Patterned Reflective Grids for LED Pixel Contrast Control
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Solution Overview
Problem
Inorganic LED arrays face a challenge in achieving high contrast ratio due to light spill from 'ON' state pixels to neighboring 'OFF' state pixels, resulting in blurry images or compromised projected beam patterns.
Innovation Solution
The implementation of patterned reflective grids, which can be formed as reflective metal grids, dielectric reflectors, or distributed Bragg reflectors, enhances the contrast ratio by reducing light leakage between pixels through improved adhesion and light confinement, and can provide electrical contact to LED diode junctions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If individual LED pixels are transferred and attached to a controller backplane, then LED arrays can be formed with desired pixel density and area, but light spill occurs from ON state pixels to neighboring OFF state pixels resulting in degraded contrast ratio
Solution Approach 1:
A reflective grid structure is introduced as an intermediary element between adjacent LED pixels. This grid acts as a light redirector that intercepts stray light from ON pixels and redirects it away from neighboring OFF pixels, thereby preventing light spill while maintaining the transferred and attached manufacturing approach
Solution Approach 2:
The reflective grid extends vertically above the pixel plane, utilizing the third dimension (height) to manage light paths. By positioning reflective surfaces at elevated positions between pixels, the structure intercepts light in three-dimensional space rather than relying solely on two-dimensional pixel spacing
2Object-affected harmful factors
If a reflective grid is added to reduce light spill, then contrast ratio is improved, but device complexity increases due to additional structural components
Solution Approach 1:
The reflective grid is merged with the existing pixel array structure, where the grid lines are positioned to align with and integrate seamlessly between adjacent pixels. This merging approach allows the light management function to be achieved without adding entirely separate complex components, as the grid becomes part of the overall array architecture
Solution Approach 2:
The reflective grid structure serves multiple functions simultaneously: it acts as a light redirector to prevent spill, provides mechanical support for the pixel array, and can be designed to match the electrical contact requirements. This multi-functionality reduces the need for additional separate components, thereby limiting the increase in device complexity
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 patterned reflective grids effectively enhance the contrast ratio, leading to sharper images and better control over light distribution, while also improving adhesion of layers on the grid, resulting in improved light extraction efficiency and beam profile in LED arrays and displays.
Implementation Method 1
The pattern on the reflective grid may also improve adhesion between the reflective grid and one or more layers of material disposed on and attached to the reflective grid. The reflective grid may be formed, for example, as a reflective metal grid
Implementation Method 2
a grid of distributed Bragg reflectors (DBRs)
Data Source
AI summary
LED arrays comprise patterned reflective grids that enhance the contrast ratio between adjacent pixels or adjacent groups of pixels in the array. The pattern on the reflective grid may also improve adhesion between the reflective grid and one or more layers of material disposed on and attached to the reflective grid. The reflective grid may be formed, for example, as a reflective metal grid, a grid of dielectric reflectors, or a grid of distributed Bragg reflectors (DBRs). If formed as a metal grid, the reflective grid may provide electrical contact to one side of the LED diode junctions. This specification also discloses fabrication processes for such LED arrays.