JP2008229980A - Liquid delivering device and liquid delivering method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To land liquid droplets from respective nozzles at accurate positions on a medium and to prevent an image from being deteriorated. <P>SOLUTION: A liquid delivering device has a first nozzle row in which a plurality of first nozzles for delivering a colored liquid on the medium are arranged in a specified direction, a second nozzle row in which a plurality of second nozzles for delivering a colored liquid on the medium are arranged in a specified direction, a third nozzle row in which a plurality of third nozzles for delivering a colored liquid on the medium are arranged in a specified direction. The third nozzle row is arranged between the first nozzle row and the second nozzle row. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a liquid ejection apparatus and a liquid ejection method.

As one of liquid ejecting apparatuses, an ink jet printer that performs printing by ejecting ink from nozzles onto various media such as paper, cloth, and film is known.
Therefore, the fibers in the solid printing area where a large amount of ink is applied expand due to moisture in the ink, while the fibers in the area where the ink is not applied or where only a small amount of ink is applied do not swell so much that the medium is wrinkled. A cockling phenomenon (cockle) may occur. In view of this, a method has been proposed in which a colorless and transparent ink containing moisture in the ink is applied to areas other than the solid-printing area so that fiber expansion is made uniform and the occurrence of cockling phenomenon is alleviated. (Patent Document 1)
JP-A-6-198868 JP 2001-205827 A

The cockling phenomenon occurs from the moment when ink droplets land on the medium. For this reason, for example, when solid printing is performed with four color inks (YMCK), if the medium is wrinkled from the middle of solid printing, the ink droplets do not land at the correct position and image degradation occurs. To do.
Accordingly, an object of the present invention is to prevent image degradation.

  A main invention for achieving the above object is to provide a first nozzle row in which a plurality of first nozzles for discharging a colored liquid to a medium are arranged in a predetermined direction, and a plurality of second nozzles for discharging a colored liquid to the medium. A second nozzle row arranged in the predetermined direction, and a third nozzle row in which a plurality of third nozzles for discharging colorless liquid onto the medium are arranged in the predetermined direction, The third nozzle row is disposed between the first nozzle row and the second nozzle row.

  Other features of the present invention will become apparent from the description of this specification and the accompanying drawings.

=== Summary of disclosure ===
At least the following will become apparent from the description of the present specification and the accompanying drawings.

That is, a first nozzle row in which a plurality of first nozzles that discharge a colored liquid to a medium are arranged in a predetermined direction, and a second nozzle that has a plurality of second nozzles that discharge a colored liquid in the medium in the predetermined direction. A liquid ejection apparatus having a nozzle row and a third nozzle row in which a plurality of third nozzles for discharging colorless liquid onto the medium are arranged in the predetermined direction, wherein the third nozzle row is the first nozzle It is possible to realize a liquid ejection apparatus that is arranged between a row and the second nozzle row.
According to such a liquid ejection device, a large amount of liquid is applied to a specific area from the first nozzle and the second nozzle first, and a cockling phenomenon occurs in the medium during the ejection of the liquid. Can be prevented. As a result, the liquid droplets from each nozzle land on the correct position on the medium, and the occurrence of image deterioration is prevented.

In this liquid ejection apparatus, the color of the liquid ejected by the first nozzle is different from the color of the liquid ejected by the second nozzle.
According to such a liquid discharge apparatus, since the liquid is discharged from the third nozzle after the liquid is discharged from the first nozzle until the liquid is discharged from the second nozzle, the first nozzle It is possible to prevent liquid droplets (dots) on the medium formed by the above and liquid droplets (dots) on the medium formed by the second nozzle from being mixed (color bleed).

This liquid ejection apparatus includes a transport mechanism that transports the medium in a transport direction that intersects the predetermined direction.
According to such a liquid ejecting apparatus, it is possible to prevent the cockling phenomenon and image degradation of the medium during the liquid ejection. In a liquid ejecting apparatus (for example, a line head printer) that transports a medium in the transport direction, the nozzles do not move and the medium is transported without stopping, so the liquid is ejected. Assuming that the rows are arranged upstream or downstream in the transport direction, a large amount of ink is applied to a specific area first, causing a cockling phenomenon on the medium and being discharged from the downstream nozzle row. Ink droplets that do not land at the correct position may cause image degradation. In addition, since the liquid is discharged at high speed without stopping the medium, the effect of preventing color bleeding can be further obtained.

In this liquid ejection apparatus, a nozzle row in which a plurality of nozzles that eject colored liquid are arranged in the predetermined direction is provided between the first nozzle row and the third nozzle row, and the second nozzle row And a nozzle row in which a plurality of nozzles for discharging colored liquid are arranged in the predetermined direction between the third nozzle row and the third nozzle row.
According to such a liquid ejecting apparatus, the third nozzle row that ejects a colorless liquid is disposed at the center of the colored ink nozzle row, so that regardless of which colored ink nozzle row the liquid is applied first. In addition, the occurrence of a cockling phenomenon during liquid discharge can be prevented. Further, when liquid is ejected from all the colored ink nozzle rows, the liquid (water) is applied on average on the image (area where the colored liquid is applied) and its periphery.

In this liquid ejecting apparatus, when the colored liquid is black ink, yellow ink, magenta ink, and cyan ink, black ink is ejected from the first nozzle, and yellow ink is ejected from the second nozzle. thing.
According to such a liquid ejecting apparatus, since the nozzle rows for ejecting liquids of colors (yellow and black) that are liable to cause image degradation due to color bleeding are arranged in the most separated state, image degradation can be further prevented. .

In such a liquid ejecting apparatus, when the liquid is ejected on both sides of the medium, the transport direction when the liquid is ejected on one surface of the medium is such that the liquid is ejected on the other surface of the medium. It must be in the direction opposite to the transport direction when
According to such a liquid ejecting apparatus, the third nozzle row that ejects a colorless liquid is arranged in the center of the colored ink when ejecting the liquid onto either surface of the medium. Therefore, since the third nozzle row is not biased toward the upstream side or the downstream side in the transport direction, it is possible to prevent the liquid from being applied to a specific region first.

