JP6724966B2 - Image forming apparatus and image forming method - Google Patents

Description

The present invention relates to an image forming apparatus and an image forming method.

Conventionally, as an example of an image forming apparatus, an inkjet printer that records (prints) an image by ejecting ink droplets toward various recording media such as paper and film to form a plurality of dots on the recording medium. Was known. An inkjet printer, for example, ejects ink droplets from each nozzle while moving (scanning) a head having a plurality of nozzles formed on a recording medium in the main scanning direction, thereby forming dots arranged in the main scanning direction of the recording medium. The dot forming operation (pass) for forming a row (raster line) and the carrying operation for moving (conveying) the recording medium in the sub-scanning direction intersecting the main scanning direction are alternately repeated. As a result, the dots are lined up in the main scanning direction and the sub scanning direction of the recording medium without a gap, and an image is formed on the recording medium.

In such an ink jet printer, the quality of the recorded image is improved as the number of passes is increased. Therefore, Patent Document 1 proposes an image forming method in which a print area is divided according to an image to be recorded on a recording medium, and an image is printed by changing the number of scans for each print area.

JP, 2010-17976, A

In the image forming method described in Patent Document 1, the recording medium is divided into a plurality of print areas, and the number of scans of only the area where banding easily occurs is increased. Here, while the head is printing across the print areas with different numbers of scans, it is necessary to always carry the medium based on the carry amount in the print area with the larger number of scans. As described above, since it is necessary to change the carry amount according to the number of passes, there is a problem that the printing speed is reduced.

The present invention has been made to solve at least a part of the problems described above, and can be realized as the following modes or application examples.

Application Example 1 An image forming apparatus according to this application example has a head having a plurality of nozzles capable of ejecting liquid onto a medium, a scanning unit for scanning the head in the main scanning direction, and a main scanning direction. A conveyance unit that conveys the medium in a sub-scanning direction that intersects with the head, the scanning unit, in the sub-scanning direction, a region between the end nozzle of the head and a nozzle of a predetermined distance is a predetermined region. And, when the medium is transported to a predetermined amount by using the transport unit and an image is formed on the medium, the number of scans for forming a dot row by using the nozzles included in the predetermined region is the predetermined region. The number of scans is greater than the number of scans for forming a dot row that does not use the included nozzles.

According to this application example, the image forming apparatus alternately repeats the scanning unit that scans the head having the nozzles arranged in the sub-scanning direction in the main scanning direction and the transporting unit that transports the medium in the sub-scanning direction. An image is formed on the medium. Specifically, the image forming apparatus is formed on the medium in the main scanning direction by moving the head in the main scanning direction while ejecting the liquid from the nozzle toward the medium (pass) and by the transporting unit. A dot row (raster line) is printed. The raster line can be formed in a plurality of passes by transporting the medium in the sub-scanning direction by a transporting device with a width narrower than the width of the head in which the nozzle is formed in the sub-scanning direction. An image is formed on the medium by printing the raster lines in the sub-scanning direction of the medium.

In the sub-scanning direction, when the area between the nozzle at the end of the head and the nozzle at the predetermined distance is set as the predetermined area, the image forming apparatus quantitatively conveys the medium by the conveying means and uses the nozzles included in the predetermined area. The raster line to be formed is formed by a larger number of scans than the raster line formed without using the nozzles included in the predetermined area.
Banding is the first pass where the liquid is ejected toward the medium due to misalignment of dots due to variations in the scanning means and the conveying means, and the liquid is ejected toward the medium after the medium is conveyed in the sub-scanning direction. It is easy to see at the boundary between the next pass and the next pass. That is, banding is easily visible on the raster line formed by the nozzles included in the predetermined area of the head in the sub-scanning direction. In this application example, the raster line formed by using the nozzles included in the predetermined area is formed by a larger number of scans than the raster line formed by using the nozzles included in the predetermined area. Moreover, the medium can be transported in a fixed amount in the sub-scanning direction regardless of the image data, and the printing speed is not reduced.

Application Example 2 In the image forming apparatus according to the application example described above, it is preferable that the number of scans for forming a dot row using the nozzles included in the predetermined region is at least three.

According to this application example, the medium can be conveyed in a fixed amount in the sub-scanning direction without depending on the image data, and the printing speed is not reduced.

Application Example 3 In the image forming apparatus described in the above application example, it is preferable that the predetermined amount is an integral multiple of the predetermined distance.

According to this application example, the medium can be conveyed in a fixed amount in the sub-scanning direction without depending on the image data, and the printing speed is not reduced.

Application Example 4 In the image forming apparatus described in the above application example, in the sub-scanning direction, a region from one end nozzle to a nozzle of a predetermined distance is the first region, and the other end nozzle is a predetermined distance. Is defined as the second region, and the region between the first region and the second region is defined as the third region, the average nozzle usage rate of the nozzles included in the first region is included in the third region. Is smaller than the average nozzle usage rate of the nozzles.

According to this application example, in the head of the image forming apparatus, in the sub-scanning direction, the predetermined area between the end nozzle on the one end side of the head and the nozzle of the predetermined distance is the first area and the end on the other end side of the head. The predetermined region between the partial nozzle and the nozzle at the predetermined distance is classified into three regions, that is, a second region and a region between the first and second regions is a third region. When liquid is ejected from a plurality of different nozzles by multiple passes to form a raster line in which dots are arranged in a line in the main scanning direction, one of the total number of dots forming the raster line is The ratio of the number of dots formed by a nozzle is called the nozzle usage rate of that nozzle. In this application example, the average nozzle usage rate of the nozzles included in the first area is smaller than the average nozzle usage rate of the nozzles included in the third area. In other words, in the raster line formed by a plurality of passes including the nozzles in the first area and the nozzles in the third area, the nozzles included in the first area on the one end side of the head where banding is easily recognized are formed. Since the number of the formed dots is smaller than the number of the dots formed by the nozzles included in the third area, it is difficult to visually recognize the banding.

Application Example 5 In the image forming apparatus according to the above application example, the average nozzle usage rate of the nozzles included in the second area is smaller than the average nozzle usage rate of the nozzles included in the third area. , Are preferred.

According to this application example, the average nozzle usage rate of the nozzles included in the second area is smaller than the average nozzle usage rate of the nozzles included in the third area. In other words, in a raster line formed by a plurality of passes including nozzles in the second area and nozzles in the third area, the nozzles included in the second area on the other end side of the head where banding is easily recognized are formed. Since the number of formed dots is smaller than the number of dots formed by the nozzles included in the third area, it is difficult to visually recognize banding.

