JP4168432B2 - Inkjet recording method and recording apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an inkjet recording method and a recording apparatus, and is particularly characterized by the proper use of black ink and composite black when forming black dots (K dots) in order to obtain a clear and high-quality image without bleeding. The present invention relates to an inkjet recording method and a recording apparatus.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, as a printer device as an information equipment terminal such as a personal computer, a wire-driven recording head that performs printing by magnetically driving a wire and pressing it against a platen via a recording paper as an ink ribbon and a recording medium. Printers used, printers using ink jet type recording heads that eject ink from nozzles by the action of piezoelectric elements, etc. are used, but there is no noise associated with printing, and the structure is simple and non-contact An impact type ink jet printer, that is, an ink jet recording apparatus, is attracting attention as being suitable for use in an office.
[0003]
In such a conventional ink jet recording system, ink is ejected from a minute nozzle by using discharge means such as deformation force of a piezo element as an ink pressurizing means or pressure fluctuation due to bubble generation force by a heater as an ink heating means. This is a system in which dots are formed by ejecting ink onto a recording medium and ejected, and various images are recorded by a dot pattern.
[0004]
When performing color recording by this ink jet recording method, it is necessary to eject at least three inks of different colors such as yellow, magenta, and cyan. To record black, yellow, magenta, and cyan are used. Three colors of ink are superimposed and recorded, and so-called composite black is formed to express black.
[0005]
However, with composite black, it is difficult to express more blackish black, so-called real black, so in addition to the three colors of yellow, magenta, and cyan, real black is recorded by using black ink. Realizes higher-quality color recording.
[0006]
In addition, black ink often records characters and the like, and bleeding along fibers exposed on the surface of the recording paper, that is, so-called feathering can be prevented to achieve high density and clear recording. As described above, ink that does not easily penetrate into the recording paper is used.
[0007]
On the other hand, in the case of color inks such as yellow, magenta, and cyan, a filled pattern, that is, a so-called solid pattern is often recorded, and color mixing due to the flow of ink at the color boundary portion, that is, so-called bleeding occurs. In order to reduce bleeding, it is common to use ink that easily penetrates into the recording paper, and in particular, when the recording paper is so-called plain paper with fibers exposed on the surface, the use of these inks Is mandatory.
[0008]
However, when black ink with low penetrability is used to perform high-quality recording, bleeding occurs at the boundary with non-black dots, i.e., color dots, due to other color inks. The situation will be described with reference to FIG.
See FIGS. 7A and 7B.
FIG. 7B is an enlarged view of the color boundary portion 46 between the yellow recording region 44 and the black recording region 45 indicated by a broken-line circle in FIG. 7A, and the dots constituting the color boundary portion 46 are schematically shown. In general, yellow dots 41 using yellow ink and black dots 43 using black ink overlap each other.
[0009]
See Fig. 7 (c)
In this case, when black ink with low permeability is used as the black ink to prevent the above-described feathering, the black ink oozes out to the yellow recording area 44 due to the low permeability and a bleed 47 is generated. It will be.
[0010]
Accordingly, since the bleed 47 is generated in the black recording area 45 of black ink which hardly penetrates into the recording paper and the color boundary portion 46 of the yellow recording area 44 recorded with the color ink, that is, the yellow ink in the drawing, when color recording is performed. In order to reduce bleed, it is sufficient to use composite black instead of black ink, but this time it is not possible to express black in color recording in real black at all, especially emphasizing the balance between colors In the natural image, there is a problem that the color becomes dull or turbid due to the composite black and the image quality is deteriorated.
[0011]
In order to solve such a problem, a method of reducing the bleed by thinning out dots to be recorded only at the color boundary portion between black and color, and reducing the amount of ink forming the dots to be recorded at the color boundary portion to reduce the bleed. Method of reducing, recording the width of a predetermined number of dots at the color boundary part with composite black, recording the other black part with black ink, and further using real black only for higher quality color recording To achieve this, there are two types of black ink, black ink with high penetrability and black ink with low penetrability, the width of a predetermined number of dots at the color boundary is recorded with black ink with high penetrability, and other black inks. A method of recording a portion with black ink having low permeability has been proposed.
[0012]
In recent years, with the spread of personal computers and digital cameras, or the spread of application software that can perform gradation color processing, ink jet recording apparatuses that can realize natural images, that is, gradation color recording, are beginning to become popular.
[0013]
Here, a basic image processing method for a conventional gradation color ink jet recording apparatus will be described with reference to FIG.
See FIG.
