JP2016043616A - Piezoelectric actuator substrate, and liquid discharge head and recording device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a piezoelectric actuator substrate having high connection reliability in a through hole portion, and a liquid discharge head and a recording device using the piezoelectric actuator substrate.SOLUTION: A piezoelectric actuator substrate 21 includes: a laminate in which a ceramic vibration plate 21a and a piezoelectric ceramic layer 21b are laminated; a first surface electrode 35 disposed on a main surface on the piezoelectric ceramic layer 21b side of the laminate; an internal electrode 34 disposed in the laminate; a through hole 38 passing through the piezoelectric ceramic layer 21b so as to be connected to the internal electrode 34; and a second surface electrode 37 disposed to cover the through hole 38 on the main surface on the piezoelectric ceramic layer 21b side. In the piezoelectric actuator substrate 21, the piezoelectric ceramic layer 21b at an edge 38a of the through hole 38 includes a protrusion section 38aa protruding from the main surface on the piezoelectric ceramic layer 21b side toward the outside.SELECTED DRAWING: Figure 6

Description

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

  Conventionally, as a liquid ejection head, for example, an inkjet head that performs various types of printing by ejecting a liquid onto a recording medium is known. The liquid discharge head is provided so as to cover, for example, a manifold (common flow path) and a flat plate-like flow path member having discharge holes connected from the manifold via a plurality of pressure chambers, and the pressure chamber, respectively. A piezoelectric actuator substrate having a plurality of displacement elements is laminated (see, for example, Patent Document 1).

  This piezoelectric actuator substrate is a laminate of a piezoelectric ceramic layer and a ceramic diaphragm, and the displacement element includes a common electrode inside the piezoelectric actuator substrate, a plurality of individual electrodes on the surface of the piezoelectric actuator substrate, and a gap therebetween. And a piezoelectric ceramic layer. The common electrode is electrically connected to the outside through a conductor in a through hole provided in the piezoelectric ceramic layer.

JP 2003-305852 A

  The piezoelectric actuator substrate described in Patent Document 1 has a high incidence of defects in which the conductor in the through hole and the common electrode are not connected in the manufacturing process, and the manufacturing cost is high. In addition, even in an electrically connected state, the connection may not be sufficient, and there is a risk of disconnection in long-term use.

  Accordingly, an object of the present invention is to provide a piezoelectric actuator substrate having a high connection reliability in a through-hole portion, a liquid discharge head using the same, and a recording apparatus.

  A piezoelectric actuator substrate according to the present invention includes a laminate in which a ceramic diaphragm and at least one piezoelectric ceramic layer are laminated, and a first surface electrode disposed on a main surface of the laminate on the piezoelectric ceramic layer side. An internal electrode disposed in the laminated body, a through-hole penetrating the piezoelectric ceramic layer so as to be connected to the internal electrode, and the through-hole in a main surface on the piezoelectric ceramic layer side A piezoelectric actuator substrate having a second surface electrode disposed so as to cover, wherein the piezoelectric ceramic layer at the edge of the through hole protrudes outward from a main surface on the piezoelectric ceramic layer side. It has the protrusion which has.

  The liquid discharge head of the present invention includes a piezoelectric actuator substrate and a flow path member that is stacked on the piezoelectric actuator substrate and has discharge holes for discharging liquid.

Furthermore, 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 piezoelectric actuator substrate. .

  According to the piezoelectric actuator substrate of the present invention, since there is a protrusion at the edge of the through hole, the second surface electrode can easily enter the through hole, and the second surface electrode and the internal electrode can be easily connected.

(A) is a side view of a recording apparatus including a liquid ejection head according to an embodiment of the present invention, and (b) is a plan view. FIG. 2 is a plan view of a head body that is a main part of 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. It is a top view of a piezoelectric actuator substrate concerning one embodiment of the present invention. (A) is the longitudinal cross-sectional view along the VV line of FIG. 3, (b) is an enlarged plan view around the through-hole of FIG. 3, (c) is X-- of (b). It is a top view of the part of X. (A)-(c) is a longitudinal cross-sectional view around a through-hole in the manufacturing process of a piezoelectric actuator board | substrate.

