JP5451009B2 - Liquid discharge head and printing apparatus using the same - Google Patents

Description

  The present invention relates to a liquid discharge head, and more particularly to a liquid discharge head mounted on an ink jet printer used for recording characters and images.

  In recent years, printing apparatuses using inkjet recording methods such as inkjet printers and inkjet plotters are not only printers for general consumers, but also, for example, formation of electronic circuits, manufacture of color filters for liquid crystal displays, manufacture of organic EL displays It is also widely used for industrial applications.

  In such an ink jet printing apparatus, a liquid discharge head for discharging liquid is mounted as a print head, and this type of liquid discharge head is added to an ink flow path filled with ink. It is equipped with a heater as a pressure means, heated and boiled by the heater, pressurized with air bubbles generated in the ink flow path, and ejected as ink droplets from the ink ejection holes, and filled with ink A piezoelectric method is generally known in which a part of a wall of an ink flow path is bent and displaced by a displacement element, and ink in the ink flow path is mechanically pressurized and discharged as ink droplets from an ink discharge hole.

By the way, as a piezoelectric ink jet head, a piezoelectric element is bonded to a flow path member filled with ink, and the heat of a substrate on which a driver IC (Integrated Circuit) for applying a voltage to the piezoelectric element is mounted is transmitted through a frame. One having a heat radiating plate for conducting to a carriage is known. (For example, see Patent Document 1).
JP 2004-90491 A

  However, in the liquid discharge head described in Patent Document 1, heat conduction to the heat radiating plate is not sufficient, and heat is also transmitted to the frame. Therefore, heat is transmitted to the flow path member via the substrate or the frame, and the flow path Since the temperature of the liquid in the member changes, there is a problem that the amount and speed of the ejected droplets fluctuate.

  Accordingly, an object of the present invention is to provide a liquid discharge head in which heat generated from the driver IC is not easily transmitted to the flow path member (liquid discharge head main body).

A liquid discharge head according to the present invention includes a flat liquid discharge head main body having a plurality of liquid discharge holes and extending in one direction, and a plurality of pressurizing units for discharging droplets from the plurality of liquid discharge holes, respectively. , A flexible flat cable for transmitting a driving signal for driving the plurality of pressurizing means, a resin substrate to which the flexible flat cable is connected and through which the driving signal passes, and a driving signal mounted on the flexible flat cable. a driver IC for processing, and frame that is fixed to the liquid discharging head body is fixed to the frame, in the liquid discharge head provided with a metal housing in which the flexible flat cable and said driver IC are housed The driver IC is formed of the flexible elastic member by a heat insulating elastic member provided on the frame. Pushed through the flat cable, the has been pressed against the inner wall surface of the housing, wherein the frame and the liquid ejection head main body, characterized in that it is fixed through the resin substrate.

Further, it is preferable that the frame is fixed to the liquid discharge head main body at an end portion in the one direction .

  Furthermore, it is preferable that a heat insulating material is interposed between the housing and the liquid discharge head main body.

  The printing apparatus of the present invention includes the liquid discharge head, a transport unit that transports a recording medium in a direction that is not parallel to the one direction with respect to the liquid discharge head, and a control unit that controls driving of the liquid discharge head. It is characterized by providing.

According to the liquid ejection head of the present invention, the heat insulating elastic member provided in front Symbol frame, said pressed through a flexible flat cable, by being pressed against the inner wall surface of the housing, the driver IC since heat is conducted mainly to the housing, the liquid ejection head body heat is transferred difficulty rather to further, since the resin substrate between said frame said liquid discharge head body is interposed hardly heat is transferred it can.

Further, when the frame is fixed to the liquid discharge head main body at the end in the one direction, heat can be hardly transmitted to the center of the liquid discharge head main body.

  Furthermore, when a heat insulating material is interposed between the housing and the liquid discharge head body, it is difficult for the heat of the driver IC to be transmitted by the liquid discharge head body.

  The printing apparatus of the present invention includes the liquid discharge head, a transport unit that transports a recording medium in a direction that is not parallel to the one direction with respect to the liquid discharge head, and a control unit that controls driving of the liquid discharge head. By providing, it is possible to suppress deterioration in printing accuracy due to the influence of heat generated by the driver IC.

  FIG. 1 is a schematic configuration diagram of a color inkjet printer including a liquid discharge head which is an embodiment of a printing apparatus of the present invention. This color inkjet printer 1 (hereinafter referred to as printer 1) has four liquid ejection heads 2. These liquid ejection heads 2 are arranged along the transport direction of the printing paper P that is a recording medium, and are fixed in the printer 1. The liquid discharge head 2 has an elongated shape in a direction from the front side to the back side in FIG.

  In the printer 1, a paper feed unit 114, a transport unit 120, and a paper receiver 116 are sequentially provided along the transport path of the printing paper P. In addition, the printer 1 is provided with a control unit 100 for controlling the operation of each unit of the printer 1 such as the liquid discharge head 2 and the paper feeding unit 114.

  The paper supply unit 114 includes a paper storage case 115 that can store a plurality of printing papers P, and a paper supply roller 145. The paper feed roller 145 can send out the uppermost print paper P among the print papers P stacked and stored in the paper storage case 115 one by one.

  Between the paper feed unit 114 and the transport unit 120, two pairs of feed rollers 118a and 118b and 119a and 119b are arranged along the transport path of the printing paper P. The printing paper P sent out from the paper supply unit 114 is guided by these feed rollers and further sent out to the transport unit 120.

  The transport unit 120 includes an endless transport belt 111 and two belt rollers 106 and 107. The conveyor belt 111 is wound around belt rollers 106 and 107. The conveyor belt 111 is adjusted to such a length that it is stretched with a predetermined tension when it is wound around two belt rollers. Thus, the conveyor belt 111 is stretched without slack along two parallel planes each including a common tangent line of the two belt rollers. Of these two planes, the plane closer to the liquid ejection head 2 is a transport surface 127 that transports the printing paper P.

