Brief analysis of the mystery of metallic ink

I remember that 20 years ago, the 20th anniversary of the freshman design school in Hong Kong was commemorated. Therefore, I wanted to have more eye-catching elements on the publicity materials. Since I had been working for several years, as in the past, Mr. Lu had a designer. After I came up with ideas, I first discussed with me those techniques that can be used and matched to achieve the best results. As the designers at that time used a stationery to create a robot as a theme, the author suggested that it would be better to add a large area of ​​metal sensation, get a hot silver effect that exceeds the area of ​​A3 as the cover of the annual publication, and also have a screening hot silver. At that time, Hong Kong was able to burn such a large area of ​​hot stamping machines only two or three, and they all said that they had not tried to make such a large area of ​​iron.

In the end, because we had to catch up with the graduation exhibition, we had to make a hundred copies, and the others had to be solved by the printing of silver, that is, the version seen by the party, and Mr. Lu, the designer, and I, of course, collected the hot silver. The limited edition, I believe that there are not many people who have seen this hot silver version, and the metal ink used by Yinyin was very different from the current one, and its sparkling effect with hot silver is even more distant. If there are so many different metallic inks available today, there is no need to give up the original design, but unfortunately a good design does not have enough money and time and often cannot be achieved, and experience tells me that time is more expensive than money. important.

With the use of metallic inks, the effect can already be achieved by replacing more expensive materials such as aluminum foils or gold-plated materials. On the other hand, metal pigments are widely used, and metal effects can be achieved by different processes, such as replacing silver and the like. In the past decade or so, metal ink technology has also been greatly improved in terms of convenience and flexibility in printing, and it also has an advantage in cost. Since the content of the metal pigment in the metallic ink is generally 2 to 4 times more than the ordinary ink, the metallic ink is much more expensive than the ordinary ink. In spite of this, ink printing is still welcomed by the packaging and printing industry because metal ink printing still has the advantages of faster production speed and lower cost compared with hot stamping and aluminized film printing processes. So now a lot of consumer product packaging, such as food, beverages, cosmetics, etc., are heavily used metal ink to stimulate the eye. It is also more convenient in application because it does not require the addition or modification of equipment, and it can be produced like ordinary ink, improving efficiency and saving costs. Of course, the printing process I am referring to is not just a lithography that Hong Kong people are familiar with, but also different technologies such as screen printing, flexo printing, and gravure printing.

What progress has made in metallic ink today? Let me start with the structure of metallic inks.

Structure of metallic ink

Metallic inks (metallic printing inks) are inks that are made by substituting small metal foils for pigments or dyes in traditional inks and have a metallic glittering effect. The general metallic inks are mainly gold and silver inks. Gold ink is generally added with copper pigments and zinc pigments. By controlling and changing their proportions, inks such as green gold, cyanine gold, and red gold are produced; and silver inks are formulated 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 common inks does not change with the viewing angle, but the hue and brightness of metallic inks will change due to different viewing angles. Therefore, when using an instrument to measure spot-colored metallic inks, ordinary spectrodensitometers cannot be used. Instead, special spectrometers for measuring reflective metals are used. If it is not clear, color misunderstandings will often occur.

To cooperate with the printing method

The shiny effect of metallic inks is the result of the combination of specular and diffuse reflections of metallic pigments. In order to achieve a better metallic effect, the specular reflection of the metallic pigment should be increased to reduce diffuse reflection. The effect of influencing the ink reflection is mainly the size of the metal pigment particle size. The larger the size of a single pigment particle, the better the mirror reflection effect and the higher the glossiness of the metal ink, but its hiding power and dot reproduction ability will become lower. Conversely, the smaller the size of the metal pigment particle size, the higher the hiding power and dot reproducibility of the metal ink, but due to the excessive diffuse reflection of the edge, the gloss of the metal ink may be reduced. Therefore, the user needs to select the proper particle size according to their own requirements, and when selecting a specific printing method, different printing methods absolutely affect the shiny effect of the metallic ink. For example, the particle size is too large during the printing process. If the ink cannot be transferred smoothly, it will cause the phenomenon of mesh clogging or squeegee ink accumulation during silk screen printing. The ink will also thicken and affect the printed matter. Color and print uniformity. On the other hand, if the particle size is too small, it will easily cause the diffusion of light, causing the ink to lose its metallic luster and cause the printing effect to be not bright. .

Experiments show that when screen printing, the mesh size should be about 3 times the average size of metal particles. The metal foil particles in the metallic ink can smoothly pass through the mesh under the action of a scraper. The average size of the general metal ink particles is 15-20 μm, and the principle is that the mesh size should be about 3 times the average size of the metal particles, and the screen mesh used should have a mesh size of at most 400/inch (its mesh size is about 60 μm). ) But with 400/inch mesh, precision is not? of. There are obvious dog teeth in the picture and text, but if you want a clear picture, you must sacrifice the shiny effect of large particles, and switch to fine-grained metal ink in exchange for smooth printing.

Classification of metal pigment particles

In addition, the particle distribution of the metallic pigment is also a factor that affects the optical properties of the metallic ink. When using different manufacturers of metal inks, although the particle size shown in the technical data is the same, the hiding power and metal gloss of metal inks after printing may sometimes differ greatly, because different ink manufacturers are manufacturing metal inks. The particle distribution of the metallic pigment is sparsely dense. The same average particles, the denser the distribution of particles, the more uniform the overall arrangement of the pigment, the better the gloss and hiding power of the produced metal ink, so the different metal pigment manufacturers technology for the distribution of particles, the metal ink The effect has a great influence. The uniform distribution of the metal sheet is taken? The characteristics of the resin and the solvent in the ink. A good resin can distribute the metal flakes very evenly, but using a poor resin ink, the metal particles are very unevenly distributed. Under the microscope, the metal flakes can be seen as a single cluster. Difficulties, so that the metallic gloss effect of prints is greatly reduced.