JP2009274226A - Liquid droplet ejecting head, ink cartridge, image forming apparatus, piezoelectric actuator, micropump, and light modulating device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid droplet ejecting head which has a large amount of variation and can be made compact. <P>SOLUTION: The liquid droplet ejecting head includes: a nozzle plate with nozzle holes for ejecting liquid droplets; partition walls which form ejection chambers corresponding to the nozzle holes; a deformable diaphragm which constitutes walls of the ejection chambers; a lower electrode formed on a surface opposite to a surface of the diaphragm where the ejection chambers are formed; a piezoelectric layer formed on the lower electrode; and an upper electrode formed on the piezoelectric layer. A membrane stress as combined membrane stresses generated by the diaphragm, lower electrode, piezoelectric layer, and upper electrode is a compressive stress in the liquid droplet ejecting head. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a droplet discharge head, an ink cartridge, an image forming apparatus, a piezoelectric actuator, a micropump, and a light modulation device.

  The ink jet recording apparatus has many advantages such as extremely low noise during recording, high-speed printing, high degree of ink freedom, and the ability to use inexpensive plain paper. . Among these, the so-called ink-on-demand method, in which ink droplets are ejected only when recording is required, does not require collection of ink droplets that are not necessary for recording, and has become the mainstream at present.

  An inkjet head, which is a droplet discharge head used in an image forming apparatus such as a printer, a facsimile machine, or a copying apparatus, or an inkjet recording apparatus used as an image forming apparatus, includes a nozzle that discharges ink droplets, and a discharge chamber ( Pressure chambers, pressure chambers, ink flow paths, etc.) and pressure generating means for generating pressure to pressurize the ink in the discharge chamber, and the ink in the discharge chamber at the pressure generated by the pressure generating means The ink droplets are ejected from the nozzles by pressurizing.

  As such a droplet discharge head, a piezoelectric type that discharges ink droplets by deforming and displacing a diaphragm that forms the wall surface of the discharge chamber using an electromechanical conversion element such as a piezoelectric element as a pressure generating means. And a bubble type (thermal type) in which ink bubbles are generated by using an electrothermal conversion element such as a heating resistor disposed in the discharge chamber to discharge ink droplets. Piezoelectric types include a longitudinal vibration type and a lateral vibration type, as well as a shear mode type using shear deformation. Among them, in recent years, patterning technology has been established due to advances in semiconductor processes and micromachining technology, and the construction of actuators that directly form pressure chambers and piezoelectric elements on low-cost Si substrates has been studied. Yes.

  In Patent Document 1, a diaphragm including an elastic film and a lower electrode formed thereon has a recess extending in the longitudinal direction at least on both sides in the width direction inside the pressure generating chamber, and the depth of the recess is The range is 0.5 times or more the thickness of the elastic film and reaches a part of the lower electrode. By providing a concave portion at the end of the diaphragm, the diaphragm can be easily deformed and the amount of displacement can be increased.

  Further, in Patent Document 2, the diaphragm is composed of a vibration film composed of a laminated film having at least two layers of a layer having a positive film stress and a layer having a negative film stress. The film tension of the film is substantially zero or negative, and the film tension obtained by adding the film tension of the piezoelectric film to the film tension of the vibration film is configured to be positive. Since the tension of all the films including the multilayer diaphragm and the piezoelectric body is positive (tensile stress), the diaphragm can be in a flat state.

Further, in Patent Document 3, in a piezoelectric actuator in which one or more intermediate layers are formed between a substrate and an electro-mechanical conversion element portion, the intermediate layer is an adhesion functional layer with a substrate, a reaction preventing functional layer, a film stress. A piezoelectric actuator composed of a single layer or a plurality of layers having a relaxation function layer is disclosed.
Japanese Patent No. 3610811 Japanese Patent No. 3451623 JP-A-11-204849

  However, in the actuator described in Patent Document 1, it is difficult to stably process a part of the diaphragm which is a thin film, and forming a recess in the pressure chamber is performed when ink is filled. The air bubbles are easily trapped in the pressure chamber, which affects the ink ejection performance.

