JP2006175811A - Micro-droplet delivering apparatus and inkjet recording apparatus using this - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a micro-droplet delivering apparatus capable of delivering a micro-droplet at a high speed and stably, and being at a low cost. <P>SOLUTION: The micro-droplet delivering apparatus delivers the micro-droplets by acting an electrostatic force on a solution comprising at least fine particles and a solvent and having an electric charge. The apparatus comprises a delivering means for delivering continuously the micro-droplets from a delivering opening by acting the electrostatic force to the solution, a deflecting means for deflecting the micro-droplets delivered from the delivering means based on a controlling signal, and a recovering means for recovering either the micro-droplets delivered from the delivering means and straightly forwarding, or the micro-droplets whose flying direction is deflected by the deflecting means. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention belongs to the field of micro droplet ejection devices that eject micro droplets, and more specifically, a micro droplet ejection device that ejects micro droplets by applying an electrostatic force to a solution containing at least fine particles, and the same The present invention relates to an ink jet recording apparatus.

  2. Description of the Related Art Conventionally, as an apparatus for ejecting micro droplets, for example, there is an electrostatic ink jet recording apparatus that ejects ink having charged fine particles by applying an electrostatic force. As such an electrostatic ink jet recording apparatus, an ink jet recording apparatus disclosed in Patent Document 1 is known.

  FIG. 8 is a conceptual diagram of an ink jet head of the ink jet recording apparatus disclosed in Patent Document 1.

  FIG. 8 is a schematic configuration diagram of an example of an ink jet head of the electrostatic ink jet recording apparatus disclosed in Patent Document 1. The inkjet head 100 shown in the figure conceptually represents only one ejection unit of the inkjet head disclosed in Patent Document 1, and includes a head substrate 102, an ink guide 104, an insulating substrate 106, and a control. An electrode 108, a counter electrode 110, a DC bias voltage source 112, and a pulse voltage source 114 are provided.

  Here, the ink guide 104 is disposed on the head substrate 102, and a through-hole (ejection port) 116 is opened in the insulating substrate 106 at a position corresponding to the arrangement of the ink guide 104. The ink guide 104 passes through the through-hole 116, and the convex tip portion 104a protrudes above the surface of the insulating substrate 106 on the recording medium P side. Further, the head substrate 102 and the insulating substrate 106 are arranged with a predetermined distance therebetween, and a flow path 118 for the ink Q is formed between them.

  The control electrode 108 is provided in a ring shape so as to surround the periphery of the through hole 116 on the surface of the insulating substrate 106 on the side of the recording medium P for each ejection unit. The control electrode 108 is connected to a pulse voltage source 114 that generates a pulse voltage in accordance with image data. The pulse voltage source 114 is grounded via a DC bias voltage source 112.

  The counter electrode 110 is disposed at a position facing the tip portion 104a of the ink guide 104 and is grounded. The recording medium P is disposed on the surface of the counter electrode 110 on the ink guide 104 side. That is, the counter electrode 110 functions as a platen that supports the recording medium P.

  During recording, ink Q including fine particles (color material particles) charged to the same polarity as the voltage applied to the control electrode 108 by an ink circulation mechanism (not shown) passes through the ink flow path 118 from the right side to the left side in the drawing. It is circulated toward. Further, a high voltage of, for example, 1.5 kV is constantly applied to the control electrode 108 by the DC bias voltage source 112. At this time, a part of the ink Q in the ink flow path 118 passes through the through hole 116 of the insulating substrate 106 due to a capillary phenomenon or the like, and is concentrated on the tip portion 104a of the ink guide 104.

  When a pulse voltage of, for example, 0 V is applied from the pulse voltage source 114 to the control electrode 108 biased to 1.5 kV by the bias voltage source 112, 1.5 kV on which both voltages are superimposed is applied to the control electrode 108. Applied. In this state, the electric field strength in the vicinity of the front end portion 104 a of the ink guide 104 is relatively low, and the ink Q containing the color material particles concentrated on the front end portion 104 a of the ink guide 104 jumps out of the front end portion 104 a of the ink guide 104. Absent.

  On the other hand, when a pulse voltage of 500 V, for example, is applied from the signal voltage source 114 to the control electrode 108 biased to 1.5 kV, 2 kV on which both voltages are superimposed is applied to the control electrode 108. As a result, the ink Q containing the coloring material particles concentrated on the tip portion 104a of the ink guide 104 is ejected as an ink droplet R from the tip portion 104a by electrostatic force, and is pulled by the grounded counter electrode 110 to be recorded. Adhering onto P, dots of colorant particles are formed.

  In this way, recording is performed with the dots of the color material particles while relatively moving the inkjet head 100 and the recording medium P supported on the counter electrode 110, whereby an image corresponding to the image data is recorded on the recording medium P. Is done.

Such an electrostatic ink jet has a feature that micro droplets can be formed and high resolution drawing is possible. In particular, among electrostatic ink jets, electrostatic ink jet methods using insulating ink in which color material particles charged as ink are dispersed are less likely to cause dot bleeding on the recording medium, and images of various recording media. Can be used for recording.
JP 10-138493 A

  However, the ink jet recording method disclosed in Patent Document 1 has excellent characteristics as described above, but has a low response from drive voltage application to droplet discharge, so there is a limit to the improvement of the recording frequency. Depending on the ejection history of the ink droplets in the ejection section, the ejection response to the drive voltage is likely to change, and the ejection of the ink droplets may become unstable. Furthermore, since the control of ink droplet ejection / non-ejection is performed with a high drive voltage, an expensive driver is required, and the control is complicated.

A first object of the present invention is to solve the above-mentioned problems of the prior art, and to provide an inexpensive micro-droplet discharge device that can discharge micro-droplets at high speed and stably. .
A second object of the present invention is to solve the above-mentioned problems of the prior art, and to provide an inkjet recording apparatus that can perform high-speed drawing, has high ejection stability, and is inexpensive.

In order to solve the first problem, a first aspect of the present invention is a microdroplet ejecting apparatus that ejects microdroplets by applying an electrostatic force to a charged solution containing at least fine particles and a solvent. An ejection unit that applies an electrostatic force to the solution to continuously eject micro droplets from the ejection port, and a deflection unit that deflects the micro droplets ejected from the ejection unit based on a control signal. And a collecting means for collecting either a fine liquid droplet discharged from the discharge means and traveling straight or a fine liquid droplet whose flight direction is deflected by the deflecting means. Providing equipment.
Here, the fine particles are preferably charged fine particles having a charge.
More preferably, the fine particles include a charge and a coloring material.

  In order to solve the second problem, a second aspect of the present invention uses the microdroplet discharge device according to any one of the above, wherein the solution is ink, and the deflection unit is an image. Based on the signal, any one of the micro liquid droplets deflected from the ejection unit and ejected from the ejection unit and traveling straight, and the micro liquid droplets whose flight direction is deflected by the deflection unit An ink jet recording apparatus is provided, in which an image is formed on the recording medium by collecting the fine droplets that are not landed on the recording medium.

It is preferable that a counter electrode is provided between the ejection head and the deflection unit and forms a predetermined electric field between the ejection head and the ejection head.
Moreover, it is preferable that the said counter electrode has an opening part on the flight path | route of the said micro droplet.
Furthermore, it is preferable to have a back electrode that is disposed at a position facing the ejection head via the deflection unit and forms a predetermined electric field between the ejection head and the ejection head.

