Solve the problem of UV printing deinking from five aspects
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The UV printing color reaches the highest limit, the gloss of the printed product is high, and the replay effect is good. Therefore, it is widely used in high-end packaging printing, especially in the packaging of cosmetics, cigarettes, wine and other products. The material of such packaging is usually composite paper (PET, PVC, BOPP, etc. and paper jam stick together), that is, UV ink is not directly printed on cardboard. In general, UV inks cannot easily adhere to the appearance of composite paper easily, and are prone to deinking problems. This is one of the common problems in UV printing homework.
To solve the problem of deinking should start from the following aspects.
Composite paper
Composite paper is composed of cardboard (substrate), adhesive layer and non-augmented film, and sometimes also includes aluminized layers. During printing, the main contact with UV ink is polyethylene film, polyvinyl chloride film, polypropylene film, metal foil and other non-authentic materials or aluminized layers. If it is appropriate to use ordinary solvent-based inks to print composite paper, a certain amount of drying time is required, and it is appropriate to use dusting and drying racks or to add other additives to the ink, and the use of UV inks can prevent the use of UV inks. These topics, but the condition is that the material must be disposed of.
(1) Disposal of non-authentic materials
Corona treatment
Corona treatment is a kind of electric shock treatment method. The positive cathode side grounding surface of the corona device and the induced air nozzle are used to use the high voltage and high frequency cycle to make the electric shock molecule to be ejected from the trapezoidal air nozzle and carry high energy and energy. The electrons accelerate toward the positive electrode, so that the polarity of the non-critical material can be changed and the appearance finish can be increased.
2 Japan primer treatment
When the exterior material of the composite paper is not suitable for corona disposal, it may be considered that the composite paper surface should be treated as a primer. The lacquer base-breaking disposal form is divided into string lacquer lacquer disposal and off-line lacquer disposal. The thickness of the lacquer must be moderate, thick and easy to cause consumption, too thin, it is easy to cause printing failure.
3 flame disposal
Normally suitable for use with irregularly shaped materials.
In the actual production, the general rule will be appropriate and a variety of disposal forms will be used at the same time. The corona treatment and the bottoming treatment of the fake paint are the most common and the effect is satisfactory. Under normal circumstances, after corona treatment, it will form a more intricate and inexact appearance. The formation of the joint force under the lacquer roller is relatively large, and it is suitable for UV printing. However, the thickness of the fake lacquer layer is also very tight, too thick or too thin may cause deinking problems.
(2) Aluminizing layer and ink bonding method
When the exterior material of the composite paper is aluminum-plated, there are two kinds of situations: one is that the aluminum-plated layer has fake lacquer, and the two are urgently connected, and the UV ink is printed on the lacquer. The ink phenomenon depends on how the aluminizing layer and the molecular compound plastic film layer cooperate. It has been proved that the deinking phenomenon under this kind of situation is more common; the other is the direct contact between the aluminized layer and the ink, and the composite paper at this time The printability is better.
2.UV ink
UV ink is an environmentally friendly ink that does not contain VOCs. It does not change its color reproduction effect and printability when it encounters solvents or water. In the printing process, the UV ink has better color stability and stickiness. Once the UV ink is debugged before printing, the amount of debugging work on the printing press is very small, and there is no need to participate in other additives. When the printing stops at halfway, the ink on the ink roller will not dry and crust. The cured UV ink layer has extremely high abrasion resistance and chemical resistance. At the same time, it also has a long covering force and gloss. UV inks also have a little lack of original: the printing needs the use of specially manufactured rubber roller, such as NBR or EPDM rubber roller; sometimes there may also be special needs blanket and cleaning agent to avoid excessive shrinkage and expansion of the blanket. Reduce quality.
When using UV ink printing, in order to prevent deinking problems, ink thickness should be added to the tanning system. Under the condition that the color is guaranteed to reach the maximum limit, the ink layer should not be thick and thick, and generally it should not exceed 4 μm, which is about half of the ordinary ink ink layer thickness.
3.UV light source
The UV light source is a device that emits UV light in a UV curing system and is generally composed of a light box, a lamp tube, a mirror, a power source, a tumbler, and a cooling device. According to the different things filled in the lamp, can be divided into metal halogen lamps, high-pressure mercury lamps and non-brominated lamps and so on. The functional parameters of the UV light source are: the length of the arc, the spectrum of the characteristics, the power, the office voltage, the office current, and the average years of survival. The UV light source radiates light in a band, but different UV light sources emit light in different wavelength ranges, and the spectral energy + ç¾ç¼• dispersion in the band is also different. It is better that the energy of the broadcasting section is 300-310 nm and 360-390 nm. To prevent the problem of deinking, we must first pay attention to the compatibility of UV light source and UV ink, followed by the selection of light source energy. Coin Indian Near Modern
The perfect match between UV light source and UV ink is to make the photopolymerization initiator in the UV ink used to select and discriminate the light wave in the UV light source spectrum. The technical data of the spectral characteristics of the relevant UV light source and the response curve of the ink according to prescriptions are required to be used in the application, so that the good match between the two can be achieved.
The fairness of the selection of light sources is also very important. Ordinary, UV-printed light sources consume more energy. When printing open-faced work, the more reasonable UV light source is equipped with 4×11kW. In some cases, it is also possible to use 1～2 7kW lamps; each lamp After using the tube for 1,000 hours, it is necessary to think about changing the subject; when using on-line curing measures, it is usually necessary to install a high-power UV light source, especially black ink, in dark ink units. Curing time curing system should also be appropriate, it should be 0.3s or so, the curing time is too short, the printed product is easy to stick dirty, curing time is too long, the printed ink layer becomes brittle, after the coating is more prone to deinking phenomenon.
4. Background control
Ordinary, UV ink deinking occurred in the cold winter temperature difference. As this production plant needs to maintain a satisfactory temperature and humidity, it is very useful to solve the problem of UV ink deinking.
5. Add additives
Participating auxiliaries can change the curing time of UV inks and increase the fixation fastness. In addition, the amount of UV lightening agent in the ink can be increased within the range of the color difference permitting, and the ink can be enhanced in experience of the UV light.