Liquid ejection head

Abstract

To provide a liquid ejection head capable of preventing an occurrence of disconnection in a film substrate formed with an interconnect for applying a drive waveform to a piezoelectric actuator.SOLUTION: A liquid ejection head comprises a laminated piezoelectric body block and a film substrate. In the laminated piezoelectric body block, pluralities of piezoelectric actuators and columns are arranged alternately. In the film substrate, a plurality of copper foil interconnects for applying drive waveforms to the respective piezoelectric actuators respectively are formed, and the respective copper foil interconnects are soldered to terminals of the respective piezoelectric actuators to be electrically connected thereto. In the copper foil interconnects of the flexible substrate, an interconnect width changes to a tapered shape before and after a boundary portion of a solder resist region, and the interconnect width on the side of the solder resist region is large and the interconnect width on the side of the solder connection region is small.SELECTED DRAWING: Figure 9

Description

Technical Field

[0001] Embodiments of the present invention relate to a liquid ejection head.

Background Art

[0002] A liquid ejection head that supplies a predetermined amount of liquid to a predetermined position is known. The liquid ejection head is mounted on, for example, an inkjet printer, a 3D printer, a dispensing device, or the like. An inkjet printer ejects ink droplets from an inkjet head to form an image or the like on the surface of a recording medium. A 3D printer ejects droplets of a modeling material from a modeling material ejection head and cures them to form a three-dimensional object. A dispensing device ejects droplets of a sample and supplies a predetermined amount to a plurality of containers or the like.

[0003] The liquid ejection head has a plurality of channels for ejecting liquid. Each channel includes a nozzle for ejecting liquid, a pressure chamber communicating with the nozzle, and a piezoelectric actuator for changing the volume of the pressure chamber. The liquid ejection head selects a channel for ejecting liquid from among the plurality of channels, and applies a drive waveform to the piezoelectric actuator of the selected channel to eject the liquid.

[0004] The drive waveform is applied to the terminals of the piezoelectric actuator via the wiring of the copper foil formed on a flexible wiring board such as an FPC (Flexible printed circuits). The wiring of each channel arranged at the terminal portion of the flexible wiring board is connected to the terminals of each piezoelectric actuator by batch soldering. However, due to reasons such as the fine pitch of the flexible wiring board, for example, the wiring width is narrow, so it is easy to break. In particular, it is easy to break at the boundary between the area where the flexible wiring board is soldered and the area where the solder resist is applied.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0006] The problem to be solved by the present invention is to provide a liquid ejection head capable of suppressing disconnection in a film substrate formed with wiring for applying a drive waveform to a piezoelectric actuator.

Means for Solving the Problems

[0007] The liquid ejection head according to an embodiment of the present invention includes a laminated piezoelectric body block and a film substrate. In the laminated piezoelectric body block, a plurality of piezoelectric actuators and columns are alternately arranged. The film substrate is formed with a plurality of copper foil wirings for respectively applying a drive waveform to each of the piezoelectric actuators, and each of the copper foil wirings is soldered to a terminal of each of the piezoelectric actuators to be electrically connected. The wiring of the copper foil of the flexible substrate has a tapered change in wiring width before and after the boundary of the solder resist region, with the wiring width on the solder resist region side being thick and the wiring width on the solder connection region side being thin.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Figure 14

Figure 15

Embodiments for Carrying Out the Invention

[0009] Hereinafter, a liquid ejection head according to an embodiment will be described in detail with reference to the accompanying drawings. In each figure, the same components are denoted by the same reference numerals.

[0010] As an example of an image forming apparatus equipped with the liquid ejection head of the embodiment, an inkjet printer 10 that prints an image on a recording medium will be described. FIG. 1 shows a schematic configuration of the inkjet printer 10. The inkjet printer 10 includes, inside a housing 11, a cassette 12 that stores a sheet S which is an example of a recording medium, an upstream conveyance path 13 of the sheet S, a conveyance belt 14 that conveys the sheet S taken out from the cassette 12, a plurality of inkjet heads 100 to 103 that eject ink droplets toward the sheet S on the conveyance belt 14, a downstream conveyance path 15 of the sheet S, a discharge tray 16, and a control board 17. An operation unit 18 which is a user interface is arranged on the upper side of the housing 11.

