JP2009231777A - Piezoelectric actuator, liquid discharge head, liquid discharge device, and method of driving piezoelectric actuator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a piezoelectric actuator, a liquid discharge head, a liquid discharge device and a method of driving the piezoelectric actuator, capable of desirably driving the piezoelectric actuator having a piezoelectric film formed by epitaxial growth method such as sputtering or orientation growth method. <P>SOLUTION: A bottom electrode 118 is formed on the upper face of a substrate, and a piezoelectric film 120 is formed on the bottom electrode 118 by the sputtering, and an upper electrode 122 is formed on the upper face of the piezoelectric film 120. Further, a restraining plate 123 is formed on the upper face of the upper electrode 122. When the restraining plate 123 is not formed, and an electric field directed opposite to the polarizing direction of the piezoelectric film 120 is applied, the piezoelectric actuator 125 is deformed in an upwardly projecting shape. On the other hand, when the restraining plate 123 is formed, and the electric field directed opposite to the polarizing direction of the piezoelectric film 120 is applied, the piezoelectric actuator 125 is deformed in a downwardly projecting shape. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a piezoelectric actuator, a liquid discharge head, a liquid discharge apparatus, and a driving method of the piezoelectric actuator, and more particularly to a driving technique of a piezoelectric element having an orientation formed by a technique such as a sputtering method.

  2. Description of the Related Art As a general-purpose image forming apparatus, an ink jet recording apparatus that forms a desired image by ejecting ink droplets onto a recording medium from an ink jet head is widely used. In an ink jet recording apparatus, a piezoelectric element (piezoelectric actuator) is preferably used as pressure applying means for ejecting ink droplets from an ink jet head.

  Ink-jet heads are required to improve printing performance, in particular, higher resolution and higher printing speed. Therefore, attempts have been made to increase the resolution and the printing speed by using a multi-nozzle head structure in which nozzles are miniaturized and arranged at high density. In order to realize a high-density arrangement of nozzles, there is a strong demand for miniaturization of piezoelectric elements that are pressure generating elements.

In order to reduce the size of the piezoelectric element, it is effective to reduce the thickness. For example, in Patent Document 1, a piezoelectric layer (piezoelectric film) is formed by sputtering. A technique for forming a film is disclosed.
JP 2003-188429 A

  As shown in FIG. 22A, a piezoelectric film produced by sputtering as described in Patent Document 1 has a lower electrode 318 formed on a substrate (vibrating plate) 315 and a piezoelectric film applied to the lower electrode 318. Considering the piezoelectric element 323 formed by forming the body film 320 by sputtering and further forming the upper electrode 322 on the piezoelectric film 320, the polarization direction A when the piezoelectric film 320 is formed is The direction is from the lower electrode 318 toward the upper electrode 322.

  On the other hand, when the piezoelectric element 323 is used in an inkjet head, a structure in which the upper electrode 322 is an address electrode and the lower electrode 318 is a ground electrode is preferable from the viewpoint of forming wiring to the upper electrode 322 and the lower electrode 318.

  However, when the upper electrode 322 of the piezoelectric element 323 shown in FIG. 22A is used as an address electrode, the lower electrode 318 is used as a ground electrode, and a positive voltage is applied to the upper electrode 322 (an electric field in a direction opposite to the polarization direction of the piezoelectric film 320). 22 (b), the piezoelectric element 323 is deflected and deformed in the extending direction (indicated by reference numeral B in FIG. 22 (b)), and the diaphragm 315 is moved to the outside of the pressure chamber 324 (see FIG. 22B). The pressure chamber 324 is deformed (in the direction of increasing the volume), and ink cannot be ejected from a nozzle (not shown).

  On the other hand, when the upper electrode 322 is an address electrode, the lower electrode 318 is a ground electrode, and a negative voltage is applied to the upper electrode 322 (when an electric field in the same direction as the polarization direction of the piezoelectric film 320 is applied), FIG. As shown, the piezoelectric element 323 is bent and deformed in the contracting direction (indicated by reference numeral B ′ in FIG. 22C), and the diaphragm 315 is placed inside the pressure chamber 324 (in the direction of decreasing the volume of the pressure chamber 324). ) It can be deformed and ink can be ejected from the nozzles.

  FIG. 23 shows the relationship between the applied voltage (V) and the displacement (nm) of the piezoelectric actuator having the structure shown in FIGS. 22 (a) to 22 (c). The “piezoelectric actuator” represents a structure in which a piezoelectric element 323 is bonded to a vibration plate 315.

  In FIG. 23, the applied voltage is the voltage of the upper electrode 322 when the lower electrode 318 is set to the ground potential, and the amount of displacement is the amount of displacement from the static state of the diaphragm 315 and is deformed inside the pressure chamber 324. The displacement direction at the time is the positive direction.

  As shown in FIG. 23, the piezoelectric film 320 (piezoelectric element 323) formed by the sputtering method includes a case where a positive voltage is applied to the upper electrode 322 with the lower electrode 318 as a reference potential (ground potential), and a lower electrode. The characteristics are different from the case where a negative voltage is applied to the upper electrode 322 using 318 as a reference potential.

  For example, the displacement when -40V is applied is approximately 600 (nm), whereas the displacement when + 40V is applied is approximately 150 (nm). That is, the amount of displacement is reduced and the direction of displacement is reversed depending on the direction of the applied electric field. That is, in FIG. 23, the characteristics are different between the case where a negative voltage is applied and the case where a positive voltage is applied.

  The method of applying an electric field in the direction corresponding to the negative voltage shown in FIG. 23 to the piezoelectric element 323 includes a method using a power supply device for negative voltage and a driving IC (driving circuit), and the upper electrode 322 as a ground electrode, A method of applying a positive voltage to the lower electrode 318 using the electrode 318 as an address electrode can be used.

  However, the method of applying a negative voltage to the upper electrode 322 is disadvantageous in terms of cost because the power supply device and drive circuit for negative voltage are extremely expensive compared to those for positive voltage. Further, in the method of applying a positive electric field using the lower electrode 318 as an address electrode, a leak current is generated between adjacent lower electrodes through the vibration plate 315, and the vibration plate can be formed even in a non-driven piezoelectric element to which no electric field is applied. It will be displaced. As a result, there is a problem of electrical crosstalk in which ink is ejected from an unintended pressure chamber (nozzle).

  The present invention has been made in view of such circumstances, and enables a piezoelectric actuator having a piezoelectric film formed by an epitaxial growth method such as a sputtering method or an orientation growth method to be driven preferably. It is an object of the present invention to provide a head, a liquid discharge device, and a driving method of a piezoelectric actuator.

In order to achieve the above object, a piezoelectric actuator according to the present invention includes a vibration plate, a lower electrode formed on an upper surface of the vibration plate, and has an orientation in one direction of epitaxial growth or orientation growth. A piezoelectric film formed on the upper surface of the electrode opposite to the diaphragm; an upper electrode formed on the upper surface of the piezoelectric film opposite to the lower electrode; and the piezoelectric film of the upper electrode; A restraint plate provided on the opposite side surface, the direction of the thickness of each member is the y direction, the position of the lower surface of the diaphragm in the y direction is y ₀ , and the position of the boundary surface between the diaphragm and the lower electrode Y ₁ , the position of the interface between the lower electrode and the piezoelectric film is y ₂ , the position of the interface between the piezoelectric film and the upper electrode is y ₃ , and the position of the interface between the upper electrode and the restraint plate the _{y 4,} the upper surface position of the restraining plate and _{y 5} The Rutoki, the Young's modulus Y _v of the _diaphragm, Poisson's ratio V _v of the vibration _plate, the Young's modulus Y _u of the lower _electrode, Poisson's ratio V _u of the lower _electrode, the Young's modulus Y _p of said piezoelectric film, Poisson's ratio V _p of the piezoelectric _film, the Young's modulus Poisson's ratio V _p of the upper _electrode, the Young's modulus Y _m of the upper _electrode, Poisson's ratio V _m of the upper _electrode, the Young's modulus Y _f of the constraining _plate, the constraining The Poisson's ratio V _{f of the} plate is given by the following formula (1)

  It is characterized by satisfying the relationship.

  According to the present invention, the upper electrode of the upper electrode of the piezoelectric actuator is provided with a constraining plate on the side opposite to the piezoelectric film, and each member constituting the piezoelectric actuator is configured to satisfy the above formula (1). Since the constraining surface is provided on the side opposite to the body film, when an electric field is applied in a direction in which the piezoelectric film is deformed so as to expand, the piezoelectric actuator is deformed to the side opposite to the restraining plate of the piezoelectric film. Accordingly, when an electric field in the direction opposite to the orientation direction is applied to the piezoelectric film having an orientation direction from the lower electrode to the upper electrode by applying a positive voltage to the upper electrode with the lower electrode as a reference potential, the piezoelectric body The film is bent and deformed in the extending direction, and the piezoelectric actuator is deformed to the diaphragm side.

