The appearance quality of printed paper and common paper diseases

A common paper disease Any paper defect that is not covered by the paper quality technical requirements can be called a paper disease. Paper sickness includes not only invisible, but only certain performance defects known through experiment or printing, such as brittle, print-through, lint-free, powder-fat, etc., as well as those that are directly visible or felt. Various defects and defects on the surface of the paper, such as dust, dirt, etc. Here the latter is called paper appearance disease.
The appearance of paper is a lot of diseases, including dust, spots, net marks, wool marks, "cloud flowers", seersuckers, wrinkles, creases, dirty spots, turf, clear spots, temperature spots, holes, embossing, scars, pulp, Hard blocks, uneven quantification, poor uniformity, etc. Some of these appearances of paper diseases are caused by paper materials before papermaking, some are caused by poor technical operation or poor technology in the papermaking process, and others are due to poor environmental hygiene in the factory. Once it appears, it is relatively continuous, such as felt marks and “cloud flowers”. Once it appears, it always exists if no measures are taken; some appearance paper diseases have some kind of chance or occur only once after a long time, such as dirty spots. , holes and so on. The presence of some paper diseases will deteriorate the quality of the paper, such as dust, felt, etc. Some paper diseases will make the paper waste, such as offset printing paper with hard blocks or copper plates with large dirty spots. Paper can only be disposed of as waste.
According to different types of common paper diseases can be divided into:
※ The fluctuation of the quantitative paper and the unevenness of the paper web ration are generally due to the periodic vibration of the flow system of the paper feed headbox, the shake of the rotary screen in front of the headbox, or the vibration of the pulp pump. The result is sometimes caused by the unreasonable bending or opening of the homogenizer roller in the headbox. The second kind of fluctuation is generally caused by reasons such as unreasonable production process or improper operation management.
※ Poor formation. The phenomenon is:
1) Tufty structure: refers to the state where the fibers are mixed together into a mass.
2) "Cloud Flower": Also called cloud organization, it means that the fibers in the paper are distributed like clouds on the paper sheet.
3) Fibrous tissue disjoint: refers to poor fiber interweaving in the running direction of the paper machine.
4) Wave-like fibrous tissue: It refers to a wavy thickening layer that curves along the width of the paper.
5) Puddle: Refers to some of the visible longitudinal strip marks on the web.
* Dust, spots, sand, and hard blocks 1) Dust: It can be classified into three types: "fibrous dust," "non-metallic dust," and "metal dust."
2) Spots: Can be divided into "moist spots and vapor spots", "cylinder spots", "calender spots", "spots", "bubble spots", "filler spots and paint spots", "bright spots and white spots ".
3) Sand: Refers to the sand, lime residue, carbon residue and Other hard mineral sand present on the surface of the paper.
4) Hard block: Refers to the occasional hard texture on the surface of the paper, block material or coarse material that is higher than the paper surface, such as knots, grass knots, pulp blocks, etc., which are the most dangerous to the printing.
※ Holes and curtains 1) Holes: It refers to the complete penetration on the surface of the paper, there is no fiber hole. Holes can be divided into pinholes, holes, and holes by size.
2) Curtain: It means that the fiber layer on the paper sheet is thin but not completely penetrated, and its light transmittance is larger than other parts of the paper sheet. The little ones are called light spots, and the big ones are called curtains.
※ Embossing and all kinds of impressions 1) Embossing: In the pressing process, the fibrous tissue forming the wet paper is broken under excessive pressure, leaving scattered distribution on the paper surface, irregular shape, and transparency. With a high gap and many small pinholes, the phenomenon that the wet paper is crushed by the press roll is called embossing. Severe embossing can easily cause the wet paper to break in the press section.
2) Streaks: refers to strip marks that are different from paper gloss or color under light irradiation.
3) Gross cloth mark: refers to the imprint of the latitude and longitude lines of the papermaking felt on the paper.
4) Other impressions: Net marks, watermark roller marks, and vacuum roller marks.
※Electric and creases 1) Creases: Folds or overlaps of paper sheets to form moiré or creases. Can be divided into dead and sub-folding two.
2) Warping and arching: Warpage refers to the state where the paper is curled on both sides or corners, and the middle is concave; the arching refers to a state in which a large area in the middle or in the middle of the paper is arched, and two sides or four corners are concave.
3) Bubbling and bubble sands: Partial shrinkage of the blistering finger sheet, resulting in protruding foam on the paper surface, and fine wrinkling on the paper surface around the bubble; bubble sand is an arrangement of the paper surface A dense, fine bubble point.
4) Various wrinkles: According to the size and shape of the wrinkles, fine oblique wrinkles, curly wrinkles and so on.
※ Other paper diseases 1) Rift: It refers to a crack or break in the middle or edge of the paper sheet.
2) The edges of the paper are not neat and unclean: The edge of the paper is not neat. On the one hand, it means that the paper edges cannot be parallel or rectangular after the paper sheet is cut or the edges of the paper are burrs, bends, and twists. On the other hand, it means cutting out the entire selection. After the paper size is uneven or the back-end surface of the rewinder has a phenomenon of "in and out". Unclean paper edges refer to burrs, zigzag edges, incomplete edges, and dirty edges on cut sheets.
3) Hue inconsistency: refers to the inconsistency of the whiteness and color of the same batch of products even with the ream.
4) "Load lace": It means that the edge of the paper, especially the longitudinal edge, loses its flat state, and it is in a curved state that is not in the same plane as the paper surface.
