JP2018176610A - Ink jet printer and printing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to perform overprinting more efficiently by transportation in only one direction when performing overprinting of an image.SOLUTION: In an ink jet printer, a first control part 41 executes first printing scan for discharging an ink of a first quantity for an image from a first nozzle 32 and forming ink dot for a first image, and a second printing scan for forming ink dot for a second image adjacent to the ink dot for the first image. A second control part 42 executes an underlayer printing scan for discharging an ink for an underlayer of a second quantity more than the first quantity from a second nozzle 34 and forming one ink dot for an underlayer larger than the ink dot for each image. A third control part 43 causes the first control part 41 to execute said first and second printing scan, and then, causes the second control part 42 to execute underlayer printing scan, and thereafter, transports a recording medium in one direction X1 of a sub-scanning direction X relatively to a discharge head 30, and causes again the first control part and the second control part to execute the first and second printing scan, and the underlayer printing scan, respectively.SELECTED DRAWING: Figure 3

Description

  The present invention relates to an inkjet printer and a printing method.

  2. Description of the Related Art Conventionally, as a printing apparatus for printing an image, an ink jet printing apparatus has been proposed which discharges ink droplets onto a recording medium and lands a plurality of droplets on the recording medium to obtain a desired printing result. Are known. In this type of printing apparatus, the ink is ejected toward the recording medium while scanning the ink head which ejects the ink in the main scanning direction, and when printing on the scanning line is finished, the recording medium has a predetermined pitch in the subscanning direction , And printing is continuously performed on the scanning line at the position after the conveyance, thereby printing an image such as characters and patterns.

  By the way, in recent years, there is an increasing need for printing an image on a recording medium such as transparent glass or sheet for the purpose of advertisement, display, and the like. As described above, when the recording medium itself transmits visible light, there are relatively few problems when a colored and transparent image such as a stained glass is used as a print target. However, when the light transmittance of the coloring material of the ink used when printing an opaque image is high or the density of the coloring material is not high, visible light transmits even the printed image, so that it is clear to human vision. It can be difficult to recognize. On the other hand, when the color of the recording medium is dark (for example, in the case of black color), the color of the recording medium may pass through the print image, and the color of the ink may not be reflected in solid. Therefore, when printing an opaque image on a recording medium other than white, the base layer is printed in advance using white pigment ink or the like having a high light reflectance, and then the target image is superimposed and printed on the base layer. By performing overprinting, an image is clearly displayed in a predetermined color (see, for example, Patent Documents 1 and 2).

  In overprinting, after printing a base layer on a recording medium, in order to print an image layer on the printed base layer, printing is performed twice at the same position. At this time, if printing is continuously performed twice by reciprocating the ink head, the drying of the ink can not catch up, and the base ink and the image ink are mixed. Therefore, in practice, there is a method of reversely conveying the recording medium from the downstream toward the upstream after printing of the entire underlayer and printing the image layer on the underlayer. On the other hand, Patent Document 2 discloses the following printing method. That is, the ink head is divided into halves on the upstream side and the downstream side in the sub scanning direction, and the base layer is first printed by the ink head on the upstream half side, and then the ink is dried by the heater and the recording medium is half the ink head. Transport only downstream. Next, the image is printed by overlapping the head of the downstream half on the base layer of the recording medium conveyed, and at the same time, the next base layer is printed by the head of the upstream half. As a result, overlapping printing can be performed by transporting the recording medium from the upstream toward the downstream only in one direction.

Utility model registration No. 3164863 Patent 5629360 gazette

  However, in the former method of reversely conveying the recording medium, the conveyance means can not contact the printing surface from the viewpoint of protection of the printing surface. Therefore, the position where the conveyance means can contact the recording medium for conveyance is limited, and accurate conveyance can not be performed, so that the printing position between the base layer and the image layer shifts, or the large-sized recording medium can not be conveyed. There was a problem. Also, in the latter method in which printing is carried out in only one direction and only printing can be performed for only half of the ink head in one printing scan, it takes about twice as much time as ordinary printing, When printing an image layer with high definition, there is a problem that it takes more time.

  The present invention has been made in view of such a point, and an object thereof is to provide an ink jet printer capable of performing overlapping printing more efficiently by conveyance in only one direction when overlapping printing of an image. . Another object of the present invention is to provide a printing method capable of performing overlapping printing more efficiently with conveyance in only one direction.

  The technology disclosed herein provides an inkjet printer including an ejection head, a scanning mechanism, a transport mechanism, and a control device. In this inkjet printer, the ejection head has a first nozzle row in which a plurality of first nozzles for ejecting image ink are arrayed in the sub scanning direction, and a plurality of second nozzles for ejecting a background ink in the sub scanning direction The first nozzle array and the second nozzle array are arranged in the main scanning direction which intersects the sub scanning direction. The scanning mechanism scans the ejection head in the main scanning direction. The transport mechanism transports the recording medium relative to the ejection head in the sub-scanning direction by moving at least one of the recording medium and the ejection head. The controller drives the ejection head, the scanning mechanism and the transport mechanism. Here, the nozzle pitch in the sub-scanning direction of the first nozzle and the nozzle pitch in the sub-scanning direction of the second nozzle are equal. The control device includes a first control unit, a second control unit, and a third control unit. The first control unit discharges the first amount of image ink from the first nozzle while moving the discharge head in the main scanning direction, and forms the first image ink dots in a predetermined area of the recording medium. In the first printing scan, a first amount of image ink is ejected from the first nozzle while moving the ejection head in the main scanning direction, and the first area is adjacent to the first image ink dot in a predetermined area of the recording medium. And 2) performing a second printing scan for forming ink dots for image. The second control unit causes the second nozzle to eject a second amount of the base ink, which is larger than the first amount, while moving the ejection head in the main scanning direction, and for each image within a predetermined area of the recording medium. A base printing scan is performed to form one base ink dot larger than the ink dot. The third control unit (1) causes the first control unit to execute the first and second printing scans and then causes the second control unit to execute the background printing scan, and then the recording medium is relative to the ejection head. Or the second control unit to execute the background printing scan, or (2) the second control. After causing the printing unit to execute the background printing scan and then causing the first control unit to execute the first and second printing scans, the recording medium is transported relative to the ejection head in one direction in the sub-scanning direction, After the second control unit executes the background printing scan, the first control unit executes the first and second printing scans.

  According to the above configuration, while the recording medium is conveyed in only one direction in the sub scanning direction, (2) the second control unit prints the base ink dots on the image ink dots printed by the first control unit. Either (1) or (2) the image control ink dots can be printed by the first control unit on the base ink dots printed by the second control unit. Thereby, desired images can be overprinted without soiling the printing surface. At this time, in order to discharge the second amount of the base ink larger than the first amount from the second nozzle, the number of the base ink dots discharged from the second nozzle is equal to the number of the image ink dots. It can be less than that. Also, conventionally, overlapping printing was performed with the same printing resolution of the image layer and the base layer, but according to the above configuration, printing of the base layer is performed because the image layer and the base layer are printed by different printing scans. The resolution can be independent and set lower than the printing resolution of the image layer. By this, the printing time of the base layer by the base ink can be suitably shortened rather than the printing time of the image layer by the image ink.

  According to the present invention, there is provided an ink jet printer capable of performing overlapping printing more efficiently with conveyance in only one direction when overlapping printing images.

