JP2014058126A - Droplet discharge head and image formation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress variation of discharge characteristic of each nozzle hole.SOLUTION: The droplet discharge head includes: a nozzle plate having a plurality of nozzle holes discharging a liquid; a liquid chamber formation substrate in which a pressure liquid chambers communicating with the nozzle holes are formed; a piezoelectric actuator in which a lower electrode, a piezoelectric layer for increasing pressure inside the pressure liquid chamber, and an upper electrode are sequentially formed on a diaphragm which constitutes a part of the pressure liquid chamber. The lower electrodes, divided for each pressure liquid chamber, are individual electrodes in which a driving voltage for driving the piezoelectric actuator is applied to each pressure liquid chamber, and the upper electrodes, conducting to each other, are common electrodes. A divided part of the lower electrodes are outside of a vibration area of the diaphragm.

Description

  According to the present invention, a piezoelectric body is displaced to displace a diaphragm that forms a part of the pressurized liquid chamber to change the pressure in the pressurized liquid chamber, thereby allowing droplets to be discharged from a nozzle hole that communicates with the pressurized liquid chamber. The present invention relates to a droplet discharge head to be discharged and an image forming apparatus.

  Conventionally, an electromechanical conversion element configured such that an electromechanical conversion film is sandwiched between electrodes includes, for example, a liquid discharge head that discharges ink droplets, and forms an image by adhering ink droplets to a sheet while conveying a medium. Used in an ink jet recording apparatus. The medium here is also referred to as “paper”, but the material is not limited, and a recording medium, a recording medium, a transfer material, a recording paper, and the like are also used synonymously. The image forming apparatus means an apparatus for forming an image by discharging a liquid onto a medium such as paper, thread, fiber, fabric, leather, metal, plastic, glass, wood, ceramics. The image formation is not only giving an image having a meaning such as a character or a figure to the medium but also giving an image having no meaning such as a pattern to the medium (simply ejecting a droplet). Also means. The ink is not limited to so-called ink, and is not particularly limited as long as it becomes liquid when ejected. For example, the ink is a generic term for liquids including DNA samples, resists, pattern materials, and the like. Use.

  An ink jet recording head in an ink jet recording apparatus, which is an example of an image forming apparatus, includes a pressurizing liquid chamber that communicates with a nozzle hole that ejects ink droplets, an actuator unit that generates energy to pressurize the pressurizing liquid chamber, and a pressurizing liquid And a common liquid chamber for supplying ink to the chamber. Then, by driving the actuator means, the pressure inside the pressurized liquid chamber is increased and ink droplets are ejected from the nozzle holes, and an ink-on-demand type that ejects ink droplets only when necessary for recording is available. Mainstream. Depending on the type of actuator means for ejecting ink droplets, it is roughly classified into methods such as a piezo method, a bubble method, and an electrostatic method.

  At present, an ink jet recording apparatus adopting a piezo method is mainly used. As the piezoelectric actuator means, those using a longitudinal vibration mode piezoelectric actuator that extends and contracts in the axial direction of the piezoelectric element and those using a flexural vibration mode piezoelectric actuator have been put into practical use. Among these, the inkjet recording apparatus using the piezoelectric actuator in the flexural vibration mode pressurizes through the vibration plate when the piezoelectric element flexurally vibrates with respect to the vibration plate formed on a part of the inner wall of the pressurized liquid chamber. Change the internal pressure of the liquid chamber. Thereby, the ink in the pressurized liquid chamber is ejected from the nozzle hole.

  As a liquid droplet ejection head using this flexural vibration mode piezoelectric actuator, one described in Patent Document 1 is known. In the liquid droplet ejection head of this Patent Document 1, a partition for partitioning each pressure chamber (pressurized liquid chamber) communicating with each nozzle hole is provided on a liquid chamber forming substrate stacked on a nozzle plate having a plurality of nozzle holes. A diaphragm is provided in a part of each pressure chamber. The diaphragm is provided with a piezoelectric element for each pressure chamber. In this piezoelectric element, a lower electrode (lower electrode), a piezoelectric body, and an upper electrode (upper electrode) are laminated in this order on a diaphragm. In the manufacturing process of the droplet discharge head disclosed in Patent Document 1, a vibration plate, a lower electrode, a piezoelectric body, and a layer serving as an upper electrode are laminated on a substrate serving as a liquid chamber forming substrate. The body and the upper electrode are subjected to dry etching and patterned to form a piezoelectric element.

  However, in the droplet discharge head of Patent Document 1 described above, a groove is formed in the vibration plate when overetching in which the etching depth reaches the vibration plate occurs in the step of etching the lower electrode. The position where the groove is formed is in the vibration region of the diaphragm, and if the depth of the groove formed in the diaphragm varies, the rigidity of the diaphragm varies individually. For this reason, the discharge characteristics vary from nozzle hole to nozzle hole.

