Backlight Wavelength Converting Film for LCD Color Gamut
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Solution Overview
Problem
Current color liquid crystal displays (LCDs) face limitations in achieving high color gamut and luminous efficacy due to inefficiencies in backlight technology, particularly in the absorption and conversion of light by photoluminescence materials, leading to suboptimal color reproduction and brightness.
Innovation Solution
Incorporating europium activated sulfide phosphors and manganese-activated fluoride phosphors in a wavelength converting layer, separate from the light emitting devices, to generate white light with improved peak emission wavelengths and reduced thermal quenching, along with the use of light scattering materials to enhance light uniformity and reduce material usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If photoluminescence materials are used in the backlight to generate white light, then color gamut is improved, but luminous efficacy deteriorates due to absorption and conversion inefficiencies
Solution Approach 1:
The backlight is divided into multiple light emitting devices, each containing specific photoluminescence materials (red and green phosphors with blue LED excitation sources). This segmentation allows optimized light conversion in each device while maintaining overall system efficiency and achieving high color gamut coverage.
Solution Approach 2:
Different photoluminescence materials are selectively placed in different light emitting devices based on their emission characteristics. Red phosphors (K2SiF6:Mn4+, CaAlSiN3:Eu) and green phosphors (β-SiAlON:Eu, SrSi2O2N2:Eu) are positioned to optimize local light conversion efficiency and minimize absorption losses while achieving uniform white light output.
2Device complexity
If photoluminescence materials are placed close to light emitting devices for compact design, then device complexity is reduced, but thermal quenching increases reducing luminous efficacy
Solution Approach 1:
A light guide plate is introduced as an intermediary component between the light emitting devices and the display panel. This allows the photoluminescence materials to be positioned optimally for thermal management while maintaining compact overall design, as the light guide plate efficiently distributes light without requiring direct contact between phosphors and LED chips.
3Illumination intensity
If more photoluminescence material is used to improve color gamut, then color reproduction is enhanced, but manufacturing cost increases
Solution Approach 1:
The invention optimizes the concentration and distribution of photoluminescence materials in the light emitting devices. By carefully controlling phosphor loading levels and selecting materials with high quantum efficiency, the patent achieves NTSC 95%+ color gamut coverage while minimizing material usage and manufacturing costs.
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 a color gamut of at least 95% of NTSC and 100% of DCI-P3 RGB color space standards, with improved luminous efficacy and reduced manufacturing costs, by minimizing absorption and maximizing light emission across the visible spectrum.
Implementation Method 1
europium activated sulfide phosphors... which when excited by excitation light (typically blue) generate white light for operating the display
Implementation Method 2
manganese-activated fluoride phosphors... which when excited by excitation light (typically blue) generate white light for operating the display
Implementation Method 3
the use of light scattering materials to enhance light uniformity and reduce material usage
Data Source
AI summary
A display includes a display panel and a backlight. The backlight includes an excitation source that generates blue excitation light with a dominant emission wavelength in a range 445 nm to 465 nm; and a wavelength converting film located remotely to the excitation source and between the excitation source and display panel. The wavelength converting film, in terms of photoluminescence material, includes a manganese-activated fluoride phosphor and a europium activated sulfide phosphor; where the manganese-activated fluoride phosphor receives at least a portion of the blue excitation light and in response emits red light with a peak emission wavelength in a range 610 nm to 650 nm; and where the europium activated sulfide phosphor receives at least a portion of the blue excitation light and in response emits green light having a peak emission wavelength in a range 525 nm to 545 nm; and where the europium activated sulfide phosphor is coated with at least one oxide material.