In this liquid ejection apparatus, the third nozzle is displaced in the predetermined direction with respect to the first nozzle and the second nozzle.
According to such a liquid ejection apparatus, when a liquid droplet is formed by the third nozzle adjacent to the liquid droplet formed by the first nozzle and the second nozzle, the liquid is ejected from the first nozzle or the second nozzle. The area where the liquid (colored liquid) and the colorless liquid come into contact with each other can be reduced, and the colored liquid can be prevented from bleeding with the colorless liquid.

In this liquid ejecting apparatus, the colorless liquid is ejected from the third nozzle around an image formed by the colored liquid.
According to such a liquid ejecting apparatus, it is possible to prevent the occurrence of cockling phenomenon and image deterioration.

In this liquid discharge apparatus, the discharge amount from the third nozzle decreases as the distance from the image increases.
According to such a liquid ejection device, it is possible to suppress consumption of colorless liquid.

In the liquid ejecting apparatus, when the deformation in the first direction of the medium caused by the image is larger than the deformation in the second direction intersecting the first direction, The amount of the colorless liquid discharged around the first direction is larger than the amount of the colorless liquid discharged around the first direction.
According to such a liquid ejection device, it is possible to suppress consumption of colorless liquid.

In this liquid ejection apparatus, when the medium is configured by fibers, and the liquid is deformed more greatly in the first direction than in the second direction when the liquid is ejected to the medium, the image On the other hand, the amount of the colorless liquid discharged around the first direction is larger than the amount of the colorless liquid discharged around the second direction.
According to such a liquid ejection device, it is possible to suppress consumption of colorless liquid.

Also, a first nozzle row in which first nozzles that discharge colored liquid to the medium are arranged in a predetermined direction, and a second nozzle row in which a plurality of second nozzles that discharge colored liquid to the medium are arranged in the predetermined direction. And a third nozzle row in which a plurality of third nozzles for discharging colorless liquid onto the medium are arranged in the predetermined direction, wherein the colored liquid is discharged from the first nozzle. It is possible to realize a liquid ejection method in which the colorless liquid is ejected to the medium, the colorless liquid is ejected to the medium from the third nozzle, and the colored liquid is ejected to the medium from the second nozzle.
According to such a liquid discharge method, it is possible to prevent the occurrence of cockling phenomenon and image deterioration during liquid discharge.

=== Configuration of Line Head Printer ===
Hereinafter, an embodiment will be described by taking a liquid ejection apparatus as an ink jet printer and a line head printer (printer 1) in the ink jet printer as an example. In the line head printer, nozzle rows arranged in the paper width direction (predetermined direction) are formed on the lower surface of the head unit, and the printing paper is conveyed without stopping so as to face the lower surface of the head unit. An image is formed.

  FIG. 1 is a block diagram showing the overall configuration of the printer 1 according to this embodiment. FIG. 2A is a cross-sectional view of the printer 1. FIG. 2B is a diagram illustrating a state in which the printer 1 transports the paper S (medium). The printer 1 that has received print data from the computer 60, which is an external device, controls each unit (conveyance unit 20, head unit 30) by the controller 10, and forms an image on the paper S. Further, the detector group 50 monitors the situation in the printer 1, and the controller 10 controls each unit based on the detection result.

  The controller 10 is a control unit for controlling the printer 1. The interface unit 11 is for transmitting and receiving data between the computer 60 as an external device and the printer 1. The CPU 12 is an arithmetic processing unit for controlling the entire printer 1. The memory 13 is for securing an area for storing the program of the CPU 12 and a work area. The CPU 12 controls each unit by a unit control circuit 14 according to a program stored in the memory 13.

  The transport unit 20 feeds the paper S to a printable position, and transports the paper S by a predetermined transport amount in the transport direction during printing. The paper feed roller 23 is a roller for automatically feeding the paper S inserted into the paper insertion opening onto the transport belt 22 in the printer 1. Then, the ring-shaped transport belt 22 is rotated by the transport rollers 21A and 21B, and the sheet S on the transport belt 22 is transported. The paper S is electrostatically adsorbed or vacuum adsorbed to the transport belt 22 (not shown).

  The head unit 30 is for ejecting ink onto the paper S, and has a plurality of heads 31. On the lower surface of the head 31, a plurality of nozzles that are ink ejection portions are provided. Each nozzle is provided with a pressure chamber (not shown) containing ink and a drive element (piezo element PZT) for changing the volume of the pressure chamber to eject ink.

=== About the printing procedure ===
When receiving a print command and print data from the computer 60, the controller 10 analyzes the contents of various commands included in the print data and performs the following processing using each unit.
First, the controller 10 rotates the paper feed roller 23 to feed the paper S to be printed onto the transport belt 22. Then, the controller 10 rotates the transport rollers 21A and 21B to position the fed paper S at the print start position. At this time, the sheet S faces at least some of the nozzles of the upstream head unit 30A.
Next, the sheet S is conveyed on the conveyor belt 22 without stopping at a constant speed, and passes under the upstream head unit 30A and the downstream head unit 30B. While the sheet S passes under the head unit 30, ink is intermittently ejected from each nozzle. As a result, a dot row (raster line) composed of a plurality of dots along the transport direction is formed on the paper S. Finally, the controller 10 discharges the paper S on which image printing has been completed from the transport roller 21B.

=== About the cockling phenomenon and countermeasures ===
FIG. 3A is a diagram illustrating a state of cockling phenomenon of the paper S. FIG. In the drawing, the surface of the sheet S on which the image A is formed, and the longitudinal and lateral sections of the sheet S are shown.

