JP2014216581A - Piezoelectric actuator substrate, liquid discharge head including the same, and recording apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a piezoelectric actuator substrate capable of being manufactured as a non-defective product even when a ceramic substrate which is currently manufactured is partially defective, and to provide a liquid discharge head including the piezoelectric actuator substrate, and a recording apparatus.SOLUTION: A piezoelectric actuator substrate 21 comprises: a diaphragm; a common electrode; a piezoelectric ceramic layer having a plurality of through holes 39; a plurality of individual electrodes 35 arranged in a region, facing the common electrode, of the piezoelectric ceramic layer; and common surface electrodes 72 arranged inside and around the plurality of through holes 39 of the piezoelectric ceramic layer. The piezoelectric actuator substrate 21 is long in a first direction and has a pair of sides 21-1 which are substantially parallel and extended in a direction crossing the first direction. The plurality of through holes 39 are arranged only near the pair of sides 21-1 so as to be arranged along each of the pair of sides 21-1.

Description

  The present invention relates to a piezoelectric actuator substrate used for a liquid discharge head for discharging 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, in such a liquid discharge head, a serial type that performs recording while moving the liquid discharge head in a direction (main scanning direction) orthogonal to the conveyance direction (sub-scanning direction) of the recording medium, and main scanning from the recording medium There is a line type in which recording is performed on a recording medium conveyed in the sub-scanning direction with a liquid discharge head that is long in the direction 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 liquid discharge holes for discharging the droplets formed in the liquid discharge head must be increased. There is a need to.

  Accordingly, the liquid discharge head includes a manifold and a flow path member having a liquid discharge hole that connects the manifold via a plurality of liquid pressurization chambers, and a plurality of displacement elements provided so as to cover the liquid pressurization chambers. A structure obtained by laminating a piezoelectric actuator substrate having the structure is known (for example, see Patent Document 1).

  In the liquid discharge head, the displacement element includes a common electrode provided on substantially the entire surface of the piezoelectric actuator substrate, individual electrodes facing the common electrode, a piezoelectric ceramic layer sandwiched between them, and a piezoelectric ceramic of the common electrode. It is comprised with the diaphragm provided in the surface on the opposite side to a layer. The connection between the common electrode and the outside is made through a through conductor provided in the piezoelectric ceramic layer at the peripheral portion of the piezoelectric actuator and a surface electrode formed at the peripheral portion of the piezoelectric actuator substrate. In addition, the liquid ejection head includes a plurality of pressurizing chambers connected to a plurality of ejection holes arranged in a matrix, and displaces a displacement element of a piezoelectric actuator provided so as to cover the chambers. For example, printing is possible in the main scanning direction at a resolution of 600 dpi.

JP 2003-305852 A

  When a piezoelectric actuator substrate as described in Patent Document 1 is manufactured, a ceramic substrate is manufactured by simultaneously firing a piezoelectric ceramic layer, a common electrode, and a diaphragm, and then individual electrodes are formed on the ceramic substrate. preferable. By doing so, the position where the individual electrodes are formed can be prevented from being affected by firing shrinkage that occurs when the ceramic substrate is fired, and the position accuracy of the individual electrodes can be increased. When the positions of the individual electrode and the pressurizing chamber are shifted, the displacement amount of the displacement element changes. Since the positional accuracy of the individual electrode is increased, the deviation of the displacement amount from the design value can be reduced. In addition, variation in the amount of displacement among a plurality of displacement elements can be reduced.

  When a defect such as adhesion of foreign matter occurs on the ceramic substrate during the manufacture of such a piezoelectric actuator substrate, there is a problem that the ceramic substrate to which the foreign matter adheres must be discarded as defective.

  Accordingly, an object of the present invention is to provide a piezoelectric actuator substrate capable of producing a non-defective product even when a defect occurs in a part of the ceramic substrate being manufactured, and a liquid discharge head and a recording apparatus using the piezoelectric actuator substrate.

  A piezoelectric actuator substrate according to the present invention includes a diaphragm, a common electrode laminated on the diaphragm, and a plurality of through-holes laminated on the common electrode and connected to the common electrode. A layer, a plurality of individual electrodes arranged in a region of the piezoelectric ceramic layer facing the common electrode, and a common provided in and around the through holes of the piezoelectric ceramic layer A piezoelectric actuator substrate having a surface electrode, the piezoelectric actuator substrate being long in one direction and having a pair of substantially parallel sides extending in a direction intersecting the one direction, The through holes are located only in the vicinity of the pair of sides, and are arranged along each of the pair of sides.

