Reflective Anode Side Mirror for Light Extraction in Displays
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Solution Overview
Problem
Light emitting display apparatuses face issues with low light extraction efficiency due to total reflection loss, waveguide loss, and surface plasmon loss, leading to trapped light and potential color coordinate changes when using reflective electrodes for improved light extraction.
Innovation Solution
A light emitting display apparatus with an overcoating layer having a base portion and a protrusion portion, where the anode has a reflective layer on its side portion acting as a side mirror to extract trapped light, and a cut-off layer is used in the blue sub-pixel area to prevent color coordinate changes by filtering out longer wavelengths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a reflective layer is added to the side portion of the protrusion portion to extract trapped light, then light extraction efficiency is improved, but color coordinates may change due to additional long wavelength light extraction
Solution Approach 1:
The patent applies local quality by implementing a cut-off layer specifically in the blue sub-pixel area where color coordinate stability is most critical, while allowing other areas to benefit from the reflective layer's light extraction enhancement. This localized approach enables different regions to have different optical properties tailored to their specific requirements.
Solution Approach 2:
The cut-off layer acts as an intermediary element between the reflective layer and the blue sub-pixel. It selectively filters out long wavelength light that would otherwise be extracted by the reflective layer, thereby preventing color coordinate shifts while allowing the reflective layer to continue enhancing overall light extraction efficiency.
2Productivity
If light is extracted upwardly through the reflective electrode in non-light emitting areas, then light extraction efficiency improves, but the extracted light exhibits photoluminescence spectrum causing color coordinate changes
Solution Approach 1:
The patent converts the harmful effect of photoluminescence-induced color coordinate shifts into a benefit by using the cut-off layer to selectively remove problematic long wavelength components. The reflective layer's ability to extract light is preserved and even enhanced, while the detrimental color coordinate changes are eliminated through spectral filtering.
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 enhances light extraction efficiency while minimizing color coordinate changes, particularly in the blue sub-pixel, by directing trapped light outward and maintaining high light efficiency across the color spectrum.
Implementation Method 1
the total reflection loss refers to a degradation of the light extraction efficiency due to the light trapped in the light emitting display apparatus due to the total reflection at an interface between a substrate and the air
Implementation Method 2
the reflective layer of the anode formed at the side portion of the protrusion portion can be as a side mirror, and some of the light trapped in the light emitting display apparatus by total reflection is extracted
Implementation Method 3
a cut-off layer is used in the blue sub-pixel area to prevent color coordinate changes by filtering out longer wavelengths
Implementation Method 4
Light emitted from a light emitting layer of a light emitting display apparatus
Data Source
AI summary
A light emitting display apparatus includes a substrate including a plurality of sub-pixels, an overcoating layer on the substrate and having a base portion and a protrusion portion, a first electrode disposed to cover the base portion and a side portion of the protrusion portion at the plurality of sub-pixels, a bank layer covering a portion of the first electrode and the overcoating layer, a light emitting layer and a second electrode on the first electrode and the bank layer at the plurality of sub-pixels, and a cut-off layer on the second electrode to overlap the bank layer.