Flexographic Relief Dots with Compound Shoulder Angles
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Solution Overview
Problem
Flexographic printing on corrugated board substrates often results in 'fluting' or 'banding' effects due to the underlying fluting structure, which is exacerbated by digital workflow processes and difficult to mitigate with increased printing pressure, leading to suboptimal print quality and potential damage to the substrate.
Innovation Solution
A relief image printing plate with relief dots featuring a planar top surface, compound shoulder angles greater than 50°, deep relief greater than 9% of the plate relief, and sharp edges with a low edge radius to dot width ratio, combined with a diffusion barrier to limit oxygen diffusion during exposure, and controlled illumination to optimize dot shape and surface roughness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If increased printing pressure is applied to eliminate striping, then print quality improves, but the corrugated board substrate is damaged
Solution Approach 1:
The invention changes the geometric parameters of the relief dots (shoulder angles, depth, edge sharpness) to optimize print quality without requiring increased printing pressure. The compound shoulder angles greater than 50° and deep relief greater than 9% create dots that maintain stability and reduce fluting effects, allowing high-quality printing at lower pressures that do not damage the corrugated board substrate
Solution Approach 2:
The invention applies different geometric characteristics to different parts of the relief dot structure. The compound shoulder angles (first angle greater than 70°, second angle less than 45°) create localized variations in dot geometry that optimize both print quality and substrate interaction, reducing fluting while maintaining image fidelity
2Productivity
If digital workflow process is used for plate production, then manufacturing efficiency improves, but fluting effect is exacerbated
Solution Approach 1:
The invention optimizes the geometric parameters of relief dots produced through digital workflow processes. By specifying compound shoulder angles greater than 50°, deep relief greater than 9% of plate relief, and sharp edges with low edge radius to dot width ratio, the invention corrects the fluting tendency inherent in digital platemaking while maintaining the efficiency benefits of digital production
Solution Approach 2:
The invention uses a diffusion barrier during the exposure process to limit oxygen diffusion into the photocurable layer. This controlled atmospheric condition during manufacturing improves the precision of the relief dot geometry, reducing fluting effects while maintaining digital workflow efficiency
3Ease of manufacture
If relief dots with conventional geometry are used, then manufacturing is simpler, but dot stability and impression resistance are reduced
Solution Approach 1:
The invention specifies precise geometric parameters for relief dots including compound shoulder angles greater than 50°, deep relief greater than 9% of plate relief, and sharp edges with low edge radius to dot width ratio. These parameter changes enhance dot stability and impression resistance while remaining compatible with standard digital platemaking processes
Solution Approach 2:
The invention creates a composite structure in the relief dot geometry by combining different angular characteristics (compound shoulder angles with first angle greater than 70° and second angle less than 45°). This composite geometric structure provides both manufacturing feasibility and enhanced operational reliability for flexographic printing
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 significantly reduces print fluting and enhances dot stability and impression resistance, resulting in superior print quality and extended print runs with improved surface roughness control.
Implementation Method 1
selectively laser ablating the laser ablatable mask 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 by deploying a diffusion barrier on top of the in-situ mask and any uncovered portions of the photocurable layer prior to step (b)
Data Source
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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 that provide optimal print performance on various substrates, including corrugated board.