Application Example 6 In the image forming apparatus according to the above application example, the average nozzle usage rate of the nozzles included in the first region and the second region that form the raster line that does not use the nozzle is the first nozzle It is preferable that the average nozzle usage rate of the nozzles included in the region is larger than the average nozzle usage rate of the nozzles included in the second region.

According to this application example, the average nozzle usage rate of the nozzles included in the first area and the second area for forming the raster line that does not use the nozzles is larger than the average nozzle usage rate of the nozzles included in the first area, It is larger than the average nozzle usage rate of the nozzles included in the second region. In other words, in one pass, the number of dots formed by the nozzles that form the raster lines that do not use the nozzles included in the first area and the second area is the number of dots formed by the nozzles in the first area. Since the number of dots is larger than the number of dots formed by the nozzles in the second area, it is difficult to visually recognize banding.

Application Example 7 It is preferable that the image forming apparatus described in the above application example has a plurality of recording modes including the recording mode for performing the image formation described in any one of Application Examples 1 to 6. ..

According to this application example, the image forming apparatus has, for example, a recording mode in which the image quality is emphasized, in addition to the recording mode in which the image quality and the printing speed are compatible with each other. Also, since the recording mode and the like that emphasize the printing speed are provided, it is possible to provide an image forming apparatus that meets a wide variety of user requests.

Application Example 8 An image forming method of an image forming apparatus according to this application example includes a scanning step of scanning a head having a plurality of nozzles in a main scanning direction to eject a liquid onto a medium, and the main scanning direction. A carrying step of carrying the medium in a crossing sub-scanning direction, the scanning step and the carrying step in which, in the sub-scanning direction, a region from an end nozzle of the head to a nozzle of a predetermined distance is a predetermined region. When a medium is transported to a predetermined amount by using a process and an image is formed on the medium, the number of scans for forming a dot row using the nozzles included in the predetermined area is the number included in the predetermined area. The number of scans is greater than the number of scans for forming a dot row that does not use nozzles.

According to this application example, the image forming method of the image forming apparatus includes a scanning step of moving the head in the main scanning direction while ejecting the liquid from the nozzle toward the medium, and a conveying step of conveying the medium in the sub-scanning direction. , Are alternately repeated to form an image on the medium. Specifically, in the image forming method, a dot row (raster line) formed along the main scanning direction is printed on the medium by a scanning step and a carrying step. The raster line can be formed by a plurality of scans by carrying the medium in the carrying process in the sub-scanning direction with a width narrower than the width of the head in which the nozzles are formed in the sub-scanning direction. An image is formed on the medium by printing this raster line in the sub-scanning direction of the medium.

In the sub-scanning direction, when the area between the end nozzle of the head and the nozzle of the predetermined distance is set as the predetermined area, the image forming method includes the raster line formed by using the nozzles included in the predetermined area in the predetermined area. The number of scans is greater than the number of raster line scans that are performed without using the nozzles.
Banding is the first scanning step of ejecting liquid toward the medium due to misalignment of dots due to variations in the scanning means and the conveying means, and the liquid toward the medium after the conveying step of conveying the medium in the sub-scanning direction. It is easily visible at the boundary between the next scanning step for discharging and the next scanning step. That is, banding is easily visible on the raster line formed by the nozzles included in the predetermined area of the head in the sub-scanning direction. In this application example, the raster lines formed by using the nozzles included in the predetermined area are formed in more scanning steps than the raster lines formed without using the nozzles included in the predetermined area. Moreover, the medium can be transported in a fixed amount in the sub-scanning direction regardless of the image data, and the printing speed is not reduced.

1 is a block diagram and a perspective view showing an overall configuration of an inkjet printer as an image forming apparatus according to Embodiment 1. FIG. Explanatory drawing which shows an example of an arrangement of nozzles. Sectional drawing which shows the internal structure of a head. The figure which shows the nozzle row and the usage rate of a nozzle. The figure explaining the method of forming a raster line by multiple passes. Explanatory drawing at the time of showing the moving average of a nozzle usage rate by linear approximation. The figure explaining the method of forming a raster line by multiple passes. 3 is a block diagram and a perspective view showing the overall configuration of an inkjet printer as an image forming apparatus according to Embodiment 2. FIG. Explanatory drawing which shows an example of the arrangement of the nozzle with which the head is equipped. Explanatory drawing which describes a headset as a virtual headset. FIG. 6 is a diagram illustrating a method of forming a raster line by a plurality of passes using two heads.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In each of the following drawings, the scale of each layer and each member is different from the actual scale in order to make each layer and each member recognizable.
In addition, in FIG. 1, FIG. 3, and FIG. 8, for convenience of description, an X-axis, a Y-axis, and a Z-axis are illustrated as three axes orthogonal to each other, and the tip end side of the arrow indicating the axial direction is the “+ side”. , And the base end side is defined as “− side”. In the following, the direction parallel to the X axis is the “X axis direction” or the “main scanning direction”, the direction parallel to the Y axis is the “Y axis direction” or the “sub scanning direction”, and the direction parallel to the Z axis is the direction. It is called "Z-axis direction".

(Embodiment 1)
<Image forming device>
FIG. 1A is a block diagram showing the overall configuration of an inkjet printer 100 as an image forming apparatus according to the first embodiment, and FIG. 1B is a perspective view.
First, the basic configuration of the inkjet printer 100 will be described.

<Basic configuration of inkjet printer>
The inkjet printer 100 includes a transport unit 20 as a transport unit, a carriage unit 30 as a scanning unit, a head unit 40, and a control unit 60. The inkjet printer 100 that receives print data (image forming data) from the computer 110 that is an external device controls each unit (the transport unit 20, the carriage unit 30, the head unit 40) by the control unit 60. The control unit 60 controls each unit based on the print data received from the computer 110, and prints an image (image formation) on the paper 10 as a medium.

The carriage unit 30 is a scanning unit for scanning (moving) the head 41 in a predetermined moving direction (X-axis direction shown in FIG. 1B, hereinafter referred to as main scanning direction). The carriage unit 30 has a carriage 31, a carriage motor 32, and the like. The carriage 31 holds a head 41 having a plurality of nozzles 43 (see FIGS. 2 and 3) capable of ejecting ink as a liquid onto the paper 10, and an ink cartridge 6. The ink cartridge 6 stores the ink ejected from the head 41 and is detachably attached to the carriage 31. The carriage 31 can reciprocate in the main scanning direction and is driven by a carriage motor 32. As a result, the head 41 is moved in the main scanning direction (±X axis direction).

