Electrostatic ink-jet recording head

Abstract: The electrostatic ink-jet recording head according to the present invention comprises: recording electrodes (31) which eject ink (50) towards the recording paper (8); an opposing electrode (40) for generating a prescribed electric field between the recording electrodes (31) and the opposing electrode (40); and ink discharge end sections (22a) formed in the vicinity of the recording electrodes (31). The ink discharge end sections (22a) are formed closer to the opposing electrode (40) than the end portions of the recording electrodes (31). In this case, the equipotential lines in the region of the ink discharge end sections when a recording voltage is applied are virtually perpendicular to the direction in which the ink is discharged. This is because, the recording electrodes are positioned slightly behind the ink discharge end sections in the ink discharge member. In this case, an electrostatic force acts on the toner particles near the ink discharge end sections in the direction of the ink discharge end sections. Therefore, even when a recording voltage is applied, there is a continuous supply of toner particles to the ink discharge end sections. As described above, in the electrostatic ink-jet recording head according to the present embodiment, a convex ink meniscus is formed in front of the recording electrodes. Therefore, toner particles gather at the discharge points, even when a recording voltage is applied, and thus a sufficient quantity of toner particles for forming a desired dot size can be supplied.

Description: 1. Field of the Invention The present invention relates to a printer which performs a recording operation by applying toner to a recording medium, such as printing paper, and more particularly, to an electrostatic ink-jet recording head used in an electrostatic ink-jet printer. 2. Description of the Related Art Conventionally, printer recording technology based on non-impact systems has the advantage that the generation of noise during recording etc. is so small as to be negligible. Ink-jet recording systems, in particular, allow printing and recording at high speed directly onto a recording medium, using a simple construction. Furthermore, they also allow recording onto normal paper, and therefore represent extremely advantageous recording systems. For example, Figs. 4 - 7 illustrate a conventional example of a recording head proposed as an ink-jet recording system. This conventional example uses an ink containing toner particles dispersed in a carrier liquid for printing onto recording paper 8. In addition to needle-shaped recording electrodes 3 provided on the recording head side, an opposing electrode 7 is also provided at the rear side of the recording paper in a position opposing the recording electrodes 3. In this system, an electric field is generated by applying a voltage to the recording electrodes 3 and the opposing electrode 7, and the toner particles in the ink are ejected towards the recording paper 8 by means of the electrostatic force created by the electric field. As shown in Fig. 4, the ink-jet recording head comprises a substrate 1 made from an insulating material of plastic, or the like, and a base film 2 covering this substrate 1. The base film 2 is made from an insulating material, such as polyimide, and has a thickness of approximately 50 µm. A plurality of recording electrodes 3 are patterned on the surface of this base film 2. The recording electrodes 3 are formed by plating a conductive material of copper (Cu), or the like, onto the surface of the base film 2 to a thickness of 20 - 30 µm, and then patterning such that the interval between adjacent electrodes is 300 dpi pitch, namely, about 85 µm. The end portion of each recording electrode 3 projects externally (towards the opposing electrode) from one edge of the base film 2 by about 80 - 500 µm. The surface of the recording electrodes 3 is covered uniformly by a film of insulating coating material 4 to a thickness of 10 µm or less, as shown in Fig. 5 and Fig. 6, which are enlargements of the portion indicated by arrow A in Fig. 4. Furthermore, in the ink-jet recording head, a portion of the upper surface of the base film 2 is covered by a cover 5. The cover 5 is formed from an insulating material and is shaped such that it does not interfere with the projecting end portions of the recording electrodes 3. An ink supply inlet 5a and an ink drain outlet (not illustrated) are provided, respectively. The space enclosed by the base film 2 and the cover 5 forms an ink chamber, and ink is introduced via the ink supply inlet 5a such that the ink 6 is always in a full state inside the chamber. A slit-shaped ink spray outlet 5b is formed at the edge of the cover 5, between the cover 5 and the base film 2. The aforementioned end portions of the recording electrodes 3 project through this ink spray outlet 5b. Thereby, an ink meniscus indicated by symbol 6a is formed at this slit-shaped ink spray outlet 5b. A constant back-pressure is applied to the ink 6 in the ink chamber. Therefore, due to the surface