JP2017209980A - Inkjet recording head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inkjet recording head which has excellent long-time withstand voltage, has drive durability and reliability, and also has high drive efficiency.SOLUTION: An inkjet recording head 100 according to embodiments comprises: a nozzle plate 20 having a plurality of nozzles 22 in communication respectively with a plurality of ink pressure chambers 12; and a plurality piezoelectric elements 30 each having a lower electrode 32 disposed on a surface 20a of the nozzle plate 20 apart from the ink pressure chamber 12 to surround each of the nozzles 22, a piezoelectric film 34 overlaid on the lower electrode 32, and an upper electrode 36 overlaid on the piezoelectric film 34. The piezoelectric film 34 has step parts 52, 54 having a reduced thickness at positions apart from end edge parts 36a, 36b of the upper electrode 36.SELECTED DRAWING: Figure 2

Description

  Embodiments described herein relate generally to an ink jet recording head of a type that ejects ink droplets from nozzles that drive a piezoelectric element and communicate with an ink pressure chamber.

  The ink jet recording head includes a nozzle that ejects ink droplets, an ink pressure chamber that communicates with the nozzle, and an actuator that pressurizes ink in the ink pressure chamber. This head drives the actuator to pressurize ink in the ink pressure chamber and eject ink droplets from the nozzles.

  As an actuator, for example, a piezoelectric type that discharges ink droplets by deforming and displacing a wall surface (vibration plate) of an ink pressure chamber using a piezoelectric element is known. Piezoelectric actuators have the advantage that there is no restriction on the type of ink used because the piezoelectric element does not directly contact the ink and the heat generation of the piezoelectric element can be ignored. Therefore, a so-called piezoelectric MEMS type ink jet recording head in which a semiconductor process technology is applied to the piezoelectric type actuator is attracting attention.

JP 2000-263785 A JP 2008-10528 A JP-A-2015-560

  The piezoelectric element has a lower electrode provided on the vibration plate of the ink pressure chamber, a piezoelectric film provided on the lower electrode, and an upper electrode provided on the piezoelectric film. The surface of the diaphragm is covered with an insulating film together with the piezoelectric element, and the lower electrode and the upper electrode are electrically insulated. This piezoelectric element is driven by applying a driving voltage between the upper and lower electrodes.

  In recent years, when driving a piezoelectric element, there has been a problem that causes dielectric breakdown due to bulk mode in which current flows inside the piezoelectric film, and dielectric breakdown due to creeping mode in which current flows through the interface between the piezoelectric film and the insulating film at the edge of the piezoelectric element. It has been reported. Bulk mode breakdown occurs in a short time when a high voltage is applied between the electrodes, and creeping mode breakdown occurs when a relatively long time elapses when a relatively low voltage is applied between the electrodes. .

  On the other hand, in order to prevent the dielectric breakdown in the creeping mode, a structure in which the piezoelectric film and the lower electrode are extended from the end of the upper electrode has been proposed (for example, Patent Document 1). However, in this structure, the piezoelectric film in the inactive portion extending outside the upper electrode has the same thickness as the active portion of the piezoelectric element sandwiched between the lower electrode and the upper electrode (the portion deformed by voltage application). Therefore, the rigidity of the inactive portion is undesirably increased and the driving efficiency is lowered.

  On the other hand, a structure in which the piezoelectric film of the inactive part is thin is known (for example, Patent Documents 2 and 3). However, in the structures of Patent Documents 2 and 3, the end face of the piezoelectric film extends from the end portion of the upper electrode so as to be inclined (curved) toward the lower electrode, so that dielectric breakdown may occur near the end portion of the upper electrode. There is sex.

  Therefore, it is desired to develop an ink jet recording head that has excellent withstand voltage for a long time, high driving durability and reliability, and high driving efficiency.

