Patent Publication Number: US-9889656-B2

Title: Channel substrate, method of producing channel substrate, liquid discharge head, ink cartridge, and liquid discharge apparatus

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This patent application is based on and claims priority pursuant to 35 U.S.C. §119(a) to Japanese Patent Application Nos. 2015-174752 filed on Sep. 4, 2015 and 2016-135758 filed on Jul. 8, 2016 in the Japan Patent Office, the entire disclosure of each of which is hereby incorporated by reference herein. 
     BACKGROUND 
     Technical Field 
     Aspects of the present disclosure relate to a channel substrate, a method of producing the channel substrate, a liquid discharge head, an ink cartridge, and a liquid discharge apparatus. 
     Related Art 
     A liquid discharge head (droplet discharge head) is known that includes a channel substrate in which individual channels are formed. For such a liquid discharge head, voltage is applied to a pressure generator, such as a piezoelectric element, to bend (expand and contract) the pressure generator. Accordingly, the volume of the pressurization chamber is changed to change the pressure in the pressurization chamber, thus discharging liquid, such as ink, a deoxyribonucleic acid (DNA) sample, and liquid resist. The individual channel includes, e.g., a nozzle orifice and a pressurization chamber (individual liquid chamber). In other words, the pressurization chamber constitutes part of the individual channels and the nozzle orifice constitutes part of the individual channel. 
     An image forming apparatus, such as a printer, a facsimile machine, a copier, a plotter, and a multifunction peripheral having at least two of the foregoing capabilities, may include a liquid discharge head to discharge recording liquid, e.g., ink. For example, a serial-type image forming apparatus includes a carriage mounting a recording head constituted of the liquid discharge head. The serial-type image forming apparatus causes the carriage to serially scan in a direction perpendicular to a direction of conveyance of a recording medium (hereinafter, simply referred to as “sheet”) and intermittently feeds the sheet according to the width of recording. By repeating the recording and feeding operations, the serial-type image forming apparatus forms an image on the sheet. A line-type image forming apparatus is also known that includes a line-type recording head having an increased number of nozzles per head. 
     There is demand for higher speed and higher image quality in the field of such an image forming apparatus. In particular, for the line-type recording head, there is demand for increasing the length of the recording head to increase the number of nozzles per head and form a complex channel shape. 
     There is also demand for cost reduction while increasing the length of the recording head. As the material of the nozzle pate, a metal material or a resin material is widely used because of relative easiness of the adaptation to the increase of the head length. 
     SUMMARY 
     In an aspect of the present disclosure, there is provided a channel substrate that includes a plurality of individual channels and a plurality of linear machining marks. The individual channels are arrayed in a row. The linear machining marks are substantially parallel to a direction in which the plurality of individual channels is arrayed in the row. 
     In another aspect of the present disclosure, there is provided a liquid discharge head including the channel substrate, to discharge liquid. 
     In still another aspect of the present disclosure, there is provided an ink cartridge that includes the liquid discharge head and an ink tank to supply ink to the liquid discharge head. 
     In still yet another aspect of the present disclosure, there is provided a liquid discharge apparatus that includes the liquid discharge head to discharge liquid. 
     In still yet another aspect of the present disclosure, there is provided a method of producing a channel substrate constituting part of a plurality of individual channels arrayed in a row. The method includes pushing a working tool into the channel substrate from a first side of the channel substrate to form recessed portions at the first side and convex portions at a second side of the channel substrate opposite the first side, and grinding the convex portions with a grinding tool in a direction substantially parallel to a direction in which the convex portions are arrayed. 
     In still yet another aspect of the present disclosure, there is provided a method of producing a channel substrate constituting part of a plurality of individual channels arrayed in a row. The method includes pushing a working tool into from a first side of the channel substrate to faun through holes at the first side and at a second side of the channel substrate opposite the first side, and grinding both the first side and the second side of the channel substrate with a grinding tool in a direction substantially parallel to a direction in which the through holes are arrayed. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
       The aforementioned and other aspects, features, and advantages of the present disclosure would be better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein: 
         FIG. 1  is a perspective view of a liquid discharge head according to an embodiment of the present disclosure; 
         FIG. 2  is an exploded perspective view of the liquid discharge head illustrated in  FIG. 1 ; 
         FIG. 3  is a cross-sectional view of the liquid discharge head cut along line A-A of  FIG. 1 ; 
         FIG. 4  is a cross-sectional view of the liquid discharge head cut along line B-B of  FIG. 1 ; 
         FIG. 5  is a schematic view of a nozzle plate in which a nozzle row is foamed; 
         FIGS. 6A to 6C  are illustrations of a process of producing nozzle orifices in the nozzle plate illustrated in  FIG. 5 ; 
         FIG. 7A  is an illustration of an example of a round machining mark and reliefs; 
         FIG. 7B  is an illustration of an example of linear machining marks and reliefs; 
         FIG. 8  is a schematic view of a nozzle plate in which an unmachined portion is disposed between nozzle rows; 
         FIGS. 9A and 9B  are illustrations of examples in which linear machining marks are substantially parallel to a nozzle array direction; 
         FIG. 10  is a schematic view of a channel plate in which pressurization chambers are formed; 
         FIGS. 11A to 11C  are illustrations of a process of producing pressurization chambers in the channel plate illustrated in  FIG. 10 ; 
         FIG. 12  is a schematic view of a channel plate in which an unmachined portion is disposed between a plurality of pressurization chambers; 
         FIG. 13  is a perspective view of a configuration example of an ink cartridge including the liquid discharge head according to an embodiment of the present disclosure; 
         FIG. 14  is a perspective view of a configuration example of an inkjet recording apparatus including the liquid discharge head according to an embodiment of the present disclosure; and 
         FIG. 15  is a side view of a configuration example of a mechanical section of an inkjet recording apparatus including the liquid discharge head according to an embodiment of the present disclosure. 
