JP6010497B2 - 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, 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 discharge holes for discharging the droplets formed in the liquid discharge head is increased. There is a need.

  Therefore, the head body is connected to the manifold (common flow path) and the flow path member having the discharge holes connecting the manifold through the plurality of pressure chambers, and the plurality of displacement elements provided so as to cover the pressure chambers, respectively. It is known that a piezoelectric actuator substrate having a laminated structure is laminated (see, for example, Patent Document 1). In this head body, pressurizing chambers connected to a plurality of ejection holes are arranged in a matrix, and ink is ejected from each ejection hole by displacing the displacement element of the piezoelectric actuator substrate provided so as to cover it. Thus, printing is possible at a resolution of 600 dpi in the main scanning direction.

JP 2010-522562 A

  In the liquid ejection head described in Patent Document 1, when the heat of the driver IC that drives the piezoelectric actuator substrate is exhausted through a housing made of metal or the like, the housing is hotter than the liquid ejection head body. Therefore, there is a problem that the liquid discharge head main body is distorted by the stress applied from the thermally expanded casing. When the liquid discharge head main body is distorted, the discharge direction of the droplets may change.

  Accordingly, an object of the present invention is to provide a liquid discharge head and a recording apparatus using the same, in which the liquid discharge head main body is less susceptible to stress from the casing due to the influence of temperature.

The liquid discharge head of the present invention includes a liquid discharge head main body that is long in one direction, one or a plurality of driver ICs that drive the liquid discharge head main body, and a casing that is joined to the liquid discharge head main body. The liquid discharge head, wherein the housing includes a side plate extending along the one direction, and one side of the side plate extends along the liquid discharge head main body and one side of the side. It is joined or fitted to the liquid discharge head main body at a fixed portion that is a portion, the driver IC is housed in the housing, and the driver IC is a surface on the inner side of the housing of the side plate. The center of gravity of the contact portion and the fixed portion are arranged on the same side in the one direction with respect to the center of the one side in the one direction. And the side An elastic member is disposed across the one side between the liquid discharge head main body, and a distance between the one side and the liquid discharge head main body increases from the central part of the one side toward both ends. It is characterized by becoming .
The liquid discharge head of the present invention includes a liquid discharge head main body that is long in one direction, one or more driver ICs that drive the liquid discharge head main body, and a casing that is joined to the liquid discharge head main body. The housing includes a side plate extending along the one direction, and one side of the side plate extends along the liquid discharge head body, and the one side The driver IC is accommodated in the casing, and the driver IC is connected to the inner side of the casing of the side plate. The center of gravity of the contact portion and the fixed portion are arranged on the same side in the one direction with respect to the center of the one side in the one direction. Before and The casing and the liquid discharge head main body are joined or fitted at both ends in the one direction of the casing, and a slit is provided between the both ends of the casing and the side plate. The slit is closed with an elastic member.

  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 via the driver IC. It is characterized by that.

  Stress caused by a temperature difference or the like is not easily transmitted to the liquid discharge head body, and deformation of the liquid discharge head body can be suppressed.

1 is a schematic configuration diagram of a printer that is a recording apparatus according to an embodiment of the present invention. (A) is a perspective view of an example of the liquid discharge head used for the recording apparatus of FIG. 1, and (b) is a side view thereof. FIG. 3 is a longitudinal sectional view of the liquid discharge head shown in FIG. 2A taken along line XX in FIG. FIG. 3 is a plan view of a flow path member and a piezoelectric actuator substrate used in the liquid ejection head of FIG. FIG. 5 is a partial longitudinal sectional view of a flow path member and a piezoelectric actuator substrate shown in FIG. 4.

