Organic polymer O-plate compensator for improved gray scale performance in twisted nematic liquid crystal displays

An optical compensator comprising:

• a first positively birefringent O-plate compensator layer of liquid crystal polymer having its optical symmetry axis oriented at an oblique tilt angle with respect to a major surface of the first O-plate layer;
• and
• a second positively birefringent O-plate compensator layer disposed on the first O-plate layer, wherein the second O-plate layer comprises a liquid crystal polymer having its optical symmetry axis oriented at an oblique tilt angle with respect to a major surface of the second O-plate layer,
• wherein the projections of the optical symmetry axes of the first and second O-plate layers, respectively, onto a major surface of the compensator are crossed with respect to each other.

A liquid crystal display adapted to be viewed at various angles with respect to a normal axis perpendicular to a major surface of the display, comprising:

• a polarizer layer;
• an analyzer layer;
• a liquid crystal layer disposed between the polarizer layer and the analyzer layer;
• a first electrode disposed between the polarizer layer and the analyzer layer and proximate to a first major surface of the liquid crystal layer;
• a second electrode disposed between the polarizer layer and the analyzer layer and proximate to a second major of the liquid crystal layer surface opposing the first major surface, the first and second electrodes being adapted to apply a voltage across the liquid crystal layer when the electrodes are connected to a source of electrical potential;
• a first positively birefringent O-plate compensator layer disposed between the polarizer layer and the analyzer layer, wherein the first O-plate layer comprises a liquid crystal polymer of a photopolymerized material with its optical symmetry axis oriented at an oblique tilt angle with respect to a major surface of the first O-plate layer;
• a second positively birefringent O-plate compensator layer disposed between the polarizer layer and the analyzer layer, wherein the second O-plate layer comprises a liquid crystal polymer of a photopolymerized material with its optical symmetry axis oriented at an oblique tilt angle with respect to a major surface of the second O-plate layer;
• and
• a positively birefringent A-plate compensator layer disposed between the polarizer layer and the analyzer layer,
• wherein the projections of the optical symmetry axes of the first and second O-plate layers, respectively, onto the major surface of the display are crossed with respect to each other such that the angle difference between the azimuthal angles of the first and second O-plate layers is between 45 degrees and 135 degrees.

An optical compensator comprising:

• a first positively birefringent O-plate compensator layer comprised of a liquid crystal polymer of a photopolymerized material having its optical symmetry axis oriented at an oblique tilt angle with respect to a major surface of the first O-plate layer;
• a second positively birefringent O-plate compensator layer disposed on the first O-plate layer, wherein the second O-plate layer comprises a liquid crystal polymer of a photopolymerized material having its optical symmetry axis oriented at an oblique tilt angle with respect to a major surface of the second O-plate layer;
• and
• a positively birefringent A-plate compensator layer disposed on the second O-plate layer,
• wherein the projections of the optical symmetry axes of the first and second O-plate layers, respectively, onto a major surface of the compensator are crossed with respect to each other such that the angle difference between the azimuthal angles of the first and second O-plate layers is between 45 degrees and 135 degrees.