Fluorescent ink

Fluorescent inks are special inks that emit visible light (400-800 nm) under ultraviolet light. According to the different wavelength of the excitation light source, it can be divided into short-wave ultraviolet excitation fluorescence printing ink (excitation wavelength 254nm) and long-wave ultraviolet excitation fluorescence printing ink (excitation wavelength of 365nm).
Fluorescent compounds are a class of compounds with special properties that change color after absorbing visible or ultraviolet light. In 1950, Dame Company Ltd. For the first time, fluorescent pigments are used in inks to form practical products. In recent years, there have been many studies on the use of organic fluorescent dyes in ink manufacturing. Another type of fluorescent compound currently most studied for producing a fluorescent ink for use in forgery prevention is a rare earth metal complex. The study of organic pigments began in the mid-1950s. Recently, due to the development of the global economy, anti-counterfeiting technology has also become increasingly important. Research in this area is also active.
At present, there are mainly three types of anti-forgery fluorescent materials in the market.
(1) Inorganic fluorescent materials have good stability, but they are difficult to disperse in oily media and have poor water resistance. They have certain wear and corrosion on the plate material.
(2) Organic Rare Earth Fluorescent Complexes These materials have the advantages of simple preparation, easy refinement, dispersion in oily media, good solubility, high stability, but high cost.
(3) Organic fluorescent materials These materials are easy to synthesize and have good dispersibility in oily media, but most of them are solar excitation, and most of them are currently less stable.
For the anti-counterfeit fluorescent compounds, the most studied at present is a rare earth metal complex. The defect of this type of compound is that the fluorescence intensity attenuates rapidly after being left for a long time.
Because of the low viscosity of the fluorescent ink, organic rare earth fluorescent complexes can easily cause emulsification in the printing process, resulting in blemishes or ink roller deinking. In particular, colorless transparent inks need to be inspected regularly to prevent deinking. Leakage phenomenon is not ideal for lithographic printing. Therefore, such fluorescent inks are generally not used in lithography. In addition, since the fluorescent ink has a large fluidity and is relatively slow to dry, if the ink layer is thick, the ink may not be completely dried due to incomplete drying of the ink. Therefore, the printing speed cannot be too fast.
In addition, an inorganic fluorescent material or the like emits light in a crystal, and if the pressure is too large, the crystal is broken and the light emission luminance is lowered. Therefore, when performing fluorescent ink printing, relief printing is generally not used; when performing gravure printing and flexographic printing, the printing pressure cannot be excessive.
In addition, some fluorescent inks made of dyes have also been reported in the country before. It is generally prepared by dissolving fluorescent dyes and materials in urea resin, melamine resin, triazine benzene resin, and the like. Such fluorescent inks are mostly used in letterpress printing and screen printing. Although this type of fluorescent ink has the advantages of bright colors, its resistance is relatively poor. The light resistance is not good and can not be placed under the sunlight for a long time. After a long time, the fluorescence intensity attenuates quickly, so the applicable printing form is limited. In order to make up for the weakness of poor resistance, the concentration of such fluorescent ink pigments can be higher, and the thickness of the ink film on the print should be as thick as possible, and the fluorescence effect will be better. In order to increase the effect of fluorescent inks, it is desirable to print on high whiteness paper. Printing color sequence is also a very important issue. It is not appropriate to use a desiccant. It is best not to add varnish or bright oil with good transparency. It should not be mixed with Other inks. Therefore, the ink roller should be washed before printing.
Unsatisfactory fluorescence results are the most common failures in the printing of fluorescent security inks. Therefore, it is necessary to develop a fluorescent ink with high fluorescence intensity, good light stability, and good printability.
