tft lcd construction price

There are different components of a TFT displays that can be modified to create a custom color LCD. Some of the modifications are not too expensive, while others can be cost prohibitive. We will cover some of the main options available and their estimated cost when customizing a TFT display module.

Note: If you need a color LCD module, but do not need video or dot matrix (Graphical) capabilities, I would suggest using a lower cost alternative such as FSC*(Field Sequential Color display) aka known as a TN color display. A second option for a lower cost and much lower power requirement would be a custom segmented display module with color overlays.

This is by far the most expensive component of the TFT module to customize. There are industry standard glass sizes for TFT’s. The list includes, but is not limited to, 2.8 inch, 3.5 inch, 5.7 inch, 7 inch, 10.2 inch and larger. If you can design your product to make use of these standard sizes, then do it. If you need a unique size, say a something between a 2.8 inch and 3.5 inch, you may be forced to invest in a custom glass size. We have seen quotes for custom glass sizes for TFT run between $100,000 dollars to $150,000 dollars. Not a minor investment for most companies.

A TFT LCD display with a modified PCB, is still considered a custom color TFT. Modification costs to customize the PCB is an estimated $400 to $1,200 one-time tooling fee. The unit cost of the TFT display, with a modified PCB will be slightly higher than the cost of the TFT with a standard PCB.

Many products that incorporate a custom color LCD display will contain a touch screen or touch panel. These can be modified to meet a customer’s particular size for an estimated tooling cost of $3,000 to $4,000.

* COG (Chip on Glass) FSC is a new type of technology and not recommended at this time. The most stable type of FSC construction at this time is a COB (Chip on Board)

LCD panel prices have risen for 4 months in a row because of your home gaming? Since this year, the whole LCD panel market has smoked. Whether after the outbreak of the epidemic, LCD panel market prices rose for four months, or the panel giants in Japan and South Korea successively sold production lines, or the Chinese mainland listed companies frequently integrated acquisition, investment, and plant construction, all make the industry full of interesting.

LCD panel prices are already a fact. Since May this year, LCD panel prices have risen for four months in a row, making the whole industry chain dynamic. Why are LCD panels going up in price in a volatile 2020? The key factor lies in the imbalance between supply and demand.

The price of LCDS for large-size TVs of 70 inches or more hasn’t budged much. In addition, LTPS screens and AMOLED screens used in high-end phones have seen little or no increase in price.

As for October, LCD panel price increases are expected to moderate. The data shows that in October 32 inches or 2 dollars; Gains of 39.5 to 43 inches will shrink to $3;55 inches will fall back below $10; The 65-inch gain will narrow to $5.

During the epidemic, people stayed at home and had no way to go out for entertainment. They relied on TV sets, PCS, and game consoles for entertainment. After the resumption of economic work and production, the market of traditional home appliances picked up rapidly, and LCD production capacity was quickly digested.

However, due to the shutdown of most factories lasting 1-2 months during the epidemic period, LCD panel production capacity was limited, leading to insufficient production capacity in the face of the market outbreak, which eventually led to the market shortage and price increase for 4 consecutive months.

In fact, the last round of price rise of LCD panels was from 2016 to 2017, and its overall market price has continued to fall since 2018. Even in 2019, individual types have fallen below the material cost, and the whole industry has experienced a general operating loss. As a result, LCD makers have been looking for ways to improve margins since last year.

A return to a reasonable price range is the most talked about topic among panel makers in 2019, according to one practitioner. Some manufacturers for the serious loss of the product made the decision to reduce production or even stop production; Some manufacturers planned to raise the price, but due to the epidemic in 2020, the downstream demand was temporarily suppressed and the price increase was postponed. After the outbreak was contained in April, LCD prices began to rise in mid-to-late May.

In fact, the market price of LCD panels continued to decline in 2018-2019 because of the accelerated rise of China’s LCD industry and the influx of a large number of local manufacturers, which doubled the global LCD panel production capacity within a few years, but there was no suitable application market to absorb it. The result of excess capacity is oversupply, ultimately making LCD panel prices remain depressed.

