Company News

Abstract

Rolic Ltd, a recently launched liquid crystal R&D company from Roche, has announced the development of several new path-forging technologies which are expected to have a major impact on the liquid crystal display (LCD) and copy-proof security industries in the future. Rolic's inventions solve many of the challenges facing the LCD industry, such as view angle dependency, high cost and response time. They represent a quantum leap in making high resolution, large area displays possible. Rolic will make essential contributions to the development of refined, ultra high resolution image and display products. Rolic's future products will enable visual computing professionals as well as the general public to work more effectively with a greater variety of new-age information displays than ever before.     

Abscheidung dünner Siliziumschichten durch Zersetzung eines Siliziumtetrahlorid-Wasserstoff-Gemisches in einer Hochfrequenz-Glimmentladung

The paper describes a technique for depositing thin films of silicon on several substrate materials by decomposition of a SiCl₄–H₂ mixture in a h.f. discharge. Depending on the growth conditions and on the substrates used the formed silicon layers are amorphous, polycrystalline or well defined monocrystalline. Vapour etching of differently orientated monocrystalline silicon substrates in the apparatus yields crystal surfaces which can be used as base for consecutive epitaxial growth.     

Conference Reports

Abstract

The 1995 Society for Information Display (90) International Symposium is the premier international gathering of scientists, engineers, technologists, manufacturers, and users of flat panel displays, where virtually all aspects of information displays are presented. The organizers, Richard H. Bruce (Symposium Chair) and Hugo Steemers (Programme Chair) of Xerox Palo Alto Research Center, did a magnificent job in arranging a programme that covered a wide range of technology and applications' from high definition flat panel displays of both emissive and liquid crystal display (LCD) technology t o the latest in CRT development and large area display projection systems. The symposium featured over 180 papers from around the world in 45 technical sessions; the conference papers are published in the SID International Symposium Digest of Technical Papers Vol. XXVI. It is very apparent just by paging through the Digest of Technical Paper that LCDs have entrenched themselves in the flat panel display community, and as the need for high information content continues t o grow, LCDs are expected to play an even bigger role. From the liquid crystal materials perspective, the conference was heavily weighted towards reflective displays, polymer dispersed liquid crystal displays for projection, alignment and viewing angle issues, and active matrix technologies.     

Russian Liquid Crystal Society awards first Freederiksz Medals

Abstract

The interest in research and development of plastic liquid crystal technology originates from the stabilization of liquid crystals with a polymer matrix for manufacturing of largearea flexible electro-optical films which can be used as electrically switchable shutters, panels and privacy windows in the building, residential and transportation sectors, as well as reflective displays. In figure 1, we show typical examples of PDLC applications as electro-optical windows. The display applications of PDLC are not within the scope of the present article.     

Liquid Crystal Display Research in Japan

The technology development of liquid crystal display started having a remarkable influence on the technology innovation of up-to-date electronic calculator. While a digital display using liquid crystal display has been developed in its earlier stage as the segment type which sets a limit of display to numeric and certain symbols, it is also spent an effort to develop the X - Y matrix type which can display alpha-numeric and moreover kana characters. As a practical application of the X - Y matrix type liquid crystal display, an alpha-numeric type scientific electronic calculator and electronic translator will be reported.

Further, the present status of liquid crystal display applications and trend of R&D in other consumer and industrial electronic industries in Japan will be reported. Finally, activities in the Japanese academic circles will be presented.     

Preparation of a Carbon Nanotube-Reinforced UV/Heat Dual-Curable Adhesive for Liquid Crystal Displays

Abstract

There is strong demand for narrow-bezel liquid crystal displays (LCDs) in the display industry. Adhesive materials for narrow-bezel LCDs require excellent adhesive properties in order to provide the same level of adhesive strength as conventional sealants, even when applied in small amounts. In this study, we prepared a previously unknown, highly adhesive, carbon nanotube-reinforced (CNT-reinforced) UV/heat dual-curable adhesive for narrow-bezel LCDs. Single-walled and multi-walled CNTs (SWCNTs and MWCNTs) were employed as fillers, resulting in superior adhesive properties; in particular, the inclusion of SWCNTs improved both adhesion and resistance to water permeability compared to a conventional adhesive.     

