JP5077382B2 - Liquid ejection apparatus and program - Google Patents

Description

  The present invention relates to a liquid ejecting apparatus and a program for ejecting a second liquid for aggregating or precipitating components in a first liquid onto a recording medium before ejecting a first droplet from an ejection port.

  In order to reduce the bleeding of dots formed on paper, a line-type ink jet printer that discharges a pretreatment liquid that aggregates or deposits pigment components in ink prior to ink droplets is known where dots are formed. (For example, refer to Patent Document 1).

JP 2008-265324 A

  When the nozzles that discharge the pretreatment liquid are adjacent to each other in the main scanning direction orthogonal to the paper conveyance direction and are arranged at different positions in the conveyance direction, they are arranged at the same position in the conveyance direction on the paper. The timing at which the pretreatment liquid is ejected is different between two pixels adjacent to each other at the printing resolution in the main scanning direction. At this time, the pretreatment liquid ejected to the pixel first oozes out to the pixel adjacent to the pixel, so that the pretreatment liquid ejected later is ejected before the paper soaks into the paper. It may overlap with the exuded part of the prepared pretreatment liquid. At this time, in the overlapped portion, the pretreatment liquid discharged later does not sufficiently soak into the paper and tends to stay in the liquid layer state, so that when the discharged ink lands on the pretreatment liquid, Dots smaller than the desired size are formed, and the density of these small dots increases, resulting in streaks and density unevenness in the printed image. As a result, the print quality decreases.

  An object of the present invention is to provide a liquid ejection apparatus and a program that are less likely to cause streaks and density unevenness in a recorded image.

  The liquid ejection apparatus according to the present invention includes a transport mechanism that transports a recording medium in a predetermined transport direction, and a first liquid in which a plurality of first ejection ports for ejecting a first liquid that forms an image on the recording medium are formed. The first liquid has a discharge head and a plurality of second discharge ports for discharging a second liquid that acts on the first liquid to aggregate or deposit components in the first liquid, and the first liquid is related to the transport direction. A second liquid discharge head provided upstream of the discharge head; and a control unit that controls the first and second liquid discharge heads. The plurality of second discharge ports of the second liquid discharge head are arranged in an orthogonal direction orthogonal to the transport direction, and at least some of the plurality of second discharge ports are arranged at different positions with respect to the transport direction. The control means has the same position in the transport direction and the orthogonal direction among a plurality of unit regions corresponding to the resolution of an image partitioned on the recording medium along the transport direction and the orthogonal direction. From the second discharge port set consisting of the two second discharge ports arranged adjacent to each other in the orthogonal direction with respect to the two unit regions adjacent to each other and at different positions with respect to the transport direction. When two liquids are discharged and the amount of the second liquid discharged first from the second discharge port set to the two unit regions is equal to or greater than a first predetermined value, at least one of the second discharge port sets Before As the amount of the second liquid discharged from the second discharge port is decreased, and controls the second liquid ejection head.

  A program of the present invention includes a transport mechanism that transports a recording medium in a predetermined transport direction, a first liquid discharge head in which a plurality of first discharge ports for discharging a first liquid that forms an image on the recording medium are formed, And a plurality of second discharge ports for discharging a second liquid that acts on the first liquid to agglomerate or deposit components in the first liquid, and the first liquid discharge head in the transport direction. The computer is caused to function as a control unit that controls the first and second liquid discharge heads according to the liquid discharge apparatus including the second liquid discharge head provided upstream of the second liquid discharge head. The plurality of second discharge ports of the second liquid discharge head are arranged in an orthogonal direction orthogonal to the transport direction, and at least some of the plurality of second discharge ports are arranged at different positions with respect to the transport direction. The control means has the same position in the transport direction and the orthogonal direction among a plurality of unit regions corresponding to the resolution of an image partitioned on the recording medium along the transport direction and the orthogonal direction. From the second discharge port set consisting of the two second discharge ports arranged adjacent to each other in the orthogonal direction with respect to the two unit regions adjacent to each other and at different positions with respect to the transport direction. When two liquids are discharged and the amount of the second liquid discharged first from the second discharge port set to the two unit regions is equal to or greater than a first predetermined value, at least one of the second discharge port sets Before As the amount of the second liquid discharged from the second discharge port is decreased, and controls the second liquid ejection head.

