Liquid ejection head, liquid ejection unit, and liquid ejection device

Abstract

To provide a liquid discharge head which can prevent occurrence of cracks without impairing displacement efficiency of a piezoelectric actuator.SOLUTION: A liquid discharge head comprises: a nozzle plate 12 with a nozzle 11; a liquid chamber substrate 14 which forms an individual liquid chamber 13 communicating with the nozzle 11; a piezoelectric actuator 16 having a piezoelectric body 16b which pressurizes an interior of the individual liquid chamber via a diaphragm 15 constituting a part of the individual liquid chamber 13; a wiring part 21; and a protective film 18a which coats a part of an area of the piezoelectric actuator 16 with non-formation of the wiring part 21. In a plan view, the piezoelectric body 16b is positioned inside the individual liquid chamber 13, widths of a separation region between an outer edge of the piezoelectric body 16b and an outer edge of the individual liquid chamber 13 are different in a longer direction, a shorter direction and at a corner part, and the protective film 18a is so provided on one end side in a direction with a narrower width of the separation region as to overlap at least a part of the separation region.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a liquid ejection head, a liquid ejection unit, and an apparatus for ejecting liquid. [Background technology]

[0002] Conventionally, image forming devices equipped with a liquid ejection head that ejects ink or other liquid for image formation onto a recording medium have been known. This liquid ejection head includes nozzles that eject the liquid, liquid chambers (also referred to as individual liquid chambers, pressurized liquid chambers, ink flow paths, etc.) that communicate with the nozzles, and pressure generating means that generate pressure on the liquid in the liquid chambers.

[0003] A known pressure generating device uses a piezoelectric actuator. A piezoelectric actuator has a vibration plate that forms part of the wall of the liquid chamber, and a piezoelectric element with an electromechanical transducer film made of a piezoelectric material sandwiched between a lower electrode and an upper electrode. When a voltage is applied to the lower electrode and the upper electrode, the piezoelectric material vibrates to deform the vibration plate.

[0004] To improve the reliability of liquid ejection heads, it is necessary to prevent damage to the piezoelectric actuator. Damage to the piezoelectric actuator can occur due to cracks or dielectric breakdown. Regarding dielectric breakdown, possible methods include optimizing the design of the components and taking measures to prevent the intrusion of foreign matter from the outside.

[0005] On the other hand, screening for cracks is difficult because there are various causes and timing of their occurrence. As an example, in order to prevent cracks from occurring due to stress, a technique has been proposed in which a protective film or layer is provided for reinforcement purposes to improve the rigidity of the liquid ejection head (see, for example, Patent Document 1). Summary of the Invention [Problem to be solved by the invention]

[0006] Patent Document 1 discloses a protective layer that can effectively protect the actuator while suppressing a decrease in actuator displacement, in which a central portion that overlaps a part of the central side of the pressure chamber when viewed from above is formed thinner than an outer peripheral portion that spans from the inside edge of the pressure chamber to the outside edge when viewed from above.

[0007] However, in a mode in which a protective film is provided over the entire periphery of the piezoelectric body, there is a problem in that a decrease in the displacement efficiency of the piezoelectric body is unavoidable.

[0008] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a liquid ejection head that can prevent the occurrence of cracks without impairing the displacement efficiency of the piezoelectric actuator. [Means for solving the problem]

[0009] In order to solve the above problem, the liquid ejection head of the present invention comprises a nozzle plate having nozzles for ejecting liquid, a liquid chamber substrate laminated on the nozzle plate and forming individual liquid chambers connected to the nozzles, a piezoelectric actuator having a piezoelectric element that pressurizes the individual liquid chamber via a vibration plate that forms part of the individual liquid chamber, a wiring section for applying a drive voltage to drive the piezoelectric element, and a protective film that covers part of the area of ​​the piezoelectric actuator where the wiring section is not formed, and is characterized in that, when viewed in a planar view from the stacking direction of the piezoelectric actuator, the piezoelectric element is located inside the individual liquid chamber, the width of the separation area between the outer edge of the piezoelectric element and the outer edge of the individual liquid chamber varies in the longitudinal direction, lateral direction and corners, and the protective film is arranged so as to overlap at least a part of the separation area at one end side in the longitudinal direction or lateral direction in which the width of the separation area is narrower. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide a liquid ejection head that can prevent the occurrence of cracks without impairing the displacement efficiency of the piezoelectric actuator. [Brief explanation of the drawings]

[0011] [Figure 1] 1A and 1B are a longitudinal cross-sectional explanatory view of a conventional liquid ejection head and an exploded plan view thereof; [Figure 2] FIG. 10 is an explanatory diagram of a conventional liquid ejection head in a plan view. [Figure 3] FIG. 10 is a cross-sectional explanatory view of a conventional liquid ejection head taken in the short side direction. [Figure 4] FIG. 1 is an explanatory diagram of a liquid ejection head according to a first embodiment of the present invention, as seen from above. [Figure 5] FIG. 10 is an explanatory diagram of a liquid ejection head according to a second embodiment of the present invention, as seen from above. [Figure 6] FIG. 10 is an explanatory diagram of a liquid ejection head according to a third embodiment of the present invention, as seen from above. [Figure 7] FIG. 10 is an explanatory diagram of a liquid ejection head according to a fourth embodiment of the present invention, as seen from above. [Figure 8] FIG. 10 is an explanatory diagram in plan view of a liquid ejection head according to a comparative example. [Figure 9] FIG. 10 is an explanatory diagram in plan view of a liquid ejection head according to a reference example. [Figure 10] FIG. 2 is a cross-sectional explanatory diagram in the short side direction showing an example of a head module including a liquid ejection head. [Figure 11] FIG. 2 is an exploded perspective view showing an example of a head module including a liquid ejection head. [Figure 12] 1A and 1B are explanatory diagrams illustrating an example of a liquid ejection unit according to the present invention. [Figure 13] 1 is an explanatory diagram showing an example of a device for discharging a liquid according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0012] A liquid ejection head, a liquid ejection unit, and a liquid ejection device according to the present invention will be described below with reference to the drawings. Note that the present invention is not limited to the following embodiments, and other modifications, additions, corrections, deletions, and other changes can be made within the scope of what a person skilled in the art can conceive. Any aspect that achieves the functions and effects of the present invention is within the scope of the present invention.

