TWI503235B - Printhead having polysilsesquioxane coating on ink ejection face - Google Patents

Description

a print head coated with a polysilsesquioxane on the inkjet surface

The present invention relates to print heads and particularly to the field of ink jet print heads. Mainly developed to improve print quality and printhead maintenance in high resolution printheads.

Many different types of printing have been invented, mostly in use today. Known print formats have a variety of methods for marking print media with associated mark media. Commonly used printing formats include plate printing, laser printing and copying equipment, dot matrix impact printers, thermal paper printers, video recorders, hot wax printers, and sublimation printers. And drop-on demand and continuous flow type inkjet printers. Each type of printer has its own advantages and problems when considering cost, speed, quality, reliability, construction simplification, and operation.

In recent years, the field of inkjet printing in which each pixel of ink is derived from one or more inkjet nozzles has become increasingly popular, primarily due to its inexpensive and multi-sample nature.

Many different ink jet printing techniques have been invented. For an overview of the field, refer to J Moore, "Non-Impact Printing: Introduction and Historical Perspective", Output Hard Copy Devices, Editors R Dubeck and S Sherr, pages 207-220 (1988).

The inkjet printer itself is available in many different types. The use of continuous ink streams in ink jet printing appears to have been traced back to at least 1929, in which a simple form of continuous flow electrostatic ink jet printing is disclosed in U.S. Patent No. 1,419,001 to Hansell.

A method of continuous ink jet printing is also disclosed in U.S. Patent No. 3,596,275, the entire disclosure of which is incorporated herein by reference. This technology is still used by many manufacturers, including Elmjet and Scitex (see also US Patent No. 3373437 to Sweet et al.).

Piezoelectric ink jet printers are also a form of ink jet printing apparatus that is commonly used. The piezoelectric system is disclosed in U.S. Patent No. 3,946,398 (1970) by Kyser et al., which is incorporated herein by reference to U.S. Pat. A bent-mode piezoelectric operation of Stemme is disclosed in U.S. Patent No. 3,747,120 (1972), which is incorporated herein by reference. The shear mode type of the device element is disclosed in U.S. Patent No. 4,584, 590 to Fischbeck.

Recently, thermal inkjet printing has become a very popular form of inkjet printing. Inkjet printing techniques include those disclosed by Endo et al. in GB 2007162 (1979) and by Vaught et al. in U.S. Patent No. 4,490,728. Both of the above documents disclose an ink jet printing technique that relies on electrothermal actuator activation, which results in the generation of bubbles in a compression space, such as a nozzle, thereby causing ink to be ejected from the opening connected to the confined space in the associated printing medium. on. Printing devices utilizing electrothermal actuators are manufactured by manufacturers such as Canon and Hewlett Packard.

From the above observations, many different types of printing techniques are effective. In theory, printing techniques should have many desirable attributes. These include inexpensive construction and operation, high speed operation, safe and continuous long term operation, and the like. Each technology has its own advantages and disadvantages in terms of cost, speed, quality, reliability, energy use, construction operation simplification, durability and consumables.

In the construction of any ink jet printing system, there are a number of important factors that must be weighed against one another, especially when constructing large scale printheads, especially those of the wide page type. Many of these factors are outlined below.

First, inkjet printheads are typically constructed using microelectromechanical systems (MEMS) technology. As such, this technique tends to rely on standard integrated circuit construction/deposition of planar layers on germanium wafers and fabrication of certain portions of the etched planar layer. Certain techniques are better than others in the context of 矽 circuit fabrication techniques. For example, techniques associated with generating CMOS circuits are likely to be more easily used than those associated with generating foreign circuits, including ferroelectrics, gallium arsenide, and the like. It is then desirable to utilize fully validated semiconductor fabrication techniques in any MEMS construction that does not require any external methods or materials. If the advantages of using foreign materials far outweigh its disadvantages, then of course a certain degree of trade-off will be accepted, and then it may become desirable to utilize foreign materials anyway. However, if it is possible to achieve some or similar properties using more common materials, the problem of foreign materials can be avoided.

A desirable ink jet printhead feature may be a hydrophobic inkjet face (front face or top face), preferably in combination with a hydrophilic nozzle chamber and ink supply channel. The hydrophilic nozzle chamber and the ink supply channel provide capillary action and are therefore most suitable for priming and resupplying ink to the nozzle chamber after each drop ejection. The hydrophobic front minimizes the tendency of the ink to overflow the front of the printhead. It is less likely that the aqueous inkjet will overflow the nozzle opening from the side with the hydrophobic front. In addition, any ink that overflows from the nozzle opening is less likely to diffuse over the front and mix on the front, which in turn forms discrete spherical droplets that can be handled more easily by suitable maintenance operations.

The applicant of the present invention has heretofore described the use of PDMS (polydimethylsiloxane) to coat the front of the printhead and to provide a hydrophobic surface. However, although PDMS has excellent hydrophobicity and can be easily incorporated into the printhead MEMS fabrication process, it has relatively poor wear resistance and can be used for wiper blade scratches for printhead maintenance. </ RTI> <RTIgt; </ RTI> <RTIgt; </ RTI> <RTIgt; </ RTI> <RTIgt; It may therefore be desirable to provide a printhead having a hydrophobic inkjet face that can be easily fabricated by MEMS fabrication methods and that has good abrasion resistance.

In a first aspect, it is provided with a printhead having an inkjet face, wherein at least a portion of the inkjet face is coated with a hydrophobic polymeric material and the polymeric material comprises polysilsesquioxane. The printhead according to the present invention has excellent durability and abrasion resistance, making it compatible with various print head maintenance operations (e.g., wiping) involving contact with the ink ejection face. Moreover, polydecylsesquioxanes can be deposited in a thin layer (0.5 to 2 microns) by spin coating, which can be easily incorporated into MEMS printhead fabrication processes.

