JP2005096338A - Liquid ejection head and manufacturing method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid ejection head which can stably eject a liquid by a low ejection voltage. <P>SOLUTION: An ink outlet 56 is provided near an ink guide 52 which is manufactured in such a manner that a tip part is sharpened by anisotropic wet etching of a monocrystalline substrate, and such an ink flow 14 as to cross a side surface of a sharpened part 54 is formed by using ink flowing out from the ink outlet 56. A part of the solution, which is guided from the ink flow 14, is guided to a tip part 75 of the ink guide 52, so that a meniscus 16 for ejecting an ink droplet can be formed. An upper lid 32, which is provided with a control electrode 44, is joined to a top surface 54 which is provided with the ink guide 52, and a control substrate 44 and a tip part 75 of the ink guide 52 are positionally fixed. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a liquid discharge head that discharges a solution in which charged particles are dispersed in a solvent by electrostatic force, and a method for manufacturing the same.

  Today, thermal-type inkjet heads that heat ink and eject ink droplets with the expansion force of bubbles generated in the ink, and piezo-type inkjet heads that eject ink droplets by applying pressure to the ink with piezoelectric elements are proposed. ing. In the thermal type ink jet head, there is a problem that the material of the ink is limited because the ink is partially heated to 300 ° C. or more, and the piezo type ink jet head has a problem that the structure is complicated and the cost is high. As an ink jet head for solving these problems, liquid discharge heads that discharge a solution in which charged particles are dispersed by electrostatic force have been proposed (for example, Patent Document 1, Patent Document 2, Patent Document 3, and Patent Document 4).

  8A and 8B are schematic configuration diagrams of an example of a recording head that is an inkjet head of an image forming apparatus disclosed in Patent Document 1 below. FIG. 8A is a schematic sectional view of the recording head, and FIG. 8B is a view of the protruding plate 120 as viewed from the right side in FIG. In the recording head 100, a pair of support members 101 and 102 each having a substantially rectangular plate shape made of an insulating material are arranged to face each other. A gap between the support members 101 and 102 serves as a recording liquid supply path (ink supply path) 104, and an upper end portion of the support members 101 and 102 in the drawing serves as a recording liquid outlet (ink outlet) 104a. ing. In the recording liquid supply path 104, the recording liquid 106 flows from the lower side to the upper side in the figure at a predetermined pressure, and flows out from the recording liquid outlet 104a. The recording liquid 106 is an ink in which positively charged chargeable color material particles 105 are dispersed. On the inner surface of the recording liquid supply path 104 (one surface of the support members 101 and 102), first electrodes 111 are formed up to the recording liquid outlet 104a. In the recording liquid supply path 104, a protrusion 122 of a protrusion plate 120, which is an ink guide member having a protrusion 122 at the tip, is disposed so as to protrude from the recording liquid outlet 104a. A second electrode 112 is formed in a region of the surface of the protruding plate 120 facing the support members 101 and 102. A counter electrode 130 is arranged in the upper part of the figure, and the counter electrode 130 is grounded. A recording medium 108 is disposed on the surface of the counter electrode 130 facing the protrusion 122.

  In such a recording head 100, a part of the recording liquid 106 overflowing from the recording liquid outlet 104a wets along the projection plate 120 in the vicinity of the recording liquid outlet 104a, and is caused by the supply pressure, surface tension, and the like of the recording liquid 106. A meniscus 140 is formed on the surface of the protrusion 122. On the other hand, most of the recording liquid 106 overflowing from the recording liquid outlet 104a flows along the support members 101 and 102 and is collected in a recording liquid tank (not shown).

  When a positive bias voltage is applied to the first electrode 111 and the second electrode 112 with the recording liquid meniscus 140 formed on the surface of the protrusion 122 in this manner, the first electrode 111, the second electrode 112, and the counter electrode 130 are applied. An electric field is formed between the two. The color material particles 105 in the recording liquid 106 rising in the recording liquid supply path 104 by this electric field move toward the tip of the protrusion 122 and are aggregated in the vicinity of the tip of the protrusion 122. In this state, when a voltage is superimposed and applied to the first electrode 111 and the second electrode 112 with a predetermined pulse width, the electric field formed between the first electrode 111 and the second electrode 112 and the counter electrode 110 is strengthened, The color material particles 105 in the meniscus 140 are attracted to the counter electrode 130 side. As a result, the recording liquid 106 including the color material particles 105 can be ejected as droplets toward the counter electrode 130. In Patent Document 1, droplets of the recording liquid 106 are ejected in this way, and the color material particles 105 are adhered on the recording medium 108.

Also, in the inkjet head disclosed in Patent Document 2 below, ink is allowed to flow along the projection plate which is an ink guide member, and a meniscus is formed on the projection of the projection plate. This protruding plate is a molded alumina electrode base having a sharpened tip by polishing.
Further, in Patent Document 3 below, a guide that guides ink from the ink layer to the tip of the sharpened portion is caused to protrude from the surface of the ink layer that flows in a direction substantially perpendicular to the ink droplet ejection direction. An ink jet head is disclosed in which a groove is provided in an ink guide member and ink droplets are ejected from the tip of the ink guide member using electrostatic force. This ink guide member is formed by molding a plastic resin.
Further, in Patent Document 4 below, an ink guide member is not provided, and a substantially hemispherical meniscus is formed at the ink outlet by the pressure of the ink flowing out from the ink supply path and the surface tension of the ink. An ink jet head that discharges ink is disclosed.
JP-A-10-76664 JP-A-11-105293 JP-A-10-230608 JP-A-9-309208

  In such an inkjet head that ejects ink as a recording liquid by electrostatic force, in order to eject small ink droplets, a meniscus formed at the tip of an ink guide member that becomes an ink droplet ejection position is formed as finely as possible. There is a need. In order to discharge droplets having a stable size and shape, it is necessary to keep the meniscus shape as constant as possible. In addition, in order to eject ink droplets with a stable shape and size at a high ejection frequency, the ink reduced by ejecting the ink droplets is supplied to the ink droplet ejection position at a high speed, and the meniscus shape after ink ejection is quickly formed. It is necessary to restore the state before ink ejection. In addition, in order to stably discharge liquid with high density and high definition, it is necessary to form a sharp portion provided at the end of the ink guide member at the ink droplet discharge position with high density and high definition.

