Low-E Vehicle Window Coating With Nanoporous Anti-Reflection Layer

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Solution Overview

Problem

Vehicle windows with emissivity-reducing coatings often suffer from interior light reflection issues, which can be distracting, especially in vehicles, and existing anti-reflection coatings may not provide sufficient mechanical and chemical stability or cost-effectiveness.

Innovation Solution

A vehicle window with an emissivity-reducing coating featuring a transparent conductive oxide layer combined with a nanoporous silicon oxide anti-reflection coating, applied using a sol-gel process, to minimize light reflection while maintaining thermal comfort and durability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Temperature

If an emissivity-reducing coating is applied to the interior surface of the vehicle window, then thermal comfort is improved by reducing heat transfer, but interior light reflection increases causing disturbing effects

Engineering Contradiction:
Improvethermal comfortVSAvoidinterior light reflection
Core Design Contradiction:
TemperatureVSObject-generated harmful factors

Solution Approach 1:

The coating is divided into multiple functional layers: an emissivity-reducing coating layer (containing transparent conductive oxide) and a separate anti-reflection coating layer (nanoporous silicon oxide). This segmentation allows each layer to perform its specific function independently - the TCO layer handles thermal radiation control while the nanoporous silicon oxide layer handles light reflection reduction, resolving the contradiction between thermal comfort and light reflection.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The invention uses a composite coating structure combining transparent conductive oxide materials with nanoporous silicon oxide. The TCO layer provides emissivity reduction for thermal management, while the nanoporous silicon oxide layer provides anti-reflection properties. This composite material approach enables simultaneous achievement of thermal comfort improvement and light reflection reduction.

Inventive Principle:
Principle #40Composite materials

2Object-generated harmful factors

If conventional anti-reflection coatings are used to reduce light reflection, then light reflection is reduced, but mechanical and chemical stability decreases

Engineering Contradiction:
Improvelight reflectionVSAvoidmechanical and chemical stability
Core Design Contradiction:
Object-generated harmful factorsVSReliability

Solution Approach 1:

The anti-reflection coating is made from nanoporous silicon oxide, where the nanoporous structure provides the necessary optical properties for light reflection reduction while the silicon oxide base material maintains high mechanical and chemical stability. The porous structure enables anti-reflection functionality without sacrificing the inherent durability of silicon oxide.

Inventive Principle:
Principle #31Porous materials

Solution Approach 2:

The refractive index of the anti-reflection coating is optimized by controlling the nanopore density and size in the silicon oxide matrix. By adjusting the porosity parameters, the coating achieves optimal anti-reflection performance across a wide range of incidence angles while maintaining the mechanical strength and chemical resistance of the silicon oxide framework.

Inventive Principle:
Principle #35Parameter changes

3Object-generated harmful factors

If multi-layer interference coatings are used to reduce light reflection, then anti-reflection performance is improved, but manufacturing complexity and cost increase

Engineering Contradiction:
Improvelight reflectionVSAvoidcoating structure complexity
Core Design Contradiction:
Object-generated harmful factorsVSDevice complexity

Solution Approach 1:

The invention extracts and simplifies the anti-reflection function by using a single nanoporous silicon oxide layer instead of multiple alternating high and low index layers. This single-layer approach achieves comparable or superior anti-reflection performance while dramatically reducing manufacturing complexity and eliminating the need for precise multi-layer thickness control.

Inventive Principle:
Principle #2Taking out (Extraction)

Solution Approach 2:

Instead of controlling multiple layer thicknesses and refractive indices in a complex multi-layer system, the invention simplifies the design by using a single layer with controllable porosity parameters. The nanopore density, size, and distribution are adjusted to achieve the desired anti-reflection performance, reducing the number of manufacturing parameters from multiple layer dimensions to primarily porosity control.

Inventive Principle:
Principle #35Parameter changes

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 effectively reduces interior light reflections, enhances mechanical and chemical stability, and lowers production costs, providing improved thermal comfort and visibility by minimizing heat transfer and reflections across a wide range of incidence angles.

Implementation Method 1

Anti-reflective coatings can be formed as a layer sequence with alternating layers of different refractive indices, whereby light reflection is reduced through interference effects

Methodology Applied
Scientific EffectInterference: Interference

Implementation Method 2

an anti-reflection coating based on nanoporous silicon oxide on the emissivity-reducing coating

Methodology Applied
Scientific EffectRefraction: Refraction

Implementation Method 3

Such coatings are also known as LowE coatings and have reflective properties against thermal radiation

Methodology Applied
Scientific EffectThermal radiation: Thermal Radiation

Implementation Method 4

the coating prevents the thermal radiation emanating from the heated pane from reaching the interior

Methodology Applied
Scientific EffectReflection: Reflection

Implementation Method 5

the porous silicon oxide layers can also be produced using sol-gel processes

Methodology Applied
Scientific EffectSol-gel process: Sol

Data Source

PatentEP4100375B1Vehicle window with reduced emissivity and light reflection
Publication Date: 2024.01.03 SAINT GOBAIN VITRAGE SA
  • EP4100375B1 patent drawingFigure 1~2
  • EP4100375B1 patent drawingFigure 3~4

AI summary

The invention relates to a vehicle pane with reduced emissivity and light reflection, at least comprising: a substrate (1) having an exposed interior-side surface (IV); an emissivity-reducing coating (10) provided on the interior-side surface (IV) and containing at least one layer (10.3) based on a transparent conductive oxide (TCO); and an anti-reflection coating (20) based on nanoporous silicon oxide on the emissivity-reducing coating (10).