Popular Science: What kind of display technologies are OLED, Mini LED, and Micro LED?

TrendForce, a research institute, recently released the top ten technology industry trends in 2020. Among them, Mini LED and Micro LED are among the trends. Especially, Mini LED will be mass-produced soon and will be widely used in high-end products. Mini LED will directly compete with OLED.

TrendForce, a research institute, recently released the top ten technology industry trends in 2020. Among them, Mini LED and Micro LED are among the trends. Especially, Mini LED will be mass-produced soon and will be widely used in high-end products. Mini LED will directly compete with OLED.

In particular, Apple has repeatedly said that it will introduce Mini LED displays on medium-sized products. Apple’s adoption of new technologies is mostly a demonstration effect. Analysts expect Apple to introduce related technologies to iPad in the fourth quarter of 2020, which is expected to produce Mini LED. A boosting effect.

TrendForce said that the demand for high refresh rate mobile phone panels will increase, and tablets will become a new battlefield for Mini LED and OLED. In terms of mobile phone panels, the current specifications of OLED or LCD panels can meet the needs of various consumers. However, with the deployment of 5G , its high transmission efficiency and low latency characteristics not only improve the dynamic performance of mobile phone content, but also open up the application of mobile phones in other fields such as AR, driving the demand for 90Hz or even 120Hz panels.

In addition, in terms of the most popular gaming applications, in addition to the existing high refresh rate panels, higher-end products that enhance contrast performance through Mini LED backlights have more and more abundant conditions for mass production. After using LCD for many years, the market has also reported that the iPad in 2020 may simultaneously launch panel technologies such as Mini LED backlight and OLED to enhance image quality performance, making the tablet another development opportunity for OLED and Mini LED.

Secondly, the industry is oversupplied, and Micro LED opens up a new blue ocean. From the perspective of the progress of Micro LED self-luminous displays, more and more panel manufacturers have launched Micro LED solutions with glass backplanes. However, due to the yield problem, the current module has a maximum of 12 traces. The cost of Micro LED is still high, but due to Micro LED combined with mass transfer technology, it can be combined with different Display backplanes to create Transparency, projection, bending, flexibility and other Display effects will have the opportunity to create a new blue ocean market in the display industry that is oversupplied in the future. For example, if combined with a foldable display screen solution, Micro LEDs may be a suitable field for entry because of their strong material structure, which does not require many protective layers and does not require polarization treatment.

Popular Science: What kind of display technologies are OLED, Mini LED, and Micro LED?

OLED (Organic Light-Emitting Diode), also known as organic electric laser display, organic light-emitting semiconductor (Organic Electroluminesence Display, OLED). OLED belongs to a current-type organic light-emitting device, which is a phenomenon of luminescence caused by the injection and recombination of carriers, and the luminous intensity is proportional to the injected current. Under the action of the electric field, the holes generated by the anode and the electrons generated by the cathode will move, injected into the hole transport layer and the electron transport layer, respectively, and migrate to the light-emitting layer. When the two meet in the light-emitting layer, energy excitons are generated, thereby exciting the light-emitting molecules and finally producing visible light. Since OLED has long been popularized and belongs to a relatively mature technology, it will not be described here.

The micro-LED technology was created in 2000 by a research group led by professors Hongxing Jiang and Jingyu Lin from Texas Tech University. Of course, the first time consumers saw a product using micro-LED technology was Sony’s 55-inch full HD resolution “Crystal LED Display” product, which officially debuted in 2012. At the time, this technology was much better than the competition in terms of contrast ratio and color gamut.

Of course, but Sony products using this technology are expensive, and because of very low production capacity, there is basically no possibility of large-scale commercialization. But that hasn’t stopped companies and businesses from continuing to invest in and improve micro-LED technology. According to industry insiders, micro-LED technology is now very close to the level of commercial mass production.

A brief introduction to micro-LED technology

There are many similarities between micro-LED and OLED, so the contrast between micro-LED and OLED is easier to understand than LCD. First of all, as you can see from the name and these have LEDs, so they are mainly composed of light-emitting diodes, so both technologies are in the form of self-illumination, each red, green, and blue sub-pixel can Generates a light source without the need for specialized backlight assemblies like LCDs. As a result, micro-LED displays are also capable of delivering extremely high contrast ratios and black levels, just like OLEDs, while also having a TFT panel that powers each pixel.

Micro LED technology, that is, LED miniaturization and matrix technology, in simple terms, is to thin, miniaturize and array LED (light emitting diode) backlight sources, which can make LED units smaller than 50 microns, and can achieve the same performance as OLED. Each pixel is individually addressed and driven to emit light (self-luminous). Its advantage is that it not only inherits the characteristics of high efficiency, high brightness, high reliability and fast response time of inorganic LED, but also has the characteristics of self-illumination without backlight, small size, light and thin, and can easily achieve the effect of energy saving.

Popular Science: What kind of display technologies are OLED, Mini LED, and Micro LED?

In terms of structure and principle, Micro LED is simpler and has better effect. TFT substrate, ultra-fine LED die, and driver IC are not a big problem, but its biggest problem is the well-known mass transfer. How to make LED Miniaturization, which requires wafer-level process levels. For example, a 4K-level Micro LED screen requires more than 8 million LEDs to be highly integrated, so it is extremely difficult to apply it to a small-sized screen in theory, and the cost and heat generation are also extremely considerable. Samsung’s first Micro LED TV The choice of 146 inches is also the reason for this.

