JP5997102B2 - Liquid discharge head and recording apparatus using the same - Google Patents

Description

  The present invention relates to a liquid discharge head that discharges droplets and a recording apparatus using the same.

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

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

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

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

  Accordingly, the liquid discharge head includes a manifold and a metal flow path member having discharge holes that connect the manifold via the plurality of pressurizing chambers, and a plurality of displacement elements provided so as to cover the pressurizing chambers, respectively. A structure in which a piezoelectric actuator substrate made of ceramics is laminated is known (see, for example, Patent Document 1). In this liquid ejection head, the pressurizing chambers connected to the plurality of ejection holes are arranged in a matrix, and the displacement element of the piezoelectric actuator substrate provided so as to cover it is displaced by deformation of the piezoelectric body, Ink is ejected from each ejection hole, and printing is possible in the main scanning direction at a resolution of 600 dpi. Each displacement element includes a common electrode, individual electrodes, and a piezoelectric layer sandwiched between them.

JP 2003-305852 A

In the liquid discharge head as described in Patent Document 1, the extraction electrode is drawn out of the pressurizing chamber from the individual electrode so that an electrode for supplying a signal for driving each displacement element from the outside can be connected. . By doing so, the displacement is hardly suppressed by the electrode connected from the outside. However, if this is done, the piezoelectric layer between the extraction electrode and the common electrode is also piezoelectrically driven, resulting in a problem of increased crosstalk.

  Accordingly, an object of the present invention is to provide a liquid discharge head capable of reducing the influence of crosstalk and a recording apparatus using the same.

  The liquid discharge head according to the present invention includes a flow path member including a plurality of discharge holes and a plurality of pressurizing chambers respectively connected to the plurality of discharge holes, and is stacked on the flow path member. A liquid discharge head including a piezoelectric actuator substrate that pressurizes each of the plurality of pressurizing chambers, wherein the piezoelectric actuator substrate is disposed on a main surface opposite to the main surface on which the flow path member is stacked. A plurality of individual electrodes, a common electrode extending between the plurality of pressurizing chambers, and a piezoelectric layer sandwiched between the plurality of individual electrodes and the common electrode. When the piezoelectric actuator substrate is viewed in plan, the individual electrode includes an individual electrode body that overlaps the pressurizing chamber, and an extraction electrode that is led out from the individual electrode body to a position that does not overlap the pressurizing chamber. Contains The flow path member immediately below the lead electrodes, wherein the non-connected to the discharge hole gap portion exists.

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

  According to the liquid ejection head of the present invention, when the piezoelectric layer sandwiched between the extraction electrode and the common electrode is piezoelectrically driven, the portion facing the gap portion immediately below it is deformed, so that Since the transmitted stress is reduced, crosstalk can be reduced.

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 the longitudinal cross-sectional view along the VV line of FIG. 3, (b) is an enlarged view of the principal part of (a), (c) is a top view of (a). is there. (A) is the fragmentary longitudinal cross-sectional view of the other liquid discharge head of this invention, (b) is a top view of (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 number of ejection holes 8 for ejecting liquid are provided on the lower surface of the head body 13 (see FIGS. 4 and 5).

Liquid droplets (ink) of the same color are ejected from the ejection holes 8 provided in one liquid ejection head 2. Each liquid discharge head 2 is supplied with liquid from an external liquid tank (not shown). The ejection holes 8 of each liquid ejection head 2 are opened in the ejection hole surface, and are in one direction (a direction parallel to the printing paper P and perpendicular to the conveyance direction of the printing paper P, the longitudinal direction of the liquid ejection head 2). Since they are arranged at equal intervals, printing can be performed without gaps in one direction. The colors of the liquid ejected from each liquid ejection head 2 are magenta (M), yellow (Y), cyan (C), and black (K), respectively. Each liquid 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 plan view showing the head main body 13 shown in FIG. FIG. 3 is an enlarged plan view of a region surrounded by the alternate long and short dash line in FIG. 2, and a part of the flow paths are omitted. FIG. 4 is an enlarged perspective view of the same position as in FIG. 3, in which some flow paths different from those in FIG. 3 are omitted so that the positions of the discharge holes 8 can be easily understood. 3 and 4, in order to make the drawings easy to understand, the pressurizing chamber 10 (pressurizing chamber group 9), the squeezing chamber 12, the discharge hole 8, and the like that are to be drawn by broken lines below the piezoelectric actuator substrate 21 are illustrated. It is drawn with a solid line. 5A is a longitudinal sectional view taken along the line VV in FIG. 3, FIG. 5B is an enlarged view of the main part of FIG. 5A, and FIG. FIG. 6 is a plan view of FIG.

