Electroluminescence Display Pixel Layer Overlap Design
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Solution Overview
Problem
In electroluminescence display devices, positional shifts during layer formation lead to unintentional light emission due to overlap of charge layers, causing color mixture and reduced light efficiency, as holes and electrons combine outside intended pixel boundaries.
Innovation Solution
The electroluminescence display device is designed with a specific layer arrangement where the second blocking layer of one pixel overlaps the light emitting layer of another, and the light emitting layer overlaps the second blocking layer, with the second blocking layer having a larger area than the light emitting layer, and its center offset from the light emitting layer's center, to prevent unwanted light emission on the bank.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If layers are formed using photolithography or vapor deposition with fine masks, then manufacturing precision is improved, but positional shifts of several μm still occur due to mechanical positioning accuracy and material dimensional errors
Solution Approach 1:
The patent applies preliminary action by forming the electron blocking layer and light emitting layer in a specific sequence before final pixel definition. The electron blocking layer is formed first across the entire substrate, then the light emitting layer is formed with pixel-specific patterns. This preliminary layer formation ensures that even with positional shifts during subsequent manufacturing steps, the charge carrier pathways are already established to prevent unintended recombination at pixel boundaries.
2Manufacturing precision
If the light emitting layer and electron blocking layer are formed independently for each pixel, then color purity is improved, but positional shifts cause overlap between adjacent pixels leading to unintentional light emission
Solution Approach 1:
The patent converts the harmful effect of positional shifts into a beneficial outcome by designing the electron blocking layer to extend beyond the light emitting layer boundaries. When positional shifts occur, the extended electron blocking layer actually prevents unintended light emission by blocking stray charge carriers that would otherwise recombine at pixel boundaries. The potential harm of layer misalignment is transformed into an enhanced charge carrier confinement mechanism.
Solution Approach 2:
The patent applies segmentation by dividing the electron blocking layer into pixel-specific regions that are independently formed and positioned. Each pixel's electron blocking layer is formed separately using photolithography masks, allowing precise control over the lateral extent of each blocking region. This segmentation enables the electron blocking layer to be optimized for each pixel's charge carrier management needs while maintaining overall device integration.
3Productivity
If holes and electrons are allowed to move freely to reach the light emitting layer, then light emission efficiency is improved, but charge carriers combine outside pixel boundaries reducing color purity
Solution Approach 1:
The patent applies local quality by creating spatially varying properties in the electron blocking layer, where each pixel region has tailored electron blocking characteristics. The electron blocking layer's thickness, material composition, and lateral extent are locally optimized for each pixel's specific light emitting layer and charge carrier generation characteristics. This local optimization allows efficient charge carrier collection within each pixel while maintaining sharp boundaries that prevent cross-pixel contamination.
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 reduces unintentional light emission on the bank, improving color purity and light efficiency by ensuring holes and electrons do not combine outside their intended pixel boundaries, even with positional shifts during manufacturing.
Implementation Method 1
holes that reach the light emitting layer 7B through the hole injection layer 5 and the electron blocking layer 6B and electrons that reach the light emitting layer 7B from the common electrode 10 through the electron injection layer 9 and the hole blocking layer 8 are combined to emit blue light
Data Source
AI summary
An electroluminescence display device includes an array of pixels in which pixels emitting light of a specific color are regularly aligned and which includes at least a plurality of pixels emitting light of different colors, and in which, in the pixel, a common electrode, a first blocking layer, a light emitting layer, a second blocking layer, and a pixel electrode are laminated in this order when viewed from a viewing direction, at least the light emitting layer, the second blocking layer, and the pixel electrode are provided independently for each pixel, adjacent pixels are separated by a bank, and, at least in a part of the array of pixels, on the bank, the second blocking layer belonging to another pixel having a light-emission color different from that of one pixel is partially overlapped on the light emitting layer belonging to the one pixel.