Thermochromic Ink Layer Thermal Conductivity Enhancement
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Solution Overview
Problem
The low thermal conductivity and thermal capacity of materials used in portable data carriers result in a slower and less effective color change of thermochromic ink layers, making it difficult to achieve a controlled and visible thermochromic effect, which is essential for security and authenticity verification.
Innovation Solution
Introducing a material with improved thermal conductivity and heat capacity, such as graphite or phase change materials, below the thermochromic ink layer to enhance the color change process, allowing for faster, more homogeneous, and controlled color shifts, and potentially eliminating the need for black printing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If materials with low thermal conductivity and thermal capacity (such as PVC, PE, PET, ABS, PC) are used to manufacture the data carrier body, then the data carrier can be produced cost-effectively with appropriate security functionalities, but the color change of the thermochromic ink layer is slowed down and becomes less effective
Solution Approach 1:
A thermally conductive intermediary material (such as aluminum foil, metal powder, or graphite) is introduced between the thermochromic ink layer and the data carrier body. This intermediary acts as a heat transfer mediator, conducting thermal energy more efficiently to the thermochromic layer while allowing the data carrier body to maintain its cost-effective low-conductivity materials. The intermediary layer decouples the thermal performance requirement from the structural material selection.
2Ease of manufacture
If materials with low thermal conductivity and thermal capacity are used in the data carrier body, then manufacturing costs are reduced, but the entire thermochromic area is not uniformly subjected to color change
Solution Approach 1:
The thermally conductive intermediary material distributes heat uniformly across the thermochromic ink layer by conducting thermal energy laterally. This ensures that the entire thermochromic area experiences uniform temperature changes and achieves uniform color change, while the data carrier body can still be manufactured using cost-effective materials with low thermal conductivity.
3Ease of operation
If heating elements are provided underneath the thermochromic layer to control individual areas, then targeted color change is achieved, but the device complexity increases
Solution Approach 1:
Instead of embedding complex heating elements within the data carrier body, a simple thermally conductive intermediary layer (such as aluminum foil or metal powder) is placed between the thermochromic ink layer and the substrate. This intermediary passively distributes heat from external sources uniformly across the thermochromic area, achieving targeted color change control without requiring complex integrated heating systems.
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 introduced material accelerates and stabilizes the color change of thermochromic ink layers, providing improved authenticity verification and security features while maintaining cost-effective production processes.
Implementation Method 1
Thermochromism is the property of certain substances to change color when heated or cooled. This process can be designed to be reversible, which means that a color change that has been produced is reversed by appropriate heat supply or heat dissipation and the original color of the starting point is retained.
Implementation Method 2
The materials used to manufacture data carrier bodies have low thermal conductivity compared to metals. The thermal conductivity λ is the property of a solid to transport thermal energy by means of heat conduction in the form of heat. A material influencing the color change is introduced into the data carrier body below the thermochromic color layer... The introduced material accelerates and stabilizes the color change of thermochromic ink layers
Implementation Method 3
Phase change materials (PCM), in particular those based on paraffin, are particularly suitable as materials. The specific heat capacity depends on the temperature change range and is in the order of 4 - 6 kJ/(kg*K). This slows down the heating or cooling of the thermochromic color layer located above the heat-storing material
Data Source
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AI summary
The invention relates to a portable data carrier, a security element for a portable data carrier and to a method for influencing color change of thermochromic color layers on a portable data carrier, a thermochromic color layer being arranged in at least sections of the data carrier base and a color change of the thermochromic color layer being induced under the influence of a change in thermal energy.