  An ink jet recording head according to an embodiment includes a nozzle plate having a plurality of nozzles respectively communicating with a plurality of ink pressure chambers, and a lower electrode provided on the surface of the nozzle plate spaced from the ink pressure chamber so as to surround each nozzle, And a plurality of piezoelectric elements each having a piezoelectric film provided on the lower electrode and an upper electrode provided on the piezoelectric film. The piezoelectric film has a stepped portion with a reduced thickness at a position away from the edge of the upper electrode.

FIG. 1 is a partially enlarged plan view showing a main part of the ink jet recording head according to the first embodiment. FIG. 2 is a partial enlarged cross-sectional view of the ink jet recording head of FIG. 1 cut along the line F2-F2. FIG. 3 is a cross-sectional view for explaining a method of manufacturing the ink jet recording head of FIG. FIG. 4 is a cross-sectional view for explaining a method of manufacturing the ink jet recording head of FIG. FIG. 5 is a cross-sectional view for explaining a method of manufacturing the ink jet recording head of FIG. FIG. 6 is a cross-sectional view for explaining a method of manufacturing the ink jet recording head of FIG. FIG. 7 is a cross-sectional view for explaining a method of manufacturing the ink jet recording head of FIG. FIG. 8 is a cross-sectional view for explaining a method of manufacturing the ink jet recording head of FIG. FIG. 9 is a cross-sectional view for explaining a method of manufacturing the ink jet recording head of FIG. FIG. 10 is a cross-sectional view for explaining a method of manufacturing the ink jet recording head of FIG. FIG. 11 is a cross-sectional view for explaining a method of manufacturing the ink jet recording head of FIG. FIG. 12 is a cross-sectional view for explaining a method of manufacturing the ink jet recording head of FIG. FIG. 13 is a partial enlarged cross-sectional view showing the main part of the ink jet recording head according to the first modification. FIG. 14 is a partial enlarged cross-sectional view showing a main part of an ink jet recording head according to a second modification. FIG. 15 is a partial enlarged cross-sectional view showing a main part of the ink jet recording head according to the second embodiment.

  Hereinafter, embodiments will be described in detail with reference to the drawings.

(First embodiment)
FIG. 1 is a partially enlarged plan view showing a main part of an ink jet recording head 100 (hereinafter simply referred to as the head 100) according to the first embodiment. FIG. 2 is a partially enlarged cross-sectional view of the head 100 of FIG. 1 cut along the line F2-F2. In FIG. 1, the illustration of the insulating film 40 is omitted to make the piezoelectric element 30 and its wiring structure easier to see. 1 and 2, only the unit for ejecting ink droplets is shown as the main part of the head 100, but the head 100 has a plurality of the illustrated structures along the same plane.

  The head 100 of this embodiment is a piezoelectric MEMS ink jet recording head. The head 100 includes a flow path substrate 10 made of, for example, Si, a nozzle plate 20 made of an Si oxide film, and a plurality of piezoelectric elements 30. An insulating film 40 is provided on the surface 20 a of the nozzle plate 20 having a plurality of piezoelectric elements 30 on the side away from the flow path substrate 10. A back plate 50 made of, for example, Si is provided on the second surface 10 b of the flow path substrate 10 on the side away from the nozzle plate 20. The back plate 50 is bonded and fixed to the Si oxide film 20 ′ on the second surface 10 b of the flow path substrate 10 using, for example, an adhesive.

  The flow path substrate 10 has a plurality of cylindrical ink pressure chambers 12 penetrating the substrate in communication with the first surface 10a on the nozzle plate 20 side and the second surface 10b on the back plate 50 side. In other words, one end (upper end in FIG. 2) of each ink pressure chamber 12 along the thickness direction of the flow path substrate 10 is blocked by the nozzle plate 20, and each ink pressure chamber 12 along the thickness direction of the flow path substrate 10. The other end (lower end in FIG. 2) is closed by the back plate 50.

  An ink supply path (not shown) for supplying ink to the plurality of ink pressure chambers 12 is formed in the flow path substrate 10 or the back plate 50. Further, the ink supply path communicates with a common ink chamber (not shown). A predetermined amount of ink is supplied to the plurality of ink pressure chambers 12.

