Retardation measurement

Flame retardant unsaturated polyesters containing chlorine or bromine Chlorendic acid or dibromoneopentyl glycol (60-70%) with addition of antimony trioxide (8 03), ZnSnOj, or triethyl phosphate as flame retarders, increases the LOl by up to 40% Inherent fire retardancy measured [39]... 

Measurement of the infrared (IR) absorption cannot be used to evaluate the anisotropy of the alignment layer of actual display devices because their substrates are made of glass and are not transparent to IR radiation. However, optical retardation measurements using ellipsometry for visible light can evaluate the anisotropy of a thin membrane, and can be used to evaluate the alignment of the molecules in the alignment material after rubbing [5, 23, 24, 29, 50, 51]. 

Although a transmittance IR absorption spectrum measurement evaluates the bulk of the alignment material, the distribution of the alignment of the molecules can he determined hy a qualitative analysis by changing the polar and azimuthal angles of the sample. The relationship between the dichroism of the polyimide and its thickness was studied using polarized infrared absorption measurements, and it was found that the dichroism was consistently less than 17 nm and decreased when the polyimide becomes thicker [22]. From these results and retardation measurements, a molecular distribution model was proposed which shows uniform anisotropy to some depth, lower anisotropy in deeper areas, and isotropy in areas which are even deeper [22]. 

The PME is more complicated than the RAE, since the modulation amplitude of the PEM must be calibrated and its small but significant static retardation measured at all wavelengths used. Eurthermore, the frequency of the PEM is about 500 times faster than the rotation speed of the RAE this improves the time resolution to 1 ms, but requires faster electronics for data collection. In its normal configuration discussed above, the PME can measure S and either N or C. However, if the PSD polarizer is replaced with a Wollaston prism polarizer and both channels are detected (measuring a total of four quantities), then it is possible to measure N, S, and C simultaneously. This implementation is called the two-channel spectroscopic polarization modulation ellipsometer (2C-SPME). 

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