JP2007168201A - Ink-jet recording device and recording method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ink-jet recording device capable of outputting a high-definition photo image without "overflow" and "end-part twist" even if it is a high-drive-frequency full-line type recording device, and a recording method. <P>SOLUTION: First (K1)/second (K2) recording heads for discharging ink of the same color are prepared. On that occasion, the number of dots recorded by the first recording head in a plurality of dots adjacent to one dot recorded by the first recording head is set to be smaller than the number of dots recorded by the second recording head. By this, the second recording head can record many of the dots adjacent to the dots recorded by the first recording head after the dots recorded by the first recording head are fixed to some extent. Consequently, it is possible to restrain a overflow since many adjacent dots are not simultaneously imparted to a recording medium. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an ink jet recording apparatus that includes a recording head having a plurality of ejection openings and performs recording by ejecting ink droplets onto a recording medium.

  With the development of OA equipment such as computers, word processors, and copying machines, many recording devices for outputting information on these equipment are also provided. Among the recording devices, the recording device adopting the ink jet recording method has many excellent features such as high definition, high speed, excellent quietness, and low cost. Widely used by a wide range of users including personal users.

  In such an ink jet recording apparatus, an image is formed by ejecting ink from a recording element called a nozzle in accordance with an image signal and attaching it to a recording medium. Therefore, in order to output a high-definition image at high speed, generally, a recording head (hereinafter also referred to as a multi-head) constituted by a large number of recording elements integrated and arranged at high density is used. Further, in order to cope with colorization, many are provided with the recording heads for a plurality of colors.

  In the case of a color inkjet recording apparatus, different from recording only a character as a monochrome printer, various image elements such as color development, gradation, and uniformity are regarded as important. In particular, with regard to uniformity, slight nozzle unit variations that occur due to differences in the multi-head manufacturing process affect the amount of ink ejected from each nozzle and the direction of the ejection direction when recording. This is a cause of deterioration in image quality as density unevenness. Even in a monochrome printer, uniformity is one of the most important issues when a monochrome photographic image is output using nozzles arranged with high definition.

  One factor that impairs uniformity is the so-called “overflow”. The “overflow” will be briefly described below.

  When outputting a photographic image or graphic, it is often necessary to express a high optical density over a wide area. In order to express a high optical density, the ink jet recording apparatus is in a state of recording ink droplets on a recording medium at a high density.

  At this time, for example, when a significantly larger amount of ink is recorded than the amount of ink that can be received by the recording medium, or when a large amount of ink is recorded in a very short time even if the amount of ink can be received by the recording medium think of. In this case, a situation occurs in which the next ink droplet is recorded at an adjacent position before the previously recorded ink droplet penetrates the recording medium. The plurality of ink droplets come into contact with each other on the recording medium and aggregate due to the surface tension between the liquids. That is, the plurality of ink droplets move to a position shifted from the originally recorded position, and remain on the recording medium for a while as large ink droplets that are not immediately absorbed. In such a state, even if the ink is absorbed or evaporated thereafter, the position where the aggregated ink is present is detected as density unevenness or blur on the image, and the uniformity is significantly deteriorated. In this specification, such a phenomenon is referred to as “overflow”.

  It can be said that “overflow” depends on the amount of ink recorded per unit time and unit area. If the amount of ink recorded per unit time and unit area increases significantly with respect to the ink storage capacity of the recording medium, the ink that cannot be absorbed overflows to the surroundings before penetrating the recording medium. “Overflow” is recognized as a large image detriment in recording apparatuses that attempt to achieve photographic image quality.

  In the case where a relatively high density object such as a document composed of a large number of characters or computer graphics is recorded locally, this “overflow” is not a subject of image damage. In such a document, there is a case where image quality is rather improved due to aggregation of adjacent ink droplets. This is because there is an effect of increasing the uniformity in the region where the recorded ink droplets aggregate. In the present specification, “overflow” refers to an adverse effect of density unevenness caused by ink aggregation that occurs when importance is attached to uniformity such as photographic image quality.

  As one of the methods for suppressing “overflow”, a method in which an ink drying and fixing unit such as a heater is mounted on a recording apparatus and an image is formed while absorbing and evaporating ink immediately after recording has been proposed. (For example, refer to Patent Document 1 and Patent Document 2.) However, in this case, the heater itself is a large-scale device, and the consumed electric power increases. In an ink jet recording apparatus that is characterized by being provided at a low price, it cannot be said to be a very practical method.

