Now the technology of flat panel monitors, including liquid crystal monitors, is the most promising. Although LCD monitors currently account for only about 10% of sales worldwide, they are the fastest growing market sector (65% per year).

Principle of operation

LCD monitor screens (Liquid Crystal Display) are made of a substance (cyanophenyl) that is in a liquid state, but at the same time has some properties inherent in crystalline bodies. In fact, these are liquids that have anisotropy of properties (in particular optical ones) associated with order in the orientation of molecules.
Oddly enough, liquid crystals are almost ten years older than CRTs; the first description of these substances was made back in 1888. However, for a long time no one knew how to use them in practice: there are such substances and everyone, and no one except physicists and chemists, they were not interesting. So, liquid crystal materials were discovered back in 1888 by the Austrian scientist F. Renitzer, but only in 1930 did researchers from the British Marconi corporation receive a patent for their industrial use. However, things did not go further than this, since the technological base at that time was still too weak. The first real breakthrough was made by scientists Fergason and Williams from RCA (Radio Corporation of America). One of them created a thermal sensor based on liquid crystals, using their selective reflective effect, the other studied the effect of an electric field on nematic crystals. And at the end of 1966, the RCA Corporation demonstrated a prototype LCD monitor - a digital clock. Sharp Corporation played a significant role in the development of LCD technology. It is still among the technology leaders. The world's first calculator CS10A was produced in 1964 by this corporation. In October 1975, the first compact digital watch was produced using TN LCD technology. In the second half of the 70s, the transition began from eight-segment liquid crystal displays to the production of matrices with addressing of each point. So, in 1976, Sharp released a black-and-white TV with a 5.5-inch screen diagonal, based on an LCD matrix with a resolution of 160x120 pixels.
The operation of LCD is based on the phenomenon of polarization of the light flux. It is known that the so-called polaroid crystals are capable of transmitting only that component of light whose electromagnetic induction vector lies in a plane parallel to the optical plane of the polaroid. For the remainder of the light output, the Polaroid will be opaque. Thus, the polaroid “sifts” the light, this effect is called polarization of light. When liquid substances were studied, the long molecules of which are sensitive to electrostatic and electromagnetic fields and are capable of polarizing light, it became possible to control polarization. These amorphous substances, due to their similarity to crystalline substances in electro-optical properties, as well as their ability to take the shape of a vessel, were called liquid crystals.
Based on this discovery and through further research, it was possible to discover a connection between increasing the electrical voltage and changing the orientation of the crystal molecules to enable image creation. Liquid crystals were first used in displays for calculators and in electronic watches, and then they began to be used in monitors for laptop computers. Today, as a result of progress in this area, LCD displays for desktop computers are becoming increasingly common.

An LCD monitor screen is an array of small segments (called pixels) that can be manipulated to display information. An LCD monitor has several layers, where the key role is played by two panels made of sodium-free and very pure glass material called a substrate or substrate, which actually contain a thin layer of liquid crystals between them [see. rice. 2.1]. The panels have grooves that guide the crystals into specific orientations. The grooves are positioned so that they are parallel on each panel but perpendicular between two panels. Longitudinal grooves are obtained by placing thin films of transparent plastic on the glass surface, which is then specially processed. In contact with the grooves, the molecules in liquid crystals are oriented identically in all cells. Molecules of one of the varieties of liquid crystals (nematics), in the absence of voltage, rotate the vector of the electric (and magnetic) field in the light wave by a certain angle in the plane perpendicular to the axis of beam propagation. Applying grooves to the surface of the glass makes it possible to ensure the same angle of rotation of the plane of polarization for all cells. The two panels are located very close to each other. The liquid crystal panel is illuminated by a light source (depending on where it is located, liquid crystal panels work by reflecting or transmitting light).

The plane of polarization of the light beam rotates 90° when passing through one panel [see. rice. 2.2].
When an electric field appears, the molecules of liquid crystals partially line up vertically along the field, the angle of rotation of the plane of polarization of light becomes different from 90 degrees, and light passes through the liquid crystals unhindered [see Fig. rice. 2.3].
The rotation of the plane of polarization of the light beam is invisible to the eye, so it became necessary to add two more layers to the glass panels, which are polarizing filters. These filters transmit only that component of the light beam whose polarization axis corresponds to a given one. Therefore, when passing through a polarizer, the light beam will be weakened depending on the angle between its plane of polarization and the axis of the polarizer. In the absence of voltage, the cell is transparent, since the first polarizer transmits only light with the corresponding polarization vector. Thanks to liquid crystals, the polarization vector of the light is rotated, and by the time the beam passes to the second polarizer, it has already been rotated so that it passes through the second polarizer without problems [see. Fig. 2.4a].

