Composite Wavelength Conversion Particles for LED Light Efficiency
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Solution Overview
Problem
Existing light emitting devices face inefficiencies in light utilization and reliability due to scattering issues with phosphor particles, leading to reduced luminance efficiency and increased color unevenness, particularly when excited by near-ultraviolet or blue light.
Innovation Solution
Dispersing phosphor particles with a refractive index of 1.6 or more in matrix particles containing fine magnesium fluoride or calcium fluoride particles, and using these composite wavelength conversion particles in a light transmitting member to enhance light utilization efficiency and reduce scattering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If phosphor particles with high refractive index (1.63-2.0) are used to achieve high light emission efficiency, then luminance efficiency is improved, but light scattering increases due to refractive index difference with binder (less than 1.6)
Solution Approach 1:
The patent creates a composite wavelength conversion particle consisting of a phosphor particle core (high refractive index 1.63-2.0) coated with a transparent resin layer (low refractive index matching the binder). This composite structure allows the phosphor to maintain its high light emission efficiency while the resin coating reduces the refractive index difference with the binder, minimizing light scattering. The coating layer acts as an optical interface that bridges the high-index phosphor and low-index binder.
Solution Approach 2:
The patent modifies the optical parameters of the phosphor particle by adding a resin coating layer with refractive index matched to the binder. This changes the effective refractive index at the particle-binder interface, reducing the optical contrast that causes scattering. The coating layer thickness and refractive index are specifically controlled to optimize both light extraction and scattering reduction.
2Loss of energy
If phosphor particle diameter is increased to reduce scattering, then light utilization efficiency is improved, but absorption and emission occur only in the front layer portion making the inner portion useless
Solution Approach 1:
The transparent resin coating layer acts as an optical intermediary that facilitates light penetration into the phosphor particle. By matching the refractive index of the coating to the binder, it reduces reflection and scattering at the particle surface, allowing excitation light to penetrate deeper into the particle and enabling the inner portions to participate in wavelength conversion.
Solution Approach 2:
The composite structure with resin coating enables larger particle sizes to be used effectively. The coating layer optimizes optical coupling, allowing excitation light to penetrate throughout the particle volume and enabling uniform utilization of phosphor material from surface to core, thus making the entire particle volume effective for wavelength conversion.
3Ease of manufacture
If phosphor particles are dispersed in organic binder or inorganic binder to create wavelength conversion film, then device fabrication is simplified, but scattering occurs due to refractive index difference between phosphor particles and binder
Solution Approach 1:
The patent maintains the simple dispersion fabrication method while modifying the phosphor particle surface with a resin coating. This coating creates a gradient optical interface that reduces scattering without complicating the manufacturing process. The coated particles can still be easily dispersed in binders, and the coating layer's refractive index is selected to match common binder materials, minimizing scattering while preserving fabrication simplicity.
4Use of energy by moving object
If phosphor particles with high refractive index are used to achieve high quantum efficiency (approximately 90% at room temperature), then light emission efficiency is improved, but scattering occurs at the interface with low refractive index binder
Solution Approach 1:
The resin-coated phosphor particle composite maintains the high quantum efficiency of the phosphor core while adding an optical interface layer that reduces scattering. The coating layer protects the phosphor surface and creates a more stable optical environment, reducing sensitivity to variations in binder composition and improving overall optical performance stability and reliability.
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 increases the efficiency of light emission and reliability by minimizing scattering and absorption, while maintaining uniform light output and reducing color variations.
Implementation Method 1
the phosphor which is used in a wavelength conversion film or the like of a light electromotive device such as a white light emitting element (a white LED element) or a solar battery is required to emit light (fluorescence) with a high level of efficiency by electron beam excitation of comparatively low energy of near-ultraviolet rays, blue light of visible light, or the like
Implementation Method 2
The refractive index of such phosphor particles having high efficiency and high reliability is approximately 1.63 to 2.0, and on the other hand, the refractive index of the organic binder or the inorganic binder is less than 1.6. Therefore, scattering occurs due to a refractive index difference between the phosphor particles and the binder
Data Source
AI summary
A composite wavelength conversion powder and a resin composition containing a composite wavelength conversion powder which have high utilization efficiency of light and high utilization efficiency of a constituent material, and are able to make highly efficient light emission and high reliability compatible are provided. The composite wavelength conversion powder is formed by dispersing phosphor particles having a refractive index of 1.6 or more in matrix particles containing fine magnesium fluoride particles or fine calcium fluoride particles.In addition, a light emitting device which is able to improve utilization efficiency of light due to the phosphor particles excited by primary irradiation light emitted by a light emitting element, is able to improve the optical output of light emission by increasing an the amount of secondary irradiation light generated from the phosphor particles, and is able to suppress limit the occurrence of color unevenness or a color variation device in light emitted to the outside of the device is provided. A light emitting device (1) includes a substrate (2), a light emitting element (3) mounted on a front surface of the substrate (2), and a light transmitting member (4) formed to cover the light emitting element (3), and the light transmitting member (4) contains phosphor particles having an average particle diameter of 500 nm or less, and composite wavelength conversion particles (12) formed of inorganic particles having an average particle diameter of 500 nm or less which are transparent with respect to visible light.