Polymer Substrate Diffractive Tracks for Durable Document Authentication
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Solution Overview
Problem
Current security documents, particularly those using polymer substrates, face challenges with security features that are prone to detachment, wear, and counterfeiting due to adhesive degradation and surface-applied security features being susceptible to damage and removal for counterfeiting purposes.
Innovation Solution
Incorporating an ordered two-dimensional array of discrete laser-modified tracks within the polymer substrate sheet, which diffract light to form observable shapes or colors, providing robust and integral security features that are less susceptible to damage and counterfeiting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If security features are applied or adhered to the substrate surface, then the document can include security features, but the adhesive may degrade over time resulting in unintentional partial or total detachment of the device
Solution Approach 1:
The patent merges the security feature with the substrate by integrating diffractive optical elements directly into the polymer substrate through laser modification. This creates a unified structure where the security feature becomes an intrinsic part of the substrate rather than a separate adhered component, eliminating adhesive degradation issues entirely.
Solution Approach 2:
The patent transitions from surface-level security features to volumetric features by creating three-dimensional diffractive structures within the substrate depth. The laser-modified tracks extend through the substrate thickness, creating optical effects from within the volume rather than from the surface, thereby eliminating detachment risks.
2Reliability
If security features are applied to the substrate surface, then the document can include security features, but the surface-applied features may be more susceptible to wearing or abrasive forces
Solution Approach 1:
The security feature is merged with the substrate material itself through laser-induced modification. The diffractive structures are created as integral parts of the polymer matrix, making them as resistant to wear and abrasion as the substrate material, rather than being separate surface coatings that can deteriorate.
Solution Approach 2:
The patent moves security features from the two-dimensional surface to the three-dimensional volume of the substrate. The laser-modified tracks extend through the substrate thickness, creating volumetric diffractive structures that are protected by the substrate material and resistant to surface wear and abrasion forces.
3Reliability
If holographic features are removed from authentic documents, then counterfeiters can manufacture new counterfeit documents, but maintaining adhesive bonds to prevent removal is difficult over time
Solution Approach 1:
The patent eliminates the separable security feature structure by merging the diffractive optical elements directly into the substrate through laser modification. This creates a non-detachable security feature that cannot be removed for counterfeiting purposes, as it is an intrinsic part of the substrate itself rather than an adhered component.
Solution Approach 2:
The patent creates volumetric diffractive structures within the substrate that extend through the material depth, making them impossible to remove without destroying the substrate itself. This dimensional integration prevents the cutting and re-attachment operations used by counterfeiters.
4Adaptability or versatility
If polymer substrates are used for security documents, then modern documents can be produced, but security features are more confined to those that can be adhered to or printed upon the surface
Solution Approach 1:
The patent replaces mechanical surface application methods (adhesion, printing) with direct laser-induced modification of the polymer substrate. This substitution enables the creation of volumetric diffractive structures within the substrate that were previously impossible to achieve with conventional surface-based techniques.
Solution Approach 2:
The patent changes the physical state and optical properties of the polymer substrate through laser-induced modification. By altering the refractive index and creating volumetric structures within the substrate, the patent expands security feature capabilities beyond surface-level options while maintaining compatibility with polymer substrates.
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 laser-modified tracks enhance the security and integrity of documents by creating durable, optically discernable features that are difficult to remove or replicate, offering improved resistance to wear and counterfeiting attempts.
Implementation Method 1
generated by a beam-shaped laser with incident laser light distributed along a laser beam longitudinal axis extending through the substrate sheet
Implementation Method 2
each laser-modified track comprising an elongate volume of modified substrate material
Implementation Method 3
wherein for each two-dimensional ordered array the laser-modified tracks collectively diffract light impinging on the substrate sheet to form an observable shape, image, or region of colour
Data Source
Figure 1
Figure 2a~2c
Figure 3a~3c
AI summary
Disclosed are optical devices suitable as security devices for document authentication, which comprise at least one two-dimensional array of elongate laser-modified tracks extending within a document substrate that have a distinct optical refractive index compared to the unmodified substrate, which can exhibit excellent diffractive effects. Also disclosed are the use of such devices for document authentication and methods for their production.