JP5183547B2 - Recording device - Google Patents

Recording device Download PDF

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JP5183547B2
JP5183547B2 JP2009075753A JP2009075753A JP5183547B2 JP 5183547 B2 JP5183547 B2 JP 5183547B2 JP 2009075753 A JP2009075753 A JP 2009075753A JP 2009075753 A JP2009075753 A JP 2009075753A JP 5183547 B2 JP5183547 B2 JP 5183547B2
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voltage
liquid
drive
electrode
piezoelectric
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JP2010228145A (en
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大輔 穂積
修三 岩下
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京セラ株式会社
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Description

  The present invention relates to a recording apparatus that prints an image by discharging droplets using a piezoelectric body.

  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 in which the actuator units are stacked is known (see, for example, Patent Document 1). In this liquid ejection head, the liquid pressurizing chambers connected to the plurality of liquid ejection holes are arranged in a matrix, and the displacement elements of the actuator unit provided so as to cover the chambers are displaced so that each liquid ejection chamber Ink is ejected and printing is possible at a resolution of 600 dpi in the main scanning direction.

  In addition, when driving the liquid discharge head, there is a drive method in which the drive voltage is set to 0.8 times or less of the coercive electric field in order to suppress drive deterioration in which the liquid discharge amount or the discharge speed decreases while driving is repeated. It has been proposed (see, for example, Patent Document 2).

JP 2003-305852 A International Publication No. 06/137528 Pamphlet

  However, in the liquid ejection head driving method described in Patent Document 2, although it is possible to suppress the occurrence of drive deterioration, the drive voltage needs to be 0.8 times or less the coercive electric field. Or there was a problem that discharge speed was restricted.

  Therefore, an object of the present invention is to suppress the occurrence of drive deterioration, so that the drive voltage can be made higher than the coercive electric field of 0.8. As a result, the degree of freedom of the drive waveform is increased, and the liquid discharge amount or discharge speed It is an object of the present invention to provide a recording apparatus that can increase the image quality.

  The recording apparatus of the present invention covers the plurality of liquid pressurizing chambers on a plate-like channel member having a plurality of liquid pressurizing chambers and a plurality of liquid discharge holes communicating with the plurality of liquid pressurizing chambers, respectively. The piezoelectric actuator is laminated, and the piezoelectric actuator is laminated in the order of the diaphragm, the common electrode, the piezoelectric body, and the plurality of drive electrodes from the flow path member side, and the drive electrode of the piezoelectric body The portion sandwiched between the common electrodes is polarized in the thickness direction, and when viewed from the stacking direction of the flow path member and the piezoelectric actuator, the plurality of drive electrodes are respectively connected to the plurality of liquid pressurizing chambers. A recording apparatus comprising: a liquid discharge head disposed so as to overlap; a transport unit that transports a recording medium to the liquid discharge head; and a control unit that controls the liquid discharge head and the transport unit A plurality of auxiliary electrodes opposed to the common electrode are provided around each of the plurality of drive electrodes when viewed from the stacking direction, and sandwiched between the auxiliary electrode and the common electrode of the piezoelectric body The control section is polarized in the thickness direction, and the control unit sets the voltage between the drive electrode and the common electrode to 0. 0 when the coercive electric field that causes domain rotational distortion in the piezoelectric body is Ec. Wait for a first voltage of 8Ec or more positive (hereinafter, a voltage that generates an electric field in the same direction as the polarization direction is a positive voltage, and a reverse voltage is a negative voltage), and the voltage is higher than the first voltage. After driving by increasing the volume of the liquid pressurizing chamber to a low second voltage, the voltage is returned to the first voltage, and the voltage between the auxiliary electrode and the common electrode is set during the standby. A negative third voltage with a generated electric field of −0.8 Ec or more And, wherein at the time of driving, in the third higher than the voltage fourth voltage, characterized by discharging the liquid from the liquid discharge hole.

  The fourth voltage is preferably a positive voltage.

  The recording apparatus of the present invention covers the plurality of liquid pressurizing chambers on a plate-like channel member having a plurality of liquid pressurizing chambers and a plurality of liquid discharge holes communicating with the plurality of liquid pressurizing chambers, respectively. The piezoelectric actuator is laminated, and the piezoelectric actuator is laminated in the order of the diaphragm, the common electrode, the piezoelectric body, and the plurality of drive electrodes from the flow path member side, and the drive electrode of the piezoelectric body The portion sandwiched between the common electrodes is polarized in the thickness direction, and when viewed from the stacking direction of the flow path member and the piezoelectric actuator, the plurality of drive electrodes are respectively connected to the plurality of liquid pressurizing chambers. A recording apparatus comprising: a liquid discharge head disposed so as to overlap; a transport unit that transports a recording medium to the liquid discharge head; and a control unit that controls the liquid discharge head and the transport unit. A plurality of auxiliary electrodes opposed to the common electrode are provided around each of the plurality of drive electrodes when viewed from the stacking direction, and sandwiched between the auxiliary electrode and the common electrode of the piezoelectric body The portion that is polarized in the thickness direction is a positive voltage, and a negative voltage that generates an electric field in the same direction as the polarization direction, and a coercive electric field that generates domain rotational distortion in the piezoelectric body is Ec. In this case, the control unit waits with the voltage between the drive electrode and the common electrode set to a fifth voltage, and increases the voltage to a positive sixth voltage at which the electric field generated is 0.8 Ec or more. Then, after the liquid pressurizing chamber is driven to reduce the volume, the voltage is returned to the fifth voltage, and the voltage between the auxiliary electrode and the common electrode is set to the seventh voltage during the standby. The driving voltage is lower than the seventh voltage. Both resulting electric field in the negative eighth voltage above -0.8Ec, characterized by discharging the liquid from the liquid discharge hole.