tension and capillary action of the ink itself, the ink 6 forms an ink meniscus 6b having a concave shape at the ink spray outlet 5b. Since the end portions of the recording electrodes 3 project from the base film 2 and the cover 5, when viewed from above as in Fig. 5, the ink meniscus 6a forms a U-shape between adjacent recording electrodes 3. Furthermore, as shown in Fig. 6, when viewed from the side, the ink meniscus 6a has a downward concave shape. Therefore, when a high-voltage pulse is supplied to one of the recording electrodes, the electric field concentrates on the end region of the ink meniscus 6a at the projecting end portion of that electrode. Induced by this electric field, the charged toner in the ink is expelled from the end region of the ink meniscus 6a. This forms an ink drop 6b, as shown in Fig. 5, which is ejected towards the recording paper 8 on the side of the opposing electrode 7 positioned opposite the recording head, and is thereby printed onto the recording paper 8. Fig. 7 shows an approximate diagram of equipotential lines showing the potential generated between the recording electrodes 3 and the opposing electrode 40 during recording in a conventional ink-jet recording head. When a voltage is supplied to a recording electrode 3, the equipotential lines in the vicinity of the projecting point 3a at the end of that recording electrode 3 assume a semi-elliptical shape surrounding the recording electrode 3, whose end portion is projecting from the ink spray outlet 5b. Furthermore, in PCT international publication (International Publication Number WO 93/11866), an invention is disclosed wherein conductive members projects towards an opposing electrode, and prescribed particles are caused to fly out from the ends of the conductive members by an electric field generated between these conductive members and the opposing electrode. However, in the conventional ink-jet recording heads described above, there have the following kinds of problems. A first problem is that it is difficult to form the ink into a desired dot size when recording onto recording paper. This is because a high-voltage pulse is supplied to the recording electrode 3 as a recording voltage, and the end portion of the recording electrode 3 itself forms a discharge point 3a for the ink 6. In this process, there is insufficient electrostatic force acting on the toner particles near the discharge point 3a in the direction of the discharge point 3a. In other words, as shown in Fig. 7, in the region surrounding the recording electrode 3, the equipotential lines 9 are virtually parallel to the direction of ink discharge, with the exception of the region in front of the discharge point 3a (opposing electrode side). Therefore, insufficient electrostatic force is generated in the direction of the discharge point 3a with respect to toner particles in the vicinity of the discharge point 3a. Since the electrostatic force acting on the toner particles is weak, the amount of toner particles supplied to the discharge point 3a is insufficient for forming the desired dot size. A second problem is that the discharge of ink droplets becomes unstable. This is because the ink meniscus 6a connects continuously across the recording electrodes 3, having vertices at the discharge points 3a, and therefore, the liquid surface in the vicinity of à discharge point 3a which has discharged ink will vibrate and effect the ink meniscus 6a, thus making it impossible to obtain an ink meniscus 6a that is stable at all times. A third problem is the occurrence of ink droplet discharge faults due to excessive concentration of toner particles in the ink spray outlet 5b. The reason for this is that the ink spray outlet 5b in the cover which supplies ink 6 to the discharge points 3a for discharge, is formed in a portion of the ink chamber in the shape of slit of size which prevents overflowing of ink. Consequently, no flow of ink 6 is produced at the ink spray outlet 5b, and there is an excessive concentration of toner particles in this region, causing the ink viscosity to rise above the required level. EP 0 764 529 A2 (NEC) discloses a recording head in which (as illustrated in Fig. 5 of the reference) the cover member 4 has a series of convex tip end portions 12 with relative spacing corresponding to that of the recording electrodes 2. This document has been used for the delineation in the two-part form of claims 1 and 5. SUMMARY OF THE INVENTION It is an object of at least the preferred embodiments of the present invention to provide an electrostatic ink-jet recording head, whereby ink droplets can be formed to a desired dot size by supplying an appropriate quantity of toner particles, preventing excessive concentration of these toner particles in the ink discharge section, and stabilizing ink discharge. In one aspect, the invention is an electrostatic ink-jet recording head that includes: (a) printing electrodes for ejecting ink towards recording paper (8); (b) an opposing electrode for generating a prescribed electric field between the printing electrodes and the opposing