Piezoelectric inkjet printing device with through-holes on piezoelectric plate

Abstract

A piezoelectric inkjet printing device includes a piezoelectric plate and a substrate with at least one row of droplet ejectors. Each droplet ejector includes a pressure chamber on a first surface of the substrate and a nozzle on a second surface of the substrate. The piezoelectric plate is connected to the substrate through a bonding layer. A first electrode layer is located on a first surface of the piezoelectric plate, which is close to the first surface of the substrate. The first electrode layer includes a signal line and a ground line corresponding to each pressure chamber. The second electrode layer is located on the outer second surface of the piezoelectric plate and includes a signal input pad and a return pad. The signal line and the ground line of the first electrode layer are respectively connected to the signal input pad and the return pad on the second electrode layer through conductive through holes.

Description

Technical Field

[0001] The present invention belongs to the field of piezoelectric inkjet printing, and more particularly, to the structure of a piezoelectric inkjet printing device. Background Art

[0002] Inkjet printing is usually done with drop-on-demand or continuous inkjet printing. In drop-on-demand printing, droplets are ejected onto a recording medium using a droplet ejector with a booster (e.g., thermal or piezoelectric) driver. The driver is selectively activated to form and eject a flying droplet of ink that passes through the space between the print head and the recording medium and impacts the recording medium. The formation of the printed image is achieved by controlling the formation of each droplet as required to print the desired image. The desired image may include any dot pattern corresponding to the image data. It may include a graphic or text image. If appropriate ink is used, it may also include a dot pattern or a three-dimensional structure for printing a practical functional device. The ink may include a colored ink, such as cyan, magenta, yellow, or black. Alternatively, the ink may include a conductive material, a dielectric material, a magnetic material, or a semiconductor material for functional printing. The ink may also include biological, chemical, or medical materials.

[0003] During droplet ejection, the motion of the recording medium relative to the printhead can be: keeping the printhead stationary while the recording medium advances past the printhead during droplet ejection; or keeping the recording medium stationary while the printhead moves. The former motion configuration is suitable if the array of droplet ejectors on the printhead can cover the entire print area of ​​interest across the width of the recording medium. Such printheads are sometimes referred to as page width printheads. The second type of printer configuration is a carriage printer, in which the printhead droplet ejector array is smaller than the extent of the print area of ​​interest on the recording medium, and the printhead is mounted on a carriage. In a carriage printer, the recording medium advances a given distance in the direction of media advance and then stops. While the recording medium stops, the carriage carries the printhead whose nozzles are ejecting droplets in a carriage scanning direction that is substantially perpendicular to the media advance direction. After the printhead mounted on the carriage traverses the print medium while printing a strip of image, the recording medium is advanced; the direction of motion of the carriage is then reversed; the printed image is thus formed strip by strip.

[0004] The drop ejector in a drop-on-demand inkjet printhead includes a pressure chamber with an ink inlet to supply ink to the pressure chamber and a nozzle orifice for ejecting ink droplets out of the pressure chamber. In a piezoelectric inkjet printing device, one wall of the pressure chamber includes a piezoelectric element, which, when a voltage pulse is applied, causes the wall to deflect and deform into the pressure chamber filled with ink, thereby forcing the ink through the nozzle orifice. Piezoelectric inkjets have significant advantages in chemical compatibility and ink jettability with a wide variety of inks (including aqueous inks, solvent-based inks, and UV-curable inks), and the ability to eject ink droplets of different sizes by modifying the electrical pulse.

[0005] There are still technical challenges to be solved for piezoelectric inkjet printing devices. Because the amount of piezoelectric displacement per volt of voltage is small, the piezoelectric chamber wall area must be much larger than the nozzle area in order to eject a useful amount of droplets, so each droplet ejector is relatively large. The width of each droplet ejector in a row of droplet ejectors is limited by the spacing between the nozzles in that row. As a result, the length dimension of the pressure chamber is usually much larger than the width dimension. Printing applications that require high resolution and high-volume printing require a large number of droplet ejector arrays with closely arranged nozzles. By properly timing the ejection of each row of droplet ejectors, the staggered rows of nozzles can produce close-range dots on the recording medium. However, for many staggered rows, the size of the piezoelectric inkjet printing device becomes very large.

[0006] Another challenge is that, unlike thermal inkjet devices, which often include integrated logic and drive electronics to reduce the number of device pins, piezoelectric inkjet devices typically have multiple individual pins per drop ejector that need to be connected to a driver circuit board. In order to independently apply voltage to the piezoelectric element across each drop ejector to eject a drop when needed, each drop ejector needs to be connected to two electrodes. These two types of electrodes are sometimes referred to as positive and negative electrodes, or as individual and common electrodes.

[0007] Some types of piezoelectric inkjet printing devices are constructed with two types of electrodes on opposite surfaces of the piezoelectric element. In order to electrically interconnect the piezoelectric inkjet printing device to a drive circuit board, it is advantageous to place the two types of electrodes on the same outer surface of the piezoelectric inkjet printing device.

