Do film labels always drop ink and have poor image quality? Master 6 practical techniques to master them easily!

Do film labels always drop ink and have poor image quality? Master 6 practical techniques to master them easily!

In the production process of film-based self-adhesive label printing, uneven printing colors, poor image texture, and ink peeling and ink shedding are common quality issues. Unlike paper-based self-adhesive labels, film materials have smooth surfaces and poor adsorption, making ink hard to adhere and drying and curing more challenging. If the process is not properly controlled, issues such as ink fading after wiping, lamination and ink loss, multicolor printing smudges, and uneven ink layer thickness can occur. This not only affects the label's appearance and texture but also leads to large-scale scrapping of defective products, increasing production costs and delaying delivery.

Many printing companies, when faced with issues like ink drop or poor printing results, often blindly adjust printing speed and stack inks, which not only fails to solve the problem but also increases production losses. In fact, the core reasons for ink shedding and poor results in film label printing mainly focus on incompatible ink selection, improper ink layer control, inadequate drying and curing, and non-standard process operations. Based on the characteristics of film printing processes, this article shares some practical methods to help everyone fundamentally solve the problems of ink dropping and poor image quality in film label printing.

Select dedicated matching consumables to avoid mismatches between ink and substrate

The surface properties and composition of film adhesive materials differ significantly from those of ordinary printing paper. General-purpose inks are difficult to adapt to film printing processes, which is the primary cause of ink shedding and poor adhesion. There are many types of inks on the market, but only specialized printing inks developed specifically for film adhesive materials can adapt to the surface properties of the film and ensure strong ink adhesion.

During production, it is recommended to use inks specifically designed for film printing whenever possible, combined with additives such as varnish, thinners, and curing agents that match the system. It is strictly forbidden to mix consumables of different systems and models. If the ink, varnish, and film substrate are mismatched, the resin in the ink cannot bond with the film surface. Even if the initial printing seems normal, issues such as ink layer peeling, peeling, and discoloration after wiping may occur, completely affecting the quality of the finished product. Dedicated supporting consumables enable precise adaptation between ink and substrate, avoiding print quality defects caused by compatibility at the source.

Matches the substrate coating characteristics to enhance ink layer adhesion

The vast majority of film label materials on the market have special coatings on their surfaces. The function and composition of the coating directly determine the ink's adhesion performance. This is the key reason why many manufacturers still experience ink dropping even when selecting the correct ink products.

For coated film materials, it is necessary to strictly select suitable specialized inks based on the coating's function and material characteristics to ensure that the ink resin matches the coating resin's properties. When ink and coating are precisely matched, the resin components inside the ink tightly bond with the film-coating resin, forming a stable adhesion structure. Even if the ink is not fully dried and cured, the ink layer will not peel or shift, greatly enhancing the adhesion and stability of the ink layer and fundamentally solving the ink shedding problem of coating film labels.

Scientifically controlling ink layer thickness and skillfully using overprinting technology

Some high-end label products have high requirements for ink thickness and color saturation, requiring a thick and full ink layer to achieve printing effects. However, film materials have poor breathability. If the single-layer ink layer is too thick, the inside may not dry thoroughly, and the outside may be dry and wet inside. During subsequent storage and use, issues such as overall ink loss, localized ink dropping, and ink layer cracking are common, along with darkened colors and rough print textures.

For printing products with high ink layer requirements, the optimal solution is to use screen printing and gravure printing processes, which can precisely control ink thickness and ensure uniform drying. For ordinary printing factories without dedicated equipment, a double-layer printing process using same-color inks can be used to replace single-pass printing with thick ink layers.

The specific procedure is: first print a thin and even layer of ink, wait until the base ink is completely dry and cured, then perform a second overprinting. By stacking thin ink twice, it not only meets the product's requirements for ink thickness and color saturation, but also avoids the problem of incomplete drying of thick ink layers, effectively improving ink layer durability, making printed images more uniform and delicate, and thoroughly solving issues of ink drop and poor image quality caused by thick ink.

