In recent years, liquor labels made of vacuum aluminized paper have been widely used. The 70g wet-strength label is used as the substrate, and the vacuum-evaporation method uses aluminum-plated paper made of aluminum on the surface of the paper. The beer bottle paste not only has the same gorgeous metal texture as the traditional aluminum foil, but also improves the grade of the product. Because its aluminum layer is very thin, only a few hundredths of that of aluminum foil, its intrinsic performance is more like paper than foil, and it can adapt to 4 to 60,000 bottles of high-speed labeling and hot alkaline water recycling bottles per hour for filling lines. Cleaning requirements, high strength, low price, biodegradable, recyclable renewable, in line with environmental protection requirements, demand growth year by year, opened a new market for metal paper printing.
The printing of domestic aluminum-plated paper labels began with a small number of printing companies leading the professional production of offset printing, and developed into the current situation of introducing large-volume printing of narrow-width flexographic production lines and regional matching of numerous manufacturers offset printing. Flexo printing is characterized by colorful, instant drying, multi-color spot color printing and long-run economics, while offset printing is superior to flexo printing in terms of low plate making cost, high overlay accuracy, and rich dot pattern levels, and is particularly suitable for ordinary offset printing. The small and medium-sized enterprises use small-volume, multi-variety, high-precision, and flexibility to print high-grade fine aluminized paper labels using the offset printing method, which meets the needs of a large number of new types of wines in the market, rapid packaging and decoration, and shortened popular cycles. The key is to overcome the disadvantages of poor ink absorption and slow drying caused by aluminum-plated paper, which is a cause of large consumption and long production cycle. According to our practical experience over the past few years, the following aspects should be noted in the process of offset printing for aluminized papers:
First, the effect of the structure and manufacturing process characteristics of aluminum-plated paper on printability and performance
The surface coating of aluminized paper is a kind of polymer material, which can prevent the oxidation of aluminum film and increase the surface energy of aluminum metal, increase the adhesion of ink, and make the paper have good printability. The direct influence of the printing quality, processing labeling and bottle washing of aluminized paper wine labels is the ink absorption, dry and wet strength, dimensional stability, aluminum film peeling resistance, alkali resistance, and alkali penetration. Sexuality and negative surface water absorption, these technical indicators are closely related to material structure, base paper quality and manufacturing process factors.
The loose structure of the aluminized layer and the top coat of the direct aluminized paper along the paper surface fiber has a large surface contact area, a very fine and porous surface, a soft metallic luster, and an ink adhesion, drying, and anti-dirtiness. Well, the metal surface has strong peel resistance. This structure also facilitates the infiltration of hot alkali water from the surface when the bottle is washed, and the trademark falls off quickly, which is suitable for printing multi-color dot patterns for high-speed labeling of fine beer marks. The transfer method of aluminized paper is the use of PET original film evaporated aluminum film and transfer to the base paper as a whole, aluminum film is good smoothness, strong metallic luster, high smoothness, but due to the aluminized film morphology and adhesive layer structure, Make printing, die-cutting, labeling and bottle washing performance slightly worse than the direct method, but also affected by the compound tension of the paper processing, paper wet factors, the curl resistance is less than the direct method, suitable for making metal gloss strong bump too Traces of wine labels.
Second, the aluminized paper wine label decoration design and plate making process characteristics Aluminized paper wine standard decoration design should take full advantage of the visual aesthetic beauty of metal color, plate making process to consider poor ink absorption on the impact of printing and post-processing, in order to ensure the printing quality and Die cutting accuracy requirements, refer to the following:
1. The graphic design strives to be concise and eye-catching, reduce the difficulty of printing and drying ink on a large area and meet the color density, and it can be printed on the 80% flat screen 120 to 150 lines with uniform color adhesion.
2. The color performance should consider the influence of the paper's metallic luster and gloss on the color rendering effect. Generally, there should be black and white color matching; the metal bottom should print dark text, and the barcode is lined with white background to make the contrast and clarity. Good degree.
3. To avoid the overprinting of complicated and small text patterns caused overprinting difficulties and metal color exposed or miscolored, the color of the block or cable can be superimposed on the small Yang, Yin to spot color version, the use of pad polyester film plus the sun Measures to thicken the font to prevent Yang character broken Yinyin paste.
4. Chromaticity and color sequence arrangements strive to be reasonable, the best four-color offset press at once. Designing golden wine labels without pure white patterns can eliminate printing directly on gold-plated aluminum paper, with better color transparency.
