JP2012254647A - Inkjet head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inkjet head with high versatility capable of striking a balance between the high image-quality printing using pre-coat inks prior to printing inks and the high-speed printing for jetting the printing inks from many nozzles at a time.SOLUTION: The inkjet head 3 includes first nozzle arrays 51a-51d which comprise a plurality of first nozzles 50a-50d arranged at prescribed pitches P along a conveyance direction of printing paper to jet the printing inks, and a second nozzle array 51e which is disposed in a region of the upstream side in the conveyance direction from the first nozzle arrays 51a-51d comprising a plurality of second nozzles 50e arranged at the same pitches as those of the plurality of first nozzles 50a-50d, and capable of jetting the printing inks or the pre-coat inks.

Description

  The present invention relates to an inkjet head that ejects ink droplets toward a print medium.

  A general inkjet head employed in an inkjet printer ejects printing ink, such as black ink and color ink, for printing characters, images, and the like toward a printing medium conveyed in a predetermined conveyance direction. Further, in recent years, in addition to printing ink, an inkjet head that can eject ink other than printing ink has also been proposed. As such an ink jet head, for the purpose of preventing bleeding of the printing ink, the ink that does not directly contribute to printing of an image or the like (hereinafter referred to as a precoat ink) can be ejected onto the printing medium prior to the printing ink. There is something that was done.

For example, an inkjet head described in Patent Document 1 includes an ink ejection nozzle array that ejects printing ink, and a reaction liquid ejection nozzle array that ejects a reaction liquid that reacts with the printing ink to prevent bleeding. And have. Note that the reaction liquid discharge nozzle row is disposed upstream of the ink discharge nozzle row in the transport direction of the print medium. As a result, the reaction liquid is first ejected from the reaction liquid ejection nozzle array to the transported print medium, and then the printing ink is ejected from the ink ejection nozzle array to the area where the reaction liquid has landed. Will be.
JP 2005-119115 A

  However, it is necessary to use a precoat ink that does not directly contribute to printing of an image or the like, such as the reaction solution of Patent Document 1, only when printing a very high quality image while suppressing bleeding of the printing ink. It is done. Therefore, the ink jet head of Patent Document 1 provided with the nozzle array dedicated to the reaction liquid is used only for high performance ink jet printers that specialize in high-quality image printing. It is not used for general-purpose printers that prioritize printing speed. In other words, the inkjet head disclosed in Patent Document 1 becomes a dedicated head for a high-performance model and lacks versatility, which increases costs.

  An object of the present invention is to provide a highly versatile inkjet head that can support both high-quality printing using pre-coated ink prior to printing ink and high-speed printing in which printing ink is ejected from many nozzles at once. Is to provide.

  An inkjet head according to a first aspect of the invention is an inkjet head that ejects 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. The first nozzle row composed of a plurality of first nozzles arranged at a predetermined pitch along the first nozzle row, and communicates with the first nozzle row and at a position adjacent to the first nozzle row in the scanning direction. A first manifold channel that extends in a direction, a first ink supply port that communicates with the first manifold channel and is connected to a supply source of printing ink, and the first nozzle row more than the first nozzle row. In a region upstream of the transport direction, a second nozzle row including a plurality of second nozzles arranged at the predetermined pitch along the transport direction in the same manner as the plurality of first nozzles, and the second nozzle A second manifold channel that extends in the transport direction at a position adjacent to the second nozzle row in the scanning direction, communicates with the second manifold channel, and A second ink supply port connected to any one of a supply source of a printing ink and a supply source of a precoat ink used prior to the printing ink, and the first nozzle row and the first ink supply port The two nozzle rows are arranged away from each other in the scanning direction, and the first ink supply port communicates with an end of the first manifold channel on the upstream side in the transport direction, and from the first nozzle row Is also an upstream area in the transport direction, and is disposed in an area adjacent to the second nozzle row in the scanning direction, and the second ink supply port is downstream in the transport direction of the second manifold channel. At the end of the And, and, an area of said downstream side than the second nozzle row, and the first nozzle row and is characterized in that it is arranged in a region adjacent to the scanning direction.

  Since the first ink supply port communicating with the first nozzle row is connected to the printing ink supply source, the first nozzle row ejects the printing ink. On the other hand, since the second ink supply port communicating with the second nozzle row is connected to either the printing ink supply source or the precoat ink supply source, the second nozzle row is connected to the connection destination supply source. The supplied printing ink or precoat ink is ejected.

  Here, the second nozzle row capable of ejecting the precoat ink is arranged farther upstream in the transport direction than the first nozzle row ejecting the printing ink. Therefore, when using the precoat ink, first, the precoat ink is ejected from the second nozzle row toward the print medium to form the underlayer on the print medium, and then the underlayer is formed from the first nozzle. Ink for printing is ejected to the area. Thereby, since the penetration of the printing ink into the printing medium is suppressed, high-quality printing is possible. Further, when the second nozzle row is separated from the first nozzle row in the transport direction, inks having completely different components such as a solvent ejected from one of the first nozzle row and the second nozzle row from the other. It is difficult to cause a problem of mixing.

  Further, in the present invention, the first nozzle row and the second nozzle row have the same nozzle arrangement pitch. Therefore, after connecting the second ink supply port communicating with the second nozzle row to the printing ink supply source, the printing ink is ejected from both the first nozzle row and the second nozzle row, so that the precoat ink In addition to high-quality printing using the printer, high-speed printing in which printing ink is ejected at once from a large number of nozzles is also possible.

  In addition, since the first nozzle row and the second nozzle row are separated from each other also in the scanning direction, it is possible to more reliably suppress ink mixing between the first nozzle row and the second nozzle row. In addition, it is possible to separately configure caps that cover the first nozzle row and the second nozzle row that are spaced apart from each other, and prevent ink mixing during capping that tends to occur when the caps are integrated. be able to. Furthermore, when the first nozzle row and the second nozzle row are separated with respect to both the carrying direction and the scanning direction, on the upstream side in the carrying direction of the first nozzle row and on the downstream side in the carrying direction of the second nozzle row, Each vacant area exists. Therefore, the ink jet head can be reduced in size by arranging the ink supply ports in these empty regions.

  The ink jet head according to a second aspect of the present invention is the ink jet head according to the first aspect, wherein the first manifold channel is disposed on a side closer to the second nozzle row in the scanning direction with respect to the first nozzle row, The second manifold channel is disposed on the side closer to the first nozzle row in the scanning direction with respect to the second nozzle row, and between the first nozzle row and the second nozzle row in the scanning direction. Further, the first manifold channel and the second manifold channel are arranged.

  An ink jet head according to a third aspect of the present invention is the ink jet head according to the first or second aspect, wherein the number of nozzle arrays in the transport direction of the first nozzle row and the second nozzle row is equal.

  The precoat ink only needs to be ejected to a region where the printing ink lands, and does not need to be ejected to a region where the printing ink does not land. Therefore, in the present invention, the first nozzle row for ejecting the printing nozzles and the second nozzle row for ejecting the precoat ink have the same nozzle arrangement pitch and the same number of nozzle arrangements. Thereby, the precoat ink ejected from the second nozzle row can be landed first in each of the regions on the printing medium where the printing ink ejected from the first nozzle row will land. . That is, the precoat ink can be reliably landed on an area (an area where the printing ink is landed) on which an image or the like of the printing medium is printed, and the precoat ink is unnecessarily ejected on an area where the printing ink is not landed. This can also be prevented.

  According to a fourth aspect of the invention, in any one of the first to third aspects, the first nozzle row and the second nozzle row are separated from each other by the predetermined pitch with respect to the transport direction. It is characterized by.

  According to this configuration, the nozzles that respectively constitute the first nozzle row and the second nozzle row are arranged in a row at a constant pitch in the transport direction. Therefore, when printing ink is ejected not only from the first nozzle row but also from the second nozzle row, a continuous wide area can be printed at a time by a single long nozzle row including both nozzle rows. it can.

  An ink jet head according to a fifth aspect of the present invention is the ink jet head according to any one of the first to fourth aspects, wherein the first nozzle array includes a black nozzle array composed of a plurality of black nozzles that respectively eject black ink, and a color ink. A color nozzle row composed of a plurality of color nozzles to be ejected, the black nozzle row and the color nozzle row are arranged side by side in the scanning direction, and the second nozzle row is the black nozzle row and the color nozzle row. Further, in the region upstream of the transport direction, the scanning nozzle is disposed at a position closer to the black nozzle row than the color nozzle row.

  When two or more nozzle rows eject the same color ink, it is preferable from the viewpoint of improving print quality that these two or more nozzle rows are close to each other. In addition, in the present invention, since the black nozzle as the first nozzle row and the second nozzle row are adjacent to each other, the black ink is also ejected from the second nozzle row to perform text printing at high speed. The improvement of printing quality can be expected.

An ink jet head according to a sixth aspect of the present invention is the ink jet head according to any one of the first to fifth aspects, further comprising a droplet ejection surface on which the first nozzle row and the second nozzle row are formed and in communication with the nozzle row. A flow path unit in which an ink flow path is formed, and a surface of the flow path unit opposite to the liquid droplet ejection surface of the flow path unit. A first actuator that applies ejection energy to the ink; and an ink in the second nozzle row that is provided in a region facing the second nozzle row on a surface of the flow path unit opposite to the droplet ejection surface. A second actuator for applying injection energy to
The first actuator and the second actuator are configured as separate bodies.