[0011] Image data to be printed on the sheet S is generated, for example, by a computer 200 which is an external connection device. The image data generated by the computer 200 is sent to the control board 17 of the inkjet printer 10 through a cable 201 and connectors 202, 203.

[0012] A pickup roller 204 supplies the sheets S one by one from the cassette 12 to the upstream conveyance path 13. The upstream conveyance path 13 is composed of a pair of feed rollers 131, 132 and sheet guide plates 133, 134. The sheet S is sent to the upper surface of the conveyance belt 14 via the upstream conveyance path 13. Arrow 104 in the figure indicates the conveyance path of the sheet S from the cassette 12 to the conveyance belt 14.

[0013] The conveyance belt 14 is a net-like endless belt having a large number of through holes formed on its surface. Three rollers, a driving roller 141, and driven rollers 142, 143 rotatably support the conveyance belt 14. A motor 205 rotates the driving roller 141 to rotate the conveyance belt 14. The motor 205 is an example of a driving device. 105 in the figure indicates the rotation direction of the conveyance belt 14. A negative pressure container 206 is arranged on the back side of the conveyance belt 14. The negative pressure container 206 is connected to a decompression fan 207. The fan 207 creates a negative pressure inside the negative pressure container 206 by the formed air flow, and adsorbs and holds the sheet S on the upper surface of the conveyance belt 14. 106 in the figure indicates the flow of the air current.

[0014] Examples of liquid ejection heads, inkjet heads 100 to 103, are arranged to face a sheet S adsorbed and held on a conveyance belt 14 with a slight gap of, for example, 1 mm therebetween. The inkjet heads 100 to 103 eject ink droplets toward the sheet S, respectively. The inkjet heads 100 to 103 print an image when the sheet S passes below. Each of the inkjet heads 100 to 103 has the same structure except that the color of the ejected ink is different. The colors of the ink are, for example, cyan, magenta, yellow, and black.

[0015] The inkjet heads 100 to 103 are respectively connected to ink tanks 315 to 318 and ink supply pressure adjusting devices 321 to 324 via ink flow paths 311 to 314. Each of the ink tanks 315 to 318 is arranged above each of the inkjet heads 100 to 103. During standby, each of the ink supply pressure adjusting devices 321 to 324 adjusts the inside of each of the inkjet heads 100 to 103 to a negative pressure with respect to the atmospheric pressure, for example, -1.2 kPa, so that ink does not leak from the nozzles 24 (see FIG. 2) of the inkjet heads 100 to 103. During image formation, the ink in each of the ink tanks 315 to 318 is supplied to each of the inkjet heads 100 to 103 by the ink supply pressure adjusting devices 321 to 324.

[0016] After image formation, the sheet S is sent from the conveyance belt 14 to a downstream conveyance path 15. The downstream conveyance path 15 includes a pair of feed rollers 151, 152, 153, 154 and sheet guide plates 155, 156 that define the conveyance path of the sheet S. The sheet S passes through the downstream conveyance path 15 and is sent from a discharge port 157 to a discharge tray 16. An arrow 107 in the figure indicates the conveyance path of the sheet S.

[0017] Subsequently, the configuration of the inkjet heads 100 to 103 will be described. The following describes the inkjet head 100 with reference to FIGS. 2 to 5, but the inkjet heads 101 to 103 also have the same structure as the inkjet head 100.

[0018] As shown in FIG. 2, the inkjet head 100 includes a head unit 2 which is an example of a liquid ejection unit. The head unit 2 includes a nozzle plate 23 which is an example of a nozzle unit. Nozzles 24 of each ejection channel for ejecting ink are arranged along, for example, the X direction in the first direction of the nozzle plate 23. The nozzle density is set, for example, within a range of 150 to 1200 dpi. The nozzles 24 are not limited to a single row and may be multiple rows. The head unit 2 is connected to the ink supply pressure adjustment device 321 in FIG. 1 via an ink flow path 311. The detailed internal configuration of the head unit 2 will be described later.

[0019] The head unit 2 is connected to a flexible printed wiring board 20. The flexible printed wiring board 20 is a flexible printed wiring board using, for example, a resin film. The flexible printed wiring board 20 is, for example, an FPC (Flexible printed circuits). The flexible printed wiring board 20 is connected to a flexible printed circuit board 21. The flexible printed circuit board 21 mounts a driving IC (Integrated Circuit) 3 which is a driver chip (hereinafter referred to as a driving IC). The flexible printed circuit board 21 is, for example, a COF (Chip on Film). The flexible printed circuit board 21 is connected to a printed board 22. The printed board 22 is a rigid through-hole board in which a glass fiber-containing epoxy resin layer and a copper wiring layer are laminated multiple times. The driving IC 3 as the control unit of the inkjet head 100 temporarily stores data sent from the control board 17 including a CPU as the control unit of the inkjet printer 10 via the printed board 22, and gives a driving signal to each ejection channel to eject ink at a predetermined timing.

