Discussion on the factors influencing the success

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Discussion on the factors affecting the success of corrugated carton printing

at the packaging industry seminar and exhibition held in Chicago, various folding cartons and cartons processed with different liners and paperboards were displayed, which can meet a wider range of printing needs. A successful printing method is to transfer the ink to the substrate in a controllable way. The printed content includes text, field and halftone images. In order to obtain a stable printing effect in the printing process, it is very important to determine and control the paper performance that affects the relationship between ink, printing process and substrate materials

first of all, we should distinguish the main differences in printing performance between paper and paperboard. The easiness of paper plays an important role in the smooth completion of printing or post press processing. The main factors affecting the paper feeding include the flatness, tear strength, hardness, ink absorption, dimensional stability, surface strength, tension and thickness of the paper

printability is a property of whether paper can replicate images stably. It includes color density, flatness of field output, hue range, hue and ink transmission performance. In order to achieve better printability and the paper routing of liner and corrugated board, it is necessary to understand the relevant paper properties

surface characteristics

the quality of printed matter is affected by the surface characteristics of paper, backing paper and paperboard, such as optical appearance, ink absorption, paper permeability, structure and thickness. The surface characteristics of lining paper or paperboard are closely related to many factors, including the natural characteristics of the fibers used, the processing methods in the production process, the form of composition, coating or post-processing procedures, and so on. One of the most important factors affecting the printing quality is the surface structure of paper, which usually refers to the smoothness or roughness of the surface

the smoothness of paper is mainly controlled by the morphology of fibers. A specific surface structure can be obtained by post-processing processes such as polishing, coating or polishing. These factors also affect the absorption and permeability of paper, as well as the final ink adhesion

the thickness of paper varies with the processing methods of paper equipment and raw materials. The thickness is directly affected by the wet composition, the pressure on the wet end, and the degree of polishing. Uniform thickness along the direction of the paper roll is an important guarantee for stable printing effect. The change of thickness in the paper will lead to problems such as uneven output results and excessive dot expansion in the printing process

the loose density of paper determines the proportion of air and solid components in the paper. This relationship is very important for determining which paper or backing material is ultimately used

compressibility refers to the degree to which the paper thickness decreases when the paper surface is vertically subjected to a certain pressure. Compressibility essentially refers to the strength performance, which affects the transmission of ink. Compressibility is affected by hardness, density and composition


absorption refers to the proportion of liquid (ink) entering the paper through capillary action. It is determined by the loose density of the paper. The structure of paper presents many tiny channels and pores, and the capillary effect depends on the relationship between the surface energy of paper and the surface tension and viscosity of ink

the loose paper surface is relatively open, with many large pores, which can absorb the pigment and binder of ink. The highly matte paper may only absorb the binder. The absorption degree of ink in liner paper or paperboard is very important. It is actually the comparison of information transmitted between ink and paper. If the pigment is only on the surface of the substrate and is not absorbed, the ink can effectively absorb light. The more ink sucked into the backing paper (corrugated paper), the more image loss will occur. Once the printing primary color ink is absorbed, it will lose luster and sometimes even show different colors. Black will lose its brightness and sometimes even appear gray. The same kind of ink will show different colors on the surface of coated and less absorbent materials. Therefore, the ability of paper to maintain ink is of great significance

the absorptive capacity of ink is also reflected in density. The absorption rate mainly depends on the composition of constituent materials, the composition of fillers, size, refining degree, matte degree, density, surface coating and other factors. The density of uncoated paper is usually lower than that of coated paper

ink film, dust, chemical structure

practical ink film should be thicker than the surface roughness of the material to ensure the smooth deposition of ink. Modern photosensitive polymer plate printing system has Shore-A hardness, which can overcome the uneven paper surface structure. However, the softness of the corrugated flexo printing plate can not reach this hardness, which will produce excessive dot expansion

PET materials under printing plates often appear in printing plates, tapes and tiles: V and ω Improper collocation with corrugated foam materials in "2.1" may lead to serious dot expansion. The softer the corrugated printing plate, the easier it is for the printing machine to overcome the problem of rough surface; However, the sharpness of printing elements will also be reduced, and the image elements seem to be compressed together

on the other hand, the use of thick ink film during printing leads to serious dot enlargement. The thicker the ink film, the harder it is to dry. Prolonging the drying time will reduce the printing speed and increase the cost. Low viscosity inks are often used in flexographic printing. In this way, the binder is more flexible and can enter the coating more quickly to leave the pigment on the surface. The image loses gloss, and the paint can be easily wiped off the surface. This kind of situation is easy to appear in the direct printing of corrugated paper with inferior backing paper. Therefore, it is very important to ensure that the absorbency of the backing paper matches the rheological ability of the ink

