Paper UV ink technology standard
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
odor
There are two indicators for evaluating the odor of UV ink. One is the odor during construction. The main source is the residual solvent in UV ink. Under normal circumstances, the residual solvent is less than 2%. Under special circumstances, such as cigarette UV ink. Requires less than 0.5%, but today, when oil prices soar, many suppliers add a large amount of solvents, such as alcohol and toluene, to reduce the cost of UV inks, up to 25%, so that the long-term development and environment of UV inks Protection is unfavorable.
Another indicator for assessing the odor of UV inks is the residual odor of UV inks after application. It can't disappear after a long period of time. The main source is the improper selection of UV inks. Some of the more expensive but cheap chemicals are used. It is difficult to fundamentally improve, mainly because of the cost and the choice of suitable materials.
UV ink discoloration or ink discoloration
UV inks are sensitive to ultraviolet light. If the UV ink after application continues to be exposed to ultraviolet light (such as sunlight and fluorescent lamps), the UV ink will continue to react and turn yellow, which is a defect of the UV ink itself. For conventional UV inks, it is currently not fundamentally improved, but the degree of yellowing of UV inks from different suppliers is different unless a specific non-yellowing or extra-white UV ink is used.
The main reason for the discoloration of the ink after UV ink glazing is the problem of the ink. There are some pigments in the ink, such as radiance blue, which is a blue acid lake pigment. It is an organic dye triphenylmethane dyed on an extender pigment such as aluminum hydroxide to form an insoluble pigment pigment in water. The price is low, the hue It is vivid, but its light resistance, solvent resistance and alkali resistance are poor. When a solvent such as an alcohol or an alkali is encountered, the red phase is easily dissolved, weakened or disappeared. These pigments, such as those used in book inks (the surface after printing is no longer glazed), are feasible, but if used in color box inks, they are very dangerous because most of the color boxes are post-processed. The detection method is to drop a drop of base oil and ink on the surface of the ink, and it is very obvious whether the ink is discolored after 1 hour.
For printed paper, if the ink is discolored, it can be forced to dry with ink, such as drying or a little more time to solve, or use neutral base oil, solvent-free UV ink, solvent-free book UV ink, etc. Ways to reduce the tendency of ink to change color.
Exploding oil and scratching
UV ink explosion refers to the phenomenon that the varnished paper is cracked by UV ink during pressing, folding, beer, or daily use. Scratch is a phenomenon in which the UV ink after construction is partially pulverized when nails or hard objects are scratched on the surface. The root cause of the above two phenomena is that the UV ink hardness is too high or the adhesion of UV oil to the substrate is poor. The specific reasons and solutions are as follows:
1. UV ink overexposure or hardness is too high, this time should pay attention to the appropriate amount of exposure (40mj / cm2 ~ 70mj / cm2), it is best to choose a good flexibility UV ink;
2. UV ink construction is too thick, the thicker the coating film is, the more likely it is to burst;
3. The paper is too bad, easy to burst, the strength of the UV ink is not enough to resist the force of paper cracking;
4. The base oil is too hard and too thick, and it does not help or prevent the UV oil cracking;
5. The ink is powdered and the cohesive strength is poor. The paper, ink, base oil and UV ink cannot form an organic whole. At this time, especially in winter, it is most likely to cause scratching.
Hot stamping
Bronzing is a process of heat transfer in which the substance on a PET substrate is transferred to paper or other printed substrate under the influence of heat and pressure. The most commonly used material is anodized aluminum. To understand the bronzing process, it is best to first understand the structure of anodized aluminum. As shown in Figure 1, it is divided into 5 layers: the first layer is PET (polyester) film base; the second layer is The separation layer can be detached from the PET film under the action of hot pressing. The commonly used material is silicone grease or other adhesive with small adhesion; the third layer is a dye layer composed of resin and pigment, and the aluminum powder is protected after bronzing, and To impart color and luster; the fourth layer is a vacuum aluminum layer to provide reflectivity; the fifth layer is a binder layer, mainly acrylic resin and other tackifying resins, which are bonded to the substrate under the action of hot pressing. This layer is the most critical layer to determine the suitability of bronzing. The strength of the bond directly determines the substrate on which the electrochemical aluminum can be burned, such as BOPP, grinding oil, water oil, UV ink and other substrates.
Conventional UV oil is a thermosetting material that does not soften when heated, and a large amount of silicone and wax substances are added to the UV oil. These materials are not easily bonded, so conventional UV oil cannot be the first in the electrochemical aluminum. 5 layers of bonding, that is to say, conventional UV inks are not bronzing.
The composition of the bronzing UV ink is very different from that of the conventional UV ink. It is mainly characterized by thermal softening but not melting and high surface tension, so it can be bronzing. On the contrary, if the fifth layer of anodized aluminum uses a binder similar to the performance of UV color box glue, it is believed that conventional UV inks can also be bronzing.
Book UV ink
In terms of formula design and chemical structure, the book UV oil is a very special UV oil. It is a book-specific UV oil developed for offset paper. It has good adhesion without primer. , anti-infiltration, can be glued to the box, can be bronzing and other properties. The book UV oil also has some adaptability when applied to ordinary cardboard, but it is best tested before use.
Other properties of paper UV oil, such as stick marks, orange peel, pinholes, shrinkage holes, pitting, etc., as well as some special-purpose products, such as gravure UV oil, mesh UV oil, etc., due to space limitations I will not introduce them here.
The development prospect of paper UV ink
In the environment of environmental protection, high efficiency, high performance and energy saving, UV oil will be further promoted and applied in the printing industry. From a personal point of view, the following UV oil products are worthy of attention in the future:
1. High-light and high-wear UV ink: Under certain preconditions, high light and high wear resistance are in conflict. How to improve the wear resistance and scratch resistance of UV ink is a technical problem under the premise of high light.
2. Harmless and tasteless food grade UV oil: Since UV ink contains a large number of small molecules with molecular weight less than 1000, and curing occurs in an instant (within 1 second), some small molecules cannot participate in the reaction completely. How to make these small molecules Complete response is also a subject that industry peers need to face.
3. Water-based UV ink: This is a product that realizes the true environmental protection of UV ink. At present, technical barriers have been overcome, but how to greatly reduce its production costs and achieve large-scale production will take time.