Direct Embossing of Optically Variable Devices in Plastic Strips
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Solution Overview
Problem
The existing methods for manufacturing secure cards with optically variable devices, such as holograms, require a secondary film and subsequent lamination, which increases complexity and cost, and poses a security risk due to potential separability of layers, and often necessitate a protective topcoating.
Innovation Solution
A method involving the direct embossing of an optically variable device into an optically transparent plastic strip during an extrusion process, using a thermoplastic resin like polycarbonate, with metallization and laser engraving, to create a secure and integral security feature within the strip.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a secondary film is used to embed the diffractive structure, then the optically variable device can be formed, but the device complexity and manufacturing cost increase
Solution Approach 1:
The patent combines the diffractive structure formation and the plastic strip manufacturing into a single integrated process. The embossing rollers directly form the optically variable device within the plastic strip material itself, eliminating the need for a separate secondary film and lamination process. This merging of processes reduces device complexity while maintaining security feature integrity.
Solution Approach 2:
The plastic strip material serves multiple functions simultaneously: it provides the structural base of the card and embeds the security feature (diffractive structure) within its matrix. This multi-functionality eliminates the need for separate security film layers, reducing overall construction complexity while enhancing security through integral embedding.
2Reliability
If a secondary film is laminated to the plastic overlay, then the diffractive structure can be protected, but a separable layer is created that poses a security risk
Solution Approach 1:
The diffractive structure is merged with the plastic strip material through direct embossing during extrusion. The security feature becomes an integral part of the strip's internal structure rather than a separate laminated layer, eliminating any separable interfaces that could be exploited for counterfeiting while maintaining optical functionality.
Solution Approach 2:
The optically variable device is nested within the plastic strip material matrix. The diffractive structure is embedded inside the bulk material rather than being applied as a surface layer, making it impossible to separate or remove without destroying the entire strip, thus enhancing security stability.
3Strength
If a protective topcoating is applied to the diffractive structure, then the structure is protected from damage, but the manufacturing complexity increases
Solution Approach 1:
The protective function is merged with the plastic strip material itself. The bulk plastic material provides inherent protection to the embedded diffractive structure, eliminating the need for additional protective topcoating layers. The strip material acts as both the substrate and the protective envelope for the security feature.
Solution Approach 2:
The protective topcoating function is extracted from the multi-layer construction and replaced by the inherent properties of the plastic strip material. The material composition and structural integrity of the strip itself provide the necessary protection, simplifying the overall construction by removing redundant protective layers.
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
This approach reduces complexity and cost, enhances security by embedding the diffractive image within the plastic strip, making it difficult to alter or remove without damaging the strip, and eliminates the need for a protective topcoating.
Implementation Method 1
extruding a polymer resin to form an optically transparent sheet
Implementation Method 2
The embossed optically transparent strip is then cooled and bonded to the face of a secure card or document
Implementation Method 3
diffractive structures, such as holograms, are added to a secondary film
Data Source
Figure 1
Figure 2~3
Figure 4
AI summary
A method for the manufacture of a polymer strip (50) useful to secure information contained on a face of a card includes the steps of extruding a polymer resin to form an optically transparent strip and then embossing an optically variable device (32) into a first surface (34) of this optically transparent strip. A time from when the optically transparent strip exits an extruder until embossing is effective to prevent the optically transparent strip from cooling to a temperature below 120°C. Subsequent to embossing, the optically variable device (32) may be entirely or partially metalized (36). Alternatively, or in addition, to the metallization (36), security features may be formed into that first surface (34).