JP2022103958A - Piezoelectric device, liquid jet head and liquid jet device - Google Patents

Abstract

To solve the problem that repeated driving of a piezoelectric actuator may cause a crack on a vibration plate.SOLUTION: An active part 310 of a piezoelectric actuator 300 is configured to have, in a region opposing to a recessed part 12, a first site 311 extending in a first direction which deforms when a voltage is applied to a space between a first electrode 60 and a second electrode 80, and a second site 312, provided at a region corresponding to a center portion of the recessed part 12 in the first direction and at a center portion of the active part 310 in a second direction, which is suppressed from deforming more than the first site 311 is, when a voltage is applied to the space between the first electrode 60 and the second electrode 80.SELECTED DRAWING: Figure 5

Description

The present invention relates to a piezoelectric device having a diaphragm and a piezoelectric actuator having a first electrode, a piezoelectric layer and a second electrode, a liquid injection head and a liquid injection device.

A typical example of a liquid injection head, which is one of the piezoelectric devices, is an inkjet recording head that ejects ink droplets. The inkjet recording head includes, for example, a flow path forming substrate in which a pressure chamber communicating with a nozzle is formed, and a piezoelectric actuator provided on one side of the flow path forming substrate via a vibrating plate. It is known that an ink droplet is ejected from a nozzle by causing a pressure change in the ink in the pressure chamber by a piezoelectric actuator.

The piezoelectric actuator includes a first electrode formed on a vibrating plate, a piezoelectric layer formed of a piezoelectric material having electromechanical conversion characteristics on the first electrode, and a second piezoelectric layer provided on the piezoelectric layer. Those provided with an electrode are known. In the piezoelectric device provided with such a piezoelectric actuator, there is a problem that a crack is generated in the diaphragm due to the bending deformation of the piezoelectric actuator. Various configurations of piezoelectric devices have been proposed for the purpose of suppressing the occurrence of cracks in such a diaphragm (see, for example, Patent Document 1).

In Patent Document 1, an adhesive is poured into a notch formed in a diaphragm overlapping a partition wall that partitions a pressure chamber to cure the diaphragm, and damage such as cracks to the diaphragm, which is a movable region, is suppressed. Is disclosed.

Japanese Unexamined Patent Publication No. 2017-80946

By increasing the strength of the diaphragm as the configuration described in Patent Document 1 and the like, it is possible to suppress the occurrence of cracks in the diaphragm. However, even when the strength of the diaphragm is increased, it is difficult to prevent the occurrence of cracks in the diaphragm.

One of the factors that cause cracks in the diaphragm is, for example, that the diaphragm is excessively deformed by air bubbles flowing into the pressure chamber when the piezoelectric actuator is repeatedly driven. It may be possible to delay the occurrence of cracks in the diaphragm due to such factors by increasing the strength of the diaphragm, but it is difficult to prevent the occurrence of cracks as long as excessive deformation is repeated.

Further, such cracks in the diaphragm differ in the place where they occur depending on the shape of the pressure chamber. For example, the shape of the pressure chamber is larger than the length in the second direction where the length in the first direction intersects with the first direction. In the case of a long shape, it is particularly likely to occur in the central portion of the pressure chamber in the first direction.

It should be noted that such a problem is not limited to the liquid injection head represented by the inkjet recording head that ejects ink, and also exists in other piezoelectric devices.

Aspects of the present invention for solving the above problems include a vibrating plate provided on one side of a substrate on which a plurality of recesses are formed, a first electrode laminated on the side of the vibrating plate opposite to the substrate, and piezoelectric. A piezoelectric device comprising a body layer and a piezoelectric actuator having a second electrode, the recess having a shape in which the length in the first direction is longer than the length in the second direction intersecting the first direction. The piezoelectric actuator includes an active portion in which the piezoelectric layer is sandwiched between the first electrode and the second electrode, and the active portion extends in the first direction in a region facing the recess. The first portion deformed when a voltage is applied between the first electrode and the second electrode, and the region corresponding to the central portion of the recess in the first direction and in the second direction. It is characterized by having a second portion provided in the central portion of the active portion and in which deformation when a voltage is applied between the first electrode and the second electrode is suppressed more than the first portion. It is in the piezoelectric device.

In another aspect of the present invention, a substrate having a plurality of recesses formed therein, a vibrating plate provided on one side of the substrate, and a first electrode laminated on the side of the vibrating plate opposite to the substrate. , A liquid injection head comprising a piezoelectric layer and a piezoelectric actuator having a second electrode, wherein the recess has a length in the second direction where the length in the first direction intersects with the first direction. The piezoelectric actuator also has a long shape, the piezoelectric actuator includes an active portion in which the piezoelectric layer is sandwiched between the first electrode and the second electrode, and the active portion is the first in a region facing the recess. A region corresponding to a first portion extending in a direction and deforming when a voltage is applied between the first electrode and the second electrode, and a central portion of the recess in the first direction, and said. A second portion provided in the central portion of the active portion in the second direction, in which deformation when a voltage is applied between the first electrode and the second electrode is suppressed more than that of the first portion. The liquid injection head is characterized by having.

Yet another aspect of the present invention is in a liquid injection device comprising the above liquid injection head.

It is an exploded perspective view of the recording head which concerns on Embodiment 1. FIG. It is a top view of the recording head which concerns on Embodiment 1. FIG. It is sectional drawing of the recording head which concerns on Embodiment 1. FIG. It is a main part plan view of the recording head which concerns on Embodiment 1. FIG. It is sectional drawing of the main part of the recording head which concerns on Embodiment 1. FIG. It is sectional drawing of the main part of the recording head which concerns on Embodiment 1. FIG. It is a main part plan view of the recording head which concerns on Embodiment 2. FIG. It is a main part plan view of the recording head which concerns on Embodiment 2. FIG. It is a main part plan view which shows the modification of the recording head which concerns on Embodiment 3. FIG. It is sectional drawing of the main part of the recording head which concerns on Embodiment 3. FIG. It is sectional drawing of the main part of the recording head which concerns on Embodiment 4. FIG. It is sectional drawing which shows the manufacturing method of the recording head which concerns on Embodiment 4. FIG. It is sectional drawing which shows the manufacturing method of the recording head which concerns on Embodiment 4. FIG. It is sectional drawing which shows the manufacturing method of the recording head which concerns on Embodiment 4. FIG. It is sectional drawing which shows the manufacturing method of the recording head which concerns on Embodiment 4. FIG. It is sectional drawing which shows the manufacturing method of the recording head which concerns on Embodiment 4. FIG. It is sectional drawing which shows the manufacturing method of the recording head which concerns on Embodiment 4. FIG. It is sectional drawing which shows the manufacturing method of the recording head which concerns on Embodiment 4. FIG. It is sectional drawing which shows the manufacturing method of the recording head which concerns on Embodiment 4. FIG. It is sectional drawing which shows the manufacturing method of the recording head which concerns on Embodiment 4. FIG. It is sectional drawing which shows the manufacturing method of the recording head which concerns on Embodiment 4. FIG. It is sectional drawing which shows the manufacturing method of the recording head which concerns on Embodiment 4. FIG. It is sectional drawing which shows the manufacturing method of the recording head which concerns on Embodiment 4. FIG. It is sectional drawing which shows the other example of the manufacturing method of the recording head which concerns on Embodiment 4. FIG. It is a figure which shows the schematic structure of the recording apparatus which concerns on one Embodiment.

Hereinafter, the present invention will be described in detail based on the embodiments. However, the following description is a description of one aspect of the present invention, and the configuration of the present invention can be arbitrarily changed within the scope of the invention. In each figure, the same members are designated by the same reference numerals, and duplicate description will be omitted.

Further, in each figure, X, Y, and Z represent three spatial axes orthogonal to each other. In the present specification, the directions along these axes are the X direction, the Y direction, and the Z direction. The X-direction and the Y-direction will be described with the direction in which the arrow in each figure points as the positive (+) direction and the opposite direction of the arrow as the negative (-) direction. Further, the Z direction indicates a vertical direction, the + Z direction indicates a vertical downward direction, and the −Z direction indicates a vertical upward direction. Further, the three X, Y, and Z spatial axes that do not limit the positive direction and the negative direction will be described as the X axis, the Y axis, and the Z axis.

(Embodiment 1)
FIG. 1 is an exploded perspective view of an inkjet recording head, which is an example of the liquid injection head according to the first embodiment of the present invention. FIG. 2 is a plan view of the inkjet recording head. FIG. 3 is a cross-sectional view taken along the line AA of FIG. FIG. 4 is an enlarged plan view of the piezoelectric actuator portion. 5 is a sectional view taken along line BB'of FIG. 4, and FIG. 6 is a sectional view taken along line CC'of FIG.

The inkjet recording head (hereinafter, also simply referred to as a recording head) 1, which is an example of the liquid injection head of the present embodiment shown in FIGS. 1 and 2, ejects ink droplets in the Z-axis direction, more specifically, in the + Z direction. It is a thing.

The inkjet recording head 1 includes a flow path forming substrate 10 as an example of the substrate. The flow path forming substrate 10 is made of, for example, a silicon substrate such as single crystal silicon, a glass substrate, an SOI substrate, various ceramic substrates, and the like. The flow path forming substrate 10 may be a (100) plane-preferred-oriented substrate or a (110) plane-preferred-oriented substrate.

