JP2010173215A - Inkjet head - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To inhibit the deterioration of printing quality by decreasing a width with regard to the transporting direction which causes color banding while avoiding the enlargement of an inkjet head with regard to the scanning direction. <P>SOLUTION: In an inkjet head 3 jetting inks of a plurality of colors while moving in the scanning direction, a plurality of nozzle arrays 41 which jet color inks are arranged in such a manner that six nozzle arrays 41 belonging to a nozzle group 42c jetting cyan are at both sides of a nozzle group 42d jetting magenta arranged as a center with regard to the scanning direction by dividing into 2 arrays for the left and 4 arrays for the right. Furthermore, six nozzle arrays 41 belonging to a nozzle group 42b jetting yellow are arranged at both farther sides with regard to the scanning direction of the nozzle arrays 41 jetting cyan which is separated to both sides with regard to the scanning direction by being divided into two arrays for the left and four arrays for the right. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an inkjet head that ejects a plurality of colors of ink onto a print medium.

  Conventionally, a serial-type inkjet head that prints a color image by ejecting a plurality of colors of ink while reciprocating along a scanning direction intersecting the conveying direction with respect to a printing medium conveyed in a predetermined conveying direction. It has been known. In an inkjet head for recording such a color image, a plurality of nozzle groups corresponding to the respective colors are arranged side by side in the scanning direction. Each nozzle group is composed of a plurality of nozzle rows in which a plurality of nozzles arranged along the transport direction intersecting the scanning direction are arranged in the scanning direction. A plurality of colors of ink are stacked and landed to form dots on the print medium.

  In general, a plurality of nozzle arrays that eject the same color of ink are often arranged adjacent to each other in the scanning direction. In this case, printing in the forward path and printing in the backward path are performed on the print medium. The landing order of each color ink is reversed. Then, even if you try to form dots of the same color by overlapping multiple colors of ink in printing on the forward and return paths, the colors of the dots formed on the print medium in printing on the forward and return paths are slightly different. End up. As a result, so-called color banding occurs in which a striped pattern is formed in the color image recorded on the print medium for each length of the nozzle row, and the print quality is deteriorated.

  Therefore, the inkjet head described in Patent Document 1 has two nozzle rows for each color. The two nozzle rows that eject ink of a certain color are set at the center in the scanning direction, and the other nozzle rows are arranged. One row is divided and arranged on both sides in the scanning direction so as to sandwich the two nozzle rows arranged in the center. In this way, by arranging the nozzles that form continuous dots in the transport direction on both sides in the scanning direction so as to sandwich the two nozzle rows arranged in the center, the width at which color banding occurs is reduced. When the entire color image recorded on the print medium is viewed, the color banding is made inconspicuous and the deterioration of the print quality is suppressed.

JP 2006-347155 A (FIG. 6)

  By the way, in recent years, in order to meet the need for higher image quality of color images, an ink jet head that includes a plurality of nozzle arrays that eject ink of each color and increases the number of ejected dots is known. In the inkjet head described in Patent Document 1, when the number of nozzle rows is increased, a common ink chamber is required for each nozzle row, the number of common ink chambers is increased, and the inkjet head in the scanning direction. Will become larger. In this way, arranging the nozzle rows while taking into account the increase in size of the inkjet head in the scanning direction and the reduction in print quality due to color banding increases the number of nozzle rows and divides the nozzle rows equally on both sides in the scanning direction. If it cannot be placed, it becomes very difficult.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an inkjet head that can suppress a decrease in print quality by reducing the width in the conveyance direction in which color banding occurs while suppressing an increase in size of the inkjet head in the scanning direction. It is.

  The inkjet head of the present invention is an inkjet head that ejects a plurality of colors of ink onto a print medium that is transported in a predetermined transport direction that intersects the scan direction while moving in a predetermined scan direction. And a plurality of common ink chambers arranged side by side in the scanning direction, and the nozzle groups are arranged at equal intervals along the transport direction. A nozzle row composed of a plurality of nozzles includes 6 or more 2 × odd even rows, and the nozzle rows are arranged side by side in the scanning direction, and are arranged for every two nozzle rows adjacent to each other in the scanning direction. The plurality of nozzles belonging to each nozzle group are arranged in a shifted manner with respect to the transport direction and are viewed from the scanning direction. The nozzle groups are arranged at equal intervals along the transport direction, and the other nozzle groups except for one nozzle group among the plurality of nozzle groups are arranged in two rows communicating with one common ink chamber. The nozzle rows are arranged separately on both sides in the scanning direction so as to sandwich the one nozzle group, and among the plurality of nozzle rows belonging to the other nozzle group, the scanning is performed with the one nozzle group interposed therebetween. The number of nozzle rows arranged on one side in the direction is different from the number of nozzle rows arranged on the other side in the scanning direction. A plurality of color inks are a plurality of color inks formed by overlapping one dot.

