JP2005223608A - Image forming method and program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To record an image excellent in color rendering properties, weatherability and gradation while realizing high coloring with a special color recording agent by performing optimal image design using the special color recording agent. <P>SOLUTION: Color separation is performed such that a predetermined special color recording agent is not used in a colorless color reproduction zone and the predetermined special color recording agent is used in all color reproduction zones of a predetermined hue (e.g. a hue corresponding to W-R line) where the predetermined special color recording agent is used. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an image forming method and program, and more particularly, to an image forming method when a recording agent having a special color (for example, green) having a hue different from the basic colors of cyan, magenta, and yellow is used as a recording agent of a recording apparatus. It is about the program.

  With the recent spread of information processing equipment such as personal computers, recording devices as image forming terminals have been rapidly developed and spread. Among various recording apparatuses, inkjet recording apparatuses that perform recording on recording media such as paper, cloth, plastic sheets, and OHP sheets by ejecting ink from ejection openings are low-noise non-impact recording systems. It has excellent features such as being capable of high-density and high-speed recording operations, being easily compatible with color recording, and being inexpensive, and is now the mainstream of personal-use recording devices. It has become.

  In an ink jet recording apparatus, basically, yellow, magenta and cyan inks, which are the three primary colors of printing, are used to perform color reproduction by subtractive color mixing. That is, for example, it is possible to form an orange or red region by mixing yellow and magenta, a green region by mixing yellow and cyan, and a blue or violet region by mixing magenta and cyan.

  Advances in inkjet recording technology have promoted higher resolution, higher image quality, colorization, and lower cost of recording, as well as personal computers and digital cameras (in addition to those that perform their functions alone, other devices such as mobile phones) In combination with the popularization of the recording apparatus, it has been a great contribution to the effect of spreading the recording apparatus to personal users. However, due to such widespread use, personal users are required to further improve image quality, and various improvements have been made to meet this demand.

  For example, while using black ink in addition to the above three primary color inks, the black component K is extracted from the data Y, M, and C of each color of yellow, magenta, and cyan and replaced with black. One of them is to improve contrast and to stably reproduce neutral colors by performing UCR processing that removes the Y color component. In addition to yellow, magenta, cyan, and black inks, and using light cyan (light cyan) and light magenta (light magenta) inks, the graininess of dots formed when the ink lands on the recording medium. Some of them improve the gradation as well as the image quality.

  However, there is a limit to color reproduction using three colors of yellow, magenta, and cyan (or four colors including black), or light inks of similar colors. Proposals using ink have been made.

  For example, in the industrial field such as printing and textile printing, ink of a color called “special color” may be used. However, it is used exclusively to express a specific color (for example, a metal color, cobalt blue, or the above four colors, or similar colors that cannot be expressed or difficult) in a mass-produced specific image. However, it does not focus on versatility.

  On the other hand, in order to support a wide range of image formation, in addition to the above yellow, magenta and cyan, the color developability is enhanced by using red, green and blue inks having intermediate hue angles in the hue space, Proposals have also been made to extend the color gamut.

  For example, in Patent Document 1, a television image signal RCRT, GCRT, BCRT is converted into a three-dimensional LUT (lookup) for the purpose of reproducing a color image with high accuracy and high image quality by expanding the color gamut with a printer or the like. After the color conversion to C ′, M ′, Y ′ by the table), the six primary color data C, M, Y, R, G, B are sorted by the sorting function using the three variables determined in advance by the calculator. A technique for recording with the six color recording agents is disclosed.

  Further, in Patent Document 2, for the purpose of enlarging the color reproduction area, an orange ink in an intermediate angle area between Y and M and a green ink in an intermediate area between yellow and cyan in the hue space. A technique using ink is disclosed.

  Further, Patent Document 3 also discloses an orange ink in an intermediate angle region between Y and M and a green ink in an intermediate angle region between yellow and cyan for the purpose of enlarging the color reproduction region. And the use of violet ink in the middle region of magenta and cyan.

  Furthermore, as a color separation method in a system using these special color inks, Patent Document 6 discloses a method for reducing the amount of special color ink used by using a special color for a gray line, and achieving both high color development by special color ink and reduction of the ink use amount. Has been.

  Patent Document 7 describes a system that uses a spot color by exchanging two of the basic colors with a spot color obtained by mixing the two basic colors with respect to the color separation obtained using the basic colors. A method for determining the color separation is disclosed.

  Patent Document 8 discloses a method for determining whether or not input image data is a color reproducible with basic color ink, and performing color separation with special color ink when it is impossible to reproduce. In Patent Document 9, for the purpose of reducing graininess, as shown in FIG. 6, among color reproduction regions that can be reproduced using spot color ink (for example, BLUE), the low density region does not use spot color ink. It is disclosed that color reproduction is performed using light ink (light cyan, light magenta), while color reproduction is performed using a special color ink in a high density region.

In Patent Document 10, a color table using a spot color is created, a color table using a basic color is created separately from the grid table, and the color table can be reproduced using the basic color among the grid points of the color table using the spot color. For the grid points, the table is synthesized by using the values of the color table using the basic color, and in order to avoid the gradation skip that occurs between the basic color table part that is the composition source and the spot color table part A method for smoothing is disclosed. In addition, this document describes that a spot color recording agent is not used in such a gray line and a low saturation region from the viewpoint of the amount of driving. In the table generated by this method, for example, in the case where only Red ink is used as the special color ink, FIG. 9A shows a gray line, a gray line, and an R point on the hue plane orthogonal to the gray line. FIG. 9B shows a hue plane formed by a straight line in the saturation direction that connects. Here, the density of the dots in FIG. 9 schematically represents the recording density of the special color Red ink. From this figure, the high saturation part is an area where a lot of special color ink generated from the special color ink table is used, and the low saturation part. Indicates that the spot color ink generated from the basic color table is not used, and the middle part is an area where the spot color ink obtained by smoothing in consideration of gradation is used a little.
JP-A-11-69176 JP 2001-138552 A JP 2003-34675 A JP 2002-069348 A International Publication WO00 / 43451 JP 2001-232825 A JP-A-10-112809 Japanese Patent Laid-Open No. 06-237351 Japanese Patent No. 02711081 JP 2000-32284 A JP 2002-33930 A

  Now, in the system using the special color ink as disclosed in Patent Documents 1 to 3 and 6 to 10 described above, the color reproduction range can be expanded as compared with the system not using the conventional special color ink. However, on the other hand, in the system using spot color ink, a new system that could not occur in a system that does not use conventional spot color ink (that is, a system using only basic colors such as cyan, magenta, yellow, and black). The present inventor has found that a serious problem occurs. Hereinafter, this problem will be described.

(Problem of color rendering)
Hereinafter, with reference to FIG. 7, the problem of color rendering that occurs when using special color ink will be described in detail.

  FIG. 7 shows the wavelength range perceived by human vision, the mixed colors of the special color inks R and G, and the basic color ink M and the basic color ink Y, the mixed color of the basic color ink C and the basic color ink Y, and the basic color in this wavelength range. The spectral reflectance obtained from a reflective original recorded with ink C single color is shown. Referring to FIG. 7, the special color ink R has a higher reflectance in a specific wavelength region than the basic color inks M and Y, and the special color ink G has a higher reflectance in the specific wavelength region. It can be seen that high saturation is achieved.

  As described above, the high-color special color ink has a high spectral reflectance in a specific wavelength region, and therefore has a property that the observed color is easily changed depending on the spectral characteristics of the light irradiating the reflective original. For example, fluorescent lamps with high color rendering properties have a relatively flat spectral characteristic over a wide area, but changes in spectral characteristics are severe with fluorescent lamps with poor color rendering properties. In contrast, the light except the wavelength range absorbed by the spot color ink is reflected from the reflected original, but under a fluorescent lamp with poor color rendering, the specific wavelength range of the irradiation light depends on the combination of the irradiation light and the spectral characteristics of the spot color ink. The difference in the observation color due to the irradiation light is caused by the reflection or absorption of the peak.

(Weather resistance problem)
Hereinafter, with reference to FIG. 8, the problem of weather resistance (particularly gas resistance and light resistance) generated when using a special color ink having a weather resistance lower than that of the basic color will be described in detail.

  FIG. 8 shows the change in saturation before and after a weather resistance test in which an output recorded using special color ink R, special color ink G, and basic color ink C is exposed to gases such as ozone and Nox, and light such as ultraviolet rays. It is a schematic diagram of the weather resistance test result showing. The vertical axis in FIG. 8 indicates the weather resistance when the saturation C * (= √ (a * ^ 2 + b * ^ 2)) of the output material using each ink before the weather resistance test is 100%. The saturation remaining rate after the weather resistance test indicating how much saturation after the test is maintained is shown.