In the presence of an electric field, the rotation of the polarization vector occurs at a smaller angle, thereby the second polarizer becomes only partially transparent to radiation. If the potential difference is such that the rotation of the plane of polarization in liquid crystals does not occur at all, then the light beam will be completely absorbed by the second polarizer, and the screen, when illuminated from behind, will appear black from the front (the backlight rays are completely absorbed in the screen) [see. Fig. 2.4b]. If you place a large number of electrodes that create different electric fields in separate places on the screen (cell), then it will be possible, with proper control of the potentials of these electrodes, to display letters and other image elements on the screen. The electrodes are placed in transparent plastic and can be of any shape. Technological innovations have made it possible to limit their dimensions to the size of a small dot; accordingly, a larger number of electrodes can be placed on the same screen area, which increases the resolution of the LCD monitor and allows us to display even complex images in color. To display a color image, the monitor needs to be backlit so that the light comes from the back of the LCD display. This is necessary so that the image can be viewed in good quality even if the surrounding environment is not bright. Color is produced by using three filters that separate three main components from the emission of a white light source. By combining the three primary colors for each point or pixel on the screen, it is possible to reproduce any color.
In fact, in the case of color, there are several possibilities: you can make several filters one after another (leading to a small fraction of transmitted radiation), you can take advantage of the property of a liquid crystal cell - when the electric field strength changes, the angle of rotation of the polarization plane of the radiation changes differently for components of light with different wavelengths. This feature can be used to reflect (or absorb) radiation of a given wavelength (the problem is the need to accurately and quickly change the voltage). Which mechanism is used depends on the specific manufacturer. The first method is simpler, the second is more effective.
The first LCD displays were very small, around 8 inches, while today they have reached 15" sizes for use in laptops, and 20" or larger LCD monitors are being produced for desktop computers. An increase in size is followed by an increase in resolution, which results in the emergence of new problems that were solved with the help of emerging special technologies; we will describe all of this below. One of the first challenges was the need for a standard to define display quality at high resolutions. The first step towards the goal was to increase the rotation angle of the plane of polarization of light in crystals from 90° to 270° using STN technology.

Advantages and disadvantages of LCD monitors

The advantages of TFT include excellent focusing, absence of geometric distortion and color registration errors. In addition, their screen never flickers. Why? The answer is simple - these displays do not use an electron beam to draw each line on the screen from left to right. When in a CRT this beam is transferred from the lower right to the upper left corner, the image goes out for a moment (beam reversal). On the contrary, the pixels of a TFT display never go out, they simply continuously change the intensity of their glow.
Table 1.1 shows all the main differences in performance characteristics for different types of displays:

Table 1.1. Comparative characteristics of CRT and LCD monitors.

Legend: ( + ) dignity, ( ~ ) is acceptable, ( - ) flaw

From Table 1.1 it follows that the further development of LCD monitors will be associated with an increase in image clarity and brightness, an increase in viewing angle and a decrease in screen thickness. For example, there are already promising developments of LCD monitors made using technology using polycrystalline silicon. This makes it possible, in particular, to create very thin devices, since the control chips are then placed directly on the glass substrate of the display. In addition, the new technology provides high resolution on a relatively small screen (1024x768 pixels on a 10.4-inch screen).

STN, DSTN, TFT, S-TFT

STN is an abbreviation for "Super Twisted Nematic". STN technology allows the torsion angle (angle of twist) of crystal orientation inside the LCD display to be increased from 90° to 270°, which provides better image contrast as the monitor size increases.
STN cells are often used in pairs. This design is called DSTN (Double Super Twisted Nematic), in which one double-layer DSTN cell consists of 2 STN cells, the molecules of which rotate in opposite directions during operation. Light passing through such a structure in a “locked” state loses most of its energy. The contrast and resolution of DSTN are quite high, so it became possible to produce a color display in which there are three LCD cells and three optical filters of primary colors for each pixel. Color displays are not capable of operating from reflected light, so a backlight lamp is a mandatory attribute. To reduce dimensions, the lamp is located on the side, and opposite it is a mirror [see. rice. 2.5], so most LCD matrices in the center have higher brightness than at the edges (this does not apply to desktop LCD monitors).