Against this background, combined with the impact of the epidemic in 2020, the operating burden of LCD companies in Japan and South Korea has been further aggravated, and it is difficult to make profits in the production of LCD panels, so they have to announce the withdrawal of LCD business.

business in June 2022. In August, Sharp bought JDI Baishan, a plant in Ishikawa prefecture that makes liquid crystal display panels for smartphones. In early September, Samsung Display sold a majority stake in its SUZHOU LCD production plant to Starlight Electronics Technology, a unit of TCL Technology Group. LGD has not only pulled out of some of its production capacity but has announced that it will close its local production line in 2020. According to DSCC, a consultancy, the share of LCD production capacity in South Korea alone will fall from 19% to 7% between 2020 and 2021.

It is worth mentioning that in industry analysis, in view of the fact that Korean companies are good at using “dig through old bonus – selling high price – the development of new technology” the cycle of development mode, another 2020 out of the LCD production capacity, the main reason may be: taking the advantage of China’s expanding aggressively LCD manufacturers, Korean companies will own LCD panel production line hot sell, eliminating capacity liquid to extract its final value, and turning to the more profitable advantage of a new generation of display technologies, such as thinner, color display better OLED, etc. Samsung, for example, has captured more than 80% of the OLED market with its first-mover advantage.

From the perspective of production capacity, the launch of LCD tracks by major manufacturers in Japan and South Korea must reduce some production capacity in the short term, which to some extent induces market price fluctuations. In the long run, some of the Japanese and Korean LCD production capacity has been bought by Chinese manufacturers, coupled with frequent investment in recent years, the overall capacity is sure to recover as before, or even more than before. But now it will take time to expand the production layout, which more or less will cause supply imbalance, the industry needs to be cautious.

The LCD panel industry started in the United States and then gradually moved to Japan, South Korea, China, and Taiwan. At present, the proportion of production capacity in The Chinese mainland has reached 52% in 2020, and there are leading LCD panel products in China represented by BOE, Huxing Optoelectronics. Meanwhile, the production capacity layout of BOE, Huike, Huxing Optoelectronics, and other manufacturers has been basically completed, making industrial integration a necessity.

On the one hand, South Korean enterprises out of the LCD track, the domestic factory horse enclosure, plant expansion action. While LCDs may not sell as well as “upstart” flexible screens, respondents believe they are still strong enough in the traditional home appliance market to warrant continued investment. Zhao Bin, general manager of TCL Huaxing Development Center, has said publicly that the next-generation display technology will be mature in four to five years, but the commercialization of products may not take place until a decade later. “LCD will still be the mainstream in this decade,” he said.

On the other hand, there is no risk of neck jam in China’s LCD panel industry, which is generally controllable. In mainland China, there will be 21 production lines capable of producing 32-inch or larger LCD panels by 2021, accounting for about two-thirds of the global total. In terms of the proportion of production capacity, the Chinese mainland accounted for 42% of the global LCD panel in 2019, 51% this year, and will continue to climb to 63% next year.

Of course, building factories and expanding production cannot be accomplished overnight. In the process of production capacity recovery, it is predicted that there will be several price fluctuations, and the cost may be passed on to the downstream LCD panel manufacturers or consumers when the price rises greatly, which requires continuous attention.

We are changing our TFT part numbers to have them better describe the parts being ordered. The change should be complete for all TFT modules shipping within the next six months.

As an option, you can order this TFT pre-assembled onto a breakout/carrier board. The board allows easy prototyping through its 0.1" headers. You can also include the carrier board in your end product to simplify construction and assembly. The carrier board contains a constant-current switching LED driver. The PCB is sized to fit neatly within the outline of the display, with a total weight of 51 grams.

