Optical Stack Adhesive Modulus for Flexible OLED Reliability
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Solution Overview
Problem
Existing adhesive materials for flexible display devices fail to maintain viscoelasticity and cohesive strength across a wide temperature range, particularly at low temperatures, leading to potential mechanical failure and optical distortion.
Innovation Solution
The development of an adhesive layer with a storage modulus ranging from 15 kPa to 30 kPa at 60°C and a ratio of storage modulus at −30°C to 60°C ranging from 6 to 16, ensuring excellent recoverability and viscoelasticity, using a hydroxyl-containing acrylic-based polymer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional adhesive materials are used in flexible display devices, then the device can be manufactured with standard bonding processes, but the adhesive fails to maintain viscoelasticity and cohesive strength at low temperatures, leading to mechanical failure
Solution Approach 1:
The patent applies parameter changes by precisely controlling the storage modulus of the adhesive material across different temperatures. The adhesive is formulated to have a storage modulus of 10-1000 kPa at 80°C and a storage modulus ratio (at -30°C to 80°C) of 1.05-5.0, which fundamentally changes the temperature-dependent mechanical properties of the adhesive to maintain reliability across wide temperature ranges
Solution Approach 2:
The patent uses composite materials by combining specific polymer components with tailored viscoelastic properties. The adhesive comprises a first component (20-80 wt%) and a second component (20-80 wt%), creating a composite adhesive system that achieves optimal balance between flexibility, cohesive strength, and temperature stability through material composition
2Length of moving object
If the adhesive film is made thinner to reduce product thickness, then the display device becomes more flexible and ultra-thin, but the adhesive strength and cohesive strength decrease
Solution Approach 1:
The patent changes the physical parameters of the adhesive by controlling its storage modulus within specific ranges. This allows the adhesive to maintain sufficient strength even at reduced thickness, as the viscoelastic properties are optimized to provide both flexibility and bonding strength simultaneously
Solution Approach 2:
The patent applies flexible shells and thin films by using an adhesive layer with optimized viscoelastic properties that can function effectively at thin thickness. The adhesive maintains flexibility and bonding capability even when the layer is thin, enabling ultra-thin display devices without compromising adhesive performance
3Stability of the object's composition
If the adhesive material is optimized for high temperature performance, then stability at elevated temperatures improves, but flexibility and recoverability at low temperatures deteriorate
Solution Approach 1:
The patent applies parameter changes by establishing specific storage modulus ranges at different temperatures. The adhesive must have storage modulus of 10-1000 kPa at 80°C for high temperature stability, while simultaneously achieving appropriate flexibility at -30°C through controlled viscoelasticity, creating a balance between thermal stability and low-temperature flexibility
Solution Approach 2:
The patent uses composite materials with specific component ratios (first component: 20-80 wt%, second component: 20-80 wt%) to achieve dual performance. The composite structure allows the adhesive to maintain both high temperature stability and low temperature flexibility through the synergistic properties of the material components
4Ease of manufacture
If tensile tests are used to evaluate adhesive performance, then the testing process is simple, but the results cannot effectively verify the adhesive state under bent/folded situations
Solution Approach 1:
The patent applies dynamics by transitioning from static tensile testing to dynamic bending testing. The bending test evaluates adhesive performance under dynamic deformation conditions that simulate actual flexible display usage, providing more comprehensive reliability verification while maintaining reasonable testing complexity
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 layer maintains stability and flexibility across a wide temperature range, preventing mechanical failure and optical distortion, ensuring long-term reliable adhesion and durability.
Implementation Method 1
the optically clear adhesive plays an important role. For example, the optically clear adhesive may absorb stress when the display device is in a bent state, so as to avoid failures of the aforementioned electrical signal processing element or optical element
Implementation Method 2
an adhesive layer capable of maintaining viscoelasticity and having excellent recoverability e.g., from a bent state back to a normal/un-bent state within a wide temperature range can be realized
Data Source
AI summary
The present invention relates to an optical stack and an organic light emitting diode display including the optical stack, wherein the optical stack has an adhesive layer. The adhesive layer is disposed between a cover plate and a circular polarizer component, between the circular polarizer component and a touch component, or between the touch component and a display component. Wherein, a storage modulus at 60° C. of the adhesive layer is between 15 kPa and 30 kPa, and a ratio of a storage modulus at −30° C. to the storage modulus at 60° C. of the adhesive layer is between 6 and 16.