A preview of the papers appearing in the February 2006issue of theJournal of the SID. To obtain access to these articles on-line, please go to www.sid.org

Edited by Aris Silzars

A rollable, organic electrophoretic QVGA display with field-shielded pixel architecture

G. H. Gelinck, H. E. A. Huitema,
M. van Mil, E. van Veenendaal,
P. J. G. van Lieshout,
F. Touwslager, S. F. Patry,
S. Sohn, T. Whitesides,
M. D. McCreary

Polymer Vision, Philips Technology Incubator

Abstract — A100-μm thin QVGA display was made by combining a 25-μm thin organic transistor active-matrix backplane with an electrophoretic display film. High contrast and low crosstalk was achieved by the addition of a field shield to the backplane. The display can be bent repeatedly to a radius of 2 mm without any performance loss. Extended mechanical tests at a radius of curvature of 7.5 mm show that the display can be rolled at least 30,000 times without noticeable degradation.

Displays on plastic substrates offer a solution to both the display area and thickness problems associated with conventional display technologies. A plastic display can be thin and flexible enough to be rolled up in a tube. Furthermore, plastic displays are impact resistant and do not need the additional protection essential for displays on glass. Passive-matrix LCDs using plastic substrates have been on the market for some time. Their disadvantages include limited size – a few hundred rows – and relatively low image quality due to high crosstalk. In contrast, active-matrix displays are characterized by low crosstalk, resulting in much better image quality. Although they require a thin-film transistor per pixel, an active matrix offers the important advantage of allowing the displays to be much larger.

FIGURE 2 — Cross section of the rollable active-matrix display. Total display thickness is 100 μm. The active-matrix layer stack is built using six photolithography steps. The third metal layer is used in order to shield the electric field of the TFT and the electrodes from the electronic-ink film.


An LTPS active-matrix process with PECVD doped N+ drain/source areas

Holger Baur
Sven Jelting
Niels Benson
Norbert Fruehauf

University of Stuttgart

Abstract — A low-temperature polysilicon active-matrix process without the need for ion implantation to dope drain and source areas of TFTs has been developed. A doped silicon layer is deposited by PECVD and structured prior to the deposition of the intrinsic silicon for the channel. The dopant is diffused and activated during the excimer-laser crystallization step. N-channel test TFTs with different geometries were realized. The TFT properties (mobility, on/off ratio, saturation, etc.) are suitable to realize AMLCDs and AMOLED displays and to integrate driver electronics on the displays. In addition to simple TFTs, a full-color 4-in. quarter-VGA AMLCD was realized. The complete display (including photolithographic masks, active-matrix backplane, and color-filter/black-matrix frontplane), and an addressing system were developed and manufactured at the Chair of Display Technology, University of Stuttgart, Germany. The substitution of ion doping by PECVD deposition overcomes a major limitation for panel sizes in poly-Si technology and avoids large investment costs for ion-implantation equipment.

Ion implantation is a major limiting factor for substrate sizes in polysilicon technology. Additionally, an ion implanter is among the most costly equipment in display technology. In order to replace ion doping, a complete active-matrix process using highly doped PECVD layers as dopant sources for the drain/source areas has been developed. A doped silicon layer is deposited by PECVD and structured prior to the deposition of the intrinsic silicon for the channel. The dopant is diffused and activated during the excimer-laser crystallization step. The idea of using pre-doped silicon layers as dopant sources for drain and source areas of poly-Si TFTs extends back to the 1980s, but none of these publications presented an operational display.

FIGURE 16 — Photograph of the poly-Si TFT active matrix with PECVD-deposited drain/source contacts.


New era for TFT-LCD size and viewing-angle performance

Sang Soo Kim
Brian H. Berkeley
Jin Hyeok Park
Taesung Kim

Samsung Electronics Co., Ltd.

Abstract — Samsung has announced the development of a full-high-definition (1920 x 1080) 82-in. TFT-LCD panel using Super-PVA (S-PVA) technology, the world's largest TFT-LCD. In addition to the size breakthrough, this product achieves 600 nits of brightness, a contrast ratio of over 1200:1, an angle of view of 180°, a color gamut of 92%, and an 8-msec response time. Several key enabling technologies were developed to achieve these specifications, including two-transistor direct-driven independently controlled S-PVA subpixels, non-even-area-ratio subpixels for optimal off-axis gamma, gate overlap driving for larger driving margin, new CCFL technology for higher color gamut, and advanced fabrication techniques including the use of Samsung's new Gen 7 line. Many of these technologies will be applied to other products within Samsung's LCD-TV product line. Samsung's broader development efforts toward the overall LCD-TV market, including production status of the Gen 7 facility, will be updated.

