JP4957892B2 - Droplet discharge device - Google Patents

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet printer that ejects ink onto a recording medium, and more particularly, an ink jet printer configured to eject black ink and three primary colors of yellow ink, magenta ink, and cyan ink, and an ink ejecting method. It is about.

  Conventionally, as an inkjet printer, a type capable of color recording has been widespread, and in addition to black ink, yellow ink, magenta ink, and cyan ink, which are three primary colors, can be individually ejected to a recording medium. Such a configuration is known. On the other hand, it is also known that yellow ink, magenta ink, and cyan ink are ejected to the same position on a recording medium and a pseudo black color (sepia color, hereinafter referred to as mixed color black) created by mixed colors is used. Yes.

In the patent document 1 (Japanese Patent No. 3,533,771), the applicant of the present invention sets each nozzle row of black ink, yellow ink, magenta ink, and cyan ink in a direction (sub-scanning direction) orthogonal to the scanning direction of the inkjet head. A structure in which the nozzle arrangement is provided in parallel with each other at the same nozzle arrangement interval, and the nozzle arrangement of the black ink is provided by being shifted by ½ of the nozzle arrangement interval in the sub-scanning direction with respect to the other nozzle arrays. In order to form continuous dots in the sub-scanning direction using only the black ink dots, it is necessary to shift the recording medium by 1/2 of the nozzle arrangement interval and run the inkjet head twice in the scanning direction. However, with the structure described in Patent Document 1, the yellow ink, the magenta ink, and the ink between the dots of black ink (single color black) adjacent in the sub-scanning direction can be obtained by simply moving the inkjet head once in the scanning direction. It can be filled with mixed color black dots mixed with cyan ink. Therefore, it is possible to improve the pixel density and increase the recording speed in monochrome recording.
Japanese Patent No. 3533771 (see FIGS. 2 and 5)

  However, when the mixed color black dots are mixed with the monochrome black dots and recorded, the inventors have found that the dots are formed unevenly. Such dot non-uniformity affects print quality.

  The present invention solves the above problem and improves the uniformity of dots formed on a recording medium in recording using mixed-color black that discharges yellow ink, magenta ink, and cyan ink to mix colors. The purpose is to obtain good recording quality. In addition, the code | symbol with the parenthesis attached | subjected to each element shown below is only the illustration of the element, and does not limit each element.

Means for Solving the Problems and Effects of the Invention

According to the first aspect of the present invention, black ink (Bk), yellow ink (Y), magenta ink (M), and cyan ink (C) are ejected from a plurality of nozzles (15) to form a recording medium (PA In the inkjet printer (1), a plurality of nozzle rows (15) arranged in a predetermined direction are arranged in a direction orthogonal to the predetermined direction, at least one row for each color. And the controller (30) for controlling the inkjet head (3). In the nozzle rows (15a to 15d) of the respective colors, the nozzles (15) adjacent in the row are connected to each other in the predetermined range. The black ink nozzle row (15a) is arranged in the direction of the black ink nozzle row (15a) with the yellow ink, magenta ink, and cyan ink nozzle rows (15a). Relative 5B～15d), are arranged offset by half the predetermined pitch P in the predetermined direction, when recording in the color mode, the monochrome black formed by ejecting the black ink (Bk) Ink is ejected from the nozzle (15) that ejects the yellow ink (Y) , magenta ink (M) , and cyan ink (C) to a position adjacent to the position of the dot (A1) in a predetermined direction , A black dot (B1) in which the yellow ink, magenta ink, and cyan ink are mixed to form a black dot continuously in the predetermined direction, while the yellow ink, magenta ink, and A single-color or two-color mixed dot by cyan ink is predetermined in the predetermined direction with respect to the position of the black dot (A1) An ink jet printer (1) is provided in which the controller controls the ink jet head so that the controller is formed at a position shifted by ½ of the interval P.

According to the second aspect of the present invention, when the mixed color black dots (B1) are mixed with the monochrome black dots (A1) and recorded, the amount of ink ejected from each nozzle (15) is set to the same amount. In this case, the ink amount per dot (B1) of the mixed color black that mixes the three colors of ink (Y, M, C) discharged from the three nozzles is equal to the amount per one dot (A1) of the monochrome black. More than the ink amount. In addition, pigment ink is used for black ink (Bk) and dye ink is used for the other three colors (Y, M, C) in order to increase the sharpness of black and make the color vivid for character recording and the like. In this case, since the pigment ink is difficult to bleed, even if it has the same ejection volume as that of the dye ink dot, it is formed into a small dot on the recording medium (PA), and a single color black dot (A1) and a mixed color black dot (B1) Becomes non-uniform in size. For this reason, the present inventors have found that the recording quality can be improved by making the size of the dots formed on the recording medium (PA) uniform.

