With the development of society, fluorescent ink has been more and more widely used. In particular, the printing process of packaging products such as bills, securities, scratch cards, trademarks, book covers, and tobacco and alcohol use anti-counterfeiting fluorescent ink for printing, which can not only improve the printing process level, but also achieve a certain anti-counterfeiting effect. Therefore, to correctly understand and understand the characteristics of fluorescent inks and master the correct application methods of fluorescent inks, not only can effectively prevent the occurrence of printing failures of one kind or another, improve printing production efficiency, but also can better improve the printing quality of products to meet The customer's printing quality requirements for anti-counterfeit products.
Correct understanding of the characteristics and uses of fluorescent ink
The so-called fluorescent ink is an ink made with fluorescent pigments. The plate printed with fluorescent ink has the characteristics of converting ultraviolet short wave into longer visible light, and then reflecting the charming colors, so it has a certain anti-counterfeiting effect. The colorant in the fluorescent ink, that is, the pigment or dye is different from the ordinary colorant, it can not only reflect visible light, but also absorb short-wave parts such as purple, blue and green light, and reflect it into visible fluorescence, so that the colored substance After being excited by sunlight or ultraviolet light, it shows fluorescence, so its colored substances can produce very pleasing colors with fluorescent effect. Whether a colorant can produce a good fluorescent effect depends mainly on the existence of certain atomic groups in its molecular structure. After the luminous fluorescent ink is printed, when the printed graphics are irradiated with ultraviolet rays, it will be reflected by the long-wavelength visible light, so it can also display bright and eye-catching color effects in the dark. The result of the action is also the basic characteristic of luminous fluorescent ink. Colorless fluorescent ink can be mixed with similar 4-color inks to prepare other colored fluorescent inks. However, its luminous color and brightness will vary depending on the color and component of the added ink. If it is improperly mixed, it will easily affect the performance of the ink. Because the wavelength difference between the transmitted light wavelength of the red and yellow inks and the wavelength of the ultraviolet fluorescent line is large, the fluorescent color produced is obvious, and when the green fluorescent ink is printed on a light background color or a white background color, only the ink layer reaches a certain thickness Only then can the ideal fluorescent effect be obtained. Fluorescent inks are used in color prints better, so it is widely used in securities, stamps, trademarks, labels, scratch cards, invoices, navigation marks and other packaging and decoration prints, the application prospect is extremely broad.
Several types and varieties of fluorescent ink
Fluorescent inks are classified according to the type of printing process: there are silk screen fluorescent inks, gravure fluorescent inks, offset fluorescent inks, relief fluorescent inks and flexographic fluorescent inks. According to the performance of the ink, fluorescent ink is used for printing general products, and fluorescent anti-counterfeiting ink is specially used for anti-counterfeiting printing of special products. In use, it is necessary to design according to the characteristics of the printing process and select the corresponding fluorescent ink to ensure that the printing process effect is not affected. Fluorescent ink is divided into invisible anti-counterfeiting ink and tangible anti-counterfeiting ink. The pictures printed with invisible fluorescent anti-counterfeiting ink, when looking at the printed matter, can hardly see the printing color, and when looking at the printing plate at an angle, you can only see a faint, trace of gloss, this kind of fluorescence Ink is often used to print scratch cards, book covers and invoices. When ultraviolet light is used to illuminate printed graphics, you will clearly see bright, clear, and colorful fluorescent graphics. Since the invisible fluorescent ink is transparent and colorless, it is difficult to clearly observe it with the naked eye during printing, which causes a certain degree of difficulty for proofreading. According to the past experience of the relief printing process, it is best not to change the color of the car wash immediately when installing the printing plate of the invisible fluorescent ink, but to change the color of the car after the version correction is completed, which is conducive to improving the version correction. Version efficiency. The printing with tangible fluorescent ink is relatively simple, and the ink color control of the plate-setting and printing process is more intuitive and clear. Therefore, the registration of the layout is easy, and the ink color of the printing process is also easy to maintain uniformity. Choosing the right fluorescent ink to print different products has a crucial role in the product's anti-counterfeiting effect. If the ink type is not suitable, the anti-counterfeiting effect of the printing is likely to be poor, and the anti-counterfeiting effect may not even be achieved. For example, colorless fluorescent blue ink is overprinted on a golden yellow background. Because the fluorescent blue ink can show blue light under ultraviolet light, and then mixed with the golden yellow light, because the yellow light and blue light are complementary colors, What appears is white light. This is the result of the absorption of part of the blue short-wavelength light by the mid-long-wave golden light in the spectrum, so the color of the fluorescent blue is hardly visible, so the anti-counterfeiting printing cannot achieve good results. Different formulas can get different colors of fluorescent inks. For example, ultraviolet fluorescent inks that add visible fluorescent compounds excited by ultraviolet light can display red, yellow, green, blue and other visible light under ultraviolet irradiation. If an infrared fluorescent ink with a visible fluorescent compound excited by infrared rays is added to the ink, green visible light can be displayed under infrared irradiation. The double-wave invisible fluorescent ink shows different fluorescent color responses under the illumination of fluorescent lamps of different wavelengths. The long wave shows one fluorescent color, and the short wave shows another color. In order to improve the anti-counterfeiting effect of ink, some products also use fluorescent encryption anti-counterfeiting ink. This kind of ink is different from the general fluorescent ink. The specific encryption component is used in the ink, which has a personalized anti-counterfeiting effect. When the authenticity of the product is to be identified, the authenticity of its printing can be identified with the help of a special testing instrument. Therefore, the anti-counterfeiting process is more effective.
