JP4933629B2 - Inkjet nozzle assembly having a thermal bending actuator that defines the main part of the nozzle chamber roof with an active beam - Google Patents

Description

  The present application relates to a thermal bending actuator. It was developed primarily to provide an improved inkjet nozzle that ejects ink via a hot bending operation.

[Cross-reference]
The following patents or patent applications filed by the applicant or assignee of this application are hereby incorporated by this cross-reference:

  Applicants have previously described a number of MEMS inkjet nozzles that utilize hot bending operation. Thermal bending operation generally refers to a bending operation that occurs due to thermal expansion of one material through which current flows relative to another material. The resulting bending motion can be used to cause ink to be ejected from the nozzle openings, optionally through paddle or vane movements that generate pressure waves in the nozzle chamber.

  Several representative types of hot-bending ink jet nozzles are illustrated in the patents and patent applications listed in the cross-reference section above, the contents of which are hereby incorporated by reference.

  Patent Document 1 describes an inkjet nozzle having a paddle disposed in a nozzle chamber and a thermal bending actuator disposed outside the nozzle chamber. The actuator takes the form of a lower active beam of conductive material (eg, titanium nitride) fused to an upper passive beam of non-conductive material (eg, silicon dioxide). The actuator is connected to the paddle via an arm received through a slot in the wall of the nozzle chamber. As current flows through the lower active beam, the actuator bends upward, with the result that the paddle moves toward the nozzle opening defined in the roof of the nozzle chamber, thereby ejecting a drop of ink. The advantage of this design is its simplicity of construction. The disadvantage of this design is that both sides of the paddle act against the relatively high viscosity ink inside the nozzle chamber.

  U.S. Patent No. 6,099,056 describes an inkjet nozzle in which an actuator forms a moving roof portion of a nozzle chamber. The actuator takes the form of a serpentine core of conductive material encapsulated by a polymer material. When actuated, the actuator bends toward the floor of the nozzle chamber, raising the pressure in the chamber and pushing ink drops out of the nozzle openings defined in the roof of the chamber. The nozzle opening is defined in a non-moving part of the roof. The advantage of this design is that only one side of the moving roof portion can act against the relatively high viscosity ink inside the nozzle chamber. A disadvantage of this design is that it is difficult to achieve an actuator configuration from a serpentine conductive element encapsulated by a polymer material in a MEMS process.

  U.S. Patent No. 6,057,049 describes an inkjet nozzle that includes a nozzle chamber having a movable roof portion in which nozzle openings are defined. The movable roof portion is connected via an arm to a thermal bending actuator disposed outside the nozzle chamber. The actuator takes the form of an upper active beam spaced from the lower passive beam. By separating the active and passive beams, thermal bending efficiency is maximized because the passive beam cannot act as a heat sink for the active beam. As current flows through the upper active beam, the movable roof portion, in which the nozzle openings are defined, rotates toward the floor of the nozzle chamber, thereby discharging from the nozzle openings. Since the nozzle opening moves with the roof portion, the drop flight direction can be controlled by appropriate deformation of the shape of the nozzle rim. The advantage of this design is that only one side of the moving roof portion must work for the relatively high viscosity ink inside the nozzle chamber. A further advantage is that minimal heat loss is achieved by separating the active and passive beam members. The disadvantage of this design is that structural stiffness is lost by separating the active and passive beam members.

  There is a need to improve the design of hot-bending inkjet nozzles to achieve more efficient drop ejection and improved mechanical robustness.

US Pat. No. 6,416,167 US Pat. No. 6,260,953 US Pat. No. 6,623,101

In the first aspect, the present invention provides:
A nozzle chamber comprising a floor and a roof, the nozzle chamber having a moving portion in which nozzle openings are defined and the roof is movable toward the floor;
A thermal bending actuator having a plurality of cantilever beams and ejecting ink from nozzle openings;
Comprising the actuator,
A first active beam for connection to the drive circuit;
A second passive beam mechanically cooperating with the first beam such that when the current is passed through the first beam, the first beam expands relative to the second beam, resulting in actuator bending. Prepare
An inkjet nozzle assembly is provided.

  In some cases, the first active beam defines at least 30% of the total area of the roof.

  In some cases, the moving part comprises an actuator.

  In some cases, the first active beam defines at least a portion of the outer surface of the roof.

  Optionally, the nozzle opening is defined in the moving part so that the nozzle opening is movable relative to the floor.

  In some cases, the actuator is movable relative to the nozzle opening.

  In some cases, the first beam is defined by a serpentine beam element, the serpentine beam element having a plurality of proximal beam members.

  Optionally, the plurality of proximal beam members includes a plurality of elongate beam members extending along the longitudinal axis of the first beam and at least one extending across the transverse axis of the first beam and interconnecting the elongate beam members. A short beam member is provided.

  In some cases, one of the plurality of beams is comprised of a porous material.

  In some cases, the porous material is porous silicon dioxide having a dielectric constant of 2 or less.

  In some cases, the thermal bending actuator further comprises a third insulating beam sandwiched between the first beam and the second beam.

  In some cases, the third insulating beam is composed of a porous material.

  Optionally, the first beam is fused or joined to the second beam.

  In some cases, the second beam is comprised of a porous material.

  In some cases, at least a portion of the first beam is spaced from the second beam.

  In some cases, the first beam is comprised of a material selected from the group comprising titanium nitride, titanium aluminum nitride, and aluminum alloys.

  In some cases, the first beam is composed of an aluminum alloy.

  In some cases, the aluminum alloy comprises aluminum and at least one other metal having a Young's modulus greater than 100 GPa.

