China's nano water-based ink R & D innovation and application (in)

1.1.1.3 Additives

Additives (adjuvants) are some of the materials added to improve the performance of the ink itself in the manufacture of nano-inks and printing applications. According to the basic composition of the ink, in some features still can not meet the requirements of the use of printing, or due to changes in conditions and can not meet the requirements of the use of printing, you must add a small amount of auxiliary materials to solve. There are many types of additives for nano-inks, which are mainly the following: coupling agents, neutralizers, solvents (co-solvents), thickeners, anti-settling agents, anti-mold agents, wetting agents and dispersants, defoamers Agents and so on.

1.1.2 Nano-aqueous ink drying mechanism [6, 8, 11]

1.1.2.1 Drying of Water Dilution Type Binder

The principle of drying of the water-diluent binder is as follows: The water-diluent binder can be dissolved in water because these polymer resins contain a COOH (carboxyl), an OH (hydroxyl), an NH2 (amino), a C One NH2 and one C, these groups are hydrophilic.

After a certain process, the polymer resin is made into organic amine salts, which can be completely dissolved in water. Therefore, it is now possible to use a reaction between a carboxyl group and an amino group to form a viscous liquid that is soluble in water. Such as:

RC00H+NH2CH2CH2OH→RCONHCH2CH20H+H20

In water, the above product will form: RCO-N+HCH2CH20H, which has good hydrophilicity. Since the latent heat of evaporation of water is relatively large, the drying speed of the ink and ink will be slowed down. At the same time, since the amine salt undergoes a decomposition reaction due to heat instability, the volatile drying is the main factor, and the reactive solidification and drying dry. Once dried, the ink film becomes water. Reconstituted. The drying process is as follows:

1.1.2.2 Drying process of water-dispersed binders

The drying process of the water-dispersed emulsion binder can be described by a three-stage drying model: 1 The water volatilizes from the surface of the wet film, the overall volume of the ink film decreases, and the dispersed polymer particles gradually concentrate; 2 The polymer particles come into contact with each other ; 3 particles agglomerate to form a dry ink film. as shown in picture 2.

Figure 2 Film formation process of nanoemulsion

1.1.3 nanometer water-based ink characteristics and characteristics

After the surface of the nano-semiconductor particles is chemically modified, the surrounding medium of the particles can strongly influence the optical properties, and the red-shift or blue-shift of the absorption spectrum occurs. Experiments have shown that there is a clear blue shift in the light-absorbing edge of the Cds nanoparticles and a large red shift in the absorption edge of the TiO2 nanoparticles. If they are added to yellow and cyan inks to make nano inks, their purity can be increased. Printing of color prints using nano-inks with specific nano-particles will increase the level, and the ability to display details in images will also increase.

A huge change has been made in pigments for the ink manufacturing industry. It no longer depends on chemical pigments, but rather selects the appropriate volume of nanoparticles to present different colors. Because some substances are in the nanometer scale, different colors of different particle sizes, or different colors of different materials, such as TiO2, SiO2 in the nanoparticles are white, Cr2O3 is green, Fe2O3 is brown. According to this, the nano-metal particles can absorb all the light waves and make themselves black, while also scattering light. Adding nano-metal particles to the black ink improves the purity and density of the black ink (characteristics of the nano-pigment in Figure 3).

In the practical verification of pigment nanocrystallization, the color appearance of nano-pigments is much darker than that of sub-micron pigments. The main reason is that the particles of pigments are large, light rays will break through, and light will scatter and emit light. Light penetrates through. The nanopigment has a small particle size, weak light scattering, a small spectral absorption area, and a light reflectance of less than 1%, so the appearance of the color is significantly deeper than the submicron pigment. Nano-pigmented pigments have a wide range of applications, such as ink-jet inks, coatings, inks, and optoelectronic displays. In the manufacturing process, adding nano pigments with a small proportion of 3% to 5% can improve inks. Shading rate, saturation, anti-rotation, water resistance and other issues. In addition, in ordinary and color laser printers, the thickness of the toner particles is an important factor that determines the quality of the output, and it is also a key to whether the resolution of the printer can be further improved. Therefore, using nanomaterials to make carbon powder for laser printing, especially color laser printing, can greatly improve the quality of the output. In addition, in the current color ink-jet printing, due to problems with the ink, not only the print quality is affected, but also the occurrence of nozzle clogging and other failures from time to time, but once the nano-material ink is developed, it is believed that these problems can be well resolved. In addition, color laser printing and color inkjet printing are the main printing devices for digital printing and on-demand printing. Nanotechnology will play an important role in this field [7, 9, 12, 19].

1.2 nano powder to improve the ink

In the production of inks, it is necessary to rely on various additives. Due to the application of nanotechnology, the quality of the ink has been improved and improved. Traditional additives are on the order of millimeters and micrometers, which is an important starting point for nanometer modification.

The "functionality" of nano additives in organic polymers is manifested in many composite systems. Through the assembly of nano additives, adjusting the amount of addition and the way of adding, it can control the properties of nanocomposite functional materials such as “X-ray switch”, blue light sensing, photoconductivity, and electroluminescence. This nano "additive switch" has been used in "banknotes" and "anti-counterfeiting labels."

In the following, the improvement of ink performance by nano-Ag, nano-TiO2, nano-SiO2, and nano-CaCO3 will be briefly described.

1.2.1 Nano Ag Application in Ink

The organic phase has many optional ingredients, such as a high cross-link density acrylic quaternary copolymer, which provides high modulus and high scratch resistance; as well as a low cross-link density terpolymer, it provides good film formation Sex. Ag particles (with a size of about 100 nm) are added to the above hybrid system to obtain bactericidal coatings or inks, and have characteristics such as ultraviolet resistance and chemical resistance. In addition, in the conductive ink, such as the Ag made of nano-level instead of micron Ag, can save 50% of the Ag powder, the conductive ink can be directly printed on the ceramic and metal, the ink film is thin and uniform smooth, very good performance it is good.

1.2.2 Nano-TiO2 Characteristics and Applications

1.2.2.1 Physicochemical properties of nano-TiO2 [34]

Nano-titanium dioxide, also known as ultra-fine titanium dioxide, transparent titanium dioxide, is one of the important varieties of nano-materials. In addition to the physicochemical properties of conventional titanium dioxide, nano-titania also has the following properties. 1 Because its particle size is much smaller than half the wavelength of visible light, it has almost no hiding power and is transparent. 2 The ability to absorb and shield ultraviolet rays is extremely high. 3 Chemical stability and thermal stability are good, completely non-toxic and non-migratory. 4 Nano-titanium dioxide is used as a filler, and the coating or plastic film made of the resin shows good-looking pearlescent and realistic ceramic texture, and its color changes with the size of the particle size, the smaller the particle size, the darker the color. For this reason, nano-titania having a suitable volume and uniform particle size can be selected to prepare various colors of paint or ink, instead of the conventional chemical pigment color matching process. The 5 nm titanium dioxide also has the optical properties of the mica titanium pearlescent pigment. Such as pearl effect, viewing angle flash effect, color transfer effect and additional color effects.