In the colorful digital world, display devices play an extremely important role as an indispensable component of human-computer interaction. At present, the most familiar one is undoubtedly the rapid development of LCD liquid crystal display technology. However, with the continuous development of organic light-emitting technology, the new technology of planar display OLED has received great attention from the industry. As early as 1963, Pope of New York University realized the electroluminescence of germanium single crystal for the first time. However, due to the single crystal thickness of 102 (Vm, the driving voltage was as high as 400V, weak blue light could be observed, which failed to attract extensive research interest. Subsequently, many scientists used different molecular crystals and different cathode materials and doping methods to obtain molecular crystal electroluminescence with a quantum efficiency of up to 5% at a driving voltage of 100~800V. 21. Because the driving voltage is too high, it is organic. Devices made of crystalline materials do not have any practical value, and the research on organic crystal electroluminescence has been stagnant.
The fundamental shift in organic electroluminescence research comes from a substantial breakthrough by Kodak in the United States. In 1987, 131 people such as Tang used ultra-thin film technology, using conductive glass (IT0) as the positive electrode, 8-hydroxyquinoline aluminum (Alq3) as the light-emitting layer, triarylamine as the hole transport layer, and Mg/Ag alloy as the negative electrode. A two-layer organic electroluminescent device with low operating voltage (10V), high luminance (1000 cd/m), and high efficiency (5 lm/W) is an epoch-making progress of organic electroluminescence.
In 1990, 141 people such as Bur-roughes from the Cavendish Laboratory at the University of Cambridge in the UK first reported the electroluminescence of polystyrene (PPV) in Nature. C. Hegger, University of California, Santa Barbara, 1991. Group 151 was spin-coated with methoxy-isooctyloxy-substituted poly-p-styrene (MEH-PPV) on 丨TO to form an orange-red LED with a quantum efficiency of 1%. The prelude to LED research.
(Pioneer) Company launched the first organic EL product: a car text information receiving device, which is used to receive visual broadcast, traffic information, etc. The use of organic EL has high brightness and wide viewing angle, and can be clearly seen in the car. Watch the text at a price of 42,000 yen per unit. In the autumn of 1998, Pioneer also built a mass production line for organic EL displays, with monthly production of 100,000 to 150,000 pieces and investment of 3 billion to 4 billion yen.
On February 23, 1998, German Der Spiegel reported that the British Cambridge Display Technology Corporation (CDT) and Japan's Seiko Epson (Epson) jointly launched -r samples of organic EL TVs with a thickness of only 2mm. Compared with the traditional LCD screen, the display has higher resolution and is very competitive in price.
In May 1999, Pioneer introduced a color organic electroluminescence product that was also used for in-vehicle information receiving devices.
The current basic structure of OLED is to use a thin and transparent conductive indium tin oxide (ITO) as the positive electrode, and sandwich the organic material layer with another metal cathode in a sandwich-like structure 7-n. The organic material layer includes a hole transport layer (HTL), a light emitting layer (EL), and an electron transport layer (ETL). When a proper current is applied, the charge from the positive electrode and the charge from the cathode can be illuminated when the light is combined, and the organic materials of different compositions emit light of different colors, so different luminescent materials are selected. Display of full color can be achieved. The organic electroluminescence can be summarized as the following four processes: (1) injection of carriers (electrons and holes are injected from the cathode and anode, respectively); (2) carrier Transmission (injection of electrons and holes in the organic layer); (3) carrier recombination to form excitons; (4) exciton decay to emit photons (the characteristics of h 2 organic electroluminescence in the luminescent layer) At present, the mainstream electronic display technologies mainly include the following: cathode ray tube (CRT), liquid crystal display (LCD), light emitting diode (LED), inorganic electroluminescent device (inorganic EL), plasma discharge display ( PDP). Compared with these display technologies, the main features of LEDs are: compared with CRT, OLED has the advantages of low driving voltage, small size, light weight and foldability, and is the ideal for realizing foldable TV. Technology; LCD It is a passive illuminating technology, and has problems such as small viewing angle and slow response speed. OLED can just look at these shortcomings. OLED is an active illuminating technology, and its response speed is more than 1000 times that of liquid crystal; OLED devices are not like LEDs are required to have a long single crystal on the substrate, so that it is difficult to achieve a large area of ​​the LED. The organic layer between the OLED electrodes is an amorphous film, and it is easy to realize a large-area, ultra-thin display.
The smallest unit of its luminescence can be several tens of nanometers; inorganic electroluminescence has some difficulties and shortcomings that are difficult to overcome, such as few types, small color adjustability, limited luminous intensity, high driving voltage, etc., which can be overcome by OLED. Compared with PDP, OLED has the advantages of low driving voltage, high luminous efficiency, thinness, clear color, simple manufacturing process and low cost.
In addition, a wide variety of organic compounds, a variety of structures, organic synthesis methods can be designed and synthesized to meet a variety of color and process requirements.