This kit consists of a CFAF240320B1-032T-TS TFT LCD module mounted on a carrier board. The carrier board supports a current driver for the LED backlight of the display. It is available under Additional Options on the website page for CFAF240320B1-032T-TS.

LCD is the abbreviation for liquid crystal display. An LCD basically consists of two glass plates with a special liquid between them. The special attribute of this liquid is that it rotates or “twists” the plane of polarized light. This effect is influenced by the creation of an electrical field. The glass plates are thus each coated with a very thin metallic film. To obtain polarized light, you apply a polarization foil, the polarizer, to the bottom glass plate. Another foil must be applied to the bottom glass plate, but this time with a plane of polarization twisted by 90°. This is referred to as the analyzer.

In the idle state, the liquid twists the plane of polarization of the incoming light by 90° so that it can pass the analyzer unhindered. The LCD is thus transparent. If a specific voltage is applied to the metallic film coating, the crystals rotate in the liquid. This twists the plane of polarization of the light by another 90°, for example: The analyzer prevents the light getting through, and the LCD thus becomes opaque.TN, STN, FSTN, blue mode, yellow-green mode

However, the different colors occur only in displays that are either not lit or that are lit with white light. If there is any color in the lighting (e.g. yellow-green LED lighting), it overrides the color of the display. A blue-mode LCD with yellow-green LED lighting will always appear yellow-green.Static or multiplex driving method

Every LCD has a preferred angle of view at which the contrast of the display is at its optimum. Most displays are produced for the 6°° angle of view, which is also known as the bottom view (BV). This angle corresponds to that of a pocket calculator that is lying flat on a desktop.

LCDs without lighting are hard to imagine these days. However, since there are basically four different types of lighting, the type selected depends very much on the application. Here is a brief overview to clarify the situation:LED

Standard LCDs have a temperature range of 0 to +50°C. High-temperature displays are designed for operation in the range from -20 to +70°C. In this case, however, additional supply voltage is generally required. Since the contrast of any LCD is dependent on the temperature, a special temperature-compensation circuit is needed in order to use the entire temperature range, and this is particularly true for high-temperature displays (-20 to +70°C). Manual adjustment is possible but rather impractical for the user.

However, the storage temperature of a display should never be exceeded under any circumstances. An excessively high temperature can destroy the display very quickly. Direct exposure to the sun, for example, can destroy an LCD: This is because an LCD becomes darker (in positive mode) as it gets hotter. As it gets darker, it absorbs more light and converts it to heat. As a result, the display becomes even hotter and darker... In this way, temperatures of over 100°C can quickly be reached.Dot-matrix, graphics and 7-segment displays

The first LCDs were 7-segment displays, and they are still found today in simple pocket calculators and digital watches. 7 segments allow all of the digits from 0 to 9 to be displayed.

The semiconductor industry now offers a very large range of LCD drivers. We generally distinguish between pure display drivers without intelligence of their own, controllers with a display memory and possibly a character set, and micro-controllers with integrated LC drivers.

Many ask themselves, "What is the difference between an LCD display and a TFT-display?" or "What is the difference between a TFT and an OLED display?". Here are these 3 sometimes extremely different display technologies briefly explained. LCD vs. TFT vs. OLED (comparison).

- The LCD (Liquid Crystal Display) is a passive display technology. The operation and the structure are described above. Passive means that an LCD can only darken or let out light. So it always depends on ambient light or a backlight. This can be an advantage because the power consumption of a LCD display is very, very low. Sometimes even less than the accumulated power consumption of an E-paper display, which in static operation requires absolutely no energy to maintain the content. To change the contents, however, a relatively large amount of power is required for an E-paper display.

LCDs can also be reflective, so they reflect incident light and are therefore legible even at maximum brightness (sunlight, surgical lighting). Compared to TFT and also OLED, they have an unbeatable advantage in terms of readability and power consumption :; the "formula" is: Sunlight = LCD.