  When the paper S is plain paper and the image A is formed on the paper S by solid printing on which a large amount of ink is applied, the fibers of the paper S absorb moisture that is a solvent component of the ink and expand. Then, if ink is not applied to other areas other than the image A on the paper S or only a small amount of ink is applied, the expansion as much as the image A does not occur in the other areas. Therefore, the area of the image A to which a large amount of ink is applied is deformed into a raised shape as compared with other areas. That is, the sheet S is wrinkled, and this phenomenon is called “cockling phenomenon”.

  The cockling phenomenon occurs when a large amount of ink is applied only to a specific location. Therefore, if ink is applied not only to the area of the image A but also to other areas, the fibers in the other areas also expand in the same manner, and the deformation of the paper S can be mitigated. In this case, since the ink applied to the other region has no relation to the print image, it needs to be as colorless and transparent as possible.

  Therefore, in this embodiment, an anti-cockling agent is applied to the periphery of the area to be solid-printed as in image A (the anti-cockling agent is not applied to the area of image A). The cockling inhibitor is a colorless and transparent liquid containing moisture caused by the cockling phenomenon. By doing so, the expansion of the fibers of the paper S can be made uniform, and the cockling phenomenon can be alleviated. Since the substance that affects the cockling phenomenon is moisture, the cockling inhibitor may be pure water. However, it is preferable that the cockling preventive agent has physical properties as close as possible to the ink so that the ink can be stably discharged by ink jetting.

  FIG. 3B is a diagram illustrating an application example of the cockling inhibitor. By applying an anti-cockling agent to the area (hatched area, hereinafter referred to as area B) of the area (black area, hereinafter referred to as area A) of the image A to be solid-printed, the cockling phenomenon Can be relaxed. At this time, for example, in the region between the outer periphery of the region A and the frame F1, a cockling inhibitor is applied so that a moisture amount of 75% of the moisture amount applied to the region A is applied, and the frame F1 An area between the frames F2 is coated with an anti-cockling agent so that 50% of the amount of moisture applied to the area A is applied, and an area between the frames F2 and F3 is an area. An anti-cockling agent is applied so that a moisture content of 25% of the moisture content applied to A is applied. As described above, the coating amount of the cockling inhibitor may be decreased as the distance from the image A increases. Further, if the cockling preventing agent is applied to the periphery of the image A, it is not necessary to apply the cockling preventing agent to the entire area other than the image A on the paper S.

  The cockling phenomenon occurs when an area where a large amount of ink is applied and an area where the ink is not applied are adjacent to each other, and the amount of moisture penetrating into the fibers of the paper S changes abruptly within a certain area. Therefore, it is not necessary to apply the same amount of moisture (anti-cockling agent) as that of image A to all areas other than image A on paper S, and the application amount of anti-cockling agent is reduced as the distance from image A increases. However, the occurrence of the cockling phenomenon can be alleviated. In addition, the consumption of the cockling inhibitor can be saved by doing so.

  FIG. 4A is a diagram illustrating a direction in which the paper S is likely to wrinkle. The paper has a fiber direction (paper eyes). For example, if the paper S is constituted by a fiber flow along the longitudinal direction, the paper S is likely to wrinkle along the lateral direction intersecting the longitudinal direction. (The cockling phenomenon is likely to occur). That is, when the image A by solid printing is formed on the entire area of the paper S, the paper S is wrinkled in the horizontal direction rather than the longitudinal direction. This is because the fibers of the paper S are easily deformed more greatly in the lateral direction than in the longitudinal direction due to moisture.

  FIG. 4B is a diagram illustrating another application example of the cockling inhibitor. When the direction in which the wrinkles are likely to shift toward the sheet S is known as in the sheet S in FIG. 4A, the cockling prevention agent is applied only in the direction in which the wrinkles in the periphery of the image A by solid printing are likely to shift (lateral direction). May be. For example, as shown in FIG. 4B, a cockling inhibitor is applied to a region other than the image A between the front end side boundary L1 and the rear end side boundary L2 of the image A. As a result, in the region in the lateral direction with respect to the image A, a rapid change in the amount of water can be suppressed, the cockling phenomenon can be suppressed, and the consumption of the cockling inhibitor can be saved. It should be noted that cockling applied in a direction (first direction) where wrinkles tend to be closer than the amount of cockling inhibitor applied in the direction (second direction) where wrinkles are difficult to shift in the periphery of image A. The amount of the inhibitor may be increased.

=== Nozzle arrangement ===
In the present embodiment, the cockling phenomenon is prevented by applying a cockling inhibitor to the area around the solid-printing area. Therefore, on the lower surface of the head unit 30, in addition to the colored nozzle that discharges the colored ink (YMCK) having the color material for image formation, a cockling preventing agent that is a colorless and transparent ink having no color material is provided. A cockling inhibitor nozzle for discharging is provided. Hereinafter, the nozzle arrangement of the present embodiment will be described after showing the nozzle arrangement of the comparative example with respect to the arrangement of nozzles provided on the lower surface of the head unit 30.

<Nozzle arrangement of comparative example>
FIG. 5 is a diagram illustrating a positional relationship between the nozzle arrangement of the comparative example and the paper S (cross-sectional view). On the lower surface of the head unit 30, nozzle rows are formed at regular intervals for each ink type along the paper width direction intersecting the transport direction (not shown). In the comparative example, the nozzle rows are arranged in the order of the black nozzle row K, the yellow nozzle row Y, the cyan nozzle row C, the magenta nozzle row M, and the cockling inhibitor nozzle row P from the upstream side in the transport direction. That is, when the paper S is conveyed from the upstream side to the downstream side, the paper S first faces the colored ink nozzle row (KYCM) and then faces the cockling inhibitor nozzle row P. Therefore, if all the colored ink (KYCM) and the cockling prevention agent are ejected to a certain area on the paper S, the cockling prevention agent is ejected after all the colored ink (KYCM) is ejected. The

  Here, as shown in FIG. 3B described above, the area A on the paper S (the white area within the thick line frame) is solid-printed by all the colored ink nozzle rows (YMCK), and the area B (hatching) is used as a countermeasure against cockling. Part) is applied with a cockling inhibitor. FIG. 5 shows a state in which the sheet S is solid-printed by the nozzle arrangement of the comparative example while being conveyed from the upstream side to the downstream side.

