4 CAST tm Digital Color Imager - The Application Of Dye Thermal Sublimation Technology As A Graphic Arts Proofing System

4CASTTM Digital Color Imager - the application of dye thermal sublimation technology as a graphic arts proofing systemMark W. Wendling and Donna L. MorrisE. I. Du Pont de Nemours & Company (Inc.), Imaging Systems DepartmentP. O. Box 6099, Eagle Run, Newark, Delaware 19714 -6099ABSTRACTThe 4CASTTM Digital Color Imager by Du Pont is the first application of thermal dye sublimation transfer technologyas a graphic arts pre -press proofing system. This unique technology, also referred to as dye diffusion thermal transfer, offers anumber of distinct advantages over other processes used to produce digital color hard copy.1. INTRODUCTIONDu Pont has long been involved as a major supplier of conventional imaging systems, principally to the graphic artsindustry. Since the introduction of the Cromalin® off -press proofing product in 1971, which is a photopolymer -based analogproofing system, Du Pont has led the revolution in off -press proofing. Prior to that breakthrough, press -proofing was theonly accurate means of predicting how a printing job was going to turn out on press. This system offered an attractivealternative to this expensive and time -consuming process. The introduction of the Cromalin® process solved many of theseproblems and established a new standard for pre -press proofing.Today the industry faces a new challenge -image data in the pre-press area is now handled in digital form in many of theoperations that formerly were performed with an image captured on film. The rapid emergence of color electronic pre -presssystems has created a gap in graphic arts image proofing technologies. The industry has been looking for a practical solutionto the problem of creating a proof directly from this digital data. Until now the various technologies employed in an attemptto answer this need have been either so expensive, so slow, or so poor in their ability to predict the final printed result, thatmany owners of color electronic pre-press systems have chosen not to adopt them.2, DYE THERMAL SUBLIMATIONOne area of technology that Du Pont recognized as offering a great deal of promise for a practical solution to this need ofthe graphic arts industry is the thermal transfer technology known as dye thermal sublimation. This technology offers someunique properties that have already been demonstrated as providing the solutions to digital proofing needs in many differentareas of graphic arts pre -press work flow. In addition to providing the solutions to this particular industry's needs, thetechnology has also demonstrated a good fit as high -quality color hard copy output in several other industries. Some of theseapplications are remote sensing output, a wide range of computer graphics applications, medical hard copy, and output ofnumerous design workstations in many different industries. The common factor is that in every case, fast and consistentcolor hard copy of the highest quality is required for the application.3. 4CAST''M DIGITAL COLOR IMAGERThe system, named the 4CASTTM Digital Color Imager, was first introduced at a major printing industry trade show inNew York in April 1988. The 4CASTTM system immediately offered the fastest, most consistent and repeatable high- qualitydigital proof the industry had seen.The 4CASTTM system consists of the marking engine and an interface with a 12- megahertz micro computer, a 180 -mbdisk drive, and a monochrome monitor and keyboard all housed inside a cabinet.There are two consumables used to make the print: a dye- impregnated donor ribbon and a receiver paper. The ribbonconsists of a repeating sequence of yellow, magenta, cyan, and black panels of dye that are transferred to the receiver paper toform the image. The dye ribbon is made up of three layers: a heat resistant, anti -stick back coating, a polyethylene film(which is the dye carrier), and a sublimable dye layer. The receiver paper also consists of three layers: a resin and siliconedye receiver layer, a core of coated natural paper and synthetic paper, and an anti -stick back coat layer. The output of the