FIG. 8 is a block diagram of a basic image data processing system for a conventional gradation color ink jet recording apparatus. First, image data is converted into R (red), G (green), and B (blue) light 3. The data of each primary color is decomposed and input to a computer that controls the ink jet recording apparatus, and color management is performed in the computer.
[0014]
In color management, each color data is first converted into three primary colors, yellow (Y), magenta (M), and cyan (C), which are suitable for controlling an inkjet recording apparatus, corresponding to the dots to be recorded. Generated data.
[0015]
Next, black (K) data is extracted from the Y, M, and C data, and depending on each method, the extracted K data, that is, black dots are recorded in composite black or black. Decide whether to record with ink.
[0016]
The dot data for each color in this case is composed of data on the recording position and density, and by referring to the density-dot diameter conversion table set for each color in advance, it corresponds to the preset number of gradations. The ink droplet amount that realizes the density of each dot is determined, and the printing position of the ink jet recording apparatus is determined based on the position to be recorded, that is, the data relating to the ejection timing and the data relating to the amount of ink droplet to be ejected, that is, the gradation level. To the department.
[0017]
The print control unit of the ink jet recording apparatus selects a drive signal capable of discharging the ink droplet amount based on the gradation level data, and controls the discharge means by the discharge unit drive unit while controlling the discharge timing by the dot control unit. By driving, four color ink droplets having different sizes are ejected to predetermined positions on the recording medium to form dots.
[0018]
As a gradation control method in such a gradation color recording method, a matrix is formed by combining a plurality of dots, and a gradation is recorded by changing the number of dots recorded therein, or dots to be recorded There is a method of recording gradation by changing the diameter.
[0019]
In particular, the latter gradation expression method for changing the dot diameter to be recorded can record an image without changing the resolution of the apparatus, and higher resolution can be achieved than the former method of recording gradation by combining the dot matrix. This method is possible and suitable for high-quality recording.
[0020]
Furthermore, in addition to these methods, smooth gradations are also expressed by using two or more types of inks with different shades. In this case, the recording head is the same as the number of ink types. Etc. will be required, which will entail a significant cost increase.
[0021]
As a method for changing the dot diameter, a method for controlling the amount of one ink droplet ejected from the nozzle, a method for controlling the number of ink droplets ejected to the same recording position, or a method in which both methods are combined. In the case of the latter method of controlling the number of ink droplets, the amount of ink that can be controlled is an integral multiple of the minimum ink amount, but in the case of the former method of controlling the amount of one ink droplet. Since the ink amount can be arbitrarily set according to the number of gradations, smoother gradation expression is possible.
[0022]
On the other hand, in the latter method of controlling the number of ink droplets, there is a problem in that the recording speed is reduced because multiple recording is performed, and from the viewpoint of high-speed recording, the former one ink droplet has a problem. A method of controlling the amount is considered advantageous.
[0023]
In such a gradation expression method for changing the dot diameter, as a method of eliminating bleeding between colors, it has been proposed to reduce the amount of ink that forms dots to be recorded at the color boundary portion (if necessary, for example, Japanese Patent Laid-Open No. 7-40548).
[0024]
For example, when the yellow recording area and the black recording area are adjacent to each other, the maximum number of ink droplets to be superimposed on the same location when forming one color dot, for example, a yellow dot, is smaller than the normally used maximum number. Thus, bleeding at the color boundary portion is reduced.
[0025]
[Problems to be solved by the invention]
However, among the various methods described above, the method of reducing the bleed by thinning out the dots recorded only in the color boundary portion between black and color, or the amount of ink forming the dots recorded in the color boundary portion is reduced. In the case of the method of reducing bleeding, there is a problem that the recording density at the color boundary is lowered and the color reproducibility is deteriorated.
[0026]
In particular, in the case of the proposal in the above Japanese Patent Laid-Open No. 7-40548, it is assumed that gradation recording is performed by forming one pixel with a plurality of ink droplets. Since the number of droplets cannot be secured, the recording density is lowered, the color reproducibility is deteriorated, and there is a problem that high-quality gradation recording cannot be performed. This situation will be described with reference to FIG. To do.
[0027]
See Fig. 9 (a)
FIG. 9A schematically shows dots constituting a color boundary portion where the yellow recording area and the black recording area are adjacent to each other. For example, the black dots 43 are formed using three drops of black ink. On the other hand, the yellow dots 41 are not formed with the originally required three drops of yellow ink indicated by the broken lines in the figure, but are formed with small yellow dots with, for example, one drop of yellow ink. Color reproducibility deteriorates.
[0028]
On the other hand, in the case of the method in which the width of the predetermined number of dots in the color boundary portion is recorded with composite black and the other black portions are recorded with black ink, the color gradation at the color boundary portion is not yet sufficient. This situation will be described with reference to FIG.
