JP5869351B2 - Piezoelectric actuator substrate for liquid discharge head, liquid discharge head using the same, and recording apparatus - Google Patents

Description

  The present invention relates to a piezoelectric actuator substrate used for a liquid discharge head that discharges droplets, a liquid discharge head using the same, and a recording apparatus.

  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. This type of print head includes a heater as a pressurizing unit in an ink flow path filled with ink, heats and boiles the ink with the heater, pressurizes the ink with bubbles generated in the ink flow path, A thermal head system that ejects ink as droplets from the ink ejection holes, and a part of the wall of the ink channel filled with ink is bent and displaced by a displacement element, and the ink in the ink channel is mechanically pressurized, and the ink A piezoelectric method for discharging liquid droplets from discharge holes is generally known.

  In addition, such a liquid ejection head has a serial type that performs recording while moving the liquid ejection head in a direction (main scanning direction) orthogonal to the conveyance direction (sub-scanning direction) of the recording medium, and is long in the main scanning direction. There is a line type in which recording is performed on a recording medium conveyed in the sub-scanning direction with the liquid discharge head fixed. The line type has the advantage that high-speed recording is possible because there is no need to move the liquid discharge head as in the serial type.

  In order to print droplets at a high density in any of the serial type and line type liquid discharge heads, the density of the discharge holes for discharging the droplets formed in the liquid discharge head is increased. There is a need.

  Accordingly, the liquid discharge head includes a manifold and a metal flow path member having discharge holes that connect the manifold via the plurality of pressurizing chambers, and a plurality of displacement elements provided so as to cover the pressurizing chambers, respectively. A structure in which a piezoelectric actuator substrate made of ceramics is laminated is known (see, for example, Patent Document 1). In this liquid ejection head, the pressurizing chambers connected to the plurality of ejection holes are arranged in a matrix, and the displacement elements of the piezoelectric actuator substrate provided so as to cover the chambers are displaced by deformation of the piezoelectric body. Ink is ejected from the ejection holes, and printing is possible at a resolution of 600 dpi in the main scanning direction. Further, the displacement element has a structure in which the diaphragm, the common electrode, the piezoelectric ceramic layer, and the individual electrode located at the position facing the pressurizing chamber are laminated from the flow path member side. Further, an ejection signal is transmitted from the outside to each displacement element through a signal transmission unit.

JP 2003-305852 A

When a flexible wiring board is used as a signal transmission unit in a liquid ejection head as described in Patent Document 1, the amount of displacement of the displacement element is small because the flexible wiring board comes into contact with the displacement element. Therefore, there are problems that the discharge amount of the liquid droplet is reduced or the liquid droplet is not discharged.

  Accordingly, an object of the present invention is to provide a piezoelectric actuator substrate for a liquid discharge head that is unlikely to be in contact with a signal transmission unit that is connected to the outside, a liquid discharge head using the same, and a recording apparatus. .

A piezoelectric actuator substrate for a liquid discharge head according to the present invention includes a vibration plate, a plurality of displacement elements arranged on one main surface of the vibration plate, and a flexible wiring substrate. a substrate, wherein the plurality of displacement elements, Propelled by one piezoelectric body FLEXIBLE viewed deformed the surface electrode, the surface electrodes, as well as exposed on the surface of the piezoelectric actuator substrate for the liquid discharge head, the average thickness is below 3μm or less, before Symbol of the surface electrode, the surface of the surface electrode the body in the region of the bending deformation, Ri height 3μm or more protrusions there, the flexible wiring board, said surface electrode together are electrically connected, characterized that you have been disposed facing the surface electrode body.

  It is preferable that the number of the protrusions on one surface electrode main body is 10 to 100.

  It is preferable that a larger number of the protrusions of the surface electrode main body are arranged at the center than the peripheral edge of the surface electrode main body.

  It is preferable that the density of the protrusions is lower than the density of the surface electrode body other than the protrusions.

Wherein the surface electrode and the flexible wiring board, wherein with are electrically connected via the connection bumps provided on the surface electrode, the low Ikoto height of the projections Ri by the height of the connecting bumps Is preferred.

