TWI679129B - Ink ejection device and ink ejection method - Google Patents

Abstract

The present invention provides an ink ejection device having a buffer tank capable of preventing bubbles from being mixed into the ink. An inkjet head and a first pump that eject ink droplets are inserted into the ink circulation path. A first buffer tank is inserted in a circulation path between the inkjet head and the first pump. The first buffer tank has a first inflow port and a first outflow port. The ink flows into the first buffer tank through the first inlet, and the ink in the buffer tank flows out through the first outlet. The first on-off valve discharges the air in the first buffer tank to the outside from a position higher than the level of the first outflow port.

Description

Ink ejection device and ink ejection method

The present invention relates to an ink ejection device and an ink ejection method using an inkjet head.

The following Patent Document 1 discloses a film forming apparatus that circulates ink (liquid film material) in an inkjet head (nozzle head) and ejects ink from a nozzle hole. A storage tank, a supply pump, an inkjet head, and a recovery pump are sequentially inserted in the ink circulation path. In order to absorb the pulsation of the ink ejected from the supply pump and the recovery pump, a buffer tank may be inserted between at least one of the supply pump and the inkjet head and between the inkjet head and the recovery pump.

The buffer tank is provided with an inflow port and an outflow port. The ink flows into the buffer tank through the inflow port, and flows out through the outflow port. When the liquid level of the ink in the buffer tank reaches the height of the inflow port and the outflow port, a space surrounded by the inner surface and the liquid level of the buffer tank and isolated from the outside is formed above the liquid level. According to the pulsation of the ink, the liquid surface in the buffer tank moves up and down. By the displacement of the liquid surface in the buffer tank, the pulsation of the ink flow rate transmitted to the inkjet head is reduced.

(Prior technical literature) (Patent Literature)

Patent Document 1: Japanese Patent Application Laid-Open No. 2014-91076

When the liquid level in the buffer tank is lowered than the level of the outflow port by vertical displacement, the air in the buffer tank enters the circulation path from the outflow port. As a result, air bubbles are mixed in the ink. If air bubbles are mixed in the ink, it is difficult to normally eject the ink from the inkjet head.

An object of the present invention is to provide an ink ejection device having a buffer tank which can prevent air bubbles from being mixed into the ink. Another object of the present invention is to provide an ink ejection method using a buffer tank which can prevent air bubbles from being mixed into the ink.

According to an aspect of the present invention, there is provided an ink ejection device having an inkjet head inserted into a circulation path of ink and ejecting the ink droplets, and a first pump inserted into the circulation path and conveying the ink. A first buffer tank is inserted into the circulation path between the inkjet head and the first pump, and is provided with a first inflow port and a first outflow port; the ink flows in through the first inflow port, and the ink Flowing out through the first outflow port; and a first on-off valve configured to be higher than the level of the first outflow port Position to exhaust the air in the first buffer tank to the outside.

According to another aspect of the present invention, there is provided an ink ejection method, which is an ink ejection method for ejecting ink from an ink ejection device. The ink ejection device includes an inkjet head inserted into a circulation path of the ink and ejecting the ink liquid. The first pump is inserted into the circulation path and conveys the ink; the first buffer tank is inserted into the circulation path between the inkjet head and the first pump, and is provided with a first inflow port and In the first outlet, the ink flows in through the first inlet, and the ink flows out through the first outlet. The first on-off valve is configured to buffer the first buffer from a position higher than the level of the first outlet. The air in the tank is discharged to the outside; and the main tank supplies the ink to the circulation path and recovers the ink from the circulation path, wherein the first pump is operated with the first on-off valve opened, Therefore, the ink flows into the first buffer tank, and is closed when the liquid level of the ink in the first buffer tank reaches a level higher than that of the first outflow port. Said first on-off valve, so that the ink-jet head is operated in the closed state of the first on-off valve of the next.

Since the liquid level of the ink in the first buffer tank is higher than that of the first outflow port High level, so even if the liquid surface moves up and down, air can be prevented from flowing out through the outflow port.

