JP2008055900A - Droplet ejector and method for manufacturing droplet ejector - Google Patents

Abstract

In a droplet ejecting apparatus, the volume of a droplet ejected for each nozzle is changed without complicating the structure.
In a flow path unit 30, an individual ink flow path 32a including a nozzle 15a and a pressure chamber 10a, an individual ink flow path 32b including a nozzle 15b and a pressure chamber 10b, and a manifold flow path 11a and a manifold flow path 11b are provided. Have the same channel structure. On the upper surface of the flow path unit 30, a unimorph type piezoelectric actuator 31 configured by laminating a diaphragm 40, an insulating layer 41, a common electrode 44, a piezoelectric layer 42, and individual electrodes 43a and 43b in order from the bottom. It is arranged. The piezoelectric layer 42 is thinner at the portion facing the pressure chamber 10a than at the portion facing the pressure chamber 10b.
[Selection] Figure 4

Description

  The present invention relates to a droplet ejecting apparatus that ejects droplets from a nozzle and a method for manufacturing the droplet ejecting apparatus.

There is known a liquid droplet ejecting apparatus that ejects liquid droplets from nozzles by applying pressure to a liquid in a pressure chamber communicating with a plurality of nozzles using a piezoelectric actuator. As such a liquid droplet ejecting apparatus, there is an apparatus in which the characteristics of ejecting liquid droplets from a nozzle are adjusted by changing the structure of a flow path communicating with the nozzle for each nozzle. For example, in the ink ejecting apparatus described in Patent Document 1 (Japanese Patent Application Laid-Open No. 8-281948), the position of the flow path communicating with the nozzle is changed for each nozzle by changing the position of the manifold flow path communicating with the corresponding ink chamber. The structure is changing.
JP-A-8-281948 (FIG. 5)

  For example, in an inkjet head (droplet ejecting apparatus) having nozzles that eject black ink droplets and nozzles that eject color ink droplets, the ejection characteristics of the droplets are changed for each nozzle that ejects different types of droplets. There may be a need. For example, when performing monochrome printing, printing is performed at high speed by ejecting black ink droplets in a large volume, and when performing color printing, high-quality printing is performed by ejecting color ink droplets in a small volume. is there. In such a case, it is possible to change the ejection characteristics of the droplets by changing the structure of the flow path for each nozzle having a different type of ejected droplets. For example, as shown in FIG. 22, by making the pressure chamber 500a for black ink larger than the pressure chamber 500b for color ink, the size of the ink droplet of black ink is made larger than the size of the ink droplet of color ink. can do. However, since the structure of the flow path communicating with the nozzle is different for each nozzle having different ejection characteristics, the structure of the flow path becomes complicated. In addition to changing the structure of the flow path, it is possible to change the voltage applied to drive the corresponding piezoelectric actuator for each nozzle with different ejection characteristics, but in this case, multiple power supplies are required. The configuration of a circuit for applying a voltage becomes complicated.

  An object of the present invention is to provide a droplet ejecting apparatus and a method for manufacturing the droplet ejecting apparatus that can change the ejecting characteristics of the droplet for each nozzle without complicating the structure.

  According to a first aspect of the present invention, there is provided a liquid droplet ejecting apparatus that ejects a liquid droplet, the first flow path including a first nozzle and a first pressure chamber communicating with the first nozzle, And a second flow path including a second nozzle and a second pressure chamber communicating with the second nozzle, the second flow path having the same flow path structure as the first flow path is formed. The flow path unit, the diaphragm disposed on one surface of the flow path unit so as to cover the first and second pressure chambers, and on the surface of the vibration plate opposite to the flow path unit, A piezoelectric layer disposed opposite to the second pressure chamber; and a pair of electrodes for applying a voltage to the piezoelectric layer, the piezoelectric plate, and a piezoelectric actuator in which the piezoelectric layer and the electrode are stacked. The portion of the diaphragm, the piezoelectric layer, and the electrode facing the first pressure chamber is a second pressure. Thin liquid droplet ejecting apparatus is provided than the opposite part. In the present invention, when the diaphragm has conductivity, the diaphragm may serve as one of the pair of electrodes for applying a voltage to the piezoelectric layer, and includes such a form.

  According to this, since the rigidity of the portion facing the first pressure chamber of the piezoelectric actuator is smaller than the rigidity of the portion facing the second pressure chamber, the first flow path and the second flow path have the same flow path structure. However, when the same voltage is applied to the portion facing the first pressure chamber and the portion facing the second pressure chamber of the piezoelectric layer, the portion facing the first pressure chamber of the diaphragm becomes the second pressure chamber. The deformation is greater than that of the opposing portion, and the volume of the first pressure chamber changes more than the volume of the second pressure. Thereby, a larger pressure than the liquid of the second pressure chamber can be applied to the liquid of the first pressure chamber, and a droplet having a volume larger than that of the second nozzle can be ejected from the first nozzle.

  In the droplet ejecting apparatus of the present invention, the droplet ejected from the first nozzle may be larger than the droplet ejected from the second nozzle, and when applying the voltage to the electrode, the piezoelectric The layer contracts in the surface direction of the diaphragm, deforms the diaphragm so as to be convex toward the first and second pressure chambers, and applies pressure to the liquid in the first and second pressure chambers. May be applied to eject droplets.

  The pressure in the pressure chamber is temporarily reduced by the piezoelectric actuator, and at this time, the negative pressure wave generated in the pressure chamber is reversed to be positive and the pressure in the pressure chamber is increased to return, thereby ejecting droplets from the nozzle. In the case of performing the striking, the propagation speed of the pressure wave in the first flow path is slower than the propagation speed of the pressure wave in the second flow path, so that the volume of the droplet ejected from the first nozzle is the second. It becomes larger than the volume of the droplet ejected from the nozzle.

  Further, in the flow path unit, the first flow path and the second flow path have the same flow path structure, and therefore, using the same flow path unit, the positions of the nozzles having different ejection characteristics and the ratio of the numbers thereof are Different droplet ejection devices can be configured.

  In the liquid droplet ejecting apparatus of the invention, the first flow path and the second flow path may each include a plurality of first individual flow paths and second individual flow paths, and the plurality of first pressure chambers may be provided. A first pressure chamber array arranged in a predetermined one direction, and a plurality of the second pressure chambers may form a second pressure chamber array arranged in the predetermined one direction, the diaphragm, A portion of the piezoelectric layer and the electrode facing the first pressure chamber row may be thinner than a portion facing the second pressure chamber row.

  In this case, each of the first and second pressure chamber rows includes a plurality of first and second individual flow paths arranged in a predetermined direction, and thus the surface of the diaphragm opposite to the flow path unit. Each of the region facing the first pressure chamber row and the region facing the second pressure chamber row has a relatively large area. Therefore, piezoelectric actuators having different thicknesses can be easily formed in the portion facing the first pressure chamber and the portion facing the second pressure chamber.

  In the liquid droplet ejecting apparatus of the present invention, the liquid may include black ink and color ink, black ink droplets are ejected from the first nozzle, and color ink droplets are ejected from the second nozzle. May be. In this case, it is possible to perform monochrome printing at high speed by ejecting black ink droplets from the first nozzle to the recording medium in a large volume, and color ink droplets from the second nozzle to the recording medium in a small volume. By jetting, high-quality color printing can be performed.

  In the liquid droplet ejecting apparatus according to the aspect of the invention, the liquid may include pigment ink and dye ink, the pigment ink may be ejected from the first nozzle, and the dye ink may be ejected from the second nozzle. In this case, high-quality printing with less bleeding is achieved by ejecting pigment ink that does not easily bleed onto the recording medium in a large volume from the first nozzle, and ejecting dye ink that oozes in a small volume from the second nozzle. It can be carried out.

  In the liquid droplet ejecting apparatus according to the aspect of the invention, the portion of the piezoelectric layer that faces the first pressure chamber may be thinner than the portion that faces the second pressure chamber. In this case, by changing the thickness of the piezoelectric layer, it is possible to easily form a piezoelectric actuator in which the rigidity of the portion facing the first pressure chamber and the portion facing the second pressure chamber of the piezoelectric layer is different. The large droplets can be discharged from the first nozzle.

  Furthermore, since the portion of the piezoelectric layer that faces the first pressure chamber is thinner than the portion that faces the second pressure chamber, it faces the first pressure chamber when the same voltage is applied to these portions of the piezoelectric layer. The electric field strength of the portion to be increased is larger than the electric field strength of the portion facing the second pressure chamber. As a result, the amount of contraction in the surface direction of the portion facing the first pressure chamber of the piezoelectric layer is larger than the amount of contraction in the surface direction of the portion facing the second pressure chamber, and faces the first pressure chamber of the diaphragm. The portion to be deformed is much larger than the portion facing the second pressure chamber. Accordingly, the volume of the droplet ejected from the first nozzle is further larger than the volume of the droplet ejected from the second nozzle.

  In the liquid droplet ejecting apparatus according to the aspect of the invention, a portion of the diaphragm facing the first pressure chamber may be thinner than a portion facing the second pressure chamber. In this case, by changing the thickness of the diaphragm, it is possible to easily form piezoelectric actuators having different thicknesses between the portion facing the first pressure chamber and the portion facing the second pressure chamber. Large droplets can be discharged from the nozzle.

