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

Abstract

To provide a liquid discharge head that can eliminate the need for a recovery operation for recovering meniscus in a nozzle, a liquid discharge unit and a liquid discharge device.SOLUTION: A liquid discharge head comprises a nozzle 2, a plurality of pressurization liquid chambers 4 communicated with the nozzle 2, and a piezoelectric element which is an electromechanical conversion element. The liquid discharge head makes the nozzle 2 discharge liquid in the pressurization liquid chambers 4 by driving the piezoelectric element. The cross sectional areas of at least the nozzle side of the pressurization liquid chambers 4 gradually decrease as going toward the nozzle 2.SELECTED DRAWING: Figure 5

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] 2. Description of the Related Art Conventionally, there is known a liquid ejection head that ejects liquid from a nozzle by driving an electromechanical conversion element in a pressurized liquid chamber that communicates with the nozzle.

[0003] Patent Document 1 describes a liquid ejection head in which the cross-sectional area of ​​the pressurized liquid chamber is constant. Summary of the Invention [Problem to be solved by the invention]

[0004] However, if the meniscus inside the nozzle is destroyed due to an impact being applied to the liquid ejection head and the meniscus moves into the pressurized liquid chamber, it is necessary to perform a predetermined meniscus recovery operation, such as sucking the liquid from the nozzle or pressurizing and filling the liquid into the liquid ejection head. [Means for solving the problem]

[0005] In order to solve the above-mentioned problems, the present invention provides a liquid ejection head that ejects liquid from a nozzle by driving an electromechanical conversion element that is arranged on the nozzle side of a pressurized liquid chamber that communicates with the nozzle, the cross-sectional area of ​​at least the nozzle side of the pressurized liquid chamber gradually decreasing toward the nozzle. The inner circumferential surface of the region of the pressurized liquid chamber whose cross-sectional area gradually decreases toward the nozzle has lyophilicity to the liquid. It is characterized by the following. [Effects of the Invention]

[0006] According to the present invention, it is possible to eliminate the need for a recovery operation to recover the meniscus in the nozzle. [Brief explanation of the drawings]

[0007] [Figure 1]FIG. 2 is a cross-sectional view schematically showing a nozzle vibration type liquid ejection head according to the present embodiment. [Figure 2] FIG. 2 is a perspective view schematically showing the liquid ejection head. [Figure 3] FIG. 2 is an enlarged cross-sectional view of part X in FIG. 1. [Figure 4] 10 is a diagram illustrating a case where the cross-sectional area of ​​the pressurized liquid chamber 4 taken in a direction perpendicular to the liquid ejection direction is constant. FIG. [Figure 5] 5A and 5B are diagrams illustrating the structure of a pressurized liquid chamber according to the embodiment. [Figure 6] 10A and 10B are diagrams illustrating modified examples of the pressurized liquid chamber. [Figure 7] 10A and 10B are diagrams illustrating an example in which the surface of the partition wall on the common liquid side is made liquid-repellent. [Figure 8] FIG. 1 is a schematic explanatory diagram of a printing apparatus according to an embodiment of the present invention. [Figure 9] FIG. 2 is an explanatory plan view of an example of a head unit of the printing apparatus. [Figure 10] FIG. 10 is an explanatory plan view of the main parts of another printing device. [Figure 11] FIG. 2 is a side view illustrating the main parts of the printing apparatus of the present embodiment. [Figure 12] FIG. 2 is a plan view illustrating a main part of the liquid ejection unit according to the embodiment. [Figure 13] FIG. 2 is a front view illustrating the liquid ejection unit of the present embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0008] An embodiment in which the present invention is applied to a liquid ejection head provided in an apparatus for ejecting liquid will be described below. The present invention is not limited to the embodiments shown below, but may be modified, added, modified, deleted, or otherwise altered within the scope of what a person skilled in the art can conceive, and any embodiment is within the scope of the present invention as long as it achieves the functions and effects of the present invention.

[0009] The liquid ejection head in this embodiment is a nozzle vibration type liquid ejection head that ejects liquid from a pressurized liquid chamber through a nozzle by varying the pressure in the pressurized liquid chamber using an actuator unit having a nozzle. The nozzle vibration type is characterized by the ability to eject droplets with less force than a typical unimorph type piezo head (which ejects liquid by vibrating a surface facing a surface having a communication port that communicates with the nozzle of the pressurized liquid chamber), thereby enabling power savings and high efficiency in the actuator. Furthermore, the nozzle vibration type allows the volume of the pressurized liquid chamber to be reduced, which also allows for a smaller head size and higher nozzle density.

[0010] 1 to 3 are diagrams that schematically show a nozzle vibration type liquid ejection head according to this embodiment, where FIG. 1 is a cross-sectional view, FIG. 2 is a perspective view, and FIG. 3 is an enlarged view of a portion X in FIG. 1. The liquid ejection head 1 includes an actuator section 110 , a vibration membrane 103 , a flow path substrate 100 , and a frame member 120 .

