Several new concept inks

With the continuous improvement of the printing quality requirements, higher requirements have been put forward for inks. With the rapid development of science and technology, various types of inks are constantly appearing in the fields of ordinary printing, special printing, and security printing. They not only require excellent quality of printed products, but also meet various special needs such as environmental protection and anti-counterfeiting. As a result, the emergence of such as magnetic ink, fluorescent ink, photo-induced changeable ink, temperature-varying ink, etc., has brought the development of the printing industry to a new height. Below, we briefly introduce the characteristics and uses of several high-tech specialty inks.

First, nano ink

We know that the fineness and color purity of inks have a great influence on the quality of prints. To print a high-quality product, we must have ink with good fineness and high color purity as guarantee. The fineness of ink refers to the size of pigments (including fillers) in the ink and the uniformity of the pigments and fillers distributed in the binder. It affects both the quality of printed products and the printing durability of printing plates. . The practice of the process shows that the area of ​​the printed version or the field version used for the color printing product contains small Yin and Yin lines. During the printing process, stencils and stencil stains are likely to occur, which leads to print quality problems. If operators do not carefully check and analyze, they may fall into the wrong operation, thinking that the consistency of the ink is not good, the viscosity is too high, the amount of ink is too large or the pressure is too high, and blind adjustments are made blindly. As everyone knows, this is caused by poor ink fineness. The fineness of the ink is directly related to the pigment, the nature of the filling section, and the size of the particles. In general, salted inks made with inorganic pigments (excluding carbon black) are coarser. This has a lot to do with the rolling process of the ink. The more the ink is ground during the rolling process, the more uniform it becomes, the greater the contact surface between the pigment particles and the binder, the finer the ink particles, and the better and more stable the printing performance. In the case of printed anilox prints, the 1 to 40% dots in the high-profile and midtones on the layout are common. If the ratio of ink particles to the dot area is relatively close, then it is easy to make the dots empty or spread, and even the dots are not clean. Printing defects. Therefore, the higher the fineness of the ink, the clearer and fuller the dots on the print.

The fineness of the ink is low, the pigment is coarse, the friction coefficient during the printing process is large, the printing plate printing rate is low, and it is easy to produce the paste plate, the ink accumulation, and the uneven distribution of ink and ink during printing. The fineness of the ink can generally be judged by naked eye observation, that is, the surface scraped by the ink knife shows a smooth and even visual effect, indicating that the fineness of the ink is good. For example, the scraped surface appears small pieces. A coarse or granular roughened layer has poor fineness of the ink. In addition, it is also possible to use a small amount of ink layer on the coated paper, and then use another layer of paper to grind the ink layer until the ink layer is dragged to a very thin, which means that the ink is fine. If traces of the ink layer appear, it is clear that the trace is caused by the coarseness of the ink pigments and filler particles. Of course, the above is judged only by experience, and the accuracy of discrimination has certain limitations. To achieve standardized, data-based judgment, only rely on fineness meter to determine the size of pigment particles in order to more accurately detect the fineness of the ink. The practice is: Dilution of the sample ink to a certain extent, placed in the depth of the fineness instrument. Then use a spatula to control the groove movement (to maintain a constant speed) to the shallowest point, the ink particle size can be seen on the scale marks on both sides of the groove, and the degree of ink pigment particle size can also be observed with a microscope.

Nanotechnology is an emerging technology. The nanometer is a length unit, which is 10-9m. The research object of this technology is mainly nanomaterials. Nanomaterials have now begun to penetrate various fields. In 1994, the XMX Corporation of Massachusetts, USA, has successfully obtained a patent for the production of nano-sized uniform fine particle materials for inks. Using nanoscale materials as ink pigments or fillers can greatly improve the fineness of the ink. Moreover, nanomaterials have characteristics that are not available in some conventionally sized materials. So you can also get some inks with new features.

Nowadays, with the help of high technology, various components (such as resins, pigments, fillers, etc.) in ink can be made into nano-scale raw materials. In this way, due to its high degree of fineness and fine flow and lubricity, it can achieve better dispersion and suspension, stability, low pigment content, high hiding power, good gloss, fine resin particle size, continuous and uniform film formation, Thin film, print images more clearly. If used in UV inks, the curing speed can be accelerated, and shrinkage and wrinkling of the ink film can be eliminated due to the fine and uniform dispersion of the filler. In the glass-ceramic ink, if the inorganic material is made into nano-scale fineness, it will save a lot of raw materials and print more refined and more beautiful high-quality images.

Studies have shown that the optical properties of some nano-scale materials after the surface of the chemical modification, some of which appear as a red shift or blue shift of the absorption spectrum. Experiments have shown that there is a significant blue shift in the light absorption of CdS nanoparticles and a large red shift in the light absorption of TiO2 nanoparticles. Accordingly, if they are added to yellow and cyan inks to make nano inks, their color purity can be improved. The use of nano-inks with specific nano-particles to reproduce printed color prints will result in a richer hierarchy, a clearer tone, and a greater ability to express the details of the image. In addition, since some materials change their colors at the nanoscale, this creates a possibility for the ink manufacturing industry that inks may no longer rely on chemical pigments, but instead select the appropriate volume of nanoparticles to present different colors. .

