JP4349961B2 - Liquid crystal display - Google Patents

Description

  The present invention relates to a liquid crystal display device, and more particularly, to a liquid crystal display device suitably used for a personal digital assistant (for example, PDA), a mobile phone, an in-vehicle liquid crystal display, a digital camera, a personal computer, an amusement device, a television, and the like.

  Information infrastructure advances day by day, and devices such as mobile phones, PDAs, digital cameras, video cameras, and in-vehicle navigation systems penetrate deeply into people's lives, and most of them employ liquid crystal display devices. These liquid crystal display devices are expected to display more information as the amount of information handled by the main body increases, and there is a market demand for high contrast, wide viewing angle, high brightness, multiple colors, and high definition. It is growing.

  As a display mode capable of realizing a high contrast and a wide viewing angle, a vertical alignment mode using a vertical alignment type liquid crystal layer has attracted attention. The vertical alignment type liquid crystal layer is generally formed using a vertical alignment film and a liquid crystal material having negative dielectric anisotropy.

  For example, Patent Document 1 discloses that an oblique electric field is generated around an opening provided in a counter electrode facing a pixel electrode via a liquid crystal layer, and liquid crystal around the liquid crystal molecules in a vertically aligned state in the opening. A liquid crystal display device in which viewing angle characteristics are improved by tilting molecules is disclosed.

  However, in the configuration described in Patent Document 1, it is difficult to form an oblique electric field in the entire region in the pixel. As a result, a region in which the response of the liquid crystal molecules to the voltage is delayed occurs in the pixel, and an afterimage phenomenon occurs. The problem of appearing arises.

  In Patent Document 2, slit electrodes (opening patterns) are provided on both sides of the pixel electrode and the common electrode on the opposite side, and at least one of the two electrodes is provided with a step in a region where the slit electrode is formed. A technique for realizing a wide viewing angle by uniformly dispersing electric field gradients in four directions using a pattern is disclosed.

  On the other hand, Patent Document 3 discloses a technique for stabilizing the alignment state of a liquid crystal domain having an inclined radial alignment that appears around a convex portion by providing a plurality of convex portions regularly in a pixel. . Further, this document discloses that the display characteristics can be improved by regulating the alignment of liquid crystal molecules using an oblique electric field by an opening provided in the electrode, together with the alignment regulating force by the convex part.

  On the other hand, in recent years, liquid crystal display devices capable of high-quality display both outdoors and indoors have been proposed (for example, Patent Document 4 and Patent Document 5). This liquid crystal display device is referred to as a transflective liquid crystal display device, and has a reflective region in a pixel for displaying in a reflective mode and a transmissive region for displaying in a transmissive mode.

  The transflective liquid crystal display devices currently on the market use the ECB mode, the TN mode, and the like. However, the above-mentioned Patent Document 3 applies not only to the transmissive liquid crystal display device but also to the transflective liquid crystal display device. A configuration is also disclosed. Further, in Patent Document 6, in a semi-transmissive liquid crystal display device having a vertical alignment type liquid crystal layer, an insulating layer provided to make the thickness of the liquid crystal layer in the transmissive region twice the thickness of the liquid crystal layer in the reflective region. A technique for controlling the alignment (multiaxial alignment) of liquid crystals by the formed recesses is disclosed. A configuration is disclosed in which the recess is formed in, for example, a regular octagon, and a projection (projection) or a slit (electrode opening) is formed at a position facing the recess via the liquid crystal layer (for example, FIG. 4 and FIG. 16).

Further, Patent Document 7 discloses a technique that suppresses display roughness and realizes a wide viewing angle characteristic with a high contrast ratio by performing dot inversion driving on a vertical alignment type liquid crystal display device. In Patent Document 7, by performing dot inversion driving at a predetermined pixel pitch, the alignment direction of the liquid crystal molecules is defined using the distortion of the electric field generated at the end of the adjacent pixel electrode. Further, it is described that the pixel electrode pitch is preferably in the range of not less than the thickness of the liquid crystal layer and not more than 20 μm in order to sufficiently exert the effect of the electric field. Further, it is described that by providing an opening at the center of the pixel electrode, the central portion of the radial alignment of liquid crystal molecules is securely fixed to the opening, and the alignment can be further stabilized.
JP-A-6-301036 JP 2002-55374 A JP 2003-167253 A Japanese Patent No. 29555277 US Pat. No. 6,195,140 JP 2002-350853 A JP 2001-125144 A

  The technique disclosed in Patent Document 3 provides a convex portion in a pixel to form a plurality of liquid crystal domains (that is, pixel division), and strengthens the alignment regulating force on the liquid crystal molecules. According to the study, in order to obtain a sufficient alignment regulating force, it is necessary to form an alignment control structure of convex portions regularly arranged inside the pixel, and there is a problem that the manufacturing process becomes complicated. Also, by providing a convex alignment regulating structure in the pixel, light leakage occurs from the periphery of the convex part, so that the contrast ratio decreases, or if a light shielding part for preventing this is provided, the effective aperture ratio is reduced. It may decrease. Furthermore, in particular, when an alignment regulating structure is provided on the counter substrate, it is affected by the alignment margin of the substrate, so the problem of roughness due to the axial center shift of the axially symmetric alignment domain, the reduction of the effective aperture ratio and / or the contrast ratio The decrease is even more pronounced.

  Further, in the technique disclosed in Patent Document 6, it is necessary to arrange a convex portion or an electrode opening on the side opposite to the concave portion provided for controlling multiaxial orientation, and the same problem as in the above-described conventional technique occurs. To do.

  On the other hand, Patent Document 7 defines a direction in which liquid crystal molecules are tilted by using a lateral electric field (an in-plane component of an oblique electric field) generated between adjacent pixel electrodes by dot inversion driving. As can be seen from the alignment directions of the liquid crystal molecules at the four corners of the pixel electrode shown in FIG. 9 of Patent Document 7, the directions of the transverse electric fields are different from each other (substantially orthogonal) in the vicinity of the corner of the pixel electrode. ). As a result, there is a problem that the alignment of the liquid crystal molecules becomes discontinuous in the vicinity of the corner of the pixel, and disclination (alignment defect) tends to occur. In addition, the stability of the alignment state depends on the shape of the electrode, and a sufficient alignment regulating force may not be obtained in a halftone display state where the electric field is low.

  The present invention has been made in view of the above-described points, and an object of the present invention is to provide a liquid crystal display device having at least one axially symmetric alignment domain in a pixel, and an excellent axially symmetric alignment domain even in a halftone display state. Is to provide a wide viewing angle liquid crystal display device with excellent display quality.

  The liquid crystal display device of the present invention includes a first substrate, a second substrate provided so as to face the first substrate, and a vertical alignment type provided between the first substrate and the second substrate. The first substrate is connected to the plurality of scanning signal lines extending in the row direction, the plurality of data signal lines extending in the column direction, the plurality of scanning signal lines, and the plurality of data signal lines. And a plurality of first electrodes connected to the plurality of data signal lines via the plurality of switching elements, and the second substrate includes the plurality of switching elements via the liquid crystal layer. Each of the plurality of first electrodes, the second electrode, and the liquid crystal provided between the first electrode and the second electrode. Multiple layers arranged in a matrix having rows and columns And a switching element connected to an arbitrary one of the plurality of scanning signal lines among the plurality of switching elements. , Alternately having a switching element connected to one of the first electrodes belonging to a pair of rows adjacent to the arbitrary one and a switching element connected to the other, wherein any row of the plurality of pixels is In a certain vertical scanning period, the first pixel having the first electrode to which a positive polarity voltage is supplied using the potential of the second electrode as a reference potential, and the first electrode to which a negative polarity voltage is supplied And the second pixel having at least one of the first electrode and the second electrode has at least one opening formed at a predetermined position in each pixel. And forming at least one liquid crystal domain exhibiting axially symmetric alignment when at least a predetermined voltage is applied to the liquid crystal layer, wherein a central axis of the axially symmetric alignment of the at least one liquid crystal domain is within the at least one opening or It is formed in the vicinity thereof.

  In one embodiment, the first substrate further has a wall structure regularly arranged on the liquid crystal layer side in the light shielding region.

  In one embodiment, an arbitrary column of the plurality of pixels includes a first pixel having the first electrode to which a positive polarity voltage is supplied using the potential of the second electrode as a reference potential in a certain vertical scanning period. The second pixels having the first electrode to which a negative polarity voltage is supplied are alternately arranged.

  In one embodiment, the polarity of the voltage supplied to the first electrode of each of the plurality of pixels is inverted every vertical scanning period.

  In one embodiment, the first electrode has at least one first opening formed at a predetermined position in the pixel, and the second electrode is at least one formed at a predetermined position in the pixel. And at least one of the at least one first opening and the at least one second opening has a central axis of axial symmetry of the at least one liquid crystal domain. Or it is formed in the vicinity.

  In one embodiment, the at least one first opening and the at least one second opening are arranged at a position where at least a part thereof overlaps with the liquid crystal layer.

  In one embodiment, the first electrode has at least one notch.

  In one embodiment, a light-shielding region is provided in the gap between the plurality of pixels, and a support that defines the thickness of the liquid crystal layer is provided in the light-shielding region.

  In one embodiment, the first electrode includes a transparent electrode that defines a transmissive region and a reflective electrode that defines a reflective region, the thickness dt of the liquid crystal layer in the transmissive region, and the first electrode in the reflective region. The thickness dr of the liquid crystal layer satisfies the relationship of 0.3 dt <dr <0.7 dt.

  In one embodiment, the first electrode includes a transparent electrode defining a transmissive region and a reflective electrode defining a reflective region, and the at least one liquid crystal domain includes a liquid crystal domain formed in the transmissive region. The first electrode has at least one first opening, the second electrode has at least one second opening, and the at least one first opening and second opening have the transmission characteristics. The first electrode includes a plurality of notches arranged symmetrically with respect to the opening, the opening corresponding to the central axis of the liquid crystal domain formed in the region.

  In one embodiment, a transparent dielectric layer is selectively provided in the reflective region of the second substrate.

  In one embodiment, the transparent dielectric layer has a function of scattering light.

  In one embodiment, the light emitting device further includes a color filter layer provided on the second substrate, and an optical density of the color filter layer in the reflection region is smaller than that of the color filter layer in the transmission region.

  In one embodiment, the first substrate and / or the second substrate and the pair of polarizing plates have a pair of polarizing plates disposed so as to face each other with the first substrate and the second substrate interposed therebetween. And at least one biaxial optically anisotropic medium layer.