  When the first nozzle row and the second nozzle row are separated from each other in both the transport direction and the scanning direction, they are provided at positions facing the first nozzle row and the second nozzle row. The two actuators that drive each will also move away from each other. However, if such two actuators are manufactured in one piece, there will be a lot of wasted parts, and the substrate of the actuator will be enlarged from a single substrate material. It is necessary to cut out, which is disadvantageous in terms of manufacturing cost. In the present invention, it is possible to reduce the manufacturing cost by configuring two actuators separately and reducing the size of each actuator.

  An ink jet head according to a seventh aspect is characterized in that, in the sixth aspect, the lengths of the first actuator and the second actuator in the transport direction are substantially equal.

  As described above, when the lengths of the two actuators in the transport direction are equal, the two actuators can be cut out from a single substrate material without waste.

  According to the present invention, the second nozzle row capable of ejecting the precoat ink is disposed farther upstream in the transport direction than the first nozzle row ejecting the printing ink. Therefore, when using the precoat ink, first, the precoat ink is ejected from the second nozzle row toward the print medium to form the underlayer on the print medium, and then the underlayer is formed from the first nozzle. Ink for printing is ejected to the area. Thereby, since the penetration of the printing ink into the printing medium is suppressed, high-quality printing is possible. Further, when the second nozzle row is separated from the first nozzle row in the transport direction, inks having completely different components such as a solvent ejected from one of the first nozzle row and the second nozzle row from the other. It is difficult to cause a problem of mixing.

  Further, in the present invention, the first nozzle row and the second nozzle row have the same nozzle arrangement pitch. Therefore, after connecting the second ink supply port communicating with the second nozzle row to the printing ink supply source, the printing ink is ejected from both the first nozzle row and the second nozzle row, so that the precoat ink In addition to high-quality printing using the printer, high-speed printing in which printing ink is ejected at once from a large number of nozzles is also possible.

  Next, an embodiment of the present invention will be described. FIG. 1 is a plan view showing a schematic configuration of an ink jet printer including the ink jet head of the present invention. As shown in FIG. 1, the printer 1 includes a carriage 2 configured to reciprocate along the scanning direction of FIG. 1, an inkjet head 3 and sub tanks 4a to 4e mounted on the carriage 2, and five inks. Cartridges 5a to 5e and a transport mechanism 6 for transporting the printing paper 100 in the transport direction of FIG.

  The carriage 2 is configured to be able to reciprocate along two guide shafts 17 extending in parallel in the left-right direction (scanning direction) in FIG. An endless belt 18 is connected to the carriage 2. When the endless belt 18 is driven to travel by the carriage drive motor 19, the carriage 2 moves in the scanning direction as the endless belt 18 travels. It has become.

  An ink jet head 3 and five sub tanks 4 a to 4 e are mounted on the carriage 2. The ink jet head 3 includes a large number of nozzles 50 for ejecting ink on the lower surface (the surface on the opposite side of the paper surface in FIG. 1). The five sub tanks 4a to 4e are arranged side by side along the scanning direction, and the tube joint 20 is integrally provided in the five sub tanks 4a to 4e. The five sub tanks 4 a to 4 e and the five ink cartridges 5 a to 5 e that are detachably attached to the holder 10 are connected to each other by the flexible tube 11 connected to the tube joint 20.

  The five ink cartridges 5a to 5e are provided with four colors of magenta, cyan, yellow, and black printing inks, and a colorless and transparent precoat that is jetted onto the printing paper 100 prior to the four colors of printing inks. A total of five types of ink are stored.

  The five types of ink respectively stored in the five ink cartridges 5a to 5e are supplied to the five sub tanks 4a to 4e via the five tubes 11 connected to the holder 10, and temporarily stored in the sub tanks 4a to 4e. After being stored, the ink is supplied to the inkjet head 3. The inkjet head 3 is reciprocated in the scanning direction together with the carriage 2 and is conveyed downward (conveying direction) in FIG. 1 by a conveying mechanism 6 from a large number of nozzles 50 provided on the lower surface (droplet ejection surface). Ink droplets are ejected onto the printing paper 100 to be printed.

  The transport mechanism 6 includes a paper feed roller 25 disposed upstream of the inkjet head 3 in the transport direction, and a paper discharge roller 26 disposed downstream of the inkjet head 3 in the transport direction. The paper feed roller 25 and the paper discharge roller 26 are rotationally driven by a paper feed motor 27 and a paper discharge motor 28, respectively. The transport mechanism 6 supplies the printing paper 100 to the inkjet head 3 from above in FIG. 1 by the paper feed roller 25, and prints in which images, characters, and the like are recorded by the inkjet head 3 by the paper discharge roller 26. The paper 100 is configured to be discharged downward in FIG.

  Next, the inkjet head 3 will be described in detail. 2 is a top view of the inkjet head 3, FIG. 3 is an enlarged view of a portion A in FIG. 2, and FIG. 4 is a sectional view taken along line IV-IV in FIG. However, in order to make the drawing easy to understand, in FIG. 2, illustration of a part of the ink flow path such as the pressure chamber 44 shown in FIG. 3 is omitted, and the nozzle 50 is illustrated larger than FIG. 3. .

  As shown in FIG. 2, the inkjet head 3 includes a flow path unit 30 in which an ink flow path including a nozzle 50 and a pressure chamber 44 is formed, and two piezoelectric actuators 31 a and 31 b disposed on the upper surface of the flow path unit 30. It has.

  As shown in FIG. 4, the flow path unit 30 includes a cavity plate 40, a base plate 41, a manifold plate 42, and a nozzle plate 43 made of a synthetic resin material, which are made of a metal material such as stainless steel. These four plates 40 to 43 are joined in a laminated state.

  Among the four plates 40 to 43, the nozzle plate 43 located in the lowermost layer is formed with a plurality of nozzles 50 that open to the lower surface (droplet ejection surface). The plurality of nozzles 50 are arranged along the transport direction (up and down direction in FIG. 2) to form five nozzle rows 51a to 51e. Here, as shown in FIG. 2, among the five nozzle rows 51 a to 51 e, the four nozzle rows 51 a to 51 d are in the downstream side region (lower half region in FIG. 2) of the nozzle plate 43 in the transport direction. Are arranged side by side in the scanning direction. On the other hand, the remaining nozzle row 51e is arranged in a region (upper half region in FIG. 2) that is separated from the four nozzle rows 51a to 51d on the upstream side in the transport direction. Hereinafter, the four nozzle rows 51a to 51d are referred to as first nozzle rows 51a to 51d, and the nozzle row 51e disposed upstream of the first nozzle rows 51a to 51d in the transport direction is referred to as a second nozzle row 51e. As will be described in detail later, when the inkjet head 3 is incorporated in the printer 1 of FIG. 1, the nozzles 50 a to 50 d (first nozzles) constituting the four first nozzle rows 51 a to 51 d are 4 While printing inks of colors (magenta, cyan, yellow, black) are respectively ejected, the nozzles 50e (second nozzles) constituting the second nozzle row 51e eject colorless and transparent precoat ink.

  Further, the second nozzle row 51e is arranged at a position away from the four first nozzle rows 51a to 51d not only in the transport direction but also in the scanning direction (left-right direction in FIG. 2). As a result, as shown in FIG. 2, the four first nozzle rows 51a to 51d are arranged in the lower right region in the figure, while the second nozzle row 51e is arranged in the upper left region in the figure. Yes.

  In the five nozzle rows 51a to 51e, the nozzle arrangement pitch P and the number of nozzle arrangements are all equal. Further, as shown in FIG. 2, four first nozzle rows 51a to 51d (more specifically, nozzles 50 positioned at the upstream end of the nozzle rows 51a to 51d in the transport direction) and second nozzle rows 51e ( The nozzle arrangement pitch P is separated from the nozzle 50) located at the downstream end of the nozzle row 51e in the transport direction.

  As shown in FIGS. 3 and 4, a plurality of pressure chambers 44 corresponding to the plurality of nozzles 50 are formed in the cavity plate 40 located in the uppermost layer of the four plates. The pressure chamber 44 has a substantially oval planar shape with the scanning direction as the longitudinal direction, and is disposed so that one end of the pressure chamber 44 overlaps the nozzle 50 in plan view. Further, through holes 45 and 46 are formed in the base plate 41 at positions overlapping with both ends in the longitudinal direction of the pressure chamber 44 in plan view.

  The manifold plate 42 is formed with five manifold channels 47 respectively corresponding to the five nozzle rows 51a to 51e. As shown in FIG. 2, each manifold channel 47 extends in the transport direction at a position next to the corresponding nozzle row 51 and, as shown in FIG. 3, is an abbreviation of the corresponding pressure chamber 44 in a plan view. It overlaps with the left half. As shown in FIG. 2, five ink supply ports 48a to 48e are formed in the uppermost cavity plate 40, and one end portion of each of the five manifold channels 47 is connected to these five ink supply ports 48a. To 48e, respectively. The five ink supply ports 48 a to 48 e are connected to the five ink cartridges 5 a to 5 e (see FIG. 1) via the tube 11.

