Common "Tricky Issues" in Film-Based Adhesive Label Processing – Find Solutions Here!
With the continuous development of China's economy, self-adhesive labels are becoming increasingly widely used in various product packaging fields. In recent years, people's demand for exquisite packaging appearance has been increasing, and the amount of film adhesive materials used has also been increasing. Thin film adhesive materials are different from paper adhesive materials in that they require higher processing technology and are prone to some problems during the processing. Below are some common problems and solutions in the processing of thin film adhesive labels.
Printing ink loss
one
Poor surface coating
Thin film materials have low surface tension and require coating treatment before being made into adhesive raw materials. Poor coating can lead to ink loss during printing. It usually manifests as large areas of ink peeling off, especially during tape testing, where the surface ink is adhered to a large area by the tape. At this point, it is necessary for the raw material supplier to replace a batch of qualified materials, or for the printing company to print another layer of primer oil to increase surface tension, but this will increase costs.
two
Poor compatibility between ink and material
Ink loss caused by this reason usually manifests as patches or sporadic. Considering factors such as material costs and customer demand, it is not possible to replace materials. At this point, ink suppliers can be used to find ink that matches the material. At the same time, printing factories can also take some auxiliary measures, such as conducting corona treatment on materials in advance.
3
Poor corona effect
The ink shedding of thin film materials is related to the surface energy of the material. The stronger the surface energy, the more firmly the ink adheres, and vice versa. But the corona effect will decay over time, which may cause ink loss during printing. This phenomenon is more common in inexpensive BOPP and PE materials. Considering the high coating cost, most manufacturers will perform corona treatment on them. In this case, the manufacturer or supplier should re corona before printing.
4Poor UV drying
Most adhesive materials are printed with UV ink, so incomplete drying can lead to ink loss. This situation manifests as one or two colors losing ink, which can be solved by simply increasing the power of the UV lamp or replacing the UV tube.
Printing is inaccurate, blurry, and has white spots
one
Poor surface flatness of the material
In general, the surface flatness of thin film materials is better than that of paper materials, but some special materials, such as thermosensitive synthetic paper materials, have a layer of thermosensitive coating on their surface, which may cause printing to be inaccurate or blurry. This is due to poor coating flatness, resulting in high-density white spots visible when enlarged. At this point, the flatness can be improved by applying oil ink as a primer on the surface of the material.
two
dust
Dust on the surface of materials can cause white spots to form during printing. There are many reasons for the generation of dust, and the most common ones are the generation of debris during cutting or the material itself falling off powder. Usually manifested as small but large white spots, and dust accumulates over time, causing the white spots to continuously increase. At this point, a dust removal cloth can be added in front of the printing unit, and for products with strict requirements or large areas, a primer ink can be printed before the first color group to avoid white spots.
three
Printing pressure
The magnitude of printing pressure directly affects the printing quality. Excessive pressure can cause distortion of graphics and text; If the pressure is too low, it is easy to print falsely or appear blurry. Usually manifested as regular printing inaccuracies, which disappear when the printing pressure is increased.
Large color difference in printing
one
Color difference of film surface material
The color difference between different batches of film surface materials is inevitable, and after printing, the color difference will be more pronounced due to the reflection of light. At this time, only the material can be replaced. There is no such thing as a film material without any color difference, so when developing new products, it is necessary to sign the upper and lower limits of the label color with the customer and confirm the range of color difference to avoid possible risks.
two
Difference in ink coverage on the surface of surface materials
Color difference may also occur when printing the same batch of film materials, which is due to the unstable surface energy of the materials causing differences in ink quality. After printing materials with color differences, the size of the dots on the surface will vary. At this point, a base coat can be applied, but ultimately the raw materials still need to be improved.
three
Differences in flatness of surface materials
The flatness of materials directly affects the reproducibility of printing dots, leading to color differences. The printing color difference and significant difference in dot size caused by this phenomenon. At this point, you can first apply ink as a base coat, and then consider replacing the material if it still cannot be solved.
Printing overprinting is not accurate
one
Printing tension setting issue
The printing tension directly affects the printing accuracy of thin film materials. If the tension is too low and the material loosens, it will cause printing errors. Conversely, if the thin film material is stretched and deformed, it will also affect the printing accuracy. Therefore, when printing thin film adhesive materials, the printing tension should be set to the minimum value that ensures the accuracy of overprinting.
2UV lamp temperature too high
Thin film materials are significantly affected by temperature, and if the UV lamp temperature is too high during printing, it will cause deformation of the thin film material and affect the printing accuracy. At this point, the UV lamp power can be reduced to lower its temperature. But in actual production, there are often contradictions, such as high UV lamp power, material deformation, and inaccurate overprinting; However, the power of the UV lamp decreases, resulting in accurate printing but less ink drying. Therefore, it is necessary to comprehensively solve the problem, such as applying ink as a base coat, selecting ink suitable for the material, or changing the printing color sequence, printing ink that is not easy to dry first, etc.
three
Poor material cutting
The uneven surface of the material can cause overprinting and misalignment during printing. If the material width is sufficient, secondary cutting can be performed by cutting 2mm off each side; If the material width is not enough, the material can only be replaced.
four
Inconsistent material tension
Thin film materials are highly sensitive to tension. If the tension at both ends of the material is not consistent, it is easy to deviate during printing, resulting in inaccurate overprinting. Usually, if one side of the material is flat and the other side is tight, lotus leaf edges will appear. At this time, it is recommended to use a continuous paper feeding printing machine with correction equipment for online coating to reduce inaccurate overprinting.
five
Material thickness error
There is a deviation in the amount of adhesive applied to self-adhesive materials, and sometimes a large deviation in the amount of adhesive applied can cause thickness errors at both ends of the material, resulting in printing deviation and affecting the accuracy of overprinting. At this point, it is necessary to replace the material or reduce its size for use.
Die cutting overflow glue
one
The glue is too thick or too soft
The glue is hard and not easy to overflow, but it will reduce fluidity and viscosity; If it is too soft, it is easy to overflow glue. The general adhesive coating amount for thin film adhesive materials is 16g/m ², and excessive coating can often cause glue overflow. Therefore, it is recommended to pay attention to these two points when choosing this type of material for coating online.
2
Excessive winding tension
Thin film materials have poor adhesion with adhesive, and when the winding tension is too high, it is easy to cause adhesive overflow on all four sides of the label. At this point, it is necessary to reduce the winding tension.
three
Die cutting knife issue
Sometimes there is glue overflow on one or both sides of the label, which is mostly caused by the die-cutting knife, such as severe wear and tear on certain parts of the die-cutting knife. At this point, it is necessary to replace the die-cutting blade.