Will LCD and OLED be replaced by Micro LED?
From the perspective of technological maturity, micro LED is still a certain distance from the real large-scale mass production, and its mass production cost is still high. In fact, OLED also experienced this period in the early years. Although the cost of large screen of OLED is still much higher than that of LCD, it has reached the range that can be accepted by ordinary home users. Based on past experience, as micro LED technology matures, will OLED and LCD (mini LED belong to the LCD category) be replaced? Perhaps the answer is not simple.
The industry defines different LED technologies according to the size of the LED chip. For example, when the size of the LED chip is less than 150μm, it is called a mini LED; when the size of the LED chip is less than 50μm, it is called a micro LED. As the size of backlight LED chips becomes smaller and smaller, the structure of the display panel also changes accordingly.
When the size of the LED chip is as small as the pixel level, each pixel corresponds to a micro LED chip. Since the micro LED can emit light by itself, it can control the brightness, brightness and color. Compared with the traditional LCD screen, the micro LED can save the liquid crystal layer and filter structure.
The screen structure of micro LED is close to that of OLED, and both have the characteristics of pixel self-illumination, simple structure and high luminous efficiency. However, the material life of micro LED is much higher than that of OLED organic light-emitting diode, and its stability is also stronger.
From the perspective of technological maturity, micro LED is still a certain distance from the real large-scale mass production, and its mass production cost is still high. In fact, OLED also experienced this period in the early years. Although the cost of large screen of OLED is still much higher than that of LCD, it has reached the range that can be accepted by ordinary home users.
Based on past experience, as micro LED technology matures, will OLED and LCD (mini LED belong to the LCD category) be replaced? Perhaps the answer is not simple.
Micro LED is still a little far from large-screen manufacturing
First of all, it needs to be clear that it is difficult to apply micro LEDs to large panels in the early stage of development. Just like OLED, the manufacturing process of micro LED large panel is greatly limited by yield and cost.
LED chips become smaller, and the value brought by them is greater than everyone expected. If you look at the manufacturing process of the micro LED, it grows from the wafer and eventually needs to be transferred to the back plane of the screen. If the resolution of a screen is 1920x1080, the number of pixels on the screen exceeds 2 million, and each pixel is composed of three sub-pixels of red, green and blue. If this is a micro LED screen, it means that there are 6 million micro LED chips on this screen.
With contemporary semiconductor manufacturing processes, it is not difficult to grow 6 million micro LED chips on the wafer, but the difficulty is to transfer these 6 million micro LED chips to the backplane. The industry calls this transfer process a mass transfer. Even the high-end mini LED screens on the market, such as the 2021 iPad Pro 12.9", have only 10,000 mini LEDs in the backlight layer. Therefore, mass transfer is a major difficulty in micro LED manufacturing.
Different solutions exist on the market for the mass transfer problem. Among them, the more mainstream two categories are: whole-piece transfer and batch pick-and-place (pick-and-place). Whole piece transfer is suitable for small-sized screens, because the screen panel is small enough, so the whole piece can be transferred; the technology of picking and placing in batches is more difficult, and large screens can only use this solution to achieve mass transfer.
Mass transfer is not the only technical difficulty in the manufacture of micro LED panels, but it is a watershed that restricts the manufacture of micro LEDs with large and small screens - of course, how big a large screen can be mainly depends on cost. Samsung and Sony first demonstrated micro LED large-screen TVs cost more than a million dollars.
At the display technology exhibitions in recent years, the micro LED products displayed by manufacturers have become more pragmatic. At this year's SID Diplay Week, the micro LED products displayed by Tianma Microelectronics, AUO, and Chitron Technology are all aimed at small-screen applications such as automotive dashboards and electronic paper. Of course, even if the display is a large-screen application, the current parameter advantages have not crushed OLED/LCD.
Opportunities at this stage: AR/VR, transparent screen, folding screen
Significant structural advantages determine the characteristics of micro LEDs with high pixel density, high brightness, high contrast, and fast response. High pixel density, high brightness and high contrast can be significantly perceived from the structure. In previous prototype product demonstrations, manufacturers have demonstrated displays with pixel densities of tens of thousands of ppi (pixels per inch).
Since the micro LED chip is as small as the pixel, it can display true black with a single pixel that does not emit light. At the same time, the ultra-small LEDs in micro LED displays are more efficient in converting electricity into photons, and micro LEDs are brighter than OLEDs and LCDs; based on higher electron mobility, micro LEDs can switch at nanosecond levels.
Due to the limitations of the manufacturing process, micro LEDs are only suitable for small screens in the early stage, for example, they are especially suitable for AR/VR (augmented reality/virtual reality) applications, including goggles for entertainment.