  FIG. 1 is a schematic configuration diagram of a color inkjet printer 1 which is a recording apparatus including a body discharge head 2 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 recording medium P such as paper 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 recording medium 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 feed unit 114 includes a paper storage case 115 that can store a plurality of recording media P, and a paper supply roller 145. The paper feed roller 145 can send out the uppermost recording medium P among the recording media 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 recording medium P. The recording medium P sent out from the paper feed 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 conveyance surface 127 that conveys the recording medium 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 recording medium 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 recording medium P is pressed against the conveying surface 127 of the conveying belt 111 and is fixed on the conveying surface 127. Then, the recording medium 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 recording medium P can be reliably 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. The liquid discharge head 2 includes a (liquid discharge) head main body 13 at the lower end and a housing 90 attached to the head main body 13. On the lower surface of the head body 13, there is an ejection hole surface 4 a provided with a number of ejection holes 8 for ejecting liquid.

  Liquid droplets (ink) of the same color are ejected from the ejection holes 8 provided in one liquid ejection head 2. The ejection holes 8 of each liquid ejection head 2 are arranged at equal intervals in one direction (a direction parallel to the recording medium P and perpendicular to the conveyance direction of the recording medium P, and the longitudinal direction of the liquid ejection head 2). Can print without gaps in the 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 ejection hole opening plane 4 a on the lower surface of the head body 13 and the conveyance surface 127 of the conveyance belt 111.

  The recording medium 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 body 13 constituting the liquid ejection head 2 toward the upper surface of the recording medium 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 recording medium 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 recording medium P on which the color image is printed is transported to the peeling plate 140 by the transport belt 111. At this time, the recording medium P is peeled from the transport surface 127 by the right end of the peeling plate 140. Then, the recording medium P is sent out to the paper receiving unit 116 by the feed rollers 121a to 122b. In this way, the printed recording medium 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 conveyance direction of the recording medium 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 recording medium P on the conveyance 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 transport motor 174, and the like based on the detection result sent from the paper surface sensor 133 so that transport of the recording medium P and image printing are synchronized.

  2A is a perspective view of the liquid discharge head 2, and FIG. 2B is a side view thereof. FIG. 3 is a vertical cross-sectional view of the liquid discharge head 2 shown in FIG. FIG. 4 is a plan view of a flow path member and a piezoelectric actuator substrate used in the liquid discharge head of FIG. FIG. 5 is a partial longitudinal sectional view of the flow path member and the piezoelectric actuator substrate shown in FIG.

  The liquid discharge head 2 includes a head main body 13, a housing 90, and an internal wiring portion. The internal wiring portion is a general term for portions that transmit drive signals supplied from the outside to the head main body 13, and includes an internal connector 82, a wiring board 84, and the like. The casing 90 is made of metal and has a rectangular parallelepiped shape and covers most of the head main body 13 and the internal wiring portion. The housing 90 has an opening 90a so that an external connector can be connected.

  The housing 90 is a surface along the longitudinal direction of the head main body 13, and has a side plate 90 b whose one side 90 ba extends along the head main body 13. One side 90ba, which is the side of the side plate 90 on the head body 13 side, is provided with a fitting portion 90c that protrudes toward the head body 13 side. The fitting portion 90c is fitted so as to enter the head main body 13, and serves as a fixing portion for fixing the housing 90 and the head main body 13 together. The fixing part may be fixed by bonding.

  A driver IC 55 that drives the piezoelectric actuator substrate 21 is in contact with the housing 90 from the inside (the contact portion may be referred to as a contact portion B), and the heat of the driver IC 55 is transmitted to the housing 90. The heat is radiated to the outside. Since the housing 90 has a higher temperature than the head main body 13, the head main body 13 may be distorted due to thermal expansion, and the ejection direction may shift.

  Although details will be described later, the area gravity center C of the contact portion C of the driver IC 55 (if there is one contact portion B, it is the area center of gravity of the shape, and if the contact portion B is two or more locations, If the center of gravity of the area of all shapes) and the center A in the longitudinal direction of the head body 13 of one side 90ba are displaced in the longitudinal direction, the distortion becomes large. Furthermore, in the two side plates 90b facing each other, if the area center of gravity C of the contact portion B of the driver IC 55 is shifted in the longitudinal direction, the distortion increases.

  Accordingly, if the position of the fitting portion 90c in the longitudinal direction is shifted in the same direction as the direction in which the area gravity center C is shifted from the center A, the distortion can be reduced.

