JP2008307722A - Recording device and recording method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a recording device and a method therefor for performing recording by scanning a recording head, wherein uneven density due to a change in strike positions of ink droplets is reduced, and then, the deterioration of image quality is reduced. <P>SOLUTION: In the recording device for recording by multi-pass recording, the recording is carried out by using a mask pattern having a masking ratio that is gradually decreased in the scanning/traveling direction of the recording head in respective forward/backward scanning operations by the recording head. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a recording apparatus and a recording method thereof, and more particularly to a recording apparatus and a recording method thereof that perform recording on a recording medium by reciprocally scanning a recording head.

  Examples of the recording apparatus include a recording apparatus used as a printing unit for an image or the like in a printer, a copying machine, a facsimile, or the like, or a recording apparatus such as a composite electronic device including a computer, a word processor, or a print output device such as a workstation. These recording apparatuses are configured to record an image or the like on a recording medium such as paper or a plastic thin plate based on image information (including all output information such as character information).

  Such a recording apparatus can be classified into an ink jet method, a wire dot method, a thermal method, a laser beam method, and the like depending on the recording method. Among these, an ink jet recording apparatus (hereinafter referred to as an ink jet recording apparatus) performs recording by discharging ink from a recording head onto a recording medium. Compared to other recording methods, it has various advantages that it is easy to achieve high definition, is fast, excellent in quietness, and inexpensive. On the other hand, in recent years, the importance of color output such as color images has increased, and many high-quality color ink jet recording apparatuses comparable to silver salt photography have been developed.

  In such an ink jet recording apparatus, in order to improve the recording speed, a recording head in which a plurality of recording elements each including an ejection port and an ink flow path are integrated is used, and a plurality of the recording heads are provided for color correspondence. Things are common.

  Among inkjet recording apparatuses, serial inkjet recording apparatuses that perform recording while reciprocally scanning the recording head in a direction intersecting the conveyance direction of the recording medium are generally widely used from the viewpoints of being inexpensive and easily miniaturized. ing. Recently, the performance of such an ink jet recording apparatus has been remarkably improved, and a recording speed as high as that of a laser beam recording apparatus has been realized. In addition, with the increase in the processing speed of personal computers and the widespread use of the Internet, the desire for higher recording speeds for color images is also increasing.

  FIG. 1 is a diagram showing an example of the arrangement of ejection openings of a recording head 101 used in such an ink jet recording apparatus, and has a plurality of head chips 102 so that different inks can be ejected. In each head chip 102, an even number of ejection port arrays are arranged on the left side of the ink supply path 105 in FIG. Ink is supplied from an ink supply path 105 through an ink flow path 104 provided corresponding to each ejection port 103.

  FIG. 2 shows the configuration of the main part of an ink jet recording apparatus for performing recording using the recording head. In the figure, reference numeral 201 denotes an ink jet cartridge. These are composed of ink tanks each containing four color inks, that is, black, cyan, magenta and yellow inks, and recording heads 101 corresponding to the respective inks.

  A paper feed roller 203 rotates in the direction of the arrow in the figure while sandwiching the recording medium P together with the auxiliary roller 204, and intermittently conveys the recording medium P in the y direction. Reference numeral 205 denotes a pair of paper feed rollers for feeding a recording medium. The pair of rollers 205 rotates while pinching the recording medium P, like the rollers 203 and 204, but generates a tension in the recording medium by lowering its rotational speed than the paper feed roller 203, and is transported without bending. Is possible.

  A carriage 206 supports the four inkjet cartridges 201 and reciprocates in the direction orthogonal to the y direction (hereinafter also referred to as scanning or scanning). The carriage 206 stands by at the home position h at the position indicated by the broken line in the figure when the recording operation is not performed or when the recovery process of the recording head 101 is performed. Then, when a recording start command is issued, the carriage 206 at the home position h before the start of recording scans in the x direction and is 128/600 inches (about 5 inches) on the recording medium by the 128 nozzles of the recording head 101. .42 mm) width is recorded. When the recording up to the end of the recording medium is completed, the carriage returns to the original home position h, and again performs scanning for recording in the x direction. Before the second recording starts after the end of the first recording, the paper feeding roller 203 rotates in the direction of the arrow to feed the paper in the y direction by a width of 128/600 inches.

  In this way, by repeating the 128/600 inch width recording and paper feeding by the recording head 101 every time the carriage 206 is scanned, for example, one page of recording can be completed. Note that a recording mode in which recording is completed by one recording scan for the same recording area (band) is referred to as a one-pass recording mode.

  Another recording mode used in the ink jet recording apparatus is a multipass recording mode. The multi-pass printing mode is a printing mode in which printing is completed in a plurality of printing scans for the same printing area by performing overprinting in multiple scans.

  Next, the multipass recording mode will be described. Here, a case where so-called two-pass printing, in which printing is completed with two printing scans in the same printing area, will be described as an example.

  When performing this two-pass recording, the carriage 206 at the home position h before the start of recording moves in the x direction when the recording start command is issued, and is moved by the recording head 101 to 64/600 inches (about approx. 2.71 mm) of width is recorded. In scanning at this time, recording is performed based on data obtained by thinning image data in which pixels to be recorded are halved with a predetermined mask pattern. When the recording up to the end of the recording area is completed, the carriage 206 returns to the home position h and again moves for recording in the x direction. The paper feed roller 203 rotates in the direction of the arrow from the end of the first recording to before the start of the second scan, and feeds the paper by a width of 64/600 inches along the y direction. After the second scan, printing is performed with a total width of 128/600 inches (about 5.42 mm) of the recording head 101. Then, all the recording areas are scanned twice by the recording head of each color, and recording is performed for each recording area based on the data thinned by the mask pattern in each scanning. In the above description, the multi-pass recording mode by two overstrikes has been described. Hereinafter, the multipass recording mode by M overstrikes will be referred to as an M-pass recording mode.

