Stacked LED Sub-Units for Brighter Micro Displays in Limited Pixel Area
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Solution Overview
Problem
Micro LED displays face challenges in handling small-sized light emitting diodes (LEDs) due to their tiny size, making it difficult to mount and replace defective LEDs, and reducing the luminous area to fit sub-pixels within a limited space, which affects brightness and increases complexity.
Innovation Solution
The use of a stacked structure of LED sub-units with a thin film transistor (TFT) substrate, where each LED sub-unit is independently driven, and connectors connect them to electrode pads, allowing for efficient light emission and simplifying the manufacturing process by reducing the need for individual pixel mounting and minimizing light interference between stacks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If sub-pixels are arranged on a two-dimensional plane to implement various colors, then the display can show different colors, but the area occupied by each pixel increases and the luminous area of each sub-pixel decreases
Solution Approach 1:
The patent transitions from a two-dimensional planar arrangement of sub-pixels to a three-dimensional stacked structure. Multiple LED stacks are arranged vertically, with each stack containing multiple sub-pixels at different heights. This vertical stacking allows the display to maintain smaller pixel footprints while increasing the effective luminous area through multiple emission layers, thereby resolving the contradiction between brightness and pixel area.
2Productivity
If micro LEDs are made very small to fit more pixels in limited space, then more pixels can be disposed on one substrate, but handling and mounting becomes difficult
Solution Approach 1:
The patent merges multiple sub-pixels into integrated LED stacks, where each stack functions as a unified component containing multiple sub-pixels of different colors. This consolidation reduces the number of individual handling operations required, as entire stacks can be mounted together rather than individually placing each micro LED, thereby improving ease of operation while maintaining high pixel density.
Solution Approach 2:
The patent implements a nested structure where multiple sub-pixels are contained within each LED stack, and multiple stacks are arranged within each pixel region. This hierarchical nesting allows for efficient space utilization and simplifies the mounting process by treating nested components as integrated units, resolving the contradiction between pixel density and handling difficulty.
3Area of stationary object
If multiple LED stacks are arranged close together to reduce pixel area, then the display area is maximized, but light interference between stacks increases
Solution Approach 1:
The patent introduces light blocking structures and color filter layers as intermediary elements between adjacent LED stacks. These intermediaries selectively block or filter light from specific stacks, preventing unwanted light interference while allowing desired light transmission. This enables close spacing of stacks to maximize display area without suffering from significant light interference issues.
4Adaptability or versatility
If the luminous area of each sub-pixel is reduced to fit more sub-pixels in limited space, then more colors can be displayed, but brightness deteriorates
Solution Approach 1:
The patent compensates for reduced sub-pixel luminous area by adding vertical dimension through multiple stacked layers. Each sub-pixel's light emission is augmented by additional sub-pixels at different heights within the same vertical column, effectively increasing the total luminous area available for each color channel without expanding the horizontal pixel footprint, thereby maintaining brightness while supporting full color display capability.
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 increases the light emitting area of each sub-pixel without expanding the pixel area, enhances reliability, and simplifies the manufacturing process, while preventing light interference and secondary light generation, leading to improved brightness and efficiency in micro LED displays.
Implementation Method 1
a first LED sub-unit disposed on the TFT substrate, a second LED sub-unit disposed on the first LED sub-unit, a third LED sub-unit disposed on the second LED sub-unit
Data Source
AI summary
A light emitting diode (LED) stack for a display including a first LED stack including a first conductivity-type semiconductor layer and a second conductivity-type semiconductor layer, a second LED stack disposed on the first LED stack, a third LED stack disposed on the second LED stack, an intermediate bonding layer disposed between the first LED stack and the second LED stack to bond the second LED stack to the first LED stack, an upper bonding layer disposed between the second LED stack and the third LED stack to couple the third LED stack to the second LED stack, and a first hydrophilic material layer disposed between the first LED stack and the upper bonding layer.