  As described above, the four first nozzle rows 51a to 51d and the second nozzle row 51e are arranged apart from each other in both the transport direction and the scanning direction. Accordingly, the upstream area in the transport direction (upper right area in FIG. 2) of the inkjet head 3 and the downstream area in the transport direction (lower left area in FIG. 2) from the second nozzle array 51e are nozzles. This is a vacant area where 50 is not arranged. Therefore, four ink supply ports 48a to 48d (first ink supply ports) communicating with the four first nozzle rows 51a to 51d are arranged in the upstream region in the transport direction from the first nozzle rows 51a to 51d. In addition, an ink supply port 48e (second ink supply port) communicating with the second nozzle row 51e is arranged in a region downstream of the second nozzle row 51e in the transport direction. As a result, the ink supply ports 48a to 48e and the ink flow passages connected to the ink supply ports 48a to 48e are provided in a vacant area where the nozzle 50 is not disposed, and the inkjet head 3 can be downsized.

  As shown in FIGS. 3 and 4, the manifold plate 42 has a through hole at a position overlapping with both the through hole 46 formed in the base plate 41 and the nozzle 50 formed in the nozzle plate 43 in plan view. 49 is formed.

  As shown in FIG. 4, in the flow path unit 30, the manifold flow path 47 that communicates with the ink supply port 48 communicates with the pressure chamber 44 through the through hole 45, and the pressure chamber 44 further includes the through holes 46 and 49. It communicates with the nozzle 50 via That is, a plurality of individual ink channels are formed in the channel unit 30 from the outlet of the manifold channel 47 to the nozzle 50 through the pressure chamber 44.

  Next, the first piezoelectric actuator 31a and the second piezoelectric actuator 31b that apply ejection energy to the inks of the first nozzle rows 51a to 51d and the second nozzle row 51e will be described. As shown in FIG. 2, the first piezoelectric actuator 31 a ejects ink from the four first nozzle rows 51 a to 51 d, and the four first nozzle rows 51 a to 51 a on the upper surface of the flow path unit 30. 51d and a region facing the pressure chamber 44 corresponding to these nozzle rows. On the other hand, the second piezoelectric actuator 31b ejects ink from the second nozzle row 51e, and is a region facing the second nozzle row 51e and the pressure chamber 44 corresponding to this nozzle row on the upper surface of the flow path unit 30. Is arranged. Note that the five nozzle rows 51a to 51e to be driven by the first piezoelectric actuator 31a and the second piezoelectric actuator 31b have the same nozzle arrangement pitch P and the same number of nozzle arrangements, and therefore the five nozzle rows 51a. The lengths of ~ 51e are all equal. Therefore, the first piezoelectric actuator 31a and the second piezoelectric actuator 31b have substantially the same length in the nozzle arrangement direction (conveying direction).

  The first piezoelectric actuator 31a and the second piezoelectric actuator 31b have substantially the same structure except for the size because the number of nozzles 50 (nozzle rows 51) to be driven is different. Therefore, in the following description regarding the structure of the piezoelectric actuator 31, the first piezoelectric actuator 31a will be representatively described, and the description of the structure of the second piezoelectric actuator 31b will be omitted.

  As shown in FIGS. 3 and 4, the first piezoelectric actuator 31 a includes a diaphragm 60, a piezoelectric layer 61, and a plurality of individual electrodes 62. The diaphragm 60 is made of a conductive material such as a metal material, and is joined to the upper surface of the cavity plate 40 so as to cover the plurality of pressure chambers 44 communicating with the first nozzle rows 51a to 51d. The diaphragm 60 having conductivity is always held at the ground potential, and an electric field in the thickness direction is applied to the portion of the piezoelectric layer 61 located between the diaphragm 60 and the plurality of individual electrodes 62. Also serves as a ground electrode.

  The piezoelectric layer 61 is a mixed crystal of lead titanate and lead zirconate, and is made of a lead zirconate titanate-based piezoelectric ceramic material having ferroelectricity, and straddles a plurality of pressure chambers 44 on the upper surface of the diaphragm 60. Are arranged continuously. The piezoelectric layer 61 is previously polarized in the thickness direction.

  The plurality of individual electrodes 62 are provided on the upper surface of the piezoelectric layer 61 so as to correspond to the plurality of pressure chambers 44. The individual electrode 62 has a substantially elliptical planar shape that is slightly smaller than the pressure chamber 44, and is disposed at a position overlapping the substantially central portion of the pressure chamber 44 in plan view. One end portion (left end portion in FIG. 3) in the longitudinal direction of the individual electrode 62 extends to a position where it does not overlap with the pressure chamber 44 in plan view, and the tip end portion is a land 62a. A head driver is connected to the land 62a via a wiring member such as a flexible printed circuit board (FPC) (not shown). Then, either a predetermined drive potential or a ground potential is selectively applied from the head driver to the plurality of individual electrodes 62.

  The operation of the piezoelectric actuator 31 having the above configuration will be described. When a predetermined drive potential is applied to an individual electrode 62 from a head driver (not shown), a potential difference is generated between the individual electrode 62 to which the drive potential is applied and the diaphragm 60 as a ground electrode. An electric field in the thickness direction is generated at a portion sandwiched between the individual electrode 62 and the diaphragm 60. Here, when the polarization direction of the piezoelectric layer 61 is the same as the electric field direction, the piezoelectric layer 61 extends in the thickness direction and contracts in the plane direction. As the piezoelectric layer 61 contracts and deforms, the portion of the diaphragm 60 facing the pressure chamber 44 is deformed so as to protrude toward the pressure chamber 44 (unimorph deformation). At this time, since the volume of the pressure chamber 44 is reduced, the pressure of the ink inside the pressure chamber 44 is increased, and ink droplets are ejected from the nozzle 50 communicating with the pressure chamber 44.

  In the present embodiment, the first piezoelectric actuator 31a that drives the first nozzle rows 51a to 51d and the second piezoelectric actuator 31b that drives the second nozzle row 51e are configured separately. A portion that drives the first nozzle row 51 and a portion that drives the second nozzle row 51e may be integrated, and a piezoelectric actuator having a large area covering almost the entire upper surface of the flow path unit 30 may be employed. However, this causes useless parts that do not contribute to driving. That is, as in the present embodiment, when the first nozzle rows 51a to 51d and the second nozzle row 51e are separated from each other in both the transport direction and the scanning direction, the first nozzle rows 51a to 51d and the first nozzle rows 51a to 51d The two actuator portions that are provided at positions facing the two nozzle rows 51e and drive the two are also separated from each other, and the diaphragm 60 and the piezoelectric layer 61 disposed in the upper right region and the lower left region in FIG. This is a useless part that does not contribute to the driving of the nozzle row 51.

  Further, as shown in FIG. 5A, when a method of cutting the piezoelectric layer 61 from one fired piezoelectric sheet 70 is adopted as a manufacturing method of the piezoelectric layer 61, when each piezoelectric layer 61 is large, The number of piezoelectric layers 61 that can be cut out from one piezoelectric sheet 70 is reduced (only 9 sheets can be cut out in FIG. 5A). The same applies to the case where the diaphragm 60 is cut out from one metal sheet. Therefore, the manufacturing cost of the piezoelectric actuator becomes high.

  Therefore, in the present embodiment, as shown in FIG. 2, by separating the two piezoelectric actuators 31a and 31b, the size of each actuator is reduced, and unnecessary portions that do not contribute to driving of the nozzle array 51 are reduced as much as possible. be able to. Further, as shown in FIG. 5 (b), the piezoelectric layer 61a of the first piezoelectric actuator 31a having a large area is cut out from one piezoelectric sheet 70, and then the piezoelectric of the second piezoelectric actuator 31b having a small area is removed. Since the layer 61b can be cut out, a larger number of piezoelectric layers 61a and 61b can be cut out from one piezoelectric sheet 70 having the same size as that in FIG. 5A (in FIG. 5B). 24 sets), manufacturing costs can be reduced. Further, when the lengths in the transport direction of the first piezoelectric actuator 31a and the second piezoelectric actuator 31b (vertical length in FIG. 5) are substantially equal, as shown in FIG. 5B, the first piezoelectric actuator 31a. Since the piezoelectric layer 61b of the second piezoelectric actuator 31b can be cut out from the remaining portion immediately next to the piezoelectric layer 61a, it can be cut out more efficiently.

  Returning to FIG. 2, the four ink supply ports 48 a to 48 d (first ink supply ports) communicating with the four first nozzle rows 51 a to 51 d respectively have four colors of printing inks (magenta, cyan, The four ink cartridges 5 a to 5 d (see FIG. 1) respectively storing yellow and black) are connected via the tube 11. Therefore, since four colors of printing ink are supplied to the inkjet head 3 from the four first ink supply ports 48a to 48d, pressure is applied to the ink in the pressure chamber 44 by the first piezoelectric actuator 31a. The nozzles 50a to 50d (first nozzles) constituting the four first nozzle rows 51a to 51d eject four colors of printing ink.

