A piezoelectric thin film head and an inkjet printing apparatus

Abstract

The present application relates to inkjet printing technology field, especially a kind of piezoelectric film nozzle and inkjet printing equipment, piezoelectric film nozzle includes first ink inlet channel, ink return channel and multiple first ink chamber, which are all arranged in the nozzle interior, each first ink chamber includes inkjet preparation chamber, ink chamber elastic diaphragm, ink inlet throttle portion, ink return throttle portion and nozzle orifice, the first ink inlet channel is communicated with the inkjet preparation chamber by the ink inlet throttle portion, the ink return channel is communicated with the inkjet preparation chamber by the ink return throttle portion, the ink chamber elastic diaphragm is used to extrude the inkjet preparation chamber and make ink from the nozzle orifice be ejected, the ink inlet throttle portion bottom surface is equipped with first isolation hole, and the first isolation hole is communicated with external space and the ink inlet throttle portion.First isolation hole is communicated with external space and ink inlet throttle portion, so as to quickly eliminate ink internal and external cavity pressure residual wave clutter, realize the quick balance of the pressure inside and outside the extrusion chamber of nozzle.

Description

Technical Field

[0001] This invention relates to the field of inkjet printing technology, and in particular to a piezoelectric thin film printhead and an inkjet printing device. Background Technology

[0002] In piezoelectric inkjet printing, the elastic vibrating plate inside the ink chamber deforms under the action of the piezoelectric film, transmitting pressure changes to the ink in the inkjet preparation chamber. This pressure change causes the ink inside the nozzle to vibrate, and the resulting vibration is directed outward from the nozzle. Due to this vibration, the crescent-shaped curved surface of the ink inside the nozzle is squeezed outward, eventually forming an ink column.

[0003] However, residual oscillations in the flow rate at the nozzle can lead to the formation of satellite droplets. Satellite droplets are small additional ink droplets generated outside of the normally ejected ink droplets due to vibration and pressure fluctuations. The presence of these satellite droplets can affect the uniformity of the ejected droplet volume, thereby affecting print quality. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide at least one beneficial option or creation condition to solve one or more technical problems existing in the prior art.

[0005] The solution to the technical problem of this invention is: a piezoelectric thin film printhead, comprising a first ink inlet channel, an ink return channel, and a plurality of first ink cavities all disposed inside the printhead. Each first ink cavity includes an inkjet preparation cavity, an ink cavity elastic vibrating plate, an ink inlet throttling section, an ink return throttling section, and a nozzle. The first ink inlet channel is connected to the inkjet preparation cavity through the ink inlet throttling section, and the ink return channel is connected to the inkjet preparation cavity through the ink return throttling section. The ink cavity elastic vibrating plate is disposed at the top of the inkjet preparation cavity, and the nozzle is disposed at the bottom of the ink return throttling section. The ink cavity elastic vibrating plate is used to squeeze the inkjet preparation cavity to eject ink from the nozzle. The bottom surface of the ink inlet throttling section is provided with a first isolation hole, which connects to the external space and the ink inlet throttling section.

[0006] The beneficial effects of this invention are as follows: ink flows in from the ink inlet channel, passes through the ink inlet throttling section, and flows into the inkjet preparation chamber; under the deformation of the elastic vibrating plate in the ink chamber, the ink is squeezed, and the ink drips out from the nozzle at the bottom of the ink return throttling section; at the same time, the remaining ink flows into the ink return channel through the ink return throttling section, and the ink return channel recycles the ink; the first isolation hole connects the external space with the ink inlet throttling section, thereby quickly eliminating residual pressure noise in the inner and outer chambers of the ink, realizing rapid balance of pressure inside and outside the ink extrusion chamber of the printhead, reducing unstable factors in the ink jetting process, and thus improving the stability and reliability of printing.

[0007] As a further improvement to the above technical solution, the ink inlet throttling section includes a flow limiting section and a flow guiding section. The flow guiding section is connected to the ink return channel, and the flow limiting section is connected to the inkjet preparation cavity. The channel cross-sectional area of ​​the flow limiting section is smaller than the channel cross-sectional area of ​​the flow guiding section. The first isolation hole connects the external space with the flow guiding section.

