KR101030152B1 - Inkjet nozzle assembly having thermal bend actuator with an active beam defining substantial part of nozzle chamber roof - Google Patents

Abstract

Provided is an inkjet nozzle assembly. The assembly includes a nozzle chamber consisting of a bottom and a ceiling. The ceiling has a nozzle opening therein and a movable portion movable toward the bottom. The assembly further includes a thermal bend actuator having a plurality of cantilever beams for ejecting ink through the nozzle opening. The first active beam of the actuator occupies at least 30% of the total area of the ceiling.

Printers, Inkjets, Nozzle Assemblies, Actuators, Thermal Bend Actuators, Beams, Cantilevers

Description

INKJET NOZZLE ASSEMBLY HAVING THERMAL BEND ACTUATOR WITH AN ACTIVE BEAM DEFINING SUBSTANTIAL PART OF NOZZLE CHAMBER ROOF}

The present invention relates to a thermal bend actuator. The present invention was primarily developed to provide improved inkjet nozzles for ejecting ink through a thermal bend actuator.

Cross-reference

The following patents or patent applications filed by the applicant or assignee of the present invention are incorporated herein by reference.

Background of the Invention

Applicant has previously described a number of MEMS inkjet nozzles using a thermal bend actuator. A thermal bend actuator generally refers to a bend movement caused by thermal expansion of another material through which a current passes through one material. The resulting bending motion can be used to selectively eject ink from the nozzle opening via the movement of a paddle or vane, causing a pressure wave in the nozzle chamber.

Some representative types of thermal bend inkjet nozzles are illustrated in the patents or patent applications listed above, the contents of which are incorporated herein by reference.

Applicant's US Pat. No. 6,416,167 describes an inkjet nozzle having a paddle located in the nozzle chamber and a thermal bend actuator located outside of the nozzle chamber. The actuator takes the form of a lower active beam of conductive material fused to an upper passive beam of non-conductive material (eg silicon dioxide). . The actuator is connected to the paddle via an arm that is received through a slot formed in the wall of the nozzle chamber. As the current passes through the lower active beam, the actuator is bent downward and the paddle moves toward the nozzle opening formed in the roof of the nozzle chamber, whereby ink droplets are ejected. This design has the advantage that the configuration is simplified. The disadvantage of this design is that both sides of the paddle counteract the relatively viscous ink inside the nozzle chamber.

Applicant's US Patent No. 6,260,953, assigned to Applicant, describes an inkjet nozzle wherein the actuator forms a moving roof portion of the nozzle chamber. This actuator takes the form of a serpentine core of a conductive material sealed by a polymer material. In operation, the actuator is bent toward the bottom of the nozzle chamber, increasing the pressure in the chamber and driving ink droplets out of the nozzle openings formed in the ceiling of the chamber. The nozzle opening is formed in the non-moving portion of the ceiling. The advantage of this design is that only one side of the movable ceiling counteracts the relatively viscous ink inside the nozzle chamber. A disadvantage of this design is that it is difficult to achieve the actuator in the MEMS process to form the actuator with a meandering conductive element sealed by polymer material.

Applicant's US Pat. No. 6,623,101 describes an inkjet nozzle comprising a nozzle chamber having a movable ceiling having a nozzle opening formed therein. The movable ceiling is connected via an arm to a thermal bend actuator located outside of the nozzle chamber. This actuator takes the form of an upper active beam spaced apart from a lower passive beam. By spacing the active beam and the passive beam, the thermal bend efficiency is maximized because the passive beam acts as a heat sink for the active beam. When the current passes through the upper active beam, the movable ceiling with the nozzle opening therein rotates toward the bottom of the nozzle chamber, thereby being injected through the nozzle opening. Since the nozzle opening moves with the ceiling, the flight direction of the ink droplets can be controlled by appropriate shape change of the nozzle rim. The advantage of this design is that only one side of the movable ceiling counteracts the relatively viscous ink inside the nozzle chamber. Another advantage is that heat loss is minimal by separating the active and passive beam elements. The disadvantage of this design is the lack of structural stiffness when separating the active and passive beam elements.

Thus, there is a need to improve the design of thermal bend inkjet nozzles to achieve more efficient ink jetting and improved mechanical robustness.

Summary of the Invention

In a first aspect, the present invention provides an apparatus comprising: a nozzle chamber comprising a floor and a roof having a nozzle opening formed therein and having a moving portion movable toward the bottom; And a thermal bend actuator having a plurality of cantilever beams and configured to eject ink through the nozzle openings; Including;

The thermal bend actuator includes a first active beam for connecting to a drive circuit and a second passive beam mechanically cooperating with the first active beam so that when the current passes through the first active beam, the first active beam 2, an inkjet nozzle assembly is provided which expands against the passive beam causing bending of the actuator.

Optionally, the first active beam occupies at least 30% of the total area of the ceiling.

Optionally, said moving part comprises said actuator.