  The liquid discharge head of the present invention includes the piezoelectric actuator substrate for the liquid discharge head, a plurality of discharge holes, and a plurality of pressurizing chambers connected to the plurality of discharge holes, respectively, A plurality of pressurizing chambers and a flow path member joined to the piezoelectric actuator substrate for the liquid discharge head so that the plurality of individual electrode bodies and the plurality of pressurizing chambers overlap each other. Features.

  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 and the transport unit. And

  Since through-holes are provided only along one pair of sides, even if a partial defect occurs in the ceramic substrate during manufacture, if the piezoelectric actuator substrate is manufactured by shifting in the direction along the pair of sides, The piezoelectric actuator substrate can be manufactured so as not to include the defect.

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 partial plan view of a piezoelectric actuator substrate according to an embodiment of the present invention, (b) is a piezoelectric actuator substrate of (a), and (c) is another embodiment of the present invention. This is a piezoelectric actuator substrate according to the above. (A) is a longitudinal cross-sectional view along the VV line of FIG. 3, (b) is a longitudinal cross-sectional view along the XX line of FIG. 5 (a).

  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 head body 13 at the lower end. A large number of liquid ejection holes 8 for ejecting liquid are provided on the lower surface of the head body 13.

  Liquid droplets (ink) of the same color are ejected from the liquid 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 liquid discharge holes 8 of each liquid discharge head 2 are arranged at equal intervals in one direction (a direction parallel to the print paper P and perpendicular to the transport direction of the print paper P and the longitudinal direction of the liquid discharge head 2). , It can be printed without gaps in one direction. The colors of the liquid ejected from each liquid ejection head 2 are magenta (M), yellow (Y), cyan (C), and black (K), respectively. Each liquid ejection head 2 is disposed with a slight gap between the lower surface of the head 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 head main 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 head main body 13 constituting the liquid discharge head of the present invention will be described. FIG. 2 is a top view showing the head main body 13 shown in FIG. FIG. 3 is an enlarged top view of a region surrounded by a one-dot chain line in FIG. 2 and is a part of the head main body 13. FIG. 4 is an enlarged perspective view of the same position as in FIG. 3, in which some of the flow paths are omitted so that the position of the liquid discharge holes 8 can be easily understood. 3 and 4, for easy understanding of the drawings, the liquid pressurization chamber 10 (liquid pressurization chamber group 9), the squeeze 12 and the liquid discharge holes which are to be drawn by broken lines below the piezoelectric actuator substrate 21 are shown. 8 is drawn with a solid line. FIG. 5A is a partial plan view of the piezoelectric actuator substrate 21. Similarly, in FIG. 5A, the through hole 39 is drawn with a solid line. FIG. 5 (b)
It is a top view of the whole piezoelectric actuator board | substrate 21, and it has abbreviate | omitted other than the principal part. 6A is a longitudinal sectional view taken along the line VV in FIG. 3, and FIG. 6B is a longitudinal sectional view taken along the line XX in FIG. 5A.

  The head main body 13 has a flat plate-like channel member 4 and a piezoelectric actuator substrate 21 on the channel 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 region 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 liquid pressurizing chamber groups 9 in which a plurality of liquid pressurizing chambers 10 are formed in a matrix (that is, two-dimensionally and regularly). The liquid pressurizing chamber 10 is a hollow region having a substantially rhombic planar shape with rounded corners. The liquid pressurizing chamber 10 is formed so as to open on the upper surface of the flow path member 4. These liquid pressurizing chambers 10 are arranged over almost the entire surface of the upper surface of the flow path member 4 facing the piezoelectric actuator substrate 21. Accordingly, each liquid pressurizing chamber group 9 formed by these liquid pressurizing chambers 10 occupies a region having almost the same shape as the piezoelectric actuator substrate 21. Further, the opening of each liquid 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 liquid pressurizing chambers 10 connected to 5a constitute a row of liquid pressurizing chambers 10 arranged in the longitudinal direction of the flow path member 4 at equal intervals, and the four rows are arranged in parallel to each other in the short direction. Yes. Two rows of liquid pressurizing chambers 10 connected to the sub-manifold 5a are arranged on both sides of the sub-manifold 5a.