[0008] As a further improvement to the above technical solution, the flow limiting section increases the fluid damping when ink flows from the inkjet preparation chamber to the ink inlet throttling section. Even when the ink is squeezed, the ink balance in the first isolation hole will not be disrupted, ensuring that the air pressure can be kept balanced in the first isolation hole. At the same time, the ink will not flow out of the first isolation hole due to pressure changes, thereby improving the stability and reliability of the entire inkjet system.

[0009] As a further improvement to the above technical solution, the first isolation hole is conical, and the width of the first isolation hole gradually decreases from the top of the first isolation hole to the bottom of the first isolation hole.

[0010] As a further improvement to the above technical solution, the principle of capillary action is utilized. During the operation of the inkjet printing system, when the ink is subjected to a certain pressure inside the printhead, due to the presence of the flow restrictor, the ink is difficult to flow out directly through the first isolation hole. The design of the gradually narrowing first isolation hole further enhances its obstruction effect on the ink, ensuring that even under high pressure, the ink can be effectively locked inside the printhead, avoiding unnecessary leakage and ensuring the system's sealing and safety.

[0011] As a further improvement to the above technical solution, the ink return throttling section is a cylindrical cavity, and the bottom end of the ink return throttling section is provided with two ink return interfaces. The two ink return interfaces are arranged along the tangent of the bottom end of the ink return throttling section, and the ink return interfaces connect the ink return throttling section and the ink return channel.

[0012] As a further improvement to the above technical solution, the two ink return interfaces are arranged along the tangential direction at the bottom of the ink return throttling section, ensuring smooth communication between the two ink return interfaces and the internal space of the ink return throttling section and the ink return channel. When ink passes through the ink return throttling section, the ink can form an orderly outflow pattern along the side wall of the ink return throttling section, improving the ink flow efficiency and reducing turbulence and air bubble generation during the ink flow process, thereby ensuring a stable ink supply and improved printing quality.

[0013] As a further improvement to the above technical solution, the first ink cavity also includes a second isolation hole, which is disposed at the connection between the ink return interface and the ink return channel, and the second isolation hole communicates with the external space.

[0014] As a further improvement to the above technical solution, the second isolation hole is directly connected to the external environment, forming an efficient acoustic energy emission channel. This channel can quickly guide the acoustic energy accumulated inside the ink to the external environment, reducing acoustic reflection and noise interference, thereby improving the operating efficiency and stability of the entire system. In addition, this structural design helps to avoid unnecessary interference between adjacent ink cavities through the ink return channel and ink return interface, ensuring ink uniformity and printing quality.

[0015] As a further improvement to the above technical solution, the cross-section of the second isolation hole is rectangular, and the cross-sectional area of ​​the second isolation hole gradually decreases from the top of the second isolation hole to the bottom of the second isolation hole.

[0016] As a further improvement to the above technical solution, the second isolation hole can ensure that the sound wave energy is captured quickly and effectively during propagation and smoothly guided to the external environment along the conical channel. This conical structure also enhances the capillary effect of the channel, making the flow of ink inside the channel more stable and controllable, and further improving the ventilation performance of the channel.

[0017] As a further improvement to the above technical solution, the nozzle is coaxially arranged with the ink return throttling section, and the nozzle connects the ink return throttling section with the external space.

[0018] As a further improvement to the above technical solution, when the ink is pressurized in the cylindrical cavity, the pressure is transmitted more evenly along the axis of the cavity. The nozzle is located on the main axis of this pressure transmission and can directly withstand and respond to large pressure changes from inside the cavity. This makes it easier for the nozzle to overcome surface tension under high pressure, causing the ink to drip out of the nozzle in a more delicate and uniform manner.

[0019] As a further improvement to the above technical solution, the nozzle is conical, and the width of the nozzle gradually decreases from the top to the bottom of the nozzle.

[0020] As a further improvement to the above technical solution, when ink flows in from the top of the nozzle, its initial width is relatively large, which can accommodate more ink. As the ink flows downward and approaches the bottom of the nozzle, the width gradually decreases, which forces the ink flow to accelerate and concentrate, thereby forming high-pressure, high-speed ink droplets at the nozzle exit. This helps to control the flow speed and direction of the ink, ensuring that the formation of ink droplets is more accurate and consistent.