  The present invention has been made in view of the above problems, and the objects thereof are as follows. It is an object of the present invention to provide a droplet discharge head and an image forming apparatus capable of suppressing variations in discharge characteristics for each nozzle hole by setting the lower electrode division position outside the vibration region of the diaphragm.

  In order to achieve the above object, the invention of claim 1 includes a nozzle plate having a plurality of nozzle holes for discharging a liquid, a liquid chamber forming substrate for forming a pressurized liquid chamber communicating with the nozzle holes, and the process. A lower electrode, a piezoelectric layer that pressurizes the pressurized liquid chamber, and a piezoelectric actuator that is formed by sequentially forming an upper electrode on a vibration plate constituting a part of the pressurized liquid chamber, In the liquid droplet ejection head, which is divided into each pressurized liquid chamber and is an individual electrode to which a driving voltage for driving the piezoelectric actuator is applied for each pressurized liquid chamber, and the upper electrode is a common electrode that conducts to each other, The portion of the electrode dividing portion is outside the vibration region of the diaphragm.

  In the present invention, the divided portions of the individual electrodes are located outside the vibration region of the diaphragm. Even if the overetching that occurs when individual electrodes are etched and individualized occurs and a groove is formed in the diaphragm, this groove is outside the vibration region of the diaphragm and has an effect on the vibration characteristics of the diaphragm. Less. As a result, it is possible to obtain a unique effect that variation in discharge characteristics for each nozzle hole can be suppressed.

It is a perspective view which shows the structure of an inkjet recording device. It is a side view of the mechanism part of an inkjet recording device. It is sectional drawing of the droplet discharge head which concerns on this embodiment. It is a schematic diagram of the conventional drive circuit. It is a schematic diagram of the drive circuit of this embodiment. It is a figure which shows the drive voltage waveform by bias voltage application. It is a figure which shows the result of having analyzed the composition of the depth direction by GD-OES. It is sectional drawing of the nozzle row direction of the droplet discharge head which concerns on this embodiment. It is a partial top view of the droplet discharge head concerning this embodiment. It is process sectional drawing which shows the Example of the manufacturing process of a droplet discharge head. It is process sectional drawing which shows the Example of the manufacturing process of a droplet discharge head. It is process sectional drawing which shows the Example of the manufacturing process of a droplet discharge head. It is process sectional drawing which shows the Example of the manufacturing process of a droplet discharge head. It is a figure explaining the modification 1 of the droplet discharge head which concerns on embodiment. It is a figure explaining the modification 2 of the droplet discharge head which concerns on embodiment. It is a characteristic view which shows a butterfly characteristic.

  First, the configuration of an ink jet recording apparatus equipped with an ink jet recording head which is an example of a liquid droplet ejection head according to the present invention will be described with reference to the drawings. FIG. 1 is a perspective view showing a configuration of an ink jet recording apparatus, and FIG. 2 is a side view of a mechanism portion of the ink jet recording apparatus.

  An ink jet recording apparatus 100 shown in FIGS. 1 and 2 accommodates a printing mechanism 103 and the like. The printing mechanism 103 and the like are configured by a droplet discharge head 1 mounted on a carriage 101 movable in the main scanning direction inside the apparatus main body and an ink cartridge 102 for supplying ink to the droplet discharge head 1. . A sheet feeding cassette (or a sheet feeding tray) 104 on which a large number of recording sheets P can be stacked from the front side is detachably attached to the lower part of the apparatus main body. Further, it has a manual feed tray 105 that is opened to manually feed the recording paper P, takes in the recording paper P fed from the paper feed cassette 104 or the manual feed tray 105, and prints a required image by the printing mechanism unit 103. After recording, the paper is discharged to a paper discharge tray 106 mounted on the rear side.

  The printing mechanism 103 holds the carriage 101 slidably in the main scanning direction with a main guide rod 107 and a sub guide rod 108 which are guide members horizontally mounted on left and right side plates (not shown). The carriage 101 has a droplet discharge head 1 that discharges ink droplets of yellow (Y), cyan (C), magenta (M), and black (Bk) in a plurality of ink discharge ports (nozzle holes). They are arranged in the sub-scanning direction orthogonal to the direction, and are mounted with the ink droplet ejection direction facing downward. In addition, each ink cartridge 102 for supplying ink of each color to the droplet discharge head 1 is replaceably mounted on the carriage 101.

  The ink cartridge 102 is provided with an atmosphere port communicating with the atmosphere above, and a supply port for supplying ink to the droplet discharge head 1 below. A porous body filled with ink is contained inside, and the ink supplied to the droplet discharge head 1 is maintained at a slight negative pressure by the capillary force of the porous body. Further, although the droplet discharge head is used for each color as the droplet discharge head 1, one droplet discharge head having nozzles for discharging ink droplets of each color may be used.

