Color Conversion Layer Air Gap Enhances Light Extraction
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Solution Overview
Problem
Liquid crystal display (LCD) devices with color conversion layers experience decreased light extraction efficiency due to total internal reflection at the boundary between external air and the upper substrate, causing trapped light to be reflected back inside the substrate rather than escaping.
Innovation Solution
Incorporating an air layer between the color conversion layer and the phosphor in the LCD device, along with a reflective surface on the partition wall and scattering particles, to reduce light reflection and enhance light extraction by scattering light and reducing the incident angle, thus minimizing total internal reflection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a color conversion layer including phosphor is used on the upper substrate, then color reproduction and viewing angle are improved, but light extraction efficiency deteriorates due to total internal reflection at the boundary between external air and the upper substrate
Solution Approach 1:
The patent introduces an air layer as an intermediary medium between the upper substrate and the phosphor layer. This air layer acts as a mediator that modifies the optical path of light, enabling light to escape the substrate more effectively by reducing the incident angle at the boundary between the upper substrate and external air, thereby resolving the contradiction between maintaining good color reproduction and improving light extraction efficiency.
Solution Approach 2:
The patent changes the physical parameter of the optical system by introducing an air layer with a different refractive index. This parameter change modifies the critical angle for total internal reflection, allowing light that would otherwise be trapped to escape at shallower angles, thus improving light extraction efficiency while preserving the color conversion function of the phosphor layer.
2Illumination intensity
If light is converted inside the color conversion layer, then color conversion function is achieved, but light extraction efficiency decreases due to total internal reflection trapping light inside the substrate
Solution Approach 1:
The air layer serves as an intermediary that facilitates light extraction after color conversion. It provides a transition zone that allows converted light to escape the substrate by reducing the incident angle, preventing total internal reflection while maintaining the color conversion function of the phosphor layer.
Solution Approach 2:
The patent converts the harmful effect of total internal reflection into a beneficial outcome. By introducing the air layer, the critical angle for total internal reflection is modified, and light that would have been trapped is now able to escape at reduced incident angles, turning the previously harmful reflection into an effective light extraction mechanism.
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 air layer and reflective partition wall configuration significantly improve light extraction efficiency by increasing the amount of light that escapes the substrate, as demonstrated by increased light output and reduced total internal reflection.
Implementation Method 1
light may not escape from the upper substrate due to total internal reflection that occurs at a boundary between the external air and the upper substrate
Implementation Method 2
The partition wall may include a reflective surface configured to reflect light toward the outside
Implementation Method 3
The phosphor may include a scattering particle
Data Source
AI summary
A display device including: a first substrate; a second substrate facing the first substrate; a light-amount adjusting layer interposed between the first substrate and the second substrate; and a backlight unit disposed under the first substrate, wherein the second substrate includes a plurality of color conversion layers respectively disposed on a plurality of pixel regions, the color conversion layer includes a partition wall; and a phosphor disposed on areas defined by the partition wall, and the color conversion layer includes an air layer between the second substrate and the phosphor.