JP2007018014A - Liquid crystal display device and electronic apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal display device with a vertical alignment mode in which a high image quality and a wide viewing angle are secured. <P>SOLUTION: The liquid crystal display device is made by interposing a liquid crystal layer including a liquid crystal whose dielectric anisotropy is negative between a pair of substrates, wherein, in a dot region constituting a display unit, a dielectric protrusion disposed on an electrode, an aperture slit disposed on the electrode or a marginal end part of the electrode are disposed on one substrate side of the pair of substrates and, in order to prevent the liquid crystal from inclining to contradictory directions on a straight line of connecting the dielectric protrusion and the aperture slit or the marginal end part as a plain view when a voltage is applied to the liquid crystal, dielectric constant ε<SB>t1</SB>of the dielectric protrusion, dielectric constant ε<SB>//</SB>of major axis of liquid crystal and dielectric constant ε<SB>⊥</SB>of minor axis thereof has the relation; ε<SB>t1</SB>>ε<SB>//</SB>. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a liquid crystal display device and an electronic apparatus.

  In recent years, liquid crystal display devices having a vertically aligned liquid crystal mode have been put into practical use. In this type of liquid crystal display device, it is necessary to appropriately control the direction in which the liquid crystal aligned vertically with respect to the substrate is tilted when a voltage is applied, and the alignment composed of slits (notches) and dielectric protrusions for the purpose of controlling the alignment. A control structure is provided on the electrode (see Patent Document 1). Studies have also been made on the arrangement conditions of the dielectric protrusions (see Non-Patent Document 1).

Japanese Patent No. 2947350 A Super-High Quality Multi-Domain Vertical Alignment LCD by New Rubbing-Less Technology, SID1998 DIGEST 41.1

  Providing an alignment control structure as in the above prior art and setting the arrangement conditions and the like appropriately is effective for improving the image quality of a vertical alignment mode liquid crystal display device. However, the present inventor has conducted research for the purpose of further improving the image quality and widening the viewing angle of the liquid crystal display device in the vertical alignment mode. When the dielectric protrusion is provided as the alignment control structure, the characteristics of the liquid crystal are reduced. Accordingly, it has been found that it is necessary to provide a dielectric protrusion having appropriate characteristics. In other words, it has been found that when such optimization is not performed, the image quality of the conventional liquid crystal display device that controls the alignment of the vertically aligned liquid crystal by the dielectric protrusion may be deteriorated. The present invention provides means for solving such problems, and an object of the present invention is to provide a vertical alignment mode liquid crystal display device realizing high image quality and wide viewing angle.

The above-described problem is a liquid crystal display device in which a liquid crystal layer having an initial state of vertical alignment is sandwiched between a pair of substrates having electrodes on opposite surfaces, and in the dot region constituting one display unit, A dielectric protrusion protruding toward the liquid crystal layer is formed on the electrode on one substrate, and is aligned at a position adjacent to the dielectric protrusion in the planar direction on the opposite surface side of the other substrate of the pair of substrates. When a control structure is provided, the dielectric constant of the dielectric protrusion is ε _t1 , the dielectric constant in the major axis direction of the liquid crystal molecules constituting the liquid crystal layer is ε _// , and the dielectric constant in the minor axis direction is ε _⊥ , according to this configuration can be solved by a relation of _{ε ⊥> ε //> ε t1} , the liquid crystal display device provided with a dielectric protrusion as a means of controlling alignment of the vertically aligned liquid crystal, the dielectric projection dielectric Field whose modulus is smaller than the dielectric constant in the long axis direction A, it is possible to satisfactorily perform the liquid crystal alignment control in the dot region, it is possible to obtain a wide viewing angle, a high-luminance display.

According to the present invention, there is provided a liquid crystal display device in which a liquid crystal layer including a liquid crystal having a negative dielectric anisotropy is sandwiched between a pair of substrates, wherein the pair of substrates are arranged in a dot region constituting a display unit. On one of the substrates, a dielectric protrusion provided on the electrode and an opening slit provided on the electrode or an edge of the electrode are provided, and when a voltage is applied to the liquid crystal, The dielectric constant of the dielectric protrusion is ε _t1 , and the major axis direction of the liquid crystal is set so that the liquid crystal does not tilt in the opposite direction on the straight line connecting the dielectric protrusion and the opening slit or the edge portion in plan view. the dielectric constant epsilon _//, a dielectric constant in the minor axis direction is taken as epsilon _⊥, to provide a liquid crystal display device, characterized in that a relation of ε _t1> ε _//. According to this configuration, in a liquid crystal display device having a dielectric protrusion as a means for controlling the alignment of vertically aligned liquid crystal, when the dielectric constant of the dielectric protrusion is larger than the dielectric constant in the major axis direction of the liquid crystal molecules, The liquid crystal orientation can be controlled well, and a display with a wide viewing angle and high luminance can be obtained. Moreover, in this structure, since the orientation control structure can be provided only on one substrate, the ease of manufacturing is improved, and an improvement in manufacturing yield can be expected.
Therefore, according to each of the above configurations, in a liquid crystal display device provided with dielectric protrusions as a means for controlling the alignment of vertically aligned liquid crystal, the behavior of liquid crystal molecules at the time of voltage application depending on the dielectric constant of the dielectric protrusions is appropriately controlled. Therefore, a liquid crystal display device capable of obtaining a display with a wide viewing angle and high luminance can be provided.

In the liquid crystal display device of the present invention, the alignment control structure adjacent to the dielectric protrusion is an opening slit formed in an electrode provided in the dot region, or an edge portion of the electrode. can do.
The alignment control structure adjacent to the dielectric protrusion is another dielectric protrusion, and when the dielectric constant of the other dielectric protrusion is ε _t2 , the dielectric constant ε _{// of the} liquid crystal molecule is , Ε _// > ε _t2 .
In the liquid crystal display device having the above configuration, as the alignment control structure adjacent to the dielectric protrusion, the alignment control of the liquid crystal molecules at the time of voltage application by the oblique electric field generated at the electrode edge, and the dielectric in the liquid crystal layer Any of those in which the orientation is controlled by distorting the electric field by providing projections having different rates can be applied.

