JP2011104788A - Printing apparatus and printing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a printing apparatus which can suppress image quality degradation in a printing image. <P>SOLUTION: In the printing apparatus, nozzles for ejecting ink of a first color are arranged in a predetermined direction in a first nozzle array, and nozzles for ejecting ink in a plurality of colors different from the first color are arranged in units of nozzles that eject the ink of the same color in the predetermined direction in a second nozzle array. The ink is ejected from nozzles in an ejection operation while moving the first nozzle array and the second nozzle array in a movement direction. The number of nozzles belonging to the first nozzle array is larger than the number of nozzles belonging to the second nozzle array for ejecting each color ink. The ink is prevented from being ejected from nozzles between a first nozzle group and a second nozzle group. The first nozzle group as a plurality of nozzles among the nozzles belonging to the first nozzle array forms a plurality of dot arrays in the movement direction in an ejection operation, which forms part of each dot array. The second nozzle group as a plurality of nozzles located on one side in a predetermined direction of the first nozzle group forms a plurality of dot arrays in another ejection operation, which forms another part of each dot array. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a printing apparatus and a printing method.

  As one of the printing devices, an image is formed while moving a nozzle row in which nozzles for ejecting ink are arranged in a predetermined direction in a moving direction crossing the predetermined direction, and a medium is conveyed in the predetermined direction with respect to the nozzle row. There are ink jet printers (hereinafter referred to as printers) that repeat the above operations. In order to increase the speed of monochrome printing, the number of nozzles that eject black ink may be larger than the number of nozzles that eject each color ink (for example, yellow, magenta, and cyan). Then, a black nozzle row in which nozzles that discharge black ink are arranged in a predetermined direction and a color nozzle row in which nozzles that discharge color ink are arranged in a predetermined direction for each nozzle that discharges the same color ink are arranged in the moving direction. An arranged printer has been proposed (see, for example, Patent Document 1). In such a printer, it is possible to lengthen a single medium conveyance amount for monochrome printing and to shorten a printing time as compared with color printing.

Japanese Patent Laid-Open No. 5-246048

  Black ink is often used for text printing, and a high-quality text image can be obtained by printing with a dark black density. Therefore, when printing using both black ink and color ink, only the same number of black nozzles as the number of nozzles of each color ink are used. For example, one dot along the moving direction is used in the same manner as the color nozzle. Suppose a row is printed with one black nozzle. As a result, a large amount of black ink is ejected to the unit area on the medium in a short period of time, the sinking amount of the black color material increases, the density of black becomes light, and the image quality of the printed image deteriorates.

  Accordingly, an object of the present invention is to suppress deterioration in image quality of a printed image.

  The main inventions for solving the above problems are: (A) a first nozzle row in which nozzles for discharging the first color ink are arranged in a predetermined direction; and (B) a movement that intersects the first nozzle row and the predetermined direction. A second nozzle row arranged in the direction, wherein the nozzles ejecting a plurality of colors of ink different from the first color are arranged in the predetermined direction for each of the nozzles ejecting the same color ink; C) A discharge operation for discharging ink from the nozzles while moving the first nozzle row and the second nozzle row in the movement direction, and a relative position of the first nozzle row, the second nozzle row, and the medium. A controller that repeats the relative movement of the predetermined direction in one direction; and (D), and (E) the number of the nozzles belonging to the first nozzle row belongs to the second nozzle row Each color ink of the nozzles The number of the nozzles of the first nozzle row forming the dot row along the moving direction is larger than the number of the nozzles to be ejected, of the second nozzle rows forming the dot row along the moving direction. A plurality of the nozzles that form a plurality of dot rows along the moving direction in a certain ejection operation among the nozzles that are more than the number of the nozzles that eject each color ink and belong to the first nozzle row, A first nozzle group that is a plurality of the nozzles that form a part of the dot row, and a plurality of the nozzles that form the plurality of dot rows in another ejection operation, and another part of each dot row Ink is not ejected from the nozzles between the plurality of nozzles forming the second nozzle group located on the one direction side in the predetermined direction with respect to the first nozzle group. ) It is a printing apparatus according to claim.

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

FIG. 1A is a block diagram of the overall configuration of a printing system, and FIG. 1B is a schematic diagram of a printer. It is a figure which shows the nozzle arrangement | sequence in a head. It is a figure explaining the printing method of a monochrome mode. It is a figure explaining the printing method of a 3 color mode. It is a figure explaining the printing method of the 4 color mode of a comparative example. It is a figure explaining the printing method of the 4 color mode of this embodiment. It is a figure explaining the printing method of a modification.

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

That is, (A) a first nozzle row in which nozzles for discharging the first color ink are arranged in a predetermined direction, and (B) a second nozzle row in which the first nozzle row is arranged in a moving direction that intersects the predetermined direction. A second nozzle row in which nozzles for ejecting a plurality of colors different from the first color are arranged in the predetermined direction for each of the nozzles ejecting the same color ink, and (C) the first nozzle row and the A discharge operation for discharging ink from the nozzles while moving the second nozzle row in the moving direction, and a relative position of the first nozzle row, the second nozzle row, and the medium relative to one direction of the predetermined direction. A controller that repeats the moving operation; and (D), (E) the number of the nozzles belonging to the first nozzle row ejects each color ink of the nozzles belonging to the second nozzle row More than the number of nozzles to The number of the nozzles of the first nozzle row that forms the dot row along the moving direction is the number of the nozzles that eject each color ink of the second nozzle row that forms the dot row along the moving direction. More than the nozzles belonging to the first nozzle row, a plurality of the nozzles forming a plurality of dot rows along the moving direction in a certain ejection operation, and forming a part of each dot row A first nozzle group that is a plurality of the nozzles; a plurality of the nozzles that form the plurality of dot rows in another ejection operation; and a plurality of the nozzles that form another part of each dot row. (F) wherein no ink is ejected from the nozzles between the first nozzle group and the second nozzle group located on the one direction side of the predetermined direction with respect to the first nozzle group. That.
According to such a printing apparatus, the amount of the first color ink ejected per unit area of the medium in a short time can be reduced, and the time interval for ejecting the first color ink can be lengthened. As a result, the density of the first color can be prevented from becoming light, and the image quality degradation of the printed image can be suppressed.