  The flow path substrate 10 has a thickness of, for example, about 100 to 600 μm, and desirably has a thickness of about 100 to 500 μm. The thickness of the flow path substrate 10 is a thickness that allows the partition between the adjacent ink pressure chambers 12 to have sufficient rigidity, and can increase the arrangement density of the ink pressure chambers 12 as much as possible. The chamber 12 is designed to have a thickness that allows the volume of the chamber 12 to be an appropriate value.

  The nozzle plate 20 is provided so as to be in contact with the first surface 10 a of the flow path substrate 10 and close the first surface 10 a side of each ink pressure chamber 12. The nozzle plate 20 has a plurality of nozzles 22 communicating with each ink pressure chamber 12 at the center of each ink pressure chamber 12. A plurality of nozzles 22 provided corresponding to each ink pressure chamber 12 penetrates the nozzle plate 20 and extends through a piezoelectric element 30 described later. That is, each ink pressure chamber 12 communicates with the outside of the head 100 via the nozzle 22.

  The nozzle plate 20 is formed of, for example, a Si oxide film (SiO 2) having a thickness of about 1 to 5 μm formed by thermal oxidation or a CVD method. The Si oxide film is desirably amorphous from the viewpoint that uniform deformation can be realized. In addition, it is desirable to form the nozzle plate 20 from a Si oxide film from the viewpoint of easy production of a film having a stable composition and characteristics. Furthermore, it is desirable to form the nozzle plate 20 with a Si oxide film from the viewpoint of good consistency with the conventional semiconductor process.

  The plurality of piezoelectric elements 30 are stacked on the surface 20a of the nozzle plate 20 so as to surround the plurality of nozzles 22, respectively. Each piezoelectric element 30 has a lower electrode 32 overlaid on the surface 20 a of the nozzle plate 20, a piezoelectric film 34 overlaid on the lower electrode 32, and an upper electrode 36 overlaid on the piezoelectric film 34. The lower electrode 32, the piezoelectric film 34, and the upper electrode 36 are each substantially circular and are concentrically stacked in this order.

  A part of the lower electrode 32 of each piezoelectric element 30 extends in one direction along the surface 20 a of the nozzle plate 20 and functions as the individual drive wiring 33. An insulating film 40 is provided on the surface 20 a of the nozzle plate 20 including the surface of the piezoelectric element 30. A via hole 42 is formed in a part of the insulating film 40 in contact with the upper electrode 36, and an extraction wiring is drawn out from the upper electrode 36 through the via hole 42 in the other direction. This lead wiring extends to the outside on the insulating film 40 and functions as the common wiring 37. The insulating film 40 extends to a position that partially covers the inner surface of the nozzle 22.

  A piezoelectric material having a large electrostriction constant such as lead zirconate titanate (Pb (Zr, Ti) O 3, PZT) is suitable for the piezoelectric film 34 of each piezoelectric element 30. When PZT is used for the piezoelectric film 34, a noble metal such as Pt, Au, or Ir or a conductive oxide such as SrRuO 3 is suitable for the lower electrode 32 and the upper electrode 36. In addition, as the piezoelectric film 34, it is possible to use a piezoelectric material suitable for a silicon process such as AlN or ZrO2. In this case, as the lower electrode 32 and the upper electrode 36, general electrode materials such as Al and Cu and wiring materials can be used.

  The piezoelectric film 34 of each piezoelectric element 30 has an annular inner stepped portion 52 in which the piezoelectric film 34 is partially thinned at an inner peripheral edge adjacent to the nozzle 22. In addition, the piezoelectric film 34 has an annular outer stepped portion 54 in which the piezoelectric film 34 is partially thinned at the edge on the outermost side farthest from the nozzle 22. The inner stepped portion 52 is provided at a position further inwardly spaced from the inner end edge portion 36a (end edge portion) of the upper electrode 36 on the nozzle 22 side. The outer step portion 54 is provided at a position further outwardly spaced from the outer end edge portion 36 b (end edge portion) farthest from the nozzle 22 of the upper electrode 36.

