Liquid crystal display device with compensation for viewing angle dependency and optical anisotropic element used therein

Abstract

In a liquid crystal display device having a driving liquid crystal cell interposed between two polarizers 1 and 4 , the cell having a liquid crystal layer 3 e held between two substrates 3 a and 3 b , the layer having a twisted molecular alignment when no voltage is applied, and the liquid crystal cell performing optical control, using the optical anisotropy of liquid crystal, there is provided with an optical anisotropic element 2 between the polarizer and the driving liquid crystal cell, the optical anisotropic element 2 comprising an optical anisotropic substance layer 2 c in which the optical rotatory power is minimal in the direction of layer thickness and the optical anisotropy is negative. The angle of the optical axis of the optical anisotropic element 2 varies continuously or in stages in the direction of layer thickness of the optical anisotropic element as against the surface of the optical anisotropic element. Furthermore, optical anisotropic element with negative optical anisotropy can be combine to the anisotropically negative element.

What is claimed is:  
     
         1 . A liquid crystal display device comprising at least one polarizer, a driving liquid crystal cell having two substrates and a liquid crystal layer held between at least the two substrates, at least one optical anisotropic element in which plural optical anisotropic units arrange in the direction of the layer thickness, wherein the optical anisotropic element is arranged for the optical anisotropy of the optical anisotropic unit to be negative to the direction of thickness, the angles of respective optical axes of the optical anisotropic units being not constant against the direction of the thickness and that the optical anisotropy having the minimum optical rotatory power in the thickness direction.  
     
     
         2 . The liquid crystal display device as claimed in  claim 1 , wherein the angle of the optical axis of the optical anisotropic units constituting the optical anisotropic element with the surface of the substrate of the driving liquid crystal cell varies continuously or stepwise in the direction of the layer thickness of the optical anisotropic element.  
     
     
         3 . The liquid crystal display device as claimed in  claim 1 , wherein the optical axis of the optical anisotropic units is substantially parallel to the surface of the optical anisotropic element adjacent to the driving liquid crystal cell and varies in the layer of the optical anisotropic element to be substantially normal on the other surface of the optical anisotropic element.  
     
     
         4 . The liquid crystal display device as claimed in  claim 1 , wherein the optical axis of the anisotropic units is substantially normal to the substrate of the driving liquid crystal cell on the surface of the optical anisotropic element adjacent to the driving liquid crystal cell and varies in the layer of the optical anisotropic element to be substantially parallel to the substrate of the driving liquid crystal cell on the other surface of the optical anisotropic element.  
     
     
         5 . The liquid crystal display device as claimed in  claim 1 , wherein the orientation, as viewed from the normal of the substrate of the liquid crystal cell, of the respective optical axes of the optical anisotropic units is aligned in a single axis.  
     
     
         6 . The liquid crystal display device as claimed in  claim 1 , wherein the orientation of the optical axes of the optical anisotropic units as viewed from the normal of the substrate of the driving liquid crystal cell is twisted toward the surface of the optical anisotropic element.  
     
     
         7 . The liquid crystal display device as claimed in  claim 1 , wherein at least one first optical anisotropic element and at least one second optical anisotropic element are arranged respectively, and the first optical anisotropic element has an optical axis whose the angle varies within the layers of the first optical anisotropic element to be parallel to the surface of the first optical anisotropic element adjacent to the driving liquid crystal cell and to be substantially normal to the other surface of the first optical anisotropic element, and the second optical anisotropic element has an optical axis whose the angle is substantially normal to the surface of the second optical anisotropic element adjacent to the driving liquid crystal cell and varies within the layers of the second optical anisotropic element to be substantially parallel to the other surface of the second optical anisotropic element.  
     
     
         8 . The liquid crystal display device as claimed in  claim 1 , wherein the optical axes of the optical anisotropic element vary in the thickness direction of the layer of the optical anisotropic element to be substantially parallel in one surface of the element and to be slanted by 10 to 80 degrees from the normal of the surface to the other surface of the optical anisotropic element.  
     