[0008] U.S. Patent No. 5,255,016 discloses a piezoelectric inkjet printing device in which positive and negative comb electrodes are formed on the outer surface of a piezoelectric plate. The teeth of the comb extend across the entire width of the drop ejector, at least in certain areas. A portion of the positive electrode extends along one edge of the piezoelectric plate, and a portion of the negative electrode extends along the opposite edge of the piezoelectric plate. Each drop ejector has a separate piezoelectric plate, which makes it difficult to manufacture large arrays of closely spaced drop ejectors.

[0009] U.S. Patent No. 6,243,114 discloses a piezoelectric inkjet printing device, wherein the common electrode on the outer surface of the piezoelectric plate is in a comb shape, one electrode tooth of which extends along each side wall of the pressure chamber, and the central common electrode tooth extends along the length of the pressure chamber. Two single electrodes extend along the length of the pressure chamber on both sides of the central common electrode tooth.

[0010] U.S. Patent No. 5,640,184 discloses a piezoelectric inkjet printing device in which pressure chambers of a row of nozzles extend alternately in opposite directions from the row of nozzles. A common electrode on the surface of a piezoelectric plate extends along the row of nozzles and has electrode teeth extending alternately in opposite directions on the side walls of the pressure chambers. Interlaced between the electrode teeth of the common electrode are spaced arrays of individual electrodes that are located directly above the pressure chambers. When a voltage is applied to the individual electrodes, the piezoelectric plate mechanically deforms in a shear mode to recess into the corresponding pressure chamber, thereby causing the ejection of ink droplets.

[0011] Chinese patent application publication No. 107344453A discloses a piezoelectric inkjet printing device, such as Figure 1 and Figure 2 shown. Figure 1 and 2 Taken from '453, reproduced for clarity in Figure 1 Some additional labels are added. The substrate 100 includes a first side 101, and a row of pressure chambers 110 are distributed on the first side 101. Each pressure chamber 110 is bounded by side walls 161 and 162. A channel 130 leads from the pressure chamber 110 to a nozzle 132 arranged on the second side 102 of the substrate 100. The width of the pressure chamber 110 between the side walls 161 and 162 is W. An ink groove 120 is fluidly connected to one end of each pressure chamber 110 to provide ink to them. A damping structure 140 including a plurality of pillars 141 is arranged in each pressure chamber 110, between the ink groove 120 and the channel 130. The drive cover plate 200 includes a piezoelectric plate 210, which can be made of, for example, lead zirconate titanate piezoelectric ceramic (PZT) material. The first surface 211 of the piezoelectric plate 210 is bonded to the first side 101 of the substrate 100. An electrode layer 220 is disposed on the outer second surface 212 of the piezoelectric plate 210. The electrode layer 220 includes a positive electrode 221 disposed along the length of the pressure chamber 110; and a negative electrode 222 disposed along the length of the side walls 161 and 162 between the pressure chambers 110. An ink inlet 230 passes through the piezoelectric plate 210 to introduce ink from an external ink supply source to the ink tank 120 in the substrate 100. The nozzle 132 extends outward from the flow channel 131 in the silicon material layer 310, passes through the oxide layer 320 and the nozzle layer 330 ( Figure 2 ).

[0012] It has been found that the displacement of the pressure chamber wall of a piezoelectric inkjet printing device in which both types of electrodes are on the outer surface of the piezoelectric plate away from the pressure chamber is highly dependent on the thickness of the piezoelectric plate. For example, the combined displacement of the plate wall of a 40 micron thick plate is 10 times higher than that of a 100 micron thick plate. In contrast, for a piezoelectric inkjet printing device in which both types of electrodes are on the inner surface of the piezoelectric plate close to the pressure chamber, the combined displacement of the plate wall of a 40 micron thick plate is only 4% higher than that of a 100 micron thick plate. In addition, for a 40 micron thick plate, the displacement of the former is twice as large as that of the latter when the electrodes are located on the outer surface of the piezoelectric plate. Therefore, a droplet ejector configuration with electrodes on the inner surface of the piezoelectric plate can operate with higher efficiency at lower voltages or smaller pressure chamber sizes. In addition, the ejected droplet velocity and volume are less sensitive to manufacturing variability in the thickness of the piezoelectric plate, thereby improving print quality.