In the liquid crystal display device of the present invention, it is preferable to have another dielectric protrusion provided inside the opening slit and having a dielectric constant ε _t2 of ε _// > ε _t2 . According to this configuration, since the other dielectric protrusion for controlling the alignment of the liquid crystal molecules is provided by the oblique electric field generated around the opening slit and the electric field distortion generated by the dielectric protrusion, the liquid crystal at a position away from the dielectric protrusion is provided. Molecules can also be well controlled in orientation, which is advantageous for improving response speed or aperture ratio.

Another solution is a liquid crystal display device in which a liquid crystal layer having an initial vertical orientation is sandwiched between a pair of substrates having electrodes on opposite surfaces, and within a dot region constituting one display unit, A first dielectric protrusion protruding toward the liquid crystal layer is formed on the electrode on one substrate of the pair of substrates, and the first dielectric protrusion and the flat surface are formed on the other substrate of the pair of substrates. A second dielectric protrusion is formed on the electrode at a position adjacent in the direction, the dielectric constant of the first dielectric protrusion is ε _t1 , the dielectric constant of the second dielectric protrusion is ε _t2 , and the liquid crystal When the dielectric constant in the major axis direction of the liquid crystal molecules constituting the layer is ε _// , and the dielectric constant in the minor axis direction is ε _⊥ , there is a relationship of ε _t1 > ε _// , and ε _t2 > ε _// Provided is a liquid crystal display device. Normally, the dielectric protrusions provided in the dot region and forming the alignment control structure are formed of the same material. However, a configuration in which the alignment control is performed by dielectric protrusions having different dielectric constants may be used. When dielectric protrusions having different dielectric constants are provided adjacent to each other, it is preferable to provide the dielectric protrusions on different substrates as in this configuration. With such a configuration, display with high image quality and wide viewing angle can be obtained.

  In addition, a reflective display area for performing reflective display and a transmissive display area for performing transmissive display can be provided in the dot area. According to this configuration, a transflective liquid crystal display device capable of transmissive / reflective display with a wide viewing angle and high image quality is provided.

  Next, the present invention provides an electronic apparatus comprising the liquid crystal display device of the present invention described above. According to the present invention, an electronic apparatus having a display unit with a wide viewing angle and high brightness is provided.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In each drawing referred to below, the size and thickness of each part are appropriately changed in order to make the drawing easy to see. FIG. 1 and FIG. 2 are cross-sectional configuration diagrams showing the main part (a part of the basic configuration) of the liquid crystal display device of the first embodiment and the second embodiment of the present invention, respectively.

In the liquid crystal display device 100 according to the first embodiment shown in FIG. 1, a liquid crystal layer 50 made of a liquid crystal having negative dielectric anisotropy is sandwiched between a first substrate 25 and a second substrate 10 which are arranged to face each other. It has a configuration. A second electrode 9, a dielectric protrusion 18, and a vertical alignment film 23 covering these second electrode 9 and dielectric protrusion 18 are formed in this order on the inner surface side (liquid crystal layer side) of the second substrate 10. Yes. On the inner surface side of the first substrate 25, a first electrode 31 and a vertical alignment film 33 are formed in this order. In the dot region constituting one display unit, the first electrode 31 is formed narrower than the second electrode 9, and the edge of the first electrode 31 in the horizontal direction in the figure (Y direction / plane direction of the first substrate 25). Portions (edge portions and cutout portions) 31 a and 31 a are planarly arranged above the second electrode 9. That is, within one dot region, the dielectric protrusion 18 is disposed between the edge 31a and the edge 31a of the first electrode 31 formed on different substrates (the dielectric protrusion 18 and the first protrusion 31). The edge portions 31a and 31a of the electrode 31 are arranged adjacent to each other in a staggered manner without overlapping in plan view).
On the other hand, the liquid crystal display device 200 of the second embodiment shown in FIG. 2 has the same basic configuration as that of the liquid crystal display device of the first embodiment, but the dielectric protrusion 18 is formed on the first electrode 31 of the first substrate 25. It differs in that it is provided. That is, within one dot region, the positional relationship (dielectric protrusion 18 and first dielectric protrusion 18 and first edge 31a) is disposed between the edge 31a and the edge 31a of the first electrode 31 formed on the same substrate. The edge portions 31a and 31a of the electrode 31 are adjacent to each other and are alternately arranged).
The dot region is a region constituting one display unit, and is generally composed of, for example, one pixel electrode formed on one substrate and a counter electrode formed on the other substrate facing the pixel electrode. ing.

  Under such a configuration, in these liquid crystal display devices 100 and 200, the liquid crystal molecules 51 constituting the liquid crystal layer 50 are in a state in which no voltage is applied to the electrodes 9 and 31 (non-selected state, initial alignment). In a state), when the vertical alignment films 23 and 33 are aligned in the vertical direction with respect to the substrates 10 and 25 due to the alignment regulating force and a voltage is applied between the electrodes (the selected state), the substrates 10 and 25 It operates so as to fall in the direction of 25 planes.

The liquid crystal display devices 100 and 200 include the dielectric protrusion 18 as an alignment control structure for controlling the alignment direction of the liquid crystal molecules 51 when the voltage is applied, and are formed narrower than the electrodes provided on the opposing substrate. The orientation of the liquid crystal molecules 51 is also controlled by the distortion of the electric field generated at the edge portion (edge portion / notch portion) 31a of the formed electrode. In the liquid crystal display devices according to the first and second embodiments, the dielectric constant (ε _t1 ) of the dielectric protrusion 18 provided substantially at the center of one dot region and the dielectric constant ( ε _// , ε _⊥ ), and the arrangement relationship between the dielectric protrusion 18 and the adjacent alignment control structures (edge portions 31a and 9a) is different based on the difference in the relationship. . Here, the dielectric constant epsilon _// of the liquid crystal molecules is the dielectric constant of the longitudinal direction of the liquid crystal molecules (the X direction), the dielectric constant epsilon _⊥ is the dielectric constant in the minor axis direction of liquid crystal molecules (the Y direction) It is. Hereinafter, ε _// and ε _⊥ are referred to as a long-axis direction dielectric constant and a short-axis direction dielectric constant, respectively.