The polysulfonium sesquioxane is optionally selected from the group consisting of poly(alkyl sesquioxanes) and poly(aryl sesquioxanes).

The polysulfonium sesquioxane is optionally selected from the group consisting of poly(methyl sesquioxanes) and poly(phenyl sesquioxanes).

The polymeric material can optionally be deposited during the fabrication of the MEMS printhead and hard baked onto the nozzle plate of the printhead.

The print head can optionally include a plurality of nozzle assemblies formed on the substrate, each nozzle assembly including: a nozzle chamber, a nozzle opening defined in a chamber top of the nozzle chamber, and an actuation for ejecting ink through the nozzle opening Device.

The polymeric material is optionally applied to the nozzle plate of the printhead, the nozzle plate being at least partially defined at the top of each of the nozzle chambers.

Each of the chamber tops optionally has a hydrophobic outer surface relative to the interior surface of each nozzle due to the hydrophobic coating.

Each nozzle chamber may optionally include a chamber top and a side wall composed of a ceramic material.

The ceramic material may be optionally selected from the group consisting of tantalum nitride, tantalum oxide, and hafnium oxynitride.

The top of the chamber and the substrate are arbitrarily spaced apart such that the sidewall of each nozzle chamber extends between the nozzle plate and the substrate.

The actuator can optionally be a heater element that is configured to heat the ink within the chamber to form a bubble, thereby forcing the ink droplets through the nozzle opening.

The heater element can be arbitrarily suspended in the nozzle chamber.

The actuator may optionally be a thermal bending actuator comprising: a first active element coupled to the drive circuit; and a second passive element mechanically cooperating with the first element such that current passes through the first element The first element expands relative to the second element causing the actuator to bend.

The thermal bending actuator can arbitrarily define at least a portion of the top of each of the nozzle chambers, whereby the action of the actuator causes the moving portion of the chamber to move toward the bottom of the nozzle chamber.

The nozzle opening is arbitrarily confined within the moving portion of the roof.

The nozzle opening can be arbitrarily defined in the stationary portion of the roof.

The polymeric material can optionally define a mechanical seal between the moving and resting portions of the chamber top, thereby minimizing ink leakage during actuation of the actuator.

In a second aspect, there is provided a printhead having an inkjet face, wherein at least a portion of the inkjet face is coated with a polymeric material comprising a polymeric siloxane that is entangled with nanoparticles. According to a second aspect, the nanoparticles impart desirable properties to the polymer coating such as durability, abrasion resistance, fatigue resistance, hydrophobicity, hydrophilicity, and the like.

The polymeric oxane can be optionally selected from the group consisting of poly(alkyl sesquioxanes), poly(aryl sesquioxanes), and polydialkyl decanes.

The polymeric oxane can be optionally selected from the group consisting of poly(methyl sesquioxanes), poly(phenyl sesquioxanes), and polydimethyl siloxanes.

The nanoparticles can be optionally selected from the group consisting of inorganic nanoparticles and organic nanoparticles.

The inorganic nanoparticles can be optionally selected from the group consisting of metal oxides, metal carbonates, and metal sulfates.

The inorganic nanoparticles can be optionally selected from the group consisting of vermiculite, zirconia, titania, alumina, calcium carbonate, tin oxide, zinc oxide, copper oxide, chromium oxide, calcium oxide, tungsten oxide, iron oxide, cobalt oxide and sulfuric acid. barium.

The organic nanoparticle may be optionally selected from the group consisting of crosslinked polyoxyn resin particles, crosslinked polyolefin resin particles, crosslinked acrylic resin particles, crosslinked styrene-acrylic resin particles, and crosslinked aggregates. Ester particles, polyimide particles, melamine resin particles, and carbon nanotubes.

The nanoparticles may optionally be incorporated into the polymeric oxirane in an amount ranging from 1 to 70% by weight.

The nanoparticles may optionally have an average particle size in the range of from 1 to 100 nm.

The print head can optionally include a plurality of nozzle assemblies formed on the substrate, each nozzle assembly including: a nozzle chamber, a nozzle opening defined in a chamber top of the nozzle chamber, and an actuation for ejecting ink through the nozzle opening Device.

The polymeric material is optionally applied to the nozzle plate of the printhead, the nozzle plate being at least partially defined at the top of each of the nozzle chambers.

Each of the nozzle chambers may optionally include a chamber top and a side wall composed of a ceramic material selected from the group consisting of tantalum nitride, tantalum oxide, and hafnium oxynitride.

The top of the chamber and the substrate are arbitrarily spaced apart such that the sidewall of each nozzle chamber extends between the nozzle plate and the substrate.

The actuator can optionally be a heater element that is configured to heat the ink within the chamber to form a bubble, thereby forcing the ink droplets through the nozzle opening.

The heater element can be optionally suspended in the nozzle chamber.

The actuator may optionally be a thermal bending actuator comprising: a first active element coupled to the drive circuit; and a second passive element mechanically cooperating with the first element such that current passes through the first element The first element expands relative to the second element causing the actuator to bend.

The thermal bending actuator is arbitrarily define at least a portion of the top of each of the nozzle chambers whereby movement of the chamber top moves the chamber portion of the chamber chamber toward the bottom of the nozzle chamber.

The nozzle opening can be arbitrarily defined in any of the following locations: the moving portion of the chamber top; or the stationary portion of the chamber top.

The polymeric material can optionally define a mechanical seal between the moving and resting portions of the chamber top, thereby minimizing ink leakage during actuation of the actuator.