Nano-scale carbon ink is conductive, has a good shielding effect on static electricity, to prevent interference by external static electricity, if it is added to the ink can be made of salty conductive ink, such as large-capacity integrated circuits, modern contact panel switches, etc. . In addition, if Ag is made into nano-scale instead of micro-sized Ag in conductive ink, 50% of Ag powder can be saved. This conductive ink can be directly printed on ceramic and metal. The ink film is thin and uniform, smooth, and conductive. well. If the Cu, Ni material made of 0.1 ~ 1 μm ultrafine particles, it can replace palladium and silver and other precious metals conductive.

In addition, some organic nanomaterials themselves have luminescent groups and may emit light by themselves. The printed matter printed with the ink added with this nano material does not need to be irradiated by an external light source, and can be recognized by the human eye by its own light emission. It can also achieve good results for anti-counterfeit printing and is used for outdoor large-scale advertising printing or printing. Photographic prints that are read at night eliminate the need for external light sources, which not only saves energy, but also greatly facilitates users.

Since nanomaterials generally have good surface wettability, in the process of manufacturing the ink, as long as a certain amount of nanomaterials are added, they are adsorbed on the surface of the pigment particles in the ink, which can greatly improve the wettability of the ink and can ensure the entire The ink dispersion is stable, so that the printability of the ink is greatly improved.

In the electrophotographic process, magnetic nanopowders are used instead of non-magnetic toners, which are widely used today, and ferromagnetic particles that are currently used as magnetic carriers can be dispensed with, and a developer for single-component copying can be produced, which can save raw materials and improve Copy quality.

With the further development of nanomaterial technology, it is believed that more nanomaterials with different characteristics will be recognized and used by people.

Second, cationic ink

In recent years, UV curing (UV) technology is playing an increasingly important role in printing. The most important characteristic of UV curing is that it can improve printing stability (drying) and shorten the waiting time for oxidative drying in the printing process. At present, UV technology has fully bloomed in the web flexographic, flexographic and offset printing markets. Nowadays, there is a new type of ink, cationic ink. This ink increases the environmental protection and quality of flexographic printing.

Compared with the free radical system, the cationic ink has the advantages of low volatility and small odor, and can be said to be a very good environmental protection ink. The odor of free radical inks is a big headache and it is harmful to the health of operators and the environment. Cationic inks (low-volatile inks) have great advantages in this regard, and are now even used in some food packaging industries. Cationic inks also have the feature of being attached to a plastic substrate. Cationic inks and coating glosses exhibit particularly good adhesion to corona-treated substrates, which is the most critical of all advantages.

Compared to radical inks, cationic inks have a moderate cure speed (which is slightly inferior to free radical inks), can be re-cured (approx. extended to 24 hours), do not prevent oxidation, have a slight moisture effect, no shrinkage, plastic attachment Excellent sexual characteristics.

Although in terms of curing speed, radical inks can be dried at high speeds, the curing speed of cationic inks is slightly behind. However, recent research and development show that the improved cationic ink can also be adapted to 150 ~ 200m/min printing.

The benefit of the secondary cure is that the ink film appears to have cured after the print has been output from the printer, but there is still some reaction (not dried). Cationic curing techniques can continue to react until most of these materials react. In contrast, radical inks can only be exposed to UV light for thorough drying. This process, in turn, leads to higher volatilization, especially if unreacted low molecular weight components are more volatile. Cationic inks have a small amount of shrinkage and therefore have good adhesion characteristics.

In the current rising demand for green environmental protection, the packaging and printing industry is more environmentally friendly products. Food packaging should comply with the CEPE standard in industry standards. From the perspective of inks, it is necessary to constantly solve the problem of harmful substances such as lead, benzene, aromatic compounds, and ethyl glycol in the ink, and ensure the safety of foods, supplies, and the health of printing personnel. From the results achieved by the ink industry, the results are still very encouraging. In 1974, lead in ink pigments was removed: In the late 1970s, cellosolve (ethyl glycol) was removed: in the early 1980s, toluene in food packaging instructions was removed: in the late 1980s, the associated benzidine was yellow Pigments: In the early 1990s, the use of phthalic acid plasticizers was reduced. In the initial stage of development of the cationic ink (in the mid-1980s), the content of some of the above-mentioned harmful substances did not meet the regulatory standards, but after continuous improvement, the content of these harmful substances finally reached the industry standard. Such as benzene, in the current production of cationic ink, its content is extremely low, using ordinary analytical techniques, simply can not be detected. Many test results on printed products and printing environments also showed that no benzene was found. Although some customers currently do not intend to use cationic inks, they have shown great advantages in the printing process and will certainly be recognized by customers.

(1) Cationic film adhesive

The printing speed of gravure printing is very fast. When using an in-line laminating process, the lamination film often becomes dry and opaque. Therefore, laminating and laminating are often used for laminating. In flexo printing, because the printing speed is relatively low, it can be coated on the machine and cured, and it can also be cut to the finished product on the line, and then handed directly to customers. If a cationic adhesive coating is used, the residual solvent content per square meter can easily be reduced to very low levels. This film-bonding adhesive can now be used on materials such as polyethylene, polyether, and metal sheet bases.

(2) Cationic Ink-Shrink Film