Organic EL Display Unit Anode Planarization for Diffraction Reflection
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Solution Overview
Problem
In organic EL display units, diffraction reflection caused by concavity and convexity in the anode surface reduces image quality due to the reflection of outside light, which is a limitation in achieving high image visibility and low power consumption.
Innovation Solution
The design includes a pixel circuit with a second transistor where the upper face of the source or drain is formed in a region opposed to the anode or cathode of the organic EL device, or features a continuous curved face in the source or drain, preventing the formation of steps under the anode or cathode and reducing diffraction reflection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the source or drain of the second transistor is formed directly under the anode or cathode of the organic EL device, then the pixel circuit layout is simplified, but concavity and convexity are generated in the anode surface causing diffraction reflection
Solution Approach 1:
The patent introduces a planarization layer (insulating film) between the transistor source/drain and the anode, adding a new dimensional layer to resolve the conflict. This planarization layer fills the concavity created by the source/drain structure, providing a flat surface for the anode without changing the underlying transistor layout, thus eliminating diffraction reflection while maintaining layout simplicity.
Solution Approach 2:
The patent uses an insulating film as an intermediary element between the source/drain and the anode. This intermediary layer serves dual purposes: it maintains the electrical isolation required for transistor operation while simultaneously planarizing the surface to prevent diffraction reflection, thus resolving the contradiction between layout simplicity and optical quality.
2Area of stationary object
If the anode surface has concavity and convexity, then the transistor source or drain can be positioned under it for compact design, but image quality deteriorates due to outside light reflection
Solution Approach 1:
By adding the planarization layer as an intermediate dimension, the patent enables the anode to be formed on a flat surface even when the source/drain occupies space below it. This resolves the conflict between compact pixel area and prevention of light reflection, as the planarization layer fills the vertical space without increasing the horizontal pixel area.
3Object-affected harmful factors
If a planarization layer is added to eliminate concavity and convexity, then diffraction reflection is suppressed, but device structure becomes more complex
Solution Approach 1:
The patent uses an insulating film material for the planarization layer that is homogeneous with the existing gate insulating film and other insulating layers in the device. This material homogeneity allows the planarization layer to be integrated into the existing device structure without introducing new material systems or complex manufacturing processes, thus minimizing the increase in device complexity.
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 suppresses diffraction reflection, thereby enhancing image quality and maintaining low power consumption by ensuring a flat surface for the anode, which minimizes the impact of outside light on the display.
Implementation Method 1
an organic EL device 121R and the like, which has an anode 127A, an organic layer 122A, and a cathode 127B
Data Source
AI summary
A display unit with which diffraction reflection is able to be decreased is provided. The display unit includes a display section having an organic EL device and a pixel circuit for every pixel. The pixel circuit has a first transistor for writing a video signal and a second transistor for driving the organic EL device based on the video signal written by the first transistor. The second transistor has a gate, a source and a drain. The organic EL device has an anode, an organic layer, and a cathode. An upper face of the source or the drain is formed at least in a region opposed to the anode or the cathode.