electrode; (c) ink-discharge end sections, each formed in the vicinity of a respective printing electrode; and, (d) partition end sections, each formed between a respective adjacent pair of the ink-discharge end sections. Each ink-discharge end section is positioned closer to the opposing electrode than is any portion of the respective printing electrode. The width of the printing electrodes in the electrostatic ink-jet recording head may be greater than that of the ink-discharge end sections. The surface of the printing electrodes may be covered with a film of insulating coating material. The ink-discharge end sections may be formed from an insulating coating material having a dielectric constant of 10 or less. In another aspect, the invention is an electrostatic ink-jet recording head that includes: (a) a head block within which are formed an ink supply chamber for supplying ink from an external source and an ink drain chamber for draining ink externally; (b) ink-discharge end sections formed in a path from the ink supply chamber to the ink drain chamber; (c) ink recycling grooves formed from the ink supply chamber to the ink-discharge end sections and from the ink-discharge end sections to the ink drain chamber; (d) printing electrodes for ejecting ink, each printing electrode being positioned in the vicinity of a respective ink-discharge end section; (e) an opposing electrode for creating an electric field between the printing electrodes and the opposing electrode; and, (f) partition end sections, each formed between a respective adjacent pair of the ink-discharge end sections. Each ink-discharge end section is positioned closer to the opposing electrode than is any portion of the respective printing electrode. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 shows oblique views of an electrostatic ink-jet recording head of the present invention; Fig. 1(A) shows a general oblique view and Fig. 1(B) shows an enlarged partial oblique view; Fig. 2 shows sectional views of the electrostatic ink-jet recording head illustrated in Fig. 1: Fig. 2(A) is a sectional view showing the vicinity of an ink discharge end section; Fig. 2(B) is a sectional view showing the whole recording head; Fig. 3 shows a plan view of an electrostatic ink-jet recording head according to the present invention, and more particularly, a plan view of an electrostatic ink-jet recording head giving a schematic illustration of equipotential lines generated in the vicinity of the ink discharge end sections; Fig. 4 is an oblique view showing a conventional electrostatic ink-jet recording head; Fig. 5 is a plan view of an electrostatic ink-jet recording head; Fig. 6 is a sectional side view along line B - B in Fig. 5; and Fig. 7 is a plan view of the electrostatic ink-jet recording head shown in Fig. 4, giving a schematic illustration of the equipotential lines generated in the vicinity of the recording electrodes during recording. DESCRIPTION OF THE PREFERRED EMBODIMENTS Below, an embodiment of an electrostatic ink-jet recording head according to the present invention is described in detail with reference to the drawings. Fig. 1 comprises a sectional oblique view of an electrostatic ink-jet recording head (Fig. 1(A)) and a sectional oblique view showing an enlarged portion thereof (Fig. 1(B)). In Fig. 1, the electrostatic ink-jet recording head according to the present mode of implementation comprises the following principal constituent parts. Namely, a quadrilateral ink discharge member 20 formed from an insulating material of ceramic, polymer material, or the like, is supported on a head block 10. The electrostatic ink-jet recording head also comprises a substrate 30, which is constituted by an insulating thin plate or polymer film, or the like. A plurality of independent recording electrodes 31 are formed in a mutually parallel pattern on the surface of the substrate 30. An opposing electrode 40 which supports the recording paper 41 from behind during printing is placed in a position opposing the substrate 30 (forward position in Fig. 1). This opposing electrode 40 is made from a conductive material, such as metal, etc. and is connected to an earth (GND) or external power supply (not illustrated). Each component is described in detail below. Firstly, the head block 10 is provided with an ink supply chamber 11 which supplies ink 50 (described later) and an ink drain chamber 12 which drains the ink externally. A supply pipe 11a for supplying ink 50 from an external source is connected to the ink supply chamber 11. The ink drain chamber 12 is provided with a drain pipe 12a, and the ink 50 can be drained externally by means of this drain pipe 12a. The head block is formed with an approximately E-shaped section, as shown in Fig. 2(B). The ink supply chamber 11 and the ink drain chamber 12 are connected by means of the ink discharge member 20, which is described later. Therefore, by supplying ink to the ink supply chamber 11 and draining ink 50 from the ink drain chamber 12, the ink 50 is recycled between the head and an external ink tank (not illustrated). It can be expected