OLED Bank Segmentation for Electrode Connectivity
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Solution Overview
Problem
Existing display apparatuses with organic light-emitting diodes (OLEDs) often experience brightness differences between pixels due to disconnection of the opposite electrode, leading to inconsistent display quality.
Innovation Solution
The display apparatus incorporates a substrate with a pixel electrode, a first bank, a second bank, and an emission layer, where the first and second banks are formed using negative-type photoresist and have different thicknesses, with the second bank being thicker and overlapping the opposite electrode, and a spacer with a positive-type photoresist, to ensure proper alignment and prevent electrode disconnection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single uniform bank structure is used, then manufacturing is simpler, but electrode disconnection occurs leading to brightness differences
Solution Approach 1:
The bank structure is divided into a first bank and a second bank with different thicknesses. The first bank has a first thickness and the second bank has a second thickness greater than the first thickness. This segmentation allows the opposite electrode to be properly connected across different regions without disconnection, resolving the reliability issue while maintaining manageable structural complexity through systematic division.
Solution Approach 2:
Different regions of the bank structure are assigned different thicknesses to meet local requirements. The first bank region has a thinner profile suitable for its function, while the second bank region has a thicker profile to ensure proper electrode connection and prevent disconnection. This local differentiation of properties ensures optimal performance in each region without requiring complete structural redesign.
2Reliability
If thicker banks are used to prevent disconnection, then electrode connectivity improves, but manufacturing precision requirements increase
Solution Approach 1:
The bank structure is formed with predetermined thickness variations before the electrode formation step. The first and second banks are created with specific thickness relationships (second thickness > first thickness) in advance, ensuring that when the opposite electrode is subsequently formed, proper connection is already structurally enabled. This preliminary structuring reduces the precision burden during later electrode fabrication steps.
3Ease of manufacture
If uniform bank thickness is used, then manufacturing process is simpler, but brightness uniformity deteriorates
Solution Approach 1:
The bank is segmented into first and second banks with different thicknesses to control light emission characteristics. The first bank with first thickness and second bank with greater second thickness create different optical paths and emission profiles in their respective regions. This segmentation enables brightness uniformity across the display while the banks are formed in a single integrated structure, maintaining manufacturing simplicity.
Solution Approach 2:
Different thicknesses are assigned to different bank regions to optimize local brightness characteristics. The first bank region's thinner profile and second bank region's thicker profile are tailored to achieve uniform overall brightness distribution. This local optimization of physical properties improves illumination uniformity without requiring complex multi-step fabrication processes.
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 reduces brightness differences between pixels, enhancing display quality by maintaining electrode connectivity and ensuring uniform light emission across the display area.
Implementation Method 1
forming, on the pixel electrode, a first organic layer including a negative-type photoresist, irradiating light onto the first organic layer by using a slit mask and developing the first organic layer into an organic pattern layer
Implementation Method 2
forming a first bank and a second bank by heating the organic pattern layer
Data Source
AI summary
A display apparatus includes a substrate, a pixel electrode disposed on the substrate, a first bank including a bank opening exposing a central portion of the pixel electrode, a second bank disposed on an outer side of the first bank and including a greater thickness than the first bank, an emission layer disposed in the bank opening and corresponding to the pixel electrode, an opposite electrode overlapping the first bank, the second bank, and the emission layer, wherein the first bank and the second bank each include a negative-type photoresist.