  However, in the ink jet heads described in Patent Document 1 and Patent Document 2 in which ink is made to flow along a protruding plate that is an ink guide member toward a sharp point and an ink meniscus is formed at the tip, the meniscus is caused by fluctuations in ink supply pressure. Fluctuates greatly. For this reason, there has been a problem that ink droplets cannot be ejected with a stable size and positional accuracy.

  In addition, in the method for producing a protruding plate, which is an ink guide member having a sharpened tip by polishing an alumina electrode base, disclosed in Patent Document 2, there is a limit to the accuracy of the sharp shape of the protruding plate, and the number of steps is large. There was a problem.

  Further, in the ink jet head disclosed in Patent Document 3 in which a meniscus is formed at the tip of the sharpened portion that becomes the ink droplet discharge position by the ink that has moved up the ink guide groove, the ink is raised to the sharpened portion by capillary action. For this reason, there is a problem that it takes time to supply ink and ink droplets having a stable size and color material component concentration cannot be continuously ejected at a high ejection frequency.

  In addition, the conventional method for producing an ink guide member by molding a plastic resin has a problem in that when the plastic resin is extracted from the mold, the plastic tears without being removed from the mold and cannot be formed into a desired shape. For this reason, it is difficult to produce a sharp ink guide member with high accuracy. Further, in this method, it is necessary to arrange a plurality of molded ink guide members on the substrate with high positional accuracy. However, there is a limit to increasing the arrangement positional accuracy of the ink guide members. There was a problem that the man-hours for the increase also increased.

  In addition, in the ink jet head disclosed in Patent Document 4 in which an ink guide member is not provided and a substantially hemispherical meniscus is formed at the ink outlet by the pressure of the ink flowing out from the ink outlet and the surface tension of the ink, In order to form a simple meniscus, it is necessary to make the ink outlet small. However, the size of the ink outlet cannot be reduced to a certain extent from the viewpoint of preventing ink clogging. In addition, the shape of the meniscus greatly fluctuates due to fluctuations in the pressure of the ink that flows out. For these reasons, there has been a problem that fine ink droplets cannot be stably ejected.

  The present invention has been made to solve the above-described problem, and is a liquid discharge head that discharges a solution as droplets by electrostatic force. The droplets have a smaller diameter and higher density than conventional ones. It is an object of the present invention to provide a liquid discharge head capable of stably discharging at a high frequency and a method of manufacturing the liquid discharge head capable of manufacturing the liquid discharge head with high accuracy and high productivity.

  In order to solve the above-described problem, the present invention provides a liquid discharge head that discharges a solution in which charged particles are dispersed toward a counter electrode, and is a first substrate that is disposed at a predetermined distance from the counter electrode. And a protrusion that is formed integrally with the first substrate and protrudes from the first substrate toward the counter electrode, and an upper surface that faces the counter electrode that is the protruding end of the protrusion. A guide for discharging the solution, wherein an inclined surface is provided so that the cross-section becomes narrower and sharpens as the tip portion protrudes from the upper surface toward the counter electrode and approaches the tip portion. A solution guide that guides the solution flowing as a solution flow to the tip portion and discharges it as droplets by electrostatic force, and a control electrode that acts on the electrostatic force, and a through hole for arranging the solution guide is perforated. The A second substrate, wherein the second substrate is in contact with and supported by a part of the upper surface of the projecting portion, and the solution guide has at least the tip portion of the second substrate. Through the through-hole, this tip protrudes toward the counter electrode rather than the surface of the second substrate facing the counter electrode, and at least the tip of the solution guide is made of a single crystal material, There is provided a liquid discharge head characterized in that the inclined surface is formed by anisotropic wet etching and the tip is sharpened.

  It is preferable that the tip of the solution guide has a slope formed by a higher-order crystal plane and is sharpened.

  The tip angle of the tip of the solution guide is preferably 60 ° or less.

  Moreover, it is preferable that the curvature radius of the said front-end | tip part of the said solution guide is 4 micrometers or less.

  In addition, a solution supply path having a solution supply port for supplying a solution in the vicinity of the solution guide so as to form the solution flow on the inclined surface of the solution guide is provided, and the solution supply path is formed from a base of the protrusion It is preferable that the protrusion is formed by a projecting portion through hole formed in a direction toward the upper surface.

  The protrusion through hole is connected to a first substrate through hole formed in the first substrate on which the protrusion is provided, and the surface of the first substrate on which the protrusion is provided. It is preferable that a solution inlet is opened on the surface opposite to the substrate, and the solution is supplied from the solution inlet through the first substrate through hole.

  And a solution recovery path having a solution recovery port for recovering the solution in the solution flow that has flowed through the inclined surface of the solution guide from the vicinity of the solution guide, and the solution recovery port is perforated in the second substrate. Preferably, the gap is formed between the inner wall of the through hole and the upper surface of the protrusion, and the solution recovery path is formed by the gap between the first substrate and the second substrate.

  The present invention also provides a first substrate, a protruding portion protruding from the first substrate, the protruding end forming an upper surface, and the solution leading to a sharp tip to discharge the droplet as a droplet by electrostatic force. A solution guide made of a single crystal material provided on the substrate and a through-hole provided so that the solution guide protrudes from the substrate surface, and is joined to the upper surface and supported and fixed to the protrusion. And a substrate having a protrusion formed on the plate-like substrate so that the protruding portion has an upper surface at the protruding end by processing the insulating substrate. A step of producing a first head member, a step of bonding the upper surface of the protruding portion and the single crystal substrate, and integrating the first head member and the single crystal substrate; and the single crystal substrate. By performing anisotropic wet etching of Forming a sharpened portion that forms the solution guide at a predetermined position on the upper surface of the shape-shaped portion, and a second head member that forms a second substrate having a through-hole drilled at a predetermined position. And a step of aligning one surface of the second head member with the upper surface of the protruding portion and fixing the second head member so as to pass through the through hole. A method for manufacturing a discharge head is provided.

