Pattern of a non-wetting coating on a fluid ejector and apparatus

A fluid ejector is provided, having an internal surface, an external surface, an orifice that allows fluid in contact with the internal surface to be ejected, a first non-wetting region of the external surface, and one or more second regions of the external surface that are more wetting than the first non-wetting region. A process for cleaning the fluid ejectors is provided that includes detachably securing a faceplate to the fluid ejector and moving a wiper laterally across the faceplate.

TECHNICAL FIELD

This invention relates to coatings on fluid ejectors, an apparatus for cleaning an exterior surface of a fluid ejector, and related methods.

BACKGROUND

A fluid ejector (e.g., an inkjet printhead) typically has an interior surface, an orifice through which fluid is ejected, and an exterior surface. When fluid is ejected from the orifice, the fluid can accumulate on the exterior surface of the fluid ejector. When fluid accumulates on the exterior surface adjacent to the orifice, further fluid ejected from the orifice can be diverted from an intended path of travel or blocked entirely by interaction with the accumulated fluid (e.g., due to surface tension).

Non-wetting coatings such as Teflon® and fluorocarbon polymers can be used to coat surfaces. However, Teflon® and fluorocarbon polymers typically are soft and are not durable coatings. These coatings also can be expensive and difficult to pattern.

SUMMARY

The disclosure features a fluid ejector having an internal surface, an external surface, an orifice that allows fluid in contact with the internal surface to be ejected, a first non-wetting region of the external surface, and one or more second regions of the external surface that are more wetting than the first non-wetting regions.

Implementations may include one or more of the following features. The first non-wetting region may be adjacent to and completely surround the orifice. The second regions may have one or more portions that are proximal to the orifice and one or more portions that are distal to the orifice. The second regions may have an increasing lateral dimension as distance from the orifice increases. The non-wetting region may be formed from a polymer or a monomer. The polymer may be a fluorocarbon polymer, and the monomer can be a silicon-based monomer. The silicon-based monomer may contain one or more fluorine atoms. The non-wetting region may be formed from a layer of gold onto which an alkanethiol monomer is adsorbed. The second regions may be formed from silicon, silicon oxide, or silicon nitride. The fluid ejector may have a plurality of orifices, and each orifice may be in a common plane. The orifices may be disposed with a spatial periodicity, and the first non-wetting region may be deposited in a pattern, the pattern comprising a unit cell replicated with the same spatial periodicity as the orifices.

The disclosure also features a method of cleaning one or more fluid ejectors. In certain implementations, the method includes detachably securing a faceplate to the fluid ejector and moving a wiper laterally across the faceplate. The wiper may not directly contact the fluid ejector. The wiper may be a blade, brush, or sponge. In alternative implementations, a stream of gas, e.g., air, may be applied to the exterior surface. In yet another implementation, vacuum suction may be applied to the exterior surface.

Certain implementations may have one of more of the following advantages. Fluid may be removed from regions immediately surrounding the orifice, resulting in more stable discharges of ejected fluids. Cleaning steps may be eliminated or may be performed fewer times on coated fluid ejectors than on uncoated fluid ejectors, resulting in increased fluid ejector lifetimes and faster printing rates. Contact between the wiper and the surface of the fluid ejector may be eliminated, reducing wear on the exterior surface and increasing fluid ejector lifetimes. A wiping unit may not be necessary, allowing smaller units to be fabricated and decreasing the unit cost of manufacturing.

DETAILED DESCRIPTION

FIG. 1Ais a cross-sectional view of an uncoated fluid ejector100(e.g., an ink-jet printhead nozzle), which can be constructed as described in U.S. patent application Ser. No. 11/256,669, filed Oct. 21, 2005, the contents of which are hereby incorporated by reference. The fluid flows through a descender102and is ejected through an orifice104. Fluid ejector100also includes an exterior surface106. Exterior surface106may be a native silicon surface, a deposited oxide surface, e.g. silicon dioxide, or another material such as silicon nitride.

Referring toFIG. 1B, a non-wetting coating120has been deposited on portions of exterior surface106. The non-wetting coating120can be hydrophobic material. The region that is not coated, e.g., the uncoated exterior surface, is more wettable (e.g., has a smaller contact angle) than the non-wetting coating120.

Non-wetting coating120may be composed of Teflon®, (tridecafluoro-1,1,2,2-tetrahydrooctyl)trichlorosilane (FOTS), 1H,1H,2H,2H-perfluorodecyltrichlorosilane (FDTS), other silicon-based monomers or fluorocarbon polymers, or similar materials. These coatings may be deposited by spin coating, spray or dip coating, molecular vapor deposition (MVD®) or other suitable methods. For some materials, patterning of the non-wetting coating can be accomplished using masking processes, e.g. depositing and patterning a photoresist layer to provide a protective mask layer over those portions of the surface which are to remain free of the non-wetting coating, depositing the non-wetting coating, and then dissolving or lifting off the photoresist layer leaving the patterned non-wetting coating on the exterior surface106. Alternatively, for some materials, patterning of the non-wetting coating can be accomplished using photolithography processes, e.g., depositing the non-wetting coating, depositing and patterning a photoresist layer to provide a protective mask layer over those portions of the surface which are to have the non-wetting coating, removing the portions of the non-wetting coating that are not covered by the photoresist (e.g., by etching), and then optionally removing the photoresist layer. To eliminate the steps of masking and removing the mask, the non-wetting coating can be patterned using laser ablation.

