ltps ips tft display free sample

If you want to buy a new monitor, you might wonder what kind of display technologies I should choose. In today’s market, there are two main types of computer monitors: TFT LCD monitors & IPS monitors.

The word TFT means Thin Film Transistor. It is the technology that is used in LCD displays.  We have additional resources if you would like to learn more about what is a TFT Display. This type of LCDs is also categorically referred to as an active-matrix LCD.

These LCDs can hold back some pixels while using other pixels so the LCD screen will be using a very minimum amount of energy to function (to modify the liquid crystal molecules between two electrodes). TFT LCDs have capacitors and transistors. These two elements play a key part in ensuring that the TFT display monitor functions by using a very small amount of energy while still generating vibrant, consistent images.

Industry nomenclature: TFT LCD panels or TFT screens can also be referred to as TN (Twisted Nematic) Type TFT displays or TN panels, or TN screen technology.

IPS (in-plane-switching) technology is like an improvement on the traditional TFT LCD display module in the sense that it has the same basic structure, but has more enhanced features and more widespread usability.

Both TFT display and IPS display are active-matrix displays, neither can’t emit light on their own like OLED displays and have to be used with a back-light of white bright light to generate the picture. Newer panels utilize LED backlight (light-emitting diodes) to generate their light hence utilizing less power and requiring less depth by design. Neither TFT display nor IPS display can produce color, there is a layer of RGB (red, green, blue) color filter in each LCD pixels to produce the color consumers see. If you use a magnifier to inspect your monitor, you will see RGB color in each pixel. With an on/off switch and different level of brightness RGB, we can get many colors.

Winner. IPS TFT screens have around 0.3 milliseconds response time while TN TFT screens responds around 10 milliseconds which makes the latter unsuitable for gaming

Winner. the images that IPS displays create are much more pristine and original than that of the TFT screen. IPS displays do this by making the pixels function in a parallel way. Because of such placing, the pixels can reflect light in a better way, and because of that, you get a better image within the display.

As the display screen made with IPS technology is mostly wide-set, it ensures that the aspect ratio of the screen would be wider. This ensures better visibility and a more realistic viewing experience with a stable effect.

Winner. While the TFT LCD has around 15% more power consumption vs IPS LCD, IPS has a lower transmittance which forces IPS displays to consume more power via backlights. TFT LCD helps battery life.

Normally, high-end products, such as Apple Mac computer monitors and Samsung mobile phones, generally use IPS panels. Some high-end TV and mobile phones even use AMOLED (Active Matrix Organic Light Emitting Diodes) displays. This cutting edge technology provides even better color reproduction, clear image quality, better color gamut, less power consumption when compared to LCD technology.

This kind of touch technology was first introduced by Steve Jobs in the first-generation iPhone. Of course, a TFT LCD display can always meet the basic needs at the most efficient price. An IPS display can make your monitor standing out.

Low-temperature polycrystalline silicon (or LTPS) LCD—also called LTPS TFT LCD—is a new-generation technology product derived from polycrystalline silicon materials. Polycrystalline silicon is synthesised at relatively low temperatures (~650°C and lower) as compared to traditional methods (above 900°C).

Standard LCDs found in many consumer electronics, including cellphones, use amorphous silicon as the liquid for the display unit. Recent technology has replaced this with polycrystalline silicon, which has boosted the screen resolution and response time of devices.

Row/column driver electronics are integrated onto the glass substrate. The number of components in an LTPS LCD module can be reduced by 40 per cent, while the connection part can be reduced by 95 per cent. The LTPS display screen is better in terms of energy consumption and durability, too.

LTPS LCDs are increasingly becoming popular these days. These have a high potential for large-scale production of electronic devices such as flat-panel LCD displays or image sensors.

This relates generally to multi-touch sensing displays, and more specifically to combining multi-touch sensing functionality and LCD display functionality.

Many types of input devices are presently available for performing operations in a computing system, such as buttons or keys, mice, trackballs, joysticks, touch sensor panels, touch screens and the like. Touch screens, in particular, are becoming increasingly popular because of their ease and versatility of operation as well as their declining price. Touch screens can include a touch sensor panel, which can be a clear panel with a touch-sensitive surface, and a display device such as a liquid crystal display (LCD) that can be positioned partially or fully behind the panel so that the touch-sensitive surface can cover at least a portion of the viewable area of the display device. Touch screens can allow a user to perform various functions by touching the touch sensor panel using a finger, stylus or other object at a location dictated by a user interface (UI) being displayed by the display device. In general, touch screens can recognize a touch event and the position of the touch event on the touch sensor panel, and the computing system can then interpret the touch event in accordance with the display appearing at the time of the touch event, and thereafter can perform one or more actions based on the touch event.

An exemplary multi-touch enabled display is disclosed by U.S. patent application Ser. No. 11/649,998 filed on Jan. 3, 2007, entitled “PROXIMITY AND MULTI-TOUCH SENSOR DETECTION AND DEMODULATION”, Pub. No. 2008/0158172 which is hereby incorporated by reference herein in its entirety for all purposes. Early multi-touch displays required manufacturing of a multi-touch sensing panel and a separate display panel. The two panels can later be laminated together to form a multi-touch display. Later generations of the technology provided for combining the display and multi-touch functionality in order to reduce power consumption, make the multi-touch display thinner, reduce costs of manufacturing, improve brightness, etc. Examples of such integrated multi-touch displays are disclosed by U.S. application Ser. No. 11/818,422 filed on Jun. 13, 2007 and entitled “INTEGRATED IN-PLANE SWITCHING”, and U.S. application Ser. No. 12/240,964, filed on Jul. 3, 2008 and entitled “DISPLAY WITH DUAL-FUNCTION CAPACITIVE ELEMENTS,” both of which are incorporate by reference herein in their entireties for all purposes.

However, some of the schemes for integration can require placing some additional non-transparent elements in the thin film transistor (TFT) layer of the display. Such additional non-transparent elements can reduce the aperture of the display (the aperture being the portion of the display that actually transmits light). Reduction of the aperture can cause reduction of the brightness of the display as well as a reduction in the viewable angle of the display.

This relates to displays including pixels with dual-function capacitive elements. Specifically, these dual-function capacitive elements form part of the display system that generates an image on the display, and also form part of a touch sensing system that senses touch events on or near the display. The capacitive elements can be, for example, capacitors in pixels of an LCD display that are configured to operate individually, each as a pixel storage capacitor, or electrode, of a pixel in the display system, and are also configured to operate collectively as elements of the touch sensing system. In this way, for example, a display with integrated touch sensing capability may be manufactured using fewer parts and/or processing steps, and the display itself may be thinner and brighter.