  Further, the step of producing the sharpened portion is performed by performing anisotropic wet etching on the surface of the single crystal substrate on which the unevenness is previously formed by anisotropic dry etching on the surface on which the unevenness is formed, You may produce the sharp part which comprises the said solution guide in the predetermined position of the said upper surface of the said protruding part.

  In the liquid discharge head of the present invention, the tip is formed on the upper surface which is the surface facing the counter electrode of the protruding portion protruding from the first substrate toward the counter electrode by using anisotropic wet etching of a semiconductor microfabrication technique. A plurality of liquid ejection heads each having a highly sharp solution guide can be manufactured simultaneously with high positional accuracy and high shape accuracy. For this reason, it is possible to produce a liquid discharge head that can stably discharge droplets at a low discharge voltage at low cost.

  In addition, the second substrate provided with the control electrode is brought into contact with and joined to the upper surface of the protruding portion. Thereby, there is no positional deviation between the solution guide and the control electrode due to the warp of the second substrate, and there is no variation in droplet discharge voltage due to this positional deviation. Thereby, the solution can be stably discharged at a low discharge voltage from the stable meniscus on the surface of each of the plurality of solution guides.

  Further, by discharging the solution from the very vicinity of the solution guide, it is possible to quickly supply the solution containing charged particles to the tip of the solution guide, which is the droplet discharge position. In addition, the outflowing solution forms a solution flow that crosses a part of the slope of the sharp part, and part of it is guided to the tip of the solution guide member to form a meniscus, which affects the pressure fluctuation of the outflowing solution. The meniscus can be formed stably without being done. For this reason, minute droplets can be stably discharged at a high frequency from the sharp tip of the solution guide.

  Hereinafter, a liquid discharge head of the present invention and a method for manufacturing the liquid discharge head will be described based on embodiments shown in the accompanying drawings. FIG. 1 is a schematic configuration diagram of an ink discharge apparatus 1 having an ink discharge head 3 which is an embodiment of a liquid discharge head of the present invention. As shown in FIG. 1, the ink ejection device 1 includes an ink reflux unit 2, an ink ejection head (ink ejection unit) 3, and a power supply unit 6. 2A and 2B are schematic configuration views of the ink discharge head 3 as viewed from the upper side in FIG. 1, and FIG. 2A shows the ink discharge head 3 from the upper side in FIG. FIG. 2B is a schematic configuration diagram that excludes the counter electrode 40 (see FIG. 1), and FIG. 2B illustrates the counter electrode 40 and the second head member when the ink ejection head 3 is viewed from the upper side in FIG. The schematic block diagram except 32 (refer FIG. 1) is shown.

The ink reflux unit 2 includes an ink circulation device 20, an ink supply pipe 22, and an ink recovery pipe 24. The ink circulation device 20 includes an ink pump 26 and an ink tank 28.
In the ink circulation device 20, an ink pump 26 and an ink tank 28 are connected. The ink pump 26 is connected to the ink storage chamber 29 via the ink supply pipe 22. The ink storage chamber 29 is a substantially rectangular space for storing ink, and the upper wall surface in FIG. 1 of the ink storage chamber 29 is constituted by the substrate surface of the head substrate 34 of the ink ejection head 3.
The ink tank 28 is connected to the ink discharge head 3 via the ink recovery pipe 24.

  The ink ejection head 3 includes a first head member 30 (hereinafter, referred to as a head member 30), an upper lid 32 that is a second head member, a counter electrode 40, and an ink guide 52. In addition, a recording medium 42 that receives the discharged liquid and records a predetermined image or the like is placed on the counter electrode 40.

The head member 30 is configured such that a protruding portion 50 protrudes from a plate-like head substrate 34 as a first substrate toward the counter electrode. The head substrate 34 is an insulating substrate such as a glass substrate, for example. The head substrate 34 is formed at a predetermined position on the surface of the head substrate 34 opposite to the counter electrode 40 so as to be integrated with the head substrate 34. A substantially rectangular parallelepiped protruding portion 50 protruding toward the electrode 40 is provided. As shown in FIG. 2B, the protrusion 50 has a substantially rectangular parallelepiped shape continuous from the upper end of the head substrate 34 in FIG. 2B to the lower end of FIG. 2B. The head substrate 34 is formed so as to protrude from the substrate surface by a uniform height.
The upper surface 54, which is the surface of the protruding portion 50 on the counter electrode 40 side, is substantially parallel to the surface of the head substrate 34 facing the counter electrode 40, and the upper surfaces 54 of the plurality of protruding portions 50 provided on the head substrate 34. Are formed on substantially the same plane.

  The protruding portion 50 is formed with a protruding portion through hole 50a penetrating the protruding portion in the protruding direction (vertical direction in FIG. 1) of the protruding portion 50. The protruding portion through hole 50a is formed on the plate-like head substrate 34. An ink supply path 55 which is a solution supply path is connected to the penetrating head substrate through hole 34a. One end of the ink supply path 55 opens an ink outlet 56 on the upper surface 54. Further, the other end of the ink supply path 55 opens an ink inflow port 57 in the upper wall surface of the ink storage chamber 29 in FIG. Further, a part of the upper surface 54 of the protruding portion 50 is formed by anisotropic etching of a single crystal substrate such as Si that protrudes in the direction from the upper surface 54 toward the counter electrode 40, and has a highly sharp tip. An ink guide 52 is provided. The ink guide 52 will be described later.

On the upper side in FIG. 1 of the head member 30 (first head member 30), an upper lid 32, which is a second head member, is joined to the head member 30 and disposed.
The upper lid 32 is fixed in contact with the upper surface 54 of the protruding portion 50 protruding from the head substrate 34 and arranged substantially parallel to the head substrate 34. The substrate surface of the head substrate 34 and the upper lid 36 are spaced apart from each other at a constant interval, and the space surrounded by the substrate surface of the head substrate 34, the substrate surface of the upper lid 36, and the wall surface of the adjacent protrusion 50 is ink. A recovery path 58 is formed.
As shown in FIGS. 2A and 2B, the gap between the head substrate 34 and the upper lid 32 is the side wall 35 on the left side, the lower side, and the right side in FIGS. 2A and 2B. The upper gap in FIGS. 2A and 2B is connected to the solution recovery pipe 24.

