New developments in seven major UV ink technologies
We are a big printing company in Shenzhen China . We offer all book publications, hardcover book printing, papercover book printing, hardcover notebook, sprial book printing, saddle stiching book printing, booklet printing,packaging box, calendars, all kinds of PVC, product brochures, notes, Children's book, stickers, all kinds of special paper color printing products, game cardand so on.
For more information please visit
http://www.joyful-printing.com. ENG only
http://www.joyful-printing.net
http://www.joyful-printing.org
email: info@joyful-printing.net
Cationic photocuring system UV ink
The cationic photocuring system UV ink is currently a research field of interest because the system UV ink has the following advantages.
(1) It is not inhibited by oxygen, which is beneficial to the high cross-linking of the ink surface, making the coating tough and shiny. The free radical photocuring system ink is severely inhibited by oxygen.
(2) Cationic photocuring system The UV ink does not produce an unpleasant odor after curing, and once it is irradiated with UV light to form a cation, the curing reaction can continue after the light is stopped, which is beneficial to the deep curing of the thick ink layer and the deep ink. Curing, and this is difficult to achieve with a free radical photocuring system.
(3) Cationic photocuring system After UV ink curing, the volume shrinkage is small (generally 3% to 5%), which is beneficial to improve the adhesion to the substrate. The free radical photocuring system ink generally shrinks by 10% after curing, and has a great influence on the adhesion of the substrate.
Therefore, the use of cationic photocuring system UV ink or free radical / cationic composite photocuring system UV ink can improve the speed of photocuring, especially for the curing of colored UV inks and thicker screen printing UV inks. For the benefit.
From the market growth rate of cationic curing materials higher than the total growth rate of the UV curing market, it can be seen that UV inks using cationic photocuring systems or free radical/cationic composite photocuring systems will be the new development direction of UV inks.
2. Water-based UV ink
In addition to the characteristics of low UV pollution of water-based UV inks, water-based UV inks have less viscosity and good rheology, and have a certain mitigation effect on oxygen inhibition. It solves some technical problems that early solvent-free UV inks cannot be applied in gravure and flexographic printing, and is very suitable for gravure and flexographic printing.
3. Mixed ink
Printing with ordinary ink, only after the ink film is completely dried, UV glazing can be used to obtain a good glazing effect. Therefore, if the on-line glazing is used, the glazing effect is not ideal. If offline glazing is carried out, in order to prevent the back surface from being smeared during the drying stage, dusting is required, and the powdering will cause a sand-like appearance on the surface of the original bright and smooth printed sheet, which affects the appearance of the printed matter after glazing.
Mixed ink is a new type of ink prepared by mixing ordinary ink components with UV curable materials. The ink is printed on a conventional sheetfed press, and after UV light irradiation, on-line UV glazing can be performed, and the UV varnish can be quickly cured on the paper to obtain a uniform high gloss glazing effect.
Printing with mixed inks has the following characteristics.
(1) Mixed ink printing combines the characteristics of UV light curing ink and traditional offset printing ink, so that the ink can maximize the characteristics of UV ink after being cured by UV light. The ink can be cured instantaneously, greatly reducing energy consumption, reducing the cost of production, storage and handling, and increasing production efficiency.
(2) It is not necessary to use special ink rollers, blankets and fountain solutions for mixed ink printing. In this way, mixed ink can be used when glazing is required, and ordinary ink is used when glazing is not applied. As with normal ink printing, the effects of different ink rollers and blankets when used with mixed inks may vary.
(3) Printing with mixed ink, the gloss will not fade after UV glazing, and it is especially suitable for printing products with high requirements for ink coverage.
(4) The ink balance of the mixed ink is relatively easy to control. Since the UV component in the mixed ink does not solidify without being irradiated with the UV lamp, the mixed ink always flows on the printing machine, and does not cause skinning on the ink roller like ordinary ink, causing printing failure.
(5) Printing with mixed ink Since the instant drying is realized, the UV glazing can be connected on the printing machine without the need of water-based glazing, and the printing quality is not inferior to the ordinary offset printing ink.
(6) The mixed ink can print clear dots and improve the printing quality.
(7) At present, most CTP plates are not suitable for printing with UV ink, but they can be printed with mixed ink.
(8) Less investment in mixed inks. For printers that already have UV technology, they only need to buy mixed inks. For those printers that have not used UV technology, after purchasing mixed inks, they only need to invest in UV curing equipment and UV lamps.
(9) The mixed ink has a wide application range, and is suitable for printing paper, printing, plastic, aluminum foil, metal paper and other very absorbent substrates. The problem of drying the ink on the non-absorbent substrate is solved.
(10) Mixed inks can be used in narrow web presses in addition to sheetfed presses.
