Ink-jet printing head and ink-jet printing equipment

Abstract

The invention discloses an ink-jet printing head capable of enabling ink to continuously flow and ink-jet printing equipment. The ink-jet printing head comprises an ink-jet unit, an ink inlet channel and an ink outlet channel, the ink-jet unit comprises a nozzle, a pressure cavity and a heater, the nozzle is located above the pressure cavity, the heater is located below the pressure cavity, and the ink inlet channel and the ink outlet channel are respectively communicated with the pressure cavity. An ink inlet channel and an ink outlet channel are respectively communicated with a pressure cavity of an ink jet unit, the pressure of the ink inlet channel is positive pressure, the pressure of the ink outlet channel is negative pressure, ink continuously flows into the pressure cavity from the ink inlet channel, penetrates through the pressure cavity and then flows out of the ink outlet channel, and the ink at a nozzle and in the pressure cavity is ensured to continuously flow, so that the nozzle is kept wet, and the ink jet efficiency is improved. And meanwhile, residual bubbles and particle precipitates in a flow channel of the ink-jet printing head are taken away, finally, the jetting capacity of the ink-jet printing head is improved, and the service life of the ink-jet printing head is prolonged.

Description

Technical Field

[0001] The invention belongs to the technical field of inkjet printing, and in particular, relates to an inkjet printing head and an inkjet printing device. Background Art

[0002] Inkjet printing technology is a technology that controls the liquid to be ejected from the nozzle of the print head into droplets, and the droplets are ejected through the flying medium onto the target substrate to form a pattern. Inkjet printing technology has the characteristics of non-contact, maskless, high throughput, and low power consumption. Since it does not need to contact the substrate, it can not only print on a flat surface, but also accurately print patterns on complex curved surfaces. In recent years, due to the rapid development of inkjet printing technology, in addition to the traditional graphic printing industry, inkjet printing technology has also been increasingly widely used in the manufacturing fields of micro-electromechanical systems (MEMS), biological tissues, and electronic products. Mainstream inkjet printing technologies include continuous inkjet printing technology and on-demand inkjet printing technology. Among them, on-demand inkjet printing technology refers to selectively controlling the deformation of the piezoelectric element in the nozzle or the heating element to generate bubbles to pressurize the liquid in the nozzle pressure chamber according to the preset printing image, and controlling the liquid to be ejected onto the substrate to form the desired printing pattern. According to the liquid driving principle, on-demand inkjet print heads can be divided into piezoelectric inkjet print heads and thermal bubble inkjet print heads.

[0003] Figure 1 , Figure 2 (U.S. Patent 7,163,278) is a schematic diagram of the structure of a conventional thermal bubble inkjet print head. Figure 1 Two adjacent injection units are shown. Figure 2 It is the cross-sectional structure of a single jet unit. The conventional hot bubble jet head comprises a substrate 10, a pressure chamber layer 20 and a nozzle plate 30. The substrate 10 comprises a silicon substrate 11 and a multilayer thin film structure 12 to 16 thereon, the pressure chamber layer 20 is fixed on the substrate 10 and forms a pressure chamber array 22, the nozzle plate 30 is fixed on the pressure chamber layer 20, and the nozzle plate 30 comprises a nozzle array 32 corresponding to the pressure chambers. When the hot bubble jet print head is working, the liquid passes through the substrate 10 from the back, flows through the ink inlet channel 24 and enters the pressure chamber 22. When the high impedance heating element 13 located on the substrate 10 receives a pulse signal of appropriate amplitude and duration, the temperature rises instantly, causing the liquid on the surface of the protective layer 16 to vaporize and generate bubbles, squeezing the liquid in the pressure chamber 22, and part of the liquid near the nozzle 32 is pushed out of the nozzle by the bubble pressure to form droplets. After the pulse drive signal is turned off, the heater stops heating, the bubble bursts, the pressure chamber is under negative pressure, and the liquid replenishes the pressure chamber 22 through the ink inlet channel 24.

