From the most commonly heard LCD, LED and OLED, to the hottest display technologies Micro LED, Mini LED and Micro OLED, have you ever wanted to understand them, only to be confused?
In this regard, we will briefly introduce the features of these new-generation display technologies and the differences between them and the old ones, so that readers can quickly understand them.
LCD is a “liquid-crystal display”, and most of the current market uses “thin-film transistor liquid crystal display” (TFT-LCD) technology, which consists of a layer of liquid crystal sandwiched between two glass substrates, the upper glass substrate is a colour filter, and the lower glass layer is inlaid with electro-crystals. The electric field created by the electric current passing through the crystal makes the original rotational arrangement of the liquid crystal molecules twist, thus changing the rotational amplitude of the light passing through and shining on the colour filter in different proportions, thus producing different colours.
▲ LCD panels are most often made using TFT-LCD technology.
It is now quite mature and is used for general computer and TV screens, and is a low-cost technology that has become the basis for consumer products.
▲ The principle of displaying images in a general LCD.
After understanding LCD, let’s move on to LED and OLED.
The LED is called “light-emitting diode”, which uses electrical energy to convert into light energy by applying voltage to the positive and negative terminals in the semiconductor, and when the current passes through, the electrons combine with the electric hole and the remaining energy is released in the form of visible light. The direct display LED is commonly used for outdoor TV walls or traffic lights, while LED chips are currently the mainstream product for TV and screen backlighting and lighting.
▲ LED technology uses electrical energy to convert into light energy.
The concept of driving LEDs is quite similar to that of OLEDs, but the materials used are completely different; OLEDs are called Organic Light-Emitting Diodes (OLEDs), and the basic structure is an organic material light-emitting layer made on Indium Tin Oxide (ITO) glass and covered with a low power function metal electrode on top of the light-emitting layer. The light-emitting diode is driven by an external voltage and the cathode electrons combine in the light-emitting layer to generate energy and emit light, producing R, G and B primary colours depending on the characteristics of the material to form the basic colours.
The biggest difference between OLED and LCD is that OLEDs are self-luminous, as LCDs require LED backplanes and filters, while OLEDs are self-luminous.
Although OLED presents a vivid picture, low power consumption and can be bent, the organic material will oxidise so the life span is relatively short and there will also be problems with colour burn-in, coupled with the high cost and high technical content, it is currently mostly used for small screens, such as mobile phone screens.
After understanding the basic differences between LCD, LED and OLED, we will look at the advanced display technologies Mini LED, Micro LED and Micro OLED.
The most intuitive difference between Mini LED and Micro LED is the size of the LED crystals, but there is a slight difference from a conceptual point of view; Mini LED is formally known as “sub-millimetre light-emitting diode”, while Micro LED refers to “micro light-emitting diode”.
▲ Micro LED technology no longer requires a filter and liquid crystal layer.
Mini LED is regarded as the transition period of Micro LED, an improved version based on the traditional LED backlight, used as the backlight of LCD panels; Micro LED is a new generation of display technology, miniaturising and matrixing the LED backlight, dedicated to driving inorganic self-lighting (self-luminous) alone, allowing longer product life and even better performance than OLED, and is regarded by the industry as the next generation of display technology. It is regarded as the next generation of display technology.
Currently, Mini LED technology is mainly used in “multi-zone backlight displays” and “large RGB small pitch displays”, where the “multi-zone backlight control” function can achieve zonal dimming, such as enhancing the high contrast ratio and high resolution of the screen, achieving HDR effect, the effect is similar to OLED displays; another technology is to use Mini LED chips to create a display with a pixel pitch lower than Pitch 1. Another technology is the use of Mini LED chips to create large screens with a pixel pitch of less than 1.0 mm, which not only improves the resolution of LED display screens but also creates a new mainstream specification for display screens.
Micro LEDs will bring a new technological breakthrough, and their use is not only limited to backlighting, as the grains of Micro LEDs are of an indistinguishable grade to the naked eye, and can directly combine the R, G and B primary colours into a single pixel, turning it into the concept of “one pixel”. The new technology will bring a new revolution to the LCD industry.
▲ The technology is different from the light-emitting structure of previous LCD screens and will bring a new revolution to the LCD industry.
In addition to creating a whole new scenario for the LCD industry, the future of Micro LED has a wide range of applications, including AR/VR devices, automotive screens, and high-resolution wearable products. However, Micro LED technology has many difficulties to be solved, from the early epitaxial technology bottleneck, Mass Transfer yield, packaging testing problems, to the subsequent inspection and maintenance are all great challenges, affecting whether Micro LED can be mass-produced.
Micro OLED has been the talk of the town this year as Apple has approached TSMC to collaborate on the development of Micro OLED panels, the most important feature of Micro OLED is that unlike traditional LCD or OLED for TVs and high-end mobile phones where the screen is built on a glass substrate, it is directly mounted on a wafer.
Micro OLED uses a single silicon wafer as the backplane, which has the advantages of making the display thinner, lighter and shorter, consuming less power, self-luminous and high luminous efficiency, especially suitable for AR, VR and other display wearable devices.