The upper lid 32 includes a control substrate 43 that is a second substrate, a separation barrier 46, a guard electrode 47, and a shield electrode 48.
The control substrate 43 is formed of, for example, SiO ₂ on the entire surface including the discharge electrode 44 and the wiring 45 of the insulating substrate 31 made of, for example, glass, provided with a control electrode 44 and wiring 45 (not shown) described later. A control substrate through-hole having a circular cross-section passing through the control substrate 43 in the vertical direction in FIG. 1 is formed at a predetermined position corresponding to the protruding portion 50 of the control substrate 43. 43a is formed. Further, a guard electrode 47 is provided on the surface (first surface) of the control substrate 43 facing the counter electrode 40 so as to surround the control electrode 44 as viewed from above in FIG. A separation barrier 46 made of an insulating material having ink repellency is provided on the upper surface of the guard electrode 47 in FIG. A shield electrode 48 that is grounded as a whole is provided on the surface (second surface) of the control substrate 43 that faces the head substrate 34.

FIGS. 3A and 3B are views for explaining one of the plurality of ink guides 52 shown in FIGS. 1 and 2 and the periphery of the ink guide 52. FIG. 3A shows an ink guide 52 and a schematic sectional view showing the periphery of the ink guide 52 in an enlarged manner, and FIG. 3B shows the ink guide 52 and the periphery of the ink guide 52 in an enlarged manner. A schematic plan view is shown.
As shown in FIGS. 3A and 3B, the ink guide 52 is provided on the upper surface 54, which is a surface facing the counter electrode 40 of the substantially rectangular parallelepiped protrusion 50, and the counter electrode 40 extends from the upper surface 54. Projecting toward the tip, the tip is sharpened.

  3A, the protrusion 50 is provided on the surface of the head substrate 34 on the side of the counter electrode 40 so as to protrude toward the counter electrode 40. The protrusion 50 has a protrusion direction (upper and lower in FIG. 3A). The ink supply path 55 is formed by connecting the protrusion through hole 50a, which is a through hole penetrating the protrusion 50 in the direction), and the head substrate through hole 34a penetrating the head substrate. One end is provided with an ink outlet 56 on the upper surface 54 which is the surface of the protruding portion 50 on the counter electrode 40 side, and the other end is provided with an ink flow on the substrate surface of the head substrate 34 constituting the wall surface of the ink containing chamber 29. The inlet 57 is opened. The ink guide 52 is provided in the vicinity of the ink outlet 56 on the upper surface 54 of the protrusion 50.

  The ink guide 52 is formed of, for example, a single crystal material made of Si by anisotropic wet etching, and has a highly sharp cone structure with a tip angle of 60 ° or less and a tip radius of curvature of 4 μm or less. The entire surface of the object 72 including the tip end portion 75 is formed by coating a conductive film 74 made of, for example, metal. A method for forming the ink guide 52 will be described in detail later.

  3A and 3B, the ink guide 52 in which the conductive film 74 is formed on the surface of the cone structure 72 and the surface is formed with inclined surfaces having two different angles with respect to the upper surface 54, respectively. It is shown. FIGS. 3A and 3B show an outline of the outer shape of the ink guide 52 and do not faithfully reproduce the shape of the ink guide 52. The ink guide 52 can have various shapes depending on the above-described anisotropic wet etching conditions. In the present invention, the ink guide 52 is not particularly limited as long as the tip is sharpened with high precision by anisotropic wet etching of a single crystal material. As described above, the ink guide 52 in the present invention desirably has a tip angle of 60 ° or less and a radius of curvature of the tip of 4 μm or less.

The upper lid 32 is in contact with and joined to the upper surface 54 of the protruding portion 50 above the head substrate 34 in FIG. 3, and the gap between the head substrate 34 and the upper lid 32 forms an ink collection path 58. The control board 43 of the upper lid 32 is formed with a circular control board through hole 43a penetrating the control board 43 in the vertical direction in FIG. 1, and at least the tip 75 of the ink guide 52 is formed from the control board through hole 43a. A part including is protruding.
As shown in FIG. 3 (b), the upper lid 32 has the center of the control board through hole 36a substantially coincided with the tip of the ink guide 52 as viewed from above in FIG. In the region in the hole 36a, the solution outlet 56 and the upper surface 54 are adjusted and arranged at a position where a part of the edge 51 of the protruding portion 50, which is the left end in FIG. 3B, is arranged. The ink recovery path 58 is an ink recovery port 59 (FIG. 3A and FIG. 3A) that is an opening formed by the end of the inner wall of the control substrate through-hole 43a on the control substrate 43 side and the edge 51 of the protrusion 50. The ink outlet 56 and the ink supply path 55 are connected spatially through (b).

The control substrate 43 is configured in a ring shape with the tip 75 of the ink guide 52 as a center so that the control electrode 44 surrounds the periphery of the control substrate through hole 43a when viewed from the upper side in FIG. , Provided on the surface of an insulating substrate 31 made of ceramics such as Al ₂ O ₃ or ZrO ₂ or resin such as polyimide. The inner diameter Da of the ejection electrode 44 and the distance from the ejection electrode 44 to the most distal portion of the ink guide 50 protruding to the recording medium 42 side, that is, the distance H from the surface of the ejection electrode 44 to the most distal portion of the ink guide 50 The ratio (Da: H) is preferably in the range of 1: 0.5 to 1: 2, more preferably 1: 0.7 to 1: 1.7 (see FIG. 1). . Note that the inner diameter Da of the ejection electrode 44 and the distance from the ejection electrode 44 to the most advanced portion of the ink guide 50 protruding toward the recording medium 42 are described in detail in Japanese Patent Application No. 2003-20585 filed by the present applicant. Has been described.