  Here, the case of unidirectional recording in which the recording operation is performed only when the carriage moves in the forward direction is shown, but when performing higher-speed recording, the recording operation is performed in both the forward and backward paths of the carriage. In general, bidirectional recording is used.

  FIG. 3 shows a 2-pass mask pattern used in the 2-pass printing mode. In FIG. 3, reference numeral 301 denotes a mask pattern for the first pass, and 302 denotes a mask pattern for the second pass. The mask pattern shown here is a mask pattern corresponding to 4 pixels × 4 pixels, and is a pixel on which pixels that overlap with white recording pixels are recorded among pixels to be recorded determined by image data in each pass. Then, a dot is recorded on the pixel. The first-pass mask pattern 301 and the second-pass mask pattern 302 are staggered and inverted staggered-mask patterns, and the first-pass mask pattern 301 and the second-pass mask pattern 302 are both in an interpolation relationship. is there. Further, in FIG. 3, reference numerals 303 and 304 denote other two-pass mask patterns, showing the first-pass mask pattern 303 and the second-pass mask pattern 304, respectively. These are randomly arranged mask patterns, and the mask pattern 303 for the first pass and the mask pattern 304 for the second pass are both in an interpolation relationship. The 2-pass mask pattern used in the 2-pass printing mode is not limited to the mask pattern shown in FIG. 3, and other patterns are also applied. In general, a mask pattern having a mask rate of 50% is used so that the image data is thinned by half in each pass for both the first pass and the second pass. Here, the recording method in the 2-pass recording mode will be described in more detail with reference to FIG.

  FIG. 4 is a schematic diagram showing a printing method in the 2-pass printing mode.

  FIG. 4 shows the relative positional relationship between the recording head and the recording area when the recording head 101 records from the first recording area to the fourth recording area in the first to fourth scans, respectively. In the figure, the width in the y direction of each recording area is a distance corresponding to 64 nozzles. That is, the length of each recording area in the y direction is equal to half the length of the ejection port array.

  In the first scan, the recording head 101 records the first recording area using a first-pass mask pattern (a staggered mask pattern with a mask rate of 50%). Thereafter, the recording medium is conveyed by a distance of 64 nozzles in the y direction. In the second scan, the recording head 101 records the first recording area using the mask pattern of the second pass (mask pattern having an inverted staggered arrangement with a mask rate of 50%), thereby completing the image of the first recording area. In the second scan, recording is simultaneously performed on the second recording area using the first pass mask pattern. Thereafter, the recording medium is conveyed by a distance of 64 nozzles in the y direction. In the third scan, the recording head 101 records the second recording area using the mask pattern of the second pass, and completes the image of the second recording area. In the third scan, the third recording area is simultaneously recorded using the first pass mask pattern. Thereafter, the recording medium is conveyed by a distance of 64 nozzles in the y direction. In the fourth scan, the recording head 101 records the third recording area using the mask pattern of the second pass, and completes the image of the third recording area. In the fourth scan, the fourth recording area is simultaneously recorded using the first pass mask pattern. Thereafter, an image is completed by performing such a recording operation on all recording areas to be recorded.

  Even in a multi-pass printing mode of two or more passes, high-quality printing is possible by printing using a mask pattern with a mask rate corresponding to the number of passes. It is generally known that the image quality improves as the number of passes increases.

  However, in the multi-pass recording mode, increasing the number of passes also increases the recording time, and there is a problem that a sufficient recording speed cannot be obtained. In order to improve the recording speed, the development of a recording head capable of discharging ink at high speed even when the scanning time for one time is shortened has been underway. Also, development of a technique for achieving high image quality while performing high-speed recording by reducing the number of passes is being promoted.

  Under such circumstances, various proposals have been made for the purpose of outputting images with high image quality and high speed.

  As a technique for achieving high image quality when the number of passes is reduced, for example, image data generated by an area gradation method such as a dither method is masked by applying a thinning pattern having an asynchronous dot arrangement. Is disclosed (see Patent Document 1). In this recording method, by using a mask pattern that is not synchronized with a predetermined dither pattern, the data recording rate in a plurality of passes is equally divided as much as possible to obtain a smooth image. However, this method has limited dither patterns that can be used, and cannot be applied to all binarization methods equally.

  Also, a recording method using a master pattern with randomness is disclosed (see Patent Document 2). According to this recording method, any binarization method can improve the problem of joints in multi-pass recording and image unevenness due to nozzle variation. By the way, when such a master pattern having randomness is used, it is necessary to provide an enormous amount of memory in order to construct a mask pattern applied to a wide range such as the entire surface of the recording medium. For this reason, in practice, a mask pattern of a predetermined size is repeatedly applied to the entire surface of the recording medium. Further, in the printing apparatus, there may be a slight deviation in the dot formation position between printing scans due to a mechanical error that occurs every printing scan. This slight deviation causes the shape (pattern) of the mask pattern applied to each recording scan to stand out on the formed image. Therefore, if a random mask pattern of a predetermined size is repeatedly used as described above, the image quality may be deteriorated such that a mask pattern of a predetermined size appears repeatedly.

