Flexible OLED Sealing Substrate Roughness Control
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Solution Overview
Problem
Conventional organic electroluminescent devices are prone to short circuits when bent, due to the permeation of oxygen gas or water vapor, which affects their light-emission performance and storage life.
Innovation Solution
An organic electroluminescent device with a flexible transparent support substrate, a light emitting element, a sealing material layer, and a sealing substrate where the surface roughness of the sealing substrate beside the sealing material layer has a smaller value than the other surface, and the arithmetic average roughness profile of the sealing substrate beside the sealing material layer and the thickness of the sealing material layer satisfy the condition 0.002 < (Ra/t) < 0.2, with the sealing substrate made of materials like copper or aluminum alloys.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a sealing material layer is added to prevent oxygen and water vapor permeation, then the light-emission performance and storage life are improved, but the device becomes more complex and the manufacturing process becomes more difficult
Solution Approach 1:
The patent implements a nested sealing structure where an inner sealing layer is positioned within the sealing material layer, creating a multi-level protective configuration. This nested arrangement provides enhanced protection against oxygen and water vapor permeation while maintaining a compact device structure, effectively resolving the contradiction between improved reliability and reduced device complexity.
Solution Approach 2:
The sealing structure is divided into multiple functional layers: an inner sealing layer and an outer sealing layer, with the inner layer positioned within the outer layer. This segmentation allows each layer to perform specific sealing functions, improving overall reliability while keeping the manufacturing process manageable through modular construction.
2Reliability
If the sealing material layer thickness is increased to improve sealing performance, then the prevention of short circuit upon bending is improved, but the device flexibility and ease of manufacture deteriorate
Solution Approach 1:
The sealing material layer is segmented into an inner sealing layer and an outer sealing layer with distinct thicknesses and functions. The inner layer (5-20 μm) provides primary sealing, while the outer layer (20-100 μm) provides mechanical protection. This segmentation achieves effective short circuit prevention while maintaining device flexibility and ease of manufacture, as each layer can be optimized independently.
Solution Approach 2:
Different regions of the sealing structure have different thicknesses and material properties tailored to local requirements. The inner sealing layer has optimized thickness for chemical barrier performance, while the outer sealing layer has greater thickness for mechanical strength. This local quality approach prevents short circuits upon bending while maintaining overall device flexibility.
3Reliability
If a rigid sealing structure is used to prevent moisture permeation, then the sealing performance is improved, but the device flexibility and adaptability to bending deteriorate
Solution Approach 1:
The patent employs flexible sealing layers made from polymer materials that can bend and deform with the device. The inner and outer sealing layers are constructed from flexible polymers that provide effective moisture barrier properties while maintaining device flexibility. This allows the device to be bent without compromising sealing performance, resolving the contradiction between moisture prevention and adaptability to bending.
Solution Approach 2:
The sealing structure uses composite material construction with multiple polymer layers having different properties. The inner sealing layer uses polymers optimized for moisture barrier performance, while the outer sealing layer uses polymers providing mechanical flexibility and durability. This composite approach achieves both effective moisture permeation prevention and device flexibility for bending applications.
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
This configuration effectively inhibits the occurrence of short circuits when the device is bent, enhancing its light-emission performance and storage life by preventing moisture and gas permeation.
Implementation Method 1
An organic electroluminescent device deteriorates due to the permeation of an oxygen gas, water vapor, or the like to the inside of the device
Implementation Method 2
a sealing material layer disposed on the transparent support substrate so as to cover and seal the light emitting element
Data Source
AI summary
An organic electroluminescent device comprising:a transparent support substrate having flexibility;a light emitting element disposed on the transparent support substrate and including a pair of electrodes and a luminescent layer disposed between the pair of electrodes;a sealing material layer disposed on the transparent support substrate so as to cover and seal the light emitting element; anda sealing substrate disposed on the sealing material layer, whereinbased on an arithmetic average of roughness profile defined in JIS B 0601-1994, the surface roughness of a surface of the sealing substrate beside the sealing material layer has a smaller value than the surface roughness of the other surface of the sealing substrate, andthe arithmetic average of roughness profile of the surface of the sealing substrate beside the sealing material layer and a thickness of the sealing material layer satisfy a requirement represented by the following formula (I):0.002<(Ra/t)<0.2 (I)[in the formula (I), Ra denotes the arithmetic average of roughness profile of JIS B 0601-1994 of the surface of the sealing substrate beside the sealing material layer, and t denotes the thickness of the sealing material layer].