JP2005257809A - Liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal display device in which display quality equal to or better than that in the conventional one is obtained by sufficiently stabilizing liquid crystal alignment in the liquid crystal display device having a plurality of axisymmetric aligning domains in a pixel. <P>SOLUTION: The liquid crystal display device has a first substrate 110a on which a first electrode 111 is formed, a second substrate 110b on which a second electrode 131 opposite to the first electrode 111 is formed, and a homeotropic alignment type liquid crystal layer 120 interposed between the first electrode 111 and the second electrode 131. A plurality of pixel regions are defined with the first electrode 111 and the second electrode 131. At least one pixel region out of the plurality of pixel regions is divided into a plurality of sub-pixel regions with dielectric structures 116 disposed on the first substrate 110a with regularity. Liquid crystal molecules of the liquid crystal layer 120 in the sub-pixel region axisymmetrically align around an axis perpendicular to the surface of the first substrate 110a as a center when a specified voltage is applied between the first electrode 111 and the second electrode 131. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a liquid crystal display device. In particular, the present invention relates to a liquid crystal display device suitably used for personal digital assistants such as PDAs (Personal Digital Assistants), mobile phones, in-vehicle liquid crystal displays, digital cameras, personal computers, amusement devices, televisions 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 liquid crystal display devices are adopted in most of these devices. These liquid crystal display devices are expected to display more information as the amount of information handled by the main body increases, and market demands for high contrast, wide viewing angle, high brightness, multiple colors, and high definition 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 a liquid crystal display device in which an opening is provided in a counter electrode that faces a pixel electrode through a liquid crystal layer, and an oblique electric field is generated around the opening. As a result, the surrounding liquid crystal molecules are tilted and aligned around the liquid crystal molecules in the vertically aligned state in the opening, so that the viewing angle characteristics are improved.

  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, and as a result, a region in which the response of the liquid crystal molecules to voltage application is delayed occurs in the pixel, and the afterimage phenomenon The problem that appears.

  In order to solve this problem, in the liquid crystal display device of Patent Document 2, a plurality of sub-pixels in which liquid crystal molecules in the liquid crystal layer are axially symmetrically aligned are provided by providing openings regularly arranged in the pixel electrode or the counter electrode. A region is formed in each pixel region.

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

  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 called a transmissive / reflective liquid crystal display device (hereinafter also simply referred to as a “bi-directional liquid crystal display device”), and includes a reflective region for displaying in a reflective mode in a pixel and a display in a transmissive mode. A transmissive region to perform.

Currently used commercially available dual-use liquid crystal display devices use an ECB (Electrically Controlled Birefringence) mode, a TN (Twisted Nematic) mode, or the like. Patent Document 3 discloses a configuration applied not only to a transmissive liquid crystal display device but also to a dual-use liquid crystal display device. Further, in Patent Document 6, in a dual-use liquid crystal display device having a vertical alignment type liquid crystal layer, the liquid crystal in the transmissive region is multiaxially aligned while the liquid crystal in the reflective region is uniaxially aligned by the recesses formed in the planarization film. Technology is disclosed. 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 of Patent Document 6). See).
JP-A-6-301036 JP 2000-47217 A JP 2003-167253 A Japanese Patent No. 2955277 US Pat. No. 6,195,140 JP 2002-350853 A

  In the techniques disclosed in Patent Document 2 and Patent Document 3, a convex portion or an opening is provided in a pixel to form a plurality of liquid crystal domains (that is, pixel division), thereby strengthening the alignment regulating force on liquid crystal molecules. ing. However, according to the study by the present inventors, in order to obtain a sufficient alignment regulating force, convex portions, openings, etc. are formed on both substrate sides of the liquid crystal layer (surfaces of the pair of substrates facing each other on the liquid crystal layer side). Therefore, there is a problem that the manufacturing process is complicated. In addition, when the alignment regulating structure is provided in the pixel, not only the effective aperture ratio of the pixel is lowered, but also light leakage occurs from the periphery of the convex portion in the pixel region, and the contrast ratio may be lowered. Further, in the case where the alignment regulating structure is provided on both substrates, since it is affected by the alignment margin of the substrates, the reduction in the effective aperture ratio and / or the reduction in the contrast ratio becomes more remarkable.

  Moreover, in the technique disclosed in Patent Document 6, it is necessary to provide a recess in order to control multiaxial alignment and to arrange a protrusion or an electrode opening at a position facing the recess through the liquid crystal layer. Therefore, the same problem as in Patent Document 2 and Patent Document 3 occurs.

  Further, in each of the above-mentioned patent documents, an electrophoretic alignment of liquid crystal molecules is defined by an effect of an electric field generated by applying a predetermined voltage by providing an opening in the display electrode. In this case, when the surface of the liquid crystal panel is pressed, the orientation state disturbed at the portion where the panel surface is pressed tends to be fixed by the electric field defined by the electrode opening, causing a feeling of roughness and a reduction in display quality. May be invited.

  The present invention has been made in view of the above points, and one of its purposes is a liquid crystal display device having a plurality of axially symmetric alignment domains in a pixel, for example, even when a display screen is pressed, An object of the present invention is to provide a liquid crystal display device of high display quality that can effectively restore the disordered axially symmetric orientation and reduce display defects such as rough feeling.

  In the liquid crystal display device of the present invention, at least one pixel region is divided into a plurality of sub-pixel regions by a dielectric structure. In addition, the liquid crystal molecules in the liquid crystal layer in the sub-pixel region are axially symmetric when a voltage is applied.

  In one aspect, a wall structure that substantially surrounds the pixel region is formed in the light shielding region. The dielectric structure and the wall structure may be formed integrally or may be made of the same dielectric material. Moreover, you may be comprised with another patterning material.

  An object of the present invention is to suppress and improve display defects due to defective alignment after alignment disorder when a liquid crystal panel is pressed. This object is achieved by dividing the region of the liquid crystal alignment domain by a dielectric structure or a wall structure. Specifically, even when the display screen is pressed and the axially symmetric orientation is lost, the alignment is stabilized from the periphery of the liquid crystal domain by the action of the wall structure and dielectric structure around the divided liquid crystal domain. Is planned. In other words, the wall structure or the dielectric structure gives the liquid crystal domain a restoring force for restoring the disordered orientation. In this specification, the “liquid crystal domain” refers to a region of a liquid crystal layer that has an axially symmetric alignment (radial tilt alignment) about one axis perpendicular to the substrate.

  The present invention includes the inventions described in the following claims.

