NIR Reflective Coating for LCD Thermal Management
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Solution Overview
Problem
Liquid crystal display (LCD) technology faces challenges in high-temperature applications due to the loss of liquid crystalline orientation above 50 °C, leading to reduced operability and the need for complex and costly heat dissipation methods, especially in outdoor environments where sunlight exposure causes significant near-infrared (NIR) radiation-induced heating.
Innovation Solution
A coated article with 6 to 20 alternating layers of SiO2 and ZrO2 or Nb2O5, topped with a TiO2 layer, is applied to a substrate, providing NIR reflectivity while maintaining optical transparency in the visible range, thus reducing heat absorption and allowing for effective temperature management without additional cooling equipment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If mechanical heat dissipation methods (fans) are used to maintain LCD operability at high temperatures, then the LCD can operate above 50°C, but the device complexity, operating cost, and bulk increase significantly
Solution Approach 1:
The patent replaces mechanical heat dissipation systems (fans, pumps) with a passive optical coating system that reflects near-infrared radiation. The multi-layer coating on the substrate reflects NIR wavelengths before they can heat the LCD, eliminating the need for active mechanical cooling while maintaining operability at elevated temperatures
Solution Approach 2:
The patent extracts the heat rejection function from the mechanical cooling system and transfers it to the optical coating. By reflecting NIR radiation at the surface level through the coating layers, the system removes harmful thermal energy before it penetrates to the LCD, separating the heat rejection function from active mechanical components
2Loss of energy
If a NIR-reflective coating is applied to maintain LCD temperature, then heat absorption is reduced, but the manufacturing complexity increases due to multiple alternating layers
Solution Approach 1:
The patent segments the coating into multiple alternating layers of different materials (e.g., SiO2 and TiO2, or other oxide combinations) with specific thicknesses. Each layer contributes to the overall NIR reflection through constructive interference, achieving superior thermal protection that cannot be obtained with single-layer coatings
Solution Approach 2:
The patent employs composite material structures with alternating layers of materials having different optical properties. The combination of materials like SiO2 (low refractive index) and TiO2 (high refractive index) creates a photonic crystal structure that selectively reflects NIR wavelengths while maintaining visible light transmission
3Illumination intensity
If the substrate is exposed to direct sunlight behind glass enclosure, then the on-surface temperature rises above 60°C, but the LCD cannot operate at such temperatures
Solution Approach 1:
The patent converts the harmful NIR radiation from sunlight into a reflected energy that never reaches the LCD. The coating system is specifically designed to reflect the NIR portion of the solar spectrum while allowing visible light to pass through, effectively using the solar energy itself to signal which wavelengths need reflection
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 coating effectively reflects over 50% of NIR radiation while transmitting over 80% of visible light, keeping LCDs within a safe temperature range without the need for mechanical heat dissipation, enhancing their operational reliability in high-temperature conditions.
Implementation Method 1
6 to 20 alternating layers of SiO2 and one of ZrO2 or Nb2O5
Implementation Method 2
coating that are substantially reflective to electromagnetic radiation in the near infrared region of the spectrum
Implementation Method 3
substantially transparent to electromagnetic radiation in the visible region of the spectrum
Data Source
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AI summary
A coating composition comprising 6 to 20 alternating layers of SiO2 and one of ZrO2 or Nb2O5 wherein the thickness of each individual layer is about 70 nm to 200 nm is described. Also described is a substrate comprising a coating on at least a first major side thereof, the coating comprising 6 to 20 alternating layers of SiO2 and one of ZrO2 or Nb2O5 wherein the thickness of each individual layer is about 70 nm to 200 nm. The substrate can be glass, plastic, or metal. Also disclosed herein are methods of making the coated substrate. The coatings have good optical transparency and NIR reflectivity.