1 is a front view of an ink jet printer according to an embodiment. It is a schematic diagram which shows the structure of the lower surface of the discharge head which concerns on one Embodiment. It is a block diagram of a control device concerning one embodiment. It is a flowchart of the printing method concerning one embodiment. FIG. 6 is an image view showing a state of printing by a printer according to an embodiment. It is the image figure which showed the mode of the printing by a printer following FIG. 5A. It is an image figure showing a situation of printing by a printer following FIG. 5B. It is an image figure showing a situation of printing by a printer following FIG. 5C. It is an image figure showing a situation of printing by a printer following FIG. 5D. It is the image figure which showed the mode of the printing by a printer following FIG. 5E. It is the image figure which showed the mode of the printing by a printer following FIG. 5F. FIG. 14 is an image view showing a state of printing by a printer according to another embodiment. It is the image figure which showed the mode of the printing by a printer following FIG. 6A. It is the image figure which showed the mode of the printing by a printer following FIG. 6B. It is the image figure which showed the mode of the printing by a printer following FIG. 6C. It is the image figure which showed the mode of the printing by a printer following FIG. 6D. It is the image figure which showed the mode of the printing by a printer following FIG. 6E. It is the image figure which showed the mode of the printing by a printer following FIG. 6F.

Hereinafter, an embodiment of an ink jet printer and a printing method according to the present invention will be described with reference to the drawings. The embodiments described herein are, of course, not intended to specifically limit the present invention. In addition, the same reference numerals are given to members and portions that exhibit the same action, and the overlapping description will be appropriately omitted or simplified.
In the present specification, “ink jet printer” (hereinafter sometimes simply referred to as “printer”) refers to discharging a liquid such as ink as fine droplets to a target recording medium etc. It means all devices that supply and record. The method of droplet formation in such a printer is not particularly limited. For example, conventionally known various methods including various continuous methods such as binary deflection method or continuous deflection method, and various on-demand methods such as thermal method or piezoelectric element method can be adopted without particular limitation.

First Embodiment
FIG. 1 is a front view of a printer 1 according to an embodiment. In the following description, when the printer 1 is viewed from the front, one moving away from the printer 1 is referred to as the front, and one approaching the printer 1 is as the rear. Further, the symbol Y in the drawing indicates the main scanning direction, and the symbols Y1 and Y2 indicate the right side and the left side when the printer 1 is viewed from the front, respectively. In the present embodiment, the direction in which the main scanning direction Y intersects with the horizontal plane is taken as the sub scanning direction X (see FIG. 2). The main scanning direction Y and the sub scanning direction X are orthogonal to each other, and the sub scanning direction X coincides with the front and back direction. In the present embodiment, the front in the sub scanning direction X is taken as a first direction X1, and the rear is taken as a second direction X2. However, these are merely directions for the convenience of description and do not limit the installation mode and the like of the ink jet printer.

  The printer 1 intermittently moves the recording medium 5 in the sub-scanning direction X and ejects ink from the discharge head 30 moving in the main scanning direction Y, whereby an image such as characters and patterns on the recording medium 5 is obtained. Print. The recording medium 5 is an object on which an image is to be printed. The type of the recording medium 5 is not particularly limited. The recording medium 5 is made of not only paper such as plain paper and inkjet paper but also resin materials such as polyvinyl chloride (PVC) and polyester, and various materials such as aluminum, iron and wood. It is also good. In addition, the shape may be a sheet having flexibility, such as a cut sheet or continuous paper, or may be a plate having a certain shape, an article having an arbitrary shape, or the like. Also, the dimensions of the recording medium 5 are not particularly limited. Since the printer 1 of the present invention can perform printing by one-way conveyance, its features are particularly suitably exhibited in a printer capable of printing a large recording medium (for example, a roll medium having a width of A1 or more) 5 in particular. obtain.

  The printer 1 includes a printer body 10 and legs 11 for supporting the printer body 10. The printer main body 10 has a box shape long in the main scanning direction Y. In the printer body 10, a guide rail 20 and a carriage 22 engaged with the guide rail 20 are accommodated. The carriage 22 is a member for holding and moving the discharge head 30 described later. The guide rail 20 is extended in the main scanning direction Y inside the printer body 10. The guide rail 20 supports the movement of the carriage 22 in the main scanning direction Y. Further, an endless belt 24 is fixed to the carriage 22. The belt 24 is wound around a pair of pulleys 26a and 26b provided on the right and left sides of the guide rail 20 without slack. A carriage motor 28 is attached to the right pulley 26a. The carriage motor 28 is electrically connected to the control device 40. The carriage motor 28 is controlled by the controller 40. When the carriage motor 28 is driven, the pulley 26a on the right side is rotated, and the belt 24 is rotationally driven around the pulleys 26a and 26b. The left pulley 26 b follows the travel of the belt 24 and supports the linear travel of the belt 24. As a result, the carriage 22 fixed to the belt 24 moves in the main scanning direction Y along the guide rail 20. As a result, the discharge head 30 can be moved in the main scanning direction Y. In the present embodiment, the carriage 22, the belt 24, the pulleys 26a and 26b, and the carriage motor 28 constitute a scanning mechanism that moves the ejection head 30 in the main scanning direction Y.

  Below the carriage 22, a platen 12 is extended in the main scanning direction Y. The platen 12 in this example is a plate-like member. The platen 12 supports the printing region of the recording medium 5 horizontally. A plurality of pairs of pinch rollers 14 and grit rollers 15 are provided along the main scanning direction Y on the rear side of the platen 12. The pinch roller 14 is provided above the platen 12 and elastically presses the recording medium 5 from above. A grit roller 15 is embedded in the platen 12 at a position facing the pinch roller 14. The grit roller 15 is configured to be rotatable about a main scanning direction Y. The grit roller 15 is connected to the feed motor 16. The grit roller 15 rotates forward or reverse in response to the driving force of the feed motor 16. The feed motor 16 is electrically connected to the controller 40. The feed motor 16 is controlled by the controller 40. The recording medium 5 is conveyed in the sub-scanning direction X by the rotation of the grit roller 15 in a state where the recording medium 5 is nipped between the pinch roller 14 and the grit roller 15. The pinch roller 14 rotates about the main scanning direction Y as the recording medium 5 is conveyed in the sub scanning direction X, thereby preventing positional deviation, floating, and the like of the recording medium 5 during conveyance. The rotation of the feed motor 16 when the recording medium 5 is sent in the first direction X1 in the sub-scanning direction X is forward rotation, and the rotation of the feed motor 16 when the recording medium 5 is sent in the second direction X2 is reverse rotation Call it In the present embodiment, the side in the first direction X1 may be referred to as the downstream side, and the side in the second direction X2 may be referred to as the upstream side. In the present embodiment, the pinch roller 14, the grit roller 15 and the feed motor 16 are a transport mechanism for moving the recording medium 5 in the sub scanning direction X.

  When the printing operation is not performed, the carriage 22 stands by at the home position HP on the left end side of the guide rail 20. The carriage 22 is provided with a discharge head 30. FIG. 2 is a schematic view showing the configuration of the surface (in the present embodiment, the lower surface) of the ejection head 30 on the side facing the recording medium 5. The ejection head 30 is provided with five nozzle rows 31W, 31C, 31M, 31Y, 31K in order from the left. Of the five nozzle rows 31W, 31C, 31M, 31Y and 31K, the four right nozzle rows 31C, 31M, 31Y and 31K respectively eject process color inks for forming a color image. The nozzle row 31C ejects cyan ink. The nozzle row 31M ejects magenta ink. The nozzle row 31Y ejects yellow ink. The nozzle row 31K ejects black ink. The leftmost nozzle row 31W ejects white ink.

