Hydrophobic Toplayer for Lithographic Plate Scratch Resistance

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Solution Overview

Problem

Lithographic printing plates are susceptible to mechanical damage during handling and transport, leading to surface defects and reduced printing quality, and the addition of organic waxes to improve handling can make them too slippery for stacking and transportation.

Innovation Solution

A negative-working photopolymer printing plate precursor with a coating comprising a hydrophobic binder and hydrophobic discrete particles, which enhances scratch resistance and reduces movement during handling and transport while maintaining sufficient static friction for stable stacking.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If organic waxes are added to the coating to improve handling properties, then scratch resistance and anti-movement properties are improved, but the plate becomes too slippery for stable stacking and transportation

Engineering Contradiction:

Improvescratch resistanceVSAvoidstacking stability

Core Design Contradiction:

StrengthVSEase of operation

Solution Approach 1:

The invention changes the chemical composition parameters of the coating by incorporating specific hydrophobic polymers (polyvinylidene chloride and/or polyvinyl fluoride) with defined molecular weights and glass transition temperatures. This compositional parameter change provides optimal balance between scratch resistance and friction properties for stable stacking, resolving the contradiction between improved handling and stacking stability.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The invention uses a composite coating system comprising multiple layers with different functions: a support layer, an imageable layer containing photopolymerizable compounds, and a protective overcoat layer containing the hydrophobic polymer. This composite structure combines the benefits of each layer to achieve both scratch resistance and appropriate surface friction for stable handling and stacking.

Inventive Principle:

Principle #40Composite materials

2Reliability

If a protective overcoat layer is added to act as an oxygen barrier, then sensitivity and image quality are improved, but the plate becomes more susceptible to mechanical damage during handling

Engineering Contradiction:

Improveimage qualityVSAvoidmechanical damage susceptibility

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The invention applies a thin film protective overcoat layer (0.5-5.0 µm) containing hydrophobic polymer that provides oxygen barrier functionality while maintaining flexibility and scratch resistance. This thin film approach protects the underlying photopolymerizable layer from mechanical damage during handling while still providing the necessary oxygen barrier for reliable image formation.

Inventive Principle:

Principle #30Flexible shells and thin films

Solution Approach 2:

The protective overcoat layer forms a composite structure with the imageable layer beneath it, creating a multi-layer system where each layer contributes specific properties. The overcoat provides oxygen barrier and mechanical protection, while the imageable layer provides photosensitivity, achieving both improved image quality and reduced mechanical damage susceptibility.

Inventive Principle:

Principle #40Composite materials

3Manufacturing precision

If the coating is made more hydrophobic to improve ink acceptance, then printing quality is improved, but the plate becomes too slippery for stable handling and transport

Engineering Contradiction:

Improveprinting qualityVSAvoidhandling stability

Core Design Contradiction:

Manufacturing precisionVSEase of operation

Solution Approach 1:

The invention optimizes the hydrophobicity parameter by selecting specific hydrophobic polymers with defined glass transition temperatures (below 25°C) and molecular weights. This controlled parameter change provides sufficient hydrophobicity for good ink acceptance and printing quality while maintaining adequate surface friction for stable handling and transport during the pre-printing phase.

Inventive Principle:

Principle #35Parameter changes

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 provides superior scratch resistance and minimizes plate movement during handling and transport, improving clean-out behavior and reducing fountain solution contamination, thus enabling efficient printing with reduced ink consumption.

Implementation Method 1

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 and/or heat.

Methodology Applied

Scientific EffectPhotopolymerisation: Photopolymerisation

Implementation Method 2

Methodology Applied

Scientific EffectFriction: Friction

Data Source

PatentEP4035897A1A lithographic printing plate precursor

Publication Date: 2022.08.03 ECO3 BV

AI summary

A lithographic printing plate precursor is disclosed including a support and a coating comprising (i) a photopolymerisable layer including a polymerisable compound and a photoinitiator, and a toplayer provided above the photopolymerisable layer; characterized in that the toplayer includes a hydrophobic binder and hydrophobic discrete particles having a melting and/or softening temperature above 50°C.