TW201702085A - Ink jetting device and ink jetting method capable of inhibiting air bubbles from mixing into the ink - Google Patents

Abstract

The invention provides an ink jetting device having a buffer tank capable of inhibiting air bubbles from mixing into the ink. An ink jet head for jetting ink droplets and a first pump are inserted into a circulation path of the ink. A first buffer tank is inserted into the circulation path between the ink jet 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 by passing through the first inflow port. The ink inside the buffer tank flows out by passing through the first outflow port. The first on-off valve outwardly discharges the air inside the first buffer tank at the position that is higher than water level of the first outflow port.

Description

Ink jet device and ink jet method

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

Patent Document 1 listed below discloses a film forming apparatus that circulates ink (a 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 circulation path of the ink. In order to absorb the pulsation of the ink ejected from the supply pump and the recovery pump, a buffer tank is inserted at at least one place between the supply pump and the ink jet head and between the ink jet head and the recovery pump.

An inflow port and an outflow port are provided in the buffer tank. The ink flows into the buffer tank through the inflow port, and flows out to the outside 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 surface of the buffer tank and separated from the outside is formed above the liquid surface. According to the pulsation of the ink, the liquid level in the buffer tank is displaced. The pulsation of the ink flow rate transmitted to the ink jet head is reduced by the displacement of the liquid level in the buffer tank.

(previous technical literature) (Patent Literature)

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

When the liquid level in the buffer tank is displaced upward and downward so that the liquid level becomes lower than the level of the outflow port, the air in the buffer tank enters the circulation path from the outflow port. As a result, bubbles are mixed in the ink. If bubbles are mixed into 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 ejecting apparatus having a buffer tank capable of suppressing the incorporation of air bubbles into the ink. Another object of the present invention is to provide an ink ejecting method using a buffer tank which can suppress bubbles from being mixed into an ink.

According to an aspect of the invention, there is provided an ink ejecting apparatus comprising: an ink jet head inserted in a circulation path of ink and ejecting the ink droplets; a first pump inserted in the circulation path and conveying the ink The first buffer tank is inserted into the circulation path between the ink jet head and the first pump, and is provided with a first inflow port and a first inflow port, and the ink flows in through the first inflow port, and the ink Flowing out through the first outlet; and the first opening and closing valve is configured to be higher than the level of the first outlet The position of the air in the first buffer tank is discharged to the outside.

According to another aspect of the present invention, there is provided an ink ejecting method which is an ink ejecting method for ejecting ink from an ink ejecting apparatus, the ink ejecting apparatus having: an ink jet head inserted into a circulation path of the ink, and ejecting the ink liquid a first pump inserted into the circulation path and transporting the ink; the first buffer tank is inserted into the circulation path between the ink jet head and the first pump, and is provided with a first inlet and In the first outlet, the ink flows in through the first inlet, the ink flows out through the first outlet, and the first opening and closing valve is configured to move the first buffer from a position higher than a 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 while the first opening and closing valve is opened. Therefore, the ink flows into the first buffer tank, and is closed in a state where the liquid level of the ink in the first buffer tank reaches a level higher than the first outlet. 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 reaches the first outflow port The high level makes it possible to suppress the air from flowing out through the outflow port even if the liquid surface is displaced.

20‧‧‧Circular path

21‧‧‧ main can

22, 23‧‧‧ pump

25‧‧‧heater

30‧‧‧buffer tank

31‧‧‧Inlet

32‧‧‧Exit

33‧‧‧Inflow pipe

34‧‧‧Outflow tube

35‧‧‧Opening and closing valve

36‧‧‧Horizontal Sensor

37‧‧‧Drain valve

40‧‧‧Inkjet head

41‧‧‧Nozzle hole

42‧‧‧ platform

43‧‧‧Substrate

50‧‧‧buffer tank

51‧‧‧Inlet

52‧‧‧Exit

53‧‧‧Inflow pipe

54‧‧‧Outflow tube

55‧‧‧Opening and closing valve

56‧‧‧ horizontal sensor

57‧‧‧Drain valve

60‧‧‧Control device

65‧‧‧Exhaust pump

70‧‧‧Ink

71‧‧‧cleaning fluid

Fig. 1 is a schematic view of an ink ejecting apparatus based on an embodiment.

Fig. 2 is a schematic view of the ink ejecting apparatus in the middle of the process from the supply of the ink to the ejection of the ink.

Fig. 3 is a schematic view of the ink ejecting apparatus in the middle of the process from the supply of the ink to the ejection of the ink.

Fig. 4 is a schematic view of the ink ejecting apparatus in the middle of the process from the supply of the ink to the ejection of the ink.

Fig. 5 is a schematic view showing an ink ejecting apparatus in the middle of the process from the supply of the ink to the ejection of the ink.

