Why is flexo printing favored?
Time:2024-04-12
Views:1039
The 21st century is the era of environmental protection, people are increasingly aware of the importance of environmental protection for human survival and sustainable development. In order to prevent environmental pollution and promote the technological progress and sustainable development of the printing industry, the Emission Standard for Air Pollutants in the Printing Industry (GB 41616-2022) was officially implemented on January 1, 2023, which urgently requires the emergence of better green packaging and more applicable green printing materials and printing methods. Flexographic printing is precisely in line with the needs of the times, so it is known as green printing, widely used in instruments, food, pharmaceuticals and other types of packaging, increasingly becoming the preferred green printing process at home and abroad.
Flexographic printing is a kind of letterpress printing, evolved from letterpress printing, the graphic part of the raised, printing anilox rollers will be a certain thickness of the ink layer evenly coated in the graphic part of the printing plate, and then in the embossing cylinder under the action of pressure, the graphic part of the ink layer transferred to the surface of the substrate, the formation of a clear graphic. In this paper, we will talk about the characteristics and advantages of flexographic printing from the ink, plate, printing speed, and the four aspects of the process.
Flexographic ink
Flexographic ink is mainly water-based ink, is an environmentally friendly ink, does not contain benzene, ester, ketone and harmful heavy metals, VOCs emissions in line with environmental requirements.
Flexo water-based ink uses water as solvent, and contains little inorganic solvent except a small amount of additives, which is made of water-based polymer emulsion, organic pigment, resin, surfactant and related additives through chemical reaction and physical mixing. As it is water to replace the organic solvents that account for 30% to 70% of the traditional ink, it does not contain volatile organic solvents, has no adverse effect on the health of employees in the printing process, and is not polluting the atmospheric environment, but also eliminates the hidden danger of flammability and explosiveness in the workplace, and improves the safety. At the same time, the use of water-based ink costs than the use of solvent-based ink cost savings of about 30% or so, this unique advantage in line with increasingly stringent environmental regulations, in the world is increasingly favored by the packaging and printing community.
A.Less harmful to the environment
Flexo water-based ink uses water as a dissolving carrier, whether in the production process or printing process, almost no volatile organic gases (VOCs) emitted into the atmosphere, the printing process does not change the physical properties, strong inking force, high dot clarity, good reproducibility of the step tone, bright and shiny ink color, adhesion is strong, and is suitable for the printing of fine products.
B.Low residue
Flexo water-based ink does not contain organic solvents, making the surface of the print residue of toxic substances is greatly reduced. This feature is widely used in packaging and printing products with strict hygiene requirements, such as cigarettes, alcohol, food, drugs, children‘s toys, etc., which reflects its safety.
C.Low energy consumption
Flexo ink is lower viscosity than other inks, generally viscosity in 2 ~ 4Pa-s (25 ℃); viscosity is stable, not easy to paste the plate pile, ink layer thickness is generally 2 ~ 5µm, curing speed is generally 60 ~ 150m/min, the fastest can be more than 500m/min, the curing of the power consumed by less than one-fifth of the traditional thermal curing.
D.Good printability
Flexo water-based ink has good adhesion on different printing carriers such as paper, aluminum foil, plastic, etc. The prints can be stacked immediately without sticking. After curing, the ink film is water-resistant, alcohol-resistant, abrasion-resistant, aging-resistant, etc., with excellent performance.
Flexographic Plates
According to the material photosensitive characteristics
According to the material photosensitive properties, flexo printing plate can be divided into two categories: photosensitive rubber plate and photosensitive resin plate, all of which are characterized by soft, bendable and elasticity, with Shaw‘s hardness generally in the range of 25-60HS, and good transfer performance of ink. The plate making method mainly includes solvent plate making, thermal plate making, water washing plate making and liquid plate making, and some of them adopt laser direct engraving plate making. In addition to solvent plate and liquid plate is still using the traditional way of plate making, the main way of plate making most of the realization of the laser direct engraving plate making, its plate making speed is much faster than the traditional handmade plate making, can be quickly converted to the image of the printing plate, and can deal with a variety of different colors of the image. At the same time, it can also be automatically adapted to different printing materials in the plate making process.
By Plate Thickness
According to the thickness of the plate, flexographic printing plate is divided into two categories: thick plate and thin plate. Thick plates are mainly used for corrugated carton printing because they have large elastic deformation and can maintain close contact with uneven substrates. Flexographic plates with a thickness greater than 3mm are generally screened with 50 to 60 lines/inch; flexographic plates with a thickness of 2 to 3mm are generally screened with 70 to 100 lines/inch. Thin version of the hardness is higher, more suitable for fine printing, print dot reproducibility is good, mesh line reduction is finer. Thin plate with a thickness of 1.70mm flexo printing plate with the largest amount, mostly used for milk packaging, cartons, plastic film, labels, paper bags and other products printing and varnishing. The higher the hardness, the higher the number of lines that can be done; the lower the hardness, the lower the number of lines that can be done. Because as the number of lines increases, the corresponding proportion of dots is smaller. The smaller the dot, the higher the strength requirements of the resin, that is, the higher the hardness requirements.
Material better thin plate platemaking accuracy can reach 100 ~ 175 lines / inch, multi-color overprinting accuracy can be achieved within 0.02mm, good graphic reproducibility, rich levels of prints, bright colors, good visual effects, field printing ink layer thick, for printing packaging products common large areas of color is very favorable, both letterpress clear, offset printing soft colors, gravure printing ink layer thick and high gloss, particularly It is especially suitable for packaging printing requirements. Because of the selection of anilox roller ink transfer, generally speaking, if the paper condition remains unchanged, the ink condition remains unchanged, whether it is the same batch of products or different batches of products can maintain the same ink color, which is precisely the most basic requirements of packaging printing. Flexographic printing plate has short cycle time, easy transportation and high print resistance, which can reach hundreds of thousands of prints to millions of prints depending on the type of products.
Flexographic Printing Speed
Flexographic printing equipment is usually used to roll-type substrate material, rotary printing, printing speed, high efficiency. Figure 1 shows the flexographic printing machine using anilox roller ink delivery system, compared with offset and letterpress, eliminating the need for a complex ink delivery mechanism and stable ink delivery, no water-ink balance and ink emulsification problems, without too much human intervention, so that the operation and maintenance of the printing machine is greatly simplified, the ink control and response is more rapid, quality and stability, color reproduction is good, no ghosting phenomenon, a low rate of scrap. Flexographic printing machine has a wide range of suitable printing media, not only can print all kinds of newspapers, books, magazines, etc., but also can print aluminum foil, plastic film, self-adhesive paper, self-adhesive film, cellophane, metal foil and textiles. Generally speaking, the printing speed of unit-type narrow-width flexo press can reach 100m/min, and the printing speed of satellite-type wide-width flexo press can reach more than 200m/min.
Flexo Printing Line Processing Mode
Flexographic printing machine is easier to realize the combination of printing, almost all of the unit-type narrow width flexographic printing machine can be on the same equipment at the same time for post-press processing, such as reverse printing, coding, hot stamping, screen printing, varnishing, laminating, die-cutting, cross-cutting, cutting, perforation, waste, etc.; in-line processing capacity, can be achieved volume to volume, volume to sheet, the function can be increased on demand, high flexibility, short production cycle; and the anilox stick, the version of stick And the anilox stick, plate stick, etc. all adopt pneumatic tensioning sleeve structure, simple structure, can realize fast and accurate conversion, high working efficiency, save manpower, material and financial resources, reduce waste, reduce production cost and environmental protection cost, improve economic efficiency.
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