JP5621366B2 - Printing apparatus and program - Google Patents

Description

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

  As one of printing apparatuses, an ink jet printer (hereinafter referred to as a printer) having a head that ejects ink from a nozzle to a medium is known. Among printers, printers that perform printing using white ink in addition to color inks such as cyan, magenta, and yellow are known (see, for example, Patent Document 1). In such a printer, for example, by printing the background image with white ink and the main image with color ink on top of each other, it is possible to print a main image with good color development without being affected by the ground color of the medium. .

JP 2002-38063 A

By the way, when printing an image on a medium having ink absorptivity, the amount of ink that can be ejected per unit area of the medium is limited. Even in a printed matter in which a main image and a background image are printed in an overlapping manner, the density of the background image may vary depending on the use of the printed matter. Therefore, regardless of the density of the background image, if the amount of ink for printing the main image is limited, the ink is ejected beyond the absorption capacity of the medium and the image is blurred or the main image is printed. The amount of ink is limited more than necessary, and the color developability of the main image is suppressed. As a result, the image quality of the printed image is degraded.
Accordingly, an object of the present invention is to suppress deterioration in image quality of a printed image.

A main invention for solving the above problems is to print a background image that overlaps the main image and a nozzle that discharges the first ink to a medium having ink absorptivity for printing the main image. The main image according to the nozzle that ejects the second ink to the medium and the amount of the second ink that is ejected from the nozzle to the unit area of the medium to print the background image possess a control unit for varying the maximum amount of the first ink that can be ejected from the nozzle with respect to the unit area of the medium for printing, the medium for printing the background image A first printing mode in which the amount of the second ink ejected to the unit region is a predetermined amount; and the second ink to be ejected to the unit region of the medium for printing the background image. The amount of A gradation value for printing the main image by superimposing the main image and the background image on the medium in any one of the second print modes less than the amount, and the print A dot generation rate table for main image that associates the dot generation rate of the first ink in the unit area, and a gradation value for printing the background image and the second in the unit area The dot generation rate table for the background image that associates the dot generation rate of the first ink differs between the first print mode and the second print mode, and the dot generation rate of the first ink for a predetermined gradation value is The main image dot generation rate table in the first print mode is lower than the main image dot generation rate table in the second print mode, and the dot generation rate of the second ink for a predetermined gradation value. Is the first A printing device towards the background image dot generation rate table of the printing mode may be higher than the background image dot generation rate table of the second printing mode.
Other features of the present invention will become apparent from the description of this specification and the accompanying drawings.

1 is an overall configuration block diagram of a printing system. FIG. 2A is a schematic diagram of the printer, and FIG. 2B is a diagram illustrating nozzle arrangement in the head. FIG. 4 is a diagram for describing print modes that can be selected by a printer. 4A is a diagram illustrating a printing method in the white usage mode / front printing mode, and FIG. 4B is a diagram illustrating a printing method in the white usage mode / back printing mode. It is a figure explaining another printing method. 6 is a flowchart for explaining print data generation processing; It is a flowchart for demonstrating the halftone process for normal modes. It is a figure which shows the dot production rate table for normal mode and K image data. It is a figure which shows the mode of the dot ON / OFF determination by a dither method. FIG. 10A is a diagram showing a dot generation rate table for high-density background mode and W image data, and FIG. 10B is a diagram showing a dot creation rate table for high-density background mode and K image data. FIG. 11A is a diagram showing a dot generation rate table for low-density background mode and W image data, and FIG. 11B is a diagram showing a dot creation rate table for low-density background mode and K image data. It is a graph which shows the difference in the ink amount discharged per unit area | region in each printing mode.

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

That is, a nozzle that discharges a first ink to a medium having ink absorbency for printing a main image, and a second ink to the medium to print a background image that overlaps the main image And the amount of the second ink ejected from the nozzle per unit area of the medium to print the background image, and the medium of the medium to print the main image And a control unit that varies a maximum amount of the first ink that can be ejected from the nozzle with respect to a unit region.
According to such a printing apparatus, it is possible to prevent the ink from being ejected beyond the absorption capability of the medium and blurring of the image, and to prevent the amount of ink for printing the main image from being limited more than necessary. Image quality degradation can be suppressed.

In this printing apparatus, in order to print the background image, a first printing mode in which the amount of the second ink ejected to the unit area of the medium is a predetermined amount, and the background image is printed. Therefore, the main image is printed on the medium in any one of the second print mode in which the amount of the second ink ejected to the unit area of the medium is smaller than the predetermined amount. The maximum amount of the first ink that can be ejected to the unit area of the medium in order to print the main image in the first printing mode by overprinting the background image and the second printing. Less than the maximum amount of the first ink that can be ejected to the unit area of the medium to print the main image in mode.
According to such a printing apparatus, it is possible to prevent the ink from being ejected beyond the absorption capability of the medium and blurring of the image, and to prevent the amount of ink for printing the main image from being limited more than necessary. Image quality degradation can be suppressed.

In this printing apparatus, in order to print the main image in the first printing mode, the maximum amount of the first ink that can be ejected to the unit area of the medium and the background in the first printing mode. The total amount of the second ink discharged to the unit area of the medium for printing an image is the unit area of the medium for printing the main image in the second print mode. The maximum amount of the first ink that can be discharged with respect to the medium and the amount of the second ink that is discharged onto the unit area of the medium in order to print the background image in the second print mode Equal to the quantity.
According to such a printing apparatus, the maximum amount of ink that can be ejected per unit area in order to print the main image can be increased as much as possible.

Any of the first printing mode, the second printing mode, and the third printing mode that prints the main image on the medium but does not print the background image on the medium. In this printing mode, an image is printed on the medium, and the maximum amount of the total amount of the first ink and the second ink that can be ejected to the unit area of the medium in the first printing mode. And the maximum amount of the total amount of the first ink and the second ink that can be ejected to the unit area of the medium in the second printing mode is the maximum amount of the medium in the third printing mode. More than the maximum amount of the first ink that can be ejected to the unit area.
According to such a printing apparatus, in the first printing mode and the second printing mode, the maximum amount of ink that can be ejected per unit area in order to print the main image can be increased as much as possible.

In this printing apparatus, the background image is printed with ink of the same color as the ink for printing the main image and ink of a color different from the ink.
According to such a printing apparatus, a background image of a desired color can be printed.

In addition, a nozzle for ejecting the first ink to a medium having ink absorptivity for printing the main image and a second ink to the medium for printing a background image overlapping the main image A program for operating a printing apparatus having a nozzle for discharging, according to the amount of the second ink discharged from the nozzle to a unit area of the medium to print the background image, Print data for printing the main image and the background image by varying the maximum amount of the first ink that can be ejected from the nozzle with respect to the unit area of the medium in order to print the main image. Is a program that allows a computer to implement the function of creating
According to such a program, it is possible to prevent the ink from being ejected beyond the absorption capability of the medium and blurring of the image, and to prevent the amount of ink for printing the main image from being restricted more than necessary. Image quality deterioration 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. 1 is a block diagram of the overall configuration of the printing system, FIG. 2A is a schematic diagram of the printer 1, and FIG. 2B is a diagram showing the nozzle arrangement in the head 41. The computer 60 is communicably connected to the printer 1 and outputs print data for causing the printer 1 to print an image to the printer 1. The computer 60 is installed with a program (printer driver) for converting image data output from the application program into print data. The printer driver may be stored in a storage medium (a computer-readable storage medium) such as a CD-ROM or downloaded to a computer 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 and prints an image on the medium S (for example, paper or transparent film). 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 ejecting ink onto the medium S and has a head 41. The head 41 is moved in the movement direction by the carriage 31. A plurality of nozzles, which are ink ejection portions, are provided on the lower surface of the head 41, and each nozzle is provided with a pressure chamber (not shown) filled with ink. FIG. 2B is a diagram in which the nozzle arrangement is virtually seen from the upper surface of the head 41. As shown in the figure, nozzle rows in which 180 nozzles are arranged at a predetermined interval D in the transport direction are formed in 5 rows in the movement direction. From left to right in the moving direction, black nozzle row K for discharging black ink, cyan nozzle row C for discharging cyan ink, magenta nozzle row M for discharging magenta ink, yellow nozzle row Y for discharging yellow ink, and white ink White nozzle rows W to be discharged are arranged.

  In such a printer 1, dot formation processing in which ink droplets are intermittently ejected from the head 41 moving in the movement direction to form dots on the medium, and the medium is conveyed with respect to the head 41 in the conveyance direction. The conveyance process is repeated. By doing so, dots can be formed at positions different from the positions of the dots formed by the previous dot formation process, and a two-dimensional image can be printed on the medium. The operation in which the head 41 moves once in the movement direction while ejecting ink droplets (one dot formation process) is referred to as “pass”.

=== About print mode ===
FIG. 3 is a diagram illustrating print modes that can be selected by the printer 1. The printer 1 uses the “normal mode” in which only the main image (color image or monochrome image) is printed on the medium using at least one of the nozzle rows (YMCK) of four colors ink, and the white nozzle row W. The image is printed on the medium in any one of the “white use mode” in which the white background image to be printed and the main image are superimposed and printed on the medium. By providing a white background image on the background of the main image as in the white usage mode, an image with good color development can be printed particularly when the medium is not white. In addition, when the medium is transparent, it is possible to prevent the opposite side of the printed matter from being seen through by printing the main image and the background image in an overlapping manner.