that air bubbles will become mixed into the ink 50 in the ink discharge member 20 during recycling of the ink 50. Since air bubbles have a detrimental effect on recording quality, they need to be suppressed. Therefore, desirably, the ink drain chamber 12 is positioned above the ink supply chamber 11 in order to prevent residual air bubbles in the head block 10. However, this is not an essential element of the present invention. A migration electrode 13 made from a conductive material, such as metal, is provided inside the ink supply chamber 11. This migration electrode 13 is connected to an external power supply (not illustrated), and it is in direct contact with the ink 50 contained in the ink supply chamber 11. A fixed bias voltage of the same polarity as the charged toner particles 50a is applied to this migration electrode 13. An earth (GND) level or a fixed bias voltage of different polarity to the charged toner particles 50a is applied constantly to the opposing electrode 40. Fig. 2 is an enlarged sectional oblique view of the ink discharge end section 22a of the ink discharge member 20 in the electrostatic ink-jet recording head shown in Fig. 1. As Fig. 2 shows, the ink discharge member 20 has two oblique faces: an upper face and a lower face, and the portion where the upper and lower faces intersect forms an ink discharge end section 22a which emits ink. A plurality of ink recycling grooves 21 are formed running along the upper face and the lower face such that they pass through the ink discharge end section 22a. The spaces between adjacent ink discharge grooves 21 form ink discharge step sections 22 having a convex sectional shape (see Fig. 1(B)), and the ink discharge grooves 21 and ink discharge step sections 22 are formed such that they are mutually connected. In other words, one corner of the ink discharge member 20 is formed as an ink discharge end section, and at this ink discharge end section 22a, the ink discharge grooves 21 and the ink discharge step section 22 form an angled structure. This angled ink discharge end section projects towards an opposing electrode 40 which supports the recording paper 41 from behind. This projecting region forms a point which discharges ink. By means of this composition, the quadrilateral ink discharge member 20 is supported by the head block 10. As shown in Fig. 1(B), the ink discharge step sections 22 are positioned at a pitch equivalent to half the dot pitch at the maximum desired resolution. Furthermore, the recording electrodes 31 are arranged at a pitch corresponding to the desired resolution. Therefore, the recording electrodes 31 are arranged at a ratio of one to every two ink discharge step sections 22. The respective central longitudinal axes of every other ink discharge step section 22 and the corresponding recording electrode 31 coincide with each other. The recording electrodes 31 are formed with a width greater than that of the corresponding ink discharge step sections 22. Desirably, the width of each ink discharge step section 22 is 20 µm or less. In this mode of implementation, of the ink discharge step sections 22, only every other ink discharge step section 22A corresponding to a recording electrode 31 functions as a point which actually discharges ink droplets (indicated by symbol 51) at its ink discharge end section 22a. The other ink discharge step sections 22B function as partitions between the ink discharge step sections 22A. In other words, after an ink droplet 51 has been discharged from the ink discharge end section 22a of an ink discharge step section 22A, the ink discharge step sections 22B function as partitions which prevent vibrations in the meniscus from being transmitted to the discharge end section 22a. As described above, in the ink discharge member 20, the ink recycling grooves 21 and the ink discharge step sections 22 are formed on the intersecting upper and lower oblique faces. It is necessary to form a recycling path for the ink 50 which connects to the ink discharge grooves 21. Therefore, as shown in Fig. 2, on the upper oblique face, the substrate 30 is placed against the ink discharge grooves 21 and the ink discharge step sections 22. Meanwhile, the lower oblique face is covered by a covering member 25, in order to prevent ink 50 flowing out from the ink discharge grooves 21 and ink discharge step sections 22. The covering member 25 is positioned several 10 µm behind the ink discharge end sections 22a of the ink discharge member 20. Furthermore, the substrate 30 is positioned behind the ink discharge end sections 22a of the ink discharge member 20. Consequently, a state is achieved wherein the ink discharge end sections 22a are exposed externally from the end of the substrate 30 on the upper side of the ink discharge member 20. The opposing electrode 40 is positioned at an interval such that a prescribed printing gap can be ensured between the recording paper 41 the ink discharge end sections 22a of the ink discharge member 20. The opposing electrode 40 also serves the function of a platen for conveying the recording paper 41. The recording