Flexographic Printing Element Dot Structure Fluting Resistance
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Solution Overview
Problem
Flexographic printing on corrugated board substrates often results in 'fluting' or 'banding' effects due to the uneven support of the underlying flute layer, which is more pronounced in digital workflows and not effectively mitigated by increasing printing pressure, leading to suboptimal dot structure and surface quality.
Innovation Solution
A method for preparing relief image printing elements involves selectively laser ablating a photosensitive printing blank with a laser ablatable layer, followed by exposure to actinic radiation, where air diffusion into the photocurable layer is limited using a barrier membrane or oil layer with a low oxygen diffusion coefficient, and adjusting the type, power, and incident angle of illumination to enhance dot shape and surface roughness control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If printing pressure is increased to reduce fluting effects, then print density improves, but corrugated board substrate is damaged
Solution Approach 1:
The invention changes the physical-chemical parameters of the photocurable layer by limiting oxygen diffusion during exposure, which modifies the curing characteristics and dot structure of the printing element. This allows achieving adequate print density without requiring excessive printing pressure that would damage the substrate.
2Productivity
If digital workflow process is used to produce printing elements, then manufacturing efficiency improves, but fluting effect is more pronounced
Solution Approach 1:
The invention creates an oxygen-limiting environment during exposure by applying a barrier membrane or oil layer to the photocurable layer. This inert environment prevents oxygen interference with the photopolymerization process, thereby improving dot structure and reducing fluting effects while maintaining digital workflow efficiency.
Solution Approach 2:
The invention modifies the chemical environment parameters during exposure by limiting oxygen diffusion, which changes the curing characteristics of the photocurable layer. This parameter change improves print quality and reduces fluting while maintaining the benefits of digital workflow production.
3Ease of manufacture
If air diffusion is allowed during exposure, then exposure process is simple, but dot structure and surface quality deteriorate
Solution Approach 1:
The invention uses a flexible barrier membrane or oil layer applied to the photocurable layer during exposure. This thin film barrier effectively limits oxygen diffusion without significantly complicating the exposure process, thereby improving dot structure and surface quality while maintaining ease of manufacture.
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 results in a printing element with improved dot structure resistance to fluting, superior surface quality, and increased impression latitude, effectively reducing print fluting and enhancing the printing performance on corrugated board substrates.
Implementation Method 1
selectively laser ablating the laser ablatable layer to create an in situ mask
Implementation Method 2
exposing the laser ablated printing blank to at least one source of actinic radiation to selectively cross link and cure portions of the photocurable layer
Implementation Method 3
the diffusion of air into the at least one photocurable layer is limited during the exposing step by a method selected from at least one of: i) laminating a barrier membrane to the in situ mask and any uncovered portions of the photocurable layer
Data Source
Figure 1
AI summary
A method of making a relief image printing element from a photosensitive printing blank is provided. A photosensitive printing blank with a laser ablatable layer disposed on at least one photocurable layer is ablated with a laser to create an In situ mask. The printing blank is then exposed to at least one source of actinic radiation through the in situ mask to selectively cross link and cure portions of the photocurable layer. Diffusion of air into the at least one photocurable layer Is limited during the exposing step and preferably at least one of the type, power and incident angle of illumination of the at least one source of actinic radiation is altered during the exposure step. The resulting relief image comprises a plurality of dots and a dot shape of the plurality of dots is produced that is highly resistant to print fluting for printing on corrugated board.