Understanding Release Film in One Article

Release film refers to a distinguishable film on the surface of a thin film. After coming into contact with specific materials under limited conditions, the release film does not exhibit adhesiveness or only slight stickiness.

Release film involves applying silicone release agents to the surface of environmentally friendly materials such as PET, PE, and OPP films. This enables the film to exhibit extremely light and stable release forces when it comes into contact with various organic pressure-sensitive adhesives.

Different organic pressure-sensitive adhesives, such as hot melt adhesives, acrylic adhesives, and rubber-based pressure-sensitive adhesives, require different release forces from the release film. The release force is adjusted correspondingly based on the varying adhesive viscosity of the isolated product, ensuring an extremely light and stable release force during peeling.

Advantages of Release Film:

1. High transparency (light transmittance of over 90%).

2. Excellent heat resistance (melting point of 230-240°C).

3. Excellent electrical properties.

4. Chemical resistance.

5. Low density (0.83g/cc).

6. Good formability and processability.

7. Safety.

Classification of Release Film:

1. Based on different base materials, release films can be divided into PE release film, PET release film, OPP release film, and composite release film (combining two or more materials).

2. Based on release force, release films can be categorized as light release film, medium release film, and heavy release film.

3. Based on color, release films can be red, yellow, green, blue, or other colors of PET release films.

4. Based on surface treatment, release films can be classified as single-sided release film, double-sided release film, silicone-free release film, fluorine plastic release film, single-sided corona treatment, double-sided corona treatment, matte release film, matte release film, etc.

Single-sided Release Film:

HDPE (high-density polyethylene) release film: Used for sealing tapes and waterproof membranes.

LDPE (low-density polyethylene) release film: Used for packaging mechanical products, hot melt adhesive packaging, sanitary products (diapers), and anti-corrosion membranes.

BOPP (biaxially oriented polypropylene) release film: Used for sealing tapes, silent tapes, etc.

PET (polyethylene terephthalate) release film: Used for adhesive backing protection.

Double-sided Release Film: 

Used for foam tapes, transparent PET double-sided release film, UV-resistant isolation film (HDPE silver-coated film), and reinforced aluminum-coated base material BOPET for waterproofing membranes.

Application of Release Film in OCA Optical Adhesive:

OCA optical adhesive, also known as OCA optical transparent adhesive, is a type of optical double-sided adhesive tape where optical acrylic adhesive is made into a substrate-free form and bonded with two layers of release film.

The composition of OCA optical adhesive is as follows:

1. Upper release film and lower release film (referred to as light release film and heavy release film due to differences in release force with the optical adhesive). Both layers of release film used in OCA are optical-grade release films, providing much higher light transmittance than general release films. The upper release film (light release film) typically has a thickness of 50um or 75um, while the lower release film (heavy release film) comes in several different thicknesses, such as 75um and 100um.

2. Optical adhesive, primarily made of optical acrylic adhesive (or acrylic optical adhesive), can achieve a light transmittance of 99%. The thickness of the optical adhesive varies depending on its application, ranging from 75um to 250um.

3. In the OCA industry, Mitsubishi OCA has always been the industry standard. Therefore, the quality requirements for the matching release film used for Mitsubishi OCA are extremely high. The release film must be optical-grade, with no fluff or debris on the cut surface of the release film material. The overall release film surface must be free from dirt and foreign substances, scratches, and must have high cleanliness and smoothness.

Application of Release Film in AB Adhesive:

AB adhesive is a double-sided adhesive specially designed for the protection of tempered glass with one side (A-side) coated with silicone and the other side (B-side) coated with OCA optical adhesive. The OCA optical adhesive is bonded to the tempered glass, while the silicone (for automatic exhaust) is bonded to the surface of the mobile phone screen. Due to its high adhesive strength, during the coating process, AB adhesive manufacturers need to cover a layer of 50μm transparent PET release film on this adhesive layer to achieve isolation and protection. The dedicated release film for this kind of tempered glass AB adhesive requires excellent flatness, high cleanliness, high light transmittance, and stable release effect.