Electrostatic coating device and electrostatic coating method

Abstract

To provide an electrostatic coating device and an electrostatic coating method capable of expanding the adjustment width of a discharge amount of liquid and more accurately controlling a discharge mode of the liquid.SOLUTION: An electrostatic coating device 1 comprises: a syringe 10 having a storage space 11 and a nozzle 12; an opposing electrode 41 that is disposed to face the syringe 10; a voltage generator 42 that applies a voltage between the syringe 10 and the opposing electrode 41; a pressure generator 22 that applies pressure to the storage space 11; a measuring device 50 that measures a property of liquid 2 in the storage space 11; and a control device 30. The control device 30 synchronously varies a voltage applied by the voltage generator 42 and a pressure applied by the pressure generator 22 to discharge the liquid 2 from the nozzle 12, and changes the voltage value and the pressure value on the basis of a measurement value obtained by the measuring device 50.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to an electrostatic coating device and an electrostatic coating method that eject a liquid by electrostatic force. [Background technology]

[0002] An example of a conventional electrostatic coating device is described in Patent Document 1. The device in Patent Document 1 creates a constant negative pressure inside a reservoir container (21) that stores ink, forming an ink meniscus in a nozzle (22) at the bottom of the container. In this state, a voltage is applied between the nozzle (22) and a gate plate (14), causing ink to be ejected from the nozzle (22) by electrostatic force. Patent Document 1 also describes that the negative pressure inside the reservoir container (21) may be adjusted depending on the viscosity of the ink. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2022-103179 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in Patent Document 1, the pressure inside the reservoir container (21) is applied to form an ink meniscus at the nozzle, and the force for ejecting the ink is provided solely by electrostatic force due to an electric field. Therefore, there is a limit to the range of adjustment for the ink ejection amount. Furthermore, various factors such as the type of ink being ejected and the environment affect the ink ejection characteristics, so it is desirable to more accurately control the ink ejection mode by taking these influences into account.

[0005] Therefore, an object of the present disclosure is to provide an electrostatic coating device and an electrostatic coating method that can expand the adjustment range of the liquid discharge amount and more accurately control the liquid discharge mode. [Means for solving the problem]

[0006] An electrostatic coating device according to a first aspect of the present disclosure includes a syringe having a storage space for storing a liquid and a nozzle for ejecting the liquid toward a recording medium, a counter electrode arranged opposite the syringe, a voltage generator for applying a voltage between the syringe and the counter electrode, a pressure generator for applying pressure to the storage space of the syringe, a measuring device for measuring the properties of the liquid in the storage space, and a control device, wherein the control device changes the voltage applied by the voltage generator and the pressure applied by the pressure generator in synchronization with each other to eject the liquid from the nozzle, and changes the value of the voltage and the value of the pressure based on the measurement value by the measuring device.

[0007] As a result, the electrostatic applicator according to the present disclosure can expand the range of adjustment for the liquid ejection force by synchronously changing the voltage and pressure. Furthermore, the liquid ejection device according to the present disclosure changes the voltage and pressure values ​​according to the measurement values, so it can apply an appropriate ejection force according to the properties of the liquid and accurately control the liquid ejection mode. [Effects of the Invention]

[0008] According to the electrostatic coating device and electrostatic coating method of the present disclosure, it is possible to widen the adjustment range of the liquid discharge amount and to more accurately control the liquid discharge mode. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic diagram showing the configuration of an electrostatic coating device according to an embodiment. [Figure 2] FIG. 2 is a flowchart showing an example of the operation of the electrostatic coating device. [Figure 3] FIG. 3 is a schematic graph showing how pressure and voltage change with changes in the properties of the liquid. [Figure 4] FIG. 4 is a schematic graph showing how pressure and voltage change with changes in the properties of the liquid. [Figure 5] FIG. 5 is a schematic diagram showing the configuration of an electrostatic coating device according to a modified example. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments of an electrostatic coating device and an electrostatic coating method according to the present disclosure will be described with reference to the drawings. Note that, hereinafter, identical or corresponding elements will be designated by the same reference numerals throughout the drawings, and redundant explanations will be omitted.