- A TFT-display (of Thin-Film Transistor) is usually a color display (RGB). From the construction and the technology it corresponds to the LCD. It is also passive, so it needs a backlight. This is in any case necessary except for a few, very expensive constructions. However, a TFT needs much more light than the monochrome relatives, because the additional structures on the glass as well as the additional color filters "swallow" light. So TFTs are not particularly energy-efficient, but can display in color and at the same time the resolution is much higher.

- OLED displays (by Organic-Light-Emitting-Diode) are as the name implies active displays - every pixel or sign generates light. This achieves an extremely wide viewing angle and high contrast values. The power consumption is dependent on the display content. Here OLEDs to TFTs and LCDs differ significantly, which have a nearly constant power consumption even with different display contents. Unfortunately, the efficiency of converting the electric current into light energy is still very poor. This means that the power consumption of OLEDs with normal content is sometimes higher than that of a TFT with the same size. Colored OLEDs are increasingly used in consumer devices, but for the industry, due to their availability and lifetime, currently only monochrome displays are suitable (usually in yellow color).

In the reaction time, the OLEDs beat each TFT and LCD by worlds. Trise and Tfall are about 10μs, which would correspond to a theoretical refresh rate of 50,000 Hz. Possibly an advantage in very special applications.

Finally the question "What is better, LCD, OLED or TFT?" Due to the physical differences you can not answer that blanket. Depending on the application, there are pros and cons to each individual technology. In addition to the above differences, there are many more details in the design and construction that need to be individually illuminated for each device. Write us an e-mail or call us: we have specialists with some 20- and 30-year experience. We are happy to compare different displays together with you.AACS and IPS technology

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 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.

The transmittance of a pixel of an LCD panel typically does not change linearly with the applied voltage,sRGB standard for computer monitors requires a specific nonlinear dependence of the amount of emitted light as a function of the RGB value.

Less expensive PVA panels often use dithering and FRC, whereas super-PVA (S-PVA) panels all use at least 8 bits per color component and do not use color simulation methods.BRAVIA LCD TVs offer 10-bit and xvYCC color support, for example, the Bravia X4500 series. S-PVA also offers fast response times using modern RTC technologies.

TFT dual-transistor pixel or cell technology is a reflective-display technology for use in very-low-power-consumption applications such as electronic shelf labels (ESL), digital watches, or metering. DTP involves adding a secondary transistor gate in the single TFT cell to maintain the display of a pixel during a period of 1s without loss of image or without degrading the TFT transistors over time. By slowing the refresh rate of the standard frequency from 60 Hz to 1 Hz, DTP claims to increase the power efficiency by multiple orders of magnitude.

Due to the very high cost of building TFT factories, there are few major OEM panel vendors for large display panels. The glass panel suppliers are as follows:

External consumer display devices like a TFT LCD feature one or more analog VGA, DVI, HDMI, or DisplayPort interface, with many featuring a selection of these interfaces. Inside external display devices there is a controller board that will convert the video signal using color mapping and image scaling usually employing the discrete cosine transform (DCT) in order to convert any video source like CVBS, VGA, DVI, HDMI, etc. into digital RGB at the native resolution of the display panel. In a laptop the graphics chip will directly produce a signal suitable for connection to the built-in TFT display. A control mechanism for the backlight is usually included on the same controller board.

The low level interface of STN, DSTN, or TFT display panels use either single ended TTL 5 V signal for older displays or TTL 3.3 V for slightly newer displays that transmits the pixel clock, horizontal sync, vertical sync, digital red, digital green, digital blue in parallel. Some models (for example the AT070TN92) also feature input/display enable, horizontal scan direction and vertical scan direction signals.

