Protective Glazing Coating for High-Temperature Infrared Reflectivity

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Solution Overview

Problem

Existing thermal protective glazing solutions fail to maintain high infrared reflectivity and stability at high temperatures, particularly above 400°C, due to degradation of transparent conductive oxide layers used in infrared reflecting coatings.

Innovation Solution

A protective glazing system comprising a glass or glass ceramic pane with a transparent conductive oxide layer as the first layer and an X-ray amorphous oxide or nitride layer as the second layer, applied using vacuum deposition techniques, where the second layer stabilizes the first layer, preventing degradation and enhancing heat resistance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If a transparent conductive oxide layer is used as infrared reflecting coating, then high infrared reflectivity is achieved, but long-term stability at high temperatures deteriorates

Engineering Contradiction:

Improveinfrared reflectivityVSAvoidstability at high temperatures

Core Design Contradiction:

Loss of energyVSReliability

Solution Approach 1:

The patent applies a composite coating structure consisting of a transparent conductive oxide layer (such as ITO, IZO, or AZO) combined with an overlying oxide or nitride layer (such as SiO2, Si3N4, Al2O3, or TiN). This composite structure allows the TCO layer to provide high infrared reflectivity while the protective outer layer prevents degradation at high temperatures, thereby simultaneously achieving both high energy reflection and long-term thermal stability.

Inventive Principle:

Principle #40Composite materials

2Reliability

If high temperature resistance is improved by using stable oxide layers, then long-term stability is achieved, but infrared reflectivity deteriorates

Engineering Contradiction:

Improvestability at high temperaturesVSAvoidinfrared reflectivity

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The patent combines materials with complementary properties: the TCO layer (with free charge carriers) provides the infrared reflection function, while the overlying oxide or nitride layer provides thermal stability. The specific composition ratios and layer thicknesses are optimized to ensure the TCO layer maintains its electrical and optical properties even when exposed to high temperatures for extended periods.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The patent carefully controls parameters such as the thickness of each layer, the doping concentration of the TCO layer, and the stoichiometry of the oxide/nitride layer. By adjusting these parameters, the coating achieves optimal balance between infrared reflectivity and high-temperature stability, preventing degradation while maintaining energy reflection efficiency.

Inventive Principle:

Principle #35Parameter changes

3Ease of manufacture

If a simple single-layer coating is used, then manufacturing complexity is reduced, but both infrared reflectivity and high temperature stability cannot be achieved simultaneously

Engineering Contradiction:

Improvecoating structure simplicityVSAvoidinfrared reflectivity

Core Design Contradiction:

Ease of manufactureVSLoss of energy

Solution Approach 1:

The patent employs a relatively simple two-layer composite structure that can be deposited using conventional vacuum coating techniques. This structure is straightforward to manufacture while achieving both high infrared reflectivity (through the TCO layer) and high-temperature stability (through the protective oxide/nitride layer), making it suitable for industrial production of oven doors and fireplace glass.

Inventive Principle:

Principle #40Composite materials

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 system achieves high infrared reflectivity (>0.8) and long-term stability at temperatures up to 500°C, with minimal color variation and improved chemical resistance, suitable for applications in ovens and fireplaces.

Implementation Method 1

the optical properties are determined by the sheet resistance of the conductive layer and by free charge carrier absorption in the infrared spectral range

Methodology Applied

Scientific EffectFree charge carrier absorption: Absorption (EM radiation)

Implementation Method 2

a first layer is applied which consists of a transparent conductive oxide (TCO, for short)... and a second layer which is formed as an amorphous, in particular an X-ray amorphous oxide layer or nitride layer

Methodology Applied

Scientific EffectPhysical vapor deposition: Physical Vapour Deposition

Implementation Method 3

long-term stability against degradation at high temperatures (100 hours at 500° C.)... improved chemical resistance

Methodology Applied

Scientific EffectThermal stability: Thermal Insulation

Data Source

PatentUS11319245B2Coated protective glazing

Publication Date: 2022.05.03 SCHOTT AG

AI summary

A protective glazing is provided that has long-term stability against degradation under high temperatures. The protective glazing includes a glass or glass ceramic pane having two opposite faces and being transparent in the visible spectral range and an infrared radiation reflecting coating on at least one of the faces. The coating includes a first layer on the face and a second layer deposited on the first layer. The first layer is a doped transparent conductive oxide and the second layer is an X-ray amorphous oxide layer or of a nitride layer.