  The inner step portion 52 of the piezoelectric film 34 has an annular inner thin portion 52a (thin portion) in which the thickness of the piezoelectric film 34 is reduced by providing this step portion. The inner peripheral diameter of the inner thin portion 52 a is slightly larger than the outer shape of the nozzle 22 by the thickness of the insulating film 40. The thick portion from the inner edge 36 a of the upper electrode 36 to the inner step 52 of the piezoelectric film 34 is an annular inner extending portion 52 b (extending portion) having the same thickness as the piezoelectric film 34. Function.

  The outer step portion 54 of the piezoelectric film 34 has an annular outer thin portion 54a (thin portion) in which the thickness of the piezoelectric film 34 is reduced by providing this step portion. The outer thin portion 54 a has an outer diameter that is substantially the same as the outer diameter of the lower electrode 32. The thick portion from the outer edge 36 b of the upper electrode 36 to the outer step 54 of the piezoelectric film 34 is an annular outer extending portion 54 b (extending portion) having the same thickness as the piezoelectric film 34. Function.

  The insulating film 40 covers the surfaces of the plurality of piezoelectric elements 30 and the surface 20 a of the nozzle plate 20 except for the via holes 42. Specifically, the insulating film 40 is formed from the upper surface of the upper electrode 36 through the inner edge portion 36a of the upper electrode 36, the inner extending portion 52b, the inner step portion 52, and the inner thin portion 52a of the piezoelectric film 34. And extends to a position covering the inner edge 32 a of the lower electrode 32. Further, the insulating film 40 is formed from the upper surface of the upper electrode 36 through the outer edge 36b of the upper electrode 36, the outer extending portion 54b of the piezoelectric film 34, the outer stepped portion 54, and the outer thin portion 54a. The electrode 32 extends to a position covering the outer edge 32b.

  As described above, by providing the inner stepped portion 52 of the piezoelectric film 34 at a position spaced from the inner edge 36a of the upper electrode 36, the inner extending portion 52b obtained by extending the piezoelectric film 34 with the same thickness is provided. Can do. The inner extending portion 52b functions to prevent a problem that causes dielectric breakdown in the vicinity of the inner end edge 36a of the upper electrode 36. On the other hand, when the width along the radial direction of the inner extending portion 52b is increased, the rigidity of the piezoelectric film of the inactive portion of the piezoelectric element 30 is increased correspondingly, and the driving efficiency is decreased. For this reason, in this embodiment, the radial width of the inner extending portion 52b is made relatively short. Specifically, the radial width of the inner extension portion 52b was made shorter than the radial width of the inner thin portion 52a.

  Similarly, by providing the outer stepped portion 54 of the piezoelectric film 34 at a position spaced from the outer edge 36b of the upper electrode 36, it is possible to provide an outer extending portion 54b obtained by extending the piezoelectric film 34 with the same thickness. . The outer extending portion 54b functions to prevent a problem that causes dielectric breakdown in the vicinity of the outer edge 36b of the upper electrode 36. On the other hand, when the width along the radial direction of the outer extending portion 54b is increased, the rigidity of the piezoelectric film of the inactive portion of the piezoelectric element 30 is increased correspondingly, and the driving efficiency is decreased. For this reason, in this embodiment, the radial width of the outer extending portion 54b is made relatively short. Specifically, the radial width of the outer extending portion 54b was made shorter than the radial width of the outer thin portion 54a.

  Further, as described above, the inner thin portion 52 a can be provided by providing the inner stepped portion 52 on the inner peripheral portion of the piezoelectric film 34 on the nozzle 22 side. By providing the inner thin portion 52a, the inner edge portion 36a of the upper electrode 36 and the inner edge portion of the lower electrode 32 along the boundary between the inner peripheral end surface including the inner step portion 52 of the piezoelectric film 34 and the insulating film 40 are provided. The creepage distance to 32a can be increased, and dielectric breakdown can be made difficult to occur at this portion. The creepage distance can be increased by increasing the radial width of the inner thin portion 52a.

