Method for producing orientation layers for liquid crystal displays and liquid crystal displays having orientation layers

DETAILED DESCRIPTION OF THE INVENTION The invention is explained in greater detail with reference to the following examples and the FIGURE, in which one embodiment of a liquid crystal display according to the present invention is shown.
EXAMPLE 1 Orientation Layers of Polybenzoxazole For the preparation of a polybenzoxazole-prepolymer, 6.
1 parts by weight isophthalic acid dichloride in 20 parts by volume cyclohexanone are added dropwise within about 30 minutes at a temperature of -5.
degree.
to -20.
degree.
C.
, with vigorous stirring, to a solution of 6.
5 parts by weight 3,3'-dihydroxybenzidine in 50 parts by volume dimethylacetamide and 9 parts by volume pyridine.
After further stirring for 3 hours at room temperature, the viscous reaction solution is left to stand overnight.
The solution then is added dropwise to 1000 parts by volume of water.
The resin precipitated is then separated, washed with water and methanol and dried in a vacuum at about 60.
degree.
C.
With a 10-% solution of the so prepared prepolymer in N-methylpyrrolidone, which solution also contains as an adhesion agent 1%, referred to the solid resin, of a vinylalkoxysilane, such as vinyl-tris (.
beta.
-methoxyethoxy)-silane, the carrier plates provided with the electrodes are coated by the so-called roller-coating method.
Border zones to which the cemented frame or the glass solder seal is applied later can be kept free by structured rollers or templates.
The preolymer solution also can be applied to the electrodes by brushing-on, immersion or spraying.
After the coating, the film coating is dried at about 100.
degree.
C.
and subsequently annealed at temperatures of about 270.
degree.
C.
and 400.
degree.
C.
(one-half hour at each temperature), whereby homogeneous layers with a layer thickness of 0.
04 .
mu.
m are obtained.
By rubbing with a brush, the grooves necessary for the orientation of the liquid crystals are then generated on the surface of the polybenzoxazole layer.
The orientation treatment, however, also can be performed with a cloth, but the rubbing must always be done in a constant direction using this method