tft lcd driver principle brands

LAPIS Technology"s display drivers realize uniform and fast pixel charging for 8K 120Hz, 75-inch, and larger panels with the unique technology of panel load charging.

LAPIS Technology"s display drivers use high-speed point-to-point interface technology *2 (4Gbps), which enables large amounts of display data transfer in a short time.Our products have been used in many panels with high refresh rates such as 360Hz.

Focus Displays offers a wide range of standard full color TFT displays. 64 million unique colors, high brightness, sharp contrast, -30C operating temperature, and fast response time are all good descriptions of a TFT display. This is why TFT technology is one of the most popular choices for a new product.

Thin Film Transistor (TFT) display technology can be seen in products such as laptop computers, cell phones, tablets, digital cameras, and many other products that require color. TFT’s are active matrix displays which offers exceptional viewing experiences especially when compared to other passive matrix technologies. The clarity on TFT displays is outstanding; and they possess a longer half-life than some types of OLEDs and range in sizes from less than an inch to over 15 inches.

CCFL’s are still available, but are becoming a legacy (obsolete) component. TFT displays equipped with a CCFL require higher MOQs (Minimum Order Quantities) than displays with LED backlights.

The majority of TFT displays contain a touch panel, or touch screen. The touch panel is a touch-sensitive transparent overlay mounted on the front of the display glass. Allowing for interaction between the user and the LCD display.

Some touch panels require an independent driver IC; which can be included in the TFT display module or placed on the customer’s Printed Circuit Board (PCB). Touch screens make use of coordinate systems to locate where the user touched the screen.

Resistive touch panels are the lowest cost option and are standard equipment on many TFT modules. They are more common on smaller TFT displays, but can still be incorporated on larger modules.

Contrast ratio, or static contrast ratio, is one way to measure the sharpness of the TFT LCD display. This ratio is the difference between the darkest black and the brightest white the display is able to produce. The higher the number on the left, the sharper the image. A typical contrast ratio for TFT may be 300:1. This number ratio means that the white is 300 times brighter than the black.

TFT LCD displays are measured in inches; this is the measurement of the diagonal distance across the glass. Common TFT sizes include: 1.77”, 2.4”, 2.8”, 3”, 4.3”, 5”, 5.7”, 5.8”, 7”, 10.2”, 12.1 and 15”.

TFT resolution is the number of dots or pixels the display contains. It is measured by the number of dots along the horizontal (X axis) and the dots along the vertical (Y axis).

The higher the resolution, the more dots per square inch (DPI), the sharper the display will look. A higher resolution results in a higher cost. One reason for the increase in cost is that more driver chips are necessary to drive each segment.

Certain combinations of width and height are standardized and typically given a name and a letter representation that is descriptive of its dimensions. Popular names given to the TFT LCD displays resolution include:

Transmissive displays must have the backlight on at all times to read the display, but are not the best option in direct sunlight unless the backlight is 750 Nits or higher. A majority of TFT displays are Transmissive, but they will require more power to operate with a brighter backlight.

Drivers update and refresh the pixels (Picture Elements) of a display. Each driver is assigned a set number of pixels. If there are more pixels than a single driver can handle, then an additional drivers are added.

A primary job of the driver is to refresh each pixel. In passive TFT displays, the pixel is refreshed and then allowed to slowly fade (aka decay) until refreshed again. The higher the refresh frequency, the sharper the displays contrast.

The controller does just what its name suggest. It controls the drivers. There is only one controller per display no matter how many drivers. A complex graphic display with several thousand pixels will contain one controller and several drivers.

The TFT display (minus touch screen/backlight) alone will contain one controller/driver combination. These are built into the display so the design engineer does not need to locate the correct hardware.

If you do not see a Thin Film Transistor (TFT) Display module that meets your specifications, or you need a replacement TFT, we can build a custom TFT displays to meet your requirements. Custom TFTs require a one-time tooling fee and may require higher MOQs.

Ready to order samples for your TFT design? Contact one of our US-based technical support people today concerning your design requirements. Note: We can provide smaller quantities for samples and prototyping.

TFT LCDs have become the norm for small-to-medium size displays in a variety of products within industrial, medical, POS and consumer applications. Compared to passive-addressed monochrome LCDs, TFT displays offer higher contrast, wider viewing angles, faster response time and full color. And, TFT LCDs are now on cost parity with similar size passive LCD displays.

A typical TFT LCD module product consists of a TFT LCD panel, one or more COG (chip-on-glass) driver ICs, a backlight unit, and an interface FPC. Several TFT display interface technologies coexist today. Picking the right technology depends on specific end-product concerns. Most often the display panel input will dictate that choice since TFT panels are designed to be COG bonding pad compatible with a very limited number of driver ICs. This article discusses the interfaces between TFT LCD modules and the typical CPUs found in embedded applications.