  Also, “overflow” can be suppressed by using a multi-pass printing method applied to many serial type ink jet printing apparatuses (see, for example, Patent Document 3). The multi-pass recording method is a serial type ink jet recording apparatus in which image data that can be recorded by a recording head in one recording scan is divided into several recording scans for recording. That is, in the recording medium, a plurality of ink droplets that tend to aggregate adjacently are gradually recorded at a plurality of times with time, so that the amount of ink recorded per unit area and unit time can be reduced. As a result, “overflow” can be suppressed. However, the serial type recording apparatus has a configuration that requires much longer recording time than the full line type in the first place. Furthermore, performing the multi-pass recording further increases the recording time. That is, in a serial type recording apparatus in which recording time and image quality are in a trade-off relationship, it is difficult to satisfy both simultaneously.

  On the other hand, in order to suppress “overflow” in a full-line type recording apparatus, the drive frequency of the recording head and the conveyance speed of the recording medium are controlled in order to adjust the amount of ink recorded per unit area and unit time. The method is adopted. Patent Document 4 discloses a configuration of a recording head and a recording method for preventing overflow in a full-line inkjet recording apparatus.

  FIG. 1 is a diagram illustrating a configuration example of a recording head disclosed in Patent Document 4. In FIG. According to this document, a full-line type ink jet recording head 10 is disclosed. In the recording head 10, the preceding nozzle row 14 for ejecting ink and the nozzle row 14 are arranged in a state shifted by a half pitch in the nozzle arrangement direction, and the subsequent nozzle row 16 for ejecting ink subsequently. The ink jet recording head has a two-row configuration. The nozzle row 16 in the rear row is arranged further downstream with respect to the conveyance direction of the recording medium. Then, the distance L between the two nozzle rows is set so that the ejection timing of the nozzle row 16 in the rear row is after a sufficient time has passed for the ink droplets recorded by the nozzle row in the front row to be almost absorbed. ing. With such a configuration, adjacent dots arranged in the nozzle arrangement direction of the recording head are recorded from different nozzle rows at different timings.

  By the way, in recent inkjet recording techniques, a technique for designing a smaller size (volume) of ink droplets has been promoted in order to reduce graininess, which has been regarded as a problem. However, in a recording head that is designed to have a smaller ink droplet size and record at a higher frequency, a new problem of “swinging edge” has also been confirmed.

  FIG. 2 is a diagram schematically showing the ejection state of the recording head 103 in order to explain the above-mentioned “shaft end”. In the figure, a recording head 103 having a plurality of recording elements ejects ink droplets from each recording element toward a recording medium substantially vertically. At this time, the ink droplets ejected from the recording elements located at both ends of the recording head proceed while being deflected toward the central portion. It has been confirmed that such a tendency appears remarkably when an image is formed with extremely small ink droplets and when the recording density is high.

  It is thought that this “edge-shaking” phenomenon occurs due to the influence of the surrounding airflow. When ink droplets are ejected at a high frequency from ejection ports arranged at a high density, an air flow is generated in a large amount around the ink droplets. If the ejected ink droplet has a sufficient mass, it is less affected by the momentum. However, if the volume of the ejected ink is small, the mass of the ink droplet is also small, so that it is easily affected by the air current, and its moving direction is deflected. At this time, it can be said that the discharge port located on the outermost side of the nozzle row is most susceptible to the influence of airflow. That is, as shown in the figure, when ink droplets are ejected from a single nozzle array arranged at high density all at once and at a high frequency, the ink droplets ejected from the end of the nozzle array It is deflected toward As a result, in the recorded image, the image recording area becomes narrow, or a darker or darker part than the desired density is confirmed as density unevenness.

  Measures have already been proposed to cope with the adverse effects caused by such “end-to-end” (see, for example, Patent Document 5). According to Patent Document 5, a method is disclosed in which nozzles capable of discharging different discharge amounts are provided at both ends in a nozzle row to alleviate the influence of airflow. Such a method can be said to be effective in a configuration in which an image is formed while repeating a plurality of scans in a serial type recording apparatus. However, when an image is formed by a single scan as in a line type recording apparatus, there is a risk that the image processing becomes complicated or the image quality deteriorates.

