Holographic images for brand protection and document authentication
Holographic images have been in use to protect security documents since the beginning of the 80’s. They were first used to protect MasterCard and VISA credit cards. The first holographic company was established in USA and later in Europe. For the last 20 years holography became a powerful industry. Many new companies specialized in security holography and packaging appear in America, Asia and Europe.
The reasons for using holograms and holographic products:
1. Security: Hologram images are impossible to copy or imitate by traditional printing equipment. Holograms are easily recognizable by the end user. Additional tricks like micro text, hidden images and other security features make them a unique optical security device.
2. Promotional effect: Holograms have an attractive appearance and are eye-catching. There is an advertising effect if a name or a logo is on the hologram. Holograms make the goods look more luxury and expensive. Customers usually trust in products with holograms.
3. Cost: When purchased in large quantities, security holograms are a cost-effective method of adding an overt authentication device to an item.
Nowadays security holography develops mainly in the following directions:
1. High Security Applications – Banknote and Document protection, lottery tickets, retail vouchers, tax stamps, personal documents (passports, visas, ID cards, driving licenses, diplomas), vehicle registration, credit cards, phone cards, checques, transport and insurance documents, certificates.
2. Brand Authentication and promotion – Alcohol and tobacco products, pharmacy, drugs, foods, fashion wear, sport goods, spare parts, jewelry, watches, mobile phones, electrical and electronic components, toys, audio and video, software.
The mass holograms production includes chain of processes resembles all other known printing technologies and goes through well-known stages: Design, Prepress, Printing, Finishing etc.
In some of the stages standard equipment is used or adapted, such as slitting and rewinding, kiss-cutting, layering, personalization and numbering, hot-stamping or laminating. The artwork is projected on well-known software products like Adobe or Corel platforms.
But some operations are different. Here we describe specific processes like Hologram origination, creating of Embossing tools and Hologram embossing, which are basic in holography. They differ holographic production from standard printing processes.
Creating a holographic images is process called Hologram Origination or Hologram Mastering. The result is single hologram recorded onto photo-resist.
Different technics for mastering are known by different names or brands on the Security holograms market: 2D/3D holograms, Dot-Matrix holograms, E-beam holograms etc. They create different types of holographic images or DOVE.
There are table top systems, easy to operate and could be managed by one operator. Other systems combines the work of a team of specialists – mathematicians, physicists, designers, engineers. Every Holographic origination studio develops his own security features and have different security level.
Generally we have two types of holograms: Analog and Digital (computer generated)
The old school Analog holograms have been created by classical way. Like in the analog photography they are recorded image of the object onto photosensitive material – glass plate with photo-resist layer. The difference between the photographic and holographic images is that the hologram consist more information about the object. Holograms need more resolution. What because it’s necessary to have special studio placed in dark room, special light source – LASER, optical vibro-isolated table, special optics, etc.
Modern holograms are computer-generated. They do not need real objects. In the design stage we create the object using computer. The result is digital format artwork file. The object is vector-format multi-layer color picture.
Then we must convert the Artwork to a real hologram. This process needs special equipment and software, which records original image onto glass plate with photo-resist. After photo-resist developing, the result is Master hologram.
The surface after the developing became a collection of microscopic peaks and valleys.
In spite of the hologram type, recording method, equipment and security level, all types of Master holograms have a similar structure – micro-relief.
The hologram manufactures use this micro-relief structures in the mass production of the holograms. Process of printing is called Hologram embossing.
Printing machines in mass holograms production are reel-to-reel equipment that use printing nickel forms and high pressure and temperature to print the holograms.This process is called Hologram embossing.The embossing (printing) machines transfer the micro-relief created by Master origination to special materials. Thin nickel replica is used to press surface pattern from Work shim into a plastic foil. No ink is used, only temperature and pressure.
The embossed pattern in the foil is provided with a very thin reflective layer of aluminum or another metal, like gold or chromium, which transforms the transmission hologram into a reflection hologram. In spite of the thinness of the metal layer, such embossed reflection holograms are completely opaque. Semitransparent alternatives can be achieved by the application of high-refractive-index layer (ZnSe, TiO2) as well as partially metallized layers, which render so-called semitransparent overlays or see-through holograms.
The first step in mass hologram production is to create printing plates called Holographic shims.
Printing process in Holography, called Hologram embossing, transfers the microscopic surface relief created during the Mater origination onto special embossing base materials.
