Phase change ink imaging component with MICA-type silicate layer

[00002] Reference is made to the following commonly assigned, copending patent applications, including U.S. patent application Ser. No. 10/177,911, filed Jun. 20, 2002, entitled, “Phase Change Ink Imaging Component Having Elastomer Outer Layer;” U.S. patent application Ser. No. 10/177,909, filed Jun. 20, 2002, entitled, “Phase Change Ink Imaging Component with Outer Layer Having Haloelastomer with Pendant Chains;” U.S. patent application Ser. No. 10/177,780, filed Jun. 20, 2002, entitled, “Phase Change Ink Imaging Component with Thermoplastic Layer;” U.S. patent application Ser. No. 10/177,907, filed Jun. 20, 2002, entitled, “Phase Change Ink Imaging Component with Thermoset Layer;” U.S. patent application Ser. No. 10/177,800, filed Jun. 20, 2002, entitled, “Phase Change Ink Imaging Component with Fluorosilicone Layer;” U.S. patent application Ser. No. 10/177,906, filed Jun. 20, 2002, entitled, “Phase Change Ink Imaging Component with Latex Fluoroelastomer Layer;” U.S. patent application Ser. No. 10/177,910, filed Jun. 20, 2002, entitled, “Phase Change Ink Imaging Component with Q-Resin Layer;” U.S. patent application Ser. No. 10/177,779, filed Jun. 20, 2002, entitled, “Phase Change Ink Imaging Component with Polymer Blend Layer;” and U.S. patent application Ser. No. 10/177,908, filed Jun. 20, 2002, entitled, “Phase Change Ink Imaging Component with Polymer Hybrid Layer.” The disclosures of each of these patent applications is hereby incorporated by reference in their entirety.

[00003] The present invention relates generally to an imaging apparatus and layers for components thereof, and for use in offset printing or ink jet printing apparatuses. The layers herein are useful for many purposes including layers for transfer components, including transfix or transfuse components, imaging components, and like components. More specifically, the present invention relates to layers comprising a silicate material, such as a mica-type silicate material. The layers of the present invention may be useful in components used in combination with ink or dye materials. In embodiments, the layers can be used in combination with phase change inks such as solid inks.

[00004] Ink jet printing systems using intermediate transfer, transfix or transfuse members are well known, such as that described in U.S. Pat. No. 4,538,156. Generally, the printing or imaging member is employed in combination with a printhead. A final receiving surface or print medium is brought into contact with the imaging surface after the image has been placed thereon by the nozzles of the printhead. The image is then transferred and fixed to a final receiving surface.

[00005] More specifically, the phase-change ink imaging process begins by first applying a thin liquid, such as, for example, silicone oil, to an imaging member surface. The solid or hot melt ink is placed into a heated reservoir where it is maintained in a liquid state. This highly engineered ink is formulated to meet a number of constraints, including low viscosity at jetting temperatures, specific visco-elastic properties at component-to-media transfer temperatures, and high durability at room temperatures. Once within the printhead, the liquid ink flows through manifolds to be ejected from microscopic orifices through use of proprietary piezoelectric transducer (PZT) printhead technology. The duration and amplitude of the electrical pulse applied to the PZT is very accurately controlled so that a repeatable and precise pressure pulse can be applied to the ink, resulting in the proper volume, velocity and trajectory of the droplet. Several rows of jets, for example four rows, can be used, each one with a different color. The individual droplets of ink are jetted onto the liquid layer on the imaging member. The imaging member and liquid layer are held at a specified temperature such that the ink hardens to a ductile visco-elastic state.

[00006] After depositing the image, a print medium is heated by feeding it through a preheater and into a nip formed between the imaging member and a pressure member, either or both of which can also be heated. A high durometer synthetic pressure member is placed against the imaging member in order to develop a high-pressure nip. As the imaging member rotates, the heated print medium is pulled through the nip and is pressed against the deposited ink image with the help of a pressure member, thereby transferring the ink to the print medium. The pressure member compresses the print medium and ink together, spreads the ink droplets, and fuses the ink droplets to the print medium. Heat from the preheated print medium heats the ink in the nip, making the ink sufficiently soft and tacky to adhere to the print medium. When the print medium leaves the nip, stripper fingers or other like members, peel it from the printer member and direct it into a media exit path.

[00007] To optimize image resolution, the transferred ink drops should spread out to cover a predetermined area, but not so much that image resolution is compromised or lost. The ink drops should not melt during the transfer process. To optimize printed image durability, the ink drops should be pressed into the paper with sufficient pressure to prevent their inadvertent removal by abrasion. Finally, image transfer conditions should be such that nearly all the ink drops are transferred from the imaging member to the print medium. Therefore, it is desirable that the imaging member has the ability to transfer the image to the media sufficiently.

[00008] The imaging member is multi-functional. First, the ink jet printhead prints images on the imaging member, and thus, it is an imaging member. Second, after the images are printed on the imaging member, they can then transfixed or transfused to a final print medium. Therefore, the imaging member provides a transfix or transfuse function, in addition to an imaging function.

