UV Varnish Unevenness Affects Surface Smoothness of Printing Products

In the daily production process, various reasons require us to dilute the UV varnish used. Usually, the most economical and convenient method is to directly add A in the UV varnish. T industry uses non-reactive solvents such as ethanol to change only the instantaneous viscosity of UV varnish without changing the inherent composition of UV varnish, improving the fluidity and transferability of the varnish, and making the surface of the printed product bright after varnishing. slip. However, when the ethanol is added in excess, the water contained in the ethanol can not be fully evaporated, and it will produce a water mist during the photocuring and heating process, which will remain in the film of the varnish, affect the transparency of the varnish after curing, and even lead to curing. Incomplete, the printed surface is tacky.
Solution: In the production process, the amount of non-reactive solvent such as ethanol should be controlled as much as possible, and ethanol with higher purity should be used.
Uniform coating of UV varnish evenly coated with UV varnish is also one of the main factors affecting the surface glossiness and brightness of printed products. UV varnish coating effects are related to glazing, printing pressure, anilox roller, and ink. There is a direct relationship.
(1) Poor height consistency of the surface relief of the printing plate will affect the condition of the varnish transfer, thereby affecting the quality of varnish coating.
(2) The uneven printing pressure will also affect the transfer of varnish to the substrate, resulting in a different thickness of the UV varnish transferred to the substrate.
(3) The blockage of the anilox roller's cells causes the surface of the anilox roller to have a non-uniform amount of ink, resulting in a deficiency in the transfer of UV varnish to the surface of the substrate.
(4) Repelling or interfering with the printing ink and UV varnish, as well as too much viscous material on the surface of the ink, will locally obstruct the UV varnish transfer to the surface of the printing material.

Shanghai Aokeli Printing Machinery Co., Ltd.

Solution: Select excellent flexographic printing plate; pay attention to the effectiveness of the developer and the quality of the washing; ensure that the surface of the printing plate has a uniform height relief; adjust the printing pressure to ensure that it is moderately stable; thoroughly clean the anilox roller and ensure the inside of the cell No foreign matter remains: Use the same manufacturer's ink and UV Varnish, try to avoid adding in the ink with high viscosity additives.
Paper surface smoothness is not suitable The paper surface is rough and directly affects the leveling performance of the UV varnish on the surface of the paper. When the surface of the paper is too rough, the speed of the UV varnish flow on the surface of the paper is slow, and the UV varnish transferred to the surface of the paper is almost completely absorbed by the rough paper, so that the film-forming substance in the UV varnish—the photosensitive resin penetrates the fiber In between, the gloss and brightness of the printed surface after UV curing were not good. In addition, the rough surface of the paper will also affect the reflection, diffraction and interference of UV light, resulting in UV light failure, affecting the curing effect.
However, the smoothness of the paper surface is not as high as possible. Because the paper sheet is too smooth and its absorptivity is poor, the printing ink cannot be effectively penetrated on its surface, causing the ink to crystallize on its surface to form a non-absorbent surface. When UV polishing is performed on such a surface, the penetrating component in the varnish is retained on the surface of the paper together with the photosensitive resin, and the varnish will not be completely cured.
Solution: Select paper with good printability. You can also pre-print and dilute the surface of the paper with white ink that has faded in order to change its surface roughness and delay its absorption. In addition, it is possible to improve the printability of the surface of the paper by using a base of water-based varnish, which also improves the resistance of the printed product to bending. Shenzhen Precision Machinery Co., Ltd.