LED Package Light Guiding Group Mitigates Yellow Ring
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Solution Overview
Problem
Conventional LED package structures suffer from the yellow ring phenomenon due to total reflection of blue light at the phosphor sheet's side region, caused by a large refractive index difference between the phosphor sheet and air.
Innovation Solution
The LED package structure incorporates a light guiding group with a refractive index matching the phosphor sheet, disposed on the ring-shaped region to reduce total reflection and mitigate the yellow ring issue.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If blue light passes through the side region of the phosphor sheet, then light extraction occurs, but total reflection causes the yellow ring problem
Solution Approach 1:
The patent introduces a light guiding group as an intermediary component between the phosphor sheet and the external environment. This light guiding group has a refractive index that forms a gradient transition, acting as a mediator to reduce the abrupt refractive index difference between the phosphor sheet and air, thereby minimizing total internal reflection and eliminating the yellow ring phenomenon while maintaining light extraction efficiency
Solution Approach 2:
The patent changes the refractive index parameter by introducing a light guiding group with a specific refractive index range (1.4-1.7) that matches or is close to the phosphor sheet's refractive index. This parameter change creates a gradual refractive index transition, reducing the critical angle for total internal reflection and preventing the yellow ring effect while preserving light extraction
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 effectively improves light uniformity and efficiency by minimizing total reflection on the ring-shaped region, addressing the yellow ring problem in LED package structures.
Implementation Method 1
the blue light emitted from the LED chip and passing through the side region of the phosphor sheet has a large incident angle with respect to the light emitting surface of the phosphor sheet. Furthermore, the difference of refractive index between the phosphor sheet and air is large, thereby resulting in the blue light being totally reflected from the light emitting surface of the phosphor sheet
Implementation Method 2
A conventional LED package structure includes an LED chip and a phosphor sheet disposed on the LED chip. The phenomenon of the yellow ring usually appears as the light emitted from the LED chip and passing through a center region of the phosphor sheet and a side region of the phosphor sheet.
Data Source
AI summary
The present disclosure discloses an LED package structure and a chip-scale light emitting unit. The chip-scale light emitting unit includes an LED chip, a phosphor sheet, and at least one light guiding group. The phosphor sheet covers entirely a top surface of the LED chip. The phosphor sheet has a light emitting surface arranged away from the LED chip, and the light emitting surface has a central region and a ring-shaped region surrounding the central region. The light guiding group is disposed on the ring-shaped region and covers at least 60% of an area of the ring-shaped region of the phosphor sheet, and the central region is not covered by the light guiding group. The light guiding group includes a plurality of light guiding micro-structures.