Monitor manufacturing technologies. Liquid crystal display (LCD) technology

Currently, there are a large number of types or types of monitors that have differences in screen manufacturing technology, and as a result, the quality of image reproduction and application in various fields of activity. Let's list the main types of monitors and give a brief description:

Electron beam monitors. Historically the very first. They consist of a vacuum electron tube in which electron beams are formed and controlled by means of a magnetic deflection system. These beams of electrons bombard the phosphor layer on which the image is projected, a glow arises and, as a result, an image appears. Since these monitors are practically superseded everywhere, we will not consider them in more detail.

The main disadvantages of these monitors:

⁃Large dimensions associated with the fundamental structure of the cathode-ray tube.

⁃Large mass associated with the first characteristic.

⁃Distortions of the image on the periphery of the monitor associated with the physical structure of the cathode-ray tube and the fundamental impossibility of producing flat-panel monitors using this technology.

⁃ The constructive need to use high voltage, up to 50 kV, which affects not the best way on energy-saving characteristics, as well as safety.

LCD monitors or LCD in English. The effect of changing the position of a liquid crystal molecule under the action of voltage has been known for a long time. The practical effect was obtained in the early 60s of the last century. Then, for the first time, miniature displays appeared in wristwatches, calculators, and various indicators. Over time, the technology has improved, a good impetus was the emergence of laptops and other portable computers.

The use of this technology in the production of monitors has completely solved the problems that their predecessors, cathode ray monitors, had. Dimensions have decreased significantly, dozens of times. Now there is no need to specially allocate a large space for the monitor. In this regard, the weight of the monitor itself has been significantly reduced. Now, in terms of weight, it is comparable to a laptop. Naturally, this applies to not very large monitors. The distortion typical of cathode ray monitors has disappeared because the LCD screen is really flat.

However, LCD monitors have their own drawbacks, which manufacturers are trying to overcome by introducing new technologies. These disadvantages include lower contrast and color saturation of the image. The response time of the matrix (a new characteristic for LCD has appeared) was long at first, this led to the fact that dynamic scenes were shown with image artifacts. This is due to the inertia of switching the state of liquid crystals. Small viewing angles, when one and the same picture, when viewed from the side, from above or below, begins to distort or invert colors.

To overcome these shortcomings, manufacturing companies began to improve the technology of liquid crystal matrices, which led to the creation of the following types of monitors, differing in the matrix manufacturing technology:

⁃TN + film (Twisted Nematic or twisted nematic), historically the first liquid crystal matrix, in which crystals are lined up one after another, but located relative to the plane of the display or view in a spiral. When voltage is applied, this spiral "twists" by an amount depending on the voltage. The pixel is colored in one color or another.

⁃S ‐ IPS, the development of Hitachi, the crystals are not twisted into a spiral, but are lined up one after the other in parallel. This allows for higher quality colors, but the response time increases, since it takes more time to rotate the entire array of crystals.

⁃MVA / PVA, Fujitsu has developed another technology that eliminates the color imperfections of TN technology and reduces response time compared to S-IPS technology. For this, it was necessary to significantly complicate the structure of both matrices and filters-polarizers. Samsung has developed its own PVA technology to avoid paying licensing fees. These technologies are similar, but the difference is in the greater contrast of the image.

⁃PLS, a technology developed by Samsung, is positioned to provide a sharper image than S-IPS technology, and is 10% cheaper than it. The manufacturing technology and device of the matrix is ​​unknown. Until recently, this type of matrix was used in mobile devices.

Plasma monitors or PDPs in English. The effect of glowing inert gases under high voltage is used. This technology eliminates the disadvantages inherent in liquid crystal matrices. The brightness and contrast of the picture are at a height, and since the matrix elements are large enough, which affects the resolution not in the best way, this is practically invisible. Dynamic scenes are also transmitted without distortion. The viewing angles are large, the picture can be seen without loss of color from any direction. The screen thickness has become even thinner compared to liquid crystal monitors.

OLED or OLED monitors. They are receivers of liquid crystal monitors. The benefits include extremely low power consumption as these LEDs light up by themselves. No need for a backlight. Extremely high contrast, fast response times, and response times are measured in microseconds, as opposed to milliseconds in LCD monitors. The depth of an OLED monitor is even thinner than a plasma monitor. And the viewing angles are 180 degrees, since we are looking at the LEDs themselves, and not at the filters, like with liquid crystal monitors.

Despite such outstanding characteristics, there are also disadvantages. This fragility of the OLED matrix with the high cost of such monitors is a decisive factor in the low demand for them. And this affects the speed of implementation of developments, because firms incur losses. Why spend large resources on an unprofitable business?

But despite this, the developers do not abandon their attempts to solve these problems, since OLED technology allows you to do fantastic things: fold the screen into a tube, create transparent displays, use in a wide range of temperatures, etc. For lovers of such things, OLED monitors are sold, costing about $ 8000, with a screen diagonal of about 60 cm.

Today these are the most common types of monitors except for the very first and last on our list. The times of the former have already passed, but the latter still has everything ahead. Let's consider in more detail the technologies for manufacturing monitor matrices.

Currently, there are a large number of types or types of monitors that have differences in screen manufacturing technology, and as a result, the quality of image reproduction and application in various fields of activity. Let's list the main types of monitors and give a brief description:

Electron beam monitors. Historically the very first. They consist of a vacuum electron tube in which electron beams are formed and controlled by means of a magnetic deflection system. These beams of electrons bombard the phosphor layer on which the image is projected, a glow arises and, as a result, an image appears. Since these monitors are practically superseded everywhere, we will not consider them in more detail.

