EP0273664A2 - Tröpfchenejektor - Google Patents

Tröpfchenejektor Download PDF

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Publication number
EP0273664A2
EP0273664A2 EP87311224A EP87311224A EP0273664A2 EP 0273664 A2 EP0273664 A2 EP 0273664A2 EP 87311224 A EP87311224 A EP 87311224A EP 87311224 A EP87311224 A EP 87311224A EP 0273664 A2 EP0273664 A2 EP 0273664A2
Authority
EP
European Patent Office
Prior art keywords
ink
droplets
ejector
acoustic
printer
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.)
Granted
Application number
EP87311224A
Other languages
English (en)
French (fr)
Other versions
EP0273664B1 (de
EP0273664A3 (en
Inventor
Scott Alan Elrod
Butrus T. Khuri-Yakub
Calvin F. Quate
Thomas Roy Vanzandt
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.)
Xerox Corp
Original Assignee
Xerox 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
Application filed by Xerox Corp filed Critical Xerox Corp
Publication of EP0273664A2 publication Critical patent/EP0273664A2/de
Publication of EP0273664A3 publication Critical patent/EP0273664A3/en
Application granted granted Critical
Publication of EP0273664B1 publication Critical patent/EP0273664B1/de
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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Classifications

    • BPERFORMING OPERATIONS; TRANSPORTING
    • B41PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
    • B41JTYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
    • B41J2/00Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
    • B41J2/005Typewriters 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
    • B41J2/01Ink jet
    • B41J2/135Nozzles
    • B41J2/14Structure thereof only for on-demand ink jet heads
    • B41J2/14008Structure of acoustic ink jet print heads
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B41PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
    • B41JTYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
    • B41J2/00Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
    • B41J2/005Typewriters 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
    • B41J2/01Ink jet
    • B41J2/21Ink jet for multi-colour printing
    • B41J2/2121Ink jet for multi-colour printing characterised by dot size, e.g. combinations of printed dots of different diameter
    • B41J2/2128Ink jet for multi-colour printing characterised by dot size, e.g. combinations of printed dots of different diameter by means of energy modulation
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B41PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
    • B41JTYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
    • B41J2/00Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
    • B41J2/005Typewriters 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
    • B41J2/01Ink jet
    • B41J2/135Nozzles
    • B41J2/14Structure thereof only for on-demand ink jet heads
    • B41J2002/14322Print head without nozzle

