Patent Application
20100189943
1. Field of the Invention
This invention relates generally to an intermediate layer and, more particularly, to a nanotube-containing intermediate layer and related members used for electrostatographic devices, and methods for making the nanotube-containing intermediate layer and the related members.
2. Background of the Invention
In electrophotography (also known as xerography, electrophotographic imaging or electrostatographic imaging), an imaging process includes forming a visible toner image on a support surface (e.g., a sheet of paper). The visible toner image is often transferred from a photoreceptor that contains an electrostatic latent image and is usually fixed or fused onto a support surface to form a permanent image using a fuser. For example, the fuser can include a surface release layer made of fluoroplastics (e.g., perfluoroalkoxy (PFA), or polytetrafluoroethylene (PTFE)) and coated on a resilient silicone rubber layer. The fluoroplastic surface can enable oil-less fusing and the conformable silicone rubber layer can enable rough paper fix, low mottle and good uniformity. In some fusers, primer layers, such as tie layers, have been used between the silicone rubber layer and the surface release layer to facilitate the adhesion therebetween.
The fluoroplastics are often crystalline materials and require high baking temperatures, typically over 300° C., to form films. Problems arise, however, since the silicone rubber starts to degrade at about 250° C. It is therefore difficult to achieve uniform fuser films without defects, even if the formation process conditions, such as the baking temperatures, the ramping temperatures and primer layer types and thickness can be tuned as desired.
Thus, there is a need to overcome these and other problems of the prior art and to provide an intermediate composite layer in a fuser member and methods for forming the intermediate composite layer and the fuser member.
According to various embodiments, the present teachings include a fuser member. The fuser member can include a substrate; a resilient layer disposed over the substrate; an intermediate layer disposed over the resilient layer, and a surface layer disposed over the intermediate layer. The intermediate layer of the fuser member can include a plurality of carbon nanotubes dispersed in a polymer matrix to protect the underlying resilient layer.
According to various embodiments, the present teachings also include a method for making a member. In this method, a composite dispersion that include a plurality of carbon nanotubes and a polymer can be formed and then deposited and cured on a resilient layer to form an intermediate layer thereon. The resilient layer can be formed over a substrate. A second dispersion can be applied to the formed intermediate layer and can be treated at a temperature of about 250° C. or higher to form a surface layer on the intermediate layer.
According to various embodiments, the present teachings further include a method for forming a member. During the formation, a composite dispersion that includes a plurality of carbon nanotubes and a polymer can be formed and deposited on a resilient layer, which is formed on a substrate. A second dispersion can then be applied to the deposited composite dispersion and can be treated at a temperature of about 250° C. or higher to form an intermediate layer on the resilient layer and to form a surface layer on the formed intermediate layer.
Additional objects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the appended claims.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed.
The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate several embodiments of the invention and together with the description, serve to explain the principles of the invention.
Reference will now be made in detail to the present embodiments (exemplary embodiments) of the invention, an example of which is illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts. In the following description, reference is made to the accompanying drawings that form a part thereof, and in which is shown by way of illustration specific exemplary embodiments in which the invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention and it is to be understood that other embodiments may be utilized and that changes may be made without departing from the scope of the invention. The following description is, therefore, merely exemplary.
While the invention has been illustrated with respect to one or more implementations, alterations and/or modifications can be made to the illustrated examples without departing from the spirit and scope of the appended claims. In addition, while a particular feature of the invention may have been disclosed with respect to only one of several implementations, such feature may be combined with one or more other features of the other implementations as may be desired and advantageous for any given or particular function. Furthermore, to the extent that the terms “including”, “includes”, “having”, “has”, “with”, or variants thereof are used in either the detailed description and the claims, such terms are intended to be inclusive in a manner similar to the term “comprising.” As used herein, the term “one or more of” with respect to a listing of items such as, for example, A and B, means A alone, B alone, or A and B. The term “at least one of” is used to mean one or more of the listed items can be selected.
Notwithstanding that the numerical ranges and parameters setting forth the broad scope of the invention are approximations, the numerical values set forth in the specific examples are reported as precisely as possible. Any numerical value, however, inherently contains certain errors necessarily resulting from the standard deviation found in their respective testing measurements. Moreover, all ranges disclosed herein are to be understood to encompass any and all sub-ranges subsumed therein. For example, a range of “less than 10” can include any and all sub-ranges between (and including) the minimum value of zero and the maximum value of 10, that is, any and all sub-ranges having a minimum value of equal to or greater than zero and a maximum value of equal to or less than 10, e.g., 1 to 5. In certain cases, the numerical values as stated for the parameter can take on negative values. In this case, the example value of range stated as “less than 10” can assume values as defined earlier plus negative values, e.g. −1, −1.2, −1.89, −2, −2.5, −3, −10, −20, −30, etc.