Japanese Patent Laid-Open No. 04-140144 Japanese Patent Laid-Open No. 04-201343 Patent No. 3,229,454 Japanese Patent Laid-Open No. 10-250059 Japanese Patent Laid-Open No. 2003-311962

  As in recent years, a demand for a full-line type recording apparatus is increasing while higher-speed image output is required. Further, even in a full-line type recording apparatus, in order to further improve the recording speed, ejection is performed from each nozzle at a higher driving frequency, and the recording medium is conveyed at a higher speed. Even in such a state, by adopting the recording apparatus and the recording method described in Patent Document 4, dots adjacent in the nozzle arrangement direction of the recording head can be recorded at different timings from different nozzle rows. Done.

  However, the method described in Patent Document 4 inevitably has a limit as the recording speed increases. According to the recording method of this document, referring to FIG. 1 again, an image is recorded by two nozzle rows 14 and 16 arranged in the same recording head 10. Therefore, in order not to cause “overflow”, it is necessary to increase the recording speed and at the same time design the distance L between the two nozzle arrays to be larger and larger. As a result, the depth width of the recording head is increased, so that it cannot be actually realized.

  As described above, in recent inkjet recording apparatuses that are expected to increase in speed, the response to “overflow” must be insufficient. Furthermore, the above-mentioned adverse effect of “end-to-end” has not been solved, and how to solve these two points has been a big problem in the full-line type recording apparatus.

  The present invention has been made to solve the above-described problems. The purpose is to provide an ink jet recording apparatus and a recording method capable of outputting high-quality photographic images without “overflow” and “end-to-end” even in a full line type recording apparatus with a high driving frequency. It is to be.

  Therefore, in the present invention, a first recording head that records dots on the recording medium by ejecting ink from a plurality of ejection openings arranged over the entire width of the recording medium; By the first recording head of the recording medium by discharging the ink of the same color as that of the first recording head later than the first recording head. In an inkjet recording apparatus comprising: a second recording head that records dots at positions different from the formed dots, among the plurality of dots adjacent to one dot recorded by the first recording head, The number N of dots recorded by the first recording head is less than or equal to the number M of dots recorded by the second recording head. To.

  Also, a first recording step of recording dots on the recording medium by ejecting ink from a plurality of ejection openings arranged over the entire width of the recording medium, and an arrangement direction of the ejection openings of the recording medium Different from the dots formed by the first recording step of the recording medium by ejecting ink of the same color as that of the first recording step after the step of moving in different directions and after the first recording step And a second recording step for recording dots at positions, wherein a plurality of dots adjacent to one dot recorded by the first recording step are recorded by the first recording step. The number N of dots formed is less than or equal to the number M of dots recorded in the second recording step.

  According to the present invention, it is possible to record many dots recorded adjacently on a recording medium at different timings, thereby preventing an “overflow” phenomenon on the recording medium. Further, by setting the dispersibility of ink droplets ejected from the same recording head to be high, it is possible to reduce the “swinging edge” phenomenon.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
(First embodiment)
FIG. 3 is a structural cross-sectional view for simply explaining the recording process of the full-line type ink jet recording apparatus applied to the present embodiment. In the figure, reference numeral 50 denotes a conveyance roller. The conveyance roller 50 rotates to convey the recording medium 3 in the direction of arrow D through the conveyance belt 51 at a predetermined speed.

  In the process of transporting the recording medium 3 in the arrow D direction, the ejected ink is recorded by the first recording head K1 and the second recording head K2. The recording apparatus of this embodiment is an inkjet recording apparatus that records a monochrome image using only black ink. Therefore, it is assumed that the first recording head K1 and the second recording head K2 eject black ink. The distance l between the first recording head K1 and the second recording head K2 is not particularly limited. However, when the area recorded by the first recording head is transported at a predetermined transport speed and is located directly below the second recording head, the ink ejected from the first recording head has already been applied to the recording medium. A distance such that sufficient time has passed to be absorbed is desirable. Of course, there is a situation in which the first head K1 records another part of the recording medium 3 while a part of the recording medium 3 is recorded under the second recording head K2. It doesn't matter.

  As described above, according to the present embodiment, by arranging two nozzle arrays for recording at different timings in different recording heads, the distance l between the two nozzle arrays affects the size of the recording head. It can be expanded without giving.