Furthermore, this relates to displays for which the use of dual function capacitive elements does not result in any decreases of the aperture of the display. Thus, touch sensitive displays that have aperture ratios that are no worse than similar non-touch sensing displays can be manufactured. More specifically, this relates to placing touch sensing opaque elements so as to ensure that they are substantially overlapped by display related opaque elements, thus ensuring that the addition of the touch sensing elements does not substantially reduce the aperture ratio. The touch sensing display elements can be, for example, common lines that connect various capacitive elements that are configured to operate collectively as an element of the touch sensing system.

FIG. 1 illustrates a partial circuit diagram of an example LCD display including a plurality of LCD pixels according to embodiments of the present invention.

FIG. 11 illustrates a patterning of a first metal layer (M1) of pixels in an example electrically controlled birefringence (ECB) LCD display using amorphous silicon (a-Si) according to embodiments of the invention.

FIG. 12 illustrates a patterning step in which island patterns of a-Si are formed in the example ECB LCD display using a-Si according to embodiments of the invention.

FIG. 14 illustrates patterning of a second metal layer (M2) of pixels in the example ECB LCD display using a-Si according to embodiments of the invention.

FIG. 18 illustrates semi-transparent conductive material (such as ITO1)) layers that form pixel electrodes in the example ECB LCD display using a-Si according to embodiments of the invention.

FIGS. 21 and 22 illustrate a comparative analysis of the storage capacitances of pixels in the example ECB LCD display using a-Si according to embodiments of the invention.

FIG. 25 illustrates the patterning of a layer of poly-Si of pixels in an example in-plane switching (IPS) LCD display using low temperature polycrystalline silicon (LTPS) according to embodiments of the invention.

FIG. 26 illustrates the patterning of a first metal layer (M1) of pixels in the example IPS LCD display using LTPS according to embodiments of the invention.

FIG. 28 illustrates the patterning of a second metal layer (M2) of pixels in the example IPS LCD display using LTPS according to embodiments of the invention.

FIG. 29 illustrates a first layer of transparent conductive material, such as ITO, formed on pixels in the example IPS LCD display using LTPS according to embodiments of the invention.

FIG. 31 illustrates a second layer of transparent conductor, such as ITO, formed on pixel in the example IPS LCD display using LTPS according to embodiments of the invention.

FIG. 35 illustrates the patterning of a layer of poly-Si of pixels in an example IPS LCD display using LTPS in which a yVcom line is formed in an M2 layer according to embodiments of the invention.

FIG. 36 illustrates the patterning of a first metal layer (M1) of pixels in the example IPS LCD display using LTPS in which a yVcom line is formed in an M2 layer according to embodiments of the invention.

FIG. 37 illustrates vias formed in pixels in the example IPS LCD display using LTPS in which a yVcom line is formed in an M2 layer according to embodiments of the invention.

FIG. 38 illustrates patterning of a second metal layer (M2) of pixels in the example IPS LCD display using LTPS in which a yVcom line is formed in an M2 layer according to embodiments of the invention.

FIG. 39 illustrates a first layer of transparent conductive material, such as ITO, formed on pixels in the example IPS LCD display using LTPS in which a yVcom line is formed in an M2 layer according to embodiments of the invention.

FIG. 40 illustrates connections in the example IPS LCD display using LTPS in which a yVcom line is formed in an M2 layer according to embodiments of the invention.

FIG. 41 illustrates a second layer of transparent conductor, such as ITO, formed on pixels in the example IPS LCD display using LTPS in which a yVcom line is formed in an M2 layer according to embodiments of the invention.

FIG. 42 illustrates a plan view of completed pixels in the example IPS LCD display using LTPS in which a yVcom line is formed in an M2 layer according to embodiments of the invention.

FIG. 43 illustrates a side view of a pixel in the example IPS LCD display using LTPS in which a yVcom line is formed in an M2 layer according to embodiments of the invention.

FIG. 53 illustrates a calculation of the storage capacitance of a pixel in the example ECB LCD display using LTPS according to embodiments of the invention.

This relates to displays including pixels with dual-function capacitive elements. Specifically, these dual-function capacitive elements form part of the display system that generates an image on the display, and also form part of a touch sensing system that senses touch events on or near the display. The capacitive elements can be, for example, capacitors in pixels of an LCD display that are configured to operate individually, each as a pixel storage capacitor, or electrode, of a pixel in the display system, and are also configured to operate collectively as elements of the touch sensing system. In this way, for example, a display with integrated touch sensing capability may be manufactured using fewer parts and/or processing steps, and the display itself may be thinner and brighter.

Furthermore, this relates to dual function displays as discussed above, that further feature additional improvements of the aperture (and thus the brightness and the viewing angle) of the display. Said additional improvements can be realized by ensuring that touch sensing related common lines are positioned in such a manner that they do not significantly degrade the aperture ratio of the display from what it would have been had no touch sensing elements been present. For example, the touch sensing related common lines can be positioned in such a manner so that they are overlapped by various opaque display related elements.

While the present invention is described in relation to specific types of displays and specific schemes of capacitance based touch sensing, it is not so limited. A person of skill in the art would recognize that embodiments of the invention can be used in conjunction with other types of displays and touch sensing schemes, as long as the displays include pixels having capacitance causing electrodes, and the touch sensing schemes at least partially rely on sensing capacitance.

FIG. 1 is a partial circuit diagram of an example LCD display 100 including a plurality of LCD pixels according to embodiments of the present invention. The pixels of panel 100 are configured such that they are capable of dual-functionality as both LCD pixels and touch sensor elements. That is, the pixels include capacitive elements or electrodes, that can operate as part of the LCD display circuitry of the pixels and that can also operate as elements of touch sensing circuitry. In this way, panel 100 can operate as an LCD display with integrated touch sensing capability. FIG. 1 shows details of pixels 101, 102, 103, and 104 of display 100.