  Since the inner thin portion 52a has a thickness that is less than half the thickness of the piezoelectric film 34, it is possible to suppress the problem that the rigidity of the piezoelectric element 30 is increased at this portion, and the problem that the drive efficiency of the piezoelectric element 30 is greatly reduced. It does not occur. Further, the width along the radial direction of the inner thin portion 52a is such that the above-mentioned creepage distance including the surface of the inner thin portion 52a is more than double the thickness of the piezoelectric film 34 so that dielectric breakdown does not occur at this portion. Designed to be

  In addition, as described above, the outer thin portion 54 a can be provided by providing the outer stepped portion 54 on the outer peripheral portion of the piezoelectric film 34 that is away from the nozzle 22. By providing the outer thin portion 54 a, the outer edge portion 32 b of the lower electrode 32 extends from the outer edge portion 36 b of the upper electrode 36 along the boundary between the outer peripheral end surface including the outer step portion 54 of the piezoelectric film 34 and the insulating film 40. It is possible to increase the creepage distance to reach and to make it difficult to cause dielectric breakdown at this portion. The creepage distance can be increased by increasing the radial width of the outer thin portion 54a.

  In addition, since the outer thin portion 54a has a thickness that is half or less of the thickness of the piezoelectric film 34, it is possible to suppress a problem that the rigidity of the piezoelectric element 30 is increased in this portion, and a problem that the driving efficiency of the piezoelectric element 30 is significantly reduced. It does not occur. Further, the width along the radial direction of the outer thin portion 54a is such that the above-mentioned creepage distance including the surface of the outer thin portion 54a is more than double the thickness of the piezoelectric film 34 so that dielectric breakdown does not occur at this portion. Designed to be

Hereinafter, the operation of the head 100 described above will be described.
First, ink is supplied from an external ink supply pump (not shown) to the plurality of ink pressure chambers 12 via an ink supply path (not shown). In this state, a drive voltage is selectively applied between the lower electrode 32 and the upper electrode 36 of each piezoelectric element 30 in accordance with a recording signal from an external drive circuit (not shown). As a result, the piezoelectric film 34 of the piezoelectric element 30 to which the drive voltage is applied contracts and the piezoelectric element 30 is bent and deformed into a concave shape, the volume of the corresponding ink pressure chamber 12 increases, and ink flows into the ink pressure chamber 12. . Next, when the drive voltage is removed, the bending deformation of the piezoelectric element 30 is restored, the volume of the ink pressure chamber 12 is reduced, the pressure in the ink pressure chamber 12 is increased, and ink droplets are ejected through the nozzles 22. To do.

Next, a method for manufacturing the head 100 described above will be described with reference to FIGS.
First, as shown in FIG. 3, the flow path substrate 10 is oxidized by thermal oxidation to form a nozzle plate 20 made of a Si oxide film. At the same time, a Si oxide film 20 ′ is formed on the second surface 10 b of the flow path substrate 10. In the present embodiment, the nozzle plate 20 is formed by thermal oxidation of the Si substrate. However, plasma CVD methods other than the thermal oxidation method, CVD methods using TEOS as a raw material, and the like can also be used.

  Thereafter, as shown in FIG. 4, a layer of the lower electrode 32 made of Ti / Pt is formed on the surface 20a of the nozzle plate 20 by sputtering, and a layer of the piezoelectric film 34 made of PZT is formed thereon, Further thereon, a layer of an upper electrode 36 made of Au is formed.

  Next, as shown in FIG. 5, the upper electrode 36 is patterned by selectively etching the layer of the upper electrode 36 by photolithography and wet etching.

  Next, as shown in FIG. 6, the layer of the piezoelectric film 34 is half-etched by photolithography and reactive ion etching, and the inner step 52 is located away from the inner edge 36 a of the upper electrode 36. And an outer stepped portion 54 is formed at a position away from the outer edge 36 b of the upper electrode 36. At the same time, the inner extension portion 52 b is formed inside the piezoelectric film 34, and the outer extension portion 54 b is formed outside the piezoelectric film 34.

