Coating applicator

Abstract

To prevent dryness of a nozzle to prevent clogging of the nozzle, caused by solidification of the liquid in the nozzle, preferably.SOLUTION: An electrostatic coating applicator 1 includes: a syringe 11 serving as a liquid discharge part having a nozzle 12 for discharging an ink 2 at a tip; and an electrostatic force generating circuit 25 which generates electrostatic force for retaining a humectant 3 for preventing dryness near the nozzle 12. The electrostatic force generating circuit 25 controls a position where the humectant 3 is present by controlling whether or not the electrostatic force is generated and a magnitude of the electrostatic force.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a coating device. [Background technology]

[0002] Electrostatic coating devices apply a voltage between a syringe with a nozzle at the tip and a counter electrode located at the coating destination, attracting the charged liquid to the coating destination. In coating devices such as electrostatic coating devices, it is necessary to prevent the liquid in the nozzle from drying out and solidifying, which can cause the nozzle to become clogged.

[0003] Regarding prevention of nozzle clogging, Patent Document 1 describes a liquid ejection device that caps a liquid ejection unit (inkjet head). The liquid ejection device described in Patent Document 1 includes a liquid ejection unit that can eject a first liquid from a nozzle, and a liquid receiving unit that can receive the first liquid discharged from the nozzle for the purpose of maintenance of the liquid ejection unit while storing a second liquid. The liquid receiving unit has a lip that can come into contact with the liquid ejection unit to cap the space including the nozzle. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 7415565 Summary of the Invention [Problem to be solved by the invention]

[0005] The liquid ejection device described in Patent Document 1 employs a method of covering the liquid ejection section to prevent the nozzle from drying out and to prevent the nozzle from being clogged due to solidification of the liquid inside the nozzle. Separately, a method is known in which atomized water vapor is generated around the nozzle to prevent the nozzle from drying out and to prevent the nozzle from being clogged due to solidification of the liquid inside the nozzle.

[0006] However, the former method requires a mechanism to cover the liquid spray unit, and this method cannot completely prevent the nozzle from drying out. The latter method has the problem that the generated steam falls on areas that do not need to be prevented from drying out, causing those areas to become flooded.

[0007] The present invention has been made in view of the above circumstances, and has as its object to provide a means for preventing the nozzles from drying out and for suitably preventing the nozzles from being clogged due to solidification of the liquid inside the nozzles. [Means for solving the problem]

[0008] (1) The coating device of the present invention includes a liquid ejection unit having a nozzle from which a first liquid is ejected, and an electrostatic force generating circuit that generates an electrostatic force to hold a second liquid in the vicinity of the nozzle to prevent it from drying.

[0009] According to the above coating device, by generating electrostatic force using the electrostatic force generating circuit and holding the second liquid near the nozzle, clogging of the nozzle due to solidification of the first liquid inside the nozzle can be effectively prevented.

[0010] (2) Preferably, the electrostatic force generating circuit may control the position where the second liquid is present by controlling whether or not the electrostatic force is generated, or the magnitude of the electrostatic force.

[0011] (3) Preferably, the liquid ejection unit is a syringe having the nozzle at its tip, and the coating device further includes a liquid storage unit located around the syringe, having an opening at its tip, and storing the second liquid, and the electrostatic force generating circuit may hold the second liquid around the nozzle by applying a voltage between the tip and rear end of the liquid storage unit.

[0012] (4) Preferably, the liquid ejection unit is a head having, on a first surface, the nozzle and another nozzle from which the first liquid is ejected, and the electrostatic force generating circuit applies a voltage between a first electrode located on the first surface of the head and a second electrode located on a second surface of the head that is the opposite surface to the first surface, and when the first liquid is not to be ejected from either the nozzle or the other nozzle, the electrostatic force generating circuit may apply, between the first electrode and the second electrode, a voltage that causes the second liquid to enter the nozzle, and when the first liquid is to be ejected from either the nozzle or the other nozzle, apply, between the first electrode and the second electrode, a voltage that prevents the second liquid from entering the nozzle.

