Flexible LED Light Sheet for Uniform Illumination
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Solution Overview
Problem
Existing solid state light sheets face challenges such as heat management, optical uniformity, reliability, and cost-effectiveness due to issues like excessive pressure, total internal reflections, and inefficiencies in LED bonding and light distribution, making them unsuitable for replacing traditional fluorescent lighting.
Innovation Solution
A flexible light sheet design featuring a conductor pattern with metal vias for heat management, a reflective layer for light distribution, and a phosphor-infused silicone mixture for uniform light emission, along with a modular structure to facilitate series and parallel connections of low-power LEDs, ensuring aesthetically pleasing and efficient illumination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If high power LEDs are used to achieve high luminous efficacy (100-200 lumens/watt), then illumination intensity is improved, but heat generation increases and packaging complexity increases
Solution Approach 1:
The patent divides the lighting system into multiple low-power LED segments arranged in arrays across the flexible substrate. Instead of using a few high-power LEDs that generate excessive heat, the system uses many low-power LEDs (each consuming less than 0.5 watt) distributed throughout the light sheet. This segmentation reduces heat generation at any single location while maintaining overall high luminous output through the collective emission of numerous LED elements.
2Illumination intensity
If high power LEDs are used to achieve high output (3000+ lumens), then illumination intensity is improved, but device complexity and cost increase
Solution Approach 1:
The patent combines multiple functional layers into a single flexible substrate structure. The conductor pattern, reflective layer, phosphor-infused silicone, and LED mounting structure are integrated directly onto the flexible substrate, eliminating the need for separate packaging components. This merging approach achieves high luminous output (3000+ lumens) while reducing device complexity and enabling cost-effective manufacturing compared to traditional high-power LED packaging.
3Ease of manufacture
If conventional LED bonding methods are used, then manufacturing is simplified, but reliability decreases due to excessive pressure and bonding failures
Solution Approach 1:
The patent applies local quality by creating designated LED recesses in the phosphor-infused silicone layer that provide precise mechanical accommodation for each LED. These recesses ensure proper positioning and contact between LED electrodes and conductor traces without requiring excessive bonding pressure. The localized structural features at each LED location improve bonding reliability while maintaining ease of manufacture through a simplified process that doesn't require high-pressure lamination.
4Device complexity
If thin LEDs are used to reduce packaging complexity, then device complexity is reduced, but heat management becomes more challenging
Solution Approach 1:
The patent introduces phosphor-infused silicone as an intermediary thermal management medium between the thin LED chips and the flexible substrate. The silicone material provides thermal conduction pathways that efficiently remove heat from the LED junctions, while the phosphor particles dispersed in the silicone also contribute to thermal management. This intermediary approach enables effective heat management for thin LEDs without increasing packaging complexity, as the thermal management function is integrated into the optical phosphor layer.
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 provides a cost-effective, reliable, and optically uniform lighting solution that can replace traditional fluorescent fixtures, offering improved heat management, reduced visibility of failed LEDs, and efficient light distribution, while being modular and energy-efficient.
Implementation Method 1
conductor pattern with metal vias for heat management
Implementation Method 2
reflective layer for light distribution, reduced total internal reflections
Implementation Method 3
phosphor-infused silicone mixture for uniform light emission
Data Source
AI summary
A solid state light sheet and method of fabricating the sheet are disclosed. In one embodiment, bare LED chips have top and bottom electrodes, where the bottom electrode is a large reflective electrode. The bottom electrodes of an array of LEDs (e.g., 500 LEDs) are bonded to an array of electrodes formed on a flexible bottom substrate. Conductive traces are formed on the bottom substrate connected to the electrodes. A transparent top substrate having conductors is then laminated over the bottom substrate. Various ways to connect the LEDs in series are described along with many embodiments. The light sheets may be formed to emit light from opposite surfaces of the light sheet, enabling it to be used in a hanging fixture to illuminate the ceiling as well as the floor. The light sheet provides a practical substitute for a standard 2×4 foot fluorescent ceiling fixture.