  The seventh voltage is preferably a positive voltage.

  According to the recording apparatus of the present invention, the plurality of liquid pressurizing chambers are disposed on the plate-like flow path member having the plurality of liquid pressurizing chambers and the plurality of liquid discharge holes communicating with the plurality of liquid pressurizing chambers. A piezoelectric actuator is laminated so as to cover the piezoelectric actuator, and the piezoelectric actuator is laminated in the order of a diaphragm, a common electrode, a piezoelectric body and a plurality of drive electrodes from the flow path member side, and the drive of the piezoelectric body The portion sandwiched between the electrode and the common electrode is polarized in the thickness direction, and when viewed from the stacking direction of the flow path member and the piezoelectric actuator, the plurality of driving electrodes respectively pressurize the plurality of liquids A liquid discharge head disposed so as to overlap the chamber; a transport unit that transports a recording medium to the liquid discharge head; and a control unit that controls the liquid discharge head and the transport unit. A recording device comprising a plurality of auxiliary electrodes facing the common electrode around each of the plurality of drive electrodes when viewed from the stacking direction, and the auxiliary electrode and the common electrode of the piezoelectric body, The sandwiched portion is polarized in the thickness direction, the voltage that generates an electric field in the same direction as the direction of polarization is a positive voltage, the reverse is a negative voltage, and the coercive electric field that causes domain rotational distortion is generated in the piezoelectric body. When Ec is set, the control unit stands by setting the voltage between the drive electrode and the common electrode to a positive first voltage at which the generated electric field is 0.8 Ec or more, and the voltage is set to the first voltage. After driving the liquid pressurizing chamber by increasing the volume of the liquid pressurizing chamber to a second voltage lower than the first voltage, the voltage is returned to the first voltage, and during the standby, the auxiliary electrode and the common electrode The generated electric field is less than -0.8Ec The occurrence of drive deterioration can be suppressed by discharging the liquid from the liquid discharge hole by setting the negative third voltage to be a fourth voltage higher than the third voltage at the time of driving. The drive voltage can be made higher than 0.8 of the coercive electric field, and as a result, the degree of freedom of the drive waveform is increased, and the liquid discharge amount or discharge speed can be increased.

  Further, when the fourth voltage is a positive voltage, drive deterioration can be further suppressed.

  According to the recording apparatus of the present invention, the plurality of liquid pressurizing chambers are disposed on the plate-like flow path member having the plurality of liquid pressurizing chambers and the plurality of liquid discharge holes communicating with the plurality of liquid pressurizing chambers. A piezoelectric actuator is laminated so as to cover the piezoelectric actuator, and the piezoelectric actuator is laminated in the order of a diaphragm, a common electrode, a piezoelectric body and a plurality of drive electrodes from the flow path member side, and the drive of the piezoelectric body The portion sandwiched between the electrode and the common electrode is polarized in the thickness direction, and when viewed from the stacking direction of the flow path member and the piezoelectric actuator, the plurality of driving electrodes respectively pressurize the plurality of liquids A liquid discharge head disposed so as to overlap the chamber; a transport unit that transports a recording medium to the liquid discharge head; and a control unit that controls the liquid discharge head and the transport unit. A recording device comprising a plurality of auxiliary electrodes facing the common electrode around each of the plurality of drive electrodes when viewed from the stacking direction, and the auxiliary electrode and the common electrode of the piezoelectric body, The sandwiched portion is polarized in the thickness direction, the voltage that generates an electric field in the same direction as the direction of polarization is a positive voltage, the reverse is a negative voltage, and the coercive electric field that causes domain rotational distortion is generated in the piezoelectric body. When Ec is set, the control unit waits with the voltage between the drive electrode and the common electrode set to a fifth voltage, and the electric field generated by increasing the voltage is a positive sixth After driving by reducing the volume of the liquid pressurizing chamber to a voltage, the voltage is returned to the fifth voltage, and the voltage between the auxiliary electrode and the common electrode is changed to a seventh voltage during the standby. To the seventh voltage at the time of driving. Since the electric field generated is a negative eighth voltage of −0.8 Ec or higher and the liquid is discharged from the liquid discharge hole, it is possible to suppress the occurrence of drive deterioration. As a result, the degree of freedom of the drive waveform is increased, and the discharge amount or discharge speed of the liquid can be increased.

  Further, when the seventh voltage is a positive voltage, drive deterioration can be further suppressed.

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 showing a head body that constitutes 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. 2. FIG. 3 is an enlarged view of a region surrounded by an alternate long and short dash line in FIG. It is a longitudinal cross-sectional view along the VV line of FIG. (A) (b) (c) It is the schematic diagram which showed the shape of the auxiliary electrode which concerns on one embodiment of this invention. It is the schematic diagram which showed the detail of the drive of the piezoelectric material which concerns on one embodiment of this invention. It is the figure which showed the drive voltage and auxiliary drive voltage which drive the piezoelectric material which concerns on one embodiment of this invention.

  FIG. 1 is a schematic configuration diagram of a color inkjet printer which is a recording apparatus 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.

  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 (see FIG. 3).