  On the other hand, a configuration that apparently does not cause periodic repetition of the random mask by shifting the application start position of the random mask pattern of a predetermined size for each recording scan or changing the shift amount at random. It has been proposed (see Patent Document 3). According to this configuration, even if a pattern of a predetermined size is generated, since it is not regularly arranged, it is possible to suppress a decrease in image quality.

  In addition, when an image is formed by scanning a plurality of times, a recording method that applies an array of mask patterns with low low frequency components and high dispersibility so that the arrangement of recording pixels and non-recording pixels is visually preferable Is disclosed (see Patent Document 4).

  Furthermore, a recording method has been proposed in which the mask ratio of the mask pattern used for each scan of the recording head is different for each scan (see Patent Document 5).

  On the other hand, development of a recording head capable of discharging ink at high speed is also in progress. However, when the ink ejection frequency of the recording head is improved, the recording time required for one scan is shortened, so the temperature rise of the recording head accompanying the ink ejection increases during the scanning, and the ejection amount increases. Will be invited. For this reason, the increase in the discharge amount tends to cause density unevenness in the recording area for each scan. Various methods have been proposed for reducing the density unevenness due to the increase in the discharge amount. For example, a method of detecting the temperature of the recording head and adjusting the ejection amount according to the detected temperature, a method of performing preliminary heating or preliminary ejection immediately before ink ejection to the recording area so as not to cause a temperature difference of the recording head, etc. is there.

  Further, in recent years, in order to achieve higher image quality, development of a recording apparatus capable of recording a high-definition image using a recording head having a small ink droplet size to be ejected has been advanced. Thus, when performing multi-pass printing using a print head with a small droplet size of ink to be ejected, the number of dots for covering the print area is greatly increased. When recording is performed, the recording speed is significantly reduced.

Therefore, even when such a recording head with a small ink droplet size is used, it is necessary to improve the performance of the recording head itself in order to maintain the same recording speed as before. As the method, there are a method of increasing the number of nozzles and increasing the recording width, a method of increasing the ejection frequency, a method of increasing the scanning speed, and a method of reducing the number of multi-pass passes. As described above, the improvement in the image quality of the recorded image and the improvement in the recording speed are gradually progressing.
Japanese Patent Laid-Open No. 5-31922 JP 7-52390 A JP-A-7-125311 JP 2002-144552 A JP 2002-166536 A

  However, as development aimed at reducing ink droplets and improving recording speed is underway, new problems that lead to a reduction in image quality have become apparent.

  Specifically, when the recording head is scanned at a higher speed than before, a phenomenon has occurred in which the flight direction changes greatly due to the air resistance received by the ink droplets ejected from the recording head. Due to the change in the flying direction, the ink landing position is largely shifted, and the image quality is deteriorated. Specifically, as shown in FIG. 5, the landing direction of the dots is such that the flying direction of the ink droplets ejected from the ejection ports at the end of the ejection port array changes, and the density in the area corresponding to the central portion of the recording head becomes higher. The position changes and band-like density unevenness occurs.

  FIG. 6A is a schematic diagram showing the state of each recording area when three types of solid images having the same gradation and different recording densities are recorded by one recording scan in the two-pass recording mode. FIG. 6B is a schematic diagram showing the relationship between the relative change in the ink landing position with respect to the position in the scanning direction (recording position) of the recording head when such recording is performed. In the present specification, the relative change amount of the ink landing position (landing position relative change amount) indicates the ratio of ink droplets whose landing position has changed at each recording position. Also, the lines described in each solid image in FIG. 6A schematically indicate that the ink ejected from the ejection ports outside the line is moved and landed in the direction of the central portion of the recording head 101. It expresses.

  As shown in FIGS. 6A and 6B, the change in the ink landing position gradually changes so that the density of the region corresponding to the central portion of the recording head increases with scanning. Further, the change in the landing position greatly affects the density of the image to be recorded. That is, it can be seen that as the solid image has a higher recording density, the relative change amount of the ink landing position increases and the scanning distance required for the change tends to be shorter.

  In addition, this phenomenon is particularly noticeable when the number of passes is small, when the print head width is long, and when the discharge frequency of the print head is high. From this, the above phenomenon is expected to be largely related to the number of nozzles used in one scan of the recording head, the frequency of use (discharge period), and the arrangement density of the nozzles themselves.

  Conventionally, a recording technique for reducing the degradation of image quality due to such a phenomenon has not been considered. For example, in Patent Document 5, the mask ratio of the mask pattern used for each scan of the recording head is varied for each scan. However, this method is proposed for the purpose of preventing bleeding between inks of different colors, and may not be a method proposed for the purpose of reducing the influence of changes in the landing position of ink droplets. The effect on the above-described density unevenness is not sufficient.

  Therefore, the present invention has been made to solve the above problems. An object of the present invention is to provide a recording apparatus capable of reducing density unevenness due to a change in the landing position of an ink droplet and reducing a decrease in image quality in a recording apparatus that performs recording by scanning a recording head, and a recording method therefor. There is.

The present invention for achieving the above-described object causes a recording head including a recording element array in which a plurality of recording elements are arranged to scan a same area on a recording medium a plurality of times including forward scanning and backward scanning, A recording apparatus that performs recording based on image data that defines pixels to be recorded and a mask pattern for determining pixels that are not to be recorded among the pixels to be recorded in each of the plurality of scans;
The ratio of the mask pattern determined as the non-recording pixel with respect to the number of pixels in the area to which the mask pattern is applied increases in the scanning direction of the recording head.

