oxide tft lcd manufacturer

LG Display"s oxide TFT technology can be applied to various display products. Since its performance is more than 50 times higher than that of the existing a-Si TFT, it can be applied to the entire product lines from mobiles to laptops and large TVs.

By reducing the size of the TFTs that make up individual pixels and increasing their performance, a display with high resolution and rich colors can be achieved.

By applying oxide TFT, the size of the circuit part of the panel outside the screen can be drastically reduced, making it possible to create a slim design display.

Oxide TFT is highly energy-efficient because the leakage current is very small when the screen is not working, so it can extend the battery life of notebooks or tablets.

LG Display is a pioneer in the industry"s first successful mass-production by researching and developing oxide TFT technology for the longest period of time. LG Display guarantees product reliability that customers can trust and use for a long time.

in-TOUCH products with built-in touch function can maintain slim design and superior image quality compared to add-on (out-cell) touch products with added touch electrodes. It is a technology unique to LG Display that can be applied not only in IT but also in various fields such as home application, health, industrial, and medical products. in-Touch has a built-in touch electrode in the LCD, optimized for slim & light products that can perform touch operation without additional touch electrodes or cover glass.

Oxide thin-film transistor (TFT) liquid crystal display (LCD) panels are increasingly adopted in mobile PCs due to their feature of high resolution while consuming low power. Global shipments of large oxide TFT LCD panels of 9 inches or larger are expected to grow from 20 million units in 2016 to 55.6 million units in 2017, according to new analysis from IHS Markit (Nasdaq: INFO). Of those, 51 million units are estimated to be applied to mobile PCs, which include notebook PCs and tablet PCs, up 200 percent from 17 million units in 2016.

“Demand for high-resolution panels has increased as media content for mobile PCs became available in higher resolutions,” said David Hsieh, senior director at IHS Markit. “Apple’ and Microsoft’s use of oxide TFT LCD panels for products – iPad, iPad Pro, and Surface, respectively – helped increase the oxide mobile PC panel market and encouraged other PC brands to follow suit.”

Low-temperature polysilicon (LTPS) and oxide TFT LCD solutions are major candidates for displaying high-resolution images, and they are expected to account for more than 19 percent of the entire mobile PC display market in 2017, according to the Large Area Display Market Tracker by IHS Markit.

While LTPS can deliver higher resolution images and consume less power than oxide TFT LCD or a-Si TFT LCD, it has its own limits: its production cost is high and the yield rate is low. In addition, it is less efficient to produce large panels. Albeit not as high resolution as LTPS, oxide TFT LCD panels still display high-resolution images better than the a-Si solution, and they are suitable to produce large panels at lower production cost than LTPS.

LG Display and Sharp have expanded their oxide mobile PC panel shipments aggressively by 180 percent and 370 percent, respectively. CEC Panda in China is estimated to increase its shipments from about 600,000 units in 2016 to 4.2 million in 2017. As some oxide panel suppliers are reducing their focus on the mobile PC display business, display makers in China and Taiwan, such as BOE and Innolux, are expected to produce more oxide panels in future, IHS Markit said.

4.5.Comparing the key attributes of different TFT technologies (a-Si, pc-Si, nc-Si, OTFT, graphene, CNT, etc). Parameters include manufacturing technique, mobility, uniformity, stability, and commercialisation stage and primary uses

7.1.Radar chart assessing the merits of different backplane technologies (LTPS, oxide, a-Si, organics) for LCD displays. The parameters considered are resolution, size, flexibility, on-pixel processing, and 3D. Here, the scale is from

7.2.Radar chart assessing the merits of different backplane technologies (LTPS, oxide, a-Si, organics) for OLED displays. The parameters considered are resolution, size, flexibility, on-pixel processing, and 3D. Here, the scale is fro

7.7.Announced annual production capacity (area) of various OLED display manufactures in 2015-2016. Two categories are developed: 1) LTPS backplanes and 2) oxide backplanes

The display industry is continuing to move toward mid-to-large-size, immersive displays in high-performance tablets, notebooks and 8K TVs. As these trends become industry standards, the oxide market emerges as an important opportunity for enabling the next-generation of high-performance displays. These displays feature: higher resolution and faster refresh rates; enhanced circuitry integration to achieve slim bezels; and cost savings for panel makers by improving the panel aperture ratio and enabling large gen size manufacturing.