  By the way, there are a reflection observation method and a transmission observation method as methods for observing the main image. The reflection observation method is a method in which a person irradiates light from the side observing the main image (that is, from the surface side of the main image) and observes the main image by reflected light. The transmission observation method is a method of irradiating light from the side opposite to the side on which the person observes the main image (that is, from the back side of the main image) and observing the main image with the transmitted light. For example, when a main image is printed on a transparent medium such as a transparent film or ground glass, the main image can be observed with transmitted light. A reflection observation method is suitable as a printing method for a main image observed in a bright place or in the daytime, and a transmission observation method is suitable as a printing method for the main image observed in a dark place or at night.

  When printing a main image observed with reflected light, the contrast between the main image and the background image can be increased by increasing the density of the background image, so that the main image is observed more clearly. Further, when the main image observed by reflected light is printed on a transparent medium, by increasing the density of the background image, the shielding property of the background image is increased and the opposite side of the printed matter can be prevented from being seen through. . On the other hand, when printing a main image observed with transmitted light, the transmittance can be increased by reducing the density of the background image, and the main image is observed more clearly. That is, it is preferable to increase the density of the background image when printing the main image observed with reflected light, and to decrease the density of the background image when printing the main image observed with transmitted light. preferable.

  In addition, since the appearance (brightness) of the main image varies depending on the density of the background image, the background image may vary depending on the density of the background image depending on the user-desired appearance of the main image, or depending on the intensity of the light source. Therefore, the background image density may vary depending on the light source.

  Therefore, in the printer 1 of the present embodiment, the white use mode is divided into a “high density background mode” for printing a background image at a relatively dark density, and a “low density background mode” for printing a background image at a relatively light density. ”. Hereinafter, a background image printed in the high density background mode is referred to as a “high density background image”, and a background image printed in the low density background mode is referred to as a “low density background image”.

  Further, the printer 1 prints an image on the medium in one of the front printing mode and the back printing mode. The front printing mode is a mode for printing an image so that the main image is viewed from the printing surface side, and the back printing mode is for the main image to be viewed from the surface opposite to the printing surface through the medium. This is a mode for printing an image. Therefore, the back printing mode can be performed when the medium has transparency. In the normal mode, since only the main image is printed on the medium, the main image is printed directly on the medium regardless of whether in the front printing mode or the back printing mode. On the other hand, in the white usage mode, the main image and the background image are overprinted, so in the front printing mode, the background image is printed first with respect to a predetermined area of the medium, and the main image is printed on the background image. Conversely, in the reverse printing mode, the main image is printed first on a predetermined area of the medium, and the background image is printed on the main image.

As described above, the printer 1 has six printing modes shown in FIG. Although the background image is white, the term “white” in this specification is not limited to white in the strict sense that is the surface color of an object that reflects 100% of all wavelengths of visible light. It is assumed that a color called “white” is included in the common sense, such as “color”. “White” means, for example, (1) color measurement mode: spot color measurement, light source: D50, backing: Black, printing medium: transparent film using x-rite colorimeter eye-onePro When colored, the mark in the L ^* a ^* b ^* color space is on the a ^* b ^* plane and within the circumference of the radius 20 and within the hue range represented by an L ^* value of 70 or more. (2) When using a Minolta colorimeter CM2022 and measuring in the measurement mode D502 ° field of view, SCF mode, and white background, the label in the L ^* a ^* b ^* color space is a ^* b ^* Whether the color is within the circumference of a circle having a radius of 20 on the plane and the inside thereof, and the color within the hue range represented by an L ^* value of 70 or more. (3) As described in Japanese Patent Application Laid-Open No. 2004-306591 The color of the ink used as the background of the image. Is not limited to the pure white if Re.

  When a background image is printed using only white ink, the color of the white ink itself becomes the color of the background image. However, even in the case of ink called white ink, the color of white is slightly different depending on the ink material. Therefore, a background image having a color different from the color desired by the user may be printed depending on the white ink used. In addition, a background image having a slight chromatic color instead of simple white may be desired. Accordingly, the printer 1 of the present embodiment prints a desired white background image (adjusted white background image) by appropriately using a small amount of four-color ink (YMCK) together with white ink. By doing so, conversely, when the white ink has a slight color, the background image can be printed together with the ink that cancels the color, and the background image can be brought close to an achromatic color. That is, the background image is printed with the same color ink (YMCK) as the ink for printing the main image and the different color ink (W), and in this embodiment, the four-color ink (YMCK) is the first ink. The white ink and the four-color ink correspond to the second ink.

=== Printing method ===
FIG. 4A is a diagram illustrating a printing method in the white usage mode / front printing mode. Hereinafter, for simplification of description, the nozzle rows (YMCK) each ejecting four color inks are collectively referred to as “color nozzle row Co”. In the figure, the number of nozzles belonging to the color nozzle row Co and the white nozzle row W is 8 (# 1 to # 8), and the interval between the nozzles arranged in the transport direction in each nozzle row is D. The nozzles belonging to the color nozzle row Co are indicated by circles, and the nozzles belonging to the white nozzle row W are indicated by triangles. 4A shows the nozzles used for printing an image, and the right figure shows the position of the head 41 (nozzle row) in the transport direction with respect to the medium for each pass. In the actual printer 1, the medium is transported downstream in the transport direction with respect to the head 41, but the state in which the head 41 is transported upstream in the transport direction is shown in the drawing.

  In the white use mode / surface printing mode, the nozzles # 1 to # 4 on the downstream side in the transport direction of the color nozzle row Co are used as main image nozzles for printing the main image (black nozzles). Background image nozzles (△ ○) for printing a background image (a background image with a white color adjusted) on the nozzles # 5 to # 8 on the upstream side in the transport direction of the white nozzle row W and the color nozzle row Co・ White nozzle). The half nozzles (# 1 to # 4) on the downstream side in the transport direction of the white nozzle row W are nozzles that are not used for printing.

  The printing method shown in FIG. 4A is band printing. Band printing is a printing method in which a raster line is not formed in a later pass between raster lines (dot rows along the movement direction) formed in a previous pass. Therefore, in FIG. 4A, the medium transport amount in one transport operation corresponds to half the length (4D) of the nozzle row. In the printing method shown in FIG. 4A, the same nozzle is opposed to a predetermined area of the medium over two passes. That is, after dots are formed in a predetermined area of the medium in a certain pass (for example, pass 1), the medium is not transported to the head 41, and then again in the predetermined area of the medium in the next pass (for example, pass 2). Dots are formed. According to such a printing method, dots arranged in the moving direction can be formed by different passes, or dots can be formed by being overlapped. However, the present invention is not limited thereto, and the operation of forming dots while the head 41 moves in the moving direction and the operation of transporting the medium alternately so that the same nozzle faces a predetermined area of the medium only once. A repeated printing method may be used.

  The half nozzles (# 5 to # 8) on the upstream side in the transport direction in the nozzle row are set as background image nozzles (ΔO), and the half nozzles (# 1 to # 4) on the downstream side in the transport direction are used for the main image. By setting the nozzle (●), for example, the area A on the medium shown in FIG. 4A first faces the background image nozzle in pass 1 and pass 2. Thereafter, when the medium is conveyed, the area A on the medium faces the main image nozzle in pass 3 and pass 4. Therefore, in the area A on the medium, the main image is printed on the background image.

  FIG. 4B is a diagram illustrating a printing method in the white use mode / back printing mode. In the reverse printing mode, the half nozzles (# 1 to # 4) on the downstream side in the transport direction of the white nozzle row W and the color nozzle row Co are used as background image nozzles (Δ · ○), and the upstream in the transport direction of the color nozzle row Co The half nozzles (# 5 to # 8) on the side are set as main image nozzles (●). By doing so, for example, the area A on the medium shown in FIG. 4B first faces the main image nozzle in pass 1 and pass 2, and then the medium is transported, so that the area A on the medium is passed. 3 and pass 4 face the background image nozzle. Therefore, in the area A on the medium, the background image is printed on the main image.

  As described above, among the main image and the background image, an image nozzle (nozzle for lower layer image) that is printed first with respect to a predetermined area of the medium is replaced with an image nozzle that is printed later with respect to the predetermined area of the medium ( The nozzle is on the upstream side in the transport direction with respect to the upper layer image nozzle. By doing so, the main image and the background image can be overlaid and printed in the order corresponding to the front printing mode or the back printing mode. Also, it is possible to print the main image and the background image that are formed so as to overlap a predetermined area of the medium with different passes. Therefore, the drying time of the image printed first with respect to the predetermined area of the medium can be made relatively long, and bleeding and color mixing of the image can be suppressed.

  In the present embodiment, the position in the transport direction of the nozzles (Δ) of the white nozzle row W that prints the background image and the position in the transport direction of the nozzles (◯) of the color nozzle row Co that also prints the background image. Make equal. By doing so, in order to print a background image, white ink and color ink are ejected in the same pass to a predetermined area of the medium. As a result, white ink and color ink are mixed, and the graininess of the background image can be reduced.