  Optionally, the at least one metal is selected from the group comprising vanadium, manganese, chromium, cobalt, and nickel.

  Optionally, the alloy includes aluminum and vanadium.

  Optionally, the alloy includes at least 80% aluminum.

In the second aspect, the present invention provides:
A first active element for connection to a drive circuit;
A second passive element that mechanically cooperates with the first element such that when the current flows through the first element, the first element expands relative to the second element, resulting in bending of the actuator;
And a thermal bending actuator having a plurality of elements, wherein the first element is made of an aluminum alloy.

  In some cases, the aluminum alloy includes aluminum and at least one other metal having a Young's modulus greater than 100 GPa.

  Optionally, the at least one metal is selected from the group comprising vanadium, manganese, chromium, cobalt, and nickel.

  Optionally, the alloy includes aluminum and vanadium.

  Optionally, the alloy includes at least 80% aluminum.

  In some cases, the first and second elements are cantilever beams.

  Optionally, the first beam is fused or joined to the second beam along the longitudinal axis.

  In some cases, at least a portion of the second beam is spaced from the first beam, thereby isolating the first beam from at least a portion of the second beam.

  In some cases, one of the plurality of elements is comprised of a porous material.

  In some cases, the porous material has a dielectric constant of about 2 or less.

  Optionally, the porous material is porous silicon dioxide.

  In some cases, a third insulating beam is sandwiched between the first beam and the second beam.

  In some cases, the third insulating beam is composed of a porous material.

  In some cases, the second beam is comprised of a porous material.

In a further aspect, the invention provides:
A nozzle chamber having a nozzle opening and an ink inlet;
A thermal bending actuator for ejecting ink through a nozzle opening having a plurality of cantilever beams;
Comprising the actuator,
A first active beam for connection to the drive circuit;
A second passive beam mechanically cooperating with the first beam such that when the current flows through the first beam, the first beam expands relative to the second beam, resulting in actuator bending;
And an ink jet nozzle assembly in which the first beam is composed of an aluminum alloy.

  In some cases, the nozzle chamber includes a floor and a roof having a moving portion, whereby actuation of the actuator moves the moving portion toward the floor.

  In some cases, the moving part comprises an actuator.

  In some cases, the first active beam defines at least 30% of the total area of the roof.

  In some cases, the first active beam defines at least a portion of the outer surface of the nozzle chamber.

  Optionally, the nozzle opening is defined in the moving part so that the nozzle opening is movable relative to the floor.

In a third aspect, the present invention provides:
A first active element for connection to a drive circuit;
A second passive element that mechanically cooperates with the first element such that when the current flows through the first element, the first element expands relative to the second element, resulting in bending of the actuator;
And one of the plurality of elements is composed of a porous material,
A thermal bending actuator having a plurality of elements is provided.

  In some cases, the porous material has a dielectric constant of about 2 or less.

  Optionally, the porous material is porous silicon dioxide.

  In some cases, the first and second elements are cantilever beams.

  In a further aspect, a thermal bending actuator is provided that further comprises a third insulating beam sandwiched between the first beam and the second beam.

  In some cases, the third insulating beam is composed of a porous material.

  Optionally, the first beam is fused or joined to the second beam along its longitudinal axis.

  In some cases, the second beam is comprised of a porous material.

  Optionally, the first element is composed of a material selected from the group comprising titanium nitride, titanium aluminum nitride, and aluminum alloys.

  In some cases, the first element is comprised of an aluminum alloy.

  Optionally, the aluminum alloy includes aluminum and at least one other metal having a Young's modulus greater than 100 GPa.

  Optionally, the at least one metal is selected from the group comprising vanadium, manganese, chromium, cobalt, and nickel.

  Optionally, the alloy includes aluminum and vanadium.

  Optionally, the alloy includes at least 80% aluminum.

In another aspect, the invention provides:
A nozzle chamber having a nozzle opening and an ink inlet;
A thermal bending actuator having a plurality of cantilever beams and ejecting ink through the nozzle openings;
Comprising the actuator,
A first active beam for connection to the drive circuit;
A second passive beam mechanically cooperating with the first beam such that when the current flows through the first beam, the first beam expands relative to the second beam, resulting in actuator bending;
An inkjet nozzle assembly, wherein one of the plurality of beams is comprised of a porous material.

  In some cases, the nozzle chamber includes a floor and a roof having a moving portion, whereby actuation of the actuator moves the moving portion toward the floor.

  In some cases, the moving part comprises an actuator.

  In some cases, the first active beam defines at least 30% of the total area of the roof.

  In some cases, the first active beam defines at least a portion of the outer surface of the nozzle chamber.

  Optionally, the nozzle opening is defined in the moving part so that the nozzle opening is movable relative to the floor.

In a fourth aspect, the present invention provides:
A nozzle chamber comprising a floor and a roof, the nozzle chamber having a moving portion in which a nozzle opening is defined and the roof is movable toward the floor;
A thermal bending actuator having a plurality of cantilever beams and ejecting ink through the nozzle openings;
Comprising the actuator,
A first active beam for connection to the drive circuit;
A second passive beam mechanically cooperating with the first beam such that when the current flows through the first beam, the first beam expands relative to the second beam, resulting in actuator bending;
An inkjet nozzle assembly, wherein the moving part comprises an actuator.

  In some cases, the first active beam defines at least 30% of the total area of the roof.

  In some cases, the first active beam defines at least a portion of the outer surface of the roof.

  In some cases, the nozzle opening is defined in the moving portion such that the nozzle opening is movable relative to the floor portion.

