Method for printing a graphic on fabric

Abstract: A method for printing a graphic on fabric using a thermal transfer printer is disclosed. According to the invention, a colorant which forms the graphic and a binder for adhering the colorant to the fabric are printed on only those portions of the fabric covered by the graphic. Thermal transfer ribbons for carrying out the method of printing are also disclosed.

Description: The present invention relates to printing graphics, such as alphanumeric symbols, designs, logos and other artwork, on fabric. More particularly, the present invention relates to printing graphics on fabric using a thermal transfer printer in a method described in the generic part of claim 1. In this method which is known from EP 0 496 337 A1, graphics are printed on fabric using a thermal transfer process. In such a process a thermal transfer ribbon, including a colorant layer of pigment dispersed in a wax, resin or wax-resin vehicle, is used to print the desired graphic onto a thermally stable substrate, such as thermal paper, coated with a resin binder. The printed paper is then placed print side down on the fabric, and the colorant is transferred to the fabric in a press by the application of heat and pressure. The resin binder is also transferred, and the resin binds the colorant to the fabric. Generally, the printed graphic is defined by one or more print areas covered by the colorant and adjacent "white" or non-print areas. However, since the entire surface of the thermal paper is coated with the binder, binder transfers to the fabric throughout this adjacent, non-print area, as well as in the areas covered by the colorant. The binder gives the non-print areas of the fabric an undesirable hand or texture and also seals the fabric weave together, which prevents the free passage air and moisture through the fabric in the non-print areas. Further, the resin binder is not transparent and leaves a shadow around the graphic. The resin shadow is particularly noticeable on colors other than white. Thus, the above-described method of printing is generally limited to use with white fabrics. According to an alternative process, typically used in most high volume applications, the thermal transfer is prepared by screen printing or lithographically printing a desired graphic onto a thermally stable substrate. Since both processes employ inks instead of the pigmented wax or resin compounds described above in connection with thermal transfer ribbons, the resin binder and its associated disadvantages are eliminated. However, screen printing and lithographic printing, are labor intensive processes requiring artwork, ink mixing, color separation, printing screens or color separation films, a UV exposure step, and the use of emulsions, developers and other chemicals in addition to the inks. Moreover, the prepared screens or films can be use to print single size designs only. It is the problem to be solved by the invention to provide a method wherein the graphic is printed using a thermal printer and the final product is coated with binder in only those areas corresponding to the print area of the graphic. The invention solves this problem by the features of the independent claim. Advantageous further developments are described in the dependent claims. The invention is useful for printing graphics by means of a transfer on a wide variety of fabrics including cotton, polyester, cotton-polyester blends, wool, nylon, silk, rayon and rayon-polyester blends. The only limitation with respect to the fabric is that the fabric must have sufficient thermal stability to withstand the heat and pressure of the transfer press. Moreover, since binder is applied only to the print area of the fabric according to the invention and the resin shadow typical of the prior art is eliminated, the invention can be used with fabric of any color. The invention will now be further described with reference to the drawings wherein : Fig. 1 is a schematic diagram illustrating a system for printing graphics on fabric according to the present invention, Fig. 2 is a schematic side view of a thermal printer for use in the system shown in Fig. 1. Figure 1 illustrates a microprocessor based system, generally designated 10, having apparatus for printing graphics on fabric. To print a graphic, such as the graphic P, the system 10 includes a digitizer 12 or other data input device which supplies a computer 14 with machine readable data defining the graphic to be printed. From the data defining the graphic, the computer 14 generates a printing program for operating a thermal printer 16 that prints the graphic on a thermally stable substrate. The program is stored in memory 18, and when the graphic is to be printed, a controller 20 reads the program and operates the printer. Once the graphic has been printed on the substrate, it is transferred from the substrate to the fabric in a thermal transfer step carried out in press 22. A thermal printer useful in practicing the invention is illustrated schematically in Fig. 2. The printer, generally designated 16, includes a roller platen 24 over which the thermally stable substrate S passes relative to a thermal print head 26. The substrate S is supplied in sheet or strip form and may be any thermally stable medium known to those skilled in the art for use in thermal transfer printing processes. However, in the illustrated embodiment of the invention, the substrate S is either a thermal paper available from, for example Hobart-Macintosh, Inc., Elk Grove Villiage, II., under the trade designation "SOFTtrans", coated with a paraffin-based wax, or a polyethylene coated paper available from, for example, Lamart Corp., Clifton, NJ. As the thermal paper passes over the platen 24, the print head is pressed downwardly onto the paper and generally establishes a linear zone of contact between the paper and the platen. A cassette 28 supplies a thermal transfer ribbon 30. The ribbon 30 extends from a supply roll 32, between the print head 26 and the platen 24, to a take-up roll 34 of the cassette. The colorant layer of the ribbon comprises pigment dispersed in a wax, a resin or wax-resin vehicle. Typical wax vehicles include, for example, carnauba montan, beeswax, ceresine, haze, candelila, spermaceti, paraffin and microcrystalline wax. Resin vehicles used in formulating the colorant layer include, for example, low molecular weight polyethylene and polystyrene, vinyl polystearate, petroleum resins, polyamide resins, acrylic resins, PVC, PVA and ethylene-vinyl acetate copolymers. Mixtures of these and other waxes and resins well-known to those skilled in the art are also used to formulate the colorant layer. The colorant layer may further include additional compounds such a softening agents and plasticizers. For multi-color graphics, the ribbon may include only a single pigment in the colorant layer, in which case the cassette 28 must be changed as each color of the graphic is printed sequentially. Alternatively, the ribbon 30 may be formulated with a standard CMYK colorant layer set, in which case process color printing can be carried out with a single cassette to print the multicolored graphic on thermal paper. The binder used for coating the thermally stable substrate must form a clear, colorless film of uniform thickness which encloses the pigment and adheres it to the fibers. Synthetic polymer binders based on acrylic acid and butadiene and vinyl acetate are preferred. Binders that have been found to be particularly suitable include an acrylic colloidal solution available from Johnson Polymer, Racine WI, under the trademark JONCRYL 91, an acrylic aqueous solution available from Lawter International, Inc. under the trade designation HYDRO-REZ 2000, and an acrylic aqueous solution available from Miles, Inc., Pittsburgh, PA under the trade designation Acramin Binder GD. According to the invention, a thermal printer, such as the printer illustrated in Fig. 2, and an associated ribbon are used to print colorant, according to data defining the graphic to be printed, onto a thermally stable substrate, such as thermal paper, coated with a film of resin binder. A computer-controlled plotter having a cutting blade and provided with machine-readable data defining the graphic is then used to cut around the graphic after which those portions of the resin film which are not covered with colorant are removed. Thus, according to this method, the thermal transfer comprises the thermally stable substrate covered with resin and colorant only in the print area corresponding to the graphic.

