OLED Pixel Electrode Thickness Optimization for Color Purity
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Solution Overview
Problem
Organic light emitting displays (OLEDs) face limitations in color reproducibility and viewing angle due to the inherent limitations of color filters, which affect the purity and range of colors displayed.
Innovation Solution
The design includes a substrate with specific regions for red, green, blue, and white pixels, featuring thin film transistors, pixel electrodes with varying thicknesses and refractive indices, and an organic overcoat, along with color filters, to enhance color purity and viewing angle by optimizing the optical path and reflectance at the interface between pixel electrodes and the overcoat.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If color filters are used to obtain light of desired color, then color range is expanded, but color purity deteriorates
Solution Approach 1:
The patent extracts and removes the color filters from the display structure, replacing them with organic light emitting members that directly emit primary colors (red, green, blue). This eliminates the color purity deterioration caused by filters while maintaining full color range through additive mixing of the three primary colors.
Solution Approach 2:
Instead of using filters to subtract unwanted wavelengths from white light, the patent inverts the approach by using organic light emitting members to directly generate only the desired primary color wavelengths, thereby achieving both full color range and high color purity simultaneously.
2Ease of manufacture
If conventional pixel electrode structure is used, then manufacturing is simplified, but viewing angle and color reproducibility are limited
Solution Approach 1:
The patent applies different thicknesses of pixel electrodes to different color regions (red, green, blue pixels have different electrode thicknesses) to optimize the optical path length for each wavelength. This local differentiation improves color reproducibility and viewing angle while maintaining a relatively simple overall structure that can be manufactured using standard processes.
3Adaptability or versatility
If color filters are used, then color range is achieved, but light transmittance and viewing angle are reduced
Solution Approach 1:
The patent removes color filters from the optical path, eliminating their inherent light absorption and scattering effects. The organic light emitting members directly emit light in the desired color ranges, significantly improving light transmittance and viewing angle while maintaining full color range through the combination of red, green, and blue emission.
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 improves color reproducibility and reduces color variation at side viewing angles, increasing light transmittance of desired wavelengths and enhancing the overall display characteristics of OLEDs.
Implementation Method 1
A refractive index difference between the overcoat and the first to fourth pixel electrodes may be 0.2 or greater
Implementation Method 2
optimizing the optical path and reflectance at the interface between pixel electrodes and the overcoat
Data Source
AI summary
An organic light emitting diode display panel includes a transparent substrate on which a matrix array of pixels is formed with each pixel including an organic light emitting diode (OLED). The OLEDS include light emitting regions sandwiched between pixel electrodes or anodes made of transparent conductive material and a common electrode made of a conductive material. The refractive index of the pixel electrodes is higher than the refractive index of the insulating layer on which the pixel electrodes are disposed so that light undergoes multiple reflections at the interface between the pixel electrodes and the insulating layer and also at the interface between the light emitting regions and the common electrode. The thickness of the pixel electrodes is chosen so that light that eventually exits the pixel electrodes after multiple reflections contains a relatively strong component of a chosen primary color.