According to the second aspect of the present invention, the amount of black ink (Bk) ejected when forming one dot (A1) of monochrome black is ejected when forming one dot (B1) of mixed color black. Since the total amount of yellow ink (Y), magenta ink (M), and cyan ink (C) is larger, when mixed color black dots (B1) and single color black dots (A1) are mixed, The dot size on the recording medium (PA) can be made uniform.
Further, in the nozzle rows (15b to 15d), adjacent nozzles (15) are arranged at a predetermined interval P in a predetermined direction, whereas only the black ink nozzle row (15a) has other nozzles. It is displaced in the predetermined direction by 1/2 of the predetermined interval P from the rows (15b to 15d). Therefore, when the inkjet head (3) travels once in the direction orthogonal to the predetermined direction with respect to the recording medium (PA), the monochrome black dots (A1) adjacent to the predetermined direction as necessary. In the meantime, yellow ink (Y), magenta ink (M), and cyan ink (C) are ejected to form mixed color black dots (B1), and the pixel density can be improved.

  In the inkjet printer (1) of the present invention, the nozzle row (15a) of the black ink is arranged in the nozzle rows (15b to 15d) of the yellow ink (Y), magenta ink (M), and cyan ink (C). On the other hand, it may be arranged shifted by a half of the predetermined interval P in the predetermined direction. In this case, only by moving the carriage (9) once in the scanning direction, the mixed color black (B1) is formed at the intermediate position between the monochrome black dots (A1) adjacent in the predetermined direction, and the monochrome black dots ( A1) and mixed color black dots (B1) can be continued in a predetermined direction, and the recording speed can be improved.

  In the ink jet printer (1) of the present invention, the hole diameter of the nozzle (15) for discharging the black ink (Bk) is any one of the yellow ink (Y), magenta ink (M), and cyan ink (C). It may be larger than the hole diameter of the plurality of nozzles (15) to be discharged. In this case, the amount of ink ejected from the nozzle (15) of the black ink (Bk) is determined by the amount of ink ejected from the nozzle (15) of each color of yellow (Y), magenta (M), and cyan (C). Can also be more. Therefore, when the mixed color black dots (B1) and the single color black dots (A1) coexist, the size of the dots on the recording medium (PA) can be made uniform.

  In the inkjet printer (1) of the present invention, when the mixed color black dot (B1) is formed between the single color black dots (A1), ejection is performed when forming the mixed color black dot (B1). The yellow ink (Y), the magenta ink (M), and the cyan ink (C) each have an ink amount of the black ink (Bk) ejected when forming one dot (A1) of monochrome black. The amount of ink can be adjusted to be smaller than the amount of ink. In this case, the mixed color black dots (B1) and the monochrome black dots (A1) formed on the recording medium (PA) can be formed in the same area, thereby improving the recording quality. Further, since the amount of each of yellow ink (Y), magenta ink (M), and cyan ink (C) discharged when forming the mixed color black dot (B1) is reduced, the piezoelectric actuator (17). The driving power applied to the piezoelectric actuator can be reduced, and the heat generation of the piezoelectric actuator (17) can also be reduced.

  In the inkjet printer (1) of the present invention, the yellow ink (Y), magenta ink (M), and cyan ink (C) are more likely to bleed into the recording medium (PA) than the black ink (Bk). The ink can be preselected. In this case, the size of the mixed-color black dot (B1) that tends to spread and the size of the monochrome black dot (A1) that has less bleeding can be made uniform, and good recording quality can be realized.

  In the inkjet printer (1) of the present invention, the amount of the black ink (Bk) ejected when forming one dot (A1) of the monochrome black is the same as that of the dot (A1) of the monochrome black. It may be 1.3 to 1.5 times the amount of each color ink (Y, M, C) discharged when forming one dot of each color. In general, pigment ink is used for black ink (Bk), and dye ink is often used for color ink (Y, M, C), and pigment ink is more difficult to bleed than dye ink. By ejecting more ink (Bk) than color ink (Y, M, C), the size of the black dots (A1) and the dots of each color can be made uniform.