  The thickness direction of each member is a joining direction when the members are laminated and joined.

  When forming the piezoelectric film, it is preferable to use at least one of a sputtering method, a CVD method, and a sol-gel method because a piezoelectric film having a very thin film thickness can be formed.

  According to a second aspect of the present invention, there is provided the piezoelectric actuator according to the first aspect, wherein the diaphragm and the lower electrode are combined.

  According to the second aspect of the invention, by using the diaphragm and the lower electrode together, the thickness of the restraint plate can be further reduced, which contributes to the miniaturization of the piezoelectric actuator. Also. The structure of the piezoelectric actuator itself is simplified.

In an aspect in which the diaphragm and the lower electrode are combined, A ₁ in the above formula (1) may be omitted and the relationship of A ₂ + A ₃ <A ₄ + A ₅ may be satisfied. When an intermediate layer such as an insulating layer is taken into consideration, an index value calculated from the Young's modulus and Poisson's ratio of the intermediate layer is obtained, and the total index value on the constraint plate side of the piezoelectric film is determined by the constraint plate. It only needs to be larger than the sum of the index values on the opposite side (including the piezoelectric film).

In order to achieve the above object, a liquid discharge head according to the invention described in claim 3 includes a nozzle that discharges liquid, a pressure chamber that communicates with the nozzle and stores liquid discharged from the nozzle, A diaphragm constituting one wall surface of the pressure chamber, a lower electrode formed on the side surface of the diaphragm opposite to the pressure chamber, and a film formed on the side surface of the lower electrode opposite to the diaphragm, epitaxial growth or orientation A grown piezoelectric film having orientation in one direction, an upper electrode formed on the side surface of the piezoelectric film opposite to the lower electrode, and a restraint plate provided on the side surface of the upper electrode opposite to the piezoelectric film. The thickness direction of each member is the y direction, the position of the lower surface of the diaphragm in the y direction is y ₀ , the position of the boundary surface between the diaphragm and the lower electrode is y ₁ , and the lower electrode And the boundary of the piezoelectric film The position of the interface is y ₂ , the position of the boundary surface between the piezoelectric film and the upper electrode is y ₃ , the position of the boundary surface between the upper electrode and the constraint plate is y ₄ , and the position of the upper surface of the constraint plate is y ₅ The Young's modulus Y _{v of} the diaphragm, the Poisson's ratio V _{v of} the diaphragm, the Young's modulus Y _{u of} the lower electrode, the Poisson's ratio V _{u of} the lower electrode, the Young's modulus Y _{p of} the piezoelectric film, Poisson's ratio V _p of the piezoelectric _film, the Young's modulus Poisson's ratio V _p of the upper _electrode, the Young's modulus Y _m of the upper _electrode, Poisson's ratio V _m of the upper _electrode, the Young's modulus Y _f of the constraining _plate, the constraining The Poisson's ratio V _{f of the} plate is given by the following formula (1)

  It is characterized by satisfying the relationship.

  According to the third aspect of the present invention, even when a positive voltage is applied to the upper electrode with the lower electrode as a reference potential, and an electric field is applied in a direction opposite to the orientation direction (polarization direction) of the piezoelectric film, the diaphragm Can be deformed inside the pressure chamber, and a displacement proportional to the applied electric field strength can be obtained. Accordingly, it is possible to discharge the liquid from the nozzle by driving the piezoelectric actuator using a positive voltage with the upper electrode as the address electrode and the lower electrode as the ground electrode.

  According to a fourth aspect of the present invention, there is provided the liquid ejection head according to the third aspect, wherein the diaphragm and the lower electrode are combined.

  According to the fourth aspect of the present invention, in the aspect including the plurality of piezoelectric actuators corresponding to the plurality of nozzles and the plurality of pressure chambers, the lower electrode can be shared as the ground electrode, and the wiring structure is simplified. Contributes to

In order to achieve the above object, a liquid ejection device according to the invention described in claim 5 includes a nozzle that ejects liquid, a pressure chamber that communicates with the nozzle and accommodates liquid ejected from the nozzle, A diaphragm constituting one wall surface of the pressure chamber, a lower electrode formed on the side surface of the diaphragm opposite to the pressure chamber, and a film formed on the side surface of the lower electrode opposite to the diaphragm, epitaxial growth or orientation A grown piezoelectric film having orientation in one direction, an upper electrode formed on the side surface of the piezoelectric film opposite to the lower electrode, and a restraint plate provided on the side surface of the upper electrode opposite to the piezoelectric film. And a liquid discharge head for applying an electric field in a direction opposite to the orientation direction of the piezoelectric film, wherein the liquid discharge head has a thickness direction of each member as a y direction, In the y direction Wherein y ₀ a position of the lower surface of the _diaphragm, position y ₁ of the boundary surface of the vibration plate and the lower _electrode, the position of the boundary surface of the piezoelectric film and the lower electrode y _{2 that,} and the piezoelectric film When the position of the boundary surface of the upper electrode is y ₃ , the position of the boundary surface of the upper electrode and the constraining plate is y ₄ , and the upper surface position of the constraining plate is y ₅ , the Young's modulus Y _{v of the} diaphragm , Poisson's ratio V _{v of} the diaphragm, Young's modulus Y _{u of} the lower electrode, Poisson's ratio V _{u of} the lower electrode, Young's modulus Y _{p of} the piezoelectric film, Poisson's ratio V _p of the piezoelectric film, The Young's modulus Poisson's ratio V _{p of} the electrode, the Young's modulus Y _{m of} the upper electrode, the Poisson's ratio V _{m of} the upper electrode, the Young's modulus Y _{f of} the constraining plate, and the Poisson's ratio V _f of the constraining plate )

  It is characterized by satisfying the relationship.

  An example of the liquid ejecting apparatus is an ink jet recording apparatus that ejects ink from nozzles to form an image on a recording medium.

  According to a sixth aspect of the present invention, there is provided the liquid ejection device according to the fifth aspect, wherein the diaphragm and the lower electrode are combined.

  A mode in which a protective treatment (insulation treatment) is performed on the portion of the lower electrode that contacts the liquid in the pressure chamber is preferable.

  The invention according to claim 7 relates to an aspect of the liquid ejection apparatus according to claim 5 or 6, wherein the piezoelectric film has an orientation direction from the lower electrode toward the upper electrode, and the electric field The applying means applies a positive voltage to the upper electrode with the lower electrode as a reference potential to apply an electric field in a direction opposite to the orientation direction of the piezoelectric film.

  According to the seventh aspect of the present invention, the piezoelectric actuator can be driven in a desired operation mode by applying a positive voltage to the upper electrode using the lower electrode as the ground electrode and the upper electrode as the address electrode. This eliminates the complexity of the wiring structure.

The present invention also provides a method invention for achieving the above object. That is, the piezoelectric actuator driving method according to claim 8 has a diaphragm, a lower electrode formed on an upper surface of the diaphragm, and has an orientation in one direction of epitaxial growth or orientation growth, and the lower electrode A piezoelectric film formed on the upper surface of the piezoelectric film opposite to the diaphragm, an upper electrode formed on the upper surface of the piezoelectric film on the opposite side of the lower electrode, and the piezoelectric film of the upper electrode opposite to the piezoelectric film A restraint plate provided on a side surface, wherein the thickness direction of each member is the y direction, the position of the lower surface of the diaphragm in the y direction is y ₀ , and the position of the boundary surface between the diaphragm and the lower electrode is y ₁ , the position of the interface between the lower electrode and the piezoelectric film is y ₂ , the position of the interface between the piezoelectric film and the upper electrode is y ₃ , and the position of the interface between the upper electrode and the restraint plate is y _4, the upper surface position of the restraining plate When _{y 5} The Young's modulus Y _v of the _diaphragm, Poisson's ratio V _v of the vibration _plate, the Young's modulus Y _u of the lower _electrode, Poisson's ratio V _u of the lower _electrode, the Young's modulus Y _p of the piezoelectric _film, the piezoelectric Poisson's ratio of the body layer V _p, Young's modulus Poisson's ratio V _p of the upper _electrode, the Young's modulus Y _m of the upper _electrode, Poisson's ratio V _m of the upper _electrode, the Young's modulus Y _f of the constraining _plate, the constraining plate Poisson's ratio V _f is given by the following formula (1)

  When driving a piezoelectric actuator that satisfies the above relationship, an electric field in a direction opposite to the orientation direction of the piezoelectric film is applied between the upper electrode and the lower electrode.

  The method for driving a piezoelectric actuator of the present invention can be applied to a method for driving a liquid discharge head including the piezoelectric actuator.