  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 area printed by driving the overlapping piezoelectric actuator substrate 21, the droplets ejected by the two piezoelectric actuator substrates 21 are mixed and landed.

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

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

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

  In the present embodiment, as shown in FIG. 3, the manifold 5 branches into four rows of E1-E4 sub-manifolds 5a arranged in parallel with each other in the short direction of the flow path member 4, and each sub-manifold The pressurizing chambers 10 connected to 5a constitute a row of the pressurizing chambers 10 arranged in the longitudinal direction of the flow path member 4 at equal intervals, and the four rows are arranged in parallel to each other in the lateral direction. Two rows of the pressure chambers 10 connected to the sub-manifold 5a are arranged on both sides of the sub-manifold 5a.

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

  That is, when the discharge hole 8 is projected so as to be orthogonal to a virtual straight line parallel to the longitudinal direction of the flow path member 4, it is connected to the four sub-manifolds 5a in the range of R of the virtual straight line shown in FIG. Four discharge holes 8, that is, a total of 16 discharge holes 8 are arranged at equal intervals of 600 dpi. Moreover, the individual flow paths 32 are connected to the sub manifolds 5a at intervals corresponding to 150 dpi on average. This is because when the discharge holes 8 for 600 dpi are divided and connected to the four sub-manifolds 5a, the individual flow paths 32 connected to the sub-manifolds 5a are not always connected at equal intervals. In other words, the individual flow paths 32 are formed at intervals of an average of 170 μm (25.4 mm / 150 = 169 μm intervals if 150 dpi) in the main scanning direction.

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

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

  The 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 body 13 has the pressurizing chamber 10 on the upper surface of the flow path member 4, the sub-manifold 5 a on the inner lower surface side, and the discharge holes 8 on the lower surface. Are arranged close to each other at different positions, and the sub-manifold 5 a and the discharge hole 8 are connected via the pressurizing chamber 10.

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

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

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

In addition to the flow path through which the liquid to be discharged flows as described above, a gap 38 is formed in the plate 22. The gap portion 38 is formed so as to be depressed on the upper side of the plate 22, but may be formed as a hole penetrating the plate 22. The gap 38 will be described in detail later.

  As shown in FIG. 5, 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, and the displacement can be increased by being 100 μm or less. The piezoelectric actuator substrate 21 is laminated on the planar surface of the flow path member 4 where the pressurizing chamber 10 is open, and the piezoelectric ceramic layers 21 a and 21 b straddle the plurality of pressurizing chambers 10. (See FIG. 3). The piezoelectric ceramic layers 21a and 21b are made of a lead zirconate titanate (PZT) ceramic material having ferroelectricity.

The piezoelectric actuator substrate 21 has a common electrode 34 made of a metal material such as Ag—Pd and an individual electrode 35 made of a metal material such as Au. If necessary, a connection electrode 36 made of an Ag-based metal material formed on the individual electrode 35 may be formed. The individual electrode 35 is disposed at a position overlapping the pressurizing chamber 10 on the upper surface of the piezoelectric actuator substrate 21, and the extraction electrode is drawn from the individual electrode main body 35 a to a position not overlapping the pressurizing chamber 10. 35b. A connection electrode 36 is formed at a position of the extraction electrode 35b where the pressurizing chamber 10 is not provided. The thickness of the individual electrode 35 is 0.3 to 1 μm. The connection electrode 36 is made of, for example, silver containing glass frit, and has a thickness of about 1 to 15 μm and is formed in a convex shape. Further, the connection electrode 36 is not shown in FPC (Flexible).
It is electrically joined to the electrode provided in the printed circuit. 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 common electrode 34 is formed over almost the entire surface in the region between the piezoelectric ceramic layer (ceramic diaphragm) 21a and the piezoelectric ceramic layer (piezoelectric layer) 21b. That is, the common electrode 34 extends so as to cover all the pressurizing chambers 10 in the region facing the piezoelectric actuator substrate 21. The thickness of the common electrode 34 is about 2 μm. The common electrode 34 is grounded in a region not shown, and is held at the ground potential. In the present embodiment, a surface electrode (not shown) different from the individual electrode 35 is formed on the piezoelectric ceramic layer 21b at a position avoiding the electrode group composed of the individual electrodes 35. The surface electrode is electrically connected to the common electrode 34 through a through-hole formed in the piezoelectric ceramic layer 21b, and is connected to another electrode in the external wiring, like the large number of individual electrodes 35. Has been.