  In addition, what is described in Patent Document 2 is different from a laminated piezo-type actuator that operates in a longitudinal vibration mode, and a thin-film piezo-type actuator that operates in a transverse vibration mode has a low generated force and is stretched with a strong tension. It is difficult to sufficiently displace with a vibrating plate.

  Moreover, in what is described in Patent Document 3, it is not easy to increase the amount of displacement of the diaphragm with a weak force.

  The present invention has been made for such a problem, and in particular, by forming a convex shape on the opposite side of the piezoelectric element forming side, the displacement amount of the diaphragm can be increased, and the low The present invention provides a droplet discharge head, an ink cartridge, an image forming apparatus, a piezoelectric actuator, a micropump, and a light modulation device that are large in displacement at a low cost.

  The present invention provides a nozzle plate having a nozzle hole for discharging droplets, a partition wall that forms a discharge chamber corresponding to the nozzle hole, a deformable vibration plate that forms a wall of the discharge chamber, and the vibration plate. A lower electrode formed on a surface opposite to the surface on which the discharge chamber is formed; a piezoelectric layer formed on the lower electrode; and an upper electrode formed on the piezoelectric layer. In the droplet discharge head, a film stress that is a combination of film stresses generated by the vibration plate, the lower electrode, the piezoelectric layer, and the upper electrode is a compressive stress.

  Further, the invention is characterized in that the diaphragm has a convex shape toward the discharge chamber when no voltage is applied.

  Further, in the present invention, the diaphragm is formed by laminating at least two films of a film having a compressive stress and a film having a tensile stress. It has a compressive stress.

  According to another aspect of the invention, there is provided the droplet discharge head described above, and an ink tank that is integrated with the droplet discharge head and supplies ink to the droplet discharge head. .

  Further, the present invention is characterized in that an image is formed by droplets ejected from the droplet ejection head described above.

  The present invention also includes a deformable diaphragm, a lower electrode formed on one surface of the diaphragm, a piezoelectric layer formed on the lower electrode, and a piezoelectric layer formed on the piezoelectric layer. A piezoelectric actuator having an upper electrode is characterized in that a film stress including a film stress generated by the diaphragm, the lower electrode, the piezoelectric layer, and the upper electrode is a compressive stress.

  Further, in the present invention, the diaphragm is formed by laminating at least two films of a film having a compressive stress and a film having a tensile stress. It has a compressive stress.

  In addition, the present invention includes the piezoelectric actuator described above and a flow path having the diaphragm in the piezoelectric actuator as a part of a wall surface, and transports liquid by deformation of the diaphragm.

  In addition, the present invention is characterized by comprising the above-described piezoelectric actuator, and a mirror that changes a light reflection direction by deformation of the piezoelectric actuator.

  According to the present invention, since the total film stress including the film stress of each of the diaphragm, the lower electrode, the piezoelectric layer, and the upper electrode is a compressive stress, a large amount of displacement can be obtained with a weak force. it can. As a result, a highly efficient actuator can be obtained, and a small and low-cost droplet discharge head, ink cartridge, and image forming apparatus can be obtained, and an efficient piezoelectric actuator, micropump, and light modulation device can be obtained. Can be obtained.

  Next, the best mode for carrying out the present invention will be described below.

[First Embodiment]
The first embodiment according to the present invention relates to a droplet discharge head. The present embodiment will be described with reference to FIGS. FIG. 1 is an exploded perspective view of a droplet discharge head according to the present embodiment, which is partially shown in cross section. 2A is a cross-sectional view of the assembled droplet discharge head according to the present embodiment, taken along the broken line A1-A2 in FIG. 1, and FIG. 2B is a top view of the droplet discharge head. It is.