  In the droplet ejecting apparatus of the present invention, the diaphragm may be made of metal, and the piezoelectric actuator is disposed on a surface of the diaphragm opposite to the flow path unit, and the diaphragm An insulating layer that insulates the electrode may be included, and a portion of the insulating layer that faces the first pressure chamber may be thinner than a portion that faces the second pressure chamber. In this case, when the piezoelectric actuator has an insulating layer that insulates the metal diaphragm and the electrode, by changing the thickness of the insulating layer, the portion facing the first pressure chamber Piezoelectric actuators having different thicknesses from the portion facing the second pressure chamber can be easily formed, and large droplets can be ejected from the first nozzle.

  According to the second aspect of the present invention, the first flow path including the first nozzle and the first pressure chamber communicating with the first nozzle, and the second nozzle and the second nozzle communicate with each other. A second flow path including the second pressure chamber, the flow path unit having a second flow path having the same flow path structure as the first flow path, and the first and second pressures A diaphragm disposed on one surface of the flow path unit so as to cover the chamber, and a piezoelectric layer disposed on the surface of the vibration plate opposite to the flow path unit and facing the first and second pressure chambers And a piezoelectric actuator including a pair of electrodes for applying a voltage to the piezoelectric layer, and the diaphragm, the piezoelectric layer, and the piezoelectric actuator, wherein the first flow path and the first Forming the flow path unit so that the two flow paths have the same flow path structure; and Forming the piezoelectric actuator in layers, and joining the diaphragm to the one surface of the flow path unit. When forming the piezoelectric actuator, the diaphragm, the piezoelectric layer, and A method of manufacturing a droplet ejecting apparatus is provided in which a portion of the electrode facing the first pressure chamber is formed thinner than a portion facing the second pressure chamber.

  According to the second aspect of the present invention, when the piezoelectric actuator is formed, one portion of the diaphragm, the piezoelectric layer, and the electrode facing the first pressure chamber is opposed to the second pressure chamber. By forming it thinner than the portion, the rigidity of the portion facing the first pressure chamber of the piezoelectric actuator can be made smaller than the rigidity of the portion facing the second pressure chamber. Therefore, when forming the channel unit, the channel unit can be formed so that the channel structures of the first channel and the second channel are the same. At this time, when the same voltage is applied to the portion of the piezoelectric layer facing the first pressure chamber and the portion facing the second pressure chamber, the portion of the diaphragm facing the first pressure chamber becomes the second pressure chamber. The deformation is greater than that of the opposing portion, and the volume of the first pressure chamber changes more than the volume of the second pressure. Thereby, a larger pressure than the liquid of the second pressure chamber can be applied to the liquid of the first pressure chamber, and a droplet having a volume larger than that of the second nozzle can be ejected from the first nozzle.

  Furthermore, when the flow path unit is formed, the flow path unit is formed so that the first flow path and the second flow path have the same flow path structure. It is possible to manufacture liquid droplet ejecting apparatuses in which the positions of the nozzle and the second nozzle, the ratio of the number of the first nozzle and the second nozzle, and the like are different. The plurality of layers of the present invention includes a diaphragm, a piezoelectric layer, and a pair of electrodes.

  In the method for manufacturing a droplet ejecting apparatus of the present invention, the droplet ejecting apparatus is configured such that the droplet ejected from the first nozzle is larger than the droplet ejected from the second nozzle, and the voltage is applied to the electrode. Is applied, the piezoelectric layer contracts in the plane direction of the diaphragm, and the diaphragm is deformed so as to be convex toward the first and second pressure chambers. A liquid droplet ejecting apparatus that ejects liquid droplets by applying pressure to the liquid in the pressure chamber may be used.

  The pressure in the pressure chamber is temporarily reduced by the piezoelectric actuator, and at this time, the negative pressure wave generated in the pressure chamber is reversed positively, and the pressure in the pressure chamber is increased and returned to eject the droplet from the nozzle. In the case of performing the pulling operation, the propagation speed of the pressure wave in the first pressure chamber is slower than the propagation speed of the pressure wave in the second pressure chamber, so that the volume of the droplet ejected from the first nozzle is the second. It becomes larger than the volume of the droplet ejected from the nozzle.

  In the method of manufacturing a droplet ejecting apparatus of the present invention, when forming the piezoelectric actuator, the vibration actuator, the piezoelectric layer, and the electrode of the piezoelectric actuator are formed of particles constituting the one layer. May be formed by using a particle deposition method in which is deposited on a predetermined substrate. In this case, if the particle deposition method is used, the thickness of the layer can be freely formed. Therefore, it is easy to form layers having different thicknesses in the portion facing the first pressure chamber and the portion facing the second pressure chamber. Can be formed.

  In the method for manufacturing a droplet ejecting apparatus of the present invention, the particle deposition method may be an aerosol deposition method or a sputtering method. In this case, by using an aerosol deposition method or a sputtering method as the particle deposition method, a portion of the piezoelectric actuator that faces the first pressure chamber of one layer of the diaphragm, the piezoelectric layer, and the electrode And the portion facing the second pressure chamber can be easily formed in different thicknesses.

  In the method of manufacturing a droplet ejecting apparatus according to the aspect of the invention, forming the piezoelectric actuator may include forming a recess on one surface of the diaphragm, and when the diaphragm is joined to the flow path unit. In addition, the diaphragm may be joined to the one surface of the flow path unit so that the concave portion and the first pressure chamber face each other. According to this, by forming the concave portion in the diaphragm by half-etching or the like, it is possible to easily form diaphragms having different thicknesses in the portion facing the first pressure chamber and the portion facing the second pressure chamber. .

  According to a third aspect of the present invention, there is provided a liquid droplet ejecting apparatus that ejects a liquid droplet, the first flow path including a first nozzle and a first pressure chamber communicating with the first nozzle, And a second flow path including a second nozzle and a second pressure chamber communicating with the second nozzle, the second flow path having the same flow path structure as the first flow path is formed. The flow path unit, the diaphragm disposed on one surface of the flow path unit so as to cover the first and second pressure chambers, and on the surface of the vibration plate opposite to the flow path unit, A piezoelectric layer disposed opposite to the second pressure chamber; and a pair of electrodes for applying a voltage to the piezoelectric layer, the piezoelectric plate, and a piezoelectric actuator in which the piezoelectric layer and the electrode are stacked. The rigidity of the portion of the piezoelectric actuator that faces the first pressure chamber is opposed to the second pressure chamber. Droplet ejection apparatus is provided smaller than the partial stiffness.

  According to the third aspect of the present invention, the rigidity of the portion facing the first pressure chamber of the piezoelectric actuator is smaller than the rigidity of the portion facing the second pressure chamber. Even if the second channel has the same channel configuration, the propagation speed of the pressure wave in the first channel can be made slower than that of the second channel. Therefore, the volume of the droplet ejected from the first nozzle can be made larger than the volume of the droplet ejected from the second nozzle. Further, since the rigidity of the portion of the piezoelectric actuator that faces the first pressure chamber is smaller than the rigidity of the portion that faces the second pressure chamber, the portion of the piezoelectric actuator that faces the first pressure chamber is not deformed. The deformation of the portion facing the second pressure chamber can be made larger. As a result, the volume of the droplet ejected from the first nozzle can be made larger than the volume of the droplet ejected from the second nozzle.

  In the liquid droplet ejecting apparatus according to the aspect of the invention, the first and second pressure chambers may have a substantially elliptical shape that is long in a predetermined length direction. A concave portion may be formed in a portion facing the substantially center of the pressure chamber. In this case, since the concave portion is formed in the portion facing the substantially center of the first pressure chamber, the rigidity of the portion of the piezoelectric actuator that faces the first pressure chamber can be reduced. The volume of the droplet ejected from the nozzle can be made larger than the volume of the droplet ejected from the second nozzle.

  In the liquid droplet ejecting apparatus according to the aspect of the invention, a cavity may be formed in a region between the diaphragm and the piezoelectric layer that overlaps with a substantially center of the first pressure chamber. Furthermore, the cavity may be filled with a low-rigidity material that is less rigid than the diaphragm and the piezoelectric layer. In any case, since the concave portion is formed in the portion facing the substantially center of the first pressure chamber, the rigidity of the portion of the piezoelectric actuator facing the first pressure chamber can be lowered. The volume of the droplet ejected from the second nozzle can be made larger than the volume of the droplet ejected from the second nozzle.

  In the liquid droplet ejecting apparatus according to the aspect of the invention, the pair of electrodes may include a ring-shaped electrode formed in a region overlapping the outer edge portion of the first and second pressure chambers of the piezoelectric layer. In this case, since the ring-shaped individual electrode is formed, the diaphragm can be deformed so that the central portion of the pressure chamber bulges when a voltage is applied to the individual electrode. Therefore, it is not necessary to always apply a voltage to the electrodes even in the case of striking, the deterioration of the piezoelectric layer can be prevented, and the power consumption can be reduced.

  In the liquid droplet ejecting apparatus according to the aspect of the invention, the first and second pressure chambers may have a substantially elliptical shape that is long in a predetermined length direction. A groove may be formed in a portion facing the outer edge portion of the pressure chamber. The groove may be filled with a low-rigidity material that is less rigid than the diaphragm and the piezoelectric layer. The groove may be formed only on one end side in the length direction of the first pressure chamber of one of the vibration plate and the piezoelectric layer. Further, the groove includes a first groove formed at one end of the first pressure chamber in the length direction of one of the diaphragm and the piezoelectric layer, and along the length direction of the pressure chamber. The formed second groove may be included, and the first groove may be deeper than the second groove. A groove surrounding the first pressure chamber may be formed outside the region of the diaphragm that overlaps both of the pair of electrodes. In any case, the rigidity of the portion of the piezoelectric actuator facing the first pressure chamber can be lowered, and the volume of the droplet ejected from the first nozzle can be reduced by the droplet ejected from the second nozzle. It can be made larger than the volume.

