Splitting Organic EL Pixels to Reduce Defects
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Solution Overview
Problem
Organic electroluminescence (EL) display devices face pixel defects due to foreign matter invading the electrodes, forming leak paths and preventing light emission, which existing technologies struggle to address effectively without increasing the number of thin film transistors.
Innovation Solution
The solution involves splitting one pixel into multiple sub-pixels with parallel-connected organic EL elements, each controlled by a thin film transistor, allowing other sub-pixels to maintain light emission even if a leak path forms, thereby minimizing the impact of defects and reducing manufacturing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If one pixel is split into multiple sub-pixels with parallel-connected organic EL elements, then pixel defect resistance is improved, but device complexity increases
Solution Approach 1:
The pixel electrode is divided into multiple sub-pixel electrodes (first, second, third sub-pixel electrodes) that are arranged in a triangular pattern. Each sub-pixel electrode connects to a separate organic EL element, allowing independent operation. This segmentation ensures that if one sub-pixel develops a leak path defect, the other sub-pixels can continue to emit light, thereby improving pixel defect resistance while maintaining a relatively simple overall structure.
2Reliability
If the area of each sub-pixel is reduced to accommodate multiple sub-pixels in one pixel, then defect impact is minimized, but luminance intensity decreases
Solution Approach 1:
The multiple sub-pixel electrodes are arranged in a triangular configuration within the pixel area, and all sub-pixels are driven simultaneously by the same drive signal. The light emission from all sub-pixels combines to provide sufficient overall luminance. This merging approach allows each sub-pixel to have reduced area (minimizing defect impact) while the collective emission maintains adequate brightness for display purposes.
3Manufacturing precision
If the number of thin film transistors is increased to control each sub-pixel independently, then control precision is improved, but manufacturing cost increases
Solution Approach 1:
A single thin film transistor is designed to control multiple sub-pixel electrodes simultaneously. The transistor's source electrode connects to the first sub-pixel electrode, the drain electrode connects to the second sub-pixel electrode, and the gate electrode controls both. This multi-functional transistor configuration enables independent control of each sub-pixel group while reducing the total number of transistors required, thereby lowering manufacturing complexity and cost.
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 approach reduces pixel defects and maintains significant luminance even with leak paths, increasing product yield and reducing manufacturing costs while minimizing the increase in thin film transistors used.
Implementation Method 1
organic EL light emitting layers, each of which emits light in a prescribed color, are stacked over one (lower electrode) of electrodes formed for each pixel
Data Source
AI summary
An organic electroluminescence (EL) display device wherein pixel defects are reduced with a minimum increase in the number of thin film transistors used is to be provided. The organic EL display device has: a plurality of power supply lines each for supplying a current to one or another of pixel circuits disposed in an area surrounded by image signal lines and scanning lines; a plurality of split organic EL elements connected in parallel, each connected to one or another of the pixel circuits; a first thin film transistor of which the gate electrode is connected to the signal lines, the source electrode is connected in parallel to the anodes of the plurality of split organic EL elements, and the drain is connected to the power supply lines, and which controls the total amperage to be supplied during the light emitting period to the plurality of split organic EL elements with signals captured from the signal lines; and a plurality of second thin film transistors each disposed between the first thin film transistor and one or another of the split organic EL elements to control the current supplied to each of the split organic EL elements from the first thin film transistor.