  The present embodiment is a side shooter type liquid discharge head that discharges ink droplets from nozzle holes provided on the surface portion of the substrate. The second substrate 2 is a nozzle substrate having nozzle holes 20 for discharging ink. , A discharge chamber 14, a vibration plate, a first substrate 1 serving as a liquid chamber substrate on which a piezoelectric element is formed, and a third substrate 3 serving as a protective substrate provided with a space 12 for protecting the piezoelectric element. A laminated structure in which these three substrates are stacked.

  The first substrate 1 is provided with a diaphragm having a structure in which a laminated film is formed on a silicon substrate 4. As will be described later, the vibration plate includes a silicon oxide film 5, a polysilicon layer 6, a silicon oxide film 7, a silicon nitride film 8, a platinum film serving as a lower electrode 9, a predetermined region on one surface of the silicon substrate 4. The piezoelectric layer 10 and the upper electrode 11 formed by patterning are stacked. On the other surface, the silicon substrate 4 is etched to form a discharge chamber 14, a fluid resistance portion 15 communicating with the discharge chamber 14, and a common liquid chamber 17.

  The second substrate 2 is formed by a nickel high speed electroforming method and has a thickness of 30 [μm]. The second substrate 2 constitutes the wall surface of the discharge chamber 14 formed in the first substrate 1, and nozzle holes 20 are provided corresponding to the respective discharge chambers 14.

  The third substrate 3 is provided with a space 12 for securing and protecting an operation region of the piezoelectric element constituted by the lower electrode 9, the piezoelectric layer 10, and the upper electrode 11.

  Next, the operation of the droplet discharge head in this embodiment will be described. Ink is supplied into each discharge chamber 14 from the ink supply hole 16 via the common liquid chamber 17. In a state where each discharge chamber 14 is filled with ink, a pulse voltage having a predetermined pulse width of 20 [V] is applied between the upper electrode 11 and the lower electrode 9 of the piezoelectric element. As a result, the piezoelectric element that is deformed in the transverse vibration mode contracts, and the entire diaphragm that is in close contact with the piezoelectric element is deformed so as to be convex toward the discharge chamber 14 side. As a result, the volume in the discharge chamber 14 decreases, the pressure in the discharge chamber 14 increases rapidly, and the ink droplets 21 are discharged toward the recording paper 40 from the nozzle holes 20. By continuously applying this pulse voltage, the ink droplets 21 can be continuously discharged from the nozzle holes 20.

  Next, a method for manufacturing the liquid discharge head in the present embodiment will be described with reference to FIG. FIG. 3 is a process diagram in a cross section cut along a broken line A1-A2 in FIG.

First, as shown in FIG. 3A, a silicon oxide (SiO ₂ ) serving as an insulating film is formed on one surface of a silicon substrate 4 having a thickness of <100> with a thickness of 250 [μm] by a wet oxidation method. A silicon oxide film 5 is formed with a thickness of about 0.3 [μm]. Incidentally, when the silicon oxide film 5 is formed, the silicon oxide film 22 is also formed on the opposite surface of the silicon substrate 4. Further thereon, a polysilicon layer 6 as a material constituting the diaphragm is formed by an LPCVD method with a thickness of about 1.0 [μm]. Further thereon, a silicon oxide film 7 made of silicon oxide (SiO ₂ ) is formed to a thickness of about 0.6 [μm] by LPCVD. Further thereon, a silicon nitride film 8 made of silicon nitride (Si ₃ O ₄ ) is formed to a thickness of about 0.1 [μm] by LPCVD. The silicon nitride film 8 is for adjusting the stress of the diaphragm on which the above-described laminated film is formed. The film thickness, film forming conditions, and the like take into account the internal stress of each film. It is desirable to define.

