TW201702084A - Ink-jet device and ink-jet method control temperature variation of ink since the heater heats ink flowing through the first path - Google Patents

Abstract

The invention provides an ink-jet device capable of suppressing the temperature variation of ink even if the flow quantity of ink supplied to the ink-jet head varies. Ink circulates in the first path. After branching from the branching portion of the first path, the second path returns to the confluent portion of the first path. The first pump inserted into the first path transports ink. A heater heats up the ink circulating in the first path. The ink-jet head inserted into the second path enables the ink flowing through the second path into droplets for jetting. The second pump inserted into the second path transports ink.

Description

Ink jet device and ink jet method

The present invention relates to an ink ejecting apparatus and an ink ejecting method for ejecting heated ink from an ink jet head.

Patent Document 1 listed below discloses an ink jet device in which an ink (liquid film material) is dropletized from an ink jet head (nozzle head) and ejected. In the ink jet device, ink is supplied to an ink jet head from a tank for storing ink, and the remaining ink is recovered from the ink jet head into the can. In order to reduce the viscosity of the ink, the ink is heated in the tank and in the ink transport path.

(previous technical literature) (Patent Literature)

Patent Document 1: International Publication No. 2013/015093

When the injection amount from the ink jet head fluctuates, the flow rate of the ink circulating in the transport path also fluctuates. Since the flow rate of the ink passing through the heater fluctuates, the temperature of the ink also changes. If the temperature of the ink supplied to the inkjet head When the degree is changed, the ejection of the ink from the inkjet head becomes unstable.

An object of the present invention is to provide an ink jet device and an ink jet method capable of suppressing variations in ink temperature even when the flow rate of ink supplied to the ink jet head fluctuates.

According to an aspect of the invention, there is provided an ink ejecting apparatus comprising: a first path in which ink is circulated; and a second path branched from a branching portion of the first path and returned to a confluent portion of the first path a first pump inserted into the first path and transporting the ink; a heater that heats the ink circulating in the first path; and an inkjet head inserted in the second path and flowing through the first The ink in the second path is dropletized and ejected, and the second pump is inserted into the second path to transport the ink.

According to another aspect of the present invention, there is provided an ink ejecting method for ejecting the ink using an ink ejecting apparatus, the ink ejecting apparatus having a first path in which ink is circulated, and a second path from the first After branching the branch portion of the path, returning to the junction portion of the first path; heating the heater to circulate the ink circulating in the first path; and inserting the inkjet head into the second path to form the ink droplet Chemical And ejecting, wherein the ink is heated by the heater while the ink is circulated in the first path, and the ink is passed through the second path in the first path to form the ink The ink is supplied to the ink jet head, and the ink supplied to the ink jet head is dropletized and ejected from the ink jet head.

When the flow rate of the ink flowing through the second path changes, the flow rate of the ink flowing through the first path also changes. At this time, the ratio of the amount of change with respect to the total flow rate of the ink flowing through the first path is smaller than the ratio of the amount of change with respect to the total flow rate of the ink flowing through the second path. Since the heater heats the ink flowing through the first path, it is possible to control the temperature fluctuation of the ink.

10‧‧‧1st path

11‧‧‧heater

12‧‧‧First pump

13‧‧‧1st temperature sensor

14‧‧‧Supply valve

15‧‧‧Supply tank

20‧‧‧2nd path

21‧‧‧Inkjet head

22‧‧‧2nd pump

23‧‧‧ Heat shield

24‧‧‧2nd temperature sensor

25‧‧‧Nozzle hole

26, 27‧‧‧ pressure sensor

28‧‧‧3rd pump

29‧‧‧buffer tank

31‧‧‧ branch

32‧‧‧Confluence

34‧‧‧buffer tank

40‧‧‧ platform

41‧‧‧Substrate

50‧‧‧Control device

60‧‧‧Supply tank

61‧‧‧Room 1

62‧‧‧Room 2

63‧‧‧Room 3

65‧‧‧Air valve

66‧‧‧Horizontal sensor

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

Fig. 2 is a schematic view showing an ink ejecting apparatus of another embodiment.

Fig. 3 is a schematic view showing a part of the first path of the ink jet device of the embodiment shown in Fig. 2 more specifically.

Fig. 4 is a schematic view showing an ink ejecting apparatus according to still another embodiment.

Fig. 5 is a flow chart showing an ink ejecting method using the ink ejecting apparatus shown in Fig. 4.