  According to the present invention, since the amount of the second liquid ejected from at least one second ejection port of the second ejection port group is reduced, in the recording medium, the first ejection port of the second ejection port group is preceded by one second ejection port. It is possible to suppress the second liquid ejected in the second liquid from being overlapped before the second liquid ejected later from the other second ejection port sufficiently soaks into the recording medium. As a result, the second liquid ejected from either of the second ejection ports sufficiently permeates the recording medium and spreads to a desired range, and the area of the second liquid remaining in the liquid layer state is reduced. When the ink lands on the second liquid, the ink forms dots of a desired size and density. Therefore, streaks and density unevenness in the recorded image are less likely to occur, and deterioration in image quality can be suppressed.

  In the present invention, the amount of the second liquid ejected from the second ejection port that ejects the second liquid first with respect to the two unit regions in the second ejection port group. However, it is preferable to control the second liquid discharge head so as to decrease below the first predetermined value. According to this, since it is possible to prevent the second liquid discharged earlier from seeping out over a wide range, the second liquid discharged first before the second liquid discharged later sufficiently permeates the recording medium. Can be effectively prevented from overlapping.

  Further, in the present invention, the control means is configured such that the second liquid is discharged from the second discharge port set to the two unit areas and the second discharge port set discharges the second liquid. When an evaluation value indicating an area where dots related to the second liquid formed in the two unit regions overlap each other obtained from the amount of two liquids is equal to or greater than a second predetermined value, the evaluation value is the second predetermined value. It is preferable to reduce the amount of the second liquid discharged from at least one of the second discharge ports of the second discharge port set so as to be less than the value. According to this, since the area where the dots related to the second liquid formed in the two unit regions overlap with each other is surely less than the second predetermined value, before the second liquid discharged later sufficiently soaks into the recording medium. It is possible to reliably suppress overlapping with the previously discharged second liquid.

  At this time, the control means is an amount of the second liquid discharged from the second discharge port that discharges the second liquid first, out of the two second discharge ports related to the second discharge port group. More preferably, the second liquid discharge head is controlled so that the amount of the liquid discharge head decreases. According to this, since it is possible to prevent the second liquid discharged earlier from seeping out over a wide range, the second liquid discharged first before the second liquid discharged later sufficiently permeates the recording medium. Can be effectively prevented from overlapping.

  In the present invention, one of the adjacent second discharge ports and the one of the two adjacent second discharge ports that are the two second discharge ports adjacent to both sides of the second discharge port set in the orthogonal direction. The second discharge port associated with the second discharge port set adjacent to the adjacent second discharge port is disposed at the same position in the transport direction, and the other adjacent second discharge port and the other of the second Adjacent to both sides of the two unit regions with respect to the orthogonal direction when the second discharge port related to the second discharge port set adjacent to the adjacent second discharge port is disposed at the same position in the transport direction. A selection unit that selects the adjacent unit region with a small amount of the second liquid to be discharged from the two adjacent unit regions that are the unit region, and the control unit includes the two unit regions Before the selection means selected As the amount of the second liquid ejected to the unit area adjacent to the adjacent unit areas is reduced, it is preferable to control the second liquid ejection head. According to this, since the amount of the second liquid can be gradually changed along the transport direction when the application tendency of the second liquid in the two unit regions and two adjacent unit regions is seen, By maintaining the continuity of the change of the second liquid in the unit region, it is possible to suppress a decrease in image quality due to density unevenness.

  Further, in the present invention, the control means discharges the second liquid from the plurality of second discharge port groups continuous in the orthogonal direction while sharing the second discharge port in the orthogonal direction. It is preferable that the second liquid discharge head is controlled so that the second discharge ports in which the amount of the second liquid discharged is reduced are not adjacent to each other in the orthogonal direction with respect to the plurality of unit regions that are connected. According to this, it is possible to suppress a decrease in image quality due to a partial shortage of the discharge amount of the second liquid in the recording medium.

  Further, in the present invention, the control means controls the second liquid discharged from one of the second discharge ports related to the second discharge port set for both of the two unit regions connected in the transport direction. When the amount decreases, it is preferable to control the second liquid discharge head so that the amount of the second liquid discharged from the other second discharge port does not decrease. According to this, since the pixels in which the amount of the second liquid is reduced do not continue in the transport direction, it is possible to suppress the occurrence of streaks along the transport direction in the recorded image.

  According to the present invention, since the amount of the second liquid ejected from at least one second ejection port of the second ejection port group is reduced, in the recording medium, the first ejection port of one of the second ejection port groups is preceded. It is possible to suppress the second liquid ejected in the second liquid from being overlapped before the second liquid ejected later from the other second ejection port sufficiently soaks into the recording medium. As a result, the second liquid ejected from either of the second ejection ports sufficiently permeates the recording medium and spreads to a desired range, and the area of the second liquid remaining in the liquid layer state is reduced. When the ink lands on the second liquid, the ink forms dots and densities of the desired size. Therefore, streaks and density unevenness in the recorded image are less likely to occur, and deterioration in image quality can be suppressed.

