OLED Display Light Extraction via Cholesteric Liquid Crystal Recycling
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Solution Overview
Problem
Organic light emitting diode (OLED) display devices suffer from low light extraction efficiency, leading to reduced luminance and increased power consumption, as well as deteriorated display quality and visibility of black colors due to high reflectance and limited viewing angles.
Innovation Solution
Incorporating a substrate with an overcoating layer featuring a microlens structure and a cholesteric liquid crystal layer to redirect and recycle light, enhancing light extraction efficiency and reducing reflectance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If more current is applied to the light emitting layer to increase luminance, then luminance is improved, but power consumption increases and lifetime is reduced
Solution Approach 1:
The patent converts the harmful effect of light being trapped and lost within the OLED device into a beneficial recycling process. By introducing a cholesteric liquid crystal layer that selectively reflects specific wavelengths back into the light emitting layer, previously lost light is now reused to generate additional useful light output, improving luminance efficiency without increasing power consumption
Solution Approach 2:
The patent changes the optical parameters of the device by introducing a selective wavelength reflection mechanism through the cholesteric liquid crystal layer. This modifies the light extraction characteristics and enables wavelength-specific light recycling, allowing the system to achieve better luminance efficiency through parameter optimization rather than increased current
2Loss of energy
If a microlens array is attached to the outer surface or microlens is formed in the overcoating layer, then light extraction efficiency is improved, but a large amount of light is confined and only a small amount is extracted to the exterior
Solution Approach 1:
The patent changes the refractive index parameter by introducing the cholesteric liquid crystal layer with its unique optical properties. This layer creates a refractive index mismatch that enhances light scattering and extraction efficiency without requiring complex microlens structures, thereby improving light extraction while maintaining simpler device architecture
Solution Approach 2:
The cholesteric liquid crystal layer acts as an intermediary between the light emitting layer and the external environment. It mediates the light extraction process by selectively reflecting certain wavelengths back into the active layer while allowing other wavelengths to pass through, thereby improving overall light extraction efficiency without direct mechanical intervention like microlenses
3Adaptability or versatility
If viewing angle is improved in the OLED display device, then display quality is enhanced, but visibility of black color is deteriorated due to relatively high reflectance
Solution Approach 1:
The patent applies local quality by making the light extraction properties wavelength-dependent through the cholesteric liquid crystal layer. Different wavelengths are treated differently - some are reflected back for recycling while others are allowed to transmit, creating localized optical properties that improve black color visibility in specific wavelength ranges while maintaining good viewing angle characteristics
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 significantly improves light extraction efficiency, extends the OLED display device's lifetime, maintains high display quality across various viewing angles, and enhances the visibility of black colors by reducing reflectance.
Implementation Method 1
a cholesteric liquid crystal layer at a transmission direction of a light emitted from the light emitting diode
Implementation Method 2
an overcoating layer on a first surface of the substrate and including a plurality of convex portions and a plurality of concave portions
Data Source
AI summary
The present disclosure is directed to an organic light emitting diode display device includes a substrate having an emitting area and a non-emitting area; an overcoating layer on a first surface of the substrate and including a plurality of convex portions and a plurality of concave portions, at least one of the plurality of convex portions including a bottom surface portion, a top surface portion and a side surface portion between the bottom and top surface portions; a light emitting diode on the overcoating layer; and a cholesteric liquid crystal layer at a transmission direction of a light emitted from the light emitting diode.