STN cells are also used in TSTN (Triple Super Twisted Nematic) mode, where two thin layers of polymer film are added to improve the color rendition of color displays or to ensure good quality of monochrome monitors.
The term passive matrix comes from dividing the monitor into points, each of which, thanks to electrodes, can set the orientation of the plane of polarization of the beam, independently of the others, so that as a result, each such element can be individually illuminated to create an image. The matrix is ​​called passive because the technology for creating LCD displays, which was described above, cannot provide a quick change of information on the screen. The image is formed line by line by sequentially applying control voltage to individual cells, making them transparent. Due to the rather large electrical capacitance of the cells, the voltage on them cannot change quickly enough, so the picture is updated slowly. This type of display has many disadvantages in terms of quality because the image does not appear smoothly and appears shaky on the screen. The low rate of change in crystal transparency does not allow moving images to be displayed correctly.
To solve some of the problems described above, special technologies are used. To improve the quality of the dynamic image, it was proposed to increase the number of control electrodes. That is, the entire matrix is ​​divided into several independent submatrices (Dual Scan DSTN - two independent image scanning fields), each of which contains a smaller number of pixels, so alternating management of them takes less time. As a result, the inertia time of the LCD can be reduced.
Also, better results in terms of stability, quality, resolution, smoothness and brightness of the image can be achieved using active matrix screens, which, however, are more expensive.
The active matrix uses separate amplification elements for each screen cell to compensate for the effect of cell capacitance and significantly reduce the time it takes to change their transparency. The active matrix has many advantages over the passive matrix. For example, better brightness and the ability to look at the screen even with a deviation of up to 45° or more (i.e. at a viewing angle of 120°-140°) without compromising image quality, which is impossible in the case of a passive matrix, which allows you to see a high-quality image only from a frontal position relative to the screen. Note that expensive models of LCD monitors with an active matrix provide a viewing angle of 160° [see fig. 2.6], and there is every reason to assume that the technology will continue to improve in the future. Active matrix can display moving images without visible judder as the response time of an active matrix display is around 50 ms versus 300 ms for a passive matrix, in addition, the contrast of active matrix monitors is higher than that of CRT monitors. It should be noted that the brightness of an individual screen element remains unchanged throughout the entire time interval between picture updates, and does not represent a short pulse of light emitted by the phosphor element of the CRT monitor immediately after the electron beam passes over this element. That is why for LCD monitors a vertical scanning frequency of 60 Hz is sufficient.

The functionality of active matrix LCD monitors is almost the same as that of passive matrix displays. The difference lies in the matrix of electrodes that controls the display's liquid crystal cells. In the case of a passive matrix, different electrodes receive an electrical charge in a cyclic manner when the display is updated line by line, and as a result of the discharge of the capacitances of the elements, the image disappears as the crystals return to their original configuration. In the case of active matrix, a memory transistor is added to each electrode, which can store digital information (binary values ​​0 or 1) and as a result, the image is stored until another signal is received. Part of the problem of delayed image attenuation in passive matrices is solved by using more liquid crystal layers to increase passivity and reduce movement, but now, with the use of active matrices, it is possible to reduce the number of liquid crystal layers. Memory transistors must be made from transparent materials that will allow light to pass through them, which means that the transistors can be placed on the back of the display, on a glass panel that contains liquid crystals. For these purposes, plastic films called "Thin Film Transistor" (or simply TFT) are used.
Thin Film Transistor (TFT), i.e. thin film transistor - these are the control elements with which each pixel on the screen is controlled. A thin film transistor is really very thin, its thickness is 0.1 - 0.01 microns.
The first TFT displays, introduced in 1972, used cadmium selenide, which has high electron mobility and supports high current densities, but over time there was a transition to amorphous silicon (a-Si), and high-resolution matrices use polycrystalline silicon ( p-Si).
The technology for creating TFTs is very complex, and there are difficulties in achieving an acceptable percentage of suitable products due to the fact that the number of transistors used is very large. Note that a monitor that can display an image with a resolution of 800x600 pixels in SVGA mode and with only three colors has 1,440,000 individual transistors. Manufacturers set standards for the maximum number of transistors that may not work in an LCD display. True, each manufacturer has its own opinion about how many transistors may not work.
The TFT-based pixel is designed as follows: three color filters (red, green and blue) are integrated one behind the other in a glass plate. Each pixel is a combination of three colored cells or subpixel elements [see rice. 2.7]. This means, for example, that a display with a resolution of 1280x1024 has exactly 3840x1024 transistors and subpixel elements. The dot (pixel) size for a 15.1" TFT display (1024x768) is approximately 0.0188 inches (or 0.30 mm), and for an 18.1" TFT display it is approximately 0.011 inches (or 0.28 mm).

TFTs have a number of advantages over CRT monitors, including reduced energy consumption and heat dissipation, a flat screen and the absence of traces from moving objects. Recent developments provide higher quality images than conventional TFTs.

