Lithographic Printing Plate Precursor with IR Dye
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Solution Overview
Problem
Conventional lithographic printing plate precursors often produce print-out images with low contrast between exposed and non-exposed areas, which fades over time, making it difficult to measure dot gain and adjust press settings before processing or printing.
Innovation Solution
A printing plate precursor with a pH-sensitive colorant precursor in the photopolymerisable layer and a heat-sensitive color-forming IR dye in the protective overcoat layer, capable of inducing significant color differences upon IR radiation or heating, providing stable contrast both before and after processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If conventional lithographic printing plate precursors are used, then the processing can be simplified, but the print-out image contrast is low and fades over time
Solution Approach 1:
The patent employs color-forming compounds that undergo color changes upon exposure to IR radiation or heat. The photopolymerisable layer contains colorant precursors that form colored compounds after exposure, while the protective overcoat layer contains heat-sensitive color-forming IR dyes that develop color upon heating. This color change mechanism provides high contrast between exposed and non-exposed areas that remains stable during handling and storage, directly resolving the technical contradiction by enabling stable print-out image contrast without complicating the processing workflow.
2Measurement precision
If the print-out image contrast is low, then the coating composition can be simpler, but it becomes difficult to measure dot gain and adjust press settings
Solution Approach 1:
The patent incorporates specific colorant precursors and heat-sensitive IR dyes that produce strong, stable color differences upon exposure and heating. This enables precise measurement of dot gain and image quality characteristics before printing, as the high contrast print-out image remains measurable during handling and storage, without requiring complex coating compositions.
3Reliability
If the print-out image fades over time, then the coating can be simpler, but it becomes difficult to adjust press settings before printing
Solution Approach 1:
The patent uses color-forming compounds with stable color characteristics that do not fade during storage. The photopolymerisable layer contains leuco dyes or other colorant precursors that form stable colored compounds, while the protective overcoat layer contains IR dyes that provide stable heat-induced coloration. This ensures reliable image contrast stability during handling and storage, enabling press settings adjustment before printing without requiring complex coating formulations.
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 achieves high image contrast that remains stable or enhances during handling and storage, allowing for convenient measurement and adjustment of press settings before printing, reducing ink, paper, and chemical consumption.
Implementation Method 1
a heat sensitive color-forming IR dye in the protective overcoat layer, capable of inducing a CIE 1976 color difference ΔE1 of 2.0 or more than 2 - upon IR radiation and/or heating
Implementation Method 2
a pH sensitive colorant precursor in the photopolymerisable layer, capable of forming a CIE 1976 color difference ΔE2 of 12.0 or more than 12.0 upon treatment with a liquid having a pH of about 4 or below 4
Implementation Method 3
Photopolymer printing plates rely on a working-mechanism whereby the coating - which typically includes free radically polymerisable compounds - hardens upon exposure. 'Hardens' means that the coating becomes insoluble or non-dispersible in the developing solution and may be achieved through polymerization and/or crosslinking of the photosensitive coating upon exposure to light
Data Source
AI summary
A lithographic printing plate precursor is disclosed which includes a support and a coating comprising a photopolymerisable layer including a polymerisable compound, an initiator and a pH sensitive colorant precursor and a protective overcoat layer provided above the photopolymerisable layer including a heat sensitive color-forming IR dye, which upon exposure to heat and/or light forms a print-out image which remains stable or increases during storage of the precursor in light or dark environment.