The team at Angstrom Technologies, Inc. believes a layered security approach is best when it comes to document security. Advanced optically variable pigments (OVPs) are one part of that solution.
The key to investing in the right OVPs for your document security is to make sure your provider has the expertise to manufacture a product that is nearly impossible to replicate using ordinary means and maintains its features under any situations your documents may face.
Read our ultimate guide to optically variable pigments to find out more details about their advantages, use cases, and how they combine with other layered security features for the best results.
Table of Contents
What Are Optically Variable Pigments?
Optically variable pigments (OVPs), also called color-shifting pigments, are highly specialized materials that change color depending on the angle of light. Optically variable inks or color-shift inks are made using these pigment, and achieve their unique properties through microscopic structures that manipulate light.
The reason OVPs are attractive in the security industry is that they can shift hues, creating a dynamic visual effect that captures attention while being difficult to replicate using ordinary means. A strong advantage of OVPs is that they do not require any detection device to see the effect. The color shift can be seen visually when the viewing angle changes and can be seen by the naked eye.
They are often used in applications where checking the authenticity of documents by the public is crucial and easy to accomplish using overt security features, such as with breeder documents, government-issued documents, currency, and retail industries where authentication protects branding.
The key to success with optically variable pigments is that they must utilize advanced manufacturing techniques like those employed by Angstrom Technologies, Inc. OVPs are complex and need exact processes to achieve the proper color shifts.
Importance in Document Security & Authentication
Optically variable pigments (OVPs) offer a reliable means to deter counterfeiting and enhance the integrity of important documents. Their dynamic properties allow for unique visual effects that can be easily verified by the naked eye, adding an extra layer of security that is effective, relatively permanent, and blends in with the aesthetics of the document.
Perhaps the most prevalent use of OVPs in action can be found in banknotes. Most countries incorporate OVPs into their currency designs to combat counterfeiting. For instance, the U.S. $100 bill features a brown inkwell on the front that changes to green when someone shifts the angle at which they look at the inkwell. Because the bill uses advanced OVPs with a complex design, it’s nearly impossible for counterfeiters to replicate accurately.
The importance of OVPs extends beyond banknotes to various other documents, such as passports and identification cards. By utilizing OVPs as part of a layered security approach, governments can ensure their documents are authentic.
How Optically Variable Pigments Work
The mechanism behind OVPs involves interference and diffraction of light. When light strikes these pigments, it reflects off different layers or structures within the pigment, causing certain wavelengths to cancel out or enhance each other, allowing them to interact with light in a way that produces striking color shifts as the viewing angle changes. This is largely accomplished through multilayer structures or iridescent particles, which reflect and refract light in intricate ways.
The chemistry of optically variable inks begins with the selection of pigments that exhibit specific optical properties. These pigments can be composed of organic or inorganic materials, often featuring layered structures that can selectively reflect different wavelengths of light.
It’s important to note what concentration or loading percentage of the OVPs is needed to achieve the desired visual effect. It may vary significantly whether the OVP is diffractive, holographic, or reflective, as to how much of the advanced pigments are used.
How OVPs Are Manufactured
As one example, multilayer thin films made from polymers or metal oxides can be engineered to create specific color effects. When light strikes these layers, it encounters boundaries between materials with different refractive indices. As a result, some wavelengths are reflected while others pass through, leading to the interference patterns that produce the characteristic color shifts.
Moreover, the formulation of optically variable inks often involves the incorporation of additives that enhance their performance. These can include dispersants, stabilizers, and resins, which help maintain the uniform distribution of pigments in the ink and improve adhesion to various substrates. The choice of solvent is also critical, as it affects the viscosity and drying properties of the ink. When applied to a surface, the solvent evaporates and/or cures, leaving behind the optically variable pigment particles. The interactions between the particles and the surface further contribute to the optical effects observed.
Diffractive, Holographic & Reflective OVPs
Optically variable pigments can use three main mechanisms to achieve their effects.
Diffractive
Diffractive pigments leverage the principles of diffraction to produce their color-changing effects. These pigments consist of micro- or nano-sized structures that create a grating pattern, which splits incoming light into various wavelengths. As the angle of incidence changes, the wavelengths that constructively interfere shift, resulting in a noticeable change in color.