[0013] (5) Preferably, the second liquid may be oil. [Effects of the Invention]

[0014] According to the present invention, it is possible to prevent the nozzle from drying out and to suitably prevent the nozzle from being clogged due to solidification of the liquid inside the nozzle. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 1 is a diagram showing the configuration of an electrostatic coating device 1 according to the first embodiment. [Figure 2] FIG. 2 is a schematic diagram showing the syringe 11 and the wetting agent storage unit 13 of the electrostatic coating device 1. [Figure 3] FIG. 3 is a diagram showing the configuration of a liquid ejection device 5 according to the second embodiment. [Figure 4] Fig. 4(A) is a schematic diagram showing the state of the head 30 when a first voltage Va is applied in the liquid ejection device 5. Fig. 4(B) is a schematic diagram showing the state of the head 30 when a second voltage Vb is applied in the liquid ejection device 5. DETAILED DESCRIPTION OF THE INVENTION

[0016] Hereinafter, coating devices according to first and second embodiments of the present invention will be described. Note that the embodiments described below are merely examples of the present invention, and it goes without saying that the embodiments of the present invention can be modified as appropriate without departing from the spirit and scope of the present invention.

[0017] [First embodiment] [Configuration of electrostatic coating device 1] In the first embodiment, an electrostatic applicator including a syringe with one nozzle will be described. As shown in Fig. 1, the electrostatic applicator 1 according to the first embodiment includes a syringe 11, a wetting agent storage unit 13, a counter electrode 17, a power supply circuit 21, a compressor 22, a regulator filter 23, a pressure gauge 24, an electrostatic force generating circuit 25, and a control unit 26.

[0018] As shown in FIGS. 1 and 2, the syringe 11 has a hollow cylindrical shape and contains the ink 2 therein. The syringe 11 has a front end and a rear end. The nozzle 12 is located at the front end of the syringe 11. The nozzle 12 is made of a conductive metal. The syringe 11 is positioned with the nozzle 12 facing downwards.

[0019] Counter electrode 17 is a flat electrode and is arranged horizontally inside electrostatic coater 1. Counter electrode 17 is arranged below (specifically, directly below) syringe 11. A medium 4 to be coated is placed on coating surface 18, which is the upper surface of counter electrode 17. Medium 4 is, for example, paper, cloth, or a metal plate.

[0020] Power supply circuit 21 has two output terminals and applies a predetermined voltage between syringe 11 and counter electrode 17. One output terminal of power supply circuit 21 is electrically connected to nozzle 12. The other output terminal of power supply circuit 21 is electrically connected to counter electrode 17. Power supply circuit 21 applies a voltage between nozzle 12 and counter electrode 17, thereby applying a voltage between syringe 11 and counter electrode 17. The voltage applied by power supply circuit 21 is, for example, several thousand volts to several tens of thousands of volts.

[0021] Compressor 22 generates compressed air. Regulator filter 23 reduces the pressure of the compressed air generated by compressor 22 to keep the pressure of the compressed air constant. Pressure gauge 24 measures the pressure of the compressed air that has passed through regulator filter 23. The compressed air generated by compressor 22 passes through regulator filter 23 and pressure gauge 24 and is applied to the rear end of syringe 11.

[0022] The control unit 26 controls the operation of the electrostatic applicator 1. The control unit 26 switches whether or not to operate the compressor 22. The control unit 26 controls the regulator filter 23 based on the pressure measured by the pressure gauge 24. The control unit 26 switches whether or not to eject the ink 2 from the nozzle 12 located at the tip of the syringe 11 by controlling the power supply circuit 21 based on image data supplied from outside the electrostatic applicator 1. The control unit 26 controls the electrostatic force generating circuit 25 as necessary.

[0023] The medium 4 placed on the coating surface 18 is moved two-dimensionally relative to the syringe 11 by a transport mechanism (not shown). By switching whether or not to eject the ink 2 from the nozzle 12 of the syringe 11 while moving the medium 4 two-dimensionally relative to the syringe 11, a desired image can be recorded on the medium 4 and coating can be performed on the medium 4.

[0024] [Wetting agent storage section 13 and electrostatic force generating circuit 25] The wetting agent storage section 13 is located around the syringe 11 and stores therein a wetting agent 3 to prevent drying. The wetting agent storage section 13 has, for example, a cylindrical shape that houses the syringe 11. The wetting agent storage section 13 has a front end section 14 and a rear end section 15, and has an opening 16 at the front end. The front end section 14 and the rear end section 15 are formed of a conductive metal.

