tft display failure factory

There’re more than 300 procedures to produce TFT LCD. The most advanced LCD, in which the array and cell process are highly automatic. Technically, every step in the process can lead to defects, and most of the defects have been eliminated through the development of TFT LCD technology.

Point defect is a kind of defect that some point on your screen don’t display correctly. There are mainly three situations: the point keeps displaying black or whitewhen the screen is working or the point can only display a single color.

For the first two situations, that’s because the circuit on the TFT and CF controlling that defective pixel point is shorted or broken. While the third situation is caused by damaged color pixel.

Unlike point defect, this larger scale defect is caused by the failure of external FPC or PCBA, or a bad connection between FPC and cell. Therefore, a bunch of pixels connected to these IC are out of control, and we see those defects.

You may notice there are some screens have uneven display, which means some white area appears in dark picture or vice versa. We call this ‘mura’, a word originated from Japanese.

Mura is very common but it doesn’t affect the screen function severely, however it still bring bad look. Hence, many high end display manufacturers have their own standards of mura, and the displays without mura are of the best quality.

The display LCD TFT is a kind of display screen that we are familiar with. Many intelligent terminal products use display LCD TFT. Liquid crystal is the most important part of display LCD TFT. Liquid crystal is a physical form, and this physical form can be used as a key factor in display by sorting. To understand the quality of display LCD wholesale tft module, we generally understand from the specific parameters. So what if the display LCD TFT is blurred? Now let Proculus introduce to you.

The LCD TFT display which becomes blurred and indistinct is divided into two cases: one is the display LCD TFT before installation, and the other is the display LCD TFT after a period of use. If you want to buy lcd module, you should the reasons for these two different time periods are also completely different.

Generally, the display LCD TFT is blurred before installation, which is likely to be the reason for the display LCD TFT itself. We generally check whether the driver is normal, and whether there is a problem with the chip and wiring. It is possible that there are some defects in the design of display LCD TFT, which leads to the blurred screen of display LCD TFT. This kind of situation needs to carry on the internal analysis to the TFT LCD display supplier and obtains the concrete solution.

There is another situation mentioned earlier, that is, it has been used for a period of time after installation, which leads to the blurring of the display LCD TFT. We need to check whether the connection with the motherboard is normal, whether the picture shows signs of jitter, whether the image can be seen clearly, and whether the tightness of the whole machine is poor, resulting in dust or water in the place where the motherboard is connected to the TFT LCD screen, all of which are likely to cause TFT LCD blurred screen. This kind of analysis should be combined with the TFT LCD screen itself, motherboard, structure and so on, and the steps are more complex.

The above content is the introduction to the treatment method of TFT LCD screen. With the continuous increase of TFT LCD display supplier, the competition in TFT LCD industry is becoming more and more fierce. The quality of many TFT LCD manufacturers is also uneven, and there is no lack of many black-hearted manufacturers to simplify the production process for profit, resulting in a lot of bad phenomena in the products. Therefore, we still have to pay more attention to the choice of TFT LCD suppliers.

Typically, the default blame starts with the supplier. However, it could be an issue with your assembly process, the design integration between the product and the display, or even a problem with a non-display component that fails (that affects the display).

Issues with non-conforming performance, where the product no longer meets the performance specification, may be tied to a lack of quality of the components, LCD manufacturing, or in some rarer circumstance a change on the end-product that affected the LCD display.

Additionally there can be mechanical non-conformities, where there are aspects exceeding the defined tolerance as described in the specification. And in some instances, there may be variations not designated in the specification, but quite different from the original qualification units. These non-conformances are capable of affecting the fit, form, or function of the LCD display when assembled.

If your supplier has excessive component variability or possible process variability, there is the potential for a number of LCD display performance-related issues. These issues can be one-off or related to a larger batch of products manufactured together. Good serialization and traceability will help in isolating these occurrences and get to the root cause quickly.

