JP6508370B2 - Liquid jet head and method of manufacturing liquid jet head - Google Patents

Description

  The present invention relates to a liquid jet head, a liquid jet apparatus, a piezoelectric element, and a method of manufacturing a liquid jet head.

Piezoelectric elements having characteristics of charging when straining a crystal and straining when placed in an electric field are widely used in liquid jet devices such as ink jet printers, actuators, sensors, and the like.
Further, as a configuration of the piezoelectric element, one in which the lower electrode is an individual electrode for each piezoelectric layer and the upper electrode is a common electrode common to a plurality of individual electrodes is known (for example, see Patent Document 1) ).

JP, 2010-42683, A

  In a piezoelectric element in which the upper electrode is a common electrode, cracks and burnout may occur in the region of the piezoelectric layer not covered by the upper electrode. It is considered that the cause is that the composition of the piezoelectric layer is made unstable by the chemical or the like used when patterning the upper electrode or the wiring.

  In view of the above, one of the objects of the present invention is to improve the stability of at least a piezoelectric element, a liquid jet head and a liquid jet apparatus.

  In order to achieve at least one of the above objects, according to the present invention, a plurality of individual electrodes, a piezoelectric layer formed on the individual electrodes, and a piezoelectric layer formed on the piezoelectric layer are provided. It has the common electrode used as a common electrode, and the protective film which covers the area | region of the said piezoelectric material layer which is not covered by the said common electrode on the said separate electrode.

  In the invention configured as described above, the piezoelectric element is configured to use the upper electrode as a common electrode. Then, a protective film covers the region of the piezoelectric layer not covered by the common electrode on the individual electrodes. Therefore, it is possible to reduce cracks and burnout in the area above the individual electrodes and not covered by the common electrode.

(A) and (b) are a partial top view and a vertical cross-sectional view showing the main part of the piezoelectric element 3 included in the liquid jet head according to the embodiment of the present invention. FIG. 2 is an exploded perspective view showing an ink jet recording head 1 as an example of a liquid jet head in an exploded manner. FIGS. 7A to 7C are cross-sectional views for explaining the manufacturing process of the recording head 1. FIGS. 7A to 7C are cross-sectional views for explaining the manufacturing process of the recording head 1. The external view of a recording apparatus (liquid ejecting apparatus) 200 having the recording head 1 described above is shown. FIGS. 7A to 7C are cross-sectional views for explaining the manufacturing process of the recording head 1. FIGS. 7A to 7C are cross-sectional views for explaining the manufacturing process of the recording head 1.

  Hereinafter, the present invention will be described in detail based on embodiments. The configuration described in this embodiment is merely an example, and the present invention is not limited to this.

(1) Configuration of liquid discharge head and piezoelectric element:
FIGS. 1A and 1B are a partial top view and a vertical cross-sectional view showing the main part of the piezoelectric element 3 included in the liquid jet head according to the embodiment of the present invention. FIG. 2 is an exploded perspective view showing the ink jet recording head 1 as an example of the liquid jet head. 3A to 3 C are cross-sectional views for explaining the manufacturing process of the recording head 1. Further, FIGS. 4A to 4C are cross-sectional views for explaining the manufacturing process of the recording head 1.

The recording head (liquid ejecting head) 1 illustrated in FIG. 2 communicates with the piezoelectric element 3 having the piezoelectric layer 30 and the electrodes (20, 40) and the nozzle opening 71, and generates pressure change caused by the piezoelectric element 3. A room 12 is provided. More specifically, the piezoelectric element 3 is configured by laminating the lower electrode 20, the piezoelectric layer 30, and the upper electrode 40 in this order on the vibrating plate 16 provided with an elastic film.
The flow path forming substrate 10 is fixed to the side of the diaphragm 16 where the piezoelectric elements 3 are not stacked. In the flow path forming substrate 10, a plurality of pressure generating chambers 12 are arranged in parallel in the width direction. Further, the communication passage 13 is formed in the region outside the longitudinal direction of the pressure generation chamber of the flow passage forming substrate 10, and the ink supply passage 14 is provided with the communication passage 13 and the pressure generation chamber 12 for each pressure generation chamber 12. It is connected via.

