Patent Publication Number: US-8120738-B2

Title: Liquid crystal display device and electronic apparatus

Description:
This is a Continuation of application Ser. No. 11/017,134 filed Dec. 21, 2004 now U.S. Pat. No. 7,564,524. This application claims the benefit of Japanese Patent Application Nos. JP 2004-006783, filed Jan. 14, 2004 and JP 2004-251482, filed Aug. 31, 2004. The disclosure of the prior applications is hereby incorporated by reference herein in its entirety. 
    
    
     BACKGROUND 
     The exemplary embodiments of the present invention relate to a liquid crystal display device and an electronic apparatus. 
     In the related art, liquid crystal display devices with a liquid crystal mode of vertical alignment were widely utilized. In this kind of liquid crystal display device, it is necessary to properly control a direction in which liquid crystal molecules aligned vertically to a substrate fall down at the time of applying a voltage, and there has been thus suggested that alignment control structures including slits (notched portions) or dielectric protrusions for the purpose of controlling the alignment of the liquid crystal molecules are provided in electrodes (see Japanese Patent No. 2947350). The arrangement conditions of the dielectric protrusions have been studied (see A Super-High Image Quality Multi-Domain Vertical Alignment LCD by New Rubbing-Less Technology, SID1998 DIGEST 41.1). 
     SUMMARY 
     It is effective for a high image quality of liquid crystal display devices with a vertical alignment mode that the alignment control structures are provided and the arrangement conditions, etc. are properly set as in the related art. However, as a result of repeated studies by the inventor of the present invention for a higher image quality and a wider viewing angle of a liquid crystal display device with a vertical alignment mode, when the dielectric protrusions are provided as the alignment control structures, it was discovered that it is necessary to provide dielectric protrusions having a proper characteristic depending upon characteristics of liquid crystal molecules. That is, it was discovered that when such optimization is not performed, the image quality may be deteriorated in the conventional liquid crystal display devices performing the alignment control of the vertically-aligned liquid crystal by way of the dielectric protrusions. Therefore, the exemplary embodiments address or solve the above and/or other problems by providing a liquid crystal display device with a vertical alignment mode for realizing a high image quality and a wide viewing angle. 
     In order to address or accomplish the above, the exemplary embodiments provide a liquid crystal display device in which a liquid crystal layer having an initial state of vertical alignment is interposed between a pair of substrates having electrodes on opposing surfaces thereof, a dot area constituting one unit of display, a dielectric protrusion protruded toward the liquid crystal layer being formed on the electrode of one substrate of the pair of substrates and an alignment control structure being provided at a position adjacent to the dielectric protrusion as seen two-dimensionally on the opposing surface of an other substrate of the pair of substrates, and when a dielectric constant of the dielectric protrusion is ε t1 , a dielectric constant of a major axis direction of liquid crystal molecules constituting the liquid crystal layer is ε // , and a dielectric constant of a minor axis direction thereof is ε ⊥ , the expression ε ⊥ &gt;ε // &gt;ε t1  is satisfied. Accordingly, in the liquid crystal display device including a dielectric protrusion as an alignment control structure of vertically-aligned liquid crystal, when the dielectric constant of the dielectric protrusion is smaller than the dielectric constant of the major axis direction of the liquid crystal molecules, the alignment control of the liquid crystal molecules in the dot area can be satisfactorily performed, so that it is possible to obtain high-brightness display. 
     The exemplary embodiments also provide a liquid crystal display device in which a liquid crystal layer having an initial state of vertical alignment is interposed between a pair of substrates having electrodes on opposing surfaces thereof, in a dot area constituting one unit of display, one substrate of the pair of substrates is provided with a dielectric protrusion protruded toward the liquid crystal layer from the electrode of the substrate and an alignment control structure disposed adjacent to the dielectric protrusion, and when that the dielectric constant of the dielectric protrusion is ε t1 , the dielectric constant of a major axis direction of liquid crystal molecules constituting the liquid crystal layer is ε // , and the dielectric constant of a minor axis direction thereof is ε ⊥ , the expression ε t1 &gt;ε //  is satisfied. Accordingly, in the liquid crystal display device including a dielectric protrusion as an alignment control structure of vertically-aligned liquid crystal, when the dielectric constant of the dielectric protrusion is greater than the dielectric constant of the major axis direction of the liquid crystal molecules, the alignment control of the liquid crystal molecules in the dot area can be satisfactorily performed, so that it is possible to obtain high-brightness display. In addition, since the alignment control structure is provided only on one substrate, the liquid crystal display device can be more easily manufactured, so that enhancement of a manufacturing yield can be expected. 
     Therefore, in accordance with each of the above described exemplary embodiments, in the liquid crystal display device having the dielectric protrusion as the alignment control structure of the vertically-aligned liquid crystal molecules, since the behavior of different liquid crystal molecules at the time of applying a voltage can be suitably controlled in accordance with the dielectric constant of the dielectric protrusion, it is possible to provide a liquid crystal display device capable of accomplishing high-quality display. 
     In the liquid crystal display device according to the exemplary embodiments, the alignment control structure adjacent to the dielectric protrusion may be one of an opening slit formed in the electrode provided in the dot area and an edge portion of the electrode. 
     In the liquid crystal display device according to the exemplary embodiments, the alignment control structure adjacent to the dielectric protrusion may be another dielectric protrusion, and when the dielectric constant of the other dielectric protrusion is ε t2  and the dielectric constant of the liquid crystal molecules is ε // , the expression ε // &gt;ε t2  may be satisfied. 
     In the liquid crystal display device according to the exemplary embodiments having the above described features, as the alignment control structure adjacent to the dielectric protrusion, the alignment control of the liquid crystal molecules at the time of applying a voltage may be performed by way of an oblique electric field generated from the edge portions of the electrode, and the alignment control may be also performed by means of distorting an electric field resulting from providing a protrusion having different dielectric constant in the liquid crystal layer. 
     In the liquid crystal display device according to the exemplary embodiments, the alignment control structure adjacent to the dielectric protrusion may include an opening slit formed on the electrode provided in the dot area and another dielectric protrusion which is provided inside the opening slit and of which the dielectric constant ε t2  satisfies the expression ε // &gt;ε t2 . Accordingly, since the alignment control structure for performing the alignment control of the liquid crystal molecules using the oblique electric field generated around the opening slit and the distortion of an electric field generated by the dielectric protrusion is provided, the liquid crystal molecules spaced from the alignment control structure can be also satisfactorily controlled, so that the construction is advantageous for enhancing a response speed and an aperture ratio. 
