Barrier film

Technology briefing

The popularity of flexible electronic devices has affected the market demand for flexible substrates and material process technology, which is different from all previous processes based on hard substrates such as silicon wafers or glass used in semiconductor or panel processes. Therefore, the development of flexible substrates with good electrical conductivity, photoelectric properties, chemical resistance, and good physical properties is an inevitable topic in the future. In the composition of flexible displays, a soft substrate that can block water vapor and oxygen like glass is a key material, because many materials used in displays, such as flexible liquid crystals or OLEDs, need this substrate to block water and oxygen to prevent oxygen corrosion without spoil the life time and quality stability of the product. Different types of electronic components have different requirements of water vapor resistance as shown in Figure 1.

The water blocking ability of the barrier film can usually be distinguished by the value of the water vapor transmission rate (WVTR). On the substrate side, materials with excellent optical properties, such as polyethylene terephthalate (PET) or other optical grade plastics, are suitable for making the barrier for flexible electronic devices. However, the water resistance of a flexible plastic substrate is inherently not good, therefore, by coating a barrier layer on the surface of optical plastic substrates has become a new research field. At present time, there are an usual workable way to make a barrier by interlace coating of  inorganic and organic layer on the substrate. That is because inorganic materials are similar to glass, and have better water and vapor barrier effects than organic materials, but internal stress inside a glass like inorganic layer make it easy to to break. Although, the organic layer is poor of vapor blocking, but it can enhance the over all reliance while interlace them with inorganic layer, to make a barrier with good water vapor blocking performance. Efun has been developing and manufacturing water-blocking films for many years, mainly for the packaging of quantum dot (Quantum dot) components, and also for some application of electronics devices.