Common problems when printing PE film with gravure water-based ink

Date: Jan 17 2025 From: Star Color

Gravure water-based inks are an environmentally friendly type of ink that have been gradually emerging in recent years. Using water as the main solvent, they significantly reduce the volatilization of organic solvents. This not only decreases environmental pollution but also creates a healthier working environment for operators. In an era where environmental awareness is increasingly growing, the application of gravure water-based inks meets the demands of the times.

When PE films are combined with gravure water-based ink printing, this combination brings new opportunities and challenges to the packaging and printing industry. This printing method has been increasingly applied in the packaging of numerous industries such as food, daily chemicals, and electronics, providing a reliable solution for product packaging and protection.

Common Problems in Gravure Water-based Ink Printing on PE Films

(1) Poor Adhesion
When gravure water-based inks are used to print on PE films, poor adhesion is a troublesome issue. Specifically, the ink fails to adhere firmly to the surface of the PE film, causing the printed pattern to be prone to falling off, scratching, and color fading during subsequent use.
This situation mainly occurs because the surface tension of the PE film is relatively low. Without proper surface treatment, it is difficult for the ink to adhere to it. It is known that before printing, the surface tension of the PE film needs to reach above 38 dynes to ensure good ink adhesion. If the surface treatment of the film is inadequate, for example, if the corona treatment intensity is insufficient, the adhesion between the ink and the film will be greatly reduced.

(2) Color Deviation
Color deviation is another common problem. It makes the color of the printed product inconsistent with the expected effect, which may have an adverse impact on the visual effect of the product and the brand image.
In actual production, errors in the ink preparation process, such as inaccurate pigment proportions or uneven stirring during color mixing, can lead to color deviations in the ink itself. At the same time, the parameter settings during the printing process, such as printing speed, pressure, and ink transfer amount, also affect the final color presentation.

(3) Drying Difficulties
Water-based inks use water as the main solvent. Compared with traditional solvent-based inks, they have a slower drying speed, which is a major challenge in gravure water-based ink printing on PE films.
If the drying speed is too slow, the ink is likely to be insufficiently dried on the film surface, resulting in problems such as ink sticking and smudging, affecting the printing quality and production efficiency.
The performance and parameter settings of the drying equipment are key factors, such as hot air temperature, wind speed, and air volume. If the hot air temperature is too low or the wind speed is insufficient, the water cannot evaporate quickly, and the ink is difficult to dry. The ventilation conditions in the workshop are also important. Good ventilation helps accelerate the evaporation of water.

Solutions

(1) Improving Adhesion
To enhance the adhesion of gravure water-based inks on PE films, the following aspects can be considered. Firstly, in the film pretreatment stage, corona treatment of the PE film is an effective method.
Through corona treatment, the surface roughness and surface energy of the film can be increased, making the contact between the ink and the film closer, thereby enhancing adhesion. In actual operation, it is necessary to ensure that the intensity and time of the corona treatment are appropriate, so that the surface tension of the film reaches above 38 dynes.

Secondly, choosing the right ink is also crucial. The ink formulation should be fully considered, and binders with good adhesion should be selected. Attention should be paid to the dispersion degree of the pigments.
Well-dispersed pigments can be evenly distributed in the ink, making the contact between the ink and the film more uniform and enhancing adhesion. Zhongzhixing water-based inks have good adhesion on the surface of PE films, which benefits from their optimization of the ink formulation and improvement of the production process.

Finally, optimizing the printing process cannot be ignored. Controlling parameters such as temperature, humidity, and pressure during the printing process has an important impact on improving ink adhesion.
An appropriate printing temperature can make the ink flow and cure better, enhancing the adhesion to the film; suitable humidity can prevent the ink from drying too quickly or too slowly, ensuring the normal film formation of the ink; and reasonable printing pressure can ensure that the ink is fully transferred to the film surface, achieving a good adhesion effect.

(2) Precise Color Control
To achieve accurate color reproduction in gravure water-based ink printing on PE films, multiple aspects need to be controlled. Firstly, in ink color matching management, establishing a strict color management system is the key. When preparing the ink, high-precision electronic scales and color mixing equipment should be used to accurately weigh various pigments and additives to ensure the accuracy of the formulation.
The use of a computer color matching system can quickly and accurately calculate the required pigment proportions according to the preset color standards, greatly improving the efficiency and accuracy of color matching.

Secondly, the adjustment of printing parameters also plays an important role in color presentation. Parameters such as printing speed, pressure, and ink transfer amount directly affect the thickness and distribution of the ink on the film, and thus affect the depth and uniformity of the color. In actual production, these parameters should be reasonably adjusted according to the performance of the printing equipment and the characteristics of the ink. Reducing the printing speed can allow the ink more time to transfer to the film, increasing the ink layer thickness and making the color more vivid; appropriately increasing the printing pressure can improve the ink transfer effect and make the color more uniform.

Finally, color detection and correction are essential links. Professional color detection instruments such as spectrophotometers and color difference meters should be used to conduct real-time detection on printed samples, promptly detect color deviations, and correct them quickly.

(3) Accelerating Drying Techniques
To address the problem of slow drying speed of gravure water-based inks on PE films, the following measures can be taken to accelerate drying. Firstly, upgrading the drying equipment is an important step. Selecting efficient hot air drying equipment can increase the temperature, wind speed, and air volume of the hot air, accelerating the evaporation of water.

The use of auxiliary drying methods such as infrared drying and ultraviolet drying can be combined with hot air drying to further improve the drying efficiency. For example, infrared drying uses the thermal effect of infrared rays to quickly penetrate the ink layer and make the internal water evaporate rapidly; ultraviolet drying triggers a reaction of the photoinitiator in the ink through ultraviolet rays to achieve rapid curing.

Secondly, optimizing the workshop environment also helps accelerate ink drying. Maintaining good ventilation conditions in the workshop can timely discharge the volatilized water, reduce the humidity in the air, and create a favorable environment for ink drying. Controlling the temperature and humidity in the workshop within an appropriate range, generally, a temperature of 25℃ - 30℃ and a humidity of 50% - 60% are more suitable, which can make the ink drying speed in an ideal state.

Finally, adjusting the ink composition can also increase the drying speed. Adding an appropriate amount of drying agent to the ink can accelerate the evaporation of water and the curing reaction in the ink. Selecting the right solvent and adjusting the solvent evaporation speed can also affect the drying speed.

Appropriately increasing the proportion of more volatile solvents such as ethanol and isopropanol can accelerate the drying of the ink, but the proportion needs to be controlled to avoid affecting other properties of the ink.

Water-based Gravure ink printing on PE films brings environmental advantages to the packaging and printing industry, but it is also accompanied by a series of challenges. Problems such as poor adhesion, color deviation, drying difficulties, and uneven ink transfer need to be highly valued and actively addressed.

Through comprehensive control of aspects such as pretreatment processes, ink selection, printing parameter optimization, and workshop environment control, we can effectively solve these common problems and improve printing quality and production efficiency.