  The nozzle plate 70 is fixed to the side of the flow path forming substrate 10 that is not fixed to the vibrating plate 16. In the nozzle plate 70, a plurality of nozzle openings 71, which become a part of a flow path for discharging ink, are bored. Further, on the side of the vibrating plate 16 to which the piezoelectric element 3 is fixed, the protective substrate 50 to which the compliance substrate 60 is fixed is fixed.

  Next, the configuration of the piezoelectric element 3 will be described with reference to FIG.

As shown in FIG. 1A, the piezoelectric element 3 has a configuration in which the upper electrode 40 is used as a common electrode, and the piezoelectric element 3 is stacked on the diaphragm 16 and formed.
That is, as shown in FIG. 1B, the lower electrode 20 having a layer containing at least one of platinum (Pt), iridium (Ir) and titanium (Ti) is laminated directly on the diaphragm 16 ing. The lower electrode 20 is an individual electrode, and is formed every four piezoelectric elements in this embodiment. Of course, setting the number of piezoelectric elements to four is an example, and is not limited to this.

The piezoelectric layer 30 containing at least lead (Pb), zirconium (Zr), and titanium (Ti) is stacked directly on the lower electrode 20. The piezoelectric layer 30 is made of a perovskite type oxide, and is made of lead zirconate titanate containing Pb as the A site element and Zr and Ti as the B site element. Such perovskite-type oxides include perovskite-type oxides having a composition represented by the following general formula.
Pb (Zr, Ti) Ox (1)
(Pb, MA) (Zr, Ti) Ox ... (2)
Pb (Zr, Ti, MB) Ox (3)
(Pb, MA) (Zr, Ti, MB) Ox ... (4)
Here, MA is one or more types of metal elements excluding Pb, and MB is one or more types of metal elements excluding Zr, Ti, and Pb. Although 3 is a standard for x, it may deviate from 3 as long as the perovskite structure can be taken. The ratio of A site element to B site element is normally 1: 1, but may be deviated from 1: 1 as long as the perovskite structure can be taken.
The MB element includes Nb (niobium), Ta (tantalum), and the like.

  The formation of the piezoelectric layer 30 of lead zirconate titanate is merely an example, and other lead-based piezoelectric materials and non-lead-based piezoelectric materials have a composition (Bi, Ba) (Zr, Ti). It may be formed of a piezoelectric material represented by Ox).

  Then, the upper electrode 40 is stacked immediately above the piezoelectric layer 30. The upper electrode 40 is a common electrode common to all the piezoelectric elements 3, and is continuously formed on each piezoelectric layer 30. As the metal constituting the upper electrode 40, iridium (Ir), gold (Au), platinum (Pt) or the like can be used. Of course, in addition to this, the above-mentioned metals may contain different metals.

  As shown in FIG. 1 (b), the longitudinal end of the lower electrode 20 extends outward from the longitudinal end of the pressure generation chamber 12. The longitudinal end of the patterned upper electrode 40 corresponding to each pressure generating chamber 12 is located in front of the longitudinal end of the region where the lower electrode 20 is formed. Further, the longitudinal end of the upper electrode 40 extends to the outside of the longitudinal end of the pressure generation chamber 12. That is, in the piezoelectric layer 30, there is a region located on the lower electrode 20 but not covered by the upper electrode 40, and a region located on the lower electrode 20 and covered by the upper electrode 40. . Of course, the positional relationship between the lower electrode 20 and the upper electrode 40 in the longitudinal direction is only an example, and for example, the longitudinal end of the upper electrode 40 is formed in front of the longitudinal end of the pressure generating chamber 12. It may be