Definitions

  • This invention relates to acoustic printing or marking and, more particularly, to methods and means for controlling the diameter of the spots printed by such a process, thereby providing a representation of the gray scale contents of the images it prints.
  • Acoustic printing is a potentially important, alternative direct marking technology. It is still in an early stage of development, but the available evidence indicates that it is likely to compare favorably with ordinary ink jet systems for printing either on plain paper or on specialized recording media, while providing significant advantages of its own. More particularly, acoustic printing has increased intrinsic reliability because there are no nozzles to clog. As will be appreciated, the elimination of clogged nozzles is especially relevant to the reliability of arrays comprising a large number of individual printing devices. Furthermore, small ejection orifices are unnecessary, so acoustic printing is compatible with a greater variety of inks than conventional ink jet printing, including inks having higher viscosities, and inks containing pigments and other particulate components.
  • the radiation pressure which the beam exerts may reach a sufficiently high level to eject individual droplets of liquid from the surface of the pool, despite the restraining force of surface tension.
  • the acoustic beam advantageously is brought to a focus on or near the surface of the pool, thereby intensifying its radiation pressure for a given amount of input power.
  • spherical piezoelectric shells as used as transducers for supplying focused acoustic beams to eject droplets of ink from the free surface of a pool of ink.
  • Acoustic horns driven by planar transducers, may also be used to eject droplets of ink from an ink-coated belt.
  • the fundamental factors which underlie the perceived quality of a printed image are its resolution (i. e., the pixel density), the optical density of its individual pixels (i. e., gray scale), and the size of the individual pixels. Images having a generally uniform, high contrast and a moderate resolution usually are satisfactory for the printing of text and other alphanumerics. However, increased resolution and controlled shading will notably enhance the perceived quality of more complex printed images, such as pictorial representations. As is known, some modern digital printers utilize half-tone screening patterns for image shading, while others utilize gray scale control techniques for that purpose. Half-tone screening involves the processing of groups of spatially adjacent pixels on a cell-by-cell basis to create a half-toning effect.
  • Gray scale control adjusts the shading of the printed image by increasing and decreasing the optical densities of its individual pixels.
  • a similar effect i. e., a psuedo-gray scale effect
  • This technique provides a gray scale representation because the resolutions which are normally used for printing are sufficiently high to cause the human eye to blur or average the adjacent pixels of the image.
  • the trajectory with which the ink droplets are propelled from the free surface of the ink supply to a nearby record medium is sufficiently well defined and repeatable that multiple droplets can be deposited on the record medium in rapid sequence, one on top of the other, before the ink has time to dry, to print variable diameter pixels or spots.
  • the control techniques of this invention may be employed for variable resolution printing and for imparting a controlled pseudo-gray scale shading to the printed image.
  • Each of the pixels of the printed image may be composed of a single cell for one spot per pixel printing or may be subdivided into a plurality of cells for multiple spot per pixel printing.
  • Fig. 1 shows an acoustic printer 11 having a droplet ejector 12 for printing an image on a suitable record medium 13.
  • This simplified embodiment illustrates the application of the present invention to acoustic printers in general because it will be understood that the droplet ejector 12 may be replicated to provide an array of such devices.
  • droplet ejector arrays of various geometries can be constructed to perform, for example, line printing, matrix printing, and multi-line raster scan printing.
  • the record medium 13 is wrapped around and secured (by means not shown) to a drum 14 which, in turn, is rotated at a fast scan rate in the direction of the arrow 15 while being axially translated at a slow scan rate in the direction of the arrow 16 (by means also not shown).
  • the record medium 13 is advanced relative to the ejector 12 in accordance with a suitable raster scanning pattern.
  • the slow-scan component of the relative motion could be provided by mounting the ejector 12 on a carriage for translation axially of the rotating drum 14 at the slow-scan rate.
  • the drum 14 could be eliminated in favor of employing pinch rollers 17, 18 and 19, 20 for translating the record medium 13 back and forth in the fast-scan direction.
  • a controller 21 supplies a pulsed rf drive voltage (Fig. 3) for driving the droplet ejector 12.
  • this drive voltage causes the droplet ejector 12 to launch a converging acoustic beam 22 into an ink supply 23, such as an ink-filled pool, such that the acoustic beam 22 is brought to focus approximately at the free surface (i. e., liquid/air interface) 24 thereof.
  • the controller 21 modulates the amplitude, frequency or duration of the rf voltage applied to the transducer to control the pressure which the acoustic beam 22 exerts against the free surface 24, so that individual droplets of ink 25 (Fig.
  • the droplet ejector 12 is submerged in the ink supply 23.
  • it may be acoustically coupled to the ink supply 23 through an intermediate medium (not shown).
  • the ink 23 can be carried on a suitable transport, such as a thin film of 'Mylar' or like sheet material, and the droplet ejector 12 can be acoustically coupled to the ink 23 via a liquid and/or solid interface layer.
  • the pressure which the acoustic beam 22 exerts against the free surface 24 of the ink supply 23 is controlled with respect to the threshold pressure required to release individual droplets of ink 25 from the surface 24.
  • This threshold is dependent on the surface tension of the particular ink that is employed and may be determined empirically.
  • provision advantageously is made for maintaining the free surface 24 of the ink supply 23 at a fixed distance from the droplet ejector 12 (i. e., in the focal plane of the droplet ejector 12).
  • Various techniques may be employed to accomplish that. For instance, as shown in Fig.
