Soft packaging materials printing characteristics adaptability processing skills
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Flexible packaging is widely used in the outer packaging of goods due to its many superior properties. This paper focuses on the analysis of the printing characteristics and printing suitability of flexible packaging materials, and points out the printing techniques of various flexible packaging materials.
plastic film
Commonly used plastic films are: PE, PP, PVC, PS, PVA, PC, PET, CA, NY. The printing characteristics of these plastic films are:
1 Plastic film is a non-polar polymer compound, which has poor adhesion to printing ink. In order to make the surface of plastic film have good ink adhesion ability and enhance the firmness of printed matter, surface activation treatment is carried out before printing:
2 hygroscopicity is mostly affected by the relative humidity of the surrounding air and is deformed by stretching and contraction, resulting in poor overprinting;
3 The change of tension affects the film during the printing process. In the range of strength allowable, the elongation increases with the increase of tension, which makes the printing overprinting accuracy difficult:
4 The surface is smooth, no pores are present, and the ink layer is not easy to be fixed or fixed. After the first color is printed, the ink of the next color is easily adhered, so that the pattern and the text are incomplete, causing defects;
5 surface oil layer seeps out. A film made by incorporating an additive, the additive portion is easily oozing out during the printing process, and an oily layer, an ink layer, a coating or other adhesive is formed on the surface of the film, and is not easily adhered to the surface of such a film;
6 Since the plastic film is a non-polar material, there is no capillary hole, and the ink is not easy to dry. These features are not conducive to printing, so the film must be surface treated before printing.
Cellophane
The characteristics of cellophane are: high transparency, strong gloss, and bright color after printing, which is not possible with plastic film; good printability, no need for any treatment before printing, and cellophane also has antistatic treatment performance. It is not easy to absorb dust, and it avoids printing failures such as graphic dust. However, the moisture resistance is poor, and the film is easily deformed by the influence of temperature and humidity, which makes the image difficult to register during printing.
Aluminum foil
The characteristics of aluminum foil are:
1 light weight, good metallic luster, good light resistance to heat and light, metallic luster and reflective ability can improve the brightness of printing color;
2 good isolation, strong protection, non-breathable body and water vapor, prevent the contents from moisture absorption, gasification, and are not easily damaged by bacteria and insects;
3 shape stability is good, not affected by humidity changes. Easy to process, can print aluminum foil, poor color, embossing, surface coating, sizing, etc.
4 can not be stressed, no sealing, pinholes and easy wrinkles, so generally not used alone, usually with paper, plastic film processed into composite materials, overcome the shortcomings of no sealing, it is isolated The advantages of sex and so on are also fully utilized.
Aluminum foil is widely used in packaging fields such as food and medicine. Aluminum foil is combined with plastic film to effectively utilize high temperature cooking and complete shading. It is made into a retort pouch, which can be used to package cooked food. Multilayer composite film is also used. It is packed in small foods such as biscuits, snacks and drinks.
Vacuum aluminum plating film
The main function of the vacuum aluminum-plated film is to replace the aluminum foil composite, so that the soft plastic packaging also has a silver-white beautiful luster, which improves the barrier light-shielding property of the flexible packaging film bag, thereby reducing the cost. The vacuum-aluminized substrate-coated substrate is a polypropylene film having a relatively high melting point, including CPP, IPP, and BOPP. PET film, NY film, and paper can also be directly vacuum-plated with aluminum after pretreatment or humidity conditioning. The PE film and PT can be indirectly plated. In order to provide the fastness of aluminum plating, the outer layer method is applied on the substrate film to be coated in foreign countries, and the bottom surface is generally uncoated in the country, and only the surface is subjected to corona treatment. There are two kinds of vacuum aluminum plating methods for the film, which can be reverse printed on the mask of the film, that is, printed on the film, and then vacuum-plated and then combined with the base film. It can also be reverse printed on the mask and dry-composited with the vacuum-aluminized base film. The latter film must be CPP or IPP which is heat resistant and heat sealable.
It should be noted that when vacuum-plating is performed on the printed mask, although it is printed, it is not necessary to use the ink to be printed, and it is only necessary to use an ink excellent in heat resistance. If the printed product is dark after vacuum aluminum plating, the desired gloss is lost because the heat resistance of the ink is poor. Vacuum aluminum plating is performed on the printing surface. Since the adhesive resin in the ink is a good undercoat layer, the fastness of the aluminum plating is relatively good, especially when the printed full version is in the ground, the fastness of the aluminum plating layer is better.
Compared with aluminum foil, vacuum aluminum plating greatly saves the amount of aluminum used. The former is only 1/100-1/200 of the latter, but it has metallic luster and insulation. Since the thickness of the vacuum aluminum plating layer is relatively thin, only O. 4 one O. 6 ̈m, can not be used to replace aluminum foil composite film that requires high barrier properties, such as vacuum packaging and high temperature cooking bags. Vacuum aluminum plating costs lower than aluminum foil, and will be greatly developed in the field of food trademarks. In recent years, vacuum aluminum-plated paper is gradually replacing aluminum foil in packaging such as cigarettes, cold paper boxes, and chewing gum.
Composite film
Composite films are widely used in food packaging, such as fast food, frozen food, and puffed food in shopping malls. These are all made of a composite film. The composite film not only maintains the excellent properties of the single-layer film, but also has its own shortcomings. After compounding, it has new characteristics to meet the different requirements of the product. For example, the food packaging requires the film to have moisture resistance. It has excellent performances such as anti-gas, light-proof, oil-resistant, high-temperature resistance and heat-sealing. It also has good printability and decorative art effect. The performance and requirements are difficult to achieve with a single film. For the most widely used PE film, although it has excellent transparency, moisture resistance, heat resistance and chemical stability, it has limited oil resistance and oxidation resistance and poor printability. PET and PA films have high tensile strength and fatigue strength, but the former has poor moisture resistance, and the latter has poor heat sealability and chemical resistance. PE (glassy) has excellent transparency, no static electricity, is not easy to be contaminated, and is easy to bond, but has poor toughness, water resistance and moisture resistance. Aluminum foil has a glittering metallic luster and thermal conductivity, which is good for blocking moisture, steam, light, and grease, but has the disadvantages of easy cracking, lack of softness, and no thermal adhesion.
The layers are thin and deserted together, and at the same time have excellent properties such as moisture proof, gas proof, lightproof, heat resistance, oil resistance and heat sealability, and become an ideal packaging material. For example, the current high-grade RP-H retort pouch is a three-layer composite film based on plastic film. The middle of it is aluminum foil, which has good insulation performance and is beneficial to the storage of food for a long period of time. The outer layer is made of BOPP film. Excellent dimensional stability, back gravure printing, composite with aluminum foil with a binder to ensure the firmness and smoothness of the printing color. The inner layer adopts PE film to take advantage of its heat resistance, softness and easy sealing. After compounding the three, it can withstand high temperature sterilization treatment at 120 °C, and the microorganisms will not be immersed, which plays a role of preserving and preserving taste.
There are many types of composite films. Commonly, there are composites of cellophane and plastic film, composite of plastic film and plastic film, composite of aluminum foil and plastic film, composite of aluminum foil, glass, paper and plastic film, various papers and their printed materials and There are 30-40 kinds of composites of plastic film, etc., and the number of composite layers is generally 2-4 layers. The basic structure of various composite films is based on non-thermoplastic or high-melting film such as PT, BOPP, NY, PET, and the inner layer is made of PP and PE. The commonly used composite film has a structural composition and a variety of uses. When selecting a composite film, it is also necessary to consider the printing performance in order to obtain a beautiful trademark pattern.