[0004] However, in Figure 1In the illustrated thermal bubble inkjet print head structure, each pressure chamber 22 is closed on three sides and has only a single liquid inlet channel 24, so that the liquid cannot circulate in the pressure chamber 22. On the one hand, when the nozzle or the jet unit is not used, the liquid surface at the nozzle 32 in contact with the outside air is prone to dryness and pore clogging due to liquid volatilization. On the other hand, when bubbles remain and particles precipitate in the pressure chamber 22, jetting failure may also occur. Summary of the invention

[0005] The technical problem solved by the present invention is: how to achieve sustainable flow of liquid inside the inkjet print head, so as to keep the nozzle moist through continuous flow of liquid, and at the same time take away residual bubbles and particle precipitation in the nozzle flow channel, increase the particle solid content of the sprayable liquid, and extend the service life of the nozzle.

[0006] The present application discloses an inkjet print head, which includes an inkjet unit, an ink inlet channel and an ink outlet channel. The inkjet unit includes a nozzle, a pressure chamber and a heater. The nozzle is located above the pressure chamber, and the heater is located below the pressure chamber. The ink inlet channel and the ink outlet channel are respectively connected to the pressure chamber. The pressure of the ink inlet channel is positive, and the pressure of the ink outlet channel is negative.

[0007] Optionally, an ink inlet and an ink outlet are provided on a side wall of the pressure chamber, the ink inlet is communicated with the ink inlet channel, and the ink outlet is communicated with the ink outlet channel.

[0008] Optionally, along the direction of the ink inlet passage toward the pressure chamber, the size of the ink inlet port decreases.

[0009] Optionally, the inkjet unit further comprises a filter, which is arranged at the ink inlet and is used to prevent large particles in the liquid from flowing into the pressure chamber and clogging the nozzle.

[0010] Optionally, the inkjet unit further comprises a flow restrictor, which is arranged at the ink outlet and slows down the rapid flow of liquid toward the ink outlet under the pressure of the bubble when the bubble in the pressure chamber expands, so as to ensure that the pressure in the pressure chamber is sufficient to push the ink out of the nozzle.

[0011] Optionally, in the flow direction of the ink in the pressure chamber, the ink inlet and the ink outlet are respectively located on opposite sides of the heater.

[0012] Optionally, the inkjet unit further comprises a nozzle disposed at the top of the pressure chamber, and in the flow direction of the ink in the pressure chamber, the ink inlet and the ink outlet are respectively located on opposite sides of the nozzle.

[0013] Optionally, there are multiple inkjet units, which are arranged in two columns, and there are two ink outlet channels, wherein the inkjet units in one column are located between the ink inlet channel and one of the ink outlet channels, and the inkjet units in the other column are located between the ink inlet channel and the other ink outlet channel.

[0014] Optionally, there are multiple inkjet units, which are arranged in two columns and staggered in the row direction. There are two ink outlet channels, with one column of inkjet units located between the ink inlet channel and one of the ink outlet channels, and the other column of inkjet units located between the ink inlet channel and another of the ink outlet channels.

[0015] The present application also discloses an inkjet printing device, which includes the above-mentioned inkjet print head.

[0016] The present invention discloses an inkjet print head and an inkjet printing device, which have the following technical effects:

[0017] The ink inlet channel and the ink outlet channel are connected to the pressure chamber of the inkjet unit respectively, and the ink continuously flows from the ink inlet channel into the pressure chamber below the nozzle, and flows out from the ink outlet channel after passing through the pressure chamber, thereby taking away the bubbles and particle precipitation that may remain in the flow channel of the inkjet print head, while keeping the nozzle moist to avoid the nozzle hole from drying out and clogging, ultimately achieving the improvement of the inkjet print head's jetting ability and extending the service life of the inkjet print head. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic diagram of the structure of a thermal bubble inkjet print head in the prior art;

[0019] Figure 2 for Figure 1 A schematic diagram of the cross-sectional structure of a single injection unit;

[0020] Figure 3 is a top view of an inkjet print head according to embodiment 1 of the present invention;

[0021] Figure 4 for Figure 3 A schematic cross-sectional structure diagram of two inkjet units;

[0022] Figure 5A , Figure 5B , Figure 5C It is a schematic diagram of the ink flow process in an ink jet cycle in the first embodiment of the present invention;