  FIG. 4 is a schematic diagram for explaining recording positions by the two recording heads K1 and K2. Each of the first recording head K1 and the second recording head K2 is provided with one nozzle row, and each nozzle row has a plurality of nozzles arranged at an interval of 1/1200 inch. With such a configuration, at each dot position on the image, recording can be performed twice (2 dots each) at a recording resolution of 1200 dpi (dots / inch; reference value) in the x direction (nozzle alignment direction).

  On the other hand, in the y direction (recording medium transport direction), the drive frequencies of the recording heads K1 and K2 and the transport speed of the recording medium are adjusted so that recording can be performed at a resolution equal to the x direction, that is, 1200 dpi. That is, in the recording apparatus according to the present embodiment, an image is formed at a recording density of 1200 dpi × y direction 1200 dpi. Further, it is designed such that about 4 pl of ink droplets are ejected from the respective ejection ports of the respective recording heads. With a resolution of 1200 dpi × 1200 dpi, the size of a region given to one pixel is about 21 μm × 21 μm. That is, an image is formed on a recording medium by arranging a plurality of the above-described regions in which whether or not 4 pl ink droplets are recorded based on the recording data are arranged in the x direction and the y direction. .

  In the recording medium, dots are recorded by every other ejection port of the first recording head K1. Similarly, in the second recording head K2, dots that are in a complementary relationship are formed by every other ejection port and at a position shifted by one from the ejection port used by the first recording head K1. Is recorded. That is, as shown in FIG. 4, the dots recorded by the first recording head K1 are recorded at a density of 600 dpi in the x direction and 1200 dpi in the y direction, and the dots recorded by the second recording head K2 are also Recorded with similar density. In the image completed by the two recording heads, the recording is performed at a density of 1200 dpi in the x direction and 1200 dpi in the y direction.

  In this case, when attention is paid to one dot, pixel positions adjacent to this dot are present in eight directions including the vertical and horizontal directions. However, according to the present embodiment, the positions recorded by the same recording head (for example, K1) are only two pixels before and after in the y direction. Furthermore, even when there are two pixels before and after, recording is actually performed when there is recording data at this position. Therefore, in an actual image, it can be said that the number of adjacent pixels in which dots are recorded by the same recording head (for example, K1) is 2 pixels or less. Other adjacent dots of 6 pixels are recorded with a sufficient time difference by the other recording head (for example, K2). That is, the risk of image deterioration due to overflow between adjacent dots is 2 dots / 8 dots, that is, 1/4 or less, compared to the case where all adjacent dots are recorded by the same recording head.

  As described above, according to the present embodiment, it is possible to suppress ink aggregation that causes “overflow” by reducing the number of dots to be recorded on adjacent pixels by the same recording head as much as possible.

  In addition, according to the present embodiment, the number of dots simultaneously ejected by one recording head is also halved, and the positions of ejection ports for performing ejection are evenly distributed throughout the recording head. Therefore, the effect of making it difficult for the airflow that causes the above-described “shaking of the end portion” to occur is also obtained.

  FIG. 5 is a diagram for explaining a modified example of the nozzle position applied to the recording of the present embodiment. In an ink jet recording head, nozzles that are frequently ejected tend to be deteriorated earlier than other nozzles and become non-ejected. In addition, in an ink jet recording head, if there is non-ejection in any one of a plurality of nozzles, it is often regarded as the life of the recording head itself. Therefore, imparting bias to the nozzles used for recording leads to shortening the life of the recording head. In other words, even if the same number of nozzles are provided in the recording heads K1 and K2, an efficient recording method cannot be performed if only a predetermined half of the nozzles are always applied to the recording. Therefore, in some cases, recording is performed using the combination of nozzles shown in FIG. 5A, and in other cases, recording is performed using the combination of nozzles shown in FIG. 5B. This makes it possible to equalize the discharge frequency of the entire plurality of nozzles provided in the two recording heads.

  Here, the form shown in FIG. 5A and the form shown in FIG. 5B may be switched at any timing. For example, switching may be performed in units of pages, or switching may be performed in units of jobs. Furthermore, it is possible to switch within the same page.

  By the way, in the above description of the present embodiment, the configuration has been described in which the black ink having the same K1 and K2 is ejected. However, the effect of the present embodiment is not limited to such a configuration. For example, even if the same black ink is used, the recording heads K1 and K2 may eject ink having different dye concentrations. Further, even when the dye concentration is the same, the discharge amount and the dot size on the recording medium may be different. The effect of this embodiment is not affected by the type of ink ejected by K1 and K2. No matter what combination of the two ink types is, the present embodiment does not depart from the present invention as long as the ink droplets ejected from both the ink droplets can be prevented from adjoining and the adverse effect of “overflow” appearing due to their aggregation can be suppressed.

