EP0739732B1 - Tête d'impression acoustique à encre avec distance focale variable - Google Patents

Tête d'impression acoustique à encre avec distance focale variable Download PDF

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Publication number
EP0739732B1
EP0739732B1 EP19960302898 EP96302898A EP0739732B1 EP 0739732 B1 EP0739732 B1 EP 0739732B1 EP 19960302898 EP19960302898 EP 19960302898 EP 96302898 A EP96302898 A EP 96302898A EP 0739732 B1 EP0739732 B1 EP 0739732B1
Authority
EP
European Patent Office
Prior art keywords
ink
acoustic
substrate
lenses
focal length
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.)
Expired - Lifetime
Application number
EP19960302898
Other languages
German (de)
English (en)
Other versions
EP0739732A1 (fr
Inventor
Martin G. Lim
Babur B. Hadimioglu
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
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Xerox Corp
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Filing date
Publication date
Application filed by Xerox Corp filed Critical Xerox Corp
Publication of EP0739732A1 publication Critical patent/EP0739732A1/fr
Application granted granted Critical
Publication of EP0739732B1 publication Critical patent/EP0739732B1/fr
Anticipated expiration legal-status Critical
Expired - Lifetime 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
    • B41J2/135—Nozzles
    • B41J2/14—Structure thereof only for on-demand ink jet heads
    • B41J2/14008—Structure of acoustic ink jet print heads
    • 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
    • B41J2/135—Nozzles
    • B41J2/14—Structure thereof only for on-demand ink jet heads
    • B41J2002/14322—Print head without nozzle

