JP2005274668A - Liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a vertical alignment type liquid crystal display device which sufficiently stabilizes alignment of liquid crystal with relatively simple constitution and obtains higher display quality than before. <P>SOLUTION: The liquid crystal display device has a vertical alignment type liquid crystal layer provided between a 1st substrate and a 2nd substrate and also has a pixel including a 1st electrode formed on the 1st substrate, a 2nd electrode formed on the 2nd substrate, and a liquid crystal layer provided between the 1st electrode and 2nd electrode and a light shielding region provided around the pixel, and a plurality of supports are regularly arranged on a liquid crystal layer side in the light shielding region on the 1st or 2nd substrate; and the liquid crystal layer forms at least one liquid crystal domain showing axially symmetrical alignment at least when applied with a prescribed voltage and tilt directions of liquid crystal molecules in at least one liquid crystal domain are prescribed by tilt flanks that the plurality of supports have. <P>COPYRIGHT: (C)2006,JPO&NCIPI

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 order to solve this problem, Patent Document 2 discloses a liquid crystal display device having a plurality of liquid crystal domains exhibiting an axially symmetric orientation in a pixel by providing openings regularly arranged in the pixel electrode or the counter electrode. doing.

  Furthermore, 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.

  Patent Document 4 discloses a multi-domain vertical alignment type liquid crystal display device in which a wall-like spacer having inclined side surfaces is provided, and the tilt direction of the liquid crystal molecules is defined using the alignment regulating force of the inclined side surfaces. Yes. According to this technique, it is not necessary to add a process for providing an alignment regulating structure, and even when the screen is enlarged, variations in the substrate interval (the thickness of the liquid crystal layer) can be suppressed.

  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 5 and Patent Document 6). 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, in Patent Document 3, the vertical alignment mode is not limited to the transmissive liquid crystal display device but also the transflective liquid crystal. A configuration applied to a display device is also disclosed. Further, in Patent Document 7, in a semi-transmissive liquid crystal display device having a vertical alignment type liquid crystal layer, an insulating layer provided in order 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 protrusion (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).
JP-A-6-301036 JP 2000-47217 A JP 2003-167253 A JP 2001-337332 A Japanese Patent No. 29555277 US Pat. No. 6,195,140 JP 2002-350853 A

  In the technique disclosed in Patent Document 2 or Patent Document 3, a plurality of liquid crystal domains are formed by providing convex portions or openings in a pixel (that is, divided into pixels), and the alignment regulation force on liquid crystal molecules is strengthened. However, according to the study of the present inventors, in order to obtain a sufficient alignment regulating force, alignment control structures such as protrusions and openings are formed on both sides of the liquid crystal layer (the liquid crystal layer side of a pair of substrates facing each other). There is a problem that the manufacturing process becomes complicated. In addition, the effective aperture ratio of the pixel provided with the alignment regulating structure in the pixel may be decreased, or the contrast ratio may be decreased due to light leakage from the periphery of the convex portion in the pixel. In the case where the alignment regulation structure is provided on both the substrates, since it is affected by the alignment margin of the substrates, the effective aperture ratio and / or the contrast ratio are further reduced.

  The technique disclosed in Patent Document 4 uses a wall spacer to form a plurality of liquid crystal domains in a pixel (the alignment direction of liquid crystal molecules in each domain is one direction, and the alignment directions are different between liquid crystal domains). Since it is formed, it is necessary to form a wall spacer in the pixel, resulting in a decrease in effective aperture ratio and / or a decrease in contrast ratio.

  Further, in the technique disclosed in Patent Document 7, it is necessary to dispose a convex part or an electrode opening on the side opposite to the concave part provided for controlling the multiaxial orientation, and the same problem as the above-described conventional technique is caused. Occur.

  The present invention has been made in view of the above points, and its purpose is to provide a vertical alignment type liquid crystal that can sufficiently stabilize the alignment of the liquid crystal with a relatively simple configuration and can obtain a display quality equivalent to or higher than that of the conventional one. It is to provide a display device.

  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. A first electrode formed on the first substrate, a second electrode formed on the second substrate, and provided between the first electrode and the second electrode. A plurality of pixels including the liquid crystal layer, and a light shielding region provided around the pixels, the liquid crystal layer on the first substrate or the second substrate in the light shielding region. A plurality of supports that define the thickness of the liquid crystal layer are regularly arranged, and the liquid crystal layer forms at least one liquid crystal domain exhibiting an axially symmetric orientation when at least a predetermined voltage is applied. , The tilt direction of the liquid crystal molecules in the at least one liquid crystal domain Characterized in that it is defined by the inclined sides lifting body has.

  In one embodiment, each of the at least one liquid crystal domain is in contact with at least four inclined side surfaces of the support.