To achieve these technical requirements, new breakthroughs are needed in thin-film-transistor (TFT) technologies. Among the display industry’s current offerings, amorphous silicon TFT (a-Si TFT) maintains a leading position among all applications, while low-temperature poly-silicon TFT (LTPS) is the predominant display technology for enabling high-performance handheld displays. The key differences between a-Si and LTPS are that an a-Si TFT has a simpler process, structure, and is easier to scale up in terms of manufacturing. However, LTPS offers better TFT performance to achieve higher resolutions and lower power consumption. The drawbacks of LTPS come in size limitations and increased manufacturing costs. For these reasons, neither a-Si or LTPS can fully meet the technical requirements for this next generation of high-performance displays.

All of these industry requirements create new process and glass composition challenges, which present the need to develop an advanced oxide TFT glass technology.

For decades, the dominant technology for flat panel displays was an amorphous silicon (a-Si) backplane. The vast majority of displays were made using a-Si backplanes due to the simplicity in manufacturing process, good economics, and scalability to larger sizes. As demands for brighter and/or higher resolution displays grew due to the introduction and proliferation of handheld mobile devices, alternative backplane technologies, such as low temperature polysilicon (LTPS), became more prevalent. LTPS is similar to a-Si, but requires higher processing temperatures and a more complicated manufacturing process. This results in advanced properties for the backplane, such as >50X higher electronic mobility. These properties allow smaller TFTs (enabling higher resolutions and brighter displays) and faster refresh rates. While clearly a superior technology to a-Si, the higher temperatures and more complex manufacturing process make LTPS considerably more expensive than a-Si. Additionally, LTPS is not easily scaled to larger sizes to enable better panel economics.

The ideal backplane technology would combine the simplicity, economics, and scalability to larger panel sizes of a-Si with the heightened performance of LTPS. This is exactly what oxide TFT technologies offer. The most commonly implemented oxide TFT technology is based on Indium-Gallium-Zinc-Oxide or “IGZO” technologies.

Though the mobility of oxide TFT is not as high as LTPS, it is an order of magnitude better than a-Si technology and capable of driving OLED displays and 8K 120Hz + LCD TVs. Additionally, the low off-current of an oxide TFT could enable low refresh frequency without flicker effects on static images (a comparison of different TFT technologies are shown in Table 1). While, like LTPS, oxide TFT backplanes have improved electrical properties relative to a-Si backplanes, oxide TFT backplanes can scale up to Gen 10.5 at reasonable costs (unlike LTPS), thereby enabling high-end, large-size LCD and OLED TVs. It is for this “just right” compromise of a-Si and LTPS properties that oxide TFT is garnering so much attention from panel makers worldwide. It offers the ability to manufacture displays far superior to a-Si at sizes and costs unachievable by LTPS.

There are two major oxide TFT processes to consider: etch-stop and back channel etch (BCE). The key difference between the processes is the use of an etch-stop layer, also known as ESL, that is required to protect the IGZO channels during the etching process.

Oxide TFT reliability was the major concern in early stage of oxide TFT development. The oxide TFT channel was usually damaged in subsequent processes, so an etch stop structure was designed to protect the oxide TFT channel. The etch-stop (ESL) oxide TFT manufacturing process begins with a bottom gate structure which is covered by a gate insulator and TFT islands. After the gate insulator (GI) layers and TFT patterning, a patterned SiO2 layer is deposited to cover the IGZO channel area in order to protect oxide TFT from following source/drain (S/D) etching. This enables better TFT reliability, and after the S/D etching, then followed by passivation, ITO layer as the Figure 1 shows. In the ESL process, temperatures may go up to 300-400°C for up to an hour or more. While these are higher temperatures than some a-Si processes, it is considerably lower than the typical LTPS processes that can exceed 500°C.

The BCE oxide TFT process (Figure 2) is very similar to the ESL oxide TFT process in the first two photo etching processes (PEP) steps. However, a high temperature (400-500°C) annealing process enhances the TFT reliability that allows the removal of the ESL. The higher temperature annealing step requires a thermally stable glass that can withstand harsh manufacturing environments and processing times relative to the conventional oxide (ESL) or a-Si processes.

To panel makers, the BCE oxide TFT process is similar to the a-Si process, which has been widely used for the past two decades. Also, there is one photo-mask process reduction compared to the ES oxide TFT process, therefore, BCE oxide TFT is becoming a mainstream process of oxide TFT manufacturing.

