Flexographic Plate Resin Composition for Stable Flat Top Dots
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Solution Overview
Problem
Flexographic printing plates face issues with defective dot formation due to oxygen inhibition, leading to blurred boundaries and unstable dot sizes, particularly when using different illuminance exposure machines, necessitating the development of a technique that can form flat top dots consistently across various exposure conditions.
Innovation Solution
The solution involves controlling the time from irradiation to heat generation peak and the amount of heat generation at the peak top in the photosensitive resin composition layer to specific numerical ranges using photo-differential scanning calorimetry, optimizing the composition with ethylenically unsaturated compounds, photopolymerization initiators, stabilizers, and dyes to enhance dot formability and suppress excessive halftone formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If digital plate-making technique with laser ablation is used, then time and effort in making negative film is saved and higher-resolution images can be made, but oxygen inhibition causes defective formation of flexographic printing plate with rounded dot edges and blurred boundaries
Solution Approach 1:
An oxygen barrier layer is introduced as an intermediary between the photosensitive resin composition layer and the ambient environment. This layer prevents oxygen from reaching the resin surface during UV exposure, eliminating oxygen inhibition effects and enabling proper dot formation with sharp boundaries and correct dimensions.
Solution Approach 2:
The oxygen barrier layer creates a locally inert environment by blocking oxygen access to the photosensitive resin during the exposure process. This inert environment allows the photopolymerization reaction to proceed without oxygen interference, resulting in accurate dot reproduction.
2Ease of manufacture
If low-illuminance exposure machine is used, then equipment cost is reduced, but oxygen inhibition impact increases causing defective dot formation
Solution Approach 1:
The oxygen barrier layer serves as a protective intermediary that compensates for the lower energy input from low-illuminance exposure machines. By preventing oxygen inhibition, it ensures that even with reduced UV intensity, the photosensitive resin can cure properly and form accurate dots.
Solution Approach 2:
The oxygen barrier layer is applied beforehand to cushion or protect the photosensitive resin from oxygen inhibition effects before exposure occurs. This pre-protection ensures that the resin remains vulnerable to UV curing while being shielded from oxygen, enabling successful plate making with cost-effective equipment.
3Speed
If high-illuminance exposure machine is used, then curing reaction speed is improved, but excessive halftone dot formation occurs with enlarged dot size and darker images
Solution Approach 1:
The oxygen barrier layer enables local control of the curing environment. By preventing oxygen inhibition only at the surface where exposure occurs, it allows the photopolymerization to proceed at the appropriate rate without excessive cross-linking, thereby controlling dot size and preventing halftone dot formation even with high-illuminance exposure.
Solution Approach 2:
The oxygen barrier layer acts as a mediator that modulates the interaction between UV light and the photosensitive resin. It allows beneficial UV energy to pass through while blocking harmful oxygen, thereby controlling the curing reaction to achieve proper dot formation without over-curing effects.
4Manufacturing precision
If different flexographic printing plates are used for different illuminance exposure machines, then dot formability under various conditions is optimized, but operation complexity increases
Solution Approach 1:
The oxygen barrier layer provides universal compatibility across different exposure machine types and illuminance levels. By incorporating this layer, a single photosensitive resin composition can be used with both low-illuminance and high-illuminance exposure machines while maintaining consistent dot formability, eliminating the need for separate plate formulations.
Solution Approach 2:
The introduction of the oxygen barrier layer changes the exposure parameters (specifically oxygen concentration at the resin surface) in a way that universalizes the photosensitive resin's performance. This parameter modification allows the same resin composition to achieve optimal dot formability across a wide range of UV illuminance conditions.
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
This approach enables the production of flexographic printing plates that form flat top dots under low-illuminance exposure and suppress excessive halftone dot formation under high-illuminance exposure, ensuring consistent printing quality across different exposure conditions.
Implementation Method 1
ultraviolet exposure (back exposure) is performed on the entire surface of the photosensitive resin composition layer through a polyester film as a support to provide a thin uniform cured layer
Implementation Method 2
an ablation layer that can be removed with an infrared laser is provided on a photosensitive resin composition layer, and the ablation layer is cut into a desired pattern with a laser
Data Source
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AI summary
An original flexographic printing plate containing at least: a support (a); a photosensitive resin composition layer (b) laminated thereon; and an infrared ray ablation layer (c) laminated thereon, wherein when a photo-differential scanning calorimetry is carried out under normal temperature and normal pressure while irradiating a molded product of 0.5 mm thickness formed of a photosensitive resin composition constituting the photosensitive resin composition layer (b) with a light of 365 nm wavelength at an illuminance of 10 mW/cm2, a time from start of irradiation to a heat generation peak is 4.0 seconds or more and 8.5 seconds or less, and an amount of heat generation at a peak top is 1500 µW/mg or more and 3000 µW/mg or less.