Innovations in Toshiba s Screen Technologies Table of Contents

Innovations in Toshiba s Screen Technologies Table of Contents Innovations in Toshiba s Display Technologies... 1 The LCD: Today s Display of Choice... 1 The Latest in Notebook and Workstation LCD Technologies... 1 How the LCD works... 2 Pixel Perfect: On the road to UXGA... 3 Sunglasses at Night: Transmissive, Reflective and Transflective Light Sources... 4 Reflective LCD... 5 Transflective LCD... 5 Screen Technologies for Today and Tomorrow... 5 Ultra-high-resolution displays: polysilicon TFT LCDs... 6 Plasma displays: Toshiba brings the future of digital TV home to you... 6 Digital Light Processor: Mirror, Mirror on the Wall... 7 Light-emitting Diode (LED) Displays: From Pilot Lights to White Light... 8 From LED to OLED: Toshiba s LEP displays... 8 An Overview of Video Standards... 10 Selected Sources... 10/10

Innovations in Toshiba s Display Technologies Toshiba s Satellite 5100 multimedia notebook, featuring a 15 Super Fine Screen UXGA (Ultra Extended Graphics Array) display provides high resolution, enhanced viewing from a wide angle and double the contrast ratio of the conventional display. With fast responses times and high-colour fidelity, this notebook is ideal for watching full-motion video, working with graphics applications or delivering stunning presentations. This innovative Liquid Crystal Display (LCD) comes as no surprise, as Toshiba has long had a record of delivering state-of-the-art displays to its customers. In 1985, Toshiba released the first commercially successful notebook, the T1100, overcoming the challenge of creating a clearly legible display for mobile products. In 1986, Toshiba demonstrated the first active-matrix standalone LCD, supporting 8 colours and 640 x 480 pixels. In this article, we explore how LCD technology has evolved since then, as well as looking at alternative display technologies that offer Toshiba customers a state-of-the-art viewing experience across a range of products, including televisions, PDAs, notebooks, displays, videowalls, televisions and flat panels. Finally, we take a look at emerging display technologies, and explore how Toshiba continues to be one of the leaders in this field. The LCD: Today s Display of Choice When notebooks were originally introduced in the 80 s, most of them came with monochrome, passive-matrix LCD screens. These displays met many of the requirements that are still important for notebook users today: the LCDs were lighter, smaller, and required less power than a CRT (cathode ray tube). However, in the early years, most mobile users were happy to switch to an external CRT monitor when working in the office. At that time, CRT monitors still offered many advantages as compared to the early TN (twisted nematic) LCDs. Conventional displays offered higher resolution, most of them supported colour, and presented the user with a much wider viewing angle. Indeed, with early LCDs, for optimal viewing, users had to sit directly in front of the TN LCD. Moreover, the early LCDs were subject to such effects as ghosting (as the cursor moves across the screen it leaves a trail of images scattered behind it) or submarining (the cursor-image disappears entirely as it moves across the screen). Even the enhanced DSTN displays suffered from these effects. It was not until active matrix displays emerged that LCD technology really matured. Today, due to advances in LCD technologies, the situation is reversed. LCD displays now truly outperform CRTs in almost all categories, making them ideal for notebooks, as well as high-end state-of-the-art displays. In addition to being light and compact, as well as consuming less power than a CRT, LCDs provide flicker-free images, offer a higher pixel-density (200 pixels per inch), and support high video resolutions. The Latest in Notebook and Workstation LCD Technologies Of course, as the number of pixels and supported colours increase, the amount of memory and processing power required to redraw the screen and support complex 1