While the oxide TFT process has clear technical benefits for the manufacture of large and high-performance TVs, it presents a unique set of challenges for the glass substrate used in the process.

When put through a typical TFT backplane process, glass substrates will change shape or size (i.e., strain) which is called a change in total pitch (TP). One of the most important glass substrate attributes is total pitch variation (TPV), which is the deviation from predictable glass movement within a glass sheet and from sheet-to-sheet. For a glass substrate to have good TPV performance, the substrate must have the required balance of physical properties to resist the various causes of strain of the substrate: elastic distortion, stress relaxation, and compaction. These sources of strain, and the corresponding glass property that resists them, are discussed below.

In TFT processes, there are several sources of stress applied to the glass substrate, such as film stresses and gate metals. In oxide TFT, the latter is particularly significant due to the substantial thickness and covered area of the gate metal. The pitch change associated with these stresses is determined by the size of the stress, the elastic modulus of the glass, and the thickness of the substrate. Since the stresses are determined by the TFT manufacturer and the industry is continually driving to thinner and thinner substrates, the only attribute within the control of the glass manufacturer is to increase the elastic modulus to increase the stiffness of the substrate. Also, because the stresses in the TFT process can vary across a sheet or sheet-to-sheet, a higher elastic modulus will reduce the strain due to variations in the applied stresses, thereby minimizing TPV from this potential cause.

The stresses from applied films and gate metal can also contribute to the overall TPV through the relaxation of those stresses during subsequent thermal treatments. As the substrate progresses through the various steps of the TFT process, the films, gate metal, and substrate itself will all undergo stress relaxation. As the stress state of the composite changes with time and temperature, the concomitant strain will accordingly change, causing a pitch change and an increase in TPV. The glass substrate resists this stress relaxation in proportion to its effective viscosity at the process temperatures. In a-Si TFT processes, the temperatures are low enough that there is a minimal amount of stress relaxation due to the glass substrate having a relatively high viscosity at these low temperatures (the viscosity of the glass increases as the temperature decreases). In oxide TFT processing, however, temperatures are higher and, therefore, the potential for stress relaxation is greater due to the lower effective viscosity of the glass. This is particularly acute for the BCE oxide TFT process, which has process steps with temperatures in excess of 400°C. Traditional glass substrates which are sufficient for the typical a-Si applications may also be sufficient for the lower temperature ESL oxide TFT processes. However, the higher temperature BCE oxide TFT process may require a substrate with a higher effective viscosity at temperatures in the range of 400°C.

The effective viscosity of the glass substrate also plays a role in the amount of viscous relaxation the glass substrate undergoes in the TFT process due to structural relaxation of the glass itself. This is commonly referred to as “compaction” or “shrinkage” in the glass industry. Compaction is due to the evolution of the glass structure from a non-equilibrium state toward a structure closer to equilibrium with the customer process. The amount of this viscous relaxation that occurs is proportional to the degree to which the glass is out of equilibrium, and inversely proportional to the effective viscosity of the glass at the TFT process temperatures. Consequently, a higher viscosity glass is beneficial for minimizing TPV, just like in stress relaxation. In glass property terms, a higher viscosity glass is a glass with a higher “annealing point” therefore glass manufacturers will often tout the high annealing point of their glass compositions.

Corning’s proprietary fusion process manufactures glass panels at Gen 10.5 sizes (2940 x 3370mm), enabling higher glass utilization for larger-screen sizes. For example, one sheet of Gen 10.5 glass could create eight 65” display panels, or six 75” display panels. This enhanced glass utilization greatly reduces cost for panel makers and is key for enabling the oxide TFT market"

For oxide TFT to be used in IT or handheld products, one of the key features is a thin and light form factor. To achieve this, the display panel usually needs to be thinned down to roughly 0.15mm / 0.15mm (for the two pieces of glass in the display) using the chemical slimming process. A faster etch rate is clearly desired to enable higher throughput and lower costs but this often comes at the cost of the generation of “sludge.” Sludge can create problems in the etch vendors’ processes and end up causing more cost than the fast etch rate reduced. By using a glass that balances maximizing etch rate while minimizing sludge generation, panel makers optimize their throughput and costs.

