Some knowledge for face shields

face visor

Why should we need to wear a face shield?

 The new coronavirus can be transmitted through droplets. In addition to being inhaled into the mouth, the droplets can cause viral infections. The bulbar conjunctiva of the eyes can also cause virus infections. Windproof glasses can effectively prevent droplets from splashing. Infection of the virus into the eyes, and wearing ordinary glasses is also an effective way to prevent the spread of droplets. However, the interference of fog on the lens is very obvious, and the lens is prone to fog, which may affect the line of sight and pose a safety risk.

Our face is one of the most vulnerable parts of the human body. Anything that harms the face can easily damage our eyes, mouth, nose, and other sensitive parts. Therefore, it is necessary to wear a face shield when performing potentially dangerous tasks. Anti-fog and splash-proof visor is a kind of personal protective equipment used to protect part or the entire face of the wearer from danger. Face visors are often used in industrial production, medical and health, police and military, construction industry, scientific research experiment, and many other fields. In medical applications, they are mainly used for medical procedures that may expose medical staff to blood or other infectious fluids. In the current epidemic, face shields are mainly used to protect the face and avoid contact with potentially infectious substances.


What is included with the face shield?

Basically, it has 2 parts for a standard face shield: the protective lens and the fixed part which is to make the face shield fixed to your head.

The lens is plastic which can be PET or PC material.

The fixed part can be various styles: Elastic band with a sponge, bracket with elastic string, eyeglasses frame or anti-drop ear hook, etc.


What materials are normally used for the lens of the face shield and their features?

Normally we use APET,  PET, PETG, and PC for making the lens of the face visor, hereunder are their features:

  1. APETfilm: high definition, double-sided anti-fogging, can be printed, conventional   double-sided laminating
  2. PET film: high definition, double-sided anti-fogging, double-sided laminating, can be printed, high-temperature resistance above 120 degrees, not easy to deform
  3. PETG film: high definition, good flexibility, food-grade, double-sided anti-fog.
  4. PC film: high definition, good flexibility, food-grade, anti-fogging on both sides


How to choose a good face shield?

 For a face shield, the main part is the lens, so how to choose a good lens?

The main index of anti-fog visor film is optical performance, which directly affects the subjective experience and feeling of the wearer. If the optical performance does not meet the requirements, the wearer will have blurred vision, dizziness, ghosting, etc., which will affect normal use. Optical quality requirements: the lens should be free of streaks, bubbles, waves or other obvious defects that may damage its optical quality. In addition, a special requirement for lens anti-fogging is put forward: According to the specified method, the sample should not fog at least within 8 seconds.


Why does the anti-fog film have no anti-fog effect?

Generally speaking, indoor air humidity is greater than outdoor air humidity. At low temperatures, the air will condense into smaller particles that adhere to the lens or around the lens. When encountering higher temperature air, the small solid water vapor particles will liquefy or evaporate, which will cause the lens to fog and affect the line of sight. In winter, the temperature difference between indoor and outdoor is extremely large, and this environment produces not only fog but also frost. Frost is solid, similar to snow. It takes a certain amount of time for the frost on the lens to dissipate. This process is also called: slow frost. In fact, this phenomenon is very common. In winter, many drivers need to slow frost on the windows or front windshield. This is the same principle as the slow frost on lenses.




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