The main disadvantages of these monitors:

Large dimensions associated with the fundamental structure of the cathode-ray tube.

Large mass associated with the first characteristic.

Distortions of the image on the periphery of the monitor associated with the physical structure of the cathode-ray tube and the fundamental impossibility of producing flat-panel monitors using this technology.

The constructive need to use high voltage, up to 50 kV, which affects not the best way on energy-saving characteristics, as well as safety.

LCD monitors or LCD in English. The effect of changing the position of a liquid crystal molecule under the action of voltage has been known for a long time. The practical effect was obtained in the early 60s of the last century. Then, for the first time, miniature displays appeared in wristwatches, calculators, and various indicators. Over time, the technology has improved, a good impetus was the emergence of laptops and other portable computers.

The use of this technology in the production of monitors has completely solved the problems that their predecessors, cathode ray monitors, had. Dimensions have decreased significantly, dozens of times. Now there is no need to specially allocate a large space for the monitor. In this regard, the weight of the monitor itself has been significantly reduced. Now, in terms of weight, it is comparable to a laptop. Naturally, this applies to not very large monitors. The distortion typical of cathode ray monitors has disappeared because the LCD screen is really flat.

However, LCD monitors have their own drawbacks, which manufacturers are trying to overcome by introducing new technologies. These disadvantages include lower contrast and color saturation of the image. The response time of the matrix (a new characteristic for LCD has appeared) was long at first, this led to the fact that dynamic scenes were shown with image artifacts. This is due to the inertia of switching the state of liquid crystals. Small viewing angles, when one and the same picture, when viewed from the side, from above or below, begins to distort or invert colors.

To overcome these shortcomings, manufacturing companies began to improve the technology of liquid crystal matrices, which led to the creation of the following types of monitors, differing in the matrix manufacturing technology:

Historically, the first liquid crystal arrays in which crystals are lined up one after the other, but located relative to the plane of the display or view in a spiral. When voltage is applied, this spiral "twists" by an amount depending on the voltage. The pixel is colored in one color or another.

Developed by Hitachi, the crystals are not twisted into a spiral, but are lined up one after the other in parallel. This allows for higher quality colors, but the response time increases, since it takes more time to rotate the entire array of crystals.

Fujitsu has developed another technology that eliminates the color imperfections of TN technology and improves response time compared to S-IPS technology. For this, it was necessary to significantly complicate the structure of both matrices and filters-polarizers. Samsung has developed its own PVA technology to avoid paying licensing fees. These technologies are similar, but the difference is in the greater contrast of the image.

The technology developed by Samsung is positioned to provide a sharper image than S-IPS technology, and is 10% cheaper than it. The manufacturing technology and device of the matrix is ​​unknown. Until recently, this type of matrix was used in mobile devices.

in English. The effect of glowing inert gases under high voltage is used. This technology eliminates the disadvantages inherent in liquid crystal matrices. The brightness and contrast of the picture are at a height, and since the matrix elements are large enough, which affects the resolution not in the best way, this is practically invisible. Dynamic scenes are also transmitted without distortion. The viewing angles are large, the picture can be seen without loss of color from any direction. The screen thickness has become even thinner compared to liquid crystal monitors.

or monitors with an OLED array. They are receivers of liquid crystal monitors. The benefits include extremely low power consumption as these LEDs light up by themselves. No need for a backlight. Extremely high contrast, fast response times, and response times are measured in microseconds, as opposed to milliseconds in LCD monitors. The depth of an OLED monitor is even thinner than a plasma monitor. And the viewing angles are 180 degrees, since we are looking at the LEDs themselves, and not at the filters, like with liquid crystal monitors.

Despite such outstanding characteristics, there are also disadvantages. This fragility of the OLED matrix with the high cost of such monitors is a decisive factor in the low demand for them. And this affects the speed of implementation of developments, because firms incur losses. Why spend large resources on an unprofitable business?

But despite this, the developers do not abandon their attempts to solve these problems, since OLED technology allows you to do fantastic things: fold the screen into a tube, create transparent displays, use in a wide range of temperatures, etc. For lovers of such things, OLED monitors are sold, costing about $ 8000, with a screen diagonal of about 60 cm.

Today these are the most common types of monitors, with the exception of the very first and last on our list. The times of the former have already passed, but the latter still has everything ahead. Let's consider in more detail the technologies for manufacturing monitor matrices.

Matrix manufacturing technologies.

The TN + film liquid crystal matrix consists of the following elements:

A pixel in a liquid crystal matrix is ​​formed from 3 cells or dots of blue, red and green colors. Turning on and off these points, combining these states, get one color or another. Matrix control is pixel-by-pixel. Here lies a big drawback of these passive matrices: until the signal reaches the last pixels, the brightness of the first will decrease due to the loss of charge. And building matrices with a large diagonal using this technology is also impractical. You will need to increase the voltage, which will lead to an increase in interference.

To overcome these obstacles, TFT (Thin Film Transistor) technology, or thin film transistor, has been developed. Since the transistor is an active element, accordingly, the matrices have become active. The use of such transistors made it possible to control each pixel separately, which made it possible to significantly increase the response time and produce large liquid crystal matrices.

In each cell of one color or another, which is part of the pixel, there are liquid crystal molecules. In TN + film technology, they are lined up one after the other, but rotated relative to each other in a spiral in such a way that the outer molecules are rotated 90 degrees relative to each other. These molecules are located in special grooves, which create such an arrangement on the glass substrate.