[0013] Although the above-described solder joint configuration is effective in facilitating electrical connection to electrodes on the inner surface of the piezoelectric plate near the pressure chamber, in certain applications, it is most preferred to make connections on the outer surface of the piezoelectric plate of a piezoelectric inkjet printing device. What is needed is an electrode and wire configuration that uses connection pads on the outer surface of the piezoelectric plate to facilitate electrical interconnection to electrodes located on the inner surface of the piezoelectric plate. Further, there is also a need for improved arrangement of drop ejectors on a piezoelectric inkjet printing device in a space-saving manner to achieve high-resolution and high-throughput printing. Summary of the invention

[0014] According to one aspect of the present invention, a piezoelectric inkjet printing device includes a piezoelectric plate and a substrate, and at least one array of droplet ejectors is arranged on the substrate so that each row is aligned along the row direction. Each droplet ejector includes a pressure chamber arranged on the first surface of the substrate, and the pressure chamber is bounded by a first side wall and a second side wall. Each droplet ejector includes a nozzle formed in a nozzle layer on the second surface of the substrate opposite to the first surface. The piezoelectric plate has a first surface arranged near the first surface of the pressure chamber, and has a second surface opposite to the first surface and outside. A first group and a second group of conductive through holes extend from the first surface to the second surface outside. A bonding layer is arranged between the piezoelectric plate and the substrate. A first electrode layer is arranged on the first surface of the piezoelectric plate. The first electrode layer includes a first signal line corresponding to each droplet ejector, and each first signal line is connected to a corresponding through hole in a first group of conductive through holes. The first electrode layer also includes ground wires arranged on both sides of each pressure chamber, and the ground wires are connected to a corresponding through hole in at least one second group of conductive through holes. The second electrode layer is located on the second surface of the piezoelectric plate. The second electrode layer includes a signal input pad corresponding to each first signal line, whereby each signal input pad is connected to a corresponding through hole in the first group of conductive through holes. The second electrode layer further includes at least one return ground pad, which is electrically connected to a plurality of through holes in the second group of conductive through holes. At least one common ground line is connected to at least one return ground pad.

[0015] The present invention has the advantage that the electrode structure configuration can achieve high efficiency droplet ejection while reducing the variability of droplet velocity and volume. In addition, the wires and corresponding connection pad structure configuration of the piezoelectric inkjet printer facilitate compact and reliable electrical interconnection to the printhead package. Another advantage is that the piezoelectric droplet ejector is constructed in a space-saving manner and can achieve high printing resolution and high printing output. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 An exploded schematic diagram showing a prior art piezoelectric drop ejector array configuration;

[0017] Figure 2 Shows Figure 1 A cross section of a single droplet ejector of the type shown;

[0018] Figure 3A A cross section of a portion of the piezoelectric plate is shown;

[0019] Figure 3B Shows the corresponding Figure 3A A cross section of a portion of a substrate of a portion of a piezoelectric plate is shown;

[0020] Figure 4A A top view of three droplet ejectors in a substrate is shown;

[0021] Figure 4B Shows the Figure 4A A top view of the circuit on the piezoelectric plate corresponding to the droplet ejector shown;

[0022] Figure 5 A top view of a single drop ejector and some corresponding wiring is shown;

[0023] Figure 6 According to one embodiment, a portion of a piezoelectric inkjet printing device is shown;

[0024] Figure 7 According to another embodiment, a portion of another piezoelectric inkjet printing device is shown;

[0025] Figure 8 The occlusion layer with windows is shown;

[0026] Fig. 9 A portion of yet another piezoelectric inkjet-printing device is shown according to yet another embodiment.

[0027] The purpose of the drawings should be understood to be for illustrating the concepts of the present invention and may not be drawn to scale. Wherever possible, the same reference numerals are used to designate the same features that are common to the drawings. DETAILED DESCRIPTION

[0028] The present invention includes various combinations of the embodiments described herein. References to "a particular embodiment" and the like refer to features present in at least one embodiment of the present invention. Separate references to "one embodiment" or "a particular embodiment" and the like do not necessarily refer to the same one or more embodiments; however, unless explicitly stated or obvious to one skilled in the art, these embodiments are not mutually exclusive. When referring to "a method" or "multiple methods" and similar terms, the use of the singular or plural is non-restrictive. It is specifically noted that the use of "or" in this article has no exclusive meaning unless otherwise explicitly stated or required by the context. Words such as "above...", "below...", "above..." or "below..." are intended to describe the positional relationship between features located in different planes, but it should be understood that in one device orientation, a feature of one device is located "above" another feature, and if the device is turned upside down, the feature of the device will be located "below" another feature.

[0029] According to an embodiment of the present invention, the piezoelectric inkjet printing device has a signal line and a ground line, and the signal line and the ground line are arranged in a first electrode layer on the inner surface of the piezoelectric plate near the pressure chamber. In order to facilitate the electrical interconnection of the piezoelectric inkjet printing device, the second electrode layer is arranged on the outer surface of the piezoelectric plate. Through the conductive through hole penetrating the piezoelectric plate, the signal line and the ground line in the first electrode layer are respectively connected to the signal input pad and at least one return pad in the second electrode layer.