  The five nozzle rows 31W, 31C, 31M, 31Y, and 31K each have a plurality of nozzles 6. The plurality of nozzles 6 are arranged in the sub-scanning direction X. The five nozzle rows 31W, 31C, 31M, 31Y, and 31K are arranged in the main scanning direction Y. In this example, the nozzle rows 31W, 31C, 31M, 31Y, and 31K are arranged in a row such that the nozzles 6 of each row are arranged in a single row in the main scanning direction Y. The positions in the sub-scanning direction X of two nozzles 6 adjacent in the main scanning direction Y coincide with each other. However, the arrangement of the nozzle rows 31W, 31C, 31M, 31Y, and 31K is not limited to this. The nozzle rows 31W, 31C, 31M, 31Y, 31K are arranged such that, for example, the nozzles 6 of the odd-numbered nozzle rows 31W, 31M, 31K from the left are aligned in the main scanning direction Y, and the remaining left So that the nozzles 6 of the even-numbered nozzle rows 31C and 31Y are positioned between the nozzles 6 of odd-numbered nozzle rows 31W, 31M and 31K in both the main scanning direction Y and the sub scanning direction X (the nozzles 6 are checkered May be arranged). In each of the nozzle rows 31W, 31C, 31M, 31Y, and 31K, the length of the nozzle row, that is, the length from the center of the nozzle 6 located most forward in the nozzle row to the center of the nozzle 6 located most backward "M" are mutually equal. Further, the pitch between the nozzles 6 in each of the nozzle rows 31W, 31C, 31M, 31Y, and 31K (distance between nozzle centers, hereinafter simply referred to as "nozzle pitch") is constant at "n". In FIG. 2, the discharge head 30 is shown with the length in the sub-scanning direction omitted. Therefore, although about 20 nozzles 6 are displayed in each of the nozzle rows 31W, 31C, 31M, 31Y, and 31K in FIG. 2, actually, more (for example, 180) nozzles 6 are provided. . The number and arrangement of the nozzles 6 are not limited at all.

  In the present embodiment, the above-mentioned process color ink corresponds to an image ink for forming an image layer. The four nozzle rows 31C, 31M, 31Y, and 31K correspond to the first nozzle row 311. Further, the nozzles 6 constituting the four nozzle rows 31C, 31M, 31Y, 31K correspond to the first nozzles. The number of colors and the color tone of the image ink are not limited to the above examples. Further, in the present embodiment, the white ink corresponds to the base ink for forming the base layer. The nozzle row 31 W corresponds to the second nozzle row 312. The nozzles 6 constituting the nozzle row 31W correspond to the second nozzles.

  In the present specification, the “base layer” refers to the reflection / light shielding disposed below (the back of) the image layer when the image layer is viewed from the side where a person is supposed to view the image layer. It means the layer for. Thus, the underlayer does not necessarily mean the layer located below the image layer when performing printing. For example, when an image layer is printed on a transparent recording medium, and it is planned that a person visually recognizes the image layer from the side of the image layer printed on the recording medium, the recording medium is an underlayer, an image layer from the bottom. Printing is performed so as to be stacked in the order of Also, for example, when it is planned that a person views the image layer through the recording medium from the side of the transparent recording medium, printing is performed on the recording medium so that the image layer and the base layer are laminated in order from the bottom.

  In the inside of the discharge head 30, actuators 32, 34 provided with piezoelectric elements and the like are provided (see FIG. 3). Inks are ejected from the nozzles 6 of the first nozzle row 311 and the second nozzle row 312 toward the recording medium 5 by the actuators 32 and 34 being instantaneously expanded or contracted by the piezoelectric drive. The actuators 32, 34 are electrically connected to the control device 40, and the drive is controlled by the control device 40. Hereinafter, to simplify the description, in the present embodiment, the actuators that control the discharge of the image ink from the first nozzle row 311 are collectively referred to as the first actuator 32, and the base ink from the second nozzle row 312. An actuator that controls the discharge of the ink is referred to as a second actuator 34.

  The nozzle rows 31W, 31C, 31M, 31Y, and 31K communicate with ink cartridges (not shown) through ink supply paths (not shown). The ink cartridge is detachably disposed, for example, at the right end of the printer body 10. In addition, the material which comprises an ink is not specifically limited, The various coloring material and medium (It may be at least one of a solvent and a dispersion medium.) Conventionally used as a material of the ink of an inkjet printer can be included. . The ink may be, for example, a solvent-based (solvent-based) pigment ink, an aqueous pigment ink, an aqueous dye ink, an ultraviolet-curable pigment ink that is cured by receiving ultraviolet light, or the like.

  As shown in FIG. 1, an operation panel 48 is provided at the right end of the printer body 10. The operation panel 48 is provided with a display unit for displaying the state of the printer 1 and the operation state of the printer 1, and an input key for the user to input an instruction. Inside the operation panel 48, a control device 40 for controlling various operations of the printer 1 is accommodated.

  The configuration of the control device 40 is not particularly limited. The control device 40 is, for example, a microcomputer. The hardware configuration of the microcomputer is not particularly limited. For example, an interface (I / F) for receiving print data and the like from an external device such as a host computer and a central processing unit (CPU: central processing unit), ROM (read only memory) storing the program to be executed by the CPU, random access memory (RAM) used as a working area for expanding the program, the above program, print data and other various data And a storage device such as a memory to be stored. The control device 40 may not necessarily be provided inside the printer body 10. For example, a computer or the like installed outside the printer body 10 and communicably connected to the printer body 10 via a wire or wirelessly It may be

  FIG. 3 is a block diagram showing the configuration of the control device 40 according to an embodiment. The control device 40 is communicably connected to the feed motor 16, the carriage motor 28, and the actuators 32, 34, respectively, and is configured to be able to control them comprehensively. The control device 40 includes a first control unit 41, a second control unit 42, a third control unit 43, and a fourth control unit 44. Each of these units of the control device 40 may be configured by hardware, or may be functionally realized by the CPU executing a computer program. In the present embodiment, the respective units are constituted by integrated circuits. The control device 40 controls the above-described components to eject the image ink from the first nozzle row 311 to print the image layer based on the print data, and ejects the background ink from the second nozzle row 312. The base layer is then printed and overprinted. In the printer 1 disclosed herein, each of the first control unit 41, the second control unit 42, the third control unit 43, and the fourth control unit 44 includes the feed motor 16, the carriage motor 28, and the actuators 32, 34. Control as follows.

  FIG. 4 is a flow diagram of the printing method disclosed herein. This printing method is essentially the first step of printing the image layer in a strip shape corresponding to the dimension of the nozzle row of the ejection head 30 in the sub-scanning direction by scanning the ejection head 30 in the main scanning direction Y S20 or S42) and a second step (S26 or S41) of printing the base layer in the same strip shape. Which one of the first step and the second step is to be printed first (that is, down) is determined based on the print data in step S1. That is, in step S1, when the printing for discharging the base ink in the print data is performed prior to the printing for discharging the image ink, it is determined that "the base layer is below", and "Y" Go in the direction. On the other hand, when the printing for discharging the base ink in the print data is performed after the printing for discharging the image ink, it is determined that "the base layer is not below", and the process proceeds to "N". Then, the overlapping printing of the image layer in the first step and the base layer in the second step is sequentially and continuously repeated while conveying the recording medium 5 only in the first direction X1 in the sub scanning direction X, thereby obtaining a predetermined dimension. The image of is superimposed and printed (S51, S52). In the following description, an image layer printed in the form of a band is referred to as an image band, and a base layer printed in the form of a band is referred to as a base band. In addition, a printing result formed by overprinting of the image band and the base band may be referred to as an overlapping band. Then, as an example of control, in the case where the image layer is printed downward and the underlayer is printed in step S1 (that is, when it is determined in step S1 that "the underlayer is not below (N)"). Control of the printer 1 in the overlapping printing will be described. FIGS. 5A to 5G are image diagrams for explaining the state of printing in each printing process by the printer 1.