(Second Embodiment)
The second embodiment of the present invention will be described below. Also in the present embodiment, the effect of reducing the “overflow” described above can be obtained. Furthermore, even when there are recording elements in the recording head K1 or K2 that are biased in the ejection direction or the ejection amount, an effect that suppresses the adverse effects on the image as much as possible is obtained at the same time.

  In the plurality of ejection openings arranged on the recording head, there are inevitably variations in the ejection amount, ejection direction, and the like in the manufacturing process. If recording as in the first embodiment is performed in such a state, the recording medium periodically generates white streaks that do not satisfy the area factor of 100%, or conversely, more dots than necessary. Overlapping points occur. As a result, there is a case where the uniformity is perceived as the density unevenness as far as the eyes of the human eyes are concerned and the uniformity is significantly deteriorated.

  In order to deal with such a problem, in the present embodiment, a recording method is adopted that mitigates the adverse effects of images caused by nozzle variations.

  FIG. 6 is a schematic diagram for explaining the effect of the present embodiment in the case where a recording head having a variation in ejection amount is used. Here, a case is shown in which the discharge amount of the nozzle (b) on the recording head K1 and the nozzle (E) on K2 is smaller than the others, and the dot diameter formed on the recording medium is also small. . In such a case, if the same recording as in the first embodiment is performed, the position where the nozzle (b) records and the position where the nozzle (E) records become white stripes extending in the y direction, and the image is displayed. It will deteriorate.

  According to the present embodiment, among the nozzles of the recording head K1 and the nozzle of the recording head K2, for the combination capable of recording the same line, dots arranged in the y direction are recorded alternately. For example, the nozzle (e) is also applied to the line to be recorded by the nozzle (E), and dots arranged in the y direction are alternately recorded by the two nozzles. By adopting such a recording method, unevenness and streaks due to nozzle variations are suppressed to approximately ½. That is, while realizing the high-speed recording peculiar to the full-line type, the same effect can be obtained in image quality as when two-pass multi-pass recording is performed in the serial type recording apparatus.

  In the case of the present embodiment, compared to the conventional configuration in which all adjacent dots are recorded by the same recording head, the number of dots recorded by the same recording head among all 8 adjacent dots is reduced to 4 dots. That is, the possibility of overflow as compared with the conventional method is suppressed to 4 dots / 8 dots = 1/2. However, when compared with the first embodiment, the number of dots recorded by the same recording head K2 is 4 dots positioned in an oblique direction, which is larger than that of the first embodiment. However, in reality, it is assumed that the contact between the dots and the cohesive force in the oblique direction are smaller than the contact between the dots in the front, rear, left and right. Therefore, the “overflow” does not always appear more noticeably than in the first embodiment due to the increase in the number of adjacent dots. Rather, it can be expected that the uniformity of the entire image can be effectively improved in the embodiment in which unevenness and streaks due to nozzle variation can be suppressed to ½ as in the present embodiment.

  In this embodiment as well, as in the first embodiment, the number of dots simultaneously ejected by one recording head is halved, and the positions of ejection ports for performing ejection are evenly distributed throughout the recording head. Has been. Therefore, it is possible to simultaneously obtain an effect that the air current causing the “end-swing” as described above is hardly generated.

(Third embodiment)
The third embodiment of the present invention will be described below. In the present embodiment as well, as in the second embodiment, one of the purposes is to suppress density unevenness due to nozzle variation provided in the recording head. However, in the present embodiment, unlike the second embodiment, it is not a method of recording dots arranged in the y direction while being shared by two recording heads. The number of discharges is set more than that of the nozzle. Such recording can be realized by setting the discharge frequency slightly higher than other nozzles only for the nozzles with a small discharge amount.

  In this way, it is possible to realize a sufficient area factor by recording a larger number of dots even in a nozzle in which the area factor is less than 100% in normal recording. Of course, the ratio of adding dots to the print data may vary depending on the duty (density) of the print data.