  Further, in the piezoelectric element 3, a region which is deformed by the action of the electric field is defined as an active portion 3a, and a region which is not deformed by the action of the electric field is defined as a non-active portion 3b. In the piezoelectric element 3 shown in FIG. 1B, the active portion 3a is a region in which the lower electrode 20 is disposed among the regions in which the piezoelectric layer 30 is disposed, and a region in which the upper electrode 40 is disposed. As the active part 3a. In addition, although the non-active portion 3b is a region where the lower electrode 20 is disposed among the regions where the piezoelectric layer 30 is disposed, the region not covered by the upper electrode 40 is the inactive portion 3b. The boundary between the active portion 3 a and the non-active portion 3 b is also affected by the position of the generated electric field, and is not necessarily defined by the positions of the lower electrode 20 and the upper electrode 40 described above.

  Then, in the region including the boundary between the active portion 3a and the nonactive portion 3b on the side where the upper electrode 40 is formed in the piezoelectric layer 30, a protective film 80 is formed so as to cover this region. In FIG. 1B, a protective film 80 is formed on the lower electrode 20 of the piezoelectric layer 30 so as to cover a region not covered by the upper electrode 40.

  Here, it is known that a crack and the occurrence of burning due to the crack become remarkable in the vicinity of the boundary between the active portion 3 a and the non-active portion 3 b in the piezoelectric layer 30. As one of the causes, in the piezoelectric element 3 in which the upper electrode 40 is a common electrode, the upper electrode film is formed on the piezoelectric layer 30 and then patterned to form the upper electrode 40 or the wiring is patterned It is known that chemicals or the like adhere to the piezoelectric layer 30 during the patterning, and the composition of the piezoelectric layer 30 is destabilized. In addition, as one of the other causes, stress concentration caused by the non-uniform occurrence of strain in the piezoelectric layer 30 in the vicinity of the boundary between the active portion 3 a and the non-active portion 3 b in the piezoelectric layer 30 is is there. Therefore, the protective film 80 is formed to cover the boundary between the active portion 3a and the nonactive portion 3b, thereby reducing the occurrence of cracks and burnout in this region.

  Further, it is preferable that the end on the upper electrode 40 side in the longitudinal direction of the protective film 80 be formed in front of the pressure generating chamber 12. That is, it is preferable that the protective film 80 be not formed above the region where the pressure generating chamber 12 is formed. This is to prevent the driving of the piezoelectric element 3 from being inhibited by preventing the protective film 80 from covering the area where the pressure generating chamber 12 is formed.

As a material of the protective film 80, an organic material such as polyimide (aromatic polyimide) can be used. When the protective film 80 is formed of polyimide, the film thickness is preferably 1.7 μm or more. In addition to this, the protective film 80 may be formed of an epoxy-based adhesive or a silicon-based adhesive. When the protective film 80 is formed of an adhesive, the film thickness is preferably 1.6 μm or more.
If the protective film 80 is an organic protective film, the protective film 80 can be easily formed.

(2) Method of Manufacturing Piezoelectric Element and Liquid Ejecting Head A method of manufacturing the above-described piezoelectric element 3 and the recording head (liquid ejecting head) 1 including the piezoelectric element 3 will be described with reference to FIGS. Here, the case where polyimide (organic protective film) is used as the protective film 80 will be described as an example.

As a method of manufacturing the recording head 1, first, the flow path forming substrate 10 is formed of a silicon single crystal substrate or the like. Then, for example, an elastic film (diaphragm 16) made of silicon dioxide (SiO ₂ ) is integrated by thermally oxidizing a relatively thick silicon substrate 15 having a relatively large film thickness of about 625 μm and high rigidity by a diffusion path of about 1100 ° C. Form. The thickness of the elastic film is not limited as long as it has elasticity, but can be, for example, about 0.5 to 2 μm.

Next, as shown in FIG. 3A, a lower electrode film for forming the lower electrode 20 is formed on the diaphragm 16 by sputtering or the like. As a constituent metal of the lower electrode 20, one or more types of metals such as Pt, Au, Ir, Ti and the like can be used. The thickness of the lower electrode is not particularly limited, but can be, for example, about 50 to 500 nm. A layer such as a TiAlN (titanium aluminum nitride) film, an Ir film, an IrO (iridium oxide) film, or a ZrO ₂ (zirconium oxide) film is formed on the diaphragm 16 as the adhesion layer or the diffusion preventing layer, The electrode 20 may be formed.

