Variable Cathode Thickness for Display Voltage Drop
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Solution Overview
Problem
As display device sizes increase, common voltage drops become noticeable, leading to visible stains in light emitting display devices, which existing technologies fail to effectively prevent.
Innovation Solution
A light emitting display device design featuring a substrate with a transistor, anode, emission layer, and a cathode where the thickness of the cathode's portions overlapping and not overlapping the emission layer differ, along with a manufacturing method that includes forming specific openings and layers to manage the cathode thickness and connection, effectively preventing common voltage drops.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the display device size is increased, then the display area is improved, but voltage drop in common voltage lines increases causing visible stains
Solution Approach 1:
The cathode is designed with different thicknesses in different regions: a first thickness in the emission region and a second thickness in the non-emission region. This local variation in cathode thickness compensates for voltage drops in different areas of the large display, preventing visible stains while maintaining the large display area.
2Ease of manufacture
If the cathode thickness is made uniform, then the manufacturing process is simplified, but voltage drop compensation is insufficient leading to visible stains
Solution Approach 1:
The cathode structure employs different thicknesses in different regions to provide localized voltage compensation. The first portion has a first thickness optimized for emission regions, while the second portion has a second thickness for non-emission regions, enabling effective voltage drop compensation across the entire display area.
Solution Approach 2:
The cathode thickness parameter is varied across different regions of the display. By changing the thickness parameter from a uniform value to multiple distinct values (first thickness and second thickness), the invention achieves effective voltage drop compensation and eliminates visible stains while maintaining manufacturability through defined fabrication processes.
Data Source
AI summary
A light emitting display device includes: a substrate; a transistor disposed on the substrate; an anode connected to the transistor; an emission layer disposed on the anode; a common voltage line disposed on the substrate; and a cathode disposed on the emission layer and the common voltage line, where a thickness of a first portion of the cathode overlapping the emission layer is different from a thickness of a second portion of the cathode not overlapping the emission layer.