Fig. 6 is a schematic view of the ink ejecting apparatus in the middle of the process from the supply of the ink to the ejection of the ink.

Fig. 7 is a schematic view of the ink ejecting apparatus in the middle of the process from the supply of the ink to the ejection of the ink.

Fig. 8 is a schematic view showing an ink ejecting apparatus in the middle of the process from the supply of the ink to the ejection of the ink.

Fig. 9 is a schematic view of an ink ejecting apparatus based on a comparative example.

Fig. 10 is a schematic view showing a state in which the ink ejecting apparatus is cleaned based on the embodiment.

Fig. 11 is a schematic view showing an ink ejecting apparatus based on another embodiment.

Fig. 1 is a schematic view showing an ink ejecting apparatus according to an embodiment. The circulation path 20 of the ink in which the autonomous tank 21 comes out and returns to the main tank 21 is formed. An inkjet head 40 is inserted in the circulation path 20. The pump 22 is inserted into the circulation path 20 on the upstream side 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. Another pump 23 is inserted in the circulation path 20 on the downstream side of the inkjet head 40. Another buffer tank 50 is inserted into the circulation path 20 between the ink jet head 40 and the pump 23.

The inkjet head 40 includes a plurality of nozzle holes 41. The nozzle hole 41 is opposed to 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, 23, for example, a diaphragm pump can be used. The flow rate of the ink flowing through the circulation paths 20 on the respective upstream and downstream sides of the pumps 22 and 23 is pulsated in accordance with the operation of the pumps 22 and 23.

An inflow pipe 33, an outflow pipe 34, an opening and closing valve 35, and a discharge valve 37 are attached to the buffer tank 30. The inflow pipe 33 and the outflow pipe 34 are inserted into the buffer tank 30 from the upper portion of the buffer tank 30. The inflow pipe 33 is connected to the 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 of 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 of the lower end of the outflow pipe 34.

The opening and closing 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 opening and closing valve 35 is attached to the upper surface of the buffer tank 30 is shown in FIG. 1, the opening and closing valve 35 may be attached to the side surface 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. If 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 ink is supplied into the buffer tank 30 in a state where the opening and closing valve 35 is opened, the liquid level rises, and the air in the closed space is discharged to the outside through the opening and closing valve 35.

A level sensor 36 is disposed in the buffer tank 30. The level sensor 36 measures the level of liquid in the buffer tank 30. The measurement result is input to the control device 60. As the level sensor 36, an ultrasonic liquid level sensor, a floating 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 opening and closing 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 the suction port of the pump 23.

The main tank 21 houses a heater 25. 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, it is also possible to cycle A heater is disposed in the middle of the path 20.

The control device 60 controls the operation of the pumps 22 and 23 and the opening and closing of the opening and closing valves 35 and 55. Further, the control device 60 controls the ejection of the ink droplets from the inkjet head 40.

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

As shown in Fig. 2, ink 70 is stored in the main tank 21. The control device 60 sets the on-off valves 35 and 55 to the closed state. At this time, the ink jet head 40 is in a stopped state. 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, the opening and closing valve 35 is opened after the liquid level in the buffer tank 30 reaches the level of the outflow port 32. As to whether the liquid level reaches the level of the outflow port 32, the determination can be made based on the measurement result of the level sensor 36.

When the opening and closing valve 35 is kept in the closed state, 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 opening and closing valve 35 is opened, the ink 70 does not flow out, and the liquid level exceeds the level of the outflow port 32 and further rises.

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 opening and closing valve 35. It is possible to detect that the liquid level reaches a level higher than the outflow port 32 in accordance with the measurement result of the level sensor 36. When the opening and closing 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 opening and closing valve 35 is closed, the ink 70 is supplied to the inkjet head 40 via 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 opening and closing valve 55. As to whether the liquid level reaches the level of the outflow port 52, the determination can be made based on the measurement result of the level sensor 56. When the opening and closing valve 55 is opened, the liquid level in the buffer tank 50 exceeds the level of the outflow port 52 and further rises.

As shown in Fig. 7, when the liquid level in the buffer tank 50 reaches a level higher than the outflow port 52, the control device 60 closes the opening and closing valve 55. After the opening and closing valve 55 is closed, the ink 70 in the buffer tank 50 flows out through the outflow port 52. The ink 70 flowing out of 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 in a state where the opening and closing valves 35, 55 are closed. In this state, the control device 60 operates the inkjet head 40. Thereby, ink droplets are ejected from the nozzle holes 41 of the inkjet head 40 toward the substrate 43.

The liquid level in the buffer tank 30 is displaced in accordance with the pulsation of the flow rate of the ink ejected from the pump 22. Similarly, the liquid in the buffer tank 50 is displaced by the pulsation of the flow rate of the ink sucked into the pump 23. The pulsation of the ink flow generated in the pumps 22, 23 is absorbed by the liquid surface displacement in the buffer tanks 30 and 50. Therefore, the pulsation of the ink flow which flows into the ink jet head 40 and flows out from the ink jet head 40 is reduced. As a result, it is stable from the inkjet head 40 jet ink.