The liquid discharge head of the present invention, the piezoelectric actuator substrate for a liquid discharge head has a discharge hole of multiple, and a plurality of pressurizing chambers are connected plurality of discharge holes and each of the diaphragm covering the plurality of pressure chambers, and a flow path member and the pressure chamber of the plurality of said surface electrode body and the front Kifuku number is bonded to the piezoelectric actuator substrate for a liquid discharge head so as to overlap each It is characterized by that.

  It is preferable that a distance between the flexible wiring substrate and the piezoelectric actuator substrate for the liquid discharge head is 10 to 50 μm.

  The recording apparatus of the present invention includes the liquid discharge head, a transport unit that transports a recording medium to the liquid discharge head, and a control unit that controls the liquid discharge head.

According to the piezoelectric actuator substrate for a liquid discharge head of the present invention, by extrusion on the front surface electrode body, since the surface electrode body and the flexible wiring board is hardly ready contact with the surface, the surface electrode body and the signal transmission unit Are not in contact with each other, and the displacement of the displacement element is hardly inhibited by the signal transmission unit. Thereby, it is hard to produce dispersion | variation in the displacement amount of a displacement element.

1 is a schematic configuration diagram of a printer that is a recording apparatus according to an embodiment of the present invention. FIG. 2 is a plan view of a flow path member and a piezoelectric actuator substrate that constitute the liquid ejection head of FIG. 1. FIG. 3 is an enlarged view of a region surrounded by an alternate long and short dash line in FIG. FIG. 3 is an enlarged view of a region surrounded by an alternate long and short dash line in FIG. (A) is a longitudinal sectional view corresponding to the portion along the line VV in FIG. 3, but shows a state in which a connection bump is formed and a signal transmission unit is connected, (b) It is an enlarged view of the principal part of (a), (c) is an enlarged plan view of the vicinity of (a) of the flow path member and the piezoelectric actuator substrate piezoelectric.

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

  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 are rotatably installed and rotate in conjunction with the conveyance 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. Each liquid discharge head 2 has a liquid discharge head main body 13 at the lower end. A number of ejection holes 8 for ejecting liquid are provided on the lower surface of the liquid ejection head body 13 (see FIGS. 4 and 5).

  Liquid droplets (ink) of the same color are ejected from the ejection holes 8 provided in one liquid ejection head 2. Each liquid discharge head 2 is supplied with liquid from an external liquid tank (not shown). The ejection holes 8 of each liquid ejection head 2 are opened in the ejection hole surface, and are in one direction (a direction parallel to the printing paper P and perpendicular to the conveyance direction of the printing paper P, the longitudinal direction of the liquid ejection head 2). Since they are arranged at equal intervals, printing can be performed 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. Each liquid discharge head 2 is arranged with a slight gap between the lower surface of the liquid discharge head main body 13 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 body 13 constituting 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.

  Next, the liquid discharge head main body 13 constituting the liquid discharge head of the present invention will be described. FIG. 2 is a top view showing the liquid discharge head main body 13 shown in FIG. FIG. 3 is an enlarged top view of a region surrounded by the alternate long and short dash line in FIG. 2 and is a part of the liquid discharge head main body 13. FIG. 4 is an enlarged perspective view of the same position as FIG. 3, in which some of the flow paths are omitted so that the positions of the discharge holes 8 can be easily understood. 3 and 4, in order to make the drawings easy to understand, the pressurizing chamber 10 (pressurizing chamber group 9), the squeezing chamber 12, and the discharge hole 8 that are to be drawn by broken lines below the piezoelectric actuator substrate 21 are shown by solid lines. It is drawn in. FIG. 5A is a longitudinal sectional view corresponding to a portion along the line V-V in FIG. 3, and shows a state in which a connection bump is formed and a signal transmission unit is connected. FIG. 5B is an enlarged view of a main part of FIG. 5A, and FIG. 5C is an enlarged plan view of the vicinity of (a) of the flow path member and the piezoelectric actuator substrate piezoelectric.