  In one embodiment, the first electrode has at least one opening, and a central axis of each axisymmetric orientation of the at least one liquid crystal domain is formed in or near the at least one opening.

  In one embodiment, the inclined side surfaces of the plurality of supports are inclined in a reverse taper shape with respect to the first substrate.

  In one embodiment, a cross-sectional shape of the plurality of supports in a plane parallel to the first substrate surface is a substantially circular shape, a substantially elliptical shape, a substantially rhombus shape, or a substantially cross shape.

  In a certain embodiment, it further has a wall structure regularly arranged in the said light shielding area | region.

  In one embodiment, the at least one liquid crystal domain includes two liquid crystal domains, the at least one opening includes two openings, and a central axis of each of the two liquid crystal domains has an axially symmetric orientation. It is formed in or near the two openings.

  In one embodiment, the first electrode includes a transparent electrode that defines a transmissive region and a reflective electrode that defines a reflective region.

  In one embodiment, the at least one liquid crystal domain includes a liquid crystal domain formed in the transmissive region and a liquid crystal domain formed in the reflective region.

  In one embodiment, the at least one opening includes an opening formed in the transparent electrode and an opening formed in the reflective electrode.

  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.

  In the liquid crystal display device of the present invention, the support (columnar spacer) that defines the thickness of the liquid crystal layer provided in the light shielding region around the pixel is regularly arranged, and the inclined side surface of the support has It acts to define the direction in which the liquid crystal molecules are tilted by the electric field. Since the support for defining the thickness of the liquid crystal layer is used as the alignment regulating structure, there is no need to add a process for providing the alignment regulating structure. In addition, since the support is disposed in the light shielding region, a decrease in effective aperture ratio and a decrease in contrast ratio are suppressed. When the support is provided so that each of the liquid crystal domains is in contact with the inclined side surfaces of at least four supports, the axially symmetric alignment domain can be stably formed. By providing the wall structure in the light shielding region, the axially symmetric alignment domain can be formed more stably.

  In addition, if the opening is provided in the first electrode, the central axis of the axially symmetric alignment of the liquid crystal domain can be fixed and stabilized in the opening or in the vicinity thereof, so that display uniformity, particularly when viewed from an oblique viewing angle, can be achieved. Roughness can be suppressed.

  As described above, according to the present invention, there is provided a vertical alignment type liquid crystal display device that can sufficiently stabilize the alignment of the liquid crystal with a relatively simple configuration and obtain a display quality equal to or higher than that of the conventional one.

  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. FIG. 1 is a diagram schematically showing the configuration of one pixel of the transmissive liquid crystal display device 100, (a) is a plan view, and (b) is 1B-1B ′ in FIG. 1 (a). It is sectional drawing along a line. FIG. 1B schematically shows the alignment state of the liquid crystal molecules 121 when a predetermined voltage (voltage equal to or higher than the threshold voltage) is applied to the liquid crystal layer.

  The liquid crystal display device 100 includes a transparent substrate (for example, a glass substrate) 110a, a transparent substrate 110b provided to face the transparent substrate 110a, and a vertical alignment type liquid crystal layer provided between the transparent substrates 110a and 110b. 120. 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, and a liquid crystal provided between the pixel electrode 111 and the counter electrode 131. Layer 120 defines the 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.

  The liquid crystal display device 100 has a light shielding region between adjacent pixels, and has a support (columnar spacer) 133 on a transparent substrate 110a in the light shielding region. The support 133 defines the thickness (also referred to as cell gap) dt of the liquid crystal layer 120. Here, the light shielding region is formed, for example, on a TFT (not shown), the gate signal wiring 102, the source signal wiring 103, or the transparent substrate 110b, which is formed in the peripheral region of the pixel electrode 111 on the transparent substrate 110a. This area is shielded by the black matrix 130 and does not contribute to display. Therefore, the support 133 disposed in the light shielding area does not adversely affect the display.

  In the liquid crystal display device 100, the support 133 is disposed at a position where the gate signal wiring 102 and the source signal wiring 103 intersect with each other, and is provided corresponding to the four corners of a substantially square pixel. In addition, the cross-sectional shape of the support 133 on the surface parallel to the transparent substrate 110a is a substantially cross shape, and has a portion parallel to the gate signal wiring 102 and a portion parallel to the source signal wiring. The support 133 has inclined side surfaces, and the support 133 acts so as to define the direction in which the liquid crystal molecules 121 are inclined by the inclined side surfaces. This is because the liquid crystal molecules 121 attempt to align substantially perpendicularly to the inclined side surface (more precisely, the vertical alignment film on the inclined side surface), and are aligned in the direction corresponding to the inclination direction and the angle of the inclined side surface. Be regulated. This orientation regulating force acts even when no voltage is applied. The inclined side surface of the support 133 exemplified here is inclined in a reverse taper shape with respect to the transparent substrate 110a. Such an inclination is preferable because the alignment regulation direction by the oblique electric field formed around the opening 114 of the pixel electrode 111 formed on the transparent substrate 110a and the alignment regulation direction by the inclined side surface coincide (align). .