As a whole, the liquid pressurizing chambers 10 connected from the manifold 5 constitute rows of the liquid pressurizing chambers 10 arranged in the longitudinal direction of the flow path member 4 at equal intervals, and the rows are 16 rows parallel to each other in the short direction. It is arranged. The number of liquid pressurizing chambers 10 included in each liquid pressurizing chamber row is arranged so as to gradually decrease from the long side toward the short side, corresponding to the outer shape of the displacement element 50 that is an actuator. ing. The liquid discharge holes 8 are also arranged in the same manner. As a result, it is possible to form an image with a resolution of 600 dpi in the longitudinal direction as a whole.

  That is, when the liquid 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 5a in the range of R of the virtual straight line shown in FIG. Four liquid discharge holes 8, that is, a total of 16 liquid discharge holes 8 are 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 the individual flow paths 32 connected to the sub-manifolds 5a are not necessarily connected at equal intervals when the 600 dpi liquid discharge holes 8 are divided and connected to the four rows of sub-manifolds 5a. 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 and dummy individual electrodes 65 described later are formed at positions facing the liquid pressurizing chambers 10 and a dummy liquid pressurizing chamber described later on the upper surface of the piezoelectric actuator substrate 21, respectively. 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 liquid pressurizing chamber 10, has a shape substantially similar to the liquid pressurizing chamber 10, and fits in a region facing the liquid pressurizing chamber 10 on the upper surface of the piezoelectric actuator substrate 21. Is arranged.

  A large number of liquid discharge holes 8 are formed in the liquid discharge surface on the lower surface of the flow path member 4. These liquid discharge holes 8 are arranged at a position avoiding a region facing the sub-manifold 5 a arranged on the lower surface side of the flow path member 4. Further, these liquid discharge holes 8 are arranged in a region facing the piezoelectric actuator substrate 21 on the lower surface side of the flow path member 4. These liquid discharge hole groups 7 occupy an area having almost the same shape as the piezoelectric actuator substrate 21, and droplets can be discharged from the liquid discharge holes 8 by displacing the corresponding displacement elements 50 of the piezoelectric actuator substrate 21. . The arrangement of the liquid discharge holes 8 will be described in detail later. The liquid discharge holes 8 in each region are arranged at equal intervals along a plurality of straight lines parallel to the longitudinal direction of the flow path member 4.

  The above-described flow channel is a flow channel that is directly related to the discharge of droplets, but the flow channel member 4 is provided with a dummy liquid pressurizing chamber that is omitted in the drawing. The dummy liquid pressurizing chambers are formed in a line around the trapezoidal region where the liquid pressurizing chamber 10 is provided. Because the dummy liquid pressurization chamber makes the rigidity of the flow path member 4 around the liquid pressurization chamber 10 on the outermost side of the liquid pressurization chamber 10 close to the state of the other liquid pressurization chambers 10, Variations in liquid ejection characteristics can be reduced. The shape of the dummy liquid pressurizing chamber is the same as that of the liquid pressurizing chamber, but it is not connected to other flow paths. The dummy liquid pressurizing chamber is arranged so as to extend the matrix-like arrangement of the liquid pressurizing chamber 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 a liquid pressurizing chamber 10 on the upper surface of the flow path member 4, the sub-manifold 5a on the inner lower surface side, and the liquid discharge holes 8 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 liquid discharge hole 8 are connected via the liquid pressurizing chamber 10.

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

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

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

  As shown in FIG. 6, the piezoelectric actuator substrate 21 has a laminated structure including two piezoelectric ceramic layers 21a and 21b. Each of these piezoelectric ceramic layers 21a and 21b has a thickness of about 20 μm. The thickness of the laminated body of the piezoelectric ceramic layers 21a and 21b of the piezoelectric actuator substrate 21 is about 40 μm. The piezoelectric actuator substrate 21 is laminated on the planar surface of the flow path member 4 where the liquid pressurizing chamber 10 is open, and any one of the piezoelectric ceramic layers 21 a and 21 b includes a plurality of liquid pressurizing chambers 10. It extends so as to straddle (see FIG. 3). These piezoelectric ceramic layers 21a and 21b are made of a lead zirconate titanate (PZT) ceramic material having ferroelectricity.