Pixel 102 includes a thin film transistor (TFT) 155 with a gate 155 a, a source 155 b, and a drain 155 c. Pixel 102 also includes a storage capacitor, Cst 157, with an upper electrode 157 aand a lower electrode 157 b, a liquid crystal capacitor, Clc 159, with a pixel electrode 159 aand a common electrode 159 b, and a color filter voltage source, Vcf 161. If a pixel is an in-plane-switching (IPS) pixel, Vcf can be, for example, a fringe field electrode connected to a common voltage line in parallel with Cst 157. If a pixel does not utilize IPS, Vcf 151 can be, for example, an ITO layer on the color filter glass. Pixel 102 also includes a portion 117 aof a data line for green (G) color data, Gdata line 117, and a portion 113 bof a gate line 113. Gate 155 ais connected to gate line portion 113 b, and source 155 bis connected to Gdata line portion 117 a. Upper electrode 157 aof Cst 157 is connected to drain 155 cof TFT 155, and lower electrode 157 bof Cst 157 is connected to a portion 121 bof a common voltage line that runs in the x-direction, xVcom 121. Pixel electrode 159 aof Clc 159 is connected to drain 155 cof TFT 155, and common electrode 159 bof Clc 159 is connected to Vcf 151.

Similar to pixels 102 and 103, pixel 101 includes a thin film transistor (TFT) 105 with a gate 105 a, a source 105 b, and a drain 105 c. Pixel 101 also includes a storage capacitor, Cst 107, with an upper electrode 107 aand a lower electrode 107 b, a liquid crystal capacitor, Clc 109, with a pixel electrode 109 aand a common electrode 109 b, and a color filter voltage source, Vcf 111. Pixel 101 also includes a portion 115 aof a data line for red (R) color data, Rdata line 115, and a portion 113 aof gate line 113. Gate 105 ais connected to gate line portion 113 a, and source 105 bis connected to Rdata line portion 115 a. Upper electrode 107 aof Cst 107 is connected to drain 105 cof TFT 105, and lower electrode 107 bof Cst 107 is connected to a portion 121 aof xVcom 121. Pixel electrode 109 aof Clc 109 is connected to drain 105 cof TFT 105, and common electrode 109 bof Clc 109 is connected to Vcf 111.

FIGS. 2A and 2B illustrate example regions formed by breaks in vertical and horizontal common voltage lines according to embodiments of the invention. FIG. 2A shows a TFT glass region layout. FIG. 2A shows a region 201, a region 205, and a region 207. Each region 201, 205, and 207 is formed by linking storage capacitors of a plurality of pixels (not shown in detail) through common voltage lines in the vertical direction (y-direction) and in the horizontal direction (x-direction). For example, the enlarged area of FIG. 2A shows pixel blocks 203 a-e. A pixel block includes one or more pixels, in which at least one of the pixels includes a vertical common line, yVcom. FIG. 1, for example, illustrates a pixel block that includes pixels 101-103, in which pixel 101 includes yVcom 123. As seen in FIG. 2A, pixel block 203 ais connected in the horizontal direction to pixel block 203 bthrough a horizontal common line, xVcom 206. Likewise, pixel block 203 ais connected in the vertical direction to pixel block 203 cthrough a vertical common line, yVcom 204. A break in xVcom 206 prevents block 203 afrom being connected to block 203 d, and a break in yVcom 204 prevents block 203 afrom being connected to block 203 e. Regions 201 and 207 form a capacitive element that can provide touch sensing information when connected to suitable touch circuitry, such as touch circuitry 213 of touch ASIC 215. The connection is established by connecting the regions to switch circuitry 217, which is described in more detail below. (Note, for IPS-type displays there are no conductive dots required. In this case, the xVcom and yVcom regions may simply extended with metal traces that go to the Touch ASIC which is bonded to the glass in a similar way as the LCD driver chip (through anisotropic conductive adhesive). However, for non-IPS-type displays, the conductive dots may be needed to bring the VCOM regions on the color filter plate into contact with the corresponding regions on the TFT plate.) Likewise, region 201 and region 205 form a capacitive element that can provide touch information when connected to touch circuitry 213. Thus, region 201 serves as a common electrode to regions 205 and 207, which are called, for example, sense electrodes. The foregoing describes mutual capacitance mode of touch sensing. It is also possible to use each region independently to measure self-capacitance.

Some embodiments of the invention are directed to fringe field switching TFT liquid crystal displays (FFS TFT LCDs), which are considered to a be specific type of in plane switching (IPS) displays. An example of an FFS TFT LCD is described by Lee, Seung Hee et al., “Ultra-FFS TFT-LCD with Super Image Quality, Fast Response Time, and Strong Pressure-Resistant Characteristics,” Journal of the Society for Information displays Oct. 2, 2002. The above publication is hereby incorporated by reference herein in its entirety for all purposes. Fringe field switching displays provide for a common electrode, which is an electrode that forms one plate of the storage capacitor for each pixel but is common for a number of pixels. In some displays the common electrode can be common for the entire display; in others, multiple common electrodes can be used for rows of pixels or the like.

In FFS TFT LCD embodiments of the present invention, the common electrodes can be cut or shaped along the touch regions. Thus, for example, touch regions 201, 205 and 207 may comprise different common electrodes that are separated from their neighboring common electrodes by empty space or by an insulator. Thus each common electrode may be an individual touch region. Since the common electrodes are conducting, VCOM lines are technically not required for the FFS TFT LCD embodiments. However, the common electrodes can be made out of transparent conductive material (such as ITO) as usually required for FFS TFT LCDs. Transparent conductors usually have relatively high resistances. This can reduce the sensitivity of touch regions 201, 205 and 207, especially at high frequencies. Therefore, some embodiments provide that even if a FFS TFT display is used, non transparent, low resistance common lines can be used to reduce the effective resistance of the touch regions. However, in these cases, the common lines can vary in density as needed and need not go through every pixel.

FIG. 2B shows a CF glass patterned ITO region layout, which may or may not be needed, depending on the type of LCD technology used by the pixel. For example, such CF ITO regions would not be needed in the case that the LCD pixel utilizes in-plane-switching (IPS). However, FIG. 2B is directed to non-IPS LCD displays in which a voltage is applied to liquid crystal between an upper and lower electrode. FIG. 2B shows upper regions 221, 223, and 225, which correspond to lower (in non-IPS displays) regions 201, 205, and 207, respectively, of FIG. 2A. FIG. 2B shows conductive dots 250 contacting regions 251, 255, and 257. Conductive dots 250 connect the corresponding upper and lower regions such that when to the upper electrodes of pixels in an upper region are driven, the corresponding lower electrodes of pixels in the lower region are also driven. As a result, the relative voltage between the upper and lower electrodes remains constant, even while the pixels are being driven by, for example, a modulated signal. Thus the voltage applied to the liquid crystal can remain constant during a touch phase, for example. In particular, the constant relative voltage can be the pixel voltage for operation of the LCD pixel. Therefore, the pixels can continue to operate (i.e., display an image) while touch input is being detected.