20‧‧‧Circular path

21‧‧‧Main tank

22, 23‧‧‧ pump

25‧‧‧heater

30‧‧‧ buffer tank

31‧‧‧Inlet

32‧‧‧ Outlet

33‧‧‧ Inflow pipe

34‧‧‧ Outflow tube

35‧‧‧Open and close valve

36‧‧‧level sensor

37‧‧‧ Drain valve

40‧‧‧ inkjet head

41‧‧‧Nozzle hole

42‧‧‧ Platform

43‧‧‧ substrate

50‧‧‧ buffer tank

51‧‧‧Inlet

52‧‧‧ Outlet

53‧‧‧Inflow pipe

54‧‧‧ Outflow tube

55‧‧‧Open and close valve

56‧‧‧level sensor

57‧‧‧ Drain valve

60‧‧‧Control device

65‧‧‧Exhaust pump

70‧‧‧ink

71‧‧‧Cleaning liquid

FIG. 1 is a schematic diagram of an ink ejection device according to the embodiment.

FIG. 2 is a schematic diagram of the ink ejection device in the middle stage from the ink supply to the ink ejection.

FIG. 3 is a schematic diagram of the ink ejection device in the middle stage from the ink supply to the ink ejection.

FIG. 4 is a schematic diagram of the ink ejection device in the middle stage from the ink supply to the ink ejection.

FIG. 5 is a schematic diagram of the ink ejection device in the middle stage from the ink supply to the ink ejection.

FIG. 6 is a schematic diagram of the ink ejection device in the middle stage from the ink supply to the ink ejection.

FIG. 7 is a schematic diagram of the ink ejection device in the middle stage from the ink supply to the ink ejection.

FIG. 8 is a schematic diagram of the ink ejection device in the middle stage from the ink supply to the ink ejection.

Fig. 9 is a schematic diagram of an ink ejection device based on a comparative example.

Fig. 10 is a schematic diagram when cleaning the ink ejection device according to the embodiment.

Fig. 11 is a schematic diagram of an ink ejection device according to another embodiment.

FIG. 1 is a schematic diagram of an ink ejection device according to the embodiment. A circulation path 20 is formed for the ink that comes out of the main tank 21 and returns to the main tank 21. An inkjet head 40 is inserted into the circulation path 20. A pump 22 is inserted into the circulation path 20 upstream of the inkjet head 40. A buffer tank 30 is inserted into the circulation path 20 between the inkjet head 40 and the pump 22. A further pump 23 is inserted into the circulation path 20 on the downstream side from the inkjet head 40. A buffer tank 50 is inserted in the circulation path 20 between the inkjet head 40 and the pump 23.

The inkjet head 40 includes a plurality of nozzle holes 41. The nozzle hole 41 faces the substrate 43 held on the stage 42. The inkjet head 40 ejects ink droplets from the nozzle holes 41 toward the substrate 43.

The pump 22 and the pump 23 transport the ink in the circulation path 20 in the same direction. As the pumps 22 and 23, for example, a diaphragm pump can be used. The flow rate of the ink flowing through the circulation paths 20 on the upstream and downstream sides of the pumps 22 and 23 is pulsated in accordance with the operations of the pumps 22 and 23.

The buffer tank 30 is provided with an inflow pipe 33, an outflow pipe 34, an on-off valve 35, and a discharge valve 37. The inflow pipe 33 and the outflow pipe 34 are inserted into the buffer tank 30 from the upper part of the buffer tank 30. The inflow pipe 33 is connected to an injection port of the pump 22. The outflow pipe 34 is connected to the inkjet head 40. The ink ejected from the pump 22 flows into the buffer tank 30 through the inflow port 31 at the lower end of the inflow pipe 33. The ink in the buffer tank 30 flows out of the buffer tank 30 through the outflow port 32 at the lower end of the outflow pipe 34.

