Hard Coating Film Elastic Modulus Control
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Solution Overview
Problem
Existing hard coating films for mobile device displays lack sufficient hardness and impact resistance, with thicker coatings prone to cracking and curling due to setting shrinkage, and current solutions do not meet the strength requirements of glass panels.
Innovation Solution
A hard coating film comprising a polyethylene terephthalate substrate with a first hard coating layer and a second hard coating layer, where the elastic moduli difference is between 500 MPa to 3,000 MPa, and the layers include photocurable crosslinking copolymers with acrylate monomers and inorganic microparticles, providing high hardness and impact resistance without curling or 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, curling, cracks, and exfoliations
Solution Approach 1:
The patent applies parameter changes by precisely controlling the elastic modulus of the coating layer (1.5-4.0 GPa) and the thickness ratio between coating layer and substrate (0.05-0.5 mm). This optimization allows the coating to achieve sufficient hardness while maintaining flexibility to avoid cracking and exfoliation. The specific parameter range for elastic modulus balances hardness requirements with stress distribution to prevent structural failures.
Solution Approach 2:
The patent employs composite materials by combining the hard coating layer with a flexible substrate having specific mechanical properties. The substrate acts as a stress-absorbing base that prevents the hard coating from cracking under stress. This composite structure integrates the hardness of the coating with the flexibility and toughness of the substrate, resolving the contradiction between hardness and structural integrity.
2Strength
If a thick hard coating layer is used to ensure sufficient hardness, then the hardness requirement is met, but the coating exhibits curling and exfoliation due to setting shrinkage
Solution Approach 1:
The patent controls the elastic modulus within 1.5-4.0 GPa and thickness ratio within 0.05-0.5 mm to balance hardness with stress distribution. This parameter optimization ensures the coating achieves required hardness while maintaining flatness by preventing excessive shrinkage stresses that would cause curling.
3Strength
If the elastic modulus of the hard coating layer is increased to improve hardness, then the hardness increases, but the impact resistance decreases due to brittleness
Solution Approach 1:
The patent optimizes the elastic modulus to a specific range (1.5-4.0 GPa) that balances hardness and impact resistance. This controlled modulus ensures the coating is hard enough for protection while remaining flexible enough to absorb impact energy without fracturing, preventing the brittleness that would result from excessively high modulus values.
Solution Approach 2:
The composite structure combines a hard coating layer with a flexible substrate. The substrate's lower elastic modulus and higher toughness compensate for the coating's brittleness, providing impact resistance while the coating maintains its hardness. This material combination resolves the contradiction between hardness and impact resistance.
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 achieves a pencil hardness of 7H or more, high impact resistance, and transparency, making it suitable for mobile terminals and displays without the issues of curling or cracking, and maintains excellent physical properties.
Implementation Method 1
a first photocurable crosslinking copolymer of a first photocurable elastic polymer and a mono- to hexa-functional acrylate monomer
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.