Adhesion Failure Failure Analysis and Solution of UV Ink Film Adhesive
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Compared to paper self-adhesive materials, film adhesive materials have the properties of good water repellency, good transparency, high strength, and good durability. Therefore, their use in daily chemical products and electronic products is increasing. Commonly used film adhesive materials
The films are: polyethylene (PE), polypropylene (PP), polyester (PET), polyvinyl chloride (PVC), polystyrene (PS), polyolefins (PE and PP blends) and the like. However, unlike paper, the film is not absorbent, so the printing of film stickers is mainly used
UV embossing and UV flexo printing. In the printing process, the problem often encountered by label printing companies is that UV inks have poor adhesion on the surface of the film. This paper will analyze the causes and describe the troubleshooting methods.
Cause Analysis
The causes of poor adhesion of UV inks to the film surface can be summarized as follows.
1.UV ink is poorly cured
In the actual printing process, the customer often encounters UV ink irradiation after UV lamp, the ink surface has been cured but the internal is not completely cured. Incompletely cured UV inks have weak adhesion to the film surface when tested with tape
It is easy to tear the ink layer off the film surface.
2. The film surface tension is not enough after the printing process
Force, the surface tension of the film must be at least 42mN/m. We know that Adobe uses corona treatment to increase the surface tension of thin-film materials (such as PE/PP), but corona treatment is also time-sensitive and can be affected by the material's storage environment, transportation environment, etc.
Factors affect. Prior to printing, the operator must check the surface tension of the film material using a Dyne pen or Dyne solution. If the surface tension does not meet the requirements of the packaging machine, UV ink adhesion will be poor.
3. The UV ink used does not match
For some film materials, such as PET, BOPP, in order to improve the printability, the material supplier will add a coating layer on the surface. Because different UV inks use different types of resins, printing on the same coating layer will often result in
Different results emerged. If the UV ink and the coating layer used do not match Epson, there will be a problem of poor adhesion of the UV ink to the film surface.
Troubleshooting
For the above three cases, we propose the following solutions.
(1) Determine if the UV ink has completely cured. We can use thumb compression method, that is, with the thumb pressing on the surface of the ink layer, and then press back and forth several times, if the thumb sticks with ink, you can determine that the UV ink is not completely cured. There are many reasons why UV inks are not completely cured. They may be problems with the ink itself, or problems with the UV curing system. Should pay attention to the following two aspects.
1 If the UV ink is not used up, be sure to cover the lid of the ink tank and be careful not to light during storage. We know that ordinary daylight also has ultraviolet light. UV inks that are irradiated by sunlight for a long time can also undergo chemical reactions. In addition, the ambient temperature of the UV ink should be around 20°C, which should not be too high.
The service life of 2UV lamps is generally around 1000 hours. Some label printers often encounter UV lamps that have been used for more than 1000 hours or they can be lit, but they cannot fully cure UV inks. This is because once the UV lamp has reached the end of its useful life, its spectral curve will change, and the emitted UV rays will no longer meet the UV ink curing requirements. Therefore, we should record the use time of the UV lamp correctly and replace the UV lamp that has reached the end of life.
(2) Thin film materials can be classified into two types according to their printability: one type is required to be printed by corona treatment; the other type has already been processed with a printable coating layer. For label printing companies, the choice of what kind of film material to buy should be based on the capabilities of the printing equipment (such as the presence of a corona treatment device, etc.). If the printing machine has a corona treatment device, you can buy the first type of film material. The surface tension of the film material should be measured before printing. If the surface tension is less than 42mN/m, the adhesion of the UV ink to the film adhesive material is poor. Analysis and Solution
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