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

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

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

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

In an actual driving procedure in the present embodiment, the individual electrode 35 is set to a potential higher than the common electrode 34 (hereinafter referred to as a high potential) in advance, and the individual electrode 35 is temporarily set to the same potential as the common electrode 34 every time there is a discharge request. (Hereinafter referred to as a low potential), and then set to a high potential again at a predetermined timing. As a result, the piezoelectric ceramic layers 21a and 21b return to their original shapes at the timing when the individual electrodes 35 become low potential, and the volume of the pressurizing chamber 10 increases compared to the initial state (the state where the potentials of both electrodes are different). To do. At this time, a negative pressure is applied to the pressurizing chamber 10 and the liquid is sucked into the pressurizing chamber 10 from the manifold 5 side. Thereafter, at the timing when the individual electrode 35 is set to a high potential again, the piezoelectric ceramic layers 21a and 21b are deformed so as to protrude toward the pressurizing chamber 10, and the pressure in the pressurizing chamber 10 is reduced due to the volume reduction of the pressurizing chamber 10. The pressure becomes positive and the pressure on the liquid rises, and droplets are ejected. That is, a drive signal including a pulse based on a high potential is supplied to the individual electrode 35 in order to eject a droplet. The ideal pulse width is AL (Acoustic Length), which is the length of time that the pressure wave propagates from the orifice 12 to the discharge hole 8. According to this, the pressure chamber 10
When the inside is reversed from the negative pressure state to the positive pressure state, both pressures are combined, and the liquid droplets can be ejected at a stronger pressure.

  In the liquid ejection head 2 as described above, the extraction electrode 35 b is extracted to the outside of the pressurizing chamber 10 so as not to inhibit the displacement of the displacement element 50 by an electrode that supplies a signal from the outside. However, by doing so, there is also a piezoelectric ceramic layer 21b directly below the extraction electrode 35b sandwiched between the extraction electrode 35b and the common electrode 34 (hereinafter, this portion may be referred to as an extraction portion drive unit). Piezoelectrically driven. When vibration or stress due to this piezoelectric drive is transmitted to the surrounding liquid ejection elements, the operation is affected, so that crosstalk occurs and printing accuracy is lowered. This phenomenon is conspicuous in the liquid discharge head 2 in which the drawer drive unit is polarized, and the present invention is particularly effective in such a liquid discharge head 2.

In order to reduce this influence, the gap member 38 is provided in the flow path member 4. The gap portion 38 is directly below the extraction electrode 35b, and provides a room for deformation when the extraction portion driving portion is piezoelectrically driven.
Thereby, the stress given to the surroundings is reduced and crosstalk is reduced. The crosstalk is affected when the piezoelectric ceramic layer 21b is connected between the adjacent displacement elements 50, so that the stress is directly transmitted. Therefore, the influence of the crosstalk is increased. This is particularly effective in a liquid discharge head 2 that is easy to use.

  Here, the term “directly below” means directly below, and the gap 38 is formed in the direction perpendicular to the boundary surface between the piezoelectric actuator substrate 21 and the flow path member 4 from the extraction electrode 35b. Located in the direction toward. In other words, when the head body 13 is viewed in plan, at least a part of the extraction electrode 35b and the gap portion 38 overlap each other. A larger overlap is preferable because the stress relaxation effect is increased.

  However, the extraction electrode 35b is a portion to which a force is applied from the outside when electrically connecting to the outside, and the piezoelectric ceramic layer 21b and the like may be damaged by the force from the outside. Therefore, the size (width, etc.) of the gap 38 is preferably 50 to 150% of the extraction electrode, particularly 80 to 120%.