dust is obviously another printability problem related to the printing process. Dust is the appendage of small pieces on the surface and edge of paper. If the ink filter is not used, dust and dirt will accumulate in the ink and transfer to the printing plate. This phenomenon is "dirty output"

the chemical composition of paper also has a certain impact on the printability. Too much acidity in the backing paper will affect the drying speed of the ink. Generally speaking, the pH value of uncoated backing paper material should be 5 or 5.5 or higher, and that of coated material should be 5, in order to ensure the optimal drying time

lining paper (corrugated paper) materials

generally speaking, the lining paper materials used in post press processing are usually divided into the following types:

kraft paper corrugated paper is often used in occasions where the surface paper has strong resistance, or when the packaging needs to have strong tear resistance. This kind of liner is usually used in type A, C and B corrugated paper

test liner is an effective and cheap liner made from waste paper recycling. It consists of two layers: a thick bottom base and an outer layer with good adhesion due to the fact that the suction looseness has become. This kind of liner is also mainly used in type A, C and B corrugated paper

decorative lining paper. There is a choice between uncoated, semi coated and fully coated liners, usually referred to as decorative liners. The white lining paper above provides a suitable surface for the product to achieve the most attractive printing quality, especially for image design with multiple colors. Decorative lining paper is more and more used in B, e and f corrugated paper

the photosensitive polymer printing stroke for post printing is 600-800mm; In the post printing process of corrugated paper, photosensitive polymer printing plates have many basic properties, which depend on the natural characteristics of the printing process, the substrate materials and the external conditions and factors in the printing process

considerations such as the quality of various backing paper materials, paper and paperboard, ink characteristics, wrinkle roll parameters and equipment limitations, as well as other products used in the paper product processing industry, play a very important role in the concept and improvement process of printing processing technology

photosensitive polymer printing plate is composed of four main parts: crosslinker, monomer, photoinitiator and additive. The change and selection of these components as well as their properties and interrelations play a vital role in printing performance. The components used to produce photosensitive polymer plates have a great impact on the choice of water-based ink system. The transmissibility and concealment of inks, the resolution, stability, oxidation resistance and printing related performance (the limitation of equipment speed) of printing plates are the main problems that should be considered when developing and improving photosensitive polymer printing plates

necessary conditions for printing plate

the development of new photosensitive polymer printing plate is challenged by problems such as high-resolution printing effect, high-resolution point and field ink transmission. Finally, printing enterprises have to use different photosensitive polymer printing plates in different combinations of paper bags, backing and backing materials, resulting in different combinations. This is to maximize the use of specific printing plate characteristics, especially hardness and ink transfer capacity, to suit a specific application and a specific substrate

in order to realize the standardization of printing quality, corrugated paper printing plants are increasingly using thinner photosensitive polymer plates and two standard calipers: 3.94mm (0.155 inch) and 3.18mm (0.125 inch). For printing plates, the most common standard is to produce smooth and dense ink transfer and low point expansion

another requirement is to accurately and clearly output the technical specification for building foundation pit support JGJ 120 ⑴ 999 FINE inversion film and line elements, reduce filling elements and smooth printing of difficult color levels. The minimum tolerance on the specification must be reached. The hardness of the printing plate should not exceed 42 Sha (ISO) of E or F corrugated paper and 34 Sha (ISO) of B, C or a corrugated paper to overcome the surface structure problem of the paperboard. At the same time, printing plants need higher plate elasticity to reduce the requirements for the performance of backing paper, reduce downtime, and facilitate the setting of printing pressure

plate makers all hope to shorten the cleaning time and drying time to improve the output and production capacity. It is desirable to have a longer back exposure time to broaden the pre exposure range and minimize the impact of fluctuations during UVA emission. In addition, shorter surface exposure time and longer main exposure range are also needed to improve efficiency. Digital printing plates usually have different needs, and these printing systems also need to meet different needs to achieve clearer printing effects

limited by the selection of specific printing plate components, the printing plate and its performance have certain limitations. These limitations conflict with many of the requirements mentioned above. These conflicting demands often cannot be solved only by means of ink composition, changing printing plates, adding padding or adjusting equipment. The combination of primary colors often has to be transformed to meet most needs. These elements range from printing plate components to applications to printing production

compressible backing paper

in order to reduce the overall degree of plate deformation in the printing process, compressible backing materials are generally used under the transmitted paper. The compressible foam material can absorb most of the additional printing pressure and improve the printing quality

the compressibility and memory of foam material affect the ink transfer performance of the photosensitive polymer printing plate above. The thickness of the foam should not be greater than the thickness of the plate material used to prevent any possible instability of the system (which may lead to uneven printing output)

post printing application

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