JP2005288949A - Inkjet recording device and control method therefor and program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce time differences occurring due to recording time differences when images are recorded by a multipass recording method in a large inkjet recording device. <P>SOLUTION: A CPU writes image data for one band in a band memory (step S401). The CPU reads all image data for one band from the band memory (Step S402). The CPU determines the recording width of the image data read and decides whether a density difference will occur from a recording width determination table (Step S403). When the device determines that no density difference will occur, an even number pass count is set as a recording pass count of a multipass recording method (Step S404). When it is judged that a density difference will occur, an odd number pass count is set by adding +1 to the even number pass count as a recording pass count (Step S414). The CPU 201 performs thinning for multipass recording in accordance with the recording pass count determined (Step S405). <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an inkjet recording apparatus that records an image by a multipass recording method, a control method thereof, and a program.

  Paper, cloth, plastic sheets, OHP as recording devices in printers, copiers, facsimiles, etc., or as recording devices used as composite electronic devices including computers and word processors, and devices that output information processed by workstations, etc. 2. Description of the Related Art Inkjet recording apparatuses that can perform recording on various recording media such as (overhead projector) sheets with a relatively simple configuration have become widespread.

  In addition, since this method is basically a non-contact recording method and the type of the recording medium is not limited, in addition to the recording media normally used as described above, cloth, leather, non-woven fabric, metal, etc. are used as the recording medium. A recording apparatus to be used has also been proposed. Further, in this type of ink jet recording apparatus, a so-called serial method, in which an image is recorded while a recording head is scanned in a direction (main scanning direction) intersecting a recording medium conveyance direction (sub-scanning direction), is mainstream. This type of recording apparatus has an advantage that it can record an image having relatively simple reproducibility and uniformity with a simple configuration. In particular, the so-called Bubble Jet (registered trademark) system, in which bubbles are generated in ink using the thermal energy generated by the electrothermal conversion element and ink is discharged by the pressure of the bubbles, has a relatively high density of discharge ports. This is a system that has various advantages such as being arranged and having a small noise generated in association with a recording operation, and has been widely used in recent years.

  On the other hand, in recent years, it is possible to support not only relatively small inkjet recording devices such as A4 and A3 sizes, but also relatively large sizes such as 36 inch width, 42 inch width, 64 inch width and 72 inch width. Large-format inkjet recording devices have also been released.

  In recent inkjet recording apparatuses, for the purpose of improving image quality, an image is recorded by causing the recording head to scan the same recording area on the recording medium a plurality of times (number of recording passes) in the main scanning direction. A completion method, a so-called multi-pass recording method is employed.

  FIG. 1 illustrates a two-pass recording method as a multi-pass recording method in which image recording is completed (the number of recording passes = 2) by scanning the recording head twice for the same recording area on the recording medium. It is a figure and shows the relationship between the position of the recording head 1000h and the recording area of the image recorded on the recording medium 1000p.

  An image is recorded on the recording medium 1000p by ejecting ink based on the image data while the recording head 1000h moves in the main scanning direction (the direction of the arrow X1). Each time a scanning operation is performed, the recording medium 1000p is conveyed in the sub-scanning direction (the direction of the arrow Y) by a width corresponding to ½ of the width of the recording head 1000h (hereinafter referred to as ½ band width). In FIG. 1, the position of the recording medium 1000p is fixed, and the recording head 1000h is expressed as moving in the direction opposite to the direction of the arrow Y in the sub-scanning direction with respect to the recording medium 1000p.

  In multi-pass printing, recording is performed based on image data thinned out for predetermined pixels in image data of one bandwidth in the first scanning operation (direction of arrow X1), and the second scanning operation (arrow In the reverse direction of X1, recording is performed based on image data obtained by thinning out pixels that have not been thinned out in the first scanning operation in the image data of one bandwidth. That is, with respect to the ½ bandwidth region in which recording is completed by two scans, the thinning-out processing in the first scan and the second scan is performed using mutually complementary mask data. For example, in the mask data, pixels that can be recorded in the first and second scans are adjacent to each other.

  Therefore, the recording of the image on the recording medium 1000p is completed by ½ bandwidth by the two scanning operations of the recording head 1000h. That is, the image data thinned out for the adjacent pixels is recorded in the first scanning operation, and the first scanning is performed in the second scanning operation, with respect to the recording area of ½ bandwidth on the recording medium 1000p. Image data obtained by thinning out pixels that were not thinned out during operation is recorded. Hereinafter, the first scan operation is referred to as the ½ pass, the second scan operation is referred to as the ½ pass, and the ½ pass for the recording area corresponding to the ½ bandwidth on the recording medium 1000p. The area where only the recording is performed is called a 1/2 pass recording area, and the area where the recording of the 2/2 pass is also performed and the image is completed is called a 2/2 pass recording area.

  FIG. 2 is a schematic diagram showing an image recorded during the recording operation when two-pass recording is performed. During the recording operation, the recording area corresponding to the ½ bandwidth at the rear end in the sub-scanning direction is a ½ pass recording area, and only the thinned image data is recorded by the ½ pass recording. The For this reason, the image is not completed in the half-pass recording area at the rear end, and the density of the area is approximately ½ that when the image is completed.

  Similarly to the contents described for the two-pass recording method, the three-pass recording method for completing image recording by scanning the recording head three times in the main scanning direction in the same recording area on the recording medium is also the same. Can be implemented.

  However, in the multi-pass recording method as described above, if the time interval between the first scan operation and the second scan operation (hereinafter referred to as a recording time difference) for the same recording area changes, 1 / N band width (N = number of recording passes, here 1/2 band width) may cause the recording density to change, resulting in density unevenness (hereinafter referred to as time difference unevenness).

  3 (a), (b), (c), and (d) and FIGS. 4 (a), (b), (c), and (d) show the time difference unevenness caused by such a change in the recording time difference. It is explanatory drawing of.