The transport unit 20 is a transport unit for transporting (moving) the paper 10 in the sub-scanning direction (Y direction shown in FIG. 1B) intersecting the main scanning direction. The transport unit 20 includes a paper feed roller 21, a transport motor 22, a transport roller 23, a platen 24, and a paper discharge roller 25. The paper feed roller 21 is a roller for feeding the paper 10 inserted into a paper insertion port (not shown) into the inkjet printer 100. The transport roller 23 is a roller that transports the paper 10 fed by the paper feed roller 21 to a printable area, and is driven by the transport motor 22. The platen 24 supports the paper 10 being printed. The paper discharge roller 25 is a roller that discharges the paper 10 to the outside of the printer, and is provided on the downstream side in the sub-scanning direction with respect to the printable area.

The head unit 40 is for ejecting ink as droplets (hereinafter also referred to as ink droplets) onto the paper 10. The head unit 40 includes a head 41 having a plurality of nozzles 43 (see FIG. 2). Since the head 41 is mounted on the carriage 31, when the carriage 31 moves in the main scanning direction, the head 41 also moves in the main scanning direction. Then, by ejecting ink while the head 41 is moving in the main scanning direction, a row of dots (raster line) along the main scanning direction is formed on the paper 10.

The control unit 60 is for controlling the inkjet printer 100. The control unit 60 includes an interface unit 61, a CPU (Central Processing Unit) 62, a memory 63, a unit control circuit 64, and a drive signal generation unit 65. The interface unit 61 transmits and receives data between the computer 110, which is an external device, and the inkjet printer 100. The CPU 62 is an arithmetic processing device for controlling the entire printer. The memory 63 is for securing an area for storing a program of the CPU 62, a work area, and the like, and has a storage element such as a RAM (Random Access Memory) and an EEPROM (Electrically Erasable Programmable Read-Only Memory).

The CPU 62 controls each unit (the transport unit 20, the carriage unit 30, the head unit 40) via the unit control circuit 64 according to the program stored in the memory 63. The drive signal generation unit 65 generates a drive signal for driving the piezoelectric element 45 (see FIG. 3) that causes the nozzles 43 to eject ink.

When performing printing, the control unit 60 moves the head 41 in the main scanning direction by the carriage 31 as a scanning unit while ejecting ink from the nozzles 43 toward the paper 10 as a medium. This operation is called "pass" or "scanning process". As a result, a row of dots (raster line) formed along the main scanning direction is printed on the paper 10. Next, the control unit 60 conveys the sheet 10 in the sub-scanning direction by the conveyance unit 20 as a conveyance unit. This operation is called a "conveyance process". By the control unit 60 repeating the scanning process and the transporting process, the raster lines are arranged in the sub-scanning direction of the paper 10, and an image is formed on the paper 10. In this embodiment, one raster line is formed in a plurality of passes by transporting the paper 10 in the sub-scanning direction with a width narrower than the width of the head 41 in the sub-scanning direction. This is called n-pass (n: integer) printing, and the n-th pass is called "pass n".

<Structure of head>
FIG. 2 is an explanatory diagram showing an example of the arrangement of the nozzles 43 included in the head 41. FIG. 3 is a cross-sectional view showing the internal configuration of the head 41.
As shown in FIG. 2, the head 41 is provided with eight nozzle rows, and the ejection ports of these nozzles 43 are opened on the lower surface of the head 41 (the surface on the −Z axis side in FIG. 1). A nozzle plate 42 is provided. The eight nozzle rows are respectively dark cyan (C), dark magenta (M), yellow (Y), dark black (K), light cyan (LC), light magenta (LM), light black (LK), and polar. Light black (LLK) ink is ejected.

In each nozzle row, for example, 180 nozzles (nozzle #1 to nozzle #180) arranged in the sub-scanning direction are provided at a nozzle pitch of 180 dpi (dots per inch). In FIG. 2, the nozzle 43 on the downstream side in the sub-scanning direction is given a smaller number #n (n=1 to 180). Note that the number of nozzle rows and the types of ink are examples, and the present invention is not limited to these.

As shown in FIG. 3, the head 41 includes a nozzle plate 42, and nozzles 43 are formed in the nozzle plate 42. A cavity 47 communicating with the nozzle 43 is formed on the upper side (+Z axis side) of the nozzle plate 42 and at a position facing the nozzle 43. Then, the ink stored in the ink cartridge 6 is supplied to the cavity 47 of the head 41.

Above the cavity 47 (+Z-axis side), a vibration plate 44 that vibrates in the vertical direction (±Z-axis direction) to expand and contract the volume inside the cavity 47, and a vibration plate that expands and contracts in the vertical direction. A piezoelectric element 45 as a pressurizing means for vibrating 44 is provided. The piezoelectric element 45 expands and contracts in the vertical direction to vibrate the vibration plate 44, and the vibration plate 44 expands and contracts the volume inside the cavity 47, so that the cavity 47 is pressurized. As a result, the pressure inside the cavity 47 fluctuates, and the ink supplied into the cavity 47 is ejected through the nozzles 43.

When the head 41 receives the drive signal for controlling and driving the piezoelectric element 45 generated by the drive signal generation unit 65 (see FIG. 1), the piezoelectric element 45 expands and the vibration plate 44 is placed in the cavity 47. Reduce volume. As a result, the reduced volume of ink is ejected as ink droplets 46 from the nozzles 43 of the head 41. In the present embodiment, the pressurizing means using the longitudinal vibration type piezoelectric element 45 has been illustrated, but the present invention is not limited to this. For example, a bending-deformation type piezoelectric element in which a lower electrode, a piezoelectric layer, and an upper electrode are laminated and formed may be used. Further, a so-called electrostatic actuator or the like may be used as the pressure generating means, in which static electricity is generated between the vibrating plate and the electrode, and the vibrating plate is deformed by electrostatic force to eject ink droplets from the nozzles. Further, the head may have a configuration in which bubbles are generated in the nozzle using a heating element and the ink is ejected as ink droplets by the bubbles.

<Nozzle row and nozzle usage rate>
FIG. 4 is a diagram showing nozzle rows and nozzle usage rates. Before describing the raster line forming method, the nozzle row and the nozzle usage rate will be described with reference to FIG. In the following description, for simplification of the description, the head 41 is provided with one nozzle row 48 formed of ten nozzles (nozzle #1 to nozzle #10), and only one color ink is used. Printing shall be performed.