First, in the liquid crystal display device 100 of the first embodiment shown in FIG. 1, the dielectric constant ε _t1 of the dielectric protrusion 18 provided to form the liquid crystal alignment control means is the long-axis direction dielectric constant ε _{/ of the} liquid crystal molecules 51. _/ It is getting smaller. That is, the dielectric constant epsilon _t1 of the dielectric protrusion 18, the dielectric constant of the liquid crystal molecules 51 ε _//, ε _⊥ and has a relation of _{ε ⊥> ε //> ε t1} . On the other hand, in the liquid crystal display device 200 of the second embodiment shown in FIG. 2, the dielectric constant ε _t1 of the dielectric protrusion 18 is larger than the dielectric constant ε _{// of the} liquid crystal molecules 51 in the major axis direction (ε _t1 > ε _// ).
The two liquid crystal display devices differ in the arrangement of the dielectric protrusions 18. As described above, the liquid crystal display device according to the present invention includes the dielectric protrusion 18 and the alignment control structure adjacent to the dielectric protrusion 18 according to the relationship between the dielectric constant of the dielectric protrusion 18 and the dielectric constant of the liquid crystal molecules 51. The arrangement relationship with the (edge portion 31a of the electrode) is appropriately set, and thereby a high-quality display with a wide viewing angle is obtained.

Hereinafter, with reference to FIGS. 3 to 10, the behavior of the liquid crystal molecules according to the relationship between the dielectric constant ε _t1 of the dielectric protrusion 18 and the dielectric constants ε _// , ε _⊥ of the liquid crystal molecules 51, and the present embodiment The operation of the liquid crystal display device will be described. 3 to 10 are cross-sectional configuration diagrams showing simulation results obtained by calculating the behavior of the liquid crystal molecules when the dielectric protrusions 18 have different dielectric constants.

In FIGS. 3 and 4, the dielectric constant epsilon _t1 of the dielectric protrusion is 1.0, the long axis direction dielectric constant epsilon _// of the liquid crystal molecules is 4.0, the minor axis direction permittivity epsilon _⊥ is 9.0 In a liquid crystal display device showing the main part (a part of the basic configuration) in one dot region, the state of the liquid crystal immediately after the voltage is applied between both electrodes 9 and 31 (FIG. 3), and 100 ms have elapsed. The state of the later liquid crystal (FIG. 4) is shown.
In the simulations showing the results in FIGS. 3 to 8, the configuration of the electrodes and the dielectric protrusions is such that the dielectric protrusions 18 are provided at the substantially central portion on the electrodes 9 of the second substrate 10 as shown in the figure. The first electrode 31 is formed to be narrower than the second electrode 9, and the edge portions 31 a and 31 a of the first electrode 31 are arranged above the second electrode 9.

5 and 6 show, the dielectric constant epsilon _t1 of the dielectric protrusion is 3.5, the long axis direction dielectric constant epsilon _// of the liquid crystal molecules is 4.0, the minor axis direction permittivity epsilon _⊥ is 9.0 In a liquid crystal display device showing the main part (a part of the basic configuration) in one dot region, the state of the liquid crystal immediately after the voltage is applied between the electrodes 9 and 31 (FIG. 5), and 100 ms have elapsed. The later liquid crystal state (FIG. 6) is shown.
FIG 7 and FIG 8, the dielectric constant epsilon _t1 of the dielectric protrusion is 5.0, the long axis direction dielectric constant epsilon _// of the liquid crystal molecules is 4.0, the minor axis direction permittivity epsilon _⊥ is 9.0 In a liquid crystal display device showing the main part (a part of the basic configuration) in one dot region, the state of the liquid crystal immediately after the voltage is applied between both electrodes 9 and 31 (FIG. 7), and 100 ms have elapsed. The state of the later liquid crystal (FIG. 8) is shown.

As shown in these drawings, the dielectric protrusions 18 and the liquid crystal molecules 51 have a relationship of ε _t1 <ε _// , and under the conditions shown in FIGS. The liquid crystal molecules 51 are tilted toward (direction), and two liquid crystal domains having the dielectric protrusions 18 as a boundary are formed symmetrically. Hereinafter, the orientation control action of the edge portion 31a and the dielectric protrusion 18 will be described.

  When there is no means for controlling the alignment of the liquid crystal molecules, the liquid crystal molecules are tilted in a random direction by voltage application. In this case, a discontinuous line (disclination) appears at the boundary between the liquid crystal domains having different alignment states, which may cause afterimages or luminance reduction. In addition, since this disclination appears at different positions depending on the applied voltage, the size of the liquid crystal domain in the dot region is not stable, and each liquid crystal domain has different viewing angle characteristics, so that it is rough when viewed from an oblique direction. It will appear as a spot-like unevenness. Therefore, by providing a liquid crystal molecule alignment control means, it becomes possible to align the liquid crystal molecules in a predetermined direction when a voltage is applied.

  First, the operation of the dielectric protrusion 18 will be described with reference to FIGS. 3 and 4. Since the alignment film 23 is formed on the surface of the second electrode 9 including the dielectric protrusions 18, the liquid crystal molecules 51 when no voltage is applied and immediately after no voltage is applied to the substrate surface as shown in FIG. It is oriented vertically. Here, when a voltage is applied to the first electrode 31 and the second electrode 9, an electric field indicated by equipotential lines 52... Is formed in the liquid crystal layer 50, and in particular around the dielectric protrusion 18, the dielectric protrusion 18 and the liquid crystal The distortion of the electric field is caused by the difference in dielectric constant from the molecule 51. When such distortion occurs, the liquid crystal molecules 51 aligned perpendicular to the substrate surface have a pretilt of a predetermined angle with respect to the electric field. Therefore, the orientation of the liquid crystal molecules 51 can be regulated by inclining the liquid crystal molecules 51 outward in the horizontal direction of the dielectric protrusions 18 (in the direction of increasing the contact angle with the inclined surface of the dielectric protrusions 18) by applying a voltage. Furthermore, the liquid crystal molecules in the peripheral region of the dielectric protrusion 18 can be tilted in the same direction in the manner of tilting dominoes.

