JP2005238673A - Inkjet recorder and method of inkjet recording - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inkjet recorder capable of outputting a recorded result with high image quality without making a deviation of a deposited position of a dot or a satellite dot conspicuous even when the number of ink colors to be used in the recording is small. <P>SOLUTION: This recorder forms an image on a recording medium by performing the recording of ejecting the ink on the recording medium from a plurality of nozzles on a recording head by moving the recording head over the recording medium two or more times, and the feeding of the recording medium in a direction different from the moving direction of the recording head during the movement in two or more number of times. The recorder has a first recording mode wherein the number of inks to be used in the color recording etc. is comparatively large and a second recording mode wherein the number of inks to be used in the monochrome recording etc. is smaller than that of the first recording mode, and then the recording methods of the recording modes are different from each other. Particularly, a driving frequency of a nozzle of the second recording mode is made to be lower than that of the first recording mode, and then the moving speed of the recording head of the second recording mode is made lower than that of the first recording mode. As a result, the accuracy of a deposited position of a dot is enhanced, and a deposited position of a satellite dot is not so much deviated from that of a main droplet dot. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an ink jet recording apparatus and an ink jet recording method using the apparatus, and more particularly to an ink jet recording apparatus and an ink jet recording method in which the recording method is changed according to the number of ink colors used for recording.

  With the widespread use of digital cameras, image quality comparable to silver halide photography is also required for inkjet recording apparatuses that can easily output captured images to a recording medium such as paper at home. Therefore, conventionally, by performing six-color recording in which low-density inks such as light cyan and light magenta are added in addition to the four color inks of cyan, magenta, yellow, and black, the image quality in the recording result of the color photographic tone image is improved. We are trying to improve.

  In addition, digital cameras of the single-lens reflex type have come to be provided at a relatively low price, and not only color photographic images but also monochrome photographic images are recorded by inkjet recording apparatuses. In this monochrome photographic tone image, cyan (or magenta) and yellow for color tone correction are used in addition to the black ink which is the basic tone of the image. Furthermore, in order to alleviate the graininess at the intermediate gradation, gray is also expressed using light cyan (light magenta) and yellow. In other words, even when recording a monochrome photographic image, the image quality is improved by performing multicolor recording in which a plurality of chromatic colors are added in addition to achromatic black. However, if the landing position deviation of the dots formed by the ejected ink occurs, the desired color is not formed, and when a color other than the achromatic color, which is the basic tone in monochrome image recording, appears in the recorded image, the point is It is very noticeable in the image. Therefore, when performing monochrome recording, it is desirable not to use chromatic ink as much as possible.

  Also, instead of a plurality of chromatic color inks such as cyan, magenta and yellow, a plurality of achromatic inks (gray inks) having different densities are mounted, and a monochrome image is generated using the achromatic inks having different densities. In some cases, recording is performed so as to express gradation, thereby improving image quality (see Patent Document 1).

  On the other hand, when recording all gradations from the highlight to the maximum recording density using only the ink that can output the maximum recording density of the basic color (for example, black ink is equivalent to a monochrome photographic image) In particular, the dot landing position shift becomes conspicuous particularly in the intermediate gradation. For example, in the case of a monochrome image, since the black ink is on a white recording medium, the contrast is higher than that of the color ink, and the spot where the dots are locally concentrated due to the landing position deviation becomes a black streak or the like and is easily noticeable.

JP 2000-177150 A JP-A-10-157102 JP-A-10-278306 JP-A-6-31921 JP-A-6-210854 JP-A-8-258391 JP 2002-337323 A JP 2003-237115 A

  By the way, when an ink jet recording apparatus ejects ink, there are cases where a satellite having a smaller amount of ink than the main droplet is ejected in addition to the main droplet forming dots.

FIG. 7 is a diagram for explaining a satellite generation phenomenon.
The nozzle in the standby state before discharge is stationary with the meniscus being stable ((a) in the figure). When the heater 71 is driven and the ink 72 in the vicinity of the heater causes film boiling ((b) in the figure), the bubbles rapidly expand, and the ink on the discharge port 73 side from the bubbles 74 is pushed out by the generation pressure of the bubbles. ((C) in the figure). The ink that has ejected from the ejection port 73 forms a droplet with its tail pulled (FIG. (D)), and eventually the tail is cut off and is divided into a main droplet 75 and a satellite 76 (FIG. (E)). (F)). Here, as shown in FIG. 8B, if the main droplet 75 and the satellite 76 overlap and land on the recording medium to form one true circular dot, the image quality is not affected.

