OLED Cathode Stack and Reflectance Control for Low-Reflection Displays
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Solution Overview
Problem
Existing light emitting display devices suffer from external light reflection, which can reduce display quality and necessitate the use of expensive polarization elements to mitigate this issue.
Innovation Solution
A light emitting display device with a low-reflection structure is implemented by incorporating a cathode electrode with a triple-layered stack of metal and conductive resin materials, and a light shielding layer with a specific refractive index difference to minimize external light reflection without the need for polarization elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a polarizing element is disposed in front of the display panel to suppress external light reflection, then external light reflection is reduced, but the amount of light provided by the display device is reduced and the cost increases
Solution Approach 1:
The patent changes the refractive index parameter of the cathode electrode by using a composite structure of metal layer and conductive resin layer. The conductive resin layer has a refractive index between 1.3-1.7, which is lower than the metal layer, creating refractive index contrast that reduces external light reflection. This parameter change allows suppression of harmful reflection without blocking display light output.
Solution Approach 2:
The patent employs a composite material structure for the cathode electrode consisting of a metal layer (first cathode layer) and a conductive resin layer (second cathode layer). This composite structure combines the electrical conductivity of metal with the optical properties of conductive resin, achieving both low reflection and high light transmission characteristics that a single material cannot provide.
2Object-affected harmful factors
If a polarizing element is disposed in front of the display panel to suppress external light reflection, then external light reflection is reduced, but the cost increases
Solution Approach 1:
The patent changes the refractive index parameter of the cathode electrode by using a composite structure of metal layer and conductive resin layer. The conductive resin layer has a refractive index between 1.3-1.7, which is lower than the metal layer, creating refractive index contrast that reduces external light reflection. This parameter change allows suppression of harmful reflection without blocking display light output.
Solution Approach 2:
The patent employs a composite material structure for the cathode electrode consisting of a metal layer (first cathode layer) and a conductive resin layer (second cathode layer). This composite structure combines the electrical conductivity of metal with the optical properties of conductive resin, achieving both low reflection and high light transmission characteristics that a single material cannot provide.
3Ease of manufacture
If the cathode electrode has thickness non-uniformity, then manufacturing is easier, but parasitic external light reflection occurs
Solution Approach 1:
The patent applies local quality by making the conductive resin layer thickness vary across different regions. The second cathode layer (conductive resin layer) has a first thickness in a first region and a second thickness in a second region, with the ratio between first and second thickness being 0.5-2.0. This local thickness variation compensates for manufacturing non-uniformity and prevents parasitic reflection in different areas of the display.
Solution Approach 2:
The patent changes the thickness parameter of the conductive resin layer across different regions to compensate for manufacturing variations. By adjusting the thickness ratio between first and second regions to be within 0.5-2.0, the optical path difference is controlled to maintain anti-reflection effectiveness across the entire display surface despite manufacturing tolerances.
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 device effectively suppresses external light reflection, maintaining display quality and luminous efficiency while avoiding the cost and light reduction associated with polarization elements.
Implementation Method 1
a reflectance control layer at any one of the bank or the planarization layer, the reflectance control layer having a refraction index that is different from a refraction index of the bank and a refraction index of the planarization layer
Data Source
AI summary
A light emitting display device having enhanced display quality by reducing reflection of external light is disclosed. An light emitting display device according to the present disclosure comprises: a driving layer on a substrate; a planarization layer on the driving layer; a plurality of anode electrodes on the planarization layer; a bank between the anode electrodes to define an emission area; an emission layer on the bank and the anode electrode; a cathode electrode on the emission layer; and a reflectance control layer at any one of an upper portion of the bank and an upper portion of the planarization layer.