[0013] The configuration of the liquid ejection head will be described with reference to FIGS. Figure 1 is an explanatory longitudinal cross-sectional view of a conventional liquid ejection head and an exploded planar view seen from the stacking direction of the piezoelectric actuator, Figure 2 is an explanatory planar view of the conventional liquid ejection head seen from the stacking direction of the piezoelectric actuator, and Figure 3 is an explanatory short-side cross-sectional view of the conventional liquid ejection head.

[0014] As shown in the upper part of Figure 1 and Figure 3, the liquid ejection head 101 comprises a nozzle substrate 12 having nozzles 11 that eject droplets of liquid such as ink, and a liquid chamber substrate 14 (hereinafter simply referred to as the "substrate") in which individual liquid chambers 13 that communicate with the nozzles 11 and contain liquid are formed. A piezoelectric actuator 16 is provided on the substrate 14. The piezoelectric actuator 16 includes a vibration plate 15 that forms one wall surface of the individual liquid chamber 13, a piezoelectric body 16b, and a lower electrode 16a and an upper electrode 16c that are provided to sandwich the piezoelectric body 16b.

[0015] In addition, a first protective film that covers the piezoelectric actuator 16, a second protective film 18 (18a, 18b), a third protective film 19, and a sub-frame 20 are provided. The sub-frame 20 has a space for arranging the piezoelectric actuator 16. It also has grooves that serve as ink flow paths from the common liquid chamber to the individual liquid chambers 13.

[0016] Piezoelectric actuator 16 includes a laminated lower electrode 16a serving as a common electrode on the diaphragm 15 side, a piezoelectric body 16b made of PZT or the like as an electromechanical transducer film, and an upper electrode 16c serving as an individual electrode on the opposite side of piezoelectric body 16b from diaphragm 15. Lower electrode 16a is connected to wiring portion 21 through contact hole 22 formed in first protective film 17, and is connected via this wiring portion 21 to a pad electrode for the common electrode serving as a terminal electrode for external connection. Upper electrode 16c is connected to wiring portion 21 through contact hole 22 formed in second protective film 18b, and is connected via this wiring portion 21 to a pad electrode for the individual electrode serving as a terminal electrode for external connection.

[0017] A drive voltage of a predetermined frequency and amplitude is applied between the lower electrode 16a and the upper electrode 16c via the wiring portion 21. The piezoelectric body 16b to which this drive voltage is applied vibrates so as to deform the vibration plate 15, and the deformation of the vibration plate 15 pressurizes the liquid in the individual liquid chambers 13, causing droplets to be ejected from the nozzles 11.

[0018] The first protective film 17 is preferably a moisture-proof film made of a material that is difficult for moisture in the atmosphere to permeate. Hereinafter, the first protective film will also be referred to as a moisture-proof film. The moisture-proof film 17 must have a thickness that ensures the protection performance of the piezoelectric actuator 16 while not inhibiting the deformation (displacement) of the diaphragm 15. The thickness of the moisture-proof film 17 is preferably, for example, in the range of 20 nm to 100 nm. If the film thickness is thicker than 100 nm, the amount of deformation (displacement) of the diaphragm 15 decreases. On the other hand, if the film thickness is thinner than 20 nm, the function as a protective layer for the piezoelectric actuator 16 may be insufficient, and the performance of the piezoelectric body 16b may be reduced.

[0019] The second protective film 18 has an insulating protective film 18b that covers the wiring portion 21, and a protective film 18a that covers a part of the region where the wiring portion 21 is not provided. In the following description, when the term "protective film" is simply used, it refers to the protective film 18a.

[0020] The second protective film 18, which is the protective film 18a and the insulating protective film 18b, are formed simultaneously in the manufacturing process and are made of the same material. However, because the required functions are different, it is preferable to select a material that satisfies both functions. Furthermore, it is preferable to select the thickness of the protective film 18a and the insulating protective film 18b appropriately based on the required functions.

[0021] The insulating protective film 18b of the second protective film 18 is required to not undergo dielectric breakdown due to the voltage applied between the lower electrode 16a and the wiring portion 21 of the upper electrode 16c. In addition, the electric field strength applied to the insulating protective film 18b needs to be set within a range that does not cause dielectric breakdown. On the other hand, the protective film 18a is required to have a compressive stress in order to prevent cracks from occurring in the piezoelectric actuator 16 in the embodiment of the liquid ejection head according to the present invention, which will be described later.

[0022] The material of the second protective film 18 may be any oxide, nitride, carbide, or composite compound thereof, or SiO2 or the like that is generally used in semiconductor devices. The thickness of the second protective film 18 must be 200 nm or more, taking into consideration the surface properties of the base, pinholes, etc., and is preferably 500 nm or more.

