Relief Printing

Relief Printing, printing using letterpress (printing plate with raised parts of graphics and text). Referred to as embossing. It is one of the main printing processes. The longest history, continuous improvement in the long-term development process. Engraving printing In the early Tang Dynasty of China, engraving printing technology was invented. It was the most primitive embossing method by engraving characters or images on wooden boards, removing non-graphic parts to make the images protruding, and then painting them with ink, covering with paper and brushing.

The principle of Relief Printing is relatively simple. In Relief Printing, the ink supply device of the printing press first distributes the ink evenly, and then transfers the ink to the printing plate through the ink roller. Since the graphic part on the relief printing plate is much higher than the non-graphic part on the printing plate, therefore, The ink on the ink roller can only be transferred to the graphic part of the printing plate, and the non-graphic part has no ink. The paper feeding mechanism of the printing press conveys the paper to the printing parts of the printing press. Under the joint action of the printing plate device and the imprinting device, the ink in the graphic part of the printing plate is transferred to the substrate to complete the printing of a piece of printed matter. . Any printed matter that has slight prints on the back of the paper, neat lines or dot edges, and the ink appears light in the center, is letterpress printing. The edge of the raised print is heavily pressed, so there is a slight print raised.

Flexographic printing was originally a printing process using molded rubber relief plates. Since printing inks prepared with aniline dyes were originally used, it was once called flexographic printing. The earliest flexographic printing press was created by the British in 1890. It was originally used for paper bag printing, and later was promoted for packaging printing for food and medicine. Because aniline dyes are poisonous and banned by the WHO, the ink formula used has long been changed, so people proposed to change the name. In 1952, it was resolved to change its name to flexography at the 14th Annual Packaging Conference. "Flexo" has the meaning of being flexible, so it is translated as flexographic printing. The flexographic plate material is a photosensitive polymer, such as DuPont's Cyrel plate, whose main component is synthetic rubber, and is developed with organic solvents. There are also alcohol-soluble, alkali-soluble and water-soluble flexographic printing plates. Due to the improvement of plates, inks and printing equipment, the quality of flexographic printing has been greatly improved. It has been used in newspapers, books and periodicals printing, and is a promising process in letterpress printing. Letterpress offset printing is a thin relief plate (usually about 0.25 mm) made of photopolymer. Like offset printing, the ink on the printing plate is first transferred to the blanket cylinder and then transferred to the printing sheet, so it is also called indirect relief printing. Since the printing plate does not need to be wetted, it is also called dry offset printing. It not only has the advantages of embossing (the ink color is thicker), but also avoids the weakness of offset printing (the side effects caused by the dampening fluid). However, the cost of plate making is relatively high, and the blanket is prone to dent marks after long-term embossing on the embossed layout, and the service life is short, so it is not widely used.