  Next, a precursor solution containing at least a lead salt, a zirconium salt, and a titanium salt is applied to the surface of the lower electrode 20. The molar ratio of metals in the precursor solution can be determined depending on the composition of the perovskite oxide to be formed. Although the molar ratio of the A site element to the B site element in the formulas (1) to (4) described above is normally 1: 1, it may deviate from 1: 1 within the range in which the perovskite oxide is formed.

Then, as shown in FIG. 3A, the applied precursor solution is crystallized to form the piezoelectric layer 30. As an example, preferably, the precursor solution is dried by heating at about 140 to 190 ° C., and then degreased at, for example, about 300 ° C. to 400 ° C., for example, heated to about 550 ° C. to 850 ° C. To crystallize.
In order to thicken the piezoelectric layer 30, the combination of the application process, the drying process, the degreasing process, and the firing process may be performed a plurality of times. In order to reduce the number of firing steps, the firing step may be performed after a plurality of combinations of the application step, the drying step, and the degreasing step. Furthermore, the combination of these steps may be performed multiple times. In the example shown in FIG. 3B, after the piezoelectric layer 30 is formed on the lower electrode film 20, the lower electrode 20 and the piezoelectric layer 30 are patterned in regions facing the pressure generating chambers 12.

  In addition, the infrared lamp annealing device etc. which are heated by irradiation of a hotplate, an infrared lamp, etc. can be used for the heating apparatus for performing above-described drying and degreasing. In addition, an infrared lamp annealing apparatus or the like can be used as a heating apparatus for performing the above-described firing. Preferably, the rate of temperature increase may be relatively fast using RTA (Rapid Thermal Annealing) method or the like.

  On the piezoelectric layer 30 thus formed, as shown in FIG. 3B, the upper electrode 40 is formed by sputtering or the like. As the metal constituting the upper electrode, one or more kinds of metals such as Ir, Au, Pt and the like can be used. The thickness of the upper electrode is not particularly limited, but can be, for example, about 10 to 200 nm. In the example shown in FIG. 3C, after the upper electrode film is formed, the upper electrode film is patterned in a region facing each pressure generating chamber 12 to form the piezoelectric element 3.

  Subsequently, the lead electrode 45 is formed. For example, as shown in FIG. 3C, after forming a gold layer over the front surface of the flow path forming substrate 10, lead electrodes are formed by patterning for each piezoelectric element 3 through a mask pattern made of a resist or the like. 45 are provided (FIG. 4 (a)). The lower electrodes 20 shown in FIG. 2 are connected to lead electrodes 45 extending to the diaphragm 16 from near the end on the ink supply path 14 side.

  The lower electrode 20, the upper electrode 40 and the lead electrode 45 can be formed by sputtering such as DC (direct current) magnetron sputtering. The thickness of each layer can be adjusted by changing the voltage applied to the sputtering apparatus or the sputtering process time.

  Then, as shown in FIG. 4A, a protective film 80 is formed to cover the boundary between the active portion and the non-active portion of the piezoelectric layer 30. As a method of forming the protective film 80, for example, first, a polyimide film is formed on the piezoelectric layer 30 including the upper electrode 40. Next, for example, the layer of polyimide is patterned through a mask pattern made of a resist or the like, and dry etching is performed to form a protective film 80. Further, when photosensitive polyimide is used as the protective film 80, after forming a film, it may be exposed, developed and patterned using a mask pattern.

  As described above, the piezoelectric element 3 having the piezoelectric layer 30 and the electrodes (20, 40) is formed, and the piezoelectric actuator including the piezoelectric element 3 and the vibration plate 16 is formed.

