Bar-Shaped Light-Emitting Device With Wide-Angle Extraction
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Solution Overview
Problem
Existing light-emitting devices are not suitable as alternatives to linear light sources, as they have high directivity and difficulty in diffusing light in all directions, especially when using fluorescent or light-diffusing materials, and are not adaptable for surface mounting on circuit boards.
Innovation Solution
A light-emitting device with an elongated bar-shaped package made of optically transparent resin, where light-emitting elements are integrated with leads and sealed with a second resin that can include fluorescent material, allowing for wide-angle light emission by guiding light through both resins, and outer lead portions for easy connection and attachment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a reflective frame is used to increase light extraction directivity, then light extraction efficiency in one direction is improved, but light diffusion in all directions deteriorates
Solution Approach 1:
The patent applies local quality by creating different optical properties in different regions of the resin. The refractive index varies from the center to the periphery, with the center having a higher refractive index for directional extraction and the periphery having a lower refractive index for omnidirectional diffusion. This gradient structure allows simultaneous optimization of both directional efficiency and overall light diffusion.
2Illumination intensity
If fluorescent material is contained in the resin, then color conversion is achieved, but placement in optimum position becomes difficult due to specific gravity relationship
Solution Approach 1:
The patent uses composite materials by combining the resin matrix with fluorescent particles having different specific gravities. The first resin (center) has a higher specific gravity than the fluorescent particles, causing them to settle toward the center during molding. The second resin (periphery) has a lower specific gravity, allowing fluorescent particles to distribute more uniformly. This composite structure enables automatic positioning of fluorescent materials in optimal locations without additional manufacturing steps.
3Adaptability or versatility
If a box-shaped package is used for surface mounting, then adaptability to circuit boards is improved, but suitability as alternative to linear light source deteriorates
Solution Approach 1:
The patent resolves the shape contradiction by transitioning from a two-dimensional surface mounting perspective to a three-dimensional light emission perspective. The package maintains a compact box shape for PCB mounting, but the internal gradient refractive index structure creates linear, omnidirectional light emission in three-dimensional space. This allows the device to function as both a surface-mount component and a linear light source alternative simultaneously.
4Ease of manufacture
If sealing resin is molded at one time, then manufacturing process is simplified, but detailed shape design becomes difficult
Solution Approach 1:
The patent applies segmentation by dividing the sealing resin into two distinct regions: a first resin for the center portion and a second resin for the periphery portion. These can be molded separately and then assembled, or molded in sequence using a two-stage injection process. This segmentation allows precise control over the shape, refractive index, and fluorescent material distribution in each region while maintaining manufacturing feasibility.
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 enables light-emitting devices to emit light in a wide area with reduced directivity, allowing for 360-degree light extraction and easy attachment of adjacent devices, mimicking the light emission of a metal filament.
Implementation Method 1
the first resin and the second resin are formed of optically transparent resin, and it is possible to make both the resins function as light guiding members
Implementation Method 2
make both the resins function as light guiding members. Thus, it is possible to guide light toward the back side of the lead
Implementation Method 3
the second resin may include fluorescent material. Thus, it is possible to change the color of light emitted from the light-emitting device with the fluorescent material included in the second resin
Data Source
AI summary
A light-emitting device is provided that can extract light in all directions and that has wide directivity. This light-emitting device includes: an elongated bar-shaped package extending sideways, the package being formed such that a plurality of leads are formed integrally with a first resin with part of the leads exposed; a light-emitting element that is fixed onto at least one of the leads and that is electrically connected to at least one of the leads; and a second resin sealing the light-emitting element. In the light-emitting device, the first resin and the second resin are formed of optically transparent resin, and the leads have outer lead portions used for external connection and protruding sideways from both left and right ends of the package.