Home> News> Why Does Large Format UV Printer Need a Coating When Printing?

Why Does Large Format UV Printer Need a Coating When Printing?

Large format UV printers are bringing a quiet revolution to the advertising and decoration industries due to the diversity of their printable materials. On many transparent materials, such as glass and acrylic sheets, a common printing technique is to add a white coating to the color of the screen before UV color printing. Usually this layer of white back coating is achieved by spraying a white UV ink on a dedicated nozzle on the printer.

During our contact with the customer, it was found that after printing for a period of time, the white ink would crack and cause pattern damage.

Mimaki large format UV printer

The white ink ejected by the UV digital printer is mainly cracked after a period of time. The UV white ink is not high in strength, and the ink layer is stretched during the heating of the material due to the difference in thermal expansion coefficient between the ink layer and the substrate.

UV curing technology has been developed in the past 20 years, and its main advantages are fast curing and environmental protection. The shortcomings are also obvious. Due to the fast curing, the internal stress of the material is relatively large and the strength is not high. This problem is more pronounced in white ink.

Mimaki large format UV printer

Generally, in order to achieve a certain hiding rate, white ink will contain a relatively large amount of whitening filler such as titanium dioxide, and the presence of these fillers will further reduce the toughness of the ink. Therefore, to avoid cracks caused by white ink, materials with higher toughness should be selected.

UV inkjet printers need to be pre-coated with a back coat if they need to print on metal, glass or ceramic tiles. The main purpose of the rubbing coating is to allow the coating to adhere to the material as much as possible while also keeping the surface of the coating clean. Because the surface density of metal, glass, and ceramic tiles is too large, the ink cannot penetrate completely into the inside, so it is necessary to wipe a layer of coating.