[00009] In order to ensure proper transfer and fusing of the ink off the imaging member to the print medium, certain nip temperature, pressure and compliance are required. Unlike laser printer imaging technology in which solid fills are produced by sheets of toner, the solid ink is placed on the imaging member one pixel at a time and the individual pixels must be spread out during the transfix process to achieve a uniform solid fill. Also, the secondary color pixels on the imaging member are physically taller than the primary color pixels because the secondary pixels are produced from two primary pixels. Therefore, compliance in the nip is required to conform around the secondary pixels and to allow the primary pixel neighbors to touch the media with enough pressure to spread and transfer. The correct amount of temperature, pressure and compliance is required to produce acceptable image quality.

[00010] Currently, the imaging member useful for solid inks or phase change inks comprises anodized aluminum. This member operates at about 57° C. to about 64° C. and can be used with a heater that preheats the print media prior to entering the nip. Otherwise, the imaging member may include a heater associated therewith. The heater may be associated anywhere on the offset printing apparatus. The current aluminum-imaging member has several drawbacks. A high nip load of up to about 770 pounds is needed for transfix or transfuse operations. Further, because of the high nip load, bulky mechanisms and supporting structures are needed, resulting in increased printer weight and cost. One example is that a fairly complex two-layer pressure roller is needed. In addition, the first copy out time is unacceptable because of the bulky weight. Moreover, low cohesive failure temperature is another drawback to use of an anodized aluminum drum.

[00011] Several coatings for the imaging member have been suggested. Examples are listed below.

[00012] U.S. Pat. No. 5,092,235 discloses a pressure fixing apparatus for ink jet inks having 1) outer shell of rigid, non-compliant material such as steel, or polymer such as acetal homopolymer or Nylon 6/6 and 2) an underlayer of elastomer material having a hardness of about 30 to 60, or about 50 to 60.

[00013] U.S. Pat. No. 5,195,430 discloses a pressure fixing apparatus for ink jet inks having 1) outer shell of rigid, non-compliant material such as steel, or polymer such as acetal homopolymer or Nylon 6/6 and 2) an underlayer of elastomer material having a hardness of about 30 to 60, or about 50 to 60, which can be polyurethane (VIBRATHANE, or REN:C:O-thane).

[00014] U.S. Pat. No. 5,389,958 discloses an intermediate transfer member/image receiving member having a surface of metal (aluminum, nickel, iron phosphate), elastomers (fluoroelastomers, perfluoroelastomers, silicone rubber, polybutadiene), plastics (polyphenylene sulfide), thermoplastics (polyethylene, polyamide (nylon), FEP), thermosets (metals, ceramics), and a pressure roller with elastomer surface.

[00015] U.S. Pat. No. 5,455,604 discloses a fixing mechanism and pressure wheels, wherein the pressure wheels can be comprised of a steel or plastic material such as DELRIN. Image-receiving drum 40 can be a rigid material such as aluminum or stainless steel with a thin shell mounted to the shaft, or plastic.

[00016] U.S. Pat. No. 5,502,476 teaches a pressure roller having a metallic core with elastomer coating such as silicones, urethanes, nitriles, or EPDM, and an intermediate transfer member surface of liquid, which can be water, fluorinated oils, glycol, surfactants, mineral oil, silicone oil, functional oils such as mercapto silicone oils or fluorinated silicone oils or the like, or combinations thereof.

[00017] U.S. Pat. No. 5,614,933 discloses an intermediate transfer member/image receiving member having a surface of metal (aluminum, nickel, iron phosphate), elastomers (fluoroelastomers, perfluoroelastomers, silicone rubber, polybutadiene), plastics (polyphenylene sulfide), thermoplastics (polyethylene, polyamide (nylon), FEP), thermosets (metals, ceramics), or polyphenylene sulfide loaded with PTFE, and a pressure roller with elastomer surface.

[00018] U.S. Pat. No. 5,790,160 discloses an intermediate transfer member/image receiving member having a surface of metal (aluminum, nickel, iron phosphate), elastomers (fluoroelastomers, perfluoroelastomers, silicone rubber, polybutadiene), plastics (polyphenylene sulfide), thermoplastics (polyethylene, polyamide (nylon), FEP), thermosets (metals, ceramics), or polyphenylene sulfide loaded with PTFE, and a pressure roller with elastomer surface.

[00019] U.S. Pat. No. 5,805,191 an intermediate transfer member/image receiving member having a surface of metal (aluminum, nickel, iron phosphate), elastomers (fluoroelastomers, perfluoroelastomers, silicone rubber, polybutadiene), plastics (polyphenylene sulfide), thermoplastics (polyethylene, polyamide (nylon), FEP), thermosets (metals, ceramics), or polyphenylene sulfide loaded with PTFE, and an outer liquid layer of liquid, which can be water, fluorinated oils, glycol, surfactants, mineral oil, silicone oil, functional oils such as mercapto silicone oils or fluorinated silicone oils or the like, or combinations thereof.

[00020] U.S. Pat. No. 5,808,645 discloses a transfer roller having a metallic core with elastomer covering of silicone, urethanes, nitrites, and EPDM.

[00021] U.S. Pat. No. 6,196,675 B1 discloses separate image transfer and fusing stations, wherein the fuser roller coatings can be silicones, urethanes, nitrites and EPDM.

