In general, UV offset printing is the same as regular offset printing, replacing regular offset ink with UV offset ink, then arranging a UV drying system after each printing unit or at the last printing unit.
When using UV silk screen printing ink, we will create many very "ART" effects and can print on many materials with high productivity & quality.
UV lamination (UV coating) has 2 types:
Full UV: is to coat the entire printed sheet, the purpose is to increase gloss, scratch resistance, ... In this case, the UV used is UV varnish (UV Vanish).
Partial, shaped, local UV: is to coat only the areas that need UV effects, for example, embossed, rough, sand-like effects, ... or when you print a printed sheet, on which there is a picture of a car, and you only coat UV on that car image, it is called local UV coating (partial UV).
UV printing uses UV ink. UV ink is a type of ink that does not contain solvents, so it cannot dry normally like other types of ink but only dries under the influence of UV radiation, so after printing the printed sheet must go through a curing system using UV lamps.
UV printing has the following advantages: the ink dries quickly (almost immediately after going through the curing system), creates many special effects (glossy, embossed, sand UV, metal ...), can be printed on many materials, and is environmentally friendly.
When printing UV, you should pay attention
A separate cleaning agent must be used (usually one of the following 3 types: 2 UV wesh 32, A3 UV wesh 58, or A3 UV wesh 75) for printing using UV ink to clean the press tubes, blankets ... these types have little impact on the body and do not damage the rubber tubes.
The press tubes in the machine, including the blanket, must be made from materials that can withstand the chemical properties of UV ink.
We must regularly monitor the composition and temperature of the water solution to avoid the situation where this solution mixes with the ink when printing, because the nature of UV printing technology requires the use of little water during printing.
It is necessary to set up a temperature monitoring device for the ink trays and ink tubes to avoid the deformation of the ink when the temperature changes.
Because the ink is dried by using a lamp, the paper is easily deformed and electrified.
After printing, use tape to test the dryness of the ink. If there is ink on the tape, the ink has not been completely dried.
UV printing can cause the gloss of the paper to be lost due to the drying lamp being used for a very short period of time.
How to calculate UV screen printing ink drying lamp:
In theory: each ink manufacturer (with quality) states the minimum energy required to dry the ink. For example: RC PEP-G ink used for screen printing on PP/PE plastic by JUJO - Japan, requires the following drying lamp: metal halide lamp (MPMA is also available) ≥ 120w/cm (this parameter will determine the radiation intensity), energy ≥ 120 mj/cm2, to know the above energy, you must use a radiation meter. There are some ink manufacturers that do not state the required energy but require the conveyor speed to be lower than a certain number, for example 40m/min.
And all the parameters are for reference only, the problem is to adjust the conveyor speed according to actual production conditions. And from reality, lamps with a capacity of 80/cm or 120w/cm, or higher, all have their own advantages and disadvantages. Depending on the main product that is often printed, you will choose the appropriate lamp.
If you already have a silk screen printing machine, you only need to invest in:
UV drying system. Reference price (drying area 25cm): 25 million - 30 million - Vietnamese machine; 17-25 million - Chinese machine, >50 million - 80 million - high quality dryer.
Material surface treatment equipment (option - to increase the adhesion of UV ink): 25cm treatment area, choose the type of treatment equipment depending on your printed product.
a. Flame: 10 million - 20 million.
b. Corona: 20 million - 150 million, depending on quality and origin.
c. Plasma: higher price than corona.
d. UV Nitro: this is a new treatment equipment, specialized in treating glass and metal surfaces, priced at about 80 million.