[0030] Figure 3A A cross section of the piezoelectric plate 210 along the dashed line 3-3 is shown ( Figure 6 ). Figure 3B A cross section of a corresponding portion of the substrate 100 is shown. The piezoelectric plate referred to herein is generally an independent component that is assembled to the substrate, rather than a thin film deposited on the substrate. The thickness T of the piezoelectric plate 210 is greater than 10 microns and less than 100 microns (usually greater than 40 microns for ease of handling during assembly). The substrate 100 includes a pair of pressure chambers 111 and 112, which extend outward from a central region. Each pressure chamber 111 and 112 includes a channel 130 leading to a nozzle 132 disposed in the nozzle layer 330. The first signal line 251 (a portion of the first electrode layer 240) on the inner first surface 211 of the piezoelectric plate 210 extends above the pressure chambers 111 and 112 in the assembled piezoelectric inkjet printing device. The first electrode layer 240 also includes a common ground line 464. A bonding layer 270 is disposed on the first signal line 251 and other portions of the first surface 211 of the piezoelectric plate 210. The bonding layer 270, for example, can be a polymer adhesive. The bonding layer 270 is located between the piezoelectric plate 210 and the substrate 100, and bonds the piezoelectric plate 210 to the first side 101 of the substrate 100. In addition, the bonding layer 270 isolates the ink in the pressure chambers 111 and 112 from the wires and the piezoelectric plate 210. In some embodiments, an additional insulating layer (not shown) may be added between the bonding layer 270 and the piezoelectric plate 210 or between the bonding layer 270 and the first side 101 of the substrate 100 to improve reliability. The additional insulating layer may be, for example, silicon oxide or silicon nitride.

[0031] like Figure 3A As shown, the second electrode layer 740 is located on the outer second surface 212 of the piezoelectric plate 210. The second electrode layer 740 includes a plurality of second signal lines 751 and signal input pads 755, and a common ground line 764. Figure 3AIn the embodiment shown, there is a common ground line 264 in the first electrode layer 240, and there is also a common ground line 764 in the second electrode layer 740. In other embodiments described below, there is a common ground line 264 or a common ground line 764, but not both. The first electrode layer 240 and the second electrode layer 740 can each include one or more layers of gold, copper, and chromium.

[0032] The conductive vias electrically connect corresponding portions of the first electrode layer 240 and the second electrode layer 740. The first group of conductive vias includes a signal via 775 for connecting the first signal line 251 to the second signal line 751. Figure 3A In the example shown, the second set of conductive vias includes ground vias 784 for connecting the common ground line 264 to the common ground line 764. The conductive vias are formed by first drilling a hole of appropriate size through the piezoelectric plate 210 using a process such as laser ablation, abrasive blasting or etching. For simplicity, Figure 3A The through holes 775 and 784 are shown to have a constant diameter through the piezoelectric plate 21, but actual through holes are typically tapered so that the area is larger at either the first surface 211 or the second surface 212. The cross-section of the through hole can be a circle, but it can also be other shapes. The hole through the piezoelectric plate 210 is then plated by electroplating and / or chemical plating, such as copper, nickel or gold. In some embodiments, only the hole walls are covered with metal. In other embodiments, the holes are filled with metal. Both types are referred to herein as conductive vias. The first signal line 251 is connected to the signal through hole 775 through the first through hole contact 771. The second signal line 751 is connected to the signal through hole 775 through the second through hole contact 772. In Figure 3A In the example shown, the common total ground line 264 is connected to the ground via 784 at the first via contact 781 , and the common total ground line 764 is connected to the ground via 784 at the second via contact 782 .

[0033] Figure 4A It is shown that on the substrate 100 ( Figure 3B ) is a top view of three droplet ejectors 150 formed in a row on a surface of a pressure chamber 110, each droplet ejector 150 comprising a pressure chamber 110 and a nozzle orifice 132. The nozzle orifices 132 (and the droplet ejectors 150) are aligned along the row direction 51, with the centers of adjacent nozzle orifices spaced at a pitch p. The pressure chamber 110 has a width W along the row direction 51 and is bounded by side walls 161 and 162, each of which has a width s, such that W+s=p. In order to provide a sufficiently large area of ​​the pressure chamber 110, it is advantageous in many embodiments for W to be greater than 0.8p. In other words, s is typically less than 0.2p. The nozzle orifice 132 is located near the first end 115 of the pressure chamber 110. At Figure 4A In the example shown, ink is drawn from ink tank 120 (eg Figure 1 and Figure 2 The ink tank 120 provides ink to the plurality of pressure chambers 110. In other examples described below, the ink enters the ink inlet 121 directly from the edge of the substrate 100. The filter 146 may include a column similar to the first end 115. Figure 1 The restrictor 145 provides flow resistance (same as the filter 146), and when a drop of ink is ejected from the pressure chamber 110, the restrictor 145 helps to limit the flow of ink to the ink inlet channel 121, thereby directing more of the pressure generated by the deformation of the piezoelectric plate to push the ink drop.