  Here, the carriage 101 is slidably fitted to the main guide rod 107 on the rear side (downstream side in the paper conveyance direction), and is slidably mounted on the secondary guide rod 108 on the front side (upstream side in the paper conveyance direction). doing. In order to move and scan the carriage 101 in the main scanning direction, a timing belt 112 is stretched between a driving pulley 110 and a driven pulley 111 that are rotationally driven by a main scanning motor 109a. The timing belt 112 is fixed to the carriage 101, and the carriage 101 is reciprocally scanned by forward and reverse rotation of the main scanning motor 109a.

  On the other hand, in order to convey the recording paper P set in the paper feeding cassette 104 to the lower side of the droplet discharge head 1, a paper feeding roller 113 and a friction pad 114 for separating and feeding the recording paper P from the paper feeding cassette 104, And a guide member 115 for guiding the recording paper P. Further, a conveyance roller 116 that reverses and conveys the fed recording paper P, a conveyance roller 117 that is pressed against the peripheral surface of the conveyance roller 116, and a leading end roller that defines a feeding angle of the recording paper P from the conveyance roller 116. 118. The conveyance roller 116 is rotationally driven via a gear train by the sub-scanning motor 109b.

  In addition, a printing receiving member 119 that is a paper guide member is provided to guide the recording paper P fed from the transport roller 116 below the droplet discharge head 1 in accordance with the moving range of the carriage 101 in the main scanning direction. ing. A conveyance roller 120 and a spur 121 that are rotationally driven to send the recording paper P in the paper discharge direction are provided on the downstream side of the printing receiving member 119 in the paper conveyance direction. Further, a paper discharge roller 123 for sending the recording paper P to the paper discharge tray 106, a spur 124, and guide members 125 and 126 for forming a paper discharge path are provided.

  When recording with the inkjet recording apparatus 100, the droplet discharge head 1 is driven in accordance with the image signal while moving the carriage 101, thereby discharging ink onto the stopped recording paper P to record one line. Thereafter, after the recording paper P is conveyed by a predetermined amount, the next line is recorded. Upon receiving a recording end signal or a signal that the trailing edge of the recording paper P reaches the recording area, the recording operation is terminated and the recording paper P is discharged.

  A recovery device 127 for recovering the ejection failure of the droplet ejection head 1 is disposed at a position outside the recording area on the right end side in the movement direction of the carriage 101. Each of the recovery devices 127 includes a cap unit, a suction unit, and a cleaning unit (not shown). During printing standby, the carriage 101 is moved to the recovery device 127 side, and the droplet discharge head 1 is capped by the capping unit to keep the discharge port portion in a wet state, thereby preventing discharge failure due to ink drying. Further, by ejecting ink that is not related to recording during recording or the like, the ink viscosity of all the ink ejection ports is made constant, and stable ejection performance is maintained.

  Further, when a discharge failure occurs, the ink discharge port of the droplet discharge head 1 is sealed with a capping unit, and bubbles and the like are sucked out from the discharge port with the suction unit through the tube. As a result, ink or dust adhering to the ink discharge port surface is removed by the cleaning means, and the discharge failure is recovered. Further, the sucked ink is discharged to a waste ink reservoir (not shown) installed at the lower part of the main body and absorbed and held by an ink absorber inside the waste ink reservoir.

  As described above, since the ink jet recording apparatus 100 includes the ink jet recording head having the actuator unit, stable ink droplet ejection characteristics can be obtained and the image quality can be improved.

  FIG. 3 is a cross-sectional view of the droplet discharge head according to the present embodiment. This embodiment is a droplet discharge head using a piezoelectric actuator, and shows an example of a side shooter system that discharges ink droplets from a nozzle provided on a surface portion of a substrate. As shown in FIG. 3A, the droplet discharge head 1 of the present embodiment is mainly configured as a stacked structure in which a nozzle substrate 10, a liquid chamber substrate 20, a vibration plate 30, and a protective substrate 40 are stacked. Yes. The nozzle substrate 10 is provided with nozzles 11 that eject ink. In addition to the pressurized liquid chamber 21 and the fluid resistance portion 22, a groove portion serving as an ink supply portion 23 is formed in the liquid chamber substrate 20. The diaphragm 30 is formed with a piezoelectric actuator such as a piezoelectric layer. The protection substrate 40 is provided with a piezoelectric element protection space 41.

