With the rapid development of time and technology, various types of LCD technology are emerging. If you want to understand or learn about LCD technology, then this article will introduce you to the main LCD technology on the market.
What is LCD?
LCD, that is, “liquid crystal display”, is a flat display technology. It is composed of a certain number of color or black and white pixels, placed in the light source or reflective environmental light source to form an image.
It is used in a wide range of applications, from small TV, cell phone and computer applications to large medical equipment, industrial automation and military applications.
The important components of the LCD
Liquid crystal layer
Liquid crystal layer is composed of liquid crystal molecules. Liquid crystal molecules have a certain long axis and short axis, you can change the direction of its arrangement through the role of the electric field, thereby controlling the transmission and blocking of light.
Glass substrate
Glass substrate is the support part of the liquid crystal display, usually consists of two glass panels, sandwiched between the liquid crystal layer. The glass substrate has good light transmission and mechanical strength, can protect the liquid crystal layer, and provide a flat surface for liquid crystal molecules in different arrangements.
Conductive layer
Conductive layer is one of the components of the liquid crystal display, it is mainly used to apply electric field and control the arrangement of liquid crystal molecules. Conductive layer is usually used transparent conductive oxide materials, such as indium oxide (In₂O₃), tin oxide (SnO₂) and so on.
Color filter
Color filter is an important part of the liquid crystal display to show color images. It is usually composed of red, green, blue three-color filter, by adjusting the intensity of light penetrating the different color filters, can produce color images.
Backlight
Backlight is the key part of the LCD brightness, it can make the image can be displayed under the backlight. Commonly used backlighting cold cathode tube (CCFL) and LED backlighting.
Driver circuit
Driver circuit is the control center of the liquid crystal display, it can control the liquid crystal molecular arrangement according to the input signal, so that the image is displayed.
The working principle of LCD
LCD is essentially two glass panels coated with a transparent conductive layer sandwiched between a layer of liquid crystal. When there is a current through the liquid crystal molecules will change according to the electric field changes in the direction of the arrangement, and then, this arrangement will affect the direction of the light through the display, to form an image on the display.
LCD technology types
According to the passive matrix LCD (PM LCD) classification
Passive matrix LCDs are addressed through common and segmented electrodes. Pixels or icons are formed at the overlapping intersection of the common and segmented electrodes.
The common electrode is addressed sequentially one at a time, while the segmented electrodes are addressed simultaneously and information corresponding to all pixels or icons connected to the current common electrode is acquired. The principle of operation is known as multiplexing.
TN: Twisted Nematic
TN technology is the most common, placing liquid crystals between glass panels, and when power is applied, the liquid crystals will be twisted and aligned at 90° parallel to the surface of the display to form a suitable viewing angle and visual effect. The display is mostly black and white.
VA: Vertical Alignment
In a VA display, the liquid crystal molecules are aligned vertically with respect to the display surface. With or without distortion, the applied voltage causes the liquid crystal molecules to lie flat. Only black masks, colored icons or symbols can be made to display.
HTN/STN: Hyper Twist Nematic
Both HTN technology and STN technology are derivatives of TN technology. The difference is that HTN technology can twist liquid crystals to an alignment greater than 90 degrees but less than 180 degrees, while STN technology can twist liquid crystals to an alignment between 210 and 270 degrees. This technology allows the multiplexing drive capability and duty cycle of STN to be greatly improved.
FSTN: Film Compensated Super Twisted Nematic
FSTN technology is composed of STN technology and thin film, using the principle of birefringence, adding the same birefringence in the opposite direction can compensate for the color. It makes FSTN display have higher contrast ratio.
WVTN: Wide Viewing Angle Twisted Nematic
WVTN technology has the same concept as FSTN technology. The difference is that the compensation film in WVTN is a twisted liquid crystal structure and polymerized into a film, whereas the compensation film in FSTN technology is a film formed with a stretched polymer. The compensation film in WVTN improves the display characteristics of a shallow viewing angle while maintaining the performance of straight line viewing.
Classification by Active Matrix LCD (AM LCD)
Active matrix LCDs are able to address one row and isolate other rows, so the requirements for the electro-optical properties of the liquid crystal configuration are less stringent.
IPS(In-Plane Switching) and FFS（Fringe Field Switching）
IPS technology and FFS technology are technologies that apply current stimulation only between electrodes on one substrate, with current stimulation applied between electrodes on two substrates. This will have a wider, more symmetrical viewing angle and better image quality.
MVA and PVA
In a display, each color sub-pixel is further divided into regions (called domains) that have different directions of molecular motion when a voltage is applied. MVA technology is achieved by carefully designed protrusions on the inner surface of the display, whereas PVA uses fine patterning of electrodes on both substrates.
ASV: Axisymmetric Vertical Alignment
ASV is called Axisymmetric Vertical Alignment and can also be referred to as Advanced Super View. ASV is a version of MVA technology in which instead of two or four domains per pixel, the liquid crystals are switched radially around the center of the pixel.
AIFF MVA: Amplified Intrinsic Fringe Field Multi-Domain Vertical Alignment
AIFF-MVA is a technology that attempts to combine the advantages of VA technology with FFS technology.
TFT: Thin Film Transistor
TFT technology means that each liquid crystal pixel point on an LCD is driven by a thin-film transistor integrated behind it. Thus, it can do high brightness and high contrast display effect.
The difference between LCD and LED display technology
Above has introduced you to the technology type of LCD, next, will be for you to distinguish between the two display technologies LCD and LED.
- Contrast ratio:The contrast ratio of LCD is 350:1, while the contrast ratio of LED display can reach 5000:1. LED display far exceeds the contrast level of LCD. The high contrast ratio can make the picture more vivid and the details more prominent.
- Brightness:The brightness of LCD is usually between 250-1500cd/m², while the brightness of LED display is usually between 700-5500cd/m². The high brightness can maintain a clear and visible picture both indoors and outdoors.
- Viewing Angle:LCD can provide a viewing angle of 120 degrees to 140 degrees, while LED display can provide a viewing angle of 160 degrees. Wide viewing angle can provide viewers with a comfortable viewing experience.
- Energy consumption:According to the data, the energy consumption ratio of LCD and LED display is about 10:1, which means that LED display not only saves electricity, but also reduces the waste of energy and reduces the burden on the environment.
- Use life:The general life of LCD is about 60,000 hours, and the life of LED display can be about 100,000 hours. Longer life can help us save costs.
- Maintenance costs:LCD screen once the leakage must be replaced, the maintenance cost is high, while the LED display only need to replace the module parts can be, the maintenance cost is low.
Conclusion
With the continuous innovation of science and technology, LCD technology is also progressing. At present, the major LCD manufacturers have also increased investment in LCD technology, and strive to break through the project bottleneck in order to carry out the industrialization process and reduce production costs. Therefore, learning LCD technology can enhance our understanding of this industry and grow our insight.
