Convex Selective Reflection Layer for Uniform LED Phosphor Lighting
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Solution Overview
Problem
Luminance unevenness occurs in lighting devices due to the blue shift phenomenon in wavelength-selective reflection layers, particularly when LEDs emit light at a high degree of straightness, leading to reduced light transmission and increased luminance variations across the device.
Innovation Solution
A lighting device design featuring a wavelength-selective reflection layer with convex shapes projecting towards the circuit substrate, a transparent resin layer, and a light reflection layer to manage incident angles and maintain light transmission efficiency, with the wavelength-selective reflection layer composed of dielectric multilayer film and positioned between the phosphor sheet and the light source to reduce blue shift effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a wavelength-selective reflection layer composed of dielectric multilayer film is used to increase light use efficiency, then light transmission is improved, but luminance unevenness occurs due to blue shift at large incident angles
Solution Approach 1:
The patent applies curvature by forming the wavelength-selective reflection layer as a convex shape (arch structure) that protrudes toward the light source. This curved configuration changes the incident angle distribution of light across the reflection layer, ensuring that light rays from different positions on the LED chip strike the reflective surface at more uniform angles, thereby reducing the blue shift effect and minimizing luminance unevenness while preserving high light use efficiency
2Object-generated harmful factors
If the incident angle of light reaching the wavelength-selective reflection layer increases, then blue light reflection increases due to blue shift, but light transmission decreases and luminance unevenness accelerates
Solution Approach 1:
The convex arch shape of the wavelength-selective reflection layer transforms the optical path of incident light. By curving the reflective surface upward toward the LED chip, the structure ensures that light rays traveling at various angles relative to the substrate normal are reflected at more consistent angles, reducing the wavelength shift effect and maintaining stable light transmission across different spatial positions
3Device complexity
If a flat wavelength-selective reflection layer is used, then the structure is simple, but luminance unevenness occurs in regions away from the LED due to blue shift
Solution Approach 1:
The patent introduces a convex arch shape to the wavelength-selective reflection layer, transforming it from a flat two-dimensional structure to a curved three-dimensional structure. This curvature modification, while adding structural complexity, effectively uniformizes the incident angle distribution and eliminates luminance unevenness in regions away from the LED chip
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 effectively inhibits luminance unevenness, increases light use efficiency, and maintains high luminance and color reproducibility by minimizing the blue shift effect and ensuring consistent light transmission across the device.
Implementation Method 1
a wavelength-selective reflection layer that is composed of dielectric multilayer film, that is disposed between the wavelength conversion member and the light source, that covers the light emission surface of the light source, that allows the part of the primary light to be transmitted therethrough, and that reflects part of the secondary light
Implementation Method 2
The wavelength-selective reflection layer is composed of dielectric multilayer film
Implementation Method 3
a phosphor sheet that converts blue light into green light and red light
Implementation Method 4
a light source that is mounted on the circuit substrate and that emits primary light in a predetermined wavelength range via a light emission surface
Data Source
AI summary
A lighting device includes a circuit substrate that includes a wiring circuit, LEDs that are mounted on the circuit substrate and that emit primary light, a phosphor sheet that faces a light emission surface of each of the LEDs and that has a function of converting part of the primary light into secondary light in another wavelength range that differs from the wavelength range, and a selective reflection layer that is composed of dielectric multilayer film, that is disposed between the phosphor sheet and the LEDs, that covers the light emission surface of each of the LEDs, that allows the part of the primary light to be transmitted therethrough, and that reflects part of the secondary light. The selective reflection layer is disposed so as to have convex shapes projecting in a direction opposite a direction toward the circuit substrate in regions that overlap the LEDs.