  Further, the ratio of the color ink constituting the background image is smaller than the ratio of the white ink. However, in order to reduce the graininess of the color ink in the background image, it is preferable to disperse the dots of the color ink as uniformly as possible on the background image. That is, the color ink density (dot density) per unit area of the background image is made smaller than the white ink density (dot density) per unit area of the background image. Therefore, although the ratio of the color ink constituting the background image is smaller than the ratio of the white ink, in the present embodiment, the number of nozzles of the white nozzle row W used for printing the background image and the nozzles of the color nozzle row Co The numbers are made equal (four in FIG. 4A). However, the present invention is not limited to this, and the number of nozzles of the color nozzle row Co for printing the background image may be smaller than the number of nozzles of the white nozzle row W.

  In the normal mode, since only the main image is printed, the main image can be printed using all the nozzles belonging to the nozzle row. By doing so, the image width that can be formed in one pass becomes larger in the normal mode than in the white use mode, and the printing time can be shortened.

  However, the present invention is not limited to this, and the main image may be printed using only half of the nozzles belonging to the nozzle row in the normal mode as in the white use mode. For example, the main image nozzle used in the front printing / normal mode is the same as the main image nozzle (nozzle on the downstream side in the transport direction) used in the front printing / white usage mode, and is used in the reverse printing / normal mode. The image nozzle may be the same as the main image nozzle (nozzle on the upstream side in the transport direction) used in the reverse printing / white use mode. In this case, the optimal print pattern and medium transport control in the front printing / normal mode and the front printing / white usage mode can be shared, and the optimal printing pattern and medium in the back printing / normal mode and back printing / white usage mode can be shared. Transport control can be shared. By doing so, in the manufacturing process of the printer 1, it is possible to simplify the process of determining the optimal print pattern and transport operation control method. In addition, it is possible to reduce the memory capacity for storing the optimum print pattern in each mode and information on the medium conveyance control. In addition, since the test printing can be performed in the normal mode before the actual printing in the white usage mode and the image quality of the color image can be confirmed, the consumption amount of the white ink can be suppressed.

  Further, an unused nozzle may be provided between the main image nozzle and the background image nozzle. By doing so, a path where the image is not printed (pass where the unused nozzle faces the medium) may be provided between the path where the lower layer image is printed and the path where the upper layer image is printed with respect to a predetermined area of the medium. And lowering the drying time of the lower layer image. In addition, the length in the transport direction of the region to which the unused nozzle belongs is preferably an integral multiple of the medium transport amount. By doing so, the number of passes between the pass for printing the lower layer image and the pass for printing the upper layer image can be made constant throughout the entire image, and uneven density of the image can be prevented.

  FIG. 5 is a diagram illustrating another printing method. The printing method for printing the main image and the background image in an overlapping manner is not limited to the band printing shown in FIGS. 4A and 4B, but may be the interlace printing shown in FIG. FIG. 5 shows a printing method in the white use mode / front printing mode, in which the half nozzles (# 1 to # 6) on the downstream side in the transport direction of the color nozzle row Co are the main image nozzles (●), and the white The half nozzles (# 7 to # 12) on the upstream side in the transport direction of the nozzle row W and the color nozzle row Co are set as background image nozzles (Δ △).

  Interlaced printing is a printing method in which raster lines are formed in another pass between raster lines formed in a certain pass. For example, in FIG. 5, a background image raster line is formed in pass 3 between the background image raster lines formed in pass 2. Therefore, in interlaced printing, the printing resolution in the transport direction is higher than in band printing.

  Further, in the printing method shown in FIG. 5, the raster lines constituting each image are formed by two different nozzles. For example, the raster line for the background image at the print start position is formed by nozzle # 10 in pass 2 and nozzle # 7 in pass 4. Thus, in interlaced printing, one raster line is formed by two different nozzles, so even if one nozzle is a defective nozzle, dots are formed by the other nozzle, which can alleviate image quality degradation. it can. In addition, since one raster line is formed by two nozzles, dots arranged in the movement direction are formed by different passes or dots are overlapped as in the printing method shown in FIGS. 4A and 4B. Can be.

=== About the amount of ink that can be ejected per unit area of the medium ===
<Ink used in this embodiment>
The ink used in the present embodiment is ink that is absorbed by a medium having ink absorbability. That is, any ink composition that can be absorbed by a medium having ink absorbability can be used, and in the present embodiment, at least water is included as a solvent in order to ensure absorbability to a medium having ink absorbability. Use “water-based ink”. In addition, the ink contains coloring materials (dyes and pigments), and if necessary, moisturizers, penetration enhancers, ph regulators, insect repellents, UV absorbers, and water-soluble organic solvents for ejection stability. Etc. may be included. Further, the white ink may contain a white pigment such as a hollow resin or titanium oxide as a color material.

  Examples of the color ink (YMC) and the black ink (K) having such a composition include inks described in JP-A-2008-81693, JP-A-2005-105135, and JP-A-2003-292934. Examples of the white ink (W) include inks described in JP2009-138078A and JP2009-137124A.

<About the medium used in this embodiment>
The (recording) medium used in this embodiment has a property of absorbing water, which is a solvent of the ink composition, and is a medium on which the coloring material is fixed by absorbing water. That is, a medium having water-based ink absorbability is used. For example, a medium using a base material that absorbs ink, such as paper or cloth, or a medium in which an ink absorption layer that absorbs ink is provided on a base material that absorbs ink or a base material that does not absorb ink may be used. For example, the medium used in the reverse printing mode is a medium having water-based ink absorbability and transparency. Examples of such a medium include media described in JP-A-2009-925, JP-A-9-99634, and JP-A-9-208870.

<About the amount of ink that can be ejected per unit area of the medium>
The printer 1 according to the present embodiment discharges water-based ink onto a medium having water-based ink absorbability (hereinafter also referred to as an ink-absorbing medium). Usually, the color development of the image can be improved as the amount of ink ejected to the unit area of the medium increases. However, the ink absorbing medium has a limit in ink absorbing ability. Therefore, if ink is ejected exceeding the ink absorption capacity of the ink-absorbing medium (particularly if a large amount of ink is ejected in a short period of time), ink that cannot be absorbed inside the medium will overflow on the medium. End up. As a result, ink droplets of different colors that have landed in the vicinity of the medium are mixed with each other to cause bleeding, and the quality of the printed image is deteriorated. It should be noted that not only the properties of the ink-absorbing medium but also the properties of the ink (for example, permeability) affect the ink-absorbing ability of the ink-absorbing medium.

  Therefore, in order to prevent bleeding, the printer 1 of the present embodiment does not exceed the maximum amount of ink that can be ejected per unit area of the ink-absorbing medium used for printing (hereinafter also referred to as maximum duty). Ink is ejected onto the absorbent medium.

  Therefore, in the printer 1 (or printer driver) of this embodiment, the duty limit value is set according to the ink absorbing medium used for printing and the properties of the ink. The printer 1 performs printing so that ink is ejected at a duty limit value or less. “Duty limit value (%)” means “dots that can be formed according to the absorption capacity of the medium per unit area of the medium” with respect to “the number of dots (ink amount) that can be formed by the printer 1 per unit area of the medium” It means the ratio of “number (maximum duty)”. Here, an area on the medium corresponding to the pixel data constituting the image data is referred to as a “pixel”, and a minimum unit area where dots are formed is defined as a pixel. Then, the number of dots that can be formed by the printer 1 per unit area of the medium corresponds to the number of pixels belonging to the unit area of the medium.

  For example, it is assumed that the number of pixels belonging to the unit area of the medium is 100 pixels, and the number of dots that can be formed in the unit area of the medium is 50 according to the absorption capacity of the medium. In this case, the duty limit value is “50% (= (50/100) × 100)”. When the number of pixels belonging to the unit area of the medium is 100 pixels and the number of dots that can be formed in the unit area of the medium is 200 according to the absorption capacity of the medium, the duty limit value is “200% (= ( 200/100) × 100) ”.

  In the present embodiment, in order for the printer 1 to perform printing below the duty limit value, the printer driver in the computer 60 generates print data in consideration of the duty limit value (details will be described later). Note that the duty limit value (and the maximum duty) varies depending on the type of the ink-absorbing medium used for printing. Therefore, in the case of a printer that prints images on a plurality of types of ink absorbent media, a duty limit value is set for each ink absorbent media. For simplicity of explanation, it is assumed that the printer 1 of the present embodiment is a printer that prints an image on one type of ink-absorbing medium.

=== About Print Data Generation Processing ===
FIG. 6 is a flowchart for explaining the print data generation process. The print data generation process is performed by a printer driver in the computer 60. First, the printer driver causes the user to select a print mode (S101). When the printer driver receives the image data of the main image from the application program, the printer driver displays a window on the display of the computer 60, for example, and allows the user to select one of the six print modes shown in FIG. . The printer driver stores the selected print mode in the memory of the computer 60. Note that the printer is not limited to allowing the user to select the print mode, and the print mode may be selected. For example, when the medium to be printed is set as a transparent medium, the printer driver may select the print mode as the white use mode.

Next, the printer driver performs resolution conversion processing (S102). The resolution conversion process is a process for converting image data received from an application program into a resolution for printing an image on a medium.
Next, the printer driver performs color conversion processing (S103). The color conversion process is a process for converting RGB image data into data represented by a YMCK color space. This color conversion process is performed by referring to a color conversion lookup table.