  Between the one side 90ba and the head body 13, a first elastic member 91a such as a silicone resin is disposed. This makes it difficult for liquid mist or the like to enter from between the side plate 90b and the head body 90, and makes it difficult for stress to be transmitted. Further, by using a member having low thermal conductivity as the first elastic member 91a, it is possible to suppress the temperature of the head main body 13 from increasing and the liquid ejection characteristics from being changed.

  Since the stress increases as the distance from the mixing portion 90c increases, the distance between the side 90ba and the head body 13 increases from the center A toward both ends of the side 90ba so that the stress is not easily transmitted. preferable. Further, the distance between the side 90ba and the head body 13 may be increased from the fitting portion 90c toward both ends of the side 90ba.

  The housing 90 is fixed by fitting or joining at both of the second fixing portions 90d, which are both ends in the longitudinal direction, and a slit 90e between the second fixing portion 90d and the side plate 90ba. It is preferable to provide the slit 90e so as to block the second elastic member 91b such as a silicone resin because stress is not easily transmitted from the second fixing portion 90d to the head main body 13.

  The head body 13 may further include a reservoir 40 provided with a reservoir channel. The reservoir channel supplies the head body 13 with the liquid supplied from the outside through the opening 41b of the reservoir channel. A part of the inner wall of the reservoir channel is a damper made of an elastically deformable material. Since the damper can be deformed in the direction facing the reservoir flow path, the damper can be elastically deformed to change the volume of the reservoir flow path, and the liquid discharge amount has changed abruptly. In some cases, the liquid can be supplied stably. In addition, it is preferable to provide a filter in the reservoir flow path so that foreign matter contained in the liquid does not easily enter the ejection head 2 and can suppress non-ejection caused by clogging of foreign matter.

  In addition, an elastic plate 96 provided with a heat insulating member 97 and a guide frame 88 for fixing a wiring board 84 for processing a drive signal for discharging liquid from the head main body 13 are fixed to the reservoir 40. . The drive signal sent from the control unit 100 passes through the external connector 82, the wiring board 84, the internal connector 86, the signal transmission unit 92, and the driver IC 55 mounted on the signal transmission unit 92, and the displacement of the piezoelectric actuator substrate 21. By driving the element 50 and pressurizing the liquid inside the flow path member 4, droplets are ejected. Note that the wiring board 84 divides the drive signal into a plurality of piezoelectric actuator boards 21 or rectifies the drive signal, for example. The signal transmission portion 92 is a flexible belt-like member, and has a metal wiring inside. A part of the wiring is exposed on the surface of the signal transmission unit 92, and is electrically connected to the internal connector 86, the driver IC 55, and the piezoelectric actuator substrate 21 by the exposed wiring. The signal transmission unit 92 is, for example, an FPC (Flexible Printed Circuit).

  The driver IC 55 generates heat when processing the drive signal. Since the driver IC 55 is pressed against the metal casing 90 by deflecting the elastic plate 96, the generated heat is mainly transmitted to the casing 90, and further spreads quickly over the entire casing 90 and is radiated to the outside. . The heat insulating member 97 makes it difficult for heat to be transferred to the reservoir channel member. The heat insulating member 97 may also be made elastic to help press the driver IC 55 against the metal housing 90.

  Next, the flow path member 4 constituting the liquid discharge head 2 will be described. FIG. 4 is a plan view showing the flow path member 4 and the piezoelectric actuator 21 in the head main body 13. FIG. 5 is a partial longitudinal sectional view of FIG.

  The head main body 13 includes a flat plate-like flow path member 4 and a piezoelectric actuator substrate 21 including a displacement element 50 as a pressurizing portion on the flow path member 4. The piezoelectric actuator substrate 21 has a trapezoidal shape, and is disposed on the upper surface of the flow path member 4 so that a pair of parallel opposing sides of the trapezoid is parallel to the longitudinal direction of the flow path member 4. In addition, two piezoelectric actuator substrates 21 are arranged on the flow path member 4 as a whole in a zigzag manner, two along each of the two virtual straight lines parallel to the longitudinal direction of the flow path member 4. Yes. The oblique sides of the piezoelectric actuator substrates 21 adjacent to each other on the flow path member 4 partially overlap in the short direction of the flow path member 4. In the area printed by driving the overlapping piezoelectric actuator unit 21, the droplets ejected by the two piezoelectric actuator substrates 21 are mixed and landed.