[0029]
Refer to FIG. 9B.
FIG. 9B also schematically shows the dots constituting the color boundary portion where the yellow recording area and the black recording area are adjacent to each other. In this case, each dot is configured with a necessary ink amount. However, all black dots in the color boundary portion are formed by composite black, and the ratio of black dots by composite black in the entire image increases, so that the desired color gradation cannot be obtained.
[0030]
Furthermore, in the case of a method in which the width of a predetermined number of dots in the color boundary portion is recorded with black ink having high penetrability and the other black portion is recorded with black ink having low penetrability, two or more types having different shades are used. In the same way as the method of expressing smooth gradation by using this ink, two recording heads are required only for the black ink, resulting in an increase in cost.
[0031]
In addition, it has been proposed to replace a part of the ink amount of the composite black with black ink when expressing the black part with composite black when performing gradation color recording by changing the dot area (necessary) In this case, the representation of real black is still insufficient, and structural changes such as making the nozzle diameter for black ink smaller than others are also necessary. There is a problem of becoming.
[0032]
Accordingly, an object of the present invention is to enable high-quality gradation color recording with less bleeding and no reduction in recording density, with the configuration of a conventional inkjet head.
[0033]
[Means for Solving the Problems]
Here, means for solving the problems in the present invention will be described with reference to a simplified flowchart showing a procedure for solving the problems of the present invention shown in FIG.
See Figure 1
(1) The present invention relates to black ink and ink dots whose size is variable on the recording medium by ejecting from the nozzles three color inks having different hues that have a greater permeability to the recording medium than the black ink. In the inkjet recording method in which gradation pattern recording is performed by forming a pattern of black, when forming a black dot, the black dot overlaps at least partly with a dot of a color other than black at a position adjacent to the black dot. In some cases, it is formed by composite black, and in other cases, it is formed by black ink.
[0034]
As shown in FIG. 1, it is checked whether or not black dots and dots of colors other than black adjacent to the black dots are overlapped among the dot data for each color after the same color management as in the past. When part of the image overlaps, it is formed with composite black. In other cases, it is possible to minimize the use of composite black by forming it with black ink. It is possible to record the black recording portion of the intermediate density that occupies with real black, thereby enabling high-quality gradation color recording.
The three colors having different hues ideally mean yellow (Y), magenta (M), and cyan (C), but are not necessarily limited to strict yellow, magenta, and cyan. It is not a thing.
[0035]
In addition, in the color boundary portion, when a non-black color dot adjacent to the black dot is superimposed on the black dot, it is possible to suppress bleed because a highly permeable composite black is used. The color boundary can be sharpened to improve image quality.
[0036]
(2) Further, according to the present invention, in (1), the diameter of the black dot having the maximum diameter among the black dots formed with black ink is the same as the maximum diameter of the three color dots having different hues, or It is less than that.
[0037]
When black ink with low penetrability is used, ink penetration is less than when three colors or composite blacks with different hues are used, and the degree of freedom in designing the dye density is greater, resulting in higher recording density. Therefore, when expressing the same recording density, recording with dots of smaller diameter can reduce the graininess in the highlight recording area where the graininess is conspicuous, thereby enabling high-quality black recording become.
[0038]
(3) Further, according to the present invention, in the above (1) or (2), the maximum diameter of the mixed color dots obtained by recording at least two of the three different colors at the same recording position is It is characterized by being made the same as the maximum diameter of three different color dots.
[0039]
In this way, when recording mixed colors of intermediate colors or composite black, the same recording position can be obtained by making the total amount of ink ejected to the same recording position the same as that of a single color dot, and therefore by making the maximum diameter of the dots the same. Bleeding due to an increase in the amount of ink discharged on the surface can be suppressed.
Note that “the same diameter” does not mean the exact same mathematically, but the dot size obtained when the total amount of ink ejected to the same recording position is controlled as much as possible. In practice, there may be a slight difference depending on the number of stages of dot diameter, the difference in penetrability of each ink, the mixing ratio for color adjustment, or the control error of the ejection means. .
[0040]
(4) Further, according to the present invention, in any of the above (1) to (3), when the diameter of a dot formed with black ink is the same as the diameter of a black dot formed with composite black, the black ink is formed with black ink. The black dot recording density is equal to or higher than the black dot recording density formed of composite black.
[0041]
In this way, the recording density of black dots formed with black ink is the same as the recording density of black dots formed with composite black by controlling the amount of coloring material such as dye or pigment in black ink, or As a result, when a predetermined average recording density is obtained as a result, it is possible to record with dots having a smaller diameter, thereby reducing graininess.