[0011] (Configuration of electrostatic coating device) FIG. 1 is a schematic diagram showing the configuration of an electrostatic coater 1 according to an embodiment of the present disclosure. As shown in FIG. 1, the electrostatic coater 1 includes a syringe 10, which is a container for storing a liquid 2. The syringe 10 has a storage space 11, which is an internal space of a predetermined capacity, and the liquid 2 is stored in this storage space 11. The syringe 10 has a nozzle 12 at its bottom that ejects the liquid 2 toward the recording medium A. The nozzle 12 has a passage through which the liquid 2 can flow. One end (top end) of this passage communicates with the storage space 11 of the syringe 10, and the other end (bottom end) forms an opening that communicates with the outside.

[0012] As will be described later, the electrostatic applicator 1 discharges the liquid 2 stored in the syringe 10 from the nozzle 12 by the action of electrostatic force and pressure (air pressure). The liquid 2 discharged by the electrostatic applicator 1 is a highly viscous liquid, for example, a liquid with a viscosity of 1,000 mPa·s or more in the environment in which electrostatic coating is performed, and more typically a liquid with a viscosity of 10 Pa·s or more.

[0013] The electrostatic coating device 1 includes a pressure system 20 for applying pressure to the liquid 2, an electric field system 40 for generating an electric field that applies an electrostatic force to the liquid 2, and a control device 30 for controlling these. Of these, the control device 30 is composed of a processor that performs arithmetic processing, a ROM that stores computer programs and various data, a RAM that temporarily stores data during calculations, and the like.

[0014] The pressure system 20 mainly includes an air pipe 21 , a pressure generator 22 , a regulator filter 23 , and a pressure gauge 24 .

[0015] Air pipe 21 is a tube that is rigid enough not to deform due to internal pressure, and is made of synthetic resin or metal. One end of air pipe 21 is connected to the top of syringe 10, and the other end is connected to pressure generator 22. Pressure generator 22 is driven in accordance with instructions from control device 30 to pressurize or depressurize air taken in from the outside and send it to air pipe 21. Various types of compressors can be used as pressure generator 22, and for example, a reciprocating compressor that compresses air by changing the volume with a reciprocating piston can be used.

[0016] A regulator filter 23 and a pressure gauge 24 are provided in air piping 21 between syringe 10 and pressure generator 22. Regulator filter 23 is an air pressure regulator and includes, for example, a valve, a biasing means such as a spring that biases the valve, a diaphragm, and an electric motor that drives the biasing means. Regulator filter 23 operates in accordance with instructions from control device 30, and, for example, adjusts high-pressure air input from an inlet to lower-pressure air and outputs the adjusted air from an outlet.

[0017] The pressure gauge 24 is disposed between the regulator filter 23 and the syringe 10, i.e., downstream of the regulator filter 22 in the pressure transmission direction. Various measuring instruments capable of measuring air pressure can be used as the pressure gauge 24, and for example, a manometer that measures pressure from the displacement of a liquid column in a pipe can be used. This pressure gauge 24 measures the pressure (air pressure) in the air pipe 21 and outputs the measurement result as an electrical signal to the control device 30.

[0018] On the other hand, the electric field system 40 mainly includes the nozzle 12, a counter electrode 41, and a voltage generator .

[0019] Voltage generator 42 is composed of a voltage source, a waveform generating circuit, etc., and outputs voltages having various waveforms in accordance with instructions from control device 30. The voltage source may be a battery as an internal power source, or an external power source such as a commercial power source may be used.

[0020] As described above, the nozzle 12 has a passage through which the liquid 2 flows, and is made of a conductive material such as metal. In the present disclosure, the counter electrode 41 is a plate-like member that supports the recording medium A, and is disposed below and facing the syringe 10. The counter electrode 41, like the nozzle 12, is made of a conductive material such as metal. A voltage output from a voltage generator 42 is applied between the nozzle 12 and the counter electrode 41.

[0021] The operation of the pressure system 20 and the electric field system 40 described above is controlled by the control device 30. For example, in the pressure system 20, the pressure generator 22 generates a predetermined pressure based on a control signal from the control device 30. At the same time, the regulator filter 23 adjusts the pressure transmitted from the pressure generator 22 through the air pipe 21 to the predetermined pressure based on the control signal from the control device 30. Meanwhile, the pressure gauge 24 measures the pressure in the air pipe 21 and outputs a signal indicating the measured value to the control device 30. The control device 30 causes the regulator filter 23 to adjust the pressure based on the input signal.

