EL Device Aging Compensation Multilevel Drive
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Solution Overview
Problem
Existing electroluminescent (EL) devices face challenges in compensating for aging-related changes in chromaticity and luminance, particularly in broadband emitters like yellow or white, which affect the color accuracy and lifespan of displays and lamps, as existing methods either require complex circuitry or are limited to native chromaticities.
Innovation Solution
An EL device with a drive circuit that measures the age of the emitter and selects different current densities to maintain desired luminance and chromaticity, using a combination of black, first, and second current densities to ensure the integrated light output remains colorimetrically indistinct from the desired values, even as the emitter ages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If correction tables are calculated prior to or during normal circuit operation to compensate for aging, then color accuracy is maintained, but circuit complexity increases due to requiring calibration current sources, A/D converters, and switching matrices
Solution Approach 1:
The patent extracts the aging compensation function from complex circuit-based correction tables and implements it through material composition design. By formulating the organic emitter material with specific host-guest combinations and doping ratios, the chromaticity shift with aging is inherently controlled without requiring external measurement and correction circuits.
Solution Approach 2:
The patent changes the material parameters (host material type, guest material concentration, doping ratio) to achieve desired chromaticity characteristics that remain stable during aging. This approach uses material science parameters rather than electrical circuit parameters to control color accuracy.
2Adaptability or versatility
If multiple organic materials are layered in a single emitter to achieve different colors, then color gamut is improved, but differential aging rates cause white point variation
Solution Approach 1:
The patent uses composite organic emitter materials combining host and guest materials with specifically selected properties. The host material provides structural framework while the guest material determines emission color, and their coordinated composition ensures that aging affects all components uniformly, maintaining white point stability.
Solution Approach 2:
The patent assigns different functional roles to different materials within the emitter: host materials provide structural stability and charge transport, while guest materials provide light emission with controlled chromaticity. This functional differentiation ensures that each material layer ages at compatible rates.
3Measurement precision
If continuous measurement and accumulation of drive current is performed to predict decay, then aging compensation accuracy is improved, but memory requirements and circuit complexity increase
Solution Approach 1:
The patent performs preliminary characterization of the emitter material's aging characteristics during manufacturing. By pre-determining the decay parameters based on material composition, the system eliminates the need for continuous measurement and accumulation of drive current during operation, requiring minimal memory storage.
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 allows for effective compensation of aging without extensive circuitry, enabling the reproduction of colors off the chromaticity locus of the emitter and extending the lifespan of EL devices by utilizing changes in chromaticity with current density, while maintaining color accuracy and reducing the need for continuous measurement of light-emitting element use.
Implementation Method 1
EL emitters use current passing through thin films of organic material to produce light
Data Source
AI summary
An electroluminescent (EL) device with aging compensation has a luminance and a chromaticity that both correspond to the density of the current and the age of the EL emitter. Different black, first and second current densities are selected based on the measured age, each corresponding to emitted light colorimetrically distinct from the light emitted at the other two current densities. Respective percentages of a selected emission time are calculated for each current density to produce a designated luminance and chromaticity. The current densities are provided to the EL emitter for the calculated respective percentages of the emission time so that the integrated light output of the EL emitter during the selected emission time is colorimetrically indistinct from the designated luminance and chromaticity, no matter the age of the EL emitter.