     
         9 . The liquid crystal display device as claimed in  claim 1 , wherein the optical axis of the optical anisotropic element has a first angle of 10 to 90 degrees on the one surface of the optical anisotropic element and varies in the layer of the element to have a second angle of 0 to 80 degree on the other surface of the optical anisotropic element, the second angle being smaller than that of the first angle.  
     
     
         10 . The liquid crystal display device as claimed in  claim 3  or  4 , wherein the orientation of the optical axis of the optical anisotropic element on the side nearly parallel to the substrate surface of the driving liquid crystal cell is substantially parallel to or substantially perpendicular with the absorption axis of the polarizers when viewed from the normal direction of the substrate.  
     
     
         11 . A liquid crystal display comprising at least one polarizer, a driving liquid crystal cell with two substrates and a liquid crystal layer held between the two substrates, and at least one optical anisotropic element with one or more optical anisotropic units arranged between the polarizer and the cell, wherein the angles of the optical axes of the optical anisotropic units with the substrate of the element unit are substantially coincident to each other on the both surfaces of the optical anisotropic element and the angles of the optical axis varies in the intermediate layer, and the optical anisotropy of the optical anisotropic element is negative to the direction of the thickness.  
     
     
         12 . A liquid crystal display device as claimed in  claim 11 , wherein the angle of the optical axis of the optical anisotropic element with the substrate surface of the driving liquid crystal cell is substantially same on the both surfaces of the optical anisotropic element, and the angle varies continuously or stepwise in its intermediate portion in the layer of the optical anisotropic element.  
     
     
         13 . A liquid crystal display device as claimed in  claim 11 , wherein the direction of the optical axis of the optical anisotropic units resides on a single axis when viewed from the direction of the normal to the substrate of the driving liquid crystal cell.  
     
     
         14 . A liquid crystal display device as claimed in  claim 11 , wherein the directions of the optical axis of the optical anisotropic units are at least two when viewed from the direction of the normal to the substrate of the driving liquid crystal cell.  
     
     
         15 . The liquid crystal display device as claimed in  claim 11 , wherein the optical axis of the optical anisotropic units is twisted continuously or stepwise.  
     
     
         16 . The liquid crystal display device as claimed in claims  1  or  11 , wherein a biaxial retardation film is disposed between a polarizer and an optical anisotropic element.  
     
     
         17 . The liquid crystal display device as claimed in claims  1  or  11 , wherein the layer of the optical anisotropic substance of the optical anisotropic element is one selected from organic, inorganic material and high molecular liquid crystal.  
     
     
         18 . The liquid crystal display device as claimed in claims  1  or  9 , wherein the optical anisotropic element is disposed within the driving liquid crystal cell.  
     
     
         19 . An optical anisotropic element comprising a plurality of optical anisotropic units arranged in the direction of the layer thickness of the element, wherein angles between optical axes of the optical anisotropic units and surfaces of the optical anisotropic element differs in the vicinity of the upper and lower surfaces of the optical anisotropic element, and the optical anisotropy of the optical anisotropic element is negative to the thickness direction.  
     
     
         20 . The optical anisotropic element as claimed in  claim 19 , wherein the angle of the optical axis of optical anisotropic units varies continuously or stepwise against the surface of the optical anisotropic element in the direction of the layer thickness of the optical anisotropic element.  
     
     
         21 . The optical anisotropic element in as claimed  claim 19  or  20 , wherein the orientation of the optical axis of the optical anisotropic units is substantially parallel to one surface of the optical anisotropic element and substantially normal to the other surface the optical anisotropic element, and the optical axis in between the layers varies continuously within the layer of the optical anisotropic element.  
     
     
         22 . The optical anisotropic element as claimed in  claim 19  or  20 , wherein the orientation of the optical axis of the optical anisotropic units is substantially normal to one surface of the optical anisotropic element and substantially parallel to the other surface of the optical anisotropic element, and the optical axis varies continuously within the layer of the optical anisotropic element.  
     
