For the screen printing factory that has introduced large format inkjet equipment, the laminating machine has become a necessary post press processing equipment. The initial purpose of film covering is to set a barrier between printed images, so as to prevent them from being worn in the process of reuse. The laminating machine used in the printing industry mainly covers a film on the surface of the printed matter to prevent the image from being scratched and damaged by chemicals. However, the laminating machine has another use, which is to apply a protective liquid coating to the printed matter. The liquid lamination technology is the focus of this paper. We will focus on introducing the equipment, coating type, application scope and benefits related to this post press process.

Liquid laminating machine

Liquid laminating machine is actually a coating equipment. From the most basic point of view, the printed matter must first be input into the laminating machine, then coated, and finally input. The intermediate and final steps of film coating mainly depend on the type of coating you choose. It can be either UV curable coating or water-based or solvent-based coating. For example, the substrate that has been UV coated must be processed by the drying unit before output, and the substrate coated with water-based coating can choose to add an infrared drying procedure according to the automation level of the laminating machine to enhance the drying effect of the printed matter.

In order to meet the different needs of users, the liquid laminating machine also has a variety of different configurations and sizes. In today's printing market, people can choose either manual or automatic laminating machine or sheet or web laminating machine.

UV laminating machine is generally divided into reverse roller or three roller system. The water-based laminating machine generally applies the coating on the substrate, and then uses a screw rod (that is, a cylindrical measuring rod) to reduce the thickness of the coating to an appropriate level. With an ink scraper or similar device, the paint can be scraped off the back of the substrate.

Ike Harris, President of Daige, said: 'it's not roll coating, it's wiping the coating onto the substrate. When people need to carry out precise coating, they need to use the special measuring rod commonly used in the laboratory. In addition, the measuring rod is also suitable for the manual and large roll to roll coating process, which can make the coating machine produce smooth and uniform coating on substrate. '

Roller coater can transfer printing image by using multiple ink rollers and finish the task of coating them. From entering the roll coater, the substrate either receives ultraviolet or infrared drying, or natural air drying, but the latter takes a long time. A substrate conveyor integrated with some coaters - usually a conveyor belt that delivers the coated substrate to a drying or curing system in a timely manner. As an alternative, the water-based coated image can also be placed horizontally to dry faster. This method is usually used in manual coater. Harris points out that the water-based coating takes about 20 to 25 minutes to dry.

Recently, many UV liquid laminating machines can cure the coating at high speed, sometimes up to 100 ft / min. In addition, they can also be designed to be very small to save space. For example, the total length of the equipment can be controlled within 5 feet, including the length of the conveyor, because only in this way can the laminating machine process materials quickly.

The characteristics and quantity of movable parts determine the type of liquid laminating machine you need. If you want to print a banner pattern on a grid plastic or pop image on a textile, it is best to choose a water-based coating system, because the dents on the printed surface of the material must be filled with liquid paint.

According to Jim Tatum, President of advanced finishing solutions, it is not the best choice to use UV liquid laminating machine to process this kind of textile material, because the laminating equipment will apply a very thin coating material to the print at a very high speed. Under the given operation parameters, this kind of coating has little chance to fill the depression of substrate surface.

Tatum points out: 'as a result, only part of the image you get is coated and cured. This kind of coating can't protect the image at all when there are bad weather conditions and other destructive factors. On the other hand, the water-based liquid film coating can evenly apply the coating on the substrate surface, so that the concave part of the image can also be properly protected. [next]

Protective coating and its application

With the increasing awareness of environmental protection in printing factories, UV coating has been recognized rapidly in recent years. At present, most of the UV coatings used for printing images do not contain VOC (volatile organic compounds), so they can be easily converted into solid without volatilizing any gas. The water-based coating is generally composed of 70% water and 30% resin, so it needs to be placed for a long time after coating, so that the water will evaporate before the substrate is rolled up or stacked. Tatum believes that evaporation should be taken into account when calculating the cost of waterborne coating.