  However, in the case of a serial type recording apparatus, the recording head always moves in a direction different from the flying direction of the main droplet. For this reason, when the moving speed of the recording head is fast, satellites that have a slower flight speed than the main droplet do not overlap and land on the main droplet, but the main droplet and the landing position shift and form two dots. (FIG. 8A), an elliptical dot may be formed. This is because satellites are smaller in mass and slower in flight speed than main droplets, and are therefore susceptible to the inertial force generated in the direction of movement of the recording head. In addition, the air density of the trajectory may decrease due to the flight of ink droplets, particularly main droplets. In particular, when the adjacent ejection ports are close or when the ejection cycle is short, the air density near the nozzles is noticeably reduced, and the air pressure acts so that the ink droplets are attracted to each other, so that they may deviate from their ideal positions. This phenomenon is greatly affected by satellites that have a smaller mass and velocity than the main droplet.

  The satellite dots overlap with the adjacent main droplet dots in the high gradation portion and are not easily noticeable, but the satellite dots tend to be more noticeable in the intermediate gradation than in the high gradation portion. In particular, with respect to the scanning direction of the recording head, there is an influence such as a reduction in image sharpness due to satellite dots.

  Furthermore, even in the same intermediate gradation, monochrome photo-tone images tend to be more conspicuous in image quality degradation due to satellite dots than color images. This is because, as symbolized when only single color ink is used, as the number of ink colors used decreases, the dot landing position shift and satellite dots tend to stand out in the intermediate gradation. That is, as the number of ink colors used increases, the total amount of ink applied to a predetermined area of the recording medium increases, and as a result, the ink coverage on the surface of the recording medium increases. When the coverage is high, landing position deviation and satellite dots are offset by adjacent dots and are not so noticeable. Conversely, when the number of ink colors to be used decreases, the total amount of ink applied to a predetermined area of the recording medium also decreases, and the coverage tends to decrease. Landing position shifts and satellite dots when the coverage is low, the distance between adjacent dots is longer than when the coverage is high, and the probability of canceling is reduced. Since the probability that many images are seen increases, the color appearance of the recording medium itself periodically fluctuates due to deviations in the landing positions of the dots and satellite dots, resulting in a reduction in image quality. In addition, in the case of a monochrome image, since the ink coverage is originally low by recording only with black ink and the contrast between the color of the recording medium and the ink color is strong, the dot landing deviation and satellite dots are more conspicuous. It will be.

  The present invention has been made in view of the problem based on the relationship between the number of ink colors to be used and the deterioration of image quality. Even if the number of ink colors to be used for recording is small, the displacement of the landing positions of the dots and satellite dots are reduced. An object of the present invention is to provide an ink jet recording apparatus and an ink jet recording method that output a high image quality recording result without conspicuous.

  The inkjet recording apparatus of the present invention scans a recording head in which a plurality of nozzles that eject inks of a plurality of colors are arranged a plurality of times in a predetermined direction on the recording medium, and the plurality of nozzles onto the recording medium at the time of each scanning By performing recording for ejecting the ink from the recording medium and paper feeding for moving the recording medium and the recording head by a predetermined amount in a direction different from the scanning direction of the recording head during the plurality of scans. An ink jet recording apparatus for forming an image on the recording medium, wherein the first recording mode has a relatively large number of ink colors used for recording, and the number of ink colors used for recording is higher than that of the first recording mode. Mode selecting means for selecting a mode for recording from a plurality of recording modes including the second recording mode with few, and recording according to the mode selected by the mode selecting means Control means for controlling the operation, and the control means sets the number of ejections for ejecting ink from the nozzles to the recording medium within a predetermined time in the second recording mode within a predetermined time in the first recording mode. Further, the number of ejections is less than the number of ejections of ink from the nozzles to the recording medium.

  In the recording system of the present invention, a recording head in which a plurality of nozzles that eject inks of a plurality of colors are arranged is scanned a plurality of times on a recording medium in a predetermined direction, and the recording medium is scanned from the plurality of nozzles during each scanning. By performing recording that ejects the ink and paper feeding that moves the recording medium and the recording head relatively by a predetermined amount in a direction different from the scanning direction of the recording head during the plurality of scans, A recording system using an ink jet recording apparatus for forming an image on the recording medium, wherein the first recording mode has a relatively large number of ink colors used for recording, and the number of ink colors used for recording is the first number. Mode selection means for selecting a mode for recording from a plurality of recording modes including a second recording mode that is less than one recording mode, and a mode selected by the mode selection means A recording method determining means for determining a corresponding recording method, and a control means for controlling the recording and paper feeding based on the recording method determined by the recording method determining means, the recording method determining means, The recording method in the second recording mode is a method in which recording is performed with a smaller number of ejections than the number of ejections of ink from the nozzles to the recording medium within a predetermined time in the first recording mode. .