  The liquid discharge head body 13 includes a flat plate-like flow path member 4 and a piezoelectric actuator substrate 21 for the liquid discharge head on the flow path member 4. The piezoelectric actuator substrate 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. In addition, two piezoelectric actuator substrates 21 are arranged on the flow path member 4 as a whole in a zigzag manner, two along each of the two virtual straight lines parallel to the longitudinal direction of the flow path member 4. Yes. The oblique sides of the piezoelectric actuator substrates 21 adjacent to each other on the flow path member 4 partially overlap in the short direction of the flow path member 4. In the area printed by driving the overlapping piezoelectric actuator substrate 21, the droplets ejected by the two piezoelectric actuator substrates 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 substrates 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 substrate 21 and is disposed so as to intersect with the longitudinal direction of the flow path member 4. In the region sandwiched between the two piezoelectric actuator substrates 21, one manifold 5 is shared by the adjacent piezoelectric actuator substrates 21, and the sub-manifold 5 a is branched from both sides of the manifold 5. These sub-manifolds 5 a extend in the longitudinal direction of the liquid discharge head main body 13 adjacent to each other in regions facing the piezoelectric actuator substrates 21 inside the flow path member 4.

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

  In the present embodiment, as shown in FIG. 3, 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 pressurizing chambers 10 connected to 5a constitute a row of the 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 lateral direction. Two rows of the pressure chambers 10 connected to the sub-manifold 5a are arranged on both sides of the sub-manifold 5a.

  As a whole, the pressurizing chambers 10 connected from the manifold 5 constitute rows of the pressurizing chambers 10 arranged in the longitudinal direction of the flow path member 4 at equal intervals, and the rows are arranged in 16 rows parallel to each other in the short side direction. ing. The number of pressurizing chambers 10 included in each 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 piezoelectric actuator substrate 21. The 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, when the discharge hole 8 is projected so as to be orthogonal to a virtual straight line parallel to the longitudinal direction of the flow path member 4, it is connected to the four sub-manifolds 5a in the range of R of the virtual straight line shown in FIG. Four discharge holes 8, that is, a total of 16 discharge holes 8 are arranged at equal intervals of 600 dpi. Moreover, the individual flow paths 32 are connected to the sub manifolds 5a at intervals corresponding to 150 dpi on average. This is because when the discharge holes 8 for 600 dpi are divided and connected to the four sub-manifolds 5a, the individual flow paths 32 connected to the sub-manifolds 5a are not always connected at equal intervals. In other words, 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 main scanning direction.

  Individual electrodes 35 are formed on the upper surface of the piezoelectric actuator substrate 21 at positions overlapping the pressurizing chambers 10 respectively. That is, the individual electrode 35 is formed on the upper surface of the piezoelectric actuator substrate 21 in a direction different from the first direction and the first direction. The individual electrode (surface electrode) 35 includes an individual electrode main body (surface electrode main body) 35a and an extraction electrode 35b extracted from the individual electrode 35a. The individual electrode main body 35 a is slightly smaller than the pressurizing chamber 10 and has a shape substantially similar to the pressurizing chamber 10, so that the individual electrode main body 35 a fits in a region facing the pressurizing chamber 10 on the upper surface of the piezoelectric actuator substrate 21. Has been placed.

  A large number of discharge holes 8 are formed in the lower surface of the flow path member 4. These discharge holes 8 are arranged at positions avoiding the area facing the sub-manifold 5a arranged on the lower surface side of the flow path member 4. Further, these discharge holes 8 are arranged in a region facing the piezoelectric actuator substrate 21 on the lower surface side of the flow path member 4. These discharge hole groups occupy regions of almost the same size and shape as the piezoelectric actuator substrate 21, and droplets can be discharged from the discharge holes 8 by displacing the displacement elements 50 of the corresponding piezoelectric actuator substrate 21. . The arrangement of the discharge holes 8 will be described in detail later. The 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.

The flow path member 4 included in the liquid discharge head body 13 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. Each plate is aligned and laminated so that these holes communicate with each other to form the individual flow path 32 and the sub-manifold 5a. As shown in FIG. 5, the liquid discharge head body 13 is configured such that the 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 discharge holes 8 are on the lower surface. Each portion constituting the path 32 is disposed close to each other at different positions, and the sub-manifold 5 a and the discharge hole 8 are connected via the pressurizing chamber 10.