     
    
    
     The accompanying drawings are intended to depict embodiments of the present disclosure and should not be interpreted to limit the scope thereof. The accompanying drawings are not to be considered as drawn to scale unless explicitly noted. 
     DETAILED DESCRIPTION 
     In describing embodiments illustrated in the drawings, specific terminology is employed for the sake of clarity. However, the disclosure of this patent specification is not intended to be limited to the specific terminology so selected and it is to be understood that each specific element includes all technical equivalents that operate in a similar manner and achieve similar results. 
     Although the embodiments are described with technical limitations with reference to the attached drawings, such description is not intended to limit the scope of the disclosure and all of the components or elements described in the embodiments of this disclosure are not necessarily indispensable. 
     Referring now to the drawings, an image forming apparatus according to some embodiments of the present disclosure is described below. 
     First, configurations of embodiments according to the present disclosure are described below with reference to  FIGS. 1 to 15 . A channel substrate according to an embodiment of the present disclosure includes channel formation members (e.g., a nozzle plate  40  and a channel plate  30 ) forming part of a plurality of individual channels (e.g., nozzle orifices  41  and pressurization chambers  31 ) arrayed in rows. Linear machining marks (e.g., linear machining marks  44  and linear machining marks  34 ) are formed substantially parallel to a direction in which the individual channels are arrayed. 
     First Embodiment 
     As a first embodiment of the present disclosure, an example is described in which linear machining marks are formed on a nozzle plate as the channel substrate. 
     Liquid Discharge Head 
       FIG. 1  is a perspective view of a liquid discharge head according to the first embodiment of the present disclosure.  FIG. 2  is an exploded perspective view of the liquid discharge head according to the first embodiment.  FIG. 3  is a cross-sectional view of the liquid discharge head cut along line A-A of  FIG. 1 .  FIG. 4  is a cross-sectional view of the liquid discharge head cut along line B-B of  FIG. 1 . 
     A liquid discharge head  1  according to the present embodiment includes a diaphragm  20 , a channel plate  30  (a channel formation member including pressurization chambers  31 ), and a nozzle plate  40  (another channel formation member including nozzle orifices  41 ) that are bonded each other and laminated one on another in this order on a frame member  10 . 
     The frame member  10  includes a base substrate  13 , piezoelectric elements  14  (laminated piezoelectric elements or electromechanical transducer elements), common liquid chambers  11 , and ink supply holes  12 . The base substrate  13  is made of highly-rigid material, such as metal or ceramic. The piezoelectric elements  14  are pressure generators bonded to the base substrate  13 , to pressurize liquid, e.g., ink, in the pressurization chambers  31  of the channel plate  30 . 
     The frame member  10  is formed by injection molding, for example, epoxy resin or polyphenylene sulfide. 
     In each piezoelectric element  14 , piezoelectric layers made of lead zirconate titanate (PZT), each having a thickness of from 10 μm to 50 μm per layer, and internal electrode layers made of silver-palladium (AgPd), each having a thickness of several um per layer, are alternately laminated one on another. Internal electrodes are electrically connected alternately to discrete electrodes and common electrodes, which are end-face electrodes (external electrodes) of end faces of the piezoelectric element  14  so that driving signals are supplied to the discrete electrodes and the common electrodes through a flexible printed circuit (FPC) cable  17 . 
     The piezoelectric element  14  has one face bonded to the base substrate  13  and the other face bonded to the diaphragm  20 . 
     When driving signals are applied to the piezoelectric element  14  and the piezoelectric element  14  is charged, the piezoelectric element  14  extends. When an electric charge of the piezoelectric element  14  is discharged, the piezoelectric element  14  contracts in a direction opposite an extending direction of the piezoelectric element  14 . The extension and contraction of the piezoelectric element  14  bend the diaphragm  20 , thus contracting and expanding the corresponding pressurization chamber  31 . 
     Between the piezoelectric elements  14 , pillars  15  are disposed corresponding to partitions  31 A between the pressurization chambers  31 . In the present embodiment, slitting is performed on a piezoelectric element substrate by half-cut dicing to divide the piezoelectric element substrate in a comb shape, thus forming the piezoelectric elements  14  and the pillars  15 . The configuration of the pillar  15  is the same as the configuration of the piezoelectric element  14  and acts as a simple support since no drive voltage is applied to the pillar  15 . 