  Referring to FIG. 8, for example, the special color R ink has the lowest saturation remaining rate, the special color ink G follows this, and the basic color C has a higher saturation remaining rate than the special color inks R and G. I understand.

  Here, for example, a highly colored special color material having the same dye concentration and a conventional basic color material are considered. Assuming that the same number of dye molecules recorded was destroyed by ozone, Nox gas, or ultraviolet light, the reflected light contributed by the lost dye was high. The coloring material is larger. Therefore, it is presumed that the higher the color material, the greater the color difference between the color materials before and after the weather resistance test in which the same number of color materials are exposed to gases such as ozone and Nox, and light such as ultraviolet rays.

  Therefore, the use of spot color ink with low weather resistance is a factor that significantly lowers the weather resistance of the printed matter to be output and promotes fading, and it is not preferable to use it in a low-saturation portion where no merit in color development can be obtained.

(Problem of color separation settings)
In the gray line, when the special color ink is used in addition to the conventional basic color ink, the combination of inks capable of realizing a specific color reproduction is dramatically increased. Then, setting of color separation in the gray line becomes complicated. For example, for gray of a specific brightness, in addition to K ink single color, mixed color of CMY basic color ink, mixed color of light ink of lc and lm and basic color ink Y, mixed color of special color ink R and basic color ink C which is the complementary color. There are many ink combinations that can realize gray, such as mixed colors of special color ink G and basic color ink M that is the complementary color, and combinations of light and shade, special colors, and mixed colors of two basic colors that achieve the same hue as special colors. It is necessary to set a color separation that does not produce a pseudo gradation between a gray point of lightness that is present and that is of interest and an adjacent peripheral point in the color space. As described above, in a system that uses special color ink for the gray line, it is very troublesome to set color separation that realizes color reproduction and does not generate pseudo gradation.

(Gray balance easily breaks due to manufacturing variations of recording heads)
When the special color ink is used for the gray line, the gray line is color-separated as shown in FIG. Further, for example, in the ink jet recording head (see FIG. 24), the discharge amount variation as shown in FIG. 25 occurs in the manufacturing process. Therefore, the gray line that is composed of three or more colors everywhere is naturally susceptible to the variation in the discharge amount for each color, and accordingly, the color balance tends to be lost. When the special color ink is further added to the gray line, it is more easily affected by the variation in the discharge amount, and the color balance is more easily broken.

  The conventional techniques described above have the following problems when examined in consideration of the above problems. In the methods of Patent Document 6, Patent Document 7 and Patent Document 8, since special color ink is used for the gray line, the color difference due to the color rendering, the color fading due to weather resistance, the complexity of the color separation setting, the recording Various problems associated with the use of special color inks, such as the color balance being lost due to variations in the manufacturing of the head, may occur, especially in gray lines where humans can easily perceive color differences, and in low-saturation areas including skin colors that are memory colors. Problems are likely to occur significantly. Therefore, in Patent Documents 6 to 8, improvement for each of these problems is desired.

  Further, in the method of Patent Document 9, a special color is not used in a low saturation portion including a gray line for the purpose of reducing graininess as shown in FIG. 6, but for example, a gray line as shown in FIG. No mention is made of gradation on the line extending from (WK) to the high saturation portion (B), and it is necessary to take measures to suppress the pseudo gradation generated along this line. In other words, unless color separation is performed in consideration of the continuity between the color reproduction area in which the special color ink is used and the color reproduction area in which the special color ink is not used, the color rendering property differs greatly or the degree of fading differs greatly between these areas. For example, there is a possibility that a pseudo gradation is generated by changing or storing illumination light. As described above, in Patent Document 9, improvements in color rendering, weather resistance, and gradation are desired.

  Further, in the method of Patent Document 10, the special color ink is mainly used in an area that can be reproduced for the first time with the special color ink. However, since the connection between the basic color part and the special color part is generated by smoothing, for example, the special color RED from gray is used. The color separation of the Red ink along the line to the line is as shown by the solid line in FIG. 11, and although the pseudo contour is taken into consideration, a sudden change in the ink amount is inevitable, and the gradation is insufficient. there were. Furthermore, Patent Document 10 does not consider any color difference due to color rendering property, and no color fading due to weather resistance, and changes in illumination light such as different color rendering properties or different degrees of fading between these regions. There is a case where pseudo gradation is generated by storage. As described above, Patent Document 10 also requires improvements in color rendering, weather resistance, and gradation.

  The present invention has been made in view of the above problems, and by performing optimal image design using a special color recording agent, while achieving high color development with the special color recording agent, color rendering, weather resistance, and flooring are achieved. An object is to enable recording of an image with excellent tonality.

  Further, the present invention provides a color rendering property in a low saturation region including a gray line and surrounding skin color, a color reproduction region to which no special color recording agent is applied, and a special color recording agent in a recording system using the special color recording agent. It is an object to realize a color separation method that takes into account continuity in color rendering with a color reproduction region.

  Further, the present invention provides a weather resistance in a low saturation region including a gray line and the surrounding skin color, a color reproduction region to which no special color recording agent is applied, and a special color recording agent in a recording system using the special color recording agent. An object of the present invention is to realize a color separation method in which a difference in weather resistance from a color reproduction region is reduced.

  Another object of the present invention is to realize a color separation method in which color separation can be set more easily in a recording system using a special color recording agent.

  Another object of the present invention is to realize a color separation method that does not easily cause a change in gray balance due to manufacturing variations of recording heads in a recording system using a special color recording agent.

  Another object of the present invention is to realize a color separation method with excellent gradation in a recording system using a special color recording agent.

  The present invention relates to an image forming method for forming an image on a recording medium using a recording agent having basic colors of cyan, magenta and yellow and a recording agent having a special color having a hue different from that of the basic color. For the color gamut, the spot color recording agent is not used, and for the color gamut indicating the predetermined hue in which the spot color recording agent is used, the spot color recording agent is used in the entire area, An image is formed on a recording medium.

  Further, the present invention provides a combination of cyan, magenta, and yellow basic color recording agents and a predetermined two basic color recording agents among the three basic colors in a color space that matches human visual characteristics. An image forming method for forming an image on a recording medium using a special color recording agent exhibiting a hue angle within a color reproduction range to be expressed, wherein the special color recording agent is not used for an achromatic color reproduction range In addition, among the color reproduction regions expressed by the combination of the two predetermined basic color recording agents, the special color recording agent is used for the entire region excluding the hues of the two predetermined basic color recording agents. Thus, an image is formed on the recording medium.

Here, the color space in accordance with the human visual characteristics is preferably a CIE-L ^* a ^* b ^* color space.

  The special color recording agent is expressed by a combination of the green recording agent showing a hue angle in a color reproduction region expressed by a combination of the two cyan and yellow recording agents, and a combination of the two recording agents of magenta and yellow. At least selected from the group of a red recording agent showing a hue angle in a color reproduction region and a blue recording agent showing a hue angle in a color reproduction region expressed by a combination of the two recording agents of cyan and magenta. One is preferred.

  Further, the present invention is a program for generating data corresponding to a special color recording agent having a hue different from the basic colors of cyan, magenta, and yellow, and for the achromatic color reproduction range, the special color recording agent Is used, and the spot color recording agent is used in the entire range from low saturation to high saturation for a color reproduction range indicating a predetermined hue in which the spot color recording agent is used. A program for causing a computer to execute a process of generating corresponding data.

The present invention also provides a color reproduction gamut represented by a combination of recording agents of two predetermined basic colors among the three basic colors of cyan, magenta and yellow in the CIE-L ^* a ^* b ^* color space. A program for generating data corresponding to a recording material of a special color indicating a hue angle,
For the achromatic color gamut, the recording material of the predetermined color is not used, and the recording of the two basic colors out of the color gamut expressed by the combination of the recording agents of the two predetermined basic colors. A program for causing a computer to execute a process of generating data corresponding to the recording material of the special color so that the recording material of the special color is used for the entire region excluding the hue of the agent.

  According to the present invention, in a recording system using a special color recording agent that is expected to have high color development, an image excellent in color rendering, weather resistance, and gradation is recorded while realizing high color development with the special color recording agent. Is possible.

(Color space based on human visual characteristics)
In this specification, the CIE-L * a * b * space is used as a color space in accordance with human visual characteristics when comparing the color gamuts and determining the hue. However, the present invention is not limited to this. Any color space such as XYZ, CIE-L * a * b *, L * u * v *, Munsell color system, Yxy, L * C * h * can be used. Of course, the portion defined by the CIE-L * a * b * color space described in this specification is determined by using a color space other than the CIE-L * a * b * color space. Is also possible.

