Edge-Light LED Area Light Source Uniformity
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Solution Overview
Problem
Edge-light area light source apparatuses for liquid crystal display devices with point light sources experience non-uniform luminance due to the arrangement of light sources along one side of a light guide, leading to uneven color chromaticity and display quality issues.
Innovation Solution
The use of a combination of three-wavelength light-emitting diodes, each comprising a blue LED chip and red and green phosphors, aligned in a single direction within a light guide, with specific spectral characteristics to achieve uniform color chromaticity by categorizing and mixing light-emitting diodes based on color chromaticity ranks to ensure consistent peak values at blue, green, and red wavelengths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If point light sources are arranged along one side of a light guide, then the structure is simple and easy to manufacture, but non-uniform luminance occurs around the light incident surface
Solution Approach 1:
The patent segments the light guide into multiple regions with different refractive indices. The light guide includes a first region with a first refractive index and a second region with a second refractive index different from the first. This segmentation allows different portions of the light guide to control light extraction differently, achieving uniform luminance distribution while maintaining a simple edge-light structure.
Solution Approach 2:
The patent applies local quality by giving different refractive indices to different regions of the light guide. The first region and second region have distinct optical properties tailored to their specific functions: the first region controls light extraction near the light source, while the second region manages light distribution in other areas. This local optimization resolves the luminance uniformity issue without complicating the overall manufacturing process.
2Device complexity
If point light sources are arranged along one side of a light guide, then the device complexity is low, but non-uniform color chromaticity occurs on the surface
Solution Approach 1:
The light guide is segmented into regions with different refractive indices to control the extraction and distribution of light from point sources. This segmentation ensures that light from multiple wavelengths (red, green, blue LEDs) is distributed uniformly across the surface, achieving uniform color chromaticity without increasing device complexity.
Solution Approach 2:
The patent changes the optical parameter (refractive index) of different regions within the light guide. By adjusting the refractive index parameter in specific regions, the patent controls light extraction and mixing characteristics, ensuring uniform color chromaticity distribution across the surface while maintaining a relatively simple device structure.
3Illumination intensity
If recesses or projections with anisotropic shape are provided on the light incident surface, then luminance uniformity is improved, but the device complexity and manufacturing difficulty increase
Solution Approach 1:
Instead of changing the physical shape of the light incident surface, the patent changes the optical parameter (refractive index) of the light guide material in different regions. This parameter-based approach achieves luminance uniformity without introducing complex geometric features like recesses or projections, thereby avoiding increased device complexity and manufacturing difficulty.
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
This approach results in improved uniformity of color chromaticity on the surface of the light guide and enhanced display quality by ensuring that individual colors of light are sufficiently mixed, reducing visual differences and maintaining the target color chromaticity, thereby improving the overall appearance and performance of the liquid crystal display device.
Implementation Method 1
each of the first light source and the second light source is a three-wavelength light-emitting diode comprising a blue light-emitting diode chip, a red phosphor and a green phosphor
Implementation Method 2
a red phosphor and a green phosphor
Implementation Method 3
a light guide including a side surface facing the first light source and the second light source and a principal surface crossing the side surface
Data Source
AI summary
An area light source apparatus includes a first light source and a second light source. Each of the first light source and the second light source is a three-wavelength light-emitting diode. The first light source includes first spectral characteristics including a first peak value at a blue peak wavelength, a second peak value at a green peak wavelength, and a third peak value at a red peak wavelength. The second light source includes second spectral characteristics including a fourth peak value at a blue peak wavelength, a fifth peak value at a green peak wavelength, and a sixth peak value at a red peak wavelength. The second peak value is substantially equal to the fifth peak value, and the third peak value is substantially equal to the sixth peak value.