While out-of-the-box nonconformance is typically the responsibility of the supplier, but it becomes a little more ambiguous when the non-conformance is not covered specifically by the governing specification. In this case, common sense and reasonable expectations of variation, the concept of the TEAM is considered. But at the end of the day, the LCD displays need to work in the finished product, and both parties should take the responsibility together to help get to the most efficient solution.

On the other hand, you need to be aware that performance degradation is sometimes caused by a change in another component upstream of the LCD display. Sometimes, a non-display component that is malfunctioning or is incompatible and interfaces with the display may cause the display to exhibit irregular behavior or render it inoperable altogether.

To verify this, swap displays to a fully functioning assembly and see whether the problem follows the display. If the issue does not reappear, the cause is likely a non-LCD display component.

The likelihood of damage, or the display being non-functional from the supplier’s end, is fairly low, as it is standard to test 300%, or three times throughout the process. Additionally, the final packaging itself is subject to drop testing during the initial development phase prior to mass production to ensure a damage-free trip despite your carrier’s best efforts to drop the packaging. That means the defect is likely latent or occurred during installation into the end-product.

Unfortunately, it is common for some failures to make it through final testing. After the vibration and thermal effects from the shipping process, these defects can be exposed and result in an out of box failure at the assembly line.

This could be a manufacturing issue during the LCD display production or a quality issue with an upstream component that exposed a failure mode. In this case, fault may lie with the design itself, which indicates the need for a more robust design. Alternatively, a burn-in test process may be needed to expose potential defects prior to final inspection.

The final assembly process could also be a problem area. If the process is complicated, difficult to maneuver, or there are new operators involved there is a much higher probability of damage while assembling the LCD display into the end-product.

Performing a failure analysis is next. Then, linking that analysis to the customer’s field environment. You’ll need to determine (1) whether the failure is caused by the environment and (2) whether a product improvement can better support the application, or whether there’s a way to limit the environmental extremes.

There is also the potential for misusing the product. A good example of this is using the product in an unintended environment such as extreme moisture. Impact is another unmistakable failure mode as it can manifest itself as a broken touch panel or cracked LCD glass.

For many years, TFT displays have been the dominating technology in visualization. TFT LCDs are all around in our daily lives — in consumer and automotive applications, in our business environments, in healthcare, and within communication devices, home appliances, and factory automation products. While there are many LCD products available today, they’re not all suitable for every application. This is especially the case for industrial LCD monitors. To determine the best LCD display for your application, it’s important to understand your target market and its unique design issues.

The vast majority of LCD displays are designed for consumer devices such as smartphones, cameras, tablet computers, and gaming devices. But they have very different requirements than those for industrial applications. Due to very competitive pricing and quick production cycles, consumer display modules don’t always incorporate the durability, reliability, and advanced features required to survive in an industrial environment. Product life cycles are also typically much shorter in consumer applications. Screens manufactured for these applications are generally only available for one, in best case two years.

In contrast, display modules for industrial applications require Long product life cycles— often up to ten years or more. Plus, when an industrial module is discontinued by the manufacturer, a successor product should be backward-compatible so as to fit into the existing enclosure without requiring a redesign of the entire system.

The ability to withstand temperature variations as well as shock and vibration is also a key consideration when selecting displays for today’s industrial applications. They must be resilient enough to withstand frequent bumps or jiggles by machine operators and surrounding equipment, and also must be able to handle various operating temperatures.

Industrial displays are typically housed in an enclosure as part of a larger piece of equipment. In these situations, the heat generated by the surrounding equipment gets trapped within the enclosure, which can be detrimental to many displays. Therefore, it’s important to keep the real storage and operating temperature requirements in mind when choosing a display. While measures can be taken to dissipate the generated heat — such as using fans within the enclosure — the most efficient way to ensure compliance with the storage and operating temperature requirements is to select a display that is optimized for these types of environments. Fortunately, improvements in liquid-crystal materials have made it possible to extend the operating temperature ranges of LCDs from –30 to 80°C presently.