  In some cases, the actuator is movable relative to the nozzle opening.

  In some cases, the first beam is defined by a serpentine beam element, the serpentine beam element having a plurality of proximal beam members.

  Optionally, the plurality of proximal beam members includes a plurality of elongate beam members extending along the longitudinal axis of the first beam and at least one extending across the transverse axis of the first beam and interconnecting the elongate beam members. A short beam member is provided.

  In some cases, at least one of the plurality of beams is comprised of a porous material.

  In some cases, the porous material is porous silicon dioxide having a dielectric constant of 2 or less.

  Optionally, the thermal bending actuator further comprises a third insulating beam sandwiched between the first beam and the second beam.

  In some cases, the third insulating beam is composed of a porous material.

  Optionally, the first beam is fused or joined to the second beam.

  In some cases, the second beam is comprised of a porous material.

  In some cases, at least a portion of the first beam is spaced from the second beam.

  In some cases, the first beam is comprised of a material selected from the group comprising titanium nitride, titanium aluminum nitride, and aluminum alloys.

  In some cases, the first beam is composed of an aluminum alloy.

  Optionally, the aluminum alloy includes aluminum and at least one other metal having a Young's modulus greater than 100 GPa.

  Optionally, the at least one metal is selected from the group comprising vanadium, manganese, chromium, cobalt, and nickel.

  Optionally, the alloy includes aluminum and vanadium.

  Optionally, the alloy includes at least 80% aluminum.

In a fifth aspect, the present invention provides:
A nozzle chamber comprising a floor and a roof, the nozzle chamber having a moving portion in which a nozzle opening is defined and the roof is movable toward the floor;
A thermal bending actuator having a plurality of cantilever beams and ejecting ink through the nozzle openings;
Comprising the actuator,
A first active beam for connection to the drive circuit;
A second passive beam mechanically cooperating with the first beam such that when the current flows through the first beam, the first beam expands relative to the second beam, resulting in actuator bending;
And an inkjet nozzle assembly in which a first active beam defines at least a portion of the outer surface of the roof.

  In some cases, the moving part comprises an actuator.

  In some cases, the first active beam defines at least 30% of the total area of the roof.

  Optionally, the nozzle opening is defined in the moving part so that the nozzle opening is movable relative to the floor.

  In some cases, the actuator is movable relative to the nozzle opening.

  In some cases, the first beam is defined by a serpentine beam element, the serpentine beam element having a plurality of proximity beam members.

  Optionally, the tortuous beam element includes a plurality of elongate beam members and at least one elongate beam member, each elongate beam member extending along the longitudinal axis of the first beam and across the transverse axis of the first beam. Interconnected by elongate beam members that extend.

  In some cases, one of the plurality of beams is comprised of a porous material.

  In some cases, the porous material is porous silicon dioxide having a dielectric constant of 2 or less.

  Optionally, the thermal bending actuator further comprises a third insulating beam sandwiched between the first beam and the second beam.

  In some cases, the third insulating beam is composed of a porous material.

  Optionally, the first beam is fused or joined to the second beam.

  In some cases, the second beam is comprised of a porous material.

  In some cases, at least a portion of the first beam is spaced from the second beam.

  In some cases, the first beam is comprised of a material selected from the group comprising titanium nitride, titanium aluminum nitride, and aluminum alloys.

  In some cases, the first beam is composed of an aluminum alloy.

  In some cases, the aluminum alloy includes aluminum and at least one other metal having a Young's modulus greater than 100 GPa.

  Optionally, the at least one metal is selected from the group comprising vanadium, manganese, chromium, cobalt, and nickel.

  Optionally, the alloy includes aluminum and vanadium.

  Optionally, the alloy includes at least 80% aluminum.

In a sixth aspect, the present invention provides:
A first active beam for connection to a drive circuit defined by a serpentine beam element having a plurality of proximity beam members;
A second passive beam mechanically cooperating with the first beam such that when the current flows through the first beam, the first beam expands relative to the second beam, resulting in actuator bending;
A plurality of elongate beam members extending along the longitudinal axis of the first beam, and at least one short beam extending across the transverse axis of the first beam and interconnecting the elongate beam members A thermal bending actuator having a plurality of elongated cantilever beams comprising a beam member is provided.

  In some cases, the first beam is connected to the drive circuit via a pair of electrical contacts located at one end of the actuator.

  Optionally, a first electrical contact is connected to the first end of the tortuous beam element and a second electrical contact is connected to the second end of the tortuous beam element.

  In some cases, one of the plurality of beams is comprised of a porous material.

  In some cases, the porous material is porous silicon dioxide having a dielectric constant of 2 or less.

  In a further aspect, a thermal bending actuator is provided that further comprises a third insulating beam sandwiched between the first beam and the second beam.

  In some cases, the third insulating beam is composed of a porous material.

  Optionally, the first beam is fused or joined to the second beam.

  In some cases, the second beam is comprised of a porous material.

  In some cases, at least a portion of the first beam is spaced from the second beam.

  In some cases, the first beam is comprised of a material selected from the group comprising titanium nitride, titanium aluminum nitride, and aluminum alloys.

In a further aspect, the invention provides:
A nozzle chamber having a nozzle opening and an ink inlet;
A thermal bending actuator for ejecting ink through a nozzle opening having a plurality of cantilever beams;
Comprising the actuator,
A first active beam for connection to a drive circuit defined by a serpentine beam element including a plurality of proximity beam members;
A second passive beam mechanically cooperating with the first beam such that the first element extends relative to the second beam when current flows through the first beam, resulting in actuator bending;
With
A plurality of elongate beam members extending along the longitudinal axis of the first beam and at least one short beam member extending across the transverse axis of the first beam and interconnecting the elongate beam members; An inkjet nozzle assembly is provided.

