lcd flexible tft display free sample

Established in 2010, Topfoison has devoted itself to the manufacturing and development of high-quality products for the Wearable device, Smart Watch, VR, Medical device, Industrial LCD display including Color LCD modules/OLED/LCD display/Round lcd screen/Round AMOLED/ Square transflective lcd screen/ IPS full wide display/ 1080p fhd AMOLED and 2K 1440p lcd. Topfoison focus on1.22-7.0 inch small size displays, all the products produced in our company enjoys the most advanced production craft and technology as well as the strictly ISO quality management system.

Established in 2010, Topfoison has devoted itself to the manufacturing and development of high-quality products for the Wearable device, Smart Watch, VR, Medical device, Industrial LCD display including Color LCD modules/OLED/LCD display/Round lcd screen/Round AMOLED/ Square transflective lcd screen/ IPS full wide display/ 1080p fhd AMOLED and 2K 1440p lcd. Topfoison focus on1.22-7.0 inch small size displays, all the products produced in our company enjoys the most advanced production craft and technology as well as the strictly ISO quality management system.

FlexEnable’s glass-free organic LCD (OLCD) delivers high-brightness, long lifetime flexible displays that are low cost and scalable to large areas, while also being thin, lightweight and shatterproof.

OLCD is a plastic display technology with full colour and video-rate capability. It enables product companies to create striking designs and realise novel use cases by merging the display into the product design rather than accommodating it by the design.

Unlike flexible OLED displays, which are predominantly adopted in flagship smartphones and smartwatches, OLCD opens up the use of flexible displays to a wider range of mass-market applications. It has several attributes that make it better suited than flexible OLED to applications across large-area consumer electronics, smart home appliances, automotive, notebooks and tablets, and digital signage.

OLCD can be conformed and wrapped around surfaces and cut into non-rectangular shapes during the production process. Holes can be also added to fit around the functional design of the system – for example around knobs and switches.

As with glass-based LCD, the lifetime of OLCD is independent of the display brightness, because it is achieved through transmission of a separate light source (the backlight), rather than emission of its own light. For example OLCD can be made ultra-bright for viewing in daylight conditions without affecting the display lifetime – an important requirement for vehicle surface-integrated displays.

OLCD is the lowest cost flexible display technology – it is three to four times lower cost that flexible OLED today. This is because it makes use of existing display factories and supply chain and deploys a low temperature process that results in low manufacturing costs and high yield.

Unlike other flexible display approaches, OLCD is naturally scalable to large sizes. It can be made as small or as large as the manufacturing equipment used for flat panel displays allows.

The flexibility of OLCD allows an ultra-narrow bezel to be implemented by folding down the borders behind the display. This brings huge value in applications like notebooks and tablets where borderless means bigger displays for the same sized device. The bezel size allowed by OLCD is independent of the display size or resolution. In addition, OLCD can make a notebook up to 100g lighter and 0.5mm thinner.

OLCD is the key to the fabrication of ultra-high contrast dual cell displays with true pixel level dimming, offering OLED-like performance at a fraction of the cost. The extremely thin OLCD substrate brings advantages in cost, viewing angle and module thickness compared to glass displays. At the same time OLCD retains the flexibility required for applications such as surface-integrated automotive displays.

Due to its unique properties, OLCD has the potential to transform how and where displays are used in products. The videos below give a glimpse into this innovative technology.

OLCD brings the benefits of being thin, light, shatterproof and conformable, while offering the same quality and performance as traditional glass LCDs. The mechanical advantages of plastic OLCD over glass LCD are further enhanced by the technology’s excellent optical performance, much of which originates from the extreme thinness of plastic TAC substrates compared to glass.

Different displays have different characteristics, just tell Panox Display your application, and operating environment, Panox Display will suggest a suitable display for you.

But Panox Display is not a school, if customers don`t know the basic knowledge to design circuit boards, we suggest using our controller board to drive the display.

First, you need to check whether this display has On-cell or In-cell touch panel, if has, it only needs to add a cover glass on it. If not, it needs an external touch panel.

If you don`t know or don`t want to write a display program on Raspberry Pi, it`s better to get an HDMI controller board from us, and Panox Display will send a config.txt file for reference.

Different displays have different characteristics, just tell Panox Display your application, and operating environment, Panox Display will suggest a suitable display for you.

But Panox Display is not a school, if customers don`t know the basic knowledge to design circuit boards, we suggest using our controller board to drive the display.

