Characteristics and Application of Electron Beam Curing Ink

A, electron beam curing ink curing principle and composition

The so-called energy-curing ink is that the ink is fixed or hardened on the substrate under irradiation of radiation energy to obtain a dry print. The current energy curing technologies mainly include UV light curing and accelerated high-energy electron beam (EB) curing. Among them, electron beam curing inks are called electron beam curing inks. The following describes the curing principle and chemical composition of electron beam curing inks.

1. Curing principle of electron beam curing ink

After the ordinary ink is printed, the ink film is dried. Generally, the binder in the ink is absorbed and volatilized by the substrate. The solid material remains on the surface of the substrate to form a thin layer of ink. The electron beam curing is a process in which the electron beam is used as an irradiation energy source, and the chemical formula of the active liquid is subjected to a radiation chemical reaction, and is rapidly dried and solidified at room temperature.

Since the electron beam is a type of radiation, electron beam radiation can also be attributed to radiation curing. Radiation curing is a new technology developed on the basis of the existing science and technology. It mainly uses a scanning electron accelerator. The electron beam of the electron accelerator in the radiation curing scans the surface of the substrate to achieve solidification processing. The basic meaning is to use ultraviolet light or electron beam as energy source to initiate a chemically active liquid formulation to achieve a rapid reaction curing process on the surface of the substrate. The greatest advantage of UV curing and electron beam curing technology over traditional techniques (such as thermal curing) is that radiation curing uses highly efficient energy sources such as UV or electron beams as the initiation means to quickly achieve coating cure. The electron beam radiation is composed of a number of accelerated electron currents. Under the action of high-energy electron beams, free radicals or ion radicals are generated, and free radicals or ion radicals are cross-linked with other substances to form a network polymer. Compared with ultraviolet light, particle energy is much higher than that of ultraviolet light, and it can ionize air. In general, electron beam curing does not require a photoinitiator and can directly initiate a chemical reaction, and the penetrating power of a substance is also greater than that of ultraviolet light.

2. Composition of electron beam curing ink

The main chemical composition of EB ink is similar to that of general ink, and is mainly composed of pigments, binders, adjuvants, colorants, and the like.

(1) Monomer (active diluent). Monomers are low-molecular-weight chemicals that determine the surface properties of the ink after the ink has dried, such as gloss, elasticity, and hardening. Other monomers are the source of the harmfulness of the energy-cured ink. In actual production, EB inks generally use a variety of monomers to obtain satisfactory curing speed, viscosity, adhesion, elasticity, hardness, impact strength, solvent resistance and other properties.

(2) Resin (prepolymer). The resin is the chemical backbone of the ink and directly affects the consistency, wetting ability and cross-linking properties of the ink. The prepolymer used in the EB ink is generally an acrylic oligomer with good fluidity. Common prepolymers include epoxy acrylic resins, polyester acrylic resins, acrylic polyurethanes, chlorinated polyester acrylic resins, and the like.

(3) Additives. The main purpose is to improve the physical and chemical properties of inks. Common ingredients include waxes, wetting agents, and ink transfer agents that change ink properties.

(4) Pigments. For general inks, the size and concentration of the toner will affect the curing rate of the ink. Therefore, the color of the toner must be considered when selecting the color material. However, since the energy of the high-energy electron beam is sufficient to cure the thick ink film layer, the electron beam The ink does not have to take this into account when selecting the colorant. Pigments are the color materials of inks. The quality of the ink determines the quality of the ink. Electron beam curing inks should firstly ensure non-toxicity in the selection of pigments. In addition, it is necessary to ensure that the pigments do not undergo color change under electron beam irradiation, and the pigment concentration is high, the color is bright, and it has excellent dispersibility and sufficient. The coloring power, the ink will not be gelled in the effective storage period after the pigments are mixed. When the pigments are used together, the amount of each pigment in the ink must be accurate.

Second, the advantages and disadvantages of electron beam curing ink

Electron beam curing ink is a type of ink with great development potential. It can be used in web offset printing, flexographic printing, screen printing and other fields. It is the same as UV ink, but it does not need to add photoinitiator. , No special odor, and will not release ozone, is a cold curing ink without heat source, the ink is not affected by the color during curing, can make the curing more thoroughly, the quality is more stable. Its advantages are mainly manifested in the following aspects:

1. Green pollution-free ink, little irritating to the human body.

The solid content of electron beam ink after curing is close to 100%, and it is generally free of organic volatiles (VOC). It is a zero-emission technology. This shows that the electron beam ink system has no pollution to the environment and substrates compared to ordinary ink systems. Good for environmental protection. In addition, the e-beam curing ink is less and less irritating to human skin, and has the same stimulability as a normal ink containing a gasoline fraction, so this type of ink has been greatly promoted and applied in recent years.