Definitions

  • the present invention relates generally to acoustic ink printers with lenses for focusing acoustic energy. More particularly, the present invention relates to an acoustic ink printer head having an ink filled channel that supports varying focal length fresnel lenses positioned along the channel.
  • Acoustic ink printing systems provide a nozzleless alternative to conventional thermal ink jet systems. Instead of supporting a large number of easily clogged nozzles, acoustic ink printing systems typically use an ink covered printhead that supports multiple acoustic lenses. Each of the acoustic lens attached to the printhead can focus a beam of sound energy against a free surface of the ink. This focused acoustic beam exerts sufficient acoustic radiation pressure against the surface to cause ejection of individual droplets of ink, which are directed to impact upon a sheet of paper or other printing medium.
  • Precise control of droplets ejected by acoustic ink printheads conventionally is performed by independently modulating the rf excitation of acoustic radiators acoustically coupled to the acoustic lenses.
  • the acoustic radiators (commonly piezoelectric transducers) are amplitude modulated in accordance with a desired input pattern that typically corresponds to pixel level representations of text or imagery. Modulating the transducers in this defined input pattern transiently increases the acoustic radiation pressure to generate brief, controlled excursions to a sufficiently high pressure level for overcoming the ink restraining force of surface tension.
  • acoustic ink printing does not rely upon easily clogged nozzles or small ejection orifices, eliminating mechanical constraints that cause many of the reliability and pixel placement accuracy problems in conventional drop on demand or continuous stream ink jet printers.
  • an acoustic ink printhead must be supplied with a constant and consistent flow of ink to present a stable ink ejection surface.
  • Use of a flowing and appropriately filtered ink supply system also simplifies stabilization of ink temperature, keeps the ink free of various contaminants, and encourages mixing of ink constituents to minimize adverse differential ink evaporation effects that may reduce uniformity of the ink composition and the associated uniformity of droplet ejection.
  • one problem with a flowing ink supply relates to equalization of hydrostatic pressure of the free ink surfaces associated with each acoustic lens. Differing hydrostatic pressures resulting from viscous resistance to fluid flow leads to differing distances between the free surface of the ink and each acoustic lens. If this change in distance is substantial (e.g., greater than a few ⁇ m), an individual acoustic lens in an array of identical lenses may be focused above or below the free surface of the ink, rather than at the surface, eliminating uniformity of droplet ejection, and reducing print reliability.
  • Equalization of pressure may be relatively simple with a small number of lenses and consequently limited ink flow path, but as the number of lenses increases (and with it the required free surface ink flow path) in higher-performance and higher-resolution printers, the ink supply system for delivering ink to the lenses becomes more complex and the equalization of pressure at each lens more difficult.
  • EP-A-550,148 discloses an acoustic ink printhead, according to the preambles of claims 1 and 5, employing a flowing stream of ink past the ejectors to maintain a fresh ink supply at the ejector sites.
  • An apertured plate-like member aligned with the ejector sites suppresses sideways droplet ejection components.
  • a secondary pressure field using acoustic pulses or a pulsed heater provides dynamic level control in addition to controlled switching of the ink droplets.
  • acoustic radiators which are focused diffractively by multi-discrete-phase binary Fresnel lenses are provided for applications, such as acoustic ink printing.
  • Standard semiconductor integrated circuit techniques are available for fabricating such lenses in compliance with design specifications having relatively tight tolerances, including specifications for integrated lens arrays demanding substantial precision in the relative spatial positioning of several lenses.
  • the diffractive performance of these lenses simulate concave refractive lenses, even though the lenses preferably have generally flat geometries.
  • the lenses are defined by patterning acoustically flat surfaces, such as an acoustically flat face of a substrate or an acoustically flat face of a layer of etchable material which is grown or otherwise deposited on an acoustically flat surface of an etch resistant substrate.
  • the present invention provides an acoustic ink printhead according to claims 1 and 5 of the appended claims.
  • the present invention substantially mitigates the problem of pressure equalization of the free ink surfaces in an acoustic ink printer with a constant flow ink transport system.
  • focal length of acoustic lenses positioned adjacent to the ink outlet is less than the focal length of acoustic lenses positioned adjacent to the ink inlet.
  • the focal length of the acoustic lenses sequentially decreases between the ink inlet and the ink outlet to compensate for the progressive reduction in surface level of the ink.
  • Each acoustic lens in an array of acoustic lenses is adjusted to have a focal length that ensures focusing a predefined acoustic frequency at the surface level of ink flowing above the respective lens, consequently reducing non-uniformity in droplet size, speed, and travel characteristics.
  • an acoustic ink printhead that includes a plurality of channels configured to receive ink has well defined hydrostatic characteristics in each channel, with the free surface level diminishing along the channel between the inlet and outlet. This is particularly true when each channel is connected to a common inlet manifold and a common outlet manifold, so that inlet pressure and outlet pressure (and ink flow velocity) in all channels is substantially equal.
