Electrostatic inkjet head and printer

Abstract

This electrostatic inkjet head discharges a liquid in a nozzle by an electrostatic suction method. The electrostatic inkjet head is provided with: a body part in which a plurality of the nozzles are arranged; a first electrode which applies a pulse voltage for charging the liquid; and a first shielding member which is arranged between the nozzles adjacent to each other from among the plurality of nozzles and inside the body part along a discharge direction of the liquid, which has an end part on the opposite side in the discharge direction and said end part on the opposite side is positioned more on the opposite side than the first electrode, and which shields an electric field generated by the first electrode.

Description

Electrostatic inkjet head and printing device

[0001] The present disclosure relates to an electrostatic inkjet head and a printing device that ejects charged liquid from nozzles using an electrostatic suction method (EHD: Electro Hydro Dynamic).

[0002] In recent years, progress has been made in the development of manufacturing technologies for printed electronics, which are formed on substrates using printing technology. One printing technology that can be used to manufacture printed electronics is electrostatic inkjet, which applies ink to a substrate by electrostatically attracting the ink from an electrode on the substrate.

[0003] In electrostatic inkjet printing, in order to improve ejection stability, it is important to suppress interference of electric fields caused by a potential difference between electrodes provided in adjacent nozzles. For example, Patent Document 1 discloses a technology for preventing interference of electric fields by using a conductive member provided between the ejection electrodes of adjacent nozzles.

[0004] Japanese Patent Application Laid-Open No. 2002-166555

[0005] In Patent Document 1, the conductive member is provided only in a portion between the ink ejection openings of adjacent nozzles, which can cause interference of the electric field between the electrodes of adjacent nozzles in areas where the conductive member is not provided.

[0006] An object of the present disclosure is to provide an electrostatic inkjet head that can reduce the influence of an electric field generated by an electrode provided in a nozzle, and a printing device that has such an electrostatic inkjet head.

[0007] An electrostatic inkjet head according to one aspect of the present disclosure is an electrostatic inkjet head that ejects liquid in nozzles by an electrostatic suction method, and includes: a main body in which a plurality of the nozzles are arranged; a first electrode that applies a pulse voltage to charge the liquid; and a first shielding member that is arranged inside the main body along the ejection direction of the liquid and between adjacent nozzles among the plurality of nozzles, has an end on the opposite side in the ejection direction, and is located on the opposite side of the first electrode, and shields an electric field generated by the first electrode.

[0008] A printing device according to one aspect of the present disclosure includes the electrostatic inkjet head described above, a moving device that moves a substrate to be printed relative to the electrostatic inkjet head, a counter electrode installed on the moving device, and a control device that controls the electrostatic inkjet device and the moving device.

[0009] According to the present invention, it is possible to reduce the influence of the electric field generated by the electrode provided in the nozzle.

[0010] FIG. 1 is a diagram for explaining an example of the configuration of a printing device according to an embodiment of the present disclosure; FIG. 2 is a schematic diagram for explaining the configuration of a printing device including an electrostatic inkjet head of a first configuration example; FIG. 3 is a schematic diagram for explaining the configuration of a printing device including an electrostatic inkjet head of a second configuration example; FIG. 4 is a diagram showing the end face of the main body of the electrostatic inkjet, viewed from the front side in the ejection direction of the main body; FIG. 5 is a diagram showing an example when the second shielding member has a mesh shape; FIG. 6 is a diagram showing an example when the second shielding member has a mesh shape; FIG. 7 is a diagram showing an example when the second shielding member has a mesh shape; FIG. 8 is a diagram for explaining the charging voltage and ejection voltage supplied to the charging electrode and ejection electrode corresponding to each of two adjacent nozzles;

[0011] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. However, more detailed explanation than necessary, such as detailed explanation of well-known matters or redundant explanation of substantially the same configuration, may be omitted.

[0012] [Printing Device 100] <Overall Configuration> Fig. 1 is a diagram illustrating an example of the configuration of a printing device 100 according to an embodiment of the present disclosure. Fig. 1 is a top view of the printing device 100. Note that in this embodiment, the installation surface of the printing device 100 is described as an XY plane, and the direction perpendicular to the installation surface is the Z-axis direction. In Fig. 1, for example, the X-axis and Y-axis are included in a horizontal plane, and the Z-axis is set along the vertical direction. However, in this disclosure, the liquid ejection device does not necessarily have to be installed on a horizontal plane, and a slight tilt may be allowed.

[0013] The printing device 100 includes an electrostatic inkjet head 10 or 20, a liquid tank 30, a stage 40, a control unit 50, a liquid supply channel 60, and a liquid recovery channel 70. The notation "electrostatic inkjet head 10 (20)" in Fig. 1 indicates that the printing device 100 includes either an electrostatic inkjet head 10 of a first configuration example described below, or an electrostatic inkjet head 20 of a second configuration example described thereafter.

[0014] In this specification, the positive side in the Z-axis direction corresponds to the upper side as viewed from the printing device 100, and the negative side in the X-axis direction corresponds to the lower side as viewed from the printing device 100. As shown in Fig. 1, the printing device 100 including the electrostatic inkjet head 10 or 20 is installed on a horizontal surface, and the electrostatic inkjet head 10 or 20 ejects liquid downward (see Fig. 2 described below). That is, in this specification, the upper side corresponds to the positive side in the Z-axis direction and the negative side in the ejection direction of the liquid. Also, in this specification, the lower side corresponds to the negative side in the Z-axis direction and the positive side in the ejection direction of the liquid.

[0015] The electrostatic inkjet head 10 or 20 ejects a liquid such as ink toward a print target medium 300 placed on a stage 40. The liquid tank 30 stores the liquid to be supplied to the electrostatic inkjet head 10. The stage 40 is a transport means for relatively moving the electrostatic inkjet head 10 or 20 and the print target medium 300 such as a substrate. The control unit 50 controls the operation of the electrostatic inkjet head 10 and the stage 40. The liquid supply flow path 60 is a flow path that supplies liquid from the liquid tank 30 to the electrostatic inkjet head 10 or 20. The liquid recovery flow path 70 is a flow path that recovers liquid from the electrostatic inkjet head 10 or 20 to the liquid tank 30.

[0016] <Electrostatic Inkjet Head> (First Configuration Example) A first configuration example of an electrostatic inkjet head according to an embodiment of the present disclosure will be described below. FIG. 2 is a schematic diagram for explaining the configuration of a printing device 100 including an electrostatic inkjet head 10 of the first configuration example. FIG. 2 shows a cross section of the electrostatic inkjet head 10 at a position where the nozzles are arranged, a counter electrode 80, and a print target medium 300 held by the counter electrode 80. The counter electrode 80 is disposed on the stage 40 shown in FIG. 1. FIG. 2 shows a cross section in a plane (XZ plane) parallel to the ejection direction of the electrostatic inkjet head 10.

[0017] The electrostatic inkjet head 10 includes a reservoir 11, a silo 12, a nozzle 13, a charging electrode 14, a main body 15, a charging voltage waveform generating unit 16, a first shielding member 17, and a second shielding member 18. The charging electrode 14 is an example of the first electrode of the present disclosure.