Exemplary embodiments provide a fuser member containing an intermediate layer and methods for forming the intermediate layer and the fuser member. In one embodiment, the fuser member can include a substrate, a resilient layer, a surface layer and an intermediate layer disposed between the resilient layer and the surface layer. The resilient layer can include, for example, a silicone rubber layer and the surface layer can include, for example, a fluoropolymer such as a fluoroplastic of PFA or PTFE. The intermediate layer can include a carbon-nanotube (CNT) polymer composite containing a plurality of carbon nanotubes in a polymer matrix. The surface layer and the fuser member can thus be treated at a temperature of about 250° C. or higher.
Although the term “fuser member” is used herein for illustrative purposes, it is intended that the term “fuser member” also encompasses other members useful for an electrostatographic printing process including, but not limited to, a fixing member, a pressure member, a heat member and/or a donor member. The “fuser member” can be in a form of, for example, a belt, a plate, a sheet, a roll or the like.
As shown, the fuser member 100 can include a substrate 110, a resilient layer 120, an intermediate layer 130 and a surface layer 140. The surface layer 140 can be formed over the resilient layer 120, which can in turn be formed over the substrate 110. The disclosed intermediate layer 130 can be formed between the resilient layer 120 and the surface layer 140 in order to provide desired properties, e.g., thermal stabilities, for forming and/or using the fuser member 100 at a temperature of about 250° C. or higher.
The substrate 110 can be in a form of, for example, a belt, plate, and/or cylindrical drum for the disclosed fuser member 100. In various embodiments, the substrate 110 can include a wide variety of materials, such as, for example, metals, metal alloys, rubbers, glass, ceramics, plastics, or fabrics. In an additional example, the metals used can include aluminum, anodized aluminum, steel, nickel, copper, and mixtures thereof, while the plastics used can include polyimides, polyester, polyetheretherketone (PEEK), poly(arylene ether)s, polyamides and mixtures thereof. In certain embodiments, the substrate 110 can include, e.g., aluminum cylinders or aluminum fuser rolls having silicone rubber formed thereon.
The resilient layer 120 can include, for example, a silicone rubber layer; and the surface layer 140 can include, for example, fluoroplastics such as PFA, and/or PTFE, depending on specific applications. In various embodiments, materials and/or methods as known to one of ordinary skill in the art for the resilient layer and/or the surface layer of a conventional fuser member can be used for the disclosed fuser member 100. In various embodiments, the surface layer 140 can include a fluoropolymer including, but not limited to, polytetrafluoroethylene, copolymer of tetrafluoroethylene and hexafluoropropylene, copolymer of tetrafluoroethylene and perfluoro(propyl vinyl ether), copolymer of tetrafluoroethylene and perfluoro(ethyl vinyl ether), copolymer of tetrafluoroethylene and perfluoro(methyl vinyl ether), and copolymer of tetrafluoroethylene, hexafluoropropylene and vinylidenefluoride.
The intermediate layer 130 can be formed between the resilient layer 120 and the surface layer 140 so as to facilitate the film quality of the resilient layer 120 and/or the surface layer 140 and/or to facilitate the adhesion therebetween. In various embodiments, the intermediate layer 130 can include a plurality of carbon nanotubes (CNTs) dispersed in a polymer matrix to provide an improved thermal stability, mechanical robustness, and/or electrical property of the fuser member 100. In various embodiments, the intermediate layer 130 can thermally and/or mechanically protect the resilient layer 120 during the formation and/or use of the member 100. For example, when the member 100, such as the surface layer 140 that is formed over the intermediate layer 130, is treated at a temperature of about 250° C. or high, defect formation can be reduced and eliminated for the resilient layer 130 due to the overlaying intermediate layer 130.
