CN102164748B - Efficient inkjet nozzle assembly - Google Patents

Efficient inkjet nozzle assembly Download PDF

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Publication number
CN102164748B
CN102164748B CN2008801312253A CN200880131225A CN102164748B CN 102164748 B CN102164748 B CN 102164748B CN 2008801312253 A CN2008801312253 A CN 2008801312253A CN 200880131225 A CN200880131225 A CN 200880131225A CN 102164748 B CN102164748 B CN 102164748B
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China
Prior art keywords
ink
nozzle assembly
actuator
active beam
inkjet nozzle
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CN2008801312253A
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CN102164748A (en
Inventor
G·J·麦克沃依
K·西尔弗布鲁克
V·P·劳勒
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Memjet Technology Ltd
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Silverbrook Research Pty Ltd
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    • 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
    • B41J2/14427—Structure of ink jet print heads with thermal bend detached actuators
    • 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
    • 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
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B81—MICROSTRUCTURAL TECHNOLOGY
    • B81B—MICROSTRUCTURAL DEVICES OR SYSTEMS, e.g. MICROMECHANICAL DEVICES
    • B81B3/00—Devices comprising flexible or deformable elements, e.g. comprising elastic tongues or membranes
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B81—MICROSTRUCTURAL TECHNOLOGY
    • B81B—MICROSTRUCTURAL DEVICES OR SYSTEMS, e.g. MICROMECHANICAL DEVICES
    • B81B7/00—Microstructural systems; Auxiliary parts of microstructural devices or systems
    • 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
    • B41J2/14427—Structure of ink jet print heads with thermal bend detached actuators
    • B41J2002/14435—Moving nozzle made of thermal bend detached actuator

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  • Engineering & Computer Science (AREA)
  • Computer Hardware Design (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • Particle Formation And Scattering Control In Inkjet Printers (AREA)

Abstract

An inkjet nozzle assembly comprising: a nozzle chamber for containing ink, the chamber having a nozzle opening and an ink inlet; a pair of electrical contacts positioned at one end of the assembly and connected to drive circuitry; and a thermal bend actuator for ejecting ink through the nozzle opening, the actuator comprising an active beam connected to the electrical contacts and extending longitudinally away from the contacts, the active beam defining a bent current flow path between the contacts; and a passive beam fused to the active beam, such that when a current is passed through the active beam, the active beam heats and expands relative to the passive beam resulting in bending of the actuator, wherein the actuator has a working face for generating a positive pressure pulse in the ink during the bending of the actuator, the working face having an area of less than 800 square microns.

Description

The inkjet nozzle assembly
Technical field
The present invention relates to the inkjet nozzle assembly.The present invention is mainly used in improving efficient and the raising drop spray characteristic that thermal flexure activates inkjet nozzle.
Background technology
The applicant had before described the numerous MEMS inkjet nozzles that use thermal flexure to activate.Thermal flexure activates and typically refers to the bending motion that a kind of electric current produces with respect to another kind of material coefficient of thermal expansion from its material that flows through.Can utilize the bending motion of generation from the nozzle opening ink-jet, randomly carry out ink-jet by the motion of blade or blade, the motion of described blade or blade produces pressure wave in nozzle chambers.
In the superincumbent cross reference part listed patent and patent application illustrated the thermal flexure inkjet nozzle of some typical types, its content is incorporated herein by reference.
Applicant's U.S. Patent No. 6,416,167 has been described a kind of inkjet nozzle, the thermal bend actuator that it has the blade that is arranged in nozzle chambers and is positioned at the nozzle chambers outside.Actuator adopts the bottom active beam form of being made by conductive material (for example titanium nitride) be fusion welded to the top passive beam made by non-conductive material (for example silica).Actuator is connected to blade by the arm that passes the slit that is arranged in nozzle chamber walls and admitted.When electric current flow through the bottom active beam, actuator was bent upwards, and therefore, the nozzle opening of blade in being limited to the nozzle chambers top moves, thus the ejection ink droplet.The advantage of this design is that it is simple in structure.The defective of this design is that two surfaces of blade all will be to the ink of thickness acting relatively in the nozzle chambers.
Applicant's U.S. Patent No. 6,260,953 has been described a kind of inkjet nozzle, and wherein, actuator forms the mobile top of nozzle chambers.Actuator is taked the form of the spiral core made by the conductive material of polymeric material parcel.When activating, actuator is towards the nozzle chambers bottom bend, increases cavity pressure and with the nozzle opening ejection of ink droplet from be limited to top of chamber.Nozzle opening is limited in the non-moving part at top.The advantage of this design is that mobile top has only a surface must the ink of the relative thickness in the nozzle chambers be done work.The defective of this design is, is difficult to realize in the MEMS manufacturing process by being aggregated the spiral transport element structure actuator that material wraps up.
