LCD liquid crystal display knowledge

Source: Internet
Author: User
Tags reflector
Q: What is LCD?
The original text of the LCD display is liquid crystal display, which consists of the first letter of each word. The Chinese name is "LCD flat display" or "LCD display 」. The working principle is to use the physical characteristics of the liquid crystal: The arrangement becomes orderly during power-on, so that the light passes easily; the arrangement becomes chaotic when no power-on is enabled, and the light passes through is prevented, to put it simply, the liquid crystal can block or let the light penetrate like a gate.
Q: Why should I buy an LCD display?
LCD has the following advantages: Compared with CRT display, LCD has the following advantages: Zero radiation, low power consumption, low heat dissipation, small size, precise image restoration, and sharp character display.
Q: What should I do if the LCD monitor flashes?
First, check the Connector pins of the signal line to eliminate poor contact conditions. After confirmation, check the refreshing rate set in the computer, which should be set to 60Hz.
Q: When the LCD monitor is switched on/off, the screen will be subject to noise. Is it normal?
Sometimes, when you click the Shutdown option of the computer, the screen will be disturbed by miscellaneous. This situation may be caused by the signal frequency of the vgacard, which is a normal phenomenon. You can also use "automatic image adjustment" in the display control menu to eliminate this situation.
Q: How can I set the resolution of an LCD display?
Different from the CRT display, the LCD has a fixed resolution, and the best image quality can be obtained at its maximum resolution. If the resolution of the output signal of the host is higher than the maximum resolution, the display enters the self-protection status and cannot be displayed. If the output signal is lower than the maximum resolution, the display quality cannot be optimal.
Therefore, the resolution of the LCD is not as high as possible. Generally, the optimal resolution (also the maximum resolution) of the 15' LCD is 1024x768, and the optimal resolution of the 17' LCD is 1280x1024.
Q: How should I set the update rate of the LCD display?
It is determined by the display characteristics of the LCD display. The LCD display does not require a high refresh rate. On the contrary, the LCD display has the best image quality at a 60Hz refresh rate. Therefore, we recommend that you set the refresh rate to 60Hz.
For LCD on the market, there must be 60 to 60 ~ 75Hz applicability, in fact, this is related to the use of elasticity and compatibility issues, as LCD display is trying to replace the CRT market position, most of today's display cards are still designed for CRT, higher elasticity and compatibility will help LCD display into the market and replace CRT display.
Q: Why is the "out of range" prompt displayed on the black screen of the monitor?
When the signal sent by the microcomputer exceeds the display range of the Monitor (usually the update rate or resolution is too high), the monitor enters the self-protection mode. If this problem occurs, you only need to reset the system update rate or resolution to restore the normal operation.
Q: How should I wipe the LCD panel?
Do not hit the Panel with hands or hard objects. If there is dust on the panel, gently wipe it with an optical mirror paper.
Q: What are precautions for LCD maintenance!
(1) Any humidity is dangerous.
This is common sense for all users who once caused keyboard damage by sprinkling drinks on the keyboard. Do not let anything with moisture into the LCD. When it is found that there is fog, use a soft cloth to gently wipe it, and then turn on the power. If the wet part has already entered the LCD, You must place the LCD in a warm place to let the moisture and organic content evaporate. Power-on the LCD containing humidity can lead to corrosion of the liquid crystal electrode, resulting in permanent damage.
(2) how to avoid internal screen burnout
Remember, CRT monitors can burn out because they work for a long time, as well as LCD. Unless you have paid a lot more to buy a more advanced LCD. Therefore, you must remember that if you do not need to use the monitor, you must disable the display or reduce the display brightness of the monitor. Otherwise, it will lead to internal burnout or aging after a long time. Once such damage occurs, it is permanent and irrecoverable. Therefore, we must pay enough attention to it. In addition, if a fixed content is continuously displayed for a long time, some LCD pixels may be overheated, resulting in internal burning.
(3) In order to avoid such internal burnout, the following measures can be taken when not used:
① Turn off the monitor when not in use;
② The display content on the screen is often changed at different intervals (for example, the screen saver is run );
③ Reduce the brightness of the display to a relatively dark level;
(3) do not vibrate strongly!
LCD Panel is very fragile, so it is necessary to avoid strong impact and vibration. LCD is almost the most sensitive electrical device in your home or office. The LCD contains a lot of glass and sensitive electrical components. falling onto the floor or other similar forced column strikes can cause damage to the LCD panel and CFL unit. Do not apply pressure on the LCD display surface.
