How to make corrugated paper printing more colorfu

2022-07-30
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How to make corrugated paper printing more colorful

water based ink is one of the three pillars of contemporary flexographic printing. Because it does not contain volatile organic compounds, it has been considered as an environmentally friendly, safe and hygienic ink among all kinds of inks. The drying speed of water-based ink is much faster than that of offset and gravure printing ink, and it has good printability and wear resistance. It also has good performance in printing density and dot increase, and has been proved to be more suitable for paper and Paperboard Printing. The following is a brief introduction on how to make water-based ink printing more beautiful

ink transfer

the ink absorption of the substrate has a great impact on the quality of ink transfer. However, if the paper is too rough and ink absorption is good, it will have a negative impact on the color and ink consumption

ink transfer is a process in which the ink penetrates into the paper surface by capillary action under the action of printing pressure. The fully mixed resin is fixed on the paper surface by capillary action. The acidity of paper also plays a role in drying ink. To achieve the best printing effect, we should use the minimum amount of ink on the premise of meeting the color density and ink transfer quality, which is usually expressed by the word ink holding capacity

paper with rough surface requires less ink, whereas paper with rough surface consumes more ink. When using paper with rough surface, even if the ink is carefully adjusted and a good print sheet is selected, it is still easy to produce dot enlargement. The point increase value is related to the paper type, surface structure and micro width. In addition, excessive separation of binder and pigment in the ink will reduce the anti friction performance of the paper after printing, and it is easy to produce chalking

overprint is an important factor that determines the printability. It refers to the overlapping of multiple colors in the same pattern. To get a good overprint effect, the first color ink should be fully dried before the second color ink is overprinted to the first color ink, especially for coated paper. Since the surface of coated paper is smoother than that of non coated paper, it is easier to cause faults. In order to reduce such faults, sometimes the color sequence is adjusted to myc

temperature effect

the fluidity of ink changes with temperature. The viscosity of ink decreases with the increase of brightness. Therefore, the control of dryness is very important. It is best to maintain normal temperature. With the ink supply device of the ink scraping system, the ink transfer balance can be maintained only when the temperature is controlled

in North America and Northern Europe, where the temperature changes greatly, printers have fully realized that the temperature of the printing workshop will also change greatly with the climate and seasons. Keep the ink viscosity stable to control the dilution dose. The higher the general degree, the less the dilution dose is required, and the dilution of the ink will reduce the field density of the printed matter. The diluent of ink is water or diluent medium

drying performance and viscosity control

water based ink is adsorbed on the surface of printing materials through volatilization, penetration, precipitation and related chemical reactions. Evaporation is the hot air that takes away the volatile organic compounds in the ink on the printing surface

the so-called osmotic drying is that the ink penetrates into the surface of the substrate under the action of the capillary. It usually refers to the liquid phase and solid phase separated by the liquid ink. The liquid phase platform is inserted into the paper fiber, and the solid phase synthetic resin is left on the paper surface. The corresponding chemical reaction helps to dry the ink layer on the printed matter. However, the post printing process of corrugated paper does not use chemical drying, and most of them use ultraviolet, infrared, electron beam or microwave drying

in order to reduce the volatilization and drying of water-based ink in the ink bucket and scraping system, modern corrugated paper back printing machines are generally equipped with closed ink conveying devices. The ink tank of most printing machines is located under the printing machine unit, and the ink is pumped into the ink bucket by the ink pump. The continuous contact between the ink and the bucket and ink roller and the convection of air during the circulation of the unit make the solvent volatilize, resulting in the increase of viscosity and printing color density. In this case, it is usually necessary to dilute to make the viscosity meet the requirements. Do not add too much water to the water-based ink, otherwise it will be too thin. Water based ink is too thin. Do not adjust the viscosity of water-based ink by pouring new ink into thin ink. Experience has shown that if you pour new ink into thinner water-based ink, you need to use a lot of new ink. An effective way is to gradually add balance ink into the new ink

the viscosity of water-based ink is controlled to ensure its performance and print color. Water-based ink has only a small amount of solvent volatilization, which is easier to adjust than solvent-based ink. As the drying of water-based ink for paper and Paperboard Printing mainly depends on the penetration part, the surface quality of printing materials has a great impact on the drying

the drying speed of water-based ink is closely related to the printing process and the dispersion of resin and water in the formula of water-based ink. The best balance between the drying speed and the printability should be found

the fast drying ink used in high-speed printing is also easy to dry and fix on the printing plate or roller during the printing process. Therefore, special attention should be paid to this kind of ink

additives do not mean that aluminum is no longer used.