  The left side of FIG. 5A is an image of the lower surface of the discharge head 30. On the lower surface of the discharge head 30, the first nozzle row 311 and the second nozzle row 312 are provided side by side in the main scanning direction Y as described above. For example, 180 nozzles 6 are provided in the first nozzle row 311 and the second nozzle row 312, respectively. That is, the nozzle resolutions of the first nozzle row 311 and the second nozzle row 312 are the same. As described above, the lengths in the sub scanning direction X of the first nozzle row 311 and the second nozzle row 312 are “m”, and the nozzle pitch is “n”. However, here, for convenience of explanation, the nozzle 6 located in the middle of the sub scanning direction X is omitted, and several nozzles 6 on the front and rear sides are displayed. Further, for convenience, the nozzle rows 31C, 31M, 31Y, and 31K for discharging the image ink are omitted and displayed as one first nozzle row 311.

  On the right side of FIG. 5A, the squares shown next to the ejection head 30 are an image of a band-like printing area of the recording medium 5. The strip-like print area is long in the main scanning direction Y (for example, A1 size width (594 mm) or more) is omitted for convenience. One square in the drawing corresponds to one pixel of print data. That is, the squares are determined based on the print resolution of the print data. Then, by discharging the image ink of a predetermined color on each square in accordance with the print data, it is possible to print a target image or the like. In the present embodiment, the print data resolution is higher than the resolution (nozzle resolution) of the ejection head 30, and printing is performed with a print resolution higher than the nozzle resolution. The print resolution in this example is, for example, twice the nozzle resolution. That is, the dimensions in the main scanning direction Y and the sub-scanning direction X of a square representing one pixel are both smaller than the nozzle pitch "n". In this example, the dimensions in the main scanning direction Y and the sub scanning direction X of a square indicating one pixel are n / 2 which is half of the nozzle pitch "n". Further, the printing resolution by the first nozzle row 311 and the printing resolution by the second nozzle row 312 are set to be the same.

  5B to 5G show a printing scan by each control unit and a print image printed by the printing scan. In FIGS. 5B to 5G, when the nozzle 6 is displayed as a white circle, it means that the ink is not ejected from the nozzle 6 in the printing scan, and when the nozzle 6 is displayed as a black circle, It means that the ink is ejected from the nozzle 6 in the printing scan. In addition, the circle above the square indicates the ink droplet ejected from the nozzle 6 in the printing scan. Also, the painted squares indicate that the ink has been ejected to the squares by the printing scan prior to the printing scan. In the present embodiment, the squares on which the base ink is discharged are indicated by hatching with dots, and the squares on which the image ink is discharged are indicated by hatching. Hereinafter, the ink droplets ejected from the first nozzle array 311 and landing on the recording medium 5 will be referred to as first ink dots d1, and the ink droplets ejected from the second nozzle array 312 and landing on the recording medium 5 will be second It is called an ink dot d2. The first ink dot d1 is formed of ink droplets of an amount (first amount) suitable for filling one pixel, that is, one square. The second ink dots d2 are formed by ink droplets of a second amount that is greater than the first amount. The size of the second ink dot d2 is larger than the size of the first ink dot d1. In other words, the second ink dot d2 is formed of ink droplets in an amount that can fill more than one square. The first ink dots d1 and the second ink dots d2 correspond to first and second image ink dots and a background ink dot, respectively.

In the present embodiment, the third control unit 43 controls the driving of the first control unit 41 and the second control unit 42. First, as shown in FIGS. 5B-5E, an image band is printed in a first step (S20). The third control unit 43 sends an instruction to the first control unit 41 to carry out the first step. In the first step, the first control unit 41 controls the drive of the feed motor 16, the carriage motor 28, and the actuator 32.
Specifically, the first control unit 41 carries out the first printing scan (S21) shown in FIG. 5B. That is, the first control unit 41 rotationally drives the carriage motor 28 in the forward direction, and moves the discharge head 30 in the right direction Y1 in the main scanning direction Y. At this time, the first control unit 41 controls the driving speed of the carriage motor 28 and the driving of the actuator 32 according to the print data, and for the image from the first nozzle row 311 to the recording medium 5 at a predetermined timing based on the print data. By discharging the ink, the first ink dot d1 is formed. Thereby, the first printing scan is performed for the first time. The interval between the first ink dots d1 is "n". At this time, the first control unit 41 does not eject the image ink from the second nozzle row 312. In this way, it is possible to land the image ink on the area of 1⁄4 of the square “n” square.

  Subsequently, as shown in FIG. 5C, the first control unit 41 performs a second printing scan (S22). That is, the first control unit 41 rotationally drives the carriage motor 28 in the reverse direction to move the discharge head 30 in the left Y 2 of the main scanning direction Y. At this time, the first control unit 41 performs the second printing scan (S22) without transporting the recording medium 5 in the sub scanning direction X. The first control unit 41 controls the driving speed of the carriage motor 28 and the driving of the actuator 32 according to the print data, and discharges the image ink from the first nozzle row 311 to the recording medium 5 at a predetermined timing based on the print data. By doing this, the first ink dot d1 is formed. A first ink dot d1 is newly formed so as to land between the first ink dots d1 ejected earlier. Thus, the first second print scan is performed. The interval between the first ink dots d1 at this time is also “n”. By this, it is possible to cause the image ink to land on the area of 1⁄4 of the square of the length “n”. As a result, it is possible to deposit the image ink on the adjacent 2/4 area of square cells having a length "n" square. In other words, a plurality of line-shaped images having a width of n / 2 along the main scanning direction Y (hereinafter sometimes referred to as image lines) are printed at a pitch of n / 2 along the sub-scanning direction X be able to.

  Thereafter, the first control unit 41 carries out the first minute conveyance shown in FIGS. 5C to 5D (S23). That is, the first control unit 41 rotationally drives the feed motor 16 in the forward direction, and conveys the recording medium 5 by a minute distance “n / 2” in the first direction X1 in the sub scanning direction X. The distance “n / 2” is the dimension in the sub-scanning direction X of the square. In the present embodiment, this distance "n / 2" corresponds to the first transport interval. Thereby, the nozzle 6 position is arranged between the above-mentioned image lines in the sub scanning direction X. Although described later, the first conveyance interval is not limited to the dimension in the sub-scanning direction X of the grid.

  Next, as shown in FIG. 5D, the first control unit 41 performs the first printing scan again (S24). That is, the first control unit 41 rotationally drives the carriage motor 28 in the forward direction, and moves the discharge head 30 in the right direction Y1 in the main scanning direction Y. At this time, the first control unit 41 controls the driving speed of the carriage motor 28 and the driving of the actuator 32 according to the print data, and for the image from the first nozzle row 311 to the recording medium 5 at a predetermined timing based on the print data. The ink is ejected to form a first ink dot d1. Thereby, the second printing scan is performed. At this time, the first control unit 41 does not eject the image ink from the second nozzle array 312. By this, it is possible to cause the image ink to land on the area of 1⁄4 of the square of the length “n”. As a result, it is possible to deposit the imaging ink in the area of 3/4 of square "length" square.