  Next, as shown in FIG. 7, the thin portion of the piezoelectric film 34 is etched by photolithography and wet etching to form an inner thin portion 52 a inside the piezoelectric film 34, and the outer thin portion is formed outside the piezoelectric film 34. A portion 54a is formed.

  Next, as shown in FIG. 8, the layer of the lower electrode 32 is etched and patterned by photolithography and reactive ion etching to form the individual drive wiring 33.

  Next, as shown in FIG. 9, a water-repellent insulating film 40 is formed so as to cover the surface of the piezoelectric element 30, the surface 20 a of the nozzle plate 20, and the surface of the individual drive wiring 33. Alternatively, the insulating film 40 may be formed of a hydrophilic material, and a water repellent film may be formed on the surface of the insulating film 40.

  Next, as shown in FIG. 9, patterning is performed by photolithography and reactive ion etching to form a via hole 42 above the upper electrode 36. Then, a layer of the common wiring 37 is formed by sputtering so as to be electrically connected to the upper electrode 36 through the via hole 42, and the common wiring 37 is formed by patterning this layer by photolithography and reactive ion etching.

  Next, as shown in FIG. 10, the nozzle plate 20 is patterned by photolithography and reactive ion etching to form the nozzle 22 at the center of the piezoelectric element 30.

  Next, as shown in FIG. 11, the ink pressure chamber 12 is formed from the second surface 10b side of the flow path substrate 10 away from the nozzle plate 20 by back surface photolithography and deep etching (D-RIE). Thereby, the nozzle 22 and the ink pressure chamber 12 communicate with each other.

  Next, as shown in FIG. 12, the back plate 50 is bonded and fixed to the Si oxide film 20 ′ on the second surface 10 b of the flow path substrate 10 to close the back surface side of the ink pressure chamber 12. As a bonding method of the back plate 50, for example, a silicon direct bonding method in which both substrate surfaces are brought into close contact after being subjected to a cleaning process in a vacuum atmosphere and bonded by pressure may be used, or an organic adhesive may be used. .

  In the series of film formation and etching described above, a large number of chips are simultaneously formed on a single wafer, and are divided into individual chips after the process is completed.

  As described above, according to the method for manufacturing the head 100 of the present embodiment, the head 100 can be manufactured by a simple process, and is particularly excellent in long-term withstand voltage and high drive durability and reliability. In addition, it is possible to provide the piezoelectric MEMS ink jet recording head 100 having high driving efficiency.

  That is, according to the present embodiment, the extended portions 52b and 54b in which the piezoelectric film 34 is slightly protruded from the end edges 36a and 36b of the upper electrode 36 are provided on the inner and outer end edges of the piezoelectric element 30. Problems that cause dielectric breakdown near the edge portions 36a and 36b of the upper electrode 36 can be prevented.

  Further, according to the present embodiment, the stepped portions 52 and 54 are formed at the inner and outer edge portions of the piezoelectric element 30 and the thin portions 52a and 54a are provided, so that the creepage distance at the boundary between the piezoelectric film 34 and the insulating film 40 is increased. And can prevent dielectric breakdown in this portion.

  Further, when the inner stepped portion 52 is provided at the inner edge of the piezoelectric element 30 as in the present embodiment, the volume of the nozzle 22 can be increased, and a large droplet can be discharged with a sufficient discharge pressure. Can do. As a result, the reliability of the operation can be improved, which is advantageous in terms of gradation expression. In this case, the condition is that the insulating film 40 is formed of a hydrophilic material and a water repellent film is provided on the surface of the insulating film 40 that covers the upper surface of the upper electrode 36 of the piezoelectric element 30 in the drawing. That is, in this case, the volume of the nozzle 22 can be increased when the inner stepped portion 52 is provided, compared to the case where the inner stepped portion 52 is not provided.

