Planographic Printing Plate Recording Layer Solubility Control
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Solution Overview
Problem
Existing methods for making planographic printing plates using infrared exposure struggle with achieving sufficient dissolution resistance in unexposed areas and solubility in exposed areas, particularly when using alkaline developers with low pH values, leading to issues like development scum and susceptibility to over- or under-development.
Innovation Solution
A method involving image-wise exposure of a positive-working planographic printing plate precursor with a copolymer containing structural units from (meth)acrylonitrile and styrene, a water-insoluble and alkali-soluble resin, and an infrared absorbing agent, using an aqueous alkaline solution with a pH of 8.5 to 10.8 containing a betaine-based amphoteric surfactant and an ammonium salt, which enhances the solubility and dissolution resistance of the recording layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a binder resin highly soluble in an alkaline developer is used to enhance the difference in solubility between unexposed and exposed areas, then the solubility of exposed areas is improved, but the developer resistance of unexposed areas becomes unstable and scratch resistance deteriorates
Solution Approach 1:
The invention changes the chemical structure parameters of the binder resin by introducing specific functional groups (carboxyl, hydroxyl, or amine groups) with controlled content ratios. This parameter modification allows the resin to exhibit dual characteristics: high solubility in alkaline developers for exposed areas while maintaining stable developer resistance and scratch resistance in unexposed areas through the protective effect of the functional groups.
Solution Approach 2:
The invention creates a composite binder resin system that combines the solubility-providing component with the protection-providing functional groups. This composite structure integrates both the high solubility characteristic needed for exposed area dissolution and the protective characteristic needed for unexposed area stability, resolving the contradiction between these opposing requirements.
2Reliability
If the interaction between IR dye and binder resin is strengthened to improve dissolution inhibition in unexposed areas, then developer resistance is enhanced, but solubility in exposed areas decreases
Solution Approach 1:
The invention modifies the chemical parameters of the binder resin by incorporating functional groups that can form multiple types of interactions (hydrogen bonding, electrostatic interactions, coordination bonds) with the IR dye. This creates an optimal balance where the interaction is strong enough to provide dissolution inhibition in unexposed areas but can be effectively disrupted by the heat generated during infrared exposure, ensuring solubility in exposed areas.
3Extent of automation
If a positive-working planographic printing plate precursor for infrared laser is used, then direct image formation from digital data is enabled, but sufficient difference in dissolution resistance between unexposed and exposed areas cannot be achieved
Solution Approach 1:
The invention optimizes the chemical composition parameters of the binder resin to be specifically suited for infrared laser exposure. By controlling the content and type of functional groups (carboxyl, hydroxyl, or amine groups) within specific ratios, the resin achieves optimal response to infrared radiation, enabling direct digital image formation while maintaining sufficient dissolution resistance difference between exposed and unexposed areas.
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
This method effectively improves the dissolution resistance of unexposed areas and solubility of exposed areas, reducing the risk of development scum and enhancing the printing durability and scratch resistance of the planographic printing plates.
Implementation Method 1
an infrared absorbing agent (hereinafter also called an 'IR dye') that absorbs infrared light and generates heat
Implementation Method 2
absorbs infrared light and generates heat
Implementation Method 3
an aqueous alkaline solution with a pH of 8.5 to 10.8 containing a betaine-based amphoteric surfactant and an ammonium salt, which enhances the solubility and dissolution resistance of the recording layer
Data Source
AI summary
A method of making a planographic printing plate includes exposing, to infrared light, a planographic printing plate precursor including a recording layer provided on a substrate, and developing the precursor using an aqueous alkaline solution. The recording layer comprises a copolymer containing a structural unit derived from (meth)acrylonitrile and at structural unit derived from styrene, a water-insoluble and alkali-soluble resin, and an infrared absorbing agent, the solubility of the recording layer in the aqueous alkaline solution being increased by the exposure. The aqueous alkaline solution has a pH of 8.5 to 10.8 and contains a betaine-based amphoteric surfactant and an ammonium salt represented by Formula (I):R1, R2, R3, and R4 each independently represent an alkyl or aryl group; the total number of carbon atoms in R1, R2, R3, and R4 is not more than 20; and X− represents a counter anion.