  • a closed loop control system 31 comprising a laser 32 for supplying a light beam 33 which strikes the free surface 24 of the ink supply 23 at a grazing angle of incidence, together with a split photodetector 34 which intercepts the light beam 33 after it reflects from the surface 24.
  • the photodetector 34 is optically aligned so that the light beam 33 centers on it only if the free surface 24 of the ink supply 23 is at its desired set level. Thus, any significant change in the level of the surface 24 unbalances the outputs of the photodetector 34, thereby causing a differential amplifier 35 to supply an error signal for energizing a motor 36.
  • the motor 36 drives a plunger 37 of an ink-filled pump 38 to add or drain ink from the ink supply 23 via a supply line 39 as required to restore its free surface 24 to the desired set level.
  • a knife-edge liquid level control technique such as shown in US-A-4,580,148 could be utilized.
  • the droplet ejector 12 comprises an acoustic lens 41 which is irradiated by an acoustic wave 42 that is generated by a piezoelectric transducer 43 in response to the rf drive voltage supplied by the controller 21.
  • the lens 41 is defined by a small part-spherical cavity or indentation which is formed in a surface (e.
  • a solid substrate 44 which, in turn, is composed of a material, such as silicon, silicon nitride, silicon carbide, alumina, sapphire, fused quartz, and certain glasses, having an acoustic velocity which is much higher than the acoustic velocity of the ink 23.
  • the piezoelectric transducer 43 is deposited on or otherwise intimately mechanically coupled to the opposite or lower surface of the substrate 44.
  • the rf voltage supplied by the controller 21 is applied across the transducer 43, thereby exciting it into oscillation to generate the acoustic wave 42 in the substrate 44.
  • the wave 42 propagates through the substrate 44 at a relatively high speed until it strikes the lens 41, from which it emerges into a medium (e. g., the ink supply 23, as shown) having a much lower acoustic velocity. Accordingly, the lens 41 imparts a spherical wavefront to the acoustic wave 42, thereby producing the converging beam 22.
  • the change in the refractive index as measured by the change in the acoustic velocity across the interface between the substrate 44 and the ink 23 is large, and the angle of refraction for rays crossing this interface also is large, with the result that the focal length of the lens 41 is roughly equal to its radius of curvature.
  • the focal length of the lens 41 is roughly equal to its radius of curvature.
  • the aperture of the lens 41 is about the same as its focal length (f number ⁇ 1)
  • the waist diameter of the acoustic beam 22 at focus is approximately equal to its wavelength.
  • the acoustic velocity of the substrate 44 may be only about 2.5 times higher than the acoustic velocity of the ink 23.
  • the aberrations can be reduced to a negligibly-low level, simply by fabricating the substrate 44 from a material having an acoustic velocity which is roughly four or more times higher than the acoustic velocity of the ink 23. That is practical because the acoustic velocity of the ink 23 typically is only about 1 - 2 km/sec.
  • this droplet size control technique is effective, its utility may be limited if the transducer 43 is tuned to have a narrow band resonant response characteristic in the interest of increasing its efficiency.
  • the frequency of the voltage supplied by the controller 21 can be switched, such as under the control of an operator, between the fundamental resonant frequency of the transducer 43 and an odd harmonic of that frequency. This is a relatively coarse adjustment, but it may be utilized, for example, to change the size of the ink droplets 25 for printing at different resolutions.
  • the size of the ink droplets 25 also may be varied by having the controller 21 modulate the duration, ⁇ (Fig. 3), of the rf pulses it applies to the transducer 43. It has been found that pulse width modulation may be employed to vary continuously the diameter of the droplets 25 over a range from about one wavelength ( ⁇ i ) to about two wavelengths (2 ⁇ i ), which means that it is well suited for imparting a controlled shading to the printed image. In practice pulse widths, ⁇ , varying between about 1 ⁇ sec and 50 ⁇ sec are adequate to affect a factor of two change in droplet diameter at 50 MHz. A similar effect can be achieved by modulating the amplitude of the rf pulses applied to the transducer 43, but amplitude modulation does not appear to provide as much control over the size of the droplets 25 as does pulse width modulation.
  • these droplets 25 appear to agglomerate to form a spot 51 having a diameter equal to approximately 2dn 1/3 , where d is the droplet diameter, and n is the number of droplets 25 that are provided to print the spot 51.
  • the factor of 2 in the foregoing expression assumes that the diameter of the droplets 25 is substantially constant and is based on the observation that the diameter of the spot printed on paper by a droplet of ink is approximately twice the diameter of the droplet.
  • each of the pixels may be composed of a plurality of cells 52a - 52d which are more or less symmetrically distributed about the center 53 of the pixel, and the size of the spots 54a - 54d printed in the cells 52a - 52d may be controlled as described above to provide a selection of X(N + 1) different apparent shades of gray for printing, where X is the number of cells per pixel. For example, it has been demonstrated that sixty four shades of gray can be produced with four cells 52a - 52d per pixel.
  • the present invention may be applied to acoustic printers having other types of droplet ejectors.
  • this invention appears to be compatible with the piezoelectric spherical shell transducer 61, which is shown in Fig. 6 and described in the aforementioned US-A-4 308 547. It also is believed to be compatible with the interdigitated transducer (IDT) 62, which is shown in Fig. 7.
  • IDT interdigitated transducer
  • the present invention provides a variety of methods and means for manually or automatically varying the size of the pixels or spots printed by an acoustic printer of the type in which one or more droplet ejectors are driven by rf voltage pulses to produce focused acoustic beams for ejecting droplets of ink on demand from a free surface of an ink supply.
  • These control techniques may be employed individually or in combination with each other for printing at different resolutions and/or for imparting a controlled gray scale shading to the printed image.
  • the droplet size control techniques of this invention are not necessarily limited to acoustic printing.

