INFRARED LASER-IMAGEABLE LITHOGRAPHIC PRINTING MEMBERS AND METHODS OF PREPARING AND IMAGING SUCH PRINTING MEMBERS

摘要

Provided are methods of imaging a wet positive working lithographic printi ng member comprising the steps of providing a positive working printing member comprising a substrate, a hydrophilic layer, an infrared-absorbing layer, an d, optionally, an ink-accepting surface layer; exposing the printing member to infrared radiation in an imagewise pattern removing by ablation greater than 10% by weight, and most preferably none of the infrared-absorbing layer and optional ink-accepting surface laye r; and removing with water the laser-exposed areas of the infrared-absorbing layer and optional ink-accepting surface layer to reveal the underlying hydrophilic layer. Thes e methods are advantageous in reducing airborne debris and vapors during laser imaging, in increasing the speed of laser imaging, and in providing excellent cleanability and imag e quality. The printing member may further comprise a primer layer underlying the infrared-absorbing layer with an adhesion-promoting agent present in the primer layer. Also provided are methods of preparing a wet lithographic printing member and wet positive working lithographic printing members prepared according to the methods of this invention.