The mystery of metal ink-to improve the quality of printed matter

I remember 20 years ago, the 20th anniversary of the freshman design college in Hong Kong, so I wanted to have more elements to attract eyeballs in the promotional materials. Since I have been cooperating for several years, as usual, President Lu wrote the designer After I came up with an idea, I first discussed with me which techniques can be used and cooperated to achieve the best results. Since the designer at the time made a robot with stationery as the theme, the author suggested that it is better to add a large area of ​​metal feeling, to get a hot silver effect that exceeds the A3 area as the cover of the graduation annual journal, and to have a hot silver screen At that time, there were only two or three sets of hot stamping machines in Hong Kong that could hot such a large area, and they all said that they had never tried such a large area of ​​hot stamping.

Finally, because I had to catch up with the graduation exhibition, I had to make a hundred copies, and the rest had to be solved with printed silver, that is, the version seen in the workshop, and of course President Lu, the designer, and I treasured this hot silver. I believe that there are not many people who have seen this hot silver version so far, and the metal ink used in silver printing was very different from the current one. The effect is different from the shiny effect of hot silver. If there are so many different metal inks to choose from today, there is no need to give up the original design, but helpless a good design does not have enough money and time, it is often impossible to achieve, and experience tells me that time is more than money important.

The effect of the metal ink used now can achieve to replace more expensive materials, such as aluminum foil or gold-plated materials. On the other hand, metallic pigments are widely used and can achieve metallic effects through different processes, such as replacing hot silver. Over the past decade, metal ink technology has also greatly improved the convenience and flexibility of printing, and it also has advantages in cost. Since the content of metal pigments in metal inks is generally 2 to 4 times higher than ordinary inks, the price of metal inks is much higher than that of ordinary inks. Nevertheless, ink printing is still welcomed by the packaging and printing industry, because compared with hot stamping and aluminum film printing, metal ink printing still has the advantages of fast production speed and low cost. Therefore, many consumer product packaging, such as food, beverages, cosmetics, etc., use a lot of metal ink to stimulate the eyes. And it is also more convenient in application, because there is no need to add or modify equipment, and it can be produced like ordinary ink to improve efficiency and save costs. Of course, the printing process I'm referring to is not just referring to lithography, which is familiar to Hong Kong people, but also includes different technologies such as silk screen, flexo, and gravure.

So what is the great progress of metal ink today? Let me start with the structure of metallic ink.

Structure of metallic ink

Metallic printing ink (metallic printing ink) refers to the ink prepared by replacing the pigment or dye in the traditional ink with fine metal flakes, which has a metallic shiny effect. The general metal ink is mainly gold and silver ink. Gold ink is generally added with copper pigments and zinc pigments, and by controlling and changing their ratios, green gold, green red gold, red gold and other inks are produced; silver ink is prepared by adding aluminum pigments.

The optical properties of metallic pigments are different from those of ordinary pigments, so the optical properties of metallic inks produced are also very different from ordinary inks. The color of ordinary ink will not change with the viewing angle, but the hue and brightness of the metal ink will change depending on the viewing angle. Instead, use a special spectrodensitometer that specifically measures reflective metals. If the result is unclear, misunderstandings of inaccurate colors often occur.

To match the printing method

The shiny effect of metallic ink is the result of the specular reflection and diffuse reflection of metallic pigments. In order to achieve a better metallic effect, the specular reflection of metal pigments should be increased to reduce diffuse reflection. The effect of the ink reflection effect is mainly the size of the metal pigment particle size. The larger the size of the individual pigment particles, the better the mirror reflection effect and the higher the gloss of the metal ink, but its hiding power and dot reproducibility will become lower. Conversely, the smaller the particle size of the metallic pigment, the higher the hiding power and dot reproducibility of the metallic ink, but due to the excessive diffuse reflection of the edges, the gloss of the metallic ink will be reduced. Therefore, users need to choose a suitable particle size according to their own requirements, and they must match the specific printing method when choosing. Different printing methods will definitely affect the shiny effect of metallic ink. If the ink cannot be transferred smoothly, it will cause a situation similar to clogged mesh or ink accumulation during the screen printing. The ink will also thicken, which affects the color and uniformity of the printed matter. Conversely, if the particle size is too small, it is easy to cause light diffusion, which makes the ink lose its metallic luster and cause the printing effect to be not bright.

The experiment proves that the screen size should be about 3 times the average size of the metal particles during screen printing. The metal flake particles in the metal ink can pass through the mesh smoothly under the action of the scraper. The average size of the general metal ink particles is 15-20μm, according to the principle that the size of the mesh should be about 3 times the average size of the metal particles, the mesh of the screen used is at most 400 / 英? Trace ㄆ 渫? 弽 弭? 0μm), but with 400 / British? Jealousy? From: ⅲ ?? 芏 仁 宮 杹 擹 M Jiamou Xia Tuo Xin Qiyuan tomb toll fee ?? 胪 嘉 那 逦? Screen boiled ostrich ??? K ?? Building Ran Xianliang loves the male Ч ???? Meng Biepa 5 Mu'e 粲 粲 流 ?? Locust ∮∷⑸ Department is sincere?

