JP2016175215A - Droplet discharge method and droplet discharge device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a droplet discharge method that reduces banding (unevenness) due to an influence of idle time during which a nozzle array (a head) is not in use.SOLUTION: Provided is a droplet discharge method that forms an image composed of a raster completed by n times of droplet discharge operations, by alternately repeating: a conveyance operation for moving a paper sheet in a conveyance direction; and a droplet discharge operation for discharging droplets on the paper sheet, while scanning and moving a first head having a plurality of nozzles arrayed in the conveyance direction to discharge droplets, and a second head aligned on a downstream side in the conveyance direction of the first head, in a scanning direction which intersects the conveyance direction. A number of times m (idle time) of continuous droplet discharge operations not using the second head is 0.5 n or less, for droplet discharge operations subsequent to a droplet discharge operation having used a first nozzle array and a second nozzle array at one droplet discharge operation.SELECTED DRAWING: Figure 13

Description

  The present invention relates to a droplet discharge method and a droplet discharge device.

  As an example of a droplet discharge device, an ink jet printer that prints (records) an image by discharging droplets (ink droplets) onto various print media such as paper and film is known. An ink jet printer, for example, performs a dot forming operation for ejecting ink droplets from each nozzle while moving (scanning) a head in which a plurality of nozzles are formed in the scanning direction with respect to the printing medium, and the printing medium in the scanning direction. The conveyance operation of moving (conveying) in the intersecting conveyance direction is alternately repeated, and dots (dot rows) arranged in the scanning direction are arranged in the conveyance direction to form an image on the print medium.

  In such an ink jet printer, a method of increasing the number of nozzles has been taken as one method for further increasing the printing speed. Specifically, it is a method of increasing the number of dots ejected in one scan and increasing the printing speed by increasing the number of nozzles per head or arranging a plurality of heads. Image formation of a region (band) having a width corresponding to the length of a row composed of a plurality of nozzles (a plurality of heads) is completed by one scan, and then the print medium is moved in the transport direction according to the width Carrying is performed, and the band is formed in the carrying direction so that the end of the formed band is in contact with the end of the band formed by the next scanning. By repeating this, an image is formed. This method makes it possible to perform higher-speed printing. However, this method sometimes causes a striped pattern (banding) along the band boundary. This is due to the influence of variations in the feeding accuracy in the transport direction and differences in ink ejection characteristics (variations in ink droplet landing positions and variations in the amount of ink droplets) at the nozzle row switching portion.

  Patent Document 1 proposes a method of dispersing variations in discharge characteristics and accuracy of discharge ports as a method for suppressing the deterioration of image quality due to banding. Specifically, as the simplest example, the lower end region of the band formed with the scanning of the head and the upper end region of the band formed with the next scanning of the head are overlapped to form first. In this method, a part of dots in the lower end region of the band and a part of dots in the upper end region of the band to be formed next overlap each other. Patent Document 2 proposes a method of forming a high-quality image using a plurality of nozzle arrays.

JP-A-6-47925 Japanese Patent Laid-Open No. 10-323978

  However, in order to obtain a higher-definition image, when the amount of ejected ink droplets is set to a very small amount and the number of dots for forming an image is increased, banding is caused by the difference in the timing of ejecting the ink droplets. There was a problem that it might occur. A plurality of adjacent dots that form an image have a different degree of drying depending on the elapsed time after the ink droplets have landed, and new ink droplets that land on adjacent positions are the surrounding ink droplets that have landed before Depending on the degree of drying, the degree of bleeding and, as a result, a difference in surface shape occurs. Therefore, in the formation of an image of a certain area, when the distribution of the time intervals at which a plurality of ink droplets for forming an image land is significantly different from that of other adjacent areas, the degree of ink droplet bleeding, A difference in surface shape occurs, resulting in visual unevenness (for example, uneven brightness) in the region. In particular, in the upper end area and lower end area of the print medium, due to the necessity of controlling the switching of the heads used, there are areas where the distribution of ink droplet landing times is different, resulting in banding. was there.

  SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following application examples or forms.

  Application Example 1 A droplet discharge method according to this application example includes a transfer operation for moving a print medium in a transfer direction, a first nozzle row having a plurality of nozzles that discharge droplets arranged in the transfer direction, The second nozzle row having a plurality of nozzles that discharge droplets arranged in the transport direction arranged upstream of the transport direction of the first nozzle row is scanned and moved in a scanning direction intersecting the transport direction. A droplet discharge method for forming an image composed of image units completed in n times of the droplet discharge operation by repeating a droplet discharge operation for discharging a droplet on the print medium a plurality of times. After the droplet discharge operation is executed once using the first nozzle row and the second nozzle row, the number of times m of continuously executing the droplet discharge operation without using the second nozzle row is It is characterized by being less than 0.5n.

  In the droplet discharge method of this application example, the droplet is applied to the print medium while the first nozzle row and the second nozzle row are scanned and moved in the scanning direction that intersects the conveyance direction with the transport operation that moves the print medium in the transport direction. An image is formed by alternately repeating the droplet discharge operation for discharging the liquid. The first nozzle row and the second nozzle row have a plurality of nozzles arranged in the carrying direction, and the second nozzle row is arranged on the downstream side in the carrying direction of the first nozzle row. Further, the droplet discharge method of this application example forms an image composed of image units that are completed by n droplet discharge operations. Note that n is a natural number.

  According to this application example, in the droplet discharge operation after the droplet discharge operation using the first nozzle row and the second nozzle row in one droplet discharge operation, the droplet discharge operation that does not use the second nozzle row Is less than 0.5n times. In other words, the idle time during which the second nozzle row is not continuously used does not become a long time of 0.5 n times or more for the droplet discharge operation. As a result, the degree of drying of the ejected droplets during the idle time is reduced, so that uneven printing caused by the difference in the degree of drying can be suppressed.

  Application Example 2 In the droplet discharge method according to the application example, when the average value of the number m is m0, the maximum value is m1, and the minimum value is m2, (m1−m2) / m0 <1. It is characterized by that.

  According to this application example, when the average value of the number m of droplet discharge operations in which the second nozzle row is not continuously used is m0, the maximum value is m1, and the minimum value is m2, (m1-m2) / m0 <1. That is, the fluctuation is suppressed so that the difference in the number of droplet discharge operations in which the second nozzle row is not continuously used does not exceed the average value m0 of the number m. As a result, the difference (variation) in the idle time when the second nozzle row is not continuously used is reduced, and the difference in the degree to which the discharged droplets are dried during the idle time is reduced. The printing unevenness caused by the difference can be further suppressed.

