Patent Application
20060115664
The invention relates to a toner receiver member for electrophotographic printing. In a preferred form it relates to an imaging element comprising a toner receiver layer that is co-extruded onto a paper support and provides photographic quality print using electrophotography and is fuser oil absorbent, glossable, and fingerprint resistant and has good toner adhesion.
The production of near photographic quality images using electrophotographic imaging technology is highly desirable. It is even more desirable to produce such images on substrates that render the print with the look and feel of a typical photographic print produced with silver halide imaging technology, such as the degree and uniformity of glossiness, stiffness and opacity, and high resolution and sharpness with corresponding low grain appearance. The advantages to producing photographic quality images on such substrates using digital electrophotography include improved environmental friendliness, ease of use, and versatility for customizing images, such as when text and images are combined.
U.S. Pat. No. 5,846,637 describes a coated xerographic photographic paper comprised of (1) a cellulosic substrate; (2) a first antistatic coating layer in contact with one surface of the substrate; (3) a second toner receiving coating on the top of the antistatic layer, and comprised of a mixture of a binder polymer, a toner spreading agent, a lightfastness inducing agent, a biocide, and a filler; and (4) a third traction controlling coating in contact with the back side of the substrate comprised of a mixture of a polymer with a glass transition temperature of from between about −50° C. to about 50° C., an antistatic agent, a lightfastness agent, a biocide and a pigment. This paper provides for the third layer on the backside of the substrate to receive toner, but this is not sufficient for ensuring high image quality should the image be created on this third layer instead of the second layer on the other surface of the substrate.
European Patent Application 1,336,901 A1 describes an electrophotographic image receiving sheet with a toner image receiving layer containing a release agent and formed on a support sheet for use in a fixing belt type electrophotography. The support used in the examples had a paper base with polyethylene layers on either side, where the image side is glossy and the backside has a matte finish. No provision is made for receiving the toner image on the backside.
US Patent Application 2003/0082354 A1 discloses an image receiving sheet for electrophotography comprising a base paper and a toner image receiving layer comprising a thermoplastic resin and less than 40 percent by mass based on the thermoplastic resin, of a reinforcing filler pigment. The thermoplastic layer is infiltrated to a depth of 1 to 50 percent of the thickness of the base paper. It is desirable that the toner image receiving layer is substantially free of any pigment or filler in order to prevent blister formation and roughening of the toner image. The resin used for toner image receiving layer is preferably applied as a coating solution, the resins being soluble in water or dispersible in water and the solution's viscosity is preferred to be in the range of 10-300 mPa·sec. Similarly, US Patent application 2003/0082473 A1 discloses use of a coating liquid whose solution viscosity is preferred to be in the range of 20-500 mPa·sec.
US Patent application 2003/0037176 A1 discloses a electrophotographic transfer sheet that comprises a substrate having an image receiving layer that contains a thermoplastic resin as a main component, which has a melt viscosity at 120° C. of about 200 to 2,000 Pa·sec. This patent application discloses that if viscosity of the thermoplastic resin exceeds 2,000 Pa·sec, then burying of the color toner image receiving layer becomes insufficient and relief of the color toner image is formed on the surface which results in deterioration of gloss uniformity. The patent application also discloses coating methods like reverse roll coater, bar coater, curtain coater, die slot coater or gravure coater for creating the toner image receiving layer. The structure of the electrophotographic transfer sheet disclosed in this patent application has the toner image receiving layer only on one side.
US Patent application 2004/0058176 A1 discloses a electrophotographic image receiving sheet where the toner receiver layer is coated on an polyethylene layer coated on a base. Though a whole host of polymers and methods for creating the toner image receiving layer have been listed, this patent application does not teach what are the necessary properties of a resin that satisfy a process like extrusion coating of resins as well as adhesion to toner. The patent application claims that the thermoplastic resin in the toner image receiving layer is a self dispersing water dispersible polyester resin emulsion that satisfies the following properties: number average molecular weight (Mn)=5000, molecular weight distribution (ratio of weight average molecular weight/number average molecular weight) ≦4, glass transition temperature (Tg) in the range of 40° C.-100° C. and volume average particle diameter in the range of 20 nm-200 nm. Another claim made by the patent application is the toner image receiving layer may also contain a polyolefin resin and this layer may be extrusion coated.
U.S. Pat. No. 6,217,708 discloses a full color transfer paper for electrophotography, which does not have a toner image receiving layer coated on it. This method has a shortcoming since it results in photographs or images that show mottle of the paper and other paper defects.
US Patent Application 2003/0175484 A1 discloses the creation of an image receiving sheet that has excellent gloss and has high offset resistance during a fixing step at a high temperature under high pressure. This is achieved by using a polyester resin containing at least 10% based on the molar number of polyhydric alcohol components of bisphenol A as a polyhydric alcohol component; and said polyester resin has an intrinsic viscosity (IV) of 0.3-0.7. This patent application does not discuss or claim about the branching of the polyester, neither does it discuss or claim the properties that enable extrusion coating.
US Patent Application 2003/0235683 A1 discloses an electrophotographic image receiving sheet comprising a support and a toner image receiving layer containing a thermoplastic resin and a pigment disposed on the surface of the support wherein the surface of the support has a glossiness of 25 percent or more at 75° and a pigment content less than 40 percent by mass based on the mass of the thermoplastic resin. In this case also it is desirable that the toner image receiving layer be substantially free of any pigment or filler in order to prevent blister formation. Toner particle size also plays a key role in determining image quality in electrophotography, smaller particles generally yielding better image quality. However, as the particles get smaller, the physics of the forces holding the particles to the photoconductor changes drastically, needing new methods to effectively transfer them from the photoconductor to the receiver. Photographic quality prints can be produced with this process if very small toner particles are used. The drawback with small particles is the difficulty in transferring them onto plain paper. One solution to this problem is explained in U.S. Pat. No. 4,968,578, where the surface of the receiver sheets are coated with a thermoplastic layer.
There exists a need for improved paper for electrophotographic printing that can provide high gloss, where differential gloss, image relief, and residual surface fuser oil are minimized and toner adhesion is maximized. Further it is desirable that such prints be fingerprint and spill resistant. Still further, customers perceive product quality in terms of stiffness for a photo quality print. Therefore there exists a need for creating media for electrophotographic printing of high stiffness for a given a caliper of the base. There also exists a need for creating low cost media for electrophotographic printing that can be created by polymer melt extrusion coating toner receiver (in prior art might be known as toner image receiving) layers.
There is a need for electrophotographic prints with improved gloss and resistance to environmental damage.
It is an object of the invention to provide a toner receiver member for electrophotographic printing that produces near photoquality prints.
It is a further object to provide a toner receiver member that contains a toner receiver layer that provides good toner adhesion.
These and other objects of the invention are accomplished by a toner receiver member comprising a base, at least one tie layer adjacent to said base, and at least one toner receiver layer adjacent said at least one tie layer on the side opposite to the base, wherein said at least one toner receiver layer comprises a layer of branched polyester or a mixture of styrene acrylate copolymer with an ethylene methacrylate copolymer or with a low density polyethylene.
The invention provides electrophotographic prints with improved gloss and resistance to environmental damage.
