Backlight Unit Diffusion Sheet Lens Patterns for Brightness Uniformity
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Solution Overview
Problem
Direct type backlight units in LCD devices face challenges in achieving uniform brightness due to visible light sources and difficulties in manufacturing thinner devices, as the arrangement of multiple light sources under the panel leads to noticeable brightness differences between lit and unlit regions.
Innovation Solution
A backlight unit design featuring a diffusion plate to primarily diffuse light from multiple light sources, combined with a diffusion sheet that includes lens pattern portions on specific regions to secondarily diffuse light, ensuring uniform luminance across the LCD panel.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If multiple light sources are arranged close to the LCD panel to reduce device thickness, then device slimness is improved, but brightness uniformity deteriorates due to visible light sources and noticeable brightness differences between lit and unlit regions
Solution Approach 1:
The diffusion sheet is divided into different regions with different optical properties: a first region with a first refractive index and a second region with a second refractive index. This local quality differentiation allows specific areas to control light distribution differently, improving brightness uniformity while maintaining thin device structure.
Solution Approach 2:
The patent changes the refractive index parameter of the diffusion sheet material across different regions. By having a first refractive index in the first region and a second refractive index in the second region, the light propagation characteristics are modified to reduce visibility of light sources and improve overall brightness uniformity.
2Illumination intensity
If the distance between light sources and diffusion plate is increased to improve brightness uniformity, then luminance difference between regions is reduced, but device thickness increases making it difficult to manufacture thin LCD devices
Solution Approach 1:
The diffusion sheet employs regional differentiation with distinct refractive indices to achieve uniform light distribution without requiring increased distance between light sources and diffusion plate. This allows thin device construction while maintaining brightness uniformity.
Solution Approach 2:
The diffusion sheet acts as an intermediary optical element between the light sources and the LCD panel. By introducing this intermediate layer with spatially varying refractive indices, the patent mediates light propagation to achieve uniformity without increasing overall device thickness.
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 brightness uniformity by minimizing luminance differences between regions with and without light sources, allowing for a thinner and more uniform LCD device design.
Implementation Method 1
a diffusion plate disposed on the light sources to primarily diffuse light emitted from the light sources
Implementation Method 2
the diffusion sheet includes lens pattern portions formed on the second regions
Data Source
AI summary
A backlight unit with uniform brightness (luminance) is disclosed.The backlight unit includes: a plurality of light sources arranged at a fixed interval; a diffusion plate disposed on the light sources to primarily diffuse light emitted from the light sources; and a diffusion sheet configured to secondarily diffuse the primarily diffused light from the diffusion plate, wherein the surface of the diffusion sheet is divided into first regions not opposite to the light and second regions opposite to the light sources, and the diffusion sheet includes lens pattern portions formed on the second regions.