Bank-Structured OLED Pixel Layout for Maskless Cathode Formation
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Solution Overview
Problem
Display devices experience afterimages due to deterioration of light emitting elements, and existing methods require a separate fine metal mask for forming light emitting layers and cathode electrodes.
Innovation Solution
A display device with a pixel circuit that includes a bank structure comprising a first and second bank layer, allowing for the formation of light emitting layers and cathode electrodes without a separate fine metal mask, and an inverted pixel structure to reduce element deterioration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a separate fine metal mask is used for forming light emitting layers and cathode electrodes, then manufacturing precision is improved, but device complexity and manufacturing cost increase
Solution Approach 1:
The patent combines the formation of light emitting layers and cathode electrodes into a single deposition process. The bank structure serves as a unified mask that defines both the light emitting layer pattern and cathode electrode pattern simultaneously, eliminating the need for separate fine metal masks and reducing process complexity while maintaining precision.
Solution Approach 2:
The bank structure acts as an intermediary mask that enables maskless formation of multiple layers. By depositing materials at angles that exploit the bank structure's geometry, the patent uses the bank structure itself as the defining mask for both light emitting layers and cathode electrodes, avoiding the need for additional separate masks.
2Ease of manufacture
If conventional pixel structure is used, then manufacturing process is simpler, but light emitting element deterioration occurs causing afterimages
Solution Approach 1:
The patent inverts the conventional pixel structure by placing the cathode electrode on the emission area directly, with the light emitting layer between the anode and cathode. This inverted configuration reduces the area where light emitting elements are formed, thereby reducing deterioration and minimizing afterimages while maintaining manufacturing feasibility through the bank structure mask.
3Device complexity
If bank structure with protruding tips is used, then light emitting layer and cathode electrode can be formed without separate fine metal mask, but manufacturing precision requirements increase
Solution Approach 1:
The patent changes the deposition parameters (angle and direction) to exploit the bank structure's protruding tips. By controlling the deposition angle, materials naturally accumulate at the tips to form the required patterns, transforming the bank structure from a simple mask into a self-defining template that reduces precision requirements.
Data Source
AI summary
A display device includes: a pixel circuit comprising a transistor on a substrate; an anode electrode on an emission area of the substrate; a pixel defining layer on a non-emission area of the substrate and defining a first opening; a bank structure on the pixel defining layer and defining a second opening, the bank structure comprising a first bank layer and a second bank layer; a first cathode electrode on the anode electrode, contacting the bank structure, and electrically connected to the transistor; and a second cathode electrode spaced apart from the first cathode electrode with the pixel defining layer and the bank structure therebetween, wherein the second cathode electrode contacts the bank structure, and the bank structure contacting the first cathode electrode and the bank structure contacting the second cathode electrode are spaced apart from each other with a third opening therebetween, in a portion overlapping the non-emission area.