  According to the ink jet head of the present invention, a plurality of nozzle rows belonging to other nozzle groups are arranged separately on both sides in the scanning direction so as to sandwich one nozzle group in units of two nozzle rows communicating with one common ink chamber. is doing. The plurality of common ink chambers are spaced apart from each other in the scanning direction so that each of the common ink chambers is divided. Therefore, as the number of common ink chambers increases, the gap between adjacent common ink chambers increases. End up. Therefore, rather than arranging one nozzle row in one common ink chamber, arranging two nozzle rows so that two nozzle rows communicate in one common ink chamber is more effective for the nozzle row. The total number of common ink chambers is smaller than the total number. Thereby, while suppressing the enlargement of the inkjet head regarding a scanning direction, the width | variety regarding the conveyance direction which color banding produces can be made small, and the fall of print quality can be suppressed.

  The plurality of nozzle rows belonging to the other nozzle group includes the number of nozzle rows arranged on one side in the scanning direction and the nozzle arranged on the other side in the scanning direction with respect to the one nozzle group. It is preferable to arrange them separately so that the difference in the number of columns is minimized. According to this, the width in the conveyance direction in which color banding occurs can be made smaller and substantially uniform, and the deterioration in print quality can be further suppressed.

  Further, the total number of the plurality of nozzle rows belonging to each nozzle group is 6, and the plurality of nozzle rows belonging to the other nozzle groups is arranged in two on one side in the scanning direction across the one nozzle group. The four rows are arranged on the other side in the scanning direction, and are divided into only two rows on the one side in the scanning direction than the nozzle spacing in the transport direction between the six nozzle rows belonging to the other nozzle group. Further, it is preferable that the nozzle interval in the transport direction between the nozzle rows is larger. According to this, when the total number of the plurality of nozzle rows belonging to each nozzle group is 6, it is possible to reduce the width in the transport direction in which color banding occurs and suppress the deterioration of the print quality.

  In addition, the number of the plurality of nozzle groups is three or more, and a plurality of the nozzles belonging to two or more other nozzle groups having different ejected inks on one side in the scanning direction with respect to the one nozzle group. The rows are alternately arranged in two rows and four rows from the side close to the one nozzle group, and belong to the other nozzle groups different from each other on the other side in the scanning direction with respect to the one nozzle group. The plurality of nozzle rows are alternately arranged in four rows and two rows from the side close to the one nozzle group, and on the one side in the scanning direction and the other side in the scanning direction with respect to the one nozzle group. The two or more other nozzle groups are arranged in the same order in a direction away from the one nozzle group with respect to the scanning direction, and belong to the three or more nozzle groups, respectively. It is preferred spacing in equal the scanning direction for three or more nozzles equal direction position. According to this, it is possible to reduce color unevenness due to a difference in the degree of ink penetration into the print medium due to a difference in ink landing timing.

  In addition, it is preferable that at least one of a plurality of inner surfaces that define each common ink chamber is formed of a damper. Thereby, the pressure wave propagated to the ink in the common ink chamber is absorbed by the elastic deformation of the damper, and crosstalk can be prevented.

  While suppressing an increase in the size of the inkjet head in the scanning direction, it is possible to reduce the width in the conveyance direction in which color banding occurs, thereby suppressing a decrease in print quality.

1 is a schematic configuration diagram of an inkjet printer according to an embodiment. It is a top view of an inkjet head. FIG. 3 is a partially enlarged view of FIG. 2. It is the IV-IV sectional view taken on the line of FIG. FIG. 6 is a diagram for explaining an ink landing sequence on a recording sheet. 6 is a top view of an ink jet head according to Modification 1. FIG. FIG. 10 is a top view of an ink jet head according to Modification 2. It is a longitudinal cross-sectional view of the inkjet head in a modification.