Optionally, said first active beam forms at least a portion of an outer surface of said ceiling.

Optionally, the nozzle opening is formed in the moving part such that the nozzle opening is movable relative to the bottom part.

Optionally, the actuator is movable relative to the nozzle opening.

Optionally, said first active beam is formed by a tortuous beam element, said meandering beam element having a plurality of adjacent beam members.

Optionally, the plurality of adjacent beam members comprises a plurality of elongated 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 long beam members. It includes.

Optionally, one of the plurality of beams is made of a porous material.

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

Optionally, said thermal bend actuator comprises a third insulation beam interposed between said first beam and said second beam.

Optionally, said third insulating beam is made of a porous material.

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

Optionally, the second beam is made of a porous material.

Optionally, at least a portion of the first beam is spaced apart from the second beam.

Optionally, the first beam is made of a material selected from the group consisting of titanium nitride, aluminum titanium nitride and aluminum alloy.

Optionally, said first beam is made of an aluminum alloy.

Optionally, the aluminum alloy consists of aluminum and at least one other metal having a Young's Modulus greater than 100.

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

Optionally, the alloy consists of aluminum and vanadium.

Optionally, the alloy consists of at least 80% aluminum.

In a second aspect, the present invention provides a thermal bend actuator having a plurality of elements, comprising: a first active element for connecting to a driving circuit; And

A second passive element that mechanically cooperates with the first active element; Including, when the current passes through the first active element, the first active element expands with respect to the second passive element, causing bending of the actuator,

The first device provides a thermal bend actuator made of an aluminum alloy.

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

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

Optionally, the alloy consists of aluminum and vanadium.

Optionally, the alloy consists of at least 80% aluminum.

Optionally, said first and second elements are cantilever beams.

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

Optionally, at least a portion of the second beam is spaced apart from the first beam, whereby the first beam is insulated from the second beam.

Optionally, one of the plurality of beams is made of a porous material.

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

Optionally, the porous material is porous silicon dioxide.

Optionally, a third insulating beam is interposed between the first beam and the second beam.

Optionally, said third insulating beam is made of a porous material.

Optionally, the second beam is made of a porous material.

In yet another aspect, the invention provides a nozzle chamber including a nozzle opening and an ink inlet; And

A thermal bend actuator having a plurality of cantilever beams and configured to eject ink through the nozzle openings; Including,

The actuator includes a first active beam for connecting to a drive circuit and a second passive beam mechanically cooperating with the first active beam such that when the current passes through the first active beam, the first active beam is second passive. Expanding with respect to the beam causes bending of the actuator, and provides the inkjet nozzle assembly wherein the first beam is made of aluminum alloy.

Optionally, the nozzle chamber includes a bottom portion and a ceiling having a moving portion such that the actuator moves the moving portion toward the bottom portion.

Optionally, said moving part comprises said actuator.

Optionally, the first active beam occupies at least 30% of the total area of the ceiling.

Optionally, said first active beam forms at least a portion of an outer surface of said ceiling.

Optionally, the nozzle opening is formed in the moving part such that the nozzle opening is movable relative to the bottom part.

In a third aspect, the present invention provides a thermal bend actuator having a plurality of elements, comprising: a first active element for connecting to a driving circuit; And

A second passive element that mechanically cooperates with the first active element; Including, when the current passes through the first active element, the first active element is expanded with respect to the second passive element to cause bending of the actuator,

One of the plurality of devices provides a thermal bend actuator made of a porous material.

Optionally, the porous material has a dielectric constant of about 2 or less.

Optionally, the porous material is porous silicon dioxide.

Optionally, said first and second elements are cantilever beams.

In still another aspect, there is provided a thermal bend actuator further comprising a third insulated beam interposed between the first beam and the second beam.

Optionally, said third insulating beam is made of a porous material.

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

Optionally, the second beam is made of a porous material.

Optionally, the first element is made of a material selected from the group consisting of titanium nitride, aluminum titanium nitride and an aluminum alloy.

Optionally, the first element is made of an aluminum alloy.

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

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

Optionally, the alloy consists of aluminum and vanadium.

Optionally, the alloy consists of at least 80% aluminum.

In yet another aspect, the invention provides a nozzle chamber including a nozzle opening and an ink inlet;

A thermal bend actuator having a plurality of cantilever beams for ejecting ink through the nozzle opening;

A first active beam for coupling to a drive circuit; And

A second passive beam mechanically cooperating with the first active beam; Including, when the current passes through the first active beam, the first active beam is expanded with respect to the second passive beam to cause bending of the actuator,

An inkjet nozzle assembly is provided in which one of the plurality of beams is made of a porous material.

Optionally, the nozzle chamber comprises a ceiling having a bottom and a moving part, whereby the moving part is movable toward the bottom when the actuator is actuated.

Optionally, said moving part comprises said actuator.

Optionally, the first active beam occupies at least 30% of the total area of the ceiling.