(Feature)
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  In this specification, “special color” refers to a color different from the hues of yellow, magenta, and cyan, which are basic color recording agents, in a broad sense. Further, in a narrow sense, in the CIE-L * a * b * color space, color reproduction expressed on a recording medium by a combination of any two of the recording agents of basic colors of magenta, yellow, and cyan. Refers to a color that can express at least one of brightness or saturation higher than that of the area and that shows a hue angle in the color reproduction area expressed by a combination of any two recording agents, or CIE-L In the * a * b * color space, a combination of any two of the magenta, yellow, and cyan basic color recording materials expresses brightness and saturation higher than the color reproduction region expressed on the recording medium. It refers to a color that exhibits a hue angle within a color reproduction region that can be expressed by a combination of any two recording agents.

  In the present invention, it is preferable to use the above-mentioned “spot color” recording agent in a narrow sense, but it is also possible to use a “spot color” recording agent in a broad sense.

(Driving amount)
In the present specification, the “printing amount” represents an ink application amount applied per unit area (for example, an area corresponding to one pixel) by monochromatic ink. The total shot amount represents the total shot amount for all ink types used in accordance with the color separation table. Note that (ink) duty, (ink) application amount, (ink) application amount, and the like are also used synonymously.

<First Embodiment>
(Print system overview)
FIG. 1 is a block diagram showing the configuration of a print system according to the first embodiment of the present invention. The printer of this embodiment performs printing with cyan, magenta, yellow, and black basic color inks, light cyan, light magenta light ink, red, and green special color inks. A recording head for discharging is used. As shown in FIG. 1, the printing system of this embodiment includes a printer as a recording apparatus using this special color ink and a personal computer (PC) as a host apparatus.

  There are applications and printer drivers as programs that operate in the operating system of the host device. The application J0001 executes processing for creating image data to be printed by the printer. This image data or data before editing or the like can be taken into a PC via various media. The PC according to the present embodiment can capture, for example, JPEG image data captured by a digital camera using a CF card. Also, for example, TIFF format image data read by a scanner or image data stored in a CD-ROM can be captured. Furthermore, data on the web can be taken in via the Internet. These captured data are displayed on the monitor of the PC and edited, processed, etc. via the application J0001, and for example, sRGB standard image data R, G, B are created. Then, the image data is transferred to the printer driver in response to a printing instruction.

  The printer driver of this embodiment has a pre-stage process J0002, a post-stage process J0003, a γ correction J0004, a halftoning J0005, and a print data creation J0006 as the processes. The pre-stage process J0002 performs color gamut mapping. The pre-stage processing J0002 of the present embodiment is a three-dimensional LUT that contains the relationship of mapping the color gamut reproduced by the image data R, G, B of the sRGB standard into the color gamut reproduced by the printer of the printing system. Using this, interpolation conversion is also used to perform data conversion for converting 8-bit image data R, G, B into data R, G, B in the printer color gamut. The post-processing J0003 is based on the data R, G, and B on which the color gamut is mapped, and the color separation data Y, M, C, K, lc, and lm corresponding to the combination of ink that reproduces the color represented by the data. , R and G are obtained. In the present embodiment, this process is performed by using a three-dimensional LUT together with an interpolation operation as in the previous process. The γ correction J0004 performs gradation value conversion for each color data of the color separation data obtained by the post-processing J0003. Specifically, by using a one-dimensional LUT corresponding to the gradation characteristics of each color ink of the printer used in this system, conversion is performed so that the color separation data is linearly associated with the gradation characteristics of the printer. . Halftoning J0005 performs quantization by converting 8-bit color separation data Y, M, C, K, lc, lm, R, and G into 4-bit data. In this embodiment, 8-bit data is converted into 4-bit data using an error diffusion method. This 4-bit data is data serving as an index for indicating an arrangement pattern in the dot arrangement patterning process in the printing apparatus. Finally, print data is created by adding print control information to the print image data containing the 4-bit index data by print data creation processing J0006. Note that the processing of the application and printer driver described above is performed by the CPU according to these programs. At this time, the program is read from the ROM or hard disk and used, and the RAM is used as a work area when executing the processing.

  The recording apparatus performs dot arrangement patterning processing J0007 and mask data conversion processing J0008 regarding data processing. The dot arrangement patterning process J0007 performs dot arrangement for each pixel corresponding to an actual print image according to a dot arrangement pattern corresponding to 4-bit index data (tone value information) that is print image data. In this way, by assigning a dot arrangement pattern corresponding to the gradation value of each pixel represented by 4-bit data, dot on / off is defined in each of a plurality of areas in the pixel, Discharge data (binary data) of “1” or “0” is arranged for each area in one pixel. The 1-bit ejection data obtained in this way is subjected to a mask process by a mask data conversion process J0008. That is, the ejection data for each scan for completing the recording of the scanning region of the predetermined width by the recording head by a plurality of scans is generated by a process using a mask corresponding to each scan. The ejection data Y, M, C, K, lc, lm, R, and G for each scan are sent to the head drive circuit J0009 at an appropriate timing, whereby the recording head J0010 is driven and each according to the ejection data. Ink is ejected. Note that the above-described dot arrangement patterning process and mask data conversion process in the printing apparatus are executed under the control of the CPU constituting the control unit of the printing apparatus using a dedicated hardware circuit for them. Note that these processes may be performed by the CPU according to a program, and the above processes may be executed by, for example, a printer driver in a PC, and the form of these processes is not limited in applying the present invention. Is clear from the following explanation.

  The printer according to the present embodiment described above uses red and green as the special color inks. These special color inks are secondary colors formed by mixing two of the basic color inks, yellow, magenta, and cyan. It is preferable that the ink can express saturation and lightness higher than those of the same hue, but is not limited to this, and any ink that can express at least one of lightness or saturation higher than the secondary color. Good. That is, “spot colors” that can be suitably used in the present embodiment are those of any two of the basic color recording materials of magenta, yellow, and cyan in the CIE-L * a * b * color space. A color that has at least one of lightness or saturation higher than the color reproduction area expressed on the recording medium by the combination and shows a hue angle in the color reproduction area expressed by the combination of the above two arbitrary recording agents. Point to. Furthermore, it is more preferable if the color can express higher brightness and saturation than the color reproduction region.

  Further, the special color ink red according to the present embodiment can realize at least one of saturation or brightness higher than a color space in which sRGB standard input image data R, G, and B such as a monitor can be reproduced. To do. In the present embodiment, a printer that uses ink as a recording agent will be described. However, the present invention is also applicable to printers and copiers that use other recording agents such as toner, except for descriptions specific to ink. This is clear from the following explanation.

  Further, in this specification, the ink which is a recording agent is written in English such as Cyan, LightCyan, Yellow, Magenta, LightMagenta, Black, Red, Green, or cyan, light cyan, yellow, magenta, light magenta, black, red, green, blue. It is expressed in katakana notation, etc., and the color or its data, and the hue are expressed by one uppercase letter such as C, lc, M, lm, Y, K, R, G, B or a combination of it and one lowercase letter To do. That is, C is cyan or its data or hue, M is magenta or its data or hue, Y is yellow or its data or hue, K is black or its data or hue, and R is red. Alternatively, the data or hue thereof, G represents the green color or the data or hue thereof, and B represents the blue color or the data or hue thereof. Paper white is expressed as White or W.

  Further, in this specification, the “pixel” is a minimum unit that can express gradation, and is a target of image processing of multi-bit multi-bit data (processing such as the preceding stage, the latter stage, γ correction, and halftoning). Is the smallest unit. As will be described later, in the halftoning process, one pixel corresponds to a pattern composed of M × N cells such as 2 × 4 or 2 × 8, and each cell in this pixel is defined as an area. To do. This “area” is the minimum unit in which dot on / off is defined. In this connection, the “image data” in the above-mentioned pre-stage processing, post-stage processing, and γ correction represents a set of pixels to be processed, and each pixel has an 8-bit gradation value as the content in this embodiment. The “pixel data” in the halftoning represents the pixel data itself to be processed. In the halftoning of the present embodiment, there are 4 pieces of pixel data containing the 8-bit gradation value. It is converted into pixel data (index data) containing bit gradation values.

  Hereinafter, processing blocks or elements of the printing system of the present embodiment described above will be described in detail.

(Pre-treatment)
As described above with reference to FIG. 1, the pre-stage processing of J0002 of the present embodiment converts 8-bit input data R, G, and B from an application by reading grid point data using an LUT and interpolation processing based thereon, Color correction data (= latter stage R ′, G ′, B ′ data) from which an appropriate reproduction color can be obtained is generated. Here, in order to obtain color reproduction of a desired photographic quality such as color reproduction of an sRGB monitor, for example, the spot colors shown by broken lines and solid lines in FIG. Color matching is performed to link the color gamut of the printer in the system to an appropriate color target in a uniform color space such as L * a * b *. As a gamut mapping technique and an interpolation technique for table interpolation used here, known techniques may be appropriately used. Further, the pre-processing method is not necessarily in the form of a table, and the pre-processing may be performed using an appropriate linear or non-linear color correction function. In this embodiment, the color separation of the gray line is preserved not only after the color separation but also after the previous processing in order to take advantage of the color rendering property and weather resistance of the gray line that are the characteristics of the present invention. As described above, the gray line in the preceding process is set on the device gray (the gray line in the subsequent stage).

