Micro-LED Cavity Reflector Layout for Light Extraction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In micro-LED display devices with a cavity structure, the thickness of the planarization film and cover glass over the LED chip leads to total reflection at the interface between the cover glass and the air layer, resulting in light loss and decreased luminous efficiency and brightness.
Innovation Solution
The display device incorporates a reflective film on an inclined surface within an opening in the planarization film, surrounding the LED chip, and a second planarization film that fills the opening, with a height from the upper end of the inclined surface to the air interface set to 20 μm or less, optimizing light extraction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a cavity structure with reflective film is implemented, then optical extraction efficiency is improved, but device complexity increases due to additional film layers and structure
Solution Approach 1:
The patent applies thin film technology by forming a reflective film (30 nm to 100 nm thick) on the inclined surface of the cavity structure. This thin film serves as the reflective layer to redirect light, achieving optical extraction enhancement without requiring bulky or complex mechanical structures. The use of thin films maintains device compactness while providing the necessary optical functionality.
Solution Approach 2:
The patent employs an inclined surface (cavity structure) instead of a flat surface above the LED chip. This curved/geometric modification creates a non-planar interface that redirects light paths, reducing total internal reflection and improving light extraction. The inclined surface geometry is a form of curvature application that optimizes optical performance.
2Loss of energy
If planarization film thickness is reduced to 20 μm or less, then light extraction efficiency is improved, but manufacturing precision requirements increase
Solution Approach 1:
The patent specifies a precise parameter range for the planarization film thickness (20 μm or less) to optimize light extraction. By controlling this dimensional parameter within a specific range, the design achieves improved optical performance. This requires precise manufacturing control to maintain the thickness within the specified limit.
Solution Approach 2:
The patent employs spin coating technology to form the planarization film with controlled thickness. Spin coating is a process that uses rotational motion and fluid dynamics to deposit uniform thin films. This method allows precise control of film thickness through process parameters (rotation speed, coating material viscosity, etc.), enabling achievement of the 20 μm or less thickness requirement with good uniformity.
3Use of energy by moving object
If a reflective film is provided on the inclined surface, then luminous efficiency is enhanced, but ease of manufacture decreases due to additional processing steps
Solution Approach 1:
The patent combines the reflective film formation step with the existing planarization film deposition process. Both films are formed using similar thin film deposition techniques (such as spin coating or sputtering) in sequence, allowing integration of multiple functions (planarization and light reflection) into a unified manufacturing flow. This merging reduces the number of separate process modules required.
Solution Approach 2:
The reflective film is designed to reflect specific wavelengths of light while allowing other wavelengths to pass through. The optical properties (reflectivity spectrum) of the film are engineered to match the LED emission characteristics, creating a wavelength-selective reflective layer that enhances luminous efficiency by redirecting useful light wavelengths.
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 brightness by reducing light loss due to total reflection, allowing more light to be extracted from the display device.
Implementation Method 1
a reflective film provided on an inclined surface inside the opening in the first planarization film
Implementation Method 2
the thickness of the planarization film and cover glass over the LED chip leads to total reflection at the interface between the cover glass and the air layer, resulting in light loss
Data Source
AI summary
A display device includes a first planarization film including an opening, a reflective film provided on an inclined surface inside the opening in the first planarization film, an LED chip surrounded by the reflective film and provided inside the opening, and a second planarization film provided on the first planarization film, surrounding the LED chip, and filling the opening, wherein a height from an upper end of the inclined surface of the first planarization film to an interface with air in the second planarization film is 20 μm or less.