As used herein, the “polymer matrix” can include one or more chemically or physically cross-linked polymers, such as, for example, thermoplastics, thermoelastomers, resins, polyperfluoroether elastomers, silicone elastomers, thermosetting polymers or other cross-linked materials. In various other embodiments, the polymers can include, for example, fluorinated polymers (i.e., fluoropolymers) including, but not limited to, fluoroelastomers (e.g. Viton), fluorinated thermoplastics including fluorinated polyethers, fluorinated polyimides, fluorinated polyetherketones, fluorinated polyamides, or fluorinated polyesters. In various embodiments, the one or more cross-linked polymers can be semi-soft and/or molten to mix with the nanotubes.
In various embodiments, the polymer matrix can include fluoroelastomers, e.g., having a monomeric repeat unit selected from the group consisting of tetrafluoroethylene, perfluoro(methyl vinyl ether), perfluoro(propyl vinyl ether), perfluoro(ethyl vinyl ether), vinylidene fluoride, hexafluoropropylene, and mixtures thereof.
Commercially available fluoroelastomer can include, for example, such as Viton A® (copolymers of hexafluoropropylene (HFP) and vinylidene fluoride (VDF or VF2)), Viton®-B, (terpolymers of tetrafluoroethylene (TFE), vinylidene fluoride (VDF) and hexafluoropropylene (HFP); and Viton®-GF, (tetrapolymers including TFE, VF2, HFP)), as well as Viton E®, Viton E 60C®, Viton E430®, Viton 910®, Viton GH® and Viton GF®. The Viton designations are Trademarks of E.I. DuPont de Nemours, Inc. Still other commercially available fluoroelastomer can include, for example, Dyneon™ fluoroelastomers from 3M Company. Additional commercially available materials can include Aflas® a poly(propylene-tetrafluoroethylene) and Fluorel II® (LII900) a poly(propylene-tetrafluoroethylenevinylidenefluoride) both also available from 3M Company, as well as the Tecnoflons identified as For-60KIR®, For-LHF®, NM®, For-THF®, For-TFS®, TH®, and TN505®, available from Solvay Solexis.
In one embodiment, the polymer matrix can include a vinylidenefluoride-containing fluoroelastomer cross-linked with an effective curing agent (also referred to herein as a cross-linking agent, bonding agent, or cross-linker), that includes, but is not limited to, a bisphenol compound, a diamino compound, an aminophenol compound, an amino-siloxane compound, an amino-silane and a phenol-silane compound.
An exemplary bisphenol cross-linker can include Viton® Curative No. 50 (VC-50) available from E. I. du Pont de Nemours, Inc. VC-50 can be soluble in a solvent suspension of the CNT and the exemplary fluoropolymer and can be readily available at the reactive sites for cross-linking. Curative VC-50 can contain Bisphenol-AF as a cross-linker and diphenylbenzylphosphonium chloride as an accelerator. Bisphenol-AF is also known as 4,4′-(hexafluoroisopropylidene)diphenol.
Cross-linked fluoropolymers can form elastomers that are relatively soft and display elastic properties. In a specific embodiment, the polymer matrix used for the intermediate layer can include Viton-GF® (E. I. du Pont de Nemours, Inc.), including tetrafluoroethylene (TFE), hexafluoropropylene (HFP), vinylidene fluoride (VF2), and a brominated peroxide cure site.
In various embodiments, the polymer matrix for the intermediate layer 130 can include a fluororesin including, but not limited to, polytetrafluoroethylene, copolymer of tetrafluoroethylene and hexafluoropropylene, copolymer of tetrafluoroethylene and perfluoro(propyl vinyl ether), copolymer of tetrafluoroethylene and perfluoro(ethyl vinyl ether), and copolymer of tetrafluoroethylene and perfluoro(methyl vinyl ether). In various embodiments, the polymer matrix can include cured silicone elastomers.
In various embodiments, the polymers and the nanotubes used for the intermediate layer 130 can include those described in related U.S. patent applications, Ser. No. 12/198,551, entitled “A Process for Making CNT/PFA Composite Coatings for Fuser Applications;” Ser. No. 12/198,460, entitled “CNT/Fluoropolymer Coating Composition;” and Ser. No. 12/245,850, entitled “Nanotube Reinforced Fluorine-Containing Composites,” which are hereby incorporated by reference in their entirety.
As used herein and unless otherwise specified, the term “nanotubes” refers to elongated materials (including organic and inorganic materials) having at least one minor dimension, for example, width or diameter, of about 100 nanometers or less. Although the term “nanotubes” is used herein for illustrative purposes, it is intended that the term also encompasses other elongated structures of like dimensions including, but not limited to, nanoshafts, nanopillars, nanowires, nanorods, and nanoneedles and their various functionalized and derivatized fibril forms, which include nanofibers with exemplary forms of thread, yarn, fabrics, etc.