  When the volume of the nozzle 22 is increased, it is possible to suppress a problem that outside air enters the ink pressure chamber 12 due to vibration of the meniscus after ink droplets are ejected, and it is possible to prevent generation of bubbles in the ink pressure chamber 12. . Further, when the volume of the nozzle 22 is increased, an ink droplet having a large dot diameter can be projected, and the range of gradation expression can be expanded. In this case, the gradation expression is based on the number of dots.

(First modification)
FIG. 13 is a partially enlarged cross-sectional view showing an ink jet recording head 110 (hereinafter simply referred to as the head 110) according to a first modification of the first embodiment. The head 110 has substantially the same structure as the head 100 of the first embodiment described above, except that the shape of the piezoelectric element 30 ′ is different. Accordingly, the same contents as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted here.

  The inner edge of the piezoelectric element 30 ′ is separated from the nozzle 22, and the outer diameter is slightly larger than that of the piezoelectric element 30 of the head 100. In the cross-sectional view of FIG. 13, the piezoelectric element 30 ′ is provided just between the inner wall 12 a of the ink pressure chamber 12 and the nozzle 22.

  As described above, when the inner edge portion of the piezoelectric element 30 ′ is disposed away from the nozzle 22, the inner thin portion 52 a provided in the piezoelectric film 34 can be elongated inward in the radial direction. As a result, the creepage distance along the boundary between the piezoelectric film 34 and the insulating film 40 in this portion can be increased, and dielectric breakdown can be prevented.

(Second modification)
FIG. 14 is a partially enlarged cross-sectional view showing an ink jet recording head 120 (hereinafter simply referred to as the head 120) according to a second modification of the first embodiment. The head 120 has substantially the same structure as the head 110 of the first modified example described above except that the shape of the piezoelectric element 30 ″ is different. Therefore, here, the same reference numerals are used for the same contents as those of the first modified example. The detailed description is omitted.

  The inner edge of the piezoelectric element 30 ″ is further away from the nozzle 22, and the outer edge extends outward from the inner wall 12a of the ink pressure chamber 12. As seen in the cross-sectional view of FIG. The outer edge of the piezoelectric element 30 ″ extends to a position overlapping the wall of the flow path substrate 10 that defines the ink pressure chamber 12. That is, the outer edge of the piezoelectric element 30 ″ is not deformed because it is fixed to a rigid body.

  For this reason, it is not necessary to provide the stepped portion 54 at the outer edge of the piezoelectric element 30 ″, and the outer extending portion 54b can be extended with the same thickness. That is, according to the present modification, the above-described first Compared with the first modification, the step portion 54 can be omitted, and the manufacturing process can be simplified correspondingly, and the manufacturing cost can be reduced.

(Second Embodiment)
FIG. 15 is a partially enlarged cross-sectional view in which a main part of an ink jet recording head 200 (hereinafter simply referred to as the head 200) according to the second embodiment is partially enlarged. The head 200 has substantially the same structure as the head 100 of the first embodiment described above, except that the shapes of the inner edge and the outer edge of the piezoelectric element 210 are different. Therefore, the same reference numerals are given to components that function in the same manner as in the first embodiment, and detailed descriptions thereof are omitted.

  The piezoelectric element 210 of the present embodiment is provided with an inner uneven portion 212 including a plurality of (two in this embodiment) stepped portions on the inner edge of the piezoelectric film 34 adjacent to the nozzle 22, and the piezoelectric element separated from the nozzle 22. It has a structure in which an outer concavo-convex portion 214 including a plurality of (two in this embodiment) stepped portions is provided on the outer edge portion of the film 34.

  As described above, by providing the uneven portions 212 and 214 including a plurality of step portions at the end edge portion of the piezoelectric element 210, insulation at the inner and outer end edge portions without changing the radial size of the piezoelectric element 210 is achieved. The creepage distance along the boundary with the film 40 can be extended, and the dielectric breakdown at this portion can be prevented more reliably.

  The embodiments of the present invention have been described above with reference to specific examples. The above embodiment is merely given as an example and does not limit the present invention. In the description of the embodiment, the description of the ink jet recording head and its manufacturing method, etc., which are not directly necessary for the description of the present invention is omitted, but the ink jet recording head and the manufacturing thereof are required. Elements related to the method and the like can be appropriately selected and used.

