Droplet dispensing head and droplet dispensing device

Abstract

To provide a droplet discharge head comprising: a piezoelectric element having a piezoelectric layer mainly formed of a KNN based complex oxide, capable of achieving preferable image quality and long service life, by considering characteristics of the piezoelectric layer and a pass number in multi pass recording.SOLUTION: A droplet discharge head for executing multi pass recording for completing recording of dot in one main scanning line, by main scanning of n times, when n is an integer of 2 or greater, comprises: a plurality of nozzles which discharges as droplets, liquid; a pressure chamber formation substrate in which a pressure chamber is formed and the pressure chamber is communicated with the nozzle; first and second electrodes; a piezoelectric element which has a piezoelectric layer, the piezoelectric layer being mainly formed of a perovskite type complex oxide including, K, Na, Nb; and a vibration plate which forms a part of the wall face of the pressure chamber, and vibrates by driving of the piezoelectric element. The pass number n in multi pass recording, a piezoelectric constant d31[m / v] of the piezoelectric element, and a ratio x of a molar fraction of Na to a total value of molar fractions of K and Na in the piezoelectric layer, satisfy a relationship expressed by a formula (1).SELECTED DRAWING: Figure 7

Description

[Technical Field]

[0001] This disclosure relates to a droplet dispensing head and a droplet dispensing device. [Background technology]

[0002] Regarding droplet dispensing heads, Patent Document 1 discloses a head that includes a piezoelectric element made primarily of lead zirconate titanate (PZT) and dispenses liquid as droplets. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2014-58169 [Overview of the project] [Problems that the invention aims to solve]

[0004] In a piezo-type droplet ejection head, from the perspective of reducing environmental impact, a lead (Pb)-free piezoelectric material with a reduced Pb content to replace PZT is desired. Among such lead-free piezoelectric materials, potassium sodium niobate (KNN)-based materials are known to have relatively excellent piezoelectric properties. Here, KNN-based materials generally have a smaller displacement amount when a voltage is applied compared with PZT. Therefore, when using a KNN-based material as the piezoelectric material of a droplet ejection head, the ejection amount of droplets per application of the same voltage is small. Further, KNN-based materials have a higher temperature dependence of the displacement amount compared with PZT and are likely to generate leakage current due to a temperature rise. Therefore, in order to achieve a desired total ejection amount, for example, simply increasing the driving frequency may cause deterioration of image quality and shortening of the lifespan of the droplet ejection head due to the temperature rise caused by the increase in the driving frequency. Therefore, when using a KNN-based material as the piezoelectric material of a droplet ejection head, it is conceivable to perform so-called multi-pass recording in which recording of dots on one main scanning line is completed by a plurality of main scans to reduce the driving frequency. However, in this case, realizing good image quality and a long lifespan of the droplet ejection head in consideration of the characteristics of the KNN-based material and the number of main scan passes has not been sufficiently studied.

Means for Solving the Problem

[0005] According to a first aspect of the present disclosure, during an interval of sub-scanning in which a medium is conveyed in a sub-scanning direction intersecting a main scanning direction, main scanning is performed in which the medium is moved in the main scanning direction to discharge droplets onto a main scanning line, thereby forming dots on the medium. When n is an integer of 2 or more, a droplet discharge head is provided for performing multi-pass recording in which recording of the dots on the main scanning line is completed by the n main scans. This droplet discharge head includes a plurality of nozzles that discharge a liquid as the droplets, a pressure chamber forming substrate in which a pressure chamber communicating with the nozzles is formed, a piezoelectric element, and a diaphragm that is disposed between the pressure chamber forming substrate and the piezoelectric element, forms a part of the wall surface of the pressure chamber, and vibrates by driving of the piezoelectric element. The piezoelectric element has a first electrode, a second electrode, and a piezoelectric layer mainly composed of a perovskite-type composite oxide containing potassium, sodium, and niobium, which is disposed between the first electrode and the second electrode. In the multi-pass recording, the number of passes n, the piezoelectric constant d 31 [m / v], and the ratio x of the molar fraction of sodium to the total value of the molar fractions of potassium and sodium in the piezoelectric layer satisfy the relationship represented by the following formula (1). 8.0×10 -8 ≦n·d 31 ·x≦9.6×10 -6 [[ID=Io]]…(1)

[0006] According to a second aspect of the present disclosure, a droplet discharge device is provided. This droplet discharge device includes the droplet discharge head of the above aspect, a conveyance mechanism that conveys the medium in the sub-scanning direction, a head movement mechanism that supports the droplet discharge head and moves the droplet discharge head in the main scanning direction, and a control unit that controls the droplet discharge head, the conveyance mechanism, and the head movement mechanism and executes the multi-pass recording.

Brief Description of the Drawings

[0007] [Figure 1] An explanatory diagram showing a schematic configuration of a droplet discharge device. [Figure 2] An explanatory diagram showing an example of the configuration of a nozzle row. [Figure 3] An explanatory diagram showing an example of recording dots onto media. [Figure 4] An exploded perspective view showing the configuration of the droplet dispensing head. [Figure 5] A schematic diagram showing cross-sections of the main part of the droplet dispensing head along the Y and Z directions. [Figure 6] Figure 5 shows a cross-sectional view of the pressure chamber and piezoelectric element from point VI to VI. [Figure 7] Figure 1 shows the results of the performance evaluation test of the droplet dispensing head. [Figure 8] Figure 2 shows the results of the performance evaluation test of the droplet dispensing head. [Figure 9] Figure 3 shows the results of the performance evaluation test of the droplet dispensing head. [Modes for carrying out the invention]

[0008] A. First Embodiment: Figure 1 is an explanatory diagram showing the schematic configuration of the droplet dispensing device 100 as a first embodiment. In Figure 1, arrows are shown along the mutually orthogonal X, Y, and Z directions. The X, Y, and Z directions are directions along the three mutually orthogonal spatial axes, the X, Y, and Z axes, and each includes both the direction along one side of the X, Y, and Z axes and the opposite direction. Specifically, the positive directions along the X, Y, and Z axes are the +X, +Y, and +Z directions, respectively, and the negative directions along the X, Y, and Z axes are the -X, -Y, and -Z directions, respectively. In Figure 1, the X and Y axes are axes along the horizontal plane, and the Z axis is an axis along the vertical line. Therefore, in this embodiment, the -Z direction is the direction of gravity. In other figures as well, arrows along the X, Y, and Z directions are shown as appropriate. The X, Y, and Z directions in Figure 1 and the X, Y, and Z directions in the other figures represent the same directions. Furthermore, in this specification, orthogonal includes the range of 90° ± 10°.

[0009] The droplet dispensing device 100 dispenses liquid as droplets. "Droplet" refers to the state of the liquid dispensed from the droplet dispensing device 100, and includes granular, teardrop-shaped, and thread-like droplets. Furthermore, "liquid" here refers to any material that the droplet dispensing device 100 can consume. For example, "liquid" can be any material in its liquid phase, including highly viscous or low viscous liquid materials, as well as liquid materials such as sols, gel water, other inorganic solvents, organic solvents, solutions, liquid resins, and liquid metals such as metal melts. In addition to liquids as a state of matter, "liquid" also includes functional material particles, such as pigments and metal particles, that are dissolved, dispersed, or mixed in a solvent. Typical examples of liquids include ink and liquid crystals. Here, "ink" includes general water-based inks and oil-based inks, as well as various liquid compositions such as gel inks and hot-melt inks.

[0010] The droplet ejection device 100 in this embodiment is an inkjet printer that prints an image on media P by ejecting ink as droplets. The droplet ejection device 100 ejects droplets onto media P, such as paper, based on print data indicating the on / off state of dots on media P, and prints an image on media P by forming dots at various positions on media P. In addition to paper, media P can be any material that can hold liquid, such as plastic, film, fiber, fabric, leather, metal, glass, wood, or ceramics.