The on-off valve 35 is configured to discharge the air in the buffer tank 30 to the outside from a position higher than the level of the outflow port 32. Although the example in which the on-off valve 35 is mounted on the buffer tank 30 is shown in FIG. 1, the on-off valve 35 may be mounted on the side of the buffer tank 30. The level of the inflow port 31 and the level of the outflow port 32 are almost equal. Here, the "level of the inflow port 31" refers to the height of the horizontal plane where the inflow port 31 is located, and the "level of the outflow port 32" refers to the height of the horizontal plane where the outflow port 32 is located.

When the ink flows into the buffer tank 30, the liquid level of the ink rises. When the ink continues to flow in, the liquid level of the ink reaches the level of the outflow port 32. In this state, a closed space surrounded by the inner surface of the buffer tank 30 and the liquid surface is formed above the liquid surface. When the on-off valve 35 is opened, when the ink flows into the buffer tank 30, the liquid level rises, and the air in the closed space is discharged to the outside through the on-off valve 35.

A level sensor 36 is disposed in the buffer tank 30. The level sensor 36 measures the liquid level in the buffer tank 30. The measurement result is input to the control device 60. As the level sensor 36, an ultrasonic type liquid level sensor, a floating type liquid level sensor, or the like can be used.

The other buffer tank 50 is also the same as the buffer tank 30 and includes an inflow pipe 53, an inflow port 51, an outflow pipe 54, an outflow port 52, an on-off valve 55, a level sensor 56, and a discharge valve 57. The inflow pipe 53 is connected to the inkjet head 40. The outflow pipe 54 is connected to a suction port of the pump 23.

The main tank 21 contains a heater 25 therein. The heater 25 heats the ink in the main tank 21. In order to keep the temperature of the ink circulating in the circulation path 20 constant, in addition to the heater 25 in the main tank 21, A heater is arranged in the middle of the path 20.

The control device 60 controls the operations of the pumps 22 and 23 and the opening and closing of the on-off valves 35 and 55. The control device 60 controls the ejection of ink droplets from the inkjet head 40.

Referring to FIGS. 2 to 7, the procedure from the ink supply to the ink ejection device to the ink ejection will be described.

As shown in FIG. 2, the ink 70 is stored in the main tank 21. The control device 60 sets the on-off valves 35 and 55 to a closed state. At this time, the inkjet head 40 is stopped. The control device 60 operates the pumps 22 and 23. Thereby, the ink 70 in the main tank 21 flows into the buffer tank 30 via the pump 22. When the ink 70 continues to flow into the buffer tank 30, the liquid level in the buffer tank 30 gradually rises.

As shown in FIG. 3, after the liquid level in the buffer tank 30 reaches the level of the outflow port 32, the on-off valve 35 is opened. As to whether the liquid level reaches the level of the outflow port 32, it can be determined based on the measurement result of the level sensor 36.

When the on-off valve 35 is kept closed, the ink 70 flows out of the buffer tank 30 through the outflow port 32 and is supplied to the inkjet head 40 after the liquid level reaches the level of the outflow port 32. However, when the on-off valve 35 is opened, the ink 70 does not flow out, and the liquid level exceeds the level of the outflow port 32 and rises further.

As shown in FIG. 4, when the liquid level in the buffer tank 30 reaches a level higher than the outflow port 32, the control device 60 closes the on-off valve 35. According to the measurement result of the level sensor 36, it can be detected that the liquid level reaches a level higher than that of the outflow port 32. When the on-off valve 35 is closed, the liquid level in the buffer tank 30 stops rising, and the ink 70 starts to flow out through the outflow port 32.

As shown in FIG. 5, when the on-off valve 35 is closed, the ink 70 is supplied to the inkjet head 40 through the buffer tank 30. When the inkjet head 40 is filled with the ink 70, the ink 70 flowing out of the inkjet head 40 flows into the buffer tank 50 through the inflow port 51.

