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- February 9, 2023
- News
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- 09 mins
Is Mini LED a transitional technology
In the digital age, as information display carriers and human-computer interaction windows, display screens can be said to be ubiquitous, including smart home, smart cockpit, smart medical care, and social media, which basically rely on the screen as the carrier of information display. At present, innovative display technologies are constantly emerging. Not only are more and thinner screens, but flexible display technology has made great progress.
In fact, displays have a history of more than one hundred years of development. During this period, they have experienced many generations of different mainstream display technologies, and gradually formed a prosperous situation of display diversification today.
CRT era
CRT (Cathode Ray Tube) is the first generation of mainstream display technology. In 1897, Braun Bosch invented this technology, which was later introduced into the display industry and became the most mainstream display technology in the 20th century.
The CRT display is mainly composed of three main parts: an electron gun, a fluorescent screen and a glass casing. If you look at it more subdivided, the CRT display includes screen glass, phosphor powder, aluminum film, inner graphite layer, outer graphite layer, deflection coil, first/second/third/fourth anode, cathode, control grid, filament and high pressure nozzle and other parts.
The imaging principle of CRT is that when the filament heats up, the cathode emits an electron beam, and the electron beam changes with the image information of the grid and cathode. Then these electron beams are accelerated by the anode and adjusted by the field deflection ring, and finally hit the fluorescent screen at high speed, forming different gray levels on the screen to complete the image display.
In 1907, Russian scientist Boris Rosing first displayed geometric figures on the screen through CRT technology, but this was not the first monitor in history. The first monitor was born in 1922; then Baird invented the first TV in 1925; in 1936, the 11th Berlin Olympic Games was broadcast live for the first time, which accelerated the popularization of CRT TV.
In the Chinese market, the first CRT TV was born in 1958. It was a black and white TV. Chinese people later gave CRT TV many easy-to-understand names, including “back head” and “big butt”. In 1970, the first color CRT TV was born in China, which produces color visual effects through the combination of red (R), green (G) and blue (B) primary colors. The electron beam gun is equipped with three cathodes, which bombard different Phosphor completes the display.
The 1980s and 1990s were the stage when CRT TVs were popularized in China on a large scale. However, due to the bulky appearance of this display technology, it was eventually lost to LCD display technology.
Liquid crystal displays
In fact, the LCD was born in 1964 and became a liquid crystal display in 1968. However, in the early stages of technology development, due to the more mature CRT technology, LCDs cannot compete with CRTs in response time, color reproduction, resolution, etc., and can only be used as simple digital displays such as electronic calculators and electronic watches.
From 1968 to 1971, liquid crystal displays were mainly produced using dynamic scattering technology, also known as DS-LCD, but this method is easy to damage liquid crystals, so it has not existed for a long time.
From 1971 to 1990, the industry successively developed TN-LCD (Twisted Nematic Liquid Crystal Display) and STN-LCD (Super Twisted Nematic Liquid Crystal Display). At the STN-LCD stage, the performance of liquid crystal display has been greatly improved, and it has begun to lead CRT display technology in terms of resolution, viewing angle and contrast.
In 1988, TFT-LCD (Thin Film Transistor Liquid Crystal Display) came out, and Japanese manufacturers took the lead in this regard. TFT-LCD has greatly reduced the production cost of liquid crystal display, and finally surpassed the market share of CRT.
TFT-LCD later developed into IPS, also known as “Super TFT”, which is a flat switching screen technology. IPS has currently derived multiple branches such as IPS, S-IPS, AS-IPS, and IPS-PRO.
In terms of panel types, while TN-LCD and IPS were developing, the industry chain headed by Sharp also invented VA LCD panels, which are actually a variant of TFT-LCD. Like TN-LCD, VA LCD is also a soft screen and can be used to make curved screens. The IPS is a hard screen, but it has excellent full viewing angle characteristics, dynamic clarity, and color reproduction effects.
So far, TN-LCD, IPS and VA have their own main positions. Among them, TN-LCD has become the mainstream in the e-sports display market due to its low manufacturing cost and fast response speed; IPS is mainly used for Professional monitors, oriented to photography, design, video editing and other scenarios; VA LCD has relatively high latitude and contrast, purer black and white, and flexible features, mainly used in high-end TVs and most curved screens on the market.
The short-lived plasma technology
While LCD dominates the global display market, in addition to defeating the original overlord CRT, it also faces competition from plasma technology at the same time.
Plasma display technology was born in 1927, and was officially applied to the display field in 1964. Plasma technology was born in the United States, but the real development was in Japan. American companies had hoped to use plasma technology for monitors and computer screens, but the results were not ideal.
In 1994, Panasonic began developing color plasma technology jointly with Plasmaco, which was acquired by Panasonic in 1996. In the 1990s, the main researchers of plasma technology were Panasonic and Fujitsu, followed by Philips, Pioneer, Samsung, LG and Changhong.