  The gap portion 38 is not connected to the discharge hole 8 so that the discharged liquid does not enter. When the liquid to be ejected enters, the gap portion 38 becomes difficult to be deformed, so that the effect of stress relaxation is reduced, and the vibration of the drawer drive portion is transmitted to other flow paths through the liquid in the gap portion 38. There is also a risk of crosstalk.

  The gap 38 may be connected to a space outside the head body 13 so that air and the like can enter and exit. However, since the amount of deformation of the gap 38 is small, the necessity for doing so is not high. Further, as described above, it is preferable that the gap portion 38 does not extend in the planar direction of the flow path member 4 away from (below) the extraction electrode 35b so that the piezoelectric actuator substrate 21 is not easily damaged. . When connecting the gap 38 to the outside, it is preferable that the gap 38 once extends toward the lower side (discharge hole surface 4-1 side) of the flow path member 4 and is connected to the outside at the end.

  If there is a channel through which the liquid to be discharged flows directly under the drawer drive unit, vibration may be applied to the liquid in the channel and crosstalk may occur. Therefore, it is preferable not to provide a flow path directly under the drawer drive unit. However, since it is necessary to reduce the size of the head body 13 in order to increase the printing accuracy, the flow paths must be arranged at a high density. difficult. In the case where the flow path is arranged immediately below the lead-out section drive section, the occurrence of crosstalk can be suppressed by providing the gap portion 38 at a position closer to the piezoelectric actuator substrate 21 than the flow path.

  When the width of the extraction electrode 35b in the direction orthogonal to the extraction direction is W [μm], the gap portion 38 (more precisely, the upper end of the gap portion 38) is set to a distance of W [μm] or less from the piezoelectric actuator substrate 21. By arranging, the effect of stress relaxation can be enhanced. W is, for example, about 30 to 100 μm. In order to make the stress relaxation effect particularly high, the gap 38 is preferably provided at the boundary between the piezoelectric actuator substrate 21 and the flow path member 4.

  As shown in FIG. 5B, the gap 38 may be formed as a recess by half-etching the upper side of the plate 22 or as a hole penetrating the plate 22. Further, when the piezoelectric actuator substrate 21 and the flow path member 4 are laminated via an adhesive layer, the gap portion 38 may be formed by preventing the adhesive from being present in that portion. Since the piezoelectric drive just below the extraction electrode 35b is about 100 nm, for example, if an adhesive layer having a thickness of 500 nm or more is formed, by providing a portion where no adhesive is present, that portion functions sufficiently as the gap 38.

  Similarly, in the case of disposing inside the gap portion 38 inside the flow path member 4, a plate having depressions or holes may be disposed. When each plate is laminated via an adhesive layer, a portion where no adhesive is present may be used as the gap 38.

  FIG. 6A is a partial cross-sectional view of another liquid discharge head of the present invention, and FIG. 6B is a partial plan view of the portion of FIG. The basic structure of the liquid discharge head is the same as that shown in FIGS. 1 to 5, and parts with little difference are given the same reference numerals and description thereof is omitted.

  The flow path member 204 has a structure in which a plate 220 is laminated on the plate 22 of the flow path member 4. The upper side of the pressurizing chamber 10 is covered with a plate 220 and closed. In the figure, the plate below the plate 22 is omitted.

  The piezoelectric actuator substrate 21 and the flow path member 204 are laminated via an adhesive layer 240. Both the plate 220 and the plate 22 are laminated via an adhesive, but are omitted in the figure. Immediately below the extraction electrode 35 b, there is a portion where the adhesive layer 240 does not exist, which is a gap 238. The adhesive layer 240 has a thickness of about 0.2 to 2 μm. If the thickness is 0.2 μm or more, even if the lead portion driving portion is piezoelectrically deformed, the piezoelectric actuator substrate 21 and the plate 220 are hardly contacted in the gap portion 238, and the stress relaxation effect is hardly lowered.

  Since the gap 238 is positioned closer to the piezoelectric actuator substrate 21 than the pressurizing chamber 10, the stress relaxation effect can be enhanced. Moreover, by arranging in this way, even if the gap portion 238 is approximately the same size as the extraction electrode 35b, the gap portion 238 and the pressurizing chamber 10 are not connected. Accordingly, the planar shape of the gap 238 can be increased to be close to the extraction electrode 35b while preventing the liquid discharged into the gap 238 from entering.

