JP2009190394A - Image processing apparatus, printing apparatus and printing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image processing apparatus preventing a degradation of granularity even when dots overlap, and to provide a printing apparatus and a printing method. <P>SOLUTION: The printing apparatus 10 capable of generating dots having granularity wherein Ink drops are jetted from a print head 25 and the ink drops adhere to print medium P, is provided with a printing data generating means 83 for generating printing data arranged in a sequence where dark ink drops with a high density among the ink drops are jetted in advance and light ink drops with a low density are jetted after jetting the dark ink drops. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an image processing apparatus, a printing apparatus, and a printing method.

  A pigment-based ink may be used in an ink jet printer or the like.

Pigment-based inks have the advantages of less bleeding on the printing medium, less fading, and excellent water resistance and light resistance. However, since the pigment-based ink is colored by forming a pigment-based ink layer (dot) on the print medium, once the pigment-based ink layer (dot) is formed on the print medium, The absorption of the layer (dots) ejected in layers.

  By the way, in an ink jet printer or the like, in the process of ejecting ink droplets from a print head and forming dots on a print medium, it is visually recognized that the graininess of the dots deteriorates, and the print image quality deteriorates. There was a problem. In particular, in the case of pigment-based inks, when dots overlap each other for the reasons described above, graininess deteriorates.

  In order to improve the graininess of the dots and improve the image quality, in addition to the inks of the basic colors of cyan (C), magenta (M), yellow (Y), and black (K) as well as dye-based inks. In some cases, inks such as light cyan (LC), light magenta (LM), and light black (LK) are used (see Patent Document 1).

Another technique for improving the granularity of dots is to reduce the size of dots (see Patent Document 2).
JP-A-11-48462 JP 2003-286453 A

  By the way, printing by an inkjet printer includes a printing method in which dots are formed later at a position during which dots are formed earlier, such as an interlace method. In such a printing method, there are very many cases where overlap between dots occurs. In particular, when dots overlap in a pigment-based ink, the graininess becomes a factor. That is, when an ink droplet of a specific color is first ejected from the nozzle row of the print head and then an ink droplet of another color is ejected from the nozzle row of the print head, the dots formed later are The state is formed above the dots to be formed.

  Here, when a dot is newly formed above the previously formed dot, the shape of the upper dot is not the same as the shape of the lower dot formed earlier. That is, the lower dots are circular when viewed from above and have good graininess. On the other hand, the upper dots are formed so as to have an irregular shape when viewed from above because of entering the gaps between the lower dots and to be wider than the lower dots.

  The influence of the irregular dot shape as described above becomes conspicuous when a low-lightness (dark) dot typified by black is formed above a high-lightness (light) dot typified by yellow. That is, since dark dots are more easily noticed by human eyes than light dots, when irregularly shaped dark dots are formed, the dots appear dirty and the overall graininess deteriorates.

  Therefore, the present invention is to provide an image processing apparatus, a printing apparatus, and a printing method in which graininess is not deteriorated even when dots are overlapped.

  In order to solve the above-described problems, the present invention provides an image processing apparatus that creates print data for forming dots having graininess by attaching ink droplets to a print medium by ejecting ink droplets from a print head. The first ink droplet of the dark color is ejected first among the ink droplets, and the ink droplet of the second light ink is ejected after the ejection of the ink droplet of the first ink. A print data creation unit for generating print data arranged in order is provided.

  In such a configuration, the print data creation unit ejects first ink droplets of dark color first, and then ejects ink droplets of light second ink. Therefore, a dot formed by jetting light-colored ink droplets exists above a dot formed by jetting dark-colored ink droplets. As a result, compared to the case where a dark dot is formed above a light dot, the dark color of the dark dot located below is somewhat brighter (lighter) with a light dot. In addition, it is possible to ensure graininess due to the influence of dark-colored dots. Therefore, the image quality of the entire print image can be improved.

According to another invention, in addition to the above-described invention, the first ink and the second ink are pigment-based inks, and the first ink includes at least a black ink, and the second ink. Includes yellow ink.
When configured in this way, yellow ink adheres above black ink, so that it is more certain that deterioration of graininess due to the influence of dark dots can be suppressed, and further graininess can be secured. Thus, it is possible to further improve the print image quality.

Furthermore, in addition to the above-described invention, in another aspect, the first ink and the second ink are pigment-based inks, and the first ink includes at least one of black, cyan, magenta, and gray. One type of ink is included, and the second ink includes at least one type of ink of light cyan, light magenta, light gray, green, orange, and yellow.
When configured in this way, it is possible to suppress the deterioration of the graininess due to the influence of dark-colored dots, and to improve the print image quality.