  On the other hand, the ink supply port 48e (second ink supply port) communicating with the second nozzle row 51e can use the precoat ink in which the ink cartridge 5e for storing the precoat ink is mounted on the holder 10 as shown in FIG. In the printer 1, the ink cartridge 5 e (see FIG. 1) is connected via the tube 11. Accordingly, since the precoat ink is supplied from the second ink supply port 48e to the inkjet head 3, the second piezoelectric actuator 31b applies pressure to the ink in the pressure chamber 44, thereby forming the second nozzle row 51e. The nozzle 50e (second nozzle) ejects precoat ink. As described above, when the precoat ink is ejected from the second nozzle row 51e onto the printing paper 100, a base layer is formed on the printing paper 100 with the precoat ink. Thereafter, printing ink is ejected from the first nozzle rows 51a to 51d located on the downstream side in the transport direction from the second nozzle row 51e in the region where the underlayer is formed. At this time, since the landed printing ink does not easily penetrate the printing paper 100 due to the presence of the underlayer, high-quality image printing is possible.

  Here, in the inkjet head 3 of the present embodiment, the second nozzle row 51e that ejects the precoat ink is arranged farther upstream in the transport direction than the first nozzle rows 51a to 51d that eject the printing ink. ing. Accordingly, it is possible to suppress a problem that inks having completely different components such as a solvent ejected from the other one of the first nozzle rows 51a to 51d and the second nozzle row 51e are mixed. Further, the first nozzle rows 51a to 51d and the second nozzle row 51e are arranged apart from each other in the scanning direction. Therefore, mixing of ink between the first nozzle rows 51a to 51d and the second nozzle row 51e can be more reliably suppressed. When the first nozzle row 51a to 51d and the second nozzle row 51e are also separated in the scanning direction, various caps (such as a drying prevention cap and a purge suction cap) that cover the nozzle 50 are attached to the ink. Different types of first nozzle rows 51a to 51d and second nozzle rows 51e can be configured separately. Thereby, it is possible to prevent ink from being mixed between the nozzle rows 51 during capping, which is likely to occur when the cap is integrated.

  In addition, the operation in which the second nozzle row 51e ejects ink prior to the first nozzle rows 51a to 51d can be performed simply by moving the second nozzle row 51e away from the first nozzle rows 51a to 51d in the scanning direction. Although feasible, if the second nozzle row 51e is separated from the first nozzle rows 51a to 51d on the upstream side in the transport direction as in the present embodiment, the printing paper is first printed from the second nozzle row 51e. After the precoat ink is ejected to 100, the landing area of the precoat ink is conveyed to a position facing the first nozzle rows 51a to 51d, and the printing ink ejected from the first nozzle rows 51a to 51d is landed. A certain amount of time has passed. For this reason, after the pre-coated ink that has landed first sufficiently penetrates the printing paper 100 and forms a base layer, the printing ink lands on the printing paper 100 and penetrates the printing ink and the printing paper 100. The problem of bleeding with the previous pre-coated ink hardly occurs.

  The precoat ink may be ejected to an area where the printing ink will land later, and it is not necessary to eject it to an area where the printing ink does not land. Therefore, in the present embodiment, as shown in FIG. 2, the first nozzle arrays 51a to 51d that eject printing ink and the second nozzle array 51e that ejects precoat ink have nozzle arrangement pitch P and the number of nozzle arrangements. Both are equal. As a result, the precoat ink ejected from the second nozzle array 51e is landed first on each of the areas on the printing paper 100 where the printing ink ejected from the first nozzle arrays 51a to 51d will land. I can keep it. That is, the precoat ink can be surely landed on the area on the printing paper 100 where the image or the like is printed (area where the printing ink is landed), and the precoat ink is unnecessarily ejected on the area where the printing ink is not landed. Can also be prevented.

  The above effects are effects when the precoat ink is ejected from the second nozzle row 51e. However, the ink jet head 3 of the present embodiment is provided with a precoat ink by mounting another ink cartridge for storing printing ink (for example, black ink) instead of the ink cartridge 5e for storing the precoat ink in FIG. It can also be used for printers that do not use the printer.

  As described above, in the present embodiment, the nozzle arrangement pitch of the second nozzle array 51e is equal to the nozzle arrangement pitch of the first nozzle array 51 that ejects printing ink. Therefore, the second ink supply port 48e that communicates with the second nozzle row 51e is connected to an ink cartridge that stores printing ink such as black ink, and not only from the first nozzle rows 51a to 51d but also from the second nozzle row 51e. Similarly, it is possible to print characters, images, and the like by ejecting printing ink. In this case, compared to the case where the printing ink is ejected from only the first nozzle rows 51a to 51d, the same color of ink is ejected from more nozzles 50 at a time, so the printing speed is increased.

  In the present embodiment, the first nozzle rows 51a to 51d and the second nozzle row 51e are separated by the same distance as the nozzle arrangement pitch P in the transport direction (nozzle arrangement direction). For this reason, the nozzles 50 constituting the first nozzle rows 51a to 51d and the second nozzle row 51e are arranged in a row at a constant pitch in the transport direction. Accordingly, when the printing ink is ejected from the second nozzle row 51e as well as the first nozzle rows 51a to 51d, the nozzle row that is a combination of both nozzle rows is long on the printing paper 100. Can be printed at once.

  In the case where the same color ink is ejected simultaneously from two or more nozzle rows 51, it is preferable that these two or more nozzle rows 51 are close to each other. This is because when the ink jet head 3 ejects ink from the nozzle 50 while moving in the scanning direction, the ink jet head 3 may be slightly inclined in the horizontal plane due to the deflection or backlash of the guide shaft 17. Even in this case, if two or more nozzle rows 51 are close to each other, the landing position deviation between the two nozzle rows 51 is reduced, and a decrease in print quality can be suppressed. In general, high-speed printing is particularly required when text printing using only black ink is performed. Therefore, in the inkjet head 3 of the present embodiment, as shown in FIG. 2, the second nozzle row 51e is more than the nozzle rows 51a to 51c that eject the color ink among the four first nozzle rows 51a to 51d. The nozzles are arranged at positions close to the nozzle row 51d that ejects black ink. As described above, since the black nozzle row 51d and the second nozzle row 51e are adjacent to each other, the print quality is improved when the black ink is ejected from the second nozzle row 51e to perform text printing at high speed. Can be expected.

  Next, modified embodiments in which various modifications are made to the 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.

  1] In the above embodiment, the first nozzle rows 51a to 51d and the second nozzle row 51e are separated from each other by the nozzle arrangement pitch P in the transport direction (nozzle arrangement direction). The separation distance in the transport direction of the nozzle rows may be larger than the nozzle arrangement pitch P. For example, as in the inkjet head 3A shown in FIG. 6, the length L (that is, the second nozzle row 51e is printed with one scan (pass) of the carriage 2 with respect to the first nozzle rows 51a to 51d (ie, , Nozzle row length) (L / 2) may be spaced apart upstream of the conveying direction.

  2] As in the inkjet head 3B shown in FIG. 7, the first nozzle rows 51a to 51d (the black nozzle row 51d in FIG. 7) and the second nozzle row 51e may be at the same position in the scanning direction. In this case, the width (dimension in the scanning direction) of the inkjet head 3B can be reduced, and the inkjet head 3B can be downsized.

  3] In the above-described embodiment, the first piezoelectric actuator 31a that drives the first nozzle rows 51a to 51d and the second piezoelectric actuator 31b that drives the second nozzle row 51e are configured separately and separated completely. However, the two piezoelectric actuators 31a and 31b may be integrally formed. Alternatively, the diaphragm 60 is provided so as to cover the entire upper surface of the flow path unit 30, and the piezoelectric plate of the two piezoelectric actuators 31a and 31b is formed after the diaphragm 60 is configured in common by the two piezoelectric actuators 31a and 31b. Only the layer 61 may be formed separately.

  4] The actuator for applying the ejection energy to the ink is not limited to the piezoelectric actuator as in the above embodiment, and other types of actuators may be employed. For example, an actuator that ejects ink from a nozzle by heating the ink with a heater to cause film boiling may be used.

1 is a schematic plan view of an ink jet printer according to an embodiment. It is a top view of an inkjet head. It is the A section enlarged view of FIG. FIG. 4 is a sectional view taken along line IV-IV in FIG. 3. It is a figure explaining the cutting-out of the piezoelectric layer from one piezoelectric sheet, (a) is a case where the piezoelectric layers of the first and second piezoelectric actuators are integrated, (b) is a view of the first and second piezoelectric actuators Each of the cases where the piezoelectric layer is a separate body is shown. It is a top view of the inkjet head of a change form. It is a top view of the inkjet head of another modification.

DESCRIPTION OF SYMBOLS 1 Printer 3, 3A, 3B Inkjet head 5a-5d Ink cartridge 5e Ink cartridge 6 Conveyance mechanism 30 Flow path unit 31a 1st piezoelectric actuator 31b 2nd piezoelectric actuator 48a-48d 1st ink supply port 48e 2nd ink supply port 50 Nozzle 51a-51d 1st nozzle row 51e 2 nozzle row 100 Printing paper

  The present invention relates to an inkjet head that ejects ink droplets toward a print medium.

  A general inkjet head employed in an inkjet printer ejects printing ink, such as black ink and color ink, for printing characters, images, and the like toward a printing medium conveyed in a predetermined conveyance direction. Further, in recent years, in addition to printing ink, an inkjet head that can eject ink other than printing ink has also been proposed. As such an ink jet head, for the purpose of preventing bleeding of the printing ink, the ink that does not directly contribute to printing of an image or the like (hereinafter referred to as a precoat ink) can be ejected onto the printing medium prior to the printing ink. There is something that was done.