More recently, Hitachi specialists have created a new technology of multilayer Super TFT LCD panels, which has significantly increased the confident viewing angle of the LCD panel. Super TFT technology uses simple metal electrodes mounted on a bottom glass plate and causes the molecules to rotate, constantly being in a plane parallel to the plane of the screen [see rice. 2.8]. Since the crystals of a conventional LCD panel are turned towards the screen surface with their ends, such LCDs are more dependent on the viewing angle than Hitachi LCD panels with Super TFT technology. As a result, the image on the display remains bright and clear even at large viewing angles, achieving quality, comparable to the image on a CRT screen.

The Japanese company NEC recently announced that its LCD displays will soon reach the level of laser printers in image quality, crossing the threshold of 200 ppi, which corresponds to 31 dots per mm 2 or a dot pitch of 0.18 mm. As reported by NEC, TN (twisted nematic) liquid crystals used today by many manufacturers make it possible to build displays with a resolution of up to 400 dpi. However, the main limiting factor in increasing resolution is the need to create appropriate filters. In the new "color filter on TFT" technology, the light filters covering the thin-film transistors are formed using photolithography on the underlying glass substrate. In conventional displays, filters are applied to a second, top substrate, which requires very precise alignment of the two plates.

At the Society for Information Display conference held in the United States in 1999, several reports were made indicating success in the creation of liquid crystal displays on a plastic substrate. Samsung has presented a prototype of a monochrome display on a polymer substrate with a diagonal of 5.9 inches and a thickness of 0.5 mm. The thickness of the substrate itself is about 0.12 mm. The display has a resolution of 480x320 pixels and a contrast ratio of 4:1. Weight - only 10 grams.

Engineers from the Film Technology Laboratory of the University of Stuttgart used not thin film transistors (TFTs), but MIM (metal-insulator-metal) diodes. The latest achievement of this team is a two-inch color display with a resolution of 96x128 pixels and a contrast ratio of 10:1.

A team of IBM specialists has developed a technology for the production of thin-film transistors using organic materials, which makes it possible to produce flexible screens for e-readers and other devices. The elements of transistors developed by IBM are sprayed onto a plastic substrate at room temperature (traditional LCD displays are manufactured at high temperatures, which excludes the use of organic materials). Instead of conventional silica, barium zirconate titonate (BZT) is used to make the gate. An organic substance called pentacene, which is a compound of phenylethylammonium with tin iodide, is used as a semiconductor.

To increase the resolution of LCD screens, Displaytech proposed not to create an image on the surface of a large LCD screen, but to display the image on a small high-resolution display, and then use an optical projection system to enlarge it to the required size. At the same time, Displaytech used the original Ferroelectric LCD (FLCD) technology. It is based on the so-called chiral-smectic liquid crystals, proposed for use back in 1980. A layer of material with ferroelectric properties and capable of reflecting polarized light with rotation of the polarization plane is deposited on a CMOS substrate that supplies control signals. When the reflected light flux passes through the second polarizer, a picture of dark and light pixels appears. A color image is obtained by quickly alternating illumination of the matrix with red, green and blue light. Based on FLCD matrices, it is possible to produce large screens with high contrast and color rendering quality, wide viewing angles and short response times. In 1999, an alliance between Hewlett-Packard and DisplayTech announced the creation of a full-color microdisplay based on FLCD technology. The matrix resolution is 320x240 pixels. Distinctive features of the device are low power consumption and the ability to play full-color “live” video. The new display is designed for use in digital cameras, camcorders, handheld communicators and wearable computer monitors.

Toshiba is developing low-temperature technology using polycrystalline silicon LTPS. According to representatives of this corporation, they are positioning new devices so far only as intended for the mobile device market, not including laptops, where a-Si TFT technology dominates. 4-inch VGA displays are already being produced, and 5.8-inch matrices are on the way. Experts believe that 2 million pixels on the screen is far from the limit. One of the distinctive features of this technology is its high resolution.

According to experts from DisplaySearch Corporation, which researches the flat-panel display market, technologies are currently being replaced in the manufacture of almost any liquid crystal matrix: TN LCD (Twisted Nematic Liquid Crystal Display) with STN (Super TN LCD) and especially with a-Si TFT LCD ( amorphous-Silicon Thin Film Transistor LCD). In the next 5-7 years, in many areas of application, conventional LCD screens will be replaced or supplemented by the following devices:

• microdisplays;
• light-emitting displays based on organic LEP materials;
• displays based on field emission FED (Field Emisson Display);
• displays using low-temperature polycrystalline silicon LTPS (Low Temperature PolySilicon);
• plasma displays PDP (Plasma Display Panel).

