermined number of relative reciprocations in the step a).

  The invention according to claim 11 is the image recording method according to claim 9 or 10, wherein the width of the pause range in the sub-scanning direction is equal to the step moving distance.

  A twelfth aspect of the present invention is the image recording method according to any one of the ninth to eleventh aspects, wherein, in the step c), the head unit continuously performs the first operation in the sub-scanning direction. A range, the pause range, the second motion range, another pause range and a third motion range are set in order, and the width of the other pause range and the third motion range in the sub-scanning direction is A pause discharge included in the other pause range among the plurality of discharge ports of the first head in parallel with the main scanning of the head unit in the step b), which is an integral multiple of the step moving distance. Ink ejection from the outlet group is stopped, ink ejection is controlled to the third operation ejection port group included in the third operation range, and the other of the plurality of ejection ports of the second head One of ejection of ink from sleep outlet group included in the rest range and the third movement range is paused.

  A thirteenth aspect of the present invention is the image recording method according to any one of the ninth to twelfth aspects, wherein one of the first head and the second head ejects color ink and the other is white ink or Clear ink is ejected.

  The invention described in claim 14 is the image recording method according to any one of claims 9 to 13, wherein the head unit is ejected from the first head and the second head onto the recording surface. An irradiation unit for irradiating the ink with radiation is provided, and the first type ink and the second type ink have radiation curability.

  A fifteenth aspect of the present invention is the image recording method according to any one of the ninth to fourteenth aspects, wherein the head unit includes a plurality of heads arranged in the main scanning direction, and each of the plurality of heads. Has a plurality of ejection openings arranged in the sub-scanning direction and ejecting ink toward the recording surface, and in the step c), the head unit has a width within the sub-scanning direction. The operation range and the rest range are alternately set in succession, the number of the operation ranges is N, the width of each operation range is an integral multiple of the step moving distance, and the width of each rest range is the step. In step b), ejection control is performed on the ejection port of any one of the heads in the step b), so that an N layer image is laminated on the recording surface.

  According to the present invention, it is possible to suppress occurrence of banding unevenness in an image recorded on a recording surface.

  In the inventions of claims 2 and 10, it is possible to prevent banding unevenness due to bidirectional printing, and in the inventions of claims 4 and 12, a three-layer image is formed on the object. Can do.

It is a perspective view which shows the external appearance of an inkjet printer. It is a bottom view which shows a head unit. It is a figure which shows the flow of the operation | movement which records an image on a base material. It is a figure for demonstrating the operation | movement which performs 2 layer printing. It is a bottom view which shows a head unit. It is a bottom view which shows the head unit of a comparative example. It is a figure for demonstrating operation | movement of another comparative example. It is a figure for demonstrating the operation | movement which performs 3 layer printing. It is a figure for demonstrating an operation | movement range and a rest range. It is a figure for demonstrating other operation | movement which performs 2 layer printing.

  FIG. 1 is a perspective view showing an appearance of an ink jet printer 1 according to an embodiment of the present invention. The ink jet printer 1 is a device that records a color image by an ink jet method on a plate-like or sheet-like base material 9 made of plastic, for example.

  The inkjet printer 1 includes a main body 11 and a control unit 4, and the main body 11 holds a base material 9 on the (+ Z) side surface in FIG. 1 and a stage moving mechanism 22 provided on the base 20. Is provided. A nut of a ball screw mechanism included in the stage moving mechanism 22 is fixed to the surface of the stage 21 opposite to the substrate 9, and a motor connected to the ball screw mechanism rotates, so that the stage 21 becomes Y in FIG. It moves smoothly in the direction (hereinafter also referred to as “sub-scanning direction”). A position detection module 23 for detecting the position of the stage 21 with respect to the base 20 is further provided on the base 20.

  Above the stage 21, a head unit 3 that ejects fine ink droplets toward a main surface (hereinafter referred to as “recording surface”) on the (+ Z) side of the substrate 9 is disposed. A head moving mechanism 24 having a ball screw mechanism and a motor is supported so as to be movable in the main scanning direction (X direction in FIG. 1) perpendicular to the sub-scanning direction and parallel to the recording surface of the substrate 9. The base 20 is provided with a frame 25 so as to straddle the stage 21, and the head moving mechanism 24 is fixed to the frame 25. A light source 39 for emitting ultraviolet rays is provided on the frame 25, and a plurality of optical fibers (actually, the plurality of optical fibers are bundled. In FIG. The light from the light source 39 is introduced into the inside of the head unit 3 through the above.

  FIG. 2 is a bottom view showing the head unit 3. As shown in FIG. 2, the head unit 3 includes a plurality of (four in FIG. 2) heads 31 that eject inks of different colors, and the plurality of heads 31 are arranged in the X direction. 3 is fixed to the main body 30. In FIG. 2, the (−X) side head 31 discharges C (cyan) color ink, and the (+ X) side head 31 of C head 31 discharges M (magenta) color ink. The (+ X) side head 31 of the M head 31 ejects K (black) color ink, and the (+ X) side head 31 of the K head 31 ejects Y (yellow) color ink. . The head unit 3 further includes one head 32 that discharges white ink, and the head 32 is disposed on the (+ X) side of the Y head 31. Thus, in the head unit 3, the plurality of heads 31 and 32 are arranged in the main scanning direction.

  In the following description, inks of colors other than white (in this embodiment, C, M, K, and Y inks) are referred to as “color inks” to distinguish them from white inks. Further, the head 31 that discharges color ink is collectively referred to as a color recording head 31, and the head 32 that discharges white ink is referred to as an additional head 32 in distinction from the color recording head 31.

  In each of the color recording head 31 and the additional head 32, a plurality of discharge ports 311 and 321 are arranged at a pitch equal to the Y direction (hereinafter referred to as “discharge port pitch”). Ink is ejected toward the recording surface 9. Each color ink and white ink contains an ultraviolet curing agent and has ultraviolet curing properties. In FIG. 2, fifteen discharge ports 311 and 321 are illustrated in each head 31 and 32, but actually each head 31 and 32 has a large number of discharge ports 311 and 321.