  Application Example 3 A droplet discharge device according to this application example includes a transfer unit that moves a print medium in the transfer direction, a first nozzle row that has a plurality of nozzles that discharge droplets arranged in the transfer direction, A second nozzle row having a plurality of nozzles for discharging droplets arranged in the transport direction arranged downstream of the first nozzle row in the transport direction; the first nozzle row and the second nozzle row; A scanning movement unit that scans and moves in a scanning direction that intersects with the conveyance direction, and moves the print medium in the conveyance direction while scanning and moving the first nozzle row and the second nozzle row. A droplet discharge device that forms an image composed of rasters that are completed by n droplet discharge operations by alternately repeating a droplet discharge operation for discharging droplets onto a print medium. The first nozzle in the droplet discharge operation In the droplet discharge operation after the droplet discharge operation using the row and the second nozzle row, the number m of continuous droplet discharge operations in which the second nozzle row is not used is less than 0.5n. It is characterized by.

  The liquid droplet ejection apparatus according to this application example includes a conveyance unit that moves a print medium in a conveyance direction, a first nozzle row that has a plurality of nozzles that eject droplets arranged in the conveyance direction, and a conveyance direction of the first nozzle row. A second nozzle row having a plurality of nozzles for discharging droplets arranged in the carrying direction arranged on the downstream side, and a scanning movement for scanning and moving the first nozzle row and the second nozzle row in a scanning direction intersecting the carrying direction Department. Further, the droplet discharge device performs a transport operation for moving the print medium in the transport direction, and a droplet discharge operation for discharging the droplet onto the print medium while scanning and moving the first nozzle row and the second nozzle row. By repeating alternately, an image composed of rasters completed by n droplet ejection operations is formed.

  According to this application example, in the droplet discharge operation after the droplet discharge operation using the first nozzle row and the second nozzle row in one droplet discharge operation, the droplet discharge operation in which the second nozzle row is not used. Is less than 0.5n times. In other words, the idle time during which the second nozzle row is not continuously used does not become a long time of 0.5 n times or more for the droplet discharge operation. As a result, the degree of drying of the ejected droplets during the idle time is reduced, so that uneven printing caused by the difference in the degree of drying can be suppressed.

1 is a perspective view showing an internal configuration of an ink jet printer as a droplet discharge device according to Embodiment 1. FIG. 1 is a block diagram illustrating an overall configuration of an ink jet printer as a droplet discharge device according to a first embodiment. Explanatory drawing showing an example of the arrangement of nozzles Explanatory drawing showing an example of the arrangement of nozzles Explanatory drawing describing a headset as a virtual headset Illustration of an example of normal processing Illustration of dot formation example in normal processing (A), (b) Explanatory drawing of an example of the upper end process by a prior art The graph which shows typically the usage rate of the head in each pass 1-6 (A), (b) Explanatory drawing when the head usage rate is expressed by linear approximation Graph showing the transition of head usage rate in the upper end processing according to the prior art The graph which shows transition of the head usage rate of each of the 1st head in the prior art, and the 2nd head The graph which shows the transition of the head usage rate of each of the first head and the second head in Example 1. The graph which shows transition of the head usage rate of each of the 1st head and the 2nd head in other examples of conventional technology The graph which shows the transition of the head usage rate of the 1st head in Example 2, and each 2nd head The graph which shows the transition of the head usage rate of each of the 1st head and 2nd head in Example 3. The graph which shows the transition of the head usage rate of each of the 1st head and the 2nd head in the modification 1.

  DESCRIPTION OF EMBODIMENTS Embodiments embodying the present invention will be described below with reference to the drawings. The following is one embodiment of the present invention and does not limit the present invention. In the following drawings, the scale may be different from the actual scale for easy understanding.

(Embodiment 1)
FIG. 1 is a perspective view illustrating an internal configuration of an ink jet printer 100 as a droplet discharge device according to Embodiment 1, and FIG. 2 is a block diagram.
Note that the inkjet printer 100 is installed on the XY plane in the XYZ axes appended to the drawing. In addition, the ± X direction (X-axis direction) will be described as a scanning direction described later, the + Y direction will be described as a transport direction described later, and the Z direction will be described as a height direction.
First, the basic configuration of the inkjet printer 100 will be described.

<Basic configuration of inkjet printer>
The ink jet printer 100 (hereinafter referred to as the printer 100) includes a transport unit 20 as a “transport unit”, a carriage unit 30 as a “scan moving unit”, a head unit 40, and a controller 60. The printer 100 that has received print data (image formation data) from a personal computer 110 (hereinafter referred to as a PC 110), which is an external device, controls each unit (conveyance unit 20, carriage unit 30, head unit 40) with a controller 60. The controller 60 controls each unit based on the print data received from the PC 110 and prints an image (image formation) on the paper 10 as a “print medium”.

  The transport unit 20 has a function of moving the paper 10 in a predetermined transport direction (+ Y direction shown in FIG. 1). The transport unit 20 includes a paper feed roller 21, a transport motor 22, a transport roller 23, a platen 24, a paper discharge roller 25, and the like. The paper feed roller 21 feeds the paper 10 inserted from the back surface (−Y direction) of the printer 100 into the printer 100. The transport roller 23 transports the paper 10 fed by the paper feed roller 21 to a printable area on the platen 24. The platen 24 supports the paper 10 being printed. The paper discharge roller 25 discharges the paper 10 to the front surface (conveyance direction) of the printer. The paper feed roller 21, the transport roller 23, and the paper discharge roller 25 are driven by the transport motor 22.

  The carriage unit 30 has a function of reciprocating (scanning) a head 41, which will be described later, in a predetermined movement direction (X-axis direction shown in FIG. 1, hereinafter referred to as a scanning direction). The carriage unit 30 includes a carriage 31, a carriage motor 32, and the like. The carriage 31 can reciprocate in the scanning direction and is driven by a carriage motor 32. The carriage 31 also detachably holds the ink cartridge 6 that stores ink.

The head unit 40 has a function of ejecting ink onto the paper 10 as “droplets” (hereinafter also referred to as ink droplets). The head unit 40 includes a head 41 having a plurality of nozzles (nozzle rows). The head 41 is mounted on the carriage 31 and moves in the scanning direction as the carriage 31 moves in the scanning direction. By ejecting ink droplets while the head 41 moves in the scanning direction, a row of dots (raster lines) along the scanning direction is formed on the paper 10.
The head 41 includes two heads (a first nozzle group 41A and a second nozzle group 41B). The configuration of the head 41 will be described later.

The controller 60 is a control unit that controls the entire printer 100. The controller 60 includes an interface unit 61, a CPU 62, a memory 63, a unit control circuit 64, and the like. The interface unit 61 transmits and receives data between the PC 110 and the printer 100. The CPU 62 is an arithmetic processing device for controlling the entire printer 100. The memory 63 is a storage medium that secures an area for storing a program for the CPU 62 to operate, an operation area for the operation, and the like, and includes a storage element such as a RAM or an EEPROM.
The CPU 62 controls each unit (conveyance unit 20, carriage unit 30, head unit 40) via the unit control circuit 64 in accordance with a program stored in the memory 63.