  Another aspect of the present invention for achieving the above object is to provide a recording head having a recording element array in which a plurality of recording elements are arranged, a plurality of times including forward scanning and backward scanning with respect to the same area on the recording medium. A recording method of performing scanning and recording based on image data defining pixels to be recorded and a mask pattern for determining pixels not to be recorded among the pixels to be recorded in each of the plurality of scans. The mask pattern is characterized in that a ratio of determining the pixel not to be recorded with respect to the number of pixels in an area to which the mask pattern is applied increases in a direction in which the recording head is scanned.

  According to the present invention, it is possible to reduce the influence due to the change in the landing position of the ink droplet, that is, the density unevenness of the recording area, and to reduce the deterioration of the image quality.

  Next, embodiments of the present invention will be described with reference to the drawings.

  In this specification, “recording” (hereinafter also referred to as “printing”) is not only for forming significant information such as characters and figures, but also for images on a wide range of recording media, regardless of significance. A case where a pattern, a pattern, or the like is formed or a medium is processed is also expressed. It does not matter whether it has been made obvious so that humans can perceive it visually.

  “Recording medium” refers not only to paper used in general recording apparatuses but also widely to cloth, plastic film, metal plate, glass, ceramics, wood, leather, and the like that can accept ink. Shall.

  Further, the term “ink” should be interpreted broadly in the same way as the definition of “recording”, and is applied to the recording medium to form an image, a pattern, a pattern, or the like, or process the recording medium. It represents a liquid that can be subjected to the treatment. Examples of the ink treatment include solidification or insolubilization of the colorant in the ink applied to the recording medium.

  Further, “nozzle” (sometimes referred to as “recording element”) collectively refers to an ejection port, a liquid path communicating with the ejection port, and an element that generates energy used for ink ejection unless otherwise specified. Shall.

  FIG. 7 is a block diagram illustrating a control configuration of the ink jet recording apparatus according to the embodiment of the present invention. The mechanical configuration of the ink jet recording apparatus of this embodiment is the same as that shown in FIG.

  In FIG. 7, a CPU 600 executes control and data processing of each part of the apparatus via a main bus line 605. That is, the CPU 600 performs control and data processing of each unit described later including the head drive control circuit 615 and the carriage drive control circuit 616 in accordance with a program stored in the ROM 601. The RAM 602 is used as a work area for data processing by the CPU 600.

  In addition, as a storage unit other than the ROM 601 and the RAM 602, a hard disk (not shown) is provided. The image input unit 603 has an interface with the host device, and temporarily holds an image input from the host device. The image signal processing unit 604 executes various data processing in addition to color conversion and binarization. Further, the image signal processing unit 604 performs a process of thinning out pixels to be recorded in the image data by applying a mask pattern to the generated image data. The operation unit 606 includes keys and the like, thereby enabling control input by the operator. A recovery system control circuit 607 controls a recovery operation such as preliminary ejection in accordance with a recovery processing program stored in the RAM 602. That is, the recovery system motor 608 drives the recording head 101 and the cleaning blade 609 facing the space, the cap 610, the suction pump 611, and the like. The head drive control circuit 615 controls the drive of the ink ejection electrothermal transducer of the recording head 101 and normally causes the recording head 101 to perform preliminary ejection and ink ejection for recording. Further, the carriage drive control circuit 616 and the paper feed control circuit 617 similarly control the movement of the carriage and the paper feed according to the program. Further, the element substrate on which the electrothermal transducer for ink ejection of the recording head 101 is provided is provided with a heat retaining heater, and the ink temperature in the recording head can be heated and adjusted to a desired set temperature. Similarly, the thermistor 612 is provided on the element substrate, and is used for measuring the substantial temperature of the ink in the recording head 101. Similarly, the thermistor 612 may be provided outside the element substrate, or may be provided near the periphery of the recording head. Reference numeral 614 denotes a head temperature control circuit that controls the temperature of the recording head 101.

  Example 1 and Example 2 will be described in detail based on the configuration of the recording apparatus described above.

Example 1
First, Example 1 of the present invention will be described. The recording head used in this embodiment has the same nozzle arrangement (recording element array) as the recording head in FIG. 1 described above, and the configuration of each nozzle is the same as that of the conventional recording head. Specifically, 128 nozzles are arranged at a pitch of 600 dpi (about 42.5 μm). Further, the recording apparatus used in this embodiment has the same configuration as that of the above-described recording apparatus of FIG. 2, and is configured to eject each ink droplet at 4.0 ± 0.5 pl. Furthermore, in this embodiment, similar to that shown in the above prior art, a so-called 2 image is completed by performing a plurality of (two) recording scans (passes) on the same area on the recording medium. Pass recording is to be performed.

  The recording head and the recording method will be described in further detail. An image 1 having a photographic image 1 as a recorded image was prepared with an ink droplet ejection driving frequency of 15 kHz. FIG. 18 schematically shows an image arrangement image of the image 1 on the recording medium. The size of the photographic image 1 is 8 inches (scanning direction of the recording head) × 10 inches (the recording medium). Transport direction).

