What are the characteristics of release films? Release films are functional films with low surface adhesion, whose core function is to "temporarily support and protect adhesive materials (such as adhesive tapes, stickers, protective films)". After processing, they can be easily peeled off without leaving residue and are widely used in electronics, packaging, medical, new energy, and other fields. Their characteristics revolve around four dimensions: "release performance, physical properties, chemical stability, and application adaptability". Different types of release films (such as PET release films and PE release films) have varying characteristics, but their core commonalities and unique features can be clearly distinguished: 1. Core commonalities: Regardless of the material or application scenario, all release films share the following four core commonalities, which form the basis for their "easy peeling and no residue" function: 1. Low surface adhesion: The core functional attribute of release films stems from their "low surface energy, making it difficult for adhesive materials to adhere". Specifically, this manifests as: controllable peeling force: The peeling force (the force required for peeling, measured in N/25mm) is a core indicator, which can be adjusted through surface coating. The conventional range is 0.5-50N/25mm (for example, "light release films" used in the electronics industry have a peeling force of 0.5-5N/25mm, facilitating rapid peeling; "heavy release films" used in the packaging industry have a peeling force of 15-50N/25mm, preventing detachment during transportation); no residue peeling: After peeling, there is no residue of release film on the surface of adhesive materials (such as glue and ink), which relies on the "low migration" of surface coatings (such as silicone oil and fluorine) - the coating molecules firmly adhere to the film substrate surface, without undergoing chemical reactions or migration with adhesive materials; consistent peeling: The peeling force deviation of the same batch of release films is ≤10% (for example, if the average peeling force of a batch of release films is 10N/25mm, the deviation for a single sheet does not exceed ±1N), avoiding damage to adhesive materials due to uneven peeling force (such as tearing during the peeling of electronic adhesive tapes).
2. Excellent physical and mechanical properties: The release film, suitable for processing and transportation, must withstand external forces during processes such as die-cutting, lamination, and winding. Therefore, it possesses characteristics of high strength, puncture resistance, and tensile resistance: high tensile strength: longitudinal (MD) tensile strength ≥150MPa, transverse (TD) tensile strength ≥100MPa (taking PET release film as an example), capable of withstanding the tension during winding (e.g., when the coil diameter is 1 meter, the tension can reach 500N without film breakage); puncture resistance and tear resistance: puncture strength ≥30N (tested with a puncture needle to simulate contact with sharp objects during processing), tear strength ≥50kN/m (to avoid coil breakage due to tearing during die-cutting); good dimensional stability: low thermal shrinkage (baked at 120℃ for 30 minutes, longitudinal shrinkage rate ≤1.5%, transverse ≤1.0%), ensuring no dimensional deformation during processing (such as high-temperature lamination) that could lead to positioning deviation of viscous materials (e.g., during the lamination of new energy battery electrode sheets, shrinkage of the release film can cause electrode sheet displacement).
3. Strong chemical stability: The release film suitable for multiple scenarios needs to be exposed to environments such as "glues, solvents, high temperatures, acids, and alkalis". Therefore, it possesses excellent chemical resistance and weatherability: solvent resistance and acid-alkali resistance: the surface coating (such as silicone oil, fluorine) is insoluble in common solvents (such as alcohol, acetone, toluene), and it is non-corrosive and non-soluble when exposed to weak acids and alkalis (pH 4-10) (for example, the performance of release film used in the medical industry remains unchanged after contact with disinfectant); high and low temperature resistance: the temperature range of conventional release film is **-40℃-150℃** (special types such as PI release film can reach -200℃-300℃), it does not melt or decompose at high temperatures (such as bonding at 120℃), and it does not become brittle or exhibit abnormal peel force at low temperatures (such as transportation at -40℃); anti-aging property: after long-term exposure to the air (such as storage for 6 months), the peel force, tensile strength, and other indicators change by ≤5%, with no yellowing or coating peeling (to avoid the inability to peel off sticky materials due to aging).
4. High surface flatness: To ensure bonding accuracy, the release film needs to be "tightly fitted and bubble-free" with the adhesive material. Therefore, it has extremely low surface roughness and excellent flatness: surface roughness (Ra) ≤ 0.1 μm. When tested with an atomic force microscope (AFM), the surface shows no obvious protrusions or depressions, and bubbles will not form during bonding due to uneven surface (such as in the bonding of OCA optical adhesive in the electronics industry, where bubbles can cause display anomalies). Good thickness uniformity: the thickness deviation of the entire roll of release film is ≤ 3% (for example, for a 50 μm thick PET release film, the thickness deviation of a single sheet does not exceed ±1.5 μm), avoiding pressure deviations during die-cutting due to uneven thickness (such as when die-cutting electronic adhesive tape, where thick areas may not be cut through and thin areas may be cut through).
