What is a Liquid Crystal Display: An Introduction to Liquid Crystal Technology
This represents "liquid crystal display." LCD is a flat panel display technology commonly used in televisions and computer monitors. It is also used in the screens of mobile devices such as laptops, tablets, and smartphones.
LCD screens not only look different from bulky CRT (cathode ray tube) monitors, but they also operate differently. Instead of emitting electrons onto a glass screen, LCDs have a backlight that provides light to individual pixels arranged in a rectangular grid. Each pixel has an RGB (red, green, and blue) sub-pixel that can be turned on or off. When all sub-pixels of a pixel are turned off, it appears black.
When all sub-pixels are turned on at 100%, it appears white. By adjusting the individual levels of red, green, and blue light, millions of color combinations can be obtained.
How are LCDs constructed?
An LCD screen consists of a thin layer of liquid crystal material sandwiched between two electrodes on glass substrates, with two polarizing films on each side. The polarizer is a type of filter that allows specific polarized light waves to pass through while blocking others. The electrodes need to be transparent, so the most popular material is ITO (indium tin oxide).
Since the LCD itself cannot emit light, a backlight is usually placed behind the LCD screen to make it visible in dark environments. The backlight source can be either LED (light-emitting diode) or CCFL (cold cathode fluorescent lamp). LED backlighting is the most popular. Of course, if you prefer color display, a layer of color filter can be added to make the LCD cell. The filter is composed of RGB color. You can also add a touch panel in front of the LCD.
How do LCDs work?
The first mass-produced LCD panel technology is called TN (Twisted Nematic). The principle behind LCDs is that the molecules in the LCD unit twist 90 degrees when an electric field is not applied to them. When light from the environment or from the backlight passes through the first polarizer, the light is polarized and twisted by the liquid crystal molecule layer. When it reaches the second polarizer, it is blocked, and the viewer sees a black display.
When an electric field is applied to the liquid crystal molecules, they untwist. When polarized light reaches the liquid crystal molecule layer, the light passes through directly, without any twisting. When it reaches the second polarizer, it also passes through, and the viewer sees a bright display.
Because LCD technology uses an electric field instead of current (electrons passing through), it has low power consumption.
A short YouTube video will explain how liquid crystal displays work concisely and effectively.
The Basics of LCD Displays
The most basic type of LCD, as described above, is called passive matrix LCD, which is mainly used in low-end or simple applications such as calculators, electric meters, early digital watches, alarm clocks, and so on. Passive matrix LCDs have many limitations, such as narrow viewing angles, slow response times, dimness, and high power consumption.
To improve these drawbacks, scientists and engineers developed active matrix LCD technology. The most widely used is TFT (thin-film transistor) LCD technology. Based on TFT LCD, more modern LCD technologies have been developed. The most famous is IPS (in-plane switching) LCD, which features ultra-wide viewing angles, excellent image quality, fast response times, high contrast, and fewer burn-in defects.
IPS LCDs are widely used in LCD monitors, LCD TVs, iPhones, iPads, and so on. Samsung has even completely changed the LED backlight to QLED (quantum dot) so that the LED can be turned off in areas where light is not needed to produce deeper black.
Different Types of LCD Monitors
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Twisted Nematic (TN) Displays: The newest TN LCD production can be done most frequently and used in various industries. These displays are most commonly used by gamers because they are cheaper and have faster response times than other displays. Their main disadvantages are their lower quality and partial contrast, viewing angle, and color reproduction. However, these devices are sufficient for everyday use.
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In-Plane Switching (IPS) Displays: IPS displays are considered the best LCD because they offer good image quality, higher viewing angles, vibrant color accuracy, and contrast. These displays are mainly used by graphic designers, where LCDs need the maximum potential standards to reproduce images and colors in other applications.
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Vertical Alignment (VA) Displays: VA displays are in the center between twisted nematic and in-plane switching panel technology. Compared to TN displays, these panels have better viewing angles and color reproduction as well as higher quality features. These panels have short response times. However, these are more reasonable and more suitable for daily use.
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This panel's structure produces deeper blacks and better colors than twisted nematic displays. Several crystal arrangements can achieve better viewing angles compared to TN displays. These displays require a trade-off because they are expensive compared to other displays. Also, their response time is slow, and the refresh rate is low.
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Advanced Fringe Field Switching (AFFS): Compared to IPS displays, AFFS LCDs can offer the best performance and wide color reproduction. The application of AFFS is highly advanced because they can reduce color distortion without affecting wide viewing angles. Typically, this type of display is used in highly advanced and professional environments, such as feasible aircraft cockpits.
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Passive and Active Matrix Displays: Passive matrix LCD uses a simple grid to work, so it can provide a charge for specific pixels on the LCD. One layer of glass forms the columns, and another layer forms the rows, which are designed using transparent conductive materials like indium tin oxide. Passive matrix systems have major disadvantages, particularly slow response times and inaccurate voltage control. The response time of a display mainly refers to the display's ability to refresh and display the image.
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Active matrix LCD mainly relies on thin-film transistors (TFTs). These transistors are small switch transistors as well as capacitors, which are placed inside a matrix on a glass substrate. When the correct row is activated, the charge can be transmitted downwards to the exact column, so that a specific pixel can be addressed, as all additional rows intersecting that column is closed, only the capacitor adjacent to the pixel needs to be charged.
Advantages over other displays
LCD technology has a huge advantage of being light, thin, and low power, which makes wall-mounted TVs, laptops, smartphones, and tablets possible. On the path of progress, it has eliminated the competition of many display technologies. We no longer see CRT displays on our office desks or plasma TVs in our homes. LCD technology now dominates the display market. But any technology has its limitations.
The response time of LCD technology is slow, especially in low temperatures, with limited viewing angles, and when backlighting is required. To address the disadvantages of LCD, OLED (Organic Light-Emitting Diode) technology has been developed. Some high-end TVs and phones have started using OLED displays, which offer better contrast, color reproduction, and faster response times than LCD displays.
This cutting-edge technology offers better color reproduction, sharper image quality, better color gamut, and lower power consumption than LCD technology. Note that OLED displays include AMOLED and PMOLED (Passive Matrix Organic Light Emitting Diodes). You need to choose AMOLED for your TV and phone, not PMOLED.
10.1" LCD Display HD+ Single Module
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