  Each of these discharge electrodes 44 is connected to an electrode pad (not shown) through a metal wiring 45 formed on the surface of the insulating substrate 31. An electrode pad (not shown) is connected to the ejection bias voltage source 64 and the ejection signal voltage source 66 of the voltage source unit 6.

The discharge bias voltage source 64 of the voltage source unit 6 always applies the bias voltage _Vb to the control electrode 44 of the control substrate 43, and the discharge signal voltage source 66 is controlled by a signal input from a signal output means (not shown). 44, has a configuration which is superimposed a discharge voltage V _c is a pulse voltage to the bias voltage V _b is applied.

In the ink ejection apparatus 1 having such a configuration, the following ink flow is formed.
In the ink reflux unit 2, a predetermined amount of ink 12 is placed in the ink tank 28. The ink 12 is a solution in which positively charged charging particles are dispersed in an insulating solvent having a resistivity of 10 ⁸ Ωcm or more together with a charge control agent and a binder. In the ink tank 28, the concentration of charging particles, the charge control agent, the binder, and the like in the insulating solvent of the ink 12 is constantly adjusted by a concentration adjusting mechanism (not shown) so as to fall within a predetermined concentration range. The ink 12 whose density is adjusted in the ink tank 28 by a density adjusting mechanism (not shown) is supplied from the ink pump 26 to the ink storage chamber 29 of the ink discharge head 3 through the ink supply pipe 22 at a predetermined pressure. The ink storage chamber 29 is filled with the ink 12, passes through the individual ink inlets 57, and is supplied from the ink supply path 55 to the individual protrusions 50 (see FIG. 1).

  In the vicinity of the protrusion 50, the ink 12 supplied to the ink storage chamber 29 by the action of the ink pump 26 flows through the ink supply path 55 from the bottom to the top in FIG. 3A and flows out from the ink outlet 56. doing. At this time, the ink 12 flowing out from the ink outlet 56 crosses the surface of the ink guide 52 provided on the upper surface 54 of the protrusion 50 (flow in the direction of arrow X in FIGS. 3A and 3B). The supply pressure of the ink 12 by the ink pump 26 is adjusted so that an ink flow 14 that passes through the ink recovery port 59 and flows into the ink recovery path 58 is formed.

  When a part of the ink 12 crosses the surface of the ink guide 52, the ink 12 is guided to the tip 75 of the ink guide 52 by the action of the surface tension of the ink 12. The ink 12 guided to the leading end portion 75 forms a meniscus 16 that covers at least the leading end portion 75 of the ink guide 72 as indicated by a dotted line in FIG. At this time, the meniscus 16 is mainly formed by the surface tension of the ink 12, and is formed in a stable shape hardly affected by a minute fluctuation in the supply pressure of the ink 12 caused by the pulsation of the ink pump 26 or the like. ing. Further, the meniscus 16 formed on the surface of the adjacent ink guide 52 is separated by the separation barrier 46 of the upper lid 32 without being connected. In the ink ejection apparatus 1, the meniscus 16 is formed by supplying the ink 12 containing the chargeable particles having a constant concentration to the tip end portions 75 of the individual ink guides 52 as described above.

  As described above, a part of the ink 12 supplied to the individual ink guides 52 forms the meniscus 16, and most of the other ink 12 flows into the ink recovery path 58 through the ink recovery port 59 and is recovered. It flows in the path 58 in a direction parallel to the head substrate 34 and the control substrate 36 (in the direction indicated by the arrow Y in FIG. 2B), and is recovered to the ink tank 28 through the ink recovery pipe 24. The concentration of the ink 12 collected in the ink tank 28 is adjusted again, and is sent out again from the ink pump 26 into the ink storage chamber 29 through the ink supply pipe 22 at a predetermined pressure. The ink discharge apparatus 1 according to the present invention is configured such that the ink reflux unit 2 always supplies the ink 12 containing the charged particles having a constant concentration to the ink discharge head 3 as described above.

  Next, a liquid discharge operation in the ink discharge apparatus 1 will be described. FIG. 4 is a diagram for explaining the liquid ejection operation of the ink ejection head 3 of the present embodiment, and is a schematic cross-sectional view showing one of the plurality of ink guides 52 shown in FIG. As described above, the ink 12 containing the chargeable particles having a constant concentration circulates in the ink ejection head 3, and the meniscus 16 covering at least the tip 75 is formed on the surface of the ink guide 52. In this state, when a bias voltage Vb of, for example, 900 V is applied from the bias power supply 62 of the power supply unit 6, an electric field is formed between the control electrode 44 and the counter electrode 40 by the bias voltage Vb. A drive voltage Vc, which is a pulse voltage of, for example, 250 V, is applied from the drive power supply 64 of the power supply unit 6 to the drive electrode 44 formed around the desired ink guide 52 by a signal input from a signal output means (not shown). A total voltage of 1150 V is applied by superimposing. Then, the electric field formed between the drive electrode 44 and the counter electrode 40 is strengthened, and by this strengthened electric field, the ink droplet 18 is ejected from the meniscus 16 toward the counter electrode 40 by electrostatic force, and the recording medium 42. Adhere to.

  At this time, an electric field from the drive electrode 44 downward in FIG. 3 is also formed. However, a shield electrode 48 facing the drive electrode 44 and grounded is provided in the lower direction of the drive electrode 44 in FIG. 4, and an electric field directed downward in FIG. 4 is concentrated toward the shield electrode 48. Shielded. As a result, the electric field directed downward from the drive electrode 44 in FIG. 4 is prevented from spreading in the left-right direction in FIG. Therefore, an electric field directed downward in FIG. 4 is not formed in the ink supply path 55, and no electrostatic force acts on the ink 12 moving in the upward direction in FIG. In this manner, the ink 12 in the ink supply path 55 is not affected by the electric field formed by applying a voltage to the drive electrode 44, and is constant in the ink supply path 55 from the lower side to the upper side in FIG. It flows with the concentration of charged particles.

  When the control voltage Vc is applied and the ink droplet 18 is ejected, immediately after that, the voltage of the control electrode 44 is returned to the bias state. Further, immediately after the ejection, the ink shortage in the meniscus 16 is supplied from the ink flow 14 flowing in the vicinity of the tip 75, and the shape of the meniscus 16 is quickly recovered.