First, you need to check whether this display has On-cell or In-cell touch panel, if has, it only needs to add a cover glass on it. If not, it needs an external touch panel.

If you don`t know or don`t want to write a display program on Raspberry Pi, it`s better to get an HDMI controller board from us, and Panox Display will send a config.txt file for reference.

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

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

Full-color (262K) 800x480 RGB display module consists of a TFT panel, a driver IC, an FFC/FPC flexible cable, and an LED backlight. This TFT LCD display module does not include an on-board LCD controller.

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.

Resistive touch panels are constructed using flexible materials with an air gap between and are coated with a resistive layer. When an object applies pressure to the top layer, it makes contact with microdots located on the bottom layer. This allows the touch screen to find the location of the touch using X and Y coordinates.

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”.

As a general rule, the larger the size of the glass the higher the cost of the display, but there are exceptions to this rule. A larger display may be less expensive than a smaller display if the manufacture produces higher quantities of the larger displays. When selecting your color display, be sure to ask what the cost is for one size smaller and one size larger. It may be worth modifying your design requirements.

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.

Transflective displays are readable with the backlight off provided there is enough ambient light. Transflective displays are more expensive than Transmissive also there may be a larger MOQ for Transflective. However, Transflective displays are the best option for direct sunlight.

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.

The Global Flexible Displays Market size is expected to reach $31.5 billion by 2025, rising at a market growth of 25.9% CAGR during the forecast period. Flexible displays are mainly OLED and AMOLED displays that are curved, bended, or fully foldable. Consumer electronics manufacturers have offered numerous smartphones, TV sets and other display devices in a rigid curved form factor in the current market scenario. Although these displays are curved in comparison to traditional rigid flat displays, these displays do not give the end-users true versatility.

Growth is driven by increased demand for display-based consumer electronics coupled with consumer inclination towards energy-efficient, flexible gadgets. Technological advances in display technology have resulted in the introduction of advanced flexible displays, creating opportunities for growth for the market"s key players. In terms of portability, non-fragility and weight, the superior features offered by flexible displays make them an attractive option for consumer electronics manufacturers. In addition, the adoption of flexible displays based on Organic Light Emitting Diode (OLED) is experiencing exponential growth in high-definition content and high-performance applications. In addition, market demand is propelled by high growth in the smart wearable market.

Based on Type, the market is segmented into OLED and Others. Based on Application, the market is segmented into Smartphone, Smart Wearbles, TV, E-reader, Automotive & Transportation and Others. The segment of smartphones and tablets was the largest market share in 2018. Smartphones have LED-LCD and OLED-based display panels, tablets are extended shape of smartphone and are mainly equipped with LED-LCD display panels. Due to the high demand on the consumer market, various smartphone and laptop manufacturers and suppliers have reached the tablet market. These are made more durable by using flexible displays in smartphones and tablets, as they provide sleek designs and better ergonomics to operate these devices. Based on Material Type, the market is segmented into Plastic, Glass and Others.

Based on Regions, the market is segmented into North America, Europe, Asia Pacific, and Latin America, Middle East & Africa. The presence of a large number of consumer electronics manufacturers and massive customer base is boosting the regional demand for flexible displays. Countries like Japan, South Korea, China, and India are the leaders in flexible display growth. China is the world"s largest producer of flexible OLED displays.

The major strategies followed by the market participants are Product launches and Partnerships & Collaborations. Based on the Analysis presented in the Cardinal matrix, Samsung Electronics Co., Ltd. (Samsung Group) and LG Corporation are some of the forerunners in the Flexible Display Market. The market research report covers the analysis of key stake holders of the market. Key companies profiled in the report include LG Display Co., Ltd. (LG Corporation), Samsung Electronics Co., Ltd. (Samsung Group), AU Optronics Corporation, Corning, Inc., Sharp Corporation, Kateeva, Inc., BOE Technology Group Co., Ltd., Royole Corporation, E Ink Holdings, Inc. and Visionox Technology, Inc.

Nov-2019: Sharp introduced a 30-inch 4K flexible organic LED (OLED) display in cooperation with Japan Broadcasting Corporation (NHK). This display has world’s largest color-filter-less (RGB light emission method), high-definition 4K flexible OLED display, and flexibility of film substrate that allows the display to be stored as a compact roll.

Oct-2019: Visionox Technology announced that it has collaborated with Peratech. In this, both the companies have started working on different integrations of Visionox’s AMOLED displays and Visionox’s AMOLED displays for fulfilling the needs of users for display-based interactive interfaces.