FIG. 4A shows the relationship between the position of each nozzle and its area. As shown in FIG. 4A, the nozzle row 48 is provided with 10 nozzles arranged in the sub-scanning direction, and in the sub-scanning direction, a portion between the end nozzle of the head 41 and a nozzle of a predetermined distance is provided. It is a predetermined area. In this embodiment, two nozzles (nozzle numbers #1 and #2) on the downstream side of the head 41 in the sub-scanning direction and two nozzles (nozzle numbers #9 and #10) on the upstream side of the head 41 in the sub-scanning direction. ) And are located in a predetermined area. The head 41 is divided into three regions, and a region from one end nozzle to a nozzle of a predetermined distance (a predetermined region on the downstream side in the sub-scanning direction) is a first region, and the other end nozzle is a nozzle of a predetermined distance. The area (a predetermined area on the upstream side in the sub-scanning direction) is called the second area, and the area between the first area and the second area is called the third area.

FIG. 4B is a diagram showing the ratio of ink droplets ejected from each nozzle in one pass as the nozzle usage rate. As described above, a row of dots (raster line) formed along the main scanning direction is printed on the paper 10 by a plurality of passes. Nozzles with a nozzle usage rate of 50% (nozzle #3 to nozzle #8) eject ink drops that form half of all dots forming one raster line in one pass. doing. For example, when one raster line is formed with 1000 dots, the nozzle #3 ejects an ink droplet that forms 500 dots in one pass.

The average nozzle usage rate of the nozzles (nozzle #1 and nozzle #2) included in the first area is set to be smaller than the average nozzle usage rate of the nozzles (nozzle #3 to nozzle #8) included in the third area. There is. The average nozzle usage rate of the nozzles (nozzle #9 and nozzle #10) included in the second area is set to be smaller than the average nozzle usage rate of the nozzles (nozzle #3 to nozzle #8) included in the third area. There is.

Specifically, the nozzle usage rate of the nozzle #1 is 12.5%, the nozzle usage rate of the nozzle #2 is 37.5%, and the average nozzle usage rate of the nozzles included in the first region is 25%. Become. Similarly, the nozzle usage rate of the nozzle #9 is 37.5%, the nozzle usage rate of the nozzle #10 is 12.5%, and the average nozzle usage rate of the nozzles included in the second region is 25%. Become. The nozzle usage rate from the nozzle #3 to the nozzle #8 is 50%, and the average nozzle usage rate of the nozzles included in the third region is 50%. Therefore, the average nozzle usage rate of the nozzles #1 and #2 included in the first area is smaller than the average nozzle usage rate of the nozzles #3 to #8 included in the third area and included in the second area. The average nozzle usage rates of the nozzles #9 and #10 are smaller than the average nozzle usage rates of the nozzles #3 to #8 included in the third region.

<Image forming method>
Next, an image forming method of the image forming apparatus will be described.
FIG. 5 is a diagram illustrating a method of forming a raster line with a plurality of passes. In FIG. 5, the position of the head 41 (see FIG. 1) is represented by the nozzle number shown in FIG. FIG. 5 shows a path (scanning process) in which the head 41 is moved in the main scanning direction while ejecting ink from the nozzles (nozzle #1 to nozzle #10) from the upper end of the paper 10, and the paper 10 is moved by the transport unit 20. The relative position between the paper 10 and the head 41 (nozzle number) in the sub-scanning direction is shown when the conveyance (conveyance step) of feeding a fixed amount (four nozzles in this embodiment) in the scanning direction is repeated six times. There is. That is, in FIG. 5, the nozzle (head 41) is depicted as moving with respect to the sheet 10, but the positional relationship between the nozzle (head 41) and the sheet 10 may be relatively changed. The head 41) may move, the paper 10 may move, or both the nozzle (head 41) and the paper 10 may move. In the present embodiment, a case where the paper 10 is conveyed in the sub-scanning direction will be described as an example. Since the nozzles (heads 41) in each pass are shown obliquely in the main scanning direction so as not to overlap, the positional relationship between the paper 10 and the nozzles (heads 41) in the main scanning direction does not make sense. Absent.

Next to each nozzle number of each pass, the nozzle usage rate corresponding to each nozzle described in FIG. 4 is shown. Further, on the right side of the sheet 10, the total nozzle usage rate in n passes for the raster line formed in n passes (n=2 or 3) is shown. From the nozzle usage rate corresponding to each pass and each nozzle, for example, in the raster line L7, 50% of the total number of dots forming the raster line L7 by the nozzle #7 of pass 1 is formed, and It can be seen that the remaining 50% of dots are formed by the nozzle #3. It should be noted that the upper end portion of the raster lines L1 to L6 where the total nozzle usage rate is less than 100% is subjected to the upper end processing by minute feeding of the paper 10, but since this upper end processing is a well-known technique, its description is omitted. Omit it.

The raster line of the portion A of the normal printing unit is at least one of the nozzles #1, #2, #9, and #10 included in the predetermined region (the first region and the second region shown in FIG. 4A). Nozzles are used and are formed using three different nozzles in three passes (control by three nozzles). The raster line of the part B is formed by using two different nozzles by two passes without using the nozzles #1, #2, #9, #10 included in the predetermined area (two nozzles are used). control). That is, the number of scans for forming a raster line using the nozzles #1, #2, #9, and #10 included in the predetermined region is at least 3 passes, and the nozzles #1 and #1 included in the predetermined region are included. This is larger than the number of scans for forming a raster line that does not use #2, #9, and #10.
Here, the partial overlap control is a method of dispersing dots formed by the same nozzle, and a method of printing such that a region printed in a certain pass overlaps a part of the region in another pass. .. As an example, one raster line is formed by using a plurality of different nozzles in a plurality of passes.
Further, nozzles (for example, nozzle #3 and nozzle #7) that form a raster line (for example, raster line L11) that does not use the nozzles #1, #2, #9, and #10 included in the first region and the second region. ) Is larger than the average nozzle usage rate of the nozzles (nozzle #1 and nozzle #2) included in the first area, and the average nozzle usage rate of the nozzles (nozzle #9 and nozzle #10) included in the second area. Greater than average nozzle usage.

Next, a method of forming the raster line L7 to the raster line L16, which is a normal printing portion, will be described.
First, the sheet 10 is conveyed to a predetermined position in the conveying step. In the scanning process of pass 1, dots are formed from the raster line L1 to the raster line L10. Here, the raster lines L7 to L10 that are the normal printing units will be described. On the raster line L7, 50% of the total number of dots forming the raster line is formed by the ink droplets ejected from the nozzle #7. Similarly, 50% of the dots are formed by the nozzle #8 on the raster line L8, 37.5% of the dots are formed by the nozzle #9 on the raster line L9, and the nozzle #10 is formed by the nozzle #10 on the raster line L10. 12.5% dots are formed.

