Normally-white twisted-nematic-mode LCD device
AssigneeNEC LCD Technologies, Ltd.
InventorsHidenori Ikeno, Yoichi Sasaki
Life of this patent
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Abstract
A normally-white twisted-nematic mode LCD device includes a first optical compensation film between a light-incident-side polarization film and an LC cell, and a second optical compensation film between a light-emitting-side polarization film and the LC cell. The optical axis of the first (second) optical compensation film projected onto the substrate surface is substantially parallel to the longer axis of an equivalent refractive index ellipsoid of a residual retardation of the LC layer in the vicinity of a light-incident-side (light-emitting-side) substrate upon display of black color.
Claims12
A normally-white liquid crystal display (LCD) device comprising
- a first polarization film, a first optical compensation film, a first substrate, a first transparent electrode, a first orientation film, a twisted-nematic liquid crystal (LC) layer, a second orientation film, a second transparent electrode, a second substrate, a second optical compensation film, and a second polarization film, which are consecutively disposed in a direction of light transmission, wherein:
- said first polarization film has a polarization axis perpendicular to a polarization axis of said second polarization film;
- an optical axis of said first optical compensation film projected onto a substrate surface of said first or second substrate is substantially parallel to a longer axis of a first equivalent refractive index ellipsoid projected onto said substrate surface,
- said first equivalent refractive index ellipsoid representing a residual retardation of said LC layer in a vicinity of a first interface of said LC layer with respect to said first substrate upon display of black color by applying a first voltage between said first transparent substrate and said second transparent substrate to determine an orientation of LC molecules in said LC layer;
- and
- an optical axis of said second optical polarization film projected onto said substrate surface is substantially parallel to a longer axis of a second equivalent refractive index ellipsoid projected onto said substrate surface,
- said second equivalent refractive index ellipsoid representing a residual retardation of said LC layer in a vicinity of a second interface of said LC layer with respect to said second substrate upon said display of black color,
- wherein said first optical compensation film comprises a plurality of LC layers each compensating a retardation of distinct LC molecules within a first portion of said LC layer on the first substrate side of said LC layer with each of said plurality of compensation film LC layers having an optical axis generally parallel to a long axis of the respective distinct LC molecule, and said second optical compensation film comprises a plurality of LC layers each compensating a retardation of distinct LC molecules within a second portion of said LC layer on the second substrate side of said LC layer with each of said plurality of compensation film LC layers having an optical axis generally parallel to a long axis of the respective distinct LC molecule, and wherein the following relationship:
- 0.5×θTw−47.5≦Δθ2≦0.5×θTw−43.8 holds,
- where θTw is a twisted angle of said LC layer, Δθ2 (Δθ2>0) is an angle measured from said optical axis of said first optical compensation film projected onto said substrate surface to said polarization axis of said first polarization film, and −Δθ2 is an angle measured from said optical axis of said second optical compensation film projected onto said substrate surface to said polarization axis of said second polarization film, assuming that the angles are positive when measured in a clockwise direction as viewed along said direction of light transmission.
A normally-white liquid crystal display (LCD) device comprising
- a first polarization film, a first optical compensation film, a first substrate, a first transparent electrode, a first orientation film, a twisted-nematic liquid crystal (LC) layer, a second orientation film, a second transparent electrode, a second substrate, a second optical compensation film, and a second polarization film, which are consecutively disposed in a direction of light transmission, wherein:
- said first optical compensation film comprises a plurality of effective compensation LC layers;
- a first one of said effective compensation LC layers nearer to said LCD device LC layer having an optical axis substantially parallel to the longer axis of a first LCD LC layer molecule disposed nearer to said first optical compensation film, upon display of black color;
- a second one of said effective compensation LC layers disposed further from said LCD device LC layer than said first effective compensation LC layer, having an optical axis substantially parallel to the longer axis of a second LC molecule disposed further into said the LCD device LC layer than said first LC molecule, upon the display of black color;
- and a third of said effective compensation LC layers disposed still further from the LCD device LC layer having an optical axis substantially parallel to the longer axis of a third LC molecule disposed still further into said LCD device LC layer than said second LC molecule, upon the display of black color, to thereby compensate with said effective compensation layers the residual retardation of said first, second and third LC molecules in said LCD device LC layer.
Dependencies are inferred from the claim text.