  Next, the printer driver determines the print mode. First, the printer driver refers to the print mode stored in the memory of the computer 60, and determines whether or not the print mode selected by the user is the normal mode (S104). When the selected print mode is the normal mode (S104 → YES), the printer driver performs a halftone process for the normal mode (S108, details will be described later).

  At this time point, the image data is data composed of a plurality of pixel data, and the pixel data is data indicating multi-stage gradation values (0 to 255) representing density. In the halftone process, pixel data indicating multi-level gradation values is converted into pixel data indicating small-level gradation values that can be expressed by the printer 1. In this specification, the larger the gradation value (for example, 255), the darker the density, and the smaller the gradation value (for example, 0), the lighter the density. The printer 1 of the present embodiment can form three types of size dots (large dots, medium dots, and small dots). Therefore, pixel data of 256 gradation values is converted to pixel data of 2 gradations (2-bit dot identification data) by halftone processing. Specifically, each pixel data is any one of [00] indicating no dot formation, [01] indicating small dot formation, [10] indicating medium dot formation, and [11] indicating large dot formation. Converted to dot identification data.

  When the selected print mode is not the normal mode (S104 → NO), that is, when the selected print mode is the white use mode, the printer driver determines whether the selected print mode is the high-density background mode. Is determined (S105). When the selected print mode is the high density background mode (S105 → YES), the printer driver creates high density background image data (S106). On the other hand, when the selected print mode is the low density background mode (S105 → NO), the printer driver creates low density background image data (S107).

By the way, the main image is printed with at least one color ink among four color inks (YMCK), and white ink is not used for printing the main image. Therefore, the main image data includes Y image data relating to yellow, M image data relating to magenta, C image data relating to cyan, and K image data relating to black. The pixel data constituting the image data of each color indicates a gradation value (0 to 255) representing the density of the color of each ink. When the main image data has W image data related to white, the gradation value is 0.
On the other hand, the background image is printed by appropriately using four colors of ink (YMCK) together with the white ink, and the white color of the background image is adjusted. Therefore, the high density background image data and the low density background image data include Y image data, M image data, C image data, K image data, and W image data.

  Although details will be described later, in the halftone process, a dot generation rate table indicating the dot generation rate per unit area in each gradation value is used. In the present embodiment, the dot generation rate table used when halftone processing high density background image data is different from the dot generation rate table used when halftone processing low density background image data. Further, even if the tone values indicated by the image data are the same so that the density of the high density background image is higher than the density of the low density background image, the high density background image data is the lower density background image. The dot generation rate table is set so that the dot generation rate is higher than the data. Therefore, in this embodiment, the gradation value indicated by the W image data included in the high density background image data and the gradation value indicated by the W image data included in the low density background image data are set to the same value. In the background image, the gradation value indicated by the W image data included in the high-density background image data and the low-density background image data are included so that white ink is applied to the entire image (so-called solid image). The gradation values indicated by the W image data are both set to the maximum gradation value 255.

  The image data (Y, M, C, K image data) of the four color inks for adjusting the white color of the background image may be stored in advance by the printer driver, or the user may monitor the printer 1 When a desired background image color is selected by looking at the computer screen or the like, the printer driver may generate the color according to the selected color.

  When high density background image data is created, the printer driver performs halftone processing for the high density background mode (S109). When low density background image data is created, the printer driver A halftone process for the background mode is performed (S110).

  Finally, the printer driver performs rasterization processing (S111). The rasterizing process is a process of changing the dot identification data obtained by the halftone process in the order of data to be transferred to the printer 1. The rasterized dot identification data is sent to the printer 1 as print data together with command data and the like. The printer 1 performs printing according to the received print data.

=== About Halftone Processing ===
<Halftone processing for normal mode>
FIG. 7 is a flowchart for explaining halftone processing for normal mode. The halftone process of this embodiment is a halftone process using a dither method. However, the present invention is not limited to this, and for example, an error diffusion method may be used.

  First, the printer driver acquires main image data (Y image data, M image data, C image data, K image data) after color conversion processing (S201 in FIG. 7). The same halftone process is performed for all of the four Y, M, C, and K image data. Therefore, for the sake of simplicity, the halftone process for K image data will be described below assuming that the main image is a monochrome image. The processing from step S202 to step S212 in FIG. 7 is executed while sequentially changing the K pixel data to be processed for all pixel data (K pixel data) included in the K image data. As a result, all the K pixel data included in the K image data includes “no dot formation [00]”, “small dot formation [01]”, “medium dot formation [10]”, and “large dot formation [11]”. Are converted into dot identification data (2-bit data) indicating any of the above.

  FIG. 8 is a diagram showing a dot generation rate table for normal mode and K image data. In the figure, the horizontal axis represents the gradation value (0 to 255) indicated by the pixel data, the left vertical axis represents the dot generation rate (%), and the right vertical axis represents the level data (0 to 255).

  “Dot generation rate” means the proportion of pixels in which dots are formed among the pixels belonging to a unit region when the gradation values indicated by all the pixels belonging to the unit region on the medium are constant. For example, it is assumed that the unit area is composed of 16 pixels × 16 pixels, the gradation values of all the K pixel data in the unit area are constant, and n black dots are formed in the unit area. In this case, the dot generation rate at the constant gradation value is {n / (16 × 16)} × 100 (%). The level data refers to data obtained by converting the dot generation rate into numerical values 0 to 255 in 256 levels. The profile SD indicated by the thin solid line in the figure indicates the generation rate of small dots, the profile MD indicated by the thick solid line indicates the generation rate of medium dots, and the profile LD indicated by the dotted line indicates generation of large dots. Shows the rate.

  By the way, when the medium used for printing is an ink absorptive medium, there is a limit to the ink absorption capacity. Therefore, the duty limit value is set according to the ink absorbing medium and the properties of the ink. In this embodiment, this duty limit value is added to the dot generation rate table. That is, when the gradation value indicated by all the pixels belonging to the unit area of the medium is the maximum gradation value 255, the number of dots (ink amount) ejected to the unit area is set so as not to exceed the duty limit value. The generation rate is set.

  Here, in the printer 1 of the present embodiment, it is assumed that a black dot is formed independently for one pixel. When the gradation value indicated by the K pixel data corresponding to a certain pixel is, for example, 255, the gradation value indicated by the Y, M, and C pixel data corresponding to that pixel is 0. On the other hand, each dot of the three-color color (YMC) is formed independently in one pixel, or is formed so as to overlap with another color dot. That is, the maximum number of dots that can be formed per pixel is one in a black ink image, whereas the maximum number of dots that can be formed per pixel is two in a three-color ink image. . Therefore, the maximum amount of ink that can be ejected per unit area in an image using black ink is greater than the maximum amount of ink that can be ejected per unit area in an image using three color inks.

  Therefore, a dot generation rate table (FIG. 8) used when halftone processing of K image data is made different from a dot generation rate table (not shown) used when halftone processing of Y, M, and C image data. By doing so, even if the gradation values indicated by the K image data and the Y, M, and C image data are the same, the dot generation rate of the K image data is larger than the dot generation rate of the Y, M, and C image data. can do. By doing so, it is possible to prevent the amount of ink discharged from being restricted more than necessary in an image using black ink, and in an image using three color inks, ink is discharged beyond the ink absorption capability of the printing medium, and bleeding occurs. It can be prevented from occurring.

  Setting the dot generation rate so as not to exceed the Duty limit value means that the amount of ink ejected per unit area when the gradation value indicated by all the pixels belonging to the unit area is the maximum gradation value (255). It can be said that it is set to be equal to or less than the maximum ink amount that can be discharged per unit area. More specifically, it is assumed that the unit area of the medium is composed of 16 pixels × 16 pixels, and the maximum ink amount that can be ejected per unit area of the medium used for printing is “X”. In this case, since the dot is formed independently in the black ink image (monochrome image), the maximum ink amount that can be ejected per unit area is “X”. On the other hand, in an image using three color inks, a maximum of two color dots are formed so as to overlap each other, so the maximum ink amount per color that can be ejected per unit area is “X / 2”.

  Then, when the gradation value is the maximum value 255 as in the dot generation rate table shown in FIG. 8, only the large dots are formed, and the ink amount for forming the large dots is “Y”. In the dot generation rate table for K image data shown in FIG. 8, when the gradation value is 255, the generation rate of large dots is Z1%. In this case, the number of large dots formed in the unit area (16 pixels × 16 pixels) of the medium is “16 × 16 × (Z1 / 100)”. Then, the value “{16 × 16 × (Z1 / 100)} × Y” obtained by converting the large dots formed in the unit region into the ink amount exceeds the maximum black ink amount “X” that can be ejected per unit region. The generation rate Z1% of large dots is set so as not to be present.

  Similarly, in the dot generation rate table for Y, M, and C image data (not shown), only large dots are formed when the gradation value is 255, and large dots when the gradation value is 255 are formed. Assume that the generation rate is Z%. In this case, the number of large dots formed in the unit area (16 pixels × 16 pixels) of the medium is “16 × 16 × (Z / 100)”. Then, the value “{16 × 16 × (Z / 100)} × Y” obtained by converting the large dots formed in the unit region into the ink amount is the maximum ink amount “3” for each of the three colors that can be ejected per unit region. The large dot generation rate Z% is set so as not to exceed “X / 2”.

