Negative-Working Radiation-Sensitive Compositions for Printing Plates
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Solution Overview
Problem
Existing negative-working imageable elements for printing plates require oxygen-impermeable overcoats and a preheat step for development, which complicates the imaging process and reduces shelf life, especially when imaged with infrared radiation.
Innovation Solution
A radiation-sensitive composition comprising a radically polymerizable component, a borate initiator, a radiation-absorbing compound, a polymeric binder with reactive vinyl groups, and a poly(alkylene glycol) or ether additive, which allows for imagewise exposure and development without a preheat step, eliminating the need for an oxygen-impermeable topcoat and enabling imaging at lower energies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional radiation-sensitive compositions are used for negative-working printing plates, then the compositions can be imaged, but they require oxygen-impermeable overcoats to prevent oxygen interference with radical polymerization
Solution Approach 1:
The patent removes the oxygen-impermeable overcoat layer from the imaging system by using a topcoat composition that is inherently resistant to oxygen interference. The composition uses specific additives (mercaptans, phenolic compounds, or amines) that scavenge oxygen and protect the polymerization process, eliminating the need for a separate overcoat structure.
Solution Approach 2:
The patent introduces oxygen-scavenging additives (mercaptans, phenolic compounds, or amines) as intermediaries that interact with oxygen to protect the radical polymerization process. These additives act as mediators between the oxygen environment and the polymerization reaction, allowing imaging without an oxygen-impermeable overcoat.
2Extent of automation
If infrared radiation is used for imaging, then direct laser control is achieved, but preheat steps are required to enhance crosslinking among binders and reactive components
Solution Approach 1:
The patent incorporates pre-reactive vinyl groups within the binder polymer structure itself, prepared in advance during binder synthesis. This preliminary incorporation eliminates the need for post-imaging preheat steps to induce crosslinking, as the reactive groups are already positioned to participate in polymerization upon irradiation.
Solution Approach 2:
The patent merges the binder function with the crosslinking function by incorporating reactive vinyl groups directly into the binder polymer structure. This combination eliminates the need for separate crosslinking agents and preheat treatment steps, streamlining the imaging process.
3Strength
If preheat steps are used before development, then crosslinking among binders and reactive components is enhanced, but the imaging process time increases
Solution Approach 1:
The patent pre-incorporates reactive vinyl groups into the binder structure during manufacturing, so that crosslinking capability is built-in from the start. This eliminates the need for time-consuming preheat steps to activate crosslinking, as the reactive groups are already in position to participate in polymerization upon irradiation.
Solution Approach 2:
The patent changes the chemical structure of the binder to include pendant vinyl groups with appropriate reactivity. This parameter change in the binder composition allows crosslinking to occur efficiently at lower temperatures and shorter times, eliminating the need for extended preheat treatment.
4Reliability
If oxygen-impermeable overcoats are applied, then oxygen interference with polymerization is prevented, but shelf life is reduced due to coating complexity
Solution Approach 1:
The patent removes the oxygen-impermeable overcoat layer and replaces it with a simplified topcoat composition containing oxygen-scavenging additives. This extraction of the complex overcoat structure eliminates the shelf life issues associated with multi-layer coatings while maintaining polymerization efficiency through chemical oxygen scavenging.
Solution Approach 2:
The patent uses oxygen-scavenging additives (mercaptans, phenolic compounds, or amines) as intermediaries that chemically interact with oxygen to protect the polymerization process. These additives provide long-term oxygen protection without requiring complex overcoat structures, thereby extending shelf life.
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 highly sensitive negative-working imageable elements with improved shelf life and imaging properties, allowing for effective development without a preheat step and without the need for an oxygen-impermeable topcoat, while maintaining good imaging performance at lower energies.
Implementation Method 1
a borate initiator composition capable of generating radicals sufficient to initiate polymerization of the radically polymerizable component upon exposure to imaging radiation
Implementation Method 2
a radiation absorbing compound
Data Source
AI summary
A radiation-sensitive composition includes a radically polymerizable component and a borate initiator composition capable of generating radicals sufficient to initiate polymerization of the radically polymerizable component upon exposure to imaging radiation. This composition also includes a radiation absorbing compound (such as an IR-sensitive dye), a polymeric binder comprising a polymer backbone to which is directly or indirectly linked a pendant group comprising a reactive vinyl group, and a primary additive that is a poly(alkylene glycol) or an ether or ester thereof that has a number average molecular weight of from about 200 and up to 4000 and comprises from about 2 to about 50 weight % based on the total composition solids content. This composition can be used to prepare a negative-working imageable element that can be imaged at relatively low energy and developed without a preheat step.