(Post-processing)
As described above with reference to FIG. 1, the subsequent processing of the present embodiment converts the input data R ′, G ′, and B ′ by reading the grid point data using the LUT and performing interpolation processing based on the data, and the color separation data C , M, Y, K, lc, lm, R, and G are generated. The LUT, whose outline is shown in FIG. 2, stores color separation data as its grid point data in order to realize gradation values or color gamuts described below.

  FIG. 3 is a diagram schematically showing a color gamut reproduced by the entire color separation data of the present embodiment, and represents one a * b * plane in the CIEL * a * b * space. .

  In the figure, a hexagon indicated by a solid line (a region surrounded by six hues of CMYRGB) indicates a color gamut that can be expressed by each ink of Cyan, LightCyan, Yellow, Magenta, LightMagenta, and Black used in this embodiment. The broken lines indicate the expanded color gamut that can be expressed when the special color inks Red and Green of this embodiment are used in addition to these inks. In this color gamut, hues Rs and Gs are hues of special color inks Red and Green, respectively. As is clear from this, the special color ink of this embodiment is selected such that the hues Rs and Gs exist between the hues Y and R and between the hues G and Y, respectively. In addition, the special color inks Red and Green used in the present embodiment have higher brightness as compared to colors of the same hue realized by a non-special color ink system that does not use special color inks, as will be described in detail later. And a color gamut of saturation can be realized. In this specification, “high chroma” or “high lightness” of the spot color recording agent is used in this sense unless otherwise specified. With such high saturation and lightness, it is possible to reproduce a color gamut that is larger than that when using the ink system. In the following, for the sake of simplicity, how the special color ink Red according to the embodiment of the present invention is used, that is, how the color separation data R corresponding to the Red ink is set at the grid points of the LUT, and as a result, How the color gamut is expanded will be described in detail. The special color ink system used in the present embodiment is a CMYKlclmRG 8-color system, and in addition to the red ink, the green ink is also used as the special color ink. In view of the gist of the present invention, the description is omitted because it is substantially the same as Red ink.

  As described above, the color reproduction range in the special color ink system has been largely dependent on the color reproduction characteristics of the special color recording agent. First, the color reproduction characteristics of the Red ink used in this embodiment will be described.

  In the following description, when the color reproduction characteristics are described, the case where the ink discharge amount of the recording head in FIG. 25 uses the central head will be described unless otherwise specified. FIG. 25 shows the manufacturing variation of the discharge amount. When the head is located on the right side of the discharge amount center indicated by the dotted line, it indicates that the head has a relatively large discharge amount, and conversely the discharge amount. When the head is located on the left side of the center, it indicates that the head has a relatively small discharge amount.

<Ink characteristics>
[Ink composition]
The basic colors yellow, magenta, cyan and black, which are preferably applied to the first embodiment of the present invention, and the special colors red and green, include a color material as an essential component.

  In the first embodiment, a dye or a pigment can be used as the color material used for the ink of the basic color (the three primary colors of yellow, magenta, and cyan plus black). Among these, dyes can be suitably used because they are excellent in reproducing colors with high brightness. Similarly, dyes or pigments can also be used as color materials for inks of special colors (red, green and blue). Among these, dyes can be suitably used because they are excellent in reproducing colors with high brightness.

  In particular, the ink that the adhering ink penetrates into the recording medium (the dye-based ink tends to be stronger) than the ink that the colorant aggregates on the surface of the recording medium (the pigment-based ink tends to be more likely). It is strongly preferred to use. In the former, most of the incident light is reflected by the uppermost ink layer attached later, whereas in the latter, the incident light is reflected by each color ink layer formed inside the recording medium. This is because the effect of appealing can be expected.

  Specific examples of the color material of the basic color ink and the special color ink used in the first embodiment include the following, and those that meet the above conditions can be selected.

Cyan coloring material C.I. I. Direct blue: 1, 15, 22, 25, 41, 76, 77, 80, 86, 90, 98, 106, 108, 120, 158, 163, 168, 199, 226, 307
C. I. Acid Blue: 1, 7, 9, 15, 22, 23, 25, 29, 40, 43, 59, 62, 74, 78, 80, 90, 100, 102, 104, 112, 117, 127, 138, 158 161, 203, 204, 221, 244
Yellow color material C.I. I. Direct yellow: 8, 11, 12, 27, 28, 33, 39, 44, 50, 58, 85, 86, 87, 88, 89, 98, 100, 110, 132, 173
C. I. Acid Yellow: 1, 3, 7, 11, 17, 23, 25, 29, 36, 38, 40, 42, 44, 76, 98, 99
Magenta color material C.I. I. Direct Red: 2, 4, 9, 11, 20, 23, 24, 31, 39, 46, 62, 75, 79, 80, 83, 89, 95, 197, 201, 218, 220, 224, 225, 226 227, 228, 229, 230
C. I. Acid Red: 6, 8, 9, 13, 14, 18, 26, 27, 32, 35, 42, 51, 52, 80, 83, 87, 89, 92, 106, 114, 115, 133, 134, 145 158, 198, 249, 265, 289
C. I. Food Red: 87, 92, 94
C. I. Direct violet 107
In addition, compounds having a structure described in Patent Document 4 can also be used.

Black color material C.I. I. Direct black: 17, 19, 22, 31, 32, 51, 62, 71, 74, 112, 113, 154, 168, 195
C. I. Acid Black: 2, 48, 51, 52, 110, 115, 156
C. I. Food black 1, 2
Carbon black In addition, compounds having the structure described in Patent Document 5 can also be used.

Red color material C.I. I. Acid Orange 7, 10, 33, 56, 67, 74, 88, 94, 116, 142
C. I. Acid Red 111, 114, 266, 374
C. I. Direct Orange 26, 29, 34, 39, 57, 102, 118
C. I. Food yellow 3
C. I. Reactive Orange 1, 4, 5, 7, 12, 13, 14, 15, 16, 20, 29, 30, 84
C. I. Disperse Orange 1, 3, 11, 13, 20, 25, 29, 30, 31, 32, 47, 55, 56
Alternatively, a material obtained by appropriately mixing the yellow color material and the magenta color material can be used.

Green color material C.I. I. Direct blue: 1, 15, 22, 25, 41, 76, 77, 80, 86, 90, 98, 106, 108, 120, 158, 163, 168, 199, 226, 307
C. I. Acid Blue: 1, 7, 9, 15, 22, 23, 25, 29, 40, 43, 59, 62, 74, 78, 80, 90, 100, 102, 104, 112, 117, 12
C. I. Food yellow 3
Or what mixed the following coloring material appropriately can be used.

C. I. Acid Green 5, 6, 9, 12, 15, 16, 19, 21, 25, 28, 81, 84
C. I. Direct green 26, 59, 67
C. I. Food Green 3
C. I. Reactive Green 5, 6, 12, 19, 21
C. I. Disperse Green 6, 9
The light cyan color material may be the same as or different from the cyan color material, and is an ink having a relatively low color material density with respect to cyan used in combination. Others that meet the requirements for recording and recovery can be used as appropriate. Also, light magenta is substantially the same as light cyan.

  If necessary, for example, in inks used in personal-use inkjet recording apparatuses, water as a carrier component, water-soluble organic solvents and humectants, surfactants, pH adjustments to prevent drying from the viewpoint of reliability Agents, preservatives and the like.

  In the present embodiment, the above-described color material is shown as an example of a suitable color material, but the combination of the color materials for which the present invention is effective is not limited to the above, and color materials other than those described above may be used.

[Ink color reproduction characteristics]
Hereinafter, the color reproduction characteristics of the Red ink used in the present embodiment will be described in detail in comparison with the color reproduction characteristics in a non-spot color system using a mixture of Magenta, LightMagenta, and Yellow ink.

  FIG. 12A is a diagram showing color separation at the line W (RGB = 0xFFFFFF) -R (RGB = 0xFF0000) in FIG. 2, and FIG. 12B is a color realized by this color separation table. The reproduction is shown in a L * (lightness) -C * (saturation) plane.

