Alignment layer with reactive mesogens for aligning liquid crystal molecules

A solution for preparing an alignment layer for aligning a layer of liquid crystal molecules, said alignment layer comprising:

• (a) a polymer film formed from a polymer or a polymer precursor and (b) at least one reactive mesogen additive in monomeric, oligomeric or polymeric form within said polymer film, wherein said at least one reactive mesogen additive is not said polymer or said polymer precursor used to form said polymer film, said solution comprising:
• a solvent, said at least one reactive mesogen additive, and a polymer or a polymer precursor, said polymer or polymer precursor comprising:
• a polyimide polymer or a precursor of said polyimide polymer,
• wherein in said solution the concentration of said at least one reactive mesogen relative to said polymer or polymer precursor before forming said film is 0.5 to 4% by weight, and said at least one reactive mesogen additive is miscible with said polymer film formed from said polymer or polymer precursor, wherein said at least one reactive mesogen additive is one of the following formulae:
• wherein
• P1, P2 and P3 are each, independently of each other, a polymerizable group, Z1 and Z2 are each, independently of each other, —O—, —S—, —CO—, —COO—, —OCO—, —O—OCO—, —OCH2—, —CH2O—, —CH2CH2—, —C≡C—, —CH═CH—COO—, —OCO—CH═CH— or a single bond,
• Z3 and Z4 are each, independently of each other, —COO—, —OCO—, —CH2CH2—, —CH2O—, —OCH2—, —CH═CH—, —CH═CH—, —C≡C— or a single bond,
• Z5 and Z6 are each, independently of each other, —O—, —COO—, —OCO—, —CH2CH2—, —CH2O—, —OCH2— or a single bond,
• Y1 and Y2 are each, independently of each other, a polar group,
• R1 and R2 are each, independently of each other, an unpolar alkyl or alkoxy group,
• A, B, C and D are each, independently of each other, 1,4-phenylene that is optionally mono-, di- or trisubstituted by L1, L2, L3, L4, L5, L6 or 1,4-cyclohexylene,
• L1, L2, L3, L4, L5 and L6 are each, independently of each other, H, F, Cl, CN or an optionally halogenated alkyl, alkoxy, alkylcarbonyl, alkoxycarbonyl or alkoxycarbonyloxy group with 1 to 7 C atoms,
• r is 0, 1, 2, 3 or 4,
• x and y are each, independently of each other, an integer from 1 to 12,
• z is 1, 2 or 3, and
• g1, g2, g3 and g4 are each, independently of each other, a single bond, —O—, —COO— or —OCO—.