In this printing apparatus, in the second nozzle row, a third nozzle group in which nozzles that eject the second color ink are arranged in the predetermined direction in order from the one direction side of the predetermined direction; A fourth nozzle group in which nozzles for ejecting color ink are arranged in the predetermined direction and a fifth nozzle group in which nozzles for ejecting fourth color ink are arranged in the predetermined direction are arranged. The position in the predetermined direction is equal to the second nozzle group, and the fourth nozzle group includes the nozzles between the first nozzle group and the second nozzle group among the nozzles belonging to the first nozzle row, and The position in the predetermined direction is equal, and the fifth nozzle group has the same position in the predetermined direction as the first nozzle group.
According to such a printing apparatus, when printing all the dot rows, the time interval for ejecting the first color ink can be lengthened.

In this printing apparatus, the first color ink is a black pigment ink.
According to such a printing apparatus, it can suppress that the density | concentration of black becomes light, and can suppress the image quality degradation of a printed image.

A first nozzle row in which nozzles that discharge the first color ink are arranged in a predetermined direction; and a second nozzle row that is arranged in a moving direction that intersects the first nozzle row and the predetermined direction. A discharge operation in which nozzles that discharge a plurality of colors different from the colors of the nozzles discharge the ink from the nozzles while moving the second nozzle row arranged in the predetermined direction for each nozzle that discharges the same color of ink. And a printing method of a printing apparatus that repeats the relative movement of the first nozzle row and the second nozzle row and the medium in one direction of the predetermined direction, wherein the first nozzle row The number of the nozzles belonging to the number of the nozzles belonging to the second nozzle row is larger than the number of the nozzles ejecting the respective color inks of the nozzles belonging to the second nozzle row, and the first nozzle row forming the dot row along the moving direction. The number of nozzles is larger than the number of nozzles that discharge each color ink in the second nozzle row that forms the dot row along the moving direction, and among the nozzles belonging to the first nozzle row, A first nozzle group that is a plurality of the nozzles that form a plurality of dot rows along the moving direction in a certain ejection operation and that forms a part of each of the dot rows; In operation, the plurality of nozzles forming the plurality of dot rows and the plurality of nozzles forming another part of each dot row, the one direction in the predetermined direction with respect to the first nozzle group In the printing method, ink is not ejected from the nozzle between the second nozzle group located on the side.
According to such a printing method, the amount of the first color ink ejected in a short period per unit area of the medium can be reduced, and the time interval for ejecting the first color ink can be lengthened. As a result, the density of the first color can be prevented from becoming light, and the image quality degradation of the printed image can be suppressed.

=== About the printing system ===
Hereinafter, an embodiment will be described with an example of a printing system in which a printer is an inkjet printer (hereinafter referred to as a printer) and the printer and the computer are connected.

  FIG. 1A is a block diagram of the overall configuration of the printing system, and FIG. 1B is a schematic diagram of the printer 1. The computer 60 is communicably connected to the printer 1 and outputs print data corresponding to the image to be printed to the printer 1 in order to cause the printer 1 to print an image. The computer 60 is installed with a program (printer driver) for converting image data output from the application program into print data. This printer driver is recorded on a recording medium (computer-readable recording medium) such as a flexible disk FD or a CD-ROM. Alternatively, the printer driver may be downloaded to the computer 60 via the Internet.

  The printer 1 that has received the print command and print data from the computer 60 controls each unit by the controller 10 (corresponding to a control unit), and prints an image on the medium 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 interface unit 11 in the controller 10 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 a program of the CPU 12, a work area, and the like. The CPU 12 controls each unit by the unit control circuit 14.

The transport unit 20 feeds the medium S to a printable position, and transports the medium S by a predetermined transport amount in the transport direction during printing.
The carriage unit 30 is for moving the head 41 in a direction crossing the transport direction (hereinafter referred to as a movement direction), and has a carriage 31.

  The head unit 40 is for forming an image and has a head 41. On the lower surface of the head 41, a plurality of nozzles that are ink discharge portions are provided, and each nozzle is provided with a pressure chamber filled with ink. The ink ejection method from the nozzle may be a piezo method in which ink is ejected by applying a voltage to the drive element (piezo element) to expand and contract the pressure chamber, or bubbles are generated in the nozzle using a heating element. Alternatively, a thermal method may be used in which ink is discharged and ink is ejected by the bubbles.

  FIG. 2 is a diagram showing the nozzle arrangement in the head 41. The figure shows a state where the nozzle arrangement is virtually viewed from the upper surface of the head 41. In the head 41, two nozzle rows in which 180 nozzles are arranged at predetermined intervals D (for example, 180 dpi) in the transport direction (predetermined direction) are arranged in the moving direction. Small numbers are assigned in order from the nozzles on the downstream side in the transport direction (# 1 to # 180). The nozzle row on the left side in the movement direction is “black nozzle row K”, and the nozzle row on the right side in the movement direction is “color nozzle row Co”.