  As in the first-stage paper S, at the beginning of solid printing, the black nozzle row K and the region A face each other, and black ink is applied to the region A. Further, when the paper S is transported, yellow ink and black ink are applied to the downstream side of the area A, and black ink is applied to the upstream side of the area A, as in the paper S in the second stage.

  The third stage conveyed downstream from the second stage shows a state immediately before the area A and the magenta nozzle row M face each other. The region A in the third stage passes under the black nozzle row K and faces the cyan nozzle row C and the yellow nozzle row Y. Therefore, in the third stage, cyan ink, yellow ink, and black ink are applied to the downstream side of the region A, and yellow ink and black ink are applied to the upstream side of the region A. On the other hand, the cockling prevention agent is not yet applied to the region B.

  By the way, the cockling phenomenon occurs from the moment when the ink droplets land on the paper S, and the wrinkle generated on the paper S increases when the difference in the amount of moisture between adjacent regions increases. In the comparative example, at the time of the third stage, the difference in the ink (moisture) application amount between the downstream area B and the downstream area A becomes large. Compared to other regions, the fibers expand and deform into a raised state (cockling phenomenon occurs).

  Then, when the sheet S is transported from the third stage, the area A faces the magenta nozzle row M. At this time, since the region A is not flat but is raised, the ink droplets ejected from the nozzles of the magenta nozzle row M cannot land at the correct position, and the image of the region A deteriorates. End up.

  That is, in the comparative example, since the cockling inhibitor nozzle row P is arranged on the downstream side of all the colored ink nozzle rows (YMCK), if solid printing is performed by a large number of colored ink nozzle rows, Before the ring inhibitor is applied to the area B, a large amount of ink is applied to the solid printing area, and a cockling phenomenon occurs on the paper S during the solid printing. As a result, the colored ink nozzle array on the downstream side (magenta nozzle array M in FIG. 5) ejects ink droplets onto the paper S in which the cockling phenomenon has occurred, and is ejected from the downstream colored ink nozzle array. The ink droplet does not land at an accurate position, and image deterioration occurs.

  On the contrary, even when the cockling inhibitor nozzle row P is provided upstream of all the colored ink nozzle rows (YMCK) (not shown), the cockling is first performed around the solid-printing region (region B). Because the inhibitor is applied, solid printing with colored ink is performed in a state where the surrounding area is wrinkled (cockling phenomenon has occurred), and ink droplets from the colored ink nozzles land on the correct position Otherwise, image degradation occurs.

  Therefore, the present embodiment aims to prevent image deterioration, and in particular, prevents deterioration of an image that is solid-printed.

<Nozzle arrangement of this embodiment>
FIG. 6 is a view showing the lower surface of the head unit 30. The head unit 30 is composed of a head group 32 (square dotted line) for each ink, and each head group 32 has a plurality of heads 31. A black head group 32K, a cyan head group 32C, a cockling inhibitor head group 32P, a magenta head group 32M, and a yellow head group 32Y are arranged in this order from the upstream side in the transport direction.

  Each head group 32 has a plurality of heads 31 (n), and the plurality of heads 31 are arranged in a staggered pattern in the paper width direction. Further, for example, in the head 31K belonging to the black head group 32K, the first head 31K (1), the second head 31K (2),..., The nth head 31K (n) are sequentially arranged from the left head 31 in the paper width direction.

  FIG. 7 is a detailed view of the nozzle surface of the black head group 32K. The head groups 32 other than the black head group 32K have the same nozzle arrangement. Four black nozzle rows K are formed on the lower surface of one black head 31K, and are labeled K1, K2, K3, and K4 in order from the upstream side. Each black nozzle row K includes 180 nozzles, and the left nozzles of the black nozzle rows K are assigned with lower numbers (# 1 to # 180). The nozzles of each black nozzle row K are aligned at a constant 180 dpi interval in the paper width direction.

  Further, the four black nozzle rows K1 to K4 formed on the black head 31K are shifted from the nozzle rows adjacent in the transport direction by an interval of 720 dpi in the paper width direction. For example, the nozzle # 1 of the most upstream black nozzle row K1 is displaced 720 dpi to the left in the paper width direction with respect to the nozzle # 1 of the adjacent black nozzle row K2. Further, the nozzle # 1 of the black nozzle row K4 on the most downstream side is displaced by 720 dpi on the left side in the paper width direction with respect to the nozzle # 2 of the black nozzle row K1 on the most upstream side. That is, by combining four black nozzle rows K1 to K4 having a nozzle interval of 180 dpi, the black nozzles are arranged at intervals of 720 dpi in the paper width direction in one black head 31K.

  In the two black heads 31K adjacent to each other in the paper width direction, the left black head with respect to the leftmost nozzle (nozzle # 1 in the black nozzle row K1) among the nozzles belonging to the right black head 31K (2). Of the nozzles belonging to 31K (1), the rightmost nozzle (nozzle # 180 in the black nozzle row K4) is shifted to the left at an interval of 720 dpi in the paper width direction. That is, when all the nozzles of the head 31K belonging to the black head group 32K are combined, the black nozzles are arranged at an interval of 720 dpi in the paper width direction, and the printer 1 can print at a resolution of 720 dpi in the paper width direction. Become. Other nozzles, that is, cyan, magenta and yellow nozzles and cockling inhibitor nozzles are arranged at intervals of 720 dpi in the paper width direction.