A plurality of pressure chambers 12 which are recesses are formed in the flow path forming substrate 10. The plurality of pressure chambers 12 are arranged in two rows in the X-axis direction, which is the first direction intersecting the Z-axis. Each pressure chamber 12 constituting each row is arranged along the Y-axis direction, which is a second direction intersecting the X-axis direction. The plurality of pressure chambers 12 constituting each row are arranged on a straight line along the Y-axis direction so that the positions in the X-axis direction are the same. The pressure chambers 12 adjacent to each other in the Y-axis direction are partitioned by a partition wall 11.

Of course, the arrangement of the pressure chamber 12 in the flow path forming substrate 10 is not particularly limited. For example, the arrangement of a plurality of pressure chambers 12 arranged in the Y-axis direction is a so-called staggered arrangement in which each pressure chamber 12 is displaced in the X-axis direction, or a zigzag arrangement in which each pressure chamber 12 is displaced in the X-axis direction. It may have a zigzag arrangement other than the above.

Here, each pressure chamber 12 is formed in a shape in which the length a1 in the X-axis direction is longer than the length b1 in the Y-axis direction in a plan view in the Z-axis direction (see FIG. 4). In the present embodiment, the pressure chamber 12 is formed so as to be rectangular in a plan view in the Z-axis direction. That is, the pressure chamber 12 is formed so that the aspect ratio is larger than 1. In the present embodiment, the pressure chamber 12 is formed so that the aspect ratio is about 9: 1. In this configuration, the longitudinal direction of the pressure chamber 12 corresponds to the X-axis direction which is the first direction, and the lateral direction of the pressure chamber 12 corresponds to the Y-axis direction which is the second direction.

The shape of the pressure chamber 12 may satisfy the relationship of length a1 in the X-axis direction> length b1 in the Y-axis direction, and includes, for example, a parallel quadrilateral shape, an elliptical shape, and the like in addition to the rectangle. It may have an oval shape or the like.

The communication plate 15, the nozzle plate 20, and the compliance substrate 45 are sequentially laminated on the + Z direction side of the flow path forming substrate 10 in which the plurality of pressure chambers 12 are formed.

The communication plate 15 is provided with a nozzle communication passage 16 that communicates the pressure chamber 12 and the nozzle 21 for injecting ink droplets. Further, the communication plate 15 is provided with a first manifold portion 17 and a second manifold portion 18 that form a part of a manifold 100 that is a common liquid chamber through which a plurality of pressure chambers 12 communicate. The first manifold portion 17 is provided so as to penetrate the communication plate 15 in the Z-axis direction. The second manifold portion 18 is provided so as to open in the surface on the + Z direction side without penetrating the communication plate 15 in the Z-axis direction.

Further, the communication plate 15 is formed with a plurality of supply communication passages 19 communicating with one end of each pressure chamber 12 in the X-axis direction. Each supply passage 19 is provided independently corresponding to each of the pressure chambers 12. These supply communication passages 19 communicate the second manifold portion 18 and each pressure chamber 12, and supply the ink in the manifold 100 to each pressure chamber 12.

As the communication plate 15, a silicon substrate, a glass substrate, an SOI substrate, various ceramic substrates, a metal substrate, or the like can be used. Examples of the metal substrate include a stainless steel substrate and the like. The communication plate 15 preferably uses a material having a thermal expansion coefficient substantially the same as that of the flow path forming substrate 10. As a result, when the temperatures of the flow path forming substrate 10 and the communication plate 15 change, the warpage of the flow path forming substrate 10 and the communication plate 15 due to the difference in the coefficient of thermal expansion can be suppressed.

The nozzle plate 20 is provided on the side of the communication plate 15 opposite to the flow path forming substrate 10, that is, on the surface on the + Z direction side. The nozzle plate 20 is formed with a plurality of nozzles 21 communicating with each pressure chamber 12 via the nozzle communication passage 16.

In the present embodiment, the plurality of nozzles 21 are arranged side by side so as to form a line along the Y-axis direction. On the nozzle plate 20, nozzle rows in which a plurality of nozzles 21 are arranged are arranged in two rows in the X-axis direction. That is, the plurality of nozzles 21 in each row are arranged so that the positions in the X-axis direction are the same. The arrangement of these nozzles 21 is not particularly limited. For example, when the arrangement of the pressure chambers 12 is a so-called staggered arrangement, the arrangement of the plurality of nozzles 21 constituting each row may be the so-called staggered arrangement according to the arrangement of the pressure chambers 12.

As the material of the nozzle plate 20, for example, a silicon substrate, a glass substrate, an SOI substrate, various ceramic substrates, a metal substrate, or the like can be used. Examples of the metal plate include a stainless steel substrate and the like. Further, as the material of the nozzle plate 20, an organic substance such as a polyimide resin can also be used. However, it is preferable to use a material for the nozzle plate 20 that is substantially the same as the coefficient of thermal expansion of the communication plate 15. As a result, when the temperatures of the nozzle plate 20 and the communication plate 15 change, it is possible to suppress the warp of the nozzle plate 20 and the communication plate 15 due to the difference in the coefficient of thermal expansion.

The compliance substrate 45 is provided together with the nozzle plate 20 on the side of the communication plate 15 opposite to the flow path forming substrate 10, that is, on the surface on the + Z direction side. The compliance board 45 is provided around the nozzle plate 20 and seals the openings of the first manifold portion 17 and the second manifold portion 18 provided in the communication plate 15. In the present embodiment, the compliance substrate 45 includes a sealing film 46 made of a flexible thin film and a fixed substrate 47 made of a hard material such as metal. The region of the fixed substrate 47 facing the manifold 100 is an opening 48 completely removed in the thickness direction. Therefore, one surface of the manifold 100 is a compliance portion 49 sealed only by the flexible sealing film 46.

On the other hand, the surface of the flow path forming substrate 10 opposite to the nozzle plate 20 and the like, that is, the surface on the −Z direction side, will be described in detail later, but the diaphragm 50 and the diaphragm 50 are flexed and deformed to form the pressure chamber 12. A piezoelectric actuator 300 that causes a pressure change in the ink inside is provided. Note that FIG. 3 is a diagram for explaining the overall configuration of the recording head 1, and the configuration of the piezoelectric actuator 300 is shown in a simplified manner.

A protective substrate 30 having substantially the same size as the flow path forming substrate 10 is further bonded to the surface of the flow path forming substrate 10 on the −Z direction side with an adhesive or the like. The protective substrate 30 has a holding portion 31 which is a space for protecting the piezoelectric actuator 300. The holding portions 31 are independently provided for each row of the piezoelectric actuators 300 arranged side by side in the Y-axis direction, and are formed by arranging two holding portions 31 side by side in the X-axis direction. Further, the protective substrate 30 is provided with a through hole 32 penetrating in the Z-axis direction between two holding portions 31 arranged side by side in the X-axis direction.

Further, on the protective substrate 30, a case member 40 for defining a manifold 100 communicating with a plurality of pressure chambers 12 together with a flow path forming substrate 10 is fixed. The case member 40 has substantially the same shape as the communication plate 15 in a plan view, and is joined to the protective substrate 30 and also to the communication plate 15.

Such a case member 40 has an accommodating portion 41, which is a space having a depth capable of accommodating the flow path forming substrate 10 and the protective substrate 30, on the protective substrate 30 side. The accommodating portion 41 has a wider opening area than the surface of the protective substrate 30 joined to the flow path forming substrate 10. Then, the opening surface of the accommodating portion 41 on the nozzle plate 20 side is sealed by the communication plate 15 in a state where the flow path forming substrate 10 and the protective substrate 30 are accommodated in the accommodating portion 41.

Further, on the case member 40, a third manifold portion 42 is defined on both outer sides of the accommodating portion 41 in the X-axis direction. The manifold 100 is composed of the first manifold portion 17 and the second manifold portion 18 provided in the communication plate 15, and the third manifold portion 42. The manifold 100 is continuously provided in the Y-axis direction, and the supply communication passages 19 that communicate each pressure chamber 12 and the manifold 100 are arranged side by side in the Y-axis direction.

Further, the case member 40 is provided with an introduction port 44 for communicating with the manifold 100 and supplying ink to each manifold 100. Further, the case member 40 is provided with a connection port 43 through which the wiring board 120 is inserted so as to communicate with the through hole 32 of the protective board 30.

In such a recording head 1 of the present embodiment, ink is taken in from an introduction port 44 connected to an external ink supply means (not shown), the inside from the manifold 100 to the nozzle 21 is filled with ink, and then the drive circuit 121 is used. According to the recorded signal, a voltage is applied to each piezoelectric actuator 300 corresponding to the pressure chamber 12. As a result, the diaphragm 50 bends and deforms together with the piezoelectric actuator 300, the pressure in each pressure chamber 12 increases, and ink droplets are ejected from each nozzle 21.

Hereinafter, the configuration of the piezoelectric actuator 300 according to the present embodiment will be described. As described above, the piezoelectric actuator 300 is provided on the surface of the flow path forming substrate 10 opposite to the nozzle plate 20 via the diaphragm 50.

As shown in FIGS. 4 to 6, the diaphragm 50 is an insulator film made of an elastic film 51 made of silicon oxide provided on the flow path forming substrate 10 side and a zirconium oxide film provided on the elastic film 51. It is composed of 52 and. The liquid flow path of the pressure chamber 12 or the like is formed by anisotropic etching the flow path forming substrate 10 from the surface on the + Z direction side, and the surface of the liquid flow path such as the pressure chamber 12 on the −Z direction side is formed. , It is composed of an elastic film 51.