  The piezoelectric actuator substrate 21 is made of a common electrode 34 made of a metal material such as an Ag-Pd material, an individual electrode 35 made of a metal material such as an Au material, and a metal material such as an Ag material formed on the individual electrode 35. A connection land 36 is provided. As described above, the individual electrode 35 is disposed on the upper surface of the piezoelectric actuator substrate 21 at a position facing the liquid pressurizing chamber 10 and the dummy liquid pressurizing chamber, and from the individual electrode main body 35a to the liquid pressurizing chamber. And a connection electrode 35b drawn to a position where there is no 10. The thickness of the individual electrode 35 is 0.3 to 1 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, connection bumps are further formed on the connection lands 36 as necessary, and are electrically joined to electrodes provided on an FPC (Flexible Printed Circuit) (not shown). Although details will be described later, a drive signal (drive voltage) is supplied to the individual electrode 35 from the control unit 100 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. 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.

  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.

  The common electrode 34 is formed over almost the entire surface in the area between the piezoelectric ceramic layer 21a and the piezoelectric ceramic layer 21b. That is, the common electrode 34 extends so as to cover all the liquid pressurizing chambers 10 in the region facing the piezoelectric actuator substrate 21. The thickness of the common electrode 34 is about 2 μm. The common electrode 34 is connected to the common surface electrode 72 by a conductor in the plurality of through holes 39. The diameter of the through hole is about 50 to 200 μm. The conductor in the through hole 39 may be filled with a via conductor in advance, or the common surface electrode 72 may enter the through hole 39.

  In order to manufacture such a piezoelectric actuator substrate 21, for example, a conductor serving as the common electrode 34 between the green sheet serving as the piezoelectric ceramic layer 21 b in which the through holes 39 are formed and the green sheet serving as the piezoelectric ceramic layer 21 a. It is preferable that the ceramic substrate is manufactured by firing in a state where the paste is sandwiched, and the individual electrode 35 and the common surface electrode 72 are formed on the ceramic substrate. If the positions of the individual electrode 35 and the pressurizing chamber 10 are shifted, the displacement amount of the displacement element 50 changes. Therefore, in order to make the displacement amount close to the design value or to reduce the difference in the variable amount of each displacement element 50, individual This is because it is preferable that the formation accuracy of the electrode 50 is not affected by firing shrinkage when firing the ceramic substrate.

  In addition, the ceramic substrate having a non-rectangular shape such as the trapezoidal shape or the parallelogram shape as described above may not be uniformly shrunk during firing shrinkage, and the shape after firing may be distorted. Moreover, when cutting into a shape different from the rectangular shape in a raw soft state before firing, accuracy may be deteriorated. Therefore, it is preferable that the ceramic substrate has a shape larger than that of the piezoelectric actuator substrate 21 and is cut after firing. It is preferable that the ceramic substrate to be fired has a rectangular shape that is easy to process and hardly distorts by firing.

  In producing such a ceramic substrate, when a defect such as adhesion of foreign matter occurs, even if the defect is localized, if it is in a region to be cut out as the piezoelectric actuator substrate 21, the piezoelectric substrate can be removed from the piezoelectric actuator. The substrate 21 cannot be manufactured.

  Therefore, in the piezoelectric actuator substrate 21, the positions where the through holes 39 are formed are only in the vicinity of a pair of substantially parallel sides 21-1 extending in a direction intersecting the one direction of the piezoelectric actuator substrate 21 that is long in one direction. And provided along each side of the pair of sides 21-1. That is, the through-hole 39 is not provided on the pair of sides 21-1 except for the vicinity. Here, the vicinity of the pair of sides 21-1 is, for example, a range from each of the pair of sides to the individual electrode 35 closest to each of the pair of sides. Further, the vicinity of the pair of sides 21-1 is, for example. A range from the pair of sides 21-1 to 1/10 of the length of the piezoelectric actuator substrate 21 in the longitudinal direction. Here, “substantially parallel” refers to a range of about ± 30 degrees at most, and the difference between the distance between one end of the pair of sides 21-1 and the distance between the other ends is a through hole. It means that it is within about 10 times the diameter of 39.