Next, the superior effects of the above embodiments will be described in comparison with the comparative examples shown in Fig. 9.

Fig. 9 is a schematic view showing an ink ejecting apparatus based on a comparative example. In the comparative example, the opening and closing valves 35 and 55 (first drawing) and the horizontal sensors 36 and 56 (first drawing) are not attached to the buffer tanks 30 and 50.

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, the ink corresponding to the inflow amount flows 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, the ink corresponding to the inflow amount flows out through the outflow port 52.

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

Similarly, the liquid level in the buffer tank 50 is maintained at almost the same level as the level of the outflow port 52, and is displaced up and down in the vicinity of the 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, air bubbles are mixed into the ink circulating in the circulation path 20. When the bubbles mixed in the ink pass through the circulation path 20 and reach the inkjet head 40, the ejection of the ink 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 level higher than that of the outflow port 32. Because the liquid level is at the flow outlet 32 is also displaced up and down in the vicinity of the high level, so the outflow port 32 is always located below the liquid level. Thereby, the air in the buffer tank 30 can be prevented from entering the circulation path 20 through the outflow port 32. Likewise, air in the buffer tank 50 can be prevented from entering the circulation path 20 through the outflow port 52.

In order to increase the effect of preventing air from entering the circulation path 20, it is preferable to increase the height from the level of the outlet 32 to the liquid level at which the liquid level is the lowest, which is sufficiently larger than the amplitude of the liquid level displacement. For example, it is preferable that the height from the level of the outflow port 32 to the liquid level at which the liquid level is lowered to the lowest level is twice or more the amplitude of the liquid level displacement.

In the operation of the inkjet head 40, when the inflow port 31 is exposed above the liquid surface, bubbles are likely to be generated in the ink when the ink falls from the inflow port 31 toward the liquid surface. In order to prevent the generation of bubbles, it is preferable to set the level of the inflow port 31 to 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 is also set to be equal to or lower than the level of the outflow port 52 in the buffer tank 50.

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

Next, refer to FIG. 10 for the circulation path 20, the pumps 22, 23, and the buffer. The cleaning methods of the cans 30 and 50 and the inkjet head 40 will be described.

Fig. 10 is a schematic view showing the ink ejecting apparatus during washing. The ink in the main tank 21 is discarded before cleaning. Further, by operating the pumps 22 and 23, the ink in the circulation path 20 is collected in the main tank 21 and discarded. The ink remaining in the buffer tanks 30, 50 is discarded by opening the discharge valves 37, 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 cleaning liquid 71 is filled in the main tank 21, the pumps 22 and 23 are operated. Thereby, the cleaning liquid 71 is circulated in the circulation path 20. The liquid level of the cleaning liquid 71 in the buffer tank 30 is maintained at a level higher than the liquid level of the ink 70 at the time of ink ejection shown in Fig. 8. This state can be achieved by delaying the closing of the opening and closing valve 35 shown in Fig. 4. Similarly, the liquid level of the cleaning liquid 71 in the buffer tank 50 is also maintained at a level higher than the liquid level of the ink 70 at the time of ink ejection 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 functions of the buffer tanks 30 and 50 that suppress the flow rate pulsation are reduced. Therefore, the flow pulsation of the cleaning liquid generated in the pumps 22, 23 is transmitted to the inkjet head 40. The cleaning effect of the ink jet head 40 can be improved by the flow pulsation of the cleaning liquid.

Further, the liquid level of the cleaning liquid 71 in the buffer tanks 30, 50 is higher than the liquid level of the ink 70 (Fig. 8) at the time of ink ejection. Therefore, it is possible to effectively remove the ink residue adhering to the wall surface near the liquid level of the ink 70.

In the above embodiment, the measurement is performed by the horizontal sensor 36 (Fig. 1). The level in the buffer tank 30. Based on the measurement result, the timing at which the opening and closing valve 35 shown in Fig. 3 is opened and the timing at which the opening and closing valve 35 shown in Fig. 4 is closed are determined. Instead of using the level sensor 36 to measure the liquid level, the liquid level may be inferred based on the elapsed time since the start of the operation of the pumps 22, 23.

For example, the control of opening the on-off valve 35 shown in FIG. 3 may be performed from the time when the ink 70 starts to flow into the buffer tank 30 and the predetermined first time has elapsed. In addition, the control of closing the on-off valve 35 shown in FIG. 4 can be performed at a time when the second time set in advance is elapsed from the time when the on-off valve 35 is opened. The horizontal sensor 36 can be omitted when the opening and closing control timing of the opening and closing valve 35 is determined in accordance with the elapsed time.