  The invention according to claim 9 relates to an aspect of the driving method of the piezoelectric actuator according to claim 8, wherein the piezoelectric film has an orientation direction from the lower electrode to the upper electrode, and the lower electrode is used as a reference. A positive voltage is applied to the upper electrode as a potential, and an electric field in a direction from the upper electrode to the lower electrode is applied to the piezoelectric film.

  According to the present invention, the upper electrode of the upper electrode of the piezoelectric actuator is provided with a constraining plate on the side opposite to the piezoelectric film, and each member constituting the piezoelectric actuator is configured to satisfy the above formula (1). Since the constraining surface is provided on the side opposite to the body film, when an electric field is applied in a direction in which the piezoelectric film is deformed so as to expand, the piezoelectric actuator is deformed to the side opposite to the restraining plate of the piezoelectric film. Accordingly, when an electric field in the direction opposite to the orientation direction is applied to the piezoelectric film having an orientation direction from the lower electrode to the upper electrode by applying a positive voltage to the upper electrode with the lower electrode as a reference potential, the piezoelectric body The film is bent and deformed in the extending direction, and the piezoelectric actuator is deformed to the diaphragm side.

  Further, when the piezoelectric actuator is applied to a liquid discharge head, a positive voltage is applied to the upper electrode with the lower electrode as a reference potential, and an electric field is applied in a direction opposite to the orientation direction (polarization direction) of the piezoelectric film. When driving the diaphragm, the diaphragm can be deformed inside the pressure chamber, and a displacement amount proportional to the applied electric field strength can be obtained. Accordingly, it is possible to discharge the liquid from the nozzle by driving the piezoelectric actuator using a positive voltage with the upper electrode as the address electrode and the lower electrode as the ground electrode.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[Description of Manufacturing Method of Liquid Discharge Head]
A method for manufacturing a liquid ejection head (a method for manufacturing a piezoelectric actuator) according to an embodiment of the present invention will be described with reference to FIGS.

(1) Lower Electrode Formation Step FIG. 1 shows an SOI substrate (a silicon substrate provided with an insulating film of SiO ₂ , hereinafter referred to as a substrate) 110 which is a surface insulating substrate. The substrate 110 shown in FIG. 1 has a structure in which a silicon base 111, an insulating layer 112 made of a silicon oxide film, a silicon base 114, and an insulating layer 116 made of a silicon oxide film are stacked in order from the bottom. ing.

  FIG. 2 shows a state in which a metal film 118 serving as a lower electrode is formed on the substrate 110 shown in FIG. A metal film 118 serving as a lower electrode is formed on the upper surface of the substrate 110 (the surface on which the insulating layer 116 is formed) using a technique such as sputtering or vapor deposition. Thereafter, as shown in FIG. 3, the metal film 118 is processed into a predetermined shape using reactive ion etching (RIE). For the metal film (lower electrode) 118, iridium (Ir), platinum (Pt), titanium (Ti), or the like is preferably used.

  In addition, the arrangement pattern of the lower electrode 118 becomes an arrangement pattern of a piezoelectric actuator including a piezoelectric element (a structure denoted by reference numeral 125 in FIGS. 8 to 11), and ink is ejected according to the arrangement pattern of the piezoelectric actuator. (Shown by reference numeral 124 in FIGS. 10 and 11). In other words, the arrangement pattern of the lower electrode 118 is determined corresponding to the arrangement of nozzles and pressure chambers that eject ink.

(2) Piezoelectric film forming step When the lower electrode (metal film) 118 is processed into a predetermined shape (pattern), the surface on the upper side of the lower electrode 118 (on the side opposite to the insulating layer 116 of the lower electrode 118) The piezoelectric film 120 having orientation is formed using a thin film formation process by an epitaxial growth method such as sputtering, CVD, or sol-gel. PZT (lead zirconate titanate, Pb (Zr, Ti) O ₃ ) is preferably used for the piezoelectric film 120. FIG. 4 illustrates a state in which the piezoelectric film 120 is formed.

(3) Upper electrode film forming step When the piezoelectric film 120 is formed, a method such as sputtering or vapor deposition is applied to the upper surface of the piezoelectric film 120 (on the side opposite to the lower electrode 118 of the piezoelectric film 120). A metal film 122 that serves as an upper electrode is formed. For the metal film (upper electrode) 122, iridium (Ir), platinum (Pt), titanium (Ti), gold (Au), or the like is preferably used. FIG. 5 illustrates a state where a metal film 122 serving as an upper electrode is formed.

  Thereafter, as shown in FIG. 6, the metal film (upper electrode) 122 is patterned into a predetermined shape. Etching is preferably used for patterning the upper electrode 122 and patterning the lower electrode 118, and the patterning (etching process) of the upper electrode 122 (lower electrode 118) is performed at a temperature of about 150 ° C.

(4) Constraining Plate Film Formation Step Next, a constraining plate 123 is formed on the side surface of the upper electrode 122 opposite to the piezoelectric film 120. A thin film forming technique such as sputtering or CVD is used for forming the constraining plate 123, and a metal oxide such as SiO ₂ , Al ₂ O ₃ , or ZrO ₂ is used as a material for the constraining plate 123. Details of the structure and function of the restraint plate 123 will be described later.

(5) Wiring Layer Formation Step When the constraining plate 123 is formed, the portion of the constraining plate 123 and the piezoelectric film 120 from which the lower electrode 118 is taken out is removed by etching (wiring layer forming step). The wiring layer forming step is performed at a temperature of 200 ° C. to 350 ° C. Illustration of the wiring layer forming step is omitted.

(6) Restraint Plate Etching Step Next, the restraint plate 123 at a portion (a portion where an FPC to be described later is joined) from which the upper electrode 122 is taken out is removed by etching. FIG. 8 illustrates a state where the restraint plate 123 is removed and a part of the upper electrode 122 is exposed.

  In this specification, a structure in which the piezoelectric film 120 is sandwiched between the lower electrode 118 and the upper electrode 122 is referred to as a “piezoelectric element”, and the piezoelectric element itself or other member is deformed by driving the piezoelectric element ( The structure to be vibrated) is called a piezoelectric actuator. In this example, the structure in which the restraint plate 123 is provided on the upper surface of the upper electrode 122 of the piezoelectric element is the piezoelectric actuator 125.

(7) Pressure Chamber Formation Step Next, an opening (shape) 124 to be a pressure chamber is formed in the silicon base material 111 using a technique such as etching. FIG. 9 illustrates a state in which an opening 124 serving as a pressure chamber is formed.

(8) Flow path substrate bonding step and nozzle substrate bonding step As shown in FIG. 9, when the pressure chamber 124 is formed, a structure (an ink flow path is formed on the side of the substrate 110 where the pressure chamber 124 is formed). A flow path substrate 126 having a groove, a hole, etc.) is joined. When the substrate 110 and the flow path substrate 126 are joined, the ink flow path and the pressure chamber 124 are accurately aligned.

  Further, the nozzle substrate 128 in which the fine holes 127 to be nozzles are formed is joined to the opposite side of the flow path substrate 126 to the substrate 110 to form the head structure 129. When the nozzle substrate 128 and the flow path substrate 126 are joined, the fine hole 127 and the discharge side flow path are accurately aligned. FIG. 10 illustrates a state in which the flow path substrate 126 and the nozzle substrate 128 are joined.

(9) Flexible cable (FPC) bonding step When the head structure 129 including the piezoelectric actuator 125 is formed through the steps (1) to (8), the driving voltage applied to the piezoelectric actuator 125 is reduced. The flexible cable (FPC) 132 in which the wiring is formed includes the contact of the lower electrode 118 formed in the wiring layer forming process of (5) and the contact of the upper electrode 122 formed by the restraining plate etching process of (6). Be joined. A conductive adhesive is preferably used for bonding the contact of the upper electrode 122 and the contact of the lower electrode 118 and the FPC, and the FPC bonding process is performed in a temperature environment of about 100 ° C.

  FIG. 11 schematically illustrates a joined state between the FPC 132 and the head structure 129. Note that the wiring may be drawn from the upper electrode 122 to the end of the head structure 129, and the upper electrode 122 and the FPC 132 may be joined via a connector provided at the end of the head structure 129.

To give an example of the dimensions of the head structure 129 produced through the steps (1) to (9) above, the thickness of the diaphragm (structure comprising the insulating layer 112, the silicon substrate 114, and the insulating layer 116) Is 1 μm, the thickness of the upper electrode 122 and the lower electrode 118 is 0.3 μm, the thickness of the piezoelectric film 120 is 4 μm, and the opening size of the pressure chamber 124 is ^□ 300 μm.

[Description of piezoelectric actuator]
Next, the piezoelectric actuator 125 manufactured through the above steps (1) to (9) will be described.