It’s important that displays used in industrial applications support clear and precise viewing from multiple angles under a variety of ambient light conditions. The brighter the environment, the more difficult it can be to read a standard transmissive LCD display with a typical brightness of 250 to 300 cd/m2. NVD has developed displays that can perform in the 800-cd/m2-and-higher range by implementing high-efficiency LEDs for the backlight unit– if necessary, in combination with special brightness enhancement films.

Increasing the display’s contrast ratio is another effective way that display manufacturers can improve display readability in bright environments. Typical contrast ratios for non-industrial displays are in the range of 200:1 to 300:1, which may not be sufficient when a machine operator is viewing the display from a distance. Displays with contrast ratios around 500:1 or greater are better suited for industrial environments. Another benefit of this method is that it doesn’t increase power consumption.

Multi-angle readability is another key selection factor. In a typical industrial environment, a machine operator is more likely to be positioned at an off-angle rather than right in front of the screen. Implementing a display designed for consumer applications typically doesn’t work well in this situation, as there is image distortion and color shifting when viewed at an angle. But, a number of technologies have been employed to improve off-angle viewing in displays, making them suitable for industrial applications. Some film-based technologies yield viewing angles of 160º horizontally and 140º vertically, but in some cases, this is still not sufficient. In-plane switching technology (IPS), multi-domain vertical alignment (MVA), and fringe field switching (FFS)offer alternatives. These proprietary technologies are able to achieve viewing angles of almost 90-degrees into all four directions without any color shift.

Size and resolution also play a role in overall readability. Displays between 2 and 15-inch diagonal sizes are used most often in industrial applications. These sizes provide sufficient area to view figures, waveforms, and other graphical data without taking up too much real estate on a piece of equipment.

From an aspect ratio 4:3 initially, industrial displays are now shifting to wide formats with WVGA to WXGA resolutions. The wide-aspect format enables users to view longer waveforms and more data on a single display. These display modules can also be designed to incorporate touch-key functions, allowing equipment manufacturers to skip physical switches and buttons and design HMIs based more on software than hardware.

New Vision Display’s experts are prepared to assist in defining appropriate solutions for all applications and in helping find the right balance between manufacturing cost and performance.

I"m asking because I "think" I just experienced this for the first time a couple days ago. Left display was White on startup, but then came on and remained normal the remainder of the day. It has a new battery, just installed by my dealer a few days ago. I"ll be keeping an eye on it, but wondering if this isn"t the start of a problem with that display. (2014 458)

The traditional mechanical instrument lacks the ability to satisfy the market with characters of favorable compatibility, easy upgrading, and fashion. Thus the design of a TFT-LCD (thin film transistor-liquid crystal display) based automobile instrument is carried out. With a 7-inch TFT-LCD and the 32-bit microcontroller MB91F599, the instrument could process various information generated by other electronic control units (ECUs) of a vehicle and display valuable driving parameters on the 7-inch TFT-LCD. The function of aided parking is also provided by the instrument. Basic principles to be obeyed in circuits designing under on-board environment are first pointed out. Then the paper analyzes the signals processed in the automobile

instrument and gives an introduction to the sampling circuits and interfaces related to these signals. Following this is the functional categorizing of the circuit modules, such as video buffer circuit, CAN bus interface circuit, and TFT-LCD drive circuit. Additionally, the external EEPROM stores information of the vehicle for history data query, and the external FLASH enables the display of high quality figures. On the whole, the accomplished automobile instrument meets the requirements of automobile instrument markets with its characters of low cost, favorable compatibility, friendly interfaces, and easy upgrading.

As an essential human-machine interface, the automobile instrument provides the drivers with important information of the vehicle. It is supposed to process various information generated by other ECUs and display important driving parameters in time, only in which way can driving safety be secured. However, the traditional mechanical automobile instrument is incompetent to provide all important information of the vehicle. Besides, the traditional instrument meets great challenge with the development of microelectronic technology, advanced materials, and the transformation of drivers’ aesthetics [1, 2]. Moreover, the parking of the vehicle is also a problem puzzling many new drivers. Given this, traditional instruments should be upgraded in terms of driving safety, cost, and fashion.