  In the inkjet printer (1) of the present invention, when the mixed color black dot (B1) is formed between the single color black dots (A1), the single color black one dot (A1) is ejected. The amount of the black ink (Bk) may be smaller than the maximum amount of ink per dot that can be ejected from the nozzle (15) that ejects the black ink (Bk). By using the mixed-color black dots (B1), at least black areas that are continuous in the sub-scanning direction are recorded without discharging the maximum ink amount that can be discharged from the nozzle (15) of the black ink (Bk). It can be formed on a medium (PA). In order to eject ink droplets of the maximum ink amount, the driving power applied to the piezoelectric actuator (17) also increases, but the power can be reduced by adjusting the ink amount to be smaller than the maximum ink amount. Further, heat generation of the piezoelectric actuator (17) can also be suppressed.

According to a second aspect of the present invention, there is provided an ink ejection method for ejecting black ink (Bk), yellow ink (Y), magenta ink (M), and cyan ink (C) from a nozzle (15), A plurality of nozzle rows (15a to 15d) in which a plurality of the nozzles (15) are arranged at a predetermined interval P in a predetermined direction are arranged in a direction perpendicular to the predetermined direction for each color, and the black ink The nozzle row (15a) of the inkjet is arranged so as to be shifted from the nozzle rows (15b to 15d) of the yellow ink, magenta ink, and cyan ink by 1/2 of the predetermined interval P in the predetermined direction. and providing a head (3), when recording in the color mode, the predetermined direction of the dot position of the single color black is formed by ejecting the black ink Are simultaneously ejected from the nozzles for ejecting the yellow ink, magenta ink, and cyan ink at positions adjacent to each other to form mixed color black dots in which the yellow ink, magenta ink, and cyan ink are mixed. Thereby forming black dots continuously in the predetermined direction;
The single-color or two-color mixed dots of the yellow ink, magenta ink, and cyan ink are formed at positions shifted by a half of the predetermined interval P in the predetermined direction with respect to the dot positions of the single-color black. Ink discharge methods are provided.

According to this method, the discharge amount of the black ink (Bk) is larger than the total amount of the color ink for forming the mixed color black dot (B1), so the mixed color black dot (B1) and the single color black dot (A1) ) Can be made uniform in dot size on the recording medium (PA). Further, in the nozzle rows (15b to 15d), the adjacent nozzles (15) are arranged at a predetermined interval P in the sub-scanning direction, whereas only the black ink nozzle row (15a) has other nozzles. It is shifted in the sub-scanning direction by 1/2 of the predetermined interval P from the rows (15b to 15d). Therefore, when the inkjet head (3) travels once in the scanning direction with respect to the recording medium (PA), a yellow ink (A1) between the monochrome black dots (A1) adjacent in the sub-scanning direction is necessary. Y), magenta ink (M), and cyan ink (C) are ejected to form mixed color black dots (B1), and the pixel density can be improved.

  Below, basic embodiment of this invention is described based on drawing.

  As shown in FIG. 1, the inkjet printer 1 of the present embodiment (first embodiment) is not only a single printer device, but also a multifunction device (MFD) having a copy function, a scanner function, a facsimile function, and the like. : Multi Function Device) can also be applied as a printer function. The ink jet printer 1 is provided inside a main body frame 2, and an ink jet head 3 that records ink by ejecting ink onto a paper PA that is a recording medium is mounted on a carriage 9 and travels along a main scanning direction (Y direction). Is configured to do.

  The carriage 9 is slidably mounted on a rear guide shaft 6 and a front guide shaft 7 which are provided in the main body frame 2 in parallel along the Y direction. The carriage 9 is moved in the main scanning direction (Y direction) along the front and rear guide shafts 6 and 7 by a carriage drive motor 10 disposed on the right rear side of the main body frame 2 and a timing belt 11 which is an endless belt. Reciprocal movement is possible. The paper PA is transported horizontally on the lower surface side of the inkjet head 3 along a sub-scanning direction (X direction) orthogonal to the main scanning direction by a known paper transport mechanism (not shown) (arrow in FIG. 1). A direction). On this paper PA, ink is ejected from the nozzles 15 (see FIG. 3) of the ink jet head 3 which is attached to the carriage 9 and moves in the main scanning direction (Y direction) to perform recording.

  As shown in FIG. 9, the inkjet printer 1 includes a controller 30 that controls the scanning of the inkjet head 3, the conveyance of the paper PA in the sub-scanning direction, and the ejection of ink from each nozzle 15. The controller 30 includes an operation panel 31 for a user to issue a recording mode instruction, a motor driver 32 for driving the carriage motor 10, a motor driver 34 for driving the LF motor 33, and a paper PA. A paper sensor 35 for detecting the leading end and an origin sensor 36 for detecting the origin position of the carriage 9 are connected. The controller 30 controls the ink jet head 3 to adjust the ejection amount of ink ejected from each nozzle 15. For this reason, the controller 30 is provided with a plurality of types of drive waveforms of the drive voltage applied to the piezoelectric actuator 17 in accordance with the ink discharge amount.