  Next, the operation of the edge portion 31a of the electrode will be described. Since the alignment film 33 is formed so as to cover the edge 31a, the liquid crystal molecules 51 when no voltage is applied are aligned perpendicular to the substrate surface. Here, when a voltage is applied to the first electrode 31 and the second electrode 9, an oblique electric field is generated around the electrode edge 31a as shown by the shape of the equipotential lines 52. The major axis direction of the liquid crystal molecules 51 when no voltage is applied is oriented at a predetermined angle when viewed from this oblique electric field, and is the same as when a pretilt is applied to the liquid crystal molecules. Therefore, the orientation of the liquid crystal molecules 51 can be regulated by inclining the liquid crystal molecules 51 from the edge 31a toward the center of the electrode by applying a voltage. Further, the liquid crystal molecules 51 arranged on the inner side (electrode center side) from the edge 31a can be tilted one after another in the same direction along the alignment direction of the liquid crystal molecules in the edge 31a in the manner of tilting dominoes. it can.

  By the above action, the liquid crystal molecules 51 whose alignment is regulated by the dielectric protrusion 18 and the edge portion 31a of the electrode are uniformly tilted in the same direction between the dielectric protrusion 18 and the one edge portion 31a. As a result, as shown in FIGS. 4 and 6, substantially symmetric liquid crystal domains around the dielectric protrusions 18 are formed. Therefore, it can be seen that the liquid crystal display device 100 of the embodiment shown in FIG. 1 having the same configuration as the conditions of FIGS. 3 to 6 can provide a good display with a wide viewing angle and high luminance.

On the other hand, the conditions shown in FIGS. 7 and 8 are that the dielectric protrusion 18 and the liquid crystal molecules 51 have a relationship of ε _t1 > ε _{// in} the dielectric constant, as shown in FIG. When the voltage is applied, the liquid crystal molecules 51 are tilted in a direction along the inclined surface of the dielectric protrusion 18 (a direction toward the top of the tip of the dielectric protrusion 18 and a direction in which the contact angle with the inclined surface of the dielectric protrusion 18 is reduced). The liquid crystal molecules 51 around the protrusion 18 are also tilted toward the dielectric protrusion 18 side. On the other hand, at the edge portion 31 a of the first electrode 31, the liquid crystal molecules 51 are tilted toward the central portion of the first electrode 31, similarly to the conditions of FIGS. As described above, as a result of the liquid crystal molecules 51 falling in the opposite direction between the dielectric protrusion 18 and the edge portion 31a, the liquid crystal molecules 51 are located at an intermediate point between the dielectric protrusion 18 and the edge portion 31a of the first electrode. It will not fall down and will cause disclination.

As described above, when the value of the dielectric constant ε _t1 of the dielectric protrusion 18 is different from the dielectric constant ε _// of the liquid crystal molecule 51, the behavior of the liquid crystal molecule 51 when a voltage is applied is different. From FIG. 6, a high luminance display can be obtained in a wide viewing angle range under the condition of ε _t1 <ε _// shown in FIG. 6, but in the condition of ε _t1 > ε _// shown in FIGS. Disclination occurs and display quality deteriorates. The difference in the behavior of the liquid crystal molecules between the above conditions is due to the difference in the shape of the electric field distortion 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 conditions shown in FIG. 4 and FIG. 6, the shape of the equipotential lines 52... Shown in both figures causes distortion of the electric field protruding upward above the dielectric protrusion 18, and the conditions shown in FIG. Then, on the contrary, a distortion of the electric field protruding downward occurs. Therefore, the tilt directions of the liquid crystal molecules 51 are different, and the liquid crystal domains formed in the liquid crystal layer 50 are also different.

As described above, good display cannot be obtained under the conditions (ε _t1 > ε _// ) shown in FIGS. Therefore, the present inventor has repeatedly studied the configuration of the liquid crystal display device in order to obtain a good display even under the conditions shown in FIGS. 7 and 8, and the dielectric protrusion 18 is subjected to other orientation control as in the configuration shown in FIG. If provided on the first substrate 25 side having the component (the edge 31a of the first electrode 31), the dielectric protrusion 18 having a relatively high dielectric constant relative to the dielectric constant ε _// of the liquid crystal molecules was used. In some cases, it was found that a good display can be obtained.

9 and 10 show simulation results in a liquid crystal display device having the same configuration as that of the liquid crystal display device 200 shown in FIG. 2 and having the dielectric protrusion 18 disposed on the electrode 31 of the first substrate 25. Permittivity epsilon _t1 of the dielectric protrusion 18 5.0 long axis permittivity epsilon _// of the liquid crystal molecules 51 is 4.0, the minor axis direction permittivity epsilon _⊥ is 9.0.
As shown in FIG. 10, when the configuration shown in FIG. 2 is adopted, a symmetric liquid crystal domain centered on the dielectric protrusion 18 is formed in the liquid crystal layer 50 when a voltage is applied, and ε _t1 > ε _{// Even under such} conditions, a liquid crystal display device capable of good display with a wide viewing angle and high luminance can be obtained.

The inventor also verified the response speed of the liquid crystal display device when the dielectric constant ε _t1 of the dielectric protrusion 18 is varied. As a result, the liquid crystal display device under the condition (ε _t1 = 1.0) shown in FIGS. 3 and 4 is 5 ms in the halftone region as compared with the liquid crystal display device under the condition (ε _t1 = 3.5) shown in FIGS. It was found that the response speed can be improved to a certain extent. As can be seen from the comparison of the distribution of equipotential lines 52 in FIG. 4 and FIG. 6, the distortion of the electric field caused by the dielectric protrusion 18 is larger in FIG. This is thought to be due to an increase in.

  In the above-described embodiment, as an example of the alignment control structure adjacent to the dielectric protrusion 18, specifically, the case of the edge portion 31 a of the first electrode 31 has been described as an example. In place of the edge portion 31a of the opening 31, an opening slit that can be formed by cutting out a part of the first electrode 31 is provided on both sides of the dielectric protrusion 18 (portions located at the end of the dot region of the first electrode 31). Even with this configuration, the same effects as described above can be obtained.