[0034] Figure 4B Shows the Figure 4A The first signal line 251 and the ground line 261 are part of the first electrode layer 240 and are arranged on the first surface 211 of the piezoelectric plate 210 ( Figure 3A The width and spacing of the first signal line 251 and the ground line 261 are set to efficiently drive the piezoelectric plate 210. The first signal line 251 is electrically connected to the second signal line 751 in the second electrode layer 740 through the signal through hole 775, and the second electrode layer 740 is located on the outer second surface 121 of the piezoelectric plate 210 ( Figure 3A ). The signal input pad 755 is disposed in the second electrode layer 740 and is connected to the second signal line 751. Figure 4B and 7 In the example shown, the ground line 261 is connected to the ground line 761 in the second electrode layer 740 through the ground line through hole 785. Figure 3A and 6 In the example shown, ground via 784 connects common total ground 264 to common total ground 764. Some embodiments have ground via 785 connecting ground 261 to ground 761. Other embodiments have ground via 784 connecting common total ground 264 to common total ground 764. Still other embodiments have both ground vias 784 and 785.

[0035] Figure 5 A top view of a single drop ejector 150 (dashed line) is shown, which is disposed in the substrate 100 below the corresponding first signal line 251 and ground line 261 on the piezoelectric plate 210. The first signal line 251 is disposed above each corresponding pressure chamber 110 and extends in a direction 52 perpendicular to the row direction 51. Figure 5In the example shown, the first signal line 251 is located above the center of the corresponding pressure chamber 110. Each first signal line 251 is connected to a second signal input line 751 and a signal input pad 755 on the second surface 121 of the corresponding piezoelectric plate through a signal through hole 775. The nozzle 132 is located near the first end 115 of the pressure chamber 110, close to the signal through hole 775. The width b of the first signal line 251 ( Figure 4B ) is greater than the width W of the pressure chamber 110 ( Figure 4A ). The first signal line width b is also greater than the thickness T of the piezoelectric plate 210 ( Figure 3A ). The ground line 261 is above the first side wall 161 and the second side wall 162 and is aligned with the side walls. The ground line 261 is generally located between the corresponding pressure chambers 110 and extends in a direction 52 perpendicular to the row direction 51. In many embodiments, the width c of the ground line 261 is ( Figure 4B ) is greater than the width s of the side walls 161 and 162 ( Figure 4A The distance d between the first signal line 251 and the adjacent ground line 261 ( Figure 4B ) is usually greater than 0.1W( Figure 4A The distance d between the first signal line 251 and the adjacent ground line 261 is usually greater than 0.5T and less than 2T ( Figure 3A ).

[0036] Overlooking Figure 6 1 shows a portion of a piezoelectric inkjet printing device 9 according to an embodiment of the present invention. A pair of staggered rows 181 and 182 of drop ejectors 150 (similar to the above referenced Figures 3A to 5 1 and 1 . The droplet ejectors 150 in each row 181 are arranged on the substrate 100. Each row of droplet ejectors 150 is aligned along the row direction 51. The first row 181 and the second row 182 are spaced apart from each other along the direction 52 perpendicular to the row direction 51. Each droplet ejector 150 in the first row 181 includes a pressure chamber 111, and each droplet ejector in the second row 182 includes a pressure chamber 112. These pressure chambers 111 and 112 are arranged on the first face 101 of the substrate 100. Figure 6In the example shown, ink is directly input to the ink inlet 121 of each drop ejector 150 from the edge of the substrate 100, and the edge of the substrate 100 extends along the row direction 51. The pressure chambers 111 and 112 are bounded by the first side wall 161 and the second side wall 162. Each drop ejector also includes a nozzle 132 fluidly connected to the corresponding pressure chamber 111 or 112. The nozzle 132 is arranged in the nozzle layer 330 on the second side 102 of the substrate 100. The first electrode layer 240 is located on the inner first surface 211 of the piezoelectric plate 210, and includes a first signal line 251, each of which corresponds to each drop ejector 150 in the rows 181 and 182 of the drop ejectors 150. Each first signal line 251 is connected to a corresponding signal input pad 755 through a signal through hole 775 and a second signal line 751, and the input pad 755 is located in the second electrode layer 740 on the outer second surface 212 of the piezoelectric plate. The second electrode layer 740 further includes at least one common ground line 764, which is connected to the common ground line 264 in the corresponding first electrode layer 240 through the ground line through hole 784. Figure 6 The common total ground line 264 is blocked by 764). The ground line 261 is above and aligned with the first and second sidewalls 161 and 162 of each pressure chamber and is connected to the common total ground line 264 in the first electrode layer 240. The common total ground line 764 extends along the row direction 51 and passes to the return ground pad 765. Figure 6 In the example shown, the common general ground line 764 is located between the signal input pads 755 of the drop ejectors 150 of the first staggered row 181 and the signal input pads 755 of the drop ejectors 150 of the second staggered row 182. In addition, the signal input pads 755 of the drop ejectors of the first staggered row 181 and the signal input pads 755 of the drop ejectors of the second staggered row 182 are located between the drop ejector orifices 132 of the first staggered row 181 and the drop ejector orifices 132 of the second staggered row 182. This structural arrangement of the signal input pads 755 and the return ground pads 765 is very conducive to providing electrical interconnection of the piezoelectric inkjet printing device 9 to the print head package (not shown) in a compact area.

