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Anisotropic retardation layers for display devices
| Details |
Inventors: Sahouani, Hassan; Vogel, Kim Marie;
Assignee: 3M Innovative Properties Company (St. Paul, MN)
Primary Examiner: Kelly; C. H.
Assistant Examiner:
Attorney, Agent or Firm: Gwin, Jr.; H. Sanders
A composition that includes the following compounds: ##STR1## wherein R.sup.1, which may be the same or different, is a hydrophilic group; R.sup.2, which may the same or different, is selected from the group consisting of electron donating groups, electron withdrawing groups, and electron neutral groups; R.sup.3 is a positively charged heteroaromatic ring linked to the triazine backbone through a nitrogen atom in the R.sup.3 ring; and X.sup.- is a counterion. If R.sup.3 is an unsubstituted pyridine, the counterion X.sup.- may be selected from any counterion other than Cl.sup.- and OH.sup.-. Otherwise, the counterion X.sup.- may be selected from any counterion. The compound may be applied to a substrate to form a birefringent optical retardation device. The retardation device may be used in display devices such as computers and the like to correct the phase and polarization states of the display's emitted light and improve image quality at viewing angles away from the normal. |
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DETAILED DESCRIPTION The present invention is an optically anisotropic layer which may be applied on an isotropic or anisotropic supporting substrate to provide a birefringent optical retardation device.
The anisotropic layer of the present invention comprises an aqueous composition of matter comprising a compound with the general structure below: ##STR3## In these formulae I, the R.
sup.
1 s, which may be the same or different, are hydrophilic groups.
The R.
sup.
2 s can be independently chosen to be hydrogen, an electron donating group, an electron withdrawing group or an electron neutral group.
R.
sup.
3 is a positively charged, substituted or unsubstituted heteroaromatic ring linked to the triazine backbone through a nitrogen atom within the ring of R.
sup.
3.
The substituent for R.
sup.
3 may be selected to determine the properties of the anisotropic layer, for example, the desired color of the layer.
If R.
sup.
3 is an unsubstituted pyridine, X.
sup.
- is a counterion that may be selected from any counterion except Cl.
sup.
- and OH.
sup.
-.
Otherwise, the counterion X.
sup.
- may be selected from any counterion.
Compounds with the above structure are soluble in basic aqueous solutions having a suitably adjusted pH.
Compounds suitable for the anisotropic layer of the present invention form highly ordered structures when coated as an aqueous solution and dried on a substrate.
The materials in the layers of the present invention have very high optical anisotropies, and may be coated in very thin layers, thereby minimizing thickness contributions to undesirable optical properties in display devices.
The anisotropic layer of the present invention has a refractive index in the thickness, or z, direction of the layer that is slightly less than or substantially equal to one of the refractive indices n.
sub.
x and n.
sub.
y in the plane of the layer.
The present invention further includes a birefringent optical retardation component which comprises at least one layer of the anisotropic material on a suitable substrate
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