The deflecting means is preferably an electric field or magnetic field applying means for deflecting the flying microdroplets.
The deflecting unit is preferably an air flow generating unit for deflecting the flying micro droplet.
Furthermore, it is preferable to have a circulation unit that supplies the ink to the ejection unit and collects ink that is not ejected by the ejection unit.
Furthermore, it is preferable to have ink density adjusting means for adjusting the ink density.
Furthermore, it is preferable that the discharge head has a plurality of discharge ports.

  According to the first aspect of the present invention, a droplet having a minute droplet diameter can be ejected at high speed and stably. In addition, the droplet can be controlled according to the control signal with a low voltage, and the cost can be reduced.

According to the second aspect of the present invention, ink droplets having a minute droplet diameter can be discharged at high speed and stably, and an image with high image quality and high drawing stability can be drawn at high speed.
Further, ink droplets can be controlled according to the image signal at a low voltage, and the cost can be reduced.
In addition, by using ink having fine particles including a charge and a coloring material, ink droplets in which the fine particles containing the coloring material are concentrated can be ejected, and the image is less blurred and forms a high-quality image. be able to.
Also, by providing a counter electrode and forming a predetermined electric field between the discharge head, the electrostatic force acting on the discharge head is more stable, and ink droplets can be discharged more stably. Can draw images with high drawing stability at high speed.
Furthermore, by providing a back electrode and forming an electric field between the ejection head and the back electrode, the flight path of the ink droplet can be controlled more accurately.

  DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a micro droplet ejection apparatus and an ink jet recording apparatus according to the present invention will be described in detail based on preferred embodiments shown in the accompanying drawings.

FIG. 1 is a schematic configuration diagram showing an example of an ink jet recording apparatus according to a second aspect of the present invention using a micro droplet discharge apparatus according to the first aspect of the present invention.
As shown in FIG. 1, an inkjet recording apparatus 10 includes an ejection head (inkjet head) 20 having an ejection port for ejecting minute droplets, a counter electrode 22 that forms a predetermined electric field between the ejection head 20, and recording. A back electrode 24 that holds the medium P, a deflecting unit 26 that deflects minute droplets ejected from the ejection head, an ink tank 28 that supplies ink to the ejection head 20, an ink supply channel 30, and a deflecting unit 26. A gutter 32 that collects the deflected minute droplets in the ink tank 28 and a second ink collection channel 34 are provided.

  Here, a plurality of the first deflection electrode 40 and the second deflection electrode 42 are arranged corresponding to the ejection part provided in the ejection head 20, but in order to easily show the configuration, in FIG. Only one first deflection electrode 40, one second deflection electrode 42 and one gutter 32 of the first deflection electrode 40 and the second deflection electrode 42 are shown.

The ejection head 20 forms an electric field having a predetermined intensity with the counter electrode 22 disposed at a position facing the surface on the ink ejection side, and continuously ejects ink droplets having a minute droplet diameter.
FIG. 2 shows an enlarged view of the periphery of the ejection head 20 and the counter electrode 22.
The ejection head 20 includes a head substrate 52, an ink guide 54, and an ejection port substrate 56 on which ejection ports 62 are formed. Discharge electrodes 58 are arranged on the discharge port substrate 56 so as to surround the discharge ports 62. Further, a counter electrode 22 is disposed at a position facing the surface on the ink ejection side of the ejection head 20.

  Further, the head substrate 52 and the discharge port substrate 56 are arranged at a predetermined interval while facing each other. An ink flow path 64 that supplies ink to each ejection port 62 is formed by a space formed between the head substrate 52 and the ejection port substrate 56.

  The discharge head 20 has a single row line structure in which a plurality of discharge ports 62 (nozzles) are arranged in a single row in order to perform image recording at high speed. FIG. 3 schematically shows a state in which a plurality of discharge ports 62 are arranged in a single row on the discharge port substrate 56 of the discharge head 20. In FIGS. 2A and 2B, only one of the plurality of discharge ports is shown in order to easily understand the configuration of the inkjet head.

In the ejection head 20 of the present invention, the number of ejection ports 62 and the physical arrangement position thereof can be freely selected. For example, not only a single-row line structure as shown in FIG. 3 but also a multi-row line structure may be used. Moreover, what is called a serial head (shuttle type) scanned in the direction orthogonal to the direction of a nozzle row may be used.
The ink jet head of the present invention can be applied to both monochrome and color recording apparatuses.

  In such an ejection head 20, for example, ink Q in which fine particles containing a color material such as a pigment (hereinafter referred to as color material particles) are dispersed in an insulating liquid (carrier liquid) can be used. Then, a bias voltage (drive voltage) is applied to the discharge electrode (control electrode) 58 provided on the discharge port substrate 56 to generate an electric field at the discharge port 62, and the ink in the discharge port 62 is discharged by electrostatic force.

  Hereinafter, the structure of the ejection head 20 of the present invention shown in FIGS. 2A and 2B will be described in more detail.

  As shown in FIG. 2A, the discharge port substrate 56 of the discharge head 20 includes an insulating substrate 66, a guard electrode 60, a discharge electrode 58, and an insulating layer 68. A guard electrode 60 and an insulating layer 68 are sequentially stacked on the upper surface of the insulating substrate 66 in the drawing (the surface opposite to the side facing the head substrate 52). A discharge electrode 58 is formed on the lower surface of the insulating substrate 66 in the figure (the surface facing the head substrate 52).

Further, the ejection port substrate 56 is formed with ejection ports 62 for ejecting ink droplets R penetrating the insulating substrate 66. As shown in FIG. 2B, the ejection port 62 is a bowl-shaped opening (slit) elongated in the ink flow direction in which both short sides of the rectangle are semicircular, and has a length L in the ink flow direction. And the length D in the direction perpendicular to the ink flow has an aspect ratio (L / D) of 1 or more.
In this embodiment, as described above, the opening 62 has an aspect ratio (L / D) between the length L in the ink flow direction and the length D in the direction perpendicular to the ink flow of 1 or more (in the ink flow direction). By making the long side a shape having anisotropy and a long hole shape having the long side in the ink flow direction, the ink can easily flow into the ejection port 62. That is, it is possible to improve the supply of ink to the ejection port 62, improve the frequency response, and prevent clogging.

  In the present embodiment, the ejection port 62 is formed as an elongated bowl-shaped opening. However, the present invention is not limited to this, and if ink can be ejected from the ejection port 62, a substantially circular, elliptical, rectangular, rhombus, parallelogram, etc. Any shape can be used. For example, a rectangular shape having a long side in the ink flow direction, or an ellipse or a rhombus having a long axis in the ink flow direction can be used. Alternatively, the upstream side of the ink flow may be an upper base, the downstream side may be a lower bottom, and the height in the ink flow direction may be longer than the lower base. In this case, the upstream side may be lengthened or the downstream side may be lengthened. Alternatively, a shape in which a circle having a diameter larger than the short side of the rectangle is connected to both short sides of the rectangle having the long side in the ink flow direction. Further, the discharge port 62 may have a symmetric shape or an asymmetric shape on the upstream side and the downstream side with respect to the center thereof. For example, the discharge port may be formed by making a semicircular shape at least one of the upstream and downstream ends of the rectangular discharge port.

