JP2017109380A - Liquid discharge device and liquid discharge method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid discharge device that can improve properties of a recorded medium and performs fast recording while maintaining recording quality when performing recording on the recorded medium using a first recording liquid used to record image data and a second recording liquid for improving properties of a surface of the recorded medium.SOLUTION: Job data is analyzed to determine an image region and a blank region, recording on the image region is carried out in an M-pass manner using a first recording liquid and in an M-out-of-N pass manner using a second recording liquid, and a recorded medium is conveyed by a conveyance amount corresponding to the M-pass recording. Recording on the blank region is performed in an M-out-of-L pass manner by applying L-pass recording, and the recorded medium is conveyed by a conveyance amount corresponding to the L-pass recording. Here, L, M and N are plus integer satisfying N>L≥M, and L is a multiple of M when L>M.SELECTED DRAWING: Figure 10

Description

  The present invention relates to a liquid ejection apparatus and a liquid ejection method.

For example, an ink jet recording apparatus that discharges a recording liquid onto a recording medium is known as a liquid ejecting apparatus that performs recording on a recording medium, for example, by discharging liquid from an ejection port provided in the liquid ejection head. In a liquid discharge head, a plurality of discharge ports are generally arranged in one or a plurality of rows. There are various types of recording methods using a liquid ejecting apparatus. In the serial type recording method, a liquid is ejected while reciprocating the liquid ejecting head, and the recording medium is in a direction different from the scanning direction of the liquid ejecting head. The desired recording is performed on the recording medium. Further, in the serial type recording method, for a certain place on the recording medium, one-pass recording in which recording is performed by only one scanning of the liquid discharge head, and liquid overlapping by a plurality of scannings while conveying the recording medium. There is multipass recording which performs recording by hitting. Multi-pass recording enables higher-quality recording than one-pass recording, but the time required for recording is longer than one-pass recording. As shown in Patent Document 1, etc., when recording data in which characters and photographs are mixed, one-pass recording is performed on the character portion, and image portions such as photographs are printed in multipass. Therefore, shortening the time required for recording has become mainstream.
As another speed-up method in the serial type liquid ejecting apparatus, for a portion where there is no image data to be recorded, the scanning of the liquid ejecting head is stopped and the recording medium is transported at an increased speed, that is, the recording operation is performed. Skipping has been done.

In a liquid ejecting apparatus, for example, an ink jet recording apparatus, it is important to improve recording quality as well as speeding up. In particular, in a liquid ejecting apparatus that uses a pigment containing a recording liquid, it is a big problem to improve the gloss of the formed recording. Since there is a difference in gloss performance between the pigment-based recording liquid and the base of the recording medium, a technique for making them uniform and improving the gloss has been proposed. For example, as a recording liquid, an almost transparent one for improving glossiness is used, and by recording this recording liquid at a predetermined position, the glossiness of a pigment-based recording liquid or a recording medium can be improved. Proposed. An almost transparent recording liquid for improving glossiness is generally called a transparent ink, a clear ink, or a gloss optimizer, but will be called a clear ink in the following description.
As the almost transparent recording liquid, there are those that improve various properties of the surface of the recording medium in addition to those that improve glossiness, and such recording liquid is also included in the category of clear ink. . As an effective recording method of clear ink, recording on the entire surface of a recording medium, particularly a ground portion of a paper has been proposed.

  In order to make the glossiness of the entire recording medium uniform, it is necessary to apply the clear ink to the entire recording surface of the recording medium including the part where there is no corresponding image data, and take advantage of the gloss characteristics of the clear ink. It is effective. However, since the clear ink is recorded even in the recording mode in which clear ink is recorded on the entire surface and the portion of the image to be recorded that has no image data, it is necessary to transport the recording medium while operating the liquid discharge head. is there. For this reason, the operation of the liquid ejection head cannot be skipped in a blank data portion where no image data exists, that is, in a blank area, resulting in a long recording time. Such a problem is not limited to a liquid ejecting apparatus such as an ink jet recording apparatus that performs recording using black and color recording liquids and clear ink. The first recording liquid for recording on the recording medium according to the image data, and in principle applied to the entire surface of the recording medium in order to improve the properties of the recording medium itself and the recording formation surface. This is a general problem in a liquid ejection apparatus that uses the second recording liquid for this purpose.

JP 2005-335192 A

For data having a region where recording is not performed, such as a blank region, recording is performed using a first recording liquid for performing recording according to the data and a second recording liquid that is also applied to the blank region. There is a need for a device that does not significantly slow down the recording time.
An object of the present invention is to improve the properties of a recording medium and realize high-speed recording while maintaining recording quality when recording is performed using a first recording liquid and a second recording liquid. It is an object to provide a liquid discharge apparatus and a liquid discharge method.

  The liquid ejection apparatus of the present invention is a liquid ejection apparatus that performs recording by ejecting a recording liquid onto a recording surface of a recording medium based on job data, and includes a plurality of ejections that eject a first recording liquid. A liquid ejection head having a first ejection port array comprising outlets and a second ejection port array comprising a plurality of second ejection ports for ejecting a second recording liquid; and a liquid ejection head for a recording medium Scanning means for scanning the recording medium in the main scanning direction, conveying means for conveying the recording medium in the sub-scanning direction, and analyzing the job data so that the recording surface of the recording medium is divided into the first area and the second area. In the first area, the number of passes in multi-pass printing is set to N, and the liquid ejection head scans the liquid ejection head with the scanning unit, and the liquid ejection head performs recording with the first recording liquid. For liquid, M out of N passes Recording is performed, and the recording medium is transported by a transport amount corresponding to the number of passes N by the transport unit. For the second area, the number of passes is set to L, and the liquid ejection head is scanned by the scanning unit. Control means for causing the liquid ejection head to perform recording with the second recording liquid in M of the passes, and transporting the recording medium by a transport amount corresponding to the number of passes L by the transport means. L, M, and N are positive integers, N> L ≧ M, and when L> M, L is a multiple of M.