  Further, the head unit 3 is provided with two light irradiation units 38 each connected to the light source 39, and the two light irradiation units 38 are arranged with the color recording head 31 and the additional head 32 interposed therebetween in the X direction. . In each light irradiation unit 38, a plurality of optical fibers are arranged along the Y direction, and each light irradiation unit 38 irradiates ultraviolet rays onto a linear region extending in the Y direction on the substrate 9. Therefore, when the head unit 3 moves in the (+ X) direction, the ink immediately after being ejected onto the recording surface is irradiated with ultraviolet rays from the (−X) side light irradiation unit 38, and the head unit 3. Is moved in the (−X) direction, the ultraviolet rays from the (+ X) side light irradiation unit 38 are irradiated to the ink immediately after being ejected onto the recording surface. Thereby, the ink discharged on the recording surface is cured in a short time.

  FIG. 3 is a diagram illustrating a flow of an operation in which the inkjet printer 1 records a color image on the base material 9. In this operation example, a layer of a uniform image with white ink (hereinafter referred to as “white ink layer”) and a layer of an image with color ink (hereinafter referred to as “color ink image”) are overlapped. Two-layer printing is performed.

  First, in the inkjet printer 1, an input for instructing printing conditions is performed by an operator via an input unit (not shown), and the input is received by the control unit 4 (step S11). Here, the printing conditions are the number of layers of an image to be recorded on the substrate 9, the number of passes of each head in interlaced printing described later, and the like. In this operation example, input for instructing two-layer printing and two passes for each layer is performed. In the case of two-layer printing, it is further assumed that input for instructing front printing or reverse printing is performed, and here, input for instructing front printing is performed. Subsequently, in the control unit 4, the operation ejection port group in which ink ejection is activated and the ink ejection in the plurality of ejection ports 311 of the color recording head 31 and the plurality of ejection ports 321 of the additional head 32. A pause discharge port group that pauses is determined according to the printing conditions (step S12).

  Specifically, in the head unit 3 of FIG. 2, in the sub-scanning direction, a range indicated by an arrow with a reference sign B1 (hereinafter referred to as “pause range”), adjacent to the pause range B1 on the (+ Y) side. And a range that is twice the width of the pause range B1 (the range indicated by the arrow labeled A1 in FIG. 2, hereinafter referred to as “first operation range”), and the pause range B1 (−Y) side and a range that is twice as wide as the resting range B1 (this is a range indicated by an arrow labeled A2 in FIG. 2 and is hereinafter referred to as “second operating range”). Is set. The discharge ports 311 of the color recording head 31 included in the first operation range A1 are determined as the first operation discharge port group, and the discharge ports 321 of the additional head 32 included in the second operation range A2 are the second operation discharge ports. Determined as a group. In FIG. 2, the first operation discharge port group is surrounded by a two-dot chain line rectangle 31A, and the second operation discharge port group is surrounded by a two-dot chain line rectangle 32A (the same applies to FIG. 5 described later). Further, the discharge ports 311 of the color recording head 31 included in the pause range B1 and the second operation range A2, and the discharge ports 321 of the additional head 32 included in the pause range B1 and the first operation range A1 are the pause discharge port group. Is done.

  In this example of operation, the range in the sub-scanning direction including all the ejection ports 311 and 321 is the head effective range, and the head effective range is determined by the number of ejection ports 311 and 321 included in each head 31 and 32. The width multiplied by. The width of the pause range B1 in the sub-scanning direction is approximately 1/5 of the width of the head effective range, and the width of each of the first operation range A1 and the second operation range A2 in the sub-scanning direction is approximately the width of the head effective range. 2/5. Accordingly, almost all the ejection ports 311 and 321 of the heads 31 and 32 are included in any one of the first operation range A1, the pause range B1, and the second operation range A2 that are continuous in the sub-scanning direction. When there are discharge ports 311 and 321 that are not included in any of the first operation range A1, the rest range B1 and the second operation range A2 near the ends of the heads 31 and 32, the discharge ports 311 and 321 are included in the pause discharge port group (the same applies hereinafter).

  When the first and second operation ejection port groups and the pause ejection port group are determined, the head unit 3 in FIG. 1 is arranged at a predetermined recording start position, and the head unit 3 is continuously moved in the main scanning direction. Movement (ie, main scanning) and intermittent relative movement (ie, sub scanning) in the sub scanning direction are started (step S13). Specifically, the head unit 3 disposed above the (−X) side and (+ Y) side end of the base material 9 performs main scanning in the (+ X) direction by the head moving mechanism 24, and the base material 9. Main scanning is stopped when reaching the upper end of the (+ X) side. Subsequently, the substrate 9 is moved by the stage moving mechanism 22 in the (+ Y) direction by the same distance as the width of the resting range B1 (hereinafter referred to as “step moving distance”) (that is, the head unit 3 is (−Y)). Then, the head unit 3 performs main scanning in the (−X) direction. When the head unit 3 reaches the upper end of the base material 9 on the (−X) side and main scanning is stopped, the base material 9 moves in the (+ Y) direction by a step movement distance.

  As described above, in the inkjet printer 1, main scanning is performed in which the head unit 3 is moved relative to the base material 9 in the main scanning direction, and the head unit 3 is moved each time one main scanning is completed. Sub-scanning that moves relative to the base material 9 by a step movement distance shorter than the width of the head unit 3 in the sub-scanning direction in the sub-scanning direction is performed. On the other hand, in the control unit 4, in parallel with the main scanning of the head unit 3, the ejection of ink from the first and second operation ejection port groups is controlled according to the drawing data (step S14).

  FIG. 4 is a diagram for explaining an operation in which the inkjet printer 1 performs two-layer printing. On the left side of FIG. 4, a combination of one color recording head 31 and additional head 32 is shown in the vicinity of the horizontal direction in FIG. 4 corresponding to the X direction, and the vertical direction in FIG. 4 corresponding to the Y direction. The relative positions in the sub-scanning direction of the color recording head 31 and the additional head 32 with respect to the base material 9 in each main scanning are shown by shifting the step movement distance d by a plurality of positions α1 to α8. . Further, a portion 31A set as a first operation discharge port group in the color recording head 31 (a portion included in the first operation range A1 in the color recording head 31, hereinafter, simply referred to as “first operation discharge port group 31A”). And a portion 32A set as a second operation discharge port group in the additional head 32 (a portion included in the second operation range A2 in the additional head 32, hereinafter simply referred to as “second operation discharge port group”). 32A ") is indicated by parallel diagonal lines. On the right side of FIG. 4, a region on the recording surface of the base material 9 through which the rest range B1 of the head unit 3 passes in each main scanning after the third time (a band-like region extending in the main scanning direction, hereinafter “swath”). Are indicated by rectangles with reference numerals 8, 8a to 8h.