Optionally, said first active beam forms at least a portion of an outer surface of said nozzle chamber.

Optionally, the nozzle opening is formed in the moving part such that the nozzle opening is movable relative to the bottom part.

In a fourth aspect, the present invention provides an apparatus comprising: a nozzle chamber comprising a bottom portion and a ceiling portion having a nozzle opening therein and a movable portion movable toward the bottom portion; And

A thermal bend actuator having a plurality of cantilever beams, for injecting ink through the nozzle opening; Including,

The actuator includes a first active beam for connecting to a drive circuit and a second passive beam mechanically cooperating with the first active beam such that when the current passes through the first active beam, the first active beam is second passive. Inflation with respect to the beam causes bending of the actuator,

The moving part provides an inkjet nozzle assembly comprising the actuator.

Optionally, the first active beam occupies at least 30% of the total area of the ceiling.

Optionally, said first active beam forms at least a portion of an outer surface of said ceiling.

Optionally, the nozzle opening is formed in the moving part such that the nozzle opening is movable relative to the bottom part.

Optionally, the actuator is movable relative to the nozzle opening.

Optionally, said first beam is formed by a meandering beam element, said meandering beam element having a plurality of adjacent beam members.

Optionally, the plurality of adjacent beam members comprises a plurality of elongated 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 long beam members. It includes.

Optionally, one of the plurality of beams is made of a porous material.

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

Optionally, said thermal bend actuator comprises a third insulating beam interposed between said first beam and said second beam.

Optionally, said third insulating beam is made of a porous material.

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

Optionally, the second beam is made of a porous material.

Optionally, at least a portion of the first beam is spaced apart from the second beam.

Optionally, the first beam is made of a material selected from the group consisting of titanium nitride, aluminum titanium nitride and aluminum alloy.

Optionally, said first beam is made of an aluminum alloy.

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

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

Optionally, the alloy consists of aluminum and vanadium.

Optionally, the alloy consists of at least 80% aluminum.

According to a fifth aspect, the present invention provides an apparatus comprising: a nozzle chamber having a bottom portion and a ceiling portion having a nozzle opening formed therein and having a movable portion movable toward the bottom portion; And

A thermal bend actuator having a plurality of cantilever beams and configured to eject ink through the nozzle openings; Including;

The actuator includes a first active beam for connecting to a drive circuit and a second passive beam mechanically cooperating with the first active beam such that when the current passes through the first active beam, the first active beam is second passive. Inflation with respect to the beam causes bending of the actuator,

The first active beam provides an inkjet nozzle assembly that forms at least a portion of an outer surface of the ceiling.

Optionally, said moving part comprises said actuator.

Optionally, the first active beam occupies at least 30% of the total area of the ceiling.

Optionally, the nozzle opening is formed in the moving part such that the nozzle opening is movable relative to the bottom part.

Optionally, the actuator is movable relative to the nozzle opening.

Optionally, said first beam is formed by a meandering beam element, said meandering beam element having a plurality of adjacent beam members.

Optionally, the plurality of adjacent beam members comprises a plurality of elongated 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 long beam members. It includes.

Optionally, one of the plurality of beams is made of a porous material.

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

Optionally, said thermal bend actuator comprises a third insulating beam interposed between said first beam and said second beam.

Optionally, said third insulating beam is made of a porous material.

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

Optionally, the second beam is made of a porous material.

Optionally, at least a portion of the first beam is spaced apart from the second beam.

Optionally, the first beam is made of a material selected from the group consisting of titanium nitride, aluminum titanium nitride and aluminum alloy.

Optionally, said first beam is made of an aluminum alloy.

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

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

Optionally, the alloy consists of aluminum and vanadium.

Optionally, the alloy consists of at least 80% aluminum.

In a sixth aspect, the present invention provides a thermal bend actuator having a plurality of elongated cantilever beams.

A first active beam for connecting to a drive circuit, the first active beam being formed by a meandering beam element having a plurality of adjacent beam members; And

A second passive beam mechanically cooperating with the first active beam; Including, when the current passes through the first active beam, the first active beam is expanded with respect to the second passive beam to cause bending of the actuator,

The plurality of adjacent beam members includes a plurality of elongated beam members extending along a longitudinal axis of the first beam, and at least one short beam member extending across a horizontal axis of the first beam and interconnecting the long beam members. A thermal bend actuator is provided.

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

Optionally, one of the plurality of beams is made of a porous material.

Optionally, the porous material is porous silicon dioxide having a dielectric constant of about 2 or less.

In still another aspect, there is provided a thermal bend actuator further comprising a third insulating beam interposed between the first beam and the first beam.

Optionally, said third insulating beam is made of a porous material.

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

Optionally, the second beam is made of a porous material.

Optionally, at least a portion of the first beam is spaced apart from the second beam.

Optionally, the first beam is made of a material selected from the group consisting of titanium nitride, aluminum titanium nitride and aluminum alloy.