The invention has numerous advantages. The invention provides a toner receiver element for electrophotographic printing that can provide near photo quality high gloss prints, where differential gloss, image relief, and residual surface fuser oil are minimized and toner adhesion is maximized, exhibits fingerprint resistance and water resistance compared to commercially available clay coated papers. The toner receiver element also provides an excellent degree of whiteness. The invention provides toner receiver material compositions that contain solution coatable polymers which are melt extrusion coated. The invention provides toner receiver layer material compositions of branched polyesters which are melt extrusion coated. The invention also provides a method to vary the stiffness of the image receiving element for a fixed caliper of the base paper and without altering the overall caliper of the image receiving element.
The toner receiver member of this invention comprises in order a support, at least one tie layer adjacent to said support, and at least one toner receiver layer adjacent said at least one tie layer on the side opposite to the support, wherein said at least one toner receiver layer comprises a layer of branched polyester or a mixture of styrene acrylate copolymer with an ethylene methacrylate copolymer or with a low density polyethylene or with blends of ethylene methacrylate and polyethylene.
The term “base” as used herein refers to a substrate support material that is the primary part of an imaging element such as paper, polyester, vinyl, synthetic paper, fabric, or other suitable material for the viewing of images. The support for use as the base in the present invention may be any support typically used in imaging applications. Typical supports may be fabrics, paper, and polymer sheets. The support may either be transparent or opaque, reflective or non-reflective. The term as used herein, “transparent” means the ability to pass radiation without significant deviation or absorption. Opaque supports include plain paper, coated paper, synthetic paper, low density foam core based support and low density foam core based paper. The support can also consist of microporous materials such as polyethylene polymer-containing material sold by PPG Industries, Inc., Pittsburgh, Pa. under the trade name of Teslin®, Tyvek® synthetic paper (DuPont Corp.), impregnated paper such as Duraform®, and OPPalyte® films (Mobil Chemical Co.) and other composite films listed in U.S. Pat. No. 5,244,861. Transparent supports include glass, cellulose derivatives, such as a cellulose ester, cellulose triacetate, cellulose diacetate, cellulose acetate propionate, cellulose acetate butyrate, polyesters, such as poly(ethylene terephthalate), poly(ethylene naphthalate), poly-1,4-cyclohexanedimethylene terephthalate, poly(butylene terephthalate), and copolymers thereof, polyimides, polyamides, polycarbonates, polystyrene, polyolefins, such as polyethylene or polypropylene, polysulfones, polyacrylates, polyether imides, and mixtures thereof. The papers listed above include a broad range of papers, from high end papers, such as photographic paper to low end papers, such as newsprint. The support used in the base of the invention may have a thickness of from about 50 to about 500 μm, preferably from about 75 to 300 μm.
The toner receiver members of the invention can comprise any number of auxiliary layers, for example, functional layers. Such auxiliary layers may include conveyance layers, barrier layers, splice providing layers, UV absorption layers, and waterproofing layers.
The base may comprise a support having any melt extrusion coatable polyolefin resin material known in the art extruded on the support, preferably a paper support. Suitable polymers for the polyolefin resin coating include polyethylene, polypropylene, polymethylpentene, polystyrene, polybutylene, and mixtures thereof. Polyolefin copolymers, including copolymers of polyethylene, propylene and ethylene such as hexene, butene, and octene are also useful. The polyolefin may also be copolymerized with one or more copolymers including polyesters, such as polyethylene terephthalate, polysulfones, polyurethanes, polyvinyls, polycarbonates, cellulose esters, such as cellulose acetate and cellulose propionate, and polyacrylates. Specific examples of copolymerizable monomers include vinyl stearate, vinyl acetate, acrylic acid, methyl acrylate, ethyl acrylate, acrylamide, methacrylic acid, methyl methacrylate, ethyl methacrylate, methacrylamide, butadiene, isoprene, and vinyl chloride.
Polyethylene is preferred for resin coated paper supports, as it is low in cost and has desirable coating properties. Preferred polyolefins are film forming and adhesive to paper. Usable polyethylenes may include high density polyethylene, low density polyethylene, linear low density polyethylene, and polyethylene blends. Polyethylene having a density in the range of from 0.90 g/cm3 to 0.980 g/cm3 is particularly preferred. The polyolefin resin, such as polypropylene, may be used when the support created is a laminated structure of paper and one or more biaxially or uniaxially oriented polypropylene films.
It is desirable to incorporate white pigments in the polyolefin resin layer to give the required optical properties for the paper. Any suitable white pigment may be incorporated in the polyolefin resin layers, such as, for example, zinc oxide, zinc sulfide, zirconium dioxide, white lead, lead sulfate, lead chloride, lead aluminate, lead phthalate, antimony trioxide, white bismuth, tin oxide, white manganese, white tungsten, and combinations thereof The preferred pigment is titanium dioxide (TiO2) because of its high refractive index, which gives excellent optical properties at a reasonable cost. The pigment is used in any form that is conveniently dispersed within the polyolefin. The preferred pigment is anatase titanium dioxide. The most preferred pigment is rutile titanium dioxide because it has the highest refractive index at the lowest cost. The average pigment diameter of the rutile TiO2 is most preferably in the range of 0.1 to 0.26 μm. The pigments that are greater than 0.26 μm are too yellow for an imaging element application and the pigments that are less than 0.1 μm are not sufficiently opaque when dispersed in polymers. Preferably, the white pigment should be employed in the range of from about 7 to about 50 percent by weight, based on the total weight of the polyolefin coating. Below 7 percent TiO2, the imaging system may not be sufficiently opaque and will have inferior optical properties. Above 50 percent TiO2, the polymer blend is not manufacturable.
The surface of the TiO2 can be treated with an inorganic compounds such as aluminum hydroxide, alumina with a fluoride compound or fluoride ions, silica with a fluoride compound or fluoride ion, silicon hydroxide, silicon dioxide, boron oxide, boria-modified silica (as described in U.S. Pat. No. 4,781,761), phosphates, zinc oxide or, ZrO2 and with organic treatments such as polyhydric alcohol, polyhydric amine, metal soap, alkyl titanate, polysiloxanes, or silanes. The organic and inorganic TiO2 treatments can be used alone or in any combination. The amount of the surface treating agents is preferably in the range of 0.2 to 2.0% for the inorganic treatment and 0.1 to 1% for the organic treatment, relative to the weight of the titanium dioxide. At these levels of treatment, the TiO2 disperses well in the polymer and does not interfere with the manufacture of the imaging support.
The polyolefin resins and TiO2 and optional other additives may be mixed with each other in the presence of a dispersing agent. Examples of dispersing agents are metal salts of higher fatty acids such as sodium palmitate, sodium stearate, calcium palmitate, sodium laurate, calcium stearate, aluminum stearate, magnesium stearate, zirconium octylate, or zinc stearate higher fatty acids, higher fatty amide, and higher fatty acids. The preferred dispersing agent is sodium stearate and the most preferred dispersing agent is zinc stearate. Both of these dispersing agents give superior whiteness to the resin coated layer.