  The ink guide 54 of the discharge head 20 is made of a ceramic flat plate having a predetermined thickness, and is disposed on the head substrate 52 corresponding to each discharge port 62 (discharge portion). The ink guide 54 is formed wide according to the length in the long side direction of the bowl-shaped discharge port 62. As described above, the ink guide 54 passes through the ejection port 62, and the tip end portion 54 a projects upward from the surface of the ejection port substrate 56 on the recording medium P side (the surface of the insulating layer 68).

The leading end portion 54a of the ink guide 54 is formed into a substantially triangular shape (or trapezoid) that gradually becomes thinner toward the counter electrode 22 side. The ink guide 54 is disposed so that the inclined surface of the tip portion 54a intersects the ink flow direction. As a result, the ink flowing into the ejection port 62 reaches the apex of the leading end portion 54 a along the inclined surface of the leading end portion 54 a of the ink guide 54, so that the ink meniscus is stably formed at the ejection port 62.
Further, by forming the ink guide 54 wider in the long side direction of the ejection port 62, the width in the direction orthogonal to the ink flow can be shortened, and the influence on the ink flow can be reduced, and A meniscus described later can be formed stably.

The shape of the ink guide 54 is not particularly limited. For example, the shape of the ink guide 54 does not have to be a shape in which the tip end portion 54a becomes thinner toward the counter electrode 22, and can be changed as appropriate. For example, a cutout serving as an ink guide groove for collecting the ink Q in the front end portion 54a by a capillary phenomenon may be formed in the center portion of the ink guide 54 in the vertical direction in the drawing.
Further, it is preferable that a metal is deposited on the most distal portion of the ink guide 54. By depositing metal on the leading edge of the ink guide 54, the dielectric constant of the tip portion 54a of the ink guide 54 is substantially increased. Thereby, it becomes easy to generate a strong electric field, and the discharge property of ink can be improved.

As shown in FIG. 2B, ejection electrodes 58 are formed on the lower surface of the insulating substrate 66 (the surface facing the head substrate 52). The discharge electrode 58 is arranged in a U-shape with one side on the upstream side of the ink flow cut out along the periphery of the discharge port 62 so as to surround the periphery of the elongated bowl-shaped discharge port 62. By forming the discharge electrode 58 into a shape that is partially missing on the upstream side in the ink flow direction, when using ink containing charged colorant particles, which will be described later, the color from the upstream side in the ink flow direction to the discharge port An electric field that prevents the inflow of the material particles is not formed, and the color material particles can be efficiently supplied to the discharge port. Further, by disposing the discharge electrode 58 on the downstream side of the ink, an electric field is formed in a direction in which the color material particles flowing into the discharge port are retained at the discharge port. As described above, by making the ejection electrode into a shape in which the upstream side in the ink flow direction is partially missing, it is possible to further improve the ability to supply particles to the ejection port.
Further, in the present embodiment, the discharge electrode 58 is formed in a U shape from the viewpoint that the above-described effect can be obtained. However, any shape can be used as long as the electrode is disposed so as to face the ink guide. Alternatively, for example, a ring-shaped circular electrode, an elliptical electrode, a divided circular electrode, a parallel electrode, a substantially parallel electrode, or the like can be changed to various shapes according to the shape of the discharge port 62.

As described above, since the ejection head 20 has a structure in which a plurality of ejection ports 62 are arranged, the ejection electrodes 58 are arranged corresponding to the ejection ports 62 as schematically shown in FIG.
Further, the ejection electrode 58 is exposed to the ink flow path 64 and is in contact with the ink Q flowing through the ink flow path 64. Thereby, the discharge property of ink droplets can be greatly improved. This point will be described later together with the action of discharge. However, the ejection electrode 58 is not necessarily exposed to the ink flow path 64 and in contact with the ink. That is, the discharge electrode 58 may be formed inside the discharge port substrate 56, or the exposed surface of the discharge electrode 58 may be covered with a thin insulating layer or the like.

  As shown in FIG. 2, the discharge electrode 58 is connected to the control unit 74. The controller 74 can control the voltage applied to the ejection electrode 58 when ink droplets are ejected and when they are not ejected.

The guard electrode 60 is formed on the surface of the insulating substrate 66, and the surface of the guard electrode 60 is covered with an insulating layer 68. FIG. 4 schematically shows the planar structure of the guard electrode 60. FIG. 4 is a view taken along the line IV-IV in FIG. 2A, and schematically shows a planar structure of the guard electrode 60 in the case of an inkjet head having a single-row line structure. As shown in FIG. 4, the guard electrode 60 is a sheet-like electrode common to each discharge electrode such as a metal plate, and is a discharge electrode 58 formed around each discharge port 62 arranged two-dimensionally. An opening 70 is provided at a position corresponding to. The opening 70 is formed in a rectangular shape. The length and width of the opening 70 of the guard electrode 60 are formed larger than the length and width of the discharge port.
The guard electrode 60 can shield electric lines of force between the adjacent ejection electrodes 58 to suppress electric field interference, and a predetermined voltage is applied to the guard electrode 60 (including 0 V due to grounding). In the illustrated example, the guard electrode 60 has a voltage (300 V) lower than the voltage applied to the ejection electrode 58 (for example, +2.7 kV is applied to the guard electrode when +3 kV is applied to the ejection electrode). Is applied. Here, you may comprise so that the voltage applied to the guard electrode 60 can be adjusted as needed.

As a preferred mode, the guard electrode 60 is formed in a layer different from the ejection electrode 58 as shown in FIG. 2A, and the entire surface is covered with an insulating layer 68.
By having such an insulating layer 68, a strong discharge electric field can be formed between the discharge electrode 58 and the guard electrode 60, and the color material particles of the ink Q are coated between the discharge electrode 58 and the guard electrode 60. Discharging can also be prevented.

  Here, the guard electrode 60 is provided so as to secure electric lines of force acting on the corresponding discharge ports 62 (hereinafter referred to as “own channel” for convenience) among electric lines of force generated from the discharge electrodes 58. There is a need.

In consideration of the above points, the width and length of the rectangular opening 70 of the guard electrode 60 are determined so that the discharge of the self-channel can be performed when viewed from the substrate plane so as not to block the electric lines of force to the self-channel. The electrode 58 is also preferably made larger. That is, the end of the guard electrode 60 on the discharge port 62 side is preferably separated (retreated) from the discharge port 62 rather than the inner edge of the discharge electrode 58 of the own channel.
Further, in order to efficiently form a discharge electric field with the discharge electrode 58, the length and width of the rectangular opening 70 of the guard electrode 60 are determined by the discharge of the own channel when viewed in the substrate plane. It is preferable to make it smaller than the interval between the outer edge portions of the electrode 58. That is, it is preferable that the inner edge portion of the guard electrode 60 is closer (advanced) to the discharge port 62 than the outer edge portion of the discharge electrode 58 of the own channel. According to the study of the present inventor, this proximity amount is preferably 5 μm or more, particularly preferably 10 μm or more.

  The opening 70 of the guard electrode 60 is substantially similar to the shape formed by the inner edge or the outer edge of the ejection electrode 58, and the inner edge of the guard electrode 60 is more ejected than the inner edge of the ejection electrode 58 of its own channel. The guard electrode 60 may be provided so as to be separated (retracted) from 62 and closer to (advance) the discharge port 62 than the outer edge of the discharge electrode (that is, the opening 70 of the guard electrode 60 may be formed). Good).