  In the first main scanning in which the color recording head 31 and the additional head 32 are arranged with the symbol α1 in FIG. 4, the (−Y) -side half of the ejection openings of the second operation ejection orifice group 32A of the additional head 32. 321 (in FIG. 4, the second operation discharge port group 32A is divided into half on the (+ Y) side and the (−Y) side by a thin broken line. The same applies to the first operation discharge port group 31A). ) Side swath 8a is passed, and white ink is discharged to swath 8a. In the following description, ink is not ejected from the ejection ports 311 and 321 not specifically mentioned (in the first main scanning, the other ejection ports 321 of the additional head 32 and all the ejection ports 311 of the color recording head 31). And

  In the second main scan (see arrangement α2 in FIG. 4), the (+ Y) -side half of the discharge ports 321 of the second operation discharge port group 32A of the additional head 32 passes over the swath 8a, and (−Y ) Side ejection port 321 passes over the swath 8b adjacent to the (−Y) side of the swath 8a, and white ink is ejected to the swaths 8a and 8b. At this time, in the plurality of dots formed by the (−Y) -side half ejection ports 321 of the second operation ejection port group 32A in the first main scanning, the interval between two dots adjacent in the sub-scanning direction is In the second main scan, interpolation is performed with any dot formed by the (+ Y) -side half of the ejection ports 321 (that is, interlaced printing is performed). The movement distance in the immediately preceding sub-scan is slightly changed from the step movement distance (the same applies to each sub-scan). In this way, when the second operation discharge port group 32A passes over the swath 8a twice (by two passes), a uniform image layer (that is, white ink) with white ink on the swath 8a. Layer) is formed.

  The amount of change from the step movement distance of the movement distance in the sub-scan is very small (in the case of two passes, for example, half of the discharge port pitch). In the description, the movement distance in scanning is equal to the step movement distance. It should be noted that when the entire width of the first operation range A1, the rest range B1 and the second operation range A2 is n times the step movement distance (n is a positive integer), the discharge included in each head 31, 32 is included. In other cases, such as when the number of the exits 311 and 321 is not divisible by n, fine correction of the moving distance during sub-scanning is performed as necessary (for example, correction of 1/10 or less of the step moving distance). It's okay.

  In the third main scan (see the arrangement α3 in FIG. 4), the (+ Y) -side half of the discharge ports 321 of the second operation discharge port group 32A of the additional head 32 passes over the swath 8b, and (−Y ) Side ejection port 321 passes over the swath 8c adjacent to the (−Y) side of the swath 8b, and white ink is ejected to the swaths 8b and 8c. Further, the resting range B1 of the head unit 3 passes over the swath 8a. In the fourth main scan (see the arrangement α4 in FIG. 4), the second operation discharge port group 32A of the additional head 32 discharges white ink to the swath 8c and the swath 8d on the (−Y) side of the swath 8c. The rest range B1 of the head unit 3 passes over the swath 8b. Further, in the first operation discharge port group 31A of the color recording head 31, the (−Y) -side half of the discharge ports 311 passes over the (+ Y) -side swath 8a, and color ink is supplied to the swath 8a. Discharging is performed.

  In the fifth main scan (see arrangement α5 in FIG. 4), white ink is discharged to the swath 8d and the swath 8e on the (−Y) side of the swath 8d by the second operation discharge port group 32A of the additional head 32. The rest range B1 of the head unit 3 passes over the swath 8c. Further, in the first operation discharge port group 31A of the color recording head 31, the (+ Y) -side half of the discharge ports 311 passes over the (+ Y) -side swath 8a, and the (−Y) -side half of the discharge ports. 311 passes over the swath 8b, and color ink is discharged to the swaths 8a and 8b. As a result, when the fifth main scan is completed, a color ink image layer of color ink is formed on the white ink layer of the swath 8a by two passes of the first operation discharge port group 31A.

  In each of the sixth and subsequent main scans (see the arrangements α6 to α8 in FIG. 4), white ink is applied to the two swaths 8 by the second operation discharge port group 32A of the additional head 32, as in the fifth main scan. The rest range B1 of the head unit 3 passes over one swath 8 adjacent to the (+ Y) side of the two swaths 8 and is discharged by the first operation discharge port group 31A of the color recording head 31. Color ink is discharged to two swaths 8 adjacent to the (+ Y) side of the swath 8. Accordingly, above each swath 8, the (−Y) side half of the second operation discharge port group 32A, the (+ Y) side half of the second operation discharge port group 32A, and the head unit in five consecutive main scans 3, the half (−Y) side half of the first operation discharge port group 31A, and the (+ Y) side half of the first operation discharge port group 31A pass in order. That is, in each swath 8, a white ink layer is formed by two passes of the second operation discharge port group 32A located on the preceding side ((−Y) side) of the sub-scan, and then one main scan. A color ink image layer is formed on the white ink layer by two passes of the first operation discharge port group 31A located on the subsequent side ((+ Y) side) of the sub-scan.

  In this way, when the white ink layer and the color ink image layer are formed on all the swaths 8 on the substrate 9, the main scanning and the sub scanning of the head unit 3 are stopped, and the inkjet printer 1 Completes the two-layer printing operation (step S15). Thereby, the printed matter printed on the surface is completed.

  When the transparent base material 9 is used and the input for instructing the reverse printing is performed in the process of step S11 in FIG. 3, the first operation range A1 is performed in the process of step S12 as shown in FIG. Is set on the (−Y) side of the pause range B1, and the second operation range A2 is set on the (+ Y) side of the pause range B1. The width of each operating range A1, A2 is twice the width of the resting range B1. The discharge ports 311 of the color recording head 31 included in the first operation range A1 are the first operation discharge port group 31A, and the discharge ports 321 of the additional head 32 included in the second operation range A2 are the second operation discharge ports. It is set as a group 32A. Further, the discharge ports 311 of the color recording head 31 included in the pause range B1 and the second operation range A2, and the discharge ports 321 of the additional head 32 included in the pause range B1 and the first operation range A1 are the pause discharge port group. Is done.