In addition, it may be necessary to use various additives such as colorants, brightening agents, antistatic agents, plasticizers, antioxidants, slip agents, or lubricants, and light stabilizers in the resin coated supports as well as biocides in the paper elements. These additives are added to improve, among other things, the dispersibility of fillers and/or colorants, as well as the thermal and color stability during processing and the manufacturability and the longevity of the finished article. For example, the polyolefin coating may contain antioxidants such as 4,4′-butylidene-bis(6-tert-butyl-meta-cresol), di-lauryl-3,3′-thiopropionate, N-butylated-p-aminophenol, 2,6-di-tert-butyl-p-cresol, 2,2-di-tert-butyl-4-methyl-phenol, N,N-disalicylidene-1,2-diaminopropane, tetra(2,4-tert-butylphenyl)-4,4′-diphenyl diphosphonite, octadecyl 3-(3′,5′-di-tert-butyl-4′-hydroxyphenyl propionate), combinations of the above, and the like; heat stabilizers, such as higher aliphatic acid metal salts such as magnesium stearate, calcium stearate, zinc stearate, aluminum stearate, calcium palmitate, zirconium octylate, sodium laurate, and salts of benzoic acid such as sodium benzoate, calcium benzoate, magnesium benzoate and zinc benzoate; light stabilizers such as hindered amine light stabilizers (HALS), of which a preferred example is poly{[6-[(1,1,3,3-tetramethylbutylamino}-1,3,5-triazine-4-piperidinyl)-imino]-1,6-hexanediyl[{2,2,6,6-tetramethyl-4-piperdinyl)imino]} (Chimassorb 944 LD/FL).
The polyolefin resin coating on the support can include multilayer polyolefin structures, such as those achieved by multiple coatings, either sequential or via coextrusion. To minimize the number of resins required, a structure consisting of 1 to 3 layers on each side is preferred. In one embodiment of the present invention, at least one or all the layers can further comprise polypropylene. In a 3-layer structure, two of the three layers on each side may have substantially similar composition, preferably the outside layers and the layers adjacent the paper support. The ratio of thickness of the center or bottom layer to a surface layer is in the range of 1 to 8 with 5 to 7 being most preferable. The polyolefin resin of the surface layers may contain, optionally, pigments and other addenda.
The coating of the paper base material for base formation with the polyolefin preferably is by extrusion from a hot melt as is known in the art. The invention may be practiced within a wide range of extrusion temperatures, for example, from 150° C. to 350° C., and speeds, for example, from 60 m/min. to 460 m/min., depending on the particular intended application of the support. For many applications, preferred extrusion temperatures are from 300° C. to 330° C.
The electrographic and electrophotographic processes and their individual steps have been well described in detail in many books and publications. The processes incorporate the basic steps of creating an electrostatic image, including charging and exposing a photoconductor, developing that image with charged, colored particles (toner), optionally transferring the resulting developed image to a secondary substrate, such as a cylinder with a rubber-like soft-elastic surface or a rubber blanket, and then transferred onto a final substrate or receiver and fixing or fusing the image onto the receiver. In terms of environmental stability and extending image quality, the intermediate transfer method is more desirable. The toner receiver member of the invention has a toner receiver layer designed to receive the toner particles. There are numerous variations in these processes and basic steps; the use of liquid toners in place of dry toners is simply one of those variations.
To fix the toner pattern to the toner receiver layer, the toner on the receiving sheet is subjected to heat and pressure, for example, by passing the sheet through the nip of fusing rolls. Both the toner polymer and the thermoplastic polymer of the toner receiver layer are softened or fused sufficiently to adhere together under the pressure of the fusing rolls. When both the toner receiver layer and the toner soften and fuse, the toner can be at least partially embedded in the thermoplastic toner receiver layer. For self-fixing toners, residual liquid is removed from the paper by air-drying or heating. Upon evaporation of the solvent these toners form a film bonded to the paper. For heat-fusible toners, thermoplastic polymers are used as part of the particle. Heating both removes residual liquid and fixes the toner to paper. The fusing step can be accomplished by the application of heat and pressure to the final image. Fusing can provide increased color saturation, improved toner adhesion to the receiver, and modification of the image surface texture. A fusing device can be a cylinder or belt. The fusing device can have an elastomeric coating which provides a conformable surface to enable improved heat transfer to the receiver. The fusing device can have a smooth or textured surface. The fusing step can be combined with the transfer step.
In forming toner images on conventional receiving sheets, the fusing and fixing of the toner to the sheet by the fusing rolls, creates gloss in the toned areas, i.e., in the so-called D max or black areas of the image. In the untoned areas, however, the so-called D min or white areas, no gloss is formed. In accordance with the present invention, however, when the toner-bearing receiver sheet is subjected to heat and pressure in the fusing roll nip, the entire surface of the sheet develops a substantially uniform gloss. The resulting electrophotographic image has the look and feel of a silver halide photographic print.
In a preferred embodiment, a belt fusing apparatus as described in U.S. Pat. No. 5,895,153 can be used to provide high gloss finish to the electrophotographically printed image receiving element of this invention. The belt fuser can be separate from or integral with the reproduction apparatus. In a preferred embodiment of the present invention, the belt fuser is a secondary step. The toned image is at first fixed by passing the electrophotographically printed sheet through the nip of fusing rolls within the reproduction apparatus and then subjected to belt fusing to obtain a high uniform glossy finish. The belt fusing apparatus includes an input transport for delivering marking particle image-bearing receiver members to a fusing assembly. The fusing assembly comprises a fusing belt entrained about a heated fusing roller and a steering roller, for movement in a predetermined direction about a closed loop path. The fusing belt is, for example, a thin metallic or heat resistant plastic belt. Metal belts can be electroformed nickel, stainless steel, aluminum, copper or other such metals, with the belt thickness being about 50.8 to 127 microns. Seamless plastic belts can be formed of materials such as polyimide, polypropylene, or the like, with the belt thickness summarily being about 50.8 to 127 microns. Usually these fusing belts are coated with thin hard coatings of release material such as silicone resins, fluoropolymers, or the like. The coatings are typically thin (1 to 10 microns), very smooth, and shiny. Such fusing belts could also be made with some textured surface to produce images of lower gloss or texture.
The belt fuser can have a pressure roller located in nip relation with the heated fusing roller. A flow of air is directed at an area of the belt run upstream of the steering roller and adjacent to the steering roller to cool such area. The cooling action provides for a commensurate cooling of a receiver member, bearing a marking particle image, while such member is in contact with the fusing belt. The cooling action for the receiver member serves as the mechanism to substantially prevent offset of the marking particle image to the pressure roller.
The belt fusing apparatus can be mounted in operative association with a belt tracking control mechanism.
High gloss finish can also be provided to the electrophotographically printed image receiver element of this invention by using calendering methods known in the art. Calendering is defined herein as a process in which pressure is applied to the imaged substrate, that has been preferably roller fused in the printing apparatus, by passing it between highly polished, metal rollers that are optionally heated, imparting a glossy, smooth surface finish to the substrate. The degree of pressure and heat controls the extent of gloss. Calendering differs from roller fusing in that the latter does not necessarily use highly polished rollers, is always carried out at high temperatures and the nip pressures are lower than those experienced at the calendering nip.
The toner used with the toner receiver member herein contains, for example, a polymer (a binder resin), a colorant and an optional releasing agent.
As the polymer, known binder resins are useable. Concretely, these binder resins include homopolymers and copolymers such as polyesters, styrenes, e.g. styrene and chlorostyrene; monoolefins, e.g. ethylene, propylene, butylene and isoprene; vinyl esters, e.g. vinyl acetate, vinyl propionate, vinyl benzoate and vinyl butyrate; α-methylene aliphatic monocarboxylic acid esters, e.g. methyl acrylate, ethyl acrylate, butyl acrylate, dodecyl acrylate, octyl acrylate, phenyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate and dodecyl methacrylate; vinyl ethers, e.g. vinyl methyl ether, vinyl ethyl ether and vinyl butyl ether; and vinyl ketones, e.g. vinyl methyl ketone, vinyl hexyl ketone and vinyl isopropenyl ketone. Particularly desirable binder resins include polystyrene resin, polyester resin, styrene/alkyl acrylate copolymers, styrene/alkyl methacrylate copolymers, styrene/acrylonitrile copolymer, styrene/butadiene copolymer, styrene/maleic anhydride copolymer, polyethylene resin and polypropylene resin. They further include polyurethane resin, epoxy resin, silicone resin, polyamide resin, modified rosin, paraffins and waxes. In these resins, styrene/acryl resins are particularly preferable.
