Stacked LED Sub-Units for Brighter High-Density Micro Displays
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Solution Overview
Problem
Micro LED displays face challenges in handling small-sized light emitting diodes, particularly in mounting and replacing defective LEDs, due to their tiny size and the increased area occupied by sub-pixels, leading to reduced brightness and complex manufacturing processes.
Innovation Solution
The development of a display apparatus with a stacked structure of LED sub-units, where each sub-unit is independently driven, and connectors are used to connect them to electrode pads, allowing for efficient light emission without color filters, thereby increasing the light emitting area of each sub-pixel and simplifying the manufacturing process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If micro LEDs are arranged on a two-dimensional plane to implement various colors, then the display can show images with different colors, but the area occupied by one pixel is relatively increased
Solution Approach 1:
The patent transitions from a two-dimensional arrangement of sub-pixels to a three-dimensional stacked structure where multiple LED layers are vertically arranged. This dimensional change allows multiple color-emitting layers to occupy the same horizontal footprint, thereby reducing the pixel area while maintaining full-color display capability through selective light emission from different layers
2Productivity
If the area of each sub-pixel is reduced to arrange sub-pixels within a limited area, then more sub-pixels can be arranged, but brightness deteriorates
Solution Approach 1:
By stacking multiple LED layers vertically, the patent increases the light-emitting volume without expanding the horizontal area. Each layer can be optimized for specific color emission, and the combined light output from multiple layers compensates for the reduced individual sub-pixel area, maintaining or even enhancing overall brightness while achieving higher pixel density
Solution Approach 2:
The patent employs a composite structure with multiple LED layers emitting different colors (e.g., blue, green, red) stacked together. This composite approach allows each layer to contribute to the overall light output, with the synergistic effect of multiple layers providing sufficient brightness while keeping the horizontal footprint small
3Adaptability or versatility
If a large number of micro LEDs are disposed on one substrate, then the display can implement various colors, but it becomes difficult to handle and mount the small-sized light emitting diodes
Solution Approach 1:
The patent combines multiple LED layers into a single integrated stacked structure that functions as one unit. This merging approach simplifies handling and mounting operations, as the entire multi-color display element can be installed as a single component rather than individually mounting numerous separate micro LEDs, thereby improving ease of operation while maintaining full-color capability
4Adaptability or versatility
If sub-pixels are arranged on a two-dimensional plane, then various colors can be displayed, but the manufacturing process becomes complex
Solution Approach 1:
The stacked three-dimensional structure simplifies manufacturing by enabling batch processing of entire pixel arrays. Multiple LED layers can be fabricated and assembled in a more straightforward vertical stacking process compared to the complex lateral alignment and individual mounting required for two-dimensional sub-pixel arrangements, thereby reducing manufacturing process complexity while maintaining color display versatility
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 enhances the reliability and manufacturing efficiency of micro LED displays by allowing for independent driving of LED sub-units, reducing light interference, and suppressing secondary light generation, resulting in improved brightness and reduced mounting time.
Implementation Method 1
light generated from the first LED sub-unit is configured to be emitted to the outside of the display apparatus by passing through the second LED sub-unit and the third LED sub-unit
Implementation Method 2
light generated from the second LED sub-unit is configured to be emitted to the outside of the display apparatus by passing through the third 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.