  The nozzle substrate 10 has a nozzle 11 formed on a SUS substrate having a thickness of 30 to 50 [μm] by pressing and polishing. Each nozzle 11 is provided so as to communicate with the pressurized liquid chamber 21 of the liquid chamber substrate 20. The liquid chamber substrate 20 is an SOI substrate in which silicon is bonded to a silicon substrate via a silicon oxide film. The diaphragm 30 has a silicon oxide film formed on the surface of the Si layer of the SOI substrate by applying a pyro-oxidation method. On the vibration plate 30, a platinum film serving as the individual electrode 51, which is the lower electrode, a piezoelectric layer (PZT) 52, and a platinum film serving as the common electrode 53, which is the upper electrode, are formed in this order to form a piezoelectric actuator. It is composed. This piezoelectric actuator is formed in a region facing the pressurized liquid chamber 21 formed by etching silicon. An interlayer insulating film 54 disposed between the individual electrode 51 and the common electrode 53 and the wiring material, and a passivation film 55 for protecting the material of the lead wiring are disposed so as to cover the upper surface and side surfaces of the actuator. Yes.

  The protective substrate 40 has a groove portion serving as an ink flow path as the common liquid chamber 42, a space for preventing protection and displacement of the piezoelectric element and a rigidity of the flow path partition wall, and a column is formed to support the entire liquid chamber. ing. The individual electrode 51 is divided for each pressurizing liquid chamber and is drawn out to the individual electrode pad portion 56 by the lead wiring 57. A line led out from the common electrode 53 by the lead-out wiring 58 is conducted by a part of the individual electrode 51, the lead-out wiring 58, and a bypass wiring 59 wired in the wiring space 60. A potential is applied. As shown in FIG. 3B, the piezoelectric layer 52 of this embodiment is polarized in a direction from the common electrode 53 toward the individual electrode 51. That is, in this embodiment, the individual electrode 51 is provided on the side facing the same direction as the polarization direction of the piezoelectric layer 52, and the common electrode 53 is provided on the side facing the direction opposite to the polarization direction of the piezoelectric layer 52. .

Next, the drive circuit configuration in the present embodiment will be described. Figure 4 is a schematic diagram of a conventional driving circuit configuration, the reference voltage V ₀ and the lower electrode and the common electrode is applied, and the driving voltages V ₁ to the upper electrode and the individual electrode is applied. On the other hand, in the present embodiment, the circuit configuration shown in FIG. 5 is obtained by using the wiring described in FIG. Both conventional and the present embodiment, the switch circuit of the driver IC to control the application of driving voltages V ₁ on the basis of the image signal is connected. Although the driver IC is not shown in FIG. 3, the output from the driver IC terminal is connected to the individual electrode pad portion 56 of FIG. The actuator operation of each pressurized liquid chamber is controlled by this voltage.

Then, in the circuit configuration of this embodiment shown in FIG. 5, the driving voltage V ₁ is applied to the individual electrodes of the lower electrode, the reference voltage V ₀ is applied to the common electrode of the upper electrode. Therefore, even if the drive voltage V ₁ and the reference voltage V ₀ are positive voltages, when viewed from the piezoelectric layer, a reverse voltage is applied to the direction of the electric field in the butterfly characteristic of FIG. . That is, the potential difference between the individual electrode and the common electrode in the piezoelectric layer is negative. The piezoelectric actuator is operated on the negative polarity side of the electric field strength with good ejection efficiency in the butterfly characteristics. This eliminates the need for a negative-polarity power source, and can suppress an increase in cost.

Also, bias driving will be described. The wiring shown in FIG. 5 uses the lower electrode as an individual electrode and the drive voltage V ₁ and the upper electrode as a common electrode and the reference voltage V _0. FIG. 6 shows an example in which a bias voltage is applied to the common electrode. ing. If not only the negative polarity side drive but also the negative polarity side bias drive is performed, the vibration displacement of the actuator can be further ensured, and the discharge efficiency can be increased to lower the voltage. Therefore, since the voltage difference applied to the piezoelectric layer is expressed as ΔV = V ₀ −V ₁ , if a normal voltage waveform (FIG. 6A) is supplied to the individual electrode and the common electrode, respectively, the negative electrode It was found that the same characteristics as the bias drive on the sex side can be obtained.

  In addition, when a piezoelectric material constituting a thin film actuator is formed by a film-forming method by liquid application such as the Sol-Gel method, density unevenness is caused by diffusion of material due to heat during baking in the film-forming process above and below the film. Occur. Due to this uneven density, the distribution of defects differs between the upper and lower sides of the film, and this defect causes deterioration of the characteristics. Further, since many defects are distributed on the upper side of the film (the surface opposite to the diaphragm), driving from the upper electrode inevitably tends to cause a characteristic deterioration (deterioration). The result of having analyzed the composition of the depth direction by GD-OES is shown in FIG. As can be seen from the figure, Pb (lead) is segregated very much in the common electrode. This becomes a defect and causes characteristic deterioration. As in this embodiment, by applying a drive voltage with the lower electrode arranged on the diaphragm side as an individual electrode, the influence of defects is minimized, deterioration is suppressed, and good characteristics are maintained to the maximum Can do.

