Common Films and Surface Treatment Methods for Self-Adhesive Labels
The commonly used film materials for self-adhesive labels can be divided into the following seven types:

(1) PVC Polyvinyl Chloride Film

It has good flexibility, shrinkage, and opacity. The processing and labeling performance of self-adhesive trademarks are good. It can be used outdoors for a long time and has strong resistance to chemical corrosion. However, its tear resistance is poor.

(2) PP Polypropylene Film

The characteristic of PP material is its excellent transparency. Transparent PP has a significant advantage among various films. There are two types of surface treatment for PP: corona treatment and coating. The vast majority of self-adhesive trademark face materials are processed by biaxial stretching, hence they are often referred to as BOPP. After treatment, the label face material is thin and tough, suitable for high-speed processing, die-cutting, and automatic labeling. Because of its good transparency, when a self-adhesive trademark is attached to a transparent container, it gives a feeling of no label.

(3) Cellulose Acetate Film

It has low strength and tear resistance but strong resistance to high temperatures and chemicals. It has high hardness and good printing performance. However, the labeling and processing performance of self-adhesive trademarks are average, and it is generally less used.

(4) PE Polyethylene Film

PE is known for its excellent flexibility and low cost. However, PE has the following disadvantages:
1.  The softness brings problems, restricting the processing and labeling of self-adhesive trademarks. The material must have a certain thickness.
2.  PE material that is not stretched has two types of surface treatment: corona treatment and coating.
3.  Poor transparency.
4.  It is prone to surface scratches, has low strength and tear resistance, and poor high-temperature and durability resistance. It is suitable for indoor self-adhesive trademarks.

(5) PRIMAX

It is a polyolefin film made by co-extrusion of PE and PP films and uniaxial stretching. The manufacturing method is to flow the two high-temperature melted plastics through the gap of a special die under pressure to form a very thin plastic sheet. This plastic sheet undergoes plastic deformation under the pressure and stretching of a metal roller in the direction of machine operation, achieving uniaxial stretching of the film material. The stretching speed and pressure are controlled to ensure the uniform thickness of the film material.

(6) PS Polystyrene Film

It has low strength, poor resistance to high temperatures and chemicals, average labeling and processing performance, and low cost.

(7) PET Durable Film

PET material has unique corrosion resistance, high tensile strength and tear strength, good high-temperature resistance, and durability. It is chemically and dimensionally stable, making it especially suitable for durable and outdoor self-adhesive trademarks. Since the inherent surface tension of the film material is lower than the surface tension required for the printing process of self-adhesive trademarks, the surface of the film must be treated in some way to ensure that the film can firmly accept ink. The surface tension of the film should be increased during printing. The commonly used film surface treatment methods are as follows:
1.  Printing treatment. In the production process of self-adhesive trademark films, a special process is used to improve the surface characteristics of the film through chemical treatment methods, thereby increasing the adhesion between ink and the film surface.
2.  Surface coating. A special coating is applied during the production of self-adhesive trademarks to improve the surface tension of the film.
3.  Corona treatment method. High-voltage electric charge is used to discharge to the surface of the film. Under the action of ionization, the surface of the film is roughened, the surface energy is increased, and the adhesion between the self-adhesive trademark film surface and the ink is enhanced.