  The inkjet head 3 is driven by a drive IC 40, and the drive IC 40 is controlled by a gate array (G / A) 41. Each electrode constituting each piezoelectric element provided in the inkjet head 3 is connected to the drive IC 40, and the drive IC 40 generates a drive signal suitable for the inkjet head 3 based on the control of the gate array 41. Apply to each electrode.

  The controller 30 and the gate array 41 are connected via an address bus 60 and a data bus 61. The controller 30 generates a recording timing signal TS and a control signal RS according to a program stored in advance, and transfers the signals TS and RS to the gate array 41. In accordance with the recording timing signal TS and the control signal RS, the gate array 41, based on the recording data stored in the image memory 42, transfer data DATA that is recording data for recording the recording data on the paper PA, A transfer clock TCK synchronized with the transfer data DATA, a strobe signal STB, and a recording clock ICK are generated, and these signals DATA, TCK, STB, and ICK are transferred to the drive IC 40.

  In addition, the gate array 41 stores recording data transferred from an external device such as a host computer (host PC) 43 in the image memory 42. Then, the gate array 41 generates a data reception interrupt signal WS based on the data transferred from the host computer 43 or the like, and transfers the signal WS to the controller 30. The gate array 41 is connected to an encoder sensor 44 that detects the travel position of the carriage 9.

  The ink discharge operation from the nozzle 15 is performed while the carriage PA moves at a constant speed in the main scanning direction (Y direction) in a state where the paper PA is stopped as is well known. Then, the paper PA is conveyed by a predetermined amount in the sub-scanning direction, and the next scanning is performed in the same manner.

  The main body frame 2 contains an ink tank 5a containing black ink (Bk), an ink tank 5b containing cyan ink (C), and magenta ink (M) for enabling color recording. The ink tank 5c and the ink tank 5d containing the yellow ink (Y) are left stationary, and the ink in each ink tank is supplied to the inkjet head 3 via the flexible ink supply tubes 14a to 14d. Is done.

  The inkjet head 3 is attached so that the nozzles 15 (see FIG. 3) are opened and exposed on the lower surface side of the carriage 9, and as shown in FIG. 2, a plurality of nozzles 15 and ink flow paths 19 for the nozzles 15 are provided. , A piezoelectric actuator 17 that applies discharge pressure to the ink in each ink flow path 19, and a flexible flat cable 18 that applies an electrical signal to the piezoelectric actuator 17.

  As shown in FIG. 3, nozzles 15 for ejecting any one of black, cyan, magenta, and yellow inks are arranged in a row in the sub-scanning direction (predetermined direction: X direction). Nozzle rows are formed, and at least one nozzle row is arranged for each color in the main scanning direction (direction perpendicular to a predetermined direction: Y direction). In this embodiment, a black ink nozzle row 15a, a cyan ink nozzle row 15b, a magenta ink nozzle row 15c, and a yellow ink nozzle row 15d are arranged one by one in the main scanning direction (Y direction). In each color nozzle row, the nozzles 15 are arranged in a staggered pattern, and the nozzles 15 adjacent in the sub-scanning direction (X direction) in the row are arranged at a predetermined interval P. The interval between the nozzles 15 located at both ends of each nozzle row is L. The predetermined interval P corresponds to the recording resolution Ndpi (dot per inch, N is a positive integer) in the sub-scanning direction (X direction).

  In this embodiment, the black ink nozzle row 15a has a predetermined interval P in the sub-scanning direction (X direction) with respect to the cyan ink nozzle row 15b, the magenta ink nozzle row 15c, and the yellow ink nozzle row 15d. They are offset by a half. The nozzles of the cyan ink nozzle row 15b, the magenta ink nozzle row 15c, and the yellow ink nozzle row 15d are arranged in a straight line in the main scanning direction (Y direction). Therefore, when the resolution in the sub-scanning direction (X direction) of the nozzle 15 in each column is Ndpi (N is a positive integer), the black ink nozzle 15 and the color ink nozzle 15 are in the sub-scanning direction. It is arranged with a resolution of 2 Ndpi. Here, as an example, if the sub-scanning direction resolution is 150 dpi for each color nozzle row, the sub-scanning direction resolution of the black ink nozzles 15 and other ink color nozzles 15 is 300 dpi.