[00022] U.S. Pat. No. 5,777,650 discloses a pressure roller having an elastomer sleeve, and an outer coating that can be metals, (aluminum, nickel, iron phosphate), elastomers (fluoroelastomers, perfluoroelastomers, silicone rubber, polybutadiene), plastics (polyphenylene sulfide with PTFE filler), thermoplastics (polyethylene, polyamide (nylon), FEP), thermosets (acetals, ceramics). Preferred is annodized aluminum.

[00023] In addition, many different types of outer coatings for transfer members, fuser members, and intermediate transfer members have been used in the electrostatographic arts using powder toner, but not with liquid inks or phase change inks. Several examples are listed herein.

[00024] U.S. Pat. No. 5,361,126 discloses an imaging apparatus including a transfer member including a heater and pressure-applying roller, wherein the transfer member includes a fabric substrate and an impurity-absorbent material as a top layer. The impurity-absorbing material can include a rubber elastomer material.

[00025] U.S. Pat. No. 5,337,129 discloses an intermediate transfer component comprising a substrate and a ceramer or grafted ceramer coating comprised of integral, interpenetrating networks of haloelastomer, silicon oxide, and optionally polyorganosiloxane.

[00026] U.S. Pat. No. 5,340,679 discloses an intermediate transfer component comprised of a substrate and thereover a coating comprised of a volume grafted elastomer, which is a substantially uniform integral interpenetrating network of a hybrid composition of a fluoroelastomer and a polyorganosiloxane.

[00027] U.S. Pat. No. 5,480,938 describes a low surface energy material comprising a volume grafted elastomer which is a substantially uniform integral interpenetrating network of a hybrid composition of a fluoroelastomer and a polyorganosiloxane, the volume graft having been formed by dehydrofluorination of fluoroelastomer by a nucleophilic dehydrofluorinating agent, followed by a hydrosilation reaction, addition of a hydrogen functionally terminated polyorganosiloxane and a hydrosilation reaction catalyst.

[00028] U.S. Pat. No. 5,366,772 describes a fuser member comprising a supporting substrate, and a outer layer comprised of an integral interpenetrating hybrid polymeric network comprised of a haloelastomer, a coupling agent, a functional polyorganosiloxane and a crosslinking agent.

[00029] U.S. Pat. No. 5,456,987 discloses an intermediate transfer component comprising a substrate and a titamer or grafted titamer coating comprised of integral, interpenetrating networks of haloelastomer, titanium dioxide, and optionally polyorganosiloxane.

[00030] U.S. Pat. No. 5,848,327 discloses an electrode member positioned near the donor member used in hybrid scavengeless development, wherein the electrode members have a composite haloelastomer coating.

[00031] U.S. Pat. No. 5,576,818 discloses an intermediate toner transfer component including: (a) an electrically conductive substrate; (b) a conformable and electrically resistive layer comprised of a first polymeric material; and (c) a toner release layer comprised of a second polymeric material selected from the group consisting of a fluorosilicone and a substantially uniform integral interpenetrating network of a hybrid composition of a fluoroelastomer and a polyorganosiloxane, wherein the resistive layer is disposed between the substrate and the release layer.

[00032] U.S. Pat. No. 6,035,780 discloses a process for forming a layer on a component of an electrostatographic apparatus, including mixing a first fluoroelastomer and a polymeric siloxane containing free radical reactive functional groups, and forming a second mixture of the resulting product with a mixture of a second fluoroelastomer and a second polysiloxane compound.

[00033] U.S. Pat. No. 5,537,194 discloses an intermediate toner transfer member comprising: (a) a substrate; and (b) an outer layer comprised of a haloelastomer having pendant hydrocarbon chains covalently bonded to the backbone of the haloelastomer.

[00034] U.S. Pat. No. 5,753,307 discloses fluoroelastomer surfaces and a method for providing a fluoroelastomer surface on a supporting substrate which includes dissolving a fluoroelastomer; adding a dehydrofluorinating agent; adding an amino silane to form a resulting homogeneous fluoroelastomer solution; and subsequently providing at least one layer of the homogeneous fluoroelastomer solution to the supporting substrate.

[00035] U.S. Pat. No. 5,840,796 describes polymer nanocomposites including a mica-type layered silicate and a fluoroelastomer, wherein the nanocomposite has a structure selected from the group consisting of an exfoliated structure and an intercalated structure.

[00036] U.S. Pat. No. 5,846,643 describes a fuser member for use in an electrostatographic printing machine, wherein the fuser member has at least one layer of an elastomer composition comprising a silicone elastomer and a mica-type layered silicate, the silicone elastomer and mica-type layered silicate form a delaminated nanocomposite with silicone elastomer inserted among the delaminated layers of the mica-type layered silicate.

[00037] It is desired to provide a multi-functional imaging member for use with phase change ink printing machines, which has the ability to receive an image, and either transfer, or transfer and fuse the image to a print medium. It is desired that the imaging member when having heat associated therewith, be thermally stable for conduction for fusing or fixing. It is further desired that the imaging member have a relatively low nip load, in order to decrease the weight and cost of the printing machine, and in order to provide an acceptable first copy out time.

[00038] The present invention provides, in embodiments: an offset printing apparatus for transferring a phase change ink onto a print medium comprising: a) a phase change ink component for applying a phase change ink in a phase change ink image; b) an imaging member for accepting the phase change ink image from the phase change ink component, and transferring the phase change ink image from the imaging member to the print medium, the imaging member comprising: i) an imaging substrate, and thereover ii) an outer coating comprising a mica-type silicate material.