[0011] The actuator section 110 is thin-film shaped and has a plurality of nozzles 2 that eject liquid, and a piezoelectric element 5 as an annular electromechanical conversion element arranged around the nozzles 2. The flow path substrate 100 has a plurality of pressurized liquid chambers (also called individual liquid chambers) 4 that communicate with the plurality of nozzles 2. The frame member 120 has a common liquid chamber 3 that communicates with the plurality of pressurized liquid chambers 4. At both ends of the liquid ejection head 1, electrical connection pads 6 are provided for connection to electrical components such as an external power supply.

[0012] 3, the flow path substrate 100 is a substrate made of SOI (Silicon on Insulator) or SI, and has a plurality of pressurized liquid chambers 4 formed therein. Alternatively, an SOI substrate may be used as the flow path substrate 100, and a drive circuit, wiring section, etc. may be provided within the substrate. The vibrating membrane 103 is formed on the flow path substrate 100, and forms the lower surface, which is part of the wall surface of the pressurized liquid chamber 4.

[0013] The actuator section 110 has a nozzle forming section (membrane) 111 on which a plurality of nozzles 2 are formed and which covers the piezoelectric elements 5. A liquid-repellent film may be formed on the nozzle surface of this nozzle forming section 111. By forming a liquid-repellent film on the nozzle surface, it is possible to prevent the liquid from adhering to the nozzle surface, and to prevent the liquid ejected from the nozzles 2 from being affected by the liquid adhering to the nozzle surface. When the liquid solvent is aqueous, perfluorodecyltrichlorosilane or perfluorooctyltrichlorosilane can be used as the material for the liquid-repellent film.

[0014] The piezoelectric element 5 of the actuator section 110 has a first electrode 51 (also called a lower electrode), a piezoelectric film 52, and a second electrode (also called an upper electrode) 53. The piezoelectric element 5 is covered with a first insulating film 8a.

[0015] First insulating film 8a is formed so as to cover piezoelectric element 5 and vibration film 103, and has formed therein hole-shaped first contact 7a for electrical connection to first electrode 51 and hole-shaped second contact 7b for electrical connection to second electrode 53. First leading wiring 9a as wiring electrically connected to first electrode 51 at first contact 7a, and second leading wiring 9b electrically connected to second electrode 53 at second contact 7b are formed in first insulating film 8a.

[0016] The first lead wire 9a extends to a pad opening 10 on one end (the left end in FIG. 1) of the liquid ejection head 1, and the portion of the first lead wire 9a at the pad opening 10 serves as an electrical connection pad 6 for connection to an electrical component such as an external power supply. The second lead wire 9b extends to a pad opening on the other end (the right end in FIG. 1) of the liquid ejection head 1, and the portion of the second lead wire 9b at the pad opening 10 serves as an electrical connection pad 6 for connection to an electrical component such as an external power supply.

[0017] The first extraction wiring 9a and the second extraction wiring 9b are covered with a second insulating film 8b. The second insulating film 8b also covers the piezoelectric element 5 and has the function of protecting the piezoelectric element 5 by preventing moisture that has entered the nozzle forming portion 111 made of resin from entering the piezoelectric element 5.

[0018] A protective film 11 having liquid-philic and liquid-resistant properties is formed on the inner peripheral surface of the pressurized liquid chamber 4 and the inner peripheral surface of the nozzle 2. The liquid-philic protective film can reduce the surface tension of the liquid on the inner peripheral surfaces of the pressurized liquid chamber 4 and the nozzle 2. If the solvent of the liquid is aqueous, a hydrophilic protective film is used, and if the solvent of the liquid is oil-based, a lipophilic protective film is used, thereby forming the liquid-philic protective film 11.

[0019] In this way, by forming the protective film 11, which has lyophilicity to the liquid filled in the pressurized liquid chamber 4, on the inner circumferential surfaces of the nozzle 2 and the pressurized liquid chamber 4, the liquid easily spreads over the inner circumferential surfaces of the pressurized liquid chamber 4 and the nozzle 2 when filling the liquid. As a result, the liquid filling property can be improved. In addition, the meniscus can be naturally restored as described below.

[0020] Because the liquid solvent in this embodiment is aqueous, the material for the protective film 11, which has liquid resistance and lyophilicity, can be a mixture of a metal oxide forming a passive body and silicon dioxide (SiO2) at the molecular level. The SiO2 of the protective film 11 has hydrophilic OH groups substituted for the O on its surface. This provides hydrophilic properties to the protective film 11. Metals in the metal oxide include tantalum (Ta), niobium (Nb), titanium (Ti), zirconium (Zr), hafnium (Hr), and tungsten (W), which have a high oxidation state compatibility. Zr and Hr, which have a valence similar to that of SiO2, and Ta, which has a valence close to or slightly different from them, are particularly desirable.

[0021] Next, the characteristic features of this embodiment will be described. FIG. 4 is a diagram illustrating a case where the cross-sectional area of ​​the pressurized liquid chamber 4 taken in a direction perpendicular to the liquid ejection direction is constant. In a liquid ejection head, in order to eject liquid, a meniscus must be formed in the nozzle 2. However, if an impact force or excessive pressure is applied to the liquid ejection head 1, the meniscus in the nozzle 2 may be destroyed, and the meniscus M may move into the pressurized liquid chamber 4, as shown in Figure 4. Because a negative pressure is applied to the liquid in the liquid ejection head 1 to prevent the liquid from dripping from the nozzle 2, the meniscus in the nozzle 2 may easily move into the pressurized liquid chamber 4 due to an impact or the like.