The digital instrument has functions of vehicle information displaying, chord alarming, rear video aided parking, LED indicating, step-motor based pointing, and data storage. The instrument adopts dedicated microcontroller MB91F599, a 7-inch LCD, and two step-motors to substitute for the traditional instrument. All the information generated by other ECUs can be acquired via not only the sample circuits but also the CAN bus.

The CAN bus interface and the 7-inch TFT-LCD make it more convenient to upgrade the instrument without changing the hardware. If the software needs to be upgraded, we need not bother to take the instrument down and program the MCU. Instead, we can upgrade the instrument via the vehicle’s CAN network without taking the instrument down, which makes the upgrading more convenient. Most of the information from other ECUs can be transmitted via the CAN bus; so, we do not have to change the hardware circuits if some of the ECUs’ signals are changed in different applications. Besides, since most of the driving parameters are displayed on the TFT-LCD, and the graphical user interface can be designed with great flexibility by programming, only the software needs to be revised to meet different requirements of what kind of driving parameters to display and so forth. These characters, together with the reserved interfaces, enhance the instrument’s compatibility in different applications.

On the one hand, there are some automobile instruments which adopt 8-bit MCUs or 16-bit MCUs which have limited peripherals, so it is difficult for them to meet some requirements such as rearview video and high real-time data processing performance. And many extra components are needed if the designer wants to accomplish some functions such as video input. On the other hand, there are some advanced automobile instruments which adopt high performance MCUs (such as i.MX 53, MPC5121e, and MPC5123) and run Linux on them. They even use larger TFT-LCDs (such as the 12.3-inch TFT-LCD with a resolution of 1280 × 480 pixels) to display driving parameters. These automobile instruments show higher performances than the instrument in this paper. However, they are more expensive than this automobile. This instrument is able to provide almost all the functions of the advanced automobile instrument with a lower cost.

Respecting the above mentioned factors, we finally chose the MB91F599 produced by Fujitsu as the microcontroller. The MB91F599 is particularly well-suited for use in automotive instrument clusters using color displays to generate flexible driver interfaces. It integrates a high performance FR81S CPU core which offers the highest CPU performance level in the industry. Besides, it has a graphics display controller with strong sprite functionality, rendering engine, and external video capture capabilities. These greatly reduce the need for extra components and enhance the stability of the system. The rendering engine can operate in combination with the video capture to enable image manipulation. Overlaid graphics such as needles or parking guidelines can be rendered in conjunction with captured video, which helps to accomplish the aided parking. What is more, multiple built-in regulators and a flexible standby mode enable the MB91F599 to operate with low power consumption.

Here, the sync signal is not present, so the clamp level is controlled by the clamp level output pin of the microcontroller, which is called “keyed clamp” [5]. The graphics display controller of the microcontroller let the clamp level output occur in coincidence with the sync pulse; that is, the clamp level output occurs during the sync tip in Figure 6, thus we get the “sync tip clamp” [5].

Since the FLASH size of the microcontroller is only 1 MB which is limited for the storage of pictures displayed on the LCD, external FLASH is needed to store different kinds of meaningful pictures such as the background of the dial. Two S29GL256N chips with a memory capacity of 256 Mb are chosen for picture data storage for their high performance and low power consumption. The application circuits of the chips are provided in their datasheets, so it is unnecessary to go into the details of them here.

The 7-inch TFT-LCD has a resolution of pixels and supports the 24-bit for three RGB colors. The interface of the 60-pin TFT-LCD can be categorized into data interface, control interface, bias voltage interface, and gamma correction interface.

The data interface supports the parallel data transmitting of 18-bit (6 bits per channel) for three RGB colors. Thus, a range of colors can be generated. The control interface consists of a “horizontal synchronization” which indicates the start of every scan line, a “vertical synchronization” which indicates the start of a new field, and a “pixel clock.” This part is controlled by the graphics display controller which is integrated in the MB91F599. We just need to connect the pins of the LCD to those of the microcontroller correspondingly.

