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Analysis of various manufacturing processes and trends of cigarette packaging
Some of the same cigarettes are expensive, while others are cheap. The expensive ones are not necessarily of much higher quality than the cheap ones. It is very likely because the cigarette packaging design and process are different. So, how are cigarette packaging made?
1: Offset printing
Offset printing process should be said to be a relatively mature printing process. Especially in layered printing, there is a set of standardized and digitized methods.
However, cigarette packaging printing is not just a reproduction of product gradation, it also involves a large number of spot color reproduction, such as large areas of red solid, gold and silver, pearlescent effects, etc. Because the spot color, especially the solid spot color, has high requirements for saturation and brightness, and offset printing is limited by the thickness of the ink layer when printing solid, it seems to be more than enough. In order to achieve the purpose, the method of "first dark and then light" printing is usually adopted (when designing, it is necessary to avoid hollowing out text on the solid plate as much as possible to avoid increasing the difficulty of overprinting). In addition, cigarette packaging printing has high requirements for color stability (consistency). Due to the existence of ink emulsification and the relatively long ink path, there are many factors that affect the stability of ink color in offset printing, and it is difficult to meet the above requirements.
In order to meet the needs of high-end cigarette packaging 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 drying on composite paper printing products. Some cigarette packaging manufacturers have begun to use offset UV ink to print fine sand, gold, silver and other processes that are difficult to achieve with ordinary offset printing. The PS plate, rubber roller, rubber cloth, etc. used in UV offset printing are different from those used in ordinary offset printing. At the same time, the number and power of UV lamps, the content of photosensitizer in UV ink, etc. can all affect the drying effect of UV ink. In terms of color sequence arrangement, the printing color sequence of white-black-cyan-yellow-red is often used. In addition, UV inks from different ink factories should not be mixed with each other, and this should be paid special attention to.
2: Flexographic printing
Flexographic printing is developing in full swing abroad, but it is somewhat "well-received but not popular" in China. The reason is that the domestic market's awareness of flexographic printing needs to be strengthened; on the other hand, foreign packaging design has always used simple and bright color blocks and lines to enhance the visual effect, while in China, packaging products are mostly large-area spot colors and image designs. At the same time, there is a big gap between the domestic flexographic printing process and its supporting raw and auxiliary materials and those of foreign countries.
However, for cigarette packages dominated by color blocks, lines or medium and dark tones, flexographic printing still has a lot to do. First, the narrow-width flexographic printing machines introduced in China are mostly 6+1 color groups, and the last color group is used for glazing, which can give full play to the advantages of flexographic printing in spot color printing; secondly, the current domestic flexographic platemaking factories have explored a set of effective flexographic platemaking process methods, which can basically meet the requirements of layered printing. In addition, flexographic printing often has online embossing, hot stamping, die-cutting and other processes, and has high production efficiency. In addition, flexographic printing uses water-based inks, which can make a big fuss about "environmental protection". The current key is to guide the market's recognition of flexographic products.
In the process of formulating the flexographic printing process for cigarette packages, the plate-making process should be determined according to specific process conditions, such as the smoothness of the paper, the parameters of the anilox roller, and the gray balance data of the ink. In the printing process, the pH value that affects the viscosity and dryness of the water-based ink should be strictly controlled; considering the problem of flexographic dot enlargement, there are a few tips: 1. Since the ink is transferred through the anilox roller, the amount of ink required for solid and layered printing is different. Therefore, the solid and screen lines of the same color should be made separately. 2. Since the angle of the anilox roller is mostly 60°, the screen 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 anilox roller should be configured to meet the needs of cigarette package printing.
3: Gravure printing
Gravure printing occupies a large market share in cigarette packaging printing due to its high saturation, high contrast, high brightness, strong consistency, and high printing plate durability.
The gravure cigarette packaging printing process is relatively mature. This is mainly because: First, there are many types of gravure printing inks and papers, and plate manufacturers do not and cannot formulate a complete set of gray balance parameters and printing characteristic curves for each printing plant; second, plate manufacturers mostly use proofing samples to evaluate the quality of plate making, and the actual printing conditions are quite different from the proofing process conditions. Since gravure cigarette packaging is mostly solid, color blocks, and lines, the requirements for color management in plate making are relatively loose. Gravure printing process control is relatively easy compared to offset printing and flexographic printing.
The in-depth understanding of the gravure plate making process by cigarette packaging printing plants helps to improve the success rate of cigarette plates on the machine. Specifically:
1. The gravure plate expresses the level through the size and depth of the mesh. In order to improve the transfer rate of ink, the solid plate often uses 37° flattened diamond dots, the angle of the engraving needle is 130°, and the number of screen lines is 70-75 lines/cm; when engraving fine text, the angle of the engraving needle is 110°, and the number of screen lines is 80 lines/cm.
