Low-E Coating with Dielectric Overcoat for Solar Heat Gain

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Solution Overview

Problem

Conventional coated articles for window applications often lack durability and fail to achieve a combination of high visible transmission, high solar heat gain coefficient (SHGC), and low emissivity, which are essential for both warm and cold climates.

Innovation Solution

A low-emissivity coating with an infrared reflecting layer of silver or gold, combined with a dielectric overcoat and undercoat, designed to increase SHGC and visible transmission while maintaining neutral color and low normal emissivity, comprising specific refractive index layers to enhance durability and performance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If conventional coated articles use traditional low-E coatings, then emissivity is reduced, but visible transmission and solar heat gain coefficient are compromised

Engineering Contradiction:

ImproveemissivityVSAvoidvisible transmission and solar heat gain

Core Design Contradiction:

Loss of energyVSUse of energy by moving object

Solution Approach 1:

The coating is divided into multiple functional layers: an infrared-reflecting layer (silver or gold) for low emissivity, dielectric overcoats with specific refractive indices (2.0-2.5) for enhancing visible transmission and SHGC, and dielectric undercoats for additional optical control. Each layer segment performs a specific function to collectively resolve the contradiction between energy reflection and light transmission.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent combines dissimilar materials with complementary properties: metals (silver, gold) for IR reflection, dielectric materials with refractive indices of 2.0-2.5 for optical enhancement, and contact layers for adhesion. This composite structure achieves simultaneous low emissivity, high visible transmission, and high SHGC by leveraging the unique properties of each material component.

Inventive Principle:

Principle #40Composite materials

2Use of energy by moving object

If dielectric overcoats with high refractive index are applied to increase SHGC and visible transmission, then optical performance is improved, but normal emissivity may increase

Engineering Contradiction:

Improvesolar heat gain coefficientVSAvoidnormal emissivity

Core Design Contradiction:

Use of energy by moving objectVSLoss of energy

Solution Approach 1:

The dielectric overcoats are engineered with specific local optical properties (refractive indices of 2.0-2.5) to selectively enhance visible transmission and SHGC in the solar spectrum while maintaining low emissivity in the thermal infrared range. The localized optical control at different wavelengths resolves the contradiction between improving solar energy transmission and maintaining thermal energy reflection.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent optimizes the refractive index parameter of dielectric materials (specifically 2.0-2.5) and layer thicknesses to achieve wavelength-selective optical performance. By changing these physical parameters, the coating enhances visible transmission and SHGC while preserving low emissivity, resolving the trade-off between solar energy utilization and thermal energy conservation.

Inventive Principle:

Principle #35Parameter changes

3Reliability

If multiple dielectric layers are added to enhance durability and optical performance, then coating robustness is improved, but manufacturing complexity increases

Engineering Contradiction:

Improvecoating durabilityVSAvoidcoating structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The coating is segmented into distinct functional layers (IR-reflecting metal layer, dielectric overcoats with refractive indices 2.0-2.5, dielectric undercoats, contact layers) where each segment contributes to durability or optical performance. This segmentation allows for targeted material selection and thickness optimization, improving overall reliability while managing complexity through functional modularity.

Inventive Principle:

Principle #1Segmentation

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 achieves high SHGC values of at least 0.60, high visible transmission of up to 85%, and low normal emissivity of no greater than 0.045, providing excellent properties for window applications in cold climates while maintaining durability.

Implementation Method 1

at least one infrared (IR) reflecting layer of a material such as silver, gold, or the like

Methodology Applied

Scientific EffectInfrared reflection: Reflection

Implementation Method 2

a dielectric overcoat designed to increase solar heat gain coefficient (SHGC) and visible transmission (Tvis) of the coated article

Methodology Applied

Scientific EffectRefraction: Refraction

Data Source

PatentUS10253560B2Coated article with IR reflecting layer(s) and overcoat for improving solar gain and visible transmission

Publication Date: 2019.04.09 GUARDIAN GLASS LLC

AI summary

A coated article includes a low-emissivity (low-E) coating. The low-E coating includes at least one infrared (IR) reflecting layer of a material such as silver, gold, or the like, and a dielectric overcoat designed to increase solar heat gain coefficient (SHGC) of the coated article. A dielectric undercoat may also be designed to increase SHGC of the coated article in certain example embodiments. In certain example embodiments, the overcoat and/or undercoat are designed to increase SHGC while also providing for desirably high visible transmission (TY or Tvis) and desirably low normal emittance (En).