  In each color nozzle 15, the hole diameter of the black ink nozzle is set in advance larger than that of the other three color nozzles, and the hole diameter of the black ink nozzle can be 20.5 ± 1 μm. The hole diameter of each nozzle can be 17.0 ± 1 μm. In this embodiment, the nozzle diameter of the black ink nozzle is 20.5 μm, whereas the hole diameters of the other three color nozzles are set to 17.0 μm. Since the nozzle diameters of the other three color inks (Y, M, and C) are set smaller than the nozzle diameter of the black ink nozzle, when the driving mode of the piezoelectric actuator 17 is the same, the nozzle diameter of the black ink nozzle is smaller than that of the black ink nozzle. The other three color ink nozzles can eject ink droplets of a smaller volume.

  Since the ink discharge amount per dot discharged from each nozzle can be adjusted by controlling the driving mode of the piezoelectric actuator 17 as is well known, the controller 30 has a plurality of ink discharge amounts different from each other in advance. A plurality of types of drive waveforms are prepared for ejecting ink droplets. Based on the data to be recorded, the controller 30 selects and applies the optimum drive waveform to the active portion of the piezoelectric actuator 17 corresponding to each nozzle. Like to do. FIG. 5 exemplifies the amount of ink ejected when dots of different sizes are formed. Three types of ink droplets, called a large ball, a middle ball, and a small ball, have a black ink nozzle and other three colors. Prepared for nozzles of ink (Y, M, C). When forming a black large ball, black ink is discharged at 24 pl, whereas the amount of yellow ink discharged when forming a yellow large ball, the amount of magenta ink discharged when forming a magenta large ball The amount of cyan ink ejected when forming large cyan balls is adjusted to 16 pl. In the case of forming the center ball, the amount of black ink is 7 pl, whereas the amount of yellow ink, the amount of magenta ink, and the amount of cyan ink are 5 pl. When forming small balls, the amount of black ink is 4 pl, while the amount of yellow ink, the amount of magenta ink, and the amount of cyan ink are each 3 pl. In general, pigment ink is used for black ink, and dye ink is often used for color ink. Since pigment ink is less likely to bleed than dye ink, the amount of black ink ejected when forming one dot is ejected when forming one dot of yellow, magenta, and cyan of the same size. It is adjusted to 1.3 to 1.5 times the ink amount of each color. Although not shown in FIG. 5, it is possible to discharge a maximal ball having a larger discharge amount than the large ball.

  Next, the recording operation of the inkjet printer 1 having the above-described configuration will be described with reference to FIG. 4 showing a part of the recording state. In FIG. 4, a monochrome black dot B1 by black ink is indicated by a mixed color black dot B1 that is a mixture of colors by ejecting A1, yellow ink, magenta ink, and cyan ink to the same position on the recording medium PA. In the inkjet printer 1, when further black dots are formed between the monochrome black dots A1 that are adjacent to each other in the sub-scanning direction (X direction) and are formed by discharging black ink, the controller 30 The inkjet head 3 is driven through the drive IC 40 so as to eject magenta ink and cyan ink, thereby forming a mixed color black dot B1 in which yellow ink, magenta ink, and cyan ink are mixed.

  That is, in the inkjet printer 1, the data to be recorded includes at least a solid black region continuous in the sub-scanning direction, or black dots need to be formed with a sub-scanning direction resolution of 2 Ndpi (300 dpi). In this case, in a single run (one pass) of the inkjet head 3 in the main scanning direction (Y direction), a mixed color black dot B1 is placed between adjacent dots A1 in the sub scanning direction (X direction). The ejection timing from the nozzle 15 is controlled so as to form. In FIG. 4, one dot is displayed with a small area in order to clarify the arrangement of each dot. However, each dot has an area where adjacent dots overlap each other without a gap. is doing.

  As a result, a black region continuous in the sub-scanning direction can be formed with a resolution of 2 Ndpi (300 dpi) only by causing the inkjet head 3 to travel once in the main scanning direction (Y direction). Of course, when the black region is continuous in the main scanning direction (Y direction), both the monochrome black dot A1 and the mixed color black dot B1 are formed continuously in the main scanning direction (Y direction). Each ink may be discharged (discharged in a continuous driving cycle). When the black region is formed to be longer in the sub-scanning direction, the paper is fed by the length L + P in the sub-scanning direction (X direction), and then the inkjet head 3 is moved in the main scanning direction (Y direction). ) And the same discharge as described above may be performed.

