In this blog post, we will look at the improvement of the driving method of mechanical engineering that made the commercialization of AMOLED possible and the process of optimizing the precise production process.
“AMOLED” is the nickname of a mobile phone released by a Korean mobile phone manufacturer in July 2009, and it refers to its display device. The official name is AMOLED, which stands for Active Matrix Organic Light Emitting Diode, which literally means ‘active organic light-emitting diode.’ This name implies the principle, material, and driving method of light emission.
An OLED (organic light-emitting diode) is a self-emitting display device that uses the principle that when an electric current flows through an organic compound, electrons in the material absorb energy and become excited, then fall back to their ground state, emitting that amount of energy as light. Here, “self-emissive” is an important feature that distinguishes it from the existing flat-panel display device, the liquid crystal display (LCD), and refers to the property of the material itself emitting light. In the case of LCD, since it cannot emit light on its own, a separate light source must be placed behind the panel. Due to this structural difference, LCD has limitations in minimizing the thickness of the panel, and there is a problem of the image quality changing depending on the viewing angle because light passes through the panel and reaches the eyes. As an alternative to solving this disadvantage, OLED was developed, and it has enabled clearer and more consistent image quality.
OLED was developed by Dr. C.W. Tang of Kodak in 1982 and a patent was filed. Since then, many laboratories have been conducting research to improve the intensity, efficiency, and duration of light. This research was actively conducted in the fields of development of organic materials used for luminescence and structural research to increase luminescence efficiency, and as a result, in 1998, a phosphorescent organic material was developed that could achieve three to four times higher efficiency than existing fluorescent materials. As OLED technology has gradually advanced, the possibility of its commercialization has increased. In addition, a structure has been developed in which layers that inject and transport electrons and holes are laminated on top and bottom of organic materials to overcome the limitations of the light emitted by a single organic material. This is one of the core technologies of OLED and has contributed to greatly improving the luminous efficiency.
However, there were still many technical challenges to be overcome before OLED technology could be commercialized. Among them, mechanical engineers played a key role in the driving method of OLED devices and the processing process for applying them to products. First of all, it was important to develop a method that could effectively drive OLEDs. In the process of receiving external signals and outputting light to the screen, the passive matrix method, which uses electrodes that are mutually perpendicular to emit light, was mainly used in the early days. However, although the passive method is simple in structure, it has the disadvantage that current flows through non-emitting pixels, resulting in large voltage loss and the inability to emit light from multiple pixels at the same time. To overcome these limitations, the active matrix drive method was introduced. The active method applies current to each pixel individually, which provides excellent resolution and minimizes power loss. For this reason, small display devices such as mobile phones mainly adopt an active driving method, which is called AMOLED.
In order for AMOLED to be commercialized, not only mechanical engineering design but also advanced processing is essential. OLED has a layered structure, and each layer is very thin. The process of precisely building up these thin layers on a substrate requires a high degree of precision. During the process, methods such as depositing a gaseous substance on a substrate or evenly spreading a liquid substance and then converting it into a solid state may be used. Determining the most suitable method and applying it during this process plays a crucial role in producing high-quality AMOLEDs.
In addition, organic materials, which are the main materials of OLEDs, are very sensitive to moisture and oxygen in the air and can be easily damaged. Therefore, the encapsulation process, which completely protects the device from such external environments, is very important in the commercialization stage. It is also essential to manage the heat and other physical stresses that occur during this process. Therefore, mechanical engineers have developed various protective designs that meet these conditions and applied them to the actual production process, making it possible to commercialize AMOLED.
Before AMOLED could be commercialized, it was essential to not only conduct research and development, but also design a mechanical engineering process that enables automation and mass production in the production process. AMOLED is a very precise display device, and it is impossible to manufacture it directly by human hands during the production process. Therefore, all processes are carried out by machines, and it is necessary to connect these machines organically and automatically to maximize production efficiency. To this end, the research and development of mechanical engineers was essential for the design and production of the machines used in each process, as well as the optimization of the production process.
For example, the development of TFT (thin-film transistor) devices has made an important contribution to maximizing the performance of AMOLED. The TFT is a device that transmits electrical signals to each pixel to enable the pixel to emit light, and it plays a major role in increasing the resolution and reducing power consumption in small displays. These technological elements have made AMOLED commercialized in various applications such as smartphones, TVs, and wearable devices.
Finally, AMOLEDs must undergo numerous tests and quality inspections before they are completed as actual products. Various tests are required to maintain the durability, reliability, and screen quality of the products, and in this process, mechanical engineers constantly improve and optimize the process to ensure that the produced products maintain the best performance.
Ultimately, the commercialization of AMOLED is the result of collaboration and research and development in various fields. Mechanical engineers played a key role in the design and manufacturing process to commercialize OLED technology, which has led to the high-performance display devices we use today.
