JP4915422B2 - Wiring structure of droplet discharge head - Google Patents

Description

  The present invention relates to a wiring structure applied to a droplet discharge head provided with a piezoelectric actuator for discharging a liquid.

  As an example of a droplet discharge head, an inkjet head mounted on an inkjet printer that records an image on a recording medium is known. In an ink jet head, in order to increase the number of nozzles and make a recorded image high quality, it is required to increase the density of pressure chambers provided corresponding to each nozzle. When the pressure chambers are made dense, the distance between the adjacent pressure chambers is shortened, so that the influence on the adjacent pressure chambers when driving the piezoelectric actuator, so-called crosstalk, occurs. For example, according to the ink-jet head of Patent Document 1, individual electrodes are formed on the layer farthest from the pressure chamber among the piezoelectric layers constituting the piezoelectric actuator, and grooves are formed on both sides of the individual electrodes. For this reason, when the active portion is deformed by the piezoelectric effect, the deformation of the region between the pressure chambers can be absorbed by this groove.

JP 2003-311954 A

  When grooves are formed on both sides of the individual electrode in this way, the deformation of the active part is less likely to propagate to the adjacent pressure chambers compared to the case where grooves are not formed, and the crosstalk can be suppressed. However, the pressure chambers are required to be arranged more densely due to the demand for higher quality, and more excellent measures against crosstalk are required.

  Therefore, the present invention has an object to provide a droplet discharge head that can satisfactorily suppress crosstalk even when the pressure chamber is made dense, and is applied to a droplet discharge head configured to achieve such an object. The purpose is to provide an appropriate wiring structure.

  In order to achieve the above object, a droplet discharge head according to the present invention is a droplet discharge head including a piezoelectric actuator for selectively discharging liquid in a plurality of pressure chambers, and the piezoelectric actuator includes In order to selectively discharge the liquid in the pressure chamber, an individual electrode to which a drive voltage is selectively applied, a first constant potential electrode to which a first constant potential is applied, and a second constant potential are applied. And a second constant potential electrode. According to this droplet discharge head, the piezoelectric actuator can be provided with an active portion formed by the individual electrode and the first constant potential electrode and an active portion formed by the individual electrode and the second constant potential electrode. So-called crosstalk can be satisfactorily suppressed by the operation of the two active portions.

  A wiring structure of a droplet discharge head according to the present invention is a wiring structure of a droplet discharge head that is applied to such a droplet discharge head and has a wiring for driving the piezoelectric actuator, A wiring board provided with wiring; and a driver that is mounted on the wiring board and selectively outputs the drive voltage, and the plurality of wirings include a power supply line for supplying power to the driver; A ground line for setting the driver to a ground potential; a first constant potential wiring for supplying the first constant potential to the first constant potential electrode; and the second constant potential for the second constant potential electrode. A second constant potential wiring for supplying to the power supply, a first short-circuit line for short-circuiting the power supply line and the first constant-potential wiring, and a second short-circuit line for short-circuiting the ground line and the second constant-potential wiring. In the width direction in the wiring board In the two opposing outer edges, one of the first and second constant potential wirings is arranged on the outermost side at the two outer edges, and the other constant potential wiring is the two outer edges. Is arranged adjacent to the inside of the one constant potential wiring at one outer edge, and the wiring that is short-circuited to the other constant potential wiring among the ground line and the power supply line connected to the driver, A wiring that is arranged adjacent to the inside of the other constant potential wiring at one outer edge and short-circuited with the one constant potential wiring is located inside the one constant potential wiring at the other outer edge of the two outer edges. The first short circuit line and the second short circuit line are provided on the same plane as the wiring to be short-circuited.

  With such a wiring structure, a predetermined potential can be applied to each electrode of the piezoelectric actuator. And a some wiring can be provided in the same surface of a wiring board including a 1st and 2nd short circuit line. Therefore, the manufacturing cost of the wiring structure can be reduced as compared with the case where wiring is provided on both the front and back surfaces. Further, the first and second short-circuit lines can be easily connected after the actuator polarization step.

  The wiring board includes a central portion joined to the piezoelectric actuator, and first and second extending portions extending in opposite directions with respect to the central portion, and the central portion includes the first The driver and the second driver are mounted, the ground line and the power line corresponding to the first driver are provided in the first extension part, and the second extension part is provided with the first extension part. The ground line and the power line corresponding to two drivers are provided, and the wiring provided in the first extension portion is arranged in the central portion with respect to the wiring provided in the second extension portion. May be arranged in a 180-degree rotational symmetry relationship.

  The second constant potential wiring may be disposed on the outermost side.

  A pair of the ground lines may be provided along each of the two outer edges, and the pair of ground lines may be connected via the driver.

  The piezoelectric actuator includes a first active portion facing a central portion of the plurality of pressure chambers and a second active portion facing a portion outside the central portion of the plurality of pressure chambers. A first active portion formed in a region sandwiched between an electrode and the first constant potential electrode; and a second active portion formed in a region sandwiched between the individual electrode and the second constant potential electrode. Each of the first and second active portions is configured to be in a deformed state that extends in a first direction toward the pressure chamber when a voltage is applied and contracts in a second direction orthogonal to the first direction, A voltage may be applied to the second active part when no voltage is applied to the second active part when a voltage is applied to the first active part, and a voltage is applied to the second active part when no voltage is applied to the first active part.

  According to the present invention, it is possible to provide a droplet discharge head that can satisfactorily suppress crosstalk even if the pressure chamber is made dense, and to provide a wiring structure suitable for the droplet discharge head that exhibits such effects. In addition, the manufacturing cost of the wiring structure can be reduced.

1 is an exploded perspective view of an inkjet head according to a first embodiment of the present invention. It is a partial longitudinal cross-sectional view of the inkjet head shown in FIG. FIG. 2 is a partial cross-sectional view of the ink jet head shown in FIG. 1. It is a top view of the wiring structure applied to the inkjet head shown in FIG. FIG. 5 is an electric circuit diagram showing an electrical configuration of the piezoelectric actuator and the wiring structure shown in FIGS. 1 to 4. It is explanatory drawing of the wiring structure of another structure contrasted with the wiring structure which concerns on 1st Embodiment of this invention shown in FIG. 4, Comprising: (a) is the top view, (b) is the back view. It is explanatory drawing of the polarization process of the piezoelectric actuator shown in FIG. 1 thru | or FIG. It is a top view of the wiring structure concerning a 2nd embodiment of the present invention.