  FIG. 1A is a schematic side view of a (color inkjet) printer 1 which is a recording apparatus including a liquid discharge head 2 according to an embodiment of the present invention, and FIG. 1B is a schematic plan view. It is. The printer 1 moves the printing paper P relative to the liquid ejection head 2 by transporting the printing paper P that is a recording medium from the transporting roller 80 a to the transporting roller 80 b. The control unit 88 controls the liquid ejection head 2 based on image and character data, ejects liquid toward the recording medium P, causes droplets to land on the printing paper P, and prints on the printing paper P. Record such as.

  In the present embodiment, the liquid discharge head 2 is fixed to the printer 1, and the printer 1 is a so-called line printer. As another embodiment of the recording apparatus of the present invention, the operation of moving the liquid ejection head 2 by reciprocating in the direction intersecting the transport direction of the printing paper P, for example, the direction substantially orthogonal, and the printing paper P There is a so-called serial printer that alternately conveys.

  A flat plate (head mounting) frame 70 is fixed to the printer 1 so as to be substantially parallel to the printing paper P. The frame 70 is provided with 20 holes (not shown), and the 20 liquid discharge heads 2 are mounted in the respective hole portions, and the portion of the liquid discharge head 2 that discharges the liquid is the printing paper P. It has come to face. The distance between the liquid ejection head 2 and the printing paper P is, for example, about 0.5 to 20 mm. The five liquid ejection heads 2 constitute one head group 72, and the printer 1 has four head groups 72.

The liquid discharge head 2 has a long and narrow shape in the direction from the front to the back in FIG. 1A and in the vertical direction in FIG. This long direction is sometimes called the longitudinal direction. Within one head group 72, the three liquid ejection heads 2 are arranged along a direction that intersects the conveyance direction of the printing paper P, for example, a substantially orthogonal direction, and the other two liquid ejection heads 2 are conveyed. One of the three liquid ejection heads 2 is arranged at a position shifted along the direction. The liquid discharge heads 2 are arranged so that the printable range of each liquid discharge head 2 is connected in the width direction of the print paper P (in the direction intersecting the conveyance direction of the print paper P) or the ends overlap. Thus, printing without gaps in the width direction of the printing paper P is possible.

  The four head groups 72 are arranged along the conveyance direction of the recording paper P. Liquid (ink) is supplied to each liquid discharge head 2 from a liquid tank (not shown). The liquid ejection heads 2 belonging to one head group 72 are supplied with the same color ink, and four color inks can be printed by the four head groups. The colors of ink ejected from each head group 72 are, for example, magenta (M), yellow (Y), cyan (C), and black (K). A color image can be printed by printing such ink under the control of the control unit 88.

  The number of liquid ejection heads 2 mounted on the printer 1 may be one if it is a single color and the range that can be printed by one liquid ejection head 2 is printed. The number of liquid ejection heads 2 included in the head group 72 and the number of head groups 72 can be changed as appropriate according to the printing target and printing conditions. For example, the number of head groups 72 may be increased in order to perform multicolor printing. Also, by arranging a plurality of head groups 72 that print in the same color and printing alternately in the transport direction, the printing speed (transport speed) can be increased. Alternatively, a plurality of head groups 72 for printing in the same color may be prepared and arranged so as to be shifted in a direction crossing the transport direction, so that the resolution in the width direction of the print paper P may be increased.

  Further, in addition to printing colored inks, a liquid such as a coating agent may be printed for surface treatment of the printing paper P.

  The printer 1 performs printing on a printing paper P that is a recording medium. The printing paper P is wound around the paper feed roller 80a, passes between the two guide rollers 82a, passes through the lower side of the liquid ejection head 2 mounted on the frame 70, and thereafter It passes between the two conveying rollers 82b and is finally collected by the collecting roller 80b. When printing, the printing paper P is conveyed at a constant speed by rotating the conveyance roller 82 b and printed by the liquid ejection head 2. The collection roller 80b winds up the printing paper P sent out from the conveyance roller 82b. The conveyance speed is, for example, 50 m / min. Each roller may be controlled by the controller 88 or may be manually operated by a person.

  In addition to the printing paper P, the recording medium may be a cloth or the like. In addition, the printer 1 is configured to convey a conveyance belt instead of the printing paper P, and the recording medium is not only a roll-shaped one, but also a sheet, cut cloth, wood, It may be a tile or the like. Furthermore, a wiring pattern of an electronic device may be printed by discharging a liquid containing conductive particles from the liquid discharge head 2. Still further, the chemical may be produced by discharging a predetermined amount of liquid chemical agent or liquid containing the chemical agent from the liquid discharge head 2 toward the reaction container or the like and reacting.