  • a linear array of channels with a sequentially decreasing hydrostatic pressure easily supports use of varying focal length acoustic lenses constructed as multiphase Fresnel lenses.
  • Standard semiconductor integrated circuit techniques are available for fabricating these lenses in compliance with design specifications. Such construction permits relatively tight tolerances, allowing for integrated lens arrays demanding substantial precision in the relative spatial positioning of several lenses.
  • the diffractive performance of these lenses simulate concave refractive lenses, even though the lenses provided by this invention preferably have generally flat geometries.
  • Use of fresnel lenses simplifies machining, etching, growing, or otherwise depositing an acoustic lens having the required focal length on a flat surface such as a channel bottom of an acoustic printhead.
  • FIG. 1 An acoustic ink printhead system is illustrated in Figures 1, 2, and 3.
  • the system 10 includes a printhead 12, with an inlet 18 and an outlet 20, coupled in fluid communication to an ink pump 14 and heater 16 for recirculation of ink.
  • Ink entering the printhead 12 through inlet 18 is distributed by inlet manifold 22 to a plurality of longitudinally extending channels 26 inscribed in the printhead 12.
  • acoustic lenses 28 typically being a spherical lens or a fresnel lens having a ring structure 42 such as shown in Figure 3-5.
  • the acoustic lenses 28 provide an array of electronically controlled ink ejectors that are capable of forcing ejection of an ink droplet from an ink surface in response to application of a suitable frequency and amplitude of focused acoustic energy.
  • the ejected ink droplet can be directed to contact a piece of paper or other recording medium (not shown).
  • the ink After moving through the channels 26, the ink enters an outlet manifold 24 that funnels the ink to the outlet 20 for passage into pump 14.
  • the ink is filtered and reheated by ink heater 16 to ensure maintenance of optimal flow characteristics, and again directed to enter the printhead through inlet 18.
  • each channel 26 in printhead 12 is defined in a top plate 34, the top plate in turn being integrally bonded to a glass substrate 36 supporting the acoustic lenses 28.
  • Ink 30 having an ink surface 32 flows along the channel over the acoustic lenses 28, which are individually controlled by application of a matching number of transducers 38.
  • the transducers 38 are positioned beneath the acoustic lenses 28 to supply acoustic energy that can be focused to emit an ink droplet 40.
  • the Fresnel-type acoustic lenses 28 positioned at the base of the ink containing channels 26 can be fabricated through the use of a conventional photolithographic patterning process.
  • a conventional photolithographic patterning process For example, an acoustically flat layer of etchable material (e.g., amorphous silicon or oxynitride) is grown or otherwise deposited on an acoustically flat face of an etch resistant substrate 36, such as a quartz or glass substrate.
  • etchable material e.g., amorphous silicon or oxynitride
  • the thickness of the acoustic lenses 28 can be controlled with sufficient precision while being deposited to yield an acoustically flat layer having a thickness essentially equal to the height of the highest desired phase steps of the Fresnel lenses, so that no further pre-etch processing is required.
  • radiofrequency (rf) drive voltages are applied across the piezoelectric transducers 38 (by means not shown) on spatially separated centers each acoustically aligned with the acoustic lenses 28.
  • the excited transducers 38 generate longitudinally propagating acoustic plane waves (schematically illustrated as waves 50 in Figure 3)within the substrate 36 for substantially independent, axial illumination of each of the acoustic lenses at near normal angles of incidence.
  • the acoustic lenses 28 are acoustically coupled to the ink 30, either directly (as shown in the Figures) or through an intermediate monolayer or multilayer acoustic coupling medium.
  • text or images based on the pattern of ejected droplets on paper (or other suitable media) can be created.
  • This focal point changes along the channel, because the distance between the ink surface 32 and the base of the channel 26 diminishes as a function of the corresponding pressure drop (attributable mainly to fluid resistance against walls and bottom of the channel) between the inlet 18 and the outlet 20.
  • a suitable mechanism must be employed to maintain focus of the acoustic lenses 28 at designated positions on the ink surface 32 along the channel, even though a pressure drop corresponding to an ink surface level drop of fifty (50) microns or more may exist in the channel between inlet and outlet.
  • the present invention alleviates the problems associated with pressure drop by adjusting the focal length of the acoustic lenses 28.
  • Fresnel lenses such as seen in top view in Figure 4, and in cross section in Figure 5, can have their ring spacing slightly altered, along with other appropriate modifications known to those skilled in the art, to decrease the focal length of acoustic lenses as one proceeds from the inlet toward the outlet of each channel in the printerhead.
  • Figure 6 illustrates a profile of a four phase Fresnel lens suitable for positioning adjacent to the inlet of the channel, with an acoustic lens to surface distance of 360 microns, and the same focal length.
  • Figure 7 illustrates a Fresnel lens suitable for positioning in the same channel, but adjacent to the outlet. At this position, the acoustic lens to surface distance is 350 ⁇ m, requiring a slightly changed focal length to ensure focusing of acoustic energy at the ink surface.