  Embodiments of the present invention will be described with reference to these drawings. Here, a case where the droplet discharge head according to the present invention is applied to an ink jet head mounted on an ink jet printer will be described as an example, and the direction in which ink is discharged from the head will be described below.

  The ink jet head 1 shown in FIGS. 1 to 3 is configured by overlapping and joining piezoelectric actuators 3 from above the flow path unit 2. Both parts 2 and 3 have a substantially rectangular shape in plan view, and the long side direction is “vertical direction” and the short side direction is “lateral direction” for convenience.

  Although only a part is shown in FIG. 3, the nozzle 4 is opened on the lower surface of the flow path unit 2, and the pressure chamber hole 5 communicating with the nozzle 4 is opened on the upper surface. Referring to FIG. 1, the pressure chamber holes 5 have a substantially rectangular shape that is long in the lateral direction, and a large number of pressure chamber holes 5 are densely arranged on the upper surface of the flow path unit 2. These pressure chamber holes 5 are arranged side by side at a substantially constant pitch in the vertical direction to form a plurality of rows, and are arranged in a staggered manner in the horizontal direction. Each pressure chamber hole 5 communicates with a corresponding one nozzle 4, and a large number of nozzles 4 are arranged in the same pattern as the pressure chamber holes 5 on the lower surface of the flow path unit 2. Returning to FIG. 3, the pressure chamber holes 5 are closed by the lower surface of the piezoelectric actuator 3, whereby a number of pressure chambers 6 are formed in the ink jet head 1. The flow path unit 2 is formed with a common ink chamber 7 that stores ink from an external ink supply source for each type, and each pressure chamber 6 communicates with one of the common ink chambers 7. FIG. 1 shows an ink supply port 47 for introducing ink into the flow path unit 2, and each nozzle is provided in the flow path unit 2 through the common ink chamber 7 and each pressure chamber 6 from the ink supply port 47. An ink flow path for supplying ink to 4 is formed.

  As shown in FIGS. 2 and 3, the piezoelectric actuator 3 is formed by laminating two piezoelectric layers 9 and 10 on a bottom layer 8 which is a diaphragm. Here, the lower side of these piezoelectric layers is referred to as “intermediate layer 9”, and the upper side is referred to as “top layer 10”. The bottom layer 8 is made of a piezoelectric material mainly composed of lead zirconate titanate, which is a mixed crystal of lead titanate and lead zirconate, and is formed on the upper surface of the flow path unit 2 so as to cover the plurality of pressure chambers 6. Has been placed. The bottom layer 8 has a thickness of about 20 μm. The material of the bottom layer 8 is not limited to the piezoelectric material. The piezoelectric layers 9 and 10 are made of the same piezoelectric material as that of the bottom layer 8 and are stacked on each other and disposed on the upper surface of the bottom layer 8. This thickness is also about 20 μm. A substantially rectangular individual electrode 11 corresponding to each pressure chamber 6 and disposed so as to face almost the entire area of each pressure chamber 6 is provided on the upper side of the top layer 10. An upper constant potential electrode 12 corresponding to each pressure chamber 6 is provided between the intermediate layer 9 and the top layer 10, and a lower constant electrode common to many pressure chambers 6 is provided between the bottom layer 8 and the intermediate layer 9. A potential electrode 13 is provided.

  As shown in FIG. 2, the vertical center of the individual electrode 11 and the upper constant potential electrode 12 substantially coincide with each other, and the vertical dimension of the individual electrode 11 is longer than that of the upper constant potential electrode 12. For this reason, the central portion of the individual electrode 11 in the vertical direction overlaps with the upper constant potential electrode 12 in plan view, and both ends in the vertical direction overlap with the lower constant potential electrode 13 in plan view. The portion sandwiched between the central portion in the vertical direction of the individual electrode 11 and the upper constant potential electrode 12 forms a first active portion 14 that is polarized between the electrodes 11 and 12. Further, a portion sandwiched between each longitudinal end portion of the individual electrode 11 and the lower constant potential electrode 12 forms a second active portion 15 polarized between the electrodes 11 and 13. That is, the first active part 14 is arranged corresponding to the central part of the pressure chamber 6, and the second active part 15 corresponds to a part outside the first active part 14 and outside the central part of the pressure chamber 6. Arranged.

  As shown in FIG. 1 and FIG. 3, each individual electrode 11 has a portion extending from the edge opposite to the nozzle 4 in the lateral direction so as to project laterally to a region not facing the pressure chamber 6. A terminal portion 17 is integrally provided at this portion. The upper and lower constant potential electrodes 12 and 13 (see FIGS. 2 and 3) are electrically connected to the terminal portions 18 and 19 provided on the upper surface of the top layer 10 through through holes that vertically penetrate regions not shown. Conducted. A wiring board 20 is provided on the upper surface side of the top layer 10 in an overlapping manner. Connection terminals corresponding to the terminal portions 17 to 19 are provided on the lower surface side of the wiring board 20, and the wiring board 20 corresponds via bumps (not shown) made of a conductive material such as metal. It is joined to the piezoelectric actuator 3 so as to be electrically connected to each of the terminal portions 17 to 19 to be performed.

  Referring to FIGS. 2 and 3, the potential applied to each individual electrode 11 is switched between a high potential and a ground potential by a driver 23 mounted on the wiring board 20. At the time of driving to change the volume of the corresponding pressure chamber 6, for example, a high potential of about 20 V (hereinafter referred to as “first potential”) is selectively applied to the individual electrode 11, and then a ground potential (hereinafter referred to as “second potential”). "). On the other hand, the second potential is applied during standby when ink ejection is not required. In addition, the first potential is always applied to the upper constant potential electrode 12 through the wiring board 20, and the second potential is always applied to the lower constant potential electrode 13. For this reason, the first active unit 14 is polarized and activated in the same direction as the voltage applied during standby, and the second active unit 15 is polarized in the same direction as the voltage applied during driving. Activated. When a potential difference is generated between the pair of electrodes forming these active portions, a voltage is applied to the piezoelectric layer sandwiched between these electrodes, and an electric field in the stacking direction is generated. When the polarization direction of the piezoelectric layer is the same as the electric field direction, an inverse piezoelectric effect occurs, and the piezoelectric layers 9 and 10 expand in the lamination direction that is the polarization direction and contract in the horizontal direction that is perpendicular to the lamination direction. To do.

