OLED Cathode Thickness Control for Viewing Angle Color Shift
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Solution Overview
Problem
Current OLED display systems face challenges with viewing angle color shift, off-angle emission intensity, and color point drift due to the angular intensity distributions of RGB OLEDs, which affect the accuracy of white color representation across different viewing angles.
Innovation Solution
The implementation of polarization sensitive diffusers, subpixel cathode thickness control, various filtermask configurations, and color filters to manage reflection performance and angular performance, including the use of a polarization sensitive diffuser layer with a quarterwave film and linear polarization film, and independent control of cathode thickness for each subpixel to match luminance distributions and adjust cavity effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If optical microcavity effect is used to enhance optical efficiency, then on-axis luminance is improved, but viewing angle color shift occurs
Solution Approach 1:
The patent applies local quality by making the cathode layer thickness vary across different spatial locations - specifically, the cathode is thinner at the center and thicker at the edges of each subpixel. This non-uniform thickness distribution creates location-specific optical cavity effects that compensate for the angular color shift, allowing the display to maintain color accuracy across different viewing angles while preserving on-axis luminance enhancement.
Solution Approach 2:
The patent changes the physical parameter of cathode layer thickness to control the optical cavity effect. By adjusting the cathode thickness from center to edge regions, the optical path length and resonance conditions are modified locally, which shifts the emission spectrum to compensate for viewing angle-dependent color changes. This parameter adjustment enables simultaneous achievement of high on-axis luminance and accurate off-angle color reproduction.
2Ease of manufacture
If uniform cathode thickness is used, then manufacturing is simplified, but off-angle color shift occurs
Solution Approach 1:
The patent implements local quality by creating a cathode layer with spatially varying thickness - thinner at the center and thicker at the periphery of each subpixel. This non-uniform structure is achieved through controlled deposition processes that deposit material for progressively longer durations at different radial positions, enabling precise local thickness control to compensate for angular color shift while maintaining manufacturing feasibility.
3Manufacturing precision
If different cathode thicknesses are used for each subpixel, then viewing angle color shift is reduced, but device complexity increases
Solution Approach 1:
The patent applies segmentation by dividing each subpixel's cathode into multiple thickness zones - typically a central region with thinner cathode and peripheral regions with thicker cathode. This segmented approach allows independent optimization of optical properties in different zones to compensate for angular color shift, while the overall structure remains integrated within each subpixel, balancing performance improvement with structural complexity.
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 approach reduces white off-angle color shift, enhances viewing angle performance, increases on-axis efficiency, and lowers panel power consumption by matching luminance distributions and adjusting cavity effects for each subpixel, thereby improving the overall color accuracy and brightness consistency across different viewing angles.
Implementation Method 1
a polarization sensitive diffuser layer over the LED
Implementation Method 2
a linear polarization film over the polarization sensitive diffuser layer and the quarterwave film
Implementation Method 3
a quarterwave film adjacent the polarization sensitive diffuser
Implementation Method 4
the liquid crystal polymer film includes a top surface characterized by a higher average surface roughness than a top surface of the isotropic film
Implementation Method 5
a filtermask over the passivation layer, the filtermask including an aperture over the first LED
Implementation Method 6
an emissive light emitting diode (LED)
Implementation Method 7
the second cathode layer area may be thicker than the first cathode layer area... independent control of cathode thickness for each subpixel to match luminance distributions and adjust cavity effects
Data Source
AI summary
Display structures for controlling viewing angle color shift are described. In various embodiments, polarization sensitive diffusers, independent controlled cathode thicknesses, filtermasks, and color filters are described.