[0042]
(5) Further, the present invention controls electric signals applied to ejection means for ejecting ink droplets of black ink and three color inks having different hues that are more penetrating into the recording medium than black ink. In an inkjet recording apparatus that performs gradation color recording by adjusting the electrical signal and changing the size of the ink dots ejected from the nozzles by adjusting the electrical signal, the black dots It is characterized in that there is provided means for forming with composite black when at least a part of non-black color dots at positions adjacent to black dots are superimposed, and with black ink in other cases. To do.
[0043]
In the case of making the ejection amount of such ink droplets variable, for example, when a piezoelectric element is used as the ejection means, the shape of an electric signal applied to the piezoelectric element, that is, the application time, applied voltage, rise time, or By adjusting the fall time or the like, the displacement operation of the piezoelectric element can be controlled, thereby making the discharge amount variable.
[0044]
DETAILED DESCRIPTION OF THE INVENTION
Here, with reference to FIG. 2 thru | or FIG. 6, embodiment of this invention is described.
First, an example of a serial type ink jet recording apparatus equipped with a recording head using a piezoelectric element used in the embodiment of the present invention will be described with reference to FIG. 2 to FIG. The configuration other than the selection mechanism for using ink or composite black is the same as that of the conventional gradation color recording ink jet recording apparatus.
[0045]
See Figure 2
FIG. 2 is a schematic perspective view of an essential part of the ink jet recording apparatus used in the embodiment of the present invention. In the ink jet recording apparatus 10, ink cartridges corresponding to each ink, that is, a yellow ink cartridge 16, magenta ink are illustrated. An ink jet head unit 11 to which a cartridge 17, a cyan ink cartridge 18, and a black ink cartridge 19 are mounted is mounted on a carrier 12, and this carrier 12 is indicated by an arrow in the main scanning direction along the stage shaft 13, that is, in the drawing. It is attached to be movable in the X direction.
The inkjet head 20 is below the inkjet head unit 11, and the lowermost surface is an ink ejection unit.
[0046]
Further, the recording paper 14 as a recording medium is conveyed by the paper feed roller 15 in the sub-scanning direction, that is, in the A direction indicated by an arrow in the drawing, and a predetermined image or information is received at a position facing the ink ejection portion of the inkjet head 20. It will be recorded.
[0047]
See Fig. 3 (a)
FIG. 3A is a schematic perspective view of the inkjet head unit 11, and a yellow ink cartridge 16, a magenta ink cartridge 17, a cyan ink cartridge 18, and a black ink cartridge 19 can be attached to and detached from the inkjet head unit 11. In this case, since the use frequency of the black ink is higher than that of the other inks, the capacity of the black ink cartridge 19 is set larger than that of the other ink cartridges.
[0048]
Refer to FIG.
FIG. 3B is a perspective view of the ink cartridge. In the drawing, the yellow ink cartridge 16 is shown as a representative, but an ink supply unit to the inkjet head 20 is shown below the yellow ink cartridge 16 in the figure. Is provided.
[0049]
See Fig. 4 (a)
FIG. 4A is a conceptual exploded perspective view of the inkjet head 20, which is roughly composed of a piezoelectric element member 21, an ink flow path member 29, and a nozzle member 31.
Among them, the piezoelectric element member 21 includes the piezoelectric material driving section 25 by providing electrodes 24 arranged in parallel to each other on the piezoelectric material 23 provided on the substrate 22.
[0050]
The ink flow path member 29 is provided with a plurality of ink flow paths 26, and the ink flow paths 26 include pressure chambers 27, and each ink flow path 26 is a rear end portion of the pressure chamber 27. And an ink supply port 28 is provided at one end of the ink supply channel (not shown), and an ink supply unit of an ink cartridge (not shown) connected to the ink supply port 28. Ink is supplied from.
[0051]
The nozzle member 31 is provided with nozzles 30 distributed corresponding to the ink flow paths 26, and the piezoelectric element member 21 and the ink flow paths so that the ink flow path 26 and the piezoelectric element drive unit 25 face each other. The basic structure of the inkjet head 20 is completed by joining the member 29 and joining the ink flow path member 29 and the nozzle member 31 so that the ink flow path 26 and the nozzle 30 face each other.
[0052]
See Fig. 4 (b)
FIG. 4B is an enlarged cross-sectional view of an example of the piezoelectric element member 21, in which an electrode 24 sandwiching the piezoelectric element is formed in a recess provided in the piezoelectric material 23 so as to correspond to the ink flow path 26, and the piezoelectric element. The drive part 25 is comprised, and the other part becomes the non-piezoelectric drive part 32, and the piezoelectric element drive part 25 is separated from each other.
