Electroluminescent Device Brightness Uniformity via Opposing Segments
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Large electroluminescent devices experience non-uniform brightness due to significant voltage drops across transparent electrodes, leading to variations in current density and brightness across the device, which is particularly problematic for large displays and non-pixelated applications like general lighting and LCD backlights.
Innovation Solution
The method involves arranging electroluminescent segments in opposing pairs or forming EL-strips with parallel but opposite electrode currents, reducing the brightness non-uniformity extent by ensuring that the brightest regions of one segment are adjacent to the dimmest regions of another, and using a diffuser to further smooth out brightness variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If large electroluminescent devices are used to increase display area and lighting coverage, then the device area is improved, but brightness uniformity deteriorates due to significant voltage drops across transparent electrodes
Solution Approach 1:
The device is divided into multiple EL segments arranged in opposing pairs, where each segment functions as an independent electroluminescent unit. This segmentation allows the voltage drop issue in each small segment to be compensated by the opposing arrangement, maintaining brightness uniformity across the entire large area device.
Solution Approach 2:
Opposing EL segments are configured with asymmetric current directions, where adjacent segments have electrode currents flowing in opposite directions. This asymmetric arrangement creates complementary brightness patterns that, when viewed together, cancel out the non-uniformity caused by voltage drops, achieving uniform overall brightness.
2Device complexity
If larger EL-segments are used to reduce device complexity, then the number of segments is reduced, but brightness non-uniformity extent increases
Solution Approach 1:
The device maintains segmentation into multiple EL segments rather than using a single large segment, allowing each segment to have controlled current density and brightness characteristics that can be compensated through opposing arrangement.
Solution Approach 2:
Multiple EL segments are merged into opposing pairs where the brightness non-uniformity of one segment is compensated by the complementary pattern of its opposite partner, achieving uniform overall appearance while using manageable segment sizes.
3Illumination intensity
If transparent electrodes with high transparency are used to maintain light output, then light transmission is improved, but voltage drops increase leading to current density variations
Solution Approach 1:
The opposing EL segment configuration creates local quality variations where adjacent segments have different current density distributions. These local variations are complementary and cancel out when viewed together, achieving uniform overall current density effect while maintaining high transparency electrodes.
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 significantly reduces brightness non-uniformity across the device, allowing for more uniform light emission and improved appearance in lighting applications, even when using larger EL-segments or EL-strips, by minimizing the brightness non-uniformity extent and maintaining consistent light distribution.
Implementation Method 1
Light is generated in the electroluminescent device when electrons and holes that are injected from the two electrodes flow through the light-emitting element and generate light by either recombination or impact ionization
Implementation Method 2
using a diffuser to further smooth out brightness variations
Data Source
Figure 1
Figure 2
Figure 3A
AI summary
An electroluminescent device having an opposing EL-segment pair, (1000) including a first EL-segment (800) that produces light in response to a first through- device current having a first transparent electrode connection (210) and a first reflective electrode connection (220) a second EL-segment (900) that produces, light in response to a second through-device current, and having a second transparent electrode connection (210) and a second reflective electrode connection and being disposed adjacent to and spaced from the first EL-segment such that the first transparent electrode connection is on the opposite edge as the second transparent electrode connection and the direction of the first transparent electrode current is parallel but opposite to the direction of the second transparent electrode current; and the first and second EL- segments are connected to a common power source such that the two EL-segments can be simultaneously forward biased.