Flexible AMOLED Display Barrier Strain Management
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Solution Overview
Problem
Current flexible OLED displays face limitations in flexibility due to tensile stresses, particularly in the permeation barrier layer, which is susceptible to cracking and delamination under high tensile stress, hindering the development of rollable and highly flexible AMOLED displays.
Innovation Solution
A flexible AMOLED display design that includes a permeation barrier layer between the OLED stack and the backplane, with a neutral plane crossing the permeation barrier, varying bus line thickness to distribute stress evenly, and incorporating a thin inorganic film or composite barrier with a glass transition temperature below 200 degrees Celsius to enhance flexibility and reduce strain.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a permeation barrier layer is used in the OLED display, then protection against moisture and oxygen is improved, but flexibility deteriorates due to tensile stress causing cracking and delamination
Solution Approach 1:
The patent changes the physical and chemical parameters of the permeation barrier layer by using low glass transition temperature materials (below 200°C) and controlling the neutral plane position. This allows the barrier layer to maintain its protective function while becoming more flexible and resistant to cracking under tensile stress during bending operations.
Solution Approach 2:
The patent employs composite material structures including the permeation barrier layer combined with the neutral plane positioning strategy and low Tg materials. This composite approach creates a multi-functional system that simultaneously provides moisture/oxygen protection and enhanced flexibility, resolving the contradiction between reliability and ease of operation.
2Ease of operation
If the neutral plane is positioned to cross the permeation barrier, then flexibility is improved by reducing tensile stress, but manufacturing precision becomes more difficult
Solution Approach 1:
The patent specifies precise parameter ranges for the neutral plane positioning and glass transition temperature (below 200°C) to achieve the desired flexibility while managing manufacturing complexity. By defining these parameters clearly, the patent provides a actionable guideline for manufacturing that balances precision requirements with flexibility goals.
3Ease of operation
If bus line thickness is varied to distribute stress evenly, then flexibility is improved, but manufacturing complexity increases
Solution Approach 1:
The patent applies local quality by varying the thickness of bus lines in specific regions to distribute stress evenly during bending. This localized modification of structural properties allows the display to achieve enhanced flexibility without requiring complete redesign of the entire bus line system, thus managing manufacturing complexity while improving ease of operation.
Data Source
AI summary
A flexible AMOLED display is disclosed including an OLED stack having an anode layer, a cathode layer and an organic light emitting layer between the anode layer and the cathode layer. A backplane includes a substrate, a plurality of bus lines, and a thin film transistor array. A permeation barrier layer is positioned between the OLED stack and the backplane, and a plurality of vias connect the OLED anode layer to the backplane thin film transistor array. In one embodiment, a neutral plane of the AMOLED display crosses the permeation barrier. In one embodiment, the thickness of at least a portion of the bus lines is greater than the thickness of the cathode layer. A method of increasing the flexibility of an AMOLED display is disclosed. A method of assembling a flexible AMOLED display under a processing temperature of less than 200 degrees Celsius is also disclosed.