  In the inkjet recording method of the present invention, a recording head in which a plurality of nozzles that eject inks of a plurality of colors are arranged is scanned a plurality of times in a predetermined direction on the recording medium, and the plurality of nozzles are applied to the recording medium during each scanning. By performing recording for ejecting the ink from the recording medium and paper feeding for moving the recording medium and the recording head by a predetermined amount in a direction different from the scanning direction of the recording head during the plurality of scans. An ink jet recording method using an ink jet recording apparatus for forming an image on the recording medium, wherein the first recording mode has a relatively large number of ink colors used for recording and the number of ink colors used for recording. A mode selection step of selecting a mode for recording from a plurality of recording modes including a second recording mode that is less than the first recording mode; and the mode selection step A recording step of forming an image on the recording medium in accordance with the selected mode, wherein the recording step includes a recording method in the second recording mode from the nozzles within a predetermined time in the first recording mode. A method is characterized in that recording is performed with a smaller number of ejections than the number of ejections of ink onto a recording medium.

  By using the present invention, since the number of ink colors used for recording is small, in the second recording mode where the ink coverage in a predetermined area of the recording medium is relatively low, the number of ink colors used for recording is large. Compared with the first recording mode, which has a relatively high rate, the number of ejections in a predetermined time is reduced, and in addition, the scanning speed of the recording head is slowed down, thereby suppressing the deviation in the ejection direction of the ink droplets ejected from the nozzles. , To suppress the difference between the landing position of the satellite and the landing position of the main droplet. Therefore, even if the number of ink colors used for recording is small, it is possible to output a high image quality recording result in which a deviation in dot landing accuracy is minimized. In addition, since the probability that the satellite dot lands away from the main droplet dot is reduced, the sharpness in the specific direction of the image due to the satellite dot is prevented from being lowered.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 shows an example of an ink jet recording apparatus applicable to the present invention. Reference numeral 1 denotes a recording medium made of paper or plastic sheet (hereinafter also referred to as “recording sheet”), and a plurality of recording sheets 1 stacked in a cassette or the like are supplied one by one by a feed roller (not shown). . 3 is a 1st conveyance roller, 4 is a 2nd conveyance roller. These are arranged at regular intervals, and are driven by individual stepping motors (not shown) to convey the recording sheet 1 in the direction of arrow A.

Reference numeral 5 denotes an ink tank connected to a recording head in which a plurality of nozzles for ejecting ink are arranged. Reference numeral 6 denotes a carriage on which the ink tank 5 and the recording head are mounted. The recording head is mounted on the carriage 6 so that the nozzle surface is located at a position facing the sheet 1.
The carriage 6 is connected to a carriage motor 10 via a belt 7 and pulleys 8a and 8b. Accordingly, the carriage 6 is configured to reciprocately scan along the guide shaft 9 by driving the carriage motor 10.

  With the above configuration, the carriage 6 moves in the direction of arrow B from the home position via one end of the recording sheet (this is referred to as “main scanning”). At this time, the recording head ejects ink onto the recording sheet 1 in accordance with the ejection signal. When the carriage 6 moves to the other end of the recording sheet 1, the carriage 6 returns to the home position as necessary to clear the nozzle clogging by the ink recovery device 2, and the conveying rollers 3 and 4 are driven to drive the recording sheet. 1 is conveyed in the direction of arrow A by one line (this is called “sub-scanning”). A mechanism for performing predetermined recording on the entire recording sheet 1 by alternately repeating these recording scanning and paper feeding.

  In this embodiment, as the ink tank 5, four housings of a black (Bk) ink tank 5a, a cyan (C) ink tank 5b, a magenta (M) ink tank 5c, and a yellow (Y) ink tank 5d are mounted. . Here, the cyan ink tank 5b has a two-tank structure with a light cyan (lc) ink tank having a lower density than the cyan ink, and the magenta ink tank 5c is similarly light magenta (lm) having a lower density than the magenta ink. It has a two-tank structure with an ink tank. The ink color to be mounted is not limited to these, and any configuration may be used. In this embodiment, cyan and magenta have a single housing consisting of two tanks of light ink and dark ink. However, the present invention is not limited to this, and the ink tank is a separate housing for each ink color. Also good.