[0021] As a further improvement to the above technical solution, the piezoelectric thin film printhead also includes a second ink inlet channel and a plurality of second ink cavities. The return ink channel is connected to the second ink inlet channel through the second ink cavities, and the first ink cavity and the second ink cavity are arranged at intervals.

[0022] As a further improvement to the aforementioned technical solution, the second ink chamber enhances the printhead's ability to distribute and control ink. The second ink chamber is arranged alternately with the first ink chamber, thus creating a more complex and refined ink flow network. By precisely controlling the amount of ink in each ink chamber and the timing of ejection, more refined and high-quality printing results can be achieved, providing greater possibilities and flexibility for personalized customization and printing of complex patterns.

[0023] An inkjet printing device, characterized in that it includes a piezoelectric film printhead as described in any of the preceding claims.

[0024] The beneficial effects of this invention are as follows: the ink inlet channel of the piezoelectric thin-film printhead is connected to the ink inlet cartridge of the inkjet printing equipment, and the ink return channel of the piezoelectric thin-film printhead is connected to the ink return cartridge of the inkjet printing equipment, ensuring smooth ink supply and recycling, thereby improving printing efficiency and ink utilization; the piezoelectric thin-film printhead, through the design of adding isolation holes, can quickly eliminate pressure residual waves and noise in the inner and outer cavities of the ink, which helps to achieve rapid pressure balance inside and outside the printhead's ink extrusion chamber; especially in OLED printing, where there are extremely high requirements for the uniformity of ink droplet volume, this pressure balance helps to improve the uniformity of the volume of droplets ejected from the printhead nozzle, thereby ensuring the stability and reliability of printing quality. Attached Figure Description

[0025] Figure 1 This is one of the structural schematic diagrams of the present invention;

[0026] Figure 2 This is the second structural schematic diagram of the present invention;

[0027] Figure 3 This is a schematic diagram of the structure of one embodiment of the present invention.

[0028] In the attached diagram: 1-First ink inlet channel, 2-Ink return channel, 3-First ink cavity, 301-Inkjet preparation cavity, 302-Ink cavity elastic vibrating plate, 303-Ink inlet throttling section, 304-Ink return throttling section, 305-Nozzle, 306-First isolation hole, 307-Flow limiting section, 308-Flow guiding section, 309-Ink return interface, 310-Second isolation hole, 4-Second ink inlet channel, 5-Second ink cavity. Detailed Implementation

[0029] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments have been briefly explained above. Obviously, the described drawings are only a part of the embodiments of the present invention, and not all of them. Those skilled in the art can obtain other design schemes and drawings based on these drawings without creative effort.

[0030] The following will clearly and completely describe the concept, specific structure, and technical effects of the present invention in conjunction with embodiments and accompanying drawings, so as to fully understand the purpose, features, and effects of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them. Other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are all within the scope of protection of the present invention. Furthermore, all connections / linkages mentioned herein do not simply refer to direct connection of components, but rather to the ability to form a better connection structure by adding or reducing connecting accessories according to specific implementation conditions. The various technical features in the present invention can be combined interactively without contradicting each other.

[0031] In piezoelectric inkjet printing, the elastic vibrating plate inside the ink chamber deforms under the action of the piezoelectric film, transmitting pressure changes to the ink in the inkjet preparation chamber 301. This pressure change causes the ink inside the nozzle to vibrate, and the resulting vibration velocity is directed outward from the nozzle. Due to this vibration, the crescent-shaped curved surface of the ink inside the nozzle is squeezed outward, eventually forming an ink column.

[0032] However, residual oscillations in the flow rate at the nozzle can lead to the formation of satellite droplets. Satellite droplets are small additional ink droplets generated outside of the normally ejected ink droplets due to vibration and pressure fluctuations. The presence of these satellite droplets can affect the uniformity of the ejected droplet volume, thereby affecting print quality.

[0033] Therefore, the present invention proposes a piezoelectric thin film nozzle, referring to... Figures 1-2It includes a first ink inlet channel 1, an ink return channel 2, and multiple first ink cavities 3, all disposed inside the printhead. Each first ink cavity 3 includes an inkjet preparation cavity 301, an ink cavity elastic vibration plate 302, an ink inlet throttling section 303, an ink return throttling section 304, and a nozzle 305. The first ink inlet channel 1 is connected to the inkjet preparation cavity 301 through the ink inlet throttling section 303, and the ink return channel 2 is connected to the inkjet preparation cavity 301 through the ink return throttling section 304. The ink cavity elastic vibration plate 302 is disposed at the top of the inkjet preparation cavity 301, and the nozzle 305 is disposed at the bottom of the ink return throttling section 304. The ink cavity elastic vibration plate 302 is used to squeeze the inkjet preparation cavity 301 to eject ink from the nozzle 305. The bottom surface of the ink inlet throttling section 303 is provided with a first isolation hole 306, which connects the external space with the ink inlet throttling section 303.

