Question: For AF(Anti-Fingerprint) coating, how much is the qualified water contact angle?

Answer:

AF (Anti-Fingerprint) coating, also known as oleophobic coating, is a high-performance functional coating based on perfluoropolyether materials, which is widely used on optical glass, display panels, touch screens and other optical components. Its core function is to endow the glass surface with excellent hydrophobic and oleophobic properties, effectively reducing the adhesion of fingerprints, oil stains and water stains, and achieving an easy-to-clean effect. The water contact angle (WCA) is the most core and authoritative quantitative index to evaluate the performance and qualification of AF coating, and its industry standards and testing principles are clearly defined as follows:

 

1. Industry Qualification Standards for Water Contact Angle

 

The water contact angle refers to the angle between the tangent of a static water drop and the glass surface, which directly reflects the surface energy of the coating: the larger the angle, the lower the surface energy, and the better the hydrophobic and anti-fingerprint performance. The industry's unified qualification standards are divided into three levels:

 

- Basic Qualified Standard (Entry Level): For general consumer electronics, daily display glass and other conventional applications, the initial water contact angle of qualified AF coating must be ≥ 105°. This is the minimum threshold to ensure basic anti-fingerprint and easy-to-clean performance, which can effectively reduce the adhesion of daily fingerprints and oil stains, and is the most widely used standard in the market.

- High-Quality Standard (Mid-to-High End): For automotive displays, industrial touch screens, outdoor display screens and other medium and high-end application scenarios with high durability requirements, the qualified standard is ≥ 110°. This level of coating has lower surface energy, better hydrophobic and oleophobic effects, and can maintain stable performance in complex environments such as high temperature and high humidity.

- Premium Flagship Standard (Top Level): For high-end smart phones, professional optical instruments, medical display glass and other top-level products, the strictest requirement is ≥ 115°. This level of AF coating has ultra-low surface energy, excellent anti-fouling performance, and can achieve a "water drop rolling without leaving a trace" effect, which is the highest standard in the industry.

 

2. Performance Grading and Unqualified Judgment

 

To help customers intuitively judge the quality of AF coating, we have formulated a clear performance grading standard based on water contact angle:

 

- WCA < 90°: Hydrophilic surface, no anti-fingerprint effect, completely unqualified. This situation usually means that the coating is missing, failed or severely aged, and cannot meet any application requirements.

- 90° < WCA < 105°: Substandard AF coating, poor anti-fingerprint performance, unqualified. The coating has weak hydrophobic and oleophobic effects, fingerprints and oil stains are easy to adhere, and cannot meet the basic use requirements.

- 105° ≤ WCA < 110°: Qualified basic grade, with good anti-fingerprint and easy-to-clean performance, suitable for conventional consumer electronics applications.

- 110° ≤ WCA < 115°: High-quality mid-to-high end grade, with excellent hydrophobic and oleophobic performance, suitable for automotive, industrial and other harsh environment applications.

- WCA ≥ 115°: Premium flagship grade, with ultra-high performance, suitable for high-end optical products and professional instruments.

 

3. Testing Principle and Additional Durability Requirements

 

The water contact angle is tested by the static sessile drop method, which is the international standard testing method:

 

1. Drop 2-5μL of pure water on the surface of the AF coating to be tested, keep the glass horizontal and static.

2. Use a professional contact angle measuring instrument to capture the shape of the water drop, and measure the angle between the tangent of the water drop and the glass surface, which is the water contact angle value.

 

In addition to the initial water contact angle, a truly qualified AF coating must also pass the friction resistance durability test, which is an important indicator to distinguish low-quality and high-quality coatings:

 

- After 3000 times of standard steel wool friction (load 1kg), the water contact angle of qualified coating should still be ≥ 100°, ensuring long-term use without performance degradation.

- For high-end automotive and industrial grade coatings, it is required to maintain a water contact angle ≥ 105° after 5000-8000 times of friction, with extremely high durability.

 

4. Our Product Advantages

 

As a professional optical glass manufacturer, our AF coating products strictly follow the highest industry standards:

 

- All products have an initial water contact angle of ≥ 110°, and the flagship series reaches ≥ 115°, far exceeding the basic qualification requirements.

- All coatings pass the 5000 times steel wool friction test, and the water contact angle remains stable, ensuring long-term service life.

- We support customized coating solutions for different application scenarios, providing professional test reports and quality certificates for each batch of products.