Printing is defined as an industrial copying process that transfers ink to the surface of the substrate through various pressures to form graphics. Traditional printing uses the printing plate as the intermediate carrier of graphics, so that the graphic area and the blank area are separated by various means, and then Transfer the ink to the surface of the product, digital printing puts the printing plate aside, and directly transfers the graphics in the computer to the surface of the product. The evolution of technology is developing in the fastest direction, but there seems to be no sign of abandonment of printing.
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 in nature that can express color. Ink experts first think of pigments and dyes with long shelf life and bright colors.
Pigments or dyes can not be printed directly on the surface of the product. The reason why the pigments and dyes 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 are indispensable for the above three components.
Pad printing ink and screen printing ink
Different printing processes have different requirements for inks, and it is necessary to add appropriate supplementary ingredients to the inks to make them easier to use in specific occasions. For example, offset printing inks are more viscous, have good water resistance, and gravure printing inks are relatively rare , Good fluidity; screen printing ink must have good permeability.
The main difference between the inks used in different printing processes is the different additives contained in the ink. This article will mainly talk about screen printing inks and pad printing inks.
In terms of substrate suitability, screen printing has great advantages, especially in the non-shaped plastic hardware electronics and direct consumer goods industries, screen printing has won a wide reputation. 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 has led to the birth of pad printing technology. It can be said that although the printing technology and screen printing are very different, but they are very similar in the industrial field.
The earliest pad printing inks were replaced with screen printing inks. Practice has proved that there is nothing absolutely unsuitable. However, the ink is used in different printing environments, there must be a difference in adaptability, such as pad printing ink, users do not require it to have the permeability of screen printing ink, but will require it to have better thixotropy and surface dryness, To ensure that the transfer process from the steel plate to the glue head and substrate is more accurate. Using special pad printing ink will undoubtedly make it easier to improve the printing quality.
MARABU was the first to develop a dedicated pad printing ink. Through the action of additives, the surface tension of the ink is kept in a constant range, so that the ink transfer in the printing process is kept absolutely consistent.
The process of ink transfer and the nature of the pad printing head are also closely connected. Controlling the surface tension of the pad printing head to a range close to that of the pad printing ink seems to be a systematic project, and the essential purpose is to improve the efficiency of ink transfer. The Japanese solved this problem from another angle. They installed a plastic head cleaning device on the pad printing machine. However, the installation of the plastic head cleaning device mainly lies in the controlled transfer amount of ink, and the transfer efficiency has not been improved.
MARABU has 6 (actually 8) pad printing inks to choose from: GL, 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 in SR. A series of screen printing inks based on improved printing inks, all materials that SR can make can use TPR in the printing process; for the same reason, TPY is an improved printing ink based on PY series of screen printing inks, TPU ink can be used on the surface of materials that are very difficult to print; TPT is a pad printing ink mainly used in oil cup pad printing machines: TPL has better stability and can maintain good uniformity under long-term friction. Two other types are TPP and TPS.
It is worth noting that screen printing inks and pad printing inks are completely versatile, except that additives are needed to change the printability. Therefore, when there is no special printing ink, silk screen ink can be used instead.
Ink colors: primary colors, spot colors, standard colors
The colors in nature are rich and colorful, and it is impossible to express them with ink. There are two methods of copying colors in printing. One is to directly match the spot color for printing, and the other is to print by four-color superposition.
The four colors are copied according to the principle of the superposition of the four colors in the CMYK color model. Generally speaking, the four-color copy technology can basically reproduce the colors we require. The layered manuscript usually uses the four-color copy technology.
The advantage of copying four-color inks is the layered manuscript. For most advertising designs and creativity, as well as industrial printing, the use of spot colors is a very common phenomenon. Spot color is more able to reflect the designer's thinking, and it is easier to prevent infringement. In theory, spot colors can also be matched with the original color, but that way not only makes the hue difficult to match exactly, but also increases the possibility of wasting ink. Therefore, the copying of printing technology colors includes two copying technologies. One is to use four-color inks to copy colors. It is mainly used when the original is layered, and there is a superposition between colors. Primary color printing is the most difficult technology to master because it involves complex color science and dot synthesis principles. How to control the change of dots from manuscript to film, printing plate and substrate is the core link of primary color printing technology.