[00039] The present invention further provides, in embodiments: an offset printing apparatus for printing a phase change ink onto a print medium comprising: a) a phase change ink component for applying a phase change ink in a phase change ink image; b) an imaging member for accepting said phase change ink image from said phase change ink component, and transferring the phase change ink image from said imaging member to said print medium and for fixing the phase change ink image to said print medium, the imaging member comprising in order: i) an imaging substrate, ii) an intermediate layer, and iii) an outer coating comprising a mica-type silicate material; and c) a heating member associated with the offset printing apparatus.

[00040] In addition, the present invention provides, in embodiments: an offset printing apparatus comprising a phase change ink component containing a phase change ink; an imaging member comprising a substrate, and thereover an outer coating comprising a mica-type silicate material; and a heating member associated with the offset printing apparatus, wherein the phase change ink component dispenses the phase change ink onto the imaging member, and wherein the phase change ink is solid at room temperature.

[00047] The present invention is directed to an offset printing apparatus useful with phase-change inks such as solid inks, and comprising a coated imaging member capable of accepting, transferring and in some embodiments, fixing an ink image to a print medium. The imaging member can be a roller such as a drum, or a film component such as a film, sheet, belt or the like. In embodiments, the imaging member comprises a substrate and an outer layer comprising a mica-type silicate material. In an alternative embodiment, the imaging member comprises a substrate, an optional intermediate layer, and outer layer comprising a mica-type silicate material. The substrate, intermediate layer, and/or outer layer can further comprise fillers dispersed or contained therein.

[00048] The details of embodiments of phase-change ink printing processes are described in the patents referred to above, such as U.S. Pat. Nos. 5,502,476; 5,389,958; and 6,196,675 B1, the disclosures of each of which are hereby incorporated by reference in their entirety.

[00049] Referring to FIG. 1, offset printing apparatus 1 is demonstrated to show transfer of an ink image from the imaging member to a final printing medium or receiving substrate. As the imaging member 3 turns in the direction of arrow 5, a liquid surface 2 is deposited on imaging member 3. The imaging member 3 is depicted in this embodiment as a drum member. However, it should be understood that other embodiments can be used, such as a belt member, film member, sheet member, or the like. The liquid layer 2 is deposited by an applicator 4 that may be positioned at any place, as long as the applicator 4 has the ability to make contact and apply liquid surface 2 to imaging member 3.

[00050] The ink used in the printing process can be a phase change ink, such as, for example, a solid ink. The term “phase change ink” means that the ink can change phases, such as a solid ink becoming liquid ink or changing from solid into a more malleable state. Specifically, in embodiments, the ink can be in solid form initially, and then can be changed to a molten state by the application of heat energy. The solid ink may be solid at room temperature, or at about 25° C. The solid ink may possess the ability to melt at relatively high temperatures above from about 85° C. to about 150° C. The ink is melted at a high temperature and then the melted ink 6 is ejected from printhead 7 onto the liquid layer 2 of imaging member 3. The ink is then cooled to an intermediate temperature of from about 20° C. to about 80° C., or about 72° C., and solidifies into a malleable state in which it can then be transferred onto a final receiving substrate 8 or print medium 8.

[00051] The ink has a viscosity of from about 5 to about 30 centipoise, or from about 8 to about 20 centipoise, or from about 10 to about 15 centipoise at about 140° C. The surface tension of suitable inks is from about 23 to about 50 dynes/cm. Examples of a suitable inks for use herein include those described in U.S. Pat. Nos. 4,889,560; 5,919,839; 6,174,937; and 6,309,453, the disclosure each of which are hereby incorporated by reference in their entirety.

[00052] Some of the liquid layer 2 is transferred to the print medium 8 along with the ink. A typical thickness of transferred liquid is about 100 angstroms to about 100 nanometer, or from about 0.1 to about 200 milligrams, or from about 0.5 to about 50 milligrams, or from about 1 to about 10 milligrams per print medium.

[00053] Suitable liquids that may be used as the print liquid surface 2 include water, fluorinated oils, glycol, surfactants, mineral oil, silicone oil, functional oils, and the like, and mixtures thereof. Functional liquids include silicone oils or polydimethylsiloxane oils having mercapto, fluoro, hydride, hydroxy, and the like functionality.

[00054] Feed guide(s) 10 and 13 help to feed the print medium 8, such as paper, transparency or the like, into the nip 9 formed between the pressure member 11 (shown as a roller), and imaging member 3. It should be understood that the pressure member can be in the form of a belt, film, sheet, or other form. In embodiments, the print medium 8 is heated prior to entering the nip 9 by heated feed guide 13. When the print medium 8 is passed between the printing medium 3 and the pressure member 11, the melted ink 6 now in a malleable state is transferred from the imaging member 3 onto the print medium 8 in image configuration. The final ink image 12 is spread, flattened, adhered, and fused or fixed to the final print medium 8 as the print medium moves between nip 9. Alternatively, there may be an additional or alternative heater or heaters (not shown) positioned in association with offset printing apparatus 1. In another embodiment, there may be a separate optional fusing station located upstream or downstream of the feed guides.

