EP0761445A2 - Gerät zum Aufzeichnen von Bildern durch Emittieren von verdampfter Tinte auf ein Aufzeichnungsmedium - Google Patents

Gerät zum Aufzeichnen von Bildern durch Emittieren von verdampfter Tinte auf ein Aufzeichnungsmedium Download PDF

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Publication number
EP0761445A2
EP0761445A2 EP96114572A EP96114572A EP0761445A2 EP 0761445 A2 EP0761445 A2 EP 0761445A2 EP 96114572 A EP96114572 A EP 96114572A EP 96114572 A EP96114572 A EP 96114572A EP 0761445 A2 EP0761445 A2 EP 0761445A2
Authority
EP
European Patent Office
Prior art keywords
ink
slit
evaporated
image recording
separate electrodes
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP96114572A
Other languages
English (en)
French (fr)
Other versions
EP0761445A3 (de
Inventor
Masaya Nagata
Masayoshi Tsunezawa
Masaaki Ozaki
Hiroshi Ishii
Kaoru Higuchi
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Sharp Corp
Original Assignee
Sharp Corp
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from JP23432395A external-priority patent/JP3153742B2/ja
Priority claimed from JP33969595A external-priority patent/JP3642617B2/ja
Application filed by Sharp Corp filed Critical Sharp Corp
Publication of EP0761445A2 publication Critical patent/EP0761445A2/de
Publication of EP0761445A3 publication Critical patent/EP0761445A3/de
Withdrawn legal-status Critical Current

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
    • B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
    • B41J2/00—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
    • B41J2/005—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by bringing liquid or particles selectively into contact with a printing material
    • B41J2/01—Ink jet
    • B41J2/015—Ink jet characterised by the jet generation process
    • B41J2/04—Ink jet characterised by the jet generation process generating single droplets or particles on demand
    • B41J2/06—Ink jet characterised by the jet generation process generating single droplets or particles on demand by electric or magnetic field
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
    • B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
    • B41J2/00—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
    • B41J2/005—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by bringing liquid or particles selectively into contact with a printing material
    • B41J2/01—Ink jet
    • B41J2/015—Ink jet characterised by the jet generation process
    • B41J2/04—Ink jet characterised by the jet generation process generating single droplets or particles on demand
    • B41J2/06—Ink jet characterised by the jet generation process generating single droplets or particles on demand by electric or magnetic field
    • B41J2002/061—Ejection by electric field of ink or of toner particles contained in ink

Definitions

  • the present invention relates to an image recording device such as a copying machine, a facsimile and a printer. More specifically, the present invention relates to an image recording device for forming an image by intermittently emitting and directing an ink gas to be selectively adhered on or infiltrated through a recording medium.
  • Conventional emitting type image recording method includes, as representatives, an ink jet method, and an electrostatic recording method.
  • the ink jet method a liquid ink contained in a tank is pressurized by using a piezoelectric element or the like by an electric signal corresponding image data, and the ink is emitted from a nozzle for printing.
  • the ink jet method when air enters the ink tank, it becomes impossible to sufficiently pressurize the ink, so that printing fails. Further, this method suffers from clogging of the nozzle with ink and inferior image quality caused by bleeding of the ink on the recording medium.
  • the electrostatic recording method powder or liquid (mist) ink is charged, the ink is drawn out from the nozzle by electrostatic attraction, and printing is done by opening/closing a shutter provided at a tip end of the nozzle by an electric signal corresponding to the image data.
  • the electrostatic recording method suffers from the problem of the nozzle clogging when the ink is in the form of powder as the ink particles are caked by blocking. If the ink is liquid ink, this method also suffers from the problems of nozzle clogging and ink bleeding as in the ink jet method.
  • a still another prior art technique includes emission of gaseous ink which is adhered on or infiltrated through a recording medium.
  • nozzle clogging is less likely, since what is emitted is a gas.
  • pixels are recorded by molecules, printing with higher resolution, high gradient and less ink bleeding is possible.
  • This method is disclosed in Japanese Patent Publication No. 56-2020. Referring to Fig. 1, a print head 101 evaporates an ink 103 therein by heating, using a heating device 102 including an electric heater 113 and its power source 114.
  • Print head 101 shoots forth the evaporated gaseous ink 103a, and gaseous ink 103a is charged, as it passes through a charging electrode 104, by a power supply 105 connected between charging electrode 104 and print head 101.
  • the charged gaseous ink 103a is focused by electrostatic lenses 106 and 107.
  • the amount of emission of the charged gaseous ink is controlled by a signal source 110 as it passes through an electrostatic shutter 115.
  • the ink of which amount thus controlled travels to a back plate electrode 111, whereby the ink is adhered on the recording medium, forming an image.
  • gaseous ink In the method in which gaseous ink is emitted and adhered on the recording medium, gaseous ink is continuously emitted. Therefore, the ink intercepted by electrostatic shutter 115 and not used for recording is wasted, increasing running cost. Further, a device for recovering the non-used gaseous ink and a device for cleaning the peripheries of the electrostatic shutter 115 are necessary, making it difficult to reduce the size of the device. Further, movement of gaseous ink 103a from print head 101 to charging electrode 104 is performed as ink 103 is evaporated at expanded in volume, the pressure in print head 101 is accordingly increased and the gaseous ink 103 is shot out. Therefore, the speed of operation during printing is not very high, and performance is much influenced by the amount of ink 103 in print head 101, resulting in nonuniformity in density and hence unsatisfactory printing quality.
  • An object of the present invention is to provide an image recording device which effectively utilizes ink enabling reduction in running cost.
  • Another object of the present invention is to provide an image recording device in which troubles such an damage to the recording medium caused by leakage of evaporated ink can be prevented.