[0025] The wetting agent 3 is a liquid that prevents the nozzle 12 from drying out. The wetting agent 3 is, for example, water or oil. Mineral oil, vegetable oil, animal oil, or a synthetic oil thereof can be used as the wetting agent 3. Mineral oil is a hydrocarbon obtained from petroleum, such as liquid paraffin. Vegetable oil is, for example, oleic acid or linoleic acid obtained from plants such as beans, sunflower, and rice. Animal oil is, for example, palmitic acid or stearic acid obtained from beef tallow.

[0026] The electrostatic force generating circuit 25 has two output terminals and applies a predetermined voltage between the front end 14 and the rear end 15 of the wetting agent storage unit 13. One output terminal of the electrostatic force generating circuit 25 is electrically connected to the front end 14 of the wetting agent storage unit 13. The other output terminal of the electrostatic force generating circuit 25 is electrically connected to the rear end 15 of the wetting agent storage unit 13. By applying a voltage between the front end 14 and the rear end 15 of the wetting agent storage unit 13, the electrostatic force generating circuit 25 generates an electrostatic force for holding the wetting agent 3 for preventing drying near the nozzle 12 of the syringe 11.

[0027] As shown in FIG. 2, if the mass of the wetting agent 3 is m, a downward force mg and an upward electrostatic force Felec act on the wetting agent 3. The magnitude of the electrostatic force Felec varies depending on the voltage applied by the electrostatic force generating circuit 25. The higher the voltage applied by the electrostatic force generating circuit 25, the greater the electrostatic force Felec, and the higher the liquid level of the wetting agent 3 becomes. On the other hand, the lower the voltage applied by the electrostatic force generating circuit 25, the smaller the electrostatic force Felec, and the lower the liquid level of the wetting agent 3 becomes. The electrostatic force generating circuit 25 controls whether or not to generate an electrostatic force by switching between applying and not applying a voltage. Alternatively, the electrostatic force generating circuit 25 controls the magnitude of the electrostatic force by controlling the magnitude of the applied voltage. In this way, the electrostatic force generating circuit 25 controls the location of the wetting agent 3 by controlling whether or not to generate an electrostatic force or the magnitude of the electrostatic force.

[0028] In the first embodiment, the syringe 11 is an example of a liquid ejection unit. The ink 2 is an example of a first liquid. The wetting agent 3 is an example of a second liquid. The wetting agent storage unit 13 is an example of a liquid storage unit.

[0029] [Effects of the first embodiment] As described above, the electrostatic coating device 1 according to the first embodiment includes a syringe 11 (liquid ejection unit) having a nozzle 12 from which ink 2 (first liquid) is ejected, and an electrostatic force generating circuit 25 that generates an electrostatic force to hold a wetting agent 3 (second liquid) in the vicinity of the nozzle 12 to prevent drying.

[0030] Therefore, according to the electrostatic coating device 1 of the first embodiment, by generating electrostatic force using the electrostatic force generating circuit 25 and holding the wetting agent 3 in the vicinity of the nozzle 12, clogging of the nozzle 12 due to solidification of the ink 2 in the nozzle 12 can be effectively prevented.

[0031] Furthermore, the electrostatic force generating circuit 25 controls whether or not an electrostatic force is generated, or the magnitude of the electrostatic force, thereby controlling the location of the wetting agent 3. Therefore, by controlling whether or not an electrostatic force is generated, or the magnitude of the electrostatic force, with the electrostatic force generating circuit 25, it is possible to switch whether or not the wetting agent 3 is held near the nozzle 12.

[0032] The liquid ejection unit is a syringe 11 having a nozzle 12 at its tip, and the electrostatic applicator 1 further includes a wetting agent container 13 (liquid container) located around the syringe 11, having an opening 16 at its tip, and containing a wetting agent 3. The electrostatic force generating circuit 25 applies a voltage between the tip 14 and rear end 15 of the wetting agent container 13, thereby holding the wetting agent 3 around the nozzle 12. Therefore, by applying a voltage between the tip 14 and rear end 15 of the wetting agent container 13, the wetting agent 3 is held around the nozzle 12, preventing clogging of the nozzle 12 due to solidification of the ink 2 in the nozzle 12.

[0033] [Second embodiment] [Configuration of liquid ejection device 5] In the second embodiment, an inkjet liquid ejection device equipped with a head having multiple nozzles will be described. As shown in Fig. 3, the liquid ejection device 5 according to the second embodiment includes a head 30, an electrostatic force generating circuit 41, and a control unit 42.