In another invention, in addition to each of the above-described inventions, the print data creation unit ejects ink droplets of the first ink first in a rasterizing process for creating print data in the order of printing, and thereafter the second ink. The print data is created so that the order of ejecting ink droplets of ink is achieved.
In such a configuration, the print data creation unit ejects the first ink drop first and then the second ink drop in the rasterization process, so that the printing order is set appropriately. It becomes possible.

According to another aspect of the invention, there is provided a printing apparatus capable of forming dots having graininess by ejecting ink droplets from a print head to form a dot having graininess. For ejecting ink droplets of the first ink of the system and generating print data arranged in the order of ejecting ink droplets of the light-colored second ink after the ejection of the ink droplets of the first ink A print data creation unit is provided.
In such a configuration, the print data creation unit ejects first ink droplets of dark color first, and then ejects ink droplets of light second ink. Therefore, a dot formed by jetting light-colored ink droplets is present above a dot formed by jetting dark-colored ink droplets. As a result, compared to the case where the dark dot is formed above the light dot, the dark color of the dark dot located below is somewhat brighter (lighter) with the light dot. In addition, it is possible to ensure graininess due to the influence of dark-colored dots. Therefore, the image quality of the entire print image can be improved.

Furthermore, another invention is a printing method capable of forming dots having graininess by ejecting ink droplets from a print head to form a dot having graininess. Printing is performed in the order of ejecting ink droplets of the first ink of the system and ejecting ink droplets of the light-colored second ink after the ejection of the ink droplets of the first ink.
When configured in this manner, the ink droplets of the dark-colored first ink are ejected first, and then the light-colored second ink droplets are ejected. Therefore, a dot formed by jetting light-colored ink droplets exists above a dot formed by jetting dark-colored ink droplets. As a result, compared to the case where the dark dot is formed above the light dot, the dark color of the dark dot located below is somewhat brighter (lighter) with the light dot. In addition, it is possible to ensure graininess due to the influence of dark-colored dots. Therefore, the image quality of the entire print image can be improved.

In addition to the above-described invention, the other invention further acquires the ink droplet amount and the ink type of the first ink, and the type of the print medium, respectively, and based on the ink droplet amount, the ink type, and the type of the print medium. Thus, the permeation time for the ink droplets of the first ink to permeate the printing medium is obtained, and the second ink is ejected after the permeation time has elapsed from the ejection of the first ink.
In this way, by ejecting the second ink after the penetration time has elapsed from the ejection of the first ink, the second ink can be ejected onto the print medium after the first ink has permeated in the print medium. Thereby, it is possible to prevent the first ink and the second ink from being mixed and spread on the print medium, thereby preventing the image quality from being deteriorated.

Further, among the ink droplets, the third ink droplet is ejected first, and after the ejection of the third ink droplet, printing is performed in the order of ejecting the fourth ink droplet, The time interval between the ejection of the three inks and the ejection of the fourth ink may be shorter than the penetration time.
Even if the same amount of ink is used, the time required to penetrate the print medium is such that the speed at which the third ink penetrates the print medium is faster than the speed at which the first ink penetrates the print medium. Since the penetration time is longer than the penetration time of the third ink, the shortest time interval between the ejection of the first ink and the ejection of the second ink is the ejection of the third ink and the ejection of the fourth ink. It must be longer than the shortest time interval. That is, the print head waits for the first ink to permeate the print medium even if it has the ability to continuously eject the first ink and the second ink at a time interval shorter than these penetration times. The second ink is ejected. Thereby, it is possible to prevent the first ink and the second ink from being mixed and spread on the print medium, thereby preventing the image quality from being deteriorated.

Furthermore, the time interval between the ejection of the first ink and the ejection of the second ink is longer when the amount of ink droplets ejected by the first ink is larger than when the amount of ink droplets ejected by the first ink is small. It may be a feature.
Even when the same ink is used, the time required to penetrate the print medium is longer when the amount of ink droplets is large than when the amount of ink droplets is small. Therefore, the shortest time interval between the ejection of the first ink and the ejection of the second ink needs to be longer when the ink droplet amount is large than when the ink droplet amount is small. That is, the print head waits for the first ink to penetrate into the print medium even if it has the ability to continuously eject the first ink and the second ink at a time interval shorter than these penetration times. The second ink is ejected. As a result, it is possible to prevent the first ink and the second ink from mixing and spreading on the print medium, thereby preventing a reduction in image quality.