[0018] 1 , the reservoir 11 stores the liquid supplied from the liquid tank 330. The reservoir 11 is connected to a liquid supply flow path 60 and a liquid recovery flow path 70. The reservoir 11 is connected to a plurality of nozzles 13 via silos 12, which are individual flow paths.

[0019] The nozzle 13 is a nozzle that ejects liquid. The liquid used in the printing device 100 according to this embodiment may be, for example, silver nano-ink, ink containing metal particles other than silver, ink made of a conductive solvent, ink made of an insulating solvent, UV ink, solder paste, etc. The viscosity of the liquid may be in the range of 3 mPa·s to 20,000 mPa·s.

[0020] The nozzle 13 has an ejection port 13A at the end on the positive side (i.e., the lower side) in the ejection direction of the liquid, and the inner diameter (nozzle diameter) of the nozzle 13 and the ejection port 13A may be formed to be, for example, 0.5 μm or more and 200 μm or less.

[0021] The nozzles 13 are formed inside a plurality of recesses 15D provided in the main body 15. More specifically, as shown in Fig. 2, the nozzles 13 are disposed in the centers of the recesses 15D, and grooves 15G are formed around the nozzles 13. The grooves 15G reduce the area of ​​the region surrounding the ejection ports 13A at the lower ends of the nozzles 13, thereby preventing the liquid from spreading over the lower end faces of the nozzles 13 due to the surface tension of the liquid.

[0022] In this way, the nozzle 13 is formed inside the recess 15D so as to protrude downward from the upper bottom surface of the recess 15D in the ejection direction.

[0023] Due to the shape of the nozzle 13, the discharge port 13A provided at the lower end of the nozzle 13 is located above the lower end surface 15S of the main body 15 in the discharge direction.

[0024] 2, the plurality of nozzles 13 are arranged in a specific arrangement direction. In the example shown in FIG. 2, the arrangement direction of the plurality of nozzles 13 is the X-axis direction.

[0025] The charged electrode 14 is an electrode that applies a pulse voltage to the liquid inside the nozzle 13 to cause it to be ejected from the nozzle. The charged electrode 14 is disposed inside the nozzle 13 and near the ejection port 13A. A charged electrode 14 is disposed for each nozzle 13. The lower end of the charged electrode 14 is located at the lower end of the nozzle 13 in the ejection direction, i.e., at the position of the ejection port 13A. The upper end of the charged electrode 14 is located a predetermined distance above the ejection port 13A in the ejection direction. The length of the charged electrode 14 along the ejection direction may be set appropriately based on factors such as the magnitude of the pulse voltage applied to the liquid inside the nozzle 13, and is, for example, 30 μm. The pulse voltage applied to the liquid by the charged electrode 14 is supplied by a charged voltage waveform generator 16.

[0026] In this specification, the liquid near the ejection port 13A includes the liquid present in the area close to the ejection port 13A inside the nozzle 13 and the liquid forming a meniscus that bulges from the ejection port 13A toward the lower side of the nozzle 13 (the opposing electrode 80 side).

[0027] The main body 15 is a member on which other components of the electrostatic inkjet head 10 are provided. As described above, the main body 15 has a plurality of recesses 15D formed along the arrangement direction of the nozzles 13. The main body 15 is made of an insulating material such as glass, ceramic, or resin.

[0028] Under the control of the control unit 50 (see FIG. 1 ), the charging voltage waveform generation unit 16 applies pulse voltages independently to the charging electrodes 14 provided on the plurality of nozzles 13. The charging voltage waveform generation unit 16 and the control unit 50 are connected to each other by, for example, a flexible cable.

[0029] The first shielding member 17 is, for example, a grounded plate-like member that shields the electric field generated by the charging electrode 14. The first shielding member 17 is disposed inside the main body 15, substantially perpendicular to the arrangement direction (X-axis direction) of the nozzles 13. In other words, the surfaces of the plate-like first shielding member 17 extend in the ejection direction and in a depth direction perpendicular to the ejection direction and the arrangement direction. The depth direction is the Y-axis direction shown in FIG. 2 .

[0030] 2, of the two end portions of the first shielding member 17 in the ejection direction, the end portion 17A on the opposite side in the ejection direction (i.e., the upper side in FIG. 2) is located above the charging electrode 14. Furthermore, of the two end portions of the first shielding member 17 in the ejection direction, the end portion 17B on the positive side in the ejection direction (i.e., the lower side in FIG. 2) is located at the position of the lower end surface 15S of the main body 15 in the ejection direction. In other words, the lower end portion 17B of the first shielding member 17 is located below the charging electrode 14.

[0031] Furthermore, the rear end of the plate-shaped first shielding member 17 in the depth direction is located further back than the rear end of the charging electrode 14. The front end of the first shielding member 17 in the depth direction is located further forward than the front end of the charging electrode 14. The rear side in the depth direction corresponds to the rear side in Fig. 2, and the front side in the depth direction corresponds to the front side in Fig. 2. As a result, the first shielding member 17 is disposed over a wider area than the charging electrode 14 in the depth direction, which is perpendicular to the arrangement direction of the multiple nozzles 13 and the ejection direction.

[0032] 2, a plurality of first shielding members 17 are formed between adjacent nozzles 13. Also, as shown in FIG. 2, the first shielding members 17 are arranged outside the nozzles 13 at both ends in the arrangement direction of the plurality of nozzles 13. The first shielding members 17 arranged outside the nozzles 13 at both ends in the arrangement direction of the nozzles 13 may be arranged symmetrically with the first shielding members 17 that are one nozzle inside the nozzle 13 at both ends, with the nozzle 13 at the center. Note that in the first configuration example, "outside the nozzles 13 at both ends in the arrangement direction" refers to a side that is farther away from the center of the electrostatic inkjet head 10 in the arrangement direction than the nozzles 13 at both ends. Also, "inside the nozzles 13 at both ends in the arrangement direction" refers to a side that is closer to the center of the electrostatic inkjet head 10 in the arrangement direction than the nozzles 13 at both ends.

[0033] In this way, the first shielding member 17 is arranged so as to cover an area wider in the ejection direction and the depth direction than the area in which the charged electrode 14 is arranged. This allows the first shielding member 17 to effectively shield the electric field generated by the charged electrode 14. By placing the first shielding member 17 between adjacent nozzles 13, it is possible to effectively prevent the charged electrode 14 formed on one nozzle 13 from affecting the liquid ejected from the adjacent nozzle 13. This makes it possible to effectively prevent the electric field generated by the charged electrode 14 formed on one nozzle 13 from attracting the liquid ejected from another nozzle 13, preventing the liquid from landing at the desired position.

[0034] Here, in the electrostatic inkjet head 10 of the first configuration example, the upper end 17A of the first shielding member 17 is positioned above the charged electrode 14, so that the component of the electric field generated by the charged electrode 14 that occurs above the charged electrode 14 can be particularly effectively shielded.

[0035] Furthermore, in the electrostatic inkjet head 10 of the first configuration example, the lower end 17B of the first shielding member 17 is positioned below the charged electrode 14, thereby making it possible to particularly effectively shield the component of the electric field generated by the charged electrode 14 that occurs below the charged electrode 14.