[0020] The flexible printed wiring board 20 such as an FPC is an example of a film substrate. Although FIG. 2 shows the flexible printed wiring board 20 and the flexible printed circuit board 21 mounting the driving IC 3 as separate substrates, they may be integrated. The detailed configuration of the flexible printed wiring board 20 will be described later.

[0021] Figs. 3 to 5 are partial cross-sectional views of the head portion 2. Fig. 4 is a cross-sectional view taken along line A-A of Fig. 3, and Fig. 5 is a cross-sectional view taken along line B-B of Fig. 3. The nozzle plate 23 is joined to one surface of the pressure chamber substrate 4. The nozzle plate 23 is a rectangular plate formed of a resin such as polyimide or a metal such as stainless steel. The diaphragm 5 is joined to one surface of the pressure chamber substrate 4 on the side opposite to the nozzle plate 23. The diaphragm 5 has flexibility to deform when an external force is applied. The diaphragm 5 is a thin plate-shaped plate formed of a metal such as nickel or stainless steel. The material of the diaphragm 5 may be other than metal, such as a polyimide film.

[0022] The pressure chamber 42 is formed in the pressure chamber substrate 4. The pressure chambers 42 of the respective discharge channels are arranged at the positions of the respective nozzles 24 and communicate with the nozzles 24 respectively. The pressure chamber substrate 4 is formed of a metal such as stainless steel, for example. The pressure chamber 42 is formed, as an example, by forming a rectangular opening penetrating in, for example, the Z direction in the second direction in the pressure chamber substrate 4 and closing both side openings with the nozzle plate 23 and the diaphragm 5 respectively.

[0023] The pressure chamber 42 communicates with a guide flow path 43 having a constriction portion, and further communicates with an ink supply manifold 45 through an ink supply port 44 which is an opening hole penetrating the diaphragm 5. The guide flow path 43 is formed in a groove shape in, for example, the Y direction in the third direction on one surface of the pressure chamber substrate 4 on the diaphragm 5 side for each pressure chamber 42. The ink supply manifold 45 is formed in a frame 46 joined to one surface of the diaphragm 5. The ink supply manifold 45 extends in the X direction and communicates with the pressure chambers 42 of the respective channels through the ink supply ports 44 and the guide flow paths 43 of the respective channels. The ink supply manifold 45 as a common ink chamber communicates with the ink flow path 311 (see Figs. 1 and 2).

[0024] The actuators 6 of each ejection channel are arranged at positions facing the pressure chambers 42 of each ejection channel with the diaphragm 5 interposed therebetween. The actuators 6 of each ejection channel join, for example, with an adhesive, the end face in the -Z direction thereof to the diaphragm 5 that forms a part of the partition wall of the pressure chamber 42. The actuator 6, which is an example of a piezoelectric actuator, is a laminated piezoelectric actuator formed by alternately laminating piezoelectric bodies 61 such as piezo elements, first internal electrodes 62, and second internal electrodes 63 in layers (see particularly FIG. 3). Each piezoelectric body 61 is arranged such that the polarization directions are opposite to each other in, for example, the Z direction, and is deformed in the d33 mode. The piezoelectric body 61 is formed of a lead-containing piezoelectric material such as lead zirconate titanate (PZT) or a lead-free piezoelectric material such as sodium potassium niobate.

[0025] The first internal electrode 62 and the second internal electrode 63 are conductive films respectively formed on the main surfaces of the piezoelectric body 61. The first internal electrode 62 and the second internal electrode 63 are formed by film deposition with a sinterable conductive material such as silver palladium. The first internal electrode 62 of the actuator 6 is formed up to one side surface of the actuator 6 in the Y direction and is connected to an individual electrode 64, which is an external electrode formed on this side surface. The second internal electrode 63 is formed up to the other side surface of the actuator 6 in the -Y direction and is connected to a common electrode 65, which is an external electrode formed on this side surface. The dummy layer 68 is made of the same material as the piezoelectric body 61. However, the dummy layer 68 is not provided with an internal electrode and is not deformed because no electric field is applied. The individual electrode 64 and the common electrode 65 are formed by film deposition with, for example, Ni, Cr, Au, or the like.