     
         23 . The optical anisotropic element as claimed in  claim 19 , wherein the respective optical axes of the optical anisotropic units align on a single axis when viewed from the direction of the normal to the surface of the optical anisotropic element.  
     
     
         24 . The optical anisotropic element as claimed in  claim 19 , wherein the respective optical axes of the optical anisotropic units is twisted in the direction of the element plane when viewed from the direction of the normal to the surface of the optical anisotropic element.  
     
     
         25 . An optical anisotropic element comprising a plurality of optical anisotropic units, wherein the optical anisotropic units have optical axes of which the angles are substantially coincident on the both units of the surfaces of the element and vary in the intermediate units, and the optical anisotropy of the optical anisotropic element is negative in the direction of the thickness.  
     
     
         26 . The optical anisotropic element as claimed in  claim 25 , wherein the angles varies continuously or stepwise in the intermediate units.  
     
     
         27 . The optical anisotropic element as claimed in  claim 25 , wherein the respective optical axes of the optical anisotropic units are on a single axis when viewed from the direction of the normal to the surface of the optical anisotropic element.  
     
     
         28 . The optical anisotropic element as claimed in  claim 25 , wherein the optical axes of the optical anisotropic units are directed toward two or more orientations when viewed from the direction of the normal to the surface of the optical anisotropic element.  
     
     
         29 . The optical anisotropic element as claimed in  claim 25 , wherein the respective optical axes of the optical anisotropic units are twisted continuously or stepwise in the direction of the element when viewed from the direction of the normal to the surface of the optical anisotropic element.  
     
     
         30 . The optical anisotropic element as claimed in claims  19  or  25 , wherein the optical anisotropic element is of any one selected from organic, inorganic material and high molecular liquid crystal.  
     
     
         31 . A liquid crystal display element comprising: 
 at least two polarizers;    a driving liquid crystal cell sandwiched between the polarizers, comprising two substrates with electrodes and a liquid crystal layer interposed between the two substrates; and    at least one optical anisotropic layer with positive optical anisotropy, and at least one optical anisotropic layer with negative optical anisotropy,    the optical anisotropic layers disposed between the polarizer and the driving liquid crystal cell and of which an optical rotatory power in a direction slanted from normal of the optical anisotropic layers is greater than that of normal to the optical anisotropic layers.    
     
     
         32 . The liquid crystal display element as claimed in  claim 31 , wherein the optical axis of the optical anisotropic layer with positive optical anisotropy is uniformly slanted to the direction of the layer thickness of the optical anisotropic layer or varies continuously in the direction of the layer thickness of the optical anisotropic layer.  
     
     
         33 . The liquid crystal display device as claimed in  claim 32 , wherein the optical axes of the optical anisotropic layer are in the same orientation.  
     
     
         34 . The liquid crystal display device as claimed in  claim 31 , wherein a set of the optical anisotropic layer with negative optical anisotropy and the optical anisotropic layer with positive optical anisotropy are arranged on both sides of the driving liquid crystal cell.  
     
     
         35 . The liquid crystal display device as claimed in  claim 34 , wherein the optical anisotropic layer with negative optical anisotropy is arranged adjacent to the driving liquid crystal cell.  
     
     
         36 . The liquid crystal display device as claimed in  claim 35 , wherein a plane with smaller oblique angle of the optical axis of the optical anisotropic layer with negative optical anisotropy, the oblique angle of the optical axis varying continuously in the thickness direction of the optical anisotropic layer, is arranged adjacent to the driving liquid crystal cell.  
     
     
         37 . The liquid crystal display device as claimed in  claim 35 , wherein the respective optical axes of the optical anisotropic layer with positive optical anisotropy and the optical anisotropic layer with negative optical anisotropy are cross at right angle to each other.  
     
     
         38 . The optical anisotropic element as claimed in  claim 1  or  3 , wherein the optical anisotropy of optical anisotropic units is negative, and the optical axis is substantially perpendicular to one surface of the optical anisotropic element and is aligned obliquely at 10 to 60 degrees without twist on the other surface of the optical anisotropic element.