  As shown in FIG. 1, a conveyance motor 174 is connected to the belt roller 106. The transport motor 174 can rotate the belt roller 106 in the direction of arrow A. The belt roller 107 can rotate in conjunction with the transport belt 111. Therefore, the conveyance belt 111 moves along the direction of arrow A by driving the conveyance motor 174 and rotating the belt roller 106.

  In the vicinity of the belt roller 107, a nip roller 138 and a nip receiving roller 139 are arranged so as to sandwich the conveyance belt 111. The nip roller 138 is urged downward by a spring (not shown). A nip receiving roller 139 below the nip roller 138 receives the nip roller 138 biased downward via the conveying belt 111. The two nip rollers 138 and 139 are rotatably installed and rotate in conjunction with the transport belt 111.

  The printing paper P sent out from the paper supply unit 114 to the transport unit 120 is sandwiched between the nip roller 138 and the transport belt 111. As a result, the printing paper P is pressed against the transport surface 127 of the transport belt 111 and is fixed on the transport surface 127. The printing paper P is transported in the direction in which the liquid ejection head 2 is installed according to the rotation of the transport belt 111. The outer peripheral surface 113 of the conveyor belt 111 may be treated with adhesive silicon rubber. Thereby, the printing paper P can be securely fixed to the transport surface 127.

  The four liquid discharge heads 2 are arranged close to each other along the conveyance direction by the conveyance belt 111. A large number of liquid discharge holes 8 for discharging liquid are provided on the lower surface of each liquid discharge head 2 (see FIGS. 9 and 10).

  Liquid droplets (ink) of the same color are ejected from the liquid ejection holes 8 provided in one liquid ejection head 2. The liquid discharge holes 8 of each liquid discharge head 2 are arranged at equal intervals in one direction (a direction parallel to the print paper P and perpendicular to the transport direction of the print paper P, and the longitudinal direction of the liquid discharge head 2). , It can be printed without gaps in one direction. The colors of the liquid ejected from each liquid ejection head 2 are magenta (M), yellow (Y), cyan (C), and black (K), respectively. A slight gap is disposed between the lower surface of each liquid discharge head 2 and the transport surface 127 of the transport belt 111.

  The printing paper P transported by the transport belt 111 passes through the gap between the liquid ejection head 2 and the transport belt 111. At that time, droplets are ejected from the liquid ejection head 2 toward the upper surface of the printing paper P. As a result, a color image based on the image data stored by the control unit 100 is formed on the upper surface of the printing paper P.

  A separation plate 140 and two pairs of feed rollers 121a and 121b and 122a and 122b are arranged between the transport unit 120 and the paper receiver 116. The printing paper P on which the color image is printed is conveyed to the peeling plate 140 by the conveying belt 111. At this time, the printing paper P is peeled from the transport surface 127 by the right end of the peeling plate 140. Then, the printing paper P is sent out to the paper receiving unit 116 by the feed rollers 121a to 122b. In this way, the printed printing paper P is sequentially sent to the paper receiving unit 116 and stacked on the paper receiving unit 116.

  Note that a paper surface sensor 133 is installed between the liquid ejection head 2 and the nip roller 138 that are the most upstream in the transport direction of the printing paper P. The paper surface sensor 133 includes a light emitting element and a light receiving element, and can detect the leading end position of the printing paper P on the transport path. The detection result by the paper surface sensor 133 is sent to the control unit 100. The control unit 100 can control the liquid ejection head 2, the conveyance motor 174, and the like so that the conveyance of the printing paper P and the printing of the image are synchronized based on the detection result sent from the paper surface sensor 133. The drive signal sent from the control unit 100 to each liquid ejection head 2 is further processed by a driver IC provided in each liquid ejection head 2 to eject droplets.

  Next, the liquid discharge head 2 of the present invention will be described. FIG. 2 is a perspective view of the liquid discharge head 2. The liquid discharge head 2 includes a liquid discharge head main body 200 and a casing 201. The casing 201 is made of metal, and a hole 202 through which a signal cable for transmitting a drive signal is partially opened. In the example of FIG. 2, a hole 202 is opened in a part of the upper surface, and a signal cable (not shown) through which a drive signal connected to the control unit 100 is transmitted passes through the hole 202 and is closed with a resin lid or the like. Can be removed. A liquid introduction hole 236 is opened in the liquid ejection head 2, and a liquid ejected from the liquid introduction hole 236 is placed therein. A side plate 210 is attached to a part of the head body 200 by screwing or bonding.

  3 is a cross-sectional view of the liquid discharge head 2 shown in FIG. The liquid discharge head body 200 includes a flow path member 4, a branch flow path member 230, a piezoelectric actuator unit 21, a flexible flat cable (hereinafter sometimes abbreviated as FPC) 220, a driver IC 222, and a side plate 210. A frame 240 with a heat insulating elastic member 242 and a substrate 232 on which a connector 234 is mounted are fixed to the liquid discharge head body 200. Although each part will be described later, a drive signal sent from the control unit 100 to the substrate 232 via a signal cable (not shown) is sent to the FPC 220 via the connector 234. The driver IC 222 mounted on the FPC 220 processes the drive signal, and the processed drive signal is transmitted to the piezoelectric actuator unit 21 having a pressurizing unit described later through the FPC 220, and the liquid inside the flow path member 4 is removed by the pressurizing unit. By applying pressure, droplets are discharged. For example, the substrate 232 may divide the ejection signal into a plurality of driver ICs 222 or perform rectification of the ejection signal. However, the substrate 232 is not provided, and the signal cable from the control unit 100 is directly connected to the FPC 220. It may be. The FPC 220 is a strip having flexibility, and has a metal wiring 224 inside, and a part of the wiring 224 is exposed on the surface of the FPC 220, and the connector 234, the driver IC 222 and the It is electrically connected to the piezoelectric actuator unit 21.

