A Planographic Direct Printing Master With Improved Image Quality.

Elastic deformation theory is used to optimize the material properties and master configuration variables for improving the image quality in direct mode lithographic printing from planographic masters. The theory is verified through several controlled experiments and the most important characteristics of a master for direct mode printing with good image quality are established. This planographic master consists of a conformable, soft, rubbery layer (2-5 mils) overcoated with a thin hydrophilic layer (1-5mu) followed by a thin image layer (.1-1mu). The image quality resulting from the soft conformable master printed in the direct mode is compared with that for a conventional hard lithographic master printed in the offset mode and in the direct mode. The image quality is determined from Wiener Spectra analyses for solid areas and from a computer controlled whole-image analyzer for halftone areas. The image quality of the printed output for the soft direct printing master is superior to that for the hard direct printing master and approaches that for the hard offset printing master.