In yet another aspect, the invention provides a nozzle chamber including a nozzle opening and an ink inlet;

A thermal bend actuator having a plurality of cantilever beams for ejecting ink through the nozzle opening;

A first active beam for connecting to a drive circuit, the first active beam being formed by a meandering beam element having a plurality of adjacent beam members; And

A second passive beam mechanically cooperating with the first active beam; Including, when the current passes through the first active beam, the first active beam is expanded with respect to the second passive beam to cause bending of the actuator,

The plurality of adjacent beam members includes a plurality of elongated beam members extending along a longitudinal axis of the first beam, and at least one short beam member extending across a horizontal axis of the first beam and interconnecting the long beam members. Provided is an inkjet nozzle assembly.

Optionally, the nozzle chamber comprises a ceiling having a bottom and a moving part, whereby the moving part is movable toward the bottom when the actuator is actuated.

Optionally, said moving part comprises said actuator.

Optionally, the first active beam occupies at least 30% of the total area of the ceiling.

Optionally, said first active beam forms at least a portion of an outer surface of said nozzle chamber.

Optionally, the nozzle opening is formed in the moving part such that the nozzle opening is movable relative to the bottom part.

Optionally, the actuator is movable relative to the nozzle opening.

In still another aspect, there is provided an inkjet nozzle assembly further comprising a pair of electrical contacts located at one end of the actuator, the electrical contacts providing electrical connection between the meandering beam element and the drive circuit.

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

1 is a schematic side view of a bi-layered thermal bend actuator comprising an active beam formed of an aluminum-vanadium alloy.

2 (A)-(C) are schematic side cross-sectional views of an inkjet nozzle assembly including a thermal bend actuator fused at various stages of operation.

3 is a perspective view of the nozzle assembly shown in FIG. 2 (A).

4 is a partial perspective view of a printhead integrated circuit including an array of nozzle assemblies, as shown in FIGS. 2A and 3.

5 is a cut away perspective view of an inkjet nozzle assembly including a spaced thermal bend actuator and a removable ceiling structure.

FIG. 6 is a cutaway perspective view of the operation of the inkjet nozzle assembly shown in FIG. 5; FIG.

FIG. 7 is a cutaway perspective view immediately after shutdown of the inkjet nozzle assembly shown in FIG. 5; FIG.

8 is a side cross-sectional view of the nozzle assembly shown in FIG. 6.

9 is a side cross-sectional view of an inkjet nozzle assembly including a ceiling having a moving portion formed by a thermal bend actuator.

FIG. 10 is a cutaway perspective view of the nozzle assembly shown in FIG. 9. FIG.

FIG. 11 is a perspective view of the nozzle assembly shown in FIG. 10. FIG.

12 is a cutaway perspective view of the array of nozzle assemblies shown in FIG. 10.

FIG. 13 is a side cross-sectional view of another inkjet nozzle assembly including a ceiling having a moving portion formed by a thermal bend actuator. FIG.

FIG. 14 is a cutaway perspective view of the nozzle assembly shown in FIG. 13. FIG.

FIG. 15 is a perspective view of the nozzle assembly shown in FIG. 13. FIG.

16 is a schematic side view of a multilayer thermal bend actuator including a sandwitched insulated beam formed of a porous material.

17 is a schematic side view of a multilayer thermal bend actuator comprising an active beam formed of a porous material.

<Detailed description of the invention>

Made of aluminum alloy Thermoelastic  Active element

Typically, MEMS thermal bend actuators (or thermoelastic actuators) comprise a pair of elements in the form of active elements and passive elements that constrain the linear expansion of the active elements. It is required to receive a greater thermoelastic expansion for the device, thereby providing a bending motion The devices can be fused or glued together for maximum structural integrity, or they can reduce heat loss for the active device. It can be spaced apart to minimize it.

So far, titanium nitride, which is a suitable substitute for an active thermoelastic element in a thermal bend actuator, has been described (see, eg, US Pat. No. 6,416,167). For example, other suitable materials described in US Pat. No. 6,428,133 are Applicants TiB ₂ , MoSi ₂ and TiAlN.

In view of its high thermal expansion and low density, aluminum is a powerful substitute for use as an active thermoelastic device. However, aluminum has a relatively low Young's modulus, which lowers its overall thermoelastic efficiency. Therefore, aluminum has been ignored as a suitable material for use as an active thermoelastic element.

However, it has now been found that aluminum alloy is an excellent material for use as a thermoelastic active element, because it has all of the advantageous properties of high thermal expansion, low density and high Young's modulus.

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

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

1 shows a bimorph thermal bend actuator 200 in the form of a cantilever beam 201 secured to a post 202. The cantilever beam 201 includes a lower active beam 210 bonded to an upper active beam 220 of silicon dioxide. The thermoelastic efficiencies of the actuators 200 are compared for an active beam consisting of (i) 100% Al, (ii) 95% Al / 5% V, and (iii) 90% Al / 10% V. It was.