  The holes formed in each plate will be described. These holes include the following. First, the pressurizing chamber 10 formed in the cavity plate 22. Secondly, there is a communication hole that constitutes a flow path that connects from one end of the pressurizing chamber 10 to the sub-manifold 5a. This communication hole is formed in each plate from the base plate 23 (specifically, the inlet of the 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 constituting a flow path communicating from the other end of the pressurizing chamber 10 to the discharge hole 8, and this communication hole is referred to as a descender (partial flow path) in the following description. The descender is formed on each plate from the base plate 23 (specifically, the outlet of the pressurizing chamber 10) to the nozzle plate 31 (specifically, the 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 extending from the liquid inflow port (the outlet of the submanifold 5a) from the submanifold 5a to the discharge hole 8. The liquid supplied to the sub-manifold 5a is discharged from the 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 pressurizing chamber 10 upward. Furthermore, it progresses horizontally along the extending direction of the pressurizing chamber 10 and reaches the other end of the pressurizing chamber 10. While moving little by little in the horizontal direction from there, it proceeds mainly downward and proceeds to the discharge hole 8 opened in the lower surface.

  As shown in FIG. 5A, the piezoelectric actuator substrate 21 has a laminated structure composed of two piezoelectric ceramic layers 21a and 21b. Each of these piezoelectric ceramic layers 21a and 21b has a thickness of about 20 μm. The thickness of the laminate of piezoelectric ceramic layers 21a and 21b of the piezoelectric actuator substrate 21 (including the individual electrodes 35 and not including the connection bumps 46) is about 43 μm, and is 100 μm or less. The amount of displacement can be increased. The piezoelectric actuator substrate 21 is laminated on the planar surface of the flow path member 4 where the pressurizing chamber 10 is open, and the piezoelectric ceramic layers 21 a and 21 b straddle the plurality of 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 substrate 21 has a common electrode 34 and individual electrodes 35 made of a metal material such as an Ag—Pd system. A pair of electrodes of the common electrode 34 and the individual electrode 35 has a piezoelectric ceramic layer 21b which is a piezoelectric body interposed therebetween, and the piezoelectric ceramic layer 21b is applied in a plane direction by applying a voltage between the pair of electrodes. The displacement element 50 is bent and deformed by expanding and contracting (which may be either expansion or contraction). Although details will be described later, a drive signal (drive voltage) is supplied from the control unit 100 to the individual electrode 35 through the flexible wiring board 60. The drive signal is supplied in a constant cycle in synchronization with the conveyance speed of the print medium P.

The individual electrode 35 is disposed at a position overlapping the pressurizing chamber 10 on the upper surface of the piezoelectric actuator substrate 21, and the extraction electrode is drawn from the individual electrode main body 35 a to a position not overlapping the pressurizing chamber 10. 35b. The extraction electrode 35b is extracted to a range that does not exceed another adjacent individual electrode body 35a. The thickness of the individual electrode 35 is
0.5-3 μm. When the piezoelectric actuator substrate 21 is as thin as about 100 μm, the influence of the thickness of the individual electrode 35 on the displacement amount is large, and the average thickness is set to 3 μm or less. In order to increase the reliability of conduction, the average thickness is preferably 0.5 μm or more. The average thickness is preferably 1.5 to 2.5 μm. A protrusion 35a-1 having a height of 3 μm or more is formed on the surface of the individual electrode body 35a.