     An outer periphery  20 A of the diaphragm  20  is bonded to the frame member  10  via adhesive. 
     The diaphragm  20  includes ink supply ports  21  communicated with the pressurization chambers  31  to supply ink from the common liquid chambers  11  of the frame member  10  to the pressurization chambers  31 . 
     The diaphragm  20  is, for example, a metal plate of nickel having a three-layer structure and is produced by, e.g., electroforming. In some embodiments, the diaphragm  20  may be other metal plate, a resin plate, a laminated member including a metal plate(s) and a resin plate(s), or a laminated member including a plurality of metal plates. 
     The channel plate  30  is produced by molding a stainless steel material in a plate shape, and includes the pressurization chambers  31 , ink supply channels  33 , and damper chambers  32 . The pressurization chambers  31  and the ink supply channels  33  are formed by pressing. The damper chambers  32  are formed by wet etching and half etching to be shallower than the pressurization chambers  31 . In some embodiments, the channel plate  30  may include the pressurization chambers  31  and other channel patterns formed by conducting anisotropic etching on a single-crystal silicon substrate of (110) crystal plane orientation using an alkaline etchant, such as potassium hydroxide solution (KOH). Note that the material of the channel plate  30  is not limited to such a single-crystal silicon. 
     The damper chambers  32  are rectangular spaces interposed between the nozzle plate  40  and the diaphragm  20 , and are communicated with ambient air through an air communication conduits  22  of the diaphragm  20 , thus achieving an air damper effect. 
     The nozzle plate  40  includes the nozzle orifices  41  corresponding to the pressurization chambers  31 . Below, the nozzle plate  40  is further described. 
     Nozzle Plate 
     In the nozzle plate  40 , the nozzle orifices  41  are formed by pressing and grinding. 
     The nozzle plate  40  is produced by forming a stainless steel (SUS) material in a plate shape. The nozzle plate  40  made of a metal material of SUS group is compatible with various types of liquid and a long shape and can reduce the material cost. Note that the material of the nozzle plate  40  is not limited to stainless steel and may be other metal material. 
     The inner shape of the nozzle orifice  41  is, for example, a straight shape, a tapered shape, or a combination of a straight shape and a tapered shape. The nozzle orifice  41  has a hole diameter of, for example, approximately 10 μm to approximately 35 μm at an exit side of ink droplet. The nozzle pitch in each nozzle row is, for example, 150 dpi. 
     A water-repellent layer surface-treated for water repellency is disposed on a nozzle face  40 A (a liquid discharge face being an outer face in a direction of discharge of liquid) of the nozzle plate  40 . The water-repellent layer is formed by a treatment selected in accordance with the physical properties of ink from, for example, polytetrafluoroethylene (PTFE)-Ni eutectoid plating, electrodeposition of fluororesin, vapor deposition of explorative fluororesin (e.g., fluorinated pitch), firing after coating of a solution of silicon-based resin or fluorine-based resin. The water-repellent layer can stabilize the shape and flying properties of ink droplet and create high-quality images. 
       FIG. 5  is a schematic view of the nozzle plate  40  (the nozzle face  40 A) including a nozzle row  41 A. The nozzle plate  40  includes the nozzle row  41 A of the plurality of nozzle orifices  41 . The nozzle plate  40  includes linear machining marks  44  parallel (or substantially parallel) to a direction (nozzle array direction) in which the nozzle row  41 A is formed. 
     A method of producing the nozzle plate  40  illustrated in  FIG. 5  is described with reference to  FIGS. 6A, 6B, and 6C . The method of producing the nozzle plate  40  include a first step (pressing step) and a second step (grinding step). In the first step, a working tool (a punch  50 ) is pushed into nozzle-orifice formation positions of a metal plate from one side of the metal plate to form recessed portions (recessed portions  42 ) at the one side and convex portions (convex portions  43 ) at the other side. In the second step, the convex portions  43  are ground with a grinding tool (grinding tool  51 ) in a direction (indicated by arrow D 1  in  FIG. 6B ) substantially parallel to a direction in which the convex portions  43  are arrayed. 
       FIGS. 6A, 6B, and 6C  are cross-sectional views of the nozzle plate  40  and illustrations of production steps of the nozzle orifices  41 . As described below, the nozzle orifices  41  in the nozzle plate  40  are formed by the pressing step and the grinding step. 
     As illustrated in  FIG. 6A , the nozzle plate  40  is deformed into the shape of the nozzle orifices  41  through plastic deformation by pressing in which the punch  50  is pushed into the nozzle-orifice formation positions of the nozzle plate  40  being a plate member made of metal material from one side of the nozzle plate  40  (the opposite side of the nozzle face  40 A). Through the pressing, the recessed portions  42  are formed in the nozzle plate  40  and the convex portions  43  projecting from the nozzle face  40 A are formed (the pressing step). 
     Next, as illustrated in  FIG. 6B , the grinding step is performed to remove the convex portions  43  using the grinding tool  51 . In the grinding, at least one of lapping grinding and polishing grinding is performed using the grinding tool  51 . The machining direction of the grinding tool  51  (indicated by arrow D in  FIG. 6B ) is parallel (or substantially parallel) to the nozzle array direction. 