Aug-2019: E Ink partnered with AU Optronics for developing thin, impact-resistant, and feather-light e-paper solutions. These solutions support OTFT backplane (Organic Thin Film Transistor) as the display driver. The OTFT backplane technology is suitable for the development and introduction of soft display products including smart clothing and wearable devices.

May-2019: BOE Technology announced its collaboration with Himax Technologies in which Himax launched flexible OLED automotive display driver and timing controller for BOE Technology Group. This technology of Himax has been adopted by BOE in its 12.3-inch three-unit curved flexible OLED automotive displays for cockpit areas with only 0.99 mm bezels.

Dec-2018: Royole partnered with Airbus in order to develop aircraft-cabin applications. In this partnership, both the companies will investigate the commercial opportunities and use of sensors and flexible displays on passenger aircraft.

Dec-2018: Visionox Technology and IDEX Biometrics collaborated on exploring the development of next-generation IDEX’s unique off-chip biometric sensors for smart cards that uses Visionox’s flexible LTPS TFT backplane technology. The collaboration is focused towards the development of feature-rich and cost-effective smart card systems supporting both biometric and display technologies.

Oct-2018: Visionox Technology teamed up with Hefei municipal government for constructing the factory that can produce 30,000 substrates per month. These substrates will be used in sixth-generation active matrix organic light emitting diode displays. Both are thinking of establishing a Joint Venture for building and operating the plant.

Apr-2019: LG Display acquired DuPont"s OLED business as well as its R&D and production facilities. The OLED technology uses an inkjet printing method for adding a soluble material to a panel, thus producing the high-performing displays in an economical manner and reducing the material waste.

Nov-2019: Visionox Technology announced the launch of a foldable clamshell smartphone and a rollable OLED panel hinting, two foldable clamshell prototype. The 6.47" big AMOLED display has been used for this prototype with on-cell technology.

Aug-2019: AU Optronics introduced most advanced 8K Ultra-HD display, which delivers full-area local dimming (FALD) backlighting solution and peak brightness.

May-2019: Corning announced the launch of Corning® Astra(TM) Glass, a new glass substrate optimized for mid-to-large size; immersive displays in notebooks, high-performance tablets, and 8K TVs. This glass has been engineered to enable the higher-pixel density of high-performance displays, which are required by panel makers in order to meet the customer demand for faster, brighter, and more lifelike images.

Apr-2019: Sharp unveiled organic light-emitting diode panels for foldable smartphones. This display has foldable 6.18-inch OLED screen, which can be folded 3, 00,000 times without any damage. The new OLED panels will be produced at Company"s display factory in Sakai.

Feb-2019: Sharp introduced four new models of its 4K Ultra-HD resolution commercial LCD display line. These displays will be ideal for business, retail, and hospitality sectors. This helps the customers to see subtler textures and finer details in photos and videos.

Jan-2019: Samsung Display introduced its first 15.6-inch OLED panel for the notebook market. This panel delivers brighter colors and deeper blacks over 4K LCD-based screens.

Oct-2018: Royole introduced the Royole FlexPai, a commercial foldable smartphone, a combination of tablet and mobile phone with flexible screen. This smartphone is based upon Royole"s Flexible+ platform; this can be easily combined into a number of products and applications across different industries.

Aug-2018: Samsung extended its curved display line-up with the launch of new CJ79 (Model name: C34J791) monitor. This monitor has the feature of Intel’s Thunderbolt™ 3 connectivity and is designed for business and creative audiences that are seeking efficient and comfortable work experience through powerful connectivity.

Aug-2019: LG Display expanded its reach to China by developing a new production line. This factory is established in Guangzhou for producing 60,000 OLED sheets in 55 inches and above and focuses on the transformation of TV landscape.

Sep-2018: Sharp expanded its reach to Asia Pacific region by launching 70X500E, its 8K professional display panel in India. This panel was incorporated with Sharp"s wealth of Ultra-High-Resolution Monitor technologies for high brightness and wide color gamut.

Being completely made of plastic, Lectum® displays are much more rugged than standard glass-based EPDs. They are also thinner and lighter per square inch than conventional EPDs and are inherently low-power, which is vital in today’s increasingly mobile world.

Orient Display sunlight readable TFT displays can be categorized into high brightness TFT displays, high contrast IPS displays, transflective TFT displays, Blanview TFT displays etc.