  Hereinafter, a printing apparatus 10 according to an embodiment of the present invention will be described with reference to FIGS. In the following description, a combination of the printer 20 and the computer 70 is referred to as a printing apparatus 10. The concept of the printing apparatus 10 includes a printer 20 and a computer 70 that are connected via a cable, a network, or the like, or a computer 70 that is built into the printer 20 and that can perform printing in a so-called stand-alone format. Both cases are included. That is, when the function of the computer 70 described later is incorporated in the printer 20, the printer 20 corresponds to the printing apparatus 10.

<Schematic configuration of printer>
First, an outline of the configuration of the printer 20 will be described. FIG. 1 is a diagram showing a schematic configuration of a printing apparatus according to an embodiment of the present invention. FIG. 2 is a block diagram showing the configuration of the main part of the printer 20 centering on the control unit 50 in the printing apparatus 10.

  As shown in FIG. 1, the printer 20 includes a sub-scan feed mechanism that transports a print medium (hereinafter referred to as print paper P) by a paper feed motor 21 and a paper feed roller 23, and a carriage 24 by a carriage motor 22. And a main scanning feed mechanism that reciprocates in the axial direction of the feed roller 23. Here, the feed direction of the printing paper P by the sub-scan feed mechanism is referred to as a sub-scan direction, and the movement direction of the carriage 24 by the main scan feed mechanism is referred to as a main scan direction.

  The printer 20 includes a print head unit 30 including a print head 25 mounted on the carriage 24. A print head 25 is provided below the carriage 24. In the print head 25, nozzles as ink ejection locations are arranged in a line in the transport direction of the print paper P, and nozzle arrays corresponding to the respective color inks are formed. Further, in this nozzle row, a piezoelectric element (not shown) that is one of electrostrictive elements and excellent in responsiveness is arranged for each nozzle. The wall surface is pushed by the operation of the piezo element, and ink droplets can be ejected from the nozzles at the end of the ink passage. Due to the difference in voltage applied to the piezo element, ink droplets of different sizes can be ejected. For example, in the present embodiment, it is possible to form three types of dots of different sizes, large, medium, and small.

  Here, as shown in FIG. 3, the print head 25 according to the present embodiment includes nozzle rows 25 a to 25 d that eject ink droplets of dark ink, which will be described later, and nozzle rows 25 e to 25 e that eject ink droplets of light ink. 25g. As will be described later, when printing on the printing paper P, based on the print signal (print data) PS, ink droplets are first ejected from the nozzle rows 25a to 25d corresponding to the dark ink, and then the light ink is supported. The nozzle rows 25e to 25g are operated to eject ink droplets.

  The print head 25 is not limited to the piezo drive method using a piezo element, and other methods may be used. Other methods include, for example, a heater method in which ink is heated with a heater and the generated foam force is used, a magnetostriction method in which a magnetostrictive element is used, an electrostatic method in which electrostatic force is used, and a mist method in which mist is controlled by an electric field. Etc. are mentioned as main methods.

  As shown in FIGS. 1 and 2, the carriage 24 has a cartridge 31A containing black (K) ink, a cartridge 31B containing cyan (C) ink, and a light black (LK) as shown in FIG. ) Ink cartridge 31C, magenta (M) ink cartridge 31D, light cyan (LC) ink cartridge 31E, light magenta (LM) ink cartridge 31F, yellow (Y) Seven ink cartridges 31 </ b> A to 31 </ b> G of the cartridge 31 </ b> G containing the ink are detachably mounted.

  Among these, in this embodiment, the black (K) cartridge 31A, the cyan (C) cartridge 31B, the light black (LK) cartridge 31C, and the magenta (M) cartridge 31D are the dark-colored first ink. The light cyan (LC) cartridge 31E, the light magenta (LM) cartridge 31F, and the yellow (Y) cartridge 31G correspond to the light ink (hereinafter referred to as dark ink) cartridges. In this case, it is assumed that it corresponds to the cartridge of the light ink. However, various boundaries can be set to separate the dark ink cartridge from the light ink cartridge. When the colors are arranged in the order from dark ink to monochromatic ink, black (K), cyan (C), light black (LK), magenta (M), light cyan (LC), light magenta (LM), yellow ( Y), and an arbitrary position in these lines may be a boundary that separates the dark ink cartridge from the light ink cartridge.

  In the following description, the cartridges 31 </ b> A to 31 </ b> G are collectively referred to as the cartridge 31. Further, the cartridge 31 is not limited to seven colors, and may have any number of colors such as 4 to 6 colors, 8 colors, or 8 colors or more. In the present embodiment, the ink filled in the cartridge 31 is a pigment-based ink.