[0023] Figure 6 Another top view of the inkjet print head according to the first embodiment of the present invention;

[0024] Figure 7Schematic diagram of the arrangement of nozzles on the nozzle plate of the first embodiment of the present invention;

[0025] Figure 8 FIG. 1 is another schematic diagram of the arrangement of the nozzles on the nozzle plate of the first embodiment of the present invention. DETAILED DESCRIPTION

[0026] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0027] Before describing the various embodiments of the present application in detail, the technical concept of the present application is briefly described first: the pressure chamber structure of the hot bubble inkjet print head in the prior art is relatively closed, usually after the ink enters the pressure chamber from the liquid inlet, it is heated by the heater and then ejected from the nozzle. There may be residual bubbles and deposited particles in the pressure chamber, which affect the inkjet effect. At the same time, when the nozzle or the ejection unit is not in use, the liquid surface in contact with the outside air at the nozzle is prone to dryness and clogging due to liquid volatilization, resulting in nozzle failure. To this end, the inkjet print head provided by the present application is provided with an ink inlet channel and an ink outlet channel, and the ink inlet channel and the ink outlet channel are connected to the pressure chamber of the inkjet unit respectively, and the pressure of the ink inlet channel is positive, and the pressure of the ink outlet channel is negative, so that the ink can continuously flow from the ink inlet channel into the pressure chamber below the nozzle, and flow out from the ink outlet channel after passing through the pressure chamber, thereby taking away the bubbles and particle precipitation that may remain in the flow channel of the inkjet print head, while keeping the nozzle moist, avoiding the nozzle from drying and clogging, and realizing the improvement of the ejection ability of the inkjet print head and extending the service life of the inkjet print head.

[0028] Specifically, Figure 3 As shown, the inkjet print head of the first embodiment includes an inkjet unit 100, an ink inlet channel 200 and an ink outlet channel 300. The inkjet unit 100 includes a nozzle 103, a pressure chamber 101 and a heater 102. The nozzle 103 is arranged at the top of the pressure chamber 101, the heater 102 is arranged at the bottom of the pressure chamber 101, and the ink inlet channel 200 and the ink outlet channel 300 are respectively connected to the pressure chamber 101.

[0029] For example, the number of inkjet units 100 of the inkjet print head is usually multiple, such as Figure 3 In the top view shown, there are six inkjet units 100, which are arranged in two columns and three rows. The ink inlet channel 200 is located between the two columns of inkjet units 100, and the two ink outlet channels 300 are respectively arranged outside the two columns of inkjet units 100. Figure 4In the cross-sectional view shown, there are two inkjet units 100, which are arranged in a row. The sizes and specifications of the inkjet units 100 may be the same or different. It should be pointed out that the improvement of the first embodiment focuses on how to achieve the flow of ink in the pressure chamber. The number of inkjet units 100 and the differences between the inkjet units 100 are not particularly limited or described in detail. The following description takes one of the inkjet units 100 as an example.

[0030] Specifically, if Figure 3 and Figure 4 As shown, the inkjet print head also includes a substrate 700 and a multilayer thin film structure 400 disposed on the substrate 700. The substrate 700 is generally made of silicon or other suitable materials, and the ink inlet channel 200 and the ink outlet channel 300 run through the substrate 700. The multilayer thin film structure 400 includes a dedicated integrated circuit layer 401, a wire layer 402, and a passivation layer 403. The wire layer 402 can be made of a metal material, such as a thin film of Al or Al alloy, Au, Ag, etc., which is deposited on the heater 102 and patterned by processes such as photolithography and etching to form a conductive lead to connect the heater to an external circuit. The passivation layer 403, such as a silicon nitride or silicon oxide film, is deposited on the conductive lead and the heater to protect the lower metal from being insulated from the liquid flow channel.

[0031] The heater 102 is arranged between the dedicated integrated circuit layer 401 and the wire layer 402. The heater 102 can be made of TaAl, TaN, TiN or other appropriate high-resistance materials. The heater structure is formed through a series of processing techniques such as thin film deposition, photolithography, and etching, and is electrically connected to the integrated circuit layer 401 and the wire layer 402.

