What is a reasonable flexible packaging process design
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Today, Xiaobian brings you the relevant knowledge of plastic flexible packaging printing production, and learn together.
Flexible packaging gravure quality requirements
Gravure printing is the main printing method for plastic film printing today. The quality of gravure plastic film products is relatively high. The quality standards for printing appearance are as follows:
(1) After the flowering process, the registration error of each color pattern is not more than 0.3 mm.
(2) Check the specifications of the film, and the registration error of each color pattern is not more than 0.3 mm.
(3) Check the color of the printed product, requiring the hue to be correct, bright, uniform, bright, bright, soft, and smooth.
(4) Printing fastness, requiring transparent tape to stick ink without discoloration.
(5) Pattern text lines, requiring clear and complete, no defects, no deformation.
(6) The netting requirements are rich in layers and the outlets are clear.
(7) The product is neat and tidy, with no obvious dirt or knives.
(8) It is required that the deviation of the same color density of the product and the same batch of the same color and the same batch meet the requirements of GB7707-87.
Process control points
In order to better meet the above quality requirements, we can control the gravure film process from the following main aspects:
1. Master the technical points of various plastic packaging film substrates
(1) BOPP is the most commonly used printing substrate. The production process is a typical plastic gravure production process; it is printed with polyamide or chlorinated polypropylene ink, with appropriate tension and embossing force, and the drying temperature is controlled below 80 °C.
(2) BOPET printing points: Because PET is usually thin, easy to wrinkle, requires a large tension during printing, has a certain selectivity to the ink, easy to use the printing ink to separate the layer, the film is static, easy to block up (not online ), raising hair and scraping marks (knife wire) phenomenon, the humidity of the workshop is good when printing.
(3) BOPA printing points: BOPA is a film that is easy to absorb moisture. Therefore, the printing machine must ensure that the ambient humidity of the printing machine should not be too high (if the environment with high humidity without dehumidification measures is not suitable for printing nylon film); the unprinted film can not destroy the original aluminum film packaging film, and should be printed immediately after opening. The nylon film needs to be preheated during printing (if the machine does not have a preheating device, the printing plate can be installed in the second color, and the first color is used for preheating), and the preheating temperature is 50 to 80 ° C; The printing tension should be properly reduced; the pressure should be moderate; the ink adaptability is strong, depending on the product structure selection, if it is the cooking bag, the cooking ink must be selected; after printing, the product must be sealed and placed in the dry and mature indoor storage, and as soon as possible. complex.
(4) K coating film (KOP, KPA, KPET) printing points: Because the K coating film is either roll-coated or spray-coated, its thickness uniformity is not very good, the surface is uneven, and PVDC is just brittle, during printing The printing tension and the embossing pressure should not be too large, the overprinting is difficult, the ink transferability is poor, and the printing of the shallow screen is easy to take place (some of the dots are lost), and it is necessary to use a higher hardness pressure roller for printing.
In addition, it is selective for the solvent. If the solvent is used improperly, the coating may be dissolved, the solvent of the printing film is large, and it is easy to stick, so special attention should be paid to drying and cooling. The printing of the matte film can be printed on the smooth surface by the OPP process, but the matte layer on the surface cannot withstand high temperatures, and the drying temperature needs to be controlled.
(5) pearlescent film is printed with surface-printing ink, and as far as possible, a transparent ink with good transparency is used. Heat shrink film printing should use a very low drying temperature, choose a special heat shrinkable ink (printed ink layer should be able to shrink by heat without falling), if it is a PVC heat shrinkable film, consider the solvent to dissolve the film. Sex.
(6) unstretched PP, PE film printing tension is small, overprinting is difficult, the design of the pattern should fully consider the amount of deformation of the printing.
2. Preparation of prepress technology
(1) plate design: At the time of plate making, the original designed by the design company needs to be modified according to the characteristics of gravure printing, making it more suitable for printing needs. For the needs of overprinting, such as small lines, text can not be multi-color overprinting, the color pattern can not have small anti-white characters, should not be left blank in the color pattern, put on other small text, require overprinting for portraits, etc. Strict version, black, blue, red, yellow version in the middle as far as possible without other color version. For printing purposes, the bar code should be arranged as if the line direction is consistent with the circumferential direction of the plate. In terms of color assurance, if there are conditions, it is best to separate the large solid background and the layer pattern, and use the special version as much as possible. The hanging version must fully consider the two color jump zones of 80% and 5%. When the network is tapped, the limit of the dot should be above 10%.
(2) ink preparation: the adjustment of the ink printing adaptability, such as the viscosity and concentration of the ink, the principle is to adjust the viscosity of the ink with a diluent (solvent) to adjust the ink viscosity according to the plate roller and machine table before printing, in printing In the process, the solvent is often added according to the solvent volatilization, but it should not be excessive, try to ensure that the viscosity of the ink is constant; when the ink is to be talked about, it is necessary to use a thinner (toner oil), and should not dilute with a solvent.
The color of the ink needs to pay attention to the following points: The light source for observing the color should use the standard light source (D65) as much as possible. If there is no standard light source, it should be in the direction of the north window with sunlight. When formulating the spot color, the original color ink should be used for the preparation. The primary color ink mentioned here refers to the ink directly produced by the ink factory, and the brightness and saturation of the ink color can be guaranteed. Color matching with as few ink colors as possible. The more the color number, the greater the color matching error, and the more difficult it is to recolor the color.
3. Proofing a set of plates
When printing, you must first confirm a standard proof. Some manufacturers take the proofs of the plate making factory as the standard samples, and the final print delivery can not be the same, so the printing machine must be used before the printing, and confirmed by the customer or the relevant personnel as a standard. Standard printing should be carried out under normal printing process conditions, otherwise it will be very difficult to trace the samples after printing.
The following points should be noted when proofing: 1 process conditions select the most basic printing process conditions; 2 ink viscosity should be selected as low as possible; 3 primary color ink should be added after adding a certain amount of dilution agent, try to use as many times as possible. Especially for contaminated inks for proofing; 4 absolutely prohibit all non-standard operations in the proofing process in order to excessively pursue the effect, such as increasing the concentration, viscosity to increase the hue, adjusting the pressure, scraping the blade to improve the transfer rate of the ink, etc.; The ink must be evenly mixed before use, especially the spot color ink; 6 the spot color ink that has been prepared by itself must be accurately recorded and recorded for future reference; 7 proofing the speed of normal printing; 8 if conditions permit, After confirming the basic color of the sample, first print a certain number of products (such as a roll of film), and then sample and confirm it as a standard sample, and keep it as a file. If the standard sample is confirmed, it should be cut 2 to 3m. The equivalent standard sample is stored in a place without heat source and no ultraviolet light, and then cut out for each printing. Sample used for printing.