Landscapes

  • Particle Formation And Scattering Control In Inkjet Printers (AREA)

Claims (10)

  1. Tête d'impression acoustique à encre (12) comprenant :
    un substrat (36) revêtu d'une couche d'encre ayant une surface d'encre (32), la distance entre le substrat (36) et la surface d'encre (32) étant variable sur toute l'étendue du substrat (36), et
    une pluralité de lentilles acoustiques (28) définies dans le substrat (36), chaque lentille acoutique (28) ayant une distance focale respective prédéfinie, caractérisée en ce que la distance focale respective varie pour correspondre à la distance variable entre le substrat (36) et la surface d'encre (32).
  2. Tête d'impression acoustique à encre selon la revendication 1, dans laquelle le substrat (36) comprend en outre une pluralité de rainures (26) ayant une configuration pour recevoir de l'encre, chaque rainure étant reliée à un distributeur d'entrée (22) et à un distributeur de sortie (24).
  3. Tête d'impression acoustique à encre selon la revendication 2, dans laquelle la distance focale des lentilles acoustiques (28) qui sont adjacentes au distributeur de sortie (24) est inférieure à la distance focale des lentilles acoustiques (28) qui sont positionnées au voisinage du distributeur d'entrée (22).
  4. Tête d'impression acoustique à encre selon la revendication 2 ou 3, dans laquelle la distance focale des lentilles acoustiques (28) diminue par séquences entre l'orifice d'entrée d'encre (18) et l'orifice de sortie d'encre (20) pour compenser une chute de pression et une réduction de distance entre le substrat (36) et la surface d'encre (32) pour une couche d'encre s'écoulant à travers la rainure (26).
  5. Tête d'impression acoustique à encre (12) comprenant :
    un substrat (36) possédant un côté entrée et un côté sortie, le substrat ayant une configuration pour supporter l'encre s'écoulant depuis le coté d'entrée vers le côté sortie,
    une pluralité de lentilles acoustiques (28) accouplées acoustiquement au substrat (36), chaque lentilles acoustiques ayant une distance focale respective prédéfinie pour focaliser l'énergie acoustique au niveau d'une position associée adjacente au substrat (36), caractérisée en ce que la dite distance focale respective de ces lentilles acoustiques (28) accouplées acoustiquement au voisinage du côté entrée du substrat (36) est plus grande que la distance focale respective des lentilles acoustiques (28) accouplées acoustiquement au voisinage du côté sortie du substrat (36).
  6. Tête d'impression acoustique à encre selon les revendications 5, dans laquelle le substrat (36) est grave pour définir la dite pluralité de lentilles acoustiques (28).
  7. Tête d'impression acoustique à encre selon la revendication 5 ou 6, dans laquelle la distance focale des lentilles acoustiques diminue par séquences entre l'orifice d'entrée d'encre (18) et l'orifice de sortie d'encre (20) pour compenser la chute de pression et la réduction du niveau de la surface de l'encre s'écoulant à travers la rainure.
  8. Tête d'impression acoustique à encre selon l'une quelconque des revendications 5 à 7, comprenant en outre une pompe à encre pour remettre en circulation l'encre provenant du côté sortie d'encre pour la faire revenir vers le côté entrée d'encre.
  9. Tête d'impression acoustique à encre selon l'une quelconque des revendications précédentes, dans laquelle les lentilles acoustiques sont des lentilles de Fresnel à plusieurs phases.
  10. Tête d'impression acoustique à encre selon l'une quelconque des revendications 5 à 7, dans laquelle le substrat (36) comprend en outre une pluralité de rainures (26) ayant une configuration pour recevoir de l'encre, chaque rainure étant reliée à un distributeur d'entrée (22) et à un distributeur de sortie (24).
EP19960302898 1995-04-27 1996-04-25 Tête d'impression acoustique à encre avec distance focale variable Expired - Lifetime EP0739732B1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US43119595A 1995-04-27 1995-04-27
US431195 1995-04-27

Publications (2)

Publication Number Publication Date
EP0739732A1 EP0739732A1 (fr) 1996-10-30
EP0739732B1 true EP0739732B1 (fr) 1998-12-30

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EP19960302898 Expired - Lifetime EP0739732B1 (fr) 1995-04-27 1996-04-25 Tête d'impression acoustique à encre avec distance focale variable

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EP (1) EP0739732B1 (fr)
JP (1) JPH08309968A (fr)
DE (1) DE69601245T2 (fr)

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6364454B1 (en) * 1998-09-30 2002-04-02 Xerox Corporation Acoustic ink printing method and system for improving uniformity by manipulating nonlinear characteristics in the system
JP2009292106A (ja) 2008-06-09 2009-12-17 Casio Comput Co Ltd 画像形成装置

Family Cites Families (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3211088A (en) * 1962-05-04 1965-10-12 Sperry Rand Corp Exponential horn printer
CA1265702A (fr) * 1985-09-16 1990-02-13 Calvin F. Quate Dispositif sans buses pour l'ejection de gouttelettes
JPH0775890B2 (ja) * 1988-12-21 1995-08-16 ゼロックス コーポレーション 音響インクプリンタ
US5041849A (en) * 1989-12-26 1991-08-20 Xerox Corporation Multi-discrete-phase Fresnel acoustic lenses and their application to acoustic ink printing
US5087931A (en) * 1990-05-15 1992-02-11 Xerox Corporation Pressure-equalized ink transport system for acoustic ink printers
US5229793A (en) * 1990-12-26 1993-07-20 Xerox Corporation Liquid surface control with an applied pressure signal in acoustic ink printing
DE69214418T2 (de) * 1991-12-30 1997-03-06 Xerox Corp Akustischer Tintendruckkopf mit einem gelöcherten Element und einem Tintenfluss
US5629724A (en) * 1992-05-29 1997-05-13 Xerox Corporation Stabilization of the free surface of a liquid

Also Published As

Publication number Publication date
DE69601245D1 (de) 1999-02-11
EP0739732A1 (fr) 1996-10-30
JPH08309968A (ja) 1996-11-26
DE69601245T2 (de) 1999-06-02

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