Lithographic Printing Plate Precursor On-Press Development
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Solution Overview
Problem
Lithographic printing plate precursors for on-press development face challenges in achieving high printing durability, excellent stain resistance, and minimizing development scum, particularly when using urethane oligomers, which often fall short in these aspects.
Innovation Solution
A lithographic printing plate precursor is developed with an image-recording layer containing an infrared absorbing agent, a radical polymerization initiator, polymer particles, and a radical polymerizable urethane oligomer. The urethane oligomer has a specific molecular weight range and includes hydrophilic groups such as sulfo, polyoxyalkylene, hydroxy, amido, ammonium, or betaine structures, and is present outside the polymer particles, enhancing the on-press development properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional high alkaline developer is used for development processing, then the unnecessary image-recording layer is effectively removed, but environmental pollution increases due to waste liquid discharge
Solution Approach 1:
The patent changes the pH parameter of the developer from high alkaline to near-neutral, and replaces the chemical development process with an on-press development process using dampening water and printing ink. This eliminates the need for harmful alkaline chemicals while maintaining effective removal of the unnecessary image-recording layer through the specific composition of the image-recording layer containing polymer particles and urethane oligomer.
2Productivity
If on-press development is implemented to simplify the plate making process, then development processing time is reduced, but printing durability and stain resistance deteriorate
Solution Approach 1:
The patent performs preliminary action by designing the image-recording layer with specific pre-selected components (polymer particles with carboxyl groups and urethane oligomer with hydrophilic groups) that are prepared in advance to enable on-press development. This preliminary structural design ensures that when dampening water and printing ink are applied during printing, the unexposed areas are effectively removed while maintaining printing durability and stain resistance.
Solution Approach 2:
The patent uses composite materials in the image-recording layer by combining polymer particles (with carboxyl groups) and urethane oligomer (with hydrophilic groups like polyoxyalkylene chains). This composite structure enables the layer to respond appropriately to dampening water and printing ink during on-press development, achieving both simplified processing and maintained printing quality.
3Device complexity
If the image-recording layer is designed for on-press development with dampening water and printing ink, then development processing is simplified, but development scum increases
Solution Approach 1:
The patent applies local quality by creating specific functional zones within the image-recording layer through the spatial distribution and chemical properties of polymer particles and urethane oligomer. The unexposed areas have a specific composition that makes them removable by dampening water and printing ink, while the exposed areas maintain their ink-receptive properties. This local differentiation allows effective on-press development with minimal development scum.
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 solution results in a lithographic printing plate precursor that exhibits improved printing durability, reduced stain resistance, and minimized development scum, effectively addressing the limitations of previous technologies.
Implementation Method 1
a lithographic printing plate precursor having provided on a support, an image-recording layer containing a polymerizable compound and a graft polymer having a polyethylene oxide chain in its side chain or a block polymer having a polyethylene oxide block
Implementation Method 2
an image-recording layer (photosensitive layer) containing an infrared absorbing agent, a radical polymerization initiator and a polymerizable compound
Data Source
AI summary
An object of the invention is to provide a lithographic printing plate precursor of on-press development type which exhibits high printing durability, excellent stain resistance and less development scum and a plate making method thereof, and is directed to a lithographic printing plate precursor including a support and an image-recording layer an unexposed area of which is capable of being removed with dampening water and/or printing ink and contains (a) an infrared absorbing agent, (b) a radical polymerization initiator, (c) a polymer particle, and (d) a radical polymerizable urethane oligomer, wherein (d) the radical polymerizable urethane oligomer has a polymerizable group and at least one hydrophilic group selected from a sulfo group, a group having a polyoxyalkylene chain, a hydroxy group, an amido group, an ammonium group and a group having a betaine structure and a weight average molecular weight (Mw) from 1,500 to 10,000 and is present outside of (c) the polymer particle.