  Further, in the present embodiment, as shown in FIG. 8 which is a sectional view in the nozzle row direction, the dividing unit 61 that divides the individual electrode 51 for each pressurized liquid chamber includes the flow path partition 62 of the pressurized liquid chamber 21. It is formed at a position that falls within a virtual range W corresponding to the wall width in the nozzle row direction. That is, the edge of the individual electrode 51 in the nozzle row direction is formed outside the opening width range of the pressurizing fluid chamber 21 in the nozzle row direction with respect to the pressurizing fluid chamber arrangement direction. Thereby, even if the diaphragm 30 is etched in the division process of the individual electrode 51 and the groove depth of the diaphragm 30 varies, the influence on the diaphragm rigidity of the pressurized liquid chamber 21 is small, and the discharge variation is reduced. It can be minimized. In addition, as shown in FIG. 9 which is a partial plan view, it is preferable to form the edge of the individual electrode 51 outside the opening of the pressurized liquid chamber 21 also in the longitudinal direction of the pressurized liquid chamber.

Next, a method for manufacturing the droplet discharge head will be described.
10, FIG. 11, FIG. 12 and FIG. 13 are process cross-sectional views showing an embodiment of a manufacturing process of a droplet discharge head. In this embodiment, an actuator is created by depositing a diaphragm material and a piezoelectric element material on a silicon substrate.
First, as shown in FIG. 10A, a silicon oxide film of 0.2 [μm] and silicon of 2.0 [μm] are bonded to the surface of a <100> silicon substrate 201 having a thickness of 400 [μm]. An SOI substrate 202 is used. A silicon oxide film of 0.3 [μm] is formed on the surface of the SOI substrate 202 by a pyro oxidation method, and this is used as a vibration plate. Thereafter, as shown in FIG. 10B, a platinum (Pt) layer 203 serving as an individual electrode of the piezoelectric element is formed by a sputtering method to a thickness of 0.2 [μm], and the piezoelectric layer 204 is formed by a sol-gel method to a thickness of 0.2 [mu] m. [Μm] A film is formed. Then, a platinum (Pt) layer 205 serving as a common electrode is formed to a thickness of 0.1 [μm].

  Next, as shown in FIG. 10C, the common electrode 205, the piezoelectric layer 204, and the individual electrodes 203 are patterned by a lithoetch method. As shown in FIG. 9, a part of the individual electrode is patterned in a state of being divided for each pressurized liquid chamber. As shown in FIG. 7, the divided portions are formed in a positional relationship that fits within the flow path partition wall width so that the change to the diaphragm rigidity is small.

  Next, as shown in FIG. 11A, an interlayer insulating film 206 is formed in a thickness of 0.3 [μm] by a plasma CVD method, and a via hole 207 for making a wiring contact is formed by a lithoetch method. The interlayer insulating film 206 patterns the conductive portion 208 between the lead-out wiring and the common electrode to be formed next, the conductive portion 209 to the bypass wiring, and the through-hole portion 210 serving as the ink supply hole. Further, as shown in FIG. 11B, lead wires 211 and 212 are formed of an aluminum material. Since the lead-out wirings 211 and 212 are subjected to stress due to vibration of the diaphragm driven by the piezoelectric body, a soft aluminum material is used and is thickly stacked by about 1 [μm] so as not to be disconnected by vibration. As shown in FIG. 3, the lead-out wiring 212 from the common electrode is electrically connected at a location outside the drive area of the piezoelectric actuator section. Then, as shown in FIG. 11C, 2 [μm] of a silicon nitride film by plasma CVD is formed as a passivation film 213 for protecting the aluminum wiring and patterned. Then, the through hole 214 serving as the ink supply port of the vibration plate 202 is etched in advance.

  Further, as shown in FIG. 12A, gold is laminated by a plating method, and a pad portion 215 of individual electrodes and a bypass wiring 216 are formed simultaneously. By forming the pad portion 215 with gold, electrical connection with a driver IC (not shown) is connected by low-temperature wire bonding. Also, gold has a low resistance value and has a great effect of reducing the common electrode resistance value as a bypass wiring. The pad portion 215 and the formation process can be separated, and copper, aluminum, or the like can be used as a material for the bypass wiring. In that case, a protective layer that protects the bypass wiring 216 from corrosion may be required.

