Absorption-type transflective LCDs

In the abovementioned transflective guest-host LCD, the inner quarter-wave film is put between the transflector and the guest-host layer. There are two optional positions for the trans-flector. If the transflector is located inside the LC ceU, then the quarter-wave film should also be 

In the abovementioned two absorption-type transflective LCDs, only one polarizer is employed instead of two. Therefore, the overall image in both T- and R-modes is relatively bright. However, due to the hmited dichroic ratio of the employed dye molecules (DR 15 1), a typical contrast ratio of the guest-host LCD is around 5 1, which is inadequate for high-end full color LCD applications [29]. Thus, the absorption-type transflective LCDs only occupy a small portion of the handheld LCD market. 

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Figure 9.6 Schematic coiifiguialions and operating principles of two absorption-type transflective LCDs with (a) nematic phase LC (host) and dye (guest) mixtures, and (b) cholesteric phase LC (host) and dye (guest) mixtures. Zhu 2006. Reproduced with permission from IEEE.

Even if the polarizer for this reflection type lets the absorption axis be at right angles like two pieces of normal polarization films because it behaves as a circularly polarizing film as described above, light leaks out. Therefore, it caimot regulate the optical properties of the broadband XjA plate by the normal method. In addition, these optical properties do not correlate with the electro-optical properties of the reflective- and transflective-type LCDs, and this will hinder the causal elucidation of defective devices. 

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