1 is a schematic side view of an inkjet printer according to a first embodiment of the present invention. It is a top view which shows the discharge surface of the inkjet head shown in FIG. It is a functional block diagram of the control apparatus shown in FIG. It is a figure for demonstrating the function of the precoat density | concentration value correction | amendment part shown in FIG. 3 is a flowchart showing a printing operation of the ink jet printer shown in FIG. 1. It is a figure for demonstrating the modification based on 1st Embodiment. It is a top view which shows the discharge surface of the inkjet head which concerns on 2nd Embodiment of this invention. It is a functional block diagram of the control apparatus which concerns on 2nd Embodiment of this invention. It is a figure for demonstrating the function of the selection part shown in FIG.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

<First Embodiment>
As shown in FIG. 1, the inkjet printer 101 includes a transport unit 20 that transports the paper P from the right to the left in FIG. 1, and yellow (Y) and cyan (paper) on the paper P transported by the transport unit 20. C) Four inkjet heads 1 that eject ink droplets of magenta (M) and black (K), respectively, and a precoat head 2 that ejects droplets of a precoat liquid (Pre) that agglomerates or deposits the pigment component of each ink. And a control device 16 that controls the entire inkjet printer 101. In the present embodiment, the sub-scanning direction is a direction parallel to the transport direction when the paper P is transported by the transport unit 20, and the main scanning direction is a direction orthogonal to the sub-scanning direction and along the horizontal plane. Direction. In addition, a precoat liquid for aggregating pigment pigments is used for pigment ink, and a precoat liquid for depositing dye pigments is used for dye ink. The material of the precoat liquid can be appropriately selected from a liquid containing a polyvalent metal salt such as a cationic polymer or a magnesium salt. When the ink lands on the region of the paper P to which such a precoat liquid has been applied in advance, the polyvalent metal salt or the like acts on the dye or pigment that is the colorant of the ink, and the insoluble or hardly soluble metal composite or the like aggregates. Formed by precipitation. As a result, the penetrability of the adhering ink into the paper P is reduced, and the ink is easily fixed on the paper P.

  The transport unit 20 includes two belt rollers 6 and 7 and an endless transport belt 8 wound around the rollers 6 and 7. The belt roller 7 is a driving roller, and rotates counterclockwise in FIG. 1 when a driving force is applied from a conveyance motor (not shown). The belt roller 6 is a driven roller and rotates as the conveyor belt 8 travels due to the rotation of the belt roller 7. A weakly adhesive silicon layer is formed on the outer peripheral surface of the conveyor belt 8 and holds the loaded paper P. The paper P placed on the outer peripheral surface of the transport belt 8 is transported to the left in FIG. A peeling plate 13 is disposed on the downstream side in the transport direction of the four inkjet heads 1. The paper P transported in the transport direction sequentially passes under the precoat head 2 and the four inkjet heads 1 and then is peeled off from the transport surface of the transport belt 8 by the peeling plate 13 and is also shown in the drawing of the transport belt 8. The paper is discharged to a paper discharge tray 14 arranged on the left side. The platen 10 is disposed to face the four inkjet heads 1 and the precoat head 2 and supports the upper loop of the conveyor belt 8 from the inside. Thereby, a predetermined gap suitable for image formation is formed between the outer peripheral surface of the conveyor belt 8 and the ejection surfaces of the four inkjet heads 1 and the precoat head 2.

  The four inkjet heads 1 and the precoat head 2 have the same structure, each extend along the main scanning direction, and are arranged in parallel to each other in the sub scanning direction. The precoat head 2 is disposed on the upstream side in the transport direction of the four inkjet heads 1. The lower surface of each inkjet head 1 and precoat head 2 is an ejection surface on which a plurality of ejection ports 108a and 108b (see FIG. 2) are arranged. That is, the ink jet printer 101 is a line type color ink jet printer in which a plurality of ejection openings 108a and 108b through which ink droplets are ejected in the main scanning direction are arranged.