  • the image recording device includes a reservoir tank for reserving evaporated ink and having an emission opening through which the evaporated ink is emitted; a charging electrode for charging the evaporated ink in the reservoir tank, and an electrostatic shutter portion arranged at the emission opening for generating an electric field based on an image data for controlling emission of the charged ink.
  • the ink evaporated in the reservoir tank is charged by the charging electrode.
  • the charged gaseous ink is emitted through the emission opening of the reservoir tank, with its emission controlled by the electrostatic shutter portion. More specifically, when the electrostatic shutter portion is generating an electric field, the gaseous ink is not emitted from the reservoir tank, while the gaseous ink is emitted from the reservoir tank when the electrostatic shutter portion is not generating the electric field. Since the gaseous ink is emitted from the reservoir tank under the control of electric field at the electrostatic shutter portion, ink is adhered on the recording medium, forming an image. Accordingly, since only an amount of ink necessary for recording is emitted, ink is not wasted, whereby running cost can be reduced.
  • the image recording device includes a reservoir tank for reserving evaporated ink and having an elongate slit at an upper portion; a charging electrode for charging the ink evaporated in the reservoir tank; a shooting portion for moving and shooting the ink electrostatically through the slit toward recording medium arranged above the reservoir tank and opposing to the slit, an electrostatic shutter portion including a plurality of separate electrodes arranged spaced by a prescribed distance from each other in the longitudinal direction of the slit on one side of the slit, and common electrode arranged opposing to the plurality of separate electrodes on the other side of the slit, and control means for selectively applying a voltage corresponding to an image data between the common electrode and each of the plurality of separate electrodes.
  • the ink evaporated in the reservoir tank is charged by the charging electrode.
  • the charged gaseous ink is emitted through the electrostatic shutter portion arranged at the slit.
  • the electrostatic shutter portion is provided with a plurality of separate electrodes each corresponding to one dot and it controls the plurality of separate electrodes corresponding to the image data to regulate emission of the evaporated ink, whereby images corresponding to a plurality of dots can be recorded at one time.
  • the image recording device includes a reservoir tank for reserving evaporated ink and having an elongate slit formed at an upper portion; a heating portion for heating the ink to evaporate the ink; a charging electrode for charging the evaporated ink in the reservoir tank; a shooting portion for moving and shooting the charged ink electrostatically through the slit toward a recording medium arranged above the reservoir tank and opposing to the slit; an electric shutter including a plurality of separate electrodes arranged by a prescribed distance from each other along the longitudinal direction of the slit on one side of the slit and a common electrode arranged opposing to the plurality of separate electrodes on the other side of slit with the slits interposed; a control portion for selectively applying a voltage corresponding to image data between each of the plurality of separate electrodes and the common electrode; a detachable ink cartridge containing the ink and having an information indicative of evaporation temperature of the ink, for supplying the
  • the ink is heated and evaporated at an optimal temperature, so that problems such as ink leakage caused by excessive heating or insufficient heating of the ink can be prevented.
  • Fig. 1 shows a conventional device in which gaseous ink is emitted and adhered on a recording medium.
  • Fig. 2 is a cross section showing an overall structure of the device in accordance with a first embodiment of the present invention.
  • Fig. 3 is a partially exploded perspective view of an upper portion of a print head in accordance with the first embodiment of the present invention shown in Fig. 2.
  • Fig. 4 is a cross section of a portion of an upper portion 16 of print head 1.
  • Fig. 5 is a partially enlarged top view of print head 1.
  • Fig. 6 is a top view showing, in enlargement, a portion of print head 1 shown in Fig. 5.
  • Fig. 7 is a top view showing, in enlargement, a portion of print head 1 in accordance with a first modification of the first embodiment of the present invention.
  • Fig. 8 is a block diagram showing an electrical structure of the first embodiment of the present invention shown in Fig. 2.
  • Fig. 9 is a time chart showing the operation of a processing circuit 21.
  • Fig. 10 is a partially enlarged top view of print head 1a showing a second modification of the first embodiment of the present invention.
  • Fig. 11 is a partially enlarged top view of a print head 1b showing a third modification of the first embodiment of the present invention.
  • Fig. 12 is a partially enlarged top view of a print head 1c showing a fourth modification of the first embodiment of the present invention.
  • Fig. 13 is a partially enlarged top view of a print head 1d showing a fifth modification of the first embodiment of the present invention.
  • Fig. 14 is a partially enlarged top view of a print head 1e showing a sixth modification of the first embodiment of the present invention.
  • Fig. 15 is a partially enlarged top view of a print head 1f in accordance with a seventh modification of the first embodiment of the present invention.
  • Fig. 16 is a cross section of a portion of an upper portion 16 of a print head 1g showing an eighth modification of the first embodiment of the present invention.
  • Fig. 17 is a cross section of a portion of an upper portion 16 of a print head 1h showing a ninth modification of the first embodiment of the present invention.
  • Fig. 18 is a cross section showing separate electrodes 8b in the ninth modification of the ninth embodiment of the present invention shown in Fig. 17.
  • Fig. 19 is an enlarged top view of the upper portion 16 of a print head 1i showing a tenth modification of the first embodiment of the present invention.
  • Fig. 20 is a cross section showing an overall structure of an eleventh modification of the first embodiment of the present invention.
  • Fig. 21 shows a force acting on charged ink particles at the electrostatic shutter portion.
  • Fig. 22 shows a force in the direction of ink emission acting on the charged ink particles at the electrostatic shutter portion.
  • Fig. 23 shows a force in the direction of the electric field acting on the charged ink particles at the electrostatic shutter portion.
  • Fig. 24 is a graph showing relation between electrostatic shutter voltage and velocity component in vertical direction of ink particles.