  A conductive film 74 is formed on the ink guide 52 of the ink ejection head 3 of the present embodiment. The conductive film 74 makes the leading end portion 75 of the ink guide 52 conductive, so that the electric field around the leading end portion 75 can be strengthened. In the present invention, the conductive film 74 is not necessarily formed as long as a predetermined electric field strength can be obtained.

Further, although the separation barrier 46 is provided around the control electrode 44 of the ink ejection head 3 of the present embodiment, it is not always necessary in the present invention. However, the meniscus 16 formed in the adjacent ink guide 52 is separated, and is formed in each ink guide 52 without being affected by the fluctuation of the meniscus 16 when the ink droplet 18 is ejected from the adjacent ink guide 52. Further, it is preferable to provide a separation barrier 46 in order to stably maintain the individual meniscus 16.
Further, at least the surface of the separation barrier 46 has ink repellency in order to prevent the ink from creeping up to the wall surface of the separation barrier 46 and to more reliably separate the meniscus 16 formed in the adjacent ink guide 52. Is preferred. The ink repellency means water repellency when the ink is water-based and hydrophilic when the ink is oil-based.

  Further, the surface of the control board of the present embodiment on the side opposite to the side facing the counter electrode 40 is formed by the shield electrode 48 so as to face the drive electrode 44, but this shield electrode 48 is not necessarily required. . However, the shielding electrode 48 shields the electric field directed downward from the drive electrode 44 in FIG. 3, thereby suppressing the spread of the electric field directed downward in FIG. 3 in the horizontal direction in FIG. 3. Thereby, it is possible to prevent the electric field opposite to the moving direction of the ink 12 in the ink supply path 55 from being formed in the ink supply path 55, and the ink 12 containing charged particles having a stable concentration can be removed from the ink outlet. 56 can flow out. Thus, it is preferable to provide the shield electrode 48 in terms of stabilizing the concentration of the charged particles in the meniscus 16 and stabilizing the size and shape of the ejected ink droplets 18.

  As described above, according to the ink discharge apparatus 1 having the ink discharge head 3 of the present embodiment, the highly accurate sharpened ink guide 52 manufactured by anisotropic wet etching of a single crystal substrate is provided. The meniscus 16 covering the front end portion 75 can be formed in a stable shape without being affected by fluctuations in the supply pressure of the ink 12 due to the pulsation of the ink pump 26 or the like. Further, since the ink 12 is supplied to the meniscus 16 from the ink flow 14 that flows in the vicinity of the tip 75 where the meniscus 16 is formed, the meniscus 16 after the ink droplets 18 are ejected can be quickly recovered. With these effects, it is possible to eject minute ink droplets 18 having a stable size and shape at a high frequency.

  The liquid ejection head produced in the present invention is not limited to ejection of ink containing colorant particles, but may be any head that ejects a solution containing chargeable particles dispersed in a solvent, and the type of the solution is not limited. .

Such an ink discharge head 3 can be manufactured as follows.
FIGS. 5A to 5E and FIGS. 6A to 6E are schematic cross-sectional views illustrating a method for producing the ink ejection head of the present invention.

  First, a glass substrate 67 made of quartz glass that has been polished on both sides, which is an insulating substrate, is prepared, and one surface (the upper surface in FIG. 5A) of the glass substrate 67 is predetermined using photolithography. The metal pattern 68 having the shape is formed. The shape of the metal pattern 68 viewed from the upper side in FIG. 5 is the same shape as the shape of the upper surface 54 of the protrusion 50 viewed from the upper side in FIG. An opening 71 corresponding to the solution supply port 56 is formed at each predetermined position of the rectangular pattern 69. Here, a quartz glass substrate is used as the insulating substrate, but a glass substrate such as borosilicate glass can also be used.

Next, as shown in FIG. 5A, the surface of the glass substrate 67 facing the metal pattern 68 (the lower surface in FIG. 5) is made of, for example, Cr or Ni using photolithography. A metal pattern 76 having a predetermined shape is formed. The metal pattern 76 is provided with a metal layer on the entire surface of the glass substrate 67 facing the metal pattern 68, and the metal layer 68 has an opening 57 of the metal pattern 68 as viewed from the lower side in FIG. And an opening 77 corresponding to the solution inflow port 57 is provided.
The metal pattern is not limited to Cr or Ni, and any metal pattern that is resistant to dry etching with CF ₄ gas may be used.

  Next, as shown in FIG. 5B, using the metal pattern 68 as an etching mask, the glass substrate 67 is dry-etched to a predetermined depth from the upper surface in FIG. It is formed. Thereby, the glass substrate 67 is processed into a shape in which a protruding portion 80 having a cross-sectional shape that conforms to the metal pattern 68 protrudes from the surface of the plate-like substrate portion 70. By this dry etching, the projecting portion 80 is formed with a projecting portion through-hole 80 a having a cross-section conforming to the opening 71.

  Next, as shown in FIG. 5C, the glass substrate 67 is dry-etched from the lower surface of the glass substrate 67 in FIG. 5 using the metal pattern 76 as an etching mask. As a result, a substrate portion through hole 70a having a cross section conforming to the opening 77 is formed, and the substrate portion through hole 70a and the projecting portion through hole 80a are connected to each other, and the glass substrate penetrates in the vertical direction of the glass substrate 67. A through hole 67a is formed. Next, the metal patterns 68 and 76 are removed by etching (see FIG. 5D). Accordingly, a substantially rectangular parallelepiped projecting portion 80 corresponding to the projecting portion 50 projects from a predetermined position of the substrate portion 70 corresponding to the head substrate 34, and the substrate portion 70 and the projecting portion 80 are moved upward and downward in FIG. The first head member 30 including the glass substrate through hole 67a corresponding to the ink supply path 55 that communicates in the direction is produced.

  Next, as shown in FIG. 5E, a single crystal Si substrate 78 having a (100) crystal plane polished on the upper surface 81 which is the upper surface in FIG. Are bonded by a surface activated bonding method. The bonding between the substrates is not limited to the surface activation bonding method, and may be performed using a KOH etchant that is durable solder or an adhesive. Further, when the glass substrate 67 is not a quartz glass substrate but a glass substrate containing alkali ions such as borosilicate glass, the substrates can be bonded to each other using an anodic bonding method.