[0036] The second shielding member 18 is grounded like the first shielding member 17, and is a member that shields the electric field generated by the charging electrode 14. The second shielding member 18 is formed along the lower end surface 15S of the main body 15 so as to exclude the position of the ejection port 13A of the nozzle 13. Note that the second shielding member 18 may be electrically connected to the first shielding member 17.

[0037] The second shielding member 18 is formed on the entire lower end surface 15S of the main body 15, excluding the recess 15D. The second shielding member 18 may be uniformly formed on the entire end surface 15S. Alternatively, the second shielding member 18 may have a mesh shape, with a portion of the end surface 15S exposed through the mesh. The mesh shape of the second shielding member 18 may include a polygonal shape, such as a triangle, a square, or a hexagon, or a circle. The main body 15, which is made of ceramic or glass, and the second shielding member 18, which is made of metal, have significantly different linear expansion coefficients, resulting in a difference in the degree of expansion when temperature changes occur. The difference in expansion degree may apply force to the second shielding member 18, causing the second shielding member 18 to peel off from the end surface 15S of the main body 15. To prevent this, it is desirable that the mesh shape of the second shielding member 18 is parallel to the arrangement direction (for example, the X-axis direction shown in Figure 2) in which the multiple nozzles 13 are arranged side by side, and does not have any straight line portions longer than the distance between adjacent nozzles 13.

[0038] This will be explained in more detail. Even if the mesh shape includes, as part thereof, straight line portions that are parallel to the arrangement direction of the multiple nozzles 13, these straight line portions are connected to parts that are not parallel to the arrangement direction of the mesh shape. The length of these straight line portions is formed to be shorter than the distance between adjacent nozzles 13. This makes it possible to prevent the electric field generated by the charged electrode 14 provided in one nozzle 13 from being transmitted to the charged electrode 14 provided in an adjacent nozzle 13 via the straight line portions of the mesh shape.

[0039] However, the present disclosure is not limited to this, and for example, the mesh shape may have a shape that is inclined at a predetermined angle with respect to the arrangement direction of the plurality of nozzles 13 .

[0040] The area of ​​the end face 15S occupied by the mesh-shaped second shielding member 18 may be, for example, 50% or less, more preferably 10% or less, of the entire area of ​​the end face 15S. By reducing the area occupied by the second shielding member 18 on the end face 15S in this way, it is possible to prevent the electric field generated in the charging electrode 14 from concentrating toward the second shielding member 18 and thereby preventing the second shielding member 18 from interfering with the discharge of liquid.

[0041] In this way, by forming the second shielding member 18 to cover the lower end surface 15S of the main body portion 15, the component of the electric field generated by the charged electrode 14 that occurs below the charged electrode 14 can be particularly effectively shielded.

[0042] The electrostatic inkjet head 10 having such a configuration is formed, for example, as follows. First, an insulating material such as glass, ceramic, or resin is prepared. The reservoir 11, silo 12, nozzle 13, and main body 15 are formed by processing the material using techniques such as drilling, etching, electric discharge machining, sandblasting, laser-induced etching, dry etching, photosensitive glass drilling, and injection molding. Alternatively, the reservoir 11, silo 12, nozzle 13, and main body 15 may be formed by stacking plates several tens of micrometers thick or by depositing films of glass, resin, ceramic, or the like using techniques such as plasma CVD (Chemical Vapor Deposition) or vapor deposition. When forming each component by stacking plates, the stacked plates may be joined together using adhesives, direct bonding, or other joining means.

[0043] Next, the charged electrode 14, the first shielding member 17, and the second shielding member 18 are formed using plating, vapor deposition, sputtering, CVD, ALD (Atomic Layer Deposition), or the like. The second shielding member 18 may be formed by the above-described method after, for example, forming holes in the main body 15. The charged electrodes 14 for the multiple nozzles 13 may be formed in a connected state and then separated for each nozzle by patterning processing such as etching. When the reservoir 11, silo 12, nozzle 13, and main body 15 are formed by stacking plates, the charged electrode 14, the first shielding member 17, and the second shielding member 18 can be formed as plates or after stacking. When the reservoir 11, silo 12, nozzle 13, and main body 15 are formed by film deposition, the charged electrode 14, the first shielding member 17, and the second shielding member 18 can be formed as appropriate depending on the thickness of the film.

[0044] An insulating film such as SiO2 may be formed on the surfaces of the charged electrode 14, the first shielding member 17, and the second shielding member 18. The insulating film may be formed by, for example, plasma CVD, vapor deposition, sputtering, or the like, or by sealing with an adhesive.

[0045] 2, a counter electrode 80, on which the print target medium 300 can be placed, is provided at a position facing the ejection port 13A of each nozzle 13 of the electrostatic inkjet head 10. A constant voltage is applied to the counter electrode 80 such that the liquid in the nozzle 13 is not ejected. Alternatively, the counter electrode 80 may be grounded. Alternatively, a pulse voltage having a polarity opposite to that applied to the charging electrode 14 may be applied to the counter electrode 80 at the timing when the liquid is ejected.

[0046] The print target medium 300 is held on an opposing electrode 80 provided on the stage 40. The print target medium 300 may be, for example, a glass, ceramic, glass epoxy substrate, a resin substrate such as polyimide or resist, or a metal substrate. The distance between the opposing electrode 80 and the ejection opening 13A of the nozzle 13 is adjusted so that the distance between the print target medium 300 and the ejection opening 13A is approximately 10 μm or more and 500 μm or less.

[0047] The stage 40 and the control unit 50 are connected to each other by, for example, a flexible cable. This allows the control unit 50 to move the electrostatic inkjet head 10 and the stage 40 relative to each other. The control unit 50 acquires position information regarding the positions of each nozzle 13 of the electrostatic inkjet head 10 and the position of the stage 40 (and thus the position on the print target medium 300) from a predetermined position sensor or the like. Based on the position information, the control unit 50 moves the electrostatic inkjet head 10 and the stage 40 relative to each other so that an arbitrary print target position on the print target medium 300 coincides with the position of a specific nozzle 13 of the electrostatic inkjet head 10 on the XY plane. The control unit 50 controls the charging voltage waveform generation unit 16 to supply a pulse voltage to the charging electrode 14 to eject liquid from the nozzle 13 at the timing when the arbitrary print target position on the print target medium 300 coincides with the position of a specific nozzle 13 of the electrostatic inkjet head 10 on the XY plane (more preferably, at a timing that takes into account the time it takes for the liquid ejected from the nozzle 13 to reach the print target position). This allows the liquid to be applied to a desired position on the print target medium 300, and by repeating this process, the desired printing can be performed on the print target medium 300.

[0048] As described above, according to the electrostatic inkjet head 10 of the first configuration example, the first shielding member 17 is arranged inside the main body 15 along the liquid ejection direction. The negative side in the ejection direction of the first shielding member 17, i.e., the upper end 17A, is located above the charged electrode 14. Furthermore, the positive side in the ejection direction of the first shielding member 17, i.e., the lower end 17B, is located below the lower end of the charged electrode 14. Furthermore, a plurality of first shielding members 17 are formed between adjacent nozzles 13.