As shown in FIG. 6, after the liquid level in the buffer tank 50 reaches the level of the outflow port 52, the control device 60 opens the on-off valve 55. As for whether the liquid level reaches the level of the outflow port 52, it can be determined based on the measurement result of the level sensor 56. When the on-off valve 55 is opened, the liquid level in the buffer tank 50 exceeds the level of the outflow port 52 and rises further.

As shown in FIG. 7, when the liquid level in the buffer tank 50 reaches a level higher than that of the outflow port 52, the control device 60 closes the on-off valve 55. After the on-off valve 55 is closed, the ink 70 in the buffer tank 50 flows out through the outflow port 52. The ink 70 flowing from the buffer tank 50 is recovered to the main tank 21 via the pump 23.

As shown in FIG. 8, the ink 70 is circulated in the circulation path 20 with the on-off valves 35 and 55 closed. In this state, the control device 60 operates the inkjet head 40. As a result, ink droplets are ejected from the nozzle holes 41 of the inkjet head 40 toward the substrate 43.

According to the pulsation of the flow rate of the ink ejected from the pump 22, the liquid surface in the buffer tank 30 is displaced up and down. Similarly, the liquid level in the buffer tank 50 is displaced up and down by the pulsation of the flow rate of the ink drawn into the pump 23. By the liquid level displacement in the buffer tanks 30 and 50, the pulsation of the ink flow rate generated in the pumps 22 and 23 is absorbed. Therefore, the pulsation of the flow rate of the ink flowing into and out of the inkjet head 40 is reduced. As a result, the inkjet head can be stabilized. 40 jet ink.

Next, it compares with the comparative example shown in FIG. 9 and demonstrates the outstanding effect of the said Example.

FIG. 9 is a schematic diagram of an ink ejection device based on a comparative example. In the comparative example, the on-off valves 35 and 55 (FIG. 1) and the level sensors 36 and 56 (FIG. 1) are not attached to the buffer tanks 30 and 50, respectively.

In the comparative example, after the liquid level in the buffer tank 30 reaches the level of the outflow port 32, if the ink flows into the buffer tank 30, it is equivalent to the amount of ink flowing out through the outflow port 32. Similarly, after the liquid level in the buffer tank 50 reaches the level of the outflow port 52, if the ink flows into the buffer tank 50, it is equivalent to the amount of ink flowing out through the outflow port 52.

Therefore, the liquid level in the buffer tank 30 is maintained at a level almost the same as the level of the outflow port 32, and is displaced up and down in the vicinity of this level. If the liquid level is lower than the level of the outlet 32, the air in the buffer tank 30 is supplied to the inkjet head 40 through the outlet 32. As a result, the ejection of ink from the inkjet head 40 becomes unstable.

Similarly, the liquid level in the buffer tank 50 is maintained at a level almost the same as the level of the outflow port 52, and is displaced up and down in the vicinity of this level. By the displacement of the liquid level, the air in the buffer tank 50 flows out together with the ink through the outflow port 52. Thereby, bubbles are mixed in the ink circulating in the circulation path 20. When the air bubbles mixed in the ink pass through the circulation path 20 and reach the inkjet head 40, the ink ejection from the inkjet head 40 becomes unstable.

In the above embodiment, as shown in FIG. 8, the liquid level in the buffer tank 30 is maintained at a higher level than the outflow port 32. Because the liquid level is at the specific outlet 32 is shifted up and down in the vicinity of a high level, so the outflow port 32 is always located below the liquid surface. Accordingly, the air in the buffer tank 30 can be prevented from entering the circulation path 20 through the outflow port 32. Similarly, the air in the buffer tank 50 can be prevented from entering the circulation path 20 through the outflow port 52.

In order to improve the effect of preventing air from entering the circulation path 20, it is preferable that the height from the level of the outflow port 32 to the liquid level when the liquid level drops to the minimum is sufficiently larger than the amplitude of the liquid level displacement. For example, the height from the level of the outflow port 32 to the liquid level when the liquid level is lowered to the minimum is preferably set to be twice or more the amplitude of the liquid surface displacement.

