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Electronic or rewritable paper and other developments from conductive film

Electronic or rewritable paper and other developments from conductive film

Electronic or �rewritable� paper has the ability of conventional paper to display fixed information without consuming power and the ability of electronic devices to display changeable information. The market for electronic paper is expected to grow rapidly in fields including e-books, mobile phones, wristwatches, electronic tags, point-of-purchase advertising, digital signage and more. The majority of electronic paper currently available on the market is made with glass substrate, but transparent conductive film is expected to be increasingly adopted as the main substrate of future electronic paper because it enables the production of lighter and thinner devices. Teijin Chemicals Limited has begun manufacturing and selling transparent conductive films that are expected to be used in new versions of electronic paper that are to be lighter and thinner than conventional products on the market. The company has begun selling two types of transparent conductive films: SS120, which uses polycarbonate (PC) film as substrate, and HP125, which uses polyethylene terephthalate (PET) film as substrate. The former is suited for electronic paper that uses liquid crystal and the latter is suited for electronic paper that uses electrically charged particles. For both films, Teijin Chemicals utilizes high-precision coating technology to form the hard coating layer; and vacuum coating technology to form the gas barrier layer and the transparent conductive layer. The high-quality transparent conductive film using polycarbonate film as substrate, produced by Teijin Chemicals, is already used widely in touch panels. In addition to electronic paper, the film is expected to find additional applications, such as organic light emitting diodes (OLEDs).
Teijin Chemicals' ELECLEAR is a transparent electro conductive film is thin, light, resilient and flexible, making it superior to glass in many ways. Utilizing such advantages, the film is used as major transparent electrodes of resistive touch panels. Generally, resistive touch panels are composed of two conductive-coated substrates separated by a narrow gap. When an object, such as a pen, presses down on a point on the panel's outer surface, both substrates come into contact with each other, and then the subsequent voltage change triggers the data transmission. ELECLEAR also is used mainly for a resistive touch panel, commanding majority market shares for game consoles, smartphones and PDAs. ELECLEAR is composed of hard coating, undercoating and indium tin oxide (ITO) layers on top of a polymer-film substrate. The hard-coating and undercoating layers incorporate proprietary coating technology to prevent glare and rainbow patterns caused by film deflection and flicker, as well as offering strong resistance to finger smudging. ELECLEAR also is highly durable - in a test, its ITO layer remained unaffected after 10,000 finger taps, while conventional films deteriorated after 5,000 taps. Teijin Chemicals is the only company in the world to produce a transparent and electro conductive PC film. PC and PET films are applicable to not only resistive but also capacitive touch panels, which detect differences between the electrostatic capacitance of a fingertip and conductive film to identify touch position. Both touch panels are used in growing markets for devices such as ATMs and ticket vending machines.
FujiFilm Corporation has developed a new transparent conductive film EXCLEAR for use in displays and touch-panels, offering a high level of transmittance, flexible performance and a wide range of sheet resistance, incorporating silver halide photographic technologies. Fujifilm has started distributing samples in a lead-up to its commercial launch scheduled for this autumn. Transparent conductive films are highly functional materials, and essential in displays and touch-panels as a transparent electrode. With its application expanding, e.g. electronic paper, organic EL light emitting elements and displays, the demand is growing for transparent conductive films that are lightweight or highly flexible. Currently, ITO (indium tin oxide) films are generally used for transparent conductive films. However, they are easy to crack when flexed, and have a limited range of sheet resistance, thereby sometimes failing to achieve desired performance, and posing various challenges that may hinder future growth. In addition, since indium is a rare metal, there are concerns for its eventual depletion or skyrocketing of prices. This film incorporates findings from functional material research, precision thin coating technology and image-processing technology conducted over many years for the development of photographic films and flat-panel display materials. Fine-pitch silver patterns and transparent conductive materials are placed on a clear PET (polyethylene terephthalate) substrate to achieve a high level of transmittance, flexible performance and a wider range of sheet resistance.
• The precision digital exposure technology is used to carry out patterning of silver lines of various thickness and density over a substrate coated with highly light sensitive silver halide materials This silver patterning has enabled broader sheet resistance ranging from ultra-low (0.2Ω/?) to high (several thousand Ω/?) with the combination of inorganic / organic transparent conductive materials.
• Combining flexibility-controlled silver halide and transparent conductive materials on a film has achieved advanced flexible performance.
• This film demonstrates a high transmittance of 80% or above, which is equivalent to that of the ITO-based transparent conductive film.
• Since the film can be supplied in a roll, it lends itself to volume production and addition of composite functions.
Taking advantage of these properties, the film will be deployed in a wide range of areas, e.g. as an alternative to ITO-based films currently used on various displays and flat light sources, or as a transparent conductive film for products that require flexible performance (touch-panels, electronic paper) and high conductivity (solar cells).
Japan - Chiba University and Chisso Corp. jointly developed a material of liquid transparent conductive film for liquid crystal displays. It can be gummed on plastic unlike the conventional conductive film, and it has paved the way to develop electronic paper. The development team will increase the conductivity and build a trial product of electronic paper in a few years. The transparent conductive film is vital for liquid crystal displays and gummed on between glass and liquid crystal to conduct electricity. Most conductive films use indium tin oxide and build a transparent film on the glass surface by applying high voltage. Theoretically, it is possible to build a bendable liquid crystal display by employing plastic instead of glass. However, the existing technology cannot prevent plastic from melting because it builds a film at several hundred degrees centigrade. The development team developed a transparent liquid conductive film can be applied to plastic. The plastic will become a bendable conductive film if it is dried after this material is applied to it. The team members first melted a conductive polymer to liquefy it. Although the polymer is green, they made the liquid transparent by adding tin to generate transparent rust. Because the newly-developed liquid conductive film has lower conductivity than the existing conductive film that uses indium tin oxide, it cannot be used for the liquid crystal TV that needs high voltage. However, the members told that they can improve conductivity of the newly-developed film by using another metal in place of tin. They are planning to build a trail product of electronic paper and liquid crystal TV in a few years.
 
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