Short-range order in non-stoichiometric amorphous silicon oxynitride and silicon-rich nitride

By de-convoluting the Si 2p X-ray photoelectronic spectra, it was found that the short-range order in amorphous silicon oxynitride (SiO_xN_y) films with different compositions can be quantitatively described by the random bonding model. In this model the SiO_xN_y consists of five types of randomly distributed tetrahedra and it indicates that metal-oxide-semiconductor transistor with this gate dielectric will not result in any gigantic potential fluctuation in the conduction channel. On the contrary, the structure of silicon-rich silicon nitride SiN_x can only be described by the random mixture model where the local composition fluctuations in this film will result in gigantic potential contra-variant fluctuation.     

ASIA Display '95

Abstract

The ultra-modern ACT City Complex of Hamamatsu was this year's venue for Asia Display' 95. Formerly known as Japan Display, the renaming of the series of International Display Research Conferences recognizes the growth of the display industry in Asia, and the increasing importance of the region to the world economy. More than 40 per cent of a total of over 200 talks and poster presentations were specifically concerned with liquid crystal displays (LCDs), and following the Conference were whole day workshops on Advanced LCDs and LCD colour filters. Without being biased it is fair to say that LCDs dominated the Conference, although advances in multicoloured Electroluminescent Displays, large area Plasma Displays and Field Emission Displays showed that the LC Display Industry cannot afford to be complacent about rival technologies.     

多晶硅晶体生长中固-液界面研究进展

论述了多晶硅晶体生长技术的研究现状,探讨了多晶硅在定向凝固过程中的生长机制,重点阐述了多晶硅定向生长中固-液界面的形貌、杂质分布、数学模型、数值模拟以及外场对界面调控的影响,归纳总结目前国内外多晶硅生长界面的研究现状,展望了多晶硅晶体生长过程中固-液界面调控技术的发展前景.     

1996 Society For Information Display, 12–17 May,San Diego,California

Abstract

The annual Society for information Display (SiD) Conference was held in beautiful San Diego, California. The SiD Symposia are certainly the best way for researchers and technologists to keep in touch with the ever changing and dynamic display arena. The 1996 SID Symposium was an exciting, highly informative, and entertaining event that made participants more knowledgeable, effective, and productive. I strongly encourage that more ILCS members take part in the SID Symposia in the future. The conference is heavily dominated by liquid crystal materials and displays. Although it is strongly focused towards electro-optic appllcations and displays, there is a lot of basic physlcs, chemistry, and engineering to be learned from the excellent papers and talks. The proceedings are published in a 1022 page volume entitled SID International Symposium Digest of Technical Papers, Volume XXVII (ISSN 0097-966X). edited by Jay Morreale, and it can be purchased from SID, 1526 Brookhollow Drlve, Suite 82, Santa Ana, CA 92705-5421, USA.     

Optical limiting action of 2-amino 5-nitro pyridinium chloride crystal for laser safety devices

ABSTRACT

The liquid crystal (LC) displays with narrow bezel design require excellent physical properties such as high adhesion, low moisture permeability, and low LC contamination. Among the adhesive components, the heat curing agent is an important component in the adhesive and plays a key role in the adhesion between the epoxy resins. In this study, new UV/heat dual-curable adhesives involving a multi-functional heat-curing agent of branched polyethylenimine have been prepared and evaluated by adhesive strength, moisture permeability, and LC contamination measurements. It is shown that the proposed adhesives offer excellent adhesive properties for narrow-bezel applications.     