  The cross-sectional shape of the support 133 on the plane parallel to the transparent substrate 110a is not limited to the substantially cross shape illustrated here, and may be a substantially polygonal shape such as a substantially circular shape, a substantially elliptical shape, or a substantially rhombus shape. The inclined side surface of the support 133 defines the direction in which the liquid crystal molecules 121 are tilted and acts to define the extension of the axially symmetric alignment domain. Therefore, depending on the shape of the liquid crystal domain and the position where the support 133 is disposed. The cross-sectional shape may be such that the axially symmetric alignment of the liquid crystal domain can be stably formed. The support 133 can be formed by a photolithography process using a photosensitive resin, for example. The support 133 may be formed on either the transparent substrate 110a or 110b. However, as described above, in order to obtain the support 133 having an inclined side surface that is reversely tapered with respect to the transparent substrate 110a, the transparent substrate Since it is easier to form a forward tapered support on 110b, it is preferable to form it on the transparent substrate 110b.

  The pixel electrode 111 has an opening 114 formed at a predetermined position. When a predetermined voltage is applied to the liquid crystal layer 120, liquid crystal domains exhibiting axially symmetric alignment are formed, and the central axis of the axially symmetric alignment of these liquid crystal domains is formed in or near the opening 114. As will be described later, the opening 114 provided in the pixel electrode 111 acts to fix the position of the central axis of the axially symmetric orientation. An oblique electric field is formed around the opening 114 by the voltage applied between the pixel electrode 111 and the counter electrode 113, and the direction in which the liquid crystal molecules are inclined is defined by the oblique electric field. Act on.

  The shape of the opening 114 provided for fixing and stabilizing the central axis of the axially symmetric orientation domain is preferably circular as illustrated, but is not limited thereto. 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.

  In this liquid crystal display device 100, when a predetermined voltage (a voltage equal to or higher than the threshold voltage) is applied to the pixel electrode 111 and the counter electrode 131, the central axes are fixed and stabilized in the opening 114 or in the vicinity thereof. Symmetric orientation domains are formed. The direction in which the liquid crystal molecules 121 in the vicinity of the extension of the liquid crystal domain fall is defined by the alignment regulating force of the inclined side surface of the support 133 provided around the pixel, and an oblique electric field formed around the opening 114 of the pixel electrode 111. The direction in which the liquid crystal molecules 121 around the opening 114 fall is defined. As described above, it is considered that the alignment regulating force by the inclined side surface of the support 133 and the alignment regulating force by the opening 114 act cooperatively, thereby stabilizing the axially symmetric alignment of the liquid crystal domain.

  The transparent substrate 110a, the TFT (not shown) provided on the liquid crystal layer 120 side of the transparent substrate 110a, circuit elements such as the gate wiring 102 and the source wiring 103 connected to the TFT, the gate insulating film 104, and the protective layer 105 The pixel electrode 111, the support 133, the alignment film (not shown), and the like described above 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.

  Further, although omitted in the above description, the liquid crystal display device 100 further includes a pair of polarizing plates arranged so as to face each other through the transparent substrates 110a and 110b. 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.

  Next, FIGS. 2A and 2B schematically show the configuration of a transmissive liquid crystal display device 100 ′ according to another embodiment of the present invention. Components having substantially the same functions as those of the liquid crystal display device 100 shown in FIG. 1 are denoted by common reference numerals, and description thereof is omitted here. FIG. 2A is a plan view, and FIG. 2B is a cross-sectional view taken along line 2B-2B 'in FIG.

  The liquid crystal display device 100 ′ has a wall structure 115 on a transparent substrate 110 a and a support 133 on the wall structure 115. The wall structure 115 acts to form an axially symmetric alignment domain, like the support 133, by the alignment regulating force of the wall surface. The wall structure 115 may be formed on the transparent substrate 110a, or may be formed on the transparent substrate 110b. In the case of forming an inversely tapered wall surface similar to the inclined side surface of the support 133, it is preferable to form it on the transparent substrate 110b, but there is a demerit that the manufacturing process increases. Conversely, when formed on the transparent substrate (active matrix substrate) 110a, the wall structure 115 is integrated with the interlayer insulating film by adjusting the exposure amount in the process of forming the interlayer insulating film using, for example, a photosensitive resin. It becomes possible to form. At this time, the wall surface of the wall structure 115 is likely to be a regular taper, but by setting the inclination angle to 40 ° or more, the alignment regulating force due to the reverse tapered inclined side surface of the support 133 and the alignment regulating force of the wall surface are reduced. Matching can be reduced. Of course, it is more preferable to form the wall surface in a reverse taper shape (inclination angle exceeding 90 °).