     The exemplary embodiments also provide a liquid crystal display device in which a liquid crystal layer having an initial state of vertical alignment is interposed between a pair of substrates having electrodes on opposing surfaces thereof, in a dot area constituting one unit of display, a first dielectric protrusion protruded toward the liquid crystal layer being formed on the electrode of one substrate of the pair of substrates and a second dielectric protrusion provided at a position adjacent to the first dielectric protrusion as seen two-dimensionally on the electrode of the other substrate of the pair of substrates, and when the dielectric constant of the first dielectric protrusion is ε t1 , the dielectric constant of the second dielectric protrusion is ε t2 , the dielectric constant of a major axis direction of liquid crystal molecules constituting the liquid crystal layer is ε // , and the dielectric constant of a minor axis direction thereof is ε ⊥ , the expressions ε t1 &gt;ε //  and ε t2 &gt;ε //  are satisfied. The dielectric protrusions provided in the dot area and forming the alignment control structure may be made of the same material, but the alignment control may be performed using the dielectric protrusions having different dielectric constants. When the dielectric protrusions having different dielectric constants are provided adjacent to each other, the dielectric protrusions may be provided on different substrates as described in the above exemplary embodiments. According to the above exemplary embodiments, it is possible to obtain a display with a high image quality and a wide viewing angle. 
     In the liquid crystal display device according to the exemplary embodiments, a reflective display area for performing reflective display and a transmissive display area for performing transmissive display may be provided in the dot area. According to exemplary embodiments, it is possible to provide a transflective liquid crystal display device capable of performing transmissive display and reflective display with a wide viewing angle and a high image quality. 
     The exemplary embodiments of the present invention also provide an electronic apparatus including the liquid crystal display device described above. According to the exemplary embodiments, an electronic apparatus including a display unit having a wide viewing angle and a high brightness is provided. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a cross-sectional schematic illustrating a basic structure of a liquid crystal display device according to an exemplary embodiment; 
         FIG. 2  is a cross-sectional schematic illustrating a basic structure of the liquid crystal display device according to an exemplary embodiment; 
         FIG. 3  is a schematic illustrating a result of simulation according to an exemplary embodiment; 
         FIG. 4  is a schematic illustrating a result of simulation according to an exemplary embodiment; 
         FIG. 5  is a schematic illustrating a result of simulation according to an exemplary embodiment; 
         FIG. 6  is a schematic illustrating a result of simulation according to an exemplary embodiment; 
         FIG. 7  is a schematic illustrating a result of simulation according to an exemplary embodiment; 
         FIG. 8  is a schematic illustrating a result of simulation according to an exemplary embodiment; 
         FIG. 9  is a schematic illustrating a result of simulation according to an exemplary embodiment; 
         FIG. 10  is a schematic illustrating a result of simulation according to an exemplary embodiment; 
         FIGS. 11A-11D  are schematics exemplifying a liquid crystal display device in an exemplary embodiment; 
         FIG. 12  is a perspective schematic illustrating a liquid crystal display device according to a structural example in an exemplary embodiment; 
         FIG. 13  is cross-sectional schematic illustrating a liquid crystal display device according to a first structural example in an exemplary embodiment; 
         FIG. 14  is a plan schematic illustrating one pixel area of the liquid crystal display device according to the first structural example in an exemplary embodiment; 
         FIG. 15  is a cross-sectional schematic illustrating a liquid crystal display device according to a second structural example in an exemplary embodiment; 
         FIG. 16  is a plan schematic illustrating one pixel area of the liquid crystal display device according to the second structural example in an exemplary embodiment; and 
         FIG. 17  is a perspective schematic illustrating an example of an electronic apparatus in an exemplary embodiment. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
     Hereinafter, the exemplary embodiments will be described with reference to the drawings. In the drawings referred to below, sizes and thicknesses of respective elements are properly different for the purpose of easily understanding the drawings.  FIGS. 1 and 2  are cross-sectional views illustrating a main part (a part of a basic structure) of a liquid crystal display device according to first and second exemplary embodiments, respectively. 
     The liquid crystal display device  100  according to the first exemplary embodiment shown in  FIG. 1  has a structure in which a liquid crystal layer  50  made of liquid crystal having a negative dielectric anisotropy is interposed between a first substrate  25  and a second substrate  10  disposed to be opposite to each other. A second electrode  9 , a dielectric protrusion  18 , and a vertical alignment film  23  covering the second electrode  9  and the dielectric protrusion  18  are formed in this order at the inner surface side of the second substrate  10 . A first electrode  31  and a vertical alignment film  33  are formed in this order at the inner surface side of the first substrate  25 . In a dot area constituting one unit of display, the first electrode  31  is formed narrower than the second electrode  9 , and edge portions (notched portion)  31   a  and  31   a  of the first electrode  31  in the left-right direction of the figure (Y direction, that is, a plane direction of the first substrate  25 ) are two-dimensionally disposed above the second electrode  9 . That is, in one dot area, there is provided a positional relation that the dielectric protrusion  18  is disposed between the edge portion  31   a  and the edge portion  31   a  of the first electrode  31  formed on the other substrate (a positional relation that the dielectric protrusion  18  and the edge portions  31   a  and  31   a  of the first electrode  31  are disposed to be discretely adjacent to each other without two-dimensionally overlapping each other). 
     On the other hand, the liquid crystal display device  200  according to the second exemplary embodiment shown in  FIG. 2  has the same basic structure as the liquid crystal display device according to the first exemplary embodiment but is different from the liquid crystal display device according to the first exemplary embodiment in that the dielectric protrusion  18  is provided on the first electrode  31  of the first substrate  25 . That is, in one dot area, there is provided a positional relation that the dielectric protrusion  18  is disposed between the edge portion  31   a  and the edge portion  31   a  of the first electrode  31  formed on the same substrate (a positional relation that the dielectric protrusion  18  and the edge portions  31   a  and  31   a  of the first electrode  31  are alternately disposed to be adjacent to each other). 
     Here, one dot area indicates an area constituting one unit of display, and generally includes one pixel electrode formed on one substrate and a counter electrode formed on the other substrate to be opposite to the pixel electrode. 