[0049] In this way, the first shielding member 17 is formed so as to cover an area in the ejection direction that is wider than the area in which the charged electrode 14 is disposed. This allows the first shielding member 17 to effectively shield the electric field generated by the charged electrode 14. By disposing the first shielding member 17 between adjacent nozzles 13, it is possible to effectively prevent the charged electrode 14 formed on one nozzle 13 from affecting the liquid ejected from the adjacent nozzle 13.

[0050] Here, in the electrostatic inkjet head 10 of the first configuration example, the upper end 17A of the first shielding member 17 is positioned above the charged electrode 14, so that the component of the electric field generated by the charged electrode 14 that occurs above the charged electrode 14 can be particularly effectively shielded.

[0051] Furthermore, in the electrostatic inkjet head 10 of the first configuration example, the lower end 17B of the first shielding member 17 is positioned below the charged electrode 14, thereby making it possible to particularly effectively shield the component of the electric field generated by the charged electrode 14 that occurs below the charged electrode 14.

[0052] Furthermore, in the electrostatic inkjet head 10 of the first configuration example, the second shielding member 18 is formed to cover the lower end surface 15S of the main body portion 15, thereby more effectively shielding the component of the electric field generated by the charging electrode 14 that occurs below the charging electrode 14.

[0053] Therefore, with this configuration, it is possible to effectively prevent the electric field generated by the charging electrode 14 formed in one nozzle 13 from attracting the liquid ejected from another nozzle 13, causing the liquid to not land in the desired position.

[0054] (Second Configuration Example) Next, a second configuration example of the electrostatic inkjet head according to an embodiment of the present disclosure will be described. Fig. 3 is a schematic diagram for explaining the configuration of a printing device 100 including an electrostatic inkjet head 20 of the second configuration example. Fig. 3 shows a cross-sectional view of the electrostatic inkjet head 20 in a plane (XZ plane) parallel to the ejection direction.

[0055] 3, the electrostatic inkjet head 20 includes a reservoir 21, a silo 22, a nozzle 23, a charging electrode 24, an ejection electrode 25, a main body 26, a charging voltage waveform generating unit 27, an ejection voltage waveform generating unit 28, a first shielding member 29, and a second shielding member 210. The charging electrode 24 is an example of a first electrode in the present disclosure. The ejection electrode 25 is an example of a second electrode in the present disclosure.

[0056] 1. A liquid supply flow path 60 and a liquid recovery flow path 70 are connected to the reservoir 21. A plurality of nozzles 23 are connected to the reservoir 21 via silos 22, which are individual flow paths.

[0057] The nozzle 23 is a nozzle that ejects liquid. The nozzle 23 has an ejection port 23A at the end on the positive side (i.e., the lower side) in the ejection direction of the liquid. The inner diameter (nozzle diameter) of the nozzle 23 and the ejection port 23A may be, for example, 0.5 μm or more and 200 μm or less.

[0058] The nozzles 23 are formed inside a plurality of recesses 26D provided in the main body 26. More specifically, as shown in Fig. 3, the nozzles 23 are disposed in the centers of the recesses 26D, and grooves 26G are formed around the nozzles 23. The grooves 26G reduce the area of ​​the region surrounding the discharge ports 23A at the lower ends of the nozzles 23, thereby preventing the liquid from spreading over the lower end faces of the nozzles 23 due to the surface tension of the liquid.

[0059] In this way, the nozzle 23 is formed inside the recess 26D so as to protrude downward from the upper bottom surface of the recess 26D in the discharge direction.

[0060] Due to the shape of the nozzle 23, the discharge port 23A provided at the lower end of the nozzle 23 is located above the lower end surface 26S of the main body 26 in the discharge direction.

[0061] 3, the nozzles 23 are arranged in a specific direction, which is the X-axis direction.

[0062] The charged electrode 24 is an electrode that applies a pulse voltage to the liquid inside the nozzle 23, the magnitude of which is not sufficient to cause ejection. A pulse voltage whose polarity is reversed for each pulse may be supplied to the charged electrode 24. The charged electrode 24 is disposed inside the nozzle 23 and near the ejection port 23A. A charged electrode 24 is disposed for each nozzle 23. The lower end of the charged electrode 24 is located at the lower end of the nozzle 23, i.e., at the position of the ejection port 23A, in the ejection direction. The upper end of the charged electrode 24 is located a predetermined distance above the ejection port 23A in the ejection direction. The length of the charged electrode 24 along the ejection direction may be appropriately set based on the magnitude of the pulse voltage applied to the liquid inside the nozzle 23, and is, for example, 30 μm. The pulse voltage applied to the liquid by the charged electrode 24 is supplied by a charged voltage waveform generator 27.

[0063] In this specification, the liquid near the ejection port 23A includes the liquid present in the area close to the ejection port 23A inside the nozzle 23 and the liquid forming a meniscus that bulges from the ejection port 23A toward the lower side of the nozzle 23 (the opposing electrode 80 side).

[0064] The ejection electrode 25 is an electrode that applies a pulse voltage to the liquid inside the nozzle 23 to eject it at any timing. A pulse voltage whose polarity is reversed for each pulse may be supplied to the ejection electrode 25. The waveform of the pulse voltage supplied to the ejection electrode 25 is synchronized with that of the pulse voltage supplied to the charging electrode 24.

[0065] The ejection electrode 25 is provided on the inner surface of the recess 26D of the main body 26, and below the ejection port 23A of the nozzle 23 in the ejection direction. An ejection electrode 25 is provided in each of the multiple recesses 26D. The liquid near the ejection port 23A, which has been charged by the pulse voltage supplied to the charging electrode 24, is attracted by electrostatic force generated by an electric field generated by the pulse voltage supplied to the ejection electrode 25, causing the liquid to be ejected from the nozzle 23 in the ejection direction. This type of ejection method is called, for example, an electrostatic attraction method.

[0066] The main body 26 is a plate-shaped member on which other components of the electrostatic inkjet head 20 are provided. As described above, the main body 26 has a plurality of recesses 26D formed along the arrangement direction of the nozzles 23. The main body 26 is made of an insulating material such as glass, ceramic, or resin.

[0067] The charging voltage waveform generating unit 27 applies a pulse voltage independently to each of the charging electrodes 24 provided in the plurality of nozzles 23 under the control of the control unit 50 (see FIG. 1 ). The ejection voltage waveform generating unit 28 applies a pulse voltage independently to each of the ejection electrodes 25 provided inside the plurality of recesses 26D under the control of the control unit 50. The charging voltage waveform generating unit 27, the ejection voltage waveform generating unit 28, and the control unit 50 are connected to each other by, for example, flexible cables.

[0068] The first shielding member 29 is, for example, grounded and is a plate-like member that shields the electric field generated by the charging electrode 24 and the ejection electrode 25. The first shielding member 29 is disposed inside the main body 26 substantially perpendicular to the arrangement direction (X-axis direction) of the nozzles 23. In other words, the surfaces of the plate-like first shielding member 29 extend in the ejection direction and in a depth direction perpendicular to the ejection direction and the arrangement direction. The depth direction is the Y-axis direction shown in FIG. 3 .

