Optical compensator for improved gray scale performance in liquid crystal display

A liquid crystal display for viewing at various angles with respect to a normal axis perpendicular to the display, comprising:

• a polarizer layer having an absorbing axis;
• an analyzer layer having an absorbing axis substantially perpendicular to the absorbing axis of the polarizer layer;
• a liquid crystal layer disposed between the polarizer layer and the analyzer layer and having a director exhibiting an azimuthal twist through the layer with respect to the normal axis;
• a first electrode proximate to a first major surface of the liquid crystal layer;
• a second electrode proximate to a second major surface of the liquid crystal layer, 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;
• and
• a compensator, including:
• a positively birefringent O-plate compensator layer disposed between the polarizer layer and the analyzer layer with its optic axis oriented at a substantially oblique angle of between 25 and 65 degrees with respect to the normal axis;
• and
• a positively birefringent A-plate compensator layer disposed between the liquid crystal layer and the O-plate layer, the A-plate layer being oriented with its optic axis relative to the optic axis of the O-plate layer such that retardation of light passing through the compensator at normal incidence is minimized.

A liquid crystal display for viewing at various angles with respect to a normal axis perpendicular to the display, comprising:

• a polarizer layer having an absorbing axis;
• an analyzer layer having an absorbing axis substantially perpendicular to the absorbing axis of the polarizer layer;
• a liquid crystal layer disposed between the polarizer layer and the analyzer layer and having a director exhibiting an azimuthal twist through the layer with respect to the normal axis;
• a first electrode proximate to a first major surface of the liquid crystal layer;
• a second electrode proximate to a second major surface of the liquid crystal layer, 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;
• and
• a compensator, including:
• a positively birefringent O-plate compensator layer disposed between the polarizer layer and the liquid crystal layer with its optic axis oriented at a substantially oblique angle of between 25 and 65 degrees with respect to the normal axis;
• a first positively birefringent A-plate compensator layer disposed between the polarizer layer and the O-plate layer;
• and
• a second positively birefringent A-plate compensator layer disposed between the O-plate layer and the liquid crystal layer, the first and second A-plate layers being oriented with their optic axes relative to the optic axis of the O-plate layer such that retardation of light passing through the compensator at normal incidence is minimized.

A liquid crystal display for viewing at various angles with respect to a normal axis perpendicular to the display, comprising:

• a polarizer layer having an absorbing axis;
• an analyzer layer having an absorbing axis substantially perpendicular to the absorbing axis of the polarizer layer;
• a liquid crystal layer disposed between the polarizer layer and the analyzer layer and having a director exhibiting an azimuthal twist through the layer with respect to the normal axis;
• a first electrode proximate to a first major surface of the liquid crystal layer;
• a second electrode proximate to a second major surface of the liquid crystal layer, 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;
• and
• a compensator, including:
• a positively birefringent O-plate compensator layer disposed between the polarizer layer and the liquid crystal layer with its optic axis oriented at a substantially oblique angle of between 25 and 65 degrees with respect to the normal axis;
• a first positively birefringent A-plate compensator layer disposed between the O-plate layer and the liquid crystal layer;
• and
• a second positively birefringent A-plate compensator layer disposed between the liquid crystal layer and the analyzer layer, the first and second A-plate layers being oriented with their optic axes relative to the optic axis of the O-plate layer such that retardation of light passing through the compensator at normal incidence is minimized.

A liquid crystal display for viewing at various angles with respect to a normal axis perpendicular to the display, comprising:

• a polarizer layer having an absorbing axis;
• an analyzer layer having an absorbing axis substantially perpendicular to the absorbing axis of the polarizer layer;
• a liquid crystal layer disposed between the polarizer layer and the analyzer layer and having a director exhibiting an azimuthal twist through the layer with respect to the normal axis;
• a first electrode proximate to a first major surface of the liquid crystal layer;
• a second electrode proximate to a second major surface of the liquid crystal layer, 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;
• and
• a compensator, including:
• a positively birefringent O-plate compensator layer disposed between the polarizer layer and the liquid crystal layer with its optic axis oriented at a substantially oblique angle with respect to the normal axis;
• a positively birefringent A-plate compensator layer disposed between the O-plate layer and the liquid crystal layer, the A-plate layer being oriented with its optic axis relative to the optic axis of the O-plate layer such that retardation of light passing through the compensator at normal incidence is minimized;
• and
• a negatively birefringent C-plate compensator layer disposed between the A-plate layer and the liquid crystal layer.

A liquid crystal display for viewing at various angles with respect to a normal axis perpendicular to the display, comprising:

• a polarizer layer having an absorbing axis;
• an analyzer layer having an absorbing axis substantially perpendicular to the absorbing axis of the polarizer layer;
• a liquid crystal layer disposed between the polarizer layer and the analyzer layer and having a director exhibiting an azimuthal twist through the layer with respect to the normal axis;
• a first electrode proximate to a first major surface of the liquid crystal layer;
• a second electrode proximate to a second major surface of the liquid crystal layer, 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;
• and
• a compensator, including:
• a first positively birefringent O-plate compensator layer disposed between the polarizer layer and the liquid crystal layer with its optic axis oriented at a substantially oblique angle with respect to the normal axis;
• a second positively birefringent O-plate compensator layer disposed between the first O-plate layer and the liquid crystal layer, with its optical axis oriented at a substantially oblique angle with respect to the normal axis and such that the azimuth angles of the first and second O-plate layers are crossed;
• a first positively birefringent A-plate compensator layer disposed between the polarizer layer and the first O-plate layer;
• and
• a second positively birefringent A-plate compensator layer disposed between the second O-plate layer and the liquid crystal layer, the first and second A-plate layers being oriented with their optic axes relative to the optic axis of the O-plate compensator layer such that retardation of light passing through the compensator at normal incidence is minimized.

A liquid crystal display for viewing at various angles with respect to a normal axis perpendicular to the display, comprising:

• a polarizer layer having an absorbing axis;
• an analyzer layer having an absorbing axis substantially perpendicular to the absorbing axis of the polarizer layer;
• a liquid crystal layer disposed between the polarizer layer and the analyzer layer and having a director exhibiting an azimuthal twist through the layer with respect to the normal axis;
• a first electrode proximate to a first major surface of the liquid crystal layer;
• a second electrode proximate to a second major surface of the liquid crystal layer, 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;
• and
• a compensator, including:
• a first positively birefringent O-plate compensator layer disposed between the polarizer layer and the liquid crystal layer with its optic axis oriented at a substantially oblique angle with respect to the normal axis;
• a second positively birefringent O-plate compensator layer disposed between the liquid crystal layer and the analyzer layer with its optic axis oriented at a substantially oblique angle with respect to the normal axis;
• a positively birefringent A-plate compensator layer disposed between the polarizer layer and the first O-plate layer, the A-plate layer being oriented with its optic axis relative to the optic axis of the first O-plate layer such that retardation of light passing through the compensator at normal incidence is minimized;
• and
• a first negatively birefringent C-plate compensator layer disposed between the first O-plate layer and the liquid crystal layer;
• and
• a second negatively birefringent C-plate compensator layer disposed between the liquid crystal layer and the second O-plate layer.