     Through the pressing step and the grinding step, the recessed portions  42  are formed and the convex portions  43  are removed. Thus, the recessed portions  42  are open toward the nozzle face  40 A and, as illustrated in  FIG. 6C , the nozzle orifices  41  are formed. 
     As described above, when the machining direction of the grinding tool  51  is parallel (or substantially parallel) to the nozzle array direction, as illustrated in  FIG. 5 , the linear machining marks  44  formed by grinding are parallel (or substantially parallel) to the nozzle row  41 A. 
       FIGS. 7A and 7B  are illustrations of reliefs.  FIG. 7A  is an illustration of an example of a round machining mark.  FIG. 7B  is an illustration of an example of linear machining marks. As illustrated in  FIG. 7A , when a flat plate  52  is pressed using a punch of a column shape to form a round machining mark  53 , as indicated by arrows in  FIG. 7A , reliefs are generated in directions (all directions indicated by arrow D 2  in  FIG. 7A ) vertical to a side face of the round machining mark  53 . 
     By contrast, as illustrated in  FIG. 7B , when the linear machining marks  44  are formed by grinding and cutting, reliefs are generated in directions perpendicular to the linear machining marks  44  as indicated by arrows D 3  in  FIG. 7B . 
     As described above, the direction of grinding is randomized to reduce, e.g., the influence of characteristics of the grinding tool. Grinding is performed on the nozzle plate  40  according to this embodiment so that the direction of the linear machining marks  44  is parallel to the nozzle array direction. The direction of relief in the grinding step is perpendicular to the nozzle array direction. In other words, the direction of relief is restricted so as not to cause a positional deviation in a direction in which nozzles are adjacent to each other. Such a configuration reduces a positional deviation in the direction in which nozzles are adjacent to each other, thus allowing the nozzle plate  40  to obtain a positional accuracy in the direction in which nozzles of the nozzle row  41 A are adjacent to each other. 
     Note that the punch  50  and the grinding tool  51  are not limited to any specific tools and may be either known or new tools. For example, a lapping film or a grinding pad may be used as the grinding tool  51 , and a grinding method in using, e.g., a surface grinder may be applicable. 
     In the example of  FIGS. 6A to 6C , the shape of the interior (the recessed portion  42 ) of the nozzle orifice  41  is tapered. In some embodiments, the interior of the nozzle orifice  41  may have, e.g., a straight shape or a straight-and-tapered shape. 
       FIG. 8  is a schematic view of the nozzle plate  40  (the nozzle face  40 A) including the plurality of nozzle rows  41 A. As illustrated in  FIG. 8 , when the plurality of nozzle rows  41 A is formed in the nozzle plate  40 , an unmachined portion  45  is preferably present between the plurality of nozzle rows  41 A. 
     In the example of  FIG. 8 , the linear machining marks  44  are formed within a predetermined range from each of the two nozzle rows  41 A in a direction perpendicular to each nozzle row  41 A, and an intermediate portion between the linear machining marks  44  of the two nozzle rows  41 A is the unmachined portion  45 . 
     The unmachined portion  45  between the adjacent nozzle rows  41 A reduces the amount of relief in a direction between the nozzle rows  41 A. Such a configuration reduces the amount and variation of positional deviation of the nozzle orifices  41 , thus enhancing the positional accuracy of the nozzle orifices  41 . 
     The linear machining marks  44  are formed parallel or substantially parallel to the nozzle array direction.  FIG. 9A  is an example in which the linear machining marks  44  are substantially parallel to the nozzle array direction. The linear machining marks  44  preferably have, for example, an angle of ±10° relative to the nozzle array direction. 
     As illustrated in  FIG. 9B , where R represents the diameter of the nozzle orifice  41 , P represents the distance between the centers of adjacent nozzle orifices  41 , and A represents the angle formed by the linear machining mark  44  and the nozzle row  41 A, the following formula 1 is preferably satisfied: arctan (R/P)&lt;A . . . (1). 
     Forming the linear machining marks  44  satisfying the above-described formula  1  can reduce incorporation of liquid from peripheral portions of nozzle orifices  41  into adjacent nozzle orifices  41  along grooves of the linear machining marks  44  during wiping. 
     Note that, when grinding is performed with an angle relative to the nozzle array direction, slight reliefs may occur in the nozzle array direction. However, since the angle is minute, the amount of relief is minute. Accordingly, the above-described configuration can achieve the effect of reducing the amount of positional deviation of nozzle orifices while obtaining the above-described effect. 
     The nozzle plate  40  according to the present embodiment described above can simplify the production process, reduce the production cost and the influence of reliefs in the grinding step, and obtain an excellent positional accuracy of nozzle orifices. The liquid discharge head  1  including the nozzle plate  40  can simplify the production process, reduce the production cost, and obtain an excellent discharging performance. 
     Second Embodiment 
     Next, the channel substrate according to another embodiment of the present disclosure is described below. Note that redundant descriptions of the same or similar components and configurations may be omitted below. In the second embodiment, a description is given of an example in which linear machining marks are formed in a channel plate as the channel substrate. 