Spot colors are used when the colors do not overlap with each other. Due to the unusually rich pigments in nature, there are many types of spot color inks. -Spot colors in the general sense refer to all colors except the primary colors, and there are infinitely many spot colors. The American PANTONE company formulates standard colors for ink spot colors, and prints color cards that are commonly used today based on the production of spot color inks.
The PANTONE color card is actually a very small part of the spot color, which we call the standard color. Now that Europe has also developed European standard colors, we can view these two standard colors as a subset of all spot colors. Of course, the standard colors of various color card printing can also be matched with each other to produce many spot colors. Color cards are the universal language of companies engaged in printing in the world.
No one can tell what kind of red is red, but if you tell you the PANTONE color card number, you will easily find this ink. Whether the ink manufacturer can provide the ink according to the standard color card is of great interest to the user. Choosing the ink color is an important content. Although the four-color printing technology is difficult to master, it seems very simple to choose the primary color ink because the ink manufacturer produces There is only one set of four-color inks. In contrast, the choice of spot color ink is much more troublesome. If the designer happens to use a certain standard color to express his design ideas, and you also just purchased this ink, then you can only choose this ink. However, fewer and fewer designers will do this, and the boss may not allow him to do so, because the easier it is to obtain, the simpler to imitate. The formulation of ink is also based on the subtractive color method in chromology, but to accurately formulate accurate colors quickly, theory is as important as experience.
Material and ink selection
Printing methods such as offset printing may not be so troublesome, because the paper has good printing suitability, and basically does not need to consider the problem of adhesion, but screen printing and pad printing are not so simple, there are many printing materials for screen printing and pad printing, and it is impossible to use Instead of an ink, ink manufacturers must produce a variety of inks to fully adapt to the market.
We can simply divide the printing materials into the following types:
1. PP and PE, in the plastics family, PP and PE are two very large amounts of materials, the first is that they have good physical properties, chemical resistance is very good, most solvents can not help them, so in coatings , Cosmetics, plastic films and electrical products have a wide range of uses. But this is also the reason why they are difficult to print, because their constituent molecules are non-polar molecules. At present, printing these two materials generally adopts the pre-press processing method, the more common methods are flame processing and high-frequency processing. The Pl-treated water produced by MARABU is actually a strong oxidizing agent, which forms a rough surface layer by oxidizing the surface of the material to achieve good adhesion of the ink. It is also the goal of many manufacturers to develop treatment-free PP ink, and the technology is basically mature, but the treatment-free ink does not adhere well to the surface of PE. MARBU's PP series inks are treatment-free inks.
Combined with pre-press processing, there are many types of inks that can be used on the surface of PP and PE. We are discussing solvent inks here. For UV inks, pre-press processing is also necessary. There is currently no UV-free ink. It should be said that in the current field of printing technology, it is difficult to achieve stable quality control by printing on PP and PE materials.
2. Some polar materials such as ABS, PC, PVC, PS and AS are easy to print. Most of these materials can be printed without pre-press processing. This part of ink is the strength of all manufacturers.
3. Substrates such as glass, metal, ceramics, etc., do not have any absorption properties on the surface, and inks manufactured according to conventional methods are difficult to work. In most cases, two-component inks are used.
Now there are more and more enterprises engaged in transfer and silk screen printing. Whether they can find ink suitable for customers' products means the ability to obtain orders. However, the supplier's information shows that it is suitable for this material. To determine whether it can really meet the requirements, the key is to test according to the requirements. If the test results are not good, you may wish to replace the ink. Sometimes you may get the wrong information and technology, so you must understand the test method. Many inks cannot achieve the printing method of the product. The wrong test method is an important reason for this result. If some problems cannot be solved, you should contact the ink manufacturer in time.
The important information provided in the previous description is that we must first understand what the customer's product is, secondly, we must be familiar with the ink selection information, and then carefully test until the customer is satisfied. In theory, there are no products that cannot be printed. In fact, many products are annoying to you. The key is whether there are enough experimental methods to solve them.
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