  FIGS. 12A and 12B schematically show operation modes of the piezoelectric actuator 125 according to the embodiment of the present invention. As shown in FIG. 12A, the piezoelectric actuator 125 applies a positive voltage from the power supply device 130 to the upper electrode 122 using the upper electrode 122 as an address electrode and the lower electrode 118 as a ground electrode (the formation of the piezoelectric film 120). When an electric field in a direction opposite to the polarization direction A at the time of film application is applied), the piezoelectric film 120 bends and deforms in the extending direction (the direction indicated by the symbol B).

  In the piezoelectric actuator 125, the restraint plate 123 is provided on the upper surface of the upper electrode 122, so that a restraint surface exists above the upper electrode 122, and the diaphragm 115 (the piezoelectric actuator 125 as a whole) Deforms inward.

  On the other hand, as shown in FIG. 12B, when a negative voltage is applied from the power supply device 130 to the upper electrode 122 using the lower electrode 118 as a reference potential (an electric field in the same direction as the polarization direction A when the piezoelectric film 120 is formed). ), The piezoelectric film 120 is flexibly deformed in a contracting direction (a method illustrated by reference numeral B ′), and the diaphragm 115 is deformed to the outside of the pressure chamber.

That is, the piezoelectric actuator 125 shown in this example includes a piezoelectric film 120 that deforms in the direction of the d ₃₁ mode, and a constraining plate 123 is provided on the upper surface of the upper electrode 122, whereby the piezoelectric actuator according to the related art (see FIG. 22). The structure of the piezoelectric element 325 and the diaphragm 315 shown in FIG.

In this example, a constraining surface is provided above the upper electrode 122 of the piezoelectric actuator 125, the upper electrode 122 side of the piezoelectric actuator 125 is constrained, and the rigidity of the upper electrode 122 side of the piezoelectric actuator 125 is greater than that of the lower electrode 118 side. by, when the piezoelectric film 120 is contracted in the lateral direction (d ₃₁ direction), the diaphragm 115 becomes convex upward direction, when the piezoelectric film 120 is extended in the lateral direction, the diaphragm 115 downward It becomes convex.

  FIG. 13 shows the relationship between the applied voltage of the piezoelectric actuator 125 and the amount of displacement. As shown in the figure, when the applied voltage is in the range of 0 (V) to 20 (V), a displacement amount proportional to the applied voltage can be obtained. Further, the piezoelectric actuator according to the prior art shown in FIG. 22 is approximately the same as when the diaphragm 315 is deformed into the pressure chamber 324 by applying a negative voltage to the upper electrode 322 with the lower electrode 318 as a reference potential. The amount of displacement can be obtained.

  The displacement shown in FIG. 13 is the displacement in the vertical direction of the lower surface of the diaphragm 115 (the inner surface of the pressure chamber 124), and the downward direction in FIGS. This is the amount of displacement when a constant state (a state where the diaphragm with the applied voltage of 0 (V) is flat) is used as a reference.

  Here, the deformation mode of the piezoelectric actuator 125 shown in this example will be described in more detail. The joining direction (thickness direction, vertical direction in FIG. 14) of each member constituting the piezoelectric actuator 125 is defined as the y direction, and the position in the y direction of each member constituting the piezoelectric actuator 125 is defined as shown in FIG.

The lower surface of the diaphragm 115 (the lowermost surface of the piezoelectric actuator 125) is y ₀ , the lower surface of the lower electrode 118 (the boundary surface between the diaphragm 115 and the lower electrode 118) is y ₁ , and the lower surface of the piezoelectric film 120 (the lower electrode 118 and the piezoelectric film). the boundary surface) of the body layer 120 _{y 2,} the lower surface of the upper electrode 122 (piezoelectric film 120 and the boundary surface of the upper electrode 122) and _{y 3,} the lower surface of the constraining plate 123 (the boundary surface of the upper electrode 122 and the restraining plate 123) Is y ₄ , and the upper surface of the restraint plate 123 (the uppermost surface of the piezoelectric actuator 125) is y ₅ .

Further, the Young's modulus of the diaphragm 115 _{Y v,} the Poisson's ratio _{V v,} the Young's modulus of the lower electrode 118 _{Y u,} the Poisson's ratio _{V u,} the Young's modulus of the piezoelectric film 120 _{Y p,} the Poisson's ratio _{V p} When the Young's modulus of the upper electrode 122 is Y _m , the Poisson's ratio is V _m , the Young's modulus of the constraining plate 123 is Y _f , and the Poisson's ratio is V _f , the following equation (1) is satisfied. The piezoelectric actuator 125 having the characteristics shown in FIGS. 12 (a), 12 (b) and FIG. 13 can be obtained.

  The above formula (1) is a member above the piezoelectric film 120 with respect to the sum of the index values of the members below the piezoelectric film 120 (including the piezoelectric film 120) among the members constituting the piezoelectric actuator 125. The physical properties and thickness of the constraining plate 123 are determined so that the total of the index values becomes large.

Table 1 below shows the measurement results of measuring the displacement of the diaphragm when the thickness of the restraint plate 123 and the Young's modulus _Yf are changed. In the evaluation experiments The results are shown in Table 1 below, the thickness of the film thickness of the diaphragm 115 (Si) is 1.0 ([mu] m), the Young's modulus _{Y V} is 73 (GPa), a lower electrode 118 (Pt) is 0.3 (μm), the Young's modulus _{Y u} is 0.99 (GPa), the thickness of the piezoelectric film (PZT) 120 is 4.0 .mu.m, the Young's modulus _{Y p} is 70 (GPa), film of the upper electrode (Pt) 122 The thickness was 0.3 μm and the Young's modulus Y _m was 150 (GPa). The Poisson's ratio of each member was 0.3.

Further, the restraint plate 123 is polyimide (Example 1 to 4), _Al 2 _{O 3} (Example 5), using a SiC (Example 6), was used a polyimide film thickness 1.0μm as a comparative example.

  As shown in Examples 1 to 4 in Table 1 above, when the thickness of the restraint plate 123 is relatively increased, the displacement of the diaphragm is relatively increased. Further, when the thickness of the constraining plate 123 cannot be increased due to manufacturing restrictions or structural restrictions, a material having a large Young's modulus may be used.

  In this example, the piezoelectric actuator 125 including the vibration plate 115 constituting the upper surface of the pressure chamber 124 is illustrated, but an aspect in which the vibration plate 115 is omitted is also possible.

For example, in the (7) pressure chamber forming step, the insulating layer 112, the silicon base material 114, and the insulating layer 116 that become the diaphragm 115 may be removed. In this structure, A ₁ in the above formula (1) is omitted (A ₂ + A ₃ <A ₄ + A ₅ ), and the thickness of the restraint plate 123 can be further reduced. If the lower electrode 118 contacts the liquid in the pressure chamber, problems such as poor insulation and corrosion of the lower electrode 118 occur. Therefore, the insulating layer 116 is left without being removed or is in contact with the liquid in the pressure chamber 124 of the lower electrode 118. It is necessary to perform protection processing on the parts to be protected.

  That is, the pressure chamber 124 side of the piezoelectric film 120 of the piezoelectric actuator 125 is composed of the first film to the n−1th film and the n-layer film of the piezoelectric film 120, while the pressure of the piezoelectric film 120 is When the opposite side of the chamber 124 is formed of (mn-1) layers of the (n + 1) th film to the mth film, a constraining surface is provided on the upper surface of the upper electrode 122, and the polarization direction of the piezoelectric film 120 is determined. When the piezoelectric actuator 125 is driven by applying an electric field in the reverse direction, the piezoelectric actuator 125 can be deformed inward of the pressure chamber 124 and a displacement amount proportional to the applied electric field strength (voltage) can be obtained. It becomes.

In other words, conditions restraint surface to the upper surface of the upper electrode 122 is provided, the relationship between the total sum and A _{n + 1} from A _m of A _n from the index value of each member (see equation (1)) A _1, the following This is when the equation (2) is satisfied.

A ₁ + A ₂ + ... + A _n <A _{n + 1} + A _{n + 2} + ... + A _m (2)
In the above formula (2), the (n−1) th film is the lower electrode 118, and the (n + 1) th film is the upper electrode 122.

  The piezoelectric actuator 125 configured as described above is provided with a restraining plate 123 on the uppermost surface, so that a restraining surface is provided on the upper side of the upper electrode 122. Therefore, when there is no restraining plate 123 (constraining surface), the piezoelectric actuator 125 is deformed upward. Even if driven to do so, the diaphragm 115 can be deformed downward and a displacement proportional to the applied voltage can be obtained.

That is, when an electric field in a direction opposite to the orientation direction is applied to the piezoelectric film 120 having an orientation direction (polarization direction) from the lower electrode 118 toward the upper electrode 122, there is no restraint plate and a deformation direction. Can be reversed, and
A displacement amount similar to the displacement amount when there is no restraint plate can be obtained.

[Example of equipment]
Next, an inkjet recording apparatus (liquid ejection apparatus) including an inkjet head (liquid ejection head) in which a piezoelectric actuator (piezoelectric element) according to an embodiment of the present invention is applied to an ejection generation element will be described.