The process of preparing tools for mass hologram production pass through the following steps:
Converting Master hologram from photo-resist to metal – usually silver;
Creating a nickel replica using electroforming process;
Multiplying a single image from a nickel original to a plastic base (recombining);
Converting multiple images from plastic to nickel. This product is called a Master shim;
After that the Master shim is used as an original for the reproduction of Working shims using electroforming again.
Electroforming and Recombining
Electroforming is the process of copying holographic images. Depend of task it maybe converting image from photo-resist or plastic to metal (nickel), or just metal-metal copying.
Recombining is the process also known as step and repeat, multiply the single image from Master hologram. The result is big size holographic plastic plate -in narrow web embossing usually up to 12″x12″
Electroforming and recombining complete prepress process for mass production of holograms. Work shims are used as instruments for embossing.
After embossing, depending on the end product, embossed foil gets through some additional operations: laminating, die cutting, adhesive coating, slitting, rewinding. Holograms can be applied to a product as an adhesive label, hot-stamped onto an item, used as a thread or tape, or used as an over-laminate of a product.
For high security applications security printers use different additional processes like numbering and selective demetalization, hot foil stamping, laminating.
Modern holography dates from 1947, when Dennis Gabor, a scientist researching the ways to improve the resolution of the electron microscope, developed what he called holography. In fact, in 1948 he coined the term hologram from the Greek words “holos”, meaning “whole,” and “gramma”, meaning “message”. Gabor did not have at his disposal coherent light source needed for continuing his work. Thirteen years later, in 1960, the LASER was invented and the serious work in holography began. In 1971 Dr. Dennis Gabor was awarded the Nobel Prize in Physics for his work in holography.
Two researchers, Emmett Leith and Juris Upatnieks, from the University of Michigan, in 1962, theorized that holography could be used as a three dimensional visual presentation. These individuals decided to apply Gabor’s theory with the newly invented laser light sources. The result was the first laser transmission hologram of 3D objects. These transmission holograms produced images with clarity and realistic depth. Unfortunately, these transmission holograms required laser light to view the holographic image. The work of Leith and Upatnieks led to standardization of the equipment used to make holograms. Today, thousands of laboratories and studios possess the necessary equipment: a continuous wave laser, optical devices (lens, mirrors and beam splitters) for directing laser light, a film holder and an isolation table on which exposures are made. Stability is absolutely essential because movement as small as a quarter wave-length of light during exposures of a few minutes or even seconds can completely spoil a hologram. The basic off-axis technique that Leith and Upatnieks developed is still the staple of holographic methodology.
In 1960 the pulsed-ruby laser was developed by Dr. T.H. Maimam of the Hughes Aircraft Corporation. This laser system (unlike the continuous wave laser normally used in holography) emits a very powerful burst of light that lasts only a few nanoseconds (a billionth of a second). It effectively freezes movement and makes it possible to produce holograms of high-speed events, such as a bullet in flight, and of living subjects. The first hologram of a person was made in 1967, paving the way for a specialized application of holography: pulsed holographic portraiture.
Like so many scientific advancements, holography was simultaneously being developed by other scientists. It was a Russian, Uri Denisyuk, who, in 1962, brought the work of Gabriel Lippmann (1908 Nobel Laureate) to holography and produced the first white-light reflection holograms that could be viewed in ordinary incandescent light bulb.
The 1967 World Book Encyclopedia Science Yearbook contained what is arguably the first mass-distributed hologram, a 4″x3″ transmission view of chess pieces on a board. An article describing the production of the hologram and basic information about the history of holography accompanied it. A .05 watt He-Ne laser was used on a nine-ton granite table in a 30-second exposure to make the original from which all the copies were produced.
The next important steps in the development of the holography were made by Stephen Benton, who, in 1968, invented white – light transmission holography. White-light holography allows the image to be viewed in ordinary white light. Undoubtedly, it was the brilliant rainbow colors that attracted artists to this new holographic technology. This type of hologram can be viewed in ordinary white light creating a “rainbow” image from the seven colors which make up the white light. This type of hologram was called “rainbow hologram”. The most important result of Stephen Benton’s work was that it led to the ability to mass-produce holographic images using optical embossing techniques. Embossing allowed the images to be reproduced by a press that stamped the image onto plastic surfaces.
With this technique, developed by Michael Foster in 1974 and brought to commercial viability by Steve McGreww in 1979, holographic information is transferred from light sensitive glass plates to nickel embossing shims. The holographic images are “printed” by stamping the interference pattern onto plastic. The resulting hologram can be duplicated millions of times for a few cents apiece. Consequently, embossed holograms are now being used by the publishing, advertising, packaging, banking and security industries.