Characterization of silicon layers epitaxially grown on metallurgical-grade polycrystalline substrates

The structural and electrical properties of silicon layers epitaxially grown on metallurgical-grade polycrystalline silicon substrates are examined to clarify the effect of grain boundaries, crystal defects and impurities in the substrates. Chemical etching of the epitaxial layer reveals that all the grain boundaries continue from the substrate into the epitaxial layer, whereas lines of high density etch pits do not always continue. The polycrystalline thin film solar cells are fabricated on the metallurgical-grade silicon substrates by successive deposition of p and n⁺ layers. These cells show short circuit current densities around 70% of that of the conventional single crystal cell. This reduction of the short circuit current is caused mainly by the short minority carrier diffusion length in the grains probably due to impurities involved in the epitaxial layers. The origins of such impurities are discussed by considering autodoping and solid-state diffusion from the substrate during growth of epitaxial layers.     

Liquid Crystals in Education

Abstract

The advancement of liquid crystal science and technology has been a truly interdisciplinary effort which combines basic principles of physics, chemistry, and engineering. The success of liquid crystal materials in flat panel displays and electro-optic applications can be attributed to the collaborations of scientists in various fields and the unique interface between academia and industry. Many scientists and engineers engaged in liquid crystal research are also educators in their respective disciplines andlor area of expertise. Those in academia routinely teach undergraduate and graduate courses in physics, chemistry, and engineering, and those in industry often find themselves teaching technical short courses and seminars. Many of us have visited elementary and high schools in the USA to speak to students about careers in science and engineering, and to present some eye-catching demonstrations that excite students about science and technology.     

Report on the 11th Annual British Liquid Crystal Society Meeting, 1–3 April 1996

Abstract

This year's meeting was held at the University of Central Lancashire in Preston and was attended by 185 delegates. The meeting was organized jointly by Professor Mike Holmes and Dr Richard McCabe and took place in the recently completed Harrington conference facilities. It provided a lively interchange of information on a wide variety of topics, led by the invited speakers who covered four important areas of interest. The Ben Sturgeon Memorial Lecture was delivered Professor Bill Doane from Kent State University. His up-to-the-minute presentation dealt with reflective cholesteric liquid crystal displays and the progress that has been made in developing low cost, low power and high-resolution displays capable of delivering the type of switching rates that will make them serious rivals to the printed page. He provided his audience with both the scientific background and the challenges remaining before commercial displays of this type are available.     

Lasing Pixels: A New Application for PDLCs

Abstract

Pixels in an intracavity polymer dispersed liquid crystal can switch lasing action on and off, yielding addressable lasing pixels for projection applications. The marriage between an efficient PDLC display element and laser illumination consolidates the positive attributes of two different approaches to projection into a very capable technology with greater application potential. This radically different approach to projection certainly meets many of the market needs where current technologies fall short. With these needs met, a new application of PDLC technology is on the horizon.     

Ferroelectric liquid crystal over silicon devices

Over the past 20 years, ferroelectric liquid crystal over silicon (FLCOS) devices have made a wide impact on applications as diverse as optical correlation and holographic projection. To cover the entire gamut of this technology would be difficult and long winded; hence, this paper describes the significant developments of FLCOS within the Engineering Department at the University of Cambridge.

The purpose of this paper is to highlight the key issues in fabricating silicon backplane spatial light modulators (SLMs) and to indicate ways in which the technology can be fabricated using cheap, low-density production and manufacturability. Three main devices have been fabricated as part of several research programmes and are documented in this paper. The fast bitplane SLM and the reconfigurable optical switches for aerospace and telecommunications systems (ROSES) SLM will form the basis of a case study to outline the overall processes involved. There is a great deal of commonality in the fabrication processes for all three devices, which indicates their potential strength and demonstrates that these processes can be made independent of the SLMs that are being assembled. What is described is a generic process that can be applied to any silicon backplane SLM on a die-by-die basis. There are hundreds of factors that can affect the yield in a manufacturing process and the purpose of a good process design procedure is to minimise these factors. One of the most important features in designing a process is fabrication experience, as so many of the lessons in this business can only be learned this way. We are working with the advantage of knowing the mistakes already made in the flat panel display industry, but we are also faced with the fact that those mistakes took many years and many millions of dollars to make.