  In the liquid droplet ejecting apparatus according to the aspect of the invention, a portion of the piezoelectric layer facing the first pressure chamber is formed of the first piezoelectric material, and a portion facing the second pressure chamber is formed of the first piezoelectric material. The piezoelectric layer may be formed of a different second piezoelectric material, and the rigidity of the portion of the piezoelectric layer facing the first pressure chamber may be lower than that of the portion facing the second pressure chamber. In this case as well, the rigidity of the portion of the piezoelectric actuator that faces the first pressure chamber can be reduced, and the volume of the liquid droplets ejected from the first nozzle can be reduced by the volume of the liquid droplets ejected from the second nozzle. It can be larger than the volume.

  Hereinafter, preferred embodiments of the present invention will be described.

  FIG. 1 is a schematic diagram of a printer according to the present embodiment. As shown in FIG. 1, the printer 1 includes a carriage 2, an ink jet head 3 (droplet ejecting device), and a paper transport roller 4. The carriage 2 reciprocates in the left-right direction (scanning direction) in FIG. The inkjet head 3 is provided on the lower surface of the carriage 2, and ejects ink droplets from nozzles 15 a and 15 b (see FIG. 2) formed on the lower surface while reciprocating in the scanning direction together with the carriage 2. The paper transport roller 4 transports the recording paper P in the front direction (paper transport direction) in FIG. In the printer 1, ink droplets are ejected onto the recording paper P transported in the paper feed direction by the paper transport roller 4 by the inkjet head 3 that reciprocates in the scanning direction together with the carriage 2. Further, the paper transport roller 4 discharges the recording paper P that has been printed.

  Next, the inkjet head 3 in FIG. 1 will be described with reference to FIGS.

  As shown in FIGS. 2 to 6, the inkjet head 3 includes a flow path unit 30 in which an ink flow path having pressure chambers 10 a and 10 b and manifold flow paths 11 a and 11 b described later is formed, and an upper surface of the flow path unit 30. And a piezoelectric actuator 31 disposed on the surface.

  As shown in FIGS. 2 to 6, the flow path unit 30 includes a cavity plate 21, a base plate 22, a manifold plate 23, and a nozzle plate 24, and these four plates are stacked on each other. The three plates 21 to 23 excluding the nozzle plate 24 are made of a metal material such as stainless steel, and the nozzle plate 24 is made of a synthetic resin material such as polyimide. Alternatively, the nozzle plate 24 may also be made of metal like the other three plates 21 to 23.

  In the cavity plate 21, two pressure chamber rows 8a (first pressure chamber rows) and six pressure chamber rows 8b (second pressure chamber rows) are arranged in the left-right direction in FIG. . The pressure chamber row 8b is disposed on the right side of the pressure chamber row 8a. Each pressure chamber row 8a includes ten pressure chambers 10a arranged in the vertical direction of FIG. 2, and each pressure chamber 8b also includes ten pressure chambers 10b arranged in the same manner. The plurality of pressure chambers 10 a and 10 b are open on the upper surface of the cavity plate 21. Each pressure chamber 10a (first pressure chamber), 10b (second pressure chamber) is substantially elliptical in plan view, and the longitudinal direction thereof coincides with the left-right direction in FIG. In the base plate 22, through holes 12a and through holes 13a are respectively formed in portions facing the both ends in the longitudinal direction of the plurality of pressure chambers 10a, and respectively in portions facing the both ends in the longitudinal direction of the plurality of pressure chambers 10b. A through hole 12b and a through hole 13b are formed. The through hole 12a and the through hole 12b have the same shape, and the through hole 13a and the through hole 13b have the same shape.

  Two manifold channels 11a extending in the vertical direction in FIG. 2 are formed in the manifold plate 23, and each manifold channel 11a overlaps with a plurality of pressure chambers 10a included in each pressure chamber row 8a. ing. That is, each manifold channel 11a overlaps with a portion excluding an end portion on the side where the through hole 13a is formed in the longitudinal direction of the plurality of pressure chambers 10a constituting each pressure chamber row 8a in plan view. Yes. Each manifold channel 11a communicates with a plurality of pressure chambers 10a constituting each pressure chamber row 8a via a plurality of through holes 12a. Black ink is supplied to the manifold channel 11a from an ink supply port 6a formed in the vicinity of the upper end portion in FIG.

  Further, six manifold channels 11b extending in the vertical direction in FIG. 2 are formed in the manifold plate 23, and each manifold channel 11b includes a plurality of pressure chambers 10b included in each pressure chamber row 8b. It overlaps with. The manifold channel 11b has the same shape as the manifold channel 11a, and is a side where the through holes 13b are formed in the longitudinal direction of the plurality of pressure chambers 10b included in each pressure chamber row 8b in plan view. It overlaps with the part except the edge part. The manifold channel 11b communicates with a plurality of through holes 12b communicating with a plurality of pressure chambers 10b included in the corresponding pressure chamber row 8b. Cyan, yellow, and magenta ink (color ink) are supplied to the manifold channel 11b in order from the one arranged on the left side of FIG. These inks are supplied from an ink supply port 6b formed in the vicinity of the upper end portion in FIG.

  A plurality of through holes 14a and 14b are formed in portions of the manifold plate 23 facing the plurality of through holes 13a and 13b, respectively. The manifold channel 11a, the ink supply port 6a, and the through hole 14a have the same shape as the manifold channel 11b, the ink supply port 6b, and the through hole 14b, respectively.

  In the nozzle plate 24, two nozzle rows 17a arranged in the left-right direction in FIG. 2 are formed corresponding to the two pressure chamber rows 8a. Each nozzle row 17a includes ten nozzles 15a (first nozzles) arranged in the vertical direction in FIG. The plurality of nozzles 15a are respectively formed at positions on the nozzle plate 24 facing the plurality of through holes 14a. The nozzle plate 24 is formed with six nozzle rows 17b arranged side by side in the left-right direction in FIG. 2 corresponding to the six pressure chamber rows 8b. Each nozzle row 17b includes ten nozzles 15b (second nozzles) arranged in the vertical direction in FIG. The plurality of nozzles 15b have the same shape as the nozzle 15a and are formed in a portion of the nozzle plate 24 that faces the plurality of through holes 14b.

  The manifold channel 11a communicates with the pressure chamber 10a through the through hole 12a, and the pressure chamber 10a further communicates with the nozzle 15a through the through holes 13a and 14a. The manifold channel 11b communicates with the pressure chamber 10b through the through hole 12b, and the pressure chamber 10b further communicates with the nozzle 15b through the through holes 13b and 14b. Thus, the flow path unit 30 includes a plurality of individual ink flow paths 32a from the outlet of the manifold flow path 11a through the pressure chamber 10a to the nozzle 15a, and a nozzle 15b from the outlet of the manifold flow path 11b through the pressure chamber 10b. A plurality of individual ink flow paths 32b are formed.

  Thus, the black ink supplied from the ink supply port 6a to the manifold channel 11a flows to the nozzle 15a along the individual ink channel 32a, and black ink droplets are ejected from the nozzle 15a as will be described later. On the other hand, the color ink supplied from the ink supply port 6b to the manifold channel 11b flows to the nozzle 15b along the individual ink channel 32b. The nozzle 15b included in the first and second nozzle rows 17b from the left in FIG. 2, the nozzle 15b included in the third and fourth nozzle rows 17b, and the fifth and sixth nozzles Cyan, yellow, and magenta ink droplets are ejected from the nozzles 15b included in the row 17b, respectively.

  Note that an ink flow path including a single manifold flow path 11a and a plurality of individual ink flow paths 32a communicating with the manifold flow path 11a corresponds to the first flow path according to the present invention. An ink flow path comprising a plurality of individual ink flow paths 32b communicating with the manifold flow path 11b corresponds to the second flow path according to the present invention. As described above, the pressure chamber 10a, the through hole 12a, the through hole 13a, the through hole 14a, the nozzle 15a, the manifold channel 11a, the pressure chamber 10b, the through hole 12b, the through hole 13b, the through hole 14b, and the nozzle 15b. Since the manifold channel 11b and the manifold channel 11b have the same shape, the first channel and the second channel have the same channel structure.

  Next, the piezoelectric actuator 31 will be described. As shown in FIGS. 2 to 5, the piezoelectric actuator 31 includes a diaphragm 40, an insulating layer 41, a piezoelectric layer 42, individual electrodes 43 a and 43 b, and a common electrode 44, and a unimorph in which these layers are stacked. Type piezoelectric actuator.

  The diaphragm 40 is a substantially rectangular metal plate having a thickness of about 20 μm, and covers the upper surface of the flow path unit 30 and is joined to the upper surface of the cavity plate 21. In other words, the diaphragm 40 defines the upper surfaces of the pressure chambers 10a and 10b. The insulating layer 41 is made of an insulating ceramic material such as alumina or zirconia, or a synthetic resin material such as polyimide. The insulating layer 41 is provided over the entire upper surface of the vibration plate 40 and has a thickness of about 2 μm.