[0023] 1, the second protective film 18 has an opening 23 between the insulating protective film 18b and the protective film 18a. In the figure, the longitudinal direction of the opening 23 is indicated by L3, and the lateral direction is indicated by S3. The second protective film 18 is not provided on the piezoelectric body 16b except in the vicinity of the wiring portion 21.

[0024] 1, in a plan view seen from the stacking direction of the piezoelectric actuator 16 (hereinafter simply referred to as "plan view"), the piezoelectric body 16b is located inside the individual liquid chamber 13. In the drawing, the longitudinal direction of the piezoelectric body 16b is indicated by L2, and the lateral direction is indicated by S2. The longitudinal direction of the individual liquid chamber is indicated by L1, and the lateral direction is indicated by S1. The outer edge of the piezoelectric body 16b and the outer edge of the individual liquid chamber 13 are rounded rectangular in a plan view.

[0025] In a plan view, since the piezoelectric body 16b is located inside the individual liquid chamber 13, a separation region is formed between the outer edge of the piezoelectric body 16b and the outer edge of the individual liquid chamber 13. In FIGS. 1 and 2, the width of the separation region in the longitudinal direction (the distance between the end of the piezoelectric body 16b and the end of the individual liquid chamber 13) is represented by A, and the width of the separation region in the short-side direction (the distance between the end of the piezoelectric body 16b and the end of the individual liquid chamber 13) is represented by B. In order to suppress the tensile stress generated in the piezoelectric body 16b and increase the discharge droplet volume from the nozzle, it is preferable that the width of the separation region is A < B.

[0026] However, in the configuration where the width of the separation region satisfies the relationship of A < B, it has become clear from the result of stress distribution analysis that a large stress is applied to the left region in FIG. 2 (the end side where the wiring portion 21 is not provided). Therefore, in the aspect where the width of the separation region is A < B, when a high load is applied, there is a risk that cracks may occur in the piezoelectric actuator 16 (particularly the piezoelectric body 16b and / or the diaphragm 15).

[0027] Therefore, in the liquid discharge head 101 according to the present invention, in order to prevent cracks from occurring in the piezoelectric actuator 16, a protective film 18a is provided in the left region in FIG. 2 (the end side where the wiring portion 21 is not provided). In the manufacturing process of the conventional liquid discharge head 101, the second protective film 18 is removed so that the opening 23 shown in the middle stage of FIG. 1 is formed. On the other hand, in the liquid discharge head according to the present invention, among the regions where the second protective film 18 has been removed as the conventional opening 23, the region where the stress concentrates in the separation region between the outer edge of the piezoelectric body 16b and the outer edge of the individual liquid chamber 13 is not removed, but is left as the protective film 18a to improve the stress resistance. As a result, even when a high load is applied, it is possible to prevent cracks from occurring in the piezoelectric actuator 16.

[0028] The basic configuration of the liquid ejection head 101 according to the present invention is the same as that of the conventional liquid ejection head described above, except that the region where the protective film 18a is provided is different. That is, the liquid ejection head according to the present invention comprises a nozzle plate 12 having nozzles 11 for ejecting liquid, a liquid chamber substrate 14 laminated on the nozzle plate 12 and forming individual liquid chambers 13 communicating with the nozzles 11, a piezoelectric body 16b that applies pressure to the individual liquid chambers 13 via a vibration plate 15 that constitutes part of the individual liquid chambers 13, a piezoelectric actuator 16 having a lower electrode 16a and an upper electrode 16c that are provided so as to sandwich the piezoelectric body 16b, and a wiring section 21 for applying a drive voltage to drive the piezoelectric body 16b. and a protective film 18a that covers a portion of the area of ​​the piezoelectric actuator 16 where the wiring portion 21 is not formed. When viewed in a plane from the stacking direction of the piezoelectric actuator 16, the piezoelectric body 16b is located inside the individual liquid chamber 13, and the width of the separation area between the outer edge of the piezoelectric body 16b and the outer edge of the individual liquid chamber 13 varies in the longitudinal direction, lateral direction and corners, and the protective film 18a is arranged so as to overlap at least a portion of the separation area at one end side in the longitudinal direction or lateral direction where the width of the separation area is narrow.

[0029] The protective film 18a is an area where the wiring portion 21 of the piezoelectric actuator 16 is not formed, and is provided on one end side of the narrower width of the separation area between the outer edge of the piezoelectric body 16b and the outer edge of the individual liquid chamber 13 (in the example of Figure 2, the left end in the longitudinal direction), and the area and shape can be selected appropriately within a range that does not significantly reduce the displacement efficiency of the piezoelectric body 16b.

[0030] The protective film 18a may be provided so as not to overlap the piezoelectric body 16b in a plan view, or may be provided so as to overlap to an extent that does not significantly reduce the displacement efficiency of the piezoelectric body 16b.

[0031] Furthermore, the protective film 18a may be provided so as to overlap one side of the separation region in the narrower width direction and a region including corners continuous with both ends of the side.

[0032] Hereinafter, similar to the examples of FIGS. 1 and 2, an example will be described in which the direction in which the width of the separation region is narrow in plan view is the longitudinal direction, and the wiring portion 21 is provided on one end side in the longitudinal direction.

[0033] Also, in plan view, the nozzle 11 is located at a position shifted to the one end side where the wiring portion 21 is not formed with respect to the center of the individual liquid chamber 13. In FIGS. 2 and each figure described below, the position of the nozzle 11 is indicated by a broken line.