FIG. 1Crepresents an alternative method of depositing a non-wetting coating. A layer130of gold, is first deposited on a portion of exterior surface106. An alkanethiol layer135is then deposited on the gold layer, forming a monolayer. The formation and selective deposition of alkanethiol monolayers on gold can be performed using conventional techniques. Alkanethiol monolayers may be wetting or non-setting. Suitable non-wetting alkanethiols include, by way of example, octadecylthiol and 1H,1H,2H,2H-perfluorodecanethiol. Selective deposition of gold (typically between a thickness of about 50 nm to about 200 nm) may be accomplished using conventional photolithography and evaporation techniques.

FIG. 2A-Eillustrate a portion of an array150of orifices in a fluid ejector.FIG. 2Ashows an uncoated exterior surface106with three orifices104, although the fluid ejector may have just one or two orifices, or more than three orifices, e.g. more than 20, e.g. more than 100. The orifices can arranged in an array, e.g., a single row with regular spacing, or multiple rows with regular spacing (in which case the rows can be offset relative to each other).

FIGS. 2B-Eillustrate alternative implementations of a portion of a fluid ejector with an array150of orifices in which non-wetting coating140and uncoated regions form various patterns. In these implementations, non-wetting coating140is deposited in an area that is adjacent to and completely surrounds orifice104. In general, the non-wetting coating is patterned to provide one or more areas without the non-wetting coating that form elongated regions extending away from the orifice.

FIG. 2Billustrates an implementation of a fluid ejectors ofFIG. 2Awhich has been coated with a patterned non-wetting coating140. The resulting pattern can be described as a series of unit cells162, each unit cell defined by a central orifice104and two uncoated regions106, each such region appearing as a trapezoid. In this implementation, each trapezoid comprises one end which is proximal to the orifice, and one end which is distal to the orifice, the distal end being wider than the proximal end. The unit cell has mirror symmetry defined by a plane that is perpendicular to the plane of the array and that bisects the orifices. The unit cell may be replicated along array150to produce a pattern with a periodicity equal to that of the orifices.

FIG. 2Cshows an alternative implementation to that depicted inFIG. 2B. In this implementation, each unit cell164contains a central orifice and four trapezoidal regions. Two trapezoidal regions are those depicted inFIG. 2Bwhile the other two trapezoidal regions are displaced laterally. As inFIG. 2B, each trapezoid comprises one end which is proximal to the orifice, and one end which is distal to the orifice, the distal end being wider than the proximal end. The unit cell has rotational symmetry about a line through the center of the orifice and perpendicular to the plane of the array. The unit cell may be replicated along array150to produce a pattern with a periodicity equal to that of the orifices.

FIG. 2Dshows another implantation of a patterned array. In this implementation, each unit cell166contains a central orifice and three trapezoidal regions. As in the examples illustrated byFIGS. 2B-C, each trapezoid comprises one end which is proximal to the orifice, and one end which is distal to the orifice, the distal end being wider than the proximal end. The unit cell has mirror symmetry defined by a plane that is perpendicular to both the line that passes through the center of the orifices and to the plane of the array. The unit cell may be replicated along array150to produce a pattern with a periodicity equal to that of the orifices.

FIG. 2Eillustrates yet another implantation of a patterned array. In contrast to the implementations depicted inFIGS. 2B-D, in which a majority of the surfaces are coated with non-wetting coating140and the non-wetting coating forms a generally continuous layer on the fluid ejector, in the implementation illustrated inFIG. 2E, a relatively small region of the array is coated with non-wetting coating140and the regions of non-wetting coating around each orifice are unconnected. In this implementation, each unit cell168can be described as non-wetting coating140in a star shape surrounding central orifice104and sharing a rotational symmetry axis with the orifice. As depicted inFIG. 2E, the star has eight points. This geometry is exemplary however, and patterns in alternative implementations may take other forms. As in the other implementation, unit cell168may be replicated along array150to produce a pattern with a periodicity equal to that of the orifices.

Referring again toFIGS. 2B-2E, non-wetting coating140may be, as described above, either a polymer or a monomer coating e.g. a fluorocarbon polymer or silicon-based monomer, or an alkanethiol monomer deposited on an underlying gold layer. The uncoated exterior surface regions106will be more wetting than regions coated with non-wetting coating140. Without being bound to any particular theory, fluid ejected from orifices may adhere to the external surface of the array. Such adhered fluid may adhere preferentially to uncoated exterior surface regions106, and may be repelled from regions coated with non-wetting coating140. Thus, various patterns of coated and uncoated regions may provide a passive transport mechanism to wick or draw adhered fluid droplets away from fluid ejector orifices.