The ink ejecting apparatus of the embodiment will be described with reference to Fig. 1.

Fig. 1 is a schematic view showing an ink jet device of an embodiment. The ink ejecting apparatus of the embodiment has the first path 10 in which the ink is circulated. At the branch portion 31 of the first path 10, the second path 20 branches from the first path 10. The second path 20 merges with the first path 10 at the merging portion 32.

The heater 11 and the first pump 12 are inserted into the first path 10. As the heater 11, for example, an electric heater can be used. As the first pump 12, for example, a diaphragm pump can be used. It is preferable that the heater 11 and the first pump 12 are inserted into the path from the merging portion 32 to the branch portion 31. The first pump 12 conveys the ink in the first path 10. Since the ink is transported by the first pump 12, the ink circulates in the first path 10. The heater 11 heats the ink circulated in the first path 10.

The first temperature sensor 13 measures the temperature of the ink circulating in the first path 10. The measurement result is input to the control device 50.

The inkjet head 21 and the second pump 22 are inserted in the second path 20. As the second pump 22, for example, a diaphragm pump can be used similarly to the first pump 12. The second pump 22 conveys the ink in the second path 20 . When the second pump 22 is operated, a part of the ink circulated in the first path 10 flows into the second path 20 at the branch portion 31. After flowing through the second path 20, the ink that has flowed into the second path 20 merges with the ink flowing through the first path 10 at the merging portion 32.

The inkjet head 21 dropletizes and flows ink flowing from the second path 20 injection. The ink that has not been ejected flows out of the inkjet head 21, and returns to the first path 10 via the second path 20. The stage 40 holds the substrate 41 at a position opposed to the ink jet head 21. Since the droplets of the ink ejected from the inkjet head 21 land on the substrate 41, the ink is applied to the substrate 41.

Next, the excellent effects of the above embodiments will be described. The flow rate of the ink flowing through the first path 10 from the branch portion 31 to the merging portion 32 is indicated by Q1, and the flow rate of the ink flowing through the second path 20 is indicated by Q2. The flow rate of the ink flowing through the first path 10 from the merging portion 32 to the branch portion 31 is set to coincide with Q1 + Q2. When the ink is ejected from the inkjet head 21, the flow rate of the ink in the second path 20 on the upstream side of the inkjet head 21 and the second path 20 on the downstream side are different. Here, a state in which the ejection of the ink from the inkjet head 21 is not performed will be described.

The flow rate of the ink flowing through the heater 11 is Q1 + Q2. When the flow rate Q2 of the ink flowing through the inkjet head 21 fluctuates and becomes Q2+ΔQ2, the flow rate of the ink flowing through the heater 11 also varies by ΔQ2. The ratio (rate of change) with respect to the amount of change in the total flow rate flowing through the heater 11 is represented by ΔQ2 / (Q1 + Q2).

As a comparative example, a structure in which an ink jet head was inserted in one circulation path was examined. An ink jet head and a heater are inserted in one cycle path. If Q2 is used to indicate the flow rate of the ink flowing through the inkjet head, the flow rate of the ink flowing through the heater is also equal to Q2. If the flow rate of the ink flowing through the ink jet head varies by ΔQ2, the flow rate of the ink flowing through the heater also varies by ΔQ2. At this time, the ratio of the change amount of the total flow rate of the ink flowing through the heater 11 The rate (rate of change) is represented by ΔQ2/Q2.

The rate of change ΔQ2/(Q1+Q2) in the examples is smaller than the rate of change ΔQ2/Q2 in the comparative example. Therefore, according to the configuration of the embodiment, the rate of change in the flow rate of the ink flowing through the heater is reduced as compared with the configuration of the comparative example. Therefore, it is possible to reduce the fluctuation range of the ink temperature when the flow rate of the ink flowing through the ink jet head 21 is changed. Since the fluctuation range of the temperature is reduced, the stability of ink ejection can be improved.

In order to reduce the rate of change of the ink flow rate through the heater 11, it is preferable to set the flow rate Q1 to be more than the flow rate Q2. This flow rate can be realized by controlling the operations of the first pump 12 and the second pump 22.

Next, as another comparative example, a structure in which a large-capacity ink tank was inserted into one circulation path and a heater was placed in the ink tank was examined. In this comparative example, by controlling the ink temperature in the large-capacity ink tank to be constant, it is possible to reduce the fluctuation range of the temperature when the ink flow rate changes. However, as the temperature of the ink increases, the deterioration of the ink is accelerated. If the deterioration of the ink is accelerated, the ink must be replaced. If a large-capacity ink is stored in a heated state, a large amount of ink must be discarded when the ink is replaced.

