The difference between LCD and CRT monitors and their maintenance

While enjoying the unique high-end display of the LCD every day, don't forget to take care of this extremely important part. Only when the LCD is well-maintained can it be possible to service the user for a long time without any problem. If you already have an LCD or flat panel display, here are some tips that are very useful to you.

The common liquid crystal display is divided into four types according to the physical structure:

1 Twisted nematic (abbreviated as TN, full name TwistedNematic, mainly used in game consoles and other fields);

2 super-twisted nematic (abbreviated as STN, full name SuperTN, is currently used by mobile phone LCD screen);

3 double super twisted nematic (DSTN, full name DualScanTrotuosityNomograph, early notebook computers and current mobile phones and other digital devices are used);

4 thin film transistor type (TFT, full name ThinFilmTransistor, the current application of the mainstream).

TN liquid crystal display screen is the originator of various LCD screens, and its technical principle is the cornerstone of the development of LCD screens. The TN liquid crystal display includes two layers of a glass substrate, an ITO film, an alignment film, a polarizing plate, and the like. The upper and lower sandwich layers are liquid crystal molecules, and the liquid crystal molecules near the upper sandwich are arranged in the direction of the upper trench, and the lower portion The liquid crystal molecules in the sandwich are arranged in the direction of the lower trenches. As a whole, the liquid crystal molecules are arranged like a twisted spiral.

Once the liquid crystal molecules are powered by the electrodes, the TN liquid crystals will be in an upright state, and two polarizers are attached to the interlayer of the liquid crystal display. The arrangement and light transmission angles of the two polarizers are the same as those of the upper and lower interlayers. In normal situations, when light is radiated from above, usually only one angle of light can penetrate.

Through the upper polarizer plate is introduced into the groove of the upper interlayer, and passes through the twisted arrangement of the liquid crystal molecules, passing through the lower polarizer plate to form a complete light penetration route. When the liquid crystal molecules are erected, the light cannot pass through, and as a result, black appears on the display screen. This will result in black when light is transmitted and black when light is not transmitted. The screen can be displayed on the screen.

At present, the mainstream TFT-type liquid crystal display is more complicated in composition, and it is mainly composed of a fluorescent tube, a light guide plate, a polarizer plate, a filter plate, a glass substrate, an alignment film, a liquid crystal material, a thin film transistor, and the like. The TFT liquid crystal display has a backlight fluorescent tube. The light source passes through a polarizer and then passes through the liquid crystal. At this time, the arrangement of the liquid crystal molecules changes the angle of light passing through the liquid crystal, and then the light must also pass through the front color filter. Optical film with another polarizer. By changing the voltage value added to the liquid crystal, it is possible to control the intensity and color of the light that appears last, so that different color combinations of colors can be changed on the liquid crystal panel.

Note one: refresh frequency

The refresh rate is also the vertical scanning frequency (field frequency) of the display. It refers to the number of times the electron gun scans the entire screen every second, in Hz (Hertz). For a CRT monitor, the image displayed on the CRT monitor is composed of a plurality of fluorescent dots. Each fluorescent dot emits light under the striking of the electron beam. However, the time for the fluorescent point to emit light is very short, so electron beams must be continuously refreshed. Phosphor powder is used to make it continue to shine, and only refreshing fast enough, the human eye can see a continuous and more stable picture, will not feel the flickering and jittering of the screen, and the eyes will not easily fatigue. Therefore, the refresh rate of the CRT monitor is not lower than 85Hz at the relevant resolution for people to see more comfortable.

And the CRT monitor divides the screen into several "scanning lines" for refreshing. The problem of screen flicker arises. Compared to LCDs, the image is not scanned by an electron gun, but by controlling whether light is transmitted to control light and dark, so the refresh of the LCD is correct. The entire frame is refreshed, and the LCD does not flicker even at a low refresh rate (eg, 60 Hz), and the image is stable.

