Analysis of the Four Problems of Ink Dropping in Adhesive Juice Label Printing

Analysis of the Four Problems of Ink Dropping in Adhesive Juice Label Printing

Problem 1: Coating Defects

Conventional films are divided into two types: coated and uncoated, and the reasons for ink dropout caused by film coating defects are correspondingly divided into two cases: for coated film materials, if the surface coating has poor firmness , will cause poor ink adhesion; and uncoated film materials often cause ink dropout due to poor bonding fastness between the surface layer and the ink.

For the ink drop caused by coating defects, it can be solved by the following methods: adopt the surface layer varnish printing treatment to protect the surface of the ink and prevent the ink drop; the surface layer is treated with corona, and the surface of the material corona The dyne value should not be lower than 38mm/m, and the dyne value lower than 36mm/m will directly affect the firmness of the printing ink; the surface layer should be primed or an enhancer with strong ink adhesion should be used (the mixing ratio is about 3%). ), it can also improve the ink adhesion of the film surface layer; some sub-surface synthetic paper materials are not suitable for testing with 3M tape because the surface coating has certain characteristics of paper coating.

Question 2: Tension

For film materials whose printing surface is corona treated, in order to achieve good ink wetting, the dyne value usually needs to be above 38mm/m, and if it is lower than 36mm/m, the problem of ink drop is easy to occur; at the same time, the dyne value of this material is It will gradually subside over time, and there will be a problem of printing ink. The essence of this problem is tension.

For the ink drop caused by this situation, there are the following solutions: use a satellite rotary machine with on-line corona function to perform on-line corona treatment to improve the surface energy of film materials; use an intermittent printing machine for surface primer coating Treatment is used to improve the adhesion of surface printing; when the dyne value subsides, corona treatment is required during printing, but the size of the dyne value cannot fully represent the adhesion between the ink and the surface material. Generally, the dyne value The decay period of the value is 3 months to 6 months, so it is recommended to minimize the long-term storage of raw materials in stock.

Finally, it is recommended to use inks with higher adhesion, and it is recommended to consult the ink supplier.

Question 3: Ink drying and tension

During the printing process, ink drying and tension may also cause ink drop. Specifically divided into: the printing ink layer is too thick, resulting in incomplete drying; insufficient UV lamp energy, lamp aging, lamp reflector aging, resulting in insufficient drying and curing of the UV lamp, and the ink layer is not dry; excessive drying of the ink, resulting in material deformation, forming The ink layer is peeled off.

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

First, the use of deep ink and thin printing is commonly known as reducing the amount of ink. For example, the spot color ink can be matched with a darker amount. The amount of ink in formal printing is smaller, and the proof effect can be achieved. At the same time, the output power of the UV lamp can be increased. , reduce the printing speed, increase the exposure time of the UV lamp, and achieve the drying effect. This solution is suitable for old batch or satellite rotary machines and old UV lamp solutions.

Second, check whether the UV lamp is aging and clean the reflector. Generally, the service life of domestic UV lamps is about 500-1000 hours, and the service life of imported lamps is about 1000-2500 hours. For details, please refer to the actual use. It is recommended that the printing factory clean the UV lamp every six months or so to ensure normal use.

Third, reduce the output power of the UV lamp. The specific operation is for the general printing factory to print the job. Most of the first few groups of colors in the color sequence are the logo or small characters. The required light is limited. High-grade over-irradiation is not allowed, because the film material absorbs limited heat energy. Excessive irradiation will cause the film material to curl, deform and become brittle, and the ink adhesion decreases. The principle of using low-grade UV lamps first and then high-grade lamps can be followed.

Question 4: Matching ink and material

Finally, the matching degree of ink and material will also cause ink drop to a certain extent. For example, the molecular tension of the ink is too large to form a uniform ink layer on the surface of the substrate material; or the use of ink models that have exceeded the shelf life or inferior domestic brand inks will cause ink dropouts.

In the above situation, you can switch to the ink that matches the printing material, such as special ink for film and light-fast and light-fast ink (you can consult the ink manufacturer for specific consultation); for expired ink, you need to check the situation before printing. Do printing tests, or print some simple characters or small logo patterns, as well as some low-end products; print large-area solid and full-screen dot and line patterns, and it is recommended to use inks with good brands and high adhesion properties (such as Hanghua Ink, etc.).

Summary of Ink Drop Influence Factors

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

1. Coated film materials have poor surface coating fastness;

2. Uncoated film materials have poor bonding fastness with ink after printing;

3. The 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 above 38mm/m;

4. The dyne value subsides, the printing surface is corona-treated film material, the dyne value may gradually subside with time, and the subsidence period is 3-6 months;

5. The printing ink layer is too thick and the UV lamp power is insufficient, resulting in insufficient curing of the ink layer;

6. The ink tension is too large to form a uniform solidified ink layer on the surface of the printing material;

7. Use expired ink or inferior domestic ink;

8. The ink is over-irradiated and over-drying.

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