(overall structure)
FIG. 15 is a schematic diagram showing the overall configuration of the inkjet recording apparatus 200. As shown in the figure, an inkjet recording apparatus 200 includes a plurality of inkjet heads (hereinafter referred to as heads) provided corresponding to black (K), cyan (C), magenta (M), and yellow (Y) inks. The printing unit 212 having 212K, 212C, 212M, and 212Y, the ink storage / loading unit 214 that stores the ink to be supplied to each of the heads 212K, 212C, 212M, and 212Y, and the recording medium (discharged medium) The paper feeding unit 218 for supplying the recording paper 216, the decurling unit 220 for removing the curl of the recording paper 216, and the nozzle surfaces of the heads 212K, 212C, 212M, and 212Y are arranged to face the recording paper 216. Adsorption belt conveyance unit 222 that conveys the recording paper 216 while maintaining flatness, and print detection that reads the printing result of the printing unit 212 And 224, a paper discharge unit 226 for discharging the recorded recording paper (printed matter) to the outside, and a.

  Although not shown in FIG. 15, the heads 212 </ b> K, 212 </ b> C, 212 </ b> C, 212 </ b> C, 212 </ b> M, 212 </ b> Y included in the printing unit 212 are respectively disposed on the upper surfaces (surfaces opposite to the surfaces facing the recording paper 216). The control boards 212M and 212Y are arranged upright.

  The ink storage / loading unit 214 has an ink supply tank (not shown in FIG. 15 and indicated by reference numeral 260 in FIG. 20) that stores inks of colors corresponding to the heads 212K, 212C, 212M, and 212Y. The ink communicates with the heads 212K, 212C, 212M, and 212Y through a required ink flow path.

  In addition, the ink storage / loading unit 214 includes notifying means (display means, warning sound generating means) for notifying when the ink remaining amount is low, and has a mechanism for preventing erroneous loading between colors. ing.

  Although details will be described later, the ink jet recording apparatus 200 of the present example includes an ink supply unit on the upper surface of each head 212K, 212C, 212M, 212Y, and each head 212K, from the ink storage / loading unit 214 via the ink supply unit. Ink is supplied to 212C, 212M, and 212Y.

  In FIG. 15, a magazine for rolled paper (continuous paper) is shown as an example of the paper supply unit 218, but a plurality of magazines having different paper widths, paper quality, and the like may be provided side by side. Further, instead of the roll paper magazine or in combination therewith, the paper may be supplied by a cassette in which cut papers are stacked and loaded.

  When multiple types of recording paper are used, an information recording body such as a barcode or wireless tag that records paper type information is attached to the magazine, and the information on the information recording body is read by a predetermined reader. Thus, it is preferable to automatically determine the type of recording medium (media type) to be used and perform ink ejection control so as to realize appropriate ink ejection according to the media type.

  The recording paper 216 delivered from the paper supply unit 218 retains curl due to having been loaded in the magazine. In order to remove the curl, the decurling unit 220 applies heat to the recording paper 216 by the heating drum 330 in the direction opposite to the curl direction of the magazine. At this time, it is more preferable to control the heating temperature so that the printed surface is slightly curled outward.

  In the case of an apparatus configuration using roll paper, a cutter (first cutter) 228 is provided as shown in FIG. 15, and the roll paper is cut to a desired size by the cutter 228. The cutter 228 includes a fixed blade 228A having a length equal to or larger than the conveyance path width of the recording paper 216, and a round blade 228B that moves along the fixed blade 228A. The fixed blade 228A is provided on the back side of the print. The round blade 228B is arranged on the printing surface side across the conveyance path. Note that the cutter 228 is not necessary when cut paper is used.

  After the decurling process, the cut recording paper 216 is sent to the suction belt conveyance unit 222. The suction belt conveyance unit 222 has a structure in which an endless belt 233 is wound between rollers 231 and 232, and at least the nozzle surfaces of the heads 212K, 212C, 212M, and 212Y (ink discharge surfaces on which nozzle openings are formed). ) Is configured to form a horizontal surface (flat surface).

  The belt 233 has a width that is greater than the width of the recording paper 216, and a plurality of suction holes (not shown) are formed on the belt surface. As shown in FIG. 15, an adsorption chamber 234 is provided at a position facing the nozzle surfaces of the heads 212K, 212C, 212M, and 212Y inside the belt 233 stretched between the rollers 231 and 232. The recording paper 216 is sucked and held on the belt 233 by sucking the chamber 234 with the fan 235 to obtain a negative pressure.

  The power of the motor (not shown in FIG. 15, not shown in FIG. 21 and indicated by reference numeral 288) is transmitted to at least one of the rollers 231 and 232 around which the belt 233 is wound, so that the belt 233 rotates in the clockwise direction in FIG. , And the recording paper 216 held on the belt 233 is conveyed from left to right in FIG.

  Since ink adheres to the belt 233 when a borderless print or the like is printed, the belt cleaning unit 236 is provided at a predetermined position outside the belt 233 (an appropriate position other than the print area). Although details of the configuration of the belt cleaning unit 236 are not shown, for example, there are a method of niping a brush roll, a water absorption roll, etc., an air blow method of spraying clean air, or a combination thereof. In the case where the cleaning roll is nipped, the cleaning effect is great if the belt linear velocity and the roller linear velocity are changed.

  Although a mode using a roller / nip conveyance mechanism instead of the suction belt conveyance unit 222 is also conceivable, if the roller / nip conveyance is performed in the print area, the roller is brought into contact with the print surface of the sheet immediately after printing, so that the image is easily stained. There is a problem. Therefore, as in this example, suction belt conveyance that does not bring the image surface into contact with each other in the print region is preferable.

  A heating fan 240 is provided on the upstream side of the printing unit 212 on the paper conveyance path formed by the suction belt conveyance unit 222. The heating fan 240 blows heated air onto the recording paper 216 before printing to heat the recording paper 216. Heating the recording paper 216 immediately before printing makes it easier for the ink to dry after landing.

  The heads 212K, 212C, 212M, and 212Y of the printing unit 212 have a length corresponding to the maximum paper width of the recording paper 216 targeted by the ink jet recording apparatus 200, and the nozzle surface has at least a recording medium of the maximum size. This is a full-line head in which a plurality of nozzles for ejecting ink are arranged over a length exceeding one side (full width of the drawable range) (see FIG. 16).

  The heads 212K, 212C, 212M, and 212Y are arranged in the order of black (K), cyan (C), magenta (M), and yellow (Y) from the upstream side along the feeding direction of the recording paper 216. 212K, 212C, 212M, and 212Y are fixedly installed so as to extend in the conveyance direction (paper feeding direction) of the recording paper 216.

  A color image can be formed on the recording paper 216 by ejecting different color inks from the heads 212K, 212C, 212M, 212Y while conveying the recording paper 216 by the suction belt conveyance unit 222.

  As described above, according to the configuration in which the full-line heads 212K, 212C, 212M, and 212Y having nozzle rows that cover the entire width of the paper are provided for each color, the recording paper 216 and the printing unit 212 are relatively arranged in the paper feeding direction. An image can be recorded on the entire surface of the recording paper 216 by performing the movement operation only once (that is, by one sub-scan). With such a configuration capable of single-pass printing, high-speed printing is possible and productivity can be improved as compared with a shuttle-type head in which the head reciprocates in a direction orthogonal to the paper conveyance direction.

  In this example, the configuration of KCMY standard colors (four colors) is illustrated, but the combination of ink color and number of colors is not limited to this embodiment, and light ink, dark ink, and special color ink are used as necessary. May be added. For example, it is possible to add an ink jet head that discharges light ink such as light cyan and light magenta. Also, the arrangement order of the color heads is not particularly limited. Further, after the treatment liquid and the ink are attached to the recording paper 216, the ink coloring material is aggregated or insolubilized on the recording paper 216, and the ink solvent and the ink coloring material are separated on the recording paper 216. In the inkjet recording apparatus, an inkjet head may be provided as means for attaching the treatment liquid to the recording paper 216.

  Further, each of the heads 212K, 212C, 212M, and 212Y has a structure in which a plurality of head modules (not shown) are connected in the width direction of the recording paper 216, but each head has a structure formed integrally. You may have.

  The print detection unit 224 provided at the subsequent stage of the printing unit 212 includes an image sensor for imaging the droplet ejection result of the printing unit 212, and checks for nozzle clogging and other ejection abnormalities from the droplet ejection image read by the image sensor. Functions as a means to

  The print detection unit 224 of this example is composed of a line sensor having a light receiving element array that is wider than at least the ink ejection width (image recording width) by the heads 212K, 212C, 212M, and 212Y. This line sensor includes an R light receiving element array in which photoelectric conversion elements (pixels) provided with a red (R) color filter are arranged in a line, and a G light receiving element array provided with a green (G) color filter. And a color separation line CCD sensor comprising a blue light receiving element array provided with a blue (B) color filter. Instead of the line sensor, an area sensor in which the light receiving elements are two-dimensionally arranged can be used.