  All nozzles belonging to the black nozzle row K (corresponding to the first nozzle row) eject black ink (first color ink). Among the nozzles belonging to the black nozzle row K, the 1/3 nozzles (# 1 to # 60) on the downstream side in the transport direction are collectively referred to as “first black nozzle group (K1) (corresponding to the first nozzle group)”. 1/3 nozzles (# 61 to # 120) in the central part in the transport direction are collectively referred to as “second black nozzle group (K2)” and 1/3 nozzles (# 121 to # 180 on the upstream side in the transport direction). ) Are collectively referred to as “third black nozzle group (K3) (corresponding to the second nozzle group)”.

  On the other hand, the color nozzle row Co (corresponding to the second nozzle row) has nozzles that eject three colors of ink. Of the nozzles belonging to the color nozzle row Co, yellow ink is ejected from 1/3 nozzles (# 1 to # 60) on the downstream side in the transport direction, and 1/3 nozzles (# 61 to ## in the center in the transport direction). 120), magenta ink is ejected, and cyan ink is ejected from 1/3 nozzles (# 121 to # 180) on the upstream side in the transport direction. The nozzles that discharge yellow ink are collectively referred to as “yellow nozzle group (corresponding to the fifth nozzle group)”, and the nozzles that discharge magenta ink are collectively referred to as “magenta nozzle group (corresponding to the fourth nozzle group)”. The nozzles that discharge cyan ink are collectively referred to as “cyan nozzle group (corresponding to the third nozzle group)”.

  Thus, in the head 41 of this embodiment, the number of nozzles that eject black ink (180) is larger than the number of nozzles that eject each color ink (YMC) (60). The total number (60 × 3 colors) of nozzles that eject three color inks (YMC) corresponds to the number of nozzles that eject black ink. That is, the number of nozzles that is three times the number of nozzles that eject each color ink corresponds to the number of nozzles that eject black ink. Further, the positions of the first black nozzle group K1 and the yellow nozzle group Y in the respective transport directions are equal, the positions of the second black nozzle group K2 and the magenta nozzle group M in the respective transport directions are equal, and the third black nozzle group K3 and cyan. The positions of the nozzle groups C in the respective transport directions are equal.

  In the printer 1 having such a configuration, an image forming process for forming an image on a medium by intermittently ejecting ink droplets from the nozzles while moving the head 41 in the moving direction, and a conveying direction of the medium with respect to the head 41. The transport process for transporting to the downstream side is repeated. As a result, an image can be formed by the next image forming process at a position different from the position of the image formed by the previous image forming process, and a two-dimensional image can be printed on the medium. The operation in which the head 41 moves once in the moving direction while ejecting ink droplets (one image forming process) is referred to as “pass”.

=== About print mode ===
In the printer 1 of the present embodiment, three types of printing modes can be selected. The first printing mode is a “monochrome mode” in which only black ink is ejected, that is, printing is performed using only the black nozzle row K. The monochrome mode is mainly used when printing a text document. The second print mode is a “three-color mode”, in which three color inks (yellow, magenta, cyan) are ejected, that is, printing is performed using only the color nozzle row Co. The three-color mode is mainly used when printing an image such as a photograph. The third printing mode is a “four-color mode”, which ejects ink of four colors of black, yellow, magenta, and cyan, that is, using both the black nozzle row K and the color nozzle row Co. Print. The 4-color mode is mainly used when printing both text documents and images.

  In the printer 1 of the present embodiment, black ink ejected from the black nozzle row K is referred to as “pigment ink”, and three color inks (YMC) ejected from the color nozzle row Co are referred to as “dye ink”. . Pigment inks are difficult to bleed and can express a strong black color (high density), but have a property that the image is not glossy because the color material remains on the medium surface. Therefore, when printing a text document, by using black pigment ink, it is possible to print a text document having a high black density and easy to read, in which character collapse due to bleeding is suppressed. On the other hand, dye ink can print glossy images, but has the property of being easy to bleed. Therefore, dye ink is suitable for printing images such as photographs.

=== About printing in each printing mode ===
When the printer driver in the computer 60 connected to the printer 1 receives a print command for image data from the application program, the printer driver displays a window on a display device (display, etc.), and the above-described three types of print modes (monochrome mode, 3 The user is allowed to select one of the print modes among the color mode and the 4-color mode. Alternatively, the print mode may be determined based on image data received by the printer driver. Hereinafter, the printing method in each printing mode will be described.

<Monochrome mode>
FIG. 3 is a diagram illustrating a printing method in the monochrome mode. In the drawing, for simplicity of explanation, the number of nozzles is reduced, the number of nozzles in the black nozzle row K is set to 9, and the number of nozzles for each color ink is set to 3. 3 shows “discharge nozzles” used for printing in the monochrome mode and “non-discharge nozzles” not used for printing. The black nozzle is indicated by a black circle, the yellow nozzle is indicated by a white circle, the magenta nozzle is indicated by a hatched circle, and the cyan nozzle is indicated by a triangle. In the monochrome mode, as illustrated, all nozzles belonging to the black nozzle row K are ejection nozzles, and yellow, magenta, and cyan nozzles are non-ejection nozzles.

  Since printing of a text document (monochrome printing) often requires high-speed printing, in this embodiment, when the monochrome mode is selected, all nozzles (K # 1 to K # 9) belonging to the black nozzle row K are selected. ) To perform band printing. The right diagram in FIG. 3 shows the state of band printing and shows the positional relationship of the black nozzles in each pass. Actually, the medium is transported in the transport direction with respect to the head 41, but in FIG. 3, the position of the head 41 (nozzle) is shifted in the transport direction. In the right figure, for example, the most downstream nozzle K # 1 of the black nozzle row K is indicated as “K1”.