The thermoelastic efficiencies were compared by stimulating a short electric pulse on the active beam 210 and measuring the energy required to establish a peak oscillatory velocity of 3 m / s as determined by the laser interferometer. The results are shown in the table below.

Active beam material Energy required to reach peak vibration velocity 100% Al 466nJ 95% Al / 5% V 224nJ 90% Al / 10% V 219nJ

As such, 95% Al / 5% V alloy required 2.08 times less energy than 100% Al element compared. In addition, 90% Al / 10% V alloy required 2.12 times less energy than 100% Al element compared. Therefore, for Al devices, it has been concluded that aluminum is an excellent substitute for use as an active thermoelastic device in the scope of MEMS applications, including thermal bend actuators for inkjet nozzles.

Thermal Bend Actuator  Containing Inkjet  Nozzle

 Hereinafter, a typical inkjet nozzle capable of integrating a thermal bend actuator having an active element made of an aluminum alloy will be described.

<Nozzle Assembly Including Fused Thermal Bend Actuator>

2A and 3, a schematic diagram of the nozzle assembly 100 according to the first embodiment is shown. The nozzle assembly 100 is formed by MEMS processing on a passivation 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 ceiling 4 and a side wall portion 5. The nozzle chamber 1 is filled with ink by an ink inlet channel 7 etched through the substrate 3. The nozzle chamber 1 further comprises a nozzle opening 8 for ejecting ink from the nozzle chamber. The ink meniscus 20 is fixed in contact with the rim 21 of the nozzle opening 8, as shown in Fig. 2A.

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

The actuator 10 includes a plurality of elongate actuator units 13 which are laterally spaced apart. Each actuator unit extends between an arm 11 and a fixed post 14 mounted on the passivation layer 2. Therefore, the post 14 provides a pivot for the bending movement of the actuator 10.

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

Referring now to FIG. 2B, when current flows through the active beam 15, the active beam 15 is heated to undergo thermal expansion with respect to the passive beam 16. This causes the upward bending movement of the actuator 10, which expands into the rotational movement of the paddle 9.

This resulting paddle movement causes an increase in the pressure around the ink meniscus that expands in a rapid manner, as illustrated in FIG. 1B. The actuator is then deactivated, causing the paddle 9 to return to its quiescent position (FIG. 2C).

During the pulse cycle, ink droplets 17 are ejected from the nozzle opening 8 and at the same time ink 6 flows back through the ink inlet 7 into the nozzle chamber 1. The forward movement of the ink outside the nozzle edge 21 and its corresponding backflow causes the neck of the ink droplet 17 advancing toward the print medium to be cut off as shown in Fig. 2C. The collapsed meniscus 20 allows ink to be sucked into the nozzle chamber 1 through the ink inlet 7. The nozzle chamber 1 is refilled so that the position in FIG. 2A is reached again and the nozzle assembly 100 is ready to spray another ink droplet.

Returning to FIG. 3, the actuator units 13 are tapered with respect to their transverse axis and have a narrower end connected to the support 14 and a wider end connected to the arm 11. Has

This tapered shape ensures that maximum resistive heating occurs near the strut 14, maximizing thermoelastic bending motion.

Typically, the passive beam 16 consists of TEOS or silicon dioxide deposited by CVD. As shown in Figs. 2 to 4, the arm 11 is formed of 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 Including Spaced Thermal Bend Actuator>

Turning now to FIGS. 5-8, a nozzle assembly 300 according to a second embodiment is shown. 5-7, the nozzle assembly 300 opens an ink supply aperature 303 through a hexagonal inlet 3030 (which may be configured in any other suitable form) in the chamber 304. It is comprised on the board | substrate 301 to form (by MEMS technique). The chamber is formed by bottom side 305, ceiling 306, and peripheral side wall portions 308, 308 that overlap in a telescopic manner, such as a telescope. The side wall portions 307 are suspended below the ceiling 306 and may move upward and downward in the upward side wall portion 308 from the bottom portion 305.

The jet nozzle is formed by an edge 309 located in the ceiling 306 to define an opening for jetting ink from the nozzle, as described in more detail below.

The ceiling 306 and the sidewall portions 307 connected below are bend actuators 310 which typically consist of layers forming a Joule heated cantilever that is constrained by a non-heated cantilever. Heating of the joule heated cantilever causes differential expansion between the unheated cantilever and the joule heated cantilever, causing the bend actuator 310 to bend.

The proximal end of the bend actuator is fastened to the substrate 301 and prevents the rearward movement by an anchor member 312 as described in more detail below, and the distal end ( 313 is fixed to the support of the inkjet nozzle, that is, the ceiling 306 and the side wall portions 307.