[0069] 3, of the two end portions of the first shielding member 29 in the ejection direction, an end portion 29A on the opposite side in the ejection direction (i.e., the upper side in FIG. 3) is located above the charging electrode 24. Furthermore, of the two end portions of the first shielding member 29 in the ejection direction, an end portion 29B on the positive side in the ejection direction (i.e., the lower side in FIG. 3) is located at the position of a lower end surface 26S in the ejection direction of the main body 26. In other words, the lower end portion 29B of the first shielding member 29 is located below the ejection electrode 25.

[0070] Furthermore, the rear end of the plate-shaped first shielding member 29 in the depth direction is located further back than the rear ends of the charged electrode 24 and the ejection electrode 25. The front end of the first shielding member 29 in the depth direction is located further forward than the front ends of the charged electrode 24 and the ejection electrode 25. The rear side in the depth direction corresponds to the rear side in Figure 2, and the front side in the depth direction corresponds to the front side in Figure 2. As a result, the first shielding member 17 is arranged in a wider area than the charged electrode 24 and the ejection electrode 25 in the depth direction, which is perpendicular to the arrangement direction of the multiple nozzles 23 and the ejection direction.

[0071] 3, a plurality of first shielding members 29 are formed between adjacent nozzles 23. Also, as shown in FIG. 3, the first shielding members 29 are also arranged outside the nozzles 23 at both ends in the arrangement direction of the plurality of nozzles 23. The first shielding members 29 arranged outside the nozzles 23 at both ends in the arrangement direction of the nozzles 23 may be arranged symmetrically with the first shielding members 29 located one nozzle inside the nozzle 23 at both ends, with the nozzle 23 at the center. In the second configuration example, "outside the nozzles 23 at both ends in the arrangement direction" refers to a side that is farther away from the center of the electrostatic inkjet head 20 in the arrangement direction than the nozzles 23 at both ends. Furthermore, "inside the nozzles 23 at both ends in the arrangement direction" refers to a side that is closer to the center of the electrostatic inkjet head 20 in the arrangement direction than the nozzles 23 at both ends.

[0072] In this way, the first shielding member 29 is formed to cover an area wider in the ejection direction than the area in which the charged electrode 24 and the ejection electrode 25 are arranged. This allows the first shielding member 29 to effectively shield the electric field generated by the charged electrode 24 and the ejection electrode 25. Because the first shielding member 29 is arranged between adjacent nozzles 23, it is possible to effectively prevent the charged electrode 24 and the ejection electrode 25 corresponding to one nozzle 23 from affecting the liquid ejected from the adjacent nozzle 23. This effectively prevents the electric field generated by the charged electrode 24 and the ejection electrode 25 corresponding to one nozzle 23 from attracting the liquid ejected from another nozzle 23, causing the liquid to not land at the desired position.

[0073] Here, in the electrostatic inkjet head 20 of the second configuration example, the upper end 29A of the first shielding member 29 is positioned above the charging electrode 24, so that the component of the electric field generated by the charging electrode 24 and the ejection electrode 25 that occurs above the charging electrode 24 can be particularly effectively shielded.

[0074] Furthermore, in the electrostatic inkjet head 20 of the second configuration example, the lower end 29B of the first shielding member 29 is positioned below the ejection electrode 25, thereby making it possible to particularly effectively shield the component of the electric field generated by the charging electrode 24 and the ejection electrode 25 that occurs below the ejection electrode 25.

[0075] The second shielding member 210 is grounded like the first shielding member 29, and is a member that shields the electric field generated by the charging electrode 24 and the ejection electrode 25. The second shielding member 210 is formed along the lower end surface 26S of the main body 26 so as to exclude the recess 26D. Note that the second shielding member 210 may be electrically connected to the first shielding member 29.

[0076] The second shielding member 210 is formed on the entire lower end surface 26S of the main body 26, excluding the recess 26D. The second shielding member 210 may be uniformly formed on the entire end surface 26S. Alternatively, the second shielding member 210 may have, for example, a mesh shape, with a portion of the end surface 26S exposed through the mesh. The mesh shape of the second shielding member 210 may include, for example, a polygon such as a triangle, a square, or a hexagon, or a circle. As in the first configuration example, the main body 26, which is made of ceramic or glass, and the second shielding member 210, which is made of metal, have significantly different linear expansion coefficients, resulting in a difference in the degree of expansion when temperature changes occur. The difference in the degree of expansion may apply force to the second shielding member 219, causing the second shielding member 210 to peel off from the end surface 26S of the main body 26. To prevent this, it is desirable that the mesh shape of the second shielding member 210 does not have a straight line portion that is parallel to the arrangement direction in which the nozzles 23 are arranged side by side (i.e., the X-axis direction shown in Figure 3) and is longer than the distance between adjacent nozzles 23 in the arrangement direction.

[0077] This will be explained in more detail. Even if the mesh shape includes, as part thereof, straight line portions that are parallel to the arrangement direction of the multiple nozzles 23, these straight line portions are connected to parts that are not parallel to the arrangement direction of the mesh shape. The length of these straight line portions is formed to be shorter than the distance between adjacent nozzles 23. This makes it possible to prevent the electric field generated by the charging electrode 24 and ejection electrode 25 provided corresponding to a certain nozzle 23 from being transmitted to the charging electrode 24 and ejection electrode 25 provided corresponding to an adjacent nozzle 23 via the straight line portions of the mesh shape.

[0078] However, the present disclosure is not limited to this, and for example, the mesh shape may have a shape that is inclined at a predetermined angle with respect to the arrangement direction of the plurality of nozzles 13 .

[0079] The area of ​​the mesh-shaped second shielding member 210 on the end face 26S may be, for example, 50% or less, and more preferably 10% or less, of the entire area of ​​the end face 26S. By reducing the area of ​​the end face 26S occupied by the second shielding member 210 in this way, it is possible to prevent an electric field generated by the voltage supplied to the charging electrode 24 and the ejection electrode 25 from being generated toward the second shielding member 210 and thereby prevent the second shielding member 210 from interfering with the ejection of liquid.

[0080] Fig. 4 is a view of the end surface 26S of the main body 26 of the electrostatic inkjet head 20, viewed from the positive side in the ejection direction of the main body 26, i.e., from the bottom. Fig. 4 shows the positional relationship between the multiple nozzles 23, the charging electrodes 24 formed inside the nozzles 23, the recesses 26D, and the grooves 26G. Also, Fig. 4 shows the positions of the ejection electrodes 25 and the first shielding members 29 formed inside the main body 26 by dashed lines. Also, Fig. 4 shows the state in which the second shielding member 210 is provided by hatching. As shown in Fig. 4, the first shielding member 29 is provided over a wider area in the depth direction (Y-axis direction) than the charging electrodes 24 and the ejection electrodes 25.

[0081] 5A to 5D are diagrams showing examples in which the second shielding member 210 has a mesh shape. FIG. 5A shows an example in which the second shielding member 210 has a mesh shape that includes quadrangles. FIG. 5B shows an example in which the second shielding member 210 has a mesh shape that includes triangles. FIG. 5C shows a part in which the second shielding member 210 has a mesh shape that includes hexagons. FIG. 5D shows a part in which the second shielding member 210 has a mesh shape that includes circles.