  The cartridge 31 is not only a so-called on-carriage type that is mounted on the carriage 24 but also a so-called off-carriage type that is mounted in a fixed place separate from the carriage 24 in the printer 20. good.

<About the printer control unit>
As shown in FIG. 2, the control unit 50 includes a CPU (Central Processing Unit) 51, a ROM
(Read Only Memory) 52, RAM (Random Access Memory) 53, EEPROM (Electronically Erasable and Programmable ROM) 54, ASIC (Application Specific Integrated Circuit) 55, communication I / F 56, head driver 57, motor driver 58, etc. . These are connected so that data can be transmitted and received between them.

  Among these, the CPU 51 is a part that executes various arithmetic processes according to programs and data stored in the ROM 52 and the EEPROM 54 and controls each part of the printer 20. The ROM 52 stores a control program for controlling the printer 20, data necessary for processing, and the like. The RAM 53 is a memory that temporarily stores a program being executed by the CPU 51 or data being calculated. The EEPROM 54 is a memory for storing various data that needs to be retained even after the printer 20 is turned off. The ROM 52 and the EEPROM 54 also have a program similar to the printer driver program 83 described later.

  The ASIC 55 is a dedicated IC for driving the print head 25 and various motors based on signals from various sensors (not shown). The communication I / F 56 is connected to the computer 70 via a connector (not shown) to perform communication. Thus, when the printer 20 receives the print signal (print data) PS from the computer 70 side, the printer 20 starts processing for printing based on the print signal (print data) PS. Further, the computer 70 receives information about the ink of each cartridge 31 from the printer 20 side via the communication I / F 56.

  In addition, the head driver 57 generates a predetermined voltage in response to a command from the ASIC 55 and applies the voltage to the piezo element in the print head 25. The motor driver 58 generates a predetermined voltage in response to a command from the ASIC 55, and applies the voltage to various motors.

<Schematic configuration of computer>
Next, the configuration of the computer 70 of the printing apparatus 10 will be described with reference to FIG. As shown in FIG. 4, the computer 70 includes a CPU 71, ROM 72, RAM 73, HDD (Hard Disk Drive) 74, video circuit 75, I / F 76, display device 77, input device 78, external storage device 79, and the like. Yes. Here, the CPU 71, the ROM 72, the RAM 73, and the I / F 76 are the same as the CPU 51, the ROM 52, the RAM 53, and the like in the above-described control unit 50, and thus description thereof is omitted.

  The HDD 74 is a recording device that reads data and programs recorded on a hard disk, which is a recording medium, in accordance with a request from the CPU 71 and records data generated by arithmetic processing of the CPU 71 on the hard disk. The program recorded on the HDD 74 will be described with reference to FIG.

  The video circuit 75 is a circuit that executes a drawing process according to a drawing command supplied from the CPU 71, converts the obtained image data into a video signal, and outputs the video signal to the display device 77. The display device 77 is configured by, for example, an LCD (Liquid Crystal Display) monitor or a CRT (Cathode Ray Tube) monitor, and displays an image corresponding to a video signal output from the video circuit 75.

  The input device 78 is, for example, a device that indicates a keyboard or mouse, generates a signal corresponding to a user operation, and supplies the signal to the I / F 76. The external storage device 79 includes, for example, a CD-ROM (Compact Disk-ROM) drive unit, an MO (Magneto Optic) drive unit, and an FDD (Flexible Disk Drive) unit, and is recorded on a CD-ROM disc, an MO disc, and an FD. It is a device that reads out the data or program that is stored and supplies it to the CPU 71. In the case of the MO drive unit and the FDD unit, the data is supplied from the CPU 71 to the MO disk or FD.

  Next, various programs installed in the computer 70 will be described with reference to FIG. A printer driver program 83 is installed in the computer 70 together with an application program 81 and a video driver program 82 for driving the video circuit 75. The printer driver program 83 operates under a predetermined operating system (OS). is doing. Then, when the printer driver program 83 is read into the RAM 73 or the like and is activated by the CPU 71, a part corresponding to the print data creation unit is functionally realized.

  The application program 81 here is, for example, a program for image processing or image display, which processes an image captured from a digital camera or the like, processes an image drawn by a user, This is executed when the image is displayed and then output to the printer driver program 83 and the video driver program 82.

  The video driver program 82 is a program for driving the video circuit 75. For example, after performing gamma processing or white balance adjustment on the image data supplied from the application program 81, the video signal is output. It is executed when it is generated and supplied to the display device 77 for display.