  Further, the controller 60 is provided with a drive signal generation unit 65. The drive signal generation unit 65 includes a first drive signal generation unit 65A and a second drive signal generation unit 65B. The first drive signal generator 65A generates a first drive signal for driving the piezo elements of the first nozzle group 41A. The second drive signal generator 65B generates a second drive signal for driving the piezo elements of the second nozzle group 41B. Each drive signal generator generates a drive signal for odd-numbered dots when forming dots on odd-numbered dots (described later), and for even-numbered dots when forming dots on even-numbered dots (described later) Drive signal is generated. The drive signal generation units are independent of each other. For example, when the first drive signal generation unit 65A generates a drive signal for odd-numbered dots, the second drive signal generation unit 65B is for odd-numbered dots. Drive signals for even-numbered dots can also be generated.

  The controller 60 alternately repeats a “droplet ejection operation” for ejecting ink as droplets from the head 41 moving in the scanning direction and a “conveying operation” for moving the paper 10 in the conveyance direction, thereby generating a plurality of dots. Is printed on the paper 10. The droplet discharge operation may be referred to as “pass”, and the n-th pass may be referred to as “pass n”.

<Configuration of head>
FIG. 3 is an explanatory diagram illustrating an example of an arrangement of nozzles included in the head 41. The head 41 includes a first nozzle group 41A and a second nozzle group 41B as two heads (nozzle groups). Each nozzle group is provided with eight nozzle rows. On the lower surface of the head 41, discharge ports of these nozzles are opened. The eight nozzle rows are respectively cyan (C), magenta (M), yellow (Y), black (K), light cyan (LC), light magenta (LM), light black (LK), and very light black ( LLK) ink is ejected.

  Each nozzle row is provided with 180 nozzles (nozzles # 1A to # 180A, nozzles # 1B to # 180B) arranged in the transport direction at a nozzle pitch of 180 dpi. In FIG. 3, the lower number is assigned to the nozzle on the downstream side (+ Y side) in the transport direction. Each nozzle is provided with a piezo element (not shown) as a drive element for ejecting ink droplets from each nozzle.

The first nozzle group 41A is provided downstream of the second nozzle group 41B in the transport direction. Also, the first nozzle group 41A and the second nozzle group 41B are provided so that the positions of the four nozzles in the transport direction overlap. For example, the position in the transport direction of the nozzle # 177A of the first nozzle group 41A is the same as the position in the transport direction of the nozzle # 1B of the second nozzle group 41B. As a result, when a dot can be formed by the nozzle # 177A of the first nozzle group 41A for a certain raster in a certain droplet discharge operation, a dot is also formed by the nozzle # 1B of the second nozzle group 41B for that raster. Is possible.
A combination of nozzle rows that eject the same ink (ink configured with the same composition) between the first nozzle group 41A and the second nozzle group 41B is referred to as a “headset”.

  FIG. 4 is an explanatory diagram showing another example of the nozzle arrangement of the head 41. In the example shown in FIG. 4, the headset shown in FIG. 3 is arranged at a closer position. More specifically, in the example of FIG. 4, the first nozzle group 41A and the second nozzle group 41B are arranged so as to be alternately arranged for every two nozzle rows. Each nozzle row is provided with 400 nozzles (nozzles # 1A to # 400A, nozzles # 1B to # 400B) arranged in the transport direction at a nozzle pitch of 300 dpi. , And ½ pitch (1/600 inch) offset.

  Further, the first nozzle group 41A and the second nozzle group 41B are provided so that the positions in the transport direction of the six nozzles overlap. For example, the position in the transport direction of the nozzle # 395A of the first nozzle group 41A is the same as the position in the transport direction of the nozzle # 1B of the second nozzle group 41B. As a result, when a dot can be formed by the nozzle # 395A of the first nozzle group 41A for a certain raster in a certain droplet discharge operation, a dot is also formed by the nozzle # 1B of the second nozzle group 41B for that raster. Is possible.

<Nozzle row and nozzle notation>
Before describing the dot formation method, the nozzle row and nozzle notation method will be described.
FIG. 5 is an explanatory diagram illustrating a headset as a virtual headset 42X.

On the left side of FIG. 5, for example, the black nozzle row of the first nozzle group 41A and the black nozzle row of the second nozzle group 41B are shown. In the following description, the black nozzle row of the first nozzle group 41A is called a first head 42A, and the black nozzle row of the second nozzle group 41B is called a second head 42B. For simplification of explanation, the number of nozzles in each nozzle row is 15. The first head 42A corresponds to the “first nozzle row” in the present invention, and the second head 42B corresponds to the “second nozzle row” in the present invention.
Four nozzles (nozzle # 12A to nozzle # 15A) on the upstream side in the transport direction of the first head 42A and four nozzles (nozzle # 1B to nozzle # 4B) on the downstream side in the transport direction of the second head 42B are: The transport direction position is duplicated. In the following description, these four nozzles in each nozzle row are referred to as overlapping nozzles.

Each nozzle of the first head 42A is indicated by a circle, and each nozzle of the second head 42B is indicated by a triangle. Further, nozzles that do not eject ink (that is, nozzles that do not form dots) are marked with a cross.
Here, among the overlapping nozzles of the first head 42A, the nozzle # 12A and the nozzle # 13A eject ink, and the nozzle # 14A and the nozzle # 15A do not eject ink. Of the overlapping nozzles of the second head 42B, the nozzle # 1B and the nozzle # 2B do not eject ink, and the nozzle # 3B and the nozzle # 4B eject ink.
In such a case, as described in the central portion of FIG. 5, the two heads (the first head 42A and the second head 42B) constituting the headset can be represented as one virtual headset 42X. . In the following description, the state of dot formation will be described using one virtual headset 42X instead of drawing two heads separately.

  As shown on the right side of FIG. 5, in this virtual headset 42X, even when the round nozzles form dots on odd-numbered dots (described later), the triangular nozzles are even-numbered dots (described later). ) Can form dots. Of course, when the round nozzles form dots on the odd-numbered dots, the triangular nozzles can also form dots on the odd-numbered dots.

  In addition, although the operation | movement which discharges an ink droplet from each nozzle and forms a dot is performed based on the print data which the controller 60 received, here, in order to demonstrate easily, discharge based on an individual print data The presence or absence of this is omitted from the explanation. That is, a description will be given based on a state in which dots are formed for dots at all positions where dots can be formed by ejecting ink droplets from the corresponding nozzles based on the print data.