In the present invention, a configuration in which the alignment control structure adjacent to the dielectric protrusion 18 is another dielectric protrusion (second dielectric protrusion) can also be applied. In this case, however, it is necessary to pay attention to the dielectric constant of the other dielectric protrusion (second dielectric protrusion). That is, as is apparent from the above description, in order to obtain a dielectric protrusion having an orientation control function equivalent to that of the edge portion 31a of the first electrode or the opening slit, the second dielectric protrusion (the epsilon _t2 notation.) dielectric constant relative to the longitudinal axis permittivity epsilon _// of the liquid crystal molecules 51, it is necessary to have a relationship of ε _t2 <ε _//.

On the other hand, when the dielectric constant ε _{t2 of} the second dielectric protrusion has a relationship of ε _t2 > ε _// with respect to the dielectric constant ε _{// of} the liquid crystal molecules in the long axis direction, the liquid crystal molecules 51 have the voltage Since the liquid crystal display device having the second dielectric protrusion is configured to fall from the periphery toward the dielectric protrusion when applied, in the configuration shown in FIG. 2 on the electrode 9 of the two substrates), and the second dielectric protrusion is provided instead of the edge 31a of the first electrode on both sides of the dielectric protrusion 18, and in the configuration shown in FIG. A second dielectric protrusion is provided instead of the edge 31a of the first electrode at the end opposite to the protrusion 18 (on the electrode 9 of the second substrate). By adopting these configurations, the second dielectric protrusions having a dielectric constant epsilon _t2 higher than the long axis direction dielectric constant epsilon _// of the liquid crystal molecules were provided as the alignment control structure adjacent the dielectric protrusion 18 Also in a liquid crystal display device, a favorable display with a wide viewing angle and high luminance can be obtained.

(Specific configuration example of liquid crystal display device)
The configuration described in the above embodiment can be applied to all liquid crystal display devices including a vertically aligned liquid crystal having negative dielectric anisotropy. FIG. 11 is a schematic configuration diagram of various types of liquid crystal display devices. 11A is a transmissive type, FIG. 11B is a reflective type, and FIGS. 11C and 11D are transflective types. FIG. 11C shows the case where the first substrate is the element substrate and the second substrate is the counter substrate, and FIG. 11D is the case where the second substrate is the element substrate and the first substrate is the counter substrate. In each of the liquid crystal display devices shown in FIG. 11, the above-described effects can be obtained by forming dielectric protrusions, opening slits, and the like on the surface of the transparent electrode. Therefore, in the embodiments described later, the transmissive liquid crystal display device shown in FIG. 11A will be described as a first configuration example. As a second configuration example, an example applied to the transflective liquid crystal display device shown in FIG. 11C will be described.

<First configuration example>
FIG. 12 is a partial perspective view illustrating a detailed configuration example of the liquid crystal display device of the previous embodiment, FIG. 13 is a partial cross-sectional configuration diagram in one dot region of the liquid crystal display device, and FIG. It is a plane block diagram which shows 1 pixel area comprised by a dot area. The liquid crystal display device shown in these figures is an active matrix type color liquid crystal display device using a TFD (Thin Film Diode) element (two-terminal nonlinear element) as a switching element, but a TFT (Thin Film Transistor) as a switching element. It is also possible to apply the present invention to an active matrix liquid crystal display device using elements. The partial cross-sectional structure shown in FIG. 13 corresponds to the cross-sectional structure along the line AA shown in FIG.

  As shown in FIG. 12, the liquid crystal display device of this example is mainly composed of an element substrate (first substrate) 25 and a counter substrate (second substrate) 10 facing each other. A liquid crystal layer (not shown) is sandwiched between 25. As conceptually shown in FIG. 13, this liquid crystal layer is composed of a liquid crystal having a negative initial dielectric anisotropy and a negative dielectric anisotropy. The element substrate 25 is a substrate made of a translucent material such as glass, plastic, or quartz, and extends on the inner surface side (lower surface side in the drawing) in a direction intersecting the scanning line 9 of the counter substrate 10. A plurality of data lines 11 are provided in a stripe shape. Further, a plurality of pixel electrodes (first electrodes) 31 having a substantially rectangular shape in plan view made of a transparent conductive material such as ITO (indium tin oxide) are arranged in a matrix and provided corresponding to each of them. The data line 11 is connected via the TFD element 13.

  On the other hand, the counter substrate 10 is also a substrate made of a light-transmitting material such as glass, plastic, quartz, and the color filter layer 22 and a plurality of scanning lines 9 are formed on the inner surface side (the upper surface side in the drawing). ing. As shown in FIG. 12, the color filter layer 22 has a structure in which color filters 22R, 22G, and 22B having a substantially rectangular shape in plan view are periodically arranged. Each of the color filters 22R, 22G, and 22B is formed corresponding to the pixel electrode 31 of the element substrate 25. The scanning line 9 is formed in a substantially strip shape by a transparent conductive material such as ITO and extends in a direction intersecting the data line 11 of the element substrate 25. The scanning line 9 is formed so as to cover the color filters 22R, 22G, and 22B arranged in the extending direction, and functions as a counter electrode (first electrode). Incidentally, one dot is constituted by the formation region of the pixel electrode 31, and one pixel is constituted by three dots provided with the color filters 22R, 22G, and 22B.

[Cross-section structure]
Next, FIG. 13 is a partial cross-sectional configuration diagram in one dot region of FIG. In FIG. 13, the description of the TFD elements and various wirings in the element substrate 25 is omitted for easy understanding.
As shown in FIG. 13, a vertical alignment film 33 made of polyimide or the like is formed on the liquid crystal layer side of the pixel electrode 31 in the element substrate 25. On the other hand, a vertical alignment film 23 made of polyimide or the like is formed on the liquid crystal layer side of the counter electrode 9 in the counter substrate 10. The alignment films 23 and 33 are both subjected to a vertical alignment process, but are not subjected to a pretilt treatment such as rubbing.