Claims: A method for printing a graphic on fabric, said method comprising the steps of: (a) providing a thermal transfer printer (16) having a ribbon (30) including a carrier layer and a layer of colorant supported on the carrier layer; (b) providing the thermal printer (16) with data defining the graphic to be printed on the fabric; (c) coating a thermally stable substrate (S) with a film of binder for the colorant; (d) causing the thermal printer (16) to print the colorant onto the substrate (S) according to the data to form a print area on the substrate (S) including binder and colorant and an adjacent non-print area of the substrate including the binder film only; and (e) thermally transferring the colorant and binder from the print area of the substrate (S) to the fabric to print the graphic on the fabric, characterized by (f) removing the binder film from the non-print area of the substrate (S) before step (e) by means of providing a computer-controlled plotter having a cutting blade and provided with machine-readable data defining the graphic; and cutting around the graphic and removing portions of the binder film which are not covered by the colorant. The method of claim 1 wherein the colorant layer comprises pigment dispersed in a vehicle selected from the group consisting of: wax, resin and wax-resin. The method of claim 1 or 2 wherein the carrier layer of the ribbon (30) is polyester. The method of claim 1, 2 or 3 wherein the step of providing the thermal printer (16) with data includes: providing a data input device (12) with machine-readable data; providing a computer (14) for operating a printing program which defines the graphic to be printed by the thermal transfer printer (16); and supplying machine-readable data from the data input device (12) to the printing program of the computer (14) for operating the thermal printer (16) to print the graphic. The method of anyone of the foregoing claims wherein the thermally stable substrate (S) is a thermal paper. The method of anyone of the foregoing claims wherein the binder is a resin binder. The method of anyone of the foregoing claims wherein the step of thermally transferring includes: providing a transfer press (22); and applying heat and pressure to the fabric via the transfer press (22).

Inventors: PRICE PETERSON MARY ELIZABETH, PRICE PETERSON, MARY ELIZABETH
Applicants: GERBER SCIENT PRODUCTS INC, GERBER SCIENTIFIC PRODUCTS, INC.
Application year: 1996
Main classification: D06P5
IPC codes: D06P5, B41J2, B44C1, B41M5