LCD Backlight Diffusion Sheet for Scratch-Free Light Guide Plates
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Solution Overview
Problem
Conventional backlight assemblies for LCDs face issues with scratching of the light-guiding plate due to abrasion between the diffusion sheet and the light guide plate, leading to degraded image display quality and poor color reproducibility, primarily because the beads in the diffusion sheet are harder than the light-guiding plate material, and the current light sources predominantly produce blue light, which degrades color accuracy.
Innovation Solution
A backlight assembly design featuring a light-guiding plate made of polycarbonate with a diffusion sheet having beads on both surfaces, where the beads on the surface facing the light-guiding plate have a hardness comparable to or less than the plate, and the diffusion sheet includes a red fluorescent agent to balance light wavelengths, generating white light and improving color reproducibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If the light-guiding plate is made thinner to reduce LCD device thickness, then the overall device thickness is reduced, but the heat resistance of the light-guiding plate deteriorates
Solution Approach 1:
The patent changes the material parameter from PMMA to PC (polycarbonate) for the light-guiding plate, which has higher heat resistance properties, allowing the plate to be made thinner while maintaining adequate thermal performance
2Illumination intensity
If the beads in the diffusion sheet are made of PMMA to achieve good optical characteristics, then light diffusion performance is improved, but scratching of the light-guiding plate occurs due to abrasion
Solution Approach 1:
The patent changes the material parameter of the beads from PMMA to PC, matching the hardness of the light-guiding plate to prevent abrasion-induced scratching while maintaining adequate light diffusion properties
3Power
If a blue light LED with yellow fluorescent material is used to generate white light, then the light source is compact and efficient, but color reproducibility deteriorates due to predominant blue light
Solution Approach 1:
The patent applies local quality enhancement by adding a red fluorescent agent layer specifically targeted at compensating for the deficient red wavelength region in the LED spectrum, while maintaining the efficient blue LED light source
Solution Approach 2:
The patent creates a composite lighting system combining blue LED light, yellow fluorescent conversion, and red fluorescent emission to produce a more balanced white light with improved color reproduction
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 scratches on the light-guiding plate, enhances the intensity of longer wavelength light, and improves color reproducibility without compromising luminance, thereby enhancing the image display quality of LCD devices.
Implementation Method 1
the diffusion sheet includes a coating having a red fluorescent agent on its surface facing the light-guiding plate
Implementation Method 2
the backlight assembly employs a blue light LED having a yellow fluorescent material disposed on it. The blue light and a yellow light are combined to form a white light
Implementation Method 3
The liquid crystals used in LCDs exhibit anisotropic refraction
Data Source
AI summary
A backlight assembly includes a light source, a light-guiding plate and a diffusion sheet that includes a first bead layer on a lower surface of the diffusion sheet facing the light-guiding plate, and a second bead layer on an upper surface of the diffusion sheet. To improve image display quality, the hardness of the beads of the first bead layer facing the light guide plate are equal to or less than that of the light guide plate to prevent scratching of the light guide plate.