  In one embodiment, the liquid crystal display device further includes a pair of polarizing plates disposed so as to face each other with the first substrate and the second substrate interposed therebetween, and the first substrate and / or the second substrate and the pair of polarizations It further has at least one uniaxial optically anisotropic medium layer between the plates.

  An arbitrary row of a plurality of pixels in the liquid crystal display device of the present invention includes a first electrode (for example, a positive polarity voltage supplied with a potential of a second electrode (for example, a counter electrode) as a reference potential in a certain vertical scanning period. Since the first pixel having the pixel electrode) and the second pixel having the first electrode to which the negative polarity voltage is supplied are alternately arranged, a steep gap is formed between the first pixel and the second pixel. A gradient electric field is generated, and this gradient electric field forms an axially symmetric alignment domain.

  In the liquid crystal display device of the present invention, the oblique electric field formed around the opening provided in the first electrode (for example, the pixel electrode) and / or the second electrode (for example, the counter electrode) is In addition, the alignment of the axially symmetric alignment domain is stabilized in cooperation with a steep oblique electric field formed between adjacent pixels. Further, when a plurality of axially symmetric alignment domains are formed in a pixel, if a notch is provided in the first electrode, the liquid crystal molecules are tilted by the influence of an oblique electric field generated in the vicinity of the notch. And the axially symmetric orientation domain is further stabilized.

  Also, the first opening and the second opening are arranged such that one end of the central axis of the axially symmetric orientation of the liquid crystal domain is fixed in or near the first opening, and the other end is fixed in or near the second opening. When the portion (a pair of openings) is arranged, the central axis of the axially symmetric orientation is more stably fixed. Furthermore, when the first opening and the second opening (a pair of openings) are arranged so that at least a part thereof overlaps with each other via the liquid crystal layer, it is possible to suppress a decrease in the effective aperture ratio due to the openings. At this time, since one central axis is fixed and stabilized by the action of the first opening and the second opening, the action that each opening (the first opening or the second opening) should express is It may be smaller than the case where the central axis is fixed and stabilized with one opening. That is, since the size of the first opening and the second opening (for example, the diameter of the circular opening) can be reduced, it is possible to further suppress the decrease in the effective aperture ratio. The size of the first opening and the second opening may be the same or different. Since the first opening and the second opening are provided to fix and stabilize the position of the central axis of the axially symmetric orientation, the size thereof is relatively small and the decrease in the effective aperture ratio is small. Moreover, it is hard to receive the influence of the misalignment at the time of bonding a 1st board | substrate and a 2nd board | substrate.

  By providing an opening at a position corresponding to the central axis of the axially symmetric alignment liquid crystal domain, the position of the central axis is fixed and stabilized, so that the center of the axially symmetric alignment liquid crystal domain extends over the entire surface of the liquid crystal display panel. As a result of the axis being arranged at a fixed position, the display uniformity is improved. For example, the feeling of roughness when the halftone display is observed obliquely is reduced. In addition, as a result of stabilizing the axially symmetric orientation, the response time in halftone display can be shortened. Furthermore, it is possible to shorten the time required for the alignment disorder (which may be referred to as an afterimage caused by pressing) generated when the liquid crystal display panel is pressed to recover normal alignment.

  Furthermore, when a configuration in which a wall structure is provided on the liquid crystal layer side in the light-shielding region of the first substrate, the direction in which the liquid crystal molecules tilt when a voltage is applied (when an electric field is generated) is defined by the tilted surface effect of the wall structure. Thus, the axially symmetric orientation domain is formed more stably. An oblique electric field generated by applying voltages of opposite polarities to the first electrodes of pixels adjacent to each other, orientation regulation due to the slope of the wall structure provided between adjacent pixels, and distortion of the electric field due to the wall structure The effect acts to stabilize the orientation of the axially symmetric orientation domain. The orientation regulation effect due to the slope of the wall structure acts regardless of the presence or absence of the electric field, and since the effect of the electric field is distorted by the wall structure, the axially symmetric orientation can be stabilized even in the halftone display state, It is possible to further shorten the time required for the alignment disorder generated when the liquid crystal display panel is pressed to recover to normal alignment.

  Furthermore, in the liquid crystal display device of the present invention, the switching element connected to any one scanning signal line is connected to one of the first electrodes belonging to a pair of rows adjacent to the scanning signal line. The switching element and the switching element connected to the other are alternately provided. That is, switching elements (and / or pixel electrodes connected via switching elements) are alternately arranged in a staggered manner with respect to an arbitrary scanning signal line. Therefore, by performing the conventional one-line inversion driving (1H inversion driving), as a result, the liquid crystal layers of the pixels adjacent in the row direction and the column direction are opposite in polarity with respect to the second electrode (counter electrode). A display signal can be applied (1H dot inversion drive).

  The vertical scanning period is typically a frame period, and corresponds to each field period when the frame is divided into a plurality of fields. Hereinafter, the driving method for controlling the polarity of the voltage applied to the first electrode is referred to as “inverted driving”. When a pixel having a reverse polarity is adjacent in a row, column inversion is performed, and a pixel having a reverse polarity is adjacent in a column. The case is called row inversion, and the case where pixels of opposite polarity are adjacent to each other in both row and column is called dot inversion.

  When applied to a transflective liquid crystal display device, if a configuration is adopted in which a transparent dielectric layer for controlling the thickness of the liquid crystal layer is provided on the second substrate side, a step is provided on the first substrate side to provide a transmission region and a reflective region. Compared to the conventional transflective liquid crystal display device that divides the area, it is possible to reduce the ineffective area that does not contribute to the display during the transmissive display, and the brightness during the transmissive display can be improved. In addition, the diffuse reflector provided to improve the brightness of the reflection region can be formed on the reflection region of the first substrate, and a light scattering layer (on the transparent dielectric layer of the second substrate). A light diffusion layer) can also be formed. In this case, it is possible to eliminate the need to form irregularities on the surface of the reflective electrode.

  The configuration of the liquid crystal display device according to the embodiment of the present invention will be specifically described below with reference to the drawings.

(Transmission type liquid crystal display)
First, the configuration of a transmissive liquid crystal display device 100 according to an embodiment of the present invention will be described with reference to FIG. 1A and 1B are diagrams schematically showing a configuration of one pixel of the transmissive liquid crystal display device 100, FIG. 1A is a plan view, and FIG. It is sectional drawing along the 1B-1B 'line in Fig.1 (a). FIG. 1A is a plan view, and FIG. 1B is a cross-sectional view taken along line 1B-1B ′ in FIG. FIG. 1C is a cross-sectional view schematically showing the configuration of one pixel of another transmissive liquid crystal display device 100 ′.

  Here, an example in which one pixel is divided into two (N = 2) is shown, but the number of divisions (= N) can be set to 3 or more in accordance with the pixel pitch. In this case, the division area on the second substrate side is an abbreviation. The number of openings (= n) provided in the center is preferably the same as the number of pixel divisions (= N). Note that as the number of divisions (= N) increases, the effective aperture ratio tends to decrease. Therefore, when applied to a high-definition display panel, it is preferable to reduce the number of divisions (= N). Also, the present invention can be applied to a case where the pixel is not divided (may be expressed as N = 1). The divided area is sometimes referred to as “sub-pixel”. A sub-pixel typically has one liquid crystal domain.

  A liquid crystal display device 100 shown in FIGS. 1A and 1B includes a transparent substrate (for example, a glass substrate) 110a, a transparent substrate 110b provided to face the transparent substrate 110a, and transparent substrates 110a and 110b. And a vertically aligned liquid crystal layer 120 provided therebetween. A vertical alignment film (not shown) is provided on the surfaces of the substrates 110a and 110b in contact with the liquid crystal layer 120. When no voltage is applied, the liquid crystal molecules of the liquid crystal layer 120 are substantially perpendicular to the surface of the vertical alignment film. Oriented. The liquid crystal layer 120 includes a nematic liquid crystal material having negative dielectric anisotropy, and further includes a chiral agent as necessary.

  The liquid crystal display device 100 includes a pixel electrode 111 formed on the transparent substrate 110a and a counter electrode 131 formed on the transparent substrate 110b provided to face the transparent substrate 110a. The liquid crystal layer 120 provided between the counter electrode 131 defines a pixel. Here, both the pixel electrode 111 and the counter electrode 131 are formed of a transparent conductive layer (for example, an ITO layer). Typically, on the liquid crystal layer 120 side of the transparent substrate 110b, a color filter 130 provided corresponding to the pixel (a plurality of color filters may be collectively referred to as the color filter layer 130), and A black matrix (light-shielding layer) 132 provided between adjacent color filters 130 is formed, and a counter electrode 131 is formed thereon. The color filter layer 130 is formed on the counter electrode 131 (the liquid crystal layer 120 side). Alternatively, the black matrix 132 may be formed.

  In the liquid crystal display device 100 shown in FIG. 1 in which the number of divisions (= N) is 2, a wall structure 115 described later is formed on a light shielding region around the pixel electrode 111 on the transparent substrate 110a. Further, the pixel electrode 111 has a number of first openings 114a corresponding to the number of divisions (n = 2 in FIG. 1) at predetermined positions in the pixel. The pixel electrode 111 further has four notches 113 at predetermined positions. On the other hand, the counter electrode 131 on the counter-side transparent substrate 110b has a number of second openings 114b corresponding to the number of divisions (n = 2 in FIG. 1) at predetermined positions.

  Here, the first opening 114 a and the second opening 114 b are arranged in a positional relationship so as to spatially overlap each other via the liquid crystal layer 120. In addition, the first opening 114a and the second opening 114b (a pair of openings facing each other may be referred to as the opening 114) have the same size (diameter). In FIG. Are overlapping each other.

  When a predetermined voltage is applied to the liquid crystal layer 120, two liquid crystal domains each having an axially symmetric orientation (the same number as the division number N) are formed, and the central axis of each of the liquid crystal domains is It is formed in or near the first opening 114a and the second opening 114b. The pair of openings 114 acts to fix the position of the central axis of the axially symmetric orientation domain and stabilize the axially symmetric orientation. As illustrated here, when the first opening 114a and the second opening 114b are arranged so as to overlap each other through the liquid crystal layer, a decrease in the effective aperture ratio due to the pair of openings 114 can be suppressed. Since one central axis is fixed and stabilized by the action of the first opening and the second opening, the action that the first opening 114a or the second opening 114b should express is the central axis in one opening. Therefore, the diameters of the first opening 114a and the second opening 114b can be reduced, and as a result, the reduction of the effective aperture ratio can be suppressed.