  3A, 3B, 3C, and 3D show the time between the first and second scan operations (1/2 pass and 2/2 pass) in the 2-pass printing method. FIG. 6 is a diagram schematically illustrating the state of ink permeation and fixing with respect to a recording medium when the ink is short. FIG. 3A is a diagram of ink droplets ejected in the 1/2 pass. FIG. 3B is a diagram illustrating penetration of the ink droplets ejected in the 1/2 pass into the recording medium. FIG. 3C is a diagram of ink droplets ejected in the 2/2 pass. FIG. 3D is a diagram showing penetration of the ink droplets ejected in the 2/2 pass into the recording medium.

  As shown in FIG. 3A, the ink droplets 101a ejected in the ½ pass penetrate in the direction perpendicular to the surface of the recording medium 102 and the direction spreading over the surface as shown in FIG. A pigment such as a dye as a component physically and chemically binds to the recording medium 102. The ink droplets 101b ejected in the second / second pass as shown in FIG. 3C also permeate in the direction perpendicular to the surface of the recording medium 102 and the direction spreading on the surface, but as shown in FIG. The ink droplet 101a that has landed first does not penetrate or fix much in the fixed area. The cause is considered to be that the ink droplet 101a that has landed first is still penetrating. For this reason, the ink droplet 101b that has landed later penetrates and fixes further downward in the region into which the ink droplet 101a that has landed earlier penetrates, as shown in FIG. 3D.

  4 (a), (b), (c), and (d) show the case where ink is applied to the recording medium when the time between the 1/2 pass and the 2/2 pass in the 2-pass printing method is long. It is the figure which represented the mode of penetration and fixation typically. FIG. 4A is a diagram of ink droplets ejected in the 1/2 pass. FIG. 4B is a diagram illustrating penetration of ink droplets ejected in the 1/2 pass into the recording medium. FIG. 4C is a diagram of ink droplets ejected in the 2/2 pass. FIG. 4D is a diagram showing penetration of the ink droplets ejected in the 2/2 pass into the recording medium.

  As shown in FIG. 4A, the ink droplet 101a ejected in the 1/2 pass penetrates in the direction perpendicular to the surface of the recording medium 102 and the direction spreading on the surface as shown in FIG. A pigment such as a dye as a component physically and chemically binds to the recording medium 102. As shown in FIG. 4C, the ink droplet 101b ejected in the 2/2 pass and subsequently landed is in a region where the first landed 101a has penetrated and fixed as shown in FIG. 4D. Permeates relatively much. This is because the ink droplet 101a that has landed first sufficiently penetrates and spreads or the volatile component thereof evaporates, so the amount of the ink droplet 101a per unit volume of the recording medium 102 decreases, and the ink droplet 101b that has landed later It may be because it has become possible to penetrate.

  As described above, the amount of ink fixed near the surface of the recording medium, that is, the amount of a dye such as a dye differs depending on the recording time difference between the ½ pass and the ½ pass. Further, since the recording density corresponds to the light absorption of the dye fixed near the surface of the recording medium, the recording density varies depending on the change in the recording time difference between the 1/2 pass and the 2/2 pass.

  As described above, when an image is recorded by the multi-pass recording method, if a change in the recording time difference between the 1/2 pass and the 2/2 pass occurs, time difference unevenness occurs in the recorded images before and after that. .

  FIG. 5 is an explanatory diagram of the recording image width and the recording time difference between the 1/2 pass and the 2/2 pass. When recording from left to right in the first scan (direction of arrow X1) and recording from right to left in the second scan (opposite direction of arrow X1), the left end area A and the right end of the recorded image are recorded. Focus on region B. In the leftmost area A, the recording head performs the recording from the left to the right after the recording of the 1/2 pass at the initial stage when the recording head performs the recording from the left to the right. Since the 2/2 pass is recorded at the last stage after recording from right to left, the recording time difference from the 1st pass to the 2/2 pass is compared. Become longer. In the rightmost area B, after the recording of the 1/2 pass is performed at the final stage in which the recording head performs recording from left to right, the recording head turns back at the right end and performs recording from right to left. Since the 2/2 pass is recorded at this stage, the recording time difference from the 1/2 pass to the 2/2 pass is relatively short.

  FIG. 6 is an explanatory diagram of how the recording time difference is generated on the recording medium, focusing on both ends of the recorded image. When the recording time difference from the recording of the 1/2 pass to the recording of the 2/2 pass is long, it is indicated by α, and when it is short, it is indicated by Β. As can be seen at a glance, the α region and the wrinkle region are alternately generated for each 1 / N bandwidth (N = the number of recording passes, here, 1/2 bandwidth), and therefore the time difference unevenness for each 1/2 bandwidth. When this occurs, it becomes a very large image defect.

  Further, as apparent from the occurrence mechanism of the time difference unevenness, the longer the recording time difference is, that is, the greater the recorded image width is, the more noticeable the time difference unevenness is. Therefore, unevenness in time difference is a serious problem in a large-format ink jet recording apparatus capable of recording a relatively large size.

  There is a technique for suppressing time difference unevenness caused by such a recording time difference (see Patent Document 1). According to this, by switching from bidirectional printing to unidirectional printing depending on the number of ink dots used for recording, time difference unevenness (expressed as density unevenness in Patent Document 1) that occurs at both ends of the recorded image is suppressed. It becomes possible to do.

JP 2003-34021 A

  However, the technique disclosed in Patent Document 1 is insufficient to cope with the time difference unevenness that occurs when the recording width becomes large as in the large-format ink jet recording apparatus. In addition, in order to count the number of ink dots used for recording, in the case of a large-format ink jet recording apparatus, the recorded image becomes large, and therefore the time required for counting becomes enormous, which is impractical. Therefore, the technique disclosed in Patent Document 1 is not very effective in solving the time difference unevenness particularly in a large-format ink jet recording apparatus.