     The channel plate  30  is produced by molding a metal material, such as a stainless steel material, in a plate shape, and includes the pressurization chambers  31 , ink supply channels  33 , and damper chambers  32 . The pressurization chambers  31  and the ink supply channels  33  are formed by, e.g., pressing. The damper chambers  32  are formed by wet etching and half etching to be shallower than the pressurization chambers  31  (see  FIGS. 2 to 4 ). 
     As the channel plate  30 , a stainless steel material is preferably used in consideration of the compatibility with various types of liquid and the reduction of material cost. Note that the material of the channel plate  30  is not limited to such stainless steel material and may be a metal material. 
     Note that the nozzle plate  40  may be made of, for example, metal, such as stainless steel or nickel, or a combination of metal and resin, such as a polyimide resin film. The nozzle plate  40  is preferably formed with, for example, Ni plating film according to electroforming. 
     Channel Plate 
     The channel plate  30  is further described below.  FIG. 10  is a schematic view of the channel plate  30  including the pressurization chambers  31 . 
     The channel plate  30  includes linear machining marks  34  parallel (or substantially parallel) to a direction (pressurization-chamber-array direction) in which a pressurization chamber row  31 B of the plurality of pressurization chambers  31  is formed. 
     A description is given of a method of producing the channel plate  30  illustrated in  FIG. 10 .  FIGS. 11A to 11C  are cross-sectional views of the channel plate  30  and illustrations of production steps of the pressurization chambers  31 . As described below, the pressurization chambers  31  in the channel plate  30  are formed by a pressing step and a grinding step. 
     First, as illustrated in  FIG. 11A , the channel plate  30  is punched by pressing and shearing with the punch  50  at positions at which the pressurization chambers  31  are formed from one face of the channel plate  30  being a plate member made of a stainless steel material. When a punched side of the channel plate  30  is fractured, the punching is completed (the pressing step). 
     For the pressing to the plate member, such as stainless steel material, from shearing to fracturing, as illustrated in  FIG. 11A , the pressurization chamber  31  has a round edge (R-portion  36   a ) at a punching side and a sheared portion  36   b,  a fractured portion  36   c,  and a burred portion  36   d,  which is formed by the punching. 
     Next, as illustrated in  FIG. 11B , grinding is performed with the grinding tool  51  to remove the R-portions  36   a  and the burred portions  36   d.  In the grinding, at least one of lapping grinding and polishing grinding is performed on both faces of the channel plate  30  separately or simultaneously using the grinding tool  51  (see  FIG. 11C ). At this time, the machining direction of the grinding tool  51  (indicated by arrow D 4  in  FIG. 11B ) is parallel (or substantially parallel) to the pressurization-chamber-array direction (the grinding step). 
     When the machining direction of the grinding tool  51  is parallel (or substantially parallel) to the pressurization-chamber-array direction, as illustrated in  FIG. 10 , the linear machining marks  34  formed by grinding are parallel (or substantially parallel) to the pressurization-chamber-array direction. Accordingly, similarly with the example illustrated in  FIG. 7B , reliefs can be generated in the direction perpendicular to the linear machining mark  34 . 
     As described above, the direction of grinding is randomized to reduce, e.g., the influence of characteristics of the grinding tool. Grinding is performed on the channel plate  30  according to the present embodiment so that the direction of the linear machining mark  34  is parallel to the pressurization-chamber-array direction. The direction of relief in the grinding step is perpendicular to the pressurization-chamber-array direction. In other words, the direction of relief is restricted so as not to cause a positional deviation between adjacent pressurization chambers  31 , thus allowing the channel plate  30  to secure a positional accuracy between adjacent pressurization chambers  31 . 
       FIG. 12  is a schematic view of the channel plate  30  including the plurality of pressurization chamber rows  31 B. As illustrated in  FIG. 12 , when the plurality of pressurization chamber rows  31 B is formed in the channel plate  30 , an unmachined portion  35  is preferably present between the plurality of pressurization chamber rows  31 B. 
     In the example of  FIG. 12 , the linear machining marks  34  are formed within a predetermined range from each of the two pressurization chamber rows  31 B in a direction perpendicular to each pressurization chamber row  31 B, and an intermediate portion between the linear machining marks  34  of the two pressurization chamber rows  31 B is the unmachined portion  35 . 
     The unmachined portion  35  between the adjacent pressurization chamber rows  31 B reduces the amount of relief in a direction between the pressurization chamber rows  31 B. Such a configuration reduces the amount and variation of positional deviation of the pressurization chambers  31 , thus enhancing the positional accuracy of the pressurization chambers  31 . 
     The channel plate  30  according to the present embodiment described above can simplify the production process, reduce the production cost and the influence of reliefs in the grinding step, and obtain an excellent positional accuracy of the pressurization chambers  31 . The liquid discharge head  1  including the channel plate  30  can simplify the production process, reduce the production cost, and obtain an excellent discharging performance. 