[0011] The droplet ejection device 100 comprises a droplet ejection head 200, a head moving mechanism 41, a transport mechanism 50, an ink cartridge 80, and a control unit 110.

[0012] The control unit 110 is comprised of a computer with one or more processors, a main memory, and an input / output interface for inputting and outputting signals to and from the outside. The control unit 110 controls the droplet ejection head 200, the head movement mechanism 41, and the transport mechanism 50 according to the print data, thereby ejecting droplets from the droplet ejection head 200 onto the media P and printing an image onto the media P. In other words, the control unit 110 controls the droplet ejection operation of the droplet ejection head 200.

[0013] The head movement mechanism 41 supports the droplet ejection head 200 and moves the supported droplet ejection head 200 along the main scanning direction. The transport mechanism 50 transports the media P along the sub-scanning direction. In this embodiment, the main scanning direction is along the Y direction and includes both one side of that direction and its opposite direction. The sub-scanning direction is along the X direction and includes both one side of that direction and its opposite direction. In other words, in this embodiment, the main scanning direction and the sub-scanning direction are orthogonal to each other, but in other embodiments, the main scanning direction and the sub-scanning direction do not have to be orthogonal to each other.

[0014] The head movement mechanism 41 in this embodiment includes a carriage 42 that holds the droplet dispensing head 200, and a drive motor 46 and a drive belt 47 for driving the carriage 42. The carriage 42 reciprocates along the main scanning direction, that is, along the Y direction, by the driving force transmitted from the drive motor 46 to the carriage 42 via the drive belt 47. As a result, the droplet dispensing head 200 reciprocates along the Y direction together with the carriage 42.

[0015] The transport mechanism 50 in this embodiment includes a transport motor 51 and rollers (not shown). The transport mechanism 50 transports the media P along the sub-scanning direction, that is, along the X direction, by driving the rollers with the transport motor 51. More specifically, in this embodiment, the transport mechanism 50 transports the media P in the +X direction. Hereinafter, the direction in which the media P is transported by the transport mechanism 50 will also be referred to as the transport direction. In other words, in this embodiment, the transport direction is the +X direction.

[0016] The ink cartridge 80 stores ink as a liquid that is supplied to the droplet ejection head 200. In this embodiment, four ink cartridges 80 are configured to be detachably attached to the carriage 42, and four different inks of different colors are stored as liquids in the four ink cartridges 80. The ink cartridges 80 may also be attached to the main body of the droplet ejection device 100, for example, without being attached to the carriage 42. In other embodiments, the mechanism for storing ink may be, for example, an ink tank or a liquid pack in the shape of a bag made of a flexible film, and the type and number of mechanisms for storing ink, as well as the type and number of inks stored, are not particularly limited.

[0017] The droplet ejection head 200 is electrically connected to the control unit 110 via a flexible cable 48. The droplet ejection head 200 moves back and forth in the main scanning direction relative to the media P being transported along the sub-scanning direction, ejecting ink supplied from the ink cartridge 80 in droplet form from nozzles 211 that constitute the nozzle row 212 (described later) onto the main scanning line. Hereinafter, this movement of the droplet ejection head 200 relative to the media P in the main scanning direction and ejection of droplets onto the main scanning line will also be referred to as main scanning. Transporting the media P along the sub-scanning direction will also be referred to as sub-scanning. More specifically, under the control of the control unit 110, the droplet ejection head 200 performs main scanning between sub-scans to form dots on the media P and record an image on the media P. The droplet ejection device 100 may include two or more droplet ejection heads 200.

[0018] Figure 2 is an explanatory diagram showing an example of the configuration of the nozzle row 212 of the droplet ejection head 200. Figure 2 schematically shows the main scanning direction dm and the sub-scanning direction ds. In the example of Figure 2, the droplet ejection head 200 has one nozzle row 212 for each type of ink. More specifically, the four nozzle rows 212a, 212b, 212c, and 212d shown in Figure 2 correspond to black, cyan, magenta, and yellow inks, respectively. Each nozzle row 212 has a plurality of nozzles 211 arranged along the sub-scanning direction ds with a constant nozzle pitch dp. The plurality of nozzles 211 that constitute one nozzle row 212 are collectively called a "nozzle set". In this embodiment, the nozzle pitch dp is equal to the pixel pitch on the media P, but in other embodiments, the nozzle pitch dp may be an integer multiple of the pixel pitch on the media P. In this case, so-called interlaced recording is performed. Interlaced recording refers to the operation of recording dots in subsequent passes to fill in the gaps between dots recorded in the main scan lines in the first pass. In other embodiments, the number of nozzle rows 212 may be 1 to 3, or 5 or more.

[0019] Figure 3 is an explanatory diagram illustrating an example of dot recording on media P. In addition to the main scanning direction dm and sub-scanning direction ds, similar to Figure 2, Figure 3 schematically shows the transport direction dc. Figure 3 shows an example in which the formation of individual dots on a main scanning line is completed in two main scans. When n is an integer of 2 or more, this dot recording operation in which the formation of individual dots on a main scanning line is completed in n main scans is called "multi-pass recording". In multi-pass recording, it can also be said that the formation of individual dots on a main scanning line is completed in n main scan passes, and the number of main scan passes in this case is also called the number of passes n. In Figure 3, nozzle position NP1 indicates the position of the nozzle row 212 in the first main scan of the two main scans used to form individual dots on a main scanning line, and nozzle position NP2 indicates the position of the nozzle row 212 in the second main scan. In this embodiment, the main scanning operation is performed bidirectionally; for example, odd-numbered main scan passes are executed on the outbound path, and even-numbered main scan passes are executed on the return path. Multipath recording is also known as "overlap recording."

[0020] In one main scan, each ink dot can be recorded on an area with a width of head height Hh as shown in Figure 2. "Head height Hh" refers to the length of the sub-scanning direction ds, which is expressed as the product of the number of nozzles M and the nozzle pitch dp. The number of nozzles M refers to the number of nozzles 211 that make up one nozzle row 212. In the example in Figure 3, with each main scan, the position of the nozzle row 212 moves in the sub-scanning direction ds by a distance equivalent to 1 / n of the head height Hh. The distance Hh / n is also called the "sub-scan feed amount". More specifically, in the example in Figure 3, the sub-scan feed amount is Hh / 2. Note that in Figure 3, for illustrative purposes, the nozzle row 212 is shown moving in the opposite direction to the transport direction dc relative to the stopped media P during the sub-scan; however, in reality, the media P is transported in the transport direction dc while the nozzle row 212 is stopped. Furthermore, the part of the nozzle row 212 that reaches the media P first during sub-scanning is called the "tip" of the nozzle row 212, and the opposite side is called the "rear end" of the nozzle row 212. The total length of the nozzle row 212 can be virtually divided into n nozzle groups, from the tip side to the rear end side. In other words, in the example in Figure 3, the total length of the nozzle row 212 can be virtually divided into a first nozzle group Nz1 and a second nozzle group Nz2.

[0021] As shown in Figure 3, the three regions Q1 to Q3 on media P are regions where dot recording is performed by the first nozzle group Nz1 and the second nozzle group Nz2 of the nozzle row 212, respectively, during a main scan with 2 passes. Of these, in region Q1, the uppermost region in Figure 3, dots are recorded using the first nozzle group Nz1 in the first main scan pass. At this time, dots are not recorded at all pixel positions in region Q1 in a single pass; dot recording is performed according to a preset recording ratio. Subsequently, in region Q1, dots are recorded using the second nozzle group Nz2 in the second main scan pass. With these two passes, dot recording at all pixel positions in region Q1 is completed. Similarly, dot recording is completed in two passes each for the other regions Q2 and Q3, and for other regions below region Q3 in Figure 3. The length of these regions Q1 to Q3 in the sub-scan direction ds is Hh / n. These regions Q1 to Q3 are also called "band regions". In this specification, "dot recording" means "the act of forming or not forming dots." In other words, for example, the state of "dot recording being completed" on a certain main scan line means that at all pixel positions on that main scan line, either dot formation or dot non-formation has been performed.