Electrodes are connected to the ends of this spiral, to which a voltage is applied to control the pixel. In response to this, depending on the voltage, the spiral begins to contract. Thus, in the absence of voltage, the light passes through the first polarizer filter, then the liquid crystal molecules rotate the light 90 degrees so that it is in the same plane with the 2 filter and passes through it. Thus, we get a white pixel.

If the maximum voltage is applied, the molecules of the crystal will take such a position in which the light will be completely absorbed by the second filter-polarizer. Accordingly, the pixel will turn black. With variations in the applied voltage, the light will be partially absorbed by the polarizer due to the arrangement of the crystals. The pixel will be grayed out, which means the light will partly pass through and partly be absorbed.

Since the matrix made using this technology has small viewing angles, we used a special film applied from above and broadening the view. The result is TN + film technology, in which when changing the viewing angle, the color intensity does not change so sharply. This technology is still used now, since it is the cheapest. But for working with graphics, it is not suitable.

high speed of the matrix;

low cost;

Disadvantages of technology:

small viewing angles;

low contrast;

color quality;

S-IPS technology is based on the same principles, the difference is that the molecules line up one after another in parallel, rather than twisting into a spiral, as in TN + film technology. The electrodes are located on the bottom substrate. In the absence of voltage, the light does not pass through the 2 polarizing filter, the polarization plane of which is located at an angle of 90 degrees. Thus, a rich black color is obtained. The viewing angles of the matrices made using this technology are up to 170 degrees horizontally and vertically, which very favorably distinguishes these monitors from previous ones.

large viewing angles horizontally and vertically;

high contrast;

Disadvantages of technology;

long response time, since it is necessary to turn the molecules at a greater angle;

more powerful lamps for panel illumination;

more powerful voltages are needed to turn the molecules, since the electrodes are in the same plane;

high price;

Based on the characteristics of matrices made using this technology, it is best to use them in design tasks, where high-speed dynamic scenes are not required, but high-quality color reproduction is required.

The compromise between the high color rendering of S-PS technology and the speed of TN + film is MVA technology. The essence of this technology is that the molecules are located parallel to each other, and in relation to 2 filters at an angle of 90 degrees. The second filter has a complex structure, it consists of triangles, to the lateral sides of which the crystal molecules are deployed in this way. Falling on the second filter through the molecules, the light is polarized 90 degrees (the work of the crystal molecules) and is absorbed by the second filter, which does not transmit such light. The result is black light.

Applying voltage, the molecules begin to turn and thereby directing the light onto the filter 2 at an angle other than 90 degrees. As a result, light begins to pass through filter 2 with an intensity proportional to the applied voltage. This technology, willingly or unwittingly, divides the screen into 2 parts, according to the direction of the molecules to the 2 filter, it turns out that being in relation to the screen from the side, the molecules of the crystals of the other side do not work for us. We see only the area that is closer to us and that does not distort the color. The use of this technology significantly complicates the structure of the filters-polarizers and the matrices themselves, since each point of the screen is duplicated from 2 zones.

Samsung was unwilling to pay for the license and developed its PVA technology, very similar to MVA, and with even greater contrast. Therefore, MVA / PVA is often indicated in the characteristics of monitors.

large viewing angles;

good color rendering and contrast;

Disadvantages of technology:

the complexity of making the matrix;

response time longer than matrices of TN + film technology

This concludes the review of liquid crystal matrix technologies. As for the PLS (Plane-to-Line Switching) technology, which was recently announced by Samsung, it is most likely a development of S-IPS technology. In this case, outside experts examined the PLS and S-IPS matrices under a microscope and found no differences. Moreover, Samsung filed a lawsuit against LG, in which it argued that the AH-IPS technology used by LG is a modification of PLS, which indirectly confirms the above.

Plasma monitors are now widespread due to the fact that production technology has fallen in price. Monitors with a large diagonal are produced, since it is technologically difficult to produce with a small diagonal. Therefore, the prices for them may be higher than for widescreen ones.

The matrix of a plasma monitor consists of cells, the walls of which are coated with phosphorus, and the cells themselves are filled with an inert gas: neon or xenon. When voltage is applied to the cell, a discharge occurs, the inert gas begins to emit photons, which in turn bombard the phosphorus coating of the cell. Phosphorus, in turn, begins to emit photons of light. Everyone knows how phosphorus luminesces even in daylight.

Plasma matrix cells have 3 colors: red, green, blue, and in this composition form a pixel. Accordingly, applying voltages of different intensities and combining colors, at the moment, the desired color is obtained. The principle is the same as for liquid crystal matrices, just instead of crystals, cells with an inert gas are used. Moreover, each pixel cell is controlled separately, which in the best way affects the color rendition and contrast.

In general, the plasma matrix screen consists of 2 glasses, external and internal, between which there are 2 dielectric layers with electrodes. One dielectric layer is adjacent to the outer glass. Supply electrodes or shield electrodes are built into this dielectric. After the dielectric layer, there is a thin layer of magnesium oxide or a protective layer. And then the layer itself with cells of inert gas.

On the side of the inner glass there is also a dielectric layer in which electrodes are embedded, which are called address or control electrodes. Thus, when a voltage is applied between the supply and address electrodes, a gas-discharge current arises, which leads to the emission of photons in a separate cell and the entire plasma panel as a whole, according to the required plot.

