Rotogravure (Roto or Gravure for short) is a type of process, where an engraved cylinder transfer the images by direct pressure onto an impression rubber coatet roller on the material to be print.
In rotogravure can be used different kind of inks:
After the printing the ink, which is a mixture of pigments and solvents, needs to be "dryed" , the drying process evaporate the solvents which is the liquid component of the ink so only the "solid" color remains on the web.
The Rotogravure process is mostly used for food packaging and publishing
The most recent technologies of "laser engraving" the printing cilynders enhanced the printing resolution which reach a quality similar to Offset printing quality.
Typical substates to be printed in gravure are:
BOPP : Bi axially oriented polypropylen
PET : Polyester
BOPA: Bi axially oriented nylon
Laminates which are structures composed by two or more layers of different materials according to the final applications
In the food packaging most of printed materials need to be laminated with another layer of film or aluminum foil in two, three or four layers structure according to the final applicaton of the packaging and barriers properties required.
The different purposes of the printing material arte mainly
Physical protection - The food enclosed in the package may require protection from, among other things, shock, vibration, compression, temperature, etc.
Barrier protection - A barrier from oxygen, water vapor, dust, etc., is often required. Permeation is a critical factor in design. Some packages contain desiccants or Oxygen absorbers to help extend shelf life. Modified atmospheres or controlled atmospheres are also maintained in some food packages. Keeping the contents clean, fresh, and safe for the intended shelf life is a primary function.
Containment or agglomeration - Small items are typically grouped together in one package to allow efficient handling. Liquids, powders, and granular materials need containment.
Information transmission - Packages and labels communicate how to use, transport, recycle, or dispose of the package or product. Some types of information are required by governments.
Marketing - The packaging and labels can be used by marketers to encourage potential buyers to purchase the product. Package design has been an important and constantly evolving phenomenon for several decades. Marketing communications and graphic design are applied to the surface of the package and (in many cases) the point of sale display.
Security - Packaging can play an important role in reducing the security risks of shipment. Packages can be made with improved tamper resistance to deter tampering and also can have tamper-evident features to help indicate tampering. Packages can be engineered to help reduce the risks of package pilferage: Some package constructions are more resistant to pilferage and some have pilfer indicating seals. Packages may include authentication seals to help indicate that the package and contents are not counterfeit. Packages also can include anti-theft devices, such as dye-packs, RFID tags, or electronic article surveillance tags, that can be activated or detected by devices at exit points and require specialized tools to deactivate. Using packaging in this way is a means of retail loss prevention.
Convenience - Packages can have features which add convenience in distribution, handling, stacking, display, sale, opening, reclosing, use, and reuse.
Portion control - Single serving packaging has a precise amount of contents to control usage. Bulk commodities (such as salt) can be divided into packages that are a more suitable size for individual households. It also aids the control of inventory: selling sealed one-liter-bottles of milk, rather than having people bring their own bottles to fill themselves. (source Wickipedia)
Rotogravure typical machine configuration