[0022] This applies a predetermined pressure to the storage space 11 of the syringe 10. This pressure keeps the liquid 2 in a state where it forms a meniscus at the lower opening of the nozzle 12, or applies a discharge force to the liquid 2 to discharge it from the lower opening of the nozzle 12.

[0023] Meanwhile, in the electric field system 40, the voltage generator 42 generates a predetermined voltage based on a control signal from the control device 30. This voltage is applied between the nozzle 12 and the counter electrode 41. As a result, the liquid 2 in the nozzle 12 is charged to a predetermined potential, and a predetermined electric field is generated between the nozzle 12 and the counter electrode 41. This electric field applies an ejection force (electrostatic force) from the nozzle 12 to the liquid 2 in the nozzle 12.

[0024] In the electrostatic applicator 1 according to the present disclosure, the liquid 2 is ejected from the nozzle 12 by the ejection force applied by the pressure system 20 and the ejection force applied by the electric field system 40, and the recording medium A is coated with the liquid 2. Furthermore, the electrostatic applicator 1 according to the present disclosure is capable of ejecting even a highly viscous liquid 2 by changing the pressure generated by the pressure system 20 and the voltage generated by the electric field system 40 in synchronization with each other.

[0025] Although the above example illustrates a configuration in which the counter electrode 41 supports the recording medium A, the present invention is not limited to this. A support that supports the recording medium A may be provided separately from the counter electrode 41. When the recording medium A is made of metal, the recording medium A may also function as a counter electrode.

[0026] The viscosity of the liquid 2 in the syringe 10 can change due to changes in the surrounding environment (for example, changes in temperature or humidity) or the progression of drying over time. When the viscosity changes, the discharge characteristics from the nozzle 12 change. In the electrostatic applicator 1 according to the present disclosure, the control device 30 controls the pressure system 20 and the electric field system 40 based on such changes in the properties of the liquid (particularly, viscosity). For this reason, the electrostatic applicator 1 is equipped with a measuring device 50 that measures the properties of the liquid 2.

[0027] The electrostatic coating device 1 in FIG. 1 is equipped with a viscometer 51 as a measuring device 50. The viscometer 51 measures the viscosity of the liquid 2 in the syringe 10 constantly or intermittently (periodically). For example, a B-type viscometer can be used as this viscometer 51. The B-type viscometer has a spindle as a measuring unit 52 that directly measures the viscosity of the liquid 2 in the storage space 11. In the example of FIG. 1, the measuring unit 52 made of a spindle is disposed near the nozzle 12, making it possible to measure the viscosity of the liquid 2 immediately before discharge. The measurement value measured by the viscometer 51 is input to the control device 30.

[0028] Although Fig. 1 shows a B-type viscometer (single cylinder type rotational viscometer), which is a type of rotational viscometer, other rotational viscometers may also be used. For example, a coaxial double cylinder type rotational viscometer or a cone-plate type (E type) rotational viscometer may also be used.

[0029] (Operation of electrostatic coating device) 2 is a flowchart showing an example of the operation of the electrostatic coater 1. An example of the electrostatic coating process, which is the operation of the electrostatic coater 1, will be described in more detail with reference to this FIG.

[0030] First, this electrostatic coating process is started when the control device 30 receives a coating command from the outside (step S1: YES). When the electrostatic coating process is started, the electrostatic coating device 1 measures the properties of the liquid 2 in the syringe 10 (step S2). Specifically, the properties of the liquid 2 are measured by the measuring device 50, and more specifically, the viscosity of the liquid 2 is measured by the viscometer 51. Then, based on the measured values, values ​​(initial values) of the pressure for imparting a discharge force to the liquid 2 and the voltage that contributes to the electrostatic force are determined (step S3).

[0031] The electrostatic applicator 1 controls the pressure system 20 based on the pressure value determined in step S3, and controls the electric field system 40 based on the voltage value determined in step S3. This applies a predetermined pressure to the syringe 10, and generates an electric field between the nozzle 12 and the counter electrode 41. As a result, an ejection force is applied to the liquid 2 in the nozzle 12, and the liquid 2 is ejected from the nozzle 12 (step S4). The ejected liquid 2 travels from the nozzle 12 toward the counter electrode 41 and lands (coats) on the recording medium A.