  The gap 238 may extend to a position overlapping the pressurizing chamber 10 along the extraction electrode 35b. By doing so, the displacement amount of the displacement element 50 can be increased.

  The displacement element 50 is bent and deformed when the piezoelectric ceramic layer 21b expands and contracts in the plane direction. For example, when the pressure chamber 10 is displaced downward so as to reduce the volume, the piezoelectric ceramic layer 21b is contracted. When the piezoelectric ceramic layer 21b near the center of the pressurizing chamber 10 is contracted, its length becomes shorter than the vibration plate (piezoelectric ceramic layer 21a and plate 220) at the corresponding portion, so that it bends downward. In order to bend downward, the piezoelectric ceramic layer 21b in the vicinity of the outer periphery of the pressurizing chamber 10 (inner side of the outer periphery) must be deformed so as to extend in the plane direction.

  If there is a portion overlapping the pressurizing chamber 10 in the gap portion 238, the piezoelectric actuator substrate 21 immediately above the portion can be displaced downward by the gap portion 238, so that the amount of displacement can be increased. In other words, when the same amount of displacement is applied, the elongation generated in the piezoelectric ceramic layer 21b immediately above that portion is reduced by the presence of the air gap 238. From there, the piezoelectric ceramic layer 21b is further reduced. The amount of displacement can be increased by deforming so as to extend.

The individual electrode main body 35 a includes an individual electrode central portion that is substantially similar to the pressurizing chamber 10 in plan view, and an individual electrode connection portion that is connected to the extraction electrode 35 b from the individual electrode central portion. As described above, the piezoelectric ceramic layer 21b near the center of the pressurizing chamber 10 is piezoelectrically driven to cause displacement. However, when the piezoelectric ceramic layer 21b near the outer periphery of the pressurizing chamber 10 is piezoelectrically driven, Conversely, since the amount of displacement is small, the central portion of the individual electrode is made smaller than the pressurizing chamber 10. Since the displacement element 50 is basically designed to increase the displacement amount, the displacement amount increases in the region where the individual electrode central portion is disposed by piezoelectrically deforming the piezoelectric ceramic layer 21b immediately below the region. It is an area. In other words, the area outside the central portion of the individual electrode is an area where the displacement is reduced when the piezoelectric drive is performed. Therefore, if the gap portion 238 extends to the boundary between the individual electrode central portion and the individual electrode connecting portion that are substantially similar to the pressurizing chamber 10, the amount of displacement can be increased.

  The liquid discharge head 2 as described above is manufactured as follows, for example. A tape made of a piezoelectric ceramic powder and an organic composition is formed by a general tape forming method such as a roll coater method or a slit coater method, and a plurality of green sheets that become piezoelectric ceramic layers 21a and 21b after firing are produced. . An electrode paste to be the common electrode 34 is formed on a part of the green sheet by a printing method or the like. Further, a via hole is formed in a part of the green sheet as necessary, and a via conductor is filled in the via hole.

  Next, each green sheet is laminated to produce a laminate, and pressure adhesion is performed. After firing the pressure-bonded laminate in a high-concentration oxygen atmosphere, the individual electrodes 35 are printed on the surface of the fired body using a gold paste and fired, and then the individual gold thin film 38 and the same gold paste are used. The piezoelectric thin film 39 is printed and fired, and the connection electrode 36 is printed and fired using Ag paste, whereby the piezoelectric actuator substrate 21 is manufactured.

  Next, the flow path member 4 is produced by laminating plates 22 to 31 obtained by a rolling method or the like via an adhesive layer. In the plates 22 to 31 to be stacked, holes to be the manifold 5, the individual supply flow path 6, the liquid pressurizing chamber 10 and the descender are processed into a predetermined shape by etching. The space 38 may be formed in any one of the plates 22 to 31 by etching a recess or a hole. The gap 38 may be formed as a portion where no adhesive is present by applying the adhesive layer at the time of lamination by patterning.

