3. The commonly used papers for printing can be classified into industrial papers, packaging papers, household papers, and cultural papers according to the different uses. Among them, cultural papers include writing papers and art papers. Printing paper. In the printing paper, it is divided into newsprint, letterpress printing paper, offset printing coating paper, dictionary paper, map and sea drawing, gravure printing paper, painting newspaper, weekly newspaper, whiteboard paper, writing paper, etc. according to the performance and characteristics of the paper. . In addition, some high-grade prints are also widely used in art-drawing papers.
Newsprint: Newsprint is mainly used for the printing of newspapers and some letterpress publications. It is soft and elastic, has strong ink-absorption capacity, and has certain mechanical strength. It can be adapted to various high-speed web presses. This type of paper uses wood paddles as raw materials for manufacturing, contains more lignin and impurities, and is susceptible to yellowing and brittle paper, and has poor water resistance. Therefore, it is not appropriate to preserve letterpress printing paper for a long period of time: this is a special paper used for letterpress printing. The nature of the paper is similar to that of newsprint. Water resistance, color purity, and paper surface smoothness are slightly better than those of newsprint. The ink absorption is more uniform, but the strong ink capacity is worse than newsprint.
Offset printing paper: Offset printing paper is a kind of paper used for offset (flat) printing, and it is divided into single-sided offset paper and offset-type offset paper. Single-sided offset paper is mainly used to print posters, packaging boxes, etc. Double-sided offset paper is mainly used for printing pictures, pictures, etc. Offset paper is compact in texture, less in flexibility, and strong in water resistance, and can effectively prevent the paper from being deformed, misplaced, napped, or removed from powder during multicolor overprinting. Can give the print better color purity.
Offset coated paper: also known as coated paper, is a kind of high-grade paper coated with a layer of inorganic coating on the surface of paper and then super-calendered. The surface of the paper is smooth and flat, and the color purity is high. Delicate and smooth network points can better reproduce the layered feeling of the manuscript, and are widely used in art pictures, albums, and commercial leaflets.
Gravure Printing Paper: Rotogravure printing paper is white and firm, with good smoothness and water resistance. It is mainly used for the printing of banknotes, stamps and other high quality and difficult to imitation prints.

Whiteboard paper: Whiteboard paper is a kind of paper with relatively uniform fibrous structure, surface layer with filler and rubber compound and coated with a layer of paint, and is produced by multi-roller calendering. The paper surface has high purity and relatively uniform color quality. The ink-absorption property has a good folding-resistance. It is mainly used for the packaging of goods, the lining of products, and the picture-charts.
Synthetic paper: Synthetic paper is made of chemical raw materials such as olefins and then added with some additives. It has a soft texture, strong tensile strength, high water resistance, light resistance to heat and cold, and can resist the corrosion of chemical substances without environmental pollution. Breathable, widely used in advanced art, maps, pictures, high-grade books and other printing.
4. Performance requirements for paper The ability of the paper to be used with high quality for printing depends on the printability of the paper. The requirements for printing on paper are: the hue of the paper should reach the purity of the same texture as much as possible, the degree of dust of the paper must not exceed the allowable range, have the minimum light transmittance, and ensure the mechanical strength during normal printing, and the thickness of the paper. The tightness, structural characteristics, etc. should be the same in the same print batch. The edge of the paper should be right angle and the slope error cannot exceed ±3mm.
The smoothness of the paper: The smoothness of the paper directly determines the print quality of the print. The paper with high smoothness can make contact with the plate better during embossing, so that the ink layer on the plate can be evenly transferred to the surface of the paper. The paper with low smoothness will be uneven on the surface during printing. The uneven contact between the surface of the plate and the paper during imprinting causes uneven transfer of the ink layer to the surface of the paper. If the paper touches a paper with low smoothness, the pressure during printing may be appropriately increased during printing. Can properly make up for the phenomenon of imprints appearing on the surface because of its uneven surface.
Ink absorption of paper: The absorption of ink by paper depends mainly on the tightness of the fibers of the paper (the size of the gap). When the gap between the paper fibers is small, due to too little deuterated fibers, the effect of the fiber capillary is affected, resulting in the paper's ink absorption; if the gap between the paper fibers is too large, it will be caused by excessive absorption of the connecting material. Ink pigments are also absorbed, making prints appear through the phenomenon.
The elasticity and plasticity of the paper: In various processes such as printing and printing, the paper will undergo various changes due to the different surrounding environments. As the external force, will instantly change their shape and size, and when the external force stops, the paper will return to the original shape and size, this deformation process is called sensitive elastic deformation; when the paper is subjected to external force In a certain period of time, it changes its shape and size. When the external force ceases to function, it slowly returns to its original shape and size. This process of deformation is called hysteretic deformation; when the external force is cancelled, the paper remains. In the state of deformation and shape caused by external forces, it is called plastic deformation. Sensitive elastic deformation and hysteretic elastic deformation are reversible deformations, while plastic deformation is irreversible deformation.
Paper surface strength: The surface strength of the paper determines the decisive influence of the surface on the surface of the paper during printing, such as wear resistance, resistance to powder fall, and fluff resistance. When printing, in order to get a clearer dot, some ink with higher viscosity will be used. If the surface strength of the paper is not enough, it will be easy to drop powder, hair loss, and adhere to the surface of the plate; if you use a lower viscosity ink In the lithographic printing, the ink and fountain solution emulsify, resulting in dirt in the blank area of ​​the printing plate.
The moisture content of the paper: How much water does the paper directly affect the quality of the printed matter. Excessive water content will reduce the strength of the paper. Under the action of the external force, the paper fibers will be pulled out and the plastic deformation will be enhanced. The drying speed is affected; if the water content is too low, the paper will be brittle and easily damaged, resulting in static electricity. Since the moisture content of the paper has a great correlation with the surrounding environment, the humidity and temperature of the printing room should be properly arranged to maintain the balance of water content of the paper.