     According to the above structure, in the liquid crystal display devices  100  and  200 , in a state (non-selection state, initial alignment state) where a voltage is not applied to both electrodes  9  and  31 , liquid crystal molecules  51  constituting the liquid crystal layer  50  are aligned in a vertical direction to the substrates  10  and  25  due to the alignment control power of the vertical alignment films  23  and  33 . When a voltage is applied to both electrodes (when it is switched to a selection state), the liquid crystal molecules fall down toward the plane direction of the substrates  10  and  25 . 
     The liquid crystal display devices  100  and  200  have a dielectric protrusion  18  as the alignment control structure for controlling the alignment direction of the liquid crystal molecules  51  at the time of applying a voltage. In addition, the alignment of the liquid crystal molecules  51  can be also controlled by way of distortion of electric field generated at the edge portions (notched portions)  31   a  of the electrode formed narrower than the electrode provided on the opposite substrate. In the liquid crystal display device according to the first exemplary embodiment and the second exemplary embodiment, the dielectric constant ε t1  of the dielectric protrusion  18  provided approximately at the center of one dot area has different relations with the respective dielectric constants ε //  and ε ⊥  of the liquid crystal molecules  51 , and on the basis of the different relations, the arrangement relation between the dielectric protrusion  18  and the alignment control structure (the edge portions  31   a ,  31   a ) adjacent to the dielectric protrusion is varied. Here, the dielectric constant ε //  of the liquid crystal molecules indicates a dielectric constant in the major axis direction (X direction in the figure) of the liquid crystal molecules, and the dielectric constant ε ⊥  indicates a dielectric constant in the minor axis direction (Y direction in the figure) of the liquid crystal molecules. Hereinafter, ε //  and ε ⊥  are referred to as the major-axis dielectric constant and the minor-axis dielectric constant, respectively. 
     First, in the liquid crystal display device  100  according to the first exemplary embodiment shown in  FIG. 1 , the dielectric constant ε t1  of the dielectric protrusion  18  provided as the alignment control device of the liquid crystal is set to be smaller than the major-axis dielectric constant ε //  of the liquid crystal molecules  51 . That is, the dielectric constant ε t1  of the dielectric protrusion  18  and the dielectric constants ε //  and ε ⊥  of the liquid crystal molecules  51  satisfy a relation ε ⊥ &gt;ε // &gt;ε t1 . On the contrary, in the liquid crystal display device  200  according to the second exemplary embodiment shown in  FIG. 2 , the dielectric constant ε t1  of the dielectric protrusion  18  is set to be greater than the major-axis dielectric constant ε //  of the liquid crystal molecules  51  (ε t1 &gt;ε // ). 
     In both liquid crystal display devices, the arrangements of the dielectric protrusion  18  are different from each other. In this way, in the liquid crystal display device according to the exemplary embodiments, the arrangement relation between the dielectric protrusion  18  and the alignment control structure (the edge portion  31   a  of the electrode) adjacent to the dielectric protrusion  18  is properly set in accordance with the relation between the dielectric constant of the dielectric protrusion  18  and the dielectric constant of the liquid crystal molecules  51 , thereby obtaining a satisfactory display with a high image quality and a wide viewing angle. 
     Referring to  FIGS. 3 to 10 , movement of the liquid crystal molecules and operation of the liquid crystal display device according to the present exemplary embodiment will be described in accordance with the relation between the dielectric constant ε t1  of the dielectric protrusion  18  and the dielectric constant ε // , and ε ⊥  of the liquid crystal molecules  51 .  FIGS. 3 to 10  are cross-sectional views illustrating a result of simulation calculating movement of the liquid crystal molecules when the dielectric constant of the dielectric protrusion  18  is varied. 
     In the liquid crystal display device showing a main part (a part of a basic structure) in one dot area in which the dielectric constant ε t1  of the dielectric protrusion is 1.0, the major-axis dielectric constant ε //  of the liquid crystal molecules is 4.0, and the minor-axis dielectric constant ε ⊥  is 9.0, a liquid crystal state ( FIG. 3 ) right after application of voltage between both electrodes  9  and  31  and a liquid crystal state ( FIG. 4 ) after 100 ms passes are shown in  FIGS. 3 and 4 . 
     In the simulations of which the results are illustrated in  FIGS. 3 to 8 , as a structure of the electrode and the dielectric protrusion, the dielectric protrusion  18  is provided approximately at the center on the electrode  9  of the second substrate  10 , the first electrode  31  is formed narrower than the second electrode  9 , and the edge portions  31   a  and  31   a  of the first electrode  31  are disposed above the second electrode  9 . 
     In the liquid crystal display device showing a main part (a part of a basic structure) in one dot area in which the dielectric constant ε t1  of the dielectric protrusion is 3.5, the major-axis dielectric constant ε //  of the liquid crystal molecules is 4.0, and the minor-axis dielectric constant ε ⊥  is 9.0, a liquid crystal state ( FIG. 5 ) right after application of voltage between both electrodes  9  and  31  and a liquid crystal state ( FIG. 6 ) after 100 ms passes are shown in  FIGS. 5 and 6 . 
     In the liquid crystal display device showing a main part (a part of a basic structure) in one dot area in which the dielectric constant ε t1  of the dielectric protrusion is 5.0, the major-axis dielectric constant ε //  of the liquid crystal molecules is 4.0, and the minor-axis dielectric constant ε ⊥  is 9.0, a liquid crystal state ( FIG. 7 ) right after application of voltage between both electrodes  9  and  31  and a liquid crystal state ( FIG. 8 ) after 100 ms passes are shown in  FIGS. 7 and 8 . 
     As shown in the figures, under the conditions shown in  FIGS. 3 and 6  in which the dielectric protrusion  18  and the liquid crystal molecules  51  satisfy a relation ε t1 &lt;ε // , the liquid crystal molecules  51  fall down toward both sides (toward the edges of the electrode) from the dielectric protrusion  18 , and two liquid crystal domains are formed symmetrically about the dielectric protrusion  18 . Now, the alignment control functions of the edge portions  31   a  and the dielectric protrusion  18  will be described. 