  In addition, a position sensor, a speed sensor, a temperature sensor, and the like may be attached to the printer 1, and the control unit 88 may control each part of the printer 1 according to the state of each part of the printer 1 that can be understood from information from each sensor. In particular, if the discharge characteristics (discharge amount, discharge speed, etc.) of the liquid discharged from the liquid discharge head 2 are affected by the outside, the temperature of the liquid discharge head 2, the temperature of the liquid in the liquid tank, the liquid tank Depending on the pressure applied by the liquid to the liquid ejection head 2, the drive signal for ejecting the liquid in the liquid ejection head 2 may be changed.

Next, the liquid discharge head 2 according to an embodiment of the present invention will be described. FIG. 2 is a plan view showing a head body 13 which is a main part of the liquid ejection head 2 shown in FIG. FIG. 3 is an enlarged plan view of a region surrounded by a one-dot chain line in FIG. 2 and is a part of the head main body 13. In FIG. 3, for the sake of explanation, some of the flow paths are omitted. FIG. 4 is an enlarged plan view at the same position as FIG. 3, and a part of the flow path different from FIG. 3 is omitted. FIG. 5 is a plan view of the piezoelectric actuator substrate 21. 6A is a longitudinal sectional view taken along the line VV in FIG. 3, FIG. 6B is an enlarged plan view around the through hole 38 of the piezoelectric actuator substrate 21, and FIG. It is a longitudinal cross-sectional view of the part in the XX line of b). 3 and 4, in order to make the drawings easy to understand, the pressurizing chamber 10 (pressurizing chamber group 9), the squeezing chamber 12, the discharge hole 8, and the like that are to be drawn by broken lines below the piezoelectric actuator substrate 21 are illustrated. It is drawn with a solid line. Similarly, in FIG. 5 and FIG. 6B, the through holes 38 and the like are drawn with solid lines.

  The head body 13 includes a flat plate-like flow path member 4 and a piezoelectric actuator substrate 21 that is bonded and laminated 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 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. Accordingly, each pressurizing chamber group 9 formed by these pressurizing chambers 10 occupies a region having substantially the same shape as the piezoelectric actuator substrate 21. Further, the opening of each pressurizing chamber 10 is closed by adhering the piezoelectric actuator substrate 21 to the upper surface of the flow path member 4.

  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 displacement element 50 that is an actuator. . 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 each sub-manifold 5 a within the range of R of the virtual straight line shown in FIG. One discharge hole 8, that is, a total of 16 discharge holes 8, is equally spaced at 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 to be described later are formed on the upper surface of the piezoelectric actuator substrate 21 at positions facing the respective pressure chambers 10 and a dummy pressure chamber to be described later. That is, the individual electrode 35 is formed on the upper surface of the piezoelectric actuator substrate 21 in the first direction and in a direction different from the first direction. The individual electrode 35 is slightly smaller than the pressurizing chamber 10, has a shape substantially similar to the pressurizing chamber 10, and is disposed so as to be within a region facing the pressurizing chamber 10 on the upper surface of the piezoelectric actuator substrate 21. ing.

  A large number of discharge holes 8 are formed in the liquid discharge surface on 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 an area having almost the same shape as the piezoelectric actuator substrate 21, and droplets can be discharged from the discharge holes 8 by displacing the corresponding displacement elements 50 of the 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 above flow paths are flow paths that are directly related to the discharge of liquid droplets, but the flow path member 4 is provided with a dummy pressurizing chamber that is omitted in the drawing. The dummy pressurizing chambers are formed in a line around the trapezoidal region where the pressurizing chamber 10 is provided. Due to the dummy pressurizing chamber, the rigidity of the flow path member 4 around the pressurizing chamber 10 that is the outermost of the pressurizing chambers 10 is close to the state of the other pressurizing chambers 10, so that the liquid ejection characteristics Variation can be reduced. The shape of the dummy pressurizing chamber is the same as that of the pressurizing chamber, but it is not connected to other flow paths. The dummy pressurizing chambers are arranged so as to extend the matrix-like arrangement of the pressurizing chambers 10.

