First, let’s look at LCD technology.
When liquid crystal display technology is used for displays above 100 inches, due to the low production yield of large-size LCD panels above 100 inches, the cost cannot be reduced and the price remains high. The 98-inch QLED TV released by Samsung in 2019 is priced at close to 1 million yuan, which is indeed very expensive.
With LCD technology, another problem with TVs over 100 inches is the difficulty of transportation and home installation. The following table shows the length and width dimensions of TVs from 100 inches to 150 inches.
Length and width dimensions of TVs above 100 inches
As can be seen from the table, when the size of a TV exceeds 100 inches, the overall size without outer packaging exceeds 2 meters in length and 1 meter in width. There are many difficulties in the transportation process. In the home entry process, it is also extremely difficult for the TV to enter the home through the elevator.
Next let’s take a look at laser projection technology.
Laser projection TV is a large-screen display technology developed in recent years, and it is also a passive light-emitting display technology. By projecting a laser short-throw projector onto an anti-light screen, a large screen display of more than 100 inches can be obtained. Laser projection TV has three inherent deficiencies that prevent it from achieving the display effects of other display technologies. One is that the contrast ratio of anti-light screens is very low compared with other display methods. The other is the greater loss of color gamut after anti-light curtain reflection. The third is the lower brightness of the projected display.
Schematic diagram of the zigzag microstructure of the anti-light curtain
The schematic diagram of the laser projection anti-light curtain is as shown in the figure. The microstructure of the anti-light curtain is a zigzag optical structure. The upper part of the zigzag structure is a light-absorbing layer coated with black material, and the lower part is a white reflective layer coated with a special material. The black layer absorbs ambient light and improves contrast, and the white reflective layer is used to reflect images during projection. From the microstructure of the anti-light curtain, it can be found that the curtain cannot be completely black, and there is still a considerable part of white. As a result, the contrast of the curtain is not high and high-quality picture display cannot be achieved.
In addition to the relatively low contrast of the anti-light curtain, the color gamut of the displayed image will also be relatively low, resulting in greater color loss. Since the curtain emits light by passive reflection, the color gamut of the projector can be improved through technological improvements in laser projection. However, the anti-light curtain itself is a display method of passive reflection and emission, which will lead to greater color loss. The color gamut of the image reflected by the curtain is lower.
The low brightness of laser projection TV is also one of the main reasons for low display quality. Due to the passive reflection display method of laser projection TV, although the nominal brightness value of the projector is very high, the brightness of the image after reflection by the anti-light curtain is very low, resulting in whitening of the image and a large loss of clarity, especially in the presence of ambient light. The whitening phenomenon is more obvious. The overall display effect is difficult to meet people's basic needs for large-screen high-quality display.
Let’s take a look at the third SMD LED small-pitch display technology.
SMD LED small-pitch display technology is used in TVs above 100 inches. There are two insurmountable technical obstacles that make it difficult for this technology to become a technology used in TVs above 100 inches. One technical obstacle is that LED lamp beads have poor anti-collision capabilities and low pixel reliability. The thrust of the LED small-pitch display made with SMD 1010 devices is an order of magnitude smaller than that of the COB display, resulting in low reliability, especially the low reliability of the point spacing below P1.0, which basically cannot achieve mass production.
Comparison of anti-collision thrust between SMD small spacing and COB micro spacing
From the perspective of failure mechanism, the common non-lighting phenomenon of 1010 small spacing may be caused by the peeling of the outer sealant from the bracket or the disconnection of the gold wire caused by external impact. To this end, we found out the cause of the failure through failure analysis, so as to further design the glue sealing or glue mechanical properties. At the same time, our COB technology eliminates the SMD bracket and SMT reflow soldering links, eliminating the risk of soldering and achieving higher reliability. In the thrust test, Ledman COB withstands thrust at least 10 times more than SMD lamps, and the lamp beads have stronger anti-collision capabilities.
