UV offset printing on non-absorptive surfaces is getting popular by the days. It gives an ultimate packaging solution for board lamination and decorative printing. The challenge, however, remains to be the availability of right kind of substrate where direct printing can be done without any primer/ treatment. This is because liquids do not wet surfaces with free energies lower than their surface tension. On the other hand, higher free energy compared to the surface tension of the ink results in poor wetting and adhesion. Thus, for best wetting and ink adhesion on to non-absorptive surfaces, the ‘dyne level’ or the surface free energy of the substrate should be about 10 dynes above the surface tension of the ink.
Unfortunately, many polymeric substrates have too low surface energy required for good printing and ink adhesion and therefore, the substrate has to be modified in order to make it printable. This modification is usually done with an adjustable corona treatment or by applying a suitable primer coating.
Corona treatment is fast and relatively inexpensive, but surface dyne levels are susceptible to loss or decay during prolonged storage and upon contact with some fountain solutions. Precautions must be taken to obtain a uniform dyne level that is not too high. Corona treatments can at times also dramatically increase troublesome static charges in the material treated. Therefore, to avoid this, primer coatings that adhere to both the substrate and to the subsequently applied inks are used. This elaborate and time-consuming process has been posing further challenges for the convertors.
Solving this problem, Noida-based Uflex Limited has engineered a speciality polyester film F-UVC film, which is suitable for direct UV offset printing without any primer/ treatment.
The film is available in both bare transparent and metallised variants, where the non-metallised side is used for UV offset printing and UV curing. The metallised polyester film, FLEXMETPROTECTTM (F-UVC-M), is available in optical density ranging from 1.4 to 2.2. The wide range of optical densities gives choice to customer to use the product for diverse range of applications. The metal bond between the metal and the film is 130-180 gms/25 mm.
There are several benefits of direct UV offset-printable PET film, including the following.
It is suitable for direct surface printing without primer/ corona treatment
The lead time is minimum at convertors’ end
Yields excellent print results, high gloss and clarity with high quality resolution for pictures and half tone jobs with good scuffing resistance
It is suitable for high-speed machines and is versatile, tear proof and crack resistant
It offers excellent smoothness, flatness and ink adhesion
JK Sharma, AGM, technical service and new product development (films), Uflex, highlighting the benefits of the direct UV offset-printable PET Film, said, “Primer coating for rendering the films printable is a cumbersome and time consuming exercise at the convertors’ end. The coating machine is a big capital investment in itself. Therefore, with this new innovation, the convertors can heave a sigh of relief. Not only does the film increase operational efficiencies of convertors but also restricts their capital expenditure.”
Pramod Sirsamkar, president, technical & new product development (films), Uflex, said, “This is a great product for UV curable offset printing giving excellent scuff resistance, adding value for both the customer and the end user. The demand for this film is very encouraging.”
Ashok Chaturvedi, chairman and managing director, Uflex, said, “Our feedback loop in the global market is very strong. We are always in touch with our clients globally and are promptly responsive to their needs. Convertors had been facing difficulties with primer coating of the films as it takes a lot of time. This had been impeding their productivity. I am happy that the team at Uflex addressed the pain point of convertors by engineering the UV offset-printable PET film, which now permits surface printing without any treatment.”
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