imaging also increases. So, it is appropriate to choose a display technology that meets the requirements of the device and the user. Here it is useful to compare some of the LCD panels for workstation and notebook use. For instance, Toshiba s 20.8-inch flat-panel TFT LCD is designed for workstation use as a desktop display. It supports up to 3,200 by 2,400 pixel QUXGA (Quad Ultra Extended Graphics Array) resolution, displays up to 16.77 million colours and has 7.7 million pixels. With a screen large enough to display a full A3-sized sheet of paper, these LCDs are used in various sectors, including science, banking, engineering, publishing and medicine, where users require screen images that are as clear as an original photograph. The display can be used for applications such as creating maps and engineering drawings, the analysis of aerial and satellite photographs, and viewing complex documents, such as patent applications, all of which demand precise images and large displays. In fact, the image quality of the new display is high enough to reproduce works of art. Although the 20.8-inch flat panel display is very narrow (mm), it weighs 14kg, making it unsuitable for notebooks. For today s notebook user, UXGA is an optimal technology. With a resolution of 1600 x 1200, approximately 1.9 million pixels, this display outperforms XGA and SXGA standards. Compared with an XGA panel, an UXGA display has more than 1.1 million additional pixels. As well, combined with Toshiba s Super Fine Screen, the display offers a high contrast ratio, high brightness and short millisecond response times. With a wide viewing angle, Toshiba s 15 UXGA display offers remarkably detailed and precise images that have almost print-like clarity. These notebook LCDs are ideal for the following applications: 3D gaming, multimedia applications, watching movies and digital image editing/viewing. Whether implemented in notebooks or used as flat panel displays, LCDs offer both notebook and desktop users enhanced viewing and usability features. To understand what makes this development possible, we need to take a step back and look at how LCD panels work, and how they have evolved. How the LCD works The Radio Corporation of America (RCA) introduced the first prototype LCD in the 1960 s, made of twisted nematic (TN) liquid crystal. Originally, most screens made use of twisted nematic (TN) liquid crystal, but enhancements, such as super twisted nematics (STN), dual scan twisted nematics (DSTN), ferroelectric liquid crystal (FLC) and surface stabilized ferroelectric liquid crystal (SSFLC), have subsequently been introduced. While these enhancements have significantly improved the user s viewing experience, the basic principle of the LCD remains the same. Liquid crystals are naturally twisted, but applying an electric field will untwist them to varying degrees, depending on the applied voltage. When the liquid crystals straighten out, they change the angle of the light passing through them. Thus, potentially, each crystal is like a shutter that can either allow light to pass through or block the light. By selectively supplying voltage, the LCD harnesses this potential to block or display light in order to create the desired image on the screen. To produce an image, glass embedded with a grid of electrodes sandwiches the liquid crystals, allowing the individual pixels to be turned on or off. 2

This grid is part of the glass substrate and functions differently depending whether passive or active matrix technology is used. Passive screens use a grid of horizontal and vertical wires to apply voltage. The horizontal grid is attached to one of the glass layers and the vertical grid to the other glass layer with the liquid crystal cells sandwiched between them. Each intersection constitutes a single pixel that can either pass or block light, depending on the applied voltage. Whereas passive-matrix displays use no transistor to drive each row and each column on the screen, active-matrix screens use at least one transistor to drive each pixel. Tiny transistors and capacitors are etched onto the glass substrate at the intersection of each row and column. For a colour display, the pixel is further separated into three using a red, green or blue filter; these colours are mixed in varying intensity to produce a full palette of colours on the screen. Colour displays require an enormous number of transistors. For example, a colour display with a resolution of 1,024 by 768 pixels requires 2,359,296 transistors (1024 columns x 768 rows x 3 cells) etched onto the glass. To give you a clear picture of how this LCD sandwich looks, here are the six layers that make up a colour TFT (thin film transistor) display (the order of layers may differ depending on the screen manufacturer and production process): backlight to generate light which flows to the surface of the display first polarising filter glass substrate with thin film transistor liquid crystal glass substrate with colour filter second polarising filter Throughout the development of the LCD panel, real enhancements and performance advantages have been won by changing the grid or matrix controls, the angle and flow of light, as well as by enhancements in the liquid crystals. Pixel Perfect: On the road to UXGA For many years, passive-matrix displays underwent a number of enhancements. However, the major revolution in LCD technology came with the introduction of the active-matrix display, making it easy for notebook users to rely on their LCD whether on the road or in the office. Here is an overview of some of the major LCD enhancements, leading to today s active-matrix UXGA display: TN uses a 90-degree twist to the molecules between one alignment layer and the other. These screens offer black imaging on a grey background and very limited viewing angle. To see the image on the screen, the user must be directly in front of the screen. STN displays improve on TN screens by increasing the rotation of the molecules in their off state from 180 to 260 degrees. This brings a higher contrast ratio and higher resolution to larger screens and offers a greater viewing angle. Yellowgreen and blue were originally possible. Coloured STN displays (CSTN) are possible. 3