Several control points of fluorescent ink printing process technology
Fluorescent inks are obviously more expensive than ordinary inks. Therefore, from the perspective of anti-counterfeiting process or the cost of ordinary printing processes, the layout of the printed fluorescent ink should not be too large, especially the field layout is not suitable for printing fluorescent ink . Therefore, fluorescent ink is more suitable for printing small areas of text, signs or patterns. For products printed with fluorescent ink, the printing effect should be fully considered in the layout design. For example, if the tangible fluorescent ink is printed directly on white paper, the fluorescent effect is not good, and the design of the overlay printed fluorescent ink on a light background, the process effect is relatively better. From the perspective of product anti-counterfeiting, invisible fluorescent ink is used to print small letters and letters, and part of the characters and letters stroked from the font are intentionally deformed to form a hidden and personalized Anti-counterfeiting secrets to improve the anti-counterfeiting effect of the printed layout.
Pay attention to the selection of printing paper according to the characteristics of fluorescent ink. Because different papers have different effects on invisible fluorescent ink. For light-colored or colored paper, the color of the paper surface can easily reduce the brightness of the ink and affect the color rendering effect. In addition, the whiter the paper, the higher the degree of treatment with fluorescent whitening agent, so that the fluorescent whitening agent will emit blue-white light under ultraviolet light, which will form a certain degree of interference with the color development of the fluorescent ink, resulting in a significant reduction in the fluorescent effect , Affect the technological effect of fluorescent ink. Therefore, the invisible fluorescent blue ink is not suitable for printing paper containing strong fluorescent whitening agents. The yellow and magenta fluorescent inks have the strongest visual impact, and papers and cardboards with high gloss can be selected, such as coated paper and glass cards. The fluorescent effect is ideal.
Pay attention to the reasonable control of the printing process. From the appearance of the fluorescent ink, the original fluorescent ink looks darker, but it is very light after printing on the substrate. This must be paid special attention when adjusting the ink, so as not to waste the ink. Fluorescent pigments have a hard texture and are not easy to roll down, so they have poor stretchability during printing. Therefore, when printing plates with fluorescent inks, it is best to print a layer of Velcro on the base color before overprinting. The printing effect is better. When printing paper with high acidity, a small amount of dry oil can be added to the ink as appropriate to improve the printing process effect, ensure that the product is dried after printing in time, and avoid the printing product from being dirty. In order to improve the printing performance of fluorescent inks, it is sometimes necessary to increase the viscosity of the ink appropriately. For example, under high-speed and high-temperature printing conditions, generally No. 19 resin oil and varnish can be used. However, if printing paper and cardboard that are prone to lint and printing in a low-temperature environment, the viscosity of the ink should be appropriately reduced. If you use fluorescent ink to print transparent film materials, you can print a white ink first, and then print fluorescent ink, which can better improve the printing effect of fluorescent ink.
Clean the inking system to prevent cross color and color cast. According to the experience of the previous printing process, when printing fluorescent ink, the machine's inking device including the rubber roller, ink fountain and printing plate should be cleaned, and then the ink of the desired printing color should be applied to the ink fountain and rubber roller for operation. Wash again, so that the machine's ink coating system can be cleaned more cleanly. When printing, there will be no cross-color development after mixing with the color of the original machine and the color of the fluorescent ink, resulting in the impure color of the fluorescent ink. Instead, there is a color cast. If conditions permit, a set of unused ink rollers can be used for printing fluorescent ink, which is conducive to improving the quality of printed colors. In particular, even if slight scratches appear on the surface of the embossed rubber roller, it is difficult to clean it. It is more scientific and reasonable to reserve a set of rubber rollers for the operation of printing color product equipment.
Pay attention to the control of ink preparation process technology. Using a small amount of color ink mixed with fluorescent ink can improve the color and concentration of fluorescent ink, such as fluorescent orange red can be adjusted to an appropriate amount of fluorescent orange, gold red; fluorescent pink can be adjusted to an appropriate amount of peach red. It is worth mentioning that the fluorescent ink should not be mixed with other ordinary inks as much as possible, otherwise, it is easy to reduce the fluorescent effect of the ink. The screen printing fluorescent ink can be mixed with phosphorescent ink, and its color effect is better. If the background tone of the printed fluorescent ink is deeper, the fluorescent effect will be worse, so you should pay attention to this when preparing the ink.