Therefore, when adjusting the LCD, you do not need to increase the refresh rate. You can use 60Hz (1024×768 resolution)/75Hz (1280×1024 resolution) or “default indicator”.

In addition, we must also choose to install an appropriate "monitor" driver. Do not simply use the "monitor" driver for the CRT monitor. Install the driver that is shipped with the LCD monitor, or the monitor "Standard monitor type" in the display properties. The "laptop display panel (1024x768 or 1280x1024)".

Note two: the number of colors

As we all know, the current mainstream CRT color displays support 32-bit true color, but LCDs are not all that. The LCD panel used in most entry-level LCDs on the market today is a 6-bit panel. It can only display 262,144 colors (64×64×64=262,144), and only 8 bit panels can display 16,777,216 colors (256×256× 256=16777216). So when you adjust the 6bit panel entry level LCD, the color will be displayed.

Note three: visual angle

The viewing angle of the display refers to the maximum angle from which all the contents of the screen can be clearly seen from different directions. The viewing angle of the CRT display can theoretically be approximately 180 degrees up/down or left and right. Since the LCD is developed with light transmission, the viewing angle of the LCD is smaller than that of the CRT display. In the LCD, both direct and oblique light penetrate the pixels of the same display area, so that the angle is larger than the viewing angle. You will notice ghosting and discoloration when viewing the screen.

Currently, the horizontal (left and right) viewing angles of the liquid crystal display on the market are generally more than 120 degrees, and the vertical (up and down) viewing angles are slightly smaller, generally more than 100 degrees. In order to obtain a better viewing angle in use, in addition to adjusting the sitting position or the angle of the display to be as far as possible facing the LCD, the brightness of the LCD may be appropriately increased, which also allows the LCD to have the maximum available viewing angle.

Note four: response time

The signal response time is the response delay of the liquid crystal cell of the liquid crystal display device and refers to the time required for the liquid crystal cell to change from one molecular arrangement state to another molecular arrangement state, that is, the speed at which the screen switches from dark to bright or from bright to dark. The shorter the response time, the better. It reflects the speed of response of LCD pixels to the input signal. Generally, the response time is divided into two parts: rise time (Risetime) and fall time (Falltime). And prevail, not one way.

At present, the mainstream LCD response time can be within 25ms, and the new mainstream models are mostly between 8ms and 16ms. 25 milliseconds = 1/0.025 = 40 frames per second display, can meet the needs of video playback; 16 milliseconds = 1/0.016 = 63 frames per second display, has been able to meet the needs of most games; 12 milliseconds = 1/0.012=83 frames per second are displayed, but due to the limit of LCD refresh rate of 60/75Hz, 12ms generally fails to reach 83 frames per second. Therefore, the current mainstream LCD monitors are fully capable of meeting the needs of general users for DVD playback and games.

Note five: resolution

As long as the line frequency and the bandwidth are sufficient, the conventional CRT monitor can stably support all the screens in the resolution supported by the full-screen stable display.

LCD pixels are fixed, so the LCD is only at the best resolution (maximum resolution, 1024x768 for 15-inch LCDs, and 1280x1024 for 17- to 19-inch LCDs). Can show the best image.

When the LCD is displayed at a low resolution, it is generally performed in two ways:

1 Center display: For example, an 800×600 screen is displayed on a screen with an optimal resolution of 1024×768. Only the centered 800×600 pixels are displayed, and other pixels remain dark.

2 Extended display: When displaying pictures below the optimal resolution, each pixel is expanded to the adjacent pixel display by a differential algorithm, so that the entire picture is stretched and expanded. But this also makes the picture lose its original sharpness and true color.

In practice, it is generally recommended to use "center display", although the screen becomes smaller, but it will not sacrifice the basic display. For example, the optimal resolution of a certain LCD is 1280×1024. To play a 3D game smoothly at such a high resolution, it is a huge test for most graphics cards within 500 yuan.