  The driver IC 222 generates heat when performing the above-described drive signal processing. When this heat is transmitted to the flow path member 4, a temperature difference occurs between the flow path member 4 and the liquid inside the flow path member 4. Since the viscosity of the liquid changes as the temperature changes, even if the pressure from the pressurizing means is constant, the discharge speed and amount of the droplets change. If the speed and amount of the ejected droplets change, the landing position on the printing paper P shifts, and the size of the pixels formed by the spreading of the droplets after landing changes, so the accuracy of the printed image is low. May be. However, since the driver IC 222 is pressed through the FPC 220 by the heat insulating elastic member 242 and pressed against the metal casing 201, the generated heat is mainly transmitted to the casing 201, and further the entire casing 201 It spreads quickly and is dissipated to the outside.

  4A is a perspective view of the liquid discharge head main body 200, the substrate, and the frame. The casing 201 and the side plate 210 are removed from the liquid discharge head 2 of FIG. 2, and one end of the FPC 220 is removed from the connector 234 and widened. It is what was in the state. FIG. 4B is a perspective view of the liquid discharge head main body 200 and the substrate 232, and FIG. 5A is a perspective view of the liquid discharge head main body 200. FIG. 5B is a perspective view of the liquid discharge head body 200 with the branch channel member 230 removed.

  FIG. 6 is a bottom view of the piezoelectric actuator unit 21, the FPC 220, and the driver IC 222.

  Four driver ICs are pressed against different surfaces of the housing 201 two by two. Thereby, the heat distribution in the housing 201 can be averaged. The different surfaces of the housing 201 are preferably opposing surfaces, and the opposing surface is preferably the widest surface among the surfaces of the housing 201.

The frame 240 does not need to be made of a specific material, but is preferably a metal because of its high strength. The casing 201 is fixed to the frame 240, and the frame 240 is fixed to the branch flow path member 230. The casing 201 and the branch flow path member 230 are not directly fixed. Heat is not easily transmitted to the member 4. Fixing is done with screws. Since the driver IC 222, the FPC 220, and the heat insulating elastic body 242 exist between the housing 201 and the frame 240, the housing 201 and the frame 240 are not in direct surface contact. It is suppressed that the heat of the body 201 is transmitted to the flow path member 4.
Further, the frame 240 connected to the branch flow channel member 230 should have a small cross-sectional area so that heat is not easily transmitted from the frame 240 to the flow channel member 4. In FIG. 4A, the frame 240 is composed of an annular claim main body and a leg portion, and the leg portion is connected at the end of the long side of the branch channel member 230, which is preferable.

  In addition, the casing 201 and the side plate 210 are in contact with each other at the end of the casing 201 by a line contact with the thickness of the metal plate that forms the casing, so that intrusion of liquid mist or the like from the outside is prevented. While suppressing, it is not a wide surface contact, Therefore It is suppressed that the heat | fever of the housing | casing 201 is transmitted to the flow-path member 4 via the side plate 210. FIG. And in order to improve this heat insulation more, you may interpose resin and rubber | gum used as a heat insulating material between the housing | casing 201 and the side plate 210. FIG.

  The branch flow path member 230 includes a flow path branched so that the liquid that has entered the liquid introduction hole 236 flows through the opening 5 b of the flow path member 4. In addition to this, the branch channel member 230 includes a filter for stopping dust in the liquid, a thin plate of resin, rubber, metal, etc. so that the fluctuation can be absorbed when the quantity of discharged liquid changes. The damper can be provided.

  In addition, if the substrate 232 is interposed when the frame 240 is fixed, the number of steps for fixing the substrate 232 can be reduced. In addition, when the substrate 232 is a resin substrate such as FR4, there is an effect of heat insulation.

  FIG. 7 is a plan view of the flow path member 4 and the piezoelectric actuator unit 21 in the liquid ejection head 2 shown in FIG. FIG. 8 is an enlarged plan view of a region surrounded by a one-dot chain line in FIG. 7 and is a part of the liquid discharge head 2. FIG. 9 is an enlarged perspective view of the same position as in FIG. 8, in which some of the flow paths are omitted so that the position of the liquid discharge holes 8 can be easily understood. 8 and 9, in order to make the drawings easy to understand, the liquid pressurizing chamber 10 (liquid pressurizing chamber group 9), the squeezing 12, and the liquid discharge holes which are to be drawn by broken lines below the piezoelectric actuator unit 21. 8 is drawn with a solid line. 10 is a vertical cross-sectional view taken along the line VV in FIG.

  The liquid discharge head 2 includes a flat plate-like channel member 4 and a piezoelectric actuator unit 21 having a plurality of pressurizing means on the channel member 4. The piezoelectric actuator unit 21 has a trapezoidal shape, and is disposed on the upper surface of the flow path member 4 so that a pair of parallel opposing sides of the trapezoid is parallel to the longitudinal direction of the flow path member 4. Further, two piezoelectric actuator units 21 are arranged on the flow path member 4 as a whole in a zigzag manner, two along each of two virtual straight lines parallel to the longitudinal direction of the flow path member 4. Yes. The oblique sides of the piezoelectric actuator units 21 adjacent to each other on the flow path member 4 partially overlap in the short direction of the flow path member 4. Although details will be described later, in the area printed by driving the overlapping piezoelectric actuator unit 21, droplets discharged by the two piezoelectric actuator units 21 are mixed and landed. .