  “Band printing” is a printing method in which raster lines of other passes are not formed between dot rows (hereinafter referred to as raster lines) formed in a certain pass along the moving direction. That is, in band printing, the printing resolution in the transport direction corresponds to the nozzle pitch D (for example, 180 dpi) of the black nozzle row K. In band printing, an operation of forming an image while the head 41 moves in the moving direction and an operation of conveying the medium by the width of the image formed in one pass (the medium conveyance amount is 9D in FIG. 3). And are repeated alternately. As a result, in the monochrome mode, black raster lines are formed every nozzle pitch D of the black nozzle row K.

  Thus, in the monochrome mode, high-speed printing is realized by carrying out band printing with a relatively large number of black ejection nozzles. That is, in order to realize high-speed printing in the monochrome mode, the nozzle arrangement shown in FIG. 2 is adopted, and the number of black nozzles is three times the number of nozzles that eject each color ink (YMC).

<3-color mode>
FIG. 4 is a diagram for explaining a printing method in the three-color mode. In the three-color mode, the black nozzle is a non-ejection nozzle, and the yellow, magenta, and cyan nozzles are ejection nozzles. In the three-color mode, it is often required to improve the printed image rather than the high-speed printing as compared with the monochrome mode (text document). Therefore, in the three-color mode, the printing resolution in the transport direction is increased compared to the monochrome mode. Here, the print resolution in the transport direction in the three-color mode is set to a resolution (eg, 360 dpi) that is twice the print resolution D in the transport direction in the monochrome mode (eg, 180 dpi). Further, the number of nozzles that eject each color ink (three in FIG. 4) is smaller than the number of nozzles that eject black ink in the monochrome mode (nine in FIG. 3). For this reason, in the three-color mode, the medium transport amount at one time is 1.5D. As a result, for example, a raster line can be formed by the cyan nozzle C7 in pass 2 between the raster lines formed by the two cyan nozzles C8 and C9 in pass 1. Further, as shown in the right diagram of FIG. 4, three types of color nozzles (cyan nozzle, magenta nozzle, yellow nozzle) are arranged in the movement direction at the nozzle upstream of the printing start position in the transport direction. This indicates that one raster line is formed by three kinds of color nozzles arranged in the moving direction.

  As described above, in the printing in the three-color mode, the medium is transported by the operation of forming an image while the head 41 moves in the moving direction and the transport amount 1.5D that is 1.5 times the nozzle pitch D of the color nozzle row Co. And the operation to be repeated alternately. As a result, one raster line can be formed with three types of color nozzles, and the printing resolution in the transport direction can be higher in the three-color mode than in the monochrome mode. However, in the three-color mode, the number of nozzles that eject each color ink (three in FIG. 4) is smaller than the number of nozzles that eject black ink in the monochrome mode (nine in FIG. 3), and printing in the transport direction Set the resolution higher than the monochrome mode. Therefore, compared with the monochrome mode, in the three-color mode, the amount of medium transported once is short and the printing time is long. However, there is no problem in the three-color mode because high-speed printing is not required compared to the monochrome mode, and the number of nozzles of each color (YMC) is set to the number of black nozzles as in the head 41 of this embodiment (FIG. 2). By reducing the number, the cost of the head 41 can be reduced and the size can be reduced.

<4-color mode>
FIG. 5 is a diagram illustrating a printing method in a four-color mode according to a comparative example. Before describing the four-color mode printing method of the present embodiment, a comparative example printing method will be described. As described above, in the four-color mode, printing is performed using both the color ink (YMC) and the black ink (K). In the four-color mode printing method of the comparative example, as shown in the left diagram of FIG. 5, all the nozzles of the color nozzle row Co, that is, the nozzles of yellow, magenta, and cyan nozzles become discharge nozzles, and the black nozzle row The 1/3 nozzles (K # 7 to K # 9, third black nozzle group K3) on the upstream side in the conveyance direction of K serve as ejection nozzles. Then, 1/3 nozzles (K # 1 to K # 3, first black nozzle group K1) on the downstream side in the transport direction of the black nozzle row K, and 1/3 nozzle (K in the center of the black nozzle row K) # 4 to K # 6, the second black nozzle group K2) are non-ejection nozzles. That is, in the comparative example, the number of nozzles that eject each color ink (YMC) (three in FIG. 5) is equal to the number of nozzles that eject black ink (three).

  Also in the 4-color mode, in order to print a higher quality image than in the monochrome mode, as in the 3-color mode, the print resolution in the transport direction in the 4-color mode is higher than the print resolution in the transport direction in the monochrome mode. To do. Here, the print resolution in the transport direction in the four-color mode is set to a resolution (eg, 360 dpi) that is twice the print resolution D (eg, 180 dpi) in the transport direction in the monochrome mode. For this reason, in the four-color mode of the comparative example, the medium transport amount per time is 1.5D. As a result, as shown in the right diagram of FIG. 5, in the nozzles on the upstream side in the transport direction from the print start position, the black nozzles and three types of color nozzles are arranged in the moving direction, and one raster line is divided into four It can be seen that printing can be performed by the nozzle (YMCK). Also, one black discharge nozzle and one three-color discharge nozzle are arranged in the moving direction. Therefore, in the four-color mode of the comparative example, each color raster line is formed by one nozzle. For example, the black raster line immediately upstream of the printing start position is formed only by the black nozzle K8, the cyan raster line is formed only by the cyan nozzle C8, the magenta raster line is formed only by the magenta nozzle M5, and yellow. This raster line is formed only by the yellow nozzle Y2. In the four-color mode of the comparative example, among the nozzles belonging to the black nozzle row K, the black nozzles (K7 to K9) corresponding to the cyan nozzles (C7 to C9) are used as the discharge nozzles. On the other hand, a pass in which cyan dots are formed is equal to a pass in which black dots are formed.