[0022] Furthermore, in a typical unimorph type piezo head (which ejects liquid by vibrating a surface opposite a surface having a communication port that communicates with a nozzle in a pressurized liquid chamber), unlike the nozzle vibration method, the member having the nozzle (nozzle plate) can be configured to be less prone to vibration, and the nozzle can also be made longer (the nozzle plate can be made thicker). As a result, the meniscus of the nozzle is not destroyed by a small impact. In contrast, in the nozzle vibration method, the member having the nozzle (the actuator part 110 in this embodiment) is made thin-film-like, configured to vibrate easily, and the nozzle is short, so the meniscus of the nozzle is destroyed by an impact and the meniscus is likely to move into the pressurized liquid chamber 4.

[0023] To move the meniscus M that has moved to the pressurized liquid chamber 4 toward the nozzle, a force greater than the negative pressure acting on the liquid is required. Therefore, it is necessary to perform a predetermined meniscus recovery operation, such as sucking the liquid from the nozzle 2 or filling the liquid into the liquid ejection head under pressure, to re-form the meniscus in the nozzle 2.

[0024] As mentioned above, with the nozzle vibration method, the nozzle meniscus is easily damaged, so damage to the meniscus of nozzle 2 occurs frequently, and the above-mentioned recovery operation must be performed each time. As a result, the device frequently experiences downtime and ink is wasted, leading to great dissatisfaction among users. Furthermore, with the nozzle vibration method, the vibrating membrane 103 is a thin film, and there is a risk of cracks occurring in the vibrating membrane 103 during the above-mentioned recovery operation. As described above, in the nozzle vibration method, the meniscus of the nozzle is easily destroyed, so in this embodiment, the liquid ejection head is configured so that even if the meniscus of the nozzle is destroyed, the meniscus of nozzle 2 will recover naturally. This will be explained in detail below with reference to the drawings.

[0025] FIG. 5 is a diagram illustrating the structure of the pressurized liquid chamber 4, which is a characteristic feature of this embodiment. 5, in this embodiment, the partition walls 4a separating adjacent pressurized liquid chambers 4 have a cross-sectional shape that becomes thinner the further away from the nozzle 2. As a result, the pressurized liquid chambers 4 have a shape such that the cross-sectional area of ​​the pressurized liquid chamber 4 cut in a direction perpendicular to the liquid ejection direction gradually decreases toward the nozzle.

[0026] Surface tension acts on the surface of the liquid (interface with the gas) that forms the meniscus of the liquid. This surface tension is a contraction force that tries to reduce the interface. In this embodiment, by gradually reducing the cross-sectional area of ​​the pressurized liquid chamber 4 toward the nozzle, the interface becomes smaller on the nozzle side. Therefore, the meniscus in the pressurized liquid chamber moves toward the nozzle due to the surface tension of the liquid. Therefore, even if the meniscus moves into the pressurized liquid chamber due to an impact applied to the liquid ejection head, the meniscus naturally moves toward the nozzle due to the surface tension of the liquid. Then, when a portion of the meniscus reaches the portion of the vibrating membrane 103 that forms the wall surface of the pressurized liquid chamber 4 (the lower surface of the pressurized liquid chamber 4), it wets and spreads over the surface of the vibrating membrane 103. Eventually, the pressurized liquid chamber is filled with liquid, and the meniscus in the nozzle naturally recovers.

[0027] Furthermore, in this embodiment, as described above, the protective film 11 having lyophilic properties is formed on the pressurized liquid chamber 4 and the inner peripheral surface of the nozzle, so that the liquid easily spreads over the inner peripheral surface of the pressurized liquid chamber 4. This makes it even easier for the meniscus in the pressurized liquid chamber to move toward the nozzle due to surface tension. Furthermore, when part of the meniscus comes into contact with the portion of the vibrating membrane 103 that forms the wall surface of the pressurized liquid chamber 4 (the lower surface of the pressurized liquid chamber 4), the liquid easily spreads over the surface of the vibrating membrane 103. This allows the meniscus of the nozzle to recover naturally in a satisfactory manner.

[0028] In the nozzle vibration method, the cross-sectional area of ​​the pressurized liquid chamber 4 cut in the direction perpendicular to the liquid ejection direction is gradually reduced toward the nozzle, allowing the meniscus to recover naturally, thereby preventing the occurrence of the predetermined meniscus recovery action and reducing downtime of the device and unnecessary consumption of ink. In addition, the occurrence of the predetermined meniscus recovery action can be prevented, and the occurrence of cracks in the vibration membrane 103, which is a thin film in the nozzle vibration method, can be prevented.