  Subsequently, as shown in FIG. 5E, the first control unit 41 executes the second printing scan again (S25). At this time, the first control unit 41 performs the second printing scan (S25) without transporting the recording medium 5 in the sub scanning direction X. The first control unit 41 rotationally drives the carriage motor 28 in the reverse direction to move the discharge head 30 in the left Y 2 of the main scanning direction Y. The first control unit 41 controls the driving speed of the carriage motor 28 and the driving of the actuator 32 according to the print data, and discharges the image ink from the first nozzle row 311 to the recording medium 5 at a predetermined timing based on the print data. To form a first ink dot d1. As a result, the second printing scan can be performed for the second printing scan, and the image ink can be discharged to the entire area (4/4) of the square “n” square. By this, it is possible to fill the space between the above image lines, and as a result, a band-like image band having a width (dimension in the sub scanning direction X) substantially matching the length "m" of the first nozzle row 311 is printed. can do.

When the printing (S20) of the image band in the first step of the first control unit 41 described above is finished, the third control unit 43 performs the second minute conveyance (S31). The third control unit 43 causes the first control unit 41 to perform the first process, and then performs the second minute conveyance. After that, printing (S41) of the base band in the second process of the second control unit 42 is performed.
In the second minute conveyance, the third control unit 43 rotationally drives the feed motor 16 in the forward direction, and conveys the recording medium 5 in the first direction X1 of the sub scanning direction X. Here, as shown in FIGS. 5E to 5F, the third control unit 43 transports the recording medium 5 by a minute distance “n / 2” calculated based on the printing resolution in the sub scanning direction X. In the present example, the distance “n / 2” is the dimension in the sub-scanning direction X of the grid. This distance "n / 2" corresponds to the second transport interval. However, the second transport interval does not have to exactly match the dimension in the sub-scanning direction X of the square. For example, in order to preferably carry out base band printing described later, for example, it is changed in the range of 0.5 times to 1.5 times or less of the dimension "n / 2" in the sub scanning direction X of the square It is also good. Thereby, the position of the second nozzle row 312 can be disposed at a position suitable for background printing with a feed width as small as possible.

Next, the base band is printed in the second step (S41). The third control unit 43 instructs the second control unit 42 to carry out the second process.
In the second step, the second control unit 42 controls the drive of the carriage motor 28, the actuator 34, and the feed motor 16 as needed. Specifically, the second control unit 42 rotates the carriage motor 28 in the forward direction to move the discharge head 30 in the right direction Y1 in the main scanning direction Y. At this time, as shown in FIG. 5F, the second control unit 42 controls the drive speed of the carriage motor 28 and the drive of the actuator 34 according to the print data, and from the second nozzle row 312 at a predetermined timing based on the print data. The second ink dot d2 is ejected onto the recording medium 5. At this time, the size of the second ink dot d2 is larger than the size of the first ink dot d1 as described above. In the present example, the second ink dot d2 is formed of, for example, droplets approximately four times the amount of the first ink dot d1. That is, it is possible to cause the base ink to land on the entire area (4/4) of the square of the length "n" by one second ink dot d2. As a result, it is possible to print a band-like base band having a width (dimension in the sub scanning direction X) substantially matching the length “m” of the second nozzle row 312 by one printing scan. At this time, the number of second ink dots d2 discharged while moving the discharge head 30 rightward Y1 can be reduced. For example, in the present example, the number of discharges of the second ink dot d2 can be reduced to 1/4. As a result, the moving speed (i.e., the scanning speed) of the ejection head 30 in the main scanning direction Y in the second process can be made faster than the scanning speed in the first process. For example, even if the scanning speed in the main scanning direction Y of the discharge head 30 in the first step) is set to the maximum speed in consideration of the discharge capacity (maximum discharge frequency) and resolution of the discharge head 30, The scanning speed of the discharge head 30 can be increased to twice the scanning speed in the first step. When this setting is made, one printing scan can be completed in a shorter time, and the printing time of the background band can be shortened.

  In the above configuration, the first minute conveyance (S23) and the second minute conveyance (S31), which are the conveyance process of the recording medium 5, are both conveyance in the first direction X1 of the sub scanning direction X. The scan of the discharge head 30 in the main scanning direction Y is four printing scans (that is, two reciprocations) for printing an image band and one printing scan (for example, 0.5) for printing a base band. Reciprocation). As described above, according to the technology disclosed herein, the image band and the base band are printed in separate steps while the conveyance direction is limited to one direction. At this time, while the printing resolution of the image band is set high, it is possible to adjust the discharge mode of the ink in the printing of the base band and reduce the number of ink droplets to be discharged. In other words, it is possible to discharge ink by thinning as compared with printing of the image band. As a result, the ground band can be printed with fewer printing scans and with a shorter scan time than the image band. As a result, strip-like overlapping printing of a width (dimension in the sub scanning direction X) substantially matching the length “m” of the first and second nozzle rows 311 and 312 is shortened by conveyance in only one direction. It can be realized in time.

  Further, according to the above configuration, the first control unit 41 forms the first ink dot next to the first ink dot printed in the first printing scan in the main scanning direction Y during the second printing scan. It was configured. As a result, high-definition, high-quality printing without gaps can be implemented.

  Furthermore, according to the above configuration, the first control unit 41 performs the first conveyance of the recording medium 5 with respect to the ejection head 30 in the first direction X1 in the sub-scanning direction X after the first printing scan and the first printing scan. During the second and first printing scans, the second ink is conveyed by the interval, and the second ink jet is printed next to the second direction X2 side of the first ink dots printed in the first and second printing scans. The first and second printing scans are configured to form the first ink dots. This also makes it possible to carry out high quality printing without gaps or the like. On the other hand, after the first printing scan, the first control unit 41 transports the recording medium 5 to the discharge head 30 in the first direction X1 in the sub scanning direction X by the first transport interval, and performs the second printing At the time of scanning, the first ink dot may be formed adjacent to the second direction X2 side in the sub scanning direction X of the first ink dot printed in the first printing scan. Thereby, the image layer can also be printed in a short time.

  Further, according to the above configuration, the first conveyance interval is smaller than the nozzle pitch n, and the print resolution is made higher than the resolution (nozzle resolution) of the ejection head 30 to perform overlapping printing of images. For example, by setting the first conveyance interval to 1/2 of the nozzle pitch, it is possible to double the printing resolution in the sub-scanning direction than the resolution of the ejection head to print a high definition image layer. Therefore, the four printing scans for the image band realize printing of a high definition image. On the other hand, printing of the underlayer can be performed faster with fewer printing scans, reducing the substantial printing resolution. This enables printing in a state in which the resolutions of the image band and the base band are substantially different while the transport direction of the recording medium 5 is the first direction X1. This makes it possible to perform overlapping printing in a shorter time as a whole while performing high-resolution image printing.

  Furthermore, in step S51, the control unit 40 determines, based on the print data, whether the overlapping printing has ended. If it is determined that the overlapping printing has ended (in the case of “Y” in S51), the control unit 40 ends the printing, and causes the ejection head 30 to stand by at the home position HP. On the other hand, when it is determined that the overlapping printing has not ended (in the case of “N” in S51), the fourth control unit 44 repeatedly and repeatedly executes the above-described strip overlapping printing in the sub scanning direction X Thus, the first control unit 41, the second control unit 42, and the third control unit 43 are controlled. Specifically, when the fourth control unit 44 determines that the overlapping printing is not completed, the fourth control unit 44 performs the third conveyance illustrated in FIGS. 5F to 5G (S61). The fourth control unit 44 rotationally drives the feed motor 16 in the forward direction, and conveys the recording medium 5 by a distance “m−2 × (n / 2)” in the first direction X1 in the sub scanning direction X. . The distance “m−2 × (n / 2)” is the distance “2 × (n / 2) at which the recording medium 5 is transported in the first direction X1 in the printing of the overlapping band from the length“ m ”of the nozzle row It is the dimension which subtracted "." In the present example, this distance “m−2 × (n / 2)” corresponds to the third transport interval. When such third conveyance is performed, the ejection head 30 and the next print area have the positional relationship shown in FIG. 5A. Therefore, the sub scanning is continuously performed by repeatedly performing the first step (S20), the second minute conveyance (S31) and the second step (S41) shown in FIGS. 5B to 5G via the third conveyance (S61). Overlap printing of predetermined dimensions can be performed along the direction X.

