The combination of display and transparency will inevitably lead to more unprecedented application scenarios. But what display technology is best suited for transparent display? The continuous attempts of LCD, OLED to Micro LED have found the "right answer"!
Micro LED display technology wins the battle of transparent display route
On the 2024 WAIC, Lenovo brings the world's first transparent display laptop, which uses a 17-inch fully transparent Micro LED screen. Au presents the world's largest 30-inch glasses-free 3D Micro LED dual-layer display at Touch Taiwan 2024. Previously, AU also showed a 60-inch transparent Micro LED display for a variety of scenarios at ISE 2024. At CES 2024, Samsung showed off its first transparent MicroLED screen. On CITE 2024, Tianma Microelectronics showcases 8.07" high PPI transparent shaped Micro LED display, PPI up to 167, transmittance up to 55%, full screen brightness >1500nits...
Not complete statistics, from 2023 to the present, more than 15 companies in the world have displayed a variety of Micro LED transparent display products, the market covers a variety of scenes such as vehicle, business display, IT and consumption, 3D, both transparent all-in-one machines, small size transparent displays, and engineering display unit products that meet the needs of 1*N splicing large screens. It can be said that the innovation and creativity of the Micro LED transparent market are entering the full flowering stage.
So, in different display technologies, why can Micro LED attract more "transparent display innovation power"? The answer is that both LCD and OLED display technologies have their own shortcomings that are not suitable for transparency.
First of all, the display device of LCD technology needs a backlight to provide brightness. The transparent display LCD must make the backlight side type. The narrow strip side backlight has small size, special shape and highly limited performance. Especially for large-size transparent display, its brightness is often not high enough, making the effect of the screen display greatly reduced.
In addition, the LCD backlight lighting system also has a lighting effect on the transparent position of non-pixels on the LCD transparent screen. This makes it difficult for the contrast contrast between the pixels of the LCD transparent screen and the non-transparent part of the display to be "very large", which further affects the picture quality effect.
Second, the transparent screen of OLED technology is currently available in many products, with a maximum coverage of 77 inches, and can be designed to support splicing applications. However, OLED display technology has always been poor in brightness performance. For example, the double-layer series OLED structure used on the IT screen is to improve the brightness level. And transparent display, because a large screen area is used as a transparent structure, rather than OLED imaging structure, the balance between brightness and transparency is also facing difficulties. Once the brightness is not sufficient, the display effect will decline in a high lighting environment.
It can be said that the biggest bottleneck for LCD and OLED transparency applications is "how to improve brightness". In this regard, Micro LED has a natural advantage. Micro LED applied to transparent screens can easily obtain brightness of more than 1000 nits. This is due to the high level and constantly improving luminous efficiency of LED technology. "The existing display technology, Micro LED is the most easy to achieve high brightness under the high penetration", industry experts said.
Micro LED transparent display, light and transparent enough
For the advantages of Micro LED display on the principle of transparency, the industry believes that in addition to the high light efficiency and high brightness of the LED itself, the small size of the Micro LED crystal is also a major advantage.
That is, the pixel structure of LCD and OLED transparent screens, in order to maintain "sufficient brightness", the pixel structure needs to meet a certain area. At present, the mainstream OLED transparent screen, pixel and other opaque structures basically occupy half of the overall panel area, which is the key to its transmittance can not be greatly improved.
In contrast, Micro LED crystals are almost true point luminescence. With a size of less than 50 microns, its area ratio on the display can be reduced to less than 95% - that is, enough area is free to provide space for pixel wiring and transparent structure. At the same time, the high-brightness LED is concentrated into point light, which is more conducive to forming a higher contrast between the pixel point and the transparent part, and the color saturation and three-dimensional sense of transparent imaging are better.
Even, taking advantage of the smaller pixel particles of the Micro LED display, AU has developed a naked eye 3D display product with a double-layer Micro LED pixel layout. The industry believes that the future may even use smaller Micro LED pixels to make multi-layer transparent Micro LED pixel screens to achieve better nade-eye 3D and even stereoscopic holographic display products.
In addition to the resolution of the contradiction between brightness and permeability, the Micro LED's tiny size and extremely high luminous efficiency can contribute to the solution. Micro LED also has certain advantages in the improvement of transparency and contrast effect of transparent display. Because, compared with liquid crystal and OLED, Micro LED itself not only shows higher brightness; Moreover, it is easy to maintain color saturation and accuracy in a wider brightness adjustable range, which can provide a wider space for transparent screen design to adjust the brightness of the Micro LED according to the ambient illumination.
Of course, as a light-emitting technology, Micro LED can't become a screen on its own - it needs a substrate. In this regard, Micro LED also has an advantage. On the one hand, Micro LED can use the mature AM TFT glass substrate technology on LCD and OLED; On the other hand, it can also use PM glass substrate products developed specifically for Micro LED display applications. The latter is conducive to reducing the cost of Micro LED display products on large-size displays.
However, although the Micro LED has the best theoretical "technical characteristics" for the transparent screen, the industry still says that the Micro LED transparent screen needs to be improved in terms of technical maturity, reliability and cost if it wants to become a universal product.
Integrated process to block the final shackles of Micro LED transparent display
Any product entering the market must first face the test of cost competitiveness. At present, the Micro LED transparent display is still not satisfactory in this respect. The fundamental reason is that the massive transfer process is not mature and stable.
The Micro LED display is a Micro LED crystal particle integrated and welded to the drive board. For 2K color display products, more than 6.22 million crystal particles need to be transferred, positioned, integrated and fixed. At the same time, it is necessary to achieve high efficiency and high yield in order to effectively control the manufacturing cost of the product. Clearly, this process will not be easy. At present, the industry generally believes that the large-scale transfer of direct integration technology requires 6 yields of 9 to truly scale mass production.
For transparent display, the Micro LED crystal integration has a new problem: in order to achieve better light mixing of RGB pixels, the sub-pixels need to be closer together; That is, it is no longer uniform placement, but to distinguish between the luminous area of the pixel and the non-luminous transparent area. If it is designed in this way, the difficulty of transferring large quantities of products will be further increased.
However, at present, the industry has developed MIP packaging technology, that is, first packaged as an independent pixel individual, and then a large amount of integration. This reduces the demand for bulk transfer yield by 1-2 orders of magnitude, and makes defect detection and repair significantly less difficult. The industry believes that the special design of transparent MIP package structure and transparent screen integrated system, the use of PM glass drive, should be able to greatly reduce the difficulty and cost of product process under the existing technology conditions.
In short, the transparent screen Micro LED technology requires continuous efforts in the massive transfer process, continuous progress in cost, and more importantly, to explore its unique product design ideas and product application markets. And then form a positive interaction between application innovation and production innovation. From the perspective of industry growth, the early Micro LED transparent screen does not necessarily have to fully attack cost-sensitive areas such as window transparent advertising, and can be prioritized in more high-end and creative application markets, that is, market areas with higher cost affordability.
The industry pointed out that the next three to five years is a critical period for the accelerated development and outbreak of Micro LED displays, and it is also a critical period for the transformation of transparent Micro LED displays from technical prototypes to landing applications. Micro LED transparent display and creative products continue to emerge in the industry pattern is bound to rise again. In the short term, the Micro LED transparent display will form a competitive situation with the OLED transparent display, and in the long term, the Micro LED transparent display has the possibility of unified transparent display market. Micro LED transparent display is an important differentiated product opportunity that the LED direct display industry must pay great attention to.