The specific spacing and geometry of these diffracting structures can be finely tuned during the manufacturing process, allowing for a wide range of color effects. This characteristic makes diffractive pigments particularly useful in security applications, as they create distinct, difficult-to-replicate patterns that are visually striking and easy to verify.
Holographic
Holographic pigments, on the other hand, utilize holography principles to create three-dimensional color effects. These pigments are produced by recording interference patterns of laser light reflected off the surface of a medium, typically a photopolymer. When light interacts with these pigments, it reconstructs the original holographic image, leading to a dynamic visual display that changes with the angle of view.
The chemistry involved in producing holographic pigments often includes complex polymer formulations that allow for precise control over the holographic patterns. This technology is widely used in high-security applications, such as banknotes and identification documents, where it serves as an effective deterrent against counterfeiting.
Reflective
Reflective pigments employ a different mechanism, primarily relying on the reflection of light off their surface to produce color variations. These pigments typically consist of metallic or high-refractive-index particles that reflect specific wavelengths of light. The reflection occurs due to the interaction of light with the surface morphology and composition of the pigment.
Reflective pigments are often combined with transparent or translucent matrices to enhance their visual properties. While they may not exhibit the same dramatic color shifts as diffractive or holographic pigments, reflective pigments still play a crucial role in enhancing visual appeal and providing security features, particularly in printing and packaging.
Use Cases for OVPs
Optically variable pigments can be used in any industry that requires specific authentication protocols that the public can easily identify without using special tools.
Security for Government & Legal Documents
Government and legal document security is, perhaps, the most widely seen use of OVPs around the world by the public. A large majority of world currencies utilize optically variable pigments in some form as part of their overall security measures.
Passports are another common government-issued document that employs OVPs. The United States Passport uses optically variable ink on its biographical data page, where the holder’s information is printed. The ink’s color shift effect serves as a visual cue to help authorities quickly identify authentic documents. Similarly, European Union passports also use optically variable inks to display intricate patterns that change color and appear more vivid under specific lighting conditions.
On the state level, Texas birth certificates may employ OVPs as part of an overall deterrent to counterfeiting. North Carolina’s new driver’s licenses use optically variable pigments, and Montana’s driver’s licenses have OVPs that include the Ponderosa pines, the state name, and the state bird. This use case shows that OVPs are not just for paper or cotton cloth.
Brand Protection
Brands protect their products through OVPs in order to deter counterfeiting. This is particularly true in highly regulated industries or companies that sell luxury products. Companies whose products are counterfeited a lot can also employ OVPs as a deterrent.
One prevalent example of this comes from product packaging on USB drives. DataTraveler® Generation 4 (G4) USB drives use OVP on the outer casing of the drive itself. For example, when looking at “32 GB” head-on, it appears purple. Shift it to the side, and it turns green.
Electronics manufacturers use OVPs on warranty cards to deter counterfeit sales. This is particularly true for high-end electronics like computers and TVs.
Product Authentication
Luxury items and pharmaceuticals are two industries that utilize optically variable pigments on a regular basis.
High-end wine and spirits companies may use OVPs coupled with digital security measures or even RFID tags to showcase the authenticity of their products. A few wineries have even incorporated their grape’s DNA into the label as a way to authenticate their vintages.
In the mid-2010s, when the manufacture of meth was a problem in the United States, pharmaceutical companies turned to tighter security features on their packaging. The goal was to ensure their products were authentic, especially when local authorities instituted the IDing of people who bought these types of OTC medications to prevent them from converting cold medications into illegal drugs. Pharmacists and retailers could easily identify these packages as authentic by the OVPs mark located on the fold of the packaging, which would also indicate if the package was tampered with.
Advantages of OVPs
Advanced color-shifting inks have three distinct advantages in the security printing industry.
Visual Appeal
Because color-shifting inks can be made in many types of patterns and colors, they can be made visually appealing to the end user.
The advanced color-shifting ink does more than deter counterfeiting. It can exude a sense of exclusivity, perceived quality, and a higher value due to the craftsmanship of the product.