  As described above, in a large-format inkjet recording apparatus that records a relatively large recorded image, a recording time difference occurs when an image is recorded by the multipass recording method, and the time difference unevenness due to the recording time difference cannot be suppressed. However, there is still room for improvement in the prior art.

  The present invention has been made in view of such a problem, and the object of the present invention is to perform recording when an image is recorded by a multi-pass recording method even in a large-format inkjet recording apparatus that records a relatively large recorded image. An object of the present invention is to provide an ink jet recording apparatus, a control method therefor, and a program that can suppress time difference unevenness caused by the time difference.

  In order to achieve such an object, the ink jet recording apparatus according to the present invention alternately performs main scanning in the forward direction and main scanning in the backward direction of the recording head that ejects ink, thereby An inkjet recording apparatus that sequentially completes recording in a region and performs recording on the recording medium, and determines whether a density difference occurs in each region when recording on the recording medium Density difference generation determination means (201, S403, FIG. 17 or 33 and FIG. 20), and 2N (N is a natural number) as the number of times of main scanning of the recording head required to complete recording in the one area Recording control means (201, S403, S404, S414) for selecting either one of 2N + 1 times or 2N + 1 times, and the recording control means is configured such that the density difference occurrence determining means generates the density difference. If it is determined that, and selects the 2N + 1 times as the number of times of the main scanning.

  In order to achieve the above object, the control method of the ink jet recording apparatus according to the present invention performs the main scanning in the forward direction and the main scanning in the backward direction of the recording head that ejects ink alternately, thereby A method for controlling an ink jet recording apparatus that sequentially completes recording in one area, and determines whether or not a density difference occurs in each area when recording on the recording medium. A density difference generation determination step and a selection step of selecting either 2N (N is a natural number) or 2N + 1 as the number of main scans of the recording head required to complete recording in the one area. And a selection step of selecting 2N + 1 as the number of times of the main scanning when it is determined in the density difference occurrence determination step that the density difference occurs. And butterflies.

  In addition, in order to make it easy to understand the correspondence between the description in the claims and the description in the specification, the reference numerals in the drawings in the embodiments corresponding to the components in the claims are indicated by (). However, the constituent elements described in the claims are not limited to the constituent elements in the embodiment of the above () part.

  According to the present invention, in a large-format ink jet recording apparatus that records a relatively large recorded image, even when a recording time difference occurs when an image is recorded by the multipass recording method, time difference unevenness due to the recording time difference is suppressed. There is an effect that makes possible.

  Embodiments to which the present invention can be applied will be described below in detail with reference to the drawings. In addition, the same code | symbol is attached | subjected to the location which has the same function in each drawing, and duplication of description is abbreviate | omitted.

(Embodiment 1)
FIG. 7 is a perspective view showing an internal configuration of a large-format ink jet recording apparatus having a maximum printing width of 64 inches according to the first embodiment. In FIG. 7, a recording head 2 is mounted on the carriage 1. The carriage 1 is instructed to the carriage guide shaft 3 so as to be movable along the carriage guide shaft 3. A part of the carriage 1 is fixed to the carriage belt 4. The carriage belt 4 is stretched around the motor pulley 5. The carriage 1 is scanned in the main scanning direction along the carriage guide shaft 3 by reciprocating the carriage belt 4 by driving the main scanning motor 6. In the figure, reference numeral 7 denotes a recording medium, and 8 denotes a conveyance roller for conveying the recording medium 7 in the sub-scanning direction.

  The carriage 1 is provided with an encoder sensor 9. By detecting the scale on the linear encoder scale 10 stretched in parallel with the carriage guide shaft 3 by the encoder sensor 9, the position, scanning speed, etc. of the carriage 1 are detected. In this case, an optical encoder is employed, and the linear encoder scale 10 has a scale drawn on the transparent film at a predetermined pitch interval. The encoder sensor 9 is composed of a photo interrupter and outputs an encoder pulse signal corresponding to this pitch by detecting a scale provided at the predetermined pitch interval. The encoder sensor 9 and the linear encoder scale 10 are not limited to the optical type, and may be a magnetic type.

  FIG. 8 is a diagram illustrating a configuration of the carriage 1 on which the recording head 2 is mounted. In FIG. 8, the recording head 2 is equipped with six chips 21 to 26 having ejection openings for ejecting ink. The chip 21 is for black (hereinafter referred to as Bk), the chip 22 is for light cyan (hereinafter Pc), the chip 23 is for cyan (hereinafter C), the chip 24 is for magenta (hereinafter M), and the chip 25 is light magenta ( The chip 26 is a chip for Pm), and the chip 26 is a chip for yellow (hereinafter Y).

  A linear encoder scale 10 is arranged along the main scanning direction of the carriage 1 (the direction of the arrow X1). An encoder sensor 9 for detecting the scale of the linear encoder scale 10 is disposed on the carriage 1. On the carriage 1, a positioning member 31 for positioning the recording head 2 in the main scanning direction (direction of arrow X1) and a positioning member 32 for positioning in the sub-scanning direction (direction of arrow Y) are arranged. Then, the recording head 2 is positioned by contacting the recording head 2 with the positioning members 31 and 32.

  A recording medium width sensor 33 is further attached to the carriage 1. The recording medium width sensor 33 is used when detecting the recording medium width. A CPU (described later) of the controller of the inkjet recording apparatus moves the recording medium width sensor 33 along the main scanning direction (direction of arrow X1) once when recording on the recording medium 7 is started, and detects the recording medium width.

  FIG. 9 is a block diagram showing a configuration of a control system in the ink jet recording apparatus of FIG. In FIG. 9, reference numeral 200 denotes a controller that constitutes a main control unit of the ink jet recording apparatus according to the first embodiment. The controller 200 includes a CPU (central processing unit) 201 in the form of a microcomputer that executes a sequence such as FIG. 10 described later, a program and table corresponding to the sequence execution procedure, and a heat pulse voltage to the head controller (described later). A ROM (read only memory) 202 for storing values, their pulse widths, and other fixed data, and a RAM (random access memory) 203 provided with an area for developing recording data, a work area, and the like.