[00055] The pressure exerted at the nip 9 is from about 10 to about 1,000 psi., or about 500 psi, or from about 200 to about 500 psi. This is approximately twice the ink yield strength of about 250 psi at 50° C. In embodiments, higher temperatures, such as from about 72 to about 75° C. can be used, and at the higher temperatures, the ink is softer. Once the ink is transferred to the final print medium 8, it is cooled to an ambient temperature of from about 20° C. to about 25° C.

[00056] Stripper fingers (not shown) may be used to assist in removing the print medium 8 having the ink image 12 formed thereon to a final receiving tray (also not shown).

[00057] FIG. 2 demonstrates an embodiment of the invention, wherein imaging member 3 comprises substrate 15, having thereover outer coating 16.

[00058] FIG. 3 depicts another embodiment of the invention. FIG. 3 depicts a three-layer configuration comprising a substrate 15, intermediate layer 17 positioned on the substrate 15, and outer layer 16 positioned on the intermediate layer 17. In embodiments, an outer liquid layer 2 (as described above) may be present on the outer layer 16.

[00059] In embodiments, the outer release layer 16 comprises a mica-type silicate material. In embodiments, the outer release layer comprises a silicone elastomer and mica-type layered silicate material. In another embodiment, the silicone elastomer and mica-type layered silicate form a delaminated nanocomposite. In a further embodiment, the mica-type layered silicate has a high aspect ratio structure. In yet another embodiment, the silicone elastomer is formed by curing a polyorganosiloxane. An example of a polyorganosiloxane is one having the following formula:
where R is hydrogen or substituted or unsubstituted alkyl, alkoxy, or alkenyl having from about 1 to about 20 carbon atoms, or from about 2 to about 10 carbon atoms, or aryl having from about 4 to about 12 carbon atoms, or from about 6 to about 10 carbon atoms; and where each of A and B may be any of alkyl or alkoxy having from about 1 to about 20 carbon atoms, or from about 2 to about 10 carbon atoms, hydroxy, or vinyl groups; and 0<m/n<about 1, and m+n>about 350.

[00061] By way of example, A, B and R can be the same or different, and can be alkyl groups including alkoxy and substituted alkoxy. Specific examples include chloropropyl, trifluoropropyl, mercaptopropyl, carboxypropyl, aminopropyl, cyanopropyl and the like, and substituted alkoxy substituents such as glycidoxypropyl, methacryloxypropyl, and the like. Typical alkenyl substituents include vinyl, propenyl, and the like, while substituted alkenyl include halogen-substituted materials such as chlorovinyl, bromopropenyl, and the like. Typical aryl or substituted aryl groups include phenyl, chlorophenyl, bromophenyl, and the like. Hydrogen, hydroxy, ethoxy and vinyl are specific examples for A, B and/or R, and allow for superior crosslinkability. Methyl, trifluoropropyl and phenyl are examples of substituents for A, B and/or R in providing superior solvent and oil resistance, higher temperature stability, and surface lubricity.

[00062] The ratio of m/n as between 0 and 1, identifies the polyorganosiloxane as a copolymer. Similarly, the sum of m+n being greater than 350, identifies it as an elastomeric material.

[00063] Other examples of polyorganosiloxanes include condensation curable polyorganosiloxanes, such as silanol-terminated polydimethylsiloxanes. Examples include those having the following formula:

• • [00064] where n′ is an integer of from about 350 to about 2700, or from about 500 to about 1500.

[00065] The terminating silanol groups render the materials susceptible to condensation under acid or mild basic conditions. These groups are produced by kinetically controlled hydrolysis of chlorosilanes. Room temperature vulcanizable (RTV's) systems are formulated from these silanol-terminated polymers with a molecular weight of from about 26,000 to about 200,000. These silanol-terminated polymers may be crosslinked with small quantities of multifunctional silanes, which condense with the silanol group.

[00066] Suitable crosslinking agents for condensation cured polyorganosiloxanes include esters of orthosilicic acid, esters of polysilic acid, and alkyl trialkoxy silanes. Specific examples of suitable crosslinking agents for the condensation cured materials include tetramethylorthosilicate, tetraethylorthosilicate, 2-methoxyethylsilicate, tetrahydrofurfurylsilicate, ethylpolysilicate, butylpolysilicate, and the like crosslinking agents. During the crosslinking reaction, an alcohol is typically split out leading to a crosslinked network. Condensed tetraethylorthosilicate is a specific example of a crosslinking agent.

[00067] A sufficient amount of crosslinking agent is needed to completely crosslink the active end groups on the disilanol polymer. The amount of crosslinking agent required depends on the number average molecular weight of the disilanol polymer employed. With higher average molecular weight polymers, fewer active end groups are present and thus a lesser amount of crosslinking agent is required, and the opposite is true for lower average molecular weight polymers. Generally, with alpha omega hydroxy polydimethyl siloxane having a number average molecular weight of between about 26,000 to about 100,000, from about 1 to about 20 parts by weight, or from about 2.5 to about 10 parts by weight of condensed tetraethylorthosilicate per 100 parts by weight of disilanol polymer can be used.

[00068] In another embodiment, a liquid addition-cured polyorganosiloxane is achieved by using siloxanes containing vinyl groups at the chain ends and/or scattered randomly along the chain, along with siloxanes having two or more silicon hydrogen bonds per molecule. Typically these materials are cured at temperatures of from about 100° C. to about 250° C.