     When no device for controlling the alignment of the liquid crystal molecules exists, the liquid crystal molecules fall down in a random direction with application of a voltage. In this case, a discontinuous line (disclination) appears in a boundary with a liquid crystal domain having a different alignment state, thereby causing a remaining image or decrease in brightness. Since the disclination appears at different positions depending upon application of a voltage, the size of the liquid crystal domain in the dot area is not stable, and since the liquid crystal domains have different viewing angle characteristics, the disclination appears like a spot shape as seen in a tilted direction. Therefore, by providing the alignment control device of the liquid crystal molecules, it is possible to bring down the liquid crystal molecules in a predetermined direction at the time of applying a voltage. 
     First, the function of the dielectric protrusion  18  will be described with reference to  FIGS. 3 and 4 . Since an alignment film  23  is formed on the surface of the second electrode  9  including the dielectric protrusion  18  (as shown in  FIGS. 1 and 2 ), the liquid crystal molecules  51  are aligned vertical to the substrate plane at the time of no application of a voltage and right after the application of a voltage is stopped. Here, when a voltage is applied to the first electrode  31  and the second electrode  9 , an electric field expressed by the equi-potential lines  52 , is formed in the liquid crystal layer  50 , and specifically, around the dielectric protrusion  18 , distortion of the electric field is generated due to the difference in dielectric constant between the dielectric protrusion  18  and the liquid crystal molecules  51 . When the distortion is generated, the liquid crystal molecules  51  aligned vertical to the substrate plane are pre-tilted by a predetermined angle about the electric field. Therefore, the liquid crystal molecules  51  can be brought down toward the lateral outsides (in a direction which the contact angle about the slope surface of the dielectric protrusion  18  is increased) of the dielectric protrusion  18  with application of a voltage, thereby controlling the alignment. The liquid crystal molecules in the periphery of the dielectric protrusion  18  can be also brought down in the same direction in the same way as bringing down dominoes. 
     Next, the function of the edge portions  31   a  of the electrode will be described. Since an alignment film  33  is formed to cover the edge portions  31   a , the liquid crystal molecules  51  at the time of no application of a voltage are aligned vertical to the substrate plane. Here, when a voltage is applied to the first electrode  31  and the second electrode  9 , as indicated by the equi-potential lines  52 , an oblique electric field is generated around the edge portions  31   a  of the electrode. Since the major axis direction of the liquid crystal molecules  51  at the time of no application of a voltage is inclined by a predetermined angle as seen from the oblique electric field, it is similar to the case where a pre-tilt angle is given to the liquid crystal molecules. Therefore, by applying a voltage, the liquid crystal molecules can be brought down toward the center of the electrode from the edge portions  31   a , thereby controlling the alignment. The liquid crystal molecules  51  disposed inside the edge portions  31   a  (at the center side of the electrode) can be sequentially brought down in the same direction in accordance with the alignment direction of the liquid crystal molecules  51  in the edge portions  31   a , similar to a domino effect. 
     Through the above operation, the liquid crystal molecules  51  of which the alignment has been controlled by the dielectric protrusion  18  and the edge portions  31   a  of the electrode are uniformly brought down in the same direction between the dielectric protrusion  18  and one edge portion  31   a , so that the liquid crystal domains, approximately symmetric about the dielectric protrusion  18 , are formed as shown in  FIGS. 4 and 6 . Therefore, in the liquid crystal display device  100  according to the exemplary embodiment shown in  FIG. 1 , which has the same condition as  FIGS. 3 to 6 , it can be seen that a satisfactory display with a wide viewing angle and a high brightness can be obtained. 
     On the contrary, under the condition shown in  FIGS. 7 and 8 , the dielectric constants of the dielectric protrusion  18  and the liquid crystal molecules  51  satisfy the expression ε t1 &gt;ε // . As shown in  FIG. 8 , the liquid crystal molecules  51  fall down in the direction (a direction toward the front tip of the dielectric protrusion  18 , that is, a direction in which the contact angle with the slope of the dielectric protrusion  18  is decreased) along the slope of the dielectric protrusion  18  at the time of applying a voltage, and the liquid crystal molecules  51  around the dielectric protrusion  18  fall down toward the dielectric protrusion  18 . On the other hand, similarly to the conditions of  FIGS. 3 to 6 , at the edge portions  31   a  of the first electrode  31 , the liquid crystal molecules  51  are brought down toward the center of the first electrode  31 . In this way, the liquid crystal molecules  51  are brought down in the opposite direction between the dielectric protrusion  18  and the edge portions  31   a , and as a result, the liquid crystal molecules  51  are not brought down at a middle position between the dielectric protrusion  18  and the edge portions  31   a  of the first electrode, thereby causing the disclination. 
     In this way, when the dielectric constant ε t1  of the dielectric protrusion  18  is different from the dielectric constant ε //  of the liquid crystal molecules  51 , the behavior of the liquid crystal molecules  51  at the time of applying a voltage is varied, so that a high-quality display having a wide viewing angle is obtained under the condition of ε t1 &lt;ε //  shown in  FIGS. 3 to 6 . However, under the condition of ε t1 &gt;ε //  shown in  FIGS. 7 and 8 , the declination is generated in the dot area, thereby deteriorating the display quality. The difference in behavior of the liquid crystal molecules depending upon the conditions resulting from different shapes of distortion of an electric field generated in the liquid crystal layer  50  due to the difference in dielectric constant between the dielectric protrusion  18  and the liquid crystal. That is, under the condition shown in  FIGS. 4 and 6 , due to the shape of the equi-potential lines  52 , shown in both figures, the electric-field distortion convex upwardly at the upside of the dielectric protrusion  18  in the figures is generated, and under the condition shown in  FIG. 8 , the electric-field distortion downwardly convex is generated. Accordingly, the falling-down direction of the liquid crystal molecules  51  are varied, so that the liquid crystal domains formed in the liquid crystal layer  50  are varied. 
     As described above, under the condition (ε t1 &gt;ε // ) shown in  FIGS. 7 and 8 , a satisfactory display cannot be obtained. Therefore, the inventor of the present invention repeatedly studied the structure of the liquid crystal display device for obtaining a satisfactory display even under the condition shown in  FIGS. 7 and 8 , and as a result, found out that by the dielectric protrusion  18  at the first substrate  25  side having another alignment control structure (the edge portions  31   a  of the first electrode  31 ) as shown in  FIG. 2 , a satisfactory display can be obtained even when the dielectric protrusion  18  having a dielectric constant higher than the dielectric constant ε //  of the liquid crystal molecules. 