  The printer driver program 83 receives image data from the application program 81 based on a print command from the application program 81 and converts it into a print signal (print data) PS supplied to the printer 20. The printer driver program 83 includes a resolution conversion module 83a, a color conversion module 83b, a halftone module 83c, a rasterizer 83d, and a color conversion table LUT.

  The resolution conversion module 83a is a process for converting the resolution of the color image data formed by the application program 81 into the resolution for printing by the printer 20 (for example, when the printer 20 is 720 dpi × 720 dpi, the image data is 720 dpi × 720 dpi). The process of converting to the resolution of the above. The image data after the resolution conversion is still image information composed of three color components of RGB. The color conversion module 83b converts RGB image data into multi-tone data of a plurality of ink colors that can be used by the printer 20 for each pixel while referring to the color conversion lookup table LUT. For example, when the printer 20 has four colors of CMYK, the color-converted multi-gradation data becomes CMYK data represented by, for example, 256 gradations of CMYK.

  The halftone module 83c is a part that performs processing for converting the above multi-gradation data (CMYK data) into data of the number of gradations formed by the printer 20. For example, when the print head 25 can express only two gradations of ink droplet ON / OFF, a process of converting each pixel (dot) into 1-bit data is performed, and the print head 25 turns the ink droplet ON / OFF. In addition to turning off, when it is possible to further turn on by large, medium, and small ink droplets, a process of converting each pixel into 1-bit data is performed. In the halftone process, image data is formed by dispersing individual pixels (dots) by a technique such as dithering, γ correction, and error diffusion.

  The rasterizer 83d is a part that performs processing for rearranging the image data after the halftone processing in the order of data to be transferred to the printer 20. In particular, in the present invention, the rasterizer 83d arranges the data order such that the dark ink droplets are ejected first, and the light ink droplets are ejected after the dark ink ejection. The image data after the rasterization process is output to the printer 20 as a final print signal (print data) PS. The print signal (print data) PS also includes data indicating the sub-scan feed amount.

<Processing flow in printing>
A processing flow for printing using the printing apparatus 10 as described above will be described with reference to FIG.

  Prior to printing, the user activates the application program 81 to display desired print target data. Then, when the user selects a predetermined printing mode, for example, for performing high-definition printing, and then instructs printing, the printer driver program 83 is started based on the printing instruction (S01). When the printer driver program 83 is activated, processing for generating print data is performed on the print target data. Specifically, resolution conversion processing according to printing by the printer 20, color conversion processing by the color conversion module 83b, and halftone processing by the halftone module 83c are performed on the print contrast data by the resolution conversion module 83a (S02). ).

  In addition, the rasterizer 83d performs processing (rasterization processing) for rearranging the image data after the halftone processing in the order of data to be transferred to the printer 20 (S03). In this rasterization process, when attention is paid to a specific pixel row in the main scanning direction, print data is arranged in principle so that ink droplets are ejected twice. Among these, the print data (print signal PS) is arranged so that the ink droplet of dark ink is ejected first (first time) and the ink droplet of light ink is ejected later (second time).

In the present embodiment, the dark ink jet nozzle rows 25a to 25d shown in FIG.
The ink droplet of dark ink is ejected first (first time). The light ink ejection nozzle rows 25e to 25g eject light ink droplets later (second time).

  The print data (print signal PS) is formed by (1) unidirectional printing in which printing is performed only in either the forward path or the backward path of the movement of the print head 25 in the reciprocating direction. The same applies to any of bidirectional printing in which printing is performed. Further, even in a method of printing while progressing by a predetermined pitch in the sub-scanning direction, such as interlaced printing, dark ink droplets are ejected first (first time), and then only a predetermined pitch in the sub-scanning direction. Print data (print signal PS) is arranged by rasterization processing so that the ink droplets of light ink are ejected after the printing paper P is conveyed (second time).

  Based on the print data (print signal PS), the printer 20 performs printing (S04). Then, the ink drop of dark ink first adheres to the printing paper P, and then the ink drop of light ink adheres.

  In the printing by the above-described method, it is determined whether or not the printing image P is repeatedly formed until the entire printing image is formed on the printing paper P (S05), and it is determined that the entire printing image is formed (Yes). In the case of), the process is terminated. On the other hand, if it is determined that the entire print image is not formed on the print paper P, the process returns to S04, and printing is continued based on the rasterized image data buffer.