[0082] As shown in Figures 5A to 5D, when the second shielding member 210 has a mesh shape, it is desirable that it does not have continuous straight lines parallel to the arrangement direction (X-axis direction in Figures 5A to 5D) in which the multiple nozzles 23 are arranged side by side, in order to prevent peeling.

[0083] Returning to the explanation of FIG. 3 , the charging voltage waveform generating unit 27 supplies a pulse voltage to the charging electrode 24 based on the control of the control unit 50. The pulse voltage supplied to the charging electrode 24 by the charging voltage waveform generating unit 27 will be referred to as the charging voltage hereinafter. The charging voltage waveform generating unit 27 may be capable of inverting the polarity for each pulse of the charging voltage. The charging voltage waveform generating unit 27 may be capable of individually changing the pulse width, pulse generation timing, whether or not polarity is inverted, etc. for each of the charging electrodes 24 corresponding to the multiple nozzles 23. The charging voltage is, for example, between −5 kV and 5 kV.

[0084] The ejection voltage waveform generating unit 28 supplies a pulse voltage to the ejection electrode 25 based on the control of the control unit 50. The pulse voltage supplied to the ejection electrode 25 by the ejection voltage waveform generating unit 28 will be referred to as the ejection voltage hereinafter. The ejection voltage waveform generating unit 28 may be capable of inverting the polarity for each pulse of the ejection voltage. The ejection voltage waveform generating unit 28 may be capable of individually changing the pulse width, pulse generation timing, whether or not to invert polarity, etc., for each of the ejection electrodes 25 corresponding to the multiple nozzles 23. The ejection voltage is, for example, between −4 kV and 4 kV.

[0085] FIG. 6 is a diagram for explaining the charging voltages and ejection voltages supplied to the charging electrodes 24_1 and 24_2 and the ejection electrodes 25_1 and 25_2 corresponding to the two nozzles 23_1 and 23_2 adjacent to each other.

[0086] 6, a pulsed charging voltage is supplied to the charging electrode 24_1 corresponding to the nozzle 23_1 and the charging electrode 24_2 corresponding to the nozzle 23_2, respectively. Also, in FIG. 6, a pulsed ejection voltage is supplied to the ejection electrode 25_1 corresponding to the nozzle 23_1 and the ejection electrode 25_2 corresponding to the nozzle 23_2, respectively.

[0087] The magnitude of the charging voltage is appropriately set to a value that prevents liquid from being ejected from the nozzles 23_1 and 23_2.

[0088] An ejection voltage is supplied to each of the ejection electrodes 25_1 and 25_2 in accordance with the desired ejection timing of the nozzles 23_1 and 23_2. The ejection voltage is supplied in accordance with the phase of one pulse of the charging voltage corresponding to the ejection timing, and is a pulse voltage with the polarity opposite to that of the charging voltage.

[0089] When not ejecting, the liquid in the nozzles 23_1 and 23_2 is charged by the charging voltage supplied to the charging electrodes 24_1 and 24_2. When an ejection voltage is supplied to the ejection electrodes 25_1 and 25_2 at the ejection timing, the ejection electrodes 25_1 and 25_2 generate an electric field. The electric field generated by the ejection electrodes 25_1 and 25_2 acts on the charged liquid in the nozzles 23_1 and 23_2, attracting it toward the ejection electrodes 25_1 and 25_2. As shown in FIGS. 3 and 4 , the ejection electrodes 25 are disposed on the more positive side (i.e., lower side) in the ejection direction than the nozzles 23 and in a circular arrangement centered on the nozzles 23. Therefore, the electric field generated by the ejection electrodes 25 causes some of the liquid in the nozzles 23_1 and 23_2 to be pulled away in the ejection direction and begin to fly.

[0090] The opposing electrode 80 on which the print target medium 300 is placed may be supplied with a constant voltage that does not cause liquid to be ejected even when a charging voltage is supplied to the charging electrode 24. Alternatively, the opposing electrode 80 may be grounded.

[0091] Here, when nozzle 23_1 and nozzle 23_2 eject liquid onto different pixels of print target medium 300 (see FIG. 1 , etc.), a difference in ejection timing occurs between nozzle 23_1 and nozzle 23_2. In such a case, a phase difference may occur between the charging voltage supplied to charging electrode 24_1 and the charging voltage supplied to charging electrode 24_2. Furthermore, when the ejection timing differs between nozzle 23_1 and nozzle 23_2, a phase difference may occur between the ejection voltage supplied to ejection electrode 25_1 and the ejection voltage supplied to ejection electrode 25_2. These phase differences may cause a large potential difference between adjacent nozzles 23_1 and 23_2. Such a potential difference may cause a droplet of liquid ejected from nozzle 23_1 or nozzle 23_2 not to travel in a straight line in the ejection direction.

[0092] 3 , in the electrostatic inkjet head 20 of the second configuration example, the first shielding member 29 and the second shielding member 210 effectively shield the electric field between adjacent nozzles 23 above the charging electrode 24, below the ejection electrode 25, and in all areas between the charging electrode 24 and the ejection electrode 25 in the ejection direction. This effectively prevents the liquid ejected from one nozzle 23 from being unable to travel straight in the ejection direction due to electric field interference from the adjacent nozzle 23, even if a large potential difference occurs between adjacent nozzles 23 due to a phase difference between the charging voltages supplied to the charging electrodes 24 corresponding to each nozzle or between the ejection voltages supplied to the ejection electrodes 25, which is caused by differences in the ejection timing between the adjacent nozzles 23.

[0093] It is also possible to prevent the liquid (droplets) ejected from the nozzle 23 from being attracted by the electric field generated in the ejection electrode 25 before reaching the printing medium 300, preventing them from traveling straight in the ejection direction or reducing their flight speed.

[0094] Fig. 7 is a diagram for explaining in more detail the positional relationship between the nozzle 23, the charging electrode 24, the ejection electrode 25, the first shielding member 29, and the second shielding member 210. Fig. 7 is a cross-sectional view in the XZ plane, similar to Fig. 3, and is an enlarged view of one of the nozzles 23 shown in Fig. 3.

[0095] 7, in a given nozzle 23, the shortest distance D1 between the charged electrode 24 and the ejection electrode 25 is shorter than the shortest distance D2 between the charged electrode 24 and the first shielding member 29. Also, as shown in FIG. 7, the shortest distance D1 between the charged electrode 24 and the ejection electrode 25 is shorter than the shortest distance D3 between the charged electrode 24 and the second shielding member 210.

[0096] Arranging the nozzle 23, the charging electrode 24, the ejection electrode 25, the first shielding member 29, and the second shielding member 210 in this positional relationship provides the following effect: That is, it is possible to prevent a situation in which the electric field generated by the ejection voltage supplied to the ejection electrode 25 acts more strongly on the first shielding member 29 or the second shielding member 210 than on the liquid near the ejection port 23A that is charged by the charging voltage supplied to the charging electrode 24. This makes it possible to suitably prevent a situation in which the arrangement of the first shielding member 29 or the second shielding member 210 adversely affects the ejection of liquid from the nozzle 23.