  Next, as shown in FIG. 4B, the protective substrate 50 on which the piezoelectric element holding portion 52 and the like are formed in advance is bonded onto the flow path forming substrate 10 by, for example, an adhesive. For the protective substrate 50, for example, a silicon single crystal substrate, glass, a ceramic material or the like can be used. The thickness of the protective substrate 50 is not particularly limited, but can be, for example, about 400 μm. The reservoir portion 51 penetrating in the thickness direction of the protective substrate 50 constitutes a reservoir 9 which becomes a common ink chamber together with the communication passage 13. The piezoelectric element holding portion 52 provided in the region facing the piezoelectric element 3 has a space that does not inhibit the movement of the piezoelectric element 3. In the through hole 53 of the protective substrate 50, the vicinity of the end of the lead electrode 45 drawn out from each piezoelectric element 3 is exposed.

Next, after the silicon substrate 15 is polished to a certain thickness, the silicon substrate 15 is made to have a predetermined thickness (for example, about 70 μm) by further wet etching with hydrofluoric-nitric acid. Next, as shown in FIG. 4B, a mask film 17 is newly formed on the silicon substrate 15 and patterned into a predetermined shape. Silicon nitride (SiN) or the like can be used for the mask film 17. Then, the silicon substrate 15 is anisotropically etched (wet etching) using an alkaline solution such as KOH. Thereby, a plurality of liquid flow paths provided with pressure generating chambers 12 and a narrow ink supply path 14 partitioned by a plurality of partition walls 11 (see FIG. 2), and a common liquid flow path connected to each ink supply path 14 The communication passage 13 is formed. The liquid flow paths (12, 14) are arranged in the width direction D1 which is the lateral direction of the pressure generation chamber 12.
The pressure generating chamber 12 may be formed before the formation of the piezoelectric element 3.

  Next, as shown in FIG. 4C, the nozzle plate 70 is bonded to the surface of the silicon substrate 15 opposite to the protective substrate 50. The nozzle plate 70 can be made of glass ceramics, a silicon single crystal substrate, stainless steel, or the like, and is fixed to the opening surface side of the flow path forming substrate 10. An adhesive agent, a heat welding film, etc. can be used for this fixation. In the nozzle plate 70, a nozzle opening 71 communicating with the vicinity of the end opposite to the ink supply path 14 of each pressure generation chamber 12 is formed. Therefore, the pressure generating chamber 12 is in communication with the nozzle opening 71 for discharging the liquid.

  Then, the compliance substrate 60 having the sealing film 61 and the fixing plate 62 is bonded onto the protective substrate 50. The sealing film 61 is made of, for example, a material having low rigidity and flexibility such as a polyphenylene sulfide (PPS) film having a thickness of about 6 μm, and seals one surface of the reservoir portion 51. The fixing plate 62 is made of, for example, a hard material such as metal such as stainless steel (SUS) having a thickness of about 30 μm, and a region facing the reservoir 9 is an opening 63.

Further, on the protective substrate 50, a drive circuit 65 for driving the piezoelectric elements 3 arranged in parallel is fixed. For the drive circuit 65, a circuit board, a semiconductor integrated circuit (IC), or the like can be used. The drive circuit 65 and the lead electrode 45 are electrically connected via the connection wiring 66. For the connection wiring 66, a conductive wire or the like such as a bonding wire can be used.
Thus, the recording head 1 is manufactured.

  The recording head 1 takes in the ink from an ink introduction port connected to an external ink supply unit (not shown) and fills the inside with the ink from the reservoir 9 to the nozzle opening 71. When a voltage is applied between the lower electrode 20 and the upper electrode 40 for each pressure generating chamber 12 in accordance with the recording signal from the drive circuit 65, deformation of the piezoelectric layer 30, the lower electrode 20 and the diaphragm 16 causes the nozzle opening 71 to Ink droplets are ejected.