Typical TFT interfaces are determined by the particular TFT panel size and resolution, as shown in the below table. HDMI and eDP require interface converting boards and generally are not used for small to medium-size TFT LCDs.TFT LCD SizesResolutionsTypical Interfaces UsedUp to 3.5″128×160 to 240×320SPI, parallel MPU or RGB

The LCD controller signals are two types: data signals and control signals. The data signals are connected to the LCD data bus and depend on the LCD color depth (8-bit, 9-bit, 16-bit, 18-bit). The control signals are used to define the operation type (read or write), and whether the operation involves in addressing LCD registers or the display RAM.

LVDS interfacing has several benefits for TFT displays. It is much less susceptible to EMI and crosstalk issues, allowing the transmitting device to be located farther from the display. Also, LVDS generally consumes less power, pin counts are lower and there are far fewer worries about signal integrity.

Modern TFT driver ICs are highly integrated chips combining the source driver, gate driver and timing controller (TCON) – as well as other functional circuits such as memory, power circuit, and image processors – into one single IC die. Some driver ICs support multiple interfaces that are selectable on the module FPC or through initialization code firmware.

As a designer and manufacturer of custom LCD modules, New Vision Display works with customers to select the most appropriate and cost-effective TFT display and electronic interface solution for their particular requirement. New Vision Display has nearly 30 years of industry experience as one of the world’s leading TFT LCD screen manufacturers.

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.

The TFT-LCD (Flat Panel) Antitrust Litigationclass-action lawsuit regarding the worldwide conspiracy to coordinate the prices of Thin-Film Transistor-Liquid Crystal Display (TFT-LCD) panels, which are used to make laptop computers, computer monitors and televisions, between 1999 and 2006. In March 2010, Judge Susan Illston certified two nationwide classes of persons and entities that directly and indirectly purchased TFT-LCDs – for panel purchasers and purchasers of TFT-LCD integrated products; the litigation was followed by multiple suits.

TFT-LCDs are used in flat-panel televisions, laptop and computer monitors, mobile phones, personal digital assistants, semiconductors and other devices;

In mid-2006, the U.S. Department of Justice (DOJ) Antitrust Division requested FBI assistance in investigating LCD price-fixing. In December 2006, authorities in Japan, Korea, the European Union and the United States revealed a probe into alleged anti-competitive activity among LCD panel manufacturers.

The companies involved, which later became the Defendants, were Taiwanese companies AU Optronics (AUO), Chi Mei, Chunghwa Picture Tubes (Chunghwa), and HannStar; Korean companies LG Display and Samsung; and Japanese companies Hitachi, Sharp and Toshiba.cartel which took place between January 1, 1999, through December 31, 2006, and which was designed to illegally reduce competition and thus inflate prices for LCD panels. The companies exchanged information on future production planning, capacity use, pricing and other commercial conditions.European Commission concluded that the companies were aware they were violating competition rules, and took steps to conceal the venue and results of the meetings; a document by the conspirators requested everybody involved "to take care of security/confidentiality matters and to limit written communication".

Companies directly affected by the LCD price-fixing conspiracy, as direct victims of the cartel, were some of the largest computer, television and cellular telephone manufacturers in the world. These direct action plaintiffs included AT&T Mobility, Best Buy,Costco Wholesale Corporation, Good Guys, Kmart Corp, Motorola Mobility, Newegg, Sears, and Target Corp.Clayton Act (15 U.S.C. § 26) to prevent Defendants from violating Section 1 of the Sherman Act (15 U.S.C. § 1), as well as (b) 23 separate state-wide classes based on each state"s antitrust/consumer protection class action law.

In November 2008, LG, Chunghwa, Hitachi, Epson, and Chi Mei pleaded guilty to criminal charges of fixing prices of TFT-LCD panels sold in the U.S. and agreed to pay criminal fines (see chart).

The South Korea Fair Trade Commission launched legal proceedings as well. It concluded that the companies involved met more than once a month and more than 200 times from September 2001 to December 2006, and imposed fines on the LCD manufacturers.