  The print detection unit 224 reads the test pattern printed by the heads 212K, 212C, 212M, and 212Y of each color, and detects ejection of the heads 212K, 212C, 212M, and 212Y. The ejection determination includes the presence / absence of ejection, measurement of dot size, measurement of dot landing position, and the like.

  A post-drying unit 242 is provided following the print detection unit 224. The post-drying unit 242 is means for drying the printed image surface, and for example, a heating fan is used. Since it is preferable to avoid contact with the printing surface until the ink after printing is dried, a method of blowing hot air is preferred.

  A heating / pressurizing unit 244 is provided following the post-drying unit 242. The heating / pressurizing unit 244 is a means for controlling the glossiness of the image surface, and pressurizes with a pressure roller 245 having a predetermined uneven surface shape while heating the image surface, and transfers the uneven shape to the image surface. To do.

  When the recording paper 216 is pressed by the heating / pressurizing unit 244, when printing is performed on the porous paper with a dye-based ink, the pores of the paper are blocked by pressurization, which causes damage to the dye molecules such as ozone. By preventing the contact with the image, the weather resistance of the image is improved.

  The printed matter generated in this manner is outputted from the paper output unit 226. It is preferable that the original image to be printed (printed target image) and the test print are discharged separately. The ink jet recording apparatus 200 is provided with a sorting means (not shown) for switching the paper discharge path so as to select the print product of the main image and the print product of the test print and send them to the discharge units 226A and 226B. Yes. When the main image and the test print are simultaneously formed in parallel on a large sheet, the test print portion is separated by the cutter (second cutter) 248. The cutter 248 is provided immediately before the paper discharge unit 226, and cuts the main image and the test print unit when the test print is performed on the image margin. The structure of the cutter 248 is the same as that of the first cutter 228 described above, and includes a fixed blade 248A and a round blade 248B.

  Although not shown in FIG. 15, the paper output unit 226A for the target prints is provided with a sorter for collecting prints according to print orders.

(Head structure)
Next, the structure of the head will be described. Since the structures of the color-specific heads 212K, 212C, 212M, and 212Y are common, the heads will be represented by the reference numeral 250 in the following.

  FIG. 17A is a perspective plan view showing an example of the structure of the head 250, and FIG. 17B is an enlarged view of a part thereof. 17C is a plan perspective view showing another example of the structure of the head 250, and FIG. 18 is a cross-sectional view showing the three-dimensional configuration of the head 250 (the XVIII-XVIII line in FIGS. 17A and 17B). FIG.

  In order to increase the dot pitch printed on the recording paper 216, it is necessary to increase the nozzle pitch in the head 250. 17A and 17B, the head 250 of this example includes a plurality of ink chamber units 253 including nozzles 251 that are ink droplet ejection holes, pressure chambers 252 corresponding to the nozzles 251 and the like. Are arranged in a matrix (two-dimensionally) in a staggered manner, and are thereby projected substantially in line along the longitudinal direction of the head 250 (main scanning direction orthogonal to the paper feed direction). High nozzle density (projection nozzle pitch) is achieved.

  The form in which one or more nozzle rows are configured over a length corresponding to the entire width of the recording paper 216 in the main scanning direction substantially orthogonal to the feeding direction of the recording paper 216 is not limited to this example. For example, instead of the configuration of FIG. 17A, as shown in FIG. 17C, short head units 250 ′ in which a plurality of nozzles 251 are two-dimensionally arranged are arranged in a staggered manner and connected. Thus, a line head having a nozzle row having a length corresponding to the entire width of the recording paper 216 may be configured. Although not shown, a line head may be configured by arranging short head units in a line.

  The pressure chamber 252 provided corresponding to each nozzle 251 has a substantially square planar shape, and the nozzle 251 and the supply port 254 are provided at both corners on the diagonal line. Each pressure chamber 252 is in communication with a common channel 255 through a supply port 254. The common flow channel 255 communicates with an ink supply tank (not shown in FIGS. 17A to 17C, indicated by reference numeral 260 in FIG. 20) as an ink supply source, and the ink supplied from the ink supply tank is It is distributed and supplied to each pressure chamber 252 via the common flow channel 255 of FIG.

  A piezoelectric element 258 having a lower electrode (ground electrode, common electrode) 257A, an upper electrode (address electrode, individual electrode) 257B, and a piezoelectric film 258A is joined to the diaphragm 256 constituting the top surface of the pressure chamber 252. Yes.

  As described above, in the piezoelectric element 258 of this example, the constraining plate 123 is provided on the upper surface of the upper electrode 257B, and the piezoelectric plate 125 is configured by the vibration plate 256, the piezoelectric element 258, and the constraining plate 123.

  The piezoelectric actuator 125 shown in this example applies a positive voltage to the upper electrode 257B with the lower electrode 257A as the ground, thereby applying an electric field in the direction opposite to the polarization direction of the piezoelectric element 258 to the piezoelectric element 258, and It is driven to be deformed inside the pressure chamber 252.

  That is, by applying a predetermined driving voltage to the upper electrode 257B and the lower electrode 257A, the piezoelectric element 258 is deformed and ink is ejected from the nozzle 251. When ink is ejected, new ink is supplied from the common flow channel 255 to the pressure chamber 252 through the supply port 254. A mode in which the diaphragm 256 and the lower electrode 257A are shared is also possible.

In addition, an insulating layer (SiO ₂ layer) 259 is provided on the surface of the diaphragm 256 on the pressure chamber 252 side, ensuring insulation between the ink in the pressure chamber 252 and the diaphragm 256, and in the pressure chamber 252. Corrosion of the diaphragm 256 due to the ink in contact with the diaphragm 256 is prevented.

  As shown in FIG. 19, the ink chamber unit 253 having such a structure is latticed in a fixed arrangement pattern along a row direction along the main scanning direction and an oblique column direction having a constant angle θ not orthogonal to the main scanning direction. The high-density nozzle head of this example is realized by arranging a large number in the shape.

  That is, with the structure in which a plurality of ink chamber units 253 are arranged at a constant pitch d along the direction of an angle θ with respect to the main scanning direction, the pitch P of the nozzles projected in the main scanning direction is d × cos θ. Thus, in the main scanning direction, each nozzle 251 can be handled equivalently as a linear arrangement with a constant pitch P. With such a configuration, it is possible to realize a high-density nozzle configuration in which 2400 nozzle rows are projected per inch (2400 nozzles / inch) so as to be aligned in the main scanning direction.

  When the nozzles are driven by a full line head having a nozzle row having a length corresponding to the entire printable width, (1) all the nozzles are driven simultaneously, (2) the nozzles are sequentially moved from one side to the other. (3) The nozzle is divided into blocks, and each block is sequentially driven from one side to the other, and the like, in the width direction of the recording paper 216 (direction perpendicular to the conveyance direction of the recording paper 216). The driving of the nozzle that prints one line (one line of dots or a line of dots of a plurality of lines) is defined as main scanning.

  In particular, when the nozzles 251 arranged in a matrix as shown in FIGS. 17A, 17B, and 19 are driven, main scanning as described in the above (3) is preferable. That is, nozzles 251-11, 251-12, 251-13, 251-14, 251-15, 251-16 are made into one block (other nozzles 251-21,..., 251-26 are made into one block, , 51-36 as one block,...), And the nozzles 251-11, 51-12,..., 51-16 are sequentially driven according to the conveyance speed of the recording paper 216, thereby recording paper. One line is printed in the 216 width direction.

  On the other hand, by moving the full line head and the recording paper 216 relative to each other, printing of one line (a line formed by one line of dots or a line composed of a plurality of lines) is repeatedly performed. This is defined as sub-scanning.

  The direction indicated by one line (or the longitudinal direction of the belt-like region) recorded by the main scanning is referred to as a main scanning direction, and the direction in which the sub scanning is performed is referred to as a sub scanning direction. That is, in the present embodiment, the conveyance direction of the recording paper 216 is the sub-scanning direction, and the width direction of the recording paper 216 orthogonal to the recording paper 216 is the main scanning direction. In the implementation of the present invention, the nozzle arrangement structure is not limited to the illustrated example.

  In the implementation of the present invention, the nozzle arrangement structure is not limited to the illustrated example, and various nozzle arrangement structures such as an arrangement structure having one nozzle row in the sub-scanning direction can be applied.