  Invention of Claim 1: Between the 1st board | substrate with which the 1st electrode was formed, the 2nd board | substrate with which the 2nd electrode facing the said 1st electrode was formed, and the said 1st electrode and the said 2nd electrode A liquid crystal display device having a vertically aligned liquid crystal layer interposed therein, wherein a plurality of pixel regions are defined by the first electrode and the second electrode, wherein at least one pixel of the plurality of pixel regions The region is divided into a plurality of sub-pixel regions by a dielectric structure regularly arranged on the first substrate, and the liquid crystal molecules in the liquid crystal layer in the sub-pixel region include the first electrode and the A liquid crystal display device that is axially symmetrically aligned about an axis perpendicular to the surface of the first substrate when a predetermined voltage is applied between the second electrode and the second electrode.

  Invention of Claim 2: The said pixel area is further surrounded by the light-shielding area in planar view, and further has a wall structure which substantially surrounds the pixel area on the liquid crystal layer side of the first substrate in the light-shielding area. The liquid crystal display device according to claim 1.

  Invention of Claim 3: The said 1st electrode and / or the said 2nd electrode have the opening part formed in the said sub-pixel area | region, and when the said voltage is applied, the said vertical axis is in the said opening part The liquid crystal display device according to claim 1, wherein the liquid crystal display device is formed in the vicinity thereof.

  Invention of Claim 4: The said pixel area is enclosed by the light shielding area in planar view, and the support body which prescribes | regulates the thickness of the said liquid-crystal layer is formed in the said light shielding area. The liquid crystal display device according to item.

  Invention of Claim 5: Said 1st electrode has a transparent electrode and a reflective electrode, and at least 1 sub-pixel area | region is a transmissive area | region, and at least 1 sub-pixel area | region is a reflective area | region. The liquid crystal display device according to claim 1, wherein:

  Invention of Claim 6: If the thickness of the liquid crystal layer in the transmissive region is dt and the thickness of the liquid crystal layer in the reflective region is dr, the relationship of 0.3 dt <dr <0.7 dt is satisfied. The liquid crystal display device according to claim 5.

  The invention according to claim 7: The liquid crystal display device according to claim 5 or 6, further comprising a transparent dielectric layer on the liquid crystal layer side of the second substrate in the reflection region.

  Invention of Claim 8: The liquid crystal display device of Claim 7 with which the said transparent dielectric material layer has a function to scatter light.

  Invention of Claim 9: The said 2nd board | substrate further has a color filter layer, The optical density of the said color filter layer in the said reflection area is smaller than the optical density of the said color filter layer in the said transmission area | region. The liquid crystal display device according to any one of 8.

  Invention of Claim 10: It further has a pair of polarizing plate arrange | positioned facing each other through the said 1st board | substrate and the said 2nd board | substrate, The said 1st board | substrate and / or the said 2nd board | substrate, and a pair of said polarization | polarized-light The liquid crystal display device according to claim 1, further comprising at least one biaxial optically anisotropic medium layer (for example, a biaxial retardation plate) between the plate and the plate.

  Invention of Claim 11: It further has a pair of polarizing plate arrange | positioned mutually facing through the said 1st board | substrate and the said 2nd board | substrate, The said 1st board | substrate and / or the said 2nd board | substrate, and a pair of said polarization | polarized-light The liquid crystal display device according to claim 1, further comprising at least one uniaxial optical anisotropic medium layer (for example, a uniaxial retardation plate) between the plate and the plate.

  Invention of Claim 12: The said pixel area is a rectangular shape which consists of a pair of long side and a pair of short side in planar view, and is divided | segmented into these sub pixel area | region by at least a pair of said dielectric material structure. 12. The pair of dielectric structures according to claim 1, wherein the pair of dielectric structures extend in a direction close to each other from the vicinity of the pair of long sides of the pixel region and are arranged in a short direction. Liquid crystal display device.

〔Operating principle〕
The reason why the liquid crystal display device 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. 1 is a diagram for explaining the action of the alignment regulating force by the dielectric structure 23 or the wall structure provided around the pixel electrode 6, and FIG. 1A shows liquid crystal molecules when no voltage is applied. FIG. 1B is a diagram schematically showing the alignment state of the liquid crystal molecules when a voltage is applied. FIG. 1B shows a state in which halftone is displayed.

  The liquid crystal display device shown in FIG. 1 has a structure in which an insulating film layer 6, a dielectric structure 23, a pixel electrode 6 having a wall structure, and a vertical alignment film 22 are sequentially formed on a transparent substrate 1. On the other transparent substrate 17, a color filter layer 18, a counter electrode 19 and a vertical alignment film 32 are sequentially formed. The liquid crystal layer 20 provided between the two substrates includes liquid crystal molecules 21 having negative dielectric anisotropy. Although not shown in FIGS. 1A and 1B, the dielectric structure 23 is also covered with the vertical alignment film 22.

  As shown in FIG. 1A, 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. 1B, the liquid crystal molecules 21 having negative dielectric anisotropy tend to have their molecular long axes perpendicular to the electric lines of force, and equipotential lines due to the influence of the electric field. In accordance with the orientation of the liquid crystal molecules 21 inclined in the direction of the electric field, and in the vicinity of the step side surface of the dielectric structure 23 or the step side surface of the wall structure. Axisymmetric alignment domains are formed according to the alignment of the tilted liquid crystal molecules. In this axially symmetric alignment domain, the liquid crystal directors are aligned in all directions (direction in the substrate surface), so that viewing angle characteristics are excellent.

  In the present invention, a wall structure or a dielectric structure is disposed at least at a part of the periphery of the liquid crystal domain. This stabilizes the tilted orientation of the liquid crystal molecules on the side surfaces of the wall structure and the dielectric structure, and the orientation of the liquid crystal molecules is disturbed even if the panel surface is pressed by the action of the wall structure or dielectric structure. The accompanying defective orientation can be reduced. Specifically, the orientation of the liquid crystal molecules in the liquid crystal domain is less disturbed compared to the conventional method in which the electric tilt direction of the liquid crystal molecules is regulated by the electric field effect generated when a voltage is applied to the slit electrode. Effectively restores the axially symmetric orientation domain. Therefore, it has the feature that the roughness can be greatly improved.

  Note that the wall structure and dielectric structure in the present invention are arranged by regular patterning at predetermined positions through a photolithography process using a photosensitive resin. In the present invention, the wall structure and the dielectric structure may be formed using the same material, or may be formed using different materials as necessary.

  In one aspect of the present invention, a plurality of pixel regions are defined by a first electrode (for example, a pixel electrode) and a second electrode. At least one pixel region among the plurality of pixel regions is divided into a plurality of sub-pixel regions by a regularly arranged dielectric structure or a wall structure formed on the light shielding region. The liquid crystal molecules contained in the liquid crystal layer (liquid crystal domain) in the sub-pixel region have an axially symmetric orientation in which a tilt direction is defined by a step side surface of the dielectric structure and a step side surface of the wall structure when a voltage is applied. By surrounding at least a part of the periphery of the liquid crystal domain with the dielectric structure or the wall structure, it is possible to suppress a change in the alignment state against the pressing of the panel surface. In addition, it is possible to prevent display quality from deteriorating due to variations in axial position and changes in axially symmetric orientation. In particular, by providing the wall structure in the light shielding region, it is possible to prevent a reduction in the effective aperture ratio of the pixel. Furthermore, since light leakage that occurs when a wall structure is provided in the pixel region can be prevented, a reduction in contrast ratio can be suppressed. Therefore, display quality is not sacrificed.