[0022] Figure 4 is an exploded perspective view showing the configuration of the droplet dispensing head 200 in this embodiment. The droplet dispensing head 200 in this embodiment is constructed by stacking a nozzle plate 210, a pressure chamber forming substrate 220, a piezoelectric unit 230, and a sealing unit 250 in the Z direction. A drive circuit 90 is provided on the +Z direction side of the sealing unit 250.

[0023] In this embodiment, the nozzle plate 210 is a thin plate-shaped member, with its plate surface arranged along the X and Y directions. Multiple nozzles 211 are formed on the nozzle plate 210, arranged in the X direction. The droplet dispensing head 200 ejects liquid as droplets from these nozzles 211. In this embodiment, the nozzle plate 210 is made of stainless steel (SUS). However, the nozzle plate 210 may also be made of other types of metals, such as nickel (Ni) alloy, or resin materials such as polyimide or dry film resist, or inorganic materials such as silicon (Si) single crystal substrates or glass ceramics.

[0024] The pressure chamber forming substrate 220 is a plate-shaped member that demarcates flow paths such as the pressure chamber 221. The pressure chamber forming substrate 220 is joined to the +Z direction surface of the nozzle plate 210, for example, via an adhesive or heat-sealable film, or directly. The pressure chamber forming substrate 220 has holes HL that penetrate the pressure chamber forming substrate 220 in the Z direction for forming the pressure chamber 221, the ink supply passage 223, and the communication section 225. In this embodiment, the pressure chamber forming substrate 220 is formed from a Si single crystal substrate. The pressure chamber forming substrate 220 may be a substrate formed from, for example, another material mainly composed of Si, or from other ceramic materials, glass materials, etc. In this specification, "main component" refers to a component that is contained in a certain material or member in a proportion of 50% by mass or more, preferably 80% by mass or more.

[0025] In this embodiment, the multiple pressure chambers 221 are formed to be arranged in a line along the X direction. By laminating the pressure chamber forming substrate 220 onto the nozzle plate 210, each of the multiple pressure chambers 221 communicates with each of the multiple nozzles 211. Each pressure chamber 221 has a substantially parallelogram shape with the Y direction as its longitudinal direction when viewed from the Z direction. Liquid ink flows through the pressure chambers 221.

[0026] The communication section 225 is a common cavity shared by each of the multiple pressure chambers 221, and communicates with the multiple pressure chambers 221, etc., to form a common liquid chamber, which will be described later. The communication section 225 communicates with each of the multiple pressure chambers 221 via the ink supply passage 223. The ink supply passage 223 has a portion that is narrower than the pressure chamber 221, suppressing pressure loss generated in the pressure chambers 221 and the occurrence of so-called crosstalk, which is the phenomenon in which the pressure generated in each pressure chamber 221 is propagated to other pressure chambers 221 via the common liquid chamber.

[0027] The piezoelectric unit 230 is constructed by stacking a diaphragm 231 and a piezoelectric element 240 on a pressure chamber forming substrate 220. The piezoelectric unit 230 vibrates the diaphragm 231, which is provided between the piezoelectric element 240 and the pressure chamber forming substrate 220, by driving the piezoelectric element 240, thereby changing the volume of the pressure chamber 221. Details of the piezoelectric unit 230 will be described later. The piezoelectric unit 230 is also sometimes called a piezoelectric device or actuator.

[0028] The sealing portion 250 is bonded to the piezoelectric portion 230 via an adhesive. The sealing portion 250 has a piezoelectric element holding portion 251, which is a space for holding the piezoelectric element 240, and a manifold portion 252 that communicates with the communication portion 225 of the pressure chamber forming substrate 220 to form a common liquid chamber. In this embodiment, the sealing portion 250 is formed using a Si single crystal substrate. The sealing portion 250 may be formed from other ceramic materials, glass materials, etc. In this case, it is preferable that the sealing portion 250 is formed from a material having a thermal expansion coefficient approximately the same as that of the pressure chamber forming substrate 220.

[0029] The drive circuit 90 supplies a drive signal to the piezoelectric element 240 to drive the piezoelectric element 240. For example, a circuit board or a semiconductor integrated circuit (IC) can be used as the drive circuit 90. The drive circuit 90 and the piezoelectric element 240 are electrically connected via lead electrodes 295 and electrical wiring (not shown). Furthermore, the drive circuit 90 and the control unit 110 are electrically connected via electrical wiring (not shown).

[0030] Figure 5 is a schematic diagram showing cross-sections of the main part of the droplet ejection head 200 along the Y and Z directions. As shown in Figure 5, the stacking of the above-mentioned components connects the manifold section 252 and the communication section 225, forming a manifold 293 which is a common liquid chamber for each of the multiple pressure chambers 221. Furthermore, the nozzle 211, pressure chambers 221, ink supply passage 223, and manifold 293 are connected, forming an ink flow path. The droplet ejection head 200 changes the volume of the pressure chamber 221 using the piezoelectric section 230, thereby ejecting the liquid supplied to the pressure chamber 221 via the aforementioned flow path as droplets from the nozzle 211. The manifold 293 is sometimes also called a common liquid chamber or reservoir.

[0031] Figure 6 is a cross-sectional view of the pressure chamber 221 and piezoelectric section 230 in Figure 5, taken from line VI-VI. As described above, the piezoelectric section 230 comprises a diaphragm 231 and a piezoelectric element 240. As shown in Figures 5 and 6, the piezoelectric element 240 has a piezoelectric layer 260, a plurality of first electrodes 270, and a second electrode 280.

[0032] As shown in Figures 5 and 6, the diaphragm 231, the piezoelectric layer 260, the first electrode 270, and the second electrode 280 are stacked along the thickness direction of the piezoelectric layer 260, more specifically along the Z direction. The first electrode 270 is positioned between the piezoelectric layer 260 and the diaphragm 231. The piezoelectric layer 260 is positioned between the first electrode 270 and the second electrode 280. In other words, in this embodiment, the diaphragm 231, the first electrode 270, the piezoelectric layer 260, and the second electrode 280 are stacked in this order along the Z direction. Generally, the droplet dispensing head 200 is used with the nozzle 211 positioned vertically downward, as in this embodiment. In this case, the first electrode 270 is also called the lower electrode, and the second electrode 280 is also called the upper electrode. In other embodiments, for example, the nozzle plate 210 may function as the diaphragm.

[0033] As described above, the diaphragm 231 is configured to vibrate by the driving of the piezoelectric element 240. As shown in Figures 5 and 6, the diaphragm 231 in this embodiment has an elastic layer 232 and an insulating layer 233. The elastic layer 232 is located on the pressure chamber forming substrate 220 and on the pressure chamber 221, and the insulating layer 233 is located on the elastic layer 232. In this embodiment, the elastic layer 232 is formed as an elastic film mainly composed of silica (SiO2), and the insulating layer 233 is formed as an insulating film mainly composed of zirconia (ZrO2). The insulating layer 233 is also called a protective layer.