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

  Subsequently, the piezoelectric actuator substrate 21 and the flow path member 4 are laminated via an adhesive layer. The gap 38 may be formed as a portion where no adhesive is present by applying the adhesive layer at this stage by patterning. After the lamination is finished, the adhesive layer is cured by heating and pressing. Thereafter, a voltage is applied between the individual electrode 35 and the common electrode 34 to polarize the piezoelectric ceramic layer 21b sandwiched between them, whereby the liquid ejection head 2 can be obtained.

DESCRIPTION OF SYMBOLS 1 ... Printer 2 ... Liquid discharge head 4, 204 ... Flow path member 4-1 ... Discharge hole surface 4-2 ... Pressure chamber surface 5 ... Manifold 5a ... Sub Manifold 5b ... Manifold opening 6 ... Individual supply flow path 8 ... Discharge hole 9 ... Pressurizing chamber group 10 ... Pressurizing chamber 11a, b, c, d ... Pressurizing chamber Row 12 ... Squeezing 13 ... Head body 15a, b, c, d ... Discharge hole row 21 ... Piezoelectric actuator substrate 21a ... Piezoelectric ceramic layer 21b ... Piezoelectric ceramic layer (piezoelectric layer) )
22-31, 220 ... plate 32 ... individual flow path 34 ... common electrode 35 ... individual electrode 35a ... individual electrode body 35b ... extraction electrode 36 ... connection electrode 38, 238 ... Gaps 240 ... Adhesive layer 50 ... Displacement element

Claims (10)

A plurality of discharge holes, a plurality of pressurizing chambers connected to the plurality of discharge holes, a plurality of individual flow paths each connected to the plurality of pressurizing chambers and each having a squeeze, and a plurality of the individual flows A flow path member having a manifold to which the path is connected;
A piezoelectric actuator substrate that is stacked on the flow path member and pressurizes each of the plurality of pressurizing chambers;
Have
The piezoelectric actuator substrate includes a piezoelectric layer, a plurality of individual electrodes arranged on a main surface of the piezoelectric layer opposite to the flow path member, and the plurality of individual electrodes sandwiched between the piezoelectric layers. A common electrode facing the individual electrode,
The individual electrode includes an individual electrode body that overlaps the pressurizing chamber, and an extraction electrode that is led out from the individual electrode body to a position that does not overlap the pressurizing chamber,
In the flow path member directly below the extraction electrode, there is a gap that is not connected to the discharge hole, and the squeeze extending in the horizontal direction is located immediately below the gap.
The squeezing has a portion whose vertical dimension is smaller than other portions in the individual flow path, the pressurizing chamber and the manifold,
The liquid discharge head according to claim 1, wherein the gap is located between the extraction electrode and the aperture.   2. The liquid ejection head according to claim 1, wherein the gap is positioned closer to the piezoelectric actuator substrate than the pressurizing chamber in the stacking direction.   3. The liquid discharge head according to claim 2, wherein when the piezoelectric actuator substrate is viewed in plan, the gap extends along the extraction electrode to a position overlapping the pressurizing chamber. When the width in the direction perpendicular to the drawing direction of the front Symbol extraction electrode was W [[mu] m], the gap portion, wherein the distance from the piezoelectric actuator substrate is characterized in that in the W [[mu] m] following positions Item 4. The liquid ejection head according to any one of Items 1 to 3. The flow path member and the piezoelectric actuator substrate are laminated via an adhesive layer, and the gap is a portion where the adhesive layer does not exist. The liquid discharge head described in 1. 2. The flow path member has a laminated structure in which a plurality of plates are laminated with an adhesive layer interposed therebetween, and the gap is a portion where the adhesive layer does not exist. The liquid discharge head according to any one of?   The liquid ejection head according to claim 1, wherein the gap is connected to an external space. The liquid ejection head according to claim 1, wherein the plurality of pressurizing chambers include 16 pressurizing chamber rows. Each of the plurality of pressurizing chambers has a shape in plan view in which a dimension in a direction in which the pressurizing chambers form a row is smaller than a dimension in a direction orthogonal to the direction in which the pressurizing chambers form a row. The liquid discharge head according to claim 8, wherein the liquid discharge head is provided. A liquid discharge head according to any one of claims 1 to 9 and a conveying unit that conveys the recording medium to the liquid discharge head, and characterized in that a control unit for controlling the liquid discharge head Recording device.

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