Organic Light Emitting Display Negative Dispersion QWP
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Solution Overview
Problem
Conventional organic light emitting display devices suffer from reduced brightness and increased reflectance, especially outdoors, due to the use of circular polarizers, which also cause issues with visibility when wearing sunglasses.
Innovation Solution
The implementation of a specific optical configuration including a first quarter wave plate (QWP) with negative dispersion characteristics, a second QWP with a 45-degree angle relative to the linear polarizer, and a third retardation layer to minimize reflectance and color cast, while enhancing brightness and maintaining visibility under sunglasses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a circular polarizer is used in the organic light emitting display device, then the brightness and contrast are improved, but the reflectance increases and visibility deteriorates when wearing sunglasses
Solution Approach 1:
The circular polarizer is divided into two separate quarter wave plates (first QWP and second QWP) positioned at different locations in the optical path. The first QWP is located between the organic light emitting element and the linear polarizer, while the second QWP is located between the linear polarizer and the external environment. This segmentation allows independent optimization of each QWP's properties, particularly the negative dispersion characteristic of the first QWP which reduces reflectance while maintaining brightness enhancement.
Solution Approach 2:
The patent changes the dispersion parameter of the first quarter wave plate to have negative dispersion characteristics, which is different from conventional positive dispersion materials. This parameter change fundamentally alters the optical path difference between orthogonal polarization components, enabling the device to achieve low reflectance (less than 2%) while maintaining high brightness and contrast ratio.
2Illumination intensity
If a circular polarizer is used to enhance brightness, then the light emission is improved, but the color cast increases and image quality deteriorates
Solution Approach 1:
The first quarter wave plate is designed with negative dispersion characteristics, which compensates for the wavelength-dependent phase delays introduced by other optical layers. This parameter change ensures that the optical path difference between orthogonal polarization components is optimized across the visible spectrum, minimizing color cast while maintaining high brightness enhancement (transmittance increased to 70%).
Solution Approach 2:
The patent employs a composite optical structure combining two quarter wave plates made of different materials with different dispersion characteristics. The first QWP uses negative dispersion material while the second QWP can use conventional positive dispersion material. This composite approach allows the system to achieve broadband polarization control with minimal color distortion across the visible spectrum.
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 configuration reduces reflectance to less than 2% and minimizes color cast, increasing transmittance to 70% without increasing reflectance, ensuring improved visibility and image recognition at all angles, even when wearing polarizing sunglasses.
Implementation Method 1
a first quarter wave plate (QWP) with negative dispersion characteristics
Implementation Method 2
a first quarter wave plate (QWP) with negative dispersion characteristics, a second QWP with a 45-degree angle relative to the linear polarizer
Implementation Method 3
an optical member including a first retardation layer, a second retardation layer, a linear polarizer and a third retardation layer which are sequentially disposed on the organic light emitting diode
Data Source
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AI summary
An organic light emitting display device according to the present invention may have the following advantages. Firstly, since a first quarterwave plate (162) having a negative dispersion characteristic and a cholestric liquid crystal layer (161) are sequentially provided under a linear polarizer (163), reflectance and brightness may be enhanced and color shift may be minimized. Further, as a second QWP (164) is provided on the linear polarizer, a user may recognize an image at all angles even when he or she wears sunglasses.