Light Emitting Device Side Surface Exposure
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Solution Overview
Problem
Conventional light emitting devices with fluorescent materials in the recess of a package suffer from inefficient light extraction due to excessive reflection of light emitted from the side surface of the light emitting element, as the side surface is coated by the light transmissive member, reducing the excitation of the fluorescent material.
Innovation Solution
The light emitting device design includes a package with a recess containing a light emitting element, where the fluorescent material is distributed more on the side of the element than above it, and a light transmissive member that protrudes from the sealing resin, exposing the side surface of the element and reducing total reflection by forming an interface with outside air that has a smaller degree of recess, thereby enhancing light extraction efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the side surface of the light emitting element is coated by the light transmissive member, then the element is protected and integrated into the package, but light emitted from the side surface is excessively reflected, reducing light extraction efficiency
Solution Approach 1:
The light transmissive member is extracted from the recessed position and protrudes from the sealing resin surface. This positional change removes the total reflection interface that was causing light loss, while the member still provides protection and light guidance functions.
Solution Approach 2:
The light transmissive member acts as an intermediary between the light emitting element and the external environment. By protruding from the sealing resin, it creates a gradual transition for light extraction without abrupt total reflection, mediating between the protected element and efficient light output.
2Productivity
If fluorescent material is distributed above the light emitting element, then light extraction path is provided, but excessive reflection occurs and excitation of fluorescent material is reduced
Solution Approach 1:
The fluorescent material distribution is made non-uniform, with greater concentration on the side of the light emitting element and less above it. This local quality variation optimizes light interaction by placing fluorescent material where it can be effectively excited without causing excessive reflection.
3Device complexity
If the light transmissive member is positioned flush with or recessed in the sealing resin, then the package structure is compact, but total reflection occurs at the interface, reducing light emission
Solution Approach 1:
Instead of positioning the light transmissive member flush with or recessed in the sealing resin (conventional approach), the invention inverts this arrangement by making the member protrude from the sealing resin surface. This inversion eliminates the total reflection interface while maintaining structural integrity.
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 configuration allows for efficient use of light emitted from the side surface to excite the fluorescent material, reducing total reflection and improving light extraction efficiency by minimizing the amount of fluorescent material above the light emitting element and optimizing the light transmissive member's protrusion to prevent deposition and enhance light emission.
Implementation Method 1
a fluorescent material contained in the sealing resin
Implementation Method 2
reducing total reflection by forming an interface with outside air
Data Source
AI summary
A light emitting device comprises a package having a recess; a light emitting element mounted in the recess of the package; a light transmissive member provided above the light emitting element; a sealing resin that seals the recess of the package; and a fluorescent material contained in the sealing resin. The fluorescent material is distributed to a side of the light emitting element in a greater amount than to above the light emitting element, a side surface of the light emitting element is exposed to the sealing resin, and a portion of the light transmissive member protrudes from the sealing resin.