  In another aspect of the present invention, the first electrode and / or the second electrode has openings regularly arranged at predetermined positions in the sub-pixel region. Since this opening acts to fix the position of the central axis of the axially symmetric orientation, the axially symmetric orientation is further stabilized.

  When the present invention is applied to a dual-use liquid crystal display device, by arranging a dielectric structure in the vicinity of the boundary between the transmissive region and the reflective region, the liquid crystal domains in the transmissive region and the reflective region are divided so that the alignment can be performed more easily. The state can be stabilized.

  According to the present invention, the stability of the alignment of liquid crystal domains having an axially symmetric alignment (radial tilt alignment) can be improved, so that the display quality of a liquid crystal display device having a conventional wide viewing angle characteristic can be further improved. Even if the axially symmetric orientation is broken by an external force, for example, even if the display screen is pressed and the axially symmetric orientation is disturbed, the axially symmetric orientation is effectively restored. Therefore, a high display quality liquid crystal display device capable of reducing display defects such as a feeling of roughness is provided. Furthermore, since a liquid crystal display device with excellent display quality can be realized with a relatively simple configuration, it can be easily manufactured.

  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. In the following embodiments, an active matrix liquid crystal display device using thin film transistors (TFTs) will be described. However, the present invention is not limited to this, and can be applied to an active matrix type liquid crystal display device and a simple matrix type liquid crystal display device using MIM (Metal Insulator Metal). In the following embodiments, a transmissive liquid crystal display device and a dual-use liquid crystal display device are exemplified, but the present invention is not limited to this, and a transflective film using a transflective film such as a reflective liquid crystal display device or a half mirror is used. The present invention can also be applied to a liquid crystal display device.

  In the present specification, an area of the liquid crystal display device corresponding to a “pixel” that is a minimum unit of display is referred to as a “pixel area”. In a color liquid crystal display device, for example, one “picture element” is composed of three “pixels” of red, green, and blue. In an active matrix type liquid crystal display device, a pixel region is defined by a pixel electrode and a counter electrode disposed opposite to the pixel electrode. In a simple matrix liquid crystal display device, each region where a column electrode provided in a stripe shape and a row electrode provided so as to intersect with the column electrode intersect with each other defines a pixel region. Note that, in a configuration in which a light blocking layer such as a black matrix is provided, strictly speaking, among regions to which a voltage is applied according to a state to be displayed, a region corresponding to the opening of the black matrix corresponds to a pixel region. .

(Embodiment 1: Transmission type liquid crystal display device)
The configuration of the transmissive liquid crystal display device 100 of this embodiment will be described with reference to FIG. FIG. 2 is a diagram schematically illustrating a configuration of one pixel included in the transmissive liquid crystal display device 100. FIG. 2A is a top view as viewed from the normal direction of the substrate, and FIG. It is sectional drawing along the 2B-2B 'line in Fig.2 (a).

  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 provided between the pair of transparent substrates 110a and 110b. Layer 120. A vertical alignment film (not shown) is provided on each surface of both the substrates 110a and 110b in contact with the liquid crystal layer 120. When no voltage is applied, the liquid crystal molecules in the liquid crystal layer 120 are in contact with the surface of the vertical alignment film. Oriented substantially vertically. The liquid crystal layer 120 includes a nematic liquid crystal material having a 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. The pixel electrode 111, the counter electrode 131, and the liquid crystal layer 120 form pixels. Stipulate. In this embodiment, both the pixel electrode 111 and the counter electrode 131 are formed of a transparent conductive film such as an ITO (Indium Tin Oxide) film. Typically, on the liquid crystal layer 120 side of the transparent substrate 110b, a color filter 130 (corresponding to a plurality of color filters may be collectively referred to as the color filter layer 130) provided corresponding to the pixel, and A black matrix (light shielding layer) 132 provided between adjacent color filters 130 is formed, and a counter electrode 131 is formed thereon. However, the color filter layer 130 and the black matrix 132 may be formed on the counter electrode 131 (the liquid crystal layer 120 side).

  In the present embodiment, the pixel electrode 111 and the counter electrode 131 define a rectangular pixel region having a pair of long sides and a pair of short sides in plan view (as viewed from the substrate normal direction). A wall structure 115 and a pair of dielectric structures 116 that substantially surround the pixel region are formed around the pixel region on the transparent substrate 110a. The pair of dielectric structures 116 is formed side by side in the short direction (the direction in which the short side extends) at approximately the center of the long side of the pixel region, and from the vicinity of the long side of the pixel region (the inner surface of the wall structure 115). They extend in directions close to each other. The length of each dielectric structure 116 (distance extending in the short direction) is about 1/3 or less of the length of the short side of the pixel region. However, the length of the dielectric structure 116 is preferably 5 μm or more. When the length of the dielectric structure 116 is less than 5 μm, the division effect by the dielectric structure 116 is reduced, and there is a possibility that the orientation regulating force is reduced. The height of the wall structure 115 and the dielectric structure 116 is preferably less than or equal to half the cell thickness (distance between the substrates 110a and 110b or the thickness of the liquid crystal layer 120) from the viewpoint of easy injection of the liquid crystal material. . In addition, when the height of the wall structure 115 and the dielectric structure 116 is less than 0.5 μm, the alignment regulating force is reduced, so the display contrast ratio may be reduced. Accordingly, the height of the wall structure 115 and the dielectric structure 116 is preferably 0.5 μm or more. The pixel region is divided into two sub-pixel regions by the wall structure 115 and the pair of dielectric structures 116. In other words, the liquid crystal layer 120 in the pixel region is divided into two liquid crystal domains.

  In the present embodiment, the pixel electrode 111 has two openings 114 formed at predetermined positions. Specifically, an opening 114 is provided in the approximate center of each sub-pixel region. When a predetermined voltage is applied to the liquid crystal layer 120, two liquid crystal domains (sub-pixel regions) each having an axially symmetric orientation are formed. The central axis of the axially symmetric orientation of each of these liquid crystal domains is formed in or near the opening 114. In other words, the opening 114 provided in the pixel electrode 111 acts to fix the position of the central axis of the axially symmetric orientation.