  The wall structure 115 is formed in a light-shielding region around the pixel and substantially surrounds the pixel, and from the portion surrounding the pixel toward the center of the pixel at a position where the longitudinal direction of the pixel is approximately divided into two equal parts. And a pair of protruding convex portions. This convex portion of the wall structure 115 acts to define the boundary between two liquid crystal domains formed in the pixel. In addition, it is preferable to provide a portion protruding toward the inside of the pixel in a region that is shielded by wiring (for example, auxiliary capacitance wiring (not shown)) arranged in the pixel because the display is not adversely affected. The wall structure 115 is provided as a continuous wall, but is not limited to this, and may be divided into a plurality of walls.The wall structure 115 is a boundary formed near the extension of the pixels in the liquid crystal domain. For example, when the wall structure is composed of a plurality of walls, the length of each wall is longer than the length between adjacent walls. Longer is preferred.

  The support 133 is disposed corresponding to each of the four corners of the two liquid crystal domains formed in the pixel, and acts to define the boundary between the liquid crystal domains. Note that the support 133 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 dt of the liquid crystal layer 120. When the support 133 is provided in a region where the wall structure 115 is not formed, the height of the support 133 is set to be the thickness dt of the liquid crystal layer 120. However, it is preferable that the height of the support 133 is higher than the height of the wall structure 115 in order to sufficiently develop the orientation regulating force due to the inclined side surface of the support 133. The support 133 may be formed on either of the transparent substrates 110a and 110b, but as described above, the support 133 is preferably formed on the transparent substrate 110b side. Moreover, although the support body 133 which has a substantially circular cross-sectional shape was illustrated here, it is not restricted to this, It can change suitably like the above-mentioned.

  The pixel electrode 111 has two openings 114 at substantially the center of two liquid crystal domains whose boundaries are defined by the support 133 and the wall structure 115. When a predetermined voltage is applied to the liquid crystal layer 120, liquid crystal domains exhibiting axially symmetric alignment are formed, and the central axis of the axially symmetric alignment of these liquid crystal domains is formed in or near the opening 114. As described above, it is considered that the alignment regulating force due to the inclined side surface of the support 133 and the wall surface of the wall structure 115 and the alignment regulating force due to the opening 114 act cooperatively, thereby stabilizing the axially symmetric alignment of the liquid crystal domain. Note that the shape of the opening 114 can be appropriately changed as described above.

(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. 3 is a diagram schematically showing a configuration of one pixel of the transflective liquid crystal display device 200 according to the embodiment of the present invention, FIG. 3A is a plan view, and FIG. It is sectional drawing along the 3B-3B 'line in Fig.3 (a).

  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 131 (the liquid crystal layer 120 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). And 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.

  The liquid crystal display device 200 includes a wall structure 215 on the transparent substrate 210 a and a support 233 on the wall structure 215. Similar to the support body 233, the wall structure 215 acts to form an axially symmetric alignment domain by the orientation regulating force of the wall surface. The wall structure 215 is formed in a light-shielding region around the pixel and substantially surrounds the pixel, and from the portion surrounding the pixel toward the center of the pixel so that the longitudinal direction of the pixel is divided into three parts. And two pairs of protruding portions protruding. The pair of convex portions are provided in the vicinity of the boundary between the transmissive region A and the reflective region B, and the other pair of convex portions are provided at positions that divide the longitudinal direction of the transmissive region A into approximately two equal parts. The support 233 is disposed corresponding to the four corners of each of the three liquid crystal domains formed in the pixel, and acts to define the boundaries of the liquid crystal domains. The direction in which the liquid crystal molecules are tilted when a voltage is applied is defined by the alignment regulating force of the inclined side surface of the support 233 and the wall surface of the wall structure 115 arranged in this way, and three liquid crystal domains (two in the transmission region A, two reflections) One is formed in the region.

  The pixel electrode 211 has three openings 214 formed so as to correspond to substantially the central part of the three liquid crystal domains. When a predetermined voltage is applied to the liquid crystal layer 220, three liquid crystal domains each having an axially symmetric orientation are formed, and the central axis of each of the liquid crystal domains is formed in or near the opening 214. Is done. The opening 214 provided in the pixel electrode 211 acts to fix the position of the central axis of the axially symmetric orientation. An oblique electric field is formed around the opening 214 by a voltage applied between the pixel electrode 211 and the counter electrode 213, and the direction in which the liquid crystal molecules are inclined is defined by the oblique electric field. Act on.