[0034] In this embodiment, the first electrode 270 is provided individually for each of the multiple pressure chambers 221. The second electrode 280 is provided in common for all of the multiple pressure chambers 221. Electrodes provided individually for each of the multiple pressure chambers 221 are sometimes called individual electrodes, and electrodes provided in common for all of them are sometimes called common electrodes. That is, in this embodiment, the lower electrode, the first electrode 270, is an individual electrode, and the upper electrode, the second electrode 280, is a common electrode. As shown in Figures 5 and 6, in this embodiment, each first electrode 270 is arranged in a line along the X direction, with its longitudinal direction aligned with the Y direction. The second electrode 280 is provided continuously in the X and Y directions across the multiple pressure chambers 221, covering the piezoelectric layer 260 from above.

[0035] The first electrode 270 and the second electrode 280 are formed from various metals such as platinum (Pt), iridium (Ir), titanium (Ti), tungsten (W), and tantalum (Ta), or conductive metal oxides such as lanthanum nickelate (LaNiO3). The first electrode 270 and the second electrode 280 may be composed of multiple layers made of the above-mentioned various metals or conductive metal oxides. Furthermore, the first electrode 270 and the second electrode 280 may be formed from different materials.

[0036] In other embodiments, an adhesion layer may be provided between the first electrode 270 and the diaphragm 231 to improve the adhesion between the first electrode 270 and the diaphragm 231. The adhesion layer may be formed from, for example, titanium (Ti) or titanium oxide.

[0037] As shown in Figure 6, the piezoelectric layer 260 has a first active part Ac and a second active part NAc. In this embodiment, the first active part Ac corresponds to the portion of the piezoelectric layer 260 that overlaps with both the first electrode 270 and the second electrode 280 when viewed along the Z direction. The second active part NAc corresponds to the portion of the piezoelectric layer 260 that does not overlap with either the first electrode 270 or the second electrode 280, or both, when viewed along the Z direction.

[0038] The piezoelectric element 240 is driven by the application of a voltage to the piezoelectric layer 260 via the first electrode 270 and the second electrode 280. More specifically, the piezoelectric element 240 is displaced by the piezoelectric strain generated in the first active part Ac of the piezoelectric layer 260 when a voltage is applied to the piezoelectric layer 260. This displacement causes the diaphragm 231 to vibrate, changing the volume of the pressure chamber 221. The piezoelectric strain generated in the second active part NAc of the piezoelectric layer 260 when a voltage is applied to the piezoelectric layer 260 is smaller than the piezoelectric strain generated in the first active part Ac of the piezoelectric layer 260 when a voltage is applied to the piezoelectric layer 260.

[0039] The piezoelectric layer 260 is mainly composed of a so-called potassium sodium niobate (KNN) composite oxide. A KNN composite oxide refers to a perovskite-type composite oxide represented by the general formula ABO3, which contains potassium (K), sodium (Na), and niobium (Nb). The KNN oxide is represented by the following formula (c1). (K 1-X Na X )NbO3…(c1)

[0040] KNN-based composite oxides are lead-free piezoelectric materials with reduced lead (Pb) content, resulting in excellent biocompatibility and low environmental impact. Furthermore, KNN-based composite oxides exhibit superior piezoelectric properties among lead-free piezoelectric materials, making them advantageous for improving various properties. In addition, KNN-based composite oxides have a relatively high Curie temperature compared to other lead-free piezoelectric materials such as BNT-BKT-BT;[(Bi,Na)TiO3]-[(Bi,K)TiO3]-[BaTiO3], and are less prone to depolarization due to temperature increases, allowing for use at high temperatures.

[0041] Furthermore, "lead-free" materials do not necessarily have to be completely Pb-free; they can be materials that contain virtually no Pb, and may, for example, contain Pb as an unavoidable component. From the viewpoint of reducing environmental impact, it is preferable that the Pb content in the piezoelectric part 230 of the droplet dispensing head 200, that is, the Pb content in the diaphragm 231 and piezoelectric element 240, be, for example, 0.1 mass% or less. This ensures that the piezoelectric part 230 has excellent biocompatibility and reduces the environmental impact of the piezoelectric part 230. Also, from a similar viewpoint, it is preferable that the piezoelectric part 230 contains virtually no bismuth (Bi).

[0042] In the above formula (c1), the Na content is preferably 10 mol% or more and 90 mol% or less relative to the total amount of metal elements constituting the A site. That is, in the above formula (1), it is preferable that 0.1 ≤ X ≤ 0.9. This results in a composite oxide having a composition advantageous for piezoelectric properties. Furthermore, the Na content is more preferably 30 mol% or more and 80 mol% or less, and even more preferably 40 mol% or more and 75 mol% or less, relative to the total amount of metal elements constituting the A site. That is, in the above formula (1), it is more preferably 0.3 ≤ X ≤ 0.8, and even more preferably 0.4 ≤ X ≤ 0.75. This results in a composite oxide having a composition even more advantageous for piezoelectric properties.

[0043] Furthermore, the alkali metals at the A site of KNN, namely K and Na, may be added in excess or in deficiency relative to the stoichiometric composition. Therefore, the composite oxide in this embodiment can also be represented by the following formula (c2). (K M(1-X) Na MX )NbO3…(c2)

[0044] In the above formula (c2), M represents the amount of alkali metal that is added in excess or deficient relative to the stoichiometric composition. For example, if M = 1.1, it means that when the amounts of K and Na in the stoichiometric composition are set to 100 mol%, a total of 110 mol% of K and Na are included. If A = 0.9, it means that when the amounts of K and Na in the stoichiometric composition are set to 100 mol%, a total of 90 mol% of K and Na are included. Note that if the alkali metal at site A is neither in excess nor deficient relative to the stoichiometric composition, then A = 1.0. From the viewpoint of improving the properties of the piezoelectric layer 260, it is preferable that 0.85 ≤ A ≤ 1.20, more preferable that 0.90 ≤ A ≤ 1.15, and even more preferable that 0.95 ≤ A ≤ 1.10.

[0045] The piezoelectric material constituting the piezoelectric layer 260 may be any KNN-based composite oxide and is not limited to the composition represented by formula (1) above. For example, the A site and B site of KNN may contain other metal elements (additives) different from potassium, sodium, and niobium. Examples of such additives include manganese (Mn), lithium (Li), barium (Ba), calcium (Ca), strontium (Sr), zirconium (Zr), titanium (Ti), bismuth (Bi), tantalum (Ta), antimony (Sb), iron (Fe), cobalt (Co), silver (Ag), magnesium (Mg), zinc (Zn), and copper (Cu). The piezoelectric material may contain one of these other metal elements or two or more. The amount of such additives is preferably 20% by mass or less, more preferably 15% by mass or less, and even more preferably 10% by mass or less, relative to the total amount of the main constituent elements. The reason for this is that while the addition of additives improves various properties of the piezoelectric layer 260, making it easier to diversify its structure and function, fewer additives allow the piezoelectric layer 260 to exhibit properties derived from KNN more easily. Furthermore, even when these additives are included, it is preferable that the piezoelectric layer 260 be configured to have an ABO3 type perovskite structure.

[0046] The piezoelectric layer 260 preferably contains Cu as an additive. This suppresses droplet ejection defects in the droplet ejection head 200. Furthermore, the piezoelectric layer 260 preferably contains Mn as an additive. This suppresses the generation of leakage current in the piezoelectric element 240. As a result, heat generation in the piezoelectric element 240 can be suppressed, and the lifespan of the piezoelectric element 240 can be extended.

[0047] In this embodiment, the piezoelectric layer 260 is constructed as a polycrystalline body of a KNN-based composite oxide, consisting of multiple single crystals. Compared to the case where the piezoelectric layer 260 is constructed as, for example, a single crystal, when stress is generated in the piezoelectric element 240, the stress within the plane of the piezoelectric element 240 is more easily dispersed and uniform, making stress fracture of the piezoelectric element 240 less likely and improving reliability.