The technology challenges and technical requirements outlined fuel an industry need for a new glass substrate with the right balance of physical properties for oxide TFT technology. For displays applications, this includes low total pitch variation, low total thickness variation, and low sag. This package of glass attributes, alongside the ability to scale-up manufacturing to large-gen sizes, will help enable the next-generation of mid-to-large-size, immersive displays in 8K TVs.

These applications require a shift toward oxide technology, versus the current a-Si and LTPS TFT technologies. As the push for oxide increases, new process and technical challenges emerge for panel makers. To build a display that meets these performance expectations, panel makers require a thermally and dimensionally stable glass to improve yields while achieving the desired resolution.

An oxide thin-film transistor (TFT) is one of the TFT technologies. Depending on the semiconductor material and properties, TFTs can be classified as amorphous silicon (a-Si), LTPS, and oxide TFTs. An oxide TFT is also used for switching and adjustment of pixel brightness. An oxide TFT, in the manufacturing process, converts ‘Indium-Gallium-Zinc (In-Ga-Zn)’ source material into an oxide that has the properties of a semiconductor (In-Ga-Zn-Oxygen), and hence the name an ‘oxide’ TFT.

As with amorphous silicon (a-Si), an oxide TFT is amorphous. However, the electron mobility in an oxide TFT is roughly 10 times as fast as the ones in amorphous silicon (a-Si), and therefore, an oxide TFT has a greater ability to manufacture displays with higher resolutions. Thanks to the high electron mobility, an oxide TFT has an advantage in integrating TFT circuits, increasing the usable space, and making the bezel thinner.

Compared to the low-temperature polysilicon (LTPS), the electron mobility in an oxide TFT is slower, but a significant portion of equipment used for the existing a-Si manufacturing process can be used for oxide TFTs, giving the oxide TFT a comparative advantage in production costs. In addition, an oxide TFT — unlike the LTPS — does not involve the excimer laser annealing (ELA) process, which removes restrictions in size that arise from the crystallization process, and the great uniformity thanks to its amorphous nature makes an oxide TFT suitable for large-sized displays.

Samsung Display said on Wednesday that it has chosen to lead a national project to develop oxide thin-film transistor (TFT) technology for 1,000ppi OLED panels.

The South Korean display panel maker will aim to develop the oxide TFT which will support electron movements ten times faster than it is currently available now by 2024.

LG Display"s oxide TFT technology can be applied to various display products. Since its performance is more than 50 times higher than that of the existing a-Si TFT, it can be applied to the entire product lines from mobiles to laptops and large TVs.

By reducing the size of the TFTs that make up individual pixels and increasing their performance, a display with high resolution and rich colors can be achieved.

By applying oxide TFT, the size of the circuit part of the panel outside the screen can be drastically reduced, making it possible to create a slim design display.

Oxide TFT is highly energy-efficient because the leakage current is very small when the screen is not working, so it can extend the battery life of notebooks or tablets.

LG Display is a pioneer in the industry"s first successful mass-production by researching and developing oxide TFT technology for the longest period of time. LG Display guarantees product reliability that customers can trust and use for a long time.

in-TOUCH products with built-in touch function can maintain slim design and superior image quality compared to add-on (out-cell) touch products with added touch electrodes. It is a technology unique to LG Display that can be applied not only in IT but also in various fields such as home application, health, industrial, and medical products. in-Touch has a built-in touch electrode in the LCD, optimized for slim & light products that can perform touch operation without additional touch electrodes or cover glass.

The statistic illustrates large oxide TFT LCD panel unit shipments in 2016 and 2017, by type. Large oxide TFT LCD panel shipments for tablet PCs are projected to reach 32.6 million units worldwide in 2017.Read moreGlobal large oxide TFT LCD panel shipments by type in 2016 and 2017 (in million units)*CharacteristicTVTablet PCNotebook PCMonitor-----

IHS. (November 6, 2017). Global large oxide TFT LCD panel shipments by type in 2016 and 2017 (in million units)* [Graph]. In Statista. Retrieved December 28, 2022, from https://www.statista.com/statistics/784229/global-large-oxide-tft-lcd-panel-shipment-by-type/

IHS. "Global large oxide TFT LCD panel shipments by type in 2016 and 2017 (in million units)*." Chart. November 6, 2017. Statista. Accessed December 28, 2022. https://www.statista.com/statistics/784229/global-large-oxide-tft-lcd-panel-shipment-by-type/