     The channel substrate (the nozzle plate  40 ) in the first embodiment and the channel substrate (the channel plate  30 ) according to the second embodiment contribute to the enhancement of the positional accuracy of individual channels in the direction in which the individual channels are arrayed. When the liquid discharge head  1  includes both the nozzle plate  40  according to the first embodiment and the channel plate  30  according to the second embodiment, the positional accuracy of individual channel in the direction in which the individual channels are arrayed can be further enhanced. 
     Ink Cartridge 
     Next, a description is given of an ink cartridge including the liquid discharge head  1  according to the present embodiment. 
       FIG. 13  is a perspective view of a configuration example of an ink cartridge including the liquid discharge head  1 . An ink cartridge  102  includes the liquid discharge head  1  (inkjet head) and an ink tank  91  integrated as a single unit. The liquid discharge head  1  includes, e.g., the above-described nozzle plate  40 . The ink tank  91  supplies ink to the liquid discharge head  1 . 
     When the liquid discharge head  1  and the ink tank  91  are integrated as a single unit, cost reduction and performance enhancement of the liquid discharge head  1  directly lead to cost reduction and performance enhancement of the entire ink cartridge  102 . Accordingly, reducing the cost and enhancing the performance of the liquid discharge head  1  allows the cost reduction and performance enhancement of the ink cartridge  102  of the head-integrated type. 
     Image Forming Apparatus 
     Next, an inkjet recording apparatus as an image forming apparatus including the liquid discharge head  1  according to the present embodiment is described below. 
       FIG. 14  is a perspective view of a configuration example of the inkjet recording apparatus including the liquid discharge head.  FIG. 15  is a side view of a configuration example of a mechanical section of the inkjet recording apparatus. 
     In an inkjet recording apparatus  100 , a printing assembly  103  is stored in an apparatus body and a sheet feeding tray (sheet feeding cassette)  104  that can load multiple recording sheets  130  from the front side is removably mounted on a lower portion of the apparatus body. In addition, the inkjet recording apparatus  100  has a bypass tray  105  openable to manually feed the recording sheet  130 . When the recording sheet  130  fed from the sheet feeding tray  104  or the bypass tray  105  is conveyed to the printing assembly  103 , the printing assembly  103  records a desired image onto the recording sheet  130 . The recording sheet  130  is ejected to an ejection tray  106  mounted on the rear side of the apparatus body. 
     The printing assembly  103  includes a carriage  101 , the liquid discharge head  1 , and the ink cartridge  102 . The carriage  101  is movable in a main scanning direction indicated by arrow MSD in  FIG. 14 . The liquid discharge head  1  is mounted on the carriage  101 . The ink cartridge  102  supplies ink to the liquid discharge head  1 . In addition, the printing assembly  103  holds the carriage  101  with a main guide rod  107  and a sub-guide rod  108  so that the carriage  101  is slidable in the main scanning direction MSD. The main guide rod  107  and the sub-guide rod  108  are guides laterally bridged between left and right side plates. The liquid discharge heads  1  to discharge ink droplets of respective colors of yellow (Y), cyan (C), magenta (M), and black (Bk) are mounted on the carriage  101  so that a plurality of ink discharge ports (nozzles) of each nozzle row is arranged in a direction crossing the main scanning direction MSD. The liquid discharge heads  1  are mounted on the carriage  101  in such a direction that ink droplets are discharged downward. The ink cartridges  102  to supply the respective color inks to the liquid discharge heads  1  are mounted on the carriage  101  in a replaceable manner. 
     The ink cartridge  102  has an air port communicated with the ambient atmosphere at an upper side of the ink cartridge  102  and has a supply port to supply ink to the corresponding liquid discharge head  1  at a lower side of the ink cartridge  102 . The ink cartridge  102  includes a porous material filled with ink. The ink to be supplied to the liquid discharge head  1  by capillary force of the porous material is maintained in slight negative pressure. In the present embodiment, the liquid discharge heads  1  discharge ink of respective colors. Note that, in some embodiments, a single liquid discharge head may be used that includes nozzles to discharge ink of different colors. 
     Here, the rear side of the carriage  101  (the downstream side of the carriage  101  in a direction (sheet conveyance direction) in which the recording sheet  130  is conveyed) is slidably fit into the main guide rod  107 . The front side the carriage  101  (the upstream side of the carriage  101  in the sheet conveyance direction) is slidably placed on the sub-guide rod  108 . In addition, a timing belt  112  is stretched taut between a driving pulley  110 , which is driven to rotate by a main scanning motor  109   a,  and a driven pulley  111  to move the carriage  101  for scanning in the main scanning direction MSD. The timing belt  112  is secured on the carriage  101 . Accordingly, the carriage  101  is reciprocatingly driven by forward and reverse rotation of the main scanning motor  109   a.    
