Liquid crystal optical element and test method for its boundary layer

Abstract

On substrates 2 a, 2 b of a chiral nematic liquid crystal optical element 1, transparent electrodes 3 a, 3 b and electrical insulation layers 4 a, 4 b are formed, and further, resin layers 5 a, 5 b having a pencil hardness of “B” or less are formed on the electrical insulation layers by a spin coating method so as to be in contact with a liquid crystal layer 7 When the surface hardness of the resin layers is to be measured, a glass substrate on which a resin layer is formed by screen-printing is prepared as a test piece, and the test piece is fitted to a pencil-scratching tester. The surface hardness is measured by scratching the test piece with two kinds of testing pencil selected from testing pencils having 17 grades of density.

What is claimed as new and is desired to be secured by Letters Patent of the United States is:  
     
         1 . In a liquid crystal optical element comprising a pair of substrates with electrodes between which a liquid crystal layer including a chiral nematic liquid crystal is interposed wherein at least one of the substrates is transparent and the liquid crystal layer exhibits two or more optically stable states in a non-voltage-application time, the liquid crystal optical element being characterized in that a boundary layer is provided between an electrode on at least one of the substrates and the liquid crystal layer, and the surface hardness of the boundary layer is B or less in terms of a pencil hardness test.  
     
     
         2 . The liquid crystal optical element according to  claim 1 , wherein the boundary layer is a resin layer.  
     
     
         3 . The liquid crystal optical element according to  claim 1 , wherein the resin layer is of polyimide.  
     
     
         4 . The liquid crystal optical element according to  claim 1 , wherein the electrode on at least one of the substrates is divided into a plurality of portions.  
     
     
         5 . The liquid crystal optical element according to  claim 2 , wherein the electrode on at least one of the substrates is divided into a plurality of portions.  
     
     
         6 . The liquid crystal optical element according to  claim 3 , wherein the electrode on at least one of the substrates is divided into a plurality of portions.  
     
     
         7 . The liquid crystal optical element according to  claim 1 , wherein the surface hardness is 3B or less.  
     
     
         8 . The liquid crystal optical element according to  claim 2 , wherein the surface hardness is 3B or less.  
     
     
         9 . The liquid crystal optical element according to  claim 3 , wherein the surface hardness is 3B or less.  
     
     
         10 . The liquid crystal optical element according to  claim 1 , wherein a dot matrix display is performed with the electrodes.  
     
     
         11 . The liquid crystal optical element according to  claim 2 , wherein a dot matrix display is performed with the electrodes.  
     
     
         12 . The liquid crystal optical element according to  claim 3 , wherein a dot matrix display is performed with the electrodes.  
     
     
         13 . The liquid crystal optical element according to  claim 1 , wherein a segment display is performed with the electrodes.  
     
     
         14 . The liquid crystal optical element according to  claim 2 , wherein a segment display is performed with the electrodes.  
     
     
         15 . The liquid crystal optical element according to  claim 3 , wherein a segment display is performed with the electrodes.  
     
     
         16 . The liquid crystal optical element according to  claim 1 , wherein the heat distortion temperature of a material for forming the boundary layer is 50° C. or more, and the coefficient of elasticity at room temperature is 1 kPa or more.  
     
     
         17 . The liquid crystal optical element according to  claim 1 , wherein the heat distortion temperature of a material for forming the boundary layer is 50° C. or more, and the coefficient of elasticity at room temperature is 1 kPa or more.  
     
     
         18 . The liquid crystal optical element according to  claim 1 , wherein the heat distortion temperature of a material for forming the boundary layer is 50° C. or more, and the coefficient of elasticity at room temperature is 1 kPa or more.  
     
     
         19 . In a test method for a liquid crystal optical element comprising a pair of substrates with electrodes between which a liquid crystal layer including a chiral nematic liquid crystal is interposed wherein at least one of the substrates is transparent and the liquid crystal layer exhibits two or more optically stable states in a non-voltage-application time, the test method being characterized in that a boundary layer is provided between an electrode on at least one of the substrates and the liquid crystal layer, and judgment is made as to the presence or absence of a image-sticking phenomenon after the liquid crystal optical element has been left for 1 hour or more in a state of maintaining a predetermined image.  
     
     
         20 . In a test method for a boundary layer of a liquid crystal optical element comprising a pair of substrates with electrodes between which a liquid crystal layer including a chiral nematic liquid crystal is interposed wherein at least one of the substrates is transparent; the liquid crystal layer exhibits two or more optically stable states in a non-voltage-application time, and a boundary layer is provided at least a part between an electrode on at least one of the substrates and liquid crystal, the test method for a boundary layer of a liquid crystal optical element being characterized in that a test means having a predetermined ranking of hardness is provided; the test means is brought to contact with the boundary layer N times (1≦N) or more while a pressure is applied to the test means, and evaluation is made as to the surface hardness of the boundary layer based on whether or not a flaw is resulted in the boundary layer, whereby applicability to the liquid crystal layer is determined.