Quantum Dot Display Light Reflecting Layer External Light
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Solution Overview
Problem
Image display devices using quantum dots suffer from decreased contrast and visibility due to external light, such as sunlight, causing the color filter to emit light even in black display modes, which impairs image quality.
Innovation Solution
A light reflecting layer with a peak wavelength matching the excitation light source is disposed on the observer side of the image display device to reduce external light incidence on the quantum dot wavelength conversion layer, using a polarizing reflective layer like a cholesteric liquid crystal layer to effectively cut external light while maintaining emitted light brightness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a color filter containing quantum dots is used to achieve narrow emission wavelength bands and high color reproducibility, then color display performance is improved, but external light causes the quantum dots to emit light unintentionally, decreasing contrast and visibility
Solution Approach 1:
The patent applies the 'Blessing in disguise' principle by converting the harmful effect of external light into a beneficial filtering mechanism. The light reflecting layer is designed to reflect specific wavelength bands (including the excitation wavelength of quantum dots) while transmitting other wavelengths, thereby converting the problematic external light into a selectively reflected component that prevents unwanted quantum dot emission and maintains display contrast.
Solution Approach 2:
The light reflecting layer serves as an intermediary element positioned between the external environment and the quantum dot-containing color filter. This intermediary layer selectively reflects harmful wavelength bands (including blue light at 450nm that excites quantum dots) while allowing other wavelengths to pass through, thereby protecting the quantum dots from unintended excitation by external light sources.
2Object-affected harmful factors
If a light reflecting layer is added to block external light, then visibility and contrast are improved, but device complexity increases
Solution Approach 1:
The light reflecting layer is designed with multi-functionality, serving both as a protective element against external light and as an optical management component within the display structure. By integrating this layer into the existing display architecture, the patent achieves external light blocking without proportionally increasing overall device complexity, as the same layer performs multiple optical functions.
Solution Approach 2:
The patent employs parameter changes by adjusting the optical properties (reflection wavelength bands, transmission characteristics) of the light reflecting layer to match the specific requirements of the quantum dot emission characteristics. By optimizing these parameters, the layer effectively blocks external light at critical wavelengths while maintaining overall device simplicity through precise parameter control rather than complex structural additions.
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 enhances visibility of the display image by efficiently reflecting external light containing the excitation wavelength, reducing its impact on the quantum dot emission and maintaining brightness, thus improving contrast and image quality even in environments with external illumination.
Implementation Method 1
a light reflecting layer which includes, in a reflection wavelength region, a peak wavelength of a light source that emits excitation light to be used for emission of the quantum dots
Implementation Method 2
when a member containing quantum dots is irradiated with excitation light from a backlight, the quantum dots are excited and emit fluorescence
Implementation Method 3
a first light reflecting layer which has a reflection center wavelength range of 430 nm to 480 nm, and is formed by fixing a cholesteric liquid crystalline phase emitting circular polarization light
Data Source
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AI summary
The present invention relates to an image display device provided with: a wavelength conversion layer (22b) containing quantum dots; and a light reflecting layer (16) provided on an observer side with respect to the wavelength conversion layer (22b) and including, in a reflection wavelength region, a peak wavelength of a light source that emits excitation light to be used for emission of the quantum dots.