  Here, the black dots are formed alone, and the three color dots are formed by superimposing two dots at the maximum, but this is not restrictive. Some printers have black dots and color dots overlap, while others have all three color dots overlap. In such a printer, the dot generation rate table is set according to the number of dots of each color overlapping with dots of other colors.

  Next, a specific flow of halftone processing for K image data will be described. First, the printer driver reads level data LVL corresponding to the gradation value indicated by the K pixel data to be processed from the profile LD for large dots (dotted line in FIG. 8) (S202 in FIG. 7). For example, as shown in FIG. 8, if the gradation value of the K pixel data to be processed is gr, the level data LVL for large dots is obtained as 1d based on the profile LD for large dots.

  FIG. 9 is a diagram showing a state of dot on / off determination by the dither method. In this embodiment, dot on / off determination is performed using a dither mask by the dither method. The dither mask is composed of a plurality of threshold values arranged two-dimensionally, and a dither mask is set for each dot size. The printer driver obtains the level data LVL related to the large dot, and then compares the level data LVL with the threshold value THL with reference to the dither mask threshold value THL corresponding to the K pixel data to be processed in the large dot dither mask. (S203). When the level data LVL is larger than the threshold value THL (S203 → YES), the printer driver converts the K pixel data to be processed into dot identification data [11] indicating large dot creation (S211).

  On the other hand, when the level data LVL is equal to or less than the threshold value THL (S203 → NO), the printer driver sets the medium dot level data LVM (S204). The medium dot level data LVM is read from the medium dot profile MD (thick line in FIG. 8) according to the gradation value indicated by the K pixel data to be processed. For example, if the gradation value of the K pixel data is gr, the level data LVM is obtained as 2d. Then, the printer driver refers to the threshold value THM of the dither mask corresponding to the K pixel data to be processed in the dither mask for medium dots, and compares the level data LVM with the threshold value THM (S205). If the level data LVM is larger than the threshold THM (S205 → YES), the printer driver converts the K pixel data to be processed into dot identification data [10] indicating medium dot creation (S210).

  On the other hand, when the level data LVM is equal to or less than the threshold value THM (S205 → NO), the printer driver sets the small dot level data LVS (S206). The small dot level data LVS is read from the small dot profile SD (thin line in FIG. 8) according to the gradation value indicated by the K pixel data to be processed. For example, if the gradation value of the K pixel data is gr, the level data LVS is obtained as 3d. Then, the printer driver refers to the threshold value THS of the dither mask corresponding to the K pixel data to be processed in the dither mask for small dots, and compares the level data LVS with the threshold value THS (S207). If the level data LVS is larger than the threshold value THS (S207 → YES), the printer driver converts the K pixel data to be processed into dot identification data [01] indicating small dot creation (S209). When the level data LVS is equal to or less than the threshold value THS (S207 → NO), the printer driver converts the K pixel data to be processed into dot identification data [00] indicating no dot (S208).

  Thus, after the K pixel data to be processed has been changed to any of the four dot identification data (S208 to S211), the printer driver determines whether or not the processing for all the K pixel data has been completed ( S212). The printer driver terminates the halftone process of the K image data when the process for all the K pixel data has been completed (S212 → YES), and if the process has not been completed, the printer driver sets the process target as an unprocessed K. It moves to pixel data and returns to step S202. Similarly, halftone processing is executed for image data of other colors.

<Halftone processing for white use mode>
FIG. 10A is a diagram showing a dot generation rate table for high-density background mode and W image data, and FIG. 10B is a diagram showing a dot creation rate table for high-density background mode and K image data. FIG. 11A is a diagram showing a dot generation rate table for low-density background mode and W image data, and FIG. 11B is a diagram showing a dot creation rate table for low-density background mode and K image data. As described above, the dot generation rate table (FIGS. 8, 10, and 11) used for the halftone process differs depending on the print mode, but the process (FIG. 7) for converting the pixel data into the dot identification data is performed in the print mode. The description is omitted because it is the same regardless. In the following description, assuming that the main image is a monochrome image, a dot generation rate table for K image data will be described as an example.

  As shown in the print data generation processing flow of FIG. 6, in this embodiment, halftone processing for normal mode (S108), halftone processing for high density background mode (S109), and halftone processing for low density background mode are performed. Different from tone processing (S110). This is because in the normal mode, only the main image is printed on the medium, whereas in the high density background mode and the low density background mode, the main image and the background image are printed on the medium in an overlapping manner.

  In this embodiment, in order to adjust the white color of the background image, the background image is printed by appropriately using the four-color ink (YMCK) together with the white ink. Compared with the white ink that constitutes the background image, the four-color ink that constitutes the background image only needs to give a slight chromatic color to the background image, and the amount is very small. In order to improve the granularity of the color ink in the background image, it is preferable that the dot size of the color ink is the smallest. That is, in order to form a background image, the amount of four-color ink ejected per unit area is a small amount compared to the amount of white ink ejected per unit area. That is, the four color inks constituting the background image have almost no influence on the duty limit value. Therefore, for the sake of simplicity, the amount of ink constituting the background image is assumed to be only the amount of white ink.

  When the main image is a monochrome image, only black ink dots are formed in one pixel in the normal mode, whereas black ink dots and white ink are formed in one pixel in the high density background mode and the low density background mode. Dots are formed overlapping. However, the maximum ink amount (Duty limit value) that can be ejected to the unit area of the medium is the same. Therefore, in the high density background mode and the low density background mode, it is necessary to reduce the maximum amount of black ink that can be ejected to the unit area of the medium by the amount of ink for printing the background image. Therefore, a dot generation rate table (FIG. 8) used for halftone processing of K image data (main image data) in the normal mode, and K image data (main image data) in the high density background mode and the low density background mode. The dot generation rate table (FIGS. 10B and 11B) used for the halftone process is different.

  Even if the gradation values indicated by the K image data are the same, the dot generation rate of the K image data in the high density background mode and the low density background mode is higher than the dot generation rate of the K image data in the normal mode. Is also set to a low value. For example, the dot generation rate table for normal mode / K image data (FIG. 8) and the dot generation rate table for high density background mode / K image data (FIG. 10B) are compared. At the maximum gradation value of 255, the large dot generation rate (Z5%) for the high density background mode / K image data is larger than the large dot generation rate (Z1%) for the normal mode / K image data. It is set to a significantly lower value.

  However, at the maximum gradation value 255, only large dots are generated in the dot generation rate table for the normal mode / K image data, whereas in the dot generation rate table for the high density background mode / K image data, Three types of dots are formed. Therefore, in the dot generation rate table for high density background mode / K image data, medium dot generation is performed so that the amount of black ink discharged to the unit area of the medium is smaller in the high density background mode than in the normal mode. The rate (Z6%) and the small dot generation rate (Z7%) are set. That is, the ink amount and unit region for forming large dots on the Z5% pixel in the unit area in the high-density background mode than the ink amount for forming large dots on the Z1% pixel in the unit region in the normal mode. The dot generation rate is set so that the total amount of the ink amount for forming medium dots on the Z6% pixel and the ink amount for forming small dots on the Z7% pixel in the unit area is smaller. Has been.

  By doing so, even when the main image and the background image are overlaid and printed as in the high density background mode and the low density background mode, the ink is ejected exceeding the absorption capacity (duty limit value) of the medium. Can be prevented. As a result, bleeding can be prevented and deterioration in the image quality of the printed image can be suppressed.

  And not only the maximum gradation value (255) but also other gradation values, the amount of ink ejected per unit area in order to print the main image in the high density background mode and the low density background mode is The dot generation rate is set so as to be smaller than the amount of ink ejected per unit area in order to print the main image in the normal mode.

  In the dot generation rate table for the low density background mode / K image data (FIG. 11B), as in the dot generation rate table for the high density background mode / K image data, three types of the maximum gradation value 255 are used. Dots are formed. This can usually increase the color development of the image in proportion to the ink discharge amount per unit area, but the unit for printing the main image in the high density background mode and the low density background mode compared to the normal mode. This is because the amount of ink that can be ejected per area is small and the color developability of the main image cannot be improved. In other words, in the high-density background mode and the low-density background mode, the ink discharge amount cannot be increased to improve the color development of the main image, but medium dots and small dots are generated even at high gradation values. Improve image graininess.

Further, the printer 1 of the present embodiment has a high density background mode and a low density background mode, and the density of the background image varies depending on the print mode.
Therefore, in this embodiment, the gradation values indicated by the W image data included in the high-density background image data and the low-density background image data are both “255”. However, the high-density background image data and the low-density background image data The dot generation rate tables (FIG. 10A and FIG. 11A) used when halftone processing is performed on the W image data that each has. Then, even with the same gradation value, the dot generation rate shown in the dot generation rate table for the high density background mode / W image data (FIG. 10A) is the dot generation rate table for the low density background mode / W image data. The dot generation rate shown in FIG. 11A is set higher. Specifically, in the dot generation rate table for high-density background mode / W image data, at the maximum gradation value 255, the generation rate of large dots is Z2%, the generation rate of medium dots is Z3%, and the generation of small dots The rate is set to Z4%. On the other hand, in the dot generation rate table for the low density background mode / W image data, the maximum dot generation rate is Z5% lower than Z2% and the medium dot generation rate is Z3% at the maximum gradation value 255. The lower Z6% and the small dot generation rate are set to Z7% lower than Z4%.