  In some cases, the nozzle chamber comprises a roof having a floor and a moving portion, whereby actuation of the actuator moves the moving portion toward the floor.

  In some cases, the moving part comprises an actuator.

  In some cases, the first active beam defines at least 30% of the total roof area.

  Optionally, the first active beam defines at least a portion of the outer surface of the nozzle chamber.

  Optionally, the nozzle opening is defined in the moving part so that the nozzle opening is movable relative to the floor.

  In some cases, the actuator is movable relative to the nozzle opening.

  In a further aspect, there is provided an inkjet nozzle assembly further comprising a pair of electrical contacts disposed at one end of the actuator to achieve an electrical connection between the tortuous beam element and the drive circuit.

  Optionally, a first electrical contact is connected to the first end of the tortuous beam element and a second electrical contact is connected to the second end of the tortuous beam element.

2 is a schematic side view of a two-layer thermal bending actuator including an active beam formed from an aluminum-vanadium alloy. FIG. FIG. 3 is a schematic side view of various stages of operation of an inkjet nozzle assembly including a fusion heat bending actuator. FIG. 3 is a perspective view of the nozzle assembly shown in FIG. FIG. 4 is a perspective view of a portion of a printhead integrated circuit comprising the array of nozzle assemblies shown in FIGS. 2A and 3. FIG. 5 is a cutaway perspective view of an inkjet nozzle assembly with a spaced thermal bending actuator and a moving roof structure. It is a notch perspective view at the time of the action | operation structure of the inkjet nozzle assembly shown in FIG. FIG. 6 is a cutaway perspective view immediately after the operation of the inkjet nozzle assembly shown in FIG. 5 is stopped. FIG. 7 is a side sectional view of the nozzle assembly shown in FIG. 6. 1 is a side cross-sectional view of an inkjet nozzle assembly including a roof having a moving portion defined by a thermal bending actuator. FIG. FIG. 10 is a cutaway perspective view of the nozzle assembly shown in FIG. 9. It is a perspective view of the nozzle assembly shown in FIG. FIG. 11 is a cutaway perspective view of the array of nozzle assemblies shown in FIG. 10. FIG. 6 is a side cross-sectional view of an alternative inkjet nozzle assembly including a roof having a moving portion defined by a thermal bending actuator. FIG. 14 is a cutaway perspective view of the nozzle assembly shown in FIG. 13. FIG. 14 is a perspective view of the nozzle assembly shown in FIG. 13. FIG. 6 is a schematic side view of a three-layer thermal bending actuator comprising a sandwiched insulated beam formed from a porous material. 1 is a schematic side view of a two-layer thermal bending actuator comprising a passive beam formed from a porous material. FIG.

Thermoelastic active elements composed of aluminum alloys Typically, MEMS thermobending actuators (or thermoelastic actuators) comprise a pair of elements in the form of active elements and passive elements that suppress the linear expansion of the active elements. The active element needs to undergo greater thermoelastic expansion compared to the passive element, thereby providing a bending action. The elements can be fused or joined together for maximum structural integrity, or they can be spaced apart to minimize heat loss to the passive elements.

So far we have described titanium nitride as a suitable candidate for the active thermoelastic element of a thermal bending actuator (see, for example, US Pat. No. 6,416,167). Other suitable materials described, for example, in Applicant's US Pat. No. 6,428,133 include TiB ₂ , MoSi ₂ , and TiAlN.

  In view of its high thermal expansion and low density, aluminum is a strong candidate for use as an active thermoelastic element. However, aluminum suffers from a relatively low Young's modulus, which detracts from its overall thermoelastic efficiency. Thus, aluminum has not previously been noted as a suitable material for active thermoelastic elements.

  However, it has now been found that aluminum alloys are excellent materials for thermoelastic active elements because they combine the advantageous properties of high thermal expansion, low density, and high Young's modulus.

  In general, aluminum is alloyed with at least one metal having a Young's modulus greater than 100 GPa. In general, aluminum is alloyed with at least one metal selected from the group comprising vanadium, manganese, chromium, cobalt, and nickel. Surprisingly, it has been found that the excellent thermal expansion properties of aluminum are not impaired when alloyed with such metals.

  Optionally, the alloy comprises at least 60% aluminum, optionally at least 70%, optionally at least 80%, or optionally at least 90% aluminum.

  FIG. 1 shows a bimorph thermal bending actuator 200 in the form of a cantilever beam (cantilever) 201 secured to a post 202. The cantilever beam 201 comprises a lower active beam 210 joined to an upper passive beam 220 of silicon dioxide. The thermoelastic efficiency of actuator 200 is determined from each of (i) 100% Al, (ii) 95% Al and 5% V (vanadium), and (iii) 90% Al and 10% V. The constructed active beams were compared.

したがって、９５％Ａｌおよび５％Ｖから成る合金は、同等の１００％Ａｌのデバイスより２．０８倍低いエネルギが必要であった。さらに９０％Ａｌおよび１０％Ｖから成る合金は、同等の１００％Ａｌのデバイスより２．１２倍低いエネルギが必要であった。したがって、アルミニウム合金は、インクジェットノズル用の熱曲げアクチュエータを含むＭＥＭＳ用途の範囲で、アクティブ熱弾性要素用としての優れた候補であると結論付けられた。 Thermoelastic efficiency was compared by stimulating the active beam 210 with a short electrical pulse and measuring the energy required to establish a peak vibration velocity of 3 m / s as determined by a laser laser interferometer. The results are shown in the table below.