Taken from http://monitors.narod.ru

Oddly enough, choosing a high-quality display for a computer monitor or laptop can only be done experimentally. This article will help you understand the parameters that you should pay attention to when choosing a monitor or laptop.

How to choose a monitor or laptop display with ideal characteristics?

A high-quality display has a huge advantage in multimedia tasks on a PC, and in relation to a laptop it’s half that. Take a look at this short list of display issues to watch out for when purchasing a new mobile computer or PC monitor:

• low brightness and contrast characteristics
• small viewing angles
• glare

Replacing a laptop screen is more difficult than buying a new monitor for a desktop computer, not to mention installing a new LCD matrix in a mobile computer, which cannot be done in all cases, so selecting a laptop screen should be approached with full responsibility.

Let me remind you once again that you cannot believe the promises of advertising materials of retail chains and computer manufacturers. Having finished reading mobile computer monitor and display selection guide, you can find difference between TN matrix and IPS matrix, evaluate the contrast, determine the required brightness level and other important parameters of the liquid crystal screen. You'll save time and money searching for a PC monitor and laptop display by choosing a quality LCD screen instead of a mediocre one.

Which is better: IPS or TN matrix?

The screens of laptops, ultrabooks, tablets and other portable computers typically use two types of LCD panels:

• IPS (In-Plane Switching)
• TN (Twisted Nematic)

Each type has its own advantages and disadvantages, but it is worth considering that they are intended for different consumer groups. Let's find out which type of matrix is ​​right for you.

IPS displays: excellent color reproduction

Displays based on IPS matrices have the following advantages:

• large viewing angles - regardless of the side and angle of human view, the image will not fade and will not lose color saturation
• excellent color reproduction - IPS displays reproduce RGB colors without distortion
• have a fairly high contrast.

If you are going to do pre-production or video editing, you will need a device with this type of screen.

Disadvantages of IPS technology compared to TN:

• long pixel response time (for this reason, displays of this type are less suitable for dynamic 3D games).
• monitors and mobile computers with IPS panels tend to be more expensive than models with screens based on TN matrices.

TN displays: inexpensive and fast

Liquid crystal displays are currently the most widely used matrices made using TN technology. Their advantages include:

• low cost
• low power consumption
• response time.

TN screens perform well in dynamic games - for example, first-person shooters (FPS) with fast scene changes. Such applications require a screen with a response time of no more than 5 ms (for IPS matrices it is usually longer). Otherwise, various kinds of visual artifacts may be observed on the display, such as trails from fast-moving objects.

If you want to use it on a monitor or laptop with a stereo screen, it is also better for you to give preference to a TN matrix. Some displays of this standard are capable of updating the image at a speed of 120 Hz, which is a necessary condition for the operation of active stereo glasses.

From disadvantages of TN displays It is worth highlighting the following:

• TN panels have limited viewing angles
• mediocre contrast
• are not capable of displaying all colors in the RGB space, so they are not suitable for professional image and video editing.

Very expensive TN panels, however, do not have some of the characteristic disadvantages and are close in quality to good IPS screens. For example, the Apple MacBook Pro with Retina uses a TN matrix, which is almost as good as IPS displays in terms of color rendering, viewing angles and contrast.

How to distinguish IPS from TN

If you like a monitor or laptop, but the technical characteristics of the display are not known, then you should look at its screen from different angles. If the image becomes dull and its colors are greatly distorted, you have a monitor or mobile computer with a mediocre TN display. If, despite all your efforts, the picture has not lost its colors, this monitor has a matrix made using IPS technology or a high-quality TN one.

Attention: avoid laptops and monitors with matrices, which show strong color distortion at high angles. For games, choose a computer monitor with an expensive TN display; for other tasks, it is better to give preference to an IPS matrix.

Important parameters: monitor brightness and contrast

Let's consider two more important display parameters:

• maximum brightness level
• contrast.

There's no such thing as too much brightness

To work in a room with artificial lighting, a display with a maximum brightness level of 200–220 cd/m2 (candelas per square meter) is sufficient. The lower the value of this setting, the darker and dimmer the image on the display will be. I do not recommend buying a mobile computer with a screen whose maximum brightness level does not exceed 160 cd/m2. For comfortable work outdoors on a sunny day, you will need a screen with a brightness of at least 300 cd/m2. In general, the brighter the display, the better.