  Reference numeral 33 denotes the above-described recording medium width sensor that detects the width of the recording medium. An output value from the recording medium width sensor 33 is input to the controller 200. Reference numeral 205 denotes a host device serving as a recording data supply source. Recording data, other commands, status signals, and the like from the host device 205 are exchanged with the controller 200 via an interface (I / F) 206. And transmitted to the band memory 207.

  Reference numeral 208 denotes a mask pattern selector, which is controlled by the CPU 201, and its output is input to the multipath data processing unit 209. Reference numeral 207 denotes a band memory. Image data for recording is transferred from the interface 206, and image data necessary for recording in a recording area divided into a predetermined width is controlled by the CPU 201. (Image data of “one band width corresponding to the width of the recording head 2 × the recording width in the main scanning direction”). The output of the band memory 207 is input to the multipath data processing unit 209.

  Under the control of the CPU 201, the multi-pass data processing unit 209 performs pixel thinning processing of image data so that the recording of the divided recording areas is completed by a plurality of scans, and generates image data for one scan. To the head controller 210. The head controller 210 drives an electrothermal transducer (heater for ink ejection) of the recording head 2 in accordance with recording data or the like during recording or preliminary ejection. The recording head 2 is controlled by the head controller 210 and performs recording for one scan by ejecting ink from the ejection port of the recording head 2 in synchronization with the carriage operation. Reference numeral 6 denotes the above-described main scanning motor serving as a drive source for moving the carriage 1 in the main scanning direction, and reference numeral 213 denotes a motor driver that drives the main scanning motor 6. Reference numeral 214 denotes a sub-scanning motor serving as a drive source for transporting the recording medium 7 in the backward scanning direction, and reference numeral 215 denotes a motor driver that drives the sub-scanning motor 214.

  FIG. 10 is a flowchart showing the control operation of the CPU 201. In FIG. 10, first, when a recording request command is input to the CPU 201 via the interface 206, the CPU 201 sends image data for one band newly transferred from the external host device 205 or the like via the interface 206. Is written in the band memory 207 (step S401). Next, the multi-pass data processing unit 209 that has received an instruction from the CPU 201 reads all image data for one band from the band memory 207 (step S402). Next, the CPU 201 determines the recording width of the read image data (the width of the image data in the main scanning direction), and based on the recording width determination table of FIG. It is determined whether or not a density difference for each (number) occurs (step S403). If it is determined that no density difference occurs, a basic even number of passes (for example, two passes) is set as the number of recording passes of the multi-pass printing method (step S404). If it is determined that a density difference occurs, an odd number of passes (for example, three passes) obtained by adding +1 to the basic even number of passes is set as the number of recording passes (step S414). In accordance with the number of recording passes determined here, the multi-pass data processing unit 209 performs a thinning process for performing multi-pass printing (step S405).

  Here, only the image data for one band is used as the recording width of the image data for determining whether a density difference occurs (step S403) (step S401, step S402), 2 You may use the image data more than the band. For example, using all band data of image data over the entire page, it is determined whether or not the number of bands corresponding to the recording width where there is a density difference is greater than or equal to a threshold in the recording width determination table of FIG. It may be determined whether a density difference occurs.

  In this case, the CPU 201 writes the image data for all bands over the entire page sequentially transferred from the external host device 205 or the like into the band memory 207 via the interface 206 (step S401). Next, in response to the instruction from the CPU 201, the multi-pass data processing unit 209 reads out image data for all bands over the entire page from the band memory 207 (step S402). Next, the CPU 201 counts the number of bands corresponding to the recording width (the width of the image data in the main scanning direction) where there is a density difference in the recording width determination table of FIG. It is determined whether or not a density difference for each 1 / N band width (N = number of recording passes) occurs depending on whether or not the number of recording width bands at which there is a density difference is greater than or equal to a threshold value (step S403). The threshold value may be an integer of 1 or more, or may be set as a percentage of the total number of bands. Specifically, the determination of whether or not a density difference occurs when 1 is set as the threshold (step S403) is as follows.

(I) When determining that there is no density difference When the maximum value of all the band data of the image data over the entire page is smaller than the recording width at which there is a density difference in the recording width determination table of FIG. Since the number of bands of the recording width where there is a density difference is 0 and does not exceed the threshold, it is determined that there is no density difference.

(Ii) When determining that there is a density difference When the maximum value of all the band data of the image data over the entire page is larger than the recording width where there is a density difference in the recording width determination table of FIG. Since the number of bands of the recording width at which there is a density difference is 1 or more and the threshold value or more, it is determined that there is a density difference.

  Step S403 and subsequent steps are the same as when only one band of image data is used.

  Next, a thinning process when performing 2-pass printing in step S405 will be described. This thinning process is realized by masking the image data read from the band memory 207 with a predetermined mask pattern selected and acquired from the mask pattern selector 208 in the multi-pass data processing unit 209. In the first embodiment, the mask pattern shown in FIGS. 11A and 11B is used. That is, as a mask pattern for thinning out image data to be recorded in the first scan of 2-pass printing, the staggered pattern shown in FIG. 11A is used, and a mask pattern for thinning out image data to be recorded in the second scan. As shown in FIG. 11B. The mask pattern shown in FIGS. 11A and 11B corresponds to data for masking pixels (pixels that are not ejected with ink) from which black grids are thinned, and image data is masked with such a mask pattern. Is done. For simplification of description, a case where the recording head 2 to which the mask pattern shown in FIGS. 11A and 11B is applied has eight ink discharge ports arranged in one row will be described. Yes.

  FIG. 12 is a diagram showing a positional relationship between the recording head 2 and the recording medium 7 when a two-pass recording operation is performed as multi-pass recording. In the following, the case where the recording head 2 performs forward scanning in the X1 direction in FIG. 12 during the first scan and the recording head 2 performs backward scanning in the X2 direction in FIG. 12 during the second scanning will be described. To do.

