Siloxane-Elastomer Hard Coating Laminate for Foldable Displays
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Solution Overview
Problem
Conventional hard coating films for foldable displays face challenges in achieving high pencil hardness, impact resistance, and bending properties while avoiding issues like curling, cracking, and poor adhesiveness due to high setting shrinkage and thickness limitations.
Innovation Solution
A hard coating laminate comprising a supporting substrate layer with a hard coating layer formed from a resin composition containing a siloxane resin and an elastomeric polymer, where the siloxane resin includes 70 mol% or more of a specific repeating unit, providing a thickness of 50 to 240 μm, enabling high pencil hardness, excellent adhesiveness, and improved internal and external bending properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the thickness of the hard coating layer is increased to improve surface hardness, then pencil hardness is improved, but setting shrinkage increases leading to wrinkling, curling, and poor external bending properties
Solution Approach 1:
The patent applies parameter changes by modifying the resin composition ratio between siloxane resin and elastomeric polymer. Specifically, it uses siloxane resin at 20-80 wt% and elastomeric polymer at 80-20 wt% to achieve optimal balance. This compositional parameter adjustment allows the coating to maintain high surface hardness while reducing setting shrinkage, thereby preventing wrinkling and curling even at thicknesses of 50-240 μm, and improving external bending properties.
Solution Approach 2:
The patent employs composite materials by combining siloxane resin with elastomeric polymer in a specific ratio range. The siloxane resin provides surface hardness and abrasion resistance, while the elastomeric polymer reduces setting shrinkage and improves flexibility. This composite approach enables the hard coating layer to simultaneously achieve high pencil hardness (5H or more) and good external bending properties without the defects associated with thick single-material coatings.
2Strength
If the thickness of the hard coating layer is increased to replace glass, then surface hardness is improved, but the coating becomes prone to cracking and peeling
Solution Approach 1:
The patent uses parameter changes by optimizing the resin composition to contain siloxane resin at 20-80 wt% and elastomeric polymer at 80-20 wt%. This specific compositional ratio controls the curing shrinkage and internal stress of the coating. As a result, the hard coating layer can be applied at thicknesses of 50-240 μm (replacing glass functionality) while maintaining high crack resistance and adhesion, preventing the cracking and peeling issues that typically occur with thick hard coatings.
Solution Approach 2:
The patent applies composite materials by formulating a resin composition that combines siloxane resin (providing hardness) with elastomeric polymer (providing flexibility and crack resistance). This composite structure enables the hard coating layer to achieve glass-replacing thickness (50-240 μm) and surface hardness (5H or more) while simultaneously improving reliability through enhanced crack resistance and peeling resistance, which would not be achievable with conventional single-material hard coatings.
3Strength
If acrylate-based resin is used for UV curing, then hard coating can be achieved, but high setting shrinkage causes severe curling
Solution Approach 1:
The patent applies parameter changes by replacing conventional acrylate-based UV-curing resin with a siloxane resin-eLASTOMERIC polymer composite system. The siloxane resin (20-80 wt%) provides UV-curable hardness, while the elastomeric polymer (80-20 wt%) significantly reduces setting shrinkage. This parameter change in resin composition resolves the severe curling issue associated with acrylate-based resins while maintaining the ability to achieve high surface hardness through UV curing.
Solution Approach 2:
The patent uses composite materials by combining siloxane resin with elastomeric polymer to create a new resin composition that overcomes the limitations of conventional acrylate-based UV-curing resins. The siloxane resin component enables UV curing and provides hardness, while the elastomeric polymer component reduces setting shrinkage to minimal levels, thereby preventing severe curling. This composite approach achieves both hardness and shape stability that cannot be obtained with acrylate-based resins alone.
4Shape
If thin coating or double-sided coating is performed to reduce setting shrinkage, then internal bending is improved, but impact resistance and scratch resistance are insufficient
Solution Approach 1:
The patent applies parameter changes by modifying the resin composition to contain siloxane resin at 20-80 wt% and elastomeric polymer at 80-20 wt%, and by optimizing the hard coating layer thickness to 50-240 μm. This parameter change allows single-sided thick coating that simultaneously achieves excellent internal bending properties (due to reduced setting shrinkage from the elastomeric polymer) and sufficient impact resistance and scratch resistance (due to the increased thickness and hardness from the siloxane resin).
Solution Approach 2:
The patent uses composite materials by formulating a resin composition of siloxane resin and elastomeric polymer that enables a single thick coating layer (50-240 μm) to perform multiple functions. The composite structure provides impact resistance and scratch resistance comparable to double-sided or thin coatings, while the elastomeric polymer content keeps setting shrinkage low for good internal bending properties. This eliminates the need for double-sided coating while maintaining all required performance characteristics.
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 laminate exhibits high pencil hardness, excellent adhesiveness, and enhanced impact resistance with improved internal and external bending properties, suitable for foldable displays, and can be applied using single-sided or double-sided coating, reducing the risk of cracking and curling.
Implementation Method 1
a hard coating layer which is formed on the supporting substrate layer and which has a thickness of 50 to 240 μm, wherein the hard coating layer includes a cured product of a resin composition including a siloxane resin and an elastomeric polymer
Data Source
AI summary
The present disclosure relates to a hard coating laminate having an internal bending property and an external bending property including: a supporting substrate layer containing a thermoplastic resin; and a hard coating layer having a thickness of 50 to 240 μm, wherein the hard coating layer includes a cured product of a resin composition including a siloxane resin having a predetermined glycidoxypropyl modified silicone structure and an elastomeric polymer.