     The inkjet recording apparatus  100  includes a sheet feed roller  113 , a friction pad  114 , and a guide  115  to convey the recording sheet  130 , which is set on the sheet feeding tray  104 , to below the liquid discharge heads  1 . The sheet feed roller  113  and the friction pad  114  separate and feed the recording sheets  130  sheet by sheet from the sheet feeding tray  104 , and the guide  115  guides the recording sheets  130 . The inkjet recording apparatus  100  further includes a conveyance roller  116 , a conveyance roller  117 , and a leading end roller  118 . The conveyance roller  116  reverses and conveys the fed recording sheets  130 . The conveyance roller  117  is pressed against an outer circumferential surface of the conveyance roller  116 . The leading end roller  118  defines a feeding angle of the recording sheet  130  from the conveyance roller  116 . The conveyance roller  116  is driven to rotate by a sub-scanning motor  109   b  via a gear train. 
     The inkjet recording apparatus  100  further includes a print receiver  119  as a sheet guide to guide the recording sheet  130 , which is fed from the conveyance roller  116 , below the liquid discharge heads  1  within a range corresponding to a movement range of the carriage  101  in the main scanning direction MSD. The inkjet recording apparatus  100  includes a conveyance roller  120  and a spur roller  121  on the downstream side of the print receiver  119  in the sheet conveyance direction. The conveyance roller  120  and the spur roller  121  are driven to rotate to feed the recording sheet  130  in a sheet ejection direction in which the recording sheet  130  is ejected. The inkjet recording apparatus  100  further includes an ejection roller  123  and a spur roller  124  to feed the recording sheet  130  to the ejection tray  106  and guides  125  and  126  forming a sheet ejection pathway through which the recording sheet  130  is ejected. 
     In recording, the inkjet recording apparatus  100  drives the liquid discharge heads  1  in accordance with image signals while moving the carriage  101 , to discharge ink onto the stopped recording sheet  130  to record one line of a desired image. Then, the recording sheet  130  is fed by a certain distance, and another line is recorded. When a recording end signal or a signal indicating that a rear end of the recording sheet  130  arrives at a recording area is received, a recording operation is terminated and the recording sheet  130  is ejected. 
     The inkjet recording apparatus  100  further includes a recovery device  127  to recover a discharge failure of the liquid discharge heads  1 , which is disposed at a position outside a recording area at the right end side in a movement direction of the carriage  101 . The recovery device  127  has a capping unit, a suction unit, and a cleaning unit. In printing standby state, the carriage  101  is placed at the side in which the recovery device  127  is disposed and the liquid discharge heads  1  are capped with the capping unit. Accordingly, the ink discharge ports are maintained in a wet state, thus preventing occurrence of a discharge failure due to ink dry. For example, during recording, the inkjet recording apparatus  100  discharges ink not relating to the recording to maintain the viscosity of ink in all of the ink discharge ports constant, thus maintaining stable discharging performance. 
     When a discharge failure occurs, the ink discharge ports (nozzles) of the liquid discharge heads  1  are sealed with the capping unit and ink and bubbles are sucked from the ink discharge ports by the suction unit through a tube. Accordingly, ink and dusts adhered to a discharge port face (nozzle face) are removed by the cleaning unit, thus recovering the discharge failure. The sucked ink is drained to a waste ink container disposed on a lower portion of the apparatus body, and is absorbed into and retained in an ink absorber of the waste ink container. As described above, the inkjet recording apparatus  100  according to the present embodiment includes the recovery device  127 . Such a configuration can recover a discharge failure of the liquid discharge heads  1 , obtain a stable ink-droplet discharge property, and enhance image qualities. 
     As described above, the inkjet recording apparatus  100  as image forming apparatus according to the present embodiment includes the liquid discharge head  1  according to the present embodiment. That is, the inkjet recording apparatus  100  includes the liquid discharge head  1  of a relatively low cost and an excellent discharge performance. 
     Note that the above-described embodiments are examples of embodiments of the claimed invention, and the embodiments of the claimed invention are not limited to the above-described embodiments. The above-described embodiments can be variously modified within the scope of the claimed invention. 
     In the above-described embodiments, the inkjet printer is described as an example of the image forming apparatus. Note that the image forming apparatus may be an inkjet copier, an inkjet facsimile machine, or a multifunctional peripheral including at least two of the foregoing capabilities. The term “image forming apparatus”, unless specified, also includes both serial-type image forming apparatus and line-type image forming apparatus. 
     The term “liquid discharge head” used herein is a functional component to discharge or jet liquid from nozzles. The pressure generator of the liquid discharge head is not limited to a particular-type of pressure generator. The pressure generator is not limited to the piezoelectric actuator (or a layered-type piezoelectric element) described in the above-described embodiments, and may be, for example, a thermal actuator that employs a thermoelectric conversion element, such as a thermal resistor or an electrostatic actuator including a diaphragm and opposed electrodes. 
     The term “image formation” means not only recording, but also printing, image printing, molding, and the like. 
     The term “liquid discharge device” is an integrated unit including the liquid discharge head and other functional parts, or the liquid discharge head and other structures, and denotes an assembly of parts relating to the liquid discharge function. For example, the liquid discharge device may be formed of a combination of a liquid discharge head with at least one of a head tank, a carriage, a supply assembly, a maintenance-and-recovery assembly, and a main scan moving assembly. 