[0034] Further, in the liquid ejection head 101 according to the present invention, it is preferable that the thickness of the protective film 18a becomes thinner toward the center of the individual liquid chamber 13 in plan view. Thereby, it is possible to suppress a decrease in the variation efficiency due to the protective film 18a covering the piezoelectric body 16b. Note that an example in which the outer edge of the piezoelectric body 16b and the outer edge of the individual liquid chamber 13 are rounded rectangular shapes in plan view will be described, but the present invention is not limited thereto, and other shapes such as circular or polygonal shapes of the outer edge of the piezoelectric body 16b and the outer edge of the individual liquid chamber 13 can also be applied.

[0035] (First Embodiment) FIG. 4 is an explanatory view in plan view of a liquid ejection head according to the first embodiment of the present invention. FIG. 4(A) is a view for explaining the relationship of the arrangement positions of the respective members, and the positions of the nozzle 11 and the contact hole 22 are indicated by broken lines. FIG. 4(B) is a view for explaining the opening 23 of the second protective film (protective film 18a and insulating protective film 18b), and FIG. 4(C) is a view for explaining the arrangement region of the protective film 18a. Note that the illustration of the insulating protective film 18b of the second protective film provided in the vicinity of the wiring portion 21 is omitted.

[0036] As shown in FIG. 4(A), in the liquid ejection head of the present embodiment, the width of the separation region in the longitudinal direction (the distance between the end of the piezoelectric body 16b and the end of the individual liquid chamber 13) A and the width of the separation region in the short hand direction (the distance between the end of the piezoelectric body 16b and the end of the individual liquid chamber 13) B have a relationship of A < B. The wiring portion 21 is provided on one end side in the longitudinal direction (right side in the figure).

[0037] The protective film 18a is provided at the left end in the longitudinal direction of a region where the wiring portion 21 of the piezoelectric actuator 16 is not formed and where the width of the separation region between the outer edge of the piezoelectric body 16b and the outer edge of the individual liquid chamber 13 is narrow, and covers a part of the separation region in the longitudinal direction. Also, the protective film 18a is provided so as not to overlap the piezoelectric body 16b in a plan view.

[0038] As schematically shown in FIGS. 〖4〗(A) and 〖4〗(C), by providing the protective film 18a, deformation of the diaphragm 15 in the longitudinal direction can be suppressed, and stress resistance can be improved, thereby preventing the occurrence of cracks in the piezoelectric actuator 16 even when a high load is applied. Specifically, after vibrating 1 trillion times with a high Pull waveform (36V, 120kHz), no cracks were observed in the diaphragm 15 and the piezoelectric body 16b. Also, since the protective film 18a does not overlap the piezoelectric body 16b in a plan view, the occurrence of cracks can be prevented without impairing the displacement efficiency of the piezoelectric actuator 16 (piezoelectric body 16b).

[0039] (Second Embodiment) FIG. 5 is an explanatory view in a plan view of a liquid ejection head according to a second embodiment of the present invention. FIG. 5(A) is a diagram for explaining the relationship of the arrangement positions of the respective members, and the positions of the nozzles 11 and the contact holes 22 are shown by broken lines. FIG. 5(B) is a diagram for explaining the openings 23 of the second protective film (protective film 18a and insulating protective film 18b), and FIG. 5(C) is a diagram for explaining the arrangement region of the protective film 18a. Note that the illustration of the insulating protective film 18b of the second protective film provided near the wiring portion 21 is omitted.

[0040] <着 As shown in FIG. 5(A), in the liquid ejection head of the present embodiment, the width of the separation region in the longitudinal direction (the distance between the end of the piezoelectric body 16b and the end of the individual liquid chamber 13) A and the width of the separation region in the short-hand direction (the distance between the end of the piezoelectric body 16b and the end of the individual liquid chamber 13) B have a relationship of A < B. The wiring portion 21 is provided on one end side in the longitudinal direction (right side in the figure).

[0041] <着 The protective film 18a is provided at the left end portion in the longitudinal direction of the separation region where the width of the separation region between the outer edge of the piezoelectric body 16b and the outer edge of the individual liquid chamber 13 is narrow, in a region where the wiring portion 21 of the piezoelectric actuator 16 is not formed, and covers a part of the separation region in the longitudinal direction. Further, the protective film 18a is provided so as to partially overlap the piezoelectric body 16b in plan view.

[0042] As schematically shown in FIGS. 5(A) and 5(C), by providing the protective film 18a, deformation in the longitudinal direction of the diaphragm 15 can be suppressed and stress resistance can be improved. Thereby, crack generation in the piezoelectric actuator 16 can be prevented even when a high load is applied. Specifically, after vibrating 1 trillion times with a high Pull waveform (36V, 120kHz), no crack generation was confirmed in the diaphragm 15 and the piezoelectric body 16b. Also, although the protective film 18a partially overlaps the piezoelectric body 16b in plan view, it does not significantly impair the displacement efficiency of the piezoelectric actuator 16 (piezoelectric body 16b), and crack generation can be prevented.

[0043] (Third Embodiment) FIG. 6 is an explanatory view in plan view of a liquid ejection head according to the third embodiment of the present invention. FIG. 6(A) is a view for explaining the relationship of the arrangement positions of the respective members, and the positions of the nozzles 11 and the contact holes 22 are shown by broken lines. FIG. 6(B) is a view for explaining the opening 23 of the second protective film (protective film 18a and insulating protective film 18b), and FIG. 6(C) is a view for explaining the arrangement region of the protective film 18a. Note that illustration of the insulating protective film 18b of the second protective film provided in the vicinity of the wiring portion 21 is omitted.