paper 41 supplied by a paper supply mechanism (not illustrated) is conveyed into the printing gap between the opposing electrode 40 and the ink discharge end section 22a such that it is always in contact with the opposing electrode. As described above, the recording electrodes 31 are patterned onto the substrate 30. More specifically, they are formed parallel to the ink discharge grooves 21 and ink discharge step sections 22 and are aligned at intervals equal to the dot pitch in the required resolution. Electrode pads for connecting to an external driver power source, which is not illustrated, are formed at the other ends of the recording electrodes 31. In the substrate 30, the recording electrodes 31 are positioned several 10 µm behind the ink discharge end sections 22a of the ink discharge member 20. By means of the compositions described above, the electrostatic ink-jet recording head according to the present mode of implementation has the following operation and action. A prescribed back pressure is applied to the ink 50 recycled from the ink supply chamber 11 to the ink drain chamber 12 in the head block 10. This back pressure is of a level such that it does not exceed the capillary action of the ink 50 in the ink discharge grooves 21. Therefore, as shown in Fig. 3, a concave meniscus 52 having vertices at each ink discharge end section 22a is formed in the region of the ink discharge end sections 22a of the ink discharge member 20. A constant bias voltage of the same polarity as the charged toner particles 50a is applied to the migration electrode 13 in the ink supply chamber 11, and an earth level or a constant bias voltage of different polarity to the charged toner particles 50a is applied constantly to the opposing electrode 40. Toner particles 50a are dispersed in the ink 50 introduced into the ink supply chamber 11 in the head block 10. The toner particles 50a are drawn towards the opposing electrode by means of the migration electrode 13 which is in contact with the ink 50. In this case, the voltage of the migration electrode 13 is of a level whereby the ink is not discharged from the discharge end section 22a. Therefore, the ink 50 is supplied to the ink discharge end sections 22a in the ink discharge member 20. During recording, a drive pulse voltage is applied to a desired recording electrode 31 by the driver, and an electrostatic force acts on the toner particles 50a in the ink 50 supplied to the ink discharge end section 22a, due to the electric field generated between the recording electrode 31 and the opposing electrode 40. The electrostatic force applied to the toner particles 50a exceeds the surface tension of the ink meniscus at the discharge end section 22a, thereby causing an ink droplet 51 containing toner particles 50a to be discharged from the ink discharge end section 22a towards the opposing electrode 40. The ink droplet 51 adheres to recording paper 41 of the opposing electrode 40, thereby conducting a recording operation by printing. The equipotential lines 60 generated during recording are shown in Fig. 3. In this case, the equipotential lines 60 in the vicinity of the ink discharge end section 22a when a recording voltage is applied are virtually perpendicular to the direction in which the ink is discharged. This is because the recording electrodes 31 are positioned slightly behind the ink discharge end sections 22a of the ink discharge member 20. An electrostatic force is generated drawing the toner particles in the vicinity of the ink discharge end section 22a towards the ink discharge end section 22a. Therefore, the supply of toner particles 50a to the ink discharge end section 22a will be continuous even when the recording voltage is applied. As described above, in the electrostatic ink-jet recording head according to the present embodiment, a concave-shaped ink meniscus 52 is formed in front of the recording electrodes 31. Consequently, even when a recording voltage is applied, toner particles 50a gather at the discharge end section 22a, and thus a sufficient quantity of toner particles 50a for forming the desired dot size can be supplied. Furthermore, by changing the time period for which the recording voltage is applied to the recording electrodes, it is possible to vary the quantity of toner particles 50a supplied to the ink discharge end section 22a. Therefore, the desired dot size can be formed. Moreover, since every other ink discharge step section 22B functions as an isolating partition between the ink discharge step sections 22A which actually discharge ink, vibrations in the ink meniscus in the region of the ink discharge end section 22a after discharge of the ink do not affect the ink meniscus at the discharge end section 22a of the ink discharge step sections 22A. Consequently, it is possible to obtain a stable ink meniscus at all times. Furthermore, since a compulsory flow of ink from the ink supply chamber 11 to the ink drain chamber 12 is generated inside the ink discharge grooves 21 formed in the vicinity of the ink discharge end sections 22a, the ink 50 is recycled smoothly in the