As you can see from this description, the technology of the matrix of plasma monitors is somewhat simpler than that of liquid crystal monitors. Let's now consider the pros and cons of this technology.

large viewing angles;

unmatched quality of color reproduction and contrast, saturation of the transmitted color;

absolutely flat screen and its small thickness;

short image regeneration time;

Every technology has a limit, so its

increased power consumption, since the gas-discharge effect is used;

large pixel size, which affects the resolution of a picture with fine details;

the resource of plasma panels is lower than that of liquid crystal panels;

panels with a small diagonal are more expensive than similar liquid crystal ones;

OLED-matrix consists of organic light-emitting diodes. An LED consists of a cathode and an anode with organic matter in between. When an electric current is passed, the cathode emits electrons and the anode emits positive ions. The electric field directs these particles towards each other and recombining with each other they emit light. An anode made of indium isoxide with tin additives transmits light in the visible range.

To create color OLED displays, substances have been selected that can emit light of different wavelengths, and, accordingly, colors. Blue, red and green LEDs form the matrix cell. This cell is controlled by applying voltage to it. The matrix controller at high speed sequentially supplies a control voltage, as in a line scan of a cathode-ray tube. Due to this, the human eye does not have time to feel the color difference when the cell received an impulse, and when it stopped acting on the cell. This OLED matrix is ​​passive.

There are also active OLED-matrices, where each cell is controlled by its own transistor, and all the diodes light up almost simultaneously. Such a matrix is ​​more expensive than a passive one due to the complexity of production.

The possibilities of OLED technology are amazing. So, for example, not only the anode, but also the cathode can be made transparent. In this case, the display will be completely transparent, and this will not affect the perception of the picture due to the brightness of the LEDs. Alternatively, instead of a glass backing, use a flexible material. In this case, the screen can be rolled up into a tube.

Mass production of OLED monitors has not yet been observed due to the high price. And it is more difficult to produce displays with large diagonals. However, firms do not stop at their research. Samsung recently announced a 55-inch monitor, so the challenges posed by OLED technology are being overcome.

the largest viewing angles compared to other technologies;

the highest contrast among existing technologies;

response time is measured in microseconds, and for liquid crystal matrices in milliseconds;

the absence of a backlight means that the power consumption is lower;

the thickness of the screen is even less;

can be used in a wide range of temperatures;

OLED lifetime;

the need for thorough sealing of the matrix from moisture;

high cost;

Prospects for the development of various display technologies.

At this stage, an interesting picture is observed: there are several technologies for manufacturing display matrices and all of them are actively developing, getting rid of their shortcomings. With all this, there is no tough confrontation between products made using different technologies.

If you need a large screen, then we choose a plasma matrix, if it is smaller, then a liquid crystal one. Do you need to solve design problems? Choose an S-IPS LCD. Do you need a picture with more or less high definition and fast response time? Choosing MVA / PVA technology. Don't want to pay big money? Then choose TN + film. Do you want something like that? OLED monitors are on the way and are already being produced, albeit for a lot of money.

Since each technology has essentially found its own niche, there is accordingly a demand for it and it will develop further, getting rid of its shortcomings. But as soon as one of them turns out to be similar to or surpass the other in terms of technological and consumer characteristics, it will accordingly oust a competitor.

The newest OLED technology is very promising, it can displace plasma displays and squeeze liquid crystal displays, but not before the issue is resolved with an increase in the lifespan of an organic light-emitting diode and a reduction in the cost of technology.

LCD monitors are now the cheapest and they also get rid of their shortcomings, but by definition they cannot surpass plasma monitors in terms of color quality, viewing angles, screen thickness, response time and diagonal size.

Accordingly, plasma monitors cannot replace the rest in the class of medium and small monitors, and, accordingly, in the degree of image detail. Small details, and even on a small monitor, will look poor.

Therefore, work on improving the characteristics of matrices manufactured using various technologies is being carried out continuously, but there is no need to talk about the decisive superiority of any technology. Exceeding in some characteristics, each of them is inferior to rivals in others. Therefore, there is only one conclusion: all these technologies will develop, and therefore they are all promising.

We have considered what exist types of monitors at the present time and the device of their matrices. In the next articles, we will continue to review the technical characteristics of monitors.

Not so long ago, cathode ray tube monitors occupied a large place on user desktops. , and even more so smartphones, have just begun to appear on store shelves. Not much time passed, and bulky CRT monitors began to replace the first liquid crystal displays, and all sorts of gadgets in which a screen was a necessary attribute filled pockets.

Over time, screens began not only to add diagonals, but the display technology also changed, and in the characteristics of devices we increasingly began to notice such incomprehensible abbreviations as TN, TN-Film, IPS, Amoled, etc.

This article was written for ordinary consumers who want to choose a monitor, smartphone or tablet. Therefore, there will not be a lot of terms and deep implementation in this or that technology, but the operation of screens will be described in an accessible language that is understandable to an ordinary user. I hope this article will shed light on new technologies in the field of information display, as well as help people in the future choice of a device that will be pleasant to use.

LCD (Liquid crystal display), aka LCD (liquid crystal display), is built on the basis of liquid crystals, which change their position when voltage is applied to them. If you look closely at the monitor, you will notice that it consists of small dots - pixels. These are liquid crystals. In turn, each pixel is made up of red, blue and green subpixels. When voltage is applied, the subpixels line up in a specific order and let light pass through them, thus forming a pixel of a specific color.

TN and TN + Film matrices

The first mainstream monitors were equipped with TN matrices. This is the simplest, but at the same time not the highest quality type of matrix. This technology is based on the fact that in the absence of voltage, the subpixels transmit light through themselves, forming a white dot on the screen. When voltage is applied to subpixels, they line up in a certain order, forming a pixel of a given color.