The configuration of the diaphragm 50 is not particularly limited. The diaphragm 50 may be composed of, for example, either an elastic film 51 or an insulator film 52, and may further include a film other than the elastic film 51 and the insulator film 52. Examples of the material of this film include silicon and silicon nitride.

The piezoelectric actuator 300 is a pressure generating means provided corresponding to each pressure chamber 12 formed on the flow path forming substrate 10 to cause a pressure change in the ink in the pressure chamber 12, and is also called a piezoelectric element. The piezoelectric actuator 300 includes a first electrode 60 sequentially laminated from the + Z direction side on the diaphragm 50 side toward the −Z direction side, a piezoelectric layer 70, and a second electrode 80. That is, the piezoelectric actuator 300 includes a first electrode 60 sequentially laminated toward the −Z direction side in the present embodiment along the Z-axis direction, which is the first direction with respect to the diaphragm 50, and the piezoelectric layer 70. And the second electrode 80.

In the piezoelectric actuator 300 having such a configuration, a portion where piezoelectric distortion occurs in the piezoelectric layer 70 when a voltage is applied between the first electrode 60 and the second electrode 80 is referred to as an active portion. On the other hand, a portion where piezoelectric strain does not occur in the piezoelectric layer 70 is referred to as an inactive portion. That is, in the piezoelectric actuator 300, the portion where the piezoelectric layer 70 is sandwiched between the first electrode 60 and the second electrode 80 becomes the active portion 310, and the piezoelectric layer 70 is formed by the first electrode 60 and the second electrode 80. The portion that is not sandwiched becomes the inactive portion 320. Further, a portion that actually deforms in the Z-axis direction when the piezoelectric actuator 300 is driven is referred to as a flexible portion, and a portion that does not deform in the Z-axis direction is referred to as a non-flexible portion. That is, of the active portion 310 of the piezoelectric actuator 300, the portion facing the pressure chamber 12 in the Z-axis direction becomes a flexible portion, and the outer portion of the pressure chamber 12 becomes a non-flexible portion.

Generally, one of the electrodes of the active portion 310 is configured as an independent individual electrode for each active portion 310, and the other electrode is configured as a common electrode common to the plurality of active portions 310. In the present embodiment, the first electrode 60 constitutes an individual electrode, and the second electrode 80 constitutes a common electrode.

Specifically, the first electrode 60 constituting the piezoelectric actuator 300 constitutes an individual electrode that is separated into each pressure chamber 12 and is independent for each active portion 310. The first electrode 60 is formed with a width narrower than the width of the pressure chamber 12, that is, the length b1 of the pressure chamber 12 in the Y-axis direction. Both ends of the first electrode 60 in the Y-axis direction are located inside the ends of the pressure chamber 12 in the Y-axis direction, respectively. That is, the active portion 310 of the piezoelectric actuator 300 is provided facing each pressure chamber 12 with a width narrower than that of the pressure chamber 12.

In the X-axis direction, the first electrode 60 extends to both outer sides of the pressure chamber 12. That is, both ends of the first electrode 60 in the X-axis direction are located outside the ends of the pressure chamber 12 in the X-axis direction, respectively. Both ends of the first electrode 60 in the X-axis direction may be located inside the ends of the pressure chamber 12, but preferably extend to the vicinity of both ends of the pressure chamber 12.

The material of the first electrode 60 is not particularly limited, but for example, a conductive material such as a metal such as iridium or platinum or a conductive metal oxide such as indium tin oxide abbreviated as ITO is used.

The piezoelectric layer 70 is continuously provided along the Y-axis direction, which is the lateral direction of the pressure chamber 12, with the length in the X-axis direction, which is the longitudinal direction of the pressure chamber 12, as a predetermined length. That is, the piezoelectric layer 70 is continuously provided with a predetermined thickness along the parallel arrangement direction of the pressure chambers 12. The thickness of the piezoelectric layer 70 is not particularly limited, but is formed, for example, with a thickness of about 1 to 4 μm. The length of the piezoelectric layer 70 in the X-axis direction is not particularly limited, but as shown in FIG. 4, it is longer than the length of the pressure chamber 12 in the X-axis direction, and the piezoelectric layer 70 has a pressure in the X-axis direction. It extends to the outside of both ends of the chamber 12.

By extending the piezoelectric layer 70 to the outside of the pressure chamber 12 in the X-axis direction in this way, the strength of the diaphragm 50 near the end portion of the pressure chamber 12 in the X-axis direction is improved. Therefore, when the piezoelectric actuator 300 is driven, it is possible to suppress the occurrence of cracks in the diaphragm 50 in the vicinity of the longitudinal end portion of the pressure chamber 12.

In the present embodiment, as described above, the + X-direction end of the piezoelectric layer 70 is located outside the + X-direction end of the first electrode 60, and the + X-direction end of the first electrode 60 is piezoelectric. It is covered by the body layer 70. On the other hand, the −X direction end of the piezoelectric layer 70 is located inside the end of the first electrode 60, and the −X direction end of the first electrode 60 is covered by the piezoelectric layer 70. It is exposed without being damaged.

Further, in each of the regions facing both ends of the pressure chamber 12 in the Y-axis direction, a groove 71 in which at least a part of the piezoelectric layer 70 is removed is provided in the Z-axis direction. In other words, the thickness of the piezoelectric layer 70 in the region facing both ends of the pressure chamber 12 in the Y-axis direction is thinner than the other portions. The groove portion 71 of the present embodiment is formed by removing substantially all of the piezoelectric layer 70 in the Z-axis direction. Of course, a part of the piezoelectric layer 70 in the Z-axis direction may be removed from the groove 71, and the piezoelectric layer 70 may remain thinner than the other parts on the bottom surface of the groove 71.

Further, the length of the groove portion 71 provided on each partition wall 11 in the Y-axis direction, that is, the width of the groove portion 71 is formed to be wider than the width of the partition wall 11. That is, each groove 71 is continuously formed from above the partition wall 11 over a region facing the two adjacent pressure chambers 12. The groove 71 may be independently provided in a region facing the end of the pressure chamber 12 in the Y-axis direction. That is, two groove 71s may be provided in the region facing each partition wall 11.

Further, the groove portion 71 is formed so as to have a rectangular shape in a plan view in the Z-axis direction. The shape of the groove 71 is not particularly limited, and may be, for example, a polygonal shape of pentagon or more, a circular shape, an elliptical shape, or the like.

Since such a groove 71 is formed in the piezoelectric layer 70, the rigidity of the portion of the diaphragm 50 facing the end in the Y-axis direction, that is, the arm portion of the diaphragm 50 is suppressed. Therefore, when a voltage is applied to the piezoelectric actuator 300, the piezoelectric actuator 300 and the diaphragm 50 can be satisfactorily deformed.

Examples of the piezoelectric layer 70 include a perovskite-structured crystal film (perovskite-type crystal) formed on the first electrode 60 and made of a strong dielectric ceramic material exhibiting an electromechanical conversion action. As the material of the piezoelectric layer 70, for example, a ferroelectric piezoelectric material such as lead zirconate titanate (PZT) or a material to which a metal oxide such as niobide oxide, nickel oxide or magnesium oxide is added is used. be able to. Specifically, lead titanate (PbTiO ₃ ), lead zirconate titanate (Pb (Zr, Ti) O ₃ ), lead zirconium acid (PbZrO ₃ ), lead titanate lantern ((Pb, La), TiO ₃ ). ), Lead zirconate titanate lanthanum ((Pb, La) (Zr, Ti) O ₃ ), lead magnesium niobate zirconium lead titanate (Pb (Zr, Ti) (Mg, Nb) O ₃ ), etc. Can be done. In this embodiment, lead zirconate titanate (PZT) was used as the piezoelectric layer 70.

Further, the material of the piezoelectric layer 70 is not limited to the lead-based piezoelectric material containing lead, and a lead-free piezoelectric material containing no lead can also be used. Examples of the lead-free piezoelectric material include bismuth iron acid ((BiFeO ₃ ), abbreviated as “BFO”), barium titanate ((BaTIO ₃ ), abbreviated as “BT”), and sodium potassium niobate ((K, Na)). ) (NbO ₃ ), abbreviated as "KNN"), lithium sodium potassium niobate ((K, Na, Li) (NbO ₃ )), lithium sodium potassium titanate niobate ((K, Na, Li) (Nb, Ta). ) O ₃ ), bismuth potassium titanate ((Bi _1/2 K _1/2 ) TiO ₃ , abbreviated as "BKT"), bismuth sodium titanate ((Bi _1/2 Na _1/2 ) TiO ₃ , abbreviated as "BNT" ”), Bismuth manganate (BimnO ₃ , abbreviated as“ BM ”), bismuth, potassium, titanium and a composite oxide having a perovskite structure containing iron (x [(Bi _x K _1-x ) TiO ₃ ]-(1-) x) [BiFeO ₃ ], abbreviated as "BKT-BF"), a composite oxide containing bismuth, iron, barium and titanium and having a perovskite structure ((1-x) [BiFeO ₃ ]-x [BaTIO ₃ ], abbreviated as " BFO-BT ”) or a substance to which metals such as manganese, cobalt, and chromium are added ((1-x) [Bi (Fe _{1- y My} ) O ₃ ]-x [BaTIO ₃ ] (M is Mn, Co or Cr)) and the like can be mentioned.

