With the continuous development of China's social economy, people's aesthetic concepts are increasing day by day. Printed matter is no longer a traditional form of printed matter. In order to reflect the artistic effect of the product, some printed matter often uses some special raw materials and special craft paper. The surface has a unique visual effect and has a personalized use function. This type of paper is collectively called special paper, and it is also called art paper in the industry. According to the author's knowledge and understanding, art paper can be collectively referred to as special paper, but special paper cannot be generally referred to as art paper, because, such as carbonless copy paper, anti-rust paper, etc. also belong to the category of special paper, but it is not suitable Called art paper. Special paper is widely used to print beautiful books, magazine covers, invitations, promotional materials, business cards, greeting cards and other high-end packaging and decoration products.
Because special paper uses a special production process, its structure and performance are significantly different from ordinary paper, and the printing effect is also significantly different. The main performances are: some special papers have uneven relief or grain marks on the surface, which can not reproduce fine dots well; some papers are acidic, and the printing drying speed is slow, which affects the effect of overprinting and is prone to imprinting. Malfunction; some papers have a certain color, which will interfere with the printing color. Therefore, to print special paper, we must pay attention to effective technical control in terms of pre-press design, ink preparation, blanket selection, printing pressure and post-press processing, in order to better ensure the quality of special paper printing and decoration processing.
1 Design the printing layout according to the characteristics of special paper
The special feature of some special papers is that the paper surface has a certain artistic effect. For example, some special paper surfaces have some special patterns, uneven reliefs, colors, gloss, etc., which make the paper produce a certain artistic visual effect. Therefore, this requires that in pre-press plate design, we must fully consider how to express the unique artistic charm of the paper itself, that is to say, can not destroy the special artistic visual appearance of the special paper after printing, in order to enhance the artistic effect of the printed matter. Therefore, the author believes that special paper should not be designed for full-page printing with a large amount of ink, so as not to affect the full performance of special paper's unique texture, uneven relief, gloss, color, etc., so that the specialty paper's personality and layout design style can reach perfect Unite. It is necessary to design the printing of small layouts as much as possible, and can design text, line plates, and pattern printing layouts of appropriate areas, or embellish the products by using local UV, concave and convex embossing, anodized aluminum hot stamping, die-cutting indentation modeling, etc. Artistic sense. In addition, for special paper with embossed relief or texture on the paper surface, it is not appropriate to design and print small dots, text, letters, numbers or line layouts, but should design layouts with mainly text and lines of appropriate size for printing. Both the layout and paper characteristics are well taken into account.
2 Select printing ink according to the characteristics of special paper
In addition to white special paper, some special papers have a certain color, so the design of the printing color must fully consider the coordination of the color of the base paper and the printing color, and it should be printed by using a suitable spot color ink, or using The process of printing gold and silver makes the printing ink color and the color of the base paper form a strong contrast, so as to achieve a simple and beautiful artistic effect. For special papers with grayish and dark paper colors, when printing spot inks, the optional inks should be used sparingly or without dark inks to avoid darker colors after printing, which makes the printing contrast less prominent and affects the artistic vision of printed products. effect. For special paper with white paper color, rough paper surface or loose fibers, you can use the "dark ink thin printing" process for printing, that is, adjust the hue of the printing ink a little deeper, so that the printing ink layer is reduced accordingly. Thinner, so that it can not only meet the requirements of printing ink color, but also better avoid the appearance of paste quality problems caused by the thick ink layer. [next]
3 Adjust the performance of the ink reasonably according to the characteristics of the special paper
In the daily printing process practice, we can find that the printing ink color drying is generally slow in special paper. Compared with offset paper and whiteboard paper, its drying is much slower. Sometimes the product is printed in a humid climate. After being left for several days, the ink layer still did not dry completely. Due to the slow drying of the paper printing ink layer, the printing process is prone to quality defects such as overprinting (that is, the back of the printed product is dirty), and at the same time, it will also affect the processing and production progress of the subsequent process. The main reason for the difficulty of drying the printing ink layer of special paper is generally determined by the characteristics of the paper. If the surface of the paper is treated by a special process, the absorption performance is poor; some papers have high moisture content or acidity, so that the paper The moisture prevents the drying of the ink or the pH value is too small and slows the drying speed of the printed ink layer. Therefore, in order to prevent the phenomenon of slow drying of imprinting, the moisture content of special paper should be controlled between 3% and 6%; the pH value should be controlled between 7 and 10. However, because the characteristics of paper often depend on the paper production process, the printing plant can only improve the drying of the printing ink layer by adjusting the characteristics of the ink. For example, special paper with a slow drying of the printing ink layer can be added by adding an appropriate amount of ink The desiccant can adjust its drying speed. For special paper with poor water absorption, it can be printed with quick-drying and fast-fixing ink in the form of oxidative conjunctiva drying to ensure the quality of printing and finishing of products.
