The choice of flexo printing after glazing oil
Time:2016-04-19 12:00Source:sankunClick: Number
The choice of flexo printing after glazing oil
For flexo printing after light is commonplace things, because glazing to a certain extent, can improve the water resistance, abrasion resistance of printed matter, such as performance, also have the effect of beautification products, improve product class, within the same price level, a lot of post-press processing method is not comparable to those of glazing effect. Therefore, in the past ten years, light oil technology development is rapid, cheaper chemical raw materials, application scope is more and more widely, also more and more stable performance.
At present, in the flexo UV glazing glazing occupies very important position, and commonly used online. The UV curing device is composed of one or two UV lamp and reflectors. Water-based ink printing again after UV light oil, can have very good protection effect of water-based ink. Requirements, of course, there are also some special occasions in water-based light oil, such as when the final products to spurt the code printing, printing with special water-based light oil, other manufacturers in the inferior smooth glaze will choose water-based light oil, because the UV matte oil in long version live easy to thicken.
In UV glazing process will often some puzzling problems, this article lists the common in flexo UV glazing 9 major problems and their solutions, in communication with you toward a common.
1. Yellow coating
UV light oil after solidification of the main causes of yellow generally has two aspects: one is the UV light oil placed too long, itself has become yellow, especially the poor light oil yellowing phenomenon is more serious; Second, excessive ultraviolet radiation, UV light oil curing is excessive.
Solution: if this is the quality problem of the UV light oil itself, it must be replaced UV light oil; If is caused overexposed yellow, will reduce the uv light source power or increase the speed of glazing.
2. Coatings in the absorbent substrate surface adhesion fastness of the poor
If the substrate is absorbent or without hole base material (such as PVC or PET film), may appear light oil coating on the surface of the substrate, the phenomenon of poor adhesion fastness.
Generally think that coating the hard, the better the results, but for the absorbent base material, the toughness of the coating is the first, can appear otherwise attached to bad questions. In order to get the "soft" coating, light oil formula need to adopt some special raw material, choose good toughness, good adhesion of the light solid resin, and active monomers.
Solution: test coating adhesion fastness general use cross test, first of all prepare sellotape and row of the grid tools, cross cross grid lines in the coating, be careful not to hurt and base material, and then tape adhesion, by tape off coating area size on behalf of the coating of curing degree and adhesion. If no coating was torn off, the coating adhesion is quite good. If the coating is peel off large area, means that the light oil is not suitable for use in a non-porous substrate, should consider to replace other types of light oil.
3. Fingerprint problem
After glazing often find a fingerprint on printing quality, especially in black ink on this kind of phenomenon is more obvious in full version of the glazing. Why will appear this kind of phenomenon? Often this is caused by the oil to add some additives to improve the performance of light oil, such as defoamer, flow ping agent, etc., these ingredients are not participating in curing cross-linking reaction, they might eventually absorbed by the base material, may also after curing migration to coating surface. If a component is not stable in light oil in the coating, it will direct the migration to coating surface, and form not curing thin layer, when the finger accidentally met will leave fingerprint.
The solution: meet with such problems, the key is to ensure that the coating thoroughly dry, reduce residual migration to coating surface.
4. Glazing effect is not stable
Glazing effect is not stable, it is to make a lot of flexo printing enterprises are a major headache. In flexo printing process, in order to make the viscosity of water-based ink stable, need to add a certain amount of ink amine substance, although can effectively adjust and keep the ink viscosity, but some of the amine substance will be negative influence on UV light oil curing effect. Sometimes, glazing instability is caused by the ink to add the amine.
Solution: try to use other new method to control the ink viscosity, if light oil, and the ink used do not match, we must change the light oil, or change the formula of the light oil.
5. Inferior smooth oil concentration instability
UV matte oil concentration instability problems in printing and coating, especially when printing long version live this problem is more outstanding. Why will appear this kind of problem? In order to reduce the UV light oil or water-based light oil gloss, in turn, to extinction effect, generally need to add a lot of silicon dioxide, this will cause the rise of oil viscosity, light and higher viscosity will directly affect the performance of light oil. If join from adhesion agent, will affect the curing speed and leads to some uncertain factors, causes coating has stripes and stain. Many printing enterprise due to can not find the right solution to the problem, as far as possible, avoid using UV matte oil.
Solution: contact with light oil supplier, choose suitable for long version live printing inferior smooth light oil.
6. Glue eligibility and printing eligibility
We often hear some vendors praise myself printing quality of the polishing effect is good, looks like a mirror. Good light oil coating on the surface of the ink layer form 100% of solid film, strictly speaking, the performance of the coating is more like a dense and smooth the surface of the plastic film. But from another point of view, the glue and other order after the processing is very bad, because the too smooth coating on the surface, adhesive and ink cannot be attached.
Solution: if the printing quality after polish pass coating or printing process, so the coating surface is not too smooth, in order to make sure the adhesive or ink adhesion. That is to say, the light oil coating must have a good glue eligibility and printing eligibility, but it is worth noting that even light oil coating glue eligibility and printing eligibility are good, and the ink is not at all the adhesives are used to, so it's best to do the test before use, if the test result is not ideal, it is best to get in touch with light oil suppliers, common to find a solution.
7. Scratch resistance is poor
The scratch resistance of UV light oil coating is bad, the root of the problem is on the adhesion fastness. On the one hand, the coating is too fragile, easy to peel, this may be caused by excessive curing; Ink layer is not completely dry, on the other hand, can also cause glazing coating scratch resistance is poor. Ink layer is not completely dry reason mainly has three aspects: one is the ink spread to residual material in the ink layer surface; Second, the ink is slow drying, ink; 3 it is to press drying device is not suitable.
Solution: check and adjust the ink drying device, can guarantee the ink completely dry; As far as possible, keep the air circulation, speed up the ink dry. If it doesn't work, only replace the light oil.
8. Poor water resistance
Universal UV light oil is generally poor water resistance, because the UV light oil contains some important contents are hydrophilic, thus affect the water resistance of the coating.
The solution: the market for water resistance, light oil but this kind of light oil curing speed slower, therefore, when using the water resistance of light oil should be appropriate to reduce the printing speed.
9. Light oil in black ink, white ink, shoot the light blue ink layer on curing
In black ink, white ink and light blue ink printed on the layer of light oil will often appear all sorts of unexpected problems, which is to make the printing enterprise one of the most headache problems.
We can understand it and think about this question: printing ink light initiator of pigment and light oil absorption of the same wavelength of ultraviolet light, both competition limited energy of uv light, and light oil curing is the need of energy, so the influence of the light oil is bigger, may cause light oil curing not thorough.
Solution: increase the UV lamp power, cleaning the reflector, replace the UV lamp, reduce the printing speed of light oil, but it can only as a temporary solution, from a long-term point of view, should be developed and developed a can achieve full curing on any color ink layer universal light oil.
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