As shown in FIGS. 5 and 6, the second electrode 80 is provided on the −Z direction side opposite to the first electrode 60 of the piezoelectric layer 70, and is a common electrode common to the plurality of piezoelectric actuators 300. Configure. The second electrode 80 is continuously provided in the Y-axis direction with a length in the X-axis direction as a predetermined length. The second electrode 80 is also provided on the inner surface of the groove portion 71, that is, on the side surface of the groove portion 71 of the piezoelectric layer 70 and on the insulator film 52 which is the bottom surface of the groove portion 71. Regarding the inside of the groove 71, the second electrode 80 may be provided only on a part of the inner surface of the groove 71.

The end portion of the second electrode 80 in the + X direction is arranged so as to be outside the end portion of the first electrode 60 covered with the piezoelectric layer 70 in the + X direction. That is, the end portion of the second electrode 80 in the + X direction is located outside the end portion of the pressure chamber 12 in the + X direction and outside the end portion of the first electrode 60. In the present embodiment, the end portion of the second electrode 80 in the + X direction substantially coincides with the end portion of the piezoelectric layer 70. Therefore, the + X direction end portion of the active portion 310, that is, the boundary between the active portion 310 and the inactive portion 320 is defined by the + X direction end portion of the first electrode 60.

On the other hand, the −X direction end portion of the second electrode 80 is arranged outside the −X direction end portion of the pressure chamber 12, but is inside the X-axis direction end portion of the piezoelectric layer 70. Have been placed. As described above, the end portion of the piezoelectric layer 70 in the −X direction is located inside the end portion of the first electrode 60. Therefore, the end portion of the second electrode 80 in the −X direction is located on the piezoelectric layer 70 inside the end portion of the first electrode 60 in the −X direction. Therefore, on the outside of the end portion of the second electrode 80 in the −X direction, there is a portion where the surface of the piezoelectric layer 70 is exposed.

As described above, since the end portion of the second electrode 80 in the −X direction is arranged on the + X direction side with respect to the end portion of the piezoelectric layer 70 and the first electrode 60 in the −X direction, the −X of the active portion 310 The end in the direction, that is, the boundary between the active portion 310 and the inactive portion 320 is defined by the end in the −X direction of the second electrode 80.

The material of the second electrode 80 is not particularly limited, but similarly to the first electrode 60, for example, a conductive material such as a metal such as iridium or platinum or a conductive metal oxide such as indium tin oxide is preferably used.

Further, on the outside of the −X direction end of the second electrode 80, that is, further on the −X direction side of the end portion of the second electrode 80, the same layer as the second electrode 80 is formed, but the second electrode 80 is electric. A wiring portion 85 that is discontinuous is provided. Further, the wiring portion 85 extends from the top of the piezoelectric layer 70 in the −X direction to the piezoelectric layer 70 in a state of being spaced so as not to come into contact with the end portion of the second electrode 80 in the −X direction. It is formed over one electrode 60. The wiring portion 85 is provided independently for each active portion 310. That is, a plurality of wiring portions 85 are arranged at predetermined intervals along the Y-axis direction. The wiring portion 85 may be formed of a layer different from that of the second electrode 80, but is preferably formed of the same layer as the second electrode 80. As a result, the manufacturing process of the wiring portion 85 can be simplified and the cost can be reduced.

The individual lead electrode 91 and the common lead electrode 92, which is a common driving electrode, are connected to the first electrode 60 and the second electrode 80 constituting the piezoelectric actuator 300 (see FIG. 2 and the like). A flexible wiring board 120 is connected to the end of the individual lead electrode 91 and the common lead electrode 92 on the opposite side to the end connected to the piezoelectric actuator 300 (see FIG. 3 and the like). In the present embodiment, the individual lead electrode 91 and the common lead electrode 92 are extended so as to be exposed in the through hole 32 formed in the protective substrate 30, and are electrically connected to the wiring board 120 in the through hole 32. Has been done. A drive circuit 121 having a switching element for driving the piezoelectric actuator 300 is mounted on the wiring board 120.

In the present embodiment, the individual lead electrode 91 and the common lead electrode 92 are made of the same layer, but are formed so as to be electrically discontinuous. As a result, the manufacturing process can be simplified and the cost can be reduced as compared with the case where the individual lead electrode 91 and the common lead electrode 92 are individually formed. Of course, the individual lead electrode 91 and the common lead electrode 92 may be formed of different layers.

The material of the individual lead electrode 91 and the common lead electrode 92 is not particularly limited as long as it is a conductive material, and for example, gold (Au), platinum (Pt), aluminum (Al), copper (Cu) and the like are used. be able to. In this embodiment, gold (Au) is used as the individual lead electrode 91 and the common lead electrode 92. Further, the individual lead electrode 91 and the common lead electrode 92 may have an adhesion layer for improving the adhesion with the first electrode 60, the second electrode 80, and the diaphragm 50.

The individual lead electrode 91 is provided for each active portion 310, that is, for each first electrode 60. The individual lead electrode 91 is connected to the vicinity of the end portion of the first electrode 60 provided on the outside of the piezoelectric layer 70 in the −X direction via a wiring portion 85, and is actually a diaphragm on the flow path forming substrate 10. It is pulled out in the -X direction up to 50. On the other hand, the common lead electrode 92 is drawn out in the −X direction from the second electrode 80 constituting the common electrode on the piezoelectric layer 70 to the diaphragm 50 at both ends in the Y-axis direction.

By the way, as described above, the piezoelectric actuator 300 has an active portion 310 and an inactive portion 320, and the portion of the active portion 310 facing the pressure chamber 12 becomes a flexible portion, and the portion outside the pressure chamber 12 is a flexible portion. It becomes a non-flexible part.

Further, in the portion of the active portion 310 facing the pressure chamber 12, that is, the flexible portion, a voltage is applied between the first portion 311 extending in the X-axis direction and the first electrode 60 and the second electrode 80. It has a second site 312, in which the deformation is suppressed more than the first site 311.

The portion of the active portion 310 facing the pressure chamber 12 is mainly composed of the first portion 311 but a second portion 312 is provided in a part thereof. The second portion 312 is provided in a region corresponding to the central portion of the pressure chamber 12 in the X-axis direction and in the central portion of the active portion 310 in the Y-axis direction. That is, the second portion 312 is provided in the region corresponding to the central portion of the pressure chamber 12 in the X-axis direction, and the first portion 311 exists on both sides of the second portion 312 in the Y-axis direction. In other words, the second part 312 is provided in an island shape in the central part of the first part 311 extending in the region facing the pressure chamber 12 in the plan view in the Z-axis direction, and the second part 312 is provided. Is surrounded by the first part 311.

Here, in the second portion 312, the resistance value of at least one of the first electrode 60 and the second electrode 80 is higher than that of the first portion 311. In the present embodiment, the resistance value of the second electrode 80 is higher than that of the first portion 311. As a result, the deformation of the piezoelectric actuator 300 when a voltage is applied between the first electrode 60 and the second electrode 80 is suppressed as compared with the first portion 311.

Specifically, the second electrode 80 of the second portion 312 is a thin film portion 81 having a thickness thinner than that of the second electrode 80 of the first portion 311. That is, the second electrode 80 of the second portion 312 becomes a thin film portion 81 as a result of forming a recessed portion in which a part of the second electrode 80 in the thickness direction is removed from the side opposite to the piezoelectric layer 70. ing.

With such a configuration, the resistance value of the second electrode 80 of the second portion 312 becomes higher than the resistance value of the second electrode 80 of the first portion 311. Therefore, when a voltage is applied between the first electrode 60 and the second electrode 80, the electric field applied to the piezoelectric layer 70 of the second portion 312 becomes weaker than that of the first portion 311. That is, the piezoelectric strain of the piezoelectric layer 70 of the second portion 312 is smaller than that of the first portion 311. Therefore, the deformation of the piezoelectric actuator 300 at the second portion 312 is suppressed to be smaller than that at the first portion 311. As a result, when the piezoelectric actuator 300 is driven, the displacement of the diaphragm 50 in the central portion of the pressure chamber 12 in the X-axis direction is partially suppressed.

As a result, it is possible to suppress the occurrence of cracks in the diaphragm 50 due to repeated driving of the piezoelectric actuator 300. In particular, it is possible to effectively suppress the occurrence of cracks in the diaphragm 50 in the central portion of the pressure chamber 12 in the X-axis direction.

When the pressure chamber 12 is formed in a rectangular shape long in the X-axis direction in a plan view in the Z-axis direction, the displacement of the vibrating plate 50 due to the drive of the piezoelectric actuator 300 is large in the central portion of the pressure chamber 12 in the X-axis direction. The crack of the vibrating plate 50 is likely to occur. Such cracks in the diaphragm 50 can be suppressed by limiting the deformation of the entire piezoelectric actuator 300 to a small extent, but there is a risk that the ejection characteristics such as the ejection amount and the ejection speed of ink droplets will deteriorate.

However, by partially reducing the deformation of the piezoelectric actuator 300 in the central portion of the pressure chamber 12 in the X-axis direction, it is possible to effectively suppress cracks in the diaphragm 50 while maintaining good discharge characteristics. ..

The thickness of the thin film portion 81, which is the second portion 312, may be appropriately determined so that the diaphragm 50 is appropriately displaced as the piezoelectric actuator 300 is driven, but the thickness of the second electrode 80 in the first portion 311 It is preferably 1/10 or less, particularly preferably 1/100 or less. That is, it is preferable that the thickness of the second electrode 80 of the second portion 312 is as thin as possible.