[00069] Typical addition-cured polyorganosiloxane materials are represented by the formula:

[00070] wherein s and r are integers and 0<s/r<about 1, about 350<r+s<about 2700. In the above formula, A″ and B″ can be the same or different and examples include hydroxy, alkoxy such as methoxy, ethoxy, propoxy, and the like, hydride, vinyl, amine and the like. R″ can be alkyl such as methyl, ethyl, propyl, butyl and the like, substituted alkyl such as chloropropyl, fluoropropyl, trifluoropropyl, and the like, phenyl, and vinyl.

[00071] For each molecule of the above formula, there can be at least a total of 2 vinyl groups in the A″, B″ and any of the several R″ sites within the formula. In the presence of suitable catalysts such as solutions or complexes of chloroplatinic acid or other platinum compounds in alcohols, ethers or divinylsiloxane, reaction occurs with temperatures of from about 100° C. to about 250° C. with the addition of polyfunctional silicon hydride to the unsaturated groups in the polysiloxane chain. Elastomers produced in this manner exhibit increased toughness, tensile strength and dimensional stability. Typically, these materials comprise the addition of two separate parts of the formulation, part A and part B, wherein part A contains the vinyl terminated polyorganosiloxane, the catalyst and the filler; and where part B contains the same or another vinyl-terminated polyorganosiloxane, the crosslinking moiety such as a hydride functional silane and the same or additional filler. Part A and part B are normally in a ratio of 1 to 1. During the additional curing operation the material is crosslinked via the equation:
≡SiH+CH₂═CHSi≡SiCH₂CH₂Si═

[00073] Because hydrogen is added across the double bond, no labile byproduct such as acids or alcohols is obtained.

[00074] Crosslinking catalysts are well-known in the art and include for the condensation cured polyorganosiloxanes, among others, stannous octoate, dibutyltin dilaurate, dibutyltin diacetate, dibutyltin dicaproate, and the like.

[00075] A nanocomposite as used herein refers to nanoscale fillers in a polymer, an example being a mica-type layered silicate. A specific example is a mica-type layered silicate in an intercalated or exfoliated state in a polymer.

[00076] The term “delaminated” (also referred to herein as exfoliated) refers to the host layers (having a thickness on a nanometer scale) being dispersed in a continuous polymer matrix.

[00077] The term “aspect ratio” shall refer to the ratio of the length to thickness of the mica-type layer silicates, and the term “high aspect ratio” shall define a large dimensional ratio of the mica-type layered silicate (MTS).

[00078] In embodiments, the mica-type layered silicate has a particle size having a maximum length of from about 1 to about 10 micrometers, or from about 3 to about 5 micrometers.

[00079] The term “mica-type layered silicate” refers to a leaf or sheet-like laminated phyllosilicate mineral, typically natural or synthetic complex hydrous silicates based on aluminum, magnesium, sodium, potassium, calcium, lithium, iron, and like silicates, having flat, six-sided monoclinic crystals, low hardness, and perfect or near-perfect basal cleavage. Typically, mica-type layered silicates have a high degree of flexibility, elasticity and toughness, and have laminas of on the order of about 10 angstroms in thickness, or from about 1 to about 20 angstroms, which under mild shear can be delaminated or exfoliated. Typical examples include the principle mica-types of the general formula:
W₂(X,Y)_4-6Z₈O₂₀(OH,F)₄
where W can be potassium or the like; X, Y are aluminum, magnesium, iron or lithium; and Z is silicon, aluminum, or both silicon and aluminum. In certain clay compositions some of the Z atoms can be silicon and the remaining Z atoms can be aluminum. Examples of mica-type silicates include muscovite, phlogopite, biotite, lepidolite, montmorillonite, bentonite, hectorite, vermiculite and saponite. The formula given above is by necessity only approximate, since mica-type silicates (MTS) are minerals having various impurities. Commercially available materials include montmorillonite, bentonite and hectorite which are available from Southern Clay Products, Gonzales Tex. A list of suitable mica-type silicates can be found in the CRC Handbook of Chemistry and Physics 58th Edition, 1977-8, pp. B-250 to B-252, or in the 77th Edition, pp. 4-137 to 4-147, the disclosures of which are hereby incorporated herein by reference in their entirety.

[00082] Two types of nanocomposites representing the end members of a structural hierarchy are possible: (a) intercalated, in which extended polymer chains are intercalated between the host layers resulting in a well-ordered multilayer, where the layers of the silicate retain their structural registry; and (b) delaminated (also referred herein as exfoliated), in which the host layers having a thickness on a nanometer scale, are dispersed in a continuous polymer matrix. In contrast to the intercalated hybrids, the interlayer expansion in delaminated nanocomposites is comparable to the radius of gyration of the polymer, and the host layers have lost their structural registry.

[00083] As previously mentioned, the mica-type layered silicate has laminas on the order of about 10 angstroms in thickness. The layered silicate also has a large length to thickness ratio because of the plate-like structure, which has a high aspect ratio. Typically the mica-type layered silicates have a maximum length on the order of about 1 micrometer, and an aspect ratio of length to thickness of from about 100 to about 1000. As a result, the mica-type layered silicates when used as a filler to enhance the thermal conductivity or modulus of the silicone elastomer, form a continuous touching path to conduct heat.