[0026] The support column 60 is arranged between the actuators 6 of each discharge channel via a groove 69, particularly as shown in FIG. 4. The support column 60 is arranged at a position corresponding to the partition wall 40 between adjacent pressure chambers 42. The driving actuator 6 and the dummy actuator serving as the support column 60 are integrally formed using a common piezoelectric body 61, a first internal electrode 62, a second internal electrode 63, an individual electrode 64, and a common electrode 65. By forming the groove 69, a comb-shaped laminated piezoelectric body block 600 is formed. The dummy layer 68 located on the proximal end side of the actuator 6 serves as a base connecting the adjacent actuators 6 and support columns 60 alternately. The laminated piezoelectric body block 600 is fixed by joining the end face in the Z direction to the surface of the substrate 47.

[0027] The individual electrodes 64 of each actuator 6 of the laminated piezoelectric body block 600 are separated for each channel in the X direction, which is the depth direction in FIG. 3, and are respectively connected to the individual wirings 66 of the flexible printed wiring board 20 (see FIG. 5). The flexible printed wiring board 20 has a resin film 26 as a base material, individual wirings 66, and a solder resist layer 27. A detailed description of the individual wirings 66 will be given later. Although not shown, for example, the common electrodes 65 of the actuators 6 connected to each other using the portion of the dummy layer 68 are led out to the individual electrode 64 side by using, for example, the side surfaces of the support columns 60 located at both ends of the laminated piezoelectric body block 600 or by extending the internal electrodes 61 of the support columns 60 located at both ends of the laminated piezoelectric body block 600, and are connected to the common wirings formed on the flexible printed wiring board 21.

[0028] Subsequently, the connection structure between the actuator 6 and the flexible printed wiring board 20 will be described in detail with reference to FIGS. 6 to 10. FIG. 6 is a plan view of the flexible printed wiring board 20. FIG. 7 is an extract view of the actuator 6 and the flexible printed wiring board 20 from FIG. 3. FIG. 8 is an extract view of the actuator 6 and the flexible printed wiring board 20 from FIG. 5. FIG. 9 is a partially enlarged view of the flexible printed wiring board 20. FIG. 10 is a plan view of the flexible printed wiring board 20, the flexible printed circuit board 21, and the printed board 22 connected to each other.

[0029] As shown in FIG. 6, the individual wirings 66 of the flexible printed wiring board 20 are formed separately for each discharge channel from the solder connection region 7, which is the terminal portion on the side connected to the actuator 6, to the terminal portion 70 on the side connected to the flexible printed circuit board 21. Although FIG. 6 shows a reduced number of individual wirings 66 for the sake of drawing convenience, the number of individual wirings 66 is the same as the number of actuators 6 to be driven. Each individual wiring 66 is formed of a copper foil on the surface of the resin film 26 serving as a base material. The solder resist region 71 (see FIG. 6) of each individual wiring 66 is covered with a solder resist layer 27 (see FIG. 7) formed by applying a solder resist resin such as epoxy. Instead of applying the solder resist resin, a cover layer made of a resin film may be bonded to the copper foil surface of the flexible printed wiring board 20, and the bonded region may be used as the solder resist region. When solder is electrolytically plated on the tip of the flexible printed wiring board 20 on which the solder resist layer 27 is formed, the surfaces of the individual wirings 66 in the solder connection region 7 are plated (solder plating) with solder 72 (see FIG. 8). Instead of electrolytic plating, cream solder may be attached to the solder connection region 7 and heated to cover the surfaces of the individual wirings 66 in the solder connection region 7 with solder. This solder is used for soldering described later. Similarly, the common wiring 67 is formed on the surface of the resin film 26 from the solder connection region 7 to the terminal portion 70 and is covered with solder by performing solder plating on the solder connection region 7 or the like. The common wiring 67 has a wider wiring width than the individual wiring 66 in order to alleviate current concentration when a plurality of actuators 6 are simultaneously charged and discharged, and is formed in a pair on both sides in the X direction of the flexible printed wiring board 20. This pair of common wirings 67 is connected to both sides of the laminated piezoelectric body block 600 and is commonly connected to the common electrodes 65 of the actuators 6 connected to each other using, for example, the portion of the dummy layer 68. The wiring width of the individual wiring 66 varies depending on the location as described later and is formed, for example, within the range of 22 to 84 μm. The wiring width of the common wiring 67 is, for example, 0.8 mm. The thicknesses of the individual wiring 66 and the common wiring 67 are, for example, 8 μm.