In the above example, the guard electrode 60 is a sheet-like electrode, but the present embodiment is not limited to this, and may have any shape or structure. For example, the guard electrode 60 may be provided in a mesh shape between the discharge ports.
Here, the shape of the opening 70 of the guard electrode 60 is substantially the same as the shape of the discharge port 62, but the shape is not limited to this and may be any shape. For example, the shape may be a circle, an ellipse, a square, a rhombus, or the like.
Here, it is preferable to provide a guard electrode from the viewpoint of obtaining the above-mentioned effect, but the guard electrode is not an essential component and is not necessarily provided.

Further, as a preferred embodiment, the ejection head 20 of the present embodiment is provided with an ink guide weir 72 that guides ink to the ejection port 62 on the head substrate 52. Hereinafter, the ink guide weir 72 will be described.
FIG. 5A is a partial cross-sectional perspective view showing the configuration in the vicinity of the ejection section in the ejection head 20 of FIG. In the drawing, in order to clearly show the structure of the ink guide weir 72, the ejection port substrate 56 is shown cut along the ink flow direction at a substantially central position of the ink guide 54.

  The ink guide weir 72 is upstream and downstream in the ink flow direction of the ink guide 54 disposed at a position corresponding to the ejection port 62 on the surface of the head substrate 52 on the ink flow path 64 side, that is, the bottom surface of the ink flow path 64. The surface is provided on the side and is inclined so as to gradually approach the discharge port substrate 56 from the vicinity of the position corresponding to the discharge port 62 toward the position corresponding to the center of the discharge port 62 with respect to the ink flow direction. have. That is, the ink guide weir 72 has a shape that is inclined toward the ejection port 62 along the ink flow direction.

  In addition, the ink guide weir 72 has a shape that has substantially the same width as the ejection port 62 in the direction perpendicular to the ink flow and has a wall surface that hangs from the bottom surface. In addition, the ink guide weir 72 does not block the ejection port 62 and secures a channel for the ink Q, so that the ink guidance weir 72 has a predetermined distance from the surface on the ink channel 64 side of the ejection port substrate 56, that is, the upper surface of the ink channel 64. It is provided at intervals. Such an ink guide weir 72 is provided in each discharge part.

  As described above, by providing the ink guide weir 72 inclined toward the ejection port 62 along the ink flow direction on the bottom surface of the ink flow path 64, an ink flow toward the ejection port 62 is formed, and the ink Q The discharge port 62 is guided to the opening on the ink flow path 64 side. Therefore, the ink Q can be suitably flown into the discharge port 62, and the ink supply property can be further improved. Furthermore, clogging can be prevented more reliably.

  The length l of the ink guide weir 72 in the ink flow direction may be set as appropriate so that the ink Q can be suitably guided to the ejection port 62 within a range that does not interfere with the adjacent ejection unit. As shown in FIG. 5, the height h of the highest part of the ink guide weir 72 is preferably 0.5 times or more (l / h ≧ 0.5), preferably 1 time or more (l / h ≧ 1). More preferably.

  The width of the ink guide weir 72 in the direction perpendicular to the ink flow is preferably equal to or slightly wider than the ejection port 62. Further, the width of the ink guide weir 72 is not limited to a uniform one as shown in the drawing, and may be one in which the width gradually decreases or one in which the width gradually increases. Further, the wall surface is not limited to a vertical surface, and may be an inclined surface or the like.

  The inclined surface (ink guiding surface) of the ink guiding weir 72 may be a shape suitable for guiding the ink Q to the ejection port 62, and may be a slope having a certain inclination angle. It may be a changing surface or a curved surface. The surface is not limited to a smooth surface, and one or more wrinkles, grooves, or the like may be formed in the ink flow direction or radially toward the center of the ejection port 62.

  Further, the vicinity of the contact portion with the ink guide 54 at the top of the ink guide weir 72 may have a shape that is smoothly connected without having a step as in the illustrated example.

  In the illustrated example, the ink guide weir 72 is arranged on the upstream side and the downstream side of the ink guide 54, but a trapezoidal ink guide weir 72 having slopes on the upstream side and the downstream side of the ejection port 62 is provided. The ink guide 54 may be erected on the top, or the ink guide 54 and the ink guide weir 72 may be formed integrally. As described above, the ink guide weir 72 may be separately or integrally formed with the ink guide 54 and attached to the head substrate 52, or the head substrate 52 may be shaved by a conventionally known excavation means. It may also be formed.

  The ink guide weir 72 may be provided on the upstream side of the ejection port 62, but the height in the ejection direction of the ink droplet R is also ejected on the downstream side of the ejection port 62 as shown in the illustrated example. It is preferable to be provided so as to become lower as the distance from the outlet 62 increases. As a result, the ink Q guided toward the ejection port 62 by the upstream ink guide weir 72 flows smoothly to the downstream side, so that the ink Q can be kept stable without being turbulent. , Discharge stability can be maintained.

  In the example of FIG. 5, the ink guide weir 72 is disposed on the upper surface of the head substrate 52. However, the present invention is not limited to this. An ink guide weir may be provided.

  For example, an ink flow groove having a predetermined depth passing through a position corresponding to the ejection port 62 is provided along the ink flow direction, and is inclined toward the ejection port 62 along the ink flow direction at a position corresponding to the ejection port. An ink guide weir having a surface is provided. Thus, by providing the ink flow groove, most of the ink Q flowing through the ink flow path 64 can be selectively flowed to the ink flow groove. By providing the ink flow path weir, the ink Q is ejected from the ejection port 62. The ink can be preferably introduced into the ink guide, and the ink supply to the ink guide tip 54a can be improved.

As shown in FIG. 2A, the counter electrode 22 is disposed so as to face the ink droplet ejection surface of the ejection head 20.
The counter electrode 22 is disposed at a position facing the front end portion 54a of the ink guide 54, and a predetermined voltage is applied thereto. The counter electrode 22 is formed with an opening on the ink droplet flight path, and in this embodiment, an opening with a predetermined diameter is formed around a contact point perpendicular to the counter electrode 22 from the tip portion 54a of the ink guide.

  In the electrostatic ink jet of this embodiment using the ink Q containing the charged color material particles as described above, the force is applied to the entire ink as in the conventional ink jet system, and the ink is used as a recording medium. The ink is mainly caused to fly by applying a force to the colorant particles, which are solid components dispersed in the carrier liquid, instead of flying toward the ink. Hereinafter, the ejection action of the ink droplet R in the ejection head 20 will be described.

As shown in FIG. 2A, in the ejection head 20, the same polarity as the voltage applied to the ejection electrode 58 when ejecting ink droplets from an ink supply flow path 30 (see FIG. 1) described later, for example, positive ( The ink Q containing the coloring material particles charged to (+) circulates in the ink flow path 64 in the direction of the arrow (from left to right in the figure).
On the other hand, as described above, a voltage having the same polarity as the color material particles, that is, a positive predetermined voltage (for example, +500 V) is applied to the counter electrode 22 during recording, as described above.
From this state, control is performed so that a predetermined voltage (for example, +3 kV (hereinafter referred to as a bias voltage)) is applied from the controller 74 to the ejection electrode 58.

Immediately after the bias voltage is applied, the ink Q has a Coulomb attractive force between the bias voltage and the charge of the color material particles of the ink Q, a Coulomb repulsive force between the color material particles, a viscosity of the carrier liquid, a surface tension, a dielectric content. As much as possible, these are kneaded, and the colorant particles and the carrier liquid move to form a meniscus shape slightly raised from the discharge port 62 as conceptually shown in FIG.
In addition, the colorant particles move toward the recording medium P charged with a bias voltage by so-called electrophoresis due to the Coulomb attractive force or the like. That is, the ink Q is concentrated at the meniscus of the discharge port 62.