  In addition, the ink tanks are arranged in the order of 5a, 5b, 5c, and 5d from the home position side. However, the present invention is not limited to this, and it is needless to say that other arrangement orders may be used.

Next, the structure of the recording head of this embodiment will be described.
FIG. 2 is a schematic diagram of the recording head of this embodiment, and shows a surface that faces the paper, that is, a nozzle surface. The cyan discharge nozzle row 11C, the light cyan discharge nozzle row 11lc, the magenta discharge nozzle row 11M, the light magenta discharge nozzle row 11lm, the yellow discharge nozzle row 11Y, and the black discharge nozzle row 11Bk are arranged as illustrated. The cyan discharge nozzle row 11C and the light cyan discharge nozzle row 11lc are the ink tank 5b, the magenta discharge nozzle row 11M and the light magenta discharge nozzle row 11lm are the ink tank 5c, the yellow discharge nozzle row 11Y is the ink tank 5d, and the black discharge nozzle. The row 11Bk is connected to the ink tank 5a.

  Each discharge nozzle row has 512 nozzles at a 1200 dpi pitch, and each nozzle is driven separately according to image data to form an image. The ink discharge nozzle rows 11C, 11M, 11Y, 11lc, 11lm, and 11Bk generate small dots with a discharge amount of about 2 ng.

  Each nozzle is filled with ink from the ink tank through the ink path to the vicinity of the ejection opening. A heater is provided for each nozzle. When ink is ejected, bubbles are generated in the ink near the ejection port by the heat generated by the heater, and a predetermined amount of ink is ejected as ink droplets in a predetermined direction by the pressure generated by the bubbles. . As described above, in this embodiment, the bubble jet (R) type ink discharge method is used, but the present invention is not limited to this, and it is needless to say that other ink discharge methods such as a piezo method may be used.

Next, the configuration of a recording system including a host computer and an ink jet recording apparatus will be described.
FIG. 3 is a block diagram showing a recording system in the present embodiment.
The system includes a host computer 101 and an inkjet recording apparatus 201. The host computer 101 includes a CPU 102, a memory 103, an external storage 104, an input unit 105, and an interface unit 106 for the inkjet recording apparatus. On the other hand, the inkjet recording apparatus 201 drives a drive unit that represents a CPU 202 that controls the entire apparatus, a ROM 203 that stores a control program, a RAM 204 that is a work memory, and a head drive unit 205 that controls the drive of the recording head. A driving unit (not shown) for controlling, an I / F unit 206 for interfacing with the host computer 101, a recording method determining unit 207 for determining a recording method according to a recording mode, and the like are provided.

  The CPU 102 of the host computer 101 executes a program stored in the memory 103 to realize color processing, quantization processing procedures, and the like, which will be described later. A portion that performs color conversion processing in the CPU is a color processing unit, and a portion that quantizes the color-processed data is a quantization processing unit. A program corresponding to each processing unit is stored in the external storage 104 or supplied from an external device. The host computer 101 is connected to the inkjet recording apparatus 201 via the interface unit 106, and transmits recording data subjected to color processing and the like to the inkjet recording apparatus 201. The inkjet recording apparatus 201 that has received the recording data determines a recording method by the recording method determination unit 207 according to the recording data, creates ejection data corresponding to each nozzle, and the head driving unit 205 uses the ejection data based on the ejection data. Then, each nozzle is driven to perform recording.

  The system of the present embodiment has a plurality of recording modes for each feature required for the recording result, and records at least a color recording mode for recording a normal color photographic image and a monochrome photographic image. It has a monochrome recording mode. It is assumed that recording is performed by a recording method suitable for each mode according to the user's mode selection.

Next, the flow of image processing in the host computer will be specifically described.
FIG. 4 is a flowchart for explaining image processing, and is a processing flow for outputting input 8-bit (256 gradations) image data for each color of RGB as 1-bit data for each color of C, M, Y, lc, lm, and Bk.

  First, 8-bit data for each color of RGB is converted into 8-bit data for each color of C, M, Y, lc, lm, and Bk according to the output color of the recording device by a three-dimensional lookup table (LUT) in the color processing unit ( Step 401). This process is a process of converting the input RGB color to the output CMY color. Specifically, since the input data is an additive color mixture of three primary colors (RGB) of a light emitter such as a display, it is a process of converting the input data into one that matches the CMY color material used in the inkjet recording apparatus.

  The three-dimensional LUT used for color processing holds data discretely, and the held data is obtained by interpolation processing, which is a well-known technique, and detailed description thereof is omitted here. To do.