[0048] When the piezoelectric layer 260 is constructed as a polycrystalline material, the various additives described above may be contained within the grain boundaries of the piezoelectric layer 260. In particular, it is preferable that Mn is contained within the grain boundaries of the piezoelectric layer 260, for example, in the form of manganese oxide. This allows for the filling of vacancies at the grain boundaries in the piezoelectric layer 260, and effectively suppresses leakage current when a voltage is applied to the piezoelectric element 240.

[0049] Preferably, the average grain size of the crystal grains in the piezoelectric layer 260 is 0.15 μm or more and 3 μm or less. This allows for a reduction in the piezoelectric properties of the piezoelectric layer 260 due to excessively small crystal grains, as the average grain size is 0.15 μm or more. Therefore, the piezoelectric properties can be further improved. Furthermore, because the average grain size is 3 μm or less, the occurrence of cracks in the piezoelectric layer 260 can be further suppressed. The average grain size of the crystal grains can be determined from a scanning electron microscope (SEM) image of the piezoelectric layer 260. More specifically, the average grain size of the crystal grains is calculated by measuring the grain size of, for example, 100 or more crystal grains in an SEM image of the piezoelectric layer 260 at the same magnification, and calculating the arithmetic mean of the measured grain sizes. In other embodiments, the average grain size of the crystal grains may be, for example, less than 0.15 μm or greater than 3 μm.

[0050] Furthermore, KNN may be a mixed crystal with other composite oxides different from KNN that have an ABO3-type perovskite structure. In other words, in this specification, "perovskite-type composite oxide containing K, Na, and Nb" includes piezoelectric materials represented as a mixed crystal containing a composite oxide with an ABO3-type perovskite structure containing K, Na, and Nb, and other composite oxides having an ABO3-type perovskite structure. The other composite oxide is not particularly limited, but is preferably a lead-free piezoelectric material so that the piezoelectric layer 260 can be configured as a lead-free piezoelectric material. It is also preferably a composite oxide that is substantially free of bismuth (Bi).

[0051] Piezoelectric materials include materials with a composition in which some elements are missing, materials with a composition in which some elements are in excess, and materials with a composition in which some elements are substituted with other elements. As long as the basic properties of the piezoelectric layer 260 remain unchanged, materials that deviate from the stoichiometric composition due to deficiencies or excesses, and materials in which some elements are substituted with other elements, are also included in the piezoelectric materials according to this embodiment.

[0052] In the piezoelectric element 240, it is preferable that the thickness of the elastic layer 232 be 0.1 μm or more and 2.0 μm or less, the thickness of the insulating layer 233 be 0.01 μm or more and 1.0 μm or less, the thickness of the piezoelectric layer 260 be 0.1 μm or more and 5.0 μm or less, the thickness of the first electrode 270 be 0.01 μm or more and 1.0 μm or less, and the thickness of the second electrode 280 be 0.01 μm or more and 1.0 μm or less. Note that the thicknesses of these elements are examples and can be changed without altering the gist of this disclosure.

[0053] In this embodiment, when manufacturing the piezoelectric part 230, first, a diaphragm 231 is prepared. The elastic layer 232 of the diaphragm 231 is formed on the pressure chamber forming substrate 220 by thermal oxidation of a Si substrate, for example, the pressure chamber forming substrate 220 in a state where holes HL have not been formed. The insulating layer 233 is formed on the elastic layer 232 by, for example, a CVD method. This forms the diaphragm 231. In other embodiments, the elastic layer 232 may be formed on the pressure chamber forming substrate 220 by, for example, a CVD method. The holes HL of the pressure chamber forming substrate 220 are formed by, for example, anisotropic etching using an alkaline solution such as potassium hydroxide (KOH) after the diaphragm 231 has been formed on the pressure chamber forming substrate 220. More specifically, in this embodiment, the holes HL are formed after the piezoelectric part 230 is completed.

[0054] Next, the first electrode 270 is patterned and formed on the diaphragm 231 by sputtering, etching, or the like.

[0055] Next, a piezoelectric layer 260 is formed on the first electrode 270 or the diaphragm 231. In this embodiment, the piezoelectric layer 260 is formed in a thin film form by a solution method such as the MOD method or the sol-gel method. Solution methods such as the MOD method and the sol-gel method are also called wet methods or liquid-phase methods. By forming the piezoelectric layer 260 by a solution method in this way, the productivity of the piezoelectric layer 260 can be increased. In other embodiments, the piezoelectric layer 260 may be formed by a gas-phase method such as sputtering or a solid-phase method such as powder compaction.

[0056] When forming the piezoelectric layer 260 by a solution method, for example, a precursor solution containing a predetermined metal complex is first prepared. The precursor solution is a sol or solution containing metal elements that will be used as raw materials for the piezoelectric layer 260. For example, a metal complex that can form a composite oxide containing K, Na, and Nb by calcination is dissolved or dispersed in an organic solvent. When adding additives such as Cu and Mn to the piezoelectric layer 260, the precursor solution may be further mixed with a metal complex containing the additive.

[0057] Examples of metal complexes containing K include potassium 2-ethylhexanoate and potassium acetate. Examples of metal complexes containing Na include sodium 2-ethylhexanoate and sodium acetate. Examples of metal complexes containing Nb include niobium 2-ethylhexanoate and pentaethoxyniobium. When Mn is added as an additive, examples of metal complexes containing Mn include manganese 2-ethylhexanoate. When Cu is added as an additive, examples of metal complexes containing Cu include copper acetate. In this case, two or more metal complexes may be used in combination. For example, potassium 2-ethylhexanoate and potassium acetate may be used in combination as metal complexes containing K. Examples of solvents include 2-n-butoxyethanol, n-octane, or a mixture thereof. The precursor solution may contain additives that stabilize the dispersion of the metal complexes containing K, Na, and Nb. Examples of such additives include 2-ethylhexanoic acid.

[0058] After preparing the precursor solution described above, a coating step is performed to form a precursor film by coating the precursor solution onto the first electrode 270 or the diaphragm 231. In the coating step, the precursor solution is coated onto the first electrode 270 or the diaphragm 231 by, for example, a spin coating method. Next, a drying step is performed in which the precursor film is heated to a predetermined temperature, for example, 130°C to 250°C, and dried for a certain period of time. Then, a degreasing step is performed in which the dried precursor film is degreased by heating it to a predetermined degreasing temperature, for example, 300°C to 450°C. Finally, a firing step is performed in which the degreased precursor film is crystallized by heating it to a higher predetermined firing temperature, for example, 600°C to 800°C. Examples of heating devices used in the drying, degreasing, and firing steps include an RTA (Rapid Thermal Annealing) device that heats by irradiation with an infrared lamp and a hot plate. By performing the coating step to firing step described above, a piezoelectric film composed mainly of KNN and structured as a polycrystalline material is formed. Furthermore, during the calcination process, Mn contained in the precursor liquid precipitates at the grain boundaries between KNN crystals.

[0059] In this embodiment, the piezoelectric layer 260 is formed by repeatedly performing the coating process and the firing process multiple times to form multiple piezoelectric films. In this embodiment, the portion of the piezoelectric layer 260 formed on the first electrode 270 corresponds to the first active part Ac described above, and the portion formed on the diaphragm 231 instead of the first electrode 270 corresponds to the second active part NAc described above. In the series of processes from the coating process to the firing process, the coating process and the degreasing process may be repeated multiple times before the firing process is performed. Furthermore, the heating rate in the drying process is preferably 30°C to 350°C / sec. In the solution method, a piezoelectric layer 260 that is not pseudocubic can be realized by firing the piezoelectric film at such a heating rate. The "heating rate" here refers to the rate of change of temperature over time from the degreasing temperature to the firing temperature in the firing process.