The characteristics of a new anti-counterfeit fluorescent agent The new anti-counterfeit fluorescent agent has found disadvantages such as overcoming the poor stability of general organic fluorescent materials. It has the following features:
1. The visual color is colorless or almost colorless, and the color is developed by ultraviolet light irradiation.
2. In solids, the fluorescence intensity is high, and exposure to ultraviolet light for a long time also causes little deterioration. Good resistance and strong light stability;
3. Anti-sweat, anti sebum;
4. With acid and alkali resistance;
5. Easy to disperse, good rub resistance;
6. Insoluble in water.
The novel anti-counterfeit fluorescent agent has good light stability, acid and alkali resistance, high fluorescence intensity, and a novel, clear, and long-lasting anti-counterfeiting fluorescent compound when excited by visible light.
Such fluorescent compounds are suitable for formulating inks for various printing methods, and are particularly suitable for preparing inks for offset printing.
The application of fluorescent ink in security printing This ink is mainly used in securities printing. The scope of securities includes a wide range of financial securities, including cheques, bonds, stocks, commercial papers, bank acceptance tickets, and large negotiable certificates of deposit.
The use of fluorescent security inks in the printing of stamps There are many countries that have issued fluorescent stamps. For example, the “T110M” “White Crane” minivan issued by China in 1986 added fluorescent substances to both yellow and red inks. Under ultraviolet light, the eyes of the crane on the small sheet were yellow and the mouth was red. Fluorescent, the pattern is very beautiful. In the 1990s, our country's fluorescent stamps began to expand. In order to achieve the purpose of authenticating stamps, by 1998, commemorative stamps and special stamps issued by our country were almost all fluorescent stamps. Fluorescent stamps have greatly improved the anti-counterfeiting function of our stamps, and also made our stamps very beautiful under ultraviolet light. For example, in the “1994-2 Plant (China Guta), zero stamps are not fluorescent, but the brown sheets in the Souvenir Sheet bear in mind that “Chinese stamps, CHINA” and denominations can emit the same color fluorescence under ultraviolet light. Another example is the "1994-10M" "Zhaojun out of the plug" sheetlet, not only in the pattern of yellow, orange and yellow can emit the same color fluorescence, and postage plans white ticket edge and small sheet edge pattern in the ultraviolet light can also be light blue and Blue fluorescence, stamps with this complex fluorescent feature are difficult to fake.
In addition, the “Yang Kiln Porcelain” stamp issued on April 8, 1999 printed a fluorescent number bar under the face value of 80 points in the full sheet No. 8. The fluorescence is particularly strong under ultraviolet light, but its function is not anti-counterfeiting. It is to prevent people from dumping new mail at a low price (actually the set of stamps can also fluoresce, but it is weaker than the digital bar).
Starting with the stamps of 1999, the printing of fluorescent strips on full-page stamps has been officially applied. The first step in the creation of stamps and fluorescent anti-counterfeit digital printing is generally in the upper right corner of the full-page stamp, and the number of fluorescent security inks is printed. The characteristics are: in the sun five colors, under the ultraviolet light shows the different colors of fluorescence. Afterwards, fluorescent anti-counterfeiting inks are constantly appearing in the printing of stamps. For example, some full-page tickets have anti-counterfeit English names and serial numbers printed on the left side of the paper.
Application of fluorescent anti-counterfeiting inks in other printed materials China's fifth set of RMB 100 yuan, 20 yuan using colorless UV fluorescent ink printing five-color fluorescent patterns, is printed under the heading underneath the offset shading at a specific wavelength of ultraviolet light You can see the denominations "100" and "20". The pattern is machine-readable.
In addition, new anti-counterfeiting technologies such as explicit and covert fluorescent inks have been used in various documents and VAT invoices.
At present, people hate counterfeit products, and many anti-counterfeiting methods have been created to combat counterfeiting. The characteristics of anti-counterfeiting technologies such as UV fluorescent inks are simple to implement, low cost, good concealment, bright colors, convenient inspection, strong reproducibility, and diverse color changes, and can be adapted to large-scale production lines or packaging printing needs. Combined with other anti-counterfeiting technologies, it can produce better anti-counterfeiting effect.
The production and use of fluorescent anti-counterfeit inks can be said to be a win-win result of economic benefits and social benefits, and has broad prospects for development.