[0097] <Functions and Effects> The following describes the functions and effects of the electrostatic inkjet head 10 (20) according to the embodiment of the present disclosure. In the following description of the functions and effects, when describing corresponding configurations in the first and second configuration examples, reference numerals in parentheses are used. For example, electrostatic inkjet head 10 (20) means electrostatic inkjet head 10 or 20, and nozzle 13 (23) means nozzle 13 or 23.

[0098] The electrostatic inkjet head 10 (20) according to an embodiment of the present disclosure is an electrostatic inkjet head 10 (20) that ejects liquid in a nozzle 13 (23) by an electrostatic suction method, and includes a main body 15 (26) in which the nozzle 13 (23) is formed, a charging electrode 14 (24) (corresponding to the first electrode in the present disclosure) that applies a pulse voltage to charge the liquid, and a first shielding member 17 (29) that is arranged inside the main body 15 (26) along the ejection direction of the liquid, has an end 17A (29A) on the opposite side in the ejection direction, and is located on the opposite side of the charging electrode 14 (24), and shields the electric field generated by the charging electrode 14 (24).

[0099] That is, the first shielding member 17 (29) is formed to cover an area wider than the area in which the charged electrode 14 (24) is disposed in the ejection direction. Therefore, the first shielding member 17 (29) can effectively shield the electric field generated by the charged electrode 14 (24). In particular, the first shielding member 17 (29) can more effectively prevent the electric field from circling around from the opposite side in the ejection direction than the charged electrode 14 (24).

[0100] Furthermore, according to the electrostatic inkjet head 10 (20) relating to the embodiment of the present disclosure, the main body 15 (26) has a plurality of nozzles 13 (23), and the first shielding member 17 (29) is formed between adjacent nozzles 13 (23) among the plurality of nozzles 13 (23).

[0101] This configuration effectively prevents the electric field generated by the charging electrode 14 (24) provided corresponding to one nozzle 13 (23) from acting on the liquid in the other nozzle 13 (23) between adjacent nozzles 23. This effectively prevents interference of electric fields between adjacent nozzles 13 (23), and ultimately effectively prevents the liquid ejected from the nozzle 13 (23) from proceeding in a straight line in the ejection direction.

[0102] Furthermore, according to the electrostatic inkjet head 20 according to the embodiment of the present disclosure, the main body 26 has a recess 26D provided on the end face on the positive side in the ejection direction, the nozzle 23 is arranged inside the recess 26D, and the first shielding member 29 has an end 29A on the positive side in the ejection direction, and the positive end 29A is located on the positive side of the charging electrode 24.

[0103] With this configuration, the first shielding member 29 can more effectively prevent the electric field from entering from the positive side in the ejection direction than the charging electrode 24 .

[0104] Furthermore, the electrostatic inkjet head 10 (20) according to the embodiment of the present disclosure further includes a second shielding member 18 (210) that is formed along the positive end surface 15S (26S) of the main body 15 (26) and shields the electric field generated by the charging electrode 14 (24).

[0105] With this configuration, the second shielding member 18 (210) can effectively prevent the electric field from the charged electrode 14 (24) from flowing around the positive end face 15S (26S) of the main body 15 (26) and affecting other nozzles 13 (23).

[0106] Furthermore, according to the electrostatic inkjet head 20 of the embodiment of the present disclosure, the main body 26 has a recess 26D provided on the end face on the positive side in the ejection direction, the nozzle 23 is arranged inside the recess 26D, and the second shielding member 210 is formed on the end face 26S in a portion excluding the recess 26D.

[0107] With this configuration, the second shielding member 210 can effectively prevent the electric field generated by the charging electrode 24 from leaking around from the positive end surface 26S of the main body 26 and affecting other nozzles 23.

[0108] Furthermore, in the electrostatic inkjet head 10 (20) according to the embodiment of the present disclosure, the second shielding member 18 (210) is formed in a mesh shape on the end surface 15S (26S).

[0109] With this configuration, the electric field generated by the voltage supplied to the charging electrode 14 (24) and the ejection electrode 25 is directed toward the second shielding member 18 (210), thereby reducing the occurrence of a situation in which the ejection of liquid is hindered by the second shielding member 18 (210).

[0110] Furthermore, according to the electrostatic inkjet head 20 of the embodiment of the present disclosure, the nozzle 23 has an outlet 23A provided at the positive end, and the outlet 23A is located on the opposite side of the positive end surface 26S of the main body portion 26 in the ejection direction.

[0111] In this way, by positioning the discharge port 23A of the nozzle 23 on the opposite side in the discharge direction from the end face 26S of the main body 26, the end of the first shielding member 29 on the positive side in the discharge direction is reliably positioned on the more positive side in the discharge direction than the discharge port 23A. This effectively prevents the electric field from the charging electrode 24 or the discharge electrode 25 from circulating around the positive end face 26S of the main body 26 and affecting other nozzles 23.

[0112] Furthermore, the electrostatic inkjet head 20 according to the embodiment of the present disclosure further includes an ejection electrode 25 (corresponding to the second electrode in the present disclosure) located inside the recess 26D and on the positive side of the charging electrode 24 in the ejection direction, and the first shielding member 29 has a positive end 29A in the ejection direction, and the positive end 29A is located on the positive side of the ejection electrode 25.

[0113] With this configuration, it is possible to effectively prevent the electric field generated by the ejection electrode 25 from leaking around from the positive end surface 26S of the main body 26 and affecting other nozzles 23.

[0114] Furthermore, in the electrostatic inkjet head 20 according to the embodiment of the present disclosure, the shortest distance D1 between the charged electrode 24 and the ejection electrode 25 is shorter than the shortest distance D2 between the charged electrode 24 and the first shielding member 29. Furthermore, the shortest distance D1 between the charged electrode 24 and the ejection electrode 25 is shorter than the shortest distance D3 between the charged electrode 24 and the second shielding member 210.

[0115] This configuration can prevent the electric field generated by the ejection voltage supplied to the ejection electrode 25 from acting more strongly on the first shielding member 29 or the second shielding member 210 than on the liquid near the ejection port 23A that has been charged by the charging voltage supplied to the charging electrode 24. Consequently, the straightness of the liquid ejected from the nozzle 23 can be sufficiently ensured.

[0116] <Modifications> The electrostatic inkjet head and printing device according to the present disclosure have been described in detail above. The electrostatic inkjet head 10 or 20 and printing device 100 described in the above embodiment are examples of the electrostatic inkjet head and printing device according to the present disclosure, and the present disclosure is not limited to the contents described in the above embodiment. The electrostatic inkjet head and printing device according to the present disclosure may be modified, for example, as follows.

[0117] In the above-described embodiment, the electrostatic inkjet head 10 (20) includes both the first shielding member 17 (29) and the second shielding member 18 (210). However, the present disclosure is not limited to this, and the electrostatic inkjet head of the present disclosure may include only a first shielding member disposed between the nozzles along the ejection direction. For example, as in the electrostatic inkjet head 20 of the second configuration example, if the first shielding member 29 extends above the charged electrode 24 (corresponding to the first electrode in the present disclosure) in the ejection direction (i.e., on the opposite side in the ejection direction) and below the ejection electrode 25 (corresponding to the second electrode in the present disclosure) (i.e., on the positive side in the ejection direction), the first shielding member 29 can also sufficiently shield the electric field generated by the charged electrode 24 and the ejection electrode 25.

