UV glazing is a very common surface finishing process in the packaging and printing industry . If the adhesion of the UV varnish is insufficient, the printed product will have various quality problems such as fading, non-wearing, varnishing and the like, which may cause a series of adverse reactions. In order to avoid such problems, comprehensive analysis should be carried out, including material procurement, process arrangement, and standardization operations, and targeted rectification should be carried out according to existing problems. The reasons and solutions for the lack of adhesion of UV varnish are summarized below.
(1) The storage time is too long, causing the UV varnish or base oil to expire. In general, the shelf life of UV varnish or base oil is from six months to one year. Some manufacturers purchase too much UV varnish at one time, which easily leads to the expiration of UV varnish or base oil.
(2) UV varnish and base oil do not match. During the use of the operator, it should be noted that the UV varnish and the base oil should be produced by the same manufacturer. If the mixing is easy, the performance will be mismatched and the quality of the printed product will be affected.
(3) The drying time of the ink is short or the drying performance is not good, and the adhesion of the UV varnish is likely to be poor. Any product that requires UV glazing must ensure that the ink has reached or exceeded the drying time of 24 hours before UV glazing, otherwise the UV varnish does not easily adhere to its surface.
(4) The illuminance of the UV lamp is insufficient, resulting in insufficient curing of the UV varnish. There are many reasons why the UV lamp may not have enough illumination, such as the UV lamp is not high, the lamp is aging, the surface of the lamp is dirty, the lamp is too high, etc. When the UV lamp is not enough, it will cause UV. The varnish is insufficiently cured. Since the illuminance cannot be accurately detected by the naked eye, the illuminance detector must be used. When the illuminance detector is illuminated by the UV lamp, the parameter value reaches or exceeds 50, indicating that the UV lamp meets the curing requirements of the UV varnish.
It should be noted that the UV lamp has a certain service life. When its usage time is close to 1000 hours, it should be replaced in time.
(5) Too much water or alcohol in the UV varnish or base oil will affect the adhesion of the UV varnish. If the amount of water or alcohol is too much in the UV varnish or base oil, it will cause the paper to get wet and not dry quickly, thus affecting the adhesion of the UV varnish.
(6) Irregular operation affects the curing effect of UV varnish. The employee's operation is not standardized. Each time the oil roller is cleaned, a large amount of water-containing residual liquid is returned to the container containing the UV varnish or the base oil, which causes the crude oil concentration to become thin, thereby affecting the curing effect of the UV varnish.
(7) In the case of low temperature and high humidity inside the workshop, the curing speed of UV varnish will be slower accordingly. In this regard, the operator should pre-heat the UV lamp in advance to reduce the operating speed of the equipment and appropriately extend the curing time of the UV varnish.
(8) The speed of the glazing device is too fast, which causes the UV glazing product to be cured by the ultraviolet light for too short a time.
(9) If the UV varnish layer is too thick, it will not only cause the UV varnish to be completely cured, but also increase the cost, and even cause the printed product after glazing to burst in the die-cutting indentation, directly causing scrapping.
(10) Factors such as large water content of the paper and too much powder on the surface of the printed product may also cause a significant drop in the adhesion of the UV varnish. In this regard, the amount of dampening solution and dusting should be strictly controlled during the printing process.
The work experience summarized by the author above can effectively avoid the recurrence of the quality problem of the UV glazing adhesion of the printed product. However, it should be emphasized that due to different equipment, materials, environment and customer requirements, the cause of insufficient adhesion of UV varnish will be complicated. When old experience encounters new problems, it still needs careful analysis, careful verification and continuous improvement. In actual combat level, we can effectively solve problems and provide better products for our customers.
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