[0060] Thereafter, a piezoelectric layer 260 composed of a plurality of piezoelectric films is patterned. As the patterning, for example, dry etching such as reactive ion etching or ion milling, or wet etching using an etching solution is performed. Thereafter, a second electrode 280 is formed on the piezoelectric layer 260, for example, in the same manner as the first electrode 270. Before and after forming the second electrode 280 on the piezoelectric layer 260, reheat treatment may be appropriately performed in a temperature range of 600°C to 800°C. By performing such reheat treatment, a good interface between the piezoelectric layer 260 and the first electrode 270 and the second electrode 280 can be formed, and the crystallinity of the piezoelectric layer 260 can be improved. The reheat treatment is also called post-annealing.

[0061] Through the above steps, a piezoelectric element 240 including a first electrode 270, a piezoelectric layer 260, and a second electrode 280, and a piezoelectric portion 230 having a diaphragm 231 are completed. In each of the above steps, for example, etching or the like may be appropriately performed for smoothing the surfaces of the respective members and adjusting the thickness.

[0062] The inventors of the present disclosure have intensively studied improving the print image quality by the droplet discharge head 200 and extending the life of the droplet discharge head 200. As a result, in the droplet discharge head 200, when the number of passes n, the piezoelectric constant d 31 [m / v], and the ratio x of Na in the piezoelectric layer 260 satisfy the relationship represented by the following formula (1), it has been found that good image quality and long life can be realized. 8.0×10 -8 ≦n·d 31 ·x≦9.6×10 -6 …(1)

[0063] More specifically, the ratio x represents the ratio of the molar fraction of Na to the total value of the molar fraction of K and the molar fraction of Na in the piezoelectric layer 260. That is, the ratio x is equivalent to X in the above formula (c1). Hereinafter, n·d 31 ·x is also represented as a parameter P1.

[0064] Furthermore, the inventors of this disclosure further state that when the piezoelectric layer 260 contains Cu, the number of passes n and the piezoelectric constant d are... 31 We found that when the ratio x and the atomic percentage y [at%] of Cu in the piezoelectric layer 260 satisfy the relationship expressed by the following formula (2), droplet ejection defects in the droplet ejection head 200 can be suppressed, and even better image quality can be achieved. Note that in the following, n·d 31 The variables x and y are also represented as the parameter P2. 8.0×10 -9 ≤n·d 31 ·x·y≦1.9×10 -5 …(2)

[0065] Furthermore, the inventors of this disclosure further state that when the piezoelectric layer 260 contains Mn, the number of passes n and the piezoelectric constant d are... 31 We found that the lifespan of the droplet ejection head 200 can be further extended when the ratio x and the atomic percentage z [at%] of Mn in the piezoelectric layer 260 satisfy the relationship expressed by the following formula (3). 31 The parameter x and z are also represented as parameter P3. 8.0×10 -9 ≤n·d 31 ·x·z≦1.9×10 -5 …(3)

[0066] To verify the effectiveness of the droplet ejection head 200 in this embodiment, multiple samples were evaluated through performance evaluation tests. More specifically, multiple samples belonging to sample group Sg1, multiple samples belonging to sample group Sg2, and multiple samples belonging to sample group Sg3 were used as samples for the performance evaluation tests. The performance evaluation tests included image quality evaluation tests and lifespan evaluation tests. In the image quality evaluation tests and lifespan evaluation tests, the image quality and lifespan of each sample were evaluated by performing multi-pass recording using each sample. Details of the image quality evaluation tests and lifespan evaluation tests will be described later.

[0067] As a sample belonging to sample group Sg1, a droplet dispensing head 200 equipped with a piezoelectric element 240 having a piezoelectric layer 260 without the aforementioned additives was used. Between samples belonging to sample group Sg1, the number of passes n and the piezoelectric constant d were as described above. 31 , and the ratio x was partially or entirely different in each case. For the samples belonging to sample group Sg2, a droplet dispensing head 200 equipped with a piezoelectric element 240 having a piezoelectric layer 260 to which Cu was added as an additive was used. Among the samples belonging to sample group Sg2, the number of passes n and the piezoelectric constant d were different. 31 The ratio x and atomic percentage y were partially or entirely different. For the samples belonging to sample group Sg3, a droplet dispensing head 200 equipped with a piezoelectric element 240 having a piezoelectric layer 260 to which Mn was added as an additive was used. Among the samples belonging to sample group Sg3, the number of passes n and the piezoelectric constant d were different. 31 The ratio x and atomic percentage z were partially or entirely different.

[0068] The piezoelectric parts 230 of the droplet dispensing head 200, as samples belonging to each sample group, were fabricated according to the procedure described above. Specifically, first, a first electrode 270 was formed on the insulating layer 233 of the diaphragm 231 by sputtering and etching. Next, a coating process was performed using a sol containing the raw materials for the piezoelectric layer 260 as a precursor liquid, followed by a drying process, a degreasing process, and a firing process to form a piezoelectric film. Subsequently, a piezoelectric layer 260 consisting of multiple piezoelectric film layers was formed by repeating the coating process and firing process. Then, a second electrode 280 was formed on the piezoelectric layer 260 in the same manner as the first electrode 270. When fabricating the piezoelectric parts 230 of the sample belonging to sample group Sg2, a precursor liquid containing Cu was used. When fabricating the piezoelectric parts 230 of the sample belonging to sample group Sg3, a precursor liquid containing Mn was used. Furthermore, the piezoelectric parts 230 of the samples belonging to each sample group were fabricated as piezoelectric parts 230 that do not contain Pb.

[0069] The ratio x of Na, the atomic percentage y of Cu, and the atomic percentage z of Mn, as described above, were adjusted by adjusting the amount of each raw material added to the precursor solution. This resulted in adjusting the ratio x in each sample to between 0.3 and 0.8, the atomic percentage y to between 0.01 and 2.50, and the atomic percentage z to between 0.01 and 2.50. The ratio x, atomic percentage y, and atomic percentage z in the completed piezoelectric element 240 were measured by EDX (Energy dispersive X-ray spectroscopy) analysis. A JEM-ARM200F manufactured by JEOL Ltd. was used for the EDX analysis.

[0070] In the image quality evaluation test, for each sample, a mixed black ink was ejected from the droplet ejection head 200 to print an image with highlights and shadows onto white printing paper. The degree of granularity in the highlights and the degree of blurring and bleeding in the shadows were visually evaluated. The print data used to print the images in the image quality evaluation test was the same for all samples. The higher the granularity in a part of the image, the stronger the roughness and unevenness perceived when viewing that part. Mixed black ink is an ink that exhibits blackness by mixing cyan, yellow, and magenta, and is also called composite black ink.

[0071] In the image quality evaluation test, an evaluation result of "A" was given if there was almost no graininess in the highlight areas and almost no blurring or smudging in the shadow areas. An evaluation result of "B" was given if either graininess in the highlight areas or blurring or smudging in the shadow areas was almost absent, and the other was slightly present. An evaluation result of "C" was given if some graininess in the highlight areas and some blurring or smudging in the shadow areas were present. An evaluation result of "D" was given if at least one of the graininess in the highlight areas or blurring or smudging in the shadow areas was significantly present.