  The piezoelectric layer 42 is continuously provided on the upper surface of the insulating layer 41 across the plurality of pressure chambers 10a and 10b. That is, the piezoelectric layer 42 is disposed opposite to the pressure chambers 10 a and 10 b on the opposite side of the insulating layer 41 from the diaphragm 40 and the flow path unit 30. As shown in FIGS. 4 to 6, the two pressure chamber rows 8 a of the piezoelectric layer 42 and the thicknesses of the portions facing the periphery thereof are about 7.5 μm, and the six pressure chamber rows 8 b and The thickness of the part facing the periphery is about 15 μm. That is, the portion of the piezoelectric layer 42 that faces the pressure chamber row 8a is thinner than the portion that faces the pressure chamber row 8b. The piezoelectric layer 42 is previously polarized in the thickness direction.

  The individual electrode 43a is made of a conductive material. The individual electrode 43a has a substantially oval shape that is slightly smaller than the pressure chamber 10a, and its thickness is about 1 μm. The individual electrode 43a is formed on a portion of the upper surface of the piezoelectric layer 42 facing the substantially central portion of the pressure chamber 10a. The individual electrode 43b is formed of the same conductive material as that of the individual electrode 43a. The individual electrode 43b has the same substantially elliptical shape as the individual electrode 43a, and the thickness thereof is about 1 μm, which is substantially the same as the thickness of the individual electrode 43a. The individual electrode 43b is formed on a portion of the upper surface of the piezoelectric layer 42 facing the substantially central portion of the pressure chamber 10b. The ends of the individual electrodes 43a and 43b on the opposite side to the nozzles 15a and 15b in the longitudinal direction extend to positions facing the ends on the opposite sides of the nozzles 15a and 15b in the longitudinal direction of the pressure chambers 10a and 10b, respectively. Each of the tips has a contact point electrically connected to a flexible printed circuit board (FPC) (not shown). A drive potential is applied to the individual electrodes 43a and 43b through an FPC and contacts by a driver IC (not shown).

  The common electrode 44 is formed of the same conductive material as that of the individual electrodes 43a and 43b, and has a thickness of about 1 μm. The common electrode 44 is formed between the insulating layer 41 and the piezoelectric layer 42 and is always held at the ground potential. As a result, the portion of the piezoelectric layer 42 facing the pressure chamber 10 a is sandwiched between the individual electrode 43 a and the common electrode 44, and the portion of the piezoelectric layer 42 facing the pressure chamber 10 b is connected to the individual electrode 43 b and the common electrode 44. It is sandwiched. The electrode pair of the individual electrode 43a and the common electrode 44 and the electrode pair of the individual electrode 43b and the common electrode 44 correspond to a pair of electrodes according to the present invention that apply a voltage to the piezoelectric layer 42, respectively.

  Here, a driving method of the piezoelectric actuator 31 will be described. FIG. 7A is a diagram showing a time change of the potential applied to the individual electrode 43a when the piezoelectric actuator 31 is driven, and FIG. 7B is applied to the individual electrode 43b when the piezoelectric actuator 31 is driven. It is a figure which shows the time change of the electric potential performed.

  As shown in FIGS. 7A and 7B, in the piezoelectric actuator 31, the drive potential V is applied in advance to the individual electrodes 43a and 43b in a state where ink droplets are not ejected. As a result, a potential difference is generated between the individual electrodes 43a and 43b and the common electrode 44 (a voltage is applied to the piezoelectric layer 42), and is sandwiched between the individual electrodes 43a and 43b of the piezoelectric layer 42 and the common electrode 44. An electric field in the thickness direction is generated in the portion. Since the direction of the electric field coincides with the polarization direction of the piezoelectric layer 42, the portion of the piezoelectric layer 42 sandwiched between these electrodes contracts in the horizontal direction (surface direction of the piezoelectric layer 42) perpendicular to the thickness direction. To do. Due to this contraction, the diaphragm 40 is deformed so as to be convex in the pressure chambers 10a and 10b.

  When ejecting ink droplets from the nozzles 15a and 15b, first, the individual electrodes 43a and 43b corresponding to the nozzles 15a and 15b that eject the ink droplets are set to the ground potential. At this time, the deformation of the portion of the vibration plate 40 facing the pressure chambers 10a and 10b corresponding to the grounded individual electrodes 43a and 43b is restored, the volume of the pressure chambers 10a and 10b is increased, and the pressure chamber 10a is increased. The pressure of the ink in 10b decreases. Thereby, ink flows into the pressure chambers 10a and 10b from the manifold channels 11a and 11b, respectively.

  Next, after a predetermined time has elapsed, the drive potential V is applied again to the individual electrodes 43a and 43b having the ground potential. At this time, as described above, the diaphragm 40 is deformed so as to protrude into the pressure chambers 10a and 10b, and the volumes of the pressure chambers 10a and 10b are reduced. Thereby, the pressure of the ink in the pressure chambers 10a and 10b is increased (pressure for ejection is applied to the ink in the pressure chambers 10a and 10b), and ink droplets are ejected from the nozzles 15a and 15b communicating with the pressure chamber 10a. Be injected.

  Thus, the ink jet head 3 performs so-called striking. That is, after the volumes in the pressure chambers 10a and 10b are once increased, the volumes of the pressure chambers 10a and 10b are decreased, and pressure is applied to the ink in the pressure chambers 10a and 10b to discharge the ink. When striking, when the individual electrodes 43a and 43b are set to the ground potential, the predetermined time from when the individual electrodes 43a and 43b are set to the ground potential to when the drive potential V is again applied to the individual electrodes 43a and 43b is set. In addition, the ink droplets can be efficiently ejected from the nozzles 15a and 15b by adjusting the time until the negative pressure wave generated in the pressure chambers 10a and 10b is reversed to be positive and returned.

  At this time, the individual ink flow path 32a and the manifold flow path 11a, and the individual ink flow path 32b and the manifold flow path 11b have the same flow path structure, and the portion of the piezoelectric layer 42 that faces the pressure chamber 10a. Is thinner than the thickness of the portion facing the pressure chamber 10b, and the rigidity is small. Here, according to the inventor's experiment, the propagation speed of the pressure wave depends on the rigidity of each plate constituting the flow path in addition to the natural frequency of the ink, the length of the ink flow path of the cavity plate, the flow path resistance, and the like. It is known that it is also affected. In the present embodiment, the thickness of the portion of the piezoelectric layer 42 facing the pressure chamber 10a is thinner than the portion of the portion facing the pressure chamber 10b, and the rigidity is lowered. As a result, the pressure chamber 10a and the manifold channel 11a It has been found that the propagation speed of the pressure wave between the pressure chamber 10 and the pressure chamber 10b is lower than the propagation speed of the pressure wave between the pressure chamber 10b and the manifold channel 11b. In other words, the time AL1 until the negative pressure wave generated in the pressure chamber 10a is reversed positively and returned is the time until the negative pressure wave generated in the pressure chamber 10b is reversed positively and returned. It becomes longer than time AL2. According to the inventor's knowledge, the volume of the ink droplet ejected from the nozzle is longer when the negative pressure wave generated in the pressure chamber is reversed in the positive direction and returned when the strike is performed. Is known to grow. Also in the inkjet head of this embodiment, the volume of the black ink droplet ejected from the nozzle 15a is larger than the volume of the color ink droplet ejected from the nozzle 15b. In the present embodiment, the time AL1 is about 7 μs and the time AL2 is about 4.5 μs.

  Further, since the rigidity of the portion facing the pressure chamber 10a of the piezoelectric layer 42 is smaller than the rigidity of the portion facing the pressure chamber 10b, the portion facing the pressure chamber 10a of the diaphragm 40 is the portion facing the pressure chamber 10b. Deforms more than. Accordingly, the change in the volume of the pressure chamber 10a is larger than the change in the volume of the pressure chamber 10b. Thereby, the volume of the black ink droplet ejected from the nozzle 15a becomes larger than the volume of the color ink droplet ejected from the nozzle 15b.

  Further, the thickness of the portion of the piezoelectric layer 42 facing the pressure chamber 10a is thinner than the thickness of the portion of the piezoelectric layer 42 facing the pressure chamber 10b. Therefore, when the same drive potential V is applied to the individual electrodes 43a and 43b, the strength of the electric field applied to the portion sandwiched between the individual electrode 43a and the common electrode 44 of the piezoelectric layer 42 is The intensity of the electric field applied to the portion sandwiched between the individual electrode 43b and the common electrode 44 becomes larger. Thereby, the horizontal contraction amount of the portion sandwiched between the individual electrode 43 a and the common electrode 44 of the piezoelectric layer 42 is larger than the horizontal contraction amount of the portion sandwiched between the individual electrode 43 b and the common electrode 44 of the piezoelectric layer 42. Also grows. Therefore, the portion of the vibration plate 40 that faces the pressure chamber 10a is deformed further than the portion that faces the pressure chamber 10b, and the volume of the pressure chamber 10a changes more greatly than the volume of the pressure chamber 10b. Therefore, the volume of the black ink droplet ejected from the nozzle 15a is further larger than the volume of the color ink droplet ejected from the nozzle 15b. In the present embodiment, the thickness of the diaphragm and the pressure chamber is adjusted as described later, and the rigidity of the portion of the diaphragm and the pressure chamber that faces the pressure chamber 10a is the portion that faces the pressure chamber 10b. In this case, the volume of black ink droplets ejected from the nozzle 15a was about 8 pl, and the volume of color ink droplets ejected from the nozzle 15b was about 5 pl. Further, when the thickness of the portion of the piezoelectric layer 42 facing the pressure chamber 10a is made thinner than the thickness of the portion facing the pressure chamber 10b, the volume of the black ink droplet ejected from the nozzle 15a is about 10 pl. The volume of the color ink droplets ejected from the nozzle 15b was about 5 pl. The increase in the volume of the black ink droplet is considered to be caused by a decrease in rigidity of the piezoelectric layer and an increase in electric field strength in the piezoelectric layer.