[0037] The orifices 132 in row 181 are spaced apart by a pitch p, and the orifices 132 in row 182 are also spaced apart by a pitch p. The two rows are offset by a distance p / 2 along the row direction 51. As a result, if the recording medium (not shown) is moved relative to the piezoelectric inkjet printing device 9 along the direction 52, a row of composite print dots with a dot pitch of p / 2 can be printed on the recording medium by appropriately timing the ejection of ink drops from the drop ejectors in row 181 relative to row 182. It is preferred that the piezoelectric inkjet printing device 9 have a smaller print area, i.e., the distance along the direction 52 between the orifices 132 in row 181 and the orifices 132 in row 182 is relatively short. To accomplish this, drop ejectors 150 in rows 181 and 182 are oriented in opposite directions such that orifices 132 in first staggered row 181 are adjacent to orifices 132 in second row 182 and such that pressure chambers 111 in first row 181 and pressure chambers 112 in second row 182 extend from their respective orifices 132 in opposite directions in direction 52. Fig. 9 In the illustrated embodiment, the printing area of ​​the piezoelectric inkjet printing device 9 can be further reduced.

[0038] Figure 7 Shows the Figure 6 A similar embodiment, but with exceptions. The common ground line 764 is connected to the common ground line 264 in the corresponding first electrode layer 240 through the ground line through hole 784 (such as Figure 6 Different from Figure 7 In the example of FIG. 7 , the ground line 261 on the first electrode layer 240 is connected to the ground line 761 on the second electrode layer 760 through the ground line through hole 785 . The ground line 761 is connected to the common total ground line 764 , and the common total ground line 764 is connected to the return pad 765 .

[0039] As if looking down Figure 8 As shown, in order to provide a more reliable, short-circuit-free electrical interconnection, an electrically insulating masking layer 280 can be set above the electrode layer 740, and the masking layer 280 includes a window 281 above the signal input pad 755 and a window 282 above the return pad 765 to expose the pads for electrical interconnection.

[0040] As above Figures 3A to 7As described, the piezoelectric inkjet printing device 9 includes a substrate 100, an array of at least one row 181 of droplet ejectors 150, a piezoelectric plate 210, a bonding layer 270, a first electrode layer 240, a second electrode layer 740 and at least one common ground line 264 or 764. The droplet ejectors 150 in each row 181 and 182 are aligned along the row direction 51. Each droplet ejector 150 includes a pressure chamber 110 or 111 or 112, which is located on the first side 101 of the substrate 100. The pressure chamber is bounded by a first side wall 161 and a second side wall 162. Each droplet ejector 150 also includes a nozzle 132, which is located in the nozzle layer 330 on the second side 102 of the substrate 100 opposite to the first side 101. The piezoelectric plate 210 has a first surface 211 close to the first side 101 of the substrate 100, and an outer second surface opposite to the first surface 211. The first and second groups of conductive vias extend from the first surface 211 to the outer second surface 212. The bonding layer 270 is located on the pressure chamber 110 or 111 or 112. The first electrode layer 240 is located on the first surface 211 of the piezoelectric plate. The first electrode layer 240 includes a first signal line 251 corresponding to each pressure chamber 110 or 111 or 112. Each first signal line 251 is connected to a corresponding signal via 775 in the first group of conductive vias. The first electrode layer 240 also includes a ground line 261 located on both sides of each pressure chamber 110 or 111 or 112. The ground line 261 is connected to at least one corresponding ground via 784 or 785 in the second group of conductive vias. The second electrode layer 740 is disposed on the second surface 212 of the piezoelectric plate 210. The second electrode layer 740 includes a signal input pad 755 corresponding to each first signal line 251, wherein each signal input pad 755 is connected to a corresponding signal via 775 in the first group of conductive vias. The second electrode layer 740 further includes at least one ground return pad 765 connected to a plurality of ground vias 784 or 785 in the second group of conductive vias. The at least one ground return pad 765 is connected to at least one common ground line 264 or 764.

[0041] exist Figure 6 and Figure 7 In the example shown, at least one common ground line 764 is disposed in the second electrode layer 740 on the second surface 212 of the piezoelectric plate 210. Figure 6-7 In the example of FIG. 1 , the array of droplet ejectors 150 includes at least two staggered rows 181 and 182 of droplet ejectors 150 disposed on a common substrate 100, wherein the droplet ejectors in each row 181 and 182 are aligned along a row direction 51 and separated from other rows along a direction 52 perpendicular to the row direction 51. Figure 6-7In the example of , the array includes at least one pair of staggered rows 181 and 182 of drop ejectors 150, wherein at least one common ground line 264 or 764 is disposed between the staggered rows 181 and 182. Further, in Figure 6-7 In the example, the nozzle holes 132 of the first staggered row 181 are adjacent to the nozzle holes 132 of the second staggered row 182, and the pressure chambers 111 of the first staggered row 181 and the pressure chambers 112 of the second staggered row 182 extend from the respective nozzle holes 132 in opposite directions.