New and large (>15") TFT displays often use LVDS signaling that transmits the same contents as the parallel interface (Hsync, Vsync, RGB) but will put control and RGB bits into a number of serial transmission lines synchronized to a clock whose rate is equal to the pixel rate. LVDS transmits seven bits per clock per data line, with six bits being data and one bit used to signal if the other six bits need to be inverted in order to maintain DC balance. Low-cost TFT displays often have three data lines and therefore only directly support 18 bits per pixel. Upscale displays have four or five data lines to support 24 bits per pixel (truecolor) or 30 bits per pixel respectively. Panel manufacturers are slowly replacing LVDS with Internal DisplayPort and Embedded DisplayPort, which allow sixfold reduction of the number of differential pairs.

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.

K. H. Lee; H. Y. Kim; K. H. Park; S. J. Jang; I. C. Park & J. Y. Lee (June 2006). "A Novel Outdoor Readability of Portable TFT-LCD with AFFS Technology". SID Symposium Digest of Technical Papers. AIP. 37 (1): 1079–82. doi:10.1889/1.2433159. S2CID 129569963.

The North America TFT LCD panel market reached a value of US$ 52 Billion in 2020. Looking forward, IMARC Group expects the market to reach a value of US$ 64.4 Billion by 2026. Keeping in mind the uncertainties of COVID-19, we are continuously tracking and evaluating the direct as well as the indirect influence of the pandemic on different end use industries. These insights are included in the report as a major market contributor.

TFT (Thin Film Transistor) is an active-matrix liquid crystal display (LCD) panel that uses the TFT technology to improve image quality in terms of addressability and contrast. Every pixel on a TFT LCD panel has a separate transistor, which controls the display illumination while enabling an easy view even in bright environments. TFTs are gaining traction in nearly all the industries as they are lightweight, slim in construction, have high-resolution and offer low power consumption. They find major applications in various electronic goods such as televisions, mobile phones, tablets, laptops, desktops, portable video game devices, etc. Apart from these, they are also used in the automotive industry, navigation and medical equipment, laser pointer astronomy, SLR cameras and digital photo frames.

The North America TFT LCD panel market is currently being driven by several factors. TFT-LCD panels provide flexibility in presenting all types of data, including pictoral representation. On account of this, they are increasingly being employed not only in the consumer electronics but also in the aerospace sector as well to display aircraft altitude information, airframe parameters, warning messages and navigational data. Moreover, TFT LCDs are less prone to reflection, viewable from a wider angle and much lighter than traditional panels, thereby having wide applications in the electronics and automotive industry. Additionally, the rising demand for TFT-LCD display is catalyzed by the increasing consumption of flat panel TVs in households, smartphones and gaming industry.

IMARC Group provides an analysis of the key trends in each sub-segment of the North America TFT LCD panel market, along with forecasts at the regional and country level from 2021-2026. Our report has categorized the market based on size and application.

This premium LCD TFT display provides high visibility, and versatile construction with Multi-domain vertical alignment (MVA) technology. The 480x272 resolution TFT display allows wide viewing up to 75° from any direction. This 24-bit display is RoHS compliant and offers high contrast images with RGB interface and a 4-wire resistive touch panel.

DUBLIN, May 24, 2019 /PRNewswire/ -- The "TFT LCD Panel Market: Global Industry Trends, Share, Size, Growth, Opportunity and Forecast 2019-2024" report has been added to ResearchAndMarkets.com"s offering.

This technology currently represents the most popular LCD display technology and accounts for the majority of the global display market. Being light in weight, slim in construction, high in resolution with low power consumption, TFT"s are gaining prominence in almost all the industries wherever displays are required.

On the basis of size, large sized panels dominated the global TFT LCD display market. Large sized panels were followed by the medium and small sized TFT-LCD panels.

A TFT LCD,  or a thin film transistor liquid crystal display, is one of the fastest growing forms of display technology today. The thin film transistor (TFT) is a type of semiconductor device used in display technology to enhance efficiency, compactness, and cost of the product. In conjunction with its semiconductor properties, the TFT LCD is an active matrix display, controlling pixels individually and actively rather than passively, furthering the benefits of this semiconductor device.

