LCD Backlight Diffusion Sheet Hardness to Prevent Light Guide Scratches
Find Innovative SolutionsGenerate Solutions
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 inadequate color reproducibility due to predominance of blue light in white light generation.
Innovation Solution
A backlight assembly with a light-guiding plate made of polycarbonate and a diffusion sheet having bead layers with beads of matching or lower hardness, and a red fluorescent agent to adjust the light spectrum, preventing scratches and enhancing color reproducibility by balancing the bluish and yellowish light components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If PMMA beads are used in the diffusion sheet, then the diffusion sheet has good optical characteristics and high hardness, but the beads are harder than the PC light-guiding plate causing scratches that degrade image display quality
Solution Approach 1:
The patent changes the material composition of the diffusion sheet from PMMA to a copolymer containing PC units and other units (such as PVB, PVAc, or acrylic acid). This parameter change in material composition reduces the hardness of the diffusion sheet to be lower than or equal to the PC light-guiding plate, preventing scratches while maintaining optical properties.
Solution Approach 2:
The patent uses a copolymer material consisting of PC units and other units (PVB, PVAc, or acrylic acid) in specific ratios. This composite material approach allows the diffusion sheet to have optimized properties: sufficient hardness for structural integrity but reduced enough to prevent scratching the PC light-guiding plate, while maintaining good optical characteristics.
2Illumination intensity
If the light source uses a blue light LED with yellow fluorescent material, then white light is generated, but the blue light predominates degrading color reproducibility
Solution Approach 1:
The patent modifies the spectral composition of the backlight by changing the material composition of the diffusion sheet. The copolymer material (PC units + other units) has different optical properties than pure PMMA, which adjusts the transmission and diffusion characteristics of different wavelengths. This parameter change in material composition balances the excessive blue light component, improving color reproducibility while maintaining luminance.
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, improves image display quality, and enhances color reproducibility by ensuring the beads do not exceed the hardness of the light-guiding plate and by adjusting the light spectrum to balance the bluish and reddish light components, thus maintaining luminance uniformity.
Implementation Method 1
the diffusion sheet may include 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
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.