  Liquid droplets (ink) of the same color are ejected from the liquid ejection holes 8 provided in one liquid ejection head 2. Since the liquid ejection holes 8 of each liquid ejection head 2 are arranged at equal intervals in one direction (a direction parallel to the printing paper P and perpendicular to the conveyance direction of the printing paper P and the longitudinal direction of the liquid ejection head 2), Printing can be performed without gaps in one direction. The colors of the liquid ejected from each liquid ejection head 2 are magenta (M), yellow (Y), cyan (C), and black (K), respectively. Each liquid 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 the alternate long and short dash 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, in order to make the drawings easy to understand, the liquid pressurizing chamber 10 (liquid pressurizing chamber group 9), the squeezing 12, and the liquid discharge holes which are to be drawn by broken lines below the piezoelectric actuator unit 21. 8 is drawn with a solid line. FIG. 5 is a longitudinal sectional view taken along line VV in FIG.

The head body 13 includes a flat plate-like flow path member 4 and a piezoelectric actuator unit 21 that is an actuator unit on the flow path member 4. The piezoelectric actuator unit 21 has a trapezoidal shape, and is disposed on the upper surface of the flow path member 4 so that a pair of parallel opposing sides of the trapezoid is parallel to the longitudinal direction of the flow path member 4. Further, two piezoelectric actuator units 21 are arranged on the flow path member 4 as a whole in a zigzag manner, two along each of two virtual straight lines parallel to the longitudinal direction of the flow path member 4. Yes. The oblique sides of the piezoelectric actuator units 21 adjacent to each other on the flow path member 4 partially overlap in the short direction of the flow path member 4. In the region printed by driving the overlapping piezoelectric actuator unit 21, the droplets ejected by the two piezoelectric actuator units 21 are mixed and landed.
A manifold 5 that is a part of the liquid flow path is formed inside the flow path member 4. The manifold 5 has an elongated shape extending along the longitudinal direction of the flow path member 4, and an opening 5 b of the manifold 5 is formed on the upper surface of the flow path member 4. A total of ten openings 5 b are formed along each of two straight lines (imaginary lines) parallel to the longitudinal direction of the flow path member 4. The opening 5b is formed at a position that avoids a region where the four piezoelectric actuator units 21 are disposed. The manifold 5 is supplied with liquid from a liquid tank (not shown) through the opening 5b.

  The manifold 5 formed in the flow path member 4 is branched into a plurality of branches (the manifold 5 at the branched portion may be referred to as a sub-manifold 5a). The manifold 5 connected to the opening 5 b extends along the oblique side of the piezoelectric actuator unit 21 and is disposed so as to intersect with the longitudinal direction of the flow path member 4. In a region sandwiched between two piezoelectric actuator units 21, one manifold 5 is shared by adjacent piezoelectric actuator units 21, and the sub-manifold 5 a branches off from both sides of the manifold 5. These sub-manifolds 5 a extend in the longitudinal direction of the head main body 13 adjacent to each other in regions facing the piezoelectric actuator units 21 inside the flow path member 4.

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

  In 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, the individual flow paths 32 are connected to each sub-manifold 5a at intervals corresponding to 150 dpi on average. This is because the individual flow paths 32 connected to the sub-manifolds 5a are not always connected at equal intervals when the 600 dpi liquid discharge holes 8 are divided and connected to the four sub-manifolds 5a. This means that the individual flow paths 32 are formed at intervals of an average of 170 μm (25.4 mm / 150 = 169 μm intervals if 150 dpi) in the extending direction of 5a, that is, the main scanning direction.

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

  A large number of liquid discharge holes 8 are formed in the liquid discharge surface on the lower surface of the flow path member 4. These liquid discharge holes 8 are arranged at a position avoiding a region facing the sub-manifold 5 a arranged on the lower surface side of the flow path member 4. Further, these liquid discharge holes 8 are arranged in a region facing the piezoelectric actuator unit 21 on the lower surface side of the flow path member 4. These liquid discharge hole groups 7 occupy an area having almost the same size and shape as the piezoelectric actuator unit 21, and the liquid discharge holes 8 are made to drop liquid by displacing the displacement element 50 of the corresponding piezoelectric actuator unit 21. Can be discharged. 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 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. 5, 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 27-30.

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

  The piezoelectric actuator unit 21 has a common electrode 34 made of a metal material such as Ag—Pd, a drive electrode 35 and an auxiliary electrode 41 made of a metal material such as Au. The drive electrode 35 is disposed at a position facing the liquid pressurizing chamber 10 on the upper surface of the piezoelectric actuator unit 21 as described above. One end of the drive electrode 35 is drawn out of a region facing the liquid pressurizing chamber 10 to form a connection electrode 36. The connection electrode 36 is made of, for example, gold containing glass frit, and has a convex shape with a thickness of about 15 μm. The connection electrode 36 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 to the drive 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 auxiliary electrode 41 is provided around the drive electrode 36 so as to face the common electrode 34. FIG. 6A shows an example of the shape of the auxiliary electrode 41. Here, the periphery of the drive electrode means that the angle from the center of gravity of the area of the liquid pressurizing chamber to the portion where the auxiliary electrode 41 is formed is 360 degrees when viewed from the stacking direction of the flow path member and the piezoelectric actuator. In other words, it is preferable that the auxiliary electrode 41 is formed in any direction on the plane, but it is sufficient that the auxiliary electrode 41 is formed approximately 360 degrees excluding the direction in which the connection electrode is formed. The angle may be 270 degrees (3/4 round) or more. Further, all the auxiliary electrodes 41 around one drive electrode 36 may not be connected. An auxiliary electrode connection electrode 46 is formed on a part of the auxiliary electrode 41. The auxiliary electrode connection electrode 46 is made of gold containing glass frit, for example, and has a convex shape with a thickness of about 15 μm. The auxiliary electrode connection electrode 36 is electrically joined to an electrode provided in an FPC (Flexible Printed Circuit) (not shown). Although details will be described later, a drive assist signal is supplied from the control unit 100 to the auxiliary electrode 41 through the FPC. The drive assist signal is supplied at a constant period in synchronization with the drive signal.