  Further, by using the step side surface 116a of the dielectric structure 116 and the step side surface 115a of the wall structure 115, the tilt direction of the liquid crystal molecules is defined, and a stable axially symmetric alignment domain is formed in the sub-pixel region. The When the dielectric structure 116 is disposed in the pixel region, at least a formation region of the dielectric structure 116, preferably the dielectric structure 116, in order to prevent a decrease in contrast due to light leakage in the vicinity of the dielectric structure 116. A light-shielding portion is formed in the formation region and the vicinity thereof. The light shielding portion is not limited to the black matrix, and may be an element that does not transmit light, such as an auxiliary capacitance wiring. Further, a notch 113 may be provided in the pixel electrode 111 around the dielectric structure 116 in order to stabilize the axially symmetric alignment domain. Thereby, the electroclinic effect by the oblique electric field at the time of voltage application can be utilized together.

  The shape of the opening 114 provided for fixing 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 more preferably a regular polygon.

  The liquid crystal display device 100 of this embodiment has a light shielding region between adjacent pixels. In other words, the pixel region is surrounded by the light shielding region in plan view. A wall structure 115 is formed on the transparent substrate 110a in the light shielding region. The light shielding region is a region that does not contribute to display and is formed around the pixel electrode 111 on the transparent substrate 110a. For example, a region shielded by a TFT, a gate signal wiring, a source signal wiring, or the like formed on the transparent substrate 110a, and a region shielded by a black matrix formed on the transparent substrate 110b. Since the light shielding area does not contribute to display, the wall structure 115 formed in the light shielding area does not adversely affect the display.

  The wall structure 115 shown in the present embodiment is provided as a continuous wall surrounding the pixel region, but is not limited to this. The wall structure 115 may be anything that substantially surrounds the pixel region, and may be divided into a plurality of walls, for example. The wall structure 115 defines a liquid crystal domain (pixel region), and therefore preferably has a certain length. For example, when the wall structure 115 is composed of a plurality of walls, the length of each wall is preferably longer than the distance between adjacent walls.

  It is preferable to form a support 133 for defining the thickness (also referred to as a cell gap) dt of the liquid crystal layer 120 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 any one of the transparent substrates 110a and 110b, and is not limited to the case where the support 133 is provided on the wall structure 115 provided in the light shielding region as illustrated in FIG. 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 approximately equal to 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 approximately equal to the thickness dt of the liquid crystal layer 120.

  The liquid crystal display device 100 of this embodiment can be manufactured using a general technique such as a photolithography method. For example, the wall structure 115, the dielectric structure 116, and the support 133 can be manufactured by the following procedure. First, a TFT, a gate signal wiring, a source signal wiring, a pixel electrode 111 having an opening 114, and the like are formed over the substrate 110a by photolithography, and then a photosensitive resin film is formed. The wall structure 115 and the dielectric structure 116 are formed by patterning the photosensitive resin film. Further, a support 133 is formed by a photolithography process using a photosensitive resin. Thereafter, a vertical alignment film (not shown) that covers the pixel electrode 111, the wall structure 115, and the dielectric structure 116 is formed.

  According to the liquid crystal display device 100 of the present embodiment, when a predetermined voltage (a voltage equal to or higher than the threshold voltage) is applied between the pixel electrode 111 and the counter electrode 131, each center is located in or near the two openings 114. Two axisymmetric orientations are formed with the axis stabilized. A pair of dielectric structures 116 provided at the center in the longitudinal direction of the pixel electrode 111 defines a direction in which the liquid crystal molecules in the two divided liquid crystal domains adjacent in the longitudinal direction fall. The wall structure 115 is formed in the vicinity of the pixel electrode 111 and in the vicinity of the dielectric structure 116. The synergistic effect of the dielectric structure 116 and the wall structure 115 defines the direction in which the liquid crystal molecules near the wall structure 115 are inclined in the pixel region. It is considered that the alignment regulating force by the opening 114, the dielectric structure 116 and the wall structure 115 acts cooperatively to stabilize the alignment of the liquid crystal domain.

  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. The transparent substrate 110a, the circuit elements formed on the transparent substrate 110a, the pixel electrode 111, the wall structure 115, the support 133, the alignment film, and the like described above may be collectively referred to as an active matrix substrate. On the other hand, the transparent substrate 110b, the color filter layer 130 formed on the transparent substrate 110b, the black matrix 132, the counter electrode 131, the alignment film, and the like 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 between the transparent substrate 110a and / or the transparent substrate 110b and the pair of polarizing plates. .

(Embodiment 2: Dual-use liquid crystal display device)
The configuration of the dual-use liquid crystal display device 200 of this embodiment will be described with reference to FIG. FIG. 3 is a diagram schematically illustrating the configuration of one pixel included in the dual-use liquid crystal display device 200. FIG. 3A is a top view viewed from the normal direction of the substrate, 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 provided between the pair of transparent substrates 210a and 210b. Layer 220. A vertical alignment film (not shown) is provided on each surface of both substrates 210a and 210b in contact with the liquid crystal layer 220. When no voltage is applied, the liquid crystal molecules in 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. The pixel electrode 211, the counter electrode 231 and the liquid crystal layer 220 form pixels. Stipulate. Circuit elements such as TFTs described later are formed on the transparent substrate 210a. The transparent substrate 210a and the components formed thereon may be collectively referred to as an active matrix substrate 210a.

  Typically, a color filter 230 (corresponding to a plurality of color filters may be collectively referred to as a 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. However, the color filter layer 230 and the black matrix 232 may be formed over the counter electrode 231 (the liquid crystal layer 120 side). The transparent substrate 210b and the components formed thereon may be collectively referred to as a counter substrate (color filter substrate) 210b.

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

  In the present embodiment, the pixel electrode 211 and the counter electrode 231 define a rectangular pixel region having a pair of long sides and a pair of short sides in plan view. Around the pixel region on the transparent substrate 210a, a wall structure 215 and two sets of dielectric structures 216 and 217 that substantially surround the pixel region are formed. The two sets of dielectric structures 216 and 217 are arranged at positions that divide each long side of the pixel region into three equal parts, and each set of dielectric structures 216 and 217 is arranged in the short direction (the direction in which the short sides extend). Are lined up. Each pair of dielectric structures 216 and 217 extends in the direction of approaching each other from the vicinity of the long side of the pixel region (the inner surface of the wall structure 215). Similar to the first embodiment, a wall structure 215 that substantially surrounds the pixel region is formed around the pixel region on the transparent substrate 210a. The length of each dielectric structure, the heights of the dielectric structures 216 and 217, and the wall structure 115 are the same as in the first embodiment. The pixel region is divided into three sub-pixel regions by the wall structure 215 and the two sets of dielectric structures 216 and 217. In other words, the liquid crystal layer 220 in the pixel region is divided into three liquid crystal domains. Of the three sub-pixel regions, two sub-pixel regions are transmissive regions A, and one sub-pixel region is a reflective region B. In the present embodiment, two transmissive areas A sandwich one subpixel area in the longitudinal direction in plan view.