  Next, as shown in FIG. 3B, a lower electrode 9 made of a Pt film is formed on the silicon nitride film 8 by sputtering to a thickness of 0.1 [μm]. Further thereon, a piezoelectric layer 10 made of PZT (lead zirconate titanate) is formed by sputtering to a thickness of about 1.0 [μm], and an upper electrode 11 is formed to a thickness of about 0.1 [μm]. . Although not shown, after the lower electrode 9 made of a Pt film is formed, a photoresist is applied thereon, pre-baked, and exposed and developed by an exposure apparatus. A resist pattern corresponding to the plate is formed. Thereafter, dry etching such as RIE is performed to remove the lower electrode 9 in the region where the resist pattern is not formed, thereby forming the lower electrode 9 in a predetermined region. Thereafter, the piezoelectric layer 10 and the upper electrode 11 are formed. The film is formed.

  Next, as shown in FIG. 3C, a piezoelectric element corresponding to a discharge chamber 14 described later is formed. That is, the piezoelectric element is composed of the lower electrode 9, the piezoelectric layer 10, and the upper electrode 11, and the piezoelectric element is formed so as to correspond to the discharge chamber 14 by a photolithography process and an etching process. Specifically, after the upper electrode 11 is formed, a photoresist is applied thereon, pre-baked, and exposed and developed by an exposure apparatus, thereby corresponding to the shape of the piezoelectric element to be formed. Form a pattern. Thereafter, dry etching such as RIE is performed to remove the upper electrode 11 and the piezoelectric layer 10 in a region where the resist pattern is not formed, whereby a piezoelectric element corresponding to the discharge chamber 14 is formed.

  Next, as shown in FIG. 3 (d), regions that serve as the discharge chamber 14, the fluid resistance portion 15, and the common liquid chamber 17 are formed on the surface of the silicon substrate 4 opposite to the surface on which the piezoelectric elements are formed. . Specifically, a photoresist is applied on the silicon oxide film 22 formed on the opposite surface of the silicon substrate 4 simultaneously with the silicon oxide film 5, prebaked, and exposed and developed by an exposure apparatus. Then, a resist pattern having an opening is formed in a region where the discharge chamber 14, the fluid resistance portion 15, and the common liquid chamber 17 are formed. Thereafter, dry etching such as RIE is performed to remove the silicon oxide film 22 in the region where the discharge chamber 14, the fluid resistance portion 15, and the common liquid chamber 17 are formed. Thereafter, the remaining photoresist is removed, and dry etching by ICP method is performed using the formed pattern of the silicon oxide film 22 as a mask, thereby forming the discharge chamber 14, the fluid resistance portion 15, and the common liquid chamber 17. Form the space of the area. In FIG. 3D and subsequent figures, the top and bottom of the figure before FIG. 3C are inverted.

  Next, as shown in FIG.3 (e), the 2nd board | substrate 2 and the 1st board | substrate 1 which are nozzle substrates produced at another process are adhere | attached. Specifically, the second substrate 2 is manufactured by a high-speed electroforming method using a sulfamic acid bath, and a nozzle hole 20 corresponding to the discharge chamber 14 in the first substrate 1 is formed. After the discharge chamber 14 of the first substrate 1 and the nozzle hole 20 are aligned, the second substrate 2 is bonded to the surface of the first substrate 1 where the piezoelectric element is not formed.

  Next, as shown in FIG. 3F, the third substrate 3 and the first substrate 1 which are protective substrates manufactured in a separate process are bonded. Specifically, the third substrate 3 is a silicon substrate of <110>, and after forming a pattern such as a resist having an opening in a region where the space 12 is formed, an alkaline etching solution such as TMAH or KOH is used. The space 12 is formed by etching to a predetermined depth. A molded part such as a resin mold or a metal injection mold may be used. In this way, the third substrate 3 having the space 12 corresponding to the region formed in the piezoelectric element of the first substrate 1 is formed. The third substrate 3 is bonded to the surface of the first substrate 1 where the piezoelectric elements are formed, and after the piezoelectric elements and the space 12 are aligned, they are bonded.

  Thereafter, the liquid discharge head of the present embodiment is completed by connecting the upper electrode 11 and the lower electrode 9 of the piezoelectric element to the drive circuit of the liquid discharge head.