  A manifold 5 that is a part of the liquid flow path is formed inside the flow path member 4. The manifold 5 has an elongated shape extending along the longitudinal direction of the flow path member 4, and an opening 5 b of the manifold 5 is formed on the upper surface of the flow path member 4. A total of ten openings 5 b are formed along each of two straight lines (imaginary lines) parallel to the longitudinal direction of the flow path member 4. The opening 5b is formed at a position that avoids a region where the four piezoelectric actuator units 21 are disposed. The manifold 5 is supplied with liquid from a liquid tank (not shown) through the opening 5b.

  The manifold 5 formed in the flow path member 4 is branched into a plurality of branches (the manifold 5 at the branched portion may be referred to as a sub-manifold 5a). The manifold 5 connected to the opening 5 b extends along the oblique side of the piezoelectric actuator unit 21 and is disposed so as to intersect with the longitudinal direction of the flow path member 4. In a region sandwiched between two piezoelectric actuator units 21, one manifold 5 is shared by adjacent piezoelectric actuator units 21, and the sub-manifold 5 a branches off from both sides of the manifold 5. These sub-manifolds 5 a extend in the longitudinal direction of the liquid discharge head 2 adjacent to each other in the region facing the piezoelectric actuator units 21 inside the flow path member 4.

  The flow path member 4 has four liquid pressurizing chamber groups 9 in which a plurality of liquid pressurizing chambers 10 are formed in a matrix (that is, two-dimensionally and regularly). The liquid pressurizing chamber 10 is a hollow region having a substantially rhombic planar shape with rounded corners. The liquid pressurizing chamber 10 is formed so as to open on the upper surface of the flow path member 4. These liquid pressurizing chambers 10 are arranged over almost the entire surface of the upper surface of the flow path member 4 facing the piezoelectric actuator unit 21. Accordingly, each liquid pressurizing chamber group 9 formed by these liquid pressurizing chambers 10 occupies a region having almost the same size and shape as the piezoelectric actuator unit 21. Further, the opening of each liquid pressurizing chamber 10 is closed by adhering the piezoelectric actuator unit 21 to the upper surface of the flow path member 4.

  In this embodiment, as shown in FIG. 8, the manifold 5 branches into four rows of E1-E4 sub-manifolds 5a arranged in parallel with each other in the short direction of the flow path member 4, and each sub-manifold The liquid pressurizing chambers 10 connected to 5a constitute a row of liquid pressurizing chambers 10 arranged in the longitudinal direction of the flow path member 4 at equal intervals, and the four rows are arranged in parallel to each other in the short direction. Yes. Two rows of liquid pressurizing chambers 10 connected to the sub-manifold 5a are arranged on both sides of the sub-manifold 5a.

  As a whole, the liquid pressurizing chambers 10 connected from the manifold 5 constitute rows of the liquid pressurizing chambers 10 arranged in the longitudinal direction of the flow path member 4 at equal intervals, and the rows are 16 rows parallel to each other in the short direction. It is arranged. The number of liquid pressurizing chambers 10 included in each liquid pressurizing chamber row is arranged so as to gradually decrease from the long side toward the short side, corresponding to the outer shape of the displacement element 50 that is an actuator. ing. The liquid discharge holes 8 are also arranged in the same manner. As a result, it is possible to form an image with a resolution of 600 dpi in the longitudinal direction as a whole. That is, the individual flow paths 32 are connected to each sub-manifold 5a at intervals corresponding to 150 dpi on average. This is because the individual flow paths 32 connected to the sub-manifolds 5a are not necessarily connected at equal intervals when the liquid ejection holes 8 for 600 dpi are divided and connected to the four sub-manifolds 5a. This means that the individual flow paths 32 are formed at intervals of an average of 170 μm (25.4 mm / 150 = 169 μm intervals if 150 dpi) in the extending direction of 5a, that is, the main scanning direction.

  Individual electrodes 35 to be described later are formed at positions facing the liquid pressurizing chambers 10 on the upper surface of the piezoelectric actuator unit 21. The individual electrode 35 is slightly smaller than the liquid pressurizing chamber 10, has a shape substantially similar to the liquid pressurizing chamber 10, and fits in a region facing the liquid pressurizing chamber 10 on the upper surface of the piezoelectric actuator unit 21. Is arranged.

  A large number of liquid discharge holes 8 are formed in the liquid discharge surface on the lower surface of the flow path member 4. These liquid discharge holes 8 are arranged at a position avoiding a region facing the sub-manifold 5 a arranged on the lower surface side of the flow path member 4. Further, these liquid discharge holes 8 are arranged in a region facing the piezoelectric actuator unit 21 on the lower surface side of the flow path member 4 and constitute a group of four liquid discharge holes. These liquid discharge hole groups occupy an area having almost the same size and shape as the piezoelectric actuator unit 21, and by displacing the displacement element 50 of the corresponding piezoelectric actuator unit 21, a droplet is discharged from the liquid discharge hole 8. Can be discharged. The liquid discharge holes 8 in each region are arranged at equal intervals along a plurality of straight lines parallel to the longitudinal direction of the flow path member 4.

  A large number of apertures 12 are formed inside the flow path member 4. These throttles 12 are arranged in a region facing the liquid pressurizing chamber group 9. The aperture 12 of the present embodiment extends along one direction parallel to the horizontal plane. One end of the squeezing 12 is connected to the sub-manifold 5a via the individual supply channel 6 described later. Further, the other end of the squeezing 12 is connected to the liquid pressurizing chamber 10.