  The liquid ejection method of the present invention provides a second ejection comprising a first ejection port array comprising a plurality of ejection ports for ejecting a first recording liquid and a plurality of second ejection ports for ejecting a second recording liquid. A liquid discharge method for performing recording by using a liquid discharge head having an exit line and discharging a recording liquid from a liquid discharge head onto a recording surface of a recording medium based on job data. Analyzing and determining the recording surface of the recording medium into a first area and a second area, and main scanning of the liquid ejection head with N as the number of passes in multi-pass recording with respect to the first area The recording is performed with the first recording liquid while scanning in the direction, and the second recording liquid is recorded with M of the N passes, and the recording medium is performed with a conveyance amount corresponding to the number N of passes. And the number of passes for the second region As described above, while the liquid discharge head is scanned in the main scanning direction, the recording with the second recording liquid is performed in M of the L passes, and the recording medium is sub-scanned with the conveyance amount corresponding to the number L of passes. And L, M, and N are positive integers, N> L ≧ M, and when L> M, L is a multiple of M. To do.

  According to the present invention, when recording is performed using the first recording liquid used for image formation or the like and the second recording liquid used for improving the properties of the surface of the recording medium, the recording is performed at high speed. While achieving recording, it is possible to maintain the recording quality and improve the properties of the recording medium.

It is a schematic perspective view which shows a liquid discharge apparatus. It is a schematic diagram which shows the discharge port surface of a liquid discharge head. It is a block diagram which shows the structure of a control circuit. It is a flowchart which shows an image process. It is a figure explaining the hand movement of a liquid discharge head. It is a figure which shows an example of the job data with respect to a recording medium. It is a figure which shows the hand movement of the clear ink data with respect to a skip area. It is a figure explaining the hand movement in 1st Embodiment. It is a figure explaining the determination of the image area | region and a blank area | region in 1st Embodiment. FIG. 6 is a diagram illustrating recording path and hand movement switching according to the first embodiment. It is a figure explaining the determination of the image area | region and a blank area | region in 2nd Embodiment. It is a figure explaining the switching of a recording path and a hand movement in 2nd Embodiment.

  Next, preferred embodiments of the present invention will be described with reference to the drawings. Hereinafter, the present invention will be described by taking the case where the liquid ejection apparatus is an inkjet recording apparatus for multicolor recording as an example. However, the liquid ejection apparatus to which the present invention is applied is not limited to the inkjet recording apparatus. FIG. 1 shows an ink jet recording apparatus which is a liquid ejection apparatus according to a first embodiment of the present invention.

The paper feed roller 101 sandwiches the recording medium 102 with a pair of rollers, and conveys the recording medium 102 in the sub-scanning direction (y direction in the figure) while rotating. The paper feed roller 101 is driven by a paper feed motor and a drive circuit, and has a configuration capable of controlling the transport amount of the recording medium. As the recording medium 102, there are various types such as a sheet form made of paper or plastic, for example. Here, it is assumed that the recording medium 102 is glossy paper. As will be described later, the liquid discharge head 105 includes a discharge port on a surface facing the platen 106.
The liquid discharge head 105 is detachably attached to the carriage 104, and the carriage 104 can be moved to the left and right together with the carriage 104 by moving the carriage 104 to the left and right along the main scanning guide 103 by a carriage motor and a drive circuit. It has become. Thus, recording can be performed by ejecting the recording liquid onto the recording medium 102 while scanning the recording medium 102 with the liquid ejection head 105. The moving direction (the x direction in the figure) of the liquid discharge head 105 is called a main scanning direction. Note that the liquid discharge head 105 is coupled to a liquid supply device (not shown), and the recording liquid is always supplied. The platen 106 is provided below the liquid discharge head 105. The recording medium 102 is disposed between the platen 106 and the liquid ejection head 105 and is held by the platen 106 so that the interval between the recording surface of the recording medium 102 and the liquid ejection head 105 is appropriate. Is set. Although not shown in FIG. 1, the liquid ejection apparatus further recovers the medium supply means for supplying the recording medium 102 to the paper feed roller 101 and the state around the ejection opening of the liquid ejection head 105. Means and a discharge means for taking out the recording medium after recording. The liquid discharge apparatus also includes a control circuit that controls the paper feed motor, the carriage motor, and the liquid discharge head 105 via drive circuits corresponding to each of them. The control circuit will be described later.

FIG. 2 shows the configuration of the liquid ejection head 105. The liquid ejection head 105 includes a plurality of ejection ports 301 that eject recording liquid, and the plurality of ejection ports 301 are arranged as one or a plurality of ejection port arrays. In order to discharge the recording liquid, an energy generating element (not shown) is provided in the vicinity of the discharge port 301, and energy is applied to the recording liquid by applying an electric signal to the energy generating element, and recording is performed from the discharge port 301. Liquid droplets are ejected. The energy generating element is, for example, a heating element, and the recording liquid is locally heated by the heating element to generate bubbles, and a droplet of the recording liquid can be discharged from the discharge port 301 by the pressure of the bubbles. Alternatively, the energy generating element is a piezo element, and droplets can be ejected from the ejection port 301 based on rapid mechanical deformation of the piezo element.
One discharge port array is configured by arranging hundreds of discharge ports, for example, 256 discharge ports at equal intervals in one row. Distance D _N of the discharge port 301 adjacent the discharge port in a column, but is appropriately set by the output resolution of the recording in the case of an ink jet recording apparatus, for example, resolution of 1200 dpi (dpi is number of pixels per 25.4mm Is a unit of about 21 μm. In the following description, it is assumed distance D _N of the discharge port 301 output resolution is a 1200dpi is about 21 [mu] m.