  In the present embodiment, the diaphragm is formed of a large number of films, and has a convex shape toward the discharge chamber 14 in an unloaded state. That is, a film containing a compressive stress to be stretched is laminated on the discharge chamber 14 side, and a film containing a tensile stress to be shrunk is laminated so as to be on the side opposite to the discharge chamber 14, whereby the load is increased. In such a state, a diaphragm having a convex shape on the discharge chamber 14 side is obtained.

具体的には、表１に示すように、酸化シリコン膜５、ポリシリコン層６、酸化シリコン膜７、窒化シリコン膜８、下部電極９により、振動板が形成されるが、この振動板の吐出室１４側の酸化シリコン膜５、ポリシリコン層６、酸化シリコン膜７は、圧縮応力が内在する膜であり、吐出室１４より離れた窒化シリコン膜８、下部電極９は引張り応力内在させた膜となる。更に、下部電極９上には、引張り応力を内在する圧電体層１０、上部電極１１が形成されている。

Specifically, as shown in Table 1, a diaphragm is formed by the silicon oxide film 5, the polysilicon layer 6, the silicon oxide film 7, the silicon nitride film 8, and the lower electrode 9. The silicon oxide film 5, the polysilicon layer 6, and the silicon oxide film 7 on the chamber 14 side are films in which compressive stress is present, and the silicon nitride film 8 and the lower electrode 9 that are separated from the discharge chamber 14 are films in which tensile stress is present. It becomes. Further, on the lower electrode 9, a piezoelectric layer 10 and an upper electrode 11 having a tensile stress are formed.

  Although the silicon oxide films 5 and 7 and the polysilicon layer 6 have a high film formation temperature of 600 to 1000 [° C.], they have a low linear expansion coefficient with respect to the silicon substrate 4 and have a compressive stress. On the other hand, the silicon nitride film 8 formed by LPCVD has a high film forming temperature but has a higher linear expansion coefficient than that of the silicon substrate 4 and therefore has a tensile stress. Further, since the Pt film to be the lower electrode 9 and the upper electrode 11 formed by sputtering and the PZT to be the piezoelectric layer 10 are also larger than the silicon substrate 4, they are films in which tensile stress is inherent.

In the present embodiment, since the film is stacked on the silicon substrate 4 and then the silicon substrate 4 in the region to be the discharge chamber 14 is etched, the diaphragm is formed in a thin membrane (film) state. The diaphragm is formed in a convex shape on the discharge chamber 14 side by the internal stress of each film, and the film as a whole has a low tension. As a result, the diaphragm can be easily deformed, and an actuator that can obtain a large amount of displacement by applying a small voltage can be formed. This makes it possible to produce a droplet discharge head that is efficient and can be miniaturized.

  In addition, since the diaphragm is formed in a convex shape in the discharge chamber 14 by the stress of each film, the diaphragm is recessed by residual vibration even when the diaphragm is continuously vibrated. The structure is difficult to prevent the deformation of the thin film piezoelectric element that contracts in the transverse vibration mode. As a result, the diaphragm can be more efficiently deformed.

  The liquid discharge head in the present embodiment may be an edge shooter system in which the shape from the ink flow path to the discharge port that is the nozzle is linear, or the ink described in the present embodiment A side shooter system in which the direction of the flow path and the direction of the discharge port as the nozzle are different may be used.

[Second Embodiment]
The second embodiment of the present invention is an ink cartridge. Specifically, a description will be given based on FIG. FIG. 4 is a perspective view of the ink cartridge in the present embodiment.

  This ink cartridge is obtained by integrating the ink jet head 61 according to any of the above embodiments having the nozzle 20 and the like, and the ink tank 62 for supplying ink to the ink jet head 61.

  In this way, in the case of an ink tank integrated head, the cost reduction and reliability improvement of the head immediately lead to the cost reduction and reliability improvement of the entire ink cartridge. Therefore, as described above, the cost reduction and high reliability are achieved. By reducing the manufacturing and manufacturing defects, the yield and reliability of the ink cartridge can be improved, and the cost of the head-integrated ink cartridge can be reduced.