In a third aspect, there is provided an ink jet print head for ejecting a jettable fluid, the print head having an ink jet surface coated with a polymer material impregnated with nanoparticles, wherein the nanoparticle is imparted The ink jet surface has one or more predetermined features, the predetermined features complementing at least one of: an intrinsic property of the jettable fluid; a printhead maintenance state associated with the printhead; and a nozzle actuator type.

According to a third aspect, the present invention enables the surface features of the inkjet face to be adjusted to predetermined printer features. For example, printhead maintenance can be given priority in some printers, whereas optimal fluid ejection can be given priority in other printers. Alternatively, the nanoparticles can be selected to provide a compromise of the printer features.

The one or more predetermined features are optionally selected from the group consisting of hydrophilicity, hydrophobicity, abrasion resistance, and fatigue resistance.

The one or more predetermined features are optionally imparted by one or more of the following: surface energy characteristics of the nanoparticle, nanoparticle size, nanoparticle amount, and nanoparticle wear resistance.

The nanoparticles can be optionally selected from the group consisting of inorganic nanoparticles and organic nanoparticles.

The inorganic nanoparticles can be optionally selected from the group consisting of vermiculite, zirconia, titania, alumina, calcium carbonate, tin oxide, zinc oxide, copper oxide, chromium oxide, calcium oxide, tungsten oxide, iron oxide, cobalt oxide and sulfuric acid. barium.

The organic nanoparticle may be optionally selected from the group consisting of crosslinked polyoxyn resin particles, crosslinked polyolefin resin particles, crosslinked acrylic resin particles, crosslinked styrene-acrylic resin particles, and crosslinked aggregates. Ester particles, polyimide particles, melamine resin particles, and carbon nanotubes.

The intrinsic properties of the jettable fluid can be arbitrarily selected from the group consisting of hydrophilicity, hydrophobicity, viscosity, surface tension and boiling point.

The sprayable fluid can be optionally selected from the group consisting of aqueous fluids and non-aqueous fluids.

The printhead maintenance state can optionally include one or more operations selected from the group consisting of: printhead cover, printhead wipe, printhead overflow, and non-contact ink removal.

The polymeric material may optionally comprise a polymeric oxane.

The polymeric oxane can be optionally selected from the group consisting of poly(alkyl sesquioxanes), poly(aryl sesquioxanes), and polydialkyl decanes.

The polymeric oxane can be optionally selected from the group consisting of poly(methyl sesquioxanes), poly(phenyl sesquioxanes), and polydimethyl siloxanes.

Other arbitrary specific examples according to the third point of view are reflected in those random specific examples according to the first and second points.

Random specific example

The invention is applicable to any type of printhead. The applicant of the present invention previously described a multi-ink ink jet print head. It is not necessary here to describe all such print heads in order to understand the invention. However, the present invention will now be described in connection with an ink jet print head that thermally forms bubbles and an ink jet print head that is actuated by mechanical thermal bending. The advantages of the present invention are readily apparent from the discussion that follows.

Inkjet print head that forms bubbles by heat

Referring to Figure 1, a portion of a printhead including a plurality of nozzle assemblies is shown. Figures 2 and 3 show side cross-sectional and cross-sectional perspective views of one of these nozzle assemblies.

Each nozzle assembly includes a nozzle chamber 24 formed on the tantalum wafer substrate 2 by MEMS fabrication techniques. The nozzle chamber 24 is defined to the chamber top 21 and extends from the chamber top 21 to the side wall 22 of the crucible substrate 2. As shown in Figure 1, each of the chamber roofs is defined by a portion of the nozzle surface 56 that spans the inkjet face of the printhead. Nozzle surface 56 and sidewall 22 are formed of the same material deposited by PECVD on the sacrificial support of the photoresist layer during MEMS fabrication. Nozzle surface 56 and sidewall 22 are typically formed from a ceramic material such as hafnium oxide or tantalum nitride. These hard materials have excellent properties for printhead robustness, and their inherent hydrophilic nature facilitates the supply of ink to the nozzle chamber 24 by capillary action. However, the outer (inkjet) surface of nozzle surface 56 is also hydrophilic, which causes any ink that overflows the surface to diffuse.

Returning to the detail of the nozzle chamber 24, the nozzle opening 26 is defined through the chamber top of each nozzle chamber 24. Each nozzle opening 26 is generally elliptical and has an associated nozzle edge 25. The nozzle edge 25 facilitates ink droplet orientation during printing and at least reduces ink overflow from the nozzle opening 26 to some extent. The actuator for ejecting ink from the nozzle chamber 24 is a heater element 29 disposed below the nozzle opening 26 and suspended over the recess 8. The current is supplied to the heater element 29 via the electrode 9 connected to the drive circuit in the CMOS layer 5 of the underlying substrate 2. As current passes through the heater element 29, it rapidly overheats the periphery of the ink to form bubbles that force the ink through the nozzle opening. When the nozzle chamber 24 is actuated, it is fully inserted into the ink by suspending the heater element 29. This improves printhead efficiency because less heat is dissipated into the underlying substrate 2 and more input energy is used to create bubbles.

As seen more clearly in Figure 1, the nozzles are arranged in columns and the ink supply channels 27 extending longitudinally along the column supply ink to each of the nozzles arranged in a row. The ink supply channel 27 conveys ink to the ink inlet passage 15 of each nozzle, which supplies ink from the nozzle opening 26 side via the ink conduit 23 in the nozzle chamber 24.

MEMS fabrication methods for making such printheads are described in detail in our U.S. Application Serial No. 11/246,684, filed on Jan. 11, 2005, the disclosure of which is incorporated herein by reference. For the sake of clarity, briefly review the latter part of this production method here.

