Non-absorbing Reflector for LED Phosphor Color Hiding
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Solution Overview
Problem
LED-phosphor based illumination devices have a visible phosphor color in the off state, which is aesthetically undesirable and previous solutions suffer from low efficiency and bulkiness due to the use of lenses or half-mirror films.
Innovation Solution
A light emitting arrangement featuring a solid state light source, a wavelength converting member, and a non-absorbing, partially transparent reflector that hides the phosphor color and provides a metallic appearance, while maintaining high efficiency and reducing phosphor degradation through a remote configuration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If a half-mirror film is used to hide the phosphor color in the off state, then the aesthetic appearance is improved, but the device efficiency decreases and the structure becomes bulky
Solution Approach 1:
The invention extracts the light shielding function from the optical path, placing the reflective element on the rear side of the phosphor layer rather than in front of it. This allows the front surface to remain fully transparent for light output while the rear reflective element provides the aesthetic appearance in off-state without blocking light during operation
Solution Approach 2:
A transparent adhesive layer serves as an intermediary between the phosphor layer and the reflective element, allowing the reflective element to be positioned close to the phosphor for aesthetic purposes while maintaining optical performance. The adhesive layer mediates between the conflicting requirements of light transmission and aesthetic appearance
2Device complexity
If the wavelength converting member is placed in direct contact with the light source, then the device structure is compact, but the phosphor degrades due to overheating and lifetime decreases
Solution Approach 1:
The invention segments the device into distinct functional layers: light source layer, transparent adhesive layer, and wavelength converting layer. This segmentation creates thermal separation between the high-temperature light source and the phosphor material, reducing thermal degradation while maintaining a compact overall structure through the thin adhesive layer
3Illumination intensity
If more phosphor is used to achieve desired color output, then the color quality is improved, but the phosphor color becomes more visible in the off state and aesthetic appearance deteriorates
Solution Approach 1:
The invention converts the harmful visible color of the phosphor in off-state into a beneficial aesthetic feature by placing a reflective element behind it. The reflective element reflects ambient light through the phosphor layer, making the device appear silver or golden in off-state while allowing full phosphor loading for optimal color quality during operation
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 neutral off-state appearance, improved efficiency, and increased phosphor lifetime with a compact design, as the non-absorbing reflector minimizes phosphor visibility and reduces overheating, allowing for a silver or golden metallic appearance.
Implementation Method 1
a wavelength converting member arranged to receive said primary light and capable of converting said primary light into secondary light
Implementation Method 2
a non-absorbing, partially transparent reflector arranged on a light output side of the wavelength converting member
Data Source
AI summary
A light emitting arrangement (100) is provided, comprising: -a solid state light source (101, 201) adapted to emit primary light; and -a wavelength converting member (105, 205) arranged to receive said primary light and capable of converting said primary light into secondary light, the wavelength converting member and the solid state light source being mutually spaced apart; and -a non-absorbing, partially transparent reflector (106, 206) arranged on a light output side of the wavelength converting member. The reflector hides the color of the phosphor and may give the arrangement a silver or golden metallic appearance, which is more desirable for many applications. By using a non-absorbing reflector, efficiency is high and also less phosphor is required, which further contributes to the improved visual appearance.