  The CPU 201 outputs the image data thinned out in the multi-pass data processing unit 209 in the process of step S405 to the head controller 210, and records based on the thinned image data while scanning the carriage 1 in the main scanning direction. Ink is ejected from the head 2 to record an image on the recording medium 7 (step S406). For example, in step S405, the image data is thinned out by the staggered pattern in FIG. 11A, and in step S406, the CPU 201 scans the recording head 2 in the X1 direction as shown in step A in FIG. Is used to record a thinned image in the entire area for one scan based on the thinned recording data.

  When the recording of the thinned image for one scan is completed, the CPU 201 conveys the recording medium 7 by the ½ bandwidth in the sub-scanning direction indicated by the arrow Y (step S407). The position of the recording head 2 in step S407 is a position B that is shifted by a half bandwidth. Subsequently, the image data newly transferred from the external host device or the like is written into the band memory 207 under the control of the CPU 201 (step S408). Next, the multi-pass data processing unit 209 reads all image data for one band from the band memory 207 (step S409). Thereafter, the CPU 201 performs the same processing as that in steps S405 to S407 described above in steps S410 to S412.

  If recording for one sheet of the recording medium 7 has not been completed, the CPU 201 outputs a transfer request for the next image data from the interface 206 (NO branch in step S413), and from the external host device 205 or the like. The newly transferred image data is written into the band memory 207 under the control of the CPU 201 (step S408). Here, during the loop processing of steps S408 to S413 until all the recording of one sheet of the recording medium 7 is completed, the CPU 201 executes the mask pattern shown in FIGS. 11A and 11B every time step S410 is executed. Are used alternately.

  The CPU 201 repeats the operations from step S408 to step S413, so that forward scan recording based on the recording data thinned using the staggered pattern and reverse scanning recording based on the recording data thinned using the reverse zigzag pattern are performed. Are alternately repeated to record images in all the recording areas on the recording medium 7. When the images for all the recording areas on the recording medium 7 are recorded, the two-pass recording operation is completed.

  FIG. 13 is a table showing the relationship between the time difference generated by two-pass recording and the recording width. The recording time difference at the left end of the recording area in FIG. 6 described in the background art described above is shown for each recording width. As in FIG. 6, when the recording time difference from the recording of the 1/2 pass to the recording of the 2/2 pass is long, it is represented by α, and when it is short, it is represented by Β. It can be seen at a glance that the difference between α and Β alternately present in the sub-scanning direction differs greatly depending on the recording width.

FIG. 14 is a table comparing the recording width and the occurrence of time difference unevenness in the above-described two-pass printing and the three-pass printing described later with reference to FIGS. As an evaluation method, five-step sensory evaluation is used, and the contents of each evaluation are as follows.
5 points: Fatal image defects 4 points: Non-fatal but serious defects 3 points: Minor defects 2 points: Extremely minor defects 1 point: No image defects are recognized

  Due to the mechanism, the time difference unevenness is generated as the time difference is large. Therefore, in the above-described two-pass recording, the time difference unevenness is more remarkable as the recording width is large.

  Even in the 3-pass printing operation, in the flowchart of FIG. 10 showing the control operation of the CPU 201 described in the above-described 2-pass printing operation, the 2-pass printing is performed by changing the transport amount and mask pattern of the printing medium 7 in the sub-scanning direction. It can be completed in the same way as the operation. That is, in FIG. 10, steps S401 to S403 are the same as the above-described two-pass printing operation. If it is determined in step S403 that a density difference occurs, an odd number of passes (for example, three passes) obtained by adding +1 to the basic even number of passes is set as the number of recording passes (step S414). In accordance with the number of recording passes determined here, the multi-pass data processing unit 209 performs a thinning process for performing multi-pass printing (step S405).

  Here, the thinning process when performing 3-pass printing in step S405 will be described. This thinning process is realized by masking the image data read from the band memory 207 with a predetermined mask pattern selected and acquired from the mask pattern selector 208 in the multi-pass data processing unit 209. In the first embodiment, the mask patterns shown in FIGS. 15A to 15C are used. That is, the first staggered pattern shown in FIG. 15A is used as a mask pattern for thinning out image data recorded in the first scan of three-pass printing, and the image data recorded in the second scan is thinned out. As the mask pattern, the second staggered pattern shown in FIG. 15B is used, and as the mask pattern for thinning out the image data recorded in the third scan, the third staggered pattern shown in FIG. Use. FIG. 15A to FIG. 15C correspond to data that masks pixels (pixels that are not ejected with ink) from which the black lattice of the mask pattern is thinned, and thinning processing is performed by masking image data with such a mask pattern. Is done. For simplification of description, a case where the recording head 2 to which the mask patterns shown in FIGS. 15A to 15C are applied has nine ink ejection openings arranged in a row will be described. Yes.

  FIG. 16 is a diagram for explaining the recording image width and the recording time difference in the 1/3 pass, 2/3 pass, and 3/3 pass in 3 pass printing. Attention is paid to the left end area A and the right end area B of the recorded image when recording is performed from left to right in the first scan and recording is performed from right to left in the second scan. In the leftmost area A, (i) the recording head performs recording from the left to the right, and after the 1/3 pass recording is performed, (ii) the recording head continues recording from the left to the right. Further, the recording head folds back at the right end and performs recording from right to left, and the 2/3 pass is recorded at the final stage. (Iii) The recording head returns at the left end and performs recording from left to right. At the stage, the 3rd pass is recorded.

  In the rightmost area B, (iv) the recording head performs the 1/3 pass recording at the final stage of recording from the left to the right, and (v) the recording head turns back at the right end and moves from right to left. (Vi) The recording head continues recording from the right to the left, and the recording head turns back at the left end and records from the left to the right. And the 3rd pass is recorded at the final stage.