  Therefore, at the time of standby, the second active part 15 to which the voltage effective for the reverse piezoelectric effect is not applied is not deformed, and the first active part 14 to which the effective voltage is applied extends in the stacking direction. Contract horizontally. At this time, since the intermediate layer 9 is bonded to the bottom layer 8, there is a difference in distortion in the horizontal direction between the top layer 10 and the intermediate layer 9. As a result, the bottom layer 8 and the piezoelectric layers 9 and 10 project and deform in the stacking direction toward the pressure chamber 6. During driving, the first active part 14 to which no voltage effective for exhibiting the reverse piezoelectric effect is applied is recovered from deformation. On the other hand, since the second active portion 15 to which an effective voltage is applied extends in the stacking direction and tends to contract in the horizontal direction, the second active portion 15 is deformed so as to warp away from the pressure chamber 6. . The volume of the pressure chamber 6 increases due to the combination of the deformation of the active portions 14 and 15, and ink is supplied from the common ink chamber 7 to the pressure chamber 6. When the electric potential of the individual electrode 11 is set to the same electric potential as that of the lower constant potential electrode 13, the bottom layer 8 and the piezoelectric layers 9 and 10 are protruded and deformed in the stacking direction so as to face the pressure chamber 6 as described above. Volume decreases instantly. As a result, the ink in the pressure chamber 6 is discharged downward from the nozzle 4.

  As described above, in the inkjet head 1, the first active portion 14 is deformed by switching between application and non-application of voltage to the first active portion 14. At the same time, switching between application and non-application of voltage to the second active part 15 is performed, and by this switching, the second active part 15 propagates deformation of the first active part 14 to the adjacent pressure chamber 6. It deforms so as to suppress this. For this reason, even if the number of pressure chambers 6 is increased, crosstalk can be suppressed satisfactorily.

  The configuration of the piezoelectric actuator 3 of the droplet discharge head 1 according to the present invention is not limited to the above. The piezoelectric actuator has two types of constant potential electrodes and one type of individual electrode for each pressure chamber. The first active portion corresponding to the central portion of the pressure chamber by these three types of electrodes, and the central portion As long as the 2nd active part corresponding to a part outside is formed, it may be constituted in any way. The second active portion 15 may include a region inside the outer peripheral edge of the pressure chamber 6. As a result, not only the first active part 14 but also the second active part 15 contributes to the volume change of the pressure chamber 6, and the volume fluctuation amount of the pressure chamber 6 becomes larger than the case of using only the first active part 14. .

  When the piezoelectric actuator 3 is manufactured, first, the bottom layer 8, the intermediate layer 9, the top layer 10, and the electrodes 11 to 13 are stacked on each other so as to have the above-described positional relationship. Next, by performing a polarization process for polarizing the first and second active portions 14 and 15 of the piezoelectric actuator 3, the piezoelectric actuator 3 operable to eject ink as described above is created. Details of this polarization step will be described later.

  Next, a wiring structure for applying a voltage to the piezoelectric actuator 3 will be described based on FIGS. 4 and 5 with reference to FIG. As shown in FIG. 4, the wiring structure includes the wiring board 20 described above. On the wiring board 20, a rectangular COF portion 21 that is superimposed on the piezoelectric actuator 3 from the upper side and joined to the upper side of the piezoelectric actuator 3, and a belt-like first FPC portion 22 joined to one end edge of the COF portion 21. And a band-shaped second FPC part 72 joined to the other end edge of the COF part 21.

  In a state where the COF unit 21 is bonded to the piezoelectric actuator 3, the first FPC unit 22 is provided so as to be drawn out in one direction from the piezoelectric actuator 3. The second FPC portion 72 is provided so as to be drawn outward from the piezoelectric actuator 3 in the direction opposite to the first FPC portion 22. The COF unit 21 and the FPC units 22 and 72 are all known flexible wiring boards. Each FPC part 22 and 72 is joined to the edge of the COF part 21 by soldering, for example, and the wiring provided in both parts 21, 22 and 72 is electrically connected by this joining. Each FPC part 22, 72 is provided with a contact for each wiring at the edge opposite to the joint part with the COF part 21. These contacts can be connected to a receptacle connector mounted on a substrate disposed at a predetermined location of the ink jet printer.

  Two drivers 23 and 73 for selectively outputting a voltage applied to each individual electrode 11 are mounted on the COF portion 21 of the wiring board 20. The first driver 23 arranged on the left side in the drawing is provided corresponding to the wiring provided in the first FPC unit 22, and the second driver 73 arranged on the right side in the drawing is provided in the second FPC unit 72. The wiring is provided corresponding to the provided wiring. The wiring board 20 includes a large number of individual wirings 24, 74, power supply lines (VDD2) 25, 125, 75, 175, ground lines (VSS2) 26, 176, upper constant potential wirings (VCOM) 127, 77, and lower parts. Constant potential wiring (COM) 28, 128, 78, 178, first short lines 29, 79, and second short lines 30, 80 are provided. Although not shown, the FPC units 22 and 72 of the wiring board 20 are additionally provided with waveform signal lines that specify the driving mode of the piezoelectric actuator 3 and drive signals output from the drivers 23 and 73 to the individual electrodes 11. A plurality of control signal lines for outputting a clock data signal, a power supply voltage line (VDD1) (for example, 3.3 V) and a ground voltage line (VSS1) (for example, 0 V) of the drivers 23 and 73 themselves Etc., and these wirings are connected to the drivers 23 and 73.

  The individual wires 24 and 74 are provided corresponding to the individual electrodes 11 and are wires for applying the first and second potentials to the individual electrodes 11 according to the ink ejection timing. The individual wires 24 and 74 extend from the corresponding drivers 23 and 73 toward the connection terminals on the wiring board 20 corresponding to the terminal portions 17 of the individual electrodes 11.

  The power supply lines (VDD2) 25, 125, 75, and 175 are wirings for supplying power to the corresponding drivers 23 and 73, and are connected to the drivers 23 and 73. The ground lines (VSS2) 26 and 176 are wirings for connecting the corresponding drivers 23 and 73 to the ground potential, and are connected to the drivers 23 and 73.