The brightness of our standard high brightness TFT displays can be from 700 to 1000 nits. With proper adding brightness enhancement film (BEF) and double brightness enhancement film (DBEF) and adjustment of the LED chips, Orient Display high brightness TFT products can achieve 1,500 to 2,000 nits or even higher luminance. Orient Display have special thermal management design to reduce the heat release and largely extend LED life time and reduce energy consumption.

Our high contrast and wide viewing angle IPS displays can achieve contrast ratio higher than 1000:1 which can make readability under strong sunlight with lower backlight luminance. High brightness IPS displays have been widely accepted by our customers with its superb display quality and it has become one of the best sellers in all our display category.Transflective display is an old monochrome display technology but it has been utilized in our color TFT line for sunlight readable application. Orient Display has 2.4” and 3.5” to choose from.

Blanview TFT displays are the new technology developed by Ortustech in Japan. It can provide around 40% of energy consumption for TFT panels which can use smaller rechargeable or disposable batteries and generate less heat. The price is also lower than traditional transflective TFT displays. Orient Display is partnering with the technology inventor to provide 4.3” and 5.0”.

Orient Display can also provide full customized or part customized solutions for our customers to enhance the viewing experience. Orient Display can provide all the different kinds of surface treatments, such as AR (Anti-reflection); AG (Anti-glare), AF (Anti-finger print or Anti-smudge); AS (Anti-smashing); AM (Anti-microbial) etc. Orient Display can also provide both dry bonding (OCA, Optical Clear Adhesive), or wet bonding (OCR, Optical Clear Resin and OCG, Optical Clear Glue) to get rid of light reflective in air bonding products to make the products much more readable under sunlight and be more robust.

Touch panels have been a much better human machine interface which become widely popular. Orient Display has been investing heavy for capacitive touch screen sensor manufacturing capacity. Now, Orient Display factory is No.1 in the world for automotive capacitive touch screen which took around 18% market share in the world automotive market.

Based on the above three types of touch panel technology, Orient Display can also add different kinds of features like different material glove touch, water environment touch, salt water environment touch, hover touch, 3D (force) touch, haptic touch etc. Orient Display can also provide from very low cost fixed area button touch, single (one) finger touch, double finger (one finger+ one gesture) touch, 5 finger touch, 10 points touch or even 16 points touch.

Considering the different shapes of the touch surface requirements, Orient Display can produce different shapes of 2D touch panel (rectangle, round, octagon etc.), or 2.5D touch screen (round edge and flat surface) or 3D (totally curved surface) touch panel.

Considering different strength requirements, Orient Display can provide low cost chemical tampered soda-lime glass, Asahi (AGC) Dragontrail glass and Corning high end Gorilla glass. With different thickness requirement, Orient Display can provide the thinnest 0.5mm OGS touch panel, to thickness more than 10mm tempered glass to prevent vandalizing, or different kinds of plastic touch panel to provide glass piece free (fear) or flexible substrates need.

Of course, Orient Display can also offer traditional RTP (Resistive Touch Panel) of 4-wire, 5-wire, 8-wire through our partners, which Orient Display can do integration to resistive touch screen displays.

Engineers are always looking for lower cost, faster, more convenient interfaces to transmit signals and to accept data and commands. The numbers of available interfaces available in the market can be dazzling. Orient Display follows market trends to produce various kind of interfaces for our customers to choose.

Genetic Interfaces: Those are the interfaces which display or touch controller manufacturers provide, including parallel, MCU, SPI(,Serial Peripheral Interface), I2C, RGB (Red Green Blue), MIPI (Mobile Industry Processor Interface), LVDS (Low-Voltage Differential Signaling), eDP ( Embedded DisplayPort) etc. Orient Display has technologies to make the above interface exchangeable.

High Level Interfaces: Orient Display has technologies to make more advanced interfaces which are more convenient to non-display engineers, such as RS232, RS485, USB, VGA, HDMI etc. more information can be found in our serious products. TFT modules, Arduino TFT display, Raspberry Pi TFT display, Control Board.

Our Main products including a Small LCD screen 0.96inch to 13.3inch, TFT LCD display modules, AMOLED displays, OLED with capacitive touchscreen display. We also expanding our product range to flexible OLED screens as well as Transparent LCD displays. We have to say, you can find a variety of different displays in our company.  Most of our products are widely used in smartwatch wearable device, automotive industry, Smart Home device, industrial control machine, Portable POS System, Gaming console, Smart home robot, Handheld devices, Household appliances like Sweeping robot, other communication devices like IP phone, Smart Security equipment, And other fields. All developed products have passed CE, ROHS, and other certifications.

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.