In the printing industry, UV Varnish has always played a role as a high gloss oil. Its unique highlighting effect is recognized by the majority of printing process personnel, but the UV varnish still has deficiencies in many post-processing performances. For example, hot stamping on a UV light oil layer can achieve very good visual effects, but the application of this technology is still very small. This is mainly due to the fact that the hot stamping adaptability of UV varnish is still not mature enough and the stamping quality is not stable enough. The UV varnish resin components and additives are also not conducive to hot stamping. All these problems require the light oil manufacturers to make further improvements to the varnish. The following is a brief analysis of the difficulties in hot stamping on the UV lacquer layer from the problems that arise during the development of the test.
(1) To form a high-brightness effect, the UV varnish must have a certain thickness, but too thick a varnish layer is not good for hot stamping. Generally, the thickness of the UV varnishes applied by offset printing is above 9g/m2.
(2) In order to ensure the curing performance, special resins and a large amount of additives need to be added in the UV varnish, which will inevitably affect the effect of hot stamping on the surface of the UV varnish layer.
(3) At present, the affinity of the resin component in the UV varnish with the hot stamping foil under high temperature and high pressure is not good enough. Therefore, it is difficult to control the hot stamping on the UV varnish layer.
Therefore, the following matters need to be taken into account when hot stamping the surface of the UV oil layer.
(1) The method of increasing the thickness of the lacquer layer is not advocated when it is required to increase the brightness of the UV varnishes. The flatness and lightening effect of the optical oil layer can be improved by adjusting the coating process parameters (the angle and the number of screen lines of the coating roller, etc.) and the performance of the printing equipment (pressing pressure and printing speed, etc.).
(2) Reasonably select the stamping material so that the adhesive layer has a good affinity with the UV varnish resin.
(3) Accurately adjust the temperature and pressure of the hot plate because high pressures and temperatures can destroy the surface properties of the ink and make hot stamping more difficult. At the same time, the hot stamping speed should not be too fast.