As a vertically aligned LC technology, PVA is normally black. PVA is a multi-domain (four-domain) VA mode. In its on-state, fringe fields are formed by patterned ITO. These fields cause the LC molecules to tilt according to the ITO patterns, forming the multi-domain LC cell. Other VA technologies rely on protrusions in order to form the multi-domain LC cell. Unlike IPS, no rubbing process is required for VA technologies. As a conventional VA mode, PVA has a viewing-angle dependence which causes off-axis performance limitations. This problem can be solved by introducing more domains, as we have done with S-PVA.

FIGURE 2 — Motion of LC molecules in eight-domain S-PVA cell.


True 3-D scanned voxel displays using single or multiple light sources

Brian T. Schowengerdt
Eric J. Seibel

University of Washington

Abstract — Conventional stereoscopic displays require viewers to unnaturally keep eye accommodation fixed at one focal distance while they dynamically change vergence to view objects at different distances. This forced decoupling of reflexively linked processes fatigues eyes, causes discomfort, compromises image quality, and may lead to pathologies in developing visual systems. Volumetric displays can overcome this conflict, but only for small objects placed within a limited range of viewing distances and accommodation levels and cannot render occlusion cues correctly. Our multi-planar true 3-D displays generate accommodation cues that match vergence and stereoscopic retinal disparity demands and can display images and objects at viewing distances throughout the full range of human accommodation (from 6.25 cm to infinity), better mimicking natural vision and minimizing eye fatigue.

The most common displays used for the presentation of three-dimensional (3-D) data are stereoscopic displays. Unfortunately, although stereoscopic displays can create a compelling perception of depth, they do not completely recreate the conditions of viewing real 3-D objects. This imperfect mimicry of true 3-D conditions creates oculomotor and sensory conflicts in the visual system, leading to eye fatigue and discomfort. This problem is similar to the better-known phenomenon of motion sickness (or "seasickness"), experienced below decks on a rocking boat. In that case, the sense of balance accurately reports that a person is moving but, because the person cannot see him/herself rocking relative to the horizon, the sense of vision asserts that the person is not moving — a sensory conflict that can cause extreme discomfort, headaches, and nausea. The conflicts within the visual system that are generated by stereoscopic displays can cause similar discomfort.

FIGURE 1 — Matching ocular accommodation and vergence when viewing real objects.


Electrically controlled light scattering in FLC cells

Alexander L. Andreev
Yury P. Bobylev
Tatiyana B. Fedosenkova
Nshan A. Gubasaryan
Igor N. Kompanets
Eugene P. Pozhidaev
Vadim M. Shoshin, Yuliya P. Shumkina

P. N. Lebedev Physical Institute

Abstract — Three types of light-scattering effects distinguished by physical mechanisms were studied in detail in monomeric ferroelectric liquid-crystal (FLC) compositions at different boundary conditions and electrical pulse regimes. The total time of the scattering switching on and switching off is less than 150, 250, and 500 μsec at ±50 V for different scattering types in helix and non-helix FLCs. They are quite fast, and FLC cells are quite transparent and were used in a stack of 30–100 light-scattering shutters for a volumetric screen of a 3-D display.

The 3-D objects are visualized in volumetric displays most effectively by the light scattering at section planes of a volumetric medium. To compose a 3-D object, one can use a stack of LC shutters and send corresponding light signals into every addressed (i.e., scattering) plane while other (non-addressed) planes are transparent (Fig. 1). The more sections, the faster the pattern must be visualized in every section, or the faster the light scattering must be switched on/off at a section plane (and vice versa) for real-time displaying. Because the time of the scattering switching on/off must be minimal with respect to the direct scattering time, the scattering must be strong and diffusive, and no scattering must be in the transparent state of a volumetric medium.

FIGURE 1 — A schematic of a volumetric screen based on a stack of electrically controlled light-scattering shutters. A section pattern is visualized only at plane C where a shutter scatters light.


Spatio-temporal scanning backlight mode for field-sequential-color optically-compensated-bend liquid-crystal display

Kälil Käläntär
Tadashi Kishimoto
Kazuo Sekiya
Tetsuya Miyashita
Tatsuo Uchida

Nippon Leiz Corp.

Abstract — A spatially and temporally scanning backlight consisting of ten isolated micro-structured light guides has been developed to be combined with a fast-response optically-compensated-bend-mode field-sequential-color LCD in which the liquid-crystal cell does not contain color filters. The sequential fields of three primary colors are generated by illumination of the red-, green-, and blue-light-emitting diodes, each illuminating for one-half of the field, resulting in a luminance of 200 cd/m2 for the LCD. The effect of light leakage between the blocks in the scanning backlight in field-sequential-color applications was measured and will be described.

