, e-books, navigators, tablets, electronic translators, calculators, watches, etc., as well as in many other electronic devices.
We must also remember the concepts we learn when we study another branch of physics, the one that deals with the nature of light, physical optics. It is she who explains what “polarized light” is. There are two theories about its nature. First, he claims that it is made of particles of pure energy, photons. The other, the wave nature theory, states that it is formed by waves. And light is such a strange thing that there are phenomena that can only be explained by one theory, and there are phenomena that can only be explained by another.
We focus on the theory of wave nature. This theory states that light is a form of radiant energy, a special case of electromagnetic waves that transmit radio programs, for example. The difference lies in the “spectrum”, i.e. in the wavelength range of one and the other. The visible light spectrum spans wavelengths from 380 nm, the wavelength of violet light, to 780 nm, the wavelength of red light. Below this spectrum are radiations known as ultraviolet, x-rays and gamma rays.
As of 2008, most desktop monitors based on TN (and some *VA) matrices, as well as all laptop displays, use matrices with 18-bit color (6 bits per RGB channel), 24-bit emulated flicker with dithering.
Just remember that light is radiation, so it travels as a wave. When a luminous wave propagates, it “vibrates” in planes that have a common line through which the light radiation passes. Imagine that one of the children begins to move his hand up and down in a normal motion. A wave will immediately form and spread along the rope. When a child shakes his hand up and down, this wave will propagate in a vertical plane, like the wave shown by the blue line of the figure.
If she moved her hand horizontally, the wave would propagate in a horizontal plane, such as the wave shown by the red line of the figure. Natural light travels in waves that vibrate in planes of all possible inclinations. Figure 1 shows only horizontal and vertical planes, but between them there are an infinity of other planes passing through the black line, which corresponds to the direction of propagation of the light beam.
A giant leap in the development of this technology occurred with the advent of the first laptops. At first the matrices were black and white, then color, but only of the “passive” type. They displayed static images and the laptop desktop quite passably, but with the slightest movement the “picture” turned into a complete blur - it was impossible to make out anything on the screen. Naturally, this limited the scope of use of the new type of display. The further evolution of liquid crystal matrices led to the creation of a new type - “active”. Such displays were already better at displaying moving objects on the screen, and this contributed to the emergence of stationary monitors. At the beginning of the 21st century, the first LCD televisions appeared. Their diagonal was still small - about 15 inches.
The only wave that could propagate beyond the crack would be one whose plane of oscillation passed through the crack, in in this case vertical plane. Everyone else will be held back because they can't fit through the cracks. This way you can make a beam of light spread out in one plane. This type of light is called "polarized light." Polarized light can be produced by producing common light through a polarizing filter, a transparent medium having a structure that functions as a set of parallel slits, as shown in Figure 2.
Specifications
The most important characteristics of LCD displays:
- the type of matrix is determined by the technology by which the LCD display is manufactured;
- matrix class; ISO 13406-2 standard distinguishes four classes of matrices;
- resolution - horizontal and vertical dimensions, expressed in pixels. Unlike CRT monitors, LCDs have one fixed resolution, the rest are achieved by interpolation (CRT monitors also have a fixed number of pixels, which also consist of red, green and blue dots. However, due to the nature of the technology, when outputting a non-standard resolution, there is no interpolation necessary);
- point size (pixel size) - the distance between the centers of adjacent pixels. Directly related to physical resolution;
- 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.);
- visible diagonal - the size of the panel itself, measured diagonally. The area of the displays also depends on the format: with the same diagonal, a 4:3 format monitor has a larger area than a 16:9 format monitor;
- 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;
- brightness - the amount of light emitted by the display (usually measured in candelas per square meter);
- response time - the minimum time required for a pixel to change its brightness. Composed of two quantities:
- buffering time ( input lag). A high value interferes with dynamic games; usually kept silent; measured by comparison with a kinescope in high-speed photography. Now (2011) within 20-50; in some early models it reached Template:Num ;
- switching time. Indicated in the monitor specifications. A high value degrades video quality; measurement methods are ambiguous. Now (2016) in almost all monitors the stated switching time is 1-6 ms;
- viewing angle - the angle at which the drop in contrast reaches a given value, for different types matrices and by different manufacturers calculated differently and often cannot be compared. Some manufacturers indicate viewing angles in the technical parameters of their monitors, such as, for example: CR 5:1 - 176/176°, CR 10:1 - 170/160°. Abbreviation CR contrast ratio) indicates the contrast level at specified viewing angles relative to the contrast when viewed perpendicular to the screen. In the example given, at viewing angles of 170°/160° the contrast in the center of the screen is reduced to a value no lower than 10:1, at viewing angles 176°/176° - no lower than 5:1.
