Classifications

• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
  • G03G7/00—Selection of materials for use in image-receiving members, i.e. for reversal by physical contact; Manufacture thereof
  • G03G7/0006—Cover layers for image-receiving members; Strippable coversheets
  • G03G7/002—Organic components thereof
  • G03G7/0026—Organic components thereof being macromolecular
  • G03G7/004—Organic components thereof being macromolecular obtained by reactions only involving carbon-to-carbon unsaturated bonds
• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
  • G03G7/00—Selection of materials for use in image-receiving members, i.e. for reversal by physical contact; Manufacture thereof
  • G03G7/0006—Cover layers for image-receiving members; Strippable coversheets
  • G03G7/002—Organic components thereof
• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
  • G03G7/00—Selection of materials for use in image-receiving members, i.e. for reversal by physical contact; Manufacture thereof
  • G03G7/0086—Back layers for image-receiving members; Strippable backsheets
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10S428/00—Stock material or miscellaneous articles
  • Y10S428/913—Material designed to be responsive to temperature, light, moisture
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10S428/00—Stock material or miscellaneous articles
  • Y10S428/914—Transfer or decalcomania
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/24—Structurally defined web or sheet [e.g., overall dimension, etc.]
  • Y10T428/24802—Discontinuous or differential coating, impregnation or bond [e.g., artwork, printing, retouched photograph, etc.]
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/31504—Composite [nonstructural laminate]
  • Y10T428/31507—Of polycarbonate
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/31504—Composite [nonstructural laminate]
  • Y10T428/31971—Of carbohydrate
  • Y10T428/31993—Of paper

Definitions

• the present invention relates generally to an imaging medium.
• the present invention relates more particularly to an imaging medium comprising a particular receptor layer and a polycarbonate backing layer particularly useful in electrophotographic printing processes with liquid toners comprising thermoplastic toner particles in a liquid carrier that is not a solvent for the particles at a first temperature and that is a solvent for the particles at a second temperature and with dry toner; methods of imaging such a medium; and such an imaged medium.
• the imaging medium which can surprisingly be made in the substantial or complete absence of ultraviolet light radiation can thus optionally contain ultraviolet light sensitive components such as inhibitors and/or absorbers thus providing a final product which demonstrates resistance to ultraviolet light radiation (i.e., an imaged media that is much less likely to experience fading of its image in sunlight).
• ultraviolet light sensitive components such as inhibitors and/or absorbers
• Electrophotographic printing generally includes imparting an image on a final receptor by forming a latent image on selectively charged areas of a photoconducter such as a charged drum, depositing a charged toner onto the charged areas of the photoconductor to thereby develop an image on the photoconductor, and transferring the developed toner from the charged drum under heat and/or pressure onto the final receptor.
• the '492 and '392 patents both disclose that a preferred toner is a liquid toner comprising carrier liquid and pigmented polymeric toner particles which
• U.S. Patent No. 5,196,246 discloses a wall decorating system that, in one embodiment, includes a SURLYN blend film that can be printed by etching, embossing, flexographic printing, silk screening, or gravure processes (column 14, lines 16-19).
• Polycarbonate films are well known for their high impact resistance, good thermal moldability, and excellent lens-like clarity.
• Many types of products in the electronics, appliance, and automotive industries such as cellular phones, air conditioners, and automotive dial displays, etc. therefore use polycarbonate sheets as a graphic overlayer.
• these polycarbonate graphic overlays are traditionally prepared with solvent based screen printing processes. These processes not only require a long time to make artwork and to prepare printing screens, but they are also less environmentally friendly. These products are not practical for short run print-on- demand type printing.
• Recently developed Indigo and Xeikon print processes yield high quality images and are suitable for short run print on demand printing processes.
• the commercially available durable product for electrophotographic digital imaging comprises an imageable modified PET, which is then modified by the application of a polycarbonate layer.
• a layer of polycarbonate previously could not be directly imaged with such methods.
• a layer of modified PET was imaged and subsequently covered with a layer of polycarbonate.
• the polycarbonate (PC) was attached to the imaged PET with a layer of pressure sensitive adhesive.
• PC polycarbonate
• a novel PC imaging medium has been provided which can be imaged directly using electrophotographic printing technology.
• the novel imaging medium of the invention not only requires fewer steps than the known product but also uses less raw material. Short run, print-on-demand type printing is becoming increasingly popular.
• Printers capable of providing such short run print on demand printing include those developed by Indigo Ltd. and those developed by Xeikon N.N.
• the Indigo printers can employ electrophotographic liquid toner whereas the Xeikon printers employ dry toner.
• an imaging medium comprising polycarbonate that can be made in the substantial absence of ultraviolet radiation and thus can include ultraviolet light stabilizers such as inhibitors and/or absorbers wherein the media can readily be printed by short run electrophotographic methods and apparatuses to produce high quality images and that is strong, durable, and abrasion-resistant.
• the present invention provides imaging media comprising a particular receptor layer and a polycarbonate backing layer.
• the receptor layer utilized surprisingly demonstrates good adhesion to polycarbonate in the absence of ultraviolet ("UN") radiation application.
• the imaging media of the present invention are particularly useful in electrophotographic printing processes with liquid toners comprising thermoplastic toner particles in a liquid carrier that is not a solvent for the particles at a first temperature and that is a solvent for the particles at a second temperature.
• the imaging media of the present invention are also particularly useful in electrophotographic printing processes employing dry toner (such as dry powder toner).
• the present invention also provides methods of imaging such imaging media, and such an imaged media.
• One advantage of the present invention is that upon extruding a receptor layer on a polycarbonate backing, it is not necessary to heat the resulting structure or subject it to irradiation (such as ultraviolet light irradiation). Thus the formation of such imaging medium can take place in the substantial or complete ultraviolet light radiation.
• a receptor layer wherein the receptor layer comprises: (I) a polymer(s) wherein each polymer independently comprises the polymerization product of a composition comprising (i) ethylene, (ii) monomer(s) selected from the group consisting of vinyl acetate, vinyl acrylate, and mixtures thereof, (iii) optionally a vinyl carboxylic acid(s), (iv) optionally an anhydride; and (II) 0 to about 3 percent by weight (typically about 0.05 to about 3 percent if used) by weight of an ultraviolet light stabilizer selected from the group consisting of ultraviolet light absorbers, ultraviolet light inhibitors, and mixtures thereof, based upon the total weight of the receptor layer; wherein the receptor layer has a melt index of at least about 2.5 grams/ 10 minutes; and (b) a polycarbonate backing layer bonded to the receptor layer;
• the receptor layer is bonded to the backing layer in the substantial absence of ultraviolet radiation, and wherein the composition of the receptor layer is selected such that the T-peel adhesion of the receptor layer to the polycarbonate backing layer is at least about 358 g/cm, and such that at least one of the following is true:
• the Taber abrasion resistance test value for an image electrophotographically formed on the receptor layer with a liquid toner is at least about 6;
• the Taber abrasion resistance test value for an image electrophotographically formed on the receptor layer with a dry thermoplastic toner is at least about 6.
• the present invention also provides a method of transferring an electrophotographically developed image from a photoconductor to an imaging medium wherein the toner employed is a liquid toner.