Bias voltages are used to drive the liquid crystal molecules in an alternating form. The compact LCD bias IC TPS65150 provides all bias voltages required by the 7-inch TFT-LCD. The detailed circuit is also provided in the datasheet of TPS65150.

The greatest effect of gamma on the representations of colors is a change in overall brightness. Almost every LCD monitor has an intensity to voltage response curve which is not a linear function. So if the LCD receives a message that a certain pixel should have certain intensity, it will actually display a pixel which has intensity not equal to the certain one. Then the brightness of the picture will be affected. Therefore, gamma correction is needed. Several approaches to gamma correction are discussed in [20–22]. For this specific 7-inch LCD, only the producer knows the relationship between the voltage sent to the LCD and the intensity it produces. The signal can be corrected according to the datasheet of the LCD before it gets to the monitor. According to the datasheet, ten gamma correction voltages are needed. These voltages can be got from a resistive subdivision circuit.

The main task for the program is to calculate the driving parameters of the vehicle and display them on the TFT-LCD. The calculation is triggered by the input signals via the sampling circuits or the CAN bus. The main program flow chart of the system is shown in Figure 10.

The design scheme of a TFT-LCD based automobile instrument is carried out form aspects of both the hardware and the main program flow chart. The MB91F599 simplifies the peripheral circuits with its rich on-chip resources and shows high performance in real-time data processing. The automobile instrument is capable of displaying the velocity of the vehicle, the engine speed, the cooling water temperature, the oil pressure, the fuel volume, the air pressure, and other information on the TFT-LCD, which contributes a lot to driving safety and satisfies drivers’ aesthetics. Besides, the rearview video makes the parking and backing easier and safer for the driver. Moreover, the CAN bus interface and TFT-LCD make it easier for the upgrading of the instrument without changing the hardware, thus saving the cost.

This is very similar to the well-known proxi alignment issue that affects Fiats right across the range; and not just those with TFT displays. The mileage reading is stored digitally both in the body computer and in the display; if the two mileage readings differ, then the display flashes.

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 temporal dithering called Frame Rate Control (FRC), which cycles between different shades with each new frame to simulate an intermediate shade. Such 18 bit panels with dithering are sometimes advertised as having "16.2 million colors". These color simulation methods are noticeable to many people and highly bothersome to some.gamut (often referred to as a percentage of the NTSC 1953 color gamut) are also due to backlighting technology. It is not uncommon for older displays to range from 10% to 26% of the NTSC color gamut, whereas other kind of displays, utilizing more complicated CCFL or LED phosphor formulations or RGB LED backlights, may extend past 100% of the NTSC color gamut, a difference quite perceivable by the human eye.

In 2004, Hydis Technologies Co., Ltd licensed its AFFS patent to Japan"s Hitachi Displays. Hitachi is using AFFS to manufacture high end panels in their product line. In 2006, Hydis also licensed its AFFS to Sanyo Epson Imaging Devices Corporation.

A technology developed by Samsung is Super PLS, which bears similarities to IPS panels, has wider viewing angles, better image quality, increased brightness, and lower production costs. PLS technology debuted in the PC display market with the release of the Samsung S27A850 and S24A850 monitors in September 2011.

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.

The bare display panel will only accept a digital video signal at the resolution determined by the panel pixel matrix designed at manufacture. Some screen panels will ignore the LSB bits of the color information to present a consistent interface (8 bit -> 6 bit/color x3).

With analogue signals like VGA, the display controller also needs to perform a high speed analog to digital conversion. With digital input signals like DVI or HDMI some simple reordering of the bits is needed before feeding it to the rescaler if the input resolution doesn"t match the display panel resolution.

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.

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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.

Kim, Sae-Bom; Kim, Woong-Ki; Chounlamany, Vanseng; Seo, Jaehwan; Yoo, Jisu; Jo, Hun-Je; Jung, Jinho (15 August 2012). "Identification of multi-level toxicity of liquid crystal display wastewater toward Daphnia magna and Moina macrocopa". Journal of Hazardous Materials. Seoul, Korea; Laos, Lao. 227–228: 327–333. doi:10.1016/j.jhazmat.2012.05.059. PMID 22677053.