  The upper constant potential wirings (VCOM) 127 and 77 are wirings for constantly applying a high first potential to the upper constant potential electrode 12, and the wiring board 20 corresponding to the terminal portion 18 of the upper constant potential electrode 12. It extends toward the upper connection terminal. The lower constant potential wirings (COM) 28, 128, 78, and 178 are wirings for constantly applying a second potential that is a ground potential to the lower constant potential electrode 13, and correspond to the terminal portion 19 of the lower constant potential electrode 13. It extends toward the connection terminal on the wiring board 20 to be connected.

  The first short-circuit lines 29 and 79 are wirings for connecting the power supply lines 125 and 75 and the upper constant potential wirings 127 and 77, and the second short-circuit lines 30 and 80 are the ground lines 26 and 176 and the lower constant potential wiring 28. , 178 are connected to each other. The first short-circuit lines 29 and 79 and the second short-circuit lines 30 and 80 are provided after the polarization process of the piezoelectric actuator 3 described later in the manufacturing process of the piezoelectric actuator 3 is completed.

  FIG. 5 shows an electrical circuit for explaining the electrical configuration of the piezoelectric actuator 3 and the wiring structure. However, FIG. 5 shows only the configuration related to the first driver 23. As shown in FIG. 5, the first and second active portions 14 and 15 are equivalent to the first and second capacitors 31 and 32 having the electrodes 11 to 13 as electrode plates, respectively. The upper constant potential wiring (VCOM) 127 and the lower constant potential wiring (COM) 28, 128 are connected via these capacitors 31, 32, and the first capacitor 31 is located on the high potential side. When the capacitors 31 and 32 are charged, the equivalent active portions 14 and 15 are deformed, and when the capacitors 31 and 32 are discharged, the equivalent active portions 14 and 15 are recovered from the deformed state.

  The driver 23 is equivalent to a circuit that switches the states of the capacitors 31 and 32 so that the charging / discharging state of the first capacitor 31 and the charging / discharging state of the second capacitor 32 are opposite to each other. The circuit includes, for example, two transistors 34 and 35 interposed in series between a power supply line (VDD2) 25 and 125 and a ground line (VSS2) 26. That is, the power supply lines 25 and 125 are connected to the collector of the first transistor 34, the emitter of the first transistor 34 is connected to the collector of the second transistor 35, and the emitter of the second transistor 35 is connected to the ground line 26. The individual wiring 24 connects between the wiring connecting the transistors 34 and 35 and the individual electrode 11. The individual electrode 11 functions as a low potential side electrode plate of the first capacitor 31 equivalent to the first active part 14 and also functions as a high potential side electrode plate of the second capacitor 32 equivalent to the second active part 15. To do.

  As described above, when ink is ejected, the potential of the individual electrode 11 is raised from the second potential, which is the ground potential, to the first potential, which is a high potential, and then lowered from the first potential to the second potential. Is taken. In addition, the second potential is applied to the individual electrode 11 during standby.

  Raising the potential of the individual electrode 11 is equivalent to turning on the first transistor 34 and turning off the second transistor 35. At this time, the power supply lines 25 and 125 are connected to the lower constant potential wirings 28 and 128 via the first transistor 34 and the second capacitor 32, and the second capacitor 32 is charged. The fall of the potential of the individual electrode 11 is equivalent to turning off the first transistor 34 and turning on the second transistor 35. At this time, the upper constant potential wiring 127 is connected to the ground line 26 via the first capacitor 31 and the second transistor 35, and the first capacitor 31 is charged. The second capacitor 32 charged at the time of start-up is on a closed circuit constituted by the individual wiring 24, the ground line 26, the second short-circuit line 30, and the lower constant potential wirings 28 and 128, and is stored in the second capacitor 32. The generated charge is discharged. The ON / OFF setting of the transistors 34 and 35 at this time is maintained even during standby. Therefore, considering again the rise of the potential of the individual electrode 11, the first capacitor 31 charged during standby is on a closed circuit constituted by the upper constant potential line 127, the first short-circuit line 29 and the individual line 24. The electric charge stored in the first capacitor 31 is discharged.

  This wiring structure includes individual wiring 24 (74), power supply lines 25 and 125 (75 and 175), ground line 26 (176), upper constant potential wiring 127 (77) and lower constant potential wirings 28 and 128 (78, 178) and two short-circuit wires 29, 30 (79, 80) are provided, the first and / or second potentials can be applied to the three types of electrodes 11-13. The two active parts 14 and 15 constituted by the electrodes 11 to 13 can be operated so that crosstalk is suppressed.

  Here, a wiring structure having another configuration shown in order to clarify the characteristics of the wiring structure according to the present embodiment will be described with reference to FIG. In the wiring board 920 having the wiring structure shown in FIG. 6, the first and second drivers 923 and 973 are mounted in the COF portion 921, and the two FPC portions 922 and 972 provided with wirings corresponding to the drivers are the COF portions. 921 is joined. The configurations of the FPC units 922 and 927 are the same. That is, in any of the FPC units 922 and 972, the power supply lines 925 and 975 and the ground lines 926 and 927 connected to the corresponding drivers 923 and 973 and the upper constant potential for applying a predetermined potential to the piezoelectric actuator 3. Wirings 927 and 977 and lower constant potential wirings 928 and 978, first short-circuit lines 929 and 979 that short-circuit the power supply lines 925 and 975 and upper constant potential wirings 927 and 977, ground lines 926 and 976, and lower constant potential wiring 928 , 978 and second short-circuit lines 930, 980 are provided. Hereinafter, only the first FPC unit 922 will be described, and description of the second FPC unit 927 will be omitted.