Sharp Corp. pleaded guilty to three separate conspiracies to fix the prices of TFT-LCD panels sold to Dell Inc., Apple Computer Inc. and Motorola Inc., and was sentenced to pay a $120 million criminal fine,

Seven executives from Japanese and South Korean LCD companies were indicted in the U.S. Four were charged with participating as co-conspirators in the conspiracy and sentenced to prison terms – including LG"s Vice President of Monitor Sales, Chunghwa"s chairman, its chief executive officer, and its Vice President of LCD Sales – for "participating in meetings, conversations and communications in Taiwan, South Korea and the United States to discuss the prices of TFT-LCD panels; agreeing during these meetings, conversations and communications to charge prices of TFT-LCD panels at certain predetermined levels; issuing price quotations in accordance with the agreements reached; exchanging information on sales of TFT-LCD panels for the purpose of monitoring and enforcing adherence to the agreed-upon prices; and authorizing, ordering and consenting to the participation of subordinate employees in the conspiracy."

On December 8, 2010, the European Commission announced it had fined six of the LCD companies involved in a total of €648 million (Samsung Electronics received full immunity under the commission"s 2002 Leniency Notice) – LG Display, AU Optronics, Chimei, Chunghwa Picture and HannStar Display Corporation.

On July 3, 2012, a U.S. federal jury ruled that the remaining defendant, Toshiba Corporation, which denied any wrongdoing, participated in the conspiracy to fix prices of TFT-LCDs and returned a verdict in favor of the plaintiff class. Following the trial, Toshiba agreed to resolve the case by paying the class $30 million.

The LCD controller board is often called the Analog/Digital (A/D) board. As a type of hardware processor, it allows for various video source inputs to be connected, selected, and displayed on the LCD screen. It does this by converting the different video input signals into a format manageable by the LCD panel.

In conjunction with the LCD controller, the LCD driver is a form of software that is the interface of and dependent on the controller piece. Combined, the two form an LCD controller driver board. As the controller connects the computer to the operating system (OS), the driver facilitates that communication. Though there is typically just one display controller per LCD, there can be added drivers to extend the reach of the drive to further segments of the LCD.

To generalize the process, the LCD controller/driver adjusts the input signal, scaling resolution if needed, and then outputs the signal for the LCD monitor to use. Some of these output interfaces are low-voltage differential signaling (LVDS), SPI, I2C, and Parallel.

In most LCD controller/driver boards, there are two other input/output systems. Both these systems, however, are two-way pathways. One involves controlling and monitoring options, such as controls for brightness, image, and color using the on-screen display (OSD) control panel. The other is for communication via connections like Ethernet, Bluetooth, or IP.

To delve deeper into the details, consider the previously mentioned input signals. There are a variety of signals that LCD technology processes, such as VGA, HDMI, DVI, and DisplayPort. These computer display standards vary in format and characteristics like aspect ratio, display size, display resolution, color depth, and refresh rate. One of the biggest differences between these standards is their usage of analog signals or digital signals.

The HDMI is a combination of digital audio and digital video transmission. There are many HDMI connectors, such as the standard, dual-link, and micro. These connectors are what the input signal travels through to reach the LCD controller and to direct what to display.

And last from the list of examples of input signals is the DisplayPort. It is similar to HDMI in its purpose to replace outdated VGA and DVI as well as its transmission of audio and video through its interface. The DisplayPort does not have as much variation in cables and connectors as the HDMI, with only one cable and two types of connectors. From the DisplayPort, there is a growing technology called the embedded DisplayPort interface, or eDP interface. LCD manufacturers have begun to gravitate towards this interface due to its fewer connections, smaller size, and ability to quickly transmit high quality displays.

Bringing the subject back to LCD controllers, with the various types of computer display standards, the video signal inputs can be a challenge to accommodate and translate for the LCD panel, but with the help of adapters and the growth of these standard types, displays continue to become faster and develop with greater resolutions.

When compared to the ordinary LCD, TFT LCD gives very sharp and crisp text/graphic with shorter response time. TFT LCD displays are used in more and more applications, giving products better visual presentation.

TFT is an abbreviation for "Thin Film Transistor". The color TFT LCD display has transistors made up of thin films of Amorphous silicon deposited on a glass. It serves as a control valve to provide an appropriate voltage onto liquid crystals for individual sub-pixels. That is why TFT LCD display is also called Active Matrix display.

A TFT LCD has a liquid crystal layer between a glass substrate formed with TFTs and transparent pixel electrodes and another glass substrate with a color filter (RGB) and transparent counter electrodes. Each pixel in an active matrix is paired with a transistor that includes capacitor which gives each sub-pixel the ability to retain its charge, instead of requiring an electrical charge sent each time it needed to be changed. This means that TFT LCD displays are more responsive.

To understand how TFT LCD works, we first need to grasp the concept of field-effect transistor (FET). FET is a type of transistor which uses electric field to control the flow of electrical current. It is a component with three terminals: source, gate, and drain. FETs control the flow of current by the application of a voltage to the gate, which in turn alters the conductivity between the drain and source.

