Flat Panel Display (FPD) has become the mainstream of future TVs. It is the general trend, but there is no strict definition in the world. Generally, this kind of display is thin and looks like a flat panel. There are many types of flat panel displays. , According to the display medium and working principle, there are liquid crystal display (LCD), plasma display (PDP), electroluminescence display (ELD), organic electroluminescence display (OLED), field emission display (FED), projection display, etc. Many FPD Equipment are made by granite. Because granite machine base has better precision and physical properties.
development trend
Compared with the traditional CRT (cathode ray tube), the flat panel display has the advantages of thin, light, low power consumption, low radiation, no flicker, and beneficial to human health. It has surpassed the CRT in global sales. By 2010, it is estimated that the ratio of the sales value of the two will reach 5:1. In the 21st century, flat panel displays will become the mainstream products in the display. According to the forecast of the famous Stanford Resources, the global flat panel display market will increase from 23 billion US dollars in 2001 to 58.7 billion US dollars in 2006, and the average annual growth rate will reach 20% in the next 4 years.
Display technology
Flat panel displays are classified into active light emitting displays and passive light emitting displays. The former refers to the display device that the display medium itself emits light and provides visible radiation, which includes plasma display (PDP), vacuum fluorescent display (VFD), field emission display (FED), electroluminescence display (LED) and organic light emitting diode display (OLED) )Wait. The latter means that it does not emit light by itself, but uses the display medium to be modulated by an electrical signal, and its optical characteristics change, modulate the ambient light and the light emitted by the external power supply (backlight, projection light source), and perform it on the display screen or screen. Display devices, including liquid crystal display (LCD), micro-electromechanical system display (DMD) and electronic ink (EL) display, etc.
LCD
Liquid crystal displays include passive matrix liquid crystal displays (PM-LCD) and active matrix liquid crystal displays (AM-LCD). Both STN and TN liquid crystal displays belong to passive matrix liquid crystal displays. In the 1990s, active-matrix liquid crystal display technology developed rapidly, especially thin film transistor liquid crystal display (TFT-LCD). As a replacement product of STN, it has the advantages of fast response speed and no flickering, and is widely used in portable computers and workstations, TVs, camcorders and handheld video game consoles. The difference between AM-LCD and PM-LCD is that the former has switching devices added to each pixel, which can overcome cross-interference and obtain high contrast and high resolution display. The current AM-LCD adopts amorphous silicon (a-Si) TFT switching device and storage capacitor scheme, which can obtain high gray level and realize true color display. However, the need for high resolution and small pixels for high-density camera and projection applications has driven the development of P-Si (polysilicon) TFT (thin film transistor) displays. The mobility of P-Si is 8 to 9 times higher than that of a-Si. The small size of P-Si TFT is not only suitable for high-density and high-resolution display, but also peripheral circuits can be integrated on the substrate.
All in all, LCD is suitable for thin, light, small and medium-sized displays with low power consumption, and is widely used in electronic devices such as notebook computers and mobile phones. 30-inch and 40-inch LCDs have been successfully developed, and some have been put into use. After large-scale production of LCD, the cost is continuously reduced. A 15-inch LCD monitor is available for $500. Its future development direction is to replace the cathode display of PC and apply it in LCD TV.
Plasma display
Plasma display is a light-emitting display technology realized by the principle of gas (such as atmosphere) discharge. Plasma displays have the advantages of cathode ray tubes, but are fabricated on very thin structures. The mainstream product size is 40-42 inches. 50 60 inch products are in development.
vacuum fluorescence
A vacuum fluorescent display is a display widely used in audio/video products and home appliances. It is a triode electron tube type vacuum display device that encapsulates the cathode, grid and anode in a vacuum tube. It is that the electrons emitted by the cathode are accelerated by the positive voltage applied to the grid and the anode, and stimulate the phosphor coated on the anode to emit light. The grid adopts a honeycomb structure.
electroluminescence)
Electroluminescent displays are made using solid-state thin-film technology. An insulating layer is placed between 2 conductive plates and a thin electroluminescent layer is deposited. The device uses zinc-coated or strontium-coated plates with broad emission spectrum as electroluminescent components. Its electroluminescent layer is 100 microns thick and can achieve the same clear display effect as an organic light emitting diode (OLED) display. Its typical drive voltage is 10KHz, 200V AC voltage, which requires more expensive driver IC. A high-resolution microdisplay using an active array driving scheme has been successfully developed.
led
Light-emitting diode displays consist of a large number of light-emitting diodes, which can be monochromatic or multi-colored. High-efficiency blue light-emitting diodes have become available, making it possible to produce full-color large-screen LED displays. LED displays have the characteristics of high brightness, high efficiency and long life, and are suitable for large-screen displays for outdoor use. However, no mid-range displays for monitors or PDAs (handheld computers) can be made with this technology. However, the LED monolithic integrated circuit can be used as a monochromatic virtual display.