When a finite time has passed after the application of the bias voltage, the force acting on the colorant particles (Coulomb force, etc.) and the carrier liquid mainly at the tip of the meniscus having a high electric field strength due to the movement of the colorant particles, etc. The balance with the surface tension of the ink collapses and the meniscus grows abruptly, and as shown conceptually in FIG. 6B, a slender ink liquid column having a diameter of about several μm to several tens of μm is formed. .
Further, when a finite time elapses, the silk thread grows, and the growth of the silk thread, vibration caused by Rayleigh / Weber instability, uneven distribution of colorant particles in the meniscus, uneven distribution of electrostatic field on the meniscus, etc. The silk thread is broken by the interaction. Then, as shown in FIG. 6C, the split string is discharged as an ink droplet R, flies toward the counter electrode, and passes through an opening formed in the counter electrode. It should be noted that the growth and splitting of the kite and the movement of the color material particles to the meniscus (the kite) occur continuously during the application of the bias voltage.

  Here, since the ink droplet R ejected immediately after the bias application (immediately after the start of splitting the string) is ejected in an unstable state of the colorant particle concentration, the droplet diameter, and the separation frequency, the non-uniform liquid Become drops. Thereafter, when a predetermined time elapses after the bias voltage is applied, the amount of ink supplied to the ejection port and the amount of ink that is divided and ejected are in an equilibrium state, and the colorant particle concentration is constant and minute while the bias voltage is applied. Ink droplets R having a uniform droplet diameter are ejected at a constant dividing frequency.

  As described above, the electrostatic ink jet head causes an electrostatic force to act on the ejection port and stably eject ink droplets having a diameter smaller than the opening diameter of the ejection port. As a result, an electrostatic ink jet head has a very small ink droplet diameter compared to a piezo or thermal ink jet head that ejects ink droplets having a diameter larger than the opening diameter of the discharge port. Can be discharged.

  In this embodiment, an example in which a DC voltage is applied as a bias voltage has been described. However, a DC voltage superimposed with a pulse voltage may be used as the bias voltage, or an AC voltage may be used. Further, perturbation may be given by ultrasonic waves, electrostatic force, heat or the like so as to stabilize the splitting of the kite string.

As shown in FIG. 1, the back electrode 24 is disposed in parallel to the counter electrode 22 at a position facing the ejection head 20 via the counter electrode 22 and is electrically grounded.
The recording medium P is held on the left surface of the back electrode 24 in the drawing, that is, the surface of the back electrode 24 on the discharge head 20 side, and the back electrode 24 functions as a platen of the recording medium P.
Here, the back electrode 24 is grounded, and a bias voltage (+500 V) is applied to the counter electrode 22, whereby a predetermined electric field is formed between the counter electrode 22 and the back electrode 24. The ink droplet R ejected from the ejection head 20 and passed through the opening of the counter electrode 22 is pulled toward the back electrode 24 side, that is, the recording medium P side by an electric field formed between the counter electrode 22 and the back electrode 24. And fly straight toward the back electrode 24.

The deflection unit 26 includes a first deflection electrode 40, a second deflection electrode 42, and a control unit 44 that are disposed between the counter electrode 22 and the back electrode 24 via the flight path of the ink droplet R.
The first deflection electrode 40 is connected to the control unit 44, and the second deflection electrode 42 is electrically grounded.
The controller 44 controls the voltage applied to the first deflection electrode 40 according to the image signal, and forms an electric field between the first deflection electrode 40 and the second deflection electrode 42. Here, a voltage having the same polarity as the ink droplet R is applied to the first deflection electrode 40 from the control unit 44 in accordance with the image signal.

  The ink droplet R ejected from the ejection head 20 passes straight through the opening formed on the flight path of the ink droplet of the counter electrode 22, then flies straight toward the back electrode 24, and the first deflecting means 40. And the second deflecting means 42. Here, when the voltage is applied from the control unit 44, the ink droplet R that has passed between the first deflection electrode 40 and the second deflection electrode 42 is transferred to the first deflection electrode 40, the second deflection electrode 42, and the like. Due to the electric field formed between the first deflection electrode 40 and the second deflection electrode 42, a force is applied to the ink droplet R in the direction from the first deflection electrode 40 to deflect the flight path toward the second deflection electrode 42 by a predetermined angle. In addition, the ink droplet R that has passed between the first deflection electrode 40 and the second deflection electrode 42 when no voltage is applied travels straight to the back electrode 24 side without deflection of the flight path, and recording is performed. Land on the medium P.

  The voltage applied to the first deflection electrode 40 and the second deflection electrode 42 is not particularly limited. For example, the first deflection electrode 40 is grounded, and a voltage having a polarity different from that of the ink droplet is applied to the second deflection electrode 42. Thus, an electric field may be formed to deflect ink droplets.

The gutter 32 collects ink droplets whose flight path is deflected by the deflecting means 26, and the flight path was not deflected between the deflecting means 26 and the back electrode 24 and by the deflecting means 26. In other words, the ink droplets are arranged at a position shifted from the flight path of the ink droplets flying straight toward the back electrode 24 toward the second deflection electrode 42 by a predetermined distance.
The ink droplet whose flight path is deflected by the deflecting unit 26 lands on the gutter 32 and is collected from the gutter 32 to the ink tank 28 through the second ink collection channel 34.

The ink tank 28 stores ink and is connected to the ejection head 20 via the ink supply flow path 30 and the first ink recovery flow path 31 and is connected to the gutter 32 via the second ink recovery flow path 34. The
The ink tank 28 supplied a fixed amount of ink to the discharge head 20 by a pump (not shown) via the ink supply flow path 30 and was not used for discharge by the discharge head 20 via the first ink recovery flow path 31. Collect the ink. In this way, a certain amount of ink is circulated between the ejection head 20 and the ink tank 28. Ink droplets that have landed on the gutter 32 are collected in the ink tank 28 via the second ink collection channel 34.

Here, the ink tank 28 includes an ink density adjusting mechanism that adjusts the ink density, and requires the density of the ink circulating between the ejection head 20 and the ink tank 28 and the density of the ink stored in the ink tank 28. Therefore, it is preferable to always supply a constant concentration of ink to the ejection head 20.
Further, a filter for removing impurities and solidified and enlarged ink is provided in at least one of the ink tank 28, the ink supply flow path 30, the first ink recovery flow path 31 and the second ink recovery flow path 32. It is preferable to provide it.

As described above, the ink jet recording apparatus of the present invention causes the electrostatic force to act on the ejection head 20 to continuously eject ink droplets, and selectively deflects the ink droplets from the deflecting means in accordance with the image signal. This is a continuous ink jet recording apparatus that forms an image by controlling ink droplets that land on a recording medium.
Thus, by using an electrostatic and continuous ink jet recording apparatus, it is possible to perform recording in a state where ink droplets are always ejected from the ejection head, and the responsiveness to image signals is improved. The recording frequency can be increased.

  Further, since the splitting of the kite string occurs at a very high frequency, the ink droplet ejection frequency becomes a high frequency, and high-speed drawing can be performed. As an example, in the inkjet head of this embodiment, ink droplets can be ejected at least at an ejection frequency of about 200 kHz.