Device
Structurally, the display consists of the following elements:
Light through a filter consists of waves that vibrate only in parallel planes. Now we can understand how a liquid crystal display works. It consists of an array of points that may or may not be passed through - intersected by a polarized beam of light. Figure 2 shows very schematically one of these points.
At the top of Figure 2 we see a beam of natural light, "incident light", represented by blue and red wavelengths, reaching a polarizing filter with vertical slits. This allows waves propagating in the vertical plane to pass through, preserving all others. This beam falls on a thin layer of twisted nematics, the molecular structure of which is also vertical. Under natural conditions, the molecules of liquid crystals remain parallel. The light that reaches them through a vertical polarizing filter and is controlled by the crystal pulsates precisely in this plane and continues until a horizontal polarizing filter is found.
- LCD matrices (initially a flat package of glass plates, between the layers of which liquid crystals are located; in the 2000s, flexible materials based on polymers began to be used);
- light sources for illumination;
- contact harness (wires);
- housing, usually plastic, with a metal frame to provide rigidity.
LCD matrix pixel composition:
Now, since it is polarized light in the vertical plane, it cannot cross the horizontal filter and the dot remains black without emitting light. Now let's look at the bottom of Figure 2 to see what happens when an electrical voltage is applied or "excites" the electrodes connected to the liquid crystal layer. When they receive tension, the structures will spin. Depending on the tension, they will spin until their ends are at right angles. Since the crystal structure is light conductive, vertically polarized light penetrates the crystal structure in the part where its molecules are also arranged vertically, it is conducted by the crystals as their structure twists and leaves the liquid crystal layer in a plane perpendicular to the plane it penetrated into it, that is, in the horizontal plane.
- two transparent electrodes;
- a layer of molecules located between the electrodes;
- two polarizing filters whose planes of polarization are (usually) perpendicular.
If there were no liquid crystals between the filters, then the light transmitted by the first filter would be almost completely blocked by the second filter.
And this light, whose plane of polarization is “twisted” at an angle of ninety degrees, can now pass through a horizontal polarizing filter. The dot then begins to emit light. If the voltage on the electrodes is removed, the crystals rearrange themselves, they return to the vertical plane, and the light beam is stopped by a horizontal filter, “erasing” the point.
This is a simplified explanation, but you can already understand how it works. The LCD screen is then made up of a number of layers. The bottom one is a luminescent layer that emits white light, general, non-polarized. Below is a vertical polarizing filter. It contains a thin layer of liquid crystal formed by independent points to which thin electrodes are attached. Above it appeared a new polarizing filter, this time horizontal and, finally, a protective layer of transparent plastic on it.
The surface of the electrodes in contact with the liquid crystals is specially treated to initially orient the molecules in one direction. In a TN matrix, these directions are mutually perpendicular, so the molecules, in the absence of tension, line up in a helical structure. This structure refracts light in such a way that the plane of its polarization rotates before the second filter and light passes through it without loss. Apart from the absorption of half of the unpolarized light by the first filter, the cell can be considered transparent.
The background layer emits light, which is polarized by the first filter and propagates through the liquid crystal layer, whether or not it rotates its plane of polarization depending on whether a voltage exists in the liquid crystal at that point or not. If there is, the plane of polarized light rotates, it passes through the second filter, and what you see through the glass is a small point of light. If this doesn't happen, the plane of light remains vertical, it is preserved by the second filter, and what you see is a black point.
If voltage is applied to the electrodes, then the molecules tend to line up in the direction of the electric field, which distorts the screw structure. In this case, elastic forces counteract this, and when the voltage is turned off, the molecules return to their original position. With a sufficient field strength, almost all molecules become parallel, which leads to an opaque structure. By varying the voltage, you can control the degree of transparency.