The nanotubes can also include single wall carbon nanotubes (SWCNTs), multi-wall carbon nanotubes (MWCNTs), and their various functionalized and derivatized fibril forms such as carbon nanofibers. In various embodiments, the nanotubes can have an inside diameter and an outside diameter. For example, the inside diameter can range from about 0.5 to about 20 nanometers, while the outside diameter can range from about 1 to about 80 nanometers. Alternatively, the nanotubes can have an aspect ratio, e.g., ranging from about 1 to about 1,000,000.
The nanotubes can have various cross sectional shapes, such as, for example, rectangular, polygonal, oval, or circular shape. Accordingly, the nanotubes can have, for example, cylindrical 3-dimensional shapes.
The nanotubes can be formed of conductive or semi-conductive materials and can provide exceptional and desired functions, such as, thermal (e.g., stability or conductivity), mechanical, and electrical (e.g., conductivity) functions. In addition, the nanotubes can be modified/functionalized nanotubes with controlled and/or increased thermal, mechanical, and electrical properties through various physical and/or chemical modifications. For example, carbon nanotubes can be surface-modified with a material chosen from perfluorocarbon, perfluoropolyether, and/or polydimethylsiloxane.
The nanotubes can further be dispersed in the polymer matrix having a weight loading of, for example, about 0.01% to about 20% of the formed intermediate layer 130.
In various embodiments, the intermediate layer 130 can further include fillers, such as inorganic particles, in the nanotube composite dispersion. In an exemplary embodiment, the filler suspension can be prepared by sonication of inorganic particles in the presents of surface treatment agents such as silanes in water. In various embodiments, the inorganic particles can include, but are not limited to, metal oxides, non-metal oxides, metals, or other suitable particles. Specifically, the metal oxides can include, for example, silicon oxide, aluminum oxide, chromium oxide, zirconium oxide, zinc oxide, tin oxide, iron oxide, magnesium oxide, manganese oxide, nickel oxide, copper oxide, antimony pentoxide, indium tin oxide, and mixtures thereof. The non-metal oxides can include, for example, boron nitride, silicon carbides (SiC) and the like. The metals can include, for example, nickel, copper, silver, gold, zinc, iron and the like. In various embodiments, other additives known to one of ordinary skill in the art can also be included in the nanotube coating composites.
In
In
In various embodiments, a CNT/polymer composite dispersion can be used to form the disclosed intermediate layer 130. The composite dispersion can be prepared to include, for example, an effective solvent in order to disperse the plurality of CNTs, one or more polymers and/or corresponding curing agents; inorganic filler particles and optionally surfactants that are known to one of the ordinary skill in the art.
Effective solvents can include, but are not limited to, methyl isobutyl ketone (MIBK), acetone, methyl ethyl ketone (MEK), and mixtures thereof. Other solvents that can form suitable dispersions can be within the scope of the embodiments herein.
Various embodiments can thus include methods for forming the fuser member 100 in accordance with the present teachings. During the formation, various layer-forming techniques, such as, for example, coating techniques, extrusion techniques and/or molding techniques, can be applied respectively to the substrate 110 to form the resilient layer 120, to the resilient layer 120 to form the intermediate layer 130, and/or to the intermediate layer 130 to form the surface layer 140.
As used herein, the term “coating technique” refers to a technique or a process for applying, forming, or depositing a dispersion to a material or a surface. Therefore, the term “coating” or “coating technique” is not particularly limited in the present teachings, and dip coating, painting, brush coating, roller coating, pad application, spray coating, spin coating, casting, or flow coating can be employed. For example, the composite dispersion for forming the intermediate layer 130 and a second dispersion for forming the surface layer 140 can be respectively coated on the resilient layer 120 and the formed intermediate layer 130 by spray-coating with an air-brush. In various embodiments, gap coating can be used to coat a flat substrate, such as a belt or plate, whereas flow coating can be used to coat a cylindrical substrate, such as a drum or fuser roll or fuser member substrate.
In various embodiments, the disclosed the fuser member can include an intermediate layer having a thickness of about 0.1 micrometer to about 50 micrometers; a surface layer having a thickness of about 1 micrometer to about 40 micrometers; and a resilient layer having a thickness of about 2 micrometers to about 10 millimeters.
