	US 7,586,656 B2
	Process for producing optimised printing forms
Carsten Gasczyk, Hannoversch Muenden (Germany)
Assigned to E. I. Du Pont De Nemours and Company, Wilmington, Del. (US)
Filed on Jun. 06, 2006, as Appl. No. 11/447,712.
Prior Publication US 2007/0279688 A1, Dec. 06, 2007
Int. Cl. H04N 1/46 (2006.01)

U.S. Cl. 358—504 [358/518; 358/3.29]

7 Claims

1. A process for producing a printing form for use on a printing press, comprising the following steps:

A) providing a printing form with a defined print image having specified raster percentages and containing at least one stepped wedge comprising a raster patch at 0%, a raster patch at 100%, and at least one other raster patch at a predetermined percentage;

B) printing onto a substrate with the printing form provided from step A) with a printing ink on the printing press to obtain a test print of the at least one stepped wedge, where the raster patch at 0% corresponds to the color shade of the substrate, and the raster patch at 100% corresponds to solid shade of the printing ink;

C) measuring a reflectance spectrum using a spectrophotometer, and determining associated colorimetric values L*,a*,b* from the reflectance spectrum, for each of the raster patch at 0%, the raster patch at 100% and the at least one other raster patch of the at least one stepped wedge of the test print,

D) transforming the colorimetric values L*,a*,b* for the at least one other raster patch in linear correlation with the colour perception of the human eye, using the formula

wherein RCD is a relative colorimetric difference expressed as a percentage, and represents an actual raster percentage achieved on the printing press,

E) determining a dot gain for the at least one other raster patch based upon a difference between the predetermined percentage of the at least one other raster patch of the plate and the RCD percentage obtained in step D);

F) correcting the predetermined raster percentage from the printing form by the dot gain from step E), thereby creating a corrected raster percentage for the at least one other raster patch;

and

G) producing a printing form with a print image using the corrected raster percentage obtained for the at least one other raster patch in step F).