[0034] Ink flows in from the ink inlet channel, passes through the ink inlet throttling section 303, and flows into the inkjet preparation chamber 301. Under the deformation of the elastic vibration plate 302 in the ink chamber, the ink is squeezed and drips out from the nozzle 305 at the bottom of the ink return throttling section 304. At the same time, the remaining ink flows into the ink return channel 2 through the ink return throttling section 304, where the ink return channel 2 recycles the ink. The first isolation hole 306 connects the external space with the ink inlet throttling section 303, thereby quickly eliminating residual pressure noise in the inner and outer chambers of the ink, achieving rapid balance of pressure inside and outside the printhead ink extrusion chamber, reducing unstable factors in the ink jetting process, and thus improving the stability and reliability of printing.

[0035] When the vibrating plate vibrates during operation, the ink is subjected to corresponding pressure, which may be transmitted to the first isolation hole 306. Therefore, in one embodiment, the ink inlet throttling section 303 includes a flow limiting section 307 and a flow guiding section 308. The flow guiding section 308 is connected to the ink return channel 2, and the flow limiting section 307 is connected to the inkjet preparation chamber 301. The cross-sectional area of ​​the flow limiting section 307 is smaller than that of the flow guiding section 308. The first isolation hole 306 connects the external space with the flow guiding section 308. The flow limiting section 307 increases the fluid damping when ink flows from the inkjet preparation chamber 301 to the ink inlet throttling section 303. Even when the ink is squeezed, the ink balance in the first isolation hole 306 will not be disrupted, ensuring that the air pressure can remain balanced in the first isolation hole 306. At the same time, ink will not flow out of the first isolation hole 306 due to pressure changes, thereby improving the stability and reliability of the entire inkjet system.

[0036] When ink is under pressure inside the printhead, leakage may occur in the first isolation orifice 306. Therefore, in one embodiment, the first isolation orifice 306 is conical, and its width gradually decreases from the top to the bottom. Utilizing the principle of capillary action, during the operation of the inkjet printing system, when ink is under pressure inside the printhead, the presence of the flow restrictor 307 prevents the ink from flowing directly out through the first isolation orifice 306. The gradually narrowing design of the first isolation orifice 306 further enhances its obstruction effect on the ink, ensuring that even under high pressure, the ink can be effectively locked inside the printhead, avoiding unnecessary leakage and ensuring the system's sealing and safety.

[0037] Problems such as poor ink flow, accumulation of air bubbles and impurities, and unstable ink supply can lead to a decline in print quality. Therefore, in one embodiment, the ink return throttling section 304 is a cylindrical cavity with two ink return ports 309 at its bottom. These two ports 309 are arranged tangentially to the bottom of the ink return throttling section 304, connecting it to the ink return channel 2. The tangential arrangement of the two ports 309 ensures smooth communication between the ports, the internal space of the ink return throttling section 304, and the ink return channel 2. When ink passes through the ink return throttling section 304, it forms an orderly outflow pattern along the sidewalls, improving ink flow efficiency and reducing turbulence and air bubble generation during ink flow, thereby ensuring a stable ink supply and improved print quality.

[0038] In the workflow of an ink jet system, especially when the ink passes through the return ink throttling section 304, the acoustic energy generated by the vibrating plate often experiences severe reflection within this narrow space, leading to the appearance of interfering noise. This noise negatively impacts the accuracy and uniformity of ink jetting. Therefore, in one embodiment, the first ink cavity 3 further includes a second isolation hole 310. The second isolation hole 310 is located at the connection between the return ink interface 309 and the return ink channel 2, and it connects to the external space. The second isolation hole 310 is directly connected to the external environment, creating a highly efficient acoustic energy emission channel. This channel can quickly guide the acoustic energy accumulated inside the ink to the external environment, reducing acoustic reflection and noise interference, thereby improving the overall system's operating efficiency and stability. Furthermore, this structural design helps prevent unnecessary interference between adjacent ink cavities through the return ink channel 2 and the return ink interface 309, ensuring ink uniformity and print quality.