  The arrangement of the support 233, the wall structure 215, the opening 214, and their preferred shapes are the same as those of the transmissive liquid crystal display device 100 'described above. Although FIG. 3 shows an example in which two liquid crystal domains are formed in the transmission region A and one liquid crystal domain is formed in the reflection 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. Further, the wall structure 215 can be omitted.

  In this liquid crystal display device 200 as well, 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, the respective central axes are stabilized in or near the three openings 214. Boundary formed in the vicinity of the extension of the pixels of the liquid crystal domain, in which eight axially symmetric orientations are formed, and the eight supports 233 and the wall structure 215 define the direction in which the liquid crystal molecules in the three adjacent liquid crystal domains are tilted by the electric field To stabilize.

  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. 3B, it is preferable to set the thickness dt of the liquid crystal layer 220 in the transmissive region A to about twice the thickness dr of the liquid crystal layer 220 in the reflective 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. 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 214 formed in the reflective electrode 211b. Benefits are gained. 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.

  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. 4 is a partially enlarged view of the active matrix substrate, and FIG. 5 is a cross-sectional view taken along line X-X ′ in FIG. 4. The active matrix substrate shown in FIGS. 4 and 5 is shown in FIG. 3 in that it has a configuration in which one liquid crystal domain is formed in the transmission region A (that is, the number of openings 214 is small). Although different from the active matrix substrate 211a, other configurations may be the same.

  The active matrix substrate shown in FIGS. 4 and 5 has 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. As described above, the opening 15 for fixing and stabilizing the central axis of the axially symmetric alignment domain is provided in a predetermined region of the pixel electrode 6.

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. doing.

  The support 33 may be formed in the peripheral region of the pixel electrode 6 on the active matrix substrate, or the support 33 is disposed in the peripheral region of the pixel electrode 6 when the counter substrate and the active matrix substrate are bonded together. Thus, the support 33 may be formed on the counter substrate. Furthermore, a wall structure 215 may be formed in the peripheral region of the pixel electrode 6 of the active matrix substrate.

  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. 3 regulates the alignment by using the support 233 for defining the thickness of the liquid crystal layer 220, as in the liquid crystal display devices 100 and 100 ′. . Furthermore, since the wall structure 215 for stably forming the liquid crystal domain and the opening 214 for fixing and stabilizing the central axis need only be formed on one substrate, the structure is relatively simple. This has the effect of sufficiently stabilizing the alignment of the liquid crystal. 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.

〔Operating principle〕
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.

  6A and 6B are diagrams for explaining the action of the alignment regulating force by the opening 15 provided in the pixel electrode 6. FIG. 6A shows a liquid crystal when no voltage is applied, and FIG. 6B shows a liquid crystal when a voltage is applied. A molecular orientation state is schematically shown. The state shown in FIG. 6B is a state where a halftone is displayed.

  The liquid crystal display device shown in FIG. 6 has an insulating film layer 16, a pixel electrode 6 having an opening 15, and an alignment film 22 in this order on a transparent substrate 1. On the other transparent substrate 17, a color filter layer 18, a counter electrode 19, a support 33, and an alignment film 32 are formed in this order. Although simplified in the drawing, the alignment film 32 is formed so as to cover the support 33. The liquid crystal layer 20 provided between the two substrates includes liquid crystal molecules 21 having negative dielectric anisotropy.

  As shown in FIG. 6A, 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. Here, the support 33 has inclined side surfaces that are inversely tapered with respect to the substrate 1, and the liquid crystal molecules 21 in the vicinity of the inclined side surfaces of the support 33 try to be aligned so as to be substantially perpendicular to the inclined side surfaces. Therefore, it is inclined with respect to the surface of the substrate 1.

  On the other hand, when a voltage is applied, as shown in FIG. 6B, the liquid crystal molecules 21 having negative dielectric anisotropy tend to have their molecular long axes perpendicular to the lines of electric force. The direction in which the liquid crystal molecules 21 are tilted is defined by the formed oblique electric field. Further, the liquid crystal molecules 21 in the vicinity of the support 33 try to further tilt in the tilted direction due to the alignment regulating force by the tilted side surface of the support 33. Therefore, for example, it is oriented in an axially symmetrical manner with the opening 15 as the center. 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.

  Furthermore, when it has a wall structure, a wall structure prescribes | regulates the direction in which the liquid crystal molecule 21 falls by the orientation control force of the side surface (wall surface). Typically, since the vertical alignment film is formed so as to cover the wall structure, the liquid crystal molecules are subjected to a regulating force so as to be aligned perpendicular to the wall surface. The wall surface of the wall structure is preferably inclined in the same direction as the support 33.

  Next, a more specific configuration example of the liquid crystal display device according to the embodiment of the present invention will be described with reference to FIG.

  The liquid crystal display device shown in FIG. 7 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. 3 is used.

  The display operation of the liquid crystal display device shown in FIG. 7 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.