[0053]
When a voltage is applied between the electrodes 24 sandwiching the piezoelectric element, the piezoelectric element driving unit 25 expands due to the electrostrictive effect to reduce the volume of the pressure chamber 27 and pressurize the ink by reducing the volume, thereby causing the ink flow. Ink is ejected from the nozzle 30 via the path 26.
The ink ejection amount can be arbitrarily controlled by controlling the application time of the electric signal applied to the electrode, the applied voltage, and the like.
[0054]
Gradation color recording is performed using such an ink jet recording apparatus, and the color management in the previous stage is the same as the conventional color management shown in FIG. 8, but in the case of the present invention, the dot diameter is changed. When gradation color recording is performed under control, bleeding occurs because of the characteristics of the control method. A relatively large diameter black dot and a relatively large diameter color dot are adjacent to each other, and a part of the dots overlap each other. In other words, when at least one of the black dots and the color dots is relatively small, even if they are adjacent to each other, they are not superimposed, and as a result, no bleed occurs.
[0055]
For example, in the case of a black dot, the maximum diameter, i.e., the case where only the highest density dot is in contact with an adjacent dot,
In the case of an apparatus with a resolution of 300 dpi, the dot pitch, that is, the interval is about 85 μm (≈2.54 × 10 ^Four .mu.m / 300 dots.apprxeq.84.67 .mu.m / dot), and therefore the maximum diameter of the dots is about 120 .mu.m (.apprxeq. ^1/2 × 2.54 × 10 ^Four μm / 300 dots≈119.74 μm / dot) or more is required.
[0056]
Therefore, when the size of the dots of the three colors Y, M, and C is adjusted to three stages of 120 μm, 80 μm, and 50 μm and four gradations are expressed,
For black ink with low penetrability, smaller dots may be used to obtain the same average recording density. However, when printing characters or the like, the maximum diameter is required to be 120 μm in the same way as color dots in order to connect diagonal lines. In addition to this, it is adjusted in three stages of 48 μm and 30 μm.
[0057]
Of these, the intermediate diameter other than the maximum diameter is not fixed to 48 μm and 30 μm, and the desired gradation expression including the number of gradation steps is included depending on the dye density and physical property value of the ink. It should be set so that it can.
[0058]
Further, in the case of gradation recording, if the recording density is too high with the maximum diameter dot of black ink, the maximum diameter dot for gradation recording is set to 80 μm, and the dot of 120 μm is used for recording characters and the like. Anyway.
[0059]
When gradation recording is performed using such three-stage diameter dots, if the maximum diameter of a black dot is 120 μm, dots of colors other than black exist at adjacent positions in the main and sub-scanning directions. When the diameter is 120 μm or 80 μm, (120 μm + 120 μm) / 2 = 120 μm> 85 μm, or (120 μm + 80 μm) / 2 = 100 μm> 85 μm, and bleed is generated by overlapping with black dots.
[0060]
Even when the maximum diameter of the black dots is 80 μm, if the diameter of the adjacent color dots is 120 μm, the black dots overlap with the black dots, but the bleed is generated. However, the black dots have a diameter of 48 μm or 30 μm. In some cases, even if a color dot having a diameter of 120 μm exists at an adjacent position, the dots do not overlap each other.
[0061]
Based on such a premise, a flowchart of data processing in the embodiment of the present invention will be described with reference to FIG.
See Figure 5
First, prior to the start, each color data d is obtained by the conventional color management shown in FIG. _{Z (0,0)} ~ D _{Z (m, n)} Is converted in advance from recording density to gradation level (ie, dot diameter) data, ie, maximum diameter 3, intermediate diameter 2, minimum diameter 1, and no recording 0 data. The black dots and the other color dots are not overlapped and recorded at the same position.
D _{Z (0,0)} ~ D _{Z (m, n)} , Z means Y, M, C, K, m and n mean that an image of one frame consists of (n + 1) rows (m + 1) columns, and d in the following _K Means black dot data, d _X Means color dot data of any one of Y, M, and C.
[0062]
Next, in step 1, the column designation number a is set to 0, the row designation number b is set to 0, and the black data d sequentially from the first pixel data. _{K (a, b)} The black data d detected in step 2 is started. _{K (a, b)} Is d _{K (a, b)} It is determined whether or not ≧ 3, that is, whether or not the diameter of the black dot is the maximum diameter. If the diameter is the maximum diameter, the process proceeds to step 3; Since there is not, go to Step 5.