When the inflow port 31 is exposed above the liquid surface during the operation of the inkjet head 40, air bubbles are easily generated in the ink when the ink drops from the inflow port 31 toward the liquid surface. In order to prevent the generation of air bubbles, it is preferable that the level of the inflow port 31 be the same as or lower than the level of the outflow port 32. Similarly, it is preferable that the level of the inflow port 51 in the buffer tank 50 be the same as or lower than the level of the outflow port 52.

In the above embodiment, as shown in FIG. 2, when the ink supply is started, the on-off valve 35 is closed. Thereafter, as shown in FIG. 3, after the liquid level in the buffer tank 30 reaches the level of the outflow port 32, the on-off valve 35 is opened. As another method, the on-off valve 35 may be opened from the time when ink supply is started. In this case, as shown in FIG. 4, the on-off valve 35 may be closed when the liquid level in the buffer tank 30 exceeds the level of the outflow port 32. Similarly, the on-off valve 55 may be opened from the time when ink supply is started.

Next, referring to Fig. 10, the circulation path 20, the pumps 22, 23, and the buffer The cleaning method of the tanks 30 and 50 and the inkjet head 40 is demonstrated.

FIG. 10 is a schematic diagram of the ink ejection device during cleaning. The ink in the main tank 21 is discarded before cleaning. In addition, by operating the pumps 22 and 23, the ink in the circulation path 20 is recovered to the main tank 21 and discarded. The ink remaining in the buffer tanks 30 and 50 is discarded by opening the discharge valves 37 and 57 respectively.

After the ink in the main tank 21 and the circulation path 20 is discarded, the cleaning liquid 71 is filled in the main tank 21. After the main tank 21 is filled with the cleaning liquid 71, the pumps 22 and 23 are operated. Thereby, the cleaning liquid 71 is circulated in the circulation path 20. The level of the cleaning liquid 71 in the buffer tank 30 is maintained at a level higher than the level of the ink 70 when the ink is ejected as shown in FIG. 8. This state can be achieved by delaying the timing of closing the on-off valve 35 shown in FIG. 4. Similarly, the level of the cleaning liquid 71 in the buffer tank 50 is maintained at a level higher than the level of the ink 70 when the ink is ejected as shown in FIG. 8.

When the liquid level of the cleaning liquid 71 in the buffer tanks 30 and 50 is set to be high, the function of the buffer tanks 30 and 50 which suppress the flow pulsation transmission is reduced. Therefore, the flow pulsation of the cleaning liquid generated in the pumps 22 and 23 is transmitted to the inkjet head 40. The cleaning effect of the inkjet head 40 can be improved by the pulsation of the flow rate of the cleaning liquid.

The level of the cleaning liquid 71 in the buffer tanks 30 and 50 is higher than the level of the ink 70 (FIG. 8) at the time of ink ejection. Therefore, the ink residue adhering to the wall surface near the liquid level of the ink 70 can be effectively removed.

In the above embodiment, the measurement is performed with the level sensor 36 (FIG. 1). Liquid level in the buffer tank 30. Based on the measurement results, the timing of opening the on-off valve 35 shown in FIG. 3 and the timing of closing the on-off valve 35 shown in FIG. 4 are determined. Instead of using the level sensor 36 to measure the liquid level, the liquid level can also be inferred based on the time elapsed since the pumps 22 and 23 started to operate.

For example, the control of opening the on-off valve 35 shown in FIG. 3 may be performed at a predetermined first time after the ink 70 starts flowing into the buffer tank 30. In addition, the control of closing the on-off valve 35 shown in FIG. 4 may be performed at a time of a preset second time from the time when the on-off valve 35 is opened. When the opening / closing control timing of the on-off valve 35 is determined based on the elapsed time, the horizontal sensor 36 may be omitted.

The liquid level of the buffer tank 50 can also be estimated from the elapsed time since the pumps 22 and 23 started to operate. Therefore, the opening / closing control of the on-off valve 55 may be performed based on the elapsed time from the start of the operation of the pumps 22 and 23.

