Thin Film Coatings that Enhance Glass with Diverse Functions and Value

Glass is usually transparent and reflective, often causing glare or unwanted reflections. However, there are situations where anti-reflective or non-glare glass is preferred, such as when enjoying a scenic view through a window or viewing paintings and artworks in museums or galleries. In addition, there are special glass types that can reflect light like mirrors, control the inner temperature by blocking infrared rays (heat rays), or repel dirt and water. These unique properties are achieved by applying thin film coatings of various metals or compounds to the surface of the glass.
In this section, we will explore these coatings, commonly known as "thin film coatings."

Glass with a thin film coating that selectively transmits, reflects, or absorbs light at specific wavelengths is known as an optical filter.
Long pass filters allow long-wavelength light to pass through while reflecting or absorbing shorter wavelengths. An example of this is UV cut filters, which shield ultraviolet light while transmitting visible light at longer wavelengths. These filters are commonly used as protective covers for devices, preventing damage from UV rays.
Short pass filters, on the other hand, transmit short-wavelength light while reflecting or absorbing longer wavelengths. A typical example is IR-cut filters, which are used in digital cameras and smartphones as optical filters for image sensors. These filters shield infrared light while transmitting visible light at shorter wavelengths, ensuring the colors of captured images closely resemble what the human eye perceives.
A bandpass filter is an optical filter that transmits light only within a specific wavelength range while shielding all other wavelengths. These filters are used in devices such as pulse oximeters, where they selectively transmit and detect light at specific wavelengths.
These optical filters serve a wide range of applications across various industries.

Water and oil-repellent coatings are designed to prevent dirt and foreign matter from sticking by effectively repelling water and oil. Ordinary glass surfaces are hydrophilic, which allows water to spread easily, making them more prone to dirt buildup. However, when a water and oil-repellent coating is applied, the surface energy decreases, the contact angle increases, and water or oil droplets form a spherical shape, allowing them to slide off easily. This property not only helps keep the glass surface clean over time but also makes maintenance easier.
Anti-fingerprint coatings take advantage of this characteristic to prevent fingerprints and other stains from adhering, while also making it easier to remove any marks. These coatings provide both antifouling and smooth sliding properties. Traditionally, fluoropolymers have been used for these coatings, but in response to global regulations, fluorine-free water and oil-repellent coatings have been developed in recent years.

Glass is typically an insulator, but by depositing a transparent conductive layer on it, conductivity can be introduced to its surface. Indium tin oxide (ITO), a widely used transparent conductive coating, functions as a transparent electrode in video displays, solar cells, heaters, and similar applications.
When both conductivity and transparency are needed, index matched indium tin oxide (IMITO), which includes a refractive index index -matching layer, is used to minimize reflections at the interface. IMITO is applied in devices that utilize liquid crystal on silicon (LCOS) technology, such as wavelength selective switches (WSS) in optical networks.

Decorative coatings are thin film coatings that add various textures to transparent glass surfaces. These coatings are commonly used in kitchen appliances, such as the top plates of gas and induction cooktops, as well as refrigerators.