  The first FPC portion 922 is provided with two groups of four wiring groups including a power supply line 925, a ground line 926, an upper constant potential wiring 927, and a lower constant potential wiring 928, and each of the wirings 925 to 928 includes the FPC portion 922. Extending in parallel with each other. In each wiring group, a lower constant potential wiring 928, an upper constant potential wiring 927, a ground line 926, and a power supply line 925 are provided in this order from the outer edge side to the center side. The two constant potential wirings 927 and 928 pass through the outer edge side region of the first driver 923 and need to be connected to the piezoelectric actuator 3 side, and it is short-circuited if the ground side is arranged outside the high potential side. The four wirings 925 to 928 are arranged in this way based on the viewpoint that it is easy to prevent electrical problems. Therefore, the first short-circuit line 929 connects the power supply line 925 and the upper constant potential wiring 927 so as not to interfere with the ground line 926 interposed between the wirings 925 and 927, and the second short-circuit line 930 is connected to the ground line. In order to connect 926 and the lower constant potential wiring 928, it is necessary to arrange them so as not to interfere with the upper constant potential wiring 927 interposed between these wirings 926 and 928. Also, two groups of wiring groups are provided on the outer edge of the wiring board 920. For example, when a wiring group is provided only on one of the outer edges, the wirings 925 to 928 and 975 to 978 are connected. The voltage is supplied only from one side with respect to the longitudinal direction of the drivers 923 and 973 and the piezoelectric actuator 3, and a voltage drop occurs inside the longitudinal direction of the drivers 923 and 973 and the piezoelectric actuator 3 inside. In some cases, the discharge characteristics may vary. For this reason, the wiring group prevents a voltage drop by supplying a voltage from both sides of the drivers 923 and 973 and the piezoelectric actuator 3 in the longitudinal direction. In addition, a plurality of control signal lines, ground voltage line (VSS1), and power supply voltage line (VDD1) (not shown) extend between the wiring groups in parallel with the extending direction of the FPC portions 922 and 972.

  In this case, the first and second short-circuit lines 929 and 930 can be realized by jumper lines 937 and 938 provided on the back surface of the substrate portion. In this embodiment, a double-sided flexible printed board is used. The jumper wires 937 and 938 are, for example, a single-sided flexible printed circuit board in which wiring is only on the surface without using a double-sided flexible printed circuit board by connecting with a general-purpose jumper cable or by providing a jumper chip. It is also possible to do this. However, since the wiring to be short-circuited is formed with high density, the connection with the jumper cable is difficult to work in the connection process and difficult to manufacture, and when a jumper chip is provided, the discharge current flowing through the jumper wire is large, so the chip The rated current may be exceeded, and the chip is fragile. By providing a jumper line with such a structure, a jumper structure can be taken without the above problem. As a result, the first and second short-circuit lines 929 and 930 on the front side surface of the substrate portion can be prevented from having a bridging structure that physically straddles the ground line 926 or the upper constant potential wiring 927. The structure can be prevented from becoming large in the thickness direction of the wiring board 920. However, according to this configuration, the wiring needs to be printed on both the front and back surfaces of the first FPC portion 922, and the manufacturing cost of the first FPC portion 922 increases. In the so-called double-sided wiring structure, the manufacturing cost of the two FPC portions 922 is increased, and the cost of the wiring structure is increased as a whole.

  Returning to FIG. 4, in the present embodiment, the first driver 23 is mounted on the upper surface side of the COF unit 21, and is disposed in the vicinity of an end edge that becomes a joint portion with the first FPC unit 22. The first driver 23 is in the form of a rectangular IC chip in plan view, and is arranged such that its longitudinal direction is parallel to the extending direction of the edge. Each individual wiring 24 corresponding to the first driver 23 extends on the COF part 21 from the driver 23 arranged in this way toward the substantially opposite edge. The second driver 73 and the corresponding individual wirings 74 have the same configuration.

  The first FPC portion 22 is formed in a substantially rectangular band shape, and two wiring groups are provided close to each of a pair of outer edges extending in the extending direction. The first wiring group provided in the vicinity of the outer edge on the upper side in the figure is composed of three wirings, that is, a power line 25 corresponding to the first driver 23, a ground line 26, and a lower constant potential wiring 28. The second wiring group provided in the vicinity of the outer edge includes three wirings, that is, a power supply line 125 corresponding to the first driver 23, an upper constant potential wiring 127, and a lower constant potential wiring 128. That is, the first wiring group includes two wirings 26 and 28 connected by the second short-circuit line 30, and is arranged so as to be sandwiched between these two wirings in another configuration shown in FIG. 6. The upper constant potential wiring that has been provided is omitted. Similarly, the second wiring group includes two wirings 125 and 127 connected by the first short-circuit line 29. In another configuration shown in FIG. 6, the second wiring group is sandwiched between these two wirings. The ground line that has been arranged in the above is omitted.

  In other words, the first wiring group is arranged such that two wirings 26 and 28 to be connected by the second short-circuit line 30 are adjacent to each other. Therefore, on the front side surface of the substrate portion of the first FPC portion 22, only by installing a conductive material such as solder so as to straddle the two wires 26 and 28, the two wires 26 and 28 are electrically connected to each other. Can be conducted. Similarly, the second wiring group is arranged such that two wirings 125 and 127 to be connected by the first short-circuit line 29 are adjacent to each other. Therefore, on the front side surface of the substrate portion of the first FPC portion 22, only by installing a conductive material such as solder so as to straddle the two wires 125 and 127, the two wires 125 and 127 are electrically connected to each other. Can be conducted.

  As described above, in the first FPC portion 22 of the present wiring structure, the wirings to be short-circuited by the first and second short-circuit lines 29 and 30 are provided so as to be adjacent to each other. Therefore, on the wiring to be short-circuited, the surface on which the first and second short-circuit lines 29 and 30 are provided and the surface on which the four types of wirings 25 to 28 short-circuited by the short-circuit lines 29 and 30 are provided. The short-circuit wires 29 and 30 can be configured simply by installing a conductive material. Accordingly, it is not necessary to print and form a wiring on the back side surface of the substrate portion of the first FPC portion 22, and the manufacturing cost of the wiring board 20 can be reduced. Further, it is not necessary to provide a short-circuit bridge structure on the front side surface, and the wiring board 20 can be prevented from being enlarged in the thickness direction and the flexibility being impaired.

  A plurality of electronic elements 36 such as resistors and capacitors are mounted on the upper surface of the first FPC unit 22. Here, the electrical action by the electronic element 36 will not be described in detail. However, as shown in FIG. 4, the conductive material constituting the first short-circuit line 29 and the second short-circuit line 30 is disposed at the electronic element 36. Are mounted in a substantially straight line in a direction orthogonal to the extending direction of the first FPC portion 22. That is, the conductive material and the electronic element 36 constituting the short-circuit lines 29 and 30 are provided at substantially the same position in the extending direction of the first FPC portion 22.