  After that, as shown in FIG. 12B, a protective substrate 217 in which a pillar is separately formed on a glass substrate by blasting is bonded to the liquid chamber substrate of the silicon substrate 201, and the surface opposite to the protective substrate bonding surface of the liquid chamber substrate. Is polished to a desired thickness. The protective substrate 217 may be a silicon substrate obtained by processing a recess by a lithoetch method, or a <110> silicon substrate processed by wet etching using an alkaline etching solution such as TMAH or KOH. Further, it may be a molded part such as a resin mold or a metal injection mold. In addition, when the driver circuit is integrally formed on the actuator substrate, the oxide film formed by the pyro oxidation method is formed by the LOCOS oxidation method, and the drive circuit is formed on the same substrate by selecting the oxide film formation region. You can also

  Thereafter, as shown in FIG. 13A, a groove serving as a pressurized liquid chamber 218, a fluid resistance portion 219, and an ink supply portion 220 is formed on the opposite surface of the silicon substrate 201 by ICP dry etching. Finally, as shown in FIG. 13B, a nozzle substrate 222 in which a nozzle 221 is formed by pressing and polishing a SUS substrate having a thickness of 30 to 50 [μm] separately from the liquid chamber substrate of the silicon substrate 201 is used. Adhere to the road partition surface. Then, an aluminum wiring portion (not shown) connected to the common electrode and the individual electrode of the piezoelectric element is connected to a driver IC (not shown) to complete the droplet discharge head.

  Further, as shown in FIG. 8, the division part 60 of the individual electrode 51 is formed so as to be within a virtual range corresponding to the range of the width in the nozzle row direction in the flow path partition wall 61 of the pressurized liquid chamber 21. . For this reason, even if a groove is formed in the diaphragm in the individual electrode dividing step, it is possible to suppress the influence on the discharge characteristics due to the depth variation of the groove. Thereby, the discharge variation by individualizing an individual electrode can be suppressed to the minimum. The division part 60 of the individual electrode 51 is covered with an interlayer insulating film 54 (interlayer insulating film 206 in FIG. 11A). This causes a potential difference between adjacent individual electrodes due to the image signal. Moreover, it is necessary to put the division part 60 of the individual electrode 51 in the flow path partition wall width. Since the distance between adjacent individual electrodes is short, exposure to the surface causes surface leakage due to humidity and shortens the head life. Thus, it is necessary to protect the division part of the pressurized liquid chamber in the column direction with the insulating film of the interlayer insulating film. In the case of a configuration with an interlayer insulating film (an interlayer insulating film is required because the lead-out wiring of the common electrode passes over the individual electrode), the configuration in which the divided portion of the individual electrode is protected by the interlayer insulating film is realized to increase the number of processes It is useful because it can.

  In this embodiment, the individual electrode is drawn from the upper part of the piezoelectric layer by an aluminum lead wiring which is a soft metal material, and is coupled to the lead wiring in a region outside the piezoelectric layer and the individual electrode. Even if a soft metal material is selected, it is not preferable to connect on the piezoelectric layer, which is a movable region, because it interferes with the operation of the piezoelectric actuator and causes extra vibration to propagate. Moreover, in the area | region with an individual electrode, since an additional electrostatic capacitance is carried, it becomes an electrical load and is not preferable. In terms of ejection efficiency and mutual interference, it is preferable that the common electrodes are connected in a region where these common electrodes are removed.

  Furthermore, lead wires are also formed on the individual electrode side to reduce the resistance value of the path to the individual electrode. Since the material of the individual electrode is subjected to a high-temperature process of firing the piezoelectric layer, materials such as aluminum and copper cannot be used. For this reason, the resistance value is high, which causes the drive voltage waveform to become dull. A dull drive voltage waveform deteriorates the discharge efficiency. Therefore, although lead wires are formed also on the individual electrode side, the process is simplified by forming simultaneously with the lead wires from the common electrode. At this time, the lead wires for the individual electrodes are wired from outside the pressurized liquid chamber. If the lead-out wiring is wired in the pressurized liquid chamber, a step is formed at the end of the lead-out wiring, and when the diaphragm is bent, stress is easily concentrated and damaged. It is preferable to form the lead-out wiring from a position avoiding the movable part of the diaphragm.

  FIG. 14 is a diagram illustrating a first modification of the droplet discharge head according to the embodiment. 14A is a plan view, and FIG. 14B is a partial cross-sectional view in the nozzle row direction of FIG. 14A. In this modified example 1, the individual electrodes are divided into individual electrodes corresponding to the respective pressurized liquid chambers within the width of the flow path partition walls, and the edge portions of the individual electrodes are separated from the projection surface of the pressurized liquid chambers. It is formed on the outside. That is, the individual electrodes that are electrically connected to the common electrode are formed between the individual electrodes that are made into individual electrodes. As the process, only the patterning of the individual electrodes is changed, so that the number of manufacturing steps is not increased and the cost is not increased. And since a lower electrode is utilized as an individual electrode, a potential difference arises in each individual electrode made into an individual electrode by an image signal. This change in potential difference affects ink ejection in adjacent channels as electrical interference due to capacitive coupling.