  The gradation values indicated by the W image data included in the high-density background image data and the low-density background image data are not limited to be the same, and may be set to different gradation values. In this case, the density difference between the high density background image and the low density background image is further increased.

  Further, in the present embodiment, the dot generation rate table (FIG. 10B) used when halftone processing is performed on the main image data (here, K image data) in the high density background mode, and the main image data in the low density background mode are half processed. The dot generation rate table (FIG. 11B) used for tone processing is different. This is because the maximum amount of ink that can be ejected to the unit area of the medium is the same, but the amount of white ink ejected to the unit area of the medium is higher in the high-density background image than in the low-density background image. .

  Assume that the dot generation rate table used when halftone processing is performed on the main image data in the high density background mode and the dot generation rate table used when halftone processing is performed on the main image data in the low density background mode. For example, the K image data in the low density background mode is obtained by the K image data dot generation rate table (FIG. 10B) set according to the amount of ink ejected per unit area in order to print the high density background image. Assume that halftone processing is performed. Then, the amount of ink that can be ejected to print the main image in the low-density background mode is limited more than necessary. As a result, the color developability of the main image is lowered and the image quality of the printed image is degraded. Conversely, the K image data in the high density background mode is generated by the K image data dot generation rate table (FIG. 11B) set in accordance with the amount of ink ejected per unit area for printing the low density background image. Is halftone processed. As a result, ink is ejected beyond the absorption capacity of the medium. As a result, bleeding occurs in the printed image, and the image quality of the printed image is deteriorated.

  Therefore, according to the density of the background image (that is, according to the amount of ink ejected from the nozzle to the unit area of the medium for printing the background image), the unit area of the medium for printing the main image. On the other hand, the maximum amount of ink that can be ejected from the nozzle is varied. In this embodiment, the dot generation rate tables (FIG. 10B and FIG. 11B) used for the halftone process are made different according to the density of the background image. Even if the gradation values indicated by the main image data are the same, the dot generation rate in the high-density background mode / main image data dot generation rate table (FIG. 10B) is set to the low-density background mode / main image data. Is set to a value lower than the dot generation rate in the dot generation rate table (FIG. 11B). In other words, the maximum amount of ink that can be ejected to the unit area of the medium for printing the main image in the high density background mode is set to the unit area of the medium for printing the main image in the low density background mode. Less than the maximum amount of ink that can be ejected.

  Specifically, in the dot generation rate table for low-density background mode (corresponding to the second print mode) and K image data (FIG. 11B), at the maximum gradation value 255, the generation rate of large dots is Z2%, medium The dot generation rate is set to Z3%, and the small dot generation rate is set to Z4%. Then, the amount of ink ejected to the unit area for printing the low-density background image (to form large dots for Z5% pixels, medium dots for Z6% pixels, and small dots for Z7% pixels in the unit area) Ink amount) and the amount of ink ejected to the unit area to print the main image having the maximum gradation value of 255 (large dots for Z2% pixels, medium dots for Z3% pixels, Z4% The dot generation rate table is created so that the total amount of the ink amount for forming a small dot in each pixel does not exceed the maximum ink amount that can be ejected per unit area of the medium.

  On the other hand, in the high density background mode (corresponding to the first printing mode) / K image data dot generation rate table (FIG. 10B), at the maximum gradation value 255, the large dot generation rate is Z5% lower than Z2%. The medium dot generation rate is set to Z6% lower than Z3%, and the small dot generation rate is set to Z7% lower than Z4%. Then, the amount of ink ejected to the unit area for printing a high-density background image (to form large dots for Z2% pixels, medium dots for Z3% pixels, and small dots for Z4% pixels in the unit area) And the amount of ink ejected to the unit area to print the main image with the maximum gradation value of 255 (large dots on Z5% pixels and Z6% pixels on the unit area) The dot generation rate table is created so that the total amount of medium dots and the amount of ink for forming small dots on Z7% pixels does not exceed the maximum amount of ink that can be ejected per unit area of the medium. Yes.

  In this way, even when printing a high-density background image, it is possible to prevent the ink for printing the main image from being discharged beyond the absorption capacity of the medium, and print a low-density background image. Even in this case, it is possible to prevent the amount of ink for printing the main image from being limited more than necessary. As a result, while preventing bleeding of the printed image, the amount of ink that can be ejected to print the main image can be increased as much as possible to improve the color developability of the main image, and the deterioration of the image quality of the printed image can be suppressed. it can.

  When adjusting the white color of the background image, the amount of ink (second ink amount) ejected to the unit area of the medium for printing the background image is white ink and white color. This is the total amount of the four color inks for adjusting. When the background image is printed with only white ink, the amount of ink (second ink amount) ejected to the unit area of the medium for printing the background image is the amount of white ink. When the main image is a monochrome image, the maximum amount of black ink (first ink) that can be ejected to the unit area of the medium differs depending on the density of the background image. When the main image is a color image using three-color ink (YMC), the maximum total amount of the three-color ink (first ink) that can be ejected to the unit area of the medium varies depending on the density of the background image. At the same time, the maximum amount of each color ink that can be ejected to the unit area of the medium is different.

  In this embodiment, the dot generation rate table (FIG. 10A) for high-density background mode / W image data (background image data) and the dot generation rate table for low-density background mode / K image data (main image data) are used. (FIG. 11B) is common. Then, a dot generation rate table (FIG. 10B) for high density background mode / K image data (main image data) and a dot generation rate table (FIG. 11A) for low density background mode / W image data (background image data). It is common. By doing so, the memory capacity for storing the dot generation rate table (the memory capacity of the printer 1 or the computer 60) can be reduced. However, the present invention is not limited to this, and the dot generation rate table may be varied depending on each print mode and each image data.

  In the case of the dot generation rate table shown in FIG. 10 or FIG. 11, the amount of ink ejected per unit area in order to print the background image in the high-density background mode is more per unit area in order to print the main image. However, the present invention is not limited to this. For example, in both high density background mode and low density background mode, the maximum amount of ink that can be ejected per unit area to print the main image, rather than the amount of ink ejected per unit area to print the background image You may set a dot production rate table so that there may be more.

  In addition, heretofore, the main image is a monochrome image and the dot generation rate table for K image data is taken as an example, but the present invention is not limited thereto. The same applies to the dot generation rate table for image data in which a maximum of 2 dots are formed per pixel, that is, Y, M, and C image data. Even with the same gradation value, the maximum ink amount that can be ejected per unit area of a color image in the high-density background mode (the total ink amount of three colors or the ink amount of each color) is the color in the low-density background mode. The dot generation rate table is set so as to be smaller than the maximum ink amount that can be ejected per unit area of the image. That is, even with the same gradation value, the dot generation rate in the dot generation rate table for the high density background mode, Y, M, and C image data is lower for the low density background mode, Y, M, and C images. A value lower than the dot generation rate in the data dot generation rate table is set.

  FIG. 12 is a graph showing a difference in ink discharge amount per unit area in each print mode. The horizontal axis indicates the gradation value indicated by the pixel data, the higher the gradation value is on the right side of the horizontal axis, the vertical axis indicates the ink discharge amount per unit area, and the higher the vertical axis is, the larger the ink discharge amount is. . It is assumed that the main image is a monochrome image and the main image is formed only with black ink.

  In the graph, the ink discharge amount for printing the main image in the low density background mode and the ink discharge amount for printing the background image in the high density background mode are indicated by thick dotted lines, and the background image in the low density background mode is printed. A thin dotted line indicates the ink discharge amount for printing and the ink discharge amount for printing the main image in the high-density background mode. The ink discharge amount for printing the main image and the background image in the low density background mode and the ink discharge amount for printing the main image and the background image in the high density background mode are indicated by thick solid lines. From this graph, it can be seen that the amount of ink ejected per unit area for printing the main image differs according to the density of the background image.

  In this embodiment, as shown in this graph, the maximum ink amount (D3 in FIG. 12) that can be ejected to a unit area of the medium to print the background image in the high density background mode and the high density background mode. The total amount (D1) of the maximum amount of ink (D4) that can be ejected to the unit area of the medium for printing the main image and the unit area of the medium for printing the background image in the low density background mode The total amount (D1) of the maximum ink amount (D4) that can be discharged and the maximum ink amount (D3) that can be discharged to a unit area of the medium for printing the main image in the low density background mode is made equal. By doing so, the maximum amount of ink that can be ejected per unit area in order to print the main image can be increased as much as possible in both the high density background mode and the low density background mode.

  In the graph of FIG. 12, the ink discharge amount for printing the main image in the normal mode (corresponding to the third print mode) is indicated by a one-dot chain line. In this embodiment, as shown in this graph, the maximum of the total that can be ejected to the unit area of the medium in order to print the main image and the background image in the respective printing modes of the high density background mode and the low density background mode. The ink amount (D1) is set to be larger than the maximum ink amount (D2) that can be ejected to a unit area of the medium for printing the main image in the normal mode. This is because the maximum amount of ink that can be ejected per unit area when ink is ejected in a plurality of times per unit area of the medium is less than once per short period of time per unit area of the medium. This is because the amount can be increased. That is, by providing a drying time between printing the main image and the background image, the maximum amount of ink that can be ejected per unit region can be increased.

