3.3 Gravure printing technology
(1) Gravure engraving technique and digital proofing
The traditional gravure has engraving gravure, etched gravure and gravure, in which the gravure gravure includes hand-carved gravure and electronic circle gravure. The modern electronic engraving gravure plate has the advantages of advanced technology, low plate making cost, high plate-making quality, stability, wide adaptability, and favorable environmental protection, and it occupies a dominant position in gravure plate making.
The modern electronic engraving system does not need to input information through the scanning unit. All the image data, device drive parameters and other information are transmitted to the electronic engraving equipment in the form of digital and electronic data. Key technologies of electronic engraving systems include drive circuit technology, digital signal processor application technology, AC servo technology, and high-frequency electromagnet technology.
Intelligent and high-frequency security technology is the main development direction of gravure electronic engraving system. The intelligent engraving system includes automatic trial carving, automatic and quick non-engraving areas, and automatic plate changer. The engraving frequency is the bottleneck that affects the efficiency of the electric carving system. Therefore, the development of higher frequency electromagnetic engraving head has been the main research direction of the electric carving system production enterprises.
Gravure proofs are analog and digital. The gravure proofer is made by simulating the principle of a gravure printer. The ink is transferred to the substrate by the roll action between the impression cylinder and the gravure cylinder to form a clear pattern. Digital proofers use inkjet and electronic imaging proofing. The use of digital technology to obtain high resolution mesh samples directly on the thermal transfer material can effectively reflect the fine level. Although proof color for digital proofing is currently difficult to achieve the color reproduction effect of the gravure ink having the sense of transparency and concentration. However, digital proofing has the characteristics of high production efficiency, reliability, and convenience, and is an important trend for future development.
(2) Improvement of gravure ink
As people's awareness of environmental protection has increased, environmental pollution brought about by conventional solvent-based inks has become more and more important. With the advancement of new-generation water-soluble polymers, water-based inks have been successfully applied to the gravure process of cigarette packages, wine labels and other paper packaging products, enabling the printing of toluene-free inks, and avoiding solvent-based inks for the environment and operators. Pollution caused. Water-based inks have shown significant impact on the packaging market and significant growth potential, which is the direction of the ink industry. Water-based coatings will also gradually replace solvent-based coatings.
In Europe and the United States, more than 90% of printing companies use water-based inks that are non-toxic to the human body and harmless to the environment to print tobacco and wine boxes, medicine boxes, food boxes and daily necessities packaging boxes (cases), avoiding the ecological environment. harm. In the field of gravure printing abroad, the replacement of solvent-based inks with water-based inks has become an inevitable trend.
Water-based gravure aluminum box ink is a kind of volatile dry heat-curing ink. It is mainly composed of film-forming substance, coloring agent, adding auxiliary agent and auxiliary solvent. The film-forming substance is a key part of determining the physical properties of the ink, and the water-soluble acrylic resin and the water-soluble self-crosslinking emulsion component colorant are often used as alkali-resistant materials. This water-based gravure ink is non-toxic, odorless, has good transfer properties and fastness, suitable for rotary gravure and other features.
(3) Advanced technology of gravure printing equipment
Most foreign advanced gravure printers use sleeve-type impression cylinders and plate roller direct drive technology. Sleeve type impression cylinders have the advantage of quick change of rollers, and do not need to break the tape when replacing the impression cylinder, thus reducing material waste. The plate cylinders of each printing unit are directly driven by a single motor, which achieves longitudinal registration in the imprinting process and a stepping motor is moved to control the lateral register. The main advantage of independent drive is that it does not need mechanical transmission shaft and register compensation roller mechanism, mechanical components are reduced, material length is shortened, so it is beneficial to improve printing quality and printing speed.
The rapid replacement, positioning and installation system can effectively reduce the device-assisted time and improve work efficiency. At present, foreign advanced gravure printing presses use pneumatically installed squeegee blade holders, printing crucibles, and carts to quickly position and install devices to achieve rapid replacement of live jobs.
(to be continued)