Applicant's U.S. Patent No. 6,623,101 has been described a kind of inkjet nozzle, and it comprises the nozzle chambers with active tip, and described active tip has the nozzle opening that is limited to wherein.Active tip is connected to the thermal bend actuator that is positioned at the nozzle chambers outside by arm.Actuator adopts the top active beam form that separates with the bottom passive beam.Because passive beam can not separate by making active beam and passive beam as the heat abstractor of active beam, it is maximum that thermal flexure efficient reaches.When electric current flows through the top active beam, cause that having the active tip that is limited to nozzle opening wherein rotates towards the nozzle chambers bottom, thereby spray by nozzle opening.Because nozzle opening moves with the top, can be by suitably improving the shape control drop heading of nozzle edge.The advantage of this design is that mobile top has only a surface must the ink of relative thickness in the nozzle chambers be done work.Another advantage is can realize the minimum thermal loss by active beam member and passive beam member are separated.The defective of this design is, active beam member and passive beam member is separated caused the loss on the rigidity of structure.
So far, should be understood that the inkjet nozzle that is activated by bend actuator need move the ink of necessary volume in order to spray the ink droplet of predetermined from nozzle opening.Therefore, the inkjet nozzle design mainly concentrates on the maximum displacement that thermal bend actuator is provided for given energy input.
Need to promote the crooked actuation efficiency of thermal bend actuator, allow simultaneously in ink jet-print head, to realize more intensive nozzle assembling and make drop spray characteristic optimization.
Summary of the invention
In first aspect, the invention provides a kind of inkjet nozzle assembly, comprising:
Nozzle chambers, it is used for holding ink, and described chamber has nozzle opening and ink inlet;
A pair of electric contact, it is positioned at an end of described assembly and is connected to drive circuit; With
Thermal bend actuator, it is used for carrying out ink-jet by described nozzle opening, and described actuator comprises:
Active beam, it is connected to described electric contact and away from described contact longitudinal extension, described active beam limits the crooked current flow path between the described contact; With
Passive beam, it is fusion welded to described active beam, make when electric current flows through described active beam, described active beam heating and with respect to described passive beam expansion so that described actuator bending,
Wherein, described actuating device is useful on the working face that produces positive pressure pulse during the described bending of described actuator in described ink, and described working face has the area less than 800 square microns.
Selectively, described working face has the area less than 600 square microns.
Selectively, described working face is limited by the surface of described passive beam.
Selectively, described inkjet nozzle assembly is configured to provide the actuator peak velocity of 2.5m/s at least.
Selectively, described drive circuit is configured to transmit activation pulse to described active beam, and each activation pulse is to the energy of described active beam transmission less than 200nJ.
Selectively, described drive circuit is configured to transmit activation pulse to described active beam, and each activation pulse has the pulse width less than 0.2 microsecond.
Selectively, described active beam and passive beam respectively have the length less than 50 microns.
Selectively, described active beam and passive beam respectively have the width less than 15 microns.
Selectively, described active beam and passive beam have at least 1.5 microns combination thickness.
Selectively, described active beam comprise the first arm from the first contact longitudinal extension, from second arm of the second contact longitudinal extension and connect described the first arm and the connecting elements of second arm.
Selectively, each in described the first arm and second arm comprises stratie separately, and described stratie has the width less than 5 microns.
Selectively, described connecting elements interconnects the far-end of described the first arm and second arm, and described far-end is positioned at the distally with respect to described electric contact.
Selectively, described active beam comprises the material that is selected from following group, and described group comprises: titanium nitride, TiAlN and vananum.
Selectively, described passive beam comprises the material that is selected from following group, and described group comprises: silica, silicon nitride and silicon oxynitride.
Selectively, described nozzle chambers comprises the bottom and has the top of movable part that the actuating of wherein said actuator makes described movable part move towards described bottom.
Selectively, described movable part comprises described actuator.
Selectively, described nozzle opening is limited in the described movable part, makes described nozzle opening to move with respect to described bottom.
Selectively, described inkjet nozzle assembly has the area occupied less than 1500 square microns.
