In the label printing process of film materials, the problem of surface ink printing is very likely to occur, which greatly affects the quality of printed products and even delays the delivery date. This article tries to summarize and list the causes and improvement methods of common ink dropouts from the daily printing experience for the industry to explore together to find the best solution.

Problem 1: Coating defects

Conventional films are divided into two types, coated and uncoated, and the reasons for the film coating defects causing the ink to fade are correspondingly divided into two cases: For coated film materials, if the surface coating is not tight , will cause poor adhesion of ink; and uncoated film materials often because the surface layer with the ink fastness is not good, causing the ink out of ink.

For ink defects caused by coating defects, can be solved by the following methods: take the surface layer of varnish printing process, protect the ink surface, play a role in preventing ink off; surface layer using corona retreatment, material surface corona The dyne value should not be lower than 38mm/m, and the dyne value below 36mm/m can directly affect the firmness of the printing ink; the surface layer is painted or the enhancer with strong ink adhesion is used (the proportion is about 3% ), can also improve the film surface coating force; some sub-synthetic paper materials because the surface coating has a certain paper coating characteristics, it is not suitable for testing with 3M tape.

Problem two: tension

For the corona-treated film material on the printing surface, to achieve good ink wetting, the dyne value usually needs to be more than 38mm/m. Below 36mm/m, it is easy to cause ink drop problem; meanwhile, the dyne value of this material is It will fade over time and there will be problems with printing. The essence of this issue is tension.

There are several solutions to the problem of ink loss caused by this situation: on-line corona treatment using a satellite webcaster with an on-line corona function to increase the surface energy of the film material, and the use of a batch printer for surface coating Treatment to improve the surface printing adhesion; When the dyne value fades, the corona needs to be processed during printing, but the dyne value does not fully represent the adhesion between the ink and the face material, generally Dyne The period for the regression of the value is 3 months to 6 months, so it is recommended to minimize the long-term storage of stocks.

Finally, it is recommended to use a higher adhesion ink, it is recommended to consult the ink supplier.

Problem 3: Ink drying and tension

In the printing process, ink drying and tension may also cause ink loss. Specifically divided into: printing ink layer is too thick so that the drying is not complete; UV lamp energy is insufficient lamp aging, lamp reflector aging, resulting in UV lamp drying and curing is not sufficient, the ink layer is not dry; ink is too dry, resulting in material deformation, the formation of The ink layer falls off.

This ink drop problem can be solved in the following three ways:

First, the use of dark ink and thin printing is commonly known as reducing the amount of ink, such as spot-colored ground ink, which can be equipped with deeper ink. When the printing is performed, the amount of ink is small, and the effect of proof can be achieved, and the output power of the UV lamp can be increased. , Reduce the printing speed, increase the exposure time by UV light, and achieve the drying effect. This solution is suitable for old intermittent or satellite rotary machines and old UV lamp solutions.

Second, check the UV lamp for aging and clean the reflector. Usually the domestic UV lamp life is about 500-1000 hours, and the imported lamp life is about 1000-2500 hours. Please refer to the actual situation. It is recommended that the printing factory cleans UV lamps every six months or so to ensure normal use.

Third, reduce the output power of the UV lamp. The specific operation is the general print job. The colors in the first few groups of the color sequence are mostly logos or small characters. The required illumination is limited. The UV light can be turned on. Can not be excessive high-grade irradiation, because the thin film material to absorb heat energy is limited, excessive irradiation can cause the film material curling deformation and brittle, ink adhesion and other consequences, can follow the first low-grade UV lamp after the use of the principle.

  Question 4: Matching inks and materials     

Finally, the degree of matching of the ink and the material will also cause ink to some extent. For example, the use of ink molecular tension is too large, can not form a uniform ink layer on the surface of the substrate material; or use more ink than the shelf life or poor domestic brand ink, will cause the ink out of printing.

In case of the above situation, the ink can be switched to match the printing materials, such as special inks for films and lightfast and lightfast inks (consultable with the ink manufacturers for specific consultation). For overdue inks, the inks need to be printed prior to printing. Do print test, or print some simple text or small logo design, and some low-grade products; print large-area field and full-size screen dot network pattern, recommend using good brand, high adhesion ink (such as Hanghua ink, etc.).

Influencing factors of ink loss

Through the above analysis, we can summarize the eight major reasons for ink loss:

1, coated film material, poor surface coating fastness;

2. Uncoated thin film material, causing poor fastness to ink after printing;

3, Dyne value is low. For the corona treated film material on the printing surface, to achieve good ink wetting, the dyne value usually needs to be more than 38mm/m;

4. The dyne value fades. The printing surface is a corona-treated film material. Its dyne value may gradually fade with time, and the elimination period is 3-6 months;

5. The ink layer is too thick and the UV lamp power is insufficient to cause the ink layer to be insufficiently cured;

6, the ink tension is too large to form a uniform cured ink layer on the surface of the substrate;

7, the use of expired ink or poor domestic ink;

8, excessive ink, excessive drying