[Third Embodiment]
The third embodiment of the present invention is an ink jet recording apparatus which is an image forming apparatus. FIG. 5 is a perspective view of the ink jet recording apparatus according to the present embodiment, and FIG. 6 is a side view of the mechanism portion of the ink jet recording apparatus according to the present embodiment.

  This ink jet recording apparatus includes a carriage movable in the main scanning direction inside the recording apparatus main body 81, a recording head composed of an ink jet head embodying the present invention mounted on the carriage, an ink cartridge for supplying ink to the recording head, and the like. A sheet feeding cassette (or a sheet feeding tray) 84 on which a large number of sheets 83 can be stacked from the front side is detachably attached to the lower part of the apparatus main body 81. The manual feed tray 85 for manually feeding the paper 83 can be opened, the paper 83 fed from the paper feed cassette 84 or the manual feed tray 85 is taken in, and the printing mechanism 82 After recording a required image, the image is discharged to a paper discharge tray 86 mounted on the rear side.

  The printing mechanism 82 holds a carriage 93 slidably in the main scanning direction by a main guide rod 91 and a sub guide rod 92 which are guide members horizontally mounted on left and right side plates (not shown). (Y), cyan (C), magenta (M), black (Bk) A head 94 comprising an ink jet head according to the present invention for ejecting ink droplets of each color has a plurality of ink ejection openings (nozzles) as the main scanning direction. They are arranged in the intersecting direction and mounted with the ink droplet ejection direction facing downward. In addition, each ink cartridge 95 for supplying ink of each color to the head 94 is replaceably mounted on the carriage 93.

  The ink cartridge 95 has an air port that communicates with the atmosphere upward, a supply port that supplies ink to the inkjet head below, and a porous body filled with ink inside, and the capillary force of the porous body. Thus, the ink supplied to the inkjet head is maintained at a slight negative pressure. Further, although the heads 94 of the respective colors are used here as the recording heads, a single head having nozzles for ejecting ink droplets of the respective colors may be used.

  Here, the carriage 93 is slidably fitted to the main guide rod 91 on the rear side (downstream side in the paper conveyance direction), and is slidably mounted on the sub guide rod 92 on the front side (upstream side in the paper conveyance direction). is doing. In order to move and scan the carriage 93 in the main scanning direction, a timing belt 100 is stretched between a driving pulley 98 and a driven pulley 99 that are rotationally driven by a main scanning motor 97, and the timing belt 100 is moved to the carriage 93. The carriage 93 is driven to reciprocate by forward and reverse rotation of the main scanning motor 97.

  On the other hand, in order to convey the paper 83 set in the paper feed cassette 84 to the lower side of the head 94, the paper feed roller 101 and the friction pad 102 for separating and feeding the paper 83 from the paper feed cassette 84 and the paper 83 are guided. A guide member 103, a transport roller 104 that reverses and transports the fed paper 83, a transport roller 105 that is pressed against the peripheral surface of the transport roller 104, and a leading end that defines a feed angle of the paper 83 from the transport roller 104 A roller 106 is provided. The transport roller 104 is rotationally driven by a sub-scanning motor 107 through a gear train.

  A printing receiving member 109 is provided as a paper guide member that guides the paper 83 sent from the transport roller 104 below the recording head 94 in accordance with the movement range of the carriage 93 in the main scanning direction. A conveyance roller 111 and a spur 112 that are rotationally driven to send the paper 83 in the paper discharge direction are provided on the downstream side of the printing receiving member 109 in the paper conveyance direction, and the paper 83 is further delivered to the paper discharge tray 86. A roller 113 and a spur 114, and guide members 115 and 116 that form a paper discharge path are disposed.

  At the time of recording, the recording head 94 is driven according to the image signal while moving the carriage 93, thereby ejecting ink onto the stopped sheet 83 to record one line. Record the line. Upon receiving a recording end signal or a signal that the trailing edge of the paper 83 has reached the recording area, the recording operation is terminated and the paper 83 is discharged.