  According to the above configuration, it is possible to repeatedly execute overlapping printing of a width corresponding to the length of the nozzle array while keeping the conveyance direction of the recording medium as the first direction. In this way, it is possible to perform overprinting of the image of the desired size.

  In the above embodiment, the image band is printed by four printing scans, whereas the base band is printed by one printing scan. However, the number of printing scans of the background band is not limited to this example. For example, while the image band is printed by four printing scans, the number of times of printing scanning of the base band may be an arbitrary number (1 to 4 in this example) equal to or less than that of the image band. Even when the printing scan of the base band is four times the same as the image band, the second ink dot d2 ejected in one printing scan is once larger than the size of the first ink dot d1. The number of dots in the printing scan of Further, for example, by reducing the number of printing scans of the base band to three or less, the time required for printing the base band can be reliably reduced.

  When the printing scan of the base band is performed a plurality of times, it may be performed without moving the discharge head 30 in the first direction X1, or after the discharge head 30 is moved in the first direction X1. May be For example, when the printing scan of the base band is performed twice, printing may be performed at the same position in the sub-scanning direction X without moving the ejection head 30 in the first direction X1. In this case, in the second printing scan, the discharge timing of the second ink dots d2 in the second printing scan may be adjusted so that the ink lands between the second ink dots d2 discharged in the first printing scan. When the printing scan of the base band is performed twice, the discharge head 30 is moved in the first direction X1 by, for example, the same n / 2 pitch as the first conveyance interval, and at different positions in the sub scanning direction X You may print it. In this case, also in the second step (S41) of FIG. 4, for example, the same printing scanning as that of the first step (S20) is repeated. At this time, it is preferable to adjust the discharge timing of the base ink in the second printing scan so that the ink lands between the second ink dots d2 discharged in the first printing scan. For example, the base ink may be discharged so that the second ink dots d2 are formed in a checkered pattern. As a result, it is possible to preferably prevent the occurrence of printing omission in printing of the base band.

  In the above embodiment, an example has been described in which the printing resolution of the image band is twice the nozzle resolution (resolution of the ejection head 30) in both the main scanning direction Y and the sub scanning direction X. However, the printing resolution of the image band is not limited to doubling the nozzle resolution. For example, the printing resolutions of the image band and the base band need not be the same in the main scanning direction Y and the sub scanning direction X. Further, for example, in each of the image band and the base band, the print resolutions in the main scanning direction Y and the sub scanning direction X can be set independently and arbitrarily.

For example, an integral multiple (e.g. alpha times. Where alpha is an integer of 2 or more .α preferably 2, 3 or 4.) of the printing resolution nozzle resolution and a print scan of the image band alpha ² times, first conveyor The interval and the second transport interval may be printed as n / α. In this case, in the flow chart of FIG. 4, the first step (S20, S42) is performed, for example, after the second printing scan S22, S25, S44, S47 and before the conveyance of the recording medium 5 is performed. The second printing scan can be repeated until it reaches a predetermined number of times (here, α-1 times). As a result, the second printing scan can be performed α times without carrying out conveyance, and the printing resolution in the main scanning direction Y can easily be made α times the nozzle resolution. In addition, the number of executions of the first printing scan S21, S24 in the first step (S20, S42) is α in a series of processes from the minute first conveyance S23, S45 to the end of the predetermined number of second printing scans. It can be done repeatedly. Thus, the printing resolution in the sub-scanning direction X can be set to α times the nozzle resolution. In this way, high-definition images can be printed according to the printing resolution.

Also, the printing resolution may be different between the main scanning direction Y and the sub scanning direction X. For example, the printing resolution in the main scanning direction Y of the image band may be three times the nozzle resolution, and the printing resolution in the sub scanning direction X may be twice the nozzle resolution. In this case, in the flow chart of FIG. 4, for example, the second printing scan may be performed again after the second printing scan S22, S44.
Furthermore, for example, even in the case where the printing resolution in the main scanning direction Y of the image band is twice the nozzle resolution, printing in the main scanning direction Y may be performed by one printing scan. In this case, for example, the scanning speed of the discharge head 30 in the main scanning direction Y can be delayed. At this time, in the flowchart of FIG. 4, the first print scan S21 and S43 are performed, and the second print scan S22 and S44 are not performed. Further, the second print scan S25, S47 may be performed without performing the first print scan S24, S46.

  The number of printing scans of the background band in the second step (S41, S32) and the first transport interval may be appropriately set so as to realize an arbitrary printing resolution as in the case of the printing of the image band described above. it can. In the conveyance 5 of the recording medium in the second step (S41, S32), the second control unit 42 rotationally drives the feed motor 16 in the forward direction, and for example, a minute distance in the first direction X1 of the sub scanning direction X This can be implemented by transporting the recording medium 5 by “n / α”. In addition, the printing of the base band should be appropriately set within a range not exceeding the number of printing scans of the image band and not less than the first conveyance interval, taking into consideration, for example, the sizes of the base ink dots and the image ink dots. Can. Thereby, the above-described overprinting can be performed at an arbitrary printing resolution in a short time.

  In the above embodiment, the first conveyance interval is set to a value smaller than the nozzle pitch n. However, the first conveyance interval is not limited to being smaller than the nozzle pitch n. For example, when the printing resolution is an integral multiple (for example, a multiple of the nozzle resolution) of the nozzle resolution, the first conveyance interval is “n / α + β × n” (where β is an integer of 0 or more. Β is preferably an integer of 0 to 10) ) May be printed. As a result, even if, for example, the nozzles 6 of the discharge head 30 are clogged, the printing position by the nozzles 6 can be thinned. As a result, it is possible to suppress the appearance of non-colored line-like (typically, white streaks) printing defects.

  In addition, as shown to FIG. 5A-5G, the dimension (Hereinafter, it may only be called "width") of the subscanning direction X of the overlapping band printed by the 1st process-the 3rd process of the said embodiment has. The length is smaller than the length “m” in the sub-scanning direction X of the first nozzle row 311 and the second nozzle row 312. Specifically, the width of printing of the overlapping band in the above embodiment is approximately "m". And the 3rd conveyance interval was "m-2 x (n / 2)." However, the width of the overlapping band and the third transport interval are not limited to “m” and “m−2 × (n / 2)”, respectively. The printing width of the overlapping band is determined based on the length "m" of the nozzle rows 311, 312 and the above-described first transport interval. In addition, the third conveyance interval can be set at a position suitable for starting strip-like overlap printing based on the above-described first conveyance interval.

  In addition, about a 3rd conveyance space | interval, when it is desired to further overlap and print overlapping bands, it is also possible to make the conveyance distance intentionally shorter. For example, the third transport interval can be an arbitrary distance that is larger than half the length of the second nozzle row 312 and smaller than the length of the second nozzle row 312. As a result, it is possible to suppress the appearance of a colorless line-like (typically, white stripe) print defect due to a gap between overlapping bands while efficiently performing overlapping printing.

