Flexo Printing Element Seamless Sealing via Diffusion Bonding
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Solution Overview
Problem
Existing methods for producing high-quality, cylindrical flexographic printing elements with seamless ends face challenges such as visible gaps and disruptions due to assembly or cutting errors, leading to suboptimal print quality and increased complexity in sealing the seam of photopolymerizable layers.
Innovation Solution
A layered composite comprising a photopolymerizable relief-forming layer and an underlying elastomeric carrier layer, where the carrier layer has a higher hardness than the relief-forming layer, is applied to a hollow cylinder, and the edges are joined using a calendering process below the melting temperature of the photopolymerizable layer, eliminating the need for a carrier film and ensuring precise sealing without gaps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a photopolymerizable layer is applied to a hollow cylinder and the edges are joined using melting process, then the seam can be sealed, but the melting process causes irregular thickness changes and requires complex grinding and smoothing operations
Solution Approach 1:
The invention changes the joining temperature parameter from above melting point to below melting point (80-130°C), transforming the joining mechanism from melting to diffusion bonding. This parameter change eliminates the irregular thickness changes caused by melting while still achieving reliable seam sealing through molecular diffusion across the interface.
Solution Approach 2:
The invention introduces a pre-heating step before the actual joining process. The photopolymerizable layer is pre-heated to 80-130°C to activate molecular mobility and facilitate diffusion bonding, then immediately joined under pressure. This preliminary heating action enables seamless joining without melting, eliminating the need for subsequent grinding and smoothing operations.
2Strength
If the photopolymerizable layer is heated above melting temperature to join edges, then the edges can be fused together, but volatile components evaporate and layer properties change adversely
Solution Approach 1:
The invention fundamentally changes the temperature parameter from above melting point (>160°C) to below melting point (80-130°C). This parameter change enables edge fusion through diffusion bonding at lower temperatures, preventing evaporation of volatile components while still achieving strong bonding through molecular diffusion and pressure-induced joining.
3Reliability
If a carrier film is used during calendering to prevent gap formation, then the photopolymerizable layer can be sealed, but the carrier film creates assembly errors and visible disruptions in printing
Solution Approach 1:
The invention extracts and eliminates the carrier film from the system. Instead of using a carrier film that causes assembly errors and visible disruptions, the invention achieves gap prevention through direct diffusion bonding of the photopolymerizable layer edges at controlled temperatures below melting, eliminating the intermediary carrier film that caused manufacturing precision issues.
4Manufacturing precision
If conventional coating techniques (solution coating or ring extrusion) are used to apply photopolymerizable layer, then complete enveloping can be achieved, but the processes are extremely complex and expensive
Solution Approach 1:
The invention uses a flexible prefabricated photopolymerizable layer that can be wrapped around the hollow cylinder. This flexible film approach eliminates the need for complex solution coating equipment or ring extrusion machinery, achieving complete enveloping through simple wrapping and sealing operations at controlled temperatures below melting point.
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 seamless, high-quality flexographic printing elements with improved concentricity and print resolution, reducing the need for rework and maintaining consistent printing behavior across the entire form.
Implementation Method 1
a) a carrier film, b) optionally a detackifying layer, c) an elastomeric carrier layer, d) a photopolymerizable relief-forming layer
Implementation Method 2
joining the cut edges by bringing the surface of the photopolymerizable layer on the hollow cylinder into contact with a rotating calender roll while heating until the cut edges are joined together
Data Source
AI summary
The invention relates to a layered composite comprising a) a photopolymerisable relief-forming layer at least containing an elastomer binding agent, ethylenically unsaturated monomers, a photoinitiator and optionally other additives, b) an optionally photopolymerisable elastomer carrier layer at least containing an elastomer binding agent, optionally ethylenically unsatured monomers, a photoinitiator, and optionally other additives. In the photopolymerised state, the relief-forming layer a) has a hardness of between 30 and 70° Shore A, and the elastomer carrier layer b) a hardness of between 75° Shore A and 70° Shore D, layer b) having a higher hardness than layer a) by at least 5° Shore A.