  In order to reduce this electrical interference, in Modification 1, by forming individual electrodes that are electrically connected to the common electrode between the individual electrodes that have been made into individual electrodes in the divided portion, the influence of the voltage on the adjacent channel is reduced. I made it smaller. As a result, the electrical interference is reduced, the influence of the ejection variation due to the image pattern is suppressed, and a good image can be obtained. In the first modification, the individual electrode is connected to the common electrode, but the common electrode may be formed from a lead wiring material. In FIG. 3, the common electrode wiring which isolate | separates an individual electrode under a flow-path partition is formed in the formation process of the extraction wiring electrically connected with a common electrode. Thereby, electrical interference can be reduced as in the above embodiment.

  FIG. 15 is a diagram for explaining a second modification of the droplet discharge head according to the embodiment. FIG. 15A is a sectional view in a direction orthogonal to the nozzle row direction, and FIG. 15B is a plan view. In the second modification, a lead-out passivation film is not formed by arranging lead-out wiring in the protective substrate. As a process, there is no process from the formation of the passivation film after the lead wiring to the etching. For this reason, manufacturing man-hours are significantly reduced and costs are reduced. The lead-out wiring is placed in a protective substrate, and the lead-out wiring is isolated from the outside. As a result, it is possible to prevent deterioration of the lead-out wiring due to environmental humidity, which is a concern, and it is not necessary to form a passivation film for protecting the lead-out wiring. In Modification 2, it is possible to eliminate resistance at the interface between the lead-out wiring, Au, and the individual electrodes by directly forming Au (gold) for the pad on the individual Pt of the individual electrodes. , Adhesion can be improved.

What has been described above is merely an example, and the present invention has a specific effect for each of the following modes.
(Aspect 1)
The part of the division part of the lower electrode is outside the vibration region of the diaphragm. According to this, as described in the above embodiment, the divided portion of the individual electrode is located outside the vibration region of the diaphragm. Even if the overetching that occurs when individual electrodes are etched and individualized occurs and a groove is formed in the diaphragm, this groove is outside the vibration region of the diaphragm and has an effect on the vibration characteristics of the diaphragm. Less. Thereby, the variation in the discharge characteristic for every nozzle hole can be suppressed.
(Aspect 2)
In (Aspect 1), the part of the division part of the lower electrode is within a virtual range corresponding to the width of the wall part that divides each pressurized liquid chamber. According to this, as described in the first modification of the above embodiment, even if the depth of the groove reaching the diaphragm varies due to the pattern etching process of the individual electrode 51, the diaphragm rigidity of the pressurized liquid chamber is does not change. Thereby, variation in droplet discharge characteristics can be suppressed.
(Aspect 3)
In (Aspect 1) or (Aspect 2), the lower electrode is covered with an insulating material. According to this, since the potential difference is generated between the individual electrodes 51 as described in the above embodiment, the probability of the occurrence of the failure can be reduced by protecting the individual electrodes 51 so as not to leak due to environmental humidity.
(Aspect 4)
In any one of (Aspect 1) to (Aspect 3), the lead-out wiring that supplies the drive voltage to the lower electrode is electrically connected to the lower electrode that extends to a region outside the arrangement region of the piezoelectric layer. According to this, as described in the above-described embodiment, as a method of conducting the common electrode 53, the connection on the virtual region of the piezoelectric layer 52 that is the movable region hinders the operation of the piezoelectric actuator, and is unnecessary. This is not preferable because it causes a large vibration to propagate. Further, an area having an individual electrode divided as the individual electrode 51 is not preferable because an extra capacity is applied. The conduction of the common electrode 53 is preferably combined in a region where these are removed from the viewpoint of ejection efficiency and mutual interference.
(Aspect 5)
In any one of (Aspect 1) to (Aspect 4), the lower electrode lead-out wiring is formed of the same material as the upper electrode lead-out wiring, and the lower electrode lead-out wiring is wired from the outside of the pressurized liquid chamber. ing. According to this, as described in the above embodiment, since the material of the individual electrode has a high wiring resistance, a lead-out wiring is also formed in the lead-out of the individual electrode. At this time, if the lead-out wiring is wired inside the pressurized liquid chamber, a step is formed at the end of the lead-out wiring, and when the diaphragm is bent, stress is concentrated and easily damaged. For this reason, since the lead-out wiring of the individual electrode is wired from the outside of the pressurized liquid chamber, the movable portion can be avoided and damage to the lead-out wiring can be prevented.
(Aspect 6)
In (Aspect 1) or (Aspect 2), an electrode pattern electrically connected to the upper electrode is formed between the divided portions of the adjacent lower electrodes. According to this, as described in the second modification of the above embodiment, since the drive voltage is applied to the individual electrode, even if it is protected by the insulating film and there is no direct leakage current, the capacitive coupling can be performed. Affects adjacent electrodes. By providing an electrode pattern that is electrically connected to the common electrode between the lower electrodes that form the individual electrodes, mutual interference due to capacitive coupling can be reduced.
(Aspect 7)
In (Aspect 1) or (Aspect 2), a pattern electrically connected to the upper electrode by the lead-out wiring member is formed between the divided portions of the adjacent lower electrodes. According to this, as described in the above embodiment, since the drive voltage is applied to the individual electrode, even if it is protected by the insulating film and there is no direct leakage current, it is possible to connect the adjacent electrode by capacitive coupling. Influence. By providing an electrode pattern that is electrically connected to the common electrode between the lower electrodes that form the individual electrodes, mutual interference due to capacitive coupling can be reduced.
(Aspect 8)
In any one of (Aspect 1) to (Aspect 7), a bias voltage not exceeding the coercive voltage of the piezoelectric element is applied to the common electrode. According to this, as described in the above embodiment, even when a voltage drive with a reverse polarity is performed, if a bias voltage that does not exceed the coercive voltage is applied, the displacement can be increased and the drive voltage can be lowered. it can.
(Aspect 9)
In (Aspect 1), a protective substrate that covers at least the piezoelectric actuator portion and protects from the outside is provided, and a lead wire for the common electrode is provided in the protective substrate. According to this, as described in the above embodiment, by inserting the lead-out wiring in the protective substrate, the protective layer of the lead-out wiring is not formed by blocking from the outside air and avoiding contact with ink. Mu
(Aspect 10)
(Aspect 1) to (Aspect 9) A recording liquid is discharged from a nozzle hole of the droplet discharge head according to any of the aspects to form an image. As described with reference to FIGS. 1 and 2, the image forming apparatus of the present embodiment can provide stable recording liquid droplet ejection characteristics and improve image quality.

