Substrate is a term used in converting process such as printing and Lamination or coating as a more general term to describe the base material onto which e.g. images will be printed and to be laminated as per the packing specification required for the product. Base materials include (though are not limited to):
Where as the converting process (Flexible packaging Unit) such as printing and lamination is concerned the above products are widely used as visual packing of electronic products, foods, and pharmaceutical products.The above Sheet / foil/ substrates are new environmental friendly packing material, featuring high lustre, high transparency,good barrier resistance , and fragrance and fresh keeping performances.Basically the nomenclature of plastic or plastic related printing /laminated,or packaging material like PET,MET-PET,PE (POLYETHYLENE),BOPP, MET-BOPP, CPP,MET-CPP, ALUMUNIUM FOIL ETC..ETC...is called film in common language but thus are the raw materials of printing, lamination, packaging products. Henceforth, in technical language, the above products are called as substrate because the products mentioned above are the basic substrate raw materials in which a printing industry used to print & laminate; in other word, the substrate do not have any coating (emulsion/electro-magnetic or other coating) which is base material to convert the plastic extruded web substrate in a film. In terms of Technology and the properties and the characteristic and application of the films and the substrates (bare substrates which are required for converting unit is totally different and even the size and thickness of the films and substrates is also not common.
Courtesy: Dictionary of Plastics and Articles