  The flow path member 4 included in the liquid ejection head 2 has a stacked structure in which a plurality of plates are stacked. These plates are a cavity plate 22, a base plate 23, an aperture (squeezing) plate 24, supply plates 25 and 26, manifold plates 27, 28 and 29, a cover plate 30 and a nozzle plate 31 in order from the upper surface of the flow path member 4. is there. A number of holes are formed in these plates. The plates 22 to 31 are laminated in alignment so that these holes communicate with each other to form the individual flow path 32 and the manifold 5. As shown in FIG. 10, the liquid discharge head 2 is configured such that the liquid pressurizing chamber 10 is on the upper surface of the flow path member 4, the sub manifold 5 a is on the inner lower surface side, and the liquid discharge holes 8 are on the lower surface. Each portion constituting the flow path 32 is disposed close to each other at a different position, and the sub manifold 5 a and the liquid discharge hole 8 are connected via the liquid pressurizing chamber 10.

  The hole formed in each plate 22-31 is demonstrated. These holes include the following. First, the liquid pressurizing chamber 10 formed in the cavity plate 22. Second, there is a communication hole that forms a flow path that connects from one end of the liquid pressurizing chamber 10 to the sub-manifold 5a. The communication holes are formed in the plates 23 to 25 from the base plate 23 (specifically, the inlet of the liquid pressurizing chamber 10) to the supply plate 25 (specifically, the outlet of the sub manifold 5a). The communication hole includes the aperture 12 formed in the aperture plate 24 and the individual supply flow path 6 formed in the supply plates 25 and 26.

  Third, there is a communication hole that constitutes a flow channel that communicates from the other end of the liquid pressurizing chamber 10 to the liquid discharge hole 8, and this communication hole is referred to as a descender (partial flow channel) in the following description. . The descender is formed on each plate from the base plate 23 (specifically, the outlet of the liquid pressurizing chamber 10) to the nozzle plate 31 (specifically, the liquid discharge hole 8). Fourthly, there is a communication hole constituting the sub-manifold 5a. The communication holes are formed in the manifold plates 27 to 29.

  Such communication holes are connected to each other to form an individual flow path 32 from the liquid inflow port (the outlet of the submanifold 5a) from the submanifold 5a to the liquid discharge hole 8. The liquid supplied to the sub manifold 5a is discharged from the liquid discharge hole 8 through the following path. First, from the sub-manifold 5a, it passes through the individual supply flow path 6 and reaches one end of the aperture 12. Next, it proceeds horizontally along the extending direction of the aperture 12 and reaches the other end of the aperture 12. From there, it reaches one end of the liquid pressurizing chamber 10 upward. Further, the liquid pressurizing chamber 10 proceeds horizontally along the extending direction of the liquid pressurizing chamber 10 and reaches the other end of the liquid pressurizing chamber 10. While moving little by little in the horizontal direction from there, it proceeds mainly downward and proceeds to the liquid discharge hole 8 opened on the lower surface.

  As shown in FIG. 10, the piezoelectric actuator unit 21 has a laminated structure including two piezoelectric ceramic layers 21a and 21b. Each of these piezoelectric ceramic layers 21a and 21b has a thickness of about 20 μm. The total thickness of the piezoelectric actuator unit 21 is about 40 μm. Each of the piezoelectric ceramic layers 21a and 21b extends so as to straddle the plurality of liquid pressurizing chambers 10 (see FIG. 3). The piezoelectric ceramic layers 21a and 21b are made of a lead zirconate titanate (PZT) ceramic material having ferroelectricity.

  The piezoelectric actuator unit 21 includes a common electrode 34 made of a metal material such as Ag—Pd and an individual electrode 35 made of a metal material such as Au. As described above, the individual electrode 35 is disposed at a position facing the liquid pressurizing chamber 10 on the upper surface of the piezoelectric actuator unit 21. One end of the individual electrode 35 is drawn out of a region facing the liquid pressurizing chamber 10 to form a connection electrode 36. The connection electrode 36 is made of, for example, gold containing glass frit, and has a convex shape with a thickness of about 15 μm.

  The common electrode 34 is formed over almost the entire surface in the area between the piezoelectric ceramic layer 21a and the piezoelectric ceramic layer 21b. That is, the common electrode 34 extends so as to cover all the liquid pressurizing chambers 10 in the region facing the piezoelectric actuator unit 21. The thickness of the common electrode 34 is about 2 μm. The common electrode 34 is grounded in a region not shown, and is held at the ground potential. In the present embodiment, a surface electrode (not shown) different from the individual electrode 35 is formed on the piezoelectric ceramic layer 21b at a position avoiding the electrode group composed of the individual electrodes 35. The surface electrode is electrically connected to the common electrode 34 through a through hole formed inside the piezoelectric ceramic layer 21b, and is connected to another electrode on the FPC 220 in the same manner as the large number of individual electrodes 35. ing.

  As will be described later, when a predetermined ejection signal is selectively supplied to the individual electrode 35, pressure is applied to the liquid in the liquid pressurizing chamber 10 corresponding to the individual electrode 35. As a result, droplets are ejected from the corresponding liquid ejection holes 8 through the individual channels 32. That is, the portion of the piezoelectric actuator unit 21 that faces each liquid pressurizing chamber 10 corresponds to an individual displacement element 50 (actuator) corresponding to each liquid pressurizing chamber 10 and the liquid discharge hole 8. That is, in the laminate composed of the two piezoelectric ceramic layers 21a and 21b, the displacement element 50 having a unit structure as shown in FIG. 10 is formed by a diaphragm 21a, a common electrode 34, a piezoelectric ceramic layer 21b, and individual electrodes 35, which are located immediately above 10, and the piezoelectric actuator unit 21 includes a plurality of displacement elements 50. In the present embodiment, the amount of liquid discharged from the liquid discharge hole 8 by one discharge operation is about 5 to 7 pL (picoliter).

  A large number of individual electrodes 35 are individually electrically connected to the control unit 100 via contacts and wirings on the FPC 220 so that potentials can be individually controlled.