  In addition, by ejecting ink droplets by applying an electrostatic force to the ejection ports, ink droplets having a diameter smaller than that of the ejection ports can be ejected, and a high-resolution image can be formed. As an example, in the ink jet head of this embodiment, ink droplets having a droplet diameter of about 0.05 pl to 2 pl can be ejected.

  Further, the ink jet recording apparatus of the present embodiment can deflect ink droplets by applying a low voltage to the deflection electrode. This makes it possible to perform control according to the image signal at a lower voltage than the on-demand inkjet recording apparatus that controls image ejection by controlling the ejection / non-ejection of ink droplets by the voltage applied to the ejection electrode. The apparatus can be made cheaper and the power consumption can be reduced.

Furthermore, since the ejected ink droplets are charged, there is no need to charge the ink droplets by the charging means, the ink droplets can be deflected by the deflecting means, and the apparatus configuration is simplified. Can do.
In addition, ink droplets are always ejected during image recording regardless of the image signal, thus preventing ink aggregation at the ejection port and clogging of the ejection port that occur when the ink droplets are not ejected for a long time. can do. As a result, failure of the ejection head can be prevented and maintenance can be simplified.

  Furthermore, when recording an image, the colorant particle concentration, the droplet diameter, and the separation are not used without using the ink droplets that are ejected in an unstable state of the colorant particle concentration, the droplet diameter, and the separation frequency immediately after the start of thread separation. By forming an image using ink droplets that are ejected at a steady frequency, the response to the image signal is constant, and a more stable image can be formed.

Here, since the ink jet recording apparatus of the present invention always discharges ink droplets and performs control according to the image signal by the deflecting means, basically the same operation is performed from all the discharge portions of the discharge head when discharging ink droplets. Ink droplets are ejected onto the surface. For this reason, in this embodiment, the ejection electrode is formed separately for each ejection section, but the present invention is not limited to this, and the ejection electrode may be a sheet-like electrode common to the plurality of ejection sections.
Further, the bias voltage applied to the ejection electrode is not limited to a DC voltage, and a pulse voltage can also be used.

FIG. 7 shows another example of the ink jet recording apparatus of the present invention.
In the present embodiment, the configuration is the same as that of the inkjet recording apparatus 10 shown in FIG. Therefore, the same reference numerals are given to the same components in both, and the detailed description thereof is saved, and the points peculiar to the ink jet recording apparatus 80 will be mainly described below.

The deflection unit 82 of the ink jet recording apparatus 80 includes an air flow generation unit 84 and a control unit 44. The air flow generation unit 84 is connected to the control unit 44.
The air flow generation unit 84 ejects an air flow with respect to the ink droplet R and deflects the ink droplet R. Further, the control unit 44 controls the air flow ejected from the air flow generation unit 84 in accordance with the image signal.

The ink droplets R deflected by the airflow ejected from the airflow generator 84 are collected in the gutter 32, and the ink droplets R that have not been deflected travel straight and land on the recording medium P to form an image.
Thus, the deflecting means is not limited to means for applying a voltage to the deflecting electrode to form a predetermined electric field and deflecting the ink droplets, but deflects the ink droplets by the air flow, and the ink liquid according to the image signal. Drop behavior can be controlled.
Further, the deflecting means is not limited to the means for deflecting the droplet by forming the electric field or generating the air flow as described above, and various deflections such as a deflecting means for deflecting the droplet by forming a magnetic field, for example. Means can be used.

Here, an example of ink that can be suitably used in the ink jet recording apparatus of the present embodiment will be described.
The ink Q is obtained by dispersing charged fine particles in a carrier liquid. The carrier liquid is preferably a dielectric liquid having a high electrical resistivity. The electrical resistivity of the carrier liquid is preferably 10 ⁹ Ω · cm to 10 ¹⁶ Ω · cm, and more preferably 10 ¹⁰ Ω · cm to 10 ¹⁵ Ω · cm. By setting the electric resistivity of the carrier liquid within the above range, it is possible to form a dark dot that is easy to concentrate charged fine particles and has little bleeding, and it is possible to prevent the voltage during discharge from becoming too high.

  The relative dielectric constant of the dielectric liquid used as the carrier liquid is preferably 1.9 or more and 5.0 or less, and more preferably 2 or more and 4 or less. By setting the relative dielectric constant of the carrier liquid in the above range, the charged fine particles are likely to be concentrated, dark dots with little bleeding can be formed, and the discharge voltage can be prevented from becoming too high.

  The dielectric liquid used as the carrier liquid is preferably a linear or branched aliphatic hydrocarbon, alicyclic hydrocarbon, or aromatic hydrocarbon, and halogen-substituted products of these hydrocarbons. For example, hexane, heptane, octane, isooctane, decane, isodecane, decalin, nonane, dodecane, isododecane, cyclohexane, cyclooctane, cyclodecane, benzene, toluene, xylene, mesitylene, Isopar C, Isopar E, Isopar G, Isopar H, Isopar L, Isopar M (isopar: trade name of Exxon), Shellsol 70, Shellsol 71 (shellsol: trade name of Shell Oil), Amsco OMS, Amsco 460 Solvent (trade name of Amsco: Spirits), Silicone oil (for example, KF-96L manufactured by Shin-Etsu Silicone) or the like can be used alone or in combination.

  The charged fine particles dispersed in the carrier liquid can contain a color material. As the particles containing the charge and the color material (color material particles), the color material itself may be dispersed in the carrier liquid as the color material particles, but preferably contains dispersed resin particles for improving fixability. Let When the dispersed resin particles are included, the pigment is generally coated with the resin material of the dispersed resin particles to form resin-coated particles, and the dye is colored with the dispersed resin particles to form colored particles. Is common.

As the color material, any pigments and dyes that have been conventionally used in inkjet ink compositions, printing (oil-based) ink compositions, or electrophotographic liquid developers can be used.
As the pigment used as the color material, regardless of inorganic pigments or organic pigments, those generally used in the technical field of printing can be used. Specifically, for example, carbon black, cadmium red, molybdenum red, chrome yellow, cadmium yellow, titanium yellow, chromium oxide, viridian, cobalt green, ultramarine blue, Prussian blue, cobalt blue, azo pigment, phthalocyanine pigment Conventionally known pigments such as quinacridone pigments, isoindolinone pigments, dioxazine pigments, selenium pigments, perylene pigments, perinone pigments, thioindigo pigments, quinophthalone pigments and metal complex pigments are used without particular limitation. be able to.
As dyes used as coloring materials, azo dyes, metal complex dyes, naphthol dyes, anthraquinone dyes, indigo dyes, carbonium dyes, quinoneimine dyes, xanthene dyes, aniline dyes, quinoline dyes, nitro dyes, nitroso dyes, benzoquinone dyes, naphthoquinone dyes And oil-soluble dyes such as phthalocyanine dyes and metal phthalocyanine dyes.

Further, as dispersed resin particles, for example, rosins, rosin-modified phenol resins, alkyd resins, (meth) acrylic polymers, polyurethane, polyester, polyamide, polyethylene, polybutadiene, polystyrene, polyvinyl acetate, polyvinyl alcohol, polyvinyl alcohol, acetal-modified Products, polycarbonate and the like.
Among these, from the viewpoint of ease of particle formation, the weight average molecular weight is in the range of 2,000 to 1,000,000 and the polydispersity (weight average molecular weight / number average molecular weight) is 1.0 to 5 Polymers in the range of 0.0 are preferred. Furthermore, from the viewpoint of ease of fixing, a polymer having any one of a softening point, a glass transition point, and a melting point within a range of 40 ° C. to 120 ° C. is preferable.