  For example, an inkjet head described in Patent Document 1 includes an ink ejection nozzle array that ejects printing ink, and a reaction liquid ejection nozzle array that ejects a reaction liquid that reacts with the printing ink to prevent bleeding. And have. Note that the reaction liquid discharge nozzle row is disposed upstream of the ink discharge nozzle row in the transport direction of the print medium. As a result, the reaction liquid is first ejected from the reaction liquid ejection nozzle array to the transported print medium, and then the printing ink is ejected from the ink ejection nozzle array to the area where the reaction liquid has landed. Will be.

JP 2005-119115 A

  However, it is necessary to use a precoat ink that does not directly contribute to printing of an image or the like, such as the reaction solution of Patent Document 1, only when printing a very high quality image while suppressing bleeding of the printing ink. It is done. Therefore, the ink jet head of Patent Document 1 provided with the nozzle array dedicated to the reaction liquid is used only for high performance ink jet printers that specialize in high-quality image printing. It is not used for general-purpose printers that prioritize printing speed. In other words, the inkjet head disclosed in Patent Document 1 becomes a dedicated head for a high-performance model and lacks versatility, which increases costs.

  An object of the present invention is to provide a highly versatile inkjet head that can support both high-quality printing using pre-coated ink prior to printing ink and high-speed printing in which printing ink is ejected from many nozzles at once. Is to provide.

The inkjet head of the first invention is
An inkjet head that ejects 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 is arranged at a predetermined pitch along the transport direction. A first nozzle row composed of a plurality of first nozzles, a first ink supply port communicating with the first nozzle row and connected to a supply source for printing ink, and the first nozzle row more than the first nozzle row. A second nozzle row composed of a plurality of second nozzles arranged at the predetermined pitch along the transport direction in the same region as the plurality of first nozzles in the upstream region in the transport direction, and communicates with the second nozzle row The second ink supply port connected to the ink supply source and an actuator provided in a region facing the second nozzle row, and imparts ejection energy to the ink of the second nozzle row The first ink supply port is disposed in a region upstream of the first nozzle row in the transport direction and adjacent to the actuator in the scanning direction. To do .

  Since the first ink supply port communicating with the first nozzle row is connected to the printing ink supply source, the first nozzle row ejects the printing ink. On the other hand, since the second ink supply port communicating with the second nozzle row is connected to either the printing ink supply source or the precoat ink supply source, the second nozzle row is connected to the connection destination supply source. The supplied printing ink or precoat ink is ejected.

  Here, the second nozzle row capable of ejecting the precoat ink is arranged farther upstream in the transport direction than the first nozzle row ejecting the printing ink. Therefore, when using the precoat ink, first, the precoat ink is ejected from the second nozzle row toward the print medium to form the underlayer on the print medium, and then the underlayer is formed from the first nozzle. Ink for printing is ejected to the area. Thereby, since the penetration of the printing ink into the printing medium is suppressed, high-quality printing is possible. Further, when the second nozzle row is separated from the first nozzle row in the transport direction, inks having completely different components such as a solvent ejected from one of the first nozzle row and the second nozzle row from the other. It is difficult to cause a problem of mixing.

Further, in the present invention, the first nozzle row and the second nozzle row have the same nozzle arrangement pitch. Therefore, after connecting the second ink supply port communicating with the second nozzle row to the printing ink supply source, the printing ink is ejected from both the first nozzle row and the second nozzle row, so that the precoat ink In addition to high-quality printing using the printer, high-speed printing in which printing ink is ejected at once from a large number of nozzles is also possible.
In the case where the same color ink is ejected from two or more nozzle rows, it is preferable from the viewpoint of improving print quality that these two or more nozzle rows are close to each other. In addition, in the present invention, since the black nozzle as the first nozzle row and the second nozzle row are adjacent to each other, the black ink is also ejected from the second nozzle row to perform text printing at high speed. The improvement of printing quality can be expected.

  An ink jet head according to a second invention is characterized in that, in the first invention, the number of nozzle arrays in the transport direction of the first nozzle row and the second nozzle row is equal.

  The precoat ink only needs to be ejected to a region where the printing ink lands, and does not need to be ejected to a region where the printing ink does not land. Therefore, in the present invention, the first nozzle row for ejecting the printing nozzles and the second nozzle row for ejecting the precoat ink have the same nozzle arrangement pitch and the same number of nozzle arrangements. Thereby, the precoat ink ejected from the second nozzle row can be landed first in each of the regions on the printing medium where the printing ink ejected from the first nozzle row will land. . That is, the precoat ink can be reliably landed on an area (an area where the printing ink is landed) on which an image or the like of the printing medium is printed, and the precoat ink is unnecessarily ejected on an area where the printing ink is not landed. This can also be prevented.

  An ink jet head according to a third invention is characterized in that, in the first or second invention, the first nozzle row and the second nozzle row are separated from each other by the predetermined pitch in the transport direction. To do.

  According to this configuration, the nozzles that respectively constitute the first nozzle row and the second nozzle row are arranged in a row at a constant pitch in the transport direction. Therefore, when printing ink is ejected not only from the first nozzle row but also from the second nozzle row, a continuous wide area can be printed at a time by a single long nozzle row including both nozzle rows. it can.

  An ink jet head according to a fourth invention is characterized in that, in any one of the first to third inventions, the first nozzle row and the second nozzle row are arranged apart from each other in the scanning direction. To do.

  According to this configuration, since the first nozzle row and the second nozzle row are separated from each other in the scanning direction, it is possible to more reliably suppress ink mixing between the first nozzle row and the second nozzle row. In addition, it is possible to separately configure caps that cover the first nozzle row and the second nozzle row that are spaced apart from each other, and prevent ink mixing during capping that tends to occur when the caps are integrated. be able to.

The inkjet head of the fifth invention is
The first actuator and the second actuator are configured as separate bodies.

  When the first nozzle row and the second nozzle row are separated from each other in both the transport direction and the scanning direction, they are provided at positions facing the first nozzle row and the second nozzle row. The two actuators that drive each will also move away from each other. However, if such two actuators are manufactured in one piece, there will be a lot of wasted parts, and the substrate of the actuator will be enlarged from a single substrate material. It is necessary to cut out, which is disadvantageous in terms of manufacturing cost. In the present invention, it is possible to reduce the manufacturing cost by configuring two actuators separately and reducing the size of each actuator.

The sixth ink jet head of the present invention is directed to the invention of the sixth, of the first actuator and the second actuator, the length relating to the conveying direction is characterized in that approximately equal.

  As described above, when the lengths of the two actuators in the transport direction are equal, the two actuators can be cut out from a single substrate material without waste.

The inkjet head according to a seventh aspect is the ink jet head according to any one of the fourth to seventh aspects, wherein the first ink supply port is disposed in a region upstream of the first nozzle row in the transport direction, The second ink supply port is arranged in a region downstream of the second nozzle row in the transport direction.

  When the first nozzle row and the second nozzle row are separated with respect to both the carrying direction and the scanning direction, they are vacant on the upstream side in the carrying direction of the first nozzle row and on the downstream side in the carrying direction of the second nozzle row, respectively. Will exist. Therefore, the ink jet head can be reduced in size by arranging the ink supply ports in these empty regions.

  According to the present invention, the second nozzle row capable of ejecting the precoat ink is disposed farther upstream in the transport direction than the first nozzle row ejecting the printing ink. Therefore, when using the precoat ink, first, the precoat ink is ejected from the second nozzle row toward the print medium to form the underlayer on the print medium, and then the underlayer is formed from the first nozzle. Ink for printing is ejected to the area. Thereby, since the penetration of the printing ink into the printing medium is suppressed, high-quality printing is possible. Further, when the second nozzle row is separated from the first nozzle row in the transport direction, inks having completely different components such as a solvent ejected from one of the first nozzle row and the second nozzle row from the other. It is difficult to cause a problem of mixing.

  Further, in the present invention, the first nozzle row and the second nozzle row have the same nozzle arrangement pitch. Therefore, after connecting the second ink supply port communicating with the second nozzle row to the printing ink supply source, the printing ink is ejected from both the first nozzle row and the second nozzle row, so that the precoat ink In addition to high-quality printing using the printer, high-speed printing in which printing ink is ejected at once from a large number of nozzles is also possible.

  Next, an embodiment of the present invention will be described. FIG. 1 is a plan view showing a schematic configuration of an ink jet printer including the ink jet head of the present invention. As shown in FIG. 1, the printer 1 includes a carriage 2 configured to reciprocate along the scanning direction of FIG. 1, an inkjet head 3 and sub tanks 4a to 4e mounted on the carriage 2, and five inks. Cartridges 5a to 5e and a transport mechanism 6 for transporting the printing paper 100 in the transport direction of FIG.

  The carriage 2 is configured to be able to reciprocate along two guide shafts 17 extending in parallel in the left-right direction (scanning direction) in FIG. An endless belt 18 is connected to the carriage 2. When the endless belt 18 is driven to travel by the carriage drive motor 19, the carriage 2 moves in the scanning direction as the endless belt 18 travels. It has become.

