Display Device Bank Undercut Structure for Dense Pixel Integration
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Solution Overview
Problem
Existing display devices face challenges in achieving high pixel integration for small form factors, particularly in glasses-type devices, due to difficulties in separating light emitting elements using mask processes, which results in reduced emission area and increased manufacturing complexity.
Innovation Solution
A display device design incorporating a bank member with a first and second bank layer, where the second layer has a tip portion protruding beyond the first, and a pixel defining layer that fills the undercut portion, allowing for reduced gaps between pixel electrodes, facilitated by different etching rates of the bank layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the display device is implemented in a very small size with high pixel integration degree, then the resolution is improved, but the emission area is reduced and light emitting elements become difficult to separate using mask processes
Solution Approach 1:
The bank member is divided into multiple bank layers (first bank layer and second bank layer) with different materials and heights. The second bank layer has a tip portion that protrudes beyond the first bank layer, creating an undercut portion. This segmentation allows the pixel electrode to be separated from adjacent pixels through selective etching of the undercut portion, enabling high pixel integration in small display devices while maintaining ease of manufacture.
2Measurement precision
If the gap between pixel electrodes is reduced to improve pixel integration, then the resolution is improved, but the manufacturing process becomes more complex
Solution Approach 1:
The bank member is designed with pre-formed undercut portions during the fabrication process. The second bank layer's tip portion protruding beyond the first bank layer creates the undercut portion that facilitates subsequent pixel electrode separation. This preliminary structural preparation simplifies the overall manufacturing process while enabling reduced gaps between pixel electrodes for high pixel integration.
3Area of stationary object
If the emission area is reduced due to small device size, then the device form factor is improved, but the light emitting element separation becomes difficult
Solution Approach 1:
The bank member structure utilizes vertical dimensionality with the second bank layer's tip portion protruding beyond the first bank layer in the height direction. This creates an undercut portion that enables pixel electrode separation without requiring additional horizontal space. This dimensional approach allows high pixel integration in small display devices while maintaining ease of manufacture through selective etching.
Data Source
AI summary
A display device includes a substrate including an emission area and a non-emission area; a bank member disposed on the emission area of the substrate and including an undercut portion; a pixel electrode disposed on the bank member; a light emitting layer on the pixel electrode; a residual pattern layer disposed in the non-emission area of the substrate, including the same material as the pixel electrode, and spaced apart from the pixel electrode; and a pixel defining layer disposed on the residual pattern layer and in contact with the bank member, the pixel electrode and the light emitting layer, wherein the bank member includes a first bank layer and a second bank layer including a tip portion protruding toward the non-emission area more than the side surface of the first bank layer.