Thus, an alloy consisting of 95% Al and 5% V required 2.08 times less energy than an equivalent 100% Al device. Furthermore, the 90% Al and 10% V alloy required 2.12 times lower energy than the equivalent 100% Al device. Thus, it was concluded that aluminum alloys are excellent candidates for active thermoelastic elements in a range of MEMS applications including thermobending actuators for inkjet nozzles.

Inkjet Nozzle Including Thermal Bending Actuator A typical inkjet nozzle that can incorporate a thermal bending actuator having an active element composed of an aluminum alloy will now be described.

Nozzle Assembly with Fused Thermal Bending Actuator Turning first to FIGS. 2A and 3, a schematic diagram of a nozzle assembly 100 according to the first embodiment is shown. The nozzle assembly 100 is formed by a MEMS process on the passive layer 2 of the silicon substrate 3 as described in US Pat. No. 6,416,167. The nozzle assembly 100 includes a nozzle chamber 1 having a roof 4 and side walls 5. The nozzle chamber 1 is filled with ink 6 using an ink inlet channel 7 etched into the substrate 3. The nozzle chamber 1 further includes a nozzle opening 8 for ejecting ink from the nozzle chamber. As shown in FIG. 2A, the ink meniscus 20 is pinned to the rim 21 of the nozzle opening 8.

  The nozzle assembly 100 further includes a paddle 9 located inside the nozzle chamber 1 that is interconnected via an arm 11 to an actuator 10 located outside the nozzle chamber. As more clearly shown in FIG. 2, the arm extends through the slot 12 of the nozzle chamber 1. The surface tension of the ink in the slot 12 is sufficient to provide a fluid seal for the ink contained in the nozzle chamber 1.

  The actuator 10 includes a plurality of elongated actuator units 13 that are spaced apart in the lateral direction. Each actuator unit extends between a fixed column 14 and an arm 11 mounted on the passive layer 2. Thus, the strut 14 provides a pivot for the bending motion of the actuator 10.

  Each actuator unit 13 includes a first active beam 15 and a second passive beam 16 fused to the upper surface of the active beam. The active beam 15 is conductive and is connected to a driving circuit of the CMOS layer of the substrate 3. The passive beam 16 is generally non-conductive.

  Referring now to FIG. 2B, when current flows through the active beam 15, it is heated and undergoes thermal expansion relative to the passive beam 16. This causes an upward bending action of the actuator 10, which is magnified by the rotational movement of the paddle 9.

  This resulting paddle movement causes a general increase in pressure near the rapidly expanding ink meniscus 20, as shown in FIG. Thereafter, the actuator is de-energized, whereby the paddle 9 returns to its rest position (FIG. 2 (C)).

  During this pulse cycle, ink droplets 17 are ejected from the nozzle openings 8 and at the same time the ink 6 flows again into the nozzle chamber 1 via the ink inlet 7. The forward momentum of ink outside the nozzle rim 21 and the corresponding backflow result in a general shrinkage and tearing of the droplet 17 traveling towards the print medium, as shown in FIG. 2C. The collapsed meniscus 20 causes the ink 6 to be sucked into the nozzle chamber 1 through the ink inlet 7. As the nozzle chamber 1 is refilled, the position of FIG. 2A is achieved again and the nozzle assembly 100 is ready to eject another drop of ink.

  Turning to FIG. 3, it can be seen that the actuator units 13 are tapered with respect to their horizontal axes and have a narrow end connected to the column 14 and a wide end connected to the arm 11. This tapering ensures that maximum resistance heating occurs near the struts 14 and thereby maximizes the thermoelastic bending motion.

  Usually, the passive beam 16 is composed of silicon dioxide or TEOS deposited by CVD. As shown in FIGS. 2-4, the arm 11 is formed from the same material.

  In the present invention, the active beam 15 is made of an aluminum alloy, preferably an aluminum-vanadium alloy, as described above.

Nozzle Assembly with Separated Thermal Bending Actuator Turning now to FIGS. 5-8, a nozzle assembly 300 according to a second embodiment is illustrated. Turning to FIGS. 5-7 of the accompanying drawings, the nozzle assembly 300 defines an ink supply aperture 302 that opens into the chamber 304 through a hexagonal inlet 303 (which can be any other suitable shape). On the substrate 301 to be built (by MEMS technology). The chamber is defined by a floor portion 305, a roof portion 306, and nested peripheral wall 307 and 308. The side wall 307 depending downward from the roof portion 306 is sized to move up and down within the side wall 308 depending downward from the floor portion 305.

  The discharge nozzle is formed by a rim 309 located in the roof portion 306 to define an opening for discharging ink from the nozzle chamber, as further described below.

  The roof portion 306 and the downwardly hanging sidewall 307 are supported by a bending actuator 310 that is typically made from a layer forming a Joule heating cantilever constrained by an unheated cantilever, so that Joule heating by heating the Joule heating cantilever A differential expansion occurs between the cantilever and the unheated cantilever, causing the bending actuator 310 to bend.

  The proximal end 311 of the bending actuator is secured to the substrate 301 and prevented from moving backward by an anchor member 312 described further below, and the distal end 313 is secured to and supports the roof portion 306 and side wall 307 of the inkjet nozzle. To do.

