Backlight with Dual Green LEDs for Color Reproducibility
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Solution Overview
Problem
The yield of light-emitting devices using only green light-emitting elements is poor due to variations in wavelength, leading to challenges in achieving desired color reproducibility and high production costs.
Innovation Solution
A light-emitting device comprising a blue light-emitting element, two green light-emitting elements with specific peak wavelength ranges, and a red phosphor or light-emitting element, where at least one green light-emitting element is connected in series to the blue light-emitting element, and the phosphor converts blue light into red light, ensuring good color reproducibility and reduced production costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If only green light-emitting elements are used, then device complexity is reduced, but manufacturing precision deteriorates due to wavelength variations
Solution Approach 1:
The green light-emitting element is segmented into two separate elements with different peak wavelengths (first green light-emitting element with peak wavelength Y, second green light-emitting element with peak wavelength Z). This segmentation allows each element to have specialized wavelength characteristics, improving overall color reproducibility while maintaining manageable device complexity through modular design.
2Manufacturing precision
If multiple light-emitting elements with different wavelengths are used, then color reproducibility is improved, but device complexity increases
Solution Approach 1:
The light-emitting device is segmented into distinct functional modules: blue light-emitting element, first green light-emitting element, second green light-emitting element, and red light-emitting element. Each module targets a specific wavelength range, enabling precise color control while organizing complexity into manageable segments.
Solution Approach 2:
The blue light-emitting element serves multiple functions: it provides blue light directly and acts as a pump source for exciting the yellow phosphor. This multi-functionality reduces the need for separate dedicated components, thereby improving color reproducibility without proportionally increasing device complexity.
3Manufacturing precision
If multiple light-emitting elements with different wavelengths are used, then color reproducibility is improved, but production cost increases
Solution Approach 1:
The blue light-emitting element performs dual functions as both a direct blue light source and a pump source for yellow phosphor excitation. This multi-functionality reduces the total number of required light-emitting elements, thereby improving color reproducibility while controlling production costs through component consolidation.
4Manufacturing precision
If green light-emitting elements with specific wavelength ranges are used, then color reproducibility is improved, but manufacturing difficulty increases
Solution Approach 1:
The patent specifies precise peak wavelength ranges for each light-emitting element (blue: 430-490 nm, first green: 490-nm to X nm, second green: X+10 nm to 570 nm, red: 600-680 nm). By controlling these wavelength parameters within defined ranges, the invention achieves improved color reproducibility while providing clear manufacturing specifications that facilitate production within controlled tolerances.
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 device achieves improved color reproducibility and lower production costs by using a combination of blue, green, and red light-emitting elements with specific wavelength ranges, enhancing the yield and color uniformity of light-emitting devices.
Implementation Method 1
a phosphor or a fourth light-emitting element... The phosphor... has a peak wavelength in a range from 580 nm to 680 nm
Data Source
AI summary
A light-emitting device includes: one or more first light-emitting elements each having a peak wavelength in a range from 430 nm to less than 490 nm; a second light-emitting element having a peak wavelength Y in a range from 490 nm to less than a wavelength X; a third light-emitting element having a peak wavelength Z in a range from more than the wavelength X to 570 nm; and a phosphor or a fourth light-emitting element having a peak wavelength in a range from 580 nm to 680 nm. At least one of the second and third light-emitting elements is connected to at least one of the first light-emitting elements in series. The wavelength X is in a range from more than 490 nm to less than 570 nm with an absolute value of difference between |X−Y| and |X−Z| being 10 nm or less.