Since multicolor recording is performed here, the liquid discharge head 105 is configured by arranging a plurality of discharge port arrays corresponding to the required number of colors so that each discharge port array corresponds to each color. In general, four colors are formed by adding black (black: K) to three colors of cyan (C), magenta (M), and yellow (Y) to form a color image. Hereinafter, cyan, magenta, yellow, and black may be abbreviated as C, M, Y, and K, respectively. In the example shown here, ejection port arrays 302 to 305 that eject recording liquids of those colors corresponding to four colors of cyan, magenta, yellow, and black are provided as ejection port arrays. Further, the liquid ejection head 105 is also provided with an ejection port array 306 for ejecting clear ink (CL) that improves the gloss performance of the recording medium.
As the clear ink increases in the amount of printing on a recording medium such as paper, the contribution of the clear ink to the gloss increases, and the gloss as a whole increases. Thereby, the difference in gloss from the recording liquids of the respective colors forming the image is reduced, the gloss characteristics of the obtained product (that is, the printed product) are made uniform, and the visual impression of the product is improved. As is clear from this explanation, the recording liquids of four colors of cyan, magenta, yellow and black correspond to the first recording liquid for recording on the recording medium according to the image data. The clear ink corresponds to a second recording liquid that changes at least one of the properties of the recording medium and the properties of the recording surface.

Next, a control circuit in the liquid ejection device will be described. FIG. 3 shows the configuration of the control circuit. The control circuit includes a control unit 401 and an interface circuit 7. The interface circuit 407 is supplied with job data including image data from an external computer or host. The control unit 401 includes a CPU (central processing unit) 402, a ROM (read only memory) 403, a RAM (random access memory) 404, an input / output port 405, and the like. The ROM 403, RAM 404 and input / output port 405 are connected to the CPU 402. A drive circuit 406 and an interface circuit 407 outside the control unit 401 are connected to the input / output port 405. The CPU 402 controls the entire liquid ejecting apparatus with a program stored in the ROM 403. A RAM 404 is used as a work area of the CPU 402, and is a memory area used for storing job data input from the interface circuit 407 and intermediate data during image processing.
The paper feed motor 408 and the carriage motor 409 are driven by a control unit 401 including a CPU 402 via drive circuits 411 and 412 connected to the paper feed motor 408 and the carriage motor 409, respectively, and operate the paper feed roller 101 and the carriage 104 by a predetermined amount at a predetermined timing, respectively. . The liquid discharge head 105 is driven for each discharge port by the control unit 401 via the drive circuit 406. Specifically, the ejection timing of each of the ejection port arrays 302 to 306 that eject the recording liquid and the clear ink of each color of CMYK is controlled for each ejection port by the drive circuit 406 that drives the energy generating element. The control unit 401 corresponds to the control unit, the paper feed motor 408 corresponds to the transport unit, and the carriage motor 409 corresponds to the scanning unit.

  The recording operation in this liquid discharge apparatus, that is, the recording liquid discharge operation is performed as follows. First, when a recording execution command signal is input to the liquid ejecting apparatus, the recording medium 102 is supplied from the upper right direction in FIG. 1 by the medium supply unit until the leading end thereof reaches the position of the paper feed roller 101. Thereafter, in response to a signal from the control unit 401, the recording medium is fed by the paper feed roller 101 so that the liquid ejection head 105 is positioned at the recording start position on the recording medium. The job data is input to the control unit 401 through the interface circuit 407, and the input job data is subjected to image processing by the control unit including the CPU 402 and the RAM 404, and converted into data that can be actually recorded. The image data of the image area given to the control unit 401 is generally in an RGB 8-bit format image format having values for each component of red (R), green (G), and blue (B). .

FIG. 4 shows an overview of image processing. When job data is generated on the host side (step 501), color correction and resolution conversion are performed on the job data by a printer driver or the like (step 502). The job data subjected to color correction and resolution conversion is stored in the RAM 404 via the input / output port 405 in the control unit 1. By resolution conversion, the resolution of job data to be supplied to the control unit 401 is converted to a predetermined input resolution. In many cases, the input resolution is 300 dpi or 600 dpi. In the example described here, it is assumed that the input resolution is 600 dpi.
Next, the control unit 401 analyzes the job data stored in the RAM 404, and records image data in an image area, which is an area where recording is actually performed on the recording medium, and recording on the recording medium. The data is divided into data corresponding to blank areas that are not performed. The image area corresponds to the first area, and the blank area corresponds to the second area. This process is called image discrimination, and this determines a blank area to which only clear ink is applied. Details of the image discrimination will be described later.

