Display Pixel Electrode Structure for Maskless Element Separation
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Solution Overview
Problem
Display devices with high pixel integration face challenges in forming light emitting elements separated from each other without a mask process, especially in small sizes, and are prone to moisture permeation, leading to issues like mura and element damage.
Innovation Solution
A display device structure with a specific electrode layer arrangement and etching process forms light emitting elements separated by an inorganic pixel defining layer, using different etchants for each layer, and includes a bank structure to prevent moisture penetration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a mask process is used to form light emitting elements in small-sized display devices, then light emitting elements can be separated for each emission area, but the manufacturing complexity and cost increase
Solution Approach 1:
The pixel electrode is segmented into multiple emission areas by the inorganic pixel defining layer, which divides the continuous electrode into discrete regions. This segmentation allows light emitting elements to be formed in separated areas without requiring a mask process, as the inorganic layer naturally defines the emission boundaries during deposition
Solution Approach 2:
The inorganic pixel defining layer acts as an intermediary between the pixel electrode and the emission areas. This intermediate layer with different etch selectivity enables precise definition of emission areas through selective etching, replacing the need for mask processes while maintaining element separation
2Shape
If the side surface of the lower transparent electrode layer is indented more than the side surface of the metal electrode layer, then the structure is formed, but moisture can penetrate through the indentation causing mura and element damage
Solution Approach 1:
The inorganic pixel defining layer is deposited in advance to cover and seal the indentation area of the lower transparent electrode layer before moisture penetration can occur. This preliminary protective layer prevents moisture from reaching the vulnerable indentation region, eliminating the risk of mura and element damage while maintaining the necessary electrode structure
Solution Approach 2:
The display device uses a composite structure combining organic and inorganic materials in the pixel defining layer. The inorganic material provides superior moisture barrier properties compared to organic materials alone, creating a robust protective seal over the electrode indentation areas and preventing moisture ingress
Data Source
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AI summary
A display device includes a pixel electrode including a lower transparent electrode layer disposed on a substrate, a metal electrode layer disposed on the lower transparent electrode layer, and an upper transparent electrode layer disposed on the metal electrode layer; an inorganic pixel defining layer disposed on the substrate and exposing the pixel electrode; a light emitting layer disposed on the pixel electrode; a common electrode disposed on the light emitting layer; a first bank disposed on the inorganic pixel defining layer; and a second bank disposed on the first bank and having a side surface protruding more than a side surface of the first bank. A side surface of the lower transparent electrode layer is aligned with a side surface of the metal electrode layer or protrudes more than the side surface of the metal electrode layer.