  Next, a preferred embodiment of the present invention will be described. In this embodiment, four types of ink (cyan, magenta, yellow, and black) are ejected from a nozzle provided in an ink jet head onto a recording paper (printing medium), whereby a desired character or color image is applied to the recording paper. The present invention is applied to an inkjet printer that prints the above.

  First, an ink jet printer will be described. FIG. 1 is a schematic configuration diagram of an ink jet printer according to the present embodiment. As shown in FIG. 1, the inkjet printer 1 includes a carriage 2 that can move in the left-right direction (scanning direction) in FIG. 1, and nozzles 40 (see FIG. 1) that are provided on the carriage 2 and eject ink onto recording paper P. 2), and a transport roller 5 that transports the recording paper P forward (paper transport direction: transport direction) in FIG. 1.

  The carriage 2 is provided so as to be capable of reciprocating in the scanning direction along a guide shaft 8 disposed over two side walls of the main body frame 4. An ink jet head 3 is mounted on the carriage 2. The inkjet head 3 ejects ink onto the recording paper P conveyed by the conveying roller 5 from the nozzles 40 provided on the lower surface thereof while reciprocating in the scanning direction together with the carriage 2.

  The conveying roller 5 is fixed to a rotating shaft 7 that is disposed across two side walls of the main body frame 4. As the rotary shaft 7 rotates about the axis, the transport roller 5 rotates together with the rotary shaft 7, and the recording paper P is transported in the paper feed direction.

  Next, the inkjet head 3 will be described in detail. FIG. 2 is a top view of the inkjet head. FIG. 3 is a partially enlarged view of FIG. 4 is a cross-sectional view taken along line IV-IV in FIG. However, in order to make the drawing easy to understand, the pressure chamber 34 and the through holes 35, 36, 39 shown in FIG. 3 are not shown in FIG. 2, and the nozzle 40 is shown larger than the actual size. For convenience of explanation, in FIG. 2, reference numerals (1) to (6) are attached from the top in the order in which the nozzles 40 are arranged in the paper feed direction when viewed from the scanning direction. That is, when one line along the paper feeding direction is recorded on the recording paper P, the ink is landed on the recording paper P in the paper feeding direction in numerical order.

  As shown in FIGS. 2 to 4, the inkjet head 3 applies pressure to the ink in the pressure chamber 34 and the flow path unit 22 in which the ink flow path including the nozzle 40 and the pressure chamber 34 is formed. And a piezoelectric actuator 23 that ejects ink from the nozzles 40 of the flow path unit 22.

  First, the flow path unit 22 will be described. The flow path unit 22 has a cavity plate 30, a base plate 31 and a manifold plate 32 formed of a metal material such as stainless steel, and a nozzle plate 33 formed of a polymer synthetic resin material such as polyimide. These four plates 30 to 33 are joined in a laminated state.

  A plurality of penetrating nozzles 40 are formed in the nozzle plate 33. The plurality of nozzles 40 are arranged along the paper feed direction (vertical direction in FIG. 2) to form a nozzle row 41, and a plurality of such nozzle rows 41 are arranged in the scanning direction. The plurality of nozzle rows 41 constitute four nozzle groups 42 a to 42 d that eject inks of different colors for every even number of six rows.

  The plurality of nozzles 40 belonging to each nozzle group 42 are displaced with respect to the paper feeding direction, and are arranged at equal intervals along the paper feeding direction when viewed from the scanning direction. In addition, two nozzles 40 are formed in each nozzle row 41, and the interval between the two nozzles 40 belonging to the same nozzle row 41 is equal in all nozzle rows 41.

  The plurality of nozzles 40 belonging to the nozzle group 42a is black, the plurality of nozzles 40 belonging to the nozzle group 42b is yellow, the plurality of nozzles 40 belonging to the nozzle group 42c is cyan, and the plurality of nozzles 40 belonging to the nozzle group 42d. The magenta ink is ejected from each.

  The six nozzle rows 41 from the leftmost in FIG. 2 belong to the nozzle group 42a. Of the remaining 18 nozzle rows 41 excluding the 6 nozzle rows 41, the 6 nozzle rows 41 located in the center in the scanning direction belong to the nozzle group 42d. Further, two nozzle rows 41 adjacent to each other located on the left side of the nozzle group 42d and four nozzle rows 41 located on the right side and adjacent to each other belong to the nozzle group 42c. Also, four nozzle rows 41 that are adjacent to each other and belong to the nozzle group 42c and that are located immediately to the left of the two nozzle rows 41, and four nozzle rows 41 that belong to the nozzle group 42c and are adjacent to each other. The two nozzle rows 41 located immediately to the right and adjacent to each other belong to the nozzle group 42b.

