Pigmented Side Reflector Coatings for pcLED Pixel Isolation
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Solution Overview
Problem
In phosphor-converted light emitting diode (pcLED) arrays, especially in miniLED and microLED arrays, there is a challenge in achieving effective light isolation and color accuracy due to light leakage and cross-talk between closely spaced pixels, which affects optical contrast and color fidelity, particularly in applications like displays and automotive lighting.
Innovation Solution
The use of a side reflector with pigments that absorb specific portions of the light spectrum, combined with light scattering particles in a binder, is implemented to reduce light leakage and enhance color accuracy. These pigments are photochemically stable and selectively absorb blue, green, or red light, while reflecting the remaining wavelengths, thereby improving isolation between adjacent pcLED pixels and tailoring the color point of the pcLEDs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If pcLED arrays are densely packed to increase pixel density, then productivity and device integration are improved, but light leakage and cross-talk between adjacent pixels increase, degrading optical contrast and color accuracy
Solution Approach 1:
A side reflector coating is applied to the side walls of each pcLED pixel to act as an intermediary optical element. This coating reflects stray light back into the pixel cavity, preventing cross-talk between adjacent pixels while maintaining high pixel density. The reflector serves as a mediator that manages light propagation without requiring increased spacing between pixels.
Solution Approach 2:
The side reflector coating is applied selectively to the side walls of individual pixels rather than uniformly across the entire array. This localized treatment allows each pixel to have enhanced light confinement properties independently, enabling high density packing while maintaining optical isolation between neighboring pixels with different color characteristics.
2Ease of manufacture
If conventional side reflectors without pigments are used, then manufacturing simplicity is maintained, but color accuracy and optical contrast are degraded due to spectrum-wide reflection
Solution Approach 1:
The side reflector coating is formulated as a composite material combining scattering particles (such as TiO2) with pigments that have complementary absorption spectra. This composite structure enables selective wavelength reflection while maintaining the scattering functionality, achieving both color accuracy and optical contrast without complicating the coating application process.
Solution Approach 2:
The optical properties of the side reflector are tuned by selecting pigments with specific absorption characteristics that complement the scattering particles. By changing the spectral parameters of the coating materials, the reflector can be optimized to reflect only the desired wavelengths while absorbing others, thereby improving color accuracy without requiring complex multi-layer structures.
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 solution effectively reduces light leakage and cross-talk, maintaining high optical contrast and color accuracy even in densely packed pcLED arrays, enhancing the performance of pcLEDs in applications requiring precise light distribution and color fidelity.
Implementation Method 1
includes one or more pigments that absorb light in at least a portion of the spectrum of light emitted by the first phosphor converted LED
Implementation Method 2
combined with light scattering particles in a binder
Data Source
Figure 1~2B
Figure 3A~3B
Figure 4A
AI summary
Phosphor-converted LED side reflectors disclosed herein comprise pigments that are photochemically stable under illumination by light from the pcLED. The pigments absorb light in at least a portion of the spectrum of light emitted by the first phosphor converted LED. The side reflector may also comprise light scattering particles or air voids. The pigments, light scattering particles, or air voids may be homogeneously distributed in the reflector. Alternatively the side reflector may be layered, with the pigments, light scattering particles, or air voids inhomogeneously distributed in the reflector. The side reflector can include phosphor particles.