  In this case, in each of the main scans in which the head unit 3 moves relative to the base material 9 in the (−Y) direction in the processes of steps S13 and S14, the first operation discharge port group 31A of the color recording head 31 performs two operations. The color ink is discharged to the swaths, and the resting range B1 of the head unit 3 passes above one swath adjacent to the (+ Y) side (sub scanning side) of the two swaths, and the additional head White ink is ejected to two swaths adjacent to the (+ Y) side of the swath by the 32nd second operation ejection port group 32A. Therefore, in each swath, a layer of a color ink image by color ink is first formed, and then a layer of white ink is formed on the layer of color ink image, thereby completing a back printed material.

  FIG. 6 is a bottom view showing a head unit 91 of a comparative example. In the head unit 91 of the comparative example of FIG. 6, for example, in the case of front printing, the head 92 that discharges color ink is included in the (+ Y) side half area (area with parallel diagonal lines in FIG. 6). The discharge ports are selected as the operation discharge port group, and the remaining discharge ports are set as the pause discharge port group. Further, in the head 93 that discharges white ink, the discharge ports included in the half area on the (−Y) side (regions with parallel diagonal lines in FIG. 6) are selected as the operation discharge port group, and the remaining discharge ports are It is a rest discharge port group. In the image recording operation in the head unit 91 of the comparative example, the area on the recording surface to which the color ink is applied in one main scan and the area on the recording surface to which the white ink is applied are in contact with each other. In the vicinity of the boundary between these areas, bleeding of the color ink and the white ink tends to occur. Such bleeding causes banding unevenness, and the quality of the recorded image is degraded.

  On the other hand, in the inkjet printer 1, in the head unit 3 shown in FIGS. 2 and 5, the first operation range A1, the pause range B1, and the second operation range A2 continuous in the sub-scanning direction are set in order, and the color recording head Among the plurality of 31 ejection openings 311, ink ejection is controlled with respect to the first operation ejection opening group 31 </ b> A included in the first operation range A <b> 1, and the pause ejection openings included in the pause range B <b> 1 and the second operation range A <b> 2. Ink ejection from the group is suspended. In addition, among the plurality of ejection ports 321 of the additional head 32, ink ejection from the pause ejection port group included in the first operation range A1 and the pause range B1 is paused, and the second operation included in the second operation range A2. Ink ejection is controlled to the ejection port group 32A. This prevents the area on the recording surface to which the color ink is applied in one main scan from contacting the area on the recording surface to which the white ink is applied. Generation of banding unevenness due to bleeding with ink can be prevented.

  FIG. 7 is a diagram for explaining the operation of another comparative example, and corresponds to FIG. In the operation of this comparative example, the width of the pause range B91 is set smaller than that in the above operation example. The width of each of the first operation range A91 and the second operation range A92 is four times the width of the pause range B91, and the step movement distance is twice the width of the pause range B91. Further, the discharge ports in the first operation range A91 in the head 95 that discharges color ink are set as the first operation discharge port group 95A, and the discharge ports in the second operation range A92 in the head 94 that discharges white ink are the second. The operation discharge port group 94A is set, and the remaining discharge ports in the heads 94 and 95 are set as the pause discharge port group. When two-layer printing is performed under such conditions, the second swath is discharged in the odd-numbered swaths (swaths 8a, 8c, 8e, and 8g) in the (−Y) direction with the swath denoted by reference numeral 8a being the first. Immediately after the white ink layer is formed by the two passes of the outlet group 94A, the color ink image layer is formed by the two passes of the first operation ejection port group 95A. In the even-numbered swaths (swaths 8b, 8d, 8f, and 8h) from the swath 8a, a white ink layer is formed by two passes of the second operation discharge port group 94A, and then one main scan is performed. On the other hand, the color ink image layer is formed by two passes of the first operation discharge port group 95A.

  Therefore, in the even-numbered swath, compared with the odd-numbered swath, the time during which the ultraviolet light is directly irradiated from the light irradiation unit 38 to the white ink on the base material 9 is longer (that is, the amount of ultraviolet irradiation is increased). ) As the white ink cures, the surface temperature of the substrate 9 when the color ink is applied also increases. As a result, the spread degree of the color ink on the substrate 9 is different between even-numbered swaths and odd-numbered swaths, and banding unevenness due to slight differences in texture and color occurs.

  On the other hand, in the operation example of FIG. 4 in the ink jet printer 1, the width of the first operation range A1 and the second operation range A2 in the sub-scanning direction is twice the step movement distance d, and the width of the pause range B1 is a step. It is equal to the movement distance d. Thus, in all the swaths 8, after the white ink layer is formed by the two passes of the second operation discharge port group 32A, the first operation discharge port group 31A is performed twice with one main scan being sandwiched therebetween. The color ink image layer can be formed by this pass. As a result, it is possible to prevent the occurrence of banding unevenness due to the difference between the swaths after the white ink layer is formed and before the color ink image layer is formed. Therefore, coupled with prevention of banding unevenness due to bleeding of color ink and white ink, banding unevenness is suppressed (prevented) in an image (two-layer image) recorded on the recording surface of the substrate 9. be able to.

  In the above operation example, the white ink layer is formed by the two passes of the second operation discharge port group 32A in accordance with the input of the printing conditions indicating the two-layer printing and the two passes of each layer, and the first operation discharge port. The color ink image layer is formed by two passes of the group 31A, and each of the white ink layer and the color ink image layer has one pass of the operation ejection port group, or three or more passes. The width of each operation range in the head unit 3 can be any integer multiple of the step moving distance. In the ink jet printer 1, the widths in the sub-scanning direction of the first operation range A1 and the second operation range A2 can be individually changed by the control unit 4, so that two-layer printing can be freely performed according to the printing conditions. be able to. As will be described later, the width of the pause range B1 may also be an arbitrary integral multiple of the step moving distance, and can be changed by the control unit 4 according to the printing conditions.

  In the ink jet printer 1, the head unit 3 is disposed at a predetermined position away from the substrate 9, and ink is ejected from a plurality of ejection ports including the pause ejection port group (by performing flushing), thereby ejecting ports. It is prevented that the ink is cured in the vicinity and the discharge port is clogged.

  Next, another operation example in which the inkjet printer 1 records a color image on the substrate 9 will be described. In this operation example, a transparent substrate 9 is used, and as described later, three-layer printing is performed in which a color ink image layer, a white ink layer, and a color ink image layer are sequentially stacked on the recording surface. Is called. The color ink image layer formed first on the substrate 9 is visually recognized from the back surface (the main surface opposite to the recording surface), and the color ink image formed on the white ink layer. Is visually recognized from the recording surface side.