  That is, when only the plurality of nozzle arrays 41 that eject color ink (yellow, cyan, magenta) are excluded except for the 6 nozzle arrays 41 that eject black, the nozzle group 42d that ejects magenta is positioned in the center in the scanning direction. The six nozzle rows 41 belonging to the nozzle group 42c that injects cyan on both sides in the scanning direction are arranged in two rows on the left side and four rows on the right side. Further, six nozzle rows 41 belonging to the nozzle group 42b that ejects yellow on both sides in the scanning direction of the nozzle row 41 that ejects cyan divided on both sides in the scanning direction include four rows on the left and two rows on the right. It is divided and arranged.

  In other words, if only the plurality of nozzle rows 41 that eject color ink (yellow, cyan, magenta) are excluded except for the six nozzle rows 41 that eject black, the nozzle group 42d that ejects magenta is scanned. On the left side of the nozzle group 42d as the center with respect to the direction, two nozzle rows 41 for ejecting cyan and four nozzle rows 41 for ejecting yellow are sequentially arranged from the side closer to the nozzle group 42d. Further, on the right side of the nozzle group 42d, four nozzle rows 41 that inject cyan in order from the side closer to the nozzle group 42d, in the same color order as the left side in order from the side closer to the nozzle group 42d, and yellow are injected. Two nozzle rows 41 are arranged in order.

  Further, the nozzle interval in the paper feed direction between the nozzle rows 41 ejecting the same color ink divided into only two rows on one side in the scanning direction is the nozzle interval in the paper feed direction between the six nozzle rows 41 ejecting the same color ink. Is bigger than. Specifically, the plurality of nozzles 40 belonging to the two nozzle rows 41 that eject cyan that is located to the left of the nozzle group 42d that ejects magenta are the third and fifth nozzles 40. The nozzle spacing in the paper feeding direction of the two nozzles 40 is larger than the nozzle spacing in the paper feeding direction of all the nozzles 40 that eject cyan. Further, three nozzles 40 that eject different colors of ink and have the same position in the paper feed direction have the same interval in the scanning direction.

  A plurality of nozzles 40 belonging to two nozzle rows 41 located between two manifold channels 37 adjacent to each other in the scanning direction described later are not adjacent to each other in the paper feeding direction. Therefore, the two nozzle rows 41 positioned between the two manifold channels 37 can be brought close to each other in the scanning direction, and the inkjet head 3 can be reduced in size in the scanning direction.

  As shown in FIGS. 3 and 4, the cavity plate 30 has a plurality of pressure chambers 34 corresponding to the plurality of nozzles 40. Each pressure chamber 34 has a substantially elliptical shape with the scanning direction as the longitudinal direction, and is arranged so that the right end of the pressure chamber 34 overlaps the nozzle 40 in plan view. Further, through holes 35 and 36 are formed in the base plate 31 at positions overlapping with both ends in the longitudinal direction of the pressure chamber 34 in plan view.

  As shown in FIGS. 2 to 4, the manifold plate 32 is formed with a plurality of manifold channels 37 (common ink chambers) extending in the paper feeding direction and arranged in the scanning direction. Each manifold channel 37 is located on both sides in the scanning direction and communicates in common with each of two adjacent nozzle rows 41. Since the plurality of manifold channels 37 are arranged so as to be separated from each other in the scanning direction, when the number of the manifold channels 37 increases, a gap between the adjacent manifolds 37 is increased. It will increase. Therefore, the two nozzle rows 41 are arranged so that the two nozzle rows 41 communicate with one manifold channel 37 rather than the one nozzle row 41 communicates with one manifold channel 37. However, the total number of manifold channels 37 is smaller than the total number of nozzle rows 41, and the inkjet head 3 can be downsized in the scanning direction. Therefore, in the present embodiment, the plurality of nozzle rows 41 arranged separately on both sides in the scanning direction with the nozzle group 42d for ejecting magenta ink interposed between the inkjet head 3 so as not to increase in size in the scanning direction. They are arranged separately for every two nozzle rows, not every nozzle row.