  Further, a recovery device 117 for recovering defective ejection of the head 94 is disposed at a position outside the recording area on the right end side in the movement direction of the carriage 93. The recovery device 117 includes a cap unit, a suction unit, and a cleaning unit. The carriage 93 is moved to the recovery device 117 side during printing standby and the head 94 is capped by the capping means, and the ejection port portion is kept in a wet state to prevent ejection 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 ejection ports is made constant and stable ejection performance is maintained.

  When a discharge failure occurs, the discharge port (nozzle) of the head 94 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. Is removed by the cleaning means to recover the ejection failure. 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 inkjet head embodying the present invention is mounted in this inkjet recording apparatus, there is no ink droplet ejection failure due to vibration plate drive failure, stable ink droplet ejection characteristics are obtained, and image quality is improved. improves.

  In the above-described embodiment, the example in which the ink jet head is applied as a liquid droplet ejecting head has been described. The present invention can also be applied to other droplet discharge heads such as a droplet discharge head (spotter) that discharges the sample as droplets.

[Fourth Embodiment]
The fourth embodiment is a piezoelectric actuator according to the present invention and a micropump using this piezoelectric actuator. The piezoelectric actuator of this embodiment will be described with reference to FIG. In the piezoelectric actuator according to the present embodiment, a lower electrode 26, a piezoelectric layer 27, and an upper electrode 28 are formed on a diaphragm including a film 24 containing compressive stress and a film 25 containing tensile stress. ing. This is a piezoelectric actuator having a structure in which a diaphragm is displaced by a piezoelectric element composed of a lower electrode 26, a piezoelectric layer 27, and an upper electrode 28. As described above, the diaphragm is formed by stacking the film 24 containing the compressive stress and the film 25 containing the tensile stress. Specifically, the film 24 having compressive stress includes a silicon oxide film made of silicon oxide (SiO ₂ ) formed by wet oxidation, a polysilicon layer formed by LPCVD, and silicon formed by LPCVD. It is formed by stacking silicon oxide films made of oxide (SiO ₂ ). The film 25 containing the tensile stress is formed of a silicon nitride film made of silicon nitride (Si ₃ O ₄ ) formed by LPCVD. The lower electrode 26, the piezoelectric layer 27, and the upper electrode 28 are all films having tensile stress.

  Next, the micropump in the present embodiment will be described with reference to FIG. The micropump in the present embodiment has a configuration including the above-described piezoelectric actuator. Specifically, the micropump in the present embodiment has a structure in which the diaphragm 30 is continuously provided in the horizontal direction on the paper surface, forms a flow path 33, and a liquid flows through the flow path 33. It has become. In the drawing, the diaphragm 30 is formed of a multilayer film.

  By sequentially driving a plurality of piezoelectric elements 37 provided on the surface opposite to the flow path of the vibration plate 30 from the right side of the drawing, the vibration plate 30 is sequentially deformed, and the fluid in the flow path 33 flows in the direction of the arrow, It becomes possible to transport the fluid.

  Since the micropump in this embodiment can obtain a large displacement by applying a small voltage, a highly efficient micropump can be obtained.

[Fifth Embodiment]
The fifth embodiment is an optical modulation device according to the present invention. Specifically, a description will be given based on FIG. The diaphragm 36 in the present embodiment has a configuration that also includes a mirror. As shown in the drawing, a plurality of piezoelectric elements 38 are two-dimensionally arranged on the surface of the diaphragm 36 opposite to the surface having a function as a mirror. The diaphragm 36 has no joints, and the surface of the diaphragm 36 is deformed by driving the piezoelectric element 38.