As the colorants, known colorants can be used. The colorants include, for example, carbon black, Aniline Blue, Calcoil Blue, Chrome Yellow, Ultramarine Blue, Du Pont Oil Red, Quinoline Yellow, Methylene Blue Chloride, Phthalocyanine Blue, Malachite Green Oxalate, Lamp Black, Rose Bengal, C.I. Pigment Red 48:1, C.I. Pigment Red 122, C.I. Pigment Red 57:1, C.I. Pigment Yellow 97, C.I. Pigment Yellow 12, C.I. Pigment Yellow 17, C.I. Pigment Blue 15:1 and C.I. Pigment Blue 15:3. The colorant content is, for example, 2 to 8% by weight. When the colorant content is 2% or more by weight, a sufficient coloring power can be obtained, and when it is 8% or less by weight, good transparency can be obtained.
The toner utilized with the toner receiver of the present invention optionally contains a releasing agent. The releasing agents preferably used herein are waxes. Concretely, the releasing agents usable herein are low-molecular weight polyolefins such as polyethylene, polypropylene and polybutene; silicone resins which can be softened by heating; fatty acid amides such as oleamide, erucamide, ricinoleamide and stearamide; vegetable waxes such as carnauba wax, rice wax, candelilla wax, Japan wax and jojoba oil; animal waxes such as bees wax; mineral and petroleum waxes such as montan wax, ozocerite, ceresine, paraffin wax, microcrystalline wax and Fischer-Tropsch wax; and modified products thereof. When a wax containing a wax ester having a high polarity, such as carnauba wax or candelilla wax, is used as the releasing agent, the amount of the wax exposed to the toner particle surface is inclined to be large. On the contrary, when a wax having a low polarity such as polyethylene wax or paraffin wax is used, the amount of the wax exposed to the toner particle surface is inclined to be small.
Irrespective of the amount of the wax inclined to be exposed to the toner particle surface, waxes having a melting point in the range of 30 to 150° C. are preferred and those having a melting point in the range of 40 to 140° C. are more preferred.
The wax is, for example, 0.1 to 10% by mass, and preferably 0.5 to 7% by mass, based on the toner.
The toner used with the image receiver of the present invention may contain an additive. Fine powders of inorganic compounds and fine particles of organic compounds are used as the additive. Fine particles of the inorganic compounds are those of, for example, SiO2, TiO2, Al2 O3, CuO, ZnO, SnO2, Fe2 O3, MgO, BaO, CaO, K2 O, Na2 O, ZrO2, CaO.SiO2 , K2 O.(TiO2 )n , Al2 O3 .2 SiO2 , CaCO3, MgCO3, BaSO4 and MgSO4. The fine particles of organic compounds are those of fatty acids and derivatives thereof and metal salts thereof, and also those of resins such as fluororesins, polyethylene resins and acrylic resins.
The average particle diameter of the toner used in the present invention is, for example, 3 to 15 micrometers, preferably 4 to 10 micrometers. The storage elastic modulus G′ of the toner per se (determined at an angular frequency of 10 rad/sec) at 150° C. is preferably in the range of 10 to 200 Pa for good fusing.
The image receiving element of the present invention further comprises a toner receiver layer containing a polymer coated on both surfaces of the above mentioned support coated with a polyolefin resin. The toner receiver layer as mentioned earlier has the function of receiving an image-forming toner from a developing drum or an intermediate transfer medium by (static) electricity, pressure, etc. in the transferring step and fixing the image by heat, pressure, etc. in the fixing step. Further, it also enables the entire surface of the element develop a substantially uniform gloss after the fusing step, particularly after the belt fusing step. The resulting electrophotographic image has the look and feel of a silver halide photographic print. This is not possible on a commercially available standard paper since during the fusing step the thermoplastic is present only in the image areas leading to high differential gloss and difficulty in belt fusing due to differential adhesion forces of various areas of the print to the heated belt.
The toner receiver layer of the present invention has a dry coverage of 5 to 50 gm/m2, or 8 to 35 gm/m2 in a preferred embodiment and may be outside of these ranges.
The toner receiver layer of this invention comprises a thermoplastic polymer or thermoplastic blend of polymers or a component of the thermoplastic blend of polymers that has a glass transition temperature or Tg that is close to that of the thermoplastic toner that is transferred to the toner receiver layer. Preferably, the Tg of the toner receiver layer or a component of the toner receiver layer is within 15° C. of the Tg of the toner. In the case of where only the resin component of the toner receiver layer has a Tg close to the Tg of the toner, then, the rest of the polymer matrix of the toner receiver layer should preferably have a significantly lower Tg but is a semi-crystalline polymer. In such a case, the preferred polymer matrix of the toner receiver layer is a polyolefin. Consequently, both the toner and the receiving layers often soften or melt when the toner is fixed to the receiving layer by heat and pressure. This contributes to the adhesion of the toner to the layer and to achieving of high gloss in both the toned (D max) and untoned (D min) areas of the image resulting in unnoticeable differential gloss. High gloss and low differential gloss give the resultant prints a photo quality look and feel.
Materials useable for the toner receiver layer include a thermoplastic polymer which is capable of being deformed at the fixing temperature and also capable of receiving the toner and providing uniform gloss after fusing. It is preferred that the Tg of the toner receiver layer or a resin component of the toner receiver layer be between 40 and 100° C. preferably between 40 and 85° C.
The toner receiver layer of the present invention contains as one of the resin components, styrene copolymers. The styrene copolymer in the toner receiver layer is a copolymer comprising from between 20 and 90 wt % styrene, preferably from between 40 and 85 weight % styrene. The copolymer also comprises one or more other vinyl or addition polymerizable monomers such as butadiene, acrylate or methacrylate monomers. The vinyl monomers that are selected to give a glass transition of the styrene copolymer from between 30 and 70° C., preferably from between 40 and 70° C. The acrylate or methacrylate monomers can be derived from one or more ethylenically unsaturated polymerizable acrylic or methacrylic acid ester or amide monomers such as methyl acrylate, ethyl acrylate, iso-propyl acrylate, methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, n-butyl acrylate, t-butyl methacrylate, isodecyl methacrylate, isobutyl methacrylate, cyclohexyl methacrylate, cyclohexyl acrylate, lauryl methacrylate allyl methacrylate, 2-ethylhexyl acrylate, methyl acrylamide, ethyl methacrylamide and others that would be readily apparent to one skilled in the art. Preferred copolymers are poly(styrene-co-butadiene), poly(styrene-co-butyl acrylate) and poly(styrene-co-2-ethylhexyl acrylate).