  As will be described in detail later, the liquid crystal display device of the present embodiment is adjacent to each other in each column and row within each vertical scanning period with respect to pixels arranged in a matrix having rows and columns. The voltage applied to the pixel electrode of the pixel to be applied is applied so as to have a reverse polarity with respect to the voltage applied to the counter electrode 131 (dot inversion driving). As described above, by adopting the dot inversion driving, the alignment stabilization effect by the oblique electric field generated between the adjacent pixels can be obtained for the four sides of the substantially rectangular pixel. Accordingly, a steep oblique electric field is formed between adjacent pixels, and acts to form an axially symmetric orientation.

  Furthermore, in the liquid crystal display device of this embodiment, the switching element connected to any one scanning signal line is connected to one of the pixel electrodes 111 belonging to a pair of rows adjacent to the scanning signal line. And switching elements connected to the other are alternately provided. Therefore, by performing the conventional one-line inversion driving (1H inversion driving), as a result, display signals having opposite polarities with respect to the counter electrode 131 are applied to the liquid crystal layers of the pixels adjacent in the row direction and the column direction. (1H dot inversion drive).

  Further, in the liquid crystal display device of the present embodiment, the center of the axially symmetric orientation is fixed and stabilized in or near the opening 114 as described above. This is because the liquid crystal molecules around the opening 114 form a continuous alignment (axisymmetric alignment) by the action of the oblique electric field formed by the opening 114. By the action of (at least one of the first opening 114a and the second opening 114b), the formation of discontinuous orientation at the corner as shown in FIG. 9 of Patent Document 7 is suppressed / prevented. The In addition, due to the action of the opening 114, a sufficiently stable axisymmetric alignment can be obtained even in a halftone display state with a low electric field, and the alignment disorder generated when the liquid crystal display panel is pressed is restored to a normal alignment. Time can be shortened.

  The shapes of the first opening 114a and the second opening 114b provided at predetermined positions of the pixel electrode 111 and the counter electrode 131 are as illustrated to obtain the continuity of the alignment of the liquid crystal molecules in the axially symmetric alignment domain. However, the shape is not limited to this. Further, the shapes of the first opening 114a and the second opening 114b may be different. However, in order to exert substantially the same orientation regulating force in all directions, the polygon is preferably a quadrilateral or more, and is preferably a regular polygon.

  Here, an example is shown in which openings are provided in both the pixel electrode 111 and the counter electrode 131. However, the effect of fixing the central axis of the axially symmetric orientation can be obtained even if an opening is provided in either one of them. Further, here, in the case where openings are provided in both the pixel electrode 111 and the counter electrode 131, the configuration in which the first opening 114a and the second opening 114b having the same size are arranged so as to overlap each other is illustrated. The configuration and arrangement of the first opening 114a and the second opening 114b are not limited to this. Even if the first opening 114a and the second opening 114b do not overlap each other, the effect of fixing and stabilizing the axially symmetric orientation can be obtained. However, if one end of the central axis of the axially symmetric alignment of the liquid crystal domain is fixed by the first opening 114a and the other end is fixed by the second opening 114b, the central axis of the axially symmetric alignment is further stabilized. Can be fixed to. Furthermore, when the first opening 114a and the second opening 114b are arranged so that at least a part thereof overlaps with each other through the liquid crystal layer, a decrease in the effective aperture ratio due to the opening 114 can be suppressed. At this time, since one central axis is fixed and stabilized by the action of the first opening and the second opening, the action that the first opening 114a or the second opening 114b should express is one opening. The center axis may be smaller than the case where the central axis is fixed and stabilized, and as illustrated here, the first opening 114a and the second opening 114b having the same size are arranged so as to overlap each other. A decrease in the aperture ratio can be minimized.

  Further, the liquid crystal display device 100 has a light shielding region between adjacent pixels, and has a wall structure 115 on the transparent substrate 110a in the light shielding region. Here, the light shielding region is shielded by, for example, a TFT, a gate signal wiring, a source signal wiring, or a black matrix formed on the transparent substrate 110b, which is formed in the peripheral region of the pixel electrode 111 on the transparent substrate 110a. This area does not contribute to display. Therefore, the wall structure 115 formed in the light shielding region does not adversely affect the display.

  The wall structure 115 acts to define the direction in which the liquid crystal molecules are inclined when a voltage is applied (when an electric field is generated) due to the inclined surface effect. The alignment regulating force due to the inclined side surface of the wall structure 115 acts even when no voltage is applied, and tilts the liquid crystal molecules. In addition, the electric field formed between the pixels is distorted by the wall structure 115 existing between adjacent pixels, and acts so as to define the direction in which the liquid crystal molecules are inclined on the wall surface of the wall structure 115.

  When the wall structure 115 is provided, in addition to the alignment regulating force due to the steep oblique electric field formed between adjacent pixels and the oblique electric field formed around the opening 114, the alignment regulating force by the wall structure 115 is increased. Acting cooperatively, an axially symmetric orientation is formed more stably. By using the wall effect of the wall structure 115 together, the stability of the axially symmetric alignment in the halftone display state in which the alignment regulating force due to the oblique electric field is small is further improved, and occurs when the liquid crystal display panel is pressed. The time for the alignment disorder to recover to the normal alignment can be further shortened.

  The wall structure 115 illustrated here is provided as a continuous wall so as to surround the pixel, but is not limited thereto, and may be divided into a plurality of walls. Since the wall structure 115 acts to define a boundary formed in the vicinity of the extension of the pixels in the liquid crystal domain, it preferably has a certain length. For example, when the wall structure is composed of a plurality of walls (wall portions), it is preferable that the length of each wall is longer than the length between adjacent walls.

  Furthermore, the notch 113 provided in the pixel electrode 111 is provided in the vicinity of the boundary of the axially symmetric alignment domain, and defines the direction in which the liquid crystal molecules are tilted by the electric field, so that the axially symmetric alignment domain is formed more stably. To do. When used in combination with the wall structure 115 as exemplified here, an oblique electric field formed around the opening 114 and the notch 113 and an electric field action on the wall formed by distortion by the wall structure 115. As a result of defining the direction in which the liquid crystal molecules are tilted, two axially symmetric orientations are stably formed as described above. Here, the notch 113 is centered on an opening 114 (here, the opening on the right side in FIG. 1) corresponding to the central axis of the liquid crystal domain formed in the pixel (here, the entire transmission region). It includes four notches 113 arranged symmetrically with respect to a point.

  By providing the notch 113 as described above, the direction in which the liquid crystal molecules fall when a voltage is applied is defined, and two liquid crystal domains are formed. In FIG. 1, the reason why the notch is not provided on the left side of the pixel electrode 111 is that the notch provided at the right end of the pixel electrode (not shown) located on the left side of the illustrated pixel electrode 111 has the same effect. Therefore, a notch that reduces the effective aperture ratio of the pixel is omitted at the left end of the pixel electrode 111. Furthermore, since the alignment regulating force by the wall structure 115 can also be obtained here, a stable liquid crystal domain can be formed as in the case of providing the notch without providing the notch at the left end of the pixel electrode 111. In addition, the effect of improving the effective aperture ratio can be obtained.

  In the liquid crystal display device 100, the four notches 113 are formed. However, at least one notch may be provided between adjacent liquid crystal domains. For example, here, the notch is elongated at the center of the pixel. A part may be provided and others may be omitted.

  The shape of the notch 113 acting so as to define the direction in which the liquid crystal molecules in the axially symmetric alignment domain are tilted by the electric field is set so as to exert an alignment regulating force substantially equal to the adjacent axially symmetric alignment. A quadrangle is preferred. In addition, a notch part can also be abbreviate | omitted.

  It is preferable that the support 133 for defining the thickness (also referred to as a cell gap) of the liquid crystal layer 120 be formed in a light shielding region (here, a region defined by the black matrix 132), since display quality is not deteriorated. . The support 133 may be formed on either of the transparent substrates 110a and 110b, and is not limited to being provided on the wall structure 115 provided in the light shielding region as illustrated. When the support 133 is formed on the wall structure 115, the sum of the height of the wall structure 115 and the height of the support 133 is set to be the thickness of the liquid crystal layer 120. When the support body 133 is provided in a region where the wall structure 115 is not formed, the height of the support body 133 is set to be the thickness of the liquid crystal layer 120. The support 133 can be formed by a photolithography process using a photosensitive resin, for example.

  In this liquid crystal display device 100, an axially symmetric alignment is formed by the action of an oblique electric field formed in adjacent pixels by performing dot inversion driving, and the central axis of the two axially symmetric alignment liquid crystal domains is the pixel electrode 111. In addition, it is fixed and stabilized in or near the two pairs of openings 114 provided at the center in the longitudinal direction of the counter electrode 131. Furthermore, the electric field distorted by the wall surface of the wall structure 115 and the wall effect of the wall structure mainly define the direction in which the liquid crystal molecules in the two adjacent liquid crystal domains are tilted by the electric field, and the oblique electric field by the pair of notches The action defines the direction in which the liquid crystal molecules in the two adjacent liquid crystal domains are tilted by the electric field, and these act cooperatively to stabilize the axially symmetric alignment of the liquid crystal domains even in the halftone display state.

  By providing the opening 114 at a position corresponding to the central axis of the axially symmetric alignment liquid crystal domain of the pixel electrode 111 and the counter electrode 131, the position of the central axis is fixed and stabilized. As a result, the central axis of the axially symmetric alignment liquid crystal domain is arranged at a fixed position, so that the display uniformity is improved. In addition, as a result of stabilizing the axially symmetric orientation, the response time in halftone display can be shortened. Furthermore, afterimages caused by pressing of the liquid crystal display panel can be reduced (recovery time can be shortened). Since the axisymmetric orientation is further stabilized by providing the wall structure 115, it is preferable to provide the wall structure, particularly in applications where it is desired to reduce afterimages due to pressing.

  Note that, on the liquid crystal layer 120 side of the transparent substrate 110a, for example, an active element such as a TFT and circuit elements (not shown) such as a gate wiring and a source wiring connected to the TFT are provided. In addition, the transparent substrate 110a, the circuit elements formed on the transparent substrate 110a, the above-described pixel electrode 111, the wall structure 115, and the support 133 (the support can be formed on either the active matrix substrate or the color filter substrate). May be collectively referred to as an active matrix substrate. On the other hand, the transparent substrate 110b and the color filter layer 130, the black matrix 132, the counter electrode 131, the alignment film, and the like formed on the transparent substrate 110b may be collectively referred to as a counter substrate or a color filter substrate.