  In the present embodiment, the pixel electrode 211 has three openings 214 (two in the transmission region A and one in the reflection region B (not shown)) formed at a predetermined position. Specifically, an opening 214 is provided in the approximate center of each sub-pixel region. When a predetermined voltage is applied to the liquid crystal layer 220, three liquid crystal domains (sub-pixel regions) each having an axially symmetric orientation are formed. The central axis of the axially symmetric orientation of each of these liquid crystal domains is formed in or near the opening 214. In other words, the opening 214 provided in the pixel electrode 211 acts to fix the position of the central axis of the axially symmetric orientation.

  Further, by using the step side surface 216a of the dielectric structure 216 and the step side surface 215a of the wall structure 215, the tilt direction of the liquid crystal molecules is defined, and a stable axially symmetric alignment domain is formed in the sub-pixel region. The When the dielectric structures 216 and 217 are arranged in the pixel region, at least a region where the dielectric structure 216 is formed, preferably a dielectric structure, in order to prevent a decrease in contrast due to light leakage near the dielectric structure 216. A light-shielding portion is formed in a region where the object 216 is formed and a region near the region. The light shielding portion is not limited to the black matrix, and may be an element that does not transmit light, such as an auxiliary capacitance wiring. Further, in order to stabilize the axially symmetric alignment domain, a notch (not shown) may be provided in the pixel electrode 211 around the dielectric structure 216. Thereby, the electroclinic effect by the oblique electric field at the time of voltage application can be utilized together.

  In the present embodiment, in the display area of one pixel, the transmissive display areas A and the reflective display areas B are alternately arranged to form corresponding pixel electrodes. In addition, two sets of dielectric structures 216 and 217 are arranged in the pixel division region near the boundary between the transmission region A and the reflection region B to form a liquid crystal division region. As a result, two liquid crystal domains are formed in the transmissive region A, and one liquid crystal domain is formed in the reflective region B. However, this embodiment is merely an example, and the present invention is not limited to this. It is preferable that each liquid crystal domain has a substantially square shape from the viewpoint of viewing angle characteristics and alignment stability.

  FIG. 4 is a schematic view when the axially symmetric alignment state according to the present embodiment and the conventional example is observed. FIG. 4A is a schematic diagram of liquid crystal domain alignment in a steady state before pressing the display surface, and FIG. 4B is a schematic diagram after pressing in a panel with pixel division arrangement according to a conventional example. FIG. 4C is a schematic diagram of orientation after pressing on the panel of the pixel division arrangement according to the present embodiment. In addition, the ellipse in FIG.4 (c) represents that a dielectric structure exists.

  In this embodiment, the transmissive display area A and the reflective display area B are alternately arranged (adjacent to each other), and the liquid crystal layer in the pixel area is divided into three by a dielectric structure or a wall structure (not shown). Three liquid crystal domains are formed. In this case, since each liquid crystal domain is uniformly divided by a dielectric structure or a wall structure, even when the panel surface is pressed, a temporarily disturbed axisymmetric alignment state appears between adjacent pixels. To restore the original good axisymmetric orientation state. Therefore, for example, compared with the case of FIG. 4B in which one pixel area is divided into three and the transmissive display areas are arranged adjacent to each other as in the transmissive display area / transmissive display area / reflective display area. It was confirmed that the axially symmetric orientation state disordered asymmetrically restored immediately and returned to the original stable axially symmetric orientation.

  The liquid crystal display device 200 of this embodiment has a light shielding region between adjacent pixels. In other words, the pixel region is surrounded by the light shielding region in plan view. A wall structure 215 is formed 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 shown in this embodiment is provided as a continuous wall surrounding the pixel region, but is not limited to this. The wall structure 215 may be anything as long as it substantially surrounds the pixel region. For example, the wall structure 215 may be divided into a plurality of walls. Since the wall structure 215 defines a liquid crystal domain (pixel region), the wall structure 215 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 distance between adjacent walls.

  It is preferable that the support 233 for defining the thickness (also referred to as a cell gap) dt of the liquid crystal layer 220 be formed in a light-shielding region (here, a region defined by the black matrix 232) because display quality is not deteriorated. The support 233 may be formed on one of the transparent substrates 210a and 210b, and is not limited to the case where the support 233 is provided on the wall structure 215 provided in the light shielding region as illustrated in FIG. 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 approximately equal to the thickness of the liquid crystal layer 220. When 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 substantially equal to the thickness dt of the liquid crystal layer 220.

  According to the liquid crystal display device 200 of this embodiment, when a predetermined voltage (a voltage equal to or higher than the threshold voltage) is applied between the pixel electrode 211 and the counter electrode 231, each center is located in or near the three openings 214. Three axisymmetric orientations are formed with the axis stabilized. The tilt direction of the liquid crystal molecules is defined by the region partitioned by the dielectric structure 216 and the wall structure 215 provided in the pixel electrode 211, and the liquid crystal domain is divided and formed.

  Next, a preferable configuration unique to the dual-use 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 of this embodiment, in order to make the thickness dt of the liquid crystal layer 220 in the reflective region B smaller than the thickness dr of the liquid crystal layer in the transmissive region A, only the reflective region B is formed on the glass substrate 210b. A transparent dielectric layer 234 is provided. 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 formed over the insulating film for providing a step in order to adjust the thickness of the liquid crystal layer 220, light used for transmissive display is formed by the reflective electrode that covers the inclined surface (tapered portion) of the insulating film. The problem of being interrupted occurs. In addition, 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. If the said structure is employ | adopted, generation | occurrence | production of these problems will be suppressed and the utilization efficiency of light can be improved.

  Furthermore, when a transparent dielectric layer 234 having a function of scattering light (diffusion or reflection function) is used, a good white display close to paper white can be obtained without providing the reflection electrode 211b with a diffusion reflection function. realizable. However, even if the transparent dielectric layer 234 is not provided with a light scattering function, a white display close to paper white can be realized by providing an uneven shape on the surface of the reflective electrode 211b. In some cases, the position of the central axis of the axially symmetric orientation is not stable. On the other hand, if the transparent dielectric layer 234 having a light scattering function and the reflective electrode 211b having a flat surface are used, the position of the central axis is more reliably stabilized by the opening 214 formed in the reflective electrode 211b. The advantage that it can be made is obtained. Examples of the method for imparting the light scattering function to the transparent dielectric layer 234 include the following methods. There is a method of dispersing ultrafine particles such as titanium oxide particles in a transparent resin, coating this resin on a support such as a polyimide film, and forming a scattering layer having a function of scattering light, particle density, The scattering characteristics can be changed by changing the particle diameter, the thickness of the scattering layer, the refractive index of the resin, and the like. In addition, a method of forming a light scattering layer by laminating thin films having different refractive indexes may be used.