4 and 5 show a partially fabricated printhead comprising a nozzle chamber 24 encapsulating a sacrificial photoresist layer 10 (〝SAC1)〞 and 16 (〝SAC2〞). The SAC1 photoresist layer 10 is used as a support for depositing heater material to form a suspended heater element 29. The SAC2 photoresist layer 16 is used as a support for the deposition sidewall 22 and the chamber top 21 (which defines a portion of the nozzle surface 56).

In prior art methods, and with reference to Figures 6 through 8, the next stage of MEMS fabrication is to define the elliptical nozzle edge 25 in the chamber top 21 by etching away the 2 micron chamber top material 20. This etch is defined using a photoresist layer (not shown) exposed by the dark-tone edge mask shown in FIG. The elliptical edge 25 includes two coaxial edge covers 25a and 25b disposed on their respective thermal actuators 29.

Referring to Figures 9 through 11, the next stage defines an elliptical nozzle opening 26 in the chamber top 21 by etching all of the path through the remaining top material, which is limited by the edge 25. This etching is defined using a photoresist layer (not shown) exposed by the dark-tone chamber top mask shown in FIG. An elliptical nozzle opening 26 is provided on the thermal actuator 29 as shown in FIG.

With all of the MEMS nozzle features now fully formed, the next stage is to remove the SAC1 and SAC2 photoresist layers 10 and 16 by O ₂ plasma ashing (Figures 12 and 13). 14 and 15 show the entire thickness (150 micrometers) of the tantalum wafer 2 after ashing the SAC1 and SAC2 photoresist layers 10 and 16.

Referring to Figures 16 through 18, upon completion of the front side MEMS processing of the wafer, the ink supply channel 27 is etched from the back side of the wafer using standard anisotropic DRIE to meet the ink inlet 15. This back side etch is defined using a photoresist layer (not shown) exposed by the dark tone mask shown in FIG. The ink supply channel 27 fluidly connects the back side of the wafer with the ink inlet 15.

Finally, and with reference to Figures 2 and 3, the wafer is thinned to 135 microns by backside etching. Figure 1 shows three adjacent nozzle rows in a cross-sectional perspective view of a completed printhead integrated circuit. Each nozzle row has a respective ink supply channel 27 extending along its length and supplying ink to a plurality of ink inlets 15 in each column. The ink inlets in turn supply ink to the columns of ink conduits 23, with each nozzle chamber receiving ink from a common ink conduit of the column.

As discussed above, this prior art MEMS fabrication method inevitably leaves a hydrophilic spray because the nozzle surface 56 is formed of a ceramic material such as hafnium oxide, tantalum nitride, hafnium oxynitride, aluminum nitride, or the like. Ink surface.

In a preferred method of hydrophobizing the nozzle face 56 (and as described in US 2009/0139961, the contents of which are incorporated herein by reference), the wafer is at the edge of the nozzle as illustrated in Figures 7 and 8 Immediately after etching, it is coated with a hydrophobic polymer 80.

A thin layer (about 1 to 2 microns) of hydrophobic polymer 100 is spin coated onto the wafer and hard baked to provide a partially fabricated printhead as shown in Figures 19 and 20.

Referring now to Figure 21, a protective metal film 90 (about 100 nanometers thick) is then deposited over the polymeric layer 80. The metal film typically comprises titanium or aluminum and protects the hydrophobic polymer 80 from oxygen ashing conditions in later stages. Polymer layer 80 is then not exposed to aggressive ashing conditions and retains its hydrophobic character throughout the MEMS processing step.

Figure 22 shows the wafer after etching through the metal film 110, the polymer layer 80, and the nozzle opening 26 of the nozzle chamber top 21. This etching step utilizes a conventional patterned photoresist layer (not shown) as a common mask for all nozzle etch steps. In a typical etch sequence, metal film 90 is first etched with a standard dry metal etch (eg, BCl ₃ /Cl ₂ ) or a wet metal etch (eg, H ₂ O ₂ or HF). A second dry etch step is then used to etch through the polymer layer 80 and the nozzle chamber top 21. The second etch step is typically a dry etch using O ₂ and a fluorinated etch gas (eg, SF ₆ or CF ₄ ).

When the nozzle opening 26 is defined as shown in FIG. 22, then the backside MEMS processing steps (eg, etching the ink supply channels, wafer thinning, etc.) and the late stage photoresist layer ashing may be similar to that described with respect to FIG. A known agreement to the above steps to 18 is carried out. Finally, the use of H ₂ O ₂ or HF rinse metal film 90 is removed to obtain the complete nozzle assembly having a hydrophobic polymer layer 80 and 24 shown in FIG. 23.

Thermal bending actuator print head

Any type of print head can be hydrophobized in a similar manner from the above understanding. However, the polymer coating is particularly advantageous for use in the applicant's thermal bending actuator assembly because the polymer layer acts as a mechanical seal between the top of the moving chamber and the stationary body of the print head. These advantages are discussed in more detail in the Applicant's U.S. Patent Publication No. 2008/0225076, the disclosure of which is incorporated herein by reference.

Figures 25 through 37 show the sequence of MEMS fabrication steps of the ink jet nozzle assembly 100 described in our earlier U.S. Patent Publication No. 2008/0309, the disclosure of which is incorporated herein by reference. The ink jet nozzle assembly 100 completed as shown in Figs. 36 and 37 is actuated by thermal bending, whereby the moving portion of the chamber top is bent toward the substrate to cause ink ejection.

The starting point for MEMS fabrication is a standard CMOS wafer with a CMOS driver circuit formed in the upper portion of the germanium wafer. At the end of the MEMS fabrication process, the wafer is slit into individual printhead integrated circuits (ICs), each of which contains a drive circuit and a plurality of nozzle assemblies.

As shown in FIGS. 25 and 26, the substrate 101 has an electrode 102 formed in an upper portion thereof. The electrode 102 is one of a pair of adjacent electrodes (positive and ground) for supplying energy to the actuator of the inkjet nozzle 100. The electrodes receive energy from CMOS drive circuits (not shown) in the upper layer of substrate 101.

