OLED Double-Layer Bank Structure for Uniform Deposition
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The existing thermal deposition method using a shadow mask in OLED display devices faces challenges with deposition uniformity and high resolution fabrication, particularly in larger displays, leading to thickness differences in the organic emitting layer, which affects emitting efficiency and results in dark images at the edges of pixel regions, reducing the aperture ratio.
Innovation Solution
A double-layered bank structure with a hydrophobic material is used, where the lower layer has a wider width and smaller thickness than the upper layer, allowing the organic emitting layer to form with a uniform thickness across the pixel region, preventing flooding and ensuring a flat top surface, thereby increasing the effective emission area and aperture ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a shadow mask is used in thermal deposition method, then the organic emitting layer can be formed, but the deposition uniformity deteriorates and thickness difference occurs in larger display devices
Solution Approach 1:
The patent removes the shadow mask component from the deposition system and replaces it with a bank structure formed directly on the substrate. This extraction eliminates the shadow mask sagging problem that causes non-uniform deposition in large displays, while the bank structure provides the necessary pattern definition without the mechanical limitations of a shadow mask.
Solution Approach 2:
The patent introduces a bank structure as an intermediary element between the substrate and the organic emitting layer. This bank, formed of hydrophobic material, serves as a mediator that defines the pixel regions and controls material deposition without requiring a shadow mask, thereby achieving uniform deposition across large display areas.
2Manufacturing precision
If a shadow mask is used in thermal deposition method, then the organic emitting layer can be formed, but the manufacturing precision for high resolution deteriorates due to shadow effect
Solution Approach 1:
The patent replaces the mechanical shadow mask system with a chemically-based bank structure formed through deposition and etching processes. This substitution eliminates the shadow effect inherent in mechanical mask systems, enabling high resolution manufacturing above 250 PPI while simplifying the fabrication process for large displays.
Solution Approach 2:
The patent changes the fundamental parameter of pattern formation from mechanical shadowing to chemical deposition control. By using a bank structure with specific hydrophobic properties and controlling the deposition process parameters, the system achieves high resolution without the limitations of shadow mask geometry.
3Manufacturing precision
If a single-layer bank is used to surround pixel region, then the liquid phase organic emitting material can be contained, but the organic emitting layer thickness becomes non-uniform with darker edges
Solution Approach 1:
The patent divides the single-layer bank into a multi-layer structure with different heights. The first bank layer provides the base containment structure, while the second bank layer adds additional containment at the pixel region edges. This segmentation allows for controlled material distribution that achieves uniform organic emitting layer thickness and consistent brightness across the entire pixel area.
Solution Approach 2:
The patent applies different bank layer heights at different locations within the pixel region. The varied bank structure creates local differences in material containment that compensate for edge effects, ensuring uniform organic emitting layer formation and consistent light emission across the pixel area.
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 solution enhances the uniformity of the organic emitting layer thickness, improves brightness uniformity, and increases the effective emission area, resulting in a higher aperture ratio and extended lifetime of the OLED display device.
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 a next pixel region P.
Implementation Method 2
The organic emitting material is dried and cured by 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 bank including a lower layer and an upper layer on the first electrode, the lower layer disposed on edges of the first electrode and having a first width and a first thickness, the upper layer disposed on the lower layer and having a second width smaller than the first width; an organic emitting layer on the first electrode and a portion of the lower layer; and a second electrode on the organic emitting layer and covering an entire surface of the display region.