  In order to make it as close as possible to the hue and lightness line (dashed line in FIG. 12B) when the red ink shown by the broken line in FIG. Is configured as Magenta, LightMagenta, and Yellow indicated by a solid line in FIG. At this time, the color gamuts in the spot color system (Red) and the non-spot color system (M, lm, Y) are as shown by the broken line and the solid line in FIG. 12B, respectively. It can be seen that color reproduction with high brightness and high saturation that cannot be achieved with special color inks can be obtained. Further, by using this special color ink (Red), a color gamut that substantially covers the color gamut of the positive film shown by the alternate long and short dash line in FIG. 12B is realized. According to this, it is possible to obtain an image quality excellent in vividness, transparency and stereoscopic effect such as an image formed on a positive film.

  Based on the above ink characteristics, the configuration of the color separation table used in the subsequent color processing of this embodiment will be described. Hereinafter, only characteristic portions using spot color ink (here, Red ink) will be described, and the other portions are the same as those of a known non-spot color system (for example, CMYKlclm 6-color system).

  In this embodiment, first, for the entire color space shown in FIG. 2, a one-dimensional color separation table is set for each of the lines indicated by the solid line and the broken line, and other parts are disclosed in, for example, Patent Document 11. The value at each lattice point is obtained by complementing using a known table interpolation technique as described above.

[Gray line color separation]
In the present invention, the special color ink is not used for the gray line in which the color difference is conspicuous in terms of human visual characteristics. The gray line color separation at this time is as shown in FIG. FIG. 13 shows the amount of each color ink used when expressing the WK line (gray line) of FIG. 2, and it is set so that the red ink which is the special color ink is not used. In this way, compared to the conventional special color systems disclosed in, for example, Patent Documents 6 to 8, in addition to being less susceptible to variations in gray balance due to manufacturing variations of the recording head, color differences due to color rendering and color fading due to weather resistance The complexity of color separation settings can be reduced.

[Color separation at the outer frame of the area where Red ink is used]
First, the color separation of the outer frame portion of the region using Red ink in the present embodiment will be described.

  Red ink is interpolated with W (RGB = 0xFFFFFF) -R (RGB = 0xFF0000) -K (0x000000) line, Y (RGB = 0xFFFF00) -R (RGB = 0xFF0000) -M (0x00FF) line in FIG. It is used for the area of the square pyramid of WYRM-K.

  In the W-R-K line, the red ink is sequentially increased from the white (W) point toward the RED point (RGB = 0xFF0000) as shown in FIG. 4 in order to take advantage of the high brightness and high coloration of the red ink. From point to black (K) point, red ink is rapidly reduced, and Mgenta and Yellow inks having low brightness are frequently used.

  For the YRM line, as shown in FIG. 5, Red ink is frequently used from the Yellow point (RGB = 0xFFFF00) toward the RED point where the red ink coloring effect is expected, and from the RED point to Magenta (RGB = 0xFF00FF) Red ink is reduced toward the point. In this way, as shown in FIG. 3, the color reproduction range in the conventional non-spot color system indicated by the solid line between the hues Y-Rs-R in the a * b * plane is as shown by the broken line. A color separation table capable of performing color gamut expansion can be configured.

  As described above, the red ink is concentrated in an area where the high color development effect of the special color ink (here, the red ink) can be expected, and the red ink is not used as a substitute for the complementary color of the cyan ink. While drawing out the coloring effect, it is possible to prevent the color rendering properties and weather resistance from being greatly reduced.

  Further, in consideration of gradation, the amount of Red ink is gradually reduced toward other areas where the high color development effect of the special color ink (Red ink in this case) cannot be expected. For example, it corresponds to the other areas. The red ink amount is set to zero at the four points of WHITE, YELLOW, MAGENTA, and BLACK. According to this configuration, since the Red ink is not used in an area where the red ink color development merit cannot be utilized, the pseudo gradation and the discoloration under the different light sources due to the color rendering property and weather resistance described above, respectively. Can be suppressed.

[Create a color table for the entire color space]
Next, the color separation table for the entire color space will be described in detail while comparing the color separation table according to the conventional technique described in Patent Document 10 and the color separation table when using the technique of the present invention.

  The color separation of the special color ink Red according to the present invention is indicated by a halftone line in FIG. 10A on the surface of W (K) -YRM when the color space in FIG. 2 is viewed perpendicular to the gray line. The red ink is not used on the gray line. In the mesh line portion in the figure, the amount of Red ink used increases as the density of the line increases. Therefore, according to FIG. 10A, the usage amount of the Red ink increases smoothly as the saturation becomes higher, and the usage amount of the Red ink used at the hue R point is different from the hue Y, and the hue. You can see how it decreases smoothly toward M. This can also be understood from FIGS. 4 and 5 described above, and if attention is paid to the R ink ejection amount line from WHITE to RED in FIG. 4, the amount of Red ink used increases smoothly as the saturation becomes higher. On the other hand, if attention is paid to the R ink ejection amount line from YELLOW to RED through MAGENTA in FIG. 5, the usage amount of the red ink used in the hue R is different from that of the hue Y, In addition, it is possible to grasp the state of smoothly decreasing toward the hue M.

  In addition, when looking at the amount of Red ink applied on the WR line in FIG. 10A, the locus indicated by the broken line in FIG. 11 follows. Note that “gray line” and “spot color” shown on the horizontal axis in FIG. 11 correspond to W and R in FIG. As is apparent from the broken line in FIG. 11, since the Red ink is used in the entire area on the R hue indicated by the WR line, the continuous tone property in the R hue can be maintained. .

  Similarly, the red ink is not used on the gray line as shown in FIG. 10B on the WKR plane along the gray line in FIG. 2, and the red ink is directed toward the high saturation portion indicated by Rs. It can be seen that the usage amount of is increasing smoothly.

  As described above, according to the method of the present embodiment, since the Red ink is not used in the gray region (achromatic region), the degree of reduction in the color rendering properties and light fastness associated with the use of the special color Red ink is reduced. In addition, it can be made less susceptible to the effects of gray balance fluctuations due to manufacturing variations in the recording head. In addition, although a large amount of Red ink is used in the high saturation region, the Red ink is gradually reduced in the peripheral region, so that only the color reproduction region in which the Red ink is used and other basic colors are used. It is not necessary to generate a pseudo gradation between the color reproduction area to be used. In short, in this embodiment, Red ink is not used in the achromatic color gamut, and Red is used in the entire color gamut of a predetermined hue (for example, a hue corresponding to the WR line) in which Red ink is used. Since the ink is used, it is possible to obtain an image having excellent color rendering properties and light fastness and excellent gradation in a predetermined hue in which the Red ink is used. Furthermore, in this embodiment, the red color is not used in the achromatic color reproduction range, and the color reproduction is expressed by a combination of two basic color inks (Yellow ink and Magenta ink) sandwiching the hue of the Red ink. In the region (region surrounded by W (K) -Y-M-R in FIG. 10), the Red ink is used for the entire region excluding the hues of Yellow and Magenta. Continuous tone characteristics can be maintained in the region surrounded by W (K) -Y-M-R in FIG.

  On the other hand, according to the method of Patent Document 10, Red ink is used as shown in FIGS. 9A and 9B, respectively. For example, when the WR line in FIG. The Red ink changes as shown by the solid line in FIG. Therefore, the amount of Red ink used on this line must be abrupt, and pseudo gradations are likely to occur compared to the method of the present invention. Furthermore, although the Red ink is used in a high saturation area in a large amount, the Red ink is not used abruptly in the peripheral area as compared with the method of the present invention. Pseudo gradations are likely to occur between the color reproduction regions in which only other basic colors are used. Although only red ink is described in the present embodiment, the color separation method can be set by a substantially similar method for Green, which is another special color ink used in the present embodiment.

  As described above, the LUT used in the subsequent process J0003 described above with reference to FIG. 1 is created by interpolating the grid point data obtained for each predetermined hue and obtaining grid point data (color separation data) for other grid points. can do.

  In this embodiment, the special color ink is not used as a complementary color instead of the basic color. However, the present invention can be easily applied to a system using the special color as a complementary color.

(Halftone processing part)
The halftone processing unit J0005 will be described below. In the following description, the minimum structural unit to be subjected to image processing for processing multi-value data represented by a plurality of bits is referred to as a pixel, and data corresponding to the pixel is referred to as pixel data. The image processing of multi-value data represented by a plurality of bits is, for example, a process of converting RGB 8-bit data into 8-bit data of each of CMYKlclmRG corresponding to the ink colors used in the printer, in light of FIG. This includes post-processing to be performed, halftone processing for performing processing of quantizing CMYKlclmRG 8-bit data into CMYKlclm 4-bit data, and the like. From another point of view, the “pixel” is a minimum unit that can express gradation, and has gradation value information of a plurality of bits.

