The colorants used in fluorescent ink are usually pigments or dyes. Unlike ordinary ink colorants, fluorescent ink can reflect visible light and absorb short-wavelength light such as violet, blue, and green, and then reflect visible fluorescence. The colored substance printed with fluorescent ink can exhibit fluorescence when exposed to sunlight or ultraviolet light, meaning it can also display fluorescent colors during the day. The key to whether fluorescent ink can produce a fluorescent effect lies in the colorant, which is determined by the presence status of certain atomic groups in the molecular structure of the colorant. Fluorescent ink can produce fluorescence under sunlight because the colorant contains benzene or heterocyclic rings with conjugated double bonds. Night-glow fluorescent ink produces fluorescence because its colorant raw materials contain sulfides such as zinc, cadmium, and strontium. When printed on paper, under ultraviolet irradiation, it can reflect visible light in the long-wave band, so it can also display colors in dark places without light and is bright and eye-catching. Compared with ordinary ink, fluorescent ink has superior performance and coloring effect, so it has a wide range of applications and a broad market. It is usually used in high-end cigarette, liquor, medicine, and cosmetic product packaging. It also has extensive application in the field of anti-counterfeiting, such as securities, stamps, trademarks, labels, scratch cards, and invoices. To make full use of the efficacy of fluorescent ink, we need to be innovative in the process design and adopt the best printing layout design. We also need to control the printing process, reasonably select printing raw materials, and control the quality of printing technology, in order to give full play to the excellent performance of fluorescent ink and improve the process level of printed products.
Under normal conditions, the lifespan of photochromic fluorescent anti-counterfeiting ink under sunlight is 30 days. With the development of printing and new material technologies, the indoor lifespan of photochromic fluorescent anti-counterfeiting ink has been greatly improved, and even can be used indefinitely. The main function of photochromic fluorescent anti-counterfeiting ink is to exhibit bright and vibrant colors in printed materials. The advantages of fluorescent ink during printing include thin ink layer, precise background, fast drying, etc., which should be determined based on the characteristics and printing method of the printed material. In the anti-counterfeiting printing of invoices, fluorescent ink is usually used, but the process requirements are relatively high, requiring advanced technology and rich experience. When printing the supervision seal with fluorescent ink on watermark anti-counterfeiting paper, there are usually quality problems such as paper fuzzing and shedding, dirty and pasted layout, especially in cold winter when the temperature is low. In addition, there are serious and prominent problems of ink viscosity and strong adhesive film. Later, through the exploration and technological innovation of printing enterprises, the addition of No. 6 ink thinner in fluorescent ink has solved these problems very well, and the overall production efficiency has also been improved.
Anti-counterfeiting printing technology involves many fields such as spectrum technology, printing technology, packaging technology, optics, chemistry, physics, electromagnetics, computer technology, spectral technology, printing technology, and packaging technology. It is an interdisciplinary and cross-border technology. Ink anti-counterfeiting technology is a technology that adds special substances such as solvents to ordinary ink and connecting materials, and then processes them into special anti-counterfeiting printing inks through special processes. It is widely used in the pharmaceutical packaging anti-counterfeiting industry. Color-changing anti-counterfeiting ink has the advantages of simple implementation, low cost, good concealment, bright colors, and easy inspection. In China, the color-changing anti-counterfeiting inks widely used in the special anti-counterfeiting printing industry include: anti-counterfeiting fluorescent ink, magnetic anti-counterfeiting ink, thermochromic anti-counterfeiting ink, daylight-excited anti-counterfeiting ink, optical variable anti-counterfeiting ink, pressure-sensitive anti-counterfeiting ink, infrared anti-counterfeiting ink, anti-tampering anti-counterfeiting ink, and anti-counterfeiting printing ink, which are widely used in anti-counterfeiting of bills, packaging, etc. Anti-counterfeiting fluorescent ink is currently the most widely used anti-counterfeiting ink in pharmaceutical packaging, and it is the most important component of anti-counterfeiting technology in pharmaceutical packaging. Practice has proved that anti-counterfeiting fluorescent ink with fluorescent pigments added has good water resistance, acid resistance, alcohol resistance, and good color-changing effect, clear anti-counterfeiting features, and is not easy to counterfeit. Therefore, it is widely used in ordinary drug packaging and blister packaging.
As more and more people use ink for printing or decoration, fluorescent ink, as a new product, is introduced here to highlight several precautions for blending. When blending fluorescent ink, it is necessary to match the ink color with the color design of the decoration, minimizing the difference and striving for consistent color tone. The quality of printing will be affected if the ink is too thick or too thin during blending. It is recommended to give the fluorescent ink a certain viscosity and fluidity. When printing cigarette, alcohol packaging, or trademarks, a certain amount of red and white desiccant oil should be added, but not exceeding 5% of the ink quantity. Too much desiccant oil may cause crystalization and make the ink color dull, while too little may cause the back to become sticky. The amount of desiccant oil should be appropriate, not too much or too little. Choose high-quality fluorescent ink. The properties and color of ink from different manufacturers are not the same. It is best to choose a manufacturer's ink product. The rougher the paper, the stronger the ink absorption, and the more ink is consumed during printing. Therefore, the properties of the printed paper should be considered when blending ink, and the temperature should be adjusted by adding or reducing the amount of desiccant oil. The blended fluorescent ink should be just enough for one use with a little extra. Avoid blending a quantity that is not sufficient, which can cause differences in ink color between two blends, and also result in waste.
