Backlight Unit Using Complementary White LEDs for LCD Color Uniformity
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Solution Overview
Problem
The production of liquid crystal display (LCD) devices faces inefficiencies due to variations in white light emission from LEDs, leading to reduced production efficiency and increased costs as only a small number of LEDs with specific color properties are utilized, while others are wasted due to binning requirements for target color properties.
Innovation Solution
A backlight unit for LCD devices that uses alternately arranged first and second white LEDs with complementary color properties to produce a target white light, allowing for the mixing of white lights from different bins to achieve uniform and desired color properties, thereby increasing production efficiency and reducing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If white LEDs with specific color properties are selected to meet target color requirements, then color uniformity is improved, but production efficiency deteriorates due to waste of LEDs from other bins
Solution Approach 1:
The patent changes the color parameters of LEDs by combining LEDs with complementary color properties (different bins) to achieve the target color. Instead of selecting only LEDs within a narrow color bin, the invention uses LEDs from broader bins that have complementary characteristics, transforming the color through combination rather than selection.
Solution Approach 2:
The patent makes the backlight system universal by accepting LEDs from multiple bins (different color characteristics) to achieve the same target color output. The system can utilize a broader range of LED products, making the production process more flexible and less dependent on tight color bin specifications.
2Manufacturing precision
If only LEDs from specific bins are used to achieve target color properties, then color accuracy is improved, but production cost increases due to LED waste
Solution Approach 1:
The patent converts the harmful effect of color variation in LEDs into a beneficial feature by using complementary color bins. LEDs that would normally be considered defective or off-spec are transformed into useful components that, when combined, produce the desired target color, thereby reducing waste and lowering costs.
Solution Approach 2:
The patent creates a composite light source by combining LEDs with different color characteristics (complementary bins). This composite approach allows the system to achieve accurate target color while utilizing a broader range of LED materials, reducing the need for strict binning and minimizing waste.
3Illumination intensity
If strict binning requirements are imposed on white LEDs, then light quality is improved, but device complexity increases due to sorting and selection processes
Solution Approach 1:
The patent inverts the traditional approach by not trying to eliminate color variation through strict binning, but rather by embracing and utilizing complementary color variations. Instead of sorting LEDs into narrow bins to achieve uniformity, the invention deliberately combines LEDs from complementary bins to achieve the target color, simplifying the selection process.
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 enables the effective utilization of a larger number of LEDs, reducing production costs and ensuring uniform light properties across LCD devices by mixing complementary white lights, resulting in improved production efficiency and cost savings.
Implementation Method 1
The white LED includes a blue LED chip and a yellow phosphor covering the blue LED chip
Implementation Method 2
The yellow phosphor is made of a YAG (Yttrium Aluminum Garnet) group and a TAG (Terbium Aluminum Garnet) group, or a silicate group. Accordingly, the white LED emits white light by mixing a blue light emitted from the blue LED chip and a yellow light emitted from the yellow phosphor
Implementation Method 3
White light emitted from the white LEDs enters the light guide plate 23 at an edge and is refracted in the light guide plate 23 toward the liquid crystal panel 10
Data Source
Figure 1~2
Figure 3
Figure 4~5
AI summary
A backlight unit for a liquid crystal display device includes a plurality of white LEDs on a PCB, along a length direction of the PCB, and emitting white lights, the plurality of white LEDs including first and second LEDs alternately arranged; and a plurality of optical sheets on a path of the white lights from the plurality of white LEDs to a liquid crystal panel, wherein the white light from the first LED and the white light from the second LED are substantially complementary in color to each other with respect to a target white light.