Hybrid inks are now increasingly being used to print products with high gloss requirements, such as photo albums, pharmaceuticals and cosmetic packaging boxes. [next]
4. New oligomers
At present, low-viscosity oligomers have been developed and used in UV inks to reduce the amount of reactive diluent that is irritating to the skin in the ink, and if printed on a porous substrate, no monomer adsorption occurs. The phenomenon to the surface. Recently, the United States has developed a new type of flexographic printing UV ink based on acrylic polyester, which does not contain a monomer component, thereby eliminating the hazard caused by the transfer of monomer to food. The use of low-viscosity oligomers is very beneficial for the formulation of low-viscosity gravure UV inks, flexo-printed UV inks, and especially inkjet UV inks that are currently gaining momentum.
In addition, with the development of cationic oligomers and aqueous oligomers in the field of UV curing, cationic photocuring systems, free radical/cationic composite photocuring systems and waterborne UV inks have been developed to improve the performance and application of UV inks. range.
5. New reactive diluent
Many acrylic functional monomers used as reactive diluents have high toxicity and affect skin application. However, the toxicity of the monomer and the irritation to the skin after alkoxylation are greatly reduced. Many alkoxylated acrylic functional monomers have been developed to date.
Another newly developed reactive diluent is a vinyl ether monomer, which has the advantages of low viscosity, high activity, weak toxicity and little irritation to the skin. At the same time, such monomers can undergo both free radical photocuring reactions and cationic photocuring reactions, and are very promising reactive diluents. In addition, some cationic reactive diluents suitable for UV ink printing have been developed.
6. New photoinitiator
In order to solidify the ink film deep and the colored film layer well, an acyl phosphorus oxide photoinitiator has been developed. It has good absorption of 400nm light wave, high light-initiating efficiency; the generated free radical absorbs to short-wave movement, has "photobleaching" effect, is beneficial to the photocuring reaction in the deep film; the final product is colorless, so Not yellow, it is very suitable for screen printing UV ink with thick ink film. This type of photoinitiation also has a newly developed organometallic photoinitiator.
Since most photoinitiators are small molecule photoinitiators, they are easily volatilized and migrated during storage, resulting in low photopolymerization efficiency, unpleasant odor of the product, and even toxicity, which affects the use of UV inks in food packaging. Some low odor, non-toxic photoinitiators have been developed. For example, a polymer photoinitiator has superior performance and can mitigate migration. At the same time, the polymer photoinitiator has the following characteristics: adjusting the distance between the photosensitive groups, obtaining a polymer photoinitiator having different reactivity; using the synergistic action of the photoactive group to improve the photosensitivity; preventing the yellow of the ink layer Change and age. UV inks using polymeric photoinitiators can be used for food packaging printing and have good curing properties.
In addition, with the development of aqueous photoinitiators, cationic photoinitiators, composite photoinitiators, and hybrid photoinitiators, the performance of UV inks has been further improved, and the range of applications has been further expanded. Among them, the composite photoinitiator is a combination of a radical photoinitiator and a cationic photoinitiator, and the curing speed of the UV ink using the composite photoinitiator is greatly improved; and the hybrid photoinitiator is under UV illumination. It can generate free radicals and can generate cations. UV inks with mixed photoinitiators can overcome the inhibition of oxygen on free radicals and the sensitivity of cationic polymerization to water, and improve the curing degree and physicochemical properties of ink films.
7. New UV curing light source
(1) Promise mercury lamp. It can be switched instantaneously, and has long life and high efficiency. Unlike the spectrum of medium pressure mercury lamps, the spectrum of the electrodeless mercury lamp used for UV curing is a continuous spectrum that can be used for the curing of thicker ink films.
(2) New light-emitting diode UV curing light source. Light-emitting diodes have many advantages, such as: instant turn-on and turn-off, illumination life of more than 50,000 hours, low operating voltage, low electrical losses, and continuous energy output, which can be said to be very convenient and economical to use. This light source itself generates very little heat and is ideal for drying temperature sensitive prints. The LED emits almost monochromatic light (the half-peak of the emission wavelength is about 25 μm). For UV curing with special requirements, the emission wavelength can reach 450 nm.
(3) Excimer lamps. The so-called excimer (excited dimer, trimer) is a molecular form that has no stable ground state and exhibits only a weak bond excited state. Some important excimers are formed by the excitation of rare gases, rare gas chlorides, halogens, and mixtures of mercury and halogens. Several excimer lamp products have been developed, mainly for light sources with UV light emission at wavelengths of 172 nm, 222 nm, 308 nm and 351 nm. The excimer lamp has a very narrow band distribution and high energy, which enables the UV ink to cure quickly. An excimer lamp with a wavelength of 172 nm allows direct activation of the acrylate. The energy generated by a ruthenium chloride excimer lamp at a wavelength of 308 nm enables the UV ink to cure quickly. In addition, excimer lamps do not produce ozone during curing of the UV ink, and there is no heat transfer to the substrate and production equipment. It is reported that an excimer lamp with a wavelength of 308 nm is particularly effective for curing a cationic photocuring system UV ink.