  In use, ink is supplied into the nozzle chamber in any suitable manner, usually through passage 302 and opening 303, as described in the above-mentioned co-pending application. If it is desired to eject ink drops from the nozzle chamber, an electric current is supplied to the bending actuator 310 to cause the actuator to bend to the position shown in FIG. 6 and move the roof portion 306 downward toward the floor portion 305. This relative movement reduces the volume of the nozzle chamber and causes the ink to rise upwardly through the nozzle rim 309 as shown at 314 (FIG. 6), where the ink is formed into droplets by the surface tension of the ink.

  When the current in the bending actuator 310 stops, the actuator returns to a straight shape as shown in FIG. 7, and the roof portion 306 of the nozzle chamber is raised to its original position. The momentum of the partially formed ink droplet 314 continues to raise the droplet, forming an ink droplet 315 as shown in FIG. 7, which is fired onto the adjacent paper surface or other print target article.

  In one form of the invention, the opening 303 in the floor portion 305 is relatively large compared to the cross section of the nozzle chamber, and the viscous resistance in the supply conduit leading from the sidewall of the aperture 302 and the ink reservoir (not shown) to the opening 302. Accordingly, when the roof portion 306 is lowered, ink droplets are ejected through the nozzle rim 309.

  In order to prevent ink from leaking out of the nozzle chamber during operation of the bending actuator 310, i.e., during bending, a fluid seal is provided on the side walls 307 and 307 as will be further described with specific reference to FIGS. Formed between 308.

  During the relative movement of the roof portion 306 and the floor portion 305, the ink is retained in the nozzle chamber by the geometric features of the side walls 307 and 308 that ensure that the ink is retained in the nozzle chamber by surface tension. . For this purpose, a very fine gap is provided between the side wall 307 that hangs down and the opposing surface 316 of the side wall 308 that hangs down. As clearly shown in FIG. 8, the ink (shown as a dark shaded area) is placed in a small aperture between the side wall 307 that hangs downward and the inward surface 316 of the side wall that extends upward due to the proximity of the two side walls. This ensures that the ink “self-seals” the free openings 317 due to surface tension due to the proximity of the sidewalls.

  In order to provide for ink that may escape surface tension suppression due to impurities or other factors that break surface tension, the side wall 308 depending downwardly has not only the inner surface 316 but also the spaced parallel outer surface 18 and has two surface It is provided in the form of an upward channel forming a U-shaped channel 319 therebetween. Ink droplets that escape the surface tension between surfaces 307 and 316 overflow into the U-shaped channel and are retained rather than “leaked” beyond the surface of the nozzle layer. In this way, a double walled fluid seal is formed that is effective to hold the ink in the moving nozzle mechanism.

  Referring to FIG. 8, it can be seen that the actuator 310 is composed of a first active beam 358 spaced above the second passive beam 360. By separating the two beams, heat transfer from the active beam 358 to the passive beam 360 is minimized. This spaced configuration thus has the advantage of maximizing thermoelastic efficiency. In the present invention, the active beam 358 can be composed of an aluminum alloy such as an aluminum-vanadium alloy as described above.

Thermal Bending Actuator Defining a Moving Nozzle Roof The embodiment illustrated by FIGS. 5-8 has shown a nozzle assembly 300 comprising a nozzle chamber 304 having a roof portion 306 that moves relative to the floor portion 305 of the chamber. The movable roof portion 306 operates to move toward the floor portion 305 by a two-layer thermal bending actuator 310 disposed outside the nozzle chamber 305.

  The moving roof reduces drop ejection energy because only one face of the moving structure has to work against the viscous ink. However, there is still a need to increase the amount of power available for droplet ejection. By increasing the amount of power, a short pulse width can be used to provide the same amount of energy. With shorter pulse widths, improved drop ejection characteristics can be achieved.

  One means for increasing the output of the actuator is to increase the size of the actuator. However, in the nozzle designs shown in FIGS. 5-8, it is clear that the increase in actuator size adversely affects nozzle spacing, which is undesirable for the production of high resolution page width printheads.

  A solution to this problem is provided by the nozzle assembly 400 shown in FIGS. The nozzle assembly 400 includes a nozzle chamber 401 formed on the passive CMOS layer 402 of the silicon substrate 403. The nozzle chamber is defined by a roof 404 and sidewalls 405 extending from the roof to the passive CMOS layer 402. Ink is supplied to the nozzle chamber 401 by an ink inlet 406 in fluid communication with an ink supply channel 407 that receives ink from the backside of the silicon substrate. Ink is ejected from the nozzle chamber 401 through nozzle openings 408 defined in the roof 404. The nozzle opening 408 is offset from the ink inlet 406.

  As clearly shown by FIG. 10, the roof 404 has a moving portion 409 that defines a substantial portion of the total area of the roof. Typically, the moving portion 409 defines at least 20%, at least 30%, at least 40%, or at least 50% of the total roof area 404. In the embodiment shown in FIGS. 9-12, the nozzle opening 408 and the nozzle rim 415 are defined in the moving portion 409 so that the nozzle opening and the nozzle rim move with the moving portion.

  The nozzle assembly 400 is characterized in that the moving portion 409 is defined by a thermal bending actuator 410 having a planar upper active beam 411 and a planar lower passive beam 412. Thus, the actuator 410 typically defines at least 20%, at least 30%, at least 40%, or at least 50% of the total roof area 404. Accordingly, the upper active beam 411 typically defines at least 20%, at least 30%, at least 40%, or at least 50% of the total roof area 404.