[0039] Inside the channel, the propagation of sound wave energy may lead to reflection and scattering, which can adversely affect the uniformity of the ink. Therefore, in one embodiment, the second isolation hole 310 has a rectangular cross-section, and the cross-sectional area of ​​the second isolation hole 310 gradually decreases from the top to the bottom of the second isolation hole 310. The second isolation hole 310 ensures that sound wave energy is captured quickly and effectively during propagation and smoothly guided to the external environment along the tapered channel. This tapered structure also enhances the capillary effect of the channel, making the ink flow inside the channel more stable and controllable, further improving the ventilation performance of the channel.

[0040] Uneven pressure transmission can affect ink ejection. Therefore, in one embodiment, the nozzle 305 is coaxially arranged with the ink return throttling section 304, and the nozzle 305 connects the ink return throttling section 304 to the external space. When ink is pressurized in the cylindrical cavity, the pressure is transmitted more evenly along the axis of the cavity. The nozzle 305 is located on this main axis of pressure transmission and can directly withstand and respond to large pressure changes from inside the cavity. This makes it easier for the nozzle 305 to overcome surface tension under high pressure, causing the ink to drip out of the nozzle 305 in a finer and more uniform manner.

[0041] Inconsistencies in droplet size, ejection speed, and other related parameters can negatively impact the quality of printed images or text. Therefore, in one embodiment, the nozzle 305 is conical, with its width gradually decreasing from the top to the bottom. When ink flows in from the top of the nozzle 305, its initial width is relatively large, accommodating a larger volume of ink. As the ink flows downwards and approaches the bottom, the gradually decreasing width forces the ink flow to accelerate and concentrate, forming high-pressure, high-speed droplets at the nozzle 305 exit. This helps control the ink flow speed and direction, ensuring more precise and consistent droplet formation.

[0042] During operation, refer to Figures 1-2. This embodiment features four first ink cavities 3, with the ink inlet channel connected to the ink cartridge. Ink is injected through the ink inlet channel and then diverted into each first ink cavity 3 before flowing into the inkjet preparation cavity 301. The elastic vibrating plate of each ink cavity can be independently controlled, and its deformation squeezes the ink. The squeezed ink drips out from the bottom nozzle 305 through the return ink throttling section 304. The first isolation hole 306 connects the external space with the ink inlet throttling section 303 to quickly balance the pressure difference between the inner and outer cavities caused by the deformation of the elastic vibrating plate and eliminate pressure fluctuations. Excess ink flows back through the return interface of the return ink channel 2, realizing ink recycling. The second isolation hole 310 at the bottom of the return interface is connected to the external environment, forming a highly efficient acoustic energy emission channel that can quickly guide the acoustic energy accumulated inside the ink to the external environment. The residual waves generated by the mutual impact of ink flowing out of adjacent return interfaces in the return ink channel 2 are also released into the external space through the second isolation hole 310, thereby avoiding interference with the ink inside the return ink throttling section 304.

[0043] If the number of nozzles 305 is insufficient, problems may arise in achieving the required level of detail during high-quality printing tasks. Therefore, in one embodiment, referring to... Figure 3 The piezoelectric film printhead further includes a second ink inlet channel 4 and multiple second ink cavities 5. The return ink channel 2 is connected to the second ink inlet channel 4 through the second ink cavities 5. The first ink cavities 3 and the second ink cavities 5 are arranged alternately. The second ink cavities 5 have the same structure as the first ink cavities 3, and will not be described again here. The second ink cavities 5 enhance the printhead's ability to distribute and control ink. The second ink cavities 5 and the first ink cavities 3 are arranged alternately, thereby constructing a more complex and fine ink flow network. By precisely controlling the amount of ink in each ink cavity and the timing of the ejection, more refined and high-quality printing results can be achieved, providing more possibilities and flexibility for personalized customization and printing of complex patterns.

[0044] An inkjet printing device, characterized in that it includes a piezoelectric film printhead as described in any of the preceding claims.