The weight average molecular weight of the styrene copolymer is from between 20,000 and 400,000 g/mole, preferably from between 40,000 and 200,000 g/mole. In general styrene copolymers mentioned above are brittle materials. They are not easily pelletizable nor are they easily extrudable. Styrene copolymers have low melt viscosities and can not be drawn down at melt extrusion temperatures. In order to overcome all the shortcomings of the styrene copolymers mentioned here, this invention discusses the use and practice of blends of styrene copolymers with other resins. Preferred resins for blending with the styrene copolymers are polyethylenes, modified polyethylenes, polypropylenes and modified polypropylenes or combinations of these resins. For example, the melt viscosity of Pliolite ACL resins at 200° C. at a shear rate of 1 sec−1 is about 107 Pa·sec. When blended in different ratios (like 10 weight % −20 weight % of Pliolite ACL) with ethylene methacrylate (EMA) e.g. TC130 from Exxon Mobil, the melt viscosities at 200° C. and at a shear rate of 1 sec−1 increases to around 500 Pa·sec and these blends can be drawn down in extrusion operations like extrusion coating. The melt viscosities can be measured using a rheometer like a capillary rheometer or a Rheometrics Ares II. Melt viscosities here were measured using a Rheometrics Ares II using a frequency sweep at temperatures in the range of 200° C.-240° C. under a dry nitrogen purge. All the samples were dried at 40° C. under vacuum for 24 hours prior to analysis.
The blends for the toner receiver layer created using styrene copolymers are in the range of 5 weight % to 60 weight % of the styrene copolymers in polyolefins, preferably the styrene copolymers are present in the range of 10 weight % to 40 weight % in polyolefins. The choice of the toner receiver composition is further determined by melt strength of the blend. The melt strength of blend is important in order for a curtain or film or sheet of the toner receiver layer to be stable during the extrusion process as well as to enhance productivity by increasing line speeds while minimizing the amount of neck-in. The melt strength of a polymer is typically measured using a melt tension apparatus like Rheotens an apparatus provided by Gottfert. Other apparatuses similar to Rheotens can also be used to characterize melt strength. This test quantifies the resistance offered by resin during a melt stretching process. Melt tension or melt strength of the resin is determined by stretching a strand of polymer extruded out of a die between two counter-rotating wheels. The frequency of rotation of the wheels is increased by a preset acceleration and this results in the polymer strand being stretched. The pulling force measured in centinewtons (cN) during the stretching process is continuously recorded until the polymer strand breaks. The maximum force obtained before break of the strand is known as melt tension or melt strength of the polymer at the particular temperature. The foregoing procedure may be performed as described by M. B. Bradley and E. M. Phillips in the Society of Plastics engineers ANTEC 1990 conference paper (page 718).
Here, a capillary die of dimension 30 mm length with 2 mm diameter was used for these measurements while keeping the air gap (distance between die to first nip) at 100 mm. Preferred melt strength of the toner receiver composition using styrene copolymer blends need to be greater than or equal to 2 cN at 200° C.
To further stabilize a curtain or film or sheet of the toner receiver layer containing styrene copolymers during an extrusion process and also to increase line speeds so as to enhance productivity, and also to adhere the toner receiver layer to a base, there is a need to co-extrude with it a supporting layer which can be a tie layer or adhesion promoting layer.
The present invention also is directed to a toner receiver layer consisting of a branched polyester, wherein the polyester preferred comprises (a) recurring dibasic acid derived units and diol derived units, at least 50 mole % of the dibasic acid derived units comprising dicarboxylic acid derived units containing an alicyclic ring comprising 4 to 10 ring carbon atoms, which ring is within two carbon atoms of each carboxyl group of the corresponding dicarboxylic acid, (b) 25 to 75 mole % of the diol derived units containing an aromatic ring not immediately adjacent to each hydroxyl group of the corresponding diol or an alicyclic ring, and (c) 25 to 75 mole % of the diol derived units of the polyester contain an alicyclic ring comprising 4 to 10 ring carbon atoms.
The polyester polymers used in the composition of the invention are condensation type polyesters based upon recurring units derived from alicyclic dibasic acids (Q) and diols (L) and (P) wherein (Q) represents one or more alicyclic ring containing dicarboxylic acid units with each carboxyl group within two carbon atoms of (preferably immediately adjacent to) the alicyclic ring and (L) represents one or more diol units each containing at least one aromatic ring not immediately adjacent to (preferably from 1 to about 4 carbon atoms away from) each hydroxyl group or an alicyclic ring which may be adjacent to the hydroxyl groups.
For the purposes of this invention, the terms “dibasic acid derived units” and “dicarboxylic acid derived units,” or “dicarboxylic acids′ and “diacids,” are intended to define units derived not only from carboxylic acids themselves, but also from equivalents thereof such as acid chlorides, acid anhydrides, and esters for these acids, as in each case the same recurring units are obtained in the resulting polymer. Each alicyclic ring of the corresponding dibasic acids may also be optionally substituted, e.g. with one or more C1 to C4 alkyl groups. Each of the diols may also optionally be substituted on the aromatic or alicyclic ring, e.g. by C1 to C6 alkyl, alkoxy, or halogen. Regarding the polyol (including all compounds, diols, triols, etc. having two or more OH or OH derived groups), the total mole percentages for this component is equal 100 mol %. Similarly, regarding the acid component (including all compounds/units having two or more acid or acid-derived groups), the total mole percentages for this component is equal to 100 mole %.
In a preferred embodiment of the invention, the polyester comprises alicyclic rings in both the dicarboxylic acid derived units and the diol derived units that contain from 4 to 10 ring carbon atoms. In a particularly preferred embodiment, the alicyclic rings contain 6 ring carbon atoms.
Such alicyclic dicarboxylic acid units, (Q), are represented by structures such as:
The aromatic diols, (L), are represented by structures such as:
The alicyclic diols, (P), are represented by structures such as:
In the case of an extrudable polyester, it has been found advantageous to employ monomers (as a replacement for either a diacid and/or diol that has three or more functional groups, preferably one more multifunctional polyols (N) or polyacids and derivatives thereof (O) that can provide branching. Multifunctional polyols, for example, include glycerin, 1,1,1-trimethylolethane, and 1,1,1-trimethylolpropane, or combinations thereof. Polyacids having more than two carboxylic acid groups (including esters or anhydrides derivatives thereof) include, for example, trimellitic acid, trimesic acid, 1,2,5-, 2,3,6- or 1,8,4-naphthalene tricarboxylic anhydride, 3,4,4′-diphenyltricarboxylic anhydride, 3,4,4′-diphenylmethanetricarboxylic anhydride, 3,4,4′-diphenylethertricarboxylic anhydride, 3,4,4′-benzophenonetricarboxylic anhydride acid and derivatives thereof. Multifunctional polyols or anhydrides, for example, include compounds represented by structures such as:
A small amount of aromatics, introduced by inclusion of aromatic diacids or anhydrides, is optional and is not preferred due to their tendency to reduce imaged dye density. Examples include, but are not limited to, terephthalic acid (S1) and isoterephthalic acid (S2).
Additional Diacids R and diols M may be added, e.g., to precisely adjust the polymer's Tg, solubility, adhesion, etc. Additional diacid comonomers could have the cyclic structure of Q or be linear aliphatic units or be aromatic to some degree. The additional diol monomers may have aliphatic or aromatic structure but are preferably not phenolic.
Some examples of suitable monomers for R include dibasic aliphatic acids such as:
Some examples of some other suitable monomers for M include diols such as:
The above-mentioned monomers may be copolymerized to produce structures such as:
wherein o+q+r+s=100 mole percent (based on the diacid component) and p+m+n+1=100 mole percent (based on the polyol component). With respect to the diacid, preferably q is at least 50 mole percent, r is less than 40 mole percent, and s is less than 10 mole percent. With respect to the polyol, preferably p is 25 to 75 mole percent, 1 is 25 to 50 mole percent, and m is 0 to 50 mole percent. With respect to the polyfunctional monomers (having more than two functional groups), the total amount of n or o is preferably 0.1 to 10 mole percent, preferably 1 to 5 mole percent.