  FIG. 8 shows a mask pattern used in this embodiment. In FIG. 8, reference numeral 801 denotes a mask pattern used for the forward direction print scan (print scan from left to right in the figure), and the size is 64 pixels (printing medium transport direction) × 4800 pixels (print head scan direction). ). This mask pattern has a length corresponding to the entire area of the recording head in the scanning direction. Further, the mask ratio of this mask pattern continuously changes from 18.75% to 81.25% in the scanning direction of the recording head (the direction from the left to the right in the figure). In other words, the ratio of determining pixels not to be recorded with respect to the number of pixels in the area to which the mask pattern is applied increases in the scanning direction of the recording head. The mask rate referred to here will be described with reference to FIG. 8. Black coating for determining a pixel to be recorded of image data as a pixel not to be recorded in the pass in a predetermined size (4 pixels × 4 pixels) of the mask pattern. Of recorded pixels. Reference numeral 802 denotes a mask pattern used in a recording scan in the backward direction (recording scan from right to left in the figure). The size of this mask pattern is the same as that of the mask pattern 801 used in the forward scanning (outward scanning). Further, the mask pattern has a mask rate that continuously changes from 18.75% to 81.25% in a direction opposite to the mask pattern 801 (the direction from right to left in the drawing). Note that the mask patterns 801 and 802 have a complementary relationship, and printing is performed by repeatedly using them in the forward scan and the backward scan (between a plurality of scans).

  FIG. 9 is a schematic diagram showing the recording operation in the two-pass recording mode using the mask pattern in the present embodiment. The recording head and each recording area when recording from the first recording area to the fourth recording area are shown. The relative positional relationship is shown.

  Each recording area has a distance of 64 nozzles in the y direction. That is, the length of each recording area in the y direction is equal to half the length of the ejection port array.

  The first scan is a print scan in the forward direction (print scan from left to right in the figure), and the first print area is printed using the mask pattern 801. Thereafter, the recording medium is conveyed by a distance of 64 nozzles along the y direction.

  The second scan is a recording scan in the backward direction (recording scan from right to left in the figure), and the first recording area is recorded using the mask pattern 802 to complete the image. At the same time, the second recording area is recorded using the mask pattern 802. Thereafter, the recording medium is conveyed by a distance of 64 nozzles in the y direction.

  The third scan is a print scan in the same outward direction as the first scan, and the second print area is printed using the mask pattern 801 to complete the image. At the same time, the third recording area is recorded using the mask pattern 801. Thereafter, the recording medium is conveyed by a distance of 64 nozzles in the y direction.

  The fourth scan is a print scan in the same backward direction as the second scan, and the third print area is printed using the mask pattern 802 to complete the image. At the same time, the fourth recording area is recorded using the mask pattern 802. Thereafter, the same recording operation is repeated for all recording areas to be recorded.

  Next, the state of the recording area and the relative change amount of the ink landing position when recording is performed by the third scan and the fourth scan will be described. FIG. 10 shows the states of the second and third recording areas recorded in the third scan of FIG. 9 (FIG. 10A) and the relative change amount of the ink landing position with respect to the recording position of the recording head when the recording is performed. It is a schematic diagram which shows the relationship (FIG. 10B).

  As shown in FIG. 10B, the ink landing position gradually changes so as to increase the density of the area corresponding to the central portion of the recording head. The amount of change in the landing position is small in the area near the start of recording scanning. However, as the scanning distance increases, the amount of change in the landing position near the central portion of the recording head increases from the region near the start of recording scanning. However, according to the present embodiment using the mask pattern in which the mask rate decreases in the scanning direction of the recording head, the amount of change is reduced compared to the case where the image having the same recording density shown in FIG. 6 is recorded. (See FIG. 6B). As a result, as shown in FIG. 10A, as the scanning distance becomes longer, the density of the central portion of the recording head gradually increases, but the amount of change in the landing position is less than that shown in FIG. Therefore, it can be seen that density unevenness that occurs can be reduced.

  FIG. 11 shows the states of the third and fourth recording areas recorded in the fourth scan of FIG. 9 (FIG. 11A) and the relative change amount of the ink landing position with respect to the recording position of the recording head when the recording is performed. It is a schematic diagram which shows the relationship (FIG. 11B). In the recording method of the present embodiment shown in FIG. 9, the recording of the third recording area by the fourth scan is performed after the recording by the third scan is performed. However, here, a case where recording is performed in a state where recording by the third scan is not performed will be described.

  Since the fourth scanning is different from the third scanning in the direction of travel, the tendency for the relative change in the ink landing position is opposite to that in the case of recording in the third scanning. Also in this case, the relative change amount of the ink landing position gradually changes so that the recording density in the area corresponding to the central portion of the recording head becomes higher as the scanning distance becomes longer.

  Since the actual recording area is overlapped by these third and fourth scans and an image is recorded, as a result, an image as shown in FIG. 12A is recorded.

  FIG. 12B is a diagram showing an optical density (OD) distribution in a cross section obtained by cutting the recording area shown in FIG. 12A in the X-X ′ direction.

  12C is a diagram showing an optical density (OD) distribution in a cross section obtained by cutting the recording area shown in FIG. 12A in the Y1-Y1 ′ and Y2-Y2 ′ directions.

  As apparent from FIGS. 12B and 12C, in this embodiment, the OD in this recording area is within a certain range, and it can be seen that the density unevenness is reduced. As described above, density unevenness caused by changes in the landing positions of the ink droplets observed near both ends in the scanning direction of each recording area and near the center of the recording head is reduced, and a high-quality image can be obtained. .