[00084] It is believed that the sheets of the mica-type layered silicate provide antioxidant properties due to their large surface area which thermally stabilizes the area that surrounds it. Further, the mica-type layered silicates provide a large surface area barrier to release agents, thereby resulting in reduction of swelling of the silicone elastomer.

[00085] The outer layer may be prepared by mixing with mechanical shear, a silicone elastomer, such as a polyorganosiloxane, with a mica-type layered silicate to delaminate the layers of the mica-type layered silicate and to disperse the delaminated layers of the mica-type layered silicate in the silicone elastomer. A crosslinking agent and catalyst are added in amounts sufficient to provide crosslinking of the silicone elastomer. The silicone elastomer delaminated nanocomposite is shaped into a layer, placed on the phase change ink imaging member, and cured.

[00086] More specifically, attention is directed now to FIG. 4, wherein the manufacture of thermally-stable, swell-resistant elastomer compositions is schematically illustrated. In this schematic, the first area 100 illustrates the laminated mica-type layered silicates 102 in a polyorganosiloxane monomer 104. When the mica-type layered silicates 102 are subjected to mechanical shear, the layers delaminate or exfoliate such that the polyorganosiloxane monomer 104 and individual layers of the mica-type layered silicate 102 are relatively uniformly mixed. This is illustrated in the second area 106 of the Figure. Upon the addition of suitable amounts of crosslinking agent and catalyst, and following the desired shaping, a delaminated nanocomposite is formed. Shaping can be accomplished by flow coating, slot coating, dipping or spraying onto a substrate surface such as a roll. Shaping can also be accomplished by molding in the form of a roll and curing the shaped silicone elastomer composition to provide a silicone elastomer filled with a mica-type layered silicate. The silicone elastomer filled with mica-type layered silicate is illustrated in the third area 108 of the FIG. 4 with the delaminated layers of the mica-type layered silicate 102 dispersed among the silicone elastomer 110.

[00087] The delaminating phenomenon starts with surface treating the mica-type layered silicate with long chain alkyl ammonium salts or amino acids such as dimethyl dioctadecyl ammonium salt or n-dodecylamino acid. Surface treating provides the mica-type silicate with an organophilic nature. This will then enhance the wetting of the mica-type layered silicate by silicone materials. On mixing the surface treated mica-type layered silicate with silicone, the silicone penetrates the mica-type layered silicate lamellae causing each lamella to be surrounded by silicone as the mica-type silicate exfoliates.

[00088] Experiments to conduct swelling evaluations of the present silicone elastomer compositions have shown that the presence of only about 5 percent by weight in the elastomer composition of the mica-type layered silicates, when made into a silicone elastomer and subjected to swelling in the presence of polydimethylsiloxane oil, resulted in a reduction in swelling of about 50 percent. That is, the amount of swell was reduced by one-half with the presence of only about 5 percent by weight of the mica-type layered silicate.

[00089] FIG. 5 is a graphical representation of the reduction in mass uptake as expressed as weight of toluene uptake in the illustrated volume fractions of the delaminated nanocomposite in toluene. FIG. 5 illustrates the swelling due to toluene in a silicone composition containing the stated volume fractions of the mica-type layered silicate. Since the ordinate axis represents the ratio of volume swell of silicone with mica-type layered silicate added to the volume swell of the silicone with no mica-type silicate added, there are no units and 1.0 represents the volume swell with no mica-type layered silicate added.

[00090] The phase change ink imaging member may then be prepared by applying the elastomer having the mica-type layered silicate and any filler dispersed therein, directly to a substrate in one application or by successively applying layers of the elastomer composition to the substrate. The coating is most conveniently carried out by spraying or dipping in a light solution of homogeneous suspension containing the mica-type layered silicate. Molding, extruding and wrapping are also alternative techniques, which may be used to make the phase change ink imaging member.

[00091] The mica-type layered silicate may be present in the polydimethylsiloxane polymer in an amount ranging, for example, from about 1 to about 50, or from about 5 to about 20, or preferred of from about 5 to about 10 percent by weight, based on the weight of the polymer.

[00092] The hardness of the mica-type silicate material layer is typically from about 10 to about 70 Shore A, or from about 35 to about 60 Shore A.

[00093] In embodiments, the thickness of the outer mica-type silicate imaging layer is from about 0.5 to about 20 mils, or from about 0.5 to about 6 mils, or from about 1 to about 4 mils.

[00094] The substrate, optional intermediate layer, and/or outer layer, in embodiments, may comprise fillers dispersed therein. These fillers can have the ability to increase the material hardness or modulus into the desired range.

[00095] Examples of fillers include fillers such as metals, metal oxides, doped metal oxides, carbon blacks, ceramics, polymers, and the like, and mixtures thereof. Examples of suitable metal oxide fillers include titanium dioxide, tin (II) oxide, aluminum oxide, indium-tin oxide, magnesium oxide, copper oxide, iron oxide, silica or silicon oxide, and the like, and mixtures thereof. Examples of carbon fillers include carbon black (such as N-990 thermal black, N330 and N110 carbon blacks, and the like), graphite, fluorinated carbon (such as ACCUFLUOR® or CARBOFLUOR®), and the like, and mixtures thereof. Examples of ceramics include silicates such as zirconium silicate, boron nitride, aluminum nitride, and the like, and mixtures thereof. Examples of polymer fillers include polytetrafluoroethylene powder, polypyrrole, polyacrylonitrile (for example, pyrolyzed polyacrylonitrile), polyaniline, polythiophenes, and the like, and mixtures thereof. The optional filler is present in the substrate, optional intermediate layer, and/or outer layer in an amount of from about 0 to about 30 percent, or from about 1 to about 20 percent, or from about 1 to about 5 percent by weight of total solids in the layer.