In use, ink is supplied to the nozzle chamber through passage 302 and opening 303 in any suitable manner, but may also be supplied in the manner described in the co-pending patent applications referenced above. In the case where ink droplets are to be ejected from the nozzle chamber, an electric current is supplied to the bend actuator 310 to cause the actuator to bend to the position shown in FIG. 6 to move the ceiling 306 downward toward the bottom 305. . This relative movement reduces the volume of the nozzle chamber, causing the ink to bulge upward through the nozzle edge 309 as indicated by 314 (FIG. 6). 314 in FIG. 6 is formed into ink droplets by the surface tension of the ink.

When the electrical current is interrupted from the bend actuator 310, the actuator returns to a straight configuration as shown in FIG. 7, moving the ceiling 306 of the nozzle chamber upwards to its original position. The momentum of the partially formed ink droplets 314 allows the ink droplets to continue to move upwards to form the ink droplets 315 shown in FIG. 7 that protrude to adjacent paper surfaces or other articles of the print object.

In one form of the invention, the opening 303 of the bottom portion 305 is relatively large compared to the cross section of the nozzle chamber and the ink droplets are opened from sidewall portions of the opening 302 and from an ink reservoir (not shown). Viscous drag in the supply conduit leading to 303 causes the ceiling 306 to be injected through the nozzle edge 309 upon upward movement of the ceiling 306.

In order to prevent ink from leaking from the nozzle chamber during operation, i.e., during bending of the bend actuator 310, the fluid seal is provided with side wall portions 307, 308, as will be described in more detail below with particular reference to FIGS. Are formed between them.

The ink is retained in the nozzle chamber during the relative movement of the ceiling 306 and the bottom 305 by the geometry of the sidewall portions 307, 308, which ensures that the ink is retained in the nozzle chamber by surface tension. For this purpose, a very fine gap is provided between the downward sidewall portion 307 and the opposite side surfaces 316 of the upward sidewall portion 308. As can be clearly seen in FIG. 8, the ink (shown as a dark shaded area) is retained in a small opening between the inner sidewall 316 and the downward sidewall portion 307 extending upward by near two sidewall portions. This ensures that the ink "self seals" across the free opening 317 by surface tension due to the very close sidewall portions.

In order to provide any ink that can avoid surface tension suppression due to impurities or other factors that can break the surface tension, the upside wall portion 308 is U-shaped between the two surfaces as well as the inner surface 316. It is installed in the form of an upwardly facing channel with spaced parallel outer surfaces 18 forming channels 319. Any ink that escapes from the surface tension between the surfaces 307 and 316 overflows into the U-shaped channel, where the ink is retained rather than "wicking" across the surface of the nozzle sttrata. As such, a double wall fluid seal is formed that is effective in retaining ink in the movable nozzle mechanism.

Referring to FIG. 8, the actuator 310 is composed of a first active beam 358 and a second passive beam 360, wherein the first active beam 358 is disposed above the second passive beam 360. It can be seen that it is spaced apart from the second passive beam 360. By spacing the two beams, heat transfer from the active beam 358 to the passive beam 360 is minimized. Thus, such spaced arrangements have the advantage of maximizing thermoelastic efficiency. In the present invention, the active beam 358 may be made of an aluminum alloy, such as an aluminum-vanadium alloy, as described above.

<Thermal Bend Actuator with Removable Nozzle Ceiling>

5-8 illustrate a nozzle assembly 300 that includes a nozzle chamber 304 having a ceiling 306 that moves relative to the bottom 305 of the nozzle chamber. The movable ceiling 306 is operated to move toward the bottom 305 by a multi-layer thermal bend actuator 310 located outside of the nozzle chamber 305.

The movable ceiling drops ink droplet ejection energy because only one side of the movable structure must act on viscous ink. However, there is still a need to increase the amount of power available for ink jetting. By increasing the amount of power, shorter pulse widths can be used to provide the same amount of energy. By shorter pulse width, improved ink drop ejection characteristics can be achieved.

One means for increasing actuator power is to increase the size of the actuator. However, in the nozzle design shown in Figures 5-8, the increase in actuator size adversely affects the nozzle spacing, which is undesirable in the manufacture of high resolution pagewidth printheads.

A solution to this problem is provided by the nozzle assembly 400 shown in FIGS. 9-12. The nozzle assembly 400 includes a nozzle chamber 401 formed on a passivated CMOS layer 402 of a silicon substrate 403. The nozzle chamber is formed by the ceiling 404 and sidewall portions 405 extending from the ceiling to the passivated CMOS layer 402. Ink is supplied to the nozzle chamber 401 by the ink inlet 406 in fluid communication with the ink supply channel 407 containing ink from the back side of the silicon substrate. Ink is ejected from the nozzle chamber 401 by the nozzle opening 408 formed in the ceiling 404. The nozzle opening 408 is offset from the ink inlet 406.

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

The nozzle assembly 400 is formed by a thermal bend actuator 410 having a planar upper active beam 411 and a planar lower passive beam 412. Thus, actuator 410 typically forms at least 20%, at least 30%, at least 40% or at least 50% of the total area of ceiling 404. Similarly, the upper active beam 411 typically forms at least 20%, at least 30%, at least 40% or at least 50% of the total area of the ceiling 404.