Therefore, most users choose to set the game to run at a low resolution, such as 1024×768 or 800×600. If they are displayed on the LCD in an “extended display” mode, the resulting image is very rough and unbearable. The "centered" display, though it can only use a large piece of liquid crystal in the middle of 800 × 600 or 1024 × 768, but it can maintain a better display.

To display in the "center display" mode, you can remove the "Extended image to panel size" option in the video driver during setup.

Note 6: Point defects

A CRT monitor basically does not have a screen "point defect", and the "point defect (including a dead point or a dark spot, a bright spot)" of the liquid crystal display has been present since the birth of the liquid crystal. The point defect of the so-called LCD is that a pixel in the liquid crystal display is damaged, and there is a continuous pixel that is bright, off, or monochrome and does not accept the extinguishing signal.

In the use to avoid the increase of point defects, the main attention should be paid to three aspects: 1 Avoid using any hard objects to touch or hit the LCD screen. 2 Avoid vibration during use or handling. 3 When you do not use the LCD, you should develop good habits and turn them off.

Knowledge: How to maintain LCD

The liquid crystal display is more delicate than a CRT monitor. How do you perform maintenance?

1. How to clean the LCD screen

After the LCD monitor is used for a period of time, you will find that the display will often attract a layer of dust (turning off the back of the LCD to see more clearly), and sometimes it will inadvertently stick to various water stains, which will certainly greatly affect the visual effects. How to clean it?

1 Turn off the LCD power and remove the plug of the power cord and the connector of the graphics card.

2 Move the LCD to a place where natural light is better so that you can see where the dust is, and it is more conducive to targeted, so as to achieve better cleaning results.

3 Clean the LCD screen does not require any special solution or wipe, in my experience, the clear water + soft lint-free cloth or pure cotton lint-free cloth is the best LCD cleaning tool (can not lose the paper towel line). When cleaning, you can use pure cotton lint-free cloth, rinse with water and wring it slightly, then gently wipe the dust on the display with a damp, soft, lint-free, damp cloth (do not forcefully squeeze the display). Wipe one side to the other until all are wiped clean, do not flutter.

Tip: Do not wipe with hard cloth or hard paper. At the same time, do not use cleaning solutions containing alcohol or acetone or chemical detergents, and do not spray liquids directly onto the screen to prevent liquids from penetrating into the protective film.

4 After cleaning the LCD screen with a damp, soft, damp cloth, clean it with a damp cloth that is relatively dry. Finally, let the water vapor on the LCD screen dry naturally in the ventilated place.

2. Other maintenance and maintenance points

(1) Avoid shocks. LCD LCD screen is very fragile, to avoid strong shock and vibration. Do not apply pressure on the LCD screen or collide with the LCD monitor back cover.

(2) Avoid prolonged use of the screen. Long-term work is not a good thing for the LCD. If you are not using it, be sure to turn off the monitor. Similarly, use wallpapers and screensavers with caution when using LCDs. Most of the wallpapers and screensavers are brightly colored, and the contrast between light and dark changes strongly. If they are used for a long time, the LCD color will be distorted, which will affect the life of the LCD display. Therefore, it is best to use a monochrome screen and cancel the screen saver when using the LCD.

(3) Anti-electromagnetic interference. Whether it is a CRT or an LCD display, keep objects away from strong magnetic fields. A strong magnetic field around the display will generate extra voltage inside the display, which will affect the stability of the display voltage. For a long time in a strong magnetic field, it will also make the color distortion, thus affecting the LCD display effect and life.

(4) Pay attention to moisture. Do not let any moisture enter the LCD. If the humidity in the room is too high, condensation may occur inside the LCD. As a result, the LCD may leak and short circuit. In severe cases, the monitor may be burned. For some southern regions where the humidity is relatively high, the LCD may be placed in a warm and dry place, or the back of the liquid crystal display may be periodically baked with a powerless desk lamp so as to evaporate the moisture therein.

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