  By the way, the time interval from the ejection of the dark ink droplets to the ejection of the light ink droplets at the time of printing in S04 is equal to or longer than the absorption time necessary for the dark ink to be absorbed by the printing medium. It is preferable to do. This absorption time is calculated based on the ink drop amount of dark ink, the ink type of dark ink, and the type of print medium.

  Here, the ink droplet amount is obtained based on on / off or large / medium / small / off of ink droplets obtained by data processing performed by the halftone module 83 c in the computer 70. That is, when the print head 25 can be expressed with only two gradations of on / off, the ink droplet amount is a preset amount when the print head 25 is on and zero when it is off. In addition, when the print head 25 can be struck with large, medium, and small ink droplets, the ink droplet amount is a preset amount when large, medium, and small, and zero when it is off. It becomes.

  The ink type is specified based on the product type of the cartridge 31 attached to the printer 25 and the ink color selected by the data processing performed by the halftone module 83c in the computer 70.

  Information about the ink droplet amount and the ink type is stored in a storage unit (for example, ROM 52) of the computer 70 as a result of data processing performed by the halftone module 83c. Further, the information regarding the type of the print medium is acquired when the operator of the printer inputs to a print medium type input receiving unit (not shown) provided in the printer 20. On the other hand, the rasterizer 83d includes a calculation formula created based on the Bristow method described later, calculates an absorption time based on the information acquired as described above, and at least the absorption time from the ink droplet ejection of the dark ink. Image data is generated so that ink droplets of light ink are ejected after elapse of time.

Next, the Bristow method for calculating the absorption time of the dark ink into the print medium will be described.
FIG. 7 is a diagram showing an apparatus for measuring the absorption speed of ink into the print medium 93 by the Bristow method. As shown in the figure, an absorption speed measuring device 90 includes a bristow wheel 92 that rotates with a print medium 93 fixed to the outer peripheral surface, and a measuring head that can move in the direction of the rotation axis of the bristow wheel 92 and includes ink. 91 is provided. The measurement head 91 scans the surface of the print medium 93 fixed on the Bristow wheel 92 while moving little by little in the direction of the rotation axis of the wheel 92, and the same condition is applied to an arbitrary position on the surface of the print medium 93. Ink penetrates the print medium 93. Here, the contact time is defined as L (mm) for the contact portion length (scanning direction) of the measurement head 91 to which ink is supplied, and L / v (s) from the peripheral speed v (mm / s) of the Bristow wheel 92. Desired. Further, after scanning until the measurement head 91 runs out of ink, the trace length remaining on the print medium 93 is D (mm) and the trace width is w (mm). ml) to V / Dw (ml / mm ² ) is the permeation amount per unit area of the ink.

  FIG. 8 is a graph showing the absorption rate of various inks to the print medium 93 by taking the penetration amount (ml) on the vertical axis and the contact time (s) on the horizontal axis. As shown in the figure, the peripheral speed v of the Bristow wheel 92 is measured in several steps, and the result is plotted on a graph. Here, the slope of the approximate straight line connecting the plotted lines indicates the ink penetration amount V / Dw (ml) with respect to the contact time L / v (s), that is, the ink absorption speed (ml / s). FIG. 9 is a table showing the absorption rates (ml / s) of various inks thus obtained. Further, the absorption time (s) can be obtained by dividing the ink droplet amount (ml) by the ink absorption rate (ml / s).

  If another print medium is measured in the same manner, the ink absorption speed of each ink type when printing on the print medium can be obtained.

  The rasterizer 83d includes the ink absorption speed for each combination of ink and print medium that can be used by the printer 20, and obtains information about the ink type and print medium type to calculate the ink absorption speed. Furthermore, the ink drop amount is acquired, and the absorption speed is calculated by dividing the ink drop quantity by the ink absorption speed.

<Effects of application of the present invention>
The effects of the printing method as described above will be described below with reference to FIGS. FIGS. 10 and 11 are diagrams showing how ink droplets are attached. FIG. 10 relates to a conventional example, and FIG. 11 relates to the present invention. As shown in FIGS. 10A and 10C, the ink droplets of the light ink are first attached to form dots on the printing paper P, and as shown in FIGS. 10B and 10D, the dark ink is later formed. A state in which ink droplets adhere and dots are formed on the printing paper P is shown.