(3) Liquid injection device:
FIG. 5 shows the appearance of a recording apparatus (liquid ejecting apparatus) 200 having the recording head 1 described above. When the recording head 1 is incorporated into the recording head units 211 and 212, the recording apparatus 200 can be manufactured. In the recording apparatus 200 shown in FIG. 5, the recording head 1 is provided for each of the recording head units 211 and 212, and ink cartridges 221 and 222, which are external ink supply means, are provided detachably. The carriage 203 on which the recording head units 211 and 212 are mounted is provided so as to be reciprocally movable along a carriage shaft 205 attached to the apparatus main body 204. When the driving force of the drive motor 206 is transmitted to the carriage 203 via a plurality of gears (not shown) and the timing belt 207, the carriage 203 moves along the carriage shaft 205. A recording sheet 290 fed by a sheet feeding roller or the like (not shown) is conveyed onto the platen 208 and printed by the ink supplied from the ink cartridges 221 and 222 and ejected from the recording head 1.

(4) Example:
Hereinafter, although an example is shown, the present invention is not limited by the following examples.

Here, the ink jet recording head of the following Example 1-3 was manufactured, and a DC conduction test was performed on the piezoelectric element.
Example 1
An ink jet recording head having a protective film made of polyimide and having a film thickness of 0.7 μm so as to cover the active part end (in the vicinity of the boundary between the active part and the nonactive part) of the piezoelectric element was made Example 1. The Young's modulus E of this polyimide is 3.0 GPa.
Example 2
An ink jet recording head similar to that of Example 1 was used as Example 2 except for a protective film made of polyimide with a film thickness of 2.6 μm.
[Example 3]
An ink jet recording head similar to that of Example 1 was used as Example 3 except for a protective film made of an adhesive having a film thickness of 3.0 μm. The Young's modulus E of the adhesive is 3.0 Gpa.

Table 1 shows each of the conditions (film thickness t, Young's modulus E, product of Young's modulus and film thickness: E × t) and the end of the active portion in Examples 1 to 4 when the withstand voltage evaluation is performed. Shows the state of burnout in That is, in the case of “o”, it shows that no burnout occurred, and in the case of “Δ”, it shows that the burnout is reduced compared to the case where the protective film is not formed.

As shown in Table 1, in Examples 2 and 3 in which the product of Young's modulus E and film thickness t is 7800 (Pa · m) or more, burnout at the end of the active portion 3a was not observed. Moreover, in Example 1 in which the product of Young's modulus E and film thickness t is 2100 (Pa · m), it was observed that the burnout at the end of the active portion 3a was reduced.
From the above, it is found that the burnout is suppressed by forming the protective film 80 so as to cover the boundary between the active portion 3a and the nonactive portion 3b. If the product of Young's modulus E and film thickness t is 2000 (Pa · m) or more, burnout can be reduced, and more preferably, the product of Young's modulus E and film thickness t is 7800 (Pa · m) or more It was found that no burning would occur if it were.

(5) Second Embodiment:
Hereinafter, as the second embodiment, the case where the protective film 80 is an inorganic protective film will be described. 6A to 6C are cross-sectional views for explaining the manufacturing process of the recording head 1. 7A to 7C are cross-sectional views for explaining the manufacturing process of the recording head 1.

  The protective film 80 according to the second embodiment is the same as the first embodiment in the configuration formed to cover the boundary between the active portion 3 a and the non-active portion 3 b in the piezoelectric layer 30. On the other hand, it differs from the first embodiment in that the order of the steps of forming the protective film 80 is immediately after the step of forming the upper electrode 40. This is because the first embodiment forms the protective film 80 with an organic material, while the second embodiment forms a protective film 80 with an inorganic material.

As an example, the protective film 80 according to the second embodiment is formed of, for example, aluminum oxide (Al ₂ O ₃ ) as an inorganic protective film. Then, the case of forming the protective film 80 with _Al 2 _{O 3} is preferably be a 25nm or more thickness.

A method of manufacturing the above-described piezoelectric element 3 and the recording head (liquid ejecting head) 1 including the piezoelectric element 3 will be described with reference to FIGS. 6 and 7. Here, the case where Al ₂ O ₃ (inorganic protective film) is used as the protective film 80 will be described as an example. The conditions for forming the recording head 1 are the same as those in the first embodiment.