Due to the fact that the standard pixel color, in the absence of voltage, is white, this type of matrix does not have the best color reproduction. Colors appear dull and faded, while blacks appear more dark gray.

But, apart from the disadvantages, such matrices have their own advantages. These include fast response times and relatively inexpensive production costs.

Considering all the advantages and disadvantages, we can say that if you need an inexpensive monitor for occasional use in working with documents or for surfing the Internet, then monitors with TN + Film matrices are perfect for these needs.

IPS matrices

The main difference from IPS technology from TN is the arrangement of the subpixels in the absence of voltage. They are located perpendicular to each other, forming a black dot. Thus, the screen remains black when at rest. This gives an advantage in color rendering over screens with TN matrices. The colors on the screen look bright, rich, and the black remains really black. When voltage is applied, the pixels change their color. Taking this feature into account, owners of smartphones and tablets with IPS screens can be advised to use dark color schemes and wallpapers on the desktop, then the smartphone will last a little longer on battery life.

Also, a nice feature of IPS matrices is the large viewing angles. On most screens, they are 178 °. For monitors, and especially for smartphones and tablets, this feature is important when the user chooses a device.

But, of course, there are also disadvantages. The main disadvantage is the longer screen response time. This affects the display in dynamic pictures such as games and movies. In modern IPS panels, the response time has been improved, so now this drawback is not so critical.

Another feature of IPS-screens is their high cost compared to TN. But recently, the price of IPS panels has dropped and became available to most users.

Thus, it is better to choose phones and tablets with IPS matrices, and then the user will receive great aesthetic pleasure from using the device. The matrix for the monitor is not so critical, but if possible, it is recommended to pay attention to modern IPS monitors.

AMOLED screens

In the past few years, smartphones have started to be equipped with AMOLED displays and at the same time advertise such phones to buyers very much. So let's figure out what the company's PR managers are trying to convey to us, and what is in their words a common advertising gimmick.

The technology for creating AMOLED matrices is based on active LEDs, which begin to glow and display color when voltage is applied to them. What does it give us? And this gives us quite contradictory features.
Let's start with color rendering. The saturation and contrast of such screens are off the charts. The colors are displayed so vividly that some users may experience eye strain after prolonged use of their smartphone. But black color is displayed even more black than even in IPS-matrices.

Another negative feature is "picture memory". With prolonged display of a static image, traces may remain on the screen, and this, in turn, affects the quality of information display.

Also, due to their rather high cost, AMOLED screens are still used only in smartphones. Monitors based on this technology are unreasonably expensive.

Conclusion

At the end of the article, I would like to say that the perception of the image is quite subjective for each user. For some, a TN matrix will be quite enough, but someone will change dozens of monitors until they find their ideal. Thus, despite all the technologies for creating displays, the choice always remains with the user and depends on his individual perception of the picture on the screen. You can read how the screens work in touch mode.

Andrey Borzenko

Experts predict that in just a few years display devices based on cathode ray tubes (CRTs) will take their place of honor in the museum of the history of technology. They will be replaced by the so-called Flat Panel Display (FPD). Various technologies are used to create flat panel displays, but more than half of the FPD market is occupied by liquid crystal displays with an active matrix (Active-Matrix Liquid Crystal Display, AM-LCD). The principle of their work is well known. Under the action of an electric field, the molecules of liquid crystals change the plane of polarization of the light passing through them. In other words, the LCD cell reflects or does not reflect light.

Such devices also steadily dominate in the computer market. Over the next few years, this trend is likely to continue.

LCD monitors

According to the estimates of Display Research, in the III quarter of 1998 about 50 thousand LCD monitors were sold (recall that the market for CRT devices is estimated at 80 - 85 million units). 15 "monitors are considered the most popular with 39% of the market, followed by 14" monitors at 26%, and high quality 16 "monitors occupy only 10%. Until now, the most significant disadvantage of AM-LCD devices is their high price. But the situation is changing literally before our eyes. For example, this is how the price of the 15-inch VPA150 model from ViewSonic Corporation (www.viewsonic.com) decreased: at the beginning of last year - $ 2200, in the spring - $ 1500, in the beginning of autumn - $ 1200. Some 15 "monitors are now under $ 1000. For example, the recommended retail price of a 15-inch multimedia monitor PanaFlat LCD50s from Panasonic Computer Peripheral (www.panasonic.com) is $ 999. It has a USB port and built-in 1-watt stereo speakers. The screen provides a brightness of at least 250 nits with a contrast ratio of 200: 1. The viewing angle is 140 degrees.

Flat panel displays are the future

The pricing situation is set to change drastically in early 2000, when several new LCD factories will be fully operational in Taiwan.

At the COMDEX'98 exhibition, almost all the leading manufacturers of screens and monitors presented new products based on AM-LCD. Of particular interest were 18-inch devices, for example, from Acer (www.acer.com), Eizo (www.eizo.com), NEC (www.nec.com), Nokia (www.nokia.com), etc. Note that the screen of an 18 "LCD monitor matches the viewable area of ​​a 21" CRT device. For example, the 18.1-inch 800Xi model from Nokia Corporation (www.nokia.com) provides brightness of at least 250 nits with a contrast ratio of 200: 1. Its viewing angle is 170 degrees. At the same time, prices vary widely: from $ 2,500 at Acer to $ 3,600 at NEC.