2. For solid, fine (reflective) text or products with the same color of lighter screen lines, if the depth of the mesh holes of the solid is to be ensured during plate making, the clarity of the text will be affected; and the angle of the scraper during printing is also different for the solid and the dots. The larger the scraper angle, the clearer the text and dots, but the thinner the solid ink layer and the poorer the glossiness, and vice versa; in addition, for the layered plate, in order to improve the transfer rate of ink, the proportion of slow-drying agent used is relatively large, while the proportion of fast-drying agent used for solid printing is relatively large, so separate plate making should be considered.
3. After the printing plate is made, its concentricity, balance, increment, etc. should be carefully checked to avoid affecting the printing overprint.
Cigarette packs have requirements for friction resistance and high temperature resistance for printing inks (no fading in 0.5s at 150~160℃). There are usually two solutions. First, choose high temperature resistant ink (nitrocellulose resin meets this requirement and is cheap, making it the preferred binder); second, choose high temperature resistant varnish. Water-based varnish is often used for cigarette pack printing (compared with solvent-based varnish, water-based varnish is used in small quantities, and the residual taste of the ethanol solvent used is much lighter than ethyl acetate).
At the same time, gravure inks must have high fluidity, good scraping properties, good transferability and drying properties. Solvents are used in printing to adjust the viscosity and drying properties of inks. Since the solubility and evaporation speed of various solvents are different, mixed solvents are often used. During printing, as the solvent continues to evaporate, the balance of the mixed solvent is broken, and printing problems are likely to occur at this time, and new solvents need to be added continuously. In addition, the requirement for solvent residues in cigarette packs is usually not more than 30mg/m2.
For the failures in gravure printing of cigarette packages, factors such as ink, printing plate, printing machine, scraper, printing environment, solvent, paper, etc. should be considered comprehensively, and specific problems should be analyzed specifically.
4: Silk screen printing
Cigarette package printing brings new vitality to silk screen printing, especially after UV modification, the frosting, refraction, ice flowers, wrinkles and other effects of silk screen printing make the cigarette package decoration icing on the cake. In addition, because the silk screen UV (local) has high brightness and strong three-dimensional sense, it is also often used in cigarette package finishing.
To well reflect the silk screen UV printing effect, in the printing process, the silk screen mesh and sand ink must be reasonably selected; the thickness of the photosensitive film and the printing mesh distance must be strictly controlled; in addition, the wavelength, power, drying time, etc. of the UV lamp also have an important influence on the final effect.
A few tips: 1. In the design of cigarette packages, 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, and can be directly printed on gold and silver cards. 3. When a large area of solid and small text are the same color, in order to reduce the jagged effect of the text edge, different screens should be used to make separate plates.
5: Post-printing processing
The post-printing processing of cigarette packages usually includes hot stamping (embossing), embossing, die-cutting, etc. Since printing manufacturers are not very familiar with the production process of hot stamping and embossing, they usually output the film according to offset film. Here, it is necessary to emphasize: ① The positive image of the hot stamping plate is positive; ② The positive image of the embossed negative plate is positive; ③ The negative image of the embossed positive mold (resin plate) is reversed, which is about 0.3mm inward than the original size; ④ The hot stamping embossed plate is the same as the hot stamping plate. Since it needs to be etched twice, the frame should be protected by lines.
In order to reduce waste, the one-time molding process of embossing and die-cutting should be used as much as possible. For products that require both hot stamping and embossing on the hot stamping pattern, electric engraving can be made, using hot stamping and embossing one-time molding process. For batch long-line products, sandwich steel templates can be used.
6: Trend Outlook
1. The development of direct platemaking technology will greatly promote the improvement of offset printing, flexographic printing and gravure printing technology, such as offset printing, flexographic printing CTP and gravure printing digital engraving cylinder. As the carrier required for mass reproduction in packaging printing, the printing plate cannot be eliminated. It will continue to develop with the development of computer technology.
2. UV ink will lead the development trend of cigarette package offset printing with its many advantages such as high adhesion, no volatile substances, and no need for powder spraying. Due to its own characteristics, gravure printing will steadily increase in the cigarette package printing market. Flexographic printing will also grow, but the amplitude will not be too large. Screen UV printing will be widely used in cigarette package finishing.
3. The demand for laser cardboard and UV ink will inevitably increase with the adjustment of cigarette package grades.
4. A combination of multiple processes will become an ideal way to print cigarette packages. For example, when printing layered products, offset printing can be selected; when printing special colors, gold and silver inks, single-sheet gravure printing can be selected.