  • Fig. 25 is a block diagram showing a control system of the image recording device in accordance with a second embodiment of the present invention.
  • Fig. 26 is a timing chart showing printing operation of the image recording device in accordance with the second embodiment of the present invention.
  • Fig. 27 is a block diagram showing a control system of the image recording device in accordance with a third embodiment of the present invention
  • Fig. 28 is a graph showing relation between an electrostatic shutter voltage and an ink heating temperature.
  • Fig. 29 is a perspective view showing another modification of the electrostatic shutter portion.
  • solid or liquid ink 3 is reserved in print head (reservoir tank) 1, and under print head 1, there is provided heating portion 2 including an electric heater 13 for heating ink 3 and a heat radiating plate 14. Heated ink 3 is evaporated to a gas 3a in gas filled portion 15 of print head 1, which gas is charged by one or a plurality of charging electrodes 4.
  • Print head 1 may be formed of an electrically insulating material such as a synthetic resin material.
  • a charging electrode 4 extends parallel to slit 17, that is, vertical to the sheet of Fig.
  • Charging electrode 4 may be formed to have the width of about 50 to about 80 ⁇ m, and a plurality of electrodes may be arranged parallel to each other, or a mesh electrode may be formed. At upper portion 16 near slit 17, an electrostatic shutter portion 8 is formed. An electrode 18 is formed at a lower portion or at the bottom of print head 1 such that it is in contact with solid or powder ink 3. Between charging electrode 4 and electrode 18, a DC power source 19 is connected, and charging electrode 4 serves as a positive electrode and electrode 18 as a negative electrode which is grounded.
  • the charged gaseous ink 3a moves upward from print head 1, and further moves to a lower surface in Fig. 2 of a recording medium 12 such as a recording paper arranged there by Coulomb force which is an electrostatic force caused by a back plate electrode 11.
  • a DC power source 20 is connected such that back plate electrode 11 is negative.
  • DC power source 20 applies a voltage of -0.5 k to -2 kV to back plate electrode 11.
  • a common electrode 8a at electrostatic shutter portion 8 is grounded, and between separate electrodes 8b and common electrode 8a, a DC voltage corresponding to image data for forming image is selectively applied from a processing portion 21.
  • the voltage is a prescribed constant voltage in the range of 50 V to 1 kV, for example.
  • electric field is generated at slit 17, which prevents traveling of the charged ink.
  • separate electrodes 8b are set to the same potential as common electrode 8a, for example, to the ground potential, the charged gaseous ink travels toward back plate electrode 11 by electrostatic force through slit 17 as described above, and adheres to or be infiltrated through recording medium 12 placed in front of back plate electrode 11, and thus image is recorded.
  • color ink As for the dye of ink 3, color ink is used.
  • substances belonging to anthoraisothiazole system, quinophthalone system, pyazolonazo system, pyridone azo system, styryl system or the like may be used.
  • magenta substances belonging to anthraquinone system, dicyanoimidazole system, thiadiazoleazo system, tricyanovinyl system or the like may be used.
  • cyan substances belonging to azo system, anthraquinone system, naphtoquinone system, indoaniline system or the like may be used.
  • ink 3 may be solid or powder, or alternatively, liquid. Liquid ink is easy to carry, and a smaller amount of energy is required by heating portion 2 for evaporation.
  • ink 3 is evaporated and the gaseous ink 3a is charged by charging electrode 4. Therefore, even if ink 3 is of an electrically insulating material, charging is possible without difficulty. Further, charging is ensured not affected by the environment, such as temperature and moisture.
  • common electrode 8a and the plurality of separate electrodes 8b are hatched. On one side of slit 17, one common electrode 8a is formed along the longitudinal direction of slit 17, and on the other side, a plurality of separate electrodes 8b are arranged spaced by a distance D from each other in the longitudinal direction of slit 17.
  • electrodes 8a and 8b are formed on upper portion 16 of print head 1, manufacturing is easy. Thickness of electrodes 8a and 8b is, for example, several hundreds ⁇ m to several mm. Therefore, electric line of force 22 is sufficiently formed to surely prevent leakage of charged gaseous ink 3a to the outside, that is, upper portion of Fig. 4, through slit 17.
  • an electrically insulating coating may be provided on the surfaces of the electrodes.
  • evaporated ink is intermittently shooted utilizing an electrostatic shutter portion in accordance with the image data corresponding to the image, the ink travels to the recording medium by electrostatic force, and the image is recorded. Therefore, only the necessary amount of ink for image recording is shooted out and ink which is not used is reserved in print head 1. Therefore, ink can be effectively used and running cost can be reduced.
  • an elongate slit 17 is formed at an upper portion of print head 1, and evaporated ink 3a is shoot out from the slit. Therefore, the ink which is not used is kept in print head 1, the evaporated ink 3a is condensed and returned to liquid or solid, and therefore, ink 3 which is not used is never discharged outside. Since ink 3 is utilized effectively, recovery of ink 3 is ensured, and there is not a possibility of external leakage. Therefore, cleaning structure, for example, equivalent for wiping the leaked ink, is not necessary.
  • a plurality of separate electrodes 8b and one or a plurality of common electrode 8a are arranged opposing to each other on both sides of slit 17, forming the electric shutter portion 8. Accordingly, clogging caused by the ink of which movement is stopped by slit 17 adhered near the slit 17 can be suppressed or eliminated. Further, it is not necessary to provide nozzle openings one for each pixel, and hence structure of print head 1 can be simplified.
  • entire length L of slit 17 corresponds to the width of printing in a line head printer, for example. More specifically, for a sheet of paper of the size A4 in accordance with Japanese Industrial Standard (JIS), the length is 200 mm, and for the sheet of paper of the size A5, it is 140 mm.