In the above embodiment, since it is not necessary to store a large-capacity ink in a heated state, the amount of ink to be discarded can be reduced when the ink is replaced.

Next, the procedure from the start of the temperature rise of the ink to the ink ejection operation at the time of starting the operation of the ink jet device of the embodiment will be described.

First, the first pump 12 and the heater 11 are operated to heat the ink while circulating the ink in the first path 10. At this time, the second pump 22 is stopped. Therefore, the ink does not flow into the second path 20. If the first flow When the temperature of the ink of the path 10 reaches the first target temperature, the ink flows into the second path 20 by operating the second pump 22. Thereafter, the inkjet head 21 is operated to eject the ink.

In the above sequence, the low-temperature ink before heating does not flow into the second path 20. Since the viscosity of the low-temperature ink is high, if the low-temperature ink flows into the second path 20, the pressure loss increases, and the flow rate of the ink decreases. Therefore, the amount of heat radiation from the ink increases during the flow of the second path 20. As a result, it takes a long time until the temperature of the ink in the inkjet head 21 reaches the target temperature. In the embodiment, since the heated ink flows into the second path 20, it is possible to set the flow rate of the ink to be large from the beginning. Therefore, the time until the ink in the ink jet head 21 reaches the target temperature can be shortened.

Next, an ink jet device according to another embodiment will be described with reference to Figs. 2 to 3 . Hereinafter, differences from the embodiment shown in Fig. 1 will be described, and the description of the common configuration will be omitted.

Fig. 2 is a schematic view showing the ink ejecting apparatus of the present embodiment. The second temperature sensor 24 measures the temperature of the ink in the inkjet head 21. The measurement result of the second temperature sensor 24 is input to the control device 50.

The pressure sensor 26 measures the ink pressure in the second path 20 connected to the input side of the inkjet head 21. The pressure sensor 27 measures the ink pressure in the second path 20 connected to the output side of the inkjet head 21. The measurement results of the pressure sensors 26, 27 are input to the control device 50. The control device 50 can calculate the ink pressure in the inkjet head 21 based on the measurement results of the pressure sensors 26 and 27.

The supply tank 15 stores the ink supplied to the first path 10. A supply valve 14 is inserted in the first path 10. The ink is supplied from the supply tank 15 to the first path 10 via the supply valve 14. The supply valve 14 can switch between the replenishment state in which the ink is supplied from the replenishing tank 15 to the first path 10 and the non-replenishment state in which the ink is not replenished. The controller 50 controls the heater 11, the first pump 12, and the makeup valve 14.

Fig. 3 is a schematic view showing a part of the first path 10 of the ink jet device of the present embodiment. A supply tank 60 is inserted into the first path 10. The first chamber 61, the second chamber 62, and the third chamber 63 are provided in the supply tank 60. After flowing into the supply tank 60, the ink flowing through the first path 10 flows into the first chamber 61 from the lower end of the first chamber 61. A heater 11 is disposed in the first chamber 61. When the ink flows through the first chamber 61 from below, it can be heated by the heater 11.

The liquid level of the ink that has flowed into the first chamber 61 rises, and if it exceeds a certain height, the ink overflows from the first chamber 61 and flows into the second chamber 62. An end portion on the upstream side of the second path 20 is connected to the lower end of the second chamber 62. The connection portion between the second chamber 62 and the second path 20 corresponds to the branch portion 31 (Fig. 2). The ink in the second chamber 62 flows through the second path 20 and is supplied to the inkjet head 21. The second path 20 from the end on the upstream side to the inkjet head 21 is covered by the heat shield 23 . A plurality of nozzle holes 25 are provided on the surface of the inkjet head 21 facing downward. The dropletized ink is ejected from each of the nozzle holes 25.

When the liquid level of the ink in the second chamber 62 exceeds a certain height, the ink overflows from the second chamber 62 and flows into the third chamber 63. The ink flowing out from the lower end of the third chamber 63 is returned to the supply tank 60 through the first path 10. 1st The chamber 61, the second chamber 62, and the third chamber 63 constitute a part of the first path 10.

The downstream end of the second path 20 is connected to the side surface of the third chamber 63. The ink flowing in the second path 20 flows into the third chamber 63. The connection portion between the second path 20 and the third chamber 63 corresponds to the merging portion 32 (second drawing).

