Epoxy Layered Optical Laminate to Reduce Display Curling
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Solution Overview
Problem
Existing flexible display cover windows suffer from curling and cracking due to curing shrinkage when thickly coated with acrylic oligomers, and require improved hardness, adhesion, and scratch resistance.
Innovation Solution
An optical laminate comprising glass with a first hard coating layer made of epoxy acrylic resin and epoxy silane coupling agent, and a second hard coating layer made of a light-transmitting resin, directly applied without intermediate substrates, to enhance adhesion and reduce curling and cracking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a thick protective coating is formed using acrylic oligomer to prevent cover glass from breaking, then protection strength is improved, but curling occurs severely due to curing shrinkage
Solution Approach 1:
The patent divides the single thick protective coating into multiple layers: a first protective coating layer (5-20 μm) and a second protective coating layer (3-20 μm). This segmentation reduces curing shrinkage-induced curling while maintaining overall protection strength, as each thinner layer experiences less shrinkage stress than a single thick layer would.
Solution Approach 2:
The patent uses different resin compositions for the first and second protective coating layers. The first layer uses acrylic oligomer while the second layer uses a different resin system, creating a composite structure that balances protection strength with reduced curling through differential shrinkage characteristics between layers.
2Strength
If a thick protective coating is formed to enhance scratch resistance, then hardness is improved, but cracks occur due to curing shrinkage
Solution Approach 1:
By dividing the protective coating into multiple thinner layers, the patent reduces the shrinkage stress within each layer, preventing crack formation while maintaining cumulative scratch resistance. The first layer (5-20 μm) and second layer (3-20 μm) together provide thick protection without the cracking issues of a single thick coating.
Solution Approach 2:
The first protective coating layer is applied and cured first to create a stable base layer with lower shrinkage stress. Then the second layer is applied on top, allowing the structure to build up protection strength progressively without inducing cracks in previously cured layers.
3Ease of manufacture
If a single thick hard coating layer is formed, then manufacturing process is simplified, but adhesion and curl characteristics deteriorate
Solution Approach 1:
The patent divides the protective coating into a first layer (5-20 μm) and a second layer (3-20 μm) with different resin compositions. This segmentation improves adhesion and curl characteristics through differential shrinkage between layers while adding only one additional coating step to the manufacturing process.
Solution Approach 2:
The patent changes the resin composition parameter between layers: the first layer uses acrylic oligomer while the second layer uses a different resin system. This parameter change optimizes adhesion and reduces curling while maintaining a relatively simple two-step coating process.
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 improved adhesion, pen usability, curl characteristics, and scratch resistance, enhancing the reliability of flexible displays by minimizing curling and cracking, and simplifying the manufacturing process.
Implementation Method 1
a first hard coating layer formed of a first hard coating composition comprising an epoxy acrylic resin and an epoxy silane coupling agent
Implementation Method 2
a second hard coating layer formed of a second hard coating composition comprising a light-transmitting resin
Data Source
AI summary
The present disclosure relates to an optical laminate including: glass; a first hard coating layer formed on the glass; and a second hard coating layer formed on the first hard coating layer, wherein the first hard coating layer is formed of a first hard coating composition comprising an epoxy acrylic resin and an epoxy silane coupling agent, and the second hard coating layer is formed of a second hard coating composition comprising a light-transmitting resin, and an image display device including the same.