[0042] Fig. 9 FIG. 2 shows a top view of a portion of a piezoelectric inkjet printing device 9 according to another embodiment of the present invention. In addition to the common ground lines 264 and 266 being disposed on the first electrode layer 240 and disposed in a different manner, Fig. 9 The structure shown in the Figure 6 and 7 Similar to that shown. Fig. 9 In the embodiment shown, the first common ground line 264 is disposed near the second end 116 of the pressure chambers 111 in the corresponding first row 181, and the second common ground line 266 is disposed near the second end 116 of the pressure chambers 112 in the corresponding second row 182. The signal via 775 connects the first signal line 251 with the second signal line 751 and the signal input pad 755, and is like Figure 6 and 7 As in the embodiment, the signal via 775 is disposed near the first end 115 of the pressure chambers 111 and 112 of the two rows 181 and 182. The first common total ground line 264 in the first electrode layer 240 is connected to the return ground pad 765 in the second electrode layer 740 through the ground via 786. The second common total ground line 266 in the first electrode layer 240 is connected to the return ground pad 767 in the second electrode layer 740 through the ground via 787. Fig. 9 In the example shown, Figure 8 A similar masking layer 280 as shown may be used to expose the signal input pads 755 and the ground return pads 765 and 767 to facilitate electrical interconnection.

[0043] The above reference Figure 3A , 3B, 4A, 4B, 5, 6, 7 and 9 are well suited for locally deflectable deformable piezoelectric plates 210, which, when a voltage pulse is applied to electrodes corresponding to pressure chambers 110 or 111 or 112, cause local deflection of the piezoelectric plates 210 into one or more pressure chambers 110 or 111 or 112, thereby ejecting ink drops. For such applications, the piezoelectric plates 210 are polarized in a direction perpendicular to the first surface 211. In order for the piezoelectric plates 210 having a thickness T to be effectively deflected into the pressure chambers 110 or 111 or 112 having a width W, it is advantageous that T is less than 0.5W, and in some embodiments, T is less than 0.3W.

[0044] In an exemplary embodiment, the pitch p of each row is 0.01 inches, so that the nozzles 132 in each row are arranged at 100 nozzles per inch, and the two rows of drop ejectors can print a composite dot row of 200 dots per inch. For the pitch p = 0.01 inches = 254 microns, the pressure chamber width W can be 224 microns, and the sidewall width s can be 30 microns, so as mentioned above Figure 4A As mentioned above, s is less than 0.2p. The piezoelectric plate 210 itself is about 50 microns thick, which is beneficial for it to be less fragile. In such an example, from Figure 4A and 4B It can be seen that the nozzle pitch p is equal to the width b of the signal line 251 plus the width c of the ground line 261 plus twice the distance d between the signal line 251 and the ground line 261, that is, p=b+c+2d. In one example, the width b of the signal line 251 is 90 microns, the width c of the ground line 261 is 90 microns, and the distance d is 37 microns. In the example where W=224 microns and d=37 microns, the distance d between the signal line 251 and the adjacent ground line 261 is greater than 0.1W. In addition, in this example, the width b of the signal line 251 is greater than 0.1W. In addition, for the piezoelectric plate 210 with a thickness T of 50 microns, the distance d=37 microns between the signal line 251 and the adjacent ground line 261 is greater than 0.5T and less than 2T, and the width b of the signal line 251 is greater than 0.2T.

[0045] The above reference Figure 6 , 7 In the embodiments described in Figures 1 and 9, there is only a single pair of staggered rows 181 and 182 of drop ejectors 150. In other embodiments (not shown), there may be more pairs of staggered rows of drop ejectors to provide higher print resolution or increase ink coverage, or each pair of staggered rows may be used to eject different types of ink (e.g., different colors of ink), or each pair of staggered rows may be used to eject ink drops of a different size range.

[0046] The invention has been described in detail herein with particular reference to certain preferred embodiments thereof, but it will be understood that variations and modifications are encompassed within the spirit and scope of the invention.

Claims

1. A piezoelectric inkjet printing device, characterized in that: include: a substrate; An array of at least one row of droplet ejectors, each row being aligned along a row direction, each droplet ejector comprising: A pressure chamber is disposed on the first side of the substrate, the pressure chamber being bounded by a first side wall and a second side wall; and A nozzle hole is arranged in the nozzle hole layer on the second surface of the substrate opposite to the first surface of the substrate; A piezoelectric plate, comprising: A first surface is adjacent to the first side of the substrate; an outer second surface opposite the first surface; and first and second sets of electrically conductive vias, each via extending from the first surface to the outer second surface; A bonding layer is disposed between the piezoelectric plate and the substrate; A first electrode layer is disposed on a first surface of the piezoelectric plate, wherein the first electrode layer comprises: a first signal line corresponding to each pressure chamber, each first signal line connected to a corresponding through hole in the first set of conductive through holes; and Ground wires are disposed on both sides of each pressure chamber, and the ground wires are connected to at least one corresponding through hole in the second set of conductive through holes; A second electrode layer is disposed on the second surface of the piezoelectric plate, wherein the second electrode layer comprises: a signal input pad corresponding to each first signal line, wherein each signal input pad is connected to a corresponding via in the first set of conductive vias; and At least one ground return pad is electrically connected to a plurality of vias in the first set of conductive vias; and At least one common main ground line is electrically connected to at least one ground return pad.