A buffer tank 34 is inserted into the second path 20 between the inkjet head 21 and the second pump 22. The buffer tank 34 suppresses the pulsation of the ink flow rate generated by the second pump 22 to the inkjet head 21.

An air valve 65 is attached to the upper surface of the supply tank 60. In the state where the air valve 65 is opened, atmospheric pressure is applied to the liquid surfaces of the ink in the first chamber 61, the second chamber 62, and the third chamber 63. In the present embodiment, the air valve 65 is opened during the operation of the ink ejecting apparatus.

The first pump 12 and the second pump 22 are controlled such that the flow rate of the ink flowing into the supply tank 60 through the first path 10 is larger than the flow rate of the ink supplied from the second chamber 62 to the inkjet head 21. Therefore, the ink always overflows from the second chamber 62 to the third chamber 63. Thereby, the liquid level of the ink in the second chamber 62 can be kept constant. The liquid level of the third chamber 63 is changed up and down depending on the amount of ink in a range lower than the liquid level of the second chamber 62.

A horizontal sensor 66 is disposed in the supply tank 60. The level sensor 66 measures the level of the ink in the third chamber 63. As the level sensor 66, for example, an ultrasonic level sensor, a floating level sensor, or the like can be used. The measurement result of the horizontal sensor 66 is input to the control device 50 (Fig. 2).

A first temperature sensor 13 is also provided in the supply tank 60. The first temperature sensor 13 measures, for example, the temperature of the ink in the second chamber 62.

The head pressure depending on the level difference from the nozzle hole 25 to the liquid level of the second chamber 62 is applied to the position of the nozzle hole 25 of the ink jet head 21. The head pressure applied to the position of the nozzle hole 25 can be adjusted by adjusting the height difference. When the total amount of ink flowing through the first path 10 and the second path 20 changes, the liquid level of the ink in the third chamber 63 changes, but the liquid level of the ink in the second chamber 62 remains constant. Therefore, even if the total amount of ink flowing through the first path 10 and the second path 20 is increased or decreased, the head pressure at the position of the nozzle hole 25 of the ink jet head 21 can be kept constant.

Next, another embodiment will be further described with reference to FIGS. 4 to 5. Hereinafter, differences from the embodiments shown in FIGS. 2 to 3 will be described, and the description of the common configuration will be omitted.

Fig. 4 is a schematic view showing the ink ejecting apparatus of the present embodiment. In the embodiment shown in FIGS. 2 and 3, the second pump 22 is inserted into the second path 20 on the downstream side of the inkjet head 21. In the embodiment shown in FIG. 4, in addition to the second pump 22, the third pump 28 is inserted into the second path 20 on the upstream side of the inkjet head 21. A buffer tank 29 is inserted into the second path 20 between the third pump 28 and the inkjet head 21.

By controlling the outputs of the second pump 22 and the third pump 28, the meniscus pressure at the position of the nozzle hole 25 of the ink jet head 21 can be adjusted.

Fig. 5 is a flow chart showing an ink ejecting method using the ink ejecting apparatus of Fig. 4. In step S1, the first pump 12 is operated by the control device 50 to circulate the ink in the first path 10. In the steps In S2, the control device 50 determines whether or not replenishment of the ink is required. Whether or not the ink needs to be replenished can be determined based on the liquid level of the ink of the third chamber 63 measured by the level sensor 66 installed in the supply tank 60. When the liquid level height is less than a predetermined reference value, it is determined that the ink needs to be replenished. If the liquid level height is equal to or higher than the reference value, it is determined that the ink is not required to be replenished.

When it is determined that the ink needs to be replenished, the first path 10 is replenished with ink in step S3. Specifically, the control device 50 switches the makeup valve 14 to the replenishing state. Thereby, the ink is supplied from the supply tank 15 to the first path 10. When the liquid level of the ink in the third chamber 63 becomes equal to or higher than the reference value, the replenishment of the ink is stopped. Specifically, the control device 50 switches the makeup valve 14 from the replenishment state to the non-replenishment state.

When it is determined in step S2 that the ink is not required to be replenished, or when the refilling of the ink is completed in step S2, the ink in the first path 10 starts to increase in temperature in step S4. Specifically, the control device 50 operates the heater 11.

In step S5, it is determined whether or not the temperature of the ink in the first path 10 has reached the first target temperature. The control device 50 can perform the determination based on the measurement result of the first temperature sensor 13. When the temperature of the ink does not reach the first target temperature, the ink is continuously circulated in the first path 10 until the first target temperature is reached.