Next, in the carrying step, the paper 10 is carried in the sub-scanning direction by a distance corresponding to four nozzles. In this embodiment, the nozzles #1 and #2 included in the first area or the nozzles #9 and #10 included in the second area are conveyed by a distance corresponding to an integral multiple of four nozzles. That is, the sheet 10 is conveyed by a distance that is an integral multiple of the predetermined distance from one end to the other end of the plurality of nozzles included in the predetermined area in the sub-scanning direction. In the scanning process of pass 2, dots are formed from the raster line L5 to the raster line L14. Here, the raster lines L7 to L14, which are the normal printing units, will be described. The remaining 50% of the total number of dots forming the raster line is formed on the raster line L7 by the ink droplets ejected from the nozzle #3. Similarly, the raster line L8 is formed by the nozzle #4 on the raster line L8. The remaining 50% of dots are formed. On the raster line L7 and the raster line L8, all dots (100%) on the raster line are formed by pass 1 and pass 2.

On the raster line L9, 50% dots are formed by the nozzle #5, and 87.5% dots are formed together with the dots formed in pass 1. On the raster line L10, 50% dots are formed by the nozzle #6, and 62.5% dots are formed together with the dots formed in pass 1.

In the raster line L11, 50% of the total number of dots forming the raster line is formed by the nozzle #7. Similarly, 50% dots are formed by the nozzle #8 on the raster line L12, 37.5% dots are formed by the nozzle #9 on the raster line L13, and nozzle #10 is formed on the raster line L14. Thus, 12.5% of dots are formed.

Next, in the carrying step, the paper 10 is carried in the sub-scanning direction by a distance corresponding to four nozzles. In the scanning process of pass 3, dots are formed from the raster line L9 to the raster line L18. Here, up to the raster line L16 will be described. In the raster line L9, the remaining 12.5% of the total number of dots forming the raster line is formed by the ink droplets ejected from the nozzle #1, and similarly, in the raster line L10, the nozzle #1 is formed. By 2 the remaining 37.5% of the dots are formed. As a result, in the raster line L9 and the raster line L10, all dots (100%) are formed on the raster line by pass 1 to pass 3.

The remaining 50% of the total number of dots forming the raster line is formed on the raster line L11 by the ink droplets ejected from the nozzle #3. Similarly, the raster line L12 is formed by the nozzle #4 on the raster line L12. The remaining 50% of dots are formed. In the raster line L11 and the raster line L12, all dots (100%) are formed on the raster line by pass 2 and pass 3.

On the raster line L13, 50% dots are formed by the nozzle #5, and 87.5% dots are formed together with the dots formed in pass 2. On the raster line L14, 50% dots are formed by the nozzle #6, and 62.5% dots are formed together with the dots formed in pass 2.

On the raster line L15, 50% of the total number of dots forming the raster line is formed by the nozzle #7. Similarly, 50% of dots are formed on the raster line L16 by the nozzle #8.

Next, in the carrying step, the paper 10 is carried in the sub-scanning direction by a distance corresponding to four nozzles. In the scanning process of pass 4, dots are formed from the raster line L13 to the raster line L22. Here, up to the raster line L16 will be described. The remaining 12.5% of the total number of dots forming the raster line is formed on the raster line L13 by the ink droplets ejected from the nozzle #1, and similarly, on the raster line L14, the nozzle #1 is formed. By 2, the remaining 37.5% of dots are formed. As a result, in the raster line L13 and the raster line L14, all dots (100%) are formed on the raster line by pass 2 to pass 4.

The remaining 50% of the total number of dots forming the raster line is formed on the raster line L15 by the ink droplets ejected from the nozzle #3, and similarly, on the raster line L16, the remaining dot is formed by the nozzle #4. 50% dots are formed. In the raster line L15 and the raster line L16, all dots (100%) are formed on the raster line by pass 3 and pass 4. After that, by repeating the scanning process and the carrying process, raster lines on which all dots are formed are aligned in the sub-scanning direction, and an image is formed on the paper 10.

According to this image forming method, a raster line using at least one nozzle of the nozzles #1, #2, #9, and #10 included in the predetermined area (first area and second area) is formed. The number of scans required for scanning is greater than the number of scans required to form a raster line that does not use the nozzles #1, #2, #9, and #10 included in the predetermined area.

More specifically, for example, the raster line L9 includes the nozzle #9 included in the second area in pass 1, the nozzle #5 included in the third area in pass 2, and the nozzle # included in the first area in pass 3. 1 and are used. That is, the raster line that uses at least one of the nozzles #1, #2, #9, and #10 included in the predetermined area (first area and second area) has three passes (control by three nozzles). Is formed of.
For example, the raster line L8 is formed using the nozzle #8 included in the third area in pass 1 and the nozzle #4 included in the third area in pass 2. That is, the raster lines that do not use the nozzles #1, #2, #9, and #10 included in the predetermined area (first area and second area) are formed by two passes (control by two nozzles).

Banding (horizontal stripe) is easily visible at the boundary in the sub-scanning direction between the printing performed by the first pass and the printing performed by the second pass. That is, banding is easily visible on the raster line formed using at least one of the nozzles #1, #2, #9, and #10 included in the predetermined area. In this embodiment, the raster line that uses at least one of the nozzles #1, #2, #9, and #10 included in the predetermined area is the nozzles #1, #2, and #9 included in the predetermined area. , #10 are formed by a larger number of scans than the raster line that does not use #10, #10, so that banding is less visible.

Further, the raster line L9 is located at the boundary between the printing performed by the pass (pass 1 and pass 2) performed first and the printing performed by the pass (pass 3) performed later, and the raster line L8. And banding is easily visible between the raster line L9. In the present embodiment, the raster line L9 formed by control with three nozzles forms 37.5% of the total number of dots forming the raster line with the nozzle #9 of pass 1, and similarly, 50% of the dots are formed by the second nozzle #5, and 12.5% of the dots are formed by the nozzle #1 of pass 3. Even in a situation where banding may occur in pass 3 due to misalignment of the sheet 10 or the like, the number of dots formed in pass 3 is 12.5% of the total number of dots forming the raster line L9. Is difficult to see.

The image forming apparatus (inkjet printer 100) of the present embodiment includes a plurality of recording modes including a recording mode that achieves both a printing speed for forming an image by the above-described image forming method and image quality. For example, by providing a recording mode in which image quality has the highest priority, a recording mode in which the printing speed has the highest priority, a recording mode in which ink consumption is suppressed, and the like, it is possible to meet a wide variety of print requests from users.