Another technical obstacle of SMD small-pitch display technology is that the clarity cannot meet the display requirements. With the continuous development of 4K and 8K display requirements, the requirements for clarity are getting higher and higher. However, SMD small-pitch technology can only realize point-pitch displays above P1.0, and it is very difficult to achieve mass production below P1.0.
Comparison of the dot pitch ranges that can be achieved by SMD small-pitch display and COB micro-pitch display
Finally, let’s take a look at COB micro-pitch LED display technology.
COB micro-display technology is called Micro LED display technology abroad. In 2018, Samsung released a 146-inch Micro LED TV product-The Wall. This is the first product released by global display giant Samsung in the LED TV video wall market. Another international display giant, Sony, released Crystal Black Crystal, a product using Micro LED as early as 2016.
COB microdisplay is an integration of LED packaging technology and LED display technology. 70% of the technology is packaging technology. Therefore, packaging technology is the main technical difficulty of COB microdisplay. Ledman Optoelectronics began to accumulate packaging patents fifteen years ago. Its COB integrated packaging technology has successively overcome nearly 100 technical difficulties in substrate, chip transfer, sealing, online maintenance, reliability, splicing, consistency, correction algorithms, etc., and has grown into a leader in domestic COB microdisplays.
Compared with LCD TVs, COB micro-display TVs over 100 inches do not have the transportation and home installation problems of LCD TVs over 100 inches due to the splicing technology used. Compared with liquid crystal display technology and laser projection technology, COB microdisplay technology has higher brightness and has overwhelming advantages in display quality. The picture below is the measured color gamut range of COB micro-display technology.
COB microdisplay measured color gamut
As can be seen from the figure, the color gamut range of COB micro-display technology is much wider than the DCI-P3 standard and ITU-R BT.709 standard currently adopted by the film and television industry. The color gamut range of COB LED micro-display technology is much wider. Compared with liquid crystal display and laser projection, it has a stronger ability to express colors.
Compared with SMD LED small-pitch display technology, COB micro-display technology has high reliability in terms of pixel reliability. When used by the user, the pixel failure rate is less than 10PPM, which is one to two orders of magnitude lower than SMD small-pitch display technology.
In terms of achieving smaller point spacing, COB micro-pitch display technology can achieve point spacing above P0.5. SMD small-pitch display technology is generally used for point spacing above P1.0. COB technology can achieve clearer displays.
Therefore, COB LED micro-display technology has very obvious technical advantages compared with SMD small-pitch technology.
With the popularity of 4K TVs, 8K TVs are also beginning to come to us. 4K and 8K TVs have higher requirements for resolution and are also calling for the emergence of larger ultra-high-definition large-size panels. International display giants such as Samsung and Sony have all chosen to use COB micro-display technology for display technologies over 100 inches. This is not a coincidence, but as market demand continues to develop towards ultra-high-definition large-size displays over 100 inches, international display giants are required to come up with technical solutions that can meet market requirements. As Mini LED and Micro LED using COB display technology continue to mature, it is natural to adopt COB micro-display technology.
Looking at the domestic market, up to now, Ledman Optoelectronics has successfully achieved mass production of P1.9, P1.5, P1.2, P0.9 and other fine-pitch products. Its products have been applied in batches in more than 20 domestic industries and regions and ten overseas countries, and its technical level is industry-leading. In the process of developing COB micro-display products, Ledman Optoelectronics has also obtained a large number of intellectual property rights. As of the first quarter of 2019, COB micro-display technology has obtained approximately 30 technology patents.
Through the above analysis, it can be found that COB LED micro-display technology is indeed the best technology for large-screen TVs above 100 inches and the best choice for large-screen TVs above 100 inches. As the mainstream domestic COB micro-display manufacturer, Ledman currently adopts the same technical route as Samsung and Sony. For the ultra-large screen display market of 100 inches or more, Ledman will gradually launch standard large-screen products of 100-300 inches to provide customers with ultra-large display solutions of 100 inches or more.
ANNA