[0044] As shown in FIG. 6(A), in the liquid ejection head of the present embodiment, the width of the separation region in the longitudinal direction (the distance between the end of the piezoelectric body 16b and the end of the individual liquid chamber 13) A and the width of the separation region in the short hand direction (the distance between the end of the piezoelectric body 16b and the end of the individual liquid chamber 13) B have a relationship of A < B. The wiring portion 21 is provided on one end side in the longitudinal direction (the right side in the figure).

[0045] The protective film 18a is provided at the left end in the longitudinal direction of a region where the wiring portion 21 of the piezoelectric actuator 16 is not formed and where the width of the separation region between the outer edge of the piezoelectric body 16b and the outer edge of the individual liquid chamber 13 is narrow, and covers a region including one side at one end side in the longitudinal direction, which is the direction in which the width of the separation region is narrow, and the corner portions continuous with both ends of the side. Further, the protective film 18a is provided so as not to overlap the piezoelectric body 16b in a plan view.

[0046] As schematically shown in FIGS. 6(A) and 6(C), by providing the protective film 18a, deformation in the longitudinal direction of the diaphragm 15 can be suppressed and stress resistance can be improved. Thereby, crack generation in the piezoelectric actuator 16 can be prevented even when a high load is applied. Specifically, after vibrating 1 trillion times with a high Pull waveform (36 V, 120 kHz), no crack generation was confirmed in the diaphragm 15 and the piezoelectric body 16b. Further, since the protective film 18a does not overlap the piezoelectric body 16b in a plan view, crack generation can be prevented without impairing the displacement efficiency of the piezoelectric actuator 16 (piezoelectric body 16b).

[0047] (Fourth Embodiment) FIG. 7 is an explanatory view in a plan view of a liquid ejection head according to the fourth embodiment of the present invention. FIG. 7(A) is a view for explaining the relationship of the arrangement positions of the respective members, and the positions of the nozzles 11 and the contact holes 22 are shown by broken lines. FIG. 7(B) is a view for explaining the opening 23 of the second protective film (protective film 18a and insulating protective film 18b), and FIG. 7(C) is a view for explaining the arrangement region of the protective film 18a. Note that the illustration of the insulating protective film 18b of the second protective film provided in the vicinity of the wiring portion 21 is omitted.

[0048] In the liquid ejection head of the present embodiment, as shown in FIG. 7(A), the width of the separation region in the longitudinal direction (the distance between the end of the piezoelectric body 16b and the end of the individual liquid chamber 13) A and the width of the separation region in the short transverse direction (the distance between the end of the piezoelectric body 16b and the end of the individual liquid chamber 13) B have a relationship of A < B. The wiring portion 21 is provided on one end side in the longitudinal direction (right side in the figure).

[0049] The protective film 18a is provided at the left end portion in the longitudinal direction of a region where the wiring portion 21 of the piezoelectric actuator 16 is not formed, and where the width of the separation region between the outer edge of the piezoelectric body 16b and the outer edge of the individual liquid chamber 13 is narrow, and covers a side in one end side in the longitudinal direction, which is the direction in which the width of the separation region is narrow, and a region including corner portions continuous with both ends of the side. Further, the protective film 18a is provided so as to overlap the piezoelectric body 16b in a plan view.

[0050] As schematically shown in FIGS. 7(A) and 7(C), by providing the protective film 18a, deformation in the longitudinal direction of the diaphragm 15 can be suppressed, and stress resistance can be improved. Thereby, generation of cracks in the piezoelectric actuator 16 can be prevented even when a high load is applied. Specifically, after vibrating one trillion times with a high Pull waveform (36 V, 120 kHz), generation of cracks in the diaphragm 15 and the piezoelectric body 16b was not confirmed. Further, although the protective film 18a partially overlaps the piezoelectric body 16b in a plan view, the displacement efficiency of the piezoelectric actuator 16 (piezoelectric body 16b) is not significantly impaired, and generation of cracks can be prevented.

[0051] (Comparative Example) FIG. 8 is an explanatory view in a plan view of a liquid ejection head of a comparative example. FIG. 8(A) is a view for explaining the relationship of the arrangement positions of the respective members, and the positions of the nozzles 11 and the contact holes 22 are indicated by broken lines. FIG. 8(B) is a view for explaining the opening 23 of the second protective film (protective film 18a and insulating protective film 18b), and FIG. 8(C) is a view showing the piezoelectric body 16b and the individual liquid chamber 13. Note that illustration of the insulating protective film 18b of the second protective film provided in the vicinity of the wiring portion 21 is omitted.

[0052] In the liquid ejection head of the comparative example, as shown in FIG. 8(A), the width of the separation region in the longitudinal direction (the distance between the end of the piezoelectric body 16b and the end of the individual liquid chamber 13) A and the width of the separation region in the short hand direction (the distance between the end of the piezoelectric body 16b and the end of the individual liquid chamber 13) B have a relationship of A < B. The wiring portion 21 is provided on one end side in the longitudinal direction (the right side in the figure).

[0053] In the comparative example, in the region where the wiring portion 21 of the piezoelectric actuator 16 is not formed, the protective film 18a is not provided at the left end portion in the longitudinal direction where the width of the separation region between the outer edge of the piezoelectric body 16b and the outer edge of the individual liquid chamber 13 is narrow. Therefore, a large stress is applied to the left end portion in the longitudinal direction where the wiring portion 21 is not formed. In the liquid ejection head of the comparative example, when vibrating 1 trillion times with a high Pull waveform (36 V, 120 kHz), crack generation in the diaphragm 15 and the piezoelectric body 16b was confirmed.