Since the second electrode 80 of the second portion 312 is the thin film portion 81 in this way, the resistance value of the second electrode 80 of the second portion 312 is higher than the resistance value of the second electrode 80 of the first portion 311. Will definitely be higher. Therefore, the piezoelectric strain of the second portion 312 when a voltage is applied between the first electrode 60 and the second electrode 80 is surely suppressed to be smaller than that of the first portion 311.

Further, since the second electrode 80 of the second portion 312 is the thin film portion 81, that is, the second electrode 80 remains in the second portion 312, the first electrode 60 and the second electrode 80 are combined. When a voltage is applied between them, electric field concentration does not occur near the boundary between the first portion 311 and the second portion 312, and damage to the piezoelectric layer 70 can be prevented.

The second electrode 80 of the second portion 312 may be completely removed from the viewpoint of making the resistance value of the second electrode 80 of the second portion 312 higher than that of the first portion 311. Therefore, the thin film portion 81 according to the present embodiment includes a thin film portion 81 having a thickness of the second electrode 80 that is substantially zero.

The method for forming the thin film portion 81 on the second electrode 80 is not particularly limited, but there are the following methods. After forming the second electrode 80 on the entire surface of the piezoelectric layer 70, for example, a portion corresponding to the second portion 312 of the second electrode 80 is removed by a photolithography method. Alternatively, after forming the second electrode 80 on the entire surface of the piezoelectric layer 70, for example, by irradiating the second electrode 80 with a laser beam, the portion corresponding to the second portion 312 of the second electrode 80 is selectively removed. Further, when the second electrode 80 of the second portion 312 is completely removed, the following method can also be adopted. Before forming the second electrode 80, a resist film for lift-off is provided on the portion corresponding to the second portion 312 on the piezoelectric layer 70, and after forming the second electrode 80 on the entire surface of the piezoelectric layer 70, the second electrode 80 is formed. The second electrode 80 of the portion corresponding to the two-site 312 is removed together with the resist film.

Further, the second portion 312 may be provided in a region facing the central portion of the pressure chamber 12 in the X-axis direction, but more specifically, as shown in FIG. 5, the pressure chamber 12 is 3 in the X-axis direction. It is preferable that the region is provided in the central region S2 when the region is equally divided into the regions S1, S2 and S3. Further, it is preferable that the second portion 312 is provided so as to straddle the center line L1 of the pressure chamber 12 in the X-axis direction.

Further, it is preferable that the second portion 312 is provided so as to straddle the active portion 310 in the region facing the pressure chamber 12, that is, the center line L2 in the X-axis direction of the flexible portion. In the present embodiment, the active portion 310 extends to the outside of both ends of the pressure chamber 12 in the X-axis direction, and the center line L2 of the flexible portion in the X-axis direction is the center line L1 of the pressure chamber 12. Match. Therefore, the second portion 312 according to the present embodiment is provided in the region S2 so as to straddle the center line L1 of the pressure chamber 12 and the center line L2 of the flexible portion.

By providing the second portion 312 at such a position, it is possible to more reliably suppress the occurrence of cracks in the diaphragm 50 due to the repeated drive of the piezoelectric actuator 300.

Further, the size of the second portion 312 in the plan view in the Z-axis direction, that is, the size of the thin film portion 81 formed on the second electrode 80 may be appropriately determined in consideration of the displacement of the vibrating plate 50. It is preferable that the length a2 of the two sites 312 in the X-axis direction is longer than the length b2 of the second site 312 in the Y-axis direction. In the present embodiment, the second portion 312 is formed into a rectangle that satisfies the relationship of length a2 in the X-axis direction> length b2 in the Y-axis direction in a plan view in the Z-axis direction.

Further, the length a2 of the second portion 312 in the X-axis direction may be appropriately determined, but the active portion 310 provided facing the pressure chamber 12, that is, the length a3 of the flexible portion in the X-axis direction 5 It is preferably about 20%, for example, about 10%. In the present embodiment, the length a3 of the flexible portion of the active portion 310 in the X-axis direction coincides with the length a1 of the pressure chamber 12 in the X-axis direction. On the other hand, the length b2 of the second portion 312 in the Y-axis direction may be appropriately determined, but is about 5 to 20% of the length b3 of the active portion 310 provided facing the pressure chamber 12 in the Y-axis direction. For example, it is preferably about 10%. The end portion of the active portion 310 in the Y-axis direction is defined by the end portion of the first electrode 60 in the Y-axis direction.

By forming the second portion 312 with such a size, it is possible to more effectively suppress cracks in the diaphragm 50 that occur at that time while maintaining good ejection characteristics due to the drive of the piezoelectric actuator 300. ..

As described above, the inkjet recording head 1 which is the liquid injection head according to the present embodiment has a flow path forming substrate 10 in which a pressure chamber 12 which is a plurality of recesses is formed and one surface of the flow path forming substrate 10. A piezoelectric actuator 300 having a vibrating plate 50 provided on the side, a first electrode 60 laminated on the side opposite to the flow path forming substrate 10 of the vibrating plate 50, a piezoelectric layer 70, and a second electrode 80. The pressure chamber 12 has a shape in which the length in the X-axis direction is longer than the length in the Y-axis direction intersecting the X-axis direction, and the piezoelectric actuator 300 has a piezoelectric layer 70 as a first electrode 60. An active portion 310 sandwiched between the first electrode 60 and the second electrode 80 is provided, and the active portion 310 extends in the X-axis direction in a region facing the pressure chamber 12 and has a voltage between the first electrode 60 and the second electrode 80. The first electrode 60 and the first electrode 60, which are provided in the region corresponding to the central portion of the pressure chamber 12 in the X-axis direction and the central portion of the active portion 310 in the Y-axis direction, and the first portion 311 that deforms when is applied. It has a second portion 312 in which deformation when a voltage is applied between the two electrodes 80 is suppressed more than that of the first portion 311. As a result, it is possible to suppress the occurrence of cracks in the diaphragm 50 while maintaining good ejection characteristics due to the drive of the piezoelectric actuator 300.

In this embodiment, the resistance value of the second electrode 80 is set to be higher than that of the first portion 311. However, instead of the second electrode 80, the resistance value of the first electrode 60 is higher than that of the first portion 311. It may be. For example, the thickness of the first electrode 60 of the second portion 312 may be made thinner than that of the first portion 311. Further, the resistance values of the first electrode 60 and the second electrode 80 may be higher than those of the first portion 311. Even with such a configuration, it is possible to suppress the occurrence of cracks in the diaphragm 50 while maintaining good ejection characteristics due to the drive of the piezoelectric actuator 300.

(Embodiment 2)
FIG. 7 is an enlarged plan view showing a second portion of the piezoelectric actuator according to the second embodiment, and FIG. 8 is an enlarged plan view showing another example of the second portion of the actuator according to the second embodiment.

This embodiment is a modification of the second portion that is a part of the piezoelectric actuator, and the other configurations are the same as those of the first embodiment. In the figure, the same members are designated by the same reference numerals, and overlapping description will be omitted.

The second portion 312 according to the first embodiment was formed into a rectangle having a length in the Y-axis direction in a plan view in the Z-axis direction having a substantially constant length. On the other hand, as shown in FIG. 7, the second portion 312A according to the present embodiment is formed in a rhombus shape in a plan view in the Z-axis direction. That is, the second portion 312A has a shape in which the length b2 in the Y-axis direction is the longest in the central portion in the X-axis direction and becomes shorter toward the end portion in the X-axis direction. Further, the second electrode 80 of the second portion 312A is a thin film portion 81 as in the first embodiment.

As a result, in the central region S4 of the active portion 310 in which the second portion 312A is formed, the displacement amount of the active portion 310 gradually changes in the X-axis direction. Specifically, the deformation in the vicinity of both ends in the central region S4 of the active portion 310 in the X-axis direction is the smallest, and the deformation amount in the central portion in the X-axis direction is the largest. Therefore, the displacement amount of the active portion 310 gradually changes in the vicinity of the end portion of the central region S4 of the active portion 310 without abrupt change. Therefore, the occurrence of cracks in the diaphragm 50 in this portion can be more reliably suppressed. Further, the load applied to the piezoelectric actuator 300 can be suppressed.

Further, it is preferable that the four corners of the second portion 312A, which is a rhombus, each have an R shape. When the second portion 312A is a rhombus, stress concentration is likely to occur in the four corners when a voltage is applied, but since each of the four corners has an R shape, this stress concentration can be suppressed.

The shape of the second portion 312A in the plan view in the Z-axis direction is limited to a diamond shape as long as the length in the Y-axis direction is the longest in the central portion in the X-axis direction and becomes shorter toward the end portion in the X-axis direction. Not done. The shape of the second portion 312A may be, for example, an ellipse as shown in FIG. 8, a polygonal shape having a pentagon or more, an oval shape, or the like. The oval shape referred to here mainly refers to a shape in which both ends in the longitudinal direction are semicircular based on a rectangle, but a so-called rounded rectangle or the like is also included.

(Embodiment 3)
9 is a plan view illustrating a second portion of the piezoelectric actuator according to the third embodiment, and FIG. 10 is a cross-sectional view taken along the line DD' of FIG.