• the method comprises the steps of: a) selectively providing desired portions of a photoconductor with a developed image, the image comprising a plurality of thermoplastic toner particles in a liquid carrier at a first temperature, wherein the liquid carrier is not a solvent for the particles at the first temperature and wherein the thermoplastic particles and the liquid carrier form substantially a single phase at or above a second temperature; b) heating the developed image to a temperature at least as high as the second temperature to thereby form a single phase of the thermoplastic particles and liquid carrier; and c) thereafter transferring the developed image to the receptor layer of the imaging medium of the invention at a temperature of about 120° to about 165°C.
• the present invention also provides a method of transferring an electrophotographically developed image from a photoconductor to an imaging medium, comprising the steps of: a) selectively providing desired portions of a photoconductor with a developed image, the image comprising a plurality of dry thermoplastic toner particles wherein the toner particles are solid at a first temperature, but which soften or melt at or above a second temperature; b) transferring the developed image onto a receptor layer of an imaging medium of the present invention; c) heating and optionally applying pressure to the developed image such that it reaches a temperature at least as high as the second temperature to soften or melt the toner particles to form a final fixed image.
• the present invention provides a method of making an imaging medium comprising the step of: bonding a polycarbonate backing layer to a receptor layer in the substantial absence of ultraviolet light radiation, wherein the receptor layer comprises: a polymer(s) wherein each polymer independently comprises the polymerization product of a composition comprising (i) ethylene, (ii) monomer(s) selected from the group consisting of vinyl acetate, vinyl acrylate, and mixtures thereof, (iii) optionally a vinyl carboxylic acid(s), (iv) optionally an anhydride;
• the receptor layer has a melt index of at least about 2.5 grams/10 minutes
• composition of the receptor layer is selected such that the T-peel adhesion of the receptor layer to the polycarbonate backing layer is at least about 358 g/cm, and such that at least one of the following is true:
• the Taber abrasion resistance test value for an image formed on the receptor layer with a solid toner is at least about 6.
• the present invention also provides a method of transferring an electrophotographically developed image from a photoconductor to an imaging medium, comprising the steps of:
• thermoplastic toner particles in a liquid carrier at a first temperature, wherein the liquid carrier is not a solvent for the particles at the first temperature and wherein the thermoplastic particles and the liquid carrier form substantially a single phase at or above a second temperature; (b) heating the developed image to a temperature at least as high as the second temperature to thereby form a single phase of the thermoplastic particles and liquid carrier;
• the present invention also provides a method of transferring an electrophotographically developed image from a photoconductor to an imaging medium comprising the steps of:
• the present invention also provides an imaged article.
• the imaged article comprises a receptor layer having an imaging surface (also referred to as an "imageable surface"), and an image on the imaging surface, the image typically comprising a substantially continuous layer.
• the layer of the image comprises the thermoplastic particles and a liquid carrier that is not a solvent for the particles at a first temperature and which is a solvent for the particles at or above a second temperature, the layer having been deposited onto the imaging surface while in substantially a single phase with a liquid carrier.
• the resultant image is at least 95% free, preferably at least 98% free, more preferably at least 99% free and most preferably 100% free of solvent.
• the layer of the image is formed from dry toner particles.
• the present invention provides an imaged article comprising:
• thermoplastic toner particles in a liquid carrier at a first temperature, wherein the liquid carrier is not a solvent for the particles at the first temperature and wherein the thermoplastic particles and the liquid carrier form substantially a single phase at or above a second temperature.
• the present invention also provides another embodiment of an imaged article comprising:
• An imaged medium of the invention may further comprises a layer of adhesive coated over a surface of the backing opposite the receptor layer and a release liner attached to a surface of the adhesive layer opposite the backing.
• An imaged media of the invention may further comprise a layer of adhesive coated over the image and the surface of the receptor layer not bonded to the backing.
• An imaging medium or imaged medium can be analyzed to determine whether it has experienced ultraviolet light degradation. This can be accomplished via electron spectroscopy for chemical analysis (ESCA).
• ESCA electron spectroscopy for chemical analysis
• the following references discuss analysis for ultraviolet light degradation: Polymer Degradation. T. Kelen, Chapter 7 (1983); Ultraviolet Light Induced Reactions in Polymers, by S. S. Labana, American Chemical Society Symposium Series #25, (1976); and Polymer Degradation and Stability. Vol. 2, p 203, (1980).
• the imaging media and imaged media of the invention are made in a manner such that they are free or substantially free of ultraviolet light degradation effects as determined by ESCA.
• electrostatic printing refers to printing processes in which an image is imparted on a receptor by forming a latent image on selectively charged areas of a photoconducter such as a charged drum, depositing a charged toner onto the charged areas of the photoconductor to thereby develop an image on the photoconductor, and transferring the developed toner from the charged drum under heat and/or pressure onto an imaging medium.
• An optional transfer member can be located between the charged drum and the imaging medium.
• electrophotographic printing apparatuses examples include, but are not limited to, the OMNIUS and E-1000 electrophotographic printers, available from Indigo, Ltd. of Rehovot, Israel; the DCP-1 printer available from Xeikon N.N. of Mortsel, Belgium; and the LA ⁇ IER 6345 copier available from Lanier Worldwide, Inc. of Atlanta, Georgia.
• the term "in the substantial absence of ultraviolet radiation” as used herein means that an artificial source of ultraviolet radiation such as a UN generating lamp is not present. Very minor amounts of ultraviolet radiation may be present due to standard room lighting (such as fluorescent or incandescent lighting) or natural lighting.
• Figure la is a cross-sectional view of a first embodiment of an imaging medium according to the present invention.
• Figure lb is a cross-sectional view of a second embodiment of an imaging medium according to the present invention.
• Figure 2 is a partial schematic view of an electrophotographic imaging apparatus for use with the present invention.
• Figure 3 is part of a simplified typical phase diagram for a preferred toner for use with the present invention.
• the present invention provides imaging media comprising a particular receptor layer and a polycarbonate backing layer which is made in the complete or substantial absence of UV radiation and thus can contain UV sensitive components.
• the imaging media of the present invention are particularly useful in electrophotographic printing processes with liquid toners comprising thermoplastic toner particles in a liquid carrier that is not a solvent for the particles at a first temperature and that is a solvent for the particles at a second temperature.
• the present invention also provides methods of making such imaging media, imaging such imaging media, and such an imaged media.
• imaging medium 40 includes receptor layer 42 joined to PC backing layer 50.
• Receptor layer 42 includes first major surface, or image surface 44, and second major surface, or back surface 46.
• Backing layer 50 includes first major surface 52 joined to the second surface 46 of the receptor layer.
• Backing layer also includes second major surface 54 opposite the first major surface 52.
• Optional layer of adhesive 20 may be provided on the second major surface 54 of the backing layer. When the adhesive layer is a pressure sensitive adhesive, then it is preferable to provide release liner 22. As shown in Figure la, direct printed image 18 has been printed on imaging surface 44 as is discussed in detail below.
• imaging medium 80 includes receptor layer 42 joined to PC backing layer 50.
• Receptor layer 42 includes first major surface, or image surface 44, and second major surface, or back surface 46.
• Backing layer 50 includes first major surface 52 joined to the second surface 46 of the receptor layer.
• Backing layer also includes second major surface 54 opposite the first major surface 52.
• Optional layer of adhesive 20 may be provided on the first major surface 44 of the receptor layer over reverse printed image 18.
• the backing layer 50 should be translucent or transparent, preferably transparent, and the receptor layer 42 should be translucent or transparent, preferably transparent, to allow observation of the image through the backing 50 and receptor layer 42.
• the adhesive layer is a pressure sensitive adhesive, then it is preferable to provide release liner 22 over the adhesive layer 20.