  In the above embodiment, the print data for the base layer is created by reducing the print position (the number of dots) while maintaining the print resolution the same as the image layer. From this, by using the technology disclosed herein, it is possible to easily carry out the above-described overprinting by creating data with a small number of printing dots while maintaining the resolution for the base layer. More specifically, printing data in a form in which printing dots are thinned out in advance, and printing data in which larger droplets are ejected at the dot positions, enables printing of the base layer in a short time and efficiently. Can be implemented. Alternatively, the second control device 42 is configured to perform printing by automatically reducing the number of print dots based on print data for which the number of print dots is not reduced for the base layer (that is, high resolution). May be In this case, for example, the image layer may print at a resolution higher than the nozzle resolution based on the print data, and the base layer may print at the same resolution as the nozzle resolution.

  In the above embodiment, the transport mechanism transports the recording medium 5 in the first direction X1 in the sub scanning direction X, thereby moving the recording medium 5 in the first direction X1 relative to the ejection head 30. It was done. However, the operation of the transport mechanism is not limited to such an aspect. For example, in the printer 1, the transport mechanism does not move the position of the recording medium 5 but moves the ejection head 30 in the sub scanning direction X by adding the ejection head 30 to the main scanning direction Y. The relative position in the sub scanning direction X may be changed. Alternatively, the transport mechanism may move both the recording medium 5 and the discharge head 30 in the sub scanning direction X to change the relative position of the recording medium 5 and the discharge head 30 in the sub scanning direction X. Thereby, the overprinting disclosed herein can be implemented even in the printer 1 provided with the transport mechanism of various configurations.

Second Embodiment
In the first embodiment described above, the case where the image layer is printed downward and the underlayer is printed upward has been described. Of course, the technology disclosed herein is not limited to the above aspect. For example, in step S1 of FIG. 4, when it is determined that “printing the underlayer is on the bottom (Y)” based on the print data, the underlayer is printed on the bottom and the image layer is printed on the top. Overprinting is performed. In this case, as shown in the right half of the flow chart of FIG. 4 and FIGS. 6A to 6G, first, the base band is printed in the second step, and then the printing of the image band in the first step is performed.

  Specifically, first, the second control unit 42 implements the second step as shown in FIG. 6B (S26). The second control unit 42 controls the drive speed of the carriage motor 28 and the drive of the actuator 34 according to the print data, and discharges the base ink from the second nozzle row 312 to the recording medium 5 at a predetermined timing based on the print data. As a result, the second ink dot d2 is formed. At this time, the discharge head 30 discharges the base ink while moving to the right Y1. The size of the second ink dot d2 is larger than the size of the first ink dot d1. Thereby, the base band can be printed. The details of the control of the second control unit 42 are the same as those of the first embodiment shown in FIG. 5F, and thus the overlapping description will be omitted (the same applies hereinafter).

  Next, as shown in FIGS. 6B to 6C, the second micro transfer is performed (S32). Specifically, the third control unit 43 rotationally drives the feed motor 16 in the forward direction, and the recording medium 5 in the first direction X1 in the sub-scanning direction X by the second transport interval "n / 2". Transport Depending on the discharge mode of the ink from the discharge head 30, although this process is not essential, it is preferable to include it in order to perform continuous printing smoothly.

  And the 1st control part 41 implements a 1st process, as shown in Drawings 6C-6F (S42). Specifically, first, the first control unit 41 controls the drive speed of the carriage motor 28 and the drive of the actuator 31 according to the print data, and as shown in FIG. A print scan (S43) is performed. Then, as shown in FIG. 6D, the first control unit 41 performs the first second print scan (S44) toward the right direction Y1. Thereafter, as shown in FIGS. 6D to 6E, the third control unit 43 implements the first minute conveyance (S45). Specifically, the third control unit 43 rotationally drives the feed motor 16 in the forward direction, and conveys the recording medium 5 in the first direction X1 of the sub-scanning direction X. Thereafter, the first and second printing scans are performed again. Specifically, the first control unit 41 controls the drive speed of the carriage motor 28 and the drive of the actuator 31 according to the print data, and as shown in FIG. 6E, the first printing scan for the second time toward the left Y2 (S46) is performed. Subsequently, as shown in FIG. 6F, the first control unit 41 performs the second printing scan (S47) for the second time toward the right direction Y1. Thereby, printing of the image band in the first step can be performed. Finally, it is possible to print a lap band.

  Then, in step S52, the control unit 40 determines, based on the print data, whether or not the overlapping printing has ended. If it is determined that the overlapping printing has ended (in the case of “Y” in S52), the control unit 40 ends the printing, and causes the ejection head 30 to stand by at the home position HP. On the other hand, when it is determined that the overprinting has not ended (in the case of “N” in S52), printing is continuously performed based on the print data. At this time, the fourth control unit 44 implements the third transport shown in FIGS. 6F to 6G (S62). That is, the fourth control unit 44 rotationally drives the feed motor 16 in the forward direction, and moves the recording medium 5 by a distance “m−2 × (n / 2)” in the first direction X1 in the sub scanning direction X. Transport Then, the fourth control unit 44 causes the third control unit 43 to repeat the second step (S26), the second minute conveyance (S32), and the first step (S42) shown in FIGS. An instruction to repeat execution is sent via the transport (S62). Based on this, the third control unit 43 first causes the second control unit 42 to carry out the second step (S26) shown in FIG. 6B, thereby printing the base band. Next, as shown in FIGS. 6B to 6C, the third control unit 43 carries out the second micro-conveyance for conveying the recording medium 5 by the second conveyance interval "n / 2" (S32). Thereafter, the third control unit 43 causes the first control unit 41 to carry out the first process shown in FIGS. 6C to 6F (S42). Specifically, the first control unit 41 first executes the first printing scan (S43) for the first time toward the left Y2 shown in FIG. 6C, and then goes to the right Y1 shown in FIG. 6D. The first second print scan (S44) is performed. This prints the image line. Thereafter, the first control unit 41 carries out the first minute conveyance (S45) shown in FIGS. 6D to 6E, and conveys the recording medium 5 in the first direction X1 by the first conveyance interval "n / 2". Then, again, the first control unit 41 carries out the first printing scan (S46) for the second time towards the left Y2 shown in FIG. 6E, and then for the second time towards the right Y1 shown in FIG. 6F. The second printing scan (S47) is performed. This allows printing of the image band in the first step. In this way, over printing can be completed by finishing all printing based on the print data (S52).

  In the above-described overprinting, the time during which the base band and the image band are performed is relatively short. In particular, in the technique disclosed herein, the printing scan of the background band is performed in a relatively short time. Thus, inter alia, the time to print the next print image band can be particularly short if, as described above, the base band is printed first and the printing of the base band is finished in one printing scan. Therefore, for example, the discharge head 30 is provided with a heater 36 (see FIG. 1) on the lower surface so that the base ink discharged in the printing of the base band and the image ink discharged in the printing of the image band do not mix. It may be The heater 36 is connected to the controller 40. The heater 36 is controlled by the controller 40. The configuration of the heater 36 and the heating mechanism are not particularly limited. The heater 36 is, for example, various heaters capable of promoting the drying of the ink ejected on the recording medium 5 in a noncontact manner. As such a heater 36, heating means, such as an infrared heater, a heating wire heater, a laser heater, etc. are mentioned, for example. The heater 36 in the present embodiment is an infrared heater. As a result, it is possible to prevent the base ink and the image ink from being mixed, and to perform the above-described overlapping printing in a short time. Needless to say, heating by the heater 36 can also be employed in the first embodiment.