  In the above description, the two-pass printing mode has been described as an example. However, the present invention can also be applied to a multi-pass printing mode of three or more times. For example, in the case of the 3-pass printing mode, a mask pattern in which the mask rate continuously changes from 60% to 80% is used in the printing of the first pass and the third pass, which are scanning in the forward direction. Then, in the second pass printing in which scanning in the backward direction is performed, a mask pattern whose mask ratio continuously changes from 40% to 80% may be used. In this way, the mask pattern having a complementary relationship is configured such that the mask rate continuously increases in the scanning direction in each scanning in the forward direction and the backward direction. Further, a different mask pattern may be used for each pass.

  Further, the present invention is not limited to the mask pattern having the mask ratio as described above. Further, it is possible to appropriately select a mask pattern for each recording scan according to the type of ink to be used, the physical properties of the ink, the type of recording medium, the image data, the recording speed, and the like.

(Example 2)
Next, Example 2 will be described. In this embodiment, what is not particularly mentioned is the same as that in the first embodiment.

  In the first embodiment, an example of the 2-pass printing mode has been described. However, in this embodiment, another example of the 2-pass printing mode is shown.

  FIG. 13 shows a recording mask used in this embodiment. In FIG. 13, reference numeral 1301 denotes a mask pattern having 4 pixels × 4 pixels and a mask rate of 18.75%. Reference numeral 1302 denotes a mask pattern having 4 pixels × 4 pixels and a mask rate of 81.25%. The mask patterns 1301 and 1302 have a complementary relationship. Reference numeral 1303 denotes a mask pattern of 4 pixels × 4 pixels and a mask rate of 25%. Reference numeral 1304 denotes a mask pattern having 4 pixels × 4 pixels and a mask rate of 75%. The mask patterns 1303 and 1304 have a complementary relationship. Reference numeral 1305 denotes a mask pattern having 4 pixels × 4 pixels and a mask rate of 37.5%. Reference numeral 1306 denotes a mask pattern having 4 pixels × 4 pixels and a mask rate of 62.5%. The mask patterns 1305 and 1306 have a complementary relationship. Reference numeral 1307 denotes a mask pattern having 4 pixels × 4 pixels and a mask rate of 50%. Reference numeral 1308 denotes a mask pattern having 4 pixels × 4 pixels and a mask rate of 50%. The mask patterns 1307 and 1308 have a complementary relationship.

  FIG. 14 is a schematic diagram showing a series of printing operations in the 2-pass printing mode using the mask pattern in this embodiment.

  FIG. 14 shows the relative positional relationship between the recording head and each recording area when recording from the first recording area to the fourth recording area. Each recording area has a distance of 64 nozzles in the y direction. That is, the length of each recording area in the y direction is equal to half the length of the ejection port array. In this embodiment, each recording area is divided into a plurality of (eight in the case of this embodiment) small areas in the scanning direction, and printing is performed by applying the mask patterns 1301 to 1308 having different mask ratios. In the following description, in order to indicate the position of each of the divided recording areas, the 1-A area to the 1-H area, the 2-A area to the 2-H area, the 3-A area to the 1st area. The description will be made by calling the 3-H region, the 4-A region to the 4-H region.

  In the first scan (recording scan from left to right in FIG. 14A), the recording head 101 records the 1-A area using the mask pattern 1301 (mask ratio 18.75%), and the 1-B area. Is recorded using a mask pattern 1303 (mask ratio 25%). The first 1-C area is recorded using a mask pattern 1305 (mask ratio 37.5%), and the first 1-D area is recorded using a mask pattern 1307 (mask ratio 50%). The first 1-E area is recorded using a mask pattern 1308 (mask ratio 50%), and the first 1-F area is recorded using a mask pattern 1306 (mask ratio 62.5%). The first 1-G area is recorded using the mask pattern 1304 (mask ratio 75%), and the first 1-H area is recorded using the mask pattern 1302 (mask ratio 82.25%). Thereafter, the recording medium is conveyed by a distance of 64 nozzles along the y direction.

  In the second scan (recording scan from right to left in FIG. 14B), the recording head 101 records the first 1-H region using the mask pattern 1301 and records the first 1-G region using the mask pattern 1303. To do. The first 1-F area is recorded using a mask pattern 1305, and the first 1-E area is recorded using a mask pattern 1307. Then, the first 1-D area is recorded using the mask pattern 1308, and the first 1-C area is recorded using the mask pattern 1306. Then, the first 1-B area is recorded using the mask pattern 1304, and the first 1-A area is recorded using the mask pattern 1302, thereby completing the image. At the same time, the second 2-H area is recorded using the mask pattern 1301 and the second 2-G area is recorded using the mask pattern 1303. Then, the second F area is recorded using the mask pattern 1305, and the second E area is recorded using the mask pattern 1307. Then, the second 2-D area is recorded using the mask pattern 1308, and the second 2-C area is recorded using the mask pattern 1306. Then, the second 2-B area is recorded using the mask pattern 1304, and the second-A area is recorded using the mask pattern 1302. Thereafter, the recording medium is conveyed by a distance of 64 nozzles in the y direction.

  In the third scan (recording scan from left to right in FIG. 14C), the recording head 101 records the second-A area using the mask pattern 1301 and the second 2-B area using the mask pattern 1303. To do. Then, the second 2-C area is recorded using the mask pattern 1305, and the second 2-D area is recorded using the mask pattern 1307. The second 2-E area is recorded using the mask pattern 1308, and the second F area is recorded using the mask pattern 1306. Then, the second G region is recorded using a mask pattern 1304, and the second H region is recorded using a mask pattern 1302, thereby completing an image. At the same time, the third-A area is recorded using the mask pattern 1301 and the third-B area is recorded using the mask pattern 1303. Then, the third C area is recorded using the mask pattern 1305, and the third D area is recorded using the mask pattern 1307. Then, the third-E area is recorded using the mask pattern 1308, and the third-F area is recorded using the mask pattern 1306. Then, the third G region is recorded using the mask pattern 1304, and the third H region is recorded using the mask pattern 1302. Thereafter, the recording medium is conveyed by a distance of 64 nozzles in the y direction.