The polyesters of the invention preferably, except in relatively small amounts, do not contain an aromatic diacid such as terephthalate or isophthalate.
The following polyester polymers E-1 through E-14, comprised of recurring units of the illustrated monomers, are examples of polyester polymers usable in the toner receiver layer of the invention.
E-1 through E-3: A polymer considered to be derived from 1,4-cyclohexanedicarboxylic acid, 1,4-cyclohexanedimethanol, 4,4′-bis(2-hydroxyethyl)bisphenol-A and 2-ethyl-2-(hydroxymethyl)-1,3-propanediol
E-4 through E-6: A polymer considered to be derived from 1,4-cyclohexanedicarboxylic acid, 1,4-cyclohexanedimethanol, 4,4′-bis(2-hydroxyethyl)bisphenol-A and glycerol
E-7 through E-8: A polymer considered to be derived from 1,4-cyclohexanedicarboxylic acid, 1,4-cyclohexanedimethanol, 4,4′-bis(2-hydroxyethyl)bisphenol-A and pentaerythritol
E-9 through E-11: A polymer considered to be derived from 1,4-cyclohexanedicarboxylic acid, trimellitic anhydride, 1,4-cyclohexanedimethanol and 4,4′-bis(2-hydroxyethyl)bisphenol-A.
E-12 through E-14: A polymer considered to be derived from 1,4-cyclohexanedicarboxylic acid, pyromellitic anhydride, 1,4-cyclohexanedimethanol and 4,4′-bis(2-hydroxyethyl)bisphenol-A.
E-14: q=94mole % o2=6 mole % x=50 mole % y=50 mole %
The following examples for synthesizing a branched polyester composition for use in a toner-image receiving layer are representative of the invention, and other branched polyesters may be prepared analogously or by other methods known in the art.
Polyester E-3(having the structural formula shown above under the Detailed Description of the Invention) was derived from a 70:30 cis:trans mixture of 1,4-cyclohexanedicarboxylic acid with a cis:trans mixture of 1,4-cyclohexanedimethanol, 4,4′-bis(2-hydroxyethyl)bisphenol-A and 2-ethyl-2-(hydroxymethyl) 1,3-propanediol.
The following quantities of reactants were charged to a single neck side-arm 500 mL reactor fitted with a 38 cm head and purged with nitrogen: 1,4-cyclohexanedicarboxylic acid (86.09 g, 0.50 mol),4,4′-bis(2-hydroxyethyl)bisphenol-A (79.1 g, 0.25 mol),1,4-cyclohexanedimethanol (33.9 g, 0.235 mol), 2-ethyl-2-(hydroxymethyl)1,3-propanediol (2.0 g, 0.015 mol), monobutyltin oxide hydrate (0.5 g),and Irganox® 1010 pentaerythrityl tetrakis(3,5-di-tert-butyl-4-hydroxyhydro-cinnamate) from Ciba Specialty Chemicals (0.1 g). The flask was heated to 220° C. in a salt bath and continuously flushed with nitrogen for distillation of methanol. After two hours the calculated amount of methanol had been distilled and the temperature was raised to 240° C. for 30 minutes. Trioctylphosphate (7 drops) was added and the reaction was continued at this temperature for one and a half hours after which the temperature was increased to 275° C.
The flask was reconfigured for mechanical stirring and evacuation. The pressure was slowly reduced to 0.45 mm mercury over 15 minutes to allow excess glycol to distill. The progress of the reaction was monitored by measuring the millivolts (mv) required to maintain a constant torque of 200 RPM. The reaction was terminated when 190 mv was reached. The flask was cooled to room temperature, rinsed with water to remove salt from the reaction flask and then broken to remove the polymer. The polymer was cooled in liquid nitrogen, broken into half inch size pieces and ground in a Wiley Mill. The Tg of the polymer was 54.1° C. and the molecular weight by size exclusion chromatography was 77,600.
Polymer E-2 (having the structure shown under the above Detailed Description) was derived from a 70:30 cis:trans mixture of 1,4-cyclohexanedicarboxylic acid with a cis:trans mixture of 1,4-cyclohexanedimethanol, 4,4′-bis(2-hydroxyethyl)bisphenol-A and 2-ethyl-2-(hydroxymethyl) 1,3-propanediol.
The following quantities of reactants were charged to a 150 gallon reactor purged with nitrogen: 157.27 kg (913.38 mol) of cis/trans 1,4-cyclohexanedicarboxylic acid, 144.49 kg (456.69 mol) of 4,4′bis(2hydroxyethyl)bisphenol-A, 2.45 kg (18.27 mol) of 2-ethyl-2-(hydroxymethyl)1,3-propanediol,65.12 kg (451.58 mol) of cis/trans 1,4-cyclohexanedimethanol, 335 gm of Irganox® 1010 pentaerythrityl tetrakis(3,5-di-tert-butyl-4-hydroxyhydro-cinnamate) from Ciba Specialty Chemicals and 82.51 gm of butylstannoic acid. Under nitrogen purge, the reactor was heated to 275° C. and maintained there for two hours. An internal temperature of 273° C. was reached after an additional two hours. At this point, the traps were drained and the drainings recorded. The reactor pressure was reduced to 2 mm Hg at 10 mm per minute. As the pressure passed 30 mm Hg, a solution of 62.3 gm of 85% phosphoric acid, 392.8 gm 1,4-cyclohexanedimethanol and 168.3 gm methanol was drawn into the reactor. After six and a half hours at 2 mm Hg the buildup was complete. The polymer was extruded from the reactor onto trays and left to cool overnight after which the solidified polyester was ground through a ¼ inch screen. The Tg of the polymer was 56.9° C.; the Mw was 129,000 and molecular weight distribution (MWD) was 10.7.
The branched polyester useful for this invention in the toner receiver layer preferably has a Tg of from about 40 to about 100° C. In a preferred embodiment of the invention, the polyesters have a number molecular weight of from about 5,000 to about 250,000, more preferably from 10,000 to 100,000. The weight average molecular weight (Me) of these branched polyesters is 80,000 to 250,000. Preferred Mw of the branched polyesters is 80,000 to 130,000, more preferred Mw is 105,000 to 130,000. The molecular weight distribution (MWD) as defined as ratio of Mw to number average molecular weight (Mn) of these polyesters is 6-15. The preferred MWD is 8-12. The melt viscosity of these resins at 200° C. at a shear rate of 1 sec−1 is in the range of 570 Pa·sec-3,500 Pa·sec. The melt strength of the branched polyesters measured using Rheotens (apparatus made by Gottfert) at 200° C. is greater than 2 cN. Preferred melt strength of the branched polyesters at 200° C. is greater than 5 cN. The melt strength of the branched polyesters can be tailored by changing the amount of branching agent and the type of branching agent. Preferred amount of branching agent is greater than 0.1 weight %. Preferred range of branching agent is 0.5 weight % to 3 weight %. Branching is also useful in tailoring shear rheology, which determines pressure drop in an extruder and in a die. Table 2 provides shear rheology for branched polyesters at 200° C. in air. The branching agent used for creating these polyesters is 1,1,1-trimethylolpropane.
So in order to optimize extrusion for pressure drop, curtain stability and also to optimize toner receiver layer characteristics there is a need to use polyesters with the appropriate amount of branching agent. For all the above reasons, these polyesters are different from those used in prior art.