The flow path member 4 included in the 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. 6, the head main body 13 has the pressurizing chamber 10 on the upper surface of the flow path member 4, the sub-manifold 5 a on the inner lower surface side, and the discharge holes 8 on the lower surface, and the individual flow paths 32. Are arranged 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 connecting 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 that constitutes a flow path that communicates from the other end of the pressurizing chamber 10 to the discharge hole 8. 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. 6, the piezoelectric actuator substrate 21 has a laminated structure including two piezoelectric ceramic layers 21a and 21b. The thickness of the piezoelectric ceramic layers 21a and 21b of the piezoelectric actuator substrate 21 is about 15 to 25 μm. 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 ceramic layer 21a functions as a ceramic diaphragm, and is not particularly required to have piezoelectricity, and other ceramic materials such as zirconia may be used.

  The piezoelectric actuator substrate 21 is formed on a common electrode 34 that is an internal electrode made of a metal material such as Ag—Pd, an individual electrode 35 that is a first surface electrode made of a metal material such as Au, and the individual electrode 35. The connection land 36 is made of a metal material such as Ag. Only the individual electrode 35 may be formed of an Ag-based metal material. As described above, the individual electrode 35 is disposed on the upper surface of the piezoelectric actuator substrate 21 at a position facing the pressurizing chamber 10 and the dummy pressurizing chamber, and the individual electrode main body 35a to the pressurizing chamber 10 is not provided. And a connection electrode 35b drawn to a position. The thickness of the individual electrode 35 when forming the Au-based conductor is 0.3 to 1 μm, and the thickness of the individual electrode 35 when forming the Ag-based conductor is 1 to 3 μm. A connection land 36 is formed on the connection electrode 35b. The connection land 36 is made of, for example, silver containing glass frit, and has a convex shape with a thickness of about 5 to 15 μm. Further, the connection land 36 is further formed with connection bumps made of a conductive resin or the like as necessary, and is electrically joined to an electrode provided in an FPC (Flexible Printed Circuit) (not shown). Although details will be described later, a drive signal (drive voltage) is supplied from the control unit 88 to the individual electrode 35 through the FPC. The drive signal is supplied in a constant cycle in synchronization with the conveyance speed of the print medium P.

  The above is the structure in the case where the piezoelectric actuator substrate 21 has two piezoelectric ceramic layers, but three or more piezoelectric ceramic layers are laminated so that the individual electrodes 35 and the common electrodes 34 are alternately arranged. May be.

  The individual electrodes 35 are formed in a matrix over substantially the entire surface of one main surface of the piezoelectric actuator substrate 21. That is, the first direction and the first direction are formed in different directions.

  Note that the individual electrodes in the rows A, B, and C among the individual electrodes 35 are dummy individual electrodes 45 that are directly below the dummy pressurizing chamber. A dummy connection land 46 is formed on a part of the connection electrode drawn from the dummy individual electrode 45. The dummy connection land 46 is also formed independently in a portion where the individual electrode 35 (including the dummy individual electrode 35) is not formed, and pressure applied when the piezoelectric actuator substrate 21 and the flow path member 4 are joined. Can be equalized.

  The common electrode 34 is formed over the substantially 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 0.7 μm. The common electrode 34 is electrically connected to a surface electrode 37 for a common electrode, which is a second surface electrode entering the plurality of through holes 38, and further electrically connected to the outside. In FIG. 5B, the material constituting the common electrode surface electrode 37 enters the upper portion of the through hole 38. The common electrode surface electrode 37 may be defined to include a portion entering the upper portion of the through hole 38, or may be defined on the basis of the surface of the piezoelectric ceramic layer 21b on the FPC side (the through hole 38). The part that enters the upper part may be regarded as a part of the through conductor 39). Below, for convenience of explanation, explanation will be made according to the former definition. The diameter of the through hole 38 is about 50 to 200 μm. The through hole 38 is a protrusion 38aa in which the edge 38a of the through hole 38 protrudes outward from the surface of the piezoelectric ceramic layer 21b so that the common electrode surface electrode 37 can easily enter. In particular, when printing a conductor paste that becomes the surface electrode 37 for the common electrode by screen printing or the like, the protruding portion 38aa exists over the entire circumference of the edge portion 38a over 1/3 to 2/3 turns. If so, the conductor paste can be easily entered into the through-hole 38 by printing the conductor paste from the side without the projection 38aa with a squeegee, and the reliability of electrical connection can be increased.

  The common electrode surface electrode 37 is made of, for example, the same conductive material as the connection land 36 and has the same thickness as the connection land 36. In addition, these may be configured by laminating a plurality of conductive layers. The common electrode surface electrode 37 and the connection land 36 may be made of different materials, or may have different thicknesses. The plane shape of the surface electrode 37 for the common electrode is appropriate such that the portion connected to the through conductor 39 and the portion where the connection bump electrically connected to the FPC is disposed are widened like a pad. May be.