  The outer peripheral surface of the upper loop of the conveyor belt 8 and each discharge surface are parallel to each other while facing each other. When the paper P conveyed by the conveyance belt 8 passes just below the precoat head 2, the precoat liquid is applied from the precoat head 2 so that the precoat liquid is applied to the area where the image is formed on the upper surface of the paper P. A droplet is ejected. Thereafter, when the paper P passes just below the four inkjet heads 1, ink droplets of each color are sequentially ejected from each inkjet head 1 to a region where the precoat liquid is applied on the upper surface of the paper P. Thereby, a desired color image is formed on the paper P. At this time, when the ink droplets land on the precoat liquid applied on the paper P, the precoat liquid causes the pigment component of the ink droplets to aggregate or precipitate, so that ink bleeding on the paper P is prevented.

  Next, the inkjet head 1 and the precoat head 2 will be described in detail. Note that the precoat head 2 has substantially the same structure as the inkjet head 1, and thus the description thereof is omitted. As described above, the lower surface of the inkjet head 1 is a discharge surface on which the discharge ports 108a and 108b are formed. As shown in FIG. 2, on the discharge surface, a plurality of discharge ports 108a and 108b are arranged in a staggered manner at an interval of 600 dpi along the main scanning direction. At this time, the plurality of ejection openings 108a arranged in the main scanning direction are located upstream of the plurality of ejection openings 108b arranged in the main scanning direction. Thereby, the discharge ports 108a and 108b are alternately arranged in the main scanning direction. When an image is formed on the conveyed paper P, the ink droplets ejected from the ejection port 108 b land on the paper P after the ink droplets ejected from the ejection port 108 a land on the paper P.

  Next, the control device 16 will be described. The control device 16 includes a CPU (Central Processing Unit), a program executed by the CPU, and an EEPROM (Electrically Erasable and Programmable Read Only Memory) that stores data used for these programs in a rewritable manner. It includes RAM (Random Access Memory) for temporary storage. Each functional unit constituting the control device 16 is constructed by cooperation of these hardware and software in the EEPROM. As shown in FIG. 3, the control device 16 controls the entire inkjet printer 101, and includes a conveyance control unit 45, an image data storage unit 41, a head control unit 42, an evaluation value calculation unit 43, and a precoat. A density value correction unit 44.

  The transport controller 45 controls the transport motor of the transport unit 20 so that the paper P is transported along the transport direction. The image data storage unit 41 stores image data relating to an image printed on the paper P. The image data includes yellow, cyan, and magenta for each of a plurality of pixels (unit areas) corresponding to the resolution of an image partitioned on the paper P along the transport direction and the main scanning direction (orthogonal direction orthogonal to the transport direction). And density values relating to the black inks and the precoat liquid. The density value is quantized into four values corresponding to no discharge, small droplet, medium droplet, and large droplet.

  The evaluation value calculation unit 43 includes, in the main scanning direction, each pixel row that appears in an odd number (may be an even number) in the transport direction among the pixel rows formed of a plurality of pixels arranged in the main scanning direction. A plurality of pixel sets composed of two adjacent pixels are defined. As described above, since the discharge ports 108a and 108b are alternately arranged in the main scanning direction, as shown in FIG. 4, one pixel of the pixel group corresponds to the discharge port 108a and the other pixel. Corresponds to the discharge port 108b. The evaluation value calculation unit 43 sets the ejection port 108a and the ejection port 108b corresponding to each pixel of the pixel group as the ejection port group 61 associated with the pixel group.

  The evaluation value calculation unit 43 discharges first in the pixel group, that is, the amount of the precoat liquid discharged from the discharge port 108a is equal to or larger than a predetermined amount (first predetermined value: large droplet in the present embodiment). For example, the area where the precoat dots 51a and 51b formed in each pixel of the pixel set overlap is calculated as the evaluation value related to the pixel set. Specifically, the evaluation value calculation unit 43, in the pixel group, the precoat liquid discharged from the discharge port 108 a first landed on the paper P and then the precoat liquid discharged from the discharge port 108 b landed on the paper P. Get the elapsed time until. This elapsed time corresponds to the time during which the paper P moves the distance in the transport direction from the discharge port 108a to the discharge port 108b. In the period until the precoat liquid that has landed on the paper P completely penetrates into the paper P, as the elapsed time becomes longer, the precoat liquid that has landed on the paper P penetrates into the paper P and the area of the precoat dots 51a increases. . The evaluation value calculation unit 43 has a table in which the concentration value and elapsed time of the precoat liquid are associated with the area of the precoat dot. The evaluation value calculation unit 43 refers to this table to calculate the area of the precoat dot 51a from the concentration value (amount) of the precoat liquid ejected to the pixel where the precoat dot 51a obtained from the image data is disposed and the elapsed time. Get. Further, the evaluation value calculation unit 43 obtains the area of the precoat dot 51b from the density value (amount) of the precoat liquid discharged to the pixel where the precoat dot 51b obtained from the image data is arranged. The evaluation value calculation unit 43 calculates, as an evaluation value, an area where the precoat dots 51a and 51b overlap from the areas and positions of the precoat dots 51a and 51b. Even if the evaluation value calculation unit 43 obtains the evaluation value related to the pixel set directly from the table in which the concentration value and elapsed time of the precoat liquid of each pixel related to the pixel set and the evaluation value are associated with each other. Good.