• the receptor layer 42 preferably comprises a polymer obtained by polymerizing ethylene with one or more monomers selected from the group consisting of vinyl acetate, esters of alkyl acrylic acid, esters of alkacrylic acid, and mixtures thereof and optional vinyl carboxylic acid(s) and optional anhydride(s).
• the receptor layer also includes ultraviolet light stabilizer(s).
• Receptor layer materials useful in the present invention have a melt index of at least about 2.5 grams/10 minutes, preferably ranging from about 3.0 to 45 grams/10 minutes. Melt index is determined by following the procedures set forth in ASTM Standard "D-1238", “Standard Test Method for Flow Rates of Thermoplastics by Extrusion Plastometer", at 190°C; 2.16 kg. Melt flow rate
• MFR melt index
• Polymer(s) are selected from the group consisting of: ethylene/vinyl acetate copolymers, each ethylene/vinyl acetate copolymer independently comprising about 52 to about 85 percent by weight ethylene and about 15 to about 48 weight percent vinyl acetate, based upon the total weight of the ethylene/vinyl acetate copolymer; ethylene/vinyl acrylate copolymers, each ethylene/vinyl acrylate copolymer independently comprising about 60 to about 90 percent by weight ethylene and about 10 to about 40 weight percent vinyl acrylate, based upon the total weight of the ethylene/vinyl acrylate copolymer; ethylene/vinyl carboxylic acid/vinyl acetate copolymers, each ethylene/vinyl carboxylic acid/vinyl acetate copolymer independently comprising about 37 to about
• ethylene/vinyl carboxylic acid/vinyl acrylate copolymers each ethylene/vinyl carboxylic acid/vinyl acrylate copolymer independently comprising about 45 to about 89 percent by weight ethylene, about 1 to about 15 weight percent vinyl carboxylic acid, and about 10 to about 40 percent by weight vinyl acrylate based upon the total weight of the ethylene/vinyl carboxylic acid/vinyl acrylate copolymer
• ethylene/anhydride/vinyl acetate copolymers each ethylene/anhydride/vinyl acetate copolymer independently comprising about 37 to about 89.9 percent by weight ethylene, about 0.1 to about 15 weight percent anhydride, and about 10 to about 48 percent by weight vinyl acetate based upon the total weight of the ethylene/vinyl carboxylic acid/vinyl acetate copolymer
• ethylene/vinyl carboxylic acid/vinyl acrylate copolymers each ethylene/vinyl carboxylic
• the polymer(s) are selected from the group consisting of: ethylene/vinyl acetate copolymers, each ethylene/vinyl acetate copolymer independently comprising about 60 to about 85 percent by weight ethylene and about 15 to about 40 weight percent vinyl acetate, based upon the total weight of the ethylene/vinyl acetate copolymer; ethylene/vinyl acrylate copolymers, each ethylene/vinyl acrylate copolymer independently comprising about 70 to about 90 percent by weight ethylene and about 10 to about 30 weight percent vinyl acrylate, based upon the total weight of the ethylene/vinyl acrylate copolymer; ethylene/vinyl carboxylic acid/vinyl acetate copolymers, each ethylene/vinyl carboxylic acid/vinyl acetate copolymer independently comprising about 48 to about 84 percent by weight ethylene, about 1 to about 12 weight percent vinyl carboxylic acid, and about 15 to about 40 percent by weight vinyl acetate
• the polymer(s) are selected from the group consisting of: ethylene/vinyl acetate copolymers, each ethylene/vinyl acetate copolymer independently comprising about 65 to about 82 percent by weight ethylene and about 18 to about 35 weight percent vinyl acetate, based upon the total weight of the ethylene/vinyl acetate copolymer; ethylene/vinyl acrylate copolymers, each ethylene/vinyl acrylate copolymer independently comprising about 75 to about 85 percent by weight ethylene and about 15 to about 25 weight percent vinyl acrylate, based upon the total weight of the ethylene/vinyl acrylate copolymer; ethylene/vinyl carboxylic acid/vinyl acetate copolymers, each ethylene/vinyl carboxylic acid/vinyl acetate copolymer independently comprising about 55 to about 81 percent by weight ethylene, about 1 to about 10 weight percent vinyl carboxylic acid, and about 18 to about 35 percent by weight vinyl a
• the polymer(s) which make up the receptor layer may be modified by the incorporation of anhydrides (e.g., maleic anhydride) or acid (e.g., methacrylic acid) into the polymer.
• those polymer(s) modified with acid may be partially neutralized by the addition of a metal cation (such as zinc, sodium, potassium or magnesium), thus forming ionomers.
• a metal cation such as zinc, sodium, potassium or magnesium
• blends of polymer(s) may be formed and used by mixing together two or more of the above polymers.
• vinyl carboxylic acid is included in the polymer(s), it is preferably selected from the group consisting of acrylic acid, methacrylic acid, and mixtures thereof.
• the polymer(s) includes an anhydride it is preferably included in an amount of at least about 0.1% by weight based upon the total weight of the polymer(s).
• the polymer(s) comprise methacrylic acid in an amount of at least about 1%, preferably at least about 2% by weight based upon the total weight of the polymer(s).
• the polymer comprises an ethylene vinyl acetate (“EVA”) copolymer.
• EVA ethylene vinyl acetate
• the EVA has a vinyl acetate (“NA”) content of at least about 15% by weight, preferably about 15% to about 40% by weight, and more preferably about 18% to about 35% by weight and a melt index of about 2.5 grams/ 10 minutes.
• the polymer(s) comprise the polymerization product of a composition comprising ethylene and vinyl acetate, the polymer(s) having a melt index of at least about 2.5 grams/ 10 minutes and a vinyl acetate content of from about 15 to about 40 percent by weight based upon the total weight of the polymer(s).
• ENAX 3175 commercially available from E.I. du Pont de Nemours & Company, Wilmington, DE (“du Pont”) and has a melt index of approximately 6.0 grams/10 minutes and a vinyl acetate content of about 28%.
• the receptor layer comprises an ENA modified with acid, for example methacrylic acid, it typically comprises at least about 1 percent by weight acid, preferably about 1% to about 12% by weight acid.
• ELNAX 4260 commercially available from du Pont which has a melt index of approximately 6.0 grams/10 minutes, a vinyl acetate content of approximately 28%, and a methacrylic acid content of approximately 1.0%.
• the polymer comprises an ENA modified with anhydride, it preferably comprises at least about 0.1% anhydride, such as maleic anhydride.
• anhydride such as maleic anhydride.
• One example of such a terpolymer is "MODIC E-300-K" available commercially from Mitsubishi Petroleum Co., Ltd. of Japan. Polymers having a vinyl acetate content below about 15% by weight tend to have poor printability characteristics; and polymers having a vinyl acetate content above about 35% by weight tend to be sticky and less practical to use in the extrusion and printing processes.
• the polymer comprises an ethylene/vinyl acrylate copolymer
• the vinyl acrylate comprising, for example, vinyl alkyl acrylates such as vinyl methyl acrylate, vinyl ethyl acrylate, vinyl propyl acrylate, vinyl n-butyl acrylate, vinyl n-pentyl acrylate, vinyl n-hexyl acrylate, and other acrylates such as vinyl alkacrylates such as vinyl methacrylate, vinyl ethacrylate, vinyl propacrylate, vinyl butacrylate, vinyl pentacrylate, vinyl hexacrylate, and mixtures thereof.