The recent development of fast-response LCDs, such as optically-compensated-bend (OCB) mode, and highly efficient light-emitting diodes (LEDs) for three primary colors have enabled the reintroduction of the field-sequential-color (FSC) displaying method, which was one method used at the very beginning of the introduction of color display systems in the mid 20th century. The FSC display is now expected to be a future color LCD with low power consumption.


FIGURE 15 — The developed OCB-mode LCD with the scanning backlight.


LED-backlight feedback control system with integrated amorphous-silicon color sensor on an LCD panel

Ki-Chan Lee 
Seung-Hwan Moon
Brian Berkeley
Sang-Soo Kim

Samsung Electronics Co., Ltd.

Abstract — TFT-LCDs have the largest market share of all digital flat-panel displays. An LCD backlighting system employing a three-color red-green-blue light-emitting-diode (RGB-LED) array is very attractive, considering its wide color gamut, tunable white point, high dimming ratio, long lifetime, and environmental compatibility. But the high-intensity LED has problems with thermal stability and degradation of brightness over time. Color and white luminance levels are not stable over a wide range of temperature due to inherent long-term aging characteristics. In order to minimize color point and brightness differences over time, optical feedback control is the key technology for any LED-backlight system. In this paper, the feasibility of an optical color-sensing feedback system for an LED backlight by integrating the amorphous-silicon (a-Si) color sensor onto the LCD panel will be presented. To minimize the photoconductivity degradation of a-Si, a new laser exposure treatment has been applied. The integrated color-sensor optical-feedback-controlled LED-backlight system minimized the color variation to less than 0.008 Δu¢v¢ (CIE1976) compared to 0.025 for an open-loop system over the temperature range of 42–76°C.

In order to minimize color-point and brightness differences over temperature and time, optical feedback control is the key technique for any LED-backlight system. There are many practical issues in implementation such as placement of the photosensor, sampling of light signals for feedback, effect of the LED drive current waveform on sensor signal integrity (crosstalk), and control system design. A three-color RGB LED-backlight system with an integrated color sensor on the LCD panel is depicted in Fig. 3.

FIGURE 3 — LED-backlight system with optical feedback control.


Architectural choices in the Aptura™ scanning backlight for large LCD TVs

A. A. S. Sluyterman
H. J. G. Gielen

Philips Lighting

Abstract — A production-ready scanning LCD backlight system for TV sets of 32 in. and larger has been designed. It improves the representation of moving objects and allows fast and deep dimming for higher contrast. The architectural choices made for these designs will be described.

Imagine an object that moves over the screen from left to right in 2 sec, which is not uncommon at all. Assume, furthermore, a frame rate of 60 Hz and an LCD panel with 1440 pixels per line. Then the image smear due to the hold effect would be 12 pixels! This is unacceptable even for standard-definition television, let alone for HDTV. Interestingly enough, the absence of an image does not contribute to image smearing, while an image at the wrong place does. This phenomenon is exploited in the CRT to the extreme, where each part of the image is only present for less than a millisecond. By adopting a dynamic scanning backlight, which illuminates each part of the panel for only a short moment, this principle can also be applied to LCDs.

FIGURE 13 — A see-through view of the Aptura™ backlight system shows eight fluorescent lamps, each with a diameter of 16 mm.


High-quality images on electrophoretic displays

Mark T. Johnson
Guofu Zhou
Robert Zehner
Karl Amundson
Alex Henzen
Jan van de Kamer

Philips Research Laboratories

Abstract — High-resolution micro-encapsulated active-matrix electrophoretic displays showing 2-bit gray-tone images and text with high contrast and high reflectance are commercially available. Methods of realizing high-quality images on these displays will be covered in this paper.

As illustrated in Fig. 2 for a dual-particle system, MEP displays operate by the motion of charged pigment particles between two planar electrodes, in response to an electric field. By applying a positive voltage on a pixel, the positively charged white particles are forced to move towards the top transparent electrode, creating a white state when the display is viewed from this side. In contrast, by applying a negative voltage on a pixel, the negatively charged black particles are forced to move towards the top electrode, creating a black state. Between these two end states exists an analog range of intermediate-reflectivity gray tones. In addition to gray-tone capability, MEP displays can exhibit high-resolution images. The resolution of a MEP display is not limited by the size of the microcapsule because the particles in the same capsule, crossing two neighboring pixels, can be partially switched to white state on one pixel and black state on the other pixel, as can be seen in Fig. 2.

FIGURE 2 — Schematic of a microcapsulated electrophoretic (MEP) display with positively charged white particles and negatively charged black particles, showing the switching between the black and white states.