[0030] The lead portion 73 (see FIG. 9) of the individual wiring 66 that overlaps the surface of the individual electrode 64 of the actuator 6 is made narrower in the wiring width L1 than the column width L2 of the actuator 6 in the X direction (see FIG. 8). Further, in the X direction, it is preferable that the width L3 after solder plating is also narrower than the column width L2 of the actuator 6. Each individual wiring 66 is arranged in parallel at equal intervals with a pitch P2 such that the center line of the lead portion 73 overlaps the center line of the column surface of the opposing actuator 6.

[0031] The individual wiring 66 changes the wiring width in a tapered shape before and after the boundary portion 74 of the solder resist region 71. In the X direction, the wiring width is wider on the solder resist region 71 side and narrower on the solder connection region 7 side. That is, the individual wiring 66 has a tapered portion 75 where the wiring width becomes wider from the lead portion 73 toward the solder resist region 71 side. As described above, in the laminated piezoelectric body block 600, the actuators 6 and the columns 60 are alternately arranged, and the individual wiring 66 is not connected to the columns 60, so the wiring width can be increased using the vacant space. As in an example of the size described later, the wiring width in the X direction can be made three times or more that of the lead portion 73. The boundary portion 74 of the solder resist region 71 passes through this tapered portion 75. The boundary portion 74 of the solder resist coating 71 is preferably positioned so as to straddle the central portion in the Z direction of the tapered portion 75. More preferably, it is at the midpoint of the length in the Z direction. The lead portion 73 of the individual wiring 66 is connected to the individual electrode 64 of the actuator 6 at the portion closer to the -Z direction (see FIG. 7). Therefore, the tapered portion 75 where the wiring width of the individual wiring 66 changes has ended its tapered change on the solder resist region 71 side rather than on the lead portion 73 where the lead is soldered to the individual electrode 64 of the actuator 6.

[0032] As an example of the size of each component, in the X direction, when the column width L2 of the actuator 6 and the column width L4 of the support column 60 are both 52.5 μm, and the pitch P1 of the alternately arranged actuators 6 and support columns 60 is 84.5 μm, the wiring width L1 of the lead portion 73 of the individual wiring 66 is set to 22 μm, and the pitch P2 is set to 169 μm, which is the same as the pitch between the actuators 6. The width L5 of the solder connection region 7 in the Z direction is 1350 μm from the edge of the flexible printed wiring board 20, and the length L6 of the lead portion 73 of the individual wiring 66 in the Z direction is 1075 μm. In the lead portion 73, it is formed with the same wiring width without changing the wiring width in the X direction.

[0033] The tapered portion 75 that continues in the Z direction in the lead portion 73 has a wiring width L7 in the X direction of 84 μm after changing in a tapered shape. The wiring interval L8 in the X direction between adjacent individual wirings 66 is 85 μm. The length L9 of the tapered portion 75 in the Z direction is 550 μm. The taper ratio in this case is approximately 1:9. The boundary portion 74 of the solder resist region 71 passes through the midpoint of the length of the tapered portion 75 in the Z direction (= 275 μm). The individual wiring 66 in the solder connection region 7 is 10 μm thick and is solder-plated.

[0034] The flexible printed wiring board 20 is aligned so that the center line of the lead portion 73 of the individual wiring 66 overlaps with the center line of the columnar surface of the opposing actuator 6, and the solder 72 is melted by heating to collectively solder the lead portion 73 of each individual wiring 66 and the individual electrode 64 of each actuator 6. As an example, as shown in FIG. 7, for an actuator 6 having a length L10 in the Y direction of 1700 μm, the length L11 of the lead portion 73 of the individual wiring 66 is overlapped with the columnar surface in the Z direction within a range of 660 μm and soldered. The flexible printed wiring board 20 generally has a coefficient of thermal expansion different from that of the actuator 6. Usually, since the flexible printed wiring board 20 has a larger coefficient of thermal expansion than the actuator 6, it is manufactured by being pre-shrunk in consideration of the deformation of the flexible printed wiring board 20 due to heat during soldering, and the center line of the lead portion 73 of the individual wiring 66 just overlaps with the center line of the columnar surface of the opposing actuator 6 due to thermal expansion during soldering, and it may be aimed to be joined.

