Polyamide Cover Window for Flexible Displays
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Solution Overview
Problem
The challenge is to develop a cover window for flexible display devices that balances high hardness with flexibility, capable of withstanding repetitive bending and folding without damage, while replacing traditional glass materials that are heavy and prone to breakage.
Innovation Solution
A cover window comprising a polymer substrate with a polyamide resin and a hard coating layer, where the polyamide resin includes a first and second polyamide segment with specific benzene-dicarbonyl group ratios, providing a balance of mechanical and optical properties, including high transparency, scratch resistance, and flexibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the thickness of the hard coating layer is increased to ensure surface hardness, then surface hardness is improved, but wrinkles or curls are formed due to curing shrinkage and cracking and peeling are likely to occur
Solution Approach 1:
The patent changes the chemical composition parameters of the polyamide resin by controlling the molar ratios of benzene-1,3-dicarbonyl group (20-40 mol%) and benzene-1,4-dicarbonyl group (60-80 mol%), which optimizes the balance between surface hardness and coating integrity, preventing wrinkles and peeling while maintaining adequate hardness
Solution Approach 2:
The patent uses a composite polyamide resin system combining multiple dicarbonyl groups with specific molar ratios to create a material that achieves both high surface hardness and resistance to cracking and peeling, resolving the contradiction between hardness and integrity
2Strength
If glass is used as a cover plate to provide high hardness, then hardness is improved, but weight increases and breakage occurs due to external impact
Solution Approach 1:
The patent changes the material composition from glass to polyamide resin with specific dicarbonyl group ratios, achieving glass-level hardness while significantly reducing weight and eliminating breakage susceptibility, directly resolving the contradiction between hardness and weight
Solution Approach 2:
The patent replaces heavy, fragile glass with lightweight polyamide resin that can be easily replaced if damaged, adopting a strategy of using lighter materials that are less prone to breakage rather than relying on heavy glass that must be protected
3Adaptability or versatility
If plastic resin is used to replace glass for flexible display, then flexibility is improved, but achieving glass-level hardness is difficult
Solution Approach 1:
The patent optimizes the chemical composition parameters of the polyamide resin by controlling the molar ratios of different benzene-dicarbonyl groups, enabling the material to achieve glass-level hardness while maintaining the flexibility needed for bendable displays
Solution Approach 2:
The patent creates a composite polyamide resin system with specific dicarbonyl group combinations that simultaneously provides both flexibility for bending and hardness comparable to glass, resolving the contradiction between flexibility and hardness
Data Source
AI summary
The present disclosure relates to a cover window for a flexible display device including a polymer substrate including a polyamide resin; and a hard coating layer formed on at least one surface of the polymer substrate, wherein a yellow index of the polymer substrate measured in accordance with STM E 313 is 4.00 or less, and an elastic modulus of the polymer substrate measured at a strain rate of 12.5 mm/min in accordance with ISO 527-3 is 4 to 9 GPa.