Hard Coating Film with Segmented Elastic Modulus Layers
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Solution Overview
Problem
Existing hard coating films for mobile device displays face challenges in achieving high hardness and impact resistance without suffering from cracking, curling, or excessive thickness-related issues, which limits their suitability as substitutes for glass.
Innovation Solution
A hard coating film comprising a supporting substrate with a first hard coating layer having an elongation strain of 4% or more and a second hard coating layer with a higher elastic modulus, both formed from photocurable crosslinking copolymers and tri- to hexa-functional acrylate monomers, ensuring a difference in elastic moduli of 500 MPa or more, which enhances hardness and impact resistance while preventing curling and cracking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the thickness of the hard coating layer is increased to improve surface hardness, then the surface hardness increases, but the coating layer becomes more prone to setting shrinkage which leads to wrinkling or curling and production of cracks or exfoliations
Solution Approach 1:
The invention divides the hard coating system into multiple layers with different functions: a first hard coating layer (5-20 μm) providing surface hardness, a second hard coating layer (20-50 μm) providing impact resistance and flexibility, and optionally a third layer for adhesion. This segmentation allows each layer to be optimized for its specific function, resolving the contradiction between hardness and cracking resistance.
Solution Approach 2:
The invention uses composite material structures combining different polymer resins with distinct properties. The first hard coating layer uses rigid resin compositions for hardness, while the second hard coating layer uses flexible resin compositions with elongation of 15-200% to prevent cracking. This composite approach enables simultaneous achievement of high hardness and crack resistance.
2Strength
If a thick hard coating layer is used to ensure sufficient surface hardness, then the hardness requirement is met, but the coating layer is more prone to setting shrinkage leading to wrinkling or curling
Solution Approach 1:
The coating system is segmented into multiple layers with the first hard coating layer (5-20 μm) providing hardness and the second hard coating layer (20-50 μm) providing flatness and curl resistance. This segmentation allows the thinner first layer to achieve hardness without excessive shrinkage, while the second layer maintains shape stability.
Solution Approach 2:
The invention changes the physical and chemical parameters of the coating layers, specifically controlling the elongation of the second hard coating layer at 15-200% and the thickness ratio between layers. These parameter changes enable the coating to maintain flatness while achieving sufficient hardness.
3Shape
If the hard coating layer is made thinner to prevent setting shrinkage and curling, then flatness is improved, but the surface hardness becomes insufficient
Solution Approach 1:
The invention segments the coating function so that the first hard coating layer (5-20 μm) is optimized for surface hardness while the second hard coating layer (20-50 μm) is optimized for flatness and flexibility. This functional segmentation allows the thinner first layer to provide adequate hardness without suffering from shrinkage-induced curling.
Solution Approach 2:
Different regions of the coating system are given different qualities: the first hard coating layer has high rigidity and hardness properties, while the second hard coating layer has high elasticity and elongation properties. This local quality differentiation enables the thin first layer to achieve hardness without the drawbacks of thick coatings.
4Weight of moving object
If a hard coating film is designed to substitute glass for mobile devices, then weight reduction and impact resistance are achieved, but sufficient hardness and scratch resistance are difficult to attain
Solution Approach 1:
The invention employs composite material structures combining rigid resin compositions in the first hard coating layer for scratch resistance with flexible resin compositions in the second layer for impact resistance. This composite approach enables plastic-based coatings to achieve glass-level hardness and scratch resistance while maintaining the advantages of light weight and impact toughness.
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 film exhibits superior hardness, impact resistance, scratch resistance, and transparency, making it suitable for use in mobile terminals and tablet PCs without the drawbacks of glass, such as weight and fragility, while maintaining high enough physical strength to be a substitute for glass.
Implementation Method 1
both formed from photocurable crosslinking copolymers
Data Source
AI summary
The present invention relates to a hard coating film, and, more particularly, to a hard coating film having hardness and excellent physical properties. According to the present invention, the hard coating film has high physical properties including hardness, scratch resistance, transparency, durability, light resistance, and light transmittance. Thus, the hard coating film can find useful applications in various fields thanks to its excellent physical properties.