Sun Chemical Corporation

Edward Rabbitts

Danny C Rich

Kent Zessin

In the development of custom SPOT color inks, there will be only a single combination of pigments that will produce the correct color for both the solid tones and for one or more halftones intermediate between the full tone and the unprinted substrate. A novel system and method is presented for finding such a combination of colorants without requiring a complex suite of software algorithms. The method includes a search of a library of known colored inks printed onto a specified substrate and printed using specified printing conditions. Each record of such a library can contain, for example, the ink formula, the combination of colorants and resin, the spectral reflectance factor of the ink and substrate, color values (XYZ and CIELAB) of the solid ink color (100% tone) and 10% steps down to 0% (unprinted substrate). In such a database halftones can be specified in units of % (0% to 100%), but can also, for example, be given as 8-bit integers (0 to 255). In exemplary embodiments of the present invention, such a search locates the solid ink color that meets the color requirements and simultaneously meets the color requirements at one or more intermediate halftone steps. The claimed method can thus achieve a printing ink formula that produces a color match to a customer proof at both the solid color and at one or more halftones with ink coverages lying between the unprinted substrate (0% tone) and the fully printed substrate (100% tone).

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Bristol, United Kingdom

Edward Rabbitts