<Dot formation method by normal processing>
FIG. 6 is an explanatory diagram of an example of normal processing. The normal processing is processing (droplet discharge operation and transport operation) performed when printing the central portion of the paper 10 (the region that is neither the upper end nor the lower end of the paper 10). The controller 60 performs normal processing described below by controlling each unit.

In FIG. 6, the relative position by the step movement for each transport amount 9D of the paper 10 by the transport unit 20 is shown in an oblique direction so that the virtual headset 42X does not overlap. That is, in FIG. 6, the virtual headset 42 </ b> X is depicted as moving with respect to the paper 10, but actually the paper 10 moves in the transport direction. In FIG. 6, the positional relationship of the virtual headset 42X in the + X direction does not make sense. Arrows P1 to P4 indicate directions in which the virtual headset 42X is scanned in the scanning direction (X-axis direction).
In the normal process, the paper 10 is transported by a transport amount 9D for nine dots in a transport operation performed between passes. For example, dots are formed by pass 1 to pass 6 in area A (area on paper 10) in FIG. 6, and dots are formed by pass 2 to pass 7 in area B.

  In the odd-numbered pass, each nozzle is positioned at an odd-numbered raster line (dot row along the scanning direction), for example. After the odd-numbered pass, the even-numbered pass is performed after the paper 10 has been transported by the transport amount 9D for nine dots. Therefore, in the even-numbered pass, each nozzle is connected to the even-numbered raster line. Become position. In this way, the positions of the nozzles are alternately odd-numbered or even-numbered raster line positions for each pass.

FIG. 7 is an explanatory diagram of an example of dot formation in the area A and the area B of FIG. Here, FIG. 7 shows a case where one raster is completed in four passes, for example.
On the left side of FIG. 7, the relative positions of the nozzles in each pass are shown. A black-filled nozzle forms one dot per pixel in the pass. For example, nozzle # 8B in pass 2 forms dots at a rate of one for two dot positions. The nozzles hatched with diagonal lines form dots at a rate of one for every two pixels. For example, nozzle # 10A in pass 4 forms dots at a rate of one for four dot positions.

  A nozzle hatched with diagonal lines forms only half of the dots compared to a black-filled nozzle. Hereinafter, the hatched nozzle is referred to as a partial overlap nozzle. Four nozzles (nozzle # 10A to nozzle # 13A) on the upstream side (-Y side) in the transport direction of the first head 42A in a certain pass, and the first head after two transport operations have been performed from that pass The four nozzles (nozzle # 1A to nozzle # 4A) on the downstream side (+ Y side) of 42A in the transport direction overlap in the transport direction. Such a nozzle becomes a partial overlap nozzle. For example, the nozzle # 10A to nozzle # 13A in pass 4 and the nozzle # 1A to nozzle # 4A in pass 6 are partially overlapping nozzles because the positions in the transport direction overlap.

  Similarly, four nozzles (nozzle # 12B to nozzle # 15B) on the upstream side in the transport direction of the second head 42B of a certain pass and the second head 42B after two transport operations are performed from that pass. The positions of the four nozzles (nozzle # 3B to nozzle # 6B) on the downstream side in the transport direction overlap in the transport direction. Such a nozzle becomes a partial overlap nozzle. For example, nozzle # 12B to nozzle # 15B in pass 2 and nozzle # 3B to nozzle # 6B in pass 4 are partially overlapping nozzles because the positions in the transport direction overlap.

  On the right side of FIG. 7, nozzles that form dots in each pixel are shown. For example, the first raster line (the line whose raster number is 1) is composed of dots formed as odd-numbered dots by nozzle # 8B and dots formed as even-numbered dots by nozzle # 10A and nozzle # 1A. Is done. Here, for simplification of explanation, each raster line is composed of only eight dots.

  In the upper left of FIG. 7, the positions of dots formed by each head are shown. For example, in pass 1, the nozzles (nozzles # 1A to # 13A) of the first head 42A form dots at odd-numbered dots, and the nozzles (nozzles # 3B to # 15B) of the second head 42B are even-numbered dots. To form dots. Also, the control for printing so that a part of the area printed in a certain pass overlaps the area printed in a certain pass as a result of printing using the partial overlap nozzle is called partial overlap control.

  Each raster line is composed of dots formed by two or three nozzles. In other words, two or three nozzles are associated with each raster line. For example, the first raster line is associated with nozzle # 8B for pass 2, nozzle # 10A for pass 4, and nozzle # 1A for pass 6. Each raster line is composed of dots formed by at least one nozzle of the first head 42A and dots formed by at least one nozzle of the second head 42B. In other words, at least one nozzle of the first head 42A and at least one nozzle of the second head 42B are associated with each raster line.

  When only one nozzle is associated with an odd-numbered dot or an even-numbered dot of a raster line, the nozzle forms dots at a rate of one for two dots. For example, only one nozzle # 8B is associated with the odd-numbered dot of the first raster line (other nozzles are not associated). Therefore, nozzle # 8B forms dots at a rate of one for two dots.

  On the other hand, when two nozzles are associated with odd-numbered dots or even-numbered dots of a raster line, each of the two nozzles forms one dot for every four dots. (It becomes a partial overlap nozzle). For example, nozzle # 10A and nozzle # 1A are associated with even-numbered dots on the first raster line. For this reason, nozzle # 10A and nozzle # 1A each form dots at a ratio of four dots (becomes partial overlap nozzles).

  In normal processing, the position at which the first head 42A forms dots (position in the scanning direction) and the position at which the second head 42B forms dots in a certain pass are different. Specifically, when the first head 42A forms dots at odd-numbered dots, the second head 42B forms dots at even-numbered dots. Conversely, when the first head 42A forms dots at even-numbered dots, the second head 42B forms dots at odd-numbered dots. Since the first drive signal generator 65A and the second drive signal generator 65B described above can generate drive signals independently of each other, such dot formation becomes possible.

  Further, in the normal process, when a certain pass is compared with the next pass, the positions where each head forms dots are different. For example, when the first head 42A forms dots in odd-numbered dots and the second head 42B forms dots in even-numbered dots in a certain pass, the first head 42A forms dots in even-numbered dots in the next pass. The second head 42B forms dots at odd-numbered dots.

  By forming dots in this way, dots are formed in a staggered pattern by one head, and dots are formed in a staggered pattern by the other head so that the space between the dots is filled. Is done. When attention is paid to the right side of FIG. 7, the round dots formed by the first head 42A have a staggered pattern, and the triangular dots formed by the second head 42B also have a staggered pattern. Yes. In terms of the dot formation order, the dots are formed by the first head 42A so that the dots are formed after the dots are formed by the second head 42B in a staggered pattern.