The other electrodes 103 shown in Figures 25 and 26 are used to supply energy to adjacent ink nozzles. Typically, the figure shows a MEMS fabrication step for a nozzle assembly that is one of the arrays of nozzle assemblies. The following describes the manufacturing steps for one of these nozzle assemblies. However, it should of course be understood that the corresponding steps are performed simultaneously on all of the nozzle assemblies formed on the wafer. Where adjacent nozzle assemblies are partially shown in the figures, this is negligible for the purposes of the present invention. Accordingly, all features of electrode 103 and adjacent nozzle assemblies are not described in detail herein. In fact, for the sake of clarity, some MEMS fabrication steps will not be shown on adjacent nozzle assemblies.

In the sequence of steps shown in Figs. 25 and 26, an 8 μm layer of ruthenium dioxide is first deposited on the substrate 101. The depth of the cerium oxide defines the depth of the nozzle chamber 105 of the ink jet nozzle. After depositing the SiO ₂ layer, the layer is etched to define a wall 104 that becomes the sidewall of the nozzle chamber 105, which is shown very clearly in FIG.

As shown in Figures 27 and 28, the nozzle chamber 105 is then filled with a photoresist or polyimine 106, which serves as a sacrificial scaffold for the subsequent deposition step. Polyimine 106 is spin coated onto the wafer using a standard technique, UV cured and/or hard baked, and subjected to chemical mechanical planarization (CMP) that stops on the top surface of the SiO ₂ wall 104.

In Figures 29 and 30, the roof element 107 of the nozzle chamber 105 is formed and the highly conductive connector post 108 extends down to the electrode 102. A 1.7 micron SiO ₂ layer was first deposited on the polyamidoline 106 and wall 104. This SiO ₂ layer defines the roof element 107 of the nozzle chamber 105. A pair of through holes are then formed in the wall 104 down to the electrode 102 using standard anisotropic DRIE. This etch exposes pairs of electrodes 102 that pass through individual vias. The vias are then filled with a highly conductive metal such as copper using electroless plating. The deposited copper pillars 108 receive CMP that is stopped on the SiO ₂ chamber top element 107 to provide a planar structure. It can be observed that the copper connector posts 108 formed during electroless copper plating meet the individual electrodes 102 to provide a linear conductive path to the top element 107.

In Figures 31 and 32, metal pad 109 is formed by depositing a 0.3 micron aluminum layer on top element 107 and connector post 108. Any highly conductive metal (e.g., aluminum, titanium, etc.) can be used and should be deposited at a thickness of about 0.5 microns or less to not severely impact the overall planarity of the nozzle assembly. A metal pad 109 is disposed on the roof element 107 within the predetermined "bending zone" of the connector post 108 and the thermoelastic active beam member.

In Figures 33 and 34, a thermoelastic active beam member 110 is formed on the SiO ₂ chamber top 107. A portion of the SiO ₂ chamber top element 107 has the function of a lower passive beam member 116 as a mechanical thermal bending actuator that is defined by the active beam member 110 and the passive beam member 116 due to fusion with the active beam member 110. The thermoelastic active beam member 110 can comprise any suitable thermoelastic material such as titanium nitride, titanium aluminum nitride, and aluminum alloy. Vanadium-aluminum alloys are preferred materials as explained in the applicant's earlier U.S. Publication No. 2008/0129793, the disclosure of which is incorporated herein by reference in its entirety, because it incorporates high thermal expansion, low density, and high The advantageous properties of Young's modulus.

To form the active beam member 110, a 1.5 micron active beam material layer is first deposited by standard PECVD. The beam material is then etched using standard metal etching to define the active beam member 110. After completion of the metal etch, and as shown in FIGS. 33 and 34, the active beam member 110 includes a portion of the nozzle opening 111 and the beam member 112, electrically coupled to the positive and ground electrode 102 via the connector post 108 at each end. The planar beam member 112 extends from the top end of the first (positive) connector post and is bent approximately 180 degrees back to the top end of the second (ground) connector post.

Still referring to Figures 33 and 34, the metal pad 109 is configured to accelerate current flow in potentially higher resistance regions. A metal pad 109 is disposed within the curved region of the beam member 112 and is sandwiched between the active beam member 110 and the passive beam member 116. Other metal pads 109 are disposed between the top end of the connector post 108 and the end of the beam member 112.

Referring to Figure 35, a hydrophobic polymer layer 80 is deposited on a wafer and covered with a protective metal layer 90 (e.g., 100 nano aluminum). After suitable masking, metal layer 90, polymer layer 80, and SiO ₂ chamber top element 107 are then etched to completely define nozzle opening 113 and moving portion 114 of the roof. The etch is typically a two-stage etch as described above with respect to FIG.

The moving portion 114 includes a thermal bending actuator 115 that itself includes an active beam member 110 and a passive beam member 116 below. The nozzle opening 113 is also defined in the moving portion 114 of the roof such that the nozzle opening moves with the actuator during actuation. It is also possible to have a configuration in which the nozzle opening 113 is stationary with respect to the moving portion 114, as described in U.S. Publication No. 2008/0129793, and which is within the scope of the present invention.

The moving portion 114 and the resting portion 118 of the roof are separated by a surrounding space or gap 117 near the moving portion 114 of the roof. This gap 117 allows the moving portion 114 to enter the nozzle chamber 105 and bend toward the substrate 101 when the actuator 115 is actuated. The hydrophobic polymer layer 80 fills the gap 117, providing a mechanical seal between the moving portion 114 of the chamber top 107 and the stationary portion 118. The polymer has a low Young's modulus sufficient to allow the actuator to bend toward the substrate 101 while avoiding ink leakage through the gap 117 during actuation.