[0029] Furthermore, in this embodiment, as shown in FIG. 5 , the angle θ1 between the partition wall 4a and the vibrating membrane 103 is an obtuse angle. This makes it less likely that the flow of liquid will be impeded during liquid filling than when the angle θ1 is 90° or less. This prevents air bubbles from forming at the corner between the partition wall 4a and the vibrating membrane 103, improving liquid filling performance. This allows for satisfactory liquid filling without actively discharging air from the pressurized liquid chamber 4 through the nozzle 2, by filling the liquid while pressurizing the pressurized liquid chamber 4 with a pump or by covering the nozzle 2 with a suction cap and filling the liquid while suctioning the nozzle 2. In the nozzle vibration method, the vibrating membrane 103 is a thin film, and there is a risk of cracks occurring in the vibrating membrane 103 if the filling is performed while applying pressure or suction. However, in this embodiment, the liquid can be filled without applying pressure or suction, thereby preventing cracks from occurring in the vibrating membrane 103.

[0030] FIG. 6 is a diagram illustrating a modified example of the pressurized liquid chamber 4. In FIG. In this modified example, only the nozzle side of the pressurized liquid chamber 4 is shaped so that the cross-sectional area of ​​the pressurized liquid chamber 4 gradually decreases toward the nozzle. As shown in Figure 5, if the cross-sectional area of ​​the entire pressurized liquid chamber 4 is gradually reduced toward the nozzle, the partition wall 4a will have a gradually expanding cross-sectional shape. This will result in a thicker partition wall 4a on the nozzle side. As a result, it will be necessary to increase the distance between the nozzles, which may prevent the nozzles from being arranged at a sufficiently high density. Furthermore, the vibrating area of ​​the vibrating membrane 103 will be reduced, which may result in a decrease in ejection efficiency, etc.

[0031] In contrast, in the modified example, only the nozzle side of the pressurized liquid chamber 4 is shaped so that the cross-sectional area of ​​the pressurized liquid chamber 4 gradually decreases toward the nozzle, and only the nozzle side of the partition 4a is made an inclined surface that forms an obtuse angle with the vibrating membrane 103. This makes it possible to prevent the thickness of the partition 4a on the nozzle side from increasing, thereby achieving a high density of nozzles. Furthermore, while preventing the thickness of the partition 4a on the nozzle side from increasing, the angle θ1 formed between the partition 4a and the vibrating membrane 103 can be increased, which prevents a reduction in the vibrable area of ​​the vibrating membrane 103 and therefore a decrease in ejection efficiency, while improving the liquid filling performance.

[0032] In this modified example, the cross-sectional area of ​​the region closer to the nozzle than the center position in the liquid ejection direction of the pressurized liquid chamber 4 is gradually reduced toward the nozzle. Specifically, the thickness of the partition 4a is gradually increased on the nozzle side than the center position in the liquid ejection direction, and the region closer to the nozzle than the center position in the liquid ejection direction of the partition 4a is formed as an inclined surface at an obtuse angle with respect to the vibrating membrane 103. This is because, in many cases, the meniscus does not move toward the common liquid chamber from the center position in the liquid ejection direction of the pressurized liquid chamber 4.

[0033] For example, even if a situation arises in which a large amount of air may flow in from the nozzle 2 due to an impact or the like, the meniscus will not move suddenly toward the common liquid chamber due to a sudden influx of air, but will instead move within the pressurized liquid chamber in the following manner: In other words, the meniscus will move toward the common liquid chamber while pulsating (going back and forth) due to pressure fluctuations such as resonance in the common liquid chamber.

[0034] In the region of the pressurized liquid chamber 4 where the cross-sectional area on the nozzle side gradually decreases toward the nozzle 2, a force is generated due to the surface tension of the liquid, moving the meniscus toward the nozzle side. Furthermore, because the angle θ1 between the partition wall 4a and the vibrating membrane 103 can be set to a sufficiently large obtuse angle, air in the pressurized liquid chamber is smoothly discharged when the meniscus returns toward the nozzle side. This ensures that the amount of movement of the meniscus toward the nozzle side when it returns toward the nozzle side is greater than the amount of movement of the meniscus toward the common liquid chamber during pulsation. As a result, even if a large amount of air may flow in from the nozzle 2, the meniscus almost never moves to the center of the pressurized liquid chamber 4 in the liquid ejection direction. Therefore, the meniscus can be kept within the region of the pressurized liquid chamber 4 where the cross-sectional area gradually decreases toward the nozzle. Therefore, if the cross-sectional area of ​​the region of the pressurized liquid chamber 4 closer to the nozzle than the center of the liquid ejection direction is gradually decreased toward the nozzle, the meniscus will almost never fail to recover naturally.

[0035] Furthermore, when the meniscus of the nozzle is destroyed, the piezoelectric element 5 may be driven so as not to eject liquid from the nozzle. For example, the piezoelectric element 5 may be driven at an output of 50% or less or at a slower drive speed than when driving it to eject liquid. This allows the air in the pressurized liquid chamber 4 to be expelled from the nozzle, and the natural recovery of the meniscus due to surface tension can be accelerated. In particular, with the nozzle vibration method, the pressure on the air layer side (nozzle side) when the meniscus moves to the pressurized liquid chamber 4 can be fluctuated by driving the piezoelectric element 5, and air can be effectively expelled from the nozzle. This allows air to be effectively expelled from the nozzle with weak vibrations of the piezoelectric element that do not cause liquid to be ejected from the nozzle. Furthermore, depending on the drive waveform, it is possible to drive the piezoelectric element 5 so that the angle θ1 formed between the partition wall 4a and the vibration film 103 becomes a larger angle, which allows air to be discharged from the nozzle more smoothly.