[0032] The electrostatic applicator 1 according to the present disclosure intermittently changes the pressure and voltage in synchronization with each other. More specifically, the pressure generator 20 generates a pulsed pressure (pressure waveform), and the voltage generator 40 generates a pulsed voltage with the same period as the pressure waveform. This allows the liquid 2 to be ejected from the nozzle 12 even if it has a relatively high viscosity, and results in an intermittent ejection mode in which the liquid is ejected with the same period as the pressure and voltage.

[0033] After discharging the liquid 2 in step S4, it is determined whether all coating has been completed (step S5). That is, it is determined whether the coating content determined in the coating instruction received in step S1 has been completed. If coating has been completed (S5: YES), the electrostatic coating process ends. On the other hand, if coating has not been completed (S5: NO), the properties (viscosity) of the liquid 2 in the syringe 12 are measured again (step S6).

[0034] If there is no change in the properties of the liquid 2 (S6: NO), the operations from step S4 are repeated. On the other hand, if the properties of the liquid 2 have changed (S6: YES), the values ​​of pressure and voltage for applying a discharge force to the liquid 2 are changed based on the changed properties (viscosity) (step S8). Then, the operations from step S4 are executed to continue coating based on the changed pressure and voltage.

[0035] (Pressure and Voltage Variations) Next, the change in pressure and voltage according to the properties of the liquid 2, which is performed in step S8 of the electrostatic coating process in Fig. 2, will be described with reference to Fig. 3 and Fig. 4. Fig. 3 and Fig. 4 are schematic graphs showing how the pressure and voltage are changed in accordance with changes in the properties of the liquid 2. Note that these graphs use viscosity as an example of the property of the liquid 2.

[0036] A first example of a modified embodiment is shown in Figure 3A. In the state shown on the left in Figure 3A, when the liquid 2 has a viscosity Vi1, a pressure of waveform Wp1 is applied to the liquid 2, and a voltage of waveform Wv1 is applied between the nozzle 12 and the counter electrode 41. Here, the pressure waveform Wp1 is a rectangular pulse waveform with a pulse width Xp1 and a pulse height Yp1, and the voltage waveform Wv1 is a rectangular pulse waveform with a pulse width Xv1 and a pulse height Yv1. Note that these pressure and voltage change in synchronization with each other at the same cycle.

[0037] From this state, as shown on the right side of FIG. 3A, let us assume that the viscosity of liquid 2 changes to viscosity Vi2, which is greater than viscosity Vi1 (S7: YES). In this case, in the example of FIG. 3A, the pressure changes from waveform Wp1 to waveform Wp2, and the voltage changes from waveform Wv1 to waveform Wv2 (S8). That is, with regard to pressure, the pulse height remains Yp1, but the pulse width increases from Xp1 to Xp2 (>Xp1). Similarly, with regard to voltage, the pulse height remains Yv1, but the pulse width increases from Xv1 to Xv2 (>Xv1).

[0038] Thus, in the example of Figure 3A, when the viscosity changes and increases, the waveforms of both the pressure and voltage are changed so that the pulse width increases. As a result, an appropriate discharging force can be applied to the liquid 2 regardless of the change in viscosity. For example, by performing a coating process including the modified embodiment described in Figure 3A, the electrostatic applicator 1 can continue to discharge the same amount of liquid 2 at the same cycle before and after the viscosity change. Of course, it is also possible to arbitrarily change the liquid discharge amount or cycle before and after the viscosity change.

[0039] A second example of the modification is shown in Figure 3B. The state shown on the left in Figure 3B is the same as the state shown on the left in Figure 3A, and therefore a detailed description thereof will be omitted. From this state, as shown on the right in Figure 3B, it is assumed that the viscosity of the liquid 2 changes to a viscosity Vi2 that is greater than the viscosity Vi1 (S7: YES). In this case, in the example of Figure 3B, the pressure waveform is changed from Wp1 to Wp3, and the voltage waveform is changed from Wv1 to Wv3 (S8).

[0040] That is, for pressure, the pulse width remains at Xp1 but the pulse height increases from Yp1 to Yp3 (>Yp1), while for voltage, the pulse height remains at Yv1 but the pulse width increases from Xv1 to Xv2 (>Xv1), similar to the waveform Wv2 shown on the right of Figure 3A.