Landscapes

  • Particle Formation And Scattering Control In Inkjet Printers (AREA)
EP19870311224 1986-12-19 1987-12-18 Tröpfchenejektor Expired - Lifetime EP0273664B1 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US94428686A 1986-12-19 1986-12-19
US944286 1986-12-19

Publications (3)

Publication Number Publication Date
EP0273664A2 true EP0273664A2 (de) 1988-07-06
EP0273664A3 EP0273664A3 (en) 1989-05-24
EP0273664B1 EP0273664B1 (de) 1993-07-14

Family

ID=25481135

Family Applications (1)

Application Number Title Priority Date Filing Date
EP19870311224 Expired - Lifetime EP0273664B1 (de) 1986-12-19 1987-12-18 Tröpfchenejektor

Country Status (3)

Country Link
EP (1) EP0273664B1 (de)
JP (1) JPS63166545A (de)
DE (1) DE3786542T2 (de)

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0375433A2 (de) * 1988-12-21 1990-06-27 Xerox Corporation Akustischer Tintendrucker mit gegenüber der Brennweite verminderter Empfindlichkeit
EP0550192A2 (de) * 1991-12-30 1993-07-07 Xerox Corporation Akustischer Tintendrucker
DE4415771A1 (de) * 1993-05-14 1994-11-17 Fujitsu Ltd Ultraschalldrucker
US5412413A (en) * 1989-12-22 1995-05-02 Ricoh Co., Ltd. Method and apparatus for making liquid drop fly to form image by generating bubble in liquid
EP0728584A2 (de) * 1995-02-21 1996-08-28 Kabushiki Kaisha Toshiba Tintenstrahldrucker
US5629724A (en) * 1992-05-29 1997-05-13 Xerox Corporation Stabilization of the free surface of a liquid
EP0845364A2 (de) * 1996-10-22 1998-06-03 Hewlett-Packard Company Verfahren und Gerät zur Verbesserung der Bildqualität
EP0881082A3 (de) * 1997-05-29 2000-05-03 Xerox Corporation Vorrichtung und Verfahren zum Bilden eines Bildes mit Reduzierung der Fehler
US6443547B1 (en) 2000-05-08 2002-09-03 Fuji Xerox Co., Ltd. Driving device for inkjet recording apparatus and inkjet recording apparatus using the same
EP1294578B2 (de) 2000-06-26 2018-10-17 Interglarion Limited Verfahren, vorrichtung und system zum herstellen von bauteilen mit vorbestimmtem oberflächenaussehen, insbesondere von frontplatten von küchenelementen

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP3296213B2 (ja) * 1996-10-30 2002-06-24 三菱電機株式会社 液体エジェクタおよび液体エジェクタを用いる印刷装置
JPH11334102A (ja) 1998-05-25 1999-12-07 Mitsubishi Electric Corp インクジェット式プリンタ、気泡検出回路及び気泡検出方法
JP2002036534A (ja) 2000-05-16 2002-02-05 Fuji Xerox Co Ltd 音響プリンタの駆動回路及び音響プリンタ
US7637585B2 (en) 2007-06-05 2009-12-29 Hewlett-Packard Development Company, L.P. Halftone printing on an inkjet printer

