Polycarbonate Security Document Composite for Colored Laser Personalization
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Solution Overview
Problem
Current methods for personalizing security and valuable documents, such as federal identity cards, are limited to black and white or grayscale representations using laser engraving, and there is a need for a technology that enables colored laser personalization without delamination and is easy to produce.
Innovation Solution
A composite of polymer layers made of polycarbonate with thermochromic leuco dyes, NIR activators, and solvents, which can be printed directly onto polycarbonate layers, allowing for multicolored personalization through NIR irradiation, and are stable at high temperatures to prevent delamination during lamination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If laser engraving is used for personalization, then high-resolution black and white or grayscale representations are achieved, but colored personalization is not possible
Solution Approach 1:
The patent divides the personalization process into multiple functional layers: a polycarbonate base layer, a printing layer with leuco dyes and developers, and a protective overlayer. Each layer performs a specific function - the printing layer contains color-forming components while the polycarbonate provides structural stability, allowing colored personalization without compromising the base material's properties
Solution Approach 2:
The patent utilizes thermochromic leuco dyes that change their chemical state and color properties in response to laser irradiation. The leuco dyes remain colorless in their initial state and transform to colored forms when exposed to specific laser parameters, enabling colored personalization through controlled parameter changes rather than traditional subtractive engraving
2Ease of manufacture
If a printing layer is added to enable colored laser personalization, then color capability is achieved, but delamination during lamination may occur
Solution Approach 1:
The patent creates a composite structure where the printing layer is formulated with polycarbonate as the base polymer and compatible solvents. This composite material approach ensures that the printing layer has similar thermal and mechanical properties to the polycarbonate base layer, enabling strong adhesion during high-temperature lamination processes while maintaining the color-forming functionality
Solution Approach 2:
The printing layer is designed with homogeneous composition using polycarbonate and compatible solvents that ensure uniform distribution of leuco dyes and developers. This homogeneity prevents differential thermal expansion and stress concentration during lamination, thereby preventing delamination while enabling colored personalization
3Ease of manufacture
If multiple layers are combined for colored personalization, then color capability is achieved, but manufacturing complexity increases
Solution Approach 1:
The patent merges multiple functional components (leuco dyes, developers, and polycarbonate binder) into a single integrated printing layer. This consolidation reduces the number of separate manufacturing steps and layers needed, simplifying the overall structure while maintaining the capability for colored laser personalization through the combined action of these components
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 enables the production of highly secure, monolithic composite documents that can be personalized in color, with the thermochromic layers reacting independently to produce cyan, magenta, and yellow colors, and additional layers provide heat insulation, UV protection, and durability, ensuring long-term security and durability.
Implementation Method 1
each preparation, especially ink, contains a specific NIR activator, also known as a photothermal conversion agent (CPA). Upon irradiation with a specific wavelength λ1, the respective NIR activator absorbs the NIR radiation, and the resulting heating causes the leuco dye LF1 to react with the developer E1 to form the dye F1
Implementation Method 2
The leuco dye LF1 contained in a preparation reacts with the developer E1, also contained in the preparation, upon heating to form a dye F1, preferably one of the colors cyan, magenta, or yellow
Data Source
Figure 1~3b
AI summary
The invention relates to a composite (11) comprising polymer layers (12) based on polycarbonate for security documents, wherein at least one polymer layer (12) is coated and in particular printed with a preparation (17) comprising a leuco dye (13), a NIR activator (14), polycarbonate, solvent and optionally a developer (15) to provide a thermochromic layer (16).