Printing is defined as an industrial copying process in which ink is transferred to the surface of a substrate to form graphics and text through various pressures. Traditional printing uses a printing plate as an intermediate carrier for graphics and text, so that the graphics and text areas are separated from blank areas by various means, and then The ink is transferred to the surface of the product, digital printing aside the printing plate, and directly transfers the graphics in the computer to the surface of the product. The evolution of technology is developing in the most rapid direction, but it seems that printing does not abandon the ink.
Composition of ink
Content is the most fundamental purpose of printing, but to convey content, color plays a very important role. There are many things that can express color in nature. Ink experts first think of those pigments and dyes that have a long shelf life and bright colors.
Whether it is a pigment or a dye, it cannot be directly printed on the surface of the product. The reason why the pigment and dye can firmly adhere to the surface of the product should be attributed to the resin. Most of the resin is solid, and most of the resin in the ink is not a simple resin, but a mixture formed by dissolving in a solvent.
The ink is composed of pigments, resins, and solvents. All printing inks cannot lack the above three components.
Pad printing ink and screen printing ink
Different printing processes have different requirements for inks. Appropriate supplementary ingredients must be added to the inks to make them easier to use in specific situations. For example, offset printing inks have high viscosity and good water resistance, and gravure printing inks are relatively thin. , Good fluidity; screen printing ink must have good permeability.
In general, the main difference between the inks used in different printing processes is that the additives contained in the inks are different. This article will mainly talk about screen printing inks and pad printing inks.
In terms of the suitability of substrates, screen printing has great advantages, especially in the non-shaped plastic, hardware, electronics and direct consumer goods industries, screen printing has gained widespread praise. However, there is no universal printing method in the world, and screen printing is no exception. In the field of industrial printing with small areas and irregular substrate surfaces, screen printing has encountered real troubles, which gave birth to the birth of pad printing technology. It can be said that although pad printing technology and screen printing are quite different, the industrial fields they involve are extremely similar.
The earliest pad printing ink was replaced by silk screen ink, and practice has proved that there is nothing absolutely unsuitable. However, the ink is used in different printing environments, and there must be differences in suitability. For example, pad printing ink. Users do not require it to have the permeability of screen printing ink, but they will require better thixotropy and surface dryness. To ensure that the transfer process from the steel plate to the plastic head and the substrate is more accurate. The use of dedicated pad printing ink will undoubtedly make it easier to improve the printing quality.
MARABU took the lead in developing a dedicated pad printing ink. The surface tension of the ink is maintained in a constant range through the action of additives, so that the ink transfer in the printing process is absolutely consistent.
The process of ink transfer is also closely related to the nature of the pad printing rubber head. Controlling the surface tension of the pad printing rubber head within a range close to that of the pad printing ink seems to be a systematic project, and the essential purpose is to improve the ink transfer efficiency. The Japanese solved this problem from another angle. They installed a rubber head cleaning device on the pad printer. However, the addition of a rubber head cleaning device was mainly to control the amount of ink transfer, and the transfer efficiency did not improve.
MARABU has 6 (actually 8) pad printing inks to choose from: GL, which is mainly used on the surface of metal, ceramics and glass. It is basically a two-component ink. It needs to add GLH hardener, TPR, which is used in SR. The improved pad printing ink based on the series of screen printing inks. Any material that SR can use can make TPR in the pad printing process; for the same reason, TPY is an improved pad printing ink based on the PY series of screen printing inks. TPU ink can be used for the surface of materials that are very difficult to print; TPT is a pad printing ink mainly used on ink cup pad printers: TPL has better stability and can maintain good uniformity under long-term friction. The other two are TPP and TPS.
It is worth noting that screen printing inks and pad printing inks are completely universal, but additives need to be added to change the printability. Therefore, when there is no special pad printing ink, silk screen ink can be used instead.
Ink color: primary color, spot color, standard color
The colors of nature are rich and colorful. It is impossible to express them all with ink. There are two ways to copy colors in printing. One is to directly allocate spot colors for printing, and the other is to print by four-color overlay. .
Four-color reproduction is based on the principle of superposition of four color materials in the CMYK color model. Generally speaking, the four-color reproduction technology can basically reproduce the colors we require. The original manuscript with gradation usually uses the four-color reproduction technology.
The advantage of four-color ink reproduction lies in the hierarchical manuscript. For most advertising designs and creativity and industrial printing, the use of spot colors is a very common phenomenon. Spot colors are more able to reflect the designer's ideas, and it is easier to prevent infringement. Theoretically speaking, spot colors can also be matched with original colors, but it is not only difficult to match the hue completely, and the possibility of wasting ink also increases. Therefore, the color reproduction of printing technology includes two aspects of reproduction technology. One is the tendency to reproduce colors with four-color ink, which is mainly used when the original is hierarchical and there is an overlap between colors. Primary color printing is the most difficult technology in printing technology because it involves complicated chromatics and the principle of dot synthesis. How to control the dot change from manuscript to film, printing plate and substrate is the core link of primary color printing technology.