The image receiving element of the present invention also may contain a fuser-oil sorbent additive. Fuser-oil sorbent additives include adsorbents and absorbents and may be any suitable material. They have specific physical and chemical properties that allow them to capture the excess fuser-oil. Sorbent additives may be organic or inorganic and may be synthetic. Typical of such materials are clay, talc, glass wool, silica, peat moss, synthetic fibers such as nylon, plastic adsorbent microspheres and the like. The preferred material are clay and talc since they are readily available in a manner that can be easily formulated into the toner receiver layer, can be obtained at a high brightness index and is inexpensive. The inorganic additive is present in an amount greater than 0.1 weight percent of the toner receiver layer and preferably from 2 to 15 weight percent of the layer. The amount of inorganic additive in the layer can also be used to control the level of mottle of the support when the support is paper and level of gloss in the imaged element, especially after belt fusing. The fuser-oil sorbent additive such as the talcs usable herein preferably have a GE brightness index greater than 88% and include various modified and unmodified clays including nanoclays. Brightness is the percent of blue light reflected of a sample measured at an effective wavelength of 457 nm. GE brightness is a directional brightness measurement utilizing essentially parallel beams of light to illuminate the paper surface at an angle of 45 degrees.
The clay materials suitable for fuser oil sorbents if used with this invention include phyllosilicates, e.g., montmorillonite, particularly sodium montmorillonite, magnesium montmorillonite, and/or calcium montmorillonite, nontronite, beidellite, volkonskoite, hectorite, saponite, sauconite, sobockite, stevensite, svinfordite, vermiculite, magadiite, kenyaite, talc, mica, kaolinite (kaolin or china clay), and mixtures thereof. Preferred clays are swellable so that other agents, usually organic ions or molecules, can intercalate or exfoliate the layered material resulting in a desirable dispersion of the inorganic phase. The aforementioned clay can be natural or synthetic, for example, synthetic smectite clay. For this invention, the clay particles in the dispersed form should have a particle size where greater then 90% of the particles are less than or equal to 2 micrometers.
The clay used as a fuser oil sorbent can be an organoclay. Organoclays are produced by interacting the unfunctionalized clay with suitable intercalants. These intercalants are typically organic compounds, which are neutral or ionic. Useful neutral organic molecules include polar molecules such as amides, esters, lactams, nitriles, ureas, carbonates, phosphates, phosphonates, sulfates, sulfonates, nitro compounds, and the like. The neutral organic intercalants can be monomeric, oligomeric or polymeric. Neutral organic molecules can cause intercalation in the layers of the clay through hydrogen bonding, without completely replacing the original charge balancing ions. Useful ionic compounds are cationic surfactants including onium species such as ammonium (primary, secondary, tertiary, and quaternary), phosphonium, or sulfonium derivatives of aliphatic, aromatic or arylaliphatic amines, phosphines and sulfides. Typically onium ions can cause intercalation in the layers through ion exchange with the metal cations of the preferred smectite clay. A number of commercial organoclays for example Cloisite 15A, a natural montmorillonite modified with a quaternary ammonium salt, are available from clay vendors, such as Southern Clay Products and Nanocor, which may be utilized with this invention.
The talcs that may be used with this invention have a median size greater than 0.2 μm. The preferred sized range of talc is such that the median size is greater than 0.5 μm and less than 3 μm. The size distribution of the talcs are preferably narrow. Since talcs are incorporated in the toner receiver layer, the preferred brightness of the talcs is such that they have a GE brightness index greater than 88.
Besides specifying toner receiver layer characteristics, this invention teaches a method of forming a toner receiver member comprising providing a base extruding on at least one side a tie layer and a toner receiver layer, wherein said at least one toner receiver layer comprises a layer of branched polyester or a mixture of styrene acrylate copolymer with an ethylene methacrylate copolymer or with a low density polyethylene. The above mentioned molecular weight and melt rheological characteristics of the branched polyesters and blends of styrene copolymers of this invention and provide for successful extrusion processes like cast extrusion and extrusion coating. The preferred extrusion process for creating the toner receiver member is extrusion coating. This process prefers resins with suitable melt viscosities that enable resin to redistribute in a die like T slot die and coathanger die and also resins that have high melt strength. Resins that do not have high melt strength are unable to be drawn down and furthermore cause curtain instabilities like wavy edges, draw resonance, and also typically tends to result in large neck-in. The toner receiver layers are extruded onto a base. Depending on the characteristics of the base the toner receiver layer is directly extruded onto it or co-extruded onto it with another layer. The preferred option is co-extrusion. The layer co-extruded with the toner receiver layer is preferably a tie layer or adhesion promoting layer. This tie layer is formed primarily of a resin which might belong to the family of polyethylenes, polypropylenes, modified polyethylenes, modified polypropylenes, copolymers of polyolefins and combinations of these resins, The preferred resins in the tie layer are ethylene methyacrylate copolymers (EMA); copolymer of ethylene, and glycidyl methacrylate ester (EGMA); terpolymer of ethylene, methylacrylate and glycidyl methacrylate ester (EMAGMA); terpolymer of ethylene butylacrylate and maleic anhydride (EBAMAH) ethylene vinyl acetate copolymers (EVA); ethylene methacrylic acid copolymers (EMAA); ethylene acrylic acid copolymers (EAA); maleated polyolefins and ionomers of polyolefins. The choice of tie layer is further governed by the type of extrusion process. In the case of extrusion coating, the tie layers need to have suitable melt strength.
The tie layer might contain additives like antioxidants, optical brighteners, colorants, opacifiers, and fillers. Preferred opacifiers and fillers are TiO2, calcium carbonate, talc, clays, and barium sulfate. In order to enable co-extrusion, the tie layer properties are typically closely matched to the properties of the toner receiver layer. This is needed for the melt rheological properties like viscosity otherwise flow defects are observed in the layers.
In order to optimize toner receiver properties with adhesion properties to the base and colorimetry of the entire imaging element, the layer ratio of the tie layer to toner receiver layer needs to be optimized. Suitable layer ratio of the tie layer and toner receiver layer can be 1:9 to 5:1. Preferred layer ratios are 1:5 to 3:2. The thickness of the toner receiver layer along with the tie layer can be between 10 μm to 50 μm. Preferred overall thickness of the toner receiver layer and the tie layer is 15 μm to 40 μm. The invention may be practiced within a wide range of extrusion temperatures, for example, from 150° C. to 350° C., and speeds, for example, from 60 m/min. to 460 m/min. For this invention, preferred extrusion temperatures for the toner receiver layer the tie layer are from 200° C. to 300° C.
The toner receiver member could have different structures. It might be a polyolefin coated base that can include multilayer polyolefin structures, such as those achieved by multiple coatings, either sequential or via co-extrusion on which a tie layer is co-extruded with the toner receiver layer. The base could be any of the various structures described above. To minimize the number of resins required, and the complexity of the support, the support could have a structure consisting of 2 to 4 layers on each side. In one preferred embodiment, the toner receiver member comprises an uppermost layer which is a toner receiver layer, a base, an tie layer and a lower most layer which is a toner receiver layer. There may be variations where the upper most layer is only the toner receiver layer while the lowermost layer is a functional layer whose one function is to balance the structure. In another preferred embodiment, the lowermost layer comprises the same composition as the uppermost layer but is not used as a toner receiver layer. The structures of the toner receiver member are so designed to fulfill overall thickness of the toner receiver member of between 100 μm to 425 μm. This invention further teaches that based on the choice of the formulation of toner receiver layer, stiffness of overall toner receiver member can be enhanced without altering the overall caliper or thickness of the support.