  By the way, black pigment ink is ejected from the black nozzle, and dye ink of each color is ejected from the color nozzle. Usually, pigment ink stays on the surface of the medium, but if a large amount of pigment ink is ejected to a unit area on the medium simultaneously or in a short period of time, the pigment ink color material (pigment) sinks inside the medium. Have the property of This is because if the amount of ink ejected to the unit area of the medium increases, the amount of solvent component (for example, water) of the ink penetrating into the medium increases, so that the color material easily sinks into the medium together with the solvent component. This is probably because the color material tends to sink into the medium due to the weight of the material (pigment). For this reason, if the amount of the pigment ink ejected simultaneously or in a short time with respect to the unit area on the medium is large, the color material (pigment) sinks inside the medium and the density of black in the printed image decreases. This phenomenon occurs when the pigment component sinks inside the medium, and particularly occurs when plain paper is used as the medium. In addition, in dye inks, there is a phenomenon that the density becomes lighter as the amount of ink ejected per unit area increases. However, since dyes are originally easily dissolved in solvents and penetrate into the medium, the density is higher than that of pigment inks. The degree of fading is low.

  In the above-described monochrome mode (FIG. 3), the printing resolution in the transport direction is lower than in the four-color mode (FIG. 5) of the comparative example, and raster lines are formed at every nozzle pitch D. On the other hand, in the four-color mode of the comparative example, a raster line is formed in the next pass between raster lines formed in a certain pass. Therefore, in the four-color mode of the comparative example, the amount of black pigment ink ejected to the unit area on the medium in a short time (between two consecutive passes) is larger than in the monochrome mode. That is, in the four-color mode of the comparative example, after the pigment ink is ejected in a previous pass to a predetermined region (region where two raster lines are formed) on the medium, the solvent of the pigment ink in the previous pass is changed. Before sinking into the medium or drying, the pigment ink is ejected in the next pass to the predetermined area. As a result, in the four-color mode of the comparative example, more pigment (coloring material) sinks inside the medium than in the monochrome mode, and the black density of the image printed in the four-color mode of the comparative example becomes lighter, and the printed image Will deteriorate. In particular, when the density of black is lowered, it is easily visible and leads to deterioration of the printed image.

  In the four-color mode of the comparative example (FIG. 5), the number of ejection nozzles for each color and the number of ejection nozzles for black are the same, and the printing method for each color nozzle and the printing method for black nozzles are the same ( A raster line is formed in the next pass between the raster lines formed in the previous pass). That is, the color dye ink, like the black pigment ink, has a large amount of color dye ink ejected to a unit area on the medium in a short time (between two consecutive passes). However, there is no problem with dye ink because, compared with pigment ink, even if the amount of ink ejected to a unit area on a medium in a short period of time is small, the density is low.

  Also, pigment black ink is often used for printing characters. If the pigment black ink is blurred, the characters are crushed and it is difficult to distinguish the characters. Although pigment ink is less likely to bleed than dye ink, if the amount of pigment ink ejected in a short time in a unit area on the medium increases, the image becomes more likely to bleed. Therefore, in the four-color mode printing (FIG. 5) of the comparative example, there is a possibility that the black ink is blurred and it is difficult to distinguish characters compared to the monochrome mode printing (FIG. 3).

  In other words, if the amount of black pigment ink that is ejected to a unit area on the medium in a short period of time increases, the pigment component (coloring material) sinks inside the medium, the density of black becomes lighter, and the image tends to bleed. The image quality will deteriorate. Therefore, in this embodiment, when printing using both the dye color ink and the pigment black ink (in the four-color mode), the amount of black pigment ink to be ejected in a short time on a unit area on the medium is set. The purpose is to suppress image quality deterioration of a printed image.

  FIG. 6 is a diagram illustrating a printing method in the four-color mode according to the present embodiment. In the four-color mode printing method of this embodiment, as shown in the left diagram of FIG. 6, all nozzles in the color nozzle row Co, that is, yellow, magenta, and cyan nozzles are used as discharge nozzles, and the black nozzle row K 1/3 nozzles (K # 1 to K # 3, first black nozzle group K1) on the downstream side in the transport direction and 1/3 nozzles (K # 7 to K # 9) on the upstream side in the transport direction are discharged. A nozzle. The 1/3 nozzles (K # 4 to k # 6) at the center in the transport direction of the black nozzle row K are set as non-ejection nozzles. That is, in the four-color mode printing of this embodiment (FIG. 6), the number of nozzles that eject black ink (six in FIG. 6) is greater than the number of nozzles that eject each color ink (three in FIG. 6). To do more. Further, in the black nozzle row K, non-ejection nozzles (K # 4 to K # 6) are provided between the ejection nozzles (K # 1 to K # 3 and K # 7 to K # 9).

  In the printer 1 of this embodiment, three types of printing modes can be selected, and the ejection nozzles and non-ejection nozzles of the black nozzle row K differ depending on the printing mode (FIGS. 3, 4, and 6). Therefore, the printer driver may assign print data to the ejection nozzles according to the print mode, or the controller 10 of the printer 1 may assign print data to the ejection nozzles according to the print mode.

