Corrugated paper printing process (1)

At present, the corrugated paperboard in China is printed with a letterpress multi-roll ink printing system and a flexographic printing water-based ink printing system. As the flexographic printing system has good printing quality and high speed, the proportion has rapidly increased and it has become the mainstream of corrugated paper printing.
First, the characteristics of the flexible version of corrugated printing Flexographic printing with ink quick-drying, high-speed printing, low cost and other characteristics, especially suitable for corrugated paper on the printing accuracy requirements are not very high printing. Flexo printing corrugated boxes have the following characteristics:
1 Use water-based fast-drying ink to replace the past aniline ink, green environmental protection in line with the development of the times;
2 The machine structure is simple, the price is relatively cheap, the investment is small, and the effect is quick;
3 The printing pressure is small, the strength of the carton is reduced less, and the effect on the strength of the corrugated cardboard is very small;
4 Flexoprinting carton printing accuracy is not high, the conventional screen line number is only 30 ~ 65/In, is a low-precision printing method, the most suitable for printing text lines.
5 The printing format is large, and the maximum width of the wide-format flexographic corrugated box printer can reach 2.0m to 2.8m. 6 flexographic printing plate is resistant to high printing force, and can be reused; ink prices are also low, can be linked to production, such as printing, open bad, indentation, set (sticky) box, bundling and other machine can be completed.
Second, the basic principle of flexible printing corrugated printing Flexographic printing is the use of flexible printing plates, printing ink transfer method through the anilox roller, is a relief printing process. The printing plates used in the printing plate are all raised in graphic parts. When printing, the anilox roller evenly applies a certain thickness of ink layer to the graphic part of the printing plate, and then under the pressure of the impression cylinder, the graphic part The ink layer is transferred to the surface of the substrate to form a clear graphic. The inking mechanism of a flexographic corrugated paper press is usually a two-roller ink transfer mechanism.
1. Two-roller ink system
As shown in Figure 2-1, the plate cylinder rotates on the side of the impression cylinder and coincides with the linear velocity of the impression cylinder. When stopped briefly, the ink fountain roller and the anilox roller are moved up and out of the plate cylinder, and the ink fountain roller and the anilox roller continue to rotate to facilitate even ink and keep the ink on the anilox roller from drying. The ink fountain roller rotates on one side of the anilox roller, and its tangential speed is lower than the tangential speed of the anilox roller in order to control the ink volume and prevent the ink from splashing. Most printing presses for printing corrugated paper are modular flexographic printing presses.
Printing materials Embossing roller Printing plate roller Anilox roller Ink roller: The units of this flexographic printing press are independent and horizontally aligned.
2. Flexo Plates Flexo Plates are divided into a rubber plate and a photosensitive resin plate: the rubber plates are made of natural rubber or synthetic rubber; the types of photosensitive resin plates are various and can be divided according to their forms. Liquid photosensitive resin plate and solid photosensitive resin plate. The seamless printing plate is made of a plate-shaped solid photosensitive resin plate. The photosensitive resin flexographic plate is composed of a protective layer, a release layer, a photosensitive layer, an adhesive layer, and a base layer. The function of the protective layer and the release layer is to protect the photosensitive layer; the role of the subbing layer is to support the photosensitive layer; the function of the adhesive layer is to tightly bond the photosensitive layer and the subbing layer together. The photosensitive layer is the main body of the printing plate. After exposure and development, it is a flexible printing plate. The photosensitive layer is mainly composed of a highly elastic unsaturated rubber polymer, a photoinitiator, a cross-linking agent, a sensitizer, a thermal polymerization inhibitor, and the like.
It should be noted that due to the rough surface of corrugated paper, a thick flexible plate must be used; if high-grade products are to be printed, a flexographic plate with high resolution and small retractility must be used. (to be continued)