Direct Backlight Quantum Dot Lens Thickness Optimization
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Solution Overview
Problem
Existing LCD devices with direct type backlight units face issues such as quantum dot degradation due to moisture and oxygen, low light utilization efficiency, increased thickness, and high costs, particularly for large-sized devices, and limited color reproduction capabilities.
Innovation Solution
A liquid crystal display device with a direct type backlight unit that includes a frame-mounted LED, a sealing member containing quantum dots dispersed in resin or organic solvent, a first polarizer, and a light-recycling structure, where the transmission axes of polarizers are aligned to enhance light utilization and prevent quantum dot degradation, using a uniaxially-oriented liquid crystal resin lens for reduced thickness and cost.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a direct type backlight unit is disposed at the rear side of the liquid crystal panel, then the structure is simplified, but the thickness of the display device increases
Solution Approach 1:
The patent changes the refractive index parameter of the lens material from conventional values (around 1.5-1.6) to a high refractive index of 1.7 or higher. This parameter change enables the lens to achieve the same light guiding function with a reduced thickness, thereby solving the contradiction between structural simplification and device thickness.
Solution Approach 2:
The patent applies a high refractive index material specifically to the lens portion of the backlight unit, rather than the entire device. This localized application of high refractive index material allows the lens to be thinner while maintaining its optical function, thus reducing overall device thickness without requiring complex changes throughout the entire backlight structure.
2Loss of energy
If a polarizing optical film with multiple layers is used to increase light utilization efficiency, then light recycling is improved, but the cost increases particularly for large-sized devices
Solution Approach 1:
The patent changes the refractive index parameter of the lens material to 1.7 or higher, which fundamentally improves light extraction and guiding efficiency. This parameter change reduces the reliance on complex multi-layer polarizing films for light recycling, thereby lowering manufacturing costs while maintaining high light utilization efficiency.
Solution Approach 2:
The patent extracts the light recycling function from the complex multi-layer polarizing film system and concentrates it into a single high refractive index lens structure. This extraction simplifies the optical system by removing the need for expensive multi-layer films while achieving the same or better light utilization efficiency through the high refractive index material's inherent optical properties.
3Length of stationary object
If a high refractive index material (refractive index about 1.7) is used to decrease lens thickness, then the display device becomes thinner, but the material cost increases
Solution Approach 1:
The patent systematically explores and identifies specific high refractive index materials (with refractive index 1.7 or higher) that can be manufactured at reasonable costs. By changing the material parameter and selecting from available options like certain glass materials and resins, the patent achieves thin lens thickness without prohibitively high material costs.
Solution Approach 2:
The patent uses homogeneous high refractive index material throughout the lens structure, eliminating the need for complex multi-layer constructions or composite materials. This homogeneous approach simplifies manufacturing processes and reduces costs compared to using multiple different materials, while still achieving the desired thin profile through the high refractive index property.
4Illumination intensity
If the wavelength range of light from the light source is narrowed to match color filter transmission, then color reproduction is improved, but light utilization efficiency decreases
Solution Approach 1:
The patent changes the refractive index parameter of the lens material to 1.7 or higher, which improves light extraction efficiency from the LED. This enhanced light extraction compensates for the narrow wavelength range filtering, allowing more of the limited wavelength-matched light to be effectively utilized and directed toward the liquid crystal panel, thereby maintaining color reproduction quality while improving overall light utilization.
Solution Approach 2:
The high refractive index lens creates an optical feedback system that efficiently recycles and redirects light that would otherwise be lost. By improving the coupling between the LED and the liquid crystal panel through enhanced total internal reflection and light guiding, the system maximizes the utilization of light within the matched wavelength range, reducing energy loss despite the narrow spectral bandwidth.
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 prevents quantum dot degradation, achieves high brightness and narrow emission spectrum, reduces power consumption, and enhances color reproduction while maintaining a thin profile, improving light utilization and design efficiency at a lower cost.
Implementation Method 1
a light-recycling structure reflecting light reflected to the frame towards the liquid crystal panel, wherein the liquid crystal panel includes a second polarizer facing the direct type backlight unit
Implementation Method 2
a first polarizer disposed over the sealing member; and a light-recycling structure reflecting light reflected to the frame towards the liquid crystal panel, wherein the liquid crystal panel includes a second polarizer facing the direct type backlight unit, and wherein a transmission axis of the first polarizer is parallel to a transmission axis of the second polarizer
Implementation Method 3
a light-recycling structure reflecting light reflected to the frame towards the liquid crystal panel
Implementation Method 4
a sealing member over the LED and containing quantum dots dispersed in resin or organic solvent
Data Source
AI summary
A liquid crystal display device includes a liquid crystal panel; and a direct type backlight unit providing light to the liquid crystal panel, wherein the direct type backlight unit includes: a frame where an LED is mounted; a sealing member over the LED and containing quantum dots dispersed in resin or organic solvent; a first polarizer disposed over the sealing member; and a light-recycling structure reflecting light reflected to the frame towards the liquid crystal panel, wherein the liquid crystal panel includes a second polarizer facing the direct type backlight unit, and wherein a transmission axis of the first polarizer is parallel to a transmission axis of the second polarizer.