Vertically Stacked Microdisplay Panel Without Color Filters
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Solution Overview
Problem
Conventional microdisplay panels face challenges in mass-producing ultra-small micro-LEDs with high resolution and high luminance due to difficulties in ultra-fine arrangement, low yield, and the need for a color filter, which affects color quality and process complexity.
Innovation Solution
A vertically-laminated microdisplay panel that eliminates the need for a color filter by using a back wafer with CMOS electrode pads and vertically stacked LED stacks that emit specific colors, employing ceramic materials for bonding and etching to improve yield and reduce electrical short circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional microdisplay panels use ultra-small micro-LEDs with pixel size less than 5 μm, then high resolution and high luminance are achieved, but mass production becomes difficult due to ultra-fine arrangement difficulties and low yield
Solution Approach 1:
The patent transitions from planar arrangement of micro-LEDs to vertical stacking configuration. Multiple micro-LED chips are stacked vertically along the thickness direction, with each chip emitting a different color (red, green, blue). This vertical dimension enables high-resolution color display while simplifying the manufacturing process, as the stacked structure can be produced using standard LED fabrication techniques followed by vertical assembly, avoiding the need for ultra-fine lateral positioning.
Solution Approach 2:
The display panel is segmented into multiple independent micro-LED chips stacked vertically, where each chip is responsible for emitting a specific color. This segmentation allows each chip to be manufactured and tested independently using conventional LED processes, then assembled vertically. The segmentation approach enables high production yield since defects in one chip do not necessarily affect the others, and facilitates mass production through modular assembly.
2Illumination intensity
If a color filter is used in conventional microdisplay panels, then color display is achieved, but color quality deteriorates and process complexity increases
Solution Approach 1:
The patent extracts and removes the color filter component from the display structure. Instead of using a color filter to select wavelengths, the invention directly emits pure spectral colors from individual micro-LED chips (red, green, blue) stacked vertically. Each micro-LED chip inherently emits a narrow spectral width light corresponding to its bandgap energy, eliminating the need for color filters and associated complex alignment and bonding processes.
Solution Approach 2:
Different regions (vertical positions) of the display structure have specialized functions: the bottom micro-LED chip emits red light, the middle chip emits green light, and the top chip emits blue light. Each chip is locally optimized for its specific color emission characteristics. This local quality approach enables pure color emission without requiring global color filtering, simplifying the overall device structure and improving color quality.
3Reliability
If metal materials are used for bonding and electrode pads, then electrical conductivity is achieved, but electrical short circuits increase and reliability decreases
Solution Approach 1:
The patent employs composite material strategy by using ceramic materials (such as aluminum oxide or aluminum nitride) for bonding layers and electrode pads instead of conventional metals. These ceramic materials provide sufficient electrical conductivity for device operation while offering superior electrical insulation properties that prevent short circuits between adjacent chips and layers. The composite structure combines the electrical functionality needed for operation with the insulation properties needed for reliability.
Solution Approach 2:
The invention uses ceramic bonding layers and electrode structures that, while providing excellent electrical insulation, can be manufactured using standard ceramic processing techniques. These ceramic components replace expensive and problematic metal interconnects, offering a cost-effective solution that improves reliability through inherent electrical insulation while maintaining manufacturability.
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 solution enhances color quality, productivity, and enables mass production of high-resolution microdisplays with ultra-fine pixels by using ceramic materials and etching techniques, reducing defects and improving reliability.
Implementation Method 1
a plurality of light-emitting diode (LED) stacks of which a plurality of light-emitting portions and a plurality of bonding layers are vertically stacked on the back wafer
Implementation Method 2
a plurality of bonding layers are vertically stacked on the back wafer
Data Source
AI summary
The present invention relates to a vertically-laminated microdisplay panel requiring no color filter, the panel comprising: a back wafer, the top surface of which has multiple CMOS electrode pads aligned thereon; multiple LED laminates, each of which includes multiple light emitting units and multiple bonding layers vertically laminated on the back wafer, and which are aligned on the multiple CMOS electrode pads, respectively; and a common electrode formed on the multiple LED laminates, wherein each of the multiple LED laminates emits only a particular color by having a short passage formed through at least one light emitting unit among the multiple light emitting units to bypass current so as to prevent the current from being injected into the light emitting unit.