Considering many aspects such as device structure, fabrication process, material development, etc., OLED is the most ideal display technology compared with various practical display devices and various display devices under development. However, as far as the current development is concerned, there are still two problems in the industrialization of organic electroluminescence from mass production: (1) selecting suitable materials to improve the efficiency and brightness of blue and red light; (2) the life of the device remains to be seen Further improvement; (3) production technology is still far from mature.
3 Research Status at Home and Abroad OLED's broad application prospects have attracted the participation of many research institutions and enterprises around the world. At present, organic electroluminescence technology is accelerating. In 1997, Japan Pioneer Electronics launched the world's first commercial organic electroluminescent product car audio display, which greatly encouraged the industry's confidence in organic electroluminescence technology. Since 2000, the industry has set off a wave of investment and development in organic electroluminescence. At present, more than 90 manufacturers in the world are engaged in the commercial development of organic electroluminescence. They are divided into two groups: organic small molecule electroluminescence and organic polymer electroluminescence. At present, among the foreign OLED products, most of the small-molecule OLED products are Japanese and Taiwanese manufacturers; while the investment in polymer OLED (PLED) products is mostly in Europe and America. According to statistics, about 85 manufacturers around the world have invested in R&D. More than 60 of them use small-molecule OLED material systems, and only about 25 manufacturers use polymer OLED materials systems.
The commercialization of small molecule OLEDs is faster than molecular OLEDs, but mainly passive. In 1996, Pioneer was the first to introduce 256x64 monochrome products. In 1997, IdemitsuKosan also released the first full-color 320x240 product. After that, Pioneer and other manufacturers published a variety of monochrome and colorful products. Leading manufacturers of passively driven small molecules have long been led by Pioneer. In terms of active driving small molecules, Eastman Kodak currently holds most of the patents for small molecule materials, and at the same time, through cooperation with Sanyo, TFT technology is used to publish active-driven small-molecule OLED products.
Polymer OLEDs are currently led by CDT, which is known for its active drive technology. Other investors such as Seiko have been transferred by CDT technology, while passively driven polymer OLEDs are dominated by Philips. Early polymer OLED manufacturing processes used spin coating technology to achieve more full color effects, and now more inkjet technology. Polymer OLEDs still have many problems in terms of material selection, control of the life of light-emitting components, unevenness of organic film, and difficulty in inkjet.
The following are the progress made by several major international companies in the research, development and industrialization of OLED products in recent years and their representative products: OLED display 7K screen of mobile phone sensible water. cMotorola company began to sell mobile phone P8767 using OLED display. DuPont invested US$5 million to form a polymer color light-emitting 6-inch test line for US UNIAX. Philips has invested $50 million to build a 14-inch test line; Siemens has also established a test line of a certain size in Malaysia.
In 2000, Sony introduced the OLED display for TV. The screen is 13 inches, the number of pixels is 800x600, the display color is 16.7 million, and each pixel is driven by 4 TFTs. eMagin introduces the first full-color small-molecule OLED microdisplay with a resolution of 600x3x852 and 16M colors. Toshiba America Electronics announced the first full-color OLED prototype with a polymer-based illuminator, 2.85 inches, 26,000 colors, 64-level grayscale, driven by LTPSTFT.
According to the computer sample, Toshiba Matsushita Display Technology Co., Ltd. developed a 17-inch LTPSTFT-driven 0LED panel with a resolution of XGA (1280x768). Pioneer also announced that the 20-inch full-color 0LED panel is ready. Recently, Kodak Company launched the world in the Chinese market. Chinese government, scientific research personnel and business people have also paid great attention to the research and development of OLED. During the period of the Ninth Five-Year Plan, the state has sponsored a number of major natural science fund projects and 863 high-tech projects. During the fifth period, OLED is still one of the national 863 key funding projects. With the support of national policies and funds, China has made great progress in the research and development of OLED. The business community has also given great attention to this. The Rainbow Group has invested in funds and Tsinghua University to jointly develop OLED displays. Shanghai University 13"4 Tsinghua University 151, Zhejiang University" 61, Southeast University, etc. have done a lot of research work on LED materials and devices, and have already achieved a certain level. Recently, Tsinghua University organic optoelectronics research room has been successfully developed recently. The 2.8-inch dot matrix organic electroluminescence display (http/3073011.shtml) has achieved important results in the preparation, production process and circuit drive of organic electroluminescence materials, and has applied for a number of patents.
4 Application of Organic Electroluminescence 1 Application of Organic Electroluminescence in Display Field In the field of display, the research and application of OLED has become a hot spot. The use of electro-optical display technology (OLEDS) for organic full-color displays will gradually replace the use of liquid crystal displays (LCDS) on laptops and desktop computers: OLEDs are a new generation of flat-panel technology following TFr-LCD. Japan's Pioneer's car stereo system multi-color display has been available, Kodak has also launched an OLED display digital camera on the market (littp:/10303/137052. Sangha, mobile phones using OLED display also Entering the practical stage, it is very likely that in the near future there will be a lightweight, foldable OLED display that can be hung on the wall, replacing the bulky cathode ray tube that has been used by the TV for 50 years.