  In the ink Q, the content of the color material particles (the total content of the color material particles or further dispersed resin particles) is preferably contained in the range of 0.5 to 30% by weight with respect to the whole ink, and more preferably. Is preferably contained in the range of 1.5 to 25% by weight, more preferably 3 to 20% by weight. If the content of the colorant particles is reduced, problems such as insufficient printed image density or difficulty in obtaining a strong image due to difficulty in obtaining the affinity between the ink Q and the surface of the recording medium P are likely to occur. On the other hand, when the content increases, it becomes difficult to obtain a uniform dispersion, or the ink Q is easily clogged with an inkjet head or the like, and it is difficult to obtain stable ink discharge. .

  The average particle diameter of the colorant particles dispersed in the carrier liquid is preferably 0.1 to 5 μm, more preferably 0.2 to 1.5 μm, and still more preferably 0.4 to 1.0 μm. . This particle size is determined by CAPA-500 (trade name, manufactured by Horiba, Ltd.).

After the colorant particles are dispersed in the carrier liquid (a dispersant may be used if necessary), the chargeant is added to the carrier liquid to charge the colorant particles, and the charged colorant The ink Q is obtained by dispersing particles in a carrier liquid. When dispersing the colorant particles, a dispersion medium may be added as necessary.
As an example of the charge control agent, various materials used in electrophotographic liquid developers can be used. Also, “Recent development and commercialization of electrophotographic development systems and toner materials”, pages 139 to 148, “The Basics and Applications of Electrophotographic Technology” edited by Electrophotographic Society, pages 497 to 505 (Corona Inc., published in 1988), Yuji Harasaki Various charge control agents described in “Electrophotography” 16 (No. 2), p. 44 (1977) can also be used.

The color material particles may be positively charged or negatively charged as long as they have the same polarity as the bias voltage applied to the ejection electrode.
The charge amount of the color material particles is preferably in the range of 5 to 200 μC / g, more preferably 10 to 150 μC / g, and still more preferably 15 to 100 μC / g.

The electrical conductivity of the ink Q is preferably 100 to 3000 pS / cm, more preferably 150 to 2500 pS / cm, and still more preferably 200 to 2000 pS / cm. By setting the electric conductivity in the above range, the voltage applied to the ejection electrodes does not become extremely high, and there is no fear of causing electrical continuity between adjacent ejection electrodes.
The surface tension of the ink Q is preferably in the range of 15 to 50 mN / m, more preferably 15.5 to 45 mN / m, and still more preferably 16 to 40 mN / m. By setting the surface tension within this range, the voltage applied to the ejection electrode does not become extremely high, and the ink does not leak around the head and become contaminated.
Furthermore, the viscosity of the ink Q is preferably 0.5 to 5 mPa · sec, more preferably 0.6 to 3.0 mPa · sec, and still more preferably 0.7 to 2.0 mPa · sec.

In addition, since the electric resistance of the dielectric solvent may change due to the addition of the charge control agent, in order to stabilize the predetermined electric resistivity of the solvent, the distribution ratio P defined below is preferably 50% or more, More preferably 60% or more, and still more preferably 70% or more.
P = 100 × (σ1−σ2) / σ1
Here, σ1 is the electrical conductivity of the ink Q, and σ2 is the electrical conductivity of the supernatant obtained by applying the ink Q to the centrifuge. The electrical conductivity was measured using an LCR meter (AG-4311 manufactured by Ando Electric Co., Ltd.) and an electrode for liquid (LP-05 type manufactured by Kawaguchi Electric Manufacturing Co., Ltd.) under the conditions of an applied voltage of 5 V and a frequency of 1 kHz. This is the measured value. Centrifugation was performed for 30 minutes using a small high-speed cooling centrifuge (Tomy Seiko Co., Ltd. SRX-201) under conditions of a rotational speed of 14500 rpm and a temperature of 23 ° C.
By using the ink Q as described above, migration of the color material particles is likely to occur and the concentration is facilitated.

As an example, such an ink Q can be prepared by dispersing color material particles in a carrier liquid to form particles, and adding a charge control agent to the dispersion medium to cause the color material particles to be charged. Specific methods include the following methods.
(1) A method in which a coloring material or further dispersed resin particles are mixed (kneaded) in advance, and then dispersed in a carrier liquid using a dispersant as necessary, and a charge control agent is added.
(2) A method in which a coloring material, or further dispersed resin particles and a dispersing agent are simultaneously added to a carrier liquid, dispersed, and a charge control agent is added.
(3) A method in which a coloring material and a charge control agent, or further dispersed resin particles and a dispersing agent are simultaneously added to the carrier liquid and dispersed.

  Hereinafter, image recording in the inkjet recording apparatus 10 will be described in detail.

First, ink is circulated in the order of the ink supply channel 30, the ejection head 20, and the first ink recovery channel 31 from the ink tank 28 by a pump (not shown), and a constant amount of ink is always supplied to the ejection head 20.
A voltage is applied to the counter electrode 22 and the discharge electrode 58 of the discharge head 20. As a result, a required potential difference is set between the ejection electrode 58 and the counter electrode 22, and an electric field capable of ejecting ink is formed on the ejection head 20, and as described above, the tailor cone is formed. Splitting of the kite string occurs, and the split kite string is ejected from the ejection port 62 as ink droplets. Further, as long as an electric field capable of ejecting ink is formed on the ejection head 20, the splitting of the string occurs continuously and ink droplets are formed.

The ejected ink droplets pass through an opening formed at a position facing the ejection port 62 of the counter electrode 22.
The ink droplet that has passed through the counter electrode 22 is pulled toward the back electrode 24 by an electric field formed between the counter electrode 22 to which a predetermined voltage is applied and the back electrode 24 that is grounded. Go straight to the side and pass between the first deflection electrode 40 and the second deflection electrode 42 of the deflection means 26.

  The ink droplets passing between the first deflection electrode 40 and the second deflection electrode 42 are formed by a voltage applied from the control unit 44 to the first deflection electrode 40 according to the image signal. The behavior (flight path) is controlled by the electric field between the second deflection electrode 42 and the second deflection electrode 42. That is, the ink droplets R used for image recording go straight without landing and land on the recording medium P, and the ink droplets R not used for image recording are deflected and land on the gutter 32.

  In this way, the behavior of the ink droplet R is controlled according to the image signal, and the ink droplet R is landed on the recording medium P, whereby an image is formed on the recording medium P. The ink that has landed on the gutter 32 is collected in the ink tank 28 via the second ink collection channel 34 and reused.

As described above, it is possible to always record an image on a recording medium by applying an electrostatic force to ink, causing ink droplets to be continuously ejected, and controlling the behavior of the ink droplets by a deflecting unit according to an image signal. Image recording can be performed in a state where ink droplets are ejected from the ejection head at a high ejection frequency, responsiveness to image signals is improved, and the recording frequency can be increased.
Furthermore, by applying an electrostatic force to the ink and ejecting ink droplets, it is possible to stably eject droplets with a small droplet diameter at a high ejection frequency, and stably produce high-quality images. It can be formed at high speed.

  Here, in the above embodiment, a predetermined electric field is formed between the ejection head 20 and the counter electrode 22 and ink droplets are ejected. However, the present invention is not limited to this, and the counter electrode is not installed. Alternatively, a predetermined electric field may be formed between the ejection head and the back electrode to eject ink droplets.

