Thermally addressed displays

To some extent, development of smectic materials has been slow and usually come as an off shoot of work on nematics. For example, the binary mixture shown in (38) exhibits a room temperature smectic A, a short range nematic, and is of positive dielectric anisotropy.Such properties may be used in thermally addressed displays where a transition from a scattering to a clear state forms the optical effect. This transition may also be effected by an electric field. Obviously, more work on useful smectics is required although their inherent high viscosity is a problem. 

D. Maydan, H. Melchior and F. Kahn, Liquid Crystal Graphic Displays Thermally Addressed by Infrared Laser Beams, IEEE Conference Record of 1972 Conference on Display Devices,... 

G. N. Taylor and F. J. Kahn, Materials Aspects of Thermally Addressed Smectic and Cholesteric Liquid Crystal Storage Displays, J. Appl. Phys. Vol. 45, No. 10, 1974, pp. 4330-4338. 

A. G. Dewey, et al., A 2000 Character Thermally-Addressed Liquid Crystal Projection Display, Proc. 1977 SID Inti. Symp., pp. 108-109. 

Thermally Addressed Electrically Erased High Resolution Liquid Crystal Matrix Display... 

Figure 49. Construction and operation of a thermally addressed liquid crystal matrix display (after reference [112]).

A crucial point that must be addressed concerns the thermal stability and the fatigue phenomenon observed in the chromophores. It is a fact that many photo-chromic compounds are irreversibly degraded upon long exposure to light, thus limiting their use for various applications. Major advances in the preparation and performance of photochromic materials have been made in the past five years. Irie et al.11271 have recently developed new photochromic compounds, 1,2-diarylethenes, which display photochromic behavior with unchanged intensity even after 104 coloration decoloration cycles. 

Not all elements are amenable to thermal ionization, positive or negative. It is obvious that elements whose natural state is a gas cannot be addressed by this technique. In addition, some elements are too volatile others have a first ionization potential too high, and a few, such as mercury, display both characteristics. Generally speaking, solid elements with first ionization potentials below about 7.5 eV can be analyzed through measurement of positive ion beams. Use of silica gel... 

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