  In addition, 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, the voltage-reflectance (transmittance) of the transmission region and the reflection region depends on the liquid crystal thickness. It is preferable that the condition of 3 dt <dr <0.7 dt is satisfied, 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.

(Example 1)
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. 7 was manufactured. A liquid crystal cell having the same configuration as that of the liquid crystal display device 200 shown in FIG. However, 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 the diffuse reflection characteristics at the time of reflective display are improved. It was adjusted. The uneven surface was formed by the method described in JP-A-9-90426.

  In addition, the opening 214 and the wall structure 215 in the liquid crystal display device 200 shown in FIG. The support 233 having a cross-sectional shape (similar shape to the support 133 in FIG. 1) was used. The support 233 was formed on the counter substrate by photolithography using a negative photosensitive resin (for example, V-259PA (manufactured by Nippon Steel Chemical Co., Ltd.)). The inclined side surface was inversely tapered with respect to the counter substrate, and the inclination angle (angle formed by the substrate surface and the inclined side surface) was about 45 °.

  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).

  When the obtained liquid crystal cell is sandwiched between two orthogonal polarizing plates, the liquid crystal molecules near the support are continuously tilted along the inclined side surface when a voltage is applied, and an axially symmetric liquid crystal domain is formed. It was confirmed.

  The configuration of the liquid crystal display device of this example is as follows. From the top, the polarizing plate (observation side), the quarter-wave plate (retardation plate 1), and the retardation plate with negative optical anisotropy (retardation plate 2 (NR) 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 addition, in the upper and lower quarter wavelength 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. Two polarizing plates (observation side and backlight side) were arranged with their transmission axes orthogonal.

  A display signal was evaluated by applying a drive signal to the liquid crystal display device (applying 4V to the liquid crystal layer).

  FIG. 8 shows the viewing angle-contrast characteristic results in the transmissive display. 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.

  On the other hand, the characteristics of the reflective display were evaluated with a spectrocolorimeter (CM 2002 manufactured by Minolta), and the contrast value of the reflective display was 21% with a standard diffuser plate as a reference, approximately 8.4% (aperture value 100% conversion value). Therefore, the contrast was high as compared with the conventional liquid crystal display device.

(Example 2)
Similarly to Example 1, a liquid crystal display device having the configuration shown in FIG. 7 was manufactured using a liquid crystal cell having the same configuration as that of the liquid crystal display device 200 shown in FIG. However, 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 the diffuse reflection characteristics at the time of reflective display are improved. It was adjusted. Further, the wall structure 215 was formed integrally with a lower layer resin layer (interlayer insulating layer) for imparting an uneven shape to the surface of the reflective electrode 211b.

  Specifically, the active matrix substrate of this example was manufactured as follows.

First, a positive photosensitive resin layer is formed under predetermined conditions so as to cover circuit elements such as TFT elements. In this photosensitive resin layer, an uneven shape is formed on the surface of the region to be the lower layer portion of the reflective electrode, and an uneven shape convex portion is formed so as to form a wall structure (see the wall structure 215 in FIG. 3). The exposure is performed under a low illuminance condition (80 mJ / cm ² ) using a first photomask having a region to be formed and a region to be a wall structure as a light shielding portion. Subsequently, in order to form a contact hole, exposure is performed under a high illuminance condition (350 mJ / cm ² ) using a second photomask having a region corresponding to the contact hole as an opening. Thereafter, by performing development, drying, baking, etc. continuously, that is, in one photolithography process including two exposure steps, the interlayer insulating film layer and the wall structure are formed from the same photosensitive resin layer. Formed.

  Through this series of steps, a through-hole electrically connected to the wall structure and the underlying connection electrode was fabricated along with an interlayer insulating layer having fine irregularities on the surface to obtain diffuse reflection characteristics during reflective display. .

  Thereafter, a transparent electrode film (ITO layer) was formed on the flat portion of the interlayer insulating layer under predetermined conditions, and a reflective electrode film was formed on the surface on which the uneven shape was formed by sputtering. Further, in the step of patterning the pixel electrode, an electrode opening (see the opening 214 in FIG. 3) for fixing and stabilizing the central axis of the axially symmetric orientation was formed at a predetermined position.

  Further, a support (columnar spacer) is formed by a photolithography process using a negative photosensitive material at a position corresponding to the light shielding region (region where the wall structure is formed) of the active matrix substrate on the color filter substrate (counter substrate). : See the support 233 in FIG. The inclined side surface was inversely tapered with respect to the counter substrate, and the inclination angle (angle formed by the substrate surface and the inclined side surface) was about 40 °. Further, a step for adjusting the thickness of the liquid crystal layer in the reflective region by providing a transparent dielectric layer was disposed in the reflective region of the color filter substrate.

