Materials and processes commonly used in the most

2022-08-21
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Materials and processes commonly used in cigarette bag printing

when low-grade cigarette bags are adjusted to medium and high grades, the quality requirements of printing paper for CFRP are generally becoming more and more harsh, and they will shift from ordinary fibers to non absorbent composite paper. There are two kinds of composite paper for cigarette packs: aluminum foil composite paper (aluminum foil is compounded with paperboard), bright film (laser film) composite paper (bright film, laser film is compounded with glass paperboard)

when printing on laser cards, UV ink is often used to improve the adhesion of ink. The following are the problems that should be paid attention to in laser card printing:

first, in the production process of laser film, black spots and dirty spots will inevitably appear due to static electricity. In order to cover up these defects and reflect the laser effect, it is usually necessary to add 20% - 40% white when designing the cigarette package printing process

second, there are two kinds of laser films: 12um PET film and 23um BOPP film. In order to ensure the molding effect and cigarette bag speed, 12um PET film is usually used

third, in order to improve the gloss of cigarette packs, laser cardboard with the aluminum coating facing outward is often used, but it is easy to be scratched when the aluminum coating faces outward, which must be paid attention to during printing

IV. during die cutting, in order to prevent burrs, the pattern peak knife can be used. Due to the weak combination of PET film and paper, delamination often occurs in die cutting. Therefore, it is necessary to carry out small batch cigarette machine trial packaging before formal production. In order to ensure the glue effect, the height of the glue tooth line at the mouth of life should be 23.7mm, and the density of the glue tooth line should be increased at the same time

analysis of the current situation of various printing processes

I Offset printing

offset printing process should be said to be a relatively mature printing process. Especially in hierarchical printing, there is a set of standardized and weekly data-based methods

however, cigarette package printing is not only the reproduction of product tone, but also involves a large number of spot color reproduction, such as large-area red field, gold silver, pearlescent effect, etc. Because spot colors, especially field spot colors, have high requirements for saturation and brightness, offset printing in the field, due to the limitation of ink layer thickness, appears to be more than enough. In order to achieve the purpose, the method of "deep first and then light" is usually used for two times of printing (the design should consider avoiding hollowing out words on the field version as far as possible to avoid increasing the difficulty of overprint). In addition, cigarette package printing requires high color stability (consistency). Due to the existence of ink emulsification and long ink path, offset printing has many factors that affect the stability of ink color, so it is difficult to meet the above requirements

in order to meet the needs of high-end cigarette bag printing, most printing manufacturers have implemented UV process transformation on offset printing machines. The emergence of UV technology has fundamentally solved the problems of ink adhesion, friction resistance and dryness on composite paper prints. Some cigarette bag manufacturers have begun to use offset UV ink to print fine sand, gold, silver and other common offset printing processes that are difficult to achieve. PS version, cot, blanket, etc. for UV offset printing are different from ordinary offset printing. At the same time, the number and power of UV lamps and the content of photosensitizer in UV ink can affect the drying effect of UV ink. In the arrangement of color sequence, the printing color sequence of white black green yellow red is often used. In addition, UV inks from different ink factories should not be mixed with each other, which should be paid special attention to

the control box is mainly composed of oil tank, oil pump, oil filter, motor, speed valve, oil return valve, etc. II. Flexographic printing

flexographic printing is in full swing abroad, but it is somewhat "popular but not popular" in China. On the one hand, the acceptance awareness of flexo printing in the domestic market needs to be strengthened; On the other hand, foreign packaging design has always used simple and lively color blocks and lines to enhance the visual effect, while in China, packaging products are often designed with large areas of spot colors and images. At the same time, domestic flexo printing technology and its supporting raw and auxiliary materials also have a big gap with foreign countries

however, for cigarette packs dominated by color patches, lines or neutral tones, flexo printing is still promising. First of all, most of the narrow width flexo printing machines introduced in China are 6+1 color groups, and the last color group is used for glazing, which can give full play to the advantages of flexo printing in spot color printing; Secondly, at present, domestic flexographic plate manufacturers have explored a set of effective flexographic plate making process methods, which can basically meet the requirements of hierarchical printing. In addition, flexo printing with online indentation, bronzing, die cutting and other processes, high production efficiency. In addition, flexo printing uses water-based ink, which can make a big fuss on "environmental protection". At present, the key is to guide the market to identify with flexographic products

in the process of formulating the cigarette bag flexo printing process, the plate making process should be determined according to the specific process conditions, such as the smoothness of the paper, the wrinkle roll parameters, the gray balance data of the ink, etc. in the printing process, the pH value that affects the viscosity and dryness of the water-based ink should be strictly controlled; Considering the expansion of flexo printing points, there are several tips: 1 Because the ink is transferred through the embossing roller, and the amount of ink required for field and hierarchical printing is different, the field and line of the same color should be made separately. 2. Since the angle of the wrinkle roll is mostly 60 °, the adding angle of the layered version should avoid 60 ° to prevent moire. 3. Considering that the ink drying method is volatile drying, in order to improve the contrast, it is recommended to use the printing color sequence of k-c-m-y, and then print the spot color. 4. As the "heart" of flexographic printing, the corrugation roller should be configured to meet the needs of cigarette packet printing

