Diffusing Layer Structure for Uniform White LED Emission
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Solution Overview
Problem
Existing white light emitting devices, such as CSP and COB LEDs, face challenges in achieving cost-effectiveness and improved color uniformity, with CSP being expensive due to individual coating of LED chips and COB suffering from low color uniformity.
Innovation Solution
A white light emitting device comprising a first and second LED on a substrate, with first and second photoluminescence material layers disposed over the LEDs, and a diffusing layer containing light scattering particles over the photoluminescence layers, enhancing color uniformity and reducing the amount of photoluminescence material required.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If CSP LEDs are used with individual uniform thickness coating of photoluminescence material on each LED chip, then color uniformity is improved, but manufacturing cost increases and manufacturing time increases
Solution Approach 1:
The invention divides the photoluminescence material application into two distinct layers: a first photoluminescence material layer applied to the LED chip and a second photoluminescence material layer applied to the mold cavity. This segmentation allows each layer to serve different functions - the first layer provides base color conversion while the second layer enhances color uniformity - thereby achieving good color uniformity without requiring expensive individual chip coating processes
Solution Approach 2:
The mold cavity acts as an intermediary medium that receives the second photoluminescence material layer. By applying photoluminescence material to the mold cavity rather than directly to each chip, the process simplifies manufacturing while maintaining color uniformity. The mold cavity serves as a carrier that distributes the photoluminescence material uniformly across all chips during injection molding
2Manufacturing precision
If CSP LEDs are used with individual uniform thickness coating of photoluminescence material on each LED chip, then color uniformity is improved, but manufacturing time increases
Solution Approach 1:
The invention merges the photoluminescence material application process with the LED packaging process. The second photoluminescence material layer is applied to the mold cavity and simultaneously molded with the LED chips in a single injection molding operation. This integration eliminates separate coating steps for each chip, significantly reducing manufacturing time while maintaining color uniformity through the dual-layer approach
3Use of energy by moving object
If COB LEDs are used with multiple LED chips on substrate before photoluminescence material, then luminous efficacy is improved, but color uniformity deteriorates
Solution Approach 1:
The invention segments the photoluminescence material into two functional layers: the first layer applied to the LED chip surface provides initial color conversion, while the second layer applied to the mold cavity provides additional color uniformity enhancement. This segmentation allows the system to maintain the high luminous efficacy of COB construction while compensating for color uniformity issues through the dual-layer approach
Solution Approach 2:
The invention applies different photoluminescence materials with specific properties to different locations: the first layer uses materials optimized for direct chip contact and initial color conversion, while the second layer uses materials optimized for filling mold cavity variations and enhancing overall color uniformity. This local optimization allows simultaneous achievement of high efficacy and good color uniformity
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 enhanced color uniformity and reduced manufacturing costs by utilizing a diffusing layer with light scattering particles, which increases the conversion of LED light to photoluminescence light, thereby reducing the need for photoluminescence material and improving luminous efficacy.
Implementation Method 1
White light emitting LEDs include one or more photoluminescence materials, which absorb a portion of the excitation light emitted by the LED and re-emit light of a different color
Implementation Method 2
a diffusing layer comprising light scattering particles... increases the probability that a photon will result in the generation of photoluminescence light by directing light back into the first or second photoluminescence layers
Data Source
AI summary
A light emitting device comprising a plurality of first LEDs disposed on a substrate a plurality of second LEDs disposed on said substrate; a first photoluminescence material layer disposed over said plurality of first LEDs; a second photoluminescence material layer disposed over said plurality of second LEDs; and a diffusing layer associated with light scattering particles; wherein said diffusing layer is disposed over said first and second photoluminescence material layers.