  Another example of the auxiliary electrode is shown in FIGS. In either case, driving electrodes 235 and 335 are formed on the piezoelectric ceramic layers 221b and 321b so as to overlap the liquid pressurizing chambers 210 and 310, and auxiliary electrodes 241 and 341 are formed around the driving electrodes 235 and 335. Yes.

  In FIG. 6B, when viewed from the stacking direction of the flow path member and the piezoelectric actuator, the angle θ from the center of gravity C of the liquid pressurizing chamber 110 to the portion where the auxiliary electrode 241 is formed is 345 degrees. It has become. In this case, the auxiliary electrode 241 is not formed around the lead-out portion of the drive electrode 235 away from the liquid pressurizing chamber 210 where the displacement actually occurs, but the shape of the auxiliary electrode 141 is effectively changed without changing the effect. It can be simplified.

  In FIG. 6C, when viewed from the stacking direction of the flow path member and the piezoelectric actuator, the angle from the center of gravity of the area of the liquid pressurizing chamber 310 to the portion where the auxiliary electrode 341 is formed is different from each auxiliary electrode. Calculate the total of 341 angles. In this case, the shape of the auxiliary electrode 341 can be further simplified.

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

  As shown in FIG. 5, the common electrode 34 and the drive electrode 35 are disposed so as to sandwich only the uppermost piezoelectric ceramic layer 21b. A region sandwiched between the drive electrode 35 and the common electrode 34 in the piezoelectric ceramic layer 21b is referred to as an active portion, and the piezoelectric ceramic in that portion is polarized. In the piezoelectric actuator unit 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 unit 21 has a so-called unimorph type configuration.

  As will be described later, when a predetermined drive signal and drive auxiliary signal are selectively supplied to the drive electrode 35 and the auxiliary electrode 41, pressure is applied to the liquid in the liquid pressurizing chamber 10 corresponding to the drive electrode 35. Is added. 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 unit 21 that faces each liquid pressurizing chamber 10 corresponds to an individual displacement element 50 (actuator) corresponding to each liquid pressurizing chamber 10 and the liquid discharge port 8. That is, in the laminate composed of two piezoelectric ceramic layers, the displacement element 50 having a unit structure as shown in FIG. 5 is 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 a drive electrode 35. The piezoelectric actuator unit 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).

  The multiple drive electrodes 35 are individually electrically connected to the actuator control means via contacts and wirings on the FPC so that the potentials can be individually controlled.

A method for driving the piezoelectric actuator unit 21 in the present embodiment will be described first with respect to a drive voltage (drive signal) supplied to the drive electrode 35. When the drive electrode 35 is set to a potential different from that of the common electrode 34 and an electric field is applied to the piezoelectric ceramic layer 21b in the polarization direction, 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 plane direction by 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 drive electrode 35 and the common electrode 34, it does not spontaneously deform. In other words, the piezoelectric actuator unit 21 uses the upper piezoelectric ceramic layer 21b (that is, the side away from the liquid pressurizing chamber 10) as a layer including the active portion and the lower side (that is, close to the liquid pressurizing chamber 10). In this configuration, the drive electrode 35 is connected to the common electrode 34 by the actuator controller so that the electric field and the polarization are in the same direction. When the potential is positive or negative, the portion (active portion) sandwiched between the electrodes of the piezoelectric ceramic layer 21b contracts in the plane 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). .

  One of the actual driving procedures in the present embodiment is called “strike”. The driving electrode 35 is set to a potential higher than the common electrode 34 (hereinafter referred to as “high potential”) in advance, and the driving electrode 35 is provided each time there is a discharge request. Is once set to the same potential as the common electrode 34 (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 drive electrode 35 becomes a 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 drive 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 inside of the liquid pressurizing chamber 10 is reduced by reducing the volume 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 with a high potential as a reference is supplied to the drive electrode 35 in order to discharge the droplet. The ideal pulse width is AL (Acoustic Length), which is the length of time during which the pressure wave propagates from the manifold 5 to the liquid discharge hole 8 in the liquid pressurizing chamber 10. According to this, when the inside of the liquid pressurizing chamber 10 is reversed from the negative pressure state to the positive pressure state, both pressures are combined, and the liquid droplet can be ejected with a stronger pressure.

  On the contrary, a driving method called pushing can be used. In the pushing, the drive electrode 35 is set to the same potential (low potential) as the common electrode 34, and the drive electrode 35 is set to a higher potential (high potential) than the common electrode 34 every time there is an ejection request. Thereby, the liquid column pushed out from the liquid discharge hole 8 due to the increase in the volume of the liquid pressurizing chamber 10 causes the liquid pressurization when the inside of the liquid pressurizing chamber 10 is reversed from the positive pressure state to the negative pressure state. The volume of the chamber 10 is increased, the root of the liquid column is cut, and the separated droplets are discharged.

