OLED Encapsulation with 50 nm Organic Flattening Layer
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The existing thin film encapsulation structures for OLED display devices have issues with moisture-resistance reliability and bendability, as the organic barrier layer formed by printing methods is not sufficiently effective in regions outside the active area, leading to water vapor ingress and reduced light emitting efficiency due to surface flatness concerns.
Innovation Solution
A thin film encapsulation structure is developed with a relatively thin organic barrier layer, where the organic flattening layer is formed with a surface roughness of 50 nm or less, and the inorganic barrier layers are designed to enclose the organic barrier layer, ensuring high moisture resistance and improved productivity, while also enhancing light emitting efficiency by maintaining surface flatness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a relatively thick organic barrier layer (5-20 μm) is used to provide sufficient water vapor barrier property, then moisture-resistance reliability is improved, but bendability of the OLED display device is limited
Solution Approach 1:
The encapsulation structure is segmented into multiple thin inorganic barrier layers (first inorganic barrier layer and second inorganic barrier layer) with a thin organic barrier layer in between. This segmentation allows each layer to be optimized for its specific function while collectively providing the required moisture barrier without compromising bendability.
Solution Approach 2:
The encapsulation structure uses a composite of inorganic and organic barrier layers. The inorganic layers provide the primary moisture barrier with excellent water vapor transmission resistance, while the thin organic layer provides flattening functionality. This composite structure achieves both moisture resistance and flexibility that neither material could achieve alone.
2Manufacturing precision
If a relatively thick organic barrier layer is formed by printing method, then surface flattening is achieved, but mass-productivity decreases due to vacuum chamber operations
Solution Approach 1:
The formation of the inorganic barrier layer and organic barrier layer is merged into a continuous process. The inorganic barrier layer is formed by vacuum deposition, and immediately afterward, the organic barrier layer is formed by coating in the same vacuum chamber without breaking the vacuum. This eliminates repeated vacuum chamber operations and significantly improves mass-productivity.
Solution Approach 2:
The film formation process maintains continuous useful action by keeping the vacuum chamber environment intact throughout the formation of both inorganic and organic barrier layers. This continuous process without vacuum breaking enables high-speed production while maintaining surface flattening quality.
3Adaptability or versatility
If the organic barrier layer is made thin to improve bendability, then flexibility is enhanced, but moisture barrier property may be insufficient
Solution Approach 1:
The barrier function is segmented between inorganic and organic layers. The thin organic layer is not required to provide the full moisture barrier, as this function is handled by the inorganic barrier layers. This segmentation allows the organic layer to be thin for flexibility while the inorganic layers provide the moisture barrier.
Solution Approach 2:
Different layers have different local qualities optimized for their specific functions. The inorganic layers are designed with high water vapor barrier properties for moisture protection, while the organic layer is designed with flattening properties and minimal thickness for flexibility. Each layer's local quality is optimized for its primary role.
4Ease of manufacture
If printing method is used to form organic barrier layer in air or nitrogen atmosphere, then process simplicity is maintained, but moisture-resistance reliability is insufficient in regions outside active area
Solution Approach 1:
The organic barrier layer is formed in a vacuum atmosphere rather than air or nitrogen atmosphere. This inert environment prevents moisture and oxygen contamination during the coating process, ensuring that the organic barrier layer achieves its full moisture-resistance potential even in regions outside the active area where printing methods typically fail.
Data Source
AI summary
An organic EL device (100D) according to an embodiment of the present invention has: a substrate (1); a drive circuit layer (2) having a plurality of TFTs formed on the substrate; interlayer insulation layers (2Pa, 2Pb) formed on the drive circuit layer; an organic EL element layer (3) formed on the interlayer insulation layers; and a thin-film sealing structure (10DE) formed so as to cover the organic EL element layer. The interlayer insulation layers have contact holes (CH1, CH2). Contact parts (C1, C2) that connect the drive circuit layer and the organic EL element layer are formed inside the contact holes. The surface (2Pb_Sb) of the interlayer insulation layers and the surface (C_Sb) of the contact parts are flush, and the arithmetic average roughness Ra of the surfaces are 50 nm or less.