  FIG. 15 is a block diagram for explaining a configuration of a halftone processing unit applicable to the embodiment of the present invention. In the figure, B0001 is an input terminal for pixel data, B0002 is a cumulative error adding unit, B0003 is a terminal for setting a quantization threshold when converting input pixel data into two or more gradation numbers, B0004 is a quantization unit, B0005 is an error calculation unit that calculates a quantization error, B0006 is an error diffusion unit that diffuses the quantization error, B0007 is a cumulative error memory that stores the cumulative error, and B0008 is an output terminal for pixel data formed after a series of processing It is.

  Pixel data of pixels selected from all images by an image scanning unit described later is sequentially input to the input terminal B0001 of the halftone processing unit. The halftone processing unit is configured to sequentially process each input pixel data and to output one pixel at a time from the output terminal B0008.

  FIG. 17 is a diagram illustrating a state of processing scanning performed by the image scanning unit. The image scanning unit selects pixels to be processed one by one from image data configured by arranging a plurality of pixels, and inputs the pixel data to the input terminal B0001 of the halftone processing unit. In the figure, each square represents an individual pixel, B0015 represents a pixel located at the upper left end of the image, and B0016 represents a pixel located at the lower right end of the image.

  Image processing scanning is started by first selecting the pixel B0015 at the upper left corner of the image area as a pixel to be selected (hereinafter also referred to as a pixel of interest), and then focusing on each pixel in the right direction in the direction of the arrow in the figure. The process proceeds while switching pixels. When the processing is completed up to the right end of the uppermost row, the pixel of interest is moved to the left end pixel of the pixel row one stage below. In this order, the process scan proceeds along the arrows in the figure, and when the process reaches the lower right pixel B0016 as the final pixel, the process scan of the main image is completed.

  FIG. 16 is a flowchart for explaining an operation process performed by the halftone processing unit of FIG. 15.

  When processing is started, image data to be processed is input by the image scanning unit (step B0009).

  Next, in the cumulative error adding unit B0002, the cumulative error value corresponding to the pixel position stored in the cumulative error memory B0007 is added to the input pixel data (step B0010).

  FIG. 18 is a diagram for explaining data stored in the cumulative error memory B0007 and a storage form of the data. The cumulative error memory B0007 has one storage area E0 and W storage areas E (x) (x = 1 to W). Here, W represents the number of pixels in the horizontal direction of the image data to be processed. Each region stores a quantization error E (x) applied to the pixel of interest. Note that the quantization error value is obtained by a method described later, but is initially initialized with an initial value of 0 in all regions.

In step B0010, the accumulated error addition unit B0002 adds the value of the error memory E (x) corresponding to the horizontal position x (0 <x ≦ W) of the pixel to the input pixel data. That is, assuming that the pixel data input to the input terminal B0001 is I and the pixel data after adding the accumulated error in step B0010 is I ′,
I ′ = I + E (x)
It becomes.

In the subsequent step B0011, the pixel data I ′ after the cumulative error addition is compared with the threshold value input through the threshold setting terminal B0003, and the quantization process is performed. In this embodiment, by comparing the eight threshold values with the pixel data I ′ after the cumulative error addition, the quantized image data is divided into nine stages, and the value of the output pixel data to be sent to the output terminal B0008 is determined. It shall be. That is, if the pixel data value input from the cumulative error addition unit B0002 is an integer value in the range of 0 to 255, the output gradation value O is determined by the following equation.
O = 0 (I ′ <16) (Formula 1)
O = 32 (16 ≦ I ′ <48) (Formula 2)
O = 64 (48 ≦ I ′ <80) (Formula 3)
O = 96 (80 ≦ I ′ <112) (Formula 4)
O = 128 (112 ≦ I ′ <144) (Formula 5)
O = 160 (144 ≦ I ′ <176) (Expression 6)
O = 192 (176 ≦ I ′ <208) (Expression 7)
O = 224 (208 ≦ I ′ <240) (Equation 8)
O = 255 (I ′ ≧ 240) (Equation 9)
Here, for convenience of explanation, the following names are given to the output gradation values O. That is, O = 0 is level 0, O = 32 is level 1, O = 64 is level 2, O = 96 is level 3, O = 128 is level 4, O = 160 is level 5, O = 192 is level 6 , O = 224 is referred to as level 7, and O = 225 is referred to as level 8.

Next, the error calculation unit B0005 calculates a difference between the pixel data I ′ after the accumulated error addition and the output pixel value O, that is, a quantization error E (step B0012).
E = I′−O (Formula 10)
Further, in step B0013, the error diffusion unit B0006 performs error diffusion processing as follows according to the horizontal position x of the pixel of interest. That is, the quantization error to be stored in the storage areas E0 and E (x) is calculated according to the following processing and stored in the accumulated error memory.

E (x + 1) ← E (x + 1) + E × 7/16 (x <W) (Expression 11)
E (x−1) ← E (x−1) + E × 3/16 (x> 1) (Equation 12)
E (x) ← E0 + E × 5/16 (1 <x <W) (Equation 13)
E (x) ← E0 + E × 8/16 (x = 1) (Expression 14)
E (x) ← E0 + E × 13/16 (x = W) (Equation 15)
E0 ← E × 1/16 (x <W) (Expression 16)
E0 ← 0 (x = W) (Expression 17)
This completes the error diffusion process for one pixel input to the input terminal B0001.

  In Step B0014, it is determined whether or not each process of Step B0009 to Step B0013 has been performed on all pixels of the image. That is, it is determined whether or not the pixel selected by the image scanning unit has reached B0016 in FIG. 17. If the pixel has not reached B0016, the target pixel is advanced by one in the direction of the arrow, and the process returns to step B0009. Return.

  If it is determined that the processing has been performed for all the pixels, the halftone processing of the present embodiment is completed.

  In the present embodiment, the above processing is performed for each ink color.

  FIG. 20 shows an example of an image having a predetermined gradation value before halftone processing and a quantized image after halftone processing. In the figure, image data B0017 created for yellow (Y) is subjected to halftone processing B0019, and image data B0018 created for special color ink Red (R) is subjected to halftone processing. These are shown as B0020.

  In B0017, the pixel data in all the pixels is 10. On the other hand, in the image B0019 after being subjected to the halftone process, pixels of two levels (density), B0021 where O = 0 (level 0) and B0022 where O = 32 (level 1), It is in a state of being uniformly distributed.

  In B0018, the pixel data in all the pixels is 100. On the other hand, in the image B0020 after the halftone process is performed, pixels at two levels (density), B0023 where O = 96 (level 4) and B0024 where O = 128 (level 5), It is in a state of being uniformly distributed.

  In both cases, the pixel data values that were the same level in all the pixels in the original image are dispersed at the multiple levels after the halftone process. The value is stored.

(Generation of print data)
The print data generation process J0006 will be described below.

  Next, the image data subjected to the halftone process is arranged in a predetermined format, and print data to be actually input to the recording apparatus is generated.

  FIG. 19 is a diagram showing a configuration diagram of print data. As shown in the figure, the print data is composed of print control information for controlling printing and print image information (also referred to as print image data). Further, the print control information includes “media information” for recording the image, “quality information” for printing, and “other control information” such as a paper feed method.

  The media information describes the type of paper to be recorded, and any one of plain paper, glossy paper, coated paper, etc. is defined. The quality information describes the quality of printing and defines either high speed printing or high quality printing. The print control information is formed based on the contents designated by the user on the host PC. Furthermore, it is assumed that the print image information (print image data) describes the image data generated by the above-described halftone process. The print data that has been subjected to the halftone process and has generated the print data is then supplied to the dot arrangement patterning process of the recording apparatus main body.

  In the description of the halftone processing and the generation of print data, the description has been made on the assumption that the processing is performed by a printer driver installed in the host device instead of the recording apparatus main body. However, the present embodiment is not limited to this. It is not something. Even if the halftone processing itself is performed inside the recording apparatus, the effects of the present invention can be obtained equally.

(Dot arrangement patterning process)
The dot arrangement patterning process J0007 will be described below.

  In the halftone processing described above, 256 levels of multi-value density information (8-bit data) corresponding to each of CMYKlclmRG is changed to 9 levels (CMYKlclmR) and 16 levels (G) of tone value information (4-bit data). Is lowered. However, information that can be actually recorded by the ink jet recording apparatus of the present embodiment is binary information indicating whether or not to record ink. In the dot arrangement patterning process, the multivalue level (CMYKlclmR) of 0 to 8 or the multivalue level (G) of 0 to 15 is reduced to a binary level that determines the presence or absence of a dot. Specifically, in this dot arrangement patterning process J0007, for each pixel represented by 4-bit data of levels 0 to 8 or 0 to 15 that is an output value from the halftone processing unit, the pixel level is calculated. A dot arrangement pattern corresponding to a tone value (level 0 to 8 or 0 to 15) is assigned, thereby defining dot on / off for each of a plurality of areas in one pixel, and for each area in one pixel One-bit ejection data (binary data) of “1” or “0” is arranged.