  The precoat density value correction unit 44 performs density value correction processing related to the precoat liquid relating to the image data stored in the image data storage unit 41. When the correction process is started, the precoat density value correction unit 44, when the evaluation value calculated by the evaluation value calculation unit 43 is equal to or greater than a predetermined value (second predetermined value), that is, the evaluation value, that is, the precoat dots 51a and 51b. In the pixel group related to the evaluation value, the concentration value of the precoat liquid of the pixel from which the precoat liquid is first discharged from the discharge port 108a is reduced so that the overlapping area is less than a predetermined value. That is, the amount of the precoat liquid discharged from the discharge port 108a of the discharge port group 61 is reduced. FIG. 4 shows an example in which the density value is reduced so that the amount of the precoat liquid to be discharged is changed from a large droplet to a medium droplet.

  Since the correction processing described above is performed only for pixel columns that appear in odd order with respect to the transport direction, pixels with reduced density values related to the precoat liquid do not adjoin each other in the transport direction. Further, when attention is paid to two discharge port groups 61 that share the same discharge ports 108a and 108b and are continuous in the main scanning direction, discharge is performed in a plurality of pixels connected in the main scanning direction corresponding to the discharge ports 108a and 108b. Pixels in which the amount of precoat liquid to be reduced are not adjacent to each other in the main scanning direction.

  Returning to FIG. 3, the head control unit 42 discharges precoat droplets having a predetermined volume at a predetermined timing based on the image data stored in the image data storage unit 41 after the above correction processing is completed. The precoat head 2 is controlled so as to be discharged from the outlets 108a and 198b, and each inkjet head 1 is controlled so that ink droplets having a predetermined volume are discharged from the discharge ports 108a and 108b at a predetermined timing. .

  Next, the printing operation of the inkjet printer 101 will be described. As shown in FIG. 5, when the inkjet printer 101 receives a print command together with image data from a host computer, the received image data is stored in the image data storage unit 41 (S101). The evaluation value calculation unit 43 defines a pixel group for each pixel column that appears in odd numbers along the transport direction. Furthermore, the evaluation value calculation unit 43 calculates an evaluation value for a pixel group in which the amount of precoat liquid ejected from the ejection port 108a is a large droplet among the defined pixel groups (S102). When the evaluation value calculated by the evaluation value calculation unit 43 is equal to or greater than a predetermined value (S103: YES), the precoat density value correction unit 44 determines whether the evaluation value is less than the predetermined value in the pixel set related to the evaluation value. The concentration value of the precoat liquid relating to the pixel corresponding to the ejection port 108a is reduced (S104). The precoat density value correction unit 44 repeats the above-described process until the correction of the precoat liquid density value is completed for all the pixel sets for which the evaluation value calculation unit 43 has calculated the evaluation value (S105: NO).

  When the correction of the density value of the precoat liquid is completed for all the pixel groups (S105: YES), the head control unit 42 removes the precoat liquid and ink droplets based on the image data corrected by the precoat density value correction unit 44. The precoat head 2 and each inkjet head 1 are controlled so as to be discharged onto the paper P (S106). Thus, the printing operation is completed, and the flowchart shown in FIG.

  As described above, according to the ink jet printer 101 of the present embodiment, correction is performed so that the amount of precoat liquid discharged from the discharge port 108a is reduced for pixel groups in which the precoat dots 51a and 51b overlap with each other with an area of a predetermined value or more. Since the processing is performed, the precoat liquid discharged from the discharge port 108a of the discharge port set 61 on the paper P before the precoat liquid discharged later from the discharge port 108b sufficiently soaks into the paper P. Can be suppressed. As a result, the precoat liquid discharged from either of the discharge ports 108a and 108b sufficiently permeates the paper P and spreads over a desired range, and the area of the precoat liquid remaining in the liquid layer state is reduced. When landing on the precoat liquid, the ink forms dots of the desired size and density. Therefore, streaks and density unevenness in the printed image are less likely to occur, and deterioration in image quality can be suppressed.

