OLED Display Bank Structure for Uniform Organic Emitter Thickness
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Solution Overview
Problem
Existing OLED display devices face challenges in achieving high resolution and uniformity due to thickness differences in the organic emitting layer, leading to reduced aperture ratio and brightness uniformity, especially in larger displays where shadow masks cause deposition issues.
Innovation Solution
The use of a hydrophobic bank structure with varying widths and thicknesses around the pixel region, combined with a liquid phase organic emitting material deposition method using an ink-jet apparatus or nozzle-coating apparatus, ensures uniform thickness and increased effective emitting area, enhancing aperture ratio and brightness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If thermal deposition using shadow mask is used, then organic emitting layer can be formed, but thickness uniformity deteriorates and effective emitting area decreases
Solution Approach 1:
The patent divides the bank structure into two segments: a first bank and a second bank with different widths. The first bank has a first width and the second bank has a second width smaller than the first width, creating a stepped structure that compensates for the shadow effect and achieves uniform thickness distribution of the organic emitting layer.
Solution Approach 2:
The patent introduces asymmetric width design where the first bank and second bank have different widths. This asymmetric structure is specifically designed to counteract the shadow effect caused by thermal deposition, enabling uniform thickness control across the pixel region while maximizing the effective emitting area.
2Manufacturing precision
If single-width bank structure is used, then fabrication is simple, but thickness uniformity and brightness uniformity deteriorate
Solution Approach 1:
The bank structure is segmented into two distinct parts with different widths. The first bank and second bank are formed sequentially with different dimensions, creating a stepped profile that controls the organic emitting layer thickness uniformly while maintaining reasonable fabrication complexity.
3Reliability
If hydrophobic bank is used, then organic emitting material is prevented from flooding, but thickness difference in organic emitting layer is not fully eliminated
Solution Approach 1:
The bank is divided into two segments with different widths. The first bank provides the primary containment barrier with hydrophobic properties, while the second bank with smaller width fine-tunes the material distribution, together achieving both reliable containment and uniform thickness.
Solution Approach 2:
Different regions of the bank structure are given different widths to serve different functions. The first bank region provides containment while the second bank region optimizes thickness uniformity, applying local quality variations to solve both problems simultaneously.
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 approach results in improved aperture ratio and brightness uniformity by concentrating the organic emitting material in the center of the pixel region, reducing thickness variations and increasing the effective emitting area, thus enhancing the overall performance and lifetime of OLED display devices.
Implementation Method 1
The bank 53 is formed of an organic material having a hydrophobic property. The hydrophobic bank 53 prevents the organic emitting material, which has a hydrophilic property, from being formed on the bank 53 and flooding into adjacent pixel region P.
Implementation Method 2
the organic emitting layer is formed by a thermal deposition using a shadow mask
Implementation Method 3
The organic emitting material is dried and cured by a heat to form the organic emitting layer 55.
Data Source
AI summary
An organic light emitting diode display device includes a substrate including a display region, wherein a plurality of pixel regions are defined in the display region; a first electrode over the substrate and in each of the plurality of pixel regions; a first bank on edges of the first electrode; a second bank on an upper surface of the first bank and covering only a portion of the first bank; an organic emitting layer on the first electrode and a portion of the first bank; and a second electrode on the organic emitting layer and covering an entire surface of the display region.