Taper Reducing Layer for OLED Substrate Planarization
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Solution Overview
Problem
Conventional OLEDs face defects such as pinhole and short-circuit issues due to large taper angles in contact and via holes, leading to reduced picture quality and increased moisture infiltration, which complicates the reduction of taper angles in high-resolution displays.
Innovation Solution
A flat panel display with a taper reducing layer is introduced, which has a smaller taper angle than the underlying layers, specifically designed to reduce the taper angle of contact and via holes, and is formed using a conductive organic layer with charge transporting capabilities to prevent defects and improve the planarization of the substrate surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the taper angle of contact and via holes is reduced to prevent pinhole and short-circuit defects, then reliability is improved, but manufacturing precision deteriorates due to difficulties in achieving small taper angles in high-resolution displays
Solution Approach 1:
The patent introduces a taper reducing layer as an intermediary structure between the contact/via holes and the organic thin film layer. This layer has a smaller taper angle than the underlying holes, serving as a mediator that prevents pinhole and short-circuit defects without requiring the holes themselves to have small taper angles, thus resolving the manufacturing difficulty while maintaining reliability
Solution Approach 2:
The patent segments the structure by dividing the taper angle reduction function into a separate taper reducing layer component. Instead of requiring the entire hole structure to have a small taper angle, the taper angle is segmented and reduced in the specific taper reducing layer portion, allowing independent optimization of hole formation and taper angle control
2Illumination intensity
If the taper angle is reduced to improve picture quality by preventing dark spots, then picture quality is improved, but device complexity increases due to additional taper reducing layer
Solution Approach 1:
The taper reducing layer is designed to perform multiple functions: it reduces the taper angle to prevent pinhole and short-circuit defects, prevents dark spot formation by ensuring uniform organic thin film deposition, and can also serve as part of the functional layer structure. This multi-functionality justifies the additional layer by providing multiple benefits simultaneously
3Reliability
If the taper angle is reduced to prevent moisture infiltration, then reliability is improved, but manufacturing difficulty increases due to process complexity
Solution Approach 1:
The taper reducing layer is formed in advance before depositing the organic thin film layer and other subsequent layers. This preliminary action of creating the taper reducing layer with the appropriate small taper angle ensures that when the organic film is deposited later, it forms uniformly without pinholes, thereby preventing future moisture infiltration paths without requiring complex processes at later stages
Data Source
AI summary
The present invention discloses an organic light emitting device for preventing element defects and improving picture quality by reducing a taper angle of a substrate surface. The flat panel display of the present invention comprises, an insulating substrate, a lower layer formed on the insulating substrate and having a first step and a first taper angle with respect to the substrate surface, and an upper layer formed on the insulating substrate and for reducing the taper angle of the lower layer. The upper layer has a second taper angle smaller than the first taper angle of the lower layer. The upper layer is a conductive layer that may be applied by a wet coating method, has a charge transporting capability, and is selected from at least one of a small-molecule organic layer including a carbazole-based, arylamine-based, hydrazone-based, stilbene-based, oxadiazole-based, starburst-based derivatives, and a polymer organic layer including PEDOT, PANI, carbazole-based, arylamine-based, perylene-based, pyrrole-based, oxadiazole-based derivatives.