Image transfer product including a phase change material

Abstract

An image transfer product is provided which includes a phase change material in one or more layers of the product to regulate the temperature of the product during printing operations. The image transfer product may be in the form of a printing blanket, printing sleeve, electrophotographic/xerographic transfer blanket, image transfer belt, or roller which includes a print surface layer and at least one layer underlying the printing surface layer. The phase change material may be included in any of the layers of the image transfer product, but is not present at the upper surface of the print surface layer. The phase change material may be in the form of a powder, fibers, capsules, or combinations thereof.

Claims

1. An image transfer product comprising a printing blanket or sleeve including a print surface layer, an elastomeric layer directly underlying said print surface layer, at least one fabric layer underlying said print surface layer, and a compressible layer underlying said print surface layer; wherein at least one of said layers includes at least one phase change material therein for regulating the temperature of said image transfer product ,said at least one phase change material has a melting point of from about 18° to about 45° C., and wherein said phase change material is not present in the upper surface of said print surface layer.

2. The image transfer product of claim 1 wherein said at least one phase change material is in the form of a powder, fibers, filled spheres/microcapsules, or a combination thereof.

3. The image transfer product of claim 1 comprising a printing blanket or sleeve including a print surface layer, an elastomeric layer directly underlying said print surface layer, at least one fabric layer underlying said print surface layer, and a compressible layer underlying said print surface layer; wherein at least one of said layers includes two phase change materials having different melting points therein for regulating the temperature of said image transfer product and wherein said phase change materials are not present in the upper surface of said print surface layer.

4. The image transfer product of claim 1 including a thermal conductivity agent.

5. The image transfer product of claim 4 wherein said thermal conductivity agent is selected from the group consisting of aluminum oxide, aluminum nitride, boron nitride, and graphite.

6. The image transfer product of claim 1 wherein said printing surface layer is selected from the group consisting of nitrile rubber, hydrogenated nitrile butadiene rubber, polysulfide rubber, butyl rubber, EPDM rubber, polyacrylate rubber, thermoplastic and thermosetting polyurethanes, silicones, fluorosilicones, fluoropolymers, and mixtures or alloys thereof.

7. The image transfer product of claim 1 wherein said phase transfer material is in the form of particles located in said print surface layer, and wherein the portion of the upper surface of said print layer in which said phase change material is not present is at least twice the diameter of the particles of said phase change material.

8. The image transfer product of claim 1 wherein all of said layers include a phase change material therein.

9. The image transfer product of claim 1 wherein said phase change material is incorporated only in said elastomeric layer.

10. The image transfer product of claim 1 wherein said phase change material is incorporated only in said at least one fabric layer.

11. The image transfer product of claim 1 wherein said printing blanket includes additional fabric layers, wherein said phase change material is incorporated only in the fabric layer in the closest proximity to said print surface layer.

12. The image transfer product of claim 1 comprising a printing sleeve including a base sleeve comprised of metal, a polymer, or a composite, wherein said print surface layer and said at least one layer directly underlying said print surface layer are over said base sleeve.

13. The image transfer product of claim 12 wherein said at least one layer directly underlying said print surface layer comprises an image reinforcement layer comprising wound cord, a polymeric film, or fabric.

14. An image transfer product comprising a printing blanket or sleeve including a print surface layer, and at least one additional layer selected from the group consisting of an elastomeric layer directly underlying said print surface layer, a fabric layer underlying said print surface layer, and a compressible layer underlying said print surface layer; wherein at least one of said print surface layer or at least one of said additional layers includes at least one phase change material having a melting point of from about 18° C. to about 45° C. therein for regulating the temperature of said image transfer product, and wherein said phase change material is not present in the upper surface of said print surface layer.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a cross-sectional view of a printing blanket construction including a phase change material therein in accordance with an embodiment of the invention;

(2) FIG. 2 is a cross-sectional view of a printing blanket construction including a phase change material in accordance with another embodiment of the invention;

(3) FIG. 3 is a cross-sectional view of a printing blanket construction including a phase change material therein in accordance with another embodiment of the invention;

(4) FIG. 4 is a cross-sectional view of a printing sleeve including a phase change material therein in accordance with another embodiment of the invention;

(5) FIG. 5 is a cross-sectional view of a printing roller including a phase change material therein in accordance with another embodiment of the invention; and

(6) FIG. 6 is a cross-sectional view of an image transfer belt including a phase change material therein in accordance with another embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

(7) The use of a phase change material in an image transfer product helps to regulate the temperature of the image transfer product, and in particular, the temperature of the print surface, to provide a consistent temperature for image transfer. For example, if the printing process is running under steady state conditions but the ambient temperature begins to rise, the phase change material will absorb sufficient energy to prevent or delay the increase of the temperature of the print surface of the image transfer product. By maintaining the temperature within a narrow range, the ink, dry toner, or liquid toner image is transferred more consistently. In instances where there is a variation in substrate thickness which could cause heating of the image transfer product, the increased heat produced is absorbed by the phase change material to reduce or delay the temperature effects on image transfer.