On the other hand, the invention provides a kind of ink jet-print head that comprises a plurality of nozzle assemblies, each assembly comprises:
Nozzle chambers, it is used for holding ink, and described chamber has nozzle opening and ink inlet;
A pair of electric contact, it is positioned at an end of described assembly and is connected to drive circuit; With
Thermal bend actuator, it is used for carrying out ink-jet by described nozzle opening, and described actuator comprises:
Active beam, it is connected to described electric contact and away from described contact longitudinal extension, described active beam limits the crooked current flow path between the described contact; With
Passive beam, it is fusion welded to described active beam, make when electric current flows through described active beam, described active beam heating and with respect to described passive beam expansion so that described actuator bending,
Wherein, described actuating device is useful on the working face that produces positive pressure pulse during the described bending of described actuator in described ink, and described working face has the area less than 800 square microns.
In second aspect, the invention provides a kind of ink-jet printer, comprising:
Printhead with a plurality of nozzle assemblies, each nozzle assembly comprises:
Nozzle chambers, it is used for holding ink, and described chamber has nozzle opening and ink inlet; With
Bend actuator is used for by producing positive pressure pulse and ink droplet is sprayed from described nozzle opening at described ink during described actuator bending; With
Ink feeding system, it is used for to described printhead supply ink; With
For the device of the hydrostatic pressure that changes the ink that is supplied to described printhead,
Wherein, increase the volume that the hydrostatic ink pressure has increased described ejection ink droplet, reduce the volume that described hydrostatic ink pressure has reduced described ejection ink droplet.
Selectively, the volume of described ejection ink droplet can increase at least 100% with respect to minimum droplet size.
Selectively, print head surface is limited by hydrophobic layer.
Selectively, described hydrophobic layer is the PDMS layer.
Selectively, described hydrophobic layer is deposited on the hydrophilic relatively nozzle plate.
Selectively, ink meniscus is pegged each nozzle opening at hydrophilic/hydrophilic interface place.
Selectively, each nozzle assembly comprises for the drive circuit that activation pulse is sent to described bend actuator.
Selectively, described drive circuit is configured to make each activation pulse to give the energy of described actuator transmission less than 200nJ.
Selectively, described bend actuator comprises:
Active beam, it is connected to a pair of electric contact; With
Passive beam, it cooperates with described active beam machinery, make when electric current flows through described active beam, described active beam heating and with respect to described passive beam expansion so that described actuator bending.
Selectively, each nozzle assembly comprises the described a pair of electric contact that is positioned at one end place, and wherein, described active beam away from described contact longitudinal extension to limit the crooked current flow path between the described contact.
Selectively, described active beam is fusion welded on the described passive beam.
Selectively, described active beam comprise the first arm from the first contact longitudinal extension, from second arm of the second contact longitudinal extension and connect described the first arm and the connecting elements of second arm.
Selectively, each in described the first arm and second arm comprises stratie separately.
Selectively, described connecting elements interconnects the far-end of described the first arm and second arm, and described far-end is positioned at the distally with respect to described electric contact.
Selectively, described active beam comprises the material that is selected from following group, and described group comprises: titanium nitride, TiAlN and vananum.
Selectively, described passive beam comprises the material that is selected from following group, and described group comprises: silica, silicon nitride and silicon oxynitride.
Selectively, each nozzle chambers comprises the bottom and has the top of movable part that the actuating of wherein said actuator makes described movable part move towards described bottom.
Selectively, described movable part comprises described actuator.
Selectively, described nozzle opening is limited in the described movable part, makes described nozzle opening to move with respect to described bottom.
In yet another aspect, the invention provides a kind of printhead of constructing with the method for the ink droplet of ejection predetermined, said method comprising the steps of:
(i) provide the printhead with a plurality of nozzle assemblies, each nozzle assembly comprises:
Nozzle chambers, it is used for holding ink, and described chamber has the nozzle opening of preliminary dimension; With
Bend actuator is used for by producing positive pressure pulse and ink droplet is sprayed from described nozzle opening at described ink during described actuator bending;
(ii) change the hydrostatic pressure of the ink that is supplied to described printhead, thereby change the volume of the ink droplet of ejection;
(iii) determine the best hydrostatic ink pressure corresponding with described scheduled volume; With
(iv) construct ink feeding system with under described best hydrostatic ink pressure to described printhead ink supply.
In the third aspect, the invention provides a kind of ink-jet printer that volume is 1 to 2.5pL ink droplet that is configured to spray, described printer comprises:
Printhead, it has a plurality of nozzle assemblies, and each nozzle assembly comprises:
Nozzle chambers, it is used for holding ink, and described chamber has nozzle opening and ink inlet, and described nozzle opening has 4 to 12 microns full-size; With
Bend actuator, it is used for by producing positive pressure pulse and ink droplet is sprayed from described nozzle opening at described ink during described actuator bending; With
Ink feeding system, it is configured to give described printhead ink supply under the positive fluid static pressure of 1 to 300 millimeter of water.