  In the fourth scan (recording scan from right to left in FIG. 14D), the recording head 101 records the third-H region using the mask pattern 1301 and records the third-G region using the mask pattern 1303. To do. Then, the third-F area is recorded using the mask pattern 1305, and the third-E area is recorded using the mask pattern 1307. Then, the third-D area is recorded using the mask pattern 1308, and the third-C area is recorded using the mask pattern 1306. Then, the 3-B area is recorded using the mask pattern 1304, and the 3-A area is recorded using the mask pattern 1302, thereby completing the image. At the same time, the 4-H area is recorded using the mask pattern 1301 and the 4-G area is recorded using the mask pattern 1303. The 4-F area is recorded using the mask pattern 1305, and the 4-E area is recorded using the mask pattern 1307. Then, the 4-D area is recorded using the mask pattern 1308, and the 4-C area is recorded using the mask pattern 1306. Then, the 4-B area is recorded using the mask pattern 1304, and the 4-A area is recorded using the mask pattern 1302. Thereafter, the same recording operation is repeated for all image areas to be recorded.

  Next, the state of the first and second recording areas and the relative change amount of the ink landing position when recording is performed by the first scanning and the second scanning will be described.

  FIG. 15 shows the relationship between the state of the first recording area recorded in the first scan of FIG. 14 (FIG. 15A) and the relative change amount of the ink landing position with respect to the recording position of the recording head when the recording is performed ( It is a schematic diagram which shows FIG. 15B).

  In FIG. 15, when recording is performed using the mask pattern having the recording density as shown in FIG. 13 in the first scan, the change amount of the ink landing position becomes longer as shown in FIG. 15B. It is getting bigger with it. Specifically, as in the case of the first embodiment, the recording density gradually changes so that the recording density in the area corresponding to the center of the recording head increases. The change amount of the ink landing position is small at the end of the recording area near the start of the recording scan. As the scanning distance becomes longer, the amount of change in the landing position near the central portion of the recording head increases compared to the region near the start of recording scanning. However, it can be seen that the amount of change in this embodiment is reduced compared to the case where the image having the same recording density shown in FIG. 6 is recorded (see FIG. 6B). As a result, as shown in FIG. 15A, the density at the central portion of the recording head gradually increases as the scanning distance increases, but the amount of change in the landing position is reduced, thereby reducing the density unevenness that occurs. You can see that it is made.

  FIG. 16 shows the state of the second and third recording areas recorded in the second scan of FIG. 14 (FIG. 16A), and the relative change amount of the ink landing position with respect to the recording position of the recording head when the recording is performed. It is a schematic diagram which shows the relationship (FIG. 16B). In the recording method of the present embodiment shown in FIG. 14, the recording by the second scan for the first recording area is performed after the recording by the first scan is performed. However, here, the case where the first recording area is recorded by the second scanning in a state where the recording by the first scanning is not performed will be described.

  Since the scanning direction of the second scanning is different from that of the first scanning, the tendency of the relative change in the ink landing position is opposite to that in the case of recording in the first scanning. Also in this case, the density gradually changes so that the density of the recording area with respect to the central portion of the recording head increases with scanning.

  Further, since an image is formed by overlapping these two recording scans on the actual recording area, an image is formed as shown in FIG. 17A.

  FIG. 17B is a diagram showing an optical density (OD) distribution in a cross section obtained by cutting the recording area shown in FIG. 17A in the X-X ′ direction.

  FIG. 17C is a diagram showing an optical density (OD) distribution in a cross section obtained by cutting the recording area shown in FIG. 17A in the Y1-Y1 ′ and Y2-Y2 ′ directions.

  From FIG. 17B and FIG. 17C, it can be seen that the OD in this recording area is within a certain range, and density unevenness is reduced. In this way, density unevenness caused by changes in the landing position of the ink droplets seen near both ends of each recording area and near the center in the main scanning direction is reduced, and good image quality with no density unevenness is achieved overall. I was able to get it.

  The present invention is not limited to the mask pattern having the recording density as described above. Further, it is possible to appropriately select a mask pattern for each recording scan according to the type of ink to be used, the physical properties of the ink, the type of recording medium, the image data, the recording speed, and the like.

  Further, in this embodiment, in order to explain the effect particularly easily, each recording area is divided into eight in the scanning direction. However, the number of divisions of the print area is appropriately changed to the optimum number according to the size of the mask pattern, the buffer size for storing the mask pattern, the print speed, the print head drive frequency, the temperature rise characteristic data, etc. May be.

  FIG. 19 is a flowchart showing the recording method of each of the above embodiments.

  First, in step S110, print scanning in the forward direction is performed using a mask pattern so that the mask rate gradually increases. Next, in step S120, the printing scan in the backward direction is performed using the mask pattern so that the mask rate gradually increases. Here, if the recording of all the image areas is completed, the recording is ended as it is. If the recording of all the image areas is not completed, the process returns to step S110 and the recording operation is continued (step S130).