2. The piezoelectric inkjet printing device according to claim 1, characterized in that: At least one common ground line is disposed in a second electrode layer on a second surface of the piezoelectric plate.

3. The piezoelectric inkjet printing device according to claim 1, characterized in that: At least one common ground line is disposed in a first electrode layer on a first surface of the piezoelectric plate.

4. The piezoelectric inkjet printing device according to claim 1, characterized in that: In the second group of conductive vias, at least a portion of the plurality of vias extend from a common main ground line located in the first electrode layer to a common main ground line located in the second electrode layer.

5. The piezoelectric inkjet printing device according to claim 1, characterized in that: The first electrode layer and the second electrode layer each contain a copper layer.

6. The piezoelectric inkjet printing device according to claim 5, characterized in that: The first electrode layer and the second electrode layer each include at least one chromium layer.

7. The piezoelectric inkjet printing device according to claim 1, characterized in that: The conductive via includes at least one of copper, gold, and nickel.

8. The piezoelectric inkjet printing device according to claim 1, characterized in that: Each conductive via is filled with a metal.

9. The piezoelectric inkjet printing device according to claim 1, characterized in that: The conductive via has a tapered shape.

10. The piezoelectric inkjet printing device according to claim 1, characterized in that: The bonding layer is a polymer adhesive layer.

11. The piezoelectric inkjet printing device according to claim 1, characterized in that: The droplet ejector array includes at least one pair of staggered droplet ejector rows disposed on a substrate, each row being aligned along a row direction and spaced apart from other rows along a direction perpendicular to the row direction.

12. The piezoelectric inkjet printing device according to claim 11, characterized in that: The droplet ejector array includes at least one pair of staggered droplet ejector rows, wherein at least one common ground line is disposed between each pair of staggered rows.

13. The piezoelectric inkjet printing device according to claim 11, characterized in that: The nozzle holes of the first staggered row are adjacent to the nozzle holes of the second staggered row, wherein the pressure chambers of the first staggered row and the pressure chambers of the second staggered row extend from the respective nozzle holes in opposite directions.

14. The piezoelectric inkjet printing device according to claim 13, characterized in that: The signal input pad of the first staggered droplet ejector row and the signal input pad of the second staggered droplet ejector row are arranged between the nozzles of the first staggered droplet ejector row and the nozzles of the second staggered droplet ejector row; the common ground line is arranged between the signal input pad of the first staggered droplet ejector row and the signal input pad of the second staggered droplet ejector row.

15. The piezoelectric inkjet printing device according to claim 1, characterized in that: The distance between the first signal line and the adjacent ground line is greater than one tenth of the width of the pressure chamber.

16. The piezoelectric inkjet printing device according to claim 1, characterized in that: The width of the first signal line is greater than one tenth of the width of the pressure chamber.

17. The piezoelectric inkjet printing device according to claim 1, characterized in that: A distance between the first signal line and the adjacent ground line is greater than half the thickness of the piezoelectric plate and less than twice the thickness of the piezoelectric plate.

18. The piezoelectric inkjet printing device according to claim 1, characterized in that: The width of the first signal line is greater than two tenths of the thickness of the piezoelectric plate.

19. The piezoelectric inkjet printing device according to claim 1, characterized in that: Each signal line extends in a direction perpendicular to the row direction and is disposed on the center of a corresponding pressure chamber.

20. The piezoelectric inkjet printing device according to claim 1, characterized in that: The ground line is disposed at a middle position between the corresponding pressure chambers and extends in a direction perpendicular to the row direction.

21. The piezoelectric inkjet printing device according to claim 1, characterized in that: The invention further comprises a shielding layer disposed on the second electrode layer, wherein the shielding layer comprises windows on the signal input pad and at least one ground return pad.

22. The piezoelectric inkjet printing device according to claim 1, characterized in that: The width of the ground line is greater than the width of the side wall of the pressure chamber.

23. The piezoelectric inkjet printing device according to claim 1, characterized in that: The piezoelectric plate is polarized in a direction perpendicular to the first surface of the piezoelectric plate.

24. The piezoelectric inkjet printing device according to claim 1, characterized in that: The thickness of the piezoelectric plate between the first surface and the second surface is greater than 10 microns and less than 100 microns.

Images