The fabrication process developed here originates and adapts earlier processes from various groups around the world. There are also a few totally new processes that have now been adopted by others in the field. Many, such as the gluing process, are still on-going and have to be worked on more before they will fully suit ‘manufacturability’.     

Investigation of 3C-SiC growth on Si(111) by vapor–liquid–solid transport using a SiGe liquid phase

The crystal growth of 3C-SiC onto silicon substrate by Vapor–Liquid–Solid (VLS) transport, where a SiGe liquid phase is fed with propane, has been investigated. Three sample configurations were used. In a preliminary approach, the VLS growth of SiC was conducted directly onto Si substrate using a Ge film as liquid catalyst. It led to the growth of a thick continuous SiC polycrystalline layer which was floating over a SiGe alloy located between the silicon substrate and the topping SiC layer. In the second configuration, a thin seeding layer of 3C-SiC grown by chemical vapor deposition (CVD) was used and the VLS growth was localized using a SiO₂ mask. The liquid phase was a CVD deposited SiGe alloy. The growth of a few hundred nanometers thick 3C-SiC epitaxial layer was demonstrated but the process was apparently affected by the presence of the oxide which was dramatically etched at the end. In the last configuration, the silicon substrate was patterned down to 10 μm and a thin seeding layer of 3C-SiC was grown by CVD onto this patterned substrate. The liquid phase was again a CVD deposited SiGe alloy. In this last configuration, the presence of epitaxial SiC was evidenced but it grew as trapezoidal islands instead of an uniform layer.     

热屏下降式单晶炉设计与研究

光伏发电以绿色、可再生、能源质量高和不受资源分布地域的限制等优点被广泛使用,单晶硅又以低衰减率和高转换效率等优点渐渐超过了多晶硅光伏电池在市场中的份额,但成本问题和产能问题一直束缚着单晶硅太阳能产业的发展.本文提出了一种在晶体生长过程中随硅液面下降而下降的直拉单晶炉热屏结构,来解决在拉晶过程中坩埚上升所造成的拉晶速度和...     

Viewing Angle and Imaging Polarization Analysis of Liquid Crystal Displays and Their Components

Optical characterization of all types of displays is mandatory to quantify the different imperfections and compare the different technologies. Standard characterization is focused on luminance and color measurements of the light emitted by the displays. Viewing angle measurements devoted to the angular characterization and homogeneity measurements are the most frequently used. In the present paper we demonstrate that the same type of measurements extended to the polarization analysis of the light emitted by the display can be a powerful tool in order to understand the origin of many imperfections. The present paper is composed of two main parts: first the different measurement tools for viewing angle and imaging characterization are presented and the method used to analyze the polarization state of the light is explained. The second part gives details on some examples of applications for the characterization of display components (brightness enhancement film, backlight), the measurement of the crystal cell rotation inside a standard LCD display, and the characterization of a passive 3D TV.     

Captured Orientational Order in Polymer Network Assemblies

Abstract

The “marriage” between low molecular weight liquid crystals and polymers burgeoned in the 1980s with the idea of dispersing liquid crystal droplets in a rigid polymer matrix to create an electrically controllable light scattering medium. The orientation of the liquid crystal droplets, and hence the refractive index match and scattering, can be systematically controlled with an electric field. Today, dispersions of liquid crystals and polymers are found in many forms depending on the concentration of polymer, which can be as large as 70% or as small as 1%. The systems most understood are those of larger concentration where the liquid crystal is segregated out in the form of droplets randomly distributed throughout the surrounding polymer (see page 2). Dispersions of liquid crystals and polymers differ from macroscopic bulk liquid crystals because of the large surface-to-volume ratio and symmetry breaking non-planar geometry imposed by the polymer. Their composite nature profoundly affects the ordering of the liquid crystal, and their susceptibility to external fields makes them suitable for many new electro-optic applications, as well as intellectually challenging to study from the basic science perspective.