(4) do not disassemble it!
There is a rule that never disassemble the LCD. Even after being disabled for a long time, the CFL converter in the background lighting component may still carry a high pressure of about V, which can cause serious personal injury. Therefore, never try to disassemble or change the LCD screen to avoid high pressure. Unlicensed repairs and changes will temporarily or permanently disable the display. So when your hands and feet are really idle, it is best to play with the lawn cutter or other playways, that is, do not touch the delicate and dangerous lcd1.

(5) Avoid unnecessary vibration
The LCD screen is very fragile, so it is necessary to avoid strong impact and vibration. LCD is almost the most sensitive electrical device in your home or office. The LCD contains a lot of glass and sensitive electrical components. falling onto the floor or other similar forced column strikes can cause damage to the LCD screen and CFL unit. Do not apply pressure on the LCD display surface.
LCD Maintenance
While enjoying the distinctive high-end display of LCD every day, do not forget the extremely important aspect of maintenance. Only after well-maintained LCD can the LCD be able to serve users without any faults for a long time. If you already have an LCD or flat panel, some tips here will be very useful to you. It should be clear that, for expensive LCD, as long as you follow some simple maintenance steps, you can be loyal to the long-term service, in the LCD, the only gradually consumable part is the background lighting of the display. After long-term use, you will find that the screen is dimmed or simply unavailable. In both cases, you only need to change the background lighting to bring the LCD back to life and become the same as the new one.
Common LCD displays are divided into four types by physical structure:
① Twisted vector model (TN), which is short for twisted nematic and mainly used in LCD screens of game consoles );
② Ultra-distorted column type (STN, full name: Super TN, most of which are used by mobile phone LCD screens );
③ Dual-layer ultra-distorted column type (dstn, full name dual scan tortuosity Nomograph, used on early laptops and digital devices such as mobile phones );
④ Thin film transistor type (TFT, full name: thin film transistor, currently mainstream applications)
Tn LCD screen is the originator of various LCD screens. Its technical principle is the cornerstone of the development of LCD screens in the future. The TN Liquid Crystal Display Screen consists of two splices made of glass substrates, itofilms, radial films, and reflectors. The upper and lower layers contain liquid crystal molecules, the liquid crystal molecules close to the upper interlayer are arranged in the direction of the upper groove, while the liquid crystal molecules in the lower interlayer are arranged in the direction of the lower groove. As a whole, the liquid crystal molecules are arranged in a reverse spiral shape.
Once the liquid crystal molecules are powered by an electrode, the TN Liquid Crystal will become erect, and the interlayer of the liquid crystal display will be attached with two partial light panels, the light emitting angle and the groove of the upper and lower layers are arranged in the same way. Normally, only one angle of light can penetrate from top to bottom.
A complete light penetration path is formed by importing the light source into the groove of the upper interlayer, and then passing through the reverse arrangement of the liquid crystal molecules from the lower reflector. When the time line of the liquid crystal molecule is erected, the result is black on the display screen. In this way, the screen can be displayed on the screen if the light is white or black.
At present, the mainstream TFT-type LCD display is more complex. It mainly consists of a fluorescent tube, a light guide board, a partial light board, a filter board, a glass substrate, a forward film, liquid crystal materials, thin film transistor, and so on. A tft LCD display has a backlight fluorescent tube. The light source first goes through a reflector and then goes through the LCD. Then, the arrangement of Liquid Crystal Molecules changes the light angle of the liquid crystal penetrating, then the light must pass through the color filter film in front of it with another light source.
As long as you change the voltage value added to the liquid crystal, you can control the final light intensity and color, so that you can change the color combinations of different colors on the liquid crystal panel.
Refresh frequency
The refresh frequency is the vertical scanning frequency (field frequency) of the monitor. It refers to the number of times the electron gun scans the entire screen per second, in Hz. For a CRT display, the image displayed on the CRT display is composed of many fluorescent points. Each fluorescent point emits light under the hitting of the electron beam, but the time for the fluorescent point to emit light is very short, therefore, it is necessary to constantly refresh the electron beam and hit the phosphor to make it shine continuously. Only when the refresh is fast enough can the human eye see a continuously more stable picture and will not feel the flickering and jitter of the picture, eyes are not prone to fatigue. Therefore, the refresh rate of the CRT display is no less than 85hz at the relevant resolution to make people look more comfortable.
