UV Micro-LED Pixel Structure With Phosphor Conversion and Reflective Barriers
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Solution Overview
Problem
Micro-LED displays with chip sizes of 100 μm or less face issues such as rapid degradation of luminous efficiency in red LED chips, variations in electric characteristics leading to color irregularity due to differences in drive voltage and current between red, green, and blue LED chips, and increased manufacturing costs due to the time-consuming process of mounting micro LED chips by pick-and-place for each color.
Innovation Solution
A micro LED display configuration that includes micro LEDs emitting ultraviolet light with a wavelength of 405 nm or less, a reflective barrier member to enhance light extraction efficiency, a film-like wiring substrate connecting adjacent micro LEDs to form one pixel, and a wavelength conversion layer with phosphors converting ultraviolet light into red, green, and blue colors, thereby eliminating the need for different types of micro LEDs for each color.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If different types of micro LED chips (GaP-based red, InGaN-based green and blue) are used for each color, then color display capability is achieved, but electric characteristics vary causing color irregularity and control complexity increases
Solution Approach 1:
The patent changes the fundamental parameter of LED material composition by using only InGaN-based micro LEDs with wavelength 405 nm or less, eliminating the need for different material systems (GaP vs InGaN). This single-material approach ensures consistent electric characteristics while achieving full color display through wavelength conversion, directly resolving the color uniformity issue.
Solution Approach 2:
The patent introduces a wavelength conversion layer as an intermediary component that converts ultraviolet light from uniform InGaN micro LEDs into visible colors. This mediator enables color display without requiring color-specific LED chips, maintaining electric characteristic consistency while achieving the desired color versatility.
2Manufacturing precision
If pick-and-place mounting is used for each color of micro LED chip, then precise positioning is achieved, but manufacturing time increases and costs rise
Solution Approach 1:
The patent merges all micro LED chips into a single uniform type (InGaN-based, wavelength 405 nm or less) that can be mounted using a single pick-and-place process. This consolidation eliminates the need for separate mounting operations for different colors, significantly improving manufacturing speed while maintaining positioning accuracy through standardized chip dimensions and mounting procedures.
Solution Approach 2:
The patent creates a universal micro LED chip design that serves multiple functions - a single chip type with wavelength 405 nm or less can generate all colors through the wavelength conversion layer. This universal chip eliminates the need for color-specific chips and their associated separate mounting processes, improving both productivity and process simplification.
3Volume of moving object
If micro LED chip size is reduced to 50 μm or less, then display resolution is improved, but luminous efficiency degrades rapidly especially in red LEDs
Solution Approach 1:
The patent changes the wavelength parameter of the micro LEDs to 405 nm or less (ultraviolet range), which fundamentally alters the emission characteristics. This parameter change enables the use of InGaN-based materials with higher efficiency at small sizes compared to traditional red LED materials, maintaining luminous efficiency even at 50 μm or less chip size.
Solution Approach 2:
The patent introduces a wavelength conversion layer as a mediator that receives ultraviolet light from the miniaturized InGaN micro LEDs and converts it to visible wavelengths. This intermediary approach allows the use of highly efficient small-sized UV LEDs while achieving full color display, bypassing the efficiency degradation problem of miniaturized red LEDs.
4Manufacturing precision
If light distribution control units with partition walls are used, then light leakage to adjacent pixels is prevented, but light transmission in front surface direction is blocked reducing luminous efficiency
Solution Approach 1:
The patent uses a reflective barrier member that copies the light path by reflecting UV light from the micro LED side surfaces back toward the front surface. Instead of blocking light with partition walls, this reflective structure redirects light that would otherwise be lost, maintaining pixel isolation while preserving and even enhancing front surface luminous efficiency.
Solution Approach 2:
The patent converts the potentially harmful effect of side surface light emission (which could cause cross-talk) into a beneficial effect by using reflective barrier members to redirect this light toward the front surface. The light that might have been wasted or caused interference is now converted into useful front surface emission, improving overall luminous efficiency.
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 configuration enhances luminous efficiency and simplifies the manufacturing process by allowing mass transfer instead of individual pick-and-place mounting, reducing color irregularity, and maintaining high light extraction efficiency.
Implementation Method 1
a film-like wavelength conversion layer provided on the wiring substrate, and including phosphors that perform wavelength conversion of respective light from the three micro LEDs into red, green, and blue colors
Implementation Method 2
a reflective barrier member erected between the plurality of micro LEDs to reflect light from side surfaces of the micro LEDs
Data Source
AI summary
A micro LED display includes a first conductive-type electrode; a plurality of micro LEDs that are separately formed on the first conductive-type electrode and each configured to emit ultraviolet light with a wavelength of 405 nm or less; and second conductive-type electrodes formed on the plurality of micro LEDs, respectively. The micro LED display further includes a reflective barrier member erected between the plurality of micro LEDs to reflect light from side surfaces of the micro LEDs; a film-like wiring substrate having a wiring structure that is connected with the second conductive-type electrodes of three micro LEDs that are adjacent to each other, out of the plurality of micro LEDs, so as to constitute one pixel; and a film-like wavelength conversion layer provided on the wiring substrate, and including phosphors that perform wavelength conversion of respective light from the three micro LEDs into red, green, and blue colors. The side surfaces of the micro LEDs are formed into inclined surfaces such that widths of the micro LEDs gradually decrease from the first conductive-type electrode toward the second conductive-type electrodes. The reflective barrier member is erected parallel to a stacking direction of the plurality of micro LEDs and up to a height equal to the micro LEDs.