  As shown in FIGS. 10A and 10C, when the light ink dots are formed first, the user can visually recognize the light ink dots at the stage where the dark ink dots are not formed. However, as shown in FIGS. 10B and 10D, when the dots are formed so as to overlap further above the dots, the color of the dots located above is larger in visibility than the dots below. affect. When the dark ink dots are positioned above, the lower dots are difficult to see through, and the user's eyes are given the impression that only dark ink dots are present. In particular, when the dark ink corresponds to black (K), only the black (K) dot can be visually recognized, and it is hardly expected to visually recognize the lower light ink dot. That is, as shown in FIG. 10D, the dark-colored dark ink dots with impaired graininess greatly affect the visibility, so that the entire printed image printed on the printing paper P is grainy. I get the impression that my sex has deteriorated.

  On the other hand, when dark ink dots are formed first (FIGS. 11A and 11C) and light ink dots are formed later (FIGS. 11B and 11D), the dark ink dots In this case, the light ink dot is located above, and the dark color of the lower dark ink dot (due to the dark ink color) due to the influence of the color of the dot located above (the influence of the light ink dot). Can be visually recognized in a state where the color of the ink is somewhat thinned (lightened; light color), which is a rule of thumb when, for example, light ink dots are formed on black printing paper. It is also clear from the fact that the blackness of the printing paper appears to be fading (lightening).

  That is, even if a dirty-shaped light ink dot having a graininess deteriorated as shown in FIG. 11D is formed, it has a stronger influence on the visibility than in the case of a dark ink dot. Not give. In addition, although the dark ink dots appear to be somewhat thin (lightened) as described above, the dark ink dots are visually recognized and appear to be granular as shown in FIG. The granularity can be ensured as compared with the case where the light ink dots are formed first and the dark ink dots are formed later.

  As described above, according to the present invention, a dot formed by ejecting a light ink droplet is present above a dot formed by ejecting a dark ink droplet. Thereby, compared to the case where the dark ink dot is formed above the light ink dot, the dark color of the dark ink dot positioned below is somewhat brighter (lighter) with the light ink dot. It is possible to ensure graininess due to the influence of the dark ink dots. Therefore, the image quality of the entire print image can be improved.

  In particular, when yellow (Y) ink adheres above black (K) ink, it is possible to further ensure the graininess due to the influence of the dots of the dark ink, and it is possible to further secure the graininess. The image quality can be further improved.

<Modification of the present invention>
Although one embodiment of the present invention has been described above, the present invention can be variously modified in addition to this. This will be described below.

  In the above-described embodiment, the print head has the nozzle rows 25a to 25g shown in FIG. However, the print head is not limited to the arrangement of the nozzle rows shown in FIG. For example, as shown in FIG. 12, the nozzle rows may be arranged along the main scanning direction in the state of nozzle rows for light ink ejection → nozzle rows for dark ink ejection → nozzle rows for light ink ejection. In this case, as shown in FIG. 12, a combination of a dark ink nozzle row and a light ink nozzle row located on the rear end side of the forward route is used in the forward path. Further, a combination of a dark ink nozzle row and a light ink nozzle row located on the rear end side of the return pass is used in the return pass. Accordingly, in a single scan, dark ink can be ejected from the dark ink ejection nozzle row first, and then light ink can be ejected from the light ink ejection nozzle row.

  Further, as shown in FIG. 13, the nozzle rows may be arranged in the state of the nozzle row for dark ink ejection → the nozzle row for light ink ejection along the sub-scanning direction. In this case, a dark ink jet nozzle array is arranged on the downstream side (paper discharge side) in the paper feed direction so that the dark ink droplets are ejected first. Even in this case, it is possible to eject dark ink from the dark ink ejection nozzle row first and then eject light ink from the light ink ejection nozzle row in one scan.

  Further, as described above, as described above, when colors are arranged in the order from dark ink to light ink, black (K), cyan (C), light black (LK), magenta (M), Light cyan (LC), light magenta (LM), and yellow (Y). Therefore, the ink droplets may be ejected first from the dark color ink. Ink other than the above (first ink, second ink) includes dark yellow, orange, green, light light black, and the like. Of these, dark yellow generally corresponds to a dark ink system, and orange, green, and light light black correspond to a light ink system, but it may be changed variously.

  In addition, the color of the ink belonging to the light-colored ink corresponds to one having high brightness. Conversely, ink colors belonging to dark inks have low brightness.

  Furthermore, in the above-described embodiment, the print head is of a scanning type that moves in the main scanning direction. However, a long line type printing head may be used. In this case, the arrangement of the nozzle rows is as shown in FIG. 13, and the row direction of the nozzle rows is in a state along the main scanning direction (direction orthogonal to the sub-scanning direction).