  Each of the above-described embodiments includes a means for generating thermal energy to cause ink discharge, particularly among inkjet recording methods, and uses a method for causing a change in the state of ink by the thermal energy, thereby providing high density recording. And high definition can be achieved.

  In addition to the cartridge-type print head, which is provided with an ink tank integrated with the print head itself, it can be attached to the main body of the device, allowing electrical connection with the main body of the device and supply of ink from the main body of the device. A replaceable chip type recording head may be used.

  In addition, it is preferable to add recovery means for the recording head, preliminary means, etc. to the configuration of the recording apparatus described above, since the recording operation can be further stabilized. Specifically, there are a capping unit for the recording head, a cleaning unit, a pressurizing or suction unit, an electrothermal converter, a heating element different from this, or a preheating unit using a combination thereof. In addition, it is effective to provide a preliminary ejection mode for performing ejection different from recording in order to perform stable recording.

  In addition, the recording mode of the recording apparatus is not limited to a recording mode of only a mainstream color such as black, but at least of a multi-color of different colors or a full color by mixing colors by configuring a recording head integrally or by combining a plurality of recording heads. A device with one can also be provided.

  Further, as a form of the recording apparatus according to the present invention, a copying apparatus combined with a reader or the like, as well as a facsimile apparatus having a transmission / reception function, in addition to an image output terminal of an information processing device such as a computer, which is provided integrally or separately. It may take the form of

FIG. 3 is a schematic diagram illustrating an example of arrangement of ejection ports of a recording head. It is a figure showing an example of composition of a principal part of an ink-jet recording device. It is a figure which shows the example of a mask pattern used for 2 pass printing mode. It is a schematic diagram showing the recording method in 2 pass recording mode. It is a figure which shows typically the recording state at the time of performing high-speed recording in the conventional 2 pass recording mode. FIG. 4 is a schematic diagram illustrating a relationship between a state of a recording area and a relative change amount of an ink landing position with respect to a recording position of a recording head. It is a block diagram which shows the control structure of the inkjet recording device which concerns on the Example of this invention. It is a schematic diagram which shows the recording mask used in Example 1 of this invention. FIG. 6 is a schematic diagram illustrating a recording operation using a recording mask in a two-pass recording mode according to the first exemplary embodiment of the present invention. FIG. 6 is a schematic diagram illustrating a relationship between a state of a recording area in a third scan and a relative change amount of an ink landing position with respect to a recording position of a recording head in Embodiment 1 of the present invention. FIG. 5 is a schematic diagram illustrating a relationship between a state of a recording area in a fourth scan and a relative change amount of an ink landing position with respect to a recording position of a recording head in Embodiment 1 of the present invention. FIG. 6 schematically shows a state in which recording is performed by overlapping the third and fourth scans in Example 1 of the present invention. FIG. It is a schematic diagram which shows the recording mask used in Example 2 of this invention. FIG. 10 is a schematic diagram illustrating a recording operation using a recording mask in a two-pass recording mode in Example 2 of the present invention. FIG. 10 is a schematic diagram illustrating a relationship between a state of a recording area in a first scan and a relative change amount of an ink landing position with respect to a recording position of a recording head in Example 2 of the present invention. FIG. 9 is a schematic diagram illustrating a relationship between a state of a recording area in a second scan and a relative change amount of an ink landing position with respect to a recording position of a recording head in Example 2 of the present invention. FIG. 6 schematically shows a state in which the first and second scans are overlapped and recorded in Example 2 of the present invention. FIG. 2 schematically shows an image arrangement image on an image recording medium used in an embodiment of the present invention. It is a flowchart which shows the recording method of this invention.

Explanation of symbols

101 Recording Head 103 Ink Ejection Port 206 Carriage 301 to 304 Mask Pattern 600 CPU
601 ROM
602 RAM
801, 802 Mask pattern 1301-1308 Mask pattern

Claims (5)

The recording head having a recording element array in which a plurality of recording elements are arranged is scanned a plurality of times including the forward scanning and the backward scanning with respect to the same area on the recording medium, and image data defining pixels to be recorded and A recording apparatus that performs recording based on a mask pattern for determining pixels not to be recorded among the pixels to be recorded in each of a plurality of scans,
The recording apparatus according to claim 1, wherein a ratio of the mask pattern determined as the non-recording pixel with respect to the number of pixels in an area to which the mask pattern is applied increases in a direction in which the recording head is scanned.   The recording apparatus according to claim 1, wherein the mask pattern is a plurality of mask patterns each having a complementary relationship between a plurality of scans that record the same region.   The recording apparatus according to claim 1, wherein the mask pattern has a length corresponding to the same region with respect to a direction in which the recording head is scanned. The mask pattern is a mask pattern composed of a plurality of mask patterns having different ratios, respectively.
Each mask pattern is applied to a small area formed by dividing the same area into a plurality of directions in which the recording head is scanned, and the mask pattern applied to the same area scans the recording head. The recording apparatus according to claim 1, wherein the recording apparatus increases in a direction in which the recording apparatus moves. The recording head having a recording element array in which a plurality of recording elements are arranged is scanned a plurality of times including the forward scanning and the backward scanning with respect to the same area on the recording medium, and image data defining pixels to be recorded and A recording method for performing recording based on a mask pattern for determining pixels not to be recorded among the pixels to be recorded in each of a plurality of scans,
The recording method according to claim 1, wherein a ratio of the mask pattern determined as the non-recording pixel with respect to the number of pixels in an area to which the mask pattern is applied increases in a direction in which the recording head is scanned.

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