  The through conductor 39 may be formed of the same conductive material as the common electrode surface electrode 37 and the common electrode 34, or may be formed of a different conductive material. The planar shape of the through conductor 39 (through hole 38) may be an appropriate shape, for example, a circle.

The lead electrode 47b of the individual electrode 35 and the pad of the FPC are joined by the connection bump. Thereby, the piezoelectric actuator substrate 21 and the FPC are arranged to face each other. When the FPC comes into contact with the displacement element 50 on the surface of the piezoelectric actuator substrate 21, the displacement of the displacement element 50 is suppressed, and the liquid ejection characteristics may change. Since the protrusion 38aa is present, the FPC is separated from the flat surface of the piezoelectric actuator substrate 21, so that the possibility of the above contact occurring can be reduced. Such a structure is particularly effective when the average distance between the piezoelectric actuator substrate 21 and the FPC is as small as 20 μm or less, for example.

  As shown in FIG. 6A, 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 discharge holes 8 through the individual flow paths 32. That is, the portion of the piezoelectric actuator substrate 21 that faces each pressure chamber 10 corresponds to an individual displacement element 50 (actuator) corresponding to each pressure chamber 10 and the discharge hole 8. That is, in the laminate composed of two piezoelectric ceramic layers, the displacement element 50 having a unit structure as shown in FIG. 6 is positioned immediately above the pressurizing chamber 10 for each pressurizing chamber 10. The diaphragm 21a, the common electrode 34, the piezoelectric ceramic layer 21b, and the individual electrode 35 are formed. The piezoelectric actuator substrate 21 includes a plurality of displacement elements 50. In the present embodiment, the amount of liquid discharged from the discharge hole 8 by one discharge operation is about 5 to 7 pL (picoliter).

  The large number of individual electrodes 35 are individually electrically connected to the control unit 88 via contacts and wirings on the FPC so that the potential can be individually controlled.

  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. When an electric field is applied, 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 plane 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 control unit 88 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 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. This pulse width is ideally AL (Acoustic Length), which is the length of time during which the pressure wave propagates from the manifold 5 to the discharge hole 8 in the pressurizing chamber 10.
According to this, when the inside of the pressurizing chamber 10 is reversed from the negative pressure state to the positive pressure state, both pressures are combined, and the liquid droplets can be discharged at a stronger pressure.

  Here, the protrusion 38aa which exists in the through-hole 38 and its edge part 38a is explained in full detail. As shown in FIGS. 6B and 6C, the piezoelectric ceramic layer 21 b has a protrusion 38 aa that protrudes toward the FPC at the edge 38 a of the through hole 38. The height H1 of the protrusion 38aa from the flat surface of the piezoelectric ceramic layer 21b (FIG. 6B) is, for example, the thickness of the individual electrode 35 and the piezoelectric ceramic layer 21b of the surface electrode 37 for the common electrode (through conductor 39). It is larger than the thickness of the portion excluding the top. Therefore, the top surface of the protrusion 38aa (a vertex or ridge line having an extremely small area is also a kind of top surface) is located on the FPC side of the surface of the individual electrode 35 on the FPC side. Further, the protrusion 38aa penetrates the common electrode surface electrode 37, and its top surface is exposed to the FPC side. The top surface of the protrusion 38aa is in contact with the FPC or opposed at a minute interval. The height of the protrusion 38aa may be set as appropriate, but as an example, the height is 5 μm or more and 10 μm or less. Note that the top surface is not necessarily exposed, and may be covered with the common electrode surface electrode 37. However, if the apex is exposed, even if it contacts the surface of the FPP, even if the apex may contact the FPC wiring through the insulating layer on the surface, it is difficult to electrically short-circuit. Therefore, it is preferable.

  As shown in FIG. 6B, the protrusion 38aa is formed so as to extend along the edge 38a of the through hole 38, and the length thereof is, for example, 1/3 of the edge of the through hole 38. No less than 2/3 laps. FIG. 6B illustrates a case where the length of the protrusion 38aa is about the half circumference of the edge of the through hole 38. The common electrode surface electrode 37 extends from the position overlapping the through conductor 39 in a plan view to the outside of the through conductor 39 via a portion of the edge of the through hole 38 where the protrusion 38aa is not formed. Yes. The cross-sectional shape and width of the protrusion 38aa may be set as appropriate. In FIG. 6C, the cross-sectional shape is triangular, but it may be dome-shaped.

