Electroluminescent Display Under-Cut Structure for Slim Bezels
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Solution Overview
Problem
Existing electroluminescent display devices face limitations in achieving a slim bezel width while ensuring moisture permeation resistance and reliability, as the cathode needs to cover the organic layer to prevent exposure during mass production.
Innovation Solution
The implementation of an under-cut structure and trench in the non-display area of the electroluminescent display device, which includes a planarization layer and bank, allows the cathode to retreat into the display area, forming a reliable bezel and blocking lateral moisture permeation routes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the cathode is formed to cover the organic layer completely, then reliability against moisture permeation is improved, but the bezel width increases
Solution Approach 1:
The patent introduces a vertical dimension solution by forming a bank structure that rises from the substrate surface. The cathode is then formed to cover the top surface of the bank, creating a stepped configuration. This vertical arrangement allows the cathode to protect the organic layer's lateral surface from moisture without extending the horizontal bezel width, thus resolving the contradiction between reliability and bezel size.
Solution Approach 2:
The bank structure is formed locally at specific regions where the organic layer needs protection, rather than uniformly across the entire device. The cathode covers only the necessary areas (top surface and lateral surfaces of the bank) to prevent moisture ingress, while the rest of the device maintains a compact form factor. This localized approach ensures reliability where needed without unnecessarily increasing overall bezel width.
2Length of stationary object
If the cathode retreats to increase reliable bezel, then bezel width is reduced, but moisture permeation resistance may be compromised
Solution Approach 1:
By utilizing the vertical dimension through the bank structure, the patent enables the cathode to provide moisture protection without requiring horizontal extension. The bank's height compensates for the reduced horizontal coverage, maintaining reliability while achieving a narrower bezel width.
Solution Approach 2:
The bank structure is formed in advance before the cathode deposition, creating a pre-positioned barrier that guides the cathode's coverage area. This preliminary structure ensures that when the cathode is formed, it automatically covers the critical lateral surfaces of the organic layer, preventing moisture ingress even with reduced horizontal extension.
Data Source
AI summary
An electroluminescent display device according to an exemplary embodiment of the present disclosure includes a display panel divided into a display area and a non-display area, a planarization layer and a bank extended to the non-display area of the display panel, an organic layer and a cathode disposed on the bank and extended to the non-display area of the display panel, a trench which is disposed in the non-display area outside the display area and from which the cathode, the organic layer, the bank and the planarization layer are removed; an under-cut structure which is disposed within the trench and composed of the bank and the planarization layer and in which the planarization layer retreats inwards from an end of the bank to generate an under-cut and an adhesive layer and an encapsulation substrate disposed on the cathode. Thus, reliability can be improved and a bezel width can be reduced.