[0035] The wiring width L1 (for example, 22 μm) in the X direction of the lead portion 72 of the individual wiring 66 is thinner than the column width L2 (for example, 52.5 μm) in the X direction of the actuator 6, and the width after solder plating with a thickness of 10 μm is also thinner than the column width of the actuator 6. Therefore, when heated, excess solder 72 does not flow into the side surface of the actuator 6, for example, to prevent the first internal electrode 62 and the second internal electrode 63 from being electrically connected. Also, it is possible to suppress the flowing solder 72 from adhering to the adjacent support column 60. As described above, when the support column 60 is formed of a dummy actuator, there is a case where the solder 72 flows to the support column 60 and is electrically connected to the individual wiring 66, resulting in conduction, but this can be prevented.

[0036] In the present embodiment, although the solder used for soldering is supplied by pre-plating the individual wiring 66 in the solder connection region 7, which is the electrode at the tip of the flexible printed wiring board 20, the solder may be supplied from the actuator 6 side by adhering the solder to the electrode 64 of the actuator 6. Also, both the electrode at the tip of the flexible printed wiring board 20 and the electrode 64 of the actuator 6 may be covered with solder and the solder may be supplied from both sides.

[0037] As shown in FIG. 10, the individual wiring 66 and the common wiring 67 led out to the terminal portion 70 are overlapped with the terminal portion 8 of the flexible printed circuit board 21 and are respectively connected to the individual wiring 81 and the common wiring 82 of the flexible printed circuit board 21. Since the pitch of the individual wiring 66 on the terminal portion 70 side is narrower than that on the solder connection region 7 side in the X direction, instead of solder connection, ACF (Anisotropic Conductive Film), ACP (Anisotropic Conductive Paste), NCF (Non-Conductive Film), NCP (Non-Conductive Paste), etc. are used for fixing and anisotropic conductive connection is made in the thickness direction.

[0038] The flexible printed circuit board 21 is a flexible film substrate using a synthetic resin film such as polyimide. The driving IC 3 is, for example, a driver chip formed on a silicon semiconductor substrate. On the flexible printed circuit board 21, an individual wiring 81, a common wiring 82, an input wiring 83, a power supply wiring 84 for voltage V1, a power supply wiring 85 for voltage V2, and a ground wiring 86 are formed. The individual wiring 81 drawn out from the driving IC 3 is an output wiring for the driving waveform generated by the driving IC 3. On the other hand, the input wiring 83 drawn out from the driving IC 3 is formed up to the terminal portion 87 on the side connected to the printed circuit board 22. Since the driving IC 3 can be controlled by serial communication, the number of the input wiring 83 can be made smaller than the number of the individual wiring 81 which is the output wiring.

[0039] The power supply wiring 84 for voltage V1, the power supply wiring 85 for voltage V2, and the ground wiring 86 are each connected to the driving IC3. The power supply wiring 84 for voltage V1, the power supply wiring 85 for voltage V2, and the ground wiring 86 are each formed up to the terminal portion 87 on the side connected to the printed circuit board 22. The individual wiring 81, the common wiring 82, the input wiring 83, the power supply wiring 84 for voltage V1, the power supply wiring 85 for voltage V2, and the ground wiring 86 are formed of, for example, copper foil. Although not shown, each wiring of the flexible printed circuit board 21 is covered with a solder resist layer except for the mounting area such as the driving IC3 and the connection portions 8, 87, etc.

[0040] On the terminal portion 9 of the printed circuit board 22, a control line 91, a power supply wiring 92 for voltage V1, a power supply wiring 93 for voltage V2, and a ground wiring 94 are formed respectively. The control line 91 is connected to the input wiring 83 of the flexible printed circuit board 21. The power supply wiring 92 for voltage V1 is connected to the power supply wiring 84 of the flexible printed circuit board 21. The power supply wiring 93 for voltage V2 is connected to the power supply wiring 85 of the flexible printed circuit board 21. The ground wiring 94 is connected to the ground wiring 86 and the common wiring 82 of the flexible printed circuit board 21. To the control line 91, signals are given to selectively drive each actuator 6 sent from the control board 17 provided with a CPU which is a control unit of the inkjet printer 10 such as print data. To the power supply wiring 92, a driving voltage V1 is given by a power supply 95. To the power supply wiring 93, a driving voltage V2 is given by a power supply 96. The ground wiring 94 is connected to the ground (GND) by, for example, the control board 17 of the inkjet printer 10.