  Each manifold channel 37 overlaps substantially half of the corresponding pressure chamber 34 in plan view. Further, as shown in FIG. 2, the same color ink is stored, and one end portion of the manifold channel 37 adjacent to each other in the scanning direction (the upstream end portion in the paper feed direction: the upper end portion in FIG. 2) communicates. And communicated with an ink supply port (not shown) formed in the uppermost cavity plate 30. The ink supply port is connected to an ink tank (not shown), and ink in the ink tank is supplied to the manifold channel 37 from the ink supply port. In the manifold plate 32, a through hole 39 is formed at a position overlapping with both the through hole 36 of the base plate 31 and the nozzle 40 of the nozzle plate 33 in plan view.

  As shown in FIG. 4, in the flow path unit 22, the manifold flow path 37 that communicates with the ink supply port 38 communicates with the pressure chamber 34 through the through hole 35, and the pressure chamber 34 further includes the through holes 36 and 39. Via the nozzle 40. That is, in the flow path unit 22, a plurality of individual ink flow paths are formed from the outlet of the manifold flow path 37 through the pressure chamber 34 to the nozzle 40.

  Next, the piezoelectric actuator 23 will be described. The piezoelectric actuator 23 has a diaphragm 50, a piezoelectric layer 51, and a plurality of individual electrodes 52. The diaphragm 50 is made of a conductive material such as a metal material, and is joined to the upper surface of the cavity plate 30 so as to cover the plurality of pressure chambers 34. The conductive diaphragm 50 also serves as a common electrode for applying an electric field to a portion disposed between the plurality of individual electrodes 52 of the piezoelectric layer 51, as will be described later. Are always held at the ground potential.

  The piezoelectric layer 51 is a mixed crystal of lead titanate and lead zirconate and is made of a piezoelectric material mainly composed of lead zirconate titanate (PZT) having ferroelectricity. It is continuously arranged across the pressure chamber 34. The piezoelectric layer 51 is previously polarized in the thickness direction.

  The plurality of individual electrodes 52 are provided on the upper surface of the piezoelectric layer 51 so as to correspond to the plurality of pressure chambers 34. The individual electrode 52 has a substantially elliptical planar shape that is slightly smaller than the pressure chamber 34, and is disposed at a position overlapping the substantially central portion of the pressure chamber 34 in plan view. Further, one end portion (left end portion in FIG. 3) in the longitudinal direction of the individual electrode 52 extends to a position where it does not overlap with the pressure chamber 34 in plan view, and its tip end portion is a contact 52a, which is not shown in the drawing. It is a connection terminal connected to a wiring member such as a substrate (FPC). Then, a driving potential is applied via the FPC by a driver IC (not shown).

  Here, the operation of the piezoelectric actuator 23 during ink ejection will be described. When ink is ejected from a certain nozzle 40, a driving potential is applied from the driver IC to the individual electrode 52 corresponding to the pressure chamber 34 communicating with the nozzle 40. Then, a potential difference is generated between the individual electrode 52 to which the driving potential is applied and the diaphragm 50 held at the ground potential, and an electric field parallel to the thickness direction is generated in the piezoelectric layer 51 sandwiched between the two. Since the direction of the electric field coincides with the polarization direction of the piezoelectric layer 51, the piezoelectric layer 51 polarized in the thickness direction contracts in a horizontal direction orthogonal to the direction of the electric field (piezoelectric lateral effect). As a result, the portion of the diaphragm 50 facing the pressure chamber 34 is deformed so as to protrude toward the pressure chamber 34 (unimorph deformation). At this time, the volume of the pressure chamber 34 decreases, the pressure of the ink inside the pressure chamber 34 increases, and ink is ejected from the nozzle 40 communicating with the pressure chamber 34.

  Next, the printing operation by the inkjet printer 1 will be described. FIG. 5 is a diagram for explaining the landing order of the ink on the recording paper. In the present embodiment, the movement of the carriage 2 from the left to the right in FIG. 1 is the forward path, and the movement from the right to the left is the backward path. Further, the black ink printing operation is omitted, and only the color ink ejection operation will be described.

  The ink jet printer 1 records an image by ejecting ink onto the recording paper P conveyed by the conveying roller 5 from a plurality of nozzles 40 of the ink jet head 3 that reciprocates in the scanning direction together with the carriage 2. Further, the ink jet printer 1 forms one dot by overlapping and landing on the recording paper P three color inks ejected from three nozzles 40 having the same position in the paper feeding direction.