[0036] 7, a liquid-repellent film 41 that is liquid-repellent to liquid may be formed in a region of the partition wall 4a where the thickness is constant, and the inner peripheral surface of the region of the pressurized liquid chamber 4 where the cross-sectional area is constant may be liquid-repellent. In this embodiment, the liquid-repellent film 41 is formed on a lyophilic protective film 11.

[0037] 7, by making the inner peripheral surface of the region of the pressurized liquid chamber 4 where the cross-sectional area is constant liquid-repellent, the meniscus is less likely to move from the region on the nozzle side where the inner peripheral surface is liquid-philic to the region on the common liquid side where the inner peripheral surface is liquid-repellent. This makes it possible to further keep the meniscus in the region where the cross-sectional area of ​​the pressurized liquid chamber 4 gradually decreases toward the nozzle 2.

[0038] In this embodiment, the protective film 11, which is liquid-resistant and liquid-philic, is formed on the inner circumferential surfaces of the pressurized liquid chamber 4 and the nozzle 2. However, the inner circumferential surfaces of the pressurized liquid chamber 4 and the nozzle 2 may be subjected to a surface modification treatment to impart liquid-resistant and liquid-philic properties. If the flow path substrate or the vibration membrane is liquid-resistant to the liquid, the inner circumferential surfaces of the pressurized liquid chamber 4 and the nozzle 2 may be coated or surface-modified to impart liquid-philic properties. Alternatively, the flow path substrate 100 and the vibration membrane 103 may be made of a material that is liquid-resistant and liquid-philic, and the inner circumferential surfaces of the pressurized liquid chamber 4 and the nozzle 2 may be made liquid-resistant and liquid-philic without being coated or surface-modified.

[0039] Next, an example of a liquid ejection device according to the present invention will be described with reference to FIGS. FIG. 8 is a schematic explanatory diagram of a printing apparatus, which is an inkjet recording apparatus serving as a device for ejecting liquid in this embodiment. FIG. 9 is an explanatory plan view of an example of a head unit of the printing device of this embodiment.

[0040] A printing apparatus 500, which is an apparatus for ejecting this liquid, includes a carry-in means 501 that carries in a continuum 510, and a guide / conveyance means 503 that guides and conveys the continuum 510 carried in from the carry-in means 501 to a printing means 505. The printing apparatus 500 also includes a printing means 505 that ejects a liquid onto the continuum 510 to form an image, a drying means 507 that dries the continuum 510, and an ejection means 509 that ejects the continuum 510.

[0041] The continuous web 510 is sent out from a main winding roller 511 of the carry-in means 501, guided and conveyed by the rollers of the carry-in means 501, the guide and conveying means 503, the drying means 507, and the conveying means 509, and wound up by a winding roller 591 of the conveying means 509. In the printing means 505, the continuous web 510 is conveyed on a conveying guide member 559 opposite the head unit 550, and an image is printed by liquid ejected from the head unit 550.

[0042] In the printing device 500 of this embodiment, the head unit 550 includes the two head modules 100A and 100B according to this embodiment described above, mounted on a common base member 552.

[0043] When the direction in which the liquid ejection heads 1 of the head modules 100A and 100B are lined up in a direction perpendicular to the transport direction is defined as the head arrangement direction, the head arrays 1A1 and 1A2 of the head module 100A eject liquid of the same color. Similarly, the head arrays 1B1 and 1B2 of the head module 100A are paired, the head arrays 1C1 and 1C2 of the head module 100B are paired, and the head arrays 1D1 and 1D2 are paired, and each ejects liquid of the required color.

[0044] Next, another example of a printing apparatus as a liquid ejecting apparatus according to the present invention will be described with reference to FIGS. FIG. 10 is an explanatory plan view of the main parts of the printing apparatus of this embodiment. FIG. 11 is an explanatory side view of the main part of the printing apparatus of this example.

[0045] The printing apparatus 500 of this example is a serial type apparatus, and a carriage 403 is moved back and forth in the main scanning direction by a main scanning movement mechanism 493. The main scanning movement mechanism 493 includes a guide member 401, a main scanning motor 405, a timing belt 408, etc. The guide member 401 is hung between left and right side plates 491A and 491B to movably hold the carriage 403. The main scanning motor 405 then moves the carriage 403 back and forth in the main scanning direction via a timing belt 408 hung between a drive pulley 406 and a driven pulley 407.

[0046] This carriage 403 is equipped with a liquid ejection unit 440 that integrates the liquid ejection head 1 according to the present invention and a head tank 441. The liquid ejection head 1 ejects liquid of each color, for example, yellow (Y), cyan (C), magenta (M), and black (K). The liquid ejection head 1 is mounted with a nozzle row consisting of multiple nozzles arranged in a sub-scanning direction perpendicular to the main scanning direction, and the ejection direction facing downward. The liquid ejection head 1 is connected to a liquid circulation device, which circulates and supplies liquid of the required color.