Since the image data 511 in the image area is an RGB image format, in step 512, the control unit 401 uses the CMYK format in which the recording liquid colors cyan, magenta, yellow, and black are represented by four color components. Convert to data. Subsequently, in step 513, the control unit 401 uses the output correction table held on the ROM 403 to correct each recording liquid color of the image data so as to match the density characteristics of the recording liquid color. Further, in step 514, the control unit 401 performs resolution conversion so that the resolution of the image data matches the resolution of the ejection port array of the liquid ejection head and the recording resolution in the main scanning direction. After the resolution conversion, the control unit 401 performs binarization processing in step 515 and converts the data into data that can be recorded by ejection from the liquid ejection head 105. Further, in step 516, the control unit 401 performs multi-pass division processing on the binarized image data and distributes the binarized image data to each path. Thereafter, recording for each pass is performed based on the distributed data of each pass (step 504).
Here, path distribution will be described. The number of passes of the liquid discharge head for recording on each point on the recording medium, that is, the number of passes varies depending on the required recording quality, but usually the number of passes N is 2 or more. Generally, the number of passes N is set to a value from 2 to 32. When printing is performed so as to form a color image during N-pass printing, data obtained by dividing the color image data by 1 / N with respect to the length of the ejection port array is used as image data for each pass. . The image data of each pass is transferred to the liquid ejection head 105 as a drive signal for ejecting the recording liquid from the corresponding ejection port of the liquid ejection head 105. Recording is performed while the liquid discharge head 105 is scanned in the main scanning direction, and when one scan (that is, recording to the pass) is completed, recording is performed for a length corresponding to 1 / N of the length of the discharge port array. The medium 102 is conveyed in the sub-scanning direction, and then the next pass recording is started. In the following description, it is assumed that the number of passes N is 8, and the recording of the image data on the recording medium is completed by the recording of 8 passes.

Next, clear ink recording will be described. Clear ink data for determining recording of the clear ink on the recording medium is generated in the control unit 401 (step 523), and image processing is performed as 8-bit single plane data, similarly to a single color plane such as cyan or magenta. Is made. In this embodiment, since the blank area 521 is recorded with clear ink in a form different from the image area, a recording ratio indicating which form is to be recorded is given to the control unit 401 in step 533. And used to generate clear ink data. By performing image processing on clear ink data as 1 plane data with 8 bits, it is possible to use the same mechanism as image processing on image data in CMYK, as if it were the fifth color data. Processing can be performed.
The generated clear ink data is subjected to resolution conversion (step 524), binarization processing (step 525), and multi-pass division (step 526) in the same manner as CMYK image data. Used for recording (step 504). However, the multi-pass division of the clear ink data is different from the multi-pass division of the CMYK image data. With respect to the clear ink data, the data is not distributed evenly to the N passes, but the data is sent only to a specific pass, and printing with the clear ink is performed only in the specific pass.

Hereinafter, the multi-pass printing of each of the image data and the clear ink data will be described. FIG. 5 is a diagram showing the movement of the liquid ejection head, and shows the division of the path for color image data and clear ink data and the operation of the liquid ejection head. FIG. 5A shows the movement of the color image area, that is, the movement of the CMYK data, and FIG. 5B shows the movement of the blank area, that is, the clear ink (CL) data. Here, the term “hand movement” means a series of controls relating to the position of the liquid ejection head with respect to the recording medium, the ejection port used for ejecting the recording liquid, and the unused ejection port where ejection of the recording liquid is restricted.
In FIG. 5 showing the hand movement and the following figures, the vertical direction indicates the direction along the conveyance direction of the recording medium, and here the recording medium is conveyed in the direction of the arrow y in the figure. The horizontal direction indicates each path. Therefore, the left and right directions indicate the passage of time, and the process progresses toward the right. The numbers indicated by [1], [2], etc. indicate the number of the path. Although black or white squares are drawn continuously in the vertical direction in the figure, the length of this continuous portion for each pass corresponds to the ejection port length in the liquid ejection head. In the illustrated example, for example, in the first pass ([1]), since eight black squares are continuous, it is shown that the discharge port array is divided into eight equal parts and each is divided into passes. Yes. The length in the vertical direction of each square in the figure indicates the conveyance amount of the recording medium for each corresponding pass. Black squares indicate that recording is performed according to image data (or clear ink data), and white squares indicate that the recording is performed without performing recording.

In the liquid ejection apparatus of this embodiment, for example, 8-pass printing is performed on the image area, and the number of divided passes is reduced for blank areas to which only clear ink is applied, so that the recording medium per pass is reduced. The conveyance amount is increased to enable high-speed recording as a whole. FIG. 5 illustrates the hand movement in the image area. Here, as a preparation for explaining the reduction of the number of passes in the blank area, the reduction of the clear ink recording ratio will be described.
In the case shown in FIG. 5, in the first pass ([1]), recording is performed using recording liquids of CMYK colors used for forming a color image as shown in FIG. As shown, clear ink is also recorded. After the first pass ends, and conveys the recording medium to 1 / N of the length L _H of the discharge port array as transport amount L _P, start a second pass ([2]). In the second pass, recording is performed using the recording liquids of each color of CMYK, but the clear ink is idled without recording. The third and fourth passes are recorded in the same manner as the second pass. In the fifth pass ([5]), recording with recording liquids of CMYK colors and recording with clear ink are performed. In the sixth to eighth passes, recording is performed with CMYK recording liquid, but recording with clear ink is not performed. When such a recording operation is performed, N-pass recording is performed on the image data, but clear ink is recorded M times smaller than N at the same location on the recording medium. This is substantially M pass recording (where N> M). M is set as a positive integer that is a divisor of N.