  Here, it is assumed that a plurality of nozzle rows 41 that eject color inks are gathered for each color. For example, from the left side of FIG. 2, it is assumed that six nozzle rows 41 that eject yellow, six nozzle rows 41 that eject cyan, and six nozzle rows 41 that eject magenta are arranged in this order.

  When a printing operation is performed with this nozzle row arrangement to form dots of a specific color in which three color inks are mixed on the recording paper P, the inks land in the order of magenta, cyan, and yellow in the forward path. On the return path, the inks land in the order of yellow, cyan, and magenta. As described above, if the landing order of the ink changes every time the movement direction of the carriage 2 is switched, the same specific color can be used without changing the amount of ink ejected from the nozzles 40 of the respective colors in printing in the forward path and the backward path. Even if each dot is to be formed, the color of the dots formed on the recording paper P is slightly different. As a result, a so-called color banding in which a striped pattern is formed for each length of the nozzle row 41 in the color image recorded on the recording paper P occurs, and the print quality is deteriorated.

  Therefore, in the present embodiment, as shown in FIG. 2, the six nozzle rows 41 that eject magenta are the center in the scanning direction, and the six nozzle rows 41 that eject cyan on both sides in the scanning direction are shown in FIG. It is divided into 2 columns on the left side of 2 and 4 columns on the right side. Further, six nozzle rows 41 for injecting yellow on both sides in the scanning direction are arranged in four rows on the left side and two rows on the right side in FIG.

  When a printing operation is performed with this arrangement of nozzle rows to form dots of a specific color in which three color inks are mixed on the recording paper P, as shown in FIG. In the first, second, fourth, and sixth positions, the inks overlap in the order of cyan, magenta, and yellow, and in the third and fifth positions, the inks land in the order of yellow, magenta, and cyan. To do. In the return path, the inks overlap in the order of yellow, magenta, and cyan at the first, second, fourth, and sixth positions along the paper feed direction, and cyan, magenta, and yellow at the third and fifth positions. The inks land in the order of. In other words, when trying to form a dot of a specific color, the color of the dot formed is slightly different at the first, second, fourth, sixth position and third, fifth position along the paper feed direction. ing. In other words, color banding is also generated in one-way printing on the forward path or the return path. Specifically, in the nozzle arrangement of the present embodiment, color banding having a length in which three dots from the sixth to the second are continuously generated occurs.

  In this way, by arranging the nozzles 40 that form continuous dots in the paper feed direction on both sides in the scanning direction across the magenta nozzle group 42d arranged in the center, the width of the color banding can be set to the nozzle row 41. Therefore, when the entire color image recorded on the recording paper P is viewed, the striped pattern becomes inconspicuous, and deterioration in print quality can be suppressed. Also, with this nozzle row arrangement, the two adjacent nozzle rows 41 that eject ink of the same color are arranged separately in the scanning direction, so the number of manifold channels 37 does not increase, and the inkjet head 3 can be prevented from being enlarged in the scanning direction.

  Further, the plurality of nozzle rows 41 belonging to the nozzle groups 42b and 42c that eject cyan and yellow include the number of nozzle rows 41 arranged on one side in the scanning direction and the other side in the scanning direction across the nozzle group 42d that ejects magenta. The nozzle rows 41 arranged on the side are arranged separately so that the difference in the number of rows is minimized. Therefore, the width in the conveyance direction in which color banding occurs can be made smaller and substantially uniform, and the deterioration of the print quality can be further suppressed.

  Also, the nozzle spacing in the paper feed direction between the nozzle rows 41 that eject the same color ink divided into only two rows on one side in the scanning direction is the nozzle spacing in the paper feed direction between the six nozzle rows 41 that eject the same color ink. Is larger, the plurality of nozzles 40 belonging to the nozzle row that ejects the same color ink divided into only two rows do not form continuous dots, so the width in the transport direction in which color banding occurs is made smaller. Therefore, it is possible to further suppress a decrease in print quality.

  Furthermore, since the three nozzles 40 that eject inks of different colors and have the same position in the paper feed direction have the same interval in the scanning direction, the degree of ink penetration into the recording paper P due to the difference in ink landing timing. Color unevenness due to differences can be reduced.

  Next, modified examples in which various changes are made to the present embodiment will be described. However, components having the same configuration as in the above embodiment are given the same reference numerals and description thereof is omitted as appropriate.

