Thin Backlight Light Guide Plate Scattering Optimization
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Solution Overview
Problem
Current thin backlight units for liquid crystal display devices face challenges in achieving uniform illumination with reduced brightness unevenness due to the relative dimensions of cold cathode tubes and reflectors, limiting their thickness and efficiency.
Innovation Solution
A planar lighting device with a light guide plate between two light sources, where the light guide plate has a rectangular contour with scattering particles that satisfy a specific expression (1.1≦Φ·Np·LG·KC≦8.2) and is shaped to increase thickness from the entrance planes to the center, along with a polarization separator film and diffusion reflectors for uniform light distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If a tandem type backlight unit is used to achieve a thin design, then the thickness is reduced, but light use efficiency decreases and brightness unevenness increases
Solution Approach 1:
The patent changes the geometric parameters of the light guide plate, specifically making it thinner with a thickness of 10mm or less while optimizing the groove dimensions and scattering particle distribution to maintain uniform light output and improve light use efficiency compared to conventional tandem type backlights
Solution Approach 2:
The patent applies local quality by positioning scattering particles specifically within the grooves of the light guide plate and creating asymmetric groove structures that are deeper near the light sources and shallower toward the center, thereby locally optimizing light extraction to reduce brightness unevenness and improve overall light efficiency
2Length of stationary object
If the light guide plate is made thinner in tandem type backlight, then the overall thickness is reduced, but brightness unevenness on the light exit plane increases
Solution Approach 1:
The patent creates non-uniform groove depths within the light guide plate, with deeper grooves near the light sources and shallower grooves toward the center, and distributes scattering particles non-uniformly to compensate for the thinner overall structure, thereby maintaining uniform brightness across the light exit plane
Solution Approach 2:
The patent transitions from a conventional symmetric tandem structure to an asymmetric structure with grooves having different depths in different locations, effectively using the depth dimension to control light extraction and achieve uniform brightness in a thinner overall design
3Illumination intensity
If a direct illumination type backlight unit is used to achieve uniform light distribution, then brightness uniformity is improved, but the thickness increases to about 30mm
Solution Approach 1:
The patent optimizes the groove depth, width, and spacing parameters along with scattering particle concentration and size to achieve uniform light distribution in a much thinner 10mm or less structure, dramatically reducing the thickness compared to conventional direct illumination type backlights while maintaining brightness uniformity
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 enables a thinner design with uniform illumination and reduced brightness unevenness, enhancing light use efficiency and maintaining high light extraction efficiency while minimizing illuminance unevenness.
Implementation Method 1
the light guide plate contains scattering particles for scattering light entering through the first and the second light entrance planes of the light guide plate and propagating inside thereof
Data Source
AI summary
Provided is a planar lighting device having a thin shape and capable of emitting uniform illumination light with less brightness unevenness. The planar lighting device includes a first and a second light sources arranged at a given distance apart from each other and a light guide plate arranged between the first and second light sources. The light guide plate includes a light exit plane, a first light entrance plane facing the first light source and containing one side of the light exit plane, and a second light entrance plane facing the second light source and containing the opposite side to the one side, and has a shape growing thicker from the first and second light entrance planes toward the center. The light guide plate contains scattering particles for scattering light entering through the first and second light entrance planes and propagating inside by a ratio satisfying 1.1≦Φ·Np·LG·KC≦8.2.