Tapered Light Guide Member for High Luminance LED
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Solution Overview
Problem
Existing light emitting devices experience reduced light extraction efficiency due to repeated scattering of light in the wavelength conversion member before reaching the emission face, leading to a decrease in emission area and brightness.
Innovation Solution
A light emitting device design featuring a light emitting element with a wavelength conversion member having a larger lower face, a first light guide member extending from the light emitting element to the wavelength conversion member, and a second light guide member extending from the wavelength conversion member to a light transmissive member with a smaller upper face, where the thickness of the second light guide member increases towards the bottom and decreases towards the top, enhancing light extraction efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If a light guide member with a smaller light emission face is disposed on the light emitting element, then the emission area decreases, but the light extraction efficiency is reduced due to repeated scattering in the wavelength conversion member
Solution Approach 1:
The patent introduces a tapered light guide member that extends in the vertical dimension with a thickness that varies from top to bottom. The bottom surface area is larger than the top surface area, creating a three-dimensional structure that allows light to travel through a longer path in the wavelength conversion member without increasing the top emission area. This dimensional transition resolves the contradiction by separating the light extraction function (larger bottom area) from the emission function (smaller top area).
Solution Approach 2:
The tapered light guide member acts as an intermediary structure between the light emitting element and the emission surface. It provides a transition zone where light can be efficiently extracted through the wavelength conversion member at the broader bottom interface, then guided through the tapered structure to the smaller top emission area, maintaining both high light extraction efficiency and compact emission footprint.
2Loss of energy
If the thickness of the light guide member is increased to reduce scattering, then the light extraction efficiency improves, but the device height increases
Solution Approach 1:
The light guide member features non-uniform thickness with different local qualities: the bottom portion has a larger cross-sectional area to maximize light extraction from the wavelength conversion member, while the top portion has a smaller cross-sectional area to maintain compact emission area. This local variation in dimensions allows the structure to optimize for different functions at different locations, achieving high light extraction efficiency without excessive overall height.
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 design improves light extraction efficiency by increasing the light emission area and reducing scattering, resulting in a higher luminance light emitting device with a smaller emission face, effectively addressing the issue of reduced brightness and emission area.
Implementation Method 1
a wavelength conversion layer disposed on the semiconductor light emitting element and containing phosphor particles
Implementation Method 2
a light-transmitting scattering member containing a scattering material and disposed on the light-transmitting plate member
Data Source
Figure 1A~1B
Figure 1C~2
Figure 3A~3E
AI summary
A light emitting device includes: a light emitting element, a wavelength conversion member disposed on an upper face of the light emitting element and having a lower face that has a larger area than the upper face of the light emitting element, a first light guide member extending from a lateral face of the light emitting element to the lower face of the wavelength conversion member, a light transmissive member disposed on an upper face of the wavelength conversion member and having a lower face that has a smaller area than the upper face of the wavelength conversion member, and a second light guide member extending from the upper face of the wavelength conversion member to a lateral face of the light transmissive member.