       FIGS. 9 and 10  show results of simulation in the liquid crystal display device having the same structure as the liquid crystal display device  200  shown in  FIG. 2 , in which the dielectric protrusion  18  is disposed on the electrode  31  of the first substrate  25 . The dielectric constant ε t1  of the dielectric protrusion  18  is 5.0, the dielectric constant ε //  in the major axis direction of the liquid crystal molecules  51  is 4.0, and the minor-axis dielectric constant ε ⊥  is 9.0. 
     As shown in  FIG. 10 , when the structure shown in  FIG. 2  is employed, the liquid crystal domains symmetric about the dielectric protrusion  18  are formed in the liquid crystal layer  50  at the time of applying a voltage, so that it is possible to provide a liquid crystal display device capable of performing a satisfactory display with a wide viewing angle and a high brightness even under the condition of ε t1 &gt;ε // . 
     The inventor of the present invention verified the response speed of the liquid crystal display device when the dielectric constant ε t1  of the dielectric protrusion  18  is changed. As a result, in the liquid crystal display device having the condition (ε t1 =1.0) of  FIGS. 3 and 4 , it was seen that it is possible to accomplish enhancement of the response speed by about 5 ms in the intermediate gray-scale area compared with the liquid crystal display device having the condition (ε t1 =3.5) of  FIGS. 5 and 6 . As can be seen from the comparison of the distributions of the equi-potential lines  52 , in  FIGS. 4 and 6 , it is because the distortion of an electric field due to the dielectric protrusion  18  of  FIG. 4  is greater, and thus the alignment control ability for the liquid crystal molecules  51  is increased. 
     Although it has been described in the above exemplary embodiment that the case where the edge portions  31   a  of the first electrode  31  are used as an example of the alignment control structure adjacent to the dielectric protrusion  18 , an opening slit formed by cutting out a part of the first electrode  31  in place of the edge portions  31   a  of the first electrode  31  may be provided at both sides (portions positioned at both ends of the first electrode  31 ) of the dielectric protrusion  18 , and in this case, the same advantage can be obtained. 
     In the exemplary embodiments, the alignment control structure adjacent to the dielectric protrusion  18  may be another dielectric protrusion (second dielectric protrusion). However, in this case, it is necessary to pay attention to the dielectric constant of another dielectric protrusion (second dielectric protrusion). That is, as can be clearly seen from the above description, in order to form a dielectric protrusion having the same alignment control function as the edge portion  31   a  or the opening slit of the first electrode, the dielectric constant (ε t2 ) of the second dielectric protrusion together with the major-axis dielectric constant ε //  of the liquid crystal molecules  51  should have the relation ε t2 &lt;ε // . 
     On the other hand, the dielectric constant ε t2  of the second dielectric protrusion together with the major-axis dielectric constant ε //  of the liquid crystal molecules has the relation ε t2 &gt;ε // , the liquid crystal molecules  51  fall down toward the dielectric protrusion from the periphery. As a result, when the liquid crystal display device having the second dielectric protrusion is embodied, in the structure shown in  FIG. 1 , the second dielectric protrusions instead of the edge portions  31   a  of the first electrode are provided at both sides with the dielectric protrusion  18  therebetween at the same side (on the electrode  9  of the second substrate) as the dielectric protrusion  18 , and in the structure shown in  FIG. 2 , the second dielectric protrusions instead of the edge portions  31   a  of the first electrode are provided at the opposite ends of the dielectric protrusion  18  (on the electrode  9  of the second substrate). When this structure is employed, it is also possible to obtain a satisfactory display with a wide viewing angle and a high brightness in the liquid crystal display device in which the second dielectric protrusions having the dielectric constant ε t2  higher than the major-axis dielectric constant ε //  of the liquid crystal molecules are provided as the alignment control structure adjacent to the dielectric protrusion  18 . 
     Specific Structural Example of Liquid Crystal Display Device 
     The construction described in the above exemplary embodiment may be also applied to the liquid crystal display device including a liquid crystal having a negative dielectric anisotropy.  FIGS. 11A-11D  schematically illustrate various types of liquid crystal display devices.  FIG. 11A  shows a transmissive liquid crystal display device,  FIG. 11B  shows a reflective liquid crystal display device, and  FIGS. 11C and 11D  show a transflective liquid crystal display device. In addition,  FIG. 11C  shows a case where the first substrate is used as the element substrate and the second substrate is used as the counter substrate, and  FIG. 11D  shows a case where the second substrate is used as the element substrate and the first substrate is used as the counter substrate. In the liquid crystal display devices shown in  FIGS. 11A-11D , it is possible to obtain the aforementioned advantages by forming the dielectric protrusions and the opening slits on the surface of a transparent electrode. Therefore, in the embodiment to be described later, the transmissive liquid crystal display device shown in  FIG. 11A  is described as a first structural example. As a second structural example, the transflective liquid crystal display device shown in  FIG. 11C  is described. 
     First Structural Example 
       FIG. 12  is a partial perspective view illustrating a specific structural example of the liquid crystal display device according to the aforementioned exemplary embodiment,  FIG. 13  is a partial cross-sectional view illustrating one dot area of the liquid crystal display device, and  FIG. 14  is a plan view illustrating one pixel area comprising three dot areas of the liquid crystal display device. The liquid crystal display device shown in the figures is an active-matrix color liquid crystal display device employing a TFD (Thin Film Diode) element (two-terminal nonlinear element) as a switching element. However, the present exemplary embodiment may be also applied to an active-matrix liquid crystal display device employing a TFT (Thin Film Transistor) as the switching element. The partial cross-section structure shown in  FIG. 13  corresponds to the cross-sectional structure taken along Line XIII-XIII shown in  FIG. 14 . 
     As shown in  FIG. 12 , the liquid crystal display device according to the present example includes an element substrate (first substrate)  25  and a counter substrate (second substrate)  10  opposite to each other as major elements, and a liquid crystal layer not shown is interposed between both substrates  10  and  25 . As conceptually shown in  FIG. 13 , the liquid crystal layer includes a liquid crystal having a negative dielectric anisotropy indicating an initial alignment of vertical alignment. The element substrate  25  is a substrate made of a light-transmitting material such as glass, plastic, quartz, etc., and a plurality of data lines  11  extending in a direction intersecting scanning lines (serving as the counter electrode  9 ) of the counter substrate  10  are provided in a stripe shape inside the inner surface (at the lower side in the figure). A plurality of pixel electrodes (first electrode)  31  having an approximately rectangular shape as seen two-dimensionally and made of a transparent conductive material such as ITO (Indium Tin Oxide) are arranged in a matrix shape, and are connected to the data lines  11  through the TFD elements  13  provided correspondingly to the respective pixel electrodes. 