  When the sub-scanning direction resolution of 2 Ndpi (300 dpi) is realized using only the monochrome black dot A1, the paper PA is moved to P / 2 after the inkjet head 3 has run once in the main scanning direction (Y direction). Only the paper is fed in the sub-scanning direction (X direction), and the inkjet head 3 must be run once (bidirectional recording is performed in the main scanning direction or unidirectional recording is performed twice). Compared to this case, if the mixed color black dot B1 is used to fill the space between the single color black dots A1, the sub-scanning direction resolution of 2 Ndpi (300 dpi) can be realized by one run, thereby reducing the recording time. Thus, the recording speed can be increased.

  In addition, the monochrome black dot A1 is formed by using the ink droplet (maximum droplet) of the maximum amount of ink that can be ejected from the black ink nozzle, and a black region continuous in the sub-scanning direction is formed with only the monochrome black A1 dot. A method of forming is also conceivable. In this case, the resolution in the sub-scanning direction is Ndpi (150 dpi), and even if a maximal droplet is used, a black region may occur due to insufficient ink droplet capacity. In this embodiment, when the mixed color black dot B1 is used to fill the space between the monochrome black dots A1, the amount of black ink ejected when forming one monochrome black dot is determined from the black ink nozzle. A continuous black region is formed by adjusting the amount to be smaller than the maximum ink amount per dot that can be ejected. By adjusting the ink amount to be smaller than the maximum ink amount, the power can be reduced and the heat generation of the piezoelectric actuator can also be suppressed.

  Also, the amount of black ink ejected when forming one black dot is larger than the total amount of yellow ink, magenta ink, and cyan ink ejected when forming one mixed color black dot. Thus, the size of the single color black dots and the mixed color black dots can be made uniform, and good recording quality can be obtained. At this time, the ink amounts of yellow ink, magenta ink, and cyan ink are all adjusted to be smaller than the ink amount of black ink. In this embodiment, the hole diameters of the yellow ink, magenta ink, and cyan ink nozzles are set smaller than the hole diameters of the black ink nozzles. It is easier to eject ink droplets with a smaller amount of ink.

  As a result, even if mixed color black dots B1 are mixed between single color black dots A1, the mixed color black B1 dots spread on the recording medium, and the size of the dots does not become uneven, improving the recording quality. be able to. In addition, it is possible to suppress wasteful consumption of ink by ejecting an amount of ink more than necessary to form a black region onto a recording medium as mixed-color black dots.

  When yellow, magenta, and cyan inks are used to form mixed color black dots, small ink droplets, such as those below the center ball, are used to reduce the driving power applied to the piezoelectric actuator 17 in order to eject them. It is possible to achieve the effect of reducing the amount of heat generated by the piezoelectric actuator 17 and the amount of heat generated. Of course, yellow ink, magenta ink, and cyan ink are used not only for the formation of mixed color black dots, but also for the formation of color dots. In color dot formation, depending on the data to be recorded, An ink drop is selected.

  In general, pigment ink is used for black ink, whereas dye ink is often used for color inks such as yellow, magenta, and cyan. Therefore, yellow, magenta, and cyan color inks are more likely to bleed than black ink, and the dot diameter on the recording medium is large even with the same ink droplet volume. For this reason, in consideration of the color ink bleeding, even if the driving mode of the piezoelectric actuator 17 is substantially the same, the color ink nozzle discharges a smaller volume of ink droplets as described above. The ink nozzles are formed larger than the other three color ink nozzles.

  Note that the mixed-color black dots described above are used not only when monochrome recording is designated for the controller 30 (monochrome mode) but also when color recording is designated (color mode). , Yellow ink, magenta ink, and cyan ink are ejected corresponding to both the color area and the black area.

  FIG. 6 shows an example of a recording state in which the ink usage is saved in the color mode. FIG. 6A shows that when black dots are continuously formed in the sub-scanning direction at each timing in the main scanning direction (Y direction) of the matrix in which each dot is arranged, as described above The dots A1 and the mixed color black dots B1 are formed adjacent to each other in the sub-scanning direction. Further, the single or mixed color dots Ca1, Cb1, Cc1 of the other three colors are formed at each position at a position shifted P / 2 in the sub-scanning direction from the position where the monochrome black dot A1 is formed. . In this case, a black portion, for example, a character in the recorded image is recorded more clearly than (b) described later.

  FIG. 6B shows a recording state in which the amount of ink used is further saved than in the case (a). Even when black dots are to be continuously formed in the sub-scanning direction, Dot B1 is omitted.