FIG. 3 shows partial circuit diagrams of a pixel 301 of a drive region and a pixel 303 of an example sense region. Pixels 301 and 303 include TFTs 307 and 309, gate lines 311 and 312, data lines 313 and 314, xVcom lines 315 and 316, fringe field electrodes 319 and 321, and storage capacitors 323 and 325. Storage capacitors 323 and 325 each have a capacitance of about 300 fF (femto-Farads). A lower electrode of fringe field electrode 321 of pixel 303 can be connected, through xVcom 316, to a charge amplifier 326 in the sense circuitry. Charge amplifier 326 holds this line at a virtual ground such that any charge that gets injected from fringe field electrode 321 shows up as a voltage output of the amplifier. While the feedback element of the amplifier is shown as a capacitor, it may also function as a resistor or a combination of a resistor and capacitor. The feedback can also be, for example, a resistor and capacitor feedback for minimizing die-size of the touch sensing circuitry. FIG. 3 also shows a finger 327 that creates a stray capacitance of approximately 3 fF with a cover glass (not shown), and shows other stray capacitances in the pixels, each of which is approximately 3 fF.

It is important to note that at the same time fringe field electrode 319 is configured to operate as a drive element for the touch sensing system, the fringe field electrode continues to operate as a part of the LCD display system. As shown in FIG. 5A, while the voltages of the comb structures of fringe field electrode are each modulated at approximately +/−2V, the relative voltage between the comb structures remains approximately constant at 2V+/−0.1V. This relative voltage is the voltage that is seen by the liquid crystal of the pixel for the LCD operation. The 0.1V AC variance in the relative voltage during the touch phase should have an acceptably low effect on the LCD display, particularly since the AC variance would typically have a frequency that is higher than the response time for the liquid crystal. For example, the stimulation signal frequency, and hence the frequency of the AC variance, would typically be more than 100 kHz. However, the response time for liquid crystal is typically less than 100 Hz. Therefore, the fringe field electrode"s function as a drive element in the touch system should not interfere with the fringe field electrode"s LCD function.

Referring now to FIGS. 3, 4B, and 5B, an example operation of the sense region will now be described. FIG. 4B shows signals applied through xVcom 316 to the pixels of the sense region, including pixel 303, during the LCD and touch phases described above. As with the drive region, xVcom 316 is driven with a square wave signal of 2.5V+/−2.5V in order to perform LCD inversion during the LCD phase. During the touch phase, xVcom 316 is connected to amplifier 326, which holds the voltage at or near a virtual ground of 2.5V. Consequently, fringe field electrode 321 is also held at 2.5V. As shown in FIG. 3, fringing electrical fields propagate from fringe field electrode 319 to fringe field electrode 321. As described above, the fringing electric fields are modulated at approximately +/−2V by the drive region. When these fields are received by the top electrode of fringing field electrode 321, most of the signal gets transferred to the lower electrode, because pixel 303 has the same or similar stray capacitances and storage capacitance as pixel 301. Because xVcom 316 is connected to charge amplifier 326, and is being held at virtual ground, any charge that gets injected will show up as an output voltage of the charge amplifier. This output voltage provides the touch sense information for the touch sensing system. For example, when finger 327 gets close to the fringing fields, it captures some fields and grounds them, which causes a disturbance in the fields. This disturbance can be detected by the touch system as a disturbance in the output voltage of charge amplifier 326. FIG. 5B shows that approximately 90% of a received fringing field at pixel 302 which impinges onto the electrode half of the capacitor which is also connected to the drain of the TFT 325 will be transferred to charge amplifier 326. 100% of the charge that impinges onto the electrode half of the capacitor which is connected directly to XVCOM 316 will be transferred to charge amplifier 326. The ratio of charge impinging onto each electrode will depend on the LCD design. For non-IPS, near 100% of the finger affected charge will impinge on the VCOM electrode because the patterned CF plate is nearest the finger. For IPS type display the ratio will be closer to half and half because each part of the electrode has approximately equal area (or ¼ vs. ¾) facing the finger. For some sub-types of IPS displays, the fringing electrodes are not coplanar, and the majority of the upward facing area is devoted to the VCOM electrode.

Example displays including pixels with dual-function capacitive elements, and the processes of manufacturing the displays, according to embodiments of the invention will now be described with reference to FIGS. 11-46. FIGS. 11-24 are directed to an example electrically controlled birefringence (ECB) LCD display using amorphous silicon (a-Si). FIGS. 25-34 are directed to an example IPS LCD display using low temperature polycrystalline silicon (LTPS). FIGS. 35-43 are directed to another example IPS LCD display using LTPS. FIGS. 44-55 are directed to an example ECB LCD display using LTPS.

An example process of manufacturing an ECB LCD display according to embodiments of the invention will now be described with reference to FIGS. 11-18. The figures show various stages of processing of two pixels, a pixel 1101 and a pixel 1102, during the manufacture of the ECB LCD display. The resulting pixels 1101 and 1102 form electrical circuits equivalent to pixels 101 and 102, respectively, of FIG. 1.

FIG. 24 illustrates an example modification according to embodiments of the invention. As a result of the modification, the aperture ratios of the different pixels in a system may be made more similar, which may improve the appearance of the display. Similar to pixel 1102, pixels 2401 and 2405 do not include connection portions in the y-direction. Pixel 2403, on the other hand, does include a connection portion in the y-direction, similar to pixel 1101.

FIGS. 25-34 are directed to an example IPS LCD display using low temperature polycrystalline silicon (LTPS). An example process of manufacturing an IPS LCD display using LTPS according to embodiments of the invention will now be described with reference to FIGS. 25-31. The figures show various stages of processing of two pixels, a pixel 2501 and a pixel 2502, during the manufacture of the IPS LCD display using LTPS. The resulting pixels 2501 and 2502 form electrical circuits equivalent to pixels 101 and 102, respectively, of FIG. 1. Because the stages of processing shown in FIGS. 25-30 are the same for pixel 2501 and pixel 2502, only one pixel is shown in each of these figures. However, it is understood that the stages of processing show in FIGS. 25-30 apply to both pixel 2501 and pixel 2502.

FIG. 25 shows the patterning of a layer of poly-Si of pixels 2501 and 2502. Semiconductor portions 2505, 2507, and 2509 form the active region of a TFT, and serve as source, gate, and drain, respectively.

