How is the most popular black technology flexible

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Black technology in everyone's eyes: how is the flexible touch screen shaped

from the hot sale of Samsung Galaxy edge flagship series to the successive advent of various song screen bracelets and TVs, there is no doubt that song screen technology has been widely valued and pursued by consumers and the industry in recent years. In the future, with the continuous development and improvement of the fixed curvature curved screen technology, the flexible touch screen that can realize arbitrary bending will become an important development direction

On the 25th, at the 13th International touch screen and display technology development forum, Huang Hanfeng, deputy general manager of touch research and development from Shenzhen oufeiguang technology, made a detailed introduction to the flexible touch screen from the perspective of the industrial chain, focusing on the four key elements of flexible display, flexible touch, flexible cover and flexible fitting

flexible display

for LCD, the LCD is usually responsible for controlling the display gray, and the three primary color filter controls the display color, which requires that they must be one-to-one corresponding in order to display normally. If the LCD panel is used as a curved screen, the inner perimeter and outer perimeter will be unequal, and the original one-to-one corresponding LCD and filter will have position deviation, resulting in color distortion. In addition, it will also cause light leakage, dark screen ghosting, snowflakes and other problems. Therefore, for the curved screen, OLED display technology represented by AMOLED has almost become the best choice

Huang Hanfeng said that at present, Samsung is the undisputed leader of AMOLED in terms of patents, production capacity, yield and technology accumulation. Its sixth generation AMOLED panel, which began mass production at the end of 2014, can now produce 50000 pieces per month, and the yield can reach 60%. The second is LG, but LG has always been focusing on large screen curved TV. At present, with the increasingly obvious trend of small screen AMOLED, LG is also accelerating the layout of small and medium-sized flexible screens. Although its output is not as good as Samsung, its yield can also reach more than 60%. The latest release of Xiaomi Note2 is the latest market analysis report of LG's flexible amolpci film consulting company (hereinafter referred to as PCI), which points out that the ED screen. In addition, Japan's JDI and sharp (which have been acquired by Hon Hai), Taiwan's Youda, and domestic screen manufacturers such as BOE and Ruoyu are also accelerating the layout of their own AMOLED technology. It is the general trend for AMOLED to replace LCD

flexible touch

in terms of touch control, ITO (indium tin oxide) transparent conductive film has become the most important touch layer material for non curved LCD and OLED display screens due to many reasons, such as good light transmittance, low thickness, excellent hardness and conductivity, mature manufacturing technology and so on. However, as ITO itself is a brittle material, it is not suitable for making flexible touch layers with large curvature or even arbitrary bending, and the cost and cost are high. At present, it accounts for about 30% - 40% of the cost of the upstream material part of the whole touch screen industry, and uses "indium", a rare metal with limited reserves. Therefore, with the advent of the era of curved surface and flexibility, it is likely to be replaced

Huang Hanfeng said that at present, the main substitutes for ITO materials are graphene, carbon nanotubes, nano silver and metal lattice. Among them, graphene and carbon nanotubes are very good substitutes for ITO because the material itself is supplied by a large flow pump to the servo actuator. However, graphene is still in the research and development stage, which is still far from mass production. The industrial mass production technology of carbon nanotubes is not perfect, and the conductivity of the thin film products made of carbon nanotubes is not as good as that of ITO. Therefore, from the perspective of technology and marketization, metal lattice and nano silver technology will be the protagonists of development in recent years. Metal lattice technology has been applied in some PC display markets

the metal lattice technology mentioned here is the conductive metal formed by pressing metal conductive materials such as silver and copper or oxides on thin film substrates such as pet. Its main advantages are low raw material cost and good folding ability. However, due to the problem of Murray interference ripple caused by yield, output and high-speed pixels, it is more suitable for applications in desktop all-in-one computers, laptops, televisions and other products with low resolution and relatively long-distance use

nano silver technology refers to coating nano silver ink material on pet or glass substrate, and then using laser lithography technology to depict the conductive complex of silver wire with nano level. Its main advantages are high yield, small linewidth, good conductivity and folding resistance, while its disadvantages are high cost. Moreover, compared with the metal lattice, the nano silver material has a smaller radius of curvature, and the resistance change rate when bending is small. In addition, due to the linewidth, it is more suitable for use in high-resolution close-up scenes such as, smart watches and bracelets

relatively speaking, the industry seems to be more optimistic about the prospect of nano silver

flexible cover plate

in order to bend at will, in addition to solving the flexible display and flexible touch control, the last and most critical part is the flexible cover plate and fitting. However, due to its hard and fragile characteristics, glass cover may not be the best choice in the flexible field

Huang Hanfeng said that compared with glass, pet and PI (polyimide) materials with high surface hardness and high light transmittance may be more suitable for flexible screens, but at present, pet and PI also have many problems to be solved. On the one hand, they are not resistant to high temperature and have poor light transmittance: pet and PI will have problems of partial melting and property change under low ambient temperature, and they do not have good light transmittance compared with glass

secondly, it is difficult to achieve a balance between hardness and folding. Huang Hanfeng said that if you want to meet certain hardness requirements, you need to coat the hardened layer, but after coating the hardened layer, after repeated folding, the hardened layer will crack and reduce its hardness. Therefore, how to achieve a balance between the two is the biggest bottleneck at present

compared with the flexible cover plate that needs further development, the 3D glass cover plate that is necessary for curved screen at present has a very good development prospect

according to the data, 2018 may become the explosion year of 3D glass cover plate. It is expected that the penetration rate of 3D glass cover plate will exceed 50% around 2020. With the maturity of 3D glass cover plate processing technology and the decline of unit price, the penetration rate will further improve. It is expected that the market scale in the future will reach more than 19billion yuan

Huang Hanfeng said that the current common 1R (single arc bending) and 2R cover plate manufacturing process has a certain guarantee for all the equipment produced. Basically, the module is cooled by metal heat sink, and basically, a bending effect is achieved by hot bending technology. But the yield is a problem to be solved. At present, it is basically only 30%, and it is difficult to improve the yield in the short term. If we want to do 4R in the future, the yield will be lower. Therefore, the yield is one of the urgent problems to be solved in the manufacturing of cover plate

flexible fitting

fitting is after the cover plate is selected, that is, integrating the cover plate with the touch and display layer below to form a complete module. At present, there are two common methods: roller type and vacuum bonding: the roller has high efficiency and needs to roll the pasted object. The efficiency of vacuum type is relatively low, but it does not need to roll the pasted object, so it is not easy to cause damage to the pasted object

Huang Hanfeng said that if the curvature is large, you can only choose vacuum fitting. However, for the possible 4R fitting in the future, due to its special four side bending characteristics, it is difficult to avoid wrinkles and bubbles in places with large radians even if the vacuum method is adopted. At present, the industry has used customized extruded air bags or plastic parts to alleviate this problem, but it has not been completely solved. Therefore, there is still room for improvement in the fitting process of multi surface and high curvature

Huang Hanfeng said frankly: "from the perspective of supply chain, it will take several years for the flexible screen to truly realize mass production, and it also requires upstream and downstream supply chains to jointly overcome relevant technical problems."

for future development, Huang Hanfeng believes that the integration of various modules will be the general trend. He said, "in the incell technology of LCD, ITO touch film and liquid crystal layer are integrated together, which is a good integration. Now the fingerprint module is independent, and it can also be integrated with touch in the future. I think there will be a process of mutual integration and progress between functional modules in the future."

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