  Further, since the signal transmission unit 92 is drawn out from the long side of the trapezoidal piezoelectric actuator unit 21, the four signal transmission units 92 are alternately drawn out to the left and right of FIG. Because of this structure, the area gravity center C of the contact portion B of the driver IC 55 mounted on each signal transmission portion 92 is shifted from the center A in the longitudinal direction. Further, since the two side plates 90b are in the opposite directions and the distortion applied to the head main body 13 is increased, it is effective to adopt the structure of the housing 90 as described above.

  A manifold 5 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). The flow path connecting from the opening 5 b to the sub manifold extends along the oblique side of the piezoelectric actuator substrate 21 and is arranged 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 is branched from both sides of the manifold 5. These sub-manifolds extend in the longitudinal direction of the head body 13 adjacent to each other in a region facing each piezoelectric actuator substrate 21 inside the flow path member 4.

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

In the present embodiment, four sub-manifolds arranged side by side as shown in FIG. 4 are connected to four rows of pressurizing chambers, respectively. Two rows of pressurizing chambers connected to one sub-manifold are arranged on both sides of the sub-manifold. As a result, a total of 16 pressurizing chamber rows are arranged, and the rows of discharge holes 8 connected from the pressurizing chamber rows are also 16 rows. The discharge holes 8 in each row of the discharge holes 8 are arranged at equal intervals, and the discharge holes 8 in each row are arranged slightly shifted. As a result, the discharge hole 8 as a whole can form an image with a resolution of 600 dpi in the longitudinal direction.

  That is, when the discharge holes 8 are projected so as to be orthogonal to a virtual straight line parallel to the longitudinal direction of the flow path member 4, the four discharges connected to each sub-manifold are within the range of R of the virtual straight line shown in FIG. The holes 8, that is, a total of 16 discharge holes 8 are equally spaced at 600 dpi. In addition, individual flow paths 32 are connected to each sub-manifold 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, the individual flow paths 32 connected to the sub-manifolds are not necessarily connected at equal intervals. The individual flow paths 32 are formed in the present direction, that is, in the main scanning direction at an average interval of 170 μm or less (25.4 mm / 150 = 169 μm interval if 150 dpi).

  Individual electrodes 35 to be described later are formed at positions facing the pressurizing chambers 10 on the upper surface of the piezoelectric actuator substrate 21. The individual electrode 35 is slightly smaller than the pressurizing chamber 10, has a shape substantially similar to the pressurizing chamber 10, and is disposed so as to be within a region facing the pressurizing chamber 10 on the upper surface of the piezoelectric actuator substrate 21. ing.

  A large number of discharge holes 8 are formed in the liquid discharge surface on the lower surface of the flow path member 4. These discharge holes 8 are arranged at positions avoiding the region facing the sub-manifold 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 holes 8 occupy an area having almost the same size and shape as the piezoelectric actuator substrate 21 as one group, and the displacement elements 50 of the corresponding piezoelectric actuator substrate 21 are displaced from the discharge holes 8. Droplets can be ejected. The discharge holes 8 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 stacked such that these holes communicate with each other to form the individual flow path 32 and the sub-manifold. As shown in FIG. 5, the head body 13 includes an individual flow path 32 in which the pressurizing chamber 10 is on the upper surface of the flow path member 4, the sub manifold is on the inner lower surface side, the discharge hole 8 is on the lower surface. The constituent parts are arranged close to each other at different positions, and the sub-manifold 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 forms a flow path connecting from one end of the pressurizing chamber 10 to the sub manifold. 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). 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
It 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).

  Fourth, there is a communication hole constituting the sub manifold. 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 inlet (submanifold outlet) to the discharge hole 8 from the submanifold. The liquid supplied to the sub manifold is discharged from the discharge hole 8 through the following path. First, from the sub-manifold, it passes through the individual supply channel 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.