  A connection bump 46 is formed at a position where the pressurizing chamber 10 of the extraction electrode 35b of the piezoelectric actuator substrate 21 is not present. The connection bumps 46 include, for example, silver particles that are hardened with a resin, or those that are baked with silver that contains glass frit, and are formed in a convex shape with a thickness of about 5 to 50 μm. In addition, the connection bumps 46 are electrically joined to the wiring 60 b provided on the flexible wiring board 60 that is a signal transmission unit disposed along the piezoelectric actuator substrate 21. The flexible wiring board 60 has a structure in which the wiring 60b is covered with a base film (covering layer) 60a and a cover film 60c (covering layer), and the connection bumps 46 penetrate the cover film 60c and connect to the wiring 60b. doing. In the flexible wiring board 60 corresponding to the piezoelectric actuator used for printing at 600 dpi, the density of the wiring 60b is high, and the number of places where the wiring 60b and the connection bumps 46 are connected is extremely large. In such a case, it is preferable to use a soft cover film 60c, or leave the cover film 60c soft (uncured or semi-cured) and pass through the cover film 60c for connection. The connection between the wiring 60b and the connection bump 46 can be maintained by the adhesiveness of the soft cover film 60c or by curing the cover film 60c after penetration.

  In such a case, the flexible wiring board 60 and the displacement element 50 may come into contact with each other, or the flexible wiring board 60 and the displacement element 50 may stick to each other. This is not preferable because the displacement of the displacement element 50 is hindered. Therefore, a protrusion 35a-1 having a height of 3 μm or more is formed on the surface of the individual electrode body 35a. Thereby, since the surface of the individual electrode main body 35a and the surface of the flexible wiring board 60 are difficult to contact each other, the individual electrode main body 35a and the flexible wiring board 60 can be prevented from coming into contact with each other. Note that the lead electrode 35b portion of the individual electrode 35 may or may not have a protrusion.

  When the number of the protrusions 35a-1 in one individual electrode body 35a is 10 or more, the protrusions 35a-1 are widely distributed in the surface electrode body 35a, and the flexible wiring board 60 can be hardly attached. Further, since the number of the protrusions 35a-1 is 100 or less, a decrease in displacement due to the presence of the protrusions 35a-1 can be reduced. The number of protrusions 35a-1 is more preferably 20-80.

  Since the protrusions 35a-1 are arranged more in the center than the peripheral edge of the individual electrode main body 35a, it is difficult to attach the flexible wiring board 60 to the center having a large influence on displacement when attached to the flexible wiring board 60. it can. In FIG. 5C, the virtual shape S is similar to the individual electrode main body 35a, has the same area centroid, and is half the area of the individual electrode main body 35a. The density of the projections 35a-1 at the central portion is higher than the density of the projections 35a-1 at the peripheral portion, with the inside of the virtual shape S as the central portion of the individual electrode main body 35a and the other as the peripheral portion of the individual electrode main body 35a. preferable. Thus, the flexible wiring board 60 can be effectively prevented from being attached with a small number of protrusions 35a-1.

Although the height h of the protrusion 35a-1 depends on the height of the connection bump 46 and the thickness of the cover film 60c, it is preferably 3 to 10 μm. If the distance is too high, the distance between the flexible wiring board 60 and the protrusion 35a-1 is shortened, so that the flexible wiring board 60 and the protrusion 35a-1 are easily attached due to a small deformation of the flexible wiring board. The height of the protrusion 35 a-1 is preferably lower than the height of the connection bump 46. Further, the height of the projection 35a-1 is preferably small fence Ri by the thickness of the cover film 60c. Thereby, even if the protrusion 35a-1 enters the cover film 60c, it can be suppressed that the protrusion 35a-1 is electrically connected to the wiring 60b that is not electrically connected to the displacement element.

The protrusion 35a-1 can be formed by putting a metal particle having a large particle diameter or a filler having a large particle diameter into the conductor paste to be the individual electrode 35 when the individual electrode 35 is formed by baking. . The particles having a large particle size may be secondary particles in which fine particles are collected by aggregation or the like. It is preferable that particles having a large particle diameter are insulative because the possibility of conduction even if the protrusion 35a-1 enters the cover film 60c is reduced. As the insulating particles, ceramic or glass particles may be exemplified high softening point than the baking temperature. As large particles having a particle size, With those less dense than the individual electrode body 35a, except for the projections 35a-1, since the projections 35a-1 can be formed in a shape jumped out from the individual electrode body 35a preferably. Further , when particles having a large particle size are made to have a low density and printed with a conductive paste having a low viscosity, the particles having a large particle size approach the central portion of the individual electrode main body 35a due to surface tension, and the protrusion 35a-1 at the central portion. The density of can be made higher than the peripheral part. Further, when a particle having a large corner is used as a particle having a large particle diameter, the protrusion 35a-1 can be more difficult to attach to the flexible wiring board 60.