FIGS. 35-43 are directed to another example IPS LCD display using LTPS. In the present example, a yVcom line is formed in an M2 layer (in comparison to the previous example IPS LCD display, in which a yVcom line is formed in a common ITO layer). An example process of manufacturing an IPS LCD display using LTPS with an M2 layer yVcom line according to embodiments of the invention will now be described with reference to FIGS. 35-41. The figures show various stages of processing of two pixels, a pixel 3501 and a pixel 3502, during the manufacture of the example IPS LCD display. The resulting pixels 3501 and 3502 form electrical circuits equivalent to pixels 101 and 102, respectively, of FIG. 1.

FIG. 35 shows the patterning of a layer of poly-Si of pixels 3501 and 3502. Semiconductor portions 3505, 3507, and 3509 form the active region of a TFT of pixel 3501, and serve as source, gate, and drain, respectively. Likewise, semiconductor portions 3506, 3508, and 3510 are the source, gate, and drain, respectively, of pixel 3502. FIG. 35 also shows that pixel 3501 has the width W′ (in the x-direction) that is slightly greater than the width W of pixel 3502.

FIGS. 44-55 are directed to an example ECB LCD display using LTPS. Like the ECB LCD display using amorphous silicon (a-Si) (shown in FIGS. 11-24), the process of manufacturing the ECB LCD display using LTPS includes construction of vias and additional M2 lines to form yVcom lines that connect the storage capacitors of pixels in the y-direction.

An example process of manufacturing an ECB LCD display using LTPS according to embodiments of the invention will now be described with reference to FIGS. 44-50. FIG. 44 shows a semiconductor layer of poly-Si. FIG. 45 shows a first layer of metal (M1). FIG. 46 shows connections including 4601 and 4602. FIG. 47 shows a second metal layer (M2). Connections 4601 and 4602 connect the M1 and M2 layers to form a yVcom line as shown in the figures. FIGS. 48-50 show a connection layer, a reflector layer, and an ITO layer, respectively. FIG. 51 shows a completed pixel including a yVcom portion that allows connection in the y-direction. FIG. 52 shows a side view of pixel 5101 along the line shown in the top view shown in FIG. 52. FIG. 53 shows a calculation of the storage capacitance of pixel 5101. FIG. 54 shows an aperture ratio estimation of pixel 5101 and a pixel 5403 that does not include a yVcom line. FIG. 55 shows that some metal, such portions of the M1, M2, and/or ITO layers can be shifted to help equalize the aperture ratios of the pixels.

FIG. 57 is a side view along the line A-A in FIG. 56, showing the portion of touch screen 5600, including a cover 5701, an adhesive 5702, a polarizer 5703, a high resistance (R) shield 5704, a color filter glass 5705, drive regions 5601 and 5602, sense regions 5603 and 5604, grounded separator region 5605, a TFT glass 5706, and a second polarizer 5707. A high resistance shield, such as high R shield 5704, may be used in touch screens using IPS LCD pixels, for example. A high R shield may help block low frequency/DC voltages near the display from disturbing the operation of the display. At the same time, a high R shield can allow high-frequency signals, such as those typically used for capacitive touch sensing, to penetrate the shield. Therefore, a high R shield may help shield the display while still allowing the display to sense touch events. High R shields may be made of, for example, a very high resistance organic material, carbon nanotubes, etc. and may have a resistance in the range of 100 Mega-ohms per square to 10 Giga-ohms per square.

FIG. 58 shows a side view of a portion of an example touch screen 5800 according to embodiments of the invention. Touch screen 5800 includes a color filter glass 5801, a pixel layer 5803 (including red (R), green (G), and blue (B) pixels, and black mask lines of a black mask, such as shown in FIG. 59). Touch screen 5800 also includes metal lines 5805 under the black mask lines. Metal lines 5805 can provide low-resistance paths, for example, between a region of pixels and bus lines in the border of a touch screen. For example, in conventional LCD non-IPS displays, the common electrode, which is typically on the CF glass, is one sheet of ITO. Therefore, the resistance of this common electrode is very low. For example, a conventional LCD may have a common electrode of ITO that has a resistance of approximately 100 ohms per square. However, in some embodiments above the common electrode is “broken up” into regions that are connected to a shared common line through relatively thin pathways. The connection between a region of pixels and a shared common electrode line can have a relatively high resistance, particularly if the region is further away from the boarder of the touch screen, in which the shared common line may reside. Metal lines 5805 may help lower the resistance of the path to such a region. Placing metal lines 5805 under the black mask can reduce the metal lines" impact on pixel aperture ratio, for example.

As discussed in the above embodiments, at least some pixels include xVcom and/or yVcom lines. These lines are generally used to connect the capacitors of various display pixels to form larger touch regions used for touch sensing (see, e.g., regions 207 and 205 of FIG. 2A and 257 and 255 of FIG. 2B).

The xVcom and yVcom lines can be made out of a non-transparent conductor (such as non-transparent metal) in order to provide for lower resistance. However, in the above discussed embodiments, the xVcom and yVcom lines can reduce the aperture of the display. While the above discussed embodiments attempt to minimize aperture reductions, some reductions as compared to a standard non-touch enabled display may still be necessary to accommodate the xVcom and yVcom lines.

Thus, in general, embodiments of the invention can feature common lines used for touch sensing that are positioned at a different layer than various opaque display elements that are used for the display functionality, and arranged so that the display elements substantially overlap the common lines. The common lines can be attached to respective storage electrodes that are parts of storage capacitors used for various display pixels. Thus, the storage electrodes attached to the common lines can serve a dual function—they can be used both for the display and the touch sensing functionalities.

An example of one such embodiment is shown in FIG. 60. FIG. 60 shows three exemplary layers of a display. First layer 6001 includes gate line 6002. The second layer 6003 includes data line 6004. The first and second layers can be, for example the M1 and M2 layers. A third layer 6005 includes an xVcom line 6006 that is positioned to overlap gate line 6002 and a yVcom line 6007 that is positioned to overlap the data line 6004. The xVcom and yVcom lines can be placed at the same layer and connect in region 6008. Layers 6001, 6003 and 6005 need not be adjacent, but may be separated from each other by dielectric or other layers. Thus, the xVcom and yVcom lines need not connect to the gate and data lines they overlap.

Thus, by providing xVcom and yVcom lines that overlap respective gate and data lines, embodiments of the invention can ensure that the addition of the xVcom and yVcom lines (or common lines) does not reduce the aperture of the display.

