Decorated Sheet Surface Protection Layer Crack Prevention
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Solution Overview
Problem
Existing decorative resin-molded articles face issues with surface protection layer cracking during three-dimensional molding due to vacuum or pressure effects, and previous solutions using ionizing radiation curable resins have complications such as uncured resin handling and mold contamination.
Innovation Solution
A decorative sheet with a surface protection layer composed of a cured ionizing radiation curable resin composition containing urethane(meth)acrylate with a polycarbonate skeleton and multi-functional (meth)acrylate in a specific mass ratio, providing enhanced damage resistance and three-dimensional moldability without cracking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the surface protection layer is made with high cross-link density using ionizing radiation curable resin, then abrasion resistance and damage resistance improve, but cracks occur on the curved surface during forming
Solution Approach 1:
The invention changes the chemical composition parameters of the curable resin by incorporating specific ratios of polycarbonate polyol (30-70 mass%) and polyester polyol (30-70 mass%), along with controlling the isocyanate index (80-120). This parameter optimization allows the surface protection layer to achieve both high damage resistance and sufficient flexibility to prevent cracking during three-dimensional forming
Solution Approach 2:
The invention uses a composite resin system combining multiple polyol types (polycarbonate and polyester) with polyisocyanate, creating a multi-component curable resin composition. This composite approach balances the rigidity needed for damage resistance with the flexibility required to accommodate forming stresses without cracking
2Shape
If the decorative sheet is drawn to fit the mold shape, then three-dimensional moldability improves, but the surface protection layer cracks due to vacuum or pressure effects
Solution Approach 1:
The invention modifies the resin composition parameters to include specific polyol combinations and isocyanate indices that provide optimal balance between elasticity and strength, enabling the surface protection layer to stretch during vacuum forming and pressure application without cracking while maintaining surface integrity
Solution Approach 2:
The resin composition is designed beforehand to include flexible components (polycarbonate and polyester polyols) that provide built-in cushioning capacity, allowing the surface protection layer to absorb the stresses of three-dimensional forming processes without developing cracks
3Strength
If the surface protection layer is half-cured at the decorative sheet stage, then handling damage is reduced, but the uncured resin contaminates the mold and complicates the manufacturing process
Solution Approach 1:
The invention performs preliminary full curing of the surface protection layer before the decorative sheet is used in molding operations. This preliminary action ensures the surface layer has adequate strength for handling while eliminating uncured resin that would otherwise contaminate molds and complicate subsequent manufacturing steps
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 ensures no cracks on the surface protection layer during molding, offering high damage resistance and three-dimensional moldability, with the surface protection layer being fully cured before molding, eliminating post-molding curing steps and reducing manufacturing complexity and costs.
Implementation Method 1
a surface protection layer which consists of a cured material of an ionizing radiation curable resin composition
Data Source
AI summary
The decorative sheet includes a surface protection layer and a substrate at least, the surface protection layer being provided on the substrate, in which the surface protection layer consists of a cured material of an ionizing radiation curable resin composition at least containing a urethane(meth)acrylate with a polycarbonate skeleton (A) and a multi-functional (meth)acrylate (B) in a mass ratio ((A)/(B)) of (98/2)-(70/30).