  The common electrode 34 and the piezoelectric ceramic layer 21 a are recessed toward the through hole 38 in a region overlapping with the through hole 38. Accordingly, a recess 21aa is formed on the surface of the piezoelectric actuator substrate 21 (piezoelectric ceramic layer 21a) on the flow path member 4 side in a region overlapping with the through hole 38. The depth and the like of the recess 21aa may be set as appropriate.

  7A to 7C are partial longitudinal sectional views of the same portion as FIG. 6C in the manufacturing process of the piezoelectric actuator substrate 21. In addition, although the state of the material which comprises each part, and the shape of each part change with progress of a manufacturing process, the same code | symbol may be attached before and after the change for convenience of explanation.

  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. . At this time, the green sheet is formed on the forming fill 90.

  As shown in FIG. 7A, the green sheet that becomes the piezoelectric ceramic layer 21 b is formed with a hole that becomes the through hole 38 by punching (punching) using the punch 91. At this time, in the green sheet and the molded film 90 that become the piezoelectric ceramic layer 21b, the edge of the hole that becomes the through hole 38 is rolled in the punching direction (burrs and dripping occur). The punching is performed, for example, in the direction from the green sheet side to be the piezoelectric ceramic layer 21b to the molded film 90 side. However, the reverse direction is also possible.

  A conductive paste to be the common electrode 34 is applied to the surface of the green sheet to be the piezoelectric ceramic layer 21a opposite to the molded film 90 by screen printing or the like.

  After each processing, the green sheet used as the piezoelectric ceramic layer 21b and the green sheet used as the piezoelectric ceramic layer 21a are bonded together to create a laminate. At this time, the green sheet that becomes the piezoelectric ceramic layer 21b has the common electrode 34 side opposite to the direction in which the edge of the hole that becomes the through hole 38 is rolled up (see FIG. 7B).

  Subsequently, as shown in FIG. 7B, the conductive paste 93 that becomes the through conductor 39 is filled into the hole that becomes the through hole 38 by screen printing. That is, the plate 92 is disposed on the piezoelectric ceramic layer 21b, the squeegee 94 is moved in the direction indicated by the arrow while pressing the squeegee 94 against the plate 92, and the conductive paste 93 on the plate 92 is piezoelectrically formed on the through hole 38. Extrusion to the ceramic layer 21b side. At this time, since the portion other than the through hole 38 of the green sheet to be the piezoelectric ceramic layer 21b is covered with the molded film 90, the screen is used to selectively print the conductive paste 93 on the through hole 38 portion. It can also be carried out without using plate making or a metal mask.

  FIG. 7C shows a state after the through-hole 38 is filled with the conductive paste 93. Of the edge portion 38 a of the through hole 38, the squeegee 94 corrects the squeezing of the portion (right side of the drawing) that has been squeezed to the opposite side of the moving direction of the squeegee 94. On the other hand, the wrinkle of the squeegee 94 in the moving direction is not corrected by the squeegee 94 or remains even after the squeegee 94 is partially corrected. And the part (burr | burr) which remained without correcting the wrinkle comprises protrusion 38aa. When the hole serving as the through-hole 38 is circular, the wrinkle over approximately a half circumference of the edge of the hole is not corrected and becomes the protrusion 38aa.

  Further, when filling the through hole 38 with the conductive paste 93, the conductive paste 93 is filled to the lower side of the green sheet that becomes the piezoelectric ceramic layer 21 b squeezed in the punching direction. The conductive paste 93 filled in the portion increases the thickness of the electrode between the piezoelectric ceramic layer 21b and the piezoelectric ceramic layer 21a. The difference in electrode thickness is maintained even after firing, and as shown in FIG. 6C, the thickness of the electrode between the piezoelectric ceramic layer 21b and the piezoelectric ceramic layer 21a varies from the periphery of the through hole 38. Whereas it is T1 at the removed portion, the edge 38a of the through hole 38 is thicker than T2. The conductor located at the edge 38a of the through hole 38 is likely to be disconnected because pressure is applied more strongly than the surroundings in the next pressurizing step, but if the portion is made thicker as described above, Disconnection can be made difficult to occur. 6 (c) and 7 (c), the internal electrode 38 and the through conductor 39 are shown separately so that it can be seen how each electrode is manufactured, but the piezoelectric ceramic layer 21a and The electrode existing between the piezoelectric ceramic layers 21b can be considered as an internal electrode as an electrode inside the piezoelectric actuator substrate 21. In this sense, the internal electrode near the edge 38a is connected to the illustrated internal electrode 38. There is a combined thickness of the through conductor 39.