DSTN screens are an enhancement of STN. DSTN divides the screen in two and scans each half simultaneously, thereby doubling the number of lines refreshed. Greater clarity is possible for DSTN, but it still suffers from a 'ghosting' effect that often causes a moving cursor to leave a trail of spectral images behind it. High-Performance Addressing (HPA) screens provide faster refresh rates, offer high resolution and provide better contrast than other passive-matrix displays. Triple Super Twisted Nematic (TSTN) uses a high polymer, double refraction film to create black-and-white LCDs of exceptional quality. The single-layer compensation film is called FSTN (Film Super Twisted Nematic), providing a better contrast ratio and the better viewing angle than TN or STN. TFT screens are faster and provide a much brighter, sharper, high contrast image. As well, they offer a wider viewing angle, and deliver richer colours than passive displays. Practically all notebook displays and LCD monitors now on the market use TFT technology. However, there are some drawbacks; as each pixel has a transistor, the power required is greater than with a passivematrix display. Also, until recently, TFT screens often displayed dead pixels. Well into the 1990 s, manufacturing quality standards still tolerated anywhere from 5-15 defective pixels per screen. Today s UXGA display takes advantage of several significant innovations in the evolution of LCD technology. In the past, the transistor that controls each pixel took up around 50 percent of the pixel's surface area, requiring a powerful backlight to shine through the transistor (particularly when you consider the number of pixels required for a UXGA display). However, with today s tinier transistors, the power and intensity of backlighting can be used to enhance the viewable image. By introducing a special optical film on the front of the display to spread the image over a wider angle, a bright image is viewable at up to approx. 140 degrees. As well, enhanced liquid crystal materials support greater climate extremes and higher contrast ratios. Finally, enhancements in the production process have all but eliminated the chance of seeing dead pixels on the TFT display. Sunglasses at Night: Transmissive, Reflective and Transflective Light Sources Most of us are familiar with the concept of polarised light in the form of Polaroid sunglasses. For LCDs, polarisation is a process that allows light to pass through, only if it is oriented in the right direction. For instance, Polaroid sunglasses are designed to allow through only vertically polarised light. This means that it makes sense to wear sunglasses when driving on wet roads at night as it cuts down on road reflection: this is because light reflected from a wet road is polarised horizontally and hence, the reflected light will be filtered out by Polaroid sunglasses. So, while it may seem cool to some to wear their sunglasses at night, it can also be practical. When it comes to LCDs, there are three kinds of polarised light transmissions that are particularly important, namely transmissive (the kind of LCDs we have been talking about up until now), reflective and transflective. Transmissive LCDs use a transparent rear polariser and a light source from behind the display (backlight), and are wellsuited for indoor use and office lighting. Transmissive LCDs are installed in Toshiba 4

notebooks and available also in the form of the 20.8-inch flat panel display. Now, let s look at some innovations in reflective and transflective displays used by Toshiba. Reflective LCD For reflective LCDs, light enters from the front, hits a reflector and a polariser at the rear, and bounces back to the user. This type uses the least power. As the rear polariser does not allow any light to pass through and not backlight is used. Removing the backlight from the display cuts by one-third the amount of power consumed by the device - an important factor in mobile devices that have a limited battery life. As well, the removal of the backlight also means the panel weighs around half as much as a conventional unit. This makes the reflective LCD ideal for such products as wristwatches, calculators and other tiny devices, such as Toshiba s Pocket PCs. Toshiba s Pocket PCs offer users a 4-inch color reflective lowtemperature polysilicon type thin-film transistor LCD panel. Transflective LCD Transflective combines the features of transmissive and reflective cells and can be adjusted to suit the designer's application. The rear polariser has partial reflectivity and can be combined with a backlight for use in all types of lighting conditions. Reflected light is used whenever possible and backlight when it is required; this means that power consumption is considerably reduced as the backlight is not constantly in use. Devices using transflective LCDs, include mobile phones and Tablet PCs. In 2001, Toshiba demonstrated its prototype transflective LCDs at EDEX (Electronic Display Exhibition) in Tokyo. Available in various sizes, including 4-inch, 8.4-inch and 10.4-inch dimensions, these screens support a wide range of mobile devices. These low-temperature polysilicon TFT-LCD panels produce images equally well in a variety of lighting conditions, ranging from bright sunlight to a dimly lit room. Approximately 80% of the pixels are reflective; the remaining 20% are transmissive. With this high ratio of reflective pixels, these LCDs can operate independently of the backlight. This means that the backlight can be used less often, reducing the power consumption. With the development of a tinier 2.2-inch screen, Toshiba will also offer LCDs for use in mobile phones. Perhaps, we can look forward to seeing these LCDs in Toshiba s own GPRS phones that will be available on the market in 2002 in Europe. Screen Technologies for Today and Tomorrow Finally, we offer a glimpse of display technologies that are important today and will become increasingly significant in years to come. Firstly, we look at role of Toshiba Matsushita Display Technology Co., LTD as a leading developer and manufacturer of polysilicon displays which are enabling the miniaturisation of mobile computing devices. Then, we look at emissive technologies where Toshiba Matsushita Display Technology is actively involved in developing and manufacturing displays. Whereas LCDs are 5

