All types of holograms (DOVIDs) are a collection of microscopic peaks and valleys (interference patterns) on the plate surface. The holographic interference pattern can be recorded in a photoresist that after development contains the pattern as a microscopic surface relief. From this relief pattern a nickel replica is derived by electroplating. Thin nickel replica is used to press this surface pattern into a plastic foil at an elevated temperature. This process is called hologram embossing. 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.
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.
The production of holograms gets through the following steps:
The first step is making the original hologram image called Master hologram. This process differs holography production from standard printing processes. The process needs special optical equipment, which records original image onto photo-resist. After developing glass plate with photo-resist, the result is Master hologram.
Electro-forming and recombining
Electro-forming – the process converts image from photo-resist or plastic to metal (nickel). Recombining – the process of multiplying a single image from nickel original to plastic base. Step by step:
Converting image from photo-resist to nickel; Multiplying a single image from a nickel original to a plastic base;
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 Work shims.
Work shims are used as instruments for embossing holograms.
Electro-forming and recombining is a complete pre-press process for mass production of holograms.
Embossing and finishing operations
Embossing is a kind of printing process where by means of high pressure and temperature micro-relief from Work nickel shim transforms to base materials (foils). In security holography base materials are special multilayer foils. After embossing, depending on the end product, embossed foil gets through some additional operations: laminating, die cutting, coating, slitting, and rewinding.
End products can be:
Hot stamping foil;
For high security applications are known different additional steps like numbering and selective demetallization.