The TFT LCD is built with three key layers. Two sandwiching layers consist of glass substrates, though one includes TFTs while the other has an RGB, or red green blue, color filter. The layer between the glass layers is a liquid crystal layer.

The Architecture of a TFT Pixelbelow) from the other substrate layer of the device and control the amount of voltage applied to their respective sub-pixels. This layer also has pixel electrodes between the substrate and the liquid crystal layer. Electrodes are conductors that channel electricity into or out of something, in this case, pixels.

The outer sides of the glass substrates (closest to the surface or closest to the back) have filter layers called polarizers. These filters allow only certain beams of light to pass through if they are polarized in a specific manner, meaning that the geometric waves of the light are appropriate for the filter. If not polarized correctly, the light does not pass through the polarizer which creates an opaque LCD screen.

The twisted nematic effect is one of the cheapest options for LCD technology, and it also allows for fast pixel response time. There are still some limits, though; color reproduction quality may not be great, and viewing angles, or the direction at which the screen is looked at, are more limited.

The light that passes through the device is sourced from the backlight which can shine light from the back or the side of the display. Because the LCD does not produce its own light, it needs to use the backlight in the OLED) have come into use as well. Typically white, this light, if polarized correctly, will pass through the RGB color filter of the surface substrate layer, displaying the color signaled for by the TFT device.

Within an LCD, each pixel can be characterized by its three sub-pixels. These three sub-pixels create the RGB colorization of that overall pixel. These sub-pixels act as capacitors, or electrical storage units within a device, each with their own independent structural and functional layers as described earlier. With the three sub-pixels per pixel, colors of almost any kind can be mixed from the light passing through the filters and polarizer at different brightness based on the liquid crystal alignment.

Let us start with the basics first; refresh the knowledge about TN and LCD displays in general, later we will talk about TFTs (Thin Film Transistors), how they differ from regular monochrome LCD displays. Then we will go on to the ghosting effect, so we will not only discuss the technology behind the construction of the TFT, but also some phenomena, like the ghosting effect, or grayscale inversion, that are important to understand when using an LCD TFT display.

Next, we will look at different technologies of the TFT LCD displays like TN, IPS, VA, and of course about transmissive and transflective LCD displays, because TFT displays also can be transmissive and transflective. In the last part we will talk about backlight.

Let us start with a short review of the most basic liquid crystal cell, which is the TN (twisted nematic) display. On the picture above, we can see that the light can be transmit through the cell or blocked by the liquid crystal cell using voltage. If you want to learn more about monochrome LCD displays and the basics of LCD displays, follow this link.

What is a TFT LCD display and how it is different from a monochrome LCD display? TFT is called an active display. Active, means we have one or more transistors in every cell, in every pixel and in every subpixel. TFT stands for Thin Film Transistor, transistors that are very small and very thin and are built into the pixel, so they are not somewhere outside in a controller, but they are in the pixel itself. For example, in a 55-inch TV set, the TFT display contains millions of transistors in the pixels. We do not see them, because they are very small and hidden, if we zoom in, however, we can see them in every corner of each pixel, like on the picture below.

On the picture above we can see subpixels, that are basic RGB (Red, Green, Blue) colors and a black part, with the transistors and electronic circuits. We just need to know that we have pixels, and subpixels, and each subpixel has transistors. This makes the display active, and thus is called  the TFT display. TFT displays are usually color displays, but there are also monochrome TFT displays, that are active, and have transistors, but have no colors. The colors in the TFT LCD display are typically added by color filters on each subpixel. Usually the filters are RGB, but we also have RGBW (Red, Green, Blue, White) LCD displays with added subpixels without the filter (White) to make the display brighter.

Going a little bit deeper, into the TFT cell, there is a part inside well known to us from the monochrome LCD display Riverdi University lecture. We have a cell, liquid crystal, polarizers, an ITO (Indium Tin Oxide) layer for the electrodes, and additionally an electronic circuit. Usually, the electronic circuit consists of one transistor and some capacitors to sustain the pixel state when we switch the pixel OFF and ON. In a TFT LCD display the pixels are much more complicated because apart from building the liquid crystal part, we also need to build an electronic part.