  In the piezoelectric actuator unit 21 in the present embodiment, when an electric field is applied in the polarization direction to the piezoelectric ceramic layer 21b by setting the individual electrode 35 to a potential different from that of the common electrode 34, the portion where the electric field is applied becomes the piezoelectric effect. Acts as an active part that is distorted by At this time, the piezoelectric ceramic layer 21b expands or contracts in the thickness direction, that is, the stacking direction, and tends to contract or extend in the direction perpendicular to the stacking direction, that is, the surface direction, due to the piezoelectric lateral effect. On the other hand, the remaining piezoelectric ceramic layer 21a is an inactive layer that does not have a region sandwiched between the individual electrode 35 and the common electrode 34, and therefore does not spontaneously deform. In other words, the piezoelectric actuator unit 21 uses the upper piezoelectric ceramic layer 21b (that is, the side away from the liquid pressurizing chamber 10) as a layer including the active portion and the lower side (that is, close to the liquid pressurizing chamber 10). This is a so-called unimorph type configuration in which the piezoelectric ceramic layer 21a on the side) is an inactive layer.

  In this configuration, when the control unit 100 sets the individual electrode 35 to a predetermined positive or negative potential with respect to the common electrode 34 so that the electric field and the polarization are in the same direction, a portion sandwiched between the electrodes of the piezoelectric ceramic layer 21b. (Active part) contracts in the surface direction. On the other hand, the piezoelectric ceramic layer 21a, which is an inactive layer, is not affected by an electric field, so that it does not spontaneously shrink and tries to restrict deformation of the active portion. As a result, there is a difference in strain in the polarization direction between the piezoelectric ceramic layer 21b and the piezoelectric ceramic layer 21a, and the piezoelectric ceramic layer 21b is deformed so as to protrude toward the liquid pressurizing chamber 10 (unimorph deformation). .

  In an actual driving procedure in the present embodiment, the individual electrode 35 is set to a potential higher than the common electrode 34 (hereinafter referred to as a high potential) in advance, and the individual electrode 35 is temporarily set to the same potential as the common electrode 34 every time there is a discharge request. (Hereinafter referred to as a low potential), and then set to a high potential again at a predetermined timing. As a result, the piezoelectric ceramic layers 21a and 21b return to the original shape at the timing when the individual electrode 35 becomes low potential, and the volume of the liquid pressurizing chamber 10 is compared with the initial state (the state where the potentials of both electrodes are different). To increase. At this time, a negative pressure is applied to the liquid pressurizing chamber 10 and the liquid is sucked into the liquid pressurizing chamber 10 from the manifold 5 side. Thereafter, at the timing when the individual electrode 35 is set to a high potential again, the piezoelectric ceramic layers 21a and 21b are deformed so as to protrude toward the liquid pressurizing chamber 10, and the volume of the liquid pressurizing chamber 10 is reduced, so Becomes a positive pressure, the pressure on the liquid rises, and droplets are ejected. That is, an ejection signal including a pulse based on a high potential is supplied to the individual electrode 35 in order to eject a droplet. The ideal pulse width is AL (Acoustic Length), which is the length of time during which the pressure wave propagates from the manifold 5 to the liquid discharge hole 8 in the liquid pressurizing chamber 10. According to this, when the inside of the liquid pressurizing chamber 10 is reversed from the negative pressure state to the positive pressure state, both pressures are combined, and the liquid droplet can be ejected with a stronger pressure.

  In gradation printing, gradation expression is performed by the number of droplets ejected continuously from the liquid ejection holes 8, that is, the droplet amount (volume) adjusted by the number of droplet ejections. For this reason, the number of droplet discharges corresponding to the specified gradation expression is continuously performed from the liquid discharge hole 8 corresponding to the specified dot region. In general, when liquid ejection is performed continuously, it is preferable that the interval between pulses supplied to eject liquid droplets is AL. As a result, the period of the residual pressure wave of the pressure generated when discharging the previously discharged liquid droplet coincides with the pressure wave of the pressure generated when discharging the liquid droplet discharged later, and these are superimposed. Thus, the pressure for discharging the droplet can be amplified.

  The preferred embodiments of the present invention have been described above. However, the present invention is not limited to the above-described embodiments, and various modifications can be made as long as they are described in the claims.

  The liquid discharge head 2 as described above is manufactured as follows, for example.

  A tape composed of a piezoelectric ceramic powder and an organic composition is formed by a general tape forming method such as a roll coater method or a slit coater method, and a plurality of green sheets that become piezoelectric ceramic layers 21a and 21b after firing are produced. . An electrode paste to be the common electrode 34 is formed on a part of the green sheet by a printing method or the like. Further, a via hole is formed in a part of the green sheet as necessary, and a via conductor is filled in the via hole.

  Next, each green sheet is laminated to produce a laminate, and pressure adhesion is performed. The laminated body after pressure contact is fired in a high-concentration oxygen atmosphere, and then the individual electrode 35 is printed on the surface of the fired body using an organic gold paste. After firing, the connection electrode 36 is printed using an Ag paste. And the piezoelectric actuator unit 21 is produced by baking.

  Next, the flow path member 4 is produced by laminating plates 22 to 31 obtained by a rolling method or the like via an adhesive layer. Holes to be the manifold 5, the individual supply flow path 6, the liquid pressurizing chamber 10, the descender, and the like are processed in the plates 22 to 31 into a predetermined shape by etching.

  These plates 22 to 31 are preferably formed of at least one metal selected from the group consisting of Fe—Cr, Fe—Ni, and WC—TiC, particularly when ink is used as a liquid. Since it is desired to be made of a material having excellent corrosion resistance against ink, Fe-Cr is more preferable.