When purchasing, you should also check the uniformity of the screen backlight. To do this, you should reproduce a white or dark blue color on the screen (this can be done in any graphics editor) and make sure that there are no light or dark spots over the entire surface of the screen.

Static and staggered contrast

Maximum static screen contrast level is the ratio of the brightness of successively displayed black and white colors. For example, a contrast ratio of 700:1 means that when outputting white, the display will be 700 times brighter than when outputting black.

However, in practice, the picture is almost never completely white or black, so for a more realistic assessment, the concept of checkerboard contrast is used.

Instead of sequentially filling the screen with black and white colors, a test pattern is displayed on it in the form of a black and white chessboard. This is a much more difficult test for displays because, due to technical limitations, you cannot turn off the backlight under the black rectangles while simultaneously illuminating the white ones at maximum brightness. A good checkerboard contrast for LCD displays is considered to be 150:1, and an excellent contrast is 170:1.

The higher the contrast, the better. To evaluate it, display a chess table on your laptop display and check the depth of black and brightness of white.

Matte or glossy screen

Probably many people paid attention to the difference in matrix coverage:

• matte
• glossy

The choice depends on where and for what purposes you plan to use the monitor or laptop. Matte LCD displays have a rough matrix coating that does not reflect external light well, so they do not glare in the sun. Obvious disadvantages include the so-called crystalline effect, which manifests itself in a slight haze of the image.

The glossy finish is smooth and better reflects light emitted from external sources. Glossy displays tend to be brighter and more contrasty than matte displays, and colors appear richer on them. However, such screens have glare, which leads to premature fatigue during long periods of work, especially if the display has insufficient brightness.

Screens with a glossy matrix coating and having insufficient brightness reserves reflect the surrounding environment, which leads to premature fatigue of the user.

Touch screen and resolution

Windows 8 was the first Microsoft operating system that had a huge impact on the development of mobile computer screens, in which the optimization of the graphical shell for touch screens is clearly visible. Leading developers produce laptops (ultrabooks and hybrids) and all-in-one PCs with touchscreens. The cost of such devices is usually higher, but they are also more convenient to manage. However, you will have to accept that the screen will quickly lose its presentable appearance due to greasy fingerprint marks, and wipe it regularly.

The smaller the screen and the higher its resolution, the greater the number of dots that form the image per unit area and the higher its density. For example, a 15.6-inch display with a resolution of 1366x768 pixels has a density of 100 ppi.

Attention! Do not buy monitors with screens with a dot density of less than 100 dpi, as they will show visible grain in the image.

Before Windows 8, high pixel density did more harm than good. Small fonts were very difficult to see on the small, high-resolution screen. Windows 8 has a new system for adapting to screens with different densities, so now the user can choose a laptop computer with the diagonal and display resolution that he deems necessary. The exception is for video game fans, as running games at ultra-high resolutions will require a powerful graphics card.

Fundamentals of monitoring. Matrix types: IPS

Quite a long time had passed since the creation of the first liquid crystal monitor, when the world realized that this could not continue - the quality produced by TN technology was clearly not enough. Those innovations that were designed to correct the shortcomings of TN matrices (discussed in detail in previous articles) only partially saved the situation. Therefore, by the mid-90s of the last century, an active search began for new solutions that could take the quality of LCD monitors to a fundamentally new level.

It just so happens in the world of technology that some are looking for solutions to emerging problems by upgrading existing developments, while others are not afraid to start from scratch. The proud Japanese, under the auspices, looked at all this noise for a long time, then sighed, rolled up their sleeves and in 1996 showed the world their own development, devoid of the disadvantages of TN technology. She was named IPS (In-Plane Switching), which can be translated as “switching in the plane.” It differed from the standard TN matrix in that, firstly, the crystals in the matrix were not twisted, but were located parallel to each other in the same plane (hence the name). And secondly, both contacts for supplying voltage were located on the same side of the cell.

Schematic representation of a cell in an IPS matrix

What was the result? In IPS matrices, in the absence of voltage, light did not pass through the polarizers, therefore, unlike TN technology, the black color here was precisely black. The first versions were distinguished by one more feature - when looking at the screen from the side, the black color gave a purple tint (later this problem was solved). When turned off, the matrix did not transmit light, so now if a pixel failed, then, unlike TN matrices, not a luminous dot appeared, but a black one. In addition, the quality of color rendering has increased by an order of magnitude.

But, as usually happens in such cases, the solution to old problems gave rise to new ones. Due to the peculiarities of the “design”, in order to rotate the crystals, it began to take much more time, and accordingly, the matrix became much “slower”. Further, since both contacts were placed on one side, this reduced the usable area (slightly, but nonetheless), which, in turn, led to a decrease in the brightness and contrast of panels created using this technology.