  As described above, the volume of the black ink droplet ejected from the nozzle 15a is larger than the volume of the color ink droplet ejected from the nozzle 15b. Therefore, when performing monochrome printing, it is possible to perform printing at high speed by ejecting black ink droplets having a large volume from the nozzles 15a. When performing color printing, color ink droplets having a small volume from the nozzles 15b. Can be printed with high image quality.

Here, as the piezoelectric actuator, in addition to a unimorph type piezoelectric actuator such as the piezoelectric actuator 31 in the present embodiment, there is a laminated type piezoelectric actuator. In the laminated piezoelectric actuator, a plurality of piezoelectric layers are laminated on the upper surface of the flow path unit, and individual electrodes and common electrodes are alternately arranged between the piezoelectric layers, and the pressure chamber is deformed by deformation in the thickness direction of the piezoelectric layers. The volume of the is directly changed. In the present embodiment, such a stacked piezoelectric actuator cannot be used in place of the piezoelectric actuator 31. This is because, in a stacked piezoelectric actuator, d ₃₃ = m / m between the displacement m of each piezoelectric layer, the piezoelectric constant d ₃₃ determined by the material constituting the piezoelectric layer, and the voltage V applied to the piezoelectric layer. It is known that there is a relationship of V. That is, the displacement amount m of each piezoelectric layer is an amount depending on d33 which is a constant inherent to the piezoelectric material and the voltage V applied to each piezoelectric layer, and is not an amount depending on the thickness of each piezoelectric layer. If the number of piezoelectric layers stacked and the applied voltage are the same, the amount of change in volume of the pressure chambers 10a and 10b will be substantially the same even if the thickness of the piezoelectric layer is changed. Therefore, in the present embodiment, the unimorph type piezoelectric actuator 31 is particularly used.

  Next, the manufacturing method of the inkjet head 3 is demonstrated using FIG. FIG. 8 is a process diagram showing the manufacturing process of the inkjet head 3.

  In order to manufacture the inkjet head 3, first, a metal base material to be the plates 21 to 23 is prepared. A pressure chamber 10a and a pressure chamber 10b having the same shape are formed on the prepared substrate by etching or the like, and holes such as a manifold channel 11a and a manifold channel 11b are formed as ink channels. Further, a base material made of a synthetic resin material to be the nozzle plate 24 is prepared, and the nozzles 15a and 15b are formed on the base material by laser processing. As shown in FIG. 8A, the plates 21 to 24 are stacked to form the flow path unit 30 (flow path unit forming step). As a result, as described above, the flow path unit 30 has the same flow path structure as the first flow path having the individual ink flow path 32a and the manifold flow path 11a, and the individual ink flow path 32b. And the 2nd flow path which has the manifold flow path 11b is formed. In the case where the nozzle plate 24 is made of a metal material, the nozzles 15a and 15b can be formed on a metal base material to be the nozzle plate 24 by pressing.

  Next, as shown in FIG. 8B, the diaphragm 40 is joined to the upper surface of the flow path unit 30 (joining step), and then, as shown in FIG. An insulating layer 41 is formed by sputtering, and a common electrode 44 is formed on the upper surface thereof by printing or the like.

  Next, as shown in FIG. 9A, particles of piezoelectric material are deposited on the surface of the diaphragm 40 (predetermined base material) having the insulating layer 41 formed on the surface by a sputtering method (particle deposition method). A piezoelectric layer 42a having a substantially constant thickness is formed. As will be described later, the piezoelectric layer 42 a corresponds to a substantially lower half of the piezoelectric layer 42. Next, as shown in FIG. 9B, a portion of the upper surface of the piezoelectric layer 42a excluding the portion facing the pressure chamber row 8b and the periphery thereof is covered with a mask M1, and the upper portion thereof is further substantially constant by sputtering. The piezoelectric layer 42b having the thickness of is formed. The piezoelectric layer 42b constitutes the upper half of the piezoelectric layer 42. As shown in FIG. 9C, when the mask M1 is removed, in the portion facing the pressure chamber row 8a (pressure chamber 10a) and its periphery, the portion facing the pressure chamber row 8b (pressure chamber 10b) and its periphery. Thus, the piezoelectric layer 42 having a smaller thickness is formed. Thereafter, an annealing process for heating the piezoelectric layer 42 is performed to impart sufficient piezoelectric characteristics to the piezoelectric layer 42.

  At this time, each of the pressure chamber rows 8a and 8b includes a plurality of pressure chambers 10a and 10b, and the pressure chamber row 8a on the upper surface of the diaphragm 40 and a region facing the periphery thereof, and the pressure chamber row 8b and the periphery thereof. The opposing regions are regions having a relatively large area. Therefore, it is possible to easily form the piezoelectric layers 42 having different thicknesses in the portion facing the pressure chamber row 8a and the periphery thereof, and the portion facing the pressure chamber row 8b and the periphery thereof.

  Furthermore, in the sputtering method, since the thickness of the piezoelectric layers 42a and 42b can be freely changed, the piezoelectric layer 42 having a desired thickness can be easily formed.

  Thereafter, a plurality of individual electrodes 43a and 43b are formed on the surface of the piezoelectric layer 42 by printing or the like, whereby the ink jet head 3 as shown in FIGS. 2 to 6 is manufactured. A process of forming the insulating layer 41, the common electrode 44, the piezoelectric layer 42, and the individual electrodes 43a and 43b on the upper surface of the vibration plate 40 corresponds to a piezoelectric actuator forming process.

  According to the embodiment described above, the thickness of the portion of the piezoelectric layer 42 facing the pressure chamber row 8a and the periphery thereof is larger than the thickness of the portion of the piezoelectric layer 42 facing the pressure chamber row 8b and the periphery thereof. By forming it thin, the rigidity of the part facing the pressure chamber 10a of the piezoelectric actuator 31 is smaller than the rigidity of the part facing the pressure chamber 10b. At this time, the first flow path including the individual ink flow path 32a and the manifold flow path 11a and the second flow path including the individual ink flow path 32b and the manifold flow path 11b of the flow path unit 30 are the same flow path. Even when the structure is formed, when the same drive potential V is applied to the individual electrode 43a and the individual electrode 43b, the portion of the diaphragm 40 that faces the pressure chamber 10a is more than the portion that faces the pressure chamber 10b. Is also greatly deformed. Thereby, the volume of the pressure chamber 10a can be changed larger than the volume of the pressure chamber 10b, and the volume of the ink droplet ejected from the nozzle 15a is made larger than the volume of the ink droplet ejected from the nozzle 15b. Can do.

  In the present embodiment, ink droplets are ejected from the nozzles 15a and 15b by pulling. As described above, since the propagation speed of the pressure wave in the pressure chamber 10a is slower than the propagation speed of the pressure wave in the pressure chamber 10b, the volume of the black ink droplet ejected from the nozzle 15a communicating with the pressure chamber 10a is The volume of the color ink ejected from the nozzle 15b communicating with 10b is further increased.

  The thickness of the piezoelectric layer 42 in the portion facing the pressure chamber 10a is thinner than the thickness of the piezoelectric layer 42 in the portion facing the pressure chamber 10b. Therefore, when the same voltage is applied between the individual electrode 43 a and the common electrode 44, and between the individual electrode 43 b and the common electrode 44, the portion sandwiched between the individual electrode 43 a and the common electrode 44 of the piezoelectric layer 42. Is greater than the electric field strength of the portion sandwiched between the individual electrode 43 b and the common electrode 44. Thereby, the horizontal contraction amount of the portion sandwiched between the individual electrode 43 a and the common electrode 44 of the piezoelectric layer 42 is larger than the horizontal contraction amount of the portion sandwiched between the individual electrode 43 b and the common electrode 44 of the piezoelectric layer 42. Also grows. Therefore, the deformation amount of the part facing the pressure chamber 10a of the diaphragm 40, the insulating layer 41, the common electrode 42, and the piezoelectric layer 42 is larger than the deformation amount of the part facing the pressure chamber 10b. Therefore, the volume of the black ink droplet ejected from the nozzle 15a is further larger than the volume of the ink droplet ejected from the nozzle 15b.

  When performing black and white printing by ejecting black ink droplets from the nozzle 15a and ejecting color ink droplets from the nozzle 15b, printing is performed at high speed by ejecting black ink droplets having a large volume from the nozzle 15a. When color printing is performed, high-quality printing can be performed by ejecting ink droplets having a small volume from the nozzle 15b.