  In addition, the precoat density value correction unit 44, when the evaluation value calculated by the evaluation value calculation unit 43 is equal to or greater than a predetermined value, in the pixel group related to the evaluation value, the ejection port 108a so that the evaluation value is less than the predetermined value. In order to reduce the concentration value of the precoat liquid of the pixels corresponding to the precoat liquid 51a and 51b formed in each pixel of the pixel set, the area where the precoat dods 51a and 51b overlap is surely less than a predetermined value, so that the precoat liquid discharged later Can be reliably suppressed from overlapping with the precoat liquid discharged before the sheet P is sufficiently soaked into the paper P.

  Furthermore, the precoat concentration value correction unit 44 is configured so that the amount of the precoat liquid discharged from the discharge port 108a that discharges the precoat liquid first out of the two discharge ports 108a and 108b of the discharge port set 61 decreases. Since the concentration value related to the precoat liquid of the pixel corresponding to the discharge port 108a of the pixel group is reduced, it is possible to suppress the precoat liquid discharged earlier in the pixel group from leaking over a wide range. Thereby, it is possible to effectively prevent the precoat liquid discharged later from overlapping with the precoat liquid discharged before the paper P is sufficiently infiltrated into the paper P.

  In addition, since the pixels with reduced density values are not adjacent to each other in the transport direction and the main scanning direction, it is possible to suppress a partial shortage of the precoat liquid on the paper P. In addition, since the pixels in which the amount of the precoat liquid is reduced do not continue in the transport direction, it is possible to suppress the occurrence of streaks along the transport direction in the printed image.

<Modification>
In the present embodiment, the precoat density value correction unit 44 is configured to reduce the density value related to the precoat liquid only for pixels belonging to each pixel column that appear in odd order with respect to the transport direction, as shown in FIG. The concentration value of the precoat liquid relating to the pixel to which the precoat liquid is discharged later from the discharge port 108b in each pixel group in the pixel row that appears in an even order in the transport direction may be further reduced. In FIG. 6, the amount of the precoat liquid discharged from the discharge port 108 b to the pixel is reduced to 0 by reducing the concentration value of the precoat liquid related to the pixel from the large droplet to 0.

  Accordingly, it is possible to further prevent the precoat liquid discharged later from overlapping with the precoat liquid discharged before the paper P is sufficiently soaked in the pixel rows appearing in the even order.

Second Embodiment
A second embodiment will be described. In addition, about the member and function part substantially the same as 1st Embodiment, the code | symbol same as 1st Embodiment is attached | subjected and the description is abbreviate | omitted. As shown in FIG. 7, on the ejection surface of the precoat head 202, there are four ejection port groups composed of a plurality of ejection ports 108c and 108d arranged at intervals of 600 dpi in the main scanning direction along the main scanning direction. Arranged in a staggered pattern. At this time, the discharge group located on the upstream side in the sub-scanning direction is constituted by the discharge port 108c, and the discharge group located on the downstream side is constituted by the discharge port 108d. For this reason, when an image is formed on the transported paper P, the ink droplets ejected from the ejection port 108d land on the paper P after the ink droplets ejected from the ejection port 108c land on the paper P. .

  As illustrated in FIG. 8, the control device 116 includes a conveyance control unit 45, an image data storage unit 41, a head control unit 42, a selection unit 243, and a precoat density value correction unit 244. As illustrated in FIG. 9, the selection unit 243 defines two discharge ports 108 c and 108 d that are arranged at different positions in the transport direction and are adjacent to each other in the main scanning direction as a discharge port group 261. For each pixel set composed of two pixels corresponding to the discharge ports 108c and 108d of the defined discharge port set 261, the selection unit 243 has two pixels adjacent to each other in the main scanning direction (adjacent unit). In the region, a pixel having a small concentration value of the precoat liquid is selected. For example, in the case of FIG. 9, among the pixels on both sides in the main scanning direction of the pixel set corresponding to the discharge port set 261, the concentration value (middle of the precoat liquid of the pixel corresponding to the discharge port 108c adjacent to the left in FIG. Since the droplet) is smaller than the concentration value (large droplet) of the precoat liquid of the pixel corresponding to the ejection port 108d adjacent to the other, the selection unit 243 selects the pixel having a small concentration value of the precoat liquid.

  The precoat density value correction unit 244 reduces the density value of the precoat liquid of the pixel adjacent to the pixel selected by the selection unit 243 among the two pixels in the pixel set. Thereby, in the example of FIG. 9, the amount of the precoat liquid discharged from the discharge port 108c of the discharge port set 261 decreases.

