Energy activated electrographic printing process

#This invention relates to a printing processes, and is specifically directed to a process of producing a permanent image on a substrate by means of an electrographic or electrostatic printer using a thermally crosslinkable toner that is cured by radiation to promote cohesive strength within the image.

#In general, textile printing involves substrates with much higher surface roughness, and much higher absorption of liquid inks than paper. Textile printing techniques known in the art for printing onto clothing, other textile materials, and other objects include silk screening, digitally produced sublimation transfers, and mechanically bonded thermal transfers. Of these methods, it is not economical to produce customized products with silk screening printing. Digitally produced sublimation transfer printing is limited to synthetic fibers or pre-treated nature fibers. Finally, direct digital textile printing requires special expensive printing devices to pretreat and post treat the fabric.

#Images printed onto garments and other textiles may be permanently bonded or crosslinked to a final substrate to obtain high adhesive strength, and crosslinked within the images to obtain high cohesive strength. Both means of crosslinking are required to provide excellent resistance to chemical processes, such as cleaners or laundry products, and deterioration from normal use. Pure cohesive strength, which mechanically bonds the image to the substrate through internal crosslinking within the printed image, does not permanently bond colorants to textile fibers. Thermal transfers, wherein the ink mechanically bonds to the substrate, are described in Hare, U.S. Pat. No. 4,773,953. The surface bonded image has a substantial ‘hand,’ with a raised, plastic-like feel to the touch, and relatively poor dimensional stability. In addition, the non-imaged area of the transfer sheet used with the process is transferred to the substrate, without chemical bonding or cross-linking processes (Hatada, U.S. Pat. No. 6,103,042, Koerner, et al. U.S. Pat. No. 5,978,077, de Beeck, et al. U.S. Pat. No. 5,985,503, Clemens, U.S. Pat. No. 4,066,802, Mammino, U.S. Pat. No. 4,064,285, Taniguchi, U.S. Pat. No. 5,981,077, Tada, et al. U.S. Pat. No. 6,017,636, DE-A 27,27,223, EP-A 466,503, JP-A 63296982, WO 90/13063). Olsen, et al. U.S. Pat. No. 5,785,790, Olsen, et al. U.S. Pat. No. 5,679,198, and Olsen, et al. U.S. Pat. No. 5,612,119 disclose a screen-printed support sheet, which may have an embedded layer of microspheres, printed with one or more layers of two-component colors based on polyester resin and an isocyanate hardener. The microspheres may have a reflective layer to allow the transferred image printed thereon to reflect light. If more than one color layer is printed onto the microspheres, then a two-component extender or glue that contains a polyester is covered on top of each color layer. On top of the extender layer or single-color layer is applied a powder of polyester or polyamide elastomer, which is then fused into the color layer. Instead of screen printing, a color copier using a two-component toner may be used for applying the color coatings. The color coatings are subsequently covered with this elastomeric powder, which is then fused into the layer prior to transfer.

#In a preferred embodiment, a video camera or scanning device is used to capture an image. The image is then input into a computer. Alternatively, a computer may create the image, or the computer may modify the captured image. The computer directs an electrographic device, such as a laser printer or photocopier, to print the image. Any means of creating or forming an image could be used, such as software generated images. Available computer design graphic software may be used, or still photography may be used. The design may be photographic, graphic/artistic, or simply letters or words. The use of cyan, yellow and magenta toner compositions allow the printer to print multi-color designs as directed by the computer. Black toner may be used. In addition, spot colors may be used to increase the color gamut or imaging efficiency.

#Electrophotographic and electrostatic printing devices are designed for imaging on limited type of substrates such as paper or other thin sheets of material. These materials have surface the characteristics and flexibility suitable for a printable substrate. Other materials, including fibrous textiles, metals, and smooth plastics, do not possess the appropriate shape, or the appropriate physical and/or chemical properties, or do not provide acceptable image adhesion required for image permanency, that will permit such materials to be used as substrates that are printable by electrophotographic and electrostatic devices. Electrographic devices are not designed to handle and print directly upon either rigid or highly flexible materials without significant modification of the device, if at all.

#In a preferred embodiment of the present invention, energy-activated electrographic toners or inks are used to produce an image on a transfer substrate or final substrate. The substrate may be a textile substrate. Preferably, at least two energy sources are used as part of the process. The energy sources may be heat and radiation applied simultaneously or separately. The toner or ink may comprise one or more combinations of heat and radiation curable components, thermoplastic resins, a colorant, one or more photoinitiators, one or more thermal initiator, wax, a heat-activated printing additive, an external additive, and an internal additive. The resulting permanent image has excellent adhesion properties, cohesive strength within the image material, improved fastnesses, controlled ‘hand’, and is energy efficient. Three dimensional and oddly shaped objects, which cannot be directly printed upon by the digital printer, can be imprinted by transferring the image from a transfer substrate, such as paper, that is directly printed upon by the printer.