IHS. (2017). Global large oxide TFT LCD panel shipments by type in 2016 and 2017 (in million units)*. Statista. Statista Inc.. Accessed: December 28, 2022. https://www.statista.com/statistics/784229/global-large-oxide-tft-lcd-panel-shipment-by-type/

IHS. "Global Large Oxide Tft Lcd Panel Shipments by Type in 2016 and 2017 (in Million Units)*." Statista, Statista Inc., 6 Nov 2017, https://www.statista.com/statistics/784229/global-large-oxide-tft-lcd-panel-shipment-by-type/

IHS, Global large oxide TFT LCD panel shipments by type in 2016 and 2017 (in million units)* Statista, https://www.statista.com/statistics/784229/global-large-oxide-tft-lcd-panel-shipment-by-type/ (last visited December 28, 2022)

Chinese display maker CSOT has placed orders for equipment to use in the production of large liquid crystal display (LCD) panels, TheElec has learned.

The company has recently placed orders for use at its Gen 8.6 (2250x2600mm) oxide thin-film transistor (TFT) LCD production line at its T9 factory in Guangzhou, people familiar with the matter said.

Oxide TFT offers fast electron movement and is power efficient. The technology is used in high-end LCD panels __ low-end LCD panels use a-Si TFT. LG Display also sues oxide TFT for the production of its large OLED panels.

At its T9 factory, the company is planning to manufacture LCD panels for TVs, IT products and automobiles, which means it will be competing with market leaders BOE and LG Display in the sectors.

A thin-film transistor (TFT) is a special type of field-effect transistor (FET) where the transistor is thin relative to the plane of the device.substrate. A common substrate is glass, because the traditional application of TFTs is in liquid-crystal displays (LCDs). This differs from the conventional bulk metal oxide field effect transistor (MOSFET), where the semiconductor material typically is the substrate, such as a silicon wafer.

TFTs can be fabricated with a wide variety of semiconductor materials. Because it is naturally abundant and well understood, amorphous or polycrystalline silicon was historically used as the semiconductor layer. However, because of the low mobility of amorphous siliconcadmium selenide,metal oxides such as indium gallium zinc oxide (IGZO) or zinc oxide,organic semiconductors,carbon nanotubes,metal halide perovskites.

Because TFTs are grown on inert substrates, rather than on wafers, the semiconductor must be deposited in a dedicated process. A variety of techniques are used to deposit semiconductors in TFTs. These include chemical vapor deposition (CVD), atomic layer deposition (ALD), and sputtering. The semiconductor can also be deposited from solution,printing

Some wide band gap semiconductors, most notable metal oxides, are optically transparent.electrodes, such as indium tin oxide (ITO), some TFT devices can be designed to be completely optically transparent.head-up displays (such as on a car windshield).The first solution-processed TTFTs, based on zinc oxide, were reported in 2003 by researchers at Oregon State University.Universidade Nova de Lisboa has produced the world"s first completely transparent TFT at room temperature.

The best known application of thin-film transistors is in TFT LCDs, an implementation of liquid-crystal display technology. Transistors are embedded within the panel itself, reducing crosstalk between pixels and improving image stability.

As of 2008LCD TVs and monitors use this technology. TFT panels are frequently used in digital radiography applications in general radiography. A TFT is used in both direct and indirect capturemedical radiography.

The most beneficial aspect of TFT technology is its use of a separate transistor for each pixel on the display. Because each transistor is small, the amount of charge needed to control it is also small. This allows for very fast re-drawing of the display.

In February 1957, John Wallmark of RCA filed a patent for a thin film MOSFET in which germanium monoxide was used as a gate dielectric. 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. In 1966, T.P. Brody and H.E. Kunig at Westinghouse Electric fabricated indium arsenide (InAs) MOS TFTs in both depletion and enhancement modes.

The idea of a TFT-based liquid-crystal display (LCD) was conceived by Bernard J. Lechner of RCA Laboratories in 1968.dynamic scattering LCD that used standard discrete MOSFETs, as TFT performance was not adequate at the time.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).electroluminescence (EL) in 1973, using CdSe.active-matrix liquid-crystal display (AM LCD) using CdSe in 1974, and then Brody coined the term "active matrix" in 1975.