[0054] (Reference Example) FIG. 9 is an explanatory view in a plan view of the liquid ejection head of the reference example. FIG. 9(A) is a view for explaining the relationship of the arrangement positions of the respective members, and the positions of the nozzles 11 and the contact holes 22 are shown by broken lines. FIG. 9(B) is a view for explaining the opening 23 of the second protective film (protective film 18a and insulating protective film 18b), and FIG. 9(C) is a view for explaining the arrangement region of the protective film 18a. Note that the illustration of the insulating protective film 18b of the second protective film provided in the vicinity of the wiring portion 21 is omitted.

[0055] In the liquid ejection head of the reference example, as shown in FIG. 9(A), the width of the separation region in the longitudinal direction (the distance between the end of the piezoelectric body 16b and the end of the individual liquid chamber 13) A and the width of the separation region in the short hand direction (the distance between the end of the piezoelectric body 16b and the end of the individual liquid chamber 13) B have a relationship of A < B. The wiring portion 21 is provided on one end side in the longitudinal direction (the right side in the figure).

[0056] In the reference example, in the region where the wiring portion 21 of the piezoelectric actuator 16 is not formed, from the left end portion in the longitudinal direction where the width of the separation region between the outer edge of the piezoelectric body 16b and the outer edge of the individual liquid chamber 13 is narrow, it is provided so as to overlap the piezoelectric body 16b in a plan view over a region including the continuous corner portion and the separation region in the short hand direction.

[0057] In the reference example, the protective film 18a is arranged to cover most of the area where the wiring portion 21 of the individual liquid chamber 13 and the piezoelectric actuator 16 of the piezoelectric body 16b is not formed, thereby suppressing longitudinal deformation of the vibration plate 15 and improving stress resistance. For example, in the liquid ejection head, no cracks were observed in the vibration plate 15 and the piezoelectric element 16b after the liquid ejection head was vibrated 1 trillion times with a high pull waveform (36V, 120kHz). However, since the piezoelectric body 16b is covered with the protective film 18a, the displacement efficiency is reduced, and liquid ejection failure may occur.

[0058] From the above results, in order to prevent cracks from occurring in the piezoelectric actuator 16 (vibration plate 15, piezoelectric body 16b) without reducing the displacement efficiency of the piezoelectric body 16b, it is preferable to provide a protective film 18a locally at the location where stress is concentrated, as in the examples shown in the first to fourth embodiments.

[0059] Next, a head module including a liquid ejection head according to the present invention, a liquid ejection head unit, and an apparatus for ejecting liquid will be described.

[0060] Fig. 10 is a cross-sectional explanatory view taken along the short side of a head module equipped with a liquid ejection head according to the present invention, and Fig. 3 is an exploded perspective explanatory view seen from the nozzle surface side of the head module. Note that Fig. 10 shows only one head portion.

[0061] The head module 100 includes a liquid ejection head (hereinafter simply referred to as "head") 101, a base member 102, a cover member 103, a heat dissipation member 104, a manifold 105, a printed circuit board (PCB) 106, and a module case 107.

[0062] The multiple heads 101 each include a nozzle plate 12 having nozzles 11 formed therein, a liquid chamber substrate (individual flow path plate) 14 having individual liquid chambers 13 communicating with the nozzles 11 formed therein, a vibration plate 15 including a piezoelectric element 40, an intermediate flow path plate 50 laminated on the vibration plate 15, and a frame member 70 laminated on the intermediate flow path plate 50 and also serving as a common flow path member.

[0063] The liquid chamber substrate (individual flow path plate) 14, together with the individual liquid chambers 13, forms supply-side individual flow paths 22 communicating with the individual liquid chambers 13 and recovery-side individual flow paths 24 communicating with the individual liquid chambers 13. The intermediate flow path plate 50 forms a supply side intermediate individual flow path 51 that communicates with the supply side individual flow path 22 through the opening 31 of the vibration plate 15, and a recovery side intermediate individual flow path 52 that communicates with the recovery side individual flow path 24 through the opening 32 of the vibration plate 15.

[0064] The frame member 70 as a common flow path member forms a supply-side common flow path 71 communicating with the supply-side intermediate individual flow path 51 and a recovery-side common flow path 72 communicating with the recovery-side intermediate individual flow path 52. The supply-side common flow path 71 communicates with a flow path 151 of the manifold 105 via a supply port 81. The manifold 105 has a supply port 181 that communicates with the internal flow path 151. The recovery-side common flow path 72 communicates with a flow path 152 of the manifold 105 via a recovery port 82. The manifold 105 has a recovery port 182 that communicates with the internal flow path 152.

[0065] The printed circuit board 106 and the piezoelectric element 160 of the head 101 are connected via a flexible wiring member 90, on which a driver IC (drive circuit) 91 is mounted.

[0066] In this embodiment, multiple heads 101 are held at intervals on a base member 102. Specifically, as shown in Fig. 11, for example, two heads 101 arranged side by side in the short direction form one set, and four sets are arranged in a staggered pattern in the long direction, forming a head module 100 with eight heads 101.

[0067] The heat dissipation member 104 is disposed opposite the plurality of heads 101 and the base member 102. Furthermore, since two heads 101 are disposed side by side in the short side direction of the heads 101, the heat dissipation member 104 is provided with through holes through which the two flexible wiring members 90 of adjacent heads 101 pass.