     On the other hand, the counter substrate  10  is a substrate made of a light-transmitting material such as glass, plastic, quartz, etc., and a color filter layer  22  and a plurality of scanning lines  9  are formed inside the inner surface (the upper side in the figure). As shown in  FIG. 12 , in the color filter layer  22 , approximately rectangular color filters  22 R,  22 G, and  22 B are periodically arranged as seen two-dimensionally. The respective color filters  22 R,  22 G, and  22 B are formed correspondingly to the pixel electrodes  31  of the element substrate  25 . The scanning lines  9  are formed in a belt shape out of a transparent conductive material such as ITO and extend in the direction intersecting the data lines  11  of the element substrate  25 . The scanning lines  9  are formed to cover the color filters  22 R,  22 G, and  22 B arranged in the extension direction thereof, and serve as the counter electrode (first electrode). The formation area of the pixel electrode  31  constitutes one dot and three dots including the color filters  22 R,  22 G, and  22 B constitute one pixel. 
     Exemplary Cross-Sectional Structure 
     Next,  FIG. 13  is a partial cross-sectional view illustrating one dot area of  FIG. 12 . In  FIG. 13 , for the purpose of easy understanding, the TFD elements and various lines on the element substrate  25  are omitted. 
     As shown in  FIG. 13 , at the liquid crystal layer side of the pixel electrode  31  in the element substrate  25 , a vertical alignment film  33  made of polyimide, etc. is formed. On the other hand, at the liquid crystal layer side of the counter electrode  9  in the counter substrate  10 , a vertical alignment film  23  made of polyimide, etc. is formed. In addition, the alignment films  23  and  33  have been subjected to the vertical alignment process, but have not been subjected to the process of giving a pre-tilt such as a rubbing. 
     A liquid crystal layer  50  made of a liquid crystal material having a negative dielectric anisotropy is interposed between the element substrate  25  and the counter substrate  10 . As conceptually shown by the liquid crystal molecules  51 , the liquid crystal material is aligned vertical to the alignment film at the time of no application of a voltage, and the liquid crystal material is aligned parallel (that is, vertical to the electric field direction) to the alignment film at the time of applying a voltage. The element substrate  25  and the counter substrate  10  are bonded to each other through a seal member (not shown) coated at the circumferential edge portions of the element substrate  25  and the counter substrate  10 , and the liquid crystal layer  50  is sealed in the space formed by the element substrate  25 , the counter substrate  10 , and the seal member. 
     On the other hand, a retardation film  36  and a polarizing film  37  are provided on the outer surface of the element substrate  25 , and a retardation film  26  and a polarizing film  27  are provided on the outer surface of the counter substrate  10 . The polarizing films  27  and  37  have a function of transmitting only the linearly-polarized light which is vibrating in a specific direction. As the retardation films  26  and  36 , λ/4 wave plates having a phase difference of a ¼ wavelength for the wavelength of visible ray are employed. The transmission axes of the polarizing films  27  and  37  and the phase-lag axes of the retardation films  26  and  36  form about 45°, and a circular polarizing film is constituted by the polarizing films  27  and  37  and the retardation films  26  and  36 . The linearly-polarized light can be converted into circularly-polarized light and the circularly-polarized light can be converted into the linearly-polarized light using the circularly-polarized light. The transmissive axis of the polarizing film  27  and the transmissive axis of the polarizing film  37  are perpendicular to each other and the phase-lag axis of the retardation film  26  and the phase-lag axis of the retardation film  36  are perpendicular to each other. At the outside of the liquid crystal cell contacting the outer surface of the counter substrate  10 , a backlight (lighting device)  60  having a light source, a reflector, a light-guiding plate, etc. is provided. 
     In the liquid crystal display device according to the present exemplary embodiment shown in  FIG. 13 , the image display is performed as follows. The light applied from the backlight  60  is converted into circularly-polarized light through the polarizing film  27  and the retardation film  26 , and then enters the liquid crystal layer  50 . Since the liquid crystal molecules do not have a refractive anisotropy, the entry light passes through the liquid crystal layer  50  with circular polarization. The entry light passing through the retardation film  36  is converted into the linearly-polarized light perpendicular to the transmissive axis of the polarizing film  37 . Then, since the linearly-polarized light does not pass through the polarizing plate  27 , in the liquid crystal display device according to the present exemplary embodiment, the black display is performed at the time of no application of a voltage (normally black mode). 
     On the other hand, when an electric field is applied to the liquid crystal layer  50 , the liquid crystal molecules are re-aligned in parallel to the substrate and have a refractive anisotropy. Accordingly, the circularly-polarized light entering the liquid crystal layer  50  from the backlight  60  is converted into elliptically-polarized light in the course of passing through the liquid crystal layer  50 . Although the entry light passes through the retardation film  36 , the entry light is not converted into the linearly-polarized light perpendicular to the transmissive axis of the polarizing film  37 , and all or a part thereof passes through the polarizing film  37 . Therefore, in the liquid crystal display device according to the present exemplary embodiment, the white display is performed at the time of applying a voltage. In addition, by adjusting the voltage applied to the liquid crystal layer  50 , the gray-scale display may be performed. 
     Exemplary Alignment Control Device 
       FIG. 14  is a plan view illustrating one pixel area including three dot areas in the liquid crystal display device shown in  FIG. 12 . Here, the constituent members of element substrate are indicated by solid lines and the constituent members of the counter substrate are indicated by dot-dashed lines. As shown in  FIG. 14 , the opening slit  31   b  or the dielectric protrusion  18 , which is the alignment control device of the liquid crystal molecules, is formed on the surface of the pixel electrode  31  and the counter electrode  9 . A plurality of opening slits  31   b  having approximately a belt shape as seen two-dimensionally is formed in the pixel electrode  31 . A plurality of dielectric protrusions  18  having approximately a belt shape as seen two-dimensionally is formed on the surface of the counter electrode  9 . The dielectric protrusions  18  formed in the counter substrate  10  and the opening slits  31   b  formed in the element substrate  25  are disposed to be alternate (to depart from each other without two-dimensionally overlapping each other) in the longitudinal direction of the pixel electrode  31 . The protrusions  18  and the slits  31   b  are disposed such that the pitch of the protrusions  18  and the pitch of the slits  31   b  are enlarged from one longitudinal side to the other longitudinal side in the pixel electrode  31 . To the contrary, the opening slits may be formed in the counter electrode  10  and the dielectric protrusions may be formed on the pixel electrode. 