[0041] Thus, in the example of Figure 3B, when the viscosity changes and increases, the pressure waveform is changed so that the pulse height increases, and the voltage waveform is changed so that the pulse width increases. As a result, an appropriate discharging force can be applied to the liquid 2 regardless of the change in viscosity. For example, by performing a coating process including the modified embodiment described in Figure 3B, the electrostatic applicator 1 can continue to discharge the same amount of liquid 2 at the same cycle before and after the viscosity change. Of course, it is also possible to arbitrarily change the liquid discharge amount or cycle before and after the viscosity change.

[0042] A third example of the modified mode is shown in Figure 4A. The state shown on the left in Figure 4A is the same as the state shown on the left in Figure 3A, and therefore a detailed description thereof will be omitted. From this state, as shown on the right in Figure 4A, it is assumed that the viscosity of the liquid 2 changes to a viscosity Vi2 that is greater than the viscosity Vi1 (S7: YES). In this case, in the example of Figure 4A, the pressure waveform is changed from Wp1 to Wp4, and the voltage waveform is changed from Wv1 to Wv4 (S8).

[0043] That is, as for pressure, the pulse width increases from Xp1 to Xp4 (>Xp1), and the pulse height also increases from Yp1 to Yp4 (>Yp1).On the other hand, as for voltage, the pulse width increases from Xv1 to Xv2 (>Xv1) while the pulse height remains Yv1, similar to the waveform Wv2 shown on the right of Figure 3A.

[0044] Thus, in the example of Figure 4A, when the viscosity changes and increases, the pressure waveform is changed so that both the pulse width and pulse height increase, and the voltage waveform is changed so that the pulse width increases. As a result, an appropriate discharging force can be applied to the liquid 2 regardless of the change in viscosity. For example, by performing a coating process including the modified embodiment described in Figure 4A, the electrostatic applicator 1 can continue to discharge the same amount of liquid 2 at the same cycle before and after the viscosity change. Of course, it is also possible to arbitrarily change the liquid discharge amount or cycle before and after the viscosity change.

[0045] In the examples of Figures 3A, 3B, and 4A described above, when the viscosity of the liquid 2 increases, the pressure waveform and voltage waveform are both changed so that the pulse width and / or pulse height increases. However, the manner in which the pressure and voltage are changed is not limited to this. One of the pressure waveform and the voltage waveform may be increased while the other is decreased. This example will be described with reference to Figure 4B.

[0046] Figure 4B shows a fourth example of the modification. The state shown on the left in Figure 4B is the same as the state shown on the left in Figure 3A, and therefore a detailed description thereof will be omitted. From this state, as shown on the right in Figure 4B, it is assumed that the viscosity of the liquid 2 changes to a viscosity Vi2 that is greater than the viscosity Vi1 (S7: YES). In this case, in the example of Figure 4B, the pressure waveform is changed from Wp1 to Wp5, and the voltage waveform is changed from Wv1 to Wv5 (S8).

[0047] That is, regarding the pressure, as the pulse width increases from Xp1 to Xp5 (>Xp1), the pulse height also increases from Yp1 to Yp5 (>Yp1). On the other hand, regarding the voltage, the pulse height remains at Yv1, but the pulse width decreases from Xv1 to Xv5 (<Xv1).

[0048] Thus, in the case of the example of FIG. 4B, similar to the example of FIG. 4A, when the viscosity changes and increases, the waveform of the pressure is changed so that both the pulse width and the pulse height increase. On the other hand, the example of FIG. 4B is different from the example of FIG. 4A regarding the voltage, and in the case of the example of FIG. 4B, the waveform is changed so that the pulse width decreases. However, in the case of FIG. 4B, the increase in the discharge output due to the change in the pressure waveform is set to be larger than the increase in the discharge output due to the change in the pressure waveform in the case of FIG. 4A. Therefore, the total discharge output applied to the liquid 2 by the pressure and the voltage can be adjusted to be the same in the case of the right waveform of FIG. 4A and the case of the right waveform of FIG. 4B, or can be adjusted to any different discharge outputs.

[0049] Therefore, even in the case of the example of FIG. 4B, regardless of the change in viscosity, an appropriate discharge output can be applied to the liquid 2. For example, the electrostatic coating device 1 can continuously discharge the same amount of the liquid 2 in the same cycle before and after the change in viscosity by executing a coating process including the modified mode described in FIG. 4B. Of course, it is also possible to arbitrarily change the discharge amount or the end period of the liquid before and after the change in viscosity.