Selectively, described nozzle opening has 6 to 10 microns full-size.
Selectively, described ink feeding system is configured to give described printhead ink supply under the positive fluid static pressure of 5 to 200 millimeters of water.
Selectively, described hydrostatic pressure provides meniscus at described nozzle opening place when the described printhead of perfusion.
Selectively, print head surface is limited by hydrophobic layer.
Selectively, described hydrophobic layer is the PDMS layer.
Selectively, described hydrophobic layer is deposited on the hydrophilic relatively nozzle plate.
Selectively, ink meniscus is pegged each nozzle opening at hydrophilic/hydrophilic interface place.
Selectively, each nozzle assembly comprises for the drive circuit that activation pulse is sent to described bend actuator.
Selectively, described drive circuit is configured to make each activation pulse to give the energy of described actuator transmission less than 200nJ.
Selectively, described bend actuator comprises:
Active beam, it is connected to a pair of electric contact; With
Passive beam, it cooperates with described active beam machinery, make when electric current flows through described active beam, described active beam heating and with respect to described passive beam expansion so that described actuator bending.
Selectively, each nozzle assembly comprises the described a pair of electric contact that is positioned at one end place, and wherein, described active beam away from described contact longitudinal extension to limit the crooked current flow path between the described contact.
Selectively, described active beam is fusion welded to described passive beam.
Selectively, described active beam comprise the first arm from the first contact longitudinal extension, from second arm of the second contact longitudinal extension and connect described the first arm and the connecting elements of second arm.
Selectively, each in described the first arm and second arm comprises stratie separately.
Selectively, described active beam comprises the material that is selected from following group, and described group comprises: titanium nitride, TiAlN and vananum.
Selectively, described passive beam comprises the material that is selected from following group, and described group comprises: silica, silicon nitride and silicon oxynitride.
Selectively, each nozzle chambers comprises the bottom and has the top of movable part that the actuating of wherein said actuator makes described movable part move towards described bottom.
Selectively, described movable part comprises described actuator.
Selectively, described nozzle opening is limited in the described movable part, makes described nozzle opening to move with respect to described bottom.
Description of drawings
With reference now to accompanying drawing, only with way of example embodiments of the invention are described, wherein:
Fig. 1 is the broken-open perspective view of the inkjet nozzle assembly made of part;
Fig. 2 is the broken-open perspective view of inkjet nozzle assembly shown in Figure 1 after finishing final manufacturing step;
Fig. 3 A has schematically shown any printhead that is provided with ink under negative hydrostatic pressure;
Fig. 3 B has schematically shown any printhead that is provided with ink under the positive fluid static pressure;
Fig. 4 has shown the inkjet nozzle assembly of perfusion ink under negative hydrostatic pressure;
Fig. 5 has shown the inkjet nozzle assembly of perfusion ink under the positive fluid static pressure; With
Fig. 6 has schematically shown the ink-jet printer with ink feeding system, and described ink feeding system is configured to supply ink under the hydrostatic pressure that changes.
The specific embodiment
Thermal bend actuator for maximum function of jet velocity structure
Fig. 1 and 2 has shown the nozzle assembly 100 that is in two different fabrication stages.Nozzle assembly is the U. S. application No.11/763 on June 15th, 2007 with the applicant the previous applying date of submitting to structurally, and the nozzle assembly of describing in 440 is similar, and the content of this application is hereby incorporated by.
Fig. 1 has shown that the nozzle assembly that partly forms is so that the feature of explanation active and passive beam layer.Therefore, with reference to figure 1, shown the nozzle assembly 100 that is formed on the CMOS silicon substrate 102.Nozzle chambers is limited by the top 104 that separates with substrate 102 and the sidewall 106 that extends to substrate 102 from described top.Top 104 comprises movable part 108 and stationary part 110, has gap 109 between described movable part and the stationary part.Nozzle opening 112 is limited in the movable part 108 to carry out ink-jet.
Movable part 108 comprises the thermal bend actuator with a pair of cantilever beam, and described cantilever beam form is the top active beam 114 that is fusion welded on the bottom passive beam 116.Bottom passive beam 116 defines the scope of the movable part 108 at top.Top active beam 114 comprises a pair of arm 114A and 114B, and it vertically stretches out from respective electrode contact 118A and 118B.Arm 114A is connected by connecting elements 115 at its far-end with 114B.Connecting elements 115 can comprise titanium conductive pad 117, and it helps the electric conductivity around this join domain.Therefore, active beam 114 defines the crooked or tortuous conducting path between electrode contacts 118A and the 118B.