  The time from when the 1/3 pass in the left end area A is recorded until the 3/3 pass is recorded is the time required for (ii) and (iii). Similarly, the right end area B The time from when the 1/3 pass is recorded until when the 3/3 pass is recorded is the time required for (v) and (vi). Since the time required for (ii) and (vi) and (iii) and (v) is equal to each other, after the 1/3 pass of the left end area A and the right end area B is recorded, the 3/3 pass The time until recording is substantially equal.

  FIG. 14 also shows a table comparing the recording width and the occurrence of time difference unevenness in the 3-pass printing described with reference to FIGS. Referring to the table of FIG. 14, in the 3-pass printing, the time from when the 1/3 pass of the leftmost area A and the rightmost area B shown in FIG. 16 is recorded until the 3/3 pass is recorded is Since they are substantially equal, the time difference unevenness is suppressed in the three-pass recording.

  FIG. 17 is a recording width determination table that is referred to in order to determine whether or not a density difference occurs in step S403 of FIG. This recording width determination table is preliminarily defined based on the evaluation shown in the table comparing the recording width and the occurrence state of the time difference unevenness in the two-pass recording and the three-pass recording in FIG. In the result shown in FIG. 14, the recording width of 36 inches or more where evaluation of three or more points occurs in the two-pass printing is defined as having a density difference in the recording width judgment table of FIG. Referring to the recording width determination table of FIG. 17, since the time difference unevenness does not occur even in the two-pass recording at the relatively short recording width, the two-pass recording that improves the throughput is selected (step S404). In the case of a relatively long recording width, if 2-pass recording is selected, time difference unevenness will occur remarkably, resulting in a fatal defect. By selecting 3-pass recording, throughput can be reduced. The time difference unevenness can be suppressed while suppressing as much as possible (step S414).

  Here, based on 2-pass printing, the number of recording passes is selected from two types of 3-pass printing in which 1 is added to 2-pass printing. For example, on the basis of 6-pass printing, 1 is set for 6-pass printing. It will be obvious to those skilled in the art that the same effect can be obtained regardless of how the basic number of recording passes is set, such as selecting the number of recording passes from two types of 7-pass recording with the addition of. .

  The number of passes that can be selected is two, even or odd, but the number of even and odd is not limited to one each. For example, a plurality of types (for example, 2 times, 4 times, etc.) may be provided as even times, and a plurality of types (3 times, 5 times, etc.) may be provided as odd times. This form is very effective particularly when it is preferable to change the number of passes due to factors other than the recording width (for example, the type of the recording medium). For example, it is preferable to set a large number of passes for glossy paper where photographic image recording is the center, while a small number of passes is set for plain paper where recording of characters and graphs is the center. Is preferred. Therefore, the glossy paper is associated with 4 times and 5 times with a relatively large number of passes, and among these, even (4 times) or odd (5 times) is selected according to the recording width, The plain paper may be associated with 2 times and 3 times with a relatively small number of passes, and among these, an even number (2 times) or an odd number (3 times) may be selected according to the recording width.

  As described above, an ink jet recording apparatus to which the present invention can be applied to one area of a recording medium by alternately performing main scanning in the forward direction and main scanning in the backward direction of the recording head that discharges ink. An ink jet recording apparatus that sequentially completes recording and recording on a recording medium, and determines whether or not a density difference occurs for each region when recording on the recording medium. And a recording control means for selecting either 2N (N is a natural number) or 2N + 1 as the number of main scans of the recording head required to complete recording in one area. Selects 2N + 1 times as the number of main scans when the density difference occurrence determining means determines that a density difference occurs.

  Here, the density difference occurrence determination means is a recording width for ejecting ink from the recording head to the recording medium, and a recording width information acquisition means for acquiring information relating to the recording width in the main scanning direction, and a recording width information acquisition means. Determining means for determining whether or not a density difference occurs based on the acquired information regarding the recording width.

  Therefore, in a large-format inkjet recording apparatus that records a relatively large recorded image, it is possible to suppress time difference unevenness that occurs due to a recording time difference when an image is recorded by the multipass recording method.

(Embodiment 2)
In the second embodiment, FIGS. 7 to 9, 11, 12, 15, and 16 are the same as those in the first embodiment. In the second embodiment, the flowchart of FIG. 10 showing the control operation of the CPU 201 in the first embodiment is changed to the flowchart of FIG. In FIG. 18, steps S501 to S514 (excluding step S503) are the same as steps S401 to S414 (excluding step S403) in FIG.

  In the second embodiment, instead of step S403 in FIG. 10, it is determined in step S503 in FIG. 18 whether a density difference occurs based on the recording medium width. That is, the CPU 201 moves the recording medium width sensor 33 along the main scanning direction to determine the recording medium width (the width of the recording medium in the main scanning direction), and based on the recording medium width determination table of FIG. It is determined whether or not a density difference occurs for each 1 / N bandwidth (N = number of recording passes) (step S503).

  FIG. 19 is a table comparing the recording medium width and the occurrence of time difference unevenness in 2-pass printing and 3-pass printing. The evaluation method is the same as the five-step sensory evaluation used in FIG. In 3-pass printing, the time from when the 1/3 pass of the leftmost area A and the rightmost area B shown in FIG. 16 is recorded until the 3/3 pass is recorded is substantially equal. The time difference unevenness is suppressed.

  FIG. 20 is a recording medium width determination table that is referred to in order to determine whether or not a density difference occurs in step S503 of FIG. This recording medium width determination table is defined in advance based on the evaluation shown in the table comparing the recording medium width and the occurrence of time difference unevenness in 2-pass recording and 3-pass recording in FIG. . In the result of FIG. 19, a recording width of 36 inches or more where evaluation of three or more points occurs in two-pass recording is defined as having a density difference in the recording medium width determination table of FIG. Referring to the recording width determination table of FIG. 20, since the time difference unevenness does not occur even in the two-pass recording when the recording medium width is relatively short, the two-pass recording that improves the throughput is selected (step S504). In the case of a relatively long recording medium width, if 2-pass printing is selected, the time difference unevenness is prominent and a fatal defect occurs. By selecting 3-pass printing, throughput is reduced. As a result, the time difference unevenness can be suppressed (step S514).