non-emissive, meaning that they require a light source and modulate transmitted or reflected light, emissive displays inherently create light and do not need a separate backlight to provide light for the image. As such, they open the way for thinner, lighter designs, as will be seen when we look at the following display technologies: - plasma displays - electromechanical or DLP (Digital Light Processor, originally developed by Texas Instruments) videowalls - LED (light-emitting diode) panels - organic light emitting displays (OLEDs). Ultra-high-resolution displays: polysilicon TFT LCDs Generally, we can expect to see developments in the area of polysilicon LCDs, a technology that is particularly suited for the miniaturisation of mobile computing devices, requires less power and supports a greater number of DPI (Dots Per Inch). Low temperature polysilicon allows electrons to flow faster than conventional displays, resulting in bright screens capable of higher resolutions. For users, this means excellent visualisation for graphics, including MPEG4 playback. We can expect to see these displays used for next-generation video-capable mobile phones, e-books, PDAs, portable PCs, desktop LCD TVs and monitors and personal DVD players. With polysilicon displays, it is possible to crowd more pixels per square inch, resulting in LCDs that approach true print quality. Let s look at a specific example. Whereas laser-printed text is 300 dpi or more, most of today s polysilicon TFT LCDs support fewer than 100 dpi. By contrast, Toshiba s low-temperature polysilicon LCDs are bringing us closer to the printed standard. In 2000, Toshiba announced a 4-inch display capable of displaying 202 pixels per inch (PPI) VGA resolution and 262,144 colours. Indeed, polysilicon displays are so legible and light that e-books are now becoming as easy to read as their printed counterparts. Toshiba Matsushita Display Technology has also introduced a 7.7-inch display, which supports Microsoft's ClearType text resolution enhancement technology and has a resolution of 150 pixels per inch. The display has a resolution of 640 x 960, can display 262,144 colours, has a contrast ratio of 250:1, and weighs 150 grams. Polysilicon displays also allow for more flexible, more reliable and slimmer designs on account of the fact that the peripheral circuitry can be fabricated along with the active matrix on a glass substrate. Polysilicon displays are Ideal for Toshiba s ultra-slim notebooks, such as the Portégé 2000: this particular LCD offers a resolution of 1,024 x 768 and is extremely slim at around 4mm. Plasma displays: Toshiba brings the future of digital TV home to you Anyone, who has seen images displayed on a plasma screen can attest to the fact that this wide-angle, bright and richly colourful viewing experience is exceptionally rich and lifelike. Just what makes the plasma viewing experience so amazing? These emissive displays use electrodes to excite the gas plasma, which then causes phosphors in each sub-pixel to produce coloured light (red, green or blue). The phosphors are the same types used in conventional CRT devices, such as televisions and standard computer monitors. However, plasma displays eliminate the need for the long picture tube of a CRT. Instead, a digitally controlled electric current flows 6