[0063]
In step 3, the black dot black data d _{K (a, b)} The four dots positioned in the main / sub-scanning direction are color dots, and data d of two dots positioned in the main-scanning direction _{X (a-1, b)} And d _{X (a + 1, b)} And data d of two dots positioned in the sub-scanning direction _{X (a, b-1)} And d _{X (a, b + 1)} It is determined whether at least one of the data is 2 or more, that is, whether or not it is a color dot having an intermediate diameter or more. If it is not a color dot having an intermediate diameter or more, a color dot other than black is used. Is not adjacent, or is not contacted even if it is adjacent, the process proceeds to step 5 which is a loop for determining the data of the pixel at the next position, and if it is equal to or larger than the intermediate diameter, the process proceeds to step 4.
[0064]
In step 4, in order to replace the black dot data with composite black, d _{K (a, b)} = 3 to d _{K (a, b)} = 0 and rewrite d _{Y (a, b)} = 3, d _{M (a, b)} = 3 and d _{C (a, b)} = 3 and go to the next step 5.
[0065]
In step 5, the black data d _{K (a, b)} , That is, whether or not the position a in the b row is the final position m. If not, the column designation number a is increased by 1 in step 9 and the process returns to step 2. The next black data is determined, and if it is the final position m, the process proceeds to step 7.
[0066]
In step 7, the black data d _{K (a, b)} It is determined whether or not the current row, i.e., row b, is the final column position n, i.e., the last row n, and if it is not the last row n, in step 8, the column designation number a is set to an initial value of 0. In addition, the line designation number b is incremented by 1 and the process returns to step 2 to determine the black data from the beginning of the next line. On the other hand, if it is the final position n, the image of one frame is checked. Since the process is completed, the process is terminated.
[0067]
Next, the data of each color for which the data processing has been completed is output to the print control unit, similarly to the case shown in FIG. 8, and the print control unit, based on the data for each color for which the processing has been completed, that is, d _{K (a, b)} To control the discharge of black ink, and d _{Y (a, b)} To control the discharge of yellow ink, and d _{M (a, b)} To control the discharge of magenta ink, and d _{C (a, b)} To control the discharge of cyan ink, and control the discharge timing and the amount of discharged ink to perform recording.
[0068]
See FIG.
FIG. 6 is an explanatory diagram of a dot pattern showing an example of a recording result in the above-described embodiment. A black dot 42 overlapping with a yellow dot 41 displayed with Y is a black dot recorded with composite black displayed with K ′. The black dots 43 that do not overlap the yellow dots 41 are black dots recorded with black ink displayed in K.
[0069]
Therefore, in the embodiment of the present invention, the black dots 42 displayed in composite black are the minimum necessary, so that black recording closer to real black is possible, and the black dots 42 overlapping the yellow dots 41 are provided. Since recording is performed with composite black using Y ink, M ink, and C ink having high penetrability, bleeding at the color boundary portion can be suppressed.
[0070]
In the description of the above embodiment, when the black dots 42 that overlap the color dots are replaced with composite black, the diameters of yellow dots, magenta dots, and cyan dots are the same as the original dot diameters. However, in this case, the total ink amount for forming the composite black increases and the dot diameter becomes too large, which causes bleeding. Therefore, for example, it is desirable to make the dot diameters finally obtained as the same as possible within a range in which almost a desired recording density can be obtained, for example, all dots are made to have a minimum diameter.
[0071]
Further, in the description of the above embodiment, for the sake of simplicity, the secondary color due to the color mixture is not mentioned, but in order to suppress bleeding even in the case of the secondary color dot due to the color mixture. It is desirable to select the size of the diameter so that the same hue can be obtained in accordance with the color mixture ratio so that the total amount of ink forming dots does not become excessive.
[0072]
However, in the case of three stages of dot diameters as described above, it is difficult to select the diameter so that the same hue can be obtained according to the color mixture ratio, but the dot diameter stages are subdivided finely. It is easy to do this, or a special dot diameter for forming a secondary color or composite black may be set.
[0073]
In any case, these settings can be achieved by changing the secondary recording color or composite black to Y, M, and C single colors, such as the recording density of the ink, that is, the recording density of the solid pattern and the relationship between the ink amount and the dot diameter. It is desirable to make various settings depending on the setting conditions when disassembling.
[0074]
In particular, in the above embodiment, the description has been made on the premise that the recording medium is a so-called plain paper in which fibers that are likely to bleed are exposed, but the present invention is not limited to plain paper, and coated paper. Alternatively, the present invention can be applied to other recording media such as glossy paper, and the dot diameter varies depending on the type of the recording medium. Therefore, it is desirable to set optimum conditions for each recording medium.
