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.