through a matrix to the pixels where it is required; each subpixel is individually controlled to produce millions of different colours. This results in a slim, relatively light display with an excellent digital picture. While plasma screens are not ideal for notebooks, as they are subject to image sticking, do not travel well and do not currently support resolutions higher than XGA, this technology is perfect for digital TV viewing. Indeed, many plasma screens available today support the 16:9 aspect ratio used by high-definition TV (HDTV) and wide-screen movies available on DVD. Moreover, you can hang these slim displays (3.5 to 6 inches thick) on the wall, making the plasma screen ideal for a home cinema. Unaffected by magnetism, there is no problem placing speakers in any position around the room for a truly dynamic entertainment experience. While digital TV is still somewhat of a niche market, the next 10 years will see the switch to digital broadcasting around the world, increasing the demand for HDTV. Today, Toshiba already offers a 50-inch wide screen HDTV monitor (50WP16/50HP81). Only 4 inches thick, it can display a 720p progressive-scan high-definition image in native resolution on its 1,366 x 768-pixel screen. The aspect ratio control supports both wide screen 16:9 format and standard 4:3 signals; a contrast ratio of 2000:1 keeps dark shadows black. Digital Light Processor: Mirror, Mirror on the Wall Most of us have seen video walls, used at trade fairs, exhibitions, modern art installations or stage productions. Rock concerts in particular often use video walls to project a larger than life image of the performer. Video walls are banks of stacked monitors or 'projection cubes' that split an image across several screens or can be used to display multiple images simultaneously. A variety of stackable units and technologies, including LCD, LED, plasma, CRT and DLP, are currently available on the market. DLP is the latest of these technologies and compares favourably to others as it offers bright images, even in low ambient conditions, and does not suffer from screen burnin. Using mirrors to reflect light, DLP panels offer high contrast, high-resolution images. Toshiba s P500DL (50-inch display supports SXGA), P410 and 411DL (41-inch displays) offer naive SVGA resolution and incorporate a DMD (digital mirror display) chip so that the fairest image of them all appears on the video wall. The DMD chip is covered with thousands of miniature mirrors. When a signal is sent to turn a pixel on, a tiny mirror rotates to reflect light towards the screen. When the off signal is sent, the mirror tilts so that light is reflected away. To produce colour, light is reflected through a spinning colour wheel. The colour wheel is a circular sheet of transparent material that is as thin as a piece of paper and textured with the three primary colours: red, green and blue. This transparent film rotates in a circular motion so only one colour of concentrated light passes at a time. The mirrors of the DMD chip turn at a high rate, carefully timed to reflect the 7

appropriate coloured light from the colour wheel. This light travels through the lens of the projector to create high-resolution images, with support for 16.7 million colours. Light-emitting Diode (LED) Displays: From Pilot Lights to White Light Most of us are familiar with the humble LED, often used as a red pilot light in appliances. Other uses include scoreboards at sporting events, clock radios and calculators. The light-emitting diode (LED) is a semiconductor device that emits visible light when an electric current passes through it. Typical monochrome outputs from a LED display include red (at a wavelength of approximately 700 nanometers) and blue-violet (about 400 nanometers). Currently, Toshiba manufactures colour LED displays for indoor and outdoor use. These units are modular, and can be configured according to the user s requirements, allowing for the display of multiple images in very large formats. Unlike the LED displays we have just mentioned, these screens offer 16.7 million colours. Using blue, red and green LEDs, each of which is controlled by 256 steps of contrast, these displays support graphic images or realistic video images in full colour. In 2001, Toshiba also announced a major innovation in LED technology: the white LED which achieves a short peak wavelength of approximately 380 nanometers. This new LED offers a high luminosity, low power consumption light source that achieves luminosity levels sufficient for incandescent lamps. Other applications include the instrument panels of motor vehicles and LCD backlighting. The new LED differs from the conventional technology used. Light emission in the visible wavelength band is controlled by excited phosphors, not by using temperature changes in the LED, to achieve a change in colour output. A greater range of operating temperatures and increased control over the image displayed are two of the main benefits of this enhanced technology. From LED to OLED: Toshiba s LEP displays OLED refers to a broad category of organic light-emitting diode displays. Compared to LCDs, OLEDs are an emissive technology that does not require a backlight and have the potential to eliminate a glass substrate in the display, as well as offering fast response times and supporting a wider viewing angle. As such, OLED promises thinner, lighter display panels that consume less power than conventional LCDs. While this technology is still under development and relatively costly, it may one day replace LCD technology. OLEDs can be broken down into two categories based on the size of the molecules in the display materials and differences in the production process. LEP (Light-Emitting Polymer) uses materials with relatively larger molecules as compared to SMOLED (Small Molecule Light-Emitting Display). LEP displays data via an organic lightemitting diode, with the pixels formed on a thin film transistor array. Each of these pixels can be turned on or off independently and can create multiple colours, resulting in a very fluid and smooth-edged display. Toshiba Matsushita Display Technology has developed the world's first prototype of a full-colour LEP display, a 2.85-inch display supporting 262,144 colours in Q-CIF format and a 64-level (6-bit) gray scale. These active matrix displays will appear initially in PDAs and mobile phones. We may also see larger displays, including wall-mounted displays, and notebook screens in coming years. 8