Samsung Electronics Corp. (www.samsungelectronics.com) has unveiled improved versions of its 15- and 17-inch SyncMaster multimedia monitors at COMDEX'98. At just 2.5 inches thin and 150: 1 contrast, they deliver 200 nits of brightness and 120-degree viewing angles. These devices allow you to scale the image on the screen by factors of 2, 4 and 8. Monitors with a screen size of 18 inches and more are expected in the spring.

Compaq Corporation (www.compaq.com) has demonstrated a 15-inch LCD model with a digital interface that meets the VESA specification. These products will be offered with Presario home computers.

Further development of LCD is associated with an increase in the clarity and brightness of the image, an increase in the viewing angle and a decrease in the thickness of the screen. Thus, at the stand of Toshiba Corporation (www.toshiba.com) one could see a new LCD-monitor, in the manufacture of which polycrystalline silicon was used. This technology allows the control ICs to be placed directly on the glass substrate of the display, resulting in very thin devices. In addition, high resolution is provided on a relatively small screen. So, a 10.4-inch AM-LCD achieves a resolution of 1024x768 pixels.

LCD Panasonic LC90S

Incidentally, the maximum dimensions of LCD screens that it is advisable to produce on an industrial basis do not exceed 20 inches (although Sharp Corporation, www.sharp.co.jp, at one time showed a 40-inch LCD-monitor with a screen obtained by connecting two 29 -inch panels). The fact is that just a year ago, the yield of suitable 10.4-inch screens was only 60 - 70%, and companies set a goal to reach 80 - 85%. Note that with an increase in screen size, the percentage of rejects also increases.

Plasma Displays

Traditionally, the market for large screens (20 inches and above) is dominated by the so-called Plasma Display Panel (PDP). Research and development in this area began in the early 60s. It is worth recalling that monochrome PDP screens were used even in some laptop computers. Color PDP displays are produced today by such companies as Panasonic, Mitsubishi, Pioneer, NEC. Fujitsu Corporation (www.fujitsu.com) is deservedly considered the leader in this market sector. To improve the quality of the image and reduce the cost, she, in particular, has developed a special technology Alternate Lighting of Surfaces (ALiS). This increased the brightness of PDP screens up to 500 nits, contrast up to 400: 1, and viewing angle up to 160 degrees. Fujitsu's ready-made PDPs are used by Grundig and Philips for home theater applications.

PDP devices are a lot like a two-electrode vacuum tube. An inert gas (argon or neon) ionizes between two transparent electrodes. An electrically charged gas (plasma) produces ultraviolet radiation that excites phosphorus droplets. The latter emit visible light.

PDP Display Panasonic PT-42P

Color PDPs are well suited for creating high definition digital TVs, but the price is still quite high: a 42-inch display costs $ 8-15 thousand.

A rather interesting symbiosis of liquid crystal and plasma technologies was implemented by Tektronix (www.tek.com). She suggested using plasma to control the rows and columns of an LCD screen. Subsequently, the license for this technology was acquired by Sony Corporation (www.sony.com), which in collaboration with Sharp was to begin production of such devices. According to Sony experts, the new approach allows displays with fast response time, good brightness and high resolution.

DLP devices

Displays created on the basis of Digital Light Processing (DLP) technology developed by Texas Instruments (www.ti.com) are especially widely used in military affairs: screens for helmets, aircraft cabins, command centers, etc. At the heart of DLP- technology is DMD-cell (Digital Micromirror Device). In fact, it is a structure consisting of a static memory cell and a microscopic aluminum mirror that can be rotated in two directions at an angle of 10 degrees. Depending on its position, the mirror reflects or does not reflect light from an external source, the result is projected onto a large screen.

FED devices

Some companies have now begun to pay a lot of attention to the creation of displays based on field emisson display (FED). Unlike LCD and DMD screens, which work with reflected light, FED panels generate light themselves, which makes them similar to CRT and plasma displays. However, unlike CRTs, which have only three electron guns, in FED devices, each pixel has its own electrode, so that the thickness of the panel does not exceed a few millimeters. Pixels are directly controlled like AM-LCD.

Several large companies are currently working on the creation of FED monitors: PixTech (www.pixtech.com), Candescent Technologies (www.candescent.com), Motorola (www.motorola.com), Raytheon (www.raytheon.com).

PixTech is already shipping 8.5- and 15-inch FED color panels with VGA resolution and 160-degree viewing angles.

The Candescent Technologies corporation is accelerating the preparation of production, and calls its technology FED-devices ThinCRT ("thin" CRT). The corporation's investors are companies such as Hewlett-Packard, Sony and Compaq. One of the problems faced by FED panel manufacturers is that a vacuum must be created between two glass plates separated by a narrow gap (i.e., air must be evacuated). But in this case, the plates begin to attract each other, and this must be avoided. Candescent Technologies' new technology is protected by at least three dozen patents. The production capacity of the company will allow by 2001 to produce about a million 14.1-inch FED-screens.

Motorola is implementing a project that is practically not advertised in the press, according to which it has completely re-equipped its plant in Arizona (USA), focusing it on the production of FED devices. The first products should appear at the beginning of next year.

Electroluminescent Displays

The production of flat panel displays based on electroluminescent (ElectroLuminescent, EL) technology is developing less intensively. The fact that some substances (for example, zinc sulfide), when current passes through them, acquire the ability to emit visible light has been known since 1937.However, this effect was practically used in the manufacture of flat displays almost 50 years later, when thin-film EL materials appeared. ... According to some experts, EL displays have a number of advantages over LCD and even FED devices. This applies to both resolution and contrast, viewing angle and even power consumption. Nevertheless, the leading manufacturer of EL-panels, Planar Systems (www.planar.com) still supplies its products mainly for various medical equipment.