[0032] A pressure chamber layer 500 and a nozzle plate 600 covering the pressure chamber layer 500 are provided on the multilayer thin film structure 400. The pressure chamber layer 500 can be made of one of the materials such as epoxy resin SU-8, polyimide, silicon oxide or electroplated Ni after patterning. The nozzle layer 600 can also be made of one of the materials such as epoxy resin SU-8, polyimide, silicon oxide or electroplated Ni after patterning. The multilayer thin film structure 400, the pressure chamber layer 500 and the nozzle plate 600 together form a pressure chamber 101 of the inkjet unit 100, and the heater 102 is located below the pressure chamber 101. Exemplarily, the heater 102 is located directly below the pressure chamber 101. A through hole is opened on the nozzle plate 600, which serves as the nozzle 103 of the inkjet unit 100, wherein the nozzle 103 and the heater 102 can be completely opposite, partially opposite or not opposite at all. Figure 3The nozzle plate 600 is omitted and the position of the nozzle 103 is shown. A protective layer 104 may be provided at the bottom of the pressure chamber 101. The protective layer 104 may be made of a corrosion-resistant metal film such as Ta, and the protective layer 104 is used to prevent the ink from damaging the multi-layer film structure 400. Furthermore, the substrate 700 and the multi-layer film structure 400 form a continuous channel, which is used as the ink inlet channel 200 and the ink outlet channel 300.

[0033] Furthermore, an ink inlet 101a and an ink outlet 101b are provided on the side wall of the pressure chamber 101. The ink inlet 101a is connected to the ink inlet channel 200, and the ink outlet 101b is connected to the ink outlet channel 300. Figure 3 , Figure 4 As shown in FIG. 5 , in one ink jetting cycle, the ink in the ink inlet channel 200 enters the pressure chamber 101 from the ink inlet port 101a of the side wall, and the heater 102 works, and the temperature rises instantaneously to vaporize the ink near the heater 102 to generate bubbles. The expansion of the bubbles causes the hydraulic pressure in the pressure chamber 101 to increase, and the ink directly below the nozzle 103 is pushed by the bubble pressure to be ejected along the nozzle 103. After the heater 102 stops heating, the ink is ejected from the nozzle 103 to form droplets, and the bubbles in the pressure chamber 101 burst. The pressure chamber 101 is in a negative pressure state, and the ink automatically replenishes the pressure chamber from the ink inlet channel 200. The ink in the pressure chamber 101 is replenished, and the liquid forms a stable half-moon curved surface at the nozzle, completing one jetting cycle. When the ink enters the pressure chamber 101, since the ink has a certain fluidity, if there are residual bubbles or particles in the pressure chamber 101, they can be flushed out to the ink outlet 101b by the ink. At the same time, the flowing ink can also take away part of the residual heat of the heater 102, which plays a certain cooling effect. After a jetting cycle is completed, the ink that continues to flow under the nozzle under the pressure of the outside world can keep the nozzle moist, thus preventing the nozzle from drying out and clogging due to liquid evaporation.

[0034] For the sake of Figure 5A , Figure 5B , Figure 5C In this way, the ink in the nozzle is kept flowing steadily, and the pressure of the ink inlet channel 200 and the ink outlet channel 300 can be controlled. Generally speaking, when the on-demand nozzle is not spraying liquid, a slight negative pressure is maintained under the nozzle to prevent the ink from flowing out of the nozzle when not spraying. Therefore, the pressure P in the ink inlet channel 200 is in It can be set to positive pressure, the pressure P in the ink outlet channel 300 out It can be set to negative pressure, and the difference between the two keeps a slight negative pressure below the nozzle 103, which on the one hand maintains the circulation of ink and takes away the bubbles or particle precipitation that affect the injection, and on the other hand can maintain the injection capacity of the nozzle.

[0035] Exemplarily, in the flow direction of the ink in the pressure chamber 101, the ink inlet 101a and the ink outlet 101b are respectively located on the opposite sides of the heater 102 and / or the nozzle 103, that is, the ink inlet 101a and the ink outlet 101b are arranged opposite to each other at this time, so that the flow path is as short as possible, which is beneficial to improving the fluidity of the ink in the pressure chamber 101 and facilitating the removal of bubbles or particles remaining in the pressure chamber 101.