  Here, when comparing the nozzle arrangement of the present embodiment (FIG. 6) and the nozzle arrangement of the comparative example (FIG. 5A), in the comparative example, the cockling inhibitor nozzle row P is located downstream of the colored ink nozzle row (YMCK). In contrast to the arrangement, in this embodiment, the cockling inhibitor nozzle row P is arranged at the center of the colored ink nozzle row (YMCK). That is, the paper S of the comparative example is opposed to the cockling inhibitor nozzle row (P) after facing all the colored ink nozzle rows (YMCK), whereas the paper S of the present embodiment is It faces two colored ink nozzle rows (KC), then faces the cockling inhibitor nozzle row (P), and again faces the two colored ink nozzle rows (MY). Therefore, if ink (anti-cockling agent) is discharged from all the nozzle rows to a certain area on the paper S, first two colored inks (KC) are discharged, and then the anti-cockling agent is discharged. The two colored inks (MY) are discharged again.

=== About the cockling countermeasure of this embodiment ===
Hereinafter, as shown in FIG. 3B described above, when the area A (thick line frame, white area) on the paper S is solid-printed by all the colored ink nozzle rows (YMCK), the area B (hatching area) is displayed. A method for suppressing the cockling phenomenon by applying a cockling inhibitor will be described.

  FIG. 8 is a diagram illustrating a positional relationship between the nozzle arrangement and the paper S according to the present embodiment. The figure shows a state in which the sheet S is solid-printed while being conveyed from the upstream side to the downstream side so that the horizontal direction (FIG. 3B) of the sheet S is the conveyance direction. As in the first-stage paper S, at the beginning of solid printing, the black nozzle row K and the region A face each other, and black ink is applied to the downstream side of the region A. Further, the first-stage paper S is in a state immediately before the region B and the anti-curl agent nozzle row P face each other, and in the second stage where the paper S is further conveyed from the first stage, the downstream-side area B and The cockling inhibitor nozzle row P is opposed, and the cockling inhibitor is applied to the region B. Further, the region A faces the cyan nozzle row C and the black nozzle row K, and cyan ink and black ink are applied to the downstream side of the region A, and black ink is applied to the upstream side of the region A. That is, in the comparative example, a large amount of ink was applied to the region A and then the cockling inhibitor was applied to the region B (FIG. 5). In this embodiment, a large amount of ink was applied to the region A. Before being applied (with only black ink and cyan ink applied), an anti-cockling agent is applied to region B.

  Then, in the third stage in which the paper S is conveyed more than in the second stage, the paper S in a state immediately before the area A and the magenta nozzle row M face each other is shown. In the third stage, an anti-curl agent is applied to the downstream area B, and cyan ink and black ink are applied to the area A. Therefore, the difference in the ink (moisture) application amount between the downstream area B and the area A is small, and the area A and the area B on the sheet S are kept flat without being wrinkled. ing. That is, in the present embodiment, ink is ejected from the downstream colored ink nozzle array (MY) in a state where the paper S is not wrinkled, and therefore, the ink droplets ejected from the downstream colored ink nozzle array are accurate. It can land on the correct position and prevent image degradation.

  Further, the fourth-stage sheet S is a diagram showing a state immediately before the upstream region B faces the cockling inhibitor nozzle row P. At this time, the cockling inhibitor has not yet been applied to the upstream region B. However, only the cyan ink and the black ink are applied on the upstream side of the region A adjacent to the upstream region B. Therefore, the difference in the amount of ink (moisture) applied between the upstream region B and the upstream side of the region A is small, and wrinkles between the region A and the region B on the paper S can be prevented. As a result, since the sheet S is further transported from the fourth stage and the upstream side of the region A faces the magenta nozzle array M, the sheet S is not wrinkled, so that the ink droplets ejected from the magenta nozzle array M are accurate. It can land on the correct position and prevent image degradation.

  That is, in this embodiment, the cockling inhibitor nozzle row (P) is not disposed downstream (or upstream) of all the colored nozzle rows (YMCK) as in the comparative example, but the colored nozzle row ( Since the cockling inhibitor nozzle row (P) is arranged between the YMCK), the ink is applied only in one of the solid-printed area (area A) and the area B where the cockling inhibitor is applied. A large amount is avoided. As a result, there is no occurrence of a cockling phenomenon on the paper S before the printing of the downstream colored ink nozzle row, and the ink droplets ejected from the downstream colored ink nozzle row land at an accurate position, Image degradation can be prevented.

  In this embodiment (FIG. 8), the cockling inhibitor nozzle row P is arranged at the center of the colored ink nozzle row (YMCK), but this is not restrictive. 12A and 12B are diagrams showing a modified example of the nozzle arrangement of the present embodiment. In FIG. 12A, the black nozzle row K, the cockling inhibitor nozzle row P, the cyan nozzle row C, the magenta nozzle row M, and the yellow nozzle row Y are arranged in this order from the upstream side in the carrying direction. In FIG. From the upstream side, the black nozzle row K, the cyan nozzle row C, the magenta nozzle row M, the cockling inhibitor nozzle P, and the yellow nozzle row Y are arranged in this order. Thus, if the cockling inhibitor nozzle row P is provided between the colored ink nozzle rows (YMCK), the occurrence of cockling phenomenon during printing is prevented and image deterioration is prevented as compared with the comparative example. However, which of the colored inks is used for solid printing is different depending on the printing pattern, so that the cockling inhibitor nozzle row P is on the upstream side or the downstream side as in the nozzle arrangement of this embodiment. Arrangement in the center without bias increases the possibility of ink being applied to the solid-printed area and its peripheral area at the same time, regardless of the printing pattern, so that the effect of preventing image deterioration can be reliably obtained. it can.

=== About Color Bleed ===
FIG. 9A is a schematic diagram illustrating a state where yellow dots and black dots are formed adjacent to each other in the nozzle array of the comparative example. In the nozzle arrangement of the comparative example (FIG. 5), the black nozzle row K and the yellow nozzle row Y are adjacent in the transport direction. Therefore, when the yellow dot and the black dot are formed adjacent to each other, as shown in FIG. 9A, before the black dot dries (before the ink penetrates the paper fiber), the yellow dot It is formed adjacent to the black dots, and there is a risk that the boundary between the two dots will blur. In this manner, a phenomenon in which colors are blurred or mixed unevenly at different color boundary portions is called “color bleed”, which can contribute to image quality degradation. In particular, when a light ink such as yellow ink and a dark ink such as black ink are mixed, the ink tends to stand out.