  The 8-bit data for each color of C, M, Y, lc, lm, and Bk subjected to color processing is subjected to output γ correction by a one-dimensional LUT (step 402). Since the relationship between the number of recording dots per unit area and output characteristics (reflection density, etc.) is not a linear relationship in many cases, by applying output γ correction, the 8-bit input level for each color and the output characteristics at that time Guarantees linear relationship.

  The above is the description of the operation of the color processing unit, and input RGB 8-bit data is converted into 8-bit data of the color materials C, M, Y, lc, lm, and Bk of the output device.

  Since the ink jet recording apparatus in the present embodiment is a binary recording apparatus, the 8-bit data for each color is quantized into binary data for each color by the quantization processing unit (step 403). As the quantization method, a conventionally known error diffusion method or dither method is used.

  Note that a plurality of three-dimensional LUTs for performing color processing are provided for each condition obtained for the composition of the ink color after conversion and the recording result, and are used properly according to the recording mode. Specifically, in this embodiment, at least two types of three-dimensional LUTs for color recording mode and monochrome recording mode are provided, and processing parameters differ for each LUT. For example, a three-dimensional LUT for a six-color recording mode converts RGB 8-bit data into C, M, Y, lc, lm, and Bk 8-bit data. Note that the color recording mode is not limited to these six colors, and may have a seven-color configuration further including red. Alternatively, it may be configured with only four colors of C, M, Y, and Bk. In addition, it goes without saying that the color recording mode may be further subdivided into a six-color mode and this four-color mode. The three-dimensional LUT for the monochrome recording mode converts RGB 8-bit data into 8-bit data of Bk, C, and Y. In this embodiment, cyan and yellow for color tone correction are added to the ink color in the monochrome recording mode, but only black may be used.

  Similarly, a plurality of one-dimensional LUTs after the three-dimensional LUT may be provided for each mode, or may have a configuration common to each mode.

The flow from user mode selection to recording data generation will be described.
FIG. 5 is a flowchart showing a flow from mode selection to print data generation in the present embodiment.
The user selects a recording mode using an operation screen or operation buttons on the host computer (step 501). For example, when the color recording mode is selected (step 502), color conversion processing is performed by the three-dimensional LUT for the color recording mode (corresponding to the processing of step 401 in FIG. 4) (step 503). On the other hand, when the monochrome recording mode is selected (step 504), color conversion processing is performed by the three-dimensional LUT for the monochrome recording mode (step 505). When the color conversion process in step 503 or 505 is completed, the output γ correction and the quantization correction described above are performed, and print data is generated (step 506).

  In the present embodiment, the recording method differs depending on the recording mode. Therefore, the ink jet recording apparatus side that has received the recording data processes the recording data to create ejection data corresponding to each nozzle in order to change the recording method according to the recording mode.

  The recording method for each recording mode will be described below. Specifically, description will be made based on the following examples. The processing on the ink jet recording apparatus side in FIG. 5 (processing after step 507) will be described in the first embodiment.

  As the number of inks used for recording decreases, the total amount of ink applied to the recording medium decreases, and the ink coverage on the surface of the recording medium decreases. For this reason, when the color recording mode that uses a large number of inks and the monochrome recording mode that uses a small number of inks are recorded by the same recording method, the recording result in the monochrome recording mode is higher than the recording result in the color recording mode. Dot landing position shifts and satellite dots tend to stand out.

  Furthermore, satellite dots tend to be more easily displaced from main droplet dots as the nozzle drive interval is shorter, that is, as the nozzle drive frequency is higher. Here, as shown in FIG. 7 (e), it takes a certain amount of time for the ink to be ejected from the ejection port 73 once and return to the pre-ejection state as shown in FIG. 7 (h). The ink inside tends to become longer as the temperature rises. Therefore, as the nozzle drive interval is shorter, the temperature of the ink in the nozzle rapidly increases, so it takes time until the nozzle returns to the state shown in FIG. That is, if the nozzle drive interval is short, the next ejection operation is performed in the state shown in FIG. 5G without waiting for the state to return to the state (h). In this case, the direction, speed, and dot size are different from ejection in a stable state, and there is a high possibility that satellite dots and main droplet dots land separately.

  Therefore, in this embodiment, in the monochrome recording mode, ink is ejected at a lower nozzle driving frequency when the recording head records a predetermined area than in the color recording mode. Thus, the next discharge can be performed after the nozzle is ready to be discharged. In addition, since the carriage movement speed is reduced in accordance with the nozzle drive frequency, the accuracy of dot landing positions is improved, and landing position deviation is less likely to occur, and the landing positions of satellite dots and main droplet dots are not displaced. The state shown in FIG.