Difficult or Impossible to Replicate Using Ordinary Means
One of the main advantages of advanced optically variable pigments is that they are extremely difficult, if not impossible, to replicate using ordinary printing or copying methods. Counterfeiters attempting to reproduce this effect face significant hurdles, as traditional printing technologies, such as inkjet or laser printers, cannot replicate the multi-layered interference pigments required for the ink’s color shift.
The difficulty in replicating these inks also comes from the proprietary techniques used to produce them. Companies often utilize specialized materials and patented technologies that are tightly controlled with a high level of chain-of-custody protocols. No one can go to the local store to buy the items and equipment to make advanced OVPs off the shelf. Plus, it would take PhD chemists with advanced knowledge and experience to replicate advanced OVIs.
The pigments are manufactured under highly specific conditions, often involving the deposition of microscopic layers of materials like titanium dioxide or magnesium fluoride. These layers reflect and refract light in precise ways that create the color-shifting effect. Without access to these proprietary processes and materials, counterfeiters are unable to recreate the inks accurately, even if they possess advanced printing equipment.
Moreover, ordinary reproduction techniques, such as photocopying or scanning, fail to capture the dynamic nature of color-shifting inks. A static image or printout cannot mimic the way the ink changes color when viewed from different angles. Even high-resolution scanners only capture a single perspective, rendering the counterfeit obvious upon close inspection.
Durability
These pigments are engineered to maintain their color-shifting properties and structural integrity even when exposed to extreme environmental factors like sunlight, moisture, or wear and tear. The durability of OVPs stems from the complex multi-layered structure of their pigments, which are often embedded with robust materials such as metallic or dielectric layers. This composition not only ensures that the pigments continue to function properly under stress but also helps them resist fading or degradation, which is a critical feature in applications like currency and passports.
The manufacturing processes behind OVPs contribute significantly to their durability. The pigments are typically created using thin-film deposition techniques, where multiple layers of materials like titanium dioxide or silicon oxide are applied in precise patterns to create the desired optical effects. These materials are highly resistant to UV radiation, moisture, and physical abrasion, meaning that even prolonged exposure to sunlight or harsh environmental conditions will not diminish the pigments’ functionality. This makes OVPs a preferred choice for documents and products that must remain secure and legible over long periods.
Combining OVPs With Other Layered Security Features
While advanced optically variable pigments are robust overt security features in and of themselves, combining OVPs with other layered security features creates more robust document security.
OVPs & UV Taggants
Some advanced OVPs can combine with UV taggants in the same feature. For instance, the feature can be printed in a way that allows the UV taggant to appear in close proximity to the OVP feature. The OVP could also point to where the UV taggant is located on the document.
So, someone could verify the color-shifting ink as an overt security feature, but the UV taggant in the same feature would be a covert feature that can only be seen with a UV light tuned to the correct frequency.
OVPs With Track & Trace Technology
Optically variable inks can be paired with track and trace technology. For example, the OVP would be used as an overt security feature. Then, someone could use a smartphone to snap a photo of a barcode or QR code linked to a database to verify the authenticity of the document further. Let’s say the document links to a database the public can use after downloading the appropriate app. The end user would scan the code, and the app would verify the document. This technology could be used in a myriad of applications, including by authorities who have a link to the correct database.
OVPs With Holographic Features
Holographic features are similar to OVPs in that the observer must shift the view of the document to see the security feature properly. The technology used in a hologram is different than that of OVPs.
However, you might have a hologram that shifts in conjunction, in opposition, or in succession with the OVP. For example, you have to tilt the OVP at a 30-degree angle to see the color shift. This could be the exact same for the hologram. Or, you might need to tilt the OVP 30 degrees and the hologram 60 degrees to observe the effect in succession to each other. Any deviation from the standard patterns of observation could be construed as a forgery and need further authentication.
Improve Your Document Security With Angstrom Technologies, Inc.
Angstrom Technologies, Inc. has led the industry with advanced optical variable pigments, fluorescent dyes, and UV taggants for decades. Talk to us about your requirements, and we can collaborate with you to create a solution that strengthens your document security with robust solutions.
Contact us or call 859-282-0020 to start the conversation.