Some embodiments of the present invention may not require exact overlap between respective xVcom and yVcom lines and gate or data lines. For example, a xVcom or yVcom line can be narrower than, wider than, or slightly displaced from a respective gate or data line. Furthermore, a common line need not only overlap a gate or data line, but may overlap any other nontransparent element required for the display functionality (such as, e.g., a pixel transistor) in order to ensure its addition does not cause a substantial reduction in aperture. For some embodiments, it is sufficient that the common line substantially overlaps another non-transparent element(s) in the display to ensure that the addition of the common line does not cause significant decrease of aperture. For example, the overlap can be such that only 70% of the common line is directly above or below a respective other non-transparent line or element.

As noted above, some embodiments of the invention relate to FFS TFT displays. As known in the art, FFS TFT displays can be provided in two possible configurations as relating to the relative placement of their common and pixel electrodes. These are referred to as the “common on top” configuration in which the common electrode is placed on top of the pixel electrode and the “pixel on top” configuration in which the pixel electrode is placed on top of the common electrode. FIGS. 61A and 61B show these configurations in more detail. FIG. 61A shows a pixel electrode on top configuration and FIG. 61B shows a common electrode on top configuration. It should be noted that to improve clarity, FIGS. 61A and 61B do not show other known elements of the display such as gate and data lines, transistors, etc.

In FIG. 61A, the common electrode is electrode 6100. Multiple pixel electrodes 6101-6104 can be positioned above it. Each pixel electrode can include two or more “fingers” or extensions. Thus, for example, fingers 6105, 6106 and 6107 can be part of pixel electrode 6102. The fingers of a single pixel electrode can be interconnected to form a single electrode (this connection is not shown in the cross section of FIG. 61A). When a pixel electrode is at a different voltage than the common electrode 6100, electrical fields appear between the pixel electrode and the common electrode. Some of these extend above the pixel electrode (see, e.g., fields 6108 of electrode 6101) and can control liquid crystals above the pixel electrode in order to change the visible state of a pixel associated with the pixel electrode. The voltage of each pixel electrode can be individually changed to control the color (or brightness) of a particular pixel, while the single common electrode 6100 can be maintained at a single voltage for all pixels (although some displays can use a plurality of different common electrodes for different rows).

FIG. 61B shows a common electrode on top configuration. In this case, pixel electrodes 6111, 6112, 6113 and 6114 can be positioned along the bottom of the display. As shown, the pixel electrodes need not be separated into fingers. The common electrode 6110 can be positioned over the pixel electrodes and form sets of fingers over each pixel electrode. All the fingers of the common electrode can be connected, thus forming a single common electrode 6110. The three fingers 6110 above pixel electrode 6111 can be connected to fingers 6110 above pixel electrodes 6112, 6113 and 6114. Again this connection is not shown in the cross section of FIG. 61B. However, as noted above, some embodiments may feature different common electrodes on different lines. Thus, the common electrode on the top embodiment is not a single solid plate but can be cut into stripes in order to allow for the forming of fingers.

In FFS TFT embodiments, the common lines (i.e., xVcom and yVcom, or generally VCOM) can be made adjacent to the common electrode in order to ensure that they are conductively connected. FIGS. 62A-D show some exemplary connections.

It should be noted that the configurations shown in FIGS. 62A-62D are not the only configurations for embodiments of this invention. For example, the common line can be placed below the common electrode but not immediately below it and may utilize connections to connect to the common electrode. Also, FIGS. 62A-D show a solid common electrode, which would indicate a common electrode on the bottom configuration. Those of skill in the art would recognize the connections of FIGS. 62A-D can be easily applied to a common electrode on top configuration. The connections of FIGS. 62A-D can also be used to connect common lines to storage electrodes in non-FFS embodiments. In the interest of clarity, FIGS. 62A-62D do not show all components of the display.

FIG. 63 is a diagram showing FFS TFT LCD embodiments of the present invention in various stages of manufacturing. Diagrams 6301-6309 represent different stages of the manufacturing of a substrate assembly that result from placing different elements on a substrate (which may be, e.g., a glass substrate). More specifically, stages 6301-6309 are progressive stages of manufacturing of a display pixel on a substrate in which various features are sequentially placed on the substrate and thus added to the substrate assembly. Thus, every stage can include all the elements of its predecessor stage.

Elements formed when manufacturing the substrate assembly are considered to be formed on the substrate and part of the substrate assembly even if they are not formed directly on the substrate but are formed on top of other elements that are formed on the substrate. There are, however, other layers that are part of the display but are not formed on the substrate or on another element that is formed on the substrate. These are instead separately produced and later combined with the substrate. These layers can include filters, polarizers, liquid crystals, other substrates, etc. They may not considered to be part of the substrate assembly.

It can be seen that the aperture ratio 6316 is not significantly decreased from what it would have been had the common lines 6321 and 6322 been absent. In other words, the placement of common lines does not overlap any areas that could have otherwise been used for the display functionality. To the contrary, the common lines overlap areas that are already opaque due to other needed elements (e.g., gate line 6310 and data line 6311).

FIG. 65 is a diagram of various manufacturing stages of an exemplary display according to one embodiment of the invention. In contrast to FIG. 63, FIG. 65 shows a common electrode on top configuration. Stages 6501-6505 are similar to stages 6301-6305, respectively. As with the embodiment of FIG. 63, a transistor 6317 is formed at stage 6504. The transistor can be the same as transistor 6317 of FIG. 63. At stage 6506, the pixel electrode 6515 is initially deposited. The pixel electrode is connected to the drain 6318 of transistor 6317. Stage 6507 is a connection and dielectric layer. At stage 6508, the common electrode 6512 is placed. In this embodiment, the common electrode is above the pixel electrode. Thus, the common electrode can be comb-like, as shown (see also FIG. 61B).

The embodiments of FIGS. 61-66 refer to FFS TFT LCDs. However, the teachings discussed therein can be used for other types of LCDs. Thus, other types of LCDs can feature xVcom and yVcom lines that overlap existing opaque elements of the display that are already used to perform display functionality (such as, e.g., gate and data lines) in order to ensure that the xVcom and yVcom lines do not cause any reductions to the aperture ratio. Non-FFS embodiments need not include a common electrode. However, they can include pixel storage capacitors. Thus, in these embodiments the xVcom and/or yVcom lines can be attached to an electrode of the pixel storage capacitor of each pixel. In some embodiments, the xVcom and yVcom lines can be positioned at the same TFT substrate assembly as the transistors and gate and data lines of each electrode. In other embodiments, the xVcom and yVcom lines can be positioned in a color filter layer above the TFT layer, as discussed above (see, e.g., FIG. 2B). In the latter embodiments, the xVcom and yVcom lines can nevertheless be lined up to overlap respective gate and data lines of the TFT layer.