[0068] The module case 107 is attached to the base member 102. The module case 107 accommodates a printed circuit board 106, a manifold 105, a heat dissipation member 104, and a part of the flexible wiring member 90 including the driver IC 91 inside.

[0069] Furthermore, the port portion 80 forming the supply port 81 and recovery port 82 of the head 101 is disposed on the outer side of the heat dissipation member 104 in the longitudinal direction, and is disposed through a through hole provided in the heat dissipation member 104 .

[0070] The port portion 80 protrudes from the upper surface of the heat dissipation member 104, and the manifold 105 is disposed above this port portion 80, so that the manifold 105 is disposed with a gap from the upper surface of the heat dissipation member 104. The cover member 103 covers at least a part of the periphery of the ejection surfaces of the plurality of heads 101, and in this embodiment, the entire periphery.

[0071] The head module can be integrated with functional parts and mechanisms to form a liquid ejection unit. For example, the head module can be combined with at least one of the following components: a head tank, a carriage, a supply mechanism, a maintenance and recovery mechanism, a main scanning movement mechanism, and a liquid circulation device. Here, integration includes, for example, a case where the head module, functional parts, and mechanism are fixed to each other by fastening, bonding, engaging, etc., or a case where one is held movably relative to the other. The head module, functional parts, and mechanism may also be configured to be detachable from each other.

[0072] FIG. 12 is a plan view illustrating a main part of an example of a liquid ejection unit including a liquid ejection head according to the present invention. 12 is made up of, among the components that make up a device for discharging liquid, a housing portion made up of side plates 491A and 491B and a back plate 491C, a main scanning movement mechanism 493, a carriage 403, and a head 101. In the figure, an arrow D1 indicates the main scanning direction. It is also possible to configure a liquid discharge unit in which the above-described maintenance and recovery mechanism 420 is further attached to, for example, the side plate 491B of this liquid discharge unit 440.

[0073] Furthermore, the "liquid ejecting device" in the present invention includes a device that is equipped with a head module or a liquid ejection unit and ejects liquid by driving a liquid ejection head. The liquid ejecting device includes not only a device that can eject liquid onto an object onto which the liquid can adhere, but also a device that ejects liquid into air or liquid. This "liquid ejecting device" can also include means for feeding, transporting, and discharging items onto which liquid can be attached, as well as pre-processing devices and post-processing devices.

[0074] FIG. 13 is a schematic explanatory diagram showing an example of a liquid ejection device equipped with a liquid ejection head according to the present invention. The printing device 500, which is a device for ejecting this liquid, includes an input means 501 for feeding a continuous body 510, a guide and conveying means 503 for guiding and conveying the continuous body 510, such as continuous paper or sheet material, fed from the input means 501 to a printing means 505, the printing means 505 for ejecting liquid onto the continuous body 510 to print and form an image, a drying means 507 for drying the continuous body 510, and an ejection means 509 for ejecting the continuous body 510.

[0075] The continuous body 510 is fed from the original winding roller 511 of the carrying-in means 501 , guided and conveyed by the rollers of the carrying-in means 501 , the guide and conveying means 503 , the drying means 507 and the carrying-out means 509 , and wound up by the winding roller 591 of the carrying-out means 509 .

[0076] In the printing means 505, this continuum 510 is transported on a transport guide member 559 opposite the head unit 550 and head unit 555, an image is formed by liquid ejected from the head unit 550, and post-processing is performed by processing liquid ejected from the head unit 555.

[0077] The "liquid ejection device" may be a device in which a liquid ejection head and an object onto which liquid can be attached move relatively, but is not limited to this. Specific examples include a serial type device in which the liquid ejection head moves, and a line type device in which the liquid ejection head does not move. "Something to which a liquid can adhere" means something to which a liquid can adhere at least temporarily, something to which the liquid can adhere and stick, something to which the liquid can adhere and penetrate, etc. Furthermore, the material of "something to which a liquid can adhere" may be any material to which the liquid can adhere even temporarily, such as paper, thread, fiber, fabric, leather, metal, plastic, glass, wood, ceramics, etc. The liquid to be ejected is not particularly limited as long as it has a viscosity and surface tension that allows it to be ejected from the head, but it is preferable that the viscosity of the liquid be 30 mPa·s or less at room temperature and normal pressure, or by heating or cooling.