  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 transmission mode, the light used for display passes through the color filter layer 230 only once, whereas in the reflection mode display, the 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 reflection region B smaller than the optical density of the color filter layer in the transmission region A. 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. Or, the thickness of the color filter layer is kept as it is, and for example, the optical density can be reduced by reducing the concentration of the added dye.

  Next, an example of the structure of an active matrix substrate that is preferably used in a dual-use liquid crystal display device will be described with reference to FIGS. FIG. 5 is a partially enlarged plan view of the active matrix substrate, and FIG. 6 is a cross-sectional view taken along line X-X ′ in FIG. 5. In the active matrix substrate shown in FIGS. 5 and 6, a pixel region is composed of one transmission region A and one reflection region B, and two liquid crystal domains are formed (that is, the number of openings is small). In other respects, the configuration is different from the active matrix substrate 210a shown in FIG. 4, but the other configurations may be the same.

  The active matrix substrate shown in FIGS. 5 and 6 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 lines 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 film 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 dielectric structure 14, the opening 15, and the wall structure (not shown) are provided in a predetermined region of the pixel electrode 6 in order to control the orientation of the axially symmetric orientation domain. The wall structure is provided in the formation region of the signal lines 2 and 3 and has a rectangular shape in plan view.

A part of the reflective electrode 8 (pixel electrode 6) is overlapped with the gate signal line 2 of the next stage through the gate insulating film 9, thereby forming an auxiliary capacitance. 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 sequentially stacked on the gate electrode 10 branched from the gate signal line 2. have. In this example, a configuration example of a bottom gate type TFT is shown; however, the present invention is not limited to this, and a top gate type TFT can also be used.

  As described above, the liquid crystal display device 200 having the configuration shown in FIG. 3 is similar to the liquid crystal display device 100 of the first embodiment in that the alignment control structure (a pixel electrode 211 has an axially symmetric alignment) only on one substrate 210a. In spite of a relatively simple configuration provided with the formed opening 214, dielectric structure 216 and wall structure 215), the liquid crystal alignment can be sufficiently stabilized. Further, by configuring the transparent dielectric layer 234 and / or the color filter layer 230 as described above, the brightness and color purity of display in the transmission mode and the reflection mode can be improved.

  Next, a more specific configuration example of the liquid crystal display device of the present embodiment will be described with reference to FIG. FIG. 7 is a schematic diagram illustrating a configuration example of the liquid crystal display device of the present embodiment. The liquid crystal display device shown in FIG. 7 includes a backlight, a dual-use liquid crystal panel 50, a pair of polarizing plates 40 and 43 provided opposite to each other via the dual-use liquid crystal panel 50, and polarizing plates 40 and 43. 1/4 wavelength plates 41 and 44 provided between the liquid crystal panel 50 and a phase difference plate 42 having negative optical anisotropy provided between the quarter wavelength plates 41 and 44 and the liquid crystal panel 50. , 45. The liquid crystal panel 50 includes an active matrix (TFT) substrate 1, a counter substrate (color filter (CF) substrate) 17, and a vertical alignment type liquid crystal layer 20 interposed between the substrates 1 and 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.

(Reflection mode display)
Incident light from the upper side of FIG. 7 passes through the polarizing plate 43 and becomes linearly polarized light. Here, since the transmission axis of the polarizing plate 43 and the slow axis of the quarter wavelength plate 44 are arranged to be 45 °, the linearly polarized light that has passed through the polarizing plate 43 is a quarter wavelength plate. When it enters 44, it becomes circularly polarized light, passes through a color filter layer (not shown) formed on the substrate 17, and enters the liquid crystal panel (liquid crystal layer 20). As the phase difference plate 45, a phase difference plate that does not give a phase difference to light incident from the normal direction of the surface of the substrate 17 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 that has entered the liquid crystal layer 20 is transmitted with a phase difference of approximately 0, and is incident on the lower substrate 1. Reflected by the formed reflective electrode (not shown). The reflected circularly polarized light passes through the liquid crystal layer 20 again, passes through the color filter layer, and again passes through the retardation plate 45 having negative optical anisotropy as circularly polarized light. Further, after passing through the quarter wavelength plate 44, the light is converted into linearly polarized light having a polarization direction orthogonal to the polarization direction when the light is first transmitted through the polarizing plate 43, and reaches the polarizing plate 43. Therefore, the 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 circularly polarized light incident on the liquid crystal layer 20 becomes elliptically polarized light due to the birefringence of the liquid crystal layer 20, and the lower side. The light is reflected by a reflective electrode (not shown) formed on the substrate 1. When the reflected light passes through the liquid crystal layer 20, the polarization state is further lost, and again passes through the color filter layer (not shown) and the retardation plate 45 having negative optical anisotropy. The light that has passed through the phase difference plate 45 is incident on the quarter-wave plate 44 as elliptically polarized light, so that not all of the incident light becomes linearly polarized light that is orthogonal to the polarization direction at the time of incidence. Light passes through the polarizing plate 43. In particular, by adjusting the applied voltage, the direction in which the liquid crystal molecules tilt can be controlled, so that the retardation of the liquid crystal layer 20 can be adjusted. Therefore, the amount of reflected light transmitted through the polarizing plate 43 can be modulated, so that gradation display is possible.

(Transparent mode display)
The upper and lower polarizing plates 43 and 40 are arranged so that their transmission axes (polarization axes) are orthogonal to each other. The light emitted from the light source (backlight) passes through the polarizing plate 40 and becomes linearly polarized light. Here, since the transmission axis of the polarizing plate 40 and the slow axis of the quarter-wave plate 41 are arranged at 45 °, the linearly polarized light that has passed through the polarizing plate 40 is a quarter-wave plate. When it enters 41, it becomes circularly polarized light, and enters the transmission region A of the lower substrate 1 through the phase difference plate 42 having negative optical anisotropy. As the phase difference plate 42, a phase difference plate that does not give a phase difference to light incident from the normal direction of the surface of the substrate 1 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 incident on the liquid crystal layer 20 is transmitted with a phase difference of approximately 0, and the upper side is in the state of circular polarization. The light passes through the substrate 17 and the upper retardation plate 45 having a negative optical anisotropy and reaches the quarter-wave plate 44. Here, by arranging the slow axis of the lower quarter wavelength plate 41 and the slow axis of the upper quarter wavelength plate 44 so as to intersect each other by 90 °, the upper quarter wavelength plate 44 is arranged. The light that has passed becomes linearly polarized light that is parallel to the linearly polarized light that has passed through the lower polarizing plate 40, so that it is absorbed by the polarizing plate 43 and becomes 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 circularly polarized light incident on the liquid crystal layer 20 becomes elliptically polarized light due to the birefringence of the liquid crystal layer 20, and the upper CF It passes through the substrate 17, the upper retardation plate 45 and the quarter wavelength plate 44 having negative optical anisotropy as elliptically polarized light. Therefore, the light that has passed through the quarter-wave plate 44 does not become linearly polarized light that is orthogonal to the transmission axis of the lower polarizing plate 40, so that the light passes through the polarizing plate 43. Since the direction in which the liquid crystal molecules are tilted can be controlled by adjusting the applied voltage, the retardation of the liquid crystal layer 20 can be adjusted. Therefore, the amount of backlight light transmitted through the polarizing plate 43 can be modulated, so that gradation display is possible.