The level of the buffer tank 50 can also be inferred based on the elapsed time since the start of the operation of the pumps 22, 23. Therefore, the opening and closing control of the opening and closing valve 55 can be performed based on the elapsed time from the start of the operation of the pumps 22 and 23.

Next, an ink ejecting apparatus based on another embodiment will be described with reference to Fig. 11. Hereinafter, differences from the embodiment shown in FIG. 1 will be described, and the description of the same configuration will be omitted.

Fig. 11 is a schematic view showing an ink ejecting apparatus based on another embodiment. In the present embodiment, the opening and closing valves 35, 55 are connected to the exhaust pump 65. When the opening and closing valve 35 is opened, the inside of the buffer tank 30 is exhausted by the exhaust pump 65. Similarly, when the opening and closing valve 55 is opened, the inside of the buffer tank 50 is exhausted by the exhaust pump 65.

By forcibly exhausting the inside of the buffer tank 30, the liquid level in the buffer tank 30 can be brought to a higher level in a state where the opening and closing valve 35 shown in Fig. 3 is opened. Similarly, when the opening and closing valve 55 shown in Fig. 6 is opened The liquid level in the buffer tank 50 can be brought to a higher level.

The present invention has been described above by way of examples, but the invention is not limited thereto. For example, various changes, modifications, combinations, and the like can be made, as will be apparent to those skilled in the art.

20‧‧‧Circular path

21‧‧‧ main can

22, 23‧‧‧ pump

25‧‧‧heater

30‧‧‧buffer tank

31‧‧‧Inlet

32‧‧‧Exit

33‧‧‧Inflow pipe

34‧‧‧Outflow tube

35‧‧‧Opening and closing valve

36‧‧‧Horizontal Sensor

37‧‧‧Drain valve

40‧‧‧Inkjet head

41‧‧‧Nozzle hole

42‧‧‧ platform

43‧‧‧Substrate

50‧‧‧buffer tank

51‧‧‧Inlet

52‧‧‧Exit

53‧‧‧Inflow pipe

54‧‧‧Outflow tube

55‧‧‧Opening and closing valve

56‧‧‧ horizontal sensor

57‧‧‧Drain valve

60‧‧‧Control device

Claims (6)

An ink ejecting apparatus having an ink jet 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; and a first buffer tank inserted a first inflow port and a first outflow port are provided in the circulation path between the inkjet head and the first pump, wherein the ink flows in through the first inflow port, and the ink flows out through the first outflow port; The first opening/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 outlet. The ink ejecting apparatus according to claim 1, further comprising: a control device that controls an operation of the first pump and an opening and closing of the first opening and closing valve, and the control device opens the first opening and closing valve When the first pump is operated, the ink flows into the first buffer tank, and the liquid level of the ink in the first buffer tank is higher than the first outlet. In the first opening and closing valve, the ink jet head is operated while the first opening/closing valve is closed. An ink jet device as claimed in claim 2, wherein The control device operates the first pump while the first opening/closing valve is closed before the first pump is opened, and the first pump is stored in the first buffer tank. After the liquid level of the ink reaches the level of the first outlet, the first opening and closing valve is opened. The ink ejecting apparatus according to any one of claims 1 to 3, further comprising: a second pump inserted into the circulation path and conveying the ink in the same direction as the first pump; The second buffer tank is inserted into the circulation path between the ink jet head and the second pump, and is provided with a second inflow port and a second outflow port, wherein the ink flows in through the second inflow port, and the ink passes through The second outlet is discharged, and the second opening/closing valve is configured to discharge the air in the second buffer tank to the outside from a position higher than the level of the second outlet. An ink ejecting method for ejecting ink from an ink ejecting apparatus, the ink ejecting apparatus having: an ink jet head inserted into a circulation path of the ink and ejecting the ink droplet; the first pump is inserted in The first buffer tank is inserted into the circulation path between the ink jet head and the first pump, and the first buffer inlet and the first flow outlet are provided in the circulation path, and the ink passes through the aforementioned The first inflow port flows in, and the ink flows out through the first outflow port; The first opening and closing valve is configured to discharge the air in the first buffer tank to a position higher than a level higher than a level of the first outlet, and a main tank that supplies the ink to the circulation path and circulates from the foregoing The first ink is operated while the first opening/closing valve is opened, and the ink flows into the first buffer tank, and the ink level of the ink in the first buffer tank is recovered. When the level is higher than the first outlet port, the first opening/closing valve is closed, and the ink jet head is operated while the first opening/closing valve is closed. The ink ejecting method according to claim 5, wherein the ink is discharged to the first buffer tank in a state where the first opening/closing valve is opened, and the first opening and closing valve is closed. The first pump operates to cause the ink to flow 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 outlet, the first one is opened. The opening and closing valve causes the ink to flow into the first buffer tank while the first opening and closing valve is opened.