In the printing field, ink is a major material, which not only determines the quality of the printed matter, but also marks an important aspect of the innovation and characteristics of the printed matter. With the continuous development of science and technology and the higher demand for printing products, researchers have continuously developed special inks suitable for different printing fields. Here are several special inks with good development prospects.
1. Bio-ink
American scientists have long been working on a protein molecule called rhodopsin. Natural materials often demonstrate complex functions that cannot be easily obtained with materials such as semiconductors. Bacteriorhodopsin is a strong purple cell membrane that grows on the body of the Yanyao marsh called "halobacterium salt product". Illuminating its protein can trigger a photochemical reaction circle. The principle is that the photochemical reaction ring transports protons along the channel surrounding the cell membrane. The purple color of this cell membrane is derived from the bacteriorhodopsin component called "retina". The amino acid in the cell membrane channel is firmly bound to the "retina". The "retina" in the dissolved state does not bind to amino acids and is pale yellow.
Two groups of lasers with different wavelengths are alternately irradiated onto this protein molecule, so that the protein molecule can be converted back and forth between the purple structure and the yellow structure. It is this habit that inspired people's research and utilization of rhodopsin. It can be used as a photosensitive element in the simulated retina, as well as a storage element in an prion-based processing device or a storage element in an optical computer. The rhodopsin film can also change its color according to the conversion of an external electric field. In conventional bacteriorhodopsin, under the action of different electric fields, a low-to-zero color change from purple to blue will be formed. However, the rhodopsin structure produced by a certain mutant bacteria will change from blue to light yellow under the action of a strong electric field. By sandwiching this protein film in a transparent plate combined with a large number of electrodes, a display plate can be made. By applying appropriate voltages to different parts of the film, you can "write" a page or "place" an image on the display panel.
Like the ink on paper, the images on the bacteriorhodopsin display can also be seen under ordinary light. The protein film also provides the advantage of high contrast. Moreover, the color transition time can be accelerated to 200μm. At present, the main difficulty facing the entire development work is the need to consume an electric field of hundreds of volts to stimulate its color change. Researchers are working on a project to achieve a breakthrough in obtaining a colorant that is highly sensitive to external electric fields.
2. Electrostatic color ink
Materials used for electrostatic image forming technologies such as electrophotography and electrostatic recording are called electrostatic toners, and have the function of selectively attaching to electrostatic latent images for physical development. In addition, there are terms such as electronic toner, electronic printing ink, developer, etc.
Practically, it is divided into liquid toner (developer) and powder toner (developer) corresponding to liquid and solid. The general characteristics required for toning inks are: (1) high-speed, long-term quality stability; (2) image quality, especially mid-tone reproducibility; (3) color (multi-color) image reproducibility. For powder color ink, liquid color ink and color color ink, they all have their own required characteristics:
1. Powder toning ink
Usually, it is a kind of fine particle powder in which toners such as pigments and dyes are mixed with binders and auxiliary agents such as resins, adhere to the surface of carriers such as glass balls and iron powders, and are used in a charged state. Powder toning inks are mainly used for electrostatic printing, indirect electrophotography, electrostatic recording, and electronic facsimile plate making and copying, etc., and have received widespread attention. At present, new manufacturing methods for powder toning inks are being studied:
(1) Mix various essential components with heating rollers, heating rollers, and dissolution methods to make a uniform dispersion. After cooling, pulverize the particles. This is the most general method.
(2) Apply a substance mixed with a solvent at normal temperature to a flat plate to make a formed film, dry and solidify it, and pulverize the particles. Its disadvantage is that it is easy to leave solvents, and it is only suitable for small-scale production.
(3) Spray dry the mixed dispersion in the preceding paragraph.
(4) Mix the polymerizable monomer with the coloring agent and other components to make them suspended and polymerized into fine particles.
(5) The solvent dispersion mixed in (2) is dissolved with a solvent, mixed and put into a large amount of non-solvent that does not dissolve each component, and precipitated as insoluble fine particles.
(6) The dispersion is mixed in a non-solvent in a dissolved state to disperse it as spherical particles, and the original is cooled and solidified to be separated into solid and liquid.
The powder toning ink obtained in this way usually takes the following properties as the main index for evaluating quality:
(1) Chargeability: charge capacity, polarity, stability, etc .; (2) granularity: particle shape, maximum (minimum) particle size, particle size distribution; (3) developability: density, paste, ghosting, gloss Etc .; (4) Fixability: melting temperature, solubility, adhesion strength; (5) Image quality: resolution, contrast; (6) strength: fatigue phenomenon, powdering.
