Refrigerator door/window
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Solution Overview
Problem
Refrigerator doors with multiple glass panes and low-E coatings suffer from reduced visible light transmission, leading to decreased marketing value and impulse sales due to increased reflectance and thermal insulation needs.
Innovation Solution
A combination anti-reflective (AR) and low-emissivity (low-E) coating using indium-tin-oxide (ITO) between silicon oxynitride and silicon oxide dielectric layers, which reduces visible reflectance while maintaining energy efficiency by reflecting infrared radiation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If multiple glass panes and low-E coatings are incorporated to increase thermal insulation, then energy efficiency is improved, but visible light transmission is reduced
Solution Approach 1:
The patent combines AR coating functionality and low-E coating functionality into a single integrated coating structure. The coating includes a TCO layer (indium tin oxide) sandwiched between two dielectric layers (silicon oxynitride and silicon oxide), which simultaneously provides anti-reflective properties and infrared reflection capabilities, eliminating the need for separate coatings and reducing overall light transmission loss.
Solution Approach 2:
The invention uses a composite coating structure consisting of multiple functional layers: a transparent conductive oxide layer (indium tin oxide) combined with dielectric layers (silicon oxynitride and silicon oxide). This composite material approach allows the coating to exhibit both AR properties (reducing visible reflectance) and low-E properties (reflecting infrared radiation), thereby maintaining high visible light transmission while providing thermal insulation.
2Loss of energy
If more low-E coatings are applied to increase infrared reflection, then thermal insulation is improved, but visible reflectance increases making merchandise harder to see
Solution Approach 1:
The coating structure is designed with different layers having specific optical properties tailored to different wavelength ranges. The TCO layer primarily reflects infrared radiation, while the dielectric layers are optimized to minimize visible light reflectance. This localized functional distribution allows the coating to reflect thermal radiation without significantly increasing visible reflectance, keeping merchandise visible to customers.
Solution Approach 2:
The invention optimizes the refractive indices and thicknesses of the coating layers to achieve desired optical performance. By carefully selecting the refractive index of the TCO layer (between 1.8-2.0) and the thickness of each layer, the coating minimizes visible reflectance while maintaining high infrared reflection capability, thus reducing visible reflectance without compromising thermal insulation.
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
Enhances energy efficiency and visible light transmission through refrigerator doors, making merchandise behind the doors more visible to customers while minimizing thermal loss.
Implementation Method 1
a transparent conductive layer (e.g., ITO) that reflects IR so as to also function as a low-E coating
Implementation Method 2
a combination anti-reflective and low-E coating on an interior surface of the first glass substrate
Data Source
Figure 1(a)
Figure 1(b)
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AI summary
Refrigerator doors (which includes freezer doors) are provided for use in display areas where refrigerated merchandise (e.g., frozen or chilled food) is displayed. It is desired to increase energy efficiency of the doors and thus of the refrigerated display system, while at the same time reducing visible reflectance from the doors to make it easier for customers to see merchandise which is being displayed behind the transparent doors. Refrigerator doors according to certain example embodiments of this invention include one or more AR coatings, some of which may include a transparent conductive layer (e.g., ITO) so as to also function as a low-E coating.