[0034] The head 30 has a nozzle surface 32 and an opposite surface 33 that is the surface opposite the nozzle surface 32. The head 30 is arranged so that the nozzle surface 32 is on the bottom and the opposite surface 33 is on the top. A plurality of nozzles 31 are formed regularly on the nozzle surface 32. Ink 2 supplied from an ink supply unit (not shown) is located inside each nozzle 31. A first electrode 34 is located in a position on the nozzle surface 32 where no nozzle 31 is formed. A second electrode 35 is located on the opposite surface 33. The head 30 has a piezoelectric element 36 corresponding to each nozzle 31.

[0035] The control unit 42 controls the plurality of piezo elements 36 included in the head 30 based on image data supplied from outside the liquid ejection device 5. Each piezo element 36 deforms according to the control of the control unit 42, and switches whether or not to eject ink 2 from the corresponding nozzle 31.

[0036] A medium 6 is positioned below the head 30. The medium 6 is, for example, paper, cloth, or a metal plate. The medium 6 is moved two-dimensionally relative to the head 30 by a transport mechanism (not shown). By switching whether or not to eject ink 2 from the multiple nozzles 31 of the head 30 while moving the medium 6 two-dimensionally relative to the head 30, a desired image can be recorded on the medium 6 and coating can be performed on the medium 4.

[0037] [Electrostatic force generating circuit 41] The electrostatic force generating circuit 41 has two output terminals and applies a voltage between the first electrode 34 and the second electrode 35 of the head 30. One output terminal of the electrostatic force generating circuit 41 is electrically connected to the first electrode 34 located on the nozzle surface 32 of the head 30. The other output terminal of the electrostatic force generating circuit 41 is electrically connected to the second electrode 35 located on the opposite surface 33 of the head 30. By applying a voltage between the first electrode 34 and the second electrode 35 of the head 30, the electrostatic force generating circuit 41 generates an electrostatic force for holding the anti-drying wetting agent 3 near the nozzles 31 of the head 30.

[0038] 3 and 4, a wetting agent 3 is attached to the nozzle surface 32 of the head 30. The wetting agent 3 is applied to the nozzle surface 32 by a maintenance mechanism (not shown) of the head 30. The control unit 42 controls the electrostatic force generating circuit 41 at the timing of the start of image recording, the end of image recording, the start of maintenance, the end of maintenance, etc.

[0039] As shown in Figures 4(A) and (B), the electrostatic force generating circuit 41 selectively applies a first voltage Va and a second voltage Vb between the first electrode 34 and the second electrode 35 of the head 30 under control of the control unit 42. The first voltage Va is a voltage at which the wetting agent 3 enters the nozzle 31. The second voltage Vb is a voltage at which the wetting agent 3 does not enter the nozzle 31. The first voltage Va is higher than the second voltage Vb. Note that the piezo element 36 is not shown in Figure 4.

[0040] When ink 2 is not being ejected from any of the multiple nozzles 31, the electrostatic force generating circuit 41 applies a first voltage Va between the first electrode 34 and the second electrode 35 of the head 30, which causes the wetting agent 3 to enter the nozzles 31 (FIG. 4(A)). As a result, the nozzles 31 of the head 30 are covered with the wetting agent 3.

[0041] When ink 2 is ejected from any of the plurality of nozzles 31, the electrostatic force generating circuit 41 applies a second voltage Vb between the first electrode 34 and the second electrode 35 of the head 30, which prevents the wetting agent 3 from entering the nozzle 31 (FIG. 4(B)). This opens the lid on the nozzle 31 of the head 30.

[0042] In the second embodiment, the head 30 is an example of a liquid ejection section. The ink 2 is an example of a first liquid. The humectant 3 is an example of a second liquid. The nozzle 31 of the head 30 is an example of a nozzle. The other nozzle 31 of the head 30 is an example of another nozzle. The nozzle surface 32 is an example of a first surface. The opposite surface 33 is an example of a second surface. The first voltage Va is an example of a voltage that causes the second liquid to enter the nozzle. The second voltage Vb is an example of a voltage that prevents the second liquid from entering the nozzle.