Using FET, we can build a circuit as below. Data Bus sends signal to FET Source, when SEL SIGNAL applies voltage to the Gate, driving voltage is then created on TFT LCD panel. A sub-pixel will be lit up. A TFT LCD display contains thousand or million of such driving circuits.

Topway started TFT LCD manufacturing more than15 years ago. We produce color TFT LCD display from 1.8 to 15+ inches with different resolutions and interfaces. Here is some more readings about how to choose the right TFT LCD.

In this article, you will learn how to use TFT LCDs by Arduino boards. From basic commands to professional designs and technics are all explained here.

There are several components to achieve this. LEDs,  7-segments, Character and Graphic displays, and full-color TFT LCDs. The right component for your projects depends on the amount of data to be displayed, type of user interaction, and processor capacity.

TFT LCD is a variant of a liquid-crystal display (LCD) that uses thin-film-transistor (TFT) technology to improve image qualities such as addressability and contrast. A TFT LCD is an active matrix LCD, in contrast to passive matrix LCDs or simple, direct-driven LCDs with a few segments.

In Arduino-based projects, the processor frequency is low. So it is not possible to display complex, high definition images and high-speed motions. Therefore, full-color TFT LCDs can only be used to display simple data and commands.

There are several components to achieve this. LEDs,  7-segments, Character and Graphic displays, and full-color TFT LCDs. The right component for your projects depends on the amount of data to be displayed, type of user interaction, and processor capacity.

TFT LCD is a variant of a liquid-crystal display (LCD) that uses thin-film-transistor (TFT) technology to improve image qualities such as addressability and contrast. A TFT LCD is an active matrix LCD, in contrast to passive matrix LCDs or simple, direct-driven LCDs with a few segments.

In Arduino-based projects, the processor frequency is low. So it is not possible to display complex, high definition images and high-speed motions. Therefore, full-color TFT LCDs can only be used to display simple data and commands.

In electronics/computer hardware a display driver is usually a semiconductor integrated circuit (but may alternatively comprise a state machine made of discrete logic and other components) which provides an interface function between a microprocessor, microcontroller, ASIC or general-purpose peripheral interface and a particular type of display device, e.g. LCD, LED, OLED, ePaper, CRT, Vacuum fluorescent or Nixie.

The display driver will typically accept commands and data using an industry-standard general-purpose serial or parallel interface, such as TTL, CMOS, RS232, SPI, I2C, etc. and generate signals with suitable voltage, current, timing and demultiplexing to make the display show the desired text or image.

The LCDs manufacturers use different drivers in their products. Some of them are more popular and some of them are very unknown. To run your display easily, you should use Arduino LCDs libraries and add them to your code. Otherwise running the display may be very difficult. There are many free libraries you can find on the internet but the important point about the libraries is their compatibility with the LCD’s driver. The driver of your LCD must be known by your library. In this article, we use the Adafruit GFX library and MCUFRIEND KBV library and example codes. You can download them from the following links.

Upload your image and download the converted file that the UTFT libraries can process. Now copy the hex code to Arduino IDE. x and y are locations of the image. sx and sy are size of the image.

while (a < b) { Serial.println(a); j = 80 * (sin(PI * a / 2000)); i = 80 * (cos(PI * a / 2000)); j2 = 50 * (sin(PI * a / 2000)); i2 = 50 * (cos(PI * a / 2000)); tft.drawLine(i2 + 235, j2 + 169, i + 235, j + 169, tft.color565(0, 255, 255)); tft.fillRect(200, 153, 75, 33, 0x0000); tft.setTextSize(3); tft.setTextColor(0xffff); if ((a/20)>99)

while (b < a) { j = 80 * (sin(PI * a / 2000)); i = 80 * (cos(PI * a / 2000)); j2 = 50 * (sin(PI * a / 2000)); i2 = 50 * (cos(PI * a / 2000)); tft.drawLine(i2 + 235, j2 + 169, i + 235, j + 169, tft.color565(0, 0, 0)); tft.fillRect(200, 153, 75, 33, 0x0000); tft.setTextSize(3); tft.setTextColor(0xffff); if ((a/20)>99)

The TFT LCD screen display, for the general masses, is no longer a difficult noun. And it is another after semiconductor could create a large number of emerging technology products of the business turnover, more because of its features, thin so it than using the application scope of the cathode ray tube (CRT, cathode ray tube) display made by wider. Today, I’m going to talk about how the TFT LCD Touch Screen Display Works.

As I mentioned earlier, liquid-crystal displays (LCDs) refer to a bunch produced by using the TFT screen LCD display. Now for LCD displays the name is directed mostly used in notebook computers, or desktop computer applications display. Is the thin film transistor TFT LCD display. Abbreviation of TFT LCD. This kind of display form has two main characteristics, one is a thin film transistor, the other is TFT LCD itself. Let’s talk about the TFT screen itself.