  In the above embodiment, the ejection head 30 is moved in the main scanning direction Y, and the recording medium 5 is moved in the sub scanning direction X. However, the movement of the ejection head 30 and the recording medium 5 corresponds to this example. It is not limited. It is sufficient that the ejection head 30 and the recording medium 5 can move relative to each other. Moreover, although the 1st nozzle row 311 and the 2nd nozzle row 312 were provided in the same discharge head 30, the art indicated here is not limited to this example. For example, the printer 1 may include a plurality of ejection heads 30, and the first nozzle array 311 and the second nozzle array 312 may be provided in different ejection heads 30.

  In the above embodiment, the process color ink is used as the image ink, and the white ink is used as the base ink. The base ink is an ink supplied to the entire surface of the area where the image ink is printed. In other words, it is a solid coating ink. Here, as described above, the base layer printed by the base ink may be printed on or below the image layer. That is, the base ink may be an ink for pre-coating (pre-printing) or an ink for post-coating (post-printing). From this point of view, the inkjet printer and printing method disclosed herein may target, for example, an ink containing a coloring material such as white ink as the “base ink”, or do not include a coloring material such as clear ink. A non-colored ink may be targeted. That is, the present invention can be applied to overprinting with any ink. When a clear ink is used as (or in place of the "base ink") ink, the image layer printed with the image ink is given a unique texture such as gloss, or the image layer is protected. It can provide a protective function.

DESCRIPTION OF SYMBOLS 1 Printer 6 nozzle 30 Discharge head 311 1st nozzle row 312 2nd nozzle row 40 control part 41 1st control part 42 2nd control part 43 3rd control part 44 4th control part

Claims (12)

A first nozzle row in which a plurality of first nozzles for ejecting image ink are arranged in the sub scanning direction, and a second nozzle in which a plurality of second nozzles for ejecting background ink are arranged in the sub scanning direction A discharge head having a row, wherein the first nozzle row and the second nozzle row are aligned in a main scanning direction intersecting the sub scanning direction;
A scanning mechanism that scans the discharge head in the main scanning direction;
A transport mechanism that transports the recording medium relative to the ejection head in the sub-scanning direction by moving at least one of the recording medium and the ejection head;
A control device for driving the discharge head, the scanning mechanism, and the transport mechanism;
Equipped with
The nozzle pitch in the sub-scanning direction of the first nozzle and the nozzle pitch in the sub-scanning direction of the second nozzle are equal,
The controller is
At least a first amount of the image ink is ejected from the first nozzle while moving the ejection head in the main scanning direction, and a first image ink dot is formed in a predetermined area of the recording medium. The first amount of the image ink is ejected from the first nozzle while moving the ejection head in the main scanning direction, and the first image is for the first image within the predetermined area of the recording medium. A first control unit for performing a second printing scan for forming a second image ink dot next to the ink dot;
A second amount of the base ink, which is larger than the first amount, is discharged from the second nozzle while moving the discharge head in the main scanning direction, and A second control unit that performs base printing scanning for forming one base ink dot larger than the image ink dot;
After causing the first control unit to execute the first and second printing scans and then causing the second control unit to perform the background printing scan, the recording medium is compared to the discharge head relative to the discharge head. A third control unit for causing the first control unit to execute the first and second printing scans and then causing the second control unit to execute the ground printing scan; After making the second control unit execute the background printing scan and then make the first control unit execute the first and second printing scans, the sub-scanning of the recording medium relative to the ejection head is performed A third control unit for causing the first control unit to execute the first and second printing scans after the sheet is conveyed in one of the directions and causes the second control unit to perform the background printing scan again;
Contains an inkjet printer.   The first control unit is configured to form the ink dots for the second image next to the ink dots for the first image in the main scanning direction at the time of the second printing scan. The inkjet printer according to 1.   The first control unit transports the recording medium relative to the ejection head in the one direction in the sub scanning direction relative to the discharge head after the first printing scan by a first transport interval, and the second printing scan is performed. 2. The inkjet printer according to claim 1, wherein the second image ink dots are formed adjacent to the first image ink dots in the sub scanning direction. 3.   The control unit causes the third control unit to execute the first and second printing scans and the base printing scan, and then, relative to the discharge head, the recording medium in the sub-scanning direction relative to the discharge head. And a fourth control unit for causing the third control unit to execute the first and second printing scans and the base printing scan again in the second transport interval corresponding to the length of the second nozzle array in the second direction. The ink jet printer according to any one of claims 1 to 3.   5. The ink jet printer according to claim 4, wherein the second conveyance interval is larger than half of the length of the first and second nozzle rows and smaller than the length of the first and second nozzle rows.   The ink jet printer according to any one of claims 1 to 3, wherein the first conveyance interval is smaller than the nozzle pitch.   The ink jet printer according to claim 6, wherein the first conveyance interval is 1/2 of the nozzle pitch.   The second control unit transports the recording medium relative to the ejection head in the one direction in the sub scanning direction relative to the discharge head after the base printing scan by a third transport interval, and executes the base printing scan again. The ink jet printer according to any one of claims 1 to 7, which is configured as follows.   The second control unit makes the scanning speed in the background printing scan faster than the scanning speed in the first and second printing scans by the first control section. An ink jet printer according to claim 1.   The third control unit is the outermost end of the direction opposite to the one direction in the sub-scanning direction of the nozzle row in the printing performed first of the printing by the first control unit and the second control unit. In the printing to be performed later without using a nozzle of a part, control the discharge of the discharge head by the first control part and the second control part so as not to use the nozzle at the end of the one direction The ink jet printer according to any one of claims 1 to 9.   The ink jet printer according to any one of claims 1 to 10, wherein the discharge head comprises a heater on the lower surface. A first nozzle row in which a plurality of first nozzles for ejecting image ink are arranged in the sub scanning direction, and a second nozzle in which a plurality of second nozzles for ejecting background ink are arranged in the sub scanning direction A discharge head having a row, wherein the first nozzle row and the second nozzle row are arranged in the main scanning direction; and a scanning mechanism for scanning the discharge head in the main scanning direction intersecting the sub scanning direction; A transport mechanism for transporting the recording medium relative to the ejection head in the sub-scanning direction by moving at least one of the recording medium and the ejection head, the ejection head, the scanning mechanism, and the conveyance mechanism; An ink jet printer including a control device for driving, and a nozzle pitch of the first nozzle in the sub scanning direction and a nozzle pitch of the second nozzle in the sub scanning direction being equal A print,
At least a first amount of the image ink is ejected from the first nozzle while moving the ejection head in the main scanning direction, and a first image ink dot is formed in a predetermined area of the recording medium. The first amount of the image ink is ejected from the first nozzle while moving the ejection head in the main scanning direction, and the first image is for the first image within the predetermined area of the recording medium. A second step of performing a second printing scan for forming a second image ink dot next to the ink dot;
A second amount of the base ink, which is larger than the first amount, is discharged from the second nozzle while moving the discharge head in the main scanning direction, and A second step of performing base printing scan to form one base ink dot larger than the image ink dot;
After performing the first step of performing the first and second printing scans and then performing the second step of performing the background printing scan, the sub-scanning of the recording medium relative to the discharge head is performed. A third step of carrying out the first step of carrying the first and second printing scans after transporting in one direction of direction and then carrying out the second step of carrying out the first printing scan, or the base printing After performing the first step of performing the first and second printing scans after performing the second step of performing the scan, one direction of the sub-scanning direction relative to the recording medium relative to the discharge head And the third step of performing the first step of performing the first and second printing scans after performing the second step of performing the base printing scan again.
Inkjet printers, including:

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