  Here, if the electronic element 36 is mounted on the first FPC portion 22 or a conductive material is installed, the first FPC portion 22 is difficult to bend freely at that location. Therefore, by arranging the conductive material and the electronic element 36 at substantially the same position with respect to the extending direction of the first FPC section 22, the number of places where it becomes difficult to bend freely is reduced as much as possible, and the ease of handling and the flexibility of the first FPC section 22 are impaired as much as possible. I try not to.

  Further, the first and second short-circuit lines 29 and 30 are arranged on the first FPC unit 22 together with the electronic element 36 as close as possible to the joint portion with the COF unit 21. Thereby, the wiring length from the 1st and 2nd active part 14 and 15 to the 1st and 2nd short circuit line 29 and 30 can be shortened as much as possible, and the voltage drop of the voltage inputted into the 1st driver 23 is made as small as possible. It is possible to prevent the driver 23 from being destroyed by adding a voltage drop to the maximum rated voltage (VDD1 + VDD2) that can be applied to the first driver 23. In addition, voltage fluctuations in the active portions 14 and 15 can be reduced as much as possible, and the piezoelectric actuator 3 can be stably operated.

  Here, the pair of outer edges of the COF portion 21 are arranged so as to overlap the terminal portion 19 of the lower constant potential electrode 13 in plan view, and are connected to the lower connecting terminals 60 and 160 which are electrically connected to the terminal portion 19, and the upper portion There are provided upper connection terminals 61 and 161 which are disposed so as to overlap the terminal portion 18 of the constant potential electrode 12 in plan view and are electrically connected to the terminal portion 18. The lower connection terminal 160 provided along the lower outer edge in the figure is connected to the lower constant potential wiring 128 constituting the second wiring group of the first FPC section 22 by joining the COF section 21 and the first FPC section 22. The upper connection terminal 161 is electrically connected to the upper constant potential wiring 127. Further, the upper connection terminal 60 provided along the upper outer edge in the drawing is electrically connected to the upper constant potential wiring 28 constituting the first wiring group of the first FPC portion 22. However, the lower connection terminal 61 is not electrically connected to the wiring provided in the first FPC portion 22 because the lower constant potential wiring 27 is omitted from the first wiring group. The lower connection terminal 61 is electrically connected to a lower constant potential wiring 77 provided in the second FPC portion 72.

  The wiring layout in the second FPC portion 72 is in a 180-degree rotationally symmetric relationship with the wiring layout in the first FPC portion 22 around the central portion of the COF portion 21. For this reason, the second FPC unit 72 can obtain the same effects such as reduction of voltage drop and securing of flexibility based on the wiring layout of the first FPC unit 22 described above.

  That is, the second FPC portion 72 is provided with two wiring groups adjacent to each of the pair of outer edges extending in the extending direction. The first wiring group provided close to the outer edge on the upper side in the figure is the same as the second wiring group of the first FPC section 22, the power line 75 corresponding to the second driver 73, the upper constant potential wiring 77 and the lower constant potential. The second wiring group that is composed of the three wirings 78 and is provided in the vicinity of the lower outer edge in the drawing is the power line 175 corresponding to the second driver 73, similar to the first wiring group of the first FPC unit 22. , A ground line 176, and a lower constant potential wiring 178.

  The first short-circuit line 79 of the second FPC portion 72 is a conductive material such as solder that is disposed so as to straddle the power supply line 75 and the upper constant potential wiring 77 that are arranged adjacent to each other in the first wiring group. It is composed of materials. The second short-circuit line 80 is made of a conductive material such as solder that is disposed so as to straddle the ground line 176 and the lower constant potential wiring 178 that are arranged adjacent to each other in the third wiring group.

  In the second FPC portion 72, the upper constant potential wiring 77 is included in the first wiring group on the upper side in the figure, and the upper constant potential wiring 77 is provided along the outer edge on the upper side in the figure of the COF portion 21. The upper connection terminal 61 is connected. On the contrary, since the upper constant potential wiring is not included in the lower second wiring group in the figure, the upper connection terminal 161 provided along the lower outer edge of the COF part 21 in the figure is the second FPC part. The wiring provided in 72 is not electrically connected. However, as described above, the application of the first potential to the connection terminal 161 is performed by the first FPC unit 22, and in this wiring structure, the application of the first potential to the two upper connection terminals 61 and 161 is performed. Is configured so that each of the two FPC units 22 and 72 performs sharing. As a result, the first potential can be applied to the upper constant potential electrode 12 from both sides with respect to the longitudinal direction of the piezoelectric actuator 3, so that the voltage drop inside the piezoelectric actuator 3 can be reduced, and the ink ejection characteristics. The impact on is reduced.

  As described above, in this wiring structure, in each of the FPCs 22 and 72 each having two wiring groups, the ground line is omitted from one wiring group. For this reason, in the drivers 23 and 73, the potential output to the individual wirings 24 and 74 extending from the side to which the ground line is connected and the individual wirings 24 and 74 extending from the side to which the ground line is not connected are output. There may be variations between the potential. If there is this variation, the ink ejection characteristics will be different for each pressure chamber, making it difficult to perform stable ink ejection control for obtaining a high-quality image.

  Here, referring to FIG. 1, four ink inlets 47 are opened on the upper surface of the flow path unit 2 of the inkjet head 1 to which the present wiring structure is applied. Each ink inlet 47 is configured to introduce different types of ink from an external ink supply source, and communicates with a common ink chamber 7 (see FIG. 3) independent of each other. For this reason, the inkjet head 1 can selectively eject a plurality of types of inks having different colors. That is, a plurality of individual electrodes 11 are provided on the upper surface of the piezoelectric actuator 3 corresponding to each of the four types of ink, and ejection is performed by selecting the individual electrodes 11 to which the first and / or second potentials are applied. The type of ink to be used is determined. In the following, for convenience of explanation, these four types of ink are assumed to be black ink, cyan ink, yellow ink and magenta ink having different colors.

  Returning to FIG. 4, the wiring board 20 is provided with a large number of individual wirings 24, 74 connected to any one of the first and second drivers 23, 73. Are arranged for each corresponding ink color. In the present embodiment, for example, the black wiring group 48 that is electrically connected to the individual electrode 11 that is used for discharging black ink and the similar cyan wiring group 49 are all connected to the first driver 23. The black wiring group 48 is firmly arranged on the side to which the ground line is connected, and the cyan wiring group 49 is firmly arranged on the opposite side. On the other hand, the yellow wiring group 50 and the magenta wiring group 51 are connected to the second driver 73, and the yellow wiring group 50 is arranged firmly on the side to which the ground line is not connected, and the magenta wiring group 51. Is placed on the opposite side.