  The retardation plates 42 and 45 having negative optical anisotropy suppress the amount of change in retardation to a minimum when the viewing angle is changed in a state where liquid crystal molecules are vertically aligned, and black on the wide viewing angle side. Reduce floating. In the liquid crystal display device shown in FIG. 7, the retardation plates 42 and 45 and the quarter-wave plates 41 and 44 are bonded together, but the retardation plate and the quarter-wave plate having negative optical anisotropy are combined. An integrated biaxial retardation plate may be used.

  As in the liquid crystal display device of this embodiment, 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 is performed in the axially symmetric alignment domain, a pair of liquid crystal display devices (panels) By providing the quarter-wave plates 41 and 44, it is possible to eliminate the extinction pattern caused by the polarizing plates 40 and 43 and improve the brightness. Further, 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 40 and 43 so as to be orthogonal to each other (crossed Nicol arrangement), in principle, the crossed Nicols are performed. The same black display as that of the pair of polarizing plates 40 and 43 arranged in the above can be realized. Therefore, a very high contrast ratio can be realized, and a wide viewing angle characteristic led to an omnidirectional orientation can be achieved.

(Relationship between the liquid crystal layer thickness dt in the transmission region and the liquid crystal layer thickness dr in the reflection region)
FIG. 8 is a graph showing the voltage-reflectance (transmittance) of the transmissive region and the reflective region in the liquid crystal display device of this embodiment, and shows the thickness dependence of the liquid crystal layer. As shown in FIG. 8, it is preferable that the condition of 0.3 dt <dr <0.7 dt is satisfied, and the range of 0.4 dt <dr <0.6 dt is more preferable. When the liquid crystal layer thickness dr in the reflective region is lower than the lower limit value, the reflectance becomes 50% or less of the maximum reflectance, so that sufficient reflectance cannot be obtained. On the other hand, when the value 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 during transmissive display in the voltage-reflectance characteristics. Also, with the optimal white display voltage in transmissive display, the reflectance tends to decrease relatively and may be 50% or less of the maximum reflectance, so that sufficient reflectance cannot be obtained. However, in the reflection region B, the optical path length of the liquid crystal layer is approximately twice that of the transmission region A. Therefore, when the same design as the optical design of the light beam transmitted through the transmission region A is used, Birefringence anisotropy (Δn) and panel cell thickness design are extremely important.

(Example)
Specific characteristics of the dual-use liquid crystal display device according to the present embodiment will be exemplified below. First, a liquid crystal display device having the configuration shown in FIG. 7 was produced. 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. 2 was used. However, a transparent dielectric layer 234 having no light scattering ability was used, and a resin layer having a continuous uneven surface was formed under the reflective electrode 211b to adjust the diffuse reflection characteristics during reflective display. .

  The pixel region in this embodiment is divided into three sub-pixel regions by a wall structure and a dielectric structure, and one pixel region is configured in the order of a transmissive region, a reflective region, and a transmissive region in the longitudinal direction. ing. The wall structure is formed on a light shielding layer formed in a non-display area (an area other than the pixel area). Thereby, an axially symmetric alignment domain is formed in each region when a voltage is applied.

  A vertical alignment film was formed by a known method using a known alignment film material. The rubbing process 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 (that is, dr = 0.55 dt).

  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 wave plates (the phase difference plate 1 and the phase difference plate 4) sandwiching 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. 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). FIG. 9 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 spectral reflectance was about 8.1% (converted value with an aperture ratio of 100%) based on the standard diffuser plate. The contrast value was 20, showing a high contrast as compared with the conventional liquid crystal display device, which was good.

(Comparative example)
In the liquid crystal display device shown in FIG. 2, the dielectric structure and the wall structure that divide the pixel area are not arranged, and only one slit area (electrode opening) is used to make one pixel area a transmissive area, a transmissive area, and a reflective area. Divided in order. In other words, the alignment region was divided into three using only the action of the electric field generated at the electrode opening when a voltage was applied.

  A liquid crystal display device was produced under the same liquid crystal layer conditions as in the above example, and the same panel evaluation was performed for this comparative example. As a result, the display characteristics such as contrast showed substantially the same characteristics as the example.

(Evaluation)
Next, for each liquid crystal display device, display roughness, halftone response characteristics, and display quality after panel pressing were compared. First, as a result of visual evaluation of display roughness from an oblique direction in a halftone (gradation level 2 at the time of 8-gradation division), no roughness was felt in the examples. On the other hand, in the liquid crystal display device of the comparative example divided only by the slit, display roughness was observed at a halftone oblique viewing angle.

  When observed with an optical microscope whose polarization axes were orthogonal to each other, an axially symmetric alignment domain with uniform central axes was observed in the examples, whereas in the comparative example, the central axes of some liquid crystal domains were sub-pixels. The thing shifted from the center part (opening part) of was also mixed. It was confirmed that the variation in the position of the central axis was the main cause of roughness.

  Comparison of the halftone response time of the liquid crystal display device (time required for changing from gradation level 3 to gradation level 5 when divided into 8 gradations; m seconds) is 38 milliseconds in the example, and in the comparative example, It was 65 milliseconds. It was confirmed that the response time in halftone display can be shortened according to the liquid crystal display device of the present invention in which the pixel region is divided by the wall structure or the dielectric structure. Furthermore, the orientation restoring force when the panel surface was pressed with a fingertip when a voltage of 4 V was applied (white display) was examined. As a result, in the case of the example, an afterimage at the pressing portion was hardly seen (immediately restored), whereas in the case of the comparative example, an afterimage for several minutes was recognized, and the alignment disorder due to pressing occurred. There was a difference in resilience when Further, in the case of the comparative example, it was confirmed that a part of the orientation disturbed by the pressing was not completely restored, and a display defect due to a rough feeling or an orientation defect was obtained.

  Based on the above evaluation results, the transmissive display area and the reflective display area are alternately arranged, and the liquid crystal area is divided by the dielectric structure and the wall structure to fix or stabilize the position of the central axis of the axially symmetric alignment domain. It has been found that there are obtained effects such as a reduction in display roughness at an oblique viewing angle in halftone, an improvement in response speed in halftone display, and a reduction in pressed afterimage. That is, according to the liquid crystal display device of the present invention, it was found that the division structure in the pixel is optimized.