In the final MEMS processing step, and as shown in FIGS. 36 and 37, the ink supply channel 120 is etched through the nozzle element 105 from the back side of the substrate 101. Although the ink supply channel 120 is shown aligned with the nozzle opening 113 in Figures 36 and 37, it can of course be disposed offset from the nozzle opening.

After etching the ink supply channel, the polyimide 19 for filling the nozzle chamber 105 is removed by ashing in the oxidizing plasma, and the metal film 90 is moved by HF or H ₂ O ₂ In addition, a nozzle assembly 100 is provided.

Polymer layer containing MSO

The hydrophobic polymer layer 80 has proven to be an important feature of the applicant's print head. Not only does it provide hydrophobicity in front of the printhead, it helps to improve overall print quality, but also by presenting a printhead with a flat hydrophobic surface for maintenance of the print head under operable conditions (eg , wiper blade) to help print head maintenance. Of course, in the case of the above described print head 100 actuated by thermal bending, the polymer 80 provides the additional function of mechanically sealing the moving portion of the nozzle from the print head entity.

So far, the applicant has proposed the use of polydimethyl siloxane (PDMS). This material can be easily incorporated into MEMS fabrication methods with excellent hydrophobicity and Young's modulus, which allows for efficient thermal bending action. However, PDMS has relatively poor wear resistance and can be scratched or otherwise damaged by repeated contact with, for example, a wiper blade.

Applicants have now found that polydecylsesquioxanes provide superior wear resistance over PDMS and still maintain all of the advantages of PDMS. Polydecylsesquioxanes belong to the comprehensive class of polymers known as polymeric oxiranes or polyoxins, and have the experimental formula (RSiO _1.5 ) _n , where R is hydrogen or an organic group and n represents a polymer chain. An integer of length. The organic group can be a C _1-12 alkyl group (eg, methyl), a C _1-10 aryl group (eg, phenyl), or a C _1-16 aralkyl group (eg, benzyl). The polymer chains can be of any length known in the art (e.g., n is from 2 to 10,000).

When poly(alkyl sesquioxanes) and poly(aryl sesquioxanes), such as poly(methyl sesquioxanes) and poly(phenyl sesquioxanes) are used as applicants When the polymer layer 80 in the print head is printed, it has been shown to have excellent hydrophobicity, durability and abrasion resistance. For example, a print head coated with MSQ or PSQ can be wiped clean without damage, even after the ink and paper fibers are baked on the print head for one hour.

Poly(methyloxime sesquioxane) is also known in the art as methyl sesquioxanes, MSQ, MSSQ, PMSQ and PMSSQ. Poly(phenylhydrazine sesquioxane) is also known in the art as phenyl sesquioxanes, PSQ, PSSQ, PPSQ, and PPSSQ. For the sake of brevity, the applicant will hereinafter refer to poly(methyl sesquioxanes) as MSQ and poly(phenyl sesquioxanes) as PSQ.

MSQ has a low dielectric constant (k = 2.7) and was previously used as an insulating material. However, it has not previously been known to use MSQ as a hydrophobic coating for MEMS inkjet printheads.

The MSQ or PSQ can be incorporated into the print head as the polymer layer 80 by the MEMS fabrication method described above. The MSQ or PSQ solution is spin coated onto the wafer to a depth of about 0.5 to 5 microns (e.g., 1 micron) and then hard baked to promote adhesion to the nozzle plate and to provide a durable ink jet surface for the printhead. Hard bake can include a UV curing step. For example, a typical hard bake method can include the following steps:

1. Immediately after coating, bake at @110 °C for 2 minutes.

2. Contact baking at @300 °C for 6.5 minutes

3. Exposure to UV for 130 seconds (~1300 mJ)

4. Oven curing for 1 hour (starting at @180°C and rising at @~4°C/min)

While the above described applicant's hard bake method provides an MSQ or PSQ coated printhead with excellent durability, it should be understood that the hard bake can be followed by any conventional procedure.

MSQ and PSQ each have a Young's modulus of about 3 GPa, which is slightly higher than PDMS. However, Applicants have found that when the polymer layer 80 contains MSQ or PSQ, the print head actuated by thermal bending is still effectively operated despite its higher Young's modulus. Moreover, the overall robustness of MSQ and PSQ often outweighs any adverse trends that occur with its higher Young's modulus. Of course, in a printhead that thermally forms bubbles without any moving parts, the Young's modulus of the polymer layer 80 is independent of the nozzle actuation.

The inventors considered that the use of MSQ or PSQ represents a major breakthrough in inkjet printhead technology. Hydrophobic inkjet printheads, especially those manufactured by MEMS fabrication methods, are considered a significant challenge by all industry competitors. The Applicant has demonstrated that MSQ or PSQ can be incorporated into MEMS fabrication methods and provide hydrophobic inkjet surfaces with excellent durability and abrasion resistance. A combination of features that did not achieve this in the prior art.

Polymer layer containing nanoparticles

As noted above, while MSQ and PSQ have advantages over PDMS as a polymer coating, there may be some examples of materials in which PDMS is still an option. For example, in a printhead that is actuated with low thermal energy bending, the low Young's modulus of the PDMS may be beneficial to reduce ink drop ejection energy to a minimum. It may be desirable to improve the wear characteristics of, for example, PDMS without including improving its low Young's modulus.

In other aspects, the polymeric coating of the printhead can have properties that render it unsuitable for ejecting a particular fluid from the printhead. It should be noted that the print head actuated by thermal bending can eject both aqueous and non-aqueous liquids (for example, polymers for printing OLEDs), and the ink jet surface of the print head can have the inherent properties of the fluid to be sprayed. Characteristics. These properties may include, for example, the hydrophilicity, hydrophobicity, viscosity, surface tension and/or boiling point of the fluid.

