Polysiloxane Hard Coating for Flexible Display Substrates
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Solution Overview
Problem
Conventional substrates for flexible display devices, such as glass, are heavy, prone to damage, and lack flexibility, while plastic resin substitutes offer insufficient hardness and scratch resistance, limiting their application in foldable or flexible devices.
Innovation Solution
An optical laminate with a polysiloxane hard coating layer containing 70 mol % or more of an epoxy group-containing functional group and an elastomeric polymer, such as polycaprolactone polyol, providing a thickness of 10 μm to 250 μm, which enhances hardness, scratch resistance, and impact resistance, suitable for bendable, flexible, or foldable devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If glass or reinforced glass is used for display substrates, then mechanical strength and scratch resistance are improved, but weight increases and flexibility is reduced
Solution Approach 1:
The patent changes the material parameters by using plastic resin substrates (PET, PEN, PC, PI, PAI, PES) instead of glass, and applies a curable resin coating layer with specific compositional parameters (polyester resin 10-50 wt%, polyacrylate resin 30-70 wt%, inorganic filler 5-40 wt%) to achieve the desired balance between strength and weight
Solution Approach 2:
The patent creates a composite structure by coating a curable resin layer containing polyester resin, polyacrylate resin, and inorganic fillers onto the plastic resin substrate. This composite approach provides enhanced mechanical strength and scratch resistance while maintaining the lightweight properties of the plastic substrate
2Weight of moving object
If plastic resin is used for display substrates, then weight is reduced and flexibility is improved, but hardness and scratch resistance are insufficient
Solution Approach 1:
The patent creates a composite structure by coating a curable resin layer containing polyester resin, polyacrylate resin, and inorganic fillers onto the plastic resin substrate. This composite approach provides enhanced mechanical strength and scratch resistance while maintaining the lightweight properties of the plastic substrate
Solution Approach 2:
The patent changes the material parameters by using plastic resin substrates (PET, PEN, PC, PI, PAI, PES) instead of glass, and applies a curable resin coating layer with specific compositional parameters (polyester resin 10-50 wt%, polyacrylate resin 30-70 wt%, inorganic filler 5-40 wt%) to achieve the desired balance between strength and weight
3Strength
If curable resin is applied for hard coating, then hardness and scratch resistance are improved, but coating thickness is limited due to shrinkage during curing
Solution Approach 1:
The patent optimizes the compositional parameters of the curable resin, specifically controlling the ratio of polyester resin (10-50 wt%) to polyacrylate resin (30-70 wt%), which reduces shrinkage during UV curing and enables application of thicker coating layers (10-250 μm) while maintaining adhesion and avoiding excessive curl
Solution Approach 2:
The patent applies a thicker coating layer (10-250 μm) specifically on the outer surface of the flexible display substrate where scratch resistance is most needed, while keeping the substrate itself thin and flexible. This localized approach provides enhanced hardness where required without compromising overall flexibility
4Shape
If thin coating layer is applied to reduce curl, then flexibility is maintained, but impact resistance is reduced
Solution Approach 1:
The patent modifies the chemical composition parameters by incorporating inorganic fillers (5-40 wt%) such as silica, alumina, or titania into the curable resin, which increases impact resistance while maintaining flexibility. The specific filler type and concentration are optimized to provide toughness without excessive rigidity
Solution Approach 2:
The patent creates a composite curable resin system combining organic polymers (polyester resin, polyacrylate resin) with inorganic fillers. This composite structure provides both flexibility from the polymer matrix and impact resistance from the inorganic filler particles, achieving a balance between softness and 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 optical laminate achieves improved toughness and impact resistance, minimizing damage from repetitive bending or folding, and is suitable for use in flexible display devices, offering high hardness and flexibility.
Implementation Method 1
the hard coating layer is a polysiloxane containing 70 mol % or more of a repeating unit including an epoxy group-containing functional group
Implementation Method 2
an elastomeric polymer including polycaprolactone polyol
Data Source
AI summary
The present disclosure relates to an optical laminate for a flexible display device comprising: a support substrate layer; and a hard coating layer positioned on at least one surface of the support substrate layer and having a thickness of 10 μm to 250 μm, wherein the hard coating layer is a polysiloxane containing 70 mol % or more of a repeating unit including an epoxy group-containing functional group; and an elastomeric polymer including polycaprolactone polyol, and wherein the polysiloxane has a number average molecular weight of more than 3,000 and less than 10,000, and a polydispersity Index (PDI) of 1.0 or more and less than 5.0, and a flexible display device including the same.