(Configuration of ink supply system)
FIG. 20 is a schematic diagram showing the configuration of an ink supply system in the inkjet recording apparatus 200. The ink supply tank 260 is a base tank that supplies ink to the head 250 and is included in the ink storage / loading unit 214 described with reference to FIG. The ink supply tank 260 includes a system that replenishes ink from a replenishment port (not shown) and a cartridge system that replaces the entire tank when the remaining amount of ink is low. The cartridge system is suitable for changing the ink type according to the intended use. In this case, it is preferable that the ink type information is identified by a barcode or the like, and ejection control is performed according to the ink type.

  As shown in FIG. 20, a filter 262 is provided between the ink supply tank 260 and the head 250 in order to remove foreign substances and bubbles. The filter mesh size is preferably equal to or smaller than the nozzle diameter (generally about 20 μm).

  Although not shown in FIG. 20, a configuration in which a sub tank is provided in the vicinity of the head 250 or integrally with the head 250 is also preferable. The sub-tank has a function of improving a damper effect and refill that prevents fluctuations in the internal pressure of the head.

  Further, the inkjet recording apparatus 200 is provided with a cap 264 as a means for preventing the nozzle 251 from drying or preventing an increase in ink viscosity near the nozzle, and a cleaning blade 266 as a means for cleaning the ink ejection surface of the head 250. Yes. The cap 264 can be moved relative to the head 250 by a moving mechanism (not shown), and is moved from a predetermined retracted position to a maintenance position below the head 250 as necessary.

  The cap 264 is displaced up and down relatively with respect to the head 250 by an elevator mechanism (not shown). The cap 264 is raised to a predetermined raised position when the power is turned off or during printing standby, and is brought into close contact with the head 250, thereby covering the nozzle surface with the cap 264.

  During printing or standby, when the frequency of use of a specific nozzle 251 is low and ink is not ejected for a certain period of time, the ink solvent near the nozzle evaporates and the ink viscosity increases. In such a state, ink cannot be ejected from the nozzle 251 even if the piezoelectric element 258 operates.

  Before such a state is reached (within the range of viscosity that can be discharged by the operation of the piezoelectric element 258), the piezoelectric element 258 is operated to cap the deteriorated ink (ink in the vicinity of the nozzle whose viscosity has increased) to be discharged. Preliminary ejection (purging, idle ejection, spit ejection, dummy ejection) is performed toward H.264 (ink receiving).

  Further, when air bubbles are mixed in the ink in the head 250 (in the pressure chamber 252), the ink cannot be ejected from the nozzle even if the piezoelectric element 258 operates. In such a case, the cap 264 is applied to the head 250, the ink in the pressure chamber 252 (ink mixed with bubbles) is removed by suction with the suction pump 267, and the suctioned and removed ink is sent to the recovery tank 268.

  In this suction operation, the deteriorated ink with increased viscosity (solidified) is sucked out when the ink is initially loaded into the head or when the ink is used after being stopped for a long time. Since the suction operation is performed on the entire ink in the pressure chamber 252, the amount of ink consumption increases. Therefore, it is preferable to perform preliminary ejection when the increase in ink viscosity is small.

(Description of control system)
FIG. 21 is a principal block diagram showing the system configuration of the inkjet recording apparatus 200. The ink jet recording apparatus 200 includes a communication interface 270, a system controller 272, a memory 274, a motor driver 276, a heater driver 278, a print control unit 280, an image buffer memory 282, a head driver 284, and the like.

  The communication interface 270 is an interface unit that receives image data sent from the host computer 286. As the communication interface 270, a serial interface such as USB (Universal Serial Bus), IEEE 1394, Ethernet (registered trademark), a wireless network, or a parallel interface such as Centronics can be applied. In this part, a buffer memory (not shown) for speeding up communication may be mounted. The image data sent from the host computer 286 is taken into the ink jet recording apparatus 200 via the communication interface 270 and temporarily stored in the memory 274.

  The memory 274 is a storage unit that temporarily stores an image input via the communication interface 270, and data is read and written through the system controller 272. The memory 274 is not limited to a memory made of a semiconductor element, and a magnetic medium such as a hard disk may be used.

  The system controller 272 includes a central processing unit (CPU) and its peripheral circuits, and functions as a control device that controls the entire inkjet recording apparatus 200 according to a predetermined program, and also functions as an arithmetic device that performs various calculations. . That is, the system controller 272 controls the communication interface 270, the memory 274, the motor driver 276, the heater driver 278, and the like, performs communication control with the host computer 286, read / write control of the memory 274, and the like. Control signals for controlling the motor 288 and the heater 289 are generated.

  The memory 274 stores programs executed by the CPU of the system controller 272 and various data necessary for control. Note that the memory 274 may be a non-rewritable storage means or a rewritable storage means such as an EEPROM. The memory 274 is used as a temporary storage area for image data, and is also used as a program development area and a calculation work area for the CPU.

  The motor driver 276 is a driver that drives the motor 288 in accordance with an instruction from the system controller 272. In FIG. 21, a motor (actuator) arranged in each part in the apparatus is represented by reference numeral 288 as a representative. For example, the motor 288 shown in FIG. 21 includes a motor that drives the drive roller 231 (232) of the belt 233 in FIG. 15, a motor of a moving mechanism that moves the cap 264 in FIG.

  The heater driver 278 is a driver that drives a heater 289 including a heater as a heat source of the heating fan 240 and a heater of the post-drying unit 242 shown in FIG. 15 according to an instruction from the system controller 272.

  The print control unit 280 has a signal processing function for performing various processes and corrections for generating a print control signal from the image data in the memory 274 according to the control of the system controller 272, and the generated print data This is a control unit that supplies (dot data) to the head driver 284. The print control unit 280 performs necessary signal processing, and controls the ejection amount and ejection timing of the ink droplets of the head 250 via the head driver 284 based on the image data. Thereby, a desired dot size and dot arrangement are realized.

  The print control unit 280 includes an image buffer memory 282, and image data, parameters, and other data are temporarily stored in the image buffer memory 282 when image data is processed in the print control unit 280. Also possible is an aspect in which the print control unit 280 and the system controller 272 are integrated to form a single processor.

  The head driver 284 generates a drive signal to be applied to the piezoelectric element 258 of the head 250 based on the image data given from the print control unit 280 and applies the drive signal to the piezoelectric element 258 to drive the piezoelectric element 258. A drive circuit (the power supply device 130 in FIGS. 12A and 12B) is included. Note that the head driver 284 shown in FIG. 21 may include a feedback control system for keeping the driving condition of the head 250 constant.

  The print detection unit 224 is a block including a line sensor as described with reference to FIG. 15. The print detection unit 224 reads an image printed on the recording paper 216, performs necessary signal processing, etc. Variation) or the like, and the detection result is provided to the print control unit 280.

  The print control unit 280 controls each unit to perform various corrections for the head 250 and maintenance of the head 250 based on information obtained from the print detection unit 224 as necessary.

  Data of an image to be printed is input from the outside via the communication interface 270 and stored in the memory 274. At this stage, RGB image data is stored in the memory 274.

  The image data stored in the memory 274 is sent to the print control unit 280 via the system controller 272, and is converted into dot data for each ink color by the print control unit 280. That is, the print control unit 280 performs processing for converting the input RGB image data into KCMY four-color dot data. The dot data generated by the print control unit 280 is stored in the image buffer memory 282.

  Various control programs are stored in the program storage unit 290, and the control programs are read and executed in accordance with instructions from the system controller 272. The program storage unit 290 may use a semiconductor memory such as a ROM or EEPROM, or may use a magnetic disk or the like. An external interface may be provided and a memory card or PC card may be used. Of course, you may provide several recording media among these recording media. The program storage unit 290 may also be used as a recording unit (not shown) for operating parameters.

  The apparatus configuration shown in FIGS. 15 to 21 is an example of an apparatus including a liquid discharge head (piezoelectric element) to which the piezoelectric actuator according to the present invention is applied, and can be changed as appropriate. For example, FIG. 15 illustrates a mode in which the recording paper 216 is conveyed by a belt. However, while the recording paper 216 is conveyed using a drum-shaped conveying member, an image is recorded by the printing unit 212 disposed on the peripheral surface of the drum. It is also possible to perform this.

  In this example, an inkjet recording apparatus including an inkjet head is illustrated as an example of an apparatus to which the present invention is applied. However, the present invention is widely applied to liquid ejection heads and apparatuses that use piezoelectric actuators as ejection generating elements. It is possible. Other examples of the apparatus include a liquid ejection apparatus (for example, a dispenser) that ejects liquid onto a substrate (medium) to form a desired shape and pattern.