LEP displays

Recently, it was reported that the British company Cambridge Display Technology (CDT), which closely cooperates with the Japanese corporation Seiko-Epson, has demonstrated a monochrome display with a resolution of 800x236 pixels based on a Light-Emitting Polymer (LEP) film. Each pixel in the LEP display, as in the AM-LCD, is controlled by a thin film transistor. To apply a polymer layer to the transistor matrix, the Epson inkjet printing method was used. CDT promises to release a color LEP display early next year.

The table shows the technical characteristics of LCD monitors offered in the Russian market.

Liquid crystal monitors in the Russian market

TN + film technology

Twisted Nematic + film (TN + film). The "film" part in the name of the technology means an additional layer used to increase the viewing angle (up to approximately 160 °). This is the simplest and cheapest technology. It has been around for a long time and is used in most monitors sold over the past few years.

Advantages of TN + film technology:

- low cost;
- the minimum response time of a pixel to a control action.

Disadvantages of TN + film technology:

- medium contrast;
- problems with accurate color reproduction;
- relatively small viewing angles.

IPS technology

In 1995 Hitachi developed In-Plane Switching (IPS) technology to overcome the disadvantages inherent in TN + film panels. Small viewing angles, very specific colors and unacceptable (at that time) response time pushed Hitachi to develop a new IPS technology, which gave a good result: decent viewing angles and good color reproduction.

In IPS matrices, the crystals do not form a spiral, but rotate when an electric field is applied all together. Changing the orientation of the crystals helped to achieve one of the main advantages of IPS-matrices - the viewing angles were increased to 170 ° horizontally and vertically. If no voltage is applied to the IPS matrix, the liquid crystal molecules do not rotate. The second polarizing filter is always rotated perpendicular to the first, and light does not pass through it. Black display is ideal. If the transistor fails, the "broken" pixel for the IPS panel will not be white, as for the TN matrix, but black. When a voltage is applied, the liquid crystal molecules rotate perpendicular to their initial position parallel to the base and transmit light.

The parallel alignment of the liquid crystals required combing the electrodes on the bottom substrate, which significantly degraded the contrast of the image, required more powerful illumination to set the normal sharpness level, and resulted in high power consumption and significant time. Therefore, the response time of an IPS panel is generally longer than that of a TN panel. IPS-panels made using the technology turn out to be much more expensive. Subsequently, Super-IPS (S-IPS) and Dual Domain IPS (DD-IPS) technologies were also developed on the basis of IPS, however, due to the high cost, manufacturers could not bring this type of panels to the lead.

For some time, Samsung has produced panels made using Advanced Coplanar Electrode (ACE) technology, an analogue of IPS technology. However, today the production of ACE panels has been phased out. On the modern market, IPS technology is represented by monitors with a large diagonal - 19 inches or more.

The significant response time when switching the pixel between the two states is more than compensated for by excellent color reproduction, especially in panels made using an upgraded technology called Super-IPS.

Super-IPS (S-IPS)... S-IPS LCD monitors are a reasonable choice for professional color work. Alas, the contrast ratio of S-IPS panels is exactly the same as that of IPS and TN + Film - it is relatively small, since the black level is 0.5-1.0 cd / m2.

Along with this, the viewing angles, if not ideal (if deviated to the side, the image loses contrast noticeably), then they are very large compared to TN panels: sitting in front of the monitor, it is impossible to notice any unevenness in color or contrast due to insufficient viewing angles.

Currently, the following types of matrices are known that can be considered derived from IPS:

Advantages of S-IPS technology:

- excellent color rendering;
- larger viewing angles than TN + Film-panels.

Disadvantages of S-IPS technology:

- high price;
- significant response time when switching a pixel between two states;
- a faulty pixel or subpixel on such matrices remains permanently in an extinguished state.

This type of panel is well suited for working with color, but at the same time, monitors on S-IPS panels are quite suitable for games that are not critical to the response time of 5-20 ms.

MVA technology

IPS technology turned out to be relatively expensive, this circumstance forced other manufacturers to develop their own technologies. Fujitsu's Vertical Alignment (VA) LCD panel technology was born, followed by Multidomain Vertical Alignment (MVA), providing the user with a reasonable compromise between viewing angles, speed and color reproduction.

So, in 1996, Fujitsu proposed another technology for making VA LCD panels - vertical alignment. The name of the technology is misleading because liquid crystal molecules (in a static state) cannot be completely vertically aligned due to protrusion. When an electric field is created, the crystals are aligned horizontally and the backlight cannot pass through the various layers of the panel.

MVA technology - Multi-Domain Vertical Alignment - came about a year after VA. The M in MVA stands for Multi-Domain; many areas in one cell.

The essence of the technology is as follows: each subpixel is divided into several zones, and the polarizing filters are directional. Fujitsu currently manufactures panels in which each cell contains up to four such domains. With the help of protrusions on the inner surface of the filters, each element is divided into zones so that the orientation of the crystals in each specific zone is most suitable for looking at the matrix from a certain angle, and the crystals in different zones move independently. Thanks to this, it was possible to achieve excellent viewing angles without noticeable color distortions of the image - the brighter zones that fall into the field of view when the observer deviates from the perpendicular to the screen will be compensated by the darker ones nearby, so the contrast will drop slightly. When an electric field is applied, the crystals in all zones are arranged in such a way that, practically regardless of the viewing angle, a point with maximum brightness is visible.

What has been achieved as a result of the application of the new technology?