  FIG. 21 shows output patterns for input levels 0 to 8 (CMYKlclmR) that are converted by the dot arrangement patterning processing of the present embodiment. Each level value shown on the left of the figure corresponds to level 0 to level 8 which are output values from the halftone processing unit. Each matrix area composed of 2 vertical areas × 4 horizontal areas (CMYKlclmR) arranged on the right side corresponds to an area of one pixel output by halftone processing. Each area in one pixel corresponds to a minimum unit in which dot on / off is defined.

  In the figure, the area filled with a circle indicates an area where dots are recorded, and the number of dots to be recorded increases by one as the number of levels increases. Therefore, for CMYKlclmR, a maximum of eight dots are arranged for one pixel. In the present embodiment, the density information of the original image is finally reflected in such a form.

  (4n) to (4n + 3) indicate the pixel positions in the horizontal direction from the left end of the input image by substituting an integer of 1 or more for n. Each pattern shown below has the same input level. This also shows that a plurality of different patterns are prepared depending on the pixel position. That is, even when the same level is input, four types of dot arrangement patterns shown in (4n) to (4n + 3) are cyclically assigned on the recording medium.

  In FIG. 21, the vertical direction is the direction in which the ejection ports of the recording head are arranged, and the horizontal direction is the scanning direction of the recording head. Therefore, as described above, it is possible to record with various dot arrangements even for the same level, such that the number of ejections is distributed between the nozzles located in the upper stage and the nozzles located in the lower stage of the dot arrangement pattern, The effect of dispersing various noises peculiar to the recording apparatus can be obtained.

  Similarly, for the green representing 16 values of levels 0 to 15, a matrix-type dot arrangement pattern constituted by two vertical areas × 8 horizontal areas (G) (not shown) is used. As the number of levels increases from 0 to 15, the number of dots to be recorded is increased by one. Therefore, for G, a maximum of 15 dots are arranged for one pixel.

  Thus, in this embodiment, for CMYKlclmR, one pixel is expressed by 8 gradations, and the maximum number of dots to be printed at that time is set to 8, while for G, 1 pixel is expressed by 16 gradations, By setting the maximum number of dots to be printed at that time to 15, the maximum amount to be printed per unit area (here, one pixel) of the green ink is made larger than that of other color inks.

  When the dot arrangement patterning process described above is completed, all dot arrangement patterns for the recording medium are determined, and 1-bit or 1-bit color ejection data of “1” or “0” is arranged for each area in one pixel. Is done. Thereafter, as described with reference to FIG. 1, each color ejection data of 1 bit is masked by the mask data conversion process J0008 to generate each color ejection data for each scan, and ejection data Y, M, C for each scan. , K, lc, lm, R, and G are sent to the head driving circuit J0009 at an appropriate timing, whereby the recording head J0010 is driven and each ink is ejected according to the ejection data.

(Recording head configuration)
The configuration of the head cartridge H1000 applied in the present embodiment will be described below. The head cartridge H1000 in this embodiment has a recording head H1001, means for mounting the ink tank H1900, and means for supplying ink from the ink tank H1900 to the recording head, and is detachable from the carriage M4000. Mounted on. The overview of the recording head will be described with reference to FIGS. 22 and 23 of a recording head for seven colors in which one color is omitted for the sake of easy viewing. This will be described in detail with reference to FIG. 24 showing eight colors corresponding to the embodiment.

  FIG. 22 is a diagram illustrating a state in which the ink tank H1900 is attached to the head cartridge H1000 applied in the present embodiment. The printing apparatus according to the present embodiment forms an image with eight colors of light cyan, light magenta, cyan, magenta, yellow, black, red, and green, and therefore, ink tank H1900 is also prepared for eight colors independently. . As shown in the figure, each is detachable from the head cartridge H1000. The ink tank H1900 can be attached and detached while the head cartridge H1000 is mounted on the carriage M4000.

  FIG. 13 is an exploded perspective view of the head cartridge H1000. In the figure, a head cartridge H1000 includes a first recording element substrate H1100 and a second recording element substrate H1101, a first plate H1200, a second plate H1400, an electric wiring substrate H1300, a tank holder H1500, and a flow path forming member H1600. , Filter H1700, seal rubber H1800, and the like.

  The first recording element substrate H1100 and the second recording element substrate H1101 are Si substrates, and a plurality of recording elements (nozzles) for ejecting ink are formed on one side thereof by photolithography. Electric wiring such as AI for supplying electric power to each recording element is formed by a film forming technique, and a plurality of ink flow paths corresponding to individual recording elements are also formed by a photolithography technique. Further, an ink supply port for supplying ink to the plurality of ink flow paths is formed to open on the back surface.

  FIG. 24 is an enlarged front view for explaining the configuration of the first recording element substrate H1100 and the second recording element substrate H1101. The thick solid lines in FIG. 24 are printing element rows (hereinafter also referred to as nozzle rows) corresponding to different ink colors. The first printing element substrate H1100 has a nozzle row to which light cyan ink is supplied and cyan ink rows. There are configured nozzle rows for four colors: a nozzle row to be supplied, a nozzle row to which magenta ink is supplied, and a nozzle row to which yellow ink is supplied. The second recording element substrate H1101 has four colors of a nozzle row to which light magenta is supplied, a nozzle row to which red ink is supplied, a nozzle row to which black ink is supplied, and a nozzle row to which green ink is supplied. A nozzle row is configured.

  Each nozzle row is composed of 768 nozzles arranged at an interval of 1200 dpi (dot / inch; reference value) in the conveyance direction of the recording medium, and ejects approximately 2 picoliters of ink droplets. The opening area at each nozzle outlet is set to about 100 square μm 2. The first recording element substrate H1100 and the second recording element substrate H1101 are bonded and fixed to the first plate H1200. Here, the first recording element substrate H1100 and the second recording element substrate H1101 are attached to the first recording element substrate H1100. An ink supply port H1201 for supplying ink is formed.

  Further, a second plate H1400 having an opening is bonded and fixed to the first plate H1200. The second plate H1400 is composed of the electric wiring substrate H1300, the first recording element substrate H1100, and the second plate H1400. The electric wiring substrate H1300 is held so that the recording element substrate H1101 is electrically connected.

  The electrical wiring substrate H1300 applies an electrical signal for ejecting ink from each nozzle formed on the first recording element substrate H1100 and the second recording element substrate H1101, and the first recording element substrate Electrical wiring corresponding to the H1100 and the second recording element substrate H1101, and an external signal input terminal H1301 for receiving an electrical signal from the recording apparatus main body located at the end of the electrical wiring. The external signal input terminal H1301 is positioned and fixed on the back side of the tank holder H1500.

  On the other hand, in a tank holder H1500 that holds the ink tank H1900, a flow path forming member H1600 is fixed by, for example, ultrasonic welding to form an ink flow path H1501 that communicates from the ink tank H1900 to the first plate H1200.

  A filter H1700 is provided at the ink tank side end of the ink flow path H1501 that engages with the ink tank H1900, and can prevent dust from entering from the outside. Further, a seal rubber H1800 is attached to the engaging portion with the ink tank H1900 so that ink can be prevented from evaporating from the engaging portion.

  Further, as described above, the tank holder portion composed of the tank holder H1500, the flow path forming member H1600, the filter H1700, and the seal rubber H1800, the first recording element substrate H1100, the second recording element substrate H1101, and the first plate. The head cartridge H1000 is configured by bonding the recording head unit H1001 including the H1200, the electric wiring substrate H1300, and the second plate H1400 by bonding or the like.

  According to the present embodiment described above, a predetermined spot color ink (for example, Red ink) is not used for an achromatic color reproduction range, and a predetermined hue (for example, a predetermined spot color ink is used) For the color reproduction range of the hue corresponding to the WR line), the predetermined special color ink is used in the entire region from the low saturation portion to the high saturation portion. While reducing the color rendering and weather resistance caused by the use of special color inks, the tone reproduction in the color reproduction range of the specified hue where special color inks are used is improved. can do. Further, in the present embodiment, a predetermined spot color ink (for example, Red ink) is not used in the achromatic color current area, and two predetermined basic color inks (for example, Yellow ink) sandwiching the hue of the predetermined spot color ink are used. , Magenta ink), the red ink is used for the entire area excluding the hues of the two predetermined basic color inks in the color gamut expressed by the combination of the predetermined Magenta ink. It is possible to maintain a continuous tone property in a color reproduction range expressed by a combination of two predetermined basic color inks that sandwich the ink hue.