  According to this embodiment, since the amount of precoat liquid discharged from one of the discharge ports 108c and 108d is reduced in each pixel group, the precoat previously discharged from the discharge port 108c of the discharge port group 261 on the paper P is reduced. It is possible to prevent the precoat liquid discharged later from the discharge port 108d from overlapping the liquid before it sufficiently permeates the paper P. As a result, the precoat liquid ejected from either of the ejection openings 108c and 108d sufficiently permeates the paper P and spreads over a desired range, and when the ejected ink lands on the precoat liquid, the ink has dots of a desired size. Form. Therefore, streaks and density unevenness in the printed image are less likely to occur, and deterioration in image quality can be suppressed.

  In addition, since the amount of the precoat liquid discharged to the pixels adjacent to the pixel selected by the selection unit 243 out of the two pixels in the pixel group is decreased, the amount of the precoat liquid is gradually changed along the transport direction. Therefore, by maintaining the continuity of the change in the precoat liquid, it is possible to suppress a decrease in image quality due to density unevenness.

  The preferred embodiments of the present invention have been described above. However, the present invention is not limited to the above-described embodiments, and various modifications can be made as long as they are described in the claims. In the first embodiment described above, for each pixel group, the amount of the precoat liquid discharged from the discharge port 108a from which the precoat liquid is discharged first is reduced, but the discharge port 108b from which the precoat liquid is discharged later. It may be configured to reduce the amount of precoat liquid discharged from the nozzles, or may be configured to reduce both the amount of precoat liquid discharged from the discharge ports 108a and 108b, and these patterns are mixed. It may be a configuration.

  Further, in the first embodiment described above, when the evaluation value calculated by the evaluation value calculation unit 43 is equal to or greater than a predetermined value, the precoat density value correction unit 44 causes the discharge port 108b so that the evaluation value is less than the predetermined value. However, the precoat density value correction unit is discharged from either one of the discharge ports 108a and 108b for each pixel set without calculating the evaluation value. The configuration may be such that the concentration value of the precoat liquid of the corresponding pixel is reduced so that the amount of the precoat liquid is less than a predetermined concentration value.

  In addition, in the first embodiment described above, the correction processing is performed so that the pixels with reduced density values are not adjacent to each other in the transport direction and the main scanning direction. However, the density values are reduced. The correction processing may be performed so that at least some of the pixels are adjacent to each other in at least one of the transport direction and the main scanning direction.

  Moreover, the structure which discharges the ink droplet of a several color and a precoat droplet may be sufficient as one inkjet head.

  The present invention is also applicable to a liquid ejecting apparatus that ejects liquid other than ink. Further, the present invention is not limited to a printer, and can be applied to a facsimile, a copier, and the like. In addition, the head controller does not drive the actuator unit of the precoat head or the actuator unit of each inkjet head, but discharges the precoat liquid or ink from the head by driving the precoat head head and the heating element of each inkjet head. It is good. In addition, the action of the precoat liquid on the ink includes agglomeration or precipitation of components (pigments and dyes) in the ink by a chemical reaction caused by mixing the ink and the precoat liquid. It also includes aggregating or precipitating components (pigments and dyes) in the ink without chemical reaction. In general, a precoat liquid for aggregating pigment pigment is used for pigment ink, and a precoat liquid for depositing dye pigment is used for dye ink as described above. It may have both effects of precipitation. Furthermore, the present invention can also be applied to application software or driver software installed in a computer.

DESCRIPTION OF SYMBOLS 1 Inkjet head 2,202 Precoat head 16,116 Control apparatus 20 Conveyance unit 41 Image data storage part 42 Head control part 43 Evaluation value calculation part 44,244 Precoat density value correction | amendment part 45 Conveyance control part 51a, 51b Precoat dot 61,261 Discharge port group 101 Inkjet printers 108a to 108d Discharge port 243 selection unit

Claims (8)