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

However, it will of course be appreciated that the active beam 411 is alternatively directly fused or glued to the passive beam 412 to improve structural rigidity. Such design changes will be readily made within the scope of the skilled person 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) via a Ti bridge layer. The contacts 416 are connected with the drive circuit in the CMOS layers.

If it is desired to eject ink droplets from the nozzle chamber 401, current flows through the active beam 411 between the two contacts 416. The active beam 411 is rapidly heated by an electric current to expand with respect to the passive beam 412, whereby the actuator 410 (which forms the moving portion 409 of the ceiling 404) toward the substrate 403. It will bend downward. This movement of actuator 410 causes ink to be ejected from nozzle opening 408 by a rapid increase in pressure in nozzle chamber 401. When the current flow stops, the moving portion 409 of the ceiling 404 returns to its stop position, which draws ink from the inlet 406 into the nozzle chamber 401 in preparation for the next injection.

Thus, the principle of ink droplet ejection is similar to that described above in connection with nozzle assembly 300. However, as the thermal bend actuator 410 forms the moving part 408 of the ceiling 404, a much larger amount of power becomes available for ink droplet ejection, because the active beam 411 is a nozzle assembly 400. This is because it has a large area compared to the total size of).

12, it will be readily appreciated that nozzle assembly 400 (also including other nozzle assemblies described herein) may be repeated with an array of nozzle assemblies to form a printhead or printhead integrated circuit. will be. 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 of the nozzle assemblies. A plurality of printhead integrated circuits are described in, for example, US Patent Application Nos. 10 / 854,491 and 5, filed on May 27, 2004 and December 20, 2004, respectively, each incorporated by reference herein. As described in 11 / 014,732, they may be adjacent or connected to form a pagewidth inkjet printhead.

The nozzle assembly 500 shown in FIGS. 13 to 15 has a thermal bend actuator 510 having an upper active beam 511 and a lower passive beam 512 that moves a moving portion of the ceiling 510 of the nozzle chamber 501. As long as it is formed, it is similar to the nozzle assembly 400. Therefore, the nozzle assembly 500 achieves the same advantages as the nozzle assembly 400 in terms of increased power.

However, in contrast to the nozzle assembly 400, the nozzle opening 508 and the edge 515 are formed by the moving portion of the ceiling 504. Rather, the nozzle opening 508 and the edge 515 are formed in the fixing portion of the ceiling 504 such that the actuator 510 moves regardless of the nozzle opening and the edge during ink jetting. The advantage of this structure is that the drop flight direction can be more easily controlled.

It is noted that an aluminum alloy having the inherent advantage of improved thermal bend efficiency can be used as an active beam on either of the thermal bend actuators 410, 510 described above in connection with the embodiments shown in FIGS. 9-15. Of course you will.

The nozzle assemblies 400, 500 can be made using suitable MEMS techniques in a manner similar to the inkjet nozzle manufacturing process illustrated in Applicants' U.S. Pat.Nos. 6,416,167 and 6,755,509, incorporated herein by reference. .

Active beam with optimal stiffness in the bending direction

Referring now to FIGS. 11 and 15, the upper active beams 411, 511 of the actuators 410, 510 may be curved (for beam 411) or meandering (for beam 511). It will be seen that each consists of a meandering beam element having either side. The meandering beam element is long and has a relatively small cross-sectional area suitable for resistive heating. In addition, the meandering shape allows each end of the beam element to be connected to each contact located at one end of the actuator, thereby simplifying the overall design and configuration of the nozzle assembly.

Specifically, referring to FIGS. 14 and 15, the elongated beam element 520 has a meandering shape to form an elongate active cantilever beam 511 of the actuator 510. The meandering beam element 520 has a planar tortuous path connecting the first electrical contact 516 to the second electrical contact 516. An electrical contact 516 (positive and ground) is located at one end of the actuator 510 and provides an electrical connection between the active circuit 511 and the drive circuitry in the CMOS layer 502.

The meandering beam element 520 is manufactured by standard lithography etching technique and formed by a plurality of adjacent beam members. In general, the beam members can be formed as a solid portion of the beam material, which extends almost straight, for example in the longitudinal or transverse direction. The beam members of the beam element 520 are composed of long beam members 521 extending along the longitudinal axis of the elongated cantilever beam 511 and short beam members 522 extending along the transverse axis of the elongated cantilever beam 511. have. An advantage of such a meandering beam element 520 structure is that it provides maximum rigidity in the bending direction of the cantilever beam 511. Stiffness in the bending direction is advantageous because it facilitates bending of the actuator 510 back to its stop position after each operation.

It will be appreciated that the curved active beam for the nozzle assembly 400 shown in FIG. 11 achieves the same or similar advantages described above with respect to the nozzle assembly 500. In FIG. 11, the longitudinally extending long beam members are indicated at 421, while the transversely extending short beam members are indicated at 422.