Compared with a CRT display that splits the screen into several "scanning lines" for Refresh, the screen flashes, and the LCD generates images not by scanning the electron gun, but by controlling whether the light is transparent to control the brightness and darkness, therefore, the LCD refresh is to refresh the entire screen. Even at a low update rate (such as 60Hz), the LCD will not flash, and the image is stable.
Therefore, you do not need to increase the refresh frequency when adjusting the LCD. Use 60Hz (1024x768 resolution) 75Hz (1280x1024 resolution) or "Default display frequency ".
Visual Angle
The visual angle of the monitor refers to the maximum angle from which all content on the screen can be clearly viewed in different directions. The visual angle of the CRT monitor is theoretically close to 180 degrees above and below. Because the LCD uses light transmission for imaging, the visual angle of the LCD is smaller than that of the CRT display-in the LCD, direct and oblique light will penetrate the pixels in the same display area, therefore, when you view the screen from a greater angle than you can view the screen, you will find that the image has a shadow, discoloration, and other phenomena.
At present, the horizontal (left and right) Visual Angle of LCD displays on the market is generally above 120 degrees, while the vertical (up and down) visual angle is slightly smaller, generally above 100 degrees. To obtain a better visual angle, in addition to adjusting the sitting posture or display angle to the LCD as much as possible, you can adjust the brightness of the LCD as much as possible, this can also maximize the available visual angle of the LCD.
Response time
The signal response time is the response delay of the LCD unit. It refers to the time required for the LCD unit to change from one molecular arrangement to another, that is, the speed at which the screen turns from dark to dark or from Bright to dark. The shorter the response time, the better. It reflects the speed at which each pixel of the LCD displays reacts to the input signal. Generally, the response time is divided into two parts: Rise Time (rise time) and fall time (fall time), indicating that the sum of the two prevails, not one way.
At present, the response time of mainstream LCD can be within 25 ms, and the new mainstream types are mostly 8 ms ~ Between 16 Ms. 25 Ms = 10.025 = 40 screenshots per second, meeting the needs of video playback; 16 Ms = 10.016 = 63 screenshots per second, meeting the needs of most games; 12 Ms = 10.012 = 83 frames per second. However, due to the LCD update rate of Hz, 12 Ms generally cannot reach 83 frames per second. Therefore, the mainstream LCD has been able to cope with the needs of normal users for DVD playing and games.
Traditional CRT Displays support full-screen and stable display of all images in the supported resolution as long as the row frequency and bandwidth are sufficient. The pixels of the LCD are fixed, so the LCD only has the optimal resolution (maximum resolution, the optimal resolution of 15 inch LCD is 1024 × 768, 17 ~ The optimal resolution of 19 inch is usually 1280 × 1024.
When the LCD is displayed at a low resolution, the following two methods are generally used:
① Center display: for example, a screen with a resolution of 1024 × 768 is displayed on the screen with an optimal resolution of 800 × 600. Only the 800 × 600 pixels in the center of the screen are displayed, and other pixels remain dark.
② Extended display: When the display is lower than the best resolution, each pixel is expanded to the display of adjacent pixels through the differential algorithm, so that the entire screen is stretched and expanded. However, this also causes the image to lose its original definition and true color.
LCD display Maintenance
Expert Suggestion 1: maintain a dry working environment and avoid contact with chemicals
It must be known that water is the natural enemy of Liquid Crystal. If the humidity is too high, the liquid crystal display will be exposed, leakage and short circuit will occur after condensation, and the liquid crystal display will become blurred. Therefore, do not place the liquid crystal display in a humid place, or let anything with moisture enter the liquid crystal display. If you find that only the screen surface is misty before starting the boot, use a soft cloth to gently wipe it. If moisture has already entered the LCD display, you can turn off the display and bring the LCD back to the sun, or use the lamp to bake and evaporate the water in it. However, do not expose the LCD screen to the sun, which will lead to aging of components. Experts remind consumers that major international manufacturers such as LG pay great attention to after-sales services. If there is a serious tidal event, it is best for normal users to contact the local brand after-sales service provider, ask them for help and comparison insurance. Because the serious moisture will damage the LCD components, the user will contain high humidity LCD power, will lead to liquid crystal electrode corrosion, resulting in permanent damage.
In addition, the daily use of hair gel and frequent use of mosquito killer agents in summer will also cause damage to Liquid Crystal Molecules and even the entire display, leading to the shortening of the overall display life, therefore, we should try to avoid contact between the display and chemicals.