Subsequently, the laminate is pressed in the laminating direction, and a green sheet to be the piezoelectric ceramic layer 21a, a conductive paste to be the common electrode 34, and a green sheet to be the piezoelectric ceramic layer 21b are pressure-bonded. The laminated body is degreased and fired after the molded film 90 is removed. Note that degreasing can be omitted.

  In the laminated body after firing, a conductor pattern on the FPC side of the individual electrode 35, the common electrode surface electrode 37, and the other piezoelectric actuator substrate 21 is formed. The conductor pattern is formed, for example, by printing and baking a conductive paste. Alternatively, the conductor pattern may be formed by forming a metal film in a predetermined pattern by vapor deposition through a mask, or by etching after forming a metal film on the entire surface by vapor deposition. Good. When forming the conductor pattern, patterning is performed so that the conductor pattern (the common electrode surface electrode 37) is not formed on the protrusion 38aa. When the conductor pattern is formed by printing, the upper portion of the protrusion 38aa may not be printed by making the printing thickness thinner than the height of the protrusion 38aa. Moreover, you may utilize that the rough shape of protrusion 38aa is a taper shape and a metal film is hard to adhere on protrusion 38aa.

  As described above, the piezoelectric actuator substrate 21 has the protrusion 38aa in which the edge 38a of the through hole 38 protrudes outward. Since the protrusion 38aa is present, the through conductor 39 is easily filled, and the reliability of electrical connection at that portion can be increased. Further, since the electrode T2 (the thickness of the internal electrode 38 and the through conductor) at the edge 38a is thicker than the thickness T1 of the surrounding electrode, the reliability of electrical connection can be further increased.

  The piezoelectric actuator substrate 21 has a piezoelectric ceramic layer 21b exposed to the FPC side. The piezoelectric ceramic layer 21 b has a through hole 38 that opens toward the FPC, and a protrusion 38 aa that protrudes toward the FPC at the edge of the through hole 38.

  Therefore, the protrusion 38aa serves as a spacer, and the FPC is prevented from contacting the piezoelectric actuator substrate 21. As a result, for example, the influence of the FPC load on the operation of the piezoelectric actuator substrate 21 is reduced. Further, for example, since air easily enters between the piezoelectric actuator substrate 21 and the FPC, a negative pressure is generated between the FPC and the piezoelectric actuator substrate 21 when the piezoelectric actuator substrate 21 is bent toward the pressurizing chamber 35. The influence of the negative pressure on the operation of the piezoelectric actuator substrate 21 is reduced. Further, for example, the FPC is vibrated by the operation of the piezoelectric actuator substrate 21, and the head body 2a is suppressed from generating abnormal noise. As described above, the mechanical interference between the FPC and the piezoelectric actuator substrate 21 is reduced by the protrusion 38aa. Further, for example, the protrusion 38aa also contributes to suppressing the connection bumps from being crushed excessively when the FPC and the piezoelectric actuator substrate 21 are joined.

  Moreover, since only the protrusions 38aa are formed at the edge of the through hole 38 of the piezoelectric ceramic layer 21b, the number of members does not increase and the configuration is simple. Further, it is possible to form the protrusion 38aa by using the burrs when forming the through hole 38, and the manufacturing process can be simplified. Normally, such burrs are not preferable, but in this embodiment, they are used for reducing interference between the FPC and the piezoelectric actuator substrate 21, and this embodiment is epoch-making.

  In the present embodiment, the piezoelectric actuator substrate 21 further includes the piezoelectric ceramic layer 21b and the individual electrode 35 that overlaps the FPC side of the piezoelectric ceramic layer 21b while avoiding the protrusion 38aa. The top surface of the protrusion 38aa is located on the FPC side of the surface of the individual electrode 35 facing the FPC.

That is, the protrusion 38aa has a sufficient height, and can more reliably reduce the interference between the FPC and the piezoelectric actuator substrate 21 described above. In addition, since the individual electrode 35 is a portion that is located on the pressurizing chamber 35 and vibrates, interference between the FPC and the piezoelectric actuator substrate 21 can be more effectively reduced.