additives are added to the ink to improve the performance of the ink. The amount of additives is generally small. In order to make the additives work, we should first understand their performance and side effects. The ink additives include defoamer, biocide, wax, surface activating agent, humidifier, transfer aid, binder, anti caking combination, slip aid, etc

surfactants can reduce additives and other fine chemicals in water-based advanced lubricants; The surface tension of synthetic inks, which are also used in the pharmaceutical industry for the analgesic ibuprofen, helps to diffuse, improve gloss, and reduce the possibility of color condensation when diluting inks

antifoam agent is used to eliminate the trouble caused by foam caused by agitation in printing process and ink production process. Foam is often difficult to eliminate. Excessive use of defoamers will make printing unable to proceed normally. Some defoamers contain hydrocarbons, which has a negative impact on flexo printing plates

the generation of foam is related to the hardness of water. The silicon-based defoamer needs to be diluted with water. It should be stirred at a constant speed when adding ink. The undiluted concentrated silicon-based defoamer will cause pinholes or white spots in the printed matter. Therefore, antifoaming agent must be used with caution. The dosage is generally not more than 1% and can be used after dilution

pH value

the change of pH value of water-based ink not only affects the ink transfer, but also affects the printing color. If the pH value is too high and the surface amino group is too high, the drying speed of water-based ink will slow down. On the contrary, if the pH value is low, the viscosity of water-based ink is easy to fluctuate, but it also meets the standard, and the resin will precipitate in the ink

the pH value of the water-based ink can be detected with a standard pH value measuring instrument. The traditional water-based ink is alkaline, and the pH value is about 7 or more. The normal application includes polycarbonate, polystyrene, TPU, pet, PBA, polyvinyl alcohol, polyformaldehyde, replaceable bioplastics, transparent materials, and flexible materials. The range is 8-9. In addition, the pH value required by different formulas of ink is also different

in order to obtain good printing quality and meet the requirements of customers, attention should be paid to the whole process from the product design stage to the final delivery of finished products to each household, to understand the process requirements of each stage, to meet the production requirements as far as possible, and to consider the following factors:

the quality of originals

bar code specification

criteria for the optimal number of lines in polychromatic halftone

ink type and quality

ink absorption and uniformity of printing materials

control elements

roller parameters and scraper type

ash balance

ink viscosity and pH value control

ink overprint

the pressure between the wrinkle roll and the plate cylinder

printing pressure

plate installation

plate loading system

plate type, thickness and quality

effect of printing plate on printing quality

a better printing plate can obtain better printing effect. It can reduce dot increase, make the printing image clearer and the ink transfer better. When printing corrugated board, the minimum pressure can be used to obtain the best printing effect. In order to reduce the point increase when the corrugated box is printed by the post printing process, and make the ink transfer in the field area good, generally, 3.18mm or 3.94mm thick photosensitive resin flexo can be used with PU foam liner. The pad under the printing plate is compressible and can absorb the printing pressure. The printing plate and foam liner work together to reduce point deformation and increase point value. There are differences in the structure, hardness, elasticity, adhesive strength, ink receiving and ink releasing properties of different types of tapes, which have different effects on the printing quality. Therefore, the tape types corresponding to the images should be selected according to different image contents for plate mounting and pasting

the depth of image and text after plate corrosion shall be determined according to different printing machines, printing materials, plates and printing materials When printing high-quality halftone or fine line graphics and text on coated paper or semi coated paper with a new flexo printer, the depth of graphics and text protrusion shall be 1-1.2mm. When printing a field or thick piece of text with an ordinary printing machine, the protrusion depth of the text shall not be too shallow, and the protrusion depth shall be 1.5-1.8mm. The thick photosensitive resin plate with a thickness of 2.84-3.18mm shall be selected for the post printing process of corrugated boxes. If the corrugated red box requires printing high-quality halftone, 80 lines/inch image and UPC bar code, it should also use thick edition

digital edition can be used in the post printing process of corrugated boxes

flexo direct plate making based on digital technology is the latest flexo printing technology. It can make flexo printing obtain excellent printing quality and reach and surpass offset and gravure printing quality in some aspects. Direct plate making process in the plate making process, oxygen will inhibit the resin chemical reaction speed, and can achieve the best balance in oxygen suppression and UVA curing, making the point more profitable and effectively increasing the point suppression. Excellent line image printing effect can be obtained by using hard compression liner material. Compared with the traditional flexo plate making technology

, the dot increase can be reduced by 15% - 25%

with the emphasis on environmental protection, the pre printing process of corrugated boxes has gradually moved from gravure printing and offset printing to flexo printing. The printing plate using digital version as the pre printing process of corrugated boxes can also make the flexo prints colorful and clear

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