Electrode contacts 118A and 118B locate adjacent to each other and are connected to by corresponding joint pin 119 on the metal cmos layer 120 of substrate 102 at an end of nozzle assembly.Cmos layer 120 holds the drive circuit for the necessity that activates bend actuator.
Passive beam 116 is typically made by any electric insulation and heat insulator, for example silica, silicon nitride etc.Thermoelasticity active beam 114 can be made by any suitable thermoelastic material, for example titanium nitride, TiAlN and aluminium alloy.As the U. S. application No.11/607 of applicant in the common pending trial of submission on December 4th, 2006, described in 976 (the attorney docket IJ70US), vananum is preferable material, because they combine the favourable character of high thermal expansion, low-density and high Young's modulus.
With reference to figure 2, shown the nozzle assembly of finishing 100 that is in subsequent stage of fabrication.Nozzle assembly shown in Figure 2 has nozzle chambers 122 and is used for ink feed is given the ink inlet 124 of nozzle chambers.In addition, top 104 (it defines the part of the rigidity nozzle plate of printhead) is coated with the polymeric material layer 126 such as dimethione (PDMS).Polymer layer 126 has multiple function, comprising: the protection bend actuator makes top 104 (and print head surface) hydrophobization and provides mechanical seal for gap 109.Polymer layer 126 has enough low Young's modulus and activates and ejection to allow ink to pass nozzle opening 112.Can be referring to the U. S. application No.11/946 that for example submits on November 29th, 2007 about the more detailed description (comprising its function and manufacturing) of polymer layer 126,840, its content is hereby incorporated by.
When needs sprayed ink droplets from nozzle chambers 122, electric current flow through the active beam 114 between the electrode contacts 118.Active beam 114 is heated rapidly by electric current and expands with respect to passive beam 116, thereby movable part 108 is bent downwardly towards substrate 102 with respect to stationary part 110.This motion raises rapidly by nozzle chambers 122 internal pressures then and causes ink from nozzle opening 112 ejections.When electric current stops to flow, allow movable part 108 to return its resting position (as illustrated in fig. 1 and 2), this from import 124 inlet nozzle chambeies 122, prepares ink for spray next time.
In designs of nozzles shown in Fig. 1 and 2, bend actuator advantageously limits at least a portion movable part 108 of each nozzle assembly 100.This has not only simplified master-plan and the manufacturing of nozzle assembly 100, and because movable part 108 has only a surface (that is, " working face " down) also to provide higher ejection efficiency to the ink acting of relative thickness.Comparatively speaking, the nozzle assembly efficient with the actuator blade that is positioned at nozzle chambers 122 inside is not high, because all must do work to the ink in the chamber in two surfaces of actuator.
Yet, still need to improve the gross efficiency of bend actuator.According to the present invention, the working face of thermal bend actuator has the area less than 800 square microns.Selectively, working face has less than 700 square microns or less than the area of 600 square microns.
As illustrated in fig. 1 and 2, the working face of thermal bend actuator is limited by the lower surface (inner surface) of passive beam 116 usually, and it will be to being contained in the ink acting in the nozzle chambers 122.
The previous design that reduces obviously to depart from thermal bend actuator of thermal bend actuator working face area.So far, should be understood that the displacement of necessary volume ink is the principal element of control drops out from nozzles opening ejection.Therefore, in order (for example, 5-15m/s) to realize that (for example, typical droplet volume 1.2-1.8pL) was understood that 1-2pL in the past, and space required is carried out displacement for the working face of at least 1500 square microns with acceptable ink ejection velocity.The trial that improves the drop spray characteristic concentrates in the past usually and maximizes and increase the area of its working face by the actuator displacement that makes that prolongs the actuator realization.Yet applicant's experiment has now found that unforeseeable is that the peak velocity of actuator between crooked period of energization provides the even more important factor that best ink droplet sprays (with regard to acceptable drop speeds and droplet volume).
If the peak velocity of the actuator of realizing is enough big, even the surface area of working face is less relatively, also can obtains outstanding ink droplet and spray.Enough big actuator peak velocity typically is at least approximately 2.5m/s.
The rapid extent control actuator peak velocity that can between period of energization, be heated by active beam.As the U. S. application No.12/114 of applicant in submission on May 5th, 2008,826 (its content is hereby incorporated by) are described, by less than the shorter activation pulse width of 0.2 microsecond (for example about 0.1 microsecond) and/or comprise (for example having small cross sectional, less than 10 square microns or less than 5 square microns) the active beam of heating element heater, can realize the rapid heating of active beam.Typically, each heating element heater has the width less than 5 microns.
