Flexible Display Adhesive Composition for Wide-Temperature Folding

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Solution Overview

Problem

Existing adhesive technologies for flexible display apparatuses face challenges in maintaining both folding reliability at low temperatures and adhesion reliability at high temperatures, leading to issues such as ooze-out, peeling, and delamination, especially in thick cover members or small curvatures.

Innovation Solution

An adhesive member comprising an acrylic copolymer with specific glass transition temperatures, an elastomer, and an inorganic nanofiller, which maintains a constant modulus across a wide temperature range, ensuring both folding and adhesion reliability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the adhesive member uses a single polymer material, then the manufacturing process is simple, but it cannot maintain both folding characteristics and adhesion reliability across a wide temperature range

Engineering Contradiction:

Improveadhesion reliabilityVSAvoidtemperature range adaptability

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

The adhesive member uses a composite material system consisting of acrylic copolymer, elastomer, and inorganic nanofiller. This composite structure enables the adhesive to maintain both folding characteristics and adhesion reliability across a wide temperature range from -30°C to 100°C, resolving the contradiction between reliability and temperature adaptability.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The patent optimizes specific parameters including the degree of crosslinking (50-70%), glass transition temperature range (-50°C to 0°C), and nanofiller content (3-20 parts by weight per 100 parts polymer). These parameter adjustments enable the adhesive to maintain appropriate modulus and adhesion properties across extreme temperature variations.

Inventive Principle:

Principle #35Parameter changes

2Strength

If the adhesive member has high adhesion strength, then bonding reliability is improved, but folding stress causes peeling and ooze-out defects

Engineering Contradiction:

Improveadhesion strengthVSAvoidfolding reliability

Core Design Contradiction:

StrengthVSReliability

Solution Approach 1:

The adhesive member exhibits different mechanical properties at different temperature conditions. At low temperatures, it maintains high adhesion strength for bonding reliability, while at high temperatures, it becomes more flexible to accommodate folding stress without peeling or ooze-out defects.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent controls the degree of crosslinking within 50-70% and glass transition temperature within -50°C to 0°C to achieve a balance between adhesion strength and folding flexibility. This prevents both peeling at high temperatures and ooze-out at low temperatures.

Inventive Principle:

Principle #35Parameter changes

3Strength

If the adhesive member uses high crosslinking density, then high temperature adhesion is improved, but low temperature flexibility deteriorates

Engineering Contradiction:

Improvehigh temperature adhesionVSAvoidlow temperature flexibility

Core Design Contradiction:

StrengthVSEase of operation

Solution Approach 1:

The patent optimizes the degree of crosslinking to 50-70% and glass transition temperature to -50°C to 0°C. This parameter combination ensures that the adhesive maintains flexibility at low temperatures for folding operations while providing sufficient adhesion strength at high temperatures.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The combination of acrylic copolymer with elastomer and inorganic nanofiller creates a composite system where the elastomer contributes to low-temperature flexibility and the crosslinked acrylic copolymer provides high-temperature adhesion strength.

Inventive Principle:

Principle #40Composite materials

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 adhesive member provides improved folding characteristics at low temperatures and adhesion reliability at high temperatures, minimizing defects like ooze-out and delamination, and enabling various folding methods in flexible display apparatuses.

Implementation Method 1

an acrylic copolymer including a first repeating unit having a glass transition temperature of −50° C. or less, a second repeat unit having a glass transition temperature of −45° C. to −10° C., and a third repeating unit having a glass transition temperature of 90° C. or more

Methodology Applied

Scientific EffectGlass transition temperature:

Implementation Method 2

the acrylic copolymer has a degree of crosslinking of 55% to 65%

Methodology Applied

Scientific EffectCrosslinking:

Data Source

PatentUS12550588B2Adhesive member and display apparatus including the same

Publication Date: 2026.02.10 LG DISPLAY CO LTD

AI summary

A display apparatus includes an adhesive layer disposed between a display panel and a cover member. The adhesive layer includes an adhesive member, and the adhesive member includes an acrylic copolymer including a first repeating unit having a glass transition temperature of −50° C. or less, a second repeat unit having a glass transition temperature of −45° C. to −10° C., and a third repeating unit having a glass transition temperature of 90° C. or more and the acrylic copolymer having a degree of crosslinking of 55% to 65%. The adhesive member further includes an elastomer and an inorganic nanofiller.