Flexible displays – testing and reliability

Rouzet Agaiby, Business Development Manager

July 29, 2019

The demand for flexible displays is growing as there are many existing and new applications that require displays that can be conformed and shaped to the product surface rather than the other way around. For example, smart speakers often have cylindrical shapes and need wrap around displays. Automotive interiors have many curved and shaped surfaces and require displays that are non-flat and non-rectangular to enable their seamless integration into the vehicle interior.

Flexible phoneSome of the most important factors for the wide adoption of flexible displays into products are their performance and longevity. In order for flexible displays to replace their rigid glass counterparts they have to achieve the same reliability standards as well as to prove that they can perform equally well when they are conformed and shaped.  

Testing flexible displays

Rigid glass-based LCDs have been around for a long time and account for more than 90% of the displays sold. Glass OLED displays are a newer technology and are increasingly being used in products today – notably in flagship smartphones and TVs. As these two technologies move to plastic-based flexible substrates, they need to go through rigorous reliability testing to prove they are commercially viable. For example, shock temperature tests of the displays have to be done to ensure that they are suitable for the end product. New testing sequences also need to be developed that are relevant to the specific application and use case. Different tests will be required depending on whether the display needs to withstand a single bend or multiple bends, and the effect of the impact at different locations on a bent display has to be tested too.

Flexible displays reliability

The reliability of flexible displays depends strongly on the materials used to make them. While both organic and inorganic materials can be used for making flexible displays, organic materials have the advantage of being inherently flexible. Over the last few years the performance of these materials has improved immensely allowing their commercial application. Organic materials are commonly known for their use in Organic Light-Emitting Diode (OLED) displays, but they are also used as semiconductor materials to make high performance organic thin-film transistors (OTFTs). OTFTs can be then combined with a well-established and mature liquid crystal frontplane technology to create Organic Liquid Crystal Displays (OLCDs).

The organic materials used for making flexible OLED displays require high vacuum deposition tools as they cannot be processed in ambient conditions and need highly specked encapsulation layers. In comparison, flexible OLCD is manufactured in ambient atmospheric conditions and does not require stringent encapsulation, ensuring high display reliability. OLCD also brings other manufacturing advantages that result from the low-cost plastic substrates and low temperature process employed. (This blog explains more about the other differences between flexible OLED and flexible OLCD.)

Reliability of flexible OLCD for automotive applications

Glass LCD has been the main technology used in automotive and has therefore created the benchmark for the adoption of any other display technology. Some of the core automotive reliability requirements include low temperature storage/operation at -40°C, high temperature storage/operation at 85°C and humidity testing at 60°C/93%RH. FlexEnable is already working with Tier 1s and OEMs on a reliability test programme to qualify OLCD modules through the same reliability test conditions that glass LCDs pass through.

Reliability of flexible OLCD for consumer electronics

Different consumer electronic applications have different display requirements. OLCD is designed to meet key high temperature and humidity tests, and many of the components in OLCD are already used in the supply chain. While additional tests need to be carried out on display modules designed for end user products, initial test results already show the potential of OLCD for consumer electronics.

For more information on our flexible display technology please get in touch with FlexEnable at info@flexenable.com.

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