[0072] In the life evaluation test, the piezoelectric constant d of the piezoelectric element 240 of the droplet dispensing head 200 immediately after manufacturing was measured for each sample. 31 The first piezoelectric constant representing and the piezoelectric constant d of the piezoelectric element 240 of the droplet ejection head 200 after 10,000 uses 31 The first piezoelectric constant was compared with the second piezoelectric constant, which is expressed as . The first and second piezoelectric constants were calculated based on the measurement results of the displacement due to piezoelectric strain of the strip sample. More specifically, first, a strip sample was prepared by cutting the piezoelectric element 240 into a strip shape with a length of 15 mm and a width of 4 mm when viewed along the Z direction. Next, with one end of the strip sample fixed in the longitudinal direction, piezoelectric strain was induced in the strip sample by continuously applying voltage waveforms of 0V, a positive voltage, and a sine difference voltage that becomes 0V to one electrode of the strip sample. At this time, the displacement of the end opposite the fixed end of the strip sample was measured with a laser displacement meter, and the piezoelectric constant was calculated based on the measured displacement. Note that the piezoelectric constant d in the above equations (1) to (3) is 31 For this purpose, the first piezoelectric constant was used.

[0073] In the life evaluation test, the evaluation result was "A" if the ratio of the second piezoelectric constant to the first piezoelectric constant was 0.95 or higher, "B" if it was 0.90 or higher but less than 0.95, "C" if it was 0.80 or higher but less than 0.90, and "D" if it was less than 0.80.

[0074] Furthermore, "using a certain droplet ejection head 200 10,000 times" means performing the same type of printing as described in the image quality evaluation test 10,000 times using that droplet ejection head 200. In addition, in the image quality evaluation test and the lifespan evaluation test, the number of passes n for each sample was set to any number between 2 and 70.

[0075] Figure 7 is the first figure showing the results of the performance evaluation test of the droplet dispensing head 200 in this embodiment. Figure 7 shows the performance evaluation results of the sample group Sg1 described above. As shown in Figure 7, in sample group Sg1, the parameter P1 was 8.0 × 10 -8If the value was less than 9.6 × 10⁻¹, the image quality and lifespan evaluation results were both D. Similarly, when parameter P1 was 9.6 × 10⁻¹, -6 When the value exceeded this, the evaluation results for both image quality and lifespan were both D. On the other hand, when parameter P1 was 8.0 × 10 -8 The above and 9.6 × 10 -6 In the following cases, the image quality evaluation result was B, and the lifespan evaluation result was C. That is, the number of passes was n, and the piezoelectric constant was d. 31 It was found that good image quality and long lifespan are achieved when the ratio x satisfies the relationship expressed by equation (1) above.

[0076] Figure 8 is a second figure showing the results of the performance evaluation test of the droplet dispensing head 200 in this embodiment. Figure 8 shows the performance evaluation results of the sample that satisfies the relationship of equation (1) above from the sample group Sg2. As shown in Figure 8, the parameter P2 is 8.0 × 10 -9 If the value was less than 1.9 × 10⁻¹⁰, the image quality evaluation result was B, and the lifespan evaluation result was C. Also, if the parameter P2 was 1.9 × 10⁻¹⁰, the image quality evaluation result was B. -5 When the value exceeded this, the evaluation results for both image quality and lifespan were both D. On the other hand, when parameter P2 was 8.0 × 10 -9 The above and 1.9 × 10 -5 In the following cases, the image quality evaluation result was A, and the lifespan evaluation result was C. That is, the number of passes was n, and the piezoelectric constant was d. 31 It was found that better image quality is achieved when the ratio x and atomic percentage y satisfy the relationship expressed by equation (2) above. This is thought to be due to the effect of suppressing ejection defects by adding Cu to the piezoelectric layer 260. Although not shown in the figures, the image quality and lifespan evaluation results for the samples in sample group Sg2 that did not satisfy the relationship in equation (1) above were both D.

[0077] Figure 9 is the third figure showing the results of the performance evaluation test of the droplet dispensing head 200 in this embodiment. Figure 9 shows the performance evaluation results of the sample that satisfies the relationship of equation (1) above from the sample group Sg3. As shown in Figure 9, the parameter P3 is 8.0 × 10 -9If the value was less than 1.9 × 10, the image quality evaluation result was B, and the lifespan evaluation result was C. Also, if the parameter P3 was 1.9 × 10 -5 When the value exceeded this, the evaluation results for both image quality and lifespan were both D. On the other hand, when parameter P3 was 8.0 × 10 -9 The above and 1.9 × 10 -5 In the following cases, the image quality evaluation result was B, and the lifespan evaluation result was A. That is, the number of passes was n, and the piezoelectric constant was d. 31 It was found that good image quality and even longer lifespan are achieved when the ratio x and atomic percentage z satisfy the relationship expressed by equation (3) above. This is thought to be due to the effect of suppressing the generation of leakage current and the heat generation of the piezoelectric layer 260 by adding Mn to the piezoelectric layer 260. Although not shown in the figures, the image quality and lifespan evaluation results for the samples in sample group Sg3 that did not satisfy the relationship in equation (1) above were both D.

[0078] Parameter P1, parameter P2, and parameter P3 may be referenced, for example, during the manufacturing of the droplet dispensing head 200, or during the use of the droplet dispensing head 200. For example, if the number of passes n is predetermined, during the manufacturing of the droplet dispensing head 200, the piezoelectric constant d may be set such that the relationships expressed in equations (1), (2), and (3) above are satisfied with respect to the predetermined number of passes n. 31 The ratio x, atomic percentage y, and atomic percentage z can be adjusted. In this case, the number of passes n may be defined, for example, as a range with a lower limit and an upper limit. When the number of passes n is defined in this way, the piezoelectric constant d must be set such that the relationships expressed in equations (1), (2), and (3) above are satisfied no matter how the number of passes n is changed within the predetermined range. 31 The ratio x, atomic percentage y, and atomic percentage z can be adjusted. This makes it possible to manufacture a droplet dispensing head 200 equipped with a piezoelectric element 240 having a desirable composition and piezoelectric properties. In addition, for example, a specific piezoelectric constant d can be adjusted. 31 When using a droplet dispensing head 200 equipped with a piezoelectric element 240 having a ratio x, the control unit 110 may adjust the range of the number of passes n to satisfy the relationship expressed in equation (1) above.

[0079] According to the droplet ejection head 200 of this embodiment described above, the number of passes n and the piezoelectric constant d 31 Furthermore, the ratio x of Na satisfies the relationship expressed by equation (1) above. This makes it possible to achieve good image quality and a longer lifespan for the droplet ejection head 200 for multi-pass recording by taking into account the relationship between the number of passes n and the components and piezoelectric properties of the piezoelectric layer 260.

[0080] Furthermore, in this embodiment, the piezoelectric layer 260 contains copper, and has a number of passes n and a piezoelectric constant d. 31 The ratio of Na x and the atomic percentage of copper y satisfy the relationship expressed in equation (2) above. This suppresses ejection defects and enables better image quality.

[0081] Furthermore, in this embodiment, the piezoelectric layer 260 contains manganese, and the number of passes is n and the piezoelectric constant is d. 31 The ratio x of Na and the atomic percentage z of manganese satisfy the relationship expressed by equation (3) above. This suppresses the generation of leakage current in the piezoelectric layer 260. As a result, the lifespan of the droplet dispensing head 200 can be further extended, and dispensing failures caused by heat generation in the piezoelectric layer 260 can be suppressed.

[0082] Furthermore, in this embodiment, manganese is included in the grain boundaries of the piezoelectric layer 260 having a polycrystalline structure. This suppresses vacancies at the grain boundaries in the piezoelectric layer, thereby achieving an even longer lifespan for the droplet ejection head 200.

[0083] Furthermore, in this embodiment, the average grain size of the crystal grains in the piezoelectric layer 260 is 0.15 μm or more and 3 μm or less. As a result, the piezoelectric properties of the piezoelectric layer 260 can be further improved because the average grain size is 0.15 μm or more. Also, because the average grain size is 3 μm or less, the occurrence of cracks in the piezoelectric layer 260 can be further suppressed.

