Flexible Display Adhesive Sheet for Polyimide Folding Durability
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Solution Overview
Problem
Existing adhesive sheets for flexible image display devices lack sufficient adhesion and flexibility, particularly when used with polyimide materials, leading to issues such as peeling and breakage during repeated folding and bending.
Innovation Solution
An adhesive sheet formed from an adhesive composition comprising an acrylic polymer without carboxy groups, a photoinitiator, and an epoxy compound, with specific storage shear modulus and adhesion ratios, ensuring excellent adhesion and flexibility, especially with polyimide.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional adhesive sheets are used for flexible image display devices, then basic adhesion is provided, but adhesion to polyimide and flexibility are insufficient, causing peeling and breakage during repeated folding
Solution Approach 1:
The patent changes the chemical composition parameters of the adhesive layer by specifying acrylic polymers with particular glass transition temperatures (−50°C to 0°C) and storage elastic moduli (10³ to 10⁶ Pa at −30°C), and by controlling the epoxy compound content (0.1 to 10 parts by mass per 100 parts of acrylic polymer). These parameter adjustments optimize both adhesion strength and flexibility to resolve the contradiction.
Solution Approach 2:
The patent creates a composite adhesive system combining acrylic polymer (without carboxy groups) and epoxy compound in specific ratios. This composite material approach leverages the flexibility of acrylic polymer and the adhesion enhancement of epoxy compound, achieving both strong adhesion to polyimide and maintained flexibility for repeated folding.
2Strength
If adhesive sheets with high adhesion are used, then bonding strength is improved, but flexibility deteriorates, causing breakage during bending operations
Solution Approach 1:
The patent carefully controls the glass transition temperature of the acrylic polymer within −50°C to 0°C and the storage elastic modulus within 10³ to 10⁶ Pa at −30°C. These parameter ranges ensure the adhesive maintains flexibility for bending operations while providing sufficient adhesion strength.
Solution Approach 2:
The patent applies different functional components locally within the adhesive layer: acrylic polymer provides the flexible matrix, while epoxy compound (0.1 to 10 parts by mass per 100 parts acrylic polymer) provides localized adhesion enhancement. This local quality differentiation resolves the flexibility-strength contradiction.
3Ease of operation
If repeated folding operations are performed, then device flexibility is demonstrated, but adhesive peeling and member breakage occur due to insufficient durability
Solution Approach 1:
The patent incorporates epoxy compound in controlled amounts (0.1 to 10 parts by mass per 100 parts acrylic polymer) into the adhesive composition before folding operations. This preliminary addition of adhesion-enhancing component cushions against the stresses of repeated folding, preventing peeling and breakage while maintaining foldability.
Solution Approach 2:
The patent optimizes the storage elastic modulus of the adhesive layer at −30°C to be within 10³ to 10⁶ Pa, which provides the right balance of softness for folding and strength for durability. This parameter control ensures the adhesive can withstand repeated folding operations without failure.
4Reliability
If adhesive composition is optimized for adhesion to polyimide, then adhesion ratio between 23°C and 60°C is improved, but flexibility may be compromised
Solution Approach 1:
The patent specifies the glass transition temperature of the acrylic polymer within −50°C to 0°C, which ensures the adhesive remains flexible across the operating temperature range (23°C to 60°C) while maintaining stable adhesion to polyimide. This temperature parameter optimization resolves the contradiction between adhesion stability and flexibility.
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 sheet provides stable adhesion and flexibility, maintaining integrity during repeated folding and bending operations, enhancing the durability of flexible image display devices.
Implementation Method 1
an adhesive composition comprising an acrylic polymer without carboxy groups, a photoinitiator, and an epoxy compound
Data Source
AI summary
As an adhesive sheet formed from an adhesive composition including an acrylic polymer (A) containing no carboxy group, a photoinitiator (B), and an epoxy compound (C).