(8) The phase change material(s) should be placed as close to the print surface layer as possible in order to stabilize the temperature of the print face as this will increase consistency of toner/ink transfer and thereby increase print quality. While the print surface layer may also contain a phase change material, it should be appreciated that the top print face, i.e., the upper surface portion of the print face layer, should not contain any phase change material in order to avoid distortion when the phase change material(s) in underlying layer(s) change from liquid to solid form and vice versa. Thus, the top surface of the print face layer should have a minimum thickness which does not contain a phase change material in order to remain flat during phase changes. Preferably, the portion of the print face layer which does not contain a phase change material should be at least two times the diameter of the largest capsules/particles of phase change material. For example, if the layer just below the print face layer contains phase change particles having a diameter of 25 micrometers, the top surface of the print face layer should have at least 50 micrometers of thickness containing no phase change materials.

(9) The phase change materials may be in the form of fibers having an encapsulated PCM core, microcapsules, or a powder comprising fine particles/granules of phase change material. The image transfer product may include any combination of these phase change materials in one or more of its layers. For example, where the phase change material comprises fibers, it may be incorporated in the fiber, fabric or wound cord layer of an image transfer product. Such phase change fibers may be incorporated into fabrics, for example, by twisting them into the threads or yarns of the fabric prior to weaving. Alternatively, the phase change materials may be added in place of certain warp or fill yarns as long as they do not prevent the resulting fabric from meeting its mechanical specifications.

(10) Where the phase change material comprises microcapsules, it may be added to the microspheres in a compressible layer. Where the phase change material is in powder form, i.e., fine particles/granules, it may be included in elastomer layers. The microencapsulated and particulate phase change materials may be added into image transfer product layers by milling into rubber materials, for example, by mixing with liquid forms of elastomers such as dissolved rubber/solvent liquids or liquid silicones prior to curing and solidification. Fabric layers may also be infused with or coated with phase change materials in microencapsulated form by methods such as dip coating.

(11) Examples of suitable image transfer product constructions and layer compositions are described in commonly assigned U.S. Pat. Nos. 4,015,046, 4,770,928, 6,205,920, and 6,703,095, the disclosures of which are incorporated herein by reference.

(12) Depending on the type of image transfer product, all three forms of a phase change material may be incorporated in the same image transfer product.

(13) Suitable phase change materials for use in embodiments of the image transfer product include microencapsulated phase change materials commercially available from Microtek Laboratories, Inc., fiber phase change materials commercially available from Outlast Technologies LLC, and powder phase change materials commercially available from Rubitherm GmbH under the designation RUBITHERM®. For example, a tensioned or non-tensioned offset transfer blanket may include granulated (PCM28) or microencapsulated (MPCM28) phase change materials from Microtek having a melting temperature of 28° C. A transfuse transfer product for liquid or solid toner transfer may utilize a solid-solid PCM powder (X120) available from PCM Products Ltd. to maintain a consistent temperature of 120° C. for thermal transfer. Such phase change materials may also be incorporated into image transfer products comprising belts or cylindrical sleeves.

(14) The phase change materials may be used in combination with thermally conductive agents including, but not limited to, aluminum oxide, aluminum nitride, boron nitride, and graphite. The thermal conductivity agents enhance the performance of the phase change materials by enhancing the flow of heat energy into and out of the PCMs, helping to maintain a uniform temperature throughout the image transfer product. The thermal conductivity agent(s) may be provided in the form of powders which are incorporated in the product layers with the phase change materials.

(15) Referring now to FIG. 1, one embodiment of an image transfer product is shown in the form of an offset printing blanket 10. Typically, the printing blanket will comprise a print surface layer (about 0.008 to 0.20 inches thick), a compressible layer (about 0.010 to 0.030 inches thick), one or more elastomeric layers (each about 0.001 to 0.010 inches thick), and one or more underlying fabric layers (each about 0.008 to 0.016 inches thick). In the embodiment shown, the blanket includes a print face layer 12, an elastomeric layer 14 directly underlying the print surface layer, a fabric layer 16, a compressible layer 18, and fabric layers 20, 22, and 24. In the embodiment shown, a phase change material 30 is incorporated just below the print surface layer in elastomeric layer 14. In the embodiment shown, the elastomeric layer 14 preferably comprises a flexible adhesive rubber formulation.