  • the width W of slit 17 is determined to be about 200 ⁇ m, when recording density is 150 dot/inch (dpi).
  • each of the separate electrodes 8b has a width B corresponding to the recording density
  • the separate electrodes 8b are spaced by a distance D from each other and are of identical shape.
  • An area in the longitudinal direction of slit 17 which should be governed by the electric field generated by one separate electrodes 8b is the width D of the separate electrode 8b + D/2 outside from each of the edges of separate electrode 8b, where D represents the width of the exposed electrically insulating material at the upper portion 16 between the separate electrodes 8b.
  • separate electrodes 8b1 at the opposing ends in the longitudinal direction of slit 17. It is necessary that the electric field acts in the range up to D/2 outer from both edges of separate electrodes 8b1. Namely, the length in the left and right directions of Fig. 5 of common electrode 8a is set longer by at least D/2 in the outward direction along the longitudinal direction of slit 17, than the outermost separate electrodes 8b1, where D represents the width of the insulating material between the separate electrodes 8b. Accordingly, electric field distribution at separate electrodes 8b1 at the opposing ends is as shown schematically by reference numerals 23 of Fig. 5, which is similar to the electric field distribution of other separate electrodes 8b. In this manner, ink dot diameter controlled by separate electrodes 8b and 8b1 can be made identical. In the following description, separate electrodes 8b and 8b1 may be generally referred to as separate electrodes 8b.
  • the evaporated ink is charged positively. However, it may be charged negatively by applying a negative voltage to wire electrode 4. However, when ink 3a is charged positively as described above, generation of harmful substance such as ozone can be reduced.
  • the voltage to be applied between common electrode 8a and separate electrodes 8b the voltage is determined taking into consideration not only the electrical Coulomb force of gaseous ink 3a generated by back plate electrode 11 but also increase in pressure in print head 1 caused by volume expansion when ink is evaporated from solid or powder or the volume expansion when ink is evaporated from liquid to gas.
  • both electrodes 8a and 8b are of parallel flat plates, and in slit 17, electric field distribution is almost uniform. Therefore, the width B of separate electrodes 8b should be as wide as possible and the distance D between separate electrodes 8b should be as narrow as possible to form more uniform electric field distribution. Conveniently, the period (B + D) between separate electrodes 8b can be determined in unique manner in accordance with resolution. For example, when recording density is 150 dpi, B + D ⁇ 200 ⁇ m .
  • the distance D between separate electrodes 8b becomes smaller in accordance with the equation D ⁇ 200 - B .
  • the distance D between separate electrodes 8b should be selected in accordance with the voltage applied.
  • slit 17 extends outer than the outermost separate electrodes 8b1 along the longitudinal direction of the slit, and hence the plurality of separate electrodes 8b may be formed at intermediate positions in the longitudinal direction of the slit. This means that it is not necessary to precisely align the separate electrodes 8b1 at outermost positions and the opposing end positions of the slit. Therefore, the formation of slit 17 and formation of separate electrodes 8b corresponding to the slit 17 can be facilitated, resulting in superior production yield.
  • the common electrode 8a is extend outer than the endmost separate electrodes 8b1 along the longitudinal direction of slit 17, and therefore, when an electric field is generated between common electrode 8a and all the separate electrodes 8b, movement of ink can be surely stopped over the entire length of slit 17, and ink leakage can be prevented.
  • the image data to be recorded on recording medium 12 is applied from an image data source 24 to processing circuit 21, which controls selective application/interruption of voltage between common electrode 8a and each of the separate electrodes 8b corresponding to each of the dot in an image recording period.
  • a voltage of about 500V is applied between the separate electrodes and common electrode 8a, whereby undesirable ink leakage is prevented.
  • voltage is selectively applied with time to separate electrodes 8b in accordance with the image data, and in synchronization therewith, recording medium 12 is moved in a direction vertical to the longitudinal direction of slit 17 (that is, in left and right directions of Fig. 2).
  • the period in which voltage is applied between common electrode 8a and all the separate electrodes 8b for preventing ink leakage is at least that period in which ink is evaporated and there is a possibility of leakage from slit 17, other than the image recording period. More specifically, it is the period from the start of heating of solid, powder or liquid ink until ink is sufficiently evaporated, allowing image recording, and the period from the end of image recording until the evaporated and mist ink is reduced or diminished and possibility of external leakage from print head diminishes. In this manner, ink leakage can surely be prevented.
  • a distance D3 between the endmost portion 25 of slit 15 and the separate electrodes 8b1 at the endmost position may be selected to D/2, for example, as in print head 1 shown in Fig. 5.
  • other structures and functions are similar to those of print head 1 shown in Fig. 5. Therefore, detailed description is not repeated.
  • a plurality of electrodes 8a are formed along the longitudinal direction of slit 17, corresponding to the separate electrodes 8b, respectively.
  • the plurality of electrodes 8a1 are commonly connected to each other by a conductor 26, and set to have the same potential.
  • respective electrodes 8a1 and corresponding separate electrodes 8b are arranged at opposing positions on both sides of slit 17 along the longitudinal direction (left and right directions of Fig. 11) of slit 17, with the same width. Therefore, in slit 17, almost uniform electric field distribution can be attained, and as in the above described modifications, ink leakage can be prevented.
  • a print head 1c in accordance with a forth modification of the first embodiment of the present invention is similar to third modification shown in Fig. 11, except that the width B1 of separate electrodes 8b is smaller than the width B.
  • ink leakage at the region between adjacent electrodes 8b' can be prevented by enlarging the electric field in slit 17, by making higher the voltage to be applied between the common electrode 8a1 and separate electrodes 8b', as compared with the modification shown in Fig. 11.