  Similarly to the flow path member 4, the branch flow path member 60 is obtained by a rolling method or the like, and is processed into a predetermined shape by etching on the plates 60a to 60c. In addition, a recess 63 is provided in which the liquid channel 61 and the piezoelectric actuator are accommodated.

  As shown in FIG. 6, the piezoelectric actuator substrate 21 has a laminated structure including two piezoelectric ceramic layers 21a and 21b. Each of these piezoelectric ceramic layers 21a and 21b has a thickness of about 20 μm. The total thickness of the piezoelectric actuator substrate 21 is about 40 μm. Each of the piezoelectric ceramic layers 21a and 21b extends so as to straddle the plurality of pressure 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. As described above, the individual electrode 35 is disposed at a position facing the pressurizing chamber 10 on the upper surface of the piezoelectric actuator substrate 21. One end of the individual electrode 35 is drawn out of a region facing the pressurizing chamber 10 to form a connection electrode 36. The connection electrode 36 is made of, for example, silver-palladium containing glass frit, and has a convex shape with a thickness of about 15 μm. Further, the connection electrode 36 is electrically joined to an electrode provided in the signal transmission unit 92. Although details will be described later, a drive signal is supplied from the control unit 100 to the individual electrode 35 through the signal transmission unit 92. 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 area between the piezoelectric ceramic layer 21a and the piezoelectric ceramic layer 21b. That is, the common electrode 34 extends so as to cover all the pressurizing chambers 10 in the region facing the piezoelectric actuator substrate 21. The thickness of the common electrode 34 is about 2 μm. The common electrode 34 is grounded in a region not shown, and is held at the ground potential. In the present embodiment, a surface electrode (not shown) different from the individual electrode 35 is formed on the piezoelectric ceramic layer 21b at a position avoiding the electrode group composed of the individual electrodes 35. The surface electrode is electrically connected to the common electrode 34 through a through-hole formed in the piezoelectric ceramic layer 21b, and, like the large number of individual electrodes 35, another electrode on the signal transmission unit 92. Connected with.

As shown in FIG. 6, 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 referred to as an active portion, and the piezoelectric ceramic in that portion is polarized. 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.

  In addition, by selectively supplying a predetermined drive signal 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 laminated body composed of two piezoelectric ceramic layers, a displacement element 50 that is a piezoelectric actuator having a structure as shown in FIG. 6 as a unit structure is provided for each pressurizing chamber 10. Is formed by a diaphragm 21a, a common electrode 34, a piezoelectric ceramic layer 21b, and an individual electrode 35. The piezoelectric actuator substrate 21 includes a plurality of displacement elements 50 as pressurizing portions. 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 large number of individual electrodes 35 are individually electrically connected to the control unit 100 via the signal transmission unit 92 and wiring so that the potential can be individually controlled.

  In the piezoelectric actuator substrate 21 in the present embodiment, when an electric field is applied in the polarization direction to the piezoelectric ceramic layer 21b by setting the individual electrode 35 to a potential different from that of the common electrode 34, the portion to which this electric field is applied is piezoelectric. It works as an active part that is distorted by the effect. At this time, the piezoelectric ceramic layer 21b expands or contracts in the thickness direction, that is, the stacking direction, and tends to contract or extend in the direction perpendicular to the stacking direction, that is, the surface direction, due to the piezoelectric lateral effect. On the other hand, since the remaining piezoelectric ceramic layer 21a is an inactive layer that does not have a region sandwiched between the individual electrode 35 and the common electrode 34, it does not spontaneously deform. That is, the piezoelectric actuator substrate 21 has the piezoelectric ceramic layer 21b on the upper side (that is, the side away from the pressurizing chamber 10) as a layer including the active portion and the lower side (that is, the side close to the pressurizing chamber 10). This piezoceramic layer 21a is a so-called unimorph type structure having an inactive layer.

