OLED Display Color Stability via Interference Wavelength Control
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Solution Overview
Problem
Conventional active matrix drive OLED displays experience significant color variations when viewed from different angles due to optical interference, which cannot be adequately controlled by focusing solely on the thickness of the electron transporting layer or optical thickness from the cathode to the anode, and require improved methods to manage interference across various wavelengths.
Innovation Solution
The display is designed with a configuration where the wavelength of maximum interference intensity at 0 degrees is shorter than the wavelength of maximum emission intensity, and the minimum interference intensity does not exist in the visible wavelength range, ensuring that as the viewing angle increases, the interference intensity extremes move away from the emission wavelength region, thereby minimizing color variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the thickness of the electron transporting layer is increased to control interference, then the color purity is improved, but the viewing angle dependence of color increases
Solution Approach 1:
The patent applies parameter changes by precisely controlling the thickness of the electron transporting layer to specific ranges (50-150nm for first electron transporting layer, 50-200nm for second electron transporting layer) to optimize the interference characteristics and achieve consistent color output across different viewing angles
Solution Approach 2:
The patent introduces a new dimensional approach by adding a third electron transporting layer between the emissive layer and the hole transporting layer, creating a multi-layer structure that provides additional control over optical interference without affecting the basic two-layer configuration
2Manufacturing precision
If the optical thickness from cathode to anode is controlled to improve color purity, then the emission spectrum is enhanced, but the color variation with viewing angle is not sufficiently reduced
Solution Approach 1:
The patent controls the optical thickness parameters of multiple layers including the electron transporting layers (50-150nm and 50-200nm), hole transporting layer (100-300nm), and encapsulation layers to achieve constructive interference at the desired emission wavelength while minimizing color variation across viewing angles
Solution Approach 2:
The patent employs feedback by measuring the emission spectrum and color coordinates at different viewing angles during development, then adjusting the layer thickness parameters iteratively to achieve the target color stability specification of Δu'v' < 0.005 at 0° and 60° viewing angles
3Ease of manufacture
If conventional OLED structure is used with standard layer thickness, then the device is simple to manufacture, but significant color variations occur due to viewing angle
Solution Approach 1:
The patent modifies the conventional OLED structure by adjusting the thickness parameters of the electron transporting layers to specific ranges (50-150nm for first layer, 50-200nm for second layer) to control optical interference, achieving color stability without complicating the manufacturing process
Solution Approach 2:
The patent adds an additional electron transporting layer in the vertical dimension between the emissive layer and hole transporting layer, creating a three-layer electron transporting structure that provides enhanced control over interference characteristics while maintaining compatibility with existing manufacturing 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
This configuration significantly reduces color variations due to viewing angle changes, enhancing emission intensity and maintaining a consistent emission spectrum, resulting in a brighter and more stable display with improved color fidelity.
Implementation Method 1
the light emitted from the emissive layer is influenced by interference
Data Source
AI summary
A light emitting display includes light-emitting devices in which unnecessary layers for the emission operation of the light-emitting device are removed in an emission region, and in a case where a wavelength of a light, of which an interference intensity to the light emitted from an emissive layer constituting the light-emitting device becomes a maximum value at 0 degree of a viewing angle, is lambdaimax and a wavelength of the light becoming a maximum in a light intensity in relation to the light emitted from the emissive layer is lambdaemax, a relationship of lambdaimax<lambdaemax is satisfied, obtaining a light emitting display with a little variation in color over a wide range of viewing angles.