[0041] Next, the control system of the inkjet head 100 will be described. FIG. 11 is a circuit diagram of the control system of the inkjet head 100. As shown in FIG. 11, the actuators 6 (#1ch, #2ch, ··· #nch) of each ejection channel are respectively connected to the output terminals of the drive driver D (i.e., the drive circuit) of the drive IC 3 via individual wirings 66, 81. Further, the actuator 6 connects the common electrode 65 to a common potential via common wirings 67, 82. The common potential is, for example, ground (GND). The power supply 95 for the drive voltage V1 and the power supply 96 for the drive voltage V2 applied to the actuator 6 are connected to the drive IC 3.

[0042] Next, the ink ejection operation will be described with reference to FIGS. 12 and 13. Each drive driver D of the drive IC 3 applies a drive waveform to the individual electrode 64 of each actuator 6 using the drive voltages V1, V2 and ground (GND). The voltage V1 is, for example, 20V. The voltage V2 is, for example, 10V. The ground (GND) is, for example, 0V. Which actuator 6 to drive is based on, for example, print data.

[0043] FIG. 12 is an example of a drive waveform applied to the actuator 6. As shown in FIG. 12, when driving the actuator 6 to which the ground potential is applied to the common electrode 65, the voltage V2 is applied to the individual electrode 64 to set it in a standby state. When the voltage V2 is applied, an electric field is applied in the direction of the polarization axis of the piezoelectric body 61, and as shown in FIG. 13(a), the actuator 6 extends in the stacking direction (Z direction) and the volume of the pressure chamber 42 is reduced. This is done prior to the ink ejection timing. Thereafter, at the ink ejection timing (time t1 in FIG. 12), first, the potential of the individual electrode 64 is lowered to ground (GND), so that as shown in FIG. 13(b), the extended actuator 6 returns to its original state, that is, relatively contracts, and the volume of the pressure chamber 42 relatively expands. As the volume of the pressure chamber 42 expands, ink flows into the pressure chamber 42 through the guide channel 43.

[0044] And for example, after elapsing a time of 1 / 2 of the pressure oscillation period of the head unit 2, when a voltage V2 is applied to the individual electrode 64 at the time t2 in FIG. 12, as shown in FIG. 13(c), the actuator 6 extends in the stacking direction (Z direction), and the volume of the pressure chamber 42 relatively decreases, so that the ink droplet R is ejected from the nozzle 24. And for example, after elapsing a time of 1 / 2 of the pressure oscillation period of the head unit 2, a voltage V1 is applied to the individual electrode 64 at the time t3 in FIG. 12, and the voltage is returned to V2 at the time t4 after a predetermined time. By the extension (FIG. 13(d)) and return (FIG. 13(a)) of the actuator 6 at that time, the volume of the pressure chamber 42 is reduced and returned, and the residual vibration is attenuated by this operation. In this way, the volume of the pressure chamber 42 changes in accordance with the longitudinal vibration of the actuator 6 in the stacking direction, and the ink can be ejected.

[0045] As described above, the flexible printed wiring board 20 changes the wiring width of the individual wiring 66 in a tapered shape before and after the boundary portion 74 of the solder resist region 71, and thickens the wiring width on the solder resist region 71 side. Thereby, even if the wiring width of the lead portion 73 connected to the individual electrode 64 of the actuator 6 is made thin, the wiring width becomes thick so as to straddle the boundary portion 74 of the solder resist region 71, and disconnection can be suppressed. Even if the wiring width is changed before and after the boundary portion 74 of the solder resist region 71, if it is not changed in a tapered shape as shown in FIGS. 14 and 15, disconnection is likely to occur. For example, as shown in FIG. 14, if the non-tapered wiring width conversion portion is at the boundary between the solder resist region 71 and the solder connection region 7 or within the solder resist region 71, the thinner wiring is likely to be disconnected when the flexible printed wiring board 20 is bent. Also, as shown in FIG. 15, if the non-tapered wiring width conversion portion is on the side of the region where the solder plating is performed, the solder plated on the thicker wiring is likely to cause a short circuit.