FIG. 67 shows an example IPS-based touch-sensing display in which the pixel regions serve multiple functions. For example, a pixel region can operate as a drive region at one time and operate as a sensing region at another time. FIG. 67 shows two types of pixel regions, pixel region type A and pixel region type B. During a first time period the A type pixel regions, i.e., touch columns, can be driven with a stimulus waveform while the capacitance at each of the B type pixel regions, i.e., touch rows, can be sensed. During a next time period, the B type pixel regions, i.e., touch rows, can be driven with a stimulus waveform while the capacitance at each of the A type pixel regions, i.e., touch columns, can be sensed. This process can then repeat. The two touch-sense periods can be about 2 ms. The stimulus waveform can take a variety of forms. In some embodiments it may be a sine wave of about 5V peak-to-peak with zero DC offset. Other time periods and waveforms may also be used.

Touch screen 6824 can be a combination of a display and touch screen as discussed above. Touch screen 6824 can include a capacitive sensing medium having a plurality of drive regions and a plurality of sense regions according to embodiments of the invention. Each intersection of drive and sense regions can represent a capacitive sensing node and can be viewed as touch picture element (touch pixel) 6826, which can be particularly useful when touch screen 6824 is viewed as capturing an “image” of touch. (In other words, after panel subsystem 6806 has determined whether a touch event has been detected at each touch sensor in the touch screen, the pattern of touch sensors in the multi-touch panel at which a touch event occurred can be viewed as an “image” of touch (e.g. a pattern of fingers touching the panel).) Each sense region of touch screen 6824 can drive sense channel 6808 (also referred to herein as an event detection and demodulation circuit) in panel subsystem 6806.

Computing system 6800 can also include host processor 6828 for receiving outputs from panel processor 6802 and performing actions based on the outputs that can include, but are not limited to, moving an object such as a cursor or pointer, scrolling or panning, adjusting control settings, opening a file or document, viewing a menu, making a selection, executing instructions, operating a peripheral device connected to the host device, answering a telephone call, placing a telephone call, terminating a telephone call, changing the volume or audio settings, storing information related to telephone communications such as addresses, frequently dialed numbers, received calls, missed calls, logging onto a computer or a computer network, permitting authorized individuals access to restricted areas of the computer or computer network, loading a user profile associated with a user"s preferred arrangement of the computer desktop, permitting access to web content, launching a particular program, encrypting or decoding a message, and/or the like. Host processor 6828 can also perform additional functions that may not be related to panel processing, and can be connected to program storage 6832. The processor can also be connected to the touch screen/display combination 6824 in order to control the display functionality. This connection can be distinct and in addition to the connection between the host processor 6828 and the touch screen display combination 6824 through the panel processor 6802, said latter connection being used to control the touch functionality of the touch screen display combination 6824.

FIG. 69C illustrates an example personal computer 6944 that can include a trackpad 6925 that is a touch screen, including pixels with dual-function capacitive elements. Alternatively or in addition, the personal computer 6944 can include a touch screen 6924 that is used as the main display of the personal computer. The touch screen 6924 can also include pixels with dual function capacitive elements according to embodiments of the invention.

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The world of smartphones has been busy for the past few months. There have been numerous revolutionary launches with groundbreaking innovations that have the capacity to change the course of the smartphone industry. But the most important attribute of a smartphone is the display, which has been the focus for all prominent players in the mobile phone industry this year.

Samsung came up with its unique 18:5:9 AMOLED display for the Galaxy S8. LG picked up its old trusted IPS LCD unit for the G6’s display. These display units have been familiar to the usual Indian smartphone buyer. Honor, on the other hand, has just unveiled the new Honor 8 Pro for the Indian market that ships with an LTPS LCD display. This has led to wonder how exactly is this technology different from the existing ones and what benefits does it give Honor to craft its flagship smartphone with. Well, let’s find out.

The LCD technology brought in the era of thin displays to screens, making the smartphone possible in the current world. LCD displays are power efficient and work on the principle of blocking light. The liquid crystal in the display unit uses some kind of a backlight, generally a LED backlight or a reflector, to make the picture visible to the viewer. There are two kinds of LCD units – passive matrix LCD that requires more power and the superior active matrix LCD unit, known to people as Thin Film Transistor (TFT) that draws less power.

The early LCD technology couldn’t maintain the colour for wide angle viewing, which led to the development of the In-Plane Switching (IPS) LCD panel. IPS panel arranges and switches the orientation of the liquid crystal molecules of standard LCD display between the glass substrates. This helps it to enhance viewing angles and improve colour reproduction as well. IPS LCD technology is responsible for accelerating the growth of the smartphone market and is the go-to display technology for prominent manufacturers.

The standard LCD display uses amorphous Silicon as the liquid for the display unit as it can be assembled into complex high-current driver circuits. This though restricts the display resolution and adds to overall device temperatures. Therefore, development of the technology led to replacing the amorphous Silicon with Polycrystalline Silicon, which boosted the screen resolution and maintains low temperatures. The larger and more uniform grains of polysilicon allow faster electron movement, resulting in higher resolution and higher refresh rates. It also was found to be cheaper to manufacture due to lower cost of certain key substrates. Therefore, the Low-Temperature PolySilicon (LTPS) LCD screen helps provide larger pixel densities, lower power consumption that standard LCD and controlled temperature ranges.

The AMOLED display technology is in a completely different league. It doesn’t bother with any liquid mechanism or complex grid structures. The panel uses an array of tiny LEDs placed on TFT modules. These LEDs have an organic construction that directly emits light and minimises its loss by eradicating certain filters. Since LEDs are physically different units, they can be asked to switch on and off as per the requirement of the display to form a picture. This is known as the Active Matrix system. Hence, an Active Matrix Organic Light Emitting Diode (AMOLED) display can produce deeper blacks by switching off individual LED pixels, resulting in high contrast pictures.

The honest answer is that it depends on the requirement of the user. If you want accurate colours from your display while wanting it to retain its vibrancy for a longer period of time, then any of the two LCD screens are the ideal choice. LTPS LCD display can provide higher picture resolution but deteriorates faster than standard IPS LCD display over time.

An AMOLED display will provide high contrast pictures any time but it too has the tendency to deteriorate faster than LCD panels. Therefore, if you are after greater picture quality, choose LTPS LCD or else settle for AMOLED for a vivid contrast picture experience.