AR/VR's requirements for display brightness, contrast, pixel density and response are much higher than those of mobile phone consumer electronics products. It is technically difficult for LCD and OLED to meet the needs of such applications. Many consumers have reported that the current AR/VR applications are prone to dizziness and lack of immersion. In fact, this is largely constrained by the technology itself of LCD and OLED. The application of micro LED in the field of AR/VR has significantly overcome this problem. Perhaps the key to the future development of AR/VR depends on the breakthrough of micro LED technology.
In addition, the miniaturization of the micro LED chip is conducive to the flexibility and transparency of the panel. Chitron Technology has demonstrated a flexible + transparent screen. "Flexible", "transparent" and "foldable" are the hotspots of screen display technology in the past two years, and to some extent are the keys to achieving industry breakthroughs.
Analysts of "International Electronics Business" learned from LED chip manufacturers upstream of the panel supply chain that the early application of micro LED will focus on wearable devices, AR, VR and small car screen products, which is a logical thing from a technical point of view.
It is worth mentioning that although micro LED has many technical advantages over LCD/OLED, some of these advantages are still in the theoretical stage. A more representative one is EQE (external quantum efficiency) - it can be understood as luminous efficiency. Compared with LCD, the screen structure of micro LED display removes liquid crystal, color filter, and polarizer. Compared with OLED, it does not require complex packaging technology. In theory, the luminous efficiency of micro LED display is much higher than the latter two.
However, the extremely small size of micro LEDs makes the chip highly affected by sidewall effects - an engineering problem that occurs during the manufacturing process, so the actual EQE of micro LEDs is extremely low, and may even be inferior to LCD and OLED. The existence of sidewall effects also makes it more difficult for micro LEDs to produce ideal large-screen applications. Therefore, the existing micro LED solutions on the market are far from reflecting the technical advantages of micro LED itself.
Complementary to applications between LCD/OLED
Various technical challenges of micro LED are difficult problems that many market players are trying to solve. The technical characteristics of micro LEDs also determine the changes in the structure of the display industry chain in the future. The miniaturization of micro LEDs further tilts panel manufacturing to semiconductor technology.
As a simple example, due to the miniaturization of micro LEDs, the backplane part of the display screen has begun to transition from amorphous silicon or low temperature polysilicon TFT (thin film transistor) to CMOS technology. Specifically, the backplane is a circuit layer used to control the lighting, extinguishing, and gray levels of each pixel. Compared with amorphous silicon and low temperature polysilicon, single crystal silicon has higher crystalline quality and electrical properties, and CMOS is beginning to become an option. Therefore, the general IC manufacturing process can be used to manufacture the backplane, which is one of the remarkable manifestations of the further integration of the display industry and the semiconductor industry.
CMOS is limited to small size screens. CMOS also faces cost issues when producing large-size screens. Therefore, amorphous silicon and low temperature polysilicon TFTs are still necessary technologies for large-screen micro LED fabrication.
Early observations of micro LEDs from Hendy Consulting suggest that there may be a value shift in the micro LED supply chain. This is determined by its technical characteristics. As micro LEDs gradually move closer to IC manufacturing, it challenges the status of traditional panel manufacturers.
It is expected that there will be four possibilities in the future industry chain: the first is that traditional display industry players (such as Samsung, LG, BOE) are still in the center, but the value will be diluted; the second is that manufacturers with vertical integration capabilities, For example, LuxVue acquired by Apple and Glo AB invested by Google will occupy a dominant position in the micro LED world; the third is the composition of the new industry structure, and the industry value may be transferred to LED chip manufacturers, semiconductor manufacturers and key IP holders. Enterprise (or multi-party cooperation) transfer; the fourth is that micro LED may not become the mainstream of the market.
Judging from the market trends in mainland China, Taiwan, and South Korea in the past two years, investment in micro LEDs is increasing on a large scale, and upstream and downstream companies in the industry chain are also actively cooperating. Before 2018, the market players of micro LED were independent, and different companies had different technical directions, and these technical directions were very different.
Considering that micro LED manufacturing technology may need to be application-oriented to customize the systematic manufacturing process - this is very different from LCD/OLED. The situation of independent management is not conducive to the market development of micro LED, and there are different technical directions and no common standards for a certain type of technology, which is just the performance of the industry in the early stage of development. Starting in 2020, there has been a lot of cooperation in the industry, which is a sign that micro LED is maturing.
The market variables are very large. Analysts of "International Electronic Business" believe that the development direction of the industry analyzed by Hendy Consulting may be too simplistic. In our opinion, not only the changes in market investment and cooperation trends in the past 1-2 years, but also the possibility of long-term development of micro LEDs in the future.
Just as OLED did not completely replace LCD in the past, as a technology with development potential in small screens and AR/VR in the early stage, micro LED is very likely to coexist with OLED and LCD for a long time. It's just that the application directions of the three are different. For example, micro LED focuses on the small screen and AR/VR market, and eats up part of the value of OLED and LCD in the high-end market. Although the market size of OLED and LCD will shrink, the three will form a subtle complementary relationship in terms of technology and market, rather than micro LED replacing OLED or LCD.