     The dielectric protrusions  18  are made of a dielectric material such as resin and are formed using a photolithography method, etc. employing a gray mask. In the liquid crystal display device according to the present example, a plurality of dielectric protrusions  18  and the alignment control structures (opening slits) are employed in the structure of the liquid crystal display device  100  shown in  FIG. 1 , so that the dielectric constant ε t1  of the dielectric protrusions  18  is set to be smaller than the major-axis dielectric constant ε //  of the liquid crystal molecules  51 . That is, since the liquid crystal display device according to the present example employs the basic structure and function of the liquid crystal display device shown in  FIG. 1  and the arrangement of the dielectric protrusions  18  and the opening slits  31   b  is suitably determined in accordance with the dielectric constant relation between the dielectric protrusions  18  and the liquid crystal layer  50 , it is possible to obtain a satisfactory display with a high contrast without generating the disclination in the dot area. 
     In the liquid crystal display device according to the present example, as seen two-dimensionally, the liquid crystal molecules fall down radially about the opening slits  31   b  of a belt shape at the time of applying an electric field. In addition, the liquid crystal molecules  51  fall down about the dielectric protrusions  18 . Due to operation of the dielectric protrusions  18  and the opening slits  31   a , the liquid crystal molecules are aligned in a predetermined direction between the dielectric protrusions  18  and the opening slits  31   b  shown in  FIG. 14 , thereby suitably controlling the alignment of the liquid crystal layer  50  in the dot area. 
     Although it has been described in the present example that the opening slits  31   b  as the alignment control structures adjacent to the dielectric protrusions  18  are formed in the electrode provided in the dot area, other dielectric protrusions having a relation ε // &gt;ε t2  with the dielectric constant ε t2  may be provided by forming other dielectric protrusions inside the opening slits. Accordingly, since there is provided an alignment control structure for performing the alignment control of the liquid crystal molecules using the oblique electric field generated around the opening slits and the distortion of an electric field generated by the dielectric protrusions, the liquid crystal molecules spaced from the alignment control structure can be satisfactorily controlled, so that it is advantageous for enhancing the response speed and the aperture ratio. 
     Although it has been described in the present example that the dielectric protrusions  18  are formed on the counter electrode  9 , slits may be formed by cutting out the counter electrode  9  into two-dimensional shapes corresponding to the dielectric protrusions  18  and the dielectric protrusions  18  may be provided inside the slits. That is, at least a part of the counter electrode  9  serving as a base of the portions formed with the dielectric protrusions  18  may be cut out (opened). Accordingly, the distortion of an electric field generated around the dielectric protrusions  18  can be enhanced at the time of applying a voltage and thus larger alignment control ability can be obtained, so that it is possible to enhance the response speed of the liquid crystal display device. 
     Second Structural Example 
     Next, a second structural example of the liquid crystal display device according to the exemplary embodiments will be described.  FIG. 15  is a cross-sectional view taken along a longitudinal direction (longitudinal side) of one dot area of the liquid crystal display device of the present structural example, and  FIG. 16  is a plan view illustrating one pixel area including three dot areas in the liquid crystal display device. The liquid crystal display device of the present structural example is a transflective liquid crystal display device. The elements similar to the first exemplary embodiment will be not described. The cross-sectional structure shown in  FIG. 15  corresponds to the cross-sectional structure taken along Line XV-XV of  FIG. 16 . 
     As shown in  FIG. 15 , in the liquid crystal display device of the second structural example, a reflective film  20  made of a metal film having a high reflectance, such as aluminum or silver, etc. is formed at the inside of the second substrate (counter substrate)  10 . An opening portion  20   a  cut out correspondingly to the transmissive display area is formed in a part of the reflective film  20 . The portion in which the formation area of the pixel electrode (first electrode)  31  and the formation area of the reflective film  20  overlaps each other forms the reflective display area, and the portion in which the formation area of the pixel electrode  31  and the non-formation area of the reflective film  20  (that is, the formation area of the opening portion  20   a ) overlap each other forms the transmissive display area. The color filter layer  22  is formed at the inside of the reflective film  20  and the substrate  10 . In order to compensate for variation in saturation of a displayed color in the reflective display and in the transmissive display, color material layers with varied color purity may be provided in the reflective display area and the transmissive display area. 
     On the other hand, at the liquid crystal layer side of the element substrate (first substrate)  25 , a pixel electrode  31 , a plurality of (three) dielectric protrusions  18 , and a vertical alignment film  33  are provided in this order. 
     An insulating film  21  is formed at the position on the color filter layer  22  corresponding to the reflective display area. The insulating film  21  is made of an organic film such as an acryl resin with a thickness of 2 μm±1 μm. The thickness of the liquid crystal layer  50  in the portion in which the insulating film  21  does not exist is about 2 to 6 μm, and the thickness of the liquid crystal layer  50  in the reflective display area is about a half the thickness of the liquid crystal layer  50  in the transmissive display area. That is, the insulating film  21  serves as a liquid-crystal-layer thickness adjusting layer for varying the thickness of the liquid crystal layer  50  in the reflective display area and the transmissive display area with its thickness, thereby embodying a multi-gap structure. According to the liquid crystal display of the present example, it is possible to a bright and high-contrast display using the above structure. A sloping surface for continuously varying the thickness of the insulating film  21  is formed around the boundary between the reflective display area and the transmissive display area. 