Precisely controls drying speed to avoid abnormal ink drying

Unbalanced ink drying speed is one of the main causes of ink shedding and printing defects on film labels. If the drying speed is too slow, the ink layer will accumulate and stick, and the ink layer will not cure or fall off; If the drying speed is too fast, it can easily cause ink layer cracking, uneven color, and image discoloration, which seriously affects printing quality.

In daily production, it is essential to strictly control ink quality, avoiding the use of expired, spoiled, or layered inks, as such inks have unstable drying properties and are prone to quality issues. Second, the drying speed can be flexibly adjusted based on workshop temperature and humidity, printing speed, and ink layer thickness. If the workshop is humid, cold, and the ink dries slowly, a special desiccant can be added to precisely improve drying efficiency and prevent the ink layer from peeling off before it dries. At the same time, the proportion of desiccants added is strictly controlled to prevent new issues such as changes in ink properties and ink layer cracking caused by excessive addition, ensuring stable and balanced ink drying speed.

Ensuring the performance of curing equipment and strengthening ink curing results

Currently, film label printing mostly uses UV ink curing technology, which lacks sufficient curing energy and is incomplete, posing a hidden risk of ink dropout. Many printing companies neglect equipment maintenance for a long time, resulting in aging UV lamps, dust accumulation and clogs in equipment, and reduced curing energy. Although labels appear fully printed, the ink layer inside is not fully cured, leading to frequent ink drops and poor wear resistance during subsequent use.

Therefore, it is necessary to establish a regular equipment operation and maintenance mechanism, regularly clean lampshades, conveyor belts, and other components of UV curing equipment, and promptly replace aging or severely degraded UV tubes to ensure sufficient and stable curing energy output. At the same time, professional testing equipment and test papers are regularly used to check the energy parameters and operating status of the UV curing equipment. Based on the test data, the ink layer thickness and printing speed are flexibly adjusted to ensure the ink fully absorbs curing energy, achieving thorough curing, maximizing ink adhesion and wear resistance, and ensuring stable print quality.

Strictly controls the speed and process of multicolor printing to prevent batch ink drops and registration defects

Multi-color multi-color printing in thin films is a critical and challenging process in label printing. Compared to single-color printing, multi-color overprinting has shorter ink layers and curing intervals, making it easy to encounter issues such as ink layer adhesion, incomplete drying, misalignment, and blurred images. It is also one of the processes with high rates of batch ink dropout and defective products. In actual production, most printing companies blindly increase printing speed in pursuit of capacity, neglecting the characteristics of film substrates that lack penetration and dry slowly. Too fast printing speed causes the first color ink layer to not fully cure and dry, and the subsequent color ink to directly overlap and cover. This not only causes insufficient interlayer adhesion and large-scale ink loss and color loss, but also leads to color contamination, misalignment of registration accuracy, blurred graphics and text, and other quality issues, resulting in large batches of material scrap and seriously affecting production efficiency.

For multi-color label printing on thin films, strict control of printing speed and process intervals is required. Each color sequence should allow sufficient drying and UV curing time to ensure the single-layer ink layer is completely dry and adhesion meets standards before proceeding to the next color overprinting. At the same time, the speed can be fine-tuned according to color depth and ink layer thickness; the speed of the thick ink layer for dark colors can be appropriately reduced, while the thin ink layer for light colors can be moderately accelerated. Standardized printing rhythms can effectively eliminate issues such as ink layer adhesion, interlayer detachment, color mixing, and registration deviations, greatly improving the clarity, color uniformity, and product pass rate of multi-color labels, thereby avoiding mass production losses at the process level.

In summary, common issues such as ink dropping, poor image quality, uneven colors, and poor finish quality in film-based label printing are not caused by single equipment or material failures, but are comprehensive process problems caused by inadequate control in consumables adaptation, ink layer control, drying and curing, equipment operation and maintenance, and process operations. Only by meticulously and standardizing every process can quality defects be completely avoided.