Use of Porous Materials to Improve Thermal Efficiency

In all the above-described and other embodiments of the thermal bend actuator described by the applicant, the active beam is bonded to the passive beam for structural stiffness (see FIGS. 1 and 2), or the active beam is at maximum heat. It is spaced apart from the passive beam for efficiency (see FIG. 8). The thermal efficiency provided by the air gap between the beams is of course desirable. However, this improvement in thermal efficiency is largely due to the cost of structural rigidity and the propensity to bend the thermal bend actuator.

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

However, Applicants have found that this type of porous material is useful for improving the efficiency of thermal bend actuators. The porous material can be used as an insulating layer between the active beam and the passive beam, or as the passive beam itself.

16 illustrates a thermal bend actuator 600 including an upper active beam 601, a lower passive beam 602, and an insulating layer 603 interposed between the upper and lower beams. The insulating beam is made of porous silicon carbide, while the active beam 601 and passive beam 602 can be made of any suitable material, such as TiN and SiO ₂ , respectively.

The porosity of the insulating layer 603 provides good thermal insulation between the active beam 601 and the passive beam 602. The insulating layer 603 also provides an actuator 600 having structural rigidity. Thus, the actuator 600 combines the advantages of both types of thermal bend actuators described above in connection with FIGS. 1, 2, and 8.

Alternatively and as shown in FIG. 17, the porous material may simply form a passive layer of a multilayer thermal bend actuator. Thus, the thermal bend actuator 650 is comprised of an upper active beam 651 made of TiN and a lower passive beam 652 made of porous silicon dioxide.

Of course, it will be appreciated that the thermal bend actuators of the types shown in FIGS. 16 and 17 can be integrated into any suitable inkjet nozzle or other MEMS device. Improving thermal efficiency and structural stiffness makes such actuators attractive for some MEMS applications that require mechanical actuators or transducers.

The thermal bend actuators of the types shown in FIGS. 16 and 17 are particularly suitable for use with the inkjet nozzle assemblies 400, 500 described above. Those skilled in the art will immediately recognize that these thermal bend actuators 400 and 500 can realize the above-described improvements in thermal efficiency and structural rigidity.

It will further be appreciated that the active beam members 601, 651 in the thermal bend actuators 600, 650 described above may be constructed of an aluminum alloy, as described herein to further improve thermal bending efficiency. .

Of course, it will be appreciated that the invention has been described only by way of example and that detailed changes may be made within the scope of the invention as defined in the appended claims.

Claims (20)

A nozzle chamber comprising a floor and a roof having a nozzle opening formed therein and having a moving portion movable toward the bottom; And A thermal bend actuator having a plurality of cantilever beams and for injecting ink through the nozzle openings; Including; The thermal bend actuator includes a first active beam for connecting to a drive circuit and a second passive beam mechanically cooperating with the first active beam to allow current to pass through the first active beam. When the first active beam expands with respect to the second passive beam causing bending of the actuator, And the first active beam occupies at least 30% of the total area of the ceiling. The method of claim 1, And the moving part comprises the actuator. The method of claim 1, And the first active beam forms at least a portion of an outer surface of the ceiling. The method of claim 1, And the nozzle opening is formed in the moving part such that the nozzle opening is movable with respect to the bottom part. The method of claim 1, And the actuator is movable relative to the nozzle opening. The method of claim 1, And the first active beam is formed by a tortuous beam element, wherein the meandering beam element has a plurality of adjacent beam members. The method of claim 6, The plurality of adjacent beam members includes a plurality of elongated beam members extending along a longitudinal axis of the first beam, and at least one short beam member extending across a horizontal axis of the first beam and interconnecting the long beam members. Inkjet nozzle assembly. The method of claim 1, An ink jet nozzle assembly in which one of the plurality of beams is made of a porous material. The method of claim 8, And the porous material is porous silicon dioxide having a dielectric constant of 2 or less. The method of claim 1, And the thermal bend actuator further comprises a third insulation beam interposed between the first beam and the second beam. The method of claim 10, And the third insulating beam is made of a porous material. The method of claim 1, And the first beam is fused or bonded to the second beam. The method of claim 12, And the second beam is made of a porous material. The method of claim 1, At least a portion of the first beam is spaced apart from the second beam. The method of claim 1, And the first beam is made of a material selected from the group consisting of titanium nitride, titanium aluminum nitride and aluminum alloy. The method of claim 1, And the first beam is made of an aluminum alloy. The method of claim 16, And the aluminum alloy is made of aluminum and at least one other metal having a Young's Modulus greater than 100 GPa. The method of claim 17, And said at least one metal is selected from the group consisting of vanadium, manganese, chromium, cobalt and nickel. The method of claim 16, And the alloy comprises aluminum and vanadium. The method of claim 16, And the alloy comprises at least 80% aluminum.

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