II. Unique Characteristics by Material: Different substrates are suitable for different scenarios. The substrate of release film determines its core characteristics (such as temperature resistance, strength, and cost). Common substrates include PET (polyethylene terephthalate), PE (polyethylene), PP (polypropylene), and PI (polyimide). The unique characteristics of each material are as follows:
Substrate Type Unique Features Typical Application Scenarios PET Release Film (Most Commonly Used) 1. Balanced Comprehensive Performance: High Strength (tensile strength ≥150MPa), Moderate Temperature Resistance (-40℃-150℃), Medium Cost; 2. Transparent/Color-displayable: Transparent PET release film has a light transmittance of ≥90% (suitable for optical scenarios), and can also be made white or black (suitable for shading scenarios); 3. Easy to Process: Can be die-cut, printed, and coated (such as aluminum plating to enhance barrier properties), suitable for complex processing needs. Electronics Industry (OCA Optical Adhesive Bearing, FPC Flexible Circuit Board Protection), Packaging Industry (High-end Gift Packaging), New Energy Industry (Lithium Battery Tab Protection) PE Release Film 1. Good Flexibility: Shore Hardness ≤50D, can be bent and folded (such as fitting curved workpieces), not prone to breakage; 2. Low Cost: Raw material price is only 1/2-2/3 of PET, suitable for low-cost, disposable scenarios; 3. Excellent Low Temperature Resistance: Remains soft at -60℃, no brittle fracture (suitable for cold chain packaging); 4. Disadvantages: Poor Temperature Resistance (≤80℃), Low Strength (tensile strength ≤50MPa), prone to stretching and deformation. Packaging Industry (Food Packaging, Express Bag Lining), Medical Industry (Disposable Medical Tape Bearing), Daily Necessities Industry (Replacement for Sanitary Napkin Release Paper) PP Release Film 1. Strong Chemical Resistance: Resistant to strong acids and alkalis (pH 1-14), resistant to organic solvents (such as gasoline, diesel), suitable for chemical scenarios; 2. Low Density (0.9g/cm³): 30% lighter weight than PET at the same thickness, reducing transportation costs; 3. Heat Sealable: PP material can be heat sealed (heat sealing temperature 120-150℃), suitable for scenarios requiring sealing; 4. Disadvantages: Low Temperature Brittleness (prone to brittle fracture below -20℃), Poor Dimensional Stability (thermal shrinkage rate higher than PET). Chemical Industry (Adhesive Packaging), Medical Industry (Medical Catheter Packaging), Automotive Industry (Automotive Interior Tape Bearing) PI Release Film (High-end Type) 1 Excellent temperature resistance: Long-term temperature resistance up to 260℃ and short-term temperature resistance up to 300℃ (suitable for high-temperature processing scenarios); 2. High strength: Tensile strength ≥250MPa, puncture strength ≥80N, suitable for high-strength processing; 3. Radiation resistance: Can withstand ultraviolet rays and γ-rays (suitable for medical sterilization scenarios); 4. Disadvantages: High cost (5-10 times that of PET), poor flexibility (prone to breaking), limited to high-end scenarios. Aerospace (protection of high-temperature components), semiconductor industry (wafer cutting protective film carrier), medical industry (high-temperature sterilization equipment packaging). 3. Exclusive characteristics classified by surface coating: Determines the difference in release performance The "release performance" of release films is determined by the surface coating, with common coatings including silicone oil, fluorine, and silicone-free (such as nano-coating). The exclusive characteristics of different coatings directly affect their application scenarios (such as compatibility with silicone rubber and environmental friendliness): 1. Silicone oil release film (accounting for over 80%): Cost-effective and preferred. Exclusive characteristics: Wide range of adjustable release force: From 0.5N/25mm (light release) to 50N/25mm (heavy release), suitable for most viscous materials (such as acrylic adhesive and rubber adhesive); Low cost: Silicone oil coating materials are cheap, and the processing technology is mature (such as roll coating and spray coating), with the whole film cost only 10%-20% higher than the substrate; Good compatibility: Can be coated on various substrates such as PET, PE, PP, and has good transparency (transparent silicone oil release film has a light transmittance of ≥88%); Disadvantages: Silicone oil may migrate (especially low molecular weight silicone oil), contaminating viscous materials (such as affecting the light transmittance of optical adhesives), and is not suitable for silicone-based viscous materials (silicone oil and silicone rubber can react chemically, resulting in abnormal peel force).
Typical applications: electronic tape carrier, lithium battery separator protection, and adhesive release layer for packaging.
2. Fluorine-based release film (high-end type): compatible with silicone and precision applications. Unique features: extremely low surface energy: surface energy ≤ 20mN/m (silicone oil release film surface energy 30-35mN/m), suitable for silicone-based adhesive materials (such as silicone tape, silicone protective film), with no residue or reaction upon peeling; no migration: fluorine molecules are firmly bound to the substrate (chemical bond), and will not migrate to the surface of adhesive materials, suitable for precision applications (such as semiconductor chip protection, optical adhesive bonding); excellent temperature resistance: fluorine coating temperature resistance ≥ 200℃ (silicone oil coating temperature resistance ≤ 150℃), suitable for high-temperature processing (such as FPC high-temperature lamination); disadvantages: high cost (3-5 times that of silicone oil release film), narrow adjustable range of release force (only 1-10N/25mm), limited to