  In the four-color mode of this embodiment, the print resolution in the transport direction is set to a resolution (eg, 360 dpi) that is twice the print resolution D in the transport direction of the monochrome mode (eg, 180 dpi), as in the three-color mode. . Therefore, the amount of medium transported once is 1.5 times the nozzle pitch D of the black nozzle row K. As a result, as shown in the right diagram of FIG. 6, in the nozzles on the upstream side in the transport direction from the printing start position, two black discharge nozzles and one three-color discharge nozzle are arranged in the moving direction. In other words, in the four-color mode of the present embodiment, two black discharge nozzles and three color discharge nozzles are respectively provided for an area on the medium where one raster line is formed (hereinafter referred to as a row area). One by one is associated. For example, in the row region immediately upstream of the print start position, the black nozzle K8 and cyan nozzle C8 in pass 1, the magenta nozzle M5 in pass 3, and the black nozzle K2 and yellow nozzle Y2 in pass 5 are associated with each other.

  That is, in the four-color mode of the comparative example (FIG. 5), the black raster line is printed by one nozzle (one pass), whereas in the four-color mode of the present embodiment (FIG. 6), the black raster line is printed. Print the line with two nozzles (in two passes). Note that each raster line (YMC) of three colors is printed by one nozzle (one pass) of each color in the four-color mode of the present embodiment, as in the four-color mode of the comparative example.

  Here, it is assumed that an area on a medium where one dot is formed is a pixel area, and one row area is composed of a plurality of pixel areas arranged in the moving direction. In the four-color mode of the present embodiment, one-color discharge nozzles for three colors are associated with one row region. For this reason, all the pixel areas belonging to one row area are assigned to each discharge nozzle of three colors. For example, when the print data instructs to form yellow dots in all pixel areas belonging to a certain row area, one yellow nozzle associated with the row area forms dots in all the pixel areas. It will be. On the other hand, two black discharge nozzles are associated with one row region. Therefore, a part of the pixel areas belonging to the row area is assigned to one of the two black nozzles associated with the row area (for example, every other pixel area is assigned). ), The remaining pixel area is assigned to the other black nozzle.

  For this reason, the print resolution in the transport direction is the same in the four-color mode of the present embodiment (FIG. 6) and the four-color mode of the comparative example (FIG. 5), but in the comparative example, one black raster line passes once. In contrast to this, in this embodiment, one black raster line is formed in two passes. Therefore, the amount of pigment ink ejected in a short time in the unit area on the medium is smaller in this embodiment than in the comparative example. Specifically, in the comparative example (FIG. 5), two raster lines arranged in the transport direction are formed in two consecutive passes (for example, pass 1 and pass 2), whereas this embodiment (FIG. 5). In 6), some dots of two raster lines arranged in the transport direction are formed in two consecutive passes (for example, pass 1 and pass 2). Then, the remaining dots of the two raster lines arranged in the transport direction are formed in two consecutive passes (for example, pass 5 and pass 6) after a predetermined time has elapsed. As described above, in the present embodiment, compared to the comparative example, the amount of black pigment ink ejected to the unit area on the medium in a short time can be reduced, so that the pigment component (coloring material) sinks inside the medium. It can be suppressed that the density of black becomes light. As a result, the four-color mode of the present embodiment can print a high-quality image with a darker black density than the four-color mode of the comparative example.

  In summary, in this embodiment, the number of nozzles for ejecting black ink (six in FIG. 6) is increased from the number of nozzles for ejecting each color ink (three in FIG. 6), and the raster for each color of color. The number of nozzles forming the black raster line (two) and the number of passes (twice) are made larger than the number of nozzles forming the line (one) and the number of passes (one). By doing so, in this embodiment, compared to the comparative example, it is possible to reduce the amount of black pigment ink ejected to the unit area on the medium in a short time, and to suppress the black density from becoming light. . Further, it is possible to suppress the black image from bleeding.

  As shown in FIG. 6, the pigment black ink and the cyan ink, and the pigment black ink and the yellow ink are ejected to the same row area in the same pass. However, the black ink and the color ink are rarely discharged on the same pixel area or discharged in the vicinity area. Therefore, even if a certain area on the medium faces the discharge nozzle of the black nozzle row K and the discharge nozzle of the cyan nozzle row C at the same time, the black pigment ink is less affected by the cyan dye ink. In addition, sinking of the pigment can be suppressed. In the comparative example, since one raster line is formed by one black nozzle, it is easily affected by the characteristics of the nozzle. However, in this embodiment, one raster line is formed by two black nozzles. The characteristic difference can be reduced.

  Furthermore, in this embodiment, in the black nozzle row K, the first black nozzle group K1 (corresponding to K # 1 to K # 3 and the first nozzle group in FIG. 6) on the downstream side in the transport direction and the first black nozzle group K1 in the transport direction on the upstream side. Three black nozzle groups K3 (corresponding to K # 7 to K # 9 and third nozzle group) are used as ejection nozzles, and the second black nozzle group K2 (K # 4 to K # 6) between them is used as a non-ejection nozzle ( Ink is not ejected from the nozzles between the first nozzle group and the second nozzle group). As shown in the right diagram of FIG. 6, for example, the row region immediately upstream of the print start position first faces the nozzle K8 and cyan nozzle C8 of the third black nozzle group K3 in pass 1 and then passes. 3, the nozzle K5 of the second black nozzle group K2 and the magenta nozzle M5 are opposed to each other, and finally, in pass 5, the nozzle K2 of the first black nozzle group K1 and the yellow nozzle Y2 are opposed. Therefore, in this embodiment, the raster line can be formed by the black nozzle K8 in pass 1 and the black nozzle K5 in pass 3 in this embodiment. Form. By doing so, in this embodiment, in order to form one raster line, the time interval for ejecting the pigment black ink is made as long as possible. As a result, the black pigment ink ejected in the previous pass 1 is dried before the black pigment ink is ejected in the subsequent pass 5, so that the black pigment ink ejected in the previous pass 1 progresses. It is possible to prevent the pigment ink from affecting the black pigment ink ejected in the subsequent pass 5, and the color material of the black pigment ink ejected in the subsequent pass sinks into the medium. Can be further suppressed. As a result, it is possible to print with a higher black density.