  In this embodiment, the nozzle group 42d that ejects magenta is the center in the scanning direction, and six nozzle rows 41 that eject cyan on both sides of the scanning direction have two rows on the left and two on the right in FIG. They are arranged in 4 rows. Furthermore, the six nozzle rows 41 for jetting yellow on both sides in the scanning direction are arranged in four rows on the left side and two rows on the right side in FIG. The other nozzle groups across the group may be arranged separately on either side of the scanning direction as long as each of the two nozzle rows. For example, as shown in FIG. 6, the nozzle group 42d for ejecting magenta is the center in the scanning direction, and four nozzle rows 41 for ejecting cyan and yellow are arranged on the left side of FIG. Two nozzle rows 41 for jetting cyan and yellow may be arranged on each side (Modification 1).

  In the present embodiment, the plurality of nozzle arrays 41 belonging to the nozzle group for ejecting yellow and cyan across the nozzle group 42d for ejecting magenta are the same in the direction away from the nozzle group 42d for ejecting magenta with respect to the scanning direction. Although arranged in order, they may be arranged in a different order on one side and the other side in the scanning direction. For example, as shown in FIG. 7, with the nozzle group 42d that ejects magenta as the center in the scanning direction, the nozzle row 41 is arranged in the order of cyan and yellow from the side close to the nozzle group 42d on the right side of FIG. The nozzle row 41 may be arranged in the order of yellow and cyan from the side close to the nozzle group 42d on the left side of FIG. 7 (Modification 2).

  Further, in the present embodiment, the suppression of deterioration in print quality due to color banding in the arrangement of the plurality of nozzles 40 that ejects three color inks of yellow, cyan, and magenta has been described. The present invention is applicable. For example, in the case of a plurality of nozzles 40 for ejecting four color inks, in addition to the arrangement of the plurality of nozzle rows 41 as shown in FIG. 2, six nozzle rows 41 for ejecting the added same color ink. Among them, two nozzle rows 41 are arranged further to the left of the four nozzle rows 41 for injecting yellow, which are located to the left of the nozzle group 42d for injecting magenta, and the remaining four nozzle rows 41 are arranged. It is only necessary to dispose to the right of the two nozzle rows 41 that eject yellow located on the right side. That is, on one side of the scanning direction divided so as to sandwich one nozzle group, a plurality of nozzle rows 41 that eject inks of different colors are alternately arranged in two rows and four rows in order from the side closer to this one nozzle group. Are arranged side by side, and on the other side in the scanning direction, a plurality of nozzle rows 41 that eject inks of different colors are arranged in the same color arrangement order as one side in the scanning direction, and closer to one nozzle group It suffices if they are arranged alternately in four rows and two rows in order.

  Further, the nozzle group 42 located in the center in the scanning direction is not limited to the nozzle group 42d that ejects magenta, but may be the nozzle group 42b that ejects yellow, or the nozzle group 42c that ejects cyan. Good.

  In the present embodiment, the nozzle interval in the paper feed direction between the nozzle rows 41 that eject the same color ink divided into only two rows on one side in the scanning direction is the same between the six nozzle rows 41 that eject the same color ink. Although it is larger than the nozzle interval in the paper feeding direction, it may be equal. That is, two nozzles that form dots that are continuous in the paper feed direction may be formed in two nozzle rows 41 that are divided into only two rows. Specifically, for example, the nozzles 40 at the first and second positions may be formed in two nozzle rows 41 divided into only two rows. However, in this case, color banding of a length in which four dots from the third to the sixth are continuously generated occurs. Therefore, it is possible to suppress a decrease in print quality by reducing the width of the color banding. Considering this, it is preferable that the nozzles 40 formed in the two nozzle rows 41 divided into only two rows are nozzles 40 that do not form continuous dots.