[0036] Furthermore, since the expansion of bubbles will also cause part of the ink in the pressure chamber 101 to enter the ink outlet channel 300, in order to minimize the ink flowing out of the ink outlet 101b and reduce the pressure loss in the pressure chamber so that more ink can be ejected from the nozzle 103 to improve the energy conversion efficiency, a flow limiter 105 is set at the ink outlet 101b without affecting the ink supply flow of the nozzle to limit the liquid in the pressure chamber from flowing quickly to the ink outlet 101b, so as to reduce the ink flowing to the ink outlet channel 300.

[0037] For example, Figure 3 As shown, the restrictor 105 is a columnar structure, and the area of ​​the first side of the restrictor 105 is greater than the area of ​​the second side, wherein the first side is the side of the restrictor 105 close to the pressure chamber 101, and the second side is the side of the restrictor 105 away from the pressure chamber 101. The first side of the restrictor 105 can effectively block the bubbles generated during the heating process. At the same time, the two side surfaces connected to the second side surface of the restrictor 105 are inclined surfaces, which is conducive to blocking the ink of the ink outlet channel 300 from flowing back to the pressure chamber 101. Among them, there are gaps between the two sides of the restrictor 105 and the pressure chamber layer 500 to prevent the restrictor 105 from completely blocking the ink outlet 101b. The second side of the restrictor 105 gradually shrinks along the direction of the liquid circulation flow to prevent the ink from being stationary near the restrictor, which is not conducive to taking away bubbles or particles, etc., thereby affecting the injection effect.

[0038] In another embodiment, the current limiter 105 may also be Figure 6 The two trapezoidal columns shown are respectively connected to the pressure chamber layer 500, and the two trapezoidal columns are spaced to form a gap, which can be used to block the bubbles generated during the heating process, and the gap can also be used to allow the flowing ink to pass through. At the same time, due to the inclined surface of the two trapezoidal columns, the size of the gap decreases along the direction from the ink outlet channel 300 to the pressure chamber 101, which is helpful to prevent the ink in the ink outlet channel 300 from flowing back to the pressure chamber 101. It should be pointed out that the structure of the flow limiter 105 can also be other, and the structures of the flow limiter 105 that are similar to, equivalent to, and can perform the above two functions are all within the protection scope of this application.

[0039] Similarly, since the expansion of bubbles during heating will also push part of the ink in the pressure chamber 101 toward the ink inlet 101a, in order to prevent bubbles from flowing out of the ink inlet 101a, the size of the ink inlet 101a is reduced while ensuring that the liquid supply flow rate meets the high-frequency injection. Exemplarily, the size of the ink inlet 101a decreases along the direction of the ink inlet channel 200 pointing to the pressure chamber 101. As one of the ways, two trapezoidal columns as shown in the figure can be set on the side wall of the pressure chamber layer 500, so that the size of one end of the ink inlet 101a is larger and the size of the other end is smaller.

[0040] Furthermore, the inkjet unit further includes a filter 106, which is disposed at the ink inlet 101a to prevent large particles in the ink from entering the pressure chamber and clogging the nozzle. The filter 106 may be composed of one or more columns, which are vertically disposed at the ink inlet 101a.

[0041] Furthermore, the plurality of inkjet units 100 are arranged in two columns and multiple rows, and the number of ink outlet channels 300 is two, wherein one column of inkjet units 100 is located between the ink inlet channel 200 and one of the ink outlet channels 300, and the other column of inkjet units 100 is located between the ink inlet channel 200 and another of the ink outlet channels 300. Figure 7 As shown, the nozzles 103 of the two inkjet units 100 in the row direction are located in the same row.