[0118] In the above-described embodiment, the first shielding member 17 (29) is a plate-shaped member, but the present disclosure is not limited to this. For example, the first shielding member 17 (29) may be a plurality of rod-shaped members extending in the discharge direction and arranged at predetermined intervals in the depth direction.

[0119] Fig. 8 is a diagram for explaining a modified example of the first shielding member of the present disclosure. Like Fig. 4, Fig. 8 shows the end surface 26S of the main body 26 of the electrostatic inkjet head 20 of the second configuration example, as viewed from the positive side in the ejection direction of the main body 26, i.e., from the bottom side. In the example shown in Fig. 8, the second shielding member 210 is configured by arranging a plurality of rod-shaped members extending in the ejection direction at predetermined intervals along the depth direction.

[0120] Even in this modified example, by setting the distance between the rod-shaped members appropriately, it is possible to obtain substantially the same effect as when the first shielding member 29 is configured as a plate-shaped member. The predetermined distance depends on the nozzle diameter and the distance between the nozzles, but may be, for example, 50 μm or less. This reduces the volume occupied by the first shielding member 29 in the space between adjacent nozzles 23 compared to when the first shielding member 29 is configured as a plate-shaped member. This prevents the electric field generated in the charging electrode 24 or the ejection electrode 25 from concentrating toward the first shielding member 29 and interfering with the ejection of liquid. By configuring the first shielding member 29 as a structure of arranged rod-shaped members, this effect can be efficiently obtained when the volume occupied by the first shielding member 29 is approximately 50% or less of that when configured as a plate-shaped member.

[0121] FIG. 8 shows a modified example of the first shielding member 29 in the electrostatic inkjet head 20 of the second configuration example, but the first shielding member 17 in the electrostatic inkjet head 10 of the first configuration may also be configured by arranging a plurality of rod-shaped members in a line.

[0122] The present disclosure is useful for an electrostatic inkjet head that charges and ejects liquid.

[0123] 100 Printing device 10 Electrostatic inkjet head 11 Reservoir 12 Silo 13 Nozzle 13A Discharge port 14 Charged electrode 15 Main body 15D Recessed portion 15G Groove 15S End surface 16 Charged voltage waveform generating unit 17 First shielding member 18 Second shielding member 20 Electrostatic inkjet head 21 Reservoir 22 Silo 23 Nozzle 23A Discharge port 24 Charged electrode 25 Discharge electrode 26 Main body 26D Recessed portion 26G Groove 26S End surface 27 Charged voltage waveform generating unit 28 Discharge voltage waveform generating unit 29 First shielding member 210 Second shielding member 30 Liquid tank 40 Stage 50 Control unit 60 Liquid supply flow path 70 Liquid recovery flow path 80 Counter electrode 300 Printing target medium

Claims

1. An electrostatic inkjet head that ejects liquid from inside a nozzle using an electrostatic suction method, comprising: a main body in which a plurality of the nozzles are arranged; a first electrode that applies a pulse voltage to charge the liquid; and a first shielding member that is arranged inside the main body along the ejection direction of the liquid and between adjacent nozzles of the plurality of nozzles, the first shielding member having an end on the opposite side in the ejection direction, the end on the opposite side being located on the opposite side of the first electrode, and that shields the electric field generated by the first electrode.

2. An electrostatic inkjet head as described in claim 1, further comprising an additional first shielding member, said additional first shielding member being arranged outside the nozzles at both ends in the arrangement direction of the plurality of nozzles, and in a position symmetrical to the first shielding member one position inward from the nozzles at both ends, with said nozzles at the center.

3. An electrostatic inkjet head as described in claim 1, wherein the main body has a plurality of recesses provided on its end face on the positive side in the ejection direction, the plurality of nozzles are respectively arranged inside the plurality of recesses, and the first shielding member has an end on the positive side in the ejection direction, the positive end being located on the positive side of the first electrode.

4. An electrostatic inkjet head according to claim 3, wherein the first shielding member is arranged over a wider area than the first electrode in a direction perpendicular to the arrangement direction of the plurality of nozzles and the ejection direction.

5. An electrostatic ink jet head according to claim 1, wherein the first shielding member is a plate-shaped member.

6. The electrostatic ink jet head according to claim 1, wherein the first shielding member is constructed by arranging a plurality of rod-shaped members at predetermined intervals.

7. The electrostatic ink jet head according to claim 1, further comprising a second shielding member formed along the end face on the positive side in the ejection direction of the main body portion, for shielding the electric field generated by the first electrode.

8. An electrostatic inkjet head as described in claim 7, wherein the main body has a plurality of recesses provided on the end face on the positive side in the ejection direction, the plurality of nozzles are respectively arranged inside the plurality of recesses, and the second shielding member is formed on a portion of the positive side end face excluding the plurality of recesses.

9. An electrostatic ink jet head according to claim 8, wherein the second shielding member is electrically connected to the first shielding member.

10. An electrostatic ink jet head according to claim 7, wherein the second shielding member is formed in a mesh shape on the end surface.

11. An electrostatic inkjet head as described in claim 10, wherein the mesh shape includes straight portions parallel to the arrangement direction of the plurality of nozzles, the straight portions are connected to portions of the mesh shape that are not parallel to the arrangement direction, and the length of the straight portions is shorter than the distance between adjacent nozzles.

12. The electrostatic ink jet head according to claim 10, wherein the mesh shape has a shape that is inclined at a predetermined angle with respect to the direction in which the plurality of nozzles are arranged.

13. An electrostatic inkjet head according to claim 3, wherein each of the plurality of nozzles has an ejection outlet provided at the end on the positive side, and the ejection outlet of each of the plurality of nozzles is located on the opposite side of the end face on the positive side of the main body in the ejection direction.

14. An electrostatic inkjet head as described in claim 13, further comprising second electrodes disposed inside the plurality of recesses and on the positive side of the first electrodes in the ejection direction, the first shielding member having an end on the positive side in the ejection direction, the positive end being located on the positive side of the second electrodes.

15. An electrostatic inkjet head according to claim 14, wherein the first shielding member is arranged over a wider area than the first electrode and the second electrode in a direction perpendicular to the arrangement direction of the plurality of nozzles and the ejection direction.

16. An electrostatic ink jet head according to claim 14, wherein the shortest distance D1 between the first electrode and the second electrode is shorter than the shortest distance D2 between the first electrode and the first shielding member.

17. An electrostatic inkjet head as described in claim 14, wherein the shortest distance D1 between the first electrode and the second electrode is shorter than the shortest distance D3 between the first electrode and a second shielding member that is formed along the end face of the main body on the positive side in the ejection direction and that shields the electric field generated by the first electrode.

18. A printing device comprising: an electrostatic inkjet head according to any one of claims 1 to 17; a moving device that moves a substrate to be printed relative to said electrostatic inkjet head; a counter electrode installed on the moving device; and a control device that controls said electrostatic inkjet head and said moving device.

Images