2. Liquid color ink
This is made by dispersing toners such as dyes and pigments and binders such as resins and charge control agents in a highly insulating liquid carrier. It is mainly used for electronic facsimile, and the surface with electrostatic latent images is immersed in toner If the dispersion is redispersed and diluted in an excess liquid carrier-liquid developer or the developer is coated on the roller, the toning ink is selectively attached to the latent image. Then, the excess developing ink is removed, the liquid carrier is evaporated, and the image is fixed on the surface.
3. Fragrance ink
Scented ink is an ink used in microcapsule printing. Its principle is to add various fragrances to the microcapsule carrier and add it to the ink, thus forming various fragrance inks. The fragrance of the scented ink can be directly inserted into the ink and printed in letterpress and lithographic methods, or it can be made into microcapsules first, then infiltrated into the ink, and screen printed.
The composition of the fragrance is very complicated, and the organic substances contained in it are mostly volatile and chemically unstable substances, so during use and storage, it will inevitably be lost or decomposed. In order to protect the fragrance from external environmental factors and extend its fragrance release period, it is best to micro-encapsulate the fragrance, slowly oxidize after contact with air, continuously release the fragrance and greatly extend its shelf life, and some fragrance micro capsules Only under the catalytic action of ultraviolet radiation, oxygen circulation, heating, humidity changes and other environmental factors will they react with each other to produce fragrance substances, which can avoid the ineffective dissipation of printed products under normal circumstances. The essence microcapsules can be transferred to the appearance of the packaged products by preparing inks and paints.
4. Ink with other special functions
1. Thick film ink
Refers to inks and lacquers designed to be printed up to 200 μm thick. It is very advantageous for UV inks with 100% solids content to assume this responsibility. Ink in this field can be said to be the exclusive territory of UV ink and lacquer. Examples of commodity applications include frames, posters that emphasize locality, etc. Another application is the function of setting gaps with the help of ink film thickness.
2. Touch ink
Refers to the ink with satin luster that feels smooth and not easily scratched, of course, it can also be made into a metallic feeling. Designed as an ink with a stretchy and sexy coating film, examples of suitable products include packaging, loose-leaf covers, decoration of home appliances, etc., which are quite versatile.
3. Mirror ink
Refers to metallic ink that can be printed into a mirror-like glossy print. It uses metal materials that have spent a lot of time on the shape, and the ink is cleverly oriented. Uses include paneling, simple mirrors, flower plates, etc. Painting operations such as spraying and rolling are also under discussion.
4. Anti-scratch lacquer
It is a matte, wrinkle-like lacquer, which is not easy to be scratched, and has a good feel and touch, similar to the function of tactile ink. This anti-scratch varnish is particularly suitable for surface decoration related to nameplates, such as surface printing that requires matt and wrinkle purposes, so that it maintains considerable resistance and physical properties. And with its functions that are not afraid of bruising, it solves the problem of reducing costs without the need for a protective layer. According to the use, it can be divided into solvent type one liquid, two liquid and UV type. In terms of products, there are surface processing for packaging, vehicle nameplates, etc.
5. Antibacterial ink
It can play the role of removing fines or inhibiting its growth. Whether it is solvent type, UV type or water type, it can be given antibacterial properties by the blending technology of antibacterial raw materials and ink components. It has been applied to the printing of antibacterial commodities, hospital equipment, appliances, office supplies, and many other articles for public use.
6. Sublimation printing ink
It refers to the phenomenon that the solid is directly vaporized without heating in the liquid state after heating, and solidifies directly after cooling. Such substances as dry ice, camphor, etc., many dyes also have sublimation, such as disperse dyes containing monoazo dye (yellow to red), scallion (cyan to purple) dye and so on. It has been used for printing on cloth and plastic molded products.
7. Moisture-cured ink
After this ink is printed on the substrate, under the action of water vapor, the resin binder in the ink precipitates out and settles, so that the ink film is fixed and dried. The binder is made of maleic acid resin and fumaric acid resin with high acid value, and the solvent is glycol. This ink has a fast drying speed and no odor. It is used for photosensitive resin plate and flexographic printing. The ink film is resistant to wax coating process, so it is also commonly used in food packaging printing.
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