This embodiment is a modification of the second portion that is a part of the piezoelectric actuator, and other configurations are the same as those of the above-described embodiment. In the figure, the same members are designated by the same reference numerals, and overlapping description will be omitted.

As shown in FIGS. 9 and 10, the second electrode 80 of the second portion 312B according to the present embodiment has a plurality of holes 82 penetrating the second electrode 80 in the thickness direction instead of the thin film portion 81. Are provided independently. The second portion 312B is set as a substantially diamond-shaped region in a plan view in the Z-axis direction, and a plurality of hole portions 82 are arranged in this region at predetermined intervals. Further, these plurality of hole portions 82 are arranged in such a size and number that the total area thereof is the same as the area of the thin film portion 81 according to the second embodiment. The opening shape of each hole 82 is not particularly limited, but is formed in a substantially circular shape in the present embodiment.

Even with such a configuration, the resistance value of the second electrode 80 of the second portion 312B is higher than that of the first portion 311 and between the first electrode 60 and the second electrode 80, as in the above-described embodiment. The deformation of the second portion 312B when a voltage is applied to the second portion 312B is suppressed to be smaller than that of the first portion 311. Therefore, even in the configuration of the present embodiment, it is possible to suppress the occurrence of cracks in the diaphragm 50 due to the repeated driving of the piezoelectric actuator 300 while maintaining good ejection characteristics by driving the piezoelectric actuator 300.

Further, since the plurality of hole portions 82 are arranged in the diamond-shaped region with a size and number such that the total area is about the same as that of the thin film portion 81 according to the second embodiment, the active portion 310 is the first. In the central region S4 of the active portion 310 in which the two sites 312B are formed, the displacement amount of the piezoelectric actuator 300 gradually changes in the X-axis direction, as in the second embodiment. Therefore, the occurrence of cracks in the diaphragm 50 can be suppressed more reliably, and the load applied to the piezoelectric actuator 300 can also be suppressed.

Further, in the present embodiment, the plurality of holes 82 are formed so as to penetrate the second electrode 80. That is, a portion is formed in a part of the second portion 312B so that the piezoelectric layer 70 does not cause piezoelectric distortion even when a voltage is applied between the first electrode 60 and the second electrode 80. As a result, even if the second electrode 80 of the second portion 312B is not used as the thin film portion 81, the deformation of the piezoelectric actuator 300 in the second portion 312 can be suppressed to be sufficiently smaller than that of the first portion 311.

Since the hole 82 is provided so as to penetrate the second electrode 80 in the thickness direction, when a voltage is applied between the first electrode 60 and the second electrode 80, the hole 82 is formed on the outer peripheral portion of the hole 82. Electrode concentration occurs. However, in the present embodiment, the second portion 312B is formed with a plurality of holes 82 having a total area of a predetermined area, instead of a single hole having a predetermined area. Therefore, even if the electric field concentration occurs, the generated points are dispersed in the outer peripheral portions of the plurality of hole portions 82. Therefore, the degree of electric field concentration generated in each part becomes relatively weak, and damage to the piezoelectric layer 70 due to the electric field concentration is less likely to occur.

Further, in the present embodiment, the second electrode 80 of the second portion 312B is not used as the thin film portion 81, and a plurality of holes 82 are formed. Of course, the second electrode 80 of the second portion 312B is formed of the thin film portion 81. Therefore, a plurality of pores 82 may be formed in the thin film portion 81. In that case, it is preferable to make the opening diameter of each hole 82 as small as possible and to form a large number of holes 82 in the thin film 81. As a result, the conduction path in the thin film portion 81 becomes narrower, so that the second electrode 80 of the second portion 312B has higher resistance. Further, by making each hole 82 a minute hole, it is possible to suppress the occurrence of electric field concentration in each hole 82.

(Embodiment 4)
FIG. 11 is an enlarged cross-sectional view of the piezoelectric actuator portion according to the fourth embodiment.

This embodiment is a modification of the second portion that is a part of the piezoelectric actuator, and other configurations are the same as those of the above-described embodiment. In the figure, the same members are designated by the same reference numerals, and overlapping description will be omitted.

As shown in FIG. 11, in the present embodiment, the second electrode 80 is formed to have the same thickness at the first portion 311 and the second portion 312C, and is a crystal of the piezoelectric layer 70 at the second portion 312C. By making at least one of the structure, crystal orientation rate, crystal phase amount, and crystallinity different from that of the first part 311, the deformation of the second part 312C is suppressed as compared with the first part 311. ing.

Specifically, in the first portion 311 of the piezoelectric actuator 300, the piezoelectric layer 70 is formed so as to have a (100) plane preferential orientation, and in the second portion 312C, the piezoelectric layer 70 has a (100) plane orientation ratio. It is formed so as to be lower than the (100) plane orientation rate of the piezoelectric layer 70 of the first portion 311. That is, the piezoelectric layer 70 includes a first alignment portion 75 having (100) plane priority orientation in the first portion 311 and a second alignment portion 76 having a lower (100) plane orientation ratio than the first orientation portion 75. It is prepared for the second part 312.

The term "priority orientation" as used herein means that 50% or more, preferably 80% or more of the crystals are oriented to a predetermined crystal plane. For example, "(100) plane-oriented orientation" means not only when all the crystals are (100) plane-oriented, but also more than half of the crystals (in other words, 50% or more, preferably 80% or more). ) Is (100) plane oriented, including.

The second alignment portion 76 may have a (100) plane orientation rate lower than that of the first alignment portion 75, and of course may have a (100) plane orientation, but the second alignment portion 76 does not have a (100) plane orientation. May be good. In the present embodiment, the second alignment portion 76 has a (111) plane priority orientation.

The first alignment portion 75 having the (100) plane priority orientation has a relatively large piezoelectric strain when a voltage is applied between the electrodes. On the other hand, in the second alignment portion 76 having a (100) plane orientation rate lower than that of the first alignment portion 75, the piezoelectric strain when a voltage is applied between the electrodes is smaller than that of the first alignment portion 75. That is, the deformation of the second portion 312C of the piezoelectric actuator 300 is suppressed as compared with that of the first portion 311.

Therefore, as in the configuration of the present embodiment, it is possible to suppress the generation of cracks in the diaphragm 50 due to the repeated drive of the piezoelectric actuator 300 while maintaining the good ejection characteristics of the piezoelectric actuator 300 as in the above-described embodiment. can.

Hereinafter, an example of a method for manufacturing an inkjet recording head 1 including such a piezoelectric actuator, particularly an example of a method for manufacturing the piezoelectric actuator 300 will be described. 12 to 22 are sectional views showing a method of manufacturing an inkjet recording head.

First, as shown in FIG. 12, an elastic film 51 is formed on the surface of a wafer 110 for a flow path forming substrate, which is a silicon wafer. In the present embodiment, the elastic film 51 made of silicon dioxide is formed by thermally oxidizing the wafer 110 for the flow path forming substrate. Of course, the material of the elastic film 51 is not limited to silicon dioxide, and may be a silicon nitride film, a polysilicon film, an organic film (polyimide, parylene, etc.) or the like. The method for forming the elastic film 51 is not limited to thermal oxidation, and the elastic film 51 may be formed by a sputtering method, a CVD method, a spin coating method, or the like.

Next, as shown in FIG. 13, an insulator film 52 made of zirconium oxide is formed on the elastic film 51. The insulator film 52 is not limited to zirconium oxide, but is not limited to titanium oxide, aluminum oxide (Al ₂ O ₃ ), hafnium oxide (HfO ₂ ), magnesium oxide (MgO), lanthanum aluminate (LaAlO ₃ ) _, and the like. May be used. Examples of the method for forming the insulator film 52 include a sputtering method, a CVD method, and a vapor deposition method.

Next, as shown in FIG. 14, the first electrode 60 is formed on the entire surface of the insulator film 52. The material of the first electrode 60 is not particularly limited, but when lead zirconate titanate (PZT) is used as the piezoelectric layer 70, it is desirable that the material has little change in conductivity due to the diffusion of lead oxide. Therefore, platinum, iridium, or the like is preferably used as the material for the first electrode 60. Further, the first electrode 60 can be formed by, for example, a sputtering method, a PVD method (physical vapor deposition method), or the like.

Next, as shown in FIG. 15, a crystal seed layer 61 made of titanium (Ti) as an orientation control layer is formed on the first electrode 60. The crystal seed layer 61 may be formed in a layered shape or an island shape. The crystal seed layer 61 functions as a seed that promotes crystallization when the piezoelectric layer 70 crystallizes, and diffuses into the piezoelectric layer 70 after firing of the piezoelectric layer 70.

When forming the crystal seed layer 61, as shown in FIG. 16, the crystal seed layer 61a at the position corresponding to the first portion 311 of the piezoelectric actuator 300 and the crystal seed layer 61b at the position corresponding to the second portion 312C Have different thicknesses. For example, the crystal seed layer 61a at the position corresponding to the first portion 311 has a predetermined thickness at which the piezoelectric layer 70 has a (100) plane preferential orientation, and the crystal seed layer 61b corresponding to the second portion 312C is a crystal species. The thickness is different from that of the layer 61a.