  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 pressurizing chambers 10 in the region facing the piezoelectric actuator substrate 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 in the piezoelectric ceramic layer 21b, and is connected to another electrode in the external wiring, like the large number of individual electrodes 35. Has been.

  The above is the structure in the case where the piezoelectric actuator substrate 21 has two piezoelectric ceramic layers. However, the piezoelectric ceramic layers having three or more phases are laminated so that the individual electrodes 35 and the common electrodes 34 are alternately arranged. You may arrange.

  As shown in FIG. 5, the common electrode 34 and the individual electrode 35 are disposed so as to sandwich only the uppermost piezoelectric ceramic layer 21b. A region sandwiched between the individual electrode 35 and the common electrode 34 in the piezoelectric ceramic layer 21b is called an active portion, and the piezoelectric ceramic in that portion is polarized in the thickness direction. In the piezoelectric actuator substrate 21 of the present embodiment, only the uppermost piezoelectric ceramic layer 21b includes an active portion, and the piezoelectric ceramic 21a does not include an active portion and functions as a diaphragm. The piezoelectric actuator substrate 21 has a so-called unimorph type configuration.

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

  An example of a driving method at the time of liquid ejection of the piezoelectric actuator substrate 21 in the present embodiment will be described with respect to a driving voltage (drive signal) supplied to the individual electrode 35. When an electric field is applied to the piezoelectric ceramic layer 21b in the polarization direction by setting the individual electrode 35 to a potential different from that of the common electrode 34, the portion to which the electric field is applied functions as an active portion that is distorted by the piezoelectric effect. 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, since 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, it does not spontaneously deform. That is, the piezoelectric actuator substrate 21 has the piezoelectric ceramic layer 21b on the upper side (that is, the side away from the pressurizing chamber 10) as a layer including the active portion and the lower side (that is, the side close to the pressurizing chamber 10). This piezoceramic layer 21a is a so-called unimorph type structure having an inactive layer.

  In this configuration, when the individual electrode 35 is set to a predetermined positive or negative potential with respect to the common electrode 34 by the actuator controller 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 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 their original shapes at the timing when the individual electrodes 35 become low potential, and the volume of the pressurizing chamber 10 increases compared to the initial state (the state where the potentials of both electrodes are different). To do. At this time, a negative pressure is applied to the pressurizing chamber 10 and the liquid is sucked into the 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 pressurizing chamber 10, and the pressure in the pressurizing chamber 10 is reduced due to the volume reduction of the pressurizing chamber 10. The pressure becomes positive and the pressure on the liquid rises, and droplets are ejected. That is, a drive 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 that the pressure wave propagates from the orifice 12 to the discharge hole 8. According to this, the pressure chamber 10
When the inside is reversed from the negative pressure state to the positive pressure state, both pressures are combined, and the liquid droplets can be ejected at a stronger pressure.

  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 was fired in a high concentration oxygen atmosphere to produce a piezoelectric actuator substrate. Thereafter, the individual electrode 35 is printed and fired on the surface of the fired body using an Ag—Pd paste to which a glass filler of 10 μm is added, and the piezoelectric actuator substrate 21 is produced. A glass filler protrusion 35 a-1 is formed on the individual electrode body 35 a of the piezoelectric actuator substrate 21.

  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 substrate 21 and the flow path member 4 can be laminated and bonded through, for example, an adhesive layer. As the adhesive layer, a known material can be used, but in order not to affect the piezoelectric actuator substrate 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 substrate 21 and the flow path member 4 can be heat-bonded.