At 210 of
At 220, the CNT/polymer composite dispersion can be deposited, coated, or extruded on a resilient layer. In various embodiments, the resilient layer (also see 120 of
The curing process for forming the intermediate layer 130 can include, for example, a step-wise curing process. In an exemplary embodiment, a coated/extruded/molded CNT/polymer composite dispersion can be placed in a convection oven at about 49° C. for about 2 hours; the temperature can be increased to about 177° C. and further curing can take place for about 2 hours; the temperature can be increased to about 204° C. and the coating can further be cured at that temperature for about 2 hours; and lastly, the oven temperature can be increased to about 232° C. and the coating can be cured for another 6 hours. Other curing schedules can be possible. Curing schedules known to those skilled in the art can be within the scope of embodiments herein.
At 230, a surface layer (also see 140 of
In various embodiments, during the preparation of the intermediate layer 130, for example, at act 220 of
In various embodiments, when preparing the intermediate layer 130 and the surface layer 140 over the resilient layer 120, the baking (or curing) process of the intermediate layer 130 and the surface layer 140 can be combined. For example, after the deposition of the CNT/polymer composite dispersion on the resilient layer 120, the composite deposition can be briefly dried, e.g., to evaporate the solvent used, followed by a deposition of the surface layer 140. The dried deposition of the intermediate composite and the deposition of the surface layer can then be thermally treated to further cure the polymer matrix of the intermediate composite and to further bake the surface layer at the same time. In various embodiments, a step-wise thermal treatment, for example, at temperatures of about 250° C. or higher, can be employed to form the disclose fuser member 100.
In this manner, because the intermediate layer 130 can provide high-temperature thermal stabilities and mechanical robustness, the high temperature baking or curing of the surface layer 140 can be performed to provide high quality to the fuser member 100, for example, without generating any defects within the underlying resilient layer 120 and the formed surface layer 140. In addition, due to the intermediate layer 130, the fuser member 100 can possess, for example, improved adhesion between layers, stability of depositions, improved thermal conductivities, and a long lifetime.
The intermediate layer was prepared by flow-coating a composite dispersion on a silicone rubber layer of a conventional fuser roll. The composite dispersion included CNT/Viton composites from a let-down process, a metal oxide of MgO, a bisphenol curing agent of VC-50 (Viton® Curative No. 50 available from E. I. du Pont de Nemours, Inc.) and optionally a surfactant in an organic solvent of methyl isobutyl ketone (MIBK).
Following the coating process of the composite deposition, a curing process was performed at ramp temperatures of about 149° C. for about 2 hours, and at about 177° C. for about 2 hours, then at about 204° C. for about 2 hours and then at about 232° C. for about 6 hours for a post cure.
In this example, the intermediate coat was prepared by flow-coating a composite dispersion containing the let-down CNT/Viton composites of Example 1, a metal oxide of MgO, an amino-silane curing agent of AO700 and optionally a surfactant in a MIBK organic solvent, on the top of the silicone layer of the fuser roll.
Following the coating process, a curing process was performed at ramp temperatures of about 149° C. for about 2 hours, and at about 177° C. for about 2 hours, then at about 204° C. for about 2 hours and then at about 232° C. for about 6 hours for a post cure.
The PFA topcoat was used as a surface layer and was prepared by spray-coating a PFA aqueous dispersion on top of the intermediate layer formed in Examples 1-2, followed by baking at high temperature of about 350° C. for 10 min.
The PFA topcoat was also used as a surface layer and was prepared by powder-coating a PFA aqueous dispersion on top of the intermediate layer formed in Examples 1-2, followed by baking at high temperature of about 350° C. for 10 min.
The fuser member was fabricated by flow-coating the CNT/Viton composite dispersion in Examples 1-2 on top of a silicone rubber layer of a conventional fuser member. The coated CNT/Viton composite dispersion was briefly dried at a temperature from about 49° C. to about 177° C. for 2 hours. A PFA layer was then coated on top of the dried composite dispersion using the spray- or powder-coating technique in Examples 3-4, followed by baking at high temperatures of about 204° C. for 2 hours, then about 232° C. for 6 hours, and then about 350° C. for 10 min for a further curing of the intermediate composite and a baking of the PFA surface layer to form the fuser member.
Other embodiments of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the invention being indicated by the following claims.