  • the structures and functions of print heads 1b and 1c shown in Figs. 11 and 12 are similar to those of print head 1 shown in Fig. 5. Therefore, detailed description is not repeated.
  • a print head 1b in accordance with a fifth modification of the first embodiment of the present invention has a similar structure as the modifications shown in Figs. 5 and 10 above, and portions corresponding to those of Figs. 5 and 10 are denoted by the same reference characters.
  • the length L of slit 17 is longer than the entire length Lew of separate electrodes 8b.
  • a shield member 30 is provided for covering an end portion 29, spaced by a distance D/2. In this manner, at the end portion of 28 of slit 17, ink leakage can be prevented similar to at other separate electrodes 8b.
  • the shield member 30 may be a metal thin film electrically connected to common electrode 8a. Alternatively, it may be a film or a flat plate formed of an electrically insulating synthetic resin. By highly precisely positioning and adhering or fixing shield member 30 onto the upper portion 16 of print head 1, it becomes possible to set the distance D/2 between the end portion 28 of slit 17 and the separate electrodes 8b1 at the endmost position with high precision.
  • a print head 1e in accordance with a sixth modification of the first embodiment in the present invention is similar to the modification shown in Fig. 12 above.
  • corresponding portions are denoted by the same reference characters.
  • electrodes 8a1 are formed divided separately, corresponding to separate electrodes 8b.
  • a distance 31 can be precisely set by shield member 30 as in the structure of Fig. 13, that is, the distance D/2 between shield member 30 and separate electrode 8b1 at the endmost position can be set higher precisely along the longitudinal direction of slit 17. Accordingly, ink leakage can be prevented as in the structure shown in Fig. 13.
  • a print head 1f in accordance with a seventh modification of the first embodiment of the present invention is similar to the first embodiment shown in Fig. 5.
  • corresponding portions are denoted by the same reference characters.
  • this modification there are a number of separate electrodes 8b and 8b1 having identical shapes, and outer than the separate electrodes 8b1 at the endmost position along the longitudinal direction of slit 17, there are ink movement preventing electrodes 8c positioned at opposing ends along the longitudinal direction. End portions of common electrode 8a extend further outward along the longitudinal directions than the opposing end portions of slit 17.
  • the length of common electrode 8a is represented by Lew, which length Lew is equal to the length between opposing ends of ink movement preventing electrodes 8c.
  • Lew is equal to the length between opposing ends of ink movement preventing electrodes 8c.
  • ink movement preventing electrode 8c has the same shape and dimension as separate electrodes 8b and 8b1 here, it is not necessarily be identical to these electrodes. What is important is that ink movement preventing electrode 8c extends outward from opposing end portions in the longitudinal direction of slit 17. By the provision of such electrodes, electric field generated by these and common electrode 8a at opposing end portions of slit 17 is not disturbed, and almost uniform electric field distribution can be attained along the longitudinal direction of slit 17.
  • a voltage is applied from processing circuit 21 to ink movement preventing electrode 8c.
  • the voltage applied between ink movement preventing electrode 8c and common electrode 8a prevents travel and movement of charged gaseous ink 3a from opposing ends of slit 17 in the time period from t1 to t3, as shown in (d) of Fig. 9.
  • the voltage applied between ink movement preventing electrode 8c and common electrode 8a should be applied at least in the period in which travel and movement of ink from print head 1 is possible. That is, the period in which the amount of heated and evaporated ink 3a is sufficiently large and there is a possibility of external leakage from slit 17.
  • the voltage may have the same value as the voltage applied to separate electrodes 8b and 8b1 with respect to common electrode 8a.
  • ink movement preventing electrodes 8c are formed extending outward in the longitudinal direction from opposing ends of slit 17 in the longitudinal direction, it becomes unnecessary to improve positional precision in forming slit 17 and separate electrodes 8b1 shown in Fig. 5. Further, it is not necessary to attach shield member 30 shown in Figs. 13 and 14 with high precision with respect to separate electrodes 8b1 at endmost positions. Therefore, manufacturing process is simple, and superior production yield becomes possible.
  • a plurality of electrodes formed separate from each other along the longitudinal direction of slit 17 and set to a common potentials, such as shown in Figs. 11, 12 and 14 may be provided.
  • the upper portion 16 of print head 1g is formed of an electrically insulating material, such as synthetic resin, as described above, and over the upper surface thereof and inner peripheral surface of slit 17, common electrode 8a and separate electrodes 8b are formed. Accordingly, electrode portions 8a3 and 8b3 formed along the inner peripheral surface of slit 17 extend along the upper shooting direction 34 of gaseous ink 3a through slit 17. Therefore, ink 3a receives electrostatic force provided by the electric field at electrostatic shutter portion 8 over a relatively long distance. This can effectively and surely prevent undesirable leakage of ink 3a to the outside.
  • Common electrodes 8a and separate electrodes 8b may be formed by thick film forming technique, by a so called thin film forming technique or by any other technique.
  • electrodes 8a and 8b extend from the upper surface of upper portion 16 of reservoir tank 1g toward the inner peripheral surface of slit 17, advantageously, electrodes 8a and 8b can be made thinner.
  • Portions 8a4 and 8b4 of common electrodes 8a and separate electrodes 8b formed on the upper surface of upper portion 16 of reservoir tank 1g function to form an electric field at slit 17. However, more important function thereof is that of leads for leading electrical signals.
  • upper portion 16 of print head 1a in accordance with a ninth modification of the first embodiment of the present invention is formed by rectangular block shaped common electrodes 8a and separate electrodes 8b.
  • an electric field perpendicular to the direction of movement 34 of ink 3a can be generated at slit 17, whereby ink movement can be surely prevented.
  • Fig. 18 is a cross section taken along the line XVII-XVII of the modification shown in Fig. 17.
