Hard Coating Layer for Flexible Displays

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Solution Overview

Problem

Existing flexible display devices face challenges in achieving a balance between hardness and flexibility, which is essential for modern electronic devices that require thin and durable forms, such as curved or rollable displays.

Innovation Solution

A flexible display device with a hard coating layer containing a photoinitiator and a polymer represented by Formula 5, along with silicon nanoparticles and a bisphenol-A-epoxy-silicone block copolymer, is developed. The hard coating layer is synthesized by catalytically reacting hard coating and cross-linking oligomers, using photoreactive groups activated by different wavelengths of light, to enhance both hardness and flexibility.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If a hard coating layer is applied to increase surface hardness, then scratch resistance improves, but flexibility and bendability deteriorate

Engineering Contradiction:

Improvesurface hardnessVSAvoidflexibility

Core Design Contradiction:

StrengthVSAdaptability or versatility

Solution Approach 1:

The patent applies composite materials by combining multiple polymer components (epoxy polymer, silicone polymer, and crosslinking agent) in the hard coating layer. This composite structure allows the coating to achieve both high surface hardness through epoxy crosslinking and flexibility through silicone polymer chains, resolving the contradiction between hardness and bendability

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The patent changes the chemical composition parameters of the hard coating layer by incorporating specific ratios of epoxy polymer (5-50 wt%), silicone polymer (10-80 wt%), and crosslinking agents. By adjusting these compositional parameters, the coating achieves optimal balance between surface hardness and flexibility for flexible display applications

Inventive Principle:

Principle #35Parameter changes

2Reliability

If the hard coating layer is made thicker to improve durability, then scratch resistance improves, but bending performance and flexibility deteriorate

Engineering Contradiction:

ImprovedurabilityVSAvoidbending performance

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

The patent employs a thin film approach by forming a hard coating layer with thickness of 1-10 micrometers. Despite the thin thickness, the coating achieves high durability through photocuring crosslinking and optimized polymer composition, eliminating the need for thicker coatings while maintaining both protection and flexibility

Inventive Principle:

Principle #30Flexible shells and thin films

Solution Approach 2:

The composite polymer system enables thin film durability by combining epoxy polymers (for crosslinked hardness), silicone polymers (for flexibility), and crosslinking agents. This composite structure provides exceptional durability in a thin layer, preventing scratches while allowing repeated bending without cracking

Inventive Principle:

Principle #40Composite materials

3Strength

If conventional hard coating materials are used to achieve high hardness, then surface scratch resistance improves, but adhesion to flexible substrates deteriorates

Engineering Contradiction:

Improvescratch resistanceVSAvoidadhesion

Core Design Contradiction:

StrengthVSStability of the object's composition

Solution Approach 1:

The patent changes the chemical composition by incorporating silane-based crosslinking agents and controlling the epoxy-to-silicone polymer ratio. These compositional changes enhance adhesion to flexible substrates through silane bonding while maintaining scratch resistance through epoxy crosslinking network formation

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent uses silane crosslinking agents as intermediaries that bond both to the flexible substrate (through silane coupling) and to the epoxy polymer matrix (through crosslinking). This intermediary mechanism ensures strong adhesion while preserving the hard coating's scratch resistance properties

Inventive Principle:

Principle #24Intermediary (Mediator)

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 solution provides a flexible display device with improved hardness and flexibility, allowing it to withstand bending and external impacts without damage, while maintaining high surface hardness and flexibility, as demonstrated by increased bending stiffness and radius of curvature.

Implementation Method 1

a polymer represented by Formula 5... containing a photoinitiator and a polymer... The hard coating layer is synthesized by catalytically reacting hard coating and cross-linking oligomers, using photoreactive groups activated by different wavelengths of light

Methodology Applied

Scientific EffectPhotopolymerisation: Photopolymerisation

Data Source

PatentUS10513630B2Flexible display device and method for preparing hard coating polymer of same

Publication Date: 2019.12.24 SAMSUNG DISPLAY CO LTD

AI summary

A flexible display device includes a hard coating layer, the hard coating layer including hard coating oligomers, cross-linking oligomers that couple the hard coating oligomers, and a photoinitiator, the cross-linking oligomers being synthesized by catalytically reacting cross-linking monomers. The hard coating layer may include long cross-linking oligomers that improve the flexibility of the hard coating layer, and damage to the hard coating layer may be prevented or reduced even when the flexible display device is bent.