  A liquid crystal display device 100 ′ shown in FIG. 1C is different from the liquid crystal display device 100 shown in FIGS. 1A and 1B in that it does not have a wall structure. In FIG. 1C, components common to the liquid crystal display device 100 are denoted by the same reference numerals as in FIG.

  Similarly to the liquid crystal display device 100, the liquid crystal display device 100 ′ has a steep oblique electric field between adjacent pixels formed by dot inversion driving, and the openings 114 provided in the pixel electrode 111 and the counter electrode 131. Two axially symmetric orientation domains whose central axis is fixed and stabilized in or near the opening 114 (at least one of the first opening 114a and the second opening 114b) by an oblique electric field formed in the periphery. It is formed stably. Further, the notch 113 provided in the pixel electrode 111 regulates the alignment direction of the liquid crystal molecules in the vicinity of the boundary between the liquid crystal domains, so that the axial symmetry alignment of the two liquid crystal domains is further stabilized.

  Further, like the liquid crystal display device 100, in the liquid crystal display device 100 ′, the switching elements connected to any one scanning signal line are included in the pixel electrodes 111 belonging to a pair of rows adjacent to the scanning signal line. The switching element connected to one of the switches and the switching element connected to the other are alternately provided. Therefore, by performing the conventional 1H inversion drive, as a result, display signals having opposite polarities can be applied to the liquid crystal layers of the pixels adjacent in the row direction and the column direction with reference to the counter electrode 131 (1H Dot inversion drive).

  Although omitted in the above description, the liquid crystal display devices 100 and 100 ′ further include a pair of polarizing plates arranged to face each other with the transparent substrates 110 a and 110 b interposed therebetween. The pair of polarizing plates are typically arranged so that the transmission axes are orthogonal to each other. Furthermore, as described later, a biaxial optically anisotropic medium layer or a uniaxial optically anisotropic medium layer may be provided.

(Transflective liquid crystal display device)
Next, the configuration of the transflective liquid crystal display device 200 according to the embodiment of the present invention will be described with reference to FIG.

  FIG. 2 is a diagram schematically showing a configuration of one pixel of the transmissive liquid crystal display device 200 according to the embodiment of the present invention, FIG. 2A is a plan view, and FIG. 2B is a diagram. It is sectional drawing along the 2B-2B 'line in 2 (a).

  Here, an example is shown in which one pixel is divided into three (N = 3, the transmission region is divided into two, and the reflection region is divided into one), but the number of divisions (= N) is at least two (transmission region) according to the pixel pitch. Is at least one division, and the reflection area is at least one division). The number of openings (= n) provided at substantially the center of the divided region (region where the axially symmetric alignment domain is formed) on the counter substrate (second substrate) side is also preferably made the same as the number of divided pixels (= N). . However, as will be described later, for example, when a transparent dielectric layer is selectively provided on the liquid crystal layer side of the reflective region of the counter substrate, an opening is not provided in the reflective region of the counter electrode (second electrode). good. Further, as the number of divisions (= N) increases, the effective aperture ratio tends to decrease. Therefore, when applied to a high-definition display panel, it is preferable to reduce the number of divisions (= N).

  The liquid crystal display device 200 includes a transparent substrate (for example, a glass substrate) 210a, a transparent substrate 210b provided to face the transparent substrate 210a, and a vertical alignment type liquid crystal layer provided between the transparent substrates 210a and 210b. 220. A vertical alignment film (not shown) is provided on the surfaces of both the substrates 210a and 210b in contact with the liquid crystal layer 220. When no voltage is applied, the liquid crystal molecules of the liquid crystal layer 220 are in contact with the surface of the vertical alignment film. Oriented substantially vertically. The liquid crystal layer 220 includes a nematic liquid crystal material having a negative dielectric anisotropy, and further includes a chiral agent as necessary.

  The liquid crystal display device 200 includes a pixel electrode 211 formed on the transparent substrate 210a and a counter electrode 231 formed on the transparent substrate 210b, and a liquid crystal provided between the pixel electrode 211 and the counter electrode 231. Layer 220 defines the pixel. Circuit elements such as TFTs are formed on the transparent substrate 210a as will be described later. The transparent substrate 210a and the components formed thereon may be collectively referred to as an active matrix substrate 210a.

  Further, typically, a color filter 230 (corresponding to a plurality of color filters may be collectively referred to as the color filter layer 230) provided corresponding to the pixel on the liquid crystal layer 220 side of the transparent substrate 210b. A black matrix (light shielding layer) 232 provided between adjacent color filters 230 is formed, and a counter electrode 231 is formed thereon, and the color filter layer 230 is formed on the counter electrode 231 (the liquid crystal layer 220 side). Alternatively, a black matrix 232 may be formed. The transparent substrate 210b and the components formed thereon may be collectively referred to as a counter substrate (color filter substrate) substrate 210b.

  The pixel electrode 211 is formed of a transparent electrode 211a formed from a transparent conductive layer (for example, an ITO layer) and a metal layer (for example, an Al layer, an alloy layer including Al, and a laminated film including any of these). A reflective electrode 211b. As a result, the pixel includes a transparent area A defined by the transparent electrode 211a and a reflective area B defined by the reflective electrode 211b. The transparent area A displays in the transmissive mode, and the reflective area B displays in the reflective mode.

  In the liquid crystal display device 200 shown in FIG. 2 in which the number of pixel divisions (= N) is 3 (the transmission region is divided into 2 and the reflection region is divided into 1), a wall structure described later on the light shielding region around the pixel electrode 211. 215 is formed. The pixel electrode 211 has a number of first openings 214a (n = 3 in FIG. 2) corresponding to the number of divisions at predetermined positions in the pixel. The pixel electrode 211 further has four notches 213 at predetermined positions. On the other hand, the counter electrode 231 on the counter-side transparent substrate 210b has two second openings 114b corresponding to the number of divisions of the transmission region.

  When a predetermined voltage is applied to the liquid crystal layer, three liquid crystal domains each having an axially symmetric alignment (the same number as the division number N) are formed, and the central axis of each of the liquid crystal domains is the first axis. It is formed in or near the opening 214a and the second opening 114b. Openings 214a and 214b provided at predetermined positions of the pixel electrode 211 and the counter electrode 231 act to fix the position of the central axis of the axially symmetric orientation and to stabilize the axially symmetric orientation. As illustrated here, when the first opening 214a and the second opening 214b are arranged so as to overlap each other through the liquid crystal layer in the transmissive region, a decrease in the effective aperture ratio due to the pair of openings 214 is suppressed. be able to. Since one central axis is fixed and stabilized by the action of the first opening and the second opening, the action that the first opening 114a or the second opening 114b should express is the central axis in one opening. Therefore, the diameters of the first opening 214a and the second opening 214b can be reduced, and as a result, a reduction in the effective aperture ratio can be suppressed.

  As will be described in detail later, the liquid crystal display device of the present embodiment is adjacent to each other in each column and row within each vertical scanning period with respect to pixels arranged in a matrix having rows and columns. The voltage applied to the pixel electrode of the pixel to be applied is applied so as to have a reverse polarity with respect to the voltage applied to the counter electrode 231 (dot inversion driving). As described above, by adopting the dot inversion driving, the alignment stabilization effect by the oblique electric field generated between the adjacent pixels can be obtained for the four sides of the substantially rectangular pixel. Accordingly, a steep oblique electric field is formed between adjacent pixels, and acts to stabilize the axially symmetric orientation.

  Furthermore, in the liquid crystal display device of this embodiment, the switching element connected to any one scanning signal line is connected to one of the pixel electrodes 211 belonging to a pair of rows adjacent to the scanning signal line. And switching elements connected to the other are alternately provided. Therefore, by performing conventional one-line inversion driving (1H inversion driving), as a result, display signals having opposite polarities with respect to the counter electrode 231 are applied to the liquid crystal layers of pixels adjacent in the row direction and the column direction. (1H dot inversion drive).

  In the liquid crystal display device of this embodiment, as described above, the center of the axially symmetric orientation is fixed and stabilized in the opening 214 or in the vicinity thereof. This is because the liquid crystal molecules around the opening 214 form a continuous alignment (axisymmetric alignment) by the action of the oblique electric field formed by the opening 214. By the action of (at least one of the first opening 214a and the second opening 214b), the formation of discontinuous orientation at the corner as shown in FIG. 9 of Patent Document 7 is suppressed / prevented. The In addition, due to the action of the opening 214, a sufficiently stable axisymmetric alignment can be obtained even in a halftone display state with a low electric field, and the alignment disorder generated when the liquid crystal display panel is pressed is restored to a normal alignment. Time can be shortened.

  Further, the liquid crystal display device 200 has a light shielding region between adjacent pixels, and has a wall structure 215 on the transparent substrate 210a in the light shielding region. Since the light shielding area does not contribute to the display, the wall structure 215 formed in the light shielding area does not adversely affect the display.

  The wall structure 215 acts to define the direction in which the liquid crystal molecules are inclined when a voltage is applied (when an electric field is generated) due to the inclined surface effect. The alignment regulating force due to the inclined side surface of the wall structure 215 acts even when no voltage is applied, and inclines the liquid crystal molecules. In addition, the electric field formed between the pixels is distorted by the wall structure 215 existing between adjacent pixels, and acts so as to define the direction in which the liquid crystal molecules are inclined on the wall surface of the wall structure 215.

  When the wall structure 215 is provided, in addition to the alignment regulating force due to the steep oblique electric field formed between adjacent pixels and the oblique electric field formed around the opening 214, the alignment regulating force due to the wall structure 215 is increased. Acting cooperatively, an axially symmetric orientation is formed more stably. By using the wall effect of the wall structure 215 together, the stability of the axisymmetric alignment in the halftone display state in which the alignment regulating force by the oblique electric field is small is further improved, and it occurs when the liquid crystal display panel is pressed. The time for the alignment disorder to recover to the normal alignment can be further shortened.

  The wall structure 215 exemplified here is provided as a continuous wall so as to surround the pixel, but is not limited thereto, and may be divided into a plurality of walls. Since the wall structure 215 acts to define a boundary formed in the vicinity of the extension of the pixels in the liquid crystal domain, it preferably has a certain length. For example, when the wall structure 215 is composed of a plurality of walls, the length of each wall is preferably longer than the length between adjacent walls.