As shown in FIGS. 9 and 10, at least a portion of the upper active beam 411 is spaced from the lower passive beam 412 to maximize the thermal insulation of the two beams. More specifically, the Ti layer is used as a bridging layer 413 between an upper active beam 411 composed of TiN and a lower passive beam 412 composed of SiO ₂ . The bridging layer 413 allows a gap 414 to be defined between the active and passive beams of the actuator 410. This gap 414 improves the overall efficiency of the actuator 410 by minimizing heat transfer from the active beam 411 to the passive beam 412.

  However, it will be appreciated that the active beam 411 can alternatively be fused or bonded directly to the passive beam 412 to improve structural rigidity. Such design changes are well within the scope of those skilled in the art and are included within the scope of the present invention.

  The active beam 411 is connected to a pair of contacts 416 (positive and ground) through a Ti bridge layer. The contact 416 is connected to the driving circuit of the CMOS layer.

  When it is necessary to eject ink droplets from the nozzle chamber 401, a current flows between the two contacts 416 via the active beam 411. The active beam 411 is rapidly heated by the electric current and stretches relative to the passive beam 412, thereby causing the actuator 410 (which defines the moving portion 409 of the roof 404) to bend downward toward the substrate 403. This movement of the actuator 410 causes ink to be ejected from the nozzle openings 408 due to a rapid increase in pressure inside the nozzle chamber 401. When the current stops flowing, the moving portion 409 of the roof 404 is returned to its rest position so that ink is sucked into the nozzle chamber 401 from the inlet 406 in preparation for the next discharge.

  Thus, the principle of ink droplet ejection is similar to that described above with respect to the nozzle assembly 300. However, because the thermal bending actuator 410 defines a moving portion 409 of the roof 404 and the active beam 411 has a large area compared to the overall size of the nozzle assembly 400, a much larger amount of power is applied to the droplet. It becomes available for discharge.

  Turning to FIG. 12, the nozzle assembly 400 (as with all other nozzle assemblies described herein) is duplicated into an array of nozzle assemblies to define a printhead or printhead integrated circuit. It can be easily understood that it can be achieved. The printhead integrated circuit includes a silicon substrate, an array of nozzle assemblies (typically arranged in rows) formed on the substrate, and a drive circuit for the nozzle assemblies. For example, as described in prior U.S. patent application Ser. No. 10 / 854,491 filed on May 27, 2004 and 11 / 014,732 filed Dec. 20, 2004. The head integrated circuit can be abutted or linked to form a page-width inkjet printhead, the contents of which are incorporated herein by reference.

  The nozzle assembly 500 shown in FIGS. 13-15 is similar to the nozzle assembly 400 as far as the thermal bending actuator 510 is concerned, has an upper active beam 511 and a lower passive beam 512 and moves the roof 504 of the nozzle chamber 501. Define the part. Thus, the nozzle assembly 500 achieves the same advantages as the nozzle assembly 400 with respect to increased power.

  However, in contrast to nozzle assembly 400, nozzle opening 508 and rim 515 are not defined by the moving portion of roof 504. Rather, since the nozzle opening 508 and rim 515 are defined in a fixed portion of the roof 504, the actuator 510 operates independently of the nozzle opening and rim during droplet ejection. The advantage of this configuration is that a simpler control of the droplet flight direction is achieved.

  An aluminum alloy with the inherent advantage of improved thermal bending efficiency is that it can be used as an active beam in either of the thermal bending actuators 410 and 510 described above in connection with the embodiment shown in FIGS. Needless to say, understood.

  Nozzle assemblies 400 and 500 use suitable MEMS technology in a manner similar to the inkjet nozzle manufacturing process illustrated in Applicants' prior US Pat. Nos. 6,416,167 and 6,755,509. The contents of the above publication are incorporated herein by reference.

Active Beam with Optimal Stiffness in Bending Direction Referring now to FIGS. 11 and 15, the upper active beams 411 and 511 of actuators 410 and 510 are either bent (for beam 411) or serpentine (for beam 511), respectively. It can be seen that it is composed of a serpentine beam element having such a shape. The serpentine beam element is elongated and has a relatively small cross-sectional area suitable for resistance heating. In addition, the serpentine shape allows each end of the beam element to be connected to a respective contact located at one end of the actuator, simplifying the overall design and construction of the nozzle assembly.

  With particular reference to FIGS. 14 and 15, the elongated beam element 520 has a serpentine shape that defines the elongated active cantilever beam 511 of the actuator 510. The serpentine beam element 520 has a planar tortuous path connecting the first electrical contact 516 with the second electrical contact 516. An electrical contact 516 (positive and ground) is disposed at one end of the actuator 510 to achieve an electrical connection between the drive circuit of the CMOS layer 502 and the active beam 511.

  The serpentine beam element 520 is made by standard lithographic etching techniques and is defined by a plurality of proximity beam members. In general, a beam member can be defined as a solid portion of a beam material extending substantially linearly in a longitudinal direction or a lateral direction, for example. The beam member of the beam element 520 is composed of a long beam member 521 extending along the longitudinal axis of the elongated cantilever beam 511 and a short beam member 522 extending across the lateral axis of the elongated cantilever beam 511. The advantage of this configuration in the case of the serpentine beam element 520 is that it achieves maximum rigidity in the bending direction of the cantilever beam 511. The stiffness in the bending direction is advantageous because it facilitates returning the bending of the actuator 510 to its rest position after each actuation.

  It will be appreciated that the bent active beam shape of the nozzle assembly 400 shown in FIG. 11 achieves the same or similar advantages as described above with respect to the nozzle assembly 500. In FIG. 11, the long beam member extending in the longitudinal direction is indicated by 421, while the short beam member for interconnection extending in the lateral direction is indicated by 422.

