Differentiated applications of PE and CPP self-adhesive films in glass screen printing processes

The unique characteristics of glass screen printing dictate highly specific requirements for the protective film, with each requirement directly impacting the yield rate of the finished product. First, adhesion stability is fundamental. The protective film must adhere tightly to the glass surface, free of bubbles, peeling, and misalignment. Especially during screen printing, the pressure of the squeegee acts on the film surface; if the adhesion is weak, the film can easily shift, resulting in blurred or misaligned patterns, affecting processing accuracy. Second, the protective film surface must possess extremely high cleanliness and smoothness, free of impurities, crystal points, and orange peel texture. This prevents defects such as pinholes and scratches from appearing in the screen printed pattern due to surface flaws. Simultaneously, a smooth surface reduces friction with the squeegee, lowering the risk of squeegee wear and pattern smudging. Furthermore, temperature and solvent resistance are core requirements. The screen printing process uses inks and thinners, so the protective film must have good solvent resistance, not reacting with the inks or thinners, and not exhibiting swelling, discoloration, or damage. Additionally, some screen-printed sections require a drying process; the protective film must withstand certain drying temperatures, maintaining its shape and not shrinking, softening, or peeling off under high temperatures. Finally, residue-free peeling is a crucial finishing requirement. After screen printing, the protective film must peel off easily, leaving no residue or marks, without damaging the glass surface gloss, and without affecting subsequent ink curing and glass processing. This is also a vital aspect of ensuring the quality of the finished glass product. In addition, the protective film must possess suitable flexibility and puncture resistance to withstand minor impacts and friction during screen printing, preventing film breakage that could damage the glass surface. It must also be easy to cut, apply, and peel off, improving production efficiency.

PE self-adhesive film, one of the most widely used protective film types in glass screen printing, is made of polyethylene as the base material and produced through a three-layer co-extrusion process. With its advantages of being soft and easy to apply, moderately priced, and leaving no residue after peeling, it is suitable for most conventional glass screen printing scenarios. The loosely arranged molecular chains and low crystallinity of PE self-adhesive film result in a soft texture and excellent flexibility, allowing it to adhere tightly to glass surfaces of varying flatness. It is particularly suitable for screen printing protection of curved and irregularly shaped glass. It is less prone to air bubbles during application, and even with minor imperfections on the glass surface, its flexibility enables seamless coverage, effectively preventing film damage caused by squeegee pressure during screen printing. In terms of surface properties, PE self-adhesive film undergoes special treatment, resulting in a high degree of surface cleanliness and freedom from impurities, meeting the smoothness requirements of conventional screen printing. Simultaneously, its moderate surface tension prevents reaction with screen printing inks, effectively protecting the ink pattern from contamination.

In terms of temperature and solvent resistance, PE self-adhesive film has a moderate temperature range, typically withstanding temperatures from -10℃ to 60℃. It is suitable for most conventional screen printing processes that do not require high-temperature drying, such as screen printing on architectural glass and ordinary household appliance glass. Its solvent resistance meets the requirements of conventional inks and thinners, without issues such as swelling or discoloration. Furthermore, the adhesive strength of PE self-adhesive film can be flexibly adjusted, with products available from ultra-low to medium-high adhesion. Ultra-low adhesion PE self-adhesive film is suitable for screen printing on surface-sensitive glass such as optical glass and high-precision electronic glass, leaving no residue upon peeling and maximizing the protection of the glass surface's smoothness. Medium-high adhesion PE self-adhesive film is suitable for screen printing on ordinary flat glass and tempered glass, providing a strong bond and effectively resisting squeegee pressure and minor friction during the screen printing process. Simultaneously, PE self-adhesive film has a low processing threshold, can be flexibly cut to fit glass dimensions, and has a relatively low cost, making it suitable for large-scale, conventional glass screen printing production. It is one of the most cost-effective choices and is widely used for screen printing protection in architectural curtain wall glass, ordinary household appliance panel glass, and civilian glass. It is worth noting that PE self-adhesive film has relatively weak puncture resistance and stiffness. It is easily damaged by sharp objects during screen printing, making it unsuitable for applications requiring extremely high protective strength.