By increasing the amount of clear ink applied to the recording medium, the gloss contribution from the clear ink becomes greater than the glossiness of the ground portion of the recording medium. As a result, the difference in gloss from the recording liquid of each color forming the image is reduced, the gloss characteristics in the product obtained by recording are made uniform, and the visual impression of the product is improved. As described above, in the recording in which the number of passes of the clear ink is limited as compared with the recording liquids for each color of CMYK, the maximum amount of clear ink to be applied is limited to 100%. However, the improvement of the gloss characteristics by the clear ink does not necessarily require a printing amount of 100%, and even when the clear ink is recorded and applied even when the clear ink is recorded at a recording ratio of 10% to 50%. The effect of improving the gloss of the product can be obtained.
The upper limit of the clear ink recording ratio is determined by the ratio of the number of passes N for the color recording liquid and the number of actual passes M for the clear ink. In the case of this embodiment, if the clear ink data is to be recorded on the entire surface of the recording medium such as a 100% solid image, N = 8. Recording at a maximum recording ratio of 12.5% is possible. Further, since M = 2 and the clear ink data is distributed to the two passes, it is possible to record the clear ink at a recording ratio of 25% at the maximum. Clear ink recording at a recording ratio of 25% has a certain effect on improving gloss performance. If the clear ink recording ratio is set to 25%, clear ink dots are recorded in white pixels at a ratio of 25% of all white data pixels. The dot arrangement of the clear ink may be a random pattern or a regular pattern, but it is desirable that the dot arrangement be as uniform as possible per area in the white data portion on the recording medium.

Methods for adjusting the clear ink recording ratio include a method of changing the distribution of the clear ink recording pass and a method of increasing or decreasing the data of the generated clear ink. In the above-described method, clear ink is recorded in the first and fifth passes. However, in the method of changing the distribution of passes, the clear ink is further recorded in the third and seventh passes. Clear ink is recorded in 4 passes. If the clear ink recording is distributed in four passes in this way, the recording ratio is 12.5% at the maximum per pass, so that the clear ink recording ratio as a whole can be set to 50% at the maximum. This method deteriorates the high-speed recording in a line where image data is not recorded, but can be an effective method when more clear ink is to be printed.
On the other hand, in the method of increasing / decreasing the clear ink data, the generated clear ink data is not 100% solid image but data corresponding to, for example, 80% image. The clear ink is recorded in two of the eight passes in total, and the maximum print ratio of 12.5% is achieved in each pass. Therefore, if the data corresponding to 80% is used, the result is the clear ink. The driving amount is 20% (= 2 × 12.5 (%) × 80 (%)). If the clear ink data to be generated can be changed by entering the recording ratio on the operation panel provided on the liquid ejection device or adjusting the increase / decrease of the recording ratio, the clear ink can be cleared within the maximum ink ejection range. It is also possible to adjust the ink recording amount. By combining these, it is possible to adjust the recording ratio for clear ink.

Next, a description will be given of shortening the overall recording time by changing the number of passes for the image area and the number of passes for the blank area, which is characteristic in the liquid ejection apparatus of the present embodiment. FIG. 6 shows an example of job data to be recorded on the recording medium. The contour of the job data 701 corresponds to the contour of the recording surface of the recording medium, and the recording medium is conveyed in the y direction in the figure. In the job data 701, image areas 702 and 703 including a color image and the like are arranged on the upper and lower sides in the figure along the y direction. Between these image areas 702 and 703, there are blank areas that are not intended to record an image. It has become. When recording the image area 702 with the recording liquids of CMYK colors, N-pass multi-pass recording is performed. Although clear ink is also recorded in the image area 702 at a small recording ratio, it is assumed here that substantial M-pass recording is performed in the same manner as described above using a limited number of N passes. Specifically, printing with clear ink is executed only in M passes among N passes in N pass printing.
As the recording medium is transported, if the position where recording is performed by the liquid ejection head is in the blank area, as shown in FIG. FIG. 7A shows the movement of image data with respect to the recording liquids of CMYK colors. In the blank area, recording with the recording liquids of CMYK colors is not performed at all. On the other hand, FIG. 7B shows the movement of the clear ink data. For clear ink data, printing is performed in M passes among L passes in L pass printing. Here, L is a number smaller than N, and is set to a multiple of M that is M or larger than M. L is preferably set to an integer multiple of N. In other words, L, M, and N, which are all positive integers, have the relationship that N> L ≧ M, and when L> M, L is a multiple of M. With such a hand movement, the conveyance amount L _P2 of the recording medium in the blank area becomes 1 / L of the length L _H of the ejection port array in the liquid ejection head per pass, and since N> L, the conveyance speed is growing. Therefore, it is possible to record at a higher speed than the N-pass recording used for the image data. Thereafter, the image area 703 is returned to the N pass recording again and the remaining image data is recorded.
By performing clear ink recording in this way, it is possible to record an image including a blank area at a higher speed as a whole than normal multi-pass recording while improving gloss characteristics. In addition, since the recording of the image portion is N-pass recording and the relationship that clear ink is performed by M-pass recording is maintained regardless of whether it is an image area or a blank area, even if the hand movement is changed, The influence can be made as small as possible.

The operation of the first embodiment described above will be described in more detail. FIG. 8 shows the movement of the image data for the image data (FIG. 8A) and the movement of the clear ink data (FIG. 8B). The way of viewing this figure is the same as that described with reference to FIG. 5. However, since the ejection port array is composed of 256 ejection ports and 8-pass printing is performed, the transport amount L _P per pass of the recording medium is This is equivalent to 32 outlets. If the input resolution is 600 dpi and the recording resolution is 1200 dpi, the transport amount L _P1 per pass corresponds to 16 pixels on the image data. Further, assuming that the liquid ejection head 105 is reciprocated by the carriage 104, recording is performed both in the forward path and in the backward path.
First, the number of passes in multi-pass printing for each color of CMYK and the number of passes used for clear ink printing are set. In the example shown in FIG. 8, recording is performed by equally dividing the recording liquid of each color of CMYK into 8 passes as shown in (a). At the same time, for clear ink, as shown in (b), the clear ink data is divided into the first pass and the fifth pass among the 8 passes for the image data, and is distributed so as to be substantially two passes. .