The difference between micro-LED and OLED is the material composition of its LED part. The “O” in OLED stands for organic material, which refers to the use of organic materials in the pixel stacks that produce light. The micro-LED technology uses inorganic gallium nitride materials, which are often used in ordinary LED lighting products. This technology can reduce the requirements for polarization and encapsulation layers, enabling thinner display panels. Therefore, the components of micro-LEDs are very small, less than 100 μm in width, which is thinner than a human hair.

If you look at this from another question, micro-LEDs are traditional LEDs arranged in an array in a smaller way. LEDs aren’t really new technology, but sorting arrays on such a small panel of components is the real difficulty. Contrary to other display panel technologies, the micro-LED screens used on small form factor devices such as smartwatches and smartphones are easier to manufacture. And it turns out that it is very difficult to increase the area of ​​​​the micro-LED display panel. Of course, due to the high requirements for welding precision, it is also very difficult to compress the higher resolution to the size of the smartphone screen.

An open question for panel makers is how to transfer large numbers of LEDs to control circuit boards. One potential solution is to group the LEDs into a larger array and then solder them to complete the display. The problem with this approach, however, is that it is currently selected and fabricated with an accuracy of ±34µm, which does not meet the ±1.5µm required for micro-LEDs.

An alternative is to etch the LED array to connect to the IC, or to transfer a separate TFT layer into the LED array. These etching methods avoid the precision problems of die bonding, but improve the requirements for small-sized components for micro-light-emitting elements, and are expensive and difficult to implement for high-resolution displays. At present, the progress of the entire manufacturing industry in this area is very slow, so if you want to increase production, you need to continue to improve.

Popular Science: What kind of display technologies are OLED, Mini LED, and Micro LED?

In the short term, round crystal bonding appears to be the most feasible process. However, this product is currently only suitable for low-pixel panels, such as smart watches with low resolution requirements, not smartphones with QHD resolution. Manufacturing high-resolution micro-LED panels is the goal of many manufacturers, but this requires continuous improvement in manufacturing precision.

Compared with the advantages and disadvantages of OLED

Popular Science: What kind of display technologies are OLED, Mini LED, and Micro LED?

Despite the manufacturing hurdles, micro-LED technology is still worth looking forward to because micro-LED offers more advancements than OLED. The first is the reduction of power at maximum brightness, that is, under the same low power conditions, micro-LEDs can achieve greater brightness. In contrast, the power consumption is 90% lower than that of LCD, and 50% lower than that of OLED. That’s a huge draw for a portable product like a smartphone where battery life is at a premium, which means lower screen power consumption and longer usage time. Compared with current OLED and LCD, manufacturers can increase the brightness of the panel, which is better for use in direct sunlight.

In addition, the display life of micro-LED is longer than that of OLED. OLED burn-in is still a big problem because organic materials have a limited lifespan, especially blue OLED panels. Micro-LEDs have no such concerns and last even longer than LCDs before color conversion.

The smaller micro-LED size also makes it easier to achieve high resolutions, such as 4K or even 8K resolution smartphones or virtual reality screens. Speaking of virtual reality technology, the response time of the OLED panel has been reduced to the microsecond level, which has a very good response time rating. And that makes them ideal for virtual reality applications. After changing to micro-LED, the response time is further reduced to the nanosecond level, which is 1000 times faster.

In addition to the above advantages, micro-LEDs also have greater advantages in contrast, color gamut and flexible displays. These all make micro-LEDs an advantage when compared to OLEDs, but micro-LEDs are also much more expensive to manufacture, even three to four times higher than current LCD or OLED panels. There is no doubt that this will increase the cost of the product a lot, and even affect the investment of the entire industry. After all, many manufacturers are still expanding the production line of OLED screens.

What is Mini LED? What is the difference with Micro LED?

Mini LED, also known as “sub-millimeter light-emitting diode”, refers to an LED with a grain size of about 100 microns, which was first proposed by Epistar. Mini LED is between traditional LED and Micro LED. In short, it is an improved version based on traditional LED backlight.

Popular Science: What kind of display technologies are OLED, Mini LED, and Micro LED?

Compared with Micro LED in terms of process, it has higher yield and has special-shaped cutting characteristics. It can also be used with flexible substrates to achieve the form of high-curved backlight. The local dimming design has better color rendering, which can bring more LCD panels. The fine HDR partition, and the thickness is also close to OLED, can save up to 80% of power, so it is suitable for mobile phones, TVs, car panels and power supply applications such as power saving, thinning, HDR, special-shaped displays and other backlight applications. Competitive notebook computers and other products.

Compared with MicroLED, in theory, Mini LED is less technically difficult, easier to achieve mass production, and can develop a large number of liquid crystal display backlight market, and the product economy is better. According to industry estimates, if the LCD TV panel with Mini LED backlight design is used, the price is only about 60% to 80% of the OLED TV panel, but the brightness and picture quality are similar to OLED, and the power saving efficiency is higher. At the same time, a 55-inch Mini LED-backlit LCD panel uses 40,000 LEDs, which will positively help LED chip manufacturers to reduce production capacity.

In general, Micro LED will have a qualitative improvement in image quality and is the next generation of revolutionary display technology, but the current technology is still not mature enough. The Mini LED is an improved version of the LED backlight, but it can still greatly improve the effect of the existing LCD screen. At the same time, the cost is relatively easy to control, and it is expected to become the mainstream of the market. We also hope that manufacturers can speed up the pace of research and development and bring Micro LED and Mini LED TV products that can satisfy ordinary consumers as soon as possible.

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