  That is, in the present embodiment, in the black nozzle row K, the non-ejection nozzle group (second black nozzle group K2) is disposed between the two ejection nozzle groups (first black nozzle group K1 and third black nozzle group K3). Provide. Thus, when printing one raster line of black in multiple passes, the time from when the black pigment ink is ejected to the next pass until the next black pigment ink is ejected is as long as possible. Secure. As a result, sinking of the pigment component (coloring material) into the medium and bleeding of the pigment black ink can be suppressed.

  In the head 41 of this embodiment (FIG. 2), three color nozzle groups are arranged in the transport direction, and each color nozzle group (YMC) corresponds to three black nozzle groups (K1 to K3). Yes. In addition, since one nozzle region is always associated with each of the three color nozzle groups (YMC), one column region has three black nozzle groups (K1 to K3). It will face the black nozzle. Therefore, the nozzles belonging to the first black nozzle group K1 corresponding to the yellow nozzle group Y and the nozzles belonging to the third black nozzle group K3 corresponding to the cyan nozzle group C are referred to as “ejection nozzles” and correspond to the magenta nozzle group M. The nozzles belonging to the second black nozzle group K2 are referred to as “non-ejection nozzles”. That is, when there are three or more nozzle groups (YMC) that discharge each color ink, two black nozzle groups respectively corresponding to the two color nozzle groups located on the upstream side and the downstream side in the transport direction are designated as “discharge nozzles”. The black nozzle group corresponding to the color nozzle group located in the center in the transport direction may be set as the “non-ejection nozzle”. By doing so, it is possible to face one non-ejection nozzle while all the row areas are opposed to two ejection nozzles, and ensure the longest possible drying time of the pigment black ink ejected in two steps. can do.

  Also, if the nozzle is not used for a long time, the ink around the nozzle will thicken and there is a risk of causing ejection failure. Therefore, when the nozzle is not used for a long time, it is necessary to perform cleaning (for example, flushing) of the nozzle. In the four-color mode printing of the comparative example (FIG. 5), only one black nozzle group K3 (K # 7 to K # 9) is used among the three black nozzle groups K1 to K3. Cleaning must be performed for K1 and K2. In contrast, in the four-color mode printing of the present embodiment (FIG. 6), two black nozzle groups K1 and K3 (K # 1 to K # 3 and K #) out of the three black nozzle groups K1 to K3. 7 to K # 9) are used, it is only necessary to perform cleaning on one black nozzle group K2. As described above, in the present embodiment, the number of nozzles to be cleaned can be reduced as compared with the comparative example, and the amount of ink consumed other than printing can be reduced.

=== Modification ===
FIG. 7 is a diagram illustrating a printing method according to a modification. Up to this point, the number of color inks is three, and the color nozzle row Co in which the three color nozzle groups (YMC) are arranged in the transport direction is taken as an example. However, the present invention is not limited to this. For example, in addition to yellow, magenta, and cyan, there are printers that discharge green G and orange O (or light magenta Lm and light cyan Lc). FIG. 7 shows an example of printing with a color nozzle row Co in which nozzle groups (YMC, O, G) that respectively discharge five color inks are arranged in the transport direction and a black nozzle row K corresponding thereto. That is, in FIG. 7, the number of nozzles belonging to the black nozzle row K corresponds to the number of nozzles five times the number of nozzles of each color ink.

  In FIG. 7, the black nozzles (K1 to K3) corresponding to the yellow nozzle group Y on the most downstream side in the transport direction, the black nozzles (K7 to K9) corresponding to the cyan nozzle group C in the center in the transport direction, and the most upstream side in the transport direction. The black nozzles (K13 to K15) corresponding to the green nozzle group G are used as discharge nozzles, and the black nozzles (K4 to K6) corresponding to the magenta nozzle group M and the black nozzles (K10 to K12) corresponding to orange O in the meantime. Is a non-ejecting nozzle. As a result, as shown by the arrangement of the nozzles in the thick frame in the figure, the black pigment ink is ejected in three times to form one raster line. Further, three passes are provided while the black pigment ink is ejected, and the black pigment ink ejected earlier during this time can be dried. That is, it is possible to reduce the amount of black pigment ink ejected in a unit area on the medium in a short time, and to suppress the sinking of the pigment into the medium and the bleeding of the pigment ink.

  However, the present invention is not limited to this. For example, black nozzles (K1 to K3) corresponding to the yellow nozzle group Y on the most downstream side in the transport direction and black nozzles (K13 to K15) corresponding to the green nozzle group G on the most upstream side in the transport direction. May be used as discharge nozzles, and the black nozzles (K4 to K12) between them may be used as non-discharge nozzles.

=== Other Embodiments ===
Each of the above embodiments is described mainly for a printing system having an ink jet printer, but includes disclosure of a printing method and the like. 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.