     In the transflective liquid crystal display device shown in  FIG. 15 , an image display is performed as follows. First, the light entering the reflective display area from the upside of the element substrate  25  is converted into the circularly-polarized light during passing through the polarizing film  37  and the retardation film  36 , and then enters the liquid crystal layer  50 . Since the liquid crystal molecules aligned vertical to the substrates at the time of applying no voltage do not have the refractive anisotropy, the entry light passes through the liquid crystal layer  50  with the circular polarization. The entry light reflected by the reflective film  20  and passing again through the retardation film  36  is converted into the linearly-polarized light perpendicular to the transmissive axis of the polarizing film  37 . The linearly-polarized light does not pass through the polarizing film  37 . On the other hand, similarly, the light entering the transmissive display area from the backlight  60  is converted into the circularly-polarized light during passing through the polarizing film  27  and the retardation film  26 , and then enters the liquid crystal layer  50 . The entry light passing through the retardation film  36  is converted into the linearly-polarized light perpendicular to the transmissive axis of the polarizing film  37 . Since the linearly-polarized light does not pass through the polarizing film  37 , black is displayed at the time of applying no voltage in the liquid crystal display device of the present exemplary embodiment (normally black mode). 
     On the other hand, when an electric field is applied to the liquid crystal layer  50 , the liquid crystal molecules are re-aligned parallel to the substrates and show the double refractive operation about the transmitted light. Accordingly, the circularly-polarized light entering the liquid crystal layer  50  in the reflective display area and the transmissive display area is converted into the elliptically-polarized light during passing through the liquid crystal layer  50 . Although the entry light passes through the retardation film  36 , it is not converted into the linearly-polarized light perpendicular to the transmissive axis of the polarizing film  37  and all or a part thereof passes through the polarizing film  37 . Therefore, in the liquid crystal display device according to the present exemplary embodiment, white is displayed at the time of applying a voltage. By adjusting a voltage applied to the liquid crystal layer  50 , the gray scale may be displayed. 
     In this way, the entry light passes through the liquid crystal layer  50  two times in the reflective display area, while the entry light passes through the liquid crystal layer  50  only one time in the transmissive display area. In this case, when the retardation (phase difference) of the liquid crystal layer  50  is varied between the reflective display area and the transmissive display area, a difference in transmittance is caused, so that it is not possible to obtain a uniform image. However, in the liquid crystal display device according to the present exemplary embodiment, since the liquid-crystal-layer thickness adjusting layer  21  is provided, the retardation can be adjusted in the reflective display area. Therefore, a uniform image display can be obtained in the reflective display area and the transmissive display area. 
     Exemplary Alignment Control Device 
       FIG. 16  is a plan view illustrating one pixel area of the liquid crystal display device shown in  FIG. 15 , where the constituent elements of the element substrate are indicated by the solid lines and the constituent elements of the counter substrate are indicated by the dot-dashed lines. As shown in  FIG. 16 , a plurality of slits  31   c  is formed toward the center from the longitudinal side in the pixel electrode  31 . That is, the pixel electrode  31  disposed correspondingly to one dot area includes three island-shaped sub pixels  32  and connecting portions connecting the sub pixels, and the connecting portions substantially constitute the slits  31   c  (notched portions of the electrodes) for controlling the alignment of the liquid crystal molecules. The pixel electrode  31  is divided into three sub pixels  32  by the slits  31   c , and the respective sub pixels are connected at the center portion thereof. At least one sub pixel of the three sub pixels  32  is assigned and formed correspondingly to the reflective display area. Therefore, on the substrate on which the pixel electrodes  31  are formed, the dielectric protrusion  18 , the slit  31   c , the dielectric protrusion  18 , the slit  31   c , and the dielectric protrusion  18  are disposed along the longitudinal direction (longitudinal side) of the pixel electrode  31  in that order. 
     On the surface of the pixel electrode  31  corresponding to the center portion of the respective sub pixels  32 , the dielectric protrusion  18  is formed. The dielectric protrusion  18  is formed approximately in a circular shape in a plan view and approximately in a triangular shape in a cross-sectional view as shown in  FIG. 15 . That is, the liquid crystal display device of the present example employs the basic structure and operation of the liquid crystal display device  200  according to the second exemplary embodiment shown in  FIG. 2 , so that a plurality of dielectric protrusions  18  is provided in the same substrate as a plurality of slits  31   c  which is an alignment control structure. 
     Using the electrode structure including the sub pixels, a plurality of liquid crystal domains can be formed in one dot area. The corner portions of the sub pixels  32  are cut out, so that the sub pixels  32  have approximately an octagonal shape or a circular shape as seen two-dimensionally. When an electric field is applied to the liquid crystal layer, the liquid crystal molecules  51  fall down vertical to the outlines (the edge portions  31   a  shown in  FIG. 1 ) of the sub pixels  32 . Around the dielectric protrusion  18 , the liquid crystal molecules  51  are aligned vertical to the slope surface of the dielectric protrusion  18  at the time of applying no voltage, and the liquid crystal molecules  51  fall down toward the dielectric protrusion  18  as shown in  FIG. 16  and the liquid crystal molecules  51  are aligned radially about the dielectric protrusion at time of applying a voltage. 
     Therefore, a plurality of directors for the liquid crystal molecules can be provided, and thus a liquid crystal display device having a wide viewing angle can be provided. To the contrary, the slits and the dielectric protrusions may be formed in the counter electrode  9 . 
     In the liquid crystal display device according to the present example shown in  FIGS. 15 and 16 , since the slits  31   c  and the dielectric protrusions  18  are provided in the pixel electrode  31 , it is not necessary to perform the positioning between the slits  31   c  and the dielectric protrusions  18  when the element substrate  25  and the counter substrate  10  are bonded to each other with the liquid crystal layer  50  therebetween, so that the liquid crystal display device can be easily manufactured and the enhancement of yield can be expected. 
     Exemplary Electronic Apparatus 
       FIG. 17  is a perspective view illustrating an example of an electronic apparatus according to the exemplary embodiments. A mobile phone  1300  shown in  FIG. 17  includes the liquid crystal display device according to the exemplary embodiments as a small-sized display unit  1301 , and further includes a plurality of manipulation buttons  1302 , a receiver  1303 , and a transmitter  1304 . 
     The display device according to the aforementioned exemplary embodiments is not limited to the mobile phone, but may be suitably used as an image display device of an electronic book, a personal computer, a digital still camera, a liquid crystal television, a view-finder or monitor direct-view video tape recorder, a car navigation apparatus, a pager, an electronic pocket book, a calculator, a word processor, a work station, a television phone, a POS terminal, an apparatus having a touch panel, and the like. Therefore, in any electronic apparatus, it is possible to perform transmissive or reflective display with a high brightness, a high contrast, and a wide viewing angle.