Silver Halide Thermochromic Coating for Temperature Indication
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Solution Overview
Problem
Existing thermal indicators for heating articles, such as cooking utensils, are difficult to read due to confusion between color changes at elevated temperatures, and previous solutions like thermochromic pigments are sensitive to cyclability and not easily perceivable, especially for non-specialist users.
Innovation Solution
A coating with a thermochromic composition comprising silver halide compounds, combined with a fluorocarbon resin or inorganic/organic hybrid polymer binder, which exhibits reversible optical and colorimetric changes between 0°C and 400°C, providing clear and distinct color transitions within the human eye's sensitivity range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If thermochromic pigments (iron oxide type and perylene red with spinel black) are used to create temperature indication patterns, then temperature change can be detected, but the color confusion at elevated temperatures makes the indicator difficult to read and understand for non-specialist users
Solution Approach 1:
The patent applies color change principles by using silver halide compounds that undergo distinct optical and colorimetric transformations at different temperature ranges. The silver halide provides clear, contrasting color changes (e.g., from colorless to yellow, orange, red, or black depending on the specific compound and temperature reached), which are easily distinguishable by non-specialist users while maintaining precise temperature measurement capability.
Solution Approach 2:
The patent utilizes parameter changes by selecting specific silver halide compounds (such as silver chloride, silver bromide, silver iodide, or their mixtures) that exhibit predictable and distinct colorimetric transitions at specific temperature thresholds. By controlling the composition and concentration of these compounds, the patent achieves both precise temperature detection and visually distinct color changes that resolve the readability issue.
2Reliability
If CuMoW oxides are used as thermochromic pigment, then reversible color changes occur under temperature variation, but the pigment is particularly sensitive to cyclability and loses its metastable alpha phase after five cycles at most
Solution Approach 1:
The patent resolves the cyclability issue by changing the fundamental parameter of the thermochromic material from CuMoW oxides to silver halide compounds. Silver halides exhibit superior cyclic stability because their colorimetric transitions are based on reversible phase changes that do not involve metastable phases susceptible to degradation. The patent specifies that these compounds maintain their thermochromic properties over many heating and cooling cycles, thereby achieving both reliability and long duration of action.
Solution Approach 2:
The patent employs composite material principles by formulating the coating with specific compositions of silver halide compounds mixed with appropriate binders and stabilizers. This composite approach enhances the cyclability and durability of the thermochromic effect, ensuring that the color changes remain reversible and distinct even after repeated thermal cycling during cooking operations.
3Measurement precision
If semiconductors are used as thermochromic material, then progressive color change occurs with temperature increase, but the color evolution is limited and not very marked
Solution Approach 1:
The patent dramatically improves color contrast by replacing semiconductors with silver halide compounds that exhibit intense and distinct colorimetric transitions. These compounds can change from completely colorless or white at room temperature to vibrant yellow, orange, red, or black at elevated temperatures, providing high visual contrast that is easily perceived. This resolves the illumination intensity issue by ensuring that the color changes are marked and highly visible without requiring special lighting conditions.
4Ease of operation
If two patterns with thermochromic pigments are used in contiguous areas, then visual perception of temperature change is improved, but the red colors of both areas have chromatic values close to each other at room temperature making the indicator difficult to understand
Solution Approach 1:
The patent eliminates color confusion by using silver halide compounds that are either colorless or exhibit very pale colors at room temperature, in contrast to the vivid colors they display at elevated temperatures. This ensures that different pattern areas have maximum chromatic distinction at room temperature (appearing nearly identical or one appearing faint), but at cooking temperatures, each pattern displays its characteristic intense color, providing clear visual information without confusion.
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 offers a clear and readable temperature indication with improved color contrast and stability, allowing users to accurately monitor temperature changes without confusion, even after repeated use.
Implementation Method 1
a thermochromic composition exhibiting a reversible variation in optical and/or colorimetric properties when the coating is subjected, in part or in whole, to a variation in temperature
Data Source
Figure 1~3
AI summary
The invention relates to a coating comprising at least one functional decorative layer. The decorative layer comprises a thermochromic composition exhibiting a reversible variation of optical and/or colorimetric properties when part or all of the coating is subjected to a temperature variation between a cold temperature and a hot temperature, the cold temperature being between 0°C and 40°C and the hot temperature being between 80°C and 400°C, and comprising at least one thermochromic compound of the family of silver halides. The invention also relates to a functional decorative layer composition, to an article comprising the coating or the decorative layer composition, and to the use of the coating or the decorative layer composition as a temperature indicator.