Die-cut Process Control for Mobile Phone Screen Protectors

As we all know, screen protectors are an essential part of electronic devices such as mobile phones, cameras, and tablets. Before they are shipped, a layer of screen protector is applied to protect the screens of these products.

The transparency, smoothness, and cleanliness of the screen protector affect the consumer's impression of the electronic device. A high-quality screen protector can also enhance the overall appearance of the product. Therefore, the die-cutting factory has strict process control for the production of screen protectors.

Selection of Screen Protector Materials

When producing screen protectors, several factors should be considered in material selection. Firstly, materials should meet customer requirements and be suitable for printing and die-cutting. For example, they should have good scratch resistance, good ink adhesion, and prevent ink smearing.

Control of Production Environment

There are two key factors to control the quality of screen protectors: avoiding scratches and dirt. To meet these requirements, a die-cutting factory must have a well-controlled production environment. The factory is equipped with a separate dust-free clean room for screen protector production. A dust-free clean room, also known as a clean room or cleanroom, is a specially designed room that excludes particles, harmful air, bacteria, and other pollutants within a certain space. It maintains specific parameters such as temperature, cleanliness, pressure, airflow velocity and distribution, noise, vibration, lighting, and electrostatic control. Depending on the production needs, the cleanliness of the clean room can be classified into different levels, such as Class 100, Class 1,000, Class 10,000, Class 100,000, and Class 300,000.

In the dynamic situation within a dust-free clean room, the operator is the main source of bacteria and dust. Therefore, before entering the clean room, operators must wear clean suits and be showered with clean air for 15 seconds in an air shower room to remove any dust particles attached to their clothes.

Control of Printing Process

Most plastic films, such as polyolefin films, are non-polar polymers with low surface tension, usually around 29-30mNm. It is known that if the surface tension of an object is lower than 33mNm, known inks and adhesives cannot adhere firmly to it. Therefore, the surface of the screen protector needs to undergo corona treatment before printing. The corona power is typically set at 4.0W, and the speed is 30m/min. After corona treatment, the screen protector should be printed within 5 minutes. If more than 10 minutes pass, corona treatment needs to be repeated before printing.

During the printing process, friction between the screen protector material and the impression roller can cause surface scratches. Therefore, a soft and clean material is used to cover all contact points with the screen protector. Before die-cutting, the rotation of the impression roller should be checked to ensure its flexibility. Any foreign objects on the impression roller can also cause scratches on the screen protector. Therefore, the impression roller should be wiped with alcohol using a clean cloth before the die-cutting process to ensure its cleanliness and absence of foreign objects.

Die-cutting Process for Screen Protectors

After printing, the screen protectors need to be die-cut using a rotary die-cutting machine. During the die-cutting process, it is important to avoid scratches and ink separation. Ink separation refers to the phenomenon where the ink layer at the edge of the product should be complete and smooth, but there are partial areas with missing ink.

The main cause of ink separation during die-cutting is insufficient adhesion between the ink and the screen protector. This can cause the ink layer to separate from the screen protector, resulting in a serrated edge. Therefore, the adhesion of the ink should be checked after printing to ensure it is firm before die-cutting. Excessive thickness of the ink layer can also lead to ink separation.

There are multiple reasons for scratching during the die-cutting process. The most common one is uneven rotation of the pressure roller, causing relative sliding and scratching between the material and the roller. Before die-cutting, the rotation of the pressure roller should be checked to ensure smooth operation. Any foreign objects on the pressure roller can also cause scratches on the screen protector, so it should be wiped with alcohol using a clean cloth before die-cutting to ensure cleanliness and absence of foreign objects.

The shape of the screen protector is usually designed based on customer requirements, especially the size and shape of the screen of their mobile phone. Typically, it is a rectangular shape with rounded corners and features a handle in the lower right corner. The handle is printed on the back and covered with a layer of PET film, making it convenient for customers to install and for consumers to remove the screen protector from the screen. Various shapes of screen protectors are die-cut using circular blades, and more complex designs may require multiple blades. For example, screen protectors with handles require two circular blades: one for cutting the handle and the other for the overall shape.

Packaging Process Control for Screen Protectors

After die-cutting, the screen protectors are usually in a roll form. They are then cut into individual pieces and packaged in sets of 500. The screen protectors are wrapped with stretch film and then placed in plastic bags for packaging. Cleanliness is a crucial factor during packaging, so operators are required to wear finger cots for manual handling. For example, for a screen protector product that requires manual application of the handle, operators need to accurately place the handle on the sticky surface (the inside) of the screen protector, ensuring cleanliness and the absence of foreign objects. All these processes are carried out in a dust-free clean room.

Mobile phone screen protectors may seem simple, and the production process may not be complicated, but each step requires strict attention to cleanliness and avoiding bending and scratching the screen protector. It is these details that determine the quality of the product.