Images are formed by groups of light and black dots. The color screen works on the same principle. The only difference is that each dot on the screen is actually formed by three tiny dots grouped together, each with a color filter, red, green and blue. It illuminates each one with the correct intensity that the colors generate.
There are many more interesting details, but there is no way to approach them in an article like this. Topic for next week, of course. This, in the end, did not bring anything significant, since the technological base at that time was too weak. One of the scientists created a temperature sensor based on liquid crystals, and another studied the effect of an electric field on crystals. The two panels contain a thin layer of liquid crystals between them. And the idea is that the light passing through the material is polarized and using the crystalline plane of polarization is rotated at an angle of 90 degrees.
If constant pressure applied for a long time, the liquid crystal structure may degrade due to ion migration. To solve this problem, alternating current or changing the polarity of the field is used each time the cell is addressed (since the change in transparency occurs when the current is turned on, regardless of its polarity).
If you place a large number of electrodes that create an electric field with different intensities in different parts of the screen, this is already possible with proper control; it can be written in letters, numbers and other objects that carry information. Manufacturers face another problem when creating color displays: these screens cannot handle reflected light. This obligatory “attribute” becomes the light of light. On one side there is a lamp, on the other there is a mirror.
Matrices are divided into passive and active. In a passive matrix, the image is formed row by row, the cells are sequentially operated at a voltage at which they become transparent. The disadvantages are that the image is not smooth and is shaky. In addition, the slow rate of change in crystal transparency prevents moving images from being reproduced correctly.
In the entire matrix, it is possible to control each of the cells individually, but as their number increases, this becomes difficult to achieve, as the number of required electrodes increases. Therefore, row and column addressing is used almost everywhere.
The light passing through the cells can be natural - reflected from the substrate (in LCD displays without backlight). But more often used, in addition to independence from external lighting, it also stabilizes the properties of the resulting image.
An active matrix has many advantages over a passive one. For example, there is better brightness and the ability to see the screen even with a deviation of 45 degrees or more, without a strong deterioration in image quality, which is impossible in a passive matrix, where the viewer's position must be frontal. In an active matrix, a transistor is added to each electrode, which can be "stored" digital data, and the resulting image is stored in receiving a control signal with a different value. Transistors are made of transparent materials so that light can pass through them without refraction.
Small-sized LCD displays without active backlighting, used in electronic watches, calculators, etc., have extremely low power consumption, which provides long-term (up to several years) autonomous operation such devices without replacing galvanic elements.
On the other hand, LCD monitors also have many disadvantages, which are often fundamentally difficult to eliminate, for example:
These are controls that help you control every pixel on the screen. These transistors are extremely thin, with thicknesses ranging from 1 to 01 microns. This technology is quite complex and therefore has difficulty in achieving an acceptable percentage of edible products because the number of transistors used is extremely high. The criteria and standards for the number of non-working transistors on one display differ from manufacturer to manufacturer.
Another important factor in display performance is response time. Or, otherwise, a delay between signal input and display. This is not the refresh rate, but a factor determined by the materials used to create the display panel. Measured in tens and hundredths of a second, there will be accurate information on this issue, as well as manufacturers jealously guarding this technological data for themselves.
- unlike CRTs, they can display a clear image at only one (“standard”) resolution. The rest are achieved by interpolation;
- Compared to CRTs, LCD monitors have low contrast and black depth. Increasing the actual contrast is often associated with simply increasing the brightness of the backlight, up to uncomfortable levels. The widely used glossy coating of the matrix only affects subjective contrast in ambient lighting conditions;
- due to strict requirements for the constant thickness of the matrices, there is a problem of unevenness of uniform color (backlight unevenness) - on some monitors there is an irremovable unevenness in brightness transmission (strips in gradients) associated with the use of linear blocks;
- the actual image change speed also remains noticeably lower than that of CRT and plasma displays. Overdrive technology solves the speed problem only partially;
- the dependence of contrast on viewing angle still remains a significant disadvantage of the technology. CRT displays completely avoid this problem;
- Mass-produced LCD monitors are poorly protected from mechanical damage. The matrix is especially sensitive if it is not protected by glass. If pressed hard, irreversible degradation may occur;
- There is a problem of defective pixels. Maximum permissible quantity defective pixels, depending on the screen size, is determined in international standard ISO 13406-2 (in Russia - GOST R 52324-2005). The standard defines Template:Num quality of LCD monitors. The highest class - 1, does not allow the presence of defective pixels at all. The lowest - 4, allows up to Template:Num pixels per Template:Num working. CRT monitors are not affected by this problem;
- The pixels of LCD monitors degrade, although the rate of degradation is the slowest of all display technologies, with the exception of laser displays, which are not subject to it at all.