5. Avoid large-scale on-site or three-color overlay dots caused by the Internet to create ink thick and dirty, more use of spot color printing, improve color saturation.
6. To highlight the good characteristics of offset printing dot layer, the color gradient network transition can be used to make the color change rich and increase the anti-counterfeiting function of the wine label, but the metal surface is poor in absorbability, the dot number is high and easy to paste, and the number is low, therefore Gradient mesh adjustment should be shortened, and the pattern is scanned with 150 lines of coarse mesh.
7. In order to ensure the accurate cutting of finished wine labels, the cutting lines are made in the same color with symmetrical pattern and high visual sensitivity. When there is room for typesetting, blanks are left between the label patterns to facilitate the observation of dirty plates during printing and prevent the printing of full plates. Ink sticky and sticky.
Third, the aluminum plated paper offset and processing difficulties
In order to meet the standard of ink color and the accuracy of overprinting and cutting, the printing pressure is required to be higher, the ink balance control is better, and a series of difficulties caused by the paper deformation caused by the multiple times of monochrome printing and drying are avoided, and multicolor should be used. Offset printing, at the same time take appropriate dry and anti-adhesive dirty measures, from the ink, fountain solution, color sequence, pressure and other factors that affect the ink balance start.
(a) the use of ink
1. Use special ink. The surface of the aluminized paper is unlike the coated paper with filler pits and voids between the fibers, allowing the ink to penetrate. The adhesion of the ink to the aluminized paper depends mainly on the infiltration of the coating on the aluminum film and the intermolecular interaction between the ink and the surface of the printing surface. force. Therefore, in order to increase the color density and speed up the drying, especially to meet the ink adhesion requirements in the use of wine labels, it is necessary to select oxidative polymerization inks for non-absorbent materials, such as POP inks, TSP inks, and the like. The special ink has high pigment content, fine particle size, good dispersibility, good film forming property of the connecting material, good surface transferability to the aluminized paper, and therefore high coloring power and good glossiness. The ink does not contain a solvent component that accelerates penetration, and it is equipped with a desiccant as a catalyst for the oxidative polymerization reaction. It can accelerate the reaction and shorten the oxidation conjunctiva process. Therefore, the special ink is faster drying, strong fixation, and ink film strength than the ordinary ink. high.
2. Choose a transparent ink with high transparency, which can reflect the characteristics of aluminum-coated paper metal with less light absorption and strong reflectivity, and improve the visual effect of metal colors. Choose opaque ink hiding power, so as to avoid the metal surface of Fei Fei î‚ƒî· î‚ƒî· îŽ¼ã‚º ç¢ ç¢?
3. The deployment of spot color inks should use varieties with high coloring power and darken printing. Use the ink with the same or similar transparency, so that the stability of the ink does not reduce the color. The transparent light color ink can be diluted with POP light oil without affecting the transparency and dryness. Different color cast and gloss of aluminized paper-bonded three-color inks have great differences in color rendering effect. In ink-transferring, the color-reducing effect of the base color and the transparency and hue changing factors of the ink layer should be taken into account to make the hue of the ink transfer accurate. The spot color ink should be used for cash transfer, and the ink color will darken and the drying time will be prolonged.
4. Reasonable use of ink adjuvants. In the case of political parties without auxiliary agents, when the printing color sequence is not sticky, the occurrence of reverse printing, overprinting of imprints or ink thick metal surface "outsole" can be added 1% JP varnish or 0.5% ~ 1% 5294 # Thinner viscosity reduction. After the white ink is printed on the machine for a period of time, it is prone to stacking ink, and the transferability is deteriorated, so that the print becomes thin and powdery and dull, and 1% to 2% JP varnish or POP varnish may be added to increase the proportion of the connection material to increase the fluidity. It can improve film formation and fixation, and improve the print fastness and gloss.
5. Special inks of different brands and grades should be reasonably selected according to the type of paper used, the quality of the trademark and the performance requirements, the design of mounting and the specific conditions of the printing process. Such as Japanese research AS ink color density, vividness and coloring force is best, printing mirror aluminum plated paper effect is better; DIC POP ink water resistance, on-board stability, white ink whiteness, fineness, hiding power and gloss degree Good, suitable for printing high-end wine labels on the silver-plated aluminum paper with fine dot patterns printed at the end. TSP inks are fast drying, thick white inks, better hiding power on gold and embossed aluminized paper, and JP black inks with good color and blackness, suitable for printing beer labels and various traditional wine labels.