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

  FIG. 7A, which will be described in detail with reference to FIG. 7, shows the cause of the drive deterioration in the basic operation as described above. FIG. 7A shows the piezoelectric ceramic layer 21b in the state where no voltage is applied, the common electrode. 34 is a longitudinal section of the drive electrode 35 and the auxiliary electrode 41. Hereinafter, the portion of the piezoelectric ceramic layer 21b sandwiched between the common electrode 34 and the drive electrode 35 is referred to as a drive unit 51, and the portion of the piezoelectric ceramic layer 21b sandwiched between the common electrode 34 and the auxiliary electrode 41 is referred to as an auxiliary drive unit 53. The portion of the piezoelectric ceramic layer 21b that is not any of the above is referred to as a non-driving portion 52. The polarization is set in the direction from the drive electrode 35 to the common electrode 34 and in the direction from the auxiliary electrode 41 to the common electrode 34. Either polarization may be performed in the opposite direction. In that case, the voltage difference applied in the following description is reversed.

  As described above, in general striking, the common electrode 34 stands by in a state of 0V and the drive electrode 35 is positive as shown in FIG. 7B (hereinafter, the state before ejection is waited). 7 (c), driving is performed by applying a driving voltage in which the common electrode 34 is 0V and the driving electrode 35 is 0V (hereinafter, a driving voltage different from the standby state is applied). Then, a series of operations of returning to the standby state shown in FIG. 7B is performed, whereby droplets are ejected from the liquid ejection holes 8. In the standby state of FIG. 7B, the drive unit 51 is contracted in the plane direction, and tensile stress is applied to the non-drive unit 52. Although the auxiliary drive unit 53 may be slightly pulled, it is ignored in FIG. 7B. Since this stress is repeatedly applied for a very long time, the non-driving unit 52 is gradually polarized in the lateral direction. Then, as the polarization in the lateral direction proceeds, the non-driving unit 52 extends in the lateral direction and acts to push the driving unit 51 in the driving state of FIG. 7C, so that the displacement in the driving state is reduced. . This is drive deterioration. In this case, when the electric field generated between the common electrode 34 and the drive electrode 35 is 0.8 times or more of the coercive electric field Ec in which the domain rotational distortion occurs in the piezoelectric ceramic layer 21b, the drive deterioration proceeds. It ’s very easy.

  On the other hand, in the recording apparatus of the present invention, when striking, the common electrode 34 is 0 V and the drive electrode 35 is a positive voltage (the electric field generated is 0.8 Ec or more) as shown in FIG. The auxiliary electrode 41 stands by in a negative voltage state and is driven by applying a driving voltage and an auxiliary driving voltage at which the common electrode 34 is 0 V, the driving electrode 35 is 0 V, and the auxiliary electrode 41 is 0 V as shown in FIG. Thereafter, a series of operations for returning to the standby state shown in FIG. 7D is performed, whereby droplets are ejected from the liquid ejection holes 8. In the standby state of FIG. 7C, the drive unit 51 is contracted in the planar direction, but a voltage is applied to the auxiliary drive unit 53 so that a reverse electric field is generated, and the auxiliary drive unit 53 extends. Therefore, ideally, no stress is generated in the non-driving unit 52. For this reason, drive deterioration does not occur for this reason. Further, since drive deterioration does not occur, the voltage applied to the drive electrode 35 in the standby state can be set to an electric field generated in the drive unit 51 of 0.8 Ec or more, thereby increasing the discharge amount and increasing the discharge speed. You can do it.

  In order to increase the density, there may be a case where the auxiliary electrode 41 cannot be formed in the same size as the drive electrode 35. Even in this case, the stress applied to the non-drive portion 52 can be reduced, and the drive electrode 35 in the standby state can be reduced. As a result, the electric field generated in the drive unit 51 can be set to 0.8 Ec or more, and the discharge amount can be increased and the discharge speed can be increased.

  As described above, the voltage in the driving state has been set to 0 V for the sake of simplicity, but other voltages may be used as long as the behavior of the dimensional change of the piezoelectric ceramic layer 21b is in the above-described state. In general, it can be expressed as:

When the coercive electric field that causes domain rotational distortion in the piezoelectric ceramic layer 21b is Ec, the voltage between the drive electrode 35 and the common electrode 34 is positive (the same direction as the direction of polarization) when the generated electric field is 0.8 Ec or more. The first voltage V1 is set to a positive voltage and the reverse voltage is set to a negative voltage. The liquid pressurization chamber is set to the second voltage V2 whose voltage is lower than the first voltage. After driving by increasing the volume of 10, the voltage is returned to the first voltage V1, and the electric field generated between the auxiliary electrode 41 and the common electrode 34 is -0.8Ec or more during standby. The negative third voltage V3 is set to a fourth voltage V4 higher than the third voltage V3 at the time of driving. The change in the drive voltage is shown in FIG. 8A, and the change in the auxiliary drive voltage is shown in FIG. ) In the figure, (0.8Ec) or (−0.8Ec) represents a voltage in which an electric field of 0.8 or −0.8 times the coercive electric field Ec is generated. When the areas of the drive electrode 35 and the auxiliary electrode 41 are different, a voltage that generates an electric field that is 0.8 times the coercive electric field Ec in the drive unit 51 and an electric field that is 0.8 times the coercive electric field Ec are generated in the auxiliary drive unit 53. Different from voltage.

  When bipolar driving is performed in which the fourth voltage V4 is set to the positive voltage V4 ′, even when the area of the auxiliary electrode 41 is small, the amount by which the non-driving unit 52 is pushed in the standby state shown in FIG. Therefore, the tensile stress generated in the non-driving unit 52 can be reduced.

