Laser-Addressed Devices

More recently, disiloxane units have been incorporated [ 16] into the alkyl chain of 4-cyano-4 -alkoxybiphenyls. The disiloxane unit (in compound 5) appears to stabilize the smectic layer arrangement, such that even in short chain length homologs, only SmA phases occur (Table 4). X-ray analysis indicates [17] that the siloxane units group together into a bilayer arrangement. 

Although most applications use smecto-gens of positive dielectric anisotropy, there are some wide temperature range smecto-gens of negative dielectric anisotropy. Some notable examples are the lateral cyano phenyl benzoates [18] (6) and the 2,3-difluoro-biphenyl carboxylic acid esters [19], e.g.. 

Laser-addressing of liquid crystal films was initially [21 ], but only briefly, carried out on N and cholesteric films in 1972 it was soon determined that SmA phases offered [7, 8] advantages, such as better bistability, higher resolution [22], and the possibility of selective erasure. Considerable effort was expended to optimize this technology during the 1970s and 1980s, and commercial devices were developed. 

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Mixtures of mesogens often exhibit spread transition temperatures which manifest themselves as biphasic regions for some applications, such as laser-addressed devices, this feature is undesirable. To overcome this problem, several mixtures have been specifically developed [11] to have narrow temperature range transitions from Sm to N and from N to isotropic, i. e., S6 in Table 2. 

Additionally, similar laser-addressed devices could be used as a mask for circuit board manufacture. 

HATn materials, electrical properties 782 ff He-Ne laser addressed devices 478 head-tail equivalence, antiferroelectrics 665 f heal capacity, OCB 450 Heck coupling, hydrocarbon cores 707 Heilmeier displays... 

Williams domains, dynamic scattering 243 ff write mechanism, low frequency 390 write speed, laser addressed devices 478 Wulf model, smectogens 417... 

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