Alternatively, the inkjet surface may have features that complement the particular type of printhead maintenance state used (e.g., printhead capping/wiping, as described in U.S. Application Serial No. 12/014,772, incorporated herein by reference. Or; printhead overflow/non-contact maintenance, as described in US 7,401,886, incorporated herein by reference. For example, wear resistance is important to the print head maintenance state involving contact with the print head, but is less important for non-contact maintenance status.

Alternatively, the inkjet face may have features that complement a particular type of nozzle actuator. For example, fatigue resistance is of importance to thermal bending actuators in which the polymeric material seals the moving portion of the nozzle to the print head entity. However, fatigue resistance is less important for non-moving nozzles, such as the above-described nozzles that form bubbles by heat.

It may be highly desirable to have the ability to adjust the inkjet surface features without fundamentally changing the MEMS fabrication method. This adjustment can improve, for example, the toughness, abrasion resistance, fatigue resistance, and/or surface energy characteristics of the inkjet surface. When a hydrophobic liquid such as a polymer is printed, the ink jet surface should preferably be relatively hydrophilic rather than hydrophobic (in contact with the printed aqueous ink) as an unimportant example.

The effectiveness of a polyoxyl polymer incorporated into a nanoparticle (sometimes referred to herein as a ruthenium filler) means that the characteristics of the polyoxyl polymer (eg, PDMS, MSQ, PSQ) can be altered by Modify the nanoparticle into it. The use of different nanoparticles will modulate the characteristics of the inkjet surface defined by the polymer layer 80 correspondingly.

Of course, the nanoparticles can have any suitable type, size and shape depending on the particular application. The nanoparticles may comprise inorganic particles, organic particles or a combination of the two. Some examples of inorganic nanoparticles are metal oxides, metal carbonates, and metal sulfates. More particularly, the inorganic nanoparticles may be, for example, vermiculite (including colloidal vermiculite), zirconia, titania, alumina, calcium carbonate, tin oxide, zinc oxide, copper oxide, chromium oxide, calcium oxide, tungsten oxide. , iron oxide, cobalt oxide, barium sulfate, and the like. Some examples of organic nanoparticles are crosslinked polyoxyl resin particles (eg, PDMS, MSQ, PSQ), crosslinked polyolefin resin particles (eg, polystyrene, polyethylene, polypropylene), crosslinked Acrylic resin particles, crosslinked styrene-acrylic resin particles, crosslinked polyester particles, polyimide particles, melamine resin particles, carbon nanotubes, and the like.

The term "nanoparticle" as used herein refers to particles having an average particle size ranging from 1 to 1000 nanometers, more often from 1 to 100 nanometers, and more often from 1 to 50 nanometers. It is usually preferred to have an average particle size of about 20 nm. The particles may be monodisperse or polydisperse.

The nanoparticles may be present in an amount ranging from 1 to 70% by weight, optionally from 5 to 60% by weight, and optionally from 10 to 50% by weight. The amount of nanoparticle present will depend on the characteristics necessary for the polymer film.

The nanoparticles can be incorporated into the polymer in any suitable manner, such as a fusion gel process, which is well known to those skilled in the art. The resulting polymer can be deposited by any suitable method, such as spin coating, and then hard baked.

PDMS polymers incorporated into vermiculite nanoparticles are known in the art and such polymers can be used as the polymer layer 80 in the present invention. The vermiculite nanoparticles impart desirable wear and fatigue properties to the PDMS polymer. PDMS can also have a relatively hydrophilic surface depending on the amount of vermiculite particles present, which is useful in some applications.

A person skilled in the art will appreciate that various changes and/or modifications may be made to the invention as shown in the specific embodiments, without departing from the spirit or scope of the invention. Specific examples of the invention are therefore considered as illustrative and not restrictive.

2. . .矽 wafer substrate

5. . . COMS layer

8. . . Groove

9. . . electrode

10. . . Sacrificial photoresist layer

15. . . Ink inlet channel

16. . . Sacrificial photoresist layer

20. . . Roof material

twenty one. . . Roof

twenty two. . . Side wall

twenty three. . . Ink catheter

twenty four. . . Nozzle chamber

25. . . Nozzle edge

25a. . . Edge cover

25b. . . Edge cover

26. . . Nozzle opening

27. . . Ink supply channel

29. . . Heater element

29. . . Thermal actuator

56. . . Nozzle surface

80. . . Hydrophobic polymer

80. . . Polymer layer

90. . . Protective metal film

100. . . Thin layer of hydrophobic polymer

100. . . Inkjet nozzle assembly

101. . . Substrate

102. . . electrode

103. . . electrode

104. . . Side wall

105. . . Nozzle chamber

106. . . Polyimine

107. . . Roof

108. . . Connector column

109. . . Metal pad

110. . . Metal film

110. . . Thermoelastic active beam

111. . . Partial nozzle opening

112. . . Plane beam

113. . . Nozzle opening

114. . . Moving part

115. . . Thermal bending actuator

116. . . Passive beam

117. . . gap

118. . . Resting part

120. . . Ink supply channel

Specific examples of the present invention are now described by way of example only with reference to the accompanying drawings, in which:

Figure 1 is a partial perspective view of an array of nozzle assemblies of a thermal inkjet printhead;

Figure 2 is a side elevational view of the unit cell of the nozzle assembly shown in Figure 1;

Figure 3 is a perspective view of the nozzle assembly shown in Figure 2;

Figure 4 shows a partially formed nozzle assembly after the sidewall and the top material are deposited on the sacrificial photoresist layer;

Figure 5 is a perspective view of the nozzle assembly shown in Figure 4;

Figure 6 is a mask associated with the edge of the nozzle shown in Figure 7;