In the first pass, clear ink is recorded in the image area, and clear ink is recorded for a blank portion in the main scanning direction as viewed from the image area. After recording, the paper feed motor is driven to transport the recording medium. Since the number of ejection ports in the liquid ejection head is 256 and the number of passes N is 8, the transport amount L _P per pass is a length corresponding to 32 ejection ports.
In the second pass, recording is performed on the return path. At this time, the recording is performed with the recording liquids of each color of CMYK, but the recording with the clear ink is not performed, and the free running is performed. After recording, the recording medium is conveyed for one pass. In the third pass, the forward recording is performed with the recording liquids of each color of CMYK, but the recording with the clear ink is not performed. After recording, the recording medium is conveyed for one pass. In the fourth pass, the return path is recorded with the recording liquids of each color of CMYK, but the recording with the clear ink is not performed. After recording, the recording medium is conveyed for one pass. In the fifth pass, recording is performed in the same manner as in the first pass, and in the sixth through eighth passes, recording is performed in the same manner as in the second through fourth passes, whereby recording by reciprocating scanning is executed. Here, since the number of passes N is 8, after the eighth pass is completed, if there is still unrecorded image data, the processing from the first pass is repeated. As a result of such recording, recording with clear ink is performed only in the first pass and the fifth pass in the recording with the recording liquids of CMYK colors, and is executed in the remaining 2-4, 6th to 8th passes. Without running. As a result, printing with clear ink is substantially two-pass printing using only the forward path.
Clear ink is effective in improving gloss if it is evenly recorded. The unevenness of the clear ink itself is less noticeable than the recording liquids of the respective colors, and therefore, even if the recording is performed by thinning out in this way, the influence on the recording quality is small. Taking into account the absorption characteristics of clear ink, it is advantageous to record in the first pass and the fifth pass that can be recorded at similar intervals in time. In addition, since it is difficult to adjust the registration of the clear ink with the liquid ejection head, printing only in the forward path or only in the backward path is advantageous in suppressing variation in dot positions due to the clear ink.

Next, an image area 702 and an image area 703 as shown in FIG. 6 are divided along the conveyance direction y of the recording medium, and there is a blank area that is not recorded with image data between them. In this case, conveyance of the recording medium and switching of the number of passes will be described. The control unit 401 reads the job data 701, analyzes the job data in the main scanning direction by dividing the image from the top in the sub-scanning direction, and includes an image area (non-white background portion) such as a photograph or a character and a blank area (blank data). ). An example of the discrimination result is shown in FIG. Assuming that the image data is in an RGB 8-bit format, the area where the values of R, G, and B components are all 255 is continuously connected within a certain range. Determine that there is. According to this determination method, the blank area is an area that does not include an image to be recorded over the entire width in the main scanning direction on the recording surface of the recording medium. Here, the unit for dividing the image is the transport amount of the recording medium per pass. As indicated by a broken line in the figure, the image is divided into a band-shaped area extending in the main scanning direction. This band-shaped area is referred to as an image data section. For example, when the number of ejection ports in the ejection port array is 256 and the number of passes N for the image area is 8, the unit for dividing the image is 32 ejection port units. The number of pixels on the image data corresponding to this is 16 pixels when the resolution of the input image is 600 dpi and the discharge port interval is equivalent to 1200 dpi.
If the image data section is a blank area, the control unit 401 records the image start position (coordinates) and the rear end coordinates in the RAM 404. Thereafter, when the blank area continues in the main scanning direction, the coordinates of the trailing edge of the blank area are updated and stored in the RAM 404. Assuming the job data shown in FIG. 6, in the determination result, the start position of the blank area is the coordinate 1001 shown in FIG. 9, and the end of the continuous blank area is the coordinate 1002 in the figure. The image areas are determined to be the areas 1003 and 1004 including the image areas 702 and 703, and the area 1005 between the coordinates 1001 and the coordinates 1002 is a blank area.

Next, a section in which the conveyance amount of the recording medium is changed according to the blank area, that is, a skip section 1010 is obtained. The control unit 401 obtains the rear end coordinate 1007 of the image data section 1006 following the rear end coordinate 1002 of the continuous blank data, and stores this coordinate 1007 in the RAM 404 as the skip position end position. Next, a blank area 1005 from the coordinate 1007 along the sub-scanning direction is a unit corresponding to the transport amount of the recording medium per pass with the number of passes L used in the clear ink only recording area (that is, the blank area). Are cut out sequentially. Then, the rear end coordinates (coordinate 1001 in the present embodiment) of the image data section at the time when the image data cannot be cut due to the appearance of the image data are stored in the RAM 404 as the skip start position.
After determining the image area, the control unit 401 determines an area for recording the clear ink. For clear ink, whether or not printing is possible can be set for each of the image area and the blank area, and printing can be performed at different recording ratios. When there is blank data other than a non-blank portion in the image area, the blank data is recorded with clear ink using a normal transport amount with respect to the recording medium. For this reason, the white data portion in the image data is determined as a clear ink region.