  When the dot number correction as in the present embodiment is executed, the dots recorded by the nozzles that eject more ink droplets are the adjacent dots recorded by the same recording head than in the first embodiment. Some parts have also increased. However, from the viewpoint of variation in the discharge amount between nozzles in a general recording head, the number of dots to be added to the extent that the area factor of 100% is satisfied is often not necessary to double. That is, it can be considered that it does not affect the “overflow”.

  In this embodiment as well, as in the first embodiment, the number of dots simultaneously ejected by one recording head is almost halved, and the positions of ejection ports for performing ejection are evenly distributed throughout the recording head. Is distributed. Therefore, it is possible to simultaneously obtain an effect that the air current causing the “end-swing” as described above is hardly generated.

(Fourth embodiment)
The fourth embodiment of the present invention will be described below. In the above-described embodiments 1 to 3, the case of recording a monochrome image using two recording heads has been described by taking black ink as an example. On the other hand, in this embodiment, a mode in which a color image is recorded using a plurality of colors of ink will be described.

  FIG. 7 is a structural cross-sectional view for briefly explaining the recording process of the full-line type ink jet recording apparatus applied to the present embodiment. In the figure, the conveyance roller 50 and the conveyance belt 51 are the same components as those described in FIG.

  In the present embodiment, the recording medium 3 is conveyed in the direction of arrow D. In the process, the first recording head K1, the second recording head K2, the third recording head C1, the fourth recording head C2, the fifth recording head M1, the sixth recording head M2, and the seventh recording. Recording is performed in the order of the head Y1 and the eighth recording head Y2. The recording apparatus of the present embodiment is an inkjet recording apparatus that records a color image using black, cyan, magenta, and yellow inks. Both the first recording head K1 and the second recording head K2 eject black ink. The third recording head C1 and the fourth recording head C2 are both cyan ink, the fifth recording head M1 and the sixth recording head M2 are both magenta ink, and the seventh recording head Y1 and the second recording head C1. The eight recording heads Y2 both discharge yellow ink.

  The distance between the two recording heads in each color, such as the distance l between the first recording head K1 and the second recording head K2, is not particularly limited. However, when the area recorded by the first recording head (K1) is transported at a predetermined transport speed and is located directly below the second recording head (K2), the ink ejected from the recording head (K1) is It is assumed that the recording medium has already been absorbed. In other words, the relationship between the distance l and the conveyance speed to the extent that sufficient time has passed is maintained. Further, since the speed absorbed by the recording medium may be different depending on the ink color, the distance between the two recording heads may be different for each color. That is, the distance between K1 and K2, the distance between C1 and C2, the distance between M1 and M2, and the distance between Y1 and Y2 may be different values. Further, the distance between the colors such as the distance d between K2 and C2 is not particularly determined. However, as with the same color ink, it is preferable to set a distance sufficient for the ink droplets recorded immediately before to be absorbed.

  Of course, while a part of the recording medium 3 is recorded under one recording head, a situation may occur in which the other head records another part. Conversely, there may be a situation in which another recording head is recording a part of another recording medium while one recording head is recording a part of a certain recording medium.

  Also in this embodiment, the recording position by the recording head of the same color can be described with reference to FIG. That is, the dots recorded from the first, third, fifth and seventh recording heads (K1, C1, M1, Y1) and the second, fourth, sixth and eighth recording heads (K2, The dots recorded from (C2, M2, Y2) are arranged at positions complementary to each other.

  When a color image is formed as in the present embodiment, it is assumed that a larger amount of ink is applied to the recording medium than in the case of the monochrome image described in the first embodiment. Therefore, the above-described “overflow” phenomenon is likely to occur, and the adverse effects caused by this “overflow” are also more easily recognized as color mixing and blurring between colors. However, according to the present embodiment, the recording at the position K1 and the position K2 shown in FIG. 4 is alternately performed a plurality of times with a sufficient time interval for absorbing the ink. Therefore, it is possible to superimpose multiple color dots while preventing the ink from aggregating between adjacent dots, which causes “overflow”, so that a color image can be output in a good state without blurring. It becomes possible.

  In the present embodiment, it is not necessary that the two recording heads eject the same type of ink in K1 and K2 and other colors. For example, the ink may be ejected with different dye concentrations, or the ejection amount and the dot size on the recording medium may be different. Moreover, the form using ink colors other than the four colors mentioned above may be sufficient. Further, a recording head of different colors may be sandwiched between two recording heads of the same color. The effect of this embodiment is that the ink droplets ejected from the same recording head are prevented from being adjacent to each other, and the “overflow” caused by the aggregation of these is suppressed, and a plurality of types of ink are overlapped by a plurality of recording heads. However, it can be obtained as long as an image is formed.