CPP self-adhesive film, made from cast polypropylene using a casting process, is a non-oriented, non-stretch film with tightly packed molecular chains. Compared to PE self-adhesive film, it possesses higher stiffness, temperature resistance, and puncture resistance. These advantages make it ideal for mid-to-high-end, high-requirement glass screen printing applications, especially those requiring secondary processing. CPP self-adhesive film has excellent stiffness, resisting wrinkles and deformation after application, maintaining a smooth surface. It is particularly suitable for high-precision screen printing processes, such as electronic glass and high-end appliance panel glass, effectively preventing misalignment and blurring of the printed pattern due to film wrinkles, thus improving printing accuracy. After undergoing corona treatment, its surface exhibits superior cleanliness and smoothness compared to PE self-adhesive film. Free from crystal points and scratches, it meets the stringent requirements of high-end screen printing for film surface quality. Furthermore, its high surface tension allows for excellent isolation with the ink, further ensuring the clarity and integrity of the screen-printed pattern.

In terms of temperature and solvent resistance, CPP self-adhesive film is particularly advantageous. Its temperature resistance range is -10℃ to 120℃, with a softening point of approximately 140℃. This makes it suitable for high-temperature drying processes after screen printing, such as screen printing on high-end household appliance glass and automotive glass. During high-temperature drying, CPP self-adhesive film will not shrink, soften, or peel off, nor will it yellow or discolor, providing stable protection for the glass surface and the screen-printed pattern. Simultaneously, CPP self-adhesive film exhibits stronger solvent resistance, resisting corrosion from various high-strength solvents. It is suitable for screen printing processes using special inks, such as abrasion-resistant and high-temperature-resistant inks, without reacting with the ink or experiencing swelling or breakage. Furthermore, CPP self-adhesive film exhibits significantly superior puncture and tear resistance compared to PE self-adhesive film. It effectively resists impacts from sharp objects and squeegee friction during screen printing, preventing film breakage and glass surface damage. This makes it suitable for scenarios requiring high protective strength, such as screen printing protection for automotive glass, electronic glass, and high-end art glass.

CPP self-adhesive film also possesses excellent moisture-proof and oxygen-barrier properties, effectively isolating moisture and impurities in the air during screen printing, protecting the cleanliness of the glass surface. Simultaneously, it is odorless, tasteless, and hygienic, making it suitable for screen printing protection in specialized fields such as food-grade glass and medical glass. However,

CPP self-adhesive film has relatively poor flexibility, making it difficult to apply to curved or irregularly shaped glass, prone to problems such as peeling and loose adhesion. Its cost is also higher than PE self-adhesive film. Therefore, it is not suitable for routine, large-scale glass screen printing production and is mainly used in mid-to-high-end, high-requirement screen printing scenarios, such as screen printing protection for electronic glass covers, automotive windshields, and high-end appliance panel glass.

In summary, the requirements for the adhesion stability, surface cleanliness, temperature and solvent resistance, and residue-free removal of protective films in glass screen printing determine the differentiated application scenarios of PE and CPP self-adhesive films. PE self-adhesive films, with their advantages of being soft and easy to apply, moderately priced, and leaving no residue after removal, dominate routine, large-scale glass screen printing scenarios, suitable for most glass screen printing needs that do not require high-temperature drying and have low requirements for protective strength. CPP self-adhesive films, on the other hand, with their advantages of high stiffness, high temperature resistance, and high puncture resistance, focus on mid-to-high-end, high-requirement glass screen printing scenarios, suitable for high-precision screen printing needs requiring high-temperature drying or special inks. In actual production, it is necessary to combine the process requirements of glass screen printing, glass type, and finished product quality requirements to rationally select either PE or CPP self-adhesive films to ensure both the stability and efficiency of the screen printing process and maximize the quality of the finished glass product, achieving a dual guarantee of protection and processing precision. Meanwhile, with the continuous upgrading of glass screen printing technology, PE and CPP self-adhesive films are also being continuously optimized. Through material modification and process innovation, performance adaptability is further improved to meet more high-end and special glass screen printing protection needs.