Inkjet Decorative Sheet Non-Continuous Clear Layer Mold Release
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Solution Overview
Problem
Existing image formation methods using inkjet systems face challenges in achieving images with excellent stretchability and preventing sticking to molds during thermal molding processes.
Innovation Solution
A method involving the sequential formation of an image layer using a radiation curable inkjet colored ink composition with a high monofunctional polymerizable compound content and a clear layer using a radiation curable inkjet clear ink composition with a high polyfunctional polymerizable compound content, where the clear layer is dispersed non-continuously over the image layer to enhance stretchability and reduce mold adhesion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a radiation curable inkjet colored ink composition with high monofunctional polymerizable compound content is used to form the image layer, then the ink composition can be used efficiently and running cost is low, but the image layer tends to stick to molds during thermal molding processes
Solution Approach 1:
A clear ink layer is introduced as an intermediary between the image layer and the mold. This clear ink layer has low mold adhesion properties and acts as a release agent, preventing the image layer from sticking to the mold during thermal molding while allowing the image layer to maintain its structural integrity and stretchability
Solution Approach 2:
The invention uses a composite structure consisting of two distinct ink compositions: a colored ink layer containing monofunctional polymerizable compounds for cost-effectiveness and a clear ink layer containing polyfunctional polymerizable compounds for mold release. This composite approach allows each layer to perform its specific function optimally
2Object-generated harmful factors
If the clear layer is formed continuously over the image layer, then mold adhesion is suppressed, but the stretchability of the image deteriorates
Solution Approach 1:
The clear ink layer is applied with locally varying coverage rather than as a uniform continuous layer. This allows regions requiring mold release to have clear ink coverage while regions requiring stretchability maintain image layer continuity, optimizing both functions through spatial differentiation
Solution Approach 2:
Instead of applying clear ink uniformly across the entire image layer, the invention uses partial coverage where clear ink is applied only in specific areas or at specific densities. This partial action provides sufficient mold release functionality while preserving the stretchability of the image layer in critical regions
3Object-generated harmful factors
If polyfunctional polymerizable compounds are used in the clear ink composition, then mold adhesion is suppressed, but the curability of the ink composition becomes insufficient
Solution Approach 1:
The invention adjusts the molecular weight and functional group composition of the polyfunctional polymerizable compounds in the clear ink to achieve optimal balance between curability and mold release. By carefully selecting compounds with appropriate parameters (molecular weight, number of functional groups, glass transition temperature), the clear ink achieves sufficient curability while maintaining low mold adhesion
Solution Approach 2:
The clear ink composition uses a composite of polyfunctional polymerizable compounds with different characteristics to achieve both curability and mold release. The combination of compounds with varying functional group numbers and molecular weights allows the system to achieve adequate crosslinking for curability while maintaining the flexibility and low adhesion required for mold release
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 method effectively achieves images with excellent stretchability and suppressed sticking to molds, ensuring the durability and integrity of the printed materials during thermal molding processes.
Implementation Method 1
an ink composition which is curable upon exposure to radiation such as UV rays
Data Source
Figure 1(a)~1(b)
Figure 2
Figure 3
AI summary
Disclosed is an image formation method comprising, in sequence, an image layer formation step of forming an image layer by discharging at least one radiation curable inkjet colored ink composition onto a recording medium, and a clear layer formation step of forming a clear layer by discharging a radiation curable inkjet clear ink composition onto the image layer, the radiation curable inkjet colored ink composition comprising a monofunctional polymerizable compound in an amount of at least 50 mass % of polymerizable compounds, the radiation curable inkjet clear ink composition comprising a polyfunctional polymerizable compound in an amount of at least 50 mass % of the polymerizable compounds, and in the clear layer formation step the radiation curable inkjet clear ink composition being dispersed above the image layer to thus form a non-continuous clear layer.