The Dell S2216M and Dell S2216H flat panel displays has an active matrix, Thin-Film Transistor (TFT), Liquid Crystal Display (LCD), and LED backlight. Some of the key features of this monitor are:

Using the On-Screen Display (OSD) Menu For more information on Using the On-Screen Display (OSD) Menu, refer to the User Guide for Dell S2216M or Dell S2216H Monitor.

The Dell S2318M flat panel display has an active matrix, Thin-Film Transistor (TFT), Liquid Crystal Display (LCD), In-plane Switching panel and LED backlight. The monitor features include:

Use the buttons at the bottom of the monitor to access the On-Screen Display (OSD) menu of the monitor. To access the On-Screen Display (OSD) menu, press Button 3 at the bottom of the monitor.

For more information on Using the On-Screen Display (OSD) Menu, refer to the Operating Your Monitor section in the User"s Guide for Dell S2318M monitor.

During the LCD Monitor manufacturing process, it is not uncommon for one or more pixels to become fixed in an unchanging state which are hard to see and do not affect the display quality or usability. For more information, refer to the Dell knowledge-base article Dell LCD Monitor Pixel Guidelines. Back to Top

Unplug the video cable from the back of the computer. To ensure proper Self-Test operation, remove the video cables (VGA, DVI, HDMI or DisplayPort) from the back of the computer.

To navigate the On-Screen Display (OSD) menu, use the buttons on the monitor. The monitor control buttons are usually on the right side , either on the side, front or bottom of the monitor. To access the On-Screen Display (OSD) menu, press Button 3 on the monitor.

For more information on using the On-Screen Display (OSD) menu and different menu options, refer to the Operating Your Monitor section of the User Guide of the Dell S2318M monitor.

Golden View Display wants you to make an informed choice among our LCD products. The tech center provides you with most of the information you will need to understand liquid crystal displays.

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.

If some elements of the picture i.e., your company logo is in the same place of the screen for a long period of time, for couple of weeks, months or a year, the crystals will memorize the state and later, when we change the image, we may see some ghosting of those elements. It really depends on many conditions like temperature and even the screen image that we display on the screen for longer periods of time. When you build your application, you can use some techniques to avoid it, like very rapid contrast change and of course to avoid the positioning the same image in the same position for a longer time.

You may have seen this phenomenon already as it is common in every display technology, and even companies like Apple put information on their websites, that users may encounter this phenomenon and how to fix it. It is called image ghosting or image persistence, and even Retina displays are not free of it.

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.

On the picture above, you can see further explanation of the grayscale inversion from Wikipedia. It says that some early panels and also nowadays TN displays, have grayscale inversion not necessary up-down, but it can be any angle, you need to check in the datasheet. The reason technologies like IPS (In-Plane Switching), used in the latest Riverdi displays, or VA, were developed, was to avoid this phenomenon. Also, we do not want to brag, but the Wikipedia definition references our website.

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.

To summarize, when you buy older technology like TN and displays, which are still very popular, and Riverdi is selling them as well, you need to be careful where you put your display. If it is a handheld device, you will see the display from the bottom, but if you put it on a wall, you will see the display from the top, so you need to define it during the design phase, because later it is usually impossible or expensive to change the direction.

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.

If we wanted to talk about disadvantages, there is a question mark over it, as some of them may be true, some of them do not rely on real cases, what kind of display, what kind of technology is it. Sometimes the IPS displays can have higher power consumption than others, in many cases however, not. They can be more expensive, but not necessarily. The new IPS panels can cost like TN panels, but IPS panels definitely have a longer response time. Again, it is not a rule, you can make IPS panels that are very fast, faster than TN panels, but if you want the fastest possible display, probably the TN panel will be the fastest. That is why the TN technology is still popular on the gaming market. Of course, you can find a lot of discussions on the internet, which technology is better, but it really depends on what you want to achieve.

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.