  In the present embodiment, the piezoelectric actuator substrate 21 is disposed in the through hole 38 and connects the conductive layers (the common electrode 34 and the common electrode surface electrode 37) disposed on the front and back of the piezoelectric ceramic layer 21b. 39 is further included.

  In other words, the through hole 38 is formed for conducting the front and back of the piezoelectric ceramic layer 21b, and is provided only for forming the protrusion 38aa for reducing interference between the FPC and the piezoelectric actuator substrate 21. It is not a thing (this is also included in the present invention). Therefore, the configuration of the piezoelectric actuator substrate 21 is simple, and the manufacturing method is also simplified.

  In the present embodiment, the protrusion 38aa is formed over 1/3 or more and 2/3 or less of the edge of the through hole 38.

  Therefore, for example, compared with the case where the protrusion is formed in a pin shape (this case is also included in the present invention), the protrusion 38aa is suppressed from contacting the FPC with a high pressure. As a result, the FPC is prevented from being damaged. On the other hand, since the common electrode surface electrode 37 can extend from the through hole 38 to the outside of the through hole 38 through the non-arranged position of the projecting part 38aa, the projecting part extends over the entire circumference of the through hole 38. Compared to the case of forming (this case is also included in the present invention), conduction can be ensured.

  In the present embodiment, the surface of the piezoelectric actuator substrate 21 that is bonded to the flow path member 4 has a concave area that overlaps with the through hole 38 (a concave portion 21aa is formed).

  Therefore, for example, when the piezoelectric actuator substrate 21 and the flow path member 4 are bonded together, excess adhesive can be retracted to the recess 21aa. As a result, high-precision bonding is realized, and manufacturing variations in the performance of the head body 2a are reduced.

DESCRIPTION OF SYMBOLS 1 ... (Color inkjet) 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 ... Pressure chamber group 10 ... Pressure chamber 11a, b, c, d ... Pressure chamber row 12 ... Through 13 ... Head body 15a, b, c , D ... discharge hole array 21 ... piezoelectric actuator substrate 21a ... piezoelectric ceramic layer (ceramic diaphragm)
21aa ... concave portion 21b ... piezoelectric ceramic layer 22-31 ... plate 32 ... individual flow path 34 ... common electrode (internal electrode)
35 ... Individual electrode (first surface electrode)
35a ... Individual electrode body 35b ... Connection electrode 36 ... Connection land 37 ... Common electrode surface electrode (second surface electrode)
38 .. through hole 38a .. edge of (through hole),
38aa: Projection 38b .. Lower end of outer periphery of through hole 39 ... Through conductor 45 ... Dummy individual electrode 46 ... Dummy connection land 50 ... Pressurizing part (displacement element)
70 ... (head mounted) frame 72 ... head group 80a ... paper feed roller 80b ... collection roller 82a ... guide roller 82b ... transport roller 88 ... control unit 90 ... Molded film 91 ... Punch 92 ... Plate 93 ... Conductive paste 94 ... Squeegee P ... Printing paper

Claims (5)

A laminate in which a ceramic diaphragm and at least one piezoelectric ceramic layer are laminated;
A first surface electrode disposed on a main surface of the laminate on the piezoelectric ceramic layer side;
An internal electrode disposed inside the laminate;
A through hole penetrating the piezoelectric ceramic layer so as to be connected to the internal electrode;
A piezoelectric actuator substrate comprising, on the main surface on the piezoelectric ceramic layer side, a second surface electrode disposed so as to cover the through-hole,
The piezoelectric actuator substrate according to claim 1, wherein the piezoelectric ceramic layer at an edge of the through hole has a protrusion protruding outward from a main surface on the piezoelectric ceramic layer side.   2. The piezoelectric actuator substrate according to claim 1, wherein the projecting portion exists over 1/3 to 2/3 of the edge of the through hole.   3. The piezoelectric actuator substrate according to claim 1, wherein a thickness of the internal electrode at a portion in contact with an inner wall of the through hole is larger than a thickness of the internal electrode around the portion.   A liquid discharge head comprising: the piezoelectric actuator substrate according to claim 1; and a flow path member that is laminated on the piezoelectric actuator substrate and has a discharge hole for discharging a liquid.   A recording apparatus comprising: the liquid discharge head according to claim 4; a transport unit that transports a recording medium to the liquid discharge head; and a control unit that controls the piezoelectric actuator substrate.

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