[0078] For example, aspects of the present invention are as follows. <1> a liquid ejection head comprising: a nozzle plate having nozzles for ejecting liquid; a liquid chamber substrate laminated on the nozzle plate and forming individual liquid chambers connected to the nozzles; a piezoelectric actuator having a piezoelectric body that pressurizes the individual liquid chambers via a vibration plate that forms part of the individual liquid chambers; a wiring section for applying a drive voltage to drive the piezoelectric body; and a protective film that covers part of the area of ​​the piezoelectric actuator where the wiring section is not formed, wherein, in a planar view seen from the stacking direction of the piezoelectric actuator, the piezoelectric body is located inside the individual liquid chamber, the width of the separation area between the outer edge of the piezoelectric body and the outer edge of the individual liquid chamber varies in the longitudinal direction, lateral direction and corners, and the protective film is arranged to overlap at least a part of the separation area at one end side in the longitudinal direction or lateral direction in which the width of the separation area is narrower. <2> In a plan view of the piezoelectric actuator from the stacking direction, the protective film is provided so as to overlap one side of the separation region in a narrower width direction and a region including corners continuous with both ends of the one side. <1> 1. The liquid ejection head according to claim 1. <3> The piezoelectric actuator is characterized in that the protective film does not overlap the piezoelectric body in a plan view seen from the stacking direction of the piezoelectric actuator. <1> or <2> 1. The liquid ejection head according to claim 1. <4> The piezoelectric actuator is characterized in that the protective film overlaps the piezoelectric body in a plan view seen from the stacking direction of the piezoelectric actuator. <1> or <2> 1. The liquid ejection head according to claim 1. <5> In a plan view of the piezoelectric actuator seen from the stacking direction, the direction in which the width of the separation region is narrow is the longitudinal direction, and the wiring portion is provided on one end side in the longitudinal direction. <1> from <4> 1. The liquid ejection head according to claim 1, wherein the liquid ejection head is a liquid ejection head having a diameter of 100 mm or less. <6> In a plan view seen from the stacking direction of the piezoelectric actuator, the nozzle is located at a position shifted from the center of the individual liquid chamber toward one end where the wiring portion is not formed. <5> 1. The liquid ejection head according to claim 1. <7> In a plan view seen from the stacking direction of the piezoelectric actuator, the outer edges of the piezoelectric body and the outer edges of the individual liquid chambers are rectangular with rounded corners. <1> from <6> 1. The liquid ejection head according to claim 1, wherein the liquid ejection head is a liquid ejection head having a diameter of 100 mm or less. <8> The protective film has a compressive stress. <1> from <7> 1. The liquid ejection head according to claim 1, wherein the liquid ejection head is a liquid ejection head having a diameter of 100 mm or less. <9> The thickness of the protective film is thinner toward the center of the individual liquid chamber in a plan view seen from the stacking direction of the piezoelectric actuator. <1> from <8> 1. The liquid ejection head according to claim 1, wherein the liquid ejection head is a liquid ejection head having a diameter of 100 mm or less. <10> The aforementioned <1> from <9> 10. A liquid ejection unit comprising the liquid ejection head according to any one of claims 1 to 9. <11> The aforementioned <1> from <9> A liquid ejection device is characterized by comprising the liquid ejection head according to any one of the above. [Explanation of symbols]

[0079] 11 nozzles 12 Nozzle plate 13 Individual liquid chamber 14 Liquid chamber substrate 15 Vibration plate 16 Piezoelectric Actuator 16a Lower electrode 16b Piezoelectric material 16c upper electrode 17 First protective film (moisture-proof film) 18 Second protective film 18a Protective film 18b Insulating protective film 21 Wiring section 23 Opening (opening in second protective film) 100 head unit 101 Liquid ejection head (head) 160 Piezoelectric element 500 Liquid ejection device (printing device) [Prior art documents] [Patent documents]

[0080] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-171196

Claims

1. a nozzle plate having nozzles for ejecting liquid; a liquid chamber substrate that is laminated on the nozzle plate and forms individual liquid chambers that communicate with the nozzles; a piezoelectric actuator having a piezoelectric body that applies pressure to the interior of the individual liquid chamber via a vibration plate that constitutes a part of the individual liquid chamber; a wiring section for applying a driving voltage to drive the piezoelectric element; a protective film that covers a part of an area of ​​the piezoelectric actuator where the wiring portion is not formed, A liquid ejection head characterized in that, when viewed in a planar view from the stacking direction of the piezoelectric actuator, the piezoelectric body is located inside the individual liquid chamber, the width of the separation area between the outer edge of the piezoelectric body and the outer edge of the individual liquid chamber varies in the longitudinal direction, the lateral direction and at the corners, and the protective film is arranged so as to overlap at least a portion of the separation area at one end side in the longitudinal direction or the lateral direction in which the width of the separation area is narrow.

2. A liquid ejection head as described in claim 1, characterized in that, when viewed in a planar view from the stacking direction of the piezoelectric actuator, the protective film is arranged to overlap one side of the separation area in the narrower width direction and an area including corners continuous to both ends of the one side.

3. 3. The liquid ejection head according to claim 1, wherein the protective film does not overlap the piezoelectric body in a plan view seen from the stacking direction of the piezoelectric actuator.

4. 3. The liquid ejection head according to claim 1, wherein the protective film overlaps the piezoelectric element in a plan view seen from the stacking direction of the piezoelectric actuator.

5. In a plan view seen from the stacking direction of the piezoelectric actuator, the direction in which the width of the separation region is narrow is the longitudinal direction, 3. The liquid ejection head according to claim 1, wherein the wiring portion is provided on one end side in the longitudinal direction.

6. A liquid ejection head as described in claim 5, characterized in that, when viewed in a planar view from the stacking direction of the piezoelectric actuator, the nozzle is located at a position shifted toward one end side where the wiring portion is not formed relative to the center of the individual liquid chamber.

7. 3. The liquid ejection head according to claim 1, wherein, in a plan view seen from the stacking direction of the piezoelectric actuator, the outer edges of the piezoelectric body and the outer edges of the individual liquid chambers are rectangular with rounded corners.

8. 3. The liquid ejection head according to claim 1, wherein the protective film has a compressive stress.

9. 3. The liquid ejection head according to claim 1, wherein the thickness of the protective film decreases toward the center of the individual liquid chamber in a plan view seen from the stacking direction of the piezoelectric actuator.

10. A liquid ejection unit comprising the liquid ejection head according to claim 1 or 2.

11. A liquid ejection device comprising the liquid ejection head according to claim 1 or 2.

Images