When the temperature of the ink circulated in the first path 10 reaches the first target temperature, the ink starts to flow through the second path 20 in step S6. Specifically, the control device 50 operates the second pump 22 and the third pump 28. Thereby, the ink supply to the ink jet head 21 is started. At this time, the second pump 22 and the third pump 28 are controlled to operate at a predetermined output.

When the second path 20 starts to supply ink, the temperature of the line constituting the second path 20, the inkjet head 21, and the like is lower than the first target temperature. Therefore, the temperature of the ink flowing into the second path 20 decreases as the ink flows through the second path 20. At this time, the piping of the second path 20, the inkjet head 21, and the like are heated by the ink.

In step S7, it is determined whether or not the temperature of the ink in the inkjet head 21 reaches the second target temperature. The control device 50 performs this determination based on the measurement result of the second temperature sensor 24. The second target temperature is set to be almost the same as the first target temperature. When the temperature of the ink in the inkjet head 21 does not reach the second target temperature, the ink continues to flow through the second path 20 until the temperature of the ink reaches the second target temperature.

When the temperature of the ink in the inkjet head 21 reaches the second target temperature, control for raising the pressure of the ink in the inkjet head 21 is started in step S8. For example, the pressure of the ink in the inkjet head 21 can be increased by lowering the output of the second pump 22 (Fig. 2, Fig. 3) by the control device 50. At this time, the flow rate of the ink flowing through the second path 20 is lowered. The second pump 22 is controlled to be lowered to a preset output.

In addition to this, the output of both the second pump 22 and the third pump 28 can be lowered. When the amount of decrease in the output of the second pump 22 is larger than the amount of decrease in the output of the third pump 28, the pressure of the ink in the inkjet head 21 rises. In this case, the flow rate of the ink flowing through the second path 20 is lowered.

It is determined in step S9 whether the pressure of the ink in the inkjet head 21 rises. To the target pressure. The control device 50 performs this determination based on the measurement results of the pressure sensors 26, 27 (Fig. 2). When the pressure of the ink in the inkjet head 21 does not rise to the target pressure, the outputs of the second pump 22 and the third pump 28 are controlled until the target pressure is reached. For example, the control device 50 increases or decreases the output at a predetermined step.

If the pressure of the ink in the inkjet head 21 reaches the target pressure, the pressure of the ink in the inkjet head 21 falls within the allowable range in step S10, and the measurement results of the pressure sensors 26 and 27 are used. Feedback control of the outputs of the second pump 22 and the third pump 28 is performed. The inkjet head 21 is operated while performing feedback control of the outputs of the second pump 22 and the third pump 28. Thereby, ink droplets are ejected from the inkjet head 21.

Next, the excellent effects of the examples shown in Figs. 4 to 5 will be described. In the present embodiment, the ink that has flowed into the second path 20 is heated to the first target temperature (step S5). Since the viscosity of the ink is lowered by heating, the flow rate of the ink flowing through the second path 20 can be made high from the beginning. Therefore, similarly to the embodiment of Fig. 1, the time until the temperature of the ink in the ink jet head 21 reaches the second target temperature can be shortened.

In the embodiment shown in FIGS. 4 to 5, the time from when the ink starts flowing in the second path 20 (step S6) to when the pressure of the ink in the inkjet head 21 rises (step S8) During this time, the pressure of the ink in the inkjet head 21 is lower than the final target pressure. Therefore, it is possible to prevent leakage of the ink from the inkjet head 21 until the ink is ejected from the inkjet head 21.

As described above, the output of the second pump 22 or the outputs of the second pump 22 and the third pump 28 are set to be higher than the output of the ink ejection operation (step S11). . Therefore, the flow rate of the ink flowing through the second path 20 is larger than the flow rate at the time of the ink ejection operation. By setting the flow rate of the ink flowing through the second path 20 to be large, it is possible to shorten the period until the temperature of the ink in the ink jet head 21 reaches the second target temperature.

Further, in the embodiment shown in Figs. 4 to 5, the feedback control is performed after the pressure of the ink in the ink jet head 21 reaches the target pressure, so that the pressure in the ink jet head 21 falls within the allowable range. When the feedback control is started in a state where the difference between the pressure of the ink in the inkjet head 21 and the target pressure is large, the feedback control may become unstable. The instability of the feedback control can be avoided in the above embodiment.