  In the present embodiment, as shown in FIGS. 4 and 5, in the high density background mode and the low density background mode, the nozzles for printing the main image and the background image are half of the nozzle row. By doing so, the pass for printing the main image and the pass for printing the background image are made different for a predetermined area of the medium. Therefore, when the nozzles that print the main image in the normal mode are all nozzles belonging to the nozzle row, the high-density background mode and the low-density background mode perform one pass for a predetermined area of the medium than the normal mode. The amount of ink ejected is small. Therefore, the maximum total amount of ink that can be ejected per unit area of the medium can be increased in the high density background mode and the low density background mode than in the normal mode (D1> D2).

  In other words, in the high-density background mode and the low-density background mode, the amount of ink that can be ejected to print the main image is less than that in the normal mode, but the main image and the background image are reduced. By providing a drying time during printing, the amount of ink that can be ejected to print the main image can be increased as much as possible. By doing so, the color developability of the main image can be enhanced.

  Note that the printing method shown in FIGS. 4 and 5 is not limited to providing a drying time between printing the main image and the background image. For example, a printing method using all the nozzles of the nozzle arrays Co and W may be used. After a background image is printed on a predetermined area of the medium in the first pass and then a predetermined drying time is provided without transporting the medium. The main image may be printed on a predetermined area of the medium in the next pass. Further, the medium may be heated during the drying time between printing the main image and the background image. In the case of a printer that prints an image by transporting a medium under a fixed head group, the main image is separated from the head group that prints the main image and the head group that prints the background image. It is advisable to provide a drying time while printing the background image.

As described above, in this embodiment, the printer driver (corresponding to the program) uses the computer 60, which is a hardware resource, to print using the dot generation rate table in which the duty limit value corresponding to the density of the background image is considered. Create data. Based on the print data, the controller 10 of the printer 1 causes ink to be ejected from the nozzles. Therefore, the controller 10 of the printer 1 and the computer 60 in which the printer driver is installed correspond to the control unit, and the printing system in which the printer 1 and the computer 60 are connected corresponds to the printing apparatus.
However, the present invention is not limited to this, and the controller 10 of the printer 1 may play the role of a printer driver. In this case, the controller 10 of the printer 1 corresponds to the control unit, and the printer 1 alone corresponds to the printing apparatus.

=== Modification ===
In the above-described embodiment, the dot generation rate table for high density background mode / W image data (for background image data) (FIG. 10A) and dot generation for low density background mode / W image data (for background image data) are generated. Although the rate table (FIG. 11A) is different, this is not restrictive.

  For example, when the gradation values indicated by the high density background image data and the low density background image data are set to different fixed values, a common dot generation rate table can be used. In this case, the memory capacity for storing the dot generation rate table can be reduced. For example, assume that the dot generation rate table of FIG. 10A is used for both high-density background image data and low-density background image data. Then, the gradation value indicated by the pixels constituting the high-density background image data is fixed and set to 255, and the gradation value indicated by the pixels constituting the low-density background image data is fixed and set to 192. In this case, since the large dot generation rate Z2% in the high density background image is larger than the large dot generation rate Z8% in the low density background image, the high density background image is printed with a darker density than the low density background image. can do.

  In the above-described embodiment, the printer driver sets the gradation values indicated by the high density background image data and the low density background image data to fixed values, but the present invention is not limited to this. For example, the user may set a desired density (tone value) of the background image instead of selecting either the high density background mode or the low density background mode. In this case, the printer driver uses the unit of the medium to print the main image so as not to exceed the maximum total amount of ink that can be ejected per unit area of the medium according to the density of the background image set by the user. The maximum amount of ink that can be ejected per area is calculated. Then, the printer driver creates print data for printing the main image so as not to exceed the maximum amount of ink that can be ejected per unit area of the medium for printing the main image.

  In the above-described embodiment, the difference in the “maximum amount of ink that can be ejected per unit area for printing the main image” between the high-density background mode and the low-density background mode is the dot generation rate used for halftone processing. Although reflected in the table (FIGS. 10B and 11B), the present invention is not limited to this. Anything that reflects the difference in the maximum amount of ink that can be ejected per unit area for printing the main image may be used, for example, it may be reflected in a color conversion lookup table used for color conversion processing, or dither It may be reflected in the dither matrix in the law.

  In the above-described embodiment, a background image in which white color is adjusted by appropriately using four-color ink (YMCK) as white ink is described as an example. An image may be printed. In addition, the background image is not limited to white, and the background image may be printed with color inks other than white ink (for example, metallic ink). In the above-described embodiment, a color image is printed using only four-color ink (YMCK). However, the present invention is not limited to this, and a main image is printed using white ink (ink for a background image) together with four-color ink. May be. By printing the main image by adding the white ink to the four color inks, it is possible to print an image that reproduces the color with high brightness and high saturation.

  In the above-described embodiment, as shown in FIG. 12, the high-density background mode and the low-density background mode are larger than the maximum ink amount (D2) that can be ejected per unit area in order to print the main image in the normal mode. The maximum total ink amount (D1) that can be ejected per unit area is increased in order to print the main image and the background image, respectively, but is not limited thereto. Maximum amount of ink that can be discharged per unit area to print the main image in normal mode, and discharge per unit area to print the main image and background image in high-density background mode and low-density background mode, respectively The maximum total ink amount may be made equal.

=== Other Embodiments ===
Each of the above embodiments has been described mainly for a printing system having an ink jet printer, but includes disclosure of creation of print data 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 ink and media>
In the present invention, ink and an absorptive medium that absorbs the ink (ink-absorbing recording medium) are used. As the ink absorptive recording medium, a recording medium composed of a substrate having ink absorptivity or a recording medium provided with an ink receiving layer on the substrate can be used. Examples of the substrate having ink absorptivity include paper and cloth. As the substrate on which the ink receiving layer is provided, either an ink-absorbing substrate or a substrate that does not absorb ink can be used. Examples of the material of the base material include polyester film, polyolefin film, resin film such as polyvinyl chloride, paper such as plain paper, coated paper, or tracing paper, resin-coated paper, or synthetic paper. .

  As the ink receiving layer, a known ink receiving layer usually provided on a recording medium for an ink jet recording method can be used. As the known ink receiving layer, for example, an ink receiving layer made of a resin is known. Examples of the resin used for the ink receiving layer include, for example, Japanese Patent Application Laid-Open Nos. 57-38185 and 62-184879. Polyvinyl pyrrolidone or vinyl pyrrolidone-vinyl acetate copolymer as disclosed in JP-A Nos. 60-168651, 60-171143, and 61-134290. Resin composition mainly, copolymer of vinyl alcohol and olefin or styrene and maleic anhydride as disclosed in JP-A-60-234879, disclosed in JP-A-61-74879 A cross-linked product of polyethylene oxide and isocyanate, as described in JP-A-61-1181679 A mixture of carboxymethyl cellulose and polyethylene oxide as shown, a polymer obtained by grafting methacrylamide to polyvinyl alcohol as disclosed in JP-A-61-2132377, JP-A-62-220383 An acrylic polymer having a carboxyl group as disclosed, a polyvinyl acetal polymer as disclosed in JP-A-4-214382, etc., and JP-A-4-282282 and 4-285650. And various ink-absorbing polymers such as crosslinkable acrylic polymers.

  As known ink receiving layers, JP-A-4-282282, 4-285650, etc. disclose an ink receiving layer using a polymer matrix composed of a crosslinkable polymer and an absorbent polymer in combination. Yes. Further, an ink receiving layer using alumina hydrate (cationic alumina hydrate) is also known, for example, JP-A-60-232990, JP-A-60-245588, and JP-B-3-24906. JP-A-6-199035 and JP-A-7-82694 disclose a recording medium in which fine pseudo boehmite type alumina hydrate is coated on a substrate surface together with a water-soluble binder. For example, Japanese Patent Application Laid-Open No. 10-203006 discloses an ink receiving layer using a synthetic silica mainly having a primary particle diameter of 3 nm to 30 nm by a vapor phase method. Furthermore, Japanese Patent Application Laid-Open No. 2001-328344 discloses an ink receiving layer containing an inorganic pigment and a polymer adhesive. In the present invention, a film substrate provided with each of the ink receiving layers can be preferably used.

  In the present invention, any white ink composition usually used in the ink jet recording method can be used as the white ink composition for the background image. Examples of such white pigments include inorganic white pigments, organic white pigments, and white hollow polymer fine particles. As the white ink composition, a water-based ink composition containing hollow polymer fine particles as a colorant component. Is preferably used.

  Examples of inorganic white pigments include alkaline earth metal sulfates such as barium sulfate, alkaline earth metal carbonates such as calcium carbonate, silicas such as finely divided silicic acid and synthetic silicates, calcium silicate, alumina, alumina Hydrates, titanium oxide, zinc oxide, talc, clay and the like can be mentioned. In particular, titanium oxide is known as a white pigment having preferable hiding properties, coloring properties, and dispersed particle sizes.

  Examples of the organic white pigment include organic compound salts disclosed in JP-A No. 11-129613 and alkylene bismelamine derivatives disclosed in JP-A Nos. 11-14365 and 2001-234093. Specific examples of the white pigment include Shigenox OWP, Shigenox OWPL, Shigenox FWP, Shigenox FWG, Shigenox UL, and Shigenox U (all trade names manufactured by Hackol Chemical Co., Ltd.).