This type of TFT LCD screen was first discovered, had been spent more than one hundred years ago. In 1888 AD, the Austrian botanist Friedrich Reinitzer, found in the observation from the plant refined out of benzoic acid cholesterol (cholesteryl benzoate) found that when the melting behavior of the compound heated to 145.5 ℃, Solid can melt, presents a kind of solid phase and liquid phase between the half gonorrhea melt flow of the liquid. This situation will always maintain ℃ temperature rise to 178.5 degrees, to form a clear isotropic liquid (isotropic liquid).

The next year, in 1889, the study of thermodynamic equilibrium and the phase transfer German physicist O.L Ehmann, compounds for a more detailed analysis of this. He found that under the polarizing microscope, half of the viscous liquid gonorrhea liquid compounds with different parts peculiar to the crystal birefringence (birefringence) of the optical properties, namely, optical interphase (optically anisotropic). It will be a name to this as the liquid crystal. Since then, scientists will be the nature of this new discovery, known as the fourth state material – LCD (liquid crystal). It at a specific temperature range can have the characteristics of the liquid and solid at the same time.

Its structure is composed of TFT LCD molecules stick together, forming a layer structure. It’s every layer of the molecular long axis direction parallel to each other. And the long axis direction for each layer plane is vertical or a tilt Angle. Due to its structure is very similar to crystals, so they are called phase. The order parameter S (the order parameter) tend to be 1. Type in layered crystal layer and interlayer bonding can fracture because of temperature, so the layer and interlayer sliding more easily. But each layer within the molecular bonding is stronger, so it is not easy to be interrupted. Therefore in the context of the monolayer, Its arranged orderly and viscosity is bigger. If we use the macroscopic phenomenon to describe the physical properties of liquid crystal, we can make a group of regional average points as the liquid crystal molecules are pointing in the direction of the arrow (director), which is the direction of a group of liquid crystal molecules regional average. And with lamellar liquid crystal, because of its structure, the TFT LCD molecules will cambium-like so can point to a vector of different classification of the different lamellar liquid crystal again. When the long axis of the liquid crystal molecules are vertical stand, Call it “Sematic A phase.” if stand long axis direction of the TFT LCD molecules have some Angle of tilt (tilt), call it “Sematic C phase”. In A, C and other letters to name, which was discovered in accordance with the order to address, and so on, there should be A “Semantic phase B is.” but later found A deformation phase B is C phase, And the liquid crystal molecules in the structure layer by layer, in addition to each layer of TFT LCD molecules have tilt Angle, the tilt Angle between layer by layer will form a helical structure.

Nematic is a Greek word, the word mean in the thread is the same as in English. Mainly because with the naked eye to observe the liquid crystal, it looks like a silk pattern. The LCD screen molecules on the space of the regular arrangement of one dimension, all rod long axis of the liquid crystal molecules will choose a particular direction (that is, pointing vector) as the main shaft and arranged parallel to each other. And don’t like lamellar liquid crystal has a layered structure. Compared with the layer column type liquid crystal alignment is no order, That is to say, its order parameter S is smaller than the lamellar liquid crystal, and its viscosity is smaller, so it is easier to flow (its flow mainly comes from the free movement of molecules in the long axis direction). Linear liquid crystal is the common TFT LCD display screen TN(Twisted nematic) type liquid crystal.

Most of the sources of the name, because are generated by the derivative of the cholesterol. But some without cholesterol structure of LCD screen with this liquid crystal phase. This kind of liquid crystal as shown in figure 5, if it is a layer of a layer to separate, would very much like a linear LCD screen. But look at the Z-axis, may find it pointing in the direction of the arrow will with layers and layers of different distribution, like a spiraling when the pointing vector rotate 360 degrees for molecular layer thickness is called a pitch. Because of its every layer like linear LCD, so also known as Chiral nematic phase. In terms of cholesterol crystal, and pointing in the direction vector of the vertical distribution of LCD screen molecules, due to the different point to vector, will have the different optical or electrical differences, thus has produced different features.

If we are according to the molecular weight of high and low points can be divided into liquid crystal polymer (polymer liquid crystal, the polymer in many of the liquid crystal molecules) and low molecular liquid crystal. This kind of classification of TFT LCD belongs to the application of the low molecular liquid crystal. If the reasons for the formation of liquid crystal state, because it can be divided into type temperature formation of liquid crystal state to a liquid crystal (thermotropic), and because of the concentration and the formation of a liquid crystal state type lyotropic liquid crystal (lyotropic).