5) Obvious two-sidedness: The gross difference between the two sides of the paper can be seen with the naked eye (except for single-sided offset paper and single-sided coated paper).
6) Incomplete, broken and shredded paper: Incomplete and broken sheets refer to papers with incomplete pages, which have missing corners, lack of edges, broken or only half, etc.; shredded paper refers to the size of paper that is not included in the paper. A small piece of paper.
The appearance quality of paper refers to the quality of paper that can be discriminated only by human senses without using equipment. It can be divided into the appearance quality of the paper itself and the appearance quality of the piece of paper formed by a sheet of paper or a long strip of paper.
No matter what kind of appearance quality affects the use of paper to varying degrees. The poor appearance quality will not only reduce the paper's use value and the printed product yield, but also cause the paper to be scrap when serious. In addition, some serious paper defects in paper, such as hard paper blocks, will also squash the plates and rollers during printing, causing damage to printing equipment. The appearance quality and physical properties of paper are also closely related. For example, papers with apparent seersuckers may also suffer from smoothness and opacity.
The appearance quality inspection of paper should achieve the following three purposes:
※ Check the quality of the paper. Mainly include: whether the shape of the paper is good, the size is qualified, the packaging quality and the degree of damage.
※ Master the basic paper quality of paper. Including color, uniform level, flexible tensile, smoothness and cleanliness.
※ Check out the approximate miss rate of lithographic paper (the percentage of paper that has significant paper disease as a percentage of total paper).
The concept of print adaptability In order to obtain excellent print quality, paper and ink must be suitable materials. In other words, the requirements of the paper must be easy to print, in addition to the ink color is bright, strong coloring, but also must have good and proper permeability, volatility and the ability to conjunctiva. In addition, the rubber rollers, blankets, plates used in printing, and the conditions in the printing shop and the operation of the printing process must also be compatible with the need to print excellent works.
Thus, printability can be broadly defined as: "The paper, ink, plate, printing process, and shop environment are suitable for printing performance."
In order to print excellent and fine prints, it depends not only on the inherent functions and characteristics of the above five aspects, but also on their mutual relations and cooperation. It must also be made clear that paper is a crucial aspect of these five aspects, and it plays a decisive role in the quality of print jobs and the quality of printed products.
Regarding the printability of paper, various countries have various definitions and explanations because of their different focuses and perspectives.
According to Kauster Carlson of Sweden, the printability of paper refers to all the properties related to qualitative and quantitative print results on a printing press. He also pointed out that: judging the printability of paper is based on the following: color uniformity on the printing surface; the clearness of the difference between the printed part and the blank part; the legibility of the printed part; and the degree of coverage of the paper base. It also shows that these are related to paper uniformity, compressibility, smoothness, opacity, ink absorption, and the like.
British expert G. L. Reed puts forward: "The printability of paper is used for the purpose of describing the physical and chemical properties of paper when it is used to manage the production of printed matter at the necessary speed, necessary quantity, and necessary quality under the specified printing method. The comprehensive vocabulary, "i.e.," where necessary to accept a proper amount of ink, requires that the paper has a satisfactory printability. That is, the expected dryness of the ink must not be given the opposite effect. Appropriate amount of smoothness, proper porosity for inks and ink media, various optical properties (opacity, color, and luster), unchanging stability in rheology, etc. Chemical properties should be Affects the durability and color of the printed image and does not adversely affect the printing plate. As a single sheet, the edges should be cut neatly, and if there is a web, it should be rolled evenly. There must be no fine fibers and paper on the surface. Paper must not be abrasive, and it should not retain static electricity or generate static electricity unreasonably."
Japan's Sato Teng Meng listed the following four articles on the printability of paper:
1. The color of white can make the depth of the picture and the gallery clear.
2. It can quickly absorb the ink, and does not appear "through the ink, through the back, the back of the dirty."
3. When printing, no paper dust or hairiness will occur, and the layout will not be worn out.
4. There should be no obstruction when passing the press.
However, Japan's Oda Tosaka made the following three factors related to the suitability of paper printing:
1. Elements directly related to printed lines. The accuracy of the printing should be based on the printing plate as it is; the coverage of the ink, the transferability of the ink, the density, gloss, and hue of the printed ink.
2. Elements related to the printed surface. Paper fluffing, translucent, wrinkling, dirt, ink bleeding, ink pulverization, ink drying, negative dirt, positive and negative through the print.
3. The elements of the printing operation. It should be easy to print, paper, and paper.
Comprehensive analysis of the above points of view, the author believes that: the printability of paper should be generalized as follows to define and explain: The printability of paper refers to the paper can adapt to the requirements of ink, printing conditions of the printing plate, to ensure the smooth operation of the print job, and Get the necessary conditions for excellent prints. The printability of the paper is not a fixed property, but a performance that is compatible with different printing conditions and different print characteristics.
The printability of paper includes both the suitability of print jobs and the suitability of print quality. The former refers to a variety of properties that the paper can handle satisfactorily for the necessary operations on the printing press, such as the absence of paper breaks, the smoothness of the paper, and so on. The latter refers to the properties of the paper that play a decisive role in the quality of the prints (including the performance of the prints), such as whiteness, opacity, surface strength, smoothness, dimensional stability, and ink absorbency. The print quality adaptability is called narrow printability, and the broad printability includes both print job suitability and print quality suitability.