"Apple has long been speculated that it will launch an AMOLED version of its new iPhone in September along with two other LTPS TFT LCD models," industry sources said.

But TRI said that the definition LTPS TFT LCD panels varies proportionally with needed power to drive backlights in handsets, a relationship that is politically-incorrect in this age of eco-awareness and would work against promotions in markets with high proportions of consumers whose buying decisions are actually influenced by the green movement than fad.

Optimization resulting from high transmissivity of LTPS TFT LCD technology achieves a high luminance of 250cd/m2, a high contrast ratio of 400:1 and a wide color gamut of 70%, despite super-high density of 229 ppi.

A combination of high transmissivity of LTPS TFT LCD technology and NEC LCD Technologies" own unique super-reflective natural light TFT (SR-NLT) technology achieves high luminance of 200cd/m2 and a high reflective ratio of 15%, despite a super-high density of 229 ppi.

Optimization based on high transmissivity of LTPS TFT LCD technology achieves high luminance of 200cd/m2, a high contrast ratio of 400:1 and a wide color gamut of 70%, despite ultra-high density of 302ppi.

A combination of high transmissivity of LTPS TFT LCD technology and NEC LCD Technologies" own unique super-reflective natural light TFT (SR-NLT) technology achieves high luminance of 180cd/m2 and a high reflective ratio of 15%, despite ultra-high density of 302ppi.

Leadis supplies display drivers supporting the major small panel display technologies, including a-Si and LTPS TFT LCD"s, color STN LCD"s, and color OLED displays.

Estimated Shipments of Small and Medium-sized Display Panels, by Category Unit: 1 million units Period LTPS TFT LCD a-Si TFT LCD CSTN LCD MSTN LCD AMOLED Q1, 2010 69 234 66 18 6 Q2, 2010 78 252 66 18 6 Q3, 2010 102 264 48 18 12 Q4, 2010 96 252 48 12 18 Q1, 2011 96 228 36 12 18 Q2, 2011 102 300 36 6 24 Q3, 2011 108 300 24 12 36 Q4, 2011 108 280 24 12 42 Q1, 2012 110 300 15 12 42 Q2, 2012 120 310 13 10 42 Q3, 2012 150 320 10 10 54 Q4, 2012 140 320 10 10 54 Source: Topology Research Institute

Shipment Share of Cellphone Main Display by Technology Sum of / Unit Share (%) 2009 Q1 "10 a-Si TFT LCD 52.3% 59.2% CSTN 20.3% 15.3% LTPS TFT LCD 20.4% 17.6% AMOLED 1.4% 1.9% MSTN 5.6% 6% PMOLED 0.1% 0% Source: Display Search Quarterly Mobile Phone Shipment and Forecast Report

Founded in 2001, AFPD is a joint venture between Toshiba Corporation and Matsushita Electric Industrial Co., Ltd., specializing in the manufacture of LTPS TFT LCDs with excellent mass production and related technologies as its intelligence properties.

A thin-film-transistor liquid-crystal display (TFT LCD) is a variant of a liquid-crystal display that uses thin-film-transistor technologyactive matrix LCD, in contrast to passive matrix LCDs or simple, direct-driven (i.e. with segments directly connected to electronics outside the LCD) LCDs with a few segments.

In February 1957, John Wallmark of RCA filed a patent for a thin film MOSFET. Paul K. Weimer, also of RCA implemented Wallmark"s ideas and developed the thin-film transistor (TFT) in 1962, a type of MOSFET distinct from the standard bulk MOSFET. It was made with thin films of cadmium selenide and cadmium sulfide. The idea of a TFT-based liquid-crystal display (LCD) was conceived by Bernard Lechner of RCA Laboratories in 1968. In 1971, Lechner, F. J. Marlowe, E. O. Nester and J. Tults demonstrated a 2-by-18 matrix display driven by a hybrid circuit using the dynamic scattering mode of LCDs.T. Peter Brody, J. A. Asars and G. D. Dixon at Westinghouse Research Laboratories developed a CdSe (cadmium selenide) TFT, which they used to demonstrate the first CdSe thin-film-transistor liquid-crystal display (TFT LCD).active-matrix liquid-crystal display (AM LCD) using CdSe TFTs in 1974, and then Brody coined the term "active matrix" in 1975.high-resolution and high-quality electronic visual display devices use TFT-based active matrix displays.

The liquid crystal displays used in calculators and other devices with similarly simple displays have direct-driven image elements, and therefore a voltage can be easily applied across just one segment of these types of displays without interfering with the other segments. This would be impractical for a large display, because it would have a large number of (color) picture elements (pixels), and thus it would require millions of connections, both top and bottom for each one of the three colors (red, green and blue) of every pixel. To avoid this issue, the pixels are addressed in rows and columns, reducing the connection count from millions down to thousands. The column and row wires attach to transistor switches, one for each pixel. The one-way current passing characteristic of the transistor prevents the charge that is being applied to each pixel from being drained between refreshes to a display"s image. Each pixel is a small capacitor with a layer of insulating liquid crystal sandwiched between transparent conductive ITO layers.

The circuit layout process of a TFT-LCD is very similar to that of semiconductor products. However, rather than fabricating the transistors from silicon, that is formed into a crystalline silicon wafer, they are made from a thin film of amorphous silicon that is deposited on a glass panel. The silicon layer for TFT-LCDs is typically deposited using the PECVD process.

Polycrystalline silicon is sometimes used in displays requiring higher TFT performance. Examples include small high-resolution displays such as those found in projectors or viewfinders. Amorphous silicon-based TFTs are by far the most common, due to their lower production cost, whereas polycrystalline silicon TFTs are more costly and much more difficult to produce.

The twisted nematic display is one of the oldest and frequently cheapest kind of LCD display technologies available. TN displays benefit from fast pixel response times and less smearing than other LCD display technology, but suffer from poor color reproduction and limited viewing angles, especially in the vertical direction. Colors will shift, potentially to the point of completely inverting, when viewed at an angle that is not perpendicular to the display. Modern, high end consumer products have developed methods to overcome the technology"s shortcomings, such as RTC (Response Time Compensation / Overdrive) technologies. Modern TN displays can look significantly better than older TN displays from decades earlier, but overall TN has inferior viewing angles and poor color in comparison to other technology.

Most TN panels can represent colors using only six bits per RGB channel, or 18 bit in total, and are unable to display the 16.7 million color shades (24-bit truecolor) that are available using 24-bit color. Instead, these panels display interpolated 24-bit color using a dithering method that combines adjacent pixels to simulate the desired shade. They can also use a form of temp