[0050] In addition, in the above-described example, the case where the viscosity of the liquid 2 increases has been described, but the electrostatic coating method according to the present disclosure can also be applied to the case where the viscosity of the liquid 2 decreases. That is, even when the viscosity of the liquid 2 decreases, the discharge amount of the liquid 2 can be accurately controlled by changing the pressure and the voltage according to the change in viscosity. Also, in the above-described example, the pulse height of the voltage is constant before and after the change in viscosity. This prevents discharge from occurring between the nozzle 12 and the counter electrode 41 by increasing the pulse height.

[0051] (Example of how to adjust pressure and voltage) Here, an example of a method for adjusting the pressure and voltage when the ejection amount (application amount) of the liquid 2 is maintained constant before and after the change in viscosity will be further described.

[0052] Three typical factors affect the ejection of the liquid 2: pressure, electrostatic force which is correlated with the square of the voltage, and viscous resistance. When the sum of the pressure and electrostatic force exceeds the viscous resistance, the liquid 2 can be ejected. Therefore, if the pressure is Fp, the electrostatic force is Fe, the viscous resistance is Fv, and the total force of these is F, the condition for ejecting the liquid 2 can be expressed as follows (1): F = Fp + Fe - Fv > 0 (1)

[0053] Next, suppose that the viscosity of liquid 2 doubles, and the viscous resistance force changes from Fv to Fv' (= 2 × Fv). In this case, if the total force F is kept constant, the total value of the pressure and electrostatic force after the change, Fp' + Fe', is calculated from equation (1) as follows: Fp'+Fe'=F+2×Fv In other words, the total value of the pressure and electrostatic force needs to be multiplied by (Fp'+Fe') / (Fp+Fe) times the original value Fp+Fe, or in other words, by (F+2×Fv) / (Fp+Fe).

[0054] Therefore, the pressure Fp' can be adjusted by multiplying the pressure Fp before the change by (F+2×Fv) / (Fp+Fe), and the electrostatic force Fe' can be adjusted by multiplying the voltage before the change by √((F+2×Fv) / (Fp+Fe)). Note that the above-described methods of adjusting the pressure and voltage are merely examples, and the specific methods of the electrostatic coating process of the present disclosure are not limited to these.

[0055] (Variation) 1 includes a measuring device 50 configured to directly measure the viscosity of the liquid 2 in the syringe 10, but the configuration of the electrostatic applicator 1 is not limited to this. That is, a configuration including a measuring device that indirectly measures the properties of the liquid 2 in the syringe 10 may also be employed. FIG. 5 is a schematic diagram showing the configuration of an electrostatic applicator 1A according to a modified example.

[0056] 1, the electrostatic coating apparatus 1A is provided with a measuring device 53. The measuring device 53 measures the amount of liquid 2 discharged from the nozzle 12. More specifically, the measuring device 53 is a weight scale, which supports the counter electrode 41 from below, for example, and can measure the weight of the liquid 2 that has landed on the recording medium A on the counter electrode 41.

[0057] Generally, when a constant discharging force is applied to the liquid 2 in the nozzle 12, if the viscosity of the liquid 2 changes, the amount of liquid 2 discharged from the nozzle 12 due to the constant discharging force also changes. In other words, there is a correlation between the viscosity of the liquid 2 and the amount of liquid 2 discharged. Therefore, by measuring the weight of the liquid 2 that has landed on the recording medium A using the measuring device 53 and comparing the weight of the liquid 2 that has landed on the recording medium A with the weight of the liquid 2 that should have been discharged, it is possible to obtain changes in the properties (viscosity) of the liquid 2. Therefore, the electrostatic coating device 1A can also perform the electrostatic coating process shown in the flowchart of FIG. 2.

[0058] Here, an example of a method for adjusting the pressure and voltage to return the discharge amount to a correct value when the discharge amount of the liquid 2 changes, that is, to suppress the change in the discharge amount and maintain it constant, will be described.

[0059] The discharge amount of liquid 2 changes when the total force F in equation (1) above changes. Therefore, for example, an increase in the discharge amount by n times is equivalent to the total force F' becoming n times the original F. Therefore, in order to maintain a constant discharge amount, it is necessary to adjust the total value of the pressure and electrostatic force to decrease, and subtract (n-1)F from the total force F', which has become n times F, to return it to its original value F.

