In the printing industry, UV varnish has always played the role of high gloss varnish. Its unique highlight effect is recognized by the majority of printing technicians, but UV varnish still has deficiencies in many post-processing properties. For example, hot stamping on the UV varnish layer, although it can obtain very good visual effects, but the application of this process is still very few. This is mainly because the current hot stamping suitability of UV varnish is not mature enough, the quality of hot stamping is not stable enough, and the resin components and additives of UV varnish are not conducive to hot stamping. These problems require varnish manufacturers to further improve varnish. The following is only a brief analysis of the difficulties in hot stamping on the UV varnish layer from the problems that occurred during the development test.
(1) To form a high-brightness effect, UV varnish must have a certain thickness, but too thick varnish layer is also detrimental to hot stamping. Generally, the thickness of the UV varnish layer applied by offset printing is above 9g / m2.
(2) In order to ensure the curing performance, special resin and a large amount of additives need to be added to the UV varnish, which will inevitably affect the effect of hot stamping on the surface of the UV varnish.
(3) At present, the compatibility of the resin component in UV varnish with hot stamping foil under high temperature and high pressure is not good enough, so it is not easy to control hot stamping on the UV varnish layer.
Therefore, pay attention to the following items when hot stamping on the surface of the UV varnish layer.
(1) When it is necessary to increase the brightness of UV varnish, it is not recommended to increase the thickness of the varnish layer. The flatness and brightness of the varnish layer can be improved by adjusting the coating process parameters (coating roller screen angle and screen number, etc.) and printing equipment performance (printing pressure and printing speed, etc.).
(2) Choose the hot stamping material reasonably so that its adhesive layer has good affinity with the resin of UV varnish.
(3) Accurately adjust the temperature and pressure of the hot stamping plate, because too high pressure and temperature will destroy the performance of the ink surface and make hot stamping more difficult. At the same time, the stamping speed should not be too fast.
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