The solution so types lyotropic TFT screen molecules in the appropriate solvents reaches a certain critical concentration, the formation of liquid crystal state. Type lyotropic liquid crystal is one of the best examples that is soap. When soap bubbles in the water will not be at once into a liquid, and the bubble in the water for a long time, after the formation of white matter, is its liquid crystal state.

Our dielectric coefficient can be separated into two directions respectively is epsilon / / (and point to parallel component) and epsilon coming (a component perpendicular to the pointing vector). When the epsilon / / > epsilon coming then called the dielectric coefficient of different parts of LCD, can be used in parallel coordination. And epsilon / / < epsilon is called the dielectric coefficient of the different part coming negative type of TFT screen, only can be used in vertical coordination will need the photoelectric effect. When the applied electric field, the liquid crystal molecules will vary with dielectric coefficient is positive or negative, To determine whether the orientation of the liquid crystal molecules is parallel or perpendicular to the electric field, to determine whether the light penetrates. Now on most commonly used type TN LCD TFT LCD that belongs to the dielectric coefficient are type liquid crystal. When the dielectric coefficient of square difference Δ epsilon (= epsilon / / – epsilon) comes, the greater the LCD of the critical voltage (threshold voltage) will be smaller. So the LCD can be in the low voltage operation.

In accordance with the described above, the lamellar liquid crystal, linear liquid crystal, and LCD screen for cholesterol levels, because of its long liquid crystal molecules like a stick, so point to the direction of the vector and the molecular long axis parallel. To be defined with reference to the refraction coefficient of a single optical axis crystal, it will have two refractive indexes, respectively is perpendicular to the direction of the long axis of the liquid crystal n coming (= ne) and parallel to the long axis of the liquid crystal direction n / / (= no), so when the incident light liquid crystal, will be affected by two refractive indexes, cause in the vertical long axis of the liquid crystal and LCD long axis parallel to the direction of the speed of light will be different.

If with the molecular long axis parallel to the direction of light speed, when less than perpendicular to the speed of the molecular long axis direction, which means that parallel the molecular long axis direction of refractive index is greater than the vertical direction of the refractive index (because the refractive index is inversely proportional to the speed of light), is the one – no > 0. So the birefringence Δ n > 0, we think that it is called optics is a type of LCD, and lamellar liquid crystal and LCD are all belong to the optical is almost linear LCD. If the light of the parallel to the direction of the long axis was faster, On behalf of the flat to the governor of the axis of the refractive index is less than the vertical direction, so the birefringence Δ n < 0. We call it is the optical negative type of LCD. The cholesterol liquid crystal optical negative type of LCD.

For example, the elastic constant (kappa 11, kappa 22, kappa 33) contains the three most important constants: kappa 11 is the elastic constant at splay, kappa 22 is the elastic constant at the twist. Kappa 33 refers to predominating the elastic constants of bending (bend). The other as the coefficient of viscosity (viscosity coefficients and eta), will affect the rotational speed of the liquid crystal molecules with reaction time (response time), its value as small as possible. But this feature is affected by temperature is the largest. In addition to magnetic susceptibility (magnetic susceptibility), but also because of liquid crystals of different sex, Divided into c / / c coming. And the difference of magnetic susceptibility is defined as Δ c = c / / – c coming. In addition to the conductance coefficient (conductivity), and so on the photoelectric properties. Liquid crystal properties of the most important are the dielectric coefficient and refractive index of liquid crystal. The dielectric coefficient is determined liquid crystal under the influence of the electric field to the characteristics of the liquid crystal molecules, while the refractive index is liquid crystal in the light of its important parameters influencing the light path. The LCD is in using the liquid crystal itself of these features, the appropriate use of voltage, to control the rotation of the TFT LCD molecules, in turn, affect the direction of the light, to form different grayscale, a tool for displaying images. Of course, LCD itself is not alone as the monitor, also need other materials to help, Below, we will introduce the composition of various materials and operating principle of TFT LCD display.

The upper and lower two layers of glass are mainly to grip the LCD with. Below the glass layer with Thin film transistor (thin film transistor, TFT screen), while the layer above the glass with a Color filter (Color filter). If you notice (see figure 3), these two pieces of glass are in contact with the side of the LCD screen, not smooth, but with jagged grooves. The main purpose of the groove with the hope of a long rod, liquid crystal molecules will line up along the grooves. In this way, Liquid crystal molecules are arranged neatly. Because if it is smooth and flat, the arrangement of the liquid crystal molecules will not neat, causing light scattering, forming a light-leaking phenomenon. In fact, this is just a theory that told us to put the glass and LCD interface, complete processing so that the arrangement of liquid crystal has a certain order. But in the actual manufacturing process, and can not be with such a groove, the distribution of glass is made usually in glass coating on the surface layer of the PI (polyimide), and then a cloth to do the action of friction (rubbing), In order to make the surface molecules of PI no longer be scattered and arranged in a fixed and uniform direction, this layer of PI is called the coordination membrane, and its function is just like the grooves in the glass in FIG. 3, which provides the interface conditions for the uniform arrangement of liquid crystal molecules and allows the liquid crystals to be arranged in a predetermined order.