  A liquid crystal layer 50 made of a liquid crystal material having negative dielectric anisotropy is sandwiched between the element substrate 25 and the counter substrate 10. As conceptually shown by the liquid crystal molecules 51, this liquid crystal material is aligned perpendicular to the alignment film when no voltage is applied, and is parallel to the alignment film when an electric field is applied (that is, with the electric field direction). Oriented vertically). The element substrate 25 and the counter substrate 10 are bonded to each other by a sealing material (not shown) applied to the peripheral portions of the element substrate 25 and the counter substrate 10, and the element substrate 25, the counter substrate 10 and the seal material A liquid crystal layer 50 is sealed in the space to be formed.

  On the other hand, a phase difference plate 36 and a polarizing plate 37 are provided on the outer surface of the element substrate 25, and a phase difference plate 26 and a polarizing plate 27 are also provided on the outer surface of the counter substrate 10. The polarizing plates 27 and 37 have a function of transmitting only linearly polarized light that vibrates in a specific direction. The retardation plates 26 and 36 are λ / 4 plates having a phase difference of approximately ¼ wavelength with respect to the wavelength of visible light. The transmission axes of the polarizing plates 27 and 37 and the slow axis of the retardation plates 26 and 36 are arranged at about 45 °, and the circular polarizing plates are formed by the polarizing plates 27 and 37 and the retardation plates 26 and 36. Is configured. With this circularly polarizing plate, linearly polarized light can be converted into circularly polarized light, and circularly polarized light can be converted into linearly polarized light. Further, the transmission axis of the polarizing plate 27 and the transmission axis of the polarizing plate 37 are arranged to be orthogonal to each other, and the slow axis of the retardation film 26 and the slow axis of the retardation film 36 are also arranged to be orthogonal. Further, a backlight (illuminating means) 60 having a light source, a reflector, a light guide plate, and the like is installed outside the liquid crystal cell corresponding to the outer surface side of the counter substrate 10.

  In the liquid crystal display device of this embodiment shown in FIG. 13, image display is performed as follows. The light emitted from the backlight 60 passes through the polarizing plate 27 and the phase difference plate 26, is converted into circularly polarized light, and enters the liquid crystal layer 50. Since no liquid crystal molecules aligned perpendicular to the substrate have no refractive index anisotropy when no voltage is applied, incident light travels through the liquid crystal layer 50 while maintaining circular polarization. Further, the incident light transmitted through the phase difference plate 36 is converted into linearly polarized light orthogonal to the transmission axis of the polarizing plate 37. Since this linearly polarized light does not pass through the polarizing plate 27, the liquid crystal display device of this embodiment performs black display when no voltage is applied (normally black mode).

  On the other hand, when an electric field is applied to the liquid crystal layer 50, the liquid crystal molecules are reoriented in parallel with the substrate and have refractive index anisotropy. Therefore, the circularly polarized light incident on the liquid crystal layer 50 from the backlight 60 is converted into elliptically polarized light in the process of passing through the liquid crystal layer 50. Even if this incident light passes through the phase difference plate 36, it is not converted into linearly polarized light orthogonal to the transmission axis of the polarizing plate 37, and all or part of it is transmitted through the polarizing plate 37. Therefore, in the liquid crystal display device of this embodiment, white display is performed when a voltage is applied. Note that gradation display can be performed by adjusting the voltage applied to the liquid crystal layer 50.

[Orientation control means]
FIG. 14 is a plan view showing one pixel region constituted by three dot regions of the liquid crystal display device shown in FIG. 12, and the constituent members of the element substrate are indicated by solid lines and the constituent members of the counter substrate are indicated by alternate long and short dash lines. ing. As shown in FIG. 14, on the surface of the pixel electrode 31 and the counter electrode 9, an opening slit 31b, dielectric protrusions 18 and the like, which are liquid crystal molecule alignment control means, are formed. In the pixel electrode 31, a plurality of opening slits 31b having a substantially band shape in plan view are formed. A plurality of dielectric protrusions 18 having a substantially band shape in plan view are formed on the surface of the counter electrode 9. The arrangement relationship between the dielectric protrusions 18 formed on the counter substrate 10 and the opening slits 31b formed on the element substrate 25 is alternate with respect to the long side direction of the pixel electrode 31 (it does not overlap in a plan view and is alternate). ). In addition, the protrusions 18 and the slits 31b are arranged so that the distance between the protrusions 18 and the distance between the slits 31b increase from one long side to the other long side of the pixel electrode 31. In contrast to the above, an opening slit may be formed in the counter electrode 10 and a dielectric protrusion may be formed in the pixel electrode 31.

The dielectric protrusion 18 is made of a dielectric material such as a resin, and is formed by photolithography using a gray mask. In the liquid crystal display device of this example, the configuration of the liquid crystal display device 100 shown in FIG. 1 employs a plurality of dielectric protrusions 18 and alignment control structures (opening slits). The dielectric constant ε _t1 of the liquid crystal molecules 51 is smaller than the dielectric constant ε _// of the long axis direction of the liquid crystal molecules 51. In other words, the liquid crystal display device of this configuration example employs the basic configuration and operation of the liquid crystal display device shown in FIG. 1, and the dielectric material depends on the dielectric constant relationship between the dielectric protrusion 18 and the liquid crystal layer 50. Since the arrangement of the protrusions 18 and the opening slits 31b is appropriately determined, it is possible to obtain a good display with a wide viewing angle and high contrast without causing disclination in the dot area.

In the liquid crystal display device of this configuration example, in a plan view, when an electric field is applied, liquid crystal molecules are inclined radially about the substantially band-shaped opening slit 31b. Further, the liquid crystal molecules 51 are inclined radially around the substantially band-shaped dielectric protrusion 18. Due to the action of the dielectric protrusion 18 and the opening slit 31a, the liquid crystal molecules are aligned in a certain direction between the dielectric protrusion 18 and the opening slit 31b shown in FIG. 14, and as a result, the liquid crystal layer 50 in the dot region is formed. The orientation is properly controlled.
Further, in this example, the alignment control structure adjacent to the dielectric protrusion 18 has a configuration in which the opening slit 31b is formed in the electrode provided in the dot region, but another dielectric protrusion is formed inside the opening slit. And having a dielectric constant ε _t2 of other dielectric protrusions having a relationship of ε _// > ε _t2 . According to this configuration, since the alignment control structure that controls the alignment of the liquid crystal molecules by the oblique electric field generated around the opening slit and the electric field distortion generated by the dielectric protrusion is provided, the liquid crystal at a position away from the alignment control structure is provided. Molecules can be well controlled in orientation, which is advantageous for improving the response speed or aperture ratio.
In this example, the dielectric protrusion 18 is formed on the counter electrode 9. However, the counter electrode 9 is notched in a planar shape corresponding to the dielectric protrusion 18 to form a slit, and the inside of the slit is formed. It is also possible to adopt a configuration in which the dielectric protrusion 18 is provided. That is, at least a part of the counter electrode 9 serving as a base of the portion where the dielectric protrusions 18 are formed may be cut out (opened). By adopting such a configuration, it is possible to increase the distortion of the electric field generated around the dielectric protrusion 18 when a voltage is applied, and to obtain a larger alignment regulating force. Therefore, the response speed of the liquid crystal display device can be increased. Can be improved.

