Display Cover Window Stack Using Modulus Mismatch for Scratch Resistance
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Solution Overview
Problem
Conventional display cover windows made of plastic lack sufficient scratch resistance despite improvements in surface hardness, as scratch resistance does not increase proportionally with surface hardness, and existing methods fail to effectively reduce frictional forces causing scratches.
Innovation Solution
A stacked structure for display cover windows is designed with a base member having an elastic modulus of 2.5 GPa to 5.5 GPa, a hard coating member with an elastic modulus 0.546 to 2.4 times that of the base member, and a damping member with an elastic modulus 0.0000018 to 0.02 times that of the base member, which absorbs and dissipates external stress to reduce normal force and frictional forces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a hard coating is applied to improve surface hardness, then surface hardness is improved, but scratch resistance is not greatly improved
Solution Approach 1:
The patent divides the cover window into multiple functional layers: a base layer (polycarbonate or similar) providing impact resistance and a skin layer (acryl-based resin) providing surface hardness. This segmentation allows each layer to optimize for its specific function rather than requiring a single material to excel at both hardness and scratch resistance.
Solution Approach 2:
The patent uses composite materials combining different resin systems - specifically a polycarbonate base layer with an acryl-based skin layer containing silica particles. This composite structure leverages the toughness of polycarbonate and the hardness of acryl-silica composite to achieve both impact resistance and improved scratch resistance.
2Strength
If multilayer laminate is used to improve hardness, then hardness is improved to some extent, but scratch resistance still deteriorates under actual use conditions
Solution Approach 1:
The patent applies local quality enhancement by incorporating silica particles specifically in the skin layer where scratch resistance is needed, while the base layer maintains its polycarbonate composition for impact resistance. The silica particles are concentrated in the region most susceptible to scratching (the outer surface) rather than distributing them uniformly throughout the entire structure.
Solution Approach 2:
The patent changes the chemical composition parameters of the skin layer by incorporating 1-10 parts by weight of silica particles per 100 parts by weight of acryl-based resin. This parameter modification transforms the skin layer from a simple polymer coating to a composite material with enhanced scratch resistance properties.
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 stacked structure significantly improves scratch resistance by reducing normal force and dissipating external stress, providing enhanced durability and resistance to scratches in various environments.
Implementation Method 1
a damping member disposed beneath the base member and having an elastic modulus of 0.0000018 times to 0.02 times the elastic modulus of the base member
Implementation Method 2
absorbing and dissipating some of external stress by a damping layer
Data Source
AI summary
The present disclosure relates to a stacked structure for a display cover window having improved scratch resistance using a difference in elastic modulus, and a method of manufacturing the same. The stacked structure for a display cover window includes a base member having an elastic modulus of 2.5 GPa to 5.5 GPa; a hard coating member disposed on the base member and having an elastic modulus of 0.546 times to 2.4 times the elastic modulus of the base member; and a damping member disposed beneath the base member and having an elastic modulus of 0.0000018 to 0.02 times the elastic modulus of the base member. The stacked structure for a display cover window has an effect of remarkably improving scratch resistance by reducing a normal force, which is a major component of frictional force that is a main cause of scratching.