[0075]
Although the embodiment of the present invention has been described above, the present invention is not limited to the configuration described in the embodiment, and various modifications are possible. For example, the description of the above embodiment is provided. The color recording resolution is the same as the black recording resolution, but the present invention can be applied to the case where the black recording resolution is higher than the color recording resolution in order to improve the black recording quality. In this case, the maximum diameter of the black dots is set to be smaller than the maximum diameter of the color dots corresponding to this resolution.
[0076]
In the description of the above embodiment, for the sake of strictness, when the diameter of the black dot is an intermediate diameter, the intermediate diameter of the black dot is not overlapped with the maximum diameter, that is, the color dot having a diameter of 120 μm. Is 48 μm, but may be 50 μm. In this case, (120 μm + 50 μm) / 2 = 85 μm> 84.67 μm and a slight overlap occurs, but in such a case, there is no effective overlap. The processing may be performed along the flow of FIG.
[0077]
In other words, how much overlap is regarded as effective overlap depends on the bleed degree. For example, an overlap of about 1 μm or less hardly affects the bleed, so that it can be considered that there is no effective overlap.
[0078]
Further, the black dot diameter may be set so that the intermediate diameter effectively overlaps the color dot of the maximum diameter. For example, the black dot diameter is set to 120 μm, 80 μm, and 50 μm, the same as the color dot. In the case, before step 2, the detected black data d _{K (a, b)} Is d _{K (a, b)} It is determined whether or not ≧ 2, that is, whether or not the diameter of the black dot is equal to or larger than the intermediate diameter. If the diameter is not equal to or larger than the intermediate diameter, contact is made regardless of the adjacent dot diameter. Therefore, the process proceeds to step 5 where the data of the pixel at the next position is determined.
[0079]
Next, in step 2, the black data d _{K (a, b)} Is d _{K (a, b)} It is determined whether or not ≧ 3, that is, whether or not the diameter of the black dot is the maximum diameter. If the diameter is the maximum diameter, the process proceeds to step 3; The black dot black data d _{K (a, b)} The four dots positioned in the main / sub-scanning direction are color dots, and data d of two dots positioned in the main-scanning direction _{X (a-1, b)} And d _{X (a + 1, b)} And data d of two dots positioned in the sub-scanning direction _{X (a, b-1)} And d _{X (a, b + 1)} It is determined whether at least one of the data is 3 or more, that is, whether it is a color dot of the maximum diameter. If it is not the color dot of the maximum diameter, it is adjacent to a color dot other than black. No, even if adjacent to each other, no contact is made, so the process proceeds to step 5 for determining the data of the pixel at the next position, and in the case of the maximum diameter, the contact is made. D to replace with black _{K (a, b)} = 2 to d _{K (a, b)} = 0 and rewrite d _{Y (a, b)} = 2, d _{M (a, b)} = 2 and d _{C (a, b)} It is sufficient to rewrite to = 2 and proceed to step 5.
[0080]
In the above description of the embodiment, a serial type ink jet recording apparatus is used. However, the present invention is applicable not only to a serial type but also to a line type ink jet recording apparatus.
[0081]
Further, in the above description of the embodiment, the description is made using an ink jet head of a type on which an ink cartridge is mounted. .
[0082]
In the description of the above embodiment, a piezoelectric element is used as the ink ejection means, but other known means such as a heater, a pressure pump, electrostatic attraction, and magnetic attraction are used instead of the piezoelectric element. It may be used.
[0083]
In the description of the above embodiment, three color inks of yellow (Y), magenta (M), and cyan (C) are used as color inks. However, strictly yellow (Y), It is not necessary to use magenta (M) and cyan (C) three-color inks. If full-color can be expressed, other three-color inks with different hues may be used. The rights of the present invention also extend to the case where three different colors of ink are developed.
[0084]
【The invention's effect】
According to the present invention, when a black dot overlaps with an adjacent non-black dot, the dot is replaced with a highly permeable composite black, so that bleeding at the color boundary portion is suppressed, and the composite black Use is minimal, so high-quality black recording that is as close to real black as possible is possible, thereby realizing high-quality gradation color images with vivid colors and good color balance. it can.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram of a basic configuration of the present invention.
FIG. 2 is a schematic perspective view of an essential part of an ink jet recording apparatus used in an embodiment of the present invention.
FIG. 3 is an explanatory diagram of an ink jet head portion of the ink jet recording apparatus used in the embodiment of the present invention.
FIG. 4 is an explanatory diagram of an inkjet head used in an embodiment of the present invention.