- Not a very wide range of operating temperatures: dynamic characteristics deteriorate (and then become inoperable) at even low negative ambient temperatures.
OLED displays (organic light-emitting diode matrix) are often considered a promising technology that can replace LCD monitors, but it has encountered many difficulties in mass production, especially for large-diagonal matrices.
And the last parameter is the resolution at which the display has optimal performance in relation to the number of horizontal and vertical pixels. These are typical standard abbreviations indicating parameters. Most substances exist in three states - solid, liquid and gas. The differences between these materials lie in the internal structure, which depends on temperature and pressure.
At low temperatures, when a material is in a solid state, atoms, ions or molecules cannot move freely. Their only movements are thermal vibrations around the equilibrium position. If the temperature rises, more energy enters the system, resulting in stronger oscillations. Finally, at a temperature between the solid state and the liquid state, the bonds are released so much that the free movement of molecules interfere with each other and change the direction of movement.
Technologies
The main technologies in the manufacture of LCD displays: TN+film, IPS (SFT, PLS) and MVA. These technologies differ in the geometry of surfaces, polymer, control plate and front electrode. Great importance have the purity and type of polymer with the properties of liquid crystals used in specific developments.
Response time of LCD monitors designed using SXRD technology. Silicon X-tal Reflective Display - silicon reflective liquid crystal matrix), reduced to Template:Num.
Template:Anchor2
TN + film (Twisted Nematic + film) is the simplest technology. The word “film” in the name of the technology means “additional layer” used to increase the viewing angle (approximately from 90 to 150°). Currently, the prefix “film” is often omitted, calling such matrices simply TN. A way to improve contrast and viewing angles for TN panels has not yet been found, and the response time is of this type The matrix is currently one of the best, but the contrast level is not.
The TN+ film array works like this: When no voltage is applied to the subpixels, the liquid crystals (and the polarized light they transmit) rotate 90° relative to each other in a horizontal plane in the space between the two plates. And since the polarization direction of the filter on the second plate is exactly 90° with the polarization direction of the filter on the first plate, light passes through it. If the red, green and blue sub-pixels are fully illuminated, a white dot will appear on the screen.
The advantages of the technology include the shortest response time among modern matrices Template:When? , as well as low cost. Disadvantages: worse color rendition, smallest viewing angles.
Template:Anchor2
AS-IPS (Advanced Super IPS - extended super-IPS) - was also developed by Hitachi Corporation in 2002. The improvements mainly concerned the contrast level of conventional S-IPS panels, bringing it closer to the contrast of S-PVA panels. AS-IPS is also used as the name for NEC monitors (such as the NEC LCD20WGX2) built using S-IPS technology, developed by the LG Display consortium.
H-IPS A-TW (Horizontal IPS with Advanced True White Polarizer ) - developed by LG Display for NEC Corporation. It is an H-IPS panel with a TW (True White) color filter to make the white color more realistic and increase viewing angles without distorting the image (the effect of glowing LCD panels at an angle is eliminated - the so-called “glow effect”) . This type of panels is used to create professional monitors High Quality.