FIGS. 10A and 10B schematically show the switching of the hand movement from the image area to the blank area. (A) shows the movement of the image data to be recorded with the recording liquids of CMYK colors, and (b) shows the movement of the clear ink. In the case of the job data 701 shown in FIG. 6, in the image determination step, as shown in FIG. 9, the recording up to the coordinates 1001 on the image stored in the RAM 404 is performed in the above-described image area path and recording medium conveyance. It is carried out with the quantity L _P1 . When the recording up to the coordinate 1001 is finished, the recording by the 8-pass recording on the image in the image area 1003 is completed, and the image is formed. With the recording until just before reaching the coordinates 1001, the recording of the clear ink is completed up to the area corresponding to the four passes of the head part of the blank area 1005 (the area corresponding to the recording of the fifth pass in FIG. 8). ing. In the recording after reaching the coordinate 1001, since it is a blank area 1005, recording with recording liquids of each color of CMYK is not performed, and only clear ink is recorded.
When recording only clear ink, the pass number L is a value smaller than N and is set to M or an integral multiple of M. When clear ink is recorded in the blank area 1005, the transport amount L _P2 of the recording medium per pass is 1 / L of the length of the ejection port array, which is the transport amount during N-pass recording. Since it is larger than L _P1, recording can be performed faster than in N-pass recording. In the example described here, N = 8 and M = 2 as described above, and L = 4, that is, a recording operation corresponding to 4-pass recording is performed.
In the blank area 1005, clear ink is recorded in the forward path of the reciprocating scan of the liquid ejection head. After recording in the forward path, the recording medium is transported by a conveyance amount corresponding to 4-pass recording, that is, 64 ejection openings, the next path (second path) is idle, and the carriage is moved in the backward direction. Thus, the recording medium is conveyed by 64 ejection openings. In the third pass, clear ink is recorded in the same manner as in the first pass, and in the fourth pass, as in the second pass, printing is not performed and the carriage is returned, and the recording medium is returned to 64. Carries only the discharge port. By repeating this operation, clear ink is recorded on the blank area by 4-pass printing.

  If recording of the blank area 1005 is continued as described above, recording proceeds to the position of the next image area 703, and image data appears. Therefore, switching of the path movement when image data appears from the blank area 1005 which is the white background data portion will be described with reference to FIGS. (C) shows the movement of the image data, and (d) shows the movement of the clear ink data. On the blank area 1005 side, the above-described clear ink four-pass printing is performed up to the coordinates 1007 which is the end of the skip section 1010. When four-pass printing with clear ink (substantially two-pass printing because only the forward path is completed), from timing 1201, the transport amount of the recording medium is a value corresponding to eight-pass printing, in this case, 32 ejection ports. Switch to the corresponding length. Thereafter, recording of the image area 1004 starts on the return path, and thereafter, the recording with the recording liquids of each color of CMYK in the above-described 8-pass recording and the recording with the clear ink by the 2-pass recording are substantially performed. Repeat until the end of the data. At this time, as described above, the recording with the clear ink is performed only in the first pass and the fifth pass in the recording with the recording liquid of each color of CMYK.

In this way, whether it is an image area or a blank area, the recording liquid of each color of CMYK is recorded by N-pass printing (here, 8-pass printing), and the clear ink is substantially printed by M-pass printing. The relationship of recording in (here, two-pass recording) is maintained. In addition, while maintaining such a relationship, the conveyance amount of the recording medium for each pass in the blank area is changed to be equivalent to L-pass printing (here, equivalent to 4-pass printing), so the blank area is faster than the image area. Can be recorded.
Regarding recording with clear ink, the only difference between the image area and the blank area is the conveyance amount of the recording medium per pass. Thereby, uneven discharge of the clear ink and occurrence of streaky discontinuities in the joint portions can be suppressed, and the difference in recording quality can be minimized. Furthermore, in the case of this embodiment, clear ink can be recorded while maintaining the relationship of the recording direction in which recording is performed only in one of the forward path and the backward path, so that the difference in recording quality can be further reduced.
After all the recording on the recording medium is performed by the above processing, the recorded product can be obtained by taking out the recorded recording medium using the discharging unit.

Next, a second embodiment of the present invention will be described.
In the first embodiment described above, the image area and the blank area are discriminated by image processing. Instead of discrimination by image processing, a command for instructing to skip recording is embedded in the job data in accordance with the blank area. You can also. For example, a skip position on coordinates can be determined by using a command indicating CAP (Current Active Pointer) movement as a command embedded in job data. However, the data indicating the CAP position in the job data does not necessarily coincide with the skip section in which the movement of the hand (that is, the change in the transport amount of the recording medium and the number of passes) is performed. Therefore, it is necessary to match the skip position on the job data with the skip position where the hand movement change is performed.
FIG. 11 is a diagram for explaining discrimination between an image area and a blank area in the second embodiment. As job data, a case in which two image areas 702 and 703 and a blank area sandwiched between these image areas are recorded on a recording medium, as shown in FIG. In the figure, image regions 702 and 703 are shown as hatched regions. A start position specified by a CAP movement command included in job data as a command indicating skip is represented by coordinates 1301. The job data includes information related to image size and image resolution in addition to information related to actually recorded image data. In addition, since the recording resolution as the liquid ejection device and the number of passes L for moving the clear ink data are fixed, it is possible to easily calculate the position of the coordinates 1301 in the recording pass. It is.
As shown in FIG. 12, the job data includes a skip start position coordinate 1301 and a skip end position coordinate 1302. A section indicated by an arrow 1311 indicates a skip section by the original CAP movement command. A space between the coordinates 1301 and the coordinates 1302 is a blank area. The control unit 401 can determine in which swath the end position of the skip is based on the coordinates 1302, the recording resolution, and the number of recording passes. At the same time as this determination, the rear end of the swath 1305 is determined. A position coordinate 1304 is obtained. The control unit 401 stores the coordinates 1304 in the RAM 404 as the end position of the skip section. Next, the control unit 401 sequentially cuts blank areas from the coordinates 1304 along the sub-scanning direction in units of transport amount per pass of the recording medium corresponding to the number of passes L used for clear ink data recording. Go. Then, the rear end coordinates (coordinates 1303 in the present embodiment) of the image data section at the time when the image data cannot be cut due to the appearance of the image data are stored in the RAM 404 as the skip start position. A new skip section 1310 is determined between the coordinates 1303 and the coordinates 1304.