  An ink jet head 3 and five sub tanks 4 a to 4 e are mounted on the carriage 2. The ink jet head 3 includes a large number of nozzles 50 for ejecting ink on the lower surface (the surface on the opposite side of the paper surface in FIG. 1). The five sub tanks 4a to 4e are arranged side by side along the scanning direction, and the tube joint 20 is integrally provided in the five sub tanks 4a to 4e. The five sub tanks 4 a to 4 e and the five ink cartridges 5 a to 5 e that are detachably attached to the holder 10 are connected to each other by the flexible tube 11 connected to the tube joint 20.

  The five ink cartridges 5a to 5e are provided with four colors of magenta, cyan, yellow, and black printing inks, and a colorless and transparent precoat that is jetted onto the printing paper 100 prior to the four colors of printing inks. A total of five types of ink are stored.

  The five types of ink respectively stored in the five ink cartridges 5a to 5e are supplied to the five sub tanks 4a to 4e via the five tubes 11 connected to the holder 10, and temporarily stored in the sub tanks 4a to 4e. After being stored, the ink is supplied to the inkjet head 3. The inkjet head 3 is reciprocated in the scanning direction together with the carriage 2 and is conveyed downward (conveying direction) in FIG. 1 by a conveying mechanism 6 from a large number of nozzles 50 provided on the lower surface (droplet ejection surface). Ink droplets are ejected onto the printing paper 100 to be printed.

  The transport mechanism 6 includes a paper feed roller 25 disposed upstream of the inkjet head 3 in the transport direction, and a paper discharge roller 26 disposed downstream of the inkjet head 3 in the transport direction. The paper feed roller 25 and the paper discharge roller 26 are rotationally driven by a paper feed motor 27 and a paper discharge motor 28, respectively. The transport mechanism 6 supplies the printing paper 100 to the inkjet head 3 from above in FIG. 1 by the paper feed roller 25, and prints in which images, characters, and the like are recorded by the inkjet head 3 by the paper discharge roller 26. The paper 100 is configured to be discharged downward in FIG.

Next, the inkjet head 3 will be described in detail. 2 is a top view of the inkjet head 3, FIG. 3 is an enlarged view of a portion A in FIG. 2, and FIG. 4 is a sectional view taken along line IV-IV in FIG. However, in order to make the drawing easy to understand, in FIG. 2, illustration of a part of the ink flow path such as the pressure chamber 44 shown in FIG. 3 is omitted, and the nozzle 50 is illustrated larger than FIG. 3. .

  As shown in FIG. 2, the inkjet head 3 includes a flow path unit 30 in which an ink flow path including a nozzle 50 and a pressure chamber 44 is formed, and two piezoelectric actuators 31 a and 31 b disposed on the upper surface of the flow path unit 30. It has.

  As shown in FIG. 4, the flow path unit 30 includes a cavity plate 40, a base plate 41, a manifold plate 42, and a nozzle plate 43 made of a synthetic resin material, which are made of a metal material such as stainless steel. These four plates 40 to 43 are joined in a laminated state.

  Among the four plates 40 to 43, the nozzle plate 43 located in the lowermost layer is formed with a plurality of nozzles 50 that open to the lower surface (droplet ejection surface). The plurality of nozzles 50 are arranged along the transport direction (up and down direction in FIG. 2) to form five nozzle rows 51a to 51e. Here, as shown in FIG. 2, among the five nozzle rows 51 a to 51 e, the four nozzle rows 51 a to 51 d are in the downstream side region (lower half region in FIG. 2) of the nozzle plate 43 in the transport direction. Are arranged side by side in the scanning direction. On the other hand, the remaining nozzle row 51e is arranged in a region (upper half region in FIG. 2) that is separated from the four nozzle rows 51a to 51d on the upstream side in the transport direction. Hereinafter, the four nozzle rows 51a to 51d are referred to as first nozzle rows 51a to 51d, and the nozzle row 51e disposed upstream of the first nozzle rows 51a to 51d in the transport direction is referred to as a second nozzle row 51e. As will be described in detail later, when the inkjet head 3 is incorporated in the printer 1 of FIG. 1, the nozzles 50 a to 50 d (first nozzles) constituting the four first nozzle rows 51 a to 51 d are 4 While printing inks of colors (magenta, cyan, yellow, black) are respectively ejected, the nozzles 50e (second nozzles) constituting the second nozzle row 51e eject colorless and transparent precoat ink.

  Further, the second nozzle row 51e is arranged at a position away from the four first nozzle rows 51a to 51d not only in the transport direction but also in the scanning direction (left-right direction in FIG. 2). As a result, as shown in FIG. 2, the four first nozzle rows 51a to 51d are arranged in the lower right region in the figure, while the second nozzle row 51e is arranged in the upper left region in the figure. Yes.

  In the five nozzle rows 51a to 51e, the nozzle arrangement pitch P and the number of nozzle arrangements are all equal. Further, as shown in FIG. 2, four first nozzle rows 51a to 51d (more specifically, nozzles 50 positioned at the upstream end of the nozzle rows 51a to 51d in the transport direction) and second nozzle rows 51e ( The nozzle arrangement pitch P is separated from the nozzle 50) located at the downstream end of the nozzle row 51e in the transport direction.

  As shown in FIGS. 3 and 4, a plurality of pressure chambers 44 corresponding to the plurality of nozzles 50 are formed in the cavity plate 40 located in the uppermost layer of the four plates. The pressure chamber 44 has a substantially oval planar shape with the scanning direction as the longitudinal direction, and is disposed so that one end of the pressure chamber 44 overlaps the nozzle 50 in plan view. Further, through holes 45 and 46 are formed in the base plate 41 at positions overlapping with both ends in the longitudinal direction of the pressure chamber 44 in plan view.

  The manifold plate 42 is formed with five manifold channels 47 respectively corresponding to the five nozzle rows 51a to 51e. As shown in FIG. 2, each manifold channel 47 extends in the transport direction at a position next to the corresponding nozzle row 51 and, as shown in FIG. 3, is an abbreviation of the corresponding pressure chamber 44 in a plan view. It overlaps with the left half. As shown in FIG. 2, five ink supply ports 48a to 48e are formed in the uppermost cavity plate 40, and one end portion of each of the five manifold channels 47 is connected to these five ink supply ports 48a. To 48e, respectively. The five ink supply ports 48 a to 48 e are connected to the five ink cartridges 5 a to 5 e (see FIG. 1) via the tube 11.

  As described above, the four first nozzle rows 51a to 51d and the second nozzle row 51e are arranged apart from each other in both the transport direction and the scanning direction. Accordingly, the upstream area in the transport direction (upper right area in FIG. 2) of the inkjet head 3 and the downstream area in the transport direction (lower left area in FIG. 2) from the second nozzle array 51e are nozzles. This is a vacant area where 50 is not arranged. Therefore, four ink supply ports 48a to 48d (first ink supply ports) communicating with the four first nozzle rows 51a to 51d are arranged in the upstream region in the transport direction from the first nozzle rows 51a to 51d. In addition, an ink supply port 48e (second ink supply port) communicating with the second nozzle row 51e is arranged in a region downstream of the second nozzle row 51e in the transport direction. As a result, the ink supply ports 48a to 48e and the ink flow passages connected to the ink supply ports 48a to 48e are provided in a vacant area where the nozzle 50 is not disposed, and the inkjet head 3 can be downsized.

  As shown in FIGS. 3 and 4, the manifold plate 42 has a through hole at a position overlapping with both the through hole 46 formed in the base plate 41 and the nozzle 50 formed in the nozzle plate 43 in plan view. 49 is formed.

  As shown in FIG. 4, in the flow path unit 30, the manifold flow path 47 that communicates with the ink supply port 48 communicates with the pressure chamber 44 through the through hole 45, and the pressure chamber 44 further includes the through holes 46 and 49. It communicates with the nozzle 50 via That is, a plurality of individual ink channels are formed in the channel unit 30 from the outlet of the manifold channel 47 to the nozzle 50 through the pressure chamber 44.

  Next, the first piezoelectric actuator 31a and the second piezoelectric actuator 31b that apply ejection energy to the inks of the first nozzle rows 51a to 51d and the second nozzle row 51e will be described. As shown in FIG. 2, the first piezoelectric actuator 31 a ejects ink from the four first nozzle rows 51 a to 51 d, and the four first nozzle rows 51 a to 51 a on the upper surface of the flow path unit 30. 51d and a region facing the pressure chamber 44 corresponding to these nozzle rows. On the other hand, the second piezoelectric actuator 31b ejects ink from the second nozzle row 51e, and is a region facing the second nozzle row 51e and the pressure chamber 44 corresponding to this nozzle row on the upper surface of the flow path unit 30. Is arranged. Note that the five nozzle rows 51a to 51e to be driven by the first piezoelectric actuator 31a and the second piezoelectric actuator 31b have the same nozzle arrangement pitch P and the same number of nozzle arrangements, and therefore the five nozzle rows 51a. The lengths of ~ 51e are all equal. Therefore, the first piezoelectric actuator 31a and the second piezoelectric actuator 31b have substantially the same length in the nozzle arrangement direction (conveying direction).

