Flat Planarization Structure for Uniform Light-Emitting Displays
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Solution Overview
Problem
In display apparatuses, the curvature of the planarization layer above the driving circuit leads to inconsistent vertical distances between the device substrate and the light-emitting device, causing luminance deviations due to differences in light emission position, which decreases image quality.
Innovation Solution
A display apparatus with a device substrate featuring a first and second planarization layer, where the second planarization layer has a flat upper surface, and the light-emitting device is stacked on it, ensuring a consistent vertical distance and preventing luminance deviations by using a connection electrode and an encapsulation unit, along with a method of forming this structure through chemical mechanical polishing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a single planarization layer is used to cover the driving circuit, then the manufacturing process is simple, but the upper surface has curvature causing luminance deviation
Solution Approach 1:
The single planarization layer is divided into two separate planarization layers. The first planarization layer covers the driving circuit and the second planarization layer is formed on the first planarization layer to provide a flat upper surface. This segmentation allows each layer to perform its specific function independently, resolving the contradiction between manufacturing simplicity and surface flatness.
Solution Approach 2:
The solution adds a vertical dimension by stacking two planarization layers instead of using a single layer. The first planarization layer handles the circuit coverage while the second planarization layer provides the flat upper surface, effectively solving the curvature problem by distributing the planarization function across multiple dimensional layers.
2Reliability
If the planarization layer follows the curvature of the driving circuit, then it provides good coverage, but the light emission position varies causing luminance deviation
Solution Approach 1:
The planarization function is segmented into two layers: the first planarization layer provides coverage over the driving circuit following its curvature, while the second planarization layer is formed on top to provide a flat upper surface. This ensures both good coverage and uniform light emission position.
Solution Approach 2:
Different parts of the planarization structure have different qualities: the first planarization layer has conformal coverage quality to match the driving circuit topology, while the second planarization layer has flat surface quality to ensure uniform light emission. Each layer is optimized for its specific local function.
3Illumination intensity
If a flat upper surface is created for the light-emitting device, then luminance uniformity is improved, but the manufacturing process becomes more complex
Solution Approach 1:
The planarization structure is segmented into two functional layers, where the first layer provides circuit coverage and the second layer provides the flat upper surface. This segmentation achieves luminance uniformity while keeping each layer's manufacturing process relatively simple and well-defined.
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
The solution ensures consistent light emission positions across pixel areas, preventing luminance deviations and maintaining image quality by minimizing curvature and thickness differences in the planarization layers.
Implementation Method 1
a method of forming this structure through chemical mechanical polishing
Data Source
AI summary
A display apparatus including a light-emitting device and a method of forming the same are provided. The light-emitting device may be electrically connected to the driving circuit. A first planarization layer may be disposed on the driving circuit, a second planarization layer may be disposed on the first planarization layer, and the light-emitting device may be disposed on the second planarization layer. An upper surface of the second planarization layer toward the light-emitting device may be parallel with a surface of a device substrate supporting the light-emitting device and the driving circuit. Thus, in the display apparatus and the method of forming the same, decreasing the quality of an image due to differences in the generation position of the light emitted from the light-emitting device may be prevented.