Next, as shown in FIG. 6A, a SiO ₂ film is formed on the surface of the single crystal Si substrate 78 by, eg, thermal oxidation or CVD, and the single crystal Si substrate 78 is formed by photolithography and etching. 110> and <1-10> crystal orientations as sides, and a square SiO ₂ pattern 82 of a predetermined size is formed at a position corresponding to the protruding portion 80 of the first head member 30.

Next, using this SiO ₂ pattern 82 as an etching mask, SF ₆ dry etching of the single crystal Si substrate 78 is performed, and a predetermined amount of Si is etched, so that a square pillar made of Si is formed as shown in FIG. A plurality of structures 84 are formed.

Next, the SiO ₂ pattern 82 is removed by performing CF ₄ dry etching (FIG. 6C). Thereafter, the whole is immersed in a solution of 34 wt% KOH aqueous solution heated to about 70 ° C., and anisotropic etching of Si is performed. In this etching, in particular, the etching rate from each edge and each apex portion of the quadrangular prism structure 84 is high, and the etching proceeds while using a higher-order crystal plane as an etching surface. By this etching, a pyramidal structure 86 made of Si having a sharp tip with a tip angle of about 60 ° or less and a radius of curvature of 4 μm or less formed of a slope made of a high-order crystal plane is a substrate of the columnar portion 80. Produced on the upper surface 81. As shown in FIG. 6D, a conductive film 87 is formed on the surface of the cone structure 86 using a sputtering method or the like, and protrudes from the surface of the head substrate 34 (substrate part 70) of the head member 30. A sharp member 88 corresponding to the ink guide 52 is formed on the upper surface 54 (substrate upper surface 81) of the protruding portion 50 (projecting portion 80).

  Next, as shown in FIG. 6 (e), on the upper surface 54 of the projecting portion 80, a separately prepared through-hole drilled at a predetermined position and the above-described hole formed so as to surround the through-hole are formed. The second head member 32 provided with the metal pattern that forms the control electrode is brought into contact with and bonded together by, for example, an adhesive, and the first head member 30 and the second head member 32 are joined. Thereafter, the ink discharge head 3 is formed by arranging and joining the above-described side wall 35 to the first head member 30 and the second head member 32 (FIGS. 1 and 2A, (2)). b)).

The inkjet head 3 according to the present invention can be manufactured as follows in the etching process of the Si single crystal substrate 78 in the first embodiment (processes shown in FIGS. 6B to 6D). is there. FIG. 7 is a schematic cross-sectional view for explaining the etching process of the Si single crystal substrate 78 in the second embodiment of the method for producing the ink ejection head 3 of the present invention.
In the second embodiment, a square SiO ₂ pattern 82 having a predetermined size with the <110> and <1-10> crystal orientations of the single crystal Si substrate 78 shown in FIG. 6A as sides. After the substrate is formed, the substrate is immersed in a solution obtained by heating a 34 wt% KOH aqueous solution to 70 ° C. using the SiO ₂ pattern 82 as an etching mask, and anisotropic etching of Si is performed. In this etching step, the single crystal Si substrate 78 is etched using the square SiO ₂ pattern 82 as an etching mask. In this etching, SiO ₂ pattern 82 undercut the corners of the square progresses, SiO ₂ pattern 82 etching is performed until detached from the surface of the single-crystal Si substrate 78. As a result, as shown in FIG. 7, a pyramid structure 86 made of Si having a sharp tip with a tip angle of about 60 ° or less and a radius of curvature of 4 μm or less formed by a slope made of a higher-order crystal plane. Is formed on the substrate upper surface 81 of the columnar section 80.
Thereafter, as in the first embodiment, the process shown in FIG. 6E is performed to manufacture the ink ejection head 3.

In the first embodiment described above, SiO ₂ is used as an etching mask for forming a Si square column structure by SF 6 reactive gas. However, a metal resistant to a fluorine-based gas such as Cr or Al is used as a mask. May be.

Further, in the first embodiment described above, the Si square pillar structure is formed by dry etching with SF ₆ reactive gas. However, the same pillar structure is obtained by directly using Si for fine processing such as sand blasting or ultrasonic processing. May be produced.

  In the first and second embodiments described above, a sharp ink guide was produced by anisotropically etching a Si single crystal substrate. In the present invention, the material of the single crystal substrate is not necessarily Si as long as a sharp ink guide can be produced by anisotropic etching. In the method for producing an ink discharge head of the present invention, if a sharp ink guide can be produced by anisotropic etching, the ink guide may be produced from, for example, a compound semiconductor single crystal substrate.

  In the first embodiment and the second embodiment described above, an ink guide having a sharp tip with a higher-order crystal plane as an inclined surface is produced by anisotropic etching. In the present invention, the ink guide does not necessarily have a high-order crystal plane as an inclined surface, and may be formed of, for example, a (111) plane.

  In the first embodiment and the second embodiment described above, the tip angle of the ink guide is set to 60 ° or less, and the radius of curvature of the tip is set to 4 μm or less. In the present invention, if the droplet is stably ejected from the tip of the ink guide at a desired ejection voltage, the tip of the ink guide does not have to be formed so sharply as this. However, in order to discharge ink more stably at a lower discharge voltage, it is preferable that the tip of the ink guide has a tip angle of 60 ° or less and a radius of curvature of the tip of 4 μm or less.

  As described above, the ink ejection head which is an embodiment of the liquid ejection head of the present invention has been described in detail. However, the present invention is not limited to the above embodiment, and various improvements and modifications can be made without departing from the gist of the present invention. Of course, you may do it.