  When a raster line is formed by normal processing, half dots are formed by the first head 42A and the remaining half dots are formed by the second head 42B in the raster line. In other words, the usage rate of each head when forming these raster lines is 50% (constant) for the first head 42A and 50% (constant) for the second head 42B.

  In the area A, dots are formed by the passes 1 to 6, and in the area B, the dots are formed by the passes 2 to 7, so that the pass is shifted by one time between the area A and the area B. Since the pass is shifted by one time, the nozzles associated with each raster line are common in each region, but the position of the dots formed by each nozzle (position in the scanning direction) is an odd number dot or an even number dot Is different. For example, for the first raster line, the nozzle # 8B for pass 2 forms dots at odd-numbered dots, but for the tenth raster line, nozzle # 8B for pass 3 forms dots at even-numbered dots. .

  Although not shown here, the 19th to 27th raster lines located on the upstream side in the transport direction from the region B are formed with dots almost in the same manner as the region A through the passes 3 to 8. For example, nozzle # 8B, nozzle # 10A, and nozzle # 1A are associated with the 19th raster line, and nozzle # 8B forms dots at odd-numbered dots on the 19th raster line. In the 28th to 36th raster lines located upstream of the 19th to 27th raster lines in the transport direction, dots are formed in substantially the same manner as in the region B by pass 4 to pass 9. As described above, when the normal processing is continuously performed, the dot formation similar to the region A and the region B is repeatedly performed.

  For example, when a high-definition image is formed on the paper 10 by forming dots on the paper 10, the paper 10 is securely held at a predetermined position (and height) during the droplet discharge operation. In the carrying operation, it is necessary to accurately move the paper 10 to a predetermined position. For this reason, the transport unit 20 fixes (holds) the paper 10 by means such as pinching, pressing, and sucking. These fixing (holding) means must be configured so as not to interfere with the movement of the carriage unit 30 and the head unit 40. In other words, printing is started and ended also in a state (position) in which the upper end portion and lower end portion of the paper 10 are securely fixed (held). As a result, for example, in the configuration in which the first nozzle group 41A and the second nozzle group 41B having nozzle rows arranged in the transport direction (+ Y direction) are arranged in the transport direction (+ Y direction) as in the present embodiment, the paper 10 In some cases, it is necessary to form dots only with nozzles that can be handled by the corresponding head (the first head 42A or the second head 42B) for each of the upper end portion and the lower end portion.

<Dot formation method by top edge processing>
Hereinafter, an example of the upper end process when an image that is partially overlapped between a plurality of heads cannot be formed will be described. The upper end process is a process (droplet discharge operation and transport operation) performed when printing the upper end region (+ Y side end region) of the paper 10. The controller 60 performs upper end processing described below by controlling each unit.

FIGS. 8A and 8B are explanatory diagrams of an example of the upper end process, and FIGS. 8A and 8B: (1) to (4) are virtual in each path of the upper end process (pass 1 to path 4). 8A and 8B show the positions of the headset 42X and the ejected ink droplets. FIGS. 8A and 8B show the virtual headset 42X in each pass (pass 5 and pass 6) of the normal process subsequent to the upper end process. And the positions of the ejected ink droplets.
FIG. 8B: (1) to (6) show dots formed on the paper 10 in pass 1 to pass 6. That is, FIG. 8B: (1) to (6) are the results of overlapping the positions of the ink droplets of FIG. 8A: (1) to (6).

In the example shown here, upper end processing is performed in pass 1 to pass 4, and normal processing is performed after pass 5. In the upper end processing, in the transport operation performed between passes, the sheet 10 is transported with a transport amount D for one dot (a transport amount shorter than the transport amount 9D in the normal process).
In the upper end processing, in the odd-numbered pass, each nozzle is positioned at the odd-numbered raster line. After the odd-numbered pass, the paper 10 is transported by a transport amount for one dot, so in the even-numbered pass, each nozzle is positioned at the even-numbered raster line. As described above, also in the upper end process, the positions of the nozzles alternately become the positions of the odd-numbered or even-numbered raster lines for each pass.

  In the normal processing described above, in order to form dots in a staggered pattern by each head, the dot formation position of the first head 42A and the dot formation position of the second head 42B in a certain pass are different. For example, when the first head 42A forms dots at odd-numbered dots, the second head 42B forms dots at even-numbered dots.

  On the other hand, in the upper end process, the dot formation position of the first head 42A and the dot formation position of the second head 42B in a certain pass are the same. For example, in pass 1, the first head 42A and the second head 42B both form dots at odd-numbered dots.

  Further, in the above-described normal processing, in order to form dots in a staggered pattern by each head, the dot formation position of each head is different between a certain pass and the next pass. For example, when the first head 42A forms dots in odd-numbered dots and the second head 42B forms dots in even-numbered dots in a certain pass, the first head 42A forms dots in even-numbered dots in the next pass. The second head 42B forms dots on odd-numbered dots.

  In contrast, in the upper end process, the dot formation position of each head is changed in the order of odd-numbered dots (pass 1) → even-numbered dots (pass 2) → even-numbered dots (pass 3) → odd-numbered dots (pass 4). Is done. That is, in the upper end process, the dot formation position of each head may not necessarily differ between a certain pass and the next pass. For example, in pass 2 and pass 3, the dot formation positions are the same even-numbered dots.

  The reason for the above difference between the normal process and the upper end process is that dots are formed in a staggered pattern by each head in the normal process, whereas in the upper end process, the first half 2 of the four passes. This is because dots are formed in a staggered pattern in a single pass, and dots are formed in a staggered pattern in the latter two passes so as to fill in the space between the dots in the staggered pattern.

  With the above dot formation method, the first to 25th raster lines (the raster lines on the upper end side of the paper 10) are formed only by the first head 42A. In other words, the usage rate of the head when forming the first to 25th raster lines is 100% for the first head 42A and 0% for the second head 42B.

FIG. 9 is a graph schematically showing the usage rates of the first head 42A and the second head 42B in each pass (pass 1 to pass 6).
Up to this point, for the sake of easy understanding, the description has been made in the range where the dots are visible. Therefore, as shown in FIG. 9, the change in the usage rate of each head (difference in the raster number direction) is shown stepwise, but in actual use, innumerable dots formed by several picoliters of ink droplets Therefore, the usage rate of each head can be shown by approximating the change to a straight line or a curve as shown in the following figures.

10A and 10B are explanatory diagrams when the head usage rate is expressed by linear approximation.
For example, FIG. 10A shows a normal process in which a maximum of three dots per nozzle are formed in one pass using two heads having six nozzles. In this normal process, as shown on the right side of FIG. 10A, there are four dots formed by each head, that is, a solid pattern in which the usage rate of each head is 50% (the arrangement of dots is shown in FIG. are arranged in a staggered pattern as shown above a).
When forming an image with innumerable dots formed with several picoliters of ink droplets, the number of dots was replaced with the usage rate of each nozzle and stacked in a pyramid shape drawn in each pass of FIG. The block can be represented by a triangle (or trapezoid) shown in FIG.
In the following description, the distribution of the nozzle usage rate in each pass (that is, the usage rate of each head for each raster line) is expressed by using the triangle (or trapezoid).