According to statistics in 2006, the global shipments of LCD TVs and plasma TVs were comparable at that time. Subsequently, plasma technology began to fall into disputes among technical genres, and its performance on the market side was gradually suppressed by liquid crystals. Finally, at the end of 2013, Panasonic announced that it would stop producing plasma panels.
Future mainstream – OLED
The birth of OLED was an accidental discovery. In 1979, Dr. Deng Qingyun, who worked for Kodak Company in the United States, forgot to bring something, and when he returned to the laboratory, he accidentally discovered that the organic battery was emitting light, so the research on OLED began. The world’s first commercial OLED came from Kodak and was released in 1987. Once released, OLED showed the characteristics of thinner, darker and faster response.
Before 2005, the development of OLED technology was dominated by Kodak, Pioneer and UDC. During this period, the industry discovered the flexible characteristics of OLED, and realized the commercial use of OLED in equipment such as automobiles, cameras and displays. At the same time, Kodak teamed up with Sanyo in 1998 to realize full-color OLED.
In 2005, Samsung invested 850 million US dollars to build an AMOLED production line. Since then, OLED has entered the mature stage of the industry, and Samsung has also become one of the main suppliers of OLED.
OLED has two technical routes, one is PMOLED and the other is AMOLED. PMOLED has a relatively simple process and a simple structure, but it cannot be made into a large size and the color display is not rich enough, so it was used for the external screen of a mobile phone; AMOLED has a complex structure and high cost, but it has richer colors and can be produced in various sizes, so AMOLED is currently the mainstream of the industry.
In the smart phone market, Siemens is the first to commercialize AMOLED, but it is Samsung that really makes it a standard configuration for high-end phones. Starting from the first-generation Galaxy S series, Samsung has deeply bound high-end flagships with AMOLED, and the screens of each generation of Samsung flagship phones are at least one generation ahead of the industry. In 2017, Apple first used AMOLED on the iPhone X.
In the TV market, Sony launched an OLED TV in 2007, but the market feedback was mediocre. Then LG entered the OLED TV market in 2013, making OLED TVs the mainstream of high-end TVs. Currently, LG and Sony are the major OLED TV brands. Among them, LG has almost monopolized the global OLED TV panel supply, and has given 82% of the production capacity to LG and Sony, and the remaining share is divided among brands such as Hisense, Skyworth, and Xiaomi.
Imaginative Micro LED
Micro LED is LED miniaturization and matrix technology. The history of LED technology can be traced back to 1907, but the commercial use of red LEDs has been in 1962. However, for more than 30 years since then, the industry has not conquered blue LED technology. It was not until 1994 that Japanese scientist Shuji Nakamura developed blue LEDs using GaN substrates, which led to the development of full-color LEDs and laid the foundation for white LEDs.
There are two main application directions of traditional LEDs. One is as a backlight, which is widely used in mobile phones, digital cameras, TVs, monitors and other fields; the other is direct display, which is mainly used for commercial splicing large screens.
From LED to Micro LED, there is still a gap in the middle, that is Mini LED, this new display technology is currently the focus of the layout of major manufacturers. However, some analysts believe that Mini LED is a transitional product.
Mini LED and Micro LED are different in chip size. Mini LED chip size is between 50-200μm, while Micro LED is less than 100μm. There is a huge difference in chip preparation, and Mini LED also needs sapphire substrate. At the end, Micro LED is completely unnecessary.
From the perspective of direct display, Mini LED is indeed a transitional product from LED to Micro LED. During this process, the industry will continue to verify technologies such as mass transfer and advanced LED packaging to prepare for the commercial use of Micro LED. However, it is the Mini LED backlight that is currently shining brightly. In this respect, Mini LED is unique because Micro LED will not be used for backlight.
Therefore, it can be said that Mini LED backlight is a major trend in the future development of traditional LCDs, and continues to extend the technical life of LCDs.
Since Satoshi Takano’s team in Japan released a set of Micro LED arrays in 2001, this technology has been developed for more than two decades. However, technologies such as mass transfer from traditional sapphire substrates to silicon substrates still plague the development of Micro LEDs, and there is still a long way to go before large-scale commercial use.
However, the potential of Micro LED cannot be ignored. Through thinning, miniaturization and arraying of LED, Micro LED inherits the high efficiency, high brightness, high reliability and fast response time of inorganic LED, and Micro LED brings display with the huge improvement in resolution, coupled with the advantages of energy saving, simple structure, small size, and thin profile, the industry will continue to invest in Micro LED.
It is expected that in 2024, Micro LED will usher in the first year of commercial use, and the first batch of products will be portable devices such as watches, VR, and high-end TVs.
Final words
As a window for human-computer interaction, display screens will continue to update related technologies driven by digitization and intelligence, and new display technologies will continue to emerge. Today, with the advantages of a mature industrial chain and the support of Mini LED backlight, LCD will still occupy the mainstream in the display market for a long time.
However, it will be a matter of time before OLED takes over. In addition to the continuous update of display technology, supporting technologies such as display video interface are also developing at a high speed. The superposition of these technologies not only brings people better visual enjoyment, but also makes people’s life more and more technological.