  Since each of the plurality of pressure chamber rows 8a includes a plurality of pressure chambers 10a and each of the plurality of pressure chamber rows 8b includes a plurality of pressure chambers 10b, the pressure chamber rows 8a on the upper surface of the piezoelectric layer 42 are opposed to the periphery thereof. Each of the region and the region facing the pressure chamber row 8b and its periphery has a relatively large area. Therefore, first, the piezoelectric layer 42a is formed over the entire surface of the common electrode 41, and then the portion of the upper surface of the piezoelectric layer 42a excluding the portion facing the pressure chamber row 8b and its periphery is covered with the mask M1, By forming the piezoelectric layer 42b from the upper surface of the layer 42a by sputtering, the thickness of the piezoelectric layer 42 is reduced between the pressure chamber row 8a and a portion facing the periphery thereof, and the pressure chamber row 8b and the portion facing the periphery thereof. It can be easily changed.

  At this time, in the sputtering method which is a particle deposition method, the thickness of the piezoelectric layers 42a and 42b can be freely changed, so that the piezoelectric layer 42 can be formed more easily.

  In the flow path unit 30, the flow path structures of the manifold flow path 11a and the individual ink flow path 32a are the same as the flow path structures of the manifold flow path 11b and the individual ink flow path 32b, respectively. Therefore, the same flow path unit 30 can be used to configure the inkjet head 3 in which the positions of the nozzles 15a and 15b and the ratio of the number of the nozzles 15a and 15b are different.

  In the above embodiment, after the diaphragm 40 is joined to the flow path unit 30, the piezoelectric layer 42 is formed on the upper surface of the diaphragm 40, and then the annealing process is performed to heat the piezoelectric layer 42. Here, since the annealing process is performed at a high temperature of several hundred degrees or more, when the nozzle plate 24 is formed of a synthetic resin material, the nozzle plate 24 may be deformed during the annealing process. Therefore, in this case, in the flow path unit forming step, the plates 21 to 23 excluding the nozzle plate 24 are joined to form the flow path unit 30, and after the annealing process is finished, the nozzle plate 24 is replaced with the flow path unit. 30 is preferable.

  In addition, if the plates 21 to 24 made of a metal material are joined with an adhesive, the adhesive may be melted and the plates 21 to 24 may be separated during the subsequent annealing process. Is preferably performed by diffusion bonding.

  Next, modified examples in which various changes are made to the present embodiment will be described. However, components having the same configuration as the present embodiment are denoted by the same reference numerals and description thereof is omitted as appropriate.

<First modification>
In the present embodiment, the piezoelectric layer 42 is formed by a sputtering method, but the piezoelectric layer 42 may be formed by an aerosol deposition method (AD method). In this case, after the insulating layer 41 and the common electrode 44 are formed on the upper surface of the vibration plate 40, as shown in FIG. The piezoelectric material particles are ejected from the film forming nozzle N while scanning over the entire area of the diaphragm 40 on which the common electrode 44 is formed. As a result, a piezoelectric layer 42d having a substantially constant thickness constituting the substantially lower half of the piezoelectric layer 42 is formed. Next, as shown in FIG. 10B, the film forming nozzle N is ejected from the film forming nozzle N while scanning over the portion facing the nozzle row 8b and its periphery above the piezoelectric layer 42d. As a result, the piezoelectric layer 42e having a substantially constant thickness constituting the substantially upper half of the piezoelectric layer 42 is formed in the pressure chamber row 8b on the upper surface of the piezoelectric layer 42d and the portion facing the periphery thereof. Alternatively, while the film forming nozzle N is scanned over the entire area of the vibration plate 40 on which the insulating layer 41 and the common electrode 44 are formed, particles of the piezoelectric material are ejected from the film forming nozzle N, and the film forming nozzle N is pressurized. The piezoelectric layer 42 may be formed by increasing the ejection amount of the piezoelectric material particles when the chamber row 8b and the periphery thereof are reached. Alternatively, the piezoelectric layer 42 may be formed by a particle deposition method (such as CVD) other than the sputtering method and the AD method.

<Second modification>
In the present embodiment, the thickness of the piezoelectric layer 42 is changed between a portion facing the pressure chamber 10a and a portion facing the pressure chamber 10b. As shown in FIG. 11, the thickness of the portion of the insulating layer 141 facing the pressure chamber 10a may be thinner than the thickness of the portion of the insulating layer 141 facing the pressure chamber 10b. Also in this case, the rigidity of the piezoelectric actuator 31 is smaller in the portion facing the pressure chamber 10a than in the portion facing the pressure chamber 10b. Therefore, as described in the embodiment, the volume of the black ink droplet ejected from the nozzle 15a can be made larger than the volume of the color ink droplet ejected from the nozzle 15b. In this case, as in the case where the piezoelectric layer 42 is formed in the above-described embodiment and modification, the insulating layer 141 having a different thickness can be easily formed by using a particle deposition method such as a sputtering method or an AD method. can do.

<Third modification>
As shown in FIG. 12, the concave portion 60 is formed in a portion of the lower surface (one surface) of the vibration plate 140 facing the pressure chamber 10a, so that the thickness of the portion of the vibration plate 140 facing the pressure chamber 10a is reduced to the pressure chamber. You may make it thinner than the part which opposes 10b. Also in this case, the rigidity of the portion of the piezoelectric actuator 31 facing the pressure chamber 10a is smaller than the rigidity of the portion facing the pressure chamber 10b. Therefore, as described in the above embodiment, the volume of the black ink droplet ejected from the nozzle 15a can be made larger than the volume of the color ink droplet ejected from the nozzle 15b. In this case, when the piezoelectric actuator 31 is formed (in the piezoelectric actuator forming step), the concave portion 60 is formed in the vibration plate 140 by half etching or the like (the concave portion forming step), and then the concave portion 60 is formed in the pressure chamber 10a. The diaphragm 140 is joined to the flow path unit 30 so as to oppose each other (joining step). In the present modification, the portion of the pressure chamber 10a constituted by the flow path unit 30, that is, the portion excluding the recess 60 corresponds to the first pressure chamber of the present invention. Similar to the embodiment, the first channel according to the present invention and the second channel according to the present invention have the same channel structure. Further, a recess may be formed on the upper surface of the diaphragm 140.

  Alternatively, the individual electrode 43a may be formed with a thickness different from that of the individual electrode 43b, and the thickness of the portion of the common electrode 44 facing the pressure chamber 10a and the portion facing the pressure chamber 10b may be different from each other. Good. Even in this case, the portion of the piezoelectric actuator 31 facing the pressure chamber 10a is thinner than the portion facing the pressure chamber 10b.

<Fourth modification>
As shown in FIGS. 13A and 13B, the individual electrodes 143a and 143b are ring-shaped, and the individual electrodes 143a and 143b are formed in a region of the piezoelectric layer 42 that overlaps the substantially central portion of the pressure chambers 10a and 10b. In addition, the recess 60a may be formed in a region overlapping the substantially central portion of the pressure chamber 10a of the diaphragm 140. Thus, when the shape of the individual electrodes 143a and 143b is a ring type, when a voltage is applied to the electrodes, the central portion of the pressure chamber of the piezoelectric layer 42 (the center electrode of the ring type individual electrodes is The portion that overlaps the portion that is not formed is deformed to be convex. That is, when a voltage is applied to the ring-type individual electrodes 143a and 143b, the piezoelectric actuator can be deformed so as to increase the capacity of the pressure chamber, and ink can be ejected by pulling. At that time, it is not necessary to apply a voltage in advance while droplets are not ejected, so that deterioration of the piezoelectric layer can be prevented and power consumption can be reduced. In such a case, by forming the recess 60a in the portion of the diaphragm 140 that overlaps the central portion of the pressure chamber 10a, the rigidity of the portion of the piezoelectric actuator that faces the pressure chamber 10a is increased. The rigidity can be lowered. Here, in addition to the vibration plate 140 or in place of the vibration plate 140, a concave portion may be formed in a portion of the piezoelectric layer 42 that overlaps the pressure chamber 10a. Accordingly, as described in the above embodiment, the volume of the black ink droplet ejected from the nozzle 15a can be made larger than the volume of the color ink droplet ejected from the nozzle 15b.

<Fifth modification>
As shown in FIGS. 14A and 14B, a region between the diaphragm 40 and the piezoelectric layer 42 that overlaps with the outer edge portion of the pressure chamber 10 a is formed of a resin having rigidity lower than that of the diaphragm 40 and the piezoelectric layer 42. An insulator layer 234 may be disposed. As described above, the insulating layer 234 surrounding the outer edge of the pressure chamber 10a is formed between the vibration plate 40 and the piezoelectric layer 42, whereby the rigidity of the portion of the piezoelectric actuator facing the pressure chamber 10a is increased. It can be made lower than the rigidity of the portion facing the. Accordingly, as described in the above embodiment, the volume of the black ink droplet ejected from the nozzle 15a can be made larger than the volume of the color ink droplet ejected from the nozzle 15b. Note that the insulator layer 234 may not completely surround the outer edge of the pressure chamber 10a. Further, it may be formed at a portion between the diaphragm 40 and the piezoelectric layer 42 and facing the outer edge of the pressure chamber 10b. In this case, for example, while the insulator layer completely surrounds the pressure chamber 10a, the rigidity of the portion facing the pressure chamber 10a of the piezoelectric actuator is opposed to the pressure chamber 10b by surrounding a part of the pressure chamber 10b. It is possible to reduce the rigidity of the portion to be reduced.