[0084] B. Other forms: This disclosure is not limited to the embodiments described above, and can be implemented in various forms without departing from its spirit. For example, this disclosure can also be implemented in the following forms. The technical features in the embodiments described below that correspond to the technical features in each of the forms described below can be replaced or combined as appropriate in order to solve some or all of the problems of this disclosure, or to achieve some or all of the effects of this disclosure. Furthermore, if such technical features are not described as essential in this specification, they can be deleted as appropriate.

[0085] (1) According to a first embodiment of the present disclosure, a droplet ejection head is provided that performs multi-pass recording, in which, between sub-scans in which the media is transported in a sub-scanning direction intersecting the main scanning direction, a main scan is performed in which the media moves in the main scanning direction and ejects droplets onto the main scanning line, thereby forming dots on the media, and when n is an integer of 2 or more, the recording of the dots on the main scanning line is completed in n main scans. The droplet ejection head comprises a plurality of nozzles for ejecting liquid as droplets, a pressure chamber forming substrate having a pressure chamber communicating with the nozzles, a piezoelectric element, and a diaphragm disposed between the pressure chamber forming substrate and the piezoelectric element, forming a part of the wall surface of the pressure chamber and vibrating by the driving of the piezoelectric element. The piezoelectric element has a first electrode, a second electrode, and a piezoelectric layer disposed between the first electrode and the second electrode, mainly composed of a perovskite-type composite oxide containing potassium, sodium and niobium. n is the number of passes in the multi-pass recording, and d is the piezoelectric constant of the piezoelectric element. 31 [m / v], and the ratio x of the mole fraction of sodium to the sum of the mole fractions of potassium and sodium in the piezoelectric layer, satisfy the relationship shown in equation (1) below. 8.0×10 -8 ≤n·d 31 x ≤ 9.6 × 10 -6 …(1) With this configuration, in a droplet ejection head for multi-pass recording, by taking into account the relationship between the number of passes, the components of the piezoelectric layer, and the piezoelectric properties, it is possible to achieve good image quality and extend the lifespan of the droplet ejection head.

[0086] (2) In the above embodiment, the piezoelectric layer contains copper, and the number of passes n and the piezoelectric constant d 31 The ratio x and the atomic percentage y [at%] of copper in the piezoelectric layer may satisfy the relationship expressed by the following formula (2). 8.0×10 -9 ≤n·d 31 ·x·y≦1.9×10 -5 …(2) This configuration can suppress ejection defects and achieve better image quality.

[0087] (3) In the above embodiment, the piezoelectric layer contains manganese, and the number of passes n and the piezoelectric constant d 31 The ratio x and the atomic percentage z [at%] of manganese in the piezoelectric layer may satisfy the relationship expressed by the following formula (3). 8.0×10 -9 ≤n·d 31 ·x·z≦1.9×10 -5 …(3) This configuration suppresses the generation of leakage current in the piezoelectric layer. As a result, the lifespan of the droplet dispensing head can be further extended, and dispensing failures caused by heat generation in the piezoelectric layer can be suppressed.

[0088] (4) In the above embodiment, the piezoelectric layer is made of polycrystalline material, and manganese may be contained in the grain boundaries of the piezoelectric layer. With this embodiment, vacancies at the crystal grain boundaries in the piezoelectric layer can be suppressed, and the lifespan of the droplet ejection head can be further extended.

[0089] (5) In the above embodiment, the average grain size of the crystal grains in the piezoelectric layer may be 0.15 μm or more and 3 μm or less. With this embodiment, since the average grain size is 0.15 μm or more, the piezoelectric properties of the piezoelectric layer can be further improved. Also, since the average grain size is 3 μm or less, the occurrence of cracks in the piezoelectric layer can be further suppressed.

[0090] (6) A droplet ejection device is provided according to a second embodiment of the present disclosure. This droplet ejection device comprises a droplet ejection head as described above, a transport mechanism for transporting the media in the sub-scanning direction, a head moving mechanism for supporting the droplet ejection head and moving the droplet ejection head in the main scanning direction, and a control unit for controlling the droplet ejection head, the transport mechanism, and the head moving mechanism and for performing the multipath recording. [Explanation of symbols]

[0091] 41...Head movement mechanism, 42...Carriage, 46...Drive motor, 47...Drive belt, 48...Flexible cable, 50...Transport mechanism, 51...Transport motor, 80...Ink cartridge, 90...Drive circuit, 100...Droplet ejection device, 110...Control unit, 200...Droplet ejection head, 210...Nozzle plate, 211...Nozzle, 212...Nozzle row, 220...Pressure chamber forming substrate, 221...Pressure chamber, 223...Ink supply path, 225...Communication section, 230...Piezoelectric section, 231...Diaphragm, 232...Elastic layer, 233...Insulating layer, 240...Piezoelectric element, 250...Sealing section, 251...Piezoelectric element holding section, 252...Manifold section, 260...Piezoelectric layer, 270...First electrode, 280...Second electrode, 293...Manifold, 295...Lead electrode

Claims

1. A droplet ejection head performs multi-path recording, in which, between sub-scans in which the media is transported in a sub-scan direction intersecting the main scan direction, the main scan is performed to move in the main scan direction relative to the media and eject droplets onto the main scan line to form dots on the media, and when n is an integer of 2 or more, the recording of the dots on the main scan line is completed in n main scans, Multiple nozzles that dispense the liquid as droplets, A pressure chamber forming substrate having a pressure chamber in which communication with the nozzle is formed, A piezoelectric element having a first electrode, a second electrode, and a piezoelectric layer disposed between the first electrode and the second electrode, the piezoelectric layer being mainly composed of a perovskite-type composite oxide containing potassium, sodium, and niobium, The system comprises a diaphragm disposed between the pressure chamber forming substrate and the piezoelectric element, forming a part of the wall surface of the pressure chamber, and vibrating when the piezoelectric element is driven, n is the number of paths in the multipath recording, and d is the piezoelectric constant of the piezoelectric element. ３１ A droplet dispensing head wherein the [m / v] and the ratio x of the mole fraction of sodium to the sum of the mole fractions of potassium and sodium in the piezoelectric layer satisfy the relationship expressed by the following formula (1). 8.0×10 －８ ≦n・d ３１ ・x≦9.6×10 －６ …(1)

2. A droplet dispensing head according to claim 1, The piezoelectric layer contains copper, The number of passes n, The piezoelectric constant d ３１ A droplet dispensing head wherein the ratio x and the atomic percentage y [at%] of copper in the piezoelectric layer satisfy the relationship shown in the following formula (2). 8.0×10 －９ ≦n・d ３１ ・x・y≦1.9×10 －５ …(2)

3. A droplet dispensing head according to claim 1, The piezoelectric layer contains manganese, The number of paths n, the piezoelectric constant d ３１ , the ratio x, and the atomic percentage z [at%] of manganese in the piezoelectric layer satisfy the relationship expressed by the following formula (3), a droplet discharge head. 8.0×10 －９ ≦n・d ３１ ・x・z≦1.9×10 －５ …(3)

4. A droplet dispensing head according to claim 3, The piezoelectric layer is constructed as a polycrystalline material. A droplet dispensing head in which manganese is contained at the grain boundaries in the piezoelectric layer.

5. A droplet dispensing head according to claim 4, A droplet dispensing head wherein the average particle size of the crystal grains in the piezoelectric layer is 0.15 μm or more and 3 μm or less.

6. A droplet dispensing head according to any one of claims 1 to 5, A transport mechanism for transporting the media in the sub-scanning direction, A head movement mechanism that supports the droplet dispensing head and moves the droplet dispensing head in the main scanning direction, A droplet dispensing device comprising: the droplet dispensing head; the transport mechanism; and a control unit that controls the head movement mechanism and performs the multipath recording.

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