For many years, TFT displays have been the dominating technology in visualization. TFT LCDs are all around in our daily lives — in consumer and automotive applications, in our business environments, in healthcare, and within communication devices, home appliances, and factory automation products. While there are many LCD products available today, they’re not all suitable for every application. This is especially the case for industrial LCD monitors. To determine the best LCD display for your application, it’s important to understand your target market and its unique design issues.

The vast majority of LCD displays are designed for consumer devices such as smartphones, cameras, tablet computers, and gaming devices. But they have very different requirements than those for industrial applications. Due to very competitive pricing and quick production cycles, consumer display modules don’t always incorporate the durability, reliability, and advanced features required to survive in an industrial environment. Product life cycles are also typically much shorter in consumer applications. Screens manufactured for these applications are generally only available for one, in best case two years.

In contrast, display modules for industrial applications require Long product life cycles— often up to ten years or more. Plus, when an industrial module is discontinued by the manufacturer, a successor product should be backward-compatible so as to fit into the existing enclosure without requiring a redesign of the entire system.

The ability to withstand temperature variations as well as shock and vibration is also a key consideration when selecting displays for today’s industrial applications. They must be resilient enough to withstand frequent bumps or jiggles by machine operators and surrounding equipment, and also must be able to handle various operating temperatures.

Industrial displays are typically housed in an enclosure as part of a larger piece of equipment. In these situations, the heat generated by the surrounding equipment gets trapped within the enclosure, which can be detrimental to many displays. Therefore, it’s important to keep the real storage and operating temperature requirements in mind when choosing a display. While measures can be taken to dissipate the generated heat — such as using fans within the enclosure — the most efficient way to ensure compliance with the storage and operating temperature requirements is to select a display that is optimized for these types of environments. Fortunately, improvements in liquid-crystal materials have made it possible to extend the operating temperature ranges of LCDs from –30 to 80°C presently.

It’s important that displays used in industrial applications support clear and precise viewing from multiple angles under a variety of ambient light conditions. The brighter the environment, the more difficult it can be to read a standard transmissive LCD display with a typical brightness of 250 to 300 cd/m2. NVD has developed displays that can perform in the 800-cd/m2-and-higher range by implementing high-efficiency LEDs for the backlight unit– if necessary, in combination with special brightness enhancement films.

Increasing the display’s contrast ratio is another effective way that display manufacturers can improve display readability in bright environments. Typical contrast ratios for non-industrial displays are in the range of 200:1 to 300:1, which may not be sufficient when a machine operator is viewing the display from a distance. Displays with contrast ratios around 500:1 or greater are better suited for industrial environments. Another benefit of this method is that it doesn’t increase power consumption.

Multi-angle readability is another key selection factor. In a typical industrial environment, a machine operator is more likely to be positioned at an off-angle rather than right in front of the screen. Implementing a display designed for consumer applications typically doesn’t work well in this situation, as there is image distortion and color shifting when viewed at an angle. But, a number of technologies have been employed to improve off-angle viewing in displays, making them suitable for industrial applications. Some film-based technologies yield viewing angles of 160º horizontally and 140º vertically, but in some cases, this is still not sufficient. In-plane switching technology (IPS), multi-domain vertical alignment (MVA), and fringe field switching (FFS)offer alternatives. These proprietary technologies are able to achieve viewing angles of almost 90-degrees into all four directions without any color shift.

Size and resolution also play a role in overall readability. Displays between 2 and 15-inch diagonal sizes are used most often in industrial applications. These sizes provide sufficient area to view figures, waveforms, and other graphical data without taking up too much real estate on a piece of equipment.

From an aspect ratio 4:3 initially, industrial displays are now shifting to wide formats with WVGA to WXGA resolutions. The wide-aspect format enables users to view longer waveforms and more data on a single display. These display modules can also be designed to incorporate touch-key functions, allowing equipment manufacturers to skip physical switches and buttons and design HMIs based more on software than hardware.

New Vision Display’s experts are prepared to assist in defining appropriate solutions for all applications and in helping find the right balance between manufacturing cost and performance.