Distribution of metallic pigment particles

In addition, the particle distribution of metal pigments is also a factor that affects the optical properties of metal inks. When using metal inks from different manufacturers, although the particle size shown in the technical information is the same, the hiding power and metal gloss of the metal ink after printing may sometimes be very different, this is because different ink manufacturers are manufacturing The distribution of the particles of the metal pigment is loose and dense. With the same average particle, the denser the particle distribution, the more neat the overall arrangement of the pigment, the better the gloss and hiding power of the produced metal ink, so the distribution of particles by different metal pigment manufacturer technologies will affect the The effect has a great impact. The uniform distribution of the metal sheet depends on the characteristics of the resin and solvent in the ink. A good resin can make the metal sheet distributed very uniformly, but with an ink made of poor resin, its metal particles are very unevenly distributed. Under the microscope, the metal sheet can be seen to stick together, distinguishing individual particles is very Difficult, the metallic gloss effect of the printed matter is greatly reduced.

Innovation of metal ink

The shape of the metal pigment particles in the traditional metal ink is irregular, but due to the irregular shape of the metal pigment particles and the uneven edges, the specular reflection effect of the particles is poor, and the edge diffuse reflection is serious, so the metallic luster and cover of the metal ink The force is correspondingly poor. The new metal pigments have an approximately circular structure with uniform size and even good specular reflection effect, while the metal effect and hiding power are excellent.

However, in some new metal inks, the metal flake particles are mostly elongated particles. On the premise of satisfying the size of the particles, the shape can reduce the thrust required for the particles to move in the ink medium, so as to achieve The purpose of reducing the viscosity of the ink. Because the metallic ink will not make the ink thick because of the increase in the fineness of the particles. This is mainly because when the metal sheet rotates or sways in the flow process, the energy required is higher than that of the ordinary particles, and the larger particles need a lot of thrust when moving in the ink medium, so the viscosity of the ink will increase If the ink is too thick, not only the ink is affected when passing through the screen mesh, but also when printing, whether it is a gravure or flexographic printing plate, there will be uneven printing density and film formation. On the contrary, when small particles require only a small amount of thrust, the flow can be smooth and natural, and the viscosity becomes very low. Larger metal particles can better increase the metal effect of the ink, but in order to achieve the effect of low viscosity and printing uniformity, often smaller particles are needed. Therefore, the choice of the two is often determined by the actual situation.

Recently, there is also an ultra-thin, non-floating electroplated aluminum paste, which is a very unique metal pigment-VMP (Vacuum Electroplating Metal Pigment), which is produced by a special vacuum electroplating process to obtain a very smooth and extremely thin scale structure Therefore, it has completely different metal effect from copper and aluminum metal pigments produced by traditional methods. If used properly, a chrome-plated surface coating can be obtained, which is very metallic. At present, the VMP super bright aluminum paste is produced, and the ink containing VMP is used as a substitute for aluminum foil cardboard during packaging printing, which can save material costs.

Myths when using metallic inks

So why sometimes we use good metal inks, but the printed results are still not ideal and not shiny enough? In addition to the quality of the metallic ink used, a reasonable production operation method is also very important.

Designers often choose metallic colors other than gold and silver. Most printers will use metal ink and four-color or other spot color inks to adjust the metal spot ink, but the metal raw materials used to produce metal ink are relatively soft and thin metal sheets, and many printing operators It is used to stir the ink with some metal tools with hard edges, and the metal raw materials are very sensitive to the shear force. Excessive shear force will cause the metal pigment particles to deform or form many fine particles. To avoid the shear force on the metal pigment The influence of particles, when adjusting the metal spot color ink, you need to use some relatively smooth tools, and at the same time to avoid high-speed stirring, otherwise the adjusted ink will lose luster.

In addition, the ink media (such as resins and solvents) used by general ink factories in making metallic spot color inks are mostly different from the metallic inks that have been made. Plus, as mentioned above, stirring the metallic spot colors The equipment used in ink is also different from that of ordinary ink, so if you want to cope with a large number of packaging and printing, order metal spot color ink directly from the ink factory to get better results.

The experience of using metallic ink

Since the materials used to make metal inks are active metal materials, the chemical properties of metal inks are also very unstable. They must be strictly sealed during use and storage to avoid absorbing too much moisture and being directly exposed to light for a long time. In lithographic printing, the use of inappropriate fountain solution will also affect its shiny effect.

In addition, the density of metal pigments is large, so compared with ordinary inks, the pigment particles of metal inks are very easy to settle. If they are not fully stirred before use, and if there is no sediment on the bottom of the ink tank before printing on the machine, the printed matter comes out. Hue and gloss differ greatly. In the printing process, the viscosity of the metal ink will gradually increase with the continuous evaporation of the solvent. In order to ensure the stability and good fluidity and transferability of the metal ink, the viscosity of the ink should be measured regularly and the solvent should be added appropriately to keep the ink viscosity at Stable state.

The price of metal ink is much higher than that of ordinary ink, but the recovery of the metal ink used in the ink lees will find that the gloss is significantly reduced. Therefore, under the premise of satisfying smooth production, it should be as many times as possible in the printing process. Add a small amount of metal ink to the principle of not waste.

In recent years, metallic tones have been of great use in promotional materials and packaging. In addition, printing companies in Hong Kong and the Mainland have set up five-color and six-color printing machines in the past decade. It is more convenient for printing metallic tones, so there is no need to worry about time. In recent years, there have been many new materials and technologies in this area. Let's talk about it later!

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