Expert suggestion 2: Avoid overload LCD display for a long time
First, do not make the LCD High Brightness for a long time. The LCD display mode is different from the CRT mode. Long-highlighted screen can easily shorten the use life of the backlight tube of the LCD display. Therefore, when you do not need it for a long time, you should disable the display. In addition, the brightness of the LCD can be adjusted to a lower value during daily use. These measures will be of great help to extend the life of the LCD.
Second, try to avoid displaying the same screen for a long time. The LCD will cause internal aging or burn-out due to long working hours, especially when the same screen is displayed for a long time. The reason is that the LCD can easily cause some pixels to overheat after a long period of operation. Once the limit is exceeded, permanent damage will occur and cannot be repaired. This forms a common "bad point ". Because the pixels of the LCD display are composed of Liquid Crystal bodies, when working at full load for more than 96 hours, it will be accelerated to aging, severe hours or even burned out. Therefore, experts remind consumers that if they have to work for a long time, it is best to take a break intermittently or change the screen display content at different time intervals. If they just leave temporarily, the Screen Saver should be started, or the brightness of the display can be reduced to a full white screen, which not only delays the aging of the LCD screen, but also avoids hardware damage.
Expert Suggestion 3: Reduce Unnecessary touch or vibration
The LCD screen is very fragile and delicate, so you should get rid of the bad habit of pointing fingers to the screen. This is because even a slight click may generate a local bad point, which may even lead to a black point, which may easily lead to more bad points, this is why some users may discover more and more bad points over a period of time. Note that the power consumption of the LCD is relatively small, but the voltage of the transformer after the LCD is very high. Pay special attention to safety. Do not open the back cover of the LCD when the LCD is powered. Even after a power failure, the voltage remains quite high. The CFL Transformer in the background lighting component still carries a high voltage of about V, so it is best not to touch it at will.
In addition, the impact resistance of liquid crystal display is also relatively poor. Even the latest products, the impact resistance is far inferior to that of CRT display. This is because LCD displays contain many precision glass elements and sensitive and delicate electrical components. Once a strong impact occurs, the LCD screen, related components or circuit may be damaged. When you move a liquid crystal display, you often do not pay attention to moving the screen, which may damage the surface of the liquid crystal display. Therefore, experts strongly recommend that you avoid great impact and apply pressure on the surface of the LCD screen.
Expert suggestion 4: Correct cleaning of liquid crystal display surface dirt
If dirt is found on the surface of the liquid crystal display, clear it in the correct way. It is best to use soft and non-fiber materials, such as skim cotton, lens paper, or glasses cloth. Generally, water can be removed. However, if the cleaning effect cannot be effectively achieved, you can purchase commercial LCD cleaning products. One expert pointed out that consumers should not clean up with cleaning liquid containing ammonia, alcohol and inorganic salts.
At present, the liquid crystal display manufacturing technology is very focused on low-definition radiation, anti-reflection, anti-glare, anti-static interference, environmental protection and other designs, so the process of each part has undergone multiple protection measures, such as multi-layer film mirror processing, or coating more special polymers, etc. These special chemicals are often damaged by chemicals that contain ammonia, alcohol and inorganic salts, resulting in the display slowly losing the true optical transmittance, it may cause color distortion caused by reduction reflection, or reduce the effect of anti-interference and anti-static. This will not only affect the eyes, but also affect the image display quality, and the original protection functions will also be damaged, the color and security are compromised, so consumers have to be cautious.
Expert suggestion 5: you cannot disassemble the LCD display if any problem occurs.

Because the LCD is too precise and delicate, you cannot change components as you would with a common CRT. Therefore, no matter what problems it has, do not disassemble the LCD display on its own, this is not the scope of DIY "game"; once the LCD display is suspected to work abnormally, be sure to seek help from professional vendors. Experts once again reminded consumers that the CFL shunt in LCD backlight lighting components may still carry a high pressure of V (although it is a micro-current) after being shut down for a certain period of time, even if there is no harm to the human body, for LCD display, non-professional personnel may cause new component faults if they are not properly handled. In severe cases, the screen may be permanently unavailable.
The above are some important maintenance methods proposed by engineers of lg LCD. It can be seen that LCD is indeed a very delicate high-end product, and its quality and performance require high manufacturing technology and technology. Therefore, it is best for ordinary users to choose some well-known brands at the beginning of the purchase. In particular, LG has recently made a commitment to keep liquid crystal display intact, that is, there are neither bright spots nor hidden spots, philips also launched the same LCD product. Because they are not only technically competent, but also have a large number of after-sales outlets distributed throughout the country, and their services are more professional and high-quality, users can buy more assured and more comfortable to use.


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