[00096] The imaging substrate can comprise any material having suitable strength for use as an imaging member substrate. Examples of suitable materials for the substrate include metals, fiberglass composites, rubbers, and fabrics. Examples of metals include steel, aluminum, nickel, and their alloys, and like metals, and alloys of like metals. The thickness of the substrate can be set appropriate to the type of imaging member employed. In embodiments wherein the substrate is a belt, film, sheet or the like, the thickness can be from about 0.5 to about 500 mils, or from about 1 to about 250 mils. In embodiments wherein the substrate is in the form of a drum, the thickness can be from about {fraction (1/32)} to about 1 inch, or from about {fraction (1/16)} to about ⅝ inch.

[00097] Examples of suitable imaging substrates include a sheet, a film, a web, a foil, a strip, a coil, a cylinder, a drum, an endless strip, a circular disc, a belt including an endless belt, an endless seamed flexible belt, an endless seamless flexible belt, an endless belt having a puzzle cut seam, a weldable seam, and the like.

[00098] In an optional embodiment, an intermediate layer may be positioned between the imaging substrate and the outer layer. Materials suitable for use in the intermediate layer include silicone materials, elastomers such as fluoroelastomers, fluorosilicones, ethylene propylene diene rubbers, and the like, and mixtures thereof. In embodiments, the intermediate layer is conformable and is of a thickness of from about 2 to about 60 mils, or from about 4 to about 25 mils.

[00099] Specific embodiments of the invention will now be described in detail. These examples are intended to be illustrative, and the invention is not limited to the materials, conditions, or process parameters set forth in these embodiments. All parts are percentages by weight of total solids as defined above unless otherwise indicated.

[00100] Two samples of mica-type layered silicate and silicone elastomer were prepared as follows. To 100 parts of a 750 centipoise alpha, omega-dihydroxysilicone obtained from United Chemical Technologies, Inc. and designated as PS342.5, 2.5 parts of tetraethoxysilane crosslinker obtained from Aldrich Chemical Company, and 2 parts of Tin(II) ethylhexanoate catalyst obtained from Chemat and designated as T722, were added. The three ingredients were well mixed using a micro-tip ultrasound probe available from Sonics & Materials. Another sample had 10 parts of montmorillonite (surface treated with an amine surfactant, dimethyl ditallow ammonium bromide) mixed into the 104.5 parts of dihydroxysilicone-crosslinker-catalyst material via a micro-tip ultrasound probe.

[00101] To 100 parts of a 750 centipoise alpha, omega-dihydroxysilicone obtained from United Chemical Technologies, Inc. and designated as PS342.5, 2.5 parts of tetraethoxysilane crosslinker obtained from Aldrich Chemical Company, and 2 parts of Tin(II) ethylhexanoate catalyst obtained from Chemat and designated as T722, were added. The three ingredients were well mixed using a micro-tip ultrasound probe available from Sonics & Materials and montmorillonite (surface treated with an amine surfactant, dimethyl ditallow ammonium bromide) was also added and mixed into the dihydroxysilicone-crosslinker-catalyst mixture using a micro-tip ultrasound probe. The specimens were made using samples ranging from 3 to 10 weight percent of surface treated montmorillonite (3 to 10 parts per hundred of the PS342.5).

[00102] The nanocomposites prepared in accordance with Examples 1 and 2 may be used as a layer for a phase change ink imaging component used in ink jet printing machines. A component having the nanocomposite prepared in accordance with Examples 1 and 2 may be applied directly to a base member or substrate in one application or by successively applying layers of the nanocomposite to the base member. The coating of the nanocomposite compositions is most conveniently carried out by conventional coating methods, such as flow coating, slot spraying or dipping.

[00103] To 100 parts of a 750 centipoise alpha, omega-dihydroxysilicone obtained from United Chemical Technologies, Inc. and designated as PS342.5, 2.5 parts of tetraethoxysilane crosslinker obtained from Aldrich Chemical Company and 2 parts of Tin(II) ethylhexanoate catalyst obtained from Chemat and designated as T722, were added. The above three ingredients along with 10 parts of montmorillonite (surface treated with an amine surfactant, dimethyl ditallow ammonium bromide) were mixed as described in the Examples 1 and 2.

[00104] This dispersion can then be coated onto an aluminum drum approximately 100 mm in diameter. Prior to coating the aluminum drum is sanded and degreased with MEK solvent, dried and primed with a silane or titanate-based primer using known methods such as flow coating, spray coating, dip coating, gravure coating, roll coating, and the like. The resulting drum is then dried and step cured. After coating, the roll can be dried and cured at ambient temperature for 12 hours.

[00105] While the invention has been described in detail with reference to specific and preferred embodiments, it will be appreciated that various modifications and variations will be apparent to the artisan. All such modifications and embodiments as may readily occur to one skilled in the art are intended to be within the scope of the appended claims.