(16) Referring now to FIG. 2, another embodiment of an image transfer product is shown comprising a printing blanket 10 in which the phase change material 30 is included only in the fabric layer 16 which is closest to the print surface layer 12.

(17) FIG. 3 illustrates yet another embodiment of an image transfer product comprising a printing blanket 10 in which the phase change material 30 is incorporated into each of the blanket layers, including a portion of the printing surface layer 12. In this embodiment, the phase change material may be provided in different forms as described above, depending on the layer composition. The phase change materials used may also have varying ranges of melting points so as to maintain the desired temperature for the image transfer product and/or print surface layer.

(18) FIG. 4 illustrates another embodiment of an image transfer product comprising a printing sleeve 40. In the embodiment shown, the sleeve includes a base layer 42, an optional compressible layer 44 containing phase change material 30, a print surface layer 12, and a layer 46 directly underlying the print surface layer which may be comprised of fabric, filaments/wound cord, or a polymeric film. In one embodiment, the sleeve may be in the form of an electrophotographic or xerographic transfer sleeve, where the layer underlying the print surface layer functions as an image reinforcement layer.

(19) FIG. 5 illustrates another embodiment of an image transfer product comprising a print roller 50 which includes a phase change material therein. As shown, the print roller includes an inner metal shaft 52, an elastomer layer 54 containing a phase change material 30, and an outer print surface layer 12.

(20) FIG. 6 illustrates yet another embodiment of the image transfer product comprising an image transfer belt 60 including a print surface layer 12, a compliant layer 62 underlying the print surface layer, and a base layer 64. The compliant layer may comprise silicones, rubbers, polyurethanes, fluorosilicones, fluorocarbons, EPDM, ethylene-propylene copolymers, elastomers, encapsulated microspheres, and blends thereof. The base layer may comprise a reinforcing layer of fabric or film. Where the base layer comprises a film, suitable polymers include, but are not limited to, polyester, polyethylene, polypropylene, polyethylene terephthalate, polyethylene naphthalate, polyethylene imine, polyphenylene sulfide, nylon, polyimide, polycarbonate, and polyetherimide. The belt may further include a compressible layer (not shown). In the embodiment shown, the phase change material 30 is included in the compliant layer 62. A phase change material may also be present in the base layer when the layer comprises fabric. The image transfer belt as shown may also include electrically conductive materials therein so that it may function in an electrophotographic/xerographic print process.

(21) As described above, the melting points of the phase change materials may vary, depending on the particular image transfer product in which they are incorporated and the press or print engine where they will operate. For example, when the phase change material(s) are used in an offset printing blanket or sleeve, the preferred melting point is between about 18° C. to 45° C., and most preferably, about 30° C. Examples of phase change materials having this melting point range include MPCM-28D (available from Microtek) and Rubitherm® PX31.

(22) It should be appreciated that if more than one phase change material is used in a product, the melting points of such materials may be chosen to provide consistent temperature control under varying conditions.

(23) For an electrophotographic blanket or image transfer belt, the phase change material(s) preferably have a melting point of between about 18 to 35° C., and more preferably, about 25° C. Examples of suitable phase change materials having melting points in this range include Rubitherm® RT25 or Microtek MPCM24.

(24) For image transfer products used on inkjet hybrid or liquid toner presses, the operating temperature will fluctuate with each print cycle/image transfer product (ITP) revolution. The image transfer product typically picks up the image at relatively low temperatures of about 100° C. (via inkjet or electrostatic transfer), then rapidly heats it on the image transfer product to a tack or melt point of about 160° C. for transfer to the intended substrate through a nip. Two different phase change materials may be added to stabilize these upper and lower temperatures for more consistent transfers at each point. For example, Rubitherm® RT90HC and PCM-X165 (available from PCM Products Ltd.) may be used in combination.

(25) It should be appreciated that for each image transfer system such as an offset printing press, there is a typical operating temperature, such that blankets produced for a particular press can be designed to function at a specific operating temperature. The melting points of the phase change materials may be selected for a blanket which operates in a particular operating range so as to provide optimal temperature control. The same consideration will apply to other types of image transfer systems which have their own respective operating temperatures or dual temperatures as described above with regard to transfuse blankets.

(26) It should also be appreciated that the image transfer products described herein may be constructed according to conventional methods known in the art and may vary in their layer structure.

(27) Having described the invention in detail and by reference to preferred embodiments thereof, it will be apparent that modifications and variations are possible without departing from the scope of the invention.