AFFS (Advanced Fringe Field Switching , unofficial name - S-IPS Pro) is a further improvement of IPS, developed by BOE Hydis in 2003. The increased electric field strength made it possible to achieve even greater viewing angles and brightness, as well as reduce the interpixel distance. AFFS-based displays are mainly used in tablet PCs, on matrices manufactured by Hitachi Displays.
| Name | Short designation | Year | Advantage | Notes |
|---|---|---|---|---|
| Super fine TFT | S.F.T. | 1996 | Wide viewing angles, deep blacks | . With improved color rendering, the brightness became slightly lower. |
| Advanced SFT | A-SFT | 1998 | Best response time | The technology has evolved to A-SFT (Advanced SFT, Nec Technologies Ltd. in 1998), significantly reducing response time. |
| Super-advanced SFT | SA-SFT | 2002 | High transparency | SA-SFT developed by Nec Technologies Ltd. in 2002, improved transparency by 1.4 times compared to A-SFT. |
| Ultra-advanced SFT | UA-SFT | 2004 | High transparency Color rendition High Contrast |
Allowed to achieve 1.2 times greater transparency compared to SA-SFT, 70% coverage of the NTSC color range and increased contrast. |
| Name | Short designation | Year | Advantage | Transparency/ Contrast |
Notes |
|---|---|---|---|---|---|
| Super TFT | IPS | 1996 | Wide viewing angles | 100/100 A basic level of |
Most panels also support realistic color rendering (8 bits per channel). These improvements came at the cost of slower response times, initially around 50ms. IPS panels were also very expensive. |
| Super-IPS | S-IPS | 1998 | No color shift | 100/137 | IPS was superseded by S-IPS (Super-IPS, Hitachi Ltd. in 1998), which inherits all the advantages of IPS technology while reducing response time |
| Advanced super-IPS | AS-IPS | 2002 | High transparency | 130/250 | AS-IPS, also developed by Hitachi Ltd. in 2002, mainly improves the contrast of traditional S-IPS panels to a level where they become second only to some S-PVA. |
| IPS-provectus | IPS-Pro | 2004 | High Contrast | 137/313 | IPS Alpha panel technology with a wider color gamut and contrast comparable to PVA and ASV displays without corner glow. |
| IPS alpha | IPS-Pro | 2008 | High Contrast | Next generation IPS-Pro | |
| IPS alpha next gen | IPS-Pro | 2010 | High Contrast | Hitachi transfers technology to Panasonic |
| Name | Short designation | Year | Notes |
|---|---|---|---|
| Super-IPS | S-IPS | 2001 | LG Display remains one of the main manufacturers of panels based on Hitachi Super-IPS technology. |
| Advanced super-IPS | AS-IPS | 2005 | Improved contrast with expanded color gamut. |
| Horizontal IPS | H-IPS | 2007 | An even greater contrast and a visually more uniform screen surface have been achieved. Also, Advanced True Wide Polarizer technology based on NEC polarizing film has additionally appeared to achieve wider viewing angles and eliminate flare when viewed at an angle. Used in professional work with graphics. |
| Enhanced IPS | e-IPS | 2009 | It has a wider aperture to increase light transmission when the pixels are fully open, which allows the use of backlights that are cheaper to produce and have lower power consumption. The diagonal viewing angle has been improved, the response time has been reduced to 5 ms. |
| Professional IPS | P-IPS | 2010 | Provides 1.07 billion colors (30-bit color depth). More possible subpixel orientations (1024 versus 256) and better true color depth. |
| Advanced high performance IPS | AH-IPS | 2011 | Improved color reproduction, increased resolution and PPI, increased brightness and reduced power consumption. |
Template:Anchor2
VA technology (short for vertical alignment- vertical alignment) was introduced in 1996 by Fujitsu. When the voltage is turned off, the liquid crystals of the VA matrix are aligned perpendicular to the second filter, that is, they do not transmit light. When voltage is applied, the crystals rotate 90° and a light dot appears on the screen. As in IPS matrices, pixels do not transmit light when there is no voltage, so when they fail they are visible as black dots.
The successor to VA technology is MVA technology ( multi-domain vertical alignment ), developed by Fujitsu as a compromise between TN and IPS technologies. Horizontal and vertical viewing angles for MVA matrices are 160° (at modern models monitors up to 176-178°), while, thanks to the use of acceleration technologies (RTC), these matrices are not far behind TN+Film in response time. They significantly exceed the characteristics of the latter in terms of color depth and accuracy of their reproduction.
The advantages of MVA technology are the deep black color (when viewed perpendicularly) and the absence of both a helical crystal structure and a double magnetic field. Disadvantages of MVA compared to S-IPS: loss of details in shadows when viewed perpendicularly, dependence of the color balance of the image on the viewing angle.