  FIG. 9B is a schematic diagram illustrating a state in which yellow dots and black dots are formed adjacent to each other in the nozzle arrangement of the present embodiment. In the nozzle arrangement of this embodiment (FIG. 8), the black nozzle row K is provided on the most upstream side in the carrying direction, and the yellow nozzle row Y is provided on the most downstream side in the carrying direction. Between the black nozzle row K and the yellow nozzle row Y, in addition to the magenta nozzle row M and the cyan nozzle row C, a cockling inhibitor nozzle row P is also provided. Therefore, in this embodiment, compared to the comparative example, the period from when the black dot is formed to when the paper S and the yellow nozzle face each other is relatively long. During this period, the drying of the black dot proceeds, and the black dot Even if a yellow dot is formed adjacent to, color bleeding is unlikely to occur.

  In other words, in the present embodiment, nozzle rows of colors (yellow and black) that are liable to deteriorate image quality due to color bleeding are provided apart from the most upstream side and the most downstream side in the transport direction, and further, the color ink nozzle row (YMCK) Since the anti-curl agent nozzle row (P) is disposed between them, when the most downstream nozzle row and the paper S face each other, drying of the dots formed by the most upstream nozzle row proceeds, and color bleeding causes Image quality is less likely to deteriorate.

  In addition, color bleeding occurs not only at yellow and black but also at the boundary between different color inks. Therefore, by providing the cockling inhibitor nozzle row P between the colored ink nozzle rows (YMCK), the dots formed by the nozzle row provided upstream of the cockling inhibitor nozzle row P, and the cock Even if the dots formed by the nozzle row provided on the downstream side of the ring inhibitor nozzle row P are adjacent to each other, color bleeding is less likely to occur than in the comparative example.

  For example, as shown in FIG. 5, in the nozzle arrangement of the comparative example, the cyan nozzle row C and the magenta nozzle row M are adjacent to each other, so that the cyan dots are adjacent to the cyan dots before the cyan dots are dried. There is a high possibility that dots are formed and color bleeding occurs. On the other hand, as shown in FIG. 8, in the nozzle arrangement of this embodiment, since the cockling inhibitor nozzle row P is provided between the cyan nozzle row C and the magenta nozzle row M, cyan dots are formed. Since the drying of the cyan dots proceeds while the paper S is transported under the cockling inhibitor nozzle row P, the comparative example may be used even if magenta dots are formed adjacent to the cyan dots. Color bleeding is less likely to occur.

In summary, the printer 1 (liquid ejecting apparatus) of the present embodiment has a first nozzle row (eg, black nozzle row) in which a plurality of first nozzles that eject colored liquid (eg, black) onto a medium are arranged in a predetermined direction. K), a second nozzle row (eg, yellow nozzle row) in which a plurality of second nozzles that discharge a colored liquid (eg, yellow) to the medium are aligned in the predetermined direction, and a colorless liquid (cockling prevention agent) And a third nozzle row (cockling inhibitor nozzle row) arranged in the predetermined direction, wherein the third nozzle row includes the first nozzle row and the second nozzle row. It is arranged between the nozzle rows.
In this way, it is possible to prevent the ink from being applied to only a specific area (for example, a solid printing area) first, thereby causing a cockling phenomenon on the medium being printed, and to prevent image deterioration. . Further, by arranging the cockling inhibitor nozzle used as a countermeasure against the cockling phenomenon between the colored ink nozzles, color bleeding between the colored inks can be prevented.

=== About double-sided printing ===
FIG. 10 is a diagram illustrating a state of double-sided printing. The printer 1 of the present embodiment is a printer capable of duplex printing, and the surface of the sheet S is printed while being conveyed from the upstream side to the downstream side in the conveyance direction, and then the sheet S is reversed by the sheet reversing unit 40. Assume that the back surface of the paper S is printed while being conveyed from the downstream side to the upstream side in the conveyance direction. That is, the transport direction when printing the front surface of the paper S and the transport direction when printing the back surface of the paper S are opposite directions.

  When the surface of the paper S is printed, the paper S faces the black nozzle row K, the cyan nozzle row C, the cockling inhibitor nozzle row P, the magenta nozzle row M, and the yellow nozzle row Y in this order. On the other hand, when the back side of the paper S is printed, the paper S faces the yellow nozzle row Y, the magenta nozzle row M, the cockling inhibitor nozzle row P, the cyan nozzle row C, and the black nozzle row K in this order. That is, in this embodiment, since the cockling inhibitor nozzle row P is arranged at the center of the colored ink nozzle row (YMCK), the paper S is used regardless of whether the front side printing or the rear side printing with different transport directions is performed. The two colored ink nozzle rows, the cockling inhibitor nozzle row P, and the two colored ink nozzle rows face each other in this order. For this reason, when solid printing is performed with colored ink, it is possible to prevent a large amount of ink from being applied to either the solid printing area or its peripheral area first, thereby suppressing the cockling phenomenon. .

=== Other Embodiments ===
Each of the above embodiments has been described mainly with respect to a printing system having an ink jet printer, but includes disclosure of measures for cockling phenomenon of printing paper. The above-described embodiments are for facilitating understanding of the present invention, and are not intended to limit the present invention. The present invention can be changed and improved without departing from the gist thereof, and it is needless to say that the present invention includes equivalents thereof. In particular, the embodiments described below are also included in the present invention.