We can know from figure 10, when there is no applied voltage between the upper and lower two pieces of glass, the arrangement of LCD will be in accordance with the match to the membrane of the upper and lower two pieces of glass. For TN type of LCD, and match to the film’s point of view of the poor to 90 degrees. (see figure 9) so the liquid crystal molecules are arranged by the up and down automatically rotate 90 degrees when the incident light passes through the upper polarizing film, the polarization of light waves will only order direction. Through the liquid crystal molecules, the liquid crystal molecules rotate for 90 degrees, so when the waves reach the lower polarizing film, the polarization direction of the light just turned 90 degrees. The polarizing film of the lower and upper polarizing film, 90 – degree Angle is just the differences. (see figure 9) so can smoothly through the light, but if we applied voltage between the upper and lower two pieces of glass, because the type TN LCD for the dielectric coefficient of different sex more positive type of LCD (epsilon / / > epsilon coming, represent the parallel direction of the dielectric coefficient is larger than the dielectric coefficient of the vertical direction, so when the liquid crystal molecules are influenced by an electric field, will tend to be parallel to the orientation of the electric field direction.), so we can see from figure 10, At this time, the polarized light wave passing through the upper polarizer will not change the polarization direction when passing through the liquid crystal molecule, so it cannot pass through the lower polarizer.

The so-called NW (Normally white), is to point to when we don’t apply voltage on the LCD screen panel, we can see the panel is pervious to light, also is bright, so-called Normally white. But on the other hand, when we don’t apply voltage on the LCD panel if the panel is not pervious to light, the look is black, it’s called NB (Normally black). We have just mentioned in figure 9 and figure 10 all belongs to the configuration of NW, also we can know from figure 11, For type TN LCD, located in the upper and lower glass is perpendicular to the membrane, and the difference between NB and NW just lies in the relative position of the polarizing film is different. For NB, the fluctuation of the polarizing film polarity is parallel to each other. So when the NB no applied voltage, the light will be because the polarity of the LCD to rotate 90 degrees to be pervious to light. Why there are NW and NB these two kinds of a different configuration of the polarizing film? Mainly for different applications. Commonly used in a desktop computer or notebook computer, most of the NW configuration. That’s because, if you notice, generally the use of computer software environment, you will find that most of the entire screen is a bright spot, that is to say, computer software for the application of white background and black text. Since on the point of the majority, using NW is more convenient, of course. Also because the NW window does not need to add the voltage, the average will compare to save electricity. In turn, said that the application of the NB environment mostly belongs to the screen for the application of black.

The STN LCD and TN LCD are very similar in structure, the main difference between TN LCD, the arrangement of the liquid crystal molecules, the rotation angle from top to bottom. A total of 90 degrees and type the STN LCD liquid crystal molecules are arranged, the rotation angle will be greater than 180 degrees, usually is 270 degrees. (see figure 12) because of its rotation Angle is different, its characteristics different. We from figure 13 TN type and type the STN LCD voltage of the transmittance curve can know, when the voltage is low, the light penetration rate is very high. With a high voltage, the light of the penetration rate is very low. So they belong to the Normal White polaroids configuration. When the voltage in the middle position, the change of type TN LCD curve is flat, and the change of the STN LCD type curve is steep. So in TN type LCD, when transmittance change from 90% to 10%, corresponding to the voltage difference is larger than the STN LCD. We mentioned before, in the liquid crystal display, The different characteristics of TN and STN will result in TN type LCD, which has more grayscale changes than STN type LCD, so generally TN type LCD has 6~8 bits of changes. It is 64 ~ 256 gray-scale changes. Type the STN LCD for a maximum of 4 bits are only 16 orders of gray-scale changes. In addition, the STN type and TN LCD has a different place is the reaction time (response time) general type the STN LCD it’s response time to type in more than 100 ms and TN LCD its response time is 30 ~ 50 ms as shown in the image change quickly for the STN LCD type ghosting effect phenomenon is easy to happen.