  Next, the case of pushing will be described. In general pushing, the common electrode 34 is set to 0 V and the drive electrode 35 is set to 0 V as shown in FIG. 7C, and the common electrode 34 is set to 0 V and the drive electrode 35 is set as shown in FIG. Then, the liquid is ejected from the liquid ejection hole 8 by performing a series of operations for returning to the standby state of FIG. 7C. In the driving state of FIG. 7B, the driving unit 51 is contracted in the planar direction, and a tensile stress is applied to the non-driving unit 52. Although the auxiliary drive unit 53 may be slightly pulled, it is ignored in FIG. 7B. Since this stress is repeatedly applied for a very long time, the non-driving unit 52 is gradually polarized in the lateral direction. And then. When the polarization in the lateral direction proceeds, the non-driving unit 52 extends in the lateral direction and acts to push the driving unit 51 in the standby state of FIG. 7C, so that the amount of displacement when changing to the driving state is increased. The difference is reduced. This is drive deterioration. In this case, when the electric field generated between the common electrode 34 and the drive electrode 35 is 0.8 times or more of the coercive electric field Ec in which the domain rotational distortion occurs in the piezoelectric ceramic layer 21b, the drive deterioration proceeds. Get faster.

  In the recording apparatus of the present invention, the tensile stress generated in the driving state can be reduced as in the case of FIG. In general, this can be expressed as:

  When the coercive electric field that causes domain rotational distortion in the piezoelectric ceramic layer 21b is Ec, the voltage between the drive electrode 35 and the common electrode 34 is set to the fifth voltage V5, and the electric field generated by raising the voltage is 0. After driving the liquid pressurizing chamber 10 by reducing the volume of the liquid pressurizing chamber 10 to a positive sixth voltage V6 that is 8Ec or higher, the voltage is returned to the fifth voltage V5 and between the auxiliary electrode 41 and the common electrode 34. Is set to a seventh voltage V7 during standby, and is set to a negative eighth voltage V8 that is lower than the seventh voltage V7 during driving and has a generated electric field of −0.8 Ec or more.

  This change in drive voltage is shown in FIG. 8C, and the change in auxiliary drive voltage is shown in FIG. 8D. (0.8Ec) in the figure represents a voltage generated by an electric field 0.8 times the coercive electric field Ec. When the areas of the drive electrode 35 and the auxiliary electrode 41 are different, a voltage that generates an electric field that is 0.8 times the coercive electric field Ec in the drive unit 51 and an electric field that is 0.8 times the coercive electric field Ec are generated in the auxiliary drive unit 53. Different from voltage.

  When bipolar driving is performed in which the seventh voltage V7 is set to the positive voltage V7 ′, even when the area of the auxiliary electrode 41 is small, the amount by which the non-driving unit 52 is pushed in the standby state shown in FIG. Therefore, the tensile stress generated in the non-driving unit 52 can be reduced.

  Note that the time during which the tensile stress is applied is longer in the standby state of the strike, and the present invention is particularly effective for the strike method.

  In addition, if the polarization direction of the drive unit 51 and the polarization direction of the auxiliary drive unit 53 are reversed, the voltage difference applied to the drive electrode 35 and the auxiliary electrode 41 can be reduced, so that the possibility of occurrence of a short circuit can be reduced.

  Further, the signal applied to the auxiliary electrode portion 41 is not simply a value equivalent to the voltage applied to the drive electrode portion 52 in order to relieve stress at the interface between the drive portion 51 and the non-drive portion 52 as much as possible. It is desirable to apply a voltage sufficient to generate a displacement corresponding to the displacement 51. Since this value varies depending on the electrode area, the displacement of the driving unit 51 and the non-driving unit 52 is adjusted to be equivalent for each electrode dimension. Specifically, the amount of displacement of the piezoelectric body varies depending on the size of the drive electrode 35, and in a vibration mode that is displaced in a direction perpendicular to the polarization direction, is proportional to the length in the radial direction. In reality, in an inkjet printer head arranged in a high density of multiple rows and columns, the spacing between the drive electrodes 35 is narrow, and the spacing becomes narrower as the density increases. Therefore, for example, in the case where a single drive electrode 35 is designed to have a head size of about 1 inch in a 600 dpi multi-line printer head having a size of about 800 μm, the width of the auxiliary electrode 41 can only be about 50 μm at maximum. In this case, it is impossible to displace the auxiliary drive unit 53 to the extent that the displacement amount of the drive electrode 35 unit is canceled due to the limit of the coercive electric field Ec.

Therefore, in the case of striking, regarding the area and applied voltage, the area of the drive electrode 35 is S1 (m 2 ), the area of the auxiliary electrode 41 is S2 (m 2 ), and the drive electrode 34 is driven by the first voltage V1. The electric field generated between the auxiliary electrode 41 and the common electrode 34 by the third voltage V3 is E2 (V / m). 0.05 ≦ S2 / S1 <1.0 and E1 ≦ E2 ≦ 0.8Ec.

In the case of pushing, the area of the drive electrode 35 is S1 (m 2 ), the area of the auxiliary electrode 41 is S2 (m 2 ), and the drive electrode 34 is driven by the fifth voltage V5. The electric field generated between the auxiliary electrode 41 and the common electrode 34 by the eighth voltage V8 is E2 (V / m). 0.05 ≦ S2 / S1 <1.0 and E1 ≦ E2 ≦ 0.8Ec.

  A piezoelectric material used for the piezoelectric ceramic layer was lead zirconate titanate (PZT), and a slurry using PZT was prepared. From this slurry, a roll coater method was adopted as a forming method to prepare a green sheet.