Specifically, after forming the crystal seed layer 61 on the entire surface of the first electrode 60 with a predetermined thickness, the crystal seed layer 61 at the position corresponding to the second portion 312C is formed by, for example, a photolithography method or a laser. It is selectively removed by irradiating it with light. As a result, as shown in FIG. 16, the crystal seed layer 61a having a predetermined thickness is located at the position corresponding to the first portion 311 of the active portion 310, that is, at the position where the first alignment portion 75 of the piezoelectric layer 70 is formed. Is formed. Further, a crystal seed layer 61b having a thickness thinner than the crystal seed layer 61a is formed at a position corresponding to the second portion 312C, that is, a position where the second alignment portion 76 of the piezoelectric layer 70 is formed. The crystal seed layer 61b may be completely removed.

Note that FIG. 16 shows the positions where the first alignment portion 75 and the second alignment portion 76 are formed by virtual lines. In the present embodiment, the crystal seed layer 61b is substantially removed, and the crystal seed layer 61 in the other region including the crystal seed layer 61a is left at a predetermined thickness. The etching method of the crystal seed layer 61 is not particularly limited, and may be, for example, an etching solution or dry etching such as ion milling.

Due to the crystal seed layer 61a formed with a predetermined thickness, the preferential orientation of the piezoelectric layer 70 can be controlled to (100) when the piezoelectric layer 70 is formed in a later step, and electromechanical conversion can be performed. A piezoelectric layer 70 suitable as an element can be obtained. On the other hand, in the crystal seed layer 61b, when the piezoelectric layer 70 is formed in a later step, the piezoelectric layer 70 grows under the influence of the first electrode 60 which is the base layer. Since the first electrode 60, which is the base layer, is made of platinum or the like and has a (111) plane preferential orientation, the piezoelectric layer 70 of the second portion 312C is affected by the first electrode 60 (111). ) Make surface priority orientation.

Next, the piezoelectric layer 70 made of lead zirconate titanate (PZT) is formed. In this embodiment, a so-called sol-gel method is used in which a so-called sol in which a metal complex is dissolved and dispersed in a solvent is applied, dried, gelled, and then calcined at a high temperature to obtain a piezoelectric layer 70 made of a metal oxide. The piezoelectric layer 70 is formed. The method for producing the piezoelectric layer 70 is not limited to the sol-gel method, and for example, a liquid phase film forming method such as a MOD method, a sputtering method, a physical vapor deposition method (PVD method), a laser ablation method, or the like. A membrane method may be used.

As a specific procedure for forming the piezoelectric layer 70, first, as shown in FIG. 17, a piezoelectric precursor film 73, which is a PZT precursor film, is formed on the first electrode 60 on which the crystal seed layer 61 is formed. Membrane. That is, a sol (solution) containing a metal complex is applied onto the flow path forming substrate wafer 110 on which the first electrode 60 (crystal seed layer 61) is formed (coating step). Next, the piezoelectric precursor membrane 73 is heated to a predetermined temperature and dried for a certain period of time. For example, the piezoelectric precursor membrane 73 is dried by holding it at 170 to 180 ° C. for 8 to 30 minutes (drying step).

Next, the dried piezoelectric precursor film 73 is degreased by heating it to a predetermined temperature and holding it for a certain period of time (defatting step). For example, the piezoelectric precursor membrane 73 is degreased by heating it to a temperature of about 300 to 400 ° C. and holding it for about 10 to 30 minutes. The degreasing referred to here is to remove the organic component contained in the piezoelectric precursor membrane 73 as, for example, NO ₂ , CO ₂ , H ₂ O, or the like.

Next, as shown in FIG. 18, the piezoelectric precursor film 73 is heated to a predetermined temperature and held for a certain period of time to crystallize the piezoelectric precursor film 73 to form the piezoelectric film 74 (firing step). In this firing step, it is preferable to heat the piezoelectric precursor film 73 to 700 ° C. or higher. In the firing step, the temperature rising rate is preferably 50 ° C./sec or more. As a result, the piezoelectric film 74 having excellent characteristics can be obtained.

Next, as shown in FIG. 19, at the stage where the first layer piezoelectric film 74 is formed on the first electrode 60, the first electrode 60 and the first layer piezoelectric film 74 are simultaneously patterned. The patterning of the first electrode 60 and the piezoelectric film 74 of the first layer can be performed by, for example, dry etching such as ion milling.

Next, as shown in FIG. 20, the piezoelectric layer 70 composed of a plurality of layers of the piezoelectric film 74 is formed by repeating the above-mentioned piezoelectric film forming step including the coating step, the drying step, the degreasing step, and the firing step a plurality of times. Form.

Next, as shown in FIG. 21, the piezoelectric layer 70 is patterned corresponding to each pressure chamber 12. In the present embodiment, a mask (not shown) formed in a predetermined shape is provided on the piezoelectric layer 70, and the piezoelectric layer 70 is etched through the mask, that is, patterning is performed by a so-called photolithography method. The patterning of the piezoelectric layer 70 includes, for example, dry etching such as reactive ion etching and ion milling.

Next, as shown in FIG. 22, a second electrode 80 made of, for example, iridium (Ir) is formed over the piezoelectric layer 70 and the insulator film 52, and the second electrode 80 is patterned into a predetermined shape. do. Next, as shown in FIG. 23, an individual lead electrode 91 and a common lead electrode 92 (not shown) are formed on the flow path forming substrate wafer 110. As a result, the piezoelectric actuator 300 is formed.

Although the subsequent steps are not shown, the flow path forming substrate is used after bonding the protective substrate wafer, which is a silicon wafer and serves as a plurality of protective substrates 30, to the piezoelectric actuator 300 side of the flow path forming substrate wafer 110. The wafer 110 is thinned to a predetermined thickness. Further, the pressure chamber 12 partitioned by the partition wall 11 is formed by anisotropic etching (wet etching) of the flow path forming substrate wafer 110 using an alkaline solution such as KOH via a mask film patterned in a predetermined shape. Form.

Further, unnecessary portions of the outer peripheral edge portion of the flow path forming substrate wafer 110 and the protective substrate wafer are removed by cutting, for example, by dicing or the like. Then, the bonded body of the flow path forming substrate wafer 110 and the protective substrate wafer is divided into one chip-sized flow path forming substrate 10 or the like as shown in FIG. Then, the recording head 1 of the present embodiment is manufactured by joining the communication plate 15, the nozzle plate 20, the case member 40, the compliance board 45, and the like to the joint body of the protective substrate 30 and the flow path forming substrate 10.

In the present embodiment, when the piezoelectric layer 70 is formed, the orientation of the piezoelectric layer 70, that is, the first alignment portion 75 and the alignment portion 75 are adjusted by adjusting the thickness of the crystal seed layer 61 formed on the first electrode 60. Although the orientation of the second alignment portion 76 is controlled, the orientation of the piezoelectric layer 70 can also be controlled by adjusting the thickness of the so-called intermediate crystal seed layer.

After patterning the first layer piezoelectric film 74 and the first electrode 60 (see FIG. 19), the intermediate crystal seed layer 62 is on the insulator film 52 and on the side surface of the first electrode 60, as shown in FIG. 24. It is formed over the side surface of the first layer piezoelectric film 74 and over the piezoelectric film 74. Similar to the crystal seed layer 61, titanium is preferably used for the intermediate crystal seed layer 62, and the intermediate crystal seed layer 62 is formed in a layered or island shape. After that, as described above, the second and subsequent layers of the piezoelectric film 74 are formed (see FIG. 20).

The orientation of the piezoelectric film 74 after the second layer can also be controlled by the intermediate crystal seed layer 62. Similar to the case of the crystal seed layer 61 described above, the thickness of the intermediate crystal seed layer 62b at the position corresponding to the second alignment portion 76 is set from the thickness of the intermediate crystal seed layer 62a at the position corresponding to the first alignment portion 75. Also thin (see FIG. 24). As a result, the first alignment portion 75 can be preferentially oriented in the (100) plane, and the second alignment portion 76 can be preferentially oriented in the (111) plane.

When the intermediate crystal seed layer 62 is formed, the crystal seed layer 61 may not be formed, or the crystal seed layer 61 may be formed together with the intermediate crystal seed layer 62. When the crystal seed layer 61 is formed together with the intermediate crystal seed layer 62, the thickness of the crystal seed layer 61 may be substantially uniform over the entire thickness.

Further, the method for manufacturing the piezoelectric actuator 300 is not limited to the above method. For example, in the present embodiment, the portion corresponding to the second portion 312C, that is, the crystal seed layer 61 corresponding to the second orientation portion 76 is selectively removed by a photolithography method or the like, but for example, the crystal seed layer. Before forming the 61, a resist film for lift-off is provided in the portion corresponding to the portion corresponding to the second portion 312C on the first electrode 60, and the crystal seed layer 61 is formed on the entire surface on the first electrode 60. Later, the crystal seed layer 61 of the portion corresponding to the second portion 312C may be removed together with the resist film.

Further, the crystal seed layer 61 of the portion corresponding to the second portion 312C may be modified by, for example, irradiating with a laser beam without removing the crystal seed layer 61 of the portion. Further, before or during the formation of the piezoelectric layer 70 on the first electrode 60, an inhibitory film made of a material that inhibits the crystallization of the piezoelectric layer 70 is provided in the portion corresponding to the second portion 312C. You may. Even in such a method, the crystal orientation of the piezoelectric layer 70 of the second portion 312C is different from the crystal orientation of the piezoelectric layer 70 of the first portion 311.