1: Offset printing
Offset printing process should be said to be a relatively mature printing process. Especially in layered printing, there is a set of standardized and digitized methods.
However, cigarette packaging printing is not just a reproduction of product gradation, it also involves a large number of spot color reproduction, such as large areas of red solid, gold and silver, pearlescent effects, etc. Because the spot color, especially the solid spot color, has high requirements for saturation and brightness, and offset printing is limited by the thickness of the ink layer when printing solid, it seems to be more than enough. In order to achieve the purpose, the method of "first dark and then light" printing is usually adopted (when designing, it is necessary to avoid hollowing out text on the solid plate as much as possible to avoid increasing the difficulty of overprinting). In addition, cigarette packaging printing has high requirements for color stability (consistency). Due to the existence of ink emulsification and the relatively long ink path, there are many factors that affect the stability of ink color in offset printing, and it is difficult to meet the above requirements.
In order to meet the needs of high-end cigarette packaging 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 drying on composite paper printing products. Some cigarette packaging manufacturers have begun to use offset UV ink to print fine sand, gold, silver and other processes that are difficult to achieve with ordinary offset printing. The PS plate, rubber roller, rubber cloth, etc. used in UV offset printing are different from those used in ordinary offset printing. At the same time, the number and power of UV lamps, the content of photosensitizer in UV ink, etc. can all affect the drying effect of UV ink. In terms of color sequence arrangement, the printing color sequence of white-black-cyan-yellow-red is often used. In addition, UV inks from different ink factories should not be mixed with each other, and this should be paid special attention to.
2: Flexographic printing
Flexographic printing is developing in full swing abroad, but it is somewhat "well-received but not popular" in China. The reason is that the domestic market's awareness of flexographic printing needs to be strengthened; on the other hand, foreign packaging design has always used simple and bright color blocks and lines to enhance the visual effect, while in China, packaging products are mostly large-area spot colors and image designs. At the same time, there is a big gap between the domestic flexographic printing process and its supporting raw and auxiliary materials and those of foreign countries.
However, for cigarette packages dominated by color blocks, lines or medium and dark tones, flexographic printing still has a lot to do. First, the narrow-width flexographic printing machines introduced in China are mostly 6+1 color groups, and the last color group is used for glazing, which can give full play to the advantages of flexographic printing in spot color printing; secondly, the current domestic flexographic platemaking factories have explored a set of effective flexographic platemaking process methods, which can basically meet the requirements of layered printing. In addition, flexographic printing often has online embossing, hot stamping, die-cutting and other processes, and has high production efficiency. In addition, flexographic printing uses water-based inks, which can make a big fuss about "environmental protection". The current key is to guide the market's recognition of flexographic products.
In the process of formulating the flexographic printing process for cigarette packages, the plate-making process should be determined according to specific process conditions, such as the smoothness of the paper, the parameters of the anilox roller, and the gray balance data of the ink. In the printing process, the pH value that affects the viscosity and dryness of the water-based ink should be strictly controlled; considering the problem of flexographic dot enlargement, there are a few tips: 1. Since the ink is transferred through the anilox roller, the amount of ink required for solid and layered printing is different. Therefore, the solid and screen lines of the same color should be made separately. 2. Since the angle of the anilox roller is mostly 60°, the screen 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 anilox roller should be configured to meet the needs of cigarette package printing.
3: Gravure printing
Gravure printing occupies a large market share in cigarette packaging printing due to its high saturation, high contrast, high brightness, strong consistency, and high printing plate durability.
The gravure cigarette packaging printing process is relatively mature. This is mainly because: First, there are many types of gravure printing inks and papers, and plate manufacturers do not and cannot formulate a complete set of gray balance parameters and printing characteristic curves for each printing plant; second, plate manufacturers mostly use proofing samples to evaluate the quality of plate making, and the actual printing conditions are quite different from the proofing process conditions. Since gravure cigarette packaging is mostly solid, color blocks, and lines, the requirements for color management in plate making are relatively loose. Gravure printing process control is relatively easy compared to offset printing and flexographic printing.
The in-depth understanding of the gravure plate making process by cigarette packaging printing plants helps to improve the success rate of cigarette plates on the machine. Specifically:
1. The gravure plate expresses the level through the size and depth of the mesh. In order to improve the transfer rate of ink, the solid plate often uses 37° flattened diamond dots, the angle of the engraving needle is 130°, and the number of screen lines is 70-75 lines/cm; when engraving fine text, the angle of the engraving needle is 110°, and the number of screen lines is 80 lines/cm.