(II) Reasonable Arrangement The printing color sequence of printing color-order aluminized paper labels is usually arranged as: white-black (or other dark colors)-red-gold (transparent yellow). Usually small text lines or dark color, small area of â€‹â€‹the first print. Transparent ink superimposes dark text patterns and prints transparent ink to make the text pattern full and full. A large area of â€‹â€‹background color is printed at the end to reduce the number of roller contacts to prevent dirt from sticking. In the four-color printing, the first color has the largest amount of elongation, and the overprinting accuracy requires the highest three-group printing. Aluminized paper wine labels are usually printed on silver paper with clear yellow or bronze brown, etc. to obtain a variety of colors of gold on the last color printing, because of which yellow ink or varnish viscosity is low, no reverse printing and ghosting under pressure The color of the previous color is good.
(III) Printing and ink balance control For the high smoothness and poor absorption of aluminum-plated paper, various factors affecting the ink-water balance, such as temperature, humidity, materials, pressure, ink volume, and moisture, should be strictly controlled during printing operations.
1. The use of alcohol fountain solution Because of the non-absorption of aluminum paper, the water consumption is much less than ordinary paper, and the control range of fountain solution is narrow, so it is suitable for the use of alcohol fountain solution. As a surface active substance, alcohol can reduce the surface tension, improve the water film formation, and take away heat and moisture when volatilizing on the printing plate, thereby reducing the amount of fountain solution, making the ink color bright and good gloss, shortening the drying time and reducing the dirt. Dirty. Note that the alcohol concentration should be controlled at 12% to 20%, and the pH of the fountain solution should be controlled at 4.8 to 5.5 because the alcohol concentration is too high. The surface tension is too low to easily accelerate the ink emulsification. The pH value is too low for the acidic ambassador to dry the ink. The failure of the agent causes the print to slow dry, so the acidity of the fountain solution should be minimized without affecting normal printing.
2. Reasonable determination of printing pressure Aluminized paper is more difficult to fix the ink, can Heidelberg four-color offset printing press plate lining increase 0.05 ~ 0.10mm, appropriate increase in printing pressure, increase the ink transfer rate, so that uniform ink blotting level. Aluminum-plated paper has high strength and small elastic deformation. It should adopt medium-soft packing and air-cushion rubber with small compressive deformation. The pressure change is small and the dot expansion value is small. The air-cushion rubber blanket has volume compression but does not expand to the side when squeezed. The characteristics of the ink in the pattern transfer to the aluminum film when the elastic buffering effect, uniform pressure, dot network smooth cleanliness, imprinted thin and flat, is conducive to the rapid oxidation of the non-absorbing surface of the conjunctiva drying.
3. Precautions in print jobs
1 Properly mastering the state of maintaining the dense water of ink, especially after the actual color density reaches a certain value, the amount of ink cannot be increased any more, so as to prevent the large amount of ink and water from printing to make it difficult to stick dirty. The product is bright and thick.
2 The printing area is small and the ink volume is small. For example, the blank area of â€‹â€‹the black version of the small text is large, and the amount of dampening fluid squeezed from the printing plate into the ink roller is also large. The ink is easily emulsified and can be separated at a certain time. Ink roller and a layer of old ink near the shovel, or add a print in the margin of the paper to increase the ink receiving area.
3 printing often use a magnifying glass to check the ink on the metal surface is exposed to the bottom, overprint the ink surface is clean and full of prints, whether the dots are enlarged or hollow, first adjust the ink balance, then consider whether to add auxiliary agent to continue observation and inspection of the ink and pay attention The status of paper, printing plates, and ink rollers controls the "three levels" and accomplishes "three tasks" so that the printed products meet the requirements for printing samples.
4 Keep the speed at 3 to 4 thousand sheets per hour and try to minimize the interruption of paper feeding. Speed â€‹â€‹too fast Imprint time is not enough, ink transfer rate is low and easy to stick paper. Due to the poor stiffness of the aluminized paper, the mouth is easy to curl when the speed is fast, and the side gauge is easy to pull too far. When the speed is slow, the paper is easily wrinkled at the tip.
5 Ink roller should be washed for a long time to avoid ink build up and down of the ink roller. The heat of the roller will decrease the viscosity of the ink and reduce the ink. The surface of the plate is not cleaned with a wetting powder and the plate is cleaned with water. Afterwards, the high concentration of dampening solution remaining on the plate is brought into the pattern ink, causing a section