Porous Reflective LED Sidewalls for MicroLED Optical Isolation
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Solution Overview
Problem
In phosphor-converted LED arrays, close spacing of pixels leads to optical cross-talk, making it difficult to achieve desired compartmentalization of light emission and efficient optical isolation, as conventional reflective sidewalls require thicknesses greater than 50 microns for effective isolation, which is mechanically unstable and prone to contamination.
Innovation Solution
The use of porous high refractive index light scattering particles dispersed in a transparent binder material, with pores filled with air or evacuated, provides effective light confinement and scattering with thinner reflective sidewall structures, allowing for pixel spacings as low as 4 microns, using materials like porous Titanium Oxide or Zirconium Oxide particles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional reflective sidewalls are used for optical isolation, then light compartmentalization is improved, but sidewall thickness must be greater than 50 microns which causes mechanical instability and contamination
Solution Approach 1:
The patent applies porous particles (such as porous TiO2 or porous ZrO2) as the core component of the reflective sidewall structure. These porous particles provide high refractive index contrast for effective light scattering while maintaining a porous structure that reduces the overall material density and enables thinner sidewall configurations. The porous nature allows for lighter weight and reduced mechanical stress while preserving optical isolation functionality.
Solution Approach 2:
The patent creates a composite reflective sidewall structure by combining porous high refractive index particles (TiO2 or ZrO2) with a transparent binder material. This composite approach allows the porous particles to provide the primary light scattering function while the binder provides mechanical cohesion, enabling the sidewall to achieve both optical effectiveness and mechanical stability at reduced thicknesses compared to conventional solid reflective structures.
2Productivity
If pixel spacing is reduced to increase array density, then productivity is improved, but optical cross-talk increases making isolation difficult
Solution Approach 1:
The porous particles with high refractive index provide enhanced light scattering capability that enables effective optical isolation even when pixels are closely spaced. The porous structure increases the surface area and scattering interfaces, allowing for better light confinement in thinner layers and at smaller pitch dimensions, thus enabling high array density without sacrificing optical isolation.
Solution Approach 2:
The patent changes the refractive index parameter by using high refractive index materials (TiO2 with n≈2.6 or ZrO2 with n≈2.2) compared to conventional materials. This parameter change enhances the scattering efficiency and allows for effective optical isolation at reduced pixel pitch, enabling higher array density while maintaining reliable light compartmentalization.
3Strength
If sidewall thickness is reduced to improve mechanical stability, then strength is improved, but light scattering effectiveness deteriorates
Solution Approach 1:
The porous structure of the particles provides a high surface-area-to-volume ratio, creating numerous scattering interfaces within the particle itself. This internal scattering mechanism compensates for the reduced overall sidewall thickness, allowing the structure to maintain light scattering effectiveness while being mechanically more stable due to the reduced thickness and lower material density.
Solution Approach 2:
By using particles with high refractive index (n≥2.0), the scattering efficiency per unit thickness is dramatically increased. This parameter change allows the sidewall to achieve the required light scattering performance with much thinner dimensions, thereby improving mechanical stability without sacrificing optical functionality.
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 approach enables efficient light confinement and scattering with sidewall thicknesses less than 25 microns, reducing optical cross-talk and improving mechanical stability and contamination resistance, allowing for closer pixel spacing and enhanced light control in LED arrays.
Implementation Method 1
reflective sidewalls comprising porous particles... porous high refractive index light scattering particles... provides effective light confinement and scattering
Implementation Method 2
porous high refractive index light scattering particles... refractive index contrast at the particle / binder interfaces
Implementation Method 3
The refractive index of the particle material is greater than or equal to about 2.0... The pores may be filled with air or another gas... light scattering can be achieved with the same particle materials (in porous form)
Data Source
Figure 1~2B
Figure 3A~3B
Figure 4A
AI summary
Sidewall reflectors disposed on the sidewalls of an LED or pcLED comprise porous (for example, hollow) high refractive index light scattering particles dispersed in a transparent binder. The porous particles exhibit a high refractive index contrast and corresponding strong scattering at the interfaces between the porous particle material and one or more pores in each particle. These sidewall reflectors can provide light confinement with thin reflector structures, allowing close spacing between LEDs and pcLEDs, and may be advantageously employed in microLED arrays.