<Sixth modification>
In the piezoelectric actuator 301 shown in FIG. 15, the individual electrode 311 a is formed on the upper surface of the piezoelectric layer 342 so as to overlap the pressure chamber 10 a, the common electrode 312 is formed on the lower surface of the piezoelectric layer 342, and the pressure chamber 10 a of the diaphragm 314 is formed. A recess 360 is formed in a region overlapping with the substantially central portion. Here, the vibration plate 314 and the common electrode 312 are fixed to each other by an adhesive or diffusion bonding, but since the concave portion 360 is formed in the vibration plate 314, the vibration plate 314 and the common electrode 312 are not formed. A cavity 360a is formed in the. Alternatively, as shown in FIG. 16, a through hole 316a is formed between the piezoelectric layer 342 on which the individual electrode 311a and the common electrode 312 are formed, and the diaphragm 314b in a region overlapping the substantially central portion of the pressure chamber 10a. By inserting the spacer 316, the cavity 360b can be formed. Alternatively, as shown in FIG. 17, the non-joint portion where the diaphragm 314 and the common electrode 312 are not fixed to each other in the region between the diaphragm 314 and the common electrode 312 that overlaps the substantially central portion of the pressure chamber 10 a. 316b may be formed. Note that the cavities 360a and 360b may be filled with a low-rigidity material formed of a resin having rigidity lower than that of the diaphragm 314 and the piezoelectric layer 342. In any case, the rigidity of the portion of the piezoelectric actuator 301 facing the region overlapping the pressure chamber 10a can be made lower than the rigidity of the portion facing the pressure chamber 10b. Accordingly, as described in the above embodiment, the volume of the black ink droplet ejected from the nozzle 15a can be made larger than the volume of the color ink droplet ejected from the nozzle 15b.

<Seventh modification>
As shown in FIG. 18A, a groove 440A may be formed in a portion of the diaphragm 414 that overlaps the outer edge of the pressure chamber 10a outside the region overlapping the individual electrode 43a, or as shown in FIG. 18B. As described above, even if the groove 440B is formed in the outer region of the diaphragm 414 that overlaps the individual electrode 43a and the outer periphery of the pressure chamber 10a (the wall that defines the pressure chamber 10a). Good. In any case, the rigidity of the portion of the piezoelectric actuator that faces the region overlapping the pressure chamber 10a can be made lower than the rigidity of the portion that faces the pressure chamber 10b. In addition, the said groove | channel may surround the outer periphery of a pressure chamber, and may surround a part. Moreover, the above-mentioned low-rigidity material may be filled in the groove. Accordingly, as described in the above embodiment, the volume of the black ink droplet ejected from the nozzle 15a can be made larger than the volume of the color ink droplet ejected from the nozzle 15b.

<Eighth modification>
As shown in FIGS. 19A and 19B, a substantially crescent-shaped recess 540 </ b> A may be formed in a region overlapping the longitudinal end of the pressure chamber 10 </ b> A in the piezoelectric layer 542. Alternatively, as shown in FIGS. 20A and 20B, a first recess 540A is formed in a region of the piezoelectric layer 542 that overlaps the longitudinal end of the pressure chamber 10A, and a region along the longitudinal direction of the outer edge of the pressure chamber 10A. A second recess 540B that is shallower than the first recess may be formed in the overlapping region. Alternatively, in addition to or instead of the piezoelectric layer 542, the diaphragm 514 overlaps with a region overlapping with the longitudinal end of the pressure chamber 10A and / or a region along the longitudinal direction of the outer edge of the pressure chamber 10A. A recess may be formed in each region. Or as FIG. 21 shows, the several hole 541 may be formed in the area | region which overlaps with the outer edge part of the pressure chamber 10a of the piezoelectric layer 542. FIG. In any case, the rigidity of the portion of the piezoelectric actuator that faces the region overlapping the pressure chamber 10a can be made lower than the rigidity of the portion that faces the pressure chamber 10b. Accordingly, as described in the above embodiment, the volume of the black ink droplet ejected from the nozzle 15a can be made larger than the volume of the color ink droplet ejected from the nozzle 15b.

<Ninth modification>
When the piezoelectric layer is formed by the above-described sputtering method, AD method, or the like, the piezoelectric layer may be formed using different piezoelectric materials in the region overlapping the pressure chamber 10a and the region overlapping the pressure chamber 10b. it can. At this time, the rigidity of the piezoelectric material forming the region overlapping the pressure chamber 10a of the piezoelectric layer is made lower than the rigidity of the piezoelectric material forming the region overlapping the pressure chamber 10b. The rigidity of the part facing the overlapping region can be made lower than the rigidity of the part facing the pressure chamber 10b. Accordingly, as described in the above embodiment, the volume of the black ink droplet ejected from the nozzle 15a can be made larger than the volume of the color ink droplet ejected from the nozzle 15b.

  Further, in the above description, the thickness of the portion of the layer constituting the piezoelectric actuator 31 (the diaphragm 40, the insulating layer 41, the common electrode 44, the individual electrodes 43a and 43b) facing the pressure chamber 10a is as follows. The thickness of the portion facing the pressure chamber 10b was different. However, two or more of these layers may be formed so that the thickness of the portion facing the pressure chamber 10a is different from the thickness of the portion facing the pressure chamber 10b.

  In this embodiment, after the diaphragm 40 is joined to the upper surface of the flow path unit 30, the insulating layer 41, the common electrode 44, the piezoelectric layer 42, and the individual electrodes 43 a and 43 b are formed on the upper surface of the diaphragm 40. That is, the piezoelectric actuator formation process according to the present invention was performed after the bonding process according to the present invention. Conversely, the insulating layer 41, the common electrode 44, the piezoelectric layer 42, and the individual electrodes 43 a and 43 b are formed on the upper surface of the vibration plate 40, and then the vibration plate 40 is bonded to the upper surface of the flow path unit 30. Good. That is, the bonding step according to the present invention may be performed after the piezoelectric actuator forming step according to the present invention.

  In the present embodiment, the common electrode 44 is formed between the insulating layer 41 and the piezoelectric layer 42, and the individual electrodes 43a and 43b are formed on the upper surface of the piezoelectric layer 42. The individual electrodes 43 a and 43 b may be formed on the portions facing the pressure chambers 10 a and 10 b between the first electrode 42 and the piezoelectric layer 42, and the common electrode 44 may be formed on the entire upper surface of the piezoelectric layer 42.

  In the present embodiment, the insulating layer 41 is formed on the upper surface of the diaphragm 40, and the common electrode 44 is formed on the upper surface of the insulating layer 41. When the diaphragm 40 is made of a metal material, the insulating layer 41 and the common electrode 44 may not be provided independently, and the diaphragm 40 may be held at the ground potential and may also serve as the common electrode.

  Further, in the present invention, ink droplets are ejected from the nozzles 15a and 15b by pulling, but pressing may be performed. When pushing, the individual electrodes 43a and 43b are held at the ground potential in advance, and a drive potential is applied to the individual electrodes 43a and 43b to reduce the volume of the pressure chambers 10a and 10b. Ink droplets are ejected from the nozzles 15a and 15b by increasing the pressures in 10a and 10b. Since the thickness of the piezoelectric layer 42 is thinner at the portion facing the pressure chamber 10a than at the portion facing the pressure chamber 10b and the rigidity is small, the nozzle 15a communicated with the pressure chamber 10a also in the case of pushing. The volume of the black ink droplet ejected can be made larger than the volume of the color ink droplet ejected from the nozzle 15b communicating with the pressure chamber 10b.

  In this embodiment, black ink droplets are ejected from the nozzles 15a, and color ink droplets are ejected from the nozzles 15b. On the other hand, pigment ink may be ejected from the nozzle 15a and dye ink may be ejected from the nozzle 15b. In this case, it is possible to perform high-quality printing with less bleeding by ejecting pigment ink that is difficult to bleed in a large volume from the nozzle 15a and ejecting dye ink that bleeds in a small volume from the nozzle 15b.

  In the above description, an example in which the present invention is applied to an inkjet head that ejects ink droplets from the nozzles 15a and 15b has been described. However, the present invention is applied to reagents, biological solutions, wiring material solutions, electronic material solutions, and refrigerants. It can also be applied to a droplet ejecting apparatus that ejects droplets other than ink droplets, such as for fuel.

1 is a schematic configuration diagram of a printer according to an embodiment of the present invention. It is a top view of the inkjet head of FIG. FIG. 3 is an enlarged view of a portion surrounded by an alternate long and short dash line in FIG. 2. It is the IV-IV sectional view taken on the line of FIG. It is the VV sectional view taken on the line of FIG. It is the VI-VI sectional view taken on the line of FIG. FIGS. 7A and 7B are diagrams showing temporal changes in potential applied to the individual electrodes. 8A, 8B, and 8C are diagrams showing the first half of the process of manufacturing the inkjet head. 9A, 9B and 9C are views showing the latter half of the process of manufacturing the ink jet head. FIG. 10A is a diagram corresponding to FIG. 9A of the first modification, and FIG. 10B is a diagram corresponding to FIG. 9C of the first modification. It is sectional drawing equivalent to FIG. 4 of a 2nd modification. It is sectional drawing equivalent to FIG. 4 of a 3rd modification. FIG. 13A is a diagram corresponding to FIG. 3 of the fourth modified embodiment, and FIG. 13B is a cross-sectional view taken along line XIIIB-XIIIB of FIG. 13A. 14A is a diagram corresponding to FIG. 3 of the fifth modified embodiment, and FIG. 14B is a cross-sectional view taken along the line XIVB-XIVB of FIG. 14A. FIG. 15 is a diagram corresponding to FIG. 4 of the first example of the sixth modification. FIG. 16 is a diagram corresponding to FIG. 5 of the second example of the sixth modification. FIG. 17 is a diagram corresponding to FIG. 5 of the third example of the sixth modification. 18A is a diagram corresponding to FIG. 4 of the first example of the seventh modification, and FIG. 18B is a diagram corresponding to FIG. 4 of the second example of the seventh modification. 19A is a view corresponding to FIG. 3 of the first example of the eighth modification, and FIG. 19B is a cross-sectional view taken along the line XIXB-XIXB in FIG. 19A. 20A is a diagram corresponding to FIG. 3 of the second example of the eighth modification, and FIG. 20B is a sectional view taken along line XXB-XXB in FIG. 20A. FIG. 21 is a diagram corresponding to FIG. 3 of the third example of the eighth modification. FIG. 22 is a view corresponding to FIG. 2 of a conventional liquid droplet ejecting apparatus.

