Negative-Working Lithographic Printing Plate Precursor

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Solution Overview

Problem

Existing negative-working lithographic printing plate precursors face challenges with crystal formation due to high efficiency free radical initiators, leading to reduced crosslinking density and inefficient infrared radiation exposure, and require development methods that avoid contamination risks without an oxygen barrier layer.

Innovation Solution

A negative-working lithographic printing plate precursor with an infrared radiation-sensitive imageable layer comprising a unique combination of iodonium salts, specifically compound A and compound B, which minimizes crystal formation and allows for on-press development using a lithographic ink or fountain solution, or both, without an oxygen barrier layer.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If high efficiency free radical initiators are used at high concentration, then infrared radiation sensitivity is improved, but crystal formation occurs reducing crosslinking density

Engineering Contradiction:

Improveinfrared radiation sensitivityVSAvoidcrosslinking density

Core Design Contradiction:

Use of energy by moving objectVSManufacturing precision

Solution Approach 1:

The patent changes the chemical parameters of the initiator system by selecting specific iodonium salts with particular counterions (BF4-, PF6-, CF3SO3-) and controlling their concentration range (3-15 wt%). This parameter optimization allows achieving high infrared sensitivity while preventing crystal formation, thereby maintaining proper crosslinking density in the photopolymerizable composition.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent employs composite initiator systems combining iodonium salts with specific counterions in defined ratios with other photopolymerization initiators. This composite approach creates a synergistic effect that enhances infrared radiation sensitivity while the specific composition prevents crystal formation, resolving the contradiction between sensitivity and crosslinking quality.

Inventive Principle:

Principle #40Composite materials

2Ease of operation

If no oxygen barrier layer is present, then on-press development capability is improved, but printing press contamination risk increases

Engineering Contradiction:

Improveon-press development capabilityVSAvoidprinting press contamination

Core Design Contradiction:

Ease of operationVSObject-affected harmful factors

Solution Approach 1:

The patent converts the potential harm of unreacted photopolymerizable composition into a benefit by formulating the composition with specific iodonium salts that enable complete photopolymerization under infrared radiation. The high efficiency and specificity of these initiators ensure thorough curing, leaving minimal residues that could cause contamination, thus allowing omission of the oxygen barrier layer while maintaining press cleanliness.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

3Power

If diaryl iodonium salts with tetraphenyl borate anions are used, then free radical formation efficiency is improved, but crystal formation occurs

Engineering Contradiction:

Improvefree radical formation efficiencyVSAvoidcrystal formation tendency

Core Design Contradiction:

PowerVSStability of the object's composition

Solution Approach 1:

The patent systematically changes the counterion parameter from tetraphenyl borate to alternative counterions including BF4-, PF6-, and CF3SO3-. This parameter substitution maintains the high free radical formation efficiency of diaryl iodonium salts while fundamentally altering the crystallization behavior, thereby eliminating crystal formation in the photopolymerizable composition.

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 precursor effectively reduces crystal formation, enabling efficient infrared radiation exposure and on-press development, while maintaining press life and ink receptivity, thus addressing the contamination risks and simplifying the printing process.

Implementation Method 1

an initiator composition that provides free radicals upon exposure of the infrared radiation-sensitive imageable layer to infrared radiation

Methodology Applied

Scientific EffectPhotopolymerisation: Photopolymerisation

Implementation Method 2

diaryl iodonium salts are among the most effective free radical initiators

Methodology Applied

Scientific EffectPhoto-initiation:

Implementation Method 3

one or more infrared radiation absorbers

Methodology Applied

Scientific EffectInfrared radiation absorption: Absorption (EM radiation)

Data Source

PatentEP3408098B1Negatively-working lithographic printing plate precursor and method

Publication Date: 2019.11.06 EASTMAN KODAK CO

AI summary

A negative-working infrared radiation-sensitive lithographic printing plate precursor can be imaged and developed on-press to provide a lithographic printing plate. Such precursor has an initiator composition that contains compound A of Structure (I) and one or more compounds collectively as compound B of Structure (II) or Structure (III): wherein R1, R2, R3, R4, R5 and R6 are independently alkyl or alkoxy groups each having 2 to 9 carbon atoms; at least one of R3 and R4 is different from R1 or R2; the difference of total number of carbon atoms in R1 and R2 and the total number of carbon atoms in R3 and R4 is 0 to 4; the difference of total number of carbon atoms in R1 and R2 and the total number of carbon atoms in R5 and R6 is 0 to 4; and X1, X2 and X3 are the same or different anions.