A transport mechanism for transporting the recording medium in a predetermined transport direction;
A first liquid discharge head in which a plurality of first discharge ports for discharging a first liquid for forming an image on a recording medium are formed;
The first liquid discharge head has a plurality of second discharge ports for discharging a second liquid that acts on the first liquid and causes the components in the first liquid to agglomerate or precipitate, and with respect to the transport direction than the first liquid discharge head. A second liquid discharge head provided upstream;
Control means for controlling the first and second liquid ejection heads,
The plurality of second discharge ports of the second liquid discharge head are arranged in an orthogonal direction orthogonal to the transport direction, and at least some of the plurality of second discharge ports are arranged at different positions with respect to the transport direction. Has been
The control means includes a plurality of unit regions corresponding to the resolution of an image partitioned on the recording medium along the transport direction and the orthogonal direction, the positions in the transport direction being the same and adjacent to the orthogonal direction. The second liquid is discharged from a second discharge port set including two second discharge ports that are arranged adjacent to each other in the orthogonal direction with respect to the two unit regions and are arranged at different positions with respect to the transport direction. And when the amount of the second liquid discharged from the second discharge port set to the two unit regions first is equal to or greater than a first predetermined value, at least one second of the second discharge port set. A liquid ejecting apparatus, wherein the second liquid ejecting head is controlled so that the amount of the second liquid ejected from an ejection port is reduced.   In the second discharge port set, the control unit is configured to determine whether the amount of the second liquid discharged from the second discharge port that discharges the second liquid first with respect to the two unit regions is the first discharge amount. The liquid ejecting apparatus according to claim 1, wherein the second liquid ejecting head is controlled so as to decrease below a predetermined value.   The control means is obtained from a difference in time during which the second liquid is discharged from the second discharge port set to the two unit regions and an amount of the second liquid discharged from the second discharge port set. When the evaluation value indicating the area where the dots related to the second liquid formed in the two unit regions overlap is greater than or equal to a second predetermined value, the evaluation value is less than the second predetermined value. The liquid ejection apparatus according to claim 1, wherein the amount of the second liquid ejected from at least one of the second ejection ports of the second ejection port group is reduced.   The control means reduces the amount of the second liquid discharged from the second discharge port that discharges the second liquid first, out of the two second discharge ports related to the second discharge port set. The liquid discharge apparatus according to claim 3, wherein the second liquid discharge head is controlled as described above. Of the two adjacent second discharge ports that are the two second discharge ports adjacent to both sides of the second discharge port group with respect to the orthogonal direction, one of the adjacent second discharge ports and the one of the adjacent second discharge ports. The second discharge port related to the second discharge port group adjacent to the discharge port is disposed at the same position in the transport direction, and the other adjacent second discharge port and the other adjacent second discharge port In the unit region adjacent to both sides of the two unit regions with respect to the orthogonal direction, when the second discharge ports related to the second discharge port group adjacent to each other are arranged at the same position in the transport direction. A selection means for selecting the adjacent unit region in which the amount of the second liquid to be discharged is small among the two adjacent unit regions;
The control unit is configured to discharge the second liquid so that an amount of the second liquid discharged to the unit region adjacent to the adjacent unit region selected by the selection unit among the two unit regions is reduced. The liquid ejecting apparatus according to claim 1, wherein the head is controlled.   The control means is configured to discharge the second liquid from the plurality of second discharge port groups that are continuous in the orthogonal direction while sharing the second discharge port, and the plurality of unit regions that are continuous in the orthogonal direction. The second liquid discharge head is controlled so that the second discharge ports from which the amount of the second liquid to be discharged decreases are not adjacent to each other in the orthogonal direction. The liquid discharge apparatus according to claim 1.   When the amount of the second liquid discharged from one of the second discharge ports related to the second discharge port set decreases for both of the two unit regions that are continuous in the transport direction, The liquid according to claim 1, wherein the second liquid discharge head is controlled so that the amount of the second liquid discharged from the other second discharge port does not decrease. Discharge device. A transport mechanism for transporting the recording medium in a predetermined transport direction, a first liquid ejection head having a plurality of first ejection ports for ejecting a first liquid for forming an image on the recording medium, and the first liquid And a plurality of second discharge ports for discharging a second liquid for aggregating or precipitating components in the first liquid, and provided upstream of the first liquid discharge head in the transport direction. A computer functioning as control means for controlling the first and second liquid ejection heads according to the liquid ejection apparatus including the second liquid ejection head;
The plurality of second discharge ports of the second liquid discharge head are arranged in an orthogonal direction orthogonal to the transport direction, and at least some of the plurality of second discharge ports are arranged at different positions with respect to the transport direction. Has been
The control means includes a plurality of unit regions corresponding to the resolution of an image partitioned on the recording medium along the transport direction and the orthogonal direction, the positions in the transport direction being the same and adjacent to the orthogonal direction. The second liquid is discharged from a second discharge port set including two second discharge ports that are arranged adjacent to each other in the orthogonal direction with respect to the two unit regions and are arranged at different positions with respect to the transport direction. And when the amount of the second liquid discharged from the second discharge port set to the two unit regions first is equal to or greater than a first predetermined value, at least one second of the second discharge port set. A program for controlling the second liquid discharge head so that the amount of the second liquid discharged from the discharge port decreases.

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