ink discharge grooves 21. Therefore, it is possible to prevent accumulation of the toner particles 50a in the vicinity of the ink discharge end section 22a nearest to the opposing electrode 40. Consequently, it is possible to prevent ink droplet discharge faults due to excessive accumulation of toner particles 50a. In the electrostatic ink-jet recording head according to the present invention, a TAB tape based on TAB (Tape Automated Bonding) mounting technology, for example, is used when forming the recording electrodes 31. Specifically, the recording electrodes 31 are formed integrally onto a base film made from this TAB tape. The process of coating the recording electrodes 31 can be carried out by coating on an insulating coating material 32 consisting of perylene resin. As described above, in the electrostatic ink-jet recording head according to the present invention, since the ink discharge end sections are formed in front of the recording electrodes and the recording electrodes are formed such that they surround the ink discharge end sections, it is possible to supply to the discharge points a sufficient quantity of toner particles for forming desired dots, by generating a reservoir of ink by means of an ink meniscus in front of the recording electrodes. The present embodiments is therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description and all changes which come within the scope of the claims are therefore intended to be embraced therein. The entire disclosure of Japanese Patent Application No. 9-086229 (Filed on April 4th, 1997), which is the priority document of this application, including specification, claims, drawings and summary, is incorporated herein by reference in its entirety. Each feature disclosed in this specification (which term includes the claims) and/or shown in the drawings may be incorporated in the invention independently of other disclosed and/or illustrated features. The description of the invention with reference to the drawings is by way of example only. In summary, the electrostatic ink-jet recording head herein described comprises: printing electrodes which eject ink towards the recording paper; an opposing electrode for generating a prescribed electric field between the printing electrodes and the opposing electrode; ink discharge end sections formed in the vicinity of the printing electrodes; and partition end sections each formed between a respective adjacent pair of the ink discharge end sections. The ink discharge end sections are formed closer to the opposing electrode than the end portions of the printing electrodes. In this case, the equipotential lines in the region of the ink discharge end sections when a recording voltage is applied are virtually perpendicular to the direction in which the ink is discharged. This is because the recording electrodes are positioned slightly behind the ink discharge end sections in the ink discharge member. In this case, an electromagnetic force acts on the toner particles near the ink discharge end sections in the direction of the ink discharge end sections. Therefore, even when a recording voltage is applied, there is a continuous supply of toner particles to the ink discharge end sections. As described above, in the electromagnetic ink-jet recording head according to the present embodiment, a convex ink meniscus is formed in front of the printing electrodes. Therefore, toner particles gather at the discharge points, even when a recording voltage is applied, and thus a sufficient quantity of toner particles for forming a desired dot size can be supplied.

Claims: An electrostatic ink-jet recording head comprising: (a) printing electrodes (31) for ejecting ink (50) towards recording paper (8); (b) an opposing electrode (40) for generating a prescribed electric field between the printing electrodes (31) and the opposing electrode (40); and, (c) ink-discharge end sections (22a), each formed in the vicinity of a respective printing electrode (31); wherein each ink-discharge end section (22a) is positioned closer to the opposing electrode (40) than is any portion of the respective printing electrode (31); the recording head being characterized by further comprising: (d) partition end sections (22b), each formed between a respective adjacent pair of the ink-discharge end sections (22a). The electrostatic ink-jet recording head according to . claim 1, wherein the width of the printing electrodes (31) is greater than that of the ink-discharge end sections (22a). The electrostatic ink-jet recording head according to claim 1, wherein the surface of the printing electrodes (31) is covered with a film of insulating coating material (32). The electrostatic ink-jet recording head according to claim 1, wherein the ink discharge end sections (22a) are formed from an insulating coating material (32) having a dielectric constant of 10 or less. An electrostatic ink-jet recording head comprising: (a) a head block (10) within which are formed an ink supply chamber (11) for supplying ink (50) from an external source and an ink drain chamber (12) for draining ink (50) externally; (b) ink-discharge end sections (22a) formed in a path from the ink supply chamber (11) to the ink drain chamber (12) ; (c) ink-recycling grooves (21) formed from the ink supply chamber (11) to the ink-discharge end sections (22a) and from the ink-discharge end sections (22a) to the ink drain chamber (12); (d) printing electrodes (31) for ejecting ink (50), each printing electrode (31) being positioned in the vicinity of a respective ink-discharge end section (22a); and, (e) an opposing electrode (40) for creating an electric field between the printing electrodes (31) and the opposing electrode (40) ; wherein each ink-discharge end section (22a) is positioned closer to the opposing electrode (40) than is any portion of the respective printing electrode (31); the recording head being characterized by further comprising: (f) partition end sections (22b), each formed between a respective adjacent pair of the ink-discharge end sections (22a). The electrostatic ink-jet recording head according to claim 5, wherein the width of the printing electrodes (31) is greater than that of the ink-discharge end sections (22a). The electrostatic ink-jet recording head according to claim 5, wherein the surface of the printing electrodes (31) is covered with a film of insulating coating material (32). The electrostatic ink-jet recording head according to claim 5, wherein the ink-discharge end sections (22a) are formed from an insulating coating material (32) having a dielectric constant of 10 or less. The electrostatic ink-jet recording head according to claim 5, wherein the ink-discharge end sections (22a) are formed by two intersecting oblique faces. The electrostatic ink-jet recording head according to claim 9, wherein the width of the printing electrodes (31) is greater than the width of the ink-discharge end sections (22a). The electrostatic ink-jet recording head according to claim 9, wherein the surface of the printing electrodes (31) is covered with a film of insulating coating material (32). The electrostatic ink-jet recording head according to claim 9, wherein the ink-discharge end sections (22a) are formed from an insulating coating material (32) having a dielectric constant of 10 or less. The electrostatic ink-jet recording head according to claim 9, wherein: (a) the ink-recycling grooves (21) are formed on both of the intersecting oblique faces; (b) a prescribed substrate (30) is positioned on one of the oblique surfaces such that it covers the ink-recycling grooves (21), the printing electrodes (31) being formed by patterning onto the substrate (30), the recording electrodes being positioned such that they confront the ink-recycling grooves (21); and, (c) a prescribed covering member (25) is provided on the other oblique surface, such that it covers the ink-recycling grooves (21). The electrostatic ink-jet recording head according to claim 13, wherein the width of the printing electrodes (31) is greater than that of the ink-discharge end sections (22a). The electrostatic ink-jet recording head according to claim 13, wherein the surface of the printing electrodes (31) is covered with a film of insulating coating material (32). The electrostatic ink-jet recording head according to claim 13, wherein the ink-discharge end sections (22a) are formed from an insulating coating material (32) having a dielectric constant of 10 or less. The electrostatic ink-jet recording head according to claim 13, wherein the printing electrodes (31) are provided at a pitch of one for every ink-discharge end section (22a), and the longitudinal central axes of the printing electrodes (31) and the ink-discharge end sections (22a) coincide with each other. The electrostatic ink-jet recording head according to claim 17, wherein a plurality of printing electrodes (31), ink-recycling grooves (21) and ink-discharge end sections (22a) are arranged in parallel to the opposing electrode (40), and prescribed partitions are provided between the ink-discharge end sections (22a) where the printing electrodes (31) are provided. The electrostatic ink-jet recording head according to claim 17, wherein the surface of the printing electrodes (31) is covered with a film of insulating coating material (32). The electrostatic ink-jet recording head according to claim 17, wherein the ink-discharge end sections (22a) are formed from an insulating coating material (32) having a dielectric constant of 10 or less. The electrostatic ink-jet recording head according to claim 5, wherein a migration electrode (13) in contact with the ink (50) is provided in the ink-supply chamber (11); and a voltage of the same polarity of the charged toner is supplied to the migration electrode (13).

Inventors: HAGIWARA YOSHIHIRO, MINEMOTO HITOSHI, MIZOGUCHI TADASHI, SAEKI TOMOYA, SHIMA KAZUO, SUETSUGU JUNICHI, TAKEMOTO HITOSHI, YAKUSHIJI TORU, HAGIWARA, YOSHIHIRO, MINEMOTO, HITOSHI, MIZOGUCHI, TADASHI, SAEKI, TOMOYA, SHIMA, KAZUO, SUETSUGU, JUNICHI, TAKEMOTO, HITOSHI, YAKUSHIJI, TORU
Applicants: NIPPON ELECTRIC CO, NEC CORPORATION
Application year: 1998
Main classification: B41J2
IPC codes: B41J2