Figure 7 shows an etch of the top layer of the chamber forming the edge of the nozzle opening;

Figure 8 is a perspective view of the nozzle assembly shown in Figure 7;

Figure 9 is a mask associated with the nozzle opening shown in Figure 10;

Figure 10 shows an etch of the top material forming the elliptical nozzle opening;

Figure 11 is a perspective view of the nozzle assembly shown in Figure 10;

Figure 12 shows oxygen plasma ashing of the first and second sacrificial layers;

Figure 13 is a perspective view of the nozzle assembly shown in Figure 12;

Figure 14 shows the nozzle assembly after ashing, and the opposite side of the wafer;

Figure 15 is a perspective view of the nozzle assembly shown in Figure 14;

Figure 16 is a mask associated with the backside etch shown in Figure 17;

Figure 17 is a back side etching showing the ink supply channel entering the wafer;

Figure 18 is a perspective view of the nozzle assembly shown in Figure 17;

Figure 19 is a nozzle assembly of Figure 7 after deposition of a hydrophobic polymer coating;

Figure 20 is a perspective view of the nozzle assembly shown in Figure 19;

Figure 21 is a nozzle assembly of Figure 19 after depositing a protective metal film;

Figure 22 shows the nozzle assembly of Figure 21 after etching through the protective metal film, the polymer coating, and the top of the nozzle chamber;

Figure 23 shows the nozzle assembly completed after the backside MEMS processing and removal of the photoresist layer;

Figure 24 is a perspective view of the nozzle assembly shown in Figure 23;

Figure 25 is a side cross-sectional view of a partially fabricated alternative ink jet nozzle assembly after a first step sequence in which the nozzle chamber sidewalls are formed;

Figure 26 is a perspective view of the partially fabricated ink jet nozzle assembly shown in Figure 25;

Figure 27 is a side cross-sectional view of the partially fabricated ink jet nozzle assembly after the second step sequence of the nozzle chamber filled with polyimide;

Figure 28 is a perspective view of the partially fabricated ink jet nozzle assembly shown in Figure 27;

Figure 29 is a side cross-sectional view of a partially fabricated ink jet nozzle assembly in which the connector post is formed in a third step sequence up to the top of the chamber;

Figure 30 is a perspective view of the partially fabricated ink jet nozzle assembly shown in Figure 29;

Figure 31 is a side cross-sectional view showing a partially fabricated ink jet nozzle assembly after a fourth step sequence in which a conductive metal plate is formed;

Figure 32 is a perspective view of the partially fabricated ink jet nozzle assembly shown in Figure 31;

Figure 33 is a side cross-sectional view of the partially fabricated ink jet nozzle assembly after the fifth step sequence of the active beam member forming the thermal bending actuator;

Figure 34 is a perspective view of the partially fabricated ink jet nozzle assembly shown in Figure 33;

Figure 35 is a side cross-sectional view of a portion of the ink jet nozzle assembly after coating the polymer layer, protecting the metal layer, and etching the nozzle opening after the sixth step sequence;

36 is a side cross-sectional view of the inkjet nozzle assembly completed after the backside MEMS processing and removal of the photoresist layer;

Figure 37 is a cross-sectional perspective view of the ink jet nozzle assembly shown in Figure 36.

80. . . Polymer layer

100. . . Inkjet nozzle assembly

101. . . Substrate

102. . . electrode

104. . . Side wall

105. . . Nozzle chamber

108. . . Connector column

109. . . Metal pad

110. . . Metal film

113. . . Nozzle opening

116. . . Passive beam

120. . . Ink supply channel

Claims (10)

A print head comprising a plurality of nozzle assemblies formed on a substrate, each nozzle assembly comprising: a nozzle chamber, a nozzle opening defined in a top of the chamber of the nozzle chamber; and a thermal bending actuator defining each a moving portion of the chamber top of the nozzle chamber, the thermal bending actuator comprising: a first active component coupled to the drive circuit; and a second passive component mechanically cooperating with the first component such that when current passes through the first In the case of a component, the first component expands relative to the second component, causing the actuator to bend toward the bottom of the nozzle chamber, wherein the nozzle plate of the printhead is coated with a hydrophobic polymer material, the nozzle plate being at least partially defined At the top of each of the nozzle chambers, and wherein the hydrophobic polymeric material is selected from the group consisting of: polydecylsesquioxanes. A printhead according to the first aspect of the patent application, wherein the hydrophobic polymer material is selected from the group consisting of poly(alkyl sesquioxanes) and poly(aryl sesquioxanes). The print head according to item 1 of the patent application, wherein the hydrophobic polymer material is selected from the group consisting of poly(methyl sesquioxanes) and poly(phenyl sesquioxanes). A printhead according to the first aspect of the patent application, wherein each of the chamber tops has a hydrophobic outer surface with respect to the inner surface of each nozzle chamber due to the hydrophobic coating. According to the first paragraph of the patent application scope, the print head, wherein each nozzle The chamber contains a roof and a side wall composed of a ceramic material. The print head according to item 5 of the patent application, wherein the ceramic material is selected from the group consisting of tantalum nitride, tantalum oxide and tantalum oxynitride. The print head of claim 1, wherein the top of the chamber is spaced apart from the substrate such that a sidewall of each nozzle chamber extends between the nozzle plate and the substrate. A print head according to the first aspect of the patent application, wherein the nozzle opening is defined in the moving portion of the top of the chamber. A printhead according to the first aspect of the patent application, wherein the nozzle opening is defined in a stationary portion of the top of the chamber. A printhead according to the first aspect of the patent application, wherein the polymeric material defines a mechanical seal between the moving portion and the stationary portion of the chamber top, thereby reducing ink leakage during actuation of the actuator To the least.