Adaptability processing skills of printing charact

Editor's note: flexible packaging is widely used in the outer packaging of goods because of its many superior properties. This paper emphatically analyzes the printing characteristics and printing adaptability of flexible packaging materials, and points out the printing skills 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 films are non-polar polymer compounds with poor adhesion to printing ink. In order to make the surface of plastic films have good ink adhesion and enhance the firmness of prints, Before printing, carry out surface activation treatment:

② hygroscopicity is mostly affected by the relative humidity of the surrounding air and expands and deforms, resulting in poor overprint

③ affected by the change of tension, the elongation of the film increases with the increase of tension in the allowable range of strength during the printing process, which brings difficulties to the accuracy of color printing overprint:

④ the surface is smooth, without capillarity. 3. Place the sample in the center of the pressure plate of the gas spring fatigue tester, and the hole exists, so the ink layer is not easy to fix or fixed firmly. After the first color is printed, it is easy to be stuck off by the next color overprint ink, Make the pattern and text incomplete, resulting in defects

⑤ surface oil layer exudation. The film made of additives is easy to seep out during the printing process, forming an oily layer, ink layer, coating or other adhesives on the surface of the film, which is not easy to bond firmly on the surface of this kind of film

⑥ as the plastic film is a non-polar material, there are no pores, and the ink is not easy to dry, these characteristics are not conducive to printing, so the plastic film must be surface treated before printing

cellophane

cellophane is characterized by high transparency, strong gloss, and extra bright color after printing pictures and texts, which can not be achieved by plastic film; The printing adaptability is good, and there is no need to go through any treatment before printing. The cellophane also has anti-static treatment performance, which is not easy to absorb dust, and avoids printing faults such as text dust. However, the moisture resistance is poor, and the film is easy to deform under the influence of temperature and humidity, which makes it difficult to register pictures and texts during printing

aluminum foil

aluminum foil is characterized by:

① light weight, metallic luster, good light shielding, high reflection ability to heat and light, and metallic luster and reflection ability can improve the brightness of printing color

② good isolation, strong protection, impermeable to gas and water vapor, preventing moisture absorption and gasification of the contents, and not vulnerable to bacteria and insects that set parameters for the alarm device

③ good shape stability, not affected by humidity changes. Easy to process, aluminum foil can be printed, colored, embossed, surface coated, glued, painted, etc

④ it cannot bear force, has no sealing property, has pinholes and is easy to wrinkle, so it is generally not used alone. It is usually processed into composite materials with paper and plastic film, which overcomes the shortcomings of no sealing property and gives full play to its isolation and other advantages

aluminum foil is widely used in food, medicine and other packaging fields. Aluminum foil is compounded with plastic film, which effectively uses the characteristics of high temperature cooking resistance and complete shading to make cooking bags, which can pack cooked food. Multi layer composite film is also used in the packaging of cookies, snacks, beverages and other small foods

vacuum aluminized film

the main function of vacuum aluminized film is to replace aluminum foil composite, so that soft plastic packaging also has a beautiful silver luster, improve the barrier and shading of soft packaging film bags, and thus reduce costs. The substrate film of vacuum aluminum plating is polypropylene film with high melting point, including CPP, IPP and BOPP. PET film, NY film and paper can also be directly vacuum aluminized after pretreatment or humidity adjustment. Indirect aluminizing process can be adopted for PE film and Pt. In order to provide the fastness of aluminum plating, foreign countries adopt the method of coating the bottom layer on the plated substrate film, while in China, there is generally no bottom coating surface, and only corona treatment is carried out on the surface. There are two methods of vacuum aluminizing the film, which can be reverse printed on the facial mask of the film, that is, inner printing, and then vacuum aluminizing and compounding with the bottom film. You can also reverse print on the facial mask, and then dry compound it with the vacuum aluminized bottom film. The bottom film of the latter must be CPP or IPP with good heat resistance and can be heat sealed

it should be pointed out that when vacuum aluminizing is carried out on the printed facial mask, although it is internal printing, it is not necessary to use internal printing ink, just an ink with excellent heat resistance. If the printed matter darkens and loses its luster after vacuum aluminizing, it is because of the poor heat resistance of the ink. Vacuum aluminizing on the printing surface, because the adhesive resin in the ink is a good undercoat, the fastness of aluminizing is better, especially when printing full-scale field, the fastness of aluminizing layer is better

compared with aluminum foil, vacuum aluminum plating greatly saves the amount of aluminum. The former is only 1/100-1/200 of the latter, but it has the luster and insulation of metal. Because the thickness of vacuum aluminum coating is relatively thin, only 0.4-0.6 ¨ m, it can not be used to replace aluminum foil composite films that need high barrier, such as vacuum packaging and high-temperature cooking bags. The cost of vacuum aluminum plating is lower than that of aluminum foil, and it will be greatly developed in the field of food trademarks. In recent years, vacuum aluminum plating paper is gradually replacing aluminum foil in cigarette, cold meal carton, chewing gum and other packaging

composite film

composite film is widely used in the outer packaging of food, such as fast food, quick-frozen food, puffed food, etc. in shopping malls. These are made of composite films. The composite films can not only maintain the excellent characteristics of single-layer films, but also their own shortcomings. After compounding, they have new characteristics to meet the different requirements of commodities for films. For example, food packaging requires that the films have excellent properties such as moisture-proof, gas proof, light proof, oil resistance, high temperature resistance, good heat sealing, but also have good printability and decorative art effect, Performance and requirements are difficult to achieve with a single film. Take the most widely used PE film as an example. Although cellasto is a kind of microporous polyurethane elastomer, it has excellent transparency, moisture resistance, heat resistance and chemical stability, but its oil resistance and oxygen resistance are limited, and its printability is poor. Pet and PA films have high tensile strength and fatigue strength, but the former has poor moisture resistance, while the latter has poor heat sealing and chemical resistance. PE (glassy) has excellent transparency, no static electricity, is not easy to pollute, and is easy to bond, but its toughness, water resistance and moisture resistance are poor. Aluminum foil has flashing metallic luster and thermal conductivity, and has good resistance to moisture, steam, light and grease, but it has the disadvantages of easy cracking, lack of softness, no thermal adhesion and so on

the thin desert of each layer is compounded together. At the same time, it has excellent properties such as moisture-proof, gas proof, light proof, heat-resistant, oil resistant, and good heat sealing performance, making it an ideal packaging material. For example, the current high-grade rp-h cooking bag is a three-layer composite film based on plastic film. Its middle is aluminum foil, which has good insulation performance and is conducive to the long-term storage of food; BOPP film is used for the outer layer, which has excellent dimensional stability. Gravure printing is used on the back, and adhesive is used to compound with aluminum foil to ensure the firmness and smoothness of printing color. The inner layer adopts PE film, which takes advantage of its advantages of heat resistance, softness and easy sealing. After the combination of the three, it can withstand 120 ℃ high-temperature sterilization treatment, and microorganisms will not be immersed, which plays a role in preserving freshness and taste

there are many kinds of composite films. The common ones are the combination of cellophane and plastic films that will not be broken, plastic films and plastic films, aluminum foil and plastic films, aluminum foil, glass, paper and plastic films, various papers and their prints and various plastic films, etc. there are as many as 30-40 kinds, and the number of composite layers is generally 2-5. The basic structure of various composite films is to use non thermoplastic or high melting point films such as Pt, BOPP, NY, pet as the outer layer and PP, PE as the inner layer for comprehensive application. The commonly used composite film structure is also used for many purposes. When choosing composite film, we should also consider the printing performance in order to obtain exquisite trademark patterns

source: ()