Non-contact alignment

Table 2.4 Polyimides (lA-19) used as alignment layers, especially as non-contact alignment layers, for LCDs.

Figure 2.19 Schematic representation of the anisotropic crosslinking of a photoreactive coumarin polymer by the action of polarised UV light to produce an anisotropic network as a non-contact alignment layer. E indicates the polarisation direction of the incident beam. ...

Figure 6.7 Plot of the relative intensity (A.U.) of polarised electroluminescence against wavelength (nm) of a bilayer OLED consisting of an electron-transport and emission layer represented by a nematic network formed by polymerising compound (86) with isotropic UV light and a combined hole-transport and a coumarin non-contact alignment layer doped with 4.4,4-tris(naphthylyl)-N-(phenylamino) triphenylamine.

In this Chapter an overview of the state of the art of liquid crystal applications is given, in particular the current market development for LCD s and the recent developments using non contact alignment techniques like photoalignment and ion-beam alignment. 

The investigation of the degree of molecular alignment in the thin films was performed by AFM measurements in contact as well as in non-contact mode. Figure 5.6a and b presents contact AFM images of the spin-coated DCNDBQT film on Ti02. 

Figure Bl.19.26. Highly resolved, non-contact AFM image of the Ti02(l 10)-(1 x i) surface (8.5 x 8.5 nm ) with a single step. The two-dimensional order of the bright spots (0.65 x 0.3 nm ) reproduces the alignment of the bridging oxygen atoms. (Taken from [121], figure 3.)...

In nondoped films of PEO-based azo LCBCs with well-defined structures macroscopic parallel patterning of PEO nanocylinders can be obtained easily in an arbitrary area by simple and convenient photocontrol. Furthermore, the non-contact method might provide the opportunity to control nanostructures even on curved surfaces. On the basis of the principle of SMCM, the orientation of microphase-separated nanocylinders dispersed in azo LC matrix should agree with the alignment direction of azo mesogens. The azo molecules can be 3-D... 

The development in rotating machinery alignment is from left to right in the above comparison. Thus, the methods used today are typically relative static methods using manual contact type procedures. Development is towards dynamic absolute or relative procedures of the automated non-contact type (Bayly et al., 1990). To expand on the underlying principles, some of the better known alignment procedures will be briefly discussed in the following. 

As video theodolites eliminate the manual target pointing, they provide a completely automatic system fen measurements and computations, with high operational speed and no human error involved (Kahmen, 1991). A videotheodolite system can be used for relative or absolute alignment and it provides a non-contact, automatic, dynamic method for hot alignment. 

Some of the typical applications were already mentioned in the second section when the alignment methods were discussed. The practical example presented in the sequel illustrates some of the advantages of the newly emerging alignment technology it is a non-contact, hot alignment, semi-automatic (with full automation possibility) and dynamic. 

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