The following examples illustrate the practice of this invention. They are not intended to be exhaustive of all possible variations of the invention. Parts and percentages are by weight unless otherwise indicated.
Examples 1-5 discuss the use of a resin coated paper as an electrophotographic imaging element. The samples were printed on the NexPress 2100 printer and tested for toner adhesion and physicals like caliper, basis weight, and stiffness. Some of the samples were glossed using the belt fuser that used a 76.2 μm polyimide belt at a temperature setting around 165° C. Stiffness was measured using a Lorentzen and Wetter (L&W) type tester according to Tappi method T556. This test measures the bending resistance in milliNewtons (mN) of a 20 mm wide vertically clamped sample is measured for a 15° deflection angle. Toner adhesion was measured by a tape test. This test is a modification of ASTM D3359-02. In this test the toner receiver member is clamped on either side to a workbench. One end of a 3M Scotch magic 810 tape is adhered to atleast 4″ of the toner receiver surface, while the free end of the tape is removed rapidly at as close to a 180° peel angle as possible. The failure mode is assessed based on location of failure. Furthermore, the surface of the resultant prints were evaluated for oil sorption using fuser oil smear test. The fuser oil smear test is carried out by running a finger across the printed surface. The oil smear was visually assessed for presence or absence of it.
Example 1 (Control) is representative of prior art and is presented here for comparison purposes. It comprises a photographic paper raw base made using standard fourdrinier paper machine utilizing a blend of mostly bleached hardwood Kraft fibers. The fiber ratio consisted primarily of bleached poplar, and maple/beech with lesser amounts of birch and softwood. Acid sizing chemical addenda utilized on a dry weight basis, included an aluminum stearate size, polyaminoamide epichlorhydrin, and polyacrylamide resin. Surface sizing using hydroethylated starch and sodium bicarbonate was also employed. This raw base was then extrusion coated on both sides using face side resin composite comprising substantially 87 weight % LDPE (LDPE D5004P), 11.4 weight % TiO2 and remaining additives. Resin coverages on both sides was 21.97 gm/m2. This toner receiver member was evaluated for caliper, stiffness and then run through the NexPress 2100 machine and some of the toner receiver members were run through the glosser. The resultant image was evaluated for toner adhesion and oil sorption.
Example 2 (blend of styrene acrylate as toner receiver layer with a tie layer) of the invention comprises a paper base of composition and caliper described in Example 1, which is then extrusion coated on both sides using a co-extrusion process with a toner receiver layer and a tie layer on both sides of paper base. The total resin coating coverage was maintained at 21.97 gm/m2 so as to give a caliper near equivalent to the control sample for the toner receiver member. The layer ratio between the tie layer and the toner receiver layer was 1:1. The toner receiver layer composition consisted of a blend of 90% ethylene methacrylate (Exxon Mobil TC130) with 10% styrene acrylate (Eliokem Pliolite AC-L). The tie layer consisted of 87.7 weight % ethylene methacrylate (Exxon Mobil TC130) with 11.4 weight % TiO2 and rest as colorants and other additives. This toner receiver member was evaluated for caliper, stiffness and then run through the NexPress 2100 machine and some of them were run through the glosser. The resultant image was evaluated for toner adhesion and oil sorption.
Example 3 (blend of styrene acrylate as toner receiver layer with a tie layer) of the invention comprises a paper base of composition and caliper described in Example 1, which is then extrusion coated on both sides using a co-extrusion process with a toner receiver layer and a tie layer on both sides of paper base. The total resin coating coverage was maintained at 21.97 gm/m2 so as to give a caliper near equivalent to the control sample for the toner receiver member. The layer ratio between the tie layer and the toner receiver layer was 1:1. The toner receiver layer composition consisted of a blend of 80 weight % ethylene methacrylate (Exxon Mobil TC130) with 20 weight % styrene acrylate (Eliokem Pliolite AC-L). The tie layer consisted of 87.7 weight % of ethylene methacrylate (Exxon Mobil TC130) with 11.4 weight %TiO2 and rest as colorants and other additives. This toner receiver member was evaluated for caliper, stiffness and then run through the NexPress 2100 machine and some of them were run through the glosser. The resultant image was evaluated for toner adhesion and oil sorption.
Example 4 (branched polyester as a toner receiver layer with a tie layer) of the invention comprises a paper base of composition and caliper described in Example 1, which is then extrusion coated on both sides using a co-extrusion process with a toner receiver layer and a tie layer on both sides of paper base. The total resin coating coverage was maintained at 21.97 gm/m2 so as to give a caliper near equivalent to the control sample for the toner receiver member. The layer ratio between the tie layer and the toner receiver layer was 1:1. The toner receiver layer composition consisted of a 99.5 weight % branched polyester made using 2 weight % branching agent and 0.5 weight % of a siloxane masterbatch MB 50-10 (Dow Coming). The tie layer consisted of 87.7 weight % ethylene methacrylate (Exxon Mobil TC130) containing 11.4 weight % TiO2 and rest as colorants and other additives. This toner receiver member was evaluated for caliper, stifffiess and then run through the NexPress 2100 machine and some of them were run through the glosser. The resultant image was evaluated for toner adhesion and oil sorption.
Example 5 (branched polyester with talc as a toner receiver layer and a tie layer) of the invention comprises a paper base of composition and caliper described in Example 1, which is then extrusion coated on both sides using a co-extrusion process with a toner receiver layer and a tie layer on both sides of paper base. The total resin coating coverage was maintained at 21.97gm/m2 so as to give a caliper near equivalent to the control sample for the toner receiver member. The layer ratio between the tie layer and the toner receiver layer was 1:1. The toner receiver layer composition consisted of a 95 weight % branched polyester of molecular weight and melt strength along with 5 weight % talc having a median particle size of 2.1 μm (Imi-Fabi, HTP 1C). The tie layer consisted of 87.7 weight % ethylene methacrylate (Exxon Mobil TC130) containing 11.4 weight % TiO2 and rest as colorants and other additives. This toner receiver member was evaluated for caliper, stiffness and then run through the NexPress 2100 machine and some of them were run through the glosser. The resultant image was evaluated for toner adhesion and oil sorption.
Table 3 summarizes the performance of samples created in Example 1-5. It is observed that stiffness can be enhanced for a given caliper by using the branched polyester as a toner receiver layer. Using this polyester as a toner receiver layer one can create products perceived to be of a superior quality without altering the manufacturing process of paper making and extrusion coating. It is observed that the toner receiver layers described in Examples 2-5 show good toner adhesion as compared to Example 1. So using formulations described in the invention enables extrusion processing of the toner receiver layers while providing good toner adhesion to the toner receiver layer.
Furthermore, using talc in the toner receiver layer formulation enables oil put at the fuser nip to be absorbed by receiving layer. This is highlighted by comparing Example 4 with Example 5, where it is observed that oil is not seen on the surface of Example 5 which contains talc.
Furthermore, a comparison of Example 1 (control) with Example 4 or Example 2 with Example 4 shows that for near equivalent caliper of the toner receiver member, an appropriate choice of toner receiver formulation enables creation of supports with various stiffness. Using the branched polyester as a toner receiver layer one can create products perceived to be of a superior quality by the customer without altering the manufacturing process of base (e.g. paper) making and extrusion coating.
The invention has been described in detail with particular reference to certain preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention.