The nozzle usage rate is not limited to the rate shown in this embodiment.
FIG. 6 is an explanatory diagram when the moving average of the nozzle usage rate is shown by linear approximation.
In the diagram of the nozzle usage rate shown in FIG. 4B, the number of nozzles is 10 so that it is shown in a stepped shape. However, when the number of nozzles is n (for example, n=180), As shown in FIG. 6A, FIG. 4B can be represented by a trapezoidal shape in which moving averages of nozzle usage rates are connected by straight lines.

FIG. 6B is a diagram showing another example of the nozzle usage rate. As shown in FIG. 6B, the third region is further divided into three, and the central region is the central portion, the central portion and the first region are the first intermediate portion, and the central portion and the second region are the central portion. Is the second intermediate portion. The average nozzle usage rate of the nozzles located in the first middle portion is higher than the average nozzle usage rate of the nozzles located in the first area, and lower than the average usage rate of the nozzles located in the central portion. .. The average nozzle usage rate of the nozzles located in the second intermediate portion is higher than the average nozzle usage rate of the nozzles located in the second area, and lower than the average usage rate of the nozzles located in the central portion. ..

As described above, by providing the first intermediate portion and the second intermediate portion, the amount of change (gradient) in the moving average of the nozzle usage rate in the first region and the second region becomes gentle. In the image formed by the above-described image forming method by using the nozzle usage rate shown in (4), banding (density unevenness) caused by landing deviation of ink droplets in the main scanning direction becomes less visible. The nozzle usage rate shown in FIG. 4B is an example, and the present invention is not limited to this. The area indicating the nozzle position may be further subdivided, or the nozzle usage rate may be changed in a curved shape.

Further, in the present embodiment, it is described that the raster line is formed by two passes or three passes, but the present invention is not limited to this.
FIG. 7 is a diagram illustrating a method of forming a raster line by a plurality of passes (4 passes or 3 passes). FIG. 7 shows a path (scanning process) in which the head 41 is moved in the main scanning direction while ejecting ink from the nozzles (nozzle #1 to nozzle #10) from the upper end of the paper 10, and the paper 10 is moved by the transport unit 20. The relative position between the paper 10 and the head 41 (nozzle number) in the sub-scanning direction is shown when the conveyance (conveying step) of feeding three nozzles in the scanning direction is repeated six times.

In the head 41 of the image forming method of FIG. 7, the nozzle #1 belongs to the first region (predetermined region), the nozzle #10 belongs to the second region (predetermined region), and the nozzles #2 to #9 belong to the third region. .. Further, the nozzle usage rate of each nozzle is set to 16.7% for nozzle #1 and nozzle #10, and 33.3% for nozzle #2 to nozzle #9.

As shown in FIG. 7, by using the carrying process of carrying the paper 10 in the sub-scanning direction by a distance corresponding to three nozzles and the scanning process repeatedly, the nozzles are used in the normal printing unit after the raster line L8. A raster line with a rate of 100% is formed. Note that the upper end portion from the raster line L1 to the raster line L7 where the total nozzle usage rate is less than 100% is subjected to the upper end processing by minutely feeding the paper 10.

The raster line of the C portion of the normal printing portion uses the nozzle #1 and the nozzle #10 included in the predetermined area, and is formed by using four different nozzles by four passes (control by four nozzles). .. The raster line of the part D is formed by using three different nozzles in three passes without using the nozzles #1 and #10 included in the predetermined area (control by three nozzles). That is, the number of scans for forming a raster line using the nozzle #1 and the nozzle #10 included in the predetermined area is 4 passes (at least 3 passes), and the nozzle #1 and the nozzle included in the predetermined area are included. More than the number of scans for forming a raster line without using #10. As described above, the number of scans for forming the raster line may be increased by changing the distance (the number of nozzles) to be carried in the carrying process and the nozzle usage rate of each nozzle. Thereby, the image quality can be further improved.

As described above, according to the image forming apparatus (inkjet printer 100) of this embodiment, the following effects can be obtained.
The inkjet printer 100 includes a path (scanning step) for quantitatively moving the head 41 in the main scanning direction by the scanning unit while ejecting ink from the nozzles to the paper 10, and a conveyance for conveying the paper 10 in the sub scanning direction. By alternately repeating the means (conveying step), the raster line along the main scanning direction is formed by a plurality of passes.
The raster lines formed by using the nozzles #1, #2, #9, #10 included in the predetermined area of the head 41 are three passes, and the nozzles #1, #2, #9, #10 included in the predetermined area are formed. The raster line formed without using is formed by two passes. The banding (horizontal stripe) is easily visible on the raster line formed by the nozzles #1, #2, #9 and #10 included in the predetermined area of the head 41, but the nozzles #1, #2 included in the predetermined area are visible. A raster line formed by using #9 and #10 is formed by a larger number of scans than a raster line formed without using the nozzles #1, #2, #9 and #10 included in a predetermined area. Therefore, the image quality can be improved. Further, since the paper 10 is conveyed in a fixed amount, the printing speed does not decrease due to the different number of scans in the image. Therefore, it is possible to provide an image forming apparatus (inkjet printer 100) and an image forming method that are compatible with the improvement of image quality and the improvement of printing speed.

Further, the average nozzle usage rate of the nozzles #1, #2, #9, and #10 included in the first region and the second region on both ends of the head 41 is the third nozzle between the first region and the second region. It is smaller than the average nozzle usage rate from nozzle #3 to nozzle #8 included in the area. Further, in one pass, nozzles #3, #4, #7, #8 that form a raster line that does not use the nozzles #1, #2, #9, #10 included in the first region and the second region. The number of dots formed in step 1 is larger than the number of dots formed by the nozzles in the first area and the second area. When the raster line is formed by a plurality of passes, the banding is formed by the nozzles #1, #2, #9 and #10 included in the first region and the second region, which are the end portions of the head 41 where the banding is easily recognized. Since the number of the formed dots is smaller than the number of the dots formed by the nozzles #3 to #8 included in the third area, it is difficult to visually recognize the banding.

The ink jet printer 100 has a plurality of recording modes including a recording mode that achieves both print speed and image quality, a recording mode that gives top priority to image quality, a recording mode that gives top priority to print speed, and ink consumption is suppressed. Since it is equipped with a recording mode, it is possible to meet a wide variety of printing requests from users.

(Embodiment 2)
The inkjet printer 200 as an image forming apparatus according to the second embodiment is different from the inkjet printer 100 of the first embodiment in that it has two heads.
FIG. 8 is a block diagram and a perspective view showing the overall configuration of an inkjet printer as an image forming apparatus according to the second embodiment. FIG. 9 is an explanatory diagram showing an example of the arrangement of nozzles. FIG. 10 is an explanatory diagram showing the headset as a virtual headset. FIG. 11 is a diagram illustrating a method of forming a raster line in multiple passes.
The image forming apparatus according to this embodiment will be described with reference to these drawings. The same components as those of the first embodiment are designated by the same reference numerals, and the duplicated description will be omitted.