But that's not all. Energy consumption has also increased - both due to technical solutions and due to the use of more powerful lighting sources. As a result, the price of these matrices is quite high.

In any case, the image quality has become much higher, which has allowed several companies to actively rush in search of upgrades in order to reduce “harmful” parameters and improve benefits. Simultaneously with Hitachi, they began to use this same technology in (only they called it Super Fine TFT, or S.F.T.).

Already in 1998, Hitachi upgraded IPS matrices, reducing response time. The technology, which was called S-IPS, were immediately adopted by such giants as . It is worth noting that today it is in the IPS direction that there are the most modifications that have gone far from the original version. And although the general points regarding these matrices remain, in many modifications some parameters have been greatly improved.

Modern devices are equipped with screens of various configurations. The main ones at the moment are based on displays, but different technologies can be used for them, in particular we are talking about TFT and IPS, which differ in a number of parameters, although they are descendants of the same invention.

Nowadays there are a huge number of terms that denote certain technologies hidden under abbreviations. For example, many may have heard or read about IPS or TFT, but few understand what the actual difference is between them. This is due to the lack of information in electronics catalogs. That is why it is worth understanding these concepts, and also deciding whether TFT or IPS is better?

Terminology

To determine what will be better or worse in each individual case, you need to find out what functions and tasks each IPS is responsible for. In fact, it is a TFT, or more precisely, a variety of it, in the manufacture of which a certain technology was used - TN-TFT. These technologies should be considered in more detail.

Differences

TFT (TN) is one of the methods for producing matrices, that is, thin-film transistor screens, in which the elements are arranged in a spiral between a pair of plates. In the absence of voltage supply, they will be turned to each other at right angles in the horizontal plane. The maximum voltage causes the crystals to rotate so that light passing through them results in the formation of black pixels, and in the absence of voltage - white pixels.

If we consider IPS or TFT, the difference between the first and the second is that the matrix is ​​made on the basis described earlier, however, the crystals in it are not arranged in a spiral, but parallel to a single plane of the screen and to each other. Unlike TFT, the crystals in this case do not rotate under no-voltage conditions.

How do we see this?

If you look at IPS or visually, the difference between them is the contrast, which is ensured by almost perfect reproduction of black. The image will appear clearer on the first screen. But the quality of color rendering when using a TN-TFT matrix cannot be called good. In this case, each pixel has its own shade, different from the others. Because of this, colors are greatly distorted. However, such a matrix also has an advantage: it is characterized by the highest response speed among all currently existing ones. An IPS screen requires a certain time during which all parallel crystals will make a complete turn. However, the human eye hardly detects the difference in response time.

Important Features

If we talk about what is better in operation: IPS or TFT, then it is worth noting that the former are more energy-intensive. This is due to the fact that turning the crystals requires a considerable amount of energy. That is why, if a manufacturer is faced with the task of making their device energy efficient, it usually uses a TN-TFT matrix.

If you choose a TFT or IPS screen, it is worth noting the wider viewing angles of the second, namely 178 degrees in both planes, this is very convenient for the user. Others have proven unable to provide the same. And another significant difference between these two technologies is the cost of products based on them. TFT matrices are currently the cheapest solution, which is used in most budget models, and IPS belongs to a higher level, but it is not top-end either.

IPS or TFT display to choose?

The first technology allows you to obtain the highest quality, clearest image, but requires more time to rotate the crystals used. This affects response time and other parameters, in particular the rate at which the battery discharges. The color rendering level of TN matrices is much lower, but their response time is minimal. The crystals here are arranged in a spiral.

In fact, one can easily note the incredible gap in the quality of screens based on these two technologies. This also applies to cost. TN technology remains on the market solely because of price, but it is not capable of providing a rich and bright picture.

IPS is a very successful continuation in the development of TFT displays. A high level of contrast and fairly large viewing angles are additional advantages of this technology. For example, on TN-based monitors, sometimes the black color itself changes its hue. However, the high energy consumption of IPS-based devices forces many manufacturers to resort to alternative technologies or reduce this figure. Most often, matrices of this type are found in wired monitors that do not operate on a battery, which allows the device not to be so energy dependent. However, developments in this area are constantly underway.

The first thing you need to decide for what purposes the monitor will be used to a greater extent. Here you can’t do without a superficial acquaintance with the existing types of LCD monitor matrices. There are at least three main types of LCD monitors.