  In the first and second embodiments, the case where both the dielectric structure and the wall structure are formed has been described. However, if at least the dielectric structure is formed, the pixel area is divided into a plurality of sub-pixel areas. Can do. By aligning the liquid crystal molecules in the vicinity of the side surface of the step of the dielectric structure, the liquid crystal molecules can be divided and aligned in the partitioned region. In this case, even if the wall structure is not disposed, the pixel region is partitioned (partitioned), so that divided orientation can be obtained. In order to further stabilize this divided orientation and further effectively improve the restoring force against pressing, it is preferable to form a wall structure or an opening. When the wall structure is not formed, it is preferable to form an opening in at least one of the pair of upper and lower electrodes.

  The liquid crystal display device of the present invention is suitably applied to a transmissive liquid crystal display device, a transflective liquid crystal display device, a reflective liquid crystal display device, and a transflective liquid crystal display device. In particular, the dual-use liquid crystal display device is suitably used as a display device for mobile devices such as mobile phones.

FIG. 1A is a schematic diagram for explaining an operation principle of a liquid crystal display device according to the present invention. FIG. 1A shows an alignment state of liquid crystal molecules when no voltage is applied, and FIG. 1B shows an alignment state of liquid crystal molecules when a voltage is applied. FIG. FIG. 2 is a diagram schematically illustrating a configuration of one pixel included in the transmissive liquid crystal display device 100. FIG. 2A is a top view as viewed from the normal direction of the substrate, and FIG. It is sectional drawing along the 2B-2B 'line in Fig.2 (a). FIG. 3 is a diagram schematically showing a configuration of one pixel included in the dual-use liquid crystal display device 200, FIG. 3A is a top view seen from the normal direction of the substrate, and FIG. 3B is FIG. It is sectional drawing which followed the 3B-3B 'line in the inside. It is the schematic when observing the axially symmetrical orientation state by Embodiment 1 and a prior art example. FIG. 4A is a schematic diagram of liquid crystal domain alignment in a steady state before pressing the display surface, and FIG. 4B is a schematic diagram after pressing in a panel with pixel division arrangement according to a conventional example. FIG. 4C is a schematic diagram of orientation after pressing on the panel of the pixel division arrangement according to the present embodiment. 4 is a partially enlarged plan view of an active matrix substrate 210a of a dual-use liquid crystal display device 200. FIG. FIG. 6 is a cross-sectional view taken along line X-X ′ in FIG. 5. 6 is a schematic diagram illustrating a configuration example of a liquid crystal display device of Embodiment 2. FIG. 6 is a graph showing voltage-reflectance (transmittance) of a transmissive region and a reflective region in the liquid crystal display device of Embodiment 2. It is a figure which shows the viewing angle-contrast ratio characteristic in the transmissive display in the liquid crystal display device of an Example.

Explanation of symbols

1 active matrix (TFT) 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 Dielectric Structure 15 Opening 16 Insulating Film 17 Counter Substrate (CF Substrate)
18 Color filter layer 19 Counter electrode 20 Liquid crystal layer 21 Liquid crystal molecule 22, 32 Alignment film 23 Dielectric structure 50 Liquid crystal panel 40, 43 Polarizing plate 41, 44 1/4 wavelength plate 42, 45 Optical anisotropy is in a negative position Phase difference plate (NR plate)
100 transmissive liquid crystal display device 110a active matrix substrate 110b counter substrate (color filter substrate)
DESCRIPTION OF SYMBOLS 111 Pixel electrode 113 Notch 114 Opening 115 Wall structure 116 Dielectric structure 130 Color filter layer 131 Counter electrode 133 Support body 200 Dual use type liquid crystal display device 210a Active matrix substrate 210b Counter substrate (color filter substrate)
211 pixel electrode 214 opening 215 wall structure 230 color filter layer 231 counter electrode 232 transparent dielectric layer (reflection step)
233 Support

Claims (12)

A first substrate on which a first electrode is formed; a second substrate on which a second electrode opposite to the first electrode is formed; and a vertical alignment type interposed between the first electrode and the second electrode. A liquid crystal display device, wherein a plurality of pixel regions are defined by the first electrode and the second electrode,
At least one pixel region of the plurality of pixel regions is divided into a plurality of sub-pixel regions by a dielectric structure regularly arranged on the first substrate,
The liquid crystal molecules in the liquid crystal layer in the sub-pixel region are symmetric about an axis perpendicular to the surface of the first substrate when a predetermined voltage is applied between the first electrode and the second electrode. Aligned liquid crystal display device.   2. The pixel region according to claim 1, further comprising a wall structure substantially surrounded by the pixel region on the liquid crystal layer side of the first substrate in the light shielding region, the pixel region being surrounded by the light shielding region in a plan view. Liquid crystal display device.   The first electrode and / or the second electrode has an opening formed in the sub-pixel region, and the vertical axis is formed in or near the opening when the voltage is applied. The liquid crystal display device according to claim 1 or 2.   4. The liquid crystal display according to claim 1, wherein the pixel region is surrounded by a light shielding region in a plan view, and a support that defines a thickness of the liquid crystal layer is formed in the light shielding region. apparatus.   The first electrode includes a transparent electrode and a reflective electrode, and in the plurality of subpixel regions, at least one subpixel region is a transmissive region, and at least one subpixel region is a reflective region. 5. The liquid crystal display device according to any one of items 1 to 4.   6. The liquid crystal according to claim 5, wherein a relationship of 0.3 dt <dr <0.7 dt is satisfied, where dt is a thickness of the liquid crystal layer in the transmissive region and dr is a thickness of the liquid crystal layer in the reflective region. Display device.   The liquid crystal display device according to claim 5, further comprising a transparent dielectric layer on the liquid crystal layer side of the second substrate in the reflection region.   The liquid crystal display device according to claim 7, wherein the transparent dielectric layer has a function of scattering light.   The said 2nd board | substrate further has a color filter layer, The optical density of the said color filter layer in the said reflection area is smaller than the optical density of the said color filter layer in the said transmission area | region. A liquid crystal display device according to 1.   It further includes a pair of polarizing plates disposed opposite to 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.   It further includes a pair of polarizing plates disposed opposite to 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 uniaxial optically anisotropic medium layer. The pixel region has a rectangular shape including a pair of long sides and a pair of short sides in plan view, and is divided into the plurality of sub-pixel regions by at least a pair of the dielectric structures;
12. The pair of dielectric structures according to claim 1, wherein the pair of dielectric structures extend in a direction close to each other from the vicinity of the pair of long sides of the pixel region and are arranged in a short direction. Liquid crystal display device.

Images