  Further, the notch portion 213 arranged as necessary is provided near the boundary of the axially symmetric alignment domain, and acts to define the direction in which the liquid crystal molecules are tilted by the electric field and form the axially symmetric alignment domain. Similar to the openings 214a and 214b, an oblique electric field is formed around the notch 213 by a voltage applied between the pixel electrode 211 and the counter electrode 213. The oblique electric field and the wall structure 215 As a result of defining the direction in which the liquid crystal molecules are tilted by the action of the electric field on the distorted wall surface, an axially symmetric orientation is formed as described above.

  In addition, here, the notch 213 is point-symmetric about the opening 214a (here, the right-side opening in FIG. 2A) corresponding to the central axis of the liquid crystal domain formed in the transmission region of the pixel. The four notches 213 arranged at the top are included. When used in combination with the wall structure 215 as exemplified here, the oblique electric field formed around the opening 214 and the notch 213 and the action of the electric field on the wall formed by distortion by the wall structure 215. As a result of defining the direction in which the liquid crystal molecules tilt, the three axially symmetric orientations are stably formed as described above. The arrangement of the wall structure 215, the opening 214, and the notch 213 and the preferable shapes thereof are the same as those of the transmissive liquid crystal display device 100 described above. Although FIG. 2 shows an example in which two liquid crystal domains are formed in the transmissive region A and one liquid crystal domain is formed in the reflective region B, the present invention is not limited to this. In addition, it is preferable that each liquid crystal domain has a substantially square shape from the viewpoint of viewing angle characteristics and alignment stability.

  If the support 233 for defining the thickness (also referred to as a cell gap) of the liquid crystal layer 220 is formed in the light-shielding region (here, the region defined by the black matrix 232), the display quality is not deteriorated. preferable. The support 233 may be formed on either of the transparent substrates 210a and 210b, and is not limited to the case of being provided on the wall structure 215 provided in the light shielding region as illustrated. When the support 233 is formed on the wall structure 215, the sum of the height of the wall structure 215 and the height of the support 233 is set to be the thickness of the liquid crystal layer 220. In the case where the support 233 is provided in a region where the wall structure 215 is not formed, the height of the support 233 is set to be the thickness of the liquid crystal layer 220.

  In this liquid crystal display device 200, when a predetermined voltage (a voltage equal to or higher than the threshold voltage) is applied to the pixel electrode 211 and the counter electrode 231, two axially symmetric liquid crystal domains are formed in the transmissive region A and one axis is formed in the reflective region B. Symmetric orientation domains are formed. The direction in which the liquid crystal molecules in the three adjacent liquid crystal domains (two transmission regions and one reflection region) are mainly tilted by the electric field is defined by the electric field distorted by the wall surface of the wall structure 215 and the wall effect of the wall structure. The alignment regulation force in which the liquid crystal molecules in the three adjacent liquid crystal domains are tilted by the electric field due to the oblique electric field action by the four notches cooperates to stabilize the axially symmetric alignment of the liquid crystal domains. Further, the central axes of the two axisymmetric alignment liquid crystal domains formed in the transmission region A are fixed and stabilized in the pair of openings 214 (214a and 214b facing each other), respectively. The central axis of one axisymmetric liquid crystal domain formed in the reflection region B is stabilized by the opening 214a.

  Here, an example of a preferable configuration of the transflective liquid crystal display device 200 having the wall structure 215 has been described. However, like the transmissive liquid crystal display device 100 ′ illustrated in FIG. It may be omitted. However, since the axially symmetric orientation is further stabilized by providing the wall structure 215, it is preferable to provide the wall structure particularly in applications where it is desired to reduce afterimages due to pressing.

  Next, a preferable configuration unique to the transflective liquid crystal display device 200 capable of performing both transmission mode display and reflection mode display will be described.

  In the transmission mode display, the light used for display passes through the liquid crystal layer 220 only once, whereas in the reflection mode display, the light used for display passes through the liquid crystal layer 220 twice. Therefore, as schematically shown in FIG. 2B, it is preferable to set the thickness dt of the liquid crystal layer 220 in the transmission region A to about twice the thickness dr of the liquid crystal layer 220 in the reflection region B. By setting in this way, the retardation that the liquid crystal layer 220 gives to the light in both display modes can be made substantially equal. Although dt = 0.5dr is most preferable, good display can be realized in both display modes as long as it is within the range of 0.3dt <dr <0.7dt. Of course, dt = dr may be used depending on the application.

  In the liquid crystal display device 200, in order to make the thickness of the liquid crystal layer 220 in the reflective region B smaller than the thickness of the liquid crystal layer in the transmissive region A, the transparent dielectric layer 234 is provided only in the reflective region B of the glass substrate 210b. Yes. As illustrated, the transparent dielectric layer 234 is preferably provided below the counter electrode 231 (on the side opposite to the liquid crystal layer). By adopting such a configuration, there is no need to provide a step using an insulating film or the like under the reflective electrode 211b, so that there is an advantage that the manufacturing of the active matrix substrate 210a can be simplified. Further, when the reflective electrode 211b is provided over the insulating film for providing a step for adjusting the thickness of the liquid crystal layer 220, light used for transmissive display is blocked by the reflective electrode that covers the inclined surface (tapered portion) of the insulating film. However, since the light reflected by the reflective electrode formed on the slope of the insulating film repeats internal reflection, there is a problem that it is not effectively used for reflective display. Occurrence of problems can be suppressed and light utilization efficiency can be improved.

  Furthermore, if the transparent dielectric layer 234 having a function of scattering light (diffuse reflection function) is used, a good white display close to paper white can be realized without providing the reflection electrode 211b with a diffuse reflection function. it can. Even if the transparent dielectric layer 234 is not provided with a light scattering ability, a white display close to paper white can be realized by providing an uneven shape on the surface of the reflective electrode 211b. The position of the central axis of the symmetric orientation may not be stable. On the other hand, if the transparent dielectric layer 234 having light scattering ability and the reflective electrode 211b having a flat surface are used, the position of the central axis can be more reliably stabilized by the opening 214a formed in the reflective electrode 211b. Benefits are gained. Of course, the central axis of the axially symmetric orientation can be further stabilized by providing the opening 214b in the reflection region B of the counter electrode 231. In addition, in order to provide a diffuse reflection function to the reflective electrode 211b, when forming unevenness on the surface, the uneven shape is preferably a continuous wave shape so that no interference color is generated, and the central axis of the axially symmetric orientation is It is preferable to set so that it can be stabilized.

  In the transmissive mode, light used for display passes through the color filter layer 230 only once, whereas in reflective mode display, light used for display passes through the color filter layer 230 twice. Therefore, when a color filter layer having the same optical density is used for the transmission region A and the reflection region B as the color filter layer 230, color purity and / or luminance in the reflection mode may be lowered. In order to suppress the occurrence of this problem, it is preferable to make the optical density of the color filter layer in the reflective region smaller than that in the transmissive region. The optical density here is a characteristic value characterizing the color filter layer, and the optical density can be reduced by reducing the thickness of the color filter layer. Alternatively, the optical density can be reduced by reducing the concentration of the added dye, for example, while maintaining the thickness of the color filter layer. Thus, forming different color filter color layers in the transmissive region A and the reflective region B is extremely effective for the purpose of improving the color reproducibility of the display.

  Next, an example of the structure of an active matrix substrate that is preferably used in a transflective liquid crystal display device will be described with reference to FIGS. 3 is a partially enlarged view of the active matrix substrate, and FIG. 4 is a cross-sectional view taken along line X-X ′ in FIG. 3. The active matrix substrate shown in FIGS. 3 and 4 has a configuration in which one liquid crystal domain is formed in the transmissive region A (that is, the number of openings 214a and notches 213 is small). Although different from the active matrix substrate 211a shown in FIG. 2, other configurations may be the same.

  The active matrix substrate shown in FIGS. 3 and 4 includes a transparent substrate 1 made of, for example, a glass substrate. On the transparent substrate 1, gate signal lines 2 and source signal lines 3 are provided so as to be orthogonal to each other. . A TFT 4 is provided in the vicinity of the intersection of these signal wires 2 and 3, and the drain electrode 5 of the TFT 4 is connected to the pixel electrode 6.

  The pixel electrode 6 includes a transparent electrode 7 formed of a transparent conductive layer such as ITO and a reflective electrode 8 formed of Al or the like. The transparent electrode 7 defines a transmission region A, and the reflective electrode 8 reflects. Region B is defined. In the predetermined region of the pixel electrode 6, as described above, the notch 14 and the first opening 214 for fixing the axial position of the axially symmetric alignment domain are provided in order to control the alignment of the axially symmetric alignment domain. It has been. Further, in order to define the alignment state of the axially symmetric alignment domain, a wall structure (not shown) surrounding the pixel region is formed in the signal line (light shielding region) portion of the non-display region outside the pixel.

The pixel electrode 6 is superimposed on the gate signal line of the next stage through the gate insulating film 9, and an auxiliary capacitor is formed. The TFT 4 has a structure in which a gate insulating film 9, a semiconductor layer 12, a channel protective layer 13 and an n ⁺ -Si layer 11 (source / drain electrodes) are stacked on the gate electrode 10 branched from the gate signal line 2. is doing.

  Note that although a configuration example of a bottom-gate TFT is shown here, the present invention is not limited to this, and a top-gate TFT can also be used.

  As described above, the liquid crystal display device 200 having the configuration shown in FIG. 2 is similar to the liquid crystal display device 100 in that the action of the oblique electric field formed on the adjacent pixels by the dot inversion driving and the periphery of the opening 214 An axially symmetric orientation is stably formed by the action of the oblique electric field formed on the substrate. Further, each pair of openings 214 provided in the substantially central portion of the pixel electrode and the counter electrode fixes and stabilizes the central axis of the axially symmetric alignment domain in the pixel, so that display is performed obliquely in the halftone display state. Effects such as reducing the feeling of roughness when viewed can be obtained. Further, the wall structure 215 and the notch 213 provided in the light-shielding region form a stable axisymmetric alignment domain even in the halftone display state.

  Furthermore, by configuring the transparent attractant layer 234 and / or the color filter layer 230 as described above, the brightness and color purity of display in the transmissive mode and the reflective mode can be improved.