4 Determine the number of screens according to the characteristics of special paper
The printing layout of the dots is color, so that the dots on the layout can be completely transferred to the paper surface, which mainly depends on the smoothness of the paper surface. Only the special paper with good smoothness can better express the levels and dots of the original tone. The shape makes the picture rich in tones and layers, with clear dots and soft tones. If fine mesh products are printed on special paper with rough paper surface, it will affect the faithful reproduction of the printed layout, especially directly affect the subtle performance of the printed product. Process practice shows that the higher the number of screen lines, the smaller the dot diameter. In this case, if there are tiny depressions on the surface of the paper, the dots on the printed product will inevitably appear incomplete. If you increase the printing pressure or increase the ink supply of the layout to compensate for the defect of poor contact between the layout and the paper, it will cause the spread of the ink and expand the dots. Therefore, when special paper with poor paper smoothness should be considered, a slightly thicker network cable should be selected appropriately, and small high-gloss dots should not be made. The process control principle for mastering the number of screen lines is generally: the better the smoothness of the paper, the higher the number of screen lines selected. Conversely, for special paper with poor smoothness, the number of screen lines on the printed surface should be lower. For special paper with general pattern structure, the screen line should be controlled at about 130 lines / inch as appropriate. For special paper with good smoothness, the screen line can be controlled above 150 lines / inch. In addition, the same special paper printing, we must also consider the differences in process characteristics, such as the flexographic printing process, because the soft half of the printing plate is prone to deformation, the number of screen lines should be slightly lower than the lithographic printing process. Because the smoothness of special papers with different texture structures is very different, it is difficult to use standard data to determine the number of screen lines suitable for various special papers. Therefore, the determination of the number of screen lines for special papers should be passed Proofing experiment can get better printing process effect. [next]
5 According to the characteristics of special paper, control the printing process of gold, silver and ink
Gold and silver colors can give people a noble and gorgeous feeling. Printing appropriate areas of gold and silver colors on special paper can improve the artistic effect of the product, increase the added value of the product, and double the value of the product. However, due to the poor surface smoothness of some special papers and the characteristic of being acidic, coupled with the adhesion, viscosity and fluidity of gold and silver inks, it is worse than ordinary inks. In this way, if the printing process technology is not properly grasped, it is very It is easy to produce unfavorable conditions such as dull color, uneven ink color, crystallization of imprinting, pasting and fading. Therefore, it is necessary to pay attention to the control of printing process technology, mix the gold powder and silver powder used for gold and silver ink, and avoid heat, moisture or contact with acid and alkali substances during use and storage. The unfinished gold and silver powder should be sealed. In addition, if the proportion of gold, silver powder and gold blending oil is improper, that is, the amount of gold or silver blending oil is too much or too little, it will affect the fluidity and transfer coating performance of gold and silver ink, which is easy in the printing process. Problems with pasting or imprinting occur. If the gold and silver inks are mixed too much at one time, the use time is too long or the printer speed is too fast, and the contact pressure between the ink rollers is too large, it is easy to oxidize the ink and darken it. Therefore, the adjustment of the fluidity of gold and silver ink should be based on the degree that the layout is not blurred, and it should be used with the adjustment. Generally, the amount of one-time preparation is suitable for continuous printing for three or four hours. The ink roller printing gold and silver ink should be properly soft, and the contact pressure of the ink roller should be adjusted as lightly as possible, so as to avoid excessive contact pressure and increased frictional heat to cause the ink color to darken.