That is why TFT LCD display technologies are very expensive to manufacture. If you are familiar with electronics, you know that the transistor is a kind of switch, and it allows us to switch the pixel ON and OFF. Because it is built into the pixel itself, it can be done very quickly and be very well controlled. We can control the exact state of every pixel not only the ON and OFF states, but also all the states in between. We can switch the light of the cells ON and OFF in several steps. Usually for TFT LCD displays it will be 8-bit steps per color, so we have 256 steps of brightness for every color, and every subpixel. Because we have three subpixels, we have a 24-bit color range, that means over 16 million combinations, we can, at least theoretically, show on our TFT LCD display over 16 million distinct colors using RGB pixels.

Now that we know how the TFT LCD display works, we can now learn some practical things one of which is LCD TFT ghosting. We know how the image is created, but what happens when we have the image on the screen for a prolonged time, and how to prevent it. In LCD displays we have something called LCD ghosting. We do not see it very often, but in some displays this phenomenon still exists.

Another issue present in TFT displays, especially TN LCD displays, is grayscale inversion. This is a phenomenon that changes the colors of the screen according to the viewing angle, and it is only one-sided. When buying a TFT LCD display, first we need to check what kind of technology it is. If it is an IPS display, like the Riverdi IPS display line, then we do not need to worry about the grayscale inversion because all the viewing angles will be the same and all of them will be very high, like 80, 85, or 89 degrees. But if you buy a more common or older display technology type, like the TN (twisted nematic) display, you need to think where it will be used, because one viewing angle will be out. It may be sometimes confusing, and you need to be careful as most factories define viewing direction of the screen and mistake this with the greyscale inversion side.

We know already that TN (twisted nematic) displays, suffer from grayscale inversion, which means the display has one viewing side, where the image color suddenly changes. It is tricky, and you need to be careful. On the picture above there is a part of the LCD TFT specification of a TN (twisted nematic) display, that has grayscale inversion, and if we go to this table, we can see the viewing angles. They are defined at 70, 70, 60 and 70 degrees, that is the maximum viewing angle, at which the user can see the image. Normally we may think that 70 degrees is better, so we will choose left and right side to be 70 degrees, and then up and down, and if we do not know the grayscale inversion phenomena, we may put our user on the bottom side which is also 70 degrees. The viewing direction will be then like a 6 o’clock direction, so we call it a 6 o’clock display. But you need to be careful! Looking at the specification, we can see that this display was defined as a 12 o’clock display, so it is best for it to be seen from a 12 o’clock direction. But we can find that the 12 o’clock has a lower viewing angle – 60 degrees. What does it mean? It means that on this side there will be no grayscale inversion. If we go to 40, 50, 60 degrees and even a little bit more, probably we will still see the image properly. Maybe with lower contrast, but the colors will not change. If we go from the bottom, from a 6 o’clock direction where we have the grayscale inversion, after 70 degrees or lower we will see a sudden color change, and of course this is something we want to avoid.

We will talk now about the other TFT technologies, that allow us to have wider viewing angles and more vivid colors. The most basic technology for monochrome and TFT LCD displays is twisted nematic (TN). As we already know, this kind of displays have a problem with grayscale inversion. On one side we have a higher retardation and will not get a clear image. That is why we have other technologies like VA (Vertical Alignment), where the liquid crystal is differently organized, and another variation of the TFT technology – IPS which is In-Plane Switching. The VA and IPS LCD displays do not have a problem with the viewing angles, you can see a clear image from all sides.