MEMS
This is a microdisplay manufactured using MEMS technology. In such displays, microscopic mechanical structures are fabricated by processing semiconductors and other materials using standard semiconductor processes. In a digital micromirror device, the structure is a micromirror supported by a hinge. Its hinges are actuated by charges on the plates connected to one of the memory cells below. The size of each micromirror is approximately the diameter of a human hair. This device is mainly used in portable commercial projectors and home theater projectors.
field emission
The basic principle of a field emission display is the same as that of a cathode ray tube, that is, electrons are attracted by a plate and made to collide with a phosphor coated on the anode to emit light. Its cathode is composed of a large number of tiny electron sources arranged in an array, that is, in the form of an array of one pixel and one cathode. Just like plasma displays, field emission displays require high voltages to work, ranging from 200V to 6000V. But so far, it has not become a mainstream flat panel display due to the high production cost of its manufacturing equipment.
organic light
In an organic light-emitting diode display (OLED), an electrical current is passed through one or more layers of plastic to produce light that resembles inorganic light-emitting diodes. This means that what is required for an OLED device is a solid-state film stack on a substrate. However, organic materials are very sensitive to water vapor and oxygen, so sealing is essential. OLEDs are active light-emitting devices and exhibit excellent light characteristics and low power consumption characteristics. They have great potential for mass production in a roll-by-roll process on flexible substrates and are therefore very inexpensive to manufacture. The technology has a wide range of applications, from simple monochromatic large-area lighting to full-color video graphics displays.
Electronic ink
E-ink displays are displays that are controlled by applying an electric field to a bistable material. It consists of a large number of micro-sealed transparent spheres, each about 100 microns in diameter, containing a black liquid dyed material and thousands of particles of white titanium dioxide. When an electric field is applied to the bistable material, the titanium dioxide particles will migrate towards one of the electrodes depending on their charge state. This causes the pixel to emit light or not. Because the material is bistable, it retains information for months. Since its working state is controlled by an electric field, its display content can be changed with very little energy.
flame light detector
Flame Photometric Detector FPD (Flame Photometric Detector, FPD for short)
1. The principle of FPD
The principle of FPD is based on the combustion of the sample in a hydrogen-rich flame, so that the compounds containing sulfur and phosphorus are reduced by hydrogen after combustion, and the excited states of S2* (the excited state of S2) and HPO* (the excited state of HPO) are generated. The two excited substances radiate spectra around 400nm and 550nm when they return to the ground state. The intensity of this spectrum is measured with a photomultiplier tube, and the light intensity is proportional to the mass flow rate of the sample. FPD is a highly sensitive and selective detector, which is widely used in the analysis of sulfur and phosphorus compounds.
2. The structure of FPD
FPD is a structure that combines FID and photometer. It started as single-flame FPD. After 1978, in order to make up for the shortcomings of single-flame FPD, dual-flame FPD was developed. It has two separate air-hydrogen flames, the lower flame converts sample molecules into combustion products containing relatively simple molecules such as S2 and HPO; the upper flame produces luminescent excited state fragments such as S2* and HPO*, there is a window aimed at the upper flame, and the intensity of chemiluminescence is detected by a photomultiplier tube. The window is made of hard glass, and the flame nozzle is made of stainless steel.
3. The performance of FPD
FPD is a selective detector for the determination of sulfur and phosphorus compounds. Its flame is a hydrogen-rich flame, and the supply of air is only enough to react with 70% of the hydrogen, so the flame temperature is low to generate excited sulfur and phosphorus. Compound fragments. The flow rate of carrier gas, hydrogen and air has a great influence on FPD, so the gas flow control should be very stable. The flame temperature for the determination of sulfur-containing compounds should be around 390 °C, which can generate excited S2*; for the determination of phosphorus-containing compounds, the ratio of hydrogen and oxygen should be between 2 and 5, and the hydrogen-to-oxygen ratio should be changed according to different samples. The carrier gas and make-up gas should also be properly adjusted to obtain a good signal-to-noise ratio.
Post time: Jan-18-2022