Single-substrate encapsulated cholesteric LCDs: Coatable, drapable, and foldable

Irina Shiyanovskaya
Asad Khan
Seth Green
Greg Magyar
Oleg Pishnyak
Duane Marhefka
J. William Doane

Kent Displays, Inc.

Abstract — The first ever, reflective cholesteric liquid-crystal displays (ChLCDs) on single textile substrates made with simple coating processes have been developed. A novel approach for fabrication of ultra-thin encapsulated ChLCDs with transparent conducting polymers as bottom and top electrodes will be reported. These displays are fabricated from the bottom-up by sequential coating of various functional layers on fabric materials. Encapsulation of the cholesteric liquid-crystal droplets in a polymer matrix and the mechanical flexibility of the conducting polymers allow for the creation of durable and highly conformable textile displays. The development and status of this next-generation display technology for both monochrome and multicolor cholesteric displays will be discussed.

Cholesteric liquid-crystal materials naturally provide high brightness and require low power due to the inherent bistability of the cholesteric textures. The pure reflective nature of the cholesteric materials does not require the use of filters, polarizers, and backlighting. All these features enable the fabrication of light-weight low-power ChLCDs on flexible substrates if special care is taken to prevent liquid-crystal flow under the pressure caused by display deformation which is unavoidable for flexible applications. The elegant solution is to confine small liquid-crystal droplets in a polymer matrix. In addition to the elimination of the material flow under pressure, encapsulation of the LC provides good film-forming properties and high durability of the encapsulated LC layer.

FIGURE 7 — Fully functional deformed ChLCDs coated on the textile substrates, segmented and 16 x 13 passive matrix.


A single-panel LCoS engine based on light guides

Jeffrey A. Shimizu
Peter J. Janssen
Khalid Shahzad

Philips Research USA

Abstract — By using light-guide components, a new scrolling-color engine for single-panel LCoS projection has been developed. Light guides allow for loss-less delivery of light leading to a simpler and more-compact system. Engine design and construction based on a single 0.88-in.-diagonal LCoS panel is described. Separate results with a multilayer optical film Cartesian PBS show that a significant improvement in system efficiency is possible.

A layout of the light-guide engine is shown in Fig. 2. The figure shows the path without the lamp. Light from the lamp is focused at the input to the light-guide assembly. The input is rectangular in shape and one-half the length of the illumination stripe. A small polarization conversion system (PCS) is used to create a full-length stripe of one polarization. The light-guide assembly splits the light into three primary colors and directs the light towards the three scanning prisms. Color splitting filters are placed on the hypotenuse of right-angle prisms in the light-guide assembly. Each colored stripe passes through a scanning prism. The colors are then recombined in the x-cross filter assembly.

FIGURE 2 — Layout of the optical path without a lamp. Distance from input plane to LCOS plane is 239 mm.


A super-fine-pitch screen for rear-projection TV

Satoshi Iwata
Akihito Kagotani
Yuki Igarashi
Susumu Takahashi
Takashi Abe

Toppan Printing Co.

Abstract — An advanced screen for use with LCD/LCoS/DMD rear-projection TV has been developed. A lenticular lens having a pitch of 64 μm has been developed without loss in any other optical property. A 70% black-stripe ratio was obtained by optimizing the patterning process, which maintains high contrast. As described in this paper, the FC-Screen manufacturing technology has been further developed.

The optimum lens pitch is determined by moiré simulation (as shown in Fig. 3). A 98-μm lenticular-lens pitch can be used for 1080pscreen diagonals larger than 40 in. A 64-μm lens pitch leads to less moiré on every pixel size. A lenticular lens pitch of 64 μm is suitable for use with QSXGA as well as 1080p. The super-fine-pitch FC Screen, which is also able to achieve a 70% black-stripe ratio, is optically identical to a conventional screen and to fine-pitch FC Screens.

FIGURE 3 — Moiré simulation: Optimum lens pitch vs. screen size.


Projection optical system for a compact rear projector

Muneharu Kuwata
Tomohiro Sasagawa
Kuniko Kojima
Junichi Aizawa
Akihisa Miyata
Shinsuke Shikama
Hiroaki Sugiura

Mitsubishi Electric Corp.

Abstract — A new projection optical system with an exceptionally wide field angle of 160° and a short projection distance of 125 mm for a 62-in. screen has been developed. It is constructed based on the Direct Projection Method which does not require a back mirror. This paper presents a new optical design concept and the characteristics of a prototype optical system.

FIGURE 9 — Outline layout of projection system.

FIGURE 15 — First prototype optical engine in a front-projection configuration.