OLED Shadow Mask Opening for 400 PPI Resolution
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Solution Overview
Problem
Conventional organic electroluminescence displays (OLEDs) are limited by the resolution of shadow masks, which restricts the accuracy of pixel alignment and material deposition, making it difficult to achieve high resolution beyond 300 PPI due to alignment errors, tolerance issues, and contamination during the vacuum thermal evaporation process.
Innovation Solution
The approach involves aligning a shadow mask opening to three sub-pixels for deposition, allowing for the arrangement of different colored sub-pixels in delta or strip configurations within pixel units, enabling increased resolution up to 400 PPI or more by optimizing the electrode pattern and material deposition process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If one opening of the shadow mask is aligned to one sub-pixel in conventional evaporation, then the material deposition is simple and direct, but the resolution is limited to about 300 PPI due to alignment errors, tolerance issues, and contamination
Solution Approach 1:
The patent divides the function of material deposition into two independent stages: first, the shadow mask defines the pixel pattern; second, the organic material is evaporated to cover multiple sub-pixels through a single opening. This segmentation allows the shadow mask to be optimized for pattern definition while the evaporation process is optimized for material coverage, resolving the contradiction between resolution and process complexity
Solution Approach 2:
The patent changes the deposition strategy from a one-to-one mapping (one opening to one sub-pixel) to a one-to-many mapping (one opening to three sub-pixels arranged in delta). This dimensional change in the deposition pattern allows higher resolution to be achieved by utilizing the spatial arrangement of sub-pixels rather than being constrained by the shadow mask opening density
2Manufacturing precision
If the shadow mask opening size and pitch are decreased to achieve higher resolution, then the resolution increases, but alignment accuracy, tolerance, and contamination resistance become more difficult to maintain
Solution Approach 1:
The patent separates the resolution-determining function (shadow mask opening size and pitch) from the alignment-critical function (material deposition accuracy). By allowing one shadow mask opening to serve multiple sub-pixels, the system can use larger, more tolerant shadow mask features while achieving high effective resolution through the delta arrangement of sub-pixels
Solution Approach 2:
The patent applies different functional requirements to different parts of the pixel structure. The shadow mask openings are designed with larger dimensions for manufacturing tolerance, while the organic material deposition is optimized to cover the specific delta-patterned sub-pixel locations, allowing each component to be optimized for its specific function rather than all components being constrained by the highest resolution requirement
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 method effectively enhances the resolution of OLEDs to 400 PPI or higher by improving the alignment and deposition accuracy, overcoming the limitations of conventional shadow mask technology.
Implementation Method 1
the small-molecule based light emitting diodes (OLEDs) material is generally deposited by vacuum thermal evaporation (VTE) through the shadow mask
Data Source
AI summary
A display includes a substrate; an electrode layer formed on the substrate and having an electrode pattern; and an organic material layer formed on the electrode layer, wherein a plurality of pixel units are configured by the combination of the electrode pattern and the organic material layer. At least one of pixel units includes plural different colored sub-pixels arranged in delta. In one embodiment, the same colored sub-pixels of adjacent pixel units are arranged in delta. In another embodiment, the same colored sub-pixels of adjacent pixel units are arranged as a stripe. According to the embodiment, an opening of the shadow mask is corresponding to at least three sub-pixels with same color when the material is evaporated through the shadow mask.