OLED Cathode Groove Contact Layout for Narrow-Bezel Displays
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Solution Overview
Problem
The misalignment between the deposition mask and the substrate during the vacuum deposition of the cathode electrode in organic EL display devices leads to the need for a large contact electrode on the outer periphery of the light-emitting pixel area, hindering the narrowing of the display panel frame.
Innovation Solution
A groove is formed along the direction of pixel arrangement in the insulating film, with a contact electrode provided at the bottom of the groove, allowing the cathode electrode to be electrically connected within the light-emitting pixel area, eliminating the need for an outer peripheral contact electrode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the contact electrode is provided on the outer periphery of the light-emitting pixel area to ensure low contact resistance, then the contact resistance is reduced, but the frame size increases
Solution Approach 1:
The contact electrode is repositioned from the outer periphery (2D plane) to the bottom of a groove formed in the insulating film (3D space). This vertical dimension allows the contact electrode to be located within the light-emitting pixel area footprint, reducing the frame size while maintaining electrical connection reliability through the groove structure that guides the cathode electrode contact.
2Reliability
If the contact electrode size is increased to secure low contact resistance, then the contact resistance is reduced, but the chip area increases
Solution Approach 1:
The contact electrode is nested within the groove structure formed in the insulating film. The groove acts as a container that houses the contact electrode at its bottom, allowing the contact electrode to be positioned within the pixel area boundaries rather than extending to the periphery. This nesting approach reduces the overall chip area while maintaining sufficient contact resistance performance.
3Ease of manufacture
If a deposition mask is used to deposit the cathode electrode, then the cathode electrode can be formed on the contact electrode, but misalignment between the base substrate and deposition mask occurs
Solution Approach 1:
The groove formed in the insulating film serves as an intermediary structure that guides and positions the cathode electrode during the vacuum deposition process. Instead of relying solely on the alignment between the base substrate and deposition mask, the groove acts as a physical guide that ensures accurate positioning of the cathode electrode on the contact electrode, compensating for potential misalignment issues.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration enables the application of a predetermined potential to the cathode electrode while narrowing the display panel frame, reducing chip size and cost.
Implementation Method 1
the cathode electrode is vacuum-deposited on the contact electrode provided on the outer periphery of the light-emitting pixel area using a deposition mask
Implementation Method 2
an organic electroluminescence (EL) element employing a phenomenon in which electroluminescence of an organic material is used to obtain light emission when an electric field is applied to an organic thin film
Data Source
AI summary
A display device of the present disclosure includes: an organic EL layer deposited on a circuit unit formed on a substrate via an insulating film; a cathode electrode deposited on the organic EL layer; a groove formed along a direction of arrangement of pixels between the pixels in the insulating film; and a contact electrode that is provided at a bottom of the groove and receives a predetermined potential. Moreover, the cathode electrode is electrically connected to the contact electrode in the groove.