2. The use of ink saves energy and saves costs.

Since the electron beam ink mainly relies on the radiation of the high-energy electron beam to achieve ink drying, etc., energy is saved, and the production cost is saved.

3. Short curing time, improve work efficiency.

The curing time of electron beam curing ink is very short, generally only 0.1s can be completely dry and fixed on the surface of the substrate, while the traditional thermosetting ink, the drying time may take several minutes or even several days to fully dry. At the same time, the curing space of electron beam curing ink is small, and the processing speed is fast and the output is high. It is a rare and highly efficient production ink.

4. The product quality is stable.

Due to the ink's curing characteristics, the ink printed by the electron beam curing ink has a strong resistance, and at the same time, the chemical substances in the ink form a polymer three-dimensional network polymer by cross-linking reaction, so the ink surface Has a strong chemical resistance and friction resistance, but also to ensure that the printed surface is clean and free of dirt, dot gain is small, the imprinting brightness is good.

5. High degree of automation, easy production and application.

The radiation curing device is compact, the processing speed is fast, the site space is small, and the production efficiency is high, which helps to improve the product performance and reduce the consumption of raw materials, all of which increase the competitiveness of the technology itself from the economic cost. Radiation curing compared with the traditional curing technology, in the temperature, process formulation and product performance have great advantages, such as general room temperature curing is conducive to the processing of heat-sensitive materials, curing formulations can be adjusted according to demand is conducive to improving the process Adaptability to ensure product performance. Radiation curing is easy to realize streamlined operation and has a high degree of automation. At the same time, since the composition of the electron beam ink and the ultraviolet ink is similar, if a certain amount of photoinitiator is added to the EB ink, ultraviolet curing can be performed, which is also another aspect of product value-added.

Of course, electron beam curing inks also have some disadvantages, and the high cost of the curing equipment is the biggest obstacle in the promotion and application. The one-time investment of energy-curing equipment requires a certain amount of money, and the current price of electron beam curing equipment has been steadily declining. Compared with ten years ago, the cost of EB curing equipment has been reduced by a factor of four. At the same time, EB inks also have degradation problems after they are discarded.

Third, the application of electron beam curing ink technology

With the continuous breakthrough of new technologies, especially the improvement of ink adhesion, electron beam curing inks have begun to develop steadily in areas where the original amount was not so impressive. A more representative example is the home appliance printing company in Chicago, the United States, the company has used this ink processing to produce thin film switches, the thick film screen printed products into the electron beam radiation drying device, the ink in the electron beam radiation It takes just a few milliseconds to dry completely, the print has a good gloss, and the film feels strong and resistant to rubbing. However, due to the high selling price of this type of ink and its radiation drying device, it is difficult to promote it at present. However, because it can save the drying time, ensure the product quality, and does not pollute the environment, it has a promising future.

Although there are some differences in the performance of ink products from different manufacturers, in view of the current situation, future EB inks should be applied in the following directions:

1.EB ink improvement in supporting curing equipment

EB inks have relatively high requirements for curing equipment. Although electron beam curing requires only one ion cathode tube, it is necessary to strictly control the active gas content in the curing chamber, which is one of the reasons for the expensive curing equipment. In the future, EB inks should be developed in the direction of the combination of curing units for continuous curing equipment, and the cost of curing equipment should be continuously reduced so as to be able to print on ordinary printing presses.

2.EB ink improvement in cleaning

Because EB ink has a certain erosion effect on rubber sticks and blankets, EB inks are currently printed using special cleaning fluids and corresponding glue sticks and blankets. In the future, the development trend may be to use a conventional cleaning agent to clean the rubber roller, blanket, etc.

3. Improvements in print quality

EB inks require higher control of ink viscosity and adhesion. The viscosity of the ink in the actual printing operation is reduced according to the printing color sequence, but the difference in viscosity between the two color sequences should not be too different, otherwise it will affect the ink transfer performance and the amount of ink transfer. EB ink also requires that the viscosity be reduced in turn, but compared with ordinary inks, the difference between EB inks requires a significant gap, otherwise it will produce a series of faults. In order to avoid failures and ensure the normal and orderly printing, it is necessary to further study the improvement of prepolymers in EB inks in order to improve the quality of printed products.

4.EB ink improvement in printability

At present, the EB ink has certain requirements for the pH and conductivity of the wetting fluid during use. It is generally considered that the pH is 3.8-4.1 and the conductivity is 1000-2800s/m. Compared with the traditional inks, the requirements are more stringent. Therefore, in the future, EB inks should also be studied in this regard in order to achieve the goal of printing. On-press printing processability is comparable to traditional solvent-based inks.

Looking into the future of EB inks in the printing industry, the most important thing is whether the cost of ink can be reduced to a level close to that of ordinary inks. However, with the development of new technologies, it is believed that EB ink will have a broader prospect.

Fourth, the development of electron beam curing ink