Next, through holes having a diameter of 100 μm were formed in the green sheet by die punching.
Then, the electrode pattern used as a common electrode was formed in the surface of each green sheet by the screen-printing method using the conductor paste containing an Ag-Pd alloy.

  Further, a via conductor paste is prepared by adding 30% by volume of piezoelectric powder as a filler to the Ag—Pd alloy, and this is filled in the through-hole formed in the green sheet by screen printing. A via electrode was formed.

  Next, two layers of this green sheet were laminated to produce a laminated molded body having a common electrode and a via electrode inside. Thereafter, this laminated molded body was fired at a temperature of 1020 ° C. to produce a piezoelectric sintered body. The obtained piezoelectric sintered body was about 20 μm per layer.

  On the surface of this piezoelectric sintered body, a width of 0.8 mm and a length of 0. 5 mm are formed in a matrix by screen printing using a conductor paste containing the main component Au so as to face the common electrode of the portion constituting the displacement element. An 8 mm drive electrode and an auxiliary electrode having a line width of 0.03 mm were simultaneously formed at a position 0.03 mm from the end of the drive electrode, and thereafter, the drive electrode and the auxiliary electrode were formed by heat treatment at 800 ° C.

  Next, in order to polarize almost the entire surface of the piezoelectric ceramic layer, a temporary electrode paste mainly composed of Ag is applied to the surface of the piezoelectric ceramic layer so as to cover the drive electrode and the auxiliary electrode, and dried to form a polarization electrode. did. In addition, the via electrode formed on the surface of the piezoelectric ceramic layer and the polarization electrode around it were not formed.

  After this entire surface polarization was performed, a voltage was applied between the common electrode and the polarization electrode to polarize almost the entire surface of the piezoelectric ceramic layer, and thereafter, the polarization electrode was removed by ultrasonic cleaning in an organic solvent.

Furthermore, on a flow path member having a groove shape (opening area 0.81 mm 2 ) having a groove width of 0.9 mm and a groove length of 0.9 mm, and having a groove pitch of 0.13 mm and matrix arrangement in a lattice shape Then, the piezoelectric actuator is bonded so that each displacement element is positioned in the opening, and a liquid discharge head is manufactured. Further, a control unit including a driver IC for controlling the operation of the liquid discharge head is connected to manufacture a recording apparatus. did.

  Drive reliability was evaluated using the obtained recording apparatus. As an index of drive reliability, first, the initial displacement amount A of the displacement element was measured in advance before driving the piezoelectric actuator. Next, after applying 10 billion cycles of a pulse wave with a peak voltage, a frequency of 2 kHz, and a duty of 80% between the driving electrode and the common electrode, the displacement amount B after driving of the displacement element is measured, and the displacement after driving with respect to the initial displacement amount A The deterioration rate of the amount B (AB) / A was calculated. In the table, the rate of decrease of 10% or less was evaluated as ◯, and the rate of decrease of 5% or less was evaluated as ◎.

  The displacement is measured by inputting a drive signal (rectangular wave) to the displacement element using an actuator drive circuit using a driver IC, and measuring the displacement with a laser Doppler displacement type manufactured by Graphtec. went.

  Further, the first voltage V1 is normalized in the ratio to the voltage at which the electric field generated in the driving unit becomes the coercive electric field Ec and is shown in Table 1. The third voltage V3 was a voltage at which an electric field of 0.8 Ec was generated in the auxiliary driving unit. The second voltage V2 and the fourth voltage V4 were set to 0V.

  The value of the coercive electric field Ec of the piezoelectric material was obtained from the value of the X-axis intercept measured by inputting a triangular wave with a measurement frequency of 1 Hz using a ferroelectric evaluation device FCE manufactured by Toyo Technica and measuring the PE hysteresis. 9 kV / cm.

  The results are shown in Table 1. Sample No. with no auxiliary drive voltage applied In the recording apparatuses 1 and 2, drive deterioration occurred at a voltage higher than the voltage at which E / Ec = 0.8. In the recording apparatuses according to the third and fourth aspects of the present invention, driving at a first voltage higher than the voltage at which E / Ec = 0.80 is possible, and compared with the case where E / Ec = 0.8 or less, ejection is performed. The amount could be increased and the discharge speed could be increased.

  The same evaluation as in Example 1 was performed except that the third voltage V3 and the fourth voltage V4 of the auxiliary drive voltage were changed to the values shown in Table 2.

  The results are shown in Table 2. Sample No. In 11 to 15, since the fourth voltage V4 of the auxiliary driving voltage is negative, the auxiliary driving unit pulls the non-driving unit at the time of driving. Therefore, even when the polarization of the non-driving unit proceeds to some extent, the liquid at the time of driving Since the volume of the pressurizing chamber can be the same as the volume of the liquid pressurizing chamber during driving in the initial stage of use, Compared with 4, drive deterioration could be further suppressed.

The method for producing the piezoelectric ceramic was the same as in Example 1. The drive electrode was formed with a width of 1.0 mm, a length of 1.0 mm, and the auxiliary electrode formed with a line width of 0.05 mm at a position 0.05 mm away from the end of the drive electrode. Then, a piezoelectric actuator was prepared in the same manner as in Example 1. Further, on the flow path member having a groove shape (opening area 1.21 mm 2 ) having a groove width of 1.1 mm and a groove length of 1.1 mm, and having a groove pitch of 0.23 mm and arranged in a matrix in a lattice shape, In the same manner as in Example 1, a liquid discharge head was manufactured by bonding a piezoelectric actuator, and a control unit including a driver IC for controlling the operation of the liquid discharge head was connected to manufacture a recording apparatus.

