Partial Reflector for OLED Color Shift Correction
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Solution Overview
Problem
Organic light emitting diode (OLED) displays experience significant color shift when viewed from different angles due to the inherent properties of conventional multilayer optical films and reflective polarizers, which affect the uniformity and quality of the displayed color.
Innovation Solution
A wavelength and polarization-dependent partial reflector is introduced, comprising an optical stack with specific optical repeat units made of alternating polymer layers, optimized to have a refractive index difference and optical thickness variation, which reduces color shift by recycling light and adjusting reflectivity based on view angle and wavelength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional multilayer optical films and reflective polarizers are used in OLED displays, then the display structure is simple and manufacturing is easier, but significant color shift occurs when viewed from different angles
Solution Approach 1:
The patent applies local quality by creating optical repeat units with varying optical thicknesses (T1, T2, T3) at different positions within the multilayer stack. Each layer position has specifically tailored refractive index differences (Δnx, Δny) and optical thickness parameters to control the reflection characteristics at different view angles, thereby achieving color uniformity across the viewing cone while maintaining a manufacturable multilayer structure.
2Stability of the object's composition
If an optical stack with varying optical thickness is implemented to reduce color shift, then color uniformity is improved, but the device complexity and manufacturing precision requirements increase
Solution Approach 1:
The patent employs parameter changes by systematically varying the optical thickness (T1, T2, T3) and refractive index differences (Δnx, Δny) of the polymer layers throughout the optical stack. These controlled parameter variations create the wavelength and polarization-dependent reflection characteristics needed to reduce color shift, while the parameters are designed to remain within manufacturable ranges for conventional OLED production processes.
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 partial reflector significantly reduces color shift at 45-degree view angles to no more than 0.8 times that of equivalent displays without the partial reflector, maintaining color uniformity and image quality across varying angles.
Implementation Method 1
a refractive index difference between the first and second polymer layers along a first axis being Δny, a refractive index difference between the first and second polymer layers along an orthogonal second axis being Δnx
Implementation Method 2
wavelength and polarization dependent partial reflector including an optical stack
Implementation Method 3
a refractive index difference between the first and second polymer layers along a first axis being Δnym a refractive index difference between the first and second polymer layers along an orthogonal second axis being Δnx
Data Source
AI summary
A partial reflector including a plurality of optical repeat units where each optical repeat unit includes first and second polymer layers is described. A refractive index difference between the first and second polymer layers along a first axis may be Δny, a refractive index difference between the first and second polymer layers along an orthogonal second axis may be Δnx, where |Δnx| is at least 0.1 and |Δny| is no more than 0.04. The optical repeat units may have a smallest optical thickness T1 proximate a first side of the optical stack and a largest optical thickness T2 proximate an opposite second side of the optical stack, where (T2−T1)/(T2+T1) can be a range of 0.05 to 0.2, and T2 can be at least 350 nm and no more 1250 nm. The partial reflector may be used in a circular polarizer for correcting color shift with view angle in a display.