As described above, in the present embodiment, as an example, the crystal orientation ratio of the piezoelectric layer 70 of the second portion 312C is different from that of the piezoelectric layer 70 of the first portion 311. However, the configuration of the second site 312C is not limited to this, although the deformation of the second site is suppressed more than that of the first site. The second portion 312C has at least one of the crystal structure, crystal orientation rate, crystal phase amount, and crystallinity of the piezoelectric layer 70 different from that of the piezoelectric layer 70 of the first portion 311. It suffices that the deformation of the two-site 312C is suppressed more than that of the first site 311.

(Other embodiments)
Although each embodiment of the present invention has been described above, the basic configuration of the present invention is not limited to the above.

For example, in the above-described embodiment, the piezoelectric actuator 300 has a configuration in which the active portion 310 extends to both outer sides of the pressure chamber 12 in the X-axis direction, that is, the length of the flexible portion of the active portion 310 is the pressure chamber 12. Although the configuration that matches the length is illustrated, the configuration of the piezoelectric actuator 300 is not particularly limited.

For example, the active portion 310 may be arranged in the pressure chamber 12 in the X-axis direction. That is, the length of the flexible portion in the X-axis direction may be shorter than the length of the pressure chamber 12. However, even in this case, it is preferable that the active portion 310 extends to the vicinity of the end portion of the pressure chamber 12, and it is preferable that the active portion 310 is arranged in the center of the pressure chamber 12 in the X-axis direction.

Further, the recording head 1 of each of these embodiments is mounted on an inkjet recording device which is an example of a liquid injection device. FIG. 25 is a schematic view showing an example of an inkjet recording device which is an example of the liquid injection device according to the embodiment.

In the inkjet recording device I shown in FIG. 25, the recording head 1 is provided with a detachable cartridge 2 constituting the ink supply means, and is mounted on the carriage 3. The carriage 3 on which the recording head 1 is mounted is provided so as to be movable in the axial direction of the carriage shaft 5 attached to the apparatus main body 4.

Then, the driving force of the drive motor 6 is transmitted to the carriage 3 via a plurality of gears and a timing belt 7 (not shown), so that the carriage 3 equipped with the recording head 1 is moved along the carriage shaft 5. On the other hand, the apparatus main body 4 is provided with a transport roller 8 as a transport means, and the recording sheet S, which is a recording medium such as paper, is transported by the transport roller 8. The transporting means for transporting the recording sheet S is not limited to the transport roller, and may be a belt, a drum, or the like.

In such an inkjet recording apparatus I, the recording sheet S is conveyed to the recording head 1 in the + X direction, and the carriage 3 is reciprocated in the Y direction with respect to the recording sheet S while inking ink droplets from the recording head 1. By injecting the ink droplets, so-called printing is executed over substantially the entire surface of the recording sheet S.

Further, in the above-mentioned inkjet recording apparatus I, an example is described in which the recording head 1 is mounted on the carriage 3 and reciprocates in the Y direction, which is the main scanning direction, but the present invention is not particularly limited to this, and for example, the recording head 1 is used. The present invention can also be applied to a so-called line-type recording device in which printing is performed by simply moving a recording sheet S such as paper in the X direction, which is a sub-scanning direction.

In the above embodiment, the ink jet recording head has been described as an example of the liquid injection head, and the ink jet recording device has been described as an example of the liquid injection device. However, the present invention broadly describes the liquid injection head and the liquid injection device. It is intended for general purposes, and can of course be applied to a liquid injection head or a liquid injection device that injects a liquid other than ink. Other liquid injection heads include, for example, various recording heads used in image recording devices such as printers, color material injection heads used in manufacturing color filters such as liquid crystal displays, organic EL displays, and FEDs (electrode emission displays). Examples thereof include an electrode material injection head used for forming an electrode, a bioorganic substance injection head used for biochip production, and the like, and the present invention can also be applied to a liquid injection device provided with such a liquid injection head.

Further, the present invention is applied not only to a liquid injection head typified by an inkjet recording head, but also to other piezoelectric devices such as an ultrasonic device such as an ultrasonic transmitter, an ultrasonic motor, a pressure sensor, and a charcoal sensor. be able to.

I ... Inkjet recording device (recording device), 1 ... Inkjet recording head (recording head), 2 ... Cartridge, 3 ... Carriage, 4 ... Device body, 5 ... Carriage shaft, 6 ... Drive motor, 7 ... Timing belt, 8 ... Conveying roller, 10 ... Flow path forming substrate (board), 11 ... Bulk partition, 12 ... Pressure chamber (recess), 15 ... Communication plate, 16 ... Nozzle communication path, 17 ... First manifold part, 18 ... Second manifold Section, 19 ... Supply communication passage, 20 ... Nozzle plate, 21 ... Nozzle, 30 ... Protective substrate, 31 ... Holding section, 32 ... Through hole, 40 ... Case member, 41 ... Accommodating section, 42 ... Third manifold section, 43 ... Connection port, 44 ... Introduction port, 45 ... Compliance board, 46 ... Sealing film, 47 ... Fixed board, 48 ... Opening, 49 ... Compliance part, 50 ... Vibration plate, 51 ... Elastic film, 52 ... Inkjet film , 60 ... 1st electrode, 61 ... Crystal seed layer (seed layer), 62 ... Intermediate crystal seed layer, 70 ... Piezoelectric layer, 71 ... Groove, 73 ... Piezoelectric precursor film, 74 ... Piezoelectric film, 75 ... 1st alignment part, 76 ... 2nd alignment part, 80 ... 2nd electrode, 81 ... thin film part, 82 ... hole part, 85 ... wiring part, 91 ... individual lead electrode, 92 ... common lead electrode, 100 ... manifold, 110 ... Wafer for flow path forming substrate, 120 ... Wiring board, 121 ... Drive circuit, 300 ... Piezoelectric actuator, 310 ... Active part, 320 ... Inactive part, 311 ... First part, 312 ... Second part

Claims (14)

A diaphragm provided on one side of the substrate on which multiple recesses are formed,
A piezoelectric device comprising a first electrode, a piezoelectric layer, and a piezoelectric actuator having a second electrode laminated on the side of the diaphragm opposite to the substrate.
The recess has a shape in which the length in the first direction is longer than the length in the second direction intersecting with the first direction.
The piezoelectric actuator comprises an active portion in which the piezoelectric layer is sandwiched between the first electrode and the second electrode.
The active part is
A first portion extending in the first direction in a region facing the recess and deforming when a voltage is applied between the first electrode and the second electrode.
When a voltage is applied between the first electrode and the second electrode provided in the region corresponding to the central portion of the concave portion in the first direction and in the central portion of the active portion in the second direction. A piezoelectric device characterized by having a second portion in which the deformation of the first portion is suppressed more than the first portion. The piezoelectric device according to claim 1.
A piezoelectric device characterized in that the resistance value of at least one of the first electrode and the second electrode in the second portion is higher than that in the first portion. The piezoelectric device according to claim 2.
A piezoelectric device characterized in that the resistance value of the second electrode at the second portion is higher than that at the first portion. The piezoelectric device according to claim 1 or 2.
A piezoelectric device characterized in that a thin film portion having a thickness thinner than that of the first portion is formed on at least one of the first electrode and the second electrode of the second portion. The piezoelectric device according to claim 4.
A piezoelectric device characterized in that the thickness of the first electrode or the second electrode in the thin film portion is 1/10 or less of the thickness in the first portion. The piezoelectric device according to claim 5.
A piezoelectric device characterized in that the thickness of the first electrode or the second electrode in the thin film portion is 1/100 or less of the thickness in the first portion. The piezoelectric device according to claim 1 or 2.
A piezoelectric device characterized in that a plurality of independent holes are formed in at least one of the first electrode and the second electrode in the second portion. The piezoelectric device according to any one of claims 1 to 7.
The piezoelectric device is characterized in that the second portion is provided in a central region when the recess is equally divided into three regions in the first direction. The piezoelectric device according to any one of claims 1 to 8.
A piezoelectric device characterized in that the length of the second portion in the first direction is longer than the length of the second portion in the second direction. The piezoelectric device according to any one of claims 1 to 9.
A piezoelectric device characterized in that the length of the second portion in the second direction is the longest in the central portion of the second portion in the first direction and shorter toward the end portion in the first direction. The piezoelectric device according to any one of claims 1 to 10.
A piezoelectric device characterized in that a groove having a thickness of the piezoelectric layer thinner than that of other portions is provided in a region facing both ends of the recess in the second direction. The piezoelectric device according to claim 1.
A piezoelectric device characterized in that at least one of the crystal structure, crystal orientation rate, crystal phase amount, and crystallinity of the piezoelectric layer at the second site is different from that at the first site. A substrate with multiple recesses and
A diaphragm provided on one side of the substrate and
A liquid injection head comprising a first electrode laminated on the side of the diaphragm opposite to the substrate, a piezoelectric layer, and a piezoelectric actuator having a second electrode.
The recess has a shape in which the length in the first direction is longer than the length in the second direction intersecting with the first direction.
The piezoelectric actuator comprises an active portion in which the piezoelectric layer is sandwiched between the first electrode and the second electrode.
The active part is
A first portion extending in the first direction in a region facing the recess and deforming when a voltage is applied between the first electrode and the second electrode.
When a voltage is applied between the first electrode and the second electrode provided in the region corresponding to the central portion of the concave portion in the first direction and in the central portion of the active portion in the second direction. A liquid injection head characterized by having a second portion in which the deformation of the first portion is suppressed more than the first portion. A liquid injection device comprising the liquid injection head according to claim 13.

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