(Orientation stabilization drive method)
In the liquid crystal display device of the above-described embodiment, the pixels arranged in a matrix having rows and columns are applied to the pixel electrodes of adjacent pixels in each column and row within each vertical scanning period. The applied voltage is applied so as to have a reverse polarity with respect to the voltage applied to the counter electrode (dot inversion driving). Here, the effect of stabilizing the alignment obtained by performing dot inversion driving will be described in detail.

  FIG. 5 schematically shows a drive circuit and pixel arrangement of the liquid crystal display device 300 according to the embodiment of the present invention. The liquid crystal display device 300 has a display area having the same configuration as the liquid crystal display device 100 or 200 described above.

  The liquid crystal display device 300 is a TFT liquid crystal display device, and includes a plurality of parallel data signal lines (source signal lines) 301 extending in the column direction and a plurality of parallel scanning signal lines (gate signal lines) extending in the row direction. 302 are connected to the source signal driving circuit 303 and the gate signal driving circuit 304, respectively. The liquid crystal display device 300 includes at least one TFT 305 for each pixel, the gate electrode of the TFT 305 is connected to the scanning signal line 302, and the data signal line 301 is connected to the source electrode. The drain electrode of the TFT 305 is connected to the pixel electrode 306. When a predetermined voltage (scanning signal voltage) is applied to the gate electrode, the TFT 305 is turned on, and the pixel electrode 306 is electrically connected to the data signal line. A predetermined data signal voltage is supplied to the pixel electrode 306. A predetermined common voltage is supplied to a counter electrode (not shown: typically facing a plurality of pixel electrodes) facing the pixel electrode 306. The difference between the common voltage supplied to the counter electrode and the data signal voltage supplied to the pixel electrode 306 is applied to the liquid crystal layer of each pixel.

  Here, the TFT 305 connected to one arbitrary scanning signal line 302 is connected to one of the pixel electrodes 306 belonging to a pair of rows adjacent to the scanning line 302 (for example, the pixel electrode 306 belonging to the upper row). The TFTs 305 and the TFTs 305 connected to the other (for example, the pixel electrode 306 belonging to the lower row) are alternately arranged. In other words, of the plurality of data signal lines 301, for example, the TFT 306 connected to the odd-numbered data signal line 301 is disposed on the upper side of the scanning signal line 302 (connected to the pixel electrode 306 in the upper row). The TFT 305 connected to the even-numbered data signal line 301 is disposed below the scanning signal line 302 (connected to the pixel electrode 306 in the lower row). That is, TFTs 305 (and pixel electrodes 306) connected to a certain scanning signal line 302 are alternately arranged in a staggered manner in the vertical direction for each data signal line 301.

  By performing the conventional one-line inversion driving for the above-described staggered panel configuration, the voltage supplied to the pixel electrode 306 is set in the row direction and the column direction with reference to the voltage supplied to the counter electrode. Switching is performed for each frame with reverse polarity between adjacent pixels. That is, the source signal line driving circuit 303 and the gate signal line driving circuit 304 can perform dot inversion driving as a result only by performing conventional one-line inversion driving.

  In the present embodiment, a counter electrode is provided for an arbitrary first pixel that is arranged in a matrix and a second pixel in the same row adjacent to the first pixel within one frame period. Are applied with voltages having opposite polarities, and the first pixel connected to the scanning line of any n-th row and the n + 1-th row connected to the data signal line in the same column as the first pixel Voltages having opposite polarities are also applied to the third pixels connected to the (or (n−1) th) scanning signal line with reference to the counter electrode (dot inversion driving). Further, the polarity of the voltage applied to all the pixels is inverted every frame (frame inversion driving). For example, FIG. 6 shows an example of the polarity pattern of the voltage applied to the pixels in a certain frame period of the liquid crystal display device 300 of the present embodiment. In the next frame shown in FIG. 6, plus and minus are reversed for all pixels.

  FIGS. 7A to 7C show the behavior of equipotential lines when a voltage is applied to the liquid crystal layer and the simulation results of the liquid crystal alignment director. Here, the driving voltage of the liquid crystal layer is set to 4 V, and in order to confirm the effect of pulling equipotential lines by the electric field, the case where the width of the gap between adjacent pixel electrodes is 3 μm is compared with the case where it is 9 μm. . In addition, when a voltage having the same polarity is applied between adjacent pixel electrodes as in the case of performing conventional line inversion driving with respect to a conventional panel configuration, and between positive and negative between adjacent pixels based on the counter electrode A case where the polarity is applied as the reverse polarity (this embodiment) will be described.

  FIG. 7A shows a driving method according to an embodiment of the present invention when a voltage having a reverse polarity is applied to adjacent pixel electrodes (gap 3 μm between the electrodes), and FIG. 7B shows a conventional driving method between adjacent pixels. This is a simulation result when a voltage having the same polarity is applied (electrode gap 3 μm), and (c) a voltage having the same polarity is applied between adjacent pixels by the conventional driving method (electrode gap 9 μm).

  It can be seen that when a reverse polarity voltage is applied between adjacent pixels, a steep potential gradient is generated at the boundary of the pixels, and the equipotential lines are drawn more effectively. For example, in the driving method of this embodiment, equipotential lines are drawn more effectively than the conventional case of the same polarity between adjacent pixels and an electrode gap of 9 μm, and the liquid crystal molecules are obliquely aligned by the electric field. I understand. Furthermore, it can be seen that in the driving method of the present embodiment, the alignment of liquid crystal molecules is effectively controlled by an electric field even when the electrode gap is 3 μm.

  As described above, one conventional line for a panel having a configuration in which TFTs 305 (and pixel electrodes 306) connected to an arbitrary scanning signal line 302 are alternately arranged in a vertical direction for each data signal line 301. A large potential gradient is formed between the pixels by performing inversion driving and applying the polarity of the voltage applied to the adjacent pixel in the row direction and the column direction with the opposite polarity to the counter electrode for each frame. This makes it possible to stabilize the axially symmetric alignment formed in the vertical alignment type liquid crystal layer by the alignment regulating force using this potential gradient.

  In addition, the driving method suitable for stabilizing the alignment is extremely effective for reducing the flicker of the liquid crystal panel.

  That is, in a general active liquid crystal panel, since the characteristics of a switching element such as a TFT element provided for each pixel are not sufficient, the sign of the data signal output from the source signal drive circuit (column direction) 303 is symmetric. However, the transmittance of the liquid crystal layer is not completely symmetric with respect to the positive and negative data voltages, and in the driving method (one frame inversion driving) that inverts the positive / negative polarity of the voltage applied to the liquid crystal layer every frame. Flicker may be noticeable.

  As such a flicker reduction measure, a driving method (1H inversion driving) in which the positive / negative polarity is inverted every horizontal scanning line and the positive / negative polarity is inverted every frame period is known. A driving method (dot inversion driving) or the like in which the positive / negative polarity of the voltage applied to the liquid crystal layer forming the pixel is inverted for each scanning signal line and for each data line is performed. The effect of suppressing flicker has the feature that it can be reduced most by the dot inversion drive similar to this embodiment. However, in the case of dot inversion drive, the pixel electrode on the same scanning line has a positive or negative polarity. It has also been pointed out that the IC withstand voltage of the source signal line driver circuit must be set high in order to apply a voltage. In contrast, in the present embodiment, a conventional panel having a configuration in which switching elements (and pixel electrodes) connected to arbitrary scanning signal lines are alternately arranged in a vertical direction for each data signal line is used. By performing one-line inversion driving, dot inversion driving can be realized as a result, so that a high IC breakdown voltage is not required unlike conventional dot inversion driving.

  In addition, in the liquid crystal display device according to the embodiment of the present invention, when a wall structure is further provided, the axially symmetric alignment can be stabilized by utilizing the alignment regulating force by the wall structure, so that a sufficient electric field can be obtained. It is possible to stabilize the axially symmetric orientation even in the case where there is no halftone, and the display quality in the halftone can be improved. Furthermore, it is possible to shorten the time required for the alignment disorder (which may be referred to as an afterimage caused by pressing) generated when the liquid crystal display panel is pressed to recover normal alignment.

〔Operating principle〕
Next, the reason why the liquid crystal display device of the embodiment of the present invention having the vertical alignment type liquid crystal layer has excellent wide viewing angle characteristics will be described with reference to FIG.

  FIG. 8 is a diagram for explaining the action of the alignment regulating force by the wall structure 15 and the opening 14a provided on the active matrix substrate side and the opening 14b provided on the color filter substrate side. ) Schematically shows the alignment state of the liquid crystal molecules when no voltage is applied, and FIG. 8B shows the alignment state of the liquid crystal molecules when the voltage is applied. The state shown in FIG. 8B is a state where a halftone is displayed.

  In the liquid crystal display device shown in FIGS. 8A and 8B, an insulating film 16, a pixel electrode 6 having an opening 14a at a predetermined position, and a wall structure 15 are formed on a transparent substrate 1, and an alignment film 12 are arranged in this order. On the other transparent substrate 17, a color filter layer 18, a counter electrode 19 having an opening 14b at a predetermined position, and an alignment film 32 are formed in this order. The liquid crystal layer 20 provided between the two substrates includes liquid crystal molecules 21 having negative dielectric anisotropy.

  As shown in FIG. 8A, when no voltage is applied, the liquid crystal molecules 21 are aligned substantially perpendicular to the substrate surface by the alignment regulating force of the vertical alignment films 22 and 32.

  On the other hand, when a voltage is applied, as shown in FIG. 8B, the liquid crystal molecules 21 having negative dielectric anisotropy tend to have the molecular long axis perpendicular to the lines of electric force, so that the pair of openings 14a and The direction in which the liquid crystal molecules 21 are tilted is defined by the oblique electric field formed around 14b, the electric field distortion of the side surface (wall surface) of the wall structure 15, and the alignment regulating force. Therefore, for example, it is oriented in an axially symmetrical manner around the openings 14a and 14b. In this axially symmetric alignment domain, the liquid crystal directors are aligned in all directions (directions in the substrate plane), so that viewing angle characteristics are excellent.

  Here, the action of the oblique electric field formed around the openings 14a and 14b and the alignment regulating force in the wall structure 15 have been described, but also in the vicinity of the notch formed at the edge of the pixel electrode 6. Similarly, an oblique electric field is formed, and the direction in which the liquid crystal molecules 21 are inclined by the electric field is defined. In particular, by performing the dot inversion driving described above, an oblique electric field generated between adjacent pixel electrodes acts so as to stably form an axially symmetric alignment of liquid crystal molecules. Even if the wall structure 15 is omitted, the axisymmetric orientation is stabilized by the action of the steep oblique electric field obtained by performing dot inversion driving and the action of the oblique electric field formed around the openings 14a and 14b. Can be formed.

