Segmented Phosphor Sheets for High-Intensity White LEDs
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Solution Overview
Problem
Existing light emitting devices using multiple semiconductor light emitting elements and phosphors face challenges in achieving high light intensity and reducing manufacturing variations due to potential light absorption and color variation issues when multiple phosphors are combined in a single layer.
Innovation Solution
The light emitting device incorporates multiple light emitting elements with distinct phosphor sheets containing different phosphors, where the peak wavelength of light converted by one phosphor is equal to or less than that of another, and a white reflection resin is used to prevent absorption, ensuring high light intensity and reduced manufacturing variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If multiple different types of phosphors are included in a phosphor layer, then the number of different wavelengths emitted increases and white light of more natural tint can be obtained, but light transmittance becomes lower and the intensity of emitted light becomes lower
Solution Approach 1:
The phosphors are divided into multiple separate phosphor layers instead of mixing them in a single layer. Each phosphor layer contains a specific type of phosphor, allowing independent optimization of phosphor composition and amount without interference from other phosphors. This segmentation prevents mutual absorption while maintaining high light intensity and natural white light output.
2Manufacturing precision
If multiple different types of phosphors are included in a phosphor layer, then white light of more natural tint can be obtained, but manufacturing variations in colors of lights emitted become larger due to errors in manufacture in the amounts of phosphors
Solution Approach 1:
By separating phosphors into distinct layers, the patent reduces the complexity of precise ratio control that would be required in a mixed phosphor layer. Each layer can be manufactured with simpler quality control, reducing variations in emitted light color while still achieving natural white light through the combination of multiple phosphor types.
3Illumination intensity
If the amount of phosphors is increased to compensate for absorption, then desired light can be obtained, but light transmittance becomes lower and the intensity of light to be emitted becomes lower
Solution Approach 1:
The patent segments phosphors into separate layers to eliminate mutual absorption that occurs when multiple phosphor types are mixed in a single layer. This allows each phosphor layer to maintain high light transmittance and intensity without requiring excessive phosphor amounts, thus avoiding energy loss while still achieving the desired light output.
Solution Approach 2:
The patent transitions from a two-dimensional mixed phosphor layer to a three-dimensional stacked structure with multiple phosphor layers. This dimensional change allows light to pass through each phosphor layer sequentially with minimal mutual absorption, maintaining high light intensity and transmittance while using multiple phosphor types for natural white light output.
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 achieves white light with higher intensity and a more natural tint (higher color rendering index) while minimizing light absorption and manufacturing errors, resulting in improved light transmittance and consistency.
Implementation Method 1
a first phosphor layer made of a first phosphor stacked on one of the LED chips and excited by light emitted from the LED chip to emit green light
Implementation Method 2
a white reflection resin is used to prevent absorption
Data Source
AI summary
A light emitting device includes a first light emitting element, a second light emitting element, a first phosphor sheet containing a first phosphor and a third phosphor, and covering a top face of the first light emitting element, and a second phosphor sheet containing a second phosphor and a fourth phosphor, and covering a top face of the second light emitting element, wherein a peak wavelength of light which is wavelength-converted by the first phosphor or the third phosphor is equal to or less than a peak wavelength of light which is wavelength-converted by the second phosphor or the fourth phosphor.