  In the ink jet recording apparatus of the above aspect, the back electrode is provided with transport means such as a transport belt, and the recording medium P is transported in a direction orthogonal to the arrangement direction of the discharge ports arranged in the single-row line structure. However, it is preferable to perform image recording.

  In the above embodiment, the ink droplets collected in the gutter are deflected. However, the present invention is not limited to this, for example, on the transport path of the ink droplets when the gutter is advanced straight without being deflected. The ink droplets may be arranged in a straight line so that the ink droplets collected in the gutters travel straight and deflect the ink droplets that land on the recording medium.

  In the above embodiment, it is preferable to use an ink in which charged particles are dispersed in a solvent having a high electrical resistivity from the viewpoint that a coloring material can be concentrated and discharged, and an image with less bleeding can be formed. The invention is not limited to this, and various inks can be used as long as the ink has a charge as a whole, that is, the ink has a charge including at least fine particles and a solvent. For example, a solvent having colorant particles that are difficult to be charged is used as an ink, and an ink having an appropriate conductivity is obtained by a charge control agent or a conductive agent, and an electrostatic force is applied to the ink solvent so that the colorant particles are not concentrated. Alternatively, it may be ejected as fine droplets.

More specifically, color material particles that are hardly charged are dispersed in a solvent having a low electrical resistivity (10 ⁹ Ω · cm or less), for example, water or a polar organic solvent (alcohol, ketone, ester, ether, amide). Ink can also be used. In this case, the solvent having a low electrical resistivity is in a charged state, and the charged solvent can be discharged as droplets together with the color material particles by applying an electrostatic force.
Further, an ink in which charged color material particles are dispersed in a solvent having a low electrical resistivity can also be used. In this case, the solvent and the color material particles are in a charged state, and the charged solvent and the color material particles can be discharged as droplets by applying an electrostatic force.
Further, an ink obtained by adding a conductive agent to the above-described solvent having a high electrical resistivity (10 ⁹ Ω · cm or more) and dispersing colorant particles that are difficult to be charged can be used. As described above, even when a solvent having a high electrical resistivity is used, a conductive agent is added to the solvent to be charged, and the electrostatic solvent is applied to the charged solvent together with the colorant particles. It can be discharged as a droplet.
In addition, an ink in which a conductive agent is added to a solvent having a high electrical resistivity and charged colorant particles are dispersed can also be used. In this case, the conductive agent and charged color material particles in the solvent are in a charged state, and the charged solvent and color material particles can be discharged as droplets by applying an electrostatic force.

Furthermore, in the present embodiment, ink having colorant particles as fine particles is used. However, the present invention is not limited to this, and a solution having various fine particles such as colorless resin particles can be used.
Here, in the solution having various fine particles such as colorless resin particles, the above-described carrier liquid, dispersed resin particles, charge control agent and the like can be used, and the above-described carrier liquid, dispersed resin particles, charge control agent and / or Or it can manufacture by selecting and mixing various other materials as needed.

  In the above embodiment, the ink jet recording apparatus has been described. However, the micro droplet ejection apparatus of the present invention is not limited to this, and may be used for, for example, a trace chemical reaction apparatus, a trace drug analysis apparatus, a coating apparatus, and the like. Can do.

  As described above, the micro droplet ejection apparatus and the ink jet recording apparatus of the present invention have been described in detail. However, the present invention is not limited to the above-described embodiment, and various improvements and modifications are made without departing from the gist of the present invention. Of course it is also good.

It is a schematic block diagram which shows an example of the inkjet recording device which is one aspect | mode of the micro droplet discharge apparatus of this invention. It is an enlarged view of a discharge head and a counter electrode peripheral part. 6 is a view schematically showing a state in which a plurality of discharge ports 62 are arranged on the discharge port substrate 56 of the discharge head 20. FIG. It is the figure which showed typically the planar structure of the guard electrode of the inkjet head of a single row line structure. (A) is a partial cross-sectional perspective view showing the configuration in the vicinity of the ejection portion in the ejection head of FIG. 2, and (B) is a diagram for explaining the shape dimensions of the ink guide weir. (A)-(C) are the conceptual diagrams for demonstrating the ink droplet discharge method of the inkjet recording device shown in FIG. It is a schematic block diagram which shows another example of the inkjet recording device of this invention. It is a schematic diagram which shows an example of the inkjet head of the conventional inkjet recording device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10, 80 Inkjet recording apparatus 20 Discharge head 22 Counter electrode 24 Back electrode 26, 80 Deflection means 28 Ink tank 30 Ink supply flow path 32 Gutter 34 Ink recovery flow path 40 First deflection electrode 42 Second deflection electrode 44 Control section 52 Head Substrate 54 Ink guide 56 Discharge electrode 58 Discharge port substrate 60 Guard electrode 62 Discharge port 64 Ink flow channel 66 Insulating substrate 68 Insulating layer 70 Opening 72 Induction weir 74 Control unit 84 Air flow generation unit

Claims (13)

A micro-droplet discharge device that discharges micro-droplets by applying an electrostatic force to a charged solution containing at least fine particles and a solvent,
Discharge means for causing electrostatic force to act on the solution and continuously discharging fine droplets from the discharge port;
Deflection means for deflecting micro droplets ejected from the ejection means based on a control signal;
A microdroplet ejecting apparatus comprising: a microdroplet ejected from the ejecting means and traveling in a straight line; and a collecting means for collecting either a microdroplet whose flight direction is deflected by the deflecting means.   The fine droplet discharge device according to claim 1, wherein the fine particles are charged fine particles having a charge.   The fine droplet discharge device according to claim 1, wherein the fine particles include a charge and a color material. Using the microdroplet ejection device according to any one of claims 1 to 3,
The solution is ink;
The deflection unit deflects the micro droplets from the ejection unit based on the image signal, the micro droplets ejected from the ejection unit and travels straight, and the micro direction whose flight direction is deflected by the deflection unit Make one of the droplets land on the recording medium,
An ink jet recording apparatus, wherein the recovery means recovers minute droplets that do not land on the recording medium, thereby forming an image on the recording medium.   The inkjet recording apparatus according to claim 4, further comprising a counter electrode disposed between the ejection unit and the deflection unit and forming a predetermined electric field between the ejection unit and the ejection unit.   The inkjet recording apparatus according to claim 5, wherein the counter electrode has an opening on a flight path of the micro droplet.   6. The ink jet recording apparatus according to claim 4, further comprising a back electrode disposed at a position facing the ejection unit and the deflection unit and forming a predetermined electric field between the ejection unit and the ejection unit.   The ink jet recording apparatus according to claim 4, wherein the deflecting unit is an electric field or magnetic field applying unit that deflects the flying microdroplet.   8. The ink jet recording apparatus according to claim 4, wherein the deflecting unit is an air flow generating unit for deflecting the flying micro droplets.   The inkjet recording apparatus according to claim 4, further comprising a circulation unit that supplies the ink to the ejection unit and collects ink that is not ejected by the ejection unit.   The ink jet recording apparatus according to claim 10, further comprising recovered ink supply means for supplying ink recovered by the recovery means to the circulation means.   The ink jet recording apparatus according to claim 4, further comprising an ink density adjusting unit that adjusts the ink density.   The inkjet recording apparatus according to claim 4, wherein the ejection unit has a plurality of ejection openings.

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