  The piezoelectric actuator unit 21 and the flow path member 4 can be laminated and bonded via an adhesive layer, for example. A well-known adhesive layer can be used as the adhesive layer, but in order not to affect the piezoelectric actuator unit 21 and the flow path member 4, an epoxy resin, phenol resin, polyphenylene having a thermosetting temperature of 100 to 150 ° C. It is preferable to use at least one thermosetting resin adhesive selected from the group of ether resins. By heating to the thermosetting temperature using such an adhesive layer, the piezoelectric actuator unit 21 and the flow path member 4 can be heat-bonded.

  Next, in order to electrically connect the piezoelectric actuator unit 21 and the control circuit 100, the silver paste is supplied to the connection electrode 36, the FPC 220 on which the driver IC 222 is mounted in advance is placed, and heat is applied to cure the silver paste. To make electrical connection. The driver IC 222 was mounted by electrically flip-chip connecting the FPC 220 with solder, and then supplying a protective resin around the solder and curing it.

  Subsequently, the branch flow channel member 230 and the flow channel member 4 can be laminated and bonded via an adhesive layer, for example. A well-known adhesive layer can be used as the adhesive layer, but in order not to affect the piezoelectric actuator unit 21 and the flow path member 4, an epoxy resin, phenol resin, polyphenylene having a thermosetting temperature of 100 to 150 ° C. It is preferable to use at least one thermosetting resin adhesive selected from the group of ether resins. By heating to the thermosetting temperature using such an adhesive layer, the branch flow channel member 230 and the flow channel member 4 can be heat-bonded. It is preferable to use at least one selected thermosetting resin adhesive.

  Subsequently, the heat insulating elastic member 242 is attached to a predetermined position of the frame 240 with a resin or the like. A substrate 232 on which a connector 234 is mounted in advance is sandwiched between a frame 240 attached with rubber as the heat-insulating conductive member 242 and the branch flow path member 230, and the frame 240 and the branch flow path member 230 are joined with screws. 232 was fixed.

  Further, the FPC 220 is turned up, and one end of the FPC 220 is inserted into the connector 234 and fixed. Further, the side plate 210 is fixed to the flow path member 4 with screws. By doing so, the side plate 210 forms a flat plate from the end connected to the piezoelectric actuator unit 21 of the FPC 220 to the portion where the driver IC 222 is mounted, so that the driver IC 222 and the heat insulating elastic member 242 Even if the position is not finely adjusted, those positions are matched. Thereafter, the casing 201 is fitted, and the casing 201 is fixed to the frame 240 with screws, whereby the liquid ejection head 2 can be manufactured.

The liquid discharge head shown in FIG. 2 was produced. That is, a PbZrTiO ₃ system powder having an average particle size of 0.5 μm is mixed with a binder and an organic solvent to prepare a slurry of a piezoelectric material. A sheet was produced.

  Moreover, Ag—Pd powder was blended so that the mixing ratio was Ag: Pd = 7: 3 by mass ratio, and a predetermined amount of organic binder and solvent were mixed to prepare a conductive paste.

  Next, the green sheet coated with the conductive paste and the green sheet not coated with the electrode paste are laminated, heat is applied to form a mother laminate, and the mother laminate is cut and laminated. The piezoelectric actuator unit 21 was produced by forming a body and firing in an oxygen atmosphere at 1000 ° C. for 2 hours.

  Next, a drive electrode 35 was formed by screen printing a metal paste mainly composed of Au on one surface of the piezoelectric actuator unit 21 and baking it at 750 ° C.

  Further, a metal paste containing Ag as a main component was screen-printed and baked at 600 ° C. to form a connection electrode 36 electrically connected to the control circuit 100, thereby completing the piezoelectric actuator unit 21.

  Next, the Fe—Cr alloy was made 30 μm in thickness by a rolling method, punched to a predetermined dimension to produce a plate 31, and punched with a mold from the back surface to form a plurality of liquid discharge holes 8.

  Next, the Fe—Cr alloy was formed into a plate shape by a rolling method, and processed into a predetermined shape by etching so that the individual flow path 32 including the manifold 5 and the liquid pressurizing chamber 10 could be formed, thereby producing plates 22 to 30. . The plates 22 to 30 were joined with an epoxy resin to produce the flow path member 4, and the piezoelectric actuator unit 21 was further joined with an epoxy adhesive.

  Next, the FPC 220 having the driver IC 222 mounted on the piezoelectric actuator unit 21 was joined with a silver paste.

  Next, a Fe—Cr alloy is formed into a plate shape by a rolling method, and a flow path is formed by etching so as to be connected to the opening 5b of the flow path member 4 from the liquid introduction hole 236 after being stacked on a plurality of plates. The plate was joined with an epoxy resin to produce a branch channel member 230.

  Next, the branch flow path member 230 and the flow path member 4 were joined with an epoxy resin.

  Next, the frame 240 having the heat insulating elastic member 242 attached at a predetermined position and the branch flow path member 230 were fixed with screws, with the substrate 232 having the connector 234 mounted therebetween.

  Next, the side plate 210 is fixed to the flow path member 4 with a screw so that the position of the driver IC 222 matches the position of the heat insulating conductive member 242. Thereafter, one end of the FPC 220 was fixed to the connector 234, and the housing 201 was fixed to fix the liquid discharge head 2.

  The liquid discharge head (head No. 1) and head No. A test was performed to compare with a liquid discharge head in which the structure of 1 was partially changed. In the test, a discharge signal is given to the liquid discharge head with a drive signal of 20 kHz, and discharge is performed under the condition that the amount of liquid droplets is maximized from the dischargeable liquid discharge hole so that the heat generation of the driver IC is maximized. Printing was performed, and the temperature of each part of the liquid discharge head was measured by thermography so that the printed result was the darkest solid. Further, a driver IC that can measure the temperature inside the IC was used, and the temperature inside the driver IC was also examined. In addition, in order to measure the temperature inside the liquid discharge head, a test was performed by making holes in a part of the side plate and the casing.

