Interleaved Release Film for Thermoforming Roll Offset
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Solution Overview
Problem
The existing digital printing processes for thermoform containers face issues with roll offset or set-off, where ink from the printed surface transfers to the backside of the plastic substrate during the thermoforming process, leading to aesthetic and quality control problems, especially in food and drug packaging applications, where conventional ink formulations and surface treatments have proven insufficient.
Innovation Solution
The implementation of a process where additional material layers, specifically low surface energy polymers like LDPE or BOPP, are interleaved between the layers of the re-rolled substrate material web to prevent ink transfer, using UV-curable inks that can stretch without cracking and are compatible with the thermoforming process, ensuring that any ink offset occurs between the ink and the interleaved material rather than the substrate's backside.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If UV-curable inks are used for digital printing on substrate material webs, then image quality and stretchability are improved, but roll offset or set-off occurs where ink transfers to the backside of the substrate
Solution Approach 1:
A release film is introduced as an intermediary layer between the printed substrate layers during rewinding. This release film has low surface energy properties that prevent ink adhesion, so any ink transfer occurs to the release film instead of the substrate backside. The release film acts as a sacrificial barrier that protects the printed surface from offsetting to the next layer.
2Shape
If the substrate material is stretched during thermoforming, then the container shape is formed, but the printed ink cracks or distorts
Solution Approach 1:
UV-curable inks are used that have been specifically formulated to maintain flexibility and adhesion through the thermoforming process. The ink formulation parameters are changed to include plasticizers and flexible binders that allow the ink layer to stretch without cracking when the substrate is heated and formed into the container shape.
3Ease of manufacture
If conventional ink formulations are used, then printing is simpler, but ink transfer to the backside occurs during storage and handling
Solution Approach 1:
A release film with low surface energy coating is placed between printed substrate layers during rewinding and storage. This intermediary layer prevents direct contact between printed surfaces, blocking the ink transfer pathway. The release film can be easily removed before thermoforming, adding minimal complexity to the overall process.
4Quantity of substance
If multiple layers of substrate are wound together, then storage efficiency increases, but ink offset between layers worsens
Solution Approach 1:
Release films are interleaved between multiple substrate layers during rewinding for storage. This allows efficient stacking and storage of printed material while the release films prevent ink offset between adjacent layers. The release films are thin and do not significantly increase roll diameter or storage space requirements.
Solution Approach 2:
Thin release films are used as barrier layers between substrate layers. These films are flexible enough to conform to the rolled configuration while providing effective prevention of ink transfer. The thin film structure minimizes space occupation while maintaining the anti-offset function throughout the stored roll.
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 solution effectively eliminates roll offset, maintaining image quality and preventing unwanted ink transfer to the backside of the substrate, thus ensuring the integrity and appearance of thermoformed containers, particularly in food and drug packaging applications.
Implementation Method 1
The images are then exposed to ultraviolet radiation to cure the ink
Implementation Method 2
the plastic substrate is fed through a marking engine where images are jetted onto the substrate with UV-curable inks
Implementation Method 3
additional material layers, specifically low surface energy polymers like LDPE or BOPP, are interleaved between the layers of the re-rolled substrate material web to prevent ink transfer
Data Source
AI summary
A system and method are provided for implementing a process by which printed rolls of substrate material web have additional material layers interleaved between the rolled material web layers to substantially eliminate back transfer or roll offset of printed images on the back sides of the rolled material substrates. In a process for pre-printing thermoforming grade plastic materials to produce rolls of substrate material for use in a thermoforming process, ink compositions, particularly adapted for the thermoforming process, are deposited on substantially continuous webs of substrate material. The webs of substrate material are then re-rolled with separate layers of low surface energy substrate material interleaved between the layers of the printed substrate material in order to substantially eliminate imaging defects produced by back transfer of printed images on to the backs of layers of the printed substrate material stored in rolls.