Yet the actuator peak velocity also area with working face is relevant, and is because when working face has than small size, less to the ink acting.Have been found that the present invention can realize best drop spray characteristic when working face has the area of 200 to 800 square microns or 250 to 700 square microns or 300 to 650 square microns.When such working face during with the peak velocity displacement of 2.5m/s at least, obtain the acceptable ink ejection velocity of 6-12m/s or 8-10m/s usually.
From above as can be known, should be understood that the present invention significantly reduces the area of the working face in the inkjet nozzle assembly that comprises thermal bend actuator.Therefore, the shared area of each inkjet nozzle assembly can reduce, thereby can obtain more intensive nozzle assembling on ink jet-print head.Typically, amass less than 1200 square microns, perhaps less than 1000 square microns, perhaps less than 800 square microns according to the shared of each nozzle assembly in the printhead of the present invention.
More particularly, can be by length less than 60 microns or reduce the area of working face less than 50 microns thermal bend actuator.The reducing of actuator length increased the rigidity of actuator along bending direction, and this has further promoted the gross efficiency of actuator.Actuator also depends on the gross thickness of actuator along the rigidity of bending direction.Selectively, bend actuator has the thickness of at least 1.3 microns or at least 1.5 microns.
In addition, can be by width less than 20 microns or reduce the area of working face less than 15 microns thermal bend actuator.The reducing of actuator width has maximum efficiency aspect the nozzle arrangement density that increases on the printhead, because can pack more nozzle in row's nozzle into.
Finally, the present invention had both realized high nozzle arrangement density and outstanding ink droplet ejection efficiency, had realized outstanding ink droplet characteristic again.Be enough to produce the actuator peak velocity of 2.5m/s at least when for example, transmitting with the pulse width of about 0.1 microsecond less than the input energy of 200nJ (or less than 150nJ).This causes the ink ejection velocity of 8-10m/s.
In addition, the ink droplet shape of injection is good, and surprising be almost not have satellite droplet.Satellite droplet is well-known in inkjet printing, and its afterbody by the ink droplet of ejection breaks down into small satellite droplet and produces, and described satellite droplet separates with main ink droplet.Satellite droplet is a problem and may influences overall print quality very much.The inventor understands that the higher actuator peak velocity of 2.5m/s can reduce satellite droplet quantity at least.Usually, satellite droplet is relevant with high ink ejection velocity, but the present invention shockingly demonstrates, even at 7m/s at least, 8m/s or also almost do not have satellite droplet under the higher ink ejection velocity of 9m/s at least at least.
In a word, aspect control drop spray characteristic, the maximum displacement of actuator reaches and compares with the actuator peak velocity than the large working area area, and importance should be much smaller; By the working face area is reduced as far as possible, can under given input energy, obtain bigger actuator peak velocity.
Utilize ink pressure control drop size
Most of ink-jet printer is worked under negative hydrostatic ink pressure.This mainly is for being avoided ink uncontrolled overflow on print head surface, especially when printing stops.In addition, when ink meniscus is pegged nozzle opening owing to surface tension, preferably have the concave meniscus opposite with meniscus (outwards swelling from printhead), because the particle that meniscus easily is printed on the head surface bumps brokenly, thereby cause small overflow.Fig. 3 A shown and utilizes negative hydrostatic ink pressure to have the typical inkjet nozzle 200 of concave meniscus 202, and Fig. 3 B has shown and utilizes the positive fluid static pressure to have the same inkjet nozzle of meniscus 204.
Knownly there are various means of hydrostatic ink pressure for the control ink jet-print head.The ink feeding system of appropriate structuring can transmit ink with the ink pressure of necessity, and known have a lot of multi-form ink feeding systems.For example, ink housing tube can provide the ink housing tube 206 of very simple pressure control form-be positioned at printhead 205 tops that positive fluid static(al) ink pressure (referring to Fig. 3 B) is provided with respect to the position of printhead; The ink housing tube 206 that is positioned at printhead 205 belows provides negative hydrostatic ink pressure (referring to Fig. 3 A).Other means that are used for the hydrostatic ink pressure of control printhead fall within those skilled in the art's the knowledge category, and the details of concrete pressure controling means and relation of the present invention are little.