Use of Porous Material to Increase Thermal Efficiency In all other embodiments described above, as well as in all other embodiments of the thermal bending actuator described by the applicant, the active beam is structurally robust. For this purpose (see FIGS. 1 and 2) or the active beam is separated from the passive beam for maximum thermal efficiency (see FIG. 8). Of course, the thermal efficiency achieved by the air gap between the beams is desirable. However, this improvement in thermal efficiency usually comes at the price of structural robustness and thermal bending actuator buckling tendency.

  US Pat. No. 6,163,066 describes a porous silicon dioxide insulator having a dielectric constant of about 2.0 or less, the contents of which are incorporated herein by reference. The material is formed by depositing silicon carbide and oxidizing the carbon component to form porous silicon dioxide. By increasing the ratio of carbon to silicon, the porosity of the resulting porous silicon dioxide can be increased. Porous silicon dioxide is known to be useful as a passive layer in integrated circuits to reduce parasitic resistance.

  However, the applicant of the present application has discovered that this type of porous material is useful in improving the efficiency of thermal bending actuators. The porous material can be used as an insulating layer between the active beam and the passive beam, or it can be used as the passive beam itself.

FIG. 16 shows a thermal bending actuator 600 comprising an upper active beam 601, a lower passive beam 602, and an insulating layer 603 sandwiched between the upper and lower beams. Insulation beam is comprised of a porous silicon dioxide can be constructed from any suitable material such as an active beam 601 and the passive beams 602, respectively TiN and SiO _2.

  The porosity of the insulating layer 603 achieves excellent thermal insulation between the active beam 601 and the passive beam 602. Insulating layer 603 also provides structural robustness to actuator 600. Thus, the actuator 600 combines the advantages of both types of thermal bending actuators described above in connection with FIGS.

  Alternatively, and as shown in FIG. 17, the porous material may simply form the passive layer of a two-layer thermal bending actuator. Accordingly, the thermal bending actuator 650 includes an upper active beam 651 composed of TiN and a lower passive beam 652 composed of porous silicon dioxide.

  Of course, it is understood that a thermal bending actuator of the type shown in FIGS. 16 and 17 can be incorporated into any suitable inkjet nozzle or other MEMS device. Improvements in thermal efficiency and structural rigidity make such actuators attractive in any MEMS application that requires mechanical actuators or transducers.

  A thermal bending actuator of the type shown in FIGS. 16 and 17 is particularly suitable for use with the inkjet nozzle assemblies 400 and 500 described above. Those skilled in the art will readily appreciate that appropriate improvements in the thermal bending actuators 410 and 510 can achieve the above improvements in thermal efficiency and structural robustness.

  Furthermore, it will be appreciated that the active beam members 601 and 651 in the thermal bending actuators 600 and 650 described above may be constructed from an aluminum alloy as described hereinabove for further improvement in thermal bending efficiency. .

  It will be understood that the present invention has been described by way of example only and that variations in detail may be made within the scope of the invention as set forth in the appended claims.

Claims (13)

A nozzle chamber comprising a floor and a roof, the nozzle chamber having a moving portion in which nozzle openings are defined and the roof is movable toward the floor;
A thermal bending actuator having a plurality of cantilever beams and ejecting ink from the nozzle openings;
With
The thermal bending actuator is
A first active beam for connection to a drive circuit , wherein the first active beam is defined by a serpentine beam element, the serpentine beam element having a plurality of proximity beam members, the plurality of proximity beams; The beam members are in close proximity to each other, the first active beam ;
A second passive beam provided away from the first active beam, wherein the first active beam thermally expands and expands with respect to the second passive beam when a current is passed through the first active beam. The second passive beam mechanically cooperating with the first active beam to result in bending of the thermal bending actuator;
With
An inkjet nozzle assembly, wherein the first active beam defines at least 30% of the total area of the roof.   The inkjet nozzle assembly of claim 1, wherein the moving portion comprises the thermal bending actuator.   The inkjet nozzle assembly of claim 1, wherein the first active beam defines at least a portion of an outer surface of the roof.   The inkjet nozzle assembly of claim 1, wherein the nozzle opening is defined in the moving portion such that the nozzle opening is movable relative to the floor.   The inkjet nozzle assembly of claim 1, wherein the thermal bending actuator is movable relative to the nozzle opening. The plurality of proximity beam members are
A plurality of elongate beam members extending along a longitudinal axis of the first active beam;
At least one short beam member extending across the transverse axis of the first active beam and interconnecting the long beam members;
The inkjet nozzle assembly of claim 1 , comprising: The inkjet nozzle assembly of claim 1, wherein the second passive beam is comprised of porous silicon dioxide having a dielectric constant of 2 or less .   The inkjet nozzle assembly of claim 1, wherein the first active beam is composed of a material selected from the group comprising titanium nitride, titanium aluminum nitride, and aluminum alloys.   The inkjet nozzle assembly of claim 1, wherein the first active beam is composed of an aluminum alloy. The aluminum alloy is
With aluminum,
At least one other metal having a Young's modulus greater than 100 GPa;
The inkjet nozzle assembly of claim 9 , comprising: The inkjet nozzle assembly of claim 10 , wherein the at least one other metal is selected from the group comprising vanadium, manganese, chromium, cobalt, and nickel. The inkjet nozzle assembly of claim 9 , wherein the aluminum alloy comprises aluminum and vanadium. The inkjet nozzle assembly of claim 9 , wherein at least 80% of the aluminum alloy comprises aluminum.

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