  • separate electrodes 8b are shown hatched.
  • the plurality of separate electrodes 8b are rectangular, as described above, and flat, with electrically insulating material interposed between each of the separate electrodes 8b, and upper portion 16 is thus formed.
  • Common electrode 8a may be a single electrode, or it may include a plurality of divided electrodes similar to the electrodes 8a1 shown in Figs. 11, 12 and 13 above.
  • common electrode 8a and separate electrodes 8b1 at endmost positions are on the inner side along the longitudinal direction of slit 17 by a distance P than the end portions of slit 17.
  • an image recording device includes a print head 1j, heating portion 2 including electric heater 13, a charging electrode 4j, electrostatic shutter portion 8, back plate electrode 11 and processing portion 21.
  • Liquid ink 3 is reserved in print head 1j, and below print head 1j, heating portion 2 including electric heater 13 for heating ink 3 and a heat radiating plate is provided, as described above.
  • two charge introducing electrodes are provided as charging electrodes 4j for charging ink 3, on both sides of reserved ink 3.
  • electrostatic shutter portion 8 is provided at an upper portion of print head 1j. Control of generation/interruption of electric field at electrostatic shutter portion 8 is performed by processing portion 21.
  • recording medium 12 is arranged, and on the upper surface thereof, back plate electrode 11 is provided.
  • slit 17 is formed as an emission opening of evaporated ink 3a.
  • electrostatic shutter portion 8 is provided on both sides of the longer sides of slit 17.
  • the length of slit 17 in the longitudinal direction is set corresponding to the printing width.
  • the width of slit 17 is set to 200 ⁇ m.
  • One electrode 8a of electrostatic shutter portion 8 is grounded and on the other side, a plurality of separate electrodes 8b are provided in comb shape at a distance of 169 ⁇ m, which corresponds to the recording density.
  • Processing portion 21 output signals corresponding to image data to be recorded, and electrostatic shutter portion 8 controls the potentials of electrodes 8b in accordance with the output signals corresponding to each of the pixels, whereby passage of gaseous ink 3a is controlled. Gaseous ink 3a which has passed through electrostatic shutter portion 8 is attracted to back plate electrode 11 and adhered on recording medium 12, whereby printing is performed.
  • the modification shown in Fig. 20 of the present invention also provides similar effect as the first embodiment shown in Fig. 2, and the emission of gaseous ink 3a can be controlled in reservoir tank 1j in accordance with image data. Therefore, emission of unnecessary amount of ink can be prevented, and printing can be done with high efficiency. Further, since heating portion 2, charging electrode 4j and electrostatic shutter portion 8 are formed integrally with reservoir tank 1j, ink intercepted by electrostatic shutter portion does not adhere to the electrostatic shutter portion 8, and hence the possibility of clogging can be reduced. Further, equipment for recovering and cleaning the adhered ink becomes unnecessary, which leads to smaller size and reduced weight of the device.
  • charging may be performed not by introducing a pair of charges as shown in Fig. 20 but by frictional electrification, for example, by stirring the powder electrically insulasive ink.
  • Use of powder ink provides an advantage that, according to the experiment performed by the inventor, the amount of ink leakage from reservoir tank 1 through slit 17 can be reduced. If liquid ink 3 is used, uniformity in charging is better than powder ink, and efficient charging is possible.
  • one or a plurality of porous accelerating electrodes may be interposed between slit 17 and recording medium 12, so that charged ink 3a from slit 17 reaches recording medium 12 through the pores, instead of back plate electrode 11.
  • other structures utilizing electrostatic force may be utilized to shoot out the charged ink.
  • the shooting may be caused by a magnetic force generated in charged ink, by means of a magnetic field between the slit 17 and recording medium 12.
  • ink mist may be used.
  • the direction of emission of ink 3a when the inner pressure increases and the direction of electric field E provided by electrostatic shutter portion 8 are perpendicular to each other. Therefore, two directions are represented by the vertical direction (coordinate z) and horizontal direction (coordinate x), respectively. Actual direction of emission of the ink is given as a vector sum of these two, which can be separated to uniform motion in vertical direction (coordinate z) and uniformly accelerated motion in the horizontal direction (coordinate x).
  • the velocity component of ink particles in z direction at and near slit 17 has only the component of +z direction, when collision of ink particles with each other is not taken into consideration, and hence it holds that v z (i) > 0.
  • i 1 ..., N
  • N number of ink particles in print head 1.
  • suffix y represents the direction perpendicular to the sheet surface (coordinate y)
  • v y (i) represents velocity component of ink particles in the y direction.
  • v ( i ) ( v x ( i ) , v y ( i ) ,
  • head inner pressure P at slit 17 is caused by the z direction velocity component v z (i) of ink Particles at slit 17. Therefore, the head inner pressure P can be represented by the following expression (2), based on kinetic theory of gases. P ⁇ m ( i ) ⁇ v z (i )2
  • the expression (3) can be represented by the following expression (6) using ink temperature T.
  • Equations of motions in vertical and horizontal directions can be obtained in the following manner.
  • the time t 1 also has distribution.
  • t 2 [(2 m ⁇ w 2 )/( q ⁇ v )]
  • V increases in quadratic function as v z (i) increases, when V is constant. Further, if v z (i) is constant, the smaller the value D, the smaller the value V. Namely, when m and q are constant, D is a function of (w/d).
  • the value w/d is a constant determined in the stage of designing print head 1. Therefore, the print head 1 is designed so that the value w/d is as small as possible. This is invariable as long as geometrical sizes of the length l and width w of slit 17 at electrostatic shutter portion 8 are not different even when shapes of other portions of print head 1 are varied.