  Here, based on 2-pass printing, the number of recording passes is selected from two types of 3-pass printing in which 1 is added to 2-pass printing. For example, on the basis of 6-pass printing, 1 is set for 6-pass printing. It will be obvious to those skilled in the art that the same effect can be obtained regardless of how the basic number of recording passes is set, such as selecting the number of recording passes from two types of 7-pass recording with the addition of. .

  The number of passes that can be selected is two, even or odd, but the number of even and odd is not limited to one each. For example, a plurality of types (for example, 2 times, 4 times, etc.) may be provided as even times, and a plurality of types (3 times, 5 times, etc.) may be provided as odd times. This form is very effective particularly when the number of passes is preferably variable due to factors other than the recording medium width (for example, the type of the recording medium). For example, it is preferable to set a large number of passes for glossy paper where photographic image recording is the center, while a small number of passes is set for plain paper where recording of characters and graphs is the center. Is preferred. Therefore, the glossy paper is associated with 4 times and 5 times with a relatively large number of passes, and among these, even (4 times) or odd (5 times) is selected according to the recording medium width. The plain paper may be associated with 2 times and 3 times with a relatively small number of passes, and among these, even (2 times) or odd (3 times) may be selected according to the recording medium width.

  In the present embodiment, the recording medium width sensor 33 provided in the ink jet recording apparatus is used to determine the recording medium width that is a reference for determining whether or not density difference has occurred. It is not limited to. For example, information regarding the recording width set by the user with a printer driver installed in the host device 205 may be acquired from the host ancestor position 205, and the acquired information may be used.

  As described above, an ink jet recording apparatus to which the present invention can be applied to one area of a recording medium by alternately performing main scanning in the forward direction and main scanning in the backward direction of the recording head that discharges ink. An ink jet recording apparatus that sequentially completes recording and recording on a recording medium, and determines whether or not a density difference occurs for each region when recording on the recording medium. And a recording control means for selecting either 2N (N is a natural number) or 2N + 1 as the number of main scans of the recording head required to complete recording in one area. Selects 2N + 1 times as the number of main scans when the density difference occurrence determining means determines that a density difference occurs.

  Here, the density difference occurrence determination unit is configured to acquire the density based on the recording medium width information acquisition unit that acquires information about the width of the recording medium in the main scanning direction and the information about the width of the recording medium acquired by the recording medium width information acquisition unit. Determining means for determining whether or not a difference occurs.

  Therefore, in a large-format inkjet recording apparatus that records a relatively large recorded image, it is possible to suppress time difference unevenness that occurs due to a recording time difference when an image is recorded by the multipass recording method.

(Other embodiments)
In the first and second embodiments described above, the CPU 201 of the inkjet recording apparatus 200 executes the flowcharts shown in FIGS. 10 and 18, but the present invention is not limited to this form. A part of the flowchart shown in FIGS. 10 and 18 may be executed by the host device 205 connected to the ink jet recording apparatus.

  For example, taking FIG. 10 as an example, the host device 205 executes the processing from step S401 to S405, transfers the thinned image data generated in step S405 to the ink jet recording apparatus, and converts the thinned image data to the transferred thinned image data. An ink jet recording apparatus may perform recording based on the above. Further, the host device 205 executes the processing from step S401 to S404 (S414), transfers information on the number of passes set in step S404 (S414) to the ink jet recording apparatus, and based on the transferred number of passes information. Alternatively, the process of creating and outputting the thinned image data may be executed by the ink jet recording apparatus.

  Also in the case of FIG. 18, part of the processing shown in FIG. 18 can be executed by the host device 205. However, in this case, the determination of the recording medium width, which is a criterion for determining whether or not there is a density difference, is obtained by acquiring information on the size of the recording medium set by the printer driver installed in the host device, and including the acquired size information. Based on this, the recording medium width is determined.

  As is apparent from the above, the presence / absence of occurrence of density difference and the setting of the number of passes based on the characteristic features of the present invention are not limited to the mode executed by the ink jet recording apparatus, but are the mode executed by the host device side. May be.

  The present invention can be applied to various ink jet recording apparatuses capable of recording an image using a recording head having a plurality of ink discharge ports. For example, a recording apparatus that records color images using inks of the same or different colors, a recording apparatus that records multi-tone images using inks of the same color and different densities, and a combination of these functions Similar effects can be achieved by similarly applying the present invention to the apparatus. Further, the present invention uses a replaceable ink jet cartridge in which a recording head and an ink tank as recording means are integrated, a recording head and an ink tank as recording means are separated, and an ink is provided between them. The same effect can be obtained by applying the present invention in the same manner regardless of the arrangement of the recording means and the ink tank, such as a configuration of connecting with a supply tube or the like.

