Printing Techniques

Flexo Printing : The most common printing method in flexible packaging is flexo printing. This method is usually the least expensive approach for (graphical) line drawings. The latest technical developments in flexo printing have also brought the use of water-based ink. Rubber and photopolymer plates are used in flexo printing. In this system, ink transfer is done with plastic protrusions on the printing cylinder. Today, as a result of the great developments in flexo printing equipment and equipment, great developments have been made in flexo printing. Ideal prints are realized by using 8-color water-based ink in flexible packaging production.

Letter Press Printing : Photosensitive polymer dies are used in advanced letterpress printing machines. The image area (ink bearing area) on the cliché is produced by photographic or direct imaging methods. The cliché, which is exposed to light, is then washed with special solutions (chemicals and water-based). Thus, areas that will and will not carry the image appear. The cliché is placed in the machine by being attached to the printing cylinder. During printing, the raised surface is covered with ink and then the print is transferred to the paper. Letterpress roll printing machines used for self-adhesive labels are produced as semi-rotary and rotary. These machines generally use UV ink and UV drying system.

Intaglio Rotogravure Printing : Ideal for long-term and high circulation packaging applications. The image and graphic to be printed is illustrated under the surface of a metal cylinder, so gravure printing is known as the intaglio process. Printing with a screened stencil to achieve the graphic design is the hallmark of gravure printing. The cost of preparing the engraving and getting started is high. These are offset by low transaction costs. Intaglio method is used in the production of flexible packaging where pictorial graphics or exact color copies are required. Because the ink transfer is made from small indentations at micron levels, a clearer image is obtained with the intaglio printing method. With the new printing machines that emerged as a result of the technical advances experienced in this printing method, 10-color printing applications are possible. It even includes the in-line lamination line of printing machines in this area. Technical marvels have been created in machines. With heat bonding lacquer, polishing and UV lacquering processes can be done at the same time. Here, too, the use of water-based inks has become widespread.

Letterpress Printing : Letterpress printing has been used for years to print on paper surfaces. This technique can produce excellent pictorial graphics and is well suited for printing on coated or uncoated papers. Letterpress inks have a consistency similar to toothpaste. Drying; heat, oxidation, absorption or a combination of these techniques are achieved. In the past, the relief print was attached to a non-cliche-free metal surface. With the development of photopolymer plates combined with the emergence of UV ink systems, the chances of letterpress printing in the field of flexible packaging production have increased.

Offset Printing : The printing method chosen by most of the dry product mix bag users is offset. With the offset printing method, pictures are easily reproduced in four colors. Offset printing is a planar printing method. Both the print and non-print items are on the same plane of the print plate. In this technique, the principle of not mixing oil and water is used. Offset inks are in the form of an oil-based paste. Chemicals are applied to the printing plate to create oil-absorbing and water-absorbing areas. The printing plate is first brought into contact with a humidifier unit that supplies water to the water-absorbing parts of the plate. Next, the cliché passes through an ink roller that transfers oily ink homogeneously, Ink transfers only to the oil-absorbing parts of the picture. The ink printing plate then comes into contact with the packaging material or transfers the image to the rubber sheet that engages the material. This second approach, which is more used than the direct offset method, is known as offset. Ultraviolet ink technology has improved the practicality of offset printing in flexible packaging.

Screen Printing : 5th printing method in flexible packaging; It is a screen printing made with a perforated mold. In screen printing, the density of the ink is in the consistency of paint. These inks are solution types that require heat and air to dry. In addition, UV inks are adapted to screen printing. The printing medium is a photomechanically developed synthetic tissue to protect the non-printed areas. The curtain is placed in a silk frame and ink is put inside the frame. The rubber roller, a movable tool, allows ink to pass through the holes in the curtain onto the packaging material. The hallmarks of screen printing are heavy ink layer, outstanding color capacity and inexpensive preparation. This printing method is used when testing and packaging market materials requires different ink properties. Except for papers, the surfaces of all flexible packaging materials should be prepared or coated with ink.

Hot Foil Printing: The matte part of the foils used for this work is attached to the printing paper and the glossy part to the cliché. Whatever color gilding is desired, that color foil is used. A metal cliche is adhered to the resistance of the machine and then the heat of the resistance is given to 80°-90° degrees. And thus, the heated foil adheres to the desired material with the help of heat. In short, it is the method of transferring the image from the metal printing cliché onto the label material by means of temperature and pressure. The printing material used is colored foil.

Printing Inks: The ink changes according to the printing method used in the production of flexible packaging. Inks are distinguished between each other by their composition, chemical, physical and printability properties. The task of the coloring material in the ink is to make the printed work visible. Intaglio inks consist of three main parts: Solvents, resins, colorants. Solvents dissolve the resin in the system, melt the dyestuff to make fluid inks, and eventually evaporate by controlling drying. Resins make up the main part of the ink. The size keeps the substance in the system, facilitates the transfer of ink onto the material and ensures the adhesion of the film. Colorants give color to the system and make the film look decorative on the material after ink transfer. The biggest development in the ink world is the development of water-based inks. The biggest feature that distinguishes water-based inks from solvent-based inks is; the use of water as a solvent. Great advances have been made in water-based inks, which represent one dimension of environmental and packaging regulations. It is inevitable that the focus of all work on printing inks will be water-based inks in the future. The development of flexible packaging has also been highly influenced by the attractive graphics on the packages. This situation necessitated the development of special ink systems for different materials and applications. It uses heat resistant, glossy inks for surface printing of flexible packaging. Special lamination inks are used in laminations where the outer film is a reverse printed contact. For ready-made bags; high temperature resistant inks are used. Inks should be chosen according to which material they will be used for and what properties the film on the material should have after printing.