1. The principle of liquid crystal display
LCD is the abbreviation of Liquid Crystal Display in English, that is, liquid crystal display. It is a digital display technology that can filter the light source through liquid crystal and color filters to produce images on a flat panel. Compared with the traditional cathode ray tube (CRT), LCD takes up small space, low power consumption, low radiation, no flicker, and reduces visual fatigue. Disadvantage: Compared with the CRT of the same size, the price is more expensive.
After occupying a leading position in the notebook computer market for many years, smooth display screens based on liquid crystal display technology are gradually entering the desktop system market. LCD has many advantages that traditional CRT display technology does not have. It can provide clearer text display, and the screen has no flicker, which can effectively reduce the visual fatigue caused by looking at the screen for a long time. The thickness of the LCD monitor is generally no more than 10 inches, so if the desktop system adopts LCD technology, it will save more space. Although LCD monitors have their attractive and unique features, it is undeniable that compared with the main competitor CRT monitors, LCDs still have shortcomings in high-quality color display. In addition, the huge price difference makes LCDs still only used A luxury product enjoyed by a few people.
As early as 1888, it was discovered that liquid crystal, a liquid chemical substance, is like a metal in a magnetic field. When it is affected by an external electric field, its molecules will have a precise and orderly arrangement. If the arrangement of the molecules is properly controlled, the liquid crystal molecules will allow light to pass through. Whether it is a laptop or a desktop system, the LCD display used is a layered structure composed of different parts. The last layer is a backlight layer made of fluorescent materials that can emit light. The light emitted from the backlight layer enters the liquid crystal layer containing thousands of crystal droplets after passing through the first polarization filter layer. The crystal droplets in the liquid crystal layer are all contained in a small cell structure, and one or more cells constitute a pixel on the screen. When the electrodes in the LCD generate an electric field, the liquid crystal molecules will be twisted, so that the light passing through it will be regularly refracted, and then filtered by the second layer of filter layer and displayed on the screen.
For simple monochromatic LCD displays, such as display screens used in handheld computers, the above structure is sufficient. However, for the more complex color displays used in notebook computers, a color filter layer that specializes in color display is also required. Generally, in a color LCD panel, each pixel is composed of three liquid crystal cells, and each cell has a red, green, or blue filter in front of it. In this way, the light passing through different cells can display different colors on the screen. Now, almost all LCDs used in notebook or desktop systems use thin film transistors (TFT) to activate cells in the liquid crystal layer. TFT LCD technology can display clearer and brighter images. Early LCDs were non-active light-emitting devices with low speed, poor efficiency, and low contrast. Although they could display clear text, they often produced shadows when displaying images quickly, which affected the display effect of videos. Therefore, they are only used today. Need black-and-white display in a handheld computer, pager or mobile phone.
Affected by the actual number of cells in the LCD liquid crystal layer, LCD displays generally can only provide a fixed display resolution. If users need to increase the resolution of 800X600 to 1024X768, they can only achieve analog resolution with the help of specific software.
Like traditional CRT monitors, LCDs used in desktop systems are also designed to receive waveform analog signals instead of digital pulse signals directly generated by PCs. This is mainly because the vast majority of standard graphics cards in current desktop systems still convert the video information from the original digital signal to an analog signal before sending it to the monitor for display. Although the LCD of the desktop system is designed to receive analog signals, the LCD itself can still only process digital information. Therefore, after receiving the analog signal from the graphics card, the LCD needs to restore the analog signal to a digital signal for processing. In order to solve the display deficiencies caused by the above problems, the latest desktop LCD adopts a special graphics card with a digital connector to directly transmit digital signals to the LCD display.
With the continuous maturity and development of LCD technology, the size of the display screen is gradually increasing. In the past, notebook computers used 8-inch (diagonal) fixed-size LCD monitors. Now, desktop system LCDs based on TFT technology can support 14 to 18-inch display panels. Because the manufacturer determines the size of the LCD according to the size of the actual viewable area, rather than the size of the picture tube as with the CRT, under normal circumstances, the size of a 15-inch LCD is equivalent to that of a traditional 17-inch color display.
2. List of LCD technology
<> PPI and resolution
Several display manufacturers, including Toshiba, the leading manufacturer of LCD displays, took advantage of this EDEX exhibition to release the newly developed 200PPI truly high-resolution TFT LCD display. PPI represents the number of pixels per square inch (Pixel). Therefore, the higher the PPI value, the higher the density the display screen can display images. Of course, the higher the density of the display, the higher the degree of realism. At present, most common TFT LCD screens are only 100PPI, and you can imagine what the effect will be if the display quality is twice as high as 200PPI.
<> Low-temperature polysilicon display exposure
In addition to the fierce battles between major manufacturers in terms of display quality, display area is of course another battleground for strategists. TFT displays with large display areas have been released one after another. Toshiba will officially apply 15-inch low-temperature polysilicon TFT technology to display screens or notebook computer products around the fall of 2000.
<> Novel resolution standard
I believe everyone is familiar with the resolution standards of VGA, SVGA, and even UXGA. But have you heard of the latest resolution standard called SXGA+? The display resolution represented by SXGA+ is 1400×1050. In fact, at the "LCD/PDP Internation 99" exhibition held in October 1999, three manufacturers including IBM, Samsung and Hitachi have already exhibited displays using the SXGA+ resolution standard. In this EDEX 2000, Sharp The company exhibited 13.3-inch/14.1-inch and 15-inch TFT display screens manufactured with this latest resolution standard for notebook computers.
<> Quad-VGA
Mitsubishi also exhibited a liquid crystal display product with the latest resolution standard. The resolution represented by "Quad-VGA" is 1280×960. Compared with the 1280×1024 display resolution of the general standard XGA, Quad-VGA will be a little bit flatter, and the aspect ratio is more than 4:3. In the future, the "Quad-VGA" standard display screen will be used by Sony in its L series VAIO notebook computers.
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