[0043] [Effects of the second embodiment] As described above, in the liquid ejection device 5 according to the second embodiment, the liquid ejection section is a head 30 having, on a nozzle surface 32 (first surface), a nozzle 31 (nozzle) from which ink 2 is ejected and another nozzle 31 (another nozzle) from which ink 2 is ejected, and the electrostatic force generating circuit 41 applies a voltage between a first electrode 34 located on the nozzle surface 32 of the head 30 and a second electrode 35 located on the opposite surface 33 opposite the nozzle surface 32. When ink 2 is not ejected from either the nozzle 31 or the other nozzles 31, the electrostatic force generating circuit 41 applies a first voltage Va between the first electrode 34 and the second electrode 35, which causes the humectant 3 to enter the nozzle 31, and when ink 2 is ejected from either the nozzle 31 or the other nozzles 31, it applies a second voltage Vb between the first electrode 34 and the second electrode 35, which prevents the ink 2 from entering the nozzle 31.

[0044] Therefore, according to the liquid ejection device 5 of the second embodiment, when the ink 2 is not being ejected from any of the multiple nozzles 31, a first voltage Va that causes the humectant 3 to enter the nozzle 31 is applied between the first electrode 34 and the second electrode 35, so that the humectant 3 that has entered the nozzle 31 prevents the ink 2 from coming into contact with the air, and prevents the nozzle 31 from clogging due to the ink 2 drying inside the nozzle 31. When the ink 2 is being ejected from any of the multiple nozzles 31, a second voltage Vb that prevents the humectant 3 from entering the nozzle 31 is applied between the first electrode 34 and the second electrode 35, so that the ink 2 can be ejected from the multiple nozzles 31 without being hindered by the humectant 3.

[0045] [Variations] Various modifications can be made to the electrostatic applicator 1 according to the first embodiment. The electrostatic applicator according to the modifications does not need to include the counter electrode 17. In this case, the medium 4 needs to be a conductor in order to function as the counter electrode. The electrostatic applicator according to the modifications does not need to include the compressor 22, regulator filter 23, or pressure gauge 24. The electrostatic applicator according to the modifications does not need to include the regulator filter 23 or pressure gauge 24. The liquid contained in the syringe 11 and discharged from the nozzle 12 may be something other than the ink 2 (for example, a cleaning liquid).

[0046] Various modifications can also be made to the liquid ejection device 5 according to the second embodiment. In the second embodiment, the first electrode 34 is located at a position on the nozzle surface 32 where no nozzles 31 are formed, and the second electrode 35 is located on the opposite surface 33. However, in electrostatic coating devices according to modifications, the first electrode 34 and the second electrode 35 may be located in a narrower range. Furthermore, in electrostatic coating devices according to modifications, the first electrode 34 may be located at the position of the medium 6 rather than on the nozzle surface 32 of the head 30. [Explanation of symbols]

[0047] 1. Electrostatic coating device (coating device) 2. Ink (first liquid) 3. Wetting agent (second liquid) 4, 6...medium 5. Liquid ejection device (coating device) 11. Syringe 12, 31 Nozzle 13 Wetting agent storage section 14...Tip 15...Rear end 25, 41... Electrostatic force generating circuit 30 heads 32 Nozzle surface (first surface) 33... Opposite side (2nd side) 34...1st electrode 35...Second electrode

Claims

1. a liquid ejection unit having a nozzle for ejecting the first liquid; an electrostatic force generating circuit that generates an electrostatic force to hold the second liquid for preventing drying near the nozzle.

2. 2. The coating device according to claim 1, wherein the electrostatic force generating circuit controls the position of the second liquid by controlling whether or not the electrostatic force is generated or the magnitude of the electrostatic force.

3. the liquid discharge unit is a syringe having the nozzle at a tip thereof, a liquid storage section located around the syringe, having an opening at a tip, and configured to store the second liquid; 3. The coating device according to claim 1, wherein the electrostatic force generating circuit applies a voltage between the front end and rear end of the liquid storage portion to hold the second liquid around the nozzle.

4. the liquid ejection unit is a head having, on a first surface, the nozzle and another nozzle from which the first liquid is ejected; the electrostatic force generating circuit applies a voltage between a first electrode located on the first surface of the head and a second electrode located on a second surface of the head that is the opposite surface to the first surface; 3. The coating device according to claim 1, wherein, when the first liquid is not ejected from either the nozzle or the other nozzle, the electrostatic force generating circuit applies a voltage between the first electrode and the second electrode that causes the second liquid to enter the nozzle, and when the first liquid is ejected from either the nozzle or the other nozzle, it applies a voltage between the first electrode and the second electrode that prevents the second liquid from entering the nozzle.

5. 3. The coating device according to claim 1, wherein the second liquid is oil.

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