III. gravure printing

gravure printing accounts for a large market share in cigarette bag printing because of its high saturation, high contrast, high brightness, strong consistency and high printing resistance

the gravure cigarette bag printing process is relatively mature. This is mainly because: first, there are many kinds of gravure printing inks and papers, and it is impossible for plate manufacturers to formulate a complete set of gray balance parameters and printing characteristic curves for each printing plant; Second, plate makers often evaluate the quality of plate making by proofing samples, while the actual printing conditions are quite different from the proofing process conditions. Due to the fact that gravure cigarette packs are mostly on the ground, color blocks and lines, the requirements for color management in plate making are relatively lax. Gravure process control is easier than offset printing and flexo printing

cigarette bag printing plants' in-depth understanding of gravure plate making process is helpful to improve the success rate of cigarette plate. Specifically:

1 Intaglio plates express levels through the size and depth of holes. In order to improve the transfer rate of ink, field plates usually use 37 ° flattened diamond points, the angle of engraving needle is 130 °, and the number of lines added is lines/cm; When carving small characters, the angle of the carving needle is 110 °, and the number of lines added is 80 lines/cm

2. For field, small (anti white) text or products with the same color of lighter lines, if you want to ensure the hole depth of the field during plate making, the clarity of the text will be affected; When printing, the angle of the scraper is also different for the field and point. The scraper angle is large, and the words and points are clear, but the field ink layer is thin, and the gloss is poor, and vice versa; In addition, for the layered version, in order to improve the ink transfer rate, the proportion of slow drying agent is larger, while the proportion of field printing fast drying agent is larger, so separate plate making should be considered

3. After the printing plate is made, carefully check its concentricity, balance, increment, etc., so as not to affect the printing overprint

cigarette packs have requirements for friction resistance and high temperature resistance of printing ink (no fading for 0.5s at 150~160 ℃). There are usually two solutions, one is to choose high temperature resistant ink (nitrocellulose resin has become the preferred binder because it meets this requirement and is cheap); Second, choose high temperature resistant varnish, and water-based varnish is often used for cigarette package printing (compared with solvent based varnish, the amount of water-based varnish is small, and the residual taste of ethanol solvent used is much lighter than that of ethyl acetate)

at the same time, gravure printing ink also has high fluidity, good scraping characteristics, good transferability and dryness. The purpose of using solvent in printing is to adjust the viscosity and dryness of ink. Due to the different solubility and volatilization speed of various solvents, mixed solvents are often used. In printing, as the solvent volatilizes continuously, the balance of the mixed solvent is broken. At this time, printing problems are easy to occur, and new solvents need to be added constantly. In addition, the requirements of cigarette packs for solvent residues are usually not higher than 30mg/m2

for the faults in the gravure printing of cigarette packs, we should comprehensively consider the factors such as ink, printing plate, printing machine, doctor blade, printing environment, solvent, paper and so on, and analyze the specific problems

IV. silk screen printing

cigarette package printing makes silk screen printing glow with new vitality, especially after UV modification, the sanding, refraction, ice flower, wrinkle and other effects of silk printing make cigarette packaging decoration even better. In addition, because silk UV (local) has high brightness and strong three-dimensional sense, it is also often used in cigarette bag decoration

to better reflect the effect of silk UV printing, silk mesh and sand ink must be reasonably selected in the printing process; Strictly control the thickness and printing distance of the photosensitive film; In addition, the wavelength, power and drying time of UV lamp also have an important impact on the final effect

tips: 1 In cigarette bag design, the frosted pattern should be 2-3mm away from the indentation and die cutting position to avoid damaging the sand ink during die cutting. 2. Considering the transparency of the sand ink, the text should not be trapped with the sand ink, but can be directly printed on gold and silver cards. 3. When a large area of the field is in the same color as a small text, to reduce the jagged effect of the text edge, you should choose different purpose silk to make plates separately

v. post press processing

the post press processing of cigarette packs usually includes bronzing (embossing), embossing, die cutting, etc. Because printing manufacturers do not know much about the production process of bronzing and embossing, they usually output the film as offset film. Here, it is necessary to emphasize: ① the positive side of the bronzing plate; ② Positive image of concave convex negative plate; ③ Concave convex male mold (resin version) negative image is reversed, about 0.3mm more than the original size; ④ The gilding embossing plate is the same as the gilding plate. Because it needs to be corroded twice, the frame should be protected by lines

in order to reduce waste products, press concave convex and die-cutting one-time forming process shall be adopted as far as possible. For products requiring both bronzing and embossing on the bronzing pattern, electric engraving can be made, and the one-time forming process of bronzing and embossing can be used. For long-term products in batches, sandwich steel templates can be used

Trend Outlook

I. the development of direct plate making technology will greatly promote the improvement of offset printing, flexo printing and gravure printing technology, such as offset printing, CTP of flexo printing and digital engraving cylinder of gravure printing. As a carrier for mass reproduction in packaging and printing, printing plate cannot be eliminated. It will continue to develop with the development of computer technology

II. UV ink will guide the development trend of cigarette offset printing with its high adhesion, no volatile substances, no powder spraying and many other advantages. Gravure printing will rise steadily in the cigarette package printing market due to its own characteristics. Flexo printing will also increase, but the range will not be too large. Silk UV printing will be widely used in cigarette bag finishing

III. The demand for laser paperboard and UV ink will inevitably increase with the adjustment of cigarette bag grade

IV. a variety of process combinations will become an ideal way of cigarette bag printing. For example, when printing layered products, offset printing can be selected; When printing spot color and gold silver ink with technical parameters, sheet fed intaglio printing can be selected

in a word, cigarette package printing has the advantages of large batch, high profit and capital return

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