  First, in the inkjet printer 1, an input for instructing printing conditions is performed by an operator via an input unit (not shown), and the input is accepted by the control unit 4 (FIG. 3: step S11). Here, it is assumed that an input for instructing three-layer printing and two passes for each layer is performed. In the control unit 4, an operation discharge port group capable of discharging ink and a discharge of ink at the discharge ports 311 of the color recording head 31 and the discharge ports 321 of the additional head 32 (see FIG. 2). A pause discharge port group that pauses is determined according to the printing conditions (step S12).

  FIG. 8 is a diagram for explaining an operation in which the inkjet printer 1 performs three-layer printing, and corresponds to FIG. 4. In the case of three-layer printing and two passes for each layer, in the head unit 3, a first operating range A1, a resting range B1, a second operating range A2, another resting range B2 that are continuous in the sub-scanning direction, and The third operation range A3 is set in order. The width in the sub-scanning direction of each of the pause range B1 and the pause range B2 is approximately 1/8 of the width of the head effective range, and each of the sub-ranges of the first motion range A1, the second motion range A2, and the third motion range A3. The width in the scanning direction is approximately ¼ of the width of the head effective range. The discharge ports 311 of the color recording head 31 included in the first operation range A1 are the first operation discharge port group 31A, and the discharge ports 321 of the additional head 32 included in the second operation range A2 are the second operation discharge ports. The discharge ports 311 of the color recording head 31 included in the group 32A and included in the third operation range A3 are set as the third operation discharge port group 33A. Further, the ejection ports 311 of the color recording head 31 included in the pause ranges B1 and B2 and the second operation range A2, and the additional head 32 included in the pause ranges B1 and B2, the first operation range A1 and the third operation range A3. The discharge port 321 is a pause discharge port group.

  Subsequently, main scanning and intermittent sub-scanning of the head unit 3 are started (step S13). That is, as the main scanning of the head unit 3 is repeated and each main scanning is completed, the step moving distance d equal to the width in the sub-scanning direction of the resting ranges B1 and B2 (1/8 of the width of the head effective range). Only the head unit 3 performs sub-scanning.

  In parallel with the main scanning of the head unit 3, the control unit 4 controls the ejection of ink to the first to third operation ejection port groups 31A, 32A, 33A of the color recording head 31 and the additional head 32. At the same time, the ejection of ink from the pause ejection port group is paused (step S14). Specifically, in each main scan of the head unit 3, the color ink is discharged to the two swaths 8 by the first operation discharge port group 31A of the color recording head 31, and the pause range B1 of the head unit 3 is set. Two swaths 8 that pass above the one swath 8 adjacent to the (+ Y) side of the two swaths 8 and are adjacent to the (+ Y) side of the swath 8 by the second operation discharge port group 32A of the additional head 32. In contrast, white ink is discharged. Further, the resting range B2 of the head unit 3 passes above one swath 8 adjacent to the (+ Y) side of the two swaths 8, and the swath 8 is swung by the third operation discharge port group 33A of the color recording head 31. Color ink is discharged to two swaths 8 adjacent to the (+ Y) side.

  When attention is paid to each swath 8, in the eight consecutive main scans, the (−Y) side half of the first operation discharge port group 31A, the (+ Y) side half of the first operation discharge port group 31A, the head unit 3 Pause range B1, half of (−Y) side of second operation discharge port group 32A, half of (+ Y) side of second operation discharge port group 32A, pause range B2 of head unit 3, third operation discharge port group The half on the (−Y) side of 33A and the half on the (+ Y) side of the third operation discharge port group 33A pass in order. Accordingly, in each swath 8 having the width of the step moving distance d, after the color ink image layer is formed with the color ink by the two passes of the first operation discharge port group 31A, the main scanning is performed once. The white ink layer is formed on the color ink image layer by two passes of the second operation discharge port group 32A. Subsequently, after performing one main scan, a color ink image layer is formed with the color ink on the white ink layer by two passes of the third operation ejection port group 33A. In this way, a color ink image layer, a white ink layer, and a color ink image layer are sequentially formed for each swath 8.

  When three layers of images are formed on all the swaths 8 on the substrate 9, the main scanning and sub scanning of the head unit 3 are stopped, and the operation of the inkjet printer 1 performing three layers printing is completed ( Step S15).

  As described above, in the inkjet printer 1, in the head unit 3, the first operation range A1, the pause range B1, the second operation range A2, the other pause range B2, and the third zone that are continuous in the sub-scanning direction. The operation range A3 is set in order. In the color recording head 31, the ejection of ink is controlled to the ejection ports 311 included in the first and third operation ranges A1 and A3, and the ejection of ink from the other ejection ports 311 is stopped. Further, in the additional head 32, the ejection of ink is controlled to the ejection ports 321 included in the second operation range A2, and the ejection of ink from the other ejection ports 321 is stopped. Thereby, while forming the image of 3 layers on the base material 9, it can suppress that a banding nonuniformity arises in the image visually recognized.

  In the above description, the case where the color ink image layer and the white ink layer are formed on the substrate 9 has been described. For example, as shown in FIG. 9, the same configuration as the color recording head 31 and the additional head 32 is provided. Another additional head 32a that discharges clear ink is provided side by side on these heads 31 and 32 in the X direction in FIG. 9 (in fact, there is a gap between the heads 31, 32, and 32a). A uniform image layer may be further formed with clear ink. Specifically, in the head unit 3, a first operation range A1, a pause range B1, a second motion range A2, a pause range B2, a third motion range A3, which are continuous in the sub-scanning direction (Y direction in FIG. 9), A pause range B3 and a fourth operating range A4 are set in order. Further, the width in the sub-scanning direction of each of the pause ranges B1 to B3 is made equal to the step moving distance d, and the width in the sub-scanning direction of each of the first to fourth operation ranges A1 to A4 is an integral multiple of the step moving distance d ( In FIG. 9, it is doubled).

  The discharge ports 311 of the color recording head 31 included in the first operation range A1 are the first operation discharge port group 31A, and the discharge ports 321 of the additional head 32 included in the second operation range A2 are the second operation discharge ports. It is set as a group 32A. Further, the discharge port 311 of the color recording head 31 included in the third operation range A3 is the third operation discharge port group 33A, and the discharge port of the additional head 32a included in the fourth operation range A4 is the fourth operation discharge port group. 34A. Further, the ejection port 311 of the color recording head 31 included in the pause range B1 to B3, the second motion range A2, and the fourth motion range A4, the pause range B1 to B3, the first motion range A1, the third motion range A3, and the third motion range A3. The discharge ports 321 of the additional head 32 included in the fourth operation range A4 and the discharge ports of the additional head 32a included in the pause ranges B1 to B3, the first operation range A1, the second operation range A2, and the third operation range A3 It is a rest discharge port group.

