Patterned photoalignment layer

Fig. 9.11. Polarisation microscope photographs of test displays composed of a patterned photoalignment layer (Staralign 2110 from Vantico) and a uniformly rubbed layer, filled with LC mixture MLC 7700 000 (Merck). The polarisers are crossed, (a) Stripe pattern with line widths of 10 and 3 pm, (b) checkerboard pattern of 10x10 and 100x100 pm.

Fig. 9.20. A schematic of the molecular order of the reactive LC molecules after director patterning. The order is forced to be planar in two domains by a dual domain photoalignment layer. The domains exhibit identical dAn values, but the effective retardation depends on the angle between the main optical axis and the transmissive axis of the polariser.

In addition, if it is possible to have patterned alignment layers, different LC modes for the subpixels can be made and optimal performance transflective displays can then be achieved. These novel designs all require patterning of either the polarizer or the retardation film, or the alignment layers. They can all be accomplished with photoalignment [34]. One such novel design that maintains a uniform cell gap is shown in Figure 5.24. 

In the previous sections we have discussed the use of the photoalignment techniques, in order to improve specific optically active parts of LCDs. We have shown that for the LC layer that forms the optical valve both in-plane and out-of-plane orientation is important to attain the correct switching behaviour. This is, however, not sufficient with respect to the front-of-screen performance, like contrast, brightness and viewing angle. In order to improve these properties of LCDs, patterned alignment for use in multidomain LCDs and retardation layers was discussed for respectively large and small... 

A new impetus in the application of photosensitive media appeared when PVCN was discovered as an LC photoaligning substance [19]. The concept for the design of a photo-patternable hybrid linear photo-polymerizable (HLPP) configuration was proposed by Schadt et al. (Figure 5.17) [20, 21]. The HLPP layers include a linearly photo-polymerized polymer (LPP) as the aligning layer and an LPP-LCP phase retarder in one compact implementation (Figure 5.17). 

An exposure system for fabricating optical film by exposing a pattern such as for photoalignment, where the optical film has a photosensitive layer and a substrate. The exposure system directs an exposure beam from a light source to a reflective polarization modulation device. The modulated exposure beam is then reflected onto the photosensitive medium for forming a pattern onto the optical film. 

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