Protective Film with PDLC Scattering for QD-OLED Light Extraction
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Solution Overview
Problem
Quantum dot color filters in QD-OLED devices suffer from low light extraction efficiency due to total reflection, resulting in poor visual effects and user experiences.
Innovation Solution
A protective film comprising a quantum dot color conversion layer, a first base substrate, a polymer dispersed liquid crystal layer, and a second base substrate, where the polymer dispersed liquid crystal layer is formed by injecting a mixture of liquid crystal monomers and a prepolymer with different refractive indices between the substrates, and an electric field is applied under ultraviolet light to align the liquid crystal monomers and polymerize the prepolymer, enhancing light scattering and extraction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a quantum dot color filter is used in QD-OLED devices, then light conversion and high color gamut are achieved, but light extraction efficiency decreases due to total reflection
Solution Approach 1:
A polymer dispersed liquid crystal layer is introduced as an intermediary between the quantum dot color filter and the external environment. This layer has a refractive index that is different from both the quantum dot color filter and air, serving as a refractive index bridge to reduce total reflection and improve light extraction efficiency
Solution Approach 2:
The refractive index parameter of the liquid crystal layer is specifically optimized to be between that of the quantum dot color filter and air. By changing this physical parameter, the patent reduces the refractive index mismatch and minimizes total reflection losses at the interface
2Productivity
If the refractive index of the quantum dot color filter is greater than air, then light conversion is effective, but light is confined due to total reflection when angle exceeds critical angle
Solution Approach 1:
The polymer dispersed liquid crystal layer acts as a mediator that gradually transitions the refractive index from the high-index quantum dot color filter to the low-index air environment, allowing light to escape at angles that would otherwise result in total reflection
Solution Approach 2:
The patent addresses the two-dimensional interface problem by introducing a third dimensional layer (the liquid crystal layer with intermediate refractive index) between the quantum dot color filter and air, creating a gradient refractive index structure that enables light extraction in multiple angular dimensions
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 solution effectively improves light extraction efficiency and overall brightness of the display panel, enhancing user experiences by scattering light that would otherwise be lost due to total reflection, increasing luminous efficiency by 20-40% compared to current devices.
Implementation Method 1
A refractive index of the liquid crystal monomers and a refractive index of the prepolymer are different
Implementation Method 2
applying an electric field between the first base substrate and the second base substrate under ultraviolet light
Implementation Method 3
the prepolymer is polymerized
Data Source
AI summary
A protective film, a method for fabricating the same, and a display device are provided. The protective film is configured to be applied to a self-luminous display panel. The protective film includes a quantum dot color conversion layer, a first base substrate, a polymer dispersed liquid crystal layer, and a second base substrate. Scattering of liquid crystal monomers in the polymer dispersed liquid crystal layer does not affect brightness of light in a front view direction, and can improve intensity of an emitted light, thereby effectively improving luminous efficiency of a display panel and user experiences.