Analogues of MVA are technologies:
- PVA ( patterned vertical alignment) from Samsung;
- Super PVA from Sony-Samsung (S-LCD);
- Super MVA from CMO;
- ASV ( advanced super view), also called ASVA ( axially symmetric vertical alignment ) from Sharp.
MVA/PVA matrices are considered a compromise between TN and IPS, both in cost and consumer properties.
Template:Anchor2
PLS matrix ( plane-to-line switching) was developed by Samsung as an alternative to IPS and was first demonstrated in December 2010. This matrix is expected to be 15% cheaper than IPS.
Advantages:
- Higher pixel density compared to IPS (and similar to *VA/TN)
, tablets, electronic translators, calculators, watches, etc., as well as in many other electronic devices.
As of 2008, most desktop monitors based on TN (and some *VA) matrices, as well as all laptop displays, use matrices with 18-bit color (6 bits per RGB channel), 24-bit emulated flicker with dithering.
Small-sized LCD displays without active backlighting, used in electronic watches, calculators, etc., have extremely low power consumption, which ensures long-term (up to several years) autonomous operation of such devices without replacing galvanic elements.
On the other hand, LCD monitors also have many disadvantages, which are often fundamentally difficult to eliminate, for example:
- unlike CRTs, they can display a clear image at only one (“standard”) resolution. The rest are achieved by interpolation;
- Compared to CRTs, LCD monitors have low contrast and black depth. Increasing the actual contrast is often associated with simply increasing the brightness of the backlight, up to uncomfortable levels. The widely used glossy coating of the matrix only affects subjective contrast in ambient lighting conditions;
- due to strict requirements for the constant thickness of the matrices, there is a problem of unevenness of uniform color (backlight unevenness) - on some monitors there is an irremovable unevenness in brightness transmission (strips in gradients) associated with the use of linear blocks;
- the actual image change speed also remains noticeably lower than that of CRT and plasma displays. Overdrive technology solves the speed problem only partially;
- the dependence of contrast on viewing angle still remains a significant disadvantage of the technology. CRT displays completely avoid this problem;
- Mass-produced LCD monitors are poorly protected from mechanical damage. The matrix is especially sensitive if it is not protected by glass. If pressed hard, irreversible degradation may occur;
- There is a problem of defective pixels. The maximum permissible number of defective pixels, depending on the screen size, is determined in the international standard ISO 13406-2 (in Russia - GOST R 52324-2005). The standard defines 4 quality classes for LCD monitors. The highest class - 1, does not allow the presence of defective pixels at all. The lowest is 4, which allows for up to 262 defective pixels per 1 million working ones. CRT monitors are not affected by this problem;
- The pixels of LCD monitors degrade, although the rate of degradation is the slowest of all display technologies, with the exception of laser displays, which are not subject to it at all.
- not a very wide range of operating temperatures: dynamic characteristics deteriorate (and then become inoperable) at even low negative ambient temperatures.
- the matrices are quite fragile, and their replacement is very expensive
OLED displays (organic light-emitting diode matrix) are often considered a promising technology that can replace LCD monitors, but it has encountered many difficulties in mass production, especially for large-diagonal matrices.
Technologies
The main technologies in the manufacture of LCD displays: TN+film, IPS (SFT, PLS) and MVA. These technologies differ in the geometry of surfaces, polymer, control plate and front electrode. The purity and type of polymer with liquid crystal properties used in specific designs are of great importance.
Response time of LCD monitors designed using SXRD technology. Silicon X-tal Reflective Display - silicon reflective liquid crystal matrix), reduced to 5 ms.
TN+film
TN + film (Twisted Nematic + film) is the simplest technology. The word “film” in the name of the technology means “additional layer” used to increase the viewing angle (approximately from 90 to 150°). Currently, the prefix “film” is often omitted, calling such matrices simply TN. A way to improve contrast and viewing angles for TN panels has not yet been found, and the response time of this type of matrix is currently one of the best, but the contrast level is not.