<Configuration example 2>
Next, a second configuration example of the liquid crystal display device according to the present invention will be described. FIG. 15 is a cross-sectional configuration diagram in the longitudinal (long side) direction of one dot region of the liquid crystal display device according to the present configuration example, and FIG. 16 is a plan configuration diagram illustrating one pixel region including the three dot regions. It is. The liquid crystal display device of this configuration example is a transflective liquid crystal display device. Note that detailed description of portions having the same configuration as in the first embodiment is omitted. The cross-sectional structure shown in FIG. 15 corresponds to the cross-sectional structure along the line BB in FIG.

As shown in FIG. 15, in the liquid crystal display device of the second configuration example, a reflective film 20 made of a highly reflective metal film such as aluminum or silver is formed inside the second substrate (counter substrate) 10. Yes. A part of the reflective film 20 is formed with an opening 20a cut out corresponding to the transmissive display region. An overlapping portion between the formation region of the pixel electrode (first electrode) 31 and the formation region of the reflective film 20 forms a reflective display region, and the formation region of the pixel electrode 31 and the non-formation region (that is, the opening) of the reflective film 20 The overlapping portion with the formation region of the portion 20a forms a transmissive display region. A color filter layer 22 is provided inside the reflective film 20 and the substrate 10. In order to compensate for the difference in display color saturation between the reflective display and the transmissive display, a color material layer having different color purity may be provided in the reflective display area and the transmissive display area.
On the other hand, on 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 on the color filter layer 22 at a plane position substantially corresponding to the reflective display region. The insulating film 21 is formed to a thickness of about 2 μm ± 1 μm by an organic film such as acrylic resin. The thickness of the liquid crystal layer 50 where 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 region is about half the thickness of the liquid crystal layer 50 in the transmissive display region. That is, the insulating film 21 functions as a liquid crystal layer thickness adjusting layer that varies the thickness of the liquid crystal layer 50 in the reflective display region and the transmissive display region depending on the film thickness of the insulating film 21, thereby realizing a multi-gap structure. Yes. The liquid crystal display device of this example is configured to obtain a bright and high contrast display. An inclined surface that continuously changes the layer thickness of the insulating film 21 is formed in the vicinity of the boundary between the reflective display region and the transmissive display region.

  In the transflective liquid crystal display device shown in FIG. 15, image display is performed as follows. First, light that has entered the reflective display region from above the element substrate 25 passes through the polarizing plate 37 and the retardation plate 36, is converted into circularly polarized light, and enters the liquid crystal layer 50. Since no liquid crystal molecules aligned perpendicular to the substrate have no refractive index anisotropy when no voltage is applied, incident light travels through the liquid crystal layer 50 while maintaining circular polarization. Further, the incident light reflected by the reflective film 20 and retransmitted through the phase difference plate 36 is converted into linearly polarized light orthogonal to the transmission axis of the polarizing plate 37. The linearly polarized light does not pass through the polarizing plate 37. On the other hand, the light incident on the transmissive display area from the backlight 60 is similarly transmitted through the polarizing plate 27 and the phase difference plate 26 to be converted into circularly polarized light, and is incident on the liquid crystal layer 50. Further, the incident light transmitted through the phase difference plate 36 is converted into linearly polarized light orthogonal to the transmission axis of the polarizing plate 37. Since this linearly polarized light does not pass through the polarizing plate 37, the liquid crystal display device of this embodiment performs black display when no voltage is applied (normally black mode).

  On the other hand, when an electric field is applied to the liquid crystal layer 50, the liquid crystal molecules are reoriented in parallel with the substrate, and have a birefringence effect on the transmitted light. Therefore, the circularly polarized light incident on the liquid crystal layer 50 in the reflective display region and the transmissive display region is converted into elliptically polarized light in the process of passing through the liquid crystal layer 50. Even if this incident light passes through the phase difference plate 36, it is not converted into linearly polarized light orthogonal to the transmission axis of the polarizing plate 37, and all or part of it is transmitted through the polarizing plate 37. Therefore, in the liquid crystal display device of this embodiment, white display is performed when a voltage is applied. Note that gradation display can be performed by adjusting the voltage applied to the liquid crystal layer 50.

  In this way, incident light is transmitted through the liquid crystal layer 50 twice in the reflective display region, but incident light is transmitted through the liquid crystal layer 50 only once in the transmissive display region. In this case, if the retardation (phase difference value) of the liquid crystal layer 50 is different between the reflective display region and the transmissive display region, a difference occurs in the light transmittance and a uniform image display cannot be obtained. However, since the liquid crystal layer thickness adjusting layer 21 is provided in the liquid crystal display device of this embodiment, it is possible to adjust the retardation in the reflective display region. Accordingly, uniform image display can be obtained in the reflective display area and the transmissive display area.