[0047] The printing apparatus 500 is equipped with a transport mechanism 495 for transporting paper 410. The transport mechanism 495 includes a transport belt 412, which is a transport means, and a sub-scanning motor 416 for driving the transport belt 412. The transport belt 412 attracts the paper 410 and transports it at a position facing the liquid ejection head 1. The transport belt 412 is an endless belt that is stretched between a transport roller 413 and a tension roller 414. The attraction can be achieved by electrostatic attraction or air suction. The transport belt 412 moves in a circular motion in the sub-scanning direction as the transport roller 413 is rotationally driven by the sub-scanning motor 416 via a timing belt 417 and a timing pulley 418.

[0048] Furthermore, a maintenance and recovery mechanism 420 that maintains and recovers the liquid ejection head 1 is disposed on one side of the carriage 403 in the main scanning direction, beside the conveyor belt 412. The maintenance and recovery mechanism 420 is composed of, for example, a cap member 421 that caps the nozzle surface of the liquid ejection head 1, a wiper member 422 that wipes the nozzle surface, and the like. The main scanning movement mechanism 493, the maintenance and recovery mechanism 420, and the conveyor mechanism 495 are attached to a housing that includes side plates 491A and 491B and a back plate 491C.

[0049] In the printing device 500 configured in this manner, the paper 410 is fed onto the conveyor belt 412 and adsorbed thereon, and the paper 410 is conveyed in the sub-scanning direction by the circular movement of the conveyor belt 412. Then, by driving the liquid ejection head 1 in accordance with an image signal while moving the carriage 403 in the main scanning direction, liquid is ejected onto the stationary paper 410 to form an image.

[0050] Next, another example of the liquid discharge unit according to the present invention will be described with reference to FIG. FIG. 12 is a plan view illustrating the main parts of the liquid discharge unit of this embodiment.

[0051] This liquid ejection unit 440 is composed of the components that make up the device for ejecting the liquid, including a housing portion consisting of side plates 491A, 491B and a back plate 491C, a main scanning movement mechanism 493, a carriage 403, and a liquid ejection head 1.

[0052] 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.

[0053] Next, still another example of the liquid discharge unit according to the present invention will be described with reference to FIG. FIG. 13 is an explanatory front view of the liquid discharge unit of this embodiment.

[0054] This liquid discharge unit 440 is composed of a liquid discharge head 1 to which a flow path part 444 is attached, and a tube 456 connected to the flow path part 444 .

[0055] The flow path part 444 is disposed inside the cover 442. A head tank 441 may be included instead of the flow path part 444. Furthermore, a contact 443 for electrically connecting with the liquid ejection head 1 is provided on the upper part of the flow path part 444.

[0056] In the present application, the liquid to be ejected may have a viscosity and surface tension that allows it to be ejected from the head, and is not particularly limited. However, it is preferable that the viscosity of the liquid be 30 mPa·s or less at room temperature and normal pressure, or upon heating or cooling. More specifically, the liquid may be a solution, suspension, emulsion, or the like containing a solvent such as water or an organic solvent, a colorant such as a dye or a pigment, a functionalizing material such as a polymerizable compound, a resin, or a surfactant, a biocompatible material such as DNA, amino acids, proteins, or calcium, or an edible material such as a natural colorant. These liquids can be used, for example, in inkjet inks, surface treatment solutions, liquids for forming components of electronic devices or light-emitting elements, liquids for forming electronic circuit resist patterns, and material liquids for 3D modeling.

[0057] Energy sources for ejecting liquid include piezoelectric actuators (laminated piezoelectric elements and thin-film piezoelectric elements), thermal actuators that use electrothermal conversion elements such as heating resistors, and electrostatic actuators consisting of a vibration plate and an opposing electrode.

[0058] A "liquid ejection unit" is a liquid ejection head integrated with functional parts and mechanisms, and includes a collection of parts related to ejecting liquid. For example, a "liquid ejection unit" includes a liquid ejection head 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.

[0059] Here, "integrated" includes, for example, a liquid ejection head and a functional part or mechanism that are fixed to each other by fastening, bonding, engaging, etc., or one that is held movably relative to the other. The liquid ejection head, functional part, or mechanism may also be configured to be detachable from each other.

[0060] For example, some liquid ejection units have a liquid ejection head and a head tank integrated together, while others have a liquid ejection head and a head tank integrated together by being connected to each other by a tube, etc. Here, a unit including a filter can be added between the head tank and the liquid ejection head of these liquid ejection units.

[0061] Furthermore, there is a liquid ejection unit in which the liquid ejection head and the carriage are integrated.

[0062] In some liquid ejection units, the liquid ejection head is movably held by a guide member that constitutes part of the scanning movement mechanism, and the liquid ejection head and the scanning movement mechanism are integrated together. In other liquid ejection units, the liquid ejection head, the carriage, and the main scanning movement mechanism are integrated together.

