The characteristics of letterpress printing
In the letterpress printing, the flexographic printing plate is mainly used in plastic packaging printing, mainly printing plastic film.
The printing plate of the letterpress printing has a printing portion higher than the blank portion, and all the printing portions are on the same plane. When printing, the printing portion is coated with ink, and since the blank portion is lower than the printing portion, the ink is adhered and then printed. The object is in contact with the printing plate, and a certain pressure is applied to transfer the printed portion of the printing plate onto the substrate to obtain a printed product. Since the blank portion is concave, the blank portion on the printed matter is slightly protruded during pressurization to form a printed product. The surface of the relief printing has an inconspicuous unevenness, which is characteristic of the relief printing.
Flexo is the main force of letterpress printing. It is widely used in the field of newspapers, books, and box printing, and is developing continuously, such as carton printing, carton printing, plastic printing, metal foil printing, napkins, toilet paper, facial tissues. Printing and so on.
Gravure printing features
The advantages of gravure are high printing quality, bright colors, thick ink layer, clear picture layer and high printing durability, but high plate-making cost and long cycle.
Gravure printing is also known as engraving gravure. The graphic portion of the intaglio is lower than the blank portion. The degree of sag is related to the level of the image, that is, the darker the image, the deeper the depth. When printing, the layout is first coated with ink, and the ink of the blank part of the stencil is scraped off with an ink knife so that the ink remains only in the concave image. In part, the ink is transferred to the substrate under the printing pressure to obtain a printed product. Because the depth of the concave is different, the amount of oil is different, and the thickness of the ink on the printed product is different. Where the ink is large, the color is thick, and the place where the ink is small is light, thereby reproducing the tone level of the image.
Gravure printing is widely used for large-volume printing, such as paper box printing, magazines, newspapers, plastic box printing, and securities, stamps, etc. Gravure printing has a large market share in box printing due to its high color saturation and rich image layers.
Screen printing features
Screen printing is characterized by a thick ink layer and a large variety of substrates. The substrate can be made of various materials or various shapes. It is widely used in the printing of metal plates, plastics and fabrics, especially in the printing of high-grade packaging boxes.
On a stenciled printing plate, the printed portion is composed of holes of different sizes or meshes of the same size but of different numbers, the holes can pass through the ink, and the blank portions cannot pass through the ink. During printing, ink is printed through holes, stencils or meshes onto paper or other substrates to form printed products. The finished ink of the stencil printing is thicker than the ink of the gravure printing. Screen printing is the main method of stencil printing. The printing plate is composed of a mesh (nylon mesh, polyester mesh, metal mesh) and a mesh frame. The screen is stretched on the frame, and the printing is carried out by the ink leaking through the mesh of the screen.
Lithography features
Offset printing mainly prints color papers on plate-making paper, offset paper and packaging paperboard. The products mainly include high-end prints such as calendars, product advertisements, albums, books and magazines.
Pure plastic packaging box printing basically does not use offset printing, but paper-plastic composite paperboard is offset.
The lithographic printing (mainly offset printing) printing surface and the blank portion have no obvious height and are almost on the same plane. The printed portion is lipophilic by means of sensitization or transfer: the blank portion is hydrophilic by chemical treatment. When the package is printed, the principle of oil and water repelling is used. First, water is placed on the plate surface, so that the blank part absorbs the water, and then the ink is transferred to the plate to make the image part of the ink, and the package is printed. At this time, the blank part has been adsorbed. Moisture, but not ink, and then the substrate is in direct or indirect contact with the printing plate, and the ink is transferred to the substrate.