  Specifically, the light from the light source 31 is applied to the surface of the diaphragm 36 serving as a mirror through the lens 34. The light incident on the region where the vibration plate 36 serving as the mirror is not driven enters the projection lens 32. On the other hand, the light incident on the vibration plate 36 serving as a mirror in the region where the voltage is applied to the piezoelectric element 38 is scattered because the surface of the vibration plate 36 serving as the mirror becomes a concave mirror. Almost no incident. The light incident on the projection lens 32 is projected onto a screen (not shown) or the like. This state will be described with reference to FIG. FIG. 10 is a perspective view of the light modulation device according to the present embodiment. As shown in the figure, a piezoelectric element 38 is two-dimensionally formed on the back surface of the vibration plate 36 serving as a mirror, and each piezoelectric element 38 can be controlled independently. Images can be displayed on the screen shown. In the drawing, the configuration in which the piezoelectric elements 38 are arranged in 4 × 4 is shown, but more piezoelectric elements can be arranged.

  As mentioned above, although the form which concerns on implementation of this invention was demonstrated, the said content does not limit the content of invention.

1 is an exploded perspective view of a droplet discharge head according to a first embodiment. 1 is a cross-sectional view and a top view of a main part of a droplet discharge head according to a first embodiment. Manufacturing process diagram of liquid droplet ejection head according to the first embodiment The perspective view of the ink cartridge which concerns on 2nd Embodiment A perspective view of an image forming apparatus according to a third embodiment Sectional drawing of the image forming apparatus which concerns on 3rd Embodiment Sectional drawing of the piezoelectric actuator which concerns on 4th Embodiment Sectional drawing of the micropump which concerns on 4th Embodiment Sectional drawing of the light modulation device which concerns on 5th Embodiment The perspective view of the light modulation device which concerns on 5th Embodiment

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 1st board | substrate 2 2nd board | substrate 3 3rd board | substrate 4 Silicon substrate 5 Silicon oxide film 6 Polysilicon layer 7 Silicon oxide film 8 Silicon nitride film 9 Lower electrode 10 Piezoelectric layer 11 Upper electrode 12 Space 14 Discharge chamber 20 Nozzle hole 22 Silicon oxide film

Claims (9)

A nozzle plate having nozzle holes for discharging droplets;
A partition wall forming a discharge chamber corresponding to the nozzle hole;
A deformable diaphragm constituting a wall of the discharge chamber;
A lower electrode formed on a surface opposite to a surface on which the discharge chamber of the diaphragm is formed;
A piezoelectric layer formed on the lower electrode;
An upper electrode formed on the piezoelectric layer;
In a droplet discharge head having
2. A droplet discharge head according to claim 1, wherein a film stress including a film stress generated by the vibration plate, the lower electrode, the piezoelectric layer, and the upper electrode is a compressive stress.   2. The droplet discharge head according to claim 1, wherein the vibration plate has a convex shape toward the discharge chamber when no voltage is applied. The diaphragm is formed by laminating two or more layers of a film having at least a compressive stress and a film having a tensile stress,
3. The droplet discharge head according to claim 1, wherein the vibration plate has a compressive stress. A droplet discharge head according to any one of claims 1 to 3,
An ink tank integrated with the droplet discharge head, for supplying ink to the droplet discharge head;
An ink cartridge comprising:   An image forming apparatus, wherein an image is formed by droplets ejected from the droplet ejection head according to claim 1. A deformable diaphragm,
A lower electrode formed on one surface of the diaphragm;
A piezoelectric layer formed on the lower electrode;
An upper electrode formed on the piezoelectric layer;
In a piezoelectric actuator having
A piezoelectric actuator characterized in that a film stress, which is a combination of film stresses generated by the diaphragm, the lower electrode, the piezoelectric layer, and the upper electrode, is a compressive stress. The diaphragm is formed by laminating two or more layers of a film having at least a compressive stress and a film having a tensile stress,
The piezoelectric actuator according to claim 6, wherein the diaphragm has a compressive stress. A piezoelectric actuator according to claim 6 or 7,
A flow path having the diaphragm in the piezoelectric actuator as a part of a wall surface;
And a liquid is transported by deformation of the diaphragm. A piezoelectric actuator according to claim 6 or 7,
A mirror that changes the reflection direction of light by deformation of the piezoelectric actuator;
A light modulation device comprising:

Images