Patent US567156A successfully refreshed from Google Patents.
EP0774682A2
Expired / Lapsed
EP
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Normally white twisted nematic LCD with positive and negative phase retarders
Assignee: Guardian Industries Corp
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Filing: 1996-11-08
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Granted: —
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Expires: 2016-11-08
Abstract
Abstract A normally white twisted nematic liquid crystal display is provided for outputting improved viewing characteristics which are defined by high contrast ratios and reduced inversion. The display includes both positive and negative retardation films, the negative films being defined by n x = n y > n z where the "z" direction is substantially perpendicular to the film plane and the "x" and "y" directions are substantially parallel to the film plane. According to certain embodiments, a pair of positive and a pair of negative retardation films are provided such that the two positive retarders sandwich both the liquid crystal layer and the negative retarders therebetween. By providing the positive and negative retarders with specific retardation values and/or ratios, improved viewing characteristics are provided.
Inventors
- 👤 Gang Xu
- 👤 John A. Vanderploeg
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-04 03:26
CPC Classifications
G; G02; G02F; G02F1/00; G02F1/01; G02F1/13; G02F1/133; G02F1/1333; G02F1/1335; G02F1/13363; G02F1/133634; G02F1/133528; G02F1/133531; G02F1/1337; G02F1/13378; G02F1/133784; G02F1/137; G02F1/139; G02F1/1396; G02F2202/00; G02F2202/40; G02F2413/00; G02F2413/02; G02F2413/04; G02F2413/08; G02F2413/13; G02F2413/14
Claims Analysis
Total Claims: 16
Claim 1
Independent Claim
111 words
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° to 100° 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.
Claim 2
Dependent Claim
22 words
The display of claim 1, wherein the retardation value of each of said negative retarders is from about -80 to -150 nm.
Claim 3
Dependent Claim
59 words
The display of claim 1, wherein n x = n y > n z 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.
Claim 4
Dependent Claim
22 words
The display of claim 3, wherein the retardation value of each of said negative retarders is from about -100 to -120 nm.
Claim 5
Dependent Claim
22 words
The display of claim 4, wherein the retardation value of each of said positive retarders is from about 120 to 160 nm.
Claim 6
Dependent Claim
82 words
The display of claim 1, wherein the thickness of said liquid crystal layer is from about 4.8 to 6.0 µm and the Δn 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 viewing angles along the 0° vertical axis of about ±60° when a driving voltage of from about 6.0 to 6.1 volts is applied to said liquid crystal layer.
Claim 7
Dependent Claim
62 words
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° vertical viewing axis of about ±50°, and of at least about 20:1 or 20 at vertical viewing angles along the 0° horizontal axis of about 0° to +40° when said 6.0 to 6.1 driving voltage is applied.
Claim 8
Dependent Claim
29 words
The display of claim 6, wherein the front buffing direction is substantially parallel to both a rear polarizer transmission axis and the optical axis of the rear positive retarder.
Claim 9
Dependent Claim
99 words
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° to 100° 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 negative retardation value on each side of said liquid crystal layer is from about 1:1 to 2:1.
Claim 10
Dependent Claim
96 words
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 x = n y > n z where n x , n y , and n 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.
Claim 11
Dependent Claim
35 words
The display of claim 10, wherein the retardation value of said negative retarders is from about -80 to -140 nm and the retardation value of said positive retarders is from about 100 to 200 nm.
Claim 12
Independent Claim
120 words
A method of making a twisted nematic liquid crystal display comprising the steps of: providing a pair of negative retarders defined by n x = n y > n z 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 positve 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° vertical viewing axis of about ±40°.
Claim 13
Dependent Claim
37 words
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 of about ±30°.
Claim 14
Dependent Claim
38 words
The display of claim 13, further comprising the steps of providing said negative retarders with retardation values of from about -60 to -200 nm and said positive retarders with retardation values of from about 80 to 200 nm.
Claim 15
Dependent Claim
58 words
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 its adjacent polarizer from about 0° to 8° so as to adjust the position of the high contrast viewing zone output by the display.
Claim 16
Dependent Claim
85 words
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° to 100° 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 x = n y > n z having a retardation value of from about -60 to -200 nm, said negative retarder disposed between said liquid crystal layer and said positive retarder.
References Cited (Backward Citations)
US4889412A
Cited
US5189538A
Cited
US5406396A
Cited
US5071997A
Cited
US5138474A
Cited
US5161041A
Cited
US5184236A
Cited
US5291323A
Cited
US5138747A
Cited
US5196953A
Cited
US5344916A
Cited
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