Энциклопедия
Decoration achieved using the offset printing technique is characterized by its excellent print quality in relation to its cost. Offset printing is a type of flat printing in which the inked image is transferred from a plate to a rubber blanket, and from the blanket to the printing surface.
This printing technique makes it possible to reproduce even the most intricate details.
The printing is done in the CMYK color model with the option of using additional colors. The printing process can be completed within a very short time period, thanks to the rapidity and ease with which a set of printing plates can be prepared.
The following types of offset printing exist:
- Cold offset printing (the ink is fixed by soaking into the paper);
- Hot offset printing (the ink is fixed by soaking into the paper and evaporating at high temperatures).
Screen printing is a quite widely used technique of printing, based on squeezing the ink with squeegee through the uncovered meshes of net spread on a frame. This method originates from the so called stencil painting that was known in ancient times in China and Japan.
The screen printing technique has many advantages that enable its application in a broader area than in case of other printing techniques. Screen printing does not create any limitations – neither when it comes to the material, nor to the shape of object that is to be printed on. This is why it can be used on various surfaces: flat, oval, round, cylindrical or conical. Moreover, screen printing gives a possibility to apply relatively thick layers of ink..
Screen printing is considered to be quite a durable and relatively cheap technique. It enables unicoloured and multicoloured printing. One can decorate plastics, metal, cardboards or foils with this technique.
The print skin has a form of a rectangular frame, usually made of aluminium, with a net that is spread on it (made of nylon, polyester or metal) with a template. Template is a hardened photosensitive surface that is not permeable to ink and constitutes a negative picture of the printed pattern. The uncovered meshes of the screen printing net that are permeable to ink are the printing part.
Label is a paper or foil product, and sometimes a direct overprint on the product. It is used to identify the product, define its content or for marketing activities (attracts the attention of consumers). Labels may differ in terms of shape, material and technique of production.
There are the following types of labels:
- Wet label - the oldest type of labels, which name comes from the method by which it is applied on the product – with wet glue. The popularity of this labels started to decrease in the 1970s. It was substituted with self-adhesive labels.
- Self-adhesive label - it is printed on a special self-adhesive material, e.g. foil or paper. On its back, there is a glue and protective layer that is removed prior to sticking the label. This type of labels is very often used on alcohol, cosmetics and food packaging.
- IML label (In Mould Label) - one of the latest achievements of the labelling branch. Its basis is made of the same plastic as the packaging. In this case, the process of joining the label with packaging is irreversible, so the final product is entirely recycled. IML labels are used in the following industries: food, chemical, building or hygienic. The advantages of this type of labels are: resistance to humidity, low temperatures, greases, dirt and other external factors. Very thin foils made of plastics (57-90mc) are used for IML labels printing.
- SSL label (Shrink Sleeve Labels) / SSE (Shrink Sleeve Etiketten) - is created as a result of printing the sleeve from foil that entirely shrinks under the influence of heat. Various materials are used for the production of labels from this group. These materials have a diversified contractility level, e.g. PVC, PETG, PS, etc. SSL label is sometimes used as a seal protecting from the opening of packaging or in order to join a few products that are sold in a promotion, e.g. 2 for 1. Currently, the SSL labels are the most often used in food, pharmaceutical and cosmetic industry. SSL label gives a possibility to overprint the entire surface of the product. Thanks to its thermoplastic features, it has no limitations when it comes to the shape of packaging – the foil sleeve after shrinking is tightly attached to the container. The foil is overprinted on the internal side, thanks to which it is resistant to mechanical damage, such as abrasions or scratches..
- Sleeving label - it is used for round surfaces, e.g. cables, pipes or wires.
- Multitag label - it has a form of a small booklet. It gives a possibility to lengthen the text on the packaging, e.g. to add a few language versions of product description.
- Reverse print label - it is a type of label with mirror overprint on a transparent foil. A glue is applied on the side of overprint, when the label is taped, the transparent foil serves as a protective layer for the print at the same time. Thanks to such method of production, labels that are resistant to abrasion and external factors are created (without the necessity of lamination). The overprint achieves also deep saturation.
- Intelligent/reactive label - it is characterized by the fact that it reacts on changes in the environment in which the product is located or in the product itself. It is the most often used in the food industry. Such labels are for example the labels with thermochromic ink overprint. An inscription appears on the properly cooled beer bottles that are decorated with this method. Another example are labels with temperature identification (they inform about the proper storage of products) or the ones on which the nanoparticles of silver were applied (they inform about the spoilage of product).
Cold-stamping is a printing technique based on the application of the decorative layer of foil on the material with the use of special glue that is hardened with UV radiation. Such glue is applied on two ways: with flexographic or offset method. When the overprinted glue is pressed to the glue layer of foil, then the pigment is detached from the support layer.
In comparison to hot-stamping, cold-stamping is cheaper and provides better elasticity of production. This method of enrichment with foil is also faster - about 60-120m/min and enables to print the tonal transitions. A great benefit of cold-stamping is the possibility to print with ink and enrich the print with foil in one line.
The cold-stamping technique is useful when it comes to decoration of materials that are sensitive to the influence of high temperatures. It is used to enrich the print, mark and protect the products, e.g. with holographic foils.
The technology of cold foil embossment is used mainly in the branch of cosmetic packaging, but also in case of high-proof alcohol.
Varnishing is used in the branch of plastics decoration because of aesthetic reasons. The possibility to achieve a colour that is perfectly matched to the vision of the designer or manufacturer of a given product is the advantage of varnishing. Thanks to varnishing of plastics, one can also achieve better gloss of colour and eliminate the existing production defects.
This method has also one more benefit – it protects the plastic from the unfavourable influence of atmospheric factors, e.g. from humidity or UV radiation. This has an influence on the durability of products, that remain aesthetic thanks to varnishing.
Metal spraying – this is a method based on the application of a layer of metals on the surface of objects. Metallizing is used to obtain layers that are abrasion and corrosion resistant. It is also used for decorative purposes.
There a few types of metallizing, including e.g.: metal spraying, hot metallizing (object is immersed directly in a liquid metal), galvanic, contact, diffusion or vacuum metallizing.
One of the basic and most popular techniques of metallic layers application on plastic or glass elements is vacuum metallizing. It main purpose is to make surfaces look like metal – polished or matt. Thanks to this method, one can achieve the appearance of gold, silver, chrome or other metallic shades of various colours.
Vacuum metallizing is used in many branches of industry, both because of excellent results that can be achieved thanks to it, and because of the fact that this method is exceptionally economical. Currently, metallizing is used for the production of cosmetic packaging, vehicle fittings or Christmas tree decorations. Metallizing enables full usage of the features of plastic, giving them an elegant look of metal.