[0046] As described above, according to the above-described embodiment, it is possible to suppress the occurrence of disconnection in the flexible printed wiring board 20 in which the individual wiring 66 for applying the drive waveform to the actuator 6 is formed of a copper foil.

[0047] Note that the actuator 6 is not limited to a stacked type in which a plurality of piezoelectric bodies 61 are stacked. The piezoelectric body 61 may be a single-layer actuator. Further, the operation of the actuator when a driving voltage is applied is not limited to longitudinal vibration. Furthermore, it is not limited to the drop-on-demand piezo method, and may be applied to the continuous method.

[0048] In the above-described embodiment, the inkjet head 100 of the inkjet printer 10 has been described as an example of a liquid ejection head. However, the liquid ejection head may be a modeling material ejection head of a 3D printer or a sample ejection head of a dispensing device.

[0049] That is, the liquid ejection head of the above-described embodiment can be expressed as follows. (1) A laminated piezoelectric body block in which a plurality of piezoelectric actuators and columns are alternately arranged, A film substrate in which a plurality of copper foil wirings for respectively applying drive waveforms to the piezoelectric actuators are formed, and the copper foil wirings are soldered to the terminals of the piezoelectric actuators and electrically connected. The copper foil wiring of the film substrate is characterized in that the wiring width changes in a tapered shape before and after the boundary portion of the solder resist region, the wiring width on the solder resist region side is thick, and the wiring width on the solder connection region side is thin. (2) The wiring width of the lead portion for soldering the copper foil wiring to the terminal of the piezoelectric actuator is thinner than the column width of the piezoelectric actuator, and changes in the tapered shape to be thicker than the column width of the piezoelectric actuator. The boundary portion of the solder resist region straddles the central portion of the portion where the wiring width changes in a tapered shape. (3) The solder resist region is formed by covering the surface of the copper foil of the film substrate with a resin film. (4) The solder resist region is formed by resin applied to the surface of the copper foil of the film substrate. (5) The soldering portion of the copper foil wiring is outside the solder resist region and is solder-plated. (6) The portion where the wiring width changes in a tapered shape widens the wiring width by utilizing the provision of the support columns between adjacent piezoelectric actuators. (7) The change in the portion where the wiring width changes in a tapered shape ends on the solder resist coating region side rather than the portion of the lead soldered to the terminal of the piezoelectric actuator.

[0050] The embodiments of the present invention are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the gist of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are also included in the invention described in the claims and the equivalent scope thereof.

Explanation of Reference Numerals

[0051] 10 Inkjet printer 100 - 103 Inkjet head 2 Head unit 20 Flexible printed wiring board 21 Flexible printed circuit board 24 Nozzle 6 Actuator 60 Support column 66 Individual wiring 7 Solder connection region 71 Solder resist region 73 Portion of the lead of the individual wiring 74 Boundary portion of the solder resist region 75 Portion where the wiring width of the individual wiring changes in a tapered shape

Claims

1. A laminated piezoelectric body block in which a plurality of piezoelectric actuators and columns are alternately arranged, a film substrate in which wiring of a plurality of copper foils for respectively applying drive waveforms to the piezoelectric actuators is formed, and the wiring of each copper foil is soldered to terminals of each piezoelectric actuator and electrically connected, wherein the wiring of the copper foil on the film substrate has a wiring width that changes in a tapered shape before and after a boundary portion of the solder resist region, the wiring width on the solder resist region side is thick, and the wiring width on the solder connection region side is thin. A liquid discharge head characterized by this.

2. In the wiring of the copper foil, the wiring width of the lead portion soldered to the terminal of the piezoelectric actuator is thinner than the column width of the piezoelectric actuator, and changes in the tapered shape to be thicker than the column width of the piezoelectric actuator, The liquid discharge head according to claim 1, wherein the boundary portion of the solder resist region straddles the central portion of the portion where the wiring width changes in a tapered shape.

3. The liquid discharge head according to claim 1, wherein the solder resist region is formed by covering the surface of the copper foil of the film substrate with a resin film.

4. The liquid discharge head according to claim 1, wherein the solder resist region is formed by a resin applied to the surface of the copper foil of the film substrate.

5. The liquid discharge head according to any one of claims 1 to 4, wherein the soldering portion of the wiring of the copper foil is outside the solder resist region and is solder-plated.

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