First, good contrast - the black level of a high-quality panel can drop below 0.5 cd / m2 (exceed 600: 1), which, although it does not allow competing on equal terms with CRT monitors, is definitely better than the results of TN- or IPS- panels. The black background of the monitor screen on the MVA-panel in the dark no longer looks so distinctly gray, and the unevenness of the backlight noticeably less affects the image.

Moreover, MVA panels also provide quite good color reproduction - not as good as S-IPS, but quite suitable for most needs. "Broken" pixels look black, the response time is about 2 times less than for IPS and old TN-panels. Thus, there is an optimal compromise in almost all areas. What's in the bottom line?

Advantages of MVA technology:

- short reaction time;
- deep black color (good contrast);
- the absence of a helical structure of crystals and a double magnetic field led to minimal power consumption;
- good color rendering (somewhat inferior to S-IPS).

However, two spoons of tar somewhat spoiled the existing idyll:

- when the difference between the initial and final states of the pixel decreases, the response time increases;
- the technology turned out to be quite expensive.

Unfortunately, the theoretical benefits of this technology have not been fully realized in practice. 2003, all analysts predict a bright future for LCD monitors equipped with an MVA panel, until AU Optronics introduced a TN + Film panel with a response time of just 16ms. In other respects, it was no better, and in some ways even worse than the existing 25 ms TN panels (reduced viewing angles, poor color rendering), but the low response time turned out to be an excellent marketing bait for consumers. In addition, the low cost of technology amid ongoing price wars, when every dollar extra per panel was a heavy burden on the manufacturer, bolstered the financial and marketing campaign. TN panels are still the cheapest today (much cheaper than both IPS and MVA panels). As a result of the combination of these two factors (a nice lure for the consumer in the form of fast response times and low price), monitors on panels other than TN + Film are currently available in limited quantities. The only exceptions are the top Samsung models on PVA and very expensive monitors on S-IPS panels, designed for professional work with color.

The developer of the MVA technology, Fujitsu, considered the LCD monitors market not interesting enough for itself and today is not developing new panels, transferring the rights to them to AU Optronics.

PVA technology

Following Fujitsu, Samsung has developed Patterned Vertical Alignment (PVA) technology, in general terms repeating the MVA technology and differing, on the one hand, with slightly larger viewing angles, but on the other hand, with worse response times.

Apparently, one of the development goals was to create a technology similar to MVA, but free from Fujitsu patents and associated license fees. Accordingly, all the disadvantages and advantages of PVA panels are the same as those of MVA.

Advantages of PVA technology:

- excellent contrast (the black level of PVA panels can be only 0.1-0.3 cd / m2);
- excellent viewing angles (when evaluating viewing angles according to the standard contrast ratio drop to 10: 1, it turns out that they are not limited by the panel, but by the plastic frame of the screen protruding above it - the latest models of monitors on PVA declared angles of 178 °);
- good color rendering.

Disadvantages of PVA technology:

- monitors on PVA-panels are of little use for dynamic games. Due to the long response time, when switching a pixel between close states, the image will be noticeably blurred;
- not the lowest cost.

Of great interest to this type of matrices is their widespread availability on the market. If a monitor on a good 19-inch MVA matrix is ​​almost impossible to find, then with PVA their developer (Samsung) tries to regularly release new models for sale. To be fair, it should be noted that other companies produce monitors based on PVA matrices a little more willingly than on MVA, but the presence of at least one serious manufacturer, such as Samsung, already gives PVA matrices a tangible advantage.

A PVA monitor is an almost ideal choice for work due to its characteristics that are closest to CRT monitors among all types of matrices (if you do not take into account the slow response time - the only serious drawback of PVA). 19-inch models based on them are easy to find on sale, and at quite reasonable prices (in comparison, say, with monitors on S-IPS matrices), so when choosing a work monitor for which behavior in dynamic games is not too important, be sure to pay attention to PVA.

Last year, Samsung introduced Dynamical Capacitance Compensation, DCC (Dynamic Capacitance Compensation) technology, which engineers claim is capable of making the switching time of a pixel independent of the difference between its final and initial states. In case of successful implementation of DCC PVA-panels will be one of the fastest among all types of panels currently existing, while retaining their other advantages.

Conclusion

There are significantly fewer LCD panel manufacturers than monitor manufacturers. This is due to the fact that the production of panels requires the construction of expensive (especially in conditions of constant competition) high-tech factories. Manufacturing a monitor based on a ready-made LCD module (usually an LCD panel is supplied complete with backlight lamps) comes down to ordinary installation operations, which do not require ultra-clean rooms or any high-tech equipment.

Today, the largest panel manufacturers and developers are a joint venture between Royal Philips Electronics and LG Electronics called LG.Philips LCD and Samsung.

LG.Philips LCD primarily specializes in IPS panels, supplying them to large third-party companies such as Sony and NEC. Samsung is better known for TN + Film and PVA panels, mainly for monitors of its own production.

It is possible to determine exactly on whose panel a particular monitor is assembled only by disassembling it, or by finding unofficial information on the Internet (the panel manufacturer is rarely indicated officially). At the same time, information about any specific model applies only to this model and does not affect other monitors of the same manufacturer in any way. For example, in different models of Sony monitors at different times, panels from LG were used.Philips, AU Optronics and Chunghwa Picture Tubes (CPT), and in NEC monitors, in addition to those listed, Hitachi, Fujitsu, Samsung and Unipac, not counting their own panels NEC. Moreover, many manufacturers install different panels in monitors of the same model, but with different release dates - as newer panel models appear, the old ones are simply replaced without changing the monitor labeling.