  In this configuration, when the control unit 100 sets the individual electrode 35 to a predetermined positive or negative potential with respect to the common electrode 34 so that the electric field and the polarization are in the same direction, a portion sandwiched between the electrodes of the piezoelectric ceramic layer 21b. (Active part) contracts in the surface direction. On the other hand, the piezoelectric ceramic layer 21a, which is an inactive layer, is not affected by an electric field, so that it does not spontaneously shrink and tries to restrict deformation of the active portion. As a result, there is a difference in strain in the polarization direction between the piezoelectric ceramic layer 21b and the piezoelectric ceramic layer 21a, and the piezoelectric ceramic layer 21b is deformed so as to protrude toward the pressurizing chamber 10 (unimorph deformation).

DESCRIPTION OF SYMBOLS 1 ... Printer 2 ... Liquid discharge head 4 ... Flow path member 4a ... Discharge hole surface 5 ... Manifold 5b ... Manifold opening 6 ... Individual supply flow path 8 ... Discharge hole 9 ... Pressure chamber group 10 ... Pressure chamber 12 ... Squeezing 13 ... (Liquid discharge) Head body 21 ... Piezoelectric actuator substrate 21a ... Piezoelectric ceramic layer (vibrating plate)
21b ... Piezoelectric ceramic layer 22-31 ... Plate 32 ... Individual flow path 34 ... Common electrode 35 ... Individual electrode 36 ... Connection electrode 40 ... Reservoir 41b ... Reservoir flow Liquid inlet hole 50 ... Displacement element (pressurizing part)
55 ... Driver IC
82 ... External connector 84 ... Wiring board 86 ... Internal connector 88 ... Guide frame 90 ... Housing 90a ... (Housing) opening 90b ... Side plate 90ba ...・ One side (of side plate) 90c ・ ・ ・ Fitting part (fixed part)
90d: second fixing portion 90e: slit 91a ... first elastic member 91b ... second elastic member 92 ... signal transmission portion 96 ... elastic plate 97 ... heat insulation A ... Center of one side B ... Contact portion of driver IC C ... Center of gravity of contact portion of driver IC

Claims (4)

A liquid discharge head including a liquid discharge head main body that is long in one direction, one or more driver ICs that drive the liquid discharge head main body, and a casing that is joined to the liquid discharge head main body,
The housing includes a side plate extending along the one direction, and one side of the side plate is along the liquid discharge head main body and is a fixed portion that is a part of the one side. It is joined or fitted to the liquid discharge head body,
The driver IC is housed in the housing, and the driver IC is in contact with a contact portion that is a part of the inner surface of the housing of the side plate,
The center of gravity of the contact portion and the fixed portion are arranged on the same side in the one direction with respect to the center of the one side in the one direction ,
Between the one side and the liquid discharge head main body, an elastic member is disposed over the one side, and from the central part of the one side toward both ends, between the one side and the liquid discharge head main body. A liquid discharge head characterized in that the distance is increased . The casing and the liquid discharge head body are joined or fitted at both ends in the one direction of the casing, and a slit is provided between the both ends of the casing and the side plate. Contact is, the slit Te is, the liquid discharge head according to claim 2, characterized in that is closed by an elastic member. A liquid discharge head including a liquid discharge head main body that is long in one direction, one or more driver ICs that drive the liquid discharge head main body, and a casing that is joined to the liquid discharge head main body,
The housing includes a side plate extending along the one direction, and one side of the side plate is along the liquid discharge head main body and is a fixed portion that is a part of the one side. It is joined or fitted to the liquid discharge head body,
The driver IC is housed in the housing, and the driver IC is in contact with a contact portion that is a part of the inner surface of the housing of the side plate,
The center of gravity of the contact portion and the fixed portion are arranged on the same side in the one direction with respect to the center of the one side in the one direction ,
The casing and the liquid discharge head body are joined or fitted at both ends in the one direction of the casing, and a slit is provided between the both ends of the casing and the side plate. A liquid discharge head , wherein the slit is closed by an elastic member . The liquid discharge head according to claim 1, a transport unit that transports a recording medium to the liquid discharge head, and a control unit that controls the liquid discharge head via the driver IC. A recording apparatus comprising:

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