  FIG. 6 is a diagram showing the relationship between gradation and ink usage rate in each mode. FIG. 4A shows the color recording mode, and FIG. 4B shows the monochrome recording mode.

  Comparing the gray levels in both figures, it will be understood that the amount of ink applied to the recording medium is clearly less in the monochrome recording mode. In the monochrome recording mode, black ink is actively used from low gradation to intermediate gradation, and the ratio of black ink in the total amount of applied ink is very high.

  Specifically, the black ink is used so that the luminance γ is about 1.8 from the highlight portion to the highest density portion. Even if black ink used as achromatic ink is used, if the amount of ink used per unit area increases, depending on the type of recording medium, it will have some saturation, resulting in a color that is not suitable for monochrome photography. There is. For this reason, in this embodiment, a small amount of cyan and yellow are added as toning components in order to obtain an original achromatic color. Of these two types of chromatic inks (here, cyan and yellow inks), one kind of chromatic ink (here, yellow ink) is used in the entire density range from the low density area to the high density area, as with black ink. The remaining chromatic color ink (here cyan ink) is used in a smaller amount than the other chromatic color ink (yellow).

  In this embodiment, cyan and yellow are used. However, depending on the recording medium, other colors such as a combination of magenta and yellow may be used. What is important here is that these chromatic color inks are only used as toning components, and are not for generating gray or process black in order to smooth gradation changes. This is to prevent the image quality from deteriorating due to the chromatic color dots appearing on the paper surface and becoming noticeable due to the landing position deviation.

  Furthermore, in order to make it easy to create the color tone and gradation of a monochrome photograph, the amount of ink used from the highlight portion to the highest density portion is designed to increase monotonously for each ink. By doing this, even if there is a mass production variation of the ink jet recording apparatus, the color tone of the highlight portion, the medium density portion, and the highest density portion can be made uniform.

  Here, as described above, in the monochrome recording mode, a recording method in which the nozzle drive frequency is lowered is executed.

  As shown in FIG. 5, in this embodiment, the recording method determination unit 207 of the ink jet recording apparatus determines a recording method based on the recording data transmitted from the host computer. In the color recording mode, high speed recording is selected (step 508). In high-speed recording, output data recorded in one main scan is recorded at a high nozzle drive frequency of 20 kHz, for example, and the carriage main scan speed is 16.7 inches / second.

  On the other hand, in the monochrome recording mode, low speed recording is selected (step 510). In low-speed recording, recording is performed at a nozzle driving frequency of 10 kHz corresponding to half of the nozzle driving frequency in the color recording mode. Then, ejection data corresponding to each recording method is created (steps 509 and 511), and recording is performed based on the ejection data (step 512). In this embodiment, the ejection data is created on the ink jet recording apparatus side, but the present invention is not limited to this and may be created on the host computer side.

  In this way, when recording is performed at a lower drive frequency in the monochrome recording mode, the effect is most effective in the intermediate gradation portion.

  For example, as shown in FIG. 6A, in the color recording mode, an image is recorded mostly with light cyan ink and light magenta ink in the intermediate gradation portion. Therefore, the landing deviations of the ink droplets for two rows of the discharge nozzle row 11lc and the discharge nozzle row 11lm as shown in FIG. 2 are thinned out to 1 / (1/4 for 4 passes) for each main scan. It is recorded in the state. If this is simply compared with the landing deviation, compared to the landing deviation in 1-pass 1-discharge nozzle row recording, since two nozzle rows are used, it is distributed eight times.

  On the other hand, in the monochrome recording mode, as shown in FIG. 6B, an image is recorded with substantially black ink alone. Therefore, if printing is performed in the same four passes as in the color recording mode, the landing deviation of the ink droplets for one row of the ejection nozzle row 11Bk as shown in FIG. 2 is thinned to ¼ for each main scanning. Recorded in state. This is only a four-fold dispersion of the landing position deviation as compared to the landing position deviation of 1-pass / one-discharge nozzle array recording. Since the contrast factor of black is further added to this, the image quality of the recording result of the 4-pass recording in the monochrome recording mode is lower than the recording result of the 4-pass recording in the color recording mode. Yes.