  In this way, the first to fourth operation discharge port groups 31A, 32A, 33A, 34A and the pause discharge port group are set, and during the main scanning of the head unit 3, the first to fourth operation discharge port groups 31A, By performing ink ejection control on 32A, 33A, and 34A, a color ink image layer, a white ink layer, a color ink image layer, and a clear ink layer (that is, a clear ink layer) on the transparent substrate 9 A uniform image layer) is formed sequentially with ink. As a result, four-layer printing is realized, and it is possible to suppress banding unevenness in an image (four-layer image) recorded on the recording surface. The clear ink can also be regarded as an overcoat agent.

  In the above four-layer printing, two color ink images may be formed by different color recording heads 31. In this case, two sets of color recording heads 31 in the head unit 3 (however, a set of CMKY heads) Are arranged in the main scanning direction together with the additional heads 32 and 32a, and the first operation discharge port group 31A is assigned to one set of the color recording heads 31. The three-operation ejection port group 33A is assigned to the other set of color recording heads 31. Five or more images may be laminated on the recording surface by the same method as described above. Further, as described above, the width of each operation range may be a step movement distance or an integer multiple of 3 or more of the step movement distance.

  As described above, the head unit 3 includes a plurality of heads arranged in the main scanning direction, and each of the plurality of heads has a plurality of ejection openings arranged in the sub-scanning direction and ejecting ink toward the recording surface. In this case, in order to suppress the occurrence of banding unevenness in an image recorded in multiple layers, the head unit 3 has an operation range and a pause range continuously within the range of the width in the sub-scanning direction (that is, the head effective range). It is set alternately. Further, the number of operation ranges is N (where N is a positive integer), the width of each operation range is an integral multiple of the step movement distance, and the width of each pause range is equal to the step movement distance. . In parallel with the main scanning of the head unit 3, the ejection control is performed on the ejection ports of any one head (that is, the operational ejection port group included in the operational range) in each operation range. As a result, an N layer image in which the occurrence of banding unevenness is suppressed can be laminated on the recording surface of the base material 9. In each head, the discharge ports other than the operation discharge port group are set as a pause discharge port group.

In this case, the width of each operation range is the same, and when the image of each layer is formed M times (where M is a positive integer), the effective range of the head in the head unit 3 is determined. When the width is W, the width V _{A in} the sub-scanning direction of the operation range is expressed by Equation 1, and the width V _{B of the} resting range (that is, the step moving distance) is expressed by Equation 2.

(Equation 1)
V _A = (W · M) / ((M + 1) · N−1)

(Equation 2)
V _B = W / ((M + 1) · N−1)

  By the way, in the operation example of FIG. 4, when the swath denoted by reference numeral 8 a is the first and the odd-numbered swaths (swaths 8 a, 8 c, 8 e, 8 g) are directed toward the (−Y) direction, The first pass through the second operation ejection port group 32A of the head 32 is performed during the main scan in the (+ X) direction of the head unit 3, and the second pass is the main scan in the (−X) direction of the head unit 3. Sometimes done. The first pass through the first operation discharge port group 31A of the color recording head 31 is performed during the main scanning of the head unit 3 in the (−X) direction, and the second pass is performed in the (+ X) direction of the head unit 3. This is performed during main scanning.

  Next, paying attention to even-numbered swaths (swaths 8b, 8d, 8f, and 8h) from the swath 8a in the (−Y) direction, in these swaths, 1 by the second operation discharge port group 32A of the additional head 32 is used. The second pass is performed during the main scan of the head unit 3 in the (−X) direction, and the second pass is performed during the main scan of the head unit 3 in the (+ X) direction. The first pass through the first operation discharge port group 31A of the color recording head 31 is performed during the main scanning of the head unit 3 in the (+ X) direction, and the second pass is performed in the (−X) direction of the head unit 3. This is performed during main scanning.

  Therefore, at the end of the swath 8 in the main scanning direction, the time from when ink is ejected in one main scan until the same kind of ink is ejected in the next main scan is equal to the odd-numbered swath and the even-numbered swath. There is a possibility that a slight banding unevenness (banding unevenness due to bidirectional printing) due to a difference in texture and color may occur.

  Next, a more preferable operation example of the inkjet printer 1 that suppresses occurrence of banding unevenness due to bidirectional printing will be described. FIG. 10 is a diagram for explaining an operation in which the inkjet printer 1 performs two-layer printing, and corresponds to FIG. In FIG. 10, the moving direction of the head unit 3 during each main scanning is indicated by arrows with symbols β1 to β8.

  In this operation example, every time the head unit 3 is reciprocated once in the main scanning direction, the sub scanning of the head unit 3 is performed. Accordingly, each of the (−Y) side half and the (+ Y) side half of the second operation discharge port group 32A of the additional head 32 passes each swath 8 twice, and the first pass of the head unit 3 ( This is performed during the main scanning in the + X) direction, and the second pass is performed during the main scanning in the (−X) direction of the head unit 3. Thus, the white ink layer is formed by four passes (two reciprocations) of the additional head 32. Each of the (−Y) side half and the (+ Y) side half of the first operation discharge port group 31 A of the color recording head 31 passes each swath 8 twice, and the first pass of the head unit 3 This is performed during main scanning in the (+ X) direction, and the second pass is performed during main scanning in the (−X) direction of the head unit 3. Therefore, a color ink image layer is formed by four passes of the color recording head 31.

  As described above, in the operation example of FIG. 10, every time the reciprocation of the head unit 3 in the main scanning direction is completed, the sub scanning of the head unit 3 is performed. In the direction position, after the ink is ejected in one main scan, the time until the same kind of ink is ejected in the next main scan can be made the same. Can be prevented. Note that after the main scanning of the head unit 3 in the (+ X) direction is completed, the head unit 3 may move slightly in the sub-scanning direction to perform interlaced printing or the like. Further, in the operation example of FIG. 8, the sub-scan of the head unit 3 may be performed every time the reciprocation of the head unit 3 is completed.