  Further, as shown in FIG. 8, a damper plate 81 and a cover plate 82 may be laminated between the manifold plate 32 and the nozzle plate 33 so that the manifold channel 37 exhibits a damper effect. The damper plate 81 is laminated on the lower surface of the manifold plate 32, and a recess 83 is formed by half etching at a position overlapping the manifold channel 37 in plan view. That is, the damper plate 81 is locally thin at the portion where the recess 83 is formed, and this thin portion functions as a damper portion that attenuates ink pressure fluctuations in the manifold channel 37. The damper plate 81 is also formed with a through hole 84 that is continuous with the through hole 39 of the manifold plate 32. The cover plate 82 has a through hole 85 communicating with the through hole 84 of the damper plate 81. A through hole 85 formed in the cover plate 82 communicates with the nozzle 40. In the manifold channel 37, the pressure wave attenuation performance is proportional to the fifth power of the width of the manifold channel 37 in the scanning direction, like the manifold disclosed as an example in Japanese Patent Application Laid-Open No. 2008-213157. The width of the manifold channel 37 does not need to be twice as large as the width of one nozzle row in order to ensure the attenuation performance of two nozzle rows. Therefore, when the two nozzle rows 41 communicate with the manifold channel 37 in common, it is possible to suppress downsizing in the scanning direction while ensuring attenuation performance.

  In the present embodiment, the number of nozzle rows 41 belonging to each nozzle group is six rows, but may be 6 × 2 rows × odd rows such as 10 rows or 14 rows. When such two nozzle rows 41 can communicate with one common ink in common and are arranged separately on both sides in the scanning direction with one nozzle group arranged at the center in the scanning direction, even numbers are even. The present invention is effective in the case where the columns cannot be divided equally.

DESCRIPTION OF SYMBOLS 1 Inkjet printer 3 Inkjet head 37 Manifold flow path 40 Nozzle 41 Nozzle row 42a-42d Nozzle group

Claims (5)

An inkjet head that ejects a plurality of colors of ink onto a print medium that is transported in a predetermined transport direction that intersects the scan direction while moving in a predetermined scan direction,
A plurality of nozzle groups each ejecting a plurality of colors of ink;
A plurality of common ink chambers arranged side by side in the scanning direction,
Each nozzle group includes 6 or more 2 × odd even rows of nozzles composed of a plurality of nozzles arranged at equal intervals along the transport direction, and these nozzle rows are arranged side by side in the scanning direction. In addition, each of the two nozzle rows adjacent to each other in the scanning direction communicates in common with one common ink chamber,
The plurality of nozzles belonging to each nozzle group are arranged shifted with respect to the conveyance direction, and are arranged at equal intervals along the conveyance direction when viewed from the scanning direction,
Among the plurality of nozzle groups, except for one nozzle group, the other nozzle groups are in the scanning direction so as to sandwich the one nozzle group in units of two nozzle rows communicating with one common ink chamber. It is arranged separately on both sides,
Among a plurality of nozzle rows belonging to the other nozzle group, the number of the nozzle rows arranged on the one side in the scanning direction across the one nozzle group and the nozzle row arranged on the other side in the scanning direction An inkjet head characterized in that the number of rows of the ink jets is different.   The plurality of nozzle rows belonging to the other nozzle group include the number of nozzle rows arranged on one side in the scanning direction and the nozzle row arranged on the other side in the scanning direction with respect to the one nozzle group. The inkjet head according to claim 1, wherein the inkjet heads are arranged separately so that a difference in the number of rows is minimized. The total number of the plurality of nozzle rows belonging to each nozzle group is 6,
The plurality of nozzle rows belonging to the other nozzle group are arranged in two rows on the one side in the scanning direction across the one nozzle group, and arranged in four rows on the other side in the scanning direction,
The nozzle interval in the carrying direction between the nozzle rows divided into only two rows on the one side in the scanning direction is larger than the nozzle interval in the carrying direction between the six nozzle rows belonging to the other nozzle group. The inkjet head according to claim 2, wherein the inkjet head is large. The number of the plurality of nozzle groups is 3 or more,
On one side in the scanning direction with respect to the one nozzle group, the plurality of nozzle rows belonging to two or more other nozzle groups with different ejected inks are arranged in two rows and four rows from the side close to the one nozzle group. And are arranged side by side,
On the other side in the scanning direction with respect to the one nozzle group, the plurality of nozzle rows belonging to the other nozzle groups different from each other are alternately arranged in four rows and two rows from the side close to the one nozzle group. Has been
On the one side in the scanning direction and the other side in the scanning direction with respect to the one nozzle group, the two or more other nozzle groups are arranged in the same order in a direction away from the one nozzle group with respect to the scanning direction. And
4. The inkjet head according to claim 3, wherein intervals in the scanning direction are the same for three or more nozzles that belong to three or more nozzle groups and have the same position in the transport direction. 5. The inkjet head according to any one of claims 1 to 4, wherein at least one of a plurality of inner surfaces defining each common ink chamber is configured by a damper.

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