  In addition, all inkjet recording heads that include the elements of the present invention and that can be appropriately modified by those skilled in the art are included in the scope of the present invention. The scope of the present invention is defined by the appended claims and equivalents thereof.

  DESCRIPTION OF SYMBOLS 10 ... Channel board | substrate, 12 ... Ink pressure chamber, 20 ... Nozzle plate, 22 ... Nozzle, 30, 30 ', 30 ", 210 ... Piezoelectric element, 32 ... Lower electrode, 34 ... Piezoelectric film, 36 ... Upper electrode, 36a ... inner edge 36b ... outer edge 40 ... insulating film 52 ... inner step 52a ... inner thin part 52b ... inner extension 54 ... outer step 54a ... outer thin part 54b ... outwardly extending portion, 100, 110, 120, 200 ... ink jet recording head, 212 ... inside uneven portion, 214 ... outside uneven portion.

An ink jet recording head according to an embodiment includes a nozzle plate having a plurality of nozzles respectively communicating with a plurality of ink pressure chambers, and a lower electrode provided on the surface of the nozzle plate spaced from the ink pressure chamber so as to surround each nozzle, And a plurality of piezoelectric elements each having a piezoelectric film provided on the lower electrode and an upper electrode provided on the piezoelectric film. The piezoelectric film has a portion that is thinner than the other portions at a position spaced from the edge of the upper electrode.

In addition, all inkjet recording heads that include the elements of the present invention and that can be appropriately modified by those skilled in the art are included in the scope of the present invention. The scope of the present invention is defined by the appended claims and equivalents thereof.
Hereinafter, the invention described in the scope of claims of the original application of the present application will be appended.
[1]
A nozzle plate having a plurality of nozzles respectively communicating with a plurality of ink pressure chambers;
A lower electrode provided on the surface of the nozzle plate spaced from the ink pressure chamber so as to surround each nozzle; a piezoelectric film provided on the lower electrode; and an upper electrode provided on the piezoelectric film. A plurality of piezoelectric elements,
The piezoelectric film has a stepped portion whose thickness is reduced at a position away from an edge of the upper electrode.
Inkjet recording head.
[2]
The length of the extended portion from the edge of the upper electrode to the step is shorter than the length of the thin portion of the step,
[1] Inkjet recording head.
[3]
The thickness of the thin portion of the stepped portion is less than or equal to half the thickness of the piezoelectric film.
[1] Inkjet recording head.
[4]
The creeping distance of the end face of the piezoelectric film from the edge of the upper electrode to the lower electrode through the stepped portion is more than twice the thickness of the piezoelectric film.
[1] Inkjet recording head.
[5]
The step portion is provided at a position spaced inward from an edge portion of the upper electrode near the nozzle,
[1] Inkjet recording head.

Claims (5)

A nozzle plate having a plurality of nozzles respectively communicating with a plurality of ink pressure chambers;
A lower electrode provided on the surface of the nozzle plate spaced from the ink pressure chamber so as to surround each nozzle; a piezoelectric film provided on the lower electrode; and an upper electrode provided on the piezoelectric film. A plurality of piezoelectric elements,
The piezoelectric film has a stepped portion whose thickness is reduced at a position away from an edge of the upper electrode.
Inkjet recording head. The length of the extended portion from the edge of the upper electrode to the step is shorter than the length of the thin portion of the step,
The ink jet recording head according to claim 1. The thickness of the thin portion of the stepped portion is less than or equal to half the thickness of the piezoelectric film.
The ink jet recording head according to claim 1. The creeping distance of the end face of the piezoelectric film from the edge of the upper electrode to the lower electrode through the stepped portion is more than twice the thickness of the piezoelectric film.
The ink jet recording head according to claim 1. The step portion is provided at a position spaced inward from an edge portion of the upper electrode near the nozzle,
The ink jet recording head according to claim 1.