[Orientation control means]
FIG. 16 is a plan view showing one pixel region of the liquid crystal display device shown in FIG. 15, in which each component in the element substrate is indicated by a solid line, and each component of the counter substrate is indicated by a one-dot chain line. As shown in FIG. 16, the pixel electrode 31 is formed with a plurality of slits 31c from its long side toward the center. That is, the pixel electrode 31 arranged corresponding to one dot region is composed of three island-shaped subpixels 32 and a connecting portion connecting them, and this connecting portion substantially controls the alignment of liquid crystal molecules. The formed slit 31c (electrode notch). The pixel electrode 31 is divided into three subpixels 32 by the slits 31c, and each subpixel is connected at the center. Of the three subpixels 32, at least one subpixel is assigned and formed corresponding to the reflective display area. Accordingly, on the same substrate on which the pixel electrode 31 is formed, the dielectric protrusion 18, the slit 31 c, the dielectric protrusion 18, the slit 31 c, and the dielectric protrusion 18 are arranged in this order in the longitudinal (long side) direction of the pixel electrode 31. It is an arranged configuration.
Dielectric protrusions 18 are formed on the surface of the pixel electrode 31 corresponding to the center of each subpixel 32. The dielectric protrusions 18 are formed in a substantially circular shape in plan view, and are formed in a substantially triangular shape in side view as shown in FIG. That is, the liquid crystal display device of this configuration example adopts the basic configuration and operation of the liquid crystal display device 200 of the second embodiment shown in FIG. 2, and the plurality of dielectric protrusions 18 are a plurality of alignment control structures. The slit 31c is provided on the same substrate.

A plurality of liquid crystal domains can be formed in one dot region by the electrode structure in which the subpixel is formed. Further, the corners of the subpixels 32 are chamfered and the like, and the subpixels 32 have a substantially octagonal shape or a substantially circular shape in plan view. When an electric field is applied to the liquid crystal layer, the liquid crystal molecules 51 are tilted perpendicularly to the contour of the subpixel 32 (the edge portion 31a shown in FIG. 1). In the vicinity of the dielectric protrusion 18, the liquid crystal molecules 51 are aligned perpendicularly to the inclined surface of the dielectric protrusion 18 when no voltage is applied, and when the voltage is applied, the liquid crystal molecules 51 are directed toward the dielectric protrusion 18 as shown in FIG. The liquid crystal molecules 51 are aligned so as to fall down and to have a planar radial shape centering on the tilted state.
Accordingly, a plurality of directors of liquid crystal molecules can be created, and a liquid crystal display device with a wide viewing angle can be provided. In contrast to the above, slits and dielectric protrusions may be formed on the counter electrode 9.

  In the liquid crystal display device of this configuration example shown in FIGS. 15 and 16, since the pixel electrode 31 is provided with the slits 31c and the dielectric protrusions 18, the element substrate 25 and the counter substrate 10 are attached to sandwich the liquid crystal layer 50. At the time of alignment, there is no need to align the slit 31c and the dielectric protrusion 18, and it is easy to manufacture the liquid crystal display device, and it is possible to expect an improvement in yield.

(Electronics)
FIG. 17 is a perspective view showing an example of an electronic apparatus according to the invention. A cellular phone 1300 shown in this figure includes the liquid crystal display device of the present invention as a small-sized display portion 1301 and includes a plurality of operation buttons 1302, an earpiece 1303, and a mouthpiece 1304.
The display device of each of the above embodiments is not limited to the mobile phone, but is an electronic book, a personal computer, a digital still camera, a liquid crystal television, a viewfinder type or a monitor direct view type video tape recorder, a car navigation device, a pager, and an electronic notebook. , Calculators, word processors, workstations, videophones, POS terminals, devices equipped with touch panels, etc., and can be suitably used as image display means. In any electronic device, it is bright, has high contrast, and has a wide viewing angle. Transmissive / reflective display is possible.

FIG. 1 is a cross-sectional configuration diagram showing a basic configuration of a liquid crystal display device according to the present invention. FIG. 2 is a cross-sectional configuration diagram showing a basic configuration of a liquid crystal display device according to the present invention. FIG. 3 is a diagram illustrating a simulation result according to the embodiment. FIG. 4 is a diagram illustrating a simulation result according to the embodiment. FIG. 5 is a diagram illustrating a simulation result according to the embodiment. FIG. 6 is a diagram illustrating a simulation result according to the embodiment. FIG. 7 is a diagram illustrating a simulation result according to the embodiment. FIG. 8 is a diagram illustrating a simulation result according to the embodiment. FIG. 9 is a diagram illustrating a simulation result according to the embodiment. FIG. 10 is a diagram illustrating a simulation result according to the embodiment. FIG. 11 is an explanatory diagram illustrating a liquid crystal display device to which the present invention can be applied. FIG. 12 is a perspective configuration diagram of a liquid crystal display device according to a configuration example. FIG. 13 is a cross-sectional configuration diagram of a liquid crystal display device according to a first configuration example. FIG. 14 is a plan configuration diagram of one pixel region. FIG. 15 is a cross-sectional configuration diagram of a liquid crystal display device according to a second configuration example. FIG. 16 is a plan configuration diagram of one pixel region. FIG. 17 is a perspective configuration diagram illustrating an example of an electronic apparatus.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 9 ... 2nd electrode (counter electrode), 10 ... 2nd substrate (counter substrate), 18 ... Dielectric protrusion, 25 ... 1st substrate (element substrate), 31 ... 1st electrode (pixel electrode), 31a ... Edge Part (alignment control structure), 31b ... opening slit (alignment control structure), 31c ... slit (alignment control structure), 50 ... liquid crystal layer, 51 ... liquid crystal molecule.

Claims (3)

A liquid crystal display device in which a liquid crystal layer including a liquid crystal having negative dielectric anisotropy is sandwiched between a pair of substrates,
In the dot region constituting the display unit, on one of the pair of substrates, a dielectric protrusion provided on the electrode and an opening slit provided on the electrode or an edge of the electrode are provided. When the voltage is applied to the liquid crystal, the dielectric does not tilt in the opposite direction on a straight line connecting the dielectric protrusion and the opening slit or the edge in a plan view. When the dielectric constant of the body protrusion is ε _t1 , the dielectric constant in the major axis direction of the liquid crystal is ε _// , and the dielectric constant in the minor axis direction is ε _⊥ , the relationship is ε _t1 > ε _// A liquid crystal display device characterized by the above. 2. The liquid crystal display device according to claim 1, further comprising another dielectric protrusion provided inside the opening slit and having a dielectric constant ε _t2 of ε _// > ε _t2 .   An electronic apparatus comprising the liquid crystal display device according to claim 1.

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