Method and apparatus for improving the viewing angle of an LCD screen by twisting the polarizers and compensating structures

A display device having a liquid crystal cell, the liquid crystal cell comprising:

• a layer of twisted nematic liquid crystal placed between first and second polarizers,
• a first compensating structure disposed between the layer of twisted nematic liquid crystal and said first polarizer arranged to receive light from a light source, and a second compensating structure disposed between the layer of twisted nematic liquid crystal and said second polarizer arranged away from the light source, wherein
• each of said first and second compensating structures includes a layer of a negative uniaxial birefringent material having an extraordinary axis perpendicular to a plane of the cell, said layer of the negative uniaxial birefringent material superimposed with a layer of a negative uniaxial birefringent material having an extraordinary axis inclined with respect to a normal to the plane of the cell;
• said second compensating structure is oriented in a direction opposite to a projection of the inclined extraordinary axis to the plane of the cell;
• pass directions of the first and second polarizers are separated by an angle of 90+A degrees, wherein A is not zero;
• and
• orientations of said first and second compensating structures are separated by an angle of 90+B degrees, wherein B is not zero.

A display device having a liquid crystal cell, the liquid crystal cell comprising:

• a layer of twisted nematic liquid crystal placed between first and second polarizers;
• a first compensating structure disposed between the layer of twisted nematic liquid crystal and said first polarizer, and a second compensating structure disposed between the layer of twisted nematic liquid crystal and said second polarizer, wherein
• each of said first and second compensating structures includes a layer of a negative uniaxial birefringent material having an extraordinary axis perpendicular to a plane of the cell, said layer of the negative uniaxial birefringent material superimposed with a layer of a negative uniaxial birefringent material having an extraordinary axis inclined with respect to the normal to the plane of the cell;
• an orientation of said negative uniaxial birefringent material of said second compensating structure is parallel to a pass direction of said first polarizer;
• each of said compensating structures is oriented in respective directions opposite to respective projections of the inclined extraordinary axes to the plane of the cell;
• the pass direction of said first polarizer and a pass direction of said second polarizer are separated by an angle of 90+A degrees, wherein A is not zero;
• and
• orientations of said first and second compensating structures are separated by an angle of 90+B degrees, wherein B is not zero.