Lithographic Printing Plate Adhesion and Clean-Out
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Solution Overview
Problem
Lithographic printing plate precursors with adhesion promoting compounds face insufficient clean-out of non-exposed areas, leading to toning and reduced hydrophilic surface properties, especially under non-aggressive processing conditions without strong alkaline solutions.
Innovation Solution
A method involving a photopolymer plate precursor with a contiguous layer containing a non-polymeric adhesion promoting compound and a second polymer, where the adhesion promoting compound has an ethylenically unsaturated bond and interacts with the support through phosphate, phosphonate, or trialkoxysilane groups, and the second polymer has hydrophilic groups, ensuring effective clean-out and resolution, even under mild processing conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If adhesion promoting compounds are used in photopolymer plate precursors, then adhesion to support is improved, but clean-out of non-exposed areas becomes insufficient leading to toning
Solution Approach 1:
The patent applies local quality by creating distinct functional zones within the coating layer: the adhesion promoting compound concentrates at the support interface to ensure strong bonding, while the hydrophilic polymer dominates the outer regions to enable effective clean-out and prevent toning. This spatial differentiation of composition and function resolves the contradiction between adhesion and clean-out quality.
Solution Approach 2:
The patent uses composite materials by combining adhesion promoting compounds (such as silanes or phosphates) with hydrophilic polymers (such as polyvinyl alcohol or carboxymethyl cellulose) in a single coating layer. This composite structure allows simultaneous achievement of strong support adhesion through the adhesion promoter and effective clean-out through the hydrophilic polymer, directly resolving the technical contradiction.
2Manufacturing precision
If conventional processing with strong alkaline solutions is used, then clean-out is improved, but additional gumming steps are required increasing process complexity
Solution Approach 1:
The patent applies self-service by incorporating hydrophilic polymers into the coating composition that automatically provide gumming protection after development. The hydrophilic polymer remains in the non-exposed areas to protect the plate surface, eliminating the need for separate gumming stations and strong alkaline processing steps, thus simplifying the overall process while maintaining clean-out quality.
Solution Approach 2:
The patent achieves universality by making the coating layer perform multiple functions simultaneously: adhesion promotion, image formation, clean-out facilitation, and surface protection. The hydrophilic polymer provides both clean-out assistance and gumming protection in a single integrated system, eliminating the need for separate processing steps and strong alkaline solutions.
3Device complexity
If mild processing conditions are used, then process simplicity is improved, but clean-out becomes insufficient leading to reduced hydrophilic surface properties
Solution Approach 1:
The patent applies parameter changes by modifying the chemical composition parameters of the coating layer to include hydrophilic polymers with specific properties (such as polyvinyl alcohol or carboxymethyl cellulose). These compositional changes enable the coating to respond effectively to mild processing conditions, providing sufficient clean-out and maintaining hydrophilic surface properties without requiring aggressive alkaline treatments.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The method achieves high resolution and extended run length with no toning, maintaining the hydrophilic surface properties and eliminating the need for additional gumming steps, suitable for off-press or on-press processing with fountain and ink.
Implementation Method 1
photopolymer plates which contain a photopolymerizable composition that hardens upon exposure to light
Implementation Method 2
an adhesion promoting compound which is a non-polymeric compound containing a group having an ethylenically unsaturated bond and a group capable of interacting with the support selected from a phosphate group, a phosphonate group and a trialkoxysilane group
Implementation Method 3
a second polymer having at least 1 mol % of a first monomeric unit having a group capable of interacting with the support and at least 30 mol % of a second monomeric unit having a hydrophilic group
Data Source
AI summary
A method of making a lithographic printing plate comprising the steps of : a) providing a lithographic printing plate precursor comprising a support having a hydrophilic surface or which is provided with a hydrophilic layer, and a coating provided thereon, said coating comprising (i) a contiguous photopolymerisable layer having a photopolymerisable composition, or (ii) a contiguous intermediate layer and thereon a photopolymerisable layer having a photopolymerisable composition, wherein said photopolymerisable composition comprises a polymerisable compound, a polymerization initiator and a first polymer, b) image-wise exposing said coating, c) optionally, heating the precursor, d) developing the precursor by treating the coating of the precursor with a gum solution or by mounting the exposed precursor on a plate cylinder of a lithographic printing press and rotating the plate cylinder while feeding dampening liquid and/or ink to the coating, wherein said contiguous photopolymerisable or intermediate layer further comprises (1) an adhesion promoting compound which is a non-polymeric compound containing a group having an ethylenically unsaturated bond and a group selected from a phosphate group, a phosphonate group and a trialkoxysilane group, and (2) a second polymer having at least 1 mol % of a first monomeric unit having a phosphate group, a phosphonate group, a carboxylic acid group, a sulphonic acid group, a phenolic group, a trialkoxysilane group, an ammonium group or a phosphonium group and at least 30 mol % of a second monomeric unit having a hydrophilic group, wherein the amount of said adhesion promoting compound is higher than the amount of said second polymer, with the proviso that, if the contiguous layer is the photopolymerisable layer, the amount of said second polymer xn the photopolymerisable layer is at least 0.01 % by weight and less than 5 % by weight.