<Nozzle arrangement>
In the above-described embodiment, the cockling inhibitor nozzle row P and the colored ink nozzle row (YMCK) are arranged without shifting in the paper width direction, but the present invention is not limited to this. For example, as shown in FIG. 11A, the cockling inhibitor nozzle row P may be shifted in the paper width direction by half the nozzle pitch (720 dpi) (1440 dpi) with respect to the colored ink (YMCK).
FIG. 11B is a diagram showing a state in which dots (hatching) of the cockling inhibitor are applied around the colored ink dots (white) by the nozzle arrangement described above. On the other hand, FIG. 11C is a diagram illustrating a state in which the dot (hatching) of the cockling inhibitor is applied around the colored ink dot (white) by the nozzle arrangement of FIG. 11A. According to the nozzle arrangement described above, the center of the colored ink dot and the center of the cockling inhibitor dot do not shift in the paper width direction. On the other hand, according to the nozzle arrangement of FIG. 11A, the center of the colored ink dot and the center of the cockling inhibitor dot are shifted by half a pixel in the paper width direction.
As shown in FIG. 11B, when the dots of the colored ink and the cockling inhibitor are equal in size, if one dot is of a size that protrudes one pixel, the colored ink dot and the cockling inhibitor The part where the dots overlap becomes larger. If it does so, it will become easy for a colored ink to bleed into a cockling prevention agent, and will cause image degradation. Thus, by shifting the centers of the colored ink dots and the cockling inhibitor dots as shown in FIG. 11C, the overlapping portion of the colored ink dots and the cockling inhibitor dots is reduced, and the bleeding of the colored ink is prevented. be able to.

  In the above-described embodiment, as shown in FIG. 6, in order to increase the resolution in the paper width direction, four nozzle rows are provided in one head 31 and the nozzle rows are arranged in a staggered manner. . All four nozzle rows in one head 31 are nozzle rows that eject the same color ink. However, the present invention is not limited to this, and as shown in FIG. 13, nozzle rows that eject different colors of ink may be arranged in one head 31. In FIG. 13, four heads 31 in which black, cyan, magenta, and yellow nozzle rows KCMY are arranged are arranged in the transport direction. Note that by arranging the nozzle rows in the heads 31 adjacent to each other in the transport direction so as to be shifted in the paper width direction, high-resolution printing is possible in the paper width direction. At this time, the cockling inhibitor nozzle row P (or the head 31 (P) in which a plurality of cockling inhibitor nozzle rows P are arranged) is arranged between the four heads 31 having the colored nozzle rows (YMCK). As a result, the occurrence of cockling phenomenon during solid printing can be suppressed, and image deterioration can be prevented. However, color bleed can be further suppressed when the nozzle rows of one color are arranged together as in the above-described embodiment.

  In addition, in the above-described embodiment, the yellow nozzle row Y and the black nozzle row K, which are likely to deteriorate image quality due to color bleed, are provided on the most upstream side and the most downstream side in the transport direction, respectively. Since color bleed occurs in the case of colored inks, nozzle rows of other colors such as magenta and cyan may be provided on the most upstream side and the most downstream side.

<Resolution of nozzle array for cockling inhibitor>
In the above-described embodiment, four nozzle rows with a nozzle pitch of 180 dpi are arranged in one head 31 to enable printing at a resolution of 720 dpi in the paper width direction, and the cockling inhibitor nozzle row is also a colored ink nozzle row. Similarly, although there are four nozzle rows in one head 31, this is not restrictive. For example, the cockling inhibitor nozzle row may have only one nozzle row having a nozzle pitch of 180 dpi. At this time, the cockling phenomenon and the color bleed can be suppressed by disposing even one cockling inhibitor nozzle row between the colored ink nozzle rows. In this case, the resolution in the paper width direction of the cockling inhibitor nozzle row is lowered, but the cockling inhibitor has no relation to the print image, and therefore the image quality is not affected even if the resolution is lowered.

<About paper curl>
In the above-described embodiment, in order to prevent the cockling phenomenon caused by the solid printing area or the like, the cockling preventing agent is applied around the solid printing area, but the invention is not limited to this. For example, in order to prevent paper curling (curling) due to a difference in the amount of moisture penetrating into the front and back fibers of the paper S, an anti-cockling agent is applied to the surface opposite to the surface on which the image is formed on the paper S. It may be applied to prevent paper curling.

<About clear ink>
In the above-described embodiment, the nozzle row that discharges the cockling prevention agent for preventing cockling is arranged between the colored inks, but is not limited thereto. For example, in order to increase the gloss and rubbing resistance of the printing unit, a clear ink nozzle row that discharges clear ink used to equalize the ink adhesion density of the entire paper S is placed between the colored ink nozzle rows (YMCK). You may arrange. By doing so, color bleeding between colored inks can be suppressed. Further, since the clear ink makes the ink adhesion density of the entire paper S equal, the cockling phenomenon can be suppressed, and when the clear ink is applied to the paper S, the clear ink is placed between the colored ink nozzle rows (YMCK). If the nozzle row is arranged, it is possible to prevent the ink from being ejected only to a specific region first, thereby preventing the occurrence of cockling during printing and preventing image deterioration.

<About serial printers>
In the above-described embodiment, the line head printer is taken as an example. However, the present invention is not limited to this. For example, the conveyance operation of moving the paper S in the conveyance direction and the movement of one head in the movement direction intersecting the conveyance direction are performed. Even with serial printers that form images while alternately repeating the dot forming operation (pass), if cockling inhibitor nozzle rows are placed between the colored ink nozzle rows, the cockling phenomenon and color bleeding can be suppressed. The effect is obtained.
However, since serial printers perform printing while one head is moving, as much as line head printers, a large amount of ink is not applied to the solid print area first. It is considered more effective.

<About liquid ejection device>
In the above-described embodiment, the ink jet printer is exemplified as the liquid ejecting apparatus, but is not limited thereto. If it is a liquid ejection device, it can be applied to various industrial devices, not a printer (printing device). For example, a textile printing device for patterning a fabric, a display manufacturing device such as a color filter manufacturing device or an organic EL display, a DNA chip manufacturing device for manufacturing a DNA chip by applying a solution in which DNA is dissolved in a chip, a circuit board manufacturing The present invention can be applied even to an apparatus or the like.