The figure explaining the board | substrate with which the piezoelectric actuator based on embodiment of this invention is formed. The figure explaining a lower electrode formation process The figure explaining the patterning process of a lower electrode The figure explaining the piezoelectric film formation process The figure explaining the upper electrode formation process The figure explaining the patterning process of an upper electrode Diagram explaining the constraining plate forming process Diagram explaining restraint plate etching process The figure explaining a pressure chamber formation process The figure explaining a channel plate joining process and a nozzle plate joining process The figure explaining FPC joining process The figure explaining operation | movement of the piezoelectric actuator which concerns on embodiment of this invention. The figure explaining the relationship between the applied voltage and displacement amount of the piezoelectric actuator shown in FIG. The figure explaining the structure of the piezoelectric actuator shown in FIG. FIG. 12 is an overall configuration diagram of an ink jet recording apparatus including a liquid discharge head including the piezoelectric actuator shown in FIG. FIG. 15 is a plan view of the main part around the printing unit of the ink jet recording apparatus shown in FIG. Plane perspective view showing a configuration example of the head shown in FIG. A sectional view taken along line XVIII-XVIII in FIG. FIG. 17 is an enlarged view showing the nozzle arrangement of the head shown in FIG. FIG. 15 is a schematic diagram showing the configuration of an ink supply system in the ink jet recording apparatus shown in FIG. Main part block diagram which shows the system configuration | structure of the inkjet recording device shown in FIG. The figure explaining operation | movement of the piezoelectric actuator which concerns on a prior art. Characteristic diagram showing the relationship of displacement to electric field strength of a piezoelectric actuator according to the prior art

Explanation of symbols

  118, 275A ... lower electrode, 120, 258A ... piezoelectric film, 122, 257B ... upper electrode, 123, 258 ... piezoelectric element, 125 ... piezoelectric actuator, 29, 212K, 212C, 212M, 212Y, 250 ... head, 30 ... Power supply device, 200 ... inkjet recording device, 284 ... head driver

Claims (9)

A diaphragm,
A lower electrode formed on the upper surface of the diaphragm;
A piezoelectric film having an orientation in one direction epitaxially grown or oriented and formed on the upper surface of the lower electrode opposite to the diaphragm;
An upper electrode formed on the upper surface of the piezoelectric film opposite to the lower electrode;
A constraining plate provided on the side surface of the upper electrode opposite to the piezoelectric film;
With
The thickness direction of each member is the y direction, the position of the lower surface of the diaphragm in the y direction is y ₀ , the position of the boundary surface between the diaphragm and the lower electrode is y ₁ , the lower electrode and the piezoelectric film Y ₂ , the boundary surface position of the piezoelectric film and the upper electrode y ₃ , the boundary surface position of the upper electrode and the restraint plate y ₄ , and the upper surface position of the restraint plate y ₅
Young's modulus Y _v of the _diaphragm, Poisson's ratio V _v of the vibration _plate, the Young's modulus Y _u of the lower _electrode, Poisson's ratio V _u of the lower _electrode, the Young's modulus Y _p of the piezoelectric _film, the piezoelectric film Poisson's ratio V _p , Young's modulus Poisson's ratio V _{p of} the upper electrode, Young's modulus Y _{m of} the upper electrode, Poisson's ratio V _{m of} the upper electrode, Young's modulus Y _{f of} the constraining plate, Poisson's ratio of the constraining plate V _f is the following formula (1)

A piezoelectric actuator characterized by satisfying the relationship   The piezoelectric actuator according to claim 1, wherein the diaphragm and the lower electrode are used together. A nozzle for discharging liquid;
A pressure chamber communicating with the nozzle and containing a liquid discharged from the nozzle;
A diaphragm constituting one wall surface of the pressure chamber;
A lower electrode formed on a side surface of the diaphragm opposite to the pressure chamber;
A piezoelectric film formed on the side surface of the lower electrode opposite to the diaphragm and having an orientation in one direction epitaxially grown or oriented;
An upper electrode formed on a side surface of the piezoelectric film opposite to the lower electrode;
A constraining plate provided on the side surface of the upper electrode opposite to the piezoelectric film;
With
The thickness direction of each member is the y direction, the position of the lower surface of the diaphragm in the y direction is y ₀ , the position of the boundary surface between the diaphragm and the lower electrode is y ₁ , the lower electrode and the piezoelectric film Y ₂ , the boundary surface position of the piezoelectric film and the upper electrode y ₃ , the boundary surface position of the upper electrode and the restraint plate y ₄ , and the upper surface position of the restraint plate y ₅
Young's modulus Y _v of the _diaphragm, Poisson's ratio V _v of the vibration _plate, the Young's modulus Y _u of the lower _electrode, Poisson's ratio V _u of the lower _electrode, the Young's modulus Y _p of the piezoelectric _film, the piezoelectric film Poisson's ratio V _p , Young's modulus Poisson's ratio V _{p of} the upper electrode, Young's modulus Y _{m of} the upper electrode, Poisson's ratio V _{m of} the upper electrode, Young's modulus Y _{f of} the constraining plate, Poisson's ratio of the constraining plate V _f is the following formula (1)

A liquid discharge head characterized by satisfying the above relationship.   The liquid ejection head according to claim 3, wherein the vibration plate and the lower electrode are combined. A nozzle for discharging liquid;
A pressure chamber communicating with the nozzle and containing a liquid discharged from the nozzle;
A diaphragm constituting one wall surface of the pressure chamber;
A lower electrode formed on a side surface of the diaphragm opposite to the pressure chamber;
A piezoelectric film formed on the side surface of the lower electrode opposite to the diaphragm and having an orientation in one direction epitaxially grown or oriented;
An upper electrode formed on a side surface of the piezoelectric film opposite to the lower electrode;
A constraining plate provided on the side surface of the upper electrode opposite to the piezoelectric film;
A liquid ejection head comprising:
An electric field applying means for applying an electric field in a direction opposite to the orientation direction of the piezoelectric film;
With
In the liquid discharge head, the thickness direction of each member is the y direction, the position of the lower surface of the diaphragm in the y direction is y ₀ , the position of the boundary surface between the diaphragm and the lower electrode is y ₁ , The position of the interface between the electrode and the piezoelectric film is y ₂ , the position of the interface between the piezoelectric film and the upper electrode is y ₃ , the position of the interface between the upper electrode and the restraint plate is y ₄ , and the constraint the upper surface position of the plate when the y _5,
Young's modulus Y _v of the _diaphragm, Poisson's ratio V _v of the vibration _plate, the Young's modulus Y _u of the lower _electrode, Poisson's ratio V _u of the lower _electrode, the Young's modulus Y _p of the piezoelectric _film, the piezoelectric film Poisson's ratio V _p , Young's modulus Poisson's ratio V _{p of} the upper electrode, Young's modulus Y _{m of} the upper electrode, Poisson's ratio V _{m of} the upper electrode, Young's modulus Y _{f of} the constraining plate, Poisson's ratio of the constraining plate V _f is the following formula (1)

A liquid discharge apparatus satisfying the relationship:   The liquid ejecting apparatus according to claim 5, wherein the diaphragm and the lower electrode are combined. The piezoelectric film has an orientation direction from the lower electrode toward the upper electrode,
The electric field applying means applies a positive voltage to the upper electrode with the lower electrode as a reference potential to apply an electric field in a direction opposite to the orientation direction of the piezoelectric film. The liquid discharge apparatus as described. A diaphragm,
A lower electrode formed on the upper surface of the diaphragm;
A piezoelectric film having an orientation in one direction epitaxially grown or oriented and formed on the upper surface of the lower electrode opposite to the diaphragm;
An upper electrode formed on the upper surface of the piezoelectric film opposite to the lower electrode;
A constraining plate provided on the side surface of the upper electrode opposite to the piezoelectric film;
With
The thickness direction of each member is the y direction, the position of the lower surface of the diaphragm in the y direction is y ₀ , the position of the boundary surface between the diaphragm and the lower electrode is y ₁ , the lower electrode and the piezoelectric film Y ₂ , the boundary surface position of the piezoelectric film and the upper electrode y ₃ , the boundary surface position of the upper electrode and the restraint plate y ₄ , and the upper surface position of the restraint plate y ₅
Young's modulus Y _v of the _diaphragm, Poisson's ratio V _v of the vibration _plate, the Young's modulus Y _u of the lower _electrode, Poisson's ratio V _u of the lower _electrode, the Young's modulus Y _p of the piezoelectric _film, the piezoelectric film Poisson's ratio V _p , Young's modulus Poisson's ratio V _{p of} the upper electrode, Young's modulus Y _{m of} the upper electrode, Poisson's ratio V _{m of} the upper electrode, Young's modulus Y _{f of} the constraining plate, Poisson's ratio of the constraining plate V _f is the following formula (1)

When driving a piezoelectric actuator that satisfies the above relationship, an electric field in a direction opposite to the orientation direction of the piezoelectric film is applied between the upper electrode and the lower electrode. The piezoelectric film has an orientation direction from the lower electrode toward the upper electrode,
9. The electric field in a direction from the upper electrode to the lower electrode is applied to the piezoelectric film by applying a positive voltage to the upper electrode with the lower electrode as a reference potential. Driving method of piezoelectric actuator.

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