However, the most exciting advantage to OLED is the possibility of moulding it into a form or embedding it in fabric, allowing for flexible design and offering usability advantages. For instance, in the future, it may enable PDAs that can be rolled up and stored in one s pocket. Alternatively you could connect a foldable screen and keyboard to a mobile computing device, enabling users to more easily enter data and even gain basic notebook functionality from the PDA. For wearable PCs, this technology promises to unfold as yet untold mobile computing possibilities. 9

An Overview of Video Standards VGA -- 640 x 480 resolution, 300,000 pixels SVGA -- 800 x 600 resolution, 480,000 pixels XGA -- 1024 x 768 resolution, 768 pixels SXGA -- 1280 x 1024 resolution, 1.3 million pixels UXGA -- 1600 x 1200 resolution, 1.9 million pixels QXGA - 2048 x 1536 resolution, 3.2 million pixels QSXGA 2560 x 2048, 15.72 million pixels QUXGA 3200 x 2400, 7.7 million pixels Selected Sources Technology Overview http://www.pctechguide.com/07pan3.htm http://www.zdnet.com/pcmag/pctech/content/17/21/tu1721.002.html http://www.zdnet.co.uk/pcmag/supp/display/ http://www.vnunet.com/analysis/88978 LCD http://www.pcworld.com/news/article/0,aid,51944,00.asp http://www.howstuffworks.com/lcd.htm http://www.pcworld.com/howto/article/0,aid,15112,00.asp http://www.toshiba.com/taec/main/faq/lcd_faq.html http://www.toshiba.co.jp/about/press/2001_03/pr1502.htm Reflective http://www.pcworld.com/news/article/0,aid,16258,00.asp http://www.toshiba.com/taec/press/to-082.shtml Transflective http://www.nikkeibp.asiabiztech.com/nea/200107/peri_134206.html Polysilicon http://www.toshiba.co.jp/about/press/2000_04/pr1101.htm http://www.microsoft.com/presspass/press/2000/jul00/highresolutionpr.asp http://www.toshiba.co.jp/about/press/2000_07/pr1001.htm Plasma http://www.howstuffworks.com/home-theater9.htm http://www.federalstereo.com/tos50newmod.html http://www.ivojo.co.uk/toshiba-50wp16.htm http://www.dtvcity.com/plasma/toshiba-50hp81.html DLP http://www.tlt-uk.co.uk/ http://www.toshiba.com/taisisd/projectors/dlpfaq.htm http://www.agocg.ac.uk/brief/lcd.htm http://www.deregle.co.uk/pages/2j.htm LED http://www.howstuffworks.com/led.htm http://www.compoundsemiconductor.net/pressreleases/2001/pr02090101.ht m 10

OLED http://www.toshiba.com/taec/press/to-128.shtml http://www.toshiba.com/taec/press/to-146.shtml http://zdnet.com.com/2100-11-265928.html http://www.cdtltd.co.uk/store/corporate%20development/acronyms_files/a cronyms%20r1.htm http://www.ualberta.ca/~kaminsky/organicelectroluminescence.htm http://www.eetimes.com/story/oeg20010410s0016 Polaroid is a registered trademark of the Polaroid Corporation. Microsoft and ClearType are registered trademarks or trademarks of Microsoft Corp. Other products and company names herein may be trademarks of their respective owner. 11