Next, an ink ejection device according to another embodiment will be described with reference to FIG. 11. Hereinafter, differences from the embodiment shown in FIG. 1 will be described, and description of the same configuration will be omitted.

FIG. 11 is a schematic diagram of an ink ejection device according to another embodiment. In this embodiment, the on-off valves 35 and 55 are connected to the exhaust pump 65. When the on-off valve 35 is opened, the inside of the buffer tank 30 is exhausted by the exhaust pump 65. Similarly, when the on-off valve 55 is opened, the inside of the buffer tank 50 is exhausted by the exhaust pump 65.

By forcibly venting the inside of the buffer tank 30, the liquid level in the buffer tank 30 can be made to a higher level when the on-off valve 35 shown in FIG. 3 is opened. Similarly, when the on-off valve 55 shown in FIG. 6 is opened, In the state, the liquid level in the buffer tank 50 can reach a higher level.

As mentioned above, although this invention was demonstrated based on an Example, this invention is not limited to these. For example, it is obvious to those skilled in the art that various changes, improvements, and combinations can be made.

Claims (3)

An ink ejection device includes an inkjet head inserted into a circulation path of ink and ejecting the ink droplets; a first pump inserted into the circulation path and conveying the ink; a first buffer tank is inserted The circulation path between the inkjet head and the first pump is provided with a first inflow port and a first outflow port, the ink flows in through the first flow port, and the ink flows out through the first flow port; The first opening and closing valve is configured to discharge the air in the first buffer tank to the outside from a position higher than the level of the first outflow port; and a control device that controls the operation of the first pump and the first opening and closing The valve is opened and closed, and the control device operates the first pump while the first on-off valve is opened, so that the ink flows into the first buffer tank, and the liquid level of the ink in the first buffer tank The first opening and closing valve is closed in a state where the level is higher than the first outflow opening, the inkjet head is operated with the first opening and closing valve closed, and the control device opens the first opening and closing valve. 1 Before operating the first pump in the state of the on-off valve, operate the first pump in the state of closing the first on-off valve, and the liquid level of the ink stored in the first buffer tank reaches the aforementioned level. After the level of the first outlet is opened, the first on-off valve is opened. The ink ejection device according to item 1 of the scope of patent application, further comprising: a second pump inserted into the circulation path and conveying the ink in the same direction as the first pump; and a second buffer tank, which is The circulation path inserted between the inkjet head and the second pump is provided with a second inlet and a second outlet. The ink flows in through the second inlet, and the ink flows out through the second outlet. And a second on-off valve configured to discharge the air in the second buffer tank to the outside from a position higher than the level of the second outflow port. An ink ejection method is an ink ejection method for ejecting ink from an ink ejection device. The ink ejection device includes: an inkjet head that is inserted into a circulation path of the ink and ejects the ink droplets; and a first pump that is inserted in The circulation path conveys the ink. The first buffer tank is inserted in the circulation path between the inkjet head and the first pump, and is provided with a first inflow port and a first outflow port. A first inlet flows in, and the ink flows out through the first outlet; a first on-off valve is configured to discharge the air in the first buffer tank to the outside from a position higher than the level of the first outlet; and The main tank supplies the ink to the circulation path, and recovers the ink from the circulation path, wherein the first pump is operated with the first on-off valve opened, so that the ink flows into the first The buffer tank closes the first on-off valve when the liquid level of the ink in the first buffer tank reaches a level higher than that of the first outflow port, and closes the first The inkjet head is operated in a state of the first on-off valve, and before the ink flows into the first buffer tank while the first on-off valve is opened, the first 1 pump is operated so that the ink flows into the first buffer tank, and after the liquid level of the ink stored in the first buffer tank reaches the level of the first outflow port, the first opening and closing are opened A valve for allowing the ink to flow into the first buffer tank in a state where the first on-off valve is opened.