FIGS. 12A and 12B schematically show the switching of the hand movement from the image area to the blank area. (A) shows the movement of the image data to be recorded with the recording liquids of CMYK colors, and (b) shows the movement of the clear ink. The image area has the same movement as that shown in FIG. When the swath recording including the coordinates 1301 is completed, the clear ink data is executed by two-pass recording and bidirectional recording from the coordinates 1303 which is the start position of the skip section. At this time, the conveyance amount L _{P2 of the} recording medium is also a value corresponding to two-pass recording. This is to realize clear ink data recording at a higher speed than in the first embodiment. Here, clear ink recording is performed in both forward and backward directions in the scanning of the liquid ejection head. For clear ink, it is difficult to adjust the registration with the liquid discharge head, so it is desirable to perform recording in one direction. However, if the clear ink recording ratio is small, the dots in the clear ink are scattered and recorded. , Uneven gloss is reduced. Therefore, when the clear ink recording ratio is set to a small value, it is possible to receive the advantage of speeding up by bidirectional recording.
FIGS. 12C and 12D schematically show the switching of the hand movement from the blank area to the image area. (C) shows the movement of the image data to be recorded with the recording liquids of CMYK colors, and (d) shows the movement of the clear ink. After recording clear ink data by two-pass bidirectional recording up to the coordinates 1304 at the rear end of the skip section, the first swath 1305 corresponding to the image area is recorded, and the recording liquid of each color of CMYK is recorded by eight passes. Switch to recording. At this time, from the timing 1310 corresponding to the coordinates 1304, it is assumed that the transport amount of the recording medium also corresponds to 8-pass printing, and the clear ink data is substantially 2-pass printing as in the first embodiment. Make a record. By the above operation, the image data can be recorded at high speed as a whole in the second embodiment as well.

105 Liquid discharge head 301 Discharge port 302 to 306 Discharge port array 401 Control unit 408 Paper feed motor 409 Carriage motor 1003, 1004 Image area 1005 Blank area

Claims (6)

A liquid ejection apparatus that performs recording by ejecting a recording liquid onto a recording surface of a recording medium based on job data,
A liquid discharge head having a first discharge port array including a plurality of discharge ports for discharging a first recording liquid and a second discharge port array including a plurality of second discharge ports for discharging a second recording liquid. When,
Scanning means for scanning the liquid discharge head in the main scanning direction with respect to the recording medium;
Conveying means for conveying the recording medium in the sub-scanning direction;
The job data is analyzed to discriminate the recording surface of the recording medium into a first area and a second area, and for the first area, the number of passes in multi-pass recording is set to N. The liquid ejecting head performs recording with the first recording liquid while scanning the liquid ejecting head with scanning means, and the second recording liquid is recorded with M passes out of N passes. The recording medium is transported by a transport amount corresponding to the number of passes N by the transport means, and the liquid ejection head is scanned by the scanning means with the number of passes set to L for the second area. On the other hand, in the M passes out of the L passes, the liquid discharge head performs recording with the second recording liquid, and the transport medium transports the recording medium by a transport amount corresponding to the number L of passes. System And means,
And L, M, and N are positive integers, N> L ≧ M, and when L> M, L is a multiple of M.   The liquid ejection apparatus according to claim 1, wherein N is a multiple of L.   The first area is an area including an image to be recorded, and the second area is a blank area on the recording surface where the image to be recorded is not included over the entire width in the main scanning direction. The liquid ejecting apparatus according to claim 1, wherein the liquid ejecting apparatus is a liquid ejecting apparatus.   The first recording liquid is a recording liquid for recording on the recording medium in accordance with image data, and the second recording liquid has at least the properties of the recording medium and the recording surface. The liquid ejection apparatus according to claim 1, wherein the liquid ejection apparatus changes one of the recording liquids.   5. The liquid according to claim 4, wherein the first recording liquid is at least one of cyan, magenta, yellow, and black, and the second recording liquid is a clear ink. Discharge device. A liquid discharge head having a first discharge port array including a plurality of discharge ports for discharging a first recording liquid and a second discharge port array including a plurality of second discharge ports for discharging a second recording liquid. A liquid ejection method for performing recording by ejecting a recording liquid from the liquid ejection head to a recording surface of a recording medium based on job data,
Analyzing the job data and determining a recording surface of the recording medium into a first area and a second area;
With respect to the first area, the number of passes in multi-pass printing is set to N, and the liquid ejection head is scanned in the main scanning direction while printing with the first recording liquid. For the second recording liquid, N Recording in M of the passes, and transporting the recording medium in the sub-scanning direction with a transport amount corresponding to the number of passes N;
Recording with the second recording liquid is performed in M of the L passes while the liquid ejection head is scanned in the main scanning direction with the number of passes set to L with respect to the second region. Transporting the recording medium in the sub-scanning direction by a transport amount corresponding to the number of passes L;
And L, M, and N are positive integers, and N> L ≧ M, and when L> M, L is a multiple of M.

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