  Head No. 1 which is an embodiment of the present invention. In No. 1, when driven continuously, the internal temperature of the driver IC became constant at 59 ° C., and ejection could be continued stably. The temperature of the portion of the housing in contact with the driver IC is as low as 32 ° C. with respect to the ambient temperature of 25 ° C., and the temperature rises little even in the vicinity of the driver IC due to the heat spreading to the metal housing. Moreover, the temperature rise on the side surface of the flow path member was 1 ° C. or less.

  Head No. 1 is partially changed, and two of the four driver ICs are pressed against the housing at a position where the position of the driver IC faces the original position (head No. 2) Was made. This is another embodiment of the present invention. In No. 2, the internal temperature of the driver IC was 59 ° C., and ejection could be continued stably. Although the temperature rise of the flow path member was 1 ° C. or less, when comparing the temperature of the flow path member on the housing side where four driver ICs are pressed against the temperature of the flow path member on the opposite side, the driver IC The temperature of the flow path member on the casing side on which the four are pressed is 0.3 ° C. higher. However, there was no difference in the print results.

  Head No. The liquid discharge head (head No. 3) outside the scope of the present invention, in which the structure of 1 is partially changed, the thickness of the conductive elastic member is reduced, and all the driver ICs are not pressed against the casing. Produced. Head No. In No. 3, when the ejection was started, the temperature inside the driver IC exceeded 80 ° C., and thus the ejection could not be continued.

Head No. A liquid discharge head (head No. 4) outside the scope of the present invention in which the structure of 1 was partially changed and the frame was pressed against the housing via a flexible flat cable was manufactured. Head No. In No. 4, the temperature inside the driver IC was 58 ° C., and ejection could be continued stably. However, the temperature of the flow path member varied depending on the location, and the flow path member immediately below the leg of the frame increased by 4 ° C., and the flow path member below the middle of the frame leg increased by 1 ° C. For this reason, the printing of the portion corresponding to the flow path member of the portion where the temperature rise was large, which compares the printing results, was dark and uneven printing was observed.

1 is a schematic configuration diagram illustrating a printer using a liquid discharge head according to an embodiment of the present invention. FIG. 2 is a perspective view of the liquid ejection head in FIG. 1. FIG. 3 is a vertical cross-sectional view of the liquid discharge head of FIG. 2 taken along line XX. FIG. 3A is a perspective view of a liquid discharge head body, a substrate, and a frame that are a part of the liquid discharge head of FIG. 2. (B) It is a perspective view of a liquid discharge head main body and a board | substrate. (A) It is a perspective view of a liquid discharge head main body. FIG. 5B is a perspective view of the liquid discharge head main body of FIG. FIG. 5 is a bottom view of a flexible flat cable that is a part of the liquid discharge head of FIG. 4A and a driver IC and a piezoelectric actuator connected to the flexible flat cable. FIG. 5 is a plan view of a flow path member that is a part of the liquid discharge head main body of FIG. FIG. 8 is an enlarged plan view of a region surrounded by an alternate long and short dash line in FIG. 7. FIG. 8 is an enlarged plan view of a region surrounded by an alternate long and short dash line in FIG. It is the VV line longitudinal cross-sectional view of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Printer 2 ... Liquid discharge head 4 ... Flow path member 5 ... Manifold 5a ... Sub manifold 5b ... Opening 6 ... Individual supply flow path 8 ... Liquid discharge hole DESCRIPTION OF SYMBOLS 9 ... Liquid pressurization chamber group 10 ... Liquid pressurization chamber 11a, b, c, d ... Liquid pressurization chamber row | line | column 12 ... Squeezing 21 ... Piezoelectric actuator unit 21a ... Piezoelectric ceramic Layer (diaphragm)
21b ... Piezoelectric ceramic layer 22-31 ... Plate 32 ... Individual flow path 34 ... Common electrode 35 ... Individual electrode 36 ... Connection electrode 50 ... Displacement element 200 ... Liquid Discharge head main body 201 ... Case 210 ... Side plate 220 ... Flexible flat cable 222 ... Driver IC
230 ... Branch channel member 232 ... Substrate 234 ... Connector 240 ... Frame 242 ... Heat-insulating elastic member 236 ... Liquid introduction hole

Claims (4)

A flat liquid discharge head body which is long in one direction and has a plurality of liquid discharge holes;
A plurality of pressurizing means for discharging droplets from the plurality of liquid discharge holes, respectively;
A flexible flat cable for transmitting a drive signal for driving the plurality of pressurizing means;
A driver IC for processing a drive signal mounted on the flexible flat cable;
The flexible flat cable is connected, and a resin substrate through which a drive signal passes,
And frame that is fixed to the liquid ejection head main body,
A liquid ejection head fixed to the frame and provided with a metal casing in which the flexible flat cable and the driver IC are housed;
The driver IC is pressed through the flexible flat cable by a heat insulating elastic member provided on the frame, and is pressed against the inner wall surface of the housing. The frame and the liquid discharge head body are: A liquid ejection head, which is fixed via the resin substrate .   The liquid discharge head according to claim 1, wherein the frame is fixed to the liquid discharge head main body at an end portion in the one direction.   The liquid discharge head according to claim 1, wherein a heat insulating material is interposed between the housing and the liquid discharge head main body. A liquid discharge head according to any one of claims 1 to 3, the conveyance unit to convey the recording medium in a direction that is not parallel to the one direction with respect to the liquid ejection head, control for controlling the driving of the liquid discharging head A recording apparatus.

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