6 Adjust the printing pressure and blanket according to the characteristics of special paper
General special paper generally has the characteristics of relatively brittle paper, especially those with embossed and textured surfaces, and the lithographic or relief printing process requires a certain printing pressure and a liner with certain characteristics to complete the ink. Good transfer. If the printing pressure is too light, the ideal imprint transfer cannot be achieved, and it is prone to defects in the quality of the layout. Conversely, if the printing pressure is too heavy, on the one hand, it is easy to destroy the relief and lines on the paper. On the other hand, the printing is prone to plate-off or paste failure. Therefore, the author believes that for special paper with embossed and textured surface and relatively thick paper fibers, no matter what printing process is used, the printing pressure should not be too large, so as not to damage the clear texture of the paper or make the paper deformed. Conversely, if the paper has special rough surface fibers, it may be appropriate to increase the printing pressure to increase the amount of ink transfer and ensure the clarity of the printing surface. For the lithographic printing process, the blanket is the medium for printing pressure and ink transfer, and its characteristics have a great influence on the printing effect of special paper. Use ordinary blanket, if the printing pressure is large, it is easy to deform, and the surface of the rubber is easy to squeeze and rub against the plate surface, which is not conducive to improving the printing durability and printing quality of the printing plate. The air cushion blanket is used, and the printing surface has relief and texture The special paper is a reliable guarantee to effectively prevent the printing plate from abrasion and ensure that the imprint is transferred well. [next]
7 Select the appropriate printing process according to the characteristics of special paper
For some special papers with embossed textures on the surface, it is very important to choose a suitable printing process to effectively protect the embossed texture of the paper from large-scale damage and maintain the artistic characteristics of the paper. We know that in lithographic and gravure printing processes, the surface of the paper is fully accepted by the pressure of the cylinder during printing, which is easy to damage the relief texture of the paper surface. Therefore, special paper with embossed texture on the paper surface should be printed by the embossing (including flexo) process or the silk screen process, because when the embossing process prints, only the protruding plate parts will generate contact pressure on the paper surface, and will not Destroy the entire paper surface, the flexographic printing plate is the softest, and the printing effect is relatively ideal. In addition, during the silk screen printing process, the scraper (scraper) scrapes the screen surface to transfer the liquid ink through the mesh to the surface of the substrate. The slight pressure is not enough to destroy the relief texture of the special paper surface. Therefore, it can be said that the special paper printed with relief texture is best to use flexo, embossing or screen printing process. The lithography process is more suitable for special paper with no obvious relief texture on the printed surface.
8 According to the characteristics of special paper, control the post-printing process
After printing some special papers, it is also necessary to use concave and convex embossing, embossing, indentation, anodized aluminum hot stamping or UV to improve the artistic level of special paper printing products, which requires good process technology, such as For the embossing and embossing process, pay attention to controlling the plate-making technology. The embossing and embossing process should be based on the thickness of the special paper, and the contour of the "gravure" graphic edge should be properly enlarged to avoid crushing the paper surface of the graphic outline edge . By making a solid resin plate, you can use the round flattening, round flattened relief printing machine or offset printing machine to perform the concave and convex embossing, embossing or indentation process. The process quality effect is significantly better than the flattening die cutting machine. Achieve more uniform pressure and obtain clearer lines and traces. For flat embossing, round embossing, embossing and embossing process, the base should be made of aluminum plate, cast iron or other metal plate holder with good flatness and high compressive strength to ensure The layout gets even pressure. When stamping aluminum foil on special paper, we should pay attention to grasping the stamping temperature and machine structure, performance, layout structure, temperature conditions of the production environment, stamping pressure, anodized aluminum material characteristics, special paper performance and stamping speed, etc. According to the comprehensive consideration of the production process, after the optimal hot stamping temperature is determined, continuous hot stamping should be continued during the production process, as far as possible to avoid downtime, and keep the temperature constant, in order to better ensure the quality of hot stamping Stability. When using special paper for the UV process, it should be noted that the UV varnish should not be placed for too long. The shelf life of the general UV varnish is 1 year. It should be stored in a low temperature and ventilated and cool place. Mix the agents to avoid problems such as poor drying, peeling of the coating, and discoloration. In the production, it should also be noted that the UV light irradiation should not be excessive, otherwise the color will easily turn yellow. For special paper that requires hot stamping or UV, do not use too much powder during printing, so as not to affect the quality of post-processed products.
To sum up, the quality of special paper printing and post-press finishing processes can not only improve production efficiency, but also effectively avoid the emergence of quality problems of one kind or another and improve products by controlling good operation technology and process technology. Artistic level. The carefully designed and produced high-quality special paper prints will not only be exquisite prints, but also beloved works of art when they are displayed in front of people's eyes. This is the product quality that customers are after and modern. The product quality goal that packaging and decoration printing process aspires to.
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