FIG. 11 is a graph showing the transition of the head usage rates of the first head 42A and the second head 42B in the region from the upper end process to the normal process.
In FIG. 11, a headset formed by the first head 42 </ b> A and the second head 42 </ b> B is represented by a row of the first head 42 </ b> A and the second head 42 </ b> B arranged in the + Y direction as in the virtual headset 42 </ b> X illustrated in FIG. 5. Similarly to FIG. 6, the relative positions due to the movement of the paper 10 by the transport unit 20 are shown in an oblique direction so that the first head 42A and the second head 42B do not overlap. That is, in FIG. 11, the first head 42 </ b> A and the second head 42 </ b> B are depicted as moving with respect to the paper 10, but actually the paper 10 moves in the transport direction (+ Y direction). In FIG. 11, the positional relationship between the first head 42A and the second head 42B in the + X direction does not make sense. Further, the usage rate of each head (the usage rate for each nozzle belonging to each head for each raster line) is shown in the same manner as in FIG.

  Passes 1 to 4 are upper end processes in which an image is formed only by the first head 42A. Passes 5 to 8 are transition processes in which the usage rate of the second head 42B gradually increases, and passes 9 and after. The usage rate of the first head 42A and the second head 42B is normal processing of 50%. An area formed after pass 5 is an image area in which partial overlap control is performed between the two heads.

  In the upper end process described so far, a transition process in which the usage rate of the second head 42B is gradually increased for each pass is performed, but when viewed for each raster line, it is shown on the right side of FIG. As described above, the usage rate of the second head 42B increases stepwise (sawtooth) in the -Y direction. For this reason, when the ejection characteristics are different between the nozzles constituting the first head 42A and the nozzles constituting the second head 42B, the influence appears in a stepped shape (sawtooth shape). Specifically, for example, when the opening diameter of the nozzle provided in the second head 42B becomes larger than that of the first head 42A due to manufacturing variation or the like, the ejected liquid droplets increase, and the second head A density difference corresponding to an increase or decrease in the usage rate of 42B appears. Therefore, in the prior art, this is improved by the method described below.

<Upper end processing in the prior art>
FIG. 12 is a graph showing the transition of the head usage rate of each of the first nozzle row (first head 42A) and the second nozzle row (second head 42B) included in the printer 100.
As in FIG. 11, FIG. 12 shows a first head 42A and a second head 42B arranged in a row in the + Y direction like the virtual head set 42X shown in FIG. It is written. Similarly to FIG. 6, the relative positions due to the movement of the paper 10 by the transport unit 20 are shown in an oblique direction so that the first head 42A and the second head 42B do not overlap. That is, in FIG. 12, the first head 42 </ b> A and the second head 42 </ b> B are depicted as moving with respect to the paper 10, but actually the paper 10 moves in the transport direction (+ Y direction). In FIG. 12, the positional relationship between the first head 42A and the second head 42B in the + X direction does not make sense. Further, the usage rate of each head (the usage rate for each nozzle belonging to each head for each raster line) is shown in the same manner as in FIG.

  The printer 100 performs upper end processing and transition processing to normal processing in printing in the upper end area of the paper 10. As a result, the area where dots are formed on the paper 10 is located in the −Y direction of the first area and the first area due to the difference in usage rates of the first head 42A and the second head 42B, and continues to the first area. The second region and the third region which are located in the −Y direction of the second region and are continuous with the second region are classified into three types. In other words, even if there is a difference in the characteristics of the head, the usage rate of the head is changed in three regions so that the influence is less visible.

First, for the first region, dots are formed using only the first head 42A.
For the second region, dots are formed using the first head 42A and the second head 42B, and dots are formed using the first head 42A in a dot row (raster line) arranged in the + X direction. The ratio of the number of dots formed using the second head 42B to the total number of dots formed using the second head 42B and the number of dots formed using the second head 42B is the second head usage rate. In a plurality of rows (that is, across a plurality of raster lines), the second head usage rate is gradually increased in the −Y direction.
For the third region, dots are formed using the first head 42A and the second head 42B, and the second head usage rate is constant (50%).
This will be specifically described below.

  As shown in FIG. 12, the upper end process is performed through paths 1 to 4, and the migration process is performed through paths 5 to 8. The transfer process (pass 5 to pass 8) carries half the length of one head with respect to the upper end process (pass 1 to pass 4), and the upper end process (pass 1 to pass 4) and transfer process ( Partial overlap control is performed between pass 5 and pass 8).

In pass 3 and pass 4 in the upper end process, the second number of dots is the sum of the number of dots formed using the first head 42A and the number of dots formed using the second head 42B in each raster line. When the ratio of the number of dots formed in one pass using the head 42B is the second head 1 pass usage rate, the second head 1 pass usage rate is distributed as follows.
In a plurality of rows of dots arranged in the + X direction (that is, a plurality of raster lines formed in one pass) formed in a single pass by a plurality of nozzles provided in the second head 42B, the second head 1 pass The usage rate is set to increase from 0% to 25% and decrease from 25% to 0% in the -Y direction.

The portion in which the usage rate of the second head 42B is distributed in this way in pass 3 and pass 4 is such that partial overlap control is performed between the first head 42A and the second head 42B in pass 7 and pass 8. 7. Set path 8.
The pass 9 and subsequent passes are normal processing passes.
A graph of the usage rate of the second head 42B is shown on the right side of FIG.
The first area formed only by the first head 42A, the first head 42A, and the second head 42B are used, and the usage rate of the second head 42B is 0% to 50% in the −Y direction for each raster line. A second region that increases up to 50%, and a third region that uses 50% of each of the first head 42A and the second head 42B is formed.

  Thus, in the second region, the usage rate of the second head 42B is configured to gradually increase in the direction from the first region to the third region. Even if there is a difference between the characteristics of ejecting droplets) and the characteristics of the second head 42B, the change is smooth.

However, in order to realize this, the second head 42B (see FIG. 11) used in the transition processing passes 5 and 6 is accelerated to use at the timing of the upper end processing passes 3 and 4, so that the pass 4 In the period from the first pass to the seventh pass, there is a free time (for two passes) in the ejection of ink droplets by the second head 42B (see FIG. 12). On the other hand, after the pass 7, the second head 42B is continuously used. In the prior art, such a free time is not particularly considered. As a result, there is a case where the effect of the free time of the second head 42B in the transition process occurs as banding (unevenness). Specifically, among the dots formed by the second head 42 </ b> B in passes 3 and 4, dots in the same area as the dots formed in the subsequent passes 7 and 8 are dried within the free time of passes 5 and 6. As this progresses, banding occurs in this area. That is, the degree and surface shape of ink droplets ejected by the second head 42B in passes 7 and 8 are different from the degree and surface shape of ink droplets ejected by the second head 42B after pass 9. There was a case that banding occurred.
In the present embodiment, this is improved by the method described below.