  The first piezoelectric actuator 31a and the second piezoelectric actuator 31b have substantially the same structure except for the size because the number of nozzles 50 (nozzle rows 51) to be driven is different. Therefore, in the following description regarding the structure of the piezoelectric actuator 31, the first piezoelectric actuator 31a will be representatively described, and the description of the structure of the second piezoelectric actuator 31b will be omitted.

  As shown in FIGS. 3 and 4, the first piezoelectric actuator 31 a includes a diaphragm 60, a piezoelectric layer 61, and a plurality of individual electrodes 62. The diaphragm 60 is made of a conductive material such as a metal material, and is joined to the upper surface of the cavity plate 40 so as to cover the plurality of pressure chambers 44 communicating with the first nozzle rows 51a to 51d. The diaphragm 60 having conductivity is always held at the ground potential, and an electric field in the thickness direction is applied to the portion of the piezoelectric layer 61 located between the diaphragm 60 and the plurality of individual electrodes 62. Also serves as a ground electrode.

  The piezoelectric layer 61 is a mixed crystal of lead titanate and lead zirconate, and is made of a lead zirconate titanate-based piezoelectric ceramic material having ferroelectricity, and straddles a plurality of pressure chambers 44 on the upper surface of the diaphragm 60. Are arranged continuously. The piezoelectric layer 61 is previously polarized in the thickness direction.

  The plurality of individual electrodes 62 are provided on the upper surface of the piezoelectric layer 61 so as to correspond to the plurality of pressure chambers 44. The individual electrode 62 has a substantially elliptical planar shape that is slightly smaller than the pressure chamber 44, and is disposed at a position overlapping the substantially central portion of the pressure chamber 44 in plan view. One end portion (left end portion in FIG. 3) in the longitudinal direction of the individual electrode 62 extends to a position where it does not overlap with the pressure chamber 44 in plan view, and the tip end portion is a land 62a. A head driver is connected to the land 62a via a wiring member such as a flexible printed circuit board (FPC) (not shown). Then, either a predetermined drive potential or a ground potential is selectively applied from the head driver to the plurality of individual electrodes 62.

  The operation of the piezoelectric actuator 31 having the above configuration will be described. When a predetermined drive potential is applied to an individual electrode 62 from a head driver (not shown), a potential difference is generated between the individual electrode 62 to which the drive potential is applied and the diaphragm 60 as a ground electrode. An electric field in the thickness direction is generated at a portion sandwiched between the individual electrode 62 and the diaphragm 60. Here, when the polarization direction of the piezoelectric layer 61 is the same as the electric field direction, the piezoelectric layer 61 extends in the thickness direction and contracts in the plane direction. As the piezoelectric layer 61 contracts and deforms, the portion of the diaphragm 60 facing the pressure chamber 44 is deformed so as to protrude toward the pressure chamber 44 (unimorph deformation). At this time, since the volume of the pressure chamber 44 is reduced, the pressure of the ink inside the pressure chamber 44 is increased, and ink droplets are ejected from the nozzle 50 communicating with the pressure chamber 44.

  In the present embodiment, the first piezoelectric actuator 31a that drives the first nozzle rows 51a to 51d and the second piezoelectric actuator 31b that drives the second nozzle row 51e are configured separately. A portion that drives the first nozzle row 51 and a portion that drives the second nozzle row 51e may be integrated, and a piezoelectric actuator having a large area covering almost the entire upper surface of the flow path unit 30 may be employed. However, this causes useless parts that do not contribute to driving. That is, as in the present embodiment, when the first nozzle rows 51a to 51d and the second nozzle row 51e are separated from each other in both the transport direction and the scanning direction, the first nozzle rows 51a to 51d and the first nozzle rows 51a to 51d The two actuator portions that are provided at positions facing the two nozzle rows 51e and drive the two are also separated from each other, and the diaphragm 60 and the piezoelectric layer 61 disposed in the upper right region and the lower left region in FIG. This is a useless part that does not contribute to the driving of the nozzle row 51.

  Further, as shown in FIG. 5A, when a method of cutting the piezoelectric layer 61 from one fired piezoelectric sheet 70 is adopted as a manufacturing method of the piezoelectric layer 61, when each piezoelectric layer 61 is large, The number of piezoelectric layers 61 that can be cut out from one piezoelectric sheet 70 is reduced (only 9 sheets can be cut out in FIG. 5A). The same applies to the case where the diaphragm 60 is cut out from one metal sheet. Therefore, the manufacturing cost of the piezoelectric actuator becomes high.

  Therefore, in the present embodiment, as shown in FIG. 2, by separating the two piezoelectric actuators 31a and 31b, the size of each actuator is reduced, and unnecessary portions that do not contribute to driving of the nozzle array 51 are reduced as much as possible. be able to. Further, as shown in FIG. 5 (b), the piezoelectric layer 61a of the first piezoelectric actuator 31a having a large area is cut out from one piezoelectric sheet 70, and then the piezoelectric of the second piezoelectric actuator 31b having a small area is removed. Since the layer 61b can be cut out, a larger number of piezoelectric layers 61a and 61b can be cut out from one piezoelectric sheet 70 having the same size as that in FIG. 5A (in FIG. 5B). 24 sets), manufacturing costs can be reduced. Further, when the lengths in the transport direction of the first piezoelectric actuator 31a and the second piezoelectric actuator 31b (vertical length in FIG. 5) are substantially equal, as shown in FIG. 5B, the first piezoelectric actuator 31a. Since the piezoelectric layer 61b of the second piezoelectric actuator 31b can be cut out from the remaining portion immediately next to the piezoelectric layer 61a, it can be cut out more efficiently.

  Returning to FIG. 2, the four ink supply ports 48 a to 48 d (first ink supply ports) communicating with the four first nozzle rows 51 a to 51 d respectively have four colors of printing inks (magenta, cyan, The four ink cartridges 5 a to 5 d (see FIG. 1) respectively storing yellow and black) are connected via the tube 11. Therefore, since four colors of printing ink are supplied to the inkjet head 3 from the four first ink supply ports 48a to 48d, pressure is applied to the ink in the pressure chamber 44 by the first piezoelectric actuator 31a. The nozzles 50a to 50d (first nozzles) constituting the four first nozzle rows 51a to 51d eject four colors of printing ink.

  On the other hand, the ink supply port 48e (second ink supply port) communicating with the second nozzle row 51e can use the precoat ink in which the ink cartridge 5e for storing the precoat ink is mounted on the holder 10 as shown in FIG. In the printer 1, the ink cartridge 5 e (see FIG. 1) is connected via the tube 11. Accordingly, since the precoat ink is supplied from the second ink supply port 48e to the inkjet head 3, the second piezoelectric actuator 31b applies pressure to the ink in the pressure chamber 44, thereby forming the second nozzle row 51e. The nozzle 50e (second nozzle) ejects precoat ink. As described above, when the precoat ink is ejected from the second nozzle row 51e onto the printing paper 100, a base layer is formed on the printing paper 100 with the precoat ink. Thereafter, printing ink is ejected from the first nozzle rows 51a to 51d located on the downstream side in the transport direction from the second nozzle row 51e in the region where the underlayer is formed. At this time, since the landed printing ink does not easily penetrate the printing paper 100 due to the presence of the underlayer, high-quality image printing is possible.

  Here, in the inkjet head 3 of the present embodiment, the second nozzle row 51e that ejects the precoat ink is arranged farther upstream in the transport direction than the first nozzle rows 51a to 51d that eject the printing ink. ing. Accordingly, it is possible to suppress a problem that inks having completely different components such as a solvent ejected from the other one of the first nozzle rows 51a to 51d and the second nozzle row 51e are mixed. Further, the first nozzle rows 51a to 51d and the second nozzle row 51e are arranged apart from each other in the scanning direction. Therefore, mixing of ink between the first nozzle rows 51a to 51d and the second nozzle row 51e can be more reliably suppressed. When the first nozzle row 51a to 51d and the second nozzle row 51e are also separated in the scanning direction, various caps (such as a drying prevention cap and a purge suction cap) that cover the nozzle 50 are attached to the ink. Different types of first nozzle rows 51a to 51d and second nozzle rows 51e can be configured separately. Thereby, it is possible to prevent ink from being mixed between the nozzle rows 51 during capping, which is likely to occur when the cap is integrated.

  In addition, the operation in which the second nozzle row 51e ejects ink prior to the first nozzle rows 51a to 51d can be performed simply by moving the second nozzle row 51e away from the first nozzle rows 51a to 51d in the scanning direction. Although feasible, if the second nozzle row 51e is separated from the first nozzle rows 51a to 51d on the upstream side in the transport direction as in the present embodiment, the printing paper is first printed from the second nozzle row 51e. After the precoat ink is ejected to 100, the landing area of the precoat ink is conveyed to a position facing the first nozzle rows 51a to 51d, and the printing ink ejected from the first nozzle rows 51a to 51d is landed. A certain amount of time has passed. For this reason, after the pre-coated ink that has landed first sufficiently penetrates the printing paper 100 and forms a base layer, the printing ink lands on the printing paper 100 and penetrates the printing ink and the printing paper 100. The problem of bleeding with the previous pre-coated ink hardly occurs.