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2623768A1 (de) * 1975-06-02 1976-12-16 Teletype Corp Verfahren und vorrichtung zur wiedergabe von halbtonbildern
US4308547A (en) * 1978-04-13 1981-12-29 Recognition Equipment Incorporated Liquid drop emitter
US4499479A (en) * 1982-08-30 1985-02-12 International Business Machines Corporation Gray scale printing with ink jet drop-on demand printing head
EP0147575A2 (de) * 1983-12-16 1985-07-10 International Business Machines Corporation Tintenstrahldrucker mit gesteuerter Tropfenerzeugung

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2623768A1 (de) * 1975-06-02 1976-12-16 Teletype Corp Verfahren und vorrichtung zur wiedergabe von halbtonbildern
US4308547A (en) * 1978-04-13 1981-12-29 Recognition Equipment Incorporated Liquid drop emitter
US4499479A (en) * 1982-08-30 1985-02-12 International Business Machines Corporation Gray scale printing with ink jet drop-on demand printing head
EP0147575A2 (de) * 1983-12-16 1985-07-10 International Business Machines Corporation Tintenstrahldrucker mit gesteuerter Tropfenerzeugung

Cited By (18)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0375433A3 (en) * 1988-12-21 1990-09-12 Xerox Corporation Acoustic ink printers having reduced focusing sensitivity
EP0375433A2 (de) * 1988-12-21 1990-06-27 Xerox Corporation Akustischer Tintendrucker mit gegenüber der Brennweite verminderter Empfindlichkeit
US5412413A (en) * 1989-12-22 1995-05-02 Ricoh Co., Ltd. Method and apparatus for making liquid drop fly to form image by generating bubble in liquid
EP0550192A2 (de) * 1991-12-30 1993-07-07 Xerox Corporation Akustischer Tintendrucker
EP0550192A3 (en) * 1991-12-30 1993-11-10 Xerox Corp Acoustic ink printer
US5629724A (en) * 1992-05-29 1997-05-13 Xerox Corporation Stabilization of the free surface of a liquid
DE4415771A1 (de) * 1993-05-14 1994-11-17 Fujitsu Ltd Ultraschalldrucker
US5612723A (en) * 1993-05-14 1997-03-18 Fujitsu Limited Ultrasonic printer
DE4415771C2 (de) * 1993-05-14 1999-10-21 Fujitsu Ltd Ultraschalldrucker
EP0728584A2 (de) * 1995-02-21 1996-08-28 Kabushiki Kaisha Toshiba Tintenstrahldrucker
EP0728584A3 (de) * 1995-02-21 1997-05-14 Toshiba Kk Tintenstrahldrucker
US5912679A (en) * 1995-02-21 1999-06-15 Kabushiki Kaisha Toshiba Ink-jet printer using RF tone burst drive signal
EP0845364A2 (de) * 1996-10-22 1998-06-03 Hewlett-Packard Company Verfahren und Gerät zur Verbesserung der Bildqualität
EP0845364A3 (de) * 1996-10-22 1998-07-01 Hewlett-Packard Company Verfahren und Gerät zur Verbesserung der Bildqualität
US5997132A (en) * 1996-10-22 1999-12-07 Hewlett-Packard Company Method and apparatus for improving image quality
EP0881082A3 (de) * 1997-05-29 2000-05-03 Xerox Corporation Vorrichtung und Verfahren zum Bilden eines Bildes mit Reduzierung der Fehler
US6443547B1 (en) 2000-05-08 2002-09-03 Fuji Xerox Co., Ltd. Driving device for inkjet recording apparatus and inkjet recording apparatus using the same
EP1294578B2 (de) 2000-06-26 2018-10-17 Interglarion Limited Verfahren, vorrichtung und system zum herstellen von bauteilen mit vorbestimmtem oberflächenaussehen, insbesondere von frontplatten von küchenelementen

Also Published As

Publication number Publication date
DE3786542D1 (de) 1993-08-19
JPS63166545A (ja) 1988-07-09
EP0273664B1 (de) 1993-07-14
DE3786542T2 (de) 1993-10-28
EP0273664A3 (en) 1989-05-24

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