SEPARATED TREATMENT OF PAPER SUBSTRATE WITH MULTIVALENT METAL SALTS AND OBAs

摘要

A process for providing printable substrates by separately treating one or both surfaces of a paper substrate with an optical brightening agent (OBA) and a multivalent metal salt drying agent, where one or both surfaces of the paper substrate is treated with one of these two agents at the size press, and where the surface(s) is treated with the other of these two agents before or after the size press.

主权项

1. A process comprising the following steps:
(a) for a paper substrate about 10% or less by weight mechanical pulp fibers and having a first surface and a second surface, treating at least one of the first and second surfaces at a size press with one of the following two agents: (1) an optical brightening agent or; (2) a multivalent metal salt drying agent, to provide a treated paper substrate having one of the two agents; and (b) before or after the size press, treating the at least one surface of the paper substrate of step (a) with the other of the two agents to provide a printable substrate; (c) wherein the least one surface after steps (a) and (b) comprises the multivalent metal salt drying agent in an amount such that the at least one surface has a percent ink transferred (“IT %”) value equal to or less than about 65% and a black print density value of at least about 1.15; (d) wherein the optical brightening agent is present after steps (a) and (b) in an amount sufficient to impart to the at least one surface an ISO brightness value of at least about 75.