  However, as shown in this embodiment, since the recording in the monochrome recording mode is performed at a low driving frequency, the probability that the ejected ink droplets land on the ideal position is higher than in the color recording mode. The amount of deviation is also reduced. In the 4-pass recording in the monochrome recording mode, the dispersion of the landing position deviation is lower than that in the color recording mode, but since the recording method in which the landing position deviation does not easily occur is used, the total is almost the same as the color recording mode. Image quality can be ensured.

  In the monochrome recording mode, since recording is performed at a low driving frequency, the probability that the satellite dot will land as shown in FIG. 8A is low, and conversely, the probability that it will land as shown in FIG. Therefore, the conventional image quality deterioration occurs, in which satellite dots land on the main droplet dots and land periodically and occur in the main scanning direction, and the black dots appear in the image due to the monochrome recording. Therefore, a high quality image can always be recorded even in the monochrome recording mode.

  Further, as shown in FIG. 9, during the ejection of ink, an air flow existing between the recording head face surface and the recording medium surface forming the nozzle row acts on the ejected ink droplets. Therefore, the flying direction of ink droplets changes. As the deflection in the flight direction increases, the ink landing position deviates from the ideal position. By the way, this airflow becomes larger as the moving speed of the carriage becomes faster, and as a result, the flying direction of the ink droplets is also made to flow largely sideways. Therefore, as described in the present embodiment, by lowering the nozzle drive frequency and lowering the carriage moving speed accordingly, this air flow can be suppressed and the flying direction of the ink droplets can be prevented. it can. As a result, the landing position of the ink droplet does not greatly deviate from the ideal position. As described above, the present invention can be expected to have an effect of increasing the landing position accuracy of ink droplets even in a head / ink configuration in which no satellite is generated.

  When recording in the monochrome recording mode, depending on the recording medium, there is a case where chromatic color toning is not required and only black ink may be used. In this case, the ink usage method, like the black ink usage method in FIG. 6B, monotonously increases the ink usage from the highlight area to the highest density area in order to make it easy to create gradation. To.

  Also in this case, if 8-pass printing is performed in the monochrome recording mode in contrast to 4-pass printing in the color recording mode, image quality deterioration due to landing deviation does not occur even in intermediate gradation recording.

  In addition to the monochrome recording mode, there is a case where color monochrome recording is required commercially. Even in such a case, the number of passes may be increased compared to the color recording mode, and recording may be performed using only ink having a hue corresponding to the required recording hue.

  In the first embodiment, the recording method in the monochrome recording mode and the color recording mode has been described. However, the means of “recording mode with a small number of ink colors used for recording in the present invention performs recording at a lower nozzle drive frequency than in a recording mode with a large number of ink colors used for recording” A color recording mode using only four colors C, M, Y, and Bk (hereinafter referred to as “four-color recording mode”) and a color recording mode using the above-described six colors or seven colors (hereinafter referred to as “six-color recording”). This is also effective in relation to “mode”.

  That is, in the four-color recording mode, the total amount of ink applied to the recording medium at the same gradation tends to be smaller than in the six-color recording mode, and as a result, the ink coverage is also low. Therefore, in the four-color recording mode, by performing recording at a slower driving frequency than in the six-color recording mode, there is a probability that the landing position deviation of the dots and the landing position deviation between the satellite dots and the main droplet dots will occur. As a result, a high-quality recording result can be provided.

1 is a perspective view illustrating an ink jet recording apparatus according to an embodiment of the present invention. FIG. 2 is a schematic diagram illustrating a nozzle row of a recording head. It is a block diagram which shows the inkjet recording system in embodiment. It is a flowchart which shows the flow of a color conversion process and a quantization process. It is a flowchart which shows the flow until recording for every recording mode. FIG. 4 is a graph showing the relationship between gradation values and ink usage ratios, where (a) shows the relationship in the color recording mode, and (b) shows the relationship in the monochrome recording mode. It is an enlarged view showing an ink drop generation phenomenon in an embodiment, and (a) to (h) are diagrams showing changes due to elapsed time of the same nozzle. 5A and 5B are diagrams illustrating landing positions of dots on a paper surface according to a carriage speed in the embodiment. FIG. 5A is an example when the carriage speed is relatively fast, and FIG. 5B is an example when the carriage speed is slow. FIG. 4 is a schematic diagram illustrating a relationship between a flying direction of ink droplets and an air flow generated between a recording head face surface and a recording medium.