  In the printer of the above-described embodiment, the liquid is ejected by applying a voltage to the driving element (piezo element) to expand and contract the ink chamber, but the invention is not limited thereto. For example, a printer that generates bubbles in the nozzles using a heating element and discharges liquid by the bubbles may be used.

1 is an overall configuration block diagram of a printer according to an embodiment. FIG. 2A is a cross-sectional view of the printer, and FIG. 2B is a diagram illustrating how the printer transports paper. FIG. 3A is a diagram showing a state of the cockling phenomenon of the paper, and FIG. 3B is a diagram showing an application example of the cockling preventing agent. FIG. 4A is a diagram showing a direction in which wrinkles are likely to come close to the paper, and FIG. 4B is a diagram showing another application example of the cockling preventing agent. It is a figure which shows the positional relationship of the nozzle arrangement | sequence and paper of a comparative example. It is a figure which shows the lower surface of a head unit. It is detail drawing of the nozzle surface of a black head group. It is a figure which shows the positional relationship of the nozzle arrangement and paper of this embodiment. FIG. 9A is a schematic diagram illustrating a state in which yellow dots and black dots are formed adjacent to each other in the nozzle array of the comparative example, and FIG. 9B is a diagram in which yellow dots and black dots are adjacent to each other in the nozzle array of the present embodiment. It is the schematic which shows a mode that it forms. It is a figure which shows the mode of double-sided printing. FIG. 11A is a diagram in which the cockling inhibitor nozzle row is shifted in the paper width direction by half the nozzle pitch with respect to the colored ink, and FIG. 11B is a cockling inhibitor around the colored ink dots by the nozzle arrangement described above. FIG. 11C is a diagram showing a state in which dots of cockling inhibitor are applied around the dots of the colored ink by the nozzle arrangement of FIG. 11A. 12A and 12B are diagrams showing a modified example of the nozzle arrangement of the present embodiment. FIG. 6 is a diagram in which four heads in which nozzle rows of black, cyan, magenta, and yellow are arranged are arranged in the transport direction.

Explanation of symbols

1 printer, 10 controller, 11 interface unit,
12 CPU, 13 memory, 14 unit control circuit,
20 transport unit, 21A transport roller, 21B transport roller,
22 transport belt, 23 paper feed roller,
30 head unit, 31 head, 32 head group 40 paper reversing unit, 41 transport roller 50 detector group, 60 computer,
S paper

Claims (12)

A first nozzle row in which a plurality of first nozzles for discharging a colored liquid to a medium are arranged in a predetermined direction;
A second nozzle row in which a plurality of second nozzles for discharging colored liquid onto the medium are arranged in the predetermined direction;
A third nozzle row in which a plurality of third nozzles for discharging colorless liquid onto the medium are arranged in the predetermined direction;
A liquid ejection device comprising:
The third nozzle row is disposed between the first nozzle row and the second nozzle row,
A liquid discharge apparatus characterized by that. The liquid ejection device according to claim 1,
The color of the liquid discharged from the first nozzle is different from the color of the liquid discharged from the second nozzle.
Liquid ejection device. The liquid ejection device according to claim 1 or 2, wherein
A transport mechanism that transports the medium in a transport direction that intersects the predetermined direction;
Liquid ejection device. The liquid ejection device according to any one of claims 1 to 3,
A nozzle row in which a plurality of nozzles that discharge colored liquids are arranged in the predetermined direction is provided between the first nozzle row and the third nozzle row, and between the second nozzle row and the third nozzle row. In addition, a nozzle row in which a plurality of nozzles that discharge colored liquid are arranged in the predetermined direction is provided.
Liquid ejection device. The liquid ejection device according to claim 4,
When the colored liquid is black ink, yellow ink, magenta ink, and cyan ink,
Black ink is ejected from the first nozzle,
Yellow ink is ejected from the second nozzle,
Liquid ejection device. The liquid ejection device according to claim 4 or 5, wherein
When liquid is ejected on both sides of the medium,
The transport direction when the liquid is discharged onto one surface of the medium is the opposite direction to the transport direction when the liquid is discharged onto the other surface of the medium.
Liquid ejection device. The liquid ejection device according to any one of claims 1 to 6,
The third nozzle is displaced in the predetermined direction with respect to the first nozzle and the second nozzle.
Liquid ejection device. A liquid ejection device according to any one of claims 1 to 7,
The colorless liquid is ejected from the third nozzle around the image formed by the colored liquid.
Liquid ejection device. The liquid ejection device according to claim 8, wherein
As the distance from the image increases, the discharge amount from the third nozzle decreases.
Liquid ejection device. The liquid ejection device according to claim 8 or 9, wherein
If the deformation in the first direction of the medium caused by the image is greater than the deformation in the second direction intersecting the first direction;
The amount of the colorless liquid ejected around the first direction is greater than the amount of the colorless liquid ejected around the second direction with respect to the image,
Liquid ejection device. The liquid ejection device according to claim 8 or 9, wherein
The medium is composed of fibers;
When the liquid is ejected to the medium, the fibers deform more greatly in the first direction than in the second direction,
The amount of the colorless liquid ejected around the first direction is greater than the amount of the colorless liquid ejected around the second direction with respect to the image,
Liquid ejection device. A first nozzle row in which first nozzles for discharging colored liquid to the medium are arranged in a predetermined direction, and a second nozzle row in which a plurality of second nozzles for discharging colored liquid to the medium are arranged in the predetermined direction. In the liquid ejecting apparatus in which a third nozzle row in which a plurality of third nozzles for ejecting colorless liquid onto the medium are arranged in the predetermined direction is disposed, the colored liquid is applied to the medium from the first nozzle. Discharged,
The colorless liquid is ejected from the third nozzle onto the medium;
The colored liquid is ejected from the second nozzle onto the medium;
Liquid ejection method.

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