A breakthrough in TFT research came with the development of the amorphous silicon (a-Si) TFT by P.G. le Comber, W.E. Spear and A. Ghaith at the University of Dundee in 1979. They reported the first functional TFT made from hydrogenated a-Si with a silicon nitride gate dielectric layer.research and development (R&D) of AM LCD panels based on a-Si TFTs in Japan.

By 1982, Pocket TVs based on AM LCD technology were developed in Japan.Fujitsu"s S. Kawai fabricated an a-Si dot-matrix display, and Canon"s Y. Okubo fabricated a-Si twisted nematic (TN) and guest-host LCD panels. In 1983, Toshiba"s K. Suzuki produced a-Si TFT arrays compatible with CMOS integrated circuits (ICs), Canon"s M. Sugata fabricated an a-Si color LCD panel, and a joint Sanyo and Sanritsu team including Mitsuhiro Yamasaki, S. Suhibuchi and Y. Sasaki fabricated a 3-inch a-SI color LCD TV.

The first commercial TFT-based AM LCD product was the 2.1-inch Epson ET-10Hitachi research team led by Akio Mimura demonstrated a low-temperature polycrystalline silicon (LTPS) process for fabricating n-channel TFTs on a silicon-on-insulator (SOI), at a relatively low temperature of 200°C.Hosiden research team led by T. Sunata in 1986 used a-Si TFTs to develop a 7-inch color AM LCD panel,Apple Computers.Sharp research team led by engineer T. Nagayasu used hydrogenated a-Si TFTs to demonstrate a 14-inch full-color LCD display,electronics industry that LCD would eventually replace cathode-ray tube (CRT) as the standard television display technology.notebook PCs.IBM Japan introduced a 12.1-inch color SVGA panel for the first commercial color laptop by IBM.

TFTs can also be made out of indium gallium zinc oxide (IGZO). TFT-LCDs with IGZO transistors first showed up in 2012, and were first manufactured by Sharp Corporation. IGZO allows for higher refresh rates and lower power consumption.polyimide substrate.

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Kawamoto, H. (2012). "The Inventors of TFT Active-Matrix LCD Receive the 2011 IEEE Nishizawa Medal". Journal of Display Technology. 8 (1): 3–4. Bibcode:2012JDisT...8....3K. doi:10.1109/JDT.2011.2177740. ISSN 1551-319X.

Morozumi, Shinji; Oguchi, Kouichi (12 October 1982). "Current Status of LCD-TV Development in Japan". Molecular Crystals and Liquid Crystals. 94 (1–2): 43–59. doi:10.1080/00268948308084246. ISSN 0026-8941.

Mimura, Akio; Oohayashi, M.; Ohue, M.; Ohwada, J.; Hosokawa, Y. (1986). "SOI TFT"s with directly contacted ITO". IEEE Electron Device Letters. 7 (2): 134–6. Bibcode:1986IEDL....7..134M. doi:10.1109/EDL.1986.26319. ISSN 0741-3106. S2CID 36089445.

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Use of Oxide Thin Film Transistor (O-TFT) technology in modern display manufacturing requires a highly conformal and pinhole-free gate dielectric with low hydrogen content. Customer had to find an alternative for PECVD, which was not anymore working for the new generation O-TFT technology.

Thin-Film Transistor Liquid Crystal Displays use thin-film transistors to control the voltage applied to the liquid crystal layer at a sub-pixel level. The structure of TFT LCDs consists of a TFT “sandwich” and a BLU (Backlight Unit). A typical configuration is shown in the schematic diagram below.

Firstly, between the back and front polarizers, TFT LCD cells are made with two glass substrates – one for color filters, the other for a TFT array – and a liquid crystal layer sandwiched in between.

For normally black TFT LCDs, if we follow along a piece of light setting off from its backlight source, it will bea)guided uniformly by LGP;b)reflected and enhanced by BEF and DBEF;c)polarized by the back polarizer;d)polarization changed by twisted LC under the voltage applied by TFT arrays;e)“tinted” red/green/blue by corresponding color filter of the subpixel;f)let through the front polarizer by matched polarization; andg)finally, it will reach the surface and appears in viewer’s eyes.

Normally black LCDs have higher contrast and wider viewing angles without grayscale inversion phenomenon compared to their normally white relatives. And whether TFT LCDs are normally black or white depends on their LC switching mode: