Lithographic Printing Plate Overcoat Layer Sludge Reduction
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Solution Overview
Problem
Conventional photopolymer printing plates face issues with sludge formation and viscosity increase during processing, leading to clogging and poor ink acceptance, especially in on-press processing with alkaline developers or gum solutions, resulting in suboptimal print quality and increased waste during start-up.
Innovation Solution
A lithographic printing plate precursor with a photopolymerisable layer and an overcoat layer containing a specific compound that improves solubility and minimizes sludge formation, comprising a moiety with a defined structure that enhances the solubility and transparency of the overcoat layer, allowing for efficient removal during processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional photopolymer printing plates are processed with alkaline developers or gum solutions, then the coating is removed from non-printing areas, but sludge formation and viscosity increase occur leading to clogging and poor ink acceptance
Solution Approach 1:
The patent modifies the chemical composition parameters of the overcoat layer by incorporating specific compounds (compounds I and II) with defined molecular structures containing hydrophilic groups. This chemical parameter change enables the overcoat to dissolve in neutral or slightly acidic aqueous solutions rather than requiring alkaline developers, thereby eliminating sludge formation and viscosity increase during processing.
Solution Approach 2:
The overcoat layer is designed as a temporary, disposable protective layer that is easily removed during processing. By using water-soluble compounds with specific molecular structures, the overcoat can be completely dissolved in neutral or slightly acidic aqueous solutions without leaving residues, ensuring clean background areas without the harmful effects of alkaline development.
2Productivity
If the overcoat layer is made more soluble to reduce sludge formation, then processing efficiency improves, but transparency for actinic radiation may be compromised
Solution Approach 1:
The patent applies local quality by designing the overcoat layer with specific local chemical properties - compounds with hydrophilic groups that provide water solubility for easy removal, while maintaining optical transparency in the same layer for laser sensitivity. The molecular structure is specifically engineered to have regions that interact with water (hydrophilic groups) and regions that maintain optical clarity, allowing both functions to coexist in the same material system.
Solution Approach 2:
The overcoat layer is formulated as a composite material system containing compounds of formula (I) and/or (II) combined with other compatible substances. This composite approach allows the layer to exhibit multiple properties simultaneously: water solubility from the hydrophilic compounds, optical transparency from the molecular structure design, and adequate thickness for protection, achieving both processing efficiency and laser sensitivity.
3Reliability
If conventional overcoat layers are used, then oxygen barrier protection is provided, but viscosity increase during processing leads to clogging and waste
Solution Approach 1:
The patent changes the chemical parameter of the overcoat layer by using compounds with specific molecular structures containing hydrophilic groups that enable dissolution in neutral or slightly acidic aqueous solutions. This parameter change maintains the oxygen barrier function during storage while enabling complete dissolution during processing without viscosity increase, thereby preventing clogging and reducing waste during start-up.
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 significantly reduces viscosity increase and sludge formation, improving processing efficiency and ink acceptance, resulting in better print quality and reduced waste during start-up, while maintaining sensitivity and transparency for actinic radiation.
Implementation Method 1
the solubility of the overcoat layer of the present invention in a developer solution and/or during on press processing, is significantly improved
Implementation Method 2
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
Implementation Method 3
thermal plates of which the imaging mechanism is triggered by heat or by light-to-heat conversion
Data Source
AI summary
A lithographic printing plate precursor including a photopolymerisable coating and an overcoat layer provided on top of said layer, characterized in that the overcoat layer includes a compound comprising at least one moiety having a structure according to Formula (I): (I).