  In the first embodiment, the black ink nozzle row 15a is shifted from the yellow ink, magenta ink, and cyan ink nozzle rows 15b to 15c by 1/2 of the predetermined interval P in the sub-scanning direction. However, it is sufficient that the amount of deviation of the black ink nozzle row 15a is less than P. A case where the amount of deviation is different from that of the first embodiment will be described as a second embodiment with reference to FIGS.

  In the second embodiment, as shown in FIG. 7, each of the black ink nozzle row 15a, the cyan ink nozzle row 15b, the magenta ink nozzle row 15c, and the yellow ink nozzle row 15d has one nozzle 15 in a straight line. Arranged in a shape. The nozzles adjacent in the sub-scanning direction (X direction) in the row are arranged at a predetermined interval Pb (sub-scanning direction resolution is Mdpi, M is a positive integer), and the black ink nozzle row 15a is cyan ink. The nozzle row 15b, the magenta ink nozzle row 15c, and the yellow ink nozzle row 15d are arranged so as to be shifted by a quarter of the predetermined interval Pb in the sub-scanning direction. The interval between the nozzles 15 located at both ends of each nozzle row is L.

  In the inkjet printer 1 of the second embodiment, for example, the data to be recorded includes at least a solid black region continuous in the sub-scanning direction, or black dots need to be formed with a resolution of 4 Mdpi in the sub-scanning direction. In some cases, as shown in FIG. 8A, the inkjet head 3 is run once in the main scanning direction (Y direction), and the monochrome black dot A1 and the mixed color black dot B1 are moved in the sub-scanning direction. 8, the paper PA is fed by Pb / 2 in the sub-scanning direction (X direction), and the next carriage 9 travels in the main scanning direction (Y direction). As shown, a monochrome black dot A2 and a mixed color black dot B2 are formed in the gap in the sub-scanning direction of the previously formed dots.

  Also in the second embodiment, as in the first embodiment, the hole diameter of the black ink nozzle is set larger than the hole diameter of the nozzles of the other color inks, and the ink discharge amount of the color ink is set to the black ink discharge amount. Since the amount is set to be smaller than the amount, the size of the mixed color black and single color black dots can be formed uniformly.

  In the first embodiment, paper is fed by an amount corresponding to P / 4 in the sub-scanning direction, and control is performed so that more dots are formed between the monochrome black dot A2 and the mixed color black dot B2. In addition, a black region can be formed with a smaller volume of dots (ie, high resolution).

  Finally, the flow of the ink ejection process in the embodiment will be briefly described with reference to the flowchart of FIG. When a printing command is issued from the user to the ink jet printer using the ink jet head described in the above embodiment (S1), it is determined whether or not the designation from the user is recording at a high resolution (S2). When high-resolution recording is specified (S2: Yes), mixed-color black dots are formed by simultaneously discharging yellow ink, magenta ink, and cyan ink between monochrome black dots adjacent in the sub-scanning direction. Form (S3). At this time, in order to form single color black dots, a larger amount of black ink is ejected than the total amount of yellow ink, magenta ink, and cyan ink ejected when forming the mixed color black dots (S4). When recording at a high resolution is not designated (S2: No), recording is performed by ejecting only black ink (S5).

  Although the ink jet printer and the ink ejection method of the present invention have been specifically described, the present invention is not limited thereto, and can be improved and modified within the scope of the appended claims. For example, the inkjet head is not limited to the piezoelectric type, and a resistance wire that generates Joule heat by a drive signal may be provided in the ink flow path. In this case, it is possible to generate bubbles by applying heat to the ink in the ink flow path to vaporize the ink, and the ink can be ejected by the pressure of the bubbles.

It is a principal part top view of the ink printer of embodiment. It is a disassembled perspective view of an inkjet head. It is a layout diagram of the nozzle of the first embodiment. FIG. 6 is a diagram for partially explaining a recording state of the first embodiment. It is a figure which shows an example of the amount of ink discharge. FIG. 6 is a diagram partially explaining another recording state of the first embodiment. It is a layout diagram of the nozzle of the second embodiment. It is a figure which partially demonstrates the recording state of 2nd Embodiment. It is a block diagram which shows the main structures of the control system of an inkjet printer. 3 is a flowchart showing a flow of ink ejection processing.