<Upper end processing in this embodiment>
The droplet discharge method according to this embodiment is a droplet discharge method for forming an image composed of rasters that are completed in n droplet discharge operations, and the first nozzle row and the second nozzle in one droplet discharge operation. In the droplet discharge operation after the droplet discharge operation using the nozzle row, the number of continuous droplet discharge operations that do not use the second nozzle row is less than 0.5n. Here, “not using” the nozzle row does not include a case where the nozzle row is not used based on image data to be printed. That is, it means not to use regardless of the image to be printed.
<Example 1>
FIG. 13 is a graph of Example 1 showing transitions in head usage rates of the first head 42A and the second head 42B included in the inkjet printer 100 according to the first embodiment. With reference to FIG. 13, a droplet discharge method as an example (Example 1) of an embodiment embodying the present invention will be described.

  The droplet discharge method in the present embodiment is a droplet discharge method for forming an image composed of rasters completed by n = 4 droplet discharge operations. In the droplet discharge operation after the droplet discharge operation using the second nozzle row, that is, in the droplet discharge operation after the start of use of the second nozzle row (second head 42B), the second nozzle row (second head) 42B), the number of consecutive droplet discharge operations is less than 0.5n = 2. Specifically, the use of the second nozzle row (second head 42B) in pass 7 shown in FIG. 12 is further advanced to use at the timing of pass 6. As a result, the empty time (number of times m) of ink droplet ejection by the second nozzle row (second head 42B) is reduced to one pass (less than 0.5n = 2), and the time when the idle time occurs. Are distributed from one place to two places.

<Example 2>
For example, FIG. 14 shows a case in which one raster is formed by n = 16 passes using two nozzle rows (first and second heads) each comprising 96 nozzles. It is a graph which shows transition of each head usage rate.
According to this prior art method, banding due to the fact that the second head is not used between pass 17 and pass 24 is likely to occur.

On the other hand, FIG. 15 is a graph showing transitions of the respective head usage rates in Example 2 according to Embodiment 1 of the present invention.
In the second embodiment, the use time of the second head in the pass 9 to the pass 16 in the upper end process and the pass 25 to the pass 28 in the transition process shown in FIG. Dispersed in batches.
That is, the continuous free time (number of times m = 8) for eight passes of the path 17 to the path 24 shown in FIG. 14 is divided into one free time (number of times m = 1) and distributed. Similarly, the continuous use of the paths 9 to 16 (FIG. 14) prior to the eight consecutive free times is also distributed so that the free time is entered once. As a result, the use and non-use of the second nozzle array (second head) are repeatedly repeated from the start of use (pass 5) to the pass (pass 29) where continuous use starts. That is, there is no free time in consecutive paths, and there is no variation in free time (number of times m).

<Example 3>
FIG. 16 is a graph showing the transition of each head usage rate in Example 3 according to Embodiment 1 of the present invention.
In the third embodiment, the use of the second head in the pass 9 to the pass 12 in the upper end process of the prior art shown in FIG. 14 is changed to the pass 5 to the pass 8, and the use of the second head in the pass 25 to the pass 28 in the transition process. To pass 21 to pass 24.
As a result, between the start of use of the second nozzle row (second head) (pass 5) and the pass (pass 29) where continuous use starts, pass 4 times and non-use of 4 times are repeated uniformly. It becomes like this. That is, there is no continuous free time of 0.5n = 8 or more, and there is no variation in the free time (number of times m).

As described above, according to the droplet discharge method and the droplet discharge apparatus according to the present embodiment, the following effects can be obtained.
The droplet discharge method of the present embodiment includes a transport operation for moving the paper 10 in the transport direction, and a first nozzle row (first head ((first head 42A in the first embodiment)) in the scanning direction that intersects the transport direction). And a second nozzle row (second head (second head 42B in the first embodiment)) are scanned and moved alternately, and a droplet discharge operation for discharging droplets onto the paper 10 is alternately repeated to form an image. In addition, when the number of droplet ejection operations (passes) for completing a raster for forming an image is n, the droplet ejection operation using the first nozzle row and the second nozzle row in one droplet ejection operation In the subsequent droplet discharge operation, that is, in the droplet discharge operation after the start of use of the second nozzle row, the number of consecutive droplet discharge operations that do not use the second nozzle row is less than 0.5n. The second nozzle row is not used continuously The time does not become a time longer than 0.5n times of the droplet discharge operation, and there is no variation in the length of the empty time. Therefore, uneven printing caused by the difference in the degree of drying can be suppressed.

  Note that the present invention is not limited to the above-described embodiment, and various modifications and improvements can be added to the above-described embodiment. A modification will be described below. Here, the same components as those in the above-described embodiment are denoted by the same reference numerals, and redundant description is omitted.

(Modification 1)
FIG. 17 is a graph showing transitions of respective head usage rates showing the droplet discharge method according to the first modification.
In the first embodiment, as shown in FIGS. 13, 15, and 16, the dispersed idle time (the number m of droplet ejection operations in which the second nozzle row is not continuously used) is each once (Example 1, implementation). Example 2) The case where there is no difference between four times (Example 3) has been described as an example, but there may be a difference in each of the dispersed free times (number of times m).

Modification 1 is a modification of the embodiment (Example 2) with respect to the prior art described in FIG. In other words, this is a modification example in which two raster lines (first and second heads) each having 96 nozzles are used to form one raster in n = 16 passes.
In the first modification, the number of continuous use of the second head from the start of use of the second head in the upper end processing area to the continuous use in the continuous processing area is 1 to 2, 3 and 4 times. And the idle time (number of times m) is gradually shortened to 2 passes, 1 pass, and none, thereby making it difficult to visually recognize the banding.

  If there is a large difference (variation) between the distributed free times, even if each free time is less than 0.5n passes, banding may be recognized slightly. Therefore, the difference is (m1−m2) / m0, where m0 is the average value of the number m of droplet discharge operations in which the second nozzle row is not continuously used, m1 is the maximum value, and m2 is the minimum value. <1. In the example shown in FIG. 17, m0 = 1.67, m1 = 2, m2 = 1, and (m1−m2) /m0=0.6. That is, the variation is suppressed so that the difference in the number m of droplet discharge operations in which the second nozzle row is not continuously used does not exceed the average value m0 of the number m. As a result, the difference (variation) in the idle time (number of times m) in which the second nozzle row is not continuously used is reduced, and the difference in the degree to which the discharged droplets are dried during the idle time is reduced. Printing unevenness caused by the difference in the degree of drying can be further suppressed.