First, as in the first embodiment, the flow path forming substrate 10 is formed of a silicon single crystal substrate or the like. Then, the silicon substrate 15 is thermally oxidized in a diffusion path of about 1100 ° C. to integrally form an elastic film (diaphragm 16) made of silicon dioxide (SiO ₂ ).

  Next, as shown in FIG. 6A, the lower electrode 20 is formed on the elastic film 16 by sputtering or the like. Then, as shown in FIG. 6B, the applied precursor solution is crystallized to form the piezoelectric layer 30. On the piezoelectric layer 30 thus formed, as shown in FIG. 6B, the upper electrode 40 is formed by sputtering or the like.

Then, a protective film 80 is formed to cover the boundary between the active portion 3 a and the non-active portion 3 b of the piezoelectric layer 30. As a method of forming the protective film 80, as shown in FIG. 6C, first, a film of Al ₂ O _{3 is formed} on the piezoelectric layer 30 including the upper electrode 40. Next, for example, the layer of aluminum oxide is patterned through a mask pattern made of a resist or the like, and dry etching is further performed to form a protective film 80.

  Subsequently, as shown in FIG. 7A, the lead electrode 45 is formed on the protective film 80. For example, the lead electrode 45 is provided by forming a gold layer over the front surface of the flow path forming substrate 10 and then patterning each of the piezoelectric elements 3 through a mask pattern made of a resist or the like. That is, in the second embodiment, after forming the protective film 80, patterning for forming the lead electrode 45 is performed. Therefore, the piezoelectric layer 30 can be protected from a chemical used when patterning the lead electrode 45 by the protective film 80.

  Then, as shown in FIG. 7B, the protective substrate 50 on which the piezoelectric element holding portion 52 and the like are formed in advance is bonded onto the flow path forming substrate 10 by, for example, an adhesive. Next, a mask film 17 is newly formed on the silicon substrate 15 and patterned into a predetermined shape. Then, as shown in FIG. 7C, the nozzle plate 70 is bonded to the surface of the silicon substrate 15 opposite to the protective substrate 50. Next, the compliance substrate 60 having the sealing film 61 and the fixing plate 62 is bonded onto the protective substrate 50 and divided into a predetermined chip size. Thus, the recording head 1 is formed.

(6) Example Hereinafter, an example according to the second embodiment will be shown, but the present invention is not limited by the following example.

Here, the ink jet recording head in Example 4 described below was manufactured, and a DC conduction test was performed on the piezoelectric element.
Example 4
Example of an ink jet recording head having a protective film made of Al ₂ O ₃ with a film thickness of 90 nm so as to cover the end of the active part of the piezoelectric layer constituting the piezoelectric element (near the boundary between the active part and the nonactive part) It was four. The Young's modulus E of this Al ₂ O ₃ is 200 GPa.
[Example 5]
An ink jet recording head similar to that of Example 4 was used as Example 5 except for a protective film made of Al ₂ O _{3 with a} film thickness of 45 nm.

Table 2 shows each of the conditions (film thickness t, Young's modulus E, product of Young's modulus and film thickness: E × t) and the end of the active portion in Examples 4 to 5 when the withstand voltage evaluation is performed. Indicates the presence or absence of burnout.

As shown in Table 2, it can be seen that the burnout of the piezoelectric layer is reduced also in the second embodiment. That is, in the protective film in which the product of the Young's modulus E and the film thickness t is 4500 (Pa · m) or more, no burnout at the end of the active portion was observed.
From the first embodiment and the second embodiment, when the product of Young's modulus E and film thickness t is 5000 (Pa · m) or more, burnout at the end of the active portion can be suppressed.
Therefore, it was found that burnout is suppressed by forming a protective film made of an inorganic material on the boundary between the active part and the non-active part.