First, a schematic configuration of the inkjet printer 200 as an image forming apparatus will be described.
The head unit 40 includes a head 241 having a plurality of nozzles. Since the head 241 is mounted on the carriage 31, when the carriage 31 moves in the main scanning direction, the head 241 also moves in the main scanning direction. Then, by ejecting ink while the head 241 is moving in the main scanning direction, a row of dots (raster line) along the main scanning direction is formed on the paper 10. The head 241 includes a first nozzle group 241A as a first head and a second nozzle group 241B as a second head.

The control unit 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 generation unit 65A generates a drive signal for driving the piezoelectric element 45 (see FIG. 3) that ejects ink from the first nozzle group 241A serving as the first head. The second drive signal generator 65B generates a drive signal for driving the piezoelectric element 45 that ejects ink from the second nozzle group 241B serving as the second head.

<Nozzle row and headset>
FIG. 9 is an explanatory diagram showing an example of an array of nozzles provided in the head 241. The head 241 includes a first nozzle group 241A as a first head and a second nozzle group 241B as a second head. Each nozzle group is provided with eight nozzle rows, and the ejection ports of these nozzles are opened on the lower surface of the head 241 (the surface in the −Z axis direction in FIG. 8).

The first nozzle group 241A is provided downstream of the second nozzle group 241B in the sub scanning direction. The first nozzle group 241A and the second nozzle group 241B are provided such that the positions of the four nozzles in the sub-scanning direction overlap. For example, the position of the nozzle #177A of the first nozzle group 241A is the same as the position of the nozzle #1B of the second nozzle group 241B in the sub-scanning direction. A combination of nozzle rows that eject the same ink (ink having the same composition) between the first nozzle group 241A and the second nozzle group 241B is called a "headset".

FIG. 10 is an explanatory diagram showing the headset as a virtual headset. In the following description, for simplification of the description, a nozzle row 242A as a first head formed of 12 nozzles (nozzle #1A to nozzle #12A) and 12 nozzles (nozzle #1B to nozzle #1B). It is assumed that a headset is provided which is combined with the nozzle row 242B as the second head formed by the nozzle #12B), and printing is performed using only one color ink.

The four nozzles (nozzle #9A to nozzle #12A) on the upstream side in the sub-scanning direction of the nozzle row 242A and the four nozzles (nozzle #1B to nozzle #4B) on the downstream side in the sub-scanning direction of the nozzle row 242B are , The positions in the sub-scanning direction overlap. In the following description, these four nozzles in each nozzle row are referred to as overlapping nozzles.

Each nozzle of the nozzle row 242A is indicated by a circle, and each nozzle of the nozzle row 242B is indicated by a triangle. Further, the nozzles that do not eject ink (that is, the nozzles that do not form dots) are hatched.
Here, among the overlapping nozzles of the nozzle row 242A, ink is ejected from the nozzle #9A and nozzle #10A, and ink is not ejected from the nozzle #11A and nozzle #12A. Further, among the overlapping nozzles in the nozzle row 242B, 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 center part of FIG. 10, one head is provided with two heads of a nozzle row 242XA as a first head and a nozzle row 242XB as a second head excluding nozzles that do not eject ink. Virtual headset 242X. In the following description, the state of dot formation will be described using one virtual headset 242X, instead of drawing two heads separately. Further, the nozzle row 242XA as the first head of the headset 242X is newly assigned with the nozzle numbers A1 to A10, and the nozzle row 242XB as the second head is newly provided with the nozzle numbers B1 to B10. Will be described.

The diagram on the right side of FIG. 10 shows the dot positions formed by the nozzle row 242XA as the first head and the nozzle row 242XB as the second head. In the inkjet printer 200 of the present embodiment, the nozzle row 242XA forms dots at odd dot positions of each raster line in the main scanning direction, and the nozzle row 242XB of the second head forms even dots of each raster line in the main scanning direction. Form dots at positions. It should be noted that dots may be formed at even dot positions by the nozzle row 242XA of the first head and dots at odd dot positions by the nozzle row 242XB of the second head.

<Image forming method>
FIG. 11 is a diagram illustrating a method of forming a raster line by a plurality of passes using two heads. In FIG. 11, the position of the headset 242X (see FIG. 10) is represented by the nozzle number shown in FIG. FIG. 11 shows a path (scanning process) in which the headset 242X is moved in the main scanning direction while ejecting ink from the nozzles (nozzles A1 to B10) from the upper end of the paper 10, and the paper 10 is sub-scanned by the transport unit 20. 4 shows the relative positions of the sheet 10 and the nozzles (nozzle numbers) provided in the headset 242X in the sub-scanning direction when the conveyance (conveyance step) of feeding four nozzles in the direction is repeated seven times. That is, in FIG. 11, the nozzle (headset 242X) is depicted as moving with respect to the sheet 10, but the positional relationship between the nozzle (headset 242X) and the sheet 10 may be relatively changed. The nozzle (headset 242X) may move, the sheet 10 may move, or both the nozzle (headset 242X) and the sheet 10 may move. In the present embodiment, a case where the paper 10 is conveyed in the sub-scanning direction will be described as an example. Since the nozzles (headsets 242X) in each pass are shown obliquely in the main scanning direction so as not to overlap, the positional relationship between the paper 10 and the nozzles (headsets 242X) in the main scanning direction is significant. I won't do it.

Next to each nozzle number of each pass, the nozzle usage rate corresponding to each nozzle is shown. In the nozzle row 242XA as the first head and the nozzle row 242XB as the second head, each 10 nozzles have a first area (predetermined area) and a second area (predetermined area) as in FIG. 4 of the first embodiment. ), corresponding to the third region. The first head forms dots at odd dot positions on the raster line (see FIG. 10) in n passes (n=2 or 3), and the second head forms dots at even dot positions on the raster line (see FIG. 10). Are formed by n passes (n=2 or 3). In other words, the first head and the second head perform control independently of each other, the first head forms a raster line only with dots at odd dot positions, and the second head only rasters with dots at even dot positions. Form a line. Therefore, the nozzle usage rates of the first head and the second head are half that of the single head shown in FIG. In the following description, a raster line formed only by dots at odd dot positions formed by the first head is an odd raster line, and a raster line formed only by dots at even dot positions formed by the second head. The line is called an even numbered raster line.