• the polymer(s) comprises ethylene/vinyl acrylate polymer(s), having a melt index of at least about 2.5 grams/ 10 minutes and a vinyl acrylate content of from about 10 to about 30% by weight based on the total weight of the polymer(s).
• the polymer comprises an ethylene/vinyl acrylate terpolymer having acid, for example methacrylic acid incorporated therein, comprises at least about 1% acid, preferably about 1% to about 12% by weight acid.
• a terpolymer is "BY ⁇ EL CXA 2002" from du Pont, a terpolymer comprising ethylene, n-butylacrylate, and methacrylic acid having a melt index of approximately 10.0 grams/10 minutes, a methacrylic acid content of about 10%, and an n-butylacrylate content of about 10%.
• a preferred polymer(s) comprise the polymerization product of a composition comprising ethylene, vinyl acrylate, and methacrylic acid, the polymer(s) having a melt index of at least about 2.5 grams/ 10 minutes, wherein the vinyl acrylate content is about 10 to about 30 percent by weight and the acid content is about 1 to about 12 percent by weight based upon the total weight of the polymer(s).
• the polymer comprises an ethylene vinyl acrylate anhydride terpolymer, it preferably comprises at least about 0.1% anhydride, such as maleic anhydride.
• the acrylate content is preferably about 10 to about 30%.
• An additive polymer component may optionally be included in the receptor layer in combination with the required polymer component.
• additive polymers include ethylene/vinyl carboxylic acid copolymers and/or its neutralized derivatives such as ionomers, and mixtures thereof.
• Such additive polymer(s) would be used at about 0 to about 35 percent by weight, typically about 1 to about 35 percent by weight) based on the total weight of the receptor layer.
• the receptor layer may optionally further comprise ultraviolet light stabilizer(s).
• ultraviolet light stabilizers are useful according to the present invention.
• One class of such components are ultraviolet light absorbers. These materials typically function by absorbing harmful ultraviolet radiation and dissipating it as heat energy. Examples of such materials include but are not limited to those selected from the group consisting of benzotriazoles (such as Tinuvin 328 and Tinuvin 900, available from Ciba-Geigy Corporation, New York), benzophenones (such as Sandover 3041 available from Clariant Corporation, Charlotte, North Carolina), and oxalanilides (such as Sandover NSU, available from Clariant Corporation) and triazines such as that available as Cyagard UN- 1164 from Cytec Industries Inc., New Jersey.
• benzotriazoles such as Tinuvin 328 and Tinuvin 900, available from Ciba-Geigy Corporation, New York
• benzophenones such as Sandover 3041 available from Clariant Corporation, Charlotte, North Carolina
• ultraviolet light inhibitors typically trap free radicals with subsequent regeneration of active stabilizer moieties, energy transfer, and peroxide decomposition.
• examples of such materials include but are not limited to those selected from the group consisting of hindered amines (such as Tinuvin 292 and Tinuvin 144, both from Ciba-Geigy Corporation).
• both ultraviolet light absorber and ultraviolet light inhibitor are present in the receptor layer at a weight ratio of ultraviolet light absorber to ultraviolet light inhibitor of about 1 :3 to about 3:1, more preferably about 1.5:2.5 to about 2.5:1.5.
• the receptor layer comprises about 0.1 to about 3 percent by weight (for example, about 0.05 to about 3 percent by weight) of a component selected from the group consisting of ultraviolet light absorber, ultraviolet light inhibitor, and mixtures thereof, based on the total weight of the receptor layer, more preferably about 0.3 to about 1.5 percent by weight and most preferably about 0.5 to about 1 percent by weight.
• a component selected from the group consisting of ultraviolet light absorber, ultraviolet light inhibitor, and mixtures thereof based on the total weight of the receptor layer, more preferably about 0.3 to about 1.5 percent by weight and most preferably about 0.5 to about 1 percent by weight.
• the thickness of the receptor layer 42 is not necessarily critical, but it is preferably from about 0.0075 to about 0.25 mm (about 0.3 to about 10 mils), more preferably from about 0.013 to about 0.13 mm (about 0.5 to about 5 mils).
• the desired thickness is determined by the intended use of the film and desired characteristics of the imaging medium affecting handling and cutting.
• pellets or powder of resin along with optional resins or additives, as obtained from the manufacturer, are mixed together with the optional ultraviolet light absorber(s) and/or optional inhibitor(s), melted, and extruded to form a film.
• the film can be extruded onto the PC backing layer 50 as described in detail below.
• the backing layer 50 comprises polycarbonate (PC).
• the backing layer 50 may be transparent, colorless, pigmented, or metallized.
• Opaque, white backing layers are useful for this invention and typically are achieved by the addition to the polymer of conventional pigmenting agents such as titania, calcium carbonate, and talc.
• Metallized backing layers are also useful and typically are prepared by vapor coating aluminum onto the polymer.
• Such pigmented or metallized backing layers are particularly preferred when the receptor layer is transparent, or nearly so.
• the backing layer when bonded to the receptor layer provides an opaque imaging medium which is desirable for many print applications.
• Such a construction also makes it unnecessary to add pigmenting additives to the receptor layer itself. Such additives may adversely affect the durability of the printed image on the receptor layer.
• the thickness of the backing layer is preferably from about 0.00025 to 0.025 cm (0.0001 to 0.01 inches), and more preferably about 0.013 to 0.13 cm (0.0005 to 0.005 inches).
• an opaque backing it preferably has an optical density of 2.5 +/- 10% as measured on a MacBeth TD927 densitometer, available from Macbeth of Newburgh, NY.
• Additives such as processing aids can optionally be included in the receptor layer. However, the amount of such additive(s) should be such that the requisite properties of the imaging medium of the invention are retained.
• the receptor layer 42 can be bonded (such as by adhesion, for example) to the polycarbonate backing layer 50 by a number of techniques. Suitable joining means include pressure sensitive adhesives, heat activated adhesives, sonic welding, and the like.
• the receptor layer 42 is extruded on to the backing layer 50 to form a composite structure.
• the material of the receptor layer 42 is coated onto the backing layer 50 in a molten state by a conventional extrusion process.
• the temperature of the material of the receptor layer when in the extruder, typically ranges from about 250°F (121°C) to about 480°F (249°C).
• the temperature of the material of the receptor layer 42 as it exits the extruder is typically from about 350°F (177°C) to about 560°F (293°C). After the material is extruded onto the backing layer, the thus-formed composite structure can be allowed to cool.
• a blend of a polymer component comprising a copolymer comprising ethylene and vinyl acetate commercially available under the trade designation "ELNAX 3175" from du Pont and the other components (ultraviolet absorber and/or inhibitor, etc.) is extruded at a thickness of about 0.025 mm (1 mil) onto a PC backing layer approximately 0.254 mm (10 mil) thick.
• imaging medium 40 can be prepared by extruding a 0.038 mm (1.5 mil) thick receptor layer 42 comprising a blend of ethylene copolymer with the other component(s) onto at least about a 0.025 cm (1 mil) thick polycarbonate backing layer 50, allowing the thus-formed composite structure to cool.
• an ethylene/vinyl acrylate/vinyl carboxylic acid copolymer such as a terpolymer comprising ethylene, n-butylacrylate, and methacrylic acid (EAMA) commercially available under the trade designation
• BY ⁇ EL CXA 2002 from du Pont is extruded as a blend with the ethylene/vinyl acetate copolymer and/or ethylene vinyl acrylate and ultraviolet light stabilizer(s) at a thickness of about 0.254 mm(l mil) (0.001 inches) onto a polycarbonate backing layer approximately 0.254 mm(l mil) (0.00056 inches) thick.