The TN+ film array works like this: When no voltage is applied to the subpixels, the liquid crystals (and the polarized light they transmit) rotate 90° relative to each other in a horizontal plane in the space between the two plates. And since the polarization direction of the filter on the second plate is exactly 90° with the polarization direction of the filter on the first plate, light passes through it. If the red, green and blue sub-pixels are fully illuminated, a white dot will appear on the screen.
The advantages of the technology include the shortest response time among modern matrices [When?] , as well as low cost. Disadvantages: worse color rendition, smallest viewing angles.
IPS (SFT)
AS-IPS (Advanced Super IPS- extended super-IPS) - was also developed by Hitachi Corporation in 2002. The improvements mainly concerned the contrast level of conventional S-IPS panels, bringing it closer to the contrast of S-PVA panels. AS-IPS is also used as the name for NEC monitors (such as the NEC LCD20WGX2) that use S-IPS technology developed by the LG Display consortium.
H-IPS A-TW (Horizontal IPS with Advanced True White Polarizer ) - developed by LG Display for NEC Corporation. It is an H-IPS panel with a TW (True White) color filter to make the white color more realistic and increase viewing angles without distorting the image (the effect of glowing LCD panels at an angle is eliminated - the so-called “glow effect”) . This type of panel is used to create high quality professional monitors.
AFFS (Advanced Fringe Field Switching , unofficial name - S-IPS Pro) is a further improvement of IPS, developed by BOE Hydis in 2003. The increased electric field strength made it possible to achieve even greater viewing angles and brightness, as well as reduce the interpixel distance. AFFS-based displays are mainly used in tablet PCs, on matrices manufactured by Hitachi Displays.
| Name | Short designation | Year | Advantage | Notes |
|---|---|---|---|---|
| Super fine TFT | S.F.T. | 1996 | Wide viewing angles, deep blacks | . With improved color rendering, the brightness became slightly lower. |
| Advanced SFT | A-SFT | 1998 | Best response time | The technology has evolved to A-SFT (Advanced SFT, Nec Technologies Ltd. in 1998), significantly reducing response time. |
| Super-advanced SFT | SA-SFT | 2002 | High transparency | SA-SFT developed by Nec Technologies Ltd. in 2002, improved transparency by 1.4 times compared to A-SFT. |
| Ultra-advanced SFT | UA-SFT | 2004 | High transparency Color rendition High Contrast |
Allowed to achieve 1.2 times greater transparency compared to SA-SFT, 70% coverage of the NTSC color range and increased contrast. |
| Name | Short designation | Year | Advantage | Transparency/ Contrast |
Notes |
|---|---|---|---|---|---|
| Super TFT | IPS | 1996 | Wide viewing angles | 100/100 A basic level of |
Most panels also support realistic color rendering (8 bits per channel). These improvements came at the cost of slower response times, initially around 50ms. IPS panels were also very expensive. |
| Super-IPS | S-IPS | 1998 | No color shift | 100/137 | IPS was superseded by S-IPS (Super-IPS, Hitachi Ltd. in 1998), which inherits all the advantages of IPS technology while reducing response time |
| Advanced super-IPS | AS-IPS | 2002 | High transparency | 130/250 | AS-IPS, also developed by Hitachi Ltd. in 2002, mainly improves the contrast of traditional S-IPS panels to a level where they become second only to some S-PVA. |
| IPS-provectus | IPS-Pro | 2004 | High Contrast | 137/313 | IPS Alpha panel technology with a wider color gamut and contrast comparable to PVA and ASV displays without corner glow. |
| IPS alpha | IPS-Pro | 2008 | High Contrast | Next generation IPS-Pro | |
| IPS alpha next gen | IPS-Pro | 2010 | High Contrast | Hitachi transfers technology to Panasonic |
| Name | Short designation | Year | Notes |
|---|---|---|---|
| Super-IPS | S-IPS | 2001 | LG Display remains one of the main manufacturers of panels based on Hitachi Super-IPS technology. |
| Advanced super-IPS | AS-IPS | 2005 | Improved contrast with expanded color gamut. |
| Horizontal IPS | H-IPS | 2007 | An even greater contrast and a visually more uniform screen surface have been achieved. Also, Advanced True Wide Polarizer technology based on NEC polarizing film has additionally appeared to achieve wider viewing angles and eliminate flare when viewed at an angle. Used in professional graphics work. |
| Enhanced IPS | e-IPS | 2009 | It has a wider aperture to increase light transmission when the pixels are fully open, which allows the use of backlights that are cheaper to produce and have lower power consumption. The diagonal viewing angle has been improved, the response time has been reduced to 5 ms. |
| Professional IPS | P-IPS | 2010 | Provides 1.07 billion colors (30-bit color depth). More possible subpixel orientations (1024 versus 256) and better true color depth. |
| Advanced high performance IPS | AH-IPS | 2011 | Improved color reproduction, increased resolution and PPI, increased brightness and reduced power consumption. |
VA/MVA/PVA
VA technology (short for vertical alignment- vertical alignment) was introduced in 1996 by Fujitsu. When the voltage is turned off, the liquid crystals of the VA matrix are aligned perpendicular to the second filter, that is, they do not transmit light. When voltage is applied, the crystals rotate 90° and a light dot appears on the screen. As in IPS matrices, pixels do not transmit light when there is no voltage, so when they fail they are visible as black dots.