     Herein, examples of the integrated unit include a combination in which the liquid discharge head and a functional part(s) are combined fixedly to each other through, e.g., fastening, bonding, or engaging, and a combination in which one of the liquid discharge head and a functional part(s) is movably held by another. In addition, the liquid discharge head can be detachably attached to the functional parts or structures each other. 
     For example, the liquid discharge head and a head tank are integrated as the liquid discharge device. The liquid discharge head and the head tank may be connected each other via, e.g., a tube to integrally form the liquid discharge device. Here, a unit including a filter may further be added to a portion between the head tank and the liquid discharge head, thereby forming another liquid discharge device. 
     In another example, the liquid discharge device may include a liquid discharge head integrated with a carriage as a single unit. 
     In still another example, the liquid discharge device includes the liquid discharge head movably held by a guide that forms part of a main-scanning moving device, so that the liquid discharge head and the main-scanning moving device are integrated as a single unit. The liquid discharge device may include the liquid discharge head, the carriage, and the main scan moving unit that are integrated as a single unit. 
     Furthermore, in another example, the cap that forms part of the recovery device is secured to the carriage mounted with the liquid discharge head so that the liquid discharge head, the carriage, and the recovery device are integrated as a single unit to form the liquid discharge device. 
     Further, in another example, the liquid discharge device includes tubes connected to the head tank or the channel member mounted on the liquid discharge head so that the liquid discharge head and the supply assembly are integrated as a single unit. Liquid is supplied from a liquid reservoir source to the liquid discharge head. 
     The main-scanning moving device may include only a guide. The supply assembly may include only a tube(s) or a loading unit. 
     The term “liquid discharge apparatus” used herein is an apparatus including the liquid discharge head or the liquid discharge device to discharge liquid by driving the liquid discharge head. As the liquid discharge apparatus, there are an apparatus capable of discharging liquid to a material on which liquid can be adhered as well as an apparatus to discharge liquid toward gas or liquid. 
     The liquid discharge apparatus may include devices to feed, convey, and eject the material on which liquid can be adhered. The liquid discharge apparatus may further include a pretreatment apparatus to coat a treatment liquid onto the material, and a post-treatment apparatus to coat a treatment liquid onto the material, onto which the liquid has been discharged. 
     Examples of the liquid discharge apparatus include an image forming apparatus to form an image on a sheet by discharging ink, and a three-dimensional apparatus to discharge a molding liquid to a powder layer in which powder material is formed in layers, so as to form a three-dimensional article. 
     In addition, the liquid discharge apparatus is not limited to such an apparatus to form and visualize meaningful images, such as letters or figures, with discharged liquid. For example, the liquid discharge apparatus may be an apparatus to form meaningless images, such as patterns, or fabricate three-dimensional objects. 
     The above-described term “material on which liquid can be adhered” represents a material on which liquid is at least temporarily adhered, a material on which liquid is adhered and fixed, or a material into which liquid is adhered to permeate. Examples of the “material on which liquid can be adhered” include recording media, such as paper sheet, recording paper, recording sheet of paper, film, and cloth, electronic component, such as electronic substrate and piezoelectric element, and media, such as powder layer, organ model, and testing cell. The “material on which liquid can be adhered” includes any material on which liquid is adhered, unless particularly limited. 
     Examples of the material on which liquid can be adhered include any materials on which liquid can be adhered even temporarily, such as paper, thread, fiber, fabric, leather, metal, plastic, glass, wood, and ceramic. 
     The “liquid” is not limited to a particular liquid as long as the liquid has a viscosity or surface tension to be discharged from a head. However, preferably, the viscosity of the liquid is not greater than 30 mPa·s under ordinary temperature and ordinary pressure or by heating or cooling. Examples of the liquid include a solution, a suspension, or an emulsion including, for example, a solvent, such as water or an organic solvent, a colorant, such as dye or pigment, a functional material, such as a polymerizable compound, a resin, a surfactant, a biocompatible material, such as DNA, amino acid, protein, or calcium, and an edible material, such as a natural colorant. Such a solution, a suspension, or an emulsion can be used for, e.g., inkjet ink, surface treatment solution, a liquid for forming components of electronic element or light-emitting element or a resist pattern of electronic circuit, or a material solution for three-dimensional fabrication. 
     The liquid discharge apparatus may be an apparatus to relatively move a liquid discharge head and a material on which liquid can be adhered. However, the liquid discharge apparatus is not limited to such an apparatus. For example, the liquid discharge apparatus may be a serial head apparatus that moves the liquid discharge head or a line head apparatus that does not move the liquid discharge head. 
     Examples of the liquid discharge apparatus further include a treatment liquid coating apparatus to discharge a treatment liquid to a sheet to coat the treatment liquid on the surface of the sheet to reform the sheet surface and an injection granulation apparatus in which a composition liquid including raw materials dispersed in a solution is injected through nozzles to granulate fine particles of the raw materials. 
     Numerous additional modifications and variations are possible in light of the above teachings. It is therefore to be understood that, within the scope of the above teachings, the present disclosure may be practiced otherwise than as specifically described herein. With some embodiments having thus been described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the scope of the present disclosure and appended claims, and all such modifications are intended to be included within the scope of the present disclosure and appended claims.