Transparent Display Capping Structure for Transmittance and Color Purity
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Solution Overview
Problem
Current transparent display devices face challenges in achieving high transmittance and uniform color efficiency across wavelengths due to the difficulty in implementing both self-luminous and transparent areas using a common formation method, leading to deviations in light intensity and reduced color purity.
Innovation Solution
A transparent display device is designed with a substrate having emission and transmission portions, featuring an organic light emitting layer, a reflective electrode structure, a transmissive electrode, and a capping structure with a high refractive index first capping layer and a low refractive index second capping layer, optimized for destructive interference to enhance light transmission and uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the thickness of the cathode or capping layer is reduced to increase transmittance, then transmittance is improved, but deviations in light intensity according to wavelength occur and color purity is lowered
Solution Approach 1:
The patent employs a composite capping layer structure consisting of multiple layers with different refractive indices (first capping layer with refractive index 1.8-2.2, second capping layer with refractive index 1.4-1.7). This composite structure allows the device to achieve high transmittance while maintaining uniform color efficiency across different wavelengths, resolving the contradiction between transmittance improvement and color purity preservation
Solution Approach 2:
The patent optimizes specific parameters including the thickness of each capping layer (first capping layer: 50-200 nm, second capping layer: 20-100 nm) and their refractive indices to control optical interference effects. By carefully adjusting these parameters, the device achieves constructive interference for visible light wavelengths, maintaining high transmittance and uniform color efficiency simultaneously
2Device complexity
If a common formation method is used for both self-luminous area and transparent area, then device complexity is reduced, but it is difficult to implement both areas with different structural requirements
Solution Approach 1:
The patent designs a universal capping layer structure that serves dual functions: in the self-luminous area, it enhances light extraction and maintains color purity; in the transparent area, it maximizes light transmittance. This multi-functional design allows a single formation method to accommodate both area types with different performance requirements, reducing device complexity while maintaining adaptability
Solution Approach 2:
The patent applies local quality optimization by configuring the capping layers with specific refractive indices and thicknesses that are optimized for their local function. The first and second capping layers have different optical properties tailored to their specific roles in light management, allowing the structure to perform differently in self-luminous versus transparent areas while using the same fabrication process
3Illumination intensity
If the emission area is reduced to accommodate transparent area, then transparency is improved, but driving voltage increases to maintain required luminance
Solution Approach 1:
The patent replaces the need for increased driving voltage with an optical solution - the optimized capping layer structure enhances light extraction efficiency and maintains luminance through improved optical interference. This substitutes the electrical approach (increasing voltage) with an optical approach (improving light management), thereby maintaining transparency while avoiding increased power consumption
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
The solution improves transmittance and color efficiency by minimizing reflectance differences at interfaces, maintaining high transmittance across the visible wavelength range and reducing color distortion, thereby achieving stable and uniform display performance.
Implementation Method 1
a first capping layer over the transmissive electrode and having destructive interference properties and a first refractive index of 2.0 or more
Implementation Method 2
a first capping layer over the transmissive electrode and having destructive interference properties and a first refractive index of 2.0 or more
Implementation Method 3
a second capping layer over the first capping layer and having a second refractive index less than the first refractive index by 0.2 or more but less than 1.2
Implementation Method 4
maintaining high transmittance across the visible wavelength range and reducing color distortion
Data Source
AI summary
Disclosed is a transparent display device which has improved transmittance and luminous uniformity according to wavelength. The transparent display device includes a capping structure. The capping structure is formed by stacking a high refractive index first capping layer having destructive interference properties and a low refractive index second capping layer.