Auxiliary Cathode Electrode for Display Aperture Ratio
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Solution Overview
Problem
The cathode contact structure in light emitting display devices faces issues with reduced adhesive force between material layers, leading to peeling phenomena and a decrease in aperture ratio due to the undercut structure, which affects the display quality and reliability.
Innovation Solution
A light emitting display device design that includes a substrate with an auxiliary power electrode, protection layers, and a metal pattern at the periphery of the contact portion, where the undercut structure is formed using a passivation and overcoat layer with good adhesive characteristics, and the metal pattern is disposed between the passivation and bank layers to enhance structural stability and aperture ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an undercut structure is formed to increase cathode contact area and block water transmission, then electrical connection and reliability are improved, but adhesive force between material layers is reduced causing peeling phenomenon
Solution Approach 1:
A separate auxiliary electrode is introduced as an intermediary element to provide additional electrical connection paths between the cathode electrode and external circuitry. This auxiliary electrode works in conjunction with the undercut structure to enhance reliability without compromising the adhesive integrity of the original cathode electrode structure.
Solution Approach 2:
The cathode contact structure is segmented into multiple functional components: the original cathode electrode, the undercut structure for water blocking, and a separate auxiliary electrode for enhanced electrical connection. This segmentation allows each component to perform its specific function optimally without interfering with the adhesive properties of others.
2Reliability
If the cathode contact structure area is increased to improve electrical connection, then reliability is improved, but the aperture ratio of the pixel is reduced
Solution Approach 1:
The auxiliary electrode is strategically positioned in specific regions where electrical connection is most critical, rather than uniformly distributing the contact structure across the entire pixel area. This localized approach enhances reliability in key areas while minimizing the impact on the overall aperture ratio.
Solution Approach 2:
The auxiliary electrode extends in directions complementary to the main cathode electrode, utilizing additional spatial dimensions to provide redundant electrical pathways. This dimensional approach increases connection reliability without significantly expanding the footprint within the pixel plane.
Data Source
AI summary
A light emitting display device includes a circuit layer including an auxiliary power electrode disposed on a substrate, at least one protection layer covering the circuit layer, a contact portion passing through the at least one protection layer to expose a portion of the auxiliary power electrode, and a metal pattern disposed on the contact portion and the at least one protection layer at a periphery of the contact portion.