• Adhesives useful in the preparation of an adhesive coated imaging medium according to the present invention include both pressure sensitive and non-pressure sensitive adhesives such as hot melt and curable adhesives.
• Pressure sensitive adhesives are normally tacky at room temperature and can be adhered to a surface by application of, at most, light finger pressure, while non-pressure sensitive adhesives include solvent, heat, or radiation activated adhesive systems.
• Pressure sensitive adhesives are a preferred class of adhesives for use in the present invention.
• adhesives useful in the invention include those based on general compositions of polyacrylate; polyvinyl ether; diene-containing rubber such as natural rubber, polyisoprene, and polyisobutylene; polychloroprene; butyl rubber; butadiene-acrylonitrile polymer; thermoplastic elastomer; block copolymers such as styrene-isoprene and styrene-isoprene-styrene block copolymers, ethylene- propylene-diene polymers, and styrene-butadiene polymer; poly-alpha-olefin; amorphous polyolefin; silicone; ethylene-containing copolymer such as ethylene vinyl acetate, ethylacrylate, and ethyl methacrylate; polyurethane; polyamide; epoxy; polyvinylpyrrolidone and vinylpyrrolidone copolymers; polyesters; and mixtures of the
• Liquid toners typically comprise pigments, binder, carrier solvent, dispersing agents, and charge additives.
• the liquid toner comprises thermoplastic toner particles in a liquid carrier that is not a solvent for the particles at a first temperature and that is a solvent for the particles at a second temperature, especially those disclosed in U.S. Patent No. 5, 192,638, "Toner for Use in
• Landa et al. '638 discloses a liquid composition for developing latent electrostatic images comprising toner particles associated with a pigment dispersed in a nonpolar liquid.
• the toner particles are formed with a plurality of fibers or tendrils from a thermoplastic polymer and carry a charge of a polarity opposite to the polarity of the latent electrostatic image.
• the polymer is insoluble or insolvatable in the dispersant liquid at room temperature.
• the toner particles are formed by plasticizing the polymer and pigment at elevated temperature and then either permitting a sponge to form and wet-grinding pieces of the sponge or diluting the plasticized polymer-pigment while cooling and constantly stirring to prevent the forming of a sponge while cooling.
• the diluted composition will have a concentration of toner particles formed with a plurality of fibers.
• These fibers are formed from a thermoplastic polymer and are such that they may interdigitate, intertwine, or interlink physically in an image developed with a developing liquid through which has been dispersed the toner particles of the instant invention.
• the result is an image on the photoconductor having good sharpness, line acuity-that is, edge acuity-and a high degree of resolution.
• the developed image on the photoconductor has good compressive strength, so that it may be transferred from the surface on which it is developed to the imaging medium without squash.
• the intertwining of the toner particle permits building a thicker image and still obtaining sharpness.
• the thickness can be controlled by varying the charge potential on the photoconductor, by varying the development time, by varying the toner-particle concentration, by varying the conductivity of the toner particles, by varying the charge characteristics of the toner particles, by varying the particle size, or by varying the surface chemistry of the particles. Any or a combination of these methods may be used.
• the polymer used in the particles of Landa et al. '683 preferably has the following characteristics: it is able to disperse a pigment (if a pigment is desired); it is insoluble in the dispersant liquid at temperatures below 40°C, so that it will not dissolve or solvate in storage; it is able to solvate at temperatures above 50°C; it is able to be ground to form particles between 0.1 micron and 5 microns in diameter; it is able to form a particle of less than 10 microns; it is able to fuse at temperatures in excess of 70°C; by solvation, the polymers forming the toner particles will become swollen or gelatinous. This indicates the formation of complexes by the combination of the molecules of the polymer with the molecules of the dispersant liquid.
• Landa et al. '683 discloses three methods of forming toner particles having the desired fibrous morphology.
• the first method briefly includes dispersing or dissolving pigment particles in a plasticized polymer at temperatures between 65°C. and 100°C.
• the plasticized material when cooled has the form of a sponge.
• the sponge is then broken into smaller pieces and ground.
• Another method includes dissolving one or more polymers in a nonpolar dispersant, together with particles of a pigment such as carbon black or the like.
• the solution is allowed to cool slowly while stirring, which is an essential step in this method of forming the fiber-bearing toner particles. As the solution cools, precipitation occurs, and the precipitated particles will be found to have fibers extending therefrom.
• a third method is to heat a polymer above its melting point and disperse a pigment through it.
• fibers are formed by pulling the pigmented thermoplastic polymer apart without first forming a sponge.
• the fibrous toner particles formed by any of the foregoing methods, are dispersed in a nonpolar carrier liquid, together with a charge director known to the art, to form a developing composition.
• Landa et al. '683 discloses a toner particle formed with a plurality of fibers- that is to say, one with such morphology.
• Such a toner particle enables forming a developing composition for developing latent electrostatic images by dispersing the toner particles in small amounts in a nonpolar liquid such as an ISOPAR.
• the weight of the toner particle may be as low as 0.2 percent by weight of the weight of the dispersant liquid.
• the toner particle is pigmented and formed of a polymeric resin.
• a charge director is added to the composition in small amounts, which may be as low as one-tenth percent by weight of the weight of the toner particles in the developing composition.
• the charge director may be selected to impart either a positive or a negative charge to the toner particles, depending on the charge of the latent image. Those in the art will understand that the charge on the toner particles is generally opposite in polarity to that carried by the latent electrostatic image.
• the nonpolar dispersant liquids are, preferably, branched-chain aliphatic hydrocarbons-more particularly, ISOPAR-G, ISOPAR-H,
• ISOPAR-K ISOPAR-K
• ISOPAR-L ISOPAR-M
• ISOPAR-M ISOPAR-M
• Light mineral oils such as MARCOL 52 or MARCOL 62, manufactured by the Humble Oil and Refining Company, may be used. These are higher boiling aliphatic hydrocarbon liquids.
• the polymers used in Landa et al. '683 are thermoplastic, and the preferred polymers are known as ELNAX II, manufactured by du Pont, including resin numbers 5550; 5610; 5640; 5650T; 5720; and 5950.
• the original ELNAX resins (ENA) were the ethylene vinyl acetate copolymers.
• the new family of ELNAX resins, designated ELNAX II are ethylene copolymers combining carboxylic acid functionality, high molecular weight, and thermal stability.
• the preferred ethylene copolymer resins of Landa et al. '683 are the ELNAX II 5720 and 5610.
• Other polymers which are usable are the original ELNAX copolymers and polybutyl terephthalate.
• Still other useful polymers made by Union Carbide are the DQDA 6479 Natural 7 and DQDA 6832 Natural 7. These are ethylene vinyl acetate resins.
• Other useful polymers are NUCREL ethylene
• Landa et al. '683 also discloses that another useful class of polymers in making the particles are those manufactured by du Pont and sold under the trademark ELNACITE. These are methacrylate resins, such as polybutyl methacrylate (Grade 2044), polyethyl methacrylate (Grade 2028), and polymethyl methacrylate (Grade 2041). If desired, a minor amount of carnauba wax may be added to the composition. However, this tends to produce bleed-through and an oil fringe on the copy and is not preferred. Furthermore, if a hard polymer such as 5650T is used, a minor amount of hydroxy-ethyl cellulose may be added. This is not preferred.
• the polymers of Landa et al. '683 are normally pigmented so as to render the latent image visible, though this need not be done in some applications.
