LED Chip Light-Blocking Layer for Glare Reduction
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Solution Overview
Problem
Conventional light-emitting devices suffer from glare issues due to scattered light and yellowing of the epoxy molding compound caused by short-wave radiation from LED chips, and the beam angle of existing LEDs complicates the design of total reflection lenses, especially in applications like backlighting.
Innovation Solution
A light-emitting device with a supporting component, an LED chip, and a light-blocking layer that surrounds the chip, covering its lateral side and exposing the top surface, with a top light exit port area smaller than or equal to the top chip surface, and a beam angle of less than 135°, to minimize light reflection and scattering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the fluorescent gel fills the bowl-shaped EMC lead frame and covers the front-mounted LED chip, then the LED chip is protected and light is emitted, but the EMC lead frame yellows due to short-wave radiation
Solution Approach 1:
The patent extracts the harmful short-wave radiation from the system by introducing a reflective layer that redirects this radiation away from the EMC lead frame. The reflective layer is positioned to intercept short-wave radiation before it can cause yellowing, while still allowing the LED chip to function normally and be protected by the fluorescent gel.
Solution Approach 2:
The reflective layer acts as an intermediary between the LED chip and the EMC lead frame. It intercepts the short-wave radiation emitted by the LED chip and redirects it, preventing direct interaction between the harmful radiation and the EMC lead frame, thus eliminating the yellowing effect while maintaining LED protection.
2Illumination intensity
If the LED chip has a large beam angle, then light is emitted in multiple directions, but the light scatters causing glare and complicates secondary optical processing
Solution Approach 1:
The patent extracts scattered light that causes glare by introducing a reflective layer positioned to intercept light exiting at problematic angles. This reflective layer redirects the scattered light back toward the optical axis, eliminating glare while preserving the useful light emission from the LED chip.
Solution Approach 2:
Instead of allowing light to scatter outward in multiple directions, the reflective layer inverts the direction of scattered light by reflecting it back toward the optical axis. This reverses the harmful scattering effect and converts it into useful directed light, reducing glare without requiring changes to the LED chip itself.
3Ease of manufacture
If the top light exit region of the vertical LED chip is lower than the opening of the bowl-shaped EMC lead frame, then the LED chip fits in the structure, but light reflects from the EMC lead frame causing glare
Solution Approach 1:
The reflective layer serves as an intermediary that intercepts light before it can reach the EMC lead frame opening. By positioning the reflective layer above the LED chip's light exit region, it blocks light from traveling to the EMC lead frame edge where it would cause glare, while still allowing the LED chip to be mounted in the bowl-shaped structure.
Solution Approach 2:
The reflective layer performs a preliminary action by intercepting and redirecting light before it has a chance to cause glare. By placing the reflective layer in the path of exiting light, it pre-empts the harmful reflection issue, preventing glare from occurring in the first place while maintaining the structural mounting arrangement.
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 reduces glare and light scattering, allowing for a highly focused beam with improved luminous efficiency and simplified secondary optical processing, suitable for applications like backlighting and projection illumination.
Implementation Method 1
The light-emitting semiconductor stack is formed between the substrate and the top chip surface to emit light toward the top chip surface
Implementation Method 2
The light-blocking layer is formed on the supporting component to surround the LED chip, and covers the lateral side of the LED chip
Data Source
AI summary
A light-emitting device includes an LED chip disposed on a supporting component. The LED chip includes a semiconductor stack formed on a substrate, a first electrode, and a second electrode. A light-blocking layer fills the supporting component to cover a lateral side of the LED chip and expose a top chip surface of the LED chip. The light-blocking layer has a top surface not lower than the top chip surface of the LED chip. A height difference among the top chip surface, the top surface of the light-blocking layer and a top end of the supporting component is less than 10 μm. A top light exit port defined by the light-blocking layer to expose the top chip surface has a cross sectional area not larger than that of the top chip surface.