The successor to VA technology is MVA technology ( multi-domain vertical alignment ), developed by Fujitsu as a compromise between TN and IPS technologies. Horizontal and vertical viewing angles for MVA matrices are 160° (on modern monitor models up to 176-178°), and, thanks to the use of acceleration technologies (RTC), these matrices are not far behind TN+Film in response time. They significantly exceed the characteristics of the latter in terms of color depth and accuracy of their reproduction.
The advantages of MVA technology are the deep black color (when viewed perpendicularly) and the absence of both a helical crystal structure and a double magnetic field. Disadvantages of MVA compared to S-IPS: loss of details in shadows when viewed perpendicularly, dependence of the color balance of the image on the viewing angle.
Analogues of MVA are technologies:
- PVA ( patterned vertical alignment) from Samsung;
- Super PVA from Sony-Samsung (S-LCD);
- Super MVA from CMO;
- ASV ( advanced super view), also called ASVA ( axially symmetric vertical alignment ) from Sharp.
MVA/PVA matrices are considered a compromise between TN and IPS, both in cost and consumer properties.
PLS
PLS matrix ( plane-to-line switching) was developed by Samsung as an alternative to IPS and was first demonstrated in December 2010. This matrix is expected to be 15% cheaper than IPS.
Advantages:
- Higher pixel density compared to IPS (and similar to *VA/TN) [source not specified 124 days] . The source can be external (for example, the Sun) or built-in (backlight). Typically, built-in backlight lamps are located behind the layer of liquid crystals and shine through it (although side lighting is also found, for example, in watches).
External lighting
Monochrome displays of wristwatches and mobile phones Most of the time they use external lighting (from the Sun, room lighting lamps, and so on). Typically behind the liquid crystal pixel layer is a mirror or matte reflective layer. For use in the dark, such displays are equipped with side lighting. There are also transflective displays, in which the reflective (mirror) layer is translucent and the backlight lamps are located behind it.
Incandescent lighting
In the past in some wristwatch with a monochrome LCD display, a subminiature incandescent lamp was used. But due to high energy consumption, incandescent lamps are unprofitable. In addition, they are not suitable for use, for example, in televisions, as they generate a lot of heat (overheating is harmful to liquid crystals) and often burn out.
Electroluminescent panel
The monochrome LCD displays of some clocks and instrument displays use an electroluminescent panel for backlighting. This panel is a thin layer of crystalline phosphorus (for example, zinc sulfide), in which electroluminescence occurs - glow under the influence of current. Typically glows greenish-blue or yellow-orange.
Illumination with gas-discharge (“plasma”) lamps
During the first decade of the 21st century, the vast majority of LCD displays were backlit by one or more gas discharge lamps (most often cold cathode lamps - CCFL, although EEFLs have recently come into use). In these lamps, the light source is plasma produced by an electrical discharge through a gas. Such displays should not be confused with plasma displays, in which each pixel is itself illuminated and is a miniature discharge lamp.
- Mukhin I. A., Ukrainsky O. V. Methods for improving the quality of television images reproduced by liquid crystal panels Materials of the report at the scientific and technical conference “Modern Television”. Moscow, March 2006.