  As described above, when there is a possibility that the ink ejection characteristics are different depending on the location connected to each of the drivers 23 and 73, by arranging the individual wiring for each ink color, However, although there may be a difference in the ejection characteristics of each other, when attention is paid to one of the wiring groups 48 to 51, the ejection characteristics of the inks can be made uniform with respect to a plurality of individual wirings constituting the wiring group. it can.

  Here, the manufacturing procedure of the inkjet head 1 and the wiring structure will be described. First, the unpolarized piezoelectric actuator 3 is laminated and bonded to the flow path unit 2, and the FPC units 22 and 72 are bonded to the unbonded COF unit 21. Thereafter, the FPC units 22 and 72 are joined to the COF unit 21, and the polarization process of the piezoelectric actuator 3 is performed. At this stage, each short-circuit line 29, 30, 79, 80 is not provided.

  In the polarization step, such an assembly is placed in an atmosphere of about 100 degrees, and the end portions of the FPC portions 22 and 72 are connected to the polarization device. Then, a high potential difference is generated between the electrodes 11 to 13 of the piezoelectric actuator 3 through the individual wires 24 and 74, the upper constant potential wires 127 and 77, and the lower constant potential wires 28, 128, 78, and 178. The first and second active parts 14 and 15 are polarized.

  For example, in FIG. 7A, a high voltage is applied to the first active portion 14 by applying a potential of 36 V to the upper constant potential electrode 12 and 0 V to the individual electrode 11, so that the first active portion 14 14 is polarized upward. In FIG. 7B, for example, by applying a potential of 28 V to the upper low potential electrode 12, −60 V to the lower constant potential electrode 13, and 28 V to the individual electrode 11, the second active portion 15. And the portion sandwiched between the first and second constant potential electrodes 12 and 13 are polarized downward.

  Thereafter, the first FPC unit 22 is removed from the polarization device to provide the first and second short-circuit wires 29 and 30, and the second FPC unit 72 is removed from the polarization device to provide the first and second short-circuit wires 79 and 80. Provided.

  Thus, in the inkjet head 1 and the wiring structure, when the polarization process is performed, the short-circuit lines 29, 30, 79, and 80 are not provided. If the polarization process is performed after providing the reverse, for example, in the case shown in FIG. 7A, the power supply line and the upper constant potential wiring have the same potential. A high potential of 36V is applied. Each of the drivers 23 and 73 has a voltage value mainly defined by a power supply voltage (for example, 3.3V) and a driving power supply voltage (for example, 28V) of each of the drivers 23 and 73 itself. When the polarization process is performed in such a state, a high potential exceeding the maximum rated voltage is applied to the drivers 23 and 73, and the drivers 23 and 73 are destroyed. Similarly, in the case shown in FIG. 7B, since the ground line and the lower constant potential wiring have the same potential, a high potential of 60 V is applied to the drivers 23 and 73 through the ground line, The drivers 23 and 73 are destroyed. For this reason, in this wiring structure, each short-circuit line 29, 30, 79, 80 is provided after the polarization process of the piezoelectric actuator 3 is completed, but each short-circuit line 29, 30, 79, 80 is provided on the front side surface of the substrate portion. Since 80 is disposed, it can be easily provided even after the polarization step of the piezoelectric actuator 2 is completed.

  FIG. 8 is a plan view showing a wiring structure according to the second embodiment of the present invention. The wiring board 220 having this wiring structure also includes the first FPC part 222 and the first FPC part 222 provided with wirings corresponding to the drivers 223 and 273 at the respective edges of the COF part 221 on which the first and second drivers 223 and 273 are mounted. The 2FPC portions 272 are joined.

  In the first FPC unit 222, four wirings of a lower constant potential wiring (COM) 228, a lower constant potential wiring (VCOM) 227, a power supply line (VDD2), and a ground line (VSS2) are adjacent to the upper outer edge in the drawing. The first wiring group consisting of is arranged in this order from the outer edge side. In the vicinity of the outer edge on the lower side in the figure, a second wiring group consisting of two wirings of a lower constant potential wiring (COM) 328 and a ground line (VSS2) 326 is provided in this order from the outer edge side. .

  The ground line 226 provided in the first wiring group and the ground line 326 provided in the second wiring group are connected to each other via the first driver 223 and are arranged in a loop shape in the first FPC unit 222. ing. By connecting in a loop like this, a voltage drop inside the first driver 223 does not occur, so that the operation is stable, and the ground line is connected in a loop as compared with the case where the power supply line is connected in a loop. Thus, the operation of the first driver 223 can be stabilized.

  In the first wiring group, the upper constant potential wiring 227 and the power supply line 225 to be short-circuited by the first short-circuit line 229 are arranged so as to be adjacent to each other. Accordingly, in the same manner as in the first embodiment, only by installing a conductive material such as solder on the front side surface of the substrate portion of the first FPC portion 222 so as to straddle these two wires 225 and 227, these two wires 225. , 227 can be configured to be short-circuited. Further, the second wiring group is composed of only the lower constant potential wiring 228 and the ground line 226 that are to be short-circuited by the second short-circuit line 230. Accordingly, the polarization process of the piezoelectric actuator 3 can be performed by simply installing a conductive material such as solder on the front side surface of the substrate portion of the first FPC portion 222 so as to straddle the two wirings 226 and 228 as in the first embodiment. A wiring that easily short-circuits these two wirings later can be configured.

  The wiring layout of the second FPC unit 272 is in a 180-degree rotationally symmetric relationship with the wiring layout of the first FPC unit 222 around the center of the COF unit 221. That is, in the vicinity of the outer edge on the upper side in the drawing, a first wiring group composed of two wires of the lower constant potential wiring 278 and the ground line 276 is provided in this order from the outer edge side. In the vicinity of the outer edge on the lower side in the figure, a second wiring group including four wirings of a lower constant potential wiring 378, an upper constant potential wiring 376, a power supply line 375, and a ground line 376 is arranged in this order from the outer edge side. Is provided. The first and second short-circuit lines 279 and 280 are each made of a conductive material such as a bump installed on the front side surface of the substrate portion of the second FPC section 272, and the first short-circuit line 279 is provided on the second wiring group side. The second short-circuit line 280 is provided on the first wiring group side.