1 is a schematic configuration diagram of an ink discharge apparatus 1 including an ink discharge head 3 that is an embodiment of a liquid discharge head of the present invention. (A) And (b) is the schematic block diagram which looked at the ink discharge head 3 from the direction different from FIG. (A) And (b) is a figure explaining one ink guide of the some ink guide 52 shown in FIG. 1 and FIG. 2, and the periphery of this ink guide. FIG. 6 is a diagram illustrating a liquid discharge operation of the ink discharge head 3 of the present embodiment. (A)-(e) is a figure explaining the manufacturing method of the ink discharge head of this invention. (A)-(e) is a figure explaining the manufacturing method of the ink discharge head of this invention, and is a figure which shows the process after the process shown by FIG.5 (e). It is a figure explaining the etching process of the Si single crystal substrate in 2nd Embodiment of the ink discharge head of this invention. It is a schematic block diagram of an example of the inkjet head of the conventional inkjet recording device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Ink discharge apparatus 2 Ink recirculation unit 3 Ink discharge head 6 Voltage source unit 14 Ink flow 16, 140 Meniscus 20 Ink circulation device 22 Ink supply pipe 24 Ink recovery pipe 26 Ink pump 28 Ink tank 29 Ink storage chamber 30 Head member 32 Top cover 34 Head substrate 35 Side wall 40, 110 Counter electrode 43 Control substrate 50 Projection part 52 Ink guide 54 Upper surface 55 Ink supply path 56 Ink outlet 57 Ink inlet 58 Ink recovery path 59 Ink recovery port 64 Ejection bias power supply 66 Ejection signal voltage source 67 Quartz glass substrate 75 Tip 76 Metal pattern

Claims (11)

A liquid discharge head for discharging a solution in which charged particles are dispersed toward a counter electrode,
A first substrate disposed at a predetermined distance from the counter electrode; a protrusion formed integrally with the first substrate and protruding from the first substrate toward the counter electrode; and A guide for discharging a solution, formed on the upper surface facing the counter electrode, which is the projecting end of the projecting portion, protrudes from the upper surface toward the counter electrode and becomes narrower as it approaches the tip. An inclined surface is provided so that the tip portion is sharpened, a solution guide that guides the solution flowing as a solution flow through the inclined surface to the tip portion and discharges it as a droplet by electrostatic force, and a control that acts on the electrostatic force A second substrate comprising an electrode and having a through hole for arranging the solution guide,
The second substrate is supported in contact with and joined to a part of the upper surface of the protrusion, and the solution guide has at least the tip passing through the through-hole, and the tip is the first. 2 projecting to the counter electrode side than the surface of the substrate facing the counter electrode, at least the tip of the solution guide is made of a single crystal material, and the inclined surface is formed by anisotropic wet etching. The liquid discharge head is characterized in that the tip is sharpened.   A plurality of the through holes are perforated in the second substrate, and a plurality of the solution guide portions are arranged so that the tip portions protrude through the through holes to the side of the counter electrode. The liquid discharge head according to claim 1, wherein the liquid discharge head is a liquid discharge head.   The liquid discharge head according to claim 1, wherein the tip portion of the solution guide has an inclined surface formed of a higher-order crystal plane and is sharpened.   The liquid discharge head according to claim 1, wherein a tip angle of the tip of the solution guide is 60 ° or less.   5. The liquid discharge head according to claim 1, wherein a radius of curvature of the tip portion of the solution guide is 4 μm or less.   A solution supply path having a solution supply port for supplying a solution in the vicinity of the solution guide so as to form the solution flow on the inclined surface of the solution guide, the solution supply path from the base portion of the projecting portion to the upper surface; The liquid discharge head according to claim 1, wherein the liquid discharge head is formed by a protruding portion through-hole formed in a direction toward the head.   The protrusion through hole is connected to a first substrate through hole formed in the first substrate on which the protrusion is provided, and is opposite to the surface of the first substrate on which the protrusion is provided. The liquid discharge head according to claim 6, wherein a solution inlet is opened on a side surface, and the solution is supplied from the solution inlet through the first substrate through hole.   A solution recovery path having a solution recovery port for recovering a solution of the solution flow that has flowed through the inclined surface of the solution guide from the vicinity of the solution guide; and the solution recovery port is perforated in the second substrate 2. The method according to claim 1, wherein the solution recovery path is formed by a gap between the inner wall of the through hole and the upper surface of the protruding portion, and the solution recovery path is formed by a gap between the first substrate and the second substrate. The liquid discharge head according to any one of 1 to 7. A single crystal provided on the upper surface, which protrudes from the first substrate, protrudes from the first substrate, and has a protruding end as an upper surface, and guides the solution to a sharp tip and discharges it as a droplet by electrostatic force. A liquid comprising: a solution guide made of a material; and a second substrate having a through hole provided so that the solution guide protrudes from the substrate surface, and is bonded to the upper surface and supported and fixed to the protrusion. A method for producing a discharge head, comprising:
Processing the insulating substrate to produce a first head member formed on the plate-like substrate so that the protruding portion forming the protruding portion has an upper surface at the protruding end;
Bonding the upper surface of the protrusion and the single crystal substrate, and integrating the first head member and the single crystal substrate;
Producing a sharpened portion that forms the solution guide at a predetermined position on the upper surface of the projecting portion by performing anisotropic wet etching of the single crystal substrate; and
A second head member forming a second substrate having a through-hole drilled at a predetermined position is aligned at a predetermined position so that the sharpened portion penetrates the through-hole, and the second head member And a step of joining and fixing one surface of the protrusion to the upper surface of the protruding portion.   The step of producing the sharpened portion is performed by performing anisotropic wet etching on the surface of the single crystal substrate having unevenness formed on the surface by anisotropic dry etching in advance. 10. The method of manufacturing a liquid discharge head according to claim 9, wherein a sharpened portion that forms the solution guide is formed at a predetermined position on the upper surface of the shape-shaped portion. In the step of producing the sharpened portion, a plurality of sharpened portions forming the solution guide by anisotropic wet etching of the single crystal substrate are produced,
In the fixing step, the second head member forming the second substrate having a plurality of through holes drilled at a predetermined position is aligned with the predetermined position so that each of the sharpened portions penetrates the through hole. The method of manufacturing a liquid ejection head according to claim 9, wherein one surface of the second head member is bonded and fixed to the upper surface of the protrusion.

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