The matrix is ​​an array of pixels that transmit and filter light. This is the main part of the LCD monitor and it determines 90% of its quality. Modern LCD monitors are equipped with three different types of matrices; each type, regardless of the specific model, has the same advantages and disadvantages in relation to each other; only the severity of these qualities and disadvantages depends on the specific model.

1) TN - the oldest and cheapest type of matrix to produce, it is characterized by minimal response time, relatively poor color reproduction, small viewing angles with noticeable color distortion when changing the viewing angle (especially vertically - “negative effect”), low contrast, gray "black color. Well suited for dynamic games, if, of course, the color rendering of a particular model is at an acceptable level for virtual entertainment.

2) VA (MVA, PVA and other names with -VA) - pixel response time is longer than on TN, but at the same time quite good color reproduction, large viewing angles without significant color distortion when changing the viewing angle, high contrast, at a price more expensive than TN . One might say, the golden mean, suitable for everything and has a relatively low price.

3) S-IPS - longer matrix response time than VA and, accordingly, TN, but at the same time excellent color reproduction, almost ideal viewing angles (virtually no visible color distortion when viewing angle decreases), good contrast, very expensive. Best suited for anything where fast pixel response is not important. However, models of S-IPS monitors with a relatively short response time, which use overdrive technology, are already beginning to appear on the market, which, although they are not able to compete with TN and VA (which use overdrive) in terms of response time, but already allow you to comfortably use Such a monitor is also suitable for demanding applications (games), however, at a fairly high, sometimes unreasonably price.

Using the Monitor

1. Monitor for games. The optimal type of matrix is ​​TN, taking into account the pixel response time. It is not recommended to work professionally with graphics programs on it. For games (gamers), such a parameter as “pixel response time” is one of the main ones. If the pixel response time is too long, then we will see the so-called “trail”, that is, smearing of the picture in dynamic scenes (games and watching movies). The minimum acceptable pixel response value for modern games is 7–8 milliseconds, the optimal is 2–5 ms, that is, for games, the lower this number, the better. Accordingly, the lower this number, the more expensive the monitor. Although, I can’t help but say that in fact our eye no longer perceives the difference between 2 ms and 5 ms, so in this case one may ask the question - why pay more? There is another interesting nuance associated with the far biased parameters indicated in those passports. The fact is that the response time may differ depending on the applied standard. Any company is interested in selling its products at a higher price, while specifying maximum parameters according to favorable standards. As a result, we get that 2–5 ms is quite enough for games and watching movies.

2. Monitor for working with graphics programs(there is also a definition – monitor for “static”). This type of monitor is adapted to a greater extent for working with static objects and to a lesser extent for watching movies and games. In most cases, it is purchased by designers, artists, photographers, and people working with static graphics. The optimal type of matrix is ​​S-IPS (also PVA, but to a lesser extent). As already mentioned, this type of S-IPS matrix is ​​the slowest and is probably the worst suited for gaming and watching videos (especially in BD and HD quality); it is also the most expensive type of monitor.

3. Universal monitor can be used both for games and for graphic work, but it should be noted that finding the optimal middle can be quite difficult. You still have to sacrifice something, deciding what is more important: a good game and watching a high-quality movie or working with graphics. The optimal type of matrix is ​​VA (MVA, PVA and other names with -VA).

The division of monitors into these three types is arbitrary, since each model has its own parameters, which should be taken into account when choosing a monitor.

Main technical indicators of the monitor.

1. Types of matrices - the technology by which the LCD display is made; the main ones are TN (TN+film), IPS, MVA/PVA.

2. Response time (matrix reaction time) - the minimum time required for a pixel to change its brightness; the shorter it is, the better. Defined in milliseconds (ms).

3. Resolution - horizontal and vertical dimensions, expressed in pixels. Unlike CRT monitors, LCDs have one fixed resolution, the rest are achieved by interpolation.

4. Point size (pixel size) - the distance between the centers of adjacent pixels. Directly related to physical resolution.

5. Screen aspect ratio (proportional format) - width to height ratio (5:4, 4:3, 3:2 (15÷10), 8:5 (16÷10), 5:3 (15÷9), 16:9, etc.)

6. Contrast - the ratio of the brightness of the lightest and darkest points at a given backlight brightness. Some monitors use an adaptive backlight level using additional lamps; the contrast figure given for them (the so-called dynamic) does not apply to a static image.

7. Brightness - The amount of light emitted by the display, usually measured in candelas per square meter.

8. Viewing angle is the maximum angle from which the viewer is able to see a clear image on the LCD monitor screen.

9. Monitor diagonal (size) is the length of the diagonal at the outer corners of the screen. Defined in inches - 1 inch = 2.54 cm.

The article will be updated.