  Similarly to the first embodiment, lower connection terminals 260 and 360 and upper connection terminals 261 and 361 are provided on a pair of outer edges of the COF portion 221, respectively. Also in the present embodiment, in each FPC unit, the upper constant potential wiring is omitted in one of the two wiring groups in order to provide the first and second short-circuit lines on the front side surface. Since the wiring layouts of the first and second FPC sections are symmetrical with each other by 180 degrees, the upper connection terminals provided on the outer edges are connected to the upper constant potential wiring provided on one of the first and second FPC sections. It becomes possible.

  Thus, also in this embodiment, there exists an effect similar to 1st Embodiment.

  Although the embodiments of the present invention have been described so far, the above configuration can be appropriately changed within the scope of the present invention.

  For example, in each wiring group of the first embodiment, the arrangement of the upper constant potential wiring (COM) and the lower constant potential wiring (VCOM) is changed, and the arrangement of the power supply line (VDD2) and the ground line (VSS2) is changed. The same effects as the first embodiment can be obtained. Furthermore, since the ground line is provided in a loop shape, the operation of the driver can be further stabilized.

  Although the “first potential” is a high potential and the “second potential” is a ground potential, the piezoelectric actuator 3 can be operated in the same manner even if this relationship is reversed. In that case, the first short-circuit line only needs to be a wiring that short-circuits the lower constant potential wiring and the power supply line on the side to which the high potential is applied, and the second short-circuit line is on the side to which the ground potential is applied. Any wiring that short-circuits the upper constant potential wiring and the ground line may be used.

  This wiring structure is not limited to an ink jet head mounted on an ink jet printer, but a liquid other than ink, for example, a coloring liquid is discharged to manufacture a color filter of a liquid crystal display device, or a conductive liquid is discharged to connect an electric wiring. The present invention can also be suitably applied to a liquid discharge head mounted on a liquid discharge apparatus used in a forming apparatus or the like.

  The present invention can provide a droplet discharge head that can satisfactorily suppress crosstalk even when the pressure chamber is made dense, and two active parts formed from three kinds of electrodes for suppressing crosstalk. It is advantageous to apply to an ink jet head of an ink jet printer which has an effect of being able to operate each of the ink jets stably and records an image on the recording medium by landing the ink on the recording medium.

1 Inkjet head (droplet discharge head)
3 Piezoelectric actuator 6 Pressure chamber 11 Individual electrode 12 Upper constant potential electrode (first constant potential electrode)
13 Lower constant potential electrode (second constant potential electrode)
14 1st active part 15 2nd active part 20 Wiring board 21 COF part (central part)
22,72 FPC part (extension part)
23, 73 Driver 24, 74 Individual wiring 25, 125, 75, 175 Power supply line 26, 176 Ground line 127, 77 Upper low potential wiring (first constant potential wiring)
28, 128, 78, 178 Lower constant potential wiring (second constant potential wiring)
29,79 1st short circuit line 30,80 2nd short circuit line

Claims (5)

A wiring structure of a liquid droplet ejection head, which is applied to a liquid droplet ejection head having a piezoelectric actuator that operates to selectively eject liquid from a plurality of nozzles, and has wiring for driving the piezoelectric actuator,
The piezoelectric actuator includes a plurality of individual electrodes to which a driving voltage is selectively supplied to discharge liquid from the nozzle, a first constant potential electrode to which a first constant potential is supplied, and a second constant potential. A second constant potential electrode supplied with
The wiring structure includes a wiring board provided with a plurality of the wirings, and a driver that is mounted on the wiring board and selectively outputs the driving voltage,
The plurality of wirings include a power line for supplying power to the driver, a ground line for setting the driver to a ground potential, and a first line for supplying the first constant potential to the first constant potential electrode. A first constant potential wiring; a second constant potential wiring for supplying the second constant potential to the second constant potential electrode; a first short-circuit line that short-circuits the power line and the first constant potential wiring; A second short-circuit line that short-circuits the ground line and the second constant-potential wiring;
In the two outer edges facing in the width direction on the wiring board, one of the first and second constant potential wirings is arranged on the outermost side at the two outer edges, and the other constant potential wiring is arranged. The potential wiring is arranged adjacent to the inside of the one constant potential wiring at one outer edge of the two outer edges,
Of the ground line and the power supply line connected to the driver, the wiring that is short-circuited with the other constant potential wiring is arranged adjacent to the inside of the other constant potential wiring at the one outer edge, and the one constant voltage wiring is connected. The wiring that is short-circuited with the potential wiring is disposed adjacent to the inside of the one constant potential wiring at the other outer edge of the two outer edges,
The wiring structure of a droplet discharge head, wherein the first short-circuit line and the second short-circuit line are provided on the same plane as the wiring that each short-circuits. The wiring board includes a central portion joined to the piezoelectric actuator, and first and second extending portions extending in opposite directions with respect to the central portion, and the central portion includes the first A driver and a second driver are mounted;
The first extension portion is provided with the ground line and the power supply line corresponding to the first driver, and the second extension portion is provided with the ground line and the power supply line corresponding to the second driver. Is provided,
The wiring provided in the first extension portion is arranged in a 180-degree rotationally symmetric relationship with respect to the wiring provided in the second extension portion with the central portion as a center. The wiring structure of the droplet discharge head according to claim 1.   The wiring structure of the droplet discharge head according to claim 1, wherein the second constant potential wiring is arranged on the outermost side.   The pair of ground lines are provided along each of the two outer edges, and the pair of ground lines are connected via the driver. The wiring structure of the droplet discharge head described in 1. The piezoelectric actuator is formed with a first active portion facing a central portion of the plurality of pressure chambers and a second active portion facing a portion outside the central portion of the plurality of pressure chambers,
A first active part formed in a region sandwiched between the individual electrode and the first constant potential electrode, and a second active unit formed in a region sandwiched between the individual electrode and the second constant potential electrode And
Each of the first and second active portions is configured to be in a deformed state that extends in a first direction toward the pressure chamber when a voltage is applied and contracts in a second direction orthogonal to the first direction. The voltage is applied to the second active part when no voltage is applied to the second active part, and the voltage is applied to the second active part when no voltage is applied to the first active part. 5. A wiring structure of a droplet discharge head according to any one of 1 to 4.

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