Display Device Multi-Layer Bank Structure for Etching Protection
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Solution Overview
Problem
Existing display devices face challenges in implementing separate light emitting elements in each emission area without a mask process, especially in small-sized devices with high pixel density, where the reduced emission area makes it difficult to incorporate separate light emitting elements.
Innovation Solution
A display device structure is developed that includes a first pixel electrode, a pixel defining layer, a light emitting layer, a common electrode, and specific bank structures, such as a third bank with a thickness of about 5 nanometers to 100 nanometers, which prevents etchant penetration and reduces damage to light emitting elements during the etching process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a mask process is used to form separate light emitting elements in each emission area, then the light emitting elements can be precisely positioned, but the manufacturing complexity and process difficulty increase significantly
Solution Approach 1:
The patent introduces a bank structure as an intermediary element that physically separates and defines the emission areas. The bank acts as a mediator between the pixel electrode and the light emitting layer, providing a structural framework that automatically positions the light emitting elements without requiring mask processes. The bank's side surfaces protruding into the emission area create natural boundaries that guide material deposition and etching.
2Measurement precision
If the emission area is reduced to achieve high pixel density in small-sized devices, then the resolution increases, but it becomes difficult to implement separate light emitting elements in each emission area
Solution Approach 1:
The patent transitions from a two-dimensional planar approach to a three-dimensional vertical approach by introducing banks with side surfaces that protrude into the emission area. This vertical dimension allows the banks to effectively partition the reduced emission areas even when the horizontal space is limited. The multi-layer bank structure (first bank, second bank, third bank) creates vertical stacking that maximizes the use of limited horizontal space while maintaining separate light emitting element formation.
3Manufacturing precision
If etching process is used to form the bank structure, then the bank structure can be precisely formed, but the light emitting elements may be damaged by etchant penetration
Solution Approach 1:
The patent performs preliminary protective actions by forming the first bank structure before depositing the light emitting layer and common electrode. This preliminary bank structure serves as a protective barrier that prevents etchant from reaching and damaging the light emitting elements during subsequent etching processes. The second bank is then formed on the first bank, creating a layered protective structure that maintains precision while protecting sensitive components.
Solution Approach 2:
The bank structure acts as an intermediary protective barrier between the etching process and the light emitting elements. The multi-layer bank structure (first bank, second bank, third bank) intermediates the harmful etchant from reaching the light emitting elements, allowing precise bank formation through etching while protecting the light emitting elements from damage.
4Reliability
If a thick bank structure is used to prevent etchant penetration, then the protection against etchant damage improves, but the manufacturing complexity and material usage increase
Solution Approach 1:
The patent divides the bank structure into multiple segmented layers: first bank, second bank, and third bank. Each layer has a specific thickness and function, with the third bank being the thickest layer (5-100 nm) that provides the primary etchant barrier. This segmentation allows the structure to achieve sufficient protection without requiring any single layer to be excessively thick, thereby reducing overall material usage and manufacturing complexity while maintaining reliability.
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 solution allows for the formation of separate light emitting elements in each emission area without a mask process, reducing the difference in light emission between pixels and minimizing damage from etching solutions and moisture.
Implementation Method 1
a third bank on (e.g., disposed on) the second bank and including side surfaces protruding more than side surfaces of the first bank
Implementation Method 2
The third bank may include a hydrophobic material
Data Source
AI summary
A display device includes: a first pixel electrode on a substrate; a pixel defining layer on the substrate and exposing the first pixel electrode; a first light emitting layer on the first pixel electrode; a first common electrode on the first light emitting layer; a first bank on the pixel defining layer; a second bank on the first bank and including side surfaces protruding more than side surfaces of the first bank; and a third bank on upper and lower surfaces of the second bank and including a hydrophobic material.