Claims
- 1. A normally white twisted nematic liquid crystal display comprising:
- a liquid crystal layer for twisting at least one normally incident visible wavelength of light from about 80.degree. to 100.degree. as it passes therethrough when said liquid crystal layer is in substantially the off-state thereby defining a twisted nematic display;
- a pair of negative retarders sandwiching said liquid crystal layer therebetween;
- a pair of positive retarders sandwiching both said liquid crystal layer and said negative retarders therebetween; and
- wherein the retardation value of each of said negative retarders is from about -60 to -200 nm and the retardation value of each of said positive retarders is from about 80 to 200 nm.
- 2. The display of claim 1, wherein the retardation value of each of said negative retarders is from about -80 to -150 nm.
- 3. The display of claim 1, wherein n.sub.x =n.sub.y >n.sub.z where n.sub.x, n.sub.y, and n.sub.z are indices of refraction and the "z" direction is substantially perpendicular to the planes defined by said negative retarders and the "x" and "y" directions are substantially parallel to the planes defined by said negative retarders for said negative retarders so that the optical axis of each of the negative retarders is substantially perpendicular to the planes of the retarders, whereby the optical axis of each said negative retarder is substantially perpendicular to the optical axis of each said positive retarder.
- 4. The display of claim 3, wherein the retardation value of each of said negative retarders is from about -100 to -120 nm.
- 5. The display of claim 4, wherein the retardation value of each of said positive retarders is from about 120 to 160 nm.
- 6. The display of claim 1, wherein the thickness of said liquid crystal layer is from about 4.8 to 6.0 .mu.m and the birefringence .DELTA.n of said liquid crystal is from about 0.075 to 0.095 at room temperature, and wherein the display outputs contrast ratios to the viewer of at least about 20:1 or 20 at horizontal viewing angles along the 0.degree. vertical viewing axis of about .+-.60.degree. when a driving voltage of from about 6.0 to 6.1 volts is applied to said liquid crystal layer.
- 7. The display of claim 6, wherein said display outputs contrast ratios of at least about 30:1 or 30 at horizontal viewing angles along the 0.degree. vertical viewing axis of about .+-.50.degree., and of at least about 20:1 or 20 at vertical viewing angles along the 0.degree. horizontal viewing axis of about 0.degree. to +40.degree. when said 6.0 to 6.1 driving voltage is applied.
- 8. The display of claim 6, wherein a buffing direction on a front side of the liquid crystal layer is substantially parallel to both a rear polarizer transmission axis and the optical axis of the rear positive retarder.
- 9. A normally white twisted nematic liquid crystal display comprising:
- a liquid crystal layer for twisting at least one normally incident visible wavelength of light from about 80.degree. to 100.degree. as it passes therethrough when said liquid crystal layer is in substantially the off-state thereby defining a twisted nematic display;
- a pair of negative retarders sandwiching said liquid crystal layer therebetween;
- a pair of positive retarders sandwiching said liquid crystal layer therebetween; and
- wherein the ratio of the positive retardation value to the absolute value of the negative negative retardation value on each side of said liquid crystal layer is from about 1:1 to 2:1.
- 10. The display of claim 9, wherein said ratio is from about 1.2:1 to 1.5:1, and the negative retarders are defined by the characteristic n.sub.x =n.sub.y >n.sub.z where n.sub.x, n.sub.y, and n.sub.z are indices of refraction and the "z" direction is substantially perpendicular to the planes defined by said negative retarders and the "x" and "y" directions are substantially parallel to the planes defined by said negative retarders, whereby the optical axes of said negative retarders are substantially perpendicular to said planes defined by said negative retarders.
- 11. The display of claim 10, wherein the retardation value of each of said negative retarders is from about -80 to -140 nm and the retardation value of each of said positive retarders is from about 100 to 200 nm.
- 12. A method of making a twisted nematic liquid crystal display comprising the steps of:
- providing a pair of negative retarders defined by n.sub.x =n.sub.y >n.sub.z where n.sub.x, n.sub.y, and n.sub.z are indices of refraction and the "z" direction is substantially perpendicular to the planes defined by said negative retarders and the "x" and "y" directions are substantially parallel to the planes defined by said negative retarders so that the optical axis of each of said negative retarders is substantially perpendicular to the planes defined by the negative retarders;
- providing a pair of positive uniaxial retarders;
- disposing a twisted nematic liquid crystal layer between said pair of negative retarders and between said pair of positive retarders; and
- disposing said pair of negative retarders between said pair of positive retarders so that the resulting display outputs contrast ratios of at least about 20:1 or 20 at horizontal viewing angles along the 0.degree. vertical viewing axis of about .+-.40.degree..
- 13. The method of claim 12, further comprising the step of providing retardation values for said retarders so that the display outputs contrast ratios of at least about 80:1 or 80 at horizontal viewing angles along the 0.degree. vertical viewing axis of about .+-.30.degree..
- 14. The display of claim 13, further comprising the steps of providing each of said negative retarders with a retardation value of from about -60 to -200 nm and each of said positive retarders with a retardation value of from about 80 to 200 nm.
- 15. The method of claim 14, further comprising the steps of arranging optical axes of said positive retarders so that the optical axis of each said positive retarder is angled from the transmission axis of the adjacent polarizer from about 0.degree. to 8.degree. so as to adjust the position of the high contrast viewing zone output by the display.
- 16. A twisted nematic liquid crystal display comprising:
- a twisted nematic liquid crystal layer for twisting at least one visible wavelength of normally incident light from about 80.degree. to 100.degree. when in the off-state;
- a positive retarder having a retardation value of from about 80 to 200 nm; and
- a negative retarder defined by n.sub.x =n.sub.y >n.sub.z where n.sub.x, n.sub.y, and n.sub.z are indices of refraction and the "z" direction is substantially perpendicular to the plane defined by said negative retarder and the "x" and "y" directions are substantially parallel to the plane defined by said negative retarder, and having a retardation value of from about -60 to -200 nm, said negative retarder disposed between said liquid crystal layer and said positive retarder.
Parent Case Info
This application is a continuation-in-part (CIP) of Ser. No. 08/167,652, filed Dec. 15, 1993.
US Referenced Citations (14)
Foreign Referenced Citations (5)
Number |
Date |
Country |
4-56802 |
Feb 1992 |
JPX |
4-97322 |
Mar 1992 |
JPX |
4311903 |
Nov 1992 |
JPX |
5257014 |
Oct 1993 |
JPX |
6-130227 |
May 1994 |
JPX |
Continuation in Parts (1)
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Number |
Date |
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Parent |
167652 |
Dec 1993 |
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