  Depending on the processing time required for image recording in the inkjet printer 1, in the operation example of FIG. 4, for example, ink ejection from each operation ejection port group is controlled only during main scanning in the (+ X) direction of the head unit 3. While the sub-scan of the head unit 3 is performed, the head unit 3 may be returned to the (−X) side of the base material 9 while stopping the ejection of ink from each ejection port. In this case, since the ink is discharged to each swath only during the main scanning in the (+ X) direction of the head unit 3, banding unevenness due to bidirectional printing as described above does not occur.

On the recording surface of the base material 9 under the same conditions as in the above formulas 1 and 2, except that the head unit 3 is sub-scanned each time one reciprocation of the head unit 3 is completed. When images of N layers (where N is a positive integer) are stacked on each other, the width V _A of each operation range in the sub-scanning direction is expressed by Equation 3, and the width V _{B of} each pause range. Is expressed by Equation 4. However, the width of the head unit 3 in the sub-scanning direction (that is, the width of the effective head range) is W, and the image of each layer is moved P times (where P is a positive integer) (2P times of main movement). Scanning).

(Equation 3)
V _A = (W · P) / ((P + 1) · N−1)

(Equation 4)
V _B = W / ((P + 1) · N−1)

  Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications can be made.

  In the operation example of FIG. 10, each time the head unit 3 is reciprocated once, the sub scanning of the head unit 3 is performed. However, when it is necessary to apply a thick ink on the substrate 9, etc. The head unit 3 may be sub-scanned each time a plurality of reciprocating movements of the head unit 3 (that is, four or more even main scans) are completed. In the inkjet printer 1, when the ejection of ink from each operation ejection port group is controlled in the forward path and the backward path of the movement of the head unit 3 in the main scanning direction, every time the head unit 3 is reciprocated a predetermined number of times. Further, by performing sub-scanning, it is possible to prevent banding unevenness due to bidirectional printing.

  Further, when it is not necessary to consider banding unevenness due to bidirectional printing, the head unit 3 may be sub-scanned every time the main scanning of the head unit 3 is performed an odd number of times. That is, in the above case, the sub scanning of the head unit 3 may be performed every time the main scanning of the head unit 3 is completed a predetermined number of times.

  In the above-described embodiment, the width of the pause range in the sub-scanning direction is made equal to the step movement distance, so that the ejection ports of each head are used efficiently. It is also possible to do. Further, the number of passes of the head in forming each layer is not necessarily the same in all layers. For example, when the white ink layer needs to be thickened, the first operation in the operation example of FIG. The width of the range A1 may be twice the step movement distance d, and the width of the second operation range A2 may be four times the step movement distance d.

  In the above embodiment, since almost the entire effective head range is used in the head unit 3, it is possible to efficiently record an image. However, a range in the sub-scanning direction shorter than the effective head range is used. The target range may be set, and multilayer printing may be performed based on the use target range. In this case, in the above formulas 1 to 4, the width of the operation target range and the width of the pause range may be determined by setting the width of the use target range as W.

  Depending on the application of the inkjet printer 1, a multi-layer image including a black ink layer may be formed. Further, it is a material for improving the adhesion of multi-layer printing only with color ink and clear ink, and a surface treatment agent (for example, color ink on the recording surface of the base material 9), and can also be regarded as ink. ) May be used. In the inkjet printer 1, the head unit 3 includes a first head that discharges the first type of ink and a second head that discharges the second type of ink arranged in the main scanning direction. Even when different types of ink are ejected in parallel during scanning, recording is performed on the recording surface by setting an operation range and a rest range, each of which is an integral multiple of the step movement distance. It is possible to suppress banding unevenness in the image.

  The photocurable ink used in the ink jet printer 1 may have curability for light in a wavelength band other than ultraviolet light. An ink that is cured by irradiation with radiation other than light, such as an electron beam, may be used. In the ink jet printer 1, the ink ejected from each head is radiation curable, and the head unit 3 is provided with an irradiation unit that irradiates the ink ejected onto the recording surface with the ink on the recording surface. Can be quickly cured.

  In the above embodiment, the head unit 3 moves relative to the stage 21 in the main scanning direction by the head moving mechanism 24 that moves the head unit 3 in the main scanning direction and the stage moving mechanism 22 that moves the stage 21 in the sub-scanning direction. The inkjet printer 1 may be provided with a mechanism for moving the stage 21 in the main scanning direction and a mechanism for moving the head unit 3 in the sub-scanning direction. That is, the moving mechanism that moves the head unit 3 in the main scanning direction and the sub-scanning direction relative to the base material 9 may be realized in any configuration.

  In each head of the head unit 3, if a plurality of ejection openings are provided at a substantially constant pitch in the sub-scanning direction, for example, the plurality of ejection openings are arranged on a horizontal line inclined with respect to the sub-scanning direction. May be. Further, the arrangement of the plurality of ejection openings in each head may be staggered.

  The inkjet printer 1 may record an image on an object other than the base material 9 such as printing paper.

  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 3 Head unit 4 Control part 9 Base material 22 Stage moving mechanism 24 Head moving mechanism 31 Color recording head 32, 32a Additional head 38 Light irradiation part 311,321 Discharge port 31A, 32A, 33A, 34A Operation | movement discharge port group A1 -A4 Operation range B1-B3 Rest range S12-S15 Steps

Claims (15)