  After forming a vertical alignment film on the active matrix substrate and the color filter substrate under predetermined conditions (no rubbing treatment), the substrates are bonded together with a seal resin, and a liquid crystal material having a negative dielectric anisotropy ( Δn; 0.1, Δε; −4.5) was injected and sealed to obtain a liquid crystal cell. In this example, the thickness dt of the liquid crystal layer in the transmissive region was 4 μm, and the thickness dr of the liquid crystal layer in the reflective region was 2.1 μm.

  When the obtained liquid crystal cell is sandwiched between two orthogonal polarizing plates, the liquid crystal molecules in the vicinity of the support and the wall structure are continuously tilted along the inclined side surface when a voltage is applied, and the axially symmetric liquid crystal domain Was confirmed to be formed.

  Next, an optical film was disposed on both sides of the liquid crystal cell to obtain a liquid crystal display device.

  The configuration of the liquid crystal display device of this example is as follows. From the top, the polarizing plate (observation side), the quarter-wave plate (retardation plate 1), and the retardation plate with negative optical anisotropy (retardation plate 2 (NR) 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 addition, in the upper and lower quarter wavelength 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. Two polarizing plates (observation side and backlight side) were arranged with their transmission axes orthogonal.

  A display signal was evaluated by applying a drive signal to the liquid crystal display device (applying 4V to the liquid crystal layer).

  FIG. 8 shows the viewing angle-contrast characteristic results in the transmissive display. 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.

  On the other hand, the characteristic of the reflective display is evaluated by a spectrocolorimeter (CM 2002 manufactured by Minolta), and is about 8.2% (converted value with an aperture ratio of 100%) with reference to the standard diffusion plate, and the contrast value of the reflective display is 22. Therefore, the contrast was high as compared with the conventional liquid crystal display device.

Furthermore, the response time of 90% change in transmittance of the liquid crystal panel (τ _ON + τ _OFF (ms), τ _ON ; time required for change when 0V → 4V voltage is applied, τ _OFF ; time required for change when voltage 4V → 0V ) And a halftone response time of a change in transmittance of 50% (time (m seconds) required for a change from gradation level 3 to gradation level 5 at the time of eight gradation division) in the first and second embodiments The results shown in the table below were obtained. In either case, the measurement temperature is 25 ° C.

  Since the liquid crystal display device of Example 2 has the wall structure and the electrode opening 214 in addition to the alignment regulating force by the support, the axially symmetric alignment is further stabilized and the response time is shortened. It was confirmed that the effect was great.

Moreover, it turned out that impact resistance improves in any of Example 1 and Example 2. For example, when a load test (1 kgf / cm ² ) is performed on a liquid crystal panel, the time required for restoring the orientation once disturbed by the application of the load is 5 minutes or less, and the orientation restoring force is sufficient. I found out. This is presumably because the density at which the support is disposed is higher than in the conventional example. Of course, Example 2 also has the contribution of a wall structure and an opening.

(Comparative Example 1)
In contrast to the above embodiment, in the liquid crystal display device shown in FIG. 3, an opening and a wall structure are not formed, and a liquid crystal cell is manufactured using the same support as in Embodiment 1, and a horizontal alignment film A liquid crystal panel of homogeneous alignment in ECB mode was produced using As the liquid crystal material, a liquid crystal material having positive dielectric anisotropy (Δn; 0.07, Δε; 8.5) is used, the liquid crystal layer thickness dt in the transmissive region is 4.3 μm, and the liquid crystal layer thickness dr in the reflective region. Was 2.3 μm (dr = 0.53 dt).

  An optical film formed of a plurality of optical layers including retardation plates such as polarizing plates and quarter-wave plates was disposed on both surfaces of the liquid crystal panel to obtain a liquid crystal display device.

  A drive signal was applied to this liquid crystal display device (4 V was applied to the liquid crystal layer), and display characteristics were evaluated according to the same evaluation method as described above.

  The viewing angle characteristics in transmissive display were ± 30 ° in the region of CR> 10, and the gradation inversion was significant. The transmission contrast was 140: 1. On the other hand, the characteristic of the reflective display is about 9.3% (converted value with an aperture ratio of 100%) with respect to the standard diffusion plate, the contrast value of the reflective display is 8, and the display image is the embodiment according to the present invention described above. Compared with the liquid crystal display device of FIG.

  In addition, as a result of performing a load test to examine the impact resistance under the same conditions as in the above examples, alignment disorder was observed after the test, and the liquid crystal display device of the comparative example was inferior in impact resistance compared to the examples. I understood.