As mentioned above, the applicant has researched and developed the ink jet-print head with hydrophobic surface.This hydrophobic surface typically is PDMS layer 126, and it is deposited on (for example, referring to the U. S. application No.11/946 of applicant in submission on November 29th, 2007,840) on the nozzle top 104 in the printhead manufacturing later stage.Because the top 104 of nozzle chambers has hydrophobicity usually, made by silica or silicon nitride, ink meniscus is pegged nozzle opening 112 at the interface at the hydrophilic/hydrophobic that is defined between top layer 104 and the PDMS layer 126.Fig. 4 has shown the ink concave meniscus 150 that has negative hydrostatic ink pressure in the aforesaid injector arrangement 100.
As U. S. application No.11/946,840 is described, and hydrophobic PDMS layer 126 helps to make the print head surface overflow to minimize.Therefore, PDMS layer 126 can make meniscus become possibility and not have the excessive risk of print head surface overflow.As shown in Figure 5, because the cause of the thickness of PDMS layer 126 and because meniscus 151 is pegged the cause at hydrophilic/hydrophobic interface, meniscus 151 does not stretch out from print head surface (outer surface 128 by the PDMS layer limits).PDMS layer 126 prevents that effectively meniscus 151 is subjected to any particle influence, playing the energy barrier effect simultaneously minimizes the print head surface overflow---and ink moves to tendency minimum on the hydrophobic PDMS layer 126 by capillarity, more helps to keep at the interface pegging at hydrophilic/hydrophobic aspect energy.
Therefore, PDMS layer 126 can not be used in combination with the negative pressure ink supply source by limits nozzle assembly 100.Do not bearing under the constraint of hydrostatic ink pressure, applicant's experiment has been found that the positive fluid static(al) ink pressure that has meniscus 151 shockingly provides very different drop spray characteristics crooked the actuating in the nozzle assembly 100 described herein.
Surprising discovery is, for the intended size (for example diameter) of nozzle opening 112, compares with the same nozzle opening of supply ink under negative hydrostatic ink pressure, and positive fluid static(al) ink pressure provides the more ejection ink droplet of large scale and volume.So far, institute is understood that, determines that the principal element of droplet volume is the diameter of nozzle opening 112.Typically, expection ejection ink droplet has the diameter identical with the nozzle opening that sprays this ink droplet.Therefore, diameter is the ink droplet that 12 microns nozzle opening typically sprays about 0.9pL (this may be too small for some are used).14 microns nozzle openings typically spray the ink droplet of about 1.4pL (it is believed that this is acceptable droplet size for most of ink-jet applications).Usually, scope is considered to acceptable droplet size at the droplet size of 1-2.5pL or 1-2pL.
Yet, when ink droplet when having the nozzle assembly shown in Figure 5 ejection of positive fluid static(al) ink pressure, compare with the nozzle assembly shown in Figure 4 with negative hydrostatic ink pressure, the droplet volume of finding ejection up to 1.5 times, 2 times or 3 times.
Therefore, have the crooked printhead that activates nozzle 100 and can carry out different designs or different operations according to the hydrostatic ink pressure that is provided by ink feeding system.For example, for the droplet size of necessity, if use positive fluid static(al) ink pressure, compare with more common negative hydrostatic pressure, nozzle opening can be made forr a short time.This allows to utilize the smaller szie nozzle opening to obtain more intensive nozzle assembling at printhead then.Typically, the positive fluid static pressure can be 1 to 300 millimeter of water, selectively is 5 to 200 millimeters of water, perhaps selectively is 10 to 100 millimeters of water.Utilize so positive ink pressure, nozzle opening can have 4 to 12 microns or selectively 5 to 11 microns or 6 to 10 microns full-size selectively, and still obtains acceptable droplet size.For the round nozzle opening, full-size is its diameter; For oval nozzle opening, full-size is the length of its major axis.
In addition, printhead can carry out different operations on the spot by the hydrostatic pressure that is provided by ink feeding system is provided.Some print head applications (for example, black text printing) may need to obtain bigger droplet size by operation under the positive fluid static pressure.Bigger droplet size is placed on more ink on the page, makes optical density (OD) maximization, this black text is printed to standard office with paper on the time particularly need.Alternatively, some print head applications (for example, photo is printed) may need to obtain less droplet size by operation under lower (for example, negative) hydrostatic ink pressure.Less droplet size obtains higher print resolution, and this particularly needs for the photo print application.
The ability that changes droplet size under the situation that does not change designs of nozzles substantially has important function for inkjet printing.The target of inkjet printing provides the SOHO printer, and it can print black text and/or photo under the situation of not sacrificing optical density (OD) or photographic quality.Similarly, to make the droplet size optimization on the different paper type on the spot be important progress for inkjet printer technologies in order to be printed on.