• the pigment may be present in the amount of 10 percent to 35 percent by weight in respect of the weight of the polymer, if the pigment be Cabot Mogul L (black pigment). If the pigment is a dye, it may be present in an amount of between 3 percent and 25 percent by weight in respect of the weight of the polymer. If no dye is used-as, for example, in making a toner for developing a latent image for a printing plate-an amount of silica such as CABOSL may be added to make the grinding easier.
• Examples of pigments are Monastral Blue G (C.I. Pigment Blue 15 C.I. No. 74160), Toluidine Red Y (C.I. Pigment Red 3), Quindo Magenta (Pigment
• Landa et al '683 also discloses that a finely ground ferromagnetic material may be used as a pigment. About 40 percent to about 80 percent by weight of
• Mapico Black is preferred, with about 65 percent Mapico Black being optimum, other suitable materials such as metals including iron, cobalt, nickel, various magnetic oxides including Fe 2 O 3 , Fe 3 O 4 , and other magnetic oxides; certain ferrites such as zinc, cadmium, barium, manganese; chromium dioxide; various of the permalloys and other alloys such as cobalt-phosphorus, cobalt-nickel, and the like; or mixtures of any of these may be used.
• metals including iron, cobalt, nickel, various magnetic oxides including Fe 2 O 3 , Fe 3 O 4 , and other magnetic oxides
• certain ferrites such as zinc, cadmium, barium, manganese
• chromium dioxide various of the permalloys and other alloys such as cobalt-phosphorus, cobalt-nickel, and the like; or mixtures of any of these may be used.
• charge directors as magnesium petronate, magnesium sulfonate, calcium petronate, calcium sulfonate, barium petronate, barium sulfonate, or the like.
• the negatively charged particles are used to develop images carrying a positive charge, as is the case with a selenium-based photoconductor.
• the latent image With a cadmium-based photoconductor, the latent image carries a negative charge and the toner particles must therefore be positively charged.
• a positive charge can be imparted to the toner particles with a charge director such as aluminum stearate.
• the amount of charge director added depends on the composition used and can be determined empirically by adding various amounts to samples of the developing liquid.
• the invention can be practiced using a variety of toner types but is especially useful for toners comprising carrier liquid and pigmented polymeric toner particles which are essentially non-soluble in the carrier liquid at room temperature, and which solvate carrier liquid at elevated temperatures.
• This is a characteristic of the toner of Example 1 of U.S. Pat. No. 4,794,651.
• Part of a simplified phase diagram of a typical toner of this type is shown in Figure 3. This diagram represents the states of the polymer portion of the toner particles and the carrier liquid.
• the pigment in the particles generally takes little part in the process, and references herein to "single phase” and to "solvation” refer to the state of the polymer part of the toner particles together with the carrier liquid.
• the toner is prepared by mixing 10 parts of EL VAX II 5950 ethylene vinyl acetate copolymer (from E. I. du Pont) and 5 parts by weight of ISOPAR L (Exxon) diluent which is not a solvent for the EL VAX II 5950 at room temperature.
• the mixing is performed at low speed in a jacketed double planetary mixer connected to an oil heating unit for one hour, the heating unit being set at 130°C.
• a mixture of 2.5 parts by weight of Mogul L carbon black (Cabot) and 5 parts by weight of ISOPAR L is then added to the mix in the double planetary mixer and the resultant mixture is further mixed for one hour at high speed.
• the preferred liquid developer prepared comprises toner particles which are formed with a plurality of fibrous extensions or tendrils as described above.
• the preferred toner is characterized in that when the concentration of toner particles is increased above 20%, the viscosity of the material increases greatly, apparently in approximately an exponential manner.
• a charge director prepared in accordance with the Example of U.S. Patent No. 5,047,306, "Humidity Tolerant Charge Director Compositions" (Almog), is preferably added to the dispersion in an amount equal to about 3% of the weight of the solids in the developer.
• thermoplastic toner particles are selected from the group consisting of ethylene vinyl acrylate copolymers, ethylene vinyl acetate copolymers, ethylene acrylic acid copolymers, ionomers of ethylene acrylic acid copolymers, and mixtures thereof.
• Dry thermoplastic toners are also useful according to this present invention.
• useful dry toners include but are not limited to those selected from the group consisting of polyester toners (such as those available from Xeikon N.N.). It is theorized that other dry toners would be useful according to the present invention such as styrene/acrylate copolymer available from Lanier Worldwide, Inc.
• an electrostatic image may be produced by providing a photoconductive layer, such as on a rotating drum, with a uniform electrostatic charge and thereafter selectively discharging the electrostatic charge by exposing it to a modulated beam of radiant energy.
• a photoconductive layer such as on a rotating drum
• other methods may be employed to form an electrostatic image, such, for example, as providing a carrier with a dielectric surface and transferring a preformed electrostatic charge to the surface.
• the charge may be formed from an array of styluses.
• a latent image is thus formed on the charged drum.
• Charged toner is deposited on the charged areas of the drum, and the toner is then transferred under heat and/or pressure to the imaging medium 40. Images may be printed on imaging medium 40 using direct image printing or reverse image printing.
• the toner can be transferred in an intermediate step to a transfer member between the charged drum and the imaging medium.
• a liquid toner image is transferred from an image forming surface to an intermediate transfer member for subsequent transfer to a final substrate.
• the liquid toner image includes a liquid portion including carrier liquid and a solids portion including pigmented polymeric toner particles which are essentially non-soluble in the carrier liquid at room temperature, and the polymer portion of which forms substantially a single phase with carrier liquid at elevated temperatures.
• the preferred imaging method generally includes the steps of concentrating the liquid toner image to a given nonvolatile solids percentage by compacting the solids portion thereof and removing carrier liquid therefrom; transferring the liquid toner image to an intermediate transfer member; heating the liquid toner image on the intermediate transfer member to a temperature at least as high as that at which the polymer portion of the toner particles and the carrier liquid form substantially a single phase at the given solids percentage; and transferring the heated liquid toner image to a final substrate.
• Liquid toner images are developed by varying the density of pigmented solids in a developer material on a latent image bearing surface in accordance with an imaged pattern. The variations in density are produced by the corresponding pattern of electric fields extending outward from the latent image bearing surface. The fields are produced by the different latent image and background voltages on the latent image bearing surface and a voltage on a developer plate or roller.
• developed liquid toner images comprise carrier liquid and toner particles and are not homogeneous.
• FIG. 2 illustrates a preferred electrophotographic imaging apparatus 100 for use with the present invention.
• the apparatus is described for liquid developer systems with negatively charged toner particles, and negatively charged photoconductors, i.e., systems operating in the reversal mode.
• toner particle and photoconductor polarity For other combinations of toner particle and photoconductor polarity, the values and polarities of the voltages are changed, in accordance with the principles of the invention.
• the apparatus 100 of Figure 2 typically comprises a drum 110 arranged for rotation about an axle 112 in a direction generally indicated by arrow 114.
• Drum 110 is formed with a cylindrical photoconductor surface 16.
• a corona discharge device 118 is operative to generally uniformly charge photoconductor surface 116 with a negative charge. Continued rotation of drum
• the 110 brings charged photoconductor surface 116 into image receiving relationship with an exposure unit including a lens 120, which focuses an image onto charged photoconductor surface 116, selectively discharging the photoconductor surface, thus producing an electrostatic latent image thereon.
• the latent image comprises image areas at a given range of potentials and background areas at a different potential.