  • the value v z (i) is, finally, determined dependent on operational conditions and environment, such as structure (volume and the like) of print head 1, the ink heating temperature (which ink heating temperature depends on ink evaporation temperature), temperature in print head 1 and so on. Therefore, if these conditions vary, it also varies. However, assuming that v z (i) is constant, the voltage V to be applied to electrostatic shutter portion 8 can be made smaller by reducing the value w/d.
  • v z (i) (T) has velocity distribution, and it is also a function of temperature. Therefore, it is not practical to satisfy the relation represented by the expression (12) for all the ink particles, especially for the particles having small velocity. Therefore, the value V is determined so that the expression (12) is satisfied at least for the square root of root mean square of v z (i) , that is, v z 2 ⁇ or the mean value of v z (i) , that is, v z ⁇ or for v z (i) which is not lower than the highest distributed value v m of v z (i) . Now, the relation represented by the following expression (16) holds between these three values. v m ⁇ v z ⁇ ⁇ v z 2 ⁇
  • the present invention utilizes the option (i).
  • the advantages provided by reducing the voltage applied to the electrostatic shutter portion 8 are as follows. First, insulation between separate electrodes 8b is ensured. Second, the power supply scale is reduced, and generation of noise to the periphery can be reduced, which leads to higher reliability of the image recording device.
  • a CPU 40 Central Processing Unit 40 is the center of the control system of the image recording device. As shown in Fig. 25, it controls heating by heating portion 2, electric conduction at emitting portion including charging electrode 4 and back plate electrode 11, and controls emission control portion including control portion 9 and electrostatic shutter portion 8, and through the control of these portions, it controls the overall printing operation of print head 1. Details are as follows.
  • heating portion 2 applies electric power to electric heater 13 at a time point B after a prescribed time lapse from time point A, where the rise (point A) of the head control signal serves as a trigger, as shown in (b) of Fig. 26.
  • a voltage of +2 k to 5 kV is applied to charging electrode 4 (see (c) of Fig. 26).
  • the time point when driving of heating portion starts may not be the same as the point B.
  • a voltage of about 50 to 1 kV may be applied to all the separate electrodes 8b of electrostatic shutter portion 8, so as to turn on the electrostatic shutter portion 8. This is because emission of ink 3a can be prevented in this state.
  • a printing start/end signal is output from CPU 40 to control portion 9.
  • whether the amount of ink 3a exceeded the threshold value or not is not directly measured. Therefore, it is estimated by CPU 40 by measuring the time from the start of heating of electric heater 13 or by measuring the temperature at print head 1.
  • indirect data is compared with time or temperature data input in advance as a target value, and CPU 40 generates a printing start/end signal accordingly.
  • Control portion 9 represents transmission of image data from an image memory, not shown, using the rise of printing start/end signal as a trigger, and as the data transfer completes, it outputs an ON/OFF signal in accordance with the image data at time point B' shown in (f) of Fig. 26 to electrostatic shutter portion 8.
  • Electrostatic shutter portion 8 is connected to a power supply device, not shown, supplying a voltage of 500 V, and conduction of 500 V is turned ON/OFF at each of the separate electrodes 8b at electrostatic shutter portion 8 in accordance with the image data.
  • print start signal falls to "L" level, and using this fall as a trigger, heating portion 2, charging electrode 4 and back plate electrode 11 are all turned off. Even when electric conduction to electric heater 13 by heating portion 2 is stopped, ink 3a is not immediately cooled but left in print head 1. Therefore, after the end of printing, electrostatic shutter portion 8 is forced ON until the time point E' which is later than the point F of the threshold value, so as to prevent leakage of ink 3a to be outside (see (f) of Fig. 26). After the time point E' until the start of the next printing operation, electrostatic shutter portion 8 is kept OFF.
  • electrostatic shutter voltage V the relation between the voltage V applied to electrostatic shutter portion 8 (hereinafter referred to as electrostatic shutter voltage V) and ink heating temperature T is considered, and leakage of ink 3a is prevented by controlling electrostatic shutter voltage V based on the relation between these two.
  • ⁇ V is a positive constant, which is determined taken into consideration variations in ambient temperature, quantity q of charges and so on.
  • ⁇ V is a positive constant, which is determined taken into consideration variations in ambient temperature, quantity q of charges and so on.
  • electrostatic shutter voltage V and ink heating temperature T have linear relation with each other.
  • ink heating temperature T can be represented by the following equation (25) based on the evaporation temperature T g of the ink.
  • T T g + ⁇ T
  • ink heating temperature T may vary dependent on stability of the control portion, influence of external disturbance, ambient temperature, change in the consumed quantity of gaseous ink 3a caused by different printing density and so on. If it is understood in advance that the temperature variation is small, such small temperature variation may be accounted in ⁇ V, and control is performed such that the value V is kept constant. Further, as the quantity of charges vary, the value q and hence the constant a may vary. However, in this case also, if such variation is small, it may be taken into account when determining ⁇ V, and the value V may be kept constant.
  • Fig. 27 shows a structure of a control system of the image recording device in accordance with the third embodiment.
  • the control system has similar structure as the control system of the image recording device in accordance with the second embodiment described above except that it includes a ink type determining device 41.
  • the ink type determining device 41 reads ink information indicated on an ink cartridge containing ink 3, and applies an ink type determination signal to CPU 40.
  • CPU 40 finds ink evaporation temperature T g from ink type determination signal, for performing subsequent control. Portions corresponding to those of the second embodiment are denoted by the same reference characters and description thereof is not repeated.
  • ink 3 is contained in a container generally referred to a cartridge. Therefore, when the cartridge is adapted to have information representing ink type, ink type can be identified.
  • a mechanical means such as a lever can be used for reading the information.
  • an optical element such as photointerrupter may be used. More specifically, when the information is represented by physical projection/recess, two projections/recesses are formed selectively, and a lever is adapted to be in contact with respective positions. Each lever serves as a binary switch.
