UV Lithographic Plate On-Press Processing
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Solution Overview
Problem
Conventional lithographic printing plates require development to produce a visible image, making it difficult to identify and inspect plate quality before mounting on a press, leading to potential errors and inefficiencies.
Innovation Solution
A method for creating lithographic printing plates using near UV or violet light exposure that produces a visible print-out image with high contrast between exposed and non-exposed areas, utilizing a combination of an onium compound as a free-radical initiator and a sensitizing dye, such as fluorenes, to form a stable image without the need for post-exposure development.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If conventional lithographic printing plates require development to produce a visible image, then the plate can be processed with standard development procedures, but it becomes difficult to identify and inspect plate quality before mounting on a press
Solution Approach 1:
The patent applies preliminary action by incorporating a visible indicium that becomes visible upon exposure to actinic radiation, allowing the plate to display identification information and image content before mounting on the press. This preliminary visibility enables inspection and identification without requiring development, thus solving the contradiction between ease of operation and time loss.
2Ease of operation
If a visible image is produced immediately after exposure, then plate inspection is enabled before mounting, but the image must remain stable without fading or degradation over time
Solution Approach 1:
The patent uses an intermediary substance - a visible indicium comprising a dye or pigment that is incorporated into the plate coating. This intermediary becomes visible upon exposure through a chemical reaction that does not require full development, allowing pre-press inspection while maintaining image stability. The visible indicium acts as a mediator between the exposed and unexposed areas, providing stable visibility without requiring complete development processing.
3Productivity
If on-press development is used to eliminate post-exposure processing steps, then workflow is simplified, but the plate must maintain a visible image through the entire process without development
Solution Approach 1:
The patent applies preliminary action by pre-incorporating a visible indicium into the plate coating that becomes visible upon exposure. This allows the plate to display a visible image and identification information before mounting on the press, enabling quality control and image verification during the printing process itself. The visible indicium is prepared in advance and remains stable throughout on-press development, eliminating the need for separate development steps while maintaining manufacturing precision.
4Ease of manufacture
If a sensitizing dye is used to enable violet light exposure, then the plate can be exposed with available laser sources, but the dye may fade or degrade under prolonged light exposure
Solution Approach 1:
The patent applies parameter changes by carefully selecting and optimizing the characteristics of the sensitizing dye, including its absorption spectrum, stability properties, and concentration. The dye is chosen to be sensitive to violet light wavelengths (405 nm) from available laser sources while maintaining stability under prolonged exposure. By adjusting these parameters - particularly the dye's molecular structure and its interaction with the plate coating matrix - the patent achieves both laser compatibility and extended durability without fading.
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 method achieves a high contrast print-out image that remains visible for an extended period, allowing for pre-press inspection and reducing errors by ensuring the plates can be evaluated and prepared without the need for immediate development, enhancing efficiency and reducing downtime.
Implementation Method 1
The coating typically comprises a polymerizable and/or crosslinkable compound and an initiator, in particular a photopolymerizable and/or photocrosslinkable compound and a photoinitiator
Implementation Method 2
Photopolymer plates can be sensitized to near UV light, in particular to the wavelength range from 350 to 400 nm, to violet light i.e. wavelengths ranging between 400 and 450 nm
Data Source
AI summary
A method of lithographic plate making is disclosed wherein a plate precursor is exposed to laser radiation in the wavelength range from 350 to 450 nm, said plate precursor comprising a hydrophilic support and a photopolymerizable or photocrosslinkable image recording layer, and then processed on-press by supplying fountain and ink. The exposure produces a visible image having a 1976 CIELAB color distance ΔE between exposed and non-exposed areas of at least 2.5.