Explanation of sign

DESCRIPTION OF SYMBOLS 1 Inkjet printer 3 Inkjet head 9 Carriage 15 Nozzle 15a-15d Nozzle row | line | column 16 Cavity unit 17 Piezoelectric actuator 18 Flexible flat cable

Claims (11)

An inkjet printer that records black ink, yellow ink, magenta ink, and cyan ink on a recording medium by ejecting them from a nozzle,
An inkjet head in which a plurality of nozzle rows in which the nozzles are arranged in a predetermined direction are arranged in a direction orthogonal to the predetermined direction, at least one row for each color;
A controller for controlling the inkjet head,
In the nozzle row, adjacent nozzles in the row are arranged at a predetermined interval P,
When the black ink nozzle row is arranged to be shifted by a half of the predetermined interval P in the predetermined direction with respect to the yellow ink, magenta ink, and cyan ink nozzle rows and printing is performed in the color mode. , Ejecting ink from nozzles that eject the yellow ink, magenta ink, and cyan ink, respectively, at positions adjacent to the positions of the dots in the predetermined direction of monochrome black formed by ejecting the black ink; By forming mixed color black dots in which the yellow ink, magenta ink, and cyan ink are mixed, black dots are continuously formed in the predetermined direction, while the yellow ink, magenta ink, and cyan ink are used. A single color or two-color mixed dot It said predetermined so as to form a half position shifted by a predetermined interval P in the direction, an ink jet printer wherein the controller is characterized by <br/> controlling the ink jet head. The controller determines the amount of the black ink ejected when forming one dot of the monochrome black, and the amount of the yellow ink, magenta ink, and cyan ink ejected when forming the one dot of the mixed color black. 2. The ink jet printer according to claim 1 , wherein the ink jet head is controlled to be larger than a total amount .   2. The ink jet printer according to claim 1, wherein a hole diameter of the nozzle that discharges the black ink is larger than a hole diameter of the nozzle that discharges any one of the yellow ink, magenta ink, and cyan ink.   When forming the mixed-color black dots between the single-color black dots, the amounts of yellow ink, magenta ink, and cyan ink ejected when forming one mixed-color black dot are all monochrome. 4. The ink jet printer according to claim 3, wherein the amount is adjusted to be smaller than the amount of the black ink ejected when forming one black dot.   4. The ink jet printer according to claim 3, wherein the yellow ink, the magenta ink, and the cyan ink are selected in advance so that the ink is more likely to spread on the recording medium than the black ink.   The amount of the black ink ejected when forming one dot of the monochrome black is the same as the amount of the ink of each color ejected when forming the dot of each color having the same size as the one dot of the monochrome black. 2. The ink jet printer according to claim 1, wherein the amount is 1.3 to 1.5 times the amount.   When forming the mixed color black dot between the single color black dots, the amount of the black ink ejected when forming the single color black dot can be ejected from a nozzle that ejects the black ink. 2. The ink jet printer according to claim 1, wherein the ink amount is smaller than a maximum ink amount per dot. An ink ejection method for ejecting black ink, yellow ink, magenta ink, and cyan ink from a nozzle,
A plurality of nozzle rows in which a plurality of the nozzles are arranged at a predetermined interval P in a predetermined direction are arranged in a direction orthogonal to the predetermined direction at least one row for each color, and the black ink nozzle row is the yellow ink Preparing an inkjet head arranged to be shifted by a half of a predetermined interval P in the predetermined direction with respect to each nozzle row of magenta ink and cyan ink;
When recording in the color mode, the yellow ink, the magenta ink, and the cyan ink are respectively ejected from nozzles that eject the black ink at positions adjacent to the positions of the dots in the predetermined direction of the monochrome black formed by ejecting the black ink. Forming black dots continuously in the predetermined direction by simultaneously ejecting ink to form mixed color black dots in which the yellow ink, magenta ink, and cyan ink are mixed;
The single-color or two-color mixed dots of the yellow ink, magenta ink, and cyan ink are formed at positions shifted by a half of the predetermined interval P in the predetermined direction with respect to the dot positions of the single-color black. An ink discharge method comprising: The amount of the black ink ejected when forming the monochrome black dot is larger than the total amount of the yellow ink, magenta ink, and cyan ink ejected when forming the mixed color black dot. The ink ejection method according to claim 8 , wherein the inkjet head is controlled so as to be an amount .   The ink ejection method according to claim 8, wherein a hole diameter of the nozzle that ejects the black ink is larger than a hole diameter of the nozzle that ejects any one of the yellow ink, the magenta ink, and the cyan ink.   9. The ink ejection method according to claim 8, wherein ink that is more likely to bleed onto the recording medium than the black ink is selected in advance as the yellow ink, magenta ink, and cyan ink.

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