For instance, Fig. 3 A and 3B have schematically shown the printer that comprises any printhead 205 and ink feeding system, and described ink feeding system can be by changing ink housing tube 206 with respect to the different hydrostatic ink pressure of height transmission of printhead.Undoubtedly, the more complicated apparatus that changes the hydrostatic ink pressure on the spot by ink feeding system it will be apparent to those skilled in the art that.For example, as shown in Figure 6, can use the reversible air pump 210 that is communicated with headroom 211 in the ink housing tube 206 and the ink pressure sensor 212 that feedback signal 214 is provided to air pump.
Undoubtedly, will be appreciated that, more than only invention has been described with way of example, in the scope of the present invention that is defined by the following claims, can carry out details and improve.

Claims (19)

1. inkjet nozzle assembly comprises:
Nozzle chambers, it is used for holding ink, and described chamber has nozzle opening and ink inlet;
A pair of electric contact, it is positioned at an end of described assembly and is connected to drive circuit; With
Thermal bend actuator, it is used for carrying out ink-jet by described nozzle opening, and described actuator comprises:
Active beam, it is connected to described electric contact and away from described contact longitudinal extension, described active beam limits the crooked current flow path between the described contact; With
Passive beam, it is fusion welded to described active beam, make when electric current flows through described active beam, described active beam heating and with respect to described passive beam expansion so that described actuator bending,
Wherein, described actuating device is useful on the working face that produces positive pressure pulse during the described bending of described actuator in described ink, and described working face has the area less than 800 square microns.
2. inkjet nozzle assembly as claimed in claim 1, wherein, described working face has the area less than 600 square microns.
3. inkjet nozzle assembly as claimed in claim 1, wherein, described working face is limited by the surface of described passive beam.
4. inkjet nozzle assembly as claimed in claim 1, it is configured to provide the actuator peak velocity of 2.5m/s at least.
5. inkjet nozzle assembly as claimed in claim 1, wherein, described drive circuit is configured to transmit activation pulse to described active beam, and each activation pulse transmits energy less than 200nJ to described active beam.
6. inkjet nozzle assembly as claimed in claim 1, wherein, described drive circuit is configured to transmit activation pulse to described active beam, and each activation pulse has the pulse width less than 0.2 microsecond.
7. inkjet nozzle assembly as claimed in claim 1, wherein, described active beam and passive beam respectively have the length less than 50 microns.
8. inkjet nozzle assembly as claimed in claim 1, wherein, described active beam and passive beam respectively have the width less than 15 microns.
9. inkjet nozzle assembly as claimed in claim 1, wherein, described active beam and passive beam have at least 1.5 microns combination thickness.
10. inkjet nozzle assembly as claimed in claim 1, wherein, described active beam comprises from the first arm of the first contact longitudinal extension, from second arm of the second contact longitudinal extension and connect described the first arm and the connecting elements of second arm.
11. inkjet nozzle assembly as claimed in claim 10, wherein, each in described the first arm and second arm comprises stratie separately, and described stratie has the width less than 5 microns.
12. inkjet nozzle assembly as claimed in claim 10, wherein, described connecting elements interconnects the far-end of described the first arm and second arm, and described far-end is positioned at the distally with respect to described electric contact.
13. inkjet nozzle assembly as claimed in claim 1, wherein, described active beam comprises the material that is selected from following group, and described group comprises that nitrogenize is admired, aluminium and vananum are admired in nitrogenize.
14. inkjet nozzle assembly as claimed in claim 1, wherein, described passive beam comprises the material that is selected from following group, and described group comprises silica, silicon nitride and silicon oxynitride.
15. inkjet nozzle assembly as claimed in claim 1, wherein, described nozzle chambers comprises the bottom and has the top of movable part that the actuating of wherein said actuator makes described movable part move towards described bottom.
16. inkjet nozzle assembly as claimed in claim 15, wherein, described movable part comprises described actuator.
17. inkjet nozzle assembly as claimed in claim 16, wherein, described nozzle opening is limited in the described movable part, makes described nozzle opening to move with respect to described bottom.
18. inkjet nozzle assembly as claimed in claim 1, wherein, described inkjet nozzle assembly has the area occupied less than 1500 square microns.
19. ink jet-print head that comprises a plurality of nozzle assemblies as claimed in claim 1.
CN2008801312253A 2008-09-29 2008-09-29 Efficient inkjet nozzle assembly Active CN102164748B (en)

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EP1419991A2 (en) * 2002-11-13 2004-05-19 Eastman Kodak Company Tapered multi-layer thermal actuator and method of operating same

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JP5362832B2 (en) 2013-12-11

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