An inkjet printer,
A first head arranged in the sub-scanning direction and having a plurality of ejection openings for ejecting the first type of ink toward the recording surface of the object; and arranged in the sub-scanning direction and directed toward the recording surface A second head having a plurality of ejection openings for ejecting the second type of ink in a main scanning direction perpendicular to the sub-scanning direction and parallel to the recording surface;
The head unit is moved relative to the object in the main scanning direction, and the head unit is moved in the sub-scanning direction every time the main scanning is completed a predetermined number of times. A moving mechanism that performs sub-scanning that moves relative to the object by a step movement distance shorter than the width in the sub-scanning direction;
A control unit that controls ejection of ink from the first head and the second head in parallel with the main scanning of the head unit;
With
In the head unit, a first operation range, a pause range, and a second operation range that are continuous in the sub-scanning direction are set in order, and the first operation range, the pause range, and the second operation range in the sub-scanning direction are set. Each width is an integer multiple of the step travel distance;
In parallel with the main scanning of the head unit by the control unit,
Ink ejection is controlled to a first operation ejection port group included in the first operation range among the plurality of ejection ports of the first head, and pauses included in the pause range and the second operation range. Ink ejection from the ejection port group is stopped,
Out of the plurality of discharge ports of the second head, the discharge of ink from the stop discharge port group included in the first operation range and the stop range is stopped, and the second operation discharge included in the second operation range. An ink jet printer, wherein ejection of ink is controlled to an outlet group. The inkjet printer according to claim 1,
The ejection of ink from the first operation ejection port group and the second operation ejection port group is controlled in the forward path and the return path of the relative movement of the head unit in the main scanning direction,
The inkjet printer according to claim 1, wherein the moving mechanism performs the sub-scanning every time a predetermined number of relative reciprocations of the head unit are completed. The inkjet printer according to claim 1 or 2,
An ink jet printer, wherein a width of the pause range in the sub-scanning direction is equal to the step moving distance. An inkjet printer according to any one of claims 1 to 3,
In the head unit, the first operating range, the resting range, the second operating range, another resting range, and a third working range that are continuous in the sub-scanning direction are sequentially set, and the other resting range and The width of the third operating range in the sub-scanning direction is an integer multiple of the step moving distance,
In parallel with the main scanning of the head unit by the control unit,
Among the plurality of ejection ports of the first head, the ejection of ink from the pause ejection port group included in the other pause range is paused, and the third operation ejection port group included in the third operation range is stopped. In contrast, the ejection of ink is controlled,
An ink jet printer characterized in that, from among the plurality of ejection ports of the second head, the ejection of ink from a pause ejection port group included in the other pause range and the third operation range is paused. An ink jet printer according to any one of claims 1 to 4,
One of the first head and the second head discharges color ink, and the other discharges white ink or clear ink. An inkjet printer according to any one of claims 1 to 5,
The head unit includes an irradiation unit that irradiates the ink ejected from the first head and the second head onto the recording surface,
An ink jet printer wherein the first type ink and the second type ink are radiation curable. An ink jet printer according to any one of claims 1 to 6,
The ink jet printer according to claim 1, wherein widths in the sub-scanning direction of the first operation range, the pause range, and the second operation range can be changed by the control unit. An ink jet printer according to any one of claims 1 to 7,
The head unit includes a plurality of heads arranged in the main scanning direction, and each of the plurality of heads has a plurality of ejection ports arranged in the sub-scanning direction and ejecting ink toward the recording surface. And
In the head unit, the operation range and the rest range are alternately set continuously within the range of the width in the sub-scanning direction, the number of the operation ranges is N, and the width of each operation range is the step moving distance. And the width of each resting range is equal to the step moving distance,
An inkjet printer characterized in that N layers of images are stacked on the recording surface by performing ejection control on the ejection port of any one head in each operation range. An image recording method executed in an inkjet printer,
The inkjet printer is
A first head arranged in the sub-scanning direction and having a plurality of ejection openings for ejecting the first type of ink toward the recording surface of the object; and arranged in the sub-scanning direction and directed toward the recording surface A second head having a plurality of ejection openings for ejecting the second type of ink and arranged in a main scanning direction perpendicular to the sub-scanning direction and parallel to the recording surface,
The image recording method comprises:
a) Performing main scanning for moving the head unit relative to the object in the main scanning direction, and moving the head unit in the sub-scanning direction every time the main scanning is completed a predetermined number of times. Performing a sub-scan that moves relative to the object by a step movement distance shorter than the width of the head unit in the sub-scan direction;
b) controlling the ejection of ink from the first head and the second head in parallel with the main scanning of the head unit;
c) before the step a), in the head unit, sequentially setting a first operation range, a pause range, and a second operation range that are continuous in the sub-scanning direction;
With
Widths in the sub-scanning direction of the first operation range, the pause range, and the second operation range are each an integral multiple of the step movement distance;
In the step b), in parallel with the main scanning of the head unit,
Ink ejection is controlled to a first operation ejection port group included in the first operation range among the plurality of ejection ports of the first head, and pauses included in the pause range and the second operation range. Ink ejection from the ejection port group is stopped,
Out of the plurality of discharge ports of the second head, the discharge of ink from the stop discharge port group included in the first operation range and the stop range is stopped, and the second operation discharge included in the second operation range. An image recording method, wherein ejection of ink is controlled to an outlet group. The image recording method according to claim 9, comprising:
In the step b), the ejection of ink from the first operation ejection port group and the second operation ejection port group is controlled in the forward path and the return path of the relative movement of the head unit in the main scanning direction.
In the step a), the sub-scanning is performed every time the head unit completes a predetermined number of relative reciprocating movements. The image recording method according to claim 9 or 10, wherein
An image recording method, wherein a width of the pause range in the sub-scanning direction is equal to the step moving distance. The image recording method according to any one of claims 9 to 11,
In the step c), in the head unit, the first operating range, the pause range, the second motion range, another pause range, and the third motion range that are continuous in the sub-scanning direction are sequentially set.
Widths in the sub-scanning direction of the another resting range and the third operating range are each an integral multiple of the step moving distance;
In the step b), in parallel with the main scanning of the head unit,
Among the plurality of ejection ports of the first head, the ejection of ink from the pause ejection port group included in the other pause range is paused, and the third operation ejection port group included in the third operation range is stopped. In contrast, the ejection of ink is controlled,
The image recording method according to claim 1, wherein ink ejection from a pause ejection port group included in the another pause range and the third operation range among the plurality of ejection ports of the second head is paused. The image recording method according to any one of claims 9 to 12,
One of the first head and the second head discharges color ink, and the other discharges white ink or clear ink. The image recording method according to any one of claims 9 to 13,
The head unit includes an irradiation unit that irradiates the ink ejected from the first head and the second head onto the recording surface,
An image recording method, wherein the first type of ink and the second type of ink are radiation curable. The image recording method according to any one of claims 9 to 14,
The head unit includes a plurality of heads arranged in the main scanning direction, and each of the plurality of heads has a plurality of ejection ports arranged in the sub-scanning direction and ejecting ink toward the recording surface. And
In the step c), in the head unit, an operation range and a rest range are alternately set continuously within a range of the width in the sub-scanning direction,
The number of the movement ranges is N, the width of each movement range is an integer multiple of the step movement distance, the width of each pause range is equal to the step movement distance,
In the step b), an image of N layers is laminated on the recording surface by performing ejection control on the ejection port of any one head in each operation range. Recording method.

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