Although the invention has been described above by way of examples, 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.

10‧‧‧1st path

11‧‧‧heater

12‧‧‧First pump

13‧‧‧1st temperature sensor

20‧‧‧2nd path

21‧‧‧Inkjet head

22‧‧‧2nd pump

31‧‧‧ branch

32‧‧‧Confluence

40‧‧‧ platform

41‧‧‧Substrate

Q1‧‧‧ Flow of ink flowing through the first path 10 from the branch portion 31 to the confluence portion 32

Q2‧‧‧Flow of ink flowing through the second path 20

50‧‧‧Control device

Claims (9)

An ink jet device having a first path in which ink is circulated, and a second path branched from a branch portion of the first path and returned to a merging portion of the first path; the first pump is inserted The ink is conveyed by the first path; the heater heats the ink circulated in the first path; and the ink jet head is inserted into the second path to dropletize the ink flowing through the second path The spraying is performed; and the second pump is inserted into the second path to convey the ink. The ink ejecting apparatus according to claim 1, further comprising: a replenishing tank that stores the ink supplied to the first path; and a replenishing valve that switches the ink from the replenishing tank to the first path a replenishment state and a non-replenishment state in which the ink is not replenished; a first temperature sensor measuring a temperature of the ink circulated in the first path; and a control device controlling the replenishing valve, the heater, and the first In the pump and the second pump, the control device sets the replenishing valve in the replenishing state and operates the first pump, and controls the heater while circulating the ink in the first path to heat the After switching the supply valve to the non-supply state, the ink is determined to circulate in the first path according to the measurement result of the first temperature sensor. When the ink temperature reaches the first target temperature, and it is determined that the ink temperature reaches the first target temperature, the second pump is operated to start supplying the ink to the second path. The ink ejecting apparatus according to claim 1 or 2, further comprising: a control device that controls an operation of the first pump and the second pump so as to be from the branching portion to the confluent portion The flow rate of the ink flowing through the first path is larger than the flow rate of the ink flowing through the second path. The ink ejecting apparatus according to claim 3, wherein the second pump is inserted into the second path on the downstream side of the ink jet head, and the ink ejecting apparatus further includes a third pump Inserting the second path on the upstream side of the inkjet head; and the second temperature sensor measures the temperature of the ink flowing through the second path, and the control device is based on the second temperature sensor The measurement result determines whether the temperature of the ink flowing through the second path reaches the second target temperature, and if it is determined that the temperature of the ink flowing through the second path reaches the second target temperature, the second pump and the aforementioned The third pump to make the front The pressure of the ink described above in the ink jet head rises. The ink ejecting apparatus according to claim 4, further comprising a pressure sensor for measuring a pressure of the ink in the ink jet head, wherein the control means uses the pressure of the ink in the ink jet head After controlling the second pump in a rising manner, it is determined whether the pressure of the ink in the ink jet head rises to a target pressure based on the measurement result of the pressure sensor, and it is determined that the pressure of the ink in the ink jet head rises. When the target pressure is reached, feedback control of the second pump and the third pump is performed in accordance with the measurement result of the pressure sensor so that the pressure of the ink in the ink jet head falls within an allowable range. An ink jet method for jetting the ink using an ink jet device having a first path in which ink is circulated, and a second path branched from a branch portion of the first path and returned to a junction portion of the first path; a heater that heats the ink circulated in the first path; and an inkjet head inserted into the second path to dropletize the ink and eject the ink The ink is circulated in the first path, and the ink is heated by the heater, and a part of the ink in the first path flows through the second path to supply the ink to the inkjet. The head, the aforementioned ink supplied to the aforementioned ink jet head is dropletized and ejected from the aforementioned ink jet head. The ink jet method according to claim 6, wherein the ink is not caused to flow through the second path before the ink is supplied to the ink jet head, and the ink is caused to be in the first path. While circulating the ink, the ink is heated by the heater, and when the temperature of the ink circulated in the first path reaches the first target temperature, a part of the ink circulated in the first path flows through the second path. . The ink jet method according to claim 7, wherein the temperature of the ink flowing through the second path after a part of the ink circulated in the first path starts flowing through the second path When the second target temperature is reached, the pressure of the ink in the ink jet head is raised. The ink jet method according to claim 8, wherein after the pressure of the ink in the ink jet head is raised, the pressure of the ink in the ink jet head falls within an allowable range. The ink is dropletized and ejected from the ink jet head while controlling the flow rate of the second path.