  The hollow polymer fine particles contained as the colorant component can be fine particles having an outer diameter of about 0.1 to 1 μm and an inner diameter of about 0.05 to 0.8 μm, and are insoluble in the solvent of the white ink composition. Thus, it is necessary that the component does not chemically react with other components, for example, a binder resin component.

  The hollow polymer fine particles are made of a synthetic polymer whose walls are permeable to liquid, and the space at the center of the hollow polymer fine particles can pass through the walls and allow liquid to enter and exit. Therefore, the space in the center of the hollow polymer fine particles is filled with the solvent in the state of the ink composition, and the specific gravity of the hollow polymer fine particles and the specific gravity of the ink composition are substantially the same. It is stably dispersed inside. On the other hand, when the ink composition is printed on the printing surface and dried, the space at the center of the hollow polymer fine particles is replaced with air, so that incident light is diffusely reflected between the resin and the space, and substantially white.

  Further, as described above, the hollow polymer fine particle contains a liquid in the fine particle before printing, but the liquid that has entered the fine particle passes through the fine particle wall after printing and diffuses. It can be of a type in which fine pores are filled with air or a completely sealed type in which air is initially contained inside.

  Since it is desired that the hollow polymer fine particles used in the white ink composition do not precipitate in the ink composition, those having a specific gravity approximately equal to the specific gravity of the ink composition solution are preferable. For this reason, it is preferable to adjust the specific gravity of the ink composition solution using a specific gravity adjusting agent such as glycerol as necessary.

  Examples of commercially available hollow polymer fine particles satisfying the above properties include Ropaque OP-62 commercially available from Rohm and Haas. This is an aqueous dispersion containing 38% by weight of hollow polymer fine particles made of an acrylic / styrene copolymer. The inner diameter of the fine particles is about 0.3 μm, the outer diameter is about 0.5 μm, and the inside is filled with water.

  The hollow polymer fine particles can also be obtained by a known production method, for example, the method disclosed in US Pat. No. 4,089,800. The hollow polymer fine particles are substantially made of an organic polymer and exhibit mature plasticity. The thermoplastic resin used for the production of the hollow polymer fine particles is preferably a cellulose derivative, acrylic resin, polyolefin, polyamide, polycarbonate, polystyrene, styrene or other vinyl monomer copolymer, vinyl acetate, vinyl alcohol. And vinyl polymers such as vinyl chloride or vinyl butyral homopolymers or copolymers, diene homopolymers and copolymers, and the like. Particularly preferred thermoplastic polymers include copolymers of 2-hexyl acrylate, copolymers of methyl methacrylate, and copolymers of styrene and other vinyl monomers such as acrylonitrile. be able to.

  The content of the hollow polymer fine particles in the white ink composition used in the present invention can be, for example, 0.1 to 20% by weight. When the content of the hollow polymer fine particles is 0.1% by weight or more, sufficient whiteness can be obtained. On the other hand, if it is 20% by weight or less, a sufficient amount of the ink binder resin component necessary for ensuring the viscosity required for the ink composition for ink jet printing can be contained, and as a result, sufficient printing adhesion can be achieved. Sex can be secured.

  In the present invention, the white pigment may be used alone or in combination. For the dispersion of the pigment, a ball mill, a sand mill, an attritor, a roll mill, an agitator, a Henschel mixer, a colloid mill, an ultrasonic homogenizer, a pearl mill, a wet jet mill, a paint shaker, or the like can be used. It is also possible to add a dispersant when dispersing the pigment.

  The white ink composition used in the present invention contains, in addition to the white colorant component, various components usually contained in an ink composition for inkjet printing, such as a resin component, a dispersant component, a solvent component (especially water), and the like. Can be contained. In the present specification, the term “solvent” and “solvent” are used interchangeably. Moreover, as a white ink composition containing hollow polymer fine particles as a white colorant, for example, the composition described in Japanese Patent No. 3562754 (Patent Document 1) or Japanese Patent No. 3639479 (Patent Document 2) is used. You can also.

  The non-white ink composition for color images used in the present invention is, for example, a color ink composition, a black ink composition, or a gray ink composition. Examples of the color ink composition include a cyan ink composition, a magenta ink composition, a yellow ink composition, a light cyan ink composition, a light magenta ink composition, and a red ink composition and a green ink composition. Or a blue ink composition. As the non-white ink composition, the various ink compositions described above can be used alone or in combination of two or more.

  As the non-white ink composition, any non-white ink composition usually used in the ink jet recording method can be used, and a water-based ink composition containing a dye or a pigment as a colorant component is preferably used. In particular, it is preferable to use an ink composition that exhibits good characteristics (for example, color developability and fixability) with respect to the transparent film substrate or the ink receiving layer.

<About the printer>
In the printer, the ink ejection method from the nozzle may be a piezo method that ejects ink by applying a voltage to the drive element (piezo element) and expanding and contracting the pressure chamber, or using a heating element in the nozzle. A thermal method in which bubbles are generated and ink is ejected by the bubbles may be used.
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, a printer that prints an image by transporting the medium under a fixed head, or an operation that prints an image while moving the head along the transport direction of the continuous medium with respect to the continuous medium transported to the printing area Alternatively, the printer may repeat the operation of moving the head in the paper width direction of the continuous paper to repeat the image printing process, and then the process of transporting the medium portion on which the image has not yet been printed to the print 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 (5)

A nozzle that ejects a first ink to a medium having ink absorptivity for printing a main image;
A nozzle for ejecting a second ink to the medium to print a background image overlapping the main image;
Depending on the amount of the second ink ejected from the nozzle to the unit area of the medium to print the background image, the unit area of the medium to print the main image A controller that varies the maximum amount of the first ink that can be ejected from a nozzle;
I have a,
A first printing mode in which the amount of the second ink ejected to the unit area of the medium to print the background image is a predetermined amount; and the unit of the medium to print the background image The main image and the background image are superimposed on the medium in any one of the second print mode in which the amount of the second ink ejected to the region is less than the predetermined amount. Print and
A main image dot generation rate table in which a gradation value for printing the main image and a dot generation rate of the first ink in the unit area are associated with each other; and a print for the background image The background image dot generation rate table in which the gradation value and the dot generation rate of the second ink in the unit area are associated with each other is different between the first print mode and the second print mode.
The dot generation rate of the first ink for a predetermined gradation value is lower in the main image dot generation rate table in the first printing mode than in the main image dot generation rate table in the second printing mode. The dot generation rate of the second ink with respect to a predetermined gradation value is higher in the background image dot generation rate table in the first printing mode than in the background image dot generation rate table in the second printing mode. Printing device characterized by being expensive . The printing apparatus according to claim 1 ,
The maximum amount of the first ink that can be ejected to the unit area of the medium to print the main image in the first printing mode and the background image to print in the first printing mode. The total amount of the second ink discharged to the unit area of the medium is
The maximum amount of the first ink that can be ejected to the unit area of the medium to print the main image in the second print mode and the background image to print in the second print mode; Equal to the total amount of the second ink discharged to the unit area of the medium,
Printing device. The printing apparatus according to claim 1 or 2 , wherein
In any one of the first printing mode, the second printing mode, and the third printing mode that prints the main image on the medium but does not print the background image on the medium, Print the image on the medium,
The maximum amount of the total amount of the first ink and the second ink that can be ejected to the unit area of the medium in the first printing mode; and the unit area of the medium in the second printing mode. The maximum amount of the total amount of the first ink and the second ink that can be discharged with respect to the medium is the maximum amount of the first ink that can be discharged onto the unit area of the medium in the third printing mode. More than a large quantity,
Printing device. The printing apparatus according to any one of claims 1 to 3 ,
Printing the background image with an ink of the same color as the ink for printing the main image and an ink of a color different from the ink;
Printing device. In order to print a background image overlapping the main image and a nozzle that discharges the first ink to a medium having ink absorbency for printing the main image, the second ink is discharged to the medium. A program for operating a printing apparatus having a nozzle,
A first printing mode in which the amount of the second ink ejected to the unit area of the medium to print the background image is a predetermined amount; and the unit of the medium to print the background image The main image and the background image are superimposed on the medium in any one of the second print mode in which the amount of the second ink ejected to the region is less than the predetermined amount. Let it print,
Depending on the amount of the second ink ejected from the nozzle to the unit area of the medium to print the background image, the unit area of the medium to print the main image In order to print the main image and the background image with different maximum amounts of the first ink that can be ejected from the nozzles ,
A main image dot generation rate table in which a gradation value for printing the main image and a dot generation rate of the first ink in the unit area are associated with each other; and a print for the background image A background image dot generation rate table in which gradation values and dot generation rates of the second ink in the unit area are associated with each other is set differently in the first print mode and the second print mode. ,
The dot generation rate of the first ink for a predetermined gradation value is lower in the main image dot generation rate table in the first print mode than in the main image dot generation rate table in the second print mode. The dot generation rate of the second ink with respect to a predetermined gradation value is such that the background image dot generation rate table in the first printing mode is more than the background image dot generation rate table in the second printing mode. A high function to create print data based on each dot generation rate table ,
A program for realizing on a computer.

Images