  Thereafter, an Ag paste containing a resin is applied and dried on the extraction electrode 35 b of the piezoelectric actuator substrate 21 to form the connection bumps 46. If the connection bumps 46 are formed, the pressure applied when the piezoelectric actuator unit 21 and the flow path member 4 are bonded becomes non-uniform. A resin to be the cover film 60c is supplied onto the base film 60a on which the wiring 60b is formed, and the wiring 60 and the connection bumps 46 are aligned in a state where the resin is uncured or semi-cured, and the piezoelectric actuator substrate 21. The connection bumps 46 pass through uncured or semi-cured resin and are connected to the wiring 60b. Thereafter, the resin is cured, and the connection between the wiring 60b and the connection bump 46 is strengthened. The cured resin becomes the cover film 60c, and the base film 60a, the wiring 60b, and the cover film 60c become the flexible wiring board (signal transmission unit) 60.

DESCRIPTION OF SYMBOLS 1 ... Printer 2 ... Liquid discharge head 4 ... Flow path member 5 ... Manifold 5a ... Sub manifold 5b ... Manifold opening 6 ... Individual supply flow path 8 ... Discharge Hole 9 ... Pressurizing chamber group 10 ... Pressurizing chamber 11a, b, c, d ... Pressurizing chamber row 12 ... Squeezing 13 ... Liquid discharge head body 15a, b, c, d ... Discharge hole array 21 ... (for liquid discharge head) Piezoelectric actuator substrate 21a ... Piezoelectric ceramic layer (ceramic diaphragm)
21b ... Piezoelectric ceramic layer 22-31 ... Plate 32 ... Individual flow path 34 ... Common electrode 35 ... Individual electrode (surface electrode)
35a ... Individual electrode body (surface electrode body)
35a-1 ... projection of individual electrode body 35b ... extraction electrode 46 ... connection bump 50 ... displacement element 60 ... flexible wiring board (signal transmission unit)
60a ... Base film (coating layer)
60b ... Wiring 60c ... Cover film (coating layer)
h ... Height of protrusion (individual electrode body)

Claims (8)

A diaphragm,
A plurality of displacement elements arranged on one main surface of the diaphragm ;
With flexible wiring board
A piezoelectric actuator substrate for a liquid discharge head having
Wherein the plurality of displacement elements has a piezoelectric body that FLEXIBLE viewed deformed the surface electrode,
The surface electrodes, as well exposed on the surface of the piezoelectric actuator substrate for the liquid discharge head, the average thickness is below 3μm or less,
Before Symbol surface electrode, on the surface of the surface electrode the body in the region of the bending deformation, Ri height 3μm or more projections there,
The flexible wiring board, wherein with being surface electrodes electrically connected to said surface electrode liquid discharge piezoelectric actuator head substrate, characterized that you have been disposed facing the body.   2. The piezoelectric actuator substrate for a liquid discharge head according to claim 1, wherein the number of the protrusions on one surface electrode body is 10 to 100. 3.   3. The piezoelectric actuator substrate for a liquid discharge head according to claim 1, wherein the protrusions of the surface electrode main body are arranged more in the center than in the peripheral portion of the surface electrode main body.   The piezoelectric actuator substrate for a liquid discharge head according to claim 1, wherein the density of the protrusions is lower than the density of the surface electrode main body other than the protrusions. Wherein the surface electrode and the flexible wiring board, wherein with are electrically connected via the connection bumps provided on the surface electrode, the low Ikoto height of the projections Ri by the height of the connecting bumps The piezoelectric actuator substrate for a liquid ejection head according to claim 1, wherein the piezoelectric actuator substrate is a liquid ejection head. A piezoelectric actuator substrate for a liquid ejection head according to any one of claims 1 to 5 ,
A plurality of discharge holes, and has a plurality of pressurizing chambers are connected plurality of discharge holes and each together with the diaphragm covering the plurality of pressure chambers, a plurality of said surface electrode body and the front Stories a liquid discharge head characterized by having a flow path member and the pressurizing chamber of the multiple is bonded to the piezoelectric actuator substrate for a liquid discharge head so as to overlap respectively.   The liquid discharge head according to claim 6, wherein a distance between the flexible wiring substrate and the piezoelectric actuator substrate for the liquid discharge head is 10 to 50 μm.   8. A recording apparatus comprising: the liquid discharge head according to claim 6; a transport unit that transports a recording medium to the liquid discharge head; and a control unit that controls the liquid discharge head. .

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