Pay attention to controlling the printing pressure. Since the inorganic phosphors of fluorescent inks emit crystals, if the printing pressure is too high, the crystals will easily break and the luminous brightness will be reduced. Therefore, the relief printing process is not suitable for printing with metal plates, but it is suitable for softness and gloss. Good, light printing pressure can make the resin plate that keeps the ink color saturated, and pay attention to the printing with the smallest possible pressure. In fact, it is more appropriate to use screen printing, gravure printing and other processes to print fluorescent ink. Its printing ink layer is thick and the fluorescent effect of the printed plate is better.
Pay attention to control the printing speed. For fluorescent inks with greater fluidity, the drying performance is relatively slow. When printing large-area plates, the coated ink layer is relatively thick. If ultra-high speed printing is used, it will easily aggravate the abnormal spread of the ink layer. There are ills of paste version. Therefore, the author believes that printing fluorescent inks to maintain medium speed for printing is an appropriate standard and certification, so that it can also maintain a relatively stable printing ink color density.
Ink adjustment for printing intaglio invoices with gold and red fluorescent inks. In the past, when I used the red and red fluorescent ink to print the tax invoice supervision stamp on the anti-counterfeiting watermark paper during the embossing process, the paper surface was rough and the hair fell seriously; the layout was easy to be dirty and paste and other quality failures. Especially in the winter when the temperature is low, the ink is thick and sticky, and the above problems are more prominent. Without taking measures to adjust the fluidity and viscosity of the ink, it is difficult to maintain normal printing. Later, by adding 6 # ink to the ink to dilute it, the phenomenon of printing quality failure was better eliminated, and the printing production efficiency was improved.
Our company's offset press used offset colorless fluorescent ink to print the initial label of the scratch card. Frequent quality failures such as pasting, dirty version, and uneven color have occurred, resulting in low printing efficiency, high product failure rate, and large consumption. Outstanding issue. After careful observation and analysis, the author found that this is due to the thick ink, high viscosity, poor fluidity, and the ink layer is easy to accumulate and dry. Later, we added a small amount of debonding agent to the ink to reduce the viscosity of the ink and increase it. After the fluidity of the ink, the above-mentioned printing defects are effectively eliminated immediately, and the printing efficiency and printing quality are simultaneously improved.
Pay attention to the reasonable arrangement of the color sequence of fluorescent ink printing. After the fluorescent ink is printed, only the full display of the fluorescent effect is the purpose of the printing process. Therefore, when printing fluorescent ink on paper or cardboard of non-transparent materials, the problem of reasonable arrangement of color sequence must be considered. Whether it is a colored or colorless transparent fluorescent ink, the fluorescent ink can be printed directly on white paper, or it can be printed on the background color. However, the background color layout must be printed first, and the layout of the fluorescent ink should be printed last. Otherwise, the fluorescent ink will be masked by other colors and affect its color rendering effect.
Pay attention to the reasonable control of the ink coating amount. The printing process shows that the thicker the ink layer of the fluorescent ink, the stronger the color rendering effect and the more striking the imprint. However, the thickness of the ink layer coating should also be controlled to an appropriate level. Lithography is based on the principle of no paste and no dirty plates, which not only wastes ink, but also ensures the color rendering effect of fluorescent ink, which meets the basic requirements of product quality. Requirements, this is also the basic principle of the process.
Pay attention to choose the appropriate post-press processing method. In general, it is best not to perform the glazing coating process, and not to use the film decoration process for the analysis and elimination of the product of printing fluorescent ink, otherwise, it is easy to fade and change color on the one hand, and affect the fluorescence on the other hand Color rendering effect. If the protective film layer needs to be coated in consideration of the product's use characteristics, it can be coated with UV-resistant varnish to achieve the effect of enhancing the lightfastness, abrasion resistance and color fading of printed products. For some special products, in order to improve the decorative quality effect of fluorescent ink printing products, local hot stamping anodized aluminum can be used appropriately, and the concave and convex embossing process can be used to set off the product to improve the beauty of the product.
In summary, fluorescent ink is different from general ink, its superior performance and color rendering effect determine its color separation in high-end cigarettes, wine, drugs, cosmetics and other packaging products, as well as securities, stamps, trademarks, labels, scratch cards , Invoices and other anti-counterfeiting printing technology in a broad application market. As long as we establish a sense of innovation in process design, from the best design of the theme decoration of the printing layout, to the appropriate use of other post-press processing technology; from the reasonable selection of printing raw materials, to the comprehensive control and control of the printing process technology, this can Without losing the good use characteristics of fluorescent ink, improve the process level of printed matter.
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