2. For solid, fine (reflective) text or products with the same color of lighter screen lines, if the depth of the mesh holes of the solid is to be ensured during plate making, the clarity of the text will be affected; and the angle of the scraper during printing is also different for the solid and the dots. The larger the scraper angle, the clearer the text and dots, but the thinner the solid ink layer and the poorer the glossiness, and vice versa; in addition, for the layered plate, in order to improve the transfer rate of ink, the proportion of slow-drying agent used is relatively large, while the proportion of fast-drying agent used for solid printing is relatively large, so separate plate making should be considered.
3. After the printing plate is made, its concentricity, balance, increment, etc. should be carefully checked to avoid affecting the printing overprint.
Cigarette packs have requirements for friction resistance and high temperature resistance for printing inks (no fading in 0.5s at 150~160℃). There are usually two solutions. First, choose high temperature resistant ink (nitrocellulose resin meets this requirement and is cheap, making it the preferred binder); second, choose high temperature resistant varnish. Water-based varnish is often used for cigarette pack printing (compared with solvent-based varnish, water-based varnish is used in small quantities, and the residual taste of the ethanol solvent used is much lighter than ethyl acetate).
At the same time, gravure inks must have high fluidity, good scraping properties, good transferability and drying properties. Solvents are used in printing to adjust the viscosity and drying properties of inks. Since the solubility and evaporation speed of various solvents are different, mixed solvents are often used. During printing, as the solvent continues to evaporate, the balance of the mixed solvent is broken, and printing problems are likely to occur at this time, and new solvents need to be added continuously. In addition, the requirement for solvent residues in cigarette packs is usually not more than 30mg/m2.
For the failures in gravure printing of cigarette packages, factors such as ink, printing plate, printing machine, scraper, printing environment, solvent, paper, etc. should be considered comprehensively, and specific problems should be analyzed specifically.
4: Silk screen printing
Cigarette package printing brings new vitality to silk screen printing, especially after UV modification, the frosting, refraction, ice flowers, wrinkles and other effects of silk screen printing make the cigarette package decoration icing on the cake. In addition, because the silk screen UV (local) has high brightness and strong three-dimensional sense, it is also often used in cigarette package finishing.
To well reflect the silk screen UV printing effect, in the printing process, the silk screen mesh and sand ink must be reasonably selected; the thickness of the photosensitive film and the printing mesh distance must be strictly controlled; in addition, the wavelength, power, drying time, etc. of the UV lamp also have an important influence on the final effect.
A few tips: 1. In the design of cigarette packages, 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, and can be directly printed on gold and silver cards. 3. When a large area of solid and small text are the same color, in order to reduce the jagged effect of the text edge, different screens should be used to make separate plates.
5: Post-printing processing
The post-printing processing of cigarette packages usually includes hot stamping (embossing), embossing, die-cutting, etc. Since printing manufacturers are not very familiar with the production process of hot stamping and embossing, they usually output the film according to offset film. Here, it is necessary to emphasize: ① The positive image of the hot stamping plate is positive; ② The positive image of the embossed negative plate is positive; ③ The negative image of the embossed positive mold (resin plate) is reversed, which is about 0.3mm inward than the original size; ④ The hot stamping embossed plate is the same as the hot stamping plate. Since it needs to be etched twice, the frame should be protected by lines.
In order to reduce waste, the one-time molding process of embossing and die-cutting should be used as much as possible. For products that require both hot stamping and embossing on the hot stamping pattern, electric engraving can be made, using hot stamping and embossing one-time molding process. For batch long-line products, sandwich steel templates can be used.
6: Trend Outlook
1. The development of direct platemaking technology will greatly promote the improvement of offset printing, flexographic printing and gravure printing technology, such as offset printing, flexographic printing CTP and gravure printing digital engraving cylinder. As the carrier required for mass reproduction in packaging printing, the printing plate cannot be eliminated. It will continue to develop with the development of computer technology.
2. UV ink will lead the development trend of cigarette package offset printing with its many advantages such as high adhesion, no volatile substances, and no need for powder spraying. Due to its own characteristics, gravure printing will steadily increase in the cigarette package printing market. Flexographic printing will also grow, but the amplitude will not be too large. Screen UV printing will be widely used in cigarette package finishing.
3. The demand for laser cardboard and UV ink will inevitably increase with the adjustment of cigarette package grades.
4. A combination of multiple processes will become an ideal way to print cigarette packages. For example, when printing layered products, offset printing can be selected; when printing special colors, gold and silver inks, single-sheet gravure printing can be selected.