Explanation of symbols

3 Inkjet heads 10a and 10b Pressure chambers 15a and 15b Nozzle 30 Flow path unit 31 Piezoelectric actuators 32a and 32b Individual ink flow path 40 Vibration plate 41 Insulating layer 42 Piezoelectric layers 43a and 43b Individual electrode 44 Common electrode 60 Recess 140 Vibration plate 141 Insulation layer

Claims (24)

A liquid droplet ejecting apparatus that ejects liquid droplets,
The first flow path including the first nozzle and the first pressure chamber communicating with the first nozzle, and the second flow including the second pressure chamber communicating with the second nozzle and the second nozzle A channel unit in which a second channel having the same channel structure as the first channel is formed;
A diaphragm disposed on one surface of the flow path unit so as to cover the first and second pressure chambers, and facing the first and second pressure chambers on the surface of the vibration plate opposite to the flow path unit. A piezoelectric layer disposed as a result, and a pair of electrodes for applying a voltage to the piezoelectric layer, the diaphragm, the piezoelectric layer and a piezoelectric actuator in which the electrodes are laminated,
The droplet ejecting apparatus according to claim 1, wherein a portion of the vibration plate, the piezoelectric layer, and the electrode facing the first pressure chamber is thinner than a portion facing the second pressure chamber.   The droplet ejected from the first nozzle is larger than the droplet ejected from the second nozzle, and when the voltage is applied to the electrode, the piezoelectric layer contracts in the surface direction of the diaphragm. The diaphragm is deformed so as to be convex toward the first and second pressure chambers, pressure is applied to the liquid in the first and second pressure chambers, and droplets are ejected. The droplet ejecting apparatus according to claim 1, wherein The first channel and the second channel each include a plurality of first individual channels and second individual channels,
A plurality of the first pressure chambers form a first pressure chamber row arranged in a predetermined direction, and a plurality of the second pressure chambers form a second pressure chamber row arranged in the predetermined one direction. And
3. The liquid according to claim 2, wherein a portion of the diaphragm, the piezoelectric layer, and the electrode facing the first pressure chamber row is thinner than a portion facing the second pressure chamber row. Drop ejector. The liquid includes black ink and color ink,
4. The droplet ejecting apparatus according to claim 2, wherein black ink droplets are ejected from the first nozzle, and color ink droplets are ejected from the second nozzle. 5. The liquid includes pigment ink and dye ink,
The liquid droplet ejecting apparatus according to claim 2, wherein pigment ink is ejected from the first nozzle and dye ink is ejected from the second nozzle.   6. The droplet ejecting apparatus according to claim 2, wherein a portion of the piezoelectric layer facing the first pressure chamber is thinner than a portion facing the second pressure chamber.   6. The droplet ejecting apparatus according to claim 2, wherein a portion of the diaphragm facing the first pressure chamber is thinner than a portion facing the second pressure chamber. The diaphragm is made of metal,
The piezoelectric actuator is disposed on a surface of the diaphragm opposite to the flow path unit, and includes an insulating layer that insulates the diaphragm and the electrode.
6. The droplet ejecting apparatus according to claim 2, wherein a portion of the insulating layer facing the first pressure chamber is thinner than a portion facing the second pressure chamber. The first flow path including the first nozzle and the first pressure chamber communicating with the first nozzle, and the second flow including the second pressure chamber communicating with the second nozzle and the second nozzle A channel unit in which a second channel having the same channel structure as the first channel is formed;
A diaphragm disposed on one surface of the flow path unit so as to cover the first and second pressure chambers, and facing the first and second pressure chambers on the surface of the vibration plate opposite to the flow path unit. And a pair of electrodes for applying a voltage to the piezoelectric layer, and a piezoelectric actuator in which the diaphragm, the piezoelectric layer, and the electrode are stacked. Because
Forming the flow path unit such that the first flow path and the second flow path have the same flow path structure;
Laminating the diaphragm, the piezoelectric layer and the electrode to form the piezoelectric actuator;
Bonding the diaphragm to the one surface of the flow path unit,
When forming the piezoelectric actuator, a portion of the vibration plate, the piezoelectric layer, and the electrode facing the first pressure chamber is formed thinner than a portion facing the second pressure chamber. A method for manufacturing a droplet ejecting apparatus.   In the liquid droplet ejecting apparatus, the liquid droplet ejected from the first nozzle is larger than the liquid droplet ejected from the second nozzle, and when the voltage is applied to the electrode, the piezoelectric layer is Contracting in the surface direction, deforming the diaphragm so as to be convex toward the first and second pressure chambers, and applying pressure to the liquid in the first and second pressure chambers, The method for manufacturing a droplet ejecting apparatus according to claim 9, wherein the droplet ejecting apparatus ejects droplets.   In forming the piezoelectric actuator, a particle deposition method is used in which one of the diaphragm, the piezoelectric layer, and the electrode of the piezoelectric actuator is deposited on a predetermined substrate with particles constituting the one layer. The method for manufacturing a droplet ejecting apparatus according to claim 10, wherein the droplet ejecting apparatus is formed.   The method for manufacturing a droplet ejecting apparatus according to claim 11, wherein the particle deposition method is an aerosol deposition method or a sputtering method. Forming the piezoelectric actuator;
Forming a recess on one surface of the diaphragm,
The said diaphragm is joined to the said one surface of the said flow path unit so that the said recessed part and 1st pressure chamber may oppose when joining the said diaphragm to the said flow path unit. The manufacturing method of the droplet ejecting apparatus according to any one of? A liquid droplet ejecting apparatus that ejects liquid droplets,
The first flow path including the first nozzle and the first pressure chamber communicating with the first nozzle, and the second flow including the second pressure chamber communicating with the second nozzle and the second nozzle A channel unit in which a second channel having the same channel structure as the first channel is formed;
A diaphragm disposed on one surface of the flow path unit so as to cover the first and second pressure chambers, and facing the first and second pressure chambers on the surface of the vibration plate opposite to the flow path unit. A piezoelectric layer disposed as a result, and a pair of electrodes for applying a voltage to the piezoelectric layer, the diaphragm, the piezoelectric layer and a piezoelectric actuator in which the electrodes are laminated,
The droplet ejecting apparatus according to claim 1, wherein a rigidity of a portion of the piezoelectric actuator facing the first pressure chamber is smaller than a rigidity of a portion facing the second pressure chamber. The first and second pressure chambers are substantially elliptical shapes long in a predetermined length direction,
The droplet ejecting apparatus according to claim 14, wherein a concave portion is formed in a portion of one of the vibration plate and the piezoelectric layer facing a substantially central portion of the first pressure chamber.   The droplet ejecting apparatus according to claim 15, wherein a cavity is formed in a region between the vibration plate and the piezoelectric layer that overlaps with a substantially center of the first pressure chamber.   The liquid droplet ejecting apparatus according to claim 16, wherein the cavity is filled with a low-rigidity material having rigidity lower than that of the vibration plate and the piezoelectric layer.   The droplet ejecting apparatus according to claim 15, wherein the pair of electrodes include a ring-shaped electrode formed in a region overlapping the outer edge portion of the first and second pressure chambers of the piezoelectric layer. . The first and second pressure chambers are substantially elliptical shapes long in a predetermined length direction,
The droplet ejecting apparatus according to claim 14, wherein a groove is formed in a portion of the vibration plate and the piezoelectric layer that faces an outer edge portion of the first pressure chamber.   The droplet ejecting apparatus according to claim 19, wherein the groove is filled with a low-rigidity material having lower rigidity than the vibration plate and the piezoelectric layer.   The droplet ejecting apparatus according to claim 19, wherein the groove is formed only on one end side in the length direction of the first pressure chamber of one of the vibration plate and the piezoelectric layer.   The groove is formed along a length direction of the pressure chamber and a first groove formed at one end of the first pressure chamber of the vibration plate and the piezoelectric layer. The liquid droplet ejecting apparatus according to claim 19, further comprising a second groove, wherein the first groove is deeper than the second groove.   The droplet ejecting apparatus according to claim 14, wherein a groove surrounding the first pressure chamber is formed outside a region of the diaphragm that overlaps both of the pair of electrodes.   The portion of the piezoelectric layer that faces the first pressure chamber is made of a first piezoelectric material, and the portion that faces the second pressure chamber is made of a second piezoelectric material that is different from the first piezoelectric material. The liquid droplet ejecting apparatus according to claim 14, wherein rigidity of a portion of the piezoelectric layer facing the first pressure chamber is lower than that of a portion facing the second pressure chamber.

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