Backlight Unit Diffusion Pattern for LCD Luminance Uniformity
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Solution Overview
Problem
Conventional liquid crystal displays using point light sources, such as LEDs, suffer from non-uniform luminance due to dark spaces between light-emitting elements, resulting in inconsistent image display across the screen.
Innovation Solution
A backlight unit with a light-guide plate and a diffusion pattern on its surfaces, combined with a point light source assembly, where the diffusion pattern density varies to compensate for light distribution, and a reflection film to enhance light reflection and uniformity, ensuring consistent luminance across the display.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If multiple point light sources (LEDs) are disposed in a row to provide illumination, then power consumption is reduced and luminance is increased, but dark spaces are formed between the LEDs resulting in non-uniform luminance
Solution Approach 1:
The patent applies local quality by creating a non-uniform diffusion pattern on the light-guide plate where the density of diffusion elements varies across different regions. Specifically, the edge portion adjacent to point light sources has a first diffusion pattern with lower density, while the center portion has a second diffusion pattern with higher density. This local variation in diffusion characteristics compensates for the non-uniform light distribution caused by discrete point sources, achieving uniform overall luminance.
2Device complexity
If point light sources are used instead of area light sources, then device complexity is reduced and energy efficiency is improved, but the light distribution becomes non-uniform with dark regions appearing
Solution Approach 1:
The patent introduces a light-guide plate with diffusion patterns as an intermediary between the point light sources and the display screen. This intermediary component transforms the non-uniform point source illumination into uniform area illumination by guiding light through total internal reflection and controlled diffusion at different densities across the plate surface.
Solution Approach 2:
The patent changes the physical parameter of light distribution by varying the density of diffusion patterns across different regions of the light-guide plate. The diffusion pattern density serves as a controllable parameter that is adjusted spatially to compensate for the inherent non-uniformity of point source lighting, transforming the light field characteristics to achieve 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 achieves uniform luminance across the entire display screen by optimizing light distribution and reflection, reducing dark regions and maintaining consistent light output.
Implementation Method 1
a light-guide plate guiding incident light and having a diffusion pattern for emitting light upward
Implementation Method 2
the diffusion pattern being formed on at least one of upper and lower surfaces of the light-guide plate
Implementation Method 3
a reflection film for dark regions disposed between the point-light-source elements, the reflection film for dark regions reflecting the light emitted from a side portion of the light-guide plate back to the light-guide plate
Data Source
AI summary
A backlight unit for a liquid crystal display which can achieve substantially uniform luminance over the entire display screen includes: a light-guide plate guiding incident light and having a diffusion pattern for emitting light upward, the diffusion pattern being formed on at least one of upper and lower surfaces of the light-guide plate; and a point light source assembly disposed on at least one side portion of the light-guide plate, the point light source assembly including a plurality of point-light-source elements and a support substrate, in which the point-light-source elements are disposed on the support substrate and supply the light to the light-guide plate. An edge portion of one surface of the light-guide plate, which is adjacent to the point light source assembly, includes a first region corresponding to the point-light-source elements and a second region corresponding to a position between the point-light-source elements. The diffusion pattern may be formed in such a manner that the second region has a higher density than the first region.