How to overcome the problem of poor adhesion of fi

How to overcome the problem of poor adhesion of film self-adhesive ink

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core tip: poor adhesion of ink is the main problem in the printing process of film self-adhesive materials. In the self-adhesive label printing industry, staff generally use 3M tape for ink adhesion test. Stick the test tape close to the test part, cover the whole test area, grasp one end of the tape with your hand, and quickly tear off the tape. When the area is too large, it is required to cover no less than 15 square centimeters. Repeat at the same position to check whether there is deinking. If the deinking area is not greater than 10% of the test area, it is considered as a normal range

[China Packaging News] poor ink adhesion is the main problem in the printing process of film self-adhesive materials. In the self-adhesive label printing industry, staff generally use 3M tape for ink adhesion test. Stick the test tape close to the test part, cover the whole test area, grasp one end of the tape with your hand, and quickly tear off the tape. When the area is too large, it is required to cover no less than 15 square centimeters. Repeat at the same position to check whether there is deinking. If the deinking area is not greater than 10% of the test area, it is considered as a normal range

in order to overcome this problem, most label printing enterprises use UV ink to print, hoping to improve the adhesion of ink on film self-adhesive materials with relatively tight financial funds of local governments through the good performance of UV ink and the characteristics of UV instant curing. But in the process of printing processing, we often encounter some problems

poor curing of ink

in actual printing production, it is often encountered that the surface of UV ink has been cured after being irradiated by UV lamp. Here we not only provide you with high-quality laboratory equipment, but the interior is not completely cured. UV ink that is not fully cured has weak adhesion with film materials, and it is easy to tear it off the surface of the material during tape testing

the surface tension of film material is not enough

before printing, workers should use dyne pen or dyne solution to check the surface tension of film material. If you want to ensure good UV ink adhesion, the surface tension of the film material should reach at least 42 dyne/cm2. If the surface tension of the film material does not meet the requirements before printing, it will cause poor ink adhesion

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3. Ink mismatch

for some thin film materials (such as pet and BOPP), it has been 510 years. In order to make the materials have strong printability, the material supplier will coat the surface. Different inks use different resins, so even if they are printed on the same coating layer, they often show different results. I would like to remind colleagues that when purchasing film materials with coating layers, they should consult the material supplier about the ink brand suitable for the material

in view of the above situation, some companies have adopted the following two solutions:

1 Thumb press method to judge the curing condition of the ink

thumb firmly press on the ink surface, and then press it back and forth several times. If there is ink on the thumb, it can be determined that the ink is not completely cured. There are many reasons why the ink is not fully cured, which may be the problem of the ink itself or the problem of the UV curing system

here we mainly pay attention to several aspects: if the UV ink is not used up, be sure to cover it well and keep it away from light during storage; The ambient temperature for storage should be about 20 ℃, and the temperature should not be too high; The service time of UV lamp is generally about 1000 hours. Once its service life is exceeded, its spectral curve will change, so we should correctly record the service time of UV lamp and replace it in time

2. Improve the surface tension of film materials

some film materials, such as PE film, do not have ideal adhesion to ink, surface "We are very flexible to meet the needs of customers for special treatment. Through surface treatment, we can improve the surface tension of thin film materials, making it greater than the surface tension of ink, so as to achieve the correct combination of ink and thin film materials. Surface treatment usually includes corona treatment and surface coating treatment. Through high-voltage charge discharge treatment to the surface of thin film materials, we can finally achieve the purpose of increasing surface energy, that is, surface tension; Or through the surface coating treatment, the ink friendly coating is coated on the surface of the film material to change the surface characteristics of the film material and make it suitable for printing

with the rapid growth of the label market, the use and proportion of film adhesive materials are increasing. As a label printing enterprise, we must pay attention to this change, analyze the printability of materials in advance in actual production, and take preventive measures, so as to prepare for the improvement of production efficiency and profits of the enterprise