[0042] For example, in another embodiment, the plurality of inkjet units 100 are arranged in two columns and the number of ink outlet channels 300 of the inkjet units 100 staggered in the row direction is two, wherein one column of inkjet units 100 is located between the ink inlet channel 200 and one of the ink outlet channels 300, and the other column of inkjet units 100 is located between the ink inlet channel 200 and another of the ink outlet channels 300. Figure 8 As shown, the nozzles 103 of the plurality of inkjet units 100 are distributed in two columns and staggered in the row direction, that is, in the row direction, two nozzles 103 are not located in the same row.

[0043] This embodiment 2 also discloses an inkjet printing device, the inkjet printing device includes the inkjet print head in embodiment 1, and the inkjet printing device can remove the local heat accumulation of the device through liquid circulation during use, improve the uniformity of the temperature distribution of the device, and extend the service life of the nozzle. The liquid circulation flow removes the residual bubbles and particles inside the flow channel, improves the injection effect, and at the same time, the liquid circulation can be used to maintain the wettability at the nozzle to avoid nozzle blockage when not working, and can also improve the uniformity of the viscosity distribution of the liquid in the channel. It should be noted that it is understandable that a complete inkjet printing device should also have other necessary basic components, but other components are not the focus of this embodiment, so they are not shown in the figure and are not described in detail in the specification, and these components are well-known technologies for those skilled in the art.

[0044] The specific implementation methods of the present invention are described in detail above. Although some embodiments have been shown and described, those skilled in the art should understand that these embodiments can be modified and improved without departing from the principles and spirit of the present invention, the scope of which is defined by the claims and their equivalents. These modifications and improvements should also be within the scope of protection of the present invention.

Claims

1. An inkjet print head, characterized in that: The inkjet print head includes an inkjet unit, an ink inlet channel and an ink outlet channel. The inkjet unit includes a nozzle, a pressure chamber and a heater. The nozzle is located above the pressure chamber, the heater is located below the pressure chamber, the ink inlet channel and the ink outlet channel are connected to the pressure chamber respectively, the pressure of the ink inlet channel is positive pressure, and the pressure of the ink outlet channel is negative pressure.

2. The inkjet print head according to claim 1, characterized in that: An ink inlet and an ink outlet are provided on the side wall of the pressure chamber. The ink inlet is communicated with the ink inlet channel, and the ink outlet is communicated with the ink outlet channel.

3. The inkjet print head according to claim 2, characterized in that: Along the direction of the ink inlet passage toward the pressure chamber, the size of the ink inlet port decreases.

4. The inkjet print head according to claim 2, characterized in that: The inkjet unit further comprises a filter, which is arranged at the ink inlet and is used to prevent large particles in the liquid from flowing into the pressure chamber and blocking the nozzle.

5. The inkjet print head according to claim 2, characterized in that: The inkjet unit also includes a flow restrictor, which is arranged at the ink outlet and has a decreasing size. The flow restrictor is used to slow down the rapid flow of liquid toward the ink outlet under the pressure of the bubble when the bubble in the pressure chamber expands, so as to ensure that the pressure in the pressure chamber is sufficient to push the ink out of the nozzle.

6. The inkjet print head according to claim 2, characterized in that: In the flow direction of ink in the pressure chamber, the ink inlet and the ink outlet are respectively located on opposite sides of the heater.

7. The inkjet print head according to claim 2, characterized in that: The inkjet unit further comprises a nozzle arranged at the top of the pressure chamber, and in the flow direction of the ink in the pressure chamber, the ink inlet and the ink outlet are respectively located at opposite sides of the nozzle.

8. The inkjet print head according to any one of claims 1 to 7, characterized in that: There are multiple inkjet units, which are arranged in two columns and multiple rows. There are two ink outlet channels, wherein one column of inkjet units is located between the ink inlet channel and one of the ink outlet channels, and the other column of inkjet units is located between the ink inlet channel and another of the ink outlet channels.

9. The inkjet print head according to any one of claims 1 to 7, characterized in that: There are multiple inkjet units, which are arranged in two columns and staggered in the row direction. There are two ink outlet channels, wherein the inkjet units in one column are located between the ink inlet channel and one of the ink outlet channels, and the inkjet units in the other column are located between the ink inlet channel and the other ink outlet channel.

10. An inkjet printing device, characterized in that: The inkjet print head comprises the inkjet print head according to any one of claims 1 to 9.

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