Photochromic ink, commonly known as color-changing ink or color-shifting ink, for example: red-green, gold-silver, etc. It has strong photochromic properties and significant color differences, making it difficult to replicate and highly counterfeit-proof. Many countries around the world use this type of ink for currency or valuable securities. The manufacturing method of photochromic anti-counterfeiting ink is generally to dissolve photochromic color-changing pigments in solvents and make them into microcapsule pigments. Adhesives are added to the dissolved pigments according to different purposes. A better manufacturing method is to dissolve photochromic color-changing pigments into monomers, crush these polymer ultrafine particles into powder, and use them as pigments. Compared with microcapsule ink, the ink made by this method has a 10 times higher light resistance. These powders can be used as pigments in water-based ink, oil-based ink, plastic ink, and all adhesives. Interference-type photochromic ink used in banknote printing is the most complex new anti-counterfeiting ink. This ink has the characteristic of showing different colors at different angles under natural light. These dynamic color changes are also the best way to distinguish counterfeit currency that uses photochromic ink. Moreover, this type of anti-counterfeiting technology cannot be copied by photocopiers or scanners, and has high counterfeit resistance. The characteristics of this anti-counterfeiting technology are simple implementation, low cost, good concealment, bright colors, simple inspection, and strong reproducibility. It is the preferred anti-counterfeiting technology for currencies, certificates, and trademarks in various countries.
Due to its special characteristics in the ink system, UV fluorescent ink has very strict requirements for printing processes, and the following issues need to be especially noted when using it: (1) Slow volatility: Advantages: Excellent reproducibility of printed images; Disadvantages: It cannot be completely volatilized, and the fluorescent ink layer is prone to adhesion, which causes anti-counterfeiting images to be blurry, the layout to be dirty, and affects anti-counterfeiting and appearance. (2) Fast volatility: It causes phenomena such as ink whiteness, roller sticking, and ink layer sticking, which leads to the dirtying of the back of the packaging material and may also affect coating and composite processes. Since different manufacturers have different printing equipment and operating environments, such as printing machine speed, drying structure, substrate material characteristics, indoor temperature and humidity, the use of solvents in the printing process needs to be considered comprehensively. It is recommended to compare the dissolution parameters of the binding resin and use 2-3 solvents with different boiling points to print a complete anti-counterfeiting effect pattern. (1) The price of fluorescent ink is more than ten times higher than that of ordinary ink; (2) Fluorescent ink cannot be reused and is easy to get dirty; (3) Long-term solvent washing of the ink system will dilute the fluorescent pigment and fail to meet the anti-counterfeiting requirements.
In the era of banknote payments, producing high-quality banknotes is difficult, and the most challenging part is anti-counterfeiting. Nowadays, the most advanced anti-counterfeiting technology is optically variable ink, which has strong color-changing properties, a significant color difference, and distinctive characteristics. It can be recognized without using any instruments, and it cannot be replicated using other devices. So far, it has not been successfully counterfeited and is widely used in various banknote printing. Optically variable ink is also known as optical variable ink and color-shifting ink. The manufacturing method of this ink is mainly to dissolve the photochromic color and then use colorants to make pigment capsules, which are added with adhesives for different uses. The color blocks on the printed matter usually present two colors that are relative to each other, such as red vs. green, green vs. blue, gold vs. silver, etc. These characteristics facilitate the identification of the authenticity of banknotes. Another higher manufacturing method is to dissolve the optically variable ink into a polymer monomer through professional techniques, break its polymerization state chemically, and then make it into a powder for use as a pigment. This manufacturing method increases the light resistance of the ink by ten times compared to ordinary ink.
I. Printing methods: Fluorescent ink is typically printed using one of four methods: screen printing, offset printing, transfer printing, or pad printing. It comes in four colors: red, yellow, blue, and green, and can be printed alone or in combination on common substrates such as paper, fabric, metal, ceramics, and plastic. II. Applications of fluorescent ink: Fluorescent ink is widely used in fields such as tickets, certificates, labels, packaging, and anti-counterfeiting for various high-end products. III. Precautions:
Optically variable materials have a distinct color change effect and can be visually distinguished at different angles, making them easily recognizable. They possess specific spectral characteristics, such as a five-layer optical interference inorganic material and multi-layer optical interference inorganic material with ultra-fine micrometer-sized particles. Production process: The production process of optically variable multilayer inorganic materials is complex and requires special coating equipment, involving high-end technologies such as inorganic fine chemical engineering, vacuum coating technology, optical technology, and nano-vacuum airflow pulverization. They are widely used in currency, passports, tax receipts, securities, certificates, as well as high-value luxury goods, pharmaceuticals, cigarette packaging, tea packaging, and various anti-counterfeit marks. They are also used in the beauty and nail industry, high-end coatings, and automotive spray painting industry. This fully reflects the social values of safe manufacturing processes, safe consumer use, and anti-counterfeiting security, and expresses the company's mission of meeting customers' unique value requirements.