<Other embodiments>
The above embodiment describes an ink jet printer, and this description includes a printing apparatus, a recording apparatus, a liquid ejection apparatus, a printing method, a recording method, a liquid ejection method, a printing system, a recording system, and a computer system. Disclosure of a program, a storage medium storing the program, a display screen, a screen display method, a printed matter manufacturing method, and the like.

  Further, although an ink jet printer as an embodiment has been described as an example, the above embodiment is for facilitating understanding of the present invention, and is not intended to limit the present invention. The present invention can be changed and improved without departing from the gist thereof, and it is needless to say that the present invention includes equivalents thereof. In particular, the embodiments described below are also included in the present invention.

<About the printer>
In the above-described embodiment, the ink jet printer has been described. However, the present invention is not limited to this. For example, color filter manufacturing apparatus, dyeing apparatus, fine processing apparatus, semiconductor manufacturing apparatus, surface processing apparatus, three-dimensional modeling machine, liquid vaporization apparatus, organic EL manufacturing apparatus (especially polymer EL manufacturing apparatus), display manufacturing apparatus, film formation The same technology as that of the present embodiment may be applied to various liquid ejection devices to which inkjet technology such as a device and a DNA chip manufacturing device is applied. These methods and manufacturing methods are also within the scope of application. Even if this technology is applied to such a field, the liquid can be directly ejected (directly drawn) toward the object, so that higher-quality printing and recording than conventional methods can be performed. Image formation is possible.

<About ink>
Since the above-described embodiment is an ink jet printer, the ejected droplets have been described as ink. However, the liquid ejected from the nozzle is not limited to ink. For example, a liquid (including water) including a metal material, an organic material (particularly a polymer material), a magnetic material, a conductive material, a wiring material, a film forming material, electronic ink, a processing liquid, a gene solution, or the like may be used. .

<About head system>
In the above-described embodiment, an example in which a piezo element is used as a drive element for ejecting ink droplets has been described. However, the head system is not limited to this, and ink is ejected into droplets for printing (recording). ) Other printing (recording) methods for forming dot groups on the medium may be used. For example, a method in which ink is continuously ejected in droplets from a nozzle with a strong electric field between the nozzle and the acceleration electrode placed in front of the nozzle, and a printing information signal is given from the deflecting electrode while the ink droplet is flying, or recording, or A method that ejects ink droplets according to the print information signal without deflecting (electrostatic suction method), pressurizes the ink with a small pump, and mechanically vibrates the nozzle with a crystal oscillator etc. to force There may be employed a system in which ink droplets are ejected, a system in which ink is heated and foamed with microelectrodes in accordance with a print information signal, and ink droplets are ejected and recorded (thermal jet system).

<About the number of heads>
In the above embodiment, the number of heads constituting the headset is two, but may be three or more. Even if the number of heads is three or more, if upper end processing or normal processing is performed, an upper end region in which dots are formed by only one head or a normal region in which dots are formed by a plurality of heads is obtained. Exists. Even when the number of heads is three or more, if the same processing as in the above embodiment is performed, unevenness due to banding is less noticeable.

<Appearance of nozzle arrangement direction>
In the present invention, the “direction in which the nozzles are arranged” is not necessarily limited to the direction in which the physically formed discharge ports are arranged.
For example, the nozzles may be arranged obliquely when the pitches of the discharge ports adjacent to the opening diameter of the discharge ports (rear and back in the row) are arranged short. When the nozzles are arranged obliquely, the ink discharge timing is shifted with respect to the scanning speed of the carriage unit 30 in the X-axis direction so that the nozzles are apparently arranged in the Y-axis direction. it can. For example, in the scanning in the + X direction, the ejection port arranged at a position shifted by the length −d is corrected by delaying the ejection timing by td (= d / scanning speed).
Even in such a case, that is, when the nozzles are not physically arranged in the Y-axis direction and are virtually arranged in the Y-axis direction, the “direction in which the nozzles are arranged” of the present invention is defined. The same can be considered.

  6 ... ink cartridge, 10 ... paper, 20 ... transport unit, 21 ... paper feed roller, 22 ... transport motor, 23 ... transport roller, 24 ... platen, 25 ... paper discharge roller, 30 ... carriage unit, 31 ... carriage, 32 ... Carriage motor, 40 ... Head unit, 41 ... Head, 41A ... First nozzle group, 41B ... Second nozzle group, 42A ... First head (first nozzle array), 42B ... Second head (second nozzle array) , 42X ... virtual headset, 60 ... controller, 61 ... interface unit, 62 ... CPU, 63 ... memory, 64 ... unit control circuit, 65 ... drive signal generator, 65A ... first drive signal generator, 65B ... second Drive signal generation unit, 100... Inkjet printer.

Claims (3)

A transport operation for moving the print medium in the transport direction;
A first nozzle row having a plurality of nozzles for discharging droplets arranged in the transport direction; and a plurality of nozzles for discharging droplets arranged in the transport direction arranged upstream of the transport direction of the first nozzle row. A droplet ejection operation for ejecting droplets onto the print medium while scanning and moving the second nozzle row in a scanning direction intersecting the transport direction;
Is a droplet discharge method for forming an image composed of image units completed by n times of the droplet discharge operation by repeating a plurality of times,
The number m of continuous executions of the droplet discharge operation without using the second nozzle row after the droplet discharge operation is executed once using the first nozzle row and the second nozzle row is 0. A droplet discharge method characterized by being less than 5 n. When the average value of the number m is m0, the maximum value is m1, and the minimum value is m2,
(M1-m2) / m0 <1
The droplet discharge method according to claim 1, wherein: A transport unit that moves the print medium in the transport direction;
A first nozzle row having a plurality of nozzles for discharging droplets arranged in the transport direction;
A second nozzle row having a plurality of nozzles for discharging droplets arranged in the transport direction arranged downstream of the transport direction of the first nozzle row;
A scanning movement unit that scans and moves the first nozzle row and the second nozzle row in a scanning direction that intersects the transport direction;
A conveyance operation for moving the print medium in the conveyance direction and a droplet discharge operation for discharging droplets onto the print medium while scanning and moving the first nozzle row and the second nozzle row are alternately repeated. A droplet discharge apparatus for forming an image composed of a raster completed by n droplet discharge operations,
The droplet discharge operation in which the second nozzle row is not used in the droplet discharge operation after the droplet discharge operation using the first nozzle row and the second nozzle row in one droplet discharge operation. The droplet ejection apparatus is characterized in that the number of consecutive m is less than 0.5n.

Images