Negative-Working Imageable Elements White Light Stability
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Solution Overview
Problem
Negative-working imageable elements used in lithographic printing plates are insufficiently stable to white light, leading to fogging or toning issues, and existing solutions involving filter dyes in topcoats or interlayers contaminate prewash baths and pose environmental concerns.
Innovation Solution
Incorporating a filter dye with a maximum absorption wavelength of 300 to 500 nm directly into the imageable layer, along with infrared radiation-sensitive compounds, to enhance white light stability without the need for additional layers, ensuring the dye does not interfere with infrared imaging and maintains imaging properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If filter dyes are incorporated into topcoats or interlayers to improve white light stability, then white light stability is improved, but prewash baths are contaminated and environmental concerns arise
Solution Approach 1:
The filter dye is merged with the imageable layer itself rather than being placed in a separate topcoat or interlayer. This integration eliminates the need for additional layers that would otherwise contaminate prewash baths, while maintaining the white light stability function within the imageable layer composition.
Solution Approach 2:
The filter dye function is extracted from the topcoat/interlayer structure and placed directly into the imageable layer. This repositioning removes the source of contamination from the prewash process while preserving the desired white light stability performance.
2Reliability
If filter dyes are added to improve white light stability, then handling stability in room light is improved, but imaging properties such as photospeed may be lost
Solution Approach 1:
The filter dye is incorporated into the imageable layer at specific local concentrations that provide white light stability without interfering with the infrared imaging function. The composition is locally optimized to balance both requirements.
Solution Approach 2:
The wavelength absorption characteristics of the filter dye are specifically selected to absorb in the 300-500 nm range, which provides white light stability while being transparent to the infrared imaging radiation. This parameter selection ensures both functions coexist.
3Ease of operation
If initiator components are present in the imageable layer, then imaging function is provided, but white light stability deteriorates due to absorption in the 300 to 500 nm spectral region
Solution Approach 1:
The filter dye acts as an intermediary that selectively absorbs harmful visible light in the 300-500 nm range while allowing infrared imaging radiation to pass through to the initiator components. This mediator protects the initiator from premature activation by white light.
Solution Approach 2:
The filter dye converts the potentially harmful absorption of visible light by initiator components into a beneficial protective effect. By absorbing the harmful 300-500 nm radiation, the filter dye prevents unwanted initiation while allowing the initiator to function properly during infrared imaging.
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 significant white light stability to the imageable elements, allowing handling in room light without fogging, while avoiding contamination of prewash baths and maintaining imaging performance, with the filter dye present in amounts that satisfy specific stability and exposure energy criteria.
Implementation Method 1
a filter dye having a λmax of from about 300 to about 500 nm
Implementation Method 2
an infrared radiation absorbing compound having a λmax of from about 750 to about 1400 nm
Implementation Method 3
a composition that provides free radicals in response to exposure to infrared radiation
Implementation Method 4
a free radical polymerizable compound
Data Source
AI summary
Negative-working imageable elements can be imaged and processed to provide lithographic printing plates. These imageable elements are sensitive to infrared radiation but are insensitive to “white” light and thus can be more easily handled under white light conditions. These properties are possible by incorporating a filter dye having a λmax of from about 300 to about 500 nm into the imageable layer of the imageable elements.