The traditional printing methods are generally divided into lithographic printing, letterpress printing, gravure printing, and stencil printing, and different printing methods often result in different printing effects.
For the cigarette pack, the offset printing process has the characteristics of rich image layer and saturated color, but the ink layer of the large-area solid dot is not thick, which is more suitable for proofing, small batch production and color printing; the screen printing process has thick ink layer and graphic The three-dimensional sense is strong, but the efficiency is low and the quality is unstable. The gravure printing process has the characteristics of high production efficiency and stable quality, but the dot printing is not exquisite, the layer is not rich, the color is not bright, the saturation is not high, and it is suitable for mass production. .
The author of this paper participated in the research and development of 8 new cigarette packages of Henan China Tobacco Industry Co., Ltd., which overcomes many technical difficulties when the offset printing and screen printing processes are converted into gravure printing process and the offset printing process is converted into gravure color processing. Here, share your accumulated experience with friends.
Offset printing process into gravure process
1. Field printing: printing 2 times change 1 time
Under normal circumstances, when the large-area solid printing of cigarette packets is carried out by the offset printing process, two printings are required, and the ink layer can be thicker. The first printing ink layer is thin and plays a role of bottoming; the second printing ink layer is thick, and the hue can be adjusted. After being converted into a gravure printing process, the printing process can achieve the effect of printing twice in the offset printing process.
Two points to note:
If you encounter the situation that the offset part is exposed to the other part of the graphic, it must be printed twice when converting to the gravure process. The hollowed out graphic is used as a spot color version separately. At the same time, pay attention to the registration problem of two printings. Two passes are placed in the adjacent front and rear color sequence to ensure the overprint accuracy.
If the first pass of the offset printing position is a fine texture, and the second pass is a solid color block, when converting to a gravure printing process, two-pass printing must also be used, and the fine texture portion is made in the ground in the first printing. In the second pass, the small texture part is made hollow, and the other parts are made in the field for accurate overprinting.
2. Small and detailed text is bold
Under normal circumstances, the offset printing process can print very fine graphics, and the printing effect is quite good, but the gravure printing process is not so good performance. Therefore, when the offset printing process is converted into a gravure printing process, the lines of the small graphic text should be appropriately thickened, and the distance between the lines should be widened to avoid the printing quality problems such as the small lines being printed and the entire graphic paste.
It is recommended that the gravure be processed by a laser engraving process, and an appropriate amount of slow-drying agent is added to the gravure ink to improve the transfer effect of the ink.
3. Color text as much as possible to use spot color printing
Offset color text is usually overprinted with vivid colors and high saturation. Converted into a gravure offset printing process, if the use of solid printing background, then the point on the printing screen background, color effects can be achieved, but since the registration accuracy gravure offset printing is not as high, tend to have bad or overprint The font becomes thicker and so on, which affects the product qualification rate. Therefore, the gravure color text should be printed by spot color as much as possible to compensate for the lack of registration accuracy of the gravure printing equipment.
4. Registration requires relatively high color adjacent
The registration accuracy of the offset printing process is better than that of the gravure printing process, and individual small graphics can be printed twice.
However, when the offset printing process is converted into a gravure printing process, it is necessary to consider the registration problem. As far as possible, the color sequence with relatively high registration requirements is placed in the adjacent color groups, and the hollow portion that needs to be overprinted is appropriately enlarged.
The halftone dot printed properly enhanced level
Dot printing is a gravure short board, especially for gradient net printing. Therefore, when designing the gradient mesh, it is necessary to appropriately lengthen the gradient effect of the dot to achieve a gentle gradient.
Add an electrostatic ink absorbing device during printing; use a slow-drying agent in an appropriate amount; use a high-viscosity ink as much as possible, otherwise it will easily lead to paste.
If you encounter a darker gradient mesh, you can use two-pass printing, one by one with the spot color in the existing color sequence to make a lighter color printing dot to lay the bottom, and the second time to print the gradient mesh on the bottoming dot, so Can show a layered gradient network effect.
6. Adjust the die cut size appropriately
Under normal circumstances, the offset cigarette package is printed with UV ink, and the high temperature irradiation of the UV lamp will cause a certain degree of deformation of the paper, thereby affecting the registration of the subsequent die cutting process. The gravure printing is performed by solvent-based ink, and the tension control is performed, and the paper deformation is small, which has less influence on the registration of the subsequent die cutting process.
Therefore, when the offset printing process is converted into a gravure printing process, the degree of influence of die-cutting shrinkage should be tested, and the size of the die-cutting plate should be appropriately adjusted.
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