<About nozzle arrangement>
In the head 41 of the above-described embodiment (FIG. 2), the positions in the transport direction of the nozzles of the black nozzle row K and the nozzles of the color nozzle row Co are the same, but this is not restrictive. For example, the nozzles of the black nozzle row K and the nozzles of the color nozzle row Co may be shifted by, for example, half the nozzle pitch D in the transport direction. In this case, the black dot row and the color dot row are formed shifted by a half nozzle pitch (D / 2) in the transport direction. The black ink and the color ink are rarely formed in an overlapping manner. For example, it is assumed that the black dot and the color dot are formed adjacent to each other in the moving direction. At this time, if the black nozzle row K and the color nozzle row Co are shifted by a half-nozzle pitch (D / 2), the black dots and the color dots will be shifted in both the moving direction and the transport direction, affecting each other. It becomes difficult to exert. That is, when the color dye ink penetrates into the medium or wets and spreads on the medium surface, the black pigment component can be prevented from sinking into the medium or spreading on the medium surface. Can be printed with a high density. Even when the black nozzle row K and the color nozzle row Co are shifted in the transport direction in a range narrower than the nozzle pitch (for example, a half nozzle pitch), the yellow nozzle group Y and the first black nozzle group K1 in the transport direction. It can be said that the positions of the magenta nozzle group M and the second black nozzle group K2 are equal in the conveyance direction, and the cyan nozzle group C and the third black nozzle group K3 are equal in the conveyance direction. Further, in the nozzle arrangement in the head 41, the black ink nozzles are not limited to one nozzle row, and the nozzles of other color inks may be one nozzle row.

<About the printer>
In the above-described embodiment, the printer 1 that repeats the operation of forming an image while moving the head 41 in the movement direction and the operation of conveying the medium in the conveyance direction is described as an example. For example, with respect to continuous paper transported to the printing area, an operation of forming an image while moving the head along the transport direction of the continuous paper and an operation of moving the head in the paper width direction intersecting the transport direction are repeated. It may be a printer that completes an image and then transports a medium portion on which an image has not yet been printed to a printing area.

1 Printer, 10 Controller, 11 Interface section,
12 CPU, 13 memory, 14 unit control circuit,
20 transport unit, 30 carriage unit, 31 carriage,
40 head units, 41 heads,
50 detector groups, 60 computers

Claims (4)

(A) a first nozzle row in which nozzles for discharging the first color ink are arranged in a predetermined direction;
(B) A second nozzle row that is arranged in a moving direction that intersects the first nozzle row and the predetermined direction, and nozzles that eject a plurality of colors of ink different from the first color eject ink of the same color. A second nozzle row arranged in the predetermined direction for each nozzle;
(C) an ejection operation for ejecting ink from the nozzles while moving the first nozzle row and the second nozzle row in the movement direction, and a relative position between the first nozzle row, the second nozzle row, and the medium. A control unit that repeats the relative movement in one direction of the predetermined direction;
(D)
(E) The number of the nozzles belonging to the first nozzle row is greater than the number of the nozzles that eject each color ink among the nozzles belonging to the second nozzle row,
The number of the nozzles of the first nozzle row that forms the dot row along the moving direction is greater than the number of the nozzles that eject each color ink of the second nozzle row that forms the dot row along the moving direction. Many
Among the nozzles belonging to the first nozzle row, the plurality of nozzles forming a plurality of dot rows along the moving direction in a certain ejection operation, and the plurality of nozzles forming a part of each dot row The first nozzle group, and the plurality of nozzles forming the plurality of dot rows in another ejection operation, and the plurality of nozzles forming another part of each dot row, the first nozzle group. Ink is not ejected from the nozzles between the nozzle group and the second nozzle group located on the one direction side of the predetermined direction from the nozzle group.
(F) The printing apparatus characterized by the above-mentioned. The printing apparatus according to claim 1,
In the second nozzle row, in order from the one direction side of the predetermined direction, there are a third nozzle group in which nozzles for discharging the second color ink are arranged in the predetermined direction, and nozzles for discharging the third color ink. A fourth nozzle group arranged in the predetermined direction and a fifth nozzle group in which nozzles for discharging the fourth color ink are arranged in the predetermined direction;
The third nozzle group has the same position in the predetermined direction as the second nozzle group,
The fourth nozzle group has the same position in the predetermined direction as the nozzle between the first nozzle group and the second nozzle group among the nozzles belonging to the first nozzle row,
The fifth nozzle group has the same position in the predetermined direction as the first nozzle group.
Printing device. The printing apparatus according to claim 1 or 2, wherein
The first color ink is a black pigment ink.
Printing device. A first nozzle row in which nozzles for discharging the first color ink are arranged in a predetermined direction; and a second nozzle row in which the first nozzle row is arranged in a moving direction that intersects the predetermined direction. An ejection operation for ejecting ink from the nozzles while moving in the moving direction a second nozzle row in which the nozzles ejecting a plurality of different colors are arranged in the predetermined direction for each nozzle ejecting the same color ink; A printing method of a printing apparatus that repeats an operation of relatively moving a relative position between the first nozzle row and the second nozzle row and a medium in one direction of the predetermined direction,
The number of the nozzles belonging to the first nozzle row is larger than the number of the nozzles for discharging each color ink among the nozzles belonging to the second nozzle row,
The number of the nozzles of the first nozzle row that forms the dot row along the moving direction is determined by the number of the nozzles that eject each color ink of the second nozzle row that forms the dot row along the moving direction. And many
Among the nozzles belonging to the first nozzle row, the plurality of nozzles forming a plurality of dot rows along the moving direction in a certain ejection operation, and the plurality of nozzles forming a part of each dot row The first nozzle group, and the plurality of nozzles forming the plurality of dot rows in another ejection operation, and the plurality of nozzles forming another part of each dot row, the first nozzle group. No ink is ejected from the nozzles between the nozzle group and the second nozzle group located on the one direction side of the predetermined direction from the nozzle group.
A printing method characterized by the above.

Images