FIG. 5 is a flowchart of data processing in the embodiment of the present invention.
FIG. 6 is an explanatory diagram of a dot pattern in the embodiment of the present invention.
FIG. 7 is an explanatory diagram of problems in conventional color dot recording.
FIG. 8 is a block diagram of a basic image data processing system for a conventional gradation color ink jet recording apparatus.
FIG. 9 is an explanatory diagram of a conventional bleed prevention method.
[Explanation of symbols]
10 Inkjet recording device
11 Inkjet head
12 Career
13 Stage shaft
14 Recording paper
15 Paper feed roller
16 Yellow ink cartridge
17 Magenta ink cartridge
18 Cyan ink cartridge
19 Black ink cartridge
20 Inkjet head
21 Piezoelectric element members
22 Substrate
23 Piezoelectric materials
24 electrodes
25 Piezoelectric drive unit
26 Ink flow path
27 Pressure chamber
28 Ink supply port
29 Ink channel member
30 nozzles
31 Nozzle member
32 Non-piezoelectric drive
41 yellow dots
42 black dots
43 Black dots
44 Yellow recording area
45 Black recording area
46 color border
47 Bleed

Claims (9)

Black ink and three color inks with different hues that are more penetrating into the recording medium than the black ink are ejected from the nozzles to form ink dot patterns of variable sizes on the recording medium. In an inkjet recording method that performs tonal color recording, when forming black dots, the diameters of black dots detected from pixel data after color management and the diameters of dots of colors other than black at positions adjacent to the black dots are determined. Originally, it is determined whether or not a black dot overlaps with a non- black color dot at a position adjacent to the black dot, and a black color dot at a position adjacent to the black dot is determined. wherein when if at least part of which is determined to be superimposed, formed by composite black that is formed with black ink in other cases The ink jet recording method of. 2. The ink jet recording method according to claim 1, wherein gradation color recording with a plurality of gradations is performed. The pixel data includes at least the maximum diameter data and the intermediate diameter data as dot diameter data. When forming a black dot, the black dot diameter is the maximum diameter other than black at a position adjacent to the black dot. When at least one of the diameters of the dots of the color is determined to be the intermediate diameter or the maximum diameter, or the diameters of the dots of the colors other than black at the positions adjacent to the black dots are the diameters of the black dots 3. The ink jet recording method according to claim 1, wherein when at least one of the first and second diameters is determined to be the maximum diameter, a composite black is used, and in other cases, black ink is used. Diameter of the black dots of the maximum diameter of the black dots formed by the black ink or equal to the maximum diameter of the three color dots of different said color, or to claim 1, characterized in that it is less 4. The inkjet recording method according to any one of items 3 . The maximum diameter of the mixed color dots obtained by recording at least two of the three colors having different hues at the same recording position is the same as the maximum diameter of the three colors having different hues. The inkjet recording method according to any one of claims 1 to 4 . When the diameter of the dot formed with the black ink is the same as the diameter of the black dot formed with the composite black, the recording density of the black dot formed with the black ink is the same as the recording density of the black dot formed with the composite black. or, an ink jet recording method according to any one of claims 1 to 5, characterized in that more. A black ink and an adjusting means for controlling an electric signal to be applied to the discharging means for discharging each ink droplet of the three color inks having different hues that have a greater permeability to the recording medium than the black ink, In an inkjet recording apparatus that performs gradation color recording by changing the size of the ink dots ejected from the nozzles by adjusting the black dots, the black dots detected from the pixel data after color management are formed when forming the black dots. Based on the diameter and the diameter of the non-black color dot at the position adjacent to the black dot, it is determined whether or not the black dot overlaps with the non-black color dot at the position adjacent to the black dot. when, and black dots at least some of the color dots other than black in a position adjacent to the black dot is determined to be superimposed, Formed by emission port JIT black ink-jet recording apparatus characterized in that a means for forming a black ink in other cases. 8. The ink jet recording apparatus according to claim 7, wherein gradation color recording with a plurality of gradations is performed. The pixel data includes at least the maximum diameter data and the intermediate diameter data as dot diameter data. When forming a black dot, the black dot diameter is the maximum diameter other than black at a position adjacent to the black dot. When at least one of the diameters of the dots of the color is determined to be the intermediate diameter or the maximum diameter, or the diameters of the dots of the colors other than black at the positions adjacent to the black dots are the diameters of the black dots 9. An ink jet printer according to claim 7, further comprising means for forming with composite black when at least one of the maximum diameter is determined to be the maximum diameter, and with black ink in other cases. Recording device.

Images