[0063] Furthermore, there is a liquid ejection unit in which a cap member, which is part of the maintenance and recovery mechanism, is fixed to a carriage on which a liquid ejection head is attached, thereby integrating the liquid ejection head, carriage, and maintenance and recovery mechanism.

[0064] In some liquid ejection units, a tube is connected to a liquid ejection head equipped with a head tank or flow path components, integrating the liquid ejection head with a supply mechanism. Liquid is supplied from a liquid storage source to the liquid ejection head via this tube.

[0065] The main scanning movement mechanism includes the guide member alone, and the supply mechanism includes the tube alone and the loading unit alone.

[0066] Here, the "liquid ejection unit" is described in combination with a liquid ejection head, but the "liquid ejection unit" also includes a head module or head unit that includes the liquid ejection head described above, and that integrates the functional components and mechanisms described above.

[0067] "Liquid ejection devices" include devices that are equipped with a liquid ejection head, a liquid ejection unit, a head module, a head unit, etc., and that eject liquid by driving the liquid ejection head. Liquid ejection devices include not only devices that can eject liquid onto objects to which the liquid can adhere, but also devices that eject liquid into air or liquid.

[0068] 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.

[0069] For example, examples of "liquid ejecting devices" include image forming devices that eject ink to form images on paper, and three-dimensional modeling devices (three-dimensional modeling devices) that eject modeling liquid onto a powder layer formed from layers of powder in order to create a three-dimensional object (a three-dimensional model).

[0070] Furthermore, the term "liquid ejection device" is not limited to devices that use ejected liquid to visualize meaningful images such as letters and figures. For example, it also includes devices that form patterns that have no meaning in themselves, and devices that create three-dimensional images.

[0071] The above-mentioned "object onto which a liquid can adhere" means an object onto which a liquid can adhere at least temporarily, an object onto which the liquid can adhere and stick, an object onto which the liquid can penetrate, etc. Specific examples include media such as paper, recording paper, film, and cloth, electronic circuit boards, electronic components such as piezoelectric elements, powder layers, organ models, and test cells, and unless otherwise specified, includes all objects onto which a liquid can adhere.

[0072] The material of the "substance to which a liquid can adhere" may be any material to which a liquid can adhere, even temporarily, such as paper, thread, fiber, fabric, leather, metal, plastic, glass, wood, or ceramics.

[0073] Furthermore, 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 a liquid ejection head moves, and a line type device in which a liquid ejection head does not move.

[0074] Other examples of "liquid ejecting devices" include treatment liquid application devices that eject treatment liquid onto paper to apply the treatment liquid to the surface of the paper for purposes such as modifying the surface of the paper, and spray granulation devices that spray a composition liquid in which raw materials are dispersed through a nozzle to granulate the raw material particles.

[0075] In the present application, the terms image formation, recording, printing, copying, printing, modeling, etc. are all synonymous.

[0076] The above description is merely an example, and each of the following aspects provides unique effects. (Aspect 1) In a liquid ejection head that ejects liquid from a pressurized liquid chamber 4 communicating with a nozzle 2 from the nozzle 2 by driving an electromechanical conversion element such as a piezoelectric element 5 arranged on the nozzle side of the pressurized liquid chamber 4, the cross-sectional area of ​​at least the nozzle side of the pressurized liquid chamber 4 is gradually reduced toward the nozzle 2. Surface tension acts on the surface of the liquid (interface with the gas) that forms the meniscus of the liquid. This surface tension is a contraction force that tries to reduce the interface. Therefore, by gradually reducing the cross-sectional area of ​​the pressurized liquid chamber toward the nozzle, as in embodiment 1, the interface becomes smaller on the nozzle side, and the meniscus in the pressurized liquid chamber moves toward the nozzle due to the surface tension of the liquid. Therefore, even if the meniscus moves into the pressurized liquid chamber due to an impact being applied to the liquid ejection head, the meniscus naturally moves toward the nozzle due to the surface tension of the liquid. Then, when part of the meniscus reaches a surface of the pressurized liquid chamber that is provided with a communication port that communicates with the nozzle, the liquid wets and spreads over the surface provided with the communication port, and eventually the pressurized liquid chamber is filled with liquid, and the meniscus in the nozzle naturally recovers. In this way, in the first aspect, the meniscus of the nozzle can be naturally restored, and it becomes possible to eliminate the need for a predetermined restoration operation for restoring the meniscus of the nozzle.

[0077] (Aspect 2) In the first embodiment, the inner circumferential surface of the region of the pressurized liquid chamber 4 where the cross-sectional area gradually decreases toward the nozzle 2 has lyophilicity to the liquid. According to this, as explained in the embodiment, the meniscus in the pressurized liquid chamber is easily moved toward the nozzle side due to surface tension, and the meniscus in the nozzle can be naturally restored in an excellent manner.

[0078] (Aspect 3) In the first or second embodiment, only on the nozzle side of the pressurized liquid chamber 4, the cross-sectional area is gradually reduced toward the nozzle 2. This makes it possible to prevent the distance between nozzles from widening and to increase the density of the nozzles, compared to the case where the entire pressurized liquid chamber is shaped so that the cross-sectional area gradually decreases toward the nozzle 2, as explained in the modified example. Also, it is possible to prevent the vibrating area of ​​the vibrating membrane 103 from narrowing, and to prevent a decrease in ejection efficiency.

