White LED Light Guide Mixing Blue and Red Diodes for Chromatic Balance
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Solution Overview
Problem
Current liquid crystal display devices face challenges in achieving high color reproducibility and intensity efficiency due to limitations in wavelength coverage and chromatic balance, particularly with pseudo white LEDs and three-wavelength white LEDs, which result in inadequate light component intensity and chromatic variations.
Innovation Solution
A light source system comprising a blue LED, a red LED, and phosphor particles for wavelength conversion, where the blue LED and red LED emit light that is mixed through a light guide member to achieve white light, with a circuit for controlling light emission intensities to adjust chromatic balance, using materials like InGaN for blue LEDs and GaP or AlGaInP for red LEDs, and phosphors such as SrGa2S4:Eu for efficient green light conversion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If pseudo white LED (blue LED + YAG phosphor) is used as light source, then intensity efficiency is high, but wavelength region of 600 nm or more is insufficient and color reproducibility is poor
Solution Approach 1:
The patent combines a blue LED with multiple phosphors (YAG phosphor for yellow light conversion and red phosphor for red light emission) to create a white LED that emits across the full visible spectrum. This merging of multiple light conversion mechanisms resolves the contradiction by maintaining the high efficiency of the blue LED while adding the missing wavelength regions through phosphor down-conversion.
Solution Approach 2:
The invention uses composite phosphor materials including YAG:Ce3+ phosphor particles and red phosphor particles (such as CaAlSiN3:Eu2+ or Sr2Si5N8:Eu2+) in specific combinations and ratios. These composite material systems enable simultaneous achievement of high intensity efficiency and complete wavelength coverage by leveraging the complementary emission characteristics of different phosphors.
2Illumination intensity
If three-wavelength white LED (blue LED + green phosphor + red phosphor) is used, then color reproducibility is improved, but intensity efficiency drops to approximately half of pseudo white LED
Solution Approach 1:
The patent optimizes the emission wavelength parameters of the phosphors used. Specifically, it selects green phosphors with peak wavelengths of 520-560 nm and red phosphors with peak wavelengths of 610-680 nm, and controls their mixing ratios to achieve optimal color reproduction while minimizing efficiency loss. This parameter optimization allows the system to approach the color quality of three-wavelength LEDs with efficiency closer to pseudo white LEDs.
3Illumination intensity
If three-wavelength white LED is used, then color reproducibility is improved, but chromatic variation is very large and color balance cannot be adjusted after assembly
Solution Approach 1:
The patent incorporates feedback mechanisms through drive circuits that monitor and adjust the drive currents to the blue LED, green phosphor-exciting components, and red LED independently. This allows real-time compensation for chromatic variations and enables post-assembly color balance adjustment, resolving the contradiction between achieving high color reproducibility and maintaining chromatic stability.
Solution Approach 2:
The invention employs dynamic control of the light emission intensities from different wavelength components through independently controllable drive circuits. By dynamically adjusting the relative intensities of blue, green, and red components, the system can compensate for chromatic variations and maintain stable color reproduction despite manufacturing tolerances and aging effects.
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 intensity and color reproducibility, allowing for adjustable white balance and improved color rendering properties in liquid crystal display devices, overcoming the limitations of previous technologies by providing a more efficient and reliable light source.
Implementation Method 1
a blue LED element (10) made of InGaN or GaN
Implementation Method 2
a resin into which phosphor particles 8 for converting blue light into green light are dispersed is potted
Implementation Method 3
a red LED element (2) made of GaP, GaAlAs, or AlGaInP
Implementation Method 4
a light guide member 3, for mixing blue-green light from the blue-green LED element (10) with red light from the red LED element (2) to make white light exit from a light exit surface of the light guide member (3)
Implementation Method 5
a light guide member 3, for mixing blue-green light from the blue-green LED element (10) with red light from the red LED element (2) to make white light exit from a light exit surface of the light guide member (3)
Data Source
AI summary
Provided is a display device including: a light guide member for mixing light from a blue LED element coated with a translucent resin mixed with phosphor particles which converts blue light into green light with light from a red LED element to make white light exit from a light exit surface; and a non-self light emission display element provided on an irradiating surface side of the light guide member. Therefore, the display element is irradiated with white light whose sufficient wavelength region is 600 nm or more and whose intensity efficiency is high. When the display device further includes a circuit for separately controlling light emission intensities of the red LED element and a blue LED element, chromatic balance can be adjusted even after manufacturing and an intensity of the display device and color reproducibility thereof can be easily set in an optimum range even after assembly.