(7) Application, others:
The present invention can be considered in various modifications.
In the above-described embodiment, a separate piezoelectric body is provided for each pressure generation chamber, but it is also possible to provide a common piezoelectric body for a plurality of pressure generation chambers and provide an individual electrode for each pressure generation chamber.
In the embodiment described above, a part of the reservoir is formed in the flow path forming substrate, but it is also possible to form the reservoir in a member other than the flow path forming substrate.
In the embodiment described above, the upper side of the piezoelectric element is covered by the piezoelectric element holder, but it is also possible to open the upper side of the piezoelectric element to the atmosphere.
In the embodiment described above, the pressure generating chamber is provided on the opposite side of the piezoelectric element with the diaphragm separated, but it is also possible to provide the pressure generating chamber on the piezoelectric element side. For example, if a space surrounded by fixed plates and between piezoelectric elements is formed, this space can be used as a pressure generation chamber.

  The liquid ejected from the fluid ejection head may be any material that can be ejected from the liquid ejection head, and a fluid such as a solution in which a dye or the like is dissolved in a solvent, or a sol in which solid particles such as a pigment or metal particles are dispersed in a dispersion medium Is included. Such fluids include inks, liquid crystals, and the like. The liquid jet head can be mounted on an image recording apparatus such as a printer, an apparatus for manufacturing a color filter such as a liquid crystal display, an apparatus for manufacturing an electrode such as an organic EL display, a biochip manufacturing apparatus, and the like.

As described above, according to the present invention, techniques and the like for improving the performance of a piezoelectric element having at least a piezoelectric layer, a liquid jet head, and a liquid jet apparatus can be provided according to various aspects.
In addition, configurations disclosed in the above-described embodiment and modifications may be mutually replaced or changed in combination, known techniques, and configurations disclosed in the above-described embodiments and modifications may be mutually exchanged. A configuration in which substitution or combination is changed can also be implemented. The present invention also includes these configurations and the like.

DESCRIPTION OF SYMBOLS 1 ... Recording head, 3 ... Piezoelectric element, 9 ... Reservoir, 10 ... Flow path formation board, 11 ... Partition, 12 ... Pressure generating chamber, 15 ... Silicon substrate, 16 ... Vibration plate, 20 ... Lower electrode, 30 ... Piezoelectric Layer 40, Upper electrode 45, Lead electrode 50, Protective substrate 60, Compliance substrate 70, Nozzle plate

Claims (5)

A pressure generation chamber,
An elastic membrane sealing at least a part of the pressure generating chamber;
A first electrode formed on the opposite side of the elastic membrane from the pressure generation chamber;
A piezoelectric layer formed on the side opposite to the pressure generating chamber of the first electrode;
A second electrode formed on the side opposite to the pressure generating chamber of the piezoelectric layer;
A protective film covering a boundary between the second electrode and the piezoelectric layer;
In a direction orthogonal to the thickness direction of the elastic film, the end of the piezoelectric layer is located outside the end of the second electrode,
The protective film is an inorganic protective film formed outside the pressure generating chamber in plan view, and has a thickness of 25 nm or more and 45 nm or less. The liquid jet head according to claim 1, wherein the second electrode has a thickness of 10 nm or more and 200 nm or less. The liquid jet head according to claim 1, wherein the first electrode has a thickness of 50 nm or more and 500 nm or less. The liquid jet head according to any one of claims 1 to 3, wherein the elastic film has a thickness of 0.5 μm to 2 μm. Forming an elastic membrane sealing at least a part of the pressure generating chamber;
Forming a first electrode on the opposite side of the elastic membrane from the pressure generating chamber;
Forming a piezoelectric layer on the side opposite to the pressure generating chamber of the first electrode;
In the first direction orthogonal to the thickness direction of the elastic film, the end of the second electrode is positioned closer to the center of the pressure generating chamber than the end of the piezoelectric layer, The second electrode is formed on the side opposite to the pressure generation chamber,
A method of manufacturing a liquid jet head, comprising: forming an inorganic protective film covering a boundary between the second electrode and the piezoelectric layer in a thickness of 25 nm or more and 45 nm or less outside the pressure generation chamber in plan view.

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