  As described above, the liquid crystal display device according to the embodiment of the present invention has a transmissive and reflective display by applying the vertical alignment mode to the transmissive display and the reflective display as compared with the conventional homogeneous liquid crystal display device and the conventionally known technology. Good contrast was obtained in both reflection displays. Furthermore, since the alignment can be regulated using a support (columnar spacer) for defining the thickness of the liquid crystal layer, an extra step for providing the alignment regulating structure is unnecessary. Moreover, as a result of the support being regularly arranged at a sufficiently high density, impact resistance is improved.

  Furthermore, by providing a liquid crystal domain alignment control structure (wall structure or opening) only on one substrate (active matrix substrate in the example), the alignment of the axially symmetric alignment domains can be further stabilized, so that Wide viewing angle characteristics can be realized. In addition, since the position of the central axis is fixed and stabilized by the opening, an effect of improving display uniformity at an oblique viewing angle can be obtained.

  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 a 1B 'line. It is a figure which shows typically the structure of one pixel of other transmissive liquid crystal display device 100 'of embodiment by this invention, (a) is a top view, (b) is a figure in Fig.2 (a). It is sectional drawing along line 2B-2B '. 4A and 4B are diagrams schematically illustrating a configuration of one pixel of a transflective liquid crystal display device 200 according to an embodiment of the present invention, in which FIG. 3A is a plan view, and FIG. 3B is 3B in FIG. It is sectional drawing along a -3B 'line. 2 is a plan view of an active matrix substrate 210a of a transflective liquid crystal display device 200. FIG. 2 is a cross-sectional view of an active matrix substrate 210a of a transflective liquid crystal display device 200. FIG. 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 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 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 33 Support (columnar spacer)
50 Liquid crystal panel 40, 43 Polarizing plate 41, 44 1/4 wavelength plate 42, 45 Phase difference plate with negative optical anisotropy (NR plate)
100 transmissive liquid crystal display device 110a active matrix substrate 110b counter substrate (color filter substrate)
111 Pixel electrode 114 Opening 115 Wall structure 130 Color filter layer 131 Counter electrode 133 Support body 200 Transflective liquid crystal display device 210a Active matrix substrate 210b Counter substrate (color filter substrate)
211 pixel electrode 211a transparent electrode 211b reflective electrode 214 opening 215 wall structure 230 color filter layer 231 counter electrode 232 transparent dielectric layer (reflective step)
233 Support

Claims (12)

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,
Each includes a first electrode formed on the first substrate, a second electrode formed on the second substrate, and the liquid crystal layer provided between the first electrode and the second electrode. Including a plurality of pixels, and a light shielding region provided around the plurality of pixels,
A plurality of supports defining the thickness of the liquid crystal layer are regularly arranged on the liquid crystal layer side on the first substrate or the second substrate of the light shielding region,
The liquid crystal layer forms at least one liquid crystal domain exhibiting axially symmetric orientation when at least a predetermined voltage is applied, and the tilt direction of the liquid crystal molecules in the at least one liquid crystal domain is the tilt of the plurality of supports. A liquid crystal display device defined by a side surface.   The liquid crystal display device according to claim 1, wherein each of the at least one liquid crystal domain is in contact with an inclined side surface of at least four supports.   The said 1st electrode has at least 1 opening part, The central axis of each axisymmetric orientation of the said at least 1 liquid crystal domain is formed in the said at least 1 opening part or its vicinity. A liquid crystal display device according to 1.   4. The liquid crystal display device according to claim 1, wherein the inclined side surfaces of the plurality of supports are inclined in a reverse taper shape with respect to the first substrate. 5.   5. The liquid crystal display according to claim 1, wherein a cross-sectional shape of the plurality of supports in a plane parallel to the first substrate surface is a substantially circular shape, a substantially oval shape, a substantially rhombus shape, or a substantially cross shape. apparatus.   The liquid crystal display device according to claim 1, further comprising a wall structure regularly arranged in the light shielding region.   The at least one liquid crystal domain includes two liquid crystal domains, the at least one opening includes two openings, and a central axis of each of the two liquid crystal domains in an axially symmetric orientation is within the two openings or The liquid crystal display device according to claim 1, formed in the vicinity thereof.   The liquid crystal display device according to claim 1, wherein the first electrode includes a transparent electrode that defines a transmissive region and a reflective electrode that defines a reflective region.   The liquid crystal display device according to claim 8, wherein the at least one liquid crystal domain includes a liquid crystal domain formed in the transmissive region and a liquid crystal domain formed in the reflective region.   The liquid crystal display device according to claim 9, wherein the at least one opening includes an opening formed in the transparent electrode and an opening formed in the reflective electrode.   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 The liquid crystal display device according to claim 1, further comprising one biaxial optically anisotropic medium layer.   Further comprising a pair of polarizing plates arranged to face each other via the first substrate and the second substrate, and between the first substrate and / or the second substrate and the pair of polarizing plates The liquid crystal display device according to claim 1, further comprising at least one uniaxial optically anisotropic medium layer.