Apart from the different organization of the liquid crystals, we also organize subpixels a little bit differently in a VA and IPS LCD displays. When we look closer at the TN display, we will just see the subpixels with color filters. If we look at the VA or IPS display they will have subpixels of subpixels. The subpixels are divided into smaller parts. In this way we can achieve even wider viewing angles and better colors for the user, but of course, it is more complicated and more expensive to do.

The picture above presents the TN display and grayscale inversion. For IPS or VA technology there is no such effect. The picture will be the same from all the sides we look so these technologies are popular where we need wide viewing angles, and TN is popular where we don’t need that, like in monitors. Other advantages of IPS LCD displays are they give accurate colors, and wide viewing angles. What is also important in practice, in our projects, is that the IPS LCD displays are less susceptible to mechanical force. When we apply mechanical force to the screen, and have an optically bonded touch screen, we push the display as well as squeeze the cells. When we have a TN display, every push on the cell changes the image suddenly, with the IPS LCD displays with in-plane switching, different liquid crystals organization, this effect is lesser. It is not completely removed but it is much less distinct. That is another reason IPS displays are very popular for smartphones, tablets, when we have the touchscreens usually optically bonded.

Now, let us look at the backlight types. As we see here, on the picture above, we have four distinct types of backlight possible. The most common, 95 or 99 per cent of the TFT LCD displays on the market are the transmissive LCD display type, where we need the backlight from the back. If you remember from our Monochrome LCD Displays lecture, for transmissive LCD displays you need the backlight to be always on. If you switch the backlight off, you will not see anything. The same as for monochrome LCD displays, but less popular for TFT displays, we have the transflective LCD display type. They are not popular because usually for transflective TFT displays, the colors lack in brightness, and the displays are not very practical to use. You can see the screen, but the application is limited. Some transflective LCD displays are used by military, in applications where power consumption is paramount; where you can switch the backlight off and you agree to have lower image quality but still see the image. Power consumption and saving energy is most important in some kind of applications and you can use transflective LCD displays there. The reflective type of LCD displays are almost never used in TFT. There is one technology called Low Power Reflective Displays (LPRD) that is used in TFT but it is not popular. Lastly, we have a variation of reflective displays with frontlight, where we add frontlight to the reflective display and have the image even without external light.

Just a few words about Low Power Reflective Displays (LPRD). This kind of display uses environmental light, ambient light to reflect, and produce some colors. The colors are not perfect, not perfectly clear, but this technology is becoming increasingly popular because it allows to have color displays in battery powered applications. For example, a smartwatch would be a case for that technology, or an electrical bike or scooter, where we can not only have a standard monochrome LCD display but also a TFT LCD color display without the backlight; we can see the image even in

strong sunlight and not need backlight at all. So, this kind of TFL LCD display technology is getting more and more popular when we have outdoor LCD displays and need a low power consumption.

On the picture above, we have some examples of how transmissive and reflective LCD displays work in the sunlight. If we have a simple image, like a black and white pattern, then on a transmissive LCD display, even with 1000 candela brightness, the image probably will be lower quality than for a reflective LCD display; if we have sunlight, we have very strong light reflections on the surface of the screen. We have talked about contrast in more detail in the lecture Sunlight Readable Displays. So, reflective LCD displays are a better solution for outdoor applications than transmissive LCD displays, where you need a really strong backlight, 1000 candela or more, to be really seen outdoors.

To show you how the backlight of LCD displays is built, we took the picture above. You can see the edge backlight there, where we have LEDs here on the small PCB on the edge, and we have a diffuser that distributes the light to the whole surface of LCD screen.

In addition to the backlight, we have something that is called a frontlight. It is similar to backlight, it also uses the LEDs to put the light into it, but the frontlight needs to be transparent as we have the display behind. On the example on the picture above we can see an e-paper display. The e-paper display is also a TFT display variation, but it is not LCD (liquid crystal), it is a different technology, but the back of the display is the same and it is reflective. The example you see is the Kindle 4 eBook reader. It uses an e-paper display and a frontlight as well, so you can read eBooks even during the night.