• the image may be laser generated as in printing from a computer or it may be the image of an original as in a copier.
• Development unit 122 may be a single color developer of any conventional type, or may be a plurality of single color developers for the production of full color images as is known in the art. Alternatively, full color images may be produced by changing the liquid toner in the development unit when the color to be printed is changed. Alternatively, highlight color development may be employed, as is known in the art.
• photoconductor surface 116 passes a typically charged rotating roller 126, preferably rotating in a direction indicated by an arrow 128.
• the spatial separation of the roller 126 from the photoconductor surface 116 is about 50 microns.
• Roller 126 thus acts as a metering roller as is known in the art, reducing the amount of carrier liquid on the background areas and reducing the amount of liquid overlaying the image.
• the potential on roller 126 is intermediate that of the latent image areas and of the background areas on the photoconductor surface. Typical approximate voltages are: roller 126: 500 N, background area: 1000 V and latent image areas: 150 V.
• the liquid toner image which passes roller 126 should be relatively free of pigmented particles except in the region of the latent image.
• Rigidizing roller 130 is preferably formed of resilient polymeric material, such as polyurethane which may have only its natural conductivity or which may be filled with carbon black to increase its conductivity. According to one embodiment of the invention, roller 130 is urged against photoconductor surface 116 as by a spring mounting (not shown). The surface of roller 130 typically moves in the same direction and with the same velocity as the photoconductor surface to remove liquid from the image.
• roller 130 is biased to a potential of at least several hundred and up to several thousand Volts with respect to the potential of the developed image on photoconductor surface 116, so that it repels the charged pigmented particles and causes them to more closely approach the image areas of photoconductor surface 116, thus compacting and rigidizing the image.
• rigidizing roller 130 comprises an aluminum core having a 20 mm diameter, coated with a 4 mm thick carbon-filled polyurethane coating having a Shore A hardness of about 30-35, and a volume resistivity of about 10 8 ohm-cm.
• roller 130 is urged against photoconductor surface 116 with a pressure of about 40-70 grams per linear cm of contact, which extends along the length of the drum.
• the core of rigidizing roller 130 is energized to between about 1800 and 2800 volts, to provide a voltage difference of preferably between about 1600 and 2700 volts between the core and the photoconductor surface in the image areas. Voltage differences of as low as 600 volts are also useful.
• the solids percentage in the image portion is believed to be as high as 35% or more, when carrier liquid absorbed as plasticizer is considered as part of the solids portion. It is preferable to have an image with at least 25-30% solids, after rigidizing.
• the solids percentage is preferably above 20% and is usually less than 30%. Values of 25% have been found to be especially useful. At these concentrations the material has a paste like consistency.
• the carbon filled polyurethane can be replaced by unfilled polyurethane with a volume resistivity of about 3 x 10 10 , and the voltage is adjusted to give proper rigidizing.
• LEDs light emitting diodes
• both red and green LEDs are provided to discharge the areas of the photoconductor behind the developed image as well as the background areas.
• an intermediate transfer member 140 which rotates in a direction opposite to that of photoconductor surface 116, as shown by arrow 141. The intermediate transfer member is operative for receiving the toner image from the photoconductor surface and for subsequently transferring the toner image to a the imaging medium 40.
• intermediate transfer member 140 is urged against photoconductor surface 116.
• One of the effects of the rigidization described above is to prevent substantial squash or other distortion of the image caused by the pressure resulting from the urging.
• the rigidization effect is especially pronounced due to the sharp increase of viscosity with concentration for the preferred toner.
• Transfer of the image to intermediate transfer member is preferably aided by providing electrical bias to the intermediate transfer member 140 to attract the charged toner thereto, although other methods known in the art may be employed.
• Subsequent transfer of the image to imaging surface 44 of receptor layer 42, respectively, on the imaging medium is preferably aided by heat and pressure, with pressure applied by a backing roller 143, although other methods known in the art may be employed.
• photoconductor surface 116 is engaged by a cleaning roller 150, which typically rotates in a direction indicated by an arrow 152, such that its surface moves in a direction opposite to the movement of adjacent photoconductor surface 116 which it operatively engages.
• Cleaning roller 150 is operative to scrub and clean surface
• a cleaning material such as toner, may be supplied to the cleaning roller 150, via a conduit 154.
• a wiper blade 156 completes the cleaning of the photoconductor surface. Any residual charge left on photoconductor surface 116 is removed by flooding the photoconductor surface with light from a lamp 158.
• the cycle is sequentially repeated for other colors which are sequentially transferred from photoconductor surface 116 to intermediate transfer member 140.
• the single color images may be sequentially transferred to the imaging medium 40 in alignment, or may alternatively be overlaid on the intermediate transfer member 140 and transferred as a group to the imaging medium.
• the state of the image i.e. of the polymer portion of the toner particles and the carrier liquid
• the state of the image depends on several factors, mainly on the temperature of the intermediate transfer member and on the concentration of toner particles.
• the percentage of toner particles is "A” and the intermediate transfer member temperature is " Y” the liquid image separates into two phases, one phase being substantially a liquid polymer/carrier-liquid phase and the other phase consisting mainly of carrier liquid.
• the percentage of toner particles is "B" at the same temperature, then substantially only one phase, a liquid polymer/carrier-liquid phase will be present.
• heating the image on the intermediate transfer member 140 is not meant to completely dry the image, although some evaporation of carrier liquid may result. Rather, the image on the intermediate transfer member remains a viscous liquid until its transfer to the final substrate.
• the receptor layers of the present invention provide a superior bond to the toners described herein when applied by electrophotographic printing methods just described. This is believed to result from the chemical compatibility between the toner's carrier resin and the receptor layer. Without desiring to be bound by any particular theory, it is presently believed that the thermoplastic toners described herein have a solubility parameter that is a close match to that of the receptor layer. This indicates a chemical compatibility between the receptor layer and the toner polymer resulting in a strong bond between the toner and the receptor layer.
• the imaging media of the present invention are particularly durable and abrasion resistant in addition to being readily printable by the short run methods described herein.
• the method of the present invention employing a dry toner can, for example, employ a copy machine such as Hewlett Packard Laser Jet copy machine available from Hewlett Packard or a Lanier 6540 copier available from Lanier Worldwide, Inc.
• a copy machine such as Hewlett Packard Laser Jet copy machine available from Hewlett Packard or a Lanier 6540 copier available from Lanier Worldwide, Inc.
• the imaging media of the present invention are well suited for use as labels, tags, tickets, signs, data cards, name plates, graphic overlays, and packaging films, for example, although the uses of the imaging media of the present invention are not thereby limited.
• the imaging medium of the present invention typically has a T-Peel adhesion value of at least about 32 oz/in (358 g/cm), preferably at least about 60 oz/in (671 g/cm), and most preferably at least about 80 oz/in (894 g/cm).
• the imaged medium of the present invention typically has a print quality value of at least about fair, preferably at least about fair/good, and most preferably at least about good, when printed by either or both the Xeikon and Indigo printing methods such as those described later herein.
• the imaged medium of the present invention typically has a Taber abrasion resistance value of at least about 6 (most typically at least 6), preferably at least about 7, and most preferably at least about 8 when printed by either or both the Xeikon and Indigo printing methods such as those described later herein (as well as other electrophotographic printing methods).
• the above described properties can, for example, be measured on an image which is produced by a four-color process (yellow, magenta, cyan, black). Such a four-color process was used according to the test methods and examples below.