As shown in FIG. 11, by repeating the carrying process of carrying the paper 10 in the sub-scanning direction by a distance corresponding to four nozzles and the scanning process, the nozzles are used in the normal printing unit after the raster line L17. A raster line with a rate of 100% is formed. It should be noted that the upper end portion of the raster lines L1 to L16 where the total nozzle usage rate is less than 100% is subjected to the upper end processing by minute feeding of the paper 10. However, since this upper end processing is a well-known technique, its description will be omitted. Omit it.

The formation of odd raster lines by the first head will be described.
The odd-numbered raster line of the E section of the normal printing section uses at least one nozzle of the nozzles A1, A2, A9, and A10 included in the predetermined area of the first head, and the first head is formed by three passes. It is formed using three different nozzles (control by three nozzles of the first head). The odd-numbered raster line of the F section of the normal printing section does not use the nozzles A1, A2, A9, A10 included in the predetermined area of the first head, but uses two different nozzles of the first head by two passes. Are formed (control by two nozzles of the first head). That is, the number of scans for forming an odd raster line using at least one of the nozzles A1, A2, A9, A10 included in the predetermined area of the first head is at least 3 passes, and This is larger than the number of scans for forming odd-numbered raster lines that do not use the nozzles A1, A2, A9, A10 included in the predetermined area of the first head.

The formation of even-numbered raster lines by the second head will be described.
For the even-numbered raster line of the F portion of the normal printing portion, at least one nozzle of the nozzles B1, B2, B9, B10 included in the predetermined area of the second head is used, and the third head passes through three passes. It is formed by using three different nozzles (control by three nozzles of the second head). The even-numbered raster line of the E section of the normal printing section does not use the nozzles B1, B2, B9, B10 included in the predetermined area of the second head, but uses two different nozzles of the second head by two passes. Are formed (control by two nozzles of the second head). That is, the number of scans for forming an even-numbered raster line using at least one of the nozzles B1, B2, B9, and B10 included in the predetermined area of the second head is at least 3 passes, and This is larger than the number of scans for forming even-numbered raster lines that do not use the nozzles B1, B2, B9, and B10 included in the predetermined area of the second head.

The raster line L21 belonging to the G section will be described in detail.
The raster line L21 is located at the boundary between the printing performed by the first pass (pass 2 to pass 5) and the printing performed by the second pass (pass 6), and the raster line L20 and the raster line L21. Banding is easily visible between the line L21. In the present embodiment, the raster line L21 is formed by an even-numbered raster line formed by control of two nozzles of the second head and an odd-numbered raster line formed by control of three nozzles of the first head. There is.

Specifically, in the even-numbered raster line of the raster line L21, 25% of the total number of dots forming the raster line is formed by the nozzle B7 of the second head of pass 2, and similarly, the nozzle B3 of pass 3 is formed. 25% of the dots are formed.
The odd-numbered raster line of the raster line L21 forms 18.75% of the total number of dots forming the raster line by the nozzle A9 of the first head of pass 4, and similarly, the nozzle A5 of pass 5 25% of the dots are formed, and the nozzle A1 of pass 6 forms 6.25% of the dots.

Even in the situation where banding may occur in pass 6 due to misalignment of the sheet 10 or the like, the number of dots formed in pass 6 is 6.25% of the total number of dots forming the raster line L21. Is difficult to see. Further, the inkjet printer 200 having two heads can print at twice the speed of the image forming apparatus having one head when printing an image with the same image quality.

As described above, according to the image forming apparatus (inkjet printer 200) of this embodiment, the following effects can be obtained.
Since the inkjet printer 200 includes two heads, the first nozzle group 241A as the first head and the second nozzle group 241B as the second head, it is possible to further improve the print quality and the printing speed. it can.

10... Paper (medium), 20... Conveying unit (conveying means), 30... Carriage unit (scanning means), 40... Head unit, 41, 241... Head, 43... Nozzle, 60... Control section, 61... Interface section, 62... CPU, 63... Memory, 64... Unit control circuit, 65... Drive signal generating section, 100, 200... Inkjet printer.

Claims (5)

A head having a plurality of nozzles capable of ejecting a liquid onto a medium;
Scanning means for relatively scanning the head in the main scanning direction with respect to the medium;
Conveying means for conveying the medium in the sub-scanning direction that intersects the main scanning direction relatively to the head,
And a control unit for forming an image on the medium by alternately performing the scanning and the conveyance,
The control unit, under the condition that the movement amount due to the conveyance is a constant value, of the first area of the plurality of nozzles, the second area, and the A section formed by the central portion and the plurality of nozzles. The first intermediate portion and the second intermediate portion of B are controlled to form image data including
The A portion and the B portion are arranged alternately in the sub-scanning direction,
The first intermediate portion is located between the first region and the central portion,
The second intermediate portion is located between the second region and the central portion,
The first number, which is the number of passes forming the A section, is larger than the second number, which is the number of passes forming the B section ,
In the section A , a plurality of raster lines are continuously formed in the sub-scanning direction,
The image forming apparatus is characterized in that a plurality of raster lines are continuously formed in the section B in the sub-scanning direction. The image forming apparatus according to claim 1, wherein the length of the section A in the sub-scanning direction is shorter than the length of the section B in the sub-scanning direction. The image forming apparatus according to claim 1, wherein the length of the section A in the sub-scanning direction is the same as the length of the section B in the sub-scanning direction. The average nozzle usage rate of the first region and the second area is smaller than the average nozzle usage rate of the first intermediate portion and the second intermediate portion. The image forming apparatus according to item 1. A head having a plurality of nozzles capable of ejecting a liquid onto a medium, a scanning unit that relatively scans the head in the main scanning direction with respect to the medium, and the medium with respect to the head. An image processing method for an image processing apparatus, comprising: a transporting unit that transports in a sub-scanning direction that intersects a main scanning direction, and forms an image on the medium by alternately performing the scanning and the transporting. hand,
Under the condition that the movement amount by the conveyance is a constant value , the A portion formed by the first region, the second region, and the central portion of the plurality of nozzles and the first intermediate portion of the plurality of nozzles And a portion B formed by the second intermediate portion forms an image,
The A portion and the B portion are alternately arranged in the sub-scanning direction,
The first intermediate portion is located between the first region and the central portion,
The second intermediate portion is located between the second region and the central portion,
The first number, which is the number of passes for forming the A section, is larger than the second number, which is the number of passes for forming the B section ,
In the section A , a plurality of raster lines are continuously formed in the sub-scanning direction,
An image forming method, wherein a plurality of raster lines are continuously formed in the sub-scanning direction in the section B.

Images