  Further, FIG. 7 illustrates an example of an absorption rate measuring device 90 that measures the rate of absorption of ink into the print medium. However, the absorption rate measuring device 90 is not limited to the method shown in FIG. 7, and may be a method that scans in a spiral manner so that a needle traces with a record player, for example. The measuring head 91 need not use up ink as long as it can measure the ink transfer amount.

  In the above-described embodiment, an example of an ink jet printer is described as the printer 20. However, the printer 20 is not limited to the ink jet type, and the present invention can be applied to, for example, a gel jet type printer. Further, the printer 20 in the above-described embodiment may be a part of a complex device such as a configuration having a function (scanner function, copy function, etc.) other than the printer function.

1 is a diagram illustrating a schematic configuration of a printing apparatus according to an embodiment of the present invention. FIG. 2 is a block diagram showing a configuration centering on a control circuit of the printing apparatus of FIG. 1. FIG. 6 is a bottom view illustrating a configuration of nozzle rows in the print head. It is a block diagram which shows schematic structure of a computer. It is a figure which shows an example of the program memorize | stored in a computer. It is a figure which shows the processing flow in the case of printing. It is a figure which shows the apparatus which measures the absorption speed to the printing medium 93 of an ink by Bristow method. It is a graph which shows the absorption speed to the printing medium 93 of various ink by taking penetration amount (ml) on a vertical axis | shaft and taking a contact time (s) on a horizontal axis | shaft. It is a table | surface which shows the absorption speed (ml / s) of various inks. It is a figure which shows the mode of adhesion of the conventional ink droplet. It is a figure which shows the mode of adhesion of the ink droplet of this invention. It is a figure which shows the modification in a main scanning direction among print heads. It is a figure which shows the modification in a subscanning direction among print heads.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Printing apparatus 20 Printer 25 Print head 25a-25g Nozzle row 31A-31G Cartridge 50 Control part 51 CPU
55 ASIC
70 Computer 83 Printer driver program (corresponding to print data creation unit)
83d Rasterizer 90 Absorption speed measuring device 91 Measuring head 92 Bristow wheel 93 Print medium

Claims (9)

An image processing apparatus that creates print data for forming dots having graininess by ejecting ink droplets from a print head and attaching the ink droplets to a print medium,
Among the ink droplets, the first ink droplet of the dark color is ejected first, and the ink droplet of the light second ink is ejected after the ejection of the first ink droplet. A print data creation unit for generating print data to be printed;
An image processing apparatus. The first ink and the second ink are pigment-based inks,
The first ink includes at least black ink, and the second ink includes yellow ink.
The image processing apparatus according to claim 1. The first ink and the second ink are pigment-based inks,
The first ink includes at least one kind of ink of black, cyan, magenta, and gray, and the second ink includes light cyan, light magenta, light gray, green, orange, and yellow. The image processing apparatus according to claim 1, wherein at least one kind of ink is included.   The print data creation unit ejects the ink droplets of the first ink first in a rasterizing process for creating the print data in the order of printing, and then ejects the ink droplets of the second ink. The image processing apparatus according to claim 1, wherein the print data is created as described above. A printing apparatus capable of forming dots having graininess by ejecting ink droplets from a print head and attaching the ink droplets to a print medium,
Among the ink droplets, the first ink droplet of the dark color is ejected first, and the ink droplet of the light second ink is ejected after the ejection of the first ink droplet. A print data creation unit for generating print data to be printed;
A printing apparatus characterized by that. A printing method capable of forming dots having graininess by ejecting ink droplets from a print head and attaching the ink droplets to a print medium,
Among the ink droplets, the first ink droplet of the dark color is ejected first, and the ink droplet of the light second ink is ejected after the ejection of the first ink droplet. Run the
A printing method characterized by the above.
Obtaining the ink droplet amount and ink type ejected by the first ink, and the type of the print medium,
Based on the ink droplet amount, the ink type, and the type of the print medium, a penetrating time for the ink droplet of the first ink to penetrate the print medium is obtained,
The second ink is ejected after the penetration time has elapsed from the ejection of the first ink;
The printing method according to claim 6. Among the ink droplets, the ink droplet of the third ink is ejected first, and after the ejection of the ink droplet of the third ink, printing is performed in the order of ejecting the ink droplet of the fourth ink,
A time interval between the ejection of the third ink and the ejection of the fourth ink is shorter than the penetration time;
The printing method according to claim 7. The time interval between the ejection of the first ink and the ejection of the second ink is longer when the amount of ink droplets ejected by the first ink is larger than when the amount of ink droplets ejected by the first ink is small. ,
The printing method according to any one of claims 6 to 8.

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