FIG. 6 is a schematic diagram showing a head position and a recorded image when performing two-pass printing, which is a method of recording an image by scanning twice in the main scanning direction as multi-pass printing. FIG. 10 is a schematic diagram illustrating an image formed during the printing operation when two-pass printing is performed. FIG. 6 is a diagram schematically illustrating the state of ink permeation and fixing with respect to a recording medium in a case where the recording time difference between the 1/2 pass and the 2/2 pass is short in 2-pass printing. FIG. 6 is a diagram schematically illustrating the state of ink permeation and fixing with respect to a recording medium in the case where the recording time difference between the 1/2 pass and the 2/2 pass is long in 2-pass printing. FIG. 6 is a diagram illustrating a recording image width and a recording time difference between a ½ pass and a ½ pass. FIG. 4 is a diagram illustrating how a recording time difference occurs on a recording medium in two-pass recording, focusing on both ends of a recorded image. 1 is a perspective view showing an internal configuration of a large-format inkjet recording apparatus having a maximum printing width of 64 inches according to a first embodiment to which the present invention can be applied. 1 is a diagram illustrating a configuration of a carriage on which a recording head is mounted according to a first embodiment to which the present invention can be applied. 1 is a block diagram illustrating a configuration of a control system in an ink jet recording apparatus according to a first embodiment to which the present invention can be applied. It is a flowchart which shows control operation of CPU201 of Embodiment 1 which can apply this invention. It is a figure which shows an example of the mask pattern in 2 pass printing of Embodiment 1 which can apply this invention. FIG. 3 is a diagram illustrating a positional relationship between a recording head and a recording medium when a two-pass recording operation is performed as multi-pass recording according to the first embodiment to which the present invention can be applied. FIG. 5 is a table showing a relationship between a recording time difference generated by two-pass recording and a recording width according to the first embodiment to which the present invention can be applied. FIG. 3 is a table comparing the recording width and occurrence of time difference unevenness in 2-pass printing and 3-pass printing according to Embodiment 1 to which the present invention can be applied. It is a figure which shows an example of the mask pattern in 3 pass printing of Embodiment 1 which can apply this invention. FIG. 3 is a diagram illustrating how a recording time difference occurs on a recording medium in three-pass recording according to Embodiment 1 to which the present invention can be applied, focusing attention on both ends of a recorded image. It is a figure of the table referred in order to determine even-numbered path or odd-numbered path of Embodiment 1 which can apply this invention. It is a flowchart which shows control operation of CPU201 of Embodiment 2 which can apply this invention. FIG. 10 is a table comparing the recording width and occurrence of time difference unevenness in 2-pass printing and 3-pass printing according to Embodiment 2 to which the present invention can be applied. It is a figure which shows the table referred in order to determine even-numbered path or odd-numbered path of Embodiment 2 which can apply this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Carriage 2 Recording head 3 Carriage guide shaft 4 Carriage belt 5 Motor pulley 6 Main scanning motor 7 Recording medium 8 Carrying roller 9 Encoder sensor 10 Linear encoder scale 21 Bk chip 22 Pc chip 23 C chip 24 M chip 25 Pm chip 26 Y chip 31 Positioning member 32 in the Xa direction Positioning member 33 in the Xb direction Recording medium width sensor 200 Controller 201 CPU
202 ROM
203 RAM
205 Host device 206 I / F (interface)
207 Band memory 208 Mask pattern selector 209 Multi-pass data processing unit 210 Head controller 213 Main scanning motor driver 214 Sub scanning motor 215 Sub scanning motor driver

Claims (8)

By alternately performing main scanning in the forward direction and main scanning in the backward direction of the recording head for ejecting ink, recording on one area of the recording medium is completed in order, and recording on the recording medium is performed. In an inkjet recording apparatus to perform,
Density difference occurrence determination means for determining whether or not a density difference for each of the areas occurs when recording on the recording medium;
Recording control means for selecting either 2N (N is a natural number) or 2N + 1 as the number of main scans of the recording head required to complete recording in the one area;
The ink jet recording apparatus, wherein the recording control unit selects 2N + 1 times as the number of times of the main scanning when the density difference generation determining unit determines that the density difference occurs. The density difference occurrence determination means includes
Recording width information acquisition means for acquiring information relating to the recording width in the main scanning direction, which is a recording width for ejecting the ink from the recording head to the recording medium;
The inkjet recording apparatus according to claim 1, further comprising: a determination unit that determines whether or not the density difference occurs based on information about the recording width acquired by the recording width information acquisition unit. The density difference occurrence determination means includes
Recording medium width information acquisition means for determining information relating to the width of the recording medium in the main scanning direction;
The inkjet recording according to claim 1, further comprising: a determination unit that determines whether or not the density difference occurs based on information about the width of the recording medium acquired by the recording medium width information acquisition unit. apparatus. In a method of controlling an ink jet recording apparatus that sequentially completes recording on one area of a recording medium by alternately performing main scanning in the forward direction and main scanning in the backward direction of a recording head that ejects ink ,
A density difference occurrence determination step of determining whether or not a density difference for each of the areas occurs when recording on the recording medium;
A selection step of selecting either 2N (N is a natural number) or 2N + 1 as the number of times of main scanning of the recording head required to complete recording in the one area, wherein the density difference is generated And a selection step of selecting 2N + 1 times as the number of times of the main scanning when it is determined in the determination step that the density difference occurs. The density difference occurrence determination step includes
A recording width information acquisition step for acquiring information relating to the recording width in the main scanning direction, which is a recording width for ejecting the ink from the recording head to the recording medium;
The control of an ink jet recording apparatus according to claim 4, further comprising: a determination step of determining whether or not the density difference occurs based on information on the recording width acquired in the recording width information acquisition step. Method. The density difference occurrence determination step includes
A recording medium width information acquisition step for acquiring information relating to the width of the recording medium in the main scanning direction;
5. The inkjet recording according to claim 4, further comprising: a determination step of determining whether or not the density difference occurs based on information on the width of the recording medium acquired in the recording medium width information acquisition step. Control method of the device. In a method of controlling an ink jet recording apparatus that sequentially completes recording on one area of a recording medium by alternately performing main scanning in the forward direction and main scanning in the backward direction of a recording head that ejects ink ,
A recording medium width information acquisition step for acquiring information relating to the width of the recording medium in the main scanning direction;
Based on the information about the width of the recording medium acquired in the recording medium width information acquisition step, 2N (N is a natural number) as the number of times of main scanning of the recording head required to complete recording in the one area And a selection step of selecting either 1N times or 2N + 1 times,
In the selection step, when the width of the recording medium indicated by the acquired information on the width of the recording medium is equal to or larger than a predetermined width, 2N + 1 is selected as the number of main scans, and the information on the width of the acquired recording medium indicates 2. A control method for an ink jet recording apparatus, wherein when the width of a recording medium is less than a predetermined width, 2N times are selected as the number of main scans.   A program for causing a computer to execute each step of the control method for an ink jet recording apparatus according to claim 4.

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