  Next, the configuration of the liquid crystal display device according to the present invention will be described.

  The liquid crystal display device shown in FIG. 9 includes a backlight, a transflective liquid crystal panel 50, a pair of polarizing plates 40 and 43 provided so as to face each other through the transflective liquid crystal panel 50, and the polarizing plate 40. Quarter wave plates 41 and 44 provided between the liquid crystal panel 50 and the liquid crystal panel 50, and the optical anisotropy provided between the quarter wave plates 41 and 44 and the liquid crystal panel 50 is negative. The phase difference plates 42 and 45 are included. The liquid crystal panel 50 includes a vertical alignment type liquid crystal layer 20 between a transparent substrate (active matrix substrate) 1 and a transparent substrate (counter substrate) 17. Here, a liquid crystal panel 50 having the same configuration as that of the liquid crystal display device 200 shown in FIG. 2 is used.

  The display operation of the liquid crystal display device shown in FIG. 9 will be briefly described below.

  For the reflection mode display, incident light from above passes through the polarizing plate 43 and becomes linearly polarized light. This linearly polarized light becomes circularly polarized light when it enters the quarter wavelength plate 44 so that the transmission axis of the polarizing plate 43 and the slow axis of the quarter wavelength plate 44 are 45 °, and is formed on the substrate 17. It passes through a color filter layer (not shown). Here, a phase difference plate 45 that does not give a phase difference to light incident from the normal direction is used.

  When no voltage is applied, since the liquid crystal molecules in the liquid crystal layer 20 are aligned substantially perpendicular to the substrate surface, the incident light is transmitted with a phase difference of approximately 0 and is reflected by the reflective electrode formed on the lower substrate 1. The The reflected circularly polarized light passes through the liquid crystal layer 20 again, passes through the color filter layer, passes again through the retardation plate 45 having negative optical anisotropy as circularly polarized light, passes through the quarter-wave plate 44, and then first. The light is converted into linearly polarized light having a polarization direction orthogonal to the polarization direction when passing through the polarizing plate 43 and reaches the polarizing plate 43, so that light cannot pass through the polarizing plate 43 and is displayed in black.

  On the other hand, when a voltage is applied, the liquid crystal molecules in the liquid crystal layer 20 are inclined in the horizontal direction from the direction perpendicular to the substrate surface, so that the incident circularly polarized light becomes elliptically polarized light due to the birefringence of the liquid crystal layer 20 and is formed on the lower substrate 1. Reflected by the reflected electrode. The reflected light is further broken in the polarization state by the liquid crystal layer 20, passes through the liquid crystal layer 20 again, passes through the color filter layer, passes through the retardation plate 45 having negative optical anisotropy again, and becomes 1/4. Since the light is incident on the wave plate 44 as elliptically polarized light, all the light does not become linearly polarized light orthogonal to the polarization direction at the time of incidence when reaching the polarizing plate 43, and part of the light is transmitted through the polarizing plate 43. In particular, by adjusting the applied voltage, the direction in which the liquid crystal molecules are tilted can be controlled, and the amount of light that can be reflected by the polarizing plate 43 is modulated, thereby enabling gradation display.

  Regarding the display of the transmission mode, the two upper and lower polarizing plates 43 and 40 are arranged so that their transmission axes are orthogonal to each other, and the light emitted from the light source becomes linearly polarized light by the polarizing plate 40, This linearly polarized light becomes circularly polarized light and has a negative optical anisotropy when incident on the ¼ wavelength plate 41 so that the slow axis between the transmission axis of the polarizing plate 40 and the ¼ wavelength plate 41 is 45 °. The light enters the transmission region A of the lower substrate 1 through the phase difference plate 42. Here, a phase difference plate 42 that does not give a phase difference to light incident from the normal direction is used.

  When no voltage is applied, the liquid crystal molecules in the liquid crystal layer 20 are aligned substantially perpendicular to the substrate surface, so that incident light is transmitted with a phase difference of approximately 0 and is incident on the lower substrate 1 in a circularly polarized state. In the state of circular polarization, the light passes through the liquid crystal layer 20 and the upper substrate 17 and passes through the retardation plate 45 having the negative optical anisotropy to reach the quarter-wave plate 44. Here, the slow axis of the lower ¼ wavelength plate 41 and the upper ¼ wavelength plate 44 intersect each other by 90 °, so that the upper ¼ wavelength plate 44 is separated by the polarizing plate 40. The linearly polarized light is orthogonal to the linearly polarized light, and is absorbed by the polarizing plate 43 to display black.

  On the other hand, when a voltage is applied, since the liquid crystal molecules 21 in the liquid crystal layer 20 are inclined in the horizontal direction from the direction perpendicular to the substrate surface, the circularly polarized light incident on the liquid crystal display device becomes elliptically polarized light due to the birefringence of the liquid crystal layer 20, and the upper side. Since the CF substrate 16 and the retardation plate 45 and the quarter wavelength plate 44 having negative optical anisotropy on the upper side reach the polarizing plate 43 as elliptically polarized light, the linearly polarized light orthogonal to the polarization component at the time of incidence is not obtained. Instead, light passes through the polarizing plate 43. In particular, by adjusting the applied voltage, the direction in which the liquid crystal molecules are tilted can be controlled, and the amount of light that can be reflected by the polarizing plate 43 is modulated, thereby enabling gradation display.

  A retardation plate having a negative optical anisotropy minimizes the amount of change in retardation when the viewing angle is changed in a vertically aligned state of liquid crystal molecules, and suppresses black floating on the wide viewing angle side. Further, a biaxial retardation plate in which a retardation plate having negative optical anisotropy and a quarter wavelength plate are integrated may be used.

  When a normally black mode in which black display is performed when no voltage is applied and white display is performed when a voltage is applied as in the present invention is performed in an axially symmetric alignment domain, a pair of quarter wavelengths are formed above and below the liquid crystal display device (panel). By providing the plate, it is possible to improve the brightness by eliminating the extinction pattern caused by the polarizing plate. In addition, when the normally black mode is performed in the axially symmetric alignment domain by arranging the transmission axes of the upper and lower polarizing plates orthogonally to each other, in principle, the same degree as that of a pair of polarizing plates arranged in crossed Nicols. Since a black display can be realized, an extremely high contrast ratio can be realized, and a wide viewing angle characteristic led to an omnidirectional orientation can be achieved.

  Further, regarding the relationship between the liquid crystal layer thickness dt of the transmission region and the liquid crystal layer thickness dr of the reflection region defined in the present invention, FIG. 10 shows the dependence of the voltage-reflectance (transmittance) of the transmission region and the reflection region on the liquid crystal thickness. As shown, it is preferable to satisfy the condition of 0.3 dt <dr <0.7 dt, and it is more preferable that the range is 0.4 dt <dr <0.6 dt. If the thickness of the liquid crystal layer in the reflection region lower than the lower limit value is 50% or less of the maximum reflectance, sufficient reflectance cannot be obtained. On the other hand, when the thickness dr of the liquid crystal layer in the reflective region is larger than the upper limit value, there is a maximum value in which the reflectance becomes maximum at a driving voltage different from that in transmissive display in the voltage-reflectance characteristics and the optimum in transmissive display. When the white display voltage is high, the relative reflectance tends to decrease, and the reflectance is 50% or less of the maximum reflectance, so that a sufficient reflectance cannot be obtained. However, in the reflection region B, the optical path length of the liquid crystal layer is twice that of the transmission region. Therefore, when the same design as the transmission region A is used, the optical birefringence anisotropy (Δn) of the liquid crystal material is Panel cell thickness design is extremely important.

  Specific characteristics of the transflective liquid crystal display device according to the embodiment of the present invention will be exemplified below.

  Here, a liquid crystal display device having the configuration shown in FIG. 9 was manufactured. As the liquid crystal cell 50, a liquid crystal cell having the same configuration as that of the liquid crystal display device 200 shown in FIG.

  In the pixel electrode on the TFT substrate side, an opening (first opening) having a diameter of 5 μm is formed at a predetermined position in each of the transmission region and the reflection region, and a wall is formed on a light shielding portion such as a signal line around the pixel. A structure was placed. Further, an opening (second opening) for fixing the axial center of the axially symmetric orientation domain having a diameter of 5 μm is arranged at a predetermined position of each of the transmission region portion and the reflection region portion on the counter electrode on the counter substrate side. . The pair of first and second openings are positioned so as to overlap each other spatially with the liquid crystal layer interposed therebetween. Here, the notch width was 3 μm, and the gap between adjacent pixel electrodes was 5 μm. In addition, a color filter substrate having a transparent dielectric layer 234 that does not have light scattering ability is used, and a resin layer having a concavo-convex continuous shape is formed on the lower layer portion of the reflective electrode 211b, so that a reflective display can be performed. The diffuse reflection characteristics were adjusted.

  A vertical alignment film was formed by a known method using a known alignment film material. Labin treatment is not performed. As the liquid crystal material, a liquid crystal material having negative dielectric anisotropy (Δn; 0.1, Δε; −4.5) was used. Here, the liquid crystal layer thickness dt in the transmission region is 4 μm, and the liquid crystal layer thickness dr in the reflection region is 2.2 μm (dr = 0.55 dt).

  The configuration of the liquid crystal display device of this example is composed of a polarizing plate (observation side), a quarter-wave plate (retardation plate 1), and a retardation plate with negative optical anisotropy (retardation plate 2 (NR) from the top. Plate)), liquid crystal layer (upper side: color filter substrate, lower side: active matrix substrate), retardation plate with negative optical anisotropy (retardation plate 3 (NR plate)), 1/4 wavelength plate (retardation) A laminated structure of a plate 4) and a polarizing plate (backlight side) was adopted. In the upper and lower quarter-wave plates (the phase difference plate 1 and the phase difference plate 4) of the liquid crystal layer, their slow axes are orthogonal to each other, and each phase difference is set to 140 nm. Retardation plates having negative optical anisotropy (retardation plate 2 and retardation plate 3) each have a retardation of 135 nm. Further, the two polarizing plates (observation side and backlight side) were arranged with their transmission axes orthogonal to each other.