<Other embodiments>
In the first embodiment described above, the ink system using ink as a recording agent has been described. However, the recording agent applicable in the present invention is not limited to ink, and for example, electrophotography using toner as a recording agent. It is also applicable to the system.

  In the first embodiment, the system using device gray in the pre-stage processing is described. However, the device gray does not have to be used in the pre-stage processing. In such a case, an effect on weather resistance and an increase in the degree of freedom in the pre-processing are expected in terms of simple color rendering. In the first embodiment described above, a total of eight inks are used, in which red and green are added as special colors to cyan, light cyan, yellow, magenta, light magenta, and black. It is not limited to this example. The light cyan and light magenta light color recording agents may not be used, or the types of the special color recording agents used may be different.

  In the first embodiment described above, Red ink and Green ink are used as the spot color recording agent. However, the present invention is not limited to this example. In the present invention, at least one color spot recording agent is used. I just need it. For example, a form using only a Green recording agent, only a Red recording agent, only a Blue recording agent, a combination of Red and Blue recording agents, a combination of Red, Green, and Blue recording agents may be used. .

  In the first embodiment, the color separation is described only for the Red ink which is the special color recording agent. However, the present embodiment can be easily extended and applied to other special color recording agents such as Green and Blue. be able to.

  In the present embodiment, the color separation in which the special color recording agent is not used in the gray line, which is the feature of the present invention, is described only for the Red ink that is the special color recording agent. However, the properties of the special color recording agent described in this specification ( For example, it is not necessary to apply the method of the present invention to a special color recording agent that does not satisfy low color rendering properties and low weather resistance. Further, in this case, the specific first special color recording material (for example, Red ink) is color-separated without using the special color recording material in the gray line, which is a feature of the present invention, and the second special color recording material (for example, Green) is used. As for (ink), a configuration using a spot color recording agent for the gray line (configuration shown in FIG. 14) can also be considered. Thus, the first special color recording agent performs color separation without using the special color recording agent for the gray line, which is a feature of the present invention, and the second recording agent has a system in which the special color recording agent is used for the gray line. It is included in the category of the present invention. Of course, even in a system using a special color recording agent that is not inferior in color rendering and weather resistance as compared with the basic color recording agent, the method of the present invention that does not use the special color recording agent in the gray line is effective. This is because the merit of being unaffected by fluctuations in the clay balance due to manufacturing variations of the head is still exhibited.

  In any case, the color reproduction of a predetermined hue (for example, a hue corresponding to the WR line) in which the predetermined spot color recording agent is not used in the achromatic color gamut and the predetermined spot color recording agent is used. Any system in which a predetermined spot color recording agent is used in the entire region is included in the scope of the present invention.

  Further, for the achromatic color gamut, a predetermined spot color recording agent is not used, and a predetermined color reproduction gamut expressed by a combination of two predetermined basic color recording agents sandwiching the hue of the predetermined spot color recording agent is used. Even a system in which Red ink is used for the entire region excluding the hues of the two basic color recording agents is within the scope of the present invention.

  It should be emphasized that several modifications can be applied to the above-described embodiments without departing from the teachings of the present invention. In particular, all matters contained in this disclosure or shown in the accompanying drawings should be construed as illustrative and not restrictive. .

1 is a block diagram illustrating a configuration of a print system according to a first embodiment of the present invention. It is a figure which shows the concept of color separation LUT. It is a figure which shows typically the color gamut (Gamut) reproduced by the whole color separation data of 1st Embodiment. It is a figure which shows the color separation data of the lattice point data on the WHITE-RED-BLACK line in the color separation LUT of 1st Embodiment. It is a figure which shows the color separation data of the lattice point data on the YELLOW-RED-MAGENTA line in the color separation LUT of 1st Embodiment. 10 is a diagram of a color separation method described in Patent Document 9. FIG. It is a figure which shows the spectral reflectance by the mixed colors M + Y and C + Y of the basic color which can implement | achieve the special color inks R and G used by embodiment of this invention, and the hue equivalent to it. It is a figure which shows the saturation residual ratio before and after the weather resistance test of the special color inks R and G used by embodiment of this invention. It is a figure which shows distribution of the usage-amount in the color space about the special color ink Red at the time of using the method of patent document 10. FIG. It is a figure which shows distribution of the usage-amount in the color space about the special color ink Red at the time of using the method of this invention. It is a figure which shows the amount of Red ink used along the CW (K) -R line of Fig.10 (a) when using Red ink by the method of patent document 10, and the method of this invention. (A) is a diagram showing red ink (broken line) and color separation (thin solid line) in a non-spot color system that reproduces the same hue and lightness. (B) is a color gamut (dashed line) reproduced by Red ink (dashed line) shown in (a), and a color gamut (thin solid line) by color separation (thin solid line) in a non-spot color system shown in (a). Solid line) is a schematic comparison view showing the reproduction range (one-dot chain line) of a positive film in a corresponding hue in a lightness (L *)-saturation (C *) plane. It is a figure which shows the color separation of the gray line by the method of this invention. It is a figure which shows color separation in the case of using special color ink Green as a complementary color component of a gray line. It is a block diagram of a halftone processing unit as the first embodiment of the present invention. It is a flowchart explaining operation | movement of a halftone process part. It is a figure which shows the detail of the scanning of an image. It is a figure which shows the detail of an accumulation error memory. FIG. 3 is a diagram illustrating a configuration of print data including print control information for controlling printing and print image information (also referred to as print image data). An example of an image having a predetermined gradation value before halftone processing and a quantized image after halftone processing are shown. It is the figure which showed the output pattern with respect to the input level converted by the dot arrangement patterning process of embodiment of this invention. FIG. 5 is a perspective view showing a state where an ink tank is mounted on the head cartridge applied in the embodiment of the present invention. It is a disassembled perspective view of the head cartridge applied in the 1st Embodiment of this invention. FIG. 3 is a front view showing a recording nozzle array arrangement on a recording element substrate in the head cartridge applied in the first embodiment of the present invention. FIG. 5 is a diagram illustrating a discharge amount distribution generated in association with manufacturing of a recording nozzle of a recording head applied in the first embodiment of the present invention.

Explanation of symbols

J0001 Application J0002 Pre-processing J0003 Post-processing J0004 γ correction J0005 Halftoning J0006 Print data creation processing J0007 Dot arrangement patterning processing J0008 Mask data conversion processing J0009 Head drive circuit

Claims (6)

An image forming method of forming an image on a recording medium using a recording agent of cyan, magenta and yellow basic colors and a recording agent of a special color having a hue different from the basic color,
The spot color recording agent is not used for the achromatic color gamut, and the spot color recording agent is used in the entire color gamut indicating the predetermined hue in which the spot color recording agent is used. An image forming method comprising forming an image on the recording medium. Within a color gamut represented by a combination of cyan, magenta, and yellow basic color recording agents and a predetermined two basic color recording agents among the three basic colors in a color space that matches human visual characteristics. An image forming method for forming an image on a recording medium using a recording agent of a special color showing a hue angle of
For the achromatic color gamut, the recording material of the predetermined color is not used, and the recording of the two basic colors out of the color gamut expressed by the combination of the recording agents of the two predetermined basic colors. An image forming method characterized in that an image is formed on the recording medium in such a manner that the recording material of the special color is used for the entire region excluding the hue of the agent. The image forming method according to claim 2, wherein the color space in accordance with human visual characteristics is a CIE-L ^* a ^* b ^* color space.   The special color recording agent is expressed by a combination of the two recording agents of green and the magenta and yellow that exhibit a hue angle in a color reproduction region expressed by a combination of the two recording agents of cyan and yellow. At least one selected from the group of a red recording agent showing a hue angle in a color reproduction region and a blue recording agent showing a hue angle in a color reproduction region expressed by a combination of the two recording agents of cyan and magenta. The image forming method according to claim 1, wherein the image forming method is an image forming method. A program for generating data corresponding to a recording material of a special color whose hue is different from the basic colors of cyan, magenta and yellow,
The aforesaid special color recording agent is not used for the achromatic color reproduction range, and the special color recording agent is used in the entire range from low saturation to high saturation for the color reproduction range indicating the predetermined hue in which the special color recording agent is used. Is a program for causing a computer to execute a process of generating data corresponding to the recording material of the special color. In the CIE-L ^* a ^* b ^* color space, among the three basic colors of cyan, magenta and yellow, a special color indicating a hue angle within a color reproduction range expressed by a combination of recording agents of two predetermined basic colors A program for generating data corresponding to a recording material,
For the achromatic color gamut, the recording material of the predetermined color is not used, and the recording of the two basic colors out of the color gamut expressed by the combination of the recording agents of the two predetermined basic colors. A program for causing a computer to execute a step of generating data corresponding to the spot color recording agent so that the spot color recording agent is used for the entire region excluding the hue of the agent.

Images