[0045] The ink inlet channel of the piezoelectric thin-film printhead is connected to the ink inlet cartridge of the inkjet printer, and the ink return channel 2 of the piezoelectric thin-film printhead is connected to the ink return cartridge of the inkjet printer, ensuring smooth ink supply and recycling, thereby improving printing efficiency and ink utilization. The piezoelectric thin-film printhead, through the design of adding isolation holes, can quickly eliminate pressure residual waves and noise in the inner and outer cavities of the ink, which helps to achieve rapid pressure balance inside and outside the printhead's ink extrusion chamber. Especially in OLED printing, there are extremely high requirements for the uniformity of ink droplet volume. This pressure balance helps to improve the uniformity of the volume of droplets ejected from the printhead nozzle, thereby ensuring the stability and reliability of print quality.

[0046] The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited to the embodiments described. Those skilled in the art can make various equivalent modifications or substitutions without departing from the spirit of the present invention, and these equivalent modifications or substitutions are all included within the scope defined by the claims of this application.

Claims

1. A piezoelectric thin film jet head, characterized by comprising: The inkjet head comprises a first ink inlet channel (1), an ink return channel (2) and a plurality of first ink chambers (3) arranged inside the head, each of the first ink chambers (3) comprises an ink preparation chamber (301), an ink chamber elastic vibration plate (302), an ink inlet throttling part (303), an ink return throttling part (304) and a nozzle (305), the first ink inlet channel (1) is communicated with the ink preparation chamber (301) through the ink inlet throttling part (303), the ink return channel (2) is communicated with the ink preparation chamber (301) through the ink return throttling part (304), the ink chamber elastic vibration plate (302) is arranged on the top of the ink preparation chamber (301), the nozzle (305) is arranged on the bottom of the ink return throttling part (304), the ink chamber elastic vibration plate (302) is used for extruding the ink preparation chamber (301) to make ink jet from the nozzle (305), the bottom surface of the ink inlet throttling part (303) is provided with a first isolation hole (306), and the first isolation hole (306) is communicated with the outside space and the ink inlet throttling part (303).

2. A piezoelectric thin film jet head according to claim 1, wherein The ink inlet throttling part (303) comprises a flow limiting part (307) and a flow guiding part (308), the flow guiding part (308) is communicated with the ink return channel (2), the flow limiting part (307) is communicated with the ink preparation chamber (301), the cross-sectional area of the flow limiting part (307) is smaller than that of the flow guiding part (308), and the first isolation hole (306) is communicated with the outside space and the flow guiding part (308).

3. A piezoelectric thin film jet head according to claim 2, wherein The first isolation hole (306) is conical, and the width of the first isolation hole (306) gradually decreases from the top to the bottom of the first isolation hole (306).

4. The piezoelectric thin film jet head according to claim 1, wherein The ink return throttling part (304) is a cylindrical cavity, two ink return interfaces (309) are arranged at the bottom end of the ink return throttling part (304) along the tangent line of the bottom end, and the ink return interfaces (309) are communicated with the ink return throttling part (304) and the ink return channel (2).

5. A piezoelectric thin film jet head according to claim 4, wherein The first ink chamber (3) further comprises a second isolation hole (310), the second isolation hole (310) is arranged at the connection between the ink return interface (309) and the ink return channel (2), and the second isolation hole (310) is communicated with the outside space.

6. A piezoelectric thin film jet head according to claim 5, wherein The cross section of the second isolation hole (310) is rectangular, and the cross-sectional area of the second isolation hole (310) gradually decreases from the top to the bottom of the second isolation hole (310).

7. A piezoelectric thin film jet head according to claim 4, wherein The nozzle (305) is coaxially arranged with the ink return throttling part (304), and the nozzle (305) is communicated with the ink return throttling part (304) and the outside space.

8. The piezoelectric thin film jet head according to claim 1, wherein The nozzle (305) is conical, and the width of the nozzle (305) gradually decreases from the top to the bottom of the nozzle (305).

9. The piezoelectric thin film printhead of claim 1, further comprising a second ink inlet channel (4) and a plurality of second ink chambers (5), the ink return channel (2) being in communication with the second ink inlet channel (4) through the second ink chambers (5), the first ink chambers (3) being spaced apart from the second ink chambers (5).

10. An inkjet printing apparatus, characterized by comprising: A piezoelectric thin film printhead as claimed in any one of claims 1 to 9.

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