As described above, the position where the piezoelectric actuator substrate 21 is cut out of the ceramic substrate can be shifted in parallel with the pair of sides 21-1 within a range where the through hole 39 and the common surface electrode 72 overlap. . Even if the position of the through hole 39 with respect to the piezoelectric actuator substrate 21 is shifted, it is sufficient that the common surface electrode 72 and the common electrode 34 are conducted through the through hole 39, and other than the vicinity of the pair of sides 21-1 such as the center of the piezoelectric actuator substrate 21. In addition, since the through-hole 39 is not disposed, the individual electrode 35 cannot be formed by being blocked by the through-hole 39, and the individual electrode 35 and the common electrode 34 are not conducted through the through-hole 39.

  Further, in addition to the through-hole 39, if the through-hole 39-1 is provided in parallel with the pair of sides 21-1, the piezoelectric actuator substrate 21 includes the through-hole 39 due to a local defect or the like generated in the ceramic substrate. If the piezoelectric actuator substrate 21 cannot be cut out, the piezoelectric actuator substrate 21 can be manufactured by cutting out the piezoelectric actuator substrate 21 so as to include the through hole 39-1.

  The piezoelectric actuator substrate 21 often has a shape close to a square due to restrictions on manufacturing equipment. If the sides parallel to the direction extending in the longitudinal direction of the piezoelectric actuator substrate 21 are used as a pair of substantially parallel sides, the piezoelectric actuator substrate 21 is limited to a range in which the piezoelectric actuator substrate 21 can be cut out from the ceramic substrate, but intersects the longitudinal direction. If the substantially parallel sides extending in the direction are used as the pair of sides 21-1, the range in which the piezoelectric actuator substrate 21 can be cut out from the ceramic substrate can be increased.

  If the common surface electrode 72 is large, the piezoelectric actuator substrate 21 may be distorted due to firing shrinkage when firing the common surface electrode 72. Further, when the length of the common surface electrode 72 in the direction orthogonal to the pair of sides 21-1 is increased, the region where the displacement element 50 can be formed is reduced. Therefore, it is preferable that the common surface electrode 72 is arranged long along the pair of sides 21-1 and the length thereof is short. Further, if there is a through hole 39 in which the common surface electrode 72 does not enter, the structure is different from other parts, which may cause a defect. Therefore, all the through holes 39 overlap the common surface electrode 72. It is preferable to make it.

  Considering the above points, it is preferable to shorten the length of the pair of sides 21-1 and to dispose the common surface electrode 72 over the length direction of the pair of sides 21-1. Further, when the position where the piezoelectric actuator substrate 21 is cut out from the ceramic substrate is shifted, if the position is shifted in the longitudinal direction of the piezoelectric actuator substrate 21, there is a possibility that the position is removed from the ceramic substrate. The side 21-1 preferably extends in a direction orthogonal to the longitudinal direction of the piezoelectric actuator substrate 21.

  As a specific shape of the piezoelectric actuator substrate 21, as shown in FIG. 5B, a trapezoid having a long side, a short side, and two oblique sides, two corners between the long side and the two oblique sides are provided. The shape which provided a pair of edge | side 21-1 in the part which notched each was preferable. Further, as shown in FIG. 5C, the shape of the piezoelectric actuator substrate 221 is a pair of sides 221- in a portion obtained by cutting out two acute angles from a parallelogram having two acute angles and two obtuse angles. 1 may be provided.

  In FIG. 5A, the portion where the surface common electrode 72 extends shortly along the long side of the trapezoidal piezoelectric actuator substrate 21 is a portion where connection bumps are formed and connected to the FPC.

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 liquid 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 facing each liquid pressurizing chamber 10 corresponds to an individual displacement element 50 (actuator) corresponding to each liquid 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. 6 is provided immediately above the liquid pressurizing chamber 10 for each liquid pressurizing chamber 10. Are formed by a diaphragm 21a, a common electrode 34, a piezoelectric ceramic layer 21b, and individual electrodes 35, 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).

  A large number of individual electrodes 35 are individually electrically connected to the actuator control means via contacts and wirings on the FPC so that potentials 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. 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 liquid pressurizing chamber 10) as a layer including the active portion and the lower side (that is, close to the liquid pressurizing chamber 10). This is a so-called unimorph type configuration in which the piezoelectric ceramic layer 21a on the side) is an inactive layer.

  In this configuration, when the 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 liquid pressurizing chamber 10 (unimorph deformation). .