[0079] (Aspect 4) In the third embodiment, the inner circumferential surface of the region with a constant cross-sectional area on the side opposite to the nozzle side of the pressurized liquid chamber 4 is liquid-repellent. According to this, as explained with reference to FIG. 7, it is possible to prevent the meniscus from moving to a region where the cross-sectional area of ​​the pressurized liquid chamber 4 on the side opposite to the nozzle side is constant.

[0080] (Aspect 5) In any of aspects 1 to 4, the device has a substrate such as a flow path substrate 100 having a pressurized liquid chamber 4, and a vibrating membrane 103 laminated on the nozzle side of the substrate and constituting part of the wall surface of the pressurized liquid chamber, and an electromechanical conversion element such as a piezoelectric element 5 is arranged on the surface of the vibrating membrane 103 opposite to the side constituting the wall surface of the pressurized liquid chamber 4, and the electromechanical conversion element vibrates the nozzle 2 and the part of the vibrating membrane 103 that constitutes the wall surface of the pressurized liquid chamber 4, thereby ejecting liquid from the nozzle 2. As explained in the embodiment, this allows droplets to be ejected with less force than with a typical unimorph piezo head, which reduces the power consumption of electromechanical conversion elements such as piezoelectric elements. It also makes it possible to reduce the area of ​​the pressurized liquid chamber, which allows for a smaller head and higher nozzle density.

[0081] (Aspect 6) In a liquid ejection unit including at least one of a head tank, a carriage, a supply mechanism, a maintenance and recovery mechanism, and a main scanning movement mechanism, and a liquid ejection head, any one of the liquid ejection heads according to aspects 1 to 5 is used as the liquid ejection head. This allows the meniscus of the nozzle to recover naturally.

[0082] (Aspect 7) A liquid ejection device includes the liquid ejection head of any one of the first to fifth aspects or the liquid ejection unit of the sixth aspect. This allows the meniscus of the nozzle to recover naturally. [Explanation of symbols]

[0083] 1: Liquid ejection head 2: Nozzle 3: Common liquid chamber 4: Pressurized liquid chamber 4a: Bulkhead 5: Piezoelectric element 6: Electrical connection pad 7a: First Contact 7b: Second Contact 8a: First insulating film 8b: second insulating film 9a: First lead-out wiring 9b: Second lead-out wiring 10: Pad opening 11:Protective film 41: Liquid repellent film 51:First electrode 52: Piezoelectric film 53:Second electrode 100: Flow channel substrate 103: Vibration membrane 110: Actuator section 111: Nozzle forming section 120: Frame member 440: Liquid dispensing unit 441: Head Tank 442: Cover M: Meniscus [Prior art documents] [Patent documents]

[0084] [Patent Document 1] Patent No. 5663538

Claims

1. A liquid ejection head that ejects liquid from a nozzle by driving an electromechanical conversion element that is disposed on the nozzle side with respect to the pressurized liquid chamber, the electromechanical conversion element being connected to the nozzle, a cross-sectional area of ​​at least the nozzle side of the pressurized liquid chamber gradually decreases toward the nozzle, A liquid ejection head, characterized in that an inner circumferential surface of a region of the pressurized liquid chamber whose cross-sectional area gradually decreases toward the nozzle has lyophilicity to the liquid.

2. In the liquid ejection head according to claim 1, A liquid ejection head characterized in that the cross-sectional area of ​​the pressurized liquid chamber is gradually reduced only on the nozzle side as it approaches the nozzle.

3. A liquid ejection head that ejects liquid from a nozzle by driving an electromechanical conversion element that is arranged on the nozzle side with respect to the pressurized liquid chamber, A liquid ejection head characterized in that the cross-sectional area of ​​the pressurized liquid chamber is gradually reduced only on the nozzle side as it approaches the nozzle.

4. 4. The liquid ejection head according to claim 2, an inner circumferential surface of a region of the pressurized liquid chamber opposite to the nozzle side, the region having a constant cross-sectional area; A liquid ejection head characterized by being liquid-repellent.

5. 5. The liquid ejection head according to claim 1, a substrate having a pressurized liquid chamber; a vibration membrane that is laminated on the nozzle side of the substrate and that constitutes a part of the wall surface of the pressurized liquid chamber, the electromechanical transducer is disposed on a surface of the vibration membrane opposite to a surface that forms a wall surface of the pressurized liquid chamber, A liquid ejection head characterized in that the electromechanical conversion element vibrates the nozzle and a portion of the vibrating membrane that constitutes a wall surface of the pressurized liquid chamber, thereby ejecting the liquid from the nozzle.

6. A liquid ejection unit including at least one of a head tank, a carriage, a supply mechanism, a maintenance and recovery mechanism, and a main scanning movement mechanism, and a liquid ejection head, A liquid ejection unit, comprising the liquid ejection head according to claim 1 .

7. In a device for discharging a liquid, 7. A liquid ejection device comprising: a liquid ejection head according to claim 1; or a liquid ejection unit according to claim 6.

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