UV Printing Troubleshooting: Questions and Answers

2.Adhesion failure

No.	Item	Printing System	Phenomenon/ Situation	Explanation	Cause	Counter-measure
201	Adhesion failure	All Systems	UV inks that are sufficiently cured fail to adhere properly to the substrate.	Adhesion performance varies between ink types, so it is important to check adhesion in advance. Additionally, if the adhesion between the ink and the substrate is weak, it may vary from color to color. Adhesion defects are also more likely to occur in winter or when using older lots of material. → Even with the same printing specifications, adhesion may not be achieved, so it should be checked during the printing process as well.	Incorrect ink selection or Incorrect substrate selection or Printing condition or Substrate aging	A) Select inks with good adhesion properties. B) Use a UV primer. C) Change the substrate if necessary. D) Apply a pre-treatment to the substrate. E) Warm up the substrate and ink before printing. F) Avoid using old lots of substrates.
202	Adhesion failure	All Systems	The ink adheres well when used with colored inks alone, but if OP varnish or coating is applied, adhesion becomes poor, and the ink may peel away from the substrate. → Pay attention to the type of paper used. This issue is more likely to occur with papers that set and dry quickly, such as cast-coated papers.	The phenomenon and causes are the same as when excessive ink feeding or overlay printing occurs, resulting from curing failure. Refer to section on “Curing failure” (overprinting). → This issue is particularly likely to occur when the underlying ink is black ink. → Trouble may arise even when interdeck UV lamps are used if the ink film underneath is too thick, but it is much more likely to happen when ID-UV lamps are not used.	Curing failure	A) Refer to section № 108 on “Curing failure” due to excessive amounts of ink. B) In some cases, ensure the underlying ink is fully cured before applying varnish.
203	Adhesion failure	All Systems	Insufficient adhesion between the substrate and ink occurred when the printed material, which had previously confirmed adhesion, was processed using film lamination and heat pressing.	Adhesion may deteriorate due to the film stretching process, even after prior confirmation between the ink and substrate. The film expands and contracts due to heat during processing, but the UV ink film cannot keep up, leading to reduced adhesion. The laminate adhesive may be stronger than the adhesive of the tape used in the verification test, causing adhesion issues.	Lack of prior confirmation	Always select inks and substrates based on the specific conditions of use for the printed material.
204	Adhesion failure	Letterpress Flexo	Adhesion stability is not achieved even when using the corona / frame treatment unit attached to the printing press.	If there are no issues with the products, substrate, or UV curing, the problem may lie with abnormalities or improper adjustments in the attached treatment units.	Maintenance failure or Mechanical adjustment failure	Implement maintenance and adjustments on the treatment unit.
205	Adhesion failure (back unit detachment)	Offset	When using interdeck UV, the ink and primer on the unit prior to the interdeck UV are transferred onto the rear unit after the interdeck UV. This issue is likely to occur white ink in particular.	This issue occurs because the curing and adhesion of the ink on the first units are insufficient and leading to printing being performed on the rear unit. In most cases, only one lamp is used for the interdeck UV, and due to the low light intensity, this increases the likelihood of problems. Furthermore, this issue is more likely to occur during the winter when adhesion tends to decrease.	Curing failure or Adhesion failure	A) Change the underlying ink to a good adhesion type or a conc type ink. B) Use a two-pass printing process to fully cure the underlying ink before printing. C) Implement seasoning of the substrate.
206	Adhesion failure (On Top Printing Defect)	All system	UV ink printed on top of underlying UV ink does not adhere properly. Additionally, UV ink printed on top of overcured UV ink layers also fails to adhere properly.	Due to overcuring or post-curing, the surface of the UV ink film becomes hard, resulting in a chemically inactive surface that is difficult to adhere to. In the case of low-viscosity types, such as coater or flexo, repellency may also occur.	Excessive curing	A) When printing on base-printed materials, recheck the adhesion and select the appropriate ink. B) When using UV primer, print on top of the primer within 2-3 days after application. C) For letterpress printing and similar processes, reduce the number of interdeck UV units or adjust the lamp output.
207	Adhesion failure (On Top Printing Defect)	All system	The primer and opaque white are well-adhered, but the color ink applied on top is not adhered properly.	After applying a high-adhesion primer and opaque white as the base ink, the use of UV inks with weaker adhesion properties for the top layer can lead to adhesion failure between the underlying ink and top inks due to differences in wettability.	Incorrect ink selection	Use the same type of ink or an ink with similar adhesion properties for the top layer as the underlying primer or opaque white ink.
208	Adhesion failure /Poor Printability (Transfer)	Offset	when perfect printing, the use of removable OP varnish resulted in poor ink transfer and poor adhesion during printing on the top side.	The migration of slip agents from the removable OP varnish to the opposite side can interfere with ink transfer and adhesion, causing issues like chemical ghosting	Incorrect varnish selection or curing failure	A) Use regular OP varnish. B) When using removable OP varnish, consider the printing sequence and design. C) Refer to section No.505 on “Printing defect” for ghosting.
209	Adhesion failure (Water resistance adhesion)	All system	Although the adhesion of the printed material itself was good, the adhesion decreased when the printed material was exposed to water, stored in refrigerated conditions, or used in retort applications. This issue can also occur with not only water, but also solvents and solutions. Examples: A) Printing on synthetic paper, where ink came off due to rainwater exposure during outdoor display. B) Printing on cups for frozen food, where ink peeled off during storage in the refrigerator (freezer). C)Ink detachment occurred when printed materials were subjected to retort processing.	The adhesion between the ink and the substrate was compromised due to the infiltration of water (or other liquids) between the ink layer and the substrate via capillary action, which caused the ink film to detach from the substrate and resulted in a loss of adhesion.	Inadequate initial verification or incorrect ink selection.	A) It is imperative to select both ink and substrate based on the specific intended use of the printed material. In the case of water-resistant adhesion, caution should be exercised, as inks with strong adhesion properties may not necessarily provide optimal performance. B) Excessive treatment, such as corona discharge, may lead to complications; therefore, it is crucial to apply the appropriate level of processing.

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