• T-peel adhesion of heat sealed samples was measured using two samples, each 4-5 inches (10.2-12.7 cm) down-web by 6 inches (15.2 cm) cross-web, cut from an imaging medium comprising a receptor layer and a backing.
• the two cut samples were placed receptor layer to receptor layer and put in a heat sealer (Model No. 12 AS, from Sentinel Machinery Packaging Industries, Montclair, NJ) set at 300°F (149°C) with a pressure of 40 p.s.i. (19.5 g/cm 2 ) and a dwell time of 1 second.
• the resultant heat sealed sample was removed from the heat sealer and stored at about 73°F (22.8°C)/50% relative humidity for about 24 hours.
• test sample Three strips, each 2.5 cm wide and 10.2 cm long, were cut from the heat sealed sample perpendicular to and across the sealed area to form a test sample of about 1 inch (2.54 cm) square with unsealed leaders on each edge.
• One leader of the test sample was clamped in the upper jaw of an INSTRON Tensile Tester (Model No. 1123) and the other leader was clamped in the lower jaw of the tensile tester.
• the test sample was separated at a rate of 12 inches (30.48 cm)/minute.
• the Indigo press utilized was a Scorpion model press available from Indigo.
• the Xeikon press utilized was a DCP-1 model press available from Xeikon.
• the imaging medium was web fed into the press at 200 steps using a blanket setup temperature of 140°C.
• the liquid toner used with the Indigo press was an ethylene vinyl acetate based toner known as ELECTROINK for E-PRINT 1000 manufactured by Indigo Ltd. of Rehovot, Israel.
• the imaging medium was also web fed by using radiation heat to fuse the powder toner of the image at approximately 400° (204.4°C)
• the dry powder toner used with the Xeikon press was a polyester toner available from Xeikon under the name Xeikon toner.
• the print quality was assessed visually by holding the printed film at normal reading distance (about 12 inches [30.5 cm]) from the naked eye. "No Printing” indicates that no portion of an image was transferred from the blanket to the receptor; “Poor” indicates that less than about 50% of the image was transferred; “Fair” indicates that 50-80% of the image was transferred; “Fair/Good” indicates that greater than 80% but less than 95% of the image was transferred; and “Good” indicates that at least about 95% of the images was transferred.
• Comparative Examples 1-2 films of each receptor layer material were independently heat sealed directly onto a 5 mil (0.13 mm) thick PC film (No. 8 A35; from General Electric).
• the receptor layer films of Comparative Examples la-lc were 2-layer composites of polyethylene terephthalate ("PET”) and polyethylene; commercially available from Minnesota Mining and Manufacturing Company (3M Company) under the trademark SCOTCHPAKTM.
• PET polyethylene terephthalate
• SCOTCHPAKTM commercially available from Minnesota Mining and Manufacturing Company
• Heat sealed samples of Comparative Examples la-lc were prepared as described in the T-Peel Adhesion Test with the PC film being placed on the bottom platen when being heat sealed. Strips cut from the heat sealed sample were tested as described in the T-Peel Adhesion Test.
• the receptor layer film as obtained from the manufacturer was heat sealed directly to the PC film.
• the PC film was on the top when heat sealed. Samples were cut, heat-sealed and strips measured for adhesion using the T-Peel Adhesion Test.
• the receptor layer polymers were independently melted and extruded at 1.5 mil (0.038 mm) coating thickness onto 0.56 mil (0.014 mm) PET film and UV irradiated at 280°F (138°C).
• the UV light power was 157 watts/cm
• the web speed was about 10 meters/minute
• the distance of the UV light source was about 5.1 cm from the receptor layer.
• Samples of the receptor layer/PET composite were cut and heat sealed to PC film according to the T-Peel Adhesion Test. For these examples, the PC film was on the bottom when heat sealed.
• the T-Peel Adhesion Test results (in g/cm) reported in TABLE I are the average of three independent determinations. "Poor" indicates that the adhesion of the receptor layer to the backing was so weak that it could not be measured by the tensile tester or that the receptor layer had delaminated from the backing.
• Print quality was assessed using the Print Quality Test.
• Ethylene/butene copolymer MI of about 3.5 g/10 min.; density of 0.900 g/cc; available from Exxon.
• Ethylene/hexene copolymer MI of about 3.5 g/10 min.; density of 0.900 g/cc; available from Exxon.
• Ethylene acrylic acid copolymer MI of about 10.5 g/10 min.; acrylic acid content of about 9.0%; available from duPont.
• Anhydride modified LDPE MI of about 5.3 g/10 min.; available from duPont.
• Anhydride modified LLDPE MI of about 4.0 g/10 min.; available from duPont.
• An imaging medium comprising a single receptor layer and a PC backing was prepared using the resin(s) set out in TABLE II as the respective receptor layers.
• pellets of the resin indicated were melted and extruded at a 1.5 mil (0.038 mm) coating thickness onto a PC film backing used for Comparative Examples 1-6.
• pellets of the two resins were mixed by dry blending. The blended resins were melted and extruded onto the PC film backing.
• the die temperature was 400°F (205°C).
• EVA Ethylene vinyl acetate
• VA vinyl acetate
• Imaging media comprising a receptor layer and a PC backing (used for
• Comparative Examples 1-6 were prepared using the resins, ELVAX 3175 and BYNEL 2002, and a UV light inhibitor (Sanduvar 3051; from Clariant Corporation, Charlotte, NC), UV light absorber (Cyasorb UV-5411; from Cytec Industries Inc., Stanford, CT) and antioxidant (Sandostab P-EPQ; from Clariant Corporation, Charlotte, NC).
• a UV light inhibitor Sanduvar 3051; from Clariant Corporation, Charlotte, NC
• UV light absorber Cyasorb UV-5411; from Cytec Industries Inc., Stanford, CT
• antioxidant Sandostab P-EPQ; from Clariant Corporation, Charlotte, NC
• pellets of the resins and the additives were dry blended, melted and extruded at 1.5 mil (0.038 mm) coating thickness onto the PC film backing.
• the extruder temperature profile and the die temperature were as described for Comparative Examples 7-9 and Examples 10-21.
• the color stability of reverse image printed samples was evaluated by measuring in reflection the L*, a* and b* color coordinates of the samples.
• the color coordinates were obtained by the CIELAB (CIE 1978) color determination methods described in Billmeyer & Saltzman, Principles of Color Technology. 2nd Ed., pp 62-65 (1981).
• Fifty samples of each Ex. No. were reverse image printed using the Indigo press.
• Two imaged samples of each example were evaluated to determine the initial sample's a* (red) color value using a Spectro Sensor II colorimeter; from ACS Applied Color Systems, Charlotte, NC).
• TABLE III Set out in TABLE III are the amounts of UV light inhibitor and UV light absorber for receptor layers each containing 82% ELVAX 3175, 18% BYNEL 2002 and 0.15% antioxidant. All the values in TABLE III are in weight percent.
• the a* Value represents the red color remaining after aging.
• the data in TABLE III show the good red color retention of the imaged medium of the invention compared to Comparative Example 26 containing no UV light inhibitor and Comparative Example 27 containing neither UV inhibitor nor UV light absorber.
• the negative a* Values for Comp. Ex. Nos. 26-27 represent the fact that all the magenta color had disappeared.
• the composition of Example 24 with 0.75% UV inhibitor and 0.75% UV absorber exhibited particularly good magenta color retention.

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• 1997
  • 1997-04-30 US US08/846,398 patent/US5858516A/en not_active Expired - Fee Related
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