  The precoat ink may be ejected to an area where the printing ink will land later, and it is not necessary to eject it to an area where the printing ink does not land. Therefore, in the present embodiment, as shown in FIG. 2, the first nozzle arrays 51a to 51d that eject printing ink and the second nozzle array 51e that ejects precoat ink have nozzle arrangement pitch P and the number of nozzle arrangements. Both are equal. As a result, the precoat ink ejected from the second nozzle array 51e is landed first on each of the areas on the printing paper 100 where the printing ink ejected from the first nozzle arrays 51a to 51d will land. I can keep it. That is, the precoat ink can be surely landed on the area on the printing paper 100 where the image or the like is printed (area where the printing ink is landed), and the precoat ink is unnecessarily ejected on the area where the printing ink is not landed. Can also be prevented.

  The above effects are effects when the precoat ink is ejected from the second nozzle row 51e. However, the ink jet head 3 of the present embodiment is provided with a precoat ink by mounting another ink cartridge for storing printing ink (for example, black ink) instead of the ink cartridge 5e for storing the precoat ink in FIG. It can also be used for printers that do not use the printer.

  As described above, in the present embodiment, the nozzle arrangement pitch of the second nozzle array 51e is equal to the nozzle arrangement pitch of the first nozzle array 51 that ejects printing ink. Therefore, the second ink supply port 48e that communicates with the second nozzle row 51e is connected to an ink cartridge that stores printing ink such as black ink, and not only from the first nozzle rows 51a to 51d but also from the second nozzle row 51e. Similarly, it is possible to print characters, images, and the like by ejecting printing ink. In this case, compared to the case where the printing ink is ejected from only the first nozzle rows 51a to 51d, the same color of ink is ejected from more nozzles 50 at a time, so the printing speed is increased.

  In the present embodiment, the first nozzle rows 51a to 51d and the second nozzle row 51e are separated by the same distance as the nozzle arrangement pitch P in the transport direction (nozzle arrangement direction). For this reason, the nozzles 50 constituting the first nozzle rows 51a to 51d and the second nozzle row 51e are arranged in a row at a constant pitch in the transport direction. Accordingly, when the printing ink is ejected from the second nozzle row 51e as well as the first nozzle rows 51a to 51d, the nozzle row that is a combination of both nozzle rows is long on the printing paper 100. Can be printed at once.

  In the case where the same color ink is ejected simultaneously from two or more nozzle rows 51, it is preferable that these two or more nozzle rows 51 are close to each other. This is because when the ink jet head 3 ejects ink from the nozzle 50 while moving in the scanning direction, the ink jet head 3 may be slightly inclined in the horizontal plane due to the deflection or backlash of the guide shaft 17. Even in this case, if two or more nozzle rows 51 are close to each other, the landing position deviation between the two nozzle rows 51 is reduced, and a decrease in print quality can be suppressed. In general, high-speed printing is particularly required when text printing using only black ink is performed. Therefore, in the inkjet head 3 of the present embodiment, as shown in FIG. 2, the second nozzle row 51e is more than the nozzle rows 51a to 51c that eject the color ink among the four first nozzle rows 51a to 51d. The nozzles are arranged at positions close to the nozzle row 51d that ejects black ink. As described above, since the black nozzle row 51d and the second nozzle row 51e are adjacent to each other, the print quality is improved when the black ink is ejected from the second nozzle row 51e to perform text printing at high speed. Can be expected.

  Next, modified embodiments in which various modifications are made to the 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.

1] In the above embodiment, the first nozzle rows 51a to 51d and the second nozzle row 51e are separated from each other by the nozzle arrangement pitch P in the transport direction (nozzle arrangement direction). The separation distance in the transport direction of the nozzle rows may be larger than the nozzle arrangement pitch P. For example, as in the inkjet head 3A shown in FIG. 6, the length L (that is, the second nozzle row 51e is printed with one scan (pass) of the carriage 2 with respect to the first nozzle rows 51a to 51d (ie, , Nozzle row length) (L / 2) may be spaced apart upstream of the conveying direction.

2] As in the inkjet head 3B shown in FIG. 7, the first nozzle rows 51a to 51d (the black nozzle row 51d in FIG. 7) and the second nozzle row 51e may be at the same position in the scanning direction. In this case, the width (dimension in the scanning direction) of the inkjet head 3B can be reduced, and the inkjet head 3B can be downsized.

3] In the above-described embodiment, the first piezoelectric actuator 31a that drives the first nozzle rows 51a to 51d and the second piezoelectric actuator 31b that drives the second nozzle row 51e are configured separately and separated completely. However, the two piezoelectric actuators 31a and 31b may be integrally formed. Alternatively, the diaphragm 60 is provided so as to cover the entire upper surface of the flow path unit 30, and the piezoelectric plate of the two piezoelectric actuators 31a and 31b is formed after the diaphragm 60 is configured in common by the two piezoelectric actuators 31a and 31b. Only the layer 61 may be formed separately.

4] The actuator for applying the ejection energy to the ink is not limited to the piezoelectric actuator as in the above embodiment, and other types of actuators may be employed. For example, an actuator that ejects ink from a nozzle by heating the ink with a heater to cause film boiling may be used.

1 is a schematic plan view of an ink jet printer according to an embodiment. It is a top view of an inkjet head. It is the A section enlarged view of FIG. FIG. 4 is a sectional view taken along line IV-IV in FIG. 3. It is a figure explaining the cutting-out of the piezoelectric layer from one piezoelectric sheet, (a) is a case where the piezoelectric layers of the first and second piezoelectric actuators are integrated, (b) is a view of the first and second piezoelectric actuators Each of the cases where the piezoelectric layer is a separate body is shown. It is a top view of the inkjet head of a change form. It is a top view of the inkjet head of another modification.

DESCRIPTION OF SYMBOLS 1 Printer 3, 3A, 3B Inkjet head 5a-5d Ink cartridge 5e Ink cartridge 6 Conveyance mechanism 30 Flow path unit 31a 1st piezoelectric actuator 31b 2nd piezoelectric actuator 48a-48d 1st ink supply port 48e 2nd ink supply port 50 Nozzle 51a-51d 1st nozzle row 51e 2 nozzle row 100 Printing paper

Claims (7)

An inkjet head that ejects 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 first nozzle row comprising a plurality of first nozzles arranged at a predetermined pitch along the transport direction;
A first manifold channel communicating with the first nozzle row and extending in the transport direction at a position adjacent to the first nozzle row in the scanning direction;
A first ink supply port communicating with the first manifold flow path and connected to a supply source of printing ink;
A second nozzle row comprising a plurality of second nozzles arranged at the predetermined pitch along the transport direction in the same region as the plurality of first nozzles in a region upstream of the first nozzle row in the transport direction; ,
A second manifold channel communicating with the second nozzle row and extending in the transport direction at a position adjacent to the second nozzle row in the scanning direction;
A second ink supply port communicating with the second manifold channel and connected to one of the supply source of the printing ink and the supply source of the precoat ink used prior to the printing ink And comprising
The first nozzle row and the second nozzle row are arranged apart from each other in the scanning direction,
The first ink supply port communicates with an end portion of the first manifold channel on the upstream side in the transport direction, and is an area upstream of the first nozzle row in the transport direction, and the second ink supply port. The nozzle row is arranged in a region adjacent to the scanning direction,
The second ink supply port communicates with an end portion on the downstream side in the transport direction of the second manifold channel, and is a region on the downstream side in the transport direction with respect to the second nozzle row, and the first ink supply port. An ink jet head, wherein the nozzle row is arranged in a region adjacent to the scanning direction. The first manifold channel is disposed on the side closer to the second nozzle row in the scanning direction with respect to the first nozzle row,
The second manifold channel is disposed on the side closer to the first nozzle row in the scanning direction with respect to the second nozzle row,
The said 1st manifold flow path and the said 2nd manifold flow path are arrange | positioned between the said 1st nozzle row and the said 2nd nozzle row in the said scanning direction, The Claim 1 characterized by the above-mentioned. Inkjet head.   The inkjet head according to claim 1, wherein the number of nozzle arrays in the transport direction of the first nozzle row and the second nozzle row is equal.   The inkjet head according to claim 1, wherein the first nozzle row and the second nozzle row are separated from each other by the predetermined pitch in the transport direction. The first nozzle row includes a black nozzle row composed of a plurality of black nozzles that respectively eject black ink, and a color nozzle row composed of a plurality of color nozzles that respectively eject color ink,
The black nozzle row and the color nozzle row are arranged side by side with respect to the scanning direction,
The second nozzle row is disposed at a position closer to the black nozzle row than the color nozzle row with respect to the scanning direction in a region upstream of the black nozzle row and the color nozzle row in the transport direction. The inkjet head according to any one of claims 1 to 4, wherein A flow path unit having a liquid droplet ejecting surface on which the first nozzle row and the second nozzle row are formed, and an ink flow path communicating with the nozzle row;
A first actuator that is provided in a region facing the first nozzle row on a surface opposite to the liquid droplet ejection surface of the flow path unit, and that imparts ejection energy to the ink of the first nozzle row;
A second actuator that is provided in a region opposite to the second nozzle row on the surface opposite to the liquid droplet ejection surface of the flow path unit and applies ejection energy to the ink of the second nozzle row;
The inkjet head according to claim 1, wherein the first actuator and the second actuator are configured separately.   The inkjet head according to claim 6, wherein the lengths of the first actuator and the second actuator in the transport direction are substantially equal.

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