  • two bar codes may be selectively formed and reflective type photo interrupter may be arranged at respective positions.
  • the value ⁇ T is set to 15°C, for example.
  • the ink heating temperature T is calculated in accordance with the equation (25) assuming that ⁇ T is constant.
  • an ink heating temperature T relative to the ink evaporation temperature T g may be prepared in the form of a look-up table (LUT) in advance, and the ink heating temperature T may be determined referring to the LUT.
  • an LUT of the electrostatic shutter voltage V relative to the ink evaporation temperature T g may be formed, and the voltage may be determined referring to the LUT.
  • CPU 40 When the ink heating temperature T and electrostatic shutter voltage V are determined in accordance with the above described steps, CPU 40 outputs a print start signal to various portions of print head 1.
  • the start signal gives timings to apply/interrupt application of the voltage.
  • the print start signal is represented by a dotted line.
  • CPU 40 inputs a heating control signal so that heating portion 2 heats ink 3 at the determined ink heating temperature T. Consequently, heating portion 2 applies electric power to electric heater 13 so as to attain the temperature represented by the equation (25). Further, CPU 40 inputs a charge start signal to charging electrode 4. Consequently, a voltage of 2 k to 5 kV is applied to charging electrode 4, and ink 3a is charged. Before a time point where the gaseous ink quantity exceeds the threshold value, CPU 40 inputs an electrostatic shutter voltage control signal to control portion 9. Consequently, a voltage is applied to all the separate electrodes 8b at electrostatic shutter 8, that is, electrostatic shutter portion 8 is turned ON, preventing leakage of ink.
  • CPU 40 When the state where printing is possible is attained, CPU 40 outputs a voltage application start signal to back plate electrode 11, and applies a voltage of -1 kV to back plate electrode 11. Simultaneously therewith, separate electrodes 8b of electrostatic shutter portion 8 are turned ON/OFF in accordance with the image data, whereby printing operation starts.
  • CPU 40 When printing operation is completed, CPU 40 outputs control signals to the aforementioned various portions. More specifically, it outputs a cancellation signal to heating portion 2, charging electrode 4 and back plate electrode 11 so as to simultaneously stop application of voltages, whereby generation and emission of gaseous ink 3a is suppressed. Further, it applies a voltage to all the separate electrodes 8b of electrostatic shutter portion 8 immediately after the end of printing, so as to prevent leakage of ink 3a. Electrostatic shutter voltage V is not cancelled until a time point where the quantity of the gaseous charged ink becomes lower than the threshold value.
  • ink heating temperature T and electrostatic shutter voltage V can be supplied to each of different inks 3 having a plurality of thermophysical properties.
  • control of heating portion 2 only causes different problems from the following reasons.
  • both the ink heating temperature and the electrostatic shutter voltage are controlled to be optimal values dependent on the ink type. Therefore, there is not a disadvantage of excessive heating or insufficient heating, nor increased power consumption or ink leakage.
  • the slit of electrostatic shutter portion 8 may be adapted to be partitioned corresponding to the width of separate electrodes 8b.
  • the present invention is particularly effective when applied to an image recording device for color printing.

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  • Particle Formation And Scattering Control In Inkjet Printers (AREA)
EP96114572A 1995-09-12 1996-09-11 Gerät zum Aufzeichnen von Bildern durch Emittieren von verdampfter Tinte auf ein Aufzeichnungsmedium Withdrawn EP0761445A3 (de)

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
JP234323/95 1995-09-12
JP23432395A JP3153742B2 (ja) 1995-09-12 1995-09-12 画像記録方法および装置
JP33969595A JP3642617B2 (ja) 1995-12-26 1995-12-26 画像記録装置
JP339695/95 1995-12-26

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EP0761445A3 EP0761445A3 (de) 1997-08-13

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Cited By (4)

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Publication number Priority date Publication date Assignee Title
EP0867299A1 (de) * 1997-03-25 1998-09-30 SHARP Corporation Verfahren und Gerät zur Erzeugung eines Bildes
WO2006017091A1 (en) * 2004-07-12 2006-02-16 Hewlett-Packard Development Company, L.P. A method and a system to deposit drops
CN102069643A (zh) * 2009-10-29 2011-05-25 精工爱普生株式会社 液体喷射装置
CN109799047A (zh) * 2019-03-12 2019-05-24 中国电建集团成都勘测设计研究院有限公司 基于光纤的面板堆石坝混凝土面板缝间渗流监测系统

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Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0867299A1 (de) * 1997-03-25 1998-09-30 SHARP Corporation Verfahren und Gerät zur Erzeugung eines Bildes
US6084614A (en) * 1997-03-25 2000-07-04 Sharp Kabushiki Kaishi Method and apparatus for forming an image using flying developing particles
WO2006017091A1 (en) * 2004-07-12 2006-02-16 Hewlett-Packard Development Company, L.P. A method and a system to deposit drops
US7334881B2 (en) 2004-07-12 2008-02-26 Hewlett-Packard Development Company, L.P. Method and system to deposit drops
CN102069643A (zh) * 2009-10-29 2011-05-25 精工爱普生株式会社 液体喷射装置
CN102069643B (zh) * 2009-10-29 2013-09-25 精工爱普生株式会社 液体喷射装置
CN109799047A (zh) * 2019-03-12 2019-05-24 中国电建集团成都勘测设计研究院有限公司 基于光纤的面板堆石坝混凝土面板缝间渗流监测系统
CN109799047B (zh) * 2019-03-12 2023-11-21 中国电建集团成都勘测设计研究院有限公司 基于光纤的面板堆石坝混凝土面板缝间渗流监测系统

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