Referring toFIG. 3A, a portion of a fluid ejector is shown with a faceplate200unattached.FIG. 3Bshows faceplate200detachably secured to the fluid ejector. Faceplate200contacts only the outer edges of the fluid ejector, leaving a substantial portion of the outer surface exposed. Faceplate200may be formed from suitable polymer, typically a polymer that is flexible and non-abrasive. Faceplate200may be detachably secured to array150during, e.g., a cleaning step.

FIGS. 4A and 4Bshow in perspective view a portion of an array150of fluid ejectors with faceplate200unattached (FIG. 4A), and attached to outer edges of the array. (FIG. 4B). Region160represents the remainder of the fluid ejector apparatus, not shown.

FIGS. 5A-Dillustrate process steps of an array of fluid ejectors in use and during a cleaning step.FIG. 5Ashows a cross-sectional view of an array150of three fluid ejectors in operation: two fluid ejectors are ejecting, through orifice104, fluid (e.g. an ink) depicted in this example in the form of droplets210; one of the fluid ejectors is not ejecting fluid. Referring toFIG. 5B, some time after fluid is ejected, droplets210may adhere to uncoated portions106of the array surface. In keeping with the theory outlined above, droplets may preferentially adhere to uncoated regions, however droplets may also adhere to regions coated with a non-wetting coating.

FIG. 5Balso shows faceplate200attached to array150, contacting only portions of the outer edges of the array.FIG. 5Cillustrates a wiper220moving laterally across the outer surface of faceplate200. Wiper220contacts faceplate200but does not directly contact array150. That is, the thickness of faceplate200may be chosen, and the faceplate may be connected to the array150, so that the faceplate200projects slightly above the external surface106of the array, e.g., by less than the diameter of a typical drop of fluid that would be ejected from the array, e.g., by 50 microns or less. Thus, the faceplate200acts as a stop so that wiper220contacts adhered droplets210and removes them from the array surface without directly contacting the array surface. Wiper220may be formed of a material which tends to absorb fluids, e.g. ink, ejected from the fluid ejectors. Referring toFIG. 5D, after moving wiper220across faceplate200, the faceplate may then be removed to reveal a clean external surface of array150, that is, an external surface with either no adhered droplets, or a reduced volume of adsorbed fluid than before the cleaning step. In certain implementations, other forms of a wiper may be used, e.g. a blade, sponge, brush, roller, or similar device. In other implementations, a blast of air, other gas, or suction may be used to remove adhered droplets from the array.

FIG. 6shows a perspective view of an implementation of array150with attached faceplate200, across which a wiper, here in the form of a roller230, is rolled. The array150includes regions coated with a non-wetting coating and uncoated regions to move fluid away from the nozzles, and the roller removes the fluid.

FIG. 7shows a top view of another implementation of a fluid ejector150which has been coated with a patterned non-wetting coating140. This implementation is similar toFIG. 2B, with uncoated regions106a,106b, e.g., trapezoidal regions, extending away from the nozzles104. However, in this implementation, the uncoated regions106aon one side of the line of nozzles are connected to a common uncoated region240athat can extend along and in parallel to the entire line of nozzles. Similarly, the uncoated regions106bon the other side of the line of nozzles are connected to a common uncoated region240bthat can extend along and in parallel to the entire line of nozzles. The uncoated regions240a,240bcan join to the wider end of the trapezoidal regions106a,106b, respectively. The uncoated regions240a,240bcan be at the edges of the substrate.

AlthoughFIG. 7is similar toFIG. 2B, the uncoated regions extending along and in parallel to the line of nozzles could be used with other implementations, e.g., with the patterns illustrated inFIGS. 2C and 2D(in the implementation ofFIG. 2D, the uncoated region could extend only along one side of the line of nozzles).

Referring toFIG. 8, a wiper, e.g., a roller230, can be positioned to directly contact an uncoated region (and not contact the coated region) of the external surface that extends parallel to the line of nozzles. The roller230can be configured to move parallel to the line of nozzles, removing the fluid that has been wicked from the coated surface140. In some implementation, illustrated inFIG. 8, two wipers, e.g., rollers230are arranged in parallel to simultaneously directly contact the uncoated regions240a,240bon opposite sides of the line of nozzles so as to remove the fluid. In the implementations in which the wiper directly contacts the uncoated region of the printhead150, the faceplate200(not shown) need not project above the surface of the module. For example, the outer surface of the faceplate could be flush, or below the surface of the module, or the faceplate might be omitted entirely.

A number of embodiments of the invention have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the invention. For example, additional patterns of non-wetting coating and uncoated regions may be envisaged, and method steps may be performed in a different order than herein depicted, and the desired results may still be produced. Accordingly, other embodiments are within the scope of the following claims.