  Using the obtained recording apparatus, drive reliability was evaluated in the same manner as in Example 1. The results are shown in Table 3. Sample No. with no auxiliary drive voltage applied In the recording apparatuses 21 to 23, the size of the displacement element was different from that in Example 1, but drive deterioration occurred at a voltage higher than the same voltage at which E / Ec = 0.8. And sample no. In the recording apparatus according to the present invention, the first voltage higher than the voltage at which E / Ec = 0.80 can be driven, and the ejection amount is smaller than that in the case of E / Ec = 0.8 or less. We were able to increase the discharge speed.

DESCRIPTION OF SYMBOLS 1 ... Printer 2 ... Liquid discharge head 4 ... Flow path member 5 ... Manifold 5a ... Sub manifold 5b ... Opening 6 ... Individual supply flow path 8 ... Liquid discharge hole DESCRIPTION OF SYMBOLS 9 ... Liquid pressurization chamber group 10 ... Liquid pressurization chamber 11a, b, c, d ... Liquid pressurization chamber row | line | column 12 ... Squeeze 15a, b, c, d ... Liquid discharge hole Row 21 ... Piezoelectric actuator unit 21a ... Piezoelectric ceramic layer (vibrating plate)
21b: Piezoelectric ceramic layer 22-31: Plate 32 ... Individual flow path 34 ... Common electrode 35 ... Drive electrode 36 ... Connection electrode 41 ... Auxiliary electrode 46 ... Auxiliary Electrode connection electrode 50 ... Displacement element

Claims (4)

  1.   A piezoelectric actuator is laminated on a flat channel member having a plurality of liquid pressurizing chambers and a plurality of liquid discharge holes communicating with the plurality of liquid pressurizing chambers so as to cover the plurality of liquid pressurizing chambers. The piezoelectric actuator is formed by laminating a diaphragm, a common electrode, a piezoelectric body, and a plurality of drive electrodes in this order from the flow path member side, and is sandwiched between the drive electrode and the common electrode of the piezoelectric body. The portions are polarized in the thickness direction, and the plurality of drive electrodes are arranged so as to overlap the plurality of liquid pressurizing chambers, respectively, when viewed from the stacking direction of the flow path member and the piezoelectric actuator. A recording apparatus comprising: a liquid ejection head; a conveyance unit that conveys a recording medium to the liquid ejection head; and a control unit that controls the liquid ejection head and the conveyance unit. A plurality of auxiliary electrodes facing the common electrode are provided around each of the plurality of drive electrodes as viewed from the direction, and a portion sandwiched between the auxiliary electrode and the common electrode of the piezoelectric body is in a thickness direction. When the voltage that is polarized and generates an electric field in the same direction as the direction of polarization is a positive voltage, the reverse is a negative voltage, and the coercive electric field that causes domain rotational distortion in the piezoelectric body is Ec, the control The unit waits for the voltage between the drive electrode and the common electrode to be a positive first voltage in which the generated electric field is 0.8 Ec or more, and the second voltage is lower than the first voltage. After driving by increasing the volume of the liquid pressurizing chamber to a voltage, the voltage is returned to the first voltage, and at the time of standby, an electric field that generates a voltage between the auxiliary electrode and the common electrode is generated. As a negative third voltage of -0.8Ec or more Wherein when the drive is in the third higher than the voltage fourth voltage, the recording apparatus characterized by discharging the liquid from the liquid discharge hole.
  2.   The recording apparatus according to claim 1, wherein the fourth voltage is a positive voltage.
  3.   A piezoelectric actuator is laminated on a flat channel member having a plurality of liquid pressurizing chambers and a plurality of liquid discharge holes communicating with the plurality of liquid pressurizing chambers so as to cover the plurality of liquid pressurizing chambers. The piezoelectric actuator is formed by laminating a diaphragm, a common electrode, a piezoelectric body, and a plurality of drive electrodes in this order from the flow path member side, and is sandwiched between the drive electrode and the common electrode of the piezoelectric body. The portions are polarized in the thickness direction, and the plurality of drive electrodes are arranged so as to overlap the plurality of liquid pressurizing chambers, respectively, when viewed from the stacking direction of the flow path member and the piezoelectric actuator. A recording apparatus comprising: a liquid ejection head; a conveyance unit that conveys a recording medium to the liquid ejection head; and a control unit that controls the liquid ejection head and the conveyance unit. A plurality of auxiliary electrodes facing the common electrode are provided around each of the plurality of drive electrodes as viewed from the direction, and a portion sandwiched between the auxiliary electrode and the common electrode of the piezoelectric body is in a thickness direction. When the voltage that is polarized and generates an electric field in the same direction as the direction of polarization is a positive voltage, the reverse is a negative voltage, and the coercive electric field that causes domain rotational distortion in the piezoelectric body is Ec, the control The unit waits by setting the voltage between the drive electrode and the common electrode to a fifth voltage, and increasing the voltage to a positive sixth voltage that generates an electric field of 0.8 Ec or more. After reducing the volume of the drive, the voltage is returned to the fifth voltage, and the voltage between the auxiliary electrode and the common electrode is set to the seventh voltage during the standby, and during the drive, Electric field generated with lower than seventh voltage In the negative voltage of the eighth or -0.8Ec, recording apparatus characterized by ejecting the liquid from the liquid discharge hole.
  4. The recording apparatus according to claim 3, wherein the seventh voltage is a positive voltage.
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