Explanation of symbols

1 Recording medium (recording sheet)
2 Head recovery position 3 First transport roller 4 Second transport roller 5 Ink tank 6 Carriage 7 Belt 8 Pulley 9 Guide shaft 10 Carriage motor 101 Host computer 102 CPU
103 Memory 104 External Storage Device 105 Input Unit 106 Interface Unit 201 Inkjet Recording Device 202 CPU
203 ROM
204 RAM
205 Head Drive Unit 206 Interface Unit 207 Recording Method Determination Unit

Claims (8)

A recording head in which a plurality of nozzles that eject inks of a plurality of colors are arranged is scanned a plurality of times in a predetermined direction on a recording medium, and the ink is ejected from the plurality of nozzles onto the recording medium during each scan. , During the plurality of scans, an image is formed on the recording medium by performing paper feeding for moving the recording medium and the recording head relatively by a predetermined amount in a direction different from the scanning direction of the recording head. An inkjet recording apparatus to be formed,
Recording is performed from a plurality of recording modes including a first recording mode in which the number of colors of ink used for recording is relatively large and a second recording mode in which the number of colors of ink used for recording is smaller than the first recording mode. Mode selection means for selecting a mode;
Control means for controlling the recording operation according to the mode selected by the mode selection means,
The control means discharges ink from the nozzles to the recording medium within a predetermined time in the second recording mode, and discharges ink from the nozzles to the recording medium within a predetermined time in the first recording mode. An inkjet recording apparatus characterized in that the number is less than the number of ejections to be performed.   2. The apparatus according to claim 1, wherein, in the second recording mode, the control unit causes ink to be ejected from the nozzles using a nozzle driving frequency lower than the nozzle driving frequency in the first recording mode. Inkjet recording device.   3. The inkjet according to claim 2, wherein in the second recording mode, the control unit scans the recording head at a scanning speed slower than a scanning speed of the recording head in the first recording mode. Recording device.   In the first recording mode and the second recording mode, the control unit is configured to perform a recording operation by scanning the recording head and a sheet having a width smaller than a recording width in the sheet feeding direction recorded by a single scanning of the recording head. 4. The ink jet recording apparatus according to claim 1, wherein the recording operation is completed by a plurality of scans of the recording head by repeating the feeding operation.   The first recording mode is a mode in which an image is recorded using a plurality of chromatic inks, and the second recording mode is not only in addition to the chromatic ink having a smaller number of colors than the first recording mode. 5. The ink jet recording apparatus according to claim 1, wherein the ink jet recording apparatus is a mode in which an image is recorded using chromatic ink.   6. The ink jet recording apparatus according to claim 5, wherein in the image recording in the second recording mode, an achromatic ink is used more than an ink of another color. A recording head in which a plurality of nozzles that eject inks of a plurality of colors are arranged is scanned a plurality of times on a recording medium in a predetermined direction, and the ink is ejected from the plurality of nozzles onto the recording medium during each scan. , During the plurality of scans, an image is formed on the recording medium by performing paper feeding for moving the recording medium and the recording head relatively by a predetermined amount in a direction different from the scanning direction of the recording head. A recording system using an inkjet recording apparatus to be formed,
Recording is performed from a plurality of recording modes including a first recording mode in which the number of colors of ink used for recording is relatively large and a second recording mode in which the number of colors of ink used for recording is smaller than the first recording mode. Mode selection means for selecting a mode;
Recording method determining means for determining a recording method according to the mode selected by the mode selecting means;
Control means for controlling the recording and paper feeding based on the recording method determined by the recording method determining means,
The recording method determining means performs the recording method in the second recording mode by performing the recording with a smaller number of ejections than the number of ejections of ejecting ink from the nozzles to the recording medium within a predetermined time in the first recording mode. And a recording system. A recording head in which a plurality of nozzles that eject inks of a plurality of colors are arranged is scanned a plurality of times in a predetermined direction on a recording medium, and the ink is ejected from the plurality of nozzles onto the recording medium during each scan. , During the plurality of scans, an image is formed on the recording medium by performing paper feeding for moving the recording medium and the recording head relatively by a predetermined amount in a direction different from the scanning direction of the recording head. An inkjet recording method using an inkjet recording apparatus to form,
Recording is performed from a plurality of recording modes including a first recording mode in which the number of colors of ink used for recording is relatively large and a second recording mode in which the number of colors of ink used for recording is smaller than the first recording mode. A mode selection process for selecting a mode;
According to the mode selected in the mode selection step, the recording step of forming an image on the recording medium,
In the recording step, the recording method in the second recording mode is a method of performing recording with a smaller number of ejections than the number of ejections of ejecting ink from the nozzles to the recording medium within a predetermined time in the first recording mode. An ink jet recording method.

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