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

  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 through hole 39 is opened in the green sheet. If necessary, a through hole 39-1 used when cutting out the piezoelectric actuator substrate 21 at a position other than the standard cutting position is opened. The common electrode 34 is formed on the entire surface so as to exist under the through hole 39-1. Furthermore, a via conductor is filled in the through hole 39 and the through hole 39-1, as necessary.

  Next, each green sheet is laminated to produce a laminate, and pressure adhesion is performed. The laminated body after pressure contact was cut into a rectangular shape and fired in a high-concentration oxygen atmosphere to produce a ceramic substrate. The ceramic substrate is subjected to an appearance inspection or the like, and if there is no defect in the standard cutting position, the piezoelectric actuator substrate 21 is cut out by dicing or the like. If there is a defect in the standard cutout position and the good piezoelectric actuator substrate 21 can be manufactured by shifting the cutout position, the positions of the common surface electrode 34 and the through-hole 39 or the through-hole 39-1 to be formed thereafter The piezoelectric actuator substrate 21 is cut out so as to match (at least one overlaps). Then, if the individual electrode 35 and the common surface electrode 72 are printed and fired with Au paste, the piezoelectric actuator substrate can be manufactured.

DESCRIPTION OF SYMBOLS 1 ... Printer 2 ... Liquid discharge head 4 ... Channel member 5 ... Manifold 5a ... Sub manifold 5b ... Manifold opening 6 ... Individual supply channel 8 ... Liquid Discharge hole 9 ... Liquid pressurization chamber group 10 ... Liquid pressurization chamber 11a, b, c, d ... Liquid pressurization chamber row 12 ... Squeeze 13 ... Liquid discharge head body 15a, b , C, d: liquid discharge hole arrays 21, 221: piezoelectric actuator substrate 21a: piezoelectric ceramic layer (vibrating plate)
21b: Piezoelectric ceramic layers 21-1, 212-1 ... (a pair of piezoelectric actuator substrates) 22-31 ... Plate 32 ... Individual flow path 34 ... Common electrode 35 ... Individual Electrode 35a ... Individual electrode body 35b ... Connection electrode 36 ... Connection land 39, 239 ... Through hole 39-1, 239-1 ... (Outside of piezoelectric actuator substrate) 50 ...・ Pressure section (displacement element)
65 ... dummy individual electrode 66 ... dummy connection land 72, 272 ... common surface electrode

Claims (6)

A diaphragm,
A common electrode laminated on the diaphragm;
A piezoelectric ceramic layer having a plurality of through-holes connected to the common electrode, laminated on the common electrode;
A plurality of individual electrodes arranged in a region of the piezoelectric ceramic layer facing the common electrode;
A piezoelectric actuator substrate comprising: a plurality of through holes in the piezoelectric ceramic layer; and a common surface electrode provided around the through holes.
The piezoelectric actuator substrate has a pair of substantially parallel sides that are long in one direction and extend in a direction crossing the one direction.
The plurality of through holes are located only in the vicinity of the pair of sides, and are arranged along each of the pair of sides.   The piezoelectric actuator substrate is provided with the pair of sides at a portion in which two corners between the long side and the two oblique sides are cut out from a trapezoid having a long side, a short side, and two oblique sides. The piezoelectric actuator according to claim 1, wherein the piezoelectric actuator has a curved shape.   2. The piezoelectric actuator substrate according to claim 1, wherein the pair of sides is provided in a portion obtained by cutting out the two acute angles from a parallelogram having two acute angles and two obtuse angles. The piezoelectric actuator described in 1.   The common surface electrode is disposed on each side of the pair of sides so as to overlap all the through holes arranged along the side. The piezoelectric actuator as described.   5. The piezoelectric actuator substrate according to claim 1, a plurality of discharge holes, and a plurality of pressurizing chambers connected to the plurality of discharge holes, respectively, wherein the diaphragm is the plurality of the vibration plates. A liquid discharge head comprising: a flow path member which covers the pressurizing chamber and is joined to the piezoelectric actuator substrate so that the plurality of individual electrodes and the plurality of pressurizing chambers overlap each other.   The liquid ejection head according to claim 5, a transport unit that transports a recording medium to the liquid discharge head, and a control unit that controls the piezoelectric actuator substrate and the transport unit. Recording device.

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