Infrared Absorbing Dye for High-Contrast Lithographic Plates
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Solution Overview
Problem
Existing heat-sensitive lithographic printing plate precursors using infrared (IR) dyes suffer from low contrast in print-out images due to side-absorption in the visible wavelength range, which limits the visibility and differentiation of exposed areas before development.
Innovation Solution
Development of an IR-absorbing dye with a specific chemical structure that undergoes a transformation upon IR exposure, increasing light absorption in the visible wavelength range, thereby enhancing the contrast of print-out images by forming a stronger electron-donor or acceptor group, and potentially forming dimers or oligomers for improved performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional IR dyes are used in heat-sensitive lithographic printing plate precursors, then the plate precursor can be exposed to IR radiation and form an image, but the print-out image shows low contrast due to side-absorption in the visible wavelength range
Solution Approach 1:
The patent modifies the chemical structure of the IR dye by introducing specific substituents (such as cyano groups, nitro groups, or carbonyl groups) at positions 5 and 6 of the indolenine ring. This structural parameter change transforms the dye's properties: it reduces side-absorption in the visible range while enhancing the formation of colored products upon IR exposure, thereby improving print-out image contrast without requiring additional contrasting dyes.
Solution Approach 2:
The patent creates a composite dye molecule combining the indolenine core structure with specific electron-withdrawing groups (cyano, nitro, or carbonyl substituents). This composite structure integrates multiple functions within a single molecule: IR absorption capability, reduced visible side-absorption, and enhanced colored product formation upon exposure, eliminating the need for separate contrasting dye components.
2Measurement precision
If additional contrasting dyes are added to improve print-out image visibility, then the contrast improves, but the device complexity and risk of dye stain increase
Solution Approach 1:
The modified IR dye performs multiple functions simultaneously: it absorbs IR radiation for image formation, provides sufficient visible contrast through colored product formation upon exposure, and maintains stability without requiring additional contrasting dye components. This multi-functionality simplifies the overall system by eliminating the need for separate contrasting dye additions.
Solution Approach 2:
The patent merges the functions of IR absorption and contrast formation into a single modified dye molecule. The electron-withdrawing substituents on the indolenine ring enable the same molecule that absorbs IR radiation to also produce high-contrast colored products upon exposure, consolidating multiple dye functions into one component and reducing system complexity.
3Measurement precision
If the IR dye forms colored products upon exposure, then the print-out image contrast improves, but the optical density in the visible spectrum must be increased
Solution Approach 1:
The patent changes the chemical parameters of the IR dye by introducing electron-withdrawing substituents that specifically enhance the optical density of the colored products formed upon IR exposure. These substituents (cyano, nitro, or carbonyl groups at positions 5 and 6) increase the visible spectrum absorption of the exposed areas, thereby improving print-out image contrast through enhanced colored product formation rather than by increasing the overall optical density of the unexposed dye.
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 new IR dye significantly improves the contrast of print-out images by increasing optical density in the visible spectrum, allowing for better differentiation between exposed and non-exposed areas without the need for additional contrasting dyes, leading to improved print quality and reduced risk of dye stain.
Implementation Method 1
The material is exposed to heat or to infrared radiation and the generated heat triggers a (physico-)chemical process
Implementation Method 2
the generated heat triggers a (physico-)chemical process, such as ablation, polymerization, insolubilization by cross-linking
Implementation Method 3
The IR dye is capable of forming a colour upon exposure to IR-radiation or heat. The coloration may be the result of a chemical transformation upon exposure to IR-light or heat of at least one Rd group
Data Source
Figure 1~2
AI summary
The present invention relates to an infrared absorbing dye as defined in claim 1. The present invention relates also to a heat- sensitive imaging element comprising said IR dye and more particularly to a heat-sensitive lithographic printing plate precursor comprising said IR dye. The present invention relates also to a method for making a lithographic printing plate whereby a print-out image of high contrast is formed upon exposure to IR- radiation or heating.