DESCRIPTION OF SYMBOLS 1 Droplet discharge head 10 Nozzle board | substrate 11 Nozzle hole 20 Liquid chamber board | substrate 21 Pressurized liquid chamber 22 Fluid resistance part 23 Supply part 30 Diaphragm 40 Protection board 41 Piezoelectric element protection space 42 Common liquid chamber 51 Individual electrode 52 Piezoelectric layer 53 Common electrode 54 Interlayer insulating film 55 Passivation layer 56 Individual electrode pad portion 57 Lead wire 58 Lead wire 59 Bypass wire 60 Wiring space 61 Dividing portion 62 Channel partition 100 Inkjet recording apparatus

JP 2008-228458 A

Claims (10)

A nozzle plate having a plurality of nozzle holes for discharging liquid, a liquid chamber forming substrate for forming a pressurized liquid chamber communicating with the nozzle holes, and a diaphragm constituting a part of the pressurized liquid chamber, An electrode, a piezoelectric layer that pressurizes the pressurized liquid chamber, and a piezoelectric actuator that is formed by sequentially forming an upper electrode, and the lower electrode is divided for each pressurized liquid chamber, and for each pressurized liquid chamber In the liquid droplet ejection head, which is an individual electrode to which a driving voltage for driving the piezoelectric actuator is applied, and the upper electrode is a common electrode that conducts to each other,
The droplet discharge head according to claim 1, wherein the portion of the division portion of the lower electrode is outside the vibration region of the diaphragm. The droplet discharge head according to claim 1,
The droplet discharge head according to claim 1, wherein the portion of the division portion of the lower electrode is within a virtual range corresponding to a width of a wall portion that divides each pressurizing liquid chamber. The droplet discharge head according to claim 1 or 2,
The droplet discharge head, wherein the lower electrode is covered with an insulating material. In the liquid droplet ejection head according to any one of claims 1 to 3,
The droplet discharge head according to claim 1, wherein a lead-out wiring for supplying a driving voltage to the lower electrode is electrically connected to the lower electrode extending to a region outside the region where the piezoelectric layer is disposed. In the droplet discharge head according to any one of claims 1 to 4,
The droplet discharge head, wherein the lower electrode lead-out wiring is formed of the same material as the lead-out wiring from the upper electrode, and the lower electrode lead-out wiring is wired from outside the pressurized liquid chamber . The droplet discharge head according to claim 1 or 2,
A liquid droplet ejection head, wherein an electrode pattern electrically connected to the upper electrode is formed between the divided portions of the adjacent lower electrodes. The droplet discharge head according to claim 1 or 2,
A droplet discharge head, wherein a pattern electrically connected to the upper electrode by a lead-out wiring member is formed between the divided portions of the adjacent lower electrodes. In the droplet discharge head according to any one of claims 1 to 7,
A droplet discharge head, wherein a bias voltage not exceeding a coercive voltage of a piezoelectric element is applied to the upper electrode. The droplet discharge head according to claim 1,
A droplet discharge head comprising: a protective substrate that covers at least the piezoelectric actuator and protects from the outside; and a lead wire for the upper electrode is provided in the protective substrate.   An image forming apparatus for forming an image by discharging a recording liquid from a nozzle hole of the droplet discharge head according to claim 1 to a recording agent.

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