Display Device Bank Structure Optical Path Control
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Solution Overview
Problem
Organic EL display devices face issues with color purity due to mixing of light components from different optical interference paths, leading to color discrepancies across the display.
Innovation Solution
The design includes a bank with specific inclining surfaces and sealing films to control the optical paths, ensuring the second optical path's length is an integral multiple of the first, and refractive index differences between films are minimized to maintain consistent chromaticity across the display.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If light components from different optical interference paths are allowed to mix, then the display can emit sufficient light intensity, but color purity deteriorates due to color discrepancies across the display
Solution Approach 1:
The patent segments the optical paths by introducing a bank structure with specific inclining surfaces that separate light components traveling along different paths. The bank divides the pixel electrode into regions where first optical paths (reflecting off the pixel electrode bottom surface) and second optical paths (reflecting off the bank inclining surfaces) are spatially separated, allowing selective control over which light components reach the observer, thereby maintaining color purity while preserving sufficient light intensity.
Solution Approach 2:
The patent applies local quality by creating different optical path characteristics in different regions of the pixel. The bank structure with specific inclining angles (55±2 degrees or 60±2 degrees) creates localized regions where second optical paths have lengths that are integral multiples of first optical path lengths. This local optimization ensures that reflected light components maintain consistent chromaticity in specific areas, improving overall color purity while maintaining adequate light output.
2Manufacturing precision
If the bank inclining angle is optimized to align optical paths for improved color purity, then manufacturing precision improves, but device complexity increases due to precise angle requirements
Solution Approach 1:
The patent utilizes parameter changes by optimizing the bank inclining angle to specific values (55±2 degrees or 60±2 degrees) that create the desired optical path length relationships. By changing the inclining angle parameter to these specific values, the patent achieves integral multiple relationships between first and second optical path lengths, ensuring consistent chromaticity. This parameter optimization improves color purity while the tolerance ranges (±2 degrees) provide manufacturing flexibility to manage complexity.
3Ease of manufacture
If sealing films with different refractive indexes are used, then ease of manufacture improves, but color purity deteriorates due to refractive index differences affecting optical paths
Solution Approach 1:
The patent applies homogeneity by requiring that the first and second sealing films have the same refractive index. This homogeneity in refractive index ensures that light components passing through different sealing films experience identical refraction, preventing color shifts and maintaining consistent chromaticity across the display. This constraint on material selection prioritizes color consistency over manufacturing ease, as it limits the range of available sealing film materials.
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 enhances color purity by aligning the chromaticity of light from both optical paths, providing a uniform color appearance across the display.
Implementation Method 1
an optical path of light emitted from any light emitting point in the light emitting layer and reflected by a corresponding pixel electrode
Implementation Method 2
an optical path of light emitted from the light emitting point and reflected by the corresponding pixel electrode to reach the bank
Implementation Method 3
the first sealing film and the second sealing film have a refractive index difference of 0.2 or less
Data Source
AI summary
A display device includes a plurality of pixel electrodes; a bank having a plurality of openings respectively exposing a part of top surfaces of the plurality of pixel electrodes, a light emitting layer provided on the top surfaces of the plurality of pixel electrodes; and a common electrode covering the bank and the light emitting layer. Where an optical path of light emitted from any light emitting point in the light emitting layer and reflected by a corresponding pixel electrode, among the plurality of pixel electrodes, to return to the light emitting point is a first optical path, and an optical path of light emitted from the light emitting point and reflected by the corresponding pixel electrode to reach the bank is a second optical path, the second optical path has a length that is an integral multiple of a length of the first optical path.