A key part of OLEDs to be used in a wider range of applications is to achieve stable and long-lasting white photoluminescence. This has always been an important topic in the field of organic electroluminescence research. Once breakthroughs in white light efficiency, brightness, color purity and stability are achieved, the process of organic full-color display devices is greatly simplified. At present, it is reported that the white light result of 1191 has a luminance of 3000 cd/m 2 at 17 V and a lumen efficiency of 0.3 lm/W. The method for preparing an organic white light device mainly has the following two methods: one is to use three primary colors to emit light and white light. White light can be obtained, but the device structure and material system are often very complicated, and there are disadvantages such as poor process repeatability, high color purity of the device, large change in driving voltage, and generally low efficiency. Another method is to obtain white light 211 by excimer emission of the organic layer interface region. A wide emission band covering the entire visible light region can be obtained by self-emission of the material molecules and excimer emission.
4.2 Application of organic electroluminescence in the field of illumination In the field of lighting, OLED is also expected to be applied on a large scale. As we all know, on October 21, 1879, the incandescent lamp invented by American scientist Edison made people bid farewell to the darkness of the night and entered the era of illumination. However, incandescent lamps can only be illuminated by turning the tungsten wire into red and illuminating. When the tungsten wire is burnt red, there are 3000 high temperatures. Tungsten filaments are constantly being vaporized while constantly emitting light at high temperatures. When it is vaporized to a very thin, finally broken, the life of the bulb ends. It has been estimated that an incandescent lamp only converts 12% and 18% of its own electrical energy into light energy, and the rest are lost in the form of heat. This type of illumination makes incandescent lamps the least efficient in all electrical lighting fixtures. Moreover, incandescent lamps work at high temperatures, and their service life usually does not exceed hours. For light-emitting diodes (LEDs), the luminous efficiency can reach 50 to 100 times that of incandescent lamps, and the service life can reach 50,000 to 100,000 hours, that is, 5 to 10 years. At present, LED lighting technology has gradually become practical.
OLEDs have taken the manufacturing technology of LEDs a step further. The new type of 0LED replaces the crystalline structural material with a plastic polymer, and has the advantages of fast running speed, light weight, high brightness, low power consumption, etc., and is very strong and has extraordinary impact resistance. OLED is flexible in application, the shape is determined by specific lighting, and it can be used as an intelligent light source. COLED technology is suitable for drum production. The system is simple, similar to the current, Taiwan. Guanglei Company successfully developed a new product for white light illumination OLED, its luminous efficiency (greater than 20lm/W) surpasses the existing white light inorganic LEDC. Because OLED is a surface light source, it is more suitable for indoor lighting use than the point light source of LED. Become the protagonist of white lighting and backlight. In the future market strategy of Guanglei, outdoor will be dominated by inorganic LEDs, while indoors will be based on lower-cost organic LEDs. C 5 industrialization prospects Currently, various manufacturers are developing OLED applications with monochrome and multi-color displays. The main targets are in mobile phones, handheld video games, audio panels and PDAs. The future will develop in two directions: one is based on text and digital display, including the mobile phone and audio panel market; the other is small full-color display, the main application market is digital camera, camera and videophone and other application products. Then try to enter the large-size full-color display market, focusing on notebooks, monitors and TVs. At present, most of the OLED displays introduced by various manufacturers are still prototypes, and there is still much room for improvement in the future commercialization.
It will reach 70 million US dollars, and will reach 700 million US dollars by 2007. If the technology can make a more significant breakthrough, the future growth will be more impressive. Display Search predicts that OLED will reach 4 in the passive drive display market in 2003. 10 million pieces, its main application products are mainly mobile phones, followed by game consoles; in 2005, the market demand will reach 120 million pieces, and the main application range is still mobile phones. Active-powered displays are expected to grow to 50 million in 2005, growing exponentially every year. Organic electroluminescent display technology will become the mainstream in the display field.
6 In the short period of more than ten years, organic electroluminescence technology has made tremendous development, and its unique advantages have attracted more and more people's attention. Governments and enterprises have invested in the research of this technology, its research And development will open up a broad market for new flat panel information display, and its research results will be widely used in various instrument displays, mobile phone displays, laptop computers, wall-mounted TVs, etc., and will bring high brightness, high life white light illumination. New product.
Xinke Protective cotton flame resistant fabric has good breath ability and wicking properties, soft and comfortable. This is a characteristic of all-cotton materials, which allows us to develop a more comfortable feel while developing flame retardant functions. Of course, other materials fabrics have their own characteristics, such as cotton polyester fr fabric, cotton nylon fr fabric, arimid fabric, modacrylic fabric etc. If you are interested, you can find their related introductions in other categories.
Cotton Flame Resistant Fabric,Flame Resistant Fabric,Fire Resistant Fabric,Stain Flame Resistant Fabric
Xinxiang Xinke Protective Technology Co, Ltd. , https://www.coverallsuits.com