  In the above-described embodiment, the ink jet recording apparatus that forms an image with a recording density of 1200 dpi × 1200 dpi has been described, but the present invention is not limited to such a recording resolution. For example, even if the resolution is higher, such as 2400 dpi × 2400 dpi, or lower resolution, such as 600 dpi × 600 dpi, the resolutions in the X direction and Y direction may be different from each other, such as 2400 dpi × 1200 dpi. . If the number N of dots recorded by the same recording head among all the pixels adjacent to one dot of interest is set to be smaller than the number M of dots recorded by different recording heads The effect of the present invention can be obtained.

  Furthermore, dots are not always recorded for all pixels adjacent to the dot of interest. In the recording apparatus, dot recording / non-recording for each pixel is determined according to an input image signal. The rate at which dots are actually recorded among adjacent pixels varies depending on the density value near the target pixel. In order to obtain the effect of the present invention more sufficiently, no matter what density value is input, the number of dots printed on the adjacent pixels by a different recording head is different from the number of dots recorded by the same recording head. It is preferable that the number of dots to be recorded is set to be smaller.

6 is a diagram illustrating a configuration example of a recording head disclosed in Patent Document 4. FIG. FIG. 6 is a diagram schematically illustrating a discharge state of a recording head in order to explain “end-to-end”. FIG. 5 is a structural cross-sectional view for simply explaining a recording process of a full-line type ink jet recording apparatus applied to an embodiment of the present invention. FIG. 4 is a schematic diagram for explaining recording positions by two recording heads K1 and K2. (A) And (b) is a figure for demonstrating the modification of the nozzle position applied to the recording of embodiment of this invention. It is a schematic diagram for explaining the effect of the present embodiment in the case of using a recording head having a variation in ejection amount. FIG. 5 is a structural cross-sectional view for simply explaining a recording process of a full-line type ink jet recording apparatus applied to an embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 3 Recording medium 10 Recording head 14 Nozzle row | line | column 16 Nozzle row | line | column 50 Conveyance roller 51 Conveyance belt 103 Recording head

Claims (9)

A first recording head that records dots on the recording medium by ejecting ink from a plurality of ejection openings arranged over the entire width of the recording medium;
Means for moving the recording medium in a direction different from the direction in which the ejection ports are arranged;
By ejecting ink of the same color as that of the first recording head later than the first recording head, a dot is recorded at a position different from the dot formed by the first recording head of the recording medium. Two recording heads;
The number N of dots recorded by the first recording head among the plurality of dots adjacent to one dot recorded by the first recording head is equal to the second recording head. An ink jet recording apparatus, wherein the number of dots recorded by the recording head is M or less.   The number N of dots recorded by the first recording head and the number M of dots recorded by the second recording head satisfy a relationship of 2 × N <M. 2. An ink jet recording apparatus according to 1.   The inkjet recording apparatus according to claim 1, wherein the dots are recorded by the second recording head after the dots recorded by the first recording head are fixed.   The inkjet recording apparatus according to claim 1, wherein the first recording head and the second recording head are provided for a plurality of ink colors.   The first recording head and the second recording head record dots on the recording medium by ejecting ink from some of the plurality of ejection ports. The ink jet recording apparatus according to any one of 1 to 4.   The inkjet recording apparatus according to claim 5, wherein the partial ejection ports are ejection ports arranged alternately in the arrangement direction.   The ink jet recording apparatus according to claim 5 or 6, wherein the first recording head and the second recording head switch the partial ejection ports at a constant timing.   The inkjet recording apparatus according to claim 7, wherein the certain timing is a timing at which recording of an image of one page is completed. A first recording step of recording dots on the recording medium by ejecting ink from a plurality of ejection openings arranged over the entire width of the recording medium;
Moving the recording medium in a direction different from the direction of arrangement of the ejection ports;
Secondly, dots are recorded at positions different from the dots formed by the first recording step of the recording medium by ejecting ink of the same color as that of the first recording step later than the first recording step. Recording process of
In the ink jet recording method, the number N of dots recorded by the first recording step among the plurality of dots adjacent to one dot recorded by the first recording step is the second recording. An ink jet recording method, wherein the number of dots recorded in the process is M or less.

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