Support For Lithographic Printing Plate and Presensitized Plate

Abstract

Disclosed is a support for a lithographic printing plate which, when measured over a 400 μm×400 μm surface region thereon using a three-dimensional non-contact roughness tester, has at most 5.0 convex portions of a height from centerline of at least 0.70 μm and an equivalent circle diameter of at least 20 μm, and has at least 800 concave portions of a depth from centerline of at least 0.50 μm and an equivalent circle diameter of at least 2.0 μm. Presensitized plates which are obtainable by using the support for a lithographic printing plate according to the present invention have an excellent scumming resistance and an extremely long press life.

Description

[0001]This is a continuation of application Ser. No. 11 / 081,770 filed Mar. 17, 2005. The entire disclosure of the prior application, application Ser. No. 11 / 081,770 is considered part of the disclosure of this application and is hereby incorporated by reference. The entire contents of literatures cited in this specification are incorporated by reference.BACKGROUND OF THE INVENTION[0002]The present invention relates to a support for a lithographic printing plate and a presensitized plate.[0003]Lithographic printing is a process that makes use of the inherent immiscibility of water and oil. Lithographic printing plates used in lithographic printing have formed on a surface thereof regions which are receptive to water and repel oil-based inks (referred to below as “non-image areas”) and regions which repel water and are receptive to oil-based inks (referred to below as “image areas”).[0004]The aluminum support employed in a lithographic printing plate (referred to below as a “support f...

AI Technical Summary

Benefits of technology

The patent text describes a new technique for improving the performance of lithographic printing plates. The inventors found that by controlling the number and size of convex and concave portions on the support of the plate, they could create a support that has excellent resistance to scumming (the buildup of ink) and has a long press life (the number of impressions that can be printed before the image recording layer wears down and ink adhesion fails). This technique also resulted in a presensitized plate that has the desired properties. Overall, this patent provides a new way to create better lithographic printing plates.

Problems solved by technology

However, the above techniques were intensively studied by the inventors and has not been found capable of providing both an excellent scumming resistance and a very long press life.

In searching for techniques to improve the press life of presensitized plates used in lithographic printing, the inventors have found that when printing is carried out using a lithographic printing plate, as the number of impressions printed from the plate increases, the image recording layer undergoes wear, sometimes uncovering and exposing convex portions of the support where the image recording layer is relatively thin, and as a result, ink fails to adhere to such uncovered areas of the support, so that areas which should become image areas instead become white specks.

Images