[0060] For example, if only the pressure is adjusted, the adjusted pressure Fp' will be Fp-(n-1)F, so the pressure should be multiplied by (Fp-(n-1)F) / Fp. Also, if only the electrostatic force is adjusted, the adjusted electrostatic force Fe' will be Fe-(n-1)F, so the voltage should be multiplied by √((Fe-(n-1)F) / Fe).

[0061] When adjusting both pressure and electrostatic force, (n-1)F, which is the value to be subtracted from the total force F' before adjustment, can be allocated to pressure adjustment and electrostatic force adjustment. For example, (n-1)F = Ftp + Fte, where Ftp is used for pressure adjustment and Fte is used for electrostatic force adjustment. In this case, the pressure can be adjusted by a factor of (Fp-Ftp) / Fp. The voltage can also be adjusted by a factor of √((Fe-Fte) / Fe).

[0062] As described above, the electrostatic coating device and electrostatic coating method disclosed herein adjust the pressure and voltage based on changes in the properties of the liquid, thereby expanding the range over which the amount of liquid discharged can be adjusted and enabling more accurate control of the liquid discharge pattern. [Industrial Applicability]

[0063] The present disclosure can be applied to an electrostatic coating device and an electrostatic coating method that eject a liquid by electrostatic force. [Explanation of symbols]

[0064] 1,1A Electrostatic Coating Device 2 liquid 10 syringes 11 Storage space 12 nozzles 22 Pressure generator 30 Control device 40 Voltage Generator 41 Counter electrode 50 Measuring Equipment 52 Measurement section

Claims

1. a syringe having a storage space for storing a liquid and a nozzle for discharging the liquid toward a recording medium; a counter electrode disposed opposite the syringe; a voltage generator that applies a voltage between the syringe and the counter electrode; a pressure generating device that applies pressure to the storage space of the syringe; a measuring device for measuring the properties of the liquid in the storage space; a control device; The control device the voltage applied by the voltage generator and the pressure applied by the pressure generator are changed in synchronization with each other to eject the liquid from the nozzle; changing the voltage value and the pressure value based on the measurement value by the measurement device; Electrostatic coating device.

2. The measuring device measures the viscosity of the liquid constantly or intermittently. The electrostatic coating device according to claim 1 .

3. the measuring device has a measuring unit that directly measures the viscosity of the liquid stored in the storage space, 3. The electrostatic coating device according to claim 2.

4. the measuring device measures the amount of liquid ejected from the nozzle; The electrostatic coating device according to claim 1 .

5. the measuring device measures the weight of the liquid that has landed on the recording medium; 5. The electrostatic coating device according to claim 4.

6. the voltage generator generates a pulse waveform voltage; the pressure generator generates a pulse waveform pressure; the control device changes the pulse width of the pulse-waveform voltage and changes the pulse height or pulse width of the pulse-waveform pressure based on the measurement value. The electrostatic coating device according to claim 1 .

7. An electrostatic coating method using an electrostatic coating device including a syringe having a storage space for storing a liquid and a nozzle for discharging the liquid toward a recording medium, and a counter electrode disposed opposite the syringe, a voltage applied between the syringe and the counter electrode and a pressure applied to the storage space of the syringe are changed in synchronization with each other to eject the liquid from the nozzle; changing the voltage value and the pressure value based on a measurement value relating to the properties of the liquid in the storage space; Electrostatic coating method.

8. As the property of the liquid, the viscosity of the liquid is measured continuously or intermittently. The electrostatic coating method according to claim 7.

9. Directly measuring the viscosity of the liquid stored in the storage space; The electrostatic coating method according to claim 8.

10. measuring the amount of liquid ejected from the nozzle as information related to the properties of the liquid; The electrostatic coating method according to claim 7.

11. measuring the weight of the liquid that has landed on the recording medium as the ejection amount of the liquid; The electrostatic coating method according to claim 10.

12. The voltage has a pulse waveform. The pressure has a pulse waveform. a pulse width of the pulse waveform voltage is changed based on the measurement value, and a pulse height or a pulse width of the pulse waveform pressure is changed based on the measurement value; The electrostatic coating method according to claim 7.

Images