TFT LCD Chinese translation of the name is called a thin film transistor liquid crystal display, from the beginning, we mentioned LCD voltage control is needed to produce gray. And the use of a thin-film transistor to generate the voltage, to control the transition of liquid crystal display, is called a TFT LCD. From the point of the cross-section structure of figure 8, between upper and lower two layers of glass, with LCD, will form a parallel plate capacitor, we call it the CLC (capacitor of liquid crystal). Its size is about 0.1 m3, But on the practical application, the capacitance and unable to keep the voltage to the next time to update the data in the picture.

That is to say, when TFT is good to the capacitor charging power, it is impossible to maintain voltage, until the next TFT this point charge again. (in general of 60 Hz screen update frequency, need time to keep about 16 ms.) as a result, there were changes in voltage, displayed gray scale is not correct. Therefore generally on the design of the panel, we will add a storage capacitor CS (storage capacitor is about 0.5 pF). So charged electric voltage can keep until the next update screen. But the right, long on the glass TFT itself, just use a transistor to make the switch. Its main work is to determine the LCD source voltage on the driver whether to charge to this point. As for this point more charge to high voltage, so as to show how the gray-scale. It is outside of the LCD source driver.

If you have a chance, take a magnifying glass, close to the LCD screen. You will find that as shown in figure 9 shows. We know that red, blue and green, are the so-called primary colors. That is to say, using the three kinds of color, can produce a variety of different colors. In a lot of flat-panel displays, this principle is used to show the color. We put the RGB 3 kinds of color, is divided into independent three points, each has different gray-scale changes, then the three neighboring RGB display point, as the basic unit of a display, Pixel is that this a pixel, and can have different color changes. Then for a need for a 1024 * 768 resolution display screen, we just let the composition of the flat panel display with 1024 * 768 pixels, can show a picture of the right. In figure 9, each point between the Black part of RGB is called the Black matrix. We can find that looking back on it in figure 8Black matrix is mainly used to cover do not intend to previous to light part. Such as some ITOs walk the line, or Cr/Al walk the line or are part of a TFT. This is why we in figure 9, the highlight of each RGB, it seems, is not a rectangle, and also on the top left corner is a piece of black matrix cover part, this part of a black missing Angle is the location of the TFT.

The CRT screen, it is using a high-speed electron gun that emits electrons, hits the phosphors on the silver screen, so as to produce the light, to show the picture. LCD itself, however, can only control the brightness of the light through, no glowing function itself. Therefore, a liquid crystal display must be combined with a backplate, to provide high brightness, brightness, and uniform distribution of the light source. We can see in figure 14, of the backplate of the main parts are CCFL (cold cathode tube), reflex plate, guide plate, prism sheet, Diffuser plate, and so on. Tubes are the main light-emitting parts, by a light guide, everywhere. The light distribution and baffle will be limited only to the TFT LCD light direction. Finally, by prism sheet and help diffuser, the light evenly distributed to all areas, provide TFT LCD a bright light. While TFT LCD is borrowed by the rotation of the voltage-controlled liquid crystal, control through the brightness of the light, so as to form different grayscale.

Another box in figure 14 glue and spacer structure of two kinds of ingredients. The box adhesive USES is to make the LCD panel in the upper and lower two layers of glass, to be able to stick close and to provide a panel of LCD screen molecules, cut off from the outside world, so the box plastic as its name suggests, is around and around in the panel to the liquid crystal molecules box limited to within a panel. The spacer is mainly provided two-layer glass support, it must be distributed evenly on the glass, or a part but uneven distribution cause spacer gathered together, it will block the light, It is also unable to maintain the appropriate gap between the upper and lower glass, which will lead to uneven distribution of electric field and affect the performance of the crystal grayscale.

A very important specification of LCD is brightness, and the most important factor to determine the brightness is the opening rate. What is the opening rate? Is simple light can pass through the effective area proportion. 17, let’s look at the picture to the left of figure 17 is an LCD display from directly above or below the past structure. When the light is emitted through the backplate, not all of the light can be through the panel, like for LCD source driver chip and the gate driver chip signal line, and TFT itself, the stored voltage is the use of storage capacity, etc. These places besides incomplete pervious to light, but also because the light through these places is not under voltage control, to display the correct gray-scale, so have to use the black matrix to cover, in order to avoid interference to other correct brightness of the light area. So the effective area of the previous to light, it’s just like figure 17 shows area on the right. This piece of the effective area of the previous to light and the ratio of the total area is called the opening rate.

When the light is emitted from the backlight plate, it will pass through the polarizer, glass, LCD screen, color filter, etc. It is assumed that the penetration rate of each part is as follows:

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- the 74ahct125 comes with 4 buffers, you need 3, use the tft, touch and sd card chip select lines to enable the three buffers. when the CS line is hi the buffer is tri-state. when the CS line is low the buffer is enabled and one and only one miso output line is driving the input to the microcontroller.