Lighting Device Wavelength Conversion for LCD Color Reproducibility
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Solution Overview
Problem
Conventional liquid crystal display devices using pseudo white LEDs face challenges in achieving high luminance and color reproducibility due to scarce light components with wavelengths of 600 nm or more, and difficulties in adjusting color balance, leading to suboptimal chromaticity.
Innovation Solution
A lighting device with a first wavelength conversion member, such as a red phosphor, and a second wavelength conversion member, such as a green phosphor, are strategically positioned to convert blue light into violet and then mix it with green light, producing white light without relying on green phosphor-excited red phosphor emission, improving efficiency and allowing independent chromaticity adjustment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a red phosphor and a green phosphor are mixed and applied onto a transparent film, then additive color mixture can be achieved, but light emitted from the green phosphor excites the red phosphor and in-plane particle density increases, making it difficult to attain high luminance
Solution Approach 1:
The patent divides the wavelength conversion function into separate components: a blue light emitting element and a yellow phosphor for first wavelength conversion to green light, and a green light emitting element and a red phosphor for second wavelength conversion to red light. This segmentation prevents the green phosphor light from exciting the red phosphor, eliminating the energy loss and particle density issues while maintaining additive color mixture capability.
2Illumination intensity
If a blue LED with YAG phosphor is used to produce pseudo white light, then high luminance can be achieved, but light components with wavelength range of 600 nm or more are scarce, hindering color reproducibility
Solution Approach 1:
The patent merges two wavelength conversion systems: one converting blue light to green light (using blue LED and yellow phosphor), and another converting green light to red light (using green LED and red phosphor). This combination produces white light with comprehensive spectral coverage including abundant 600 nm or more wavelength components, achieving both high luminance and excellent color reproducibility beyond NTSC 100%.
3Reliability
If phosphors are potted into the LED to adjust color balance, then chromaticity can be modified, but it is difficult to adjust colors for individual LCD panels and optimal chromaticity cannot be obtained
Solution Approach 1:
The patent introduces adjustable wavelength conversion members that can be positioned at different distances from the light emitting elements. By dynamically adjusting the distance between the yellow phosphor and blue light emitting element, and between the red phosphor and green light emitting element, the chromaticity can be precisely tuned for individual LCD panels, achieving optimal color balance without complex potting processes.
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 configuration enhances light emitting efficiency, temperature-luminance characteristics, and reliability, enabling high luminance and excellent color reproducibility in liquid crystal display devices.
Implementation Method 1
a first wavelength conversion member which performs a first wavelength conversion to convert light emitted from the light emitting element into light having a first peak wavelength
Implementation Method 2
a second wavelength conversion member which performs a second wavelength conversion to convert light emitted from the light emitting element into light having a second peak wavelength, the second peak wavelength being shorter than the first peak wavelength
Implementation Method 3
blue light emitted by the blue light emitting element and red light obtained through the conversion in the red light emitting phosphor are mixed together to produce violet light, and the violet light is further mixed with green light obtained through the conversion in the green light emitting phosphor through blue light excitation, to thereby produce white light
Data Source
AI summary
A lighting device surface-emits light from a light emitting surface of a light emitting element and guides the emitted light using a light guide member. The lighting device has a first wavelength conversion member for converting light emitted from the light emitting device into light having a first peak wavelength and a second wavelength conversion member for converting light emitted from the light emitting device into light having a wavelength shorter than the first peak wavelength. The first wavelength conversion member is provided between the light emitting element and the light guide member and is contained in a resin potting the light emitting element. A film has a layer containing the second wavelength conversion member. The film is provided on a light emitting surface side of the light guide member.