  A display signal was evaluated by applying a drive signal to the liquid crystal display device (applying 4V to the liquid crystal layer). In particular, here, as described above, the switching elements are alternately arranged in a staggered manner in the vertical direction for each data signal line, and pseudo-dot inversion is performed on the liquid crystal layer by performing 1H line inversion. Apply the same drive signal as above, apply + 4V and -4V signals between adjacent pixels with reference to the counter electrode in one frame, and drive the polarity inversion in the next one frame to improve the display characteristics of the liquid crystal panel evaluated.

  A viewing angle-contrast characteristic result in the transmissive display is shown in FIG. The viewing angle characteristics in the transmissive display are almost omnidirectional and symmetric, the CR> 10 region is as good as ± 80 °, and the transmissive contrast is as high as 300: 1 or more in the front. In addition, the gap between adjacent pixel electrodes can be made narrower than in the case of applying a conventional driving method such as line inversion, in which a driving signal having the same polarity is applied between adjacent pixels. The improvement effect was confirmed.

  On the other hand, the characteristics of the reflective display are evaluated with a spectrocolorimeter (CM 2002 manufactured by Minolta), the reflectance is about 9.5% (converted value of the aperture ratio 100%) based on the standard diffusion plate, and the contrast value of the reflective display. Was 25, which was good, showing high contrast as compared with conventional liquid crystal display devices.

  Further, in the evaluation of the roughness from the diagonal direction in the gray scale of the halftone (gradation level 2 when divided into 8 gradations), the feeling of roughness was not felt at all.

  In addition, the halftone response time in the liquid crystal display device when a pair of electrode openings are provided on the upper and lower substrates (time required for the change from gradation level 3 to gradation level 5 at the time of eight gradation division; m seconds ) Is 35 milliseconds, and it was confirmed that the response time was greatly improved by adopting the liquid crystal panel configuration of the present invention. Further, with respect to the orientation restoring force when the panel surface was pressed with the fingertip when a voltage of 4 V was applied (white display), an afterimage at the pressing portion was hardly seen.

  When the liquid crystal panel of the present invention is driven by the conventional 1H line inversion driving method in which the applied voltage between adjacent pixels has the same polarity, when the gap between adjacent pixel electrodes is 3 μm, FIG. However, as shown, the phenomenon of disclination occurring in the liquid crystal region was observed without sufficient alignment control of the liquid crystal molecules. In this case, the display contrast and the response speed are not sufficient, and the display quality is significantly deteriorated.

  As described above, the liquid crystal display device according to the present invention can realize a liquid crystal display device with excellent display quality with a relatively simple configuration. The present invention is suitably applied to a transmissive liquid crystal display device and a transflective (transmission / reflection) liquid crystal display device. In particular, the transflective liquid crystal display device is suitably used as a display device for mobile devices such as mobile phones.

It is a figure which shows typically the structure of one pixel of the transmissive liquid crystal display device 100 of embodiment by this invention, (a) is a top view, (b) is 1B- in FIG. 1 (a). It is sectional drawing along line 1B ', (c) is sectional drawing which shows typically the structure of one pixel of other transmissive liquid crystal display device 100' of embodiment by this invention. It is a figure which shows typically the structure of one pixel of the transflective liquid crystal display device 200 of embodiment by this invention, (a) is a top view, (b) is 2B in Fig.1 (a). It is sectional drawing along a -2B 'line. 2 is a plan view of an active matrix substrate 210a of a transflective liquid crystal display device 200. FIG. 4 is a sectional view of an active matrix substrate 210a of a transflective liquid crystal display device 200. FIG. It is a figure which shows typically the drive circuit and pixel arrangement | positioning of the liquid crystal display device 300 of embodiment by this invention. 6 is a diagram illustrating an example of a polarity pattern of a voltage applied to pixels in a certain frame period of the liquid crystal display device 300. FIG. It is a figure which shows typically the behavior of an equipotential line at the time of applying a voltage to a liquid-crystal layer, and the simulation result of a liquid-crystal aligning director, (a) is the case of the drive method of embodiment by this invention, (b) and (C) is a case of the conventional drive method. It is the schematic explaining the operation | movement principle of the liquid crystal display device of embodiment by this invention, (a) shows the time at the time of no voltage application, and (b) at the time of voltage application, respectively. It is a schematic diagram which shows an example of a structure of the liquid crystal display device of embodiment by this invention. It is a graph which shows the thickness dependence of the liquid crystal layer of the voltage-reflectance (transmittance) of the transmission area | region and reflection area | region in the liquid crystal display device of embodiment by this invention. It is a figure which shows the viewing angle-contrast ratio characteristic of the liquid crystal display device of embodiment by this invention.

Explanation of symbols

1 TFT (active matrix) substrate 2 Gate signal line 3 Source signal line 4 TFT
5 Drain electrode 6 Pixel electrode 7 Transparent electrode 8 Reflective electrode 9 Gate insulating film 10 Gate electrode 11 Source / drain electrode (n + -Si layer)
12 Semiconductor Layer 13 Channel Protection Layer 14 Opening Structure 15 Opening 16 Insulating Film 17 Transparent Substrate (Counter (CF) Substrate)
18 Color filter layer 19 Counter electrode 20 Liquid crystal layer 21 Liquid crystal molecule 22, 32 Alignment film 50 Liquid crystal panel 40, 43 Polarizing plate 41, 44 1/4 wavelength plate 42, 45 Retardation plate with negative optical anisotropy (NR plate) )
100, 100 'Transmission type liquid crystal display device 110a Active matrix substrate 110b Counter substrate (color filter substrate)
111 pixel electrode 113 notch 114 opening 115 wall structure 130 color filter layer 131 counter electrode 133 support 200 transflective liquid crystal display device 210a active matrix substrate 210b counter substrate (color filter substrate)
211 Pixel electrode 213 Notch 214 Opening 215 Wall structure 230 Color filter layer 231 Counter electrode 232 Transparent dielectric layer (reflection step)
233 Support 300 Liquid crystal display 301 Data signal line (source signal line)
302 Scanning signal line (gate signal line)
303 Source signal line drive circuit 304 Gate signal line drive circuit 305 Switching element 306 Pixel electrode

Claims (14)

A first substrate, a second substrate provided to face the first substrate, and a vertical alignment type liquid crystal layer provided between the first substrate and the second substrate,
The first substrate includes a plurality of scanning signal lines extending in a row direction, a plurality of data signal lines extending in a column direction, and a plurality of switching elements connected to the plurality of scanning signal lines and the plurality of data signal lines. A plurality of first electrodes connected to the plurality of data signal lines via the plurality of switching elements,
The second substrate has a second electrode facing the plurality of first electrodes through the liquid crystal layer,
Each of the plurality of first electrodes, the second electrode, and the liquid crystal layer provided between the first electrode and the second electrode are arranged in a matrix having rows and columns. A plurality of pixels, and a liquid crystal display device having a light-shielding region in a gap between the plurality of pixels ,
The first electrode has at least one first opening formed at a predetermined position in the pixel, and the second electrode has at least one second opening formed at a predetermined position in the pixel. In addition, the central axis of the axially symmetric orientation of at least one liquid crystal domain formed when a predetermined voltage is applied to at least the liquid crystal layer is the at least one first opening and the at least one second opening. Formed in or near at least one opening in
The liquid crystal display device , wherein the at least one first opening and the at least one second opening are arranged at a position where at least a part thereof overlaps with the liquid crystal layer .   The liquid crystal display device according to claim 1, wherein the first substrate further has a wall structure regularly arranged on the liquid crystal layer side in the light shielding region.   An arbitrary column of the plurality of pixels includes a first pixel having the first electrode to which a positive polarity voltage is supplied using the potential of the second electrode as a reference potential in a vertical scanning period, and a negative polarity 3. The liquid crystal display device according to claim 1, wherein the second pixels having the first electrode to which a voltage is supplied are alternately arranged. 4.   4. The liquid crystal display device according to claim 1, wherein the polarity of the voltage supplied to the first electrode of each of the plurality of pixels is inverted every vertical scanning period. 5. The first electrode has at least one notch, the liquid crystal display device according to any one of claims 1 to 4. It said support defining a thickness of the liquid crystal layer in the light shielding region is provided, the liquid crystal display device according to any one of claims 1 to 5. The first electrode includes a transparent electrode that defines a transmissive region and a reflective electrode that defines a reflective region, the thickness dt of the liquid crystal layer in the transmissive region, and the thickness of the liquid crystal layer in the reflective region. dr and is, 0.3dt <dr <satisfies the relationship 0.7Dt, the liquid crystal display device according to any one of claims 1 to 6. The first electrode includes a transparent electrode defining a transmissive region and a reflective electrode defining a reflective region, and the at least one liquid crystal domain includes a liquid crystal domain formed in the transmissive region. Has at least one first opening, the second electrode has at least one second opening, and the at least one first opening and the second opening are formed in the transmission region. Including an opening corresponding to the central axis of the liquid crystal domain;
The first electrode has a plurality of cutout portions arranged in point symmetry about the opening, the liquid crystal display device according to any one of claims 1 to 7. The liquid crystal display device according to claim 7 or 8 optically transparent dielectric layer is provided in the reflective region of the second substrate. The liquid crystal display device according to claim 9 , wherein the transparent dielectric layer has a function of scattering light. Wherein further comprising a color filter layer provided on the second substrate, the optical density of the color filter layer in the reflection region is smaller than the color filter layer of the transmissive region, according to claim 7 10 Liquid crystal display device. A pair of polarizing plates arranged to face each other with the first substrate and the second substrate interposed therebetween, and at least between the first substrate and / or the second substrate and the pair of polarizing plates further comprising one biaxial optically anisotropic medium layer, a liquid crystal display device according to any one of claims 1 to 11. It further has a pair of polarizing plates arranged so as to face each other with the first substrate and the second substrate interposed therebetween, and between the first substrate and / or the second substrate and the pair of polarizing plates. further comprising at least one uniaxial optically anisotropic medium layer, a liquid crystal display device according to any one of claims 1 to 11.   A switching element connected to any one of the plurality of scanning signal lines among